Luteinizing hormone, oestrogen and progesterone levels in peripheral serum of anoestrous and cyclic ewes as determined by radioimmunoassay.

Jugular vein blood was collected daily from four mature ewes throughout anoestrus and the first oestrous cycle of the breeding season until 4 days after the second oestrus. The levels of oestrogen, progesterone and LH were determined by radioimmunoassay. There were fluctuations in the LH level throughout most of the observed anoestrous period with a mean plus or minus S.E. value of 2-3 plus or minus 0-9 ng/ml. High LH values of 20-0, 41-2 and 137-5 ng/ml were observed in three ewes on Day - 24 of anoestrus. A brief minor rise in progesterone level was also observed around this period. Progesterone levels were consistently low (0.11 plus or minus 0-01 ng/ml) before Day - 25 of anoestrus. A major rise occurred on Day - 12 of anoestrous and this was followed by patterns similar to those that have been previously reported for the oestrous cycle of the ewe. Random fluctuations of oestrogens deviating from a mean level of 4-40 plus or minus 0-1 pg/ml were observed during anoestrus and the mean level during the period from the first to the second oestrus was 5-2 plus or minus 0-3 pg/ml. A well-defined peak of 13-3 plus or minus 0-7 pg/ml was seen in all ewes on the day of the second oestrus. Results of the present study suggest that episodic releases of LH occur during anoestrus and periods of low luteal activity. The fluctuations in LH levels, as observed during the period of low luteal activity, i.e. before Day - 25 of anoestrus, were less pronounced during the periods of high luteal activity. The view that luteal activity precedes the first behavioural oestrus of the breeding season is supported.     

Total unconjugated oestrogen and progesterone concentrations in peripheral blood during the oestrous cycle of the dog.

From the beginning of pro-oestrus to the end of metoestrus, daily peripheral blood samples were withdrawn from six bitches. Further samples were obtained during anoestrus. Oestrogen values rose from the onset of pro-oestrus to attain a peak value of 25-3 +/- 4-8 pg/ml on Day 1 of oestrus. Progesterone concentrations began to rise 2 days before the oestrogen peak, and reached their highest levels of 18-9 +/- 1-0 ng/ml 16 days after the end of oestrus. After oestrus, an oestrogen rise was detected which reached a peak at Day 18 of metoestrus. The duration of oestrus was unrelated to the length of time that oestrogen levels were raised, or the maximum values were attained. No significant oestrogen levels were detected during anoestrus.     

Pregnancy, lactation and the oestrous cycle of the pouched mouse, Saccostomus campestris

The anatomy and histology of pouched mouse ovaries were studied during the oestrous cycle, pregnancy and lactation along with the relationship between the ovarian structures and circulating concentrations of progesterone. The structure of the ovaries resembled that of most rodents. Follicular development indicated that ovulation takes place on the night between pro-oestrus and oestrus, i.e. at the time when mating normally occurs. Corpora lutea were accumulating in cyclic females, while successively disappearing during pregnancy, leaving only the set formed after conception. After parturition luteal regression was rapid. Theca interna, included in the corpora lutea, formed glandular stromal tissue after regression of the luteal tissue formed from granulosa cells. The progesterone profile of non-pregnant females indicated a short but functional luteal phase (peak at metoestrus) during the cycle. During pregnancy three peaks of progesterone stood out: (1) when implantation starts, (2) when older sets of corpora lutea showed rejuvenation and placental signs were found in the vaginal smears, and (3) 3 days before expected parturition when luteal development (as judged by histology) reached a peak. The placenta may participate in but not 'take over' the progesterone production during later stages of pregnancy. Very low concentrations of peripheral progesterone during lactation and a very low level of follicular development at that time support an earlier suggestion of a lactational anoestrus in pouched mice.     

Effect of diethylstilboestrol on the relationship between LH, PMSG and progesterone during pregnancy in the mare.

Two studies were conducted to determine the relationship between LH and progesterone and between PMSG and progesterone during pregnancy in mares. In the first, samples of jugular blood were collected daily from 7 mares from the first day of oestrus until Day 28 of pregnancy, and in the second, samples were collected weekly from 14 mares from Day 35 of gestation until parturition. In an attempt to prolong secretion of progesterone from accessory corpora lutea, 7 of these 14 mares were injected with increasing doses (2--10 mg) of diethylstilboestrol (DES) between Days 84 and 142 of gestation. The remaining 7 mares received injections of vehicle. Concentrations of LH, PMSG and progesterone in serum were determined by radioimmunoassay. From the onset of oestrus until Day 4 of gestation, serum concentrations of LH and progesterone were negatively correlated (r = 0.67, P less than 0.01), but from Days 5 to 28 a positive correlation (r = 0.80, P less than 0.01) was noted. Likewise, serum concentrations of PMSG and progesterone were highly correlated between Days 35 and 196 in mares injected with DES (r = 0.72, P less than 0.01) and the vehicle (r = 0.75, P less than 0.01). Injections of DES did not influence serum concentrations of LH, PMSG or progesterone, or affect the length of gestation. It was concluded that DES does not influence the maintenance of pregnancy in the mare.     

Cholinesterase Activities in Uterus of Normal and Fenchlorphos Treated Blue Foxes (Alopex Lagopus) during Various Reproductive States

The uterine acetylcholinesterase and total cholinesterase (acetylcholinesterase plus butyrylcholinesterase) activities in normal and fenchlorphos treated blue fox vixens were determined during various reproductive states. AChE and Total-ChE of non-medicated vixens in oestrus were about one half of those in anoestrus. In pregnant uteri (luteal phase) the activities were 25 % and 30% compared to anoestrus. In vixens given 100 mg/kg fenchlorphos for 3 weeks during anoestrus, the remaining activity of AChE in uterus were in average 37%. Pregnant and non-pregnant vixens in the luteal phase medicated prior to mating and during time of implantation, displayed AChE activities which were only moderabely reduced (remaining activities 83% and 72% compared to medicated animals in anoestrus: remaining activity 37%). Plasma ChE-activity increased during pregnancy in the controls while enzyme activity was strongly reduced in animals given 100 mg/kg fenchlorphos daily through the whole pregnancy. It was concluded that the previous reported embryotoxic effect of fenchlorphos in the blue fox did not seem to be directed towards the moderate inhibition of the uterine cholinesterases.     

Long-term reversible suppression of oestrus in bitches with nafarelin acetate, a potent LHRH agonist

Adult cyclic beagle bitches were treated for up to 18 months with nafarelin acetate via subcutaneously implanted osmotic pumps, starting during the first week of a pro-oestrous vaginal discharge. The imminent ovulation appeared to be unaffected by treatment, but doses of 8 or 32 micrograms analogue/day reduced the integrated luteal progesterone values. No new oestrus was detected in 3 bitches during 18 months of treatment with 32 micrograms/day, which resulted in mean plasma levels of 0.4 ng analogue/ml. A return to oestrus was observed in all 3 bitches between 3 and 18 weeks after cessation of treatment: 2 of the bitches mated at those times and produced normal litters. Another 2 bitches were similarly treated with 32 micrograms analogue/day; they were mated at the oestrus at start of treatment and dosing was continued for about 63 days. One of the bitches conceived and produced a normal litter. Nafarelin acetate treatment begun during anoestrus resulted in an induced heat 1-2 weeks after the start of treatment. The induced heat consisted of pro-oestrous vaginal discharge, oestrous vaginal cytology, and ovulation (judged by increased circulating levels of progesterone). Three bitches mated at the induced heat and treated for the normal duration of gestation did not litter. Nafarelin treatment of 3 bitches before puberty did not induce signs of oestrus and prevented the occurrence of oestrus through 18 months of treatment. The first oestrus in these bitches occurred 3.5-4 months after cessation of treatment, but mating at that time did not result in pregnancy. These studies have established the feasibility of and dosage requirement for the use of the LHRH agonist as a contraceptive in the bitch.     

Two-dimensional polyacrylamide gel electrophoresis of proteins synthesized and released by conceptuses and endometria from pony mares

Conceptuses were obtained from pony mares on each day of pregnancy between Days 12 and 28, and on Days 39, 45, 65 and 100. Endometrium was obtained from mares at Days 12, 14, 16, 18, 39, 45, 65 and 100 of pregnancy, and from non-pregnant mares during anoestrus, during transition into the breeding season, at oestrus, or during dioestrus. Tissues were incubated in vitro for 24 h with L-[3H]leucine. Proteins synthesized and released into the culture medium were analysed by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and fluorography. Conceptuses obtained before Day 14 after ovulation released a characteristic pattern of labelled proteins. These included two groups of apparent isoelectric variants of relative molecular weights (Mr) 30,000-40,000 (pI values 4.5-5.5 and 6-7), one group of Mr approximately 22,000 (pI 6.5-7), and large protein(s) that did not enter the 10% polyacrylamide gel. After Day 14 the array of labelled proteins had changed and resembled that produced by isolated yolk sac at the later stages of pregnancy studied. Included amongst these were several acidic polypeptides with Mr 20,000 (pI 5-6). The endometrial samples released an array of non-dialysable polypeptides into the culture medium. Fluorograms could be assigned to one of three general groups, with endometrium from mares within each group producing similar patterns of labelled proteins. The first group consisted of anoestrous, transitional and ovariectomized mares, and mares at oestrus or Day 1 or Day 18 after ovulation. The second group was comprised of mares at Days 12-16 of dioestrus or Days 12-18 of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Urinary steroid concentrations during natural and gonadotrophin-induced oestrus and pregnancy in the giant panda (Ailuropoda melanoleuca)

Urinary concentrations of conjugated oestrone and pregnanediol-3-glucuronide were measured during and after spontaneous and induced oestrus and during pregnancy. Behavioural oestrus was preceded by a rise in oestrone values from less than 10 ng/mg creatinine (Cr) to peaks of 45 ng/mg Cr. Maximal lordotic response and mating activity coincided with the decline in oestrone levels. After presumed ovulation, urinary pregnanediol glucuronide concentrations increased from less than 5 to 15-30 ng/mg Cr. Further increases in this steroid (to 60-80 ng/mg Cr) occurred 114 days after mating, presumably coincident with implantation. These high levels of pregnanediol glucuronide were maintained for 3 weeks, began to decline 1 week before parturition and fell to a nadir (less than 5 ng/mg Cr) immediately after delivery. When FSH was administered i.m. for 5 days, urinary oestrone values rose markedly and were maximal (580 ng/mg Cr) on Day 7. Mating first occurred on Day 20 and 500 i.u. hCG were given i.m. Urinary pregnanediol glucuronide levels during the next 5 months were similar to those in the previous year during pregnancy with values rising 105-108 days after mating. However, no birth occurred. These results support the suggestion that pandas exhibit delayed implantation and demonstrate that the panda is responsive to exogenous gonadotrophins.     

Peripheral plasma levels of oestradiol-17 beta and progesterone in the bitch during the oestrous cycle, in normal pregnancy and after dexamethasone treatment.

Plasma oestradiol-17 beta concentrations in Labradors increased during pro-oestrus to an average maximal concentration of of 79-7 +/- 10-9 (S.D.) pg/ml, and then fell rapidly. In 6/7 bitches the peak occurred within 1 day of oestrus. No consistent changes in plasma oestradiol levels were observed during pregnancy and at parturition and the values were similar to those in late anoestrus. Plasma progesterone levels did not increase markedly during pro-oestrus. At oestrus, progesterone values rose and maximal concentrations, which varied from about 20 to about 55 ng/ml, were reached within a few days of the oestradiol peak. Plasma progesterone decreased in late pregnancy and in one of the three bitches studied in detail low or undetectable levels were reached 10 days before parturition. In the other two bitches an abrupt decrease in progesterone occurred just before parturition. Dexamethasone treatment (2 X 5 mg daily for 10 days) from Day 30 of pregnancy resulted in intrauterine death and resorption of the fetuses in the two bitches studied. Treatment from about Day 45 resulted in the birth of dead fetuses at Days 55 and 59 of pregnancy. The changes in plasma oestradiol levels were very small. No changes in plasma progesterone levels were seen when dexamethasone was given in late pregnancy, but an accelerated decline occurred after treatment in mid-pregnancy.     

Distribution of sialoglycoconjugates in the oviductal isthmus of the horse during anoestrus, oestrus and pregnancy: a lectin histochemistry study

The distribution of sialic acid residues as well as other glycosidic sugars has been investigated in the horse oviductal isthmus during anoestrus, oestrus and pregnancy by means of lectin and pre-lectin methods. Ciliated cells and non-ciliated (secretory) cells exhibited different lectin binding profiles that were found to change during the investigated stages. Ciliated cells did not show any reactivity in the basal cytoplasm, while the supra-nuclear cytoplasm displayed a few of oligosaccharides with terminal and internal alphamannose (Man) and/or alphaglucose (Glc) during oestrus and pregnancy and a moderate presence of oligosaccharides terminating in alphafucose (Fuc) during oestrus; cilia exhibited a more complex glycoconjugate pattern for the presence of oligosaccharides terminating in N-acetylgalactosamine (GalNAc), GalNAcalpha1,3 GalNAcalpha1,3galactose(Gal)beta1,4Galbeta1,4N-acetylglucosamine(GlcNAc), Fuc, sialic acid (Neu5Ac)-aGalNAc belonging or not to the GalNAca1,3GalNAca1,3 Galb1,4 Galb1, 4GlcNAc sequence, and. alphaGalNAc and Neu5Aca 2,6Gal/GalNAc increased during oestrus. Cilia displayed terminal Galbeta1,3 GalNAc in pregnancy, terminal alphaGal in anoestrus and pregnancy and terminal or internal D-GlcNAc during anoestrus and pregnancy, respectively. The whole cytoplasm of non-ciliated cells showed oligosaccharides terminating with alphaGalNAc, Neu5Aca2,6Gal/GalNAc, Neu5Ac GalNAca 1,3GalNAcalpha1,3Galbeta1,4Galbeta1,4GlcNAc during the investigated stages, as well as GlcNAc in anoestrus and pregnancy. The supra-nuclear zone of non-ciliated cells exhibited oligosaccharides with terminal Galbeta1,4GlcNAc and internal Man during oestrus and pregnancy as well as terminal alphaGal and Fuc in oestrus and Neu5Ac-Galbeta1,3GalNAc in pregnancy. The luminal surface of non-ciliated cells showed glycans terminating with alphaGalNAc and/or Neu5Ac GalNAcalpha1,3 GalNAcalpha1,3Galbeta1,4Galbeta1,4GlcNAc in all specimens, oligosaccharides with terminal Galbeta1,4GlcNAc and internal Man during oestrus and pregnancy, Neu5Ac alpha2,6Gal/GalNAc in anoestrus and oestrus, and glycans terminating with Galbeta1,3GalNAc, Neu5A acalpha2,3 Galbeta1, 4GlcNac, Neu5ac-Galbeta1,3GalNAc, Neu5Ac-Galbeta1,4 GlcNAc in pregnancy. These findings show the presence of sialoglycoconjugates in the oviductal isthmus of the mare as well as the existence of great modifications in the glycoconjugates linked to different physiological conditions.     

Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year

The characteristics of the oestrous and ovarian cycles of local goats were studied over 2 years, on 96 females in March, 60 in July and 100 in November. After 3 weeks of separation between sexes, the females with inactive ovaries were identified and harnessed males were introduced. Detection of oestrus was undertaken daily and the date and rate of ovulation were checked at laparoscopies. The proportion of females with non-cyclic ovaries before the mating period varied according to the season and whether the females were nulliparous or suckling. Among the females with inactive ovaries before the mating period, 97% ovulated 2 . 8 days after the introduction of males; 68% of these initial ovulations were accompanied by oestrus and 76% resulted in short luteal phases (5 . 3 days) followed by a second ovulation accompanied by oestrus 89% of the time. The proportions of initial ovulations with oestrus and of initial ovulations followed by a short luteal phase were in linear relationship with the proportion of females with non-cyclic ovaries before the mating period. For the females with cyclic ovaries before the mating period, the distribution of first oestrus during the 8 days after the introduction of males was significantly different from the expected uniform distribution. A possible luteolytic action of teasing was suspected. The fertility of females in all groups was high (greater than 79%). Litter size was not different for non-cyclic and for cyclic females.     

Concentrations of oestradiol-17 beta in plasma and corpora lutea throughout pregnancy in the tammar, Macropus eugenii

Oestradiol-17 beta concentrations were measured by radioimmunoassay in peripheral blood samples from 10 tammar wallabies after their pouch young were removed to terminate embryonic diapause. Oestradiol concentrations rose from 8.3 +/- 1.2 pg/ml on Days 3 and 4 to peak of 15.8 +/- 2.9 pg/ml on Day 5, coincident with an increase in 'progesterone' concentrations, and then fell to 10.5 +/- 2.7 pg/ml on Day 7. No changes in oestradiol concentrations were associated with parturition. Five females came into oestrus and mated 9.8 +/- 6.1 h post partum; peak concentrations of plasma oestradiol (20.9 +/- 2.1 pg/ml) occurred around the time of mating. None of the females that did not mate up to the end of the experiment at Day 30 had a rise in plasma oestradiol concentrations. Corpora lutea contained 20-100 pg oestradiol during pregnancy. The highest ovarian oestradiol content (greater than 1200 pg) was measured in whole ovaries containing Graafian follicles from full-term pregnant females. The rise in oestradiol concentrations at Day 5 may be important in the termination of diapause. The post-partum increase in plasma oestradiol concentrations coincides with oestrus. The source of this oestrogen appears to be the preovulatory follicle.     

Observations on variability in LH release and fertility during oestrus in the domestic cat (Felis catus)

Hormonal changes, behaviour, ovulation and fertility were examined in response to coitus at two different times during oestrus in the female domestic cat housed in conditions of natural light (N = 13). On Day 2 or Day 4/5 of oestrus females were allowed 1 copulation in 15 min (single matings) or 2-3 copulations in 30 min (multiple matings). Plasma LH, oestradiol-17 beta and progesterone concentrations during the 24-h period after coitus were measured by radioimmunoassay; ovulation was assumed to have occurred if progesterone values were elevated 7-30 days after coitus. With the exception of 2 out of 3 animals receiving single matings on Day 2 of oestrus, all animals showed subsequent elevated progesterone values. Females receiving multiple matings had significantly greater releases of LH as measured by the area under the curve than those receiving single matings. There was significantly greater variability in the LH response of queens on Day 2 of oestrus compared to those on Day 4/5 for peak values and area under the curve; the only failure in release of LH was in queens on Day 2. Oestradiol levels did not differ significantly between Day 2 and Day 4/5 of oestrus. Progesterone values remained less than 1 ng/ml for 24 h after coitus. Both LH peak values and area under the curve were significantly greater for animals that became pregnant. There were also significant differences in coital behaviour between queens on Day 2 and those on Day 4/5 of oestrus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Overfeeding during early pregnancy reduces peripheral progesterone concentration and pregnancy rate in sheep

The 330 Merino ewes used in the study were placed with rams at a synchronized oestrus and, on Days 2-14 after mating, the ewes were placed in a feed lot and fed daily a low, medium or high ration (25%, 100% or 200% of maintenance respectively). Progesterone supplement was given to some ewes on Days 8-14 after mating by using a device containing 340 mg progesterone. Blood samples were taken from all ewes on Day 12 for measurement of plasma progesterone concentrations. On Day 14 after mating all ewes were returned to pasture. Pregnancy rate was determined by returns to oestrus and was later confirmed using ultrasound. There was a decline in the peripheral progesterone concentrations with increasing ration. The pregnancy rate in ewes fed a high ration was significantly reduced when compared with those of ewes fed a medium or low ration (48% vs 68 and 67% respectively; P less than 0.05). In ewes fed the high ration exogenous progesterone increased the pregnancy rate from 48 to 76% (P less than 0.01). Progesterone treatment did not influence pregnancy rates in ewes fed medium or low rations. The number of fetuses per ewe pregnant was not influenced by level of nutrition or progesterone treatment.     

Influence of time of mating and paced copulation on induction of pseudopregnancy in cyclic female rats

The present experiment was designed to examine whether changes occur during the course of behavioural oestrus in the sensitivity of the female to copulatory stimulation and in patterns of sexual behaviour which might influence the likelihood of luteal maintenance. Cyclic female rats were mated on the evening of pro-oestrus (21:00 h) or early on the morning of oestrus (05:00 h) and received either 5 or 10 intromissions from males under conditions which allowed or did not allow pacing of contacts with males to occur. During mating, the levels of sexual receptivity, the timing of sexual mounts from males, and pacing behaviours were measured. The occurrence of pseudopregnancy or pregnancy in each animal was determined by examining vaginal smears for 14 days after mating and by examining the uterus for the presence of fetuses at the end of the experiment. At both mating times, pacing of copulation with males increased the likelihood of prolonged luteal activity. However, females were more likely to become pseudopregnant following non-paced mating at 05:00 h than at 21:00 h the previous evening. Of those females receiving an ejaculation during mating, no difference were seen between groups in the incidence of pregnancy. This change in sensitivity to cervical-vaginal stimulation during oestrus was not associated with changes in sexual receptivity or pacing behaviour. The ability of cervical-vaginal stimulation to induce pseudopregnancy therefore increases toward the end of the period of oestrus, but the behavioural mechanisms which regulate receipt of such stimulation remain constant during that time.     

Controlled sheep breeding: update 1980-1985

This contribution to the Symposium concerns four topics which have been addressed in our laboratory over the past five years. First, the responses to a controlled light environment of Merino ewes and rams have been compared with those of two British breeds. The endocrinological patterns were similar in all breeds but cyclic ovarian activity and ram libido were different. While showing a degree of entrainment to photoperiod, the breeding patterns were much less rigidly controlled in the Merinos than in the others. Second, the effectiveness of establishment of a cervical reservoir of spermatozoa, in ewes in which oestrus and ovulation have been controlled, has been re-examined. This is highly dependent on the time of insemination relative to that of the release of LH. Maximum numbers are found when ewes are inseminated shortly after the LH peak, i.e. some 6-10 h after the onset of oestrus. Third, the quantitative and temporal endocrinological and behavioural events following standard, progestagen-PMSG treatment have been quantified. Contrary to earlier expressed beliefs, these events are remarkably predictable provided an intensive system of mating or detection of oestrus is used. The onset of oestrus in treated anoestrous crossbred ewes has a normal distribution, with a range of 24 h, centred around a mean of 33 h after withdrawal of a 30 mg Cronolone intravaginal sponge and injection of 500 i.u. PMSG. This period of time is dose-dependent. The LH peak occurs 4.5 +/- 0.7 h later and the times of onset of oestrus and of LH release are highly correlated (r = 0.93). Ovulation is some 24 h later again. Fourth, differences in the response of ewes to different batches of PMSG have been defined. While the three commercial preparations studied regularly induced ovulation in anoestrous ewes at doses of 250 i.u. and above, the quantitative responses varied greatly. One preparation would not induce multiple ovulation, even at high doses. There are differences in steroidogenesis and in pregnancy rates, associated with dose of PMSG and the consequent ovulation rate: the ideal would be for every ewe to shed two or three ova. A higher ovulation rate is acceptable, as early embryonic mortality generally reduces the litter size. This is particularly important in deep anoestrus. However, this does not solve the problem of breeding in early lactation.     

Ovulation rate in induced oestrous cycles of anoestrous ewes given bromocriptine

The suppression of prolactin in anoestrous ewes by daily injections of bromocriptine reduced the average number of corpora lutea on Day 8 after induced oestrus from 2.8 to 1.6 (P less than 0.02). There was a significant correlation (r = 0.87, P less than 0.05) between the preovulatory peak values for prolactin and ovulation rate in treated but not in control ewes. Bromocriptine failed to prevent the ewes from returning to anoestrus after the induced oestrus.     

Effects of an antiandrogen, flutamide, on oocyte quality and embryo development in rats superovulated with pregnant mare's serum gonadotropin

Increased oocyte degeneration in rats is associated with enhanced ovarian androgen secretion following superovulation with pregnant mare's serum gonadotropin (PMSG). To determine whether androgens may be causally related to oocyte degeneration, we examined the effects of an antiandrogen, flutamide, on oocyte quality and embryo development after induction of superovulation with PMSG. Immature female Sprague-Dawley rats were used for two experiments. In the first experiment, the females received either 5 mg flutamide or vehicle alone 30 and 36 h after 40 IU PMSG and were killed at 48, 60, and 72 h. Although total number of oocytes was not significantly different between the two groups, flutamide significantly reduced the percentage of degenerate oocytes ovulated at all the time intervals examined (p less than 0.01). In the second experiment, the females were given 4 IU PMSG (control) or 40 IU PMSG with either 5 mg flutamide or vehicle. The rats were mated and then killed on Days 2, 3, 4, and 5 of pregnancy. Compared to control, flutamide did not effectively prevent the early loss of preimplantation embryos nor the developmental retardation which took place in the vehicle-treated rats after Day 2. However, flutamide treatment was associated with a significant decrease in embryo degeneration and a significant increase in the percentage of cleaved embryos on Day 2 (p less than 0.01). Compared to levels associated with the vehicle regimen, ovarian and/or serum androgen levels in the flutamide-treated rats significantly decreased at 60 h (p less than 0.01) and on Day 2 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Early embryonic development and in vitro culture of in vivo produced embryos in the farmed European polecat (Mustela putorius)

Early embryonic development and in vitro culture of in vivo produced embryos in the farmed European polecat (Mustela putorius) was investigated as a part of an ex situ conservation program of the endangered European mink (Mustela lutreola), using the European polecat as a model species. The oestrus cycles of 34 yearling polecat females were monitored by visual examination of the vulval swelling and, to induce ovulation, the females were mated once daily on two consecutive days. Sixteen yearling males were used for mating. The females were humanely killed 3-14 days after the first mating and the uteri and oviducts were collected for embryo recovery. Uterine and oviductal flushings yielded a total number of 295 embryos, representing developmental stages from the 1-cell stage to large expanded and hatched blastocysts. On Day 3 after the first mating, only 1-16-cell stage embryos were recovered. Between Days 4 and 6 after the first mating, 1-16-cell stage embryos and morulae were found. The first blastocysts were recovered on Day 7 after the first mating. The first implanted blastocysts were detected on Day 11 after the first mating. A total number of 85 embryos were in vitro cultured after recovery. Blastocyst production rates for in vitro cultured 1-16-cell stage embryos and for morulae/compact morulae were 68 and 84%, respectively. For all cultured embryos, the hatching rate was 15%. The in vitro culture requirements for the preimplantation embryos of the farmed European polecat remain to be determined before further utilization of the technique.     

Uterine blood flow of cows during the oestrous cycle and early pregnancy: effect of the conceptus on the uterine blood supply.

Blood flow to each uterine horn of cows during the oestrous cycle and early pregnancy was determined daily by use of electromagnetic blood flow probes placed around both middle uterine arteries. The pattern of blood flow to uteri of pregnant and non-pregnant cows was similar until Day 14 after mating or oestrus. Between Days 14 and 18 of pregnancy blood flow to the uterine horn containing the conceptus increased (P less than 0.01) 2- to 3-fold, whereas blood flow to the non-gravid uterine horn in these cows remained constant. No corresponding increase in blood flow to the uterine horn ipsilateral to the ovary bearing the CL was observed in non-pregnant cows during this 4-day period. By Day 19 of pregnancy, blood flow to the gravid uterine horn had returned to a level similar to that observed on Day 13. Blood flow to both uterine horns of pregnant cows remained constant from Days 19 to 25 and then increased to the gravid horn (P less than 0.01) markedly until Day 30 whereas blood flow to the non-gravid horn remained low. Uterine blood flow during the oestrous cycle of non-pregnant cows was positively correlated (P less than 0.01) with systemic concentrations of oestradiol and the ratio of oestradiol (pg/ml) to progesterone (ng/ml). There was no association between oestradiol concentrations and blood flow to the gravid uterine horn. These data indicate local control of uterine blood flow by the bovine conceptus which may function to create optimal conditions for the continuation of pregnancy.