Resumption Of Estrous Cycles Research Articles

PSX-38 Reproductive performance of Dorper ewes with varying days post-partum to ram introduction in the non-breeding season

Abstract With the decrease of a wool favored market, hair type sheep have become increasingly popular for lamb markets. In Texas, the most popular hair type breed of sheep is the Dorper. Various breed characteristics make the Dorper sheep an excellent candidate for an accelerated lambing system. Reproductive performance of Dorper ewes with various lengths of post-partum interval, during the traditional non-breeding season, was determined. During May (13L:11D), 2+ yr-old multiparous ewes (n = 28) were joined with a fertile ram for 30 d. Weekly blood samples were taken for progesterone analysis. Ewes were blocked according to length of post-partum interval (lamb to ram): short (SPP; n = 10, 100 ± 2.7 d), mid (MPP; n = 11, 130 ± 0.68 d) and long (LPP; n = 7, >200 d). Weaning age of lamb(s) from previous parturition was similar for SPP (62 ± 3.2 d) and MPP (67 ± 0.6 d). Interestingly, 11% of the ewes had a functional CL at initiation of the study (P4 > 1.5 ng/mL). Mean body condition score for SPP, MPP, and LPP ewes were 2.8 ± 0.08, 3.1 ± 0.09, and 3.7 ± 0.08, respectively. Pregnancy rates were similar between MPP (100%), LPP (100%) and SPP (60%). Overall, pregnancy rate was 87% and a lamb crop (lambs per ewe exposed) was 1.3 ± 0.09. Twinning rate for SPP, MPP, and LPP was 20%, 73%, and 43%, respectively. Pregnancy rate in SPP ewes may indicate carryover of the suppressive effects of lactation and suckling. Results suggest a lamb to ram interval of >100 d is sufficient for response to the ram effect and resumption of estrous cycles in a majority of ewes during photoperiod of 13L:11D. We conclude Dorper sheep have the reproductive capacity to successfully meet the production goals of accelerated lambing systems and thus, the potential for optimized lamb production.

Effect of Local Basic Fibroblast Growth Factor and Vascular Endothelial Growth Factor on Subcutaneously Allotransplanted Ovarian Tissue in Ovariectomized Mice.

ObjectiveOne of the major obstacles to ovarian tissue preservation is delayed angiogenesis that leads follicles lost after transplantation. The aim of the present study was to investigate the effects of bFGF and VEGF on heterotopic transplanted ovarian tissue using a mouse model.MethodsFemale mice underwent bilateral ovariectomy. Ovarian tissues encapsulated by fibrin hydrogels were transplanted subcutaneously into recipient mice, in which ovarian hormonal cyclicity was absent. The fibrinogen solution was mixed with bFGF, VEGF, or a mixture of bFGF and VEGF. The grafts were recovered 21 days after transplantation. Follicle morphology and follicle numbers were observed by H&E staining. Blood vessels were observed in transplanted intra-ovarian tissue by CD31 antibody IHC staining. Daily vaginal cytology was performed to determine estrous cycle and functional restoration of transplanted ovarian tissue. Blood was collected weekly and serum FSH levels were measured with a radioimmunoassay kit. Apoptosis analysis was performed by anti-AC-3 staining and survivin mRNA expression.ResultsThe number of primordial follicles and secondary follicles in the bFGF+VEGF group was significantly higher than in the control group. The vascular density in the bFGF+VEGF groups were significantly higher than in the bFGF and the VEGF groups; there was no significant difference between the bFGF and VEGF groups. Estrous cycle was earlier in the bFGF+VEGF group compared with the control group; all mice in this group restored ovarian function. Serum FSH levels in the bFGF+VEGF group were significantly lower than in the control group by day 14 post-transplantation. The AC-3-positive in control group was significantly higher compared with bFGF group and VEGF group, and in bFGF+VEGF group was significantly lower than bFGF group and VEGF group. Survivin mRNA expression in bFGF+VEGF group was significantly higher than control group.ConclusionThe combination of bFGF and VEGF has beneficial effects on follicle survival, angiogenesis, and resumption of estrous cycles.

Effect of intrauterine dextrose on reproductive performance of lactating dairy cows diagnosed with purulent vaginal discharge under certified organic management

The objectives of the study were to assess responses to treatments (clinical cure and resumption of estrous cycles) of cows with purulent vaginal discharge (PVD) that received intrauterine infusion of a hypertonic solution of 50% dextrose (DEX) or untreated control (CON) cows and the subsequent pregnancy per artificial insemination (PAI) in cows with and without PVD. Cows (n=2,852) from 2 dairy herds were screened for PVD using the gloved hand technique at exam 1 [26±3d in milk (DIM)]. Cows with vaginal discharge scores of 2 or 3 (0–3 scale) were stratified by parity and randomly allocated into 1 of 2 treatment groups: (1) intrauterine infusion (~200mL) of 50% DEX solution (n=456), or (2) untreated control animals (CON, n=491). Fourteen days posttherapy (40±3 DIM), cows with PVD were re-examined at exam 2 (40±3 DIM) to assess the response to treatments. All cows were subjected to the same reproductive program, which consisted of estrus detection twice daily (using tail chalking and visual observation) for the first 5 artificial inseminations; then, open lactating cows were turned out with bulls. Cows displaying signs of standing estrus underwent AI and no reproductive hormones were used. Pregnancy diagnosis (PD) was performed via transrectal palpation at 40±3d post-AI. The risk of culling within 14d posttherapy was not different among treatment groups. Cows with PVD had greater cervical diameter at exam 1 and decreased PAI compared with cows without PVD. Treatment with DEX increased the proportion of cows with clear vaginal discharge (clinical cure) and cyclicity 14d posttherapy compared with CON cows. Pregnancy per AI for DEX (29.2±2%) cows was significantly greater than that for CON (22.5±2%) cows. Cows without PVD had a greater proportion of cycling cows (65.6%) and PAI (37%) with reduced pregnancy losses (5.7%) compared with DEX or CON cows. The use of intrauterine DEX alone improved reproductive performance of cows with PVD.

Increased longevity of old infertile mice after allo-transplantation of young mice ovaries

OBJECTIVE: Most mammalian species are destined to die when their reproductive life is finished. If the most important evolutionary role of the individual is to produce the next generation, then the extension of reproductive life and increased longevity might be selectively correlated.DESIGN: To investigate this hypothesis, a young donor ovary was transplanted into old infertile mice, and the resumption of the reproductive cycle and life span of the mice were examined.MATERIALS AND METHODS: Female C57BL/6J mice (CLEA Japan inc.) were maintained for more than 525 days until they ceased to exhibit estrus, as determined by histology of vaginal smears. In Experiment 1, both ovaries were removed from young female mice (∼140 days old) that were immunologically compatible with the recipients, and these two ovaries were orthotopically transplanted into each of six aged, infertile recipient mice (>525 days old). In Experiment 2, one ovary was removed from intact young mice and transplanted into each of eight aged mice just as in Experiment 1.RESULTS: In Experiment 1 and Experimental 2, resumption of estrous cycles was obtained in all aged mice (resumption rate 100%), and normal estrous cycles continued for more than 80-130 days after the resumption. All the recipients in both experiments 1 and 2 resumed the normal reproductive behavior of young mice. Aged recipients that received young ovaries lived for an average of 836 (Exp.1) and 915 (Exp.2) days. The lifespan of mice who received young ovaries was thus much longer than that of intact mice (636 days). There was a 31-44% increase in lifespan in mice who received a transplant of young donor ovaries.CONCLUSION: The results in the present study suggest that transplanted normal ovaries can function in old infertile mice, which then not only resume the reproductive behavior of young mice, but also extend their lifespan. These results in mice may suggest the possibility of preventing the reproductive functional disorder of aging women by transplantation of a normal ovary. OBJECTIVE: Most mammalian species are destined to die when their reproductive life is finished. If the most important evolutionary role of the individual is to produce the next generation, then the extension of reproductive life and increased longevity might be selectively correlated. DESIGN: To investigate this hypothesis, a young donor ovary was transplanted into old infertile mice, and the resumption of the reproductive cycle and life span of the mice were examined. MATERIALS AND METHODS: Female C57BL/6J mice (CLEA Japan inc.) were maintained for more than 525 days until they ceased to exhibit estrus, as determined by histology of vaginal smears. In Experiment 1, both ovaries were removed from young female mice (∼140 days old) that were immunologically compatible with the recipients, and these two ovaries were orthotopically transplanted into each of six aged, infertile recipient mice (>525 days old). In Experiment 2, one ovary was removed from intact young mice and transplanted into each of eight aged mice just as in Experiment 1. RESULTS: In Experiment 1 and Experimental 2, resumption of estrous cycles was obtained in all aged mice (resumption rate 100%), and normal estrous cycles continued for more than 80-130 days after the resumption. All the recipients in both experiments 1 and 2 resumed the normal reproductive behavior of young mice. Aged recipients that received young ovaries lived for an average of 836 (Exp.1) and 915 (Exp.2) days. The lifespan of mice who received young ovaries was thus much longer than that of intact mice (636 days). There was a 31-44% increase in lifespan in mice who received a transplant of young donor ovaries. CONCLUSION: The results in the present study suggest that transplanted normal ovaries can function in old infertile mice, which then not only resume the reproductive behavior of young mice, but also extend their lifespan. These results in mice may suggest the possibility of preventing the reproductive functional disorder of aging women by transplantation of a normal ovary.

Is caspase inhibition a valid therapeutic strategy in cryopreservation of ovarian tissue?

The aim of this study is to determine whether inclusion of caspase inhibitor can improve the efficacy of cryopreservation of ovarian tissue. Mice were randomly assigned to the Group A (fresh control group) Group B (inclusion of caspase inhibitor) and Group C (non-inclusion of caspase inhibitor). Ovarian tissue in Group B and Group C was vitrified-thawed. TUNEL assay and Bax protein detection were measured after cryopreservation. The mice in all groups received autotransplantation. The number of days before the resumption of estrous cycles was measured daily from the 5th day after surgery, and the percentage of cells expressing PCNA in grafts was measured one month following transplantation. The incidence of TUNEL positive follicles in Group B was significantly higher than that in Group C. Similarly, the percentage of follicles expressing Bax protein in Group B was significantly higher than that in Group C. The number of days before the resumption of estrous cycles in Group B was significantly less than that in Group C. In addition, the percentage of follicular and stromal cells expressing PCNA of grafts in Group B was significantly higher than that in Group C. The global caspase inhibitor Z-VAD-FMK decreases the incidence of apoptosis of ovarian tissue induced by cryopreservation, and inclusion of caspase inhibitor improves the efficacy of cryopreservation of ovarian tissue.

Initial body condition score affects hormone and metabolite response to nutritional restriction and repletion in yearling postpubertal beef heifers1

Twenty Simmental x Angus, half-sibling, postpubertal heifers (initial BW of 443 +/- 9 kg) were allotted randomly into 2 treatment groups to evaluate if initial BCS affects response of the hypothalamic-pituitary-ovarian axis to metabolic signals elicited by energy restriction and repletion. During a preliminary feeding period, diets were formulated so that each heifer in the designated treatment would reach a BCS of 5 (moderate condition; MOD) or a BCS of 7 (heavy condition; FAT). Once each heifer had reached desired BCS, diets were formulated to supply 30% of NE(m) requirements until each heifer became anestrous (serum concentrations of progesterone < 1 ng/mL; restriction period). Blood collections took place on d 1 of each period, on d 43 of energy restriction and d 44 of energy repletion, and when heifers were confirmed to recommence estrous cycles. When heifers were cycling, their estrous cycles were synchronized to ensure hormone sampling occurred during late diestrus or early proestrus. Energy restriction resulted in decreased concentrations of LH (FAT, P = 0.02; MOD, P < 0.001), IGF-1 (FAT, P < 0.001; MOD, P = 0.003), and insulin (P < 0.001); in contrast, concentrations of GH (P < 0.001) and plasma urea nitrogen (P < 0.001) increased. During repletion, LH concentration increased (P = 0.03) in MOD condition heifers but was still less (P = 0.002) than d 1 of restriction, whereas LH concentration tended to increase in FAT heifers (P = 0.06) until it was similar (P = 0.40) to d 1 of restriction. Repletion also increased concentrations of IGF-1 (P < 0.001), insulin (P < 0.001), and glucose (P < 0.001), whereas concentrations of GH (P < 0.001), NEFA (P < 0.001), and plasma urea nitrogen (P < 0.001) decreased. For both treatments, concentrations of GH after repletion were similar (FAT, P = 0.88; MOD, P = 0.10) to those on d 1 of restriction. After repletion, FAT condition heifers had decreased concentrations of IGF-1 (P < 0.001), insulin (P < 0.05), and glucose (P < 0.001), but greater concentrations of acetate (P < 0.01) and butyrate (P < 0.05), than MOD heifers. Anestrus or resumption of estrous cycles seems to be activated gradually in response to dietary manipulation, unrelated to certain metabolite changes.

Sucrose affecting successful transplantation of vitrified-thawed mouse ovarian tissues

The aim of this experiment is to detect effects of varying levels of sucrose on vitrified ovarian tissues. Ovarian tissues of mice were vitrified-thawed. Mice were randomly assigned to the fresh control group and experimental groups. According to different concentration of sucrose in vitrification solution, the experimental groups were randomly divided into Group I (0.2 M sucrose), Group II (0.4 M sucrose), Group III (0.8 M sucrose) and Group IV (1.6 M sucrose). Cytology was followed throughout the oophorectomy and transplantation period. Hormone levels and density of follicle were measured 1 month after transplantation. The number of days before the resumption of estrous cycles in control group was significantly smaller than those in all of experimental groups. The serum estradiol levels of mice and the follicular density of ovarian grafts in control group were significantly higher than those in all of experimental groups. In addition, the number of days before the resumption of estrous cycles in Group II and Group III were smaller than those in Group I and Group IV. The serum estradiol levels of mice and the follicular density of ovarian grafts in Group II and Group III were significantly higher than those in Group I and Group IV. However, no difference was observed in the number of days before the resumption of estrous cycles and the serum estradiol levels between Group II and Group III. A similar follicular density was also observed in Group II and Group III. Sucrose concentration of 0.4 M or 0.8 M in cryoprotective media is suitable for vitrifying mouse ovarian tissues.

Validation of a 13,14-dihydro-15-keto-PGF 2α enzymeimmunoassay and its application for reproductive health monitoring in postpartum buffaloes

The objective of the present study was to validate a simple, sensitive and direct enzymeimmunoassay (EIA) procedure for 13,14-dihydro-15-keto-PGF 2α (PGFM) for use in buffaloes with postpartum reproductive disorders and determine the practicalities of using plasma concentrations of 13,14-dihydro-15-keto-PGF 2α for monitoring their reproductive health. The EIA was used for determination of the circulating levels of PGFM associated with the retention of fetal membranes, postpartum endometritis and variable postpartum intervals. The concentrations of PGFM with retention of fetal membranes in the periparturient period were lower as compared to buffaloes that had uneventful parturitions. Concentrations of PGFM associated with postpartum endometritis were elevated as compared to those in buffaloes free of reproductive tract infections. Buffaloes having higher plasma concentrations of PGFM in early postpartum period had shorter postpartum intervals, indicating the association between PGFM concentrations postpartum and uterine involution as well as the resumption of estrous cycle in this species. The study presents the possibility of using circulating PGFM concentrations for monitoring the postpartum reproductive health of buffaloes.

Inhibin is present in the corpus luteum of pseudopregnant rats and can interact with progesterone to inhibit resumption of estrous cycles.

The corpora lutea (CL) of ovaries of adult pseudopregnant (PSP) rats were stained by immunohistochemistry for inhibin alpha subunit using sheep alpha-chain1-27 antibody as a measure of inhibin content. Staining was light in estrous cycle CL (stage III), increased in Day 2 and Day 4 PSP CL and reached maximal density on day 6 PSP when both large cells and many small cells stained. Staining was decreased in CL from 8 and 10 day PSP. Granulosa cells of growing follicles showed light stain on days 8 and 10 of PSP. Adult female rats were treated for 5 days beginning at estrous cycle Stage III (cornified masses). In Experiment 1, three groups of rats were used: 1. implanted with 30mm progesterone capsules and injected with saline, 2. implanted with 30mm progesterone capsules and injected with 10 ng rh inhibin A daily, 3. implanted with empty capsules and injected with 10 ng rh inhibin A daily. Both groups of rats with progesterone implants had significantly slower return of cycling after removal of the capsules than did the rats injected with 10ng rh inhibin A alone. In Experiment 2, the same treatments were given except that 20ng of rh inhibin A (10ng 2x/day) was given to both inhibin treatment groups. Rats treated with progesterone and 20ng inhibin had a significantly slower return of cyclic activity (4.4 days) over that found in the other two treatment groups. We conclude that the absence of cyclic activity in PSP rats is possibly due to the secretion of both inhibin and progesterone by the CL.

Endocrine changes and ultrasonography of ovaries in suckled beef cows during resumption of postpartum estrous cycles.

Changes in follicular and luteal structures were assessed and concentrations of estradiol and progesterone were measured in 13 Hereford X Angus suckled beef cows during resumption of estrous cycles. Transrectal ultrasonography was used to monitor follicular size, ovulation, and formation and regression of the corpus luteum (CL). The interval from parturition to first postpartum ovulation (FO) was 82 +/- 4.7 d. Serum progesterone remained low before FO. One cow exhibited standing estrus, two cows showed other signs of estrus, and 10 displayed no signs of behavioral estrus preceding FO. All cows exhibited standing estrus before the second postpartum ovulation (SO). All cows had a short luteal phase after FO, with an average interval of 8.5 +/- .2 d between FO and SO. Concentrations of estradiol in serum during the 8 d preceding ovulation were similar before FO and SO. Maximal diameter of the preovulatory follicle was similar before FO and SO. However, the ovulatory follicle was larger in diameter at 2 d (P = .02) and 3 to 8 d (P less than .005) before FO than before SO. The time from detection until ovulation was less (P = .005) for the ovulatory follicle preceding SO than for the follicle associated with FO (8.5 vs 10.2 d, respectively, SE = .4). The second-largest follicle was larger (P less than .005) in diameter during the 8 d preceding the FO than before the SO. The difference in size between the ovulatory follicle and the second-largest follicle on the day before ovulation was greater (P less than .005) preceding SO than preceding FO (8.7 vs 6.6 mm, respectively, SE = .4).(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of naloxone binding sites in brains from suckled beef cows during postpartum anestrus and resumption of estrous cycles.

Thirty beef cows, approximately 3 yr of age, were randomly assigned to be slaughtered on d 7, 14, 28, 42 or 56 postpartum. Each cow suckled one calf until slaughter. Data from cows slaughtered on d 42 and 56 were pooled and further classified as anestrous or cyclic based on the presence of a corpus luteum and elevated serum concentrations of progesterone at slaughter. Specific binding of [3H]naloxone (3H-NAL) to homogenates of tissue from hypothalamus (HYP), preoptic area (POA) and basal forebrain (BF) was assessed using multiple-point Scatchard analyses. Nonspecific binding was estimated in the presence of 10(-6) M naloxone. Separation of bound from free 3H-NAL was achieved by centrifugation at 20,000 X g. Concentration (fmol/mg original tissue wet wt) of 3H-NAL binding sites in POA tissue was higher (P less than .05) on d 28 postpartum in anestrous cows than in cyclic cows on d 42 + 56 postpartum (2.58 +/- .32 vs 1.58 +/- .10). When all anestrous cows were compared with cyclic cows, concentrations of 3H-NAL binding sites in POA tissues and in BF tissue were higher (P less than .05) in anestrous cows (anestrous POA, 2.12 +/- .17, cyclic POA, 1.58 +/- .10; anestrous BF, 2.94 +/- .41, cyclic BF, 2.19 +/- .16). Compared across brain regions for all cows, the concentration of specific binding sites for 3H-NAL was greater (P less than .01) in BF (2.5 +/- .2) than in POA (1.9 +/- .1) and greater (P less than .01) in POA than in HYP (1.5 +/- .1).(ABSTRACT TRUNCATED AT 250 WORDS)

Nutritionally-induced anestrus in gilts: metabolic and endocrine changes associated with cessation and resumption of estrous cycles.

Two experiments determined how feed restriction and realimentation altered metabolism and ovarian function in gilts. In Exp. 1, cyclic (INTACT-R, n=6) and ovariectomized (OVEX-R, n=6) gilts were fed restricted diets (.23 kg feed.d-1) or ovariectomized (OVEX-C, n=6) gilts were fed control diets (1.81 kg.d-1). Estrous cycles stopped after 46 +/- 9 d of feed restriction. Average weight (WT), backfat thickness (BF) and concentrations of insulin (INS) were lower and free fatty acids (FFA) were greater in OVEX-R than in OVEX-C gilts. Frequency of luteinizing hormone (LH) release (peaks.6 h-1) was reduced by feed restriction (.2 +/- .2, 1.8 +/- 1.0 and 5.8 +/- .2 in INTACT-R, OVEX-R and OVEX-C gilts, respectively). Patterns of secretion of LH and follicle stimulating hormone (FSH) after gonadotropin releasing hormone (GnRH) or estradiol benzoate were not altered by feed restriction. Feed intake was then increased in INTACT-R and OVEX-R gilts beginning on d 80 and 82, respectively. Resumption of estrous cycles in INTACT-R gilts occurred on d 116.0 +/- 4.0 and was preceded by a significant increase in WT, but not BF, and a linear increase in concentration and frequency of release of LH. Increasing feed intake in OVEX-R gilts increased WT and frequency of LH release, while FFA decreased and INS increased to concentrations not different from those of OVEX-C gilts. The hypothesis that nutritionally-induced anestrus resulted from decreased activity of the hypothalamic pulse-generator was evaluated in Exp. 2 by providing 144 hourly pulses (iv) of saline (n=3), GnRH (n=3) or LH (n=4) to nutritionally-anestrous gilts.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of exposure to bulls on resumption of estrous cycles following parturition in beef cows.

The effect of bull exposure on the resumption of estrous activity following parturition was studied in an experiment using mature Hereford and Hereford X Angus beef cows. In the spring of 1981 and 1982, cows were assigned by breed and calving date to one of two treatment groups. Cows were exposed to bulls either from 3 to 85 d postpartum (BE; n = 45, 1981; n = 35, 1982) or from 53 to 85 d postpartum (NE; n = 39, 1981, n = 36, 1982). Blood samples were collected from all cows once weekly from calving until 85 d postpartum to determine progesterone concentrations. The first increase in progesterone, which indicated onset of estrous cycles occurred at 43 +/- 2 vs 63 +/- 2 d (P less than .01) in 1981 and at 39 +/- 2 vs 61 +/- 3 d (P less than .01) postpartum in 1982 in BE cows and NE cows, respectively. Early postpartum exposure of cows to bulls reduced the postpartum anestrous interval.

Cysteamine depletes prolactin in young and old hyperprolactinemic rats.

Studies were undertaken to evaluate the effects of cysteamine on serum and anterior pituitary concentrations of prolactin in hyperprolactinemic female rats. Serum prolactin was elevated in young (4 to 5 months old) rats by implantation of 17 beta-estradiol while 26- to 28-month-old rats were in constant estrus and exhibited an age-related hyperprolactinemia. At 4 h after treatment with cysteamine (90 mg/kg body wt) serum and anterior pituitary prolactin concentrations were reduced in young animals by 98 and 85%, respectively. In old constant-estrous rats, cysteamine reduced serum prolactin by 92% and anterior pituitary prolactin by 82%. In young pseudopregnant rats, cysteamine induced a prompt resumption of estrous cycles. These studies indicate that cysteamine is an effective depletor of serum and pituitary prolactin in hyperprolactinemic rats.

Effect of lactation upon the postpartum interval.

Several physiological aspects of lactation in the ewe, sow and cow were reviewed relative to possible delaying effects upon postpartum interval to ovulation, estrus and conception. Specifically considered were the possibilities that: high blood flow to the mammary gland and perturbations of that flow may disrupt vascular regulatory mechanisms in the reproductive tract, metabolism of gonadal and adrenal hormones by mammary tissue may disrupt endocrine controls essential for reproduction, suckling or milking-induced release of prolactin and oxytocin may inhibit ovarian or pituitary function and effects of social interactions associated with lactation and suckling may delay resumption of estrous cycles. The postpartum interval appears to be related to suckling intensity. An attractive hypothesis is that pituitary release of gonadotropins is inhibited during lactation as a result of pituitary desensitization to estrogen by suckling-induced surges of prolactin. Evidence for this role of prolactin is, however, circumstantial for all three species and the relationship of prolactin to the postpartum interval in cattle remains nebulous. Therefore, management practices to minimize lactational anestrus should be based upon the generalized concept that "suckling" delays postpartum cycles, rather than upon more specific hypothetical mechanisms.

An orally active compound with anti-fertility effects in rats.

When female rats are treated for a brief postcopulatory period with an adequate dose of 1-(rho-2-diethylaminoethoxyphenyl)-1-phenyl-2-p-anis ylethanol (MER-25) implantation never occurs. The animals enter a period of pseudopregnancy characteristic of rats following sterile mating and upon resumption of estrous cycles are completely capable of bearing normal litters. Results of experiments indicate that the antife rtility effects of MER-25 are exerted prior to exit of ova from the oviducts. The compound does not act by preventing decidua development nor by interfering with postcopulatory maintenance of luteal body function. Histologic evidence indicates that ova of females treated with MER-25 undergo degeneration after extrusion of the second polar body.(AUTHORS MODIFIED)