Various stages of immature human oocytes were imaged for microtubule, microfilament and chromatin organization. After germinal vesicle breakdown, a small microtubule aster was observed near the condensed chromatin. The asters appeared to elongate and encompass the condensed chromatin. At metaphase I stage, microtubules were detected in the meiotic spindle. The meiotic spindle in metaphase II wa...

A study was conducted opportunistically to evaluate the potential of rescuing immature oocytes from the ovaries of the Sumatran rhinoceros postmortem. Recovered oocytes (n = 30) were placed in maturation culture for 36 hr and inseminated with frozen-thawed homologous spermatozoa. After culture, evaluation of nuclear maturation status revealed that a large number of oocytes were degenerated (n =...

The spindle assembly checkpoint (SAC) functions as a surveillance mechanism to detect chromosome misalignment and to delay anaphase until the errors are corrected. The SAC is thought to control mitosis and meiosis, including meiosis in mammalian eggs. However, it remains unknown if meiosis in the eggs of nonmammalian vertebrate species is also regulated by SAC. Using a novel karyotyping techniq...

A spontaneous male-sterile, female-fertile mutation affecting bivalent arrangement at the metaphase plate and cytokinesis was detected in line BR98-197 of the soybean breeding program developed by Embrapa - National Soybean Research Centre. Untill diakinesis, meiosis was normal with chromosome pairing as bivalents. From this phase, in several meiocytes, bivalents were not able to organize a sin...

When removed from the follicles, during the 44 h process of in vitro maturation (IVM) fully grown porcine oocytes resume meiosis spontaneously from the late diplotene stage of the first meiotic prophase and proceed to the metaphase-II (MII) stage at which they remain arrested until fertilization. However, the resumption may start at various times causing heterogeneity in the nuclear stage and a...

Both microRNAs (miRNAs) and endogenous small interfering RNAs (endo-siRNAs) play key regulatory roles in gene expression. Some studies have demonstrated that the function of miRNA is suppressed in mouse oocytes, suggesting that endo-siRNA, not miRNA, is essential for female meiosis. This finding has yet to be confirmed in other species. In this study, by knockdown of DICER1, DROSHA and its cofa...

BACKGROUND In humans, little is known about the mechanisms of non-disjunction working in male meiosis, although considerable attention has been given to these mechanisms in female meiosis. The present study explores the origin of meiotic non-disjunction during human spermatogenesis and the chromosomes most commonly involved in this process. METHODS We used Multiplex fluorescence in situ hybri...