Ovarian functions, such as follicular development and ovulation, are often suppressed in lactating animals. This may be a strategic adaptation to ensure the survival of lactating mothers by avoiding another pregnancy. The suppression of ovarian functions is assumed to be primarily due to the suckling-induced inhibition of hypothalamic kisspeptin neurons (the master regulators of mammalian reproductive function), followed by the inhibition of gonadotropin-releasing hormone (GnRH) and subsequent gonadotropin release. However, the mechanism mediating this inhibition is not fully understood. Sugimoto et al. demonstrated that central antagonism of somatostatin receptor 2 (SSTR2) increased kisspeptin gene expression levels in the hypothalamus of lactating rats, and that some hypothalamic glutamatergic neurons expressed SSTR2. Additionally, SSTR2 antagonism increased luteinizing hormone (LH) release in lactating rats and central glutamate receptor antagonism reversed this effect. Overall, these results suggest that central somatostatin-SSTR2 signaling, at least partly, mediates the suppression of kisspeptin gene expression and subsequent GnRH/LH release by inhibiting glutamatergic interneurons in lactating rats (Sugimoto et al. Central somatostatin-somatostatin receptor 2 signaling mediates lactational suppression of luteinizing hormone release via the inhibition of glutamatergic interneurons during late lactation in rats. pp. 190–197).
To understand the cellular processes associated with non-invasive mode of conceptus implantation to the maternal endometrium, Yamada et al. observed the conceptus implantation process via adhesion of trophoblast cells to the uterine epithelium (Yamada et al., Epithelial-mesenchymal transition and bi- and multi-nucleated trophoblast cell formation in ovine conceptuses during the peri-implantation period, pp. 110–117). Similar to human syncytiotrophoblast, ruminant trophoblasts form bi- and multi-nucleated trophoblast cells. Using pregnancy associated glycoproteins (PAGs) specific antibody, bi- and multi-nucleated trophoblast cells in cross sections of day 21 ovine uteri (day 0 = day of estrus), including elongated conceptuses, were observed, and it was found that bi- and multi-nucleated trophoblast cells existed on the uterine epithelium or next to the uterine stroma. These results suggest that the formation of bi- and multi-nucleated trophoblast cells facilitates the placental formation in ruminants.
Ogata et al. investigated the effects of reduced glutathione (GSH) supplementation in a freezing extender on frozen-thawed semen quality and subsequent in vitro fertilization (IVF) results (Ogata et al. pp. 53–61). GSH supplementation did not affect sperm viability or acrosome integrity (left panel, FITC-PNA staining) in any of the bulls, although few bulls displayed increased DNA damage (right panel, TUNEL staining). However, pronucleus formation and embryonic development after IVF improved in those bulls. These results suggest that supplementing the freezing extender with GSH may improve in vitro embryo production from frozen semen.
Green Fluorescent Protein as a Novel Vital Marker in Transgenic Mouse
Released on J-STAGE: October 20, 2010 | Volume 43 Issue 6 Pages j19-j25
Masaru OKABE, Masahito IKAWA, Shuichi YAMADA, Tomoko NAKANISHI, Tadashi BABA
Central somatostatin-somatostatin receptor 2 signaling mediates lactational suppression of luteinizing hormone release via the inhibition of glutamatergic interneurons during late lactation in rats
Released on J-STAGE: June 01, 2022 | Volume 68 Issue 3 Pages 190-197
Arisa SUGIMOTO, Hitomi TSUCHIDA, Mayuko NAGAE, Naoko INOUE, Yoshihisa UENOYAMA, Hiroko TSUKAMURA