Date of Award

1980

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

A technique for production of experimental cobalt cardiomyopathy in the dog is described. A chronic indwelling venous catheter is inserted retrograde into the posterior vena cava via the femoral vein. Colbalt chloride in a solution of sterile saline was infused with a variable speed infusion pump twice weekly over a 24 hour period. The dogs were divided into four groups; Group A (5 dogs) was the normal controls, Group B (5 dogs) was maintained on a protein and thiamine deficient diet, Group C (5 dogs) was on a normal diet with cobalt infusions, and Group D (6 dogs) was on a protein and thiamine deficient diet with cobalt infusions. The primary clinical findings observed in dogs in Group C and D were dyspnea, exercise intolerance, mild systolic murmors with a prominent gallop rhythm, abnormal electrocardiograms illustrating sinus tachycardia and lowered QRS complexes in limb leads, microcardia on thoracic radiographs, elevated left ventricular end diastolic pressure and lowered systolic pressures and angiographic evidence of a small end systolic volume and mildly enlarged left diastolic volume. The principle gross lesions found in dogs in both Group C and D were marked right ventricular dilatation, mild hypertrophy of the left ventricle, uniform paleness of the myocardium and dilatation of both atria. Histologic lesions included vacuolation of myofibers, loss of myofibers with hypertrophy of remaining fibers and randomly scattered areas of coagulation necrosis. Histochemical stains for succinic dehydrogenase and reduced diphosphopyridine nucleotide diaphorase were applied to frozen sections of heart muscle. There was no differences in reduced DPN-diaphorase activity exhibited between groups. Staining for succinic dehydrogenase revealed marked mitochondrial dysfunction and loss of enzyme activity in dogs in the two cobalt treated groups. Ultrastructurally, the treated groups had mitochondria that were extremely swollen with loss of cristae. Electron dense particles were seen in some damaged mitochondria. The sarcoplasmic reticulum and the T system contained numerous dilated vesicles in cells with mitochondrial and myofibrillar damage. Loss of cross striations and Z-band thickening were present in affected fibers. Lipid droplets of varying sizes were observed, some containing dense osmiophilic particles at the periphery.

Pages

102

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