Effects of low temperatures on larvae of the genus Trichinella.

We examined the effect of an exposure to -25 degrees C (for 8 days) on the histochemistry and the fine structure of 30-day-old Trichinella larvae from muscle fibres of the diaphragm. The larvae of T. pseudospiralis and T. nelsoni were either destroyed in the muscle fibres, dead, eosinophile, or were not found. The structureless mass of a degenerating, changed sarcoplasm was highly AIP-active, and gave a weak positive reaction for SS-groups of proteins. The wall of the deformed capsule around T. nelsoni, and the cuticle of the larva, stained diffusely; it did not contain AM. In a few muscle fibres exposed to -25 degrees C, histochemical reactions of the capsule surrounding larvae of T. nativa and sometimes of larvae of T. spiralis, and reaction of the changed sarcoplasm, were similar to those of the controls. A few mobile larvae were isolated by digestion only from a diaphragm infected with T. nativa. Deterrent to a prolonged survival of larvae were the formation of ice crystals and a denaturation of proteins by which the sarcoplasm of the infected muscle fibre was changed gradually into both a plasmolytically and karyolytically altered mass. Degenerative changes in the fine structure of infected muscle fibres were demonstrated by the presence of "spheromembranous bodies" in the sarcoplasm resembling myeline formations observed after exposure to poisonous substances, e.g., colchicine.