In vivo experiments were conducted to determine if elevated plasma glucocorticoid concentrations would suppress intrafollicular prostaglandin F2$ alpha$ (PGF2$ alpha$) synthesis and, thereby, inhibit ovulation in the pig. Following ACTH administration, PGF2$ alpha$ concentrations in FF tended to be lower than in controls. Injections of betamethasone partially suppressed the preovulatory rise of PGF2$ alpha$ in FF at 40h, although the effect was less marked than that produced by indomethacin. While no ovulations occurred in the indomethacin-treated group at any time, betamethasone resulted in a lower number of ovulated follicles at 44h than in the control animals. Progesterone concentrations were unaffected by the treatments. / In vitro studies were conducted with a spontaneously established cell line developed through continuous culturing of primary granulosa cells collected from prepuberal gilts six hours after they had received PMSG. Characterization of these cells revealed that aromatase and steroidogenesis were functional but gonadotropin receptors were not present. When extracellular PGF2$ alpha$ levels were measured, dexamethasone was able to significantly suppress PGF$ sb{2 alpha}$ concentrations, but not as effectively as with indomethacin. (Abstract shortened by UMI.)

Experiments were conducted with littermate gilts maintained in stainless steel metabolism cages within environmentally controlled rooms and consuming a corn-soybean meal based diet. The objectives of these studies were to investigate the impact of different dietary levels of manganese (Mn) and/or stage of the reproductive cycle on mineral metabolism and more specifically Mn metabolism in primigravid gilts and rats. Nutritional status was assessed using conventional balance studies, the analyses of physiological fluids (urine, plasma, colostrum, milk), tissues of the dam and offspring, and by a radioisotope dilution-balance technique. Trace element retention in the first-litter gilt was not significantly altered by dietary Mn restriction (11 $ mu$g/g DM) or by different stages of the reproductive cycle. In contrast, among the macro elements, phosphorus and perhaps calcium retention were improved in late gestation, whereas magnesium and nitrogen retention were unchanged. The weight of the litter at birth from dams consuming the low Mn (LMn) diet was significantly less than high Mn (HMn) gilts (96 $ mu$g/g DM). The Mn concentration in the liver and kidney of HMn gilts were significantly higher than in LMn gilts at the end of lactation. Likewise, the bones from HMn piglets contained higher concentrations of Mn at birth, and the liver and kidney concentrations were greater at weaning. Dietary Mn intake did not influence the rate of $ sp{54}$Mn excretion by the gilt during late gestation. The endogenous fecal Mn component was of similar magnitude, averaging 0.26 and 0.21 mg/d for the HMn and LMn gilts, respectively. However, the endogenous contribution to total fecal Mn was almost 8 fold different, representing 0.12% and 0.82% of total fecal Mn for the HMn and LMn gilts, respectively. The biological half-life of Mn in the body of the gilt was not influenced by dietary Mn within the intake range of 26 to 210 mg/d and averaged 54 days. The turnover rate (TR) of Mn was es

Factors affecting bovine ovarian responsiveness to stimulation by pregnant mare's serum gonadotropin (PMSG) were studied. Initially, the effects of plasma progesterone concentration on the response were considered using a progesterone-releasing intravaginal device (PRID) to provide an artificial source of the hormone. Due to inherent biological variation in vivo, in vitro methods were developed in which cAMP and progesterone production by granulosa cells were measured. Regardless of the size of the follicles from which the cells originated, PMSG stimulated significant cAMP accumulation. Cyclic AMP production was similar between aspirated granulosa cells and those scraped from the follicle wall, between ovaries with and without a corpus luteum from the same animal, and between follicles from animals early ( 10 days) in their estrous cycles. The PMSG failed to stimulate bovine granulosa cells to synthesize significantly more progesterone than untreated cells. Unlike porcine granulosa cells, bovine cells from antral follicles of any size appeared to luteinize spontaneously in culture. / Hormonal changes in the preovulatory follicle were measured using the PMSG/hCG-treated prepubertal gilt as a model. After hCG administration, follicular fluid levels of cAMP peaked at 4 hr followed 24 hr later by a rise in prostaglandins F and E (PGF, PGE) concentrations which peaked near the expected time of ovulation. Indomethacin injection blocked ovulation and the prostaglandin rise, although the inhibition could be reversed by the administration of PGF(,2)(alpha). Temporal changes in estrone, estradiol-17(beta), progesterone, androstenedione, testosterone and 5 (alpha)-dihydrotestosterone were also measured. / In an effort to decrease endogenous levels of inhibin, thereby increasing endogenous FSH and thence follicular development, heifers, ewes and does were actively immunized against porcine follicular fluid or proteinaceous fractions of bovine seminal plasma. In some animals, plasma FSH concentrations were elevated although ovulation rates and estrous cycle lengths were not altered. / A culdoscopy technique was developed for repeated monitoring of ovarian morphological changes in cows.

It is widely accepted that prostaglandins (PGs), produced via the cyclooxygenase pathway from arachidonic acid, are essential to the ovulatory process in the pig. In support of this, ovulation is preceded by an increase in follicular fluid (FF) PG concentration, indomethacin (INDO) suppresses both the PG increase and ovulation, and ovulation can be restored by administration of exogenous PGs (Downey and Ainsworth, 1980; Prostaglandins 19: 17-22). Recent studies in the rat have shown that ovulation is also preceded by a rise in ovarian concentrations of 15-hydroxyeicosatetraenoic acid (15-HETE), a product of the lipoxygenase pathway (Tanaka et al., 1989; Endocrinology 15: 1373-1377) and inhibition of this pathway suppresses ovulation (Reich et al., 1983; Prostaglandins 26: 1011-1020). Furthermore, INDO, a cyclooxygenase inhibitor, inhibits 15-lipoxygenase as well as PG synthesis (Tanaka et al., 1989 Endocrinology 15: 1373-1377). The PMSG/hCG prepuberal gilt model was used to investigate the involvement of 15-HETE in the procine ovulatory process, and the effect of INDO on the 15-lipoxygenase pathway. Follicular fluid concentrations of 15-HETE were elevated 40 h post hCG (p $<$ 0.01). The effects of INDO and nordihydroguaiaretic acid (NDGA), an inhibitor of lipoxygenase activity, on ovulation rate, FF 15-HETE and FF PGF$ rm sb{2a}$ were investigated by intraovarian administration of INDO or NDGA. INDO inhibited ovulation rate (p $<$ 0.01) and PGF$ rm sb{2a}$ (p $<$ 0.01) as well as 15-HETE (p $<$ 0.01). NDGA also suppressed ovulation rate (p $<$ 0.01) but did not inhibit 15-HETE or PGF$ rm sb{2a}$ production. In in vitro experiments, 15-HETE production by both granulosa cell (GC) and theca interna cell (TIC) cultures 40 h post hCG was greater (p $<$ 0.01) than at 0 h post hCG. INDO inhibited 15-HETE production in 40 h post hCG TIC cultures (p $<$ 0.01) but not GC cultures, while NDGA inhibited 15-HETE production by both cell types (p $<$ 0.01). These results sugges

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The objectives were: (1) to determine the pre-ovulatory changes in plasminogen activator (PA) and (PA) inhibitor (PAI) activities in the porcine follicle, and, (2) to determine if changes in the PA/plasmin system associated with ovulation were prostaglandin (PG)-dependent. PA activity (change in absorbance/h/mg wet tissue weight, three gilts per treatment group) was elevated in both granulosa cells (GC) and theca interna cells (TIC) prior to human chorionic gonadotropin (hCG) administration (0.582 $ pm$ 0.171 and 0.718 $ pm$ 0.221, respectively) but returned to basal levels in these two compartments (0.023 $ pm$ 0.013 and 0.052 $ pm$ 0.024, respectively) at 29 h post-hCG. PA activity remained basal thereafter in GC but increased approximately ten-fold in the TIC (0.549 $ pm$ 0.239) at the time of ovulation (three gilts at 41 h and one of three gilts at 38 h). PAI activity did not change in TIC over the pre-ovulatory period but increased in GC as ovulation approached. PAI activity in GC peaked at 38 h (being significantly different (p $<$ 0.05) to all other times except 41 h). Although indomethacin (INDO) effectively inhibited both PG synthesis (1.1 $ pm$ 0.2 vs. 9.2 $ pm$ 0.9 ng/ml in controls) and ovulation (0 vs. 27-61% in controls), elevated PA activity (0.801 and 0.349) was detected in the TIC of two out of nine INDO-treated gilts. Levels were basal (0.074 $ pm$ 0.028) in the other gilts. These inconclusive results are believed to reflect the occurrence of ovulation earlier than predicted, in as many as 40% of control gilts, and the short duration of increased PA activity at this time. In conclusion, elevated PA activity, in GC and TIC prior to ovulation induction, may play a role in follicular development. Elevated TIC PA activity may play an important role in the ovulatory process, but is probably PG-independent.

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