Obstetrician & Gynecologist (OB/GYN)
30 years of experience
Video profile
Accepting new patients
717 SW 4th Ave
Gainesville, FL 32601
352-378-4689
Locations and availability (1)

Education ?

Medical School Score Rankings
Meharry Medical College (1980)
Obstetrics & Gynecology
  • Currently 3 of 4 apples
Top 50%

Awards & Distinctions ?

Awards  
Compassionate Doctor Recognition (2011, 2013)

Affiliations ?

Dr. Buchanan is affiliated with 8 hospitals.

Hospital Affilations

Score

Rankings

  • Shands at Starke
    922 E Call St, Starke, FL 32091
    • Currently 4 of 4 crosses
    Top 25%
  • North Florida Regional Medical Center
    6500 W Newberry Rd, Gainesville, FL 32605
    • Currently 4 of 4 crosses
    Top 25%
  • Shands Hospital at The Univ. of Florida
    1600 Sw Archer Rd, Gainesville, FL 32610
    • Currently 4 of 4 crosses
    Top 25%
  • Shands at AGH
    Obstetrician & Gynecologist
    801 SW 2nd Ave, Gainesville, FL 32601
    • Currently 2 of 4 crosses
  • Shands at Lake Shore
    368 NE Franklin St, Lake City, FL 32055
    • Currently 2 of 4 crosses
  • Shands at Live Oak
    1600 Sw Archer Rd, Gainesville, FL 32610
    • Currently 2 of 4 crosses
  • Shands at UF
  • Shands A G H, Gainesville, Fl
  • Publications & Research

    Dr. Buchanan has contributed to 98 publications.
    Title Androgen Receptor and Nutrient Signaling Pathways Coordinate the Demand for Increased Amino Acid Transport During Prostate Cancer Progression.
    Date March 2012
    Journal Cancer Research
    Excerpt

    L-Type amino acid transporters such as LAT1 and LAT3 mediate the uptake of essential amino acids. Here, we report that prostate cancer cells coordinate the expression of LAT1 and LAT3 to maintain sufficient levels of leucine needed for mTORC1 signaling and cell growth. Inhibiting LAT function was sufficient to decrease cell growth and mTORC1 signaling in prostate cancer cells. These cells maintained levels of amino acid influx through androgen receptor-mediated regulation of LAT3 expression and ATF4 regulation of LAT1 expression after amino acid deprivation. These responses remained intact in primary prostate cancer, as indicated by high levels of LAT3 in primary disease, and by increased levels of LAT1 after hormone ablation and in metastatic lesions. Taken together, our results show how prostate cancer cells respond to demands for increased essential amino acids by coordinately activating amino acid transporter pathways vital for tumor outgrowth.

    Title Global Levels of Specific Histone Modifications and an Epigenetic Gene Signature Predict Prostate Cancer Progression and Development.
    Date February 2011
    Journal Cancer Epidemiology, Biomarkers & Prevention : a Publication of the American Association for Cancer Research, Cosponsored by the American Society of Preventive Oncology
    Excerpt

    Epigenetic alterations are common in prostate cancer, yet how these modifications contribute to carcinogenesis is poorly understood. We investigated whether specific histone modifications are prognostic for prostate cancer relapse, and whether the expression of epigenetic genes is altered in prostate tumorigenesis.

    Title Lack of Correlation Between Epidermal Growth Factor Receptor Status and Response to Panitumumab Monotherapy in Metastatic Colorectal Cancer.
    Date August 2010
    Journal Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
    Excerpt

    Panitumumab, a fully human anti-epidermal growth factor receptor (EGFR) monoclonal antibody, is approved as monotherapy for the treatment of metastatic colorectal cancer. We evaluated the association of tumor EGFR expression levels with outcomes in patients with chemorefractory metastatic colorectal cancer.

    Title Severe Sickle Cell Disease--pathophysiology and Therapy.
    Date June 2010
    Journal Biology of Blood and Marrow Transplantation : Journal of the American Society for Blood and Marrow Transplantation
    Excerpt

    Over 70,000 people live with sickle cell disease (SCD) in the United States and multitudes worldwide. About 2000 afflicted babies are born in this country each year. In African countries such as Nigeria, over 100,000 babies are born with the disease each year. Great strides have been made in the conservative management of SCD. However, the medical and psychosocial cost of supporting patients with this chronic illness is enormous and spans a lifetime. Hematopoietic stem cell transplantation (HSCT) can abrogate SCD manifestations, and is the best option for cure today. Yet, this treatment modality is underutilized as less than 500 transplants are reported in the Center for International Blood and Marrow Transplant Research (CIBMTR) database because of its significant risk of morbidity and mortality. There is growing understanding of the pathophysiology of the disease, and this, coupled with advances in transplantation and new approaches to therapy, continue to improve care of patients with SCD both in children and during adulthood. Continuing investigation seeks to predict the course of the disease and to determine timing and modality of therapy in order to optimize outcomes.

    Title Remnant Signal Peptides on Non-exported Enzymes: Implications for the Evolution of Prokaryotic Respiratory Chains.
    Date April 2010
    Journal Microbiology (reading, England)
    Excerpt

    The twin-arginine translocation (Tat) pathway is a prokaryotic protein targeting system dedicated to the transmembrane translocation of folded proteins. Substrate proteins are directed to the Tat translocase by signal peptides bearing a conserved SRRxFLK 'twin-arginine' motif. In Escherichia coli, most of the 27 periplasmically located Tat substrates are cofactor-containing respiratory enzymes, and many of these harbour a molybdenum cofactor at their active site. Molybdenum cofactor-containing proteins are not exclusively located in the periplasm, however, with the major respiratory nitrate reductase (NarG) and the biotin sulfoxide reductase (BisC), for example, being located at the cytoplasmic side of the membrane. Interestingly, both NarG and BisC contain 'N-tail' regions that bear some sequence similarity to twin-arginine signal peptides. In this work, we have examined the relationship between the non-exported N-tails and the Tat system. Using a sensitive genetic screen for Tat transport, variant N-tails were identified that displayed Tat transport activity. For the NarG 36-residue N-tail, six amino acid changes were needed to induce transport activity. However, these changes interfered with binding by the NarJ biosynthetic chaperone and impaired biosynthesis of the native enzyme. For the BisC 36-residue N-tail, only five amino acid substitutions were needed to restore Tat transport activity. These modifications also impaired in vivo BisC activity, but it was not possible to identify a biosynthetic chaperone for this enzyme. These data highlight an intimate genetic and evolutionary link between some non-exported redox enzymes and those transported across membranes by the Tat translocation system.

    Title Serum Testosterone Bioassay Evaluation in a Large Male Cohort.
    Date March 2010
    Journal Clinical Endocrinology
    Excerpt

    To assess if a cell-based readout of androgen action in serum demonstrates a closer association with recognized classical parameters of androgen action in men than current measures of serum testosterone (T).

    Title Tgf-beta Signalling and Immunity in Prostate Tumourigenesis.
    Date March 2010
    Journal Expert Opinion on Therapeutic Targets
    Excerpt

    The TGF-beta's are pleiotropic cytokines that regulate multiple cellular functions. Their role in the prostate is important for normal prostate development and also in prostate tumourigenesis.

    Title Repression of Runx2 by Androgen Receptor (ar) in Osteoblasts and Prostate Cancer Cells: Ar Binds Runx2 and Abrogates Its Recruitment to Dna.
    Date January 2010
    Journal Molecular Endocrinology (baltimore, Md.)
    Excerpt

    Runx2 and androgen receptor (AR) are master transcription factors with pivotal roles in bone metabolism and prostate cancer (PCa). We dissected AR-mediated repression of Runx2 in dihydrotestosterone (DHT)-treated osteoblastic and PCa cells using reporter assays and endogenous Runx2 target genes. Repression required DHT, but not AR's transactivation function, and was associated with nuclear colocalization of the two proteins. Runx2 and AR coimmunoprecipitated and interacted directly in glutathione-S-transferase pull-down assays. Interaction was ionic in nature. Intact AR DNA-binding domain (DBD) was necessary and sufficient for both interaction with Runx2 and its repression. Runx2 sequences required for interaction were the C-terminal 132 amino acid residues together with the Runt DBD. Runx2 DNA binding was abrogated by endogenous AR in chromatin immunoprecipitation assays and by recombinant AR-DBD in gel shift assays. Furthermore, AR caused increased nuclear mobility of Runx2 as indicated by faster fluorescence recovery after photobleaching. Thus, AR binds Runx2 and abrogates its binding to DNA and possibly to other nuclear components. Clinical relevance of our results was suggested by an inverse correlation between expression of AR-responsive prostate-specific antigen and osteocalcin genes in PCa biopsies. Given the tumor suppressor properties of Runx2, its repression by AR may constitute a mechanism of hormone carcinogenesis. Attenuation of Runx2 by AR in osteoblasts may play a role in skeletal metabolism: the bone-sparing effect of androgens is attributable, in part, to keeping Runx2 activity in check and preventing high-turnover bone disease such as seen after castration and in transgenic mice overexpressing Runx2 in osteoblasts.

    Title Is Early Laparoscopic Cholecystectomy Safe After the "safe Period"?
    Date October 2009
    Journal Journal of Laparoendoscopic & Advanced Surgical Techniques. Part A
    Excerpt

    Early laparoscopic cholecystectomy (ELC) in acute cholecystitis improves hospital stay and outcome. Operative difficulty is said to increase with delay, and surgery is usually advised within 3 days of presentation. It can be difficult to accommodate all these patients within 3 days; this study evaluates results within and after this "safe period."

    Title Structural Analysis of Substrate Binding by the Tatbc Component of the Twin-arginine Protein Transport System.
    Date September 2009
    Journal Proceedings of the National Academy of Sciences of the United States of America
    Excerpt

    The Tat system transports folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane of plant chloroplasts. In Escherichia coli substrate proteins initially bind to the integral membrane TatBC complex which then recruits the protein TatA to effect translocation. Overproduction of TatBC and the substrate protein SufI in the absence of TatA led to the accumulation of TatBC-SufI complexes that could be purified using an affinity tag on the substrate. Three-dimensional structures of the TatBC-SufI complexes and unliganded TatBC were obtained by single-particle electron microscopy and random conical tilt reconstruction. Comparison of the structures shows that substrate molecules bind on the periphery of the TatBC complex and that substrate binding causes a significant reduction in diameter of the TatBC part of the complex. Although the TatBC complex contains multiple copies of the signal peptide-binding TatC protomer, purified TatBC-SufI complexes contain only 1 or 2 SufI molecules. Where 2 substrates are present in the TatBC-SufI complex, they are bound at adjacent sites. These observations imply that only certain TatC protomers within the complex interact with substrate or that there is a negative cooperativity of substrate binding. Similar TatBC-substrate complexes can be generated by an alternative in vitro reconstitution method and using a different substrate protein.

    Title Androgen Receptor Inhibits Estrogen Receptor-alpha Activity and is Prognostic in Breast Cancer.
    Date September 2009
    Journal Cancer Research
    Excerpt

    There is emerging evidence that the balance between estrogen receptor-alpha (ER(alpha)) and androgen receptor (AR) signaling is a critical determinant of growth in the normal and malignant breast. In this study, we assessed AR status in a cohort of 215 invasive ductal breast carcinomas. AR and (ER(alpha)) were coexpressed in the majority (80-90%) of breast tumor cells. Kaplan-Meier product limit analysis and multivariate Cox regression showed that AR is an independent prognostic factor in (ER(alpha))-positive disease, with a low level of AR (less than median of 75% positive cells) conferring a 4.6-fold increased risk of cancer-related death (P = 0.002). Consistent with a role for AR in breast cancer outcome, AR potently inhibited (ER(alpha))transactivation activity and 17beta-estradiol-stimulated growth of breast cancer cells. Transfection of MDA-MB-231 breast cancer cells with either functionally impaired AR variants or the DNA-binding domain of the AR indicated that the latter is both necessary and sufficient for inhibition of (ER(alpha)) signaling. Consistent with molecular modeling, electrophoretic mobility shift assays showed binding of the AR to an estrogen-responsive element (ERE). Evidence for a functional interaction of the AR with an ERE in vivo was provided by chromatin immunoprecipitation data, revealing recruitment of the AR to the progesterone receptor promoter in T-47D breast cancer cells. We conclude that, by binding to a subset of EREs, the AR can prevent activation of target genes that mediate the stimulatory effects of 17beta-estradiol on breast cancer cells.

    Title Conserved Network of Proteins Essential for Bacterial Viability.
    Date August 2009
    Journal Journal of Bacteriology
    Excerpt

    The yjeE, yeaZ, and ygjD genes are highly conserved in the genomes of eubacteria, and ygjD orthologs are also found throughout the Archaea and eukaryotes. In this study, we have constructed conditional expression strains for each of these genes in the model organism Escherichia coli K12. We show that each gene is essential for the viability of E. coli under laboratory growth conditions. Growth of the conditional strains under nonpermissive conditions results in dramatic changes in cell ultrastructure. Deliberate repression of the expression of yeaZ results in cells with highly condensed nucleoids, while repression of yjeE and ygjD expression results in at least a proportion of very enlarged cells with an unusual peripheral distribution of DNA. Each of the three conditional expression strains can be complemented by multicopy clones harboring the rstA gene, which encodes a two-component-system response regulator, strongly suggesting that these proteins are involved in the same essential cellular pathway. The results of bacterial two-hybrid experiments show that YeaZ can interact with both YjeE and YgjD but that YgjD is the preferred interaction partner. The results of in vitro experiments indicate that YeaZ mediates the proteolysis of YgjD, suggesting that YeaZ and YjeE act as regulators to control the activity of this protein. Our results are consistent with these proteins forming a link between DNA metabolism and cell division.

    Title A Novel Androgen Receptor Amino Terminal Region Reveals Two Classes of Amino/carboxyl Interaction-deficient Variants with Divergent Capacity to Activate Responsive Sites in Chromatin.
    Date June 2009
    Journal Endocrinology
    Excerpt

    The androgen receptor (AR) is an important signaling molecule in multiple tissues, yet its mode of action and cell-specific activities remain enigmatic. AR function has been best studied in the prostate, in which it is essential for growth and homeostasis of the normal organ as well as each stage of cancer development. Investigation of mechanisms responsible for continued AR action that evolve during prostate cancer progression or after hormonal management of the disease have been instructive in defining AR signaling pathways. In the current paper, we use sequence similarity and the collocation of somatic mutations in prostate cancer to define residues 501-535 of the AR amino-terminal domain as an important mediator of receptor function. Specifically, the 501-535 region is required for optimal interaction of the amino-terminal domain with both the p160 coactivator, nuclear receptor coactivator-2, and the AR-ligand binding domain in the amino/carboxyl (N/C) interaction. The N/C interaction is decreased by deletion of the 501-535 region but is distinct from deletion of the (23)FQNLF(27) peptide in that it does not affect the capacity of the AR to activate transcription from a chromatin integrated reporter or recruitment of the receptor to androgen-responsive loci in vivo. Collectively, we have been able to outline two classes of N/C-deficient AR variant that are divergent in their capacity to act in a chromatin context, thereby further defining the interplay between N/C interaction and coregulator recruitment via multiple receptor domains. These mechanisms are likely to be key determinants of the cell and promoter specific activities of the AR.

    Title Features of a Twin-arginine Signal Peptide Required for Recognition by a Tat Proofreading Chaperone.
    Date February 2009
    Journal Febs Letters
    Excerpt

    The twin-arginine translocation (Tat) system is a bacterial protein targeting pathway. Tat-targeted proteins display signal peptides containing a distinctive SRRxFLK 'twin-arginine' motif. The Escherichia coli trimethylamine N-oxide reductase (TorA) bears a bifunctional Tat signal peptide, which directs protein export and serves as a binding site for the TorD biosynthetic chaperone. Here, the physical interaction between TorD and the TorA signal peptide was investigated. A single substitution within the TorA signal peptide (L31Q) was sufficient to impair TorD binding. Screening of a random torD mutant library identified a variant TorD protein (Q7L) that displayed increased binding affinity for the TorA signal peptide.

    Title Biosynthesis of the Respiratory Formate Dehydrogenases from Escherichia Coli: Characterization of the Fdhe Protein.
    Date January 2009
    Journal Archives of Microbiology
    Excerpt

    Escherichia coli can perform two modes of formate metabolism. Under respiratory conditions, two periplasmically-located formate dehydrogenase isoenzymes couple formate oxidation to the generation of a transmembrane electrochemical gradient; and under fermentative conditions a third cytoplasmic isoenzyme is involved in the disproportionation of formate to CO(2) and H(2). The respiratory formate dehydrogenases are redox enzymes that comprise three subunits: a molybdenum cofactor- and FeS cluster-containing catalytic subunit; an electron-transferring ferredoxin; and a membrane-integral cytochrome b. The catalytic subunit and its ferredoxin partner are targeted to the periplasm as a complex by the twin-arginine transport (Tat) pathway. Biosynthesis of these enzymes is under control of an accessory protein termed FdhE. In this study, it is shown that E. coli FdhE interacts with the catalytic subunits of the respiratory formate dehydrogenases. Purification of recombinant FdhE demonstrates the protein is an iron-binding rubredoxin that can adopt monomeric and homodimeric forms. Bacterial two-hybrid analysis suggests the homodimer form of FdhE is stabilized by anaerobiosis. Site-directed mutagenesis shows that conserved cysteine motifs are essential for the physiological activity of the FdhE protein and are also involved in iron ligation.

    Title Genomic Androgen Receptor-occupied Regions with Different Functions, Defined by Histone Acetylation, Coregulators and Transcriptional Capacity.
    Date December 2008
    Journal Plos One
    Excerpt

    BACKGROUND: The androgen receptor (AR) is a steroid-activated transcription factor that binds at specific DNA locations and plays a key role in the etiology of prostate cancer. While numerous studies have identified a clear connection between AR binding and expression of target genes for a limited number of loci, high-throughput elucidation of these sites allows for a deeper understanding of the complexities of this process. METHODOLOGY/PRINCIPAL FINDINGS: We have mapped 189 AR occupied regions (ARORs) and 1,388 histone H3 acetylation (AcH3) loci to a 3% continuous stretch of human genomic DNA using chromatin immunoprecipitation (ChIP) microarray analysis. Of 62 highly reproducible ARORs, 32 (52%) were also marked by AcH3. While the number of ARORs detected in prostate cancer cells exceeded the number of nearby DHT-responsive genes, the AcH3 mark defined a subclass of ARORs much more highly associated with such genes -- 12% of the genes flanking AcH3+ARORs were DHT-responsive, compared to only 1% of genes flanking AcH3-ARORs. Most ARORs contained enhancer activities as detected in luciferase reporter assays. Analysis of the AROR sequences, followed by site-directed ChIP, identified binding sites for AR transcriptional coregulators FoxA1, CEBPbeta, NFI and GATA2, which had diverse effects on endogenous AR target gene expression levels in siRNA knockout experiments. CONCLUSIONS/SIGNIFICANCE: We suggest that only some ARORs function under the given physiological conditions, utilizing diverse mechanisms. This diversity points to differential regulation of gene expression by the same transcription factor related to the chromatin structure.

    Title Variable Stoichiometry of the Tata Component of the Twin-arginine Protein Transport System Observed by in Vivo Single-molecule Imaging.
    Date November 2008
    Journal Proceedings of the National Academy of Sciences of the United States of America
    Excerpt

    The twin-arginine translocation (Tat) system transports folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane of plant chloroplasts. The essential components of the Tat pathway are the membrane proteins TatA, TatB, and TatC. TatA is thought to form the protein translocating element of the Tat system. Current models for Tat transport make predictions about the oligomeric state of TatA and whether, and how, this state changes during the transport cycle. We determined the oligomeric state of TatA directly at native levels of expression in living cells by photophysical analysis of individual yellow fluorescent protein-labeled TatA complexes. TatA forms complexes exhibiting a broad range of stoichiometries with an average of approximately 25 TatA subunits per complex. Fourier analysis of the stoichiometry distribution suggests the complexes are assembled from tetramer units. Modeling the diffusion behavior of the complexes suggests that TatA protomers associate as a ring and not a bundle. Each cell contains approximately 15 mobile TatA complexes and a pool of approximately 100 TatA molecules in a more disperse state in the membrane. Dissipation of the protonmotive force that drives Tat transport has no affect on TatA complex stoichiometry. TatA complexes do not form in cells lacking TatBC, suggesting that TatBC controls the oligomeric state of TatA. Our data support the TatA polymerization model for the mechanism of Tat transport.

    Title Managing Behavioural Symptoms of Dementia: Effectiveness of Staff Education and Peer Support.
    Date June 2008
    Journal Aging & Mental Health
    Excerpt

    This study was designed to investigate the impact of staff education on the behaviour and quality of life of residents with dementia and on staff members' attitudes about working with people with dementia and level of burnout. Staff from three aged care facilities participated in the study (n=52). These facilities were randomly assigned to one of two intervention groups or a control group. Staff assigned to the intervention groups received an eight-week behaviourally-based programme. Staff from one aged care facility also participated in a peer support group designed to reinforce educational material and facilitate positive changes among staff members. Behavioural symptoms displayed by residents (n=76) in each of the facilities were also assessed. Assessments were conducted at pre-intervention, post-intervention, three- and six-month follow-up. The results of this study indicated that education or peer support was not associated with an improvement in resident behaviour or quality of life. Education or peer support also did not impact on staff members' level of burnout. There was, however, a change in staff members' attitudes about working with people with dementia. Possible explanations for these findings and implication for further research are considered.

    Title Large Bowel Obstruction in an Adult After Soave for Hirschsprung's Disease in Childhood.
    Date May 2008
    Journal Journal of Pediatric Surgery
    Excerpt

    Whereas Hirschsprung's disease is usually managed by surgery in infancy, late complications in adult life are rarely described. We report on a 36-year-old male presenting with an unusual complication after definitive treatment of Hirschsprung's disease as an infant.

    Title Controlled Trial of Dementia Training with a Peer Support Group for Aged Care Staff.
    Date April 2008
    Journal International Journal of Geriatric Psychiatry
    Excerpt

    This study evaluated the impact of an eight-session training program for aged care staff in managing dementia-related challenging behaviours. Participation in the training program with an additional five-session peer support group was compared with both participation in training only and a wait-list control condition.

    Title An Individualized Psychosocial Approach for "treatment Resistant" Behavioral Symptoms of Dementia Among Aged Care Residents.
    Date January 2008
    Journal International Psychogeriatrics / Ipa
    Excerpt

    Behavioral symptoms of dementia are common among residents in mainstream aged care settings, and have a substantial impact on residents and professional caregivers. This study evaluated the impact of individualized psychosocial interventions for behavioral symptoms through a small preliminary study.

    Title Control of Androgen Receptor Signaling in Prostate Cancer by the Cochaperone Small Glutamine Rich Tetratricopeptide Repeat Containing Protein Alpha.
    Date December 2007
    Journal Cancer Research
    Excerpt

    Although the androgen receptor (AR) is accepted as the major determinant of prostate cancer cell survival throughout disease progression, it is currently unclear how the receptor sustains genomic signaling under conditions of systemic androgen ablation. Here, we show that the evolutionarily conserved Hsp70/Hsp90 cochaperone, small glutamine-rich tetratricopeptide repeat containing protein alpha (alphaSGT), interacts with the hinge region of the human AR in yeast and mammalian cells. Overexpression and RNA interference revealed that alphaSGT acts to (a) promote cytoplasmic compartmentalization of the AR, thereby silencing the receptors basal/ligand-independent transcriptional activity, (b) regulate the sensitivity of receptor signaling by androgens, and (c) limit the capacity of noncanonical ligands to induce AR agonist activity. Immunofluorescence, coactivator, and chromatin immunoprecipitation analyses strongly suggest that these effects of alphaSGT on AR function are mediated by interaction in the cytoplasm and are distinct from the receptors response to classic coregulators. Quantitative immunohistochemical analysis of alphaSGT and AR levels in a cohort of 32 primary and 64 metastatic human prostate cancers revealed dysregulation in the level of both proteins during disease progression. The significantly higher AR/alphaSGT ratio in metastatic samples is consistent with the sensitization of prostate tumor cells to androgen signaling with disease progression, particularly in a low-hormone environment. These findings implicate alphaSGT as a molecular rheostat of in vivo signaling competence by the AR, and provide new insight into the determinants of androgen sensitivity during prostate cancer progression.

    Title Structural Diversity in Twin-arginine Signal Peptide-binding Proteins.
    Date November 2007
    Journal Proceedings of the National Academy of Sciences of the United States of America
    Excerpt

    The twin-arginine transport (Tat) system is dedicated to the translocation of folded proteins across the bacterial cytoplasmic membrane. Proteins are targeted to the Tat system by signal peptides containing a twin-arginine motif. In Escherichia coli, many Tat substrates bind redox-active cofactors in the cytoplasm before transport. Coordination of cofactor insertion with protein export involves a "Tat proofreading" process in which chaperones bind twin-arginine signal peptides, thus preventing premature export. The initial Tat signal-binding proteins described belonged to the TorD family, which are required for assembly of N- and S-oxide reductases. Here, we report that E. coli NapD is a Tat signal peptide-binding chaperone involved in biosynthesis of the Tat-dependent nitrate reductase NapA. NapD binds tightly and specifically to the NapA twin-arginine signal peptide and suppresses signal peptide translocation activity such that transport via the Tat pathway is retarded. High-resolution, heteronuclear, multidimensional NMR spectroscopy reveals the 3D solution structure of NapD. The chaperone adopts a ferredoxin-type fold, which is completely distinct from the TorD family. Thus, NapD represents a new family of twin-arginine signal-peptide-binding proteins.

    Title Disruption of Androgen Receptor Signaling by Synthetic Progestins May Increase Risk of Developing Breast Cancer.
    Date November 2007
    Journal The Faseb Journal : Official Publication of the Federation of American Societies for Experimental Biology
    Excerpt

    There is now considerable evidence that using a combination of synthetic progestins and estrogens in hormone replacement therapy (HRT) increases the risk of breast cancer compared with estrogen alone. Furthermore, the World Health Organization has recently cited combination contraceptives, which contain synthetic progestins, as potentially carcinogenic to humans, particularly for increased breast cancer risk. Given the above observations and the current trend toward progestin-only contraception, it is important that we have a comprehensive understanding of how progestins act in the millions of women worldwide who regularly take these medications. While synthetic progestins, such as medroxyprogesterone acetate (MPA), which are currently used in both HRT and oral contraceptives were designed to act exclusively through the progesterone receptor, it is clear from both clinical and experimental settings that their effects may be mediated, in part, by binding to the androgen receptor (AR). Disruption of androgen action by synthetic progestins may have serious deleterious side effects in the breast, where the balance between estrogen signaling and androgen signaling plays a critical role in breast homeostasis. Here, we review the role of androgen signaling in the normal breast and in breast cancer and present new data demonstrating that androgen receptor function can be perturbed by low doses of MPA, similar to doses achieved in serum of women taking HRT. We propose that the observed excess of breast malignancies associated with combined HRT may be explained, in part, by synthetic progestins such as MPA acting as endocrine disruptors to negate the protective effects of androgen signaling in the breast. Understanding the role of androgen signaling in the breast and how this is modulated by synthetic progestins is necessary to determine how combined HRT alters breast cancer risk, and to inform the development of optimal preventive and treatment strategies for this disease.

    Title Cysteine Scanning Mutagenesis and Disulfide Mapping Studies of the Tata Component of the Bacterial Twin Arginine Translocase.
    Date October 2007
    Journal The Journal of Biological Chemistry
    Excerpt

    The Tat (twin arginine translocation) system transports folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane of plant chloroplasts. The integral membrane proteins TatA, TatB, and TatC are essential components of the Tat pathway. TatA forms high order oligomers and is thought to constitute the protein-translocating unit of the Tat system. Cysteine scanning mutagenesis was used to systematically investigate the functional importance of residues in the essential N-terminal transmembrane and amphipathic helices of Escherichia coli TatA. Cysteine substitutions of most residues in the amphipathic helix, including all the residues on the hydrophobic face of the helix, severely compromise Tat function. Glutamine 8 was identified as the only residue in the transmembrane helix that is critical for TatA function. The cysteine variants in the transmembrane helix were used in disulfide mapping experiments to probe the oligomeric arrangement of TatA protomers within the larger TatA complex. Residues in the center of the transmembrane helix (including residues 10-16) show a distinct pattern of cross-linking indicating that this region of the protein forms well defined interactions with other protomers. At least two interacting faces were detected. The results of our TatA studies are compared with analogous data for the homologous, but functionally distinct, TatB protein. This comparison reveals that it is only in TatA that the amphipathic helix is sensitive to amino acid substitutions. The TatA amphipathic helix may play a role in forming and controlling the path of substrate movement across the membrane.

    Title Identification of Novel Androgen Receptor Target Genes in Prostate Cancer.
    Date August 2007
    Journal Molecular Cancer
    Excerpt

    BACKGROUND: The androgen receptor (AR) plays critical roles in both androgen-dependent and castrate-resistant prostate cancer (PCa). However, little is known about AR target genes that mediate the receptor's roles in disease progression. RESULTS: Using Chromatin Immunoprecipitation (ChIP) Display, we discovered 19 novel loci occupied by the AR in castrate resistant C4-2B PCa cells. Only four of the 19 AR-occupied regions were within 10-kb 5'-flanking regulatory sequences. Three were located up to 4-kb 3' of the nearest gene, eight were intragenic and four were in gene deserts. Whereas the AR occupied the same loci in C4-2B (castrate resistant) and LNCaP (androgen-dependent) PCa cells, differences between the two cell lines were observed in the response of nearby genes to androgens. Among the genes strongly stimulated by DHT in C4-2B cells--D-dopachrome tautomerase (DDT), Protein kinase C delta (PRKCD), Glutathione S- transferase theta 2 (GSTT2), Transient receptor potential cation channel subfamily V member 3 (TRPV3), and Pyrroline-5-carboxylate reductase 1 (PYCR1)--most were less strongly or hardly stimulated in LNCaP cells. Another AR target gene, ornithine aminotransferase (OAT), was AR-stimulated in a ligand-independent manner, since it was repressed by AR siRNA knockdown, but not stimulated by DHT. We also present evidence for in vivo AR-mediated regulation of several genes identified by ChIP Display. For example, PRKCD and PYCR1, which may contribute to PCa cell growth and survival, are expressed in PCa biopsies from primary tumors before and after ablation and in metastatic lesions in a manner consistent with AR-mediated stimulation. CONCLUSION: AR genomic occupancy is similar between LNCaP and C4-2B cells and is not biased towards 5' gene flanking sequences. The AR transcriptionally regulates less than half the genes nearby AR-occupied regions, usually but not always, in a ligand-dependent manner. Most are stimulated and a few are repressed. In general, response is stronger in C4-2B compared to LNCaP cells. Some of the genes near AR-occupied regions appear to be regulated by the AR in vivo as evidenced by their expression levels in prostate cancer tumors of various stages. Several AR target genes discovered in the present study, for example PRKCD and PYCR1, may open avenues in PCa research and aid the development of new approaches for disease management.

    Title Uncoupling of Hormone-dependence from Chaperone-dependence in the L701h Mutation of the Androgen Receptor.
    Date May 2007
    Journal Molecular and Cellular Endocrinology
    Excerpt

    The mechanisms underlying androgen receptor (AR)-mediated progression of prostate cancer following androgen ablation have yet to be fully determined. On this basis we screened naturally occurring mutants of human AR for hormone-independent activity using a yeast model system. An initial screen of 43 different mutants revealed that ARs having a Leu701His mutation (AR(L701H)) exhibited hormone-independent activation of a lacZ reporter gene. The AR(L701H) mutant bound dihydrotestosterone to a similar extent as did wild type AR, although its ability to be induced by hormone for transactivation was reduced substantially. Subsequent studies focused on the dependence of AR(L701H) on molecular chaperones for folding to the active state. We found that AR(L701H) was highly dependent on Hsp90 for its hormone-independent activation, suggesting that this chaperone functions in AR(L701H) folding. However, the mutant did not respond specifically to increased levels of FKBP52, suggesting that this chaperone functions at the hormone-dependent activation stage in the folding process. Further studies of AR(L701H) in PC3 cells suggested that this mutant is prohibited from hormone-independent transactivation in mammalian cells. However, basal expression of a reporter gene by AR(L701H) was not impaired by the presence of 17-allylamino-17-demethoxygeldanamycin as was wild type AR, suggesting differential interactions of these receptors with molecular chaperones in animal cells.

    Title The Entire N-terminal Half of Tatc is Involved in Twin-arginine Precursor Binding.
    Date May 2007
    Journal Biochemistry
    Excerpt

    Translocation of twin-arginine precursor proteins across the cytoplasmic membrane of Escherichia coli requires the three membrane proteins TatA, TatB, and TatC. TatC and TatB were shown to be involved in precursor binding. We have analyzed in vitro a number of single alanine substitutions in tatC that were previously shown to compromise in vivo the function of the Tat translocase. All tatC mutants that were defective in precursor translocation into cytoplasmic membrane vesicles concomitantly interfered with precursor binding not only to TatC but also to TatB. Hence structural changes of TatC that affect precursor targeting simultaneously abolish engagement of the twin-arginine signal sequence with TatB and block the formation of a functional Tat translocase. Since these phenotypes were observed for tatC mutations spread over the first half of TatC, this entire part of the molecule must globally be involved in precursor binding.

    Title Androgen Receptor Coregulators and Their Involvement in the Development and Progression of Prostate Cancer.
    Date May 2007
    Journal International Journal of Cancer. Journal International Du Cancer
    Excerpt

    The androgen receptor signaling axis plays an essential role in the development, function and homeostasis of male urogenital structures including the prostate gland although the mechanism by which the AR axis contributes to the initiation, progression and metastatic spread of prostate cancer remains somewhat enigmatic. A number of molecular events have been proposed to act at the level of the AR and associated coregulators to influence the natural history of prostate cancer including deregulated expression, somatic mutation, and post-translational modification. The purpose of this article is to review the evidence for deregulated expression and function of the AR and associated coactivators and corepressors and how such events might contribute to the progression of prostate cancer by controlling the selection and expression of AR targets.

    Title Hdlalert - a Healthcare Dl Alerting System: from User Needs to Implementation.
    Date February 2007
    Journal Health Informatics Journal
    Excerpt

    In the health domain, there are many circumstances where clinicians (i.e. doctors, nurses, allied health professionals) and patients wish to track changes in medical knowledge. However, existing 'news' or 'alert' services provide relatively limited means for selecting which information to receive. The result is that clinicians and patients often receive information that is inappropriate, irrelevant or simply too much. In this paper, we detail alert-relevant findings from several international user studies (e.g. UK, Germany and New Zealand) incorporating both clinical staff (across several hospitals) and patients' perceptions. These findings demonstrate the importance of context, in terms of both the user's task and immediate environment. We introduce a novel alerting architecture that can provide a finely tailored stream of alerts to the user, and provides further support to assist the interpretation of received material.

    Title Subunit Composition and in Vivo Substrate-binding Characteristics of Escherichia Coli Tat Protein Complexes Expressed at Native Levels.
    Date February 2007
    Journal The Febs Journal
    Excerpt

    The Tat system transports folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane of plant chloroplasts. Substrates are targeted to the Tat pathway by signal peptides containing a pair of consecutive arginine residues. The membrane proteins TatA, TatB and TatC are the essential components of this pathway in Escherichia coli. The complexes that these proteins form at native levels of expression have been investigated by the use of affinity tag-coding sequences fused to chromosomal tat genes. Distinct TatA and TatBC complexes were identified using size-exclusion chromatography and shown to have apparent molecular masses of approximately 700 and 500 kDa, respectively. Following in vivo expression, the Tat substrate protein SufI was found to copurify with the TatBC, but not the TatA, complex. This binding required the SufI signal peptide. Substitution of the twin-arginine residues in the SufI signal peptide by either twin lysine or twin alanine residues abolished export. However, both variant SufI proteins still copurified with the TatBC complex. These data show that the twin-arginine residues of the Tat consensus motif are not essential for binding of precursor to the TatBC complex but are required for the successful entry of the precursor into the transport cycle. The effect on substrate binding of single amino acid substitutions in TatC that affect Tat transport were studied using TatC variants Phe94Ala, Glu103Ala, Glu103Arg and Asp211Ala. Only variant Glu103Arg showed reduced copurification of SufI with TatBC. The transport defects associated with the other TatC variants do not, therefore, arise from an inability to bind substrate proteins.

    Title Cysteine-scanning Mutagenesis and Disulfide Mapping Studies of the Conserved Domain of the Twin-arginine Translocase Tatb Component.
    Date December 2006
    Journal The Journal of Biological Chemistry
    Excerpt

    The cytoplasmic membrane protein TatB is an essential component of the Escherichia coli twin-arginine (Tat) protein translocation pathway. Together with the TatC component it forms a complex that functions as a membrane receptor for substrate proteins. Structural predictions suggest that TatB is anchored to the membrane via an N-terminal transmembrane alpha-helix that precedes an amphipathic alpha-helical section of the protein. From truncation analysis it is known that both these regions of the protein are essential for function. Here we construct 31 unique cysteine substitutions in the first 42 residues of TatB. Each of the substitutions results in a TatB protein that is competent to support Tat-dependent protein translocation. Oxidant-induced disulfide cross-linking shows that both the N-terminal and amphipathic helices form contacts with at least one other TatB protomer. For the transmembrane helix these contacts are localized to one face of the helix. Molecular modeling and molecular dynamics simulations provide insight into the possible structural basis of the transmembrane helix interactions. Using variants with double cysteine substitutions in the transmembrane helix, we were able to detect cross-links between up to five TatB molecules. Protein purification showed that species containing at least four cross-linked TatB molecules are found in correctly assembled TatBC complexes. Our results suggest that the transmembrane helices of TatB protomers are in the center rather than the periphery of the TatBC complex.

    Title Androgen Metabolic Genes in Prostate Cancer Predisposition and Progression.
    Date September 2006
    Journal Frontiers in Bioscience : a Journal and Virtual Library
    Excerpt

    Significant evidence implicates androgens in prostate cancer etiology. We review recent data with regard to the association between several allelic variants of specific androgen-metabolic genes and the predisposition to prostate cancer. We also review the emerging evidence regarding the role of genetic variants of these genes as well as the androgen receptor in prostate cancer progression. Based on the prostate cancer paradigm, we propose that a multidisciplinary attack on the problem--involving biochemistry, genetics, pharmacogenetics, endocrinology and molecular epidemiology--may be important for the understanding and successful treatment of complex (in terms of etiology) human diseases.

    Title Formation of Functional Tat Translocases from Heterologous Components.
    Date September 2006
    Journal Bmc Microbiology
    Excerpt

    The Tat pathway transports folded proteins across the cytoplasmic membrane of bacteria and the thylakoid membrane of plants. In Eschericha coli, Tat transport requires the integral membrane proteins TatA, TatB and TatC. In this study we have tested the ability of tat genes from the eubacterial species Pseudomonas syringae, Streptomyces coelicolor and Aquifex aeolicus, to compensate for the absence of the cognate E. coli tat gene, and thus to form functional Tat translocases with E. coli Tat components.

    Title Suppression of Androgen Receptor Signaling in Prostate Cancer Cells by an Inhibitory Receptor Variant.
    Date July 2006
    Journal Molecular Endocrinology (baltimore, Md.)
    Excerpt

    There is increasing evidence that sensitization of the androgen receptor (AR) signaling pathway contributes to the failure of androgen ablation therapy for prostate cancer, and that direct targeting of the AR may be a useful therapeutic approach. To better understand how AR function could be abrogated in prostate cancer cells, we have developed a series of putative dominant-negative variants of the human AR, containing deletions or mutations in activation functions AF-1, AF-5, and/or AF-2. One construct, AR inhibitor (ARi)-410, containing a deletion of AF-1 and part of AF-5 of the AR, had no intrinsic transactivation activity but inhibited wild-type AR (wtAR) in a ligand-dependent manner by at least 95% when transfected at a 4:1 molar ratio. ARi-410 was an equally potent inhibitor of gain-of-function AR variants. Ectopic expression of ARi-410 inhibited the proliferation of AR-positive LNCaP cells, but not AR-negative PC-3 cells. Whereas ARi-410 also marginally inhibited progesterone receptor activity, this was far less pronounced than the effect on AR (50% vs. 95% maximal inhibition, respectively), and there was no inhibition of either vitamin D or estrogen receptor activity. In the presence of ligand, ARi-410 interacted with wtAR, and both receptors translocated into the nucleus. Whereas the amino-carboxy terminal interaction was not necessary for optimal dominant-negative activity, disruption of dimerization through the ligand binding domain reduced the efficacy of ARi-410. In addition, although inhibition of AR function by ARi-410 was not dependent on DNA binding, the DNA binding domain was required for dominant-negative activity. Taken together, our results suggest that interaction between ARi-410 and the endogenous AR in prostate cancer cells, potentially through the DNA binding and ligand binding domains, results in a functionally significant reduction in AR signaling and AR-dependent cell growth.

    Title Decreased Androgen Receptor Levels and Receptor Function in Breast Cancer Contribute to the Failure of Response to Medroxyprogesterone Acetate.
    Date November 2005
    Journal Cancer Research
    Excerpt

    Previously, we reported that androgen receptor (AR), but not estrogen receptor (ER) or progesterone receptor (PR), is predictive of response to the synthetic progestin, medroxyprogesterone acetate (MPA), in a cohort of 83 patients with metastatic breast cancer. To further investigate the role of AR in determining response to MPA in this cohort, we analyzed AR levels by immunohistochemistry with two discrete antisera directed at either the NH2 or the COOH termini of the receptor. Compared with tumors that responded to MPA (n = 31), there was a significant decrease in the intensity and extent of AR immunoreactivity with both AR antisera in tumors from nonresponders (n = 52). Whereas only a single AR immunostaining pattern was detected in responders to MPA, reflecting concordance of immunoreactivity with the two AR antisera, tumors from nonresponders exhibited four distinct AR immunostaining patterns: (a) concordance with the two antibodies (31%), (b) staining only with the COOH-terminal antibody (33%), (c) staining only with the NH2-terminal antibody (22%), or (d) no immunoreactivity with either NH2- or COOH-terminal antibody (14%). DNA sequencing and functional analysis identified inactivating missense gene mutations in the ligand-binding domain of the AR in tumors from two of nine nonresponders positive with the NH2-terminal AR antisera but negative for COOH-terminal immunoreactivity and lacking specific, high-affinity dihydrotestosterone binding in tumor cytosol fractions. Tumors with more AR than the median level (37 fmol/mg protein) had significantly lower levels of PR (30 fmol/mg protein) than tumors with low AR (PR; 127 fmol/mg protein) despite comparable levels of ER. Ligand-dependent activation of the AR in human T47D and MCF-7 breast cancer cells resulted in inhibition of estradiol-stimulated cell proliferation and a reduction in the capacity of the ER to induce expression of the PR. These effects could be reversed using a specific AR antisense oligonucleotide. Increasing the ratio of AR to ER resulted in a greater androgen-dependent inhibition of ER function. Collectively, these data suggest that reduced levels of AR or impaired AR function contribute to the failure of MPA therapy potentially due to abrogation of the inhibitory effect of AR on ER signaling.

    Title Intellectual and Functional Outcome of Children 3 Years Old or Younger Who Have Cns Malignancies.
    Date November 2005
    Journal Journal of Clinical Oncology : Official Journal of the American Society of Clinical Oncology
    Excerpt

    PURPOSE: To evaluate the impact of tumor location, clinical parameters, and therapy on neurocognitive, neuroendocrine, and functional outcomes in children < or = 3 years old with intracranial CNS malignancies who survived at least 2 years after diagnosis. PATIENTS AND METHODS: Records were retrospectively reviewed for 194 children diagnosed from 1985 to 1999 at St Jude Children's Research Hospital (Memphis, TN). RESULTS: The median age at diagnosis was 1.8 years (range, 0.1 to 3.5 years). Median follow-up was 7.64 years (2.0 to 19.4 years). Tumors were infratentorial (102), diencephalic (53), and hemispheric (39); 47% required ventriculoperitoneal shunts, 36% developed seizure disorders, and 20% developed severe ototoxicity. Therapy included no radiation therapy (RT) in 57 (30%), local RT in 87 (45%), and craniospinal irradiation (CSI) in 49 (25%). Overall survival at 10 years was 78 +/- 4%. In a longitudinal analysis of 126 patients with at least one neurocognitive evaluation (NE), the mean rate of intelligence quotient (IQ) change for patients who received CSI (-1.34 points per year) and local RT (-0.51 points per year) was significantly different from the no RT group (0.91 points per year; P = .005 and P = .036, respectively). Patients with hemispheric tumors had a significantly greater IQ decline (-1.52 points per year) than those with midline tumors (0.59 points per year; P = .038). Among those with NE > or = 5 years after diagnosis, 71.4% of CSI recipients compared with 23% of local RT recipients had IQ less than 70 (P = .021). Patients undergoing CSI were more likely to develop endocrinopathies (P < .0001) and to require special education (P = .0007). CONCLUSION: In young children with CNS tumors, CSI and hemispheric location are associated with significant declines in IQ scores.

    Title Grip1 Mediates the Interaction Between the Amino- and Carboxyl-termini of the Androgen Receptor.
    Date August 2005
    Journal Biological Chemistry
    Excerpt

    The androgen receptor (AR) mediates transactivation of target genes by acting as a dimer in which its amino-terminal domain (AR-NTD) interacts with its carboxyl-terminal, ligand-binding domain (AR-LBD) (N/C interaction). Here we assessed if and how AR N/C interaction relates to AR transactivation activity and how the p160 coactivator GRIP1 participates in both processes. The concentration of dihydrotestosterone needed for half-maximal N/C interaction was approximately 10-fold higher than for half-maximal transactivation, indicating a disparity between the two processes. Although a mutation of an LXXLL-like motif, 23 FQNLF 27 --> 23 FQNAA 27 , in the AR-NTD abolished AR N/C interaction, it could be restored by the co-expression of the coactivator GRIP1. Co-expression of mutated forms of GRIP1, possessing alterations known to abolish either of the two AR interaction domains, could not restore AR N/C interaction, suggesting that wild-type GRIP1 normally bridges the two AR domains. Although AR transactivation activity can proceed without AR N/C interaction, we propose that part of the GRIP1 coactivation activity resides in its ability to bind both AR-NTD and -LBD, to stabilize the N/C complex and allow for secondary cofactors to be recruited more efficiently. Our results also indicate that AR N/C interaction enhances but is not necessary for AR transactivation activity.

    Title Androgen Receptor Levels in Prostate Cancer Epithelial and Peritumoral Stromal Cells Identify Non-organ Confined Disease.
    Date April 2005
    Journal The Prostate
    Excerpt

    Although up to 30% of men who undergo radical prostatectomy for clinically organ-confined prostate cancer will relapse with disseminated disease, currently it is not possible to predict these patients.

    Title Targeting the Androgen Receptor: Improving Outcomes for Castration-resistant Prostate Cancer.
    Date March 2005
    Journal Endocrine-related Cancer
    Excerpt

    The categorization of prostate cancers that are progressing after castration as 'hormone-refractory' evolved from the clinical observation that surgical or medical castration (i.e. androgen ablation therapy; AAT) is not curative and, despite an initial response, virtually all tumors eventually regrow. Successful AAT is contingent on the dependence of prostate cancer cells for androgen signaling through an intracellular mediator, the androgen receptor (AR) for survival. Current preclinical and clinical data imply that the AR is expressed and continues to mediate androgen signaling after failure of AAT. As AAT does not completely eliminate circulating androgens, sufficient concentrations of dihydrotestosterone may accumulate in tumor cells to maintain AR signaling, especially in the context of upregulated receptor levels or increased sensitivity of the AR for activation. In addition, ligands of non-testicular origin or ligand-independent activation can contribute to continued AR signaling. In many cases, therefore, from the perspective of the AR, a 'hormone-refractory' classification after failure of AAT is inappropriate. Classifying prostate tumors that progress after AAT as 'castration-resistant' may be more relevant. Clinical responses to second- and third-line hormonal therapies suggest that the mechanisms of AR activation are in part a function of previously administered AAT. Accordingly, the increasing trend to utilize AAT earlier in the course of the clinical disease may have a greater influence on the genotype and phenotype of the resistant tumor. In this article, we detail strategies to inhibit the growth of prostate cancer cells that specifically target the AR in addition to those practiced traditionally that indirectly target the receptor by reducing the amount of circulating ligand. We propose that treatment regimes combining AAT with direct AR targeting strategies may provide a more complete blockade of androgen signaling, thereby preventing or significantly delaying the emergence of treatment-resistant disease.

    Title Mutation of the Androgen Receptor Causes Oncogenic Transformation of the Prostate.
    Date February 2005
    Journal Proceedings of the National Academy of Sciences of the United States of America
    Excerpt

    Recent evidence demonstrates that the androgen receptor (AR) continues to influence prostate cancer growth despite medical therapies that reduce circulating androgen ligands to castrate levels and/or block ligand binding. Whereas the mutation, amplification, overexpression of AR, or cross-talk between AR and other growth factor pathways may explain the failure of androgen ablation therapies in some cases, there is little evidence supporting a causal role between AR and prostate cancer. In this study, we functionally and directly address the role whereby AR contributes to spontaneous cancer progression by generating transgenic mice expressing (i) AR-WT to recapitulate increased AR levels and ligand sensitivity, (ii) AR-T857A to represent a promiscuous AR ligand response, and (iii) AR-E231G to model altered AR function. Whereas transgenes encoding either AR-WT or AR-T857A did not cause prostate cancer when expressed at equivalent levels, expression of AR-E231G, which carries a mutation in the most highly conserved signature motif of the NH2-terminal domain that also influences interactions with cellular coregulators, caused rapid development of prostatic intraepithelial neoplasia that progressed to invasive and metastatic disease in 100% of mice examined. Taken together, our data now demonstrate the oncogenic potential of steroid receptors and implicate altered AR function and receptor coregulator interaction as critical determinants of prostate cancer initiation, invasion, and metastasis.

    Title Structural and Functional Consequences of Glutamine Tract Variation in the Androgen Receptor.
    Date February 2005
    Journal Human Molecular Genetics
    Excerpt

    The androgen receptor (AR) gene contains a polymorphic trinucleotide repeat region, (CAG)(n), in its N-terminal transactivation domain (NTD) that encodes a polyglutamine (polyQ) tract in the receptor protein. Whereas the length of the CAG repeat ranges from 6 to 39 in healthy individuals, the variations in repeat length both within and outside the normal range are associated with disease, including impaired spermatogenesis and Kennedy's disease, and with the risk of developing breast and prostate cancer. Whereas it has been proposed that the inverse relationship between polyQ tract length within the normal range and AR transactivation potential may be responsible for altered risk of disease, the molecular mechanisms underlying polyQ length modulation of AR function have not been elucidated. In this study, we provide detailed characterization of a somatic AR gene mutation detected in a human prostate tumor that results in interruption of the polyQ tract by two non-consecutive leucine residues (AR-polyQ2L). Compared with wtAR, AR-polyQ2L exhibits disrupted inter-domain communication (N/C interaction) and a lower protein level, but paradoxically has markedly increased transactivation activity. Molecular modeling and the response to cofactors indicate that the increased activity of AR-polyQ2L results from the presentation of a more stable platform for the recruitment of accessory proteins than wild-type AR. Analysis of the relationship between polyQ tract length and AR function revealed a critical size (Q16-Q29) for maintenance of N/C interaction. That between 91 and 99% of AR alleles in different racial-ethnic groups encode a polyQ tract in the range of Q16-Q29 suggests that N/C interaction has been preserved as an essential component of androgen-induced AR signaling.

    Title Coordinating Assembly and Export of Complex Bacterial Proteins.
    Date December 2004
    Journal The Embo Journal
    Excerpt

    The Escherichia coli twin-arginine protein transport (Tat) system is a molecular machine dedicated to the translocation of fully folded substrate proteins across the energy-transducing inner membrane. Complex cofactor-containing Tat substrates, such as the model (NiFe) hydrogenase-2 and trimethylamine N-oxide reductase (TorA) systems, acquire their redox cofactors prior to export from the cell and require to be correctly assembled before transport can proceed. It is likely, therefore, that cellular mechanisms exist to prevent premature export of immature substrates. Using a combination of genetic and biochemical approaches including gene knockouts, signal peptide swapping, complementation, and site-directed mutagenesis, we highlight here this crucial 'proofreading' or 'quality control' activity in operation during assembly of complex endogenous Tat substrates. Our experiments successfully uncouple the Tat transport and cofactor-insertion activities of the TorA-specific chaperone TorD and demonstrate unequivocally that TorD recognises the TorA twin-arginine signal peptide. It is proposed that some Tat signal peptides operate in tandem with cognate binding chaperones to orchestrate the assembly and transport of complex enzymes.

    Title How Do I Judge the "medical Homeness" of My Practice?
    Date September 2004
    Journal Clinical Pediatrics
    Excerpt

    A Medical Home provides care to infants, children, and adolescents that is accessible, continuous, comprehensive, family-centered, coordinated, compassionate, and culturally effective. These desirable characteristics are often difficult to assess in a practice. A recent policy statement from the American Academy of Pediatrics provides clarification and functional definitions of these characteristics. Tools and resources are available to aid physicians, clinic administrators and client-families in assessing their clinic's compliance with Medical Home characteristics, as part of a long-term quality improvement program for their practice.

    Title Pc-3 Cells with Enhanced Androgen Receptor Signaling: a Model for Clonal Selection in Prostate Cancer.
    Date August 2004
    Journal The Prostate
    Excerpt

    Two sublines of the human prostate cancer cell line, PC-3, which is widely used as a model of prostate cancer progression, have been reported: PC-3(AR-) that do not express androgen receptor (AR), and PC-3AR+ that have measurable AR RNA but little protein.

    Title Role of the Escherichia Coli Tat Pathway in Outer Membrane Integrity.
    Date December 2003
    Journal Molecular Microbiology
    Excerpt

    The Escherichia coli Tat system serves to export folded proteins harbouring an N-terminal twin-arginine signal peptide across the cytoplasmic membrane. Previous work has demonstrated that strains mutated in genes encoding essential Tat pathway components are highly defective in the integrity of their cell envelope. Here, we report the isolation, by transposon mutagenesis, of tat mutant strains that have their outer membrane integrity restored. This outer membrane repair of the tat mutant arises as a result of upregulation of the amiB gene, which encodes a cell wall amidase. Overexpression of the genes encoding the two additional amidases, amiA and amiC, does not compensate for the outer membrane defect of the tatC strain. Analysis of the amiA and amiC coding sequences indicates that the proteins may be synthesized with plausible twin-arginine signal sequences, and we demonstrate that they are translocated to the periplasm by the Tat pathway. A Tat+ strain that has mislocalized AmiA and AmiC proteins because of deletion of their signal peptides displays an identical defective cell envelope phenotype. The presence of genes encoding amidases with twin-arginine signal sequences in the genomes of other Gram-negative bacteria suggests that a similar cell envelope defect may be a common feature of tat mutant strains.

    Title Mr Imaging of Fistula-in-ano.
    Date December 2003
    Journal European Journal of Radiology
    Excerpt

    Accurate preoperative assessment of fistula-in-ano is mandatory if the fistula is not to recur. In recent years, MRI has become pre-eminent for fistula assessment and recent studies have shown that not only is MRI more accurate than surgical assessment, but that surgery based on MRI can reduce further disease recurrence by approximately 75%. The main role of MRI is to alert the surgeon to fistula tracks and extensions that would otherwise have gone undetected and, thus, untreated at the time of surgical assessment under general anaesthetic.

    Title Biochemical and Structural Analysis of the Molybdenum Cofactor Biosynthesis Protein Moba.
    Date August 2003
    Journal The Journal of Biological Chemistry
    Excerpt

    Molybdopterin guanine dinucleotide (MGD) is the form of the molybdenum cofactor that is required for the activity of most bacterial molybdoenzymes. MGD is synthesized from molybdopterin (MPT) and GTP in a reaction catalyzed by the MobA protein. Here we report that wild type MobA can be copurified along with bound MPT and MGD, demonstrating a tight binding of both its substrate and product. To study structure-function relationships, we have constructed a number of site-specific mutations of the most highly conserved amino acid residues of the MobA protein family. Variant MobA proteins were characterized for their ability to support the synthesis of active molybdenum enzymes, to bind MPT and MGD, to interact with the molybdenum cofactor biosynthesis proteins MobB and MoeA. They were also characterized by x-ray structural analysis. Our results suggest an essential role for glycine 15 of MobA, either for GTP binding and/or catalysis, and an involvement of glycine 82 in the stabilization of the product-bound form of the enzyme. Surprisingly, the individual and double substitution of asparagines 180 and 182 to aspartate did not affect MPT binding, catalysis, and product stabilization.

    Title [endoanal Mr Imaging: Diagnostic Assessment].
    Date June 2003
    Journal Der Chirurg; Zeitschrift Für Alle Gebiete Der Operativen Medizen
    Excerpt

    Endoanal MR imaging is an alternative to anal endosonography for the acquisition of high-resolution images of the external and internal anal sphincter. A dedicated anal receiver coil is placed in the anus so that it spans the sphincter complex. Highly detailed images of the sphincters can be obtained in any plane and the morphological abnormalities found in various types of anal incontinence can be demonstrated. Whilst MR demonstrates external sphincter disruption with an efficacy similar to that of endosonography, it is better able to demonstrate external sphincter atrophy that is presumed secondary to neuropathy. The finding of coexisting muscular atrophy on MR may prejudice the effects of anal sphincter repair for obstetric disruption.

    Title A Novel Androgen Receptor Mutant, A748t, Exhibits Hormone Concentration-dependent Defects in Nuclear Accumulation and Activity Despite Normal Hormone-binding Affinity.
    Date June 2003
    Journal Molecular Endocrinology (baltimore, Md.)
    Excerpt

    Functional analysis of androgen receptor (AR) gene mutations isolated from prostate cancer has led to the identification of residues that play important roles in the structure and function of the receptor. Here we report the characteristics of a novel AR mutation A748T located in helix 5 of the ligand-binding domain, which was identified in metastatic prostate cancer. Despite a normal hormone-binding affinity, A748T causes hormone concentration-dependent defects in nuclear accumulation and transcriptional activation. Moreover, when equivalent amounts of DNA are transfected, the mutant is expressed at much lower levels than the wild-type AR (ARWT). Treatment with geldanamycin to disrupt receptor-heat shock protein complexes rapidly decreases the levels of ARWT but not A748T, suggesting that the lower expression and rapid degradation rate of A748T is due to weaker interactions with heat shock proteins. Further analysis revealed that hormone dissociates from A748T five times faster than from ARWT. Loss of the ability to form stable amino/carboxyl-terminal interactions causes accelerated dissociation rates in some AR mutants. However, A748T exhibits normal amino/carboxyl-terminal interactions at high hormone concentrations, suggesting that the mutation alters interactions with ligand. Consistent with this conclusion, our structural model predicts that A748T disrupts crucial contact points with ligand, thereby altering the conformation of the ligand-binding domain.

    Title The Escherichia Coli Twin-arginine Translocase: Conserved Residues of Tata and Tatb Family Components Involved in Protein Transport.
    Date April 2003
    Journal Febs Letters
    Excerpt

    The Escherichia coli Tat system serves to export folded proteins harbouring an N-terminal twin-arginine signal peptide across the cytoplasmic membrane. In this report we have studied the functions of conserved residues within the structurally related TatA and TatB proteins. Our results demonstrate that there are two regions within each protein of high sequence conservation that are critical for efficient Tat translocase function. The first region is the interdomain hinge between the transmembrane and the amphipathic alpha-helices of TatA and TatB proteins. The second region is within the amphipathic helices of TatA and TatB. In particular an invariant phenylalanine residue within TatA proteins is essential for activity, whereas a string of glutamic acid residues on the same face of the amphipathic helix of TatB is important for function.

    Title Imaging Anal Fistula.
    Date April 2003
    Journal Radiologic Clinics of North America
    Excerpt

    The management of fistula-in-ano has been based on digital examination and operative findings. MR imaging has shown significant limitations to this approach, particularly in the management of recurrent fistula. The most cost-effective approach may be using a combination of endosonography and MR imaging. Preoperative confirmation of fistula complexity facilitates surgery planning of sphincter saving techniques and prevents sepsis being missed, which has been shown to reduce recurrence. Imaging has a significant role to play in this condition to improve patient outcome.

    Title Contribution of the Androgen Receptor to Prostate Cancer Predisposition and Progression.
    Date December 2002
    Journal Cancer Metastasis Reviews
    Excerpt

    Although prostate cancer is heterogeneous in its etiology and progression, androgen signaling through the androgen receptor (AR) appears to be involved in all aspects of the disease, from initiation to development of treatment resistance. Lifetime exposure to a constitutively more active AR, encoded by AR alleles as defined by two translated polymorphic microsatellites (CAG and GGC), results in a significant increase in prostate cancer risk. The AR gene is amplified or a target for somatic gain-of-function mutations in metastatic prostate cancer. Gain-of-function AR gene mutations may result in inappropriate activation of the AR, thereby contributing to the failure of conventional androgen-ablation treatments. In cases where no genetically altered receptors are observed, altered signaling through the AR, achieved by cross-talk with other signaling pathways (e.g. kinase-mediated pathways) and/or inappropriate expression of coregulatory proteins, may contribute to disease progression. Thus, the AR-signaling axis contributes to many aspects of prostate cancer, including initiation, progression and resistance to current forms of therapy. This recognition represents a paradigm shift in our understanding of the molecular mechanisms involved in progression of prostate cancer, and provides insight into novel AR-targeted therapies which ultimately may be more effective than current forms of androgen ablation.

    Title Effect of Mri on Clinical Outcome of Recurrent Fistula-in-ano.
    Date December 2002
    Journal Lancet
    Excerpt

    Recurrent fistula-in-ano is usually due to sepsis missed at surgery, which can be identified by MRI. We aimed to establish the therapeutic effect of MRI in patients with fistula-in-ano. We did MRI in 71 patients with recurrent fistula, with further surgery done at the discretion of the surgeon. Surgery and MRI agreed in 40 patients, five (13%) of whom had further recurrence, compared with 16 (52%) of 31 in whom surgery and MRI disagreed (p=0.0005). Further recurrence in all 16 was at the site predicted by MRI. For surgeons who always acted on MRI, further recurrences arose in four of 25 (16%) operations versus eight of 14 (57%) operations for those who ignored imaging (p=0.008). Surgery guided by MRI reduces further recurrence of fistula-in-ano by 75% and should be done in all patients with recurrent fistula.

    Title Truncation Analysis of Tata and Tatb Defines the Minimal Functional Units Required for Protein Translocation.
    Date November 2002
    Journal Journal of Bacteriology
    Excerpt

    The TatA and TatB proteins are essential components of the twin arginine protein translocation pathway in Escherichia coli. C-terminal truncation analysis of the TatA protein revealed that a plasmid-expressed TatA protein shortened by 40 amino acids is still fully competent to support protein translocation. Similar truncation analysis of TatB indicated that the final 30 residues of TatB are dispensable for function. Further deletion experiments with TatB indicated that removal of even 70 residues from its C terminus still allowed significant transport. These results imply that the transmembrane and amphipathic helical regions of TatA and TatB are critical for their function but that the C-terminal domains are not essential for Tat transport activity. A chimeric protein comprising the N-terminal region of TatA fused to the amphipathic and C-terminal domains of TatB supports a low level of Tat activity in a strain in which the wild-type copy of either tatA or tatB (but not both) is deleted.

    Title Functional Complexity of the Twin-arginine Translocase Tatc Component Revealed by Site-directed Mutagenesis.
    Date August 2002
    Journal Molecular Microbiology
    Excerpt

    The Escherichia coli Tat apparatus is a membrane-bound protein translocase that serves to export folded proteins synthesized with N-terminal twin-arginine signal peptides. The essential TatC component of the Tat translocase is an integral membrane protein probably containing six transmembrane helices. Sequence analysis identified conserved TatC amino acid residues, and the role of these side-chains was assessed by single alanine substitution. This approach identified three classes of TatC mutants. Class I mutants included F94A, E103A and D211A, which were completely devoid of Tat-dependent protein export activity and thus represented residues essential for TatC function. Cross-complementation experiments with class I mutants showed that co-expression of D211A with either F94A or E103A regenerated an active Tat apparatus. These data suggest that different class I mutants may be blocked at different steps in protein transport and point to the co-existence of at least two TatC molecules within each Tat translocon. Class II mutations identified residues important, but not essential, for Tat activity, the most severely affected being L99A and Y126A. Class III mutants showed no significant defects in protein export. All but three of the essential and important residues are predicted to cluster around the cytoplasmic N-tail and first cytoplasmic loop regions of the TatC protein.

    Title Behaviour of Topological Marker Proteins Targeted to the Tat Protein Transport Pathway.
    Date July 2002
    Journal Molecular Microbiology
    Excerpt

    The Escherichia coli Tat system mediates Sec-independent export of protein precursors bearing twin arginine signal peptides. Formate dehydrogenase-N is a three-subunit membrane-bound enzyme, in which localization of the FdnG subunit to the membrane is Tat dependent. FdnG was found in the periplasmic fraction of a mutant lacking the membrane anchor subunit FdnI, confirming that FdnG is located at the periplasmic face of the cytoplasmic membrane. However, the phenotypes of gene fusions between fdnG and the subcellular reporter genes phoA (encoding alkaline phosphatase) or lacZ (encoding beta-galactosidase) were the opposite of those expected for analogous fusions targeted to the Sec translocase. PhoA fusion experiments have previously been used to argue that the peripheral membrane DmsAB subunits of the Tat-dependent enzyme dimethyl sulphoxide reductase are located at the cytoplasmic face of the inner membrane. Biochemical data are presented that instead show DmsAB to be at the periplasmic side of the membrane. The behaviour of reporter proteins targeted to the Tat system was analysed in more detail. These data suggest that the Tat and Sec pathways differ in their ability to transport heterologous passenger proteins. They also suggest that caution should be observed when using subcellular reporter fusions to determine the topological organization of Tat-dependent membrane protein complexes.

    Title A Genetic Screen for Suppressors of Escherichia Coli Tat Signal Peptide Mutations Establishes a Critical Role for the Second Arginine Within the Twin-arginine Motif.
    Date April 2002
    Journal Archives of Microbiology
    Excerpt

    The Escherichia coli Tat protein export pathway transports folded proteins synthesized with N-terminal twin-arginine signal peptides. Twin-arginine signal sequences contain a conserved SRRxFLK "twin-arginine" amino acid sequence motif which is required for protein export by the Tat pathway. The E. coli trimethylamine N-oxide reductase (TorA) is a Tat-dependent periplasmic molybdoenzyme that facilitates anaerobic respiration with trimethylamine N-oxide as terminal electron acceptor. Here, we describe mutant strains constructed with modified TorA twin-arginine signal peptides. Substitution of the second arginine residue of the TorA signal peptide twin-arginine motif with either lysine or aspartate, or the simultaneous substitution of both arginines with lysine residues, completely abolished export. In each case, the now cytoplasmically localised TorA retained full enzymatic activity with the artificial electron donor benzyl viologen. However, the mutant strains were incapable of anaerobic growth with trimethylamine N-oxide and the non-fermentable carbon-source glycerol. The growth phenotype of the mutant strains was exploited in a genetic screen with the aim of identifying second-site suppressor mutations that allowed export of the modified TorA precursors.

    Title Redox Centers of 4-hydroxybenzoyl-coa Reductase, a Member of the Xanthine Oxidase Family of Molybdenum-containing Enzymes.
    Date January 2002
    Journal The Journal of Biological Chemistry
    Excerpt

    4-Hydroxybenzoyl-CoA reductase (4-HBCR) is a key enzyme in the anaerobic metabolism of phenolic compounds. It catalyzes the reductive removal of the hydroxyl group from the aromatic ring yielding benzoyl-CoA and water. The subunit architecture, amino acid sequence, and the cofactor/metal content indicate that it belongs to the xanthine oxidase (XO) family of molybdenum cofactor-containing enzymes. 4-HBCR is an unusual XO family member as it catalyzes the irreversible reduction of a CoA-thioester substrate. A radical mechanism has been proposed for the enzymatic removal of phenolic hydroxyl groups. In this work we studied the spectroscopic and electrochemical properties of 4-HBCR by EPR and Mössbauer spectroscopy and identified the pterin cofactor as molybdopterin mononucleotide. In addition to two different [2Fe-2S] clusters, one FAD and one molybdenum species per monomer, we also identified a [4Fe-4S] cluster/monomer, which is unique among members of the XO family. The reduced [4Fe-4S] cluster interacted magnetically with the Mo(V) species, suggesting that the centers are in close proximity, (<15 A apart). Additionally, reduction of the [4Fe-4S] cluster resulted in a loss of the EPR signals of the [2Fe-2S] clusters probably because of magnetic interactions between the Fe-S clusters as evidenced in power saturation studies. The Mo(V) EPR signals of 4-HBCR were typical for XO family members. Under steady-state conditions of substrate reduction, in the presence of excess dithionite, the [4Fe-4S] clusters were in the fully oxidized state while the [2Fe-2S] clusters remained reduced. The redox potentials of the redox cofactors were determined to be: [2Fe-2S](+1/+2) I, -205 mV; [2Fe-2S] (+1/+2) II, -255 mV; FAD/FADH( small middle dot)/FADH, -250 mV/-470 mV; [4Fe-4S](+1/+2), -465 mV and Mo(VI)/(V)/(VI), -380 mV/-500 mV. A catalytic cycle is proposed that takes into account the common properties of molybdenum cofactor enzymes and the special one-electron chemistry of dehydroxylation of phenolic compounds.

    Title Characterisation of the Mob Locus of Rhodobacter Sphaeroides Ws8: Moba is the Only Gene Required for Molybdopterin Guanine Dinucleotide Synthesis.
    Date December 2001
    Journal Archives of Microbiology
    Excerpt

    The mob genes of several bacteria have been implicated in the conversion of molybdopterin to molybdopterin guanine dinucleotide. The mob locus of Rhodobacter sphaeroides WS8 comprises three genes, mobABC. Chromosomal in-frame deletions in each of the mob genes have been constructed. The mobA mutant strain has inactive DMSO reductase and periplasmic nitrate reductase activities (both molybdopterin guanine dinucleotide-requiring enzymes), but the activity of xanthine dehydrogenase, a molybdopterin enzyme, is unaffected. The inability of a mobA mutant to synthesise molybdopterin guanine dinucleotide is confirmed by analysis of cell extracts of the mobA strain for molybdenum cofactor forms following iodine oxidation. Mutations in mobB and mobC are not impaired for molybdoenzyme activities and accumulate wild-type levels of molybdopterin and molybdopterin guanine dinucleotide, indicating they are not compromised in molybdenum cofactor synthesis. In the mobA mutant strain, the inactive DMSO reductase is found in the periplasm, suggesting that molybdenum cofactor insertion is not necessarily a pre-requisite for export.

    Title Chronic Subcutaneous Octreotide Decreases Gastrointestinal Blood Loss in Blue Rubber-bleb Nevus Syndrome.
    Date October 2001
    Journal Journal of Pediatric Gastroenterology and Nutrition
    Excerpt

    BACKGROUND: A patient affected by blue rubber-bleb nevus syndrome had chronic gastrointestinal bleeding requiring weekly blood transfusions. Despite multiple surgical and endoscopic procedures to treat the venous malformations, the patient continued to bleed primarily from lesions in the small bowel. Therefore, this patient was treated with octreotide, a somatostatin analog known to decrease splanchnic blood flow and that is used for acute and chronic gastrointestinal bleeding. METHODS: Octreotide therapy, 5.7 microg/kg subcutaneously twice daily, was initiated, and the patient was followed up clinically. Complete blood counts, blood glucose concentration, pancreatic enzyme concentration, liver function tests, and growth hormone concentration were monitored during treatments. RESULTS: During the 4 weeks after initiation of octreotide therapy, hemoglobin concentration was maintained without the need for transfusions. Octreotide decreased the patient's monthly need for blood transfusion from 52 +/- 7 mL. kg-1. mo-1 of packed red blood cells to 23 +/- 7 mL. kg-1. mo-1. She had no detectable side effects or growth inhibition. Other medical interventions including -epsilonaminocaproic acid, nadolol, and total parenteral nutrition with bowel rest were not as effective as octreotide alone. CONCLUSION: Octreotide decreased the patient's need for blood transfusions. Possible mechanisms include altering blood flow to the gastrointestinal tract and direct effects on the venous malformations.

    Title Collocation of Androgen Receptor Gene Mutations in Prostate Cancer.
    Date July 2001
    Journal Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
    Excerpt

    Consistent with both the development of the normal prostate gland and prostate tumorigenesis being dependent on testicular androgens, targeting the androgen-signaling axis (i.e., androgen ablation therapy) remains the predominant treatment regime for patients with metastatic prostate cancer. Although there is a very good initial response to androgen ablation, these treatments are essentially palliative. Recent evidence suggests that treatment failure may not result from a loss of androgen signaling but, rather, from the acquisition of genetic changes that lead to aberrant activation of the androgen-signaling axis. A consistent finding is that androgen receptor (AR) gene mutations, present in metastatic prostate cancer and in human prostate cancer cell lines as well as in xenograft and other animal models, result in decreased specificity of ligand-binding and inappropriate receptor activation by estrogens, progestins, adrenal androgens, glucocorticoids and/or AR antagonists. Because a significant proportion of missense mutations in the AR gene reported in prostate cancer collocate to the signature sequence and AF-2, two discrete regions of the ligand-binding domain critical for androgen signaling, we recently proposed that collocation of mutations identified in prostate cancer would identify additional regions of the AR important in receptor function. This approach led to the identification of a four-amino acid region at the boundary of the hinge and ligand-binding domains of the receptor that forms half of a potential protein-protein binding site. AR gene mutations have also been identified that collocate to areas in the DNA-binding domain, to the NH(2)-terminal transactivation domain, and to the hinge region in prostate tumors. In nearly every case, missense mutations in the AR gene identified in prostate cancer that collocate to discrete regions of the receptor contribute to altered androgen signaling and provide a potential mechanism to explain the reemergence of tumor growth during the course of hormone ablation therapies.

    Title A Novel Protein Transport System Involved in the Biogenesis of Bacterial Electron Transfer Chains.
    Date June 2001
    Journal Biochimica Et Biophysica Acta
    Excerpt

    The Tat system is a recently discovered bacterial protein transport pathway that functions primarily in the biosynthesis of proteins containing redox active cofactors. Analogous transport systems are found in plant organelles. Remarkably and uniquely the Tat system functions to transported a diverse range of folded proteins across a biological membrane, a feat that must be achieved without rendering the membrane freely permeable to protons and other ions. Here we review the operation of the bacterial Tat system and propose a model for the structural organisation of the Tat preprotein translocase.

    Title Hormone Status Selects for Spontaneous Somatic Androgen Receptor Variants That Demonstrate Specific Ligand and Cofactor Dependent Activities in Autochthonous Prostate Cancer.
    Date May 2001
    Journal The Journal of Biological Chemistry
    Excerpt

    We have used the autochthonous transgenic adenocarcinoma of mouse prostate (TRAMP) model to investigate the relationship between somatic mutation in the androgen receptor (AR) and the emergence of androgen-independent prostate cancer. Here we report the identification, isolation, and characterization of distinct classes of AR variants from spontaneous prostate tumors in the TRAMP model. Using cDNA cloning, single stranded conformation polymorphism and sequencing strategies, 15 unique somatic mutations in the AR were identified in prostate tumors obtained from eight TRAMP mice between 24 and 29 weeks of age. At least one mutation was isolated from each mouse. All mutations were single base substitutions, 10 were missense and 5 were silent. Nine mutations in the AR were identified in tumors of four mice that were castrated at 12 weeks of age. Interestingly, the majority of mutations (seven out of nine, 78%) identified in the androgen-independent tumors colocalized in the AR transactivation domain. The remaining mutations colocalized in the AR ligand binding domain. In general, the AR variants demonstrated promoter-, cell-, and cofactor-specific activities in response to various hormones. All AR variants isolated in this study maintained strong sensitivity for androgens, and four AR variants isolated from castrated mice demonstrated increased activities in the absence of ligand. The K638M and F677S variants demonstrated increased activities in response to androgen, and K638M also demonstrated increased response to estradiol. In the presence of AR coactivator ARA70 the E231G variant demonstrated increased activity in response to both androgen and estradiol. However, in the presence of AR coactivator ARA160 the E231G variant was selectively responsive to androgen. Collectively these analyses not only indicate that somatic mutations in the AR gene occur spontaneously in TRAMP tumors but also how changes in the hormonal environment may drive the selection of spontaneous somatic mutations that provide a growth advantage.

    Title Crystal Structure of the Molybdenum Cofactor Biosynthesis Protein Moba from Escherichia Coli at Near-atomic Resolution.
    Date February 2001
    Journal Structure (london, England : 1993)
    Excerpt

    All mononuclear molybdoenzymes bind molybdenum in a complex with an organic cofactor termed molybdopterin (MPT). In many bacteria, including Escherichia coli, molybdopterin can be further modified by attachment of a GMP group to the terminal phosphate of molybdopterin to form molybdopterin guanine dinucleotide (MGD). This modification reaction is required for the functioning of many bacterial molybdoenzymes, including the nitrate reductases, dimethylsulfoxide (DMSO) and trimethylamine-N-oxide (TMAO) reductases, and formate dehydrogenases. The GMP attachment step is catalyzed by the cellular enzyme MobA.

    Title Mutations at the Boundary of the Hinge and Ligand Binding Domain of the Androgen Receptor Confer Increased Transactivation Function.
    Date February 2001
    Journal Molecular Endocrinology (baltimore, Md.)
    Excerpt

    The androgen receptor (AR), a member of the steroid receptor superfamily of nuclear transcription factors, mediates androgen signaling in diverse target tissues. Here we report AR gene mutations identified in human prostate cancer and the autochthonous transgenic adenocarcinoma of the mouse prostate model that colocate to residues (668)QPIF(671) at the boundary of the hinge and ligand-binding domain, resulting in receptors that exhibit 2- to 4-fold increased activity compared with wild-type AR in response to dihydrotestosterone, estradiol, progesterone, adrenal androgens, and the AR antagonist, hydroxyflutamide, without an apparent effect on receptor levels, ligand binding kinetics, or DNA binding. The expression of these or similar variants could explain the emergence of hormone refractory disease in a subset of patients. Homology modeling indicates that amino acid residues (668)QPIF(671) form a ridge bordering a potential protein-protein interaction surface. The naturally occurring AR gene mutations reported in this study result in decreased hydrophobicity of this surface, suggesting that altered receptor-protein interaction mediates the precocious activity of the AR variants.

    Title Breast Cancer Susceptibility Gene 1 (brcai) is a Coactivator of the Androgen Receptor.
    Date November 2000
    Journal Cancer Research
    Excerpt

    In the present study, the role of BRCA1 in ligand-dependent androgen receptor (AR) signaling was assessed. In transfected prostate and breast cancer cell lines, BRCA1 enhanced AR-dependent transactivation of a probasin-derived reporter gene. The effects of BRCA1 were mediated through the NH2-terminal activation function (AF-1) of the receptor. Cotransfection of p160 coactivators markedly potentiated BRCA1-mediated enhancement of AR signaling. In addition, BRCA1 was shown to interact physically with both the AR and the p160 coactivator, glucocorticoid receptor interacting protein 1. These findings suggest that BRCA1 may directly modulate AR signaling and, therefore, may have implications regarding the proliferation of normal and malignant androgen-regulated tissues.

    Title Non-hodgkin Lymphoma Diagnosed from a Tracheal Window Biopsy.
    Date March 2000
    Journal Journal of the Royal Society of Medicine
    Title Mutations in the Androgen Receptor Gene Are Associated with Progression of Human Prostate Cancer to Androgen Independence.
    Date February 1999
    Journal Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
    Excerpt

    Progression to androgen-independent growth of human prostate cancers may be mediated by alterations in the structure and/or expression of the androgen receptor (AR) gene. To date, mutations in the AR gene have largely been identified in hormone refractory tumors. In this study, single-strand conformational polymorphism analysis and DNA sequencing of the entire AR gene coding region was performed on 25 primary prostate tumors sampled prior to initiation of hormonal (i.e. , androgen ablation) therapy. Base changes leading to amino acid substitutions in the AR were identified in 11 (44%) tumors. The presence of AR amino acid substitutions was associated with decreased immunohistochemical staining for AR in tumor cells and the rapid failure of subsequent hormonal therapies. Single-strand conformational polymorphism analysis of exons 2, 3, and 8 of the X-linked hypoxanthine guanine phosphoribosyl transferase (HPRT) gene in the same samples revealed no bandshifts, suggesting that the high frequency of AR gene mutations detected was not a consequence of generalized genetic instability. These data indicate that AR gene mutations occur commonly in advanced prostate cancers prior to endocrine treatment of disease and may contribute to altered androgen responsiveness of the tumors.

    Title Oat Cell Carcinoma of the Tongue from an Unknown Primary.
    Date May 1998
    Journal Ear, Nose, & Throat Journal
    Excerpt

    Oat cell carcinoma is rarely diagnosed in the head and neck and can be primary or secondary. Primary tumors arise from amine precursor uptake and decarboxylation cells which are found throughout the head and neck. Secondary deposits metastasize most commonly from the lungs. We report a 64-year-old woman with a known pancreatic oat cell carcinoma who came to the ENT Department with dysphagia. On examination, a lesion was seen at the base of the tongue and was histologically an oat cell carcinoma. No treatment was administered and the patient died one month after discharge. This report highlights the difficulty in determining the primary site when a rare tumor metastasizes to the head and neck and no autopsy findings are obtained. To our knowledge, oat cell carcinoma of the tongue has not been previously reported.

    Title Cervical Lymphadenopathy Secondary to Atypical Mycobacteria in Children.
    Date October 1996
    Journal The Journal of Laryngology and Otology
    Excerpt

    Non-tuberculous mycobacterial (NTM) infections usually present as an enlarged lymph node in the neck of a non-immunocompromised child. The differential diagnosis includes bacterial adenitis, malignant disease and tuberculosis. The definitive diagnosis relies upon isolating the organisms in culture. The treatment is complete surgical excision with, or without, anti-tuberculous chemotherapy. Ten cases of NTM infections are presented with a discussion of the aetiology and treatment of this condition.

    Title Neutrophil Pool Sizes and Granulocyte Colony-stimulating Factor Production in Human Mid-trimester Fetuses.
    Date September 1995
    Journal Pediatric Research
    Excerpt

    We quantified neutrophils and neutrophil progenitors, and assessed granulocyte colony-stimulating factor (G-CSF) production in the liver and bone marrow of 20 human abortuses after elective pregnancy termination between 14 and 24 wk of gestation. Mature neutrophils were not observed in any of the liver specimens, but were present in the bone marrow as early as 14 wk. The concentrations of neutrophils in the fetal marrow were extremely low, by comparison with term infants and adults, with less than 5% of the nucleated cells being segmented neutrophils, band neutrophils, or metamyelocytes compared with 31-69% in term infants. Despite the low neutrophil populations, progenitors which had the capacity for clonal maturation into neutrophils in vitro were abundant in the fetal liver and fetal bone marrow. In addition, such progenitors had a dose-response relationship to recombinant G-CSF similar to that of progenitors from the bone marrow of healthy adults. At each gestational age tested, stimulation of mononuclear cells from fetal liver with IL-1 alpha generated less G-CSF protein and fewer G-CSF mRNA transcripts than did stimulation of mononuclear cells from fetal bone marrow. Mononuclear cells from the fetal bone marrow produced less G-CSF protein and mRNA than did mononuclear cells from the blood of adults. Thus, the liver of the mid-trimester human fetus is almost devoid of neutrophils, and the bone marrow contains a significantly lower proportion of neutrophils than does the marrow of term neonates or adults. These findings correlate with IL-1 alpha-induced production of G-CSF in these organs.(ABSTRACT TRUNCATED AT 250 WORDS)

    Title Treatment of Cns Relapse in Children with Acute Lymphoblastic Leukemia: A Pediatric Oncology Group Study.
    Date March 1993
    Journal Journal of Clinical Oncology : Official Journal of the American Society of Clinical Oncology
    Excerpt

    PURPOSE: To assess the efficacy and toxicity of chemotherapy and cranial radiation for the treatment of children with acute lymphoblastic leukemia (ALL) following first isolated CNS relapse. PATIENTS AND METHODS: One hundred twenty children were treated on Pediatric Oncology Group (POG) protocol 8304. All children had received prophylactic CNS therapy during their initial treatment. The treatment protocol included a four-drug reinduction and six weekly doses of triple intrathecal therapy (TIT). Cranial radiation, 24 Gy, was followed by monthly TIT. Systemic consolidation and maintenance therapy included 6-week cycles of mercaptopurine/methotrexate (6MP/MTX) and vincristine/cyclophosphamide (VCR/CTX), with randomization to intervening pulses of prednisone/doxorubicin (PDN/DOX) or teniposide (VM26)/cytarabine (Ara-C) for a total of 88 weeks. RESULTS: All 120 patients achieved a second complete remission. There have been 61 protocol failures. Thirty-five patients had a bone marrow relapse, four with simultaneous CNS involvement and one with concurrent testicular leukemia. Thirteen patients had a second isolated CNS relapse, 10 a testicular relapse, and two relapsed in other sites. One patient died in remission. Overall event-free survival (EFS) at 4 years was 46% +/- 7%. The toxicity associated with this protocol was minimal except for leukoencephalopathy, which occurred in 20 (17%) patients. The treatment comparison between VM26/Ara-C or PDN/DOX pulses showed a trend toward superior EFS (P = .12) in favor of VM-26/Ara-C. CONCLUSION: To date, this represents the largest series of patients with ALL treated uniformly for an isolated CNS relapse. Since marrow relapse remains the primary site of failure, future protocols must intensify systemic therapy.

    Title A Multicenter Study of Viral Hepatitis in a United States Hemophilic Population.
    Date February 1993
    Journal Blood
    Excerpt

    Hemophilia A and B patients seen at nine US regional treatment centers were tested for serologic markers of hepatitis B virus (HBV), hepatitis C virus (HCV), and hepatitis delta virus (HDV) during 1987 and 1988. Because human immunodeficiency virus (HIV) infection, a potentially confounding variable, was present in 53% of the group, the population was divided by HIV status for analysis purposes. In the HIV-positive group (N = 382), less than 1% had not been infected with HBV, HCV, or HDV, whereas 75% had evidence of infection with HBV and 98% with HCV. HBsAg, a marker of active HBV infection, was present in 12% of subjects; 96% of these were HCV positive. Anti-HDV was detected in 35 subjects (9.1%); all were anti-HBc positive. Ten of the 35 (29%) also were positive for IgM anti-HDV, indicating current infection. All 10 were HBsAg positive and 7 of the 9 tested were HDV RNA positive. Severe/moderate hemophilia B patients were more likely to have experienced an HBV infection and to be anti-HDV positive than were similar hemophilia A patients (22% v 8%, P < .05). In the HIV-negative group (N = 345), the subjects were younger and had less severe hemophilia than the HIV-positive patients. No evidence of HBV, HCV, or HDV infection was found in 18%, whereas 33% had experienced HBV infection and 79% were anti-HCV positive. Within this group, 4% were HBsAg positive. All 13 subjects with anti-HDV (4% of the HIV-negative group) also possessed anti-HBc. One (7.7%) was IgM anti-HDV positive and the serum from another contained HDV RNA. Both of these individuals were HBsAg positive. As in the HIV-positive group, severe/moderate hemophilia B patients were more likely to be HBV and HDV positive than were hemophilia A patients (9% v 3%, P < .05). A prevalence study of viral hepatitis in a large US hemophilic population showed that active infection with HCV is common, occurring in 89% of all study patients regardless of HIV status. Evidence of active HBV infection was found in 8%; 19% of these were actively infected with HDV. HDV was more common in hemophilia B patients after controlling for disease severity.

    Title Long-term Sulfamethoxazole-trimethoprim in Wegener's Granulomatosis.
    Date February 1993
    Journal Archives of Otolaryngology--head & Neck Surgery
    Excerpt

    Since 1985, a number of reports have highlighted the effectiveness of a short course of sulfamethoxazole-trimethoprim as an adjuvant to immunosuppressive drugs in the treatment of Wegener's granulomatosis. We report our experience with long-term sulfamethoxazole-trimethoprim therapy in patients with Wegener's granulomatosis. We describe recent advances in the pathogenesis of Wegener's granulomatosis, suggest a complementary mechanism of action of sulfamethoxazole-trimethoprim, and advocate long-term sulfamethoxazole-trimethoprim therapy as a treatment option in Wegener's granulomatosis.

    Title A Study of Toxicity and Comparative Therapeutic Efficacy of Vindesine-prednisone Vs. Vincristine-prednisone in Children with Acute Lymphoblastic Leukemia in Relapse. A Pediatric Oncology Group Study.
    Date December 1992
    Journal Investigational New Drugs
    Excerpt

    Vindesine (des-acetyl Vinblastine) is a synthetic derivative of vinblastine, and was produced with the hope that it would have less neurotoxicity and hematopoietic toxicity than other vinca alkaloids. Phase I and II studies also demonstrated significant activity in lymphoid malignancies, especially Acute Lymphoblastic Leukemia (ALL). The present study was designed to compare therapeutic effectiveness of twice weekly vindesine (2 mg/M2/dose) plus Prednisone (60 mg/M2/dose) (Treatment 1) to weekly Vincristine (2 mg/M2/dose) plus Prednisone (60 mg/M2/day) (Treatment 2). All patients were less than 21 years of age, and had documented bone marrow relapse (blast count > 25%). In 39 patients presumed sensitive to vincristine, there were 11 complete responses out of 20 patients (55%) randomized to receive vindesine/prednisone and 7 complete responses out of 19 patients (37%) treated with Vincristine/Prednisone. In 37 patients resistant to vincristine, there were 7 complete responses (19%). Vindesine was more toxic than Vincristine. Major toxicities of vindesine included paraesthesias, peripheral neuropathy and ileus. Vindesine hematological toxicity appeared greater, but such toxicity is hard to assess in patients with bone marrow disease. In this study, vindesine and vincristine had similar efficacy, but vindesine use was associated with more toxicity.

    Title Metastatic Cervical Lymph Nodes: General Practitioner Referral Patterns.
    Date August 1992
    Journal Postgraduate Medical Journal
    Excerpt

    Premature excision biopsy of a cervical lymph node infiltrated by metastatic carcinoma may compromise patient survival since it is associated with an increased incidence of local wound recurrence and distant metastases. Seventy per cent of such patients have an identifiable head and neck primary, obviating the need for an excision biopsy. It is important therefore that they are examined by surgeons who are experienced in inspecting the upper aerodigestive tract and who are competent in performing definitive head and neck surgery. A questionnaire sent to all general practitioners of an Inner London and a District Health Authority revealed that only 18% and 33% respectively referred patients who they suspected of having a metastatic neck node to a department with an experienced head and neck surgeon. We conclude that greater emphasis on the correct management of these patients at both an undergraduate and postgraduate level may encourage subsequent generations of general practitioners to review their referral patterns.

    Title Teniposide (vm-26) and Continuous Infusion Cytosine Arabinoside for Initial Induction Failure in Childhood Acute Lymphoblastic Leukemia. A Pediatric Oncology Group Pilot Study.
    Date November 1990
    Journal Cancer
    Excerpt

    Twenty-six evaluable children with newly diagnosed acute lymphoblastic leukemia (ALL) who failed to achieve initial remission after receiving two to seven drugs for at least a 4-week period were given teniposide (VM-26) and continuous infusion cytosine arabinoside (Ara-C). Twenty-two received 150 mg/m2 of VM-26 on days 1 and 2 with 100 mg/2 of Ara-C as a continuous infusion on days 1 through 5; a second shortened course was given on day 14 to eight patients who had evidence of some antileukemic effect or were clinically judged able to tolerate a second course. The last four patients received three daily doses of VM-26 and a 7-day infusion of Ara-C at the same daily dosages. Twelve (48%) achieved complete remission (CR) of ALL. There was a trend toward decreasing response rates with an increasing number of drugs used in the initial induction regimen, i.e., five CR among seven patients with a prior two-drug induction attempt, six CR among 14 patients with a prior three- to four-drug induction attempt, and one CR among four patients with a prior five- to seven-drug induction attempt (P = 0.14). Ten of 17 non-T-cell patients and two of nine T-cell patients achieved remission (P = 0.10). The median time required to achieve a complete remission from the initiation of treatment was 26 days (range, 14-72 days). This period was shorter in those who required one course compared with those who required two induction courses, i.e., 25 days median vs. 44 days median. Toxicity was significant and due mainly to marrow aplasia and infection; one patient had severe prolonged VM-26-induced hypotension. Of the 12 patients entering remission, two were removed for marrow transplant and one was removed due to parental request. In the remaining nine patients, median remission duration was only 2 months (range, 1-18 months). All nine patients relapsed in the marrow. Among the entire group of 26 patients, only one patient is alive and a long-term event-free survivor (after allogeneic marrow transplant). Due to the current use of more aggressive initial induction regimens and the extremely poor prognosis in children who fail to achieve initial remission, more intensive regimens of continuation therapy or alternative therapies, such as bone marrow transplant, should be considered.

    Title Site-specific Recombination of the Tal-1 Gene is a Common Occurrence in Human T Cell Leukemia.
    Date November 1990
    Journal The Embo Journal
    Excerpt

    The tal-1 gene is altered as a consequence of the t(1;14) (p32;q11) chromosome translocation observed in 3% of patients with T cell acute lymphoblastic leukemia (T-ALL). tal-1 encodes a helix-loop-helix (HLH) domain, a DNA binding and dimerization motif found in a number of proteins involved in cell growth and differentiation. We now report that an additional 25% of T-ALL patients bear tal-1 gene rearrangements that are not detected by karyotype analysis. These rearrangements result from a precise 90 kb deletion (designated tald) that arises independently in different patients by site-specific DNA recombination. Since the deletion junctions resemble the coding joints of assembled immunoglobulin genes, tald rearrangements are likely to be mediated by aberrant activity of the immunoglobulin recombinase. Moreover, t(1;14)(p32;q11) translocations and tald rearrangements disrupt the coding potential of tal-1 in an equivalent manner, and thereby generate a common genetic lesion shared by a significant proportion of T-ALL patients.

    Title The Tal Gene Undergoes Chromosome Translocation in T Cell Leukemia and Potentially Encodes a Helix-loop-helix Protein.
    Date March 1990
    Journal The Embo Journal
    Excerpt

    We have analyzed t(1;14)(p32;q11) chromosome translocations from two patients with T cell acute lymphocytic leukemia. The chromosome 1 breakpoints of these patients lie within a kilobasepair of each other, and thus define a genetic locus (designated tal) involved in T cell oncogenesis. Moreover, we have identified sequences within tal that potentially encode an amphipathic helix-loop-helix motif, a DNA-binding domain found in a variety of proteins that control cell growth and differentiation. The homology domain of tal is especially related to that of lyl-1, a gene on chromosome 19 that has also been implicated in T cell oncogenesis. Hence, tal and lyl-1 encode a distinct family of helix-loop-helix proteins involved in the malignant development of lymphocytes.

    Title Isolated Thrombocytopenia in Children with Acute Lymphoblastic Leukemia: a Rare Event in a Pediatric Oncology Group Study.
    Date December 1989
    Journal Pediatrics
    Excerpt

    To determine how many children with acute lymphoblastic leukemia were initially referred to a pediatric hematologist because of isolated significant thrombocytopenia ([platelet count less than 50,000/mm3] and an otherwise normal complete blood cell count and physical findings), a retrospective review of the Pediatric Oncology Group's charts was undertaken. Review of the records of 2239 children enrolled in the past two acute lymphoblastic leukemia protocols showed that none of these children had significant thrombocytopenia with no other hematologic or physical manifestations of acute lymphoblastic leukemia when they were first seen by the hematologist. The results suggest that routine bone marrow aspiration in the child with isolated thrombocytopenia may be unnecessary to rule out acute lymphocytic leukemia.

    Title The Chromosome Translocation (11;14)(p13;q11) Associated with T-cell Acute Lymphocytic Leukemia: an 11p13 Breakpoint Cluster Region.
    Date August 1989
    Journal Blood
    Excerpt

    The translocation (11;14)(p13;q11) was observed in karyotypes of leukemic cells from a 3-year-old boy with T-cell acute lymphocytic leukemia (T-ALL). Since this translocation is a recurrent marker of T-ALL, we undertook to investigate its mode of formation and role in leukemogenesis. The cytogenetic breakpoint on chromosome 14 occurs in 14q11, the same band wherein lies the T-cell receptor alpha/delta chain gene; and Southern hybridization analysis of peripheral blood and bone marrow DNA uncovered a tumor-specific rearrangement in the D delta-J delta region of this locus. DNA encompassing the rearrangement was isolated by molecular cloning, and further analysis revealed it to be the t(11;14)(p13;q11) junction. Nucleotide sequence determination of the junction indicates that the 14q11 breakpoint occurs immediately adjacent to the D delta 2 gene segment. Hence, the translocation arose as an aberrant rearrangement between the downstream recombination signal of D delta 2 and a pseudo recombination signal adjacent to the chromosome 11 breakpoint. Finally, comparison of the breakpoint in band 11p13 with those of other translocations (11;14)(p13;q11) identified a breakpoint cluster region of approximately 1.2 kilobase-pairs (kb), alterations of which may promote the development of T-ALL.

    Title Acute Lymphocytic Leukemia of Childhood: the Problem of Relapses.
    Date June 1989
    Journal Bone Marrow Transplantation
    Excerpt

    Developing improved therapy for the one-third or more of patients who can be expected to relapse after initial treatment for acute lymphoblastic leukemia would be less difficult if one could identify potential failures unequivocally at diagnosis. Subgroups of patients who should be considered candidates for highly experimental therapy include infants (less than 1 year of age), patients with the Philadelphia chromosome and perhaps patients with B-cell leukemia. The most important factor that determines the success of therapy after relapse is the length of the patient's initial remission. We recommend bone marrow transplantation for children whose first remission did not exceed 18 months. For all others, it appears that intensive chemotherapy affords as great a potential for cure as one could expect from transplantation. We favor intensive chemotherapy over transplantation in cases of late bone marrow relapse (greater than 18 months), because of the currently high peritransplantation mortality rate. It is not clear whether either modality will be adequate for patients relapsing on contemporary treatment programs.

    Title Tuberculous Mastoiditis.
    Date August 1988
    Journal The Journal of Laryngology and Otology
    Excerpt

    Two cases of aural tuberculosis in Caucasian adults are described. Stress is laid on the need to consider tuberculosis in cases of chronic otitis presenting unusual features. Lack of suspicion of tuberculosis frequently leads to long delays in diagnosis and subsequent needless disability.

    Title Intensive Retreatment of Childhood Acute Lymphoblastic Leukemia in First Bone Marrow Relapse. A Pediatric Oncology Group Study.
    Date August 1986
    Journal The New England Journal of Medicine
    Excerpt

    We devised a plan of intensive chemotherapy to address the problem of inadequate results of treatment in children with acute lymphoblastic leukemia in first bone marrow relapse. Immediately after remission was induced with four conventional drugs, a two-week intensification course of teniposide and cytarabine was given to eradicate subclinical leukemia. Patients in remission were then treated for two years with rapid rotation of pairs of drugs that were not cross-resistant and periodic courses of the same agents used to induce remission. A second complete remission was induced in 31 of the 39 patients in whom response to chemotherapy could be assessed. The probability of maintaining bone marrow remission in these patients for one year was 0.38 +/- 0.19 (95 percent confidence interval); the two-year probability was 0.29 +/- 0.17. Seven patients completed the treatment program, five of whom have been in continuous second complete remission 17 to 20 months after the cessation of therapy. Children whose initial bone marrow remission lasted less than 18 months had significantly poorer responses to retreatment than did those with a longer first remission (P = 0.004). Intensive chemotherapy, as described here, may save half of the children with acute lymphoblastic leukemia in whom bone marrow relapse occurs after a relatively long initial remission.

    Title Merkel Cell Tumour of the Skin.
    Date June 1986
    Journal The Journal of Laryngology and Otology
    Excerpt

    Two cases of a rare neuroendocrine skin tumour (Merkel cell carcinoma) are reported. The tumour affects mainly old women and men. It has a great tendency to metastasize to lymph nodes and distant sites. The primary treatment is surgical but radiotherapy has an important role to play. Merkel cell tumours are capable of producing NSE and have also been documented to secrete calcitonin and ACTH. Difficulties in histological diagnosis are frequent. The definitive diagnosis can only be made by electron microscopic examination.

    Title Light Fantastic.
    Date November 1984
    Journal Nursing Mirror
    Title The Mondini Defect in Turner's Syndrome. A Temporal Bone Report.
    Date September 1982
    Journal Clinical Otolaryngology and Allied Sciences
    Excerpt

    The histopathology of the right temporal bone of a 47 year old deaf woman with Turner's Syndrome (gonadal dysgenesis) is described. The appearances are of the Mondini deformity, the cochlea consisting of a single basal turn with a bulbous apical dilatation. The organ of Corti was absent. The remainder of the bony labyrinth save for the cochlear aqueduct was normal. The patient's death was due to a cerebral astrocytoma. Previous reports concerning the co-existence of gonadal dysgenesis, congenital deafness and non-gonadal neoplasia are discussed.

    Title Radical Resection for Cancer of the Hypopharynx and Cervical Oesophagus with Repair by Stomach Transposition.
    Date January 1982
    Journal The British Journal of Surgery
    Excerpt

    The results of 58 consecutive cases of pharyngolaryngo-oesophagectomy and pharyngogastric anastomosis are presented. The Grey Turner technique is used, but modified by adding bilateral chest drainage established by guidance from below the diaphragm and a jejunostomy. The immediate postoperative therapy management of hypocalcaemia with calcium gluconate and long term control with calciferol is described. An overall 3-year survival rate of 29 per cent has been obtained. Seven patients survived longer than 7 years, the longest living over 10 years. The authors conclude that, with careful management this technique is within the compass of competent surgeons with good facilities and should be the surgical treatment of choice for these difficult tumours.

    Title Giant Functioning Cervicomediastinal Parathyroid Cyst.
    Date October 1979
    Journal The Annals of Otology, Rhinology, and Laryngology
    Excerpt

    A rare case of a large cervicomediastinal parathyroid cyst associated with hypercalcemia and an elevation of serum parathyroid hormone is presented. The pathogenesis of such a large cyst is discussed, hemorrhage into an adenoma being the most likely cause. Clinical investigations which should be carried out for any cystic mass at the root of the neck should include a serum calcium, and if this is found to be elevated, the possibility of the cyst being of parathyroid origin should be considered. In view of the high concentration of parathyroid hormone found within the cyst, aspiration of the cyst contents for parathyroid hormone estimation might well prove a valuable test to confirm the diagnosis.

    Title Unexplained Infertility. A Reappraisal.
    Date January 1978
    Journal Obstetrics and Gynecology
    Excerpt

    During a 30-month period 229 couples were evaluated for infertility at the Naval Regional Medical Center, Oakland. Laparoscopy was used in all cases of otherwise unexplained infertility. The resulting laparoscopic examination of the female partner of 24 such couples demonstrated abnormal findings in 18 (75%). Of these 18 subjects, unsuspected endometriosis was found in 11 (46%) and peritubal adhesions in 7 (29%). Of the 229 couples evaluated, only 8 (3.5%) failed to show some etiologic factor associated with infertility. Thus, the previously reported 10 to 20% incidence of unexplained infertility is too high an estimate in view of the additional information made available through pelvic endoscopy.

    Title Research Opportunities at the Institute of Laryngology and Otology, London.
    Date March 1976
    Journal Canadian Journal of Otolaryngology. Journal Canadien D'otolaryngologie
    Excerpt

    Emphasis is placed on the need to encourage original research in our training programs. This implies an obligation to help trainees inexperienced in research to bridge the gap between theory and practice. Four examples of patterns of research at a postgraduate institute are presented. All are in areas in some way relevant to carcinoma of the larynx: a) the effect of experimental hypothermia on transplanted tumors in rats; b) isotope detection of deep vein thrombosis following head and neck surgery; c) stomal calibre after laryngectomy related to airflow, esophageal voice and cineradiographic appearances; d) a case-controlled study of the etiologic role of asbestos in laryngeal cancer. These studies are still in progress but some preliminary observations can be reported.

    Title Hypoparathyroidism Following Pharyngolaryngo-oesophagectomy.
    Date January 1976
    Journal Clinical Oncology
    Title Two Rare Tumours Involving the Infratemporal Fossa: Alveolar Soft Part Sarcoma and Haemangiopericytoma.
    Date August 1975
    Journal The Journal of Laryngology and Otology
    Title Tumours of the Nose and Sinuses. A Clinico-pathological Study.
    Date September 1972
    Journal The Journal of Laryngology and Otology
    Title Surgical Intervention As an Aid to Orthodontics.
    Date August 1969
    Journal Annals of the Australian College of Dental Surgeons
    Title Surgical Aspects of Porocephalosis.
    Date December 1967
    Journal Transactions of the Royal Society of Tropical Medicine and Hygiene

    Similar doctors nearby

    Dr. Linda Morgan

    Obstetrics & Gynecology
    Gainesville, FL

    Dr. Meera Saraswathinair

    Obstetrics & Gynecology
    14 years experience
    Gainesville, FL

    Dr. George Samraj

    Family Medicine
    28 years experience
    Gainesville, FL

    Dr. Ronald Freeman

    Anesthesiology
    23 years experience
    Gainesville, FL

    Dr. Rogers Bartley

    Obstetrics & Gynecology
    34 years experience
    Gainesville, FL

    Dr. Gabriel Gonzalez

    Obstetrics & Gynecology
    Gainesville, FL
    Search All Similar Doctors