Reproduction

Spiteri-Grech, J.; Nieschlag, E.

doi: 10.1530/jrf.0.0980001pmid: 8345452

IntroductionIn the last two decades, it has become increasingly evident that disturbances of the hypothalamic–pituitary–gonadal axis account for only a small percentage of the cases seen in male infertility clinics. In an attempt to clarify the pathophysiology of idiopathic male infertility and also for the development of new methods for male contraception, researchers have focused on local regulators of intratesticular events (Bartlett et al., 1989; Hamilton and Waites, 1989). The number of factors implicated in paracrine regulation has been steadily increasing and it is essential that the data available are critically examined. The object of this review is to pinpoint the factors of potential or proven physiological significance and to concentrate on the more recent advances made in the field.The two major areas of activity within the testis centre on steroidogenesis and spermatogenesis. The intratesticular control of steroidogenesis has already been extensively reviewed (Sharpe, 1990) and this paper

Schweigert, F. J.; Schams, D.

doi: 10.1530/jrf.0.0980015pmid: 8345458

During the period of lactational oestrus, the corpus luteum of ovaries of grey seals decreased in size following the birth of the pup, while on the contralateral ovary one major large follicle rapidly expanded. These large follicles had the highest concentration of oestradiol (4282 ± 609 ng ml−1) and progesterone (499 ± 168 ng ml−1). Osmolality (322 ± 3 mosmol kg−1) and the intrafollicular concentration of electrolytes (Na: 126 ± 1; Cl: 96 ± 1; Ca: 1.3 ± 0.1 μmol ml−1) and proteins (94 ± 1 mg ml−1) were independent of stage of lactation and follicle size. Concentrations were lower in follicular fluid than in plasma. The concentrations of triglycerides and, to some extent, those of vitamin E, cholesterol and phospholipids were affected by the decrease in the plasma concentration of these components with the onset of lactation and the increase in follicle size. These two events resulted in a marked decrease of these components in the largest follicles at the end of lactational oestrus. Vitamin A (exclusively as retinol), although a blood-borne component in follicular fluid, was the only component with a higher concentration in small and medium follicles than in plasma and decreased with increasing follicle size despite an increase in plasma retinol. This decrease and the negative correlation with intrafollicular oestradiol might indicate a high demand of preovulatory follicle structures for vitamin A owing to its possible importance in steroid hormone or protein synthesis or in both processes. Changes in the chemical composition of follicular fluid and the morphological findings indicate a continuous development of the dominant follicle throughout the lactational oestrus in grey seals.

Chapple, R. S.; English, A. W.; Mulley, R. C.

doi: 10.1530/jrf.0.0980023pmid: 8345466

Duration of oestrous cycle and gestation, and characteristics of postpartum oestrus of chital hinds are described. Mean duration of the oestrous cycle of chital hinds was 19.3 ± 1.3 days, with a range of 17–21 days. Serum progesterone profiles are shown, with minimum progesterone concentrations near oestrus less than 2.7 nmol l−1, and maximum luteal values 16–26 nmol l−1. Mean duration of gestation was 234.5 ± 3.0 days (n = 17).

Gobbetti, A.; Zerani, M.

doi: 10.1530/jrf.0.0980027pmid: 8345472

Concentrations of PGE2, PGF2α, androgens and oestradiol in plasma, and ovary weights were measured in the female frog, Rana esculenta, during the annual breeding cycle. Experiments were carried out in vivo to study the effects of PGE2 and PGF2α on plasma sex steroids during the following stages: pre-reproduction (April), reproduction (May), post-reproduction (June) and recovery (October). Experiments were performed in vitro during these stages to evaluate the effects of these two prostaglandins on the secretion of ovarian steroids. Concentrations of PGE2 were low in plasma during winter hibernation, the reproduction and post-reproduction stages, whereas they were high during the pre-reproduction and recovery stages. PGE2 treatment in vivo increased androgen secretion in April, whereas PGF2α treatment increased oestradiol secretion in June and October. In experiments in vitro, PGE2 increased androgen secretion and decreased oestradiol secretion from ovaries collected in April, whereas PGF2α increased oestradiol secretion from ovaries collected in October. These results suggest that a seasonal increase in plasma PGE2 may inhibit breeding activity, probably by stimulating ovarian androgen secretion, whereas, as previously reported, a seasonal increase in plasma PGF2α may inhibit breeding, by stimulating ovarian oestradiol secretion.

Tanaka, N.; Miyazaki, K.; Tashiro, H.; Mizutani, H.; Okamura, H.

doi: 10.1530/jrf.0.0980033pmid: 8345477

Adenylyl cyclase activity was studied in human endometrium during the menstrual cycle and in human decidua during pregnancy. Higher adenylyl cyclase activity was found in the endometrium than in the myometrium, corpus luteum or Fallopian tubes. In the endometrium, the basal and stimulated activities were highest in the fundus and decreased slightly from the fundus to the isthmus. Prostaglandin-stimulated adenylyl cyclase activity increased gradually from the proliferative phase to the secretory phase, and then quickly reached its highest value in the late secretory phase. Catecholamine-stimulated adenylyl cyclase activity reached a peak in the late proliferative phase and decreased significantly thereafter. Forskolin-stimulated activity was significantly higher throughout the secretory phase than in the proliferative phase. In the decidua, prostaglandin-, catecholamine- and forskolin-stimulated adenylyl cyclase activities in late pregnancy were significantly lower than those in early pregnancy. Our results demonstrate dramatic alterations in adenylyl cyclase activity in human endometrium during the menstrual cycle and in human decidua during pregnancy.

Smith, P.; O, W-S.; Hudson, N. L.; Shaw, L.; Heath, D. A.; Condell, L.; Phillips, D. J.; McNatty, K. P.

doi: 10.1530/jrf.0.0980041pmid: 8345478

The aim of this study was to determine whether the FecB gene influenced some aspects of fetal development in sheep. Carrier (BB/B+) and non-carrier (++) female fetuses were recovered at specific times of gestation, namely, days 40, 55, 75, 90, 95 and 135. The results showed that the FecB gene influenced litter size, body weight and ovarian development during fetal life. The mean litter sizes were larger (P < 0.05) and body weights were lighter (P < 0.05) at most gestational ages in BB/B+ than in ++ fetuses. Morphometric studies of the ovary showed that the development of the BB/B+ ovaries was retarded: the ++ genotype had more oogonia at day 40 (P < 0.01), more germ cells entering meiosis at day 55, more primordial follicles developing at days 75, 90 and 95 (P < 0.05), a greater loss of germ cells by atresia at day 90 (P < 0.01) and more growing follicles (P < 0.01) and more antral follicles (P < 0.05) at day 135. Differences between the BB/B+ and ++ genotypes in the plasma concentrations of immunoreactive (i) inhibin, i-FSH, bioactive (b)-FSH or (i)-LH were not apparent at any age except for i-LH at day 75 (BB/B+ > ++; P < 0.05). Likewise no differences were noted in the contents of ovarian or adrenal oestradiol or i-inhibin except for i-inhibin in the adrenal at day 75 (++ > BB/B+, P < 0.01). No differences between the genotypes were noted in the i-inhibin contents of the mesonephros at day 40. In mid- to late but not early gestation (i.e. days 40 and 55) significant correlations (i.e. P < 0.05) were noted between litter size and body weight at days 75, 90 and 135, and between litter size and ovary weight, ovary volume, adrenal weight and pituitary weight at day 135. To eliminate the effect of litter size, equal numbers of BB/B+ and ++ embryos were transferred to respective recipient ewes, and fetuses were recovered at the equivalent of days 40 and 90 of gestation. The results showed that the genotypic difference in fetal body weight at day 40 (++ > BB, P < 0.001) and in number of oogonia at day 90 (++ > BB/B+, P < 0.05) were independent of litter size. We hypothesize that many of the differences between the Booroola genotypes in ovarian follicular development and pituitary function in neonatal and adult life may be a consequence of differences in the timing or rate of body weight or organ development in fetal life.

Allen, W. R.; Skidmore, J. A.; Stewart, F.; Antczak, D. F.

doi: 10.1530/jrf.0.0980055pmid: 8345479

Measurement of the concentrations of equine chorionic gonadotrophin (eCG) in the serum of pregnant mares and Jenny donkeys carrying normal intraspecies and hybrid interspecies pregnancies suggested that the production of this hormone may be influenced by parental gene imprinting. Specifically, a differential expression of maternal and paternal genes may control the size and secretory activity of the structures that secrete eCG, the fetal endometrial cups. However, bisection of an interspecies mule embryo followed by transfer of the resulting demi-embryos and other intact mule embryos to horse and donkey recipients resulted in striking differences in the size, secretory activity and lifespan of the endometrial cups in the two types of surrogate mother. This finding has therefore demonstrated the ability of uterine factors to alter profoundly the development and characteristic phenotype of the specialized invasive chorionic girdle portion of the equine trophoblast that gives rise to the endometrial cups.

Thibodeaux, J. K.; Del Vecchio, R. P.; Hansel, W.

doi: 10.1530/jrf.0.0980061pmid: 8345480

This experiment was designed to determine whether the stimulatory effects of bovine oviductal epithelial cells (BOEC) on development of early bovine embryos are due to platelet-derived growth factor (PDGF). Four hundred and twenty five 8-cell bovine embryos derived from in vitro maturation and in vitro fertilization procedures were equally and randomly allotted to one of the following culture treatment groups: control medium alone (Menezo's B2 medium; MB2), MB2 with 1 ng PDGF ml−1 (PDGF), 1 ng PDGF ml−1 and 10 μg anti-PDGF antibody ml−1 (PDGF + Ab), BOEC or BOEC and 10 μg anti-PDGF antibody ml−1 (BOEC + Ab). All embryos were cultured in 100 μl of serum-free MB2 medium supplemented with 2 mg fatty-acid-free bovine serum albumin ml−1. Embryos for all treatment groups were incubated at 39°C and 5% CO2 in humidified air in groups of five embryos per well in 96-well culture plates until 7 days after in vitro insemination. A higher proportion of embryos developed to > 8-cell and to the morula stage following culture with PDGF, BOEC or BOEC + Ab than with MB2 alone. Incubation of PDGF and BOEC-treated embryos with anti-PDGF reduced development to the morula and blastocyst stages. However, anti-PDGF did not completely inhibit blastocyst development when added to BOEC. In addition, embryos incubated with BOEC and anti-PDGF contained a reduced number of inner cell mass cells compared with embryos incubated with BOEC alone. These results indicate that PDGF provides a developmental stimulus similar to BOEC for bovine embryos at the fourth cell cycle. The addition of PDGF antibodies appears to reduce early embryo development by inhibiting PDGF action. However, BOEC may also produce factors other than PDGF that are beneficial to early bovine embryo development during in vitro culture.

Martelli, M.; Campana, A.; Bischof, P.

doi: 10.1530/jrf.0.0980067pmid: 8345481

At each menstrual cycle, the uterine endometrium undergoes intense remodelling. Of the many factors implicated in tissue remodelling, the matrix metalloproteinases (MMPs) play a central role owing to their capacity to degrade the extracellular matrix. The aim of this study was to examine the nature and cellular origin of endometrial proteases as evaluated in culture systems with clearly characterized cell types. Endometrial cells from hysterectomy specimens were prepared using collagenase digestion. Bone-marrow-derived cells (a known source of proteases) were removed by immunopurification. Cells were cultured on different substrates (matrigel, agarose, glass or plastic). Purity of cell preparations was examined by immunocytochemistry, and proteases were characterized by zymography on SDS-PAGE containing gelatin. The cell phenotype in culture was largely influenced by the type of substrate. Gelatindegrading enzymes detected in culture supernatants of stromal and epithelial cells had molecular masses ranging from 42 to 248 kDa, and were identified as metalloproteinases. We conclude that human endometrial stromal and epithelial cells express several matrix metalloproteinases, the expression of which clearly depended on the purity of cell preparation, on cell adhesion and on the nature of the substrate on which the cells grew. These enzymes might be involved in endometrium remodelling, blastocyst implantation and trophoblast invasion.

Savio, J. D.; Thatcher, W. W.; Morris, G. R.; Entwistle, K.; Drost, M.; Mattiacci, M. R.

doi: 10.1530/jrf.0.0980077pmid: 8345482

The effects of concentration of progesterone in plasma on development and fertility of the first wave dominant follicle were studied in cattle. To identify a source of exogenous progesterone that would permit extension of the first wave dominant follicle, nonlactating Holstein cows (n = 6) received on day 8 of two successive oestrous cycles an injection of PGF2α (25 mg) and a new (1.9 g of progesterone (Period 1)) or used (≈ 1.2 g of progesterone (Period 2)) CIDR-B device that was removed on day 17. Control cows (n = 6) received a new CIDR-B device on day 8 that was removed on day 17 and a PGF2α injection (25 mg) on day 17. Ultrasonography and collection of blood samples were performed on alternate days throughout the experiment. Plasma concentrations of progesterone and oestradiol were different between treatments (P < 0.0001 and P < 0.05, respectively). The dominant follicle was maintained until day 17 and ovulated upon removal of the intravaginal device in 1 of 6, 6 of 6 and 0 of 6 in new CIDR-B, used CIDR-B and control groups, respectively (P < 0.01). The preovulatory dominant follicles were 14.2 ± 1.6 mm, 20 ± 1.3 mm and 10 ± 1.3 mm, respectively (P < 0.001) on day 17. There were fewer 5–9 mm follicles in cows having a persistent dominant follicle (P < 0.01). The interval to onset of oestrus was negatively correlated with size of the dominant follicle on day 17 (P < 0.001). In Expt 2, the fertility of oocytes ovulated from new (PGF2α on day 7; T1; n = 91) and persistent dominant follicles (PGF2α on day 7 and a used CIDR-B device inserted on day 7 and withdrawn on day 16; T2; n = 91) was tested using Holstein heifers. Size of the dominant follicle and plasma concentrations of progesterone and oestradiol on days 7 (T1) and 16 (T2) were different between treatments: 11.3 ± 0.2 versus 16.2 ± 0.3 mm (P < 0.001); 4.2 ± 0.2 versus 2.9 ± 0.3 ng ml−1 (P < 0.01) and 3.5 ± 0.3 versus 11.7 ± 1.7 pg ml−1 (P < 0.01), respectively. Pregnancy rates at first artificial insemination were 64.8% (46 of 71) and 37.1% (26 of 70) for new and persistent dominant follicles, respectively (P < 0.01). Pregnancy rates at second service were 50% and 52.8%, respectively. Low plasma concentrations of progesterone, therefore, resulted in persistency of the dominant follicle and temporarily impaired fertility.