Apoptosis in the canine endometrium during the estrous cycle

Apoptotic cell death in the endometria of 58 female dogs in different stages of the estrous cycle was assessed (in formalin-fixed, paraffin-embedded sections) with both the terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay and immunohistochemical detection of caspase-3 activity. For both techniques, the apoptotic index was determined in the surface epithelium, stroma, crypts, and basal glands by counting the percentage of stained cells in a total of 500 cells in each category. In the surface epithelium and stroma, TUNEL- and caspase-3-positive cells were rare (apoptotic index<1) throughout the estrous cycle. However, caspase-3 detection showed a significant increase in the apoptotic index in the stroma during anestrus as well as an increase in the index in both the stroma and surface epithelium in late metestrus. The apoptotic index increased during late metestrus and anestrus in the crypts and basal glands; in the crypts, this increase was significant only when caspase-3 detection was used, whereas in basal glands, significant differences were found for both techniques. In conclusion, apoptosis was present in canine endometrial cells during the estrous cycle, but caspase-3 detection showed more significant differences than the TUNEL assay. Furthermore, a high apoptotic index (suggestive of endometrial desquamation) was not detected in the surface epithelium and there was no significant correlation between the apoptotic index in any cell group and serum progesterone concentrations.     

Apoptosis in endometrium of mouse during estrous cycle

The present study was carried out to evaluate apoptosis in endometrium and to correlate these changes with the circulating levels of estradiol and progesterone in the mouse. Apoptosis was observed in various compartments of mouse uterus i.e. stroma, glandular epithelium and luminal epithelium depending on the stage of cycle. Stromal cell apoptosis was observed during various stages of cyclicity except on estrus day. Luminal epithelial cells showed apoptotic changes during all stages of cyclicity except on diestrus day. During metestrus, apoptosis was observed in glandular and luminal epithelia as well as stromal cells. Steroid antagonists such as tamoxifen and onapristone altered the apoptotic changes in the uterus. The results suggest that epithelial cell apoptosis is regulated by estrogen while stromal cell apoptosis is under the control of progesterone.     

Proliferation patterns in the canine endometrium during the estrous cycle

The proliferative activity in the endometrium of 58 bitches in different stages of the estrous cycle was assessed by immunohistochemical detection of the Ki-67 proliferation associated nuclear antigen and by counting mitotic figures. The Ki-67 labelling index and the mitotic index were determined in the surface epithelium, the stroma, the crypts and the basal glands by calculating the percentage of Ki-67 positive cells and mitotic figures, respectively, on a total of 500 cells of each category. Endometrial vascular proliferation was also verified by counting the number of Ki-67 positive cells on a total of 100 endothelial cells. The present study showed two proliferation peaks involving different cell groups. In the surface epithelium, the stroma, the blood vessels and the crypts, the highest labelling and mitotic indexes were noticed during proestrus, whereas for the basal glands these indexes significantly increased (P < 0.05) during estrus compared to late metestrus and anestrus. Furthermore, a slightly positive correlation (P < 0.05) was found between the labelling index in the basal glands and the serum progesterone levels, whereas the labelling indexes in the other cell groups were positively correlated with the estradiol-17 beta levels, although not always significantly. These findings suggest that regulation of the proliferation in the surface epithelium, the stroma, the blood vessels and the crypts is different from the proliferation in the basal glands.     

Conjugated estrogens in the endometrium during the estrous cycle in pigs

Estrogen metabolism results in the formation of inactive estrogen sulphates and glucuronides. Despite the lack of receptor binding, circulating conjugated estrogens might serve as a reservoir for the active form through the involvement of specific cleaving enzymes. In order to elucidate the potential role that estrogen conjugates play in the regulation of the estrous cycle, we determined the concentration of progesterone, estrogen and estrogen conjugates in serum and endometrial homogenates of cycling gilts. In addition, we determined the mRNA expression changes of enzymes (UDP glucuronosyltransferase (UGT), β-glucuronidase (GUSB), sulphotransferases (SULT) and steroid sulphatase (STS)) and transporters (multidrug resistance-associated protein (MRP), organic anion-transporting polypeptide (OATPs)) involved in the estrogen metabolism in the endometrium across the estrous cycle. GUSB displayed highest expression at estrous (day 0), decreasing expression during metestrus (day 3 and 6), minimal expression on day 10 and 12, and increasing expression towards proestrus (day 18), suggesting either a stimulation by estrogens or a negative impact of progesterone. The mRNA expression of the influx-transporter OATP1A2 significantly increased from day 0 to 6 and decreased again by day 10, while the efflux-transporters (MRP1, MRP2, and MDR1) displayed minimal expression at day 3 and 6. The mRNA expression of the UDP-glucuronsyltransferases followed a similar pattern, with minimal expression found at day 6. The analyses of the concentration of local and circulating steroid hormones points towards an interaction of the analyzed transporters and enzymes with steroid hormones, thereby possibly regulating the reservoir of active steroids contributing to the endometrial function.     

Changes in EGF concentrations during estrous cycle in bovine endometrium and their alterations in repeat breeder cows

The objective of the present study was to determine if abnormalities in the cyclic changes of endometrial EGF concentrations can be a diagnostic tool for repeat breeder cows. First, the profile of EGF concentrations during the estrous cycle was determined using endometrial tissues obtained from 31 Holstein cows after slaughter. Cyclic cows had two peaks of EGF concentrations. Then, endometrial tissues were obtained from 12 control and 20 repeat breeder cows by biopsy on Days 3, 7, and 14 of the same estrous cycle. Endometrial EGF concentrations in biopsied samples of the controls were similar to those found in slaughterhouse materials; they were high on Days 3 and 14 (9.2 and 10.4 ng/g tissue, respectively) and low on Day 7 (3.8 ng/g tissue). Concentrations of EGF in repeat breeder cows had a different profile; they were similar on Days 3, 7, and 14 (4.4, 3.4, and 4.0 ng/g tissue, respectively). In conclusion, changes in endometrial EGF concentrations were altered in repeat breeders; these alterations may be a potential diagnostic marker for repeat breeder cows.     

Oxytocin receptors in the porcine endometrium during the estrous cycle and early pregnancy

Oxytocin (OT) receptors in the porcine endometrium were investigated at four stages of the estrous cycle (Days (D) 0, 5, 10 and 15, n = 3), and at two stages of early pregnancy (D5 and D15 after mating, n = 3) by a radioreceptor assay using ¹²⁵I-labeled OT antagonist [d(CH₂)₅,Tyr(Me)²,Thr⁴,Tyr-NH⁹₂]-vasotocin. Binding specificity was demonstrated by displacement with four peptides related to oxytocin ([Arg⁷]-vasopressin, [Thr⁴,Gly⁷]-OT, OVT, OT) and two peptides unrelated to oxytocin (luteinizing hormone-releasing hormone, [Ile³]-pressinoic acid (tocinoic acid)). The dissociation constant (K_d) of endometrial OT receptors on D0 (0.59 ± 0.10 nM) was similar to those on D10 and D15 (D10, 0.75 ± 0.21; D15, 0.60 ± 0.14 nM; mean ± SEM). In the early luteal stage (D5), K_d (2.41 ± 0.24 nM) was higher than on D0, D10 and D15 (P < 0.01). In early pregnancy, K_d values were 3.25 ± 0.29 nM on D5 and 2.44 ± 0.44 nM on D15. Binding site concentration (B_max) on D0 (910.0 ± 25.1 fmol mg⁻¹ protein) was significantly higher than on D5 and D10 (D5, 322.5 ± 71.7; D10, 147.5 ± 25.8 fmol mg⁻¹ protein; P < 0.01) of the estrous cycle and D5 and D15 (D5, 302.5 ± 82.6; D15, 315.0 ± 20.1 fmol mg⁻¹ protein; P < 0.01) of early pregnancy. In the two stages of early pregnancy, B_max values were constant and similar to that on D5 of the early luteal stage.Our results reveal the existence of specific OT binding sites in the porcine endometrium during the estrous cycle and early pregnancy. Furthermore, the fluctuation in the binding of OT to the endometrium during the different stages of the estrous cycle suggests that OT plays an important role in regulating the estrous cycle of the pig as seen in other animals.     

Estrogen and progesterone concentrations in bovine milk during the estrous cycle

Estrogen and progesterone concentrations in milk during the estrous cycle were estimated in 18 normally cycling Holstein dairy cows. The estrogen and progesterone concentrations in milk during the estrous cycle followed the pattern described for them in blood in the corresponding period. During most of the estrous cycle, estrogen concentration remained at approximately 200 pg/ml and reached a proestrous peak of 360 +/- 127 pg/ml on day 19. The progesterone concentration in milk during the estrous cycle increased to a peak on day 13 (45.5 +/- 6.6 ng/ml) and thereafter declined towards estrus. Estrus detection/prediction based on milk progesterone concentrations appears feasible in view of the significant differences in milk progesterone concentrations between the early luteal (post-ovulatory), luteal and rapid follicular growth periods of the estrous cycle.     

Steroid hormone modulation of prostaglandin secretion in the ruminant endometrium during the estrous cycle

Prostaglandins, produced from membrane phospholipids by the action of phospholipase A2, cyclooxygenase, and specific prostaglandin synthases, are important regulators of ovulation, luteolysis, implantation, and parturition in reproductive tissues. Destruction of the corpus luteum at the end of the estrous cycle in nonpregnant animals is brought about by the pulsatile secretion of prostaglandin F(2alpha) (PGF(2alpha)) from the endometrium. It has been known for many years that progesterone, estradiol, and oxytocin are the hormones responsible for luteolysis. To achieve luteolysis, two independent processes have to be coordinated; the first is an increase in the prostaglandin synthetic capability of the endometrium and the second is an increase in oxytocin receptor number. Although progesterone and estradiol can modulate the expression of the enzymes involved in prostaglandin synthesis, the primary reason for the initiation of luteolysis is the increase in oxytocin receptor on the endometrial epithelial cells. Results of many in vivo studies have shown that progesterone and estradiol are required for luteolysis, but it is still not fully understood exactly how these steroid hormones act. The purpose of this article is to review the recent data related to how progesterone and estradiol could regulate (initiate and then turn off) the uterine pulsatile secretion of PGF(2alpha) observed at luteolysis.     

Expression of superoxide dismutases in the bovine oviduct during the estrous cycle

The superoxide dismutases (SODs) are first-line enzymatic antioxidants that dismute superoxide anion (O(2)(-)) to produce hydrogen peroxide (H(2)O(2)). The primary objective was to characterize, by western blot analysis, the expression of two SODs, the cytosolic (Cu,ZnSOD or SOD1) and the mitochondrial (MnSOD or SOD2) forms in three sections of the oviduct, i.e. isthmus (I), ishtmic-ampullary junction (IA), and ampulla (A), during the estrous cycle. The Cu,ZnSOD and MnSOD proteins were mostly expressed in the ampulla (I相似文献   

A stereological study of medium antral follicles during the bovine estrous cycle

Stereological methods were applied to bovine cumulus-oocyte complexes (COCs) in order to characterize them quantitatively during the estrous cycle. COCs from medium (4-8mm) antral follicles with a compact and complete cumulus mass, and with an uniform or a non-visible ooplasm were aspirated from ovaries of Holstein-Friesian cows, fixed in glutaraldehyde, randomly embedded in glycol-methacrylate, and sectioned at 20 microm. The unbiased nucleator principle was used for estimating the mean volumes of complexes, oocytes, cumulus cells, and nuclei of oocytes and cumulus cells. The thickness of the zona pellucida and the relative numerical percentages of the several morphological types (C1-C3) of cumulus cells were also evaluated. The optical disector procedure was used for cumulus cell sampling. Quantitative data show that COCs appear heterogeneous for all studied parameters. From metestrus to proestrus the volumes of COCs and oocytes remained constant, the volumes of oocytes and oocyte nuclei were correlated, the thickness of the outer zona pellucida decreased, and the relative numerical frequency of follicular type C3 cells increased. Results suggest that COCs from distinct estrus stages are structurally different, with type C3 follicular cells gradually differentiating from cell types C1 and C2.     

Soybean-derived phytoestrogens regulate prostaglandin secretion in endometrium during cattle estrous cycle and early pregnancy

Phytoestrogens acting as endocrine disruptors may induce various pathologies in the female reproductive tract. The purpose of this study was to determine whether phytoestrogens present in the soybean and/or their metabolites are detectable in the plasma of cows fed a diet rich in soy and whether these phytoestrogens influence reproductive efficiency and prostaglandin (PG) synthesis during the estrous cycle and early pregnancy in the bovine endometrium. In in vivo Experiment 1, we found significant levels of daidzein and genistein in the fodder and their metabolites (equol and p-ethyl-phenol) in bovine serum and urine. The mean number of artificial inseminations (AIs) and pregnancy rates in two kinds of herds, control and experimental (cows fed with soybean 2.5 kg/day), were almost double in the soy-diet herd in comparison with the control animals. In in vivo Experiment 2, three out of five heifers fed soybean (2.5 kg/day) became pregnant whereas four out of five heifers in the control group became pregnant. The concentrations of a metabolite of PGF2alpha (PGFM) were significantly higher in the blood plasma of heifers fed a diet rich in soybean than those in the control heifers throughout the first 21 days after ovulation and AI. The higher levels of PGFM were positively correlated with equol and p-ethyl phenol concentrations in the blood. In in vitro experiments, the influence of isoflavones on PG secretion in different stages of the estrous cycle was studied. Although all phytoestrogens augmented the output of both PGs throughout the estrous cycle, equol and p-ethyl-phenol preferentially stimulated PGF2alpha output. The results obtained lead to the conclusion that soy-derived phytoestrogens and their metabolites disrupt reproductive efficiency and uterus function by modulating the ratio of PGF2alpha to PGE2, which leads to high, nonphysiological production of luteolytic PGF2alpha in cattle during the estrous cycle and early pregnancy.     

Behavioral, follicular and gonadotropin changes during the estrous cycle in donkeys

Sexual behavior, follicular development and ovulation, and concentrations of circulating gonadotropins during the estrous cycle were studied during the summer in 7 jennies. Mean behavioral estrous length was 6.4 +/- 0.6 days (mean +/- SEM, n=19; 5.6 +/- 0.5 days preovulatory and 0.8 +/- 0.2 days post-ovulatory). Mean diestrous length was 19.3 +/- 0.6 days (n=14). Females in estrus typically showed posturing, mouth clapping, clitoral winking, urinating and tail raising. Mouth clapping began approximately one day sooner and lasted approximately one day longer than winking and tail raising, so that the total duration of clapping was significantly greater than for the other two signs. Follicular changes and concentrations of gonadotropins were determined for 14 estrous cycles (2 per jenny). The follicular end points [diameter of the largest follicle and number of large (>25 mm), medium (20-24 mm), and small follicles (<20 mm)] showed a significant day effect. The diameter of the largest follicle and the number of large follicles began to increase significantly 7 days prior to ovulation with a maximum value the day before ovulation. Medium follicles reached a maximum number 4 days prior to ovulation, and small follicles decreased significantly prior to ovulation. After ovulation, all follicular end points, except the number of small follicles, remained low for the next 12 days. Mean values of FSH were low during estrus and high during diestrus with 2 significant peaks, one 3 days and one 9 days after ovulation. In contrast, mean levels of LH were low during diestrus and high during estrus with a maximum value the day after ovulation. The LH profile showed a more prolonged gradual increase prior to ovulation, than that which has been reported for ponies and horses.     

Ultrastructural changes in guinea pig endometrial cells during the estrous cycle.

In the guinea pig, the estrous cycle is characterized by a constant measurable level of plasma progesterone with two peaks: the first one associated with the peak of plasma estradiol-17 beta occurring at proestrus and the second, during diestrus, more pronounced at the time at which the level of estradiol-17 beta is undetectable. The progesterone receptor content is the highest on day 1 and the lowest on day 10 of the estrous cycle, which lasts 16.3 +/- 1.5 days (n = 37; mean +/- SD). There is a positive correlation between the plasma level of estradiol-17 beta and the progesterone receptors detected immunocytochemically in both endometrial epithelial and stromal cells. The general morphology of the endometrium during proestrus and estrus is consistent with an estrogenic stimulation, i.e., a smooth and regular surface of the endometrium and the presence of numerous microvilli on the cell surface. However, a moderate secretory activity also occurs in proestrus and estrus. During postestrus, the glandular cells display an increase in characteristic secretory features which parallels the rise of progesterone in the plasma.