Investigation of childhood central nervous system vasculitis: magnetic resonance angiography versus catheter cerebral angiography

Aim We compared the clinical utility of magnetic resonance angiography (MRA) to catheter cerebral angiography (CA) in the investigation of children with suspected central nervous system (CNS) vasculitis. Method Single‐centre retrospective review of children with a suspected diagnosis of CNS vasculitis studied with both MRA and CA. MRA and CA‐detected abnormalities (location, multiplicity, and morphology) were compared; sensitivity and specificity were calculated on a per lesion and per patient basis for MRA, with CA as the reference standard. Results Findings in fourteen patients (median age at presentation of 5y 10mo [range 1y 5mo–14y 5mo]; eight males, six females) relating to sixteen paired studies of MRA and CA were reviewed. CA‐detected lesions were commonly bilateral (13/16 studies, p<0.05), and likely to be proximally distributed (15/16 studies, p<0.05).The sensitivity and specificity of MRA for CA lesion detection was 63% (95% confidence interval [CI] 48–78) and 89% (95% CI 81–93), respectively with moderate agreement between the two modalities (κ=0.51, 95% CI 0.37–0.66). The majority of the false negative observations involved the posterior circulation (9/14). The overall sensitivity for MRA diagnosis of vasculitis per patient was 94% (95% CI 67–99). Interpretation MRA failed to identify all lesions detected on CA, particularly those in the posterior circulation. MRA is a reasonable initial modality in the investigation of suspected CNS vasculitis but in cases of abnormal parenchymal MRI and normal MRA, CA should be considered.     

Synthesis and immunological characterization of a 134-mer synthetic peptide corresponding to the N-terminal half of the HIV-1 nucleoprotein,p24

A 134-mer peptide corresponding to the N-terminal sequence of p24 (residues 146–279 of the gag gene product of the LAV strain) was chemically synthesized using highly optimised protocols on an ABI 430A synthesizer. The crude peptide was obtained by treating the peptide-resin with HF, then purified by a combination of size exclusion and RP-HPLC. One hundred milligram of 90% pure 134-mer can be obtained within a month. Both mice and rabbit polyclonal antisera raised against a commercial preparation of recombinant p24, and a pooled sera from HIV-1 infected individuals reacted strongly with the 134-mer peptide in ELISA. Both mice and rabbits immunized with the free peptide emulsified in Freund's complete adjuvant generated strong anti-peptide and anti-p24 antibody responses as judged by immunoblots and ELISAs. Immunodominant epitopes were mapped to residues 201–227 (LKETINEEAAEWDRVHPVHAGPIAPG). These B-cell epitopes had previously been identified by mouse monoclonal antibodies raised against HIV-1 virus or gag gene products. Furthermore, murine T-cell lines generated against the 134-mer peptide were found to respond to two short peptides, P24B (residues 195–215) and P24D1 (residues 268–279). These two T-cell epitopes were previously reported as human helper T-cell and CTL epitopes, respectively. These results clearly indicate that the synthetic 134-mer peptide could elicit both T- and B-cell responses to HIV-1 similar to those obtained with the natural viral gag protein, and could be useful for the development of a synthetic HIV vaccine     

The impact of performance uncertainty on the postimperative negative variation

In a delayed matching-to-sample task, the impact of clear or ambiguous go versus clear no-go signals on the post-imperative negative variation (PINV) was examined in 11 patients with a chronic schizophrenic disorder (DSM-III-R) and in a control group of 13 healthy subjects matched to the patient sample by age, sex, and education. Size and spatial position of a visual S2 had to be matched to one of two visual patterns in the S1 presented 4 s earlier. In 96 trials, the S2 was identical in size with one of the two patterns of S1 (clear matching). These trials varied pseudorandomly, with 60 trials in which the S2 was of intermediate size. On a randomly interspersed additional 48 trials, an S2 differing in color and shape signaled no-go. The electroencephalogram was recorded from Fz, Cz, Pz, F3, F4, C3, C4, P3, and P4. Although groups did not differ in contingent negative variation amplitude the PINV was generally more pronounced in patients than in controls. In both groups, ambiguity of the to-be-matched S2 produced larger PINV amplitudes; the no-go signal elicited only a small PINV. Differential effects of ambiguity and no-go on PINV amplitude and its scalp distribution suggest that “performance” and “action” uncertainty contribute to PINV generation and that thresholds for both effects are reduced in schizophrenics.