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Biomedical subjects

R Schwartz

Publications and source records attributed to R Schwartz.

At least 397 records · Page 22Linked to original sources
PubMed1975

Effects of estrogen on gene expression in chick oviduct: nuclear receptor levels and initiation of transcription.

Estrogen (diethylstilbesterol) was administered in vivo to chicks for various time periods. Chromatin was then prepared from oviduct nuclei and assayed for its capacity to support initiation of RNA chain synthesis in vitro in the presence of saturating levels of Escherichia coli RNA polymerase (RNA nucleotidyltransferase; nucleosidetriphosphate:RNA nucleotidyltransferase; EC 2.7.7.6). These same nuclei were also assayed by a [3H]estradiol exchange assay for their endogenous receptor content. The number of available initiation sites for RNA synthesis on chromatin was shown to correlate with the endogenous levels of nuclear estrogen receptor. A decrease in the nuclear concentration of estrogen receptor molecules and the concentration of initiation sites for RNA synthesis occurred during withdrawal of estrogen from previously stimulated chicks. Both parameters declined with a similar half-life. When estrogen was readministered to withdrawn chicks, the number of initiation sites increased 2-fold as early as 30 min and approached a maximal level (3-fold) by 1 hr. During the same period of restimulation with estrogen, the number of estrogen receptor molecules bound to nuclei increased to a maximum at 20 min and then declined at 1 hr to a steady-state level 2-fold higher than the withdrawn chicks. Simultaneous measurements of RNA chain length and RNA chain propagation rate demonstrated that parameters remained relatively constant throughout estrogen withdrawal as well as secondary stimulation. The temporal correlation between changes in the levels of nuclear-bound estrogen receptor and the number of RNA chain initiation sites on chromatin prepared from these same nuclei strongly suggested that the hormone receptor complexes act on chromatin to mediate these changes in genetic transcriptional activity.

Animals↗
PubMed1975

Phenethylamine in normal urine: failure to verify high values.

The phenethylamine (PEA) level in daytime urine samples of 18 normal subjects was measured by an isotope dilution technique. Purification of PEA from other urinary substance, after the addition of 1-14C-PEA to urine samples, was achieved by the sequence: thin-layer chromatography (TLC), derivatization, TLC, and finally, gas chromatography (electron capture). The estimated mean daily output of PEA was 10.3 mug/day. A circadian rhythm was not evident on the basis of analyses of 24-hr urine collections from four normal subjects. Three acute schizophrenics had levels within the normal means.

Carbon Radioisotopes↗
PubMed1973

Gonadal effects of vasectomy and vasoligation.

During a 28-week study, vasectomy and vasoligation of immature male Wistar rats revealed that there was a significant decrease in urinary 17-ketosteroid in the vasectomized group at week 15; at week 28 there were significant decreases in the weights of the testes of the test groups, as compared to those receiving sham operations, with maximum alterations in the vasectomized rats. Small, soft discolored testes with cysts in the cauda epididymis and vas deferens regions occurred frequently in the test groups. The output of 17-ketosteroid in the urine and the findings in the testes indicate significant alterations in the morphology and function of the testes and suggest the need for caution and extensive investigations in man before recommending vasectomy as a simple, innocuous, "physiologic" means to ensure conception control.

17-Ketosteroids↗