A sensitive and specific double-antibody RIA for a bovine pregnancy-associated glycoprotein (bPAG) is described. The limit of detection was 0.2 ng/ml. The assay was specific for bPAG in that pituitary and placental gonadotropic hormones and other placental or serum proteins assayed in serial dilutions did not cross-react. The RIA allowed measurement of bPAG in placental extracts, fetal serum, fetal fluids, and serum or plasma of pregnant cows. About 20% of unbred heifers and nonpregnant cows had detectable levels ranging from 0.30 +/- 0.09 to 0.50 +/- 0.17 ng/ml (mean +/- SD), and 15% of bull sera showed higher concentrations (3.01 +/- 1.73 ng/ml) of bPAG or bPAG-like protein. Variations among animals was observed in fetal serum bPAG concentrations. Bovine PAG was detected in maternal peripheral blood at Day 22 of pregnancy (mean +/- SD, 0.38 +/- 0.13 ng/ml) in some animals and at Day 30 in all pregnant cows. Peripheral serum bPAG levels increased progressively to 3.60 +/- 1.73 ng/ml (mean +/- SD) at Day 30 of pregnancy, to 24.53 +/- 8.81 ng/ml at Day 120, and to 1551.91 +/- 589.68 ng/ml at Day 270. Peak concentration of bPAG was 2462.42 +/- 1017.88 ng/ml and it occurred 1-5 days prior to parturition. After delivery, bPAG concentrations decreased steadily to 499.63 +/- 267.20 ng/ml at Day 14 postpartum (pp), 10.12 +/- 7.84 ng/ml at Day 60 pp, and 1.44 +/- 1.08 ng/ml at Day 90 pp. The undetectable concentration (less than 0.20 ng/ml) was reached by Day 100 +/- 20 pp. An investigation undertaken in Holstein heifers, Holstein cows, and Hereford cows used as recipients for purebred Holstein embryos supplied evidence of the influence of breed of recipient and sex of fetuses on peripheral concentrations of bPAG. A herd of 430 Holstein-Friesian heifers that had received transferred embryos were bled at Day 35 postestrus (pe) for measurement of bPAG. The bPAG was detected in 287 of 430 serum samples analyzed. By rectal palpation performed at Day 45 pe, 267 heifers with detectable levels of bPAG at Day 35 pe were confirmed to be pregnant as were 3 of 143 heifers previously diagnosed as not pregnant by RIA. These results suggest that detection of this placental-specific antigen in the serum could be used as a specific serological method for early pregnancy diagnosis in cattle from 28 days after breeding.

Epithelial and stromal cells were isolated from endometrium of cyclic heifers by enzymic dispersion. These cells exhibited specific morphological and functional properties. Epithelial cells appeared cuboidal or columnal and showed contact inhibition as they reached confluence. Stromal cells were fibroblast-like and enlarged at the time of confluence after which they overgrew in multiple layers. The presence of specific receptors for PGE-2 and \g=b\-adrenergic catecholamines (isoproterenol) was estimated by activation of adenylate cyclase. Stromal cells had more adenylate cyclase activity (P < 0\m=.\01) than did epithelial cells before (basal) and after stimulation with guanosine triphosphate (GTP) and PGE-2. However, epithelial cells were much more responsive to isoproterenol (P < 0\m=.\01). Treatment of cultured cells with indomethacin to block PG synthesis increased the sensitivity and maximal response to PGE-2 in stromal (P < 0\m=.\01) but not in epithelial (P > 0\m=.\1) cells. The latter result suggested autologous desensitization of the PGE-2 response resulting from synthesis of PGs in cultured cells. Both cell types synthesized PGs in culture: PGF-2\g=a\was synthesized in greater quantity in epithelial than in stromal cells (P < 0\m=.\05) while stromal cells synthesized more PGE-2 than did epithelial cells (P < 0\m=.\001). Endometrial cells separated in this way should prove useful for study of their specific role in the processes of implantation and maternal recognition of pregnancy.

Treatment with GnRH and PGF2 alpha is a practical method for controlling ovarian follicular and luteal functions and increasing the precision of estrus synchronization in cyclic and acyclic postpartum cows and heifers. This method reduces considerably the period of time needed for estrus detection; it synchronizes the estrous cycle of 70 to 80% of the cyclic cows to within a 4-d interval without any detrimental effect on the fertility rate (65 to 85%). Moreover, resumption of ovarian activity and normal fertility in acyclic cows in favored. Administration of GnRH eliminates the large follicles by ovulation or atresia and induces emergence of a new follicular wave within 3 to 4 d after treatment at any stage of the estrous cycle, but it limits further growth of these emerging follicles by increasing atresia. The precision of estrus and the unaltered fertility rate is due to the synchronized selection of a new larger growing follicle, which becomes the ovulatory follicle after PGF(2 alpha)-induced luteolysis 6 d after GnRH treatment. Also, fixed-time AI programs without the need for estrus detection may be possible using a second injection of GnRH in a GnRH-PGF(2 alpha)-GnRH protocol to ovulate the selected follicle at a precise time. We describe a physiological model to explain how the precision of estrus is improved following PGF(2 alpha)-induced luteolysis, via the effect of pretreatment with GnRH on follicular development and luteal functions in cattle. Application of this model to the development of reliable methods of fixed-time insemination is also explored.

No abstract

No abstract

Dairy heifers were superovulated in the presence (dominant group, N = 8) or absence (non-dominant group, N = 6) of a dominant follicle at the start of a a superovulatory treatment on Days 7-12 of the oestrous cycle (Day 0 = oestrus). Daily ultrasonographic observations of ovaries (recorded on videotape) starting on Day 3 were used to assess the presence or absence of a dominant follicle (diameter greater than 9 mm, in a growing phase or at a stable diameter for less than 4 days) and to monitor follicular development before and during treatment. The number of CL estimated by ultrasonography (7.1 +/- 1.8 vs 13.5 +/- 1.4) or by rectal palpation (6.9 +/- 2.0 vs 16.3 +/- 1.6) and mean progesterone concentrations (32.5 +/- 19 vs 80.7 +/- 16 ng/ml) after treatment were lower (P less than 0.01) in the dominant than in the non-dominant group. Based on number of CL, two populations of heifers were identified in the dominant group, i.e. those that had a high (dominant-high, N = 4; greater than 7 CL) or a low (dominant-low, N = 4; less than 7 CL) response to treatment. During treatment, the increases in number of follicles 7-10 mm and greater than 10 mm in diameter occurred sooner and were of higher magnitude in the non-dominant than in the dominant-high or dominant-low groups (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The objectives were to determine the relationships between changes in the levels of histological and biochemical (estradiol [E2]:androstenedione [A], E2:A ratio) atresia and changes in inhibin contents of morphologically dominant follicles collected during the growing or the regressing phase of the first wave of follicular development in cycling crossbred beef heifers. Heifers were slaughtered either when the dominant follicle (> or = 9 mm; diameter of the antral cavity as assessed by ultrasonography) of the first wave was still growing (n = 7) or when the first dominant follicle (> or = 9 mm; n = 7) was regressing or was at the end of the plateau phase. Following ovary collection, the dominant follicle was dissected and level of histological atresia was determined on sections of follicular walls. Aliquots of follicular fluid from each of the dominant follicles were collected to measure concentrations of E2, A, and inhibin alpha subunit by RIA and to measure concentrations of dimeric (alpha-beta dimer) inhibin by a two-site immunoradiometric assay. Heifers were slaughtered on Days 5.4 +/- 0.5 (growing phase) and 11.8 +/- 0.5 (regressing phase) of the estrous cycle, and mean diameter of the dominant follicles was similar in both phases (9.9 +/- 0.4 vs. 10.8 +/- 0.4 mm; p > 0.09). All morphologically dominant follicles collected during the growing phase (7/7) were histologically healthy and estrogen-active (E2:A ratio > 1), while those collected during the regressing phase (7/7) were histologically atretic and estrogen-inactive (E2:A ratio < 1; chi 2 = 14.0, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Functional subpopulations of granulosa cells exist in bovine follicles. This study was designed to compare the in vitro steroid production by cultured bovine antral and mural granulosa cells in response to various amounts of FSH. Antral and mural granulosa cells (600,000 viable cells/well) harvested from ovaries of PMSG-treated prepuberal calves were cultured in serum-free conditions for 4 d in wells containing 1 mL of defined Ham's F-12 medium, supplemented with 0, 2, or 10 ng/mL of FSH. Culture medium was collected and replaced each day. The mean concentration of estradiol in culture media of bovine granulosa cells decreased from d 1 to d 4 (P < .001). Granulosa cell production of estradiol increased in antral cells following addition of 2 ng/mL FSH (P < .001) but decreased following addition of 10 ng/mL FSH (P < .001) as determined on d 4 by RIA and thin layer chromatography. In contrast, there was no response to FSH stimulation in mural granulosa cells. Progesterone production increased (P < .01) in a dose-dependent manner following stimulation with 2 or 10 ng/mL FSH and was consistently higher (P < .001) in antral than in mural granulosa cells. Addition of LH on d 4 stimulated estradiol and progesterone production in antral (P < .01) but not in mural cells (P > .10). This suggests that FSH- and LH-induced estradiol and progesterone productions are considerably lower in mural than in antral bovine granulosa cells. This suggests that functional differences between these two cell compartments need to be considered in studies involving in vitro cultures of bovine granulosa cells.