In order to study the effects of a severe bacterial infection on thyroid function rats were subjected to group A streptococcal pneumonia, and thyroid activity determined by measurement of the rate of discharge of I(131) from the thyroid gland. Decreased thyroid activity of moderate to marked degree was observed in the majority of infected animals. Infected animals ate less than normal animals. Since fasting leads to decreased thyroid function, I(131) release rates were measured in control animals pair-fed with infected animals and in control and infected animals force-fed a normal intake. The reduction in thyroid activity seen in acute infection was found to be partly but not entirely due to the associated voluntary food restriction. Although the adrenal glands of rats dying of pneumonia were very large, the thyroid inhibition occurring during the course of experimental pneumonia was not secondary to increased adrenocortical function since infected, adrenalectomized animals, receiving injections of cortisone, showed thyroid inhibition comparable to that observed in intact infected animals. The possible influence of the level of thyroid activity on resistance was evaluated. In two experiments a total of 80 rats in 3 groups was pretreated with propylthiouracil and injected daily with 3 dosage levels of 7-thyroxine for 3 weeks prior to inoculation. Under these conditions mortality rates in infected animals fell with decreasing levels of thyroid function. However, induced hypothyroidism was found to afford no protective effect in comparison with untreated infected animals.

Animals↗

PubMed1958

Evaluation of the applicant for medical education.

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Education, Medical↗

PubMed1956

The incidence and pathogenesis of myocarditis in rabbits after group A streptococcal pharyngeal infections.

Rabbits subjected to single pharyngeal infections with group A streptococci developed cardiac lesions characterized by myofiber necrosis and a non-granulocytic cellular reaction with histiocytes, lymphocytes, and Anitschkow myocytes. The histopathologic changes were demonstrable in some animals within 24 hours of inoculation, apparently were maximal 72 hours after induction of infection (at which time they were seen in the hearts of all nine rabbits studied), and thereafter healed in the course of the following 2 weeks. The extent of involvement was variable, and with healing the necrotic areas were replaced by fibrous tissue. When intradermal infections with the same organisms were produced in rabbits, cardiac lesions, indistinguishable from those observed in the pharyngeally infected group, appeared in a much smaller number of animals. The hearts of five of six rabbits sacrificed a month or more following the last of a series of streptococcal pharyngeal infections exhibited lesions characterized chiefly by fibrosis, although mononuclear cellular infiltrations were also noted. In these repetitively infected animals the presence of occasional multinucleated giant cells and a few small foci of calcification were features not encountered in the single infection group. In a second series of rabbits sacrificed 3 days after the last of three pharyngeal infections with different strains of streptococci, acute as well as more chronic changes were observed. In none of the lesions in rabbits subjected to single or multiple streptococcal infections were bacteria demonstrable, either in histologic sections or in cultures of myocardial tissue. A large number of control animals was studied concomitantly, and in only one instance was a lesion, considered comparable to those described in the streptococcal series, encountered. The implications of these findings, particularly in terms of the non-suppurative sequelae of streptococcal infections in man, are discussed.

Animals↗

PubMed1956