A Calcium‐sensitive lanthanum inhibition of amoeboid movement

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Abstract
The effects of lanthanum ions upon amoeboid movement and upon the redistribution of dense cytoplasmic inclusions following centrifugation were investigated in Amoeba discoides. Treatment with low lanthanum concentrations produced a characteristic inhibited condition in which locomotion ceased while saltatory movements continued. The resorting of stratified cytoplasm by local internal cytoplasmic flow was unaffected. This contrasted with p‐hydroxymercuribenzoate treatment which inhibited both locomotion and saltatory movements. The inhibitory effects of lanthanum ions were antagonised by calcium ions but not by magnesium ions. It is reasoned that lanthanum competes for a peripheral binding site thereby disrupting a calcium‐mediated regulatory mechanism of amoeboid movement.