No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Synaptic transmission is coordinated by a litany of protein-protein interactions that rely on the proper localization and function of pre- and post-synaptic Ca2+ channels. The axonal guidance/specification collapsin response mediator protein-2 (CRMP-2) was identified as a potential partner of the pre-synaptic N-type voltage-gated Ca2+ channel (CaV2.2). CRMP-2 bound directly to CaV2.2 in two regions; the channel domain I-II intracellular loop and the distal C-terminus. Both proteins co-localized within presynaptic sites in hippocampal neurons. Overexpression in hippocampal neurons of a CRMP-2 protein fused to EGFP caused a significant increase in Ca2+ channel current density whereas lentivirus-mediated CRMP-2 knockdown abolished this effect. Cell surface biotinylation studies showed an increased number of CaV2.2 at the cell surface in CRMP-2–overexpressing neurons. Both activity- and CRMP-2-phosphoryation altered the interaction between CaV2.2 and CRMP-2. I identified a CRMP-2-derived peptide (called CBD3) that bound CaV2.2 and effectively disrupted the interaction between CaV2.2 and CRMP-2. CBD3 peptide fused to the HIV TAT protein (TAT-CBD3) decreased neuropeptide release from sensory neurons and excitatory synaptic transmission in dorsal horn neurons, and reversed neuropathic hypersensitivity produced by an antiretroviral drug. Unchecked Ca2+ influx via N-methyl-D-aspartate receptors (NMDARs) has been linked to activation of neurotoxic cascades culminating in cell death (i.e. excitotoxicity). CRMP-2 was suggested to affect NMDAR trafficking and possibly involved in neuronal survival following excitotoxicity. Based upon these studies, I hypothesized that a peptide from CRMP2 could preserve neurons in the face of excitotoxic challenges. Lentiviral–mediated CRMP2 knockdown or treatment with TAT-CBD3 blocked neuronal death following glutamate exposure likely via blunting toxicity from NMDAR-mediated delayed calcium deregulation. TAT-CBD3 induced internalization of the NMDAR subunit NR2B in dendritic spines without altering somal surface expression. TAT-CBD3 reduced NMDA-mediated Ca2+-influx and currents in cultured neurons. The presented work validates CRMP-2 as a novel modulator of pre- and post-synaptic Ca2+ channels and provides evidence that the TAT-CBD3 peptide could be useful as a potential therapeutic for both chronic neuropathic pain and excitotoxicity following stroke or other neuronal insults.

This study examined the effect of neurotoxic chemical exposures on brain processes using Single Photon Emission Computed Tomography (SPECT). A control group carefully screened for good health and minimal chemical exposures was compared to two groups of patients diagnosed with health problems following exposure to pesticides or to organic solvents.

Le glufosinate d’ammonium (GLA) est un herbicide largement utilisé dans l'agriculture. Comme cela est le cas pour la plupart des pesticides, ses effets neurotoxiques et développementaux n'ont été que partiellement étudiés. L'exposition précoce des pesticides peut affaiblir la structure de base du développement du cerveau et provoquer des changements permanents conduisant un large éventail d'effets à long terme sur la santé et/ou sur le comportement. Mes travaux de thèse ont permis de montrer que l’exposition périnatale à de faibles doses de GLA induisait des perturbations de la neurogenèse et de la migration des neuroblastes au niveau de la zone sous ventriculaire vers les bulbes olfactifs. De plus l’analyse transcriptomique cérébrale montre une modification significative de l’expression de nombreux gènes responsables de la dynamique du cytosquelette impliqué dans la régulation de la migration des neuroblastes. Etant un analogue structural du glutamate, le GLA pourrait agir sur le cytosquelette via la modification de la polyglutamylation de la tubuline. Cette hypothèse expliquerait les altérations cellulaires observées. Par ailleurs, avons mis en évidence dans cette étude, des troubles du comportement des souris exposées semblables à ceux observables chez les modèles murins des « troubles du spectre autistique » (ASD-like). / Glufosinate ammonium (GLA) is one of the most widely used herbicides in agriculture. As for almost all pesticides, potential adverse effects of GLA have not been investigated in the brain developmental neurotoxicity perspective. Indeed, early pesticides exposure may weaken the developing brain and cause permanent brain alteration which could lead to a wide range of the lifelong effects on health and/or behavior. As an illustration, we showed that perinatal exposure to low doses of GLA induced behavioral defects in mice adulthood, characterized by many similarities with Autism Spectrum Disorders phenotype. My thesis deals with the molecular aspect of this perinatal GLA exposure. I demonstrated that GLA induced disturbances of proliferation and neuroblast migration from the subventricular zone to the olfactory bulbs. These defects were associated with significant change in the expression of many genes involved in neuroblast migration and cytoskeleton regulation as observed by brain transcriptome analysis. I showed that GLA act on the cytoskeleton through modification of polyglutamylation of tubulin which lead to cell division/migration disturbances and cell differentiation defect. My work thus provides a new molecular link between pre- and post-natal exposure to the herbicide GLA and the onset of ASD like phenotype later in life. It also raises the fundamental concerns about the ability of current safety testing to assess risks of pesticide exposure during critical developmental periods.

M.A. (Psychology) / The study of behavioural toxicology was started in 1972 with the Port Pirie Cohort study and therefor a relative young field. Little information is available about the effect of cigarette smoke, containing the toxic substance carbon monoxide, on the neurocognitive functioning of children. The purpose of this study was to determine whether carbon monoxide has an effect on the neurocognitive functioning of children, more specifically as it relates to school performance. A group of school children was selected in the Vaal Triangle area who were sUbjected to a large quantity of cigarette smoke during the day and a group of children was selected who had no contact with any cigarette smoke during the day. The results of these groups were compared. From the results obtained it appears that cigarette smoke, would have a negative neurocognitive functioning of the children.

Neuropsychological toxicology investigates the impact of chemical exposure on the structure and functioning of the nervous system and by implication the neuropsychological performance of affected individuals. As in mainstream neuropsychology, brain damage is assessed by measuring changes in the cognitive, psychomotor and emotional domains using diagnostic neuropsychological tests. The field of neuropsychological toxicology has undergone significant growth in the last 20 years, amongst growing concerns over people’s potential everyday exposure to approximately 70 000 chemicals. Growing awareness of the possible dangers associated with neurotoxic exposure has lead to the increased regulation of exposure levels especially in industrial settings. This in turn has lead to a gradual shift in neuropsychological toxicology from the assessment of severe neurotoxic damage to the evaluation of subclinical signs, which may develop into disabling damage over many years of exposure. The assessment of these subclinical signs has proven to be tricky as they cannot always be measured through diagnostic tests and may be mimicked or hidden by numerous confounding variables. The need for the effective assessment of these subclinical signs has created a need for more sensitive tests and improved research methodology. This paper uses evidence from cellular pathology and anatomical pathology (dynamic brain localisation theory) as a guide for the selection of neuropsychological tests. The purpose of the paper is to review the neuropsychological outcomes of toxic exposure, with an emphasis on test sensitivity (screening) and specificity (diagnostic) to carbon disulphide (solvent), manganese (metal) and organophosphate (pesticide) exposure. Findings from this review point to the possible advantages of the continued use of standardised neuropsychological batteries that enable the assessment of global functions in addition to tests that measure deficits associated with the toxicodynamics of the neurotoxin under investigation. Methodological recommendations include the use of simultaneous cross-sectional and longitudinal designs to control for numerous confounding variables and correlation designs to determine dose-response relationships. Future studies need to address the sensitivity and specificity criteria of various neuropsychological measures utilising the principle of neurotoxicodynamics. / Dissertation (MA (Research Psychology))--University of Pretoria, 2007. / Psychology / MA / unrestricted

No description available.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Glutamate clearance by astrocytes is an essential part of physiological excitatory neurotransmission. Failure to adapt or maintain low levels of glutamate in the central nervous system is associated with multiple acute and chronic neurodegenerative diseases. The primary excitatory amino acid transporters (EAATs) in human astrocytes are EAAT1 and EAAT2 (GLAST and GLT-1 respectively in rodents). While the inhibition of a ubiquitously-expressed serine/threonine protein kinase, the calcium/calmodulindependent kinase (CaMKII) results in diminished glutamate uptake in cultured primary rodent astrocytes, the molecular mechanism underlying this regulation is unknown. In order to delineate this mechanism, we use a heterologous expression model to explore CaMKII regulation of EAAT1 and EAAT2. In transiently transfected HEK293T cells, pharmacological inhibition of CaMKII and overexpression of a dominant-negative version of CaMKII (Asp136Asn) reduces [3H]-glutamate uptake by EAAT1, without altering EAAT2 mediated glutamate uptake. Surprisingly, overexpression of a constitutively active autophosphorylation mutant (Thr287Asp) to increase autonomous CaMKII activity and a mutant incapable of autophosphorylation (Thr287Val) had no effect on either EAAT1 or EAAT2 mediated glutamate uptake. Pulldown of FLAGtagged glutamate transporters suggests CaMKII does not interact with EAAT1 or EAAT2. SPOTS peptide arrays and recombinant GST-fusion proteins of the intracellular N- and C-termini of EAAT1 identified two potential phosphorylation sites at residues Thr26 and Thr37 in the N-terminus. Introducing an Ala (a non-phospho mimetic) but not an Asp (phosphomimetic) at Thr37 diminished EAAT1-mediated glutamate uptake, suggesting that the phosphorylation state of this residue is important for constitutive EAAT1 function. In sum, this is the first report of a glutamate transporter being identified as a direct CaMKII substrate. These findings indicate that CaMKII signaling is a critical driver of homeostatic glutamate uptake by EAAT1. Aberrations in basal CaMKII activity disrupt glutamate uptake, which can perpetuate glutamate-mediated excitotoxicity and result in cellular death.

Indiana University-Purdue University Indianapolis (IUPUI) / Research in the alcohol preferring (P) rat has indicated that peri-adolescent alcohol (EtOH) consumption enhances the acquisition of oral operant EtOH self-administration, inhibits the extinction of responding for EtOH, augments EtOH-seeking behaviors, and increases relative reward value of EtOH during adulthood. Experiment 1 was conducted to determine if these adult effects of peri-adolescent EtOH intake could be observed using an Intracranial Self-Administration (ICSA) model. It was hypothesized that an increased sensitivity to the rewarding actions of EtOH would be manifested in peri-adolescent-EtOH-exposed subjects compared to naive subjects when the opportunity to self-administer EtOH to the posterior ventral tegmental area (pVTA) is available in adulthood. The pVTA is a primary site for EtOH’s reinforcing and rewarding properties in the mesolimbic dopamine (DA) system. Experiment 2 was a dose-response examination of the effects of EtOH administered to the pVTA on downstream DA efflux in the nucleus accumbens shell (AcbSh) via a joint Microinjection-Microdialysis (MicroMicro) procedure. Male P rats were given 24-h free-choice exposure to 15% volume/volume EtOH from postnatal day (PD) 30 to PD 60, or remained experimentally naive, with ad lib food and water. By the end of the periadolescent exposure period, average consumption was 7.3 g/kg/day of EtOH. After PD 75, periadolescent-EtOH-exposed and naïve rats were either implanted with an injector guide cannula aimed at the right pVTA for ICSA (Experiment 1), or two cannulae, one aimed at the right pVTA (injector) and one at the ipsilateral AcbSh (microdialysis) for MicroMicro (Experiment 2). Following one week of recovery from surgery, ICSA subjects were placed in standard two-lever (active and inactive) operant chambers. Test sessions were 60 min in duration and occurred every other day for a total of 7 sessions. Rats were randomly assigned to one of 5 groups (n=4-9/group) that self-infused (FR1 schedule) either aCSF (vehicle, 0 mg%), 50, 75, 100, or 150 mg% EtOH during 4 sessions, aCSF only for sessions 5 and 6 (extinction), and the initial concentration again for session 7 (reinstatement). MicroMicro subjects received six days of recovery from surgery, probe implantation the day before testing, and then continuous microdialysis for DA with 15 min microdialysis samples collected before, during, and then two hrs after 10-min pulse microinjection of either aCSF (vehicle, 0 mg%), 50, 75, 100, or 150 mg% EtOH. Neither EtOH-exposed nor naive groups of P rats self-infused the aCSF or 50 mg% EtOH concentration. While the naive group did not self-infuse the 75 or 100 mg% EtOH concentrations, the peri-adolescent EtOH-exposed group of P rats did readily discriminate the active lever from the inactive lever at these concentrations. Both groups self-infused the 150 mg% EtOH concentration. Pulse microinjections of EtOH during the MicroMicro procedure revealed that 75 and 100 mg% concentrations of EtOH increased downstream DA in the AcbSh of EtOH-exposed, but not naïve, subjects. 150 mg% EtOH increased downstream DA in both adolescent treatment groups. Overall, the results indicate that consumption of EtOH by P rats during peri-adolescence increases the reinforcing properties of EtOH in the pVTA in adulthood. The results also indicate that there were differential effects of peri-adolescent EtOH exposure on DA efflux in the AcbSh. This provides evidence that peri-adolescent EtOH-exposure produces long-lasting alterations in neural circuitry involved in EtOH-reinforcement, during adulthood.