title: Development of four-cell hamster embryos to the blastocyst stage in vitro and its regulation by components of the culture milieu.
abstract: Constituents of the culture milieu known to influence development of hamster 2-cell and 8-cell embryos were examined for effects on the 4-cell stage. Embryos were collected at the mid 4-cell stage (approx. 45-46 h after egg activation) from superovulated females and cultured for 24 h in a chemically defined medium (TLP-PVA). As with the 2-cell stage, inorganic phosphate (Pi) strongly inhibited development of 4-cell embryos, although some (14%) were able to reach the 8-cell stage or further in the presence of Pi. However, unlike 2-cell embryos, no significant inhibitory effect of glucose on development of 4-cell embryos was found. In the absence of glucose and Pi, development of 4-cell embryos was sensitive to amino acids in the medium: the mean cell number was increased using 21 amino acids compared with 4 amino acids, similarly to the 2-cell stage; however, late blastocyst development (blastocele formation) from 4-cell embryos was reduced using 21 compared with 4 amino acids, as with 8-cell embryos. Similarly to the 2-cell and 8-cell stages, raising the CO2 concentration from 5% to 10% in the gas atmosphere for culture increased the percentage of total blastocysts developing from the 4-cell stage, but did not affect the proportions of late-stage blastocysts. These data show that 4-cell-stage hamster embryos are somewhat similar to 2-cell embryos with respect to the regulation of development by constituents of the culture milieu, but, to some extent, the 4-cell embryo is a transitional stage of development.
authors.affiliation: Department of Veterinary Science, University of Wisconsin-Madison 53706.
authors.forename: H
authors.initials: H
authors.lastname: Monis
authors.forename: B D
authors.initials: BD
authors.lastname: Bavister
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001755:Blastocyst / Q000166:cytology*; D006224:Cricetinae; D003470:Culture Media; D004622:Embryo, Mammalian / Q000166:cytology*; D005260:Female; D005947:Glucose / Q000494:pharmacology; D008647:Mesocricetus; D010710:Phosphates / Q000494:pharmacology; D011247:Pregnancy; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000596:Amino Acids; D003470:Culture Media; D010710:Phosphates; D005947:Glucose