Relation of cytoplasmic calcium to contractility in Physarum polycephalum.
In a dumbbell-shaped plasmodium of Physarum polycephalum showing active shuttle streaming Ca was precipitated with potassium pyroantimonate (K[Sb(OH)6]), and the distribution of Ca between the cytoplasm and cellular organelles, especially vacuoles, was examined by electron microscopy. The contracting half-mass, where many empty vacuoles were present, was rich in the small Ca precipitates located in the cytoplasm. The relaxing half-mass, where many Ca-containing vacuoles were present, was poor in the cytoplasmic Ca precipitates. One half-mass of a dumbbell-shaped plasmodium was treated with Ca ionophore, X-537A, and its effect on the motive force for endoplasmic streaming and the distribution of Ca was investigated. The motive force was increased by X-537A, but the period of shuttle streaming was not changed. X-537A also induced a significant increase in the number of the cytoplasmic Ca precipitates in the X-537A-treated contracting half-mass, so that the asymmetry of the distribution of cytoplasmic Ca precipitates was enhanced. A large portion of the vacuoles were empty in the contracting half-mass, and Ca-containing in the relaxing one as in the case of the untreated plasmodium.
D002118:Calcium / Q000378:metabolism*; D002465:Cell Movement; D003593:Cytoplasm / Q000378:metabolism; D007832:Lasalocid / Q000494:pharmacology; D010507:Periodicity; D010804:Physarum / Q000502:physiology*; D014617:Vacuoles / Q000378:metabolism
D002118:Calcium; D007832:Lasalocid