Growth and DNA replication in rabbit blastocysts.
DNA content and DNA polymerase activity were measured on rabbit blastocysts removed from the uterus at 24-hr intervals over the period of days 4-7 postcoitum (pc). Median DNA content increased 53 times over the 72-hr period, from 25.3 ng on day 4 to 1,360 ng on day 7. Median DNA polymerase activity (fmole of radiolabeled nucleotide incorporated in 30 min at 37 degrees C) increased 393-fold from day 4 to day 7: 32.8 to 12,900. These embryos also increased in surface area and volume by 334-fold and 6,078-fold, respectively. Litters containing individuals with high DNA content also tended to have similar individuals with high DNA polymerase activity. Therefore, DNA polymerase activity may be a useful measure of the potential for the next cell division. A large amount of variation existed between blastocysts in all parameters measured. An analysis of variance, conducted to partition variation between litters and within litters, determined that within-litter variation was actually greater than that between litters, resulting in intraclass correlation coefficients less than 0.5. There was also a positive regression of DNA content and DNA polymerase activity on surface area in 6- and 7-day-old blastocysts after eliminating variation attributable to litters. The developmental pattern of DNA polymerase activity in the rabbit may be quantitatively different from that described in the mouse. The pattern in mammals is very different from that described in several nonmammalian species.
Lawitts
J A
JA
Department of Cellular and Molecular Physiology, Harvard Medical School, Boston, Massachusetts.
Butler
J E
JE
Kiessling
A A
AA
Biggers
J D
JD
D000818:Animals; D001755:Blastocyst / Q000201:enzymology / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D005260:Female; D011817:Rabbits; D013045:Species Specificity; D013223:Statistics as Topic; D013997:Time Factors
D004247:DNA; D004259:DNA-Directed DNA Polymerase