Contraction of protoplasm. IV. Cinematographic analysis of the contraction of some peritrichs

Abstract

The contraction and relaxation of Vorticella dificilis, V . campanula and Carchesium sp. were studied by high speed cinematography. In Vorticella it was shown that coiling of the stalk usually started near the zooid and spread downwards; the point of initiation bore no relation to the position of the stimulating electrodes. Contraction took about 5 msec to complete, and the fully contracted animals were 2 9 1 3.9% of their original lengths. The zooids were 6 6 2 5.0% and the stalks 14?6.0%of their original lengths (V. dificilis). The shortening of the stalk was mostly in the form of coiling. Measurement of the myoneme length demonstrated that its real shortening was less than 10%. Thus the contraction is virtually isometric, producing a helical deformation of the stalk. As the stalk contracts it takes the form of a steeply pitched helix. This change in shape should produce rotational forces on the zooid (torque). Physical models of similar proportions produced about 1.5 revolutions of torque for similar changes in pitch. However during contraction no turning of the zooid was detected, though rotation did occur after the completion of contraction.In Carchesium the contraction is not so isometric, the myoneme apparently shortening by 20%. While the coiled shape of the contracted Vorticella stalk can be explained by its acentric structures, the stalk of Carchesium is much more symmetrical in cross-section, demonstrating that a high acentricity is not necessary for helical coiling. In all three species there seems to be some separation of the control of zooid and stalk contraction.

Ca2+-induced tension development in the stalks of glycerinatedVorticella convallaria

“…Their experiment was, in other words, quite different from ours. Amos [1975] calculated the minimum spasmoneme tension value from the high speed film data of Jones et al [1970]. When Vorticellu contracts, the zooid, which may be approximated to a sphere of radius 20 bm, may be pulled 80 pm…”

Contractile proteins and hypotheses concerning their role in phloem transport

“…When the concentration of free calcium ion is raised from to M, the filaments reversibly bind calcium contracting to less than one third of their initial length. The maximum contraction rate of 200 lengths s-I (Jones et al 1970;Amos et al 1975) is almost an order of magnitude faster than that reported for muscle (Close 1965) and the tension of up to 80 kN m-2 (Rahat et al 1973) is comparable to that developed by vertebrate striated muscle, 50 to 400 kN mP2 (Wilkie 1954). The contraction of this organelle depends on the calcium concentration.…”

Contraction and extension of Vorticella and its mechanical characterization under flow loading

“…Contraction begins at the body and travels down the stalk. 5 Therefore the part of the stalk nearest the zooid is the first to receive the strongest force before breakage of other parts can arise. Figure 5 shows a decrease in stalk contractions as loading flow increases.…”

“…The maximum isometric tension of Vorticella convallaria is 4 ϫ 10 −8 N. For live cell measurement, high speed video acquisition is the primary means of characterizing the contraction because the rapid movement of Vorticella is not readily amenable to other methods of study. 5,7,8 Jones et al 5 obtained high speed images of Vorticella difficilis and measured its contraction speed and length change. Moriyama et al 7 estimated the maximum tension as 5.58ϫ 10 −8 N. Upadhyaya et al 8 measured contraction dynamics such as speed, force, and energy of live Vorticella in various viscous solutions.…”