EFFECTS OF A DIET DEFICIENT IN TYROSINE AND QUEUINE ON GERM-FREE MICE

A chemically-defined diet consisting of amino acids (including tyrosin e), vitamins, trace elements, glucose, etc., known to support growth a nd reproduction through many generations when fed to germfree mice has been in use for many years in our laboratory. Classical nutritional s tudies showed that tyrosine was not a dietary requirement for higher m ammals if an adequate amount of phenylalanine was present. Therefore, it was unexpected that when tyrosine was removed from this diet, the g ermfree mice developed ocular, neurological and other abnormalities wh ich resulted in 100% fatalities usually within two weeks. adding tyros ine back to the diet prevented the abnormalities from occurring. Conve ntional mice with a normal intestinal flora showed none of these sympt oms when fed the same tyrosine deficient diet. We added queuine to the tyrosine-deficient diet at a concentration of 0.1 mu M. The germfree mice that were fed the diet supplemented with queuine were asymptomati c and remained alive until the termination of the experiments. (C) 199 7 Academic Press