The effect of hCG treatment on Day 12 post-mating on ovarian function and reproductive performance of ewes and ewe lambs

The objectives of this study were to determine the effect of a single intramuscular injection of 200 IU hCG (Chorulon) on Day 12 post-mating on ovarian function and subsequent lambing performance in ewes and ewe lambs bred at synchronised oestrus during the breeding season and on the lambing performance of ewes induced to breed during late anoestrus. All animals were mated to rams at synchronised oestrus and on Day 12 post-mating given normal saline or 200 IU hCG.In Experiment 1, laparoscopic results showed that hCG treatment induced accessory corpora lutea in ewes (control = 0/7; hCG = 5/7) but not in ewe lambs (control = 0/7; hCG = 0/7).In Experiment 2, hCG treatment did not improve the lambing rate (control = 50; hCG = 57) or the litter size (control = 1.80; hCG = 1.96) in ewes (control = 100; hCG = 91). However, hCG treatment significantly (P > 0.05) improved the lambing rate (control = 29; hCG = 58; P < 0.05) in ewes conceiving at the first oestrus after treatment. hCG treatment (control = 42; hCG = 42) also failed to improve the lambing rate in ewe lambs (control = 48; hCG = 41).In Experiment 3, hCG treatment had no significant (P > 0.05) effect on the lambing rate (control = 72; hCG = 62) or the litter size (control = 1.59; hCG = 1.58) in ewes (control = 111; hCG = 115) induced to breed during anoestrus or on ewes returning to oestrus and conceiving after treatment (lambing rate: control = 86; hCG = 72; litter size: control = 1.44; hCG = 1.35). In conclusion, the data obtained in this study suggest that during the breeding season hCG may, by stimulating ovarian function, improve embryo survival in ewes conceiving at the first post-treatment oestrus. This effect, however was not observed in ewe lambs.     

alpha-Glucosidase activity in the reproductive tract of the ewe.

alpha-Glucosidase activity has been estimated in the tissues and rinsings of the reproductive tract of the ewe. There were peaks of activity in the oviducal mucosa at pH 4.0 and 5.7. In the endometrium, caruncles and cervical mucosa and pH optimum occurred from pH 4.0 to pH 5.7. A sharp peak in the activity in the vaginal mucosa occurred at pH 5.7. The only tissue in which changes in enzyme activity were consistently related to one endocrinological state of the ewe was the cervical mucosa. Cervical alpha-glucosidase activity was greater at oestrus than during the rest of the oestrous cycle, declined during early pregnancy, and increased in ovariectomized ewes following the injection of oestradiol-17 beta.     

Effects of neonatal progestin exposure on female reproductive tract structure and function in the adult ewe

Endometrial glands are present in all mammalian uteri and produce secretions that are hypothesized to support conceptus (i.e., embryo/fetus and placental membranes) survival and development. In sheep, endometrial gland morphogenesis occurs postnatally and can be epigenetically ablated by chronic neonatal exposure to a progestin from birth, thereby producing an adult uterine gland knock-out (UGKO) phenotype. This study determined the long-term effects of neonatal progestin exposure on adult ovine reproductive tract structure and function. Neonatal ewes were exposed to norgestomet (Nor) from birth to 32 wk of age. Unexposed ewes served as controls. After puberty, adult Nor-treated (n = 6) and control (n = 6) ewes were repeatedly bred at estrus (Day 0) to intact rams of proven fertility. In contrast to a pregnancy rate of 80% for control ewes, pregnancy was never detected on Day 25 after mating (or thereafter) in bred UGKO ewes. Control and Nor-treated ewes were then bred and necropsied on Day 9. Similar numbers of hatched blastocysts were present in uterine flushings from control and Nor-treated ewes. Weights of the ovaries and cervices were not affected by treatment. No histoarchitectural differences between control and Nor-treated ewes were detected for ovaries, oviducts, cervices, or vaginae. However, uterocervical and uterine weight as well as uterine horn length were less for Nor-treated ewes. The uteri of Nor-treated ewes were devoid of endometrial glands and lacked the stromal delineation characteristic of intercaruncular endometrium in control ewes. Endometrial width, area, and lumenal epithelial length were decreased in uteri from Nor-treated ewes, but myometrial width and morphology were not affected. Expression of a number of mRNAs that are expressed predominantly in the endometrial epithelia was not different between uteri from control and from Nor-treated ewes. Collectively, these results indicate that neonatal exposure of ewes to a progestin from birth appears to only affect development of the uterus and not any extrauterine reproductive tract tissues. The infertility of the UGKO ewes appears to result from a lack of endometrial glands and, by extension, of their secretions that are required to support growth and development of peri-implantation conceptuses.     

The effect of allyl compounds on hepatic microsomal mixed function oxidation and porphyrogenesis.

The activities of 5-aminolaevulinate (5-ALA) synthetase and of various microsomat drug-metabolising enzymes have been determined in the livers of rats pretreated with different drugs and chemicals containing the allyl group. Safrole, isosafrole and secobarbital gave rise to slight increases in 5-ALA synthetase, whereas alclophenac and triallyl cyanurate almost doubled the enzyme activity and the known porphyrogenic agents, allylisopropylacetamide (AIA) and allobarbital caused increases of 1.5- and 2.5-fold, respectively. Allobarbital induced the microsomal drug-metabolising enzymes while secobarbital had only a weak effect and alclophenac and triallyl cyanurate had no effect at all. From these results it is suggested that induction of the synthesis of cytochrome P-450 is not rate dependent on the synthesis haem and induction of porphyrin biosynthesis.     

The effect of labour on uterine blood flow in the pregnant ewe.

The effect of labour on cardiac output and uterine blood flow was measured in pregnant ewes at a mean gestation of 124 days using radioactive microspheres labelled with 169Yb and 85Sr. Labour was induced by a continuous infusion of ACTH into the foetal circulation. Cardiac ouput measured before ACTH infusion in seven ewes was 5234 +/- 175-9 ml./min (mean +/- S.E.) and total uterine blood flow was 732 +/- 57-9 ml./min (mean +/- S.E.). Measurements during labour in six ewes showed a significant increase in cardiac output to 6175 +/- 149-6 ml./min (P less than 0-005) but no significant change in uterine blood flow. However, the partition of blood flow was altered; thus myometrial flow increased by 67% from 114 +/- 15-4 ml./min to 190 +/- 13-2 ml./min (P less than 0-005) while placental blood flow decreased, although not significantly, from 618 +/- 55-9 ml./min to 575 +/- 40-7 ml./min. Similar changes were observed in one ewe in spontaneous labour at term and in another ewe receiving an infusion of 4 mg oestradiol 17beta over a 24 hr period. It is concluded that labour is not associated with any major alternation in total uterine blood flow although myometrial blood flow is increased. It is not known whether this is due to the rise in circulating oestrogens which occurs prior to parturition in the ewe, or to other factors such as the work of uterine muscle during labour.     

Prenatal programming of reproductive neuroendocrine function: the effect of prenatal androgens on the development of estrogen positive feedback and ovarian cycles in the ewe

Exposure of the female ovine fetus to male hormones during a sensitive window of in utero life causes disruption to reproductive function. In some animals, androgen exposure completely abolishes reproductive cycles, but in others, cycles are progressively lost with age. The present study tested two predictions: that noncycling, androgenized animals are unable to respond to estrogen with a preovulatory-like surge of LH (estrogen positive feedback), and that the androgenized animals that exhibit a progressive loss of cycles also show a progressive loss of estrogen positive feedback. Androgenized ewes were generated by injection of their mothers with testosterone propionate twice per week from Day 30 to Day 90 of pregnancy (term, 147 days). Control ewes received no injections. Whether ewes could exhibit estrogen positive feedback was tested on five occasions before puberty (30 wk) and once during the anestrous period. All control animals had repeated reproductive cycles in both the first and second breeding season, and all showed robust LH surges during test periods. Despite the fact that 64% of androgenized animals showed reproductive cycles, estrogen positive feedback could be demonstrated in only 6.1% of trials. Subsequent experiments revealed that the lack of response to estrogen in androgenized animals was not because of pituitary insensitivity to GnRH, a requirement for higher concentrations of estrogen, or a surge that was delayed relative to the time of estrogen administration. The mechanisms by which some androgenized ewes can produce normal reproductive cycles in the apparent absence of estrogen positive feedback are currently unknown.     

Beta-cypermethrin impairs reproductive function in male mice by inducing oxidative stress

Cypermethrin (CYP), an insecticide, has deleterious effects on male reproductive function. The objective was to identify whether the effects of beta-CYP on male reproductive organs were associated with oxidative stress. Three doses of beta-CYP (1, 10, and 20 mg/kg) were administered to male mice for 35 d, with or without vitamin E (20 mg/kg). The moderate (10 mg/kg) and high (20 mg/kg) doses of beta-CYP not only decreased body weight and the weight of the testes, epididymides, seminal vesicles, and prostate (P < 0.05) but also reduced serum testosterone concentration and the expression of steroidogenic acute regulatory protein (P < 0.05), in addition to damaging the seminiferous tubules and sperm development. Furthermore, moderate and high doses of beta-CYP administration decreased sperm number, sperm motility, and intact acrosome rate (P < 0.05). Based on ultrastructural analyses, high doses of beta-CYP produced swelling and degeneration of mitochondria and the smooth endoplasmic reticulum of Leydig cells and caused the formation of concentric circles. These toxic effects of beta-CYP may be mediated by increasing oxidative stress, as the moderate and high doses of this compound increased malondialdehyde and nitric oxide in testes (P < 0.05); reduced the activity of catalase, glutathione peroxidase (GSH-Px), and superoxide dismutase (P < 0.05); and activated ERK1/2 (P < 0.05). Vitamin E reversed the effects of beta-CYP on testosterone production and testis damage (P < 0.05 vs. the high-dose group). Therefore, we inferred that beta-CYP damaged the structure of testes and decreased sperm output by inducing oxidative stress.     

Sterol sulfatase activity in the reproductive tract of the ewe

Sterol sulfatase activity was probed with tritiated cholesteryl sulfate in the reproductive tract of seven non-pregnant Suffolk ewes. The enzyme activity was expressed in endometrial, ovarian and oviducal tissue homogenates. The highest specific activities were found in oviducal fluids recovered by flushing the excised oviducts with buffer. Sterol sulfatase was also highly active in oviducal fluids collected during oestrus in conscious ewes through surgically inserted catheters. While part of the enzymatic activity in oviducal fluids was present in a soluble form, most was associated with secretory granules as evidenced by electron microscopy. In view of the fact that oviducal fluid is the medium in which the mammalian egg is normally fertilized, these findings support the hypothesis that sterol sulfatase plays a role in the process of sperm capacitation in the ewe.     

The effect of undernutrition on the establishment of pregnancy in the ewe

The relationship between nutrition and reproduction in sheep has been the subject of research in several international groups. This review will particularly focus on the effects of undernutrition on the potential causes of reproductive failure including abnormalities of the ovum or the embryo, luteal inadequacy and failure of the supply of progesterone to the uterus, or the mechanisms involved in maternal recognition of pregnancy. The level of nutrition and peripheral progesterone concentrations are inversely related, and increased rates of embryo loss, associated with higher progesterone concentrations in ewes with low levels of nutrition have been reported. Undernutrition may act through changes in the distribution of progesterone in the endometrium. Thus, lower endometrial levels on day 5 of the cycle in ewes fed half of their maintenance requirements have been observed, providing a link between the known role of progesterone in embryo survival by the modulation of uterine function and the higher embryo losses found in undernourished ewes. The evidence of an effect of maternal nutrition on IFNtau secretion from the conceptus and of PGF2alpha production from the uterus is presented. Moreover, undernutrition provokes a reduction in the sensitivity of the endometrium to progesterone that may affect embryo survival. Finally, a state of undernutrition induces changes in the endometrial sensitivity to steroid hormones at early stages of pregnancy that could adversely alter uterine environment to the detriment of embryo survival.     

The microsomal glucose-6-phosphatase enzyme of pancreatic islets.

Microsomal fractions isolated from pancreatic islet cells were shown to contain high specific glucose-6-phosphatase activity. The islet-cell glucose-6-phosphatase enzyme has the same Mr (36,500), similar immunological properties and kinetic characteristics to the hepatic microsomal glucose-6-phosphatase enzyme.