[Development of isolated loach blastoderm during cultivation in different salt media]

The loach blastoderms were isolated from the yolk during the periods of cleavage and blastulation (5--14.5 tau0) and incubated in various isotonic saline media which differed by the content of K+ and Na+. The survival of blastoderms upon the short-term incubation (up to 60 tau0) varied insignificantly in all the media and upon the longer one (up to 120 tau0) was the maximal in the medium with isotonic content of K+ and Na+ and the minimal in the medium with the low content of K+. The cell proliferation upon incubation in the medium with the low content of K+ was inhibited when the blastoderms were isolated at the stage of 8 tau0 and suffered no changes at the stage of 14 tau0. The ability of differentiation manifested itself earlier and the percentage of differentiated embryos was higher in the media with the high content of K+. The content of K+ in the blastoderms isolated at the stage of 7 tau0 changes with its content in the incubation medium; upon isolation at the stages of 8--9 tau0 to blastoderms accumulate K+ irrespective of its content in the medium and at the stage of 10 tau0 maintain the constant level of K+. Hence, the development of isolated blastoderms depends on the content of K+ in the medium and this dependence reduces with the age.