Occurrence of N-formylkynurenine in extracts of Neurospora crassa: evidence for the activity of tryptophan pyrrolase

N-formylkynurenine and kynurenine have been detected in extracts of tryptophan-grown Neurospora crassa. When the mycelia were grown in medium supplemented with l-[2-(14)C]tryptophan, the radioactivity was detected in N-formylkynurenine and N-formylanthranilic acid; with l-[beta-(14)C]tryptophan, radioactivity was detected in N-formylkynurenine, kynurenine, kynurenic acid, and xanthurenic acid. The occurrence of N-formylkynurenine in extracts of tryptophan-grown Neurospora is interpreted as direct evidence for the activity of tryptophan pyrrolase in this organism. The presence of this enzyme was expected on the basis of several earlier studies, but its activity in vitro has so far escaped detection. The in vivo evidence presented here suggests its presence and contributes importantly to our understanding of the tryptophan-anthranilic acid cycle.

Fatal primary Epstein-Barr virus infection masquerading as histiocytic medullary reticulosis in young children in Taiwan

We reported 3 fatal cases of primary Epstein-Barr virus (EBV) infection resembling histiocytic medullary reticulosis (HMR) in young children in Taiwan, where an HMR-like illness has been previously found to be prevalent. The disease ran a fulminant course, manifesting as fever, anemia, jaundice, skin rash, pulmonary infiltration, and/or hepatosplenomegaly lasting for only 1-3 weeks. Laboratory tests revealed no hemolytic anemia and Coombs test was negative. Sepsis or HMR was the main clinical differential. At autopsy, the spleen, liver, lymph node, lung, and bone marrow showed infiltration of atypical "histiocytes" or blasts, lymphocytes, and mature histiocytes with hemophagocytosis. Immunophenotype and gene rearrangement studies of the lymphoid tissues revealed that these atypical "histiocytes" were actually polyclonal B immunoblasts in one case and transformed T lymphocytes in the remaining 2 cases, representing two different types of virus-host interaction. Southern blot and in situ hybridization studies on frozen lymphoid tissues demonstrated the presence of EBV DNA in all 3 patients; the study for cytomegalovirus was negative. The young age of these patients, closely correlated with the prevalent age of primary EBV infection in the general populations in Taiwan, strongly suggest that these childhood cases of previously diagnosed HMR-like disease may actually represent a lethal form of primary EBV infection or fatal infectious mononucleosis.