No abstract

The development of hepatocellular, putatively preneoplastic, gamma-glutamyl transpeptidase positive (GGT+) foci and tumors induced by aflatoxin B1 (AFB1) has been shown to be reduced in male F344 rats fed a diet containing 6% protein (as casein). This reduction occurs despite increased energy intake, when compared with animals fed a diet containing 22% protein. Among its many effects, low protein intake is known to increase the proportion of energy intake expended in the form of heat (thermogenesis); thus, this investigation examined the association between the development of GGT+ foci and alterations in indices of thermogenesis induced by feeding varying levels of dietary protein. Five days following the completion of AFB1 dosing, animals were assigned to groups fed 4%, 8%, 12%, 16%, or 22% dietary protein for 6 weeks. Foci development (% liver volume occupied) was markedly reduced in animals fed the low-protein diet (4%, 8%), yet calorie consumption per 100 g body wt was greater. A modest negative linear trend was observed in oxygen consumption with increasing levels of dietary protein intake. Urinary norepinephrine levels were elevated in the groups fed 4% and 8% protein; urinary dopamine and norepinephrine turnover rates in brown adipose tissue were highest in animals fed 4% protein. These results suggest that GGT+ foci development occurs when a "critical level" (approx 12%) of dietary protein intake is reached. Inhibition of foci development at lower levels of protein intake is associated with several indicators of increased thermogenesis.

The charts of twenty-four patients from whom Mycobacterium simiae was isolated from the sputum were reviewed and the patients seen in follow-up examination when possible. They were divided into 3 groups: 2 patients were felt to have had definite infection with M. simiae, 3 were felt to have had probable infection, and 19 showed no evidence of infection during follow-up for as long as 6 yr. All patients in the study had underlying pulmonary abnormalities. The results of PPD skin tests were negative in patients without evidence of tuberculosis. The patients without evidence of M. simiae infection were found to have had negative initial Acid Fast Bacillus smears, fewer sputum cultures positive for M. simiae, and lighter yields from cultures of M. simiae compared with those in the patients with M. simiae infection. We conclude that M. simiae is a nontuberculous mycobacterium capable of causing progressive granulomatous lung infection, but that it may also be identified as a causal isolate from the sputum of susceptible persons. Antituberculosis chemotherapy should not be employed in this latter group.