Low Progesterone Concentrations Research Articles

Endocrine milieu and developmental dynamics of ovarian cysts and persistent follicles in postpartum dairy cows

Ovarian follicular cysts and persistent follicles are follicular pathologies involved in reduced fertility of dairy cows. Two separate experiments were performed on high-yielding Holstein cows to characterize ovarian cyclicity and evaluate the developmental dynamics of follicle pathologies postpartum. In experiment 1, 58 cows were monitored by ultrasonography twice weekly from d 18±1 to 69±2 postpartum. First ovulation occurred 38±3, 27±2, 20±1, and 25±3 d postpartum in cows with 1 cycle (n=11), 2 cycles (n=21), 3 cycles (n=13), and 4 cycles (n=7), respectively. Follicular pathologies were developed in cows that were either acyclic (n=6) or had 1 or 2 cycles, but not in cows with more than 2 cycles. In experiment 2, 47 cows were monitored twice weekly from 10 d postpartum to second ovulation. Follicles ≥17mm in diameter in 2 consecutive scans were aspirated, and concentrations of various hormones were measured. Cows were defined as cyclic (n=30; 64%) or with the potential to develop follicular pathology (n=17; 36%). Aspirated follicles (n=27) were classified into 3 main groups based on follicular growth rate, follicular diameter, and ovarian activity before and after follicular aspiration. Dominant follicles (n=4) were defined as large follicles (20mm in diameter) with growth rate ≤1mm/d and normal ovarian activity. Persistent follicles (n=6) had the same growth rate and diameter as the dominant follicles, but persisted at the same diameter for ≥10d. Ovarian cysts (n=17) were defined as the largest follicular structures (19 to 32mm in diameter), with abnormal growth rate (>1mm/d) and abnormal ovarian activity. Single or turnover cysts did not differ in their growth parameters and were therefore combined and further classified according to follicular-fluid hormone concentrations. Estradiol-dominant cysts (n=7) were characterized by normal estradiol (284 to 659ng/mL) and progesterone (20 to 113ng/mL) concentrations, similar to those of the dominant follicle (554 to 993ng/mL and 44 to 106ng/mL, respectively). Progesterone-dominant cysts (n=5) were characterized by low estradiol (0.06 to 330ng/mL) and high progesterone (586 to 3,288ng/mL) concentrations. Low-steroidogenic active cysts (n=5) were characterized by low concentrations of both estradiol (23 to 61ng/mL) and progesterone (17 to 205ng/mL). Characterization of spontaneously forming cysts might enable definition of the formation of ovarian follicular pathologies in postpartum cows.

Embryo losses in sheep during short-term nutritional supplementation

To test whether a nutritional supplement fed from 6 days before until 15 days after insemination reduces progesterone concentrations and increases embryo losses, Merino ewes were artificially inseminated (Day 0). Control ewes (n = 116) were not supplemented whereas Lupin6 ewes (n = 112) were supplemented with 500 g lupin grain daily for 6 days before insemination, and Lupin6+15 ewes (n = 122) from 6 days before until 15 days after insemination. There were no major differences between treatment groups in progesterone concentrations over the first 17 days of pregnancy. Embryo losses over Days 10-17 were lower in the Lupin6+15 than in the Control and Lupin6 groups, but the opposite occurred from Day 17-30. The concentrations of insulin and IGF-I were higher in Lupin6+15 ewes on Days 5, 12 and 17, compared with Lupin6 and Control ewes, while leptin concentrations decreased by Day 17 in the Lupin6+15 group. We conclude that feeding ewes for 15 days after mating improved embryo survival, which was associated with an increase in the concentrations of metabolic hormones and lower progesterone concentrations. However, the decrease in leptin concentrations promoted by the interruption of supplementation seems be linked to increased embryo mortality up to Day 30.

Effect of asynchronous transfer on bovine embryonic development and relationship with early cycle uterine proteome profiles

The uterus provides the nurturing environment that supports the growth of the early preimplantation bovine conceptus. To determine critical time points of uterine influence, in vitro-produced Day 7 blastocysts were transferred into synchronous (Day 7) uteri and asynchronous uteri (Days 5 or 9). Embryo growth was evaluated 7 and 15 days after transfer and compared with that of embryos generated by AI. Conceptuses recovered from asynchronous Day 9 transfers were fourfold larger than synchronous transfer or gestational Day 14 AI conceptuses; by 15 days after transfer, differences were less marked. Two-dimensional gel electrophoresis was used to compare the histotroph protein composition of uterine luminal flushings (ULF) on Days 5 and 9 after oestrous to determine any protein differences that would promote embryo growth. The ULF were collected by serially flushing the uteri of the same heifers and mature cows at different times of the cycle. Ten proteins that differed in abundance between Day 5 and 9 were identified by mass spectrometry. Three, namely phosphoserine aminotransferase 1, purine nucleoside phosphorylase and aldose reductase, were verified by western blot analysis as more abundant on Day 9 (P<0.002). Myostatin was present in only in Day 9 ULF, whereas tissue inhibitor of matrix metalloproteinase 2 (TIMP2) and legumain were only detected in Day 14 ULF. Although mature cows had lower progesterone concentrations on Days 5 and 14 (P<0.05) and tended to have less TIMP2 than heifer groups, no other protein differences were detected. Thus, the embryo growth-enhancing environment on Day 9 was associated with temporal changes in the expression of several proteins of the histotroph.

Androgen Receptor Signaling in Prostate Cancer: New Twists for an Old Pathway

Secretory leukocyte protease inhibitor is a multifunctional protein with a variety of activities attributed to it. A significant increase in the expression of Secretory leukocyte protease inhibitor was noticed in syncytiotrophoblasts following differentiation of cytotrophoblasts in to syncytiotrophoblasts by addition of Forskolin. Using the BeWo cells which are derived from choriocarcinoma, the effect of addition of progesterone and estradiol on the expression of Secretory leukocyte protease inhibitor by Reverse Transcription Polymerase Chain Reaction was assessed. It was found that while addition of low concentration of progesterone resulted in a significant increase in expression of Secretory leukocyte protease inhibitor, addition of estradiol even at high concentration had no effect. The specificity of effect of progesterone was established by the observation that addition of Progesterone along with progesterone receptor antagonist (RU484) resulted in decrease in the level of expression of Secretory leukocyte protease inhibitor. These results suggest that Secretory protease leukocyte protease inhibitor is a progesterone regulated gene.

Impact of Taenia solium neurocysticercosis upon endocrine status and its relation with immuno-inflammatory parameters

Neurocysticercosis (NC) is a parasitic disease caused by the infiltration of the larval stage of Taenia solium in the central nervous system. Clinical presentations are heterogeneous and particularly depend, on the age and gender of the host. We designed a clinical study to evaluate the hormonal changes associated with neurocysticercosis and the relationships between disease heterogeneity, endocrine and immunological status. A total of 50 patients and 22 healthy subjects were included. A precise clinical and radiological description of disease for each patient was recorded. A broad hormonal profile was assessed for each participant and, in a sub-group of patients, immunological features were also evaluated. Compared with controls, all patients had lower dehydroepiandrosterone (DHEA) concentration; male patients also had lower concentrations of 17β-estradiol and higher concentrations of luteinising hormone (LH). In the clinically severe patients, lower concentrations of progesterone and androstenedione were found in women. Higher concentrations of follicle stimulating hormone (FSH) and lower concentrations of testosterone were found in men when compared with the less clinically severe patients. Significant correlations were found between estradiol and IL-10 in male patients, and between dehydroepiandrosterone (DHEA) and IL-1β, and androstenedione and IL-17 in female patients. To our knowledge the present study constitutes the first demonstration that the presence of T. solium larvae in the central nervous system can modify the host environment by the induction of endocrine and immunological changes. These results provide a stimulating background to analyse the repercussions of these changes on the course of the disease and on patient reproductive health.

Alterations in systemic concentrations of progesterone during the early luteal phase affect RBP4 expression in the bovine uterus

Systemic progesterone affects the timing and duration of uterine endometrial gene and protein expression and has significant effects on conceptus development. The objective of the present study was to examine how changes in progesterone concentrations during the early luteal phase affect retinol-binding protein (RBP4) mRNA and protein concentrations in the uterus. Endometrial tissue and uterine flushings were recovered on Days 7 and 13 of the oestrous cycle in heifers with high, normal and low progesterone concentrations. RBP4 mRNA and protein concentrations were higher (P<0.05) on Day 13 compared with Day 7 in heifers with high and control progesterone concentrations. However, there was no difference in RBP4 protein concentrations between Days 7 and 13 in heifers with low progesterone (P>0.05). On Day 7, although heifers with low progesterone had lower RBP4 mRNA expression compared with controls (P<0.05) there was no difference in protein concentrations between treatment groups. On Day 13, RBP4 mRNA was 2-fold higher (P<0.001) in heifers with high and control progesterone compared with their low-progesterone counterparts and RBP4 protein concentrations were over 2-fold higher (P<0.001) in heifers with high compared to low progesterone. In conclusion, progesterone modulates uterine RBP4 mRNA and protein abundance in a time- and concentration-dependent manner.

Histological changes in the endometrial of pregnant Sprague-Dawley rats under supplementation levels of n-6:n-3 fatty acid ratio

This study describes a changed uterine morphometry and its application to the endometrial structure of a pregnant rat. The number and the size of uterine gland and blood vessels changed during the pregnancy period of the rat. This effect on day 15 was significantly changed in the different groups. When the endometrial morphology was related to the circulating progesterone concentrations on day 15, it was observed that relationships were found on day 15 and a high progesterone concentration in the Diet 1:1 group was associated with an increased number of the uterine gland and blood vessel. Furthermore, animals in the Diet 1:30 group were slaughtered on day 15 and a low progesterone concentration on that same day was associated with the decreased uterine gland size, though a simultaneous decrease was found in the number of endometrial gland. In contrast, the number of implanted embryos was significantly lower in the Diet 3 group at 15 days of gestation The results suggest that the endometrial glands do not only grow and regress during the supplementation of high ratio n-6:n-3 fatty acids, but the number and size of the endometrial glands in the endometrial area are controlled by progesterone, which leads to changes in the structure and maintenance of the uterine during the pregnancy period.

Effects of prostaglandin administration on ovarian follicular dynamics, conception, prolificacy, and fecundity in sheep

Two experiments were conducted to determine the effects of prostaglandin administration on ovarian follicular dynamics, conception, prolificacy, and fecundity in sheep. During the breeding season, multiparous Corriedale ewes were randomly allocated to two groups: 1) PG group (n = 15 and n = 135 in Experiments I and II, respectively): synchronized with two injections of DL-Cloprostenol (125 μg) given 7 d apart, and inseminated at a fixed time (Day 0), 48 h after the second injection; and 2) Control group (n = 15 and n = 73 in Experiments I and II): ewes in spontaneous estrus inseminated at detected estrus. Ewes received 100 × 106 sperm by intrauterine AI. Ultrasonography was used to evaluate growth of the ovulatory follicle, ovulation rate (OR), conception rate, and prolificacy on Days 30 and 60. Ewes from the group PG had a larger (4.8 ± 0.5 mm, mean ± SEM; P < 0.05) ovulatory follicle that grew faster (1.2 ± 0.3 mm/d, P = 0.08), and a lower OR (1.37 ± 0.1, P < 0.05), compared to ewes from the Control group (3.9 ± 0.2 mm, 0.7 ± 0.2 mm/d, and 1.61 ± 0.1 respectively). Plasma progesterone concentrations from Days −6 to 1 were lower in the PG group (P < 0.05), but plasma estradiol concentrations were similar between groups (P > 0.05). Progesterone concentrations were similar between groups during the early luteal phase and on Days 12 and 17 (P > 0.05). The embryo recovery rate (Day 7) tended to be lower in the PG group (39 vs 64%, P = 0.08), but embryo quality did not differ between groups. Conception, prolificacy and fecundity, were lower in the PG than in the Control group (P < 0.05). Cumulative reproductive losses were similar between groups, but more twins were lost in the PG group (P < 0.05). We concluded that in ewes synchronized with PGF2α given twice, 7 d apart, lower reproductive performance was associated with an environment dominated by lower progesterone concentrations that stimulated the preovulatory follicle to grow faster and become larger; this was associated with lower rates of ovulation, conception, prolificacy, and fecundity.

Low plasma progesterone concentrations are accompanied by reduced luteal blood flow and increased size of the dominant follicle in dairy cows

To investigate the influence of low plasma progesterone (P 4) concentrations on luteal and ovarian follicular development as well as endometrial gene expression in the concomitant and subsequent estrous cycle, 20 lactating dairy (Holstein Friesian and Brown Swiss x Holstein Friesian) cows received either a single treatment with 25 mg prostaglandin F 2α (PGF 2α) on Day 4 Hour 12 (PG1; n = 8), or two treatments (25 mg PGF 2α each) on Day 4 Hours 0 and 12 (PG2; n = 12) of the estrous cycle (Day 1, Hour 0 = ovulation). In four cows, ovulation occurred between 4 and 6 d after the second PGF 2α treatment; these cows and one lame cow were excluded. In the 15 remaining cows with physiological interovulatory intervals (18 to 24 d), P 4, luteal size (LS) and blood flow (LBF), as well as follicular size (FS) and blood flow (FBF), were determined daily until Day 4, immediately prior to (0 h) and 12 h after each PGF 2α treatment, and then every 2 d, from Day 5 to 8 d after the subsequent ovulation. Because P 4 did not differ (P > 0.05) between PG1 and PG2, cows were regrouped according to their mean P 4 concentration from Days 7 to 15, either P 4 <2 ng/mL (P 4L; n = 7) or P 4 >2 ng/mL (P 4H; n = 8). In the treatment cycle, LS was smaller in P 4L than P 4H on Days 13 (P = 0.01) and 15 (P = 0.03), and LBF was lower in P 4L than P 4H on Day 15 (P = 0.02). The dominant follicle of the first follicular wave was larger in P 4L than P 4H on Days 13 (P = 0.03), 15 (P = 0.03), and 17 (P = 0.01). In the subsequent cycle, there were no significant differences between P 4L and P 4H for P 4, FS, LS, and LBF; however, FBF was lower (P = 0.01) in P 4L than P 4H on Day 7. In Group P 4L, endometrial expressions of estrogen receptor α and oxytocin receptor were lower (P = 0.05 and P = 0.03, respectively) at the estrus that preceded treatment compared to the post-treatment estrus. In summary, low P 4 during diestrus was associated with smaller LS, reduced LBF, and larger FS in the treatment cycle, but not in the subsequent cycle.

Body temperature around induced estrus in dairy cows

The overall objective of this study was to study the influence of induced estrus on body temperature, comparing 5 distinct intervals around induced estrus and to determine the diurnal pattern from 4±1 d before to 4±1 d after induced estrus. Sixteen estrous cycles of 9 postpartum dairy cows were synchronized with 2 injections of PGF2α, 10 d apart. After the second PGF2α injection on d 10, temperature loggers were inserted into the vaginal cavity for a 12±1-d period. Two days later, a third dose of PGF2α was injected to induce estrus. After confirmation of a corpus luteum, loggers were removed on d 5±1. Observation of estrus, rectal palpation, and ultrasound scanning to determine ovulation were carried out every 4±1h, beginning at 12h after the third PGF2α injection. Blood samples from the vena coccygea mediana were collected twice daily from d 11 to 12 and every 4±1h after the third PGF2α injection until ovulation. Vaginal temperature was recorded every 5min and averaged to hourly means for the following 5 periods: 1) 48h preceding the third PGF2α injection, 2) from the third PGF2α injection to first signs of estrus, 3) estrus to ovulation, 4) a 4-h interval in which ovulation occurred, and 5) a 96-h post-ovulation period. High body temperatures (39.0±0.5°C) and low progesterone (P4) concentrations (<0.5ng/mL) were observed during estrus, whereas low body temperatures were observed from PGF2α injection to estrus (38.6±0.3°C) and around ovulation (38.5±0.2°C), respectively. An association between body temperature and serum P4 concentrations did not exist. However, P4 concentrations on d 11 and 12 were high (5.0±1.5ng/mL) and decreased (0.9±0.2ng/mL) after ovulation. Diurnal temperature rhythms were similar before and after estrus. Vaginal temperature before estrus (d 11 and 12) was slightly (0.1°C) higher compared with the post-ovulation period.

Expression of Cytosolic Phospholipase A2 in Equine Endometrium during the Oestrous Cycle and Early Pregnancy

Phospholipase A2 (PLA2) is a key enzyme for biosynthesis of PGF2α. Real-time RT-PCR and immunohistochemistry were used to determine transcription and cellular distribution of cytosolic PLA2 (cPLA2) in the equine endometrium during the oestrous cycle and early pregnancy. Endometrial biopsy and blood samples were collected from cycling mares on days (d) 8, 11, 15 and 18 (oestrus) (Day 0 = Day of ovulation; n = 5 for each day) and from pregnant mares (n = 4) on d15. Except for mares on d18 and some cyclic mares (n = 2) on d15 with low progesterone (P₄) concentrations (< 3.18 nm), P₄ concentrations were high. Cytosolic PLA2 was mainly localized in the luminal epithelium and stroma was negative. Cytosolic PLA2 expression was negatively correlated with P₄ concentration (r = -0.75, P < 0.001) and differed according to the stage of the oestrous cycle (P < 0.05). Cytosolic PLA2 expression was high during oestrus and declined to basal levels on d8 (P < 0.05). Thereafter, there was a trend for increased cPLA2 expression as luteal phase progressed. However, as P₄ dropped below 3.18 nm on d15, cPLA2 expression increased (P < 0.05). In pregnant mares, cPLA2 expression was not different from cyclic mares on d15 with high P₄ concentrations. However, it was lower than cyclic mares with low P₄ concentrations (p < 0.05). In conclusion, cPLA2 isoform, a member of the PLA2 family that controls PGF2α secretion, is highly expressed in the endometrium at the expected time of luteolysis. Progesterone may be an inhibitor for cPLA2 expression. During pregnancy, cPLA2 expression may be sufficient to initiate the cascade for PGF2α secretion and does not play a direct role in maternal recognition of pregnancy.

Induction of ovulation in Xenopuswithout hCG injection: the effect of adding steroids into the aquatic environment

BackgroundThe African clawed frog, Xenopus laevis, is widely used in studies of oogenesis, meiotic cell cycle and early embryonic development. However, in order to perform such studies, eggs are normally collected after the injection of hCG into the dorsal lymph sac of fully-grown female frogs following pre-injection of PMSF. Although this protocol is established and used as standard laboratory approach, there are some concerns over whether the injections could cause the transmission of deleterious microorganisms. Moreover, these injection protocols require a competent skilled worker to carry out the procedure efficiently.MethodsRecently, we established a novel method to induce fish ovulation by simply adding the natural maturation-inducing hormone of teleosts, 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-DHP), into the surrounding water. In the present study, we demonstrate how we can induce ovulation in frogs using the same methodology.ResultsIn frogs, progesterone was effective in the induction of oocyte maturation in vitro. We then examined the ability of progesterone to induce ovulation in frogs. However treatment of frogs with progesterone alone only occasionally induced ovulation in vivo. The number of oocytes and the frequency of ovulation were significantly lower than that induced by hCG-injection. Thus, conditions were improved by using a combination of progesterone with estradiol and by pre-treating frogs with low concentrations of progesterone or estradiol. Finally, we established an efficient means of inducing ovulation in frogs which involved pre-treatment of frogs with salt solution followed by a mixture of estradiol and progesterone at high concentration. The frequency and numbers of oocytes obtained were identical to those resulting from PMSG-hCG induction. Fertilization rate of eggs ovulated by the new treatment method was comparable to eggs obtained by hCG-injection and juveniles developed normally.ConclusionsTo conclude, we have successfully developed a novel method to induce ovulation in frogs but without the need for a potentially harmful injection strategy.

Regulation of Expression of Secretory Leukocyte Protease Inhibitor by Progesterone in BeWo Choriocarcinoma Cells

Secretory leukocyte protease inhibitor is a multifunctional protein with a variety of activities attributed to it. A significant increase in the expression of Secretory leukocyte protease inhibitor was noticed in syncytiotrophoblasts following differentiation of cytotrophoblasts in to syncytiotrophoblasts by addition of Forskolin. Using the BeWo cells which are derived from choriocarcinoma, the effect of addition of progesterone and estradiol on the expression of Secretory leukocyte protease inhibitor by Reverse Transcription Polymerase Chain Reaction was assessed. It was found that while addition of low concentration of progesterone resulted in a significant increase in expression of Secretory leukocyte protease inhibitor, addition of estradiol even at high concentration had no effect. The specificity of effect of progesterone was established by the observation that addition of Progesterone along with progesterone receptor antagonist (RU484) resulted in decrease in the level of expression of Secretory leukocyte protease inhibitor. These results suggest that Secretory protease leukocyte protease inhibitor is a progesterone regulated gene.

Therapeutic Approaches to Pregnancy Loss of Non‐infectious Cause During the Late Embryonic/Early Foetal Period in Dairy Cattle. A Review

The problem of pregnancy loss during the late embryonic/early foetal period due to non-infectious causes in dairy cattle is on the rise, especially in high milk producing cows. This review discusses recent therapeutic approaches designed to reduce the incidence of early foetal loss. These strategies are based on the fact that low plasma concentrations of progesterone are commonly related to foetal loss. Progesterone supplementation during the late embryonic/early foetal period has proven useful in curtailing losses, mainly in single pregnancies, whereas a more positive effect of treatment with GnRH than progesterone has been found in twin pregnancies. Therapeutics is not necessary in cows with an additional corpus luteum. In practical terms, suggestions include recording the number of embryos and corpora lutea on first pregnancy diagnosis and checking for normal pregnancy progression on day 60 post-insemination.

Diabetes Mellitus in Elkhounds Is Associated with Diestrus and Pregnancy

Female Elkhounds are shown to be at increased risk for diabetes mellitus, and occurrence of diabetes during pregnancy has been described in several cases. Onset of diabetes mellitus in Elkhounds is associated with diestrus. Sixty-three Elkhounds with diabetes mellitus and 26 healthy controls. Medical records from 63 Elkhounds with diabetes were reviewed and owners were contacted for follow-up information. Blood samples from the day of diagnosis were available for 26 dogs. Glucose, fructosamine, C-peptide, growth hormone (GH), insulin-like growth factor-1, progesterone, and glutamate decarboxylase isoform 65-autoantibodies were analyzed and compared with 26 healthy dogs. Logistic models were used to evaluate the association of clinical variables with the probability of diabetes and with permanent diabetes mellitus after ovariohysterectomy (OHE). All dogs in the study were intact females and 7 dogs (11%) were pregnant at diagnosis. The 1st clinical signs of diabetes mellitus occurred at a median of 30 days (interquartile range [IQR], 3-45) after estrus, and diagnosis was made at a median of 46 days (IQR, 27-62) after estrus. Diabetes was associated with higher concentrations of GH and lower concentrations of progesterone compared with controls matched for time after estrus. Forty-six percent of dogs that underwent OHE recovered from diabetes with a lower probability of remission in dogs with higher glucose concentrations (odds ratio [OR], 1.2; P=.03) at diagnosis and longer time (weeks) from diagnosis to surgery (OR, 1.5; P=.05). Diabetes mellitus in Elkhounds develops mainly during diestrus and pregnancy. Immediate OHE improves the prognosis for remission of diabetes.

Progesterone regulation of uterine dendritic cell function in rodents is dependent on the stage of estrous cycle

Steroid hormones, such as progesterone, are able to modify immunity and influence disease outcome. Dendritic cells (DCs) drive potent immune responses, express receptors for steroid hormones, and may be a primary target of steroid hormone actions during infection of the genital tract, including uterine tissue. Here, we report that progesterone limited DC-associated activation marker expression and inhibited cytokine secretion by uterine DCs, which was associated with changes in signal transducer and activator of transcription 1 (STAT1) activity. We also found that DCs from mice at stages with higher progesterone concentrations (diestrus, metaestrus) were more sensitive to progesterone than those in stages with lower progesterone concentrations (proestrus, estrus), both in vitro and in vivo. This difference correlated with the levels of progesterone receptor expressed by DCs. These data suggest that progesterone regulates DC function and could contribute to the susceptibility of females to uterine and other genital tract infections at selected time periods throughout the life cycle.

Follicular wave of the ovulatory follicle and not cyclic status influences fertility of dairy cows

Two experiments evaluated the influence of follicular wave at artificial insemination (AI) on fertility of dairy cows. In experiment 1, data from 5,607 lactating cows enrolled in estrous and ovulation synchronization programs for AI were evaluated. Cows’ blood was analyzed for progesterone 7 to 14 d apart, with the second sample collected on the day of the first GnRH (GnRH1) of the synchronization protocol. Cows were classified as cyclic if progesterone was ≥1 ng/mL in at least 1 of the 2 samples and as anovular if both samples were <1 ng/mL. Cyclic cows were categorized as low (CLOW;<1 ng/mL) or high (CHIGH; ≥ 1 ng/mL) progesterone on the day of GnRH1, which would result in ovulation of the dominant follicle of the first (FW) and second (SW) follicular waves, respectively, at AI. Pregnancy per AI (P/AI) was determined 30 and 53 d after AI. In experiment 2, 220 cyclic Holstein cows received 2 injections of PGF2α administered 14 d apart. The Ovsynch protocol (d 0 GnRH, d 7 PGF2α, d 9 GnRH, d 9.5 timed AI) was initiated either 3 or 10 d after the second PGF2α of the presynchronization to result in insemination to the FW or SW dominant follicles. Blood was analyzed for progesterone and ovaries were scanned to determine ovulatory responses and follicle diameter. Pregnancy was determined on d 32 and 67 after timed AI. In experiment 1, P/AI on d 30 was greater for CHIGH cows than for CLOW and anovular cows (43.0, 31.3, and 29.7%, respectively), but because of pregnancy loss, P/AI on d 53 was lowest for anovular cows. Proportions of cows with short reinsemination intervals differed among groups and were 7.1, 15.7, and 11.9% for CHIGH, CLOW, and anovular cows, respectively. Pregnancy loss was greater for anovular cows than for CLOW cows (15.0 vs. 10.0%) and was intermediate for CHIGH cows (13.5%). In experiment 2, 9.8 and 97.2% of the FW and SW cows, respectively, had progesterone ≥1 ng/mL at GnRH1. Concentrations of progesterone at the GnRH1 and PGF2α injections of the Ovsynch protocol were greater for SW cows than FW cows. Pregnancy per AI was greater for SW cows than for FW cows (41.7 vs. 30.4%) despite less ovulation to GnRH1 in SW cows than in FW cows (78.7 vs. 88.4%). Collectively, these data indicate that follicular wave of the ovulatory follicle and not cyclic status caused the greatest reduction in P/AI in dairy cows. Whether the culprit is the follicle itself or the hormonal milieu characteristic of the first follicular wave and the early stage of the estrous cycle remains to be elucidated. Synchronization programs that induced ovulation of the FW follicle at AI reduced P/AI in lactating dairy cows, and ovulation of the FW follicle, or development of the ovulatory follicle under low progesterone concentrations, or both, might be mechanisms for reduced fertility in anovular cows.

EFEITO DO MANEJO E DE VARIÁVEIS BIOCLIMÁTICAS SOBRE A TAXA DE GESTAÇÃO EM VACAS RECEPTORAS DE EMBRIÕES

This work aimed to verify the effects of the handling and thermal environment on the pregnancy rate of embryo-recipient zebu x European cows (n=94) as well as the behavioral and clinical aspects at the moment of embryo transfer. Cortisol was analyzed by plasmatic samplers collected on D0, D9 and D16 of the hormonal treatment for estrous synchronization; blood was also sampled to analyze progesterone levels at the moment of embryo transfer. There was no difference (p>0.05) between pregnant and not pregnant females for maturation stage and embryo classification, coat, and reactivity between fresh and frozen embryos. The cortisol concentrations decreased (p>0.001) between D0 and D16, and the concentration of progesterone was similar in function of the pregnancy stage. Nevertheless progesterone in D16 for non pregnant cows was lower than for pregnant ones in the same day. Moreover, pregnant cows showed lower skin temperature. The values of Black Globe-Humidity Index were at very high limits, indicating that all animals could be under heat stress. The regression analysis indicated a tendency (p=0.08) to increase the pregnancy probability of 25% between the beginning and end of the afternoon. Thus, low plasmatic concentration of progesterone and high skin temperature represents a factor of thermal discomfort at the moment of the embryo receiving, influencing the pregnancy rate of recipient cows. As observed, heat stress decreased the probability of the pregnancy of recipient cows in tropical environment. KEYSWORDS: Beef cattle, cortisol, handling, heat stress, pregnancy rate.

Ciliary beat frequency controlled by oestradiol and progesterone during ovarian cycle in guinea‐pig Fallopian tube

The ciliary beat frequency (CBF) of guinea-pig fimbria during the ovarian cycle was measured by video microscopy using a high-speed camera (500 Hz). In the follicular phase, with increasing concentrations of beta-oestradiol ([betaE(2)]) and a low concentration of progesterone ([PRG]), CBF increased from 13.5 to 16 Hz. In the ovulatory phase, with further increase of [betaE(2)], CBF decreased gradually from 16 to 13.5 Hz. In the early luteal phase, with low [PRG] and [betaE(2)], CBF increased to 17 Hz; however, in the middle luteal phase, with increasing [PRG], CBF decreased (12 Hz), and in the late luteal phase, with decreasing [PRG], CBF increased to 15 Hz. Then, in the resting phase, with low [betaE(2)] and [PRG], CBF decreased immediately to 14 Hz. The CBF of the fimbria was measured in guinea-pigs treated with beta-oestradiol benzoate (betaE(2)B) or medroxyprogesterone (mPRG). A low dose of betaE(2)B increased CBF to 14.5 Hz, whereas a high dose decreased it to 11 Hz. A betaE(2) receptor blocker, ICI-182,780, abolished the betaE(2)B-induced CBF changes and maintained CBF at 12.0 Hz. Medroxyprogesterone decreased CBF to 12.5 Hz, and mifepristone (a PRG receptor blocker) abolished the mPRG-induced CBF decrease and maintained CBF at 15 Hz. The addition of both blockers increased CBF to 18 Hz, suggesting that activation of betaE(2) or PRG receptors decreases the CBF of the fimbria. In conclusion, a moderate [betaE(2)] increase maintains a high CBF (15.5 Hz) in the follicular phase, and then further [betaE(2)] increase decreases CBF to 13.5 Hz in the ovulatory phase. In the early and late luteal phase, low [betaE(2)] and [PRG] increase CBF to 17 and 15 Hz, respectively, and in the middle luteal phase a high [PRG] decreases CBF (to 12 Hz). Thus, the CBF of the fimbria was controlled by signals via betaE(2) and PRG receptors in guinea-pigs.

Endocrine alterations around the time of abortion in mares impregnated with donkey or horse semen

The objective of this study was to monitor and compare the concentrations of equine chorionic gonadotropin (eCG), progesterone and estrone sulphate during normal and failed pregnancies of mares impregnated with donkey or horse semen, relating their individual endocrine profiles to the time of pregnancy loss, and to the histopathologic findings in the aborted fetuses and placenta. Mares ( n = 54) were used, 32 of them impregnated with donkey semen and 22 impregnated with horse semen. Blood samples were taken twice a week from Day 35 to 120 of pregnancy. Ultrasonographic observations of the fetus were carried out twice a week. The incidence of abortion in mares impregnated with donkey semen (30%) was greater ( P < 0.05) than the 5% observed in mares impregnated with horse semen. From Week 8 to the end of the sampling period, the mean progesterone concentrations of mares with normal mule pregnancies were less ( P < 0.05) than those of mares with normal pregnancies with equine fetuses. The concentrations of eCG were less ( P < 0.05) in mule pregnancies from Week 6. Estrone sulphate concentrations were only different ( P < 0.05) between types of pregnancy on Weeks 13 and 14, being in this case greater with the mule pregnancies. Most of the abortions of mule fetuses were associated with lesser progesterone concentrations than the average for mares with successful mule pregnancies. Four of the abortions of mule fetuses and the only abortion of horse fetus occurred in mares with lesser progesterone and very low eCG concentrations, and were classified as caused by luteal impairment secondary to eCG deficiency; estrone sulphate concentrations were less than normal or absent before these abortions. Two mares aborted after several weeks of low progesterone concentrations in the presence of eCG concentrations that were normal for mule pregnancies, suggesting primary luteal deficiency. In three mares carrying a mule fetus, the concentrations of progesterone and estrone sulphate decreased abruptly immediately before fetal death, suggesting luteolysis due to active prostaglandin F2 alpha (PGF2α) secretion. It is concluded that the greater incidence of abortion in mares impregnated by donkeys is associated with different kinds of luteal malfunction. Deficiency of eCG may be a primary cause of many of these cases, either by failing to stimulate enough luteal progesterone secretion and/or by failing to protect the corpora lutea (CL) of pregnancy from endogenous PGF2α secretion.