Protein Synthesis and Differentiation During Pulmonate Development

An analysis of the changing patterns of protein synthesis duringearly development of Lymnaea palustris has been undertaken.An examination of the ingestion of capsule fluid protein suggeststhat after gastrulation 30 to 65% of the total embryo proteinis undigested food protein. Starch gel electrophoresis revealsa sudden increase in the number of hydrolases from four to twenty-siximmediately following the trochophore stage with the latterbeing present also in adult organs. Studies reported here andelsewhere demonstrate rhythmic changes in uridine incorporationduring early cleavage which peaks at the trochophore stage.Continuous treatment of embryos with 50 to 100µ.g of actinomycin-D(AMD) starting at the 2-cell stage slowed development throughthe trochophore stage but did not prevent normal larval organdevelopment. This AMD application reduced ³H uridine incorporationmore than 90% but did not appreciably alter the pattern of totalor ¹⁴C leucine pulse labeled peptides on sodium dodecyl sulfate(SDS) ultrathin slab electrophoresis gels. However, pronouncedand numerous changes in the patterns of both labeled and unlabeledpeptides were observed during development through 4 days withthe most notable alterations occurring at the 2.5 post-gastrulastage. This was true in normal and continuously treated AMDembryos. The morphological and biochemical data suggest Lymnaeaearly development is controlled by stable maternal messengerRNA.