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Biomedical subjects

G Roussel

Publications and source records attributed to G Roussel.

At least 73 records · Page 4Linked to original sources
PubMed1983

[Stereospecificity of the action of alpha-aminoadipic acid on the retina: a morphological and electrophysiological study].

An intravitreal injection of the D isomer of the alpha-amino adipic acid (alpha-aa) entails the progressive disappearance of the ERG b wave as well as that of tectal evoked potentials (TEP). These physiological effects are concomitant with a specific glial cell damage in frog and chicken retinas. At low concentrations, the L isomer is more gliotoxic than the D isomer; the ERG b wave is suppressed while TEP are always recorded. At higher concentrations, the L isomer suppresses TEP and damages both glial and neuronal cells.

2-Aminoadipic Acid↗
PubMed1983

[Effects of sodium molybdate on molecular forms of steroid receptors in human breast tumors. The value of high performance liquid chromatography (HPLC)].

Estrogen, progesterone and glucocorticoid receptors from 124 breast cancer cytosols were studied by high performance liquid chromatography (HPLC), in comparison with sephadex chromatography and density gradient ultracentrifugation. Sodium molybdate was used as a receptor-hormone complex stabilizer, and as a tool allowing to study the different molecular forms of the receptors. In the presence of molybdate during the entire saturation process, more receptor sites were detected, without modification of equilibrium reaction kinetics. HPLC receptors analysis was rapid, with an high relative separation efficiency. Multiple molecular forms of steroid receptors were observed: five forms each for progesterone and glucocorticoid receptors, and six forms for estrogen receptors. The presence or absence of one of these forms emphasized the biological variability of the tumors and provides further questions or hormone-dependence.

Breast Neoplasms↗
PubMed1982

Surface labelling of oligodendrocytes with anti-myelin serum in cell cultures from the rat brain. Light- and electron-microscopic immunocytochemical studies.

Antiserum produced in rabbits against purified myelin contains antibodies that bind to the surface of cells having multiple branched processes in live cultures of cerebral hemispheres of newborn rats. The identity of these cells was determined by double immunolabelling experiments with other specific antigenic markers (W1 Wolfgram protein, myelin basic proteins, glial fibrillary acidic protein). It was demonstrated that the cells are a subclass of oligodendrocytes which have reached a certain degree of maturation; nearly all of them contain basic proteins. Indeed, a number of oligodendrocytes, that contain the W1 protein, and may or may not have processes, are not surface-labelled in similar conditions. The usefulness of such an anti-myelin serum in the isolation of pure oligodendrocytes is discussed.

Animals↗
PubMed1981

Effects of DL-alpha-amino adipic acid on Müller cells in frog and chicken retinae in vivo: relation to ERG b wave, ganglion cell discharge and tectal evoked potentials.

In both frog and chicken, an intravitreal injection of DL-alpha-amino-adipic acid, (DL-alpha aaa) provoked a progressive depression and eventually the disappearance of the ERG b wave that was concomitant with severe damage to the Müller cells without any apparent damage to retinal neurons. Ganglion cell discharges as well as tectal evoked potentials were still recorded, i.e. a visual message was still generated in the retina and transmitted to the optic tectum, when the Müller cells had been damaged to as to provoke an abolition of the ERG b-wave. The whole of the drug-induced effects proved to be reversible.

2-Aminoadipic Acid↗
PubMed1981

Comparative localization of Wolfgram W1 and myelin basic proteins in the rat brain during ontogenesis.

Antisera raised in rabbits against myelin basic proteins (MBP) and Wolfgram W1 protein isolated from rat myelin were used to study the maturation of oligodendrocytes in the developing rat nervous system. Both proteins were localized immunohistochemically at the light and electron microscopical levels in rat brain from the time of their first appearance to the adult stage. Oligodendrocytes were first detected by their positive staining with W1 antiserum two days after birth and at 1-3 days later with MBP antiserum. At 8-10 days, the number of oligodendrocytes labelled with both sera increases and the myelinated fibre pathways were clearly visible. Labelling with W1 antiserum was observed in oligodendrocytes at all stages from 2 days after birth to adulthood and in myelin fibers when they were present. In contrast, staining of oligodendroglial cells with MBP declined during the period of rapid myelination (20-25 days after birth) and finally disappeared, whereas myelin staining was still apparent. The electron microscopical study revealed that the synthesis of Wolfgram proteins occurred mostly at the peripheral cytoplasmic ribosomes of the cells, from where they were probably transported to processes engaged in myelination. The electron micrographs also showed that the sites of MBP synthesis seemed to be more uniformly distributed over the entire cytoplasm.

Aging↗
PubMed1980

Effects of some amino acids (GABA, glycine, taurine) and of their antagonists (picrotoxin, strychnine) on spatial and temporal features of frog retinal ganglion cell responses.

When intravitreally injected in the frog, GABA reduced the receptive field area of transient retinal ganglion cells, and it decreased the response duration and the number of spikes both at ON and at OFF. Conversely, its antagonist picrotoxin provoked an increase in the duration of both ON and OFF discharges as well as a marked increase in the number of spikes. Furthermore, picrotoxin provoked a marked increase in the size of the receptive field of both sustained and ON-OFF cells by abolishing the inhibition exerted by the surround upon the centre of the field. Glycine and taurine did not affect the size of the receptive field of these ganglion cells. They had no effect on the responses of sustained ganglion cells, while they totally suppressed OFF discharges of transient ganglion cells, without modifying their ON discharges. Conversely, their antagonist strychnine totally suppressed the ON dishcarges while the OFF discharges were still recorded, though with a reduced number of spikes and an increased latency, An histoautoradiographic study, carried out in parallel, showed that GABA is taken up by both horizontal cells and amacrine cells, while glycine and taurine are taken up by the amacrine cells only.

Amino Acids↗
PubMed1979

Demonstration of a specific localization of carbonic anhydrase C in the glial cells of rat CNS by an immunohistochemical method.

The localization of carbonic anhydrase C isoenzyme in the central nervous system (CNS) of the rat has been investigated using the indirect immunoperoxidase technique, at both optic and electron microscopic levels. Evidence is presented for a specific localization of the enzyme in the cytoplasm of the oligodendrocytes and astrocytes. Myelinated fibers show a weak staining. The positive reaction is restricted to the cytoplasmic areas of the myelin sheath and does not appear in the compact myelin. Neuronal cell bodies do not stain at all. A strong positive reaction to the antiserum was also observed in the choroid plexus.

Animals↗
PubMed1979

GABA binding processes in rat brain and liver.

Although these studies have provided some further insight into GABA binding processes associated with transport and receptor-activation, such attempts remain limited due to the lack of specificity of the ligands used to displace these components. Thus, BMI appeared to interact with both transport and synaptic receptor sites for GABA. Perhaps certain GABA-agonists (e.g., muscimol, isoguvacine) will be shown to interact more specifically with synaptic GABA-receptors? So-called "specific" binding of GABA and its analogues, or antagonists might not be the issue to be kept in focus in this type of experiment, especially since it cannot be separated into presynaptic, postsynaptic and non-synaptic components. The specificity of an interaction of ligand with membrane site may be determined by other requirements of the particular system concerned. In any case, it seems essential to examine the binding sites, themselves, in order to define more clearly which of these are involved in receptor-activation and in uptake. An approach involving the isolation and purification of GABA-receptors should provide evidence for specific binding of GABA to its postsynaptic receptors.

Animals↗
PubMed1979

Comparison of high-affinity binding of [3H]GABA to subcellular particles of rat brain and liver.

The binding of [3H]GABA and retention of [14C]sucrose have been studied in freshly prepared "synaptosomal-mitochondrial" (P2) fractions of rat cerebral cortex and liver using bicarbonate-buffered medium (containing 147 mEq/liter of Na+), and in frozen/thawed crude membrane fractions of rat whole brain and liver using Na+-free Tris HCl medium. GABA-sensitive sites (GSS) and bicuculline-methiodide- (BMI-) sensitive sites (BMI-SS) were defined as those amounts of [3H]GABA that were sensitive to the displacement by 10(-3) M unlabeled GABA or BMI. In the presence of added Na+, two high-affinity GABA-binding processes were detected in the P2 fraction of cerebral cortex. The lower-affinity process (likely related mainly to uptake sites) had KB approximately equal to 10(-5) M, Bmax for GSS approximately equal to 3 nmol/mg protein, and Bmax for BMI-SS approximately equal to 0.5 nmol/mg protein, whereas the higher-affinity process (likely related to synaptic GABA receptors) had KB approximately equal to 10(-7) M, BMAX for GSS approximately equal to 43 pmol/mg protein, and BMAX for BMI-SS approximately equal to 2 pmol/mg proteins. Only the higher-affinity process was detected in the liver P2 fraction, and it had KB approximately equal to 3.7 x 10(-8) M, BMAX for GSS approximately equal to 0.48 pmol/mg protein, and BMAX for BMI-SS approximately equal to 0.1 pmol/mg protein (i.e., about 1/100 and 1/20 the receptive BMAX values of cerebral cortex). This binding process of the liver P2 fraction could represent sites involved in mitochondrial GABA transport. In Na+-free Tris HCl medium, high-affinity [3H]GABA binding appeared to exist in frozen/thawed membrane preparations of both brain and liver when data were expressed on a protein basis. However, this binding to liver membranes was not displaceable by 10(-5) M unlabeled GABA, and when these data were expressed on a weight basis and corrected for [3H]GABA present in trapped supernatant fluid of the pellets, no [3H]GABA binding was detected in the liver preparation.

Animals↗
PubMed1978

Postnatal development of rat cerebellum: massive and transient accumulation of concanavalin A binding glycoproteins in parallel fiber axolemma.

Modifications of protein-bound sugars during postnatal development of rat cerebellum were studied. Glycoprotein-bound mannose accumulates, in the particulate fractions, at an earlier age than the bulk of glycoprotein sugar. This corresponds to a transient and massive accumulation of glycoproteins which bind to Concanavalin A (Con A). These glycoproteins were localized by using fluorescent Con A and the horseradish peroxidase-Con A method. Cerebellar white matter and the molecular layer bind massive amounts of Con A. The binding in the molecular layer is transient. It follows the same time course as the Con A-binding glycoproteins of particulate fractions, and it is largely confined to the axolemma of parallel fibers. Only growing or newly formed parallel fibers bind Con A. The disappearance of the binding is simultaneous with the maturation of parallel fibers and their synapse formation. These phenomena can be related to fiber growth and maturation and, also, to synapse formation. The possibility of a specific role of Con A-binding glycoproteins is discussed.

Age Factors↗