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The reproductive biology of the bat Pipistrellus hesperus was investigated histologically using animals obtained from nature at monthly intervals throughout the year. The female shows proestrous morphological changes in late summer and autumn, which continue until early spring. Insemination is probably effected several times during proestrous, since both sexes are intermittently active throughout this period (August--April). Permanent arousal from torpor and return to normal metabolism in the spring results in ovulation. Both ovaries are functional and both uterine horns may be utilized. P. hesperus is monestrous; two young per bat is usual. The male spermatogenic cycle is initiated in late June and the first sperm are available for ejaculation in September. Some sperm remain in the seminiferous tubules until early March. The epididymides also serve in sperm storage with the caput emptied by late February and the cauda in April. Leydig cells are largely nonsecretory from March through July, a few are secretory in August and most are secretory in September and October. Active cells gradually decline in number until few are secretory in late March. Accessory sex glands are functionally cyclic: they are small from April through August, hypertrophy in September, and gradually involute to the resting stage through March, to achieve total involution in April. The penis, similar in structure to that of other vespertilionids, is thought specialized to insure effective insemination.

A description is given of a technique devised to allow repeated endoscopic observations to be made of ovarian changes occurring during an oestrus cycle in the ewe. The use of a chronic peritoneal fistula is illustrated and the methods used to maintain its patency discussed. The technique was carried out in a small number of ewes and the ovarian changes occurring in an ovary of one of these ewes, over a 22 day period, are shown in photographic and diagrammatic form.

Plasma concentrations of estradiol-17beta, progesterone, LH and 13, 14-dihydro-15-keto-PGF2alpha were determined by radioimmunoassay on 2-hourly samples obtained around luteolysis and estrus in three dairy cows. The decline in progesterone occurred before the preestrous rise in estrogen and no pre-estrous peak of progesterone could be detected. The major activity of prostaglandin coincided, with declining progesterone levels and the active stage of estrogen secretion.

The acute effect of abdominal and vaginal hysterectomy on the ovarian production of estradiol-17-beta (E2) and progesterone (P) was studied in a group of patients undergoing hysterectomy for various gynecologic indications. Plasma levels of steroids as well as gonadotropins (FSH and LH) were measured by RIA. There was a significant but transient drop of plasma E2 during the follicular phase and of plasma E2 and P during the luteal phase, following hysterectomy. No significant variations in the steroid plasma levels were found in a control group of patients undergoing laparoscopy for diagnostic purposes. No changes were noted in either group in the plasma levels of gonadotropins. The changes seen appear to be related to the surgical manipulation in the ovarian region rather than to the type of hysterectomy performed or the stress of surgery.

The role of LH in the leuteotrophic process was examined by evaluating progesterone secretion in pregnant, lactating, and pregnant lactating rats, and the response of these rats to antisera against LH (LHAS) was observed. Ovarian venous progesterone concentration in lactating rats was elevated as litter size increased. Treatment with LHAS on day 8 postpartum of rats nursing 12 pups significantly decreased peripheral progesterone levels within 24 hr. Treatment with LHAS on days 8 and 9 of pregnancy terminated gestation in all normal pregnant animals by in similarly treated pregnant lactating rats gestation was maintained until day 14 in 4 of 10 rats. If the litter was removed from pregnant lactating dams at the time of initiation of LHAS treatment, pregnancy was interrupted in all 12 animals. Ovarian venous progesterone concentration was reduced by greater than 90% 24 hr after LHAS treatment on day 8 of normal pregnant rats and 20alpha-OH-P increased such that the concentration of total progestins remained constant. Ovarian venous progesterone concentration 24 hr after LHAS treatment of pregnant lactating rats was reduced by 50% in animals receiving daily estradiol treatment by LHAS had little effect in pregnant lactating animals which received a single injection of estradiol on day 4 postpartum. The level of 20alpha-OH-P in pregnant lactating animals was not affected by LHAS. The results of these studies demonstrate that in lactating rats nursing a large litter (12 pups) LH is part of the luteotrophic complex, and the data obtained from studies in pregnant lactating rats suggest that when pregnancy and lactation are superimposed the role of LH in the luteotrophic process on day 8 of gestation is diminished.

Two experiments were conducted to determine whether the increased serum LH which occurs within 12 hr after a luteolytic dose of PGF2alpha is dependent upon changes in progesterone or estradiol secretion. In the first experiment, exogenous progesterone abolished the increase in serum LH caused by a subcutaneous injection of 25 mg PGF2alpha in diestrous heifers, but not in ovariectomized heifers. In the second experiment, progesterone pessaries were removed at 6 hr after a subcutaneous injection of 25 mg PGF2alpha. LH remained at pre-PGF2alpha values while the pessaries were in place, but began to increase within 1 hr after they were removed. Blood estradiol also remained at pre-PGF2alpha values until the pessaries were removed, and began to increase at 2 hr after pessary removal. We conclude that the increase in serum LH within 12 hr after PGF2alpha treatment in diestrous cattle is dependent upon withdrawal of progesterone; it is not due to increased serum estradiol.

The content of estradiol receptor in cytosol and nuclear cell fractions of rat corpora lutea changed during pregnancy. The binding of (3-H)) estradiol to luteal cell cytosol was high early in pregnancy between days 3-11, decreased on days 12and15 and was low throughout of the remainder of pregnancy. In contrast, the binding of (3-H) estradiol to nuclear receptor, as measured by nuclear exchange assay, was low early in pregnancy, increased between days 10-15, remained high through day 18 and decreased on days 20 and 22. The administration in vivo of estradiol-17beta (40 mug) 1 hr prior to sacrifice stimulated an increase in nuclear receptor content early in pregnancy (days 3,6,8,10-12) but not later in pregnancy (15,18,20, and 22,). These results suggested that the estradiol binding component(s) present in rat luteal cell cytosol early in pregnancy represented available estradiol receptor capable of being translocated to the nucleus in the presence of sufficient estradiol. However, once available receptor has been saturated by endogenous hormone at midgestation, exogenous hormones hasno further effect on no nuclear receptor content. Importantly,loss of nuclear receptor content late in pregnancy appears to reflect decreased levels of total cellular receptor indicating that corpora lutea at the end of pregnancy have lost the primary mecchanism for responding to estrogens Thus, various stages of luteal cell differentiation are associated with changes in the intra-cellular distribution and total cellular content of estradiol receptor suggesting that luteal cell function may be regulated selectively and separately by hormone concentrations and hormone receptor availability.

Five guinea-pigs actively immunized against a prostaglandin F2alpha(PGF2alpha)-bovine serum albumin conjugate showed elongated oestrous cycles. During these, corpora lutea were maintained in a functional secretory state as indicated by plasma progesterone levels. The results are compatible with the view that the PGF2alpha antibodies neutralized the PGF2alpha released from the uterus and thus prevented its normal luteolytic effect. Similar patterns of progesterone secretion were observed in two hysterectomized animals and in two animals with intra-uterine implants of indomethacin.

Radioimmunoassay determination of plasma progesterone in the cow without chromatographic purification was developed. The level ranged from 0.6 ng/ml during estrus to 6.4 ng/ml during the luteal phase. The progesterone level declined rapidly 48 to 72 h before estrus beginning.

By use of lanthanum tracer and freeze-fracture procedures it was found that granulosa-lutein cells of the pregnant mouse and rat ovaries are connected by gap junctions and septate-like zones of contact. Lutein cell gap junctions enlarge and become partially internalized by the end of the first week of gestation. Expansion of the gap junction domain appears to be due initially to intercalation of particles along borders of small gap junctions devoid of smaller non-junctional particles. The number of gap junction lined processes appearing at the cell border increases concomitantly with hypertrophy of the lutein cell during the second week of pregnancy. Strands of particulate or grooved membrane emanate from the margin of larger gap junctions undergoing interiorization. Most large gap junctions are intimately associated with elements of the smooth endoplasmic reticulum. Spherical gap junctional profiles assume a deeper location in the lutein cell and may form concentric arrays by term while true surface gap junctions appear to fragment in the post-partum corpus luteum. The modifications observed are interpreted with respect to biogenesis of the gap junction and the hormonal control of lutein cell function.

Using the puberal rat and the PMS-treated rat as animal systems, ovarian events associated with follicular and luteal development have been characterized by measuring gonadotrophic hormone (LH, FSH and prolactin) and progesterone concentrations in peripheral serum; and selected enzymic (NAD-kinase:NAD-K and glucose-6-phosphate dehydrogenase: G6PD) activities and nucleotide (NAD, NADH, NADP, NADPH, ATP) concentrations in ovarian tissue. In the puberal rat, the period of follicular development was characterized by increased ovarian NAD-K SA, NAD and NADH concentrations and decreased ATP and NADP concentrations. The first pro-oestrus was characterized by greatly elevated LH, FSH, prolactin and progesterone concentrations, significant decreases in ovarian NAD-K SA, NAD, NADP and ATP concentrations, and an increase in NADPH concentrations. The development of new corpora lutea was associated with striking increases in ovarian NAD-K SA and G6PD SA. Increased activity of both enzymes exhibited a significant positive coefficient of correlation with the number of corpora lutea contained within the ovarian tissue. PMS (4 IU) stimulation of follicular activity resulted in events leading to the induction of an endogenous LH surge and ovulation. Associated with increased follicular activity was increased ovarian NAD-K SA. In contrast to the puberal rat, no rise in progesterone concentrations was associated with the LH surge or the formation of corpora lutea.

The hormonal factors associated with converting a corpus luteum of estrous cycle into a corpus luteum of pseudopregnancy were studied by measuring LH and FSH prolactin, estradiol and progesterone levels in decapitated rats during the 4-day estrous cycle and a comparable time of pseudopregnancy (lights on 0600-0800 hr.). During the estrous cycle, prolactin, LH and FSH remained low and unchanging except on the afternoon of proestrus, when typical proestrous surges were observed. In contrast, estradiol levels began to increase on D-1, from baseline values of 7 pg/ml to approximately 15-20 pg/ml. These levels were maintained until the afternoon of D-2 when estradiol further increased to reach peak levels of 40-50 pg/ml by 0900 hr on proestrus. Estradiol then declined in relation to the increase in LH secreation and had returned to baseline by estrus. Progesterone secretion by the corpora lutea of the cycle also increased on the afternoon of D-1 and reached a maximum value of 25-30 ng/ml early on the morning of D-2. At this time, a precipitious fall in progesterone occurred, returning to baseline values of 5-1- ng/ml by 0700 on D-2 signifying the regression of the corpora lutea of the cycle. Progesterone remained low thereafter until the afternoon of proestrus when levels increased in response to the proestrus when levels increased in response to the proestrous surge of LH. Following cervical stimulation at 1900 hr on proestrus, no differences were noted, with respect to the estrous cycle, in LH, FSH or estradiol secreation through the afternoon of D-2. Surprisingly, progesterone levels did not differ in the cycle and pseudopregnancy until the early morning of D-29 instead of progesterone levels falling to baseline as they had during the cycle, the corpora lutea of pseudopregnancy were rescused, progesterone increasing dramatically to reach levels of 45-50 ng/ml by 1700 hr on that same day. The only difference in hormone secretion that was noted which could account for this marked divergence in progesterone secretion was the pattern of prolactin secretion following cervical stimulation. In contrast to the low levels seen during the estrous cycle, biphasio surges of prolactin secretion occured each day, one being nocturnal (0100-0900 hr) and the other diurnal (1500-2100 hr). The rescue of the corpus luteum occured in association with the nocturnal surge on D-2. These results suggest that nocturnal surge on D-2, PROLACTIN IS THE MAJOR Luteotropic stimulus which transforms and estrous cycle into pseudopregnancy by prolonging progesterone secretion from the corpus luteum. Moreover, if LH is important for progesterone secretion, no changes were observed in the pattern of LH secretion which can account for the rescue of the corpus luteum.

17-beta-Estradiol, which is luteotropic in rabbits, was administered during pseudopregnancy via polydimethylsiloxane (Silastic) implants to determine the effects on serum progesterone concentrations. Implants which released estradiol at a rate of approximately 2 mug/day were place beneath the skin the day after sterile mating and ovulation (day 0). Blood (3 ml) was obtained from the marginal ear vein on days 3, 6, 9, 10, 11 and 12. Serum estradiol levels, determined by radioimmunoassay, were 2- to 3-fold higher in estradiol-treated rabbits (11.7 plus or minus 1.2 pg/ml) than in untreated pseudopregnant controls (5.9 plus or minus 1.4 pg/ml). Weights of corpora lutea in treated and control rabbits were not different at the conclusion of the experiment on day 12. Serum progesterone concentrations, also determined by radioimmunoassay, were not significantly different between treated and control animals. However, when estradiol implants were removed from other rabbits on day 10, a rapid decline in serum progesterone occurred, from 14.0 plus or minus 2.4 to 2.6 plus or minus 0.8 ng/ml 24 h later. By comparison, serum progesterone concentrations in rabbits with estradiol implants left in place and in untreated rabbits on day 12 were similar (similar to 12 ng/ml). The premature decline in serum progesterone was accompanied by a decrease in the wet weight of corpora lutea. Other experiments revealed: 1) a precipitous fall in serum estradiol to basal values within 2 h after estradiol implants were removed, preceding the decline in serum progesterone by approximately 6 to 10 h; 2) reduced levels of estradiol in ovarian venous blood, but elevated levels of estradiol in peripheral arterial blood of rabbits with estradiol impants. The inability to elevated estradiol to increase serum progesterone or weights of corpora litea suggests that the luteotropic effect is maximal when estradiol is present at physiological concentrations. Following the continuous administration of estradiol, ovarian secretion of estradiol appears diminished and the corpora lutea become dependent upon the exogenous estradiol for luteotropic support. Although the ovaries continue to release measureable quantities of estradiol, this is inmeasurable quantities of estradiol, this is insufficient to prevent regression of corpora lutea when exogenous estradiol is rapidly withdrawn from the circulation.

Injections of arachidonic acid directly into the corpora lutea of normal cattle at the 12th or 13th day of the estrous cycle resulted in (a) a decline in jugular vein plasma progesterone levels from an average of 6 ng/ml to 2.5 ng/ml (p smaller than0.05), (b) an immediate rise in PGF levels in ovarian venous plasma, and (c) a sharp rise in jugular vein plasma estrogen levels. Jugular plasma estrogen peaks were associated with each ovarian vein PGF Peak in each animal; jugular plasma LH levels did not change. These results show that the bovine ovary can convert arachidonic acid to PGF and that arachidonic acid administered directly into the corpus luteum results in partial regression of the corpus luteum.PGF appears to stimulate estrogen production by the ovary in the absence of measurable changes of plasma LH.