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Biomedical subjects

J A Simon

Publications and source records attributed to J A Simon.

At least 19 recordsLinked to original sources
PubMed2004

Statin use and stroke outcomes in the Heart and Estrogen-Progestin Replacement Study (HERS).

The authors investigated the relationship between statin use and the risk of stroke in the Heart and Estrogen-Progestin Replacement Study (HERS). Despite large reductions in relative risk point estimates, statin use was not associated with differences in the risks of all fatal stroke (relative hazard [RH] 0.52, 95% CI 0.23 to 1.18, p = 0.12), fatal ischemic stroke (RH 0.51, 95% CI 0.18 to 1.45, p = 0.21), fatal hemorrhagic stroke (RH 0.18, 95% CI 0.02 to 1.46, p = 0.11), or TIA (RH 1.32, 95% CI 0.84 to 2.09, p = 0.23).

Aged↗
PubMed2001

Identification of a small molecule inhibitor of Sir2p.

Sir2p is an NAD(+)-dependent histone deacetylase required for chromatin-dependent silencing in yeast. In a cell-based screen for inhibitors of Sir2p, we identified a compound, splitomicin, that creates a conditional phenocopy of a sir2 deletion mutant in Saccharomyces cerevisiae. Cells grown in the presence of the drug have silencing defects at telomeres, silent mating-type loci, and the ribosomal DNA. In addition, whole genome microarray experiments show that splitomicin selectively inhibits Sir2p. In vitro, splitomicin inhibits NAD(+)-dependent histone deacetylase activity (HDA) of the Sir2 protein. Mutations in SIR2 that confer resistance to the drug map to the likely acetylated histone tail binding domain of the protein. By using splitomicin as a chemical genetic probe, we demonstrate that continuous HDA of Sir2p is required for maintaining a silenced state in nondividing cells.

Amino Acid Sequence↗
PubMed2001

Effect of estrogen plus progestin on risk for biliary tract surgery in postmenopausal women with coronary artery disease. The Heart and Estrogen/progestin Replacement Study.

BACKGROUND: Animal and observational epidemiologic studies have reported that estrogens may increase the risk for gallstones. No major clinical trials have examined the effect of estrogen plus progestin therapy in postmenopausal women on the risk for biliary tract surgery. OBJECTIVE: To determine the effect of estrogen plus progestin on the risk for biliary tract surgery in postmenopausal women with known coronary artery disease. DESIGN: Randomized, double-blind placebo-controlled trial of postmenopausal hormone therapy for coronary heart disease. SETTING: 20 U.S. clinical centers. PARTICIPANTS: 2253 postmenopausal women with a gallbladder, 44 to 79 years of age at baseline, in the Heart and Estrogen/progestin Replacement Study (HERS). INTERVENTION: Conjugated equine estrogens, 0.625 mg, plus medroxyprogesterone acetate, 2.5 mg, daily in one tablet or identical placebo. MEASUREMENTS: Documented biliary tract surgery. RESULTS: A total of 147 women (7%) were hospitalized for biliary tract surgery in HERS. Treatment with estrogen plus progestin resulted in a marginally significant 38% increase in the relative risk for biliary tract surgery (P = 0.05). A small absolute difference in risk suggested that for every 185 women treated with estrogen plus progestin, one additional woman had biliary tract surgery per year. After adjustment for baseline and in-study statin use, the association was attenuated further (P = 0.09). After adjustment for treatment assignment and other variables, increased body mass index, fibric acid use, and a history of nonsurgical gallbladder disease were associated with an increased risk for biliary tract surgery, whereas statin use was associated with a decreased risk (for each comparison, P < 0.05). CONCLUSION: Estrogen plus progestin therapy among postmenopausal women with known coronary disease resulted in a marginally significant increase in the risk for biliary tract surgery.

Adult↗
PubMed2001

Relation of ascorbic acid to bone mineral density and self-reported fractures among US adults.

Ascorbic acid is an essential nutrient involved in collagen formation, and its deficiency is associated with abnormal bone development. To examine the relation of ascorbic acid to bone mineral density and the prevalence of self-reported fractures, the authors analyzed data collected from 13,080 adults enrolled in the Third National Health and Nutrition Examination Survey (NHANES III) during 1988-1994. Because they identified three-way interactions among smoking, history of estrogen use, and dietary and serum ascorbic acid in postmenopausal women, they analyzed these relations stratified by smoking and estrogen use. Dietary ascorbic acid intake was independently associated with bone mineral density among premenopausal women (p = 0.002). Among men, serum ascorbic acid was associated in a nonlinear fashion with bone mineral density (p < 0.05), and dietary ascorbic acid intake was associated in a nonlinear fashion with self-reported fracture (p = 0.05). Among postmenopausal women without a history of smoking or estrogen use, serum ascorbic acid was unexpectedly associated with lower bone mineral density (p = 0.01). However, among postmenopausal women with a history of smoking and estrogen use, a standard deviation increase in serum ascorbic acid was associated with a 49% decrease in fracture prevalence (p = 0.001). Dietary and serum ascorbic acid measures were associated inconsistently with bone mineral density and self-reported fracture among adult participants in NHANES III.

Adult↗
PubMed2001

Interactions of Exo1p with components of MutLalpha in Saccharomyces cerevisiae.

Previously, we reported evidence suggesting that Saccharomyces cerevisiae MutLalpha, composed of Mlh1p and Pms1p, was a functional member of the gyrase b/Hsp90/MutL (GHL) dimeric ATPase superfamily characterized by highly conserved ATPase domains. Similar to other GHL ATPases, these putative ATPase domains of MutLalpha may be important for the recruitment and/or activation of downstream effectors. One downstream effector candidate is Exo1p, a 5'-3' double stranded DNA exonuclease that has previously been implicated in DNA mismatch repair (MMR). Here we report yeast two-hybrid results suggesting that Exo1p can interact physically with MutLalpha through the Mlh1p subunit. We also report epistasis analysis involving MutLalpha ATPase mutations combined with exo1Delta. One interpretation of our genetic results is that MutLalpha ATPase domains function to direct Exo1p and other functionally redundant exonucleases during MMR. Finally, our results show that much of the increase in spontaneous mutation observed in an exo1Delta strain is REV3-dependent, in turn suggesting that Exo1p is also involved in one or more MMR-independent mutation avoidance pathways.

Adaptor Proteins, Signal Transducing↗
PubMed2001

The predicted beta12-beta13 loop is important for inhibition of PP2Acalpha by the antitumor drug fostriecin.

The potential anticancer agent fostriecin (FOS) is a potent inhibitor of the protein Ser/Thr phosphatases PP2A and PP4 and a weaker inhibitor of PP1. Random mutagenesis and automated screening in yeast identified residues in human PP2Acalpha important for inhibitory FOS binding. A C269S substitution in the predicted beta12-beta13 loop decreased the FOS sensitivity of intact cells and increased the IC(50) of PP2Acalpha by 10-fold in vitro. Changing PP2Acalpha Cys-269 to phenylalanine, the equivalent residue in PP1, and the Y267G and G270D substitutions caused a similar effect. The results provide information relevant to the design of novel protein Ser/Thr phosphatase inhibitory drugs.

Alkenes↗
PubMed2001

Postmenopausal hormone therapy and risk of stroke: The Heart and Estrogen-progestin Replacement Study (HERS).

BACKGROUND: Observational studies have shown that postmenopausal hormone therapy may increase, decrease, or have no effect on the risk of stroke. To date, no clinical trial has examined this question. To investigate the relation between estrogen plus progestin therapy and risk of stroke among postmenopausal women, we analyzed data collected from the Heart & Estrogen-progestin Replacement Study (HERS), a secondary coronary heart disease prevention trial. METHODS AND RESULTS: Postmenopausal women (n=2763) were randomly assigned to take conjugated estrogen plus progestin or placebo. Primary outcomes for these analyses were stroke incidence and stroke death during a mean follow-up of 4.1 years. The number of women with strokes was compared with the number of women without strokes. A total of 149 women (5%) had 1 or more strokes, 85% of which were ischemic, resulting in 26 deaths. Hormone therapy was not significantly associated with risk of nonfatal stroke (relative hazard [RH] 1.18; 95% CI 0.83 to 1.66), fatal stroke (RH 1.61; 95% CI 0.73 to 3.55), or transient ischemic attack (RH 0.90; 95% CI 0.57 to 1.42). Independent predictors of stroke events included increasing age, hypertension, diabetes, current cigarette smoking, and atrial fibrillation. Black women were at increased risk compared with white women, and unexpectedly, body mass index was inversely associated with stroke risk. CONCLUSIONS: Hormone therapy with conjugated equine estrogen and progestin had no significant effect on the risk for stroke among postmenopausal women with coronary disease.

Aged↗
PubMed2001

Renal insufficiency and cardiovascular events in postmenopausal women with coronary heart disease.

OBJECTIVES: This study sought to determine the independent association of renal insufficiency with cardiovascular risk among women with known coronary heart disease (CHD). BACKGROUND: Although patients with end-stage renal disease and proteinuria are at high risk for cardiovascular events, little is known about the cardiovascular risk associated with moderate renal insufficiency. METHODS: The Heart and Estrogen/progestin Replacement Study (HERS) was a clinical trial among 2,763 women with coronary disease who were randomized to conjugated estrogen plus progestins or identical placebo and followed for a mean of 4.1 years. Women were categorized as having normal renal function (creatinine < 1.2 mg/dl; n = 2,012), mild renal insufficiency (1.2 mg/dl to 1.4 mg/dl; n = 567) and moderate renal insufficiency (>1.4 mg/dl; n = 182). We examined the independent association of renal function with incident cardiovascular events including CHD death, nonfatal myocardial infarction, hospitalization for unstable angina, stroke and transient ischemic attacks. RESULTS: Compared with women with normal renal function, those with mild and moderate renal insufficiency were older, more likely to be black, have a history of hypertension and diabetes and have higher serum levels of triglycerides and lipoprotein(a). After multivariate adjustment, both mild (relative hazards [RH] = 1.24; 95% confidence interval [CI]: 1.0 to 1.5) and moderate renal insufficiency (RH = 1.57; 95% CI: 1.2 to 2.1) were independently associated with increased risk for cardiovascular events compared with women with normal renal function. CONCLUSIONS: Renal insufficiency is an independent risk factor for cardiovascular events in postmenopausal women with known coronary artery disease. Renal function may add helpful information to CHD risk stratification.

Aged↗
PubMed2001

Surgically induced endometriosis attenuates accrual of bone mineral density in growing rats.

OBJECTIVE: A possible association of endometriosis with decreased bone mineral density in women has been proposed. It has been reported that cortical and trabecular bone mass of the distal portion of the radius is decreased in patients with endometriosis. The objective of this study was to investigate the relationship between endometriosis and bone mineral density with the use of a rat model. STUDY DESIGN: Cycling female Sprague-Dawley rats (180 days old) were randomly assigned to 1 of 2 groups. The treatment group (n = 16) underwent surgical induction of endometriosis. Female rats (n = 17) with surgically transplanted abdominal muscle served as control animals. Dual-energy x-ray absorptiometry measurements were obtained before surgery and after 90 days with a Lunar DPX-MD+ (GE Lunar, GE Medical Systems, Milwaukee, Wis) bone densitometer, with software standardized for small animal research. RESULTS: Experimental animals had grossly visible endometriotic disease at necropsy (90 days). The mean net change in total bone mineral density from baseline to 90 days in the control group was +0.019 +/- 0.002 g/cm2, whereas the mean net change in total bone mineral density for the experimental group was +0.013 +/- 0.002 g/cm2. The experimental group gained less bone than the control group (P = .02). CONCLUSION: The age-appropriate increase in bone mineral density known to occur in this animal model is attenuated by surgically induced endometriosis. This finding supports the idea that endometriosis might be associated with decreased bone mineral density.

Absorptiometry, Photon↗
PubMed2001

Relation of serum ascorbic acid to mortality among US adults.

PURPOSE: To examine the relation between serum ascorbic acid (SAA), a marker of dietary intake (including supplements), and cause-specific mortality. SUBJECTS AND METHODS: We analyzed data from a probability sample of 8,453 Americans age > or = 30 years at baseline enrolled in the Second National Health and Nutrition Examination Survey (NHANES II), who were followed for mortality endpoints. We calculated relative hazard ratios as measures of disease association comparing the mortality rates in three biologically relevant SAA categories. RESULTS: Participants with normal to high SAA levels had a marginally significant 21% to 25% decreased risk of fatal cardiovascular disease (CVD) (p for trend = 0.09) and a 25% to 29% decreased risk of all-cause mortality (p for trend <0.001) compared to participants with low levels. Because we determined that gender modified the association between SAA levels and cancer death, we analyzed these associations stratified by gender. Among men, normal to high SAA levels were associated with an approximately 30% decreased risk of cancer deaths, whereas such SAA levels were associated with an approximately two-fold increased risk of cancer deaths among women. This association among women persisted even after adjustment for baseline prevalent cancer and exclusion for early cancer death or exclusion for prevalent cancer. CONCLUSIONS: Low SAA levels were marginally associated with an increased risk of fatal CVD and significantly associated with an increased risk for all-cause mortality. Low SAA levels were also a risk factor for cancer death in men, but unexpectedly were associated with a decreased risk of cancer death in women. If the association between low SAA levels and all-cause mortality is causal, increasing the consumption of ascorbic acid, and thereby SAA levels, could decrease the risk of death among Americans with low ascorbic acid intakes.

Adult↗
PubMed2001

Long-range repression by multiple polycomb group (PcG) proteins targeted by fusion to a defined DNA-binding domain in Drosophila.

A tethering assay was developed to study the effects of Polycomb group (PcG) proteins on gene expression in vivo. This system employed the Su(Hw) DNA-binding domain (ZnF) to direct PcG proteins to transposons that carried the white and yellow reporter genes. These reporters constituted naive sensors of PcG effects, as bona fide PcG response elements (PREs) were absent from the constructs. To assess the effects of different genomic environments, reporter transposons integrated at nearly 40 chromosomal sites were analyzed. Three PcG fusion proteins, ZnF-PC, ZnF-SCM, and ZnF-ESC, were studied, since biochemical analyses place these PcG proteins in distinct complexes. Tethered ZnF-PcG proteins repressed white and yellow expression at the majority of sites tested, with each fusion protein displaying a characteristic degree of silencing. Repression by ZnF-PC was stronger than ZnF-SCM, which was stronger than ZnF-ESC, as judged by the percentage of insertion lines affected and the magnitude of the conferred repression. ZnF-PcG repression was more effective at centric and telomeric reporter insertion sites, as compared to euchromatic sites. ZnF-PcG proteins tethered as far as 3.0 kb away from the target promoter produced silencing, indicating that these effects were long range. Repression by ZnF-SCM required a protein interaction domain, the SPM domain, which suggests that this domain is not primarily used to direct SCM to chromosomal loci. This targeting system is useful for studying protein domains and mechanisms involved in PcG repression in vivo.

ATP-Binding Cassette Transporters↗
PubMed2001

Yeast as a model system for anticancer drug discovery.

Saccharomyces cerevisiae has been used extensively as a model for higher eukaryotes in the study of basic cellular processes. The high degree of conservation in terms of sequence similarity and function has made this organism useful in elucidating biological pathways, both yeast and human. Among these are pathways responsible for DNA damage repair and cell cycle control. This review presents an overview of opportunities for using yeast as a model system for anticancer drug discovery. It covers screens directed against specific cancer-related targets as well as contexts created by cancer-related alterations. The methodologies covered include pharmacological and genetic screens, as well as genome-wide approaches to drug target identification.

Journal Article↗
PubMed2001

Thymidine incorporation is highly predictive of colony formation and can be used for high-throughput screening.

The primary goal of anticancer chemotherapy is to kill cancer cells. Therefore, it is of critical importance that any assay that is used to determine the toxicity of a potential anticancer drug accurately measures viability. While colony formation is widely regarded as the most accurate measure of viability following drug treatment, it is laborious, time consuming, and difficult to carry out with non-adherent cells. For these reasons, it is not suitable for moderate- to high-throughput screening applications. We sought to identify a convenient and reliable assay that would accurately reproduce colony formation results and be amenable to high-throughput applications. Here, we describe a modification of the 3H-thymidine incorporation assay that meets these criteria. The assay can be carried out in 96-well plates with minimal handling of reagents and media. It can be performed with non-adherent and adherent cell lines. Most importantly, LC50 values obtained with this assay show excellent agreement with colony formation results. Taken together, these advantages make the modified 3H-thymidine incorporation assay well suited for high-throughput viability assays in anticancer drug discovery and development.

Animals↗
PubMed2001

Safety of estrogen/androgen regimens.

A persistent view of testosterone as the "male hormone" deprives many clinically androgen deficient women of effective treatment, although data from the 1960s to the present have indicted the importance of androgens to libido and feelings of well-being in women, providing relief from vasomotor symptoms that are unresponsive to estrogen alone. The safety of androgen replacement therapy is reviewed in this article. The risk of androgen toxicity is influenced by dosage and route of administration. Most products developed for use in men produce androgen levels that are too high for safety in women. Low-dose androgen replacement therapy as used in women, 1.25 mg esterified estrogen (EE) + 2.5 mg methyltestosterone (MT), or a half-strength preparation, 0.625 mg EE plus 1.25 mg MT, is unlikely to produce commonly described side effects: liver dysfunction, adverse lipid effects or virilization, as reviewed in this article. The potential for adverse endometrial effects if used by women with uteri unless a progestogen is used is also discussed. Low-dose estrogen/androgen therapy offers beneficial cardiovascular effects, primarily regarding lipids, atherogenesis and vasodilation. Androgens may act independently on the cardiovascular system and may be mediated by estrogen metabolites (aromatization products) or by secondary effects of androgens on estrogen bioavailability and metabolism (sex hormone binding globulin [SHBG] effects). They may improve vasomotor stability and reduce triglyceride (TG) levels. The marked reduction in TG in the estrogen/androgen (E/A) regimen is of note because women who experience oophorectomy have significantly increased levels of TG as compared with women who are naturally menopausal. Androgens offer positive effects on bone. Various types of studies--including cell culture, preclinical and observational--have attempted to document potential associations between androgens and breast cancer. Androgen administration has been shown to induce down-regulation of mammary epithelial proliferation and estrogen receptor expression, suggesting that E/A therapy might reduce the risk of breast cancer associated with ERT. However, studies of the relation of breast cancer to elevated circulating androgen levels have yielded inconsistent results. Testosterone may have an indirect effect on breast cancer risk because of its association with estrogen levels. Testosterone's effect on estrogen bioavailability may be of importance since an increase in serum testosterone levels could lead to a decrease in the percent of estradiol bound to SHBG. For the surgically menopausal woman faced with significant symptoms and health risks associated with estrogen withdrawal, E/A supplementation offers a reasonable course of treatment.

Androgens↗
PubMed2001

Perimenopausal women in estrogen vasomotor trials: contribution to placebo effect and efficacy outcome.

OBJECTIVE: To determine the difference, if any, in the placebo response when both perimenopausal and postmenopausal women are enrolled, compared with postmenopausal women alone, in a study assessing the efficacy of synthetic conjugated estrogen tablets on moderate-to-severe vasomotor symptoms (MSVS). METHODS: A total of 120 healthy women (72 active; 48 placebo) complaining of moderate-to-severe vasomotor symptoms were enrolled in a randomized, placebo-controlled, double-blind, multicenter clinical trial. In all, 109 patients completed treatment to week 12. Women were enrolled using minimal inclusion and exclusion criteria, and included perimenopausal women (n = 34; 0 to 6 months since last menses) as well as menopausal women (n = 79; > 12 months since last menses). RESULTS: Changes in MSVS in the intent-to-treat (ITT) population showed differences between the active and placebo treatments at weeks 4 (p < 0.022), 8 (p < 0.010) and 12 (p < 0.010). At week 12, the mean percentage reduction in MSVS was 81% for the active treatment group and 58% in the placebo treatment group. To examine the placebo response, the ITT population was broken down into groups defined by the time since their last menses. The perimenopausal group (0 to 6 months since last menses) demonstrated a consistently higher placebo response than that of the postmenopausal groups (> 12 months since last menses). CONCLUSIONS: Perimenopausal women contributed to a higher placebo response, compared with the rate of response previously reported in clinical studies of estrogen replacement in postmenopausal women. Including perimenopausal women in future vasomotor symptom trials will require study populations of sufficient size to maintain the statistical power to demonstrate a difference between therapeutic response to active or placebo treatment.

Administration, Oral↗
PubMed2000

Peripheral arterial disease in randomized trial of estrogen with progestin in women with coronary heart disease: the Heart and Estrogen/Progestin Replacement Study.

BACKGROUND: Postmenopausal estrogen use has been associated with reduced carotid atherosclerosis in observational studies, but this relationship has not been confirmed in a clinical trial. The impact of estrogen on atherosclerotic disease in other peripheral arteries is unknown. METHODS AND RESULTS: Postmenopausal women with coronary heart disease (CHD) and an intact uterus (n=2763) were randomly assigned to conjugated equine estrogens (0.625 mg) combined with medroxyprogesterone acetate (2.5 mg) daily or to placebo in a secondary CHD prevention trial. This analysis focuses on incident peripheral arterial procedures and deaths in the 2 treatment groups; peripheral vascular disease was a predefined secondary outcome. During a mean of 4.1 years of follow-up, 311 peripheral arterial events were reported in 213 women, an annual incidence of 2.9%. The number of women who had peripheral arterial events was 99 among those assigned to active estrogen/progestin and 114 among those assigned to placebo, a nonsignificant difference (relative hazard 0. 87, 95% CI 0.66 to 1.14). In the placebo group, hypertension and diabetes mellitus were independently associated with higher rates of peripheral arterial events, and plasma HDL cholesterol and body mass index were associated with lower rates of peripheral arterial events. In the estrogen/progestin group, current smoking and diabetes were independent predictors of peripheral arterial events. Incident peripheral arterial disease was not a significant predictor of coronary, cardiovascular, or total mortality. CONCLUSIONS: Treatment with oral conjugated estrogen plus medroxyprogesterone acetate was not associated with a significant reduction in incident peripheral arterial events in postmenopausal women with preexisting CHD.

Aged↗
PubMed2000

Transdermal testosterone treatment in women with impaired sexual function after oophorectomy.

BACKGROUND: The ovaries provide approximately half the circulating testosterone in premenopausal women. After bilateral oophorectomy, many women report impaired sexual functioning despite estrogen replacement. We evaluated the effects of transdermal testosterone in women who had impaired sexual function after surgically induced menopause. METHODS: Seventy-five women, 31 to 56 years old, who had undergone oophorectomy and hysterectomy received conjugated equine estrogens (at least 0.625 mg per day orally) and, in random order, placebo, 150 microg of testosterone, and 300 microg of testosterone per day transdermally for 12 weeks each. Outcome measures included scores on the Brief Index of Sexual Functioning for Women, the Psychological General Well-Being Index, and a sexual-function diary completed over the telephone. RESULTS: The mean (+/-SD) serum free testosterone concentration increased from 1.2+/-0.8 pg per milliliter (4.2+/-2.8 pmol per liter) during placebo treatment to 3.9+/-2.4 pg per milliliter (13.5+/-8.3 pmol per liter) and 5.9+/-4.8 pg per milliliter (20.5+/-16.6 pmol per liter) during treatment with 150 and 300 microg of testosterone per day, respectively (normal range, 1.3 to 6.8 pg per milliliter [4.5 to 23.6 pmol per liter]). Despite an appreciable placebo response, the higher testosterone dose resulted in further increases in scores for frequency of sexual activity and pleasure-orgasm in the Brief index of Sexual Functioning for Women (P=0.03 for both comparisons with placebo). At the higher dose the percentages of women who had sexual fantasies, masturbated, or engaged in sexual intercourse at least once a week increased two to three times from base line. The positive-well-being, depressed-mood, and composite scores of the Psychological General Well-Being Index also improved at the higher dose (P=0.04, P=0.03, and P=0.04, respectively, for the comparison with placebo), but the scores on the telephone-based diary did not increase significantly. CONCLUSIONS: In women who have undergone oophorectomy and hysterectomy, transdermal testosterone improves sexual function and psychological well-being.

Administration, Cutaneous↗