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).     

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.     

Prostaglandin E2 hastens oviductal transport of equine embryos.

The hypothesis that treatment of pregnant mares with prostaglandin E2 (PGE2) hastens the oviductal transport of equine embryos was tested by treating bred mares with PGE2 on Day 3 after ovulation and subsequently measuring the rate of hastened oviductal transport (estimated by the uterine embryo recovery rate on Day 4 after ovulation). In a preliminary, noncontrolled experiment, oviductal transport was apparently not hastened after intramuscular, intrauterine, or intraperitoneal PGE2 administration to bred mares (0/6, 0/3, and 0/3 mares, respectively). Oviductal transport appeared to be hastened in 1/13 mares after a single intraoviductal administration of PGE2, and in 2/2 mares after continuous intraoviductal administration of PGE2. In a subsequent, controlled experiment, treatment with a continuous intraoviductal infusion of PGE2 hastened oviductal transport in significantly more (p less than 0.01) mares versus a continuous intraoviductal infusion of vehicle or no treatment (6/11 vs. 0/11 or 0/11 mares, respectively). Unfertilized oocytes and oviductal masses were also recovered from mare uteri after continuous intraoviductal PGE2 administration, but were not recovered after vehicle administration or no treatment. These results support the hypothesis that PGE2 treatment hastens the oviductal transport of equine embryos, and suggest a role for embryonic PGE2 in the initiation of selective oviductal transport in the mare.     

Influence of exogenous progesterone on early embryonic development in the mare

The influence of exogenous progesterone on the development of equine oviductal embryos was determined based upon the recovery of Day-7 uterine blastocysts from treated mares (n=13) that were given 450 mg progesterone daily between Days 0 and 6 and from untreated control mares (n=13). Daily administration of 450 mg progesterone in oil significantly (P<0.02) increased serum progesterone concentrations in the treated mares. There was no significant difference in the recovery rate of Day-7 embryos between treated and control mares (8/13 versus 6/13, respectively). Embryonic development, assessed by morphologic evaluation, embryo diameter, and number of cell nuclei was not significantly different for embryos from treated and from control mares. The results of this study indicate that administration of progesterone beginning on the day of ovulation does not affect the embryo recovery rate or embryonic development, based on evaluation of uterine blastocysts recovered at Day 7 after ovulation.     

Survival of equine embryos co-cultured with equine oviductal epithelium from the four- to eight-cell to the blastocyst stage after transfer to synchronous recipient mares

In this study we examined the ability of equine oviductal epithelial cells (OEC) to support the development of four- to eight-cell equine embryos in vitro and investigated the ability of co-cultured embryos to continue normal development after transfer to synchronous recipient mares. Equine embryos obtained at Day 2 after ovulation were cultured with or without OEC for 5 days. Those OEC co-cultured embryos that reached the blastocyst stage and embryos recovered from the uterus at Day 7 were surgically transferred to synchronous recipient mares. Co-culture with OEC improved (P < 0.01) development of four- to eight-cell embryos to blastocysts compared to medium alone (11/15 vs 0/6) during 5 days in vitro. Embryos co-cultured with OEC were smaller (P < 0.05) and more delayed in development than Day-7 uterine blastocysts. There was no difference in the Day-30 survival rate of co-cultured blastocysts (3/8) or Day-7 uterine blastocysts (5/8) after transfer to recipient mares. These results indicate that co-culture with OEC can support development of four- to eight-cell equine embryos in vitro and that co-cultured embryos can continue normal development after transfer to recipient mares.     

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.     

Mobility of twin embryonic vesicles in mares

The patterns of intrauterine mobility and fixation of multiple embryos were studied by ultrasonography in 33 mares with twins, six mares with more than two embryos, and 18 mares with singletons. For both single and multiple embryos, the embryonic vesicles showed a preference for the uterine body on days 11 (57% in body) and 12 (58%) and for the uterine horns on days 13 (40% in body), 14 (20%), 15 (15%), and 16 (1%). The preference for the uterine body was characteristic of vesicles that were 3 to 9 mm in diameter. Based on the number of individual embryos which were in different locations between two successive daily examinations, fixation (cessation of mobility) occurred for 97% of the embryos by day 16 and for all embryos by day 18. For 33 mares with twins, fixation involved one uterine horn in 23 mares and both horns in 10 mares (significantly different from equality). Location determinations were made every five minutes during two-hour trials on days 12, 13, or 14 in nine mares with singletons and ten mares with twins. Individual embryos of twin sets had mobility patterns similar to those of singletons. Summed over singletons and twins, the vesicles moved from one horn to another a mean of 0.9 times per two-hour trial (equivalent to 11 times per day). The smaller embryo of twin sets on the average spent more time in the uterine body, but this finding was attributed to their smaller diameter. The observed frequency with which both embryos of twin sets were simultaneously in a given segment of the uterus (28%) was greater (P<0.01) than the expected frequency if each embryo moved independently of the other (18%). Results indicated that 64% of the location changes of twin embryos occurred independently of one another, supporting the hypothesis that the embryonic vesicle plays an active role in its mobility.     

Effects of postparturient uterine lavage on uterine involution in the mare

Eighteen postparturient mares were used to evaluate effects of uterine lavage on uterine involution. Mares were randomly assigned to one of three treatment groups: Group 1 (seven mares), no lavage; Group 2 (five mares), lavage on Day 3 post partum; and Group 3 (six mares), lavage on Days 3, 4, and 5 post partum. Five liters sterile physiologic saline, prewarmed to 42 degrees C, were used for each lavage. Transrectal ultrasound examination of the reproductive tract was performed on Day 11 post partum to detect the presence of free fluid in the uterine lumen, to estimate the cross-sectional diameter of the uterine horns and body, and to determine if ovulation had occurred. Endometrial biopsies were also taken on Day 11 post partum to evaluate endometrial histologic characteristics. Lavage had no effect (P>0.05) on diameter of the uterine body or previously gravid uterine horn, presence of fluid in the uterine lumen, or number of mares which had ovulated by Day 11 post partum. Histologic characteristics of the endometrium (height of luminal epithelium, gland depth, relative gland vclume, and inflammatory-cell score) were not affected by treatment (P>0.05). Postpartum uterine lavage did not significantly affect uterine involution by the parameters measured in normal-foaling mares at Day 11 post partum.     

Effects of cervical dilation and intrauterine infusions on the timing of oviductal transport of equine embryos

Equine embryos spend 5 to 6 d in the oviduct before entering the uterus as expanded blastocysts, and cannot be consistently collected nonsurgically until Day 7. Technologies such as cryopreservation and embryo splitting, which are most successful with embryos at the morula or early blastocyst stage, have not been used in mares because equine morulae and early blastocysts are located in the oviduct and cannot be recovered nonsurgically. These experiments test the hypothesis that transport of equine embryos through the oviduct can be hastened by cervical dilation or by acute, sterile endometritis induced by intrauterine oyster glycogen treatment. Cervical dilation with or without intrauterine infusion of 0.5 ml PBS on Day 4 did not appear to hasten the transport of embryos into the uterus since Day 5 uterine embryo recovery rates were not higher (P > 0.1) for mares with cervical dilation or cervical dilation plus PBS infusion vs mares receiving no treatments (0 of 5 and 0 of 5 vs 0 of 10, respectively). Intrauterine infusions of 40 ml of 1% oyster glycogen or 40 ml of PBS on Day 3 did not appear to hasten the transport of embryos into the uterus since Day 5 uterine embryo recovery rates were not higher (P > 0.1) for oyster glycogen- or PBS-treated vs untreated mares (2 of 12 and 3 of 11 vs 0 of 10, respectively). Cervical and uterine treatments on Day 3 or Day 4 and uterine lavages on Day 5 decreased (P < 0.05) Days 11 to Day 15 pregnancy rates compared with that of untreated mares. Day 11 to Day 15 pregnancy rates were 1 of 5 for mares with Day 4 cervical dilation and Day 5 uterine lavage, 1 of 5 for mares with Day 4 PBS infusion and Day 5 uterine lavage, 2 of 12 for mares with Day 3 oyster glycogen infusion and Day 5 uterine lavage, and 3 of 11 for mares with Day 3 PBS infusion and Day 5 uterine lavage vs 7 of 10 for mares that received no treatment or lavage. Cervical and uterine manipulations on Day 3 or 4 and uterine lavage on Day 5 appeared to decrease pregnancy rates by Days 11 to 15. The results of these experiments do not support the hypothesis that cervical dilation or uterine infusion hasten oviductal transport, since neither cervical manipulation nor transcervical infusion of oyster glycogen or PBS into the uterus significantly hastened the rate of embryo transport into the uterus.     

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.     

Autotransfer of Day 4 embryos from oviduct to oviduct versus oviduct to uterus in the mare

Embryo autotransfer is defined as the collection of an embryo from and the transfer of this embryo into the same animal. The objectives of this study were to: 1) test the hypothesis that oviduct transport of the equine embryo from the oviduct into the uterus is not dependent on a unilateral embryo-corpus luteum interaction, 2) develop an embryo autotransfer technique for the mare and 3) compare the success rates of Day 4 embryos surgically autotransferred from the oviduct ipsilateral to ovulation to either the oviduct (n=10 mares) or the uterine horn (n=10 mares) contralateral to ovulation. Seventy percent (7 10 ) of the Day 4 embryos which were autotransferred to the oviduct contralateral to ovulation were transported through the oviduct and subsequently developed into embryonic vesicles detectable by ultrasonography between 10 and 21 days postovulation. This finding supported the hypothesis that oviductal embryo transport is not dependent upon the ipsilateral corpus luteum. Overall, sixty percent (12 20 ) of the autotransfers were successful. The success rate of uterine-transferred embryos was not significantly less (P>0.3) than that of oviductal-transferred embryos (5 10 vs 7 10 , respectively). Therefore, the Day 4 equine embryos were apparently mature enough to survive in the mare's uterus.     

Prostaglandin E2 secretion by day-6 to day-9 equine embryos.

Prostaglandin E2 (PGE2) secreted by Day-6, Day-7, Day-8 and Day-9 equine embryos (ovulation = Day 0) during in vitro incubation was measured by radioimmunoassay. Embryonic PGE2 secretion (ng/embryo/24 hr) was detectable on Day 6 (0.27 +/- 0.39), tended to increase (P less than 0.1) on Day 7 (0.57 +/- 0.88), and increased significantly (P less than 0.05) on Day 8 (2.23 +/- 0.86) and Day 9 (4.13 +/- 0.71). Embryo diameter at the start of the incubation period was linearly correlated (P less than 0.01) to embryonic PGE2 secretion.     

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.     

Prostaglandin E2 secretion by oviductal transport-stage equine embryos.

This study was conducted to identify embryonic products whose secretion was temporally associated with the oviductal transport period of the mare. Chemicals secreted by oviductal-transport-stage equine embryos were identified by incubating Day 6 or Day 7 early uterine embryos with 35S-methionine/cysteine, 3H-progesterone, or 3H-arachidonic acid for 24 h, and subsequently identifying radioactively labeled proteins (SDS-PAGE; n = 3 embryos), steroids (HPLC; n = 3 embryos), or prostaglandins (HPLC; n = 3 embryos) in the culture medium. Early uterine embryos secreted 116.1 +/- 45.5 pg of prostaglandin (PG) E2/embryo, 1.0 +/- 0.2 pg of 17 alpha-hydroxy progesterone/embryo, 4.8 +/- 0.6 pg of androstenedione/embryo, and 11.5 +/- 4.5 pg of PGF2 alpha/embryo. They did not secrete detectable quantities of protein, testosterone, or estradiol-17 beta. A second experiment was conducted to measure temporal changes in embryonic PGE2 secretion during the oviductal and early uterine period. Day 3, Day 4, Day 5, and Day 6 embryos (n = 8 embryos/day) were incubated with 3H-arachidonic acid for 24 h, and the concentration of 3H-PGE2 in the culture medium was subsequently measured by HPLC. Embryos did not secrete detectable amounts of PGE2 prior to the expected time of oviductal transport (Day 3 and Day 4). They secreted 5.7 +/- 1.0 pg of PGE2/embryo immediately before and during the expected time of oviductal transport (Day 5), and they secreted significantly of PGE2/embryo immediately before and during the expected time of oviductal transport (Day 5), and they secreted significantly (p less than 0.01) higher amounts (42.0 +/- 11.5 pg) of PGE2/embryo immediately after uterine entry (Day 6).(ABSTRACT TRUNCATED AT 250 WORDS)     

Pregnancies following transfer of equine embryos cryopreserved by vitrification

The objective of this study was to investigate the in vitro and in vivo developmental abilities of equine embryos cryopreserved by vitrification. Twenty-eight embryos were recovered from Native pony and Thoroughbred mares at Days 5 to 7 by nonsurgical uterine flushing (detection of ovulation=Day 0). The vitrification solution contained 40% ethylene glycol, 18% Ficoll, and 0.3 M sucrose in PBS. The embryos were placed for 1 to 2 min in vitrification solution (Group 1) or following exposure to 20% ethylene glycol in PBS for 10 to 20 min (Groups 2 and 3). Single embryos were loaded in 0.25-ml straws, cooled for 1 min in liquid nitrogen vapor and immersed in liquid nitrogen. Straws were warmed in water (20 degrees C, 20 sec), and the contents were expelled with 0.5 M sucrose in PBS. Then the sucrose was diluted in 1-step (Groups 1 and 2) or 4-steps (Group 3). Embryos (n=21) were cultured for 120 h in TCM199 supplemented with 10% fetal bovine serum at 37 degrees C in 5% CO(2) in air and evaluated morphologically. Development to the hatching or hatched blastocyst stage was obtained in 0 7 , 4 7 and 4 7 embryos in Groups 1, 2 and 3, respectively. An additional 7 embryos were vitrified-warmed according to the treatment of Group 2 (4 embryos) and Group 3 (3 embryos). Five embryos were selected after in vitro culture for 4 h and were transferred nonsurgically into the uterine horn of Day-4 recipient mares. Transfer of 2 embryos (both Day-6 blastocysts: Group-2 treatment) resulted in pregnancies with a viable fetus at Day-60 of the gestation period.     

Survival of day-4 embryos from young, normal mares and aged, subfertile mares after transfer to normal recipient mares

The estimated embryonic loss rate between Days 4 and 14 after ovulation for young, normal mares (9%) was significantly lower (P less than 0.01) than the estimated embryonic loss rate for aged subfertile mares (62%). Fertilization rates, which were based on the recovery of embryos at Day 4 after ovulation, were 96% and 81% (P less than 0.1) for normal and subfertile mares, respectively. Day-4 embryos were collected from the oviducts of normal and subfertile donors mares. These embryos were transferred to the uteri of synchronized, normal recipient mares to test the hypothesis that the high incidence of embryonic loss in subfertile mares was related to embryonic defects. The hypothesis was supported because embryo survival rates were significantly higher (P less than 0.05) for Day-4 embryos from normal compared to subfertile mares. These defects may have been intrinsic to the embryo or might have arisen due to the influence of the oviducal environment before Day 4 after ovulation.     

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   

Embryo-initiated oviductal transport in mares.

The hypothesis that equine embryos initiate oviductal transport in mares was tested by placing day 6 uterine embryos in the oviducts of day 2 (n = 10) or day 5 (n = 10) recipient mares and attempting to collect the embryos from the uterus 48 h later. To determine whether the surgical transfer procedure initiated oviductal transport, medium alone was placed in the oviducts of day 2 (n = 10) inseminated mares (sham transfer), and uterine embryo collections were attempted 48 h later. Embryos were transported through the oviduct of day 2 recipients by day 4 (instead of day 5 to 6) in six of ten mares, which was not significantly less (P greater than 0.1) than in day 5 recipients (9 of 10). Oviductal transport was not primarily initiated by the surgical transfer procedure, since oviductal transport occurred in only one sham transfer. There was no significant difference (P greater than 0.1) in the diameter of embryos placed in the oviducts of day 2 and day 5 recipient mares (180 +/- 13.8 versus 187 +/- 11.3 microns, respectively). However, embryos collected from the uterus were significantly smaller (P less than 0.05) in day 2 than in day 5 recipients (375 +/- 85.4 versus 659 +/- 43.6 microns, respectively). One uterine embryo had shed its zona pellucida before being placed in, and transported through, the oviduct of the recipient mare.     

Corpus luteal function in nonpregnant mares following intrauterine administration of prostaglandin E(2) or estradiol-17beta

The objective of this study was to test the hypothesis that intrauterine administration of prostaglandin E(2) (PGE(2)) or estradiol-17beta (E-17beta) would prolong CL function in nonpregnant mares. Nonpregnant mares were continuously infused with 240 mug/d of PGE(2), 6 mug/d of E-17beta, or vehicle (sham-treated) on Days 10 to 16 post ovulation (ovulation = Day 0), using osmotic minipumps surgically placed into the uterine lumen on Day 10 (n = 11 per group). Nonpregnant and pregnant mares served as negative and positive controls, respectively (n = 11 per group). Mares were defined as having prolonged CL function if plasma progesterone remained > 2.5 ng/ml and if ovulation did not occur on Days 9 to 30. Corpus luteal function was prolonged until Day 30 in 1 11 nonpregnant mares, 4 11 sham-treated mares, 6 11 E-17beta-treated mares, 8 11 PGE(2)-treated mares, and 11 11 pregnant mares. The incidence of prolonged CL function was similar (P=0.16) in the sham-treated and nonpregnant mares. The hypothesis that PGE(2) would prolong CL function in nonpregnant mares was supported, since the incidence of prolonged CL function was higher (P=0.003) in PGE(2)-treated versus nonpregnant mares, tended to be higher (P=0.09) in PGE(2)-versus sham-treated mares, and was not lower (P=0.11) in PGE(2)-treated versus pregnant mares. The hypothesis that E-17beta would prolong CL function in nonpregnant mares was not supported, since the incidence of prolonged CL function was not higher (P=0.34) in E-17beta-versus sham-treated mares, and was lower (P=0.02) in E-17beta-treated versus pregnant mares. These results demonstrate that intrauterine administration of a pharmacologic dose of PGE(2) initiated prolonged CL function in nonpregnant mares. Further experiments are needed to confirm the role of conceptus secretion of PGE(2) in CL maintenance, and to determine the mechanism of action of PGE(2) within the equine reproductive tract.     

Mobility of the early equine conceptus

Movement of the conceptus within the uterine lumen of barren mares was studied by daily ultrasound examinations on days 11-20 and by rectal palpation on days 15-48 (Experiment 1) and by ultrasound examinations 3 or 4 times per day at 2-4 hour intervals on days 11-16 (Experiment 2). In addition, broodfarm records were analyzed to compare side of ovulation with side of embryo attachment (Experiment 3). The vesicle was found in opposite uterine horns for 43% of the successive, daily, ultrasound examinations on days 11 and 12, 12 and 13, 13 and 14, and 14 and 15; 24% of the successive examinations on days 15 and 16; and 8% on days 16 and 17. No movement was detected after day 17. The vesicle was found in opposite horns during 41% of the successive examinations at 2-4 hour intervals on days 11, 12, 13, 14, and 15, but no movement was detected on day 16. In addition, no transuterine migration was found by rectal palpation between the day of first detection of an embryonal enlargement (mean, day 17) and day 48. During ultrasound examination on days 11-15, the vesicle was found significantly more frequently in the left horn (66% of the observations) than in the right horn (34%); however, final attachment occurred more frequently in the right horn (63% of the mares). In analyses of brood-farm records, ovulation occurred with equal frequency in left and right ovaries in barren and lactating mares, but with significantly greater frequency in the left ovary (63%) in maiden mares. Regardless of the side of ovulation, final attachment of the conceptus occurred significantly more frequently in the right horn (66%) in barren and maiden mares, but not in lactating mares.