The alteration of mitotic events by ionophore A23187 and carbonyl cyanide n-chlorophenylhydrazone

Rapid clearance of Plasmodium yoelii-infected erythrocytes after exposure to the ionophore A23187

1. The effects of Ca2+ and the calcium ionophore A23187 on the intraerythrocytic development of the asexual forms of Plasmodium yoelii were examined. 2. Erythrocyte-free parasites obtained by saponin lysis of infected cells remained viable after exposure to 1 mM Ca2+. 3. A23187 inhibited the growth of P. yoelii and the inhibition was augmented by Ca2+ in cells infected with parasites at young stage of development. 4. A23187-treated infected cells disappeared from the circulation shortly after intravenous injection and this disappearance was profound in infected cells treated with the ionophore in the presence of Ca2+.

The role of the phosphatidylinositol cycle in mitosis in sea urchin zygotes. Lithium inhibition is overcome by myo-inositol but not by other cyclitols or sugars

We have investigated the role of the phosphatidylinositol (PI) cycle in cellular events between fertilization and first cleavage in zygotes of the sea urchin Lytechinus pictus. The effects of lithium were studied: The lithium-induced changes due to effects on the PI cycle were reversed by myo-inositol, the next step in the cycle after the lithium block, but were not reversed by scyllo-inositol or other cyclitols or sugars. In this way we implicated the PI cycle in the formation of streak birefringence, in nuclear membrane breakdown, in onset of anaphase, and in cytokinesis. With respect to karyokinesis, mitotic apparatus (MA) structure often was altered when the PI cycle was blocked, and anaphase was blocked when the PI cycle was blocked. For all stages, the effects of 400 mM lithium were overcome by 10-100 microM myo-inositol. Excess myo-inositol potentiated the effect of lithium on MA structure (and on cytokinesis), suggesting that there is a negative feedback loop in the control of the PI cycle.