Motor Vehicle Mismatch-Related Spinal Injury

Abstract

Background/Objective: Motor vehicle collision (MVC)-related spinal cord injury (SCI) is the mostprevalent etiology of SCI. Few studies have defined SCI risk factors. Vehicle mismatch occurs in 2-vehicleMVCs in which there are significant differences in vehicle weight, stiffness, and height. This study examinedSCI risk and vehicle mismatch.

Methods: A matched case-control study using the 1995 to 2003 National Automotive Sampling System(NASS). Study subjects were identified from 2-vehicle MVCs. Cases were occupants who had suffereda cervical, thoracic, or lumbar SCI. Odds ratios (ORs) and 95% confidence intervals (Cis) were calculated.

Results: There were 101,682 cases of SCI matched to 805,091 controls. Occupants of passenger vehiclesinvolved in MVCs with a light truck or van (LTV) were at increased risk for SCI (OR= 1.87, 95% Cl= 1.07-3.24) and this risk was greatest for thoracic SCI (OR= 5.09, 95% Cl= 2.33-11.13). In addition, occupants ofL TVs involved in MVCs with passenger vehicles were at significant increased risk for cervical (OR= 1. 39) andlumbar (OR= 2.65) SCI; and occupants of LTVs involved in MVCs with other LTVs were at increased risk ofany SCI (OR= 2.02, 95% Cl= 1.52-2.69). For these subjects, significant increased risks were seen for all spineregions: cervical (OR= 1.41), thoracic (OR= 2.86), and lumbar (OR= 2.38).

Conclusions: The results of this study suggest that occupants of passenger vehicles are at increased SCI riskwhen involved in 2-vehicle MVCs with L TVs; and that occupants of L TVs are at increased SCI risk, regardless     

Priming with an adenovirus 35-circumsporozoite protein (CS) vaccine followed by RTS,S/AS01B boosting significantly improves immunogenicity to Plasmodium falciparum CS compared to that with either malaria vaccine alone

The RTS,S/AS02A protein-based vaccine consistently demonstrates significant protection against infection with Plasmodium falciparum malaria and also against clinical malaria and severe disease in children in areas of endemicity. Here we demonstrate with rhesus macaques that priming with a replication-defective human adenovirus serotype 35 (Ad35) vector encoding circumsporozoite protein (CS) (Ad35.CS), followed by boosting with RTS,S in an improved MPL- and QS21-based adjuvant formulation, AS01B, maintains antibody responses and dramatically increases levels of T cells producing gamma interferon and other Th1 cytokines in response to CS peptides. The increased T-cell responses induced by the combination of Ad35.CS and RTS,S/AS01B are sustained for at least 6 months postvaccination and may translate to improved and more durable protection against P. falciparum infection in humans.     

Global changes in the hippocampal proteome following exposure to an enriched environment

Exposure to an enriched environment promotes neurochemical, structural and neurophysiological changes in the brain and is associated with enhanced synaptic plasticity and improved hippocampal-dependent learning. Using a global proteomics-based approach we have now been able to reveal the altered expression of a diverse range of hippocampal proteins following exposure to an enriched environment. Male Hooded Lister rats (8 weeks) were subjected to a 6-week regimen in which they were housed in either non-enriched (open field) or enriched conditions (toys, wheels etc.). Whole protein extracts from stratum pyramidale and stratum radiatum of area CA1 were then isolated and subjected to differential gel electrophoresis [McNair K, Davies CH, Cobb SR (2006) Plasticity-related regulation of the hippocampal proteome. Eur J Neurosci 23(2):575-580]. Of the 2469 resolvable protein spots detected in this study, 42 spots (1.7% of the detectable proteome) derived from predominantly somatic fractions and 32 proteins spots from dendritic fractions (1.3% of detectable proteome) were significantly altered in abundance following exposure to an enriched environment (somatic: 14 increased/28 decreased abundance, range -1.5 to +1.4-fold change; dendritic: 16 increased, 16 decreased abundance, range -1.6 to +3.0-fold change). Following in-gel tryptic digestion and Maldi-Tof/Q-star mass spectrometry, database searching revealed the identity of 50 protein spots displaying environmental enrichment-related modulation of expression. Identified proteins belonged to a variety of functional classes with gene ontology analysis revealing the majority (>70%) of regulated proteins to be part of the energy metabolism, cytoplasmic organization/biogenesis and signal transduction processes.     

Perceived influence of intrinsic/extrinsic factors on participation in life activities after spinal cord injury

Background

Various types of limitations on community participation are experienced by people with spinal cord injury (SCI).

Implicit alcohol cognitions in risky drinking nicotine users with and without co-morbid major depressive disorder

Objective

Alcohol consumption, nicotine use, and major depressive disorder (MDD) are highly co-morbid. The negative reinforcement model of addiction would suggest that smokers may consume alcohol to relieve negative affective symptoms, such as those associated with MDD and withdrawal from nicotine. Over time, these behaviors may become so strongly paired together that they automatically activate a desire to use alcohol, even in the absence of conscious or deliberate intention. This study examined implicit alcohol cognitions in 146 risky drinking nicotine users (n = 83) and non-users (n = 63), to help uncover cognitive mechanisms that link drinking, nicotine use, and depression together. We proposed that nicotine users with a history of MDD would have stronger implicit motivations to drink than non-nicotine users without MDD.

Method

Participants were assessed on lifetime MDD (n = 84) or no MDD (n = 62), and then completed an Implicit Association Task designed to test the strength of associations between alcohol pictures and “approach” words.

Results

Regression analyses showed that implicit alcohol–approach attitudes were stronger among risky drinking nicotine users than non-users. Alcohol–approach motivations were also stronger among risky drinking nicotine users compared to non-users with a history of MDD; nicotine use was unrelated to implicit alcohol cognitions for risky drinkers without MDD.

Conclusions

Implicit cognitive processes may be targeted in behavioral and pharmacological treatments in risky drinking nicotine users, particularly those with depression comorbidity.     

Proliferation and cytogenetic analysis of hairy cell leukemia upon stimulation via the CD40 antigen

Using the CD40 system, in vitro proliferation of hairy cell leukemia (HCL) was examined in 43 patients. In this culture system, cells were stimulated by interleukin-4 (IL-4) and anti-CD40 monoclonal antibodies (MoAbs) that were added in soluble form or were cross-linked via their Fc part using Fc gamma RII-transfected mouse fibroblast cells. Proliferation was induced and confirmed by 3H-thymidine incorporation in 14 cases and by the presence of metaphases in 42 cases. 3H-thymidine incorporation showed a heterogeneous pattern: cross-linking of anti- CD40 gave the highest proliferation in 8 cases; in 11 cases, stimulation with anti-CD40 MoAbs alone, without cross-linking also resulted in proliferation; the addition of IL-4 further enhanced 3H- thymidine incorporation in 5 cases, but suppressed this phenomenon in 5 other cases. The CD40 system proved to be very effective in obtaining cytogenetic data. With a success rate of 42 of 43 patients tested, we found clonal abnormalities in 8 cases (19%) and nonclonal abnormalities with involvement of one or two abnormal metaphases in another 7 cases. The chromosomes most frequently involved in the abnormal karyotypes, both structurally and numerically, were chromosomes 5, 7, and 14. By fluorescence-activated cell-sorting analysis of the cultured cells, and by immunophenotypic analysis of metaphase spreads, T-cell growth could be excluded and the HCL-lineage confirmed. Stimulation via the CD40 antigen is an excellent tool for growing hairy cell leukemia cells.     

Microtubule-associated protein 2 kinases, ERK1 and ERK2, undergo autophosphorylation on both tyrosine and threonine residues: implications for their mechanism of activation.

Microtubule-associated protein 2 kinase (MAP kinase), which exists in several forms, is a protein serine/threonine kinase that participates in a growth factor-activated protein kinase cascade in which it activates a ribosomal protein S6 kinase (pp90rsk) while being regulated itself by a cytoplasmic factor (MAP kinase activator). Experiments with recombinant MAP kinase, ERK2, purified from Escherichia coli in a nonactivated form revealed a self-catalyzed phosphate incorporation into both tyrosine and threonine residues. Another MAP kinase, ERK1, purified from insulin-stimulated cells also autophosphorylated on tyrosine and threonine residues. Autophosphorylation of ERK2 correlated with its autoactivation, although both autophosphorylation and autoactivation were slow compared to that occurring in the presence of MAP kinase activator. Therefore, we propose that autophosphorylation is probably involved in the MAP kinase activation process in vitro, but it may not be sufficient for full activation. The specificity toward tyrosine and threonine residues indicates that the MAP kinases ERK1 and ERK2 are members of a group of kinases with specificity for tyrosine as well as serine and threonine residues.     

Tau mutants bind tubulin heterodimers with enhanced affinity

Tau is a microtubule binding protein that forms pathological aggregates in the brain in Alzheimer’s disease and other tauopathies. Disease etiology is thought to arise from loss of native interactions between tau and microtubules, as well as from gain of toxicity tied to tau aggregation, although neither mechanism is well understood. Here we investigate the link between function and disease using disease-associated and disease-motivated mutants of tau. We find that mutations to highly conserved proline residues in repeats 2 and 3 of the microtubule binding domain have differential effects on tau binding to tubulin and the capacity of tau to enhance tubulin polymerization. Notably, mutations to these residues result in an increased affinity for tubulin dimers while having a negligible effect on binding to stabilized microtubules. We measure conformational changes in tau on binding to tubulin that provide a structural framework for the observed altered affinity and function. Additionally, we find that these mutations do not necessarily enhance aggregation, which could have important implications for tau therapeutic strategies that focus solely on searching for tau aggregation inhibitors. We propose a model that describes tau binding to tubulin dimers and a mechanism by which disease-relevant alterations to tau impact its function. Together, these results draw attention to the interaction between tau and free tubulin as playing an important role in mechanisms of tau pathology.Tau is a microtubule (MT)-associated protein that plays a critical role in the pathology of several neurodegenerative disorders including Alzheimer’s disease, frontotemporal dementias, and traumatic brain injury (1). Normally, tau is found primarily in the axons of neurons where it regulates the dynamic instability of MTs (2, 3) and plays an important role in axonal transport (4, 5). Both in vitro and in vivo measurements find that tau increases the rate of MT polymerization, as well as decreasing rates of catastrophe (2, 6, 7). In disease, tau is found as aggregated, filamentous deposits that are the defining feature of a diverse class of neurodegenerative diseases, called tauopathies (1, 8). Pathological mutations to tau are thought to alter the native interactions of tau with MTs, in addition to increasing the propensity of tau to aggregate (9–11). Although the precise cause or mechanism by which tau contributes to toxicity in disease is unknown, both a loss of native function and a gain of toxic function are implicated (1, 12, 13).Tau consists of a C-terminal microtubule binding domain (MTBR) composed of imperfect repeats (R1–R4; Fig. 1A) (14), a flanking proline-rich region that enhances MT binding and assembly (3), and an N-terminal projection domain with putative roles in MT spacing (15) and membrane anchoring (16). Alternative splicing results in the expression of six isoforms of tau in the adult human brain, with zero, one, or two N-terminal inserts and three or four MT binding repeat units. The repeat units contain an 18-residue imperfect repeat sequence, which terminates with a highly conserved proline-glycine-glycine-glycine (PGGG), and are linked by a 13–14 residue interrepeat sequence (Fig. 1C). Early biochemical studies depicted the conserved regions as binding weakly to MTs, with the interrepeats acting as spacers between them (14, 17). More recently, it was shown that the interrepeats are also directly involved in binding and polymerization (18, 19), with the N-terminal proline-rich region playing a regulatory role (20). Tau binds MTs with a biphasic pattern indicative of two distinct binding sites on the MT lattice with unequal affinities (21, 22). Binding to MTs is negatively regulated by phosphorylation on sites in the MTBR and adjacent regions (23). Tau derived from aggregates in the brain is hyperphosphorylated (24), suggesting a role for aberrant phosphorylation in disease.Open in a separate windowFig. 1.Schematic of tau constructs and an MTBR repeat. The functional domains of tau are indicated on the longest full-length isoform with alternatively spliced regions marked by dashed lines (A). The interrepeat regions that link the conserved repeat sequences are indicated by cross-hatching. On the fragments used in this study (B), K16 (residues 198–372) and K18 (residues 244–372), the residues mutated to cysteine for attachment of fluorophores (residues 244, 322, and 354), and proline to leucine/serine mutation sites (301 and 332) are indicated. A schematic of a repeat within the MTBR (C) illustrates interrepeat and repeats sequences, with the conserved residues shown.Attempts to obtain resolution structural information of tau have been hindered by the fact that it is intrinsically disordered under physiological conditions (25) and remains largely disordered even on binding to MTs. Contrasting models derived from cryo-EM suggest tau binds either along the outer protofilament ridge (26) or to the inner surface (27) of MTs. The MTBR carries a net positive charge, and binding of tau to the acidic carboxy termini of α and β tubulin has been observed both in the context of MTs (28) and for the isolated peptides corresponding to these tubulin sequences (29, 30). In addition, a secondary binding site has been mapped to an independent region within the C-terminal third of tubulin (30). Cleavage of the C-terminal tail of tubulin is sufficient to increase polymerization rates (30), and it has been suggested that tau may promote MT polymerization through a similar charge neutralization mechanism.The MTBR also plays a central role in tau pathology in that it forms the core of the aggregates found in disease (31) and contains the minimum sequence necessary to recapitulate relevant features of aggregation in vitro (32). Moreover, the majority of mutations to tau implicated in tauopathies are either point mutations within the MTBR or mutations that interfere with alternative splicing, altering the normal ∼1:1 ratio of 3R:4R tau (8, 9). Notable among the point mutants is P301L (tau_P301L) (Fig. 1B), implicated in frontotemporal dementia with Parkinsonism-17, which provided one of the first genetic links between tau and neurodegenerative disease (33). The P301L variant has emerged as a particularly reliable model for tau-based neurodegenerative disease, having successfully reproduced aspects of pathology in animal models of Alzheimer’s disease and other tauopathies (34).Although significant work has focused on tau interactions with MTs, very little is known about the mechanistic details of tau-mediated MT polymerization, including interactions of tau with tubulin dimers during the assembly process. Although many alterations to tau implicated in disease have been shown to affect MT polymerization both in vitro and in vivo, virtually nothing is known about the mechanism by which these changes occur. Tau_P301L exhibits impaired tubulin polymerization (35), as well as increased aggregation propensity relative to WT protein (tau_WT) (32) and thus serves as a model for both loss of function and gain of toxic function aspects of disease. This mutation is in the highly conserved PGGG sequence of R2 (Fig. 1C). To broaden our understanding of the impact of this point mutation on pathology, we designed a tau variant with the analogous proline to leucine substitution in the PGGG sequence of R3, tau_P332L, as well as a double mutant, tau_P301L/P332L. We use single molecule fluorescence to investigate structural and functional aspects of the interaction between tau and tubulin. In combination with ensemble polymerization and aggregation assays, this work provides insight into the relationship between functional and dysfunctional roles of tau.