Early Diestrus Research Articles

217LUTEAL REGRESSION AND FOLLICLE DEVELOPMENT FOLLOWING PROSTAGLANDIN-F2± TREATMENT 3 DAYS AFTER OVULATION IN MARES

The corpus luteum (CL) is responsive to exogenous prostaglandin-F2α (PGF) 1 to 2 days after ovulation in the mare (Troedsson et al. 2001 Theriogenology 55, 1891–1899); however, complete and sustained demise of the CL beginning less than 5 days after ovulation in response to PGF treatment has not been documented. The present study was designed to compare the morphological and physiological response of the primary CL to PGF given at early diestrus with a more conventional treatment given at about mid-cycle. In addition, follicle status pre- and post-treatment were examined and compared between the treatment groups. On the day of pretreatment ovulation (Day 0), riding-type horse mares were randomly assigned to receive a single dose of PGF (Lutalyse, Upjohn, Kalamazoo, MI, USA;; 10mg/mare, i.m.) on Day 3 (n=17) or Day 10 (n=17). Beginning on either Days 3 or 10, transrectal ultrasonography was used to determine follicle and CL diameters, determine luteal tissue gray-scale scores (echogenicity), and to detect ovulation. Follicular and luteal measurements and jugular blood samples were collected daily until the post-treatment ovulation. Structural and functional regression of the CL was indicated by: 1) a progressive decrease (day effect;; P<0.0001) in mean diameter of the CL beginning 24h after PGF treatment in the Day 3 and Day 10 groups;; 2) a precipitous decrease (P<0.009) in mean plasma progesterone concentrations within 24h in both groups followed by a more gradual decline to basal concentrations by the second day in the Day 10 group or after the fourth day in the Day 3 group;; and 3) an increase (P<0.02) in mean luteal tissue echogenicity in both groups after the second day following PGF treatment. The mean intervals from PGF treatment to ovulation were not different (P>0.2) between groups (combined, 9.9 days) but the mean (±SEM) interovulatory interval was shorter (P<0.0001) in the Day 3 group (13.2±0.9 days;; range, 7 to 20 days) than in the Day 10 group (19.2±0.7 days;; range, 14 to 26 days). The greater the diameter of the largest follicle at the time of PGF treatment, the shorter the interval to post-treatment ovulation in the Day 3 (r=−0.57, P<0.02) and Day 10 (r=−0.74, P<0.001) groups. Growth rates of the preovulatory follicles were similar (P>0.59) between groups (combined, 3.6mm/day) but the maximum diameter was smaller (P<0.05) in the Day 3 group (40.5±1.2mm) compared to the Day 10 group (43.4±0.8mm). Unexpectedly, more (P<0.03) double ovulations occurred in the Day 3 group (6/17, 35%) than in the Day 10 group (1/17, 6%). In conclusion, an immature CL at early diestrus responded to PGF treatment in a manner comparable to a mature CL at mid-cycle. The Day 3 group ovulated an average of 6 days earlier than the Day 10 group as a result of the difference in timing of the PGF treatment between groups. Thus, these results warrant a reassessment of the prevailing concept that the equine CL is resistant to PGF-induced regression before 5 days after ovulation, especially when considering the potential benefits of a shortened interovulatory interval and an increased double ovulation rate.

Evidence for centrally initiated genital vasocongestive engorgement in the female rat: findings from a new model of female sexual arousal response.

In spite of rapidly growing interest, few research tools have been developed to study female sexual dysfunction. Using the D(1)/D(2) agonist, apomorphine (APO), our objective was to develop a new model of the sexual arousal response in female rats based on one previously established for the male condition. APO (80 micro g/kg, s.c.) was given during proestrus (P), estrus (E), metestrus (M), early diestrus (DI) and late diestrus (DII), and in ovariectomized (OVX) female Wistar rats. APO-induced behavioral and genital responses were characterized (30 min) using video monitoring. APO-induced reproducible, periodic morphological changes in the external genitalia. The onset, timing and duration of these female APO responses were consistent with genital vasocongestive arousal (GVA) responses in males (ie erections). APO-induced GVAs occurred throughout the estrous cycle, peaking in E (1.4+/-1.21 overall; 0.9+/-0.64 in DII; 1.8+/-1.66 in E) and were markedly diminished by ovariectomy (OVX, 0.4+/-0.51). APO induced a reproducible sexual arousal response in female rats involving obvious genital vasocongestive engorgement. Further, the findings demonstrate that the APO-induced genital arousal responses are hormonally regulated.

Magnetic resonance image attributes of the bovine corpus luteum during development and regression.

To determine whether magnetic resonance (MR) image attributes of the corpus luteum (CL) reflect its physiologic status at different phases of the bovine ovarian cycle, we analyzed the numerical pixel values (NPVs), relaxation rates, proton densities (PDs), and apparent diffusion coefficients (ADCs) from T(1)-, T(2)-, and diffusion-weighted in vitro images and maps of the CL acquired at defined phases of luteal function. Ovaries were removed and serum samples taken on days 3, 6, and 10, or >/=17 (day 0 = ovulation), representing metestrus (n = 10), early diestrus (n = 7), mid-diestrus (n = 9), and proestrus (n = 7), respectively. Regions of interest (ROIs) in each quadrant of the CL (which occupied at least 20% of the quadrant) were selected for analysis. Three MR image slices were analyzed: the slice with the greatest cross-sectional area of the CL, and the slices acquired immediately before and after that slice. The mean NPVs of the CL in T(1)-weighted images increased at each phase from metestrus (1,104 +/- 40 msec) to early diestrus (1,119 +/- 77 msec), to late diestrus (1,206 +/- 43 msec) and proestrus (1446 +/- 80 msec; P < 0.001). The mean NPVs in T(1)-weighted images were higher in regressing CL (proestrous) than in any other phase (P < 0.002). Grayscale heterogeneity of CL in T(1)-weighted images tended to increase during regression (P < 0.07). Regressing CL (proestrus) exhibited higher T(1)-weighted mean NPVs (P < 0.01) and tended to have greater heterogeneity (P < 0.06) than growing (metestrus) and mature (diestrus) CL, even though similar progesterone concentrations were observed. The increased brightness and heterogeneity of regressing CL in T(1)-weighted images appeared to be correlated with increased connective tissue and triglyceride content and decreased vascularity. It is anticipated that diagnostic markers for luteal viability and atresia in the in vitro bovine model will be applied to in vivo studies in women.

Molecular Cloning, Genomic Mapping, and Expression of TwoSecretor Blood Group α(1,2)Fucosyltransferase Genes Differentially Regulated in Mouse Uterine Epithelium and Gastrointestinal Tract

Fucosylated oligosaccharides have been proposed to be involved in multiple cell-cell interactions, including mouse blastocyst adhesion and intestine-microbe interactions. To begin to define the regulation and function of terminal alpha(1,2)fucosylated carbohydrates in these and other tissues, we isolated and characterized a 85-kilobase (kb) genomic region of mouse chromosome 7, 23.2 centimorgans analogous to human chromosome 19q13.3 that encodes three alpha(1,2)fucosyltransferases. Gene-specific DNA probes from the open reading frames of the mouse fucosyltransferase genes corresponding to human FUT1, FUT2, and SEC1 demonstrate distinct tissue-specific expression patterns by Northern blot analyses. Flow cytometry profiles of cultured cells transfected with DNA segments containing the open reading frames of the mouse genes confirm that each encodes an alpha(1,2)fucosyltransferase. In uterus and colon, a 3.3-kb FUT2 mRNA represents the major fucosyltransferase gene expressed. Steady-state FUT2 mRNA levels are cyclically regulated during the estrus cycle, increasing 10-fold from early diestrus to a relative maximum in proestrus. In contrast, SEC1 and FUT1 do not show prominently regulated expression in uterus. FUT2 expression localizes to luminal uterine epithelium by in situ hybridization, implying that this gene determines expression of cell surface Fucalpha1-->2Galbeta epitopes proposed to mediate blastocyst adhesion.

Stage of Cycle, Incidence, and Timing of Ovulation, and Pregnancy Rates in Dairy Cattle after Three Timed Breeding Protocols

In experiment 1, 705 cows were assigned to three treatments: 1) the Ovsynch protocol (a GnRH injection given 7 d before and another 48h after one PGF2α injection); 2) PGF2α + Ovsynch (one PGF2α injection given 12 d (d –22) before initiating Ovsynch (d –10); and 3) 2xPG12 (two PGF2α injections 12 d apart; d –15 and –3, followed 48h later by a GnRH injection. All cows were inseminated (d 0) 16 to 20h after the GnRH injection on d –1. Cyclic status was estimated by serum progesterone. More cows were in early diestrus at d –10 for PGF2α + Ovsynch (36%) and 2 x PG12 (29%) versus Ovsynch (19%). Multiparous cows receiving PGF2α + Ovsynch had greater pregnancy rates via ultrasonography at d 28 after AI (42%) than contemporaries after Ovsynch (28%) or 2×PG12 (27%) but did not differ significantly at palpation 10 to 30 d later (28, 19, and 17%, respectively). Pregnancy of first-parity cows was similar across treatments at 28 d (41%) or at palpation (33%). Pregnancy rates for 128 anestrous cows were lower, regardless of treatment. Overall embryo survival from d 28 until palpation was 72% but was only 44% in 2×PG12 cows that were anestrus through d –10. Experiment 2 included the three treatments above plus controls (one GnRH injection 7 d before PGF2α and AI after estrus). Preovulatory follicles were 6 to 11% larger near estrus in controls than on d –1 in cows receiving GnRH. More controls ovulated by 32h after onset of estrus than were treated cows by 32h after GnRH, but percentages (79 to 94%) were similar by 40h. In multiparous cows, PGF2α before Ovsynch increased pregnancy rates, whereas the 2×PG12 protocol produced similar pregnancy rates as Ovsynch across parities. Ovulation was effectively induced by 40h after GnRH.

Expression of insulin-like growth factor binding protein (IGFBP)-3, and the effects of IGFBP-2 and -3 in the bovine corpus luteum

The present study was conducted to gain insight into the insulin-like growth factor (IGF) system in the bovine corpus luteum (CL). Specific aims were to measure the levels of IGF binding protein-3 (IGFBP-3) and RNA encoding IGFBP-3 in the CL throughout diestrus, and to investigate the effects of IGFBP-2 and -3 on IGF-I-stimulated progesterone (P4) production and IGF-I-receptor binding. Bovine CL were collected from a local abattoir and classified according to stage of diestrus based on anatomical characteristics. Corpora lutea from early, mid and late diestrus were each analyzed for the presence of IGFBP-3 by ligand blot analysis, and for RNA encoding IGFBP-3 by Northern blot analysis. Dissociated cells from mid-cycle CL were treated with IGF-I, IGFBP-2 or -3, or a combination of IGF-I and IGFBP-2 or -3. The effect of IGFBP-2 and IGFBP-3 on [ 125I] IGF-I binding to its receptor on CL plasma membranes also was investigated. IGFBP-3 protein and RNA expression were higher in early CL, compared to mid or late CL ( p < 0.05). IGF-I stimulated P4 production in a dose-dependant manner ( p < 0.05). IGFBP-2 and -3 blocked the stimulatory effect of IGF-I on P4 production ( p < 0.05). Both IGFBP-2 and -3 inhibited [ 125I]-IGF-I binding to its receptor in a dose-dependant manner. These results demonstrate that IGFBP-3 protein and RNA are expressed predominantly during early diestrus in the bovine CL. Moreover, both IGFBP-2 and -3 can modulate IGF-I actions in the CL by interfering with binding of IGF-I to its receptor.

Does increased PGF 2α receptor concentration mediate PGF 2α-induced luteolysis during early diestrus in the pig?

The mechanism by which multiple injections of PGF 2α result in premature luteolysis in pigs is unknown. In the present study we evaluated whether PGF2 2α receptor concentrations on large luteal cells changed when gilts were injected IM with 12.5 mg of PGF 2α every 12 hours from the morning of day 5 of an estrous cycle (estrus = day 0) until ovariectomy on day 6, 7, 8, or 9. Luteal PGF2 2α receptor concentrations remained constant from day 6 through 9 in the PGF 2α-treated group, but increased linearly ( P > 0.05) in control gilts from day 6 to 9. Receptor affinity for PGF 2α did not change throughout the study in either PGF 2α-treated or control gilts. Luteal progesterone concentrations were significantly lower in PGF 2α-treated gilts than in control gilts only on day 9. Histological examination of luteal tissue obtained from PGF 2α-treated gilts revealed definite evidence of luteolysis by day 8. We conclude that PGF 2α-induced premature luteolysis is not mediated by an increase in luteal PGF2 2α receptor concentrations and, based on luteal progesterone concentrations and histological features, that the PGF 2α-based protocol used to shorten the estrous cycle is accompanied by premature functional and structural luteal regression.

Physical characteristics of the uterus during the bovine estrous cycle and early pregnancy

Uterine tone, uterine contractility and endometrial echotexture were monitored daily in heifers during the estrous cycle (n = 6; Days 0 to 21; ovulation = Day 0) and during early pregnancy (n = 7; Days 0 to 26). Uterine tone was assessed by transrectal palpation and scored from 1 (flaccid) to 5 (turgid) by an operator who had no knowledge of reproductive status, day, or group. The main effect of day was significant, but the group effect and the group-by-day interaction were not. Uterine tone scores were high during the periovulatory period (Days -1, 0, 1), decreased (P < 0.05) to low levels on Days 3 and 4, and then increased (P < 0.05) from Days 4 to 10. The increase in tone during early diestrus was confirmed (P < 0.05) in a second experiment. Uterine contractility was assessed by transrectal ultrasonography during a five-minute scan of the caudal portions of the uterine horns and scored from 1 (minimal contractility) to 4 (maximal contractility). The main effects of day and the group-by-day interaction were significant. Contractility scores in both groups were highest just before or on the day of ovulation (Days -1,0) and then decreased (P < 0.05) until Day 11. After Day 16, the scores increased (P < 0.05) in the nonbred heifers and remained low in the pregnant heifers. Endometrial echotexture scores were different among days (P < 0.0001), between the 2 groups (P < 0.02), and for the group-by-day interaction (P < 0.0001). Echotexture scores in both groups peaked just before ovulation (Day -1) and then decreased (P < 0.05) until Day 4. After Day 16, the scores increased in the nonbred group but remained low in pregnant heifers. In summary, uterine contractility and endometrial scores had similar profiles, being high during the periovulatory period and low thereafter; the levels rose in association with the end of the interovulatory interval in nonbred heifers, but remained at low levels in pregnant heifers. Uterine tone scores were also high during the periovulatory period and decreased to low levels several days postovulation, but then, in contrast with the other end points, began to increase in both the nonbred and pregnant heifers.

Changes in Equine Endometrial Retinol-Binding Protein RNA during the Estrous Cycle and Early Pregnancy and with Exogenous Steroids1

A cDNA library was constructed from poly(A) RNA obtained from Day 14 nonbred equine endometrium. A cDNA probe for porcine retinol-binding protein (RBP) was used to screen the library, and a complete cDNA sequence (1133 bp, excluding the poly(A) tail) was obtained. Endometrial biopsies were obtained from cycling, nonbred mares at Days 0, 1, 4, 8, 10, 11, 13, and 15 and from pregnant mares at Days 11, 13, 15, and 17 after ovulation (n = 2 mares each day). Endometrial biopsies were also taken from 18 noncycling anestrous mares after the following treatments: C (vehicle control for 1 day, n = 3), E (estradiol-17 valerate, 5 mg/day for 6 days, n = 3), P (progesterone, 250 mg/day for 6 days, n = 4), ESP (E for 6 days followed by, P for 6 days, n = 4), and ELP (E for 6 days followed by P for 12 days, n = 4). Northern blot analyses were performed on total RNA (30 micrograms) using cDNA probes to equine (e) RBP and human glyceraldehyde-3 phosphate dehydrogenase (G3PDH). The RBP RNA levels (normalized to G3PDH) from nonbred mares were low during early diestrus and increased after Day 10, and RBP RNA levels from pregnant mares were similar to those of nonbred mares for corresponding days. E tended to decrease endometrial RBP RNA; and P, ESP, and ELP increased it compared to C. There were no significant differences among P, ESP, and ELP RBP RNA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in amounts of different forms of inhibin during follicular atresia.

An inhibin immunoblot procedure was validated for measurement of inhibins (alpha beta) and inhibin alpha subunits in bovine follicular fluid (bFF) from individual follicles. Bovine FF was removed from nonovulatory follicles (> or = 6 mm in diameter) of cows during early diestrus. Ratio of progesterone (P) to estradiol (E) concentrations was used to classify follicles into three different stages of differentiation and atresia: estrogen-active (EA; PE ratio < 1), atretic (PE = 1-100), and highly atretic (PE = > 100). Bovine inhibin (bINH) was analyzed by an immunoblot procedure, an RIA that cross-reacts with inhibin alpha beta dimers and alpha subunits, and a two-site alpha beta dimer-specific immunoradiometric assay (IRMA). Immunoblots consistently detected 9 different bINH forms in bFF of each follicle. The average molecular mass for the bINH forms ranged from 29 to > 160 kDa, which was similar to those for purified bINH and bINH alpha subunits. The predominant bINH forms were > or = 122 kDa. Amounts of most bINH forms decreased several fold during atresia of EA follicles. However, the 34-kDa form increased 1.9-fold. To examine whether amounts of each bINH form varied independently during atresia, proportion of total bINH immunoblot activity represented by each bINH form was statistically analyzed. The results indicated that the proportion of total immunoblot activity for the 34-, 68-, and > 160-kDa bINH forms increased during atresia, whereas proportions for the 48-, 49-, and 122-kDa forms decreased. Alterations in amounts of most bINH forms were positively correlated with intrafollicular concentrations of E and negatively correlated with P. In contrast, the 34-kDa bINH form was negatively correlated with E, but positively correlated with P. Total bINH concentrations determined by RIA decreased 3-fold during atresia. However, amounts of most forms of bINH, except the 29-kDa form (r = 0.72), were relatively weakly correlated (r < 0.41) or not correlated with the RIA results. In contrast to RIA results, concentration of dimeric forms of bINH measured by IRMA increased 2.5-fold during atresia, but only the 34-kDa form of bINH was correlated (r = 0.77) with IRMA results.(ABSTRACT TRUNCATED AT 400 WORDS)

Ultrasonographic characteristics of the follicular and uterine dynamics in belgian mares

Summary Changes in the follicular development and visualiza- tion of endometrial folds during the estrous cycle were characterized by ultrasonography in Belgian mares. The secondary follicular wave was observed in only 2 of 7 mares and began in early diestrus (day 1; day 0 = day of ovulation). The dominant follicle of the ovulatory primary wave was retrospectively detected on 8.1 ± 3 days after the day of ovulation (day 0 = day of ovulation). The largest subordinate of the primary follicular wave was first de- tected at day 7.6 ± 1.6. The endometrial folds were most prominent 6.6 ± 1.3 days before ovulation. Regression of the endometria] folds was observed to occur 5.5 ±1.5 days before ovulation. In conclusion Belgian mares appear to have follicular dynamics similar to those reported for Thoroughbred horses. The cyclic uterine changes observed with ultrasound were more sudden, could only be observed for a short period of time and were observed earlier in relation to ovulation when compared with observations made in other breeds.

Inhibitory Effect of Bovine Follicular Fluid on In Vitro Maturation of Bovine Oocytes

To investigate its inhibitory properties, bovine follicular fluid was collected at different stages of the estrous cycle from small, medium, and large follicles. Follicular fluids were incubated with germinal vesicle stage, bovine oocytes aspirated from small follicles. Nuclear maturation was determined at 24h. Bovine follicular fluid inhibited the spontaneous maturation of bovine oocytes. The inhibition was reversed when follicular fluid was removed from oocyte cultures by 24h. Follicular fluid varied in its ability to inhibit germinal vesicle breakdown according to follicle size and estrual stage.Follicular fluid from both small and medium follicles at estrus had the greatest ability to prevent germinal vesicle breakdown but became less potent postestrus. Follicular fluid from large follicles at estrus had less ability to inhibit germinal vesicle breakdown than fluid from small and medium follicles. Strong germinal vesicle breakdown inhibiting activity was present in large, probably atretic follicles at late metestrus, early diestrus, and mid diestrus. However, follicular fluid from large follicles had less germinal vesicle breakdown inhibiting activity at proestrus than, follicular fluid from large follicles at late metestrus, early diestrus, and mid diestrus. This proestrual activity was similar to that in Graafian follicles at estrus.

Major and Minor Follicular waves During the Equine Estrous Cycle

Summary Follicular waves were characterized by a mathematical method for estrous cycles occurring during the fall (n=9) and spring (n=20) in mares of pmnarily Quarter Horse and Appaloosa breeding. Waves were classified as major (diver- gence of follicles of a wave into dominant and subordinates) and minor (no divergence). The major waves were sub- grouped into secondary waves (emerging during esmls or early diestrus and giving origin to a dominant anovulatory follicle or a diestrous ovulation) and primary waves (emerg- ing during diestms and giving origin to the primary or estrous ovulation). The primary waves originated on mean Day 7.4±0.5 (ovulation=Day 0) when the follicles were a mean of 12.l±0.5mm. Day of emergence of primary waves was positively correlated (P

Initiation of superovulation in mares 5 or 12 days after ovulation using equine pituitary extract with or without GnRH analogue

Cyclic mares were assigned to 1 of 3 treatments (n=15 per group): Group 1 received equine pituitary extract (EPE; 25 mg, i.m.) on Day 5 after ovulation; Group 2 received EPE on Day 12 after ovulation; while Group 3 received 3.3 mg of GnRH analogue (buserelin implant) on the day of ovulation and 25 mg, i.m. EPE on Day 12. Mares in each group were given 10 mg PGF 2α on the first and second day of EPE treatment. The EPE treatment was continued daily until the first spontaneous ovulation, at which time 3,300 IU of human chorionic gonadotropin (hCG) were given to induce further ovulations. Mares in estrus with a ≥35 mm follicle were inseminated every other day with pooled semen from 2 stallions. Embryo recovery was attempted 7 days after the last ovulation. Follicular changes and embryo recovery during 15 estrous cycles prior to treatment were used as control data. During treatment, the number of follicles ≥25 mm was higher (P<0.05) for Day 5 than for Day 12 or control mares, but the number for Day-5 mares was similar (P>0.05) to that of mares treated with buserelin implants (Group 3). Initiation of EPE treatment on Day 5 resulted in a greater (P<0.05) number of ovulation (2.9) than on Day 12 (1.1) or in the control mares (1.3) but not in the buserelin-treated mares (1.8). The number of embryos recovered from mares in the Day 5 (1.2), Day 12 (1.0), buserelin (0.9) and control (0.9) groups was similar (P>0.05). The conclusions were 1) EPE initiated in early diestrus increased follicular development and ovulation and 2) treatment with GnRH analogue marginally improved response to EPE treatment.

Synthesis of uterine endometrial proteins during early diestrus in the cyclic and pregnant dog, and after estrogen and progesterone treatment.

The objectives of this study were to identify and characterize dog uterine endometrial proteins synthesized de novo in explant culture during early luteal phase, to examine distribution of these proteins prior to the embryo's entering the uterus and during its free-floating period prior to implantation, and to examine regulation of endometrial proteins by estrogen and progesterone (P4) treatments. Uterine endometrium was collected from cyclic and pregnant bitches on diestrus Days 3, 7, and 10 as determined by loss of cornification of vaginal epithelium, and from ovariectomized dogs after treatment with corn oil, estrogen, P4, or estrogen followed by 1 or 2 wk of P4. Tissue was incubated in an explant culture system in the presence of [3H]leucine or [35S]methionine. The rate of incorporation of [3H]leucine into nondialyzable macromolecules indicated no significant change in rates of incorporation by status (pregnant vs. nonpregnant), day, or steroid treatment. Uterine endometrial-conditioned culture medium, analyzed by two-dimensional SDS-PAGE and fluorography, revealed a complex array of at least ten proteins or protein complexes in cyclic and pregnant bitches. No difference in protein pattern was detected by status; however, differences in distribution were apparent by day of cycle or early pregnancy. Two major proteins, cP5 (M(r) 54,686) and cP6 (M(r) 23,010) appeared to be differentially expressed. Expression of cP5, maximal on diestrus Day 3, decreased as the cycle or pregnancy progressed to diestrus Day 10. In contrast, expression of cP6, a minor protein on diestrus Day 3, appeared to be up-regulated for each status to Day 10, with increased intensity and multiple isoelectric and molecular-weight variants. In ovariectomized steroid-treated dogs, two-dimensional SDS-PAGE showed that pattern and distribution of specific proteins were affected by treatment. Acidic protein cP1 (M(r) 87,600), synthesized after corn oil and P4 treatment, was suppressed with estradiol (E2). Proteins cP2 (M(r) 40,000 and M(r) 42,000), present with all treatments, were intensified with P4. A high-M(r) basic protein complex (cP3) and acidic protein cP4 were expressed with E2 and maintained with P4 treatment. Proteins cP5 and cP6, while not induced by E2 or P4 alone, required E2 priming for P4 induction. Protein cP5 was down-regulated while cP6 was up-regulated with P4 for 2 wk. Proteins induced by estrogen followed by 1 or 2 wk of P4 treatments were similar to those released by endometrial explants collected from pregnant and cyclic bitches on Days 3, 7, and 10 of spontaneous diestrus.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of aminoglutethimide phosphate on litter size and birth weight in superovulated rats

In this study, litter sizes, birth weights and survival rates of neonates in superovulated rats treated with aminoglutethimide phosphate (AGP) were studied. Young (8- to 9-week old) and adult (14- to 16-week old) rats were treated with 20 or 40 IU PMSG between 1100 and 1300 hours on the day of early diestrus, followed by identical doses of hCG 52 to 54 hours later. These rats received 10 mg AGP on Days 0 to 2 of pregnancy (AGP rats). The duration of pregnancy in the AGP-treated and control rats was about the same. Mean live litter sizes in young and in adult AGP rats treated with 20 IU PMSG and 20 IU hCG were significantly higher (15.5 and 15.4; P<0.01) than in the control rats (11.5 and 12.6). When AGP was given to young and adult rats pretreated with 40 IU PMSG and 40 IU hCG, they produced means of 17.7 and 17.3 live neonates, respectively. The birth weights for young (5.55 to 5.88 g) and adult (5.89 to 5.96 g) AGP rats were smaller than those of respective control rats (6.44 and 6.40 g; P < 0.05−0.01). When the number of neonates was adjusted to 8 per dam for nursing and rearing, all of them were alive at 5 weeks after birth and showed normal growth. However, body weight gains of the progeny of AGP dams were lower than those of controls. These results indicate that rats treated with large doses of gonadotropins and AGP produce larger litter sizes than nontreated controls.

A transient increase in uterine tone during early diestrus in mares

Uterine tone was assessed digitally by transrectal palpation in 20 pony mares (nonbred, n=7; pregnant, n=13) and scored on a scale of 1 to 4 (minimal or flaccid to maximal or turgid). Tone was evaluated without knowledge of reproductive status or day of estrous cycle or pregnancy. A transient peak in uterine tone was detected on Day 6 (Day 0 = day of ovulation) in both the nonbred and pregnant mares. The hypothesis that the increase in tone was an early uterine response to entry of the conceptus was not supported. Data combined for both groups indicated that tone increased (P<0.05) between Days 0 and 2, Days 2 and 3 and Days 3 and 6, including a significant increase between Days 5 and 6; tone decreased (P<0.002) between Days 6 and 8. Temporal relationships among the observed peak in uterine tone and reported transient surges in estrogen secretion as well as ultrasonically detected endometrial folding and the reported effects of exogenous steroids on uterine tone suggest that the peak in tone was a result of a secondary or early diestrous surge in estrogens.

Endocrinological observation and morphology of the corpus luteurn and large follicles of bovine ovaries in early diestrus

Endocrinological observation and morphology of the corpus luteurn and large follicles of bovine ovaries in early diestrus

Reproductive response of mares after treatment with progestogens with and without the additional of estradiol

A study involving 60 light-horse mares was conducted both to evaluate the response of mares to injectable progester- one or altrenogest and to determine ifestradiol in combination with either progestogen provided any added benefit. Treatments were initiated at either early estrus, late estrus, early diestrus, mid-diestrus or late diestrus in order to assess the effect of stage of cycle at onset of treatment. Within each of these stages of the cycle, mares were randomly assigned to 1 of 4 treatments: 150 mg progesterone injected i.m. (P); 150 mg progesterone + 10 mg estradio11713 injected i.m. (P+); .044 mg altrenogest per kg body weight orally (A); and .044 mg per kg body weight orally plus 10 mg estradiol 1713 i.m. (A+). All treatments were given daily for 7 days with 10 mg PGFaCt given on day 7 to all mares. The number of mares ovulating by day 14 after treatment (N=15/group) was 13, 7,11 and 8 forA, A+, P and P+, respectively. The response of mares to progesterone and altrenogest was similar. Fewer (Pì0.05) mares given combined steroid treatments ovulated within 14 days (15 of 30) than those given progestogen treatments. Stage of cycle had no affect (Pì0.05) on response of mares ovulating within 14 days or after 14 days of treatment. Mares that ovulated within 14 days of treatment had larger foUieles after progestogen treatment than those not ovulating by 14 days.

Recruitment and maturation of small subsets of luteinizing hormone gonadotropes during the estrous cycle.

Small and medium-sized gonadotropes may enlarge and produce more LH in order to contribute to the proestrous surge. To test this hypothesis, dispersed pituitary cells from cycling female rats were separated by centrifugal elutriation into small, medium, and large fractions and labeled for LH beta antigens or mRNA (by in situ hybridization with a biotinylated oligonucleotide probe complementary to sequences encoding amino acids 28-40). The percentage of cells bearing LH beta mRNA in the pituitary cell population increased from 6 +/- 0.4% in the evening of diestrous day 2 to 16 +/- 0.7% in the morning of estrus (average +/- SEM). Over 80% of these labeled cells were large or small subtypes. The proportion of small gonadotropes labeled with LH beta mRNA declined from 43 +/- 3% at metestrus to 29 +/- 1% on the evening of proestrus as the proportion of medium-sized gonadotropes labeled for LH beta antigens (15 +/- 1%) or mRNA (17 +/- 1%) increased to 25 +/- 2% or 38 +/- 2%, respectively. Because the overall percentage of immunoreactive LH cells did not change after diestrus, small LH cells may have enlarged or increased their density to join the medium-sized pool. During proestrus, the proportion of large immunoreactive LH gonadotropes increased from 41 +/- 2% to 65 +/- 2% (by the morning of estrus) as the proportion of small or medium-sized LH cells declined to 17-18 +/- 1%, suggesting further increases in size or density. These data suggest that small or medium-sized gonadotropes are activated during early diestrus to enlarge and produce LH beta. They contribute to the increased number of cells in medium-sized and large fractions in proestrous or estrous rats. The predominance of the smaller subtypes during metestrus and diestrus suggests that LH gonadotropes may revert to a smaller or lighter subset to await activation during the next cycle.