Myocardial ultrastructural alterations in ducklings fed tellurium.

Seventy newly hatched ducklings were fed a commercial ration with 500 mg of added Te (as tetrachloride)/kg of feed for up to 28 days. Ducklings were euthanatized at day 14, 21, and 28, the hearts were studied by gross, microscopic, and ultrastructural examination. Cardiac damage was apparent grossly as hydropericardium and myocardial hemorrhage. Histopathologically, the ventricular myocardium had areas of acute hemorrhagic necrosis (often with mineralization), edema, and congestion. Resolving areas of necrosis appeared cellular with macrophages, heterophils, fibroblasts, and pale vacuolated cells with large vesicular nuclei that were identified as dedifferentiated myocytes. Ultrastructurally, necrotic fibers had disrupted contractile material and mineralized mitochondria. In resolving lesions, macrophages were numerous in the interstitium and within necrotic fibers. Also, a population of sublethally injured myocytes was present and appeared as dedifferentiated cardiac muscle cells with few myofibrils, scattered free filaments, prominent sarcoplasmic reticulum, abundant glycogen, and large nuclei with prominent nucleoli. These dedifferentiated myocytes represented a reparative phase of the Te-induced myocardial injury which has been termed "reactive hyperplasia" and "rejuvenating reorganization" in previous models of myocardial damage.