Biomedical subjects

G Rondouin

Publications and source records attributed to G Rondouin.

At least 19 recordsLinked to original sources

PubMed2003

Neuroprotective activity of antazoline against neuronal damage induced by limbic status epilepticus.

Imidazoline drugs exert neuroprotective effects in cerebral ischaemia models. They also have effects against mouse cerebellar and striatal neuronal death induced by N-methyl-D-aspartate (NMDA) through the blockade of NMDA currents. Here, we investigated the effects of antazoline on NMDA toxicity and current in rat hippocampal neuronal cultures, and on an in vivo model of status epilepticus. In hippocampal cultures, antazoline (30 microM) decreased NMDA-mediated neurotoxicity and also blocked the NMDA current with voltage-dependent and fast-reversible action (inhibition by 85+/-3% at -60 mV). Status epilepticus was induced by injecting pilocarpine (200 nmol) directly into the right pyriform cortex of male adult rats. The rats then received immediately three consecutive i.p. injections at 30-min intervals of either PBS (control group) or antazoline at 10 mg/kg (low-dose group) or at 45 mg/kg (high-dose group). During the 6-h recording, status epilepticus lasted more than 200 min in all groups. In the high-dose group only, seizures completely ceased 1 h after the third injection of antazoline, then started again 1 h later. Rats were killed 1 week later, and Cresyl Violet-stained sections of their brain were analysed for damage quantification. On the ipsilateral side to the pilocarpine injection, pyriform cortex and hippocampal CA1 and CA3 areas were significantly protected in both antazoline-treated groups, whilst prepyriform and entorhinal cortices were only in the high-dose group. On the contralateral side to the pilocarpine injection, only the hippocampal CA3 area was significantly protected in the low-dose group, but all investigated structures were in the high-dose group. In conclusion, antazoline is a potent neuroprotective drug in different models of neuronal primary culture, as previously shown in striatal and cerebellar granule neurons [Neuropharmacology 39 (2000) 2244], and here in hippocampal neurons. Antazoline is also neuroprotective in vivo in the intra-pyriform pilocarpine-induced status epilepticus model.

Animals↗

PubMed2003

Microsurgical intraluminal middle cerebral artery occlusion model in rodents.

OBJECTIVES: Focal brain ischemia induced in rodents by occlusion of the middle cerebral artery (MCA) is a widely used paradigm of human brain infarct. The objective of this study is to compare the effectiveness and reproducibility of MCA filament occlusion model in rats and mice. MATERIALS AND METHODS: A total of 140 rodents (69 rats and 71 mice) were operated. Ninety-five animals were subjected to MCA occlusion; the surgical procedure consisted of introducing an uncoated surgical nylon monofilament into the cervical common carotid artery (CCA) and advancing it intracranially to permanently block blood flow into the right MCA. Forty-five sham-occluded rodents underwent CCA ligation. Surgical success, autopsy confirmed success and mortality rate were evaluated. Effective MCA occlusion was confirmed by the evidence of motor neurological deficit, by histopathology, immunohistochemistry (IHC) and reverse transcriptase-polymerase chain reaction (RT-PCR). IHC was performed in a randomly selected number of animals to detect the protein product of monocyte chemoattractant protein-1. The brain tissue in mice was examined by RT-PCR for the expression of macrophage inflammatory protein-1 alpha mRNA. RESULTS: Surgical success rate was 89% in the rats, significantly lower than that in the mice (100%, P < 0.05). Autopsy confirmed success rate in the rats, 60%, was also significantly different from that in the mice (92.5%, P < 0.001). The operative mortality rate was 4.3% in the rats and 15% in the mice. CONCLUSION: The present study demonstrates that the microsurgical filament occlusion of the MCA can be more successfully performed in mice. The lower rate of success in rats seems to be as a result of the architecture of the carotid canal in this animal. No previous reports, using a considerable number of animals, have compared the feasibility of intraluminal model in the rat with that in the mouse.

Animals↗

PubMed2001

Molecular events involved in neuronal death induced in the mouse hippocampus by in-vivo injection of kainic acid.

Apoptosis results from the activation of a programmed cellular cascade involving several mechanisms. In the present study, we have investigated the implication of three molecules of this cascade, p53, Bax and caspase-3, in neuronal death induced by kainic acid (KA) administration in mouse hippocampus. Using immunocytochemistry, western blot and quantification of enzyme activity, we observed in p53+/+ and p53-/- animals that KA induced neuronal death by both p53-dependent and independent pathways. Moreover, apoptosis (labeled by TUNEL) and the increase of bax and caspase-3 protein expression after the neurotoxic insult appeared to clearly depend on p53 expression.

Animals↗

PubMed2001

Effects of thienylphencyclidine (TCP) on seizure activity and brain damage produced by soman in guinea-pigs: ECoG correlates of neurotoxicity.

The capacity of thienylcyclohexylpiperidine (TCP), a non-competitive blocker of the N-methyl-D-aspartate (NMDA) receptor, to counteract the convulsant, lethal, and neuropathological effects of 2 x LD50 of soman (an irreversible inhibitor of cholinesterase) was investigated in guinea-pigs treated by pyridostigmine and atropine sulphate. The effects of a weak dose of TCP (1 mg/kg) used in the present study globally reproduced those previously obtained with a higher dose (2.5 mg/kg; [Neurotoxicology 15 (1994) 837]): TCP was again most protective when given curatively within the first hour of soman-induced seizures. In this condition, (a) paroxysmal activity ceased in 10-20 min, (b) all the animals survived, (c) the majority of them recovered remarkably well and did not show any brain damage 24 h after the intoxication, and (d) the minimal duration of seizure activity normally required for producing soman-induced brain damage in other pharmacological environments was increased from 10 to 40 min to 80 min. Strikingly, when TCP was given 120 min after seizure onset, it failed to show any anticonvulsant activity but still provided neuroprotection in the hippocampus. The present study also gives additional evidence (see [Neurotoxicology 21 (4) (2000) 521]) that in soman poisoning, (a) the development of brain damage depends on the occurrence of ECoG seizures, (b) the topographical distribution of lesions depends on seizure duration, and (c) an increase of the relative power in the lowest (delta) frequency band might be a reliable marker of neuronal degradation. All these findings confirm that (a) glutamatergic NMDA receptors are involved in the mechanisms of soman-induced seizures and brain damage, (b) non-competitive antagonists of NMDA receptors might be promising candidates for post-treatment of soman poisoning, and (c) ECoG parameters from ECoG tracings and power spectrum might serve as useful external predictors for soman-induced neuropathological changes.

Animals↗

PubMed2001

Diagnostic value of quantitative EEG in Alzheimer's disease.

The aim of this study was to determine the performance of several spectral indices of the EEG (ratios between fast and slow EEG activities) as descriptors of the EEG changes occurring at the onset and during the evolution of Alzheimer's disease (AD). These indices were calculated from quantitative analysis of EEGs recorded in AD patients and from a matched non-demented group of control subjects. One advantage of such indices is to be independent of the absolute value of power spectral densities, which may vary from subject to subject, another being to take into account fast EEG activities. Conventional statistic tests and Receiver Operating Curves (ROC) analysis were performed upon these data to determine the accuracy of the power ratios to discriminate a) between controls and patients (i.e., to detect dementia) and b) between subgroups of patients defined according to the Global Deterioration Scale of Reisberg (GDS). The defined ratios provided a good classification of AD patients for all cerebral regions except the frontal areas, because of eye movement artefacts; the results confirm the increase in slow activities and the concomitant decrease in fast activities early in AD patients. Moreover, our results demonstrate that these indices are adapted tools to perform a good discrimination between demented and non-demented patients in routine clinical practice. We therefore propose the use of these EEG power ratios to discriminate between different stages of Alzheimer's disease, and to perform long-term monitoring of AD patients.

Aged↗

PubMed2001

[Physiopathology of idiopathic hypersomnia. Current studies and new orientations].

In 1976 Bedrich Roth coined the term "idiopathic hypersomnia" and described two forms of the disease, one monosymptomatic, manifested only by excessive daytime sleepiness, and one polysymptomatic, characterized by excessive daytime sleepiness, nocturnal sleep of abnormally long duration and signs of "sleep drunkenness" on awakening. In comparison with that of narcolepsy, the pathophysiology of idiopathic hypersomnia remains poorly known. There are two main reasons for that: the absence of clinical and polysomnographic criteria pathognomonic or at least characteristic of the condition, as the cataplexies and the sleep onset REM periods of narcolepsy, and also the absence of a natural animal model comparable with the canine model of narcolepsy. The first investigations have stressed the frequent familial pattern of idiopathic hypersomnia. Later on biochemical assays have been performed in the CSF with results in favour of a dysfunction of noradrenergic systems. In the light of the two process model of sleep regulation in which sleep propensity is determined by a homeostatic process S and a circadian process C and of the later three-process model of regulation in which sleepiness/alertness are simulated by the combined action of a homeostatic process, a circadian process and sleep inertia, we suggest that idiopathic hypersomnia is not a pathological entity in itself, but rather the consequence of chronic sleep deprivation in very long sleepers.

Arousal↗

PubMed2000

p53 and Bax implication in NMDA induced-apoptosis in mouse hippocampus.

Seven days after in vivo intrahippocampal administration of NMDA, 3'-OH DNA fragmentations and Bax protein expression were detected in hippocampal neurons of p53+/+ but not p53-/- transgenic mice. Interestingly, neurons showing pycnosis, an early apoptotic phenomena, were present in all genotypes. These results confirm that apoptotic 3'OH DNA fragmentations and Bax protein induction during NMDA-induced apoptosis in adult hippocampal neurons are p53 dependent.

Animals↗

PubMed2000

Sequential expression of surface antigens and transcription factor NFkappaB by hippocampal cells in excitotoxicity and experimental epilepsy.

Neurodegeneration and gliosis have been extensively described after long-lasting seizures; evidence for cytokine involvement in neuron-glia interactions does exist. We have therefore studied the hippocampal expression of molecules responsible for immune and inflammatory reactions, at different time-points following either experimental status epilepticus (SE) or direct excitotoxic damage. Experiments consisting of immunohistochemical labeling of glial markers, major histocompatibility complex (MHC) and nuclear factor kappaB (NFkappaB), were performed. NFkappaB nuclear translocation was controlled and measured using the electrophoretic mobility shift assay. One day after SE, neurodegeneration was obvious in CA3 pyramidal layers; NFkappaB staining in neurons and its translocation to the nucleus enhanced. From day 4 to at least day 8 post-SE, MHC-positive microglia, NFkappaB over-expression in thickened astrocytes, and increased levels of its activated form could be observed. The excitotoxic model caused more severe lesions, but NFkappaB and MHC expression were similar in both models. These results suggest that during long-lasting seizures: (i) neuronal firing activates NFkappaB expression and translocation; (ii) microglia expresses MHC; (iii) astrocytes, probably stimulated by microglial cytokines, over-express NFkappaB, the activation of which induces a cascade of reactions, particularly the transcription of cytokines and or neuroprotective molecules. Further clarification of the toxic or protective consequences of delayed inflammatory responses may be interesting in therapy of epilepsy.

Animals↗

PubMed2000

Effects of atropine sulphate on seizure activity and brain damage produced by soman in guinea-pigs: ECoG correlates of neuropathology.

The present study describes the effects of pyridostigmine (PYR; 0.2 mg/kg) and atropine sulphate (AS; 5 mg/kg) on guinea-pigs intoxicated by a high dose (2xLD50) of the organophosphate compound, soman, an irreversible inhibitor of acetylcholinesterase. The medication was shown to counteract the acute respiratory distress and lethality normally produced by the intoxication. Moreover, due to the central activity of AS, soman-induced electrocorticographic (ECoG) seizure activity was either totally prevented, or reduced in duration and overall intensity. In addition, as established in the 24-hr survivors, seizure-related neuropathology was either prevented, or reduced in topographical extent and severity. An attempt to correlate our electrographic and morphological findings gives evidence that (a), the occurrence of seizure activity is the primary factor necessary for the development of acute neuropathology; (b), the duration of ECoG seizures is a secondary factor, on which the topographical distribution of brain damage finally depends; (c), the minimal duration of seizures necessary to produce 24 hr-damage in the most sensitive areas (e.g. the amygdala) is less than 70 min; (d), the overall intensity/power of epileptiform discharges is a tertiary factor which influences the severity of damage; (e), in addition, ECoG power spectral analysis suggested that an acute increase of relative power in the lower (delta) frequency band might be a real-time external marker of the starting cerebral lesions and is thus predictive for their future installation. All these data confirm the tight relationships which exist between seizure activity and neuropathology in soman poisoning, and suggest that refined, standardized analysis of electrographic parameters drawn from ECoG tracings and power spectrum might serve as a useful tool to predict the presence, localization, and severity of soman-induced brain damage.

Animals↗

PubMed1999

Hippocampal alterations of apolipoprotein E and D mRNA levels in vivo and in vitro following kainate excitotoxicity.

Alteration in the expression of apolipoprotein E (ApoE) and apolipoprotein D (ApoD) genes was evaluated in rat, 7 days following status epilepticus (SE) induced by intra-amygdala injection of kainate (KA), and in organotypic hippocampal cultures, 2 days after a single 1 h exposure to KA. Global polyadenylated RNA (poly A+) steady state, assessing global regulation of mRNA transcription was first measured in cortices and hippocampi from each animal and in the organotypic cultures. No alteration due to KA treatment was observed and individual concentrations of ApoE and ApoD mRNA species were therefore measured and comparative analysis performed. In the cortices of KA-treated animals, ApoE and ApoD mRNA levels did not show statistically significant changes. In contrast, in hippocampi, 7 days after SE, ApoE and ApoD mRNA levels were significantly increased, respectively, by 123 and 138%. This in vivo effect was confirmed in vitro on organotypic cultures, where KA treatment increased ApoE and ApoD mRNA expressions, respectively, by 72 and 61%. These observations indicate that lipidic metabolism is modified in the lesioned structure and suggest an increased traffic of lipids and a need for more ApoE and D in the hippocampus during the period of recovery and restructuration that follows severe seizures.

Animals↗

PubMed1998

Alterations of metallothionein II and apolipoprotein J mRNA levels in kainate-treated rats.

Although different mechanisms have been proposed, it has been suggested that apolipoprotein J (ApoJ) and metallothionein II (MTII), expressed by astrocytes, are protective proteins. Alterations in their expression may contribute to the involvement of astrocytes in epileptogenesis. We studied the expression of MTII and ApoJ genes 7 days following status epilepticus induced in rats by intra-amygdala injection of kainate (KA). ApoJ mRNA levels were increased in both cortex (77%, p < 0.01) and hippocampus (64%, p < 0.02), whereas, in contrast to previous findings 3 days after KA injection, DNA fragmentation was not detected on agarose gel electrophoresis. These results show that ApoJ is induced along with early genes during massive apoptosis, and remains induced after the acute phase. MTII mRNA levels were altered only in hippocampus (62%, p < 0.05), whereas KA-treated rats had no seizure for 7 days. The sustained induction of MTII mRNA shows that zinc homeostasis is not returned to normal or alternatively that astrocytes maintain an altered phenotype in spite of normal zinc release. Polyadenylated RNA and beta-actin mRNA levels were in contrast unaltered in cortex or hippocampus at this time point. These specific variations in ApoJ and MTII mRNA expression during the latent period suggest that they are part of long term biochemical and/or phenotypic alterations in astrocytes, following a single episode of severe seizures.

Actins↗

PubMed1998

The neuronal death induced by endotoxic shock but not that induced by excitatory amino acids requires TNF-alpha.

We studied, using organotypic hippocampal slices in culture, the role of pro-inflammatory cytokines, oxygen radicals and nitric oxide in neuronal death induced either by endotoxic insult [interferon (IFN) gamma, 24 h followed by lipopolysaccharide, 24 h] or by glutamate receptor-mediated excitotoxic insult. We demonstrated that neuronal death induced by endotoxic insult was absolutely dependent on the synthesis of tumour necrosis factor alpha (TNF-alpha). Indeed, TNF-alpha antibodies and SB203580, an inhibitor of p38 stress kinase known to block TNF-alpha and other cytokine synthesis, completely protected neurons from the endotoxic insult. Inhibiting oxygen radical and nitric oxide productions also reduced the endotoxic shock. We also showed that after priming the cultures with IFN-gamma, TNF-alpha was unable to induce neuronal death unless oxygen-free radicals were exogenously provided. In contrast, although glutamate receptor-induced excitotoxicity was associated with a low TNF-alpha synthesis and a modest activation of p38 stress kinase, neither TNF-alpha antibodies nor SB203580 were able to decrease excitotoxic neuronal insult. We did not reduce glutamate receptor-induced neuronal death with superoxide dismutase plus catalase. In conclusion, although inflammation follows glutamate receptor-mediated neurotoxicity, the mechanisms by which an endotoxic insult triggers neuronal death are different from those involved in excitotoxicity.

Animals↗

PubMed1997

c-fos antisense oligonucleotide prevents delayed induction of hsp70 mRNA after soman-induced seizures.

Previous studies have shown the successive expression of c-fos and hsp70 genes, especially in the hippocampal formation, during soman-induced seizures. In order to detect a possible link between the induction of these two genes, antisense strategies have been used. First, the ability of unilateral intrahippocampal infusion of c-fos antisense oligonucleotides to inhibit ipsilateral, seizure-related, c-FOS-like immunoreactivity, was verified. Second, induction of hsp70 mRNA was investigated using in situ hybridization. Unilateral inhibition of c-fos induction clearly reduced levels of hsp70 mRNA in the c-fos antisense-infused hippocampus relative to the non-infused contralateral side. Infusion of c-fos sense probe or vehicle did not affect bsp70 mRNA induction. This study suggests a role of c-FOS in regulating bsp70 mRNA induction.

Animals↗

PubMed1996

Time course and regional expression of C-FOS and HSP70 in hippocampus and piriform cortex following soman-induced seizures.

The time course of induction of the proto-oncogene c-fos and the inducible heat shock hsp70 gene was studied from 5 minutes to 24 hours at both transcriptional (c-fos and hsp70 mRNA) and translational levels (C-FOS and HSP72 proteins) in the rat hippocampus and piriform cortex (Pir) after soman-induced seizures. Induction of c-fos was noticed as early as 5 minutes after seizures onset in all fields of hippocampal formation (CA1, CA3, CA4, and dentate gyrus) and in piriform cortex. The most intense induction was observed in piriform cortex. A sustained activation of c-fos occurred in Pir and in CA1, CA3, and CA4 areas of hippocampus. Nevertheless, histological analysis showed rare affected neurons in CA4, whereas damage was severe in Pir and in CA1 and CA3 hippocampal subfields. Induction of hsp70 mRNA occurred but was delayed in all areas previously exhibiting c-fos expression. Nevertheless HSP72 protein was never expressed in the structures where injury was high (i.e., CA1 and piriform cortex) and mainly occurred in the less damaged structure (i.e., CA4 area of hippocampus). Regional expression of glial fibrillary acidic protein mRNA was also studied in order to exclude an astroglial origin of the c-fos and hsp70 gene inductions. Our results demonstrated that after soman induced-seizures 1) there was no strict correlation between time course or intensity of neuronal c-fos induction and subsequent neuropathology, and 2) the most lesioned areas did not express HSP72 protein in spite of intense mRNA induction, suggesting that transcriptional and translational events for hsp70 gene might vary according to the severity of seizure insult.

Animals↗

PubMed1996

Release of TNF alpha in the rat hippocampus following epileptic seizures and excitotoxic neuronal damage.

We studied the production of tumor necrosis factor alpha (TNF alpha) and interleukin-6 (IL-6) 2 and 7 days following status epilepticus (SE), induced in rats by intra-amygdala injection of kainate. At day 2 the release of both cytokines by hippocampal slices prepared from epileptic animals was increased compared to controls, whereas at day 7 only TNF alpha secretion was enhanced. Since SE-induced neuronal damage is probably due to excitotoxicity, we investigated the effects of agonists of glutamate receptors on TNF alpha release in organotypic hippocampal cultures. A correlation was found between the damage intensity and the release of TNF alpha, suggesting production of this cytokine by macrophagic microglia. We propose a role for TNF alpha and IL-6 in the adaptive phenomena which follow severe limbic seizures.

Amygdala↗

PubMed1995

Early regional changes of GFAP mRNA in rat hippocampus and dentate gyrus during soman-induced seizures.

We investigated the time course of GFAP levels in the hippocampal formation during the first 24 h following soman intoxication in rats. GFAP mRNA expression was detected by in situ hybridization. Intense GFAP mRNA expression was present in the molecular layer of the dentate gyrus as early as 6 h after intoxication. This expression was comparatively lower in other dentate gyrus layers and hippocampal CA1, CA3 and CA4 areas and seemed to be related to excessive neuronal activity. Histopathological examination demonstrated that GFAP expression in dentate gyrus is not correlated with lesions. The high astrocytic reactivity in the molecular layer of the dentate gyrus is discussed in relation to the maintenance of the homeostasis of glutamate and of synaptic plasticity in this area during soman intoxication.

Animals↗

PubMed1995

Increase in GAP-43 and GFAP immunoreactivity in the rat hippocampus subsequent to perforant path kindling.

Kindling is an animal model of epilepsy which is accompanied by morphological and biochemical changes in the brain, including sprouting of fibers and increased transmitter release. Here we have examined the immunocytochemical expression of 1) GAP-43, a growth-associated protein, which is a neuron-specific PKC substrate, particularly expressed in development and regeneration and 2) glial fibrillary acidic protein (GFAP), part of the astrocytic cytoskeleton, after perforant path kindling. Subsequent to kindling, GAP-43 immunoreactivity was increased in CA1 stratum lacunosum-moleculare and the inner and outer molecular layer of the fascia dentata. Other hippocampal subregions showed a lower increase. GFAP immunoreactivity was increased in the entire hippocampus, but especially in stratum lacunosum-moleculare of the CA1 and the hilus of fascia dentata. The difference between the number of GFAP-positive profiles in the hippocampus of control rats and in fully kindled rats was found to be non-significant. We interpret these findings as being related to both plastic neuronal changes and possible neuronal degeneration.

Animals↗

PubMed1995

Differential impairments of spatial memory and social behavior in two models of limbic epilepsy.

To explore memory impairments in temporal lobe epilepsy, we used two experimental models in the rats: (a) kainate-induced status epilepticus (SE) resulting in excitotoxic damage and in later spontaneous seizures; and (b) amygdala kindling, known to induce no lesions (or only minor) and neuronal reorganization. Long-term effects of these models on memory were investigated with a spatial learning task in a radial-arm maze, and a social interaction test that implies degree of short-term memory. An histological analysis was made to determine neuronal damage or loss caused by epileptic activity in brain regions that could be related to memory functions. Kainate-induced epilepsy produced large memory deficits in animals tested 5 months after the injection. The rats showed severe lesions in amygdala and hippocampus and piriform and entorhinal cortex. Spatial memory was strongly diminished. The social memory test was severely impaired, probably due to the extent of amygdala injury, which is known to disturb social behavior. On the contrary, kindled rats showed no evident lesion in any brain region and displayed performances as good as those of controls in both tests. These experiments demonstrated that memory deficits appear to be related to the severity of neuronal damage in limbic areas, and the ability to develop seizures (permanence) is not solely responsible for these memory disturbances.

Animals↗