Impact of Forced Exercise and Fasting on Salmonella typhimurium Induced Myocarditis and on Myocardial Protein and Lipid Content in Rats
ARMY MEDICAL RESEARCH INST OF INFECTIOUS DISEASES FORT DETRICK MD
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A generally nonlethal Salmonella typhimurium infection in weanling rats produced bacterial myocarditis and myocardial hyperplasia. Myocardial lesions were characterized by focal infiltrates of inflammatory cells predominantly mononuclear, segmental myocyte necrosis, and incipient fibrosis. Although bacterial infections are infrequently associated with myocarditis, the S. typhimurium infection in young rats produced a new experimental model of diffuse myocardial inflammatory foci. Biochemical changes in the myocardium included great increases in total myocardial contents of protein 23, RNA 39 and DNA 43 and several lipid fractions 35-55 as well as in tissue activities of acid hydrolases, such as cathespin D 124 and beta-glucuronidase 135, all of which contrasted with the relatively limited areas of histologic involvement 1.5. To study the effects of additional stress in this model infection, some rats were exercised by forced running in wheels for 2 hours and others were fasted for 24 hours before samples were obtained. The short period of forced exercise in this infection caused an additional increase of myocardial protein content 47 but with no additional change in histology. The expected fasting-induced degradation of protein as well as an infection-associated increase in myocardial lipids were each prevented when rats were fasted during ongoing acute infection.
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