An improved culture medium for mouse blastocysts.

Eagle's basal medium, modified to contain essential amino acids at the concentrations optimal for mouse blastocyst hatching, attachment, and outgrowth, supported in vitro development of the mouse blastocyst better than other tissue culture media tested. This medium was improved for growth and differentiation of the inner cell mass by doubling the concentration of amino acids and glucose and by adding uridine (10(-5) M) and beta-mercaptoethanol (10(-5) M). In this improved medium nearly all blastocysts grown from the two-cell stage hatched and formed trophoblast outgrowths, and 62% developed into two-layer egg cylinders.