We noted the earliest morphological changes in the motor endplates 8 weeks after the induction of streptozotocin diabetes in rats. Morphometric measurements showed reduced axonal areas of the lateral plantar and the sciatic nerves in the diabetic rats 28 but not 2 and 8 weeks after the experiment. These findings suggested distal axonopathy.

The myosin isozyme distribution in the left ventricle and in the interventricular septum of rabbits was studied after 3 7,11,14 and 21 days of L-thyroxine (500 µg/kg/day) administration. Histochemical procedures were employed to identify V₁ and V₃ by their Ca²⁺ ATPase activity and their proportions were quantified through polyacrylamide gel electrophoresis. In the left ventricle, the subepicardium was the first to show the shift fromV₃ to V₁ followed by the subendocardium. The intermediate region became heterogeneous by 11 days and remained so until 21 days. The right subendocardial and the intermediate regions of the interventricular septum were heterogeneous in the normal rabbit and hyperthyroidism resulted in a shift from V₃ to V₁ in both the right and left subendocardial regions of the septum. Like the left ventricle, the intermediate region of the interventricular septum remained heterogeneous. Localized accumulations of collagen were seen in all regions of the left ventricle and interventricular septum. From these results we conclude that in thyrotoxic myocardial hypertrophy the isozymic shift from V₃ to V₁ is progressive, region-specific and is directly correlated with the period of hyperthyroidism in the first 2 weeks. Prolonged hyperthyroidism results in localized accumulation of collagen which does not exhibit any regional specificity.

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