O-acetylation of cryptococcal capsular glucuronoxylomannan is essential for interference with neutrophil migration.

The capsular polysaccharide glucuronoxylomannan (GXM) of Cryptococcus neoformans has been shown to interfere with neutrophil migration. Although several receptors have been implied to mediate this process, the structural perspectives are unknown. Here, we assess the contribution of 6-O-acetylation and xylose substitution of the (1-->3)-alpha-d-mannan backbone of GXM, the variable structural features of GXM, to the interference with neutrophil migration. We compare chemically deacetylated GXM and acetyl- or xylose-deficient GXM from genetically modified strains with wild-type GXM in their ability to inhibit the different phases of neutrophil migration. Additionally, we verify the effects of de-O-acetylation on neutrophil migration in vivo. De-O-acetylation caused a dramatic reduction of the inhibitory capacity of GXM in the in vitro assays for neutrophil chemokinesis, rolling on E-selectin and firm adhesion to endothelium. Genetic removal of xylose only marginally reduced the ability of GXM to reduce firm adhesion. In vivo, chemical deacetylation of GXM significantly reduced its ability to interfere with neutrophil recruitment in a model of myocardial ischemia (65% reduction vs a nonsignificant reduction in tissue myeloperoxidase, respectively). Our findings indicate that 6-O-acetylated mannose of GXM is a crucial motive for the inhibition of neutrophil recruitment.

Generation of Arabidopsis thaliana plants with complex N-glycans lacking beta1,2-linked xylose and core alpha1,3-linked fucose.

The plant glycosyltransferases, beta1,2-xylosyltransferase (XylT) and core alpha1,3-fucosyltransferase (FucT), are responsible for the transfer of beta1,2-linked xylose and core alpha1,3-linked fucose residues to glycoprotein N-glycans. These glycan epitopes are not present in humans and thus may cause immunological responses, which represent a limitation for the therapeutic use of recombinant mammalian glycoproteins produced in transgenic plants. Here we report the genetic modification of the N-glycosylation pathway in Arabidopsis thaliana plants. Knockout plants were generated with complete deficiency of XylT and FucT. These plants lack antigenic protein-bound N-glycans and instead synthesise predominantly structures with two terminal betaN-acetylglucosamine residues (GlcNAc(2)Man(3)GlcNAc(2)).

Mala absorción tropical en Bogotá / Tropical malabsorption in Bogota

Se presentan 75 casos de mala absorción tropical, 65 adultos y 10 niños, estudiados desde el año de 1968 en el Hospital San Juan de Dios de Bogotá. La mayoría de los pacientes provenían de Cundinamarca y del Distrito Especial de Bogotá. En todos hubo mala absorción de la D-xilosa y esteatorrea. La biopsia peroral de la mucosa intestinal practicada en 64, mostró atrofia de 1+ en 16, de 2+ en 30, de 3+ en 18 y en ninguno se observó atrofia de 4+. Se encontró anemia en 58 pacientes, la cual fue de tipo megaloblástico en 45 (60 por ciento), ocasionada a su vez por deficiencia de ácido fólico, en 4, de Vitamina B12 en 9 y de ácido fólico y Vitamina B12 en 32. Fueron hallazgos frecuentes además del peso bajo, la glositis, la carotinemia baja (<40ug/dl) la colesterolemia inferior a 150mg/dl y la albuminemia por debajo de 3.5 g/dl. Fueron tratados exitosamente con dieta balanceada, ácido fólico, Vitamina B12, tetraciclina o sulfas, en forma aislada o empleando combinaciones de estos medicamentos. En presencia de megaloblastosis la terapia ideal es el tratamiento "triconjugado" de Vitamina B12, ácido fólico y tetraciclina; solamente falleció un paciente, por tromboembolismo pulmonar. El diagnóstico diferencial debe hacerse principalmente con la enteropatía por Gluten y con la anemia perniciosa

A Col E1 hybrid plasmid containing Escherichia coli genes complementing d-xylose negative mutants of Escherichia coli and Salmonella typhimurium.

The Clarke and Carbon bank of Col El - Escherichia coli DNa hybrid plasmids was screened for complementation of d-xylose negative mutants of E. coli. Of several obtained, the smallest, pRM10, was chosen for detailed study. Its size was 16 kilobases (kb) and that of the insert was 9.7 kg. By transformation or F'-mediated conjugation this plasmid complemented mutants of E. coli defective in either D-xylose isomerase or D-xylulose kinase activity, or both. The activity of D-xylulose kinase in E. coli transformants which bear an intact chromosomal gene for this enzyme was greater than that for the host, due to a gene dosage effect. The plasmid also complemented D-xylose negative mutants of Salmonella typhimurium by F'-mediated conjugation between E. coli and S. typhimurium. Salmonella typhimurium mutants complemented were those for D-xylose isomerase and for D-xylulose kinase in addition to pleiotropic D-xylose mutants which were defective in a regulatory gene of the D-xylose operon. In addition, the plasmid complemented the glyS mutation in E. coli and S. typhimurium. The glyS mutant of E. coli was temperature sensitive, indicating that the plasmid carried the structural gene for glycine synthetase. The glyS mutation in E. coli maps at 79 min, as do the xyl genes. The behaviour of the plasmid is consistent with the existence of a d-xylose operon in E. coli. The data also suggest that the plasmid carries three of the genes of this operon, specifically those for D-xylose isomerase, D-xylulose kinase, and a regulatory gene.