PubMed HealthSearch

Biomedical subjects

C D Humphrey

Publications and source records attributed to C D Humphrey.

4 recordsLinked to original sources

Light and electron microscopic studies of antibiotic associated colitis in the hamster.

Lincomycin and its analogue, clindamycin, are capable of producing mild to severe colonic mucosal injury in humans (antibiotic associated colitis). Patients with the disorder may have severe diarrhoea, pseudomembranous plaques, confluent pseudomembranes, and/or a frank, diffuse haemorrhagic colitis. The present study was designed to assess the Golden Syrian hamster as an animal model for antibiotic associated colitis and to describe lesions seen in the animal model by light, transmission electron, and scanning electron microscopy. A colitis was produced in Golden Syrian hamsters by oral or parenteral administration of lincomycin, clindamycin, or N-demethyl clindamycin. Animals were killed at intervals and microscopic studies made of sequential morphological changes in the ileum, caecum, and colon. The microscopic lesions in the early stages of the disorder were abnormalities within the brush border, cellular oedema, and hyperaemia. Changes in the intracellular organelles were observed in more severely damaged epithelial cells. Epithelial hyperplasia resulted in the piling up of cells on the mucosal surfaces. In specimens with the most severe damage, complete loss of epithelium from the mucosal surface was observed. Pseudomembranous plaques were occasionally seen. Comparison of the clinical, gross, and histological features of the animal disease with the human disorder suggest that, although minor differences are present, the hamster model is suitable for experimental studies of antibiotic associated colitis.

Animals

Partial purification of a toxin found in hamsters with antibiotic-associated colitis. Reversible binding of the toxin by cholestyramine.

A toxin with cytotoxic and enterotoxic activities was isolated from cecal contents of hamsters receiving lincomycin. The toxin was partially purified by ultracentrifugation, ultrafiltration, (NH4)2SO4 precipitation, and gel filtration. Cytotoxic activity, assayed on monolayers of HeLa cells, was restricted to material that eluted in the molecular weight range of 107,000 +/- 6,000 daltons. Cytotoxicity of crude AAC toxin could be demonstrated at concentrations as low as 0.04 microgram/ml. The toxin was heat labile (55 degrees-60 degrees C for 0.5 hr) and sensitive to trypsinization, acidification at pH 3, or alkalinization at pH 9. Cytotoxic activity was inhibited by Clostridium sordellii antitoxin. Enterotoxic activity of the crude toxin and the cytotoxic fraction from gel filtration was demonstrated by fluid secretion in ligated rabbit ileal loops. Studies were done in vitro with cholestyramine resin, vancomycin, or gentamicin to determine if the toxin was bound or denatured by these drugs. It was demonstrated that cholestyramine bound the toxin, significantly reducing its cytotoxicity. Reversible binding of the cytotoxic material was demonstrated by salt gradient elution. Neither vancomycin nor gentamicin had any effect on the in vitro cytotoxic activity of the toxin.

Ammonium Sulfate

Influence of mounting media on the fading of basic aniline dyes in epoxy embedded tissues.

A simple cytophotometric technique is used to quantitate stain fading of basic aniline dye-stained epoxy-embedded tissues mounted in six different commonly used mountants. Significant fading was detected with all six mountants, although rates varied. The lowest rate of fading was observed with immersion oil and the highest rate of fading with Canada balsam. No significant differences in fading rates of four synthetic mounting preparations were observed.

Animals