Galactose branching modulates the action of cellulase on seed storage xyloglucans

Xyloglucan is a cell wall polysaccharide that has a main beta-D-(1 --> 4)-glucan backbone branched at regular intervals with alpha(1 --> 6) linked D-xylopyranosyl or beta-D-galactopyranosyl(1 --> 2)D-xylopyranosyl residues. These residues compromise almost all the structure of xyloglucan when it occurs as a storage polymer in seeds. This polymer is susceptible to the action of endo-P(1,4)glucanase (cellulase) at the non-branched glucosyl residues and this enzyme has been widely used in the study of the structure of xyloglucan. Storage xyloglucans from Copaifera langsdorffii and Hymenaea courbaril were hydrolysed with cellulase and the equilibrium reached after 24 It was analysed by gel filtration and high performance anion exchange chromatography. The equilibrium contained limit digest oligosaccharides (LDOs) and dimers and trimers of these LDOs that, despite their susceptibility to the enzyme, were not hydrolysed. Our data suggest that the side-chains of the polysaccharides can modulate the recognition of the fragments of xyloglucan by the enzyme: (1) the presence of a P-galactosidase in the system avoided the accumulation of these dimmers and trimmers, (2) less-branched LDOs are attacked preferentially by the enzyme, (3) polymers with different fine structures are hydrolysed at a different rates by the same enzyme. Considering that the branching pattern of the polysaccharide seems to have direct influence on the interaction of the enzyme with the substrate, we suggest that the structure of the polysaccharide would code at least part of the information required for its own metabolism. (C) 2003 Published by Elsevier Science Ltd.52213514

Xyloglucan mobilisation in cotyledons of developing plantlets of Hymenaea courbaril L. (Leguminosae-Caesalpinoideae)

Many seeds contain storage compounds that are used by the embryo/plantlet as a source of nutrients after germination. In seeds of Hymenaea courbaril, a leguminous tree, the main reserve consists of a structurally unusual xyloglucan stored in thickened walls of the cotyledon cells. The present work aimed to study H. courbaril xyloglucan metabolism during and after germination in order to compare its degrading system with the other known xyloglucan containing seeds. Polysaccharide degradation occurred after germination between 35 and 55 days after planting. The activities of alpha-xylosidase, beta-glucosidase, beta-galactosidase and XET rose during the period of xyloglucan disassembling but a low level of endo-beta-glucanase activity was detected, suggesting that this XET has high affinity for the oligosaccharides. The pH optimum of beta-galactosidase was different from the alpha-xylosidase, beta-glucosidase and XET optima suggesting that the former may be important in the control of the mobilisation process. A tentative model for xyloglucan disassembling in vivo is proposed, where beta-galactosidase allows the free oligosaccharides to bypass a transglycosylation cycle and be disassembled by the other exo-enzymes. Some ecophysiological comparisons among H. courbaril and other xyloglucan storing seeds are discussed. (C) 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.154211712

Low dose alpha interferon therapy can be effective in chronic active hepatitis C. Results of a multicentre, randomised trial

BACKGROUND--There is some controversy concerning the efficacy of low dose alpha interferon therapy in chronic hepatitis C. AIMS--To evaluate the effectiveness of treatment with low doses of alpha interferon in chronic hepatitis C. PATIENTS--One hundred and forty one patients with anti-HCV positive chronic active hepatitis C from six hospitals were enrolled in the study. METHODS--Patients were randomised to treatment with 5 MU (group A) or 1.5 MU (group B) injections. The dose was reduced in responders from group A or increased in non-responders from group B to maintain treatment with the minimal effective dose. Patients were treated for 48 weeks and followed up for 24 additional weeks with no treatment. Normalisation of alanine aminotransferase (ALT) was used to evaluate response. RESULTS--A sustained response was seen in eight patients from group A (12%) and in 15 (21%) from group B. This difference was not statistically significant. Increasing the dose of interferon led to sustained response in only five of 58 patients (9%) from group B who did not respond to 1.5 MU injections. In contrast, 15 of 21 patients (71%) in whom ALT remained normal with 1.5 MU injections developed a sustained response. By multivariate analysis sustained response seemed associated with young age and was more frequent in patients with genotype 3 HCV infection. Sustained response was preceded by a rapid normalisation of ALT and was inversely related to the amount of alpha interferon necessary to maintain ALT at low values during treatment. CONCLUSIONS--Some patients with chronic hepatitis C are very sensitive to alpha interferon and can be successfully treated with low doses. Treatment with higher doses may be effective in a minority of patients who do not respond to low doses

Outbreak of urogenital schistosomiasis in Corsica (France): an epidemiological case study

International audienceBackground: Schistosomiasis is a snail-borne parasitic disease endemic in several tropical and subtropical countries. However, in the summer of 2013, an unexpected outbreak of urogenital schistosomiasis occurred in Corsica, with more than 120 local people or tourists infected. We used a multidisciplinary approach to investigate the epidemiology of urogenital schistosomiasis in Corsica, aiming to elucidate the origin of the outbreak.Methods: We did parasitological and malacological surveys at nine potential sites of infection. With the snails found, we carried out snail–parasite compatibility experiments by exposing snails to schistosome larvae recovered from the urine of a locally infected Corsican patient. Genetic analysis of both mitochondrial (cox1) and nuclear (internal transcribed spacer) DNA data from the Schistosoma eggs or miracidia recovered from the infected patients was conducted to elucidate the epidemiology of this outbreak.Findings: We identified two main infection foci along the Cavu River, with many Bulinus truncatus snails found in both locations. Of the 3544 snails recovered across all sites, none were naturally infected, but laboratory-based experimental infections confirmed their compatibility with the schistosomes isolated from patients. Molecular characterisation of 73 eggs or miracidia isolated from 12 patients showed infection with Schistosoma haematobium, S haematobium–Schistosoma bovis hybrids, and S bovis. Further sequence data analysis also showed that the Corsican schistosomes were closely related to those from Senegal in west Africa.Interpretation: The freshwater swimming pools of the Cavu River harbour many B truncatus snails, which are capable of transmitting S haematobium-group schistosomes. Our molecular data suggest that the parasites were imported into Corsica by individuals infected in west Africa, specifically Senegal. Hybridisation between S haematobium and the cattle schistosome S bovis had a putative role in this outbreak, showing how easily and rapidly urogenital schistosomiasis can be introduced and spread into novel areas where Bulinus snails are endemic, and how hybridisation could increase the colonisation potential of schistosomes. Furthermore our results show the potential risk of schistosomiasis outbreaks in other European areas, warranting close monitoring and surveillance of all potential transmission foci