Comparative histopathologic evaluation of animal studies: murine studies with L-tryptophan and constitutents

Following a 1994 collaborative research workshop on animal studies of the eosinophilia-myalgia syndrome (EMS), the Research Advisory Council (RAC) concluded that it would be instructive to have histopathologic slides from the different investigators and laboratories evaluated simultaneously using the same pathologist, pathologic criteria, and scoring system for cross-study comparisons of effects. The author evaluated the skin, underlying fascia and supporting tissues, and muscles, stained with hematoxylin and eosin, from 20 separate studies, representing 4 mouse strains, several protocols, and tissues from over 250 mice. The author concluded that, based on the material available, the findings are inconsistent, nonreproducible, and do not support a conclusion that L-tryptophan, case associated L-tryptophan, 1,1'-ethylidenebis(tryptophan), 3-phenylamino alanine, or a combination thereof, under the conditions of the studies, induce lesions of skin or muscle in the C57 Black, Balb/c, SJL, or B10.s strains of mice.