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M Tardy

Publications and source records attributed to M Tardy.

At least 73 records · Page 4Linked to original sources
PubMed1986

Protein synthesis in astrocytes: 'spontaneous' and cyclic AMP-induced differentiation.

Primary cultures of mouse astrocytes have been used to study astroglial protein synthesis during 'in vitro' differentiation. Spontaneous age-related differentiation was compared to the effect of DBcAMP or forskolin, a drug which directly stimulates the adenylate cyclase and induces 'morphological differentiation' in these cells. Cell differentiation was followed in parallel by phase contrast microscopy and immunofluorescence techniques. Two antisera, one raised against GFA, the other against microtubule-associated protein 2 (MAP2) were used. Anti-GFA serum labelled the cells as early as 7 days in vitro. Anti-MAP2 serum revealed a dense fibrous network at later stages of the culture, whereas the dividing astroblasts appeared poorly stained by this antibody. Both phase contrast microscopy and immunofluorescence techniques suggested that most of the cells spontaneously differentiate after 3 weeks of culture even in the absence of DBcAMP or forskolin. Forskolin, while accelerating differentiation after 7 days of culture, produced smaller cells than DBcAMP and had biphasic effects on cell morphology. Mono- and two-dimensional gel electrophoresis of the 35S-methionine labelled cells also showed that the major changes in protein synthetic activity occur spontaneously during the time course of the culture. Whatever the stage of the culture, DBcAMP or forskolin induced changes in the synthesis of only a few proteins. However, depending on the culture stage the proteins, which were positively or negatively controlled by these drugs, were not the same.

Animals↗
PubMed1985

Further characterization of [3H] flunitrazepam binding sites on cultured mouse astroglia.

Astroglial cells in primary cultures bind [3H]flunitrazepam with a high affinity on a single type of site and on a number of binding sites which increased during astroglial growth and differentiation. These binding sites show a particular pharmacological spectrum characterized by an inhibition of high affinity by RO-5-4864 (4'-chlorodiazepam), an anticonvulsant of the benzodiazepine family and by an inhibition of binding of lower affinities by diazepam clonazepam and clobazam. RO-5-4864 and clonazepam compete for the same binding site in astroglia. The heat stability and the hormonal modulation by thyroxine are similar for astroglia and neuronal-cells. Benzodiazepines modulate the astroglial 5-HT receptor. Such an effect could be a possible physiological response to benzodiazepines for astroglial cells in primary cultures.

Animals↗
PubMed1985

Microtubule-associated proteins and in vitro astrocyte differentiation.

Primary cultures of mouse brain astrocytes have been used to identify the microtubule-associated proteins (MAPs) present in this cell type at different stages of in vitro differentiation. The MAPs of the astrocyte have been identified by polyacrylamide gel electrophoresis and immunological detection. Two antisera were raised against two brain MAPs, tau and MAP-2. These antisera were also used to label the microtubular network in the intact astrocytes at different stages of the culture. The mature astrocyte contains a variety of MAP-like proteins. Anti-MAP-2 serum detected several proteins of high molecular weight (380,000, 260,000, 205,000 and 165,000 mol wt) and one microheterogeneous peak of 83,000 mol wt. Anti-tau also detected high molecular weight components (380,000 to approximately 200,000 mol wt) but not the 165,000-mol-wt peak; in addition two microheterogeneous peaks of 83,000 and 62,000 mol wt were detected by the anti-tau serum. The 62,000-mol-wt peak was therefore detected only by the anti-tau serum whereas the 83,000-mol-wt component cross-reacted with both antisera. At early stages of the culture the immature cell contained about two times less immunoreactive material than at mature stages. Qualitative changes of the high molecular weight components were also observed. In the intact cell both antisera revealed a dense fibrous network. At early stages of the culture the astroblasts were stained by the antisera but the reaction was very diffuse in the cytoplasm; few fibrous cells were intensively stained. Morphological differentiation, which began after serum deprivation and which was accelerated by forskolin (a drug that induces cyclic AMP accumulation), led to high labeling of both the cell body and the cellular processes. In the presence of colchicine the staining regressed, the processes shortened, and the cell returned to a less-apparently differentiated state.

Animals↗
PubMed1984

Astroglial cells: glucocorticoid target cells in the brain.

Glutamine synthetase (GS), an enzyme localized in astroglial cells in the brain, is directly implicated in brain detoxification. An ontogenic study of GS activity was performed in homogenates from four distinct brain areas in comparison with the respective astrocytes obtained in primary cultures. GS was induced by hydrocortisone in the astrocytes of all brain areas studied; only cerebellum and cerebral hemisphere astroglial cells had a higher specific activity when compared with the corresponding homogenates. N6O2-Dibutyryl adenosine 3',5'-cyclic monophosphate (dBc AMP), insulin, soluble brain factors, and noradrenaline (NA) were also able to modulate GS activity. Brain factors as well as dBc AMP interfered with hydrocortisone induction of GS. Regulation by hydrocortisone paralleled the variation in its concentration in brain during development. We conclude that astroglial cells are target cells for glucocorticoids, which may modulate ammonia detoxification in these cells.

Animals↗
PubMed1982

Glutamine synthetase activity during mouse brain development.

The specific activity of glutamine synthetase (GS) in mouse brain was 2-fold higher in the olfactory bulbs than in other regions. After birth, the specific activity of GS increased more rapidly in medulla oblongata and in olfactory bulbs, than in cerebral and cerebellar cortex. The activity of GS in primary cultures of brain hemispheres increased more slowly than in homogenates of whole brains. However, when astroblasts were treated in vitro with glucocorticoids or mouse brain extracts, GS activity reached 4 times the level measured in the homogenate of an adult mouse brain. We conclude that levels of GS activity may relate to the maturation of astrocytes, and propose that GS may be used as a marker of astrocytic maturation.

Animals↗
PubMed1982

Uptake and binding of serotonin by primary cultures of mouse astrocytes.

Primary cultures of glia contain a high glial fibrillary acidic protein level and exhibit important glutamine synthetase activity. They take up serotonin via a high affinity carrier-mediated system with a Km of micromolar range. The Km of this transport process does not vary during cell growth or maturation; however, during the last period of morphological change induced by dibutyryl cyclic AMP, an increase in Vmax is observed. Chlorimipramine, fluoxetine and fenfluramine at 10-4 M inhibit this uptake. 3H-5-HT still binds to partially purified astrocytic membranes on a single type of site. During growth, neither KD nor Bmax were modified. During the maturation period, KD decreased to about 50% of its control level. Methysergide inhibits that binding.

Animals↗
PubMed1982

[Biological diagnosis of pulmonary parasitoses and mycoses].

Pulmonary involvement in parasitic disease is now due above all to the visceral Larva migrans syndrome, the diagnosis of which is serological, and to imported distomatosis due to Paragonimus sp, confirmed by the discovery of eggs in the sputum. An immature immunological status or immunodepression is necessary for the development of Pneumocystis carinii, where all of the stages of diagnosis, including that of the obtaining of sample material, are difficult. Pulmonary mycoses are represented above all by candidiosis, aspergillosis and rarely cryptococcosis which also commonly occur in the presence of an impaired underlying state. Diagnosis of these opportunistic fungi is sometimes difficult and it is necessary to take all clinical, laboratory and immunological data together in order to obtain confirmation.

Humans↗
PubMed1981

Effect of prostaglandins and dibutyryl cyclic AMP on the morphology of cells in primary astroglial cultures and on metabolic enzymes of GABA and glutamate metabolism.

Prostaglandins (PGE1) and dibutyryl cyclic AMP (dBc AMP) induce similar morphological changes in astrocytes obtained in primary cultures. PGE1 and dBc AMP increased 2 enzymes of GABA and glutamate metabolism, GABA-T and AAT, but did not modify GDH and GLN-S. Prostaglandins probably affect the cAMP content of glial cells and act in the same way as dBc AMP on glial cell differentiation.

4-Aminobutyrate Transaminase↗
PubMed1981

Receptor-specific large-scale purification of cholera toxin on silica beads derivatized with lysoGM1 ganglioside.

1. A receptor-specific affinity chromatographic method for large-scale purification of cholera toxin is described. The receptor ganglioside for cholera toxin, GM1, is hydrolysed to lysoGM1 which is then covalently coupled, via stabilized Schiff's bases, to porous silica beads (Spherosil) onto which a layer of DEAE-dextran has been adsorbed and cross-linked before coupling. Columns of these Spherosil-DEAE-dextran-lysoGM1 beads, in contrast to particles derivatized with lysoGA1, bound the cholera toxin of Vibrio cholerae culture filtrates, after which the toxin could be eluted with the aid of an acid citrate buffer (pH 2.8). 2. The toxin-binding capacity was directly proportional to the amount of lysoGM1 in the column: 2.3 mg/mu mol lysoGM1. The yield of purified toxin after acid elution and pH neutralization was essentially quantitative (83-107%). 3. The affinity-purified toxin contained less than 5% impurities, but consisted of a mixture of predominantly intact holotoxin and B subunit protomer which could readily be separated by gel filtration on Sephadex G-100. 4. Scaling up of the technique was possible: a 1 kg column enabled us to treat 1000-1 cultures of V. cholerae and thus to isolate 20 g of cholera toxin per cycle.

Animals↗
PubMed1981

Benzodiazepine receptors on primary cultures of mouse astrocytes.

Benzodiazepines bind to glial membranes on a single type of site, with a high affinity (KD = 5 x 10(-9) M) on about 100 fmol of sites per mg protein. The number of binding sites is increased when the membranes are treated with Triton X-100. Antiepileptic drugs such as clonazepam and phenobarbital and hypnotic drugs such as Ro-11-3128 and Ro-11-6896 are able in pharmacological concentrations to displace [3H]flunitrazepam from its glial binding sites.

Animals↗
PubMed1979

GABA metabolism in cultured glial cells.

GABA-transaminase has been characterized in cultured astrocytes. It is identical to the synaptosomal and perikaryal enzyme in terms of charge, molecular weight, and stability, but it differs in its affinity for GABA, which is much higher in the glial compartment. GABA-transaminase has been shown to be inducible by high GABA concentrations, which suggests that astrocytes have the possibility not only to transport GABA but also to metabolize the amino acid which is taken up.

4-Aminobutyrate Transaminase↗