Influence of bacitracin on microbial functions in the gastrointestinal tract of horses.

This study investigated the influence of zinc bacitracin on the intestinal flora of horses. The functionally active intestinal flora was examined in 6 horses during treatment with zinc bacitracin. Utilising gas chromatography, spectrophotometry, gel electrophoresis and paper chromatography, samples were analysed on biochemical markers reflecting the action of parts of the intestinal flora. The following 5 flora-related functions were studied in faecal samples and intestinal samples from different sections of the hindgut: conversion of cholesterol to coprostanol and of bilirubin to urobilinogens, degradation of mucin and of beta-aspartylglycine and inactivation of tryptic activity. Conversion to coprostanol, conversion to urobilinogens and degradation of mucin were affected by treatment of zinc bacitracin and conversion to coprostanol was most sensitive. All functions were normalised in a short time, in contrast to man and rats. Differences in environmental exposures are probably the reason for a more rapid normalisation of the intestinal flora functions in horses.

Malignant chromatophoroma in a canebrake rattlesnake (Crotalus horridus atricaudatus).

An adult female canebrake rattlesnake (Crotalus horridus atricaudatus) at Zoo Atlanta (Atlanta, Georgia, USA) had a subcutaneous mass on the left lateral abdomen. Microscopically, the tumor contained a pleomorphic population of cells with abundant intracytoplasmic brown to gold nonrefractile pigment (chromatophores), large stellate cells resembling neurons, and small stellate cells whose cytoplasmic processes formed a fibrillar matrix. The pigment stained black with the Fontana-Masson technique and was positive with the periodic acid-Schiff technique (prior to and after diastase treatment). Neuron-specific enolase was detected in the large stellate cells using an immunohistochemical staining technique. In addition, glial fibrillary acidic and S-100 proteins were detected in the chromatophores with immunohistochemical staining. The smaller stellate cells were strongly S-100 positive. Ultrastructurally, chromatophores contained intracytoplasmic structures composed of concentric lamellar membranes bordered by a triple-layer outer membrane. The morphology of these structures was compatible with pterinosomes. Three fluorescent pigments were isolated from the neoplasm by one-dimensional chromatography and characterized by spectrophotometry and spectrofluorometry.