Cytogenetic analysis of day-7 bovine embryos by cytophotometric DNA measurements

Abstract

A Feulgen staining procedure that stains the DNA of individual fixed nuclei stoichiometrically was used to analyse cytophotometrically the incidence of total ploidy and mixoploidy in 28 day-7 bovine embryos that had been fixed after collection ('non-cultured' embryos). The influence of culture on the incidence of chromosome abnormalities was further studied in another group of 24 embryos ('cultured' embryos) by culturing them for 24 h in Whittingham's medium. Of the total 52 embryos studied, two appeared to be entirely abnormal: one embryo was completely haploid, whereas the other embryo was completely triploid. Individual hyperdiploid nuclei and hypodiploid nuclei were frequently observed in the otherwise diploid embryos. As haploid polar bodies can still be present in morulae and blastocysts (to a maximum of three), only embryos with more than three hypodiploid nuclei were considered as abnormal. Of the 'non-cultured' embryos, 33.3% had one or more hyperdiploid nuclei, whereas 51.9% had more than three hypodiploid nuclei. In this latter group, 35.7% of the embryos also had hyperdiploid nuclei. The results also showed that day-7 bovine embryos that are completely haploid, completely triploid or mixoploid cannot be detected only by examining their morphology. It is concluded that the incidence of, especially, mixoploidy in embryos can be better studied by measuring the DNA content of the individual nuclei of an embryo rather than by analysing chromosomes, as in the latter method only dividing cells can be analysed. The presence of hyperdiploid and hypodiploid nuclei may indicate the frequent occurrence of mitotic segregation failures during mitosis in bovine embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Transition of Cell Numbers in Bovine Preimplantation Embryos: In Vivo Collected and In Vitro Produced Embryos

“…Vandaele et al [35] reported that the ratio of the apoptotic index in blastocysts increases at 8 d after IVF. In addition, IVF embryos are known to have reduced developmental viability during the process of IVC because of chromosomal abnormalities and decreased ICM content ratios [29,31]. These type of findings indicate that conventional IVC conditions reduce embryo viability and that the conditions are suboptimal for further embryo development.…”

“…We also know that the developmental speed of bovine preimplantation embryos changes during periods of early cleavage stages, such as pronuclear formation in the first CD and genomic shift from the maternal to embryonic genome in the 3-4th CD [10,11,27,28], and during periods of morphological change, such as compact formation and hatching from zona pellucidae [10,27,29]. Characteristic changes in cell division, such as chromosomal abnormalities [29][30][31] and a difference in the developmental process because of the sex of embryos [32,33], were also found after blastocyst formation. Using VIVO embryos collected from superovulated donors, we previously observed developmentally retarded embryos and embryos with degenerated blastomeres, as described in other similar reports [20][21][22].…”

Chromosome variation in the embryos of domestic animals

“…The most frequent abnormality noted was polyploid cells within diploid embryos resulting in 2n/4n mixoploids although diploid/triploid and diploid/haploid mixoploids were also seen (King and Picard, 1985;King, 1990;Slimane-Bureau and King, 2002). Relatively few entirely polyploid or aneuploid embryos were identified (Dorland et al, 1993). As cytogenetic techniques applied to embryos became more refined as with fluorescent in situ hybridization (FISH), it became possible to assess the chromosomal status of all cells (metaphase and interphase) in individual embryos (Slimane- Bureau and King, 2002).…”

Chromosomal Abnormalities and Embryonic Development into the Blastocyst Stage in Mammalian Embryos Derived In Vitro

“…The incidence of total ploidy and mixoploidy on day 7 bovine embryos, especially mixoploidy, could be better studied by a Feulgen staining procedure measuring the DNA content of the individual nuclei of an embryo, and it was suggested that the presence of hyperdiploid and hypodiplo id nuclei might i ndicate t he f requent occurrence of mitotic segregation failures during mitosis in bovine embryos [44].…”