Meiotic chromosomes of cattle oocytes in relation to seasonal variation

The aim of the present work was to study the effect of changes on recovery rate, oocyte quality and chromosomes of cattle oocytes in vitro. The follicular oocytes were collected from ovarian follicles [2-5 mm in diameter] of slaughtered cattle by aspiration method. The recovered oocytes were classified morphologically into three categories [A, B and C]. The oocytes [class A and B] were matured in tissue culture medium-199 supplemented with 10% fetal calf serum and antibiotics at 39 degree sign C, 5% CO[2] and high humidity for 22-24 hr. Cultured cumulus-oocyte complexes [COCs] were analyzed for meiotic chromosome during the four seasons. The results indicated that, the average number of cattle oocytes per ovary was significantly increased [P<0.05] in season than other seasons. A higher percentage [P<0.05] of high quality oocytes were obtained in winter, spring and autumn than during summer season. Moreover, the percentage of oocytes suitable for maturation was significantly decreased [P<0.05] in hot seasons than in cooled seasons. The number of oocytes showing meiotic chromosomes, which are represented by telophase I and metaphase II was significantly [P<0.01] reduced in summer and autumn than in winter and spring. The highest incidence of diploid oocytes was recorded in spring while the lowest was reported in autumn. It is concluded that both the number and quality of cattle oocytes and meiotic chromosomes were affected by the seasonal variations In fact, they increased during the cool seasons and decreased in hot seasons

Chromosome configuration during in vitro maturation of dromedary camel oocytes

The aim of the present study was to examine the changes in the chromosomal configuration of camel oocyte during in vitro maturation [IVM] at different culture periods of 24, 30, 36 and 48 hours and to compare the influence of pregnant camel serum and fetal calf serum on IVM of camel oocytes at 24-30 hours. A total of 1978 oocytes was collected from 390 ovaries of slaughtered camels by aspiration method. The average number of camel oocytes per ovary was 5.30 +/- 0.22. The proportion of COC, POC and DO oocytes was 29.27%, 32.90% and 32.61%, respectively. In addition, 5.21% of oocytes were degenerated. A high percentage of maturation was obtained at 24-30 hours [47.70% and 48.35%, respectively]. At 48 hours post-maturation, all metaphases were undefined due to the degeneration of chromatin. It was found that the addition of pregnant camel serum had no beneficial effect on IVM of camel oocytes in comparison with the fetal calf serum [40.10% vs. 45.34%, respectively]

Cytogenetic evaluation of in-vitro matured buffalo oocytes in different culture conditions

Ocytes were collected by aspiration from ovaries of slaughtered buffaloes. A total of 1240 oocytes were selected for in vitro maturation [IVM] procedure in culture media for 22- 24 hr and 25 -28 hr at 39°C in 5% CO[2] incubator. For both cultured periods oocytes were matured in droplets of TCM-199 + estrous buffalo serum [EBS], TCM-199 + foetal calf serum [FCS], Ham's F-10 + EBS and Ham's F-10 + FCS. Cytogenetic analysis of 582 oocytes cultured in the four media conditions in both periods of time showed wide range of meiotic configurations : metaphase-I, anaphase-I, telophase-I and metaphase-11. Also, the cytogenetic analysis identified matured oocytes at metaphase-II with diploid number of chromosomes [3.95%]. Analysis of variance showed that, the maturation rate in the two media and sera didn't differ significantly. The maturation rate to the second metaphase were significantly higher [P0.01] at 25 - 28 hr than in the same media for 22 - 24 hr period of time

Cytogenetic analaysis of early stage buffalo embryos matured and fertilized in vitro

The in vitro fertilization technique offers the opportunity to study the karyotype of gametes and early embryos. Follicular buffalo oocytes were matured in TC-199 medium enriched with FCS, fertilized in vitro using thawed frozen buffalo semen and cultured at 38.5°C, 5% CO[2] and high humidity. Chromosome preparations were made from 232 buffalo embryos at 4 - to 8-cell stage after culturing for 48 hr in vitro. Only 74 embryos from 170 fixed embryos provided analyzable chromosome spreads. The percentage of embryos with chromosomal aberrations was 12.16%. The observed abnormal embryos were 5.41% haploid, 4.05% polyploid [2.70% triploid and 1.35% pentaploid] and 2.70 haploid/ diploid mosaicism. It is concluded that cytogenetic analysis of buffalo embryos is valuable for detection of chromosomal abnormalities which hinder the cleavage processes to reach to blastocyst stage