Effects of day of estrous cycle, time of day, luteolysis, and embryo on uterine contractility in mares

One-minute continuous ultrasonic scans of longitudinal sections of the uterine body were videotaped, and contractility scores (1 to 5, minimal to maximal contractility) were assigned without knowledge of mare identity, day of the estrous cycle or pregnancy status. Contractility was assessed, and plasma progesterone concentrations were determined for each of 3 daily examinations (at 0800, 1600 and 2400 hours) from Day 9 to Day 19 (Day 0 = day of ovulation). For both the nonbred (n=11) and pregnant (n=11) mares, there was no effect of hour of scan on the extent of uterine contractility. When data for the nonbred mares were normalized to the onset of luteolysis (defined for each mare as the first >/=25% decrease in plasma progesterone concentrations between successive samples), there was an abrupt increase (P<0.05) in contractility 24 hours prior to the onset of luteolysis. Contractility was also assessed daily in 20 nonbred and 27 pregnant mares from Day 0 to Day 17. For the nonbred mares, a biphasic profile in contractility occurred during the estrous cycle as indicated by the following significant changes: a decrease between Days 0 and 2, an increase between Days 2 and 4, a plateau between Days 4 and 7, a decrease between Days 7 and 11, an increase between Days 11 and 13, and a decrease between Days 14 and 16. For pregnant mares, contractility increased (P<0.05) prior to the late-diestrous increase for nonbred mares. In addition, a significant reduction in contractility was detected on Day 5 in these mares compared with that in the nonbred mares. Contractility in the uterine body in 7 mares was assessed every 5 minutes after departure of the embryonic vesicle from the uterine body. Levels of contractility in the uterine body were lower (P<0.05) 55 minutes after the vesicle had exited the body than 相似文献   

Effect of oxytocin, prostaglandin F2 alpha, and clenbuterol on uterine dynamics in mares

The effects of oxytocin, prostaglandin F2 alpha (PGF2 alpha), and clenbuterol on uterine contractility and tone during anestrus and diestrus, and during mobility and postfixation of the embryonic vesicle were studied in 51 pony mares. Contractility was assessed by scoring real-time ultrasound images, and tone was assessed by transrectal digital compression. Scoring was done by an operator who had no knowledge of treatment assignments. In anovulatory mares primed with progesterone for 16 d, oxytocin did not significantly alter contractility but did stimulate an increase in tone, whereas clenbuterol depressed both contractility and tone. The PGF2 alpha given on Days 12, 15, and 18 did not significantly alter uterine contractility in pregnant mares, but it increased contractility on all days in nonpregnant mares. Clenbuterol decreased both tone and contractility when given to pregnant mares on the day of embryonic-vesicle fixation, while it decreased tone but not contractility when given on Day 19. Clenbuterol treatment was associated with dislodgment of the fixed embryo in only 1 of 5 mares. However, on Day 19, clenbuterol treatment was associated with a change in shape of the conceptus when viewed in a cross section of the uterine horn. The conceptus shape became more circular rather than irregular or triangular, as indicated by a significant decrease in the variation in the distances between adjacent walls measured in 4 different directions. Results indicated that: 1) oxytocin increased uterine tone but did not alter contractility in progesterone-primed anestrous mares; 2) on Days 12, 15 and 18, PGF2 alpha increased uterine contractility in nonpregnant mares but not in pregnant mares; 3) clenbuterol decreased both tone and contractility at all reproductive states except for a lack of a decrease in contractility on Day 19 of pregnancy; and 4) reduction in uterine tone from clenbuterol treatment on Day 19 was associated with a change in the two-dimensional shape of the in situ conceptus from irregular to a more circular form.     

Factors related to the time of fixation of the conceptus in mares

The temporal relationships among day of conceptus fixation (cessation of mobility), conceptus diameter, uterine tone, uterine contractility, and myometrial and endometrial thickness of the middle and caudal segments of the uterine horns were assessed in 13 pony mares with fixation in the caudal segment of a uterine horn. The mean day of fixation (14.9 +/- 0.3) was established by 2-h mobility trials. Uterine tone increased (P < 0.0001) gradually over Days 11 to 21, whereas uterine contractility decreased (P < 0.0001) between Days 14 and 18. The diameter of the spherical embryonic vesicle increased (P < 0.0001) between Days 11 and 17. The day of fixation and vesicle diameter on Day 14 were negatively correlated (r = -0.9, P < 0.007); the larger the vesicle, the earlier fixation occurred. Each of 4 uterine-horn diameters (endometrium and endometrium plus myometrium of middle and caudal segments) decreased (P < 0.0001) correspondingly over Days 11 to 21. On the day of fixation conceptus diameter (21.5 +/- 1.0 mm) was similar to endometrial diameter (21.1 +/- 0.4 mm) at the caudal segment. The endometrial diameter represents the distance between the inner opposite walls of the myometrium. The percentage of change between the day before and day of fixation was greater for the conceptus (18.1% increase) than for the endometrial diameter at the caudal segment (1.0% decrease). The results suggest that fixation occurred when the mobile and growing conceptus attained, on the average, a diameter equivalent to the distance between opposite inner myometrial walls at the caudal segment. The uterus became turgid by this time and presumably did not expand adequately to accommodate continued mobility of the expanding conceptus.     

Changes in vascular perfusion of the endometrium in association with changes in location of the embryonic vesicle in mares

The equine embryonic vesicle is mobile on Days 12-14 (Day 0 = ovulation), when it is approximately 9-15 mm in diameter. Movement from one uterine horn to another occurs, on average, approximately 0.5 times per hour. Mobility ceases (fixation) on Days 15-17. Transrectal color Doppler ultrasonography was used to study the relationship of embryo mobility (experiment 1) and fixation (experiment 2) to endometrial vascular perfusion. In experiment 1, mares were bred and examined daily from Day 1 to Day 16 and were assigned, retrospectively, to a group in which an embryo was detected (pregnant mares; n = 16) or not detected (n = 8) by Day 12. Endometrial vascularity (scored 1-4, for none to maximal, respectively) did not differ on Days 1-8 between groups or between the sides with and without the corpus luteum. Endometrial vascularity scores were higher (P < 0.05) on Days 12-16 in both horns of pregnant mares compared to mares with no embryo. In pregnant mares, the scores increased (P < 0.05) between Day 10 and Day 12 in the horn with the embryo and were higher (P < 0.05) than scores in the opposite horn on Days 12-15. In experiment 2, 14 pregnant mares were examined from Day 13 to 6 days after fixation. Endometrial vascularity scores and number of colored pixels per cross-section of endometrium were greater (P < 0.05) in the endometrium surrounding the fixed vesicle than in the middle portion of the horn of fixation. Results supported the hypothesis that transient changes in endometrial vascular perfusion accompany the embryonic vesicle as the vesicle changes location during embryo mobility.     

Role of progesterone in mobility, fixation, orientation, and survival of the equine embryonic vesicle

Luteal progesterone was removed by an injection of prostaglandin F(2alpha) or bilateral ovariectomy on Day 12 of pregnancy in pony mares. The embryonic vesicle remained mobile in the uterus until loss occurred on Days 13, 13, 15, or 19 in four prostaglandin-treated mares and Days 15, 17, 19, or 26 in four ovariectomized mares. Exogenous progesterone given daily, starting on Day 12, maintained pregnancy until Day 40 in five of five prostaglandin-treated and three of four ovariectomized mares. During two-hour mobility trials on Day 14, embryonic vesicles in mares without luteal or exogenous progesterone (n = 9) moved to a different uterine segment less frequently (mean number of location changes per two-hour trial: 7.2 +/-1.0 vs 10.4 +/-1.1, P < 0.05) and were observed more often in the uterine body (14.9 +/-2.9 vs 8.9 +/-1.3, P < 0.10) compared to vesicles in mares with a progesterone influence (n = 15). Of mares that still had a vesicle present on Day 18, fixation occurred by Day 17 in all (12 12 ) mares under the influence of luteal or exogenous progesterone but failed to occur in the three mares that were not under progesterone influence. Progesterone replacement was started on Day 16 in three mares that received prostaglandin F(2alpha) on Day 12 and still had a vesicle on Day 16. The vesicle was maintained and continued to develop in all three mares, indicating that the vesicles were viable four days after PGF(2alpha) treatment. However, fixation tended to be delayed (P < 0.15) and orientation of the embryo proper was altered (P < 0.005) compared to mares that were continuously under the influence of progesterone. The results demonstrated the importance of luteal progesterone to mobility, fixation, orientation, and survival of the embryonic vesicle.     

Mobility of the conceptus and uterine contractions in the mare

Location of the embryonic vesicle within the uterus of mares was recorded every. five minutes for two consecutive hours (25 location determinations per trial) in three experiments. In Experiment 1 (n=7), the number of location changes among nine uterine segments (three body segments and three segments for each horn) was greater (P<0.05) on Day 13 than on Day 10. The vesicle was located in the body more frequently (P<0.05) and tended (P<0.1) to move to a more caudal position more frequently on Day 10 than on Day 13. Fixation occurred on Day 15 in four of seven mares and on Day 16 in the remaining three mares. The number of location changes was not significantly different between two days prior to fixation and one day prior to fixation. In Experiment 2, the effect of clenbuterol, a B₂ sympathomimetic blocker of uterine contractions, was studied on Days 12 or 13 of pregnancy. Location changes occurred less frequently (P<0.05) in treated mares (n=9) than in controls (n=10), indicating involvement of uterine contractions in the mobility of the embryonic vesicle. In Experiment 3, when the initial direction of location changes was caudal within a horn and cranial within the uterine body, the vesicle was more likely (P<0.05) to continue moving in the same direction than in the opposite direction. However, when the direction within a horn was cranial, the next location change was as likely to be in the opposite direction as in the same direction (not significantly different from equality). When the direction within the uterine body was caudal, the next location change was more likely (P<0.05) to be in the opposite direction.     

Uterine contractile activity in mares during the estrous cycle and early pregnancy

Transrectal ultrasonography was used to quantitate uterine contractile activity during the estrous cycle and early pregnancy in pony mares (nonbred, n = 9; pregnant, n = 16). Continuous 1-min scans of longitudinal sections of the uterine body were videotaped, and uterine activity scores (1=minimal activity, 5=maximal activity) were assigned to each tape segment. There was a tendency (P<0.06) for a main effect of reproductive status (nonbred versus pregnant), a main effect of day (P<0.0001), and a reproductive status by day interaction (P<0.006). Uterine activity scores were higher (P<0.05) in pregnant mares on Days 1, 11, 12, and 17 (Day 0=day of ovulation) than in nonbred mares. Maximal activity in pregnant mares occurred on Days 11 to 14 during the reported period of maximal embryo mobility. Activity scores decreased (P<0.05) between the day prior to and the day of fixation (mean = Day 15) of the embryonic vesicle. Activity scores were maintained at an intermediate level for several days following fixation before declining to minimal levels by 7 d postfixation. A postovulatory decrease (P<0.04) in activity scores was observed in nonbred mares, but not in pregnant mares, between Days 0 and 1 followed by a progressive increase (P<0.03) between Days 2 and 4. Maximal activity in nonbred mares occurred during the late luteal phase (Days 13 to 14), corresponding temporally to the reported onset of luteolysis.     

Embryonic loss in mares: Pregnancy rate, length of interovulatory intervals, and progesterone concentrations associated with loss during days 11 to 15

Pregnancy rates, length of interovulatory intervals, and progesterone concentrations were examined in mares which had ultrasonically detected collections of fluid in the uterine lumen and in mares which lost the embryonic vesicle during Days 11 to 15 and did not become pseudopregnant. In mares with embryonic loss, the loss rate for mares with re-established pregnancies (9 18 ) was greater (P<0.05) than the loss rate for all pregnancies (38 154 ), indicating repeatability. Pregnancy rates were higher (P<0.01) in controls (100 177 ) than in mares with intrauterine fluid collections (2 34 ) or mares with embryonic loss (10 33 ), excluding the pregnancy associated with embryonic loss. The mean length (days) of the interovulatory interval was reduced (P<0.05) in mares with intrauterine fluid collections (20.4 +/-0.9) and in mares with embryonic loss both for the intervals in which loss occurred (19.6 +/-0.7) and for intervals in which pregnancy was not detected (21.0 +/-1.0; controls, 23.5 +/-0.6). Mean progesterone concentration (ng/ml) on Day 7 was lower (P<0.05) in mares with intrauterine fluid collections (8.8 +/-1.8) and in mares with embryonic loss (12.1 +/-1.1) than in pregnant controls (17.2 +/-0.9) and nonpregnant controls (17.5 +/-0.1). The embryonic loss seemed attributable to uterine-induced luteolysis in association with uterine inflammation, but the possibility of involvement of a primary luteal inadequacy or other factors in at least some of the mares was not eliminated.     

Characterization of intrauterine mobility of the early equine conceptus

Intrauterine mobility patterns of the embryonic vesicle were characterized on Days 9 to 17 after ovulation in pony mares using real-time ultrasonography (n=5 or 7 mares per day). The location of the vesicle was determined by dividing the uterus into right horn, left horn, and body. Each uterine horn was further divided into three approximately equal portions (cranial third, middle third, caudal third), yielding seven segments (body plus three portions of each horn). Location of the vesicle within the uterus was recorded every five minutes for two consecutive hours (25 location determinations per trial). The number of times the vesicle was found in the uterine body versus one of the uterine horns was greater for the body on Day 9 (15.2 vs 9.8; not significant) and Day 10 (17.3 vs 7.7 P<0.05) and greater (P<0.05) for the horns on Days 12 (7.3 vs 17.7) through 17 (0.0 vs 25.0). Averaged over all days, when the vesicle was in one of the uterine horns it was present 56% of the time in the caudal third, 30% of the time in the middle third, and 14% of the time in the cranial third. Mobility was determined by the number of times the vesicle changed locations during successive examinations. On Day 9, the mean number of location changes per trial was minimal (horn to horn, 0.2; body to horn or vice versa, 1.8; between two segments, 4.2). The extent of mobility increased on Day 10 and reached an apparent plateau from Day 11 to Day 14. The mean number of location changes per trial during the plateau was as follows: horn to horn, 1.6; body to horn or vice versa, 5.6; between two segments, 10.7. Fixation (cessation of mobility) occurred in one of the horns in 5 7 mares on Day 15 and in 7 7 mares by Day 16. Mobility was present on the earliest day the embryonic vesicle was detected (Day 9), but Days 11 to 14 were characterized as the days of maximum mobility.     

Transrectal Doppler sonography of uterine blood flow during early pregnancy in mares

Transrectal color Doppler sonography was used for the noninvasive investigation of uterine blood flow in five mares. Both the left and right uterine arteries were scanned to obtain blood flow velocity waveforms during two consecutive estrous cycles and two early pregnancies in each mare. Blood flow was expressed as the time-averaged maximum velocity (TAMV) and the resistance index (RI). In all pregnancies the embryonic vesicle could be detected for the first time on Day 11 (day of ovulation: Day 0). No differences in mean TAMV and RI values of both uterine arteries were observed in comparison to the corresponding days of the estrous cycle until Day 11 of pregnancy (P>0.05). From Day 11 onwards, mean TAMV values were higher and mean RI values lower in pregnant mares than in cyclic mares (P<0.05). During the estrous cycle TAMV and RI values did not differ between the right and left uterine arteries (P>0.05). From Days 15 to 29 of pregnancy, TAMV values were consistently higher and RI values lower in the uterine artery ipsilateral to the conceptus and they had a more distinct rise and decline, respectively, compared to the contralateral uterine artery (P<0.05). The variance component estimates for the effect of mare on TAMV and RI values during pregnancy were 60 and 53%, respectively, and for the effect of day of pregnancy, they were 29 and 34%, respectively (P<0.0001). Within mares there were no significant differences between the two pregnancies with regard to blood flow (P>0.05). The results show that uterine blood supply increases in mares during the second week of pregnancy compared to cyclic mares. Furthermore there are individual variations in blood flow between mares.     

Effects of estrous cycle and season on ultrasonic uterine anatomy in mares

The morphological changes in ultrasound images of the uterus at various times of the year were characterized in nonbred mares, using a linear-array scanner. The uterus was recorded as having an ultrasonic morphology characteristic of diestrus (uterine score 1, endometrial folds not visible), estrus (score 3, distinct endometrial folds), or an intermediate stage (score 2). In Experiment I, uterine scores for the first ovulatory period of the year were compared to scores for the second period in 23 pony mares. More mares (P<0.05) showed endometrial folding prior to the second ovulation of the year (14 23 ) than prior to the first (5 23 ). Mean uterine scores were higher (P<0.05) on Day -10 (ovulation = Day 0) and tended to be higher (P<0.1) on Days -14, -13, and -11 of the first ovulatory period than on the corresponding days of the second period. Uterine scores for the first ovulatory period were lower (P<0.05) on Days -5, -4, -3, -2, -1, and 0 and tended to be lower (P<0.01) on Day -6. In addition, the pattern of change in uterine scores paralleled the pattern of change in the intensity of estrous behavior. In Experiment II, in 20 horse mares, the curve for uterine scores during interovulatory intervals in May-June, but not in September-October, was bimodal due to a small rise (P<0.05) and subsequent return to baseline between Days +3 and +6. The mean uterine scores for both May-June and September-October began to increase on Day -7 or -8, reached maximum on Day -3, declined between Days -2 and 0, continued to decline after Day 0, and reached a value characteristic of diestrus by Day +2. Results indicated that the ultrasonic characteristics of the uterus may provide an instant indicator of estrogen exposure and may have practical value in judging the optimal time to breed.     

An early endometrial vascular indicator of completed orientation of the embryo and the role of dorsal endometrial encroachment in mares

The spherical equine embryonic vesicle is mobile throughout the uterine lumen for several days before becoming fixed in the caudal segment of a uterine horn on Day 16 (ovulation = Day 0). Orientation refers to the position of the embryo proper at the periphery of the vesicle relative to the position of the mesometrial attachment. In mares, the embryonic pole of the vesicle is antimesometrial after completion of orientation. Day of vesicle fixation, differential thickening of the endometrium near the mesometrial attachment, and orientation of the embryonic vesicle were studied in 30 ponies, using B-mode and color-Doppler transrectal ultrasonography. The thickness of the endometrium at the mesometrial aspect of the vesicle divided by the thickness at the antimesometrial aspect was termed the encroachment ratio. At the future site of fixation, the first increase (P < 0.05) in the encroachment ratio occurred between 4 and 1 days before fixation. An early vascular indicator of the future position of the embryo proper was discovered by color-Doppler imaging and consisted of a colored spot in the image of the endometrium close to the wall of the embryonic pole. The early indicator was detected in each mare 0.5 +/- 0.1 days after fixation and 2.5 +/- 0.2 days before first detection of the embryo proper. The position of the early indicator when first detected at the periphery of the embryonic vesicle was not significantly different from the position of the embryo proper when first detected. Results supported the hypothesis that differential thickening of the endometrium precedes orientation and indicated that orientation occurs immediately after fixation.     

Hastened transport of equine embryos through the oviduct of the mare

The purposes of this experiment were 1) to test the hypothesis that placing rabbit embryos into the mare's uterus would hasten oviduct transport and 2) to determine if placing fluid into the uterus of bred mares on Day 4 and/or Day 5 would subsequently disrupt the mare's pregnancy. The hypothesis that placing rabbit embryos into the mare's uterus would hasten oviduct transport was not supported, since the uterine recovery rate of equine embryos on Day 5 was not significantly higher (P>0.05) for mares receiving rabbit embryos on Day 4 than for mares receiving no uterine infusion on Day 4 (1 10 vs 0 10 , respectively). However, placing fluid into the mare's uterus on Day 4 was apparently responsible for hastened oviduct transport, since mares with media infused into the uterus on Day 4 had a significantly higher (P<0.05) recovery rate of equine embryos on Day 5 than did mares receiving either rabbit embryos or no uterine infusion on Day 4 post ovulation (5 10 vs 1 10 or 0 10 , respectively). The Day-14 pregnancy rate was significantly higher (P<0.05) for mares receiving no uterine infusion on Day 4 or Day 5 than for mares receiving uterine infusion on Day 5 or uterine infusion on both Days 4 and 5 (9 10 vs 4 10 , 2 10 and 0 10 , respectively).     

Uterine transport of prostaglandin E(2)-releasing simulated embryonic vesicles in mares

Transrectal ultrasonography was used to test the hypothesis that prostaglandin E(2) (PGE(2)) would increase the uterine transport of simulated embryonic vesicles in mares. Uterine transport of PGE(2)-releasing (PGE) vesicles, vehicle-releasing (sham) vesicles, and equine embryos was contrasted on Day 12 or Day 13 post ovulation. In Experiment 1, there was no difference (P>0.10) in transport of PGE vesicles, sham vesicles, Day-12 embryos, and Day-12 embryos after cervical manipulation (n = 3 per group). In Experiments 2 and 3, respectively, transport of PGE and sham vesicles was contrasted with transport of Day-13 embryos after the vesicles (1 vesicle per mare) were placed into the uterine lumen with the embryo, (n = 7 per group). In Experiment 2, PGE vesicles were transported less often (P<0.05) from horn to body and from segment to segment than Day-13 embryos before vesicle insertion. In Experiment 3, sham vesicles were transported less often from horn to body (P<0.10) and from segment to segment (P<0.01) than Day-13 embryos before vesicle insertion. However, there was no difference (P>0.10) in the transport of PGE vesicles and embryos (Experiment 2) or sham vesicles and embryos (Experiment 3) together in the uterine lumen. In Experiment 4, transport of PGE and sham vesicles was contrasted by placing them together into the uterine lumen of nonpregnant mares on Day 13 (n = 7). There was no difference (P>0.10) in the transport of PGE and sham vesicles together in the uterine lumen. These results do not support the hypothesis that PGE(2) increases uterine transport of simulated embryonic vesicles. In addition, these results do not support the hypothesis that equine embryos stimulate uterine transport.     

Embryonic loss in mares: Nature of loss after experimental induction by ovariectomy or prostaglandin F(2alpha)

Twenty-one pregnant pony mares were assigned to one of the following groups: 1) controls, 2) ovariectomy at Day 12, 3) ovariectomy at Day 12 plus daily progesterone treatment on Days 12 to 40, 4) PGF(2alpha) on Day 12, 5) PGF(2alpha) on Day 21, and 6) PGF(2alpha) on Day 30. Based on daily examinations by ultrasound, the embryonic vesicle was maintained to Day 40 in all control mares and in mares that were ovariectomized on Day 12 and given progesterone. The embryonic vesicle was lost in all mares of the other four groups. Administration of progesterone prevented the embryonic loss associated with ovariectomy at Day 12, indicating that progesterone may be the only ovarian substance required for survival of the early embryo. The mean number of days to embryonic loss was greater for mares treated with PGF(2alpha) on Day 12 (6.8 days) than for mares ovariectomized on Day 12 (3.0 days). In the PGF(2alpha)-treated group, the vesicles did not become fixed at the expected time (Day 15), and mobility continued until the day of loss. In the mares treated with PGF(2alpha) on Day 21 and in one of the mares treated on Day 30, the vesicle was lost within one to three days without prior indication. Loss may have occurred by expulsion through the cervix, since the cervix was patent on the day of loss in these mares and in the mares ovariectomized or treated with PGF(2alpha) on Day 12. In the remaining mares treated on Day 30, the intact embryonic vesicle was dislodged on Day 31 or 32. The dislodged vesicle was mobile within the uterus and was frequently found in the uterine body. The fluid volume of the dislodged vesicle gradually decreased, and the fluid was no longer detected by Day 38 to 42. Some of the placental fluids may have been eliminated by resorption since the cervix remained closed while the fluid volume decreased.     

Effect of PGE2 on uterine contractility and tone in mares

A technique for transvaginal, ultrasound-guided intrauterine injection was developed. After preliminary study using different approaches, the procedure was successful in 24 of 25 (96%) mares, based on detecting fluid in the uterine lumen during and after the injection. The technique was used to study the effect of PGE2, reportedly produced by the embryonic vesicle, on uterine contractility on Day 12 (Day 0 = ovulation). Uterine contractility was scored (1 = minimal, 4 = maximal) every 10 min for 1 h and every 30 min for the next hour by a continuous 1-min ultrasound examination of a longitudinal section of the uterine body without knowledge of group. In Experiment 1, the main effect of group (1-mL vehicle, n = 6; 0.25 microgram PGE2, n = 7) tended to be significant (P < 0.09), and the effect of time was significant (P < 0.008). The mean score was higher for the PGE2 group (2.0 +/- 0.1) than for the vehicle group (1.7 +/- 0.1). An increase in contractility occurred between 0 and 5 min in the vehicle group (P < 0.0004) and between 0 and 10 min in the PGE2 group (P < 0.04). In Experiment 2, there was a tendency (P < 0.08) for effect of group (control without injection, n = 6; 1-mL vehicle, n = 6; 0.025 microgram PGE2, n = 6). The PGE2 group (2.0 +/- 0.1) was different from the vehicle group (1.6 +/- 0.1) and the control group (1.6 +/- 0.1). An increase in contractility occurred between 0 and 20 min in the PGE2 group, and the changes were not significant in the other groups. However, scores were higher in the PGE2 group before treatment, and there were no significant effects when data were converted to percentage changes. The results for an effect of intrauterine treatment of PGE2 on uterine contractility are considered uncertain because of the transient increase in contractility from vehicle injections in Experiment 1 and the higher score in the PGE2 group before treatment, with no significant differences in percentages in Experiment 2. Indirectly, however, an effect of PGE2 was suggested by a shorter (P < 0.05) period of detectability of intrauterine fluid in the PGE2 groups (21 +/- 31 min) than in the vehicle groups (50 +/- 42 min). The shorter period was attributable to greater dispersion of the fluid as a result of increased contractility. In Experiment 3, PGE2 (10 mg, n = 5) and vehicle (4 mL, n = 5) were given intravenously. In addition to uterine contractility, uterine tone was scored (1 = minimal, 4 = maximal) by transrectal digital compression. The main effect of group was significant (P < 0.03) for uterine contractility score, which increased between 0 and 20 min after PGE2 injection. The time effect and interaction were highly significant (P < 0.0001) for uterine tone score, and tone increased in the PGE2 group between 0 and 20 min after injection. The results indicated that PGE2 should be considered as a potential stimulator of both uterine contractions and uterine tone during the time of embryo mobility in mares.     

Effects of grazing endophyte-infected tall fescue on eCG and progestogen concentrations from gestation days 21 to 300 in the mare

The influence of grazing endophyte-infected tall fescue on endometrial cup formation and function, progestogen production, and embryonic and fetal development were examined in pregnant mares between Day 21 and Day 300 of gestation. Total immunoreactive progestogens and equine chorionic gonadotropin (eCG) concentrations were compared between untreated controls (endophyte-free, n = 12) and treated mares (endophyte-infected, n = 12). There were no differences in endometrial cup formation or function, as determined by eCG concentrations at Days 45, 60, 75, 90 and 120 (P > 0.05) between mares grazing endophyte-infected and endophyte-free tall fescue. Mares grazing the endophyte-infected tall fescue had lower total progestogen concentrations (P < 0.01) from Days 90 to 120 than the mares grazing endophyte-free tall fescue. Embryonic development based on mean vesicle height was not affected by endophyte exposure. No pregnancies were lost by mares in either treatment group during the trial period. The results of this study indicate that grazing endophyte-infected tall fescue between Day 21 and Day 300 does not alter endometrial cup formation and function, or result in increased pregnancy losses during this period. Lower progestogen concentrations between Days 90 and 120 with exposure to endophyte-infected tall fescue could reflect decreased luteal progesterone production.     

Fixation and orientation of the early equine conceptus

Fixation and orientation of the conceptus within the uterine lumen of 40 barren mares were examined by ultrasound daily on days 11-21 and at three-day intervals thereafter until day 48. The growth curve of the in situ conceptus had a distinct plateau between days 17-24, as determined by measurements of the width and area of conceptuses on the ultrasound images. The vesicle expanded at an average daily rate of 3-4 mm before the plateau and 2-3 mm after the plateau. Dramatic changes occurred in the shape of conceptus. The predominant shapes were approximately as follows: days 11-16, spherical; day 17, oblong; days 18-21, triangular; and days 24-48, irregular. The embryo was detected in some mares on day 20 and in most mares by day 21. When first detected, the embryo was always on the ventral aspect of the vesicle, opposite to the mesometrial attachment. The embryo gradually moved toward the mesometrial attachment over days 21-36 in association with the growth of the allantois beneath the embryo. It was hypothesized that: 1) vesicle fixation (cessation of mobility) was due to increasing uterine tone with impingement of the endometrial folds upon the vesicle, and 2) vesicle orientation was due to greater strength of the yolk sac wall at the embryonal pole coupled with greater impingement upon the vesicle by the dorsal uterine wall than by the ventral wall.     

Interaction of 4-hydroxylated estradiol and potential-sensitive Ca2+ channels in altering uterine blood flow during the estrous cycle and early pregnancy in gilts

This study was conducted to define further the role of catechol estrogens (CE) as intermediates in estrogen-stimulated uterine hyperemia. Previous studies from our laboratory strongly suggest that changes in uterine blood flow (UBF) result from alterations in uterine arterial tone (distensibility) and/or contractility (reactivity to alpha 1-adrenergic agonists). Tone changes appear to set the baseline rate of flow, whereas contractility changes result in short-term reductions in luminal diameter. Changes in uterine arterial tone and contractility result from alterations in Ca2+ uptake through potential-sensitive channels (PSCs) and receptor-operated channels (ROCs), respectively. Uterine and mesenteric arteries were removed from 6 gilts at estrus (Day 0), 9 gilts on Day 13 of gestation (high estrogen, high UBF), and 8 gilts on Day 13 of the estrous cycle (low estrogen, low UBF). Arterial measurements included initial tone (baseline perfusion pressure [BPP] to a constant intraluminal flow) and increased tone after exposure to KCl, the contractility in response to the alpha 1-agonist phenylephrine, and specific uptake of 45Ca before and after exposure to the CE 4-hydroxylated estradiol (4OH-E2). Contractility of uterine arteries from Day 13 nonpregnant (NP) and Day 13 pregnant (P) gilts to phenylephrine were similar and significantly greater (p less than 0.01) than contractility of vessels from estrous gilts. The BPP and responses of uterine arteries from Day 13 NP gilts to KCl were greater (p less than 0.05) than the BPP and responses of arteries from Day 13 P and estrous gilts, which were similar to each other.(ABSTRACT TRUNCATED AT 250 WORDS)     

Embryo loss following GnRH-induced ovulation in anovulatory mares

Two experiments were conducted using a 21-day GnRH analogue treatment regimen to induce ovulation in seasonally anovulatory mares. In Experiment 1, nontreated (n=20) and treated (n=83) mares were defined as having inactive ovaries (largest follicle相似文献