In this study, a simple time-lapse video recording system was used to
compare developmental kinetics of female and male bovine embryos produced
in vitro. Following embryo sex determination, the timing of each cleavage
up to the 4-cell stage was compared between the sexes from the videotapes
after culture in the presence and absence of glucose. In the second
experiment, the consequences of exposure to a time-lapse video recording
(TL) environment were studied by culturing embryos further until day 7
in an incubator, followed by collection and sex determination of morulae
and blastocysts. In the absence of glucose, female embryos cleaved earlier
than male ones. In the presence of glucose, however, male embryos cleaved
earlier than female ones. There was no difference in the number of
morulae/blastocysts in the absence of glucose, but in the presence of
glucose more male than female embryos reached the morula and blastocyst
stage. Exposure to the TL environment itself also had a sex-related
effect, being more detrimental to male than female embryos. The difference
in the number of functional X chromosomes between the sexes during early
preimplantation development could explain these findings. In females, an
increased capacity for oxygen radical detoxification through the pentose
phosphate pathway could result in a reduced cleavage rate. Furthermore,
glucose may influence the expression of enzymes located on the X
chromosome. According to these results, a simple time-lapse video
recording system is suitable for investigating embryo developmental
kinetics and perhaps for the selection of embryos with the greatest
developmental potential.
Individual cell motility studied by time-lapse video recording: Influence of experimental conditions