Biomedical subjects

D Montaudon

Publications and source records attributed to D Montaudon.

At least 19 recordsLinked to original sources

PubMed2006

Unr, a cytoplasmic RNA-binding protein with cold-shock domains, is involved in control of apoptosis in ES and HuH7 cells.

Unr (upstream of N-ras) is a cytoplasmic RNA-binding protein involved in the regulation of messenger RNA stability and internal initiation of translation. We have used Unr-deficient murine embryonic stem (ES) cells to analyse Unr role in cell proliferation and response to stress. Disruption of both unr gene copies had no effect on ES cell proliferation. However, after ionizing radiation (IR), clonogenic survival of unr(-/-) ES cells was approximately 3-fold enhanced as compared to unr(+/+) cells. We further determined that IR-induced apoptosis was decreased in unr(-/-) ES cells, and that reintroduction of the unr gene in unr(-/-) cells restored normal IR-induced apoptosis. Three pro-apoptotic genes, p53, caspase-3 and Gadd45gamma, were downregulated in unr(-/-) ES cells, indicating that Unr, as other cytoplasmic RNA-binding proteins, regulates a complex genetic program, promoting cell death after IR. In contrast, in the human hepatoma cell line HuH7, Unr knockdown using unr-specific small interfering RNAs induced apoptosis, both in untreated and gamma-irradiated cells. Thus, our results establish that Unr acts as a positive or negative regulator of cell death, depending on the cell type. Manipulating the level of Unr may constitute a specific approach to sensitize cancer cells to anticancer treatments.

Animals↗

PubMed2005

[Fecal elastase-1: a useful test in pediatric practice].

AIM: To study fecal elastase-1 (E1F) and chymotrypsin (ChT) in stools for the diagnosis of pancreatic insufficiency in pediatric practice. MATERIALS AND METHODS: E1F and ChT were measured in stools of 198 children divided in 3 groups: 49 children without any digestive disease (group A), 71 children with pancreatic diseases (group B), and 78 children with non-pancreatic digestive diseases (group C). RESULTS: In group B, E1F values were very low in 64 children and normal in 7 children without pancreatic insufficiency (6 children with cystic fibrosis and 1 with chronic pancreatitis). ChT values were normal in children without pancreatic insufficiency but also in half of children treated with pancreatic enzymes. Decreased E1F values were seen in 2 children (4%) in the group A and 22 children (28%) in the group C, especially those with acute gastroenteritis or celiac disease. CONCLUSION: E1F is a simple, non-invasive, useful tool for the diagnosis of pancreatic insufficiency in children with growth failure or chronic diarrhea, and those with cystic fibrosis. Nevertheless, low values may be found in diseases with villous atrophy or very liquid stools.

Adolescent↗

PubMed2001

Effects of the combination of camptothecin and doxorubicin or etoposide on rat glioma cells and camptothecin-resistant variants.

From the rat C6 glioma cell line in culture, we selected camptothecin-resistant variants by growth in the presence of increasing amounts of this drug (C6(CPT10), C6(CPT50)and C6(CPT100), growing respectively with 10, 50 and 100 ng ml(-1)camptothecin). The degree of resistance to camptothecin ranged between 15-fold (C6(CPT10)) and 30-fold (C6(CPT50)and C6(CPT100)). The C6(CPT10)cell line presented a collateral sensitivity to etoposide (3.6-fold), while the C6(CPT50)and C6(CPT100)cell lines were cross-resistant to etoposide (1.8-fold) The resistant lines were characterised by a two-fold reduced content and catalytic activity of topoisomerase I, and C6(CPT50)and C6(CPT100)presented a significant increase in topoisomerase IIalpha content and catalytic activity and a marked overexpression of P-glycoprotein. We explored the cytotoxicity of combinations of a topoisomerase I inhibitor (camptothecin) and a topoisomerase II inhibitor (doxorubicin or etoposide) at several molar ratios, allowing the evaluation of their synergistic or antagonistic effects on cell survival using the median effect principle. The simultaneous combination of camptothecin and doxorubicin or etoposide was additive or antagonistic in C6 cells, slightly synergistic in the C6(CPT10)line and never more than additive in the C6(CPT50)and C6(CPT100)cell lines. The sequential combination of doxorubicin and camptothecin gave additivity in the order camptothecin --> doxorubicin and antagonism in the order doxorubicin --> camptothecin. Clinical protocols combining a topoisomerase I and a topoisomerase II inhibitor should be considered with caution because antagonistic effects have been observed with combinations of camptothecin and doxorubicin.

Animals↗

PubMed2001

Procalcitonin: a new marker of inflammation in haemodialysis patients?

BACKGROUND: Although procalcitonin (PCT) has been described as a new marker of infection and inflammation, it has not been extensively studied in dialysis patients. METHODS: We measured plasma PCT levels in 62 patients on maintenance haemodialysis (30 M/32 F, age 61.8+/-17.1 years, on dialysis for 75+/-93 months, 12 h/week, with a Kt/V of 1.53+/-0.31, high-flux membrane being used in 25 patients and low-flux in 37 patients, without reuse). PCT levels were compared with other markers of inflammation and nutritional status, including C-reactive protein (CRP), fibrinogen, interleukin-6 (IL-6), leukocytes, urea, creatinine, albumin, prealbumin, normalized protein catabolic rate (nPCR), haemoglobin (Hb), and epoetin (Epo) doses. Patients were divided into different groups according to their infectious and vascular status. RESULTS: PCT plasma levels before dialysis were 0.69+/-0.81 ng/ml. Fifty-seven per cent of PCT values were higher than the upper normal limit of 0.5 ng/ml. CRP and PCT concentrations were high in patients with a current infection, while IL-6 values were elevated in all patients regardless of infection status. Plasma CRP concentrations before dialysis were 21.2+/-31.4 mg/l, and 70% of these values were higher than the upper normal limit. CRP, PCT, IL-6, and fibrinogen were positively correlated with each other and were all negatively correlated with albumin. Prealbumin was negatively correlated with CRP and IL-6. In the 43 patients treated with Epo, haemoglobin was negatively correlated with IL-6 and Epo doses, while Epo doses were positively correlated with IL-6 but not with CRP or PCT. The 23 patients with both elevated PCT and CRP plasma levels had the lowest Hb, albumin, and prealbumin concentrations, and the highest fibrinogen concentrations and Epo doses. CONCLUSION: PCT in haemodialysis patients is positively correlated with currently used markers of inflammation such as CRP and fibrinogen, and negatively correlated with markers of nutritional status such as albumin. The concomitant elevations in PCT and CRP could be more sensitive in the evaluation of inflammation than each marker separately.

Aged↗

PubMed1998

Doxorubicin-induced alterations of c-myc and c-jun gene expression in rat glioblastoma cells: role of c-jun in drug resistance and cell death.

We studied the effect of doxorubicin on the expression of c-myc and c-jun in the rat glioblastoma cell line C6 and its doxorubicin-resistant variant C6 0.5, at equitoxic exposures. For quantitation, the mRNA levels of these oncogenes were related to those of two domestic genes, beta-actin and glyceraldehyde phosphate dehydrogenase. After a transient overexpression of the genes during the first hour of incubation, there was a selective, dose-dependent down-regulation of both genes by doxorubicin in the sensitive cells. In the resistant cell line, c-myc expression was also decreased in response to doxorubicin incubation, but the expression of c-jun remained unchanged over the whole range of concentrations. In contrast, vincristine had no effect on the amounts of c-myc and c-jun mRNAs in either line. The effect of doxorubicin on the mRNA levels of c-jun was also observed on the JUN proteins by immunoblotting, but the MYC protein levels remained unchanged upon doxorubicin treatment. There was a significant correlation between the levels of c-myc and c-jun gene expression and the degree of growth inhibition induced by doxorubicin. In addition, doxorubicin induced a fragmentation of DNA in sensitive cells, but not in resistant cells, thus revealing a resistance to apoptosis in this line. Doxorubicin-induced cell death did not appear to be mediated by p53 in either cell line.

Animals↗

PubMed1997

Differential stabilization of topoisomerase-II-DNA cleavable complexes by doxorubicin and etoposide in doxorubicin-resistant rat glioblastoma cells.

Using the technique of alkaline filter elution, we have evaluated the DNA damage induced by doxorubicin and etoposide in a rat glioblastoma cell line, C6, and its doxorubicin-selected resistant variant, C6 0.5. DNA damage paralleled drug-induced cytotoxicity, but it appeared that the same DNA damage generated much less cytotoxicity in resistant cells than in sensitive ones, resistant cells being able to tolerate more DNA damage than sensitive cells. We have then quantified the doxorubicin- and etoposide-induced complexes between topoisomerase II (topoII) DNA with the technique of SDS/KCl precipitation. Etoposide produced a concentration-dependent increase in topoII-DNA complexes, which was higher in resistant cells at equitoxicity, just as was DNA damage. In contrast, doxorubicin-induced topoII-DNA complexes, which were much less abundant than those induced by etoposide, were not differently produced in sensitive and resistant cells. This indicates that the DNA damage occurring in resistant cells at high doxorubicin concentrations might originate from source other than topoII-DNA complex formation. When verapamil was added during drug exposure, it restored doxorubicin intracellular accumulation to the level reached in sensitive cells, partially reversed both doxorubicin and etoposide resistance, increased the formation of etoposide-induced topoII-DNA complexes, but not those induced by doxorubicin. Immunoblot analysis of topoII as well as the measure of its catalytic activity in nuclear extracts revealed a quantitative defect of this enzyme in the resistant line. When inhibiting this activity by doxorubicin and etoposide, we observed that the concentrations of etoposide required for a given inhibition of kinetoplast DNA decatenation are much higher that those of doxorubicin. The topoII extracted from both cell lines is, therefore, much more sensitive to doxorubicin than to etoposide, but no difference in drug sensitivity was evident between sensitive and resistant cells, indicating that no qualitative alteration in topoII catalytic activity was likely to occur.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1990

Development of mechanisms of protection against oxidative stress in doxorubicin-resistant rat tumoral cells in culture.

We have compared some mechanisms involved in the defense against doxorubicin-induced free radical damage in rat hepatoma and glioblastoma cell lines and their doxorubicin-resistant variants presenting an overexpression of the multidrug resistance gene. Immediate in vivo production of malondialdehyde was minor and was not different in sensitive and resistant cells. Alpha-tocopherol was undetectable in all cell lines. Glutathione levels were not different in sensitive and resistant cells and these levels did not vary upon doxorubicin treatment. Resistant cells exhibited either a 50% decrease (hepatoma) or a 25% increase (glioblastoma) of glutathione-S-transferase activity. Glutathione reductase presented no important change upon acquisition of resistance. In contrast, selenium-dependent glutathione peroxidase activity was consistently 2-6-fold increased in the resistant cells, which suggests a magnification of protection mechanisms against hydroxyle radical formation from H2O2 in resistant cells. Depletion of glutathione levels by buthionine sulfoximine sensitized hepatoma resistant cells to doxorubicin, but had no effect on doxorubicin cytotoxicity to glioblastoma cells.

Animals↗

PubMed1988

Alteration of ganglioside composition and metabolism in doxorubicin-resistant rat tumoral cells.

We have investigated the ganglioside levels, composition and metabolism in two lines of doxorubicin-resistant cells and in the corresponding wild strains, the C6 rat glioblastoma and the HTC rat hepatoma. The only ganglioside present was GM3, and its level was increased 2-fold in C6 resistant cells and decreased nearly 2-fold in HTC resistant cells. A decrease of cytidine 5'-monophospho-N-acetylneuraminic acid:galactosylglucosylceramide sialyltransferase activity was observed in both resistant lines as compared to sensitive ones, and could not, therefore, explain the increase in the GM3 level observed in the C6 resistant line. Alterations of acid neuraminidase activity were also observed; a 5-fold decrease was noticed in the C6 resistant line and could account for the increase in the GM3 level observed in these cells; in contrast, a 2-fold increase of acid neuraminidase activity was noticed in the HTC resistant cells: together, with reduced synthesis, it could explain the decrease in the GM3 level observed in these cells. No alterations of exogenous ganglioside transport was exhibited by the C6 resistant cells.

Animals↗

PubMed1986

Fluorescence anisotropy of kidney lipids and membranes of a hibernating mammal.

The fluorescence anisotropy of lipids and membranes isolated from kidneys of European hamsters (Cricetus cricetus L.) has been estimated using 1,6-diphenyl-1,3,5-hexatriene as a probe. We have compared in this study the results obtained for two critical periods for a hibernator: winter (torpid state), and summer (active state). The differences were of very low magnitude. A slight increase in anisotropy was noticed in the kidney lipids and microsomal membrane preparations from torpid animals. In contrast, a small decrease in anisotropy was observed in the microsomal lipid extracts of torpid animals. A difference in triglyceride content of winter and summer total kidney lipids was detected, as well as a difference in microsomal protein content between winter and summer membrane preparations. It is hypothesized that the latter observations may explain why the behavior of kidney total lipids and microsomal preparations were different from that presented by kidney microsomal lipids in respect to fluorescence anisotropy. Therefore, only a little, if any, homeoviscous adaptation is exhibited by kidney membranes during hibernation of this mammal.

Animals↗

PubMed1986

Fatty acid composition transport and metabolism in doxorubicin-sensitive and-resistant rat glioblastoma cells.

We have studied the lipid composition and the acyl group composition, transport, and metabolism of doxorubicin-sensitive and -resistant rat glioblastoma cells in monolayer cultures (C6 clone). No difference in lipid composition was evidenced; the acyl group composition was, in contrast, highly modified in resistant cells, and these modifications appeared progressively during the acquisition of the resistance. Resistant cells were characterized by a decrease of n-9 eicosatrienoic acid and by a 2-3-fold increase of the proportions of the polyunsaturated fatty acids of the n-6 and n-3 families, especially arachidonic acid and n-3 docosahexaenoic acid. These differences were probably due to a 2-fold increase of the uptake of fatty acids by resistant cells as compared to sensitive cells, this increase allowing the suppression of an essential fatty acid deficiency. Only small changes in the transformations of 16 and 18-carbon atoms' fatty acids to higher analogues were evidenced. A small reduction of the desaturation of stearic acid to oleic acid and of linoleic acid to arachidonic acid was the main characteristic of resistant cells; these differences can be explained as a consequence of the suppression of the essential fatty acid deficiency.

Animals↗

PubMed1986

Fluorescence anisotropy of cell membranes of doxorubicin-sensitive and -resistant rodent tumoral cells.

We have studied the plasma membrane fluidity of rat C6 glioblastoma cells and simian virus 40-transformed mouse liver cells in culture that had been rendered resistant to doxorubicin. This was done by the evaluation of fluorescence anisotropy of two probes; diphenylhexatriene was used on membrane microsomal fractions, and trimethylammonium-diphenylhexatriene was used on whole cell suspensions as a plasma membrane-specific probe since it does not enter the cells. A higher degree of membrane fluidity was exhibited with both techniques by doxorubicin-resistant glioblastoma cells as compared to the doxorubicin-sensitive strain, but in the transformed liver cells no such alteration was seen in the physical properties of their plasma membranes. A higher degree of acyl group unsaturation was noticed in the glioblastoma cells but not in the transformed liver cells upon acquisition of doxorubicin resistance. A similar simultaneous increase in acyl group unsaturation and membrane fluidity can be obtained easily by growing the sensitive cells with a medium supplemented with exogenous polyunsaturated fatty acids. This alteration does not modify the sensitivity of the cells to doxorubicin. We conclude from our work that the increase in membrane fluidity, which is frequently associated with drug resistance, is neither necessary nor sufficient for the expression of the resistance. The reason for a link between cell resistance to doxorubicin and plasma membrane fluidity remains to be found.

Animals↗

PubMed1985

Incorporation and turnover of phospholipid precursors in normal and tumoral glial cells in culture.

The incorporation and turnover of phospholipid precursors in cultured normal and tumoral glial cells was investigated during the plateau phase of growth. Glycerol was incorporated similarly by all cell types, and was renewed with a half-life of 19-37 hr. Acetate had a much longer half-life in primary cultures (50-75 hr) than in proliferative tumor cells (20-40 hr). Phosphate had a more rapid turnover rate in primary cultures (25 hr) than in proliferative tumor cells (50 hr). For all precursors, inositol- and choline phosphoglycerides had a faster turnover rate than other phospholipids.

Acetates↗

PubMed1984

Fluorescence polarization study of lipids and membranes prepared from brain hemispheres of a hibernating mammal.

The physical behavior of total lipids, microsomes and microsomal lipids prepared from brain hemispheres of European Hamsters (Cricetus cricetus) was approached by the measure of the fluorescence polarization of the probe 1,6-diphenyl 1,3,5-hexatriene. We compare in this study the results obtained for two critical periods for a hibernator: winter (torpid state) and summer (active state). An increase in fluidity was noticed in the winter lipid and membrane preparations. The difference was however of very low magnitude, suggesting that only the microenvironment of some proteins was involved, rather than the bulk membrane fluidity.

Animals↗

PubMed1983

Incorporation and metabolism of exogenous fatty acids by cultured normal and tumoral glial cells.

We have investigated the transformation of exogenous radioactive free fatty acids by cultured glial cells and their incorporation into complex lipids. The cells were either tumor lines (C6 and NN) or primary cultures from newborn rat hemispheres. The tumor lines could undergo morphological differentiation with dibutyryl cyclic AMP or bromodeoxyuridine. The fatty acid precursors used were palmitic, stearic, oleic, linoleic and linolenic acids. Tumor cells presented a higher incorporation of the precursors in the cell lipid acyl groups than did normal cells. Tumor cells desaturated and/or elongated palmitic, stearic and oleic acid to a higher extent than did normal cells. In contrast, tumor cells transformed linoleic and linolenic acids to their polyunsaturated derivatives to a lower extent than did normal cells. In differentiated tumor cells, these patterns of metabolism were shifted toward the patterns of normal cells. Tumor cells did not exhibit delta 4-desaturase activity, but such activity was restored in the C6 line upon dibutyryl cyclic AMP-induced differentiation. Transformation of linoleic and linolenic acid is likely to proceed through initial delta 6 desaturation. Phospholipids were preferentially labelled with the radioactive fatty acids, and only a little radioactivity was found in the neutral lipid fraction, mainly in diacylglycerols. Each fatty acid precursor label was incorporated in individual phospholipids to a proportion which reflected the typical acyl group composition of glycerophospholipids; we observed high levels of incorporation of palmitic acid and its derivatives into choline glycerophospholipids, and high levels of incorporation of linolenic acid and its derivatives into ethanolamine glycerophospholipids. This pattern was more marked in tumor cells than in normal cells, and the differentiation of tumor cells partially restored the normal pattern, mainly in bromodeoxyuridine-treated NN cells. Both types of differentiation of glial cell lines can be useful as models for the understanding of membrane physiology in normal and tumor cells.

Animals↗

PubMed1982

Changes in lipid composition of the brain cellular membranes of an hibernating mammal during its circannual rhythm.

The lipid composition of whole brain hemispheres and subcellular fractions of European Hamsters (Cricetus cricetus) was investigated at four different periods of the year. 1. No difference was observed in winter between hibernating animals and active animals awake for 24 hr. 2. A slight increase of cholesterol/phospholipid molar ratio was observed in winter. 3. A slight increase of the ratio ethanolamine phosphoglycerides/choline phosphoglycerides was observed in summer and autumn. 4. Some changes in sugar moieties proportions of gangliosides were observed, with a tendency of increased polysialylation in winter. 5. An increase of docosahexaenoic acid was observed in summer, while a slight increase of linoleic acid and of the monounsaturated fatty acids was observed in winter. These changes were mainly exhibited in the synaptosomal fraction. All the changes observed were of very small magnitude and might not be sufficient for the maintenance of a fluid state of membranes during hibernation.

Animals↗

PubMed1981

Phospholipid acyl group composition in normal and tumoral nerve cells in culture.

We have studied the fatty acid composition of total phosphoglycerides from various types of nerve cells in culture. Primary cell cultures were compared with tumoral cell strains. Glial cells exhibited no characteristic pattern when compared to neurons. Tumoral cell phosphoglycerides contained much higher levels of octadecenoic acid and lower levels of C-20 to C-22 polyunsaturated fatty acids than normal cell phosphoglycerides. This observation seems to be a general feature in tumoral cell membranes. It could be of interest in respect to the membrane fluidity of cancer cells.

Animals↗

PubMed1980

[Membrane polyunsaturated fatty acids of mammalian nerve cells in culture].

We have observed some important changes in the distribution of fatty acid classes in cultured nerve cells according to the normal or tumoral origin of the cells: normal cells exhibit higher levels of polyunsaturated fatty acids and lower levels of monounsaturated fatty acids than tumoral cells do. When the culture medium of neuroblastoma cells is supplemented with polyunsaturated fatty acids, these fatty acids are incorporated into membrane phospholipids and some specific alterations of membrane functions occur: modification of the kinetic parameters of ecto-enzyme activities, modification of amino-acid transport characteristics. A brief review of the literature shows that polyunsaturated fatty acids are not essential for cell life in vitro, provided that monounsaturated fatty acids can be present in the cells. Polyunsaturated fatty acids seem therefore play only a regulatory role of some membrane functions.

Amino Acids↗

PubMedDate not supplied

Lipid composition, lipid fluidity and radioresistance of Deinococcus radiodurans and two mutant strains.

The lipid composition of D. radiodurans strain R1 and of two mutant strains has been studied in relation to membrane fluidity and sensitivity to X-ray radiation. No significant difference in the unsaturation degree of fatty acids was found between parental and mutant strains. An important decrease of carbohydrate-containing lipids was observed in the radiosensitive mutant strain. We also observed a higher fluidity in both mutant strains than in the parental one. Modification of membrane lipid fluidity by growing the parental strain at 39 degrees C did not lead to modified radioresistance. These results suggest that a particular chemical composition of the membrane leading to a special lipid phase may be an important parameter in controlling radiosensitivity.

Carbohydrates↗