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Biomedical subjects

A Nouvelot

Publications and source records attributed to A Nouvelot.

At least 19 recordsLinked to original sources
PubMed2002

[Protection of synaptosomal polyunsaturated fatty acids from by extract of Ginkgo biloba-EGb 761].

Previous studies have demonstrated that ascorbic acid associated with ferrous ions induced deleterious effects on several targets or functions of striatal dopaminergic nerve endings, which were prevented by the Ginkgo biloba extract EGb 761. The present study attempted to assess whether a peroxidation of polyunsaturated fatty acids of their membranes could be associated with (or even responsible for) these alterations. Synaptosomes were prepared from mice striata. Their 1 h incubation with ascorbic acid (0.1 mM) resulted in a marked increase (+300%) of thiobarbituric acid reactive substances, that roughly are considered to correspond to the malondialydehyde level. Under these conditions the level of polyunsaturated fatty acids, measured by gas chromatography, decreased by -23% whereas the level of saturated fatty acids was not modified. Both the increase in thiobarbituric acid reactive substances and the decrease in polyunsaturated fatty acids were prevented by EGb 761 (10 micro g/ml). Similarly, the increase of TBARS was prevented by the vitamin E analogue trolox C (0.1mM) as well as by the ferrous ions chelating agent desferrioxamine (0.1mM). These data suggest that the polyunsaturated fatty acids peroxidation could be the origin of previously reported synaptosomal alterations induced by ascorbic acid/Fe(2 +).

Animals↗
PubMed2000

Expression of receptors for complement anaphylatoxins C3a and C5a following permanent focal cerebral ischemia in the mouse.

In the present study, we have examined the expression of anaphylatoxin C3a and C5a receptors (C3aR and C5aR) at the mRNA and protein levels in ischemic brain tissues following permanent middle cerebral artery (MCA) occlusion in the mouse. C3aR and C5aR mRNAs were both detected by semiquantitative reverse transcription and polymerase chain reaction (RT-PCR) and the cellular distribution of each receptor was analyzed by immunohistochemistry. Significant increases in the expression of C3aR and C5aR mRNAs in the ischemic cortex were observed; the expression of both reached a peak at 2 days after MCA occlusion (4.3- and 3.4-fold increases, respectively, compared with nonoperated control cortical samples; P < 0.00625 with Bonferroni's correction, n = 3). C3aR and C5aR stainings were found constitutively on neurons and astrocytes. In ischemic tissues, we observed that C3aR and C5aR were expressed de novo on endothelial cells of blood vessels, at 6 h and 2 days after MCA occlusion, respectively. C3aR and C5aR immunostaining was increased in macrophage-like cells and reactive astrocytes 7 days postocclusion. C3a and C5a may play an important role in promoting inflammatory and/or repair processes in the ischemic brain by regulating glial cell activation and chemotaxis.

Animals↗
PubMed2000

Ischemia-induced interleukin-6 as a potential endogenous neuroprotective cytokine against NMDA receptor-mediated excitotoxicity in the brain.

In the brain, the expression of the pleiotropic cytokine interleukin-6 (IL-6) is enhanced in various chronic or acute central nervous system disorders. However, the significance of IL-6 production in such neuropathologic states remains controversial. The present study investigated the role of IL-6 after cerebral ischemia. First, the authors showed that focal cerebral ischemia in rats early up-regulated the expression of IL-6 mRNA, without affecting the transcription of its receptors (IL-6Ralpha and gp130). Similarly, the striatal injection of N-methyl-D-aspartate (NMDA) in rats, a paradigm of excitotoxic injury, activated the expression of IL-6 mRNA. The involvement of glutamatergic receptor activation was further investigated by incubating cortical neurons with NMDA or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA). NMDA and ionomycin (a calcium ionophore) up-regulated IL-6 mRNA, suggesting that neurons may produce IL-6 in response to the calcium influx mediated through NMDA receptors. The potential role of IL-6 during ischemic/excitotoxic insults was then studied by testing the effect of IL-6 against apoptotic or excitotoxic challenges in cortical cultures. IL-6 did not prevent serum deprivation- or staurosporine-induced apoptotic neuronal death, or AMPA/kainate-mediated excitotoxicity. However, in both mixed and pure neuronal cultures, IL-6 dose-dependently protected neurons against NMDA toxicity. This effect was blocked by a competitive inhibitor of IL-6. Overall, the results suggest that the up-regulation of IL-6 induced by cerebral ischemia could represent an endogenous neuroprotective mechanism against NMDA receptor-mediated injury.

Animals↗
PubMed1999

Focal cerebral ischaemia induces a decrease in activity and a shift in ouabain affinity of Na+, K+-ATPase isoforms without modifications in mRNA and protein expression.

In a mouse model of focal cerebral ischaemia, we observed after 1 h of ischaemia, that the total Na+, K+-ATPase activity was decreased by 39.4%, and then did not vary significantly up to 6 h post-occlusion. In the sham group, the dose-response curves for ouabain disclosed three inhibitory sites of low (LA), high (HA) and very high (VHA) affinity. In ischaemic animals, we detected the presence of only two inhibitory sites for ouabain. After 1 h of permanent occlusion, the first site exhibited a low affinity while the second site presented an affinity intermediate between those of HA and VHA sites, which evolved after 3 h and 6 h of occlusion towards that of the VHA site. The presence of only two ouabain sites for Na+, K+-ATPase after ischaemia could result from a change in ouabain affinity of both HA and VHA sites (alpha2 and alpha3 isoforms, respectively) to form a unique component. Irrespective of the duration of ischaemia, the smaller activity of this second site accounted entirely for the loss in total activity. Surprisingly, no modifications in protein and mRNA expression of any alpha or beta isoforms of the enzyme were observed, thus suggesting that ischaemia could induce intrinsic modifications of the Na+, K+-ATPase.

Animals↗
PubMed1999

Ginkgo biloba extract (EGb 761) protects Na,K-ATPase activity during cerebral ischemia in mice.

Neuroprotective drugs such as Ginkgo biloba extract (EGb 761) could prevent the ischemia-induced impairment of the Na,K-ATPase activity. In this study, Na,K-ATPase activity and expression, contents in fatty acids and malondialdehyde, an index of lipoperoxidation, were compared in the ipsilateral (ischemic) and the contralateral (unlesioned) cortices after 1 h of unilateral focal cortices cerebral ischemia in the mouse. EGb 761 (110 mg/kg) was administered daily to half of the animals for 10 days before ischemia. Ischemia significantly reduced Na,K-ATPase activity by about 40% and increased malondialdehyde content; EGb 761 pretreatment abolished these effects. The free radical scavenger properties of EGb 761 are a potential mechanism by which Na,K-ATPase injury and lipoperoxidation are prevented.

Animals↗
PubMed1999

Early neurological and neuropsychological development of the preterm infant and polyunsaturated fatty acids supply.

OBJECTIVES: To compare the early neurological maturation of premature newborns (PT) fed breast milk (BM) or a formula containing only 18-carbon polyunsaturated fatty acids (PUFA) (A) or enriched with long chain (LC) PUFA (B). METHODS: PT enrolled the 2nd day of enteral feeding (D0) were fed BM (n = 15; 4 dropped out) or randomly assigned to A (n = 11; 2) or B (n = 14; 1) for at least 30 days (D30). Auditory and visual evoked potentials (EPs) and nerve conduction velocity (NCV) and plasma and red blood cell (RBC) phospholipid composition were determined at D0 and D30. No difference was found between groups for the D0-D30 changes in EP parameters. The maturation of motor NCV was slower in the B group than in the two other groups. In plasma, the changes were higher in B than in the BM and A groups for linoleic acid (P < 0.05), in BM versus B group for arachidonic acid (P < 0.02). In RBC, formula groups displayed higher linoleic acid level than the BM group (P < 0.05). No difference was found between groups for the changes in arachidonic and docosahexaenoic acids. CONCLUSIONS: A balanced supply of n-6 and n-3 PUFA without addition of LC-PUFA allowed an adequate early maturation of the central nerve system. The effects of LC-PUFA on the maturation of NCV remain to be confirmed.

Double-Blind Method↗
PubMed1999

A potential role for erythropoietin in focal permanent cerebral ischemia in mice.

The present study describes, for the first time, a temporal and spatial cellular expression of erythropoietin (Epo) and Epo receptor (Epo-R) with the evolution of a cerebral infarct after focal permanent ischemia in mice. In addition to a basal expression of Epo in neurons and astrocytes, a postischemic Epo expression has been localized specifically to endothelial cells (1 day), microglia/macrophage-like cells (3 days), and reactive astrocytes (7 days after occlusion). Under these conditions, the Epo-R expression always precedes that of Epo for each cell type. These results support the hypothesis that there is a continuous formation of Epo, with its corresponding receptor, during the active evolution of a focal cerebral infarct and that the Epo/Epo-R system might be implicated in the processes of neuroprotection and restructuring (such as angiogenesis and gliosis) after ischemia. To support this hypothesis, a significant reduction in infarct volume (47%; P < 0.0002) was found in mice treated with recombinant Epo 24 hours before induction of cerebral ischemia. Based on the above, we propose that the Epo/Epo-R system is an endogenous mechanism that protects the brain against damages consequent to a reduction in blood flow, a mechanism that can be amplified by the intracerebroventricular application of exogenous recombinant Epo.

Animals↗
PubMed1999

Dietary fish oil promotes positive inotropy of ouabain in the rat heart.

We tested the hypothesis that a fish oil (FO) diet promotes positive inotropy of ouabain without increased toxicity. For 2 mo, two groups of adult male rats were fed 1) a regular food diet supplemented with dietary long-chain polyunsaturated fatty acid from FO or 2) a regular food diet (control). The responsiveness to ouabain was evaluated for the two groups in Langendorff-perfused hearts, by (31)P nuclear magnetic resonance spectroscopy, and on purified membrane-bound Na-K-ATPase. The maximum positive inotropy achieved with ouabain was nearly two times higher in the FO than in the control group and was not associated with significant changes in energetics. Alteration of function and energetic metabolism and inhibition of Na-K-ATPase in response to 3 x 10(-4) M ouabain were delayed in the FO group. This study demonstrates that dietary FO, by a cardiac membrane incorporation of n-3 polyunsaturated fatty acid, promotes positive inotropy of ouabain without toxicity and changes in cardiac metabolism.

Animals↗
PubMed1999

Longitudinal multicentric study of plasma and red blood cell fatty acids and lipids in preterm newborns fed human milk.

The present multicentric study (three centers) deals with the values of plasma and red blood cell fatty acids obtained in a group of 18 preterm newborns after 2 days (D2), 15 days (D15) and 5 weeks (37th week postconception: 37th wk) of human milk feeding. Analytical methods were randomized between the three centers and quality control was evaluated by repeated analysis of reference samples. 20:4 n-6 varied from 10.71 +/- 1.58% to 9.51 +/- 1.65 and 10.10 +/- 1.42% in plasma phospholipids and from 16.59 +/- 3.30% to 14.68 +/- 3.14 and 18.24 +/- 4.09% in red blood cell phosphatidylethanolamine (RBC-PE) at D2, D15 and 37th wk, respectively, contrasting with the important rise of the precursor (18:2 n-6) in all the fractions studied. In RBC-PE, 22:6 n-3 significantly declined from 3.52 +/- 1. 03% at D2 to 2.56 +/- 0.83% at D15 (p < 0.02) and recovered its initial level at 37th wk (4.08 +/- 1.94%). The recovery of long chain polyunsaturated fatty acid homeostasis at that time was also confirmed by the decline of 16:1 n-7 in cholesterol esters (10.69 +/- 3.92 to 4.32 +/- 2.38%).

Cholesterol↗
PubMed1998

Selective neuronal vulnerability and specific glial reactions in hippocampal and neocortical organotypic cultures submitted to ischemia.

Neurons from cerebral neocortex and hippocampus exhibit a striking difference in vulnerability to transient global ischemia. In order to study the contribution of neuronal connections and neuron-glia interactions to this variation in neuronal vulnerability, we used hippocampal and neocortical cultures submitted to various periods of histotoxic ischemia. Organotypic cultures were exposed at 37 degrees C for 0, 7, 30 and 60 min to a glucose-free NaCN-containing medium. Histological analysis using thionin staining and MAP2 immunostaining showed differences in the temporal profile of neuronal damage in hippocampal and neocortical structures, i.e., in decreasing order, CA1 (7 min) > CA3 and neocortical layers II, III, V, VI (30 min) > DG and neocortical layer IV (60 min). In parallel to the neurodegeneration study, the time course and the regional pattern of microglial and astroglial changes were also examined using GS-B4 isolectin and GFAP as immunohistochemical markers, respectively. The GS-B4 isolectin staining revealed an early (at 7 min for the hippocampus) and a specific microglial activation located in areas undergoing neuronal damage. For both organotypic cultures, astrogliosis occurred later (after 30 min of stress) with no specific regional distribution. Both hippocampal and neocortical cultures submitted to histotoxic ischemia allowed the replication of many of the cellular events observed in response to global ischemia in vivo. These findings support the hypothesis that neuron-neuron connections as well as interactions between neurons and glial cells are essential to reproduce in vitro the selective neuronal vulnerability described in vivo.

Adaptation, Physiological↗
PubMed1998

High protection by grape seed proanthocyanidins (GSPC) of polyunsaturated fatty acids against UV-C induced peroxidation.

The antioxidative effects of grape seed proanthocyanidins (GSPC) were studied in three in-vitro models in which polyunsaturated fatty acids (PUFAs) in aqueous solution and mice liver or brain microsomes were used as oxidative substrates, and UV-C irradiation as the pro-oxidant system. Analysis of UV-C induced lipid peroxidation was carried out by two methods: gas liquid chromatography of residual PUFAs and release of thiobarbituric acid-reactive substances (TBARs) measured by TBA reaction. Results indicate that PUFAs are more radiosensitive when incorporated in single component micelles than in mixed component micelles or microsomes. In every case, PUFA peroxidation was inhibited by low concentrations of GSPC (2 mg/L) while epigallocatecin (EGC) and epigallocatechin gallate (EGCG) monomers, at an equivalent level of epicatechin, exhibited no efficacy in our experimental conditions. This latter effect might be explained by a synergistic action of flavan-3-ol monomers, dimers and oligomers contained in the grape seed extract.

Animals↗
PubMed1998

Evidence of type I and type II transforming growth factor-beta receptors in central nervous tissues: changes induced by focal cerebral ischemia.

The peptides of the transforming growth factor-beta (TGF-beta) family transduce their signal through ligand-induced heteromeric complexes that consist of type I and type II serine/threonine kinases. Both TGF-beta receptors are abundant in many peripheral tissues, but clear evidence of their expression in cortical astrocytes and neurons has not been published so far. In this study, we investigated the expression of type I and type II TGF-beta receptors and their potential ligands (TGF-beta1, TGF-beta2, and TGF-beta3) in the CNS by using RT-PCR and immunohistochemistry. Moreover, to further the study of those cell types that exhibit TGF-beta isoforms and related receptors, we examined through the use of RT-PCR whether cortical neurons and astrocytes in culture express the mRNAs for TGF-betas and their receptors. We show that the three TGF-beta isoform mRNAs are present in the CNS. However, although astrocytes in culture display all three isoforms, neurons in culture express only TGF-beta2. We have demonstrated that both type I and type II TGF-beta receptor mRNAs and proteins are present in the CNS and in cultures of cortical neurons and astrocytes. Thus, TGF-betas may act as autocrine and paracrine signals in the CNS between both neurons and astrocytes via the same receptor systems as those found in peripheral tissues. TGF-beta1 has been shown to be induced following hypoxic-ischemic brain injury and may play a critical role in the pathophysiology of degenerative processes in the CNS. In the present investigation, we confirmed that the expression of TGF-beta1 was increased markedly up until 24 h and thereafter was stable over the first 3 days following permanent occlusion of the middle cerebral artery in mice. However, whereas the expression of the type I TGF-beta receptor was not altered by the ischemic insult, the pattern of the type II TGF-beta receptors was modified dramatically in the ischemic area 3 days after the occlusion. These data show that, even if ligands are present, they may not be able to transduce their signal. Finally, the present study clearly demonstrates that a knowledge of the expression of ligand-specific receptors following brain injury is a fundamental step in clarifying the involvement of cytokines in neurodegenerative diseases.

Activin Receptors, Type I↗
PubMed1998

Alterations of Na,K-ATPase isoenzymes in the rat diabetic neuropathy: protective effect of dietary supplementation with n-3 fatty acids.

Diabetic neuropathy is a degenerative complication of diabetes accompanied by an alteration of nerve conduction velocity (NCV) and Na,K-ATPase activity. The present study in rats was designed first to measure diabetes-induced abnormalities in Na,K-ATPase activity, isoenzyme expression, fatty acid content in sciatic nerve membranes, and NCV and second to assess the preventive ability of a fish oil-rich diet (rich in n-3 fatty acids) on these abnormalities. Diabetes was induced by intravenous streptozotocin injection. Diabetic animals (D) and nondiabetic control animals (C) were fed the standard rat chow either without supplementation or supplemented with either fish oil (DM, CM) or olive oil (DO, CO) at a daily dose of 0.5 g/kg by gavage during 8 weeks. Analysis of the fatty acid composition of purified sciatic nerve membranes from diabetic animals showed a decreased incorporation of C16:1(n-7) fatty acids and arachidonic acids. Fish oil supplementation changed the fatty acid content of sciatic nerve membranes, decreasing C18:2(n-6) fatty acids and preventing the decreases of arachidonic acids and C18:1(n-9) fatty acids. Protein expression of Na,K-ATPase alpha subunits, Na,K-ATPase activity, and ouabain affinity were assayed in purified sciatic nerve membranes from CO, DO, and DM. Na,K-ATPase activity was significantly lower in sciatic nerve membranes of diabetic rats and significantly restored in diabetic animals that received fish oil supplementation. Diabetes induced a specific decrease of alpha1- and alpha3-isoform activity and protein expression in sciatic nerve membranes. Fish oil supplementation restored partial activity and expression to varying degrees depending on the isoenzyme. These effects were associated with a significant beneficial effect on NCV. This study indicates that fish oil has beneficial effects on diabetes-induced alterations in sciatic nerve Na,K-ATPase activity and function.

Animals↗
PubMed1997

Changes in ouabain affinity of Na+, K+-ATPase during focal cerebral ischaemia in the mouse.

We investigated the effect of focal cerebral ischaemia on the activity and the affinity of the ouabain sites of Na+,K+-ATPase in the mouse. The Na+,K+-ATPase activity was decreased by 38% as early as 30 min following ischaemia. In the sham group, the dose-response curves for ouabain disclosed three inhibitory states which contribute, respectively, 24.9 +/- 6.7%, 39.1 +/- 7.5% and 36.0% of the total activity (low affinity, LA; high affinity, HA and very high affinity, VHA, respectively). Their computed IC50 values are, respectively: 1.3 X 10(-3) M, 4.5 X 10(-6) M and 2.9 X 10(-9) M. Surprisingly, in ischaemic cortices, only two sites for ouabain were detected. The first site exhibits a LA (IC50 = 2.0 X 10[-4] M) but its relative contribution to the total activity (46.1 +/- 5.2%) is twice that noted for the LA site in non-ischaemic tissues. The second site presents an affinity intermediate between those of HA and VHA sites of the sham group (IC50 = 1.7 X 10[-7] M) and contributes 53.9% to the total activity. Loss in the specific activity of the second site explains that of the total activity. The most likely explanation in the presence of only two ouabain sites of Na+,K+-ATPase following ischaemia may be a change in ouabain affinity of alpha2 and/or alpha3 isoforms, as the presence of all three alpha isoforms has been observed by Western blotting. These results suggest that ischaemia induces intrinsic modifications in Na+,K+-ATPase which result from perturbations in membrane integrity and/or association of the alpha isoforms of this enzyme.

Animals↗
PubMed1997

Plasma superoxide dismutase and glutathione peroxidase activity in sporadic amyotrophic lateral sclerosis.

To determine the possible role of oxydative stress in the pathology of amyotrophic lateral sclerosis (SALS), we measured the plasma activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX), together with GPX and malone dialdehyde (MDA, a marker of lipoperoxydation) plasma concentrations in a sample of 21 SALS patients and 7 normal control (NC) subjects. MDA concentration and SOD activity were significantly higher, whereas GPX activity was significantly lower in SALS patients than in NC. Increased MDA concentration provides indirect confirmation of excess lipoperoxydation. Increased plasma SOD activity might reflect the involvement of extra-cellular SOD (SOD3), a hitherto unreported finding in SALS. Impaired GPX activity, which has already been found in red blood cells and brain tissue of SALS patients, might play a part in the pathogenesis of this disease.

Adult↗
PubMed1997

Alteration of Na,K-ATPase isoenzymes in diabetic cardiomyopathy: effect of dietary supplementation with fish oil (n-3 fatty acids) in rats.

Diabetic cardiomyopathy has been associated with a decrease in Na,K-ATPase activity and expression, as well as alterations in membrane lipid composition. The aim of this study was twofold: 1) to document in rats the effect of streptozotocin-induced diabetes on myocardial Na,K-ATPase and fatty acids, and 2) to evaluate the potential effect of a dietary supplementation with fish oil (n-3 fatty acids) on the streptozotocin-induced changes. Assays were performed in purified cardiac plasma membranes to determine Na,K-ATPase activity, expression of the different alpha- and beta-subunits of Na,K-ATPase, and the fatty acid content of total phospholipids. Relative abundance of the mRNAs encoding the alpha 1, alpha 2 and beta 1 isoforms was studied by Northern blot analysis. Results demonstrated that diabetes significantly decreased activities of alpha 1 and alpha 2 isoforms and mRNA levels of alpha 2 and beta 1 isoforms, and, at the protein level, increased alpha 1-isoforms and decreased both alpha 2- and beta 1-isoforms. Changes in fatty acid content of the membrane were consistent with inhibition of desaturase. Fish-oil supplementation produced an increase in membrane incorporation of eicosapentaenoic acid. It also increased the level of beta 1-isoforms and restored the activity of the alpha 2-isoenzyme without significant changes in the level of alpha 1- and alpha 2-isoforms. Northern blot analysis showed no effect of fish oil supplementation. Experimental diabetes and prevention by the fish oil rich (n-3 fatty acids) diet induced specific effects on the activity and expression of alpha and beta Na,K-ATPase subunit isoforms. These studies suggest that fish oil therapy may be effective in preventing some of the adverse consequences of diabetes.

Analysis of Variance↗