Sea urchins are members of a limited group of animals in which meiotic maturation of oocytes is completed prior to fertilization. This is different from oocytes of most animals such as mammals and amphibians in which fertilization reactivates an arrested meiotic cycle. Using a recently developed technique for in vitro maturation of sea urchin oocytes, we analyzed the role of cyclin B, the regul...

In Xenopus oocytes, the mos proto-oncogene product is required during meiosis I for the activation of maturation promoting factor (MPF) and the subsequent breakdown of the germinal vesicle (GVBD). In addition, the mos product has been shown to be a candidate "initiator" of meiotic maturation and is an active component of cytostatic factor (CSF), an activity responsible for metaphase II arrest. ...

1. The use of floral resource subsidies to improve herbivore suppression by parasitoids requires certain trophic interactions and physiological changes to occur. While the longevity and fecundity of parasitoids are positively affected by nectar subsidies in laboratory studies, the impacts of floral subsidies on the fecundity and longevity of freely foraging parasitoids have not been studied. 2....

developing a culture system for preantral follicles has important biotechnological implications due to the potential to produce a large number of oocytes for embryo production and transfer. to accomplish this goal, the present study was aimed to culture preantral follicles in the presence of different media, sera and fsh concentrations. six-week-old preantral follicles (95 ± 5 µm) were cultured...

We have observed the presence of membrane junctions formed between the plasma membrane and cortical endoplasmic reticulum of mature, unactivated eggs of Xenopus laevis. The parallel, paired membranes of the junction are separated by a 10-nm gap within which electron-dense material is present. This material occurs in patches with an average center-to-center distance of ~30 nm. These junctions ar...

Oocyte maturation arrest is a complex problem not clearly understood; only few cases showing a complete oocyte maturation failure has been reported previously, still the exact incidence remains unknown. Failure to resume meiosis (a specialized type of cell division that reduces the chromosome number by half) in vivo may arise at one of the following three levels: absent or incomplete luteinizin...

Oocyte maturation arrest is a complex problem not clearly understood; only few cases showing a complete oocyte maturation failure has been reported previously, still the exact incidence remains unknown. Failure to resume meiosis (a specialized type of cell division that reduces the chromosome number by half) in vivo may arise at one of the following three levels: absent or incomplete luteinizin...

The osmotic challenges facing maturing spermatozoa and their responses to them are discussed in relation to the concept of sperm maturation, defined as the increased ability of more distally recovered epididymal spermatozoa to fertilize eggs when inseminated into the female tract. One explanation could be that the more distal cells are better able to regulate their volume, and reach the oviduct...

The scyphozoan Pelagia noctiluca has potential value for research and a wide variety of industrial applications. However, its holoplanktonic life cycle makes it difficult to maintain permanent stock in aquaculture, unlike the continuous supply newly-released ephyrae from jellyfish species with benthic stage. We investigated optimal feeding conditions captive breeding P. , monitoring total body ...