The effect of an LH pulse on 3H-thymidine incorporation into cultured ovaries of metestrous rats

Summary The effect of an LH pulse on the rate at which ³H-thymidine is incorporated into cultured ovaries of metestrous rats was studied. In comparison to ovaries cultured with tonic LH, an LH pulse (1) rescued follicles from atresia, (2) induced thecal cell proliferation, and (3) increased the rate at which granulosa cells enter mitosis. It is concluded that LH pulses increase follicular growth by first triggering thecal cell proliferation and then inducing mitotic divisions within the granulosa cells of both atretic and non-atretic follicles.     

Pattern of follicular development during the estrous cycle of aged rats

Summary The pattern of follicular development during the estrous cycles of aged rats was examined and compared with that of mature rats. In both, preovulatory follicles are derived from a select group of small pre-Graafian follicles which begin to develop at estrus and reach the preovulatory size by the morning of proestrus, but the rate of growth, as judged by an increase in the percentage of granulosa cells incorporating ³H-thymidine, is accelerated in the follicles of aged rats. A second mechanism, which accounts for preovulatory follicles in aged rats, involves the rescue from atresia of pre-Graafian and preovulatory follicles. The existence of this mechanism is supported by the observation that at metestrus in aged rats virtually all follicles, regardless of their state of atresia, possess a high percentage of granulosa cells incorporating ³H-thymidine, indicating that the follicles are growing rapidly. However, some of these rapidly growing follicles show signs of atresia such as pyknotic nuclei within their granulosa cell layers. Since follicles in the initial stage of atresia contain defective oocytes (Peluso et al. 1979b), their rescue and development into preovulatory follicles would result in the ovulation of defective oocytes, a fact which accounts in part of the lower fertility in these older animals.     

Development of gonadotrophin-binding sites in the immature rat ovary.

There was a temporal relationship between ovarian development and the sites to which 125I-labelled gonadotrophins became bound. Labelled human LH and FSH bound uniformly to 5- and 15-day-old ovaries. At 21 days, heavy FSH and light LH binding was observed over the granulosa cells increased at Day 33 and again at Day 38. Quantitative determination by gamma-ray spectrophotometry of binding to ovarian sections showed that LH binding gradually increased with advancing age, but FSH binding remained relatively constant between Days 5 and 33 with a significant increase between Days 33 and 38.     

Structure of a protein catalyzing the formation of 11cis-retinal in the visual cycle of invertebrate eyes

A pigment made up of a protein able to bind retinal as well as retinol is described. The molecule consists of a dimer with a molecular weight of 50,000 which binds one molecule of retinal. The binding site for retinal is a Schiff base buried in the interior of the protein. Retinol is probably bound to the protein in the same site as for retinal, although not covalently, as suggested by the absorbance spectra. The protein, extracted from honeybee retina, is involved in visual pigment metabolism (1), and its structure may elucidate the mechanism of the stereospecific photoisomerization of alltrans-retinal to 11-cis-retinal.     

Gonadotropin binding and testicular function in old rats.

Serum testosterone levels, testicular LH binding and the spermatogenic cycle were analyzed in rats 4 and 22 mo of age. With age, serum testosterone levels decreased from 3.2 to 0.63 ng/ml serum. There was no age related decline in testicular LH binding or changes in the spermatogenic cycle.     

Sequential changes associated with the degeneration of preovulatory rat follicles.

In 26-day-old rats, follicles capable of ovulation were present 48 h after PMSG injection and they degenerated if not exposed to an ovulating dose of HCG. In such follicles 125I-labelled LH bound to the thecal and granulosa cells. By 60 h after PMSG, LH binding to the granulosa cells was reduced by 46% although these follicles retained their ability to ovulate. LH binding to the granulosa cells was lost in most follicles by 72 h and ovulation could not be induced. The thecal cells still possessed LH binding sites at 72 h after PMSG. HCG stimulation of these follicles resulted in disruption of the granulosa and the invasion of blood cells into the antrum.     

Methodology of laboratory measurements in prospective studies on gene-environment interactions: the experience of GenAir

Several large prospective investigations are under way or are planned in different parts of the world, aiming at the investigation of gene-environment interactions for chronic diseases. Technical, practical and ethical issues are raised by such large investigations. Here we describe how such issues were approached within a case-control study nested in EPIC, a large European cohort, and the kind of validation studies that have been set up. The GenAir investigation aimed at measuring the effects of air pollution and environmental tobacco smoke on human health in EPIC with a nested design and with biological measures. Validation studies included (a) comparisons between cotinine measurements, hemoglobin adducts and questionnaire data; (b) an analysis of the determinants of DNA adduct concentration; (c) comparison among different genotyping methods; (d) an analysis of the determinants of plasma DNA amounts. We also describe how the ethical issues were dealt with in our investigation.     

Reliability of bulky DNA adducts measurement by the nuclease P1 32P-post-labelling technique.

The aim was to assess the reliability of bulky DNA adducts measurement by means of the 32P-post-labelling assay. The research design consisted of an intramethod reliability study. Buffy coats from 41 subjects were used to obtain two aliquots of 1-5 microg DNA for each subject; bulky DNA adducts were measured using the nuclease P1 32P-post-labelling technique. The reliability of the measurement was assessed by means of the intraclass correlation coefficient (ICC), the distribution of the differences between the two measurements and the limits of agreement. The estimated ICC was 0.977, with a 95% confidence interval between 0.921 and 0.977. The limits of agreement were +/- 0.44 (DNA adducts per 10(8) nucleotides). Only three subjects had differences lying out of such limits. Bulky DNA adduct levels measured by the 32P-post-labelling technique showed good reliability. Only one measurement is needed to use DNA adducts as a biomarker of exposure and, possibly, cancer risk. Besides, as a validation analysis, 32P-post-labelling measurements can be repeated in only 20-30% of samples.