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Pamela Brown

Publications and source records attributed to Pamela Brown.

15 recordsLinked to original sources
PubMed2006

Reciprocal cross talk between gonadotropin-releasing hormone (GnRH) and prostaglandin receptors regulates GnRH receptor expression and differential gonadotropin secretion.

The asynchronous secretion of gonadotrope LH and FSH under the control of GnRH is crucial for ovarian cyclicity but the underlying mechanism is not fully resolved. Because prostaglandins (PG) are autocrine regulators in many tissues, we determined whether they have this role in gonadotropes. We first demonstrated that GnRH stimulates PG synthesis by induction of cyclooxygenase-2, via the protein kinase C/c-Src/phosphatidylinositol 3'-kinase/MAPK pathway in the LbetaT2 gonadotrope cell line. We then demonstrated that PGF(2alpha) and PGI2, but not PGE2 inhibited GnRH receptor expression by inhibition of phosphoinositide turnover. PGF(2alpha), but not PGI2 or PGE2, reduced GnRH-induction of LHbeta gene expression, but not the alpha-gonadotropin subunit or the FSHbeta subunit genes. The prostanoid receptors EP1, EP2, FP, and IP were expressed in rat gonadotropes. Incubations of rat pituitaries with PGF(2alpha), but not PGI2 or PGE2, inhibited GnRH-induced LH secretion, whereas the cyclooxygenase inhibitor, indomethacin, stimulated GnRH-induced LH secretion. None of these treatments had any effect on GnRH-induced FSH secretion. The findings have thus elaborated a novel GnRH signaling pathway mediated by PGF(2alpha)-FP and PGI2-IP, which acts through an autocrine/paracrine modality to limit autoregulation of the GnRH receptor and differentially inhibit LH and FSH release. These findings provide a mechanism for asynchronous LH and FSH secretions and suggest the use of combination therapies of GnRH and prostanoid analogs to treat infertility, diseases with unbalanced LH and FSH secretion and in hormone-dependent diseases such as prostatic cancer.

Animals↗
PubMed2006

Fanconi anemia A is a nucleocytoplasmic shuttling molecule required for gonadotropin-releasing hormone (GnRH) transduction of the GnRH receptor.

GnRH binds its cognate G protein-coupled GnRH receptor (GnRHR) located on pituitary gonadotropes and drives expression of gonadotropin hormones. There are two gonadotropin hormones, comprised of a common alpha- and hormone-specific beta-subunit, which are required for gonadal function. Recently we identified that Fanconi anemia a (Fanca), a DNA damage repair gene, is differentially expressed within the LbetaT2 gonadotrope cell line in response to stimulation with GnRH. FANCA is mutated in more than 60% of cases of Fanconi anemia (FA), a rare genetically heterogeneous autosomal recessive disorder characterized by bone marrow failure, endocrine tissue cancer susceptibility, and infertility. Here we show that induction of FANCA protein is mediated by the GnRHR and that the protein constitutively adopts a nucleocytoplasmic intracellular distribution pattern. Using inhibitors to block nuclear import and export and a GnRHR antagonist, we demonstrated that GnRH induces nuclear accumulation of FANCA and green fluorescent protein (GFP)-FANCA before exporting back to the cytoplasm using the nuclear export receptor CRM1. Using FANCA point mutations that locate GFP-FANCA to the cytoplasm (H1110P) or functionally uncouple GFP-FANCA (Q1128E) from the wild-type nucleocytoplasmic distribution pattern, we demonstrated that wild-type FANCA was required for GnRH-induced activation of gonadotrope cell markers. Cotransfection of H1110P and Q1128E blocked GnRH activation of the alphaGsu and GnRHR but not the beta-subunit gene promoters. We conclude that nucleocytoplasmic shuttling of FANCA is required for GnRH transduction of the alphaGSU and GnRHR gene promoters and propose that FANCA functions as a GnRH-induced signal transducer.

Active Transport, Cell Nucleus↗
PubMed2005

Pediatric short bowel syndrome: redefining predictors of success.

OBJECTIVE: To determine predictors of survival and of weaning off parenteral nutrition (PN) in pediatric short bowel syndrome (SBS) patients. SUMMARY BACKGROUND DATA: Pediatric SBS carries extensive morbidity and high mortality, but factors believed to predict survival or weaning from PN have been based on limited studies. This study reviews outcomes of a large number of SBS infants and identifies predictors of success. METHODS: Multivariate Cox proportional hazards analysis was conducted on 80 pediatric SBS patients. Primary outcome was survival; secondary outcome was ability to wean off PN. Nonsignificant covariates were eliminated. P < 0.05 was considered significant. RESULTS: Over a mean of 5.1 years of follow-up, survival was 58 of 80 (72.5%) and 51 weaned off PN (63.8%). Cholestasis (conjugated bilirubin > or =2.5 mg/dL) was the strongest predictor of mortality (relative risk [RR] 22.7, P = 0.005). Although absolute small bowel length was only slightly predictive, percentage of normal bowel length (for a given infant's gestational age) was strongly predictive of mortality (if <10% of normal length, RR of death was 5.7, P = 0.003) and of weaning PN (if > or =10% of normal, RR of weaning PN was 11.8, P = 0.001). Presence of the ileocecal valve (ICV) also strongly predicted weaning PN (RR 3.9, P < 0.0005); however, ICV was not predictive of survival. CONCLUSIONS: Cholestasis and age-adjusted small bowel length are the major predictors of mortality in pediatric SBS. Age-adjusted small bowel length and ICV are the major predictors of weaning from PN. These data permit better prediction of outcomes of pediatric SBS, which may help to direct future management of these challenging patients.

Child Nutritional Physiological Phenomena↗
PubMed2004

Definition of the heterocyclic pharmacophore of bacterial methionyl tRNA synthetase inhibitors: potent antibacterially active non-quinolone analogues.

Potent inhibitors of bacterial methionyl tRNA synthetase (MRS) have previously been reported. Through SAR of the quinolone moiety, the right hand side pharmacophore for MRS inhibition has now been defined as an NH-C-NH functionality in the context of a bicyclic heteroaromatic system. Potent antibacterial fused-pyrimidone and fused-imidazole analogues have been obtained and enantioselective activity demonstrated. Compound 46 demonstrated very good antibacterial activity against panels of antibiotic-resistant staphylococci and enterococci.

Anti-Bacterial Agents↗
PubMed2004

Gonadotropin-releasing hormone regulates expression of the DNA damage repair gene, Fanconi anemia A, in pituitary gonadotroph cells.

Gonadal function is critically dependant on regulated secretion of the gonadotropin hormones from anterior pituitary gonadotroph cells. Gonadotropin biosynthesis and release is triggered by the binding of hypothalamic GnRH to GnRH receptor expressed on the gonadotroph cell surface. The repertoire of regulatory molecules involved in this process are still being defined. We used the mouse L beta T2 gonadotroph cell line, which expresses both gonadotropin hormones, as a model to investigate GnRH regulation of gene expression and differential display reverse transcription-polymerase chain reaction (RT-PCR) to identify and isolate hormonally induced changes. This approach identified Fanconi anemia a (Fanca), a gene implicated in DNA damage repair, as a differentially expressed transcript. Mutations in Fanca account for the majority of cases of Fanconi anemia (FA), a recessively inherited disease identified by congenital defects, bone marrow failure, infertility, and cancer susceptibility. We confirmed expression and hormonal regulation of Fanca mRNA by quantitative RT-PCR, which showed that GnRH induced a rapid, transient increase in Fanca mRNA. Fanca protein was also acutely upregulated after GnRH treatment of L beta T2 cells. In addition, Fanca gene expression was confined to mature pituitary gonadotrophs and adult mouse pituitary and was not expressed in the immature alpha T3-1 gonadotroph cell line. Thus, this study extends the expression profile of Fanca into a highly specialized endocrine cell and demonstrates hormonal regulation of expression of the Fanca locus. We suggest that this regulatory mechanism may have a crucial role in the GnRH-response mechanism of mature gonadotrophs and perhaps the etiology of FA.

Animals↗
PubMed2004

Rural cancer patients' perspectives on clinical trials: a qualitative study.

BACKGROUND: To increase the participation of low-income, rural cancer patients in clinical trials, a better understanding of patients' attitudes, knowledge, and beliefs is needed. METHODS: In-depth interviews were conducted with 17 cancer patients living in rural West Virginia. RESULTS: Patients had limited knowledge regarding clinical trials. Factors that might influence their decisions to participate include location of the treatment facility, physician recommendation, disease status, side effects of the treatment, and the perceived effectiveness of treatment. CONCLUSIONS: Rural, low-income cancer patients should be better informed about clinical trials, when applicable. Physician trust may enhance willingness to participate if clinical trials are close to home.

Adult↗
PubMed2003

Conformational restriction of methionyl tRNA synthetase inhibitors leading to analogues with potent inhibition and excellent gram-positive antibacterial activity.

Conformationally restricted analogues of the central linker unit of bacterial methionyl tRNA synthetase (MRS) inhibitors have been prepared. The (1S,2R)-cyclopentylmethyl moiety was identified as the preferred cyclic linker, with significant diastereo- and enantioselectivity of activity. Combination of this linker with an optimal substituted aryl right-hand side has resulted in a compound with exceptionally good antibacterial activity against staphylococci and enterococci, including antibiotic resistant strains.

Animals↗
PubMed2003

Optimisation of aryl substitution leading to potent methionyl tRNA synthetase inhibitors with excellent gram-positive antibacterial activity.

Optimisation of the left-hand-side aryl moiety of a file compound screening hit against Staphylococcus aureus methionyl tRNA synthetase led to the identification of a series of potent nanomolar inhibitors. The best compounds showed excellent antibacterial activity against staphylococcal and enterococcal pathogens, including strains resistant to clinical antibiotics.

Anti-Infective Agents↗
PubMed2003

Identification of a novel missense mutation that is as damaging to DAX-1 repressor function as a nonsense mutation.

Mutations in the DAX-1 (NROB1) gene result in X-linked congenital adrenal hypoplasia (AHC) and hypogonadotropic hypogonadism. The clinical presentation is usually as adrenal insufficiency in early life, with hypogonadotropic hypogonadism detected at the time of expected puberty. In this study we identified mutations in the DAX-1 gene of two patients with AHC. One mutation, Y399X, resulted in a premature stop codon and was associated with loss of Leydig cell responsiveness to human chorionic gonadotropin. The second, L297P, was a missense mutation, and human chorionic gonadotropin responsiveness was maintained. Kindred analysis established that the mutations had been inherited from the proband's mothers. The L297P has not been described previously and occurs within a highly conserved binding motif (LLXLXL). Transient transfection assays demonstrated that both mutations resulted in a severe loss of DAX-1 repressor activity. Immunohistochemical analysis of testicular tissue obtained from an affected sibling of the subject with the Y399X mutation, who had died with adrenal failure as a neonate, showed normal testicular morphology and expression of DAX-1, steroidogenic factor-1, and anti-Mullerian hormone protein. These data extend the clinical and molecular information on DAX-1 mutations, confirm normal testicular development at the neonatal stage, and illustrate variability in Leydig cell function.

Adrenal Glands↗
PubMed2002

Care management, dementia care and specialist mental health services: an evaluation.

OBJECTIVE: To evaluate a model of intensive case management for people with dementia based in a community-based mental health service for older people. METHOD: Quasi-experimental design. Individuals in one community team setting received case management and were compared with those in a similar team without such a service. Forty-three matched pairs were identified. Eligible older people and their carers were interviewed at uptake and again at 6 and 12 months. RESULTS: The impact of the scheme upon placement occurred in the second year at the end of which 51% of the experimental group remained at home compared with 33% of the comparison group. For the experimental group significant improvements in the social contacts of older people were noted; a decrease in the stress of their carers was observed, together with a reduction in their input to the care of the client; and there were significant improvements on ratings of overall need reduction, aspects of daily living and level of risk. Differences between the two groups based on service receipt showed higher costs for the experimental group. DISCUSSION: The benefits to older people and their carers confirms previous findings that the most effective case management interventions are those targeted on a highly specific client group. Issues which influence the cost-effectiveness of intensive case management are discussed. The benefits of locating this service within a specialist mental health team are explored in the context of current initiatives to promote greater service integration between health and social services.

Activities of Daily Living↗
PubMedDate not supplied

Obesity linked to some forms of cancer.

Researchers have found a consistent relationship between a number of diseases, including diabetes, heart disease, high blood pressure and stroke. Although study results related to cancer have been conflicting, with some showing an increased risk and others not showing such an association, obesity does appear to increase the risk of cancers of the breast, colon, prostate, endometrium, cervix, ovary, kidney and gallbladder. Studies have also found an increased risk for cancers of the liver, pancreas, rectum and esophagus. Although there are many theories about how obesity increases cancer risk, the exact mechanisms are not known. They may be different for different types of cancer. In addition, because obesity develops through a complex interaction of heredity and lifestyle factors, researchers may not be able to tell whether the obesity or something else led to the development of cancer.

Comorbidity↗