Most primordial follicles present in ovaries are dormant and only a few of them are activated in every estrus cycle. However, the mechanism controlling the activation of dormant primordial follicles in vivo remains unclear. In this study, Komatsu et al. found that almost all the activated primordial follicles (black arrows) made contact with blood vessels (red arrows) in mouse ovaries (Komatsu et al. Increased supply from blood vessels promotes the activation of dormant primordial follicles in mouse ovaries. pp. 105–113). To confirm the hypothesis that angiogenesis is crucial for activation of the dormant primordial follicles in vivo, Komatsu et al. induced angiogenesis using recombinant VEGF. They found that the activation of dormant primordial follicles was promoted by an increase in the number of blood vessels in the ovaries. Furthermore, the number of activated follicles increased in cultured ovarian tissues depending on the serum concentration in the medium. These results confirm that the supply of serum components through new blood vessels formed via angiogenesis is a cue for the activation of dormant primordial follicles in the ovaries.
Improving artificial oocyte activation is essential for animal biotechnology, to obtain healthy offspring with a high success rate. Yamamoto et al. investigated whether the equine sperm-specific phospholipase C zeta (ePLCζ) mRNA, which has the strongest oocyte activation potential in mammals, could improve the mouse oocyte activation rate and subsequent embryonic development using inactivated spermatozoa (Yamamoto et al. Production of mouse offspring from inactivated spermatozoa using horse PLCζ mRNA. pp. 67–73). The activation potential of ePLCζ was ten times greater than that of murine (m) PLCζ and normal blastocysts were obtained. However, the birth rate was slightly, but significantly, decreased in oocytes activated by ePLCζ compared to those activated by mPLCζ. These results suggest that activation rate does not always correlate birth rate.
The oocyte is the only cell that can reprogram a somatic nucleus to totipotency. The process of reprogramming is, however, only partially understood, and is accompanied by both epigenetic and structural changes in the somatic nucleus. The oocyte components that are necessary for a successful reprogramming and remodeling are unknown. In this issue, Fulka H et al. demonstrate that rather than the insoluble nuclear envelope, together with chromatin-bound factors, or the cytoplasm alone, it is the soluble nuclear fraction that has a major effect upon the somatic nucleus (Fulka H, et al.: Dissecting the role of the germinal vesicle nuclear envelope and soluble content in the process of somatic cell remodeling and reprogramming. pp. 433-441). This fraction is essential for altering the size of the somatic nucleus as well as transcriptional silencing and efficient histone H3.3 incorporation.
Mammary Growth and Regression -Regulation of Milk Synthesis-
Released: October 20, 2010 | Volume 42 Issue 6 Pages j143-j150
Follicular Growth and Atresia in Mammalian Ovaries: Regulation by Survival and Death of Granulosa Cells
Released: March 22, 2012 | Volume 58 Issue 1 Pages 44-50
Fuko MATSUDA, Naoko INOUE, Noboru MANABE, Satoshi OHKURA
Corpus Luteum and Its Control by Intra-Luteal Regulators
Released: October 20, 2010 | Volume 43 Issue 6 Pages j65-j73
Kiyoshi OKUDA, Yoshihisa UENOYAMA, Ryosuke SAKUMOTO
Monitoring Metabolic Health of Dairy Cattle in the Transition Period
Released: August 10, 2010 | Volume 56 Issue S Pages S29-S35
In vitro Production of Porcine Embryos: On the Developmental Competence
Released: October 20, 2010 | Volume 44 Issue 6 Pages j47-j52