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An oocyte (/ ˈ oʊ ə s aɪ t /, oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction.In other words, it is an immature ovum, or egg cell.An oocyte is produced in a female fetus in the ovary during female gametogenesis.
Studies performed on humans, dogs, and cats in the 1870s suggested that the production of oocytes (immature egg cells) stops at or shortly after birth. A review of reports from 1900 to 1950 by zoologist Solomon Zuckerman cemented the belief that females have a finite number of oocytes that are formed before they are born. This dogma has been ...
Oocyte abnormalities can be caused by a variety of genetic factors affecting different stages in meiosis. [1] Moreover, ageing is associated with oocyte abnormalities since higher maternal age is associated with oocytes with a reduced gene expression of spindle assembly checkpoints which are important in maintaining stability in the genome.
An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries.It secretes hormones that influence stages of the menstrual cycle.In humans, women have approximately 200,000 to 300,000 follicles at the time of puberty, [1] [2] each with the potential to release an egg cell (ovum) at ovulation for fertilization. [3]
Ovum quality is the measure of the ability of an oocyte (the female gamete) to achieve successful fertilisation.The quality is determined by the maturity of the oocyte and the cells that it comprises, which are susceptible to various factors which impact quality and thus reproductive success. [1]
Titus et al. [13] (2013) found that, as humans (and mice) age, expression of four key DNA repair genes necessary for homologous recombinational repair declines in oocytes. They hypothesized that DNA double-strand break repair is vital for the maintenance of oocyte reserve, and that a decline in efficiency of repair with age plays a key role in ...
Although about 1 million oocytes are present at birth in the human ovary, only about 500 (about 0.05%) of these ovulate, and the rest do not ovulate. The decline in ovarian reserve appears to occur at a constantly increasing rate with age, [ 17 ] and leads to nearly complete exhaustion of the reserve by about age 52.
Plating density (number of cells per volume of culture medium) plays a critical role for the differentiation. A lower plating density makes granulosa cells exhibit estrogen production, while a higher plating density makes them appear as progesterone producing theca lutein cells .