. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 48 A. G. CARROLL AND W. R. ECKBERG. FIGURE 4. Ameboid contractions induced in Spisula oocytes by treatment with 75 nM chlorpromazine. A. Primary oocyte prior to treatment. B. KCl-stimulated oocyte that has undergone GVBD. C., D., E. Examples of oocytes showing severe ameboid contractions after treatment with 75 juA/ chlorpromazine. Note that in C the germinal vesicle is eccentric and contains a nucleolus, in D the eccentric remnant of the nucleolus lacks a nucleolus, and in E the germinal vesicle has been obliterated. This t
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 48 A. G. CARROLL AND W. R. ECKBERG. FIGURE 4. Ameboid contractions induced in Spisula oocytes by treatment with 75 nM chlorpromazine. A. Primary oocyte prior to treatment. B. KCl-stimulated oocyte that has undergone GVBD. C., D., E. Examples of oocytes showing severe ameboid contractions after treatment with 75 juA/ chlorpromazine. Note that in C the germinal vesicle is eccentric and contains a nucleolus, in D the eccentric remnant of the nucleolus lacks a nucleolus, and in E the germinal vesicle has been obliterated. This type of behavior is typical. F. An oocyte treated with 75 nM chlorpromazine and Mg/ml cytochalasin B. The ameboid contractions have been prevented. N = nucleolus. ment blocked contractions when CB was added simultaneously with the calmodulin antagonist and stopped the contractions when added after they had begun. CB treatment also showed that the apparent obliteration of the germinal vesicles in ameboid oocytes (Fig. 4e) also resulted from the contractile activity. When the ameboid contractions were prevented, the germinal vesicles persisted (Fig. 4f). DISCUSSION The results of this study provide important new evidence concerning the involve- ment of calcium and calmodulin in germinal vesicle breakdown. Calmodulin involve- ment is demonstrated by the fact that several structurally different calmodulin antag- onists block GVBD at concentrations similar to those at which they are known to affect calmodulin (Hidaka et al, 1980; Weiss and Wallace, 1980), and that an analog of one of the antagonists which has little anticalmodulin activity has no effect on GVBD. Calmodulin had been implicated previously in GVBD in starfish (Meijer and Guerrier, 1981), amphibians (Wasserman and Smith, 1981), and the mouse (Borns- laeger et al., 1984), which normally undergo GVBD in response to hormonal stimu-. Please note that these images are extracted from scanned page images that may have been
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