Metaphase Of Meiotic Division Research Articles

Actin Colocalization with Metaphase Chromosomes of the Second Meiosis in Ovulated Mouse Oocytes

Functional interrelation of nuclear actin with transcriptional active chromatin in the interphase nucleus was reliably established in numerous experiments, but the relationship between actin and transcriptional silent chromatin is still unclear. We examined localization area of the second meiotic division metaphase plate in ovulated mouse oocytes with the aim to study the possibility of actin-chromatin colocalization and uncovering the distribution patterns of different functional forms of actin near the metaphase chromosomes. Confocal microscopy and probes for actin that are distinguished from each other by the mechanism of actin binding (TRITC-phalloidin, fluorescent DNase-I, and antibodies against fragment of C-terminal and fragment of N-terminal domain of actin) were used for actin visualization. Despite the fact that TRITC-phalloidin could not detect F-actin in the area of metaphase plate, oocytes staining with antibody against fragment of the actin N-terminal domain demonstrates the presence near the metaphase chromosomes of some spindle-like structure composed of actin filaments. Among all used probes for actin, only the antibody against fragment of the C-terminal domain detected accurate actin colocalization with metaphase chromosomes. We conclude that this antibody labeled noncanonical form of the nuclear actin existing in long-term association with highly condensed chromatin.

Cytological Changes of Ovarian Oocytes in the Polycystic Ovary Induced by Injection of Testosterone Propionate in Mice

Polycystic ovary syndrome (PCOS) is the most common etiology of menstrual disorders and hyperandrogenism, and The understanding of PCOS has advanced significantly. However, a fully convincing animal model for study of polycystic ovaries, or of PCOS, has not been established in the mouse. In the present study, polycystic ovary (PCO) was induced by a single intraperitoneal injection of testosterone propionate (TP; 0.1 mg, dissolved in sesame oil) in female mice at 4–5 days of age. The mice exhibited either constant estrus or diestrus for 5 weeks after TP administration, and this resulted in anovulatory polycystic ovaries. These ovaries contained multiple large follicles and no corpus luteum. The morphology and ovulatory failure were similar to those of the PCOs of humans and other animals. In these ovaries, we found that only the oocytes in the secondary follicles had the following cytological changes: first meiotic division metaphase, second meiotic division metaphase, parthenogenesis and fragmentation. This mouse model has potential for application in studies of folliculogenesis and the mechanism of androgen-induced PCO.