Journal of reproduction and fertility最新文献

Immunization of female mammals with native zona pellucida (ZP) proteins is known to cause infertility. Since each human ZP protein is now available as a purified recombinant protein, is it possible to compare the immunocontraceptive potential of each ZP protein. A breeding study was conducted in cynomolgus monkeys (Macaca fasicularis) after immunization with recombinant human ZP (rhZP) proteins (ZPA, ZPB, ZPC) separately and in combinations. This study demonstrated that immunization with recombinant human ZPB (rhZPB) protein caused cynomolgus monkeys to become infertile for 9-35 months. A second study was conducted in baboons (Papio cynocephalus), which yielded a similar result. The baboons immunized with rhZPB became infertile for 9 to > 20 months. During the time of maximum antibody titre, some animals experienced disruption of the menstrual cycle, but eventually all of the animals resumed normal menstrual cycles. Control animals and animals immunized with other rhZP proteins all became pregnant before any of the rhZPB-treated animals. This is the first study in which a recombinant ZP protein has consistently induced infertility in a primate without permanent disruption of the normal menstrual cycle.

The increase in uterine oxytocin receptor concentrations over the late luteal phase of the oestrous cycle in sheep is thought to play an important role in the regulation of the duration of the cycle by facilitating the effect of oxytocin on uterine prostaglandin release. Experiments indicated that oxytocin receptor mRNA expression in the endometrium was high at oestrus compared with at days 2, 7 and 12 of the oestrous cycle. The amount of oxytocin receptor mRNA expression in the pituitary gland did not show any significant differences during the oestrous cycle. Oxytocin receptor cDNA was obtained and characterized from ovine uterine endometrium on day 15 of the oestrous cycle, using RT-PCR techniques, to study the mechanisms underlying the resolution of oxytocin receptor expression. The cDNA sequence for the oxytocin receptor gene in sheep was found to be similar to that described previously, except for a difference of seven nucleotides. These nucleotide differences resulted in changes in four of the deduced amino acids in the oxytocin receptor sequence. The heterogeneity of the different sized oxytocin receptor transcripts in sheep is due, at least in part, to the alternative use of polyadenylation sites. Northern hybridization confirmed that the oxytocin receptor gene is expressed in ovine corpus luteum. The investigations on oxytocin receptor gene expression indicate that the patten of oxytocin receptor gene expression in sheep is not only tissue-specific, but also highly function-related. Evidence was obtained of mRNA editing in both the coding and the 3'-untranslated (3'UTR) regions of oxytocin receptor gene transcripts in ovine endometrium; this was the first demonstration of this phenomenon for oxytocin receptor mRNA. The present results indicate that the observed differences in oxytocin receptor mRNA sequences for the different oxytocin receptor populations in endometrium are due to mRNA editing. mRNA editing of oxytocin receptor transcripts may be reflected in changes in the amino acid composition of the carboxyl terminus of the receptor, which would explain the differences in the observed responses to an oxytocin challenge.

Enhanced prostaglandin production and release by the placenta is an essential element in the normal transition to labour in many animal species. In sheep, expression of prostaglandin G/H synthase (PGHS) is the central enzyme regulating this process. In this study immunohistochemistry was used to examine the distribution of cells expressing PGHS-1 and PGHS-2 in ovine placenta in association with spontaneous parturition (n = 6) and glucocorticoid-induced labour (n = 5). Labour was induced in ewes after the intrafetal injection of betamethasone on day 131 of gestation. Animals administered an intrafetal injection of isotonic saline (n = 5) acted as non-labour controls. In placentomes collected from all groups, immunoreactive PGHS-1 was present in the mononuclear trophoblast cells of the fetal placenta. Cells in the maternal mesenchyme and epithelial syncytium were weakly immunopositive for this enzyme. PGHS-1 immunoreactivity was also demonstrated in the endothelial cells of the chorionic vessels. The PGHS-2 isozyme was localized exclusively to the trophoblast epithelial cells. Immunoreactive PGHS-2 was not detectable in the maternal epithelial syncytium or the stroma of the cotyledons. The binucleate cells of the fetal placenta were consistently immunonegative for both PGHS isozymes. These results indicate that the cellular localization of PGHS-1 and PGHS-2 in ovine placenta does not change during the last 15 days of pregnancy. Co-localization of these isozymes indicates that the source of arachidonic acid and the site of prostanoid formation are the same. Quantitation of the percentage area of positive staining for PGHS-1 and PGHS-2 using image analysis software demonstrated a significant increase in PGHS-2 in the fetal trophoblast after glucocorticoid-induced labour and spontaneous parturition. This finding indicates that increased formation of the PGHS-2 isozyme is responsible for the large increase in prostaglandin production by the ovine placenta at term labour.

Angiotensin II is a hormone with a wide array of physiological effects that exerts its effect via interaction with two major subtypes of receptor. The results of this study show that angiotensin II (from 1 to 100 nmol l(-1)) initiates acrosomal exocytosis in equine spermatozoa that have undergone capacitation in vitro in a TALP-TEST (Tyrode's albumin lactate pyruvate; 188.7 mmol TES l(-1), 84.8 mmol Tris l(-1)) buffer with cAMP. The acrosome reaction and sperm viability were assessed with fluorescein isothiocyanate-Pisum sativum agglutinin (FITC-PSA) and Hoechst 33258, respectively. The initiation of the acrosome reaction by angiotensin II was strongly inhibited by losartan, a specific angiotensin II type 1 receptor antagonist. Although angiotensin II as well as progesterone both initiated the acrosome reaction in equine spermatozoa, there was no synergistic effect when both agonists were added simultaneously. Initiation of acrosomal exocytosis by angiotensin II was accompanied by a rapid and transient calcium influx that was assessed in capacitated spermatozoa loaded with Fura-2AM. In addition, the angiotensin II-mediated calcium influx was inhibited when spermatozoa were preincubated with losartan. Western blotting with an antibody against angiotensin II type 1 receptor detected a major sperm protein of 60 kDa. Indirect immunofluorescence of non-capacitated spermatozoa with the angiotensin II type 1 receptor antibody revealed labelling in the midpiece and tail. In capacitated spermatozoa, the angiotensin II type 1 receptor was localized mainly over the anterior region of the sperm head, the equatorial segment and occasionally on the postacrosomal region in addition to the sperm tail. In conclusion, this study demonstrated the ability of angiotensin II to stimulate the acrosome reaction in capacitated equine spermatozoa. This effect is mediated via the angiotensin II type 1 receptor and is accompanied by an increase in intracellular calcium.

To obtain further perspective on reproduction and particularly gamete function among so-called primitive mammals presently grouped in the Order Insectivora, we have examined the African hedgehog, Atelerix albiventris, in light of unusual features reported in shrews and moles. Atelerix proves to share many but not all of the characteristics seen in these other insectivores. The penis of Atelerix has a 'snail-like' form, but lacks the surface spines common in insectivores and a number of other mammals. Hedgehog spermatozoa display an eccentric insertion of the tail on the sperm head, and they manifest the barbs on the perforatorium that, in shrews, probably effect the initial binding of the sperm head to the zona pellucida. As a possible correlate, the structural matrix of the hedgehog acrosome comprises only two main components, as judged by immunoblotting, rather than the complex of peptides seen in the matrix of some higher mammals. The Fallopian tube of Atelerix is relatively simple; it displays only minor differences in width and in the arborized epithelium between the isthmus and ampulla, and shows no evidence of the unusual sperm crypts that characterize the isthmus or ampulla, depending on the species, in shrews and moles. In common with other insectivores, Atelerix appears to be an induced ovulator, as judged by the ovulation of some 6-8 eggs by about 23 h after injection of hCG. The dense cumulus oophorus appeared to have little matrix, in keeping with the modest dimensions of the tubal ampulla and, while it was not quite as discrete as that of soricids, it did show the same insensitivity to 0.5% (w/v) ovine or bovine hyaluronidase.