In mammals, oocytes are arrested at the diplotene stage of meiosis I until the pre-ovulatory luteinizing hormone (LH) surge triggers meiotic resumption through the signals in follicular granulosa cells. In this study, we show that the estradiol (E2)-estrogen receptors (ERs) system in follicular granulosa cells has a dominant role in controlling oocyte meiotic resumption in mammals. We found that the expression of ERs was controlled by gonadotropins under physiological conditions. E2-ERs system was functional in maintaining oocyte meiotic arrest by regulating the expression of natriuretic peptide C and natriuretic peptide receptor 2 (NPPC/NPR2), which was achieved through binding to the promoter regions of Nppc and Npr2 genes directly. In ER knockout mice, meiotic arrest was not sustained by E2 in most cumulus–oocyte complexes in vitro and meiosis resumed precociously in pre-ovulatory follicles in vivo. In human granulosa cells, similar conclusions are reached that ER levels were controlled by gonadotropins and E2-ERs regulated the expression of NPPC/NPR2 levels. In addition, our results revealed that the different regulating patterns of follicle-stimulating hormone and LH on ER levels in vivo versus in vitro determined their distinct actions on oocyte maturation. Taken together, these findings suggest a critical role of E2-ERs system during oocyte meiotic progression and may propose a novel approach for oocyte in vitro maturation treatment in clinical practice.

Recent studies have shown that C-type natriuretic peptide (CNP) serves as a key control system during mouse oocyte maturation. We used pig models (in vitro and in vivo) to explore the role played by the natriuretic peptide family in porcine oocyte maturation. We reported the expression and location of natriuretic peptide system in different stages of porcine antral follicles. Atrial natriuretic peptide (ANP) and CNP were expressed primarily in granulosa cells, whereas brain natriuretic peptide (BNP) and natriuretic peptide receptor-B (NPRB) receptor were expressed in granulosa cells (both cumulus and mural granulosa cells) and thecal internal cells, and the natriuretic peptide receptor-A (NPRA) receptor predominantly in thecal cells. Upon in vitro culture, BNP and CNP maintained meiotic arrest of oocytes associated with cumulus cells. The expression levels of BNP, CNP, and the NPRB receptor increased upon treatment of prepubertal gilts with pregnant mare's serum gonadotropin and decreased upon subsequent human chorionic gonadotropin injection. Such dynamic changes in the expression of natriuretic peptides and their receptor paralleled the proportions of oocytes exhibiting nuclear maturation in vivo. These data indicated that BNP and CNP co-contributed to maintaining porcine meiotic arrest under physiological condition and lutenizing hormone (LH) relieved this inhibitory effect by decreasing the expression levels of BNP and CNP in vivo. Our present work, combined with previous data, improved the understanding of the oocyte meiotic arrest mechanisms and further revealed that natriuretic peptides serve as oocyte maturation inhibitor (OMI) to inhibit oocyte maturation in mammals.

Fifteen bacterial strains isolated from molasses grass (Melinis minutiflora Beauv.) were identified as nitrogen-fixers by using the acetylene-reduction assay and PCR amplification of nifH gene fragments. These strains were classified as a unique group by insertion sequence-PCR fingerprinting, SDS-PAGE protein patterns, DNA-DNA hybridization, 16S rRNA gene sequencing and morphological characterization. Phylogenetic analysis of the 16S rRNA gene indicated that these diazotrophic strains belonged to the genus Azospirillum and were closely related to Azospirillum lipoferum (with 97?5 % similarity). In all the analyses, including in addition phenotypic characterization using Biolog MicroPlates and comparison of cellular fatty acids, this novel group was found to be different from the most closely related species, Azospirillum lipoferum. Based on these data, a novel species, Azospirillum melinis sp. nov., is proposed for these endophytic diazotrophs of M. minutiflora, with TMCY 0552 T (=CCBAU 5106001 T =LMG 23364 T =CGMCC 1.5340 T ) as the type strain. INTRODUCTIONAssociation of nitrogen-fixing bacteria and herbaceous plants is a common phenomenon in nature. From this association, wild grasses can obtain nitrogen fixed by the bacteria and grow in nitrogen-deficient soils. Diverse endophytic diazotrophs have been isolated from maize, rice, sorghum, sugar cane, cameroon grass and other gramineous plants (Baldani et al., 1986 Olivares et al., 1996;Reis et al., 2004). Some of these plants could associate with a wide range of bacteria, such as in the case of Kallar grass [Leptochloa fusca (L.) Kunth], a pioneer plant grown on salt-affected, often flooded, low-fertility soils in the Punjab of Pakistan, which has been found to be associated with five nitrogen-fixing endophytic bacterial species (ReinholdHurek et al., 1993;Tan & Reinhold-Hurek, 2003).To date, diverse nitrogen-fixing bacteria, including Azospirillum lipoferum, Azospirillum brasilense, Azospirillum halopraeferens, Azoarcus indigens, Azoarcus communis, Azovibrio restrictus, Azospira oryzae and Burkholderia tropica, have been isolated from the roots of numerous wild and cultivated grasses grown in tropical, subtropical and temperate regions all over the world (Kirchhof et al., 1997;Reinhold et al., 1986Reinhold et al., , 1987Reinhold & Hurek, 1988;Reinhold-Hurek et al., 1993;Reis et al., 2004;Tarrand et al., 1978). Among these bacteria, Azospirillum species have been isolated from roots of numerous wild and cultivated grasses, cereals, food crops and soils in various regions. Based on their microaerophilic and nitrogen-fixing characteristics, semi-solid nitrogen-free medium (Döbereiner, 1980) was the key to the successful isolation of these bacteria. At present, eight species have been described within this genus, including the two original species, Azospirillum lipoferum and Azospirillum brasilense (Tarrand et al., 1978), and the later-described species Azospirillum amazonense (Magalhães et al., 1983), Azospirillum halopraeferens (Reinhold et al., 1987) supplie...

In female mammals, the size of the initially established primordial follicle (PF) pool within the ovaries determines the reproductive lifespan of females. Interestingly, the establishment of the PF pool is accompanied by a remarkable programmed oocyte loss for unclear reasons. Although apoptosis and autophagy are involved in the process of oocyte loss, the underlying mechanisms require substantial study. Here, we identify a new role of lysine‐specific demethylase 1 (LSD1) in controlling the fate of oocytes in perinatal mice through regulating the level of autophagy. Our results show that the relatively higher level of LSD1 in fetal ovaries sharply reduces from 18.5 postcoitus (dpc). Meanwhile, the level of autophagy increases while oocytes are initiating programmed death. Specific disruption of LSD1 resulted in significantly increased autophagy and obviously decreased oocyte number compared with the control. Conversely, the oocyte number is remarkably increased by the overexpression of Lsd1 in ovaries. We further demonstrated that LSD1 exerts its role by regulating the transcription of p62 and affecting autophagy level through its H3K4me2 demethylase activity. Finally, in physiological conditions, a decrease in LSD1 level leads to an increased level of autophagy in the oocyte when a large number of oocytes are being lost. Collectively, LSD1 may be one of indispensible epigenetic molecules who protects oocytes against preterm death through repressing the autophagy level in a time‐specific manner. And epigenetic modulation contributes to programmed oocyte death by regulating autophagy in mice.

Most adults have more experience in identifying faces of their own race than in identifying faces from another race, and thus may be considered as own-race face experts. This effect was investigated by recording and analyzing ERPs as well as induced gamma oscillations. The race modulation occurred post the stage of structural processing revealed by N170. Larger P2 component and induced gamma activity for own-race than other-race faces could be associated with more elaborate processing on the basis of configural computation due to more experience that we have for own-race faces.