Effect of culture systems on mouse early embryo development.

The amount of oxygen available to embryos in drop cultures under paraffin may be limited by the gas mixture employed, the method of equilibration or by the use of positive or negative pressure filtration. When these factors were varied, in experiments using Swiss outbred (SO) embryos, the only significant difference detected was the poorer development of embryos from the 1-cell to blastocyst stage when cultured in medium without prior equilibration. Also under these conditions, the inclusion of glucose in the medium did not increase the incidence of 2-cell block, and glutamine in the presence of glucose enhanced the development of 1-cell embryos to blastocysts. One-cell (C57BL/6 x SJL) F1 x SO embryos were successfully cultured in HEPES buffered CZB medium with added bicarbonate, under an atmosphere of air. The proportion of blastocysts formed in this medium, with a concentration of 10 mM sodium bicarbonate, was not different from that developed in CZB under 5% CO2 in air.