Studies on the Nematode Parasite, Gongylonema Neoplasticum (Spiroptera Neoplasticum), and Avitaminosis a in the Forestomach of Rats: Comparison with Fibiger's Results2

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Abstract
Expts. were performed utilizing the spiropteran parasite G. neoplasticum and synthetic vit. A-deficient diet, attempting to produce lesions in the forestomach of the rat closely resembling those of Fibiger. A nematode found in rats in a suburb of Minneapolis corresponds in all details to G. neoplasticum. descr. by Ditlevsen and Fibiger in 1914 Trapped wild rats were used for survey study and also for laboratory expts. Tame and wild rats were infected with G. neoplasticum and fed a synthetic vit. A-deficient diet. Controls consisted of uninfected rats (tame and wild), fed a vit. A- deficient diet, and infected tame rats eating a nutritious diet of fox chow. Mild to moderate hyperplasia and hyperkeratosis of the squamous epithelium of the forestomach appeared in all groups of rats, but marked lesions with epithelial disorganization and extensive downgrowths developed only in animals infected with the parasite and receiving vit. A-deficient diet. The same diet fed to uninfected rats produced ulcerations in the squamous stomach with edema and inflammatory reaction in the submucosa; these findings agree with previous results of vit. deficiency studies in the rat. Infected rats receiving nutritious diet had minimal to no changes in the squamous forestomach. In 3 tame rats (infected with G. neoplasticum and fed the vit. A-deficient diet) lesions appeared having features descr. by Fibiger in his "carcinomas." The authors consider them to be hyperplastic, hyperkeratotic papillomas with epithelial disorganization and downgrowths. Photomicrographs of these lesions were compared with recently made photomicrographs of Fibiger''s original slides. Pathological features such as submucous edema, inflammation, hyperplasia, hyperkeratosis, and tissue pattern disorganization, common to all lesions, are emphasized. Evidence from the literature substantiates the concept that pulmonary lesions in Fibiger''s rats were in all probability metaplastic areas of respiratory tract epithelium. The authors agree with Bullock and Rohdenburg, considering nests of epithelial cells in the one lymph node presented by Fibiger to be epithelial inclusions or arrests. Difficulties inherent in evaluation of data from expts. on the forestomach of the rat are created by the labile nature of the squamous epithelium found there. Many seemingly obtuse discrepancies are readily understood when this well-documented fact is considered. The following conclusions were reached: (1) All critical expts. to date using G. neoplasticum in the forestomach of the rat have failed to produce acceptable malignant lesions. (2) Many pathologic changes in the rat forestomach described and illustrated by Fibiger appeared only in those rats from this expt. having a vit. A-deficient diet as 1 exptl. factor. Addition of G. neoplasticum infection heightens these effects. The corollary fact also was demonstrated, that vit. A deficiency heightens the effect of the parasites. (3) G. neoplasticum apparently affects the forestomach of the rat as a biologic chronic irritant, but produces only minimal effects on the squamous epithelium when present without nutritional deficiency effects also manifested.

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