FORM-STABILITY OF CILIATES IN RELATION TO PRESSURE AND TEMPERATURE

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Abstract
1. Two ciliates, Blepharisma undulans and Paramecium caudatum, were studied with reference to form stability and integrity (resistance to cytolysis) under varying conditions of hydrostatic pressure (up to 10,000 lbs./in.2) and of temperature (12°-25° C.). 2. At lower pressures the specimens retained their elongate form, but at higher levels, depending on temperature, species, and age of the cloned cultures, the cells gradually become shorter and more rounded. Following this form change, cytolysis occurred in a varying percentage of the specimens. Older cloned cultures showed a greater and more variable susceptibility to the pressure-temperature effects, so that selected younger cultures were used for the quantitative evaluations. 3. For Blepharisma, the critical pressure, which gave 50 per cent cytolysis within a 15-minute compression period, displayed a distinct temperature dependence, being 8000 psi. at 12° C., 8700 at 15° C., 9200 at 20° C., and 9300 at 25° C. Paramecium, in contrast, showed a distinctly greater sensitivity, the critical pressure for 50 per cent cytolysis at 20° C. being some 2000 psi. lower than for Blepharisma. 4. Rapid decompression, following any critical or super-critical pressure treatment, produced an abrupt further shortening (contraction) of the specimens, accompanied by a cytolysis of some of the previously resistant individuals. For Blepharisma, decompression cytolysis involved only about 5 per cent of the animals. Paramecium, however, was much more sensitive and virtually 100 per cent became involved. 5. An interpretation of these changes in cell form and integrity is given in terms of pressure-temperature effects upon protoplasmic gel structure, particularly with reference to the solation of the peripheral plasmagel layer of the cytoplasm.