Unilateral uteroovarian relationship in pregnant cattle and role of uterine vein

The hypothesis of a unilateral uteroovarian relationship between location of embryos and maintenance of corpora lutea (CL) was tested in superovulated cattle. Ovulations were induced in both ovaries and a uterine horn was isolated subsequent to insemination to produce unilateral pregnancy. The mean weight of CL on day 24 was greater (P<.05) on the gravid side (2580 mg) than on the nongravid side (1200 mg; n=5), supporting the hypothesis. Involvement of the main uterine vein in the unilateral pathway between a gravid horn and the adjacent ovary was demonstrated in an experiment which utilized separation of uterine horns, anastomosis of uterine veins between sides, and insertion of embryos into one side by embryo transfer. Mean weight of CL on day 24 was less (P<.05) when the gravid horn was contralateral to the CL (950 mg; n=3), than when the gravid horn was ipsilateral to the CL (4760 mg) or when the gravid horn was contralateral to the CL and the uterine vein from the contralateral side was anastomosed to the vein on the ipsilateral side (3580 mg; n=3).     

Prostaglandin F-2 alpha causes regression of an hCG-induced corpus luteum before day 5 of its lifespan in cattle

The experimental objective was to evaluate how a spontaneously formed corpus luteum (CL) differed in its response to prostaglandin (PG) F-2 alpha, given during the first 5 days after ovulation, from a CL induced during dioestrus with hCG. Sixteen Holstein heifers were used during each of 2 consecutive oestrous cycles. During the first cycle (sham cycle), heifers were given no PGF-2 alpha (control) or PGF-2 alpha (25 mg, i.m.) on Day 2, 4 or 6 (oestrus = Day 0). During the second cycle (hCG-treated cycle), heifers were given hCG (5000 i.u., i.m.) on Day 10, followed by no PGF-2 alpha (control) or PGF-2 alpha on Day 12, 14 or 16, corresponding to 2, 4 or 6 days after the ovulatory dose of hCG. A new ovulation was induced in 13 of 16 heifers given hCG on Day 10. Luteolysis did not occur immediately in heifers given PGF-2 alpha on Day 2 or 4 during the sham cycle, but concentration of progesterone in serum during the remainder of the cycle was lower in heifers given PGF-2 alpha on Day 4 than in sham controls or heifers given PGF-2 alpha on Day 2 (P less than 0.05). Luteolysis occurred immediately in heifers given PGF-2 alpha on Day 6 of the sham cycle or on Day 12, 14 or 16 of the hCG-treated cycle, with concentration of progesterone in serum decreasing to less than 1 ng/ml within 2 days.(ABSTRACT TRUNCATED AT 250 WORDS)     

Unilateral luteotropic effect of uterine venous effluent of a gravid uterine horn in sheep.

The involvement of the main uterine vein in the unilateral maintenance of CL was studied in bilaterally ovulating unilaterally pregnant ewes. Ewes were mated at estrus (Day 0) and bilaterally ovulating ewes were randomized into three groups at surgery on Day 5. In all ewes, the uterine horns were separated through the intercornual area and one was ligated and transected near the internal bifurcation to produce a nongravid horn. One group served as controls (five ewes). In the other two groups the main uterine vein on one side was surgically anastomosed (end to side) to the corresponding vein of the opposite side (gravid side to nongravid side in one group--three ewes, and nongravid side to gravid side in the other--three ewes). Necropsies were done on Day 20. Mean CL weight was less, (P less than .01) on the nongravid side in control ewes than on the gravid side in control ewes or for either side in the other two groups. There were no significant differences among mean weights of CL on the gravid side in control ewes and either side in the other two groups. The CL regressed when the ipsilateral uterine vein contained blood from only the nongravid horn whereas the CL was maintained when the ipsilateral uterine vein contained venous blood from a gravid horn, whether or not it also contained blood from a nongravid horn. Results indicate that the uterine venous effluent from a gravid uterine horn in sheep has a luteotropic effect on the ipsilateral CL.     

Premature luteal regression in goats superovulated with PMSG: effect of hCG or GnRH administration during the early luteal phase

Twenty-two goats were superovulated with PMSG; 84 h after the onset of estrus the goats were treated with saline solution (control group n = 7), hCG (hCG group, n = 7), or GnRH (GnRH group, n = 8). The ovaries of all the goats were laparoscopically examined 3 and 6 d after the onset of estrus. In each case the CL were counted and classified according to their appearance as normal-looking or as regressing. Blood samples for progesterone determination were collected every 12 h from Day 1 to Day 6. Premature luteal regression was considered to have occurred if progesterone concentrations declined to less than 1 ng/mL by Day 6. According to progesterone concentrations, 57.5, 0 and 37.5% of the goats underwent premature luteal regression in the control, hCG and GnRH groups, respectively. Progesterone concentrations were higher in the hCG group than in the other groups on Days 5 and 6 post estrus (P < 0.05). The control group was the only one in which there was a significant (P < 0.05) increase in the number of regressing CL between Day 3 (1.6 +/- 1.4) and Day 6 (7.3 +/- 1.4). It was also the only group in which there was a significant decrease in the number of normal-looking CL between Day 3 (12.6 +/- 2.1) and Day 6 (2.6 +/- 2.1). On Day 6 the animals treated with hCG had significantly more normal-looking CL (12.0 +/- 2.3) than those in the control group (2.6 +/- 2.1). The number of large follicles present on the ovaries on Day 6 post estrus had negative correlations with progesterone concentrations (P = 0.05) and with the number of normal-looking CL (P < 0.05). It is concluded that the administration of hCG 84 h after the onset of estrus prevents premature luteal regression in goats superovulated with PMSG.     

Ability of induced corpora lutea to maintain pregnancy from the third month of gestation to term in cattle

The local relationship between the pregnant uterine horn and the CL during maternal recognition of pregnancy is well-documented. It continues beyond that time; pregnancies were maintained in lutectomized cows when CL were induced on the ovary ipsilateral, but not contralateral, to the uterine horn of pregnancy during Days 28-53. This study evaluated factors affecting maintenance of pregnancy by CL induced after Day 53, in lutectomized cows that had received exogenous progesterone from Day 29 to 15 days after induction of a CL. Twenty-four suckled beef cows were lutectomized on Day 29 of gestation; pregnancy was maintained with progesterone from two controlled internal drug releasing (CIDR) inserts, exchanged every 5 days. Beginning on Day 53, ovaries and viability of pregnancy were evaluated by ultrasonography every 5 days. When a follicle >or=10 mm in diameter was present ipsilateral to the fetus, each cow received 1,000 IU of hCG. Following induction of a CL (20 of 24), progesterone was reduced to a single CIDR for 5 days, then removed. Retention of pregnancy was confirmed by rectal palpation and calving. Cows with induced CL maintained pregnancy to term, including four with the CL contralateral to the fetus. Three cows failed to form normal CL by Day 98 and lost pregnancy after removal of exogenous progesterone. One cow that did not respond to hCG lost pregnancy during exogenous progesterone. In conclusion, CL induced after Day 53 maintained pregnancy to term, even when induced contralateral to the pregnant uterine horn.     

Direct effects of oestradiol-17 beta and prostaglandin E-2 in protecting pig corpora lutea from a luteolytic dose of prostaglandin F-2 alpha

Implants containing vehicle or oestradiol-17 beta (10 mg) were placed into pairs of corpora lutea (CL) with and without prostaglandin F-2 alpha (PGF-2 alpha) (100 micrograms) on Day 11 and CL were collected on Day 19, in cyclic gilts (Exp. 1). The results demonstrated that CL implanted with PGF-2 alpha with or without oestradiol-17 beta had a markedly lower (P less than 0.01) weight (mg) and progesterone concentration (ng/mg) than CL with vehicle-or oestradiol-17 beta-implanted or unimplanted CL, which were similar (149 and 7.2 vs. 304 and 49.6, respectively). In Exp. 2, CL implanted with vehicle, oestradiol-17 beta or PGE-2 remained fully functional until Day 19, whereas CL implanted with oestradiol-17 beta +/- PGF-2 alpha and PGE-2 + PGF-2 alpha exhibited lower (P less than 0.05) weight and progesterone concentrations; CL implanted with PGE-2 + PGF-2 alpha were heavier (P less than 0.05) and tended (P less than 0.10) to have greater progesterone concentrations than CL implanted with oestradiol-17 beta + PGF-2 alpha. In Exp. 3, a dose-dependent (P less than 0.05) effect of PGE-2 on preventing regression induced by PGF-2 alpha was observed on Day 19. These data demonstrate a direct effect of PGE-2, but not of oestradiol-17 beta in protecting the CL against luteolysis induced by PGF-2 alpha.     

Plasma gonadotropins and prolactin in pseudopregnancy in the rat

Radioimmunoassay presented a method of measuring plasma levels of FSH,LH and prolactin in pseudopregnant rats. Plasma prolactin levels doubled 15 minutes following cervical probing (p .01) on the day of estrus. Plasma LH levels were not significantly elevated. Due to the use of ether anesthesia at blood collecting 3 hr before and 15 minutes after stimulation, only 1 of 16 rats developed pseudopregnancy. On Day 4 of pseudopregnancy in rats mated with vasectomized males; plasma LH was lower (p .05) than in normal rats on the first day of diestrus, perhaps due to the suppressive action of ovarian progesterone and some estrogen. FSH was higher than in normal rats (p .05) perhaps due to the lesser sensitivity of FSH to the inhibitory effect of progesterone. Large decidoumata developed by Day 9 in uterine horns traumatized on Day 4 (153 plus or minus 8 mg uterus weight compared to 1510 plus or minus 204 mg). Thus, the corpora remain functional after LH and prolactin are at normal and subnormal levels. On Day 9 plasma prolactin was lower than at Day 1 of diestrus (p .001). Plasma FSH was elevated (p .01). Plasma LH was unchanged. The degree of rise of LH levels 5 days following ovariectomy on Day 4 of psuedopregnancy or on the first day of diestrus was greater in the former group (p .02), perhaps due to rebound of LH from suppression by ovarian steroids. FSH rose equally in both groups. Prolactin remain about the same. Increased prolactin release by the adenohypophysis was briefer than expected.     

Switching of largest follicle from dominant to subordinate status when follicle and CL are in same ovary in heifers

It has been reported that early development of wave 3 in three-wave interovulatory intervals occurs during the luteolytic period, and the frequency of the ipsilateral relationship between the preovulatory follicle and CL is lower (e.g., 33%) than for the contralateral relationship (67%). In this study, luteolysis was induced with PGF2α when the largest follicle of wave 2 reached 8.5 mm or more (diameter at expected deviation). A two-way interaction (P < 0.004) of follicle (first follicle to reach 8.5 mm and the next-largest follicle) by group (ipsilateral and contralateral relationship between the 8.5-mm follicle and CL) represented smaller posttreatment diameter difference between the two follicles within the ipsilateral group than within the contralateral group; the 8.5-mm follicle was smaller and the next-largest follicle was larger in the ipsilateral than in the contralateral group. Switching in the destiny of the 8.5-mm follicle from dominant to subordinate occurred in 3 of 8 (41%) and 0 of 5 (0%) heifers in the ipsilateral and contralateral groups, respectively. These novel findings supported the hypothesis that follicle deviation during luteolysis may result in decreased diameter of the largest follicle and increased frequency of switching of the largest follicle from future dominant to subordinate status when the follicle and CL are ipsilateral. Support for the switching hypothesis indicated that the reported lower frequency of an ipsilateral than contralateral relationship between the preovulatory follicle and CL for wave 3 of three-wave interovulatory intervals can be attributed to development of the wave during luteolysis.     

Complex interrelationships among CL,preovulatory follicle,number of follicular waves,and right or left ovaries in heifers

The diameter of the dominant follicle (DF) of wave 1 was studied on Days 9 to 17 (Day 0 = ovulation) in a survey of the ipsilateral and contralateral relationships between the location of the DF and CL, and number of follicular waves per interovulatory interval (IOI). For contralateral relationships, regardless of number of waves the diameter of the DF of wave 1 decreased (P < 0.03) between Days 11 and 13 when referenced to the follicle–CL relationship of wave 1 and decreased (P < 0.008) between Days 9 and 11 when referenced to the preovulatory follicle (PF)–CL relationship. For wave 2 in two-wave IOIs, the CL ovary of ipsilateral relationships had more (P < 0.05) follicles that reached at least 6 mm than the non-CL ovary. In three-wave IOIs, frequency of IOIs with the DF in the CL ovary was greater (P < 0.02) for wave 2 than for wave 3. In wave 3, the preovulatory and the largest subordinate follicles were located more frequently (P < 0.005) in the contralateral ovary. Ovulation in two-wave IOIs occurred more frequently (P < 0.0009) from the right ovary. In three-wave IOIs with a contralateral relationship ovulation occurred more frequently (P < 0.003) from the left ovary; a negative intraovarian effect of the CL on location of the PF may account for more ovulations from the left ovary and a reported greater frequency of the contralateral relationship. The hypothesis was supported that the ipsilateral versus contralateral relationship between the PF and CL is affected by the DF–CL relationship during the previous follicular waves and by the number and identity of waves per IOI.     

Comparison of the fetal survival rate in heifers after the transfer of a embryo surgically to one uterine horn and non-surgically to the other

When transfer of Day 7 embryos was surgically to the horn ipsilateral to the CL and non-surgically to the contralateral horn, fetal survival rate was 85 and 35% respectively. After non-surgical transfer to the ipsilateral and surgical transfer to the contralateral horn, fetal survival rate was 20 and 30% respectively.     

Progesterone in uterine and arterial tissue and in jugular and uterine venous plasma of sheep

Concentrations of progesterone in uterine and arterial tissue and in uterine and jugular venous plasma were determined. Blood was collected on Days 4 and 9 postestrus from the jugular vein and the first and last venous branches draining each uterine cornu; uterine tissue and arteries were subsequently collected. Progesterone was greater (p less than 0.05) in the cranial third than in the middle or caudal thirds of the uterine horn adjacent to the corpus luteum (CL)-bearing ovary or in any third of the contralateral horn. Progesterone in uterine arterial segments adjacent to the CL-bearing ovary was higher (p less than 0.05) than in contralateral segments. Progesterone was higher (p less than 0.05) in blood from the first venous branch of the cranial third of the uterine cornu adjacent to the ovary with the CL, than in the last branch of the caudal third, or contralateral horn, or in jugular blood. When oviductal veins were resected on Day 9 postestrus, progesterone in the first vein draining the cranial third of the uterine cornu adjacent to the CL-containing ovary was not different (p greater than 0.05) 48 h after resection than in the same vessel in the opposite horn or in jugular blood. We concluded that progesterone and other ovarian products may be delivered to the uterus locally.     

Effect of intraovarian proximity between dominant follicle and corpus luteum on dimensions and blood flow of each structure in heifers

An intraovarian positive physiologic coupling between the extant CL and the ipsilateral preovulatory follicle (PF) or the future or established postovulatory dominant follicle (DF) was studied in 26 heifers. Ovaries were scanned by ultrasonic imaging from Day 16 (Day 0 = ovulation) of the preovulatory period until Day 6 of the postovulatory period. Hemodynamics of the follicles and CL were assessed by color-Doppler ultrasonography. When the PF and CL were ipsilateral compared with contralateral, blood-flow resistance in wall of the PF was lower (P < 0.04) on Days –2 and –1, and percentage blood-flow signals in the CL approached being greater (P < 0.08) on Days –4 to –1. During the postovulatory period, percentage of DF wall with blood-flow signals (44.1 ± 1.2% vs. 31.4 ± 2.8%) and percentage of CL with blood-flow signals (51.8 ± 1.2% vs. 42.5 ± 3.1%) were each greater (P < 0.05) when the two ipsilateral structures were adjacent (distance between antrum and CL wall, ≤ 3 mm) than when separated. On Day 0, the distance between follicle and ipsilateral CL was less (P < 0.02) for the future DF than for the future largest subordinate. Growth rate between Days 0 and 2 averaged over all growing follicles was greater (P < 0.01) when the follicles were ≤3 mm from the CL (1.1 ± 0.1 mm/day) than when farther from the CL (0.9 ± 0.1 mm/day). Results supported the hypotheses that (1) a positive intraovarian coupling occurs between the PF or postovulatory DF and the extant CL and (2) the coupling is enhanced when the ipsilateral DF and CL are in close proximity.     

Changes in rabbit corpus luteum progesterone secretion and cellular morphology following unilateral luteectomy or ovariectomy.

The objective of this study was to determine whether removal of corpora lutea (CL) from one ovary (unilateral luteectomy; ULL) or removal of the entire ovary (unilateral ovariectomy; ULO) of pseudopregnant rabbits would cause compensatory growth and progesterone production by the contralateral ovary. Pseudopregnancy was induced in rabbits with hCG (Day 0). On the first day of pseudopregnancy, one group of rabbits received a sham operation (controls), another group underwent ULL, and a third group underwent ULO. On Day 11 of pseudopregnancy, each rabbit underwent laparotomy, the ovarian artery and vein were cannulated, and the ovary(ies) was removed and perfused in vitro for 6 h. The mean CL weight increased by 33% in the ULL group and by 28% in the ULO group as compared to sham-operated controls. Peripheral estradiol and progesterone levels in sham-operated control, ULL, and ULO groups were similar. Ovarian venous estradiol levels were similar in the control and ULL groups, but were significantly increased in the remaining ovary of the ULO group. Both ovarian venous progesterone in vivo and progesterone secretion in vitro increased significantly in contralateral ovaries from ULL and ULO rabbits as compared to sham-operated controls. Progesterone secretion by ovaries perfused in vitro increased significantly in the contralateral ovary of the ULL and ULO groups. Mean number of luteal cells per CL increased significantly in the ULL group, but not in the ULO group. In contrast, luteal cell volume increased significantly in the ULO, but not in the ULL group. The stimuli responsible for increased progesterone production following ULL and ULO result in morphological changes in the remaining CL.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exposure to nuclear magnetic resonance imaging procedure attenuates morphine-induced analgesia in mice

Adult male mice exposed to a Nuclear Magnetic Resonance Imaging (NMRI) procedure during the mid-dark period and injected with morphine (10 mg/kg) failed to exhibit the normal nocturnally enhanced morphine analgesia response to a thermal stimulus that was displayed by mice exposed to a sham imaging procedure and treated with morphine (p less than .01). When tested during the mid-light period, animals exposed to the NMRI procedure and given morphine displayed attenuated analgesia levels relative to sham exposed mice (p less than .01) treated with morphine. However, the morphine induced analgesia was not totally abolished since the imaged mice still exhibited analgesia relative to saline treated mice (p less than .01). These results suggest that the magnetic and/or radio-frequency fields associated with the NMRI procedure alter both day- and night-time responses to morphine. These results may reflect magnetic field induced alterations in neuronal calcium binding and/or alterations in nocturnal pineal gland activity.     

Counter current transfer and back transport of 3H-PGF2 alpha in the cow's broad ligament vasculature ipsilateral and contralateral to the corpus luteum

Eight cows of similar age (5-7 years) were chosen for the experiment. Isolated reproductive tract was supplied with autologous oxygenated and heated (40 degrees C) blood through the uterine artery and ovarian artery. 3H-PGF2 alpha in total dose of 2 MBq (10(7) cpm) was injected into each of the uterine lumen of isolated organ. Blood samples were collected at 5 min intervals during 120 min of experiment using cannulae inserted into the branches of uterine arteries about 1 cm below the horns and from ovarian arteries inserted 0.5 cm below the ovaries. The concentration of 3H-PGF2 alpha found in blood plasma taken from uterine artery or from ovarian artery on the side with active corpus luteum (CL) was significantly lower (p less than 0.001) compare with contralateral side to active CL. Radioactive PGF2 alpha found in branches of uterine arteries on both ipsilateral and contralateral side to CL was significantly higher (p less than 0.001) compare to ovarian artery of the same side. It is concluded that absorption of 3H-PGF2 alpha from uterine lumen into venous blood as well as its counter current transfer in area of broad ligament vasculature were reduced on the side of uterine horn with active CL probably as an effect of estrogen:progesterone ratio on vascular constriction in area of uterine vasculature.     

The postpartum induced corpus luteum: functional differences from that of cycling cows and the effects of progesterone pretreatment

Anestrous postpartum (PP) Hereford cows (n = 41) were used to compare corpora lutea (CL) from gonadotropin-releasing hormone (GnRH)-induced ovulation with CL from cycling cows. Postpartum cows were injected i.m. daily with 100 mg progesterone (P4) or oil on Days 25 through 28 PP and then given 200 micrograms GnRH i.m. on Day 30 PP. Corpora lutea were removed from one-half of the PP cows in the oil- and P4-treated groups 6.5 days after GnRH injection, and from the cycling cows 7 days after estrus. Intact PP cows were used to evaluate cycle length. Blood was collected daily from all PP cows from Day 25 PP through luteectomy and on Days 9, 11, and 13 post-GnRH from the oil- and P4-intact cows to determine short (SHORT) versus normal (NORM) luteal phases. Cycling cows were bled daily from estrus until CL removal NORM PP cows had higher (P less than 0.001) P4 levels than did SHORT PP cows from Day 7 through Day 13 post-GnRH, and more (P less than 0.05) P4-intact cows were NORM compared with oil-intact cows (45.5% vs. 14.3%, respectively). Corpora lutea from cycling cows were heavier (P less than 0.05) and had a higher luteinizing hormone (LH) receptor concentration (P less than 0.05), but CL P4 concentration did not differ from PP cows. Corpora lutea weight, LH receptor and P4 concentration, and in vitro P4 production were similar in the oil-and P4-treated PP cows. NORM cows had heavier CL (P less than 0.05) than SHORT cows, although P4 content and LH receptor concentration did not differ.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of 2',5'-oligoadenylate synthetase activity in sheep endometrium during pregnancy, by intrauterine infusion of ovine trophoblast protein-1, and by intramuscular administration of recombinant bovine interferon-alpha I1.

In Expt 1, activity of 2',5'-oligoadenylate (2',5'-A) synthetase in endometrium collected on Day 16 (oestrus is Day 0) from the uterine horn ipsilateral to the corpus luteum was greater (P less than 0.001) for pregnant (135.5 +/- 1.72 nmol/mg protein/h) than for cyclic ewes (58.5 +/- 0.99 nmol/mg protein/h). In pregnant ewes, activity of 2',5'-A synthetase in endometrium collected from the contralateral uterine horn (119.5 +/- 1.72 nmol/mg protein/h) did not differ from that of the ipsilateral horn. In Expt 2, three ovariectomized ewes were treated with progesterone for 10 days and then with oestrogen for 2 days. Activity of 2',5'-A synthetase on Day 13 was 18% greater (P less than 0.10) in endometrium collected from the uterine horn receiving infusions of 30 micrograms ovine trophoblast protein-1 (oTP-1) twice a day on Days 10, 11 and 12(57.7 +/- 0.22 nmol/mg protein/h) than from the uterine horn receiving control infusions of serum protein (SP; 48.8 +/- 0.22 nmol/mg protein/h). In Expt 3, activity of 2',5'-A synthetase on Day 15 was not significantly greater in endometrium collected from the uterine horn of cyclic ewes receiving infusions of 30 micrograms oTP-1 twice a day on Days 12, 13 and 14 (46.5 +/- 0.37 nmol/mg protein/h) than in endometrium from the uterine horn receiving infusions of SP (38.2 +/- 0.37 nmol/mg protein/h). When results of Expt 2 and Expt 3 were combined, intrauterine infusion of oTP-1 increased (P less than 0.05) activity of 2',5'-A synthetase in endometrium by 20%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Expression of major histocompatibility complex antigens on the bovine corpus luteum during the estrous cycle, luteolysis, and early pregnancy.

Treatment of cultured bovine luteal cells with the cytokine, interferon-gamma, induces the expression of Class II major histocompatibility complex antigens (MHC Ags). To determine if Class II MHC Ags are present on the CL in vivo and if the degree of Ag expression changes during luteal life span, bovine corpora lutea were obtained on Day 6, Days 10-12, and Day 18 of the estrous cycle and MHC Ag expression was evaluated via indirect immunofluorescence. Flow cytometry was used to determine the percentage of MHC Ag-positive cells on cell populations distinguished by cell size and intracellular density. Minimal Class II MHC Ag expression was detected on Day 6 CL (approximately 25%), which consisted primarily of smaller cells. The midcycle and late CL consisted of these small cells (SC) and two populations of large cells that differed in intracellular density, or right-angle light scatter. In midcycle CL, few (less than 25%) SC or large, dense cells (LDC) expressed the Class II MHC Ag whereas a high percentage (75%) of the large, less-dense cells (LLDC) were Class II MHC Ag-positive. Class II MHC Ag expression remained negligible on the LDC of the Day 18 CL; however, there was an elevation in the percentage of SC and LLDC expressing Class II Ag (p less than 0.05). To determine if Class II MHC Ag expression also varied with different functional states of the CL, bovine CL were collected after prostaglandin (PG) F2 alpha-induced regression and on Day 18 of early pregnancy. When luteolysis was allowed to progress in vivo, the percentage of Class II MHC Ag-positive cells was increased in all cell populations (p less than 0.05). Class II MHC Ag expression was significantly lower (p less than 0.05) on the three cell populations comprising the CL of pregnancy as compared to the Day 18 cyclic CL. It is hypothesized that enhanced expression of Class II MHC Ags on the late CL and during PGF2 alpha-induced regression may potentiate immune response mechanisms for luteolysis.     

Characterization of endometrial receptors for ovine trophoblast protein-1 during the estrous cycle and early pregnancy in sheep

Scatchard analysis was used to determine the distribution, number, and affinity of unoccupied receptors for ovine trophoblast protein-1 (oTP-1) in endometrium of sheep throughout the estrous cycle and early pregnancy. In Experiment I, oTP-1 receptor characteristics were determined in membrane preparations of caruncular and intercaruncular regions of endometrium collected from uterine horns ipsilateral and contralateral to the ovary bearing the corpus luteum. Receptor concentrations and affinity constants for oTP-1 were not different (p greater than 0.1) between the four endometrial regions examined, suggesting that the expression of receptors for oTP-1 occurs uniformly throughout the endometrium. Endometrial receptor characteristics for oTP-1, luteal wet weights, and progesterone contents were determined throughout the estrous cycle and early pregnancy in Experiment II. Concentration of receptors and affinity constants for oTP-1 varied throughout the estrous cycle and early pregnancy (p less than 0.01), with the pattern of change differing between cyclic and pregnant ewes (p less than 0.01). Numbers of receptors for oTP-1 were maximal on Day 4 of the estrous cycle and declined progressively to Day 12 (p less than 0.05) in both cyclic and pregnant ewes. After Day 12, the quantity of unoccupied receptors for oTP-1 increased (p less than 0.05) gradually to Day 16 in cyclic ewes, but declined (p less than 0.05) further in the endometrium of pregnant ewes. The affinity constants of endometrial receptors for oTP-1 were similar in cyclic and pregnant ewes prior to Day 12, increasing threefold from Days 4 to 12 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of ovarian status on response to estrus synchronization treatment in dairy goats during the breeding season

The influence of ovarian status (presence of a corpora lutea and follicles) on the times of the onset of estrus, LH peak and ovulation rate at a synchronized estrus was evaluated in 73 Alpine and Saanen cyclic goats. Does were treated for 11 d with 3 mg norgestomet implants or 45mg fluorogestone acetate (FGA) sponges. They also received 400 IU of PMSG and 50 μg of a PGF_2α analog on Day 9 of progestagen priming. Follicles (1 to 7 mm) and corpora lutea (CL) were counted by laparoscopy on Days 0 and 9 of progestagen treatment and 5 or 6 d after the synchronized estrus. Estrus was detected every 4 h from 16 to 60 h after the end of progestagen treatment using a vasectomized buck. The LH concentration was determined by radioimmunoassay (RIA) in blood samples collected every 4 h for 24 h beginning at the time of the onset of estrus. The number of follicles on Days 0 and 9 of progestagen treatment was not related to the time of the onset of estrus and occurrence of the LH peak or to ovulation rate. The number of CL on Day 9 influenced the time of occurrence of the LH peak but not the time of the onset of estrus. Thus, in does with 2 or 3 CL on Day 9, the LH peak occurred at 46.9 h after the end of progestagen treatment, and in does with 1 or 0 CL at 42.2 and 42.5 h, respectively, after treatment, suggesting that the number of CL at luteolysis is a factor in the variability of response after the synchronization of estrus.