1,721,021 research outputs found
L’oocita acquisisce la capacità di rimodellare la cromatina dello spermatozoo durante il processo di maturazione meiotica
No full textEffetto dei crioprotettori sulle potenzialità di sviluppo in vitro dei follicoli preantrali di pecora
No full textP-type Ca channel activation by membrane depolarisation induces maturation in pig oocytes
No full textThe presence on pig oolemma of voltage gated Ca channels (VGCC), whose activity can be influenced by depolarisation, has been investigated exposing the oocytes to a chemical depolarisation reproducing the physiological one. To this aim and to characterise the type of VGCC present, we analysed intracellular Ca variations during perfusion of oocytes with physiological or depolarising solutions containing different selective inhibitors of VGCC. We also evaluated the effect of their activation or inhibition on oocyte maturation and the pathway involved in transduction of the depolarising stimulus to the oocyte. The results demonstrate that P type VGCC are present on pig oolemma and that their activation by depolarisation produces a prompt a sustained Ca raise able to induce the resumption of oocyte meiotic maturation through the transduction pathway involving the Ca-calmodulin dependent kinase (CaMKII).[...
The capability of reprogramming the male chromatin after fertilization is dependent on the quality of oocyte maturation
No full textThe present experiments compared the ability of pig oocytes matured either in vivo or in vitro to structurally reorganize the penetrated sperm chromatin into male pronucleus (PN) and to carry out, in parallel, the epigenetic processes of global chromatin methylation and acetylation, 12-14 h after in vitro fertilization (IVF). In addition, PN distribution of histone deacetylase (HDAC), a major enzyme interfacing DNA methylation and histone acetylation, was investigated. The ability of the oocyte to operate an efficient block to polyspermy was markedly affected by maturation. The monospermic fertilization rate was significantly higher for in vivo than for in vitro matured (IVM) oocytes (P < 0.01) which, furthermore, showed a reduced ability to transform the chromatin of penetrated sperm into male PN (P< 0.01). Indirect immunofluorescence analysis of global DNA methylation, histone acetylation and HDAC distribution (HDAC-1, -2 and -3), carried out in monospermic zygotes that reached the late PN stage, showed that IVM oocytes also had a reduced epigenetic competence. In fact, while in about 80% of in vivo matured and IVF oocytes the male PN underwent a process of active demethylation and showed a condition of histone H4 hyperacetylation, only 40% of IVM/IVF zygotes displayed a similar PIN remodelling asymmetry. Oocytes that carried out the first part of maturation in vivo (up to germinal vesicle breakdown; GVBD) and then completed the process in vitro, displayed the same PN asymmetry as oocytes matured entirely in vivo. A crucial role of HDAC in the establishment of PN acetylation asymmetry seems to be confirmed by the use of HDAC inhibitors as well as by the abnormal distribution of the enzyme between the two PN in IVM zygotes. Collectively, these data demonstrated that some pig IVM oocytes fail to acquire full remodelling competence which is independent from their ooplasmic ability to morphologically reorganize the sperm nucleus into PN.[...
Production of meiotically competent oocytes using an in vitro folliculogenesis culture system
No full textComplessi cumulo-oocita isolati da follicoli antrali migliorano la competenza meiotica di oociti in accrescimento
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