SYNOPSIS. The helical coiling state of a glycerinated stalk in the familyVorticellidae had been regarded, without any evidence, as a reversible and completely equilibrated mechano-chemical system regulated by the external free Ca2+ concentration. Our present detailed observations of many individual stalks of glycerinated Vorticella coni,allaria revealed that the contraction-extension cycle of the helical stalks caused by increasing and decreasing free Ca2+ concentrations in the medium represents a kind of hysteresis. This 13. Sugi H. 1960. Propagation of contraction in the stalk muscle of Biophys. Acts 27, 247-58. 255-7. 69-76. Carchesium. J . Fac. Sci. Univ. Tokyo 8, 603-15.
An improved method for the preparation of glycerinated Vorticella convallaria was investigated. The pretreatment of living vorticellas with a medium containing 0.1% saponins and subsequent treatment with an extraction medium containing 35% glycerol at about 0 degrees C was satisfactory. The equilibrium average length of contractile stalks of glycerinated vorticellas was measured at various free calcium concentrations in the reaction medium. It was found that the contractile element in the spasmoneme of the stalk is contracted by a cooperative interaction involving at least two calcium ions.
It was found that some ciliates, Stentor, Spirostomum and Blepharisma, which can contract rapidly like the stalks of Vorticellidae, have Ca2+-binding proteins that are very similar to spasmins, in the immunological sense. The presence of spasmins in other Protozoa and in some Metazoa was also investigated.
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