The effect of myosin antibody on the division of starfish blastomeres

Antiserum against starfish egg myosin was produced in rabbits. Antibody specificity to myosin was demonstrated by Ouchterlony's immunodiffusion test and by immunoelectrophoresis in the presence of sodium dodecylsulfate (SDS). The latter technique showed that the antibody binds to both heavy and light chains of egg myosin. Furthermore, the antibody reacted with starfish sperm mysosin and starfish adult muscle myosin at both the heavy and light chains. It did not react with bovine platelet mysosin or rabbit skeletal muscle myosin in Ouchterlony's test; however, a weak reaction was observed in the presence of SDS between the antibody and these myosin heavy chains. Ca- and Mg-ATPase activities of egg myosin were not affected by the antibody, but it did inhibit actin-activated ATPase activity of egg myosin. Microinjection of the antibody into blastomeres of starfish eggs at the two-cell stage was carried out. Anti-egg myosin γ-globulin inhibited the subsequent cleavages at an amount of more than 0.3 ng when injected at interphase. The inhibition was reduced when the injection was carried out near the initiation of cleavage. At the onset of the second cleavage the antibody was not inhibitory; however, an appropriate amount inhibited the third cleavage. Although the disappearance of the nuclear membrane was observed in the presence of the antibody, the formation of the mitotic apparatus was more or less disturbed. However the formation of daughter nuclei seemed to be scarcely affected by the antibody except that the distance between the nuclei was significantly smaller than normal.