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.     

Ultrasonic evaluation of the corpus luteum of the mare

Two distinct luteal morphologies were observed in the ovaries of mares studied by daily ultrasound examinations. Luteal glands that formed after 48.5% of 95 ovulations were uniformly echogenic over 90 to 100 percent of the area of the image of the gland throughout the period of detectability. The remaining luteal structures (51.5%) exhibited a centrally located nonechogenic area. The nonechogenic area was first detected on day 0 (28%), day 1 (62%), day 2 (6%) or day 3 (4%) postovulation. Glands classified as centrally nonechogenic were echogenic over 80 to 100 percent of the area of the image of the gland on day 0; mean percentages of echogenic tissue decreased to 45 percent by day three then gradually increased to 95 percent before the glands became unidentifiable. The echogenic portion of the luteal glands of both morphologies had a bright echogenicity (gray-scale zone 4.5 to 5) on day 0. The echogenicity decreased (zones 3 to 3.5) by day 8 and was maintained at approximately that level until day 12. Mean gray-scale values tended to increase (zone 4 to 4.5) prior to the time the luteal glands became ultrasonically unidentifiable. These changes in grayscale values may have reflected changes in luteal hemodynamics. The nonechogenic area of centrally nonechogenic glands was attributed to clotted blood (corpus hemorrhagicum). The formation of a corpus hemorrhagicum was apparently not functionally important because it was present in only one half of the luteal glands. In addition, the mean length of time that the luteal gland was identifiable (17 days) or the mean length of the interovulatory interval (21 days) was not significantly different between the two luteal morphologies. Therefore, the hypothesis that the formation of a corpus hemorrhagicum is a necessary step in luteogenesis was not supported.     

Characterization of plasma progesterone concentrations for two distinct luteal morphologies in mares

Plasma progesterone concentrations in mares were determined in two experiments during the time that the luteal glands were detectable by transrectal ultrasonography. In both experiments, corpora lutea were classified into two tupes of morphologies based on their ultrasonic appearance: centrally nonechogenic luteal glands (fluid-filled) and uniformly echogenic luteal glands (non-fluid-filled). In Experiment 1, daily blood samples were taken from horse mares during August through October and May through July. There were no significant effects of season or luteal morphology on progesterone concentration. There was a significant main effect of day, but no day-by-season or day-by-morphology interactions. Progesterone increased significantly between Days 1 and 3 (mean progesterone concentration, 2.5 vs 5.2 ng/ml, respectively), between Days 3 and 4 (5.2 vs 7.8 ng/ml), and between Days 4 and 5 (7.8 vs 11.0 ng/ml). Progesterone did not decrease significantly until between Days 11 and 15 (11.6 and 6.1 ng/ml). Subsequent decreases occurred between Days 15 and 16 (6.1 vs 3.9 ng/ml), and Days 16 and 17 (3.9 vs 2.5 ng/ml). In Experiment 2, blood samples were obtained from pony mares at 1 2 - h intervals for 3 h before and 2 h after the defined onset of luteal development (end of evacuation of the ovulatory follicle). Additional blood samples were taken at 5, 8 and 12 h after the onset of luteal development, and thereafter at 12-h intervals for 5d. There were no significant differences between centrally nonechogenic luteal glands (n = 7) and uniformly echogenic luteal glands (n = 5) during the first 5 d of luteal development. There was no time-by-morphology interaction, but there was a significant time effect. The first significant increase in progesterone concentration occurred between Hours 12 and 24 (0.5 vs 1.1 ng/ml). Additional increases were detected between Hours 24 and 36 (1.1 vs 2.6 ng/ml), Hours 36 and 48 (2.6 vs 4.3 ng/ml), Hours 48 and 60 (4.3 vs 6.1 ng/ml), Hours 60 and 72 (6.1 vs 9.4 ng/ml), and Hours 72 and 96 (9.4 vs 13.8 ng/ml). The hypothesis was supported that fluid-filled corpora lutea do not differ from non-fluid-filled corpora lutea with regard to progesterone production.     

Ultrasonography for detection of pregnancy and study of embryonic development in heifers

Real-time B-mode ultrasonography was used to evaluate uterine changes associated with the estrous cycle in 22 ovulatory periods in 12 nulliparous heifers. Irregular, nonechogenic (black) areas were seen on the images of uterine horns during the periovulatory period. These nonechogenic areas were presumably due to intraluminal fluids since they coincided with the discharge of clear, viscous mucus preceding ovulation and blood-tinged mucus after ovulation. Eight heifers were bred until five pregnant heifers were obtained for study of the ultrasonic morphology of the conceptus. Ultrasound examinations were done daily to day 50 of pregnancy. Discrete, nonechogenic areas were first visible within the uterus between days 12 and 14, when they were approximately 2 mm in diameter. These discrete nonechogenic structures were identified as the embryonic vesicle, since they were observed only in heifers later confirmed to be pregnant and were always in the uterine horn ipsilateral to the corpus luteum. The presence of an embryo within the embryonic vesicle was confirmed by observing an echogenic (white) area with rhythmic pulsations (heartbeat). The embryonic vesicle gradually increased in length from the day of first observation until day 26 when it extended past the curvature of the horn and began to encroach into the contralateral horn. In all heifers, by day 32 the vesicle extended to the tip of the contralateral horn. The embryo was first visible between days 26 and 29 when the mean length was 10 mm. The embryo increased in length an average of 1.1 mm per day. A heartbeat was detectable in the embryo on the first day observed. In one superovulated heifer, five vesicles were visible in the uterine horns by day 14 and by day 33 seven embryos were observed; two of the seven embryos apparently resorbed by day 43.     

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.     

Embryonic loss in pony mares induced by intrauterine infusion of Candida parapsilosis

Pony mares which were detected pregnant by transrectal ultrasonography received a single intrauterine infusion of either sterile saline (control, n = 12 mares) or 10(6)Candida parapsilosis (treated, n = 12 mares) between Days 11 to 14 postovulation. Subsequent embryonic loss was studied by daily ultrasonography of the mare's uterus, by serum progesterone levels, by endometrial swabs for cytologic and microbiologic examination and by endometrial biopsies that were taken after embryonic loss was detected. Significantly fewer (P<0.01) embryonic losses occurred in control than in treated mares (4 12 vs 12 12 ). The mean interval from intrauterine infusion until embryonic loss was 5.8 +/- 2.8 d for control mares (n = 4) and 2.1 +/- 0.2 d for treated mares (n = 12). Prior to embryonic loss, moderate to marked edema of the endometrial folds in 12 of 12 treated mares and free fluid in the uterine lumen of 5 of 12 treated mares were detected by ultrasonography. After embryonic loss, Candida parapsilosis was cultured from the uteri of 8 of 12 treated mares, and E . coli was cultured from the uteri of 2 of 4 control mares. Postloss endometrial smears had cytologic evidence of inflammation in 10 of 12 treated mares and 3 of 4 control mares. Intrauterine inoculation of C. parapsilosis consistently induced embryonic loss and may provide a basis to further study the relationship between endometritis and embryonic loss in mares.     

Mechanisms behind intrauterine device-induced luteal persistence in mares

Intrauterine glass balls are used to prevent oestrous signs in sports mares, but the mechanism of action is unknown. It has been suggested that the glass ball can mimic an embryo or act via an induced chronic uterine inflammation and absent or continuous low-grade prostaglandin (PG) release. The purpose of this study was to induce prolonged luteal function in mares using a small intrauterine device (IUD) and to study the mechanisms behind prolonged IUD-induced luteal function. A uterine swab and a biopsy specimen were obtained in early oestrus. A water-filled plastic ball, diameter 20mm and weight 3.6g, was inserted into the uterus 2-4 days after ovulation; the control mares underwent similar cervical manipulation without ball insertion. The mares were examined three times per week until day 23 and twice weekly thereafter until they returned to oestrus (transrectal palpation, ultrasonography and progesterone determination). The location of the IUD was recorded and ultrasound scans were video-recorded to assess the frequency of uterine contractions. When the mare returned to oestrus, a uterine swab and biopsy specimen were obtained and the bacteriological, cytological and histological (inflammation and glandular dilation) results compared with the samples obtained before the IUD insertion. The PG F(2alpha) metabolite levels were measured in the plasma of four control mares and eight IUD mares on days 11-16. The IUD induced a prolonged luteal phase in 75% of the mares (9/12; IUD-P); the mean dioestrous length was 57.0 days. The three mares that did not respond to the IUD (IUD-N) showed a mean dioestrous length of 15.7 days and the 12 control mares 16.1 days. The inflammation and glandular dilation scores were not significantly different in pre- and post-manipulation biopsy specimens. Although locational changes of the IUD were observed, they occurred over very small distances and were mostly limited within the body-bifurcation area. The IUD-N and control mares showed increased uterine contractility 11-16 days post-ovulation, whereas the IUD-P mares did not. The control mares (n=4) and IUD-N mares (n=2) showed increased PG levels from day 14 post-ovulation, while the IUD-P mares (n=6) showed basal levels only. We concluded that the IUD did not cause continuous PG release and suggest that close contact of the IUD with the endometrium may prevent the endometrial cells from releasing PGF(2alpha).     

Ultrasonographic assessment of the endometrium in rhesus monkeys during the normal menstrual cycle

This study was undertaken to determine whether cyclical changes in the endometrium of the rhesus monkey could be observed by using ultrasound. Three indices of endometrial size were examined: the antero-posterior (or ventro-dorsal), longitudinal, and transverse diameters. Changes in the ultrasonic reflectivity of the endometrium were also assessed. We have attempted to correlate these endometrial parameters with the hormonal status of the animal. Ultrasonography was performed for an average of 12 consecutive days during 19 menstrual cycles. All ultrasonic recordings were normalized to the day of the estradiol (E2) peak (Day 0). We found that the reflectivity of the endometrium was dependent on the stage of the cycle: during the follicular phase, the endometrium appeared less echogenic (darker) compared to the myometrium; in the luteal phase, the endometrium was more echogenic (lighter). During the follicular phase (Days -9 to 0), there was a linear increase in the antero-posterior (p less than 0.001), longitudinal (p less than 0.05), and transverse (p less than 0.001) diameters. In the luteal phase (Days 1-15), no significant changes were observed in these diameters. An estimated endometrial volume (EEV) was obtained by the product of the antero-posterior, longitudinal, and transverse diameters. Each animal observed during the follicular phase (n = 14) exhibited a peak in the EEV, which correlated with the day of the E2 peak (p less than 0.01). From this study, we conclude that the sonographic appearance of the endometrium of the rhesus monkey reflects the cyclical changes that occur during the menstrual cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphologic Evaluation of Acute Endometritis in Mares with Differing Resistance to Uterine Infections

The study was designed to determine differences between normal mares and mares with endometrial pathology in the inflammatory response after bacterial challenge. Six normal mares (biopsy category I) and 4 mares with pathological endometrial changes (biopsy category II) were given an intrauterine infusion of β-hemolytic streptococci on the second day of estrus. All mares had a similar kind of inflammatory response after the bacterial inoculation as assessed by rectal and vaginal examinations. There were no significant differences in the amount of discharge, uterine tone, uterine size and cervical relaxation between the groups. Leukocytic response, as determined by endometrial smears and biopsies, was of the same magnitude in both groups. Two mares from the pathological group were not able to eliminate the infection, but had vaginal discharge and bacteriologically positive uterine swabs until the end of the experiment. It is concluded that the inability of some mares to clear uterine infections cannot be explained by a deficient inflammatory response.     

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.     

Equine fetal kinetics: entry and retention of fetal hind limbs in a uterine horn

Transrectal ultrasonic examinations were made in 31 pregnant pony mares once a week during Months 6 to 11. Each uterine horn was divided into 3 approximately equal segments (caudal, middle, cranial). The percentage of examinations with cranial fetal presentation increased (P<0.05) progressively from 58% at Month 6 to 99% at Month 9 and was followed in all mares by entry of the fetal hind limbs into one uterine horn. The mean number of uterinehorn segments with limb parts increased (P<0.05) between each set of consecutive months from Month 6 to Month 10. Initially (Months 7 and 8), retraction of limbs after entry into the caudal and middle segments of the horn was common (31% incidence). The mean day of final entry of the limbs without detection of subsequent retraction was Day 230 +/- 2.2. Both uterine horns were closed during the examination preceding final entry of the hind limbs into one horn in 25 of 29 (86%) mares. The limbs reached the cranial segment in most examinations by Months 9 and 10 (73% and 98%). The cross-sectional height, as seen on the ultrasound screen, of both uterine horns increased (P<0.05) progressively during Months 7 to 10. Between Months 10 and 11, the height of the horn containing the limbs decreased (P<0.05); this result was attributable to a flattening of the horn and thinning (P<0.05) of the horn wall above a hoof and metatarsal bone. Apparent placental fluid (nonechogenic areas >5 mm in height) between the hind limbs and the cornual wall was detected in 0, 10, 25, and 63% (P<0.01) of examinations for Months 8 to 11, respectively. Results indicated that entry of the fetal hind limbs into a uterine horn was initially tentative and became final during a mean of Month 8. The apposition between the cornual wall and limbs was close during Months 7 to 11. By Month 11, the fetal-limb horn became flatter and thin-walled and usually contained placental fluid.     

Use of a semen extender containing antibiotic to improve the fertility of a stallion with seminal vesiculitis due to Pseudomonas aeruginosa

A breeding trial was conducted to determine if a semen extender containing polymixin-B sulfate would improve the fertility of a stallion with seminal vesiculitis due to Pseudomonas aeruginosa . Twenty-three mares were bred to the stallion by one of three methods: artificial insemination with raw semen (Group 1, n = 10), artificial insemination with semen mixed 1:1 with a nonfat dry skim milk/glucose extender containing 1000 units/ml polymixin-B sulfate (Group 2, n = 9), or natural service immediately following infusion of the uterus with 100 ml of the same extender (Group 3, n = 4). Artificial breedings contained a minimum insemination dose of 500 x 10(6) progressively motile spermatozoa. All mares were bred every other day while in estrus. Pregnancy status was determined by transrectal ultrasound examination 15 d after the last breeding. First-cycle pregnancy rate for Group 2 mares (78%) was greater (P < 0.01) than for Group 1 mares (10%). There was a tendency (P = 0.10) for the pregnancy rate of Group 3 mares (50%) to be greater than Group 1 mares. The use of a semen extender containing polymixin-B sulfate improved the fertility of this stallion.     

Short-term mode of secretion of equine chorionic gonadotrop in and the effect of GNRH

Five mature Quarterhorse mares were bled every 30 min for 25 h on day 50 of pregnancy to determine the short-term mode of secretion of equine chorionic gonadotropin (eCG). Three other mares with persistent endometrial cups after abortion were administered gonadotropin releasing hormone (GnRH; 1.0 mug/kg of body weight) and were bled immediately prior to and at 15, 30, 45, 60, 90, 120, 180 and 240 min after GnRH. Concentrations of eCG in plasma of pregnant mares were constant over the 24-h period; the variation of each mare's individual values was no greater (P>.05) than the predicted random variation of the radioimmunoassay. Administration of GnRH had no significant effect on eCG concentrations of mares with persistent endometrial cups over a 4-h period. These data are consistent with a model of eCG secretion in the pregnant mare in which there is little short-term regulation of secretion other than the factors which affect the number of healthy endometrial cup cells within the uterus.     

Postfixation embryo reduction in unilateral and bilateral twins in mares

Multiple ovulations were induced with a pituitary extract in mares, and the development of multiple conceptuses was monitored daily by ultrasound on days 11 to 40. The incidence of abortion (loss of all embryos) was not significantly different between mares with multiple embryos (5 38 mares; 13%) and mares with singletons (4 36 ; 11%). Embryo reduction (elimination of excess embryos) was not detected during the embryo mobility phase (days 11-15) or on the day of fixation of embryos (day 16) in any of 38 mares with multiple embryos. The incidence of postfixation embryo reduction for mares with twins was 64% (18 28 ); however, the incidence for unilateral twins (17 19 ; 89%) was greater (P<0.01) than for bilateral twins (1 9 ; 11%). Reduction of unilateral twin embryos seemed to occur earlier (53% before day 20 and 82% before day 30) than for the set of bilateral twins (day 36). The remaining embryo in all mares in which embryo reduction occurred seemed normal in size and appearance on the last day of examination. However, in four of eighteen mares in which unilateral reduction occurred, the umbilical cord of the remaining embryo was attached in the ventral hemisphere of the all antochorion. This apparent disorientation was not seen in any of 16 bilaterally located embryos or in 16 singletons.     

Pregnancy rates, LH and progesterone concentrations in mares treated with a GnRH agonist

The aim of the study was to investigate the effect of the GnRH agonist Buserelin given on day 10 after ovulation on pregnancy rate and concentrations of progesterone and LH. Altogether 191 warmblood mares were used for two trials. Fresh or frozen/thawed semen from 27 stallions was used for A.I. In trial A 171 mares received either Buserelin (Receptal, Hoechst, Germany, 40 microg/animal) or 10 ml 0.9% NaCl (placebo). On day 16 after A.I. pregnancy diagnosis was performed by ultrasound scanning of the uterus. For statistical analysis, data were analyzed by a mixed model, with four fixed factors (treatment, type of spermatozoa, A.I. number, reproductive status of the mare) and a random factor (stallion). Least Square Means (LSM) for pregnancy rate were 46.0% in GnRH agonist treated mares and 36.4% in the control group (P=0.22). In trial B 20 lactating and cycling mares were used for endocrine studies. Blood samples were recovered for analyses of progesterone and LH from days 0 to 11. The mean progesterone concentrations increased continuously from days 0 to 8 after ovulation in both groups (GnRH group: from 0.81+/-0.48 to 5.47+/-0.48 ng/ml, control group: from 0.63+/-0.68 to 5.83+/-0.68 ng/ml). Moreover, the progesterone concentrations from days 9 to 11 were not different between the GnRH and the control group. In contrast to this LH concentrations were markedly influenced by the GnRH agonist. On day 10 LH concentrations were significantly higher in GnRH agonist treated than in placebo treated animals. From the data obtained from individual animals it can be concluded that GnRH agonist, given during luteal phase may have different effect on luteal function.     

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.     

Embryo transport through the mare's oviduct depends upon cleavage and is independent of the ipsilateral corpus luteum.

Two experiments were conducted using 14 mares. In Exp. 1, mares were inseminated with semen treated with TEPA, which, in other species, has been shown to lead to an arrest in ovum cleavage at 2--4 cells. The oviducts and/or uterus were then flushed 7--10 days after ovulation in 6 mares (Group A) or 2--6 days after ovulation in 5 mares (Group B). Fresh eggs were found in the oviduct flushes of 5 Group A and 5 Group B mares: 9 of the 10 eggs appeared to have cleaved, but none had developed beyond 16-cells. Seven eggs contained spermatozoa and 3 of 4 eggs from each group showed evidence of fertilization when examined ultrastructurally. Group A mares had thus retained fertilized eggs in the oviduct beyond the time at which they would normally have entered the uterus (6 days), indicating that development beyond at least the 2- to 4-cell stage is necessary for normal transport. In Exp. 2, 5 attempts were made to recover the embryo within 4 days of ovulation and transfer it to the contralateral oviduct. A single pregnancy resulted, indicating that a unilateral interaction with the corpus luteum was not necessary for the transport of the embryo to the uterus.     

Ultrasonographic evaluation of uterine involution and postpartum follicular dynamics in French jennies (Equus asinus)

Uterine involution and follicular dynamics during postpartum period were studied ultrasonographically in French jennies. For the study of uterine involution in postpartum jennies (n = 6, Group S), sonographic measurements of different parts of the uterus and endometrium were made at three-day interval, starting from the day of foaling and continued up to 33 days postpartum. Uterine dimensions were also recorded in non-pregnant jennies (n = 3, Group C) throughout a cycle and compared with the dimensions of Group S jennies observed on the day of complete involution. Follicular dynamics of first and second postpartum ovulatory cycles were studied and compared with that of the single estrous cycle of Group C jennies. Jugular venous blood samples of Group S jennies were collected at weekly intervals for 49 days, commencing at the appearance of first preovulatory follicle, to support the sonographic findings. The average involution period was 22.5 +/- 1.7 days. However, it was significantly delayed (P < 0.05) in jennies which came into first postpartum ovulatory heat within Day 9 than those who came later (25.0 +/- 1.0 versus 20.0 +/- 1.0). The endometrial layer was not discernible beyond Day 15 postpartum and thus was found to be unreliable index of uterine involution. The follicular growth rate (mm per day) and diameter (mm) of preovulatory follicle in postpartum jennies were similar to that in normal cycling jennies (P > 0.05). The first and second ovulations occurred at 14.6 +/- 0.8 and 39.0 +/- 0.8 days postpartum in Group S jennies. All the corpora lutea, either echogenic or centrally non-echogenic were functionally similar and had similar life span (P > 0.05). In conclusion, the postpartum reproductive events related to uterine involution and ovarian cyclicity apparently resemble that of mares.     

Prostaglandin H synthase Type 2 is differentially expressed in endometrium based on pregnancy status in pony mares and responds to oxytocin and conceptus secretions in explant culture

The equine embryo must signal its presence to the uterus for pregnancy to continue to term. Mobility of the conceptus throughout the uterus is crucial for its survival, and this action presumably permits the conceptus to transmit its antiluteolytic signal to the endometrium. Studies were completed to establish whether this unidentified antiluteolytic signal targets prostaglandin G/H synthase 2 (PGHS2), a rate limiting enzyme in converting arachidonic acid to prostaglandins (PGs). In the first study, quantitative RT-PCR was used to determine the relative abundance of PGHS2 mRNA in endometrium derived from estrous cyclic and pregnant mares on day 14 post-ovulation. PGHS2 mRNA abundance was substantially greater in endometrium from estrous cyclic mares. Additional studies were completed to better understand PGHS2 in equine endometrium. An estrogen and progesterone treatment regimen in ovariectomized mares was developed as a test model for detecting endometrial PGHS2 mRNA. Also, exposing endometrial explants to conceptus secretions (conditioned culture medium) decreased PGHS2 mRNA abundance whereas exposing explants to oxytocin increased PGHS2 mRNA abundance. Exposure to conceptus secretions also decreased PGF2α concentrations in explant-conditioned medium whereas oxytocin supplementation increased PGF2α concentrations in medium. These data support the hypothesis that PGHS2 is a target for the antiluteolytic signal produced by equine conceptuses during early pregnancy. Also, the endometrial explant culture system used for these studies can serve as a model for identifying and characterizing the maternal recognition of pregnancy factor in equids.     

Real time ultrasonic monitoring of hepatic cryosurgery

Cryosurgery has a number of advantages that make it particularly appealing in the treatment of liver cancer. However, a major problem in the clinical application of hepatic cryosurgery is the lack of a precise means of monitoring the freezing process in situ. Preliminary investigations on simulated tissue have shown that standard ultrasonography is capable of accurately determining the amount of frozen material during a cryosurgical procedure. To extend these results to living tissue, cryosurgery was performed, in vivo, on the livers of four mongrel dogs. An ultrasound imaging device using a new intraoperative ultrasound transducer monitored the entire process in real time. The results indicate that the entire freezing and thawing cycle can be monitored easily using real time ultrasound. During freezing, the solidification interface can be seen to move through the tissue allowing clear imaging of the cryolesion. After complete thawing, the cryolesion became less echogenic than before freezing and was therefore distinguishable under ultrasound. Postsurgical pathologic examination showed excellent correlation between the lesion size and its ultrasonic image.