Day Of Vaginal Cornification Research Articles

Ultrastructure of decidualization in the pseudopregnant rat.

The ultrastructure of the endometrial stroma in rats bearing deciduomata was examined in detail on day 9 (day of vaginal cornification = day 0) of pseudopregnancy, together with the development of deciduomata from day 4 to day 8. Five major regions were recognizable on day 9. 1) In the basal zone, which contributes to endometrial regeneration following decidualization, stromal cells remained fibrocyte-like and were separated by wide bands of collagen fibrils. Capillaries were fenestrated and large. 2) The capsule surrounding the antimesometrial (region of the) deciduoma was composed of flattened cells, showing mitosis, which appeared to provide a source of appositional growth of the deciduoma. 3) The large, tightly packed, polyploid cells of the antimesometrial deciduoma showed morphological evidence of protein synthesis activity, an absence of smooth endoplasmic reticulum, and surface specializations suggestive of adhesion (adherens junctions), communication (gap junctions), and maintenance of an extensive surface area (lamellar processes). These cells came into very close apposition with capillary endothelial cells, which were seldom fenestrated, lacked any continuous basal lamina, and showed evidence of high metabolic activity. 4) The loosely packed mesometrial deciduoma contained a structurally supportive, "fixed" population of spiny cells and a "free" population of granulated cells and their putative precursors, together with a meshwork of large, sinusoidal capillaries whose endothelium was generally supported by a basal lamina. 5) The peripheral parts of the glycogenic area, which was structurally similar to the mesometrial deciduoma, contained many grossly enlarged intercellular spaces of undetermined function. The stromal cells at day 4, which give rise to all non-vascular elements except the granulated cells mentioned above, were structurally simple and fibrocyte-like. Only two distinct regions, subepithelial and deep, were recognizable. Capillaries at day 4 generally possessed a continuous endothelium, with a complete basal lamina and many pericytes. Between days 5 and 8, the stromal cells showed divergent forms of differentiation according to their position in the endometrium. Ultrastructural differentiation of the vasculature also showed divergence according to position, leading to the various types of capillaries seen at day 9. Regional variation, and high levels of structural organization, characterize the "programmed" decidual response in the pseudopregnant rat.

Effects of hypothalamic knife cuts on estrogenic control of feeding behavior

Changes in food intake (FI) and body weight (BWt) were measured in female rats prior to and following frontal (FC) and fronto-lateral (FLC) retrochiasmatic hypothalamic knife cuts produced by an extrudable Halasz-type knife. Vaginal cycles and changes in FI and BWt were monitored after surgery and following ovariectomy and estrogen treatment. Animals were also tested twice with a 30% calorically adulterated diet before and during daily estrogen treatment. FC produced predominantly cornified vaginal smears, and small polyfollicular ovaries, whereas FLC produced predominantly diestrous smears and atrophic gonads. FLC rats ate and weighed more than sham rats after brain surgery and ovariectomy attenuated group differences. A single injection of estrogen produced a comparable period of anorexia in all groups; but the effects on BWt were attenuated in the FLC rats. When presented with a diet adulterated 30% with Alphacel FLC animals showed a small but reliable regulatory deficit relative to sham rats. However, estrogen treatment increased group differences in response to the adulterated diet such that FC rats ate significantly less than the sham group, and FLC rats ate significantly less than FC animals. Finally, a multiple regression analysis of histological reconstructions of the brain surgeries accounted for 87% of the variation in vaginal cycle data for the FC animals such that the more anterior and medial the cut location, the greater the number of days of vaginal cornification. Cut locations were also related to FI during the dietary adulteration test, but only when tested with estrogen. This latter analysis accounted for 61% of the variation in experimental animals and revealed that more posterior and lateral cuts produced lower FI. These results indicate that retrochiasmatic knife cuts produce systematic changes in both ovarian function, and the neural control of feeding behavior. Thus, accurate assessment of hypothalamic lesion effects on feeding behavior require adequate control of the postlesion hormone environment.

Effects of adrenalectomy and constant light on the rat estrous cycle.

Adult female ARS/Sprague-Dawley rats were allowed to acclimatize to a a lighting schedule of 12L:12D (LD) for 5 weeks. At that time, half the animals were adrenalectomized, and all rats remained in LD for an additional 4 to 5 weeks. Subsequently, half of the control and half of the adrenalectomized rats were exposed to constant light (LL) for an additional 8 weeks, at which time all animals were sacificed. Operated rats with regenerated adrenal tissue, determined either by macroscopic examination or serum corticosterone assay (about 50% of the rats), were excluded from all data calculations. Acute disturbances of estrous cycle length were minor. The long-term effects revealed a significant increase in 5-day cycles among the adrenalectomized rats, although the majority of cycles recorded (80%) were still 4 days in length. None of the rats in LD showed spontaneous persistent estrus. Adrenalectomy did not affect the number of ova shed. When placed in LL, the adrenalectomized rats continued to cycle longer than the unoperated controls, but all rats showed persistent estrus (5 or more consecutive days of vaginal cornification) within 7--8 weeks. Adrenalectomized rats had significantly higher body weights than controls. Relative uterine weight was decreased in these animals in both lighting regimens but only reached statistical significance in LD. Ovarian weight, by contrast, was significantly increased among adrenalectomized rats in LD but was identical in both groups in LL. Adrenal weight of intact rats was not altered by LL. Since estrous cycles can continue for at least 6 months in the absence of the adrenal gland, the persistent estrus that occurs in LL is not merely due to the loss of a diurnal rhythm of corticosteroids. Indeed, when adrenalectomized rats are placed in LL, they continue to show estrous cycles longer than do intact rats. Adrenalectomy does appear to increase the length of the cycle in some animals, and the hormonal basis for this warrants further study.

Autonomic innervation and plasma estradiol-17beta and progesterone levels in rats with subcutaneous ovarian autografts.

Ovaries were removed from female rats and immediately autografted into a subcutaneous pouch in the flank in order to quantitate the relationship of graft re-innervation, steroid secretion and vaginal smear pattern. Animals were killed at thre time periods: three days after grafting, on the first day a cornified vaginal smear appeared and at the first metestrus. In addition, control animals were killed at metestrus. Plasma samples were obtained from all rats and analyzed for estradiol-17beta and progesterone concentration by radioimmunoassay. At the first day of vaginal cornification after grafting, plasma estradiol-17beta (45.8+/-4.0 pg/ml) was elevated in comparison to controls at metestrus (24.0+/-2.6 pg/ml), but plasma progesterone (21.5+/-4.0 ng/ml) was not different (30.6+/-1.7 ng/ml). Subsequently, at the first metestrus following grafting, plasma estradiol-17beta (23.0+/-3.5 pg/ml) was comparable to control values. In contrast, progesterone was decreased (17.5+/-1.9 ng/ml). A definite correlation was detected between the vaginal smear and plasma levels of steroid hormones in the castrated female rat with subcutaneous ovarian autographs Histochemical techniques were used to study the adrenergic and cholinergic innervations of grafts three days after grafting, at the first day of vaginal cornification, and at the first metestrus. No correlation was shown between density of adrenergic or cholinergic innervation and plasma levels of estradiol-17beta and progesterone or onset of a cycling vaginal smear.

Effects of pinealectomy and constant light on the estrous cycles of female rats.

Adult Charles River female rats were pinealectomized, sham-operated or left intact, and half of each group was placed in 12L:12D while the other half we exposed to constant light (LL). Daily vaginal smears permitted the calculation, at weekly intervals, of the percent of rats in each group in LL showing 5 or more consecutive days of vaginal cornification. After 11 weeks in LL, those rats were returned to LD for 6 weeks and then put back into LL until the termination of the experiment 3 weeks later.

Blood pregesterone levels in pseudopregnant rats: effects of partial removal of luteal tissue.

Progesterone levels in peripheral blood were measured throughout the pseudopregnancy period by a competitive protein-binding technique in individual female (R × U) F1 hybrid rats. Rats made pseudopregnant by sterile copulation or electrical stimulation of the uterine cervix showed similar changes in progesterone levels during pseudopregnancy. Blood progesterone levels increased gradually from 3 µg/100 ml on day 0 (=day of vaginal cornification) until a plateau of 10 µg/100 ml was reached on day 5 of pseudopregnancy. After day 8 a very gradual decreased was observed which resulted in a level of about 2 µg/100 ml on days 14–15. In order to investigate a possible compensatory reaction of corpora lutea (CL) during pseudopregnancy progesterone levels were measured after unilateral ovariectomy (ULO) at various days of pseudopregnancy and after cauterization of CL on days 1 and 2 of pseudopregnancy. After ULO on day 0 the maximal progesterone levels remained low (5 µg/100 ml vs 9 µg/100 ml in sham-operated anima...

Effect of progesterone and Nembutal in altering estrous running and vaginal periodicity in the female rat.

Hormonal regulation of activity wheel running and vaginal cycles was studied in female rats using agents and methods known to influence estrous receptivity, ovulation, and ovarian hormone levels. Injection of 0.5 mg/100 g bw progesterone on proestrus did not alter running or vaginal periodicity, whereas, when given on diestrus. it delayed both by one day. Progesterone dosages of 2 mg/100 g bw and 4 mg/100 g bw injected on diestrus increased mean delay of vaginal and activity estrus from approximately 1 to 2 and 2.5 days, respectively, and on metestrus, from 0 to 1 and 1.5 days, respectively. Peak running occurred on days of vaginal cornification. Induced delays in estrous activity were present only during the cycle in which progesterone was administered. Advancement of 1 day in estrous activity was obtained by injecting 0.5 mg/100 g bw progesterone on the day before proestrus in 5–day cyclic rats. Nembutal (3.3 mg/100 g bw) was found to delay both peak running and vaginal cornification by 1 day when injec...

A biological clock controlling the estrous cycle of the hamster.

Onset of estrus was observed every 4 days in the same hamsters exposed either to 24-hr light:dark cycles (LD 16:8) or to constant light (LL). Regression analysis indicated that only LL hamsters maintained estrous cycle periods significantly greater than 96 hr (p >0.05). These “circa-quadridian” (CQ) rhythms indicate that an endogenous timing mechanism capable of entrainment by 24-hr LD cycles (the Zeitgeber) controls the estrous cycle. Pituitary gonadotropin release and ovulation maintained constant time relationships to onset of estrus in both LD and LL. Pregnancy and pseudopregnancy reset the CQ rhythm to an earlier hr. However, spontaneous extensions from a 4- to 5-day estrous cycle followed by a day of vaginal cornification did not cause a phase shift in the CQ rhythm. This indicates that the endogenous timer functions with circadian rather than CQ rhythmicity. In LL, periods of the endogenous circadian timer ranged from 23.84 to 24.39 hr. Most values are significantly greater than 24 hr (p > 0.05). I...

Induction of polycystic ovarian disease in rats by continuous light. I. The reproductive cycle, organ weights, and histology of the ovaries

Changes in the estrous cycle, organ weights, and histology of the ovaries were investigated in a group of adult albino rats exposed to constant light. By the end of 6 weeks of constant light exposure, 56 of 60 rats (93.3 per cent) showed persistent vaginal estrus—as defined by the presence of at least 10 consecutive days of vaginal cornification. Although there was a progressive atrophy (decrease in weight) of the ovaries, the adrenals were initially hypertrophied (increase in weight), but they eventually became atrophied as the duration of constant light was advanced. The most consistent finding of the polycystic ovaries in the constant-light-treated rats was the presence of markedly distended and cystic tertiary follicles. On changing the light schedule from constant light to light-dark, not only the estrous cycles reappeared, but also the ovaries became normal in gross as well as microscopic appearance. On the basis of the present study and other studies, it is concluded that polycystic ovaries due to constant light exposure in rats represent a progressive multiglandular endocrinopathy.

Changes in sleep-wakefulness in female rats during circadian and estrous cycles

Continuous EEG records from chronically implanted cerebral electrodes have been made of sleep-wakefulness in 5 female rats throughout their 4-day or 5-day estrous cycles, under controlled lighting conditions with 14 h light and 10 h darkness per day. Percentages of alertness, slow wave sleep (SS) and paradoxical sleep (PS) in each 10-min period were punched on IBM cards and introduced to a computer system capable of plotting these percentages daily in each rat and averaging across animals for each time period on corresponding days of the estrous cycle. The results reveal rapid shifts from relative alertness to sleep after the lights come on in the morning. Highest levels of alertness generally occur during the early evening and PS during the afternoon, including the afternoon of proestrus. The day of vaginal cornification (‘estrus’) shows a high percentage of PS — after a night characterized by alertness and virtual absence of PS, i.e., the night of behavioral estrus and ovulation. The female rat, like the male, sleeps on the average about two-thirds of the daylight hours and only one-third of the dark period. Hormonal changes during the day of proestrus appear to increase alertness that night, compensated by an increase in sleep, especially PS, the following day.

Sleep and wakefulness in female rats under various hormonal and physiological conditions

Sleep cycles were studied by electroencephalographic (EEG) methods during the estrous cycle in female rats with chronic electrodes implanted in their brains. Results were expressed as percentages of EEG arousal (AR), spindle or slow-wave sleep (SS), and activated or paradoxical sleep (PS). Sleep cycles were not completely regular, but 40%–50% of the PS episodes were separated by AR-SS intervals of 10–20 minutes duration in all stages of the estrous cycle. During proestrus the rats showed maximal AR and minimal PS even though running activity had increased the previous night. Running activity was maximal on the night between proestrus and estrus, and the latter day (vaginal cornification) appeared to be a period of recovery, with increased amounts of both types of sleep. Results of ovariectomy and estrogen replacement suggest that the primary influence of hormone is upon activity, from which recovery by sleep is a secondary effect. This suggestion is supported by results of forced-running (sleep-deprivation) experiments in spayed rats in which recovery involved amounts of SS and PS similar to those encountered on the day of vaginal cornification in cyclic rats.

Pituitary concentration of luteinizing hormone in three types of "constant estrous" rats.

compare the mechanisms involved in the production of persistent vaginal cornification, pituitary concentrations of LH were measured in rats made “persistent estrus” with hypothalamic lesions, testosterone injection at 5 days of age, or exposure to constant light. Pituitary LH was measured in pooled saline extracts, using the ovarian ascorbic acid depletion method, in all groups following 35–40 days of vaginal cornification and also after 10–13 days of cornification in constant light-and testosterone-treated rats. Pituitaries collected from normal animals during each of the days of the estrous cycle were used for reference; since testosterone-treated rats were younger than the other experimental groups at autopsy, glands from normal estrous litter mates were used for comparison. In normals, LH concentration was 2.45 μg/rag at proestrus and 1.19 μg/mg at estrus. Progressive increases in LH were found during the 3 days of diestrus. While glands from rats with constant light- and testosterone-induced “persist...