High performance size-exclusion chromatography of anionic polymers in aqueous solutions

The applicability of high performance size-exclusion chromatography was tested for anionic polymers with a new type of column. It was found that a solvent salt concentration of 0.1M and an elevated temperature (60°C) prevented adsorption of the polystyrene sulfonate standards on the column packing. The calibration curve and the effect of the concentration on the retention volume remained, however, colum-dependent. We concluded also that the use of the column was restricted to the linear range of the calibration curve and to concentrations below 1 mg mL^?1 for the highest molecular weight standards. The influence of the flow rate (below 1 mL min^?1) on the retention volume was negligible. The main cause of errors when the universal calibration technique is used originated in the experimental determination of the intrinsic viscosities of the standards. The combination of the errors on the viscosity and on the experimentally determined retention volume easily introduced an error of 15% on the determined molecular weight of the sulfated polysaccharide k-carrageenan. The use of the universal calibration method for an exact molecular weight determination of anionic natural polymers is therefore still questionable.     

Measles vaccine effectiveness in standard and early immunization strategies, Niger, 1995

BACKGROUND: An Expanded Programme on Immunization was started in late 1987 in Niger, including vaccination against measles with one dose of standard titer Schwarz vaccine given to infants after 9 months of age. During epidemics an early two-dose strategy was implemented (one dose between 6 and 8 months and one dose after 9 months). From January 1, 1995, until May 7, 1995, 13 892 measles cases were reported in Niamey, Niger. METHODS: A retrospective cohort study was conducted in a crowded area of Niamey at the end of the outbreak to assess the effectiveness of measles vaccine in standard (after 9 months) and early (before 9 months) immunization strategies under field conditions. RESULTS: Highest measles incidence rates were observed among children <1 year of age. Vaccine effectiveness estimates increased with age at vaccination from 78% with a single dose administered at 6 months of age to 95% at 9 months. Vaccine effectiveness with the early two dose strategy was 93%. CONCLUSIONS: Immunization with a single dose of standard titer Schwarz vaccine before 9 months of age provided higher clinical protection than expected from seropositivity studies. The early two dose strategy is justified in contexts where measles incidence is high before 9 months of age. Our results raise the issue of lowering the recommended age for measles vaccination in developing countries.     

Suppression of TNF-alpha expression, inhibition of Th1 activity, and amelioration of collagen-induced arthritis by rolipram

Rolipram is a type IV phosphodiesterase inhibitor that suppresses inflammation and TNF-alpha production. As anti-TNF-alpha therapy is effective in rheumatoid arthritis, we investigated the effect of rolipram on collagen-induced arthritis (CIA), a murine model of rheumatoid arthritis. Rolipram was administered after the onset of clinical arthritis at doses of 0.5, 3, 5, or 10 mg/kg twice daily, with a dose-dependent therapeutic effect on clinical severity and joint erosion. Immunohistochemical analysis of joints of rolipram-treated mice revealed 67% reduction in TNF-alpha-expressing cells compared with control arthritic mice. In vitro studies using bone marrow-derived macrophages confirmed that rolipram directly suppressed TNF-alpha and IL-12 production following stimulation with IFN-gamma and LPS. The effect of rolipram on T cell activity was studied by measuring Th1/Th2 cytokine production by collagen-stimulated draining lymph node cells from arthritic mice treated in vivo with rolipram. Rolipram reduced IFN-gamma production and increased IL-10, indicating that rolipram down-regulated the ongoing Th1 response to type II collagen. Finally, the effect on CIA of combination therapy was studied using rolipram plus either anti-TNF-alpha or anti-CD4 mAbs. Rolipram plus anti-TNF-alpha was not therapeutically additive, whereas rolipram plus anti-CD4 mAb was clearly additive. This result indicates that the therapeutic effects of rolipram overlap with TNF-alpha blockade, but are complementary to anti-CD4 treatment. It is therefore proposed that a major mechanism of action of rolipram in CIA is suppression of TNF-alpha activity. These findings suggest that type IV phosphodiesterase inhibitors may be effective in pathologic conditions, such as RA, with overexpression of TNF-alpha.     

Wavelet-based image denoising using a Markov random field a priorimodel

This paper describes a new method for the suppression of noise in images via the wavelet transform. The method relies on two measures. The first is a classic measure of smoothness of the image and is based on an approximation of the local Holder exponent via the wavelet coefficients. The second, novel measure takes into account geometrical constraints, which are generally valid for natural images. The smoothness measure and the constraints are combined in a Bayesian probabilistic formulation, and are implemented as a Markov random field (MRF) image model. The manipulation of the wavelet coefficients is consequently based on the obtained probabilities. A comparison of quantitative and qualitative results for test images demonstrates the improved noise suppression performance with respect to previous wavelet-based image denoising methods.     

Convergence of concurrent Markov chain Monte-Carlo algorithms

We examine the parallel execution of a class of stochastic algorithms called Markov chain Monte-Carlo (MCMC) algorithms. We focus on MCMC algorithms in the context of image processing, using Markov random field models. Our parallelisation approach is based on several, concurrently running, instances of the same stochastic algorithm that deal with the whole data set. Firstly we show that the speed-up of the parallel algorithm is limited because of the statistical properties of the MCMC algorithm. We examine coupled MCMC as a remedy for this problem. Secondly, we exploit the parallel execution to monitor the convergence of the stochastic algorithms in a statistically reliable manner. This new convergence measure for MCMC algorithms performs well, and is an improvement on known convergence measures. We also link our findings with recent work in the statistical theory of MCMC.     

Blockade of IL-12 during the induction of collagen-induced arthritis (CIA) markedly attenuates the severity of the arthritis

Human urinary trypsin inhibitor (UTI) was digested with various enzymes to obtain O-glycoside linked N-terminal glycopeptide (UTIm1), N-glycoside linked C-terminal tandem Kunitz-domains (domain I and II, UTIm2), UTI lacking O-glycoside (UTIc), asialo UTI (UTIa) and UTI lacking N-glycoside (UTIn). We investigated the membrane stabilizing effect of these UTI derivatives on rat renal lysosome by measurement of lysosomal enzyme N-acetyl-beta-D-glucosaminidase (NAG) release after hypotonic treatment. Intact UTI suppressed NAG release, but aprotinin, gabexate mesilate (FOY), nafamostat mesilate (FUT) and recombinant domain II of UTI (R-020) had no effect, indicating that inhibition of serine proteases was not involved and the carbohydrate moiety of UTI might be necessary for this property. Among UTI derivatives, UTIm1, UTIm2, UTIm1+ UTIm2, and UTIc had no effect. In contrast, UTIa or UTIn suppressed NAG release. From these results, we conclude that O-glycoside linked core protein without N-glycoside is essential to the lysosomal membrane-stabilizing property of UTI.