Intestinal infection of neonatal dogs with canine coronavirus 1-71: studies by virologic, histologic, histochemical, and immunofluorescent techniques.

Enteritis induced in neonatal dogs by oral inoculation of coronavirus 1-71 was studied by virologic, histologic, histochemical, and immunofluorescent antibody methods. The enteritis, accompanied by diarrhea, developed in 4 to 7 days and was characterized by atrophy and fusion of intestinal villi and deepening of crypts, increase in cellularity of the lamina propria, flattening of epithelial cells, and discharge of goblet cells. Intra-epithelial enzyme activities generally were depressed. Specific immunofluorescent antibody reactions were present in villous epithelium of the duodenum starting on postinoculation day 2 and of the ileum on day 4. Epiehtlium of the colon showed no reaction. Virus was present in the feces for 6 to 9 days and was recovered from the small and large intestines from day 2 through day 10. The infection was not fatal and was self limiting; the diarrhea stopped between 1 and 2 weeks. The intestinal mucosa also started recovering by the end of week 1, proceeding caudally from the duodenum.

Comparative histochemistry of gastrointestinal mucosubstances.

Two histochemical sequential staining techniques, Alcian blue-PAS (AB-PAS) and high-iron-diamine-Alcian blue (HID-AB), which differentiate neutral from sulfated and non-sulfated acid mucosubstances, were applied to sections from the gastrointestinal tract of eleven mammalian species, including man, to study patterns of distribution of gastrointestinal epithelial mucosubstances. The application of these techniques under uniform laboratory conditions enabled a detailed description of epithelial mucosubstances throughout the gastrointestinal tract relative to location in each species as well as a comparison of their distribution among various species. The results showed that all of the 11 species studied had a distinctly different distribution of epithelial mucosubstances throughout the entire gastrointestinal tract. These differences were most obvious in the stomach and duodenum. In each species, neutral mucosubstances were most evident in the stomach and acid mucosubstances in the intestines, with sulfomucins most prominent in the large bowel. Acid mucosubstances were noted in Paneth cell granules of rodent species only. These histochemical observations make available a uniform comparative basis for the normal distribution of mammalian gastrointestinal mucosubstances which should facilitate their study in diverse pathological conditions.

Proliferation of renal interstitial cells following injury induced by ureteral obstruction.

The proliferation of renal interstitial cells was studied by the use of tritiated thymidine incorporation following unilateral ureteral obstruction in the rabbit. There was a nonuniform response with significant increase in nuclear labeling in the obstructed kidney in all zones at 24, 48, and 72 hours following obstruction with the exception of the inner medulla where the counts at 24 and 48 hours were not significantly different from sham-operated controls. The major labeling occurred in interstitial fibroblasts. Within the zones of high labeling (cortex and outer medulla) these cells were separated by widening of the intersittial space. In the zone of low labeling (inner medulla) the interstitial cells maintained their normal spatial relationships.

Small intestinal mucosal injury in the experimental blind loop syndrome. Light- and electron-microscopic and histochemical studies.

Microscopic (light and electron) and histochemical abnormalities have been demonstrated in the jejunum of rats with the blind loop syndrome. Three groups of animals were studied: normal control animals, and animals with either self-filling (SF) or self-emptying (SE) blind loops. Vitamin B12 malabsorption and bacterial overgrowth occurred only in those animals with SF blind loops. Three jejunal segments were studied: the blind loop segment and the jejunal segments proximal and distal to the blind loop. In the animals with the blind loop syndrome, those with SF blind loops, the most striking findings occurred in the blind loop itself, with similar but less marked changes in the jejunum distal but not proximal to the blind loop segment. Hypertrophy of both crypts and villi was evident with focal abnormalities of villus architecture. Approximately 10 to 20% of the columnar cells in the upper half of the villi were swollen and vesiculated. By electron microscopy microvilli demonstrated a variety of degeneration changes and the glycocalyx and terminal web were disrupted. Mitochondria and endoplasmic reticulum (ER), both smooth and rough, were swollen. Concentric whorls of parallel membranes and long, curvilinear rough ER were present in the cytoplasm. Histochemically, there was loss of enzymatic activity in the epithelial brush border, mitochondria and ER. Inasmuch as bacterial invasion of the jejunal mucosa was not seen, the etiology of these changes is not known but may involve bacterial "toxins" or products of bacterial metabolism. These morphological observations demonstrate that both brush border and intracellular injury occur in the jejunal epithelial cell of rats with the experimental blind loop syndrome.

Electron microscope study of experimental enteric infection in neonatal dogs with a canine coronavirus.

Neonatal dogs, inoculated orally with coronavirus 1-71, grown in canine kidney cell cultures, developed diarrhea and a severe enteritis characterized by atrophy of the villi, changes in the enterocytes, and accelerated epithelial cell loss. Electron microscopy of the mucosal epithelium, 4 days after challenge, showed that the virus penetrated into the enterocytes between microvilli, possibly by pinocytotic mechanism. In the enterocytes, virions were most often enclosed, singly or in groups, in cytoplasmic vesicles. They were less frequently found in the cisternae of the Golgi apparatus, the endoplasmic reticulum, or in the dilated perinuclear space and only rarely, free in the cytoplasm. Virions replicated by budding only on the smooth.membranes of the cytoplasmic vesicles. The infected cells showed a variety of cytopathic effects, some nonspecific, such as disruption of the microvilli, loss of density of the cytoplasm, presence of lipid inclusions, alteration of mitochondria, and dilation of the endoplasmic reticulum and Golgi cisternae and of the perinuclear space. Other cytopathic effects, characteristic of the coronavirus infection, consisted of formation of dense filamentous structures and of membrane-bound bodies. Progeny virions appeared to discharge into the gut lumen through the disrupted cell membranes of infected enterocytes still in situ or following their premature shedding.