Biomedical subjects

A Privat

Publications and source records attributed to A Privat.

At least 109 records · Page 6Linked to original sources

PubMed1995

Distinct neuroprotective profiles for sigma ligands against N-methyl-D-aspartate (NMDA), and hypoxia-mediated neurotoxicity in neuronal culture toxicity studies.

Substantiating evidence has raised the possibility that sigma ligands may have therapeutic potential as neuroprotective agents in brain ischemia. It has been suggested that the neuroprotective capacity of sigma ligands is related primarily to their affinity for the NMDA receptor complex and not to any selective action at the sigma binding site. However, sigma specific ligands, devoid of significant affinity for the NMDA receptor, are also neuroprotective via an inhibition of the ischemic-induced presynaptic release of excitotoxic amino acids. In the present study, we have investigated the potential neuroprotective effect of a comprehensive series of sigma ligands, with either significant (sigma/PCP) or negligible (sigma) affinity for the PCP site of the NMDA receptor, in order to delineate a selective sigma site-dependent neuroprotective effect. For this aim, we have employed two different neuronal culture toxicity paradigms implicating either postsynaptic-mediated neurotoxicity, (brief exposure of cultures to a low concentration of NMDA or Kainate) or pre- and postsynaptic mechanisms (exposure to hypoxic/hypoglycemic conditions). Only sigma ligands with affinity for the NMDA receptor [(+) and (-) cyclazocine, (+) pentazocine, (+) SKF-10047, ifenprodil and haloperidol] were capable of attenuating NMDA-induced toxicity whereas the sigma [(+)BMY-14802, DTG, JO1784, JO1783, and (+)3-PPP] and kappa-opioid [CI-977, U-50488H] ligands, with very low affinity for the NMDA receptor, were inactive. The rank order of potency, based on the 50% protective concentration (PC50) value, of sigma/PCP ligands against NMDA-mediated neurotoxicity correlates with their affinity for the PCP site of the NMDA receptor, and not with their affinity for the sigma site. In addition sigma/PCP, sigma or kappa-opioid ligands failed to attenuate kainate-mediated neurotoxicity. On the other hand, sigma/PCP, sigma and kappa-opioid ligands were potent inhibitors of hypoxia/hypoglycemia-induced neurotoxicity, although their neuroprotective potency did not correlate with their affinity for either the sigma or PCP binding sites. In conclusion, the ability of sigma and kappa-opioid ligands to attenuate hypoxia/hypoglycemia, but not NMDA or kainate-induced toxicity, suggests that these drugs exert their neuroprotective role by a predominantly presynaptic mechanism possibly by inhibiting ischemic-mediated glutamate release.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1995

A N-methyl-D-aspartate receptor-mediated neurotoxic effect of aspartate-based hydroxamate compounds in rat primary neuronal cultures.

In a previous study (Lockhart et al., Brain Res., 630 (1993) 32-40) we demonstrated a NMDA receptor-mediated neurotoxic effect for the anti-HIV drugs D-aspartate beta-hydroxamate and structurally related analogues in rat primary cortical neurons. Herein, we have examined the neurotoxic action and pharmacology of a novel series of hydroxamate compounds, with potential anti-HIV activity, in a similar paradigm. In this aim, the aspartate-based hydroxamates L-VHS.126 and its stereoisomer D-VHS.126 selectively destroyed (EC50 = 300 microM) rat primary neurons. The D-VHS.126 analogue, VHS.134 was also neurotoxic (EC50 = 450 microM) whereas VHS.129 and VHS.137, or the D-aspartate beta-hydroxamate analogues VHS.128, VHS.135, VHS.132 and VHS.127 or hydroxyurea demonstrated no significant neurotoxicity. The neurotoxic action of L- and D-VHS.126, and VHS.134 was attenuated with MK-801, CGS-19755 but not with CNQX. These observations demonstrate a potent NMDA receptor-mediated excitotoxic action for novel aspartate-based hydroxamate compounds, and further extends this series of potential hydroxamate-based anti-HIV drugs lacking neurotoxicity in vitro.

Animals↗

PubMed1995

B-50 (GAP-43) immunoreactivity is rarely detected within intact catecholaminergic and serotonergic axons innervating the brain and spinal cord of the adult rat, but is associated with these axons following lesion.

The persistence of high levels of B-50 (GAP-43) in fibers innervating various regions of the adult central nervous system is generally thought to characterize neuronal systems capable of undergoing morphological plasticity. In a recent series of in situ hybridization studies, it has been shown that most catecholaminergic and serotonergic neurons of the adult rat brain express high levels of B-50 mRNA. The present study addresses the question whether high expression of B-50 mRNA in the catecholaminergic and serotonergic perikarya corresponds with detectable high levels of the B-50 protein in the efferent axonal fibers that innervate various regions of the adult rat brain and spinal cord. For this purpose, vibratome sections were doubly immunostained for B-50 and for tyrosine hydroxylase or serotonin and were analyzed by laser scanning confocal microscope. Colocalizations were investigated either (1) in regions of intact rat brain and spinal cord in which particular concentrations of B-50 immunoreactive fibers appeared codistributed with catecholaminergic or serotonergic fibers or (2) in intrahypothalamic portions of the medial forebrain bundle in which a surgical lesion was made. In the intact brain, frequent colocalizations of B-50 and tyrosine hydroxylase were detected in fibers innervating both the mediobasal hypothalamus and the neurointermediate hypophysial lobe. In all the other regions examined, the analysis of thin optical sections demonstrated that immunoreactivity to B-50 was only rarely associated with axonal profiles immunoreactive to tyrosine hydroxylase or to serotonin. By contrast, in the lesioned medial forebrain bundle B-50 immunoreactivity was found to be associated with numerous catecholaminergic and serotonergic axonal sprouts that regenerate around the surgical lesion. These data indicate that the majority of intact catecholaminergic and serotonergic axons innervating the adult rat brain and spinal cord contains low levels of B-50. However, following axotomy, B-50 is immunocytochemically detectable in the regenerating sprouts produced by both types of axonal fibers. This suggests that under basal conditions the relatively high content of B-50 mRNA in monoaminergic perikarya does not lead to appreciable accumulation of B-50 within corresponding axonal fibers and terminals, whereas conditions of morphological reorganization induce increased production of B-50 that accumulates within monoaminergic axonal sprouts.

Animals↗

PubMed1995

Fictive motor activities in adult chronic spinal rats transplanted with embryonic brainstem neurons.

The present study was designed to examine the effects of an intraspinal transplantation of embryonic brainstem neurons on fictive motor patterns which can develop in hindlimb nerves of adult chronic spinal rats. Seventeen adult rats were spinalized at T8-9 level and, 8 days later, a suspension of embryonic cells obtained either from the raphe region (RR, n = 8) or from the locus coeruleus (LC, n = 9) was injected caudally (T12-13) to the cord transection. Eight control animals (control rats) were spinalized and injected with vehicle under the same conditions. One to three months later, the animals were decorticated and fictive motor patterns were recorded in representative hindlimb nerves. The data revealed that both control and grafted spinal rats could exhibit two distinctly different fictive motor patterns, one which could be associated with stepping and the other with hindlimb paw shaking. They further showed that following transplantation of embryonic RR or LC neurons the excitability of the spinal stepping generator was increased, whereas that of the spinal neural circuits which generate hindlimb paw shaking was not significantly affected. A histological analysis performed on the spinal cord segments below the transection revealed complete absence of serotonin and noradrenaline immunoreactivity in control spinal animals and, in both types of grafted rats, an extensive monoaminergic reinnervation with synaptic contacts between monoaminergic transplanted neurons and host interneurons and/or motoneurons. The possible mechanisms by which grafted monoaminergic neurons can influence the spinal motor networks are discussed.

Animals↗

PubMed1995

Primary dissociated cultures of human brainstem cells: a useful tool for their characterization and neuroprotection study.

Dissociated cell cultures were prepared from brainstems of 5- to 10-week-old human fetuses. Catecholamine- as well as indolamine-containing cells were visualized using respectively dopamine (DA), noradrenaline (NA) and serotonin (5HT) as immunocytochemical markers. NA-, DA-, and 5HT-stained cells were characterized in the rhombencephalic cultures, representing respectively the fetal localization of the locus coeruleus and raphe nuclei. DA-stained cells were characterized in the mesencephalic cultures; these DA-cells originating from the substantia nigra presented morphological aspects different from the DA-rhombencephalic cells. Two types of GABA neurons and glial cells presenting glial fibrillary acidic protein (GFA-P) reactivity were also found in all the cultures. Two non-competitive N-methyl-D-aspartate antagonists, 1-[1-(2-thienyl)cyclohexyl]piperidine (TCP) and cis-Pip/Me 1-[1-(2-thienyl)-2-methylcyclohexyl]piperidine (GK11) in enantiomeric form (-), have been investigated for survival on rhombencephalic cultured cells. The number of 5HT-cells was found to be greater in the treated cultures than in the control ones. This in vitro system appears to be a useful tool for the investigation of the development of central nervous system (CNS) cells as well as the study of neuroprotection.

Brain Stem↗

PubMed1995

Prevention of nimodipine-induced impairment of learning by the selective sigma ligand PRE-084.

The high selectivity of the phencyclidine derivative PRE-084 for sigma (sigma) sites is demonstrated. We previously reported that this compound is able to markedly attenuate the impairment of learning induced in mice by the non-competitive NMDA antagonist MK-801, and the cholinergic nicotinic antagonist mecamylamine. In this study, we examined the effect of PRE-084 on the impairment of learning induced by acute administration of the calcium channel antagonist nimodipine. Nimodipine (0.3 mg/kg i.p.) impaired the spontaneous alternation behaviour in a Y-maze, decreased the step-down latency (SDL) in a passive avoidance task, and altered place learning and retention in a water-maze paradigm, with no marked effect on the motility observed using an open-field test. Preadministration of PRE-084 resulted in an attenuation of the impairment of alternation, in the 0.3-1 mg/kg s.c. range, in a marked increase in SDL, at 1-3 mg/kg, and improved place learning and retention in the water-maze, at 1 mg/kg. The effects on alternation behaviour and passive avoidance were completely prevented by co-administration of the purported sigma antagonist BMY-14802 (10 mg/kg i.p.), implicating the sigma sites. These results confirm the beneficial effect of the sigma ligand PRE-084 on pharmacological models of learning impairments, and indicate that sigma sites may modulate Ca2+ fluxes through VDCC, which may in turn bear some as yet unknown relationship to the previously described interaction with neurotransmitter systems.

Animals↗

PubMed1995

Immunolocalization of B-50 (GAP-43) in intact and lesioned neurohypophysis of adult rats.

The persistence of high levels of B-50 in the adult brain is generally assumed to characterize neuronal systems capable of undergoing some form of plasticity such as axonal sprouting and regeneration. Since adult hypothalamo-neurohypophysial neurons are known to rapidly regenerate after being transected, the present study was undertaken to determine if such a capacity for regeneration could be related to the expression of this protein. Adult rats were killed by intraaortic perfusion of fixative either without lesion or at different delays after a surgical transection of the hypophysial stalk. Electron microscopy and laser scanning confocal microscopy were used to examine the regenerating axons after single or double immunocytochemical labeling of vibratome sections for B-50 and for various neuronal markers characterizing different types of neurohypophysial axons. In intact neurohypophysis, B-50 immunostaining was frequently associated with fibers immunoreactive to GABA or to tyrosine hydroxylase, whereas it was not detected within peptidergic neurohypophysial axons. In the lesioned neurohypophysis, B-50 was again frequently localized within axonal fibers immunoreactive to tyrosine hydroxylase or GABA. On the other hand, B-50 immunostaining was never detected within the numerous vasopressinergic or oxytocinergic axonal sprouts that regenerate all along the median eminence proximal to the lesion. These data indicate that persistence of high levels of B-50 within the neurohypophysis of adult rats is a specific feature of catecholaminergic and/or GABA-ergic axons innervating this region and that, contrasting to other neuronal systems, B-50 is not involved in the remarkable capacity for regeneration exhibited by the vasopressinergic and oxytocinergic neurohypophysial axons.

Animals↗

PubMed1995

Immunocytochemical study of phenotypic plasticity of cultured dorsal root ganglion neurons during development.

Rat dorsal root ganglia (DRG) were cultured from different stages of development ranging from embryonic day-14 to adult. The expression of eight neurotransmitter phenotypes was examined with immunocytochemical detection and the percentages of each phenotype were calculated with reference to the whole neuronal population defined by the expression of neuron-specific enolase (NSE). The expression of peptides, calcitonin gene-related peptide (CGRP), substance P (SP), cholecystokinin (CCK) and neuropeptide Y (NPY) was always present whatever the age at onset of the cultures. Although the percentage of CGRP remained stable, that of the other peptides declined progressively. Their in-vitro expression did not differ markedly from that found in vivo. Another group of neurotransmitters, including 5-hydroxytryptamine (5-HT), thyrotropin-releasing hormone (TRH) and gamma-aminobutyric acid (GABA) was never expressed in situ in DRG neurons. In culture, they were expressed in a high percentage of neurons, especially for 5-HT and TRH, and they showed a similar evolution, with a decrease at early postnatal ages followed by a further increase. This profile suggests that the expression of these transmitters is strongly environment-dependent and may be repressed in situ. Finally, somatostatin (SOM) was found only in cultures prepared from adult tissues, whereas it was present in situ from the embryo onwards. The expression of this peptide would thus require a stabilization by a long exposure to environmental factors. We can conclude that the great diversity of phenotypic expression found in DRG neurons in situ is the result of a wide variety of influences occurring at different stages of development in a large potential repertory present in these neurons.

Animals↗

PubMed1995

Induction of neuronal apoptosis by excitotoxins associated with long-lasting increase of 12-O-tetradecanoylphorbol 13-acetate-responsive element-binding activity.

We show that excitotoxic cell death, which is associated with pathological neurodegenerative processes, can display morphological and biochemical features characteristic of apoptosis, a mode of cell death typical of physiological neuronal elimination during development. Cortical neurons cultured in the absence of serum, stimulated with NMDA, glutamate, or quisqualate after 3-5 days in vitro, showed significant degeneration. This death was blocked by 1 microM MK-801, indicating that it was mediated by the activation of NMDA receptors. Dying cells displayed an apoptotic morphology, characterized by cytoplasm and chromatin condensation. No internucleosomal DNA degradation was observed, confirming that morphological changes of apoptosis can be dissociated from DNA laddering. Inhibitors of protein or RNA synthesis abolished cell death, and the protective effect of cycloheximide was similar when the drug was applied 2 h before or 8 h after glutamate. These experiments suggest the participation of active gene transcription in the mechanism of death. We thus analyzed the modulation of transcription factors in dying cells using electrophoretic mobility shift assays. The level of factors binding to the 12-O-tetradecanoylphorbol 13-acetate-responsive element (TRE) displayed a late and sustained increase preceding neuronal death, which was not found for factors complexing the Sp1 P, Oct, and USF binding sites. These results raise the possibility that apoptosis is one of the mechanisms of death in the pathologies linked to excitotoxicity and that activation of TRE-binding factors could play a role in these processes.

Animals↗

PubMed1995

Presence of the long and the short forms of Bcl-X in several human and murine tissues.

Bcl-X protein, which is related to Bcl-2, is present essentially in the nervous system and the immune system, under 2 different forms: Bcl-XL, like Bcl-2, is able to prevent apoptotic death of cultured lymphocytes; in contrast, Bcl-XS, which differs from the former one by a deletion of 63 amino acids in the region of greatest homology between Bcl-XL and Bcl-2, is unable to prevent this apoptotic death and even counteracts the protective effect of Bcl-2. It has been reported that the adult nervous system contains exclusively the RNA encoding Bcl-XL whereas the immune system would contain exclusively the RNA encoding Bcl-XS. We show here, by using reverse transcription coupled to PCR, that adult rat brain contains not only the RNA encoding Bcl-XL but also the RNA encoding Bcl-XS. Similarly we show that human lymphocytes, whether infected or not by the HIV, contain both forms of Bcl-X messenger RNA (mRNA). Furthermore we have observed that both forms of mRNA are present in adult rat liver and in cultured mouse hepatocytes. All these results have been confirmed by hybridizing the PCR products transferred to a nylon membrane with a probe specific of Bcl-XL or a non discriminative probe.

Animals↗

PubMed1994

Inhibitors of free radical formation fail to attenuate direct beta-amyloid25-35 peptide-mediated neurotoxicity in rat hippocampal cultures.

The direct neurotoxic action of the beta-amyloid protein, the major constituent of senile plaques, may represent the underlying cause of neuronal degeneration observed in Alzheimer's disease. The apoptotic-mediated neuronal death induced by beta-amyloid appears to reside in its ability to form Ca(2+)-permeable pores in neuronal membranes resulting in an excessive influx of Ca2+ and the induction of neurotoxic cascades. It is possible that during beta-amyloid exposure a Ca(2+)-mediated increase in free radical generation may exceed the defensive capacity of cells and thus lead to cell death. Consequently, in the present study we have investigated the effect of a panoply of antioxidants and inhibitors of free radical formation on the development of beta-amyloid neurotoxicity. Acute exposure of rat hippocampal neurons to "aged" beta-amyloid25-35 peptide (5-50 microM) induced a slow, concentration-dependent apoptotic neurotoxicity (25-85%) during a 6 day exposure. Co-incubation of cultures with beta-amyloid25-35 peptide (25 microM) and inhibitors of nitric oxide synthase and/or xanthine oxidase (NG-monomethyl-L-arginine [1 mM), N omega-nitro-L-arginine [1 mM], oxypurinol [100 microM], allopurinol [100 microM]), important mediators of nitric oxide, superoxide, and hydroxyl radical formation, did not attenuate beta-amyloid neurotoxicity. Similarly, a reduction in free radical generation by selective inhibition of phospholipase-A2 cyclooxygenase, and lipoxygenase activities with quinacrine (0.5 microM), indomethacin (50 microM), and nor-dihydroguaiaretic acid (0.5 microM), respectively, did not reduce the proclivity of beta-amyloid to induce cell death. Exposure of cultures to catalase (25 U/ml) and/or superoxide dismutase (10 U/ml) as well as the free radical scavengers vitamin E (100 microM), vitamin C (100 microM), glutathione (100 microM), L-cysteine (100 microM), N-acetyl-cysteine (100 microM), deferoxamine (5 microM), or haemoglobin (35 micrograms/ml) failed to attenuate the neurotoxic action of beta-amyloid. On the other hand, pre-treatment of cultures with subtoxic concentrations of beta-amyloid peptide significantly increased the vulnerability of neurons to H2O2 exposure and suggest that beta-amyloid peptide renders neurons more sensitive to free radical attack. However, a potential beta-amyloid-mediated increase in free radical formation is not a proximate cause of the neurotoxic mechanism of beta-amyloid in vitro.

Allopurinol↗

PubMed1994

Light and electron microscopic studies of the effects of p-chloroamphetamine on the monoaminergic innervation of the rat spinal cord.

A previous report has shown that small diameter serotoninergic (5-HT) axons innervating the forebrain are selectively eliminated by treatment with an amphetamine derivative, (+/-)p-chloroamphetamine (PCA; Mamounas et al., [1991] J. Comp. Neurol. 314:558-586). It is well known that the spinal cord is the target of numerous monoaminergic fibers of different types. We have previously shown that the dorsal and ventral horns and the intermediolateral cell column are innervated by numerous serotonin-, noradrenaline- and dopamine-containing axons, including both thin axons with small varicosities and beaded axons with large varicosities. In all these regions, the large majority of fine indolaminergic fibers do not establish synaptic contacts, contrasting with the beaded axons which mostly exhibit synapses. The present work was conducted to study the effect of PCA on the monoaminergic innervation of the adult rat spinal cord. Animals received two subcutaneous doses of PCA 24 hours apart and were perfused 3 weeks later. Immunocytochemistry was performed to detect 5-HT, noradrenergic and dopaminergic fibers by using light and electron microscopy. Light microscopy revealed that PCA treatment caused a marked and selective elimination of the fine 5-HT-immunoreactive fibers, mainly found in the dorsal horn, but spared all other larger axons. This selective effect on the dorsal horn innervating thin 5-HT fibers was confirmed with the electron microscope by calculating the synaptic incidence(s) of monoaminergic innervation. These results suggest that fine and beaded 5-HT axons correspond to two anatomically, biochemically and pharmacologically different types of fibers, which could arise from two subpopulations of brainstem neurons. In addition, this drug could be used to provide an experimental animal, devoid of 5-HT nonsynaptic fibers, thereby facilitating a study on the role of dorsal horn nonsynaptic system in pain modulation.

Animals↗

PubMed1994

Direct immunocytochemical localization of 5-hydroxytryptamine receptors in the adult rat spinal cord: a light and electron microscopic study using an anti-idiotypic antiserum.

In the present study, we performed the immunodetection of serotonergic (5-HT) receptor subtypes in the spinal cord by using an anti-idiotypic antiserum (TH8) at light and electron microscopic levels. This antibody has been shown to recognize 5-HT1B, 5-HT1C, and 5-HT2 receptor subtypes (Tamir et al.: J Neurochem 57:930-942, 1991). The TH8 immunoreactivity was observed in the dorsal and ventral horns of the gray matter. Light microscopy revealed that small cell bodies located in laminae I-III of the dorsal horn were intensely immunolabeled. A more homogenous and discrete staining was also observed throughout the entire dorsal horn. In the ventral horn, motoneurons were also immunoreactive (IR). Peroxidase deposits were observed as numerous patches covering the motoneuronal surface. Numerous interneurons were moderately and homogeneously immunostained. With the electron microscope, most of the labeled structures were identified as neurons (dendrites and perikarya) in both the dorsal and ventral horns. In the dorsal horn, immunoreactivity was present in dendrites and neuronal perikarya. A large majority of the immunoreactivity found in dendrites was not associated with synaptic differentiations. Indeed, the dendrites, in which peroxidase deposit was seen, were not locally involved in synapses. Very scarce synaptic varicosities were observed in close apposition with IR dendrites. In the ventral horn, TH8 immunoreactivity was present in dendrites, with an accumulation of peroxidase deposit on the active zone of synapses, facing presynaptic membranes. Both the postsynaptic membrane and the submembrane area were IR. In addition, a few astroglial fine processes were immunostained; most of them were observed in the dorsal horn. Scarce IR astroglial profiles were observed in the ventral horn. These observations show that such an antiserum constitutes a useful tool for the ultrastructural analysis of 5-HT receptor distribution. Finally, correlation between the immunocytochemical localization of 5-HT receptor subtypes and the modes of 5-HT transmission in the spinal cord (wiring and volume transmissions) is discussed in the present report.

Animals↗

PubMed1994

Local administration of 7 beta-hydroxycholesteryl-3-oleate inhibits growth of experimental rat C6 glioblastoma.

The effect of 7 beta-hydroxycholesteryl-3-oleate on rat brain C6 glioblastoma cells was studied. Three days after the inoculation of 2 x 10(5) C6 cells into the frontal cortex of 6-day-old Wistar rats, two types of liposomes [consisting of either phosphatidylcholine and monosialoganglioside (PG:GM1, 10:1 mol/mol) only, or containing 7 beta-hydroxycholesterol, 7 beta-hydroxycholesteryl-3-oleate, 7 alpha-hydroxycholesteryl-3-oleate, or 7-ketocholesteryl-3-oleate] were injected into the xenograft. Ten days later, the animals were sacrificed, the tumors were stained with cresyl violet or hematoxylin/eosin, their volumes determined by image analysis, and their development followed by magnetic resonance imaging. The mean (+/- SE) tumor volume was 4.4 +/- 1.0 mm3. The injection of liposomes without oxysterol had no effect on tumor growth, whereas injection of liposomes containing 7 beta-hydroxycholesteryl-3-oleate (36 nmol) gave rise to a marked decrease in tumor volume (from 4.4 +/- 1.0 to 0.7 +/- 0.4 mm3). Seven nmol had no effect on tumor growth, 72 nmol were as efficient as 36 nmol, and 144 nmol attenuated the tumor volume by 50% only. Liposomes containing 72 nmol of oleic acid enhanced the tumor volume 4-fold. These findings were confirmed by magnetic resonance imaging. Thus, following induction of tumors in both the right and left sides of the cortex and treatment of the right side, magnetic resonance imaging indicated a significant decrease in tumor volume on the right side only. When C6 cells and 7 beta-hydroxycholesteryl-3-oleate were simultaneously injected, tumors did not develop in 80% of the animals. The clearance of [3H]7 beta-hydroxycholesteryl-3-oleate, of which 75% was converted to cholesterol, reached 99% after 48 h. Other oxysterols did not affect the tumor volume except that 7-keto-cholesteryl-3-oleate decreased the tumor volume by 50%. Thus, the 3-fatty acyl ester and 7 beta-hydroxyl groups are apparently required for the antitumor growth effect. Taken together, these data suggest that 7 beta-hydroxycholesteryl-3-oleate might be useful for local glioblastoma chemotherapy.

Administration, Topical↗

PubMed1994

Normal and pathological expression of GFAP promoter elements in transgenic mice.

The expression of the glial fibrillary acidic protein (GFAP), a component of astroglial intermediate filaments, is regulated under developmental and pathological conditions. In order to characterize DNA sequences involved in such regulations, we produced transgenic mice bearing 2 kb of the 5' flanking region of the murine GFAP gene linked to the Escherichia coli beta-galactosidase (beta-gal) reporter gene. Seven transgenic lines were obtained. We observed that the regulatory elements present in the transgene GFAP-nls-LacZ direct an expression in the neural and non-neural tissue and target in vivo an unexpected subpopulation of astrocyte. In the developing brain, beta-gal activity and GFAP appeared simultaneously and in the same region, on embryonic day 18 (E18), suggesting that the 2 kb of the promoter contains the regulatory sequences responsible for the perinatal vimentin/GFAP switch. In addition, we demonstrated that the 2 kb sequence of the GFAP promoter used in the transgene possess elements which are activated after a surgical injury, thus permitting to study some aspects of reactive gliosis in these transgenic mice. These transgenic lines provide a useful tool by enabling further studies of astroglial and, probably, neuronal physiologies.

Animals↗

PubMed1994

PRE-084, a sigma selective PCP derivative, attenuates MK-801-induced impairment of learning in mice.

We investigated the effect of the sigma selective PCP derivative PRE-084 on the impairment of learning induced in mice by the noncompetitive NMDA antagonist MK-801. Learning capacities were evaluated using the spontaneous alternation in a Y-maze test for spatial working memory, the step-down passive avoidance and the elevated plus-maze test for long-term memory. At doses about 1 mg/kg IP, PRE-084 significantly attenuated MK-801 (0.2 mg/kg IP) induced impairment of learning. The dose-response curve was bell-shaped which is typical for cognition enhancers. The effect of PRE-084 was antagonized by BMY-14802 (10 mg/kg IP) and suppressed by a chronic treatment with haloperidol (4 mg/kg/day SC for 7 days). Furthermore, PRE-084 did not affect scopolamine (1 mg/kg SC) induced amnesia but significantly attenuated mecamylamine (10 mg/kg IP) induced amnesia. These results show that sigma sites mediate a modulation of the NMDA receptor complex-dependent learning processes and may similarly affect the cholinergic nicotinic memory processes. Moreover, the PCP derivative PRE-084, acting selectively at sigma sites, reverses the amnesia induced by a drug acting at the PCP site.

Amnesia↗

PubMed1994

Study of 5-HT release with a chronically implanted microdialysis probe in the ventral horn of the spinal cord of unrestrained rats during exercise on a treadmill.

The ventral horn of the spinal cord is profusely innervated by serotonin (5-hydroxytryptamine, 5-HT) which presumably modulates locomotor activity through motoneurons. However, direct evidence of correlation between 5-HT release and activation of motoneurons is still lacking. In order to appreciate the functional characteristics of this innervation, we have used microdialysis to monitor the release of 5-HT in the spinal cord of rats spontaneously running on a treadmill. For this purpose, we developed an original surgical procedure adapted for the chronic implantation of a microdialysis probe in the lumbar spinal cord. The probe was kept in place for 40 days, and microdialysis experiments were carried out at days 8, 16, 20 and 32. 5-HT was detected with HPLC coupled to electrochemistry. This technique demonstrated that release of 5-HT is not increased during exercise. However, a significant decrease was measured during postexercise rest. 5-HT could still be detected 32 days after probe implantation. Detailed histological and immunocytochemical analysis based on glial fibrillary acidic protein and 5-HT immunocytochemistry showed minimal gliosis and the presence of serotonergic varicose fibers, respectively, at the probe contact. It thus appears that microdialysis can be performed through a probe implanted chronically in the spinal cord of unrestrained rat during an endurance running exercise.

Animals↗

PubMed1994

CD4 expression in neurons of the central nervous system.

CD4 is a member of the Ig gene super family expressed on the surface of many thymocytes and of a subset of T lymphocytes. Human CD4 is the receptor for HIV envelope glycoprotein gp120. Human and mouse CD4 transcripts are expressed in human and mouse central nervous system (CNS), but no corresponding proteins have been reported yet. We have analyzed mRNA expression and carried out immunological experiments on adult mouse brain with probes specific for the long and short CD4 transcripts and with antibodies monospecific for mouse CD4. The main result of these experiments is that the full length CD4 transcript and the CD4 protein are expressed coordinately in neurons throughout the adult mouse brain. CD4 immunoreactivity is also present in brain small vessel walls, ependymal cells, and choroid plexus. The brain mouse CD4 protein is indistinguishable from the thymus protein. In addition, we show that neuronal cells in primary cultures from human fetal CNS are immunoreactive to human CD4 mAbs.

Animals↗