![]() This model was adopted by many groups and significantly contributed to our present understanding of oocyte maturation and ovulation. This led to the development of the model of explanted rat pre-ovulatory follicles (or follicle-enclosed oocyte, FEO) allowing mechanistic studies meiosis (1,4). ![]() ![]() Stimulation of meiosis in vitro and reveal the pathways involved in the regulation of this process. The discrepancy between the spontaneous resumption of meiosis when oocytes were dislodged from their follicles, observed by Pincus and Enzmann already in 1935, and its dependence on LH-stimulation prompted us to establish a model for exploring the hormonal Oocyte maturation, as other ovulatory responses, is triggered by the pre-ovulatory surge of luteinizing hormone (LH). The meiotic process is arrested again (second meiotic arrest) and is completed, upon fertilization, by the extrusion of the second polar body (PBII). This resumption of meiosis and its progression to the metaphase of the second meiotic division is usually referred to as “oocyte maturation”. The first round of meiosis is completed with extrusion of the first polar body (PBI) and progress to the second meiotic metaphase. The hallmark of the dictyate oocyte is the large nucleus known as “germinal vesicle” (GV).ĭuring each reproductive cycle a number of oocytes, characteristic of the species, re-enter meiosis, manifested by germinal vesicle breakdown (GVBD). Meiosis is arrested, in most mammals, in neonatal life at diplotene/dictyate stage of the first meiotic prophase. The oocyte initiates the first meiotic division during embryonic life or shortly after birth. Oocyte meiosis in mammals is a protracted process, subject to several stop-go controls.
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