Serum testosterone levels were found to be significantly higher in male rats aged 83 days compared to rats aged 37 days, whereas serum luteinizing hormone (LH) levels in the same samples were not different. Serum testosterone levels in 90-day-old male rats were elevated by 30 min after the ip administration of 10 Âµg LH/100 g body wt and remained elevated through 150 min. In a similar experiment with 31-day-old males, testosterone levels were elevated at 90 min but not at 30 or 180 min, and with 37-day-old rats testosterone levels were elevated by 60 min and remained elevated through 150 min. One hundred minutes after receiving 1 Âµg LH/100 g body wt testosterone levels in 36-day-old rats were slightly elevated, 10 Âµg raised their testosterone levels to the normal adult male range, but 100 Âµg caused no further increase. Seventy-six-day-old males did not respond to 1 Âµg LH/100 g body wt but testosterone levels were greatly elevated by 10 Âµg/l00 g body wt. The serum testosterone level attained by the adults in response to 10 Âµg LH/100 g body wt (31.7 Â± 7.34 ng/ml) was significantly higher than the level attained by the immature rats (5.85 Â± 0.89 ng/ml) in response to the same LH dose. The significantly higher serum testosterone levels found in the adult rats receiving 10 Âµg LH/100 g body wt indicate that changes in the responsiveness of the testis to LH may be an important part of puberty in the male rat.
Peripheral plasma levels of progesterone, cortisol, and corticosterone were measured every other day throughout pregnancy in primiparous rabbits by competitive protein-binding techniques. Progesterone concentrations rose immediately after breeding and reached peak levels on Days 16-18, after which there was a decrease to prepartum levels by Day 32. Corticosterone remained constant for the first 24 days of gestation (7.3 ng/ml) with a slight rise to 17.0 ng/ml during the last few days of pregnancy. Cortisol levels (7.1 ng/ml) also remained constant for the first 24 days of gestation, although, in contrast to corticosterone, an abrupt increase began on Day 26 with peak levels (96.7 ng/ml) on Day 30. By Day 32, cortisol levels were similar to those in early pregnancy. Declining progesterone levels plus increased cortisol levels appear to be important preparturient changes in the rabbit.
The intravenous injection of copper salts into pregnant hamsters on the eighth day of gestation caused an increase in embryonic resorptions as well as the appearance of developmental malformations in surviving offspring. Malformations of the heart appeared to be a specific result of the toxicity of these copper compounds. Copper in a chelated form (copper citrate) was only slightly more embryocidal, but considerably more embryopathic than that in the uncomplexed form (copper sulfate). Additional studies on the permeability of the early hamster placenta during the critical stages of organogenesis (Day 8) revealed that the placenta was permeable to radioactive copper (citrate form), indicating that this metal may have a direct teratogenic effect upon the developing embryo.
The stages of the seminiferous epithelial cycle are recognizable in freshly isolated rat seminiferous tubules by a simple transillumination technique. By phase contrast microscopy on cells squeezed out from an isolated piece of tubule, the developmental stage of live germinal cells can be accurately determined. The kinetics of some organelles in early postmeiotic spermatids were followed by means of videotape recording and time-lapse cinemicrography. Pieces of tubules containing cells of corresponding developmental stages were prepared for electron microscopy. Immediately after the second meiotic division the chromatoid body and the Golgi apparatus are dispersed in the cytoplasm of the young spermatid as small dark bodies. But very soon, during stage 1 of spermiogenesis, these organelles assume the compacted form typical of the next stages. This morphogenesis involves the presence of vesicles of continuously and rather rapidly changing configuration. During stage 2, the chromatoid body rapidly moves on the nuclear envelope. It continuously sends and receives small dark particles and light vesicles and produces transient shallow depressions or occasionally deep indentations in the nuclear envelope. During its movements the chromatoid body also makes transient contacts with the Golgi apparatus. At stage 3 these movements slow down and practically cease at the stage 5. The rapid nonrandom movements of the chromatoid body and associated granules and vesicles suggest that this organelle participates from the early stages of spermiogenesis in spermatid maturation. The early activities of the chromatoid body, especially at stage I, may be heat labile.
The necessity of RNA synthesis within the ovarian follicle cells for gonadotropin-induced oocyte maturation was examined using isolated ovarian tissues of Xenopus laevis . Studies using [5- 3 H]uridine revealed that the radioactivity incorporated into the RNA of the theca epithelium was much higher than that incorporated into the RNA of the follicle cells and oocyte. No difference was observed in the quantity of radioactivity that was incorporated into the RNA of hormone-treated ovarian tissues as compared to that for untreated tissues. However, inhibitor studies indicated that actinomycin D and Î±-amanitin had a variable inhibitory effect on gonadotropin-induced maturation when they were applied to the ovarian follicles prior to the gonadotropin. On the contrary, no significant inhibitory effect on maturation was observed if these inhibitors were applied either simultaneously with or after the initiation of gonadotropin treatment, even though bulk RNA synthesis was always inhibited by approximately 85% with actinomycin D. Ethidium bromide, on the other hand, was always effective in inhibiting gonadotropin-induced maturation, although there was no detectable suppression in the incorporation of [ 3 H]uridine into bulk RNA. All three drugs had no inhibitory effect on progesterone-induced maturation. A working hypothesis has been proposed that can account for the variable inhibitory effect of actinomycin D and Î±-amanitin on gonadotropin-induced oocyte maturation.
Resting hemodynamic adjustments during pregnancy and early postpartum were studied in eight trained, unanesthetized Pygmy goats. Studies were made in triplicate at 3-wk intervals beginning prior to conception and continuing 6 wks postpartum. Nine nonpregnant animals were studied concurrently and at the same frequency. Extreme changes during pregnancy were compared with the mean postpartum values of the same animals. Those characteristics which changed significantly during pregnancy were: body weight increased 15%, peaking at term (30.1 Vs 26.1 kg; p 0.05) change during pregnancy were: mean pulmonary artery pressure, systemic arterial pulse pressure, hematocrit, hemoglobin concentration, red cell volume and blood volume per kilogram.
Blastocysts from ovariectomized mice treated with progesterone in oil or oil only were freeze-dried and weighed with a Lowry quartz fiber balance to determine whether or not significant changes in weight occur during the prolonged free living phase of delayed implantation. An increase in weight of blastocysts from progesterone and oil-treated animals was observed until day 10 of delayed implantation. Between day 10 and day 30, the weight of blastocysts from progesterone-treated animals changed little, while the weight of blastocysts from oil-treated animals increased steadily. These results demonstrate that delayed implanting mouse blastocysts accumulate more exogenous material than they consume and, thus, that depletion of stored nutrients does not appear to be a limiting factor in their survival. Furthermore, it is shown that progesterone influences the balance between uptake and utilization of exogenous materials by the embryos during delayed implantation.
The present study was undertaken to evaluate the effects of daily duration, intensity, and spectral composition of light exposure on the sexual maturation of female rats. Pregnant rats (Holtzman) delivered their young in a controlled environment with various illuminations of defined duration, intensity, and spectral composition. Pups were weaned at 22 days of age and separated by sex. Only females were used in the present study. They were checked for vaginal opening twice daily starting at 29 days of age. A group of 5-6 rats was sacrificed from each experimental condition 2-3 days prior to and after the expected date of vaginal opening. Results indicate that exposure to either 22 or 24 h of light/day significantly advanced vaginal opening when compared to 14-h/day exposure. No difference was obtained between animals in 6- and 14-h/day exposure. Light intensity was a significant variable at 14-h/day exposure, but not at 24 h/day. Animals exposed to 14 h of light at 100 lm/m 2 matured faster than those at 30 or 600 lm/m 2 , but not significantly earlier than those at 2400 lm/m 2 . Animals in blue light exhibited vaginal opening significantly earlier than in red light if exposure was provided for 14 h/day. In continuous exposure, red light was more stimulating. No significant differences between yellow and green light were detected either with 14- or 24-h/day exposure, except for a small population of rats in continuous green light in which vaginal opening was significantly delayed. A significant seasonal variation was also detected in animals raised in white fluorescent light of 14-h/day exposure. Rats raised in the summer months showed vaginal opening significantly earlier than those in the winter. Examination of ovarian and uterine weights prior to vaginal opening revealed no significant differences with increased daily duration but equal intensity of illumination. Increasing intensity between 30 and 600 lm/m 2 , on the other hand, produced significantly heavier weights prior to vaginal opening. Uterine weights were heaviest at 100 lm/m 2 . Animals exposed to blue light had significantly heavier ovarian weights before vaginal opening than those in red light, regardless of the duration of exposure. No other differences were detected with various spectral compositions. After vaginal opening, ovarian weights were greater in 22-h/day light exposure than in either 6 or 14 h/day. However, one of two experiments revealed significantly smaller ovaries in rats kept in continuous light than in rats kept in 14 h of daily light exposure. No differences in uterine weights were noted. No differences in ovarian weights were observed following vaginal opening in animals raised in various light intensities. A significant difference in uterine weights was detected between animals raised in 30 and 100 lm/m 2 of light intensity at continuous exposure. Differences in spectral composition did not result in significant differences in either ovarian or uterine weights following vaginal opening. Results are interpreted to indicate, first, that variations in the daily duration, intensity, and spectral composition of light exposure can significantly influence the age at which vaginal opening occurs and, therefore, suggest that light can play a significant role in the timing of sexual maturation and should be carefully controlled in studying the role of photoperiods in reproductive function. Secondly, the present data suggest that while in long exposures, intensity may not play a significant role, in 14-h/day-exposure intensity can be a highly significant factor. Finally, our data give no evidence for a chronic stimulation of gonadotropin release as a result of increased photoperiods, but, in the case of increased light intensity, early maturation may have resulted from increased FSH and/or LH release, as evidenced by increased ovarian and uterine weights.
Mitochondria, dense bodies, lysosomes, lipid, and rough endoplasmic reticulum (RER) were quantitated in the endometrial stromal cells of ewes after either ovariectomy alone or ovariectomy and treatment with estradiol or progesterone. The most striking change in the endometrial stromal cell was seen in the RER. After ovariectomy, the RER was scant and poorly developed. In ewes treated with estradiol, the RER was abundant and extensively dilated. In progesterone-treated ewes, the RER was less well-developed than in estradiol-treated ewes but somewhat more abundant than in ovariectomized control ewes. The increased RER in estradiol-treated ewes probably reflects increased protein synthesis by the endometrial stromal cells.
The ability of prolactin and progesterone to inhibit ovulation was utilized to investigate the relationship between ovulation and luteolysis. The first estrus and ovulation were synchronized in 27-day-old, prepubertal rats by the subcutaneous (sc) administration of 4 IU of pregnant mane serum gonadotropin (PMS). Pseudopregnancy was induced by the sc administration of prolactin (100 Âµg, NIH-P-B 2 administered twice daily) beginning on the day of ovulation (Day 0) and maintained through Day 2. If prolactin therapy was discontinued on Day 2, a second injection of PMS on Day 3 resulted in ovulation accompanied by involution of the original corpora lutea. Continuous prolactin treatment from Day 0 through Day 6 not only prevented ovulation as a result of PMS administration on Day 3, but prevented luteolysis as well. Progesterone (8 mg/day), if administered on Days 3 through 6, inhibited ovulation in response to PMS administered on Day 3. It did not, however, prevent the luteolysis as a result of the ovulatory stimulus provided by PMS. Progesterone, in the absence of PMS, did not affect luteal weight. The dissociation of luteolysis from ovulation demonstrated that actual ovulation was not a requirement for luteolysis to occur, but leaves open the possibility that an ovulatory stimulus may be an effective luteolytic stimulus.