Reactivation of a glycerinated model of Amoeba

Summary Motile models ofAmoeba proteus prepared by extraction at –20 °C with a 50% buffered glycerol solution showed remarkable contraction on addition of Mg-ATP with retainment of Ca⁺⁺ sensitivity. The initial contraction around the nucleus occurred on addition of Mg-ATP independently of the Ca⁺⁺ concentration, and was followed by contractions of three different patterns. In 10^–8M Ca⁺⁺, the granuloplasm contracted as a whole and separated from the membrane leaving no detectable particles in the anterior region. In 10^–6M Ca⁺⁺, the granuloplasm contracted leaving some granules which showed active and vigorous two-directional streaming similar to that in the living cell. Sometimes a part of the plasma membrane twitched. The streaming lasted up to 20 minutes. In 10^–4M Ca⁺⁺, after the initial contraction around the nucleus, no significant movement was observed. All these movements in the models were inhibited by cytochalasin B or N-ethylmaleimide. The relationship between the Mg-ATP and the Ca⁺⁺ concentrations was examined.