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C Fages

Publications and source records attributed to C Fages.

At least 19 recordsLinked to original sources
PubMed1992

Transcriptional regulation of glial fibrillary acidic protein (GFAP)-mRNA expression during postnatal development of mouse brain.

During mouse brain maturation, GFAP-mRNA undergoes a two-step developmental expression. It increases between birth and day 15 (period of astrocytic proliferation) and then decreases until day 55 (period of astrocytic morphological differentiation). We have developed an in vitro transcription procedure, as a mean to study the part of transcriptional control in this biphasic expression. After RNA synthesis by endogenous RNA polymerases in nuclei isolated from mouse brain (of 3 to 55 days and 217 days), the relative rates of GFAP-mRNA transcripts were analysed by hybridization with a specific cDNA probe. As early as 3 days after birth, the rate of GFAP-mRNA transcripts was maximal, whereas unexpectedly, it showed a significant decrease in mice of 15 days and stayed low until the 55th day. Therefore, a transcriptional control may take place early in mouse brain postnatal development by increasing the transcriptional rate of the GFAP gene in astrocytes, and during the transition from proliferation to differentiation phase of astrocytes (that occurs at the 15th day after birth) by decreasing this rate. However, posttranscriptional events may also occur to modulate the level of the cytoplasmic GFAP-mRNA. In older mice (217 days), the low rate of GFAP-mRNA transcripts found is not concordant with the high cytoplasmic level generally observed in gliosis of the aging brain. Our data suggest posttranscriptional events at this age.

Aging↗
PubMed1991

Effect of thyroid deficiency on glial fibrillary acidic protein (GFAP) and GFAP-mRNA in the cerebellum and hippocampal formation of the developing rat.

The concentrations of glial fibrillary acidic protein (GFAP) and its encoding mRNA in the cerebellum and hippocampal formation were assayed during the development of normal and hypothyroid rats. Neonatal hypothyroidism induced a significant reduction in the GFAP concentration in both regions from day 14. The reduction was especially marked on day 35 in the cerebellum (-43%) and the hippocampal formation (-55%). The immunocytochemical study of vimentin showed that the developmental disappearance of this protein from the Bergmann and internal astrocytes is greatly delayed in the cerebellum of the hypothyroid rats. The reduction in GFAP concentration together with the delayed vimentin-GFAP transition could explain how astrocyte morphogenesis is impaired by neonatal thyroid deficiency. The GFAP-mRNA concentration in the hippocampal formation was reduced throughout the development of thyroid-deficient rats, while the GFAP-mRNA concentration in the cerebellum first increased between birth and day 14 to reach a peak well above the normal value (+78%) and decreased thereafter to reach 53% of the normal value by day 35. This transient increase in the cerebellar GFAP-mRNA concentration may be related to the astroglial hyperplasia that occurs in these animals. The difference between the developmental profile of GFAP and its encoding mRNA, especially under pathological conditions, indicates that two distinct mechanisms control the synthesis or stability of the protein and its messenger RNA, as was previously found in the forebrain of the developing normal rat.

Animals↗
PubMed1991

DBcAMP effect on the expression of GFAP and of its encoding mRNA in astroglial primary cultures.

Short term and chronic dBcAMP effects on the expression of glial fibrillary acidic protein (GFAP) in astroglial primary cultures are investigated. Short (48 h) and long (more than 7 days) treatments with the cAMP derivative induce both cell shape changes and an increase in GFAP immunolabelling. Such effects are only associated with an increase in GFAP and in GFAP-mRNA levels in the long term treatment. These results suggest that the short term effect of dBcAMP induces post-translational modifications of the protein whereas the long term effect is associated with an increase in GFAP mRNA transcription and/or stability.

Animals↗
PubMed1990

GFAP turnover during astroglial proliferation and differentiation.

The expression and turnover of the glial fibrillary acidic protein (GFAP) were studied in astroglial primary cultures during postnatal proliferation and maturation. 1. Immunocytochemical studies demonstrated that in immature proliferating astrocytes. GFAP was expressed as a filamentous organized crown around the nucleus whereas in the maturating cells, a GFAP labelled network began to radiate throughout the cytoplasm and GFAP was highly expressed in the astroglial processes. 2. GFAP turnover was studied at 3 periods of culture. The decay of radioactivity from prelabelled GFAP was followed from day 4-12 (immature stage), 11-19 (maturing stage) and 21-29 (morphologically differentiated stage). GFAP displayed a biphasic decay kinetic at each considered period. Two pools of GFAP distinctly appeared. The first one was a fast decaying pool with a half life of 16-18 h and of 5-6 days for the stable one. The unstable pool decreased from 70% to 30% of the total incorporated radioactivity from the proliferating stage to the most mature stage, whereas the stable pool increased proportionally.

Animals↗
PubMed1990

Glutamine synthetase modulation in astrocyte cultures of different mouse brain areas.

Astroglial cells from mouse cerebral hemispheres, cerebellum, olfactory bulbs, and medulla oblongata were grown in the presence of either hormones (hydrocortisone, insulin) or cell second messengers (dBcAMP, dBcGMP). Glutamine synthetase (GS) specific activity, GS protein level, and GS translation were investigated under the effect of these factors. Hydrocortisone produced a simultaneous increase in GS translation, GS level, and activity. This increase was observed in the astrocytes cultured from the four brain areas but at a variable magnitude depending on the area. The hydrocortisone effect appeared at the transcriptional level. Inversely, insulin decreased both the GS activity and the in vitro translated GS. This effect was seen only in the olfactory bulbs and the medulla. DBcAMP increased the GS biological activity only in the cerebral hemisphere cultures. It raised, however, the level of translated GS and GS protein in astrocytes from all the areas, suggesting a post-translational effect for intracellular cAMP. DBcGMP only affected GS in the astrocytes from cerebral hemispheres and the medulla modulating either the GS transcription or the messenger RNA stability. These results suggest specific regulation for GS expression, depending on the brain area from which the cells were dissociated or on the astroglial cell population present in these cultures affecting either the transcription, the mRNA stability, or the biological activity of the protein.

Animals↗
PubMed1989

Developmental expression of the glial fibrillary acidic protein mRNA in the central nervous system and in cultured astrocytes.

The expression of glial fibrillary acidic protein (GFAP)-mRNA during mouse brain development and in astroglial primary cultures has been investigated by using two approaches: Northern-blot evaluation using a specific cDNA probe, and cell-free translation associated with immunoprecipitation. During brain maturation (4-56 days postnatal), the GFAP-mRNA underwent a biphasic evolution. An increase was observed between birth and day 15 (i.e., during the period of astroglial proliferation), which was followed by a decrease until day 56 (i.e., during astroglial cell differentiation). At older stages (300 days), an increase was observed, which might reflect gliosis. During astroglial in vitro development (7-32 days in culture), the GFAP-mRNA showed similar variations. An increase, observed during the period of astroglial proliferation (7-18 days), was followed by a decrease which occurred in parallel to marked changes in cell shape, cell process outgrowth, and the organization and accumulation of gliofilaments. During the same culture period (7-32 days), alpha-tubulin mRNA, which was used as an internal standard, did not vary significantly. These results show that the increase of the GFAP protein and of gliofilaments observed both in vivo and in vitro during astroglial differentiation cannot be ascribed to an accumulation of the GFAP-mRNA. It might be that more than one mechanism regulates the levels of free and polymerized GFAP and of its encoding mRNA.

Animals↗
PubMed1988

Insulin effect on GABA uptake in astroglial primary cultures.

Astroglial cultures from newborn mouse cerebral cortex contain [125I]Insulin binding sites. Binding was specific, reversible, time dependent and reached equilibrium after 45 min. Insulin analogues compete for this [125I]Insulin binding. Incubation of cerebral cortex astroglial cultures with insulin induced a time- and dose-dependent inhibition of the [3H]GABA high affinity uptake. A decrease in the Vmax rather than an effect on the Km was observed. This effect was dose-dependent and effective at 10(-10) M. Autoradiographic observations on the cell monolayer showed the presence of two groups of cells: one which strongly takes up [3H]GABA and consist in smaller GFAP positive process-bearing cells and another group of much flatter and larger GFAP positive cells which uptake was lower. The smaller stellate cells were apparently the most sensitive to insulin effect. These results: 1) confirm the presence of insulin binding sites on astroglial primary cultures, 2) show an effect of insulin on [3H]GABA high affinity uptake of these cells; this effect being optimal on a stellate-like population of astrocytes, and 3) indicate that insulin may interfere in neuromodulation through astroglial signals.

Animals↗
PubMed1988

Glutamine synthetase: a marker of an astroglial subpopulation in primary cultures of defined brain areas.

Primary cultures from various areas of newborn mouse brain were developed and characterized. Enriched astroglial cultures of the cerebral hemispheres, cerebellum, medulla oblongata and olfactory bulbs contained about 80-90% glial fibrillary acidic protein (GFA) immunolabelled cells. These cultures were composed of a majority of flat, 'protoplasmic-like' cells. The aim of this culture model was used: (1) to study glutamine synthetase (GS) activity during in vitro astroglial development; (2) to consider the hydrocortisone effect on GS activity during both growth and maturation periods, and (3) to determine the development of GS immunoreactivity in the cells and eventual GFA and GS expression in these cells. We observed that GS increased during brain maturation in vivo and in vitro, and that addition of hydrocortisone (1 microM, 48 h) to the culture medium induced varying GS activity depending on the developmental stage and the area. In the four areas studied, the number and intensity of GS-immunolabelled cells reached an optimum between 18 and 30 days in vitro. Only about 50-70% of the cell population was GS positive. Double-labelling experiments showed that three groups of cells coexist whatever the considered area. Two expressed both GFA and GS proteins, the last marker at either a low or a high level, and the third was devoid of GS immunoreactivity. Regional differences in GS-specific activity, GS inducibility and GS immunoreactivity exist in the astroglial population, but the factors responsible for these variations are not yet known.

Animals↗
PubMed1986

Differential immunocytochemical staining for glial fibrillary acidic (GFA) protein, S-100 protein and glutamine synthetase in the rat subcommissural organ, nonspecialized ventricular ependyma and adjacent neuropil.

Antibodies raised against glial fibrillary acidic protein (GFA), S-100 protein (S100) and glutamine synthetase (GS) are currently used as glial markers. The distribution of GFA, S100 and GS in the ependyma of the rat subcommissural organ (SCO), as well as in the adjacent nonspecialized ventricular ependyma and neuropil of the periaqueductal grey matter, was studied by use of the immunocytochemical peroxidase-antiperoxidase technique. In the neuropil, GFA, S100 and GS were found in glial elements, i.e., in fibrous (GFA, S100) and protoplasmic astrocytes (S100, GS). The presence of S100 in the majority of the ventricular ependymal cells and tanycytes, and the presence of GFA in a limited number of ventricular ependymal cells and tanycytes confirm the glial nature of these cells. The absence of S100, GFA and GS from the ependymocytes of the SCO, which are considered to be modified ependymal cells, suggests either a non-astrocytic lineage of these cells or an extreme specialization of the SCO-cells as glycoprotein-synthesizing and secreting elements, a process that may have led to the disappearance of the glial markers.

Animals↗
PubMed1986

Absence of correlations between glutamine-synthetase activity and dysmyelination-associated modifications of astroglia in the brain of murine mutants.

Glutamine Synthetase (GS) activity was investigated in cerebellum (ce), cerebral cortex (cc), olfactory bulb (ob), and medulla oblongata (mo) of murine dysmyelinating mutants for correlations with modifications of astroglia associated with genetic dysmyelination. One of these mutants, jimpy, develops a strong gliosis throughout the CNS. The other three mutants: shiverer, mld, and quaking, exhibit various astrocytic responses to dysmyelination, but reduced gliosis if any. Comparison between CNS areas in control animals showed a higher GS activity in the olfactory bulb than in the cerebral cortex, medulla, and cerebellum. The developmental patterns of GS activity were similar in mutants and in controls in all four areas investigated. Data on Jimpy suggest that GS activity is not associated with reactive astrocytes.

Animals↗
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↗