Experimental chronic entrapment of the sciatic nerve in adult hamsters: an ultrastructural and morphometric study

Entrapment neuropathy is a group of clinical disorders involving compression of a peripheral nerve and interference with nerve function mostly through traction injury. We have investigated the chronic compression of peripheral nerves as an experimental procedure for detecting changes in ultrastructural nerve morphology. Adult hamsters (Mesocricetus auratus, N = 30) were anesthetized with a 25 percent pentobarbital solution and received a cuff around the right sciatic nerve. Left sciatic nerves were not operated (control group). Animals survived for varying times (up to 15 weeks), after which they were sacrificed and both sciatic nerves were immediately fixed with a paraformaldehyde solution. Experimental nerves were divided into segments based upon their distance from the site of compression (proximal, entrapment and distal). Semithin and ultrathin sections were obtained and examined by light and electron microscopy. Ultrastructural changes were qualitatively described and data from semithin sections were morphometrically analyzed both in control and in compressed nerves. We observed endoneurial edema along with both perineurial and endoneurial thickening and also the existence of whorled cell-sparse structures (Renaut bodies) in the subperineurial space of compressed sciatic nerves. Morphometric analyses of myelinated axons at the compression sites displayed a remarkable increase in the number of small axons (up to 60 percent) in comparison with the control axonal number. The distal segment of compressed nerves presented a distinct decrease in axon number (up to 40 percent) comparatively to the control group. The present experimental model of nerve entrapment in adult hamsters was shown to promote consistent histopathologic alterations analogous to those found in chronic compressive neuropathies

Intraretinal neurotrophic activity prevents the degeneration of ganglion cells in retinal explants

The degeneration of ganglion cells was studied in neural retina explanted from the eyes of newborn rats. The ganglion cells were detected by the presence of retrogradely transported horseradish peroxidase injected into the superior colliculus. The time course of cell death among the axotomized ganglion cells in the explants was similar to that found in vivo after axotomy in neonatal rats. The effect of culture media conditioned with retinal cells from either newborn rats or chick embryos was tested on the survival of ganglion cells in the explants. Both conditioned media increased 2- to 3-fold the survival of rat retinal ganglion cells after 2 days in culture. The data show that soluble trophic factors released by retinae of distinct species can influence the survival of ganglion cells within their histotypic microenvironment