Claude Fuentes

Désafférentation expérimentale de l'écorce cérébrale: Étude par la méthode de Golgi-Cox en microscopies optique et électronique

SummaryThe auditive cortical area of the cat, which had been deafferentated from the medial geniculate body by electrolytic lesion and impregnated by the Golgi-Cox method, was studied by light and electron microscopy at various intervals after the intervention and compared with normal animals. In light microscopy the gradual breakdown of the dendrites, followed by that of cellular body of the majority of the impregnated neurons was observed. On the 25th day after the intervention the only visible cellular elements were neuroglial. In the thin sections the impregnated neurons revealed similar modifications to those mentioned above and coexisted with the unimpregnated neurons and the neuroglial elements. In electron microscopy, the impregnated neurons appeared dark and homogenous in the normal animal. The disappearance of the endoplasmic organisation contrasted with the conservation of the nucleus. After deafferentation the cytoplasm revealed an ever increasing loss of substance in the form of rounded shapes corresponding approximately to the size of the metallic deposits.On the basis of previous results, where the deafferentation was studied by electron microscopy without metallic impregnation, these results can be interpreted as expressing, on the part of the deafferented neurons, the gradual loss of affinity for the mercury. However this fact does not exclude the possibility of a certain number of neurons, already impregnated by the mercury actually desintegrating after the first 3 weeks following the intervention.

A propos d'un cas d'encéphalopathie cirrhotique alcoolique

SummaryThe neuropathologic study of an alcoholic cirrhotic encephalopathy was made after the fixation of the brain by immersion in a solution specially prepared for the electronic microscopy. The histological technics were used then, the Golgi-Cox method among others, confirmed the classic notions of neuronal rarefaction and of the proliferation of the glia cells, particularly in the cerebral cortex. The Bodian method for its part showed in the remaining cortical neuronic population, the existence of voluminous intracytoplasmic aggregates and the hypertrophy of the dendritic apparatus.

Aspects tridimensionnels du cortex cérébral:Étude par la méthode de Golgi-Cox souséclairage incident

Summary Three-dimensional aspects of the cerebral cortex: a study by the Golgi-Cox method with reflected light

Cinétique des processus de dégénérescence axonique dans le système nerveux central: Étude expérimentale à court terme dans le corps calleux chez le rat

SummaryTransection of the corpus callosum was carried out on 20 adult rats and the spatio-temporal pattern of the degeneration process was studied on the 2nd, 8th, 15th and 30th days following the operation for 3 segments of the axon, from the point of severance to the cerebral cortex.In the distal segment of the severed axons degeneration set in simultaneously at the point of severance and in the terminal boutons. Anterograde progression of the process may exist, at least over a short distance. There is definite, though perhaps limited retrograde progression starting from the terminal boutons.The conditions under which the total length of the fibre is affected, kinetically speaking, are the subject of a discussion. At the stages chosen for examination, only a part of the proximal endings are affected by Wallerian degeneration. At the same periods the proximal segment of the axons leading in the opposite direction in the corpus callosum, still appears intact, although the corresponding cellular bodies are in an advanced state of chromatolysis. During the degeneration of the distal segments the myelin sheath remains apparently normal, whereas the axoplasm is in an advanced state of desintegration.

Dégénérescence Wallérienne expérimentale dans les noyaux vestibulaires: Etude en microscopies optique et électronique après imprégnation argentique

SummaryA study of Wallerian degeneration in the vestibular fibres was carried out on the adult cat after electrolytic destruction of the nerve at its point of entry in the brain stem. Histological observation was restricted to the ventral part of the lateral vestibular nucleus and the adjacent portion of the descending vestibular nucleus: — the classic insertion points of primary afferent fibres —. Once embedded in paraffin wax and stained by ammoniacal silver (following Nauta and Gygax, 1951), the sections were studied conjointly by light and electron microscopy. Ultrastructural analysis revealed the high density of the silver deposit inside the neurons and its relative rareness in the terminal boutons. As a result the latter were basely identifiable by light microscopy, in spite of their being larger than the preterminal segment of the neuron. These results are compared with those obtained by methods which have undergone similar stringent tests, such as those of Fink and Heimer.

Le procédé de Bodian

The Bodian method was used for an ultrastructural study on the optic nerve of the adult cat in order to compare the effects of two fixation techniques on the normal nerve and on the nerve during Wallerian degeneration after unilateral enucleation. Immersion fixation causes a predominately metallic deposit in the myelin sheath; the perfusion has no effect. During the Wallerian degeneration the two fixation methods lead to a metallic deposit located in the axon which is in large grains after immersion and extremely dense after perfusion. Various diffraction methods were used to identify the nature of the metallic deposit. These results emphasize the positive elements in systemically associating the electron microscope with the optic microscope for studies concerning Wallerian degeneration after metallic impregnation in the central nervous system

La réaction de Marchi: Aspects ultrastructuraux

SummaryA secondary demyelination process was brought about in the optic tract by unilateral enucleation of 10 adult rats which were sacrificed at 8, 15, 20, 30 and 45 days respectively, after the intervention. The Marchi reaction, which is identifiable by the presence of granular bodies, is positive at all stages, but tends to lessen towards the 45th day. The granular bodies are inside the disintegrating myelin sheath, and gradually fill the space made available by the degenerate axoplasm. The granular bodies are at first bulky and compact before breaking up and disappearing. The remains of the myelin sheath are then resorbed. Satellite cells occur from the 15th day onwards. The interest of the Marchi reaction for the tracing of nervous pathways is confirmed by these findings.