DEVELOPMENT OF MORPHOLOGICAL-CHANGES AND ILEAL GLUCAGON GENE-EXPRESSION IN THE SMALL-INTESTINE OF LAMBS INFECTED WITH TRICHOSTRONGYLUS-COLUBRIFORMIS

To investigate the consequences of subclinical Trichostrongylus colubr iformis infection on the intestinal mucosa and the associated changes in enteroglucagon gene expression, sheep were infected with 30000 larv ae and killed 5, 10, 15 or 20 days after infection. Histological and c ytological changes were examined. In the main site of infection, the u pper duodenum, villous atrophy associated with crypt hyperplasia devel oped gradually. Cytological changes in the enterocytes appeared concur rently, characterized by a progressive reduction in brush border and i n the number of ribosomes in the cytoplasm, changes in the internal st ructure of mitochondria, and enlargement of the intercellular spaces. Neither histological nor cytological modifications were found before d ay 15. At the same time, villous hypertrophy developed distally, beyon d the main site of infection; this was interpreted as an adaptive resp onse to parasitism. Enteroglucagon gene expression in the ileum was me asured in parallel with the mucosal changes but did not reveal any dif ference between infected and control sheep. The results indicate that this gastrointestinal hormone does not have a major role in the respon se to nematode parasitism. (C) 1996 W.B. Saunders Company Limited