Total Corpora Lutea Research Articles

Ovine interferon-tau inhibits estrogen receptor up-regulation and estrogen-induced luteolysis in cyclic ewes

This study determined whether intrauterine injection of interferon-tau (IFN tau) could block luteolysis in cyclic ewes treated with a luteolytic dose of 17 beta-estradiol benzoate (E) on day 12 of the estrous cycle. Thirty-two ewes were fitted with uterine catheters on day 5 of the estrous cycle and treated with recombinant ovine IFN tau (2 x 10(7) antiviral units/ewe/day) or control proteins (6 mg/day) by intrauterine injection from day 10 until hysterectomy. At 1900 h on day 12, all ewes received 750 micrograms E, im, and were hysterectomized 12, 24, 36, or 48 h post-E administration. Plasma concentrations of progesterone declined in control animals but increased in IFN tau-treated ewes after E injection (P < 0.01, treatment x day interaction). Likewise, total corpus luteum weight decreased in control but not IFN tau-treated ewes after E administration (P < 0.02, treatment x time interaction). In control ewes, endometrial estrogen receptor (ER) messenger RNA (mRNA; P < 0.03) and progesterone receptor (PR) mRNA (P < 0.10) increased after 12 h, whereas concentrations of ER protein (P < 0.02) and PR protein (P < 0.04) increased after 24 h. In situ hybridization and immunohistochemical analyses indicated that ER gene expression increased first in the epithelium at 12 h and then in the stroma by 48 h, whereas PR gene expression first increased in the stroma and then in the epithelium. In control ewes, endometrial oxytocin receptor (OTR) density increased (P < 0.10) after 12 h, with the largest increase occurring between 36-48 h. In IFN tau-treated ewes, endometrial ER mRNA and protein and OTR density did not increase after E administration. Levels of PR mRNA increased (P < 0.01) between 12-36 h, but decreased after 36 h. PR mRNA abundance increased between 12-36 h in the stroma, but not in the epithelium. Concentrations of PR protein were low and did not change in IFN tau-treated ewes. Immunoreactive PR protein was present at low levels in the stroma of all IFN tau-treated ewes. The results indicate that induction of luteolysis by E in control ewes involved sequential increases in endometrial ER mRNA and ER protein in the epithelium that preceded maximal increases in OTR density. Intrauterine injection of recombinant ovine IFN tau prevented luteolysis by inhibiting estrogen-induced increases in endometrial ER and OTR gene expression.

A note on ovarian measurements in cows with or without a history of twinning

Abstract Ovaries were recovered at slaughter from 30 cows in either a twinning (T; n = 16) or control (C; n = 14) herd. Weights of ovaries and corpora lutea (CL) and records of follicle numbers and their diameters were obtained. Mean CL numbers/cow were 1.38 ± 0.12 and 1.07 ± 0.07 in the T and C cows respectively (P < 0.10). The objective was to compare the herds for ovary weights, CL weights, and follicle data, taking account of ovary side (left or right), luteal stage (Days 4–8, 9–13, 14–18, where oestrus = Day 0), and numbers of CLs on each ovary (0 or ≥1). Ovary weights were not affected by herd, and averaged 15.0 g when a CL was present compared with 9.1 g without a CL (P < 0.001). Single CL weights averaged 5.6 and 3.2 g in ovaries from cows which had produced single or double CLs respectively (P < 0.05). Total CL weight/cow was not significantly different in T and C herds. Numbers of ovarian follicles of given size were similar in the two herds. The diameters of the largest follicle on the right ov...

Changes in progesterone and oestrogen receptor mRNA and protein during maternal recognition of pregnancy and luteolysis in ewes.

This study characterized changes in levels of mRNA and protein for endometrial oestrogen receptors (ERs) and progesterone receptors (PRs) during luteolysis and maternal recognition of pregnancy. For cyclic and pregnant ewes, endometrium was collected on days 10, 12, 14, or 16 post-oestrus (4 ewes/day for each status) for the measurement of ER and PR mRNA and protein. The amount of receptor mRNA is expressed in relative units above background, measured from radiographs of dot-blot hybridization of total endometrial RNA with ER and PR cDNAs. At hysterectomy, jugular vein blood samples were collected and assayed for progesterone, total corpus luteum weight was recorded and, in vitro, endometrial oxytocin-stimulated inositol phosphate formation was estimated. In pregnant ewes, plasma progesterone increased gradually between days 10 and 16 (P < 0.01), corpus luteum weight was stable at approximately 0.8 g and oxytocin did not stimulate endometrial formation of inositol phosphates in vitro. In contrast, in cyclic ewes, plasma progesterone decreased from day 10 to day 16 (P < 0.01), corpus luteum weight decreased after day 14 to approximately 0.48 g (P = 0.05) and oxytocin stimulated an increase of approximately 1300% in the endometrial formation of inositol phosphates on day 16. cDNAs specifically hybridized with 1.6 and 3.1 kb transcripts for PR mRNA and a 6.5 kb transcript for ER mRNA. In cyclic ewes, the amount of PR mRNA increased from day 10 to maximum levels on days 14-16. The number of PRs decreased from day 10 (2.25 pmol/mg DNA) to day 12 (0.98 pmol/mg DNA) and then increased from day 14 to day 16 (2.8 pmol/mg DNA). In pregnant ewes, PR mRNA levels were greatest on days 10-12 and decreased by approximately 50% by day 16. In contrast, the number of PRs was relatively unchanged from day 10 to day 16 (1.53 to 1.03 pmol/mg DNA). In cyclic ewes, the amount of ER mRNA was lowest at day 10 and increased fivefold by day 16. The number of ERs remained relatively unchanged from day 10 to day 14 (6.07 pmol/mg DNA) and increased by day 16 (16.12 pmol/mg DNA). In pregnant ewes, ER mRNA decreased by approximately 80% from day 12 to day 16. Similarly, the number of ERs decreased from day 10 to day 16 (5.41 to 2.05 pmol/mg DNA). Correlations between ER mRNA and PR mRNA (r = 0.68), ERs and PRs (r = 0.50) and ER mRNA and ERs (r = 0.50) were high (P < 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

Apoptosis during luteal regression in cattle.

The present studies were conducted to evaluate whether apoptosis occurs during spontaneous and prostaglandin F2 alpha (PGF2 alpha)-induced luteolysis and, if so, to determine the relationship between the onset of luteolysis and oligonucleosome formation (a characteristic of apoptosis). In the first study, nine normally cycling heifers were ovariectomized (ovx) during the midluteal phase (day 10 or 15; day 0 = estrus) or after luteal regression (day 19; n = 3/time point). While there was no evidence of oligonucleosome formation in DNA from corpora lutea (CL) collected on days 10 and 15, each CL collected on day 19 exhibited DNA fragmentation, represented by distinct bands of DNA in approximately 185-basepair multiples. In the second study, heifers were ovx (n = 5; controls) or given 25 mg PGF2 alpha 15-16 days after estrus. Heifers receiving PGF2 alpha were subsequently ovx 4, 8, 12, 24, or 48 h (n = 5/time point) after the injection of PGF2 alpha. The concentration of progesterone in venous sera collected at ovx was not different (P > 0.20) in control and 4 h groups, but was decreased (P < 0.01) in the 8, 12, 24, and 48 h groups. Total CL weight (mean +/- SEM; grams) did not change (P > 0.10) from 0 h (controls) to 24 h after injection (range, 3.2 +/- 0.5 to 4.1 +/- 0.6), but decreased (P < 0.06) to 2.0 +/- 0.3 at 48 h. With ethidium bromide (EtBr) staining, no oligonucleosome formation was detected in CL collected from 0-12 h after PGF2 alpha injection. However, pronounced oligonucleosome formation was observed in all 10 CL collected 24 and 48 h after the injection of PGF2 alpha. The absence of oligonucleosomes in 0 and 4 h samples was confirmed by the more sensitive technique of 3'-end labeling of DNA fragments. Some samples in both the 8 and 12 h groups had slight oligonucleosome formation, while all samples in the 24 and 48 h groups showed evidence of intense oligonucleosome formation. Histological analysis of tissue sections indicated an increase (P < 0.001) in the percentage of degenerated luteal cells in the 24 and 48 h groups compared to that in the 0-12 h groups. These data indicate that apoptosis occurs during both spontaneous and PGF2 alpha-induced luteal regression in cattle; however, apoptosis, as indicated by oligonucleosome formation, is not apparent until after serum progesterone concentrations have begun to decrease.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of human chorionic gonadotrophin on dominant follicles in cows: formation of accessory corpora lutea, progesterone production and pregnancy rates.

Thirty-four lactating Holstein cows were randomly assigned to four groups for treatment with human chorionic gonadotrophin (hCG, 1000 iu) at insemination day 0 (n = 8) or 7 (n = 9) or 14 days (n = 9) after insemination or with no hCG treatment (control, n = 8). Ultrasound imaging of the ovaries and plasma progesterone measurements were carried out to determine follicular dynamics and corpus luteum growth and function. Rates of formation of accessory corpora lutea were higher among cows treated on days 0 (three cows), 7 (seven cows) or 14 (four cows) than in the controls (one cow). Total corpus luteum diameter was greater (P less than 0.01) among hCG-treated cows than in controls 7-42 days after insemination. Concentrations of progesterone in plasma were significantly (P less than 0.05) higher in cows treated with hCG on days 7 or 14 than in those treated on day 0 or in controls, at days 18, 35 or 42 after insemination. Seven of the cows treated on day 7 became pregnant, whereas four, four and three cows treated on days 0 or 14 and control cows became pregnant, respectively. The results suggest that hCG treatment at 7 days after insemination could be used to produce accessory corpora lutea, raise plasma progesterone concentration and hence reduce the incidence of early embryonic mortality in cattle.

Superovulation and embryo quality in beef cows using PMSG and a monoclonal anti-PMSG

The long half-life of pregnant mare serum gonadotrophin (PMSG) reduces its application in the superovulation of cattle; thus, a monoclonal antibody to PMSG (anti-PMSG) was administered at the onset of estrus to increase the number of transferable embryos. Angus, Hereford and Angus × Hereford cows (n = 149) 3 to 9 yr old were assigned randomly to one of three dosages of PMSG (1500, 3000 or 6000 IU) with or without an equivalent dosage of anti-PMSG. Embryos were collected nonsurgically on Day 8 (estrus = Day 0), and all cows were ovariectomized on Day 9. The percentage of cows exhibiting estrus and ovulating decreased (P<0.05) with an increasing dosage of PMSG (82, 76 and 44% for 1500, 3000 and 6000 IU, respectively). Ovarian and total corpora lutea (CL) weight increased (P<0.001) linearly as PMSG dosage increased, but were reduced (P<0.001) curvilinearly by anti-PMSG, resulting in a PMSG by anti-PMSG interaction (P<0.001); the interaction was also significant (P<0.05) for ovulation rate (14.0 vs 14.3, 21.5 vs 24.4 and 29.2 vs 6.6 CL for 1500, 3000 and 6000 IU PMSG, without vs with anti-PMSG, respectively). Anti-PMSG increased (P<0.001) the number of small ovarian follicles (1 to 3 mm diameter) and decreased (P<0.001) the number of large follicles (>10 mm) at ovariectomy; the number of large follicles increased (P<0.001) with PMSG dosage. The number of total and transferable embryos recovered did not differ among PMSG and anti-PMSG dosages; however, the percentage of transferable embryos decreased (P<0.01) with increasing PMSG dosage. In general, neither PMSG dosage nor anti-PMSG influenced embryo quality.

Effect of heterosis on performance of mice across three environments.

Performance of six genetic groups of mice was studied in three different environments in order to determine the effect of heterosis on consistency of performance in varied environments. Designed as a 3 x 6 factorial, data were analyzed using least squares analyses of variance. Genetic group effects, environmental effects, genetic group x environment interaction, and heterosis were examined for 42-d weight, age and weight at vaginal opening, age and weight at puberty, ovulation rate (determined by total corpora lutea), number of implantations, and number of fetuses at 10 d of gestation. Weight at vaginal opening, ovulation rate, implantation rate and total number of fetuses exhibited significant heterosis. Regression of these traits against an environmental index (mean performance of all genetic groups over environments) provided an estimate of stability of performance. In general, genetic groups exhibiting heterosis expressed more consistent performance across environments than pure lines did. We conclude that a stability model could be used to aid in identification of lines with consistent performance for production traits in variable environments.

Dynamics of steroid biosynthesis during the luteal-placental shift in rhesus monkeys.

We studied the dynamics of steroid secretion during the luteal-placental shift of early pregnancy in rhesus monkeys. Daily blood samples were obtained from six pregnant rhesus monkeys during the cycle of conception and for the first 44 days of pregnancy to examine the relationships among aromatizable androgens, estrogens, progesterone (P), and CG in the peripheral circulation. To elucidate the biosynthetic mechanisms involved in the changes in hormonal patterns, minces of placentae and corpora lutea (CL) were incubated in vitro with [3H]pregnenolone ([3H]P5) and [3H]androstenedione ([3H]A), and steroid metabolites were isolated and identified by reverse isotope dilution. After a brief rise (corresponding to the approximate time of implantation of the blastocyst), serum P levels declined despite rising serum CG levels and reached a nadir at the time of maximal CG secretion. In contrast, serum androstenedione (A), testosterone (T), estrone (E1), and estradiol (E2) concentrations rose and fell in parallel with CG and reached peak levels near day 24 of pregnancy 2- to 10-fold higher than those during the luteal phase. The CL of early pregnancy produced less than one third as much P from [3H]P5 as did the CL of the cycle, but had a 9-fold greater capacity for estrogen biosynthesis. Total CL aromatase activity did not differ between the nonfertile cycle and early pregnancy. 17-Hydroxylase and C17-20 lyase activities increased in the CL during early pregnancy, since 17-hydroxyprogesterone and A (but not T) syntheses were 3- to 5-fold greater in the CL of early pregnancy than in the CL of the cycle. Although serum E1 and E2 concentrations during early pregnancy were similar, E1 was the predominant estrogen produced from [3H]P5 or [3H] A by luteal tissue in vitro. Placental tissue obtained on days 23-27 of pregnancy produced large amounts of P from [3H]P5, but only trace amounts of estrogens were formed from [3H]A. By day 45 of pregnancy, however, the placenta had acquired substantial amounts of aromatase activity. Neither estrogens nor androgens were formed from [3H]P5 by the placenta.(ABSTRACT TRUNCATED AT 400 WORDS)

Quantitative light microscopic analysis of corpus luteum growth during pseudopregnancy in the rabbit.

We employed stereological methods at the light-microscope level to examine the mechanism by which corpora lutea (CL) grow during the course of pseudopregnancy in the rabbit. Corpus luteum volume per ovary, the absolute volume of luteal cells per CL, individual luteal cell volume, the number of luteal and endothelial cells per CL, and capillary surface area per CL were examined in rabbits at Days 1, 4, 7, 11, and 18 of pseudopregnancy. Total CL volume increased from 3.7 +/- 0.1 microliter to 30.3 +/- 0.5 microliter over Days 1 to 11 and thereafter decreased to 15.2 +/- 1.1 microliter by Day 18. Stereological analyses showed that the increases in CL volume from Day 1 to Day 11 were due primarily to increases in the volume of individual luteal cells (from 2.6 +/- 0.2 pl on Day 1 to 23.5 +/- 1.7 pl on Day 11, 1 pl = (10 mu)3; r = 0.96), and that the decrease in CL volume after Day 11 resulted largely from a decrease in luteal cell volume (to 12.8 +/- 1.5 pl). In contrast, no change was seen in the number of luteal cells per CL (range 9.1 x 10(5)-12.5 x 10(5)). These data show that CL growth and subsequent regression during pseudopregnancy result primarily from changes in the volume of individual luteal cells, and not from changes in the number of luteal cells. These data support the hypothesis that modulation of progesterone production during pseudopregnancy is due to changes in individual luteal cell volume and not to changes in cell number.

Luteal characteristics and embryonic survival in gilts treated with human chorionic gonadotrophin during early pregnancy

In an attempt to increase the number of corpora lutea (CL) and increase luteal weight in early pregnancy, gilts were treated with human chorionic gonadotrophin (hCG) during the first 12 days after mating. Total numbers of CL and total luteal weights per animal (23 to 25 days after mating) did not vary between an untreated control group and groups of gilts (7–12 gilts/group) injected with single doses of hCG (500 i.u., i.m.) on Days 3, 6, 8, 9, 10 or 12 after mating, or with consecutive doses on Days 3 and 9 or Days 3 and 6 after mating ( P > 0.05; Kruskal-Wallis). However, total numbers of CL dissected from ovaries of animals treated with hCG on Days 6 and 9 (median 43) or on Days 3, 6, and 9 (median 49) after coitus exceeded the control value (median 18; P < 0.05). The total weight of luteal tissue present at slaughter, between 23 and 25 days of gestation, was also enhanced by hCG treatment on Days 3, 6 and 9 post-coitum (median 14.5 g compared to 7.1 g for control animals; P < 0.05). Levels of steroids (pregnenolone, pregnenolone sulphate, progesterone, androstenedione and testosterone) in plasma collected post-mortem did not differ between treatment groups ( P > 0.05), although progesterone and pregnenolone values were positively related to total CL weights in the combined data (Spearman rank correlation; P < 0.05). None of the luteal or plasma hormone parameters was correlated with embryo numbers between Days 23 and 25 gestation, refuting speculation that luteal insufficiency accounts for a major component of embryonic mortality in the pig.

Influence of insulin and energy intake on ovulation rate, luteinizing hormone and progesterone in beef heifers.

Ovarian and gonadotropin responses to insulin and energy restriction were investigated in a 2 X 2 factorial experiment using 2-yr-old Brangus heifers. Thirty heifers were paired by weight and body condition, then assigned to treatment groups receiving 75 (LE) or 180% (HE) of NRC recommendations for dietary energy for maintenance. Diets were adjusted weekly to maintain daily .25 to .5 kg weight loss or 0 to .25 kg weight gain, respectively. On d 10 of the first estrous cycle subsequent to the initial 45 d of feeding, heifers within each dietary group were allocated to receive twice daily infusions of either 40 U insulin (I) or saline (C). Infusions began at 5 and 10 h postprandial and were given in six boluses, 20 min apart. Infusions continued daily until d 20 or estrus, whichever occurred first. On d 11, blood samples were collected at 15-min intervals for 12 h to determine luteinizing hormone (LH) and insulin concentrations. On d 16 to 20, twice daily im injections of 1 mg follicle stimulating hormone (FSH) were administered. Heifers were ovariectomized on d 11 after estrus. Number of corpora lutea (CL) in LE-I heifers was greater (P less than .05) in LE-C, HE-C or HE-I. Total CL weight (g) per heifer was greater (P less than .05) in HE-C and LE-I heifers than in LE-C. Individual CL wt was heavier in HE than in LE heifers (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Dominant lethal testing of theobromine in rats

Theobromine (TBR) 3,7-dimethylxanthine, the major purine alkaloid present in chocolate and cocoa products, was evaluated for dominant lethality in male Sprague-Dawley rats after administration of subacute oral doses of 0, 50, 150 and 450 mg/kg. Dominant lethal mutations were assessed weekly for a 10-week period by killing the females 13 days after the midweek of presumptive mating with treated males and counting total implants (living and dead), corpora lutea and number of pregnant females. Dead implants per total implants and preimplantation loss per total corpora lutea were evaluated statistically. No significant dose-dependent effects were observed in the % dead implants of preimplantation loss throughout the study; pregnancy rate averaged 94%. These results indicated no induction of dominant lethal mutations or adverse effects on pregnancy rate after TBR doses equivalent to 25–225 times the maximum human consumption level.

Ovarian function during pregnancy in young and aged rabbits: temporal relationship between fetal death and corpus luteum regression.

Corpus luteum (CL) progesterone concentration and total progestins in the peripheral plasma were measured at various stages of pregnancy in 18 young rabbits 35 weeks old and 26 aged rabbits 250 weeks old. Fertilization rate, average number of CL, and viable fetuses in the young does were 83, 7.7, and 5.8%, respectively. Corresponding values in the aged does were 81, 6.2, and 1.1%. There were no differences between young and aged does in any of the parameters of ovarian function measured until after Day 12 of pregnancy. This was true even though five of nine aged animals did not have viable fetuses at this time. Significant differences were detected in aged animals without viable fetuses only at Day 24. At this time average CL weight (6.3 mg) total luteal tissue (30.9 mg), and total CL progesterone content (0.49 , g) in aged animals without viable fetuses were significantly (P < 0.05) less than corresponding values in aged animals with viable fetuses (15.1 mg, 110.6 mg, 2.55 g) and in young animals all with viable fetuses (16.5 mg, 120.7 mg, 2.83 pg). These latter two groups did not differ. Peripheral plasma progestins on Day 24 of planned pregnancy in aged animals without viable fetuses (3.2 ng/ml) were also significantly (P < 0.05) less than in aged animals with viable fetuses (16.8 ng/ml) and in young animals (11.4 ng/ml). Again, these latter two groups did not differ. It is concluded that the decrease in fecundity in aged animals is not caused by a lack of progestin secretion, but rather the absence of viable fetuses may cause luteal regression. Thus, reproductive failure in aged does appears to be directly associated with uterine dysfunction.