Production and characterization of monoclonal antibodies specific for the murine T cell receptor ζ chain

The T cell receptor (TCR) comprises an antigen-specific β heterodimer non-covalently associated with the CD3 γδε and TCR ζ subunits. Both the CD3 and TCR ζ subunits are proposed to be responsible for the intracellular signal-transduction events. We report here the production of eight monoclonal antibodies (mAbs) that bind in an ELISA assay to a 113 amino acid synthetic peptide corresponding to the cytoplasmic domain of TCR ζ. Western blot analysis of anti-CD8 precipitates of lysates of transfectants expressing chimeric CD8/ζ constructs encoding increasing COOH-terminal truncations of TCR ζ indicates that four of these mAbs recognized the region of TCR ζ chain comprising the last 29 COOH-terminal residues. Thus, this region of TCR ζ may encode an immunodominant epitope. Furthermore, one of these mAbs, G3, is capable of precipitating both non-phosphorylated and tyrosine phosphorylated TCR ζ. The G3 mAb should be useful for elucidiating the structural and signalling characteristics of the TCR ζ chain.     

Neuropsychological Deficit and Academic Performance in Children and Adolescents Following Traumatic Brain Injury

Evaluated the utility of neuropsychological testing in predictingacademic outcome in children 1 year following traumatic braininjury (TBI). Fifty-one schoolage children who were admittedto hospital after TBI were assessed with a battery of neuropsychologicalmeasures at 3 months postinjury. Academic achievement was assessedat 3 and 12 months postinjury. The neuropsychological batteryincluded intelligence testing and measures of memory, learning,and speed of information processing. Academic outcome was assessedin terms of post-TBI changes in reading, spelling, and arithmetic;changes in teacher ratings of school performance; and changein school placement. According to logistic regression analysis,change in placement from regular to special education at 1-yearpost-TBI was predicted by injury severity and by neuropsychologicalperformance at 3 months post-TBI. Findings suggest that neuropsychologicaltesting is useful in identifying children with special educationalneeds subsequent to TBI.     

Dynamics of excitation and inhibition underlying stimulus selectivity in rat somatosensory cortex

Neurons in sensory systems respond to stimuli within their receptive fields, but the magnitude of the response depends on specific stimulus features. In the rodent whisker system, the response magnitude to the deflection of a particular whisker is, in most cells, dependent on the direction of deflection. Here we use in vivo intracellular recordings from thalamorecipient neurons in layers 3 and 4 of the rat barrel cortex to elucidate the dynamics of the synaptic inputs underlying direction selectivity. We show that cells are direction selective despite a broadly tuned excitatory and inhibitory synaptic input. Selectivity emerges from a direction-dependent temporal shift of excitation relative to inhibition. For preferred direction deflections, excitation precedes inhibition, but as the direction diverges from the preferred, this separation decreases. Our results illustrate a mechanism by which the timing of the synaptic inputs, and not their relative peak amplitudes, primarily determine feature selectivity.     

Detecting symptom- and test-coached simulators with the test of memory malingering.

The ability of the Test of Memory Malingering (TOMM; Tombaugh, 1996) to detect feigned-memory impairment was explored. The TOMM was administered to three groups: (a) a control group instructed to perform optimally, (b) a symptom-coached group instructed to feign memory problems after being educated about traumatic brain injury symptomatology, and (c) a test-coached group instructed to feign memory problems after being educated about test-taking strategies to avoid detection. The recommended cutoff scores (Tombaugh, 1996) on Trial 2 and the Retention Trial produced overall classification accuracy rates of 96%, with high levels of sensitivity and specificity. Although the symptom-coached group performed more poorly on the TOMM relative to the test-coached group, the test was equally sensitive in detecting suboptimal effort across the different coaching paradigms.     

The stability and chemical stress relaxation of peroxide cured polyurethane elastomers

The chemical stress relaxation of two polyurethane elastomers Genthane S and Adiprene CM has been studied in air and in nitrogen in the temperature range 60 to 150°C. Both continuous and intermittent stress relaxation measurements were made on well characterized samples covering a range of crosslink densities. Scission and crosslinking reactions were observed for both the polyester based Genthane S and the polyether based Adiprene CM. The degradation of Genthane S is largely non oxidative and the scission reaction involves the main chain. The behaviour of Adiprene CM under nitrogen broadly resembles that of Genthane S; it differs from Genthane S in that it also undergoes an oxidative reaction. Activation energies for the scission and crosslinking processes were evaluated from kinetic analysis. Pretreatment of the elastomers with isocyanates inhibits both of these reactions. A mechanism involving the urethane group is proposed to account for the degradation behaviour and the role of water in this respect is discussed briefly.     

Identification and characterization of 13 new mutations in mucopolysaccharidosis type I patients

In this study we have investigated a group of 29 Brazilian patients, who had been diagnosed with the lysosomal storage disorder, Mucopolysaccharidosis type I (MPS-I). MPS I is caused by a deficiency in the lysosomal hydrolase, alpha-L-iduronidase. Ninety percent of the MPS I patients in this study were genotyped and revealed 10 recurrent and thirteen novel IDUA gene mutations. Eight of these new mutations and three common mutations W402X, P533R, and R383H were individually expressed in CHO-K1 cells and analyzed for alpha-L-iduronidase protein and enzyme activity. A correlation was observed between the MPS I patient clinical phenotype and the associated mutant alpha-L-iduronidase protein/enzyme activity expressed in CHO-K1 cells. This was the first time that Brazilian MPS I patients had been thoroughly analyzed and highlighted the difficulties of mutation screening and clinical phenotype assessment in populations with high numbers of unique mutations.     

Impermeability to quinolones in gram-positive and gram-negative bacteria

The initial step in the accumulation of fluoroquinolone antimicrobial agents is binding to cell surface components reduced by lowered pH and divalent cations. Uptake into gram-negative and gram-positive bacteria is by simple diffusion. Entry through the outer membrane occurs preferentially for most agents by the porin route but a second process using the self-promoted uptake pathway is active especially for more hydrophobic agents. Fluoroquinolones bind to vesicles of phospholipid which may be the initiating step in cross-cytoplasmic membrane diffusion. An active efflux system has been described inEscherichia coli with evidence supporting its presence in several other bacteria. Total uptake is not altered by a resistant gyrase. Resistant isolates associated with reduced total quinolone accumulation due to lowered uptake have been described for laboratory mutants and clinical isolates. Most but not all of these have had alterations in outer membrane proteins. A functionally dominant resistance gene has been cloned from resistantStaphylococcus aureus and codes for a highly hydrophobic protein most likely membrane associated. This gene is expressed inEscherichia coli and specifies resistance especially to hydrophilic quinolones, possibly by altered accumulation.