Philippe van den Bosch de Aguilar

Neuron migration within the radial glial fiber system of the developing murine cerebrum an electron microscopic autoradiographic analysis

The present analysis provides direct evidence in the mouse that in the course of course of neocortical histogenesis, contact between migrating neurons and the surfaces of radial glial fibers is both invariant and relatively selective. The analysis characterizes in detail the migratory behavior of the individual migrating cell with respect to the overall radial glial fiber system as this system varies systematically in its structure with ascent through the strata of the cerebral wall. A quantitative study of the relationships between the radial glial fibers confidently identified by their glycogen content and the migrating neurons marked autoradiographically by injection of [3H]thymidine was also performed at the ultrastructural level on tangential sections at different pallial levels in E16 and E17 embryos. The overall set of observations lend support to the hypothesis that radial glial fibers act specifically as guides to neuronal migration and illustrate the nature of the cell-to-cell interaction which serves this cellular process critical to neocortical histogenesis.

Paired Helical Filaments in Spinal Ganglion Neurons of Elderly Rats

SummaryUltrastructural study of spinal ganglion neurons in elderly rats (aged from 24 to 32 months) allowed the observation of spontaneously occurring paired helical filaments (PHFs). On the basis of this finding the rat may provide an animal model for the study of the morphogenesis and nature of the PHFs which are characteristic of human senile dementia of the Alzheimer type.

Expression of integrins by murine MSC80 Schwann cell line: relationship to cell adhesion and migration.

Schwann cells (Sc) are one of the most important factors promoting regeneration of both the peripheral and the central nervous system. They provide a permissive environment for neurite outgrowth and the making of this environment requires interactions between Sc and extracellular matrix proteins that are mediated via integrin receptors. This study characterized, by immunoprecipitation, the integrins expressed by the mouse MSC80 Sc line. Our results showed that MSC80 Sc expressed alpha1beta1, alpha5beta1 and alpha6beta1 integrins as well as the alpha v-subunit associated with an unidentified 80-90 kDa beta-subunit. Adhesion and migration assays revealed a hierarchy of protein influences that are dependent upon the type of cellular behaviour. Integrin expression correlated with MSC80 Sc line adhesion and migration on extracellular matrix proteins. The MSC80 Sc line expressed a pattern of integrins which allowed adherence on vitronectin and collagen IV, and faster migration on merosin and laminin. As the integrin pattern and the behaviour of MSC80 on ECM were similar to primary Sc, MSC80 are a potential abundant source of Sc for further in vitro and in vivo experiments.

Les caractéristiques tinctoriales des cellules neurosécrétrices chez Daphnia pulex (Crustacea: Cladocera)

Resume Diverses methodes de colorations sont appliquees a letude des groupes cellulaires neurosecreteurs de Daphnia pulex. Des affinites tinctoriales differentes temoignent de la liberation par chacun des groupes dun produit de secretion bien precis auquel correspondrait un role physiologique defini.

Le Système Neurosécréteur De L'Argulus Foliaceus (L.) (Branchiura)

The study of the nervous system of Argulus, using various colorations, allows to identify a large number of neurosecretory cell groups and isolated cells that positively react to signaletic stains. The APS + secretory cells are also detected. A topology for these different groups of cells is proposed. The principal characteristics of the cells are described.

Effects of Aluminum on Glutamate Metabolism

Definition of Al toxicity is traditionally presented in terms of neurone injury and glial cells are generally relagated to a secondary role involving reactive or suportive responses. However, the observations of the present work point out the astrocyte population as a potential target for Al toxic action. In vivo, significant increase in glutamine concentration was observed during aging and after Al exposure in brain regions characterized by Al accumulation, the hippocampus and the neocortex. In vitro, exposure of astrocytes to Al significantly increased GS activity. Some steps of glutamate metabolism appeared therefore to increase in the brain of rats after Al exposure.