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A Privat

Publications and source records attributed to A Privat.

At least 19 recordsLinked to original sources
PubMed2006

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP panel: spontaneous recovery after spinal cord injury and statistical power needed for therapeutic clinical trials.

The International Campaign for Cures of Spinal Cord Injury Paralysis (ICCP) supported an international panel tasked with reviewing the methodology for clinical trials in spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the first of four papers. Here, we examine the spontaneous rate of recovery after SCI and resulting consequences for achieving statistically significant results in clinical trials. We have reanalysed data from the Sygen trial to provide some of this information. Almost all people living with SCI show some recovery of motor function below the initial spinal injury level. While the spontaneous recovery of motor function in patients with motor-complete SCI is fairly limited and predictable, recovery in incomplete SCI patients (American spinal injury Association impairment scale (AIS) C and AIS D) is both more substantial and highly variable. With motor complete lesions (AIS A/AIS B) the majority of functional return is within the zone of partial preservation, and may be sufficient to reclassify the injury level to a lower spinal level. The vast majority of recovery occurs in the first 3 months, but a small amount can persist for up to 18 months or longer. Some sensory recovery occurs after SCI, on roughly the same time course as motor recovery. Based on previous data of the magnitude of spontaneous recovery after SCI, as measured by changes in ASIA motor scores, power calculations suggest that the number of subjects required to achieve a significant result from a trial declines considerably as the start of the study is delayed after SCI. Trials of treatments that are most efficacious when given soon after injury will therefore, require larger patient numbers than trials of treatments that are effective at later time points. As AIS B patients show greater spontaneous recovery than AIS A patients, the number of AIS A patients requiring to be enrolled into a trial is lower. This factor will have to be balanced against the possibility that some treatments will be more effective in incomplete patients. Trials involving motor incomplete SCI patients, or trials where an accurate assessment of AIS grade cannot be made before the start of the trial, will require large subject numbers and/or better objective assessment methods.

Clinical Trials as Topic↗
PubMed2006

Guidelines for the conduct of clinical trials for spinal cord injury (SCI) as developed by the ICCP panel: clinical trial outcome measures.

An international panel reviewed the methodology for clinical trials of spinal cord injury (SCI), and provided recommendations for the valid conduct of future trials. This is the second of four papers. It examines clinical trial end points that have been used previously, reviews alternative outcome tools and identifies unmet needs for demonstrating the efficacy of an experimental intervention after SCI. The panel focused on outcome measures that are relevant to clinical trials of experimental cell-based and pharmaceutical drug treatments. Outcome measures are of three main classes: (1) those that provide an anatomical or neurological assessment for the connectivity of the spinal cord, (2) those that categorize a subject's functional ability to engage in activities of daily living, and (3) those that measure an individual's quality of life (QoL). The American Spinal Injury Association impairment scale forms the standard basis for measuring neurologic outcomes. Various electrophysiological measures and imaging tools are in development, which may provide more precise information on functional changes following treatment and/or the therapeutic action of experimental agents. When compared to appropriate controls, an improved functional outcome, in response to an experimental treatment, is the necessary goal of a clinical trial program. Several new functional outcome tools are being developed for measuring an individual's ability to engage in activities of daily living. Such clinical end points will need to be incorporated into Phase 2 and Phase 3 trials. QoL measures often do not correlate tightly with the above outcome tools, but may need to form part of Phase 3 trial measures.

Activities of Daily Living↗
PubMed2006

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP Panel: clinical trial inclusion/exclusion criteria and ethics.

The International Campaign for Cures of Spinal Cord Injury Paralysis established a panel tasked with reviewing the methodology for clinical trials for spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the third of four papers. It examines inclusion and exclusion criteria that can influence the design and analysis of clinical trials in SCI, together with confounding variables and ethical considerations. Inclusion and exclusion criteria for clinical trials should consider several factors. Among these are (1) the enrollment of subjects at appropriate stages after SCI, where there is supporting data from animal models or previous human studies; (2) the severity, level, type, or size of the cord injury, which can influence spontaneous recovery rate and likelihood that an experimental treatment will clinically benefit the subject; and (3) the confounding effects of various independent variables such as pre-existing or concomitant medical conditions, other medications, surgical interventions, and rehabilitation regimens. An issue of substantial importance in the design of clinical trials for SCI is the inclusion of blinded assessments and sham surgery controls: every effort should be made to address these major issues prospectively and carefully, if clear and objective information is to be gained from a clinical trial. The highest ethical standards must be respected in the performance of clinical trials, including the adequacy and clarity of informed consent.

Clinical Trials as Topic↗
PubMed2006

Guidelines for the conduct of clinical trials for spinal cord injury as developed by the ICCP panel: clinical trial design.

The International Campaign for Cures of Spinal Cord Injury Paralysis established a panel tasked with reviewing the methodology for clinical trials for spinal cord injury (SCI), and making recommendations on the conduct of future trials. This is the fourth of four papers. Here, we examine the phases of a clinical trial program, the elements, types, and protocols for valid clinical trial design. The most rigorous and valid SCI clinical trial would be a prospective double-blind randomized control trial utilizing appropriate placebo control subjects. However, in specific situations, it is recognized that other trial procedures may have to be considered. We review the strengths and limitations of the various types of clinical trials with specific reference to SCI. It is imperative that the design and conduct of SCI clinical trials should meet appropriate standards of scientific inquiry to insure that meaningful conclusions about efficacy and safety can be achieved and that the interests of trial subjects are protected. We propose these clinical trials guidelines for use by the SCI clinical research community.

Clinical Trials as Topic↗
PubMed2004

Glial scar and axonal regeneration in the CNS: lessons from GFAP and vimentin transgenic mice.

Astrocytes play an active role in the brain and spinal cord. For example, they have a function in formation and maintenance of the blood-brain barrier, ion homeostasis, neurotransmitter transport, production of extracellular matrix, and neuromodulation. Moreover, they play a role in preserving or even restoring the structural and physiological integrity after tissue injury. Currently, the function of astrocytes was studied with regard to the controversially discussed aspects of permissivity on the one-hand-side and inhibition of the other side exerted by reactive astrocytes for axonal regrowth in the adult CNS. Accordingly, knock-out mice deficient in vimentin (VIM) and/or glial fibrillary acidic protein (GFAP), the two major IF-proteins of astrocytes, were investigated. In addition, in vitro studies were carried out, on whether the absence of one or both proteins (VIM, GFAP) influences axonal regeneration. In experimental animals, a hemisection of the spinal cord was performed utilizing the above mentioned double-mutant mice. The knock-out mice were generated by gene targeting. Double-mutants were obtained by crossing single null mice. The in vitro results indicate that both VIM and GFAP were absent in astrocytic cultures obtained from double-mutant mice. On the other side, the proteins were detected in more than 85%, of cultured cells from wild types. Co-culture of mutant mice astrocytes with neurons revealed that the neuronal density was different from that obtained in culture with wild type astrocytes. On the other side, there was a marked increase in neuronal density in co-cultures utilizing both GFAP knock-out- or double-mutant mice astrocytes again as compared to co-cultures with wild type astrocytes. Moreover, the neurite length of neurons was significantly increased in experiments with neurons growing on astrocytes from GFAP-knock-out or double-mutant mice. The in vivo experiments demonstrate an increase of nestin (NES) immunoreactivity at three days in the sectioned side of the spinal cord, in the perikaryon and astroglial processes. In double-mutant mice only a slight increase in NES-immunoreactivity was found in the lesion side, albeit confined to the perikaryon of astrocytes. Below the lesion, serotonin immunostaining was dramatically reduced three days after the insult in both sides, particularly in the lesion side. The decrease was more pronounced in double-mutant than in wild type mice. On the other side, double-mutant mice had a much higher density of serotonergic fibers in the ventral horn in the lesioned side. In conclusion, the findings demonstrate that in the absence of important astrocytic proteins as VIM and GFAP, the astroglial response to injury is significantly modified underlying reduced scar formation. Attenuation of scar formation may enhance axonal sprouting of serotonergic axons below the lesion, which specifically reinnervate motoneuron pools.

Animals↗
PubMed2003

Axonal plasticity and functional recovery after spinal cord injury in mice deficient in both glial fibrillary acidic protein and vimentin genes.

The lack of axonal regeneration in the injured adult mammalian spinal cord leads to permanent functional disabilities. The inability of neurons to regenerate their axon is appreciably due to an inhospitable environment made of an astrocytic scar. We generated mice knock-out for glial fibrillary acidic protein and vimentin, the major proteins of the astrocyte cytoskeleton, which are upregulated in reactive astrocytes. These animals, after a hemisection of the spinal cord, presented reduced astroglial reactivity associated with increased plastic sprouting of supraspinal axons, including the reconstruction of circuits leading to functional restoration. Therefore, improved anatomical and functional recovery in the absence of both proteins highlights the pivotal role of reactive astrocytes in axonal regenerative failure in adult CNS and could lead to new therapies of spinal cord lesions.

Animals↗
PubMed2003

Early programmed cell death in human NT2 cell cultures during differentiation induced by all-trans-retinoic acid.

Previous studies have demonstrated that programmed cell death takes place at different stages during the development of the CNS in vivo. Our purpose in this study was to detect early programmed cell death associated with the induction of differentiation by retinoic acid (RA) in the NT2 cell line. By using the annexin V labeling as a marker of apoptosis, a significant apoptotic cell death was quantified during the third and the fourth days of the RA treatment. Double-labeling studies using the staining of the genomic DNA strand breaks with the terminal deoxyribosyl-transferase-mediated dUTP nick end-labeling (TUNEL) assay and either nestin or microtubule-associated protein 2 (MAP2) showed that 1) the early apoptotic cell death affected mostly nestin-positive cells and 2) after 8 days of differentiation, although cells with neuronal phenotypes are present, no colabeled TUNEL/MAP2 cells were detected. With regard to the neuronal protein MAP2, we observed discrete immunolabeling of a few NT2 cells as early as day 3 of the differentiation and a significant emergence of MAP2-immunopositive cells at days 6-8. Thus, our results show that, when as a whole the differentiating NT2 cell population is considered, 1) the apoptotic cell death observed during the third day of differentiation occurs mostly in undifferentiated cells, 2) this process coincides with the first detection of the neuronal phenotype in NT2 cell cultures, and 3) the end of the cell death period in NT2 cell cultures is marked by both the accumulation of MAP2-positive cells and the beginning of expression of the Bcl-2 protein in the cultures.

Annexin A5↗
PubMed2003

Astrocytes as support for axonal regeneration in the central nervous system of mammals.

Reactive astrocytes are one of the main impediments for axonal regeneration in the central nervous system of mammals. Using mice KO for GFAP and vimentin, we show that reinnervation occurs after an hemisection of the spinal cord, mainly through sprouting of controlateral intact serotoninergic and cortico-spinal axons, thanks to the absence of glial reactivity. This reinnervation is paralleled by the restoration of impaired locomotion of the ipselateral hindleg. Future applications to spinal cord injured patients are discussed.

Animals↗
PubMed2003

The human NTERA2 neural cell line generates neurons on growth under neural stem cell conditions and exhibits characteristics of radial glial cells.

NTERA2 cells are a human neural cell line generating neurons after exposure to retinoic acid and, as such, are widely used as a model of neurogenesis. We report that these cells form spheres when grown in serum-free medium supplemented with basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). These spheres were found to express markers of radial glial cells such as, Pax6, glutamate transporter (GLAST), tenascin C, brain lipid-binding protein (BLBP), and the 3CB2 antigen. On plating on an adhesive substrate, NTERA2 spheres generate a large percentage of immature neurons (30-50%) together with a minority of cells of the oligodendrocyte lineage. Thus NTERA2 cells share properties with neural stem cells. However, at variance with the latter, we found that they produce their own bFGF implicated in an autocrine or paracrine proliferative loop and that they do not generate astrocytes after differentiation. These results provide an interesting model to study radial glial cells and their role in human neurogenesis.

Animals↗
PubMed2001

Effects of radiofrequency exposure on the GABAergic system in the rat cerebellum: clues from semi-quantitative immunohistochemistry.

The widespread use of cellular phones raises the problem of interaction of electromagnetic fields with the central nervous system (CNS). In order to measure these effects on neurotransmitter content in the CNS, we developed a protocol of neurotransmitter detection based on immunohistochemistry and image analysis. Gamma-vinyl-GABA (GVG), an inhibitor of the GABA-transaminase was injected in rats to increase GABA concentration in the CNS. The cellular GABA contents were then revealed by immunohistochemistry and semi-quantified by image analysis thanks to three parameters: optical density (O.D.), staining area, and number of positive cells. The increase in cerebellar GABA content induced by GVG 1200 mg/kg was reflected in these three parameters in the molecular and the granular layers. Therefore, control of immunohistochemistry parameters, together with appropriate image analysis, allowed both the location and the detection of variations in cellular neurotransmitter content. This protocol was used to investigate the effects of exposure to 900 MHz radiofrequencies on cerebellar GABA content. Both pulsed emission with a specific absorption rate (SAR) of 4 W/kg and continuous emission with high SAR (32 W/kg) were tested. We observed a selective diminution of the stained processes area in the Purkinje cell layer after exposure to pulsed radiofrequency and, in addition, a decrease in O.D. in the three cell layers after exposure to continuous waves. Whether this effect is, at least partly, due to a local heating of the tissues is not known. Overall, it appears that high energetic radiofrequency exposure induces a diminution in cellular GABA content in the cerebellum.

4-Aminobutyrate Transaminase↗
PubMed2001

Inactivation of the glial fibrillary acidic protein gene, but not that of vimentin, improves neuronal survival and neurite growth by modifying adhesion molecule expression.

Intermediate filaments (IFs) are a major component of the cytoskeleton in astrocytes. Their role is far from being completely understood. Immature astrocytes play a major role in neuronal migration and neuritogenesis, and their IFs are mainly composed of vimentin. In mature differentiated astrocytes, vimentin is replaced by the IF protein glial fibrillary acidic protein (GFAP). In response to injury of the CNS in the adult, astrocytes become reactive, upregulate the expression of GFAP, and reexpress vimentin. These modifications contribute to the formation of a glial scar that is obstructive to axonal regeneration. Nevertheless, astrocytes in vitro are considered to be the ideal substratum for the growth of embryonic CNS axons. In the present study, we have examined the potential role of these two major IF proteins in both neuronal survival and neurite growth. For this purpose, we cocultured wild-type neurons on astrocytes from three types of knock-out (KO) mice for GFAP or/and vimentin in a neuron-astrocyte coculture model. We show that the double KO astrocytes present many features of immaturity and greatly improve survival and neurite growth of cocultured neurons by increasing cell-cell contact and secreting diffusible factors. Moreover, our data suggest that the absence of vimentin is not a key element in the permissivity of the mutant astrocytes. Finally, we show that only the absence of GFAP is associated with an increased expression of some extracellular matrix and adhesion molecules. To conclude, our results suggest that GFAP expression is able to modulate key biochemical properties of astrocytes that are implicated in their permissivity.

Animals↗
PubMed2001

The anti-amnesic effects of sigma1 (sigma1) receptor agonists confirmed by in vivo antisense strategy in the mouse.

The sigma1 (sigma1) receptor cDNA was recently cloned in several animal species, including the mouse. In order to firmly establish the implication of sigma1 receptors in memory, a phosphorothioate-modified antisense oligodeoxynucleotide (aODN) targeting the sigma1 receptor mRNA and a mismatched analog (mODN) were administered intracerebroventricularly for 3 days in mice. Scatchard analyses of in vitro (+)-[3H]SKF-10,047 binding to sigma1 sites showed that Bmax values were significantly decreased in the hippocampus (-58.5%) and cortex (-38.1%), but not in the cerebellum, of aODN treated mice, as compared to saline- or mODN-treated animals. In vivo binding levels were also significantly decreased after aODN treatment in the hippocampus and cortex but not in the cerebellum. The anti-amnesic effects of the selective sigma1 agonists PRE-084 or SA4503 were evaluated against the learning impairments induced by dizocilpine or scopolamine, respectively, using spontaneous alternation behavior and passive avoidance task. The anti-amnesic effects of PRE-084 or SA4503, observed after saline- or mODN-treatment, were blocked after aODN administration. These observations bring a molecular basis to the modulatory role of sigma1 receptors in memory processes.

Amnesia↗
PubMed2001

Interaction of gacyclidine enantiomers with 'non-NMDA' binding sites in the rat central nervous system.

Gacyclidine, a channel blocker of N-methyl-D-aspartate receptors (NMDAR), exhibits potent neuroprotective properties and a low self-neurotoxicity. Preventing its interaction with NMDARs we demonstrate, through the use of its enantiomers, that gacyclidine also interacts with other ('non-NMDA') binding sites. The autoradiographic study showed that these sites displayed a uniform specific binding in the forebrain and a more discrete distribution in the molecular layer of the cerebellum. The 'non-NMDA' binding sites could exert a modulatory control on glutamatergic neurotransmission.

Animals↗
PubMed2001

Characterization of 'non-N-methyl-D-Aspartate' binding sites for gacyclidine enantiomers in the rat cerebellar and telencephalic structures.

Gacyclidine is a non-competitive NMDA receptor antagonist with potent neuroprotective properties. However, we have previously demonstrated that gacyclidine enantiomers [(-) and (+)GK11] interact with other ('non-NMDA') binding sites which may play a role in the lower self-neurotoxicity of this compound relative to the other NMDA receptor antagonists. Evidence for these binding sites has been obtained from autoradiographic and membrane binding experiments. They were found to be expressed at high levels in the molecular layer of the cerebellum, although they can also been seen in the granular layer and in telencephalic regions. The present study was designed to further characterize these gacyclidine 'non-NMDA' binding sites. The pharmacological profiles obtained on cerebellar and telencephalic membrane homogenates showed that they could not be linked directly to the main receptors or uptake complexes of the central nervous system (CNS). However, the comparison of (-) and (+)[(3)H]GK11 binding distribution in different mutant animals bearing specific cellular deficits in the cerebellum has demonstrated that the gacyclidine 'non-NMDA' binding sites are associated with the dendritic trees of Purkinje cells. Interestingly, our study also shows that the radioligand binding to both cerebellar and telencephalic structures could be modulated by endogenous factors which can be removed by a stringent prewashing procedure.

Animals↗
PubMed2000

Neuroprotective effects of a novel NMDA antagonist, Gacyclidine, after experimental contusive spinal cord injury in adult rats.

The aim of this study was to analyze the optimal time-window for neuroprotection by a novel NMDA antagonist, Gacyclidine, after experimental spinal cord injury, in terms of its functional, histopathological and electrophysiological effects. This molecule has already demonstrated its capacity for reducing the extent of an ischemic lesion and is currently experimented in a clinical trial of spinal cord injury. In this study, the spinal cord of rats was damaged by a contusive method and the animals were treated by saline or 1 mg/kg of Gacyclidine i.v., 10, 30, 60 and 120 min after injury. The time-course of the motor score was evaluated on days 1, 7 and 18 after injury, and somatosensory evoked potentials were determined on day 20. The animals were then killed and the cross-sectional area of the spinal cord (at the epicenter of the injury, above and below the injury), was measured. Walking recovery was better (P<0.0125) in the group treated 10 min after injury than in the untreated injured animals after 18 days of injury. Motor performances were related to the preservation of a larger undamaged area of spinal cord at the level of the injury (P<0.0125). Somatosensory evoked potential amplitudes were also higher in this group. These results confirm that Gacyclidine attenuates spinal cord damage after an experimental spinal cord lesion. Recovery was better within the group treated 10 min after injury compared with the other groups, which certainly confirms that the acute time-course of glutamate release requires rapid pharmacological intervention to achieve good results.

Animals↗