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T Fair

Publications and source records attributed to T Fair.

22 records · Page 2Linked to original sources
PubMed1995

Bovine oocyte diameter in relation to maturational competence and transcriptional activity.

The aims of the present series of experiments were to establish a possible relationship between bovine oocyte diameter and follicle size, investigate the developmental ability of oocytes of different diameter groups, and investigate the relationship between oocyte diameter and RNA transcriptional activity of the oocyte. Follicles were recovered from slaughterhouse ovaries by mechanical dissection, measured, and assigned to one of the following size categories: > or = 4 mm, < 3-4 mm, < 2-3 mm, < 1-2 mm, and < 1 mm. Oocytes were liberated from the follicles and their diameters recorded. The correlation coefficient between oocyte diameter and follicle size was 0.32 (P < 0.0001). Oocytes were recovered by aspiration and/or slicing of slaughterhouse ovaries and divided into four groups ( < 100 microns, 100- < 110 microns, 110- < 120 microns, and > 120 microns) based on diameter. Oocytes were processed through standard procedures for in vitro maturation and stained in order to assess nuclear development. Rates of in vitro development to metaphase II were 21.2%, 42.3%, 75.9%, and 80.7%, respectively, for the four groups. On a separate occasion immature oocytes from the above diameter groups were cultured in the presence of 3H-uridine for 45 min and scored for degree of RNA synthesis as indicated by the presence of autoradiographic labeling. Oocytes < 110 microns showed a greater degree of 3H-uridine incorporation than those > or = 110 microns, suggesting that they were involved in RNA synthesis and therefore still in the growth phase.

Animals↗
PubMedDate not supplied

Ultrastructure and viability of isolated bovine preantral follicles.

Techniques for the isolation of ovarian follicles and maturation of oocytes in vitro have enormous reproductive potential. Preservation of normal tissue function is vital. This study emphasizes the ultrastructure and viability of mechanically isolated bovine small (diameter 40-100 microm) preantral and large (140-450 microm) preantral/early antral follicles. Viability studies were performed for small preantral follicles. The presence of esterase activity, active mitochondria and dead cells served as parameters of oocyte and granulosa cell viability. After 1 day of culture, all follicles had a viable granulosa, displaying active mitochondria and/or esterase activity in all their cells, although a few (generally <5) dead granulosa cells were present in 17% of the follicles. Of the oocytes, 35 and 80% had esterase activity and active mitochondria respectively, whereas 8% appeared dead. The percentages of oocytes showing esterase activity and active mitochondria decreased during culture, whereas the percentage of follicles with dead oocytes or dead granulosa cells strongly increased. More than 90% of the isolated small follicles showed a poor ultrastructure, especially of their oocyte, which points to a negative selective isolation of poor follicles in the present study and/or an isolation procedure-induced damage of follicles. With respect to large preantral follicles, 42% of those distributed in the cortex and 64% of those isolated and cultured for 1 day had a poor ultrastructure. In contrast with the small ones, the percentage of ultrastructurally poor large preantral follicles had decreased to 27% after 5 days of culture, possibly due to better isolation and culture conditions. It is recommended to use ultrastructural and/or viability cell markers for in-vitro grown follicles to evaluate their quality, and particularly that of their oocytes.

Animals↗
PubMedDate not supplied

[Oocyte apoptosis: when, how, why?].

The store of primordial follicles used for folliculogenesis is formed during oogenesis. Its size is the consequence of three processes: oogonia multiplication, time of meiosis initiation and extent of loss of germ cells (atretic oogonia, oocytes at the pachytene stage and newly formed primordial follicles). Apoptosis is causing this loss but its mechanisms are poorly documented. Both death signals (TNT alpha, Fas ligand) and survival signals (LIF, kit ligand) are present in the embryonic gonad. The apoptotic cascade then involves bclz, bax and caspases since knock out of these genes alters the store of primordial follicles. Apoptosis also exists within primordial follicles in adult ovaries and involves oocyte death. Its control has not been extensively studied.

Adult↗