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Biomedical subjects

G Rebel

Publications and source records attributed to G Rebel.

At least 37 records · Page 2Linked to original sources
PubMed1991

Changes in glial fibrillary acidic protein and karyotype during culturing of two cell lines established from human glioblastoma multiforme.

Two human cell lines (GL15 and GL22) derived from glioblastoma multiforme were established and characterized by immunohistochemical and cytogenetic techniques. The expression of glial fibrillary acidic proteins and the karyotype were analyzed at different passages for both cell lines. The course of marker-pattern differed in the two cell lines. The main findings were a cell-density-dependent expression of glial fibrillary acidic protein in the cell line GL15 at all passages and a decreased expression of this protein over time in the cell line GL22. Both cell lines had hyperdiploid karyotypes and exhibited glioma-specific chromosomal abnormalities (gain of chromosome 7 and loss of chromosome 10). In the GL15 cell line no relevant chromosomal changes were produced during culturing, whereas in the GL22 cell line a hypodiploid clone appeared at the 42nd passage. The immunohistochemical and cytogenetic data resulting from this study confirm that the two cell lines established in our laboratory originated from astrocytic tumor cells.

Brain Neoplasms↗
PubMed1991

Interference of Good's buffers and other biological buffers with protein determination.

Interference of low concentrations of Hepes and other buffers commonly used in protein determination was studied. The data show that some of these buffers interfere to differing degrees with protein determination according to the Lowry method. A study of the structure-interference relationship suggests that the group ethanolamine is involved in this interference. No interference was observed when protein was measured using bicinchonic acid at the same concentration as the Lowry reagent.

Buffers↗
PubMed1991

Expression of plasma membrane and cell surface phospholipids and gangliosides of chick embryo neurons grown in primary cultures: developmental studies.

Plasma membranes isolated from chick embryo neurons after 2 days (division phase) and 5 days (maturation phase) in culture showed no differences in the phospholipid (PL) pattern or in the plasma membrane average fluidity. Significant ganglioside (Ggl) variations were only found in GM1 and GD3 which represent 35% of the total plasma membrane N-acetylneuraminic acid (NeuNac) content (1.8-fold GM1 NeuNac increase, 1.4-fold GD3 NeuNac reduction). Lactoperoxidase-catalyzed radioiodination (125I) under saturating conditions indicated that the hydrophobic core of cell surface Ggl was more exposed to the hydrophilic extracellular environment than that of PL. Nevertheless, when interneuronal contacts start to form, the 125I-labelling of both PL and Ggl dropped progressively throughout the maturation phase. Further analysis revealed that (1) plasma membrane GD3 was not accessible to the enzymatic labelling, and (2) surface phosphatidylethanolamine (PE) and GT1b became more accessible to the external medium during development, whereas the opposite was found for phosphatidylcholine (PC) and GM1. The overall profile of radioiodinated PL and Ggl was unaltered when poly-L-lysine was substituted for polyethyleneimine as culture substratum, except for an increase in GT1b labelling 24 h after plating. These results suggest the existence of a 'buffering' mechanism protecting the neuronal plasma membrane during cellular growth from marked changes in fluidity, polar lipid composition and relative localization of polar lipids with regard to the extracellular environment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effect of HEPES on the Na+,Cl-dependent uptake of taurine and beta-alanine by cultured glial cells. Modulation by composition and osmolarity of medium.

The effect of HEPES on the Na+,Cl-dependent uptake of taurine and beta-alanine by cultured glial cells was investigated. Whatever the culture medium used, a similar inhibition of the uptake of taurine by HEPES was found. In a previous paper it was shown that this buffer was able to inhibit the uptake of taurine through a slow and a fast "mechanism", when present in the culture or in the incubation medium, respectively. Comparison of the effect of HEPES on the uptake of taurine and beta-alanine suggested that only the slow "mechanism" was common to the uptake of the beta-aminoacid. Therefore, the uptake of the beta-aminoacid might be affected by HEPES. On the other hand, a small increase of the osmolarity of the media altered the uptake of taurine, suggesting that caution is needed when interpreting pharmacological experiments.

Alanine↗
PubMed1990

Comparison of the mechanisms of action of insulin and triiodothyronine on the synthesis of cerebroside sulfotransferase in cultures of cells dissociated from brains of embryonic mice.

The effect of low (physiological) concentrations of insulin (2 and 20 ng/ml) and L-triiodothyronine (T3) were studied on two myelin-related enzymes: (1) the 3'-phosphoadenosine-5'-phosphosulfate:cerebroside sulfotransferase (CST, EC 2.8.2.11) catalyzing the production of sulfatide, and (2) the myelin enzyme, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP, EC 3.1.4.3.7) in myelinogenic cultures of cells dissociated from embryonic mouse brain. Insulin treatment (20 ng/ml) of the cells in the presence of serum increased CST activity at 18 and 25 days in vitro (DIV) by 86 and 211%, respectively. At 18 DIV and under the same conditions, CNP was significantly stimulated (95%) by high doses of insulin (2,000 ng/ml) only, while arylsulfatase A (EC 3.1.6.1) or cerebroside sulfatase activities, both of which are involved in sulfatide degradation, were unchanged. Thus, it can be assumed that the observed increase of the incorporation of [35S]O4 into sulfatide after insulin treatment of mixed cell cultures is the result of CST induction rather than a decreased catabolism. The level of CST activity in insulin-treated cells (20 ng/ml) in serum-free medium was also increased at 18 and 25 DIV by about 50 and 70%, respectively. Conversely, none of the insulin concentrations used in the absence of serum (even at high doses) had any effect, either at 18 or 25 DIV on CNP and ASA activities. The involvement of insulin in the regulation of sulfatide synthesis was further confirmed by dose-response curves relating the activity of CST to hormone concentration in the medium. The increase in the activity of CST in insulin-treated cells was due only to the increase in the Vmax of this enzyme, suggesting that it may be attributed to enzyme induction. A study of kinetic parameters of CST indicated that there were no differences in pH optimum and Km values between control and induced enzyme. Further experiments using cycloheximide point to a direct effect of insulin on oligodendrocyte CST induction. Data similar to those described above for insulin were also obtained with T3. As for insulin, T3 stimulated the induction of CST but in serum-free medium only. This effect was prevented by cycloheximide. In addition, the induction of CST by T3 was blocked by actinomycin D. This was not the case for insulin. These results suggest that T3 and insulin act on CST by different mechanisms, i.e. at transcriptional and post-translational levels, respectively. Apart from this, the insulin effect on CST activity was additive to that of T3.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Effect of HEPES on the taurine uptake by cultured glial cells.

HEPES inhibited the taurine uptake in glial cells. A different kind of inhibition was observed when HEPES was present in the culture medium or in the incubation medium used for the taurine-uptake measurement. As an example of a possible interference of HEPES in pharmacological experiments, we have studied the effect of this buffer on the modulation of taurine uptake by beta agonists or ionic concentration.

Animals↗
PubMed1988

Latex beads phagocytosis capacity and ecto-NAD+ glycohydrolase activity of rat brain microglia cells in vitro.

Conditions are described which allow the preparation in vitro of pure (greater than 95%) microglial cell cultures isolated from newborn rat brain. Such ameboid cells cultivated in vitro can efficiently phagocytize opsonized latex beads and are capable of ingesting more (100-200 beads of 1.1 micron diameter per cell) and larger (6.4 microns) particles than other nerve cells, such as oligodendrocytes and astroglia. The microglial cells also show an important ecto-NAD+ glycohydrolase activity which is characteristic of phagocytic cells. We noted that the phagocytic capacity and ecto-NAD+ glycohydrolase of these cells were correlated and increased notably during the in vitro culture. Microglia cultivated in vitro appear to be a good model to study the activation of phagocytic properties in the central nervous system and corresponding modulation by natural or pharmacological immunomodulators.

Animals↗
PubMed1988

Phagocytosis of polystyrene latex beads by rat brain microglia cell cultures is increased by treatment with gangliosides.

Cultures of microglial cells were prepared from primary rat brain cultures of astrocytes. Microglia appeared under two main forms: ameboid and ramified. Only the former were capable of ingesting opsonized latex particles of 1 and 6 micron; while the latter, which appeared later in culture, were not capable of phagocytosis. When gangliosides (10(-6) M), which are known for their neuronotrophic capacity in vitro, were added to the growth medium (for 20 min) they stimulated the phagocytosis of ameboid microglia 2-fold.

Animals↗
PubMed1987

Rat liver nuclear lipids. Composition and biosynthesis.

A characteristic of rat liver nuclear lipids is their high content in neutral lipids especially of tryglycerides and free fatty acids. These compounds do not arise due to hydrolysis of more complex lipids during the isolation of the nuclei. The neutral lipids fatty acid pattern is more saturated than the phospholipid one. The presence of phosphatidylinositol mono- and diphosphate in nuclei has been confirmed. Nuclei are unable to synthesize de novo phospholipids but are capable of incorporating inorganic phosphate into lipids synthesized via a kinase pathway.

Animals↗
PubMed1987

Adaptation of Zajdela ascitic hepatoma cells to monolayer growth: change in the cell ganglioside pattern.

The Zajdela hepatoma is a transplantable ascitic tumor of the rat, characterized by a very simple ganglioside pattern, GM3 being the main compound. When these cells are adapted to monolayer culture, they undergo a maturation process and the total cellular ganglioside concentration increases progressively; GM2, GM1 and GD3 amounts rose and GD1a accumulated. These modifications in the ganglioside pattern complexity are not affected by the addition of ascitic fluid to the cultures, nor by growth in serum free, hormone-supplemented medium. They are totally reversible when the cultured hepatoma cells are reinjected into a rat and developed an ascitic tumour. Cell growth control and adhesion processes could be related to the maturation process of these hepatoma cells growing in monolayer, which may constitute a convenient model for further investigations on the regulation of membrane glycolipid composition by the external environment.

Adaptation, Biological↗
PubMed1986

Plasma membrane lipids of bovine adrenal chromaffin cells.

The lipid composition of plasma membranes isolated from bovine adrenal chromaffin cells has been determined. Choline and ethanolamine phosphatides were predominant; the level of lyso compounds was very low. The amount of cholesterol and the cholesterol/phospholipid molar ratio was low compared to those of the other subcellular fractions of chromaffin cells. A complex pattern of neutral glycolipids was observed in contrast to that of gangliosides.

Adrenal Medulla↗
PubMed1986

Triiodothyronine receptors in developing mouse neuronal and glial cell cultures and in chick-cultured neurones and astrocytes.

The evolution of L-triiodothyronine (T3) receptors was studied in developing cultures of cells dissociated from cerebral hemispheres of 14-day-old mouse embryos, which present successive distinct periods of cell proliferation and/or maturation. These periods are characterized essentially as neuronal from 1 to 12 days in vitro (DIV) and glial between 12 and 60 DIV. Furthermore myelin-related membranes are produced in this culture system. Binding capacities of the T3 nuclear receptors increased from 1 to 6 DIV, when it reached a maximum (16 fmol/100 micrograms DNA). A similar increase of the DNA content of the cell was observed until 8 DIV. Thereafter a sharp fall of receptor concentration leading to a 5-fold decrease in the binding capacity occurred until day 15, a period at which neurones disappeared from the cultures. From 25 to 50 DIV (coinciding with the glial period), the concentration of receptor remained more or less constant (1-2 fmol/100 micrograms DNA). In parallel, the DNA content did not vary greatly between 30 and 50 DIV. Scatchard analysis revealed the presence of a single class of receptors at 6 and 20 DIV, representative of 'neuronal' and 'glial' periods, respectively. The equilibrium dissociation constant (Kd) of the nuclear receptor from cells at 6 DIV (2 X 10(-10) M) was similar to that found at 20 DIV. These results were confirmed using pure cultured neurones and astrocytes prepared from embryonic chick brain. The effect of T3 on the cellular gangliosides used as an index of neuronal cell maturation, and on cerebroside sulfotransferase (CST), an enzyme involved in the production of myelin sulfatides, was studied to determine a possible correlation between the binding capacity of the T3 nuclear receptor and the response of the cultured cells to thyroid hormone. Our data demonstrate that T3 had no significant effect either on the content of gangliosides or on their developmental pattern, while it increased the level of CST activity by 75% between 18 and 25 DIV. These results show that, although the concentration of T3 receptors per 100 micrograms DNA in glial cells was lower than that in neurones, it was nevertheless sufficient to elicit a response in oligodendrocytes.

Animals↗
PubMed1986

Evidence for sialidase activity in K 562 cells: inhibition by adriamycin treatment.

Sialidase activity has been studied in the human erythroleukemia K 562 cell line grown in vitro. The total sialidase activity was determined using disialoganglioside GD1a and fetuin as exogenous substrates. The enzymatic activity was stimulated by 0.08% Triton X-100 and reached the highest level at pH 4.0. Results obtained showed that gangliosides are hydrolysed more extensively than glycoproteins by K 562 sialidases. This finding could suggest that endogenous gangliosides may be the main source of metabolically available sialic acid in K 562 cell line. After treatment of K 562 cells by Adriamycin (40 nM), a potent anticancer drug, sialidase activity decreased by 40% as compared to control cells. This decrease occurs early during the first day of incubation with Adriamycin. This inhibition of sialidase activity could explain previous results obtained in our laboratory which show an enhanced sialylation of the membrane glycoconjugates after Adriamycin treatment.

Cell Line↗
PubMed1985

Brain myelin of genetically obese mice.

Brain myelin was studied in genetically obese (ob/ob) mice and compared with that of normal (+/+) mice from the same strain. The brain from obese mice had a significantly lower amount of myelin, and marked changes in the fatty acid composition of myelin were observed. In contrast, the myelin cholesterol: phospholipid: galactolipid and the cerebroside: sulfatide molar ratios and also the phospholipid composition were normal. 2',3'-Cyclic nucleotide 3'-phosphohydrolase (CNP) and UDP-galactose ceramide galactosyltransferase (CGalT) enzymatic activities were normal, and 3'-phosphoadenosine 5'-phosphosulfate (PAPS): cerebroside sulfotransferase (CST) was only slightly decreased. Cholesterol esters were not present in the mutant. These results indicate that brain myelination is affected in obese mutant mice.

2',3'-Cyclic Nucleotide 3'-Phosphodiesterase↗
PubMed1985

[Isolation and characterization of a new cell line of spontaneously transformed astrocytes of the rat brain].

A new cell line of transformed astrocytes was obtained from primary new born rat brain cultures. rat brain cultures. These transformed cell line possess a normal karyotype, a doubling time of 17-24 hrs. and astrocyte specific protein marquers: glial fibrillar acidic protein (GFA) and glutamine synthetase. The ganglioside pattern is more differentiated than that of other known astrocyte lines.

Animals↗