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In vitro isometric contractile tension was measured in heart and skeletal muscle in 3 groups of mice: 1. a control group, 2. a group maintained for 27 weeks on 20% alcohol, and 3. a group whose fluid intake was restricted to the extent equaling that which occurred in the alcohol treated animals. Results showed a reduction in cardiac twitch tension in both the alcohol and fluid restricted group, as compared to normal controls. We therefore consider that dehydration per se may play an important role in the etiology of alcoholic cardiomyopathy.

The ultrastrlucture of Z discs in nonglycerinated, striated muscle fibers of the barnacle Balanus nubilus Darwin was examined in contracted, resting, and stretched preparations. At all sarcomnere lengths, the Z discs are perforated sheets comprised of "Z rimns" and "Z perforations," extending continuously across the myofibril; the dimensions of the rims and perforations change with changes in sarcomere length. Accordingly, with shortening of the sarcomere, there was an accompanying decrease in the transverse width of the Z rims and an increase in the diameter of the Z perforations.