The endometrium plays an important role during attachment and implantation of embryos. Using histological techniques, we evaluated the morphological changes of the endometrium in repeat breeder cows. Endometrial biopsy specimens were obtained from 5 Holstein repeat breeder cows, 5 normally cyclic Holstein cows and 5 normally cyclic Holstein heifers on Days 1 and 8 after estrus. On Day 1, in the repeat breeder cows, the glandular secretions and supranuclear vacuolation were observed, but glandular mitoses were not observed, whereas these secretory characteristics were not observed in the normal cows. However, the appearance of stomal mitoses, stromal edema and pseudodecidual reaction was observed as in the normal cyclic cows. On Day 8, in the repeat breeder cows, the characteristics on the glandular indices were not different from those on Day 1, and were similar to those of the normal cows on Day 8. But, the characteristics on the stromal indices, the stromal mitoses and pseudodecidual reaction, were not observed, although these characteristics were observed in the normally cyclic cows. The presence of advanced morphology in the gland on Day 1 and the stroma on Day 8 indicates that these two events are controlled independently. These endometrial asynchrony might result in cows repeat breeding.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFurther Aspects of Gramicidin and Tyrocidine Biosynthesis in the Cell-free System of Bacillus brevis*K. Okuda, I. Uemura, J. W. Bodley, and T. WinnickCite this: Biochemistry 1964, 3, 1, 108–113Publication Date (Print):January 1, 1964Publication History Published online1 May 2002Published inissue 1 January 1964https://pubs.acs.org/doi/10.1021/bi00889a017https://doi.org/10.1021/bi00889a017research-articleACS PublicationsRequest reuse permissionsArticle Views43Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
The corpus luteum (CL) is essential for establishing pregnancy. If pregnancy does not occur during the estrous cycle, luteolysis is induced by prostaglandin (PG) F2alpha secreted from the uterus. Galectin-1, a beta-galactose-binding protein, is expressed in the functional CL of cows and increases the viability of bovine luteal steroidogenic cells (LSCs) by modifying the functions of membrane glycoproteins. The binding of galectin-1 to glycoproteins is blocked by alpha2,6-sialylation of the terminal galactose residues of glycoconjugates, which is catalyzed by a sialyltransferase (ST6Gal-I). However, the physiological role of alpha2,6-sialic acid in bovine CL is unclear. The level of alpha2,6-sialylation of the bovine CL was higher during the regressed-luteal stage than in other luteal stages. Lectin histochemistry revealed that alpha2,6-sialylated glycoconjugates were localized to luteal endothelial cells throughout the estrous cycle. In addition, alpha2,6-sialylated glycoconjugates concentrated to the membrane of LSCs during the regressed-luteal stage. PGF2alpha treatment for 72 h enhanced the expression of ST6Gal-I mRNA and the level of alpha2,6-sialylated glycoproteins in mid-LSCs. The level of alpha2,6-sialylated glycoproteins of late-stage LSCs (Days 15–17 after ovulation) was higher than that of mid-stage LSCs (Days 8–12 after ovulation), and galectin-1 increased the viability of mid-LSCs but not that of late-stage LSCs. Furthermore, galectin-1 increased the viability of late-LSCs when alpha2,6-sialic acid residues were removed by neuraminidase. The overall findings suggest that alpha2,6-sialylation stimulated by PGF2alpha contributes to luteolysis by inhibiting the luteotropic effects of galectin-1 in bovine CL.
Contents The main function of the corpus luteum (CL) is production of progesterone (P4). Adequate luteal function to secrete P4 is crucial for determining the physiological duration of the oestrous cycle and for achieving a successful pregnancy. The bovine CL grows very fast and regresses within a few days at luteolysis. Mechanisms controlling development and secretory function of the bovine CL may involve many factors that are produced both within and outside the CL. Some of these regulators seem to be prostaglandins (PGs), oxytocin, growth and adrenergic factors. Moreover, there is evidence that P4 acts within the CL as an autocrine or paracrine regulator. Each of these factors may act on the CL independently or may modify the actions of others. Although uterine PGF 2α is known to be a principal luteolytic factor, its direct action on the CL is mediated by local factors: cytokines, endothelin‐1, nitric oxide. The changes in ovarian blood flow have also been suggested to have some role in regulation of CL development, maintenance and regression.
One of the many roles of tumor necrosis factor (TNF)-α is to control mammalian corpus luteum (CL) PG synthesis and apoptotic cell death. Here, the cellular localization of TNF-α and its type I (TNF-RI) and type II (TNF-RII) receptors in bovine luteal tissue were analyzed using in situ hybridization, immunohistochemistry, and quantitative real-time PCR. Transcripts for TNF-α were expressed in bovine CL throughout the estrous cycle, but were significantly more abundant (P < 0.01) at the regressed luteal stage than at the other stages. Localization of TNF-α transcripts and protein were observed in large and small bovine luteal cells, as well as in immune cells. Moreover, transcripts for TNF-RI and TNF-RII were expressed in bovine CL throughout the estrous cycle. The abundance of TNF-RII transcripts was greater (P < 0.01) at the regressed luteal stage than at the other stages, whereas TNF-RI transcript abundance did not significantly change. Expression of TNF-RI and TNF-RII transcripts and proteins were observed in both the large and small luteal cells, and the proteins were also expressed in the immune cells and vascular endothelial cells. These results suggest that TNF-α sources include immune cells, as well as large and small luteal cells, and that TNF-RI and TNF-RII are present in the luteal cells of the bovine CL.
The bovine corpus luteum (CL) grows very fast and regresses within a few days at luteolysis. Mechanisms controlling development and secretory function of the bovine CL may involve many factors that are produced both within and outside the CL. In the cow, luteolysis is initiated by uterine prostaglandin (PG)F2α released at the late luteal stage. It can also be induced by injection of exogenous PGF2α given at the mid luteal stage. Luteolysis consists of a phase of rapid decrease in progesterone (P4) production by the CL, followed by a phase of structural regression. Although uterine PGF2α is known to be the main luteolytic factor, its direct action on the CL is mediated by the products of accessory luteal cells: immune cells, endothelial cells, pericytes and fibroblasts. There are studies showing that beside endothelin-1, cytokines (tumor necrosis factor-α, interferons) and nitric oxide play critical roles in functional and structural luteolysis in cattle by stimulating leukotrienes and PGF2α, decreasing P4 secretion and apoptosis induction. Because of luteal blood flow and P4 concentrations decrease in parallel during both spontaneous and PGF2α-induced luteolysis, a decrease in luteal blood flow resulting in hypoxia has been proposed as one of the main luteolytic mechanisms in the cow. Hypoxia inhibits P4 synthesis in luteal cells by inhibiting the steroidogenic enzymes and promotes apoptosis of luteal cells by increasing pro-apoptotic proteins. Although reduction of luteal blood flow and hypoxia contribute to the late events of luteolysis, little is known about the physiological relevance and the cause of the transient increase in luteal blood flow and reactive oxygen species during the initial step of luteolysis.
