PubMed · 8681650
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S Romero, A Candela, J M Arriero. 1996. Keep testing the waters.. https://doi.org/10.1378/chest.110.1.299
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Estradiol (E2) has been shown to exert organizational, neurotrophic, and neuroprotective effects in the CNS. The present study assessed the specificity of the neuroprotective effects of estradiol for the potent 17 beta-isomer. SK-N-SH cells from a human neuroblastoma cell line, which we have shown to be estrogen-responsive, were cultured at low or high plating density. Then cells were exposed to 17 beta-E2 (0.2 or 2 nM), 17 alpha-E2 (0.2 or 2 nM), or cholesterol, testosterone, dihydrotestosterone, progesterone, or corticosterone (all at 2 nM). Cultures were insulted by serum deprivation, which caused a profound loss of cells. At 1 or 2 d of serum deprivation and steroid hormone replacement, the protection afforded cells by the steroid addition was assessed. Serum deprivation killed approximately 90% of cells cultured at both low and high plating density. Both 17 alpha- and 17 beta-E2 provided protection of SK-N-SH cells at either plating density. Further, a 10-fold molar excess of tamoxifen antagonized only approximately one-third of the neuroprotective effects of either isomer of estradiol, and a 100-fold excess of tamoxifen had no additional effect on the neuroprotection by 17 beta-E2. By contrast, none of the other steroids tested protected cells from the insult of serum deprivation. These results indicate that the neuroprotective effects of estrogens are not attributable to the general steroid structure, and the majority of the neuroprotection may not be mediated via a tamoxifenantagonized receptor mechanism.
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The selection process in the Multiple Risk Factor Intervention Trial caused relations between risk factors to differ between participants who were randomly assigned into the study and the screening population. Cigarette smoking, blood pressure, and serum cholesterol were moderately inversely related to each other in the randomly assigned population whereas these relations in the unselected population were direct and small in magnitude. This problem was addressed by covariate adjustment in analyses. The selection process also created an artificially high initial mean concentration of serum cholesterol; the mean plasma concentration at the second screening was 15 mg/dL lower than at the first screening. Most of this difference is attributable to regression to the mean. To account for this problem, emphasis was placed on change in plasma cholesterol over time, calculated from the second-screening measurement. Examination of the reliability of nutrition data based on one 24-h dietary recall showed that nutrient-biochemical relations are subject to considerable regression-dilution bias. The ratios of "within" to "between" components of variability were typically between one and four. Analyses in which multiple follow-up measures were averaged are emphasized in this monograph. Men assigned to the special intervention group reported considerable reductions in total energy intake, which was not consistent with observed weight loss. The most likely explanation for this is underreporting or underconsumption the day before the recall. To partially adjust for this, nutrient data are often expressed both in absolute units and as nutrient densities.