title: Quantitative histological analysis of equine embryos at exactly 156 and 168 h after ovulation.
abstract: Equine embryos were collected at exactly 156 +/- 0.5 (n=8) and 168 +/- 0.5 h (n=11) after ovulation. The embryos were fixed in glutaraldehyde, sectioned serially and observed using light microscopy. In the 156 h group, all embryos were early blastocysts except for one, which was a morula. The morula and one early blastocyst had no capsule. The capsules of the other embryos were thin. The mean +/- SD total number of cells was 275 +/- 105 (range 117-417). The mean +/- SD proportions of mitotic and pycnotic cells were 2.5 +/- 1.2 and 1.1 +/- 1.8%, respectively, and there were no differences between each inner cell mass (ICM) and trophoblast. The mean +/- SD proportion of ICM cells was 36.5 +/- 5.2%. In the 168 h group, there were early, mid- and expanded blastocysts, all of which had a capsule. The mean +/- SD total number of cells was 1093 +/- 666 (range 272-2217). The mean +/- SD proportions of mitotic and pycnotic cells were 3.5 +/- 1.4% and 0.1 +/- 0.03%, respectively, and there were no differences between each ICM and trophoblast. The mean +/- SD proportion of ICM cells was 21.1 +/- 9.7%. In the 168 h group, there was a significant correlation (P < 0.01) between the total number of cells and the diameters and proportions of ICM cells. The 168 h embryos were composed of significantly (P < 0.01) more cells (approximately four times) than were the 156 h embryos but had lower proportions of ICM cells. These results indicate that in equine embryos there is: (i) an individual (perhaps seasonal) variability in the rate of development; (ii) a doubling in the number of cells every 6 h between 156 h and 168 h after ovulation; and (iii) a decrease in the proportion of ICM cells between the early and expanded blastocyst stages of development.
authors.affiliation: Pathologie de la Reproduction, Ecole Nationale Vétérinaire de Nantes, BP 40706, 44307 Nantes Cedex 03, France.
authors.forename: S
authors.initials: S
authors.lastname: Colchen
authors.forename: I
authors.initials: I
authors.lastname: Battut
authors.forename: F
authors.initials: F
authors.lastname: Fiéni
authors.forename: D
authors.initials: D
authors.lastname: Tainturier
authors.forename: B
authors.initials: B
authors.lastname: Siliart
authors.forename: J F
authors.initials: JF
authors.lastname: Bruyas
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology*; D004622:Embryo, Mammalian / Q000166:cytology*; D005260:Female; D006736:Horses / Q000196:embryology* / Q000502:physiology*; D008853:Microscopy; D010060:Ovulation / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D013997:Time Factors
chemical_list: D011374:Progesterone