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Notizen: Hamsters injected at 0900 on day 1 of the cycle (metestrus) with either 0, 5 or 15 IU pregnant mare's serum (PMS) were killed at 1500 of days 1 to 4 of the cycle and the ovaries prepared for light microscopy and for a quantitative evaluation of follicular development. In the untreated cyclic hamster, the maximal number of preantral follicles with eight or more layers of granulosa cells occurred between the afternoon of day 4 (proestrus) and day 1, coinciding with the highest blood levels of FSH and LH. It is concluded that the elevated preovulatory levels of gonadotropins not only induce the ovulation of the mature antral follicles but at the same time recruit the next set of follicles for development during the new cycle.By the afternoon of day 1, treatment with either 5 or 15 IU PMS recruited more follicles into large preantral and incipient antral stages than in the untreated hamsters. However, by day 2 the pattern of follicular distribution was similar between the 5 IU PMS and untreated group whereas considerably more antral follicles had differentiated in the animals given 15 IU PMS. The ability of 15 IU PMS to elicit superovulation therefore depends on the levels being initially high enough to mature more follicles at critical stages of their development; the prolonged biological half life of PMS then sustains these follicles throughout the cycle.

Notizen: Five-day-old mouse blastocysts were transferred into the oviducts of recipients on the second day of pregnancy. S35 methionine was then injected into the recipients and the blastocysts and native 2-celled eggs were recovered six hours later. Radioautographs reveal that the blastocysts incorporate S35 methionine while exposed to the tubal environment to the same degree that they would in the uterus. However, the 2-celled eggs in the same oviducal environment incorporate little or no methionine. It is therefore concluded that the difference in the incorporation of S35 methionine is due to maturational changes in the blastocyst rather than to a deficiency of the labelled amino acid in the tubal lumen.

Notizen: The surge in plasma luteinizing hormone (LH) in the proestrous hamster begins at 1430 (Turgeon and Greenwald, '72) and this is followed by a sharp increase in follicular and interstitially derived progesterone at 1500 (Norman and Greenwald, '71). The purpose of the present study was to relate various histologic events in the ovary of the preovulatory hamster to these physiological changes, dating from the LH increase between 1430 and 1500. The earliest maturational changes in the oocyte occurred at 1600 as the nuclear membrane began to disappear, correlating with an increase in the number of pycnotic nuclei in the surrounding cumulus cells and an abrupt reduction in mitotic activity in the membrana granulosa. It is possible that the latter event is related to increased progesterone secretion by the follicle at 1500. The most rapid increase in follicular diameter occurred between 2000 and 2200 - five to seven hours after the LH surge and was accompanied by a pronounced stromal edema especially of the medullary portion of the ovary. During this same time period, meiosis proceeded to the metaphase stage and the cumulus cells began to disperse to form the corona radiata. Of the eight hours required for the first meiotic division, four to six hours are spent in metaphase. The majority of animals (75%) ovulated by 0100 and all animals ovulated by 0200. Therefore, ovulation occurred 10 to 11 hours after the LH surge at 1500.

Notizen: Follicular activity in the ovary of the pregnant hamster is divided into two periods. During the first eight days (corresponding to the duration of pseudopregnancy) an average of 11 follicles per ovary from 277 to 553 μ are present. From day 10 to 16 of pregnancy, the ovary contains 22 follicles ranging from 277 to 600 μ and larger. The day after parturition, atresia destroys all large multilayered and vesicular follicles.Hamsters injected with human chorionic gonadotropin on day 4 of pregnancy ovulated ten ova, whereas similary treated day 12 animals ovulated 35 eggs. No cyclic follicular activity corresponding to the length of the estrous cycle occurred during gestation. On the contrary, a constant increment of small follicles took place throughout pregnancy.

Notizen: Various parameters of ovarian activity were determined for the intact or hypophysectomized pregnant mouse, as a baseline to establish the nature of luteotropic hormones in this species.Seventeen per cent of White Swiss mice with a vaginal plug were not pregnant at subsequent stages of gestation. The greatest number of failures occurred between days 12 and 15 of pregnancy, coinciding with the temporary absence of antral follicles and regressive changes in the vaginal epithelium. This suggests that there is a period of transient hormonal imbalance before full placental function is established, which is responsible at this time for the peak in embryonic mortality.Two periods of luteal growth were apparent between days 1 and 4 and 10 to 14 of pregnancy. The first histologic evidence of luteal regression occurred at day 16, correlating with renewed squamous cell proliferation of the vaginal mucosa.There were no significant differences in the number of ova shed on day 1 of pregnancy (11.0 ∓ 0.5 ova) and the subsequent number of embryonic swellings at any stage. Gestation in intact pregnant mice lasted 18 days (n = 2) or 19 days (n = 36). The number of young counted late on day 1 post partum (9.1 ± 0.5) was significantly less than the number of embryonic swellings as a result of maternal cannibalism.Hypophysectomy on day 1 of pregnancy led to rapid histologic degeneration of the corpus luteum. In this feature, the mouse resembled the hamster rather than the rat. Day 10 of pregnancy represented the earliest time at which, at least in some animals the pituitary could be removed and pregnancy continue. Following hypophysectomy from day 11 on, luteal activity, continuation of pregnancy, fetal and placental weight and vaginal histology were comparable to intact, pregnant mice. This is similar to the hypophysectomized rat in the latter half of pregnancy but differs from the situation in the hamster.On the basis of the present findings and results in the following paper, it appears likely that the mouse placenta, in addition to secreting a prolactin-like hormone, also produces other gonadotropins.

Notizen: The hamster ovary has been studied histochemically for various lipids. The granulosa cells of normal follicles contain lipid bodies of various sizes composed mainly of phospholipids. Some lipid bodies also contain triglycerides, cholesterol and its esters. The theca cells contain lipid granules consisting of phospholipids. At the onset of atresia, the granulosa stores lipids abundantly which consist of triglycerides, cholesterol and its esters and a slight amount of phospholipids. The theca of atretic follicles, also stores lipids consisting of phospholipids first, and then in sequence phospholipids and triglycerides and finally phospholipids, triglycerides, cholesterol and its esters. The theca hypertrophies and persists to form the interstitial gland whereas the granulosa cells, with their lipid droplets, regress and disappear. The interstitial gland in the hamster ovary occurs as patches of various sizes and these are derived from the theca of atretic preantral and antral follicles. Most of the lipid droplets of the interstitial gland, are mobilized within the preovulatory ovary. The replenishment of lipid droplets begins on day 1 of the cycle (metestrus). On day 2, the interstitial gland is again filled with lipid droplets which are rich in cholesterol and its esters, triglycerides and phospholipids.In ovaries treated with pregnant mare's serum (PMS) on each of the days of the estrous cycle, numerous large preantral follicles having 4-7 layered granulosa, are stimulated to ovulate. Normally such follicles become atretic, indicating that a lack of sufficient endogenous pituitary gonadotrophins prevents these follicles from maturing. Neutral lipids, especially cholesterol and its esters, could not be demonstrated in the normal granulosa in the PMS-treated ovaries. The follicles, which were atretic at the time of injections, were not affected by exogenous hormones. Human chorionic gonadotrophin (HCG) did not conspicuously affect the growth of follicles. Both PMS and HCG caused mobilization of lipid droplets from the interstitial gland.

Notizen: Ovarian follicular development was analyzed in intact and unilaterally ovariectomized cyclic rats. Holtzman rats, followed for three successive cycles, were classified as 4- or 5-day animals, with estrus designated as day 1. Intact 4- and 5-day animals were killed on each day of the estrous cycle and one ovary from each animal was saved for histology and examined for normal follicles larger than 352 μ. Cycling rats were unilaterally ovariectomized on day 1 and killed on each of the remaining days of the immediate estrous cycle and day 1 of the next cycle. The follicular population (normal follicles larger than 352 μ) was studied in the remaining ovary.During the estrous cycle of intact rats, there was a gradual increase in the number of follicles with a diameter of 518 to 571 μ and greater; however, the total number of follicles ranging in size from 352 to 571 μ and larger remained relatively constant. At day 5, in the 5-day cycling rat, the ovaries were depleted of follicles measuring from 395 to 570 μ.Following unilateral ovariectomy on day 1, there was a temporary decrease in the number of follicles larger than 448 μ. This agreed with the finding that animals semi-spayed on day 1 and injected with 20 I.U. human chorionic gonadotropin on day 2 (PM) did not ovulate, whereas intact animals ovulated an average of seven eggs after the same treatment. The remaining ovary of animals unilaterally ovariectomized on day 1 showed a significant increase by the next estrus in the number of follicles larger than 448 μ.The method of compensatory ovulation in the rat involved doubling the number of large follicles which ultimately matured during the estrous cycle. This resulted from increased proliferation of smaller follicles in the course of the cycle rather than from decreased follicular atresia.

Notizen: To determine the rate of follicular development in long-term hypophysectomized (H) hamsters, single IP injections of 3H-thymidine were given six days after H and autoradiographs were prepared from animals killed on days 6-15. Only follicles in stages 1 (2-3 layers of granulosa cells), 2 (4-5 layers) and 3 (6-7 layers) were present and there were fewer follicles than in intact, cyclic hamsters. The entire population of follicles in stages 1 and 2 was replaced every five to six days in hypophysectomized hamsters, whereas in cyclic hamsters, complete turnover takes eight days (Chiras and Greenwald, '77).Other groups of H hamsters were treated on days 4-6 with either estradiol benzoate (EB  -  10 μg), progesterone (P  -  1 mg) or EB and P and then given 3H-thymidine at 0900 hours of day 6 and killed one hour later. Steroid treatment affected early stages of follicular development: EB stimulated growth of these follicles; P alone had little effect; given with EB, P acted as an antagonist.Other H hamsters were treated with FSH (100 μg), LH (10 μg), FSH + LH, PMS (30 IU) or saline vehicle at 0900 hours six days post-hypophysectomy. They were injected with 3H-thymidine at 2100 hours on day 6 and killed one hour later. LH- and saline-treated animals had approximately the same number of follicles; however, there were no stage-3 follicles in the LH-treated group and the percentage of labelled follicles in stages 1 and 2 was significantly lower after LH treatment. FSH enhanced follicular development and thymidine uptake. Twice as many stage-3 follicles were seen in FSH-treated animals as controls; stage-4 follicles (〉8 layers of granulosa cells) were also encountered after FSH treatment. Labelling Index (LI) and Intensity (L. Int.) for the FSH-treated group were the highest of all treatments. LH antagonized some of the effects of FSH. PMS resulted in follicular growth similar to that achieved by FSH; however, PMS markedly depressed LI and L. Int., which was probably due to the LH-like component of PMS. These results demonstrate that the gonadotropins affect the development of small follicles. FSH stimulates growth; LH depresses follicular growth when administered alone and antagonizes some of the effects of FSH.Hamsters pretreated with EB or P on days 4-6 and then given a single, subcutaneous (SC) injection of FSH at 0900 hours on day 6, were treated with 3H-thymidine at 2100 hours on day 6 to assess the interaction of steroids and FSH. EB pretreatment caused the development of stage-5 follicles (early antral follicles) but did not increase thymidine uptake (measured by LI and L. Int.) in the small follicles above that attained by FSH alone. P pretreatment diminished thymidine uptake in small follicles, but did not reduce their number.These results demonstrate that in the hamster the population of small follicles, i.e., the often misnamed “pituitary-independent” follicles, can be influenced quantitatively and qualitatively by steroids and gonadotropins.

Notizen: Spayed ginea pigs injected daily for 6 to 10 days with 10, 50, 150 μg of estradiol cyclopentylpropionate (ECP) developed a mucified vaginal epithelium, similar to that observed during pregnancy or following treatment of ovariectomized animals with 5 mg progesterone and 1 μg of ECP.The epithelium did not mucify in spayed guinea pigs given 0.01 to 1.0 μg ECP daily for 10 or more days. Vaginal cornification developed only in animals treated with 1 μg ECP but the reaction was transitory and the keratinized cells were soon replaced by a stratified squamous epithelium.Spayed and adrenalectomized guinea pigs injected daily with 150 μg ECP developed a stratified squamous epithelium rather than a mucified type. However, the vaginal epithelium was mucified in ovariectomized-adrenalectomized guinea pigs receiving 150 μg ECP and corticoids or progesterone. This suggests that after treatment with large doses of estrogen the adrenal of the spayed guinea pig produces progestin-like hormones. These progestins interacting with exogenous estrogen are responsible for vaginal mucification.On the other hand, spayed rats maintained on 1 or 150 μg of ECP showed continuous vaginal cornification, which indicates that there are species differences in the ability of large doses of estrogen to influence the adrenal.