[Localization of aldolase activity in the embryos of loach]

The activity of aldolase was determined in different parts of the loach (Misgurnus fossilis L.) embryo at the stages from the formation of axial organs till the beginning of embryonic movements (from 19 till 38 hrs of development at 21.5 degrees). In all parts of the embryo, the activity of aldolase at first decreased (21-23 hrs) and then increased. The region of somites is characterized by the highest absolute and specific activity at all developmental stages. The increase in the number of somites is accompanied by the fall and subsequent rise of aldolase activity. In the somites of different degree of differentiation, the enzyme activity changes in a similar way. Hence, there is no correlation between the morphological and biochemical differentiation of somites. Differences in the specific aldolase activity between the anterior and posterior halves of the embryo and the regions of head, somites and tail were found at the stages of 19-23 hrs of development. The maternal aldolase only is present at these stages, as was shown earlier. It means that the early stages of biochemical differentiation may be realized not by means of differential activation of genes controlling the enzyme, but by means of regylation of translation on the templates stored in oogenesis.