Low sialic acid-bearing mouse thymocytes do not express helper T cell properties in vitro

Immature, presumably cortical, mouse thymocytes were isolated by removing mature thymocytes by agglutination with the sialic acid-specific lectin, lobster agglutinin 1 (LAg1). These immature cells do not respond to the mitogenic effects of concanavalin A (Con A), even in the presence of interleukin 2. Moreover, they do not exhibit two properties of helper T cells; they do not secrete interleukin 2 when stimulated with Con A, nor do they provide T help for an in vitro immune response by spleen B cells to the T-dependent antigen, sheep erythrocytes. LAg1-negative thymocytes fail to provide T help even though Con A is added to the cultures, regardless of the number of LAg1-negative thymocytes added per culture, and even in the presence of exogenous macrophages. Unseparated thymocytes, LAg1-positive thymocytes and cortisone-resistant thymocytes all provide T cell help under these conditions. These experiments indicate that immature, presumably cortical mouse thymocytes, isolated by virtue of their low levels of surface sialic acid, are inherently unable to provide T cell help in vitro.     

Muscle relaxant action of excitatory amino acid antagonists

Antagonists of neuronal excitation induced by dicarboxylic amino acids were tested in genetically spastic rats of the Han-Wistar strain. These animals exhibit an increased muscle tone which can be measured as a spontaneous tonic activity in the electromyogram of the gastrocnemius-soleus muscle. Compounds that block excitation due to N-methyl-D-aspartic acid reduced the spontaneous activity measured in the electromyogram in a dose-related manner. The most potent compounds, 2-amino-7-phosphonoheptanoic and kynurenic acids were effective muscle relaxants when given either intraperitoneally or intracerebroventricularly. 2-Amino-5-phosphonopentanoic acid possessed much weaker muscle relaxant activity, while L-glutamic acid diethylester was inactive by either route. The results suggest that blockade of N-methyl-D-aspartic acid receptors results in a myorelaxant effect. Specific antagonists of excitation at N-methyl-D-aspartic acid receptors may provide a new class of muscle relaxants.     

Monoclonal antibodies produced against sporozoites of the human parasite Plasmodium malariae abolish infectivity of sporozoites of the simian parasite Plasmodium brasilianum.

We have used a sporozoite neutralization assay to define the biological relevance of the cross-reactivity of two monoclonal antibodies, raised against sporozoites of the human parasite Plasmodium malariae (Uganda 1/CDC), with sporozoites of the simian parasite Plasmodium brasilianum (Colombian). In vitro incubation of each of these two monoclonal antibodies with sporozoites of P. brasilianum totally abolished the infectivity of these parasites for Saimiri sciureus. Using Western blot analysis and one of the P. malariae monoclonal antibodies, we identified two sporozoite proteins characteristic of the Colombian isolate of P. brasilianum with apparent molecular weights of 56,000 and 66,000. The same monoclonal antibody identified two proteins in an extract of the Peruvian isolate of P. brasilianum with apparent molecular weights of 59,000 and 69,000.     

Pathogenicity and phylogenetic evaluation of the variant Newcastle disease viruses termed “pigeon PMV-1 viruses” based on the nucleotide sequence of the fusion protein gene

Summary The nucleotide sequences of the entire F genes of two isolates of the pigeon PMV-1 (PPMV-1) variant of Newcastle disease virus (NDV) were determined using RTPCR. The deduced amino acid sequences of the F0 protein showed four differences between isolate 760/83 which had been passaged 4 times in chickens and gave an intravenous pathogenicity index in chickens (IVPI) of 2.01 and isolate 1168/84 which had received six passages in chickens and had an IVPI of 0.00. The F genes of virus from two passage levels of isolate 1447/84, 0 with IVPI value 0.00 and six with IVPI value 0.58, were partially sequenced to cover the areas of variation between 760/83 and 1168/84. The two passage levels of 1447/84 showed identical sequences in these areas which in turn were identical to those of 760/83. It was concluded that the recorded differences in intravenous pathogenicity were unlikely to be associated with differences in the primary structure of the F0 protein. Phylogenetic comparisons of the F gene sequences of the two PPMV-1 viruses with those published for other NDV strains and isolates showed that the PPMV-1 viruses formed a new fourth lineage but were closely related to strain Warwick with which they presumably shared a common origin.     

Influence of vascular endothelial growth factor single nucleotide polymorphisms on tumour development in cutaneous malignant melanoma

Vascular endothelial growth factor (VEGF) is a potent regulator of vasculogenesis and tumour angiogenesis. We have investigated whether the VEGF -2578, -1154, +405 and +936 SNPs and associated haplotypes confer susceptibility to and/or influence prognosis in cutaneous malignant melanoma (CMM) skin cancer. A total of 152 CMM patients and 266 controls were genotyped for VEGF promoter SNPs by ARMS-PCR. Strong linkage disequilibrium between the -2578, -1154 and +405 SNPs was detected (association, rho = 0.488-0.965), but not between these SNPs and SNP +936 (association, rho = 0.004-0.130). No SNPs or three SNP haplotypes (-2578, -1154, +405) were significantly associated with CMM, although a number of non-significant trends were observed. However, the VEGF -1154 AA genotype and -2578, -1154, +405 CAC haplotype were both significantly associated with less advanced (Stage 1) disease (P = 0.03). In addition, the VEGF -1154 AA genotype was associated with thinner primary vertical growth phase tumours (P = 0.002), while VEGF -1154 GG was associated with thicker primary tumours (P = 0.02). These preliminary results indicate that VEGF genotype may influence tumour growth in CMM, possibly via the effects of differential VEGF expression on tumour angiogenesis.     

Nutritional supplementation with antioxidants decreases chromosomal damage in humans

In order to investigate the effects of antioxidant supplementation on chromosome damage, a 3 month antioxidant supplementation trial was conducted on groups of 28 myocardial infarction survivors and 57 rural controls, all male. The supplement consisted of vitamin C (100 mg/day), vitamin E (100 mg/day), beta-carotene (6 mg/day) and selenium (50 microg/day). Dietary antioxidants in plasma were measured, as well as the ferric reducing ability of plasma (a measure of total plasma antioxidant status) and the concentration of malondialdehyde as an indicator of oxidative stress. Lymphocytes collected at the beginning and end of the supplementation period were stimulated to proliferate and metaphases accumulated for scoring of chromosome aberrations: per cent aberrant cells and chromatid and chromosome breaks. Supplementation with antioxidants was associated with a decrease in the percentage of cells with chromosome aberrations in the group of rural controls (0.63% before compared with 0.27% after supplementation; P = 0.03). The largest effect of supplementation was seen in smokers in this group (0.12% aberrant cells in supplemented compared with 0.81% in placebo group; P > 0.001). The results support the hypothesis that antioxidants decrease genetic damage.     

Differential effect of ecologic risk factors on the low birthweight components of African-American, Mexican-American, and non-Latino white infants in Chicago.

This study explored the relationship between ecologic risk factors and infant birthweight. A stratified analysis was performed on all African-American, Mexican-American, and white infants born in Chicago in 1990. One half of African-American mothers (n = 26,799) resided in communities with multiple ecologic risk factors, yet their very low birthweight rates were unaffected by the number of these factors. By contrast, only 5% of Mexican-American mothers (n = 9913) and 5% of white mothers (n = 13,596) lived in communities with multiple ecologic risk factors. Their very low birthweights were twice that of infants born to mothers who resided in communities with no ecologic risk factors. These results indicate that ecologic risk factors affect the very low birthweight rates of Mexican Americans and whites but not African Americans.     

Dual-contrast echo planar imaging with keyhole: application to dynamic contrast-enhanced perfusion studies

A new EPI-based method is presented which features optimized sampling of k-space enabling the integrated acquisition of two gradient echo images. The first of these images is predominantly T1 weighted and the second is T*2 weighted. The new method combines echo sharing of sparsely acquired high spatial frequency components with the keyhole technique and half-Fourier image reconstruction. The feasibility of acquiring high spatial and temporal resolution in vivo images for perfusion mapping is demonstrated. In contrast to most current perfusion methods, which acquire the T1- and T*2-weighted images in separate acquisitions, the need for image co-registration here is obviated since both sets of images are EPI-based and are acquired within the same measurement.