Spontaneous Oocyte Maturation Research Articles

Developmental potential of LT/Sv parthenotes derived from oocytes matured in vivo and in vitro

Release of oocytes of LT/Sv mice from the meiosis-inhibiting influence of antral follicles promotes parthenogenetic activation and development to early cleavage stages of 14% of the eggs. However, to attain the potential to develop to blastocysts under the culture conditions used, the oocytes must mature within follicles for 8–9 hr after human chorionic gonadotropin (HCG) administration. The results suggest that some positive influence, which does not occur during spontaneous oocyte maturation under defined conditions in vitro, occurs within preovulatory follicles and imparts developmental competence to the maturing oocytes.

Effects of progesterone and oestradiol-17beta on the spontaneous meiotic maturation of mouse oocytes.

The spontaneous meiotic maturation of cumulus-free oocytes was not affected by progesterone or oestradiol-17beta at 2 microgram/ml, but both steroids decreased polar body production at 10 microgram/ml and progesterone decreased the number undergoing germinal vesicle breakdown.

Cellular, hormonal and ionic interactions related to induced and spontaneous oocyte maturation

Cellular, hormonal and ionic interactions related to induced and spontaneous oocyte maturation

Oocyte Maturation and Ovulation Induced in Hypophysectomized Winter Flounder (Pseudopleuronectes americanus) by Preparations from Pituitary Glands of American Plaice (Hippoglossoides platessoides)

Hypophysectomized winter flounder (Pseudopleuronectes americanus) did not undergo spontaneous oocyte maturation, but the glycoprotein fraction of extracts of American plaice (Hippoglossoides platessoides) pituitaries induced maturation and ovulation. The nonglycoprotein fractions, previously shown to contain a vitellogenic factor, were less efficient than the glycoprotein fractions in the induction of maturation and ovulation. The activity of the nonglycoprotein fraction was further reduced by rechromatography on Con-A Sepharose, suggesting that its action on oocyte maturation and ovulation was due to contamination by the glycoprotein gonadotropin. Key words: hypophysectomy, gonadotropin, oocyte, maturation, ovulation, vitellogenesis, flounder, plaice, Pseudopleuronectes, Hippoglossoides

Mouse oocyte development in vitro with various culture systems

These experiments were designed to determine whether or not hormones are required for the growth of mouse oocytes and to assess the possible role of companion granulosa cells in oocyte growth. To approach these problems, four systems for the culture of oocytes, either alone or in association with granulosa cells, were utilized: (1) isolated oocyte culture, (2) isolated oocyte-ovarian cell coculture, (3) isolated follicle culture, and (4) ovarian organ culture. Oocytes from 8-day-old B6D2F 1 mice failed to grow in isolated oocyte culture. Addition of follicle-stimulating hormone (FSH), 17β-estradiol (E 2), or serum to the medium failed to prevent oocyte degeneration or to promote oocyte growth. On the other hand, oocytes in isolated follicle culture or in organ culture grew significantly in defined medium. The results showed that oocytes grown in isolated follicle culture under defined conditions and in the absence of gonadotropins resemble oocytes grown in vivo in terms of their ultrastructural characteristics, with the exception of enlarged mitochondria. In addition, these oocytes were shown to exhibit some normal functional characteristics in terms of their increased levels of CO 2 evolution from exogenous pyruvate, and the ability of the fully grown oocytes to initiate meiotic maturation when freed from granulosa cells. It was concluded that gonadotropins are not necessary for oocyte growth and that gonadotropins are not required to potentiate the spontaneous meiotic maturation of oocytes which occurs after their isolation from granulosa cells. The results indicated that association of granulosa cells and oocytes was necessary for oocyte growth. However, isolated oocytes in coculture with ovarian cells failed to grow. Addition of FSH or E 2 to the cocultures failed to promote oocyte growth or delay oocyte degeneration. It was concluded that, under the culture conditions used, granulosa cells must be in contact with the oocyte, perhaps by means of specialized cell junctions, for oocyte growth to occur.

A reversible, hydrogen ion blockade of spontaneous oocyte maturation in the starfish: locus of action.

Starfish (Asterias forbesi) oocytes encased within their follicle cells mature spontaneously during a portion of the normal reproductive period when released from the ovary into seawater. A previous report has shown that oocytes isolated in acidic seawater do not mature spontaneously but retain the capacity to do so when returned to normal seawater. The object of this study was to determine the mechanism by which acidic pH reversibly blocks spontaneous oocyte maturation in isolated follicles. Incidence of spontaneous oocyte maturation in follicles isolated in acidic seawater decreased as pH decreased from 7 to 4. Oocytes in which spontaneous maturation was inhibited (ASW at pH 4.7 TO 5.4) underwent germinal vesicle breakdown with the addition of 1-methyladenine. Oocytes isolated in acidic seawater (pH 4 or 5) with intact follicle cells matured spontaneously when transferred immediately to normal seawater pH 8); after four hours, 60-65% of the follicles incubated in seawater at pH 5 matured spontaneously when returned to normal seawater as compared to less than 10% of the follicles maintained at pH 4. Inhibition of spontaneous maturation was not reversible in the absence of the follicle cells. Oocytes isolated in acidic seawater with their follicle cells did not spontaneously mature when transferred to calcium-free seawater at pH 8. The results obtained support the hypothesis that acidic seawater reversibly inhibits spontaneous oocyte maturation by interfering with the release of meiosis-inducing substance from the follicle cells.

Inhibition of oocyte maturation by porcine follicular fluid: partial characterization of the inhibitor.

ABSTRACTThe present study was undertaken inorder tocharacterize further the inhibitory activity ofporcine follicular fluid (FF1) upon thespontaneous maturation ofisolated oocytes. The inhibitoryaction of FF1 upon oocyte maturation was not destroyed byheating to60#{176}Corby repeatedfreezing and thawing and could not beremoved byextraction with charcoal. The inhibitory actionwas, however, abolished by trypsin digestion. The activity was concentrated by Amicon UM-2membrane filtration. Further purification was achieved by the use ofSephadex G-25 columnchromatography. The data areconsistent with the suggestion that theinhibitor isapeptide with amolecular weight ofabout 2,000. The inhibitory activity ofFF1could beovercome bytheadditionofovine LH (5tg/ml) tothe culture medium but notbybovine prolactin (10Mg/mI) ordibutyrylcyclic AMP (0.04-0.4 mM).INTRODUCTIONAn inhibitory effect of follicular fluid (FF1)upon the spontaneous maturation of isolatedrabbit oocytes was first described by Chang(1955). We have demonstrated asimilar inhibi-tory action ofporcine FF1 upon the maturationof isolated porcine oocytes (Tsafriri and

Spontaneous maturation of oocytes isolated from ovaries of immature hypophysectomized rats

Oocytes were collected from preantral follicles (200-300 mu in diameter) from 30-day-old immature rats 7 days after hypophysectomy. The ova were cultured in vitro for 17 hrs in a chemically defined medium and scored cytologically for meiotic maturation. Of 534 oocytes that were cultured 89% resumed meiosis; however, 98% of these oocytes arrested in either metaphase or anaphase I. In contrast, 82% of the oocytes isolated from preovulatory follicles (approximately 600 mu in diameter) of adult proestrus rats progressed to metaphase II. These results are discussed in terms of functional FSH and LH receptors on the granulosa cells.

Maturation-Inducing Substances in Asteroid and Echinoid Oocytes

In starfish a hormonal peptide, gonad-stimulating substance (GSS), which is released from nervous tissue, acts on the gonad to produce a maturation-inducing substance (MIS), an inducer of oocyte maturation and spawning. MIS is 1-methyladenine (1-MA). This substance acts on the surface of the oocyte. Cytoplasmic maturation as revealed by fertilizability is also induced by 1-MA. The amount of 1-MA can be determined very accurately with a bioassay method using isolated oocytes. In 1-MA formation, GSS seems to enhance the methylation of some compound which contains a purine nucleus at its N1 site. The methyl donor is probably S-adenosylmethionine. 1-Methylated precursor seems to be transformed to 1-methyl AMP and then hydrolyzed into 1-methyladenosine and phosphate by phosphomonoesterase. 1-Methyladenosine is finally split into 1-MA and ribose by 1-methyladenosine ribohydrolase. So-called spontaneous maturation of oocytes isolated in sea water is due to the action of 1-MA produced in follicle cells even in the absence of GSS. 1-MA is present in echinoid gonads and seems to act as MIS also in these animals. Disulfidereducing agents such as dithiothreitol and 2,3-dimercapto-1-propanol induce starfish oocyte maturation. On the other hand, sulfhydryl reagents such as p -chloromercuribenzoate, iodoacetamide, and N -ethylmaleimide suppressed 1-MA-induced oocyte maturation. Since Concanavalin A acts on the follicle cells to produce 1-MA, the action of this substance seems to be quite similar to that of GSS.

Effect of l-phenylalanine on 1-methyladenine production and spontaneous oocyte maturation in starfish

Production of 1-methyladenine (1-MA) in isolated ovarian fragment under the influence of the gonad-stimulating substance (GSS) was found to be inhibited by treatment with phenylalanine at concentrations higher than 10 mM in the starfish, Asterina pectinifera. The so-called ‘spontaneous’ maturation of the oocytes of Asterias amurensis isolated in sea water was also inhibited in the presence of phenylalanine. 1-MA was produced in the isolated follicle cells of this species in sea water in the absence of GSS. Such production of 1-MA was greatly reduced by lack of calcium ions, corresponding to the failure of spontaneous maturation in calcium-free sea water. Production of 1-MA in the isolated follicle cells of Asterias amurensis in sea water was suppressed by phenylalanine. The so-called ‘spontaneous’ oocyte maturation observed in the genus Asterias appears to be induced by 1-MA produced in the follicle cells in the absence of GSS. Therefore, it is concluded that oocyte maturation in starfish is invariably induced by 1-MA produced in the follicle cells. Failure of oocyte maturation in the presence of phenylalanine or in calcium deficiency does not seem to be due to the failure of release of pooled 1-MA from the follicle cells but to the inhibition of its synthesis in these cells.

Role of hormones in oocyte maturation.

Role of hormones in oocyte maturation.

Spontaneous maturation of starfish oocytes: Role of follicle cells and calcium ions

Starfish oocytes released from the ovary into sea water during the breeding season underwent spontaneous meiotic maturation. In the absence of calcium ions, follicle cells surrounding the oocyte were dispersed and oocyte maturation did not occur. Immature oocytes in the absence of follicle cells did not mature even when calcium was available. Calcium ions stimulated the release of a meiosis-inducing substance from follicle cells which had been isolated in calcium-free sea water. Increasing numbers of follicle cells produced a parallel increase in the amount of meiosis inducing substance released. Spontaneous oocyte maturation appeared to be initiated and mediated in part by calcium sensitive processes in the follicle cells rather than the oocyte.