Toward a global and reproducible science for brain imaging in neurotrauma: the ENIGMA adult moderate/severe traumatic brain injury working group.

The global burden of mortality and morbidity caused by traumatic brain injury (TBI) is significant, and the heterogeneity of TBI patients and the relatively small sample sizes of most current neuroimaging studies is a major challenge for scientific advances and clinical translation. The ENIGMA (Enhancing NeuroImaging Genetics through Meta-Analysis) Adult moderate/severe TBI (AMS-TBI) working group aims to be a driving force for new discoveries in AMS-TBI by providing researchers world-wide with an effective framework and platform for large-scale cross-border collaboration and data sharing. Based on the principles of transparency, rigor, reproducibility and collaboration, we will facilitate the development and dissemination of multiscale and big data analysis pipelines for harmonized analyses in AMS-TBI using structural and functional neuroimaging in combination with non-imaging biomarkers, genetics, as well as clinical and behavioral measures. Ultimately, we will offer investigators an unprecedented opportunity to test important hypotheses about recovery and morbidity in AMS-TBI by taking advantage of our robust methods for large-scale neuroimaging data analysis. In this consensus statement we outline the working group's short-term, intermediate, and long-term goals.

Electrophysiological Characterization of Networks and Single Cells in the Hippocampal Region of a Transgenic Rat Model of Alzheimer's Disease.

The hippocampus and entorhinal cortex (EC) are areas affected early and severely in Alzheimer's disease (AD), and this is associated with deficits in episodic memory. Amyloid-ß (Aß), the main protein found in amyloid plaques, can affect neuronal physiology and excitability, and several AD mouse models with memory impairments display aberrant network activity, including hyperexcitability and seizures. In this study, we investigated single cell physiology in EC and network activity in EC and dentate gyrus (DG) in the McGill-R-Thy1-APP transgenic rat model, using whole-cell patch clamp recordings and voltage-sensitive dye imaging (VSDI) in acute slices. In slices from transgenic animals up to 4 months of age, the majority of the principal neurons in Layer II of EC, fan cells and stellate cells, expressed intracellular Aß (iAß). Whereas the electrophysiological properties of fan cells were unaltered, stellate cells were more excitable in transgenic than in control rats. Stimulation in the DG resulted in comparable patterns in both groups at three and nine months, but at 12 months, the elicited responses in the transgenic group showed a significant preference for the enclosed blade, without any change in overall excitability. Only transient changes in the local network activity were seen in the medial EC (MEC). Although the observed changes in the McGill rat model are subtle, they are specific, pointing to a differential and selective involvement of specific parts of the hippocampal circuitry in Aß pathology.

Stereological estimation of neuron number and plaque load in the hippocampal region of a transgenic rat model of Alzheimer's disease.

The main hallmarks of Alzheimer's disease (AD) are senile plaques, neurofibrillary tangles and neuronal death. The McGill-R-Thy1-APP rat is one of the few transgenic rat models of AD that displays progressive amyloid pathology. This study aimed to further characterise this rat model, focusing on the pathological changes in the hippocampal formation and the parahippocampal region. These structures, that are important for episodic memory and spatial navigation, are affected in the early stages of the disease. This study used unbiased stereology to investigate possible neuronal loss in the CA1, subiculum and entorhinal cortex of 18-month-old homozygous McGill-R-Thy1-APP rats, and also quantified the plaque load in all the areas of the hippocampal formation and parahippocampal region from 9 to 18 months old. A significant reduction of neurons at 18 months was only seen in the subiculum. The first plaque pathology was seen at 9 months in the subiculum. Although the quantified plaque load was variable between animals, the pattern of spatiotemporal progression was similar for all animals. The spread of plaque pathology mainly affected anatomically connected regions. Overall, the plaque pathology observed in the transgenic rats was similar to the early phases of amyloid beta (Aß)-deposition described in human patients. The findings here thus indicate that the McGill-R-Thy1-APP rat could be a good model of the Aß pathology in AD, but less so with respect to neuron loss.

Pregnancy outcomes among female dental personnel--a registry-based retrospective cohort study.

OBJECTIVES: The aim of this study was to investigate whether women who have worked as dental personnel in Norway, a group with possible previous exposure to mercury vapor, have had an excess risk of having children with congenital malformations or other adverse pregnancy outcomes compared to the general population. METHODS: A cohort of female dental personnel was identified from the archives of the public dental healthcare and the national trade unions in Norway. Data on births and pregnancy outcomes during 1967-2006 were obtained from the Medical Birth Registry of Norway (MBRN). The final cohort of dental personnel consisted of 4482 dental assistants and 1011 dentists. All other women registered in the MBRN were assigned to the control group, in total 1,124,758. Excess risks of several adverse pregnancy outcomes for dental personnel compared to the general population were estimated. Analyses were conducted for the whole time period as well as stratified by 10-year periods. RESULTS: Female dental personnel had no observed increased occurrence of congenital malformations (including malformations of the central nervous system, dysplasia of the hip, clubfoot, malformations of the heart and great vessels), low birth weight, preterm birth, small for gestational age, changed gender ratio, multiple birth, stillbirth, or prenatal death. CONCLUSION: On a group level, we did not observe any excess risks of congenital malformations or other adverse pregnancy outcomes among female dental personnel in Norway during 1967-2006 compared to the general population.

Uptake and efflux of methylmercury in vitro: comparison of transport mechanisms in C6, B35 and RBE4 cells.

Methylmercury (MeHg) is a neurotoxicant which enters the brain and may cause permanent change. Thus, the properties of MeHg transport across cell membranes are a key factor in designing an appropriate model for MeHg neurotoxicity. This study uses cell cultures to examine the uptake and efflux mechanisms of methylmercury in C6 glioma, B35 neuroblastoma and rat brain endothelial (RBE4) cells. The cellular uptake and efflux of MeHg was investigated using (14)C-labeled MeHg. The uptake of MeHg-chloride was temperature-independent while the uptake of MeHg-L-cysteine was temperature-dependent in all the three cell types. This indicates that uptake of MeHg-chloride is due to passive diffusion and uptake of MeHg-L-cysteine is due to a protein carrier. Substrates of the amino acid transport system L inhibited uptake of MeHg-L-cysteine in C6 and RBE4 cells, but not B35 cells, indicating a role for system L in MeHg-uptake in the former two. Probenecid, Na(+)-free medium, MeHg and several L-amino acids did not alter the efflux of MeHg from C6 and RBE4 cells. The amino acids L-cysteine and cystine however, increased the efflux. Both cysteine and cystine are important in the generation of glutathione (GSH), suggesting the involvement of GSH in MeHg efflux. HgCl(2) at low concentrations (0.5 and 1.0 microM) decreased the MeHg efflux and at high concentrations (5.0 and 10.0 microM) increased the efflux. This inhibiting effect of HgCl(2) at low concentrations is possibly due to binding to GSH while the effect of high HgCl(2) concentrations is attributed to disrupted membrane integrity, as measured by Trypan blue. This study demonstrates differing transport mechanisms of MeHg in the cell lines C6, B35 and RBE4.

Docosahexaenoic acid may act as a neuroprotector for methylmercury-induced neurotoxicity in primary neural cell cultures.

The ability of docosahexaenoic acid (DHA) to modulate methylmercury (MeHg)-induced neurotoxicity was investigated in primary astrocytes and neurons from the cerebellum. Gas chromatography measurements indicated increased DHA content in both cell types after 24h supplementation. After individual or combined treatment with MeHg (10microM) and DHA (30 and 90microM), the cell-associated MeHg measurements were done using (14)C-labelled MeHg. In addition, mitochondrial activity was evaluated by MTT reduction, glutathione (GSH) content was measured with the fluorescent indicator monochlorobimane (MCB) and reactive oxygen species (ROS) were detected with the fluorescent indicator-chloro methyl derivative of di-chloro di-hydro fluorescein diacetate (CMH(2)DCFDA). For all the tested treatments, i.e. DHA, MeHg or DHA+MeHg treatment, the neurons differed significantly (p<0.001) from astrocytes exhibiting increased ROS production and decreased MTT activity. After MeHg and 30microM DHA treatment there were no changes in MTT or GSH content but significant decrease (p<0.001) in ROS was observed in both the cell types when compared to MeHg alone. The cell-associated MeHg measurements indicated reduced MeHg-accumulation in both cell types (p<0.05) upon 30microM DHA exposure. Taken together, this study, for the first time establishes that DHA pretreatment effectively reduces cell-associated MeHg and prooxidant response from MeHg in both cerebellar astrocytes and neurons and thus supports the hypothesis that fish-derived nutrients offer possible neuroprotection from MeHg.

The use of fluorescence for detecting MeHg-induced ROS in cell cultures.

The effect of methylmercury (MeHg) on reactive oxygen species (ROS) induction in neural cell lines was measured by the fluorescent probe, chloro methyl derivative of di-chloro di-hydro fluoresceindiacetate (CMH2DCFDA). Three different MeHg concentrations (5, 10 and 25 microM) and time periods (30, 50 and 90 min) were studied in C6-glial and B35-neuronal cell lines. In addition, the relationship between MeHg-induced ROS and cell density (day 3 vs. day 4) was also explored. The 14C-labelled MeHg measurements were done to determine the cell associated-MeHg content. At 30 and 50 min exposure, a significant increase (p<0.05) in MeHg-induced ROS was observed at 10 and 25 microM MeHg for C6 cells and at 25 microM MeHg for B35 cells. However, the amount of ROS produced with 25 microM MeHg varied significantly (p<0.001) at different time periods. For both the cell lines, significant cell density dependent differences (p<0.05) were observed at 10 microM MeHg treatment for 50 min. MeHg treatments were associated with a concentration as well as cell-density dependent increase in cell associated-MeHg. These findings provide experimental evidence that special attention should be focused upon concentration, exposure time and cell density when assessing MeHg-induced ROS via fluorescence.