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Schiff, Isaac

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Schiff

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Isaac

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Schiff, Isaac
Author's Publications: search.filters.isAuthorOfPublication.cb019280-f82a-4163-a949-95806988b044

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    Effects of Postmenopausal Estrogen Replacement on the Concentrations and Metabolism of Plasma Lipoproteins
    (Massachusetts Medical Society, 1991-10-24) Walsh, Brian; Schiff, Isaac; Rosner, Bernard; Greenberg, Louise; Ravnikar, Veronica; Sacks, Frank
    BACKGROUND. Postmenopausal estrogen-replacement therapy may reduce the risk of cardiovascular disease, and this beneficial effect may be mediated in part by favorable changes in plasma lipid levels. However, the effects on plasma lipoprotein levels of postmenopausal estrogens in the low doses currently used have not been precisely quantified, and the mechanism of these effects is unknown. METHODS. We conducted two randomized, double-blind crossover studies in healthy postmenopausal women who had normal lipid values at base line. In study 1, 31 women received placebo and conjugated estrogens at two doses (0.625 mg and 1.25 mg per day), each treatment for three months. In study 2, nine women received placebo, oral micronized estradiol (2 mg per day), and transdermal estradiol (0.1 mg twice a week), each treatment for six weeks. The metabolism of very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) was measured by endogenously labeling their protein component, apolipoprotein B. RESULTS. In study 1, the conjugated estrogens at doses of 0.625 mg per day and 1.25 mg per day decreased the mean LDL cholesterol level by 15 percent (95 percent confidence interval, 11 to 19 percent; P<0.0001) and 19 percent (95 percent confidence interval, 15 to 23 percent; P<0.0001), respectively; increased the HDL cholesterol level by 16 percent (95 percent confidence interval, 12 to 20 percent; P<0.0001) and 18 percent (95 percent confidence interval, 14 to 22 percent; P<0.0001), respectively; and increased VLDL triglyceride levels by 24 percent (95 percent confidence interval, 8 to 40 percent; P<0.003) and 42 percent (95 percent confidence interval, 26 to 58 percent; P<0.0001), respectively. In study 2, oral estradiol increased the mean concentration of large VLDL apolipoprotein B by 30±10 percent (P = 0.05) by increasing its production rate by 82±18 percent (P<0.01). Most of this additional large VLDL was cleared directly from the circulation and was not converted to small VLDL or LDL. Oral estradiol reduced LDL cholesterol concentrations by 14±3 percent (P<0.005), because LDL catabolism increased by 36±7 percent (P<0.005). The oral estradiol increased the HDL cholesterol level by 15±2 percent (P<0.0001). Transdermal estradiol had no effect. CONCLUSIONS. The postmenopausal use of oral estrogens in low doses favorably alters LDL and HDL levels that may protect women against atherosclerosis, while minimizing potentially adverse effects on triglyceride levels. The decrease in LDL levels results from accelerated LDL catabolism; the increase in triglyceride levels results from increased production of large, triglyceride-rich VLDL.
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    Environmental Organochlorines and Semen Quality: Results of a Pilot Study
    (National Institute of Environmental Health Sciences, 2002) Hauser, Russ; Altshul, Larisa; Chen, Zuying; Ryan, Louise; Overstreet, James; Schiff, Isaac; Christiani, David
    There have been numerous studies that suggest that sperm concentrations (sperm counts) are declining in men. However, other studies suggest that sperm counts are not declining or may be increasing in some areas. Although there is disagreement on whether there is a downward temporal trend in sperm counts, the studies provide evidence that sperm counts vary by geographic location. It has been hypothesized that the geographic variation in sperm concentrations may be due to environmental exposures, lifestyle factors, or some unknown causes. To determine whether contemporary ambient levels of polychlorinated biphenyls (PCBs) and p,p'-DDE are associated with altered semen quantity and quality, we selected a study population without specific exposure to PCBs or p,p'-DDE. The present study presents the results from a pilot study on the relationship between serum PCBs and p,p'-DDE and semen quality in 29 subjects recruited from the Massachusetts General Hospital Andrology Laboratory. Of the 29 subjects, 3 had sperm concentrations < 20 million/mL, 7 had < 50% motile sperm, 9 had < 4% normal morphology, and 6 were below normal in more than one semen parameter. The 18 subjects with normal spermatozoa concentration, motility, and morphology were used as comparison subjects. The mean (SE) concentration of the sum of PCBs and p,p'-DDE was 242 ng/g lipids (34.0) and 354 ng/g lipids (120), respectively, for men with below normal motility as compared to 202 ng/g lipids (16.6) and 240 ng/g lipids (31.1), respectively, for the comparison subjects. The data showed general trends that were suggestive of an association between PCBs and p,p'-DDE and abnormal motility, as well as with sperm concentration and morphology. A full-scale study is currently in progress.
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    Impact of Seasonal Variation, Age and Smoking Status on Human Semen Parameters: The Massachusetts General Hospital Experience
    (BioMed Central, 2004) Chen, Zuying; Godfrey-Bailey, Linda; Schiff, Isaac; Hauser, Russ
    Background: To investigate the relationship of human semen parameters with season, age and smoking status. Methods: The present study used data from subjects recruited into an ongoing cross-sectional study on the relationship between environmental agents and semen characteristics. Our population consisted of 306 patients who presented to the Vincent Memorial Andrology Laboratory of Massachusetts General Hospital for semen evaluation. Sperm concentration and motility were measured with computer aided sperm analysis (CASA). Sperm morphology was scored using Tygerberg Kruger strict criteria. Regression analyses were used to investigate the relationships between semen parameters and season, age and smoking status, adjusting for abstinence interval. Results: Sperm concentration in the spring was significantly higher than in winter, fall and summer (p < 0.05). There was suggestive evidence of higher sperm motility and percent of sperm with normal morphology in the spring than in the other seasons. There were no statistically significant relationships between semen parameters and smoking status, though current smokers tended to have lower sperm concentration. We also did not find a statistically significant relationship between age and semen parameters. Conclusions: We found seasonal variations in sperm concentration and suggestive evidence of seasonal variation in sperm motility and percent sperm with normal morphology. Although smoking status was not a significant predictor of semen parameters, this may have been due to the small number of current smokers in the study.