Staphylococcus aureus and Wegener's granulomatosis

Wegener's granulomatosis (WG) is a form of systemic vasculitis. It is characterized by granulomatous inflammation in the upper and lower airways, vasculitis and necrotizing glomerulonephritis, and is strongly associated with antineutrophil cytoplasmic antibodies against proteinase 3. Since the etiology of the disease is not clear, treatment, consisting of corticosteroids and immunosuppressives, is nonspecific and associated with severe side effects. Pinpointing the trigger(s) of the disease would highly improve treatment. Clinical evidence shows that an infectious agent, the bacterium Staphylococcus aureus, is a risk factor for disease relapse, suggesting its involvement in the pathogenesis of WG. Here we review both clinical and experimental data that either indicate or support a role for S. aureus in WG.     

Autoantibodies directed to novel components of the PM/Scl complex, the human exosome

The autoantigenic polymyositis/scleroderma (PM/Scl) complex was recently shown to be the human homologue of the yeast exosome, which is an RNA-processing complex. Our aim was to assess whether, in addition to targeting the known autoantigens PM/Scl-100 and PM/Scl-75, autoantibodies also target recently identified components of the PM/Scl complex. The prevalence of autoantibodies directed to six novel human exosome components (hRrp4p, hRrp40p, hRrp41p, hRrp42p, hRrp46p, hCsl4p) was determined in sera from patients with idiopathic inflammatory myopathy (n = 48), scleroderma (n = 11), or the PM/Scl overlap syndrome (n = 10). The sera were analyzed by enzyme-linked immunosorbent assays and western blotting using the affinity-purified recombinant proteins. Our results show that each human exosome component is recognized by autoantibodies. The hRrp4p and hRrp42p components were most frequently targeted. The presence of autoantibodies directed to the novel components of the human exosome was correlated with the presence of the anti-PM/Scl-100 autoantibody in the sera of patients with idiopathic inflammatory myopathy (IIM), as was previously found for the anti-PM/Scl-75 autoantibody. Other clear associations between autoantibody activities were not found. These results further support the conception that the autoimmune response may initially be directed to PM/Scl-100, whereas intermolecular epitope spreading may have caused the autoantibody response directed to the associated components.     

A novel use of the hyperinsulinemic-euglycemic clamp technique to estimate insulin sensitivity of systemic lipolysis.

The aim of the present study was to assess whether a standard hyperinsulinemic-euglycemic clamp can provide an estimate for the antilipolytic insulin sensitivity. For this purpose, we infused 9 non-obese, healthy volunteers with [2H5]glycerol and used the glycerol rate of appearance (Ra) in plasma as an index for systemic lipolysis during a standard (1 mU/kg x min, 120 min) and a 3-step (0.1, 0.25, 1.0 mU/kg x min) hyperinsulinemic-euglycemic clamp. The insulin concentration, which half-maximally suppressed lipolysis (EC50) in the three-step clamp, was considered to be the gold standard for the antilipolytic insulin sensitivity. Glycerol Ra decreased from 1.53+/-0.11 micromol/kg x min to 0.60+/-0.09 micromol/kg x min (p <0.001) during the standard clamp. The decrease in Ra at most time points during the standard clamp significantly correlated with the EC50. The highest correlation for the % decrease of glycerol Ra from baseline was found at 60 min (r = 0.96, p < 0.001) making this parameter a useful index for the antilipoytic insulin sensitivity. Neither plasma glycerol nor plasma free fatty acid (FFA) concentrations were significantly correlated with the EC50. In conclusion, the standard hyperinsulinemic-euglycemic clamp in combination with isotopic determination of glycerol Ra provides a reasonable estimate for the antilipolytic insulin sensitivity. In healthy subjects, the parameter best suited to estimate the insulin EC50 (by linear correlation) was the percentage decrease of glycerol Ra at 60 min.     

Restricted nitrate influx and reduction in corn seedlings exposed to ammonium

The effect of ambient ammonium (0.5 millimolar [¹⁴NH₄]₂SO₄) added to a nutrient solution containing 1.0 millimolar K¹⁵NO₃, 99 atom per cent ¹⁵N, upon [¹⁵N]nitrate assimilation and utilization of previously accumulated [¹⁴N]nitrate was investigated. Corn seedlings, 5-day-old dark-grown decapitated (experiment I) and 10-day-old light-grown intact (experiment II), which had previously been grown on K¹⁴NO₃ nutrient solution, were used. In both experiments, the presence of ambient ammonium decreased [¹⁵N]nitrate influx (20% after 6 hours) without significantly affecting the efflux of previously accumulated [¹⁴N]nitrate. In experiment I, relative reduction of [¹⁵N]nitrate (reduction as a percentage of influx) was inhibited more than was [¹⁵N]nitrate influx. Nevertheless, in experiment I, where all reduction could be assigned to the root system, the absolute inhibition of reduction during the 12 hours (13 micromoles/root) was less than the absolute inhibition in influx (24 micromoles/root). The data suggest that the influence of ammonium on [¹⁵N]nitrate influx could not be totally accounted for by the decrease in the potential driving force which resulted from restricted reduction; an additional impact on the influx process is indicated. Reduction of [¹⁵N]nitrate in experiment II after 6 hours accounted for 30 and 18% of the tissue excess ¹⁵N in the control and ammonium treatments, respectively. Relative distribution of ¹⁵N between roots and exudate (experiment I), or between roots and shoots (experiment II) was not affected by ammonium. On the other hand, the accumulation of [¹⁵N]nitrate in roots, shoots, and xylem exudate was enhanced by ammonium treatment compared to the control, whereas the accumulation of reduced ¹⁵N was inhibited.     

Biosynthesis of riboflavin: cloning, sequencing, mapping, and expression of the gene coding for GTP cyclohydrolase II in Escherichia coli.

GTP cyclohydrolase II catalyzes the first committed step in the biosynthesis of riboflavin. The gene coding for this enzyme in Escherichia coli has been cloned by marker rescue. Sequencing indicated an open reading frame of 588 bp coding for a 21.8-kDa peptide of 196 amino acids. The gene was mapped to a position at 28.2 min on the E. coli chromosome and is identical with ribA. GTP cyclohydrolase II was overexpressed in a recombinant strain carrying a plasmid with the cloned gene. The enzyme was purified to homogeneity from the recombinant strain. The N-terminal sequence determined by Edman degradation was identical to the predicted sequence. The sequence is homologous to the 3' part of the central open reading frame in the riboflavin operon of Bacillus subtilis.     

Monoclonal antibodies to the glycoprotein of vesicular stomatitis virus: comparative neutralizing activity.

Nineteen independently isolated hybridomas producing monoclonal antibodies to the glycoprotein of vesicular stomatitis virus were isolated and studied for their capacity to neutralize viral infectivity. By measuring competitive binding of 125I-labeled monoclonal antibodies in a radioimmunoassay. 11 different, non-cross-reacting antigenic determinants were identified on the vesicular stomatitis virus G protein. All monoclonal antibodies reacting with determinants 1, 2, 3, and 4 resulted in viral neutralization, whereas those binding to the other seven determinants did not neutralize infectivity. The mixture of two monoclonal antibodies binding to different determinants resulted in a more rapid neutralization than either antibody alone, suggesting that different antibodies can exert a synergistic effect on viral neutralization. Kinetic experiments revealed biphasic neutralization curves similar to those expected for heterologous antibody. No evidence could be obtained to relate biphasic kinetics of viral neutralization to heterogeneous populations either of antibody molecules or of virus. The possible significance of the kinetic data with monoclonal antibodies is discussed.     

Photorespiratory phenomena in maize: oxygen uptake, isotope discrimination, and carbon dioxide efflux

Concurrent O₂ evolution, O₂ uptake, and CO₂ uptake by illuminated maize (Zea mays) leaves were measured using ¹³CO₂ and ¹⁸O₂. Considerable O₂ uptake occurred during active photosynthesis. At CO₂ compensation, O₂ uptake increased. Associated with this increase was a decrease in O₂ release such that a stoichiometric exchange of O₂ occurred. The rate of O₂ exchange at CO₂ compensation was directly related to O₂ concentration in the atmosphere at least up to 8% (v/v).     

Questions in Lessons: Activity Settings in the Homes and School of Two Puerto Rican Kindergartners

This ethnographic study describes continuities and discontinuities between a bilingual kindergarten and the homes of two Spanish-dominant Puerto Rican children. The concept of activity setting was used to explore the relation of culture to question use in lessons taught in both settings. Findings highlight a complex web of continuities and discontinuities and the importance of the joint construction of a culture of teaching and learning by parents, teachers, and children.     

Thoracic and Lumbar Vertebral Bone Mineral Density Changes in a Natural Occurring Dog Model of Diffuse Idiopathic Skeletal Hyperostosis

Ankylosing spinal disorders can be associated with alterations in vertebral bone mineral density (BMD). There is however controversy about vertebral BMD in patients wuse idiopathic skeletal hyperostosis (DISH). DISH in Boxer dogs has been considered a natural occurring disease model for DISH in people. The purpose of this study was to compare vertebral BMD between Boxers with and without DISH. Fifty-nine Boxers with (n=30) or without (n=29) DISH that underwent computed tomography were included. Vertebral BMD was calculated for each thoracic and lumbar vertebra by using an earlier reported and validated protocol. For each vertebral body, a region of interest was drawn on the axial computed tomographic images at three separate locations: immediately inferior to the superior end plate, in the middle of the vertebral body, and superior to the inferior end plate. Values from the three axial slices were averaged to give a mean Hounsfield Unit value for each vertebral body. Univariate statistical analysis was performed to identify factors to be included in a multivariate model. The multivariate model including all dogs demonstrated that vertebral DISH status (Coefficient 24.63; 95% CI 16.07 to 33.19; p <0.001), lumbar vertebrae (Coefficient -17.25; 95% CI -23.42 to -11.09; p < 0.01), and to a lesser extent higher age (Coefficient -0.56; 95% CI -1.07 to -0.05; p = 0.03) were significant predictors for vertebral BMD. When the multivariate model was repeated using only dogs with DISH, vertebral DISH status (Coefficient 20.67; 95% CI, 10.98 to 30.37; p < 0.001) and lumbar anatomical region (Coefficient -38.24; 95% CI, -47.75 to -28.73; p < 0.001) were again predictors for vertebral BMD but age was not. The results of this study indicate that DISH can be associated with decreased vertebral BMD. Further studies are necessary to evaluate the clinical importance and pathophysiology of this finding.