Renaut bodies in the sciatic nerve of beagle dogs.

182 control Beagle dogs from 23 historical studies (14 chronic, 9 subchronic) were reviewed histologically for the presence of Renaut bodies in the sciatic nerve. Renaut bodies were found in 36.1 percent of the subchronic-study dogs and in 46.4 percent of the chronic-study dogs. The Renaut bodies most often resided in the distal sections of the sciatic nerve, specifically in the tibial branch as it traversed the knee joint in situ. There was no sex predilection. Renaut bodies were located predominately in the endoneurium, in the center of the nerve sections. There was no associated axonal degeneration, reactive gliosis, or encapsulation. The Renaut bodies were characterized as large (20 to 500 microns diameter in cross section), well-demarcated elliptical structures with an onion-skin arrangement of loosely textured, filamentous strands intermixed with sparse numbers of dark spindle-shaped nuclei. Occasionally the core displayed a more dense, intensely eosinophilic arrangement of fibers. Histochemical results included: positive acidic alcian blue, Gomori's trichrome, and Verhoeff Van Gieson's; and negative Periodic-acid Schiff, Congo Red, and Luxol fast blue/cresyl violet. Immunohistochemical results included: positive vimentin and collagen (subtypes I, II, and VI); and negative NSE, S-100, GFAP, amyloid A component, desmin, alpha-sarcomeric actin, pancytokeratin, EMA, and von Willebrand factor. Transmission electron microscopy revealed loosely arrayed, circumferentially oriented collagen fibers intermixed with varying amounts of amorphous substance and finely fibrillar material. Most of the cells comprising the Renaut body were identified as fibroblasts. No nerve fibers entered or left the Renaut body, and nearby nerves appeared to be normal structurally. Based on this characterization of Renaut bodies and in conjunction with the past literature, Renaut bodies appear to have little or no pathological significance, but rather are suggestive of a physiological adaptation in response to mechanical stress imposed on nerves.

Tumors in long-term rat studies associated with microchip animal identification devices.

Tumors surrounding implanted microchip animal identification devices were noted in two separate chronic toxicity/oncogenicity studies using F344 rats. The tumors occurred at a low incidence rate (approximately 1 percent), but did result in the early sacrifice of most affected animals, due to tumor size and occasional metastases. No sex-related trends were noted. All tumors occurred during the second year of the studies, were located in the subcutaneous dorsal thoracic area (the site of microchip implantation) and contained embedded microchip devices. All were mesenchymal in origin and consisted of the following types, listed in order of frequency: malignant schwannoma, fibrosarcoma, anaplastic sarcoma, and histiocytic sarcoma. The following diagnostic techniques were employed: light microscopy, scanning electron microscopy, and immunohistochemistry. The mechanism of carcinogenicity appeared to be that of foreign-body induced tumorigenesis.

An electroretinogram protocol for toxicological screening in the canine model.

A five-step electroretinogram protocol was developed for the dog to be used as a painless screening test for ocular effects of drugs or pesticides. Standard conditions of frequency band width, stimulus intensity, dark adaptation time and non-confounding anesthesia method were selected to allow analysis of wave components. The protocol demonstrated an acceptable level of inter-subject variability for compiling an age appropriate database, and for the detection of possible retinal component toxicities in chronic dog studies. This electrophysiologic procedure may serve to corroborate biochemical, clinical and pathology data, in establishing a compound's no-observable-effect-level (NOEL).