Early activation of NK cells after lung infection with the intracellular bacterium, Francisella tularensis LVS

Francisella tularensis is a gram-negative intracellular bacterium that has been classified as a Category A biothreat because of its ability to induce deadly pneumonic tularemia when inhaled. In the present study, an experimental model of F. tularensis LVS intranasal infection was used to study the immune cells involved in cytokine secretion in the lungs after infection. Dramatic increases in the numbers of cells secreting IFN-gamma were observed 72 h after intranasal infection of BALB/c and C57BL/6 mice with sublethal (1000 CFU) or lethal (10,000 CFU) doses of F. tularensis LVS and the cells primarily responsible for this IFN-gamma expression were identified as CD11b+ DX5+ NK cells. The findings were further confirmed in C57BL/6 mice showing that cells responsible for IFN-gamma secretion in the lungs were CD11b+ DX5+ NK1.1+. NK cell depletion studies showed a decrease in the percentage of IFN-gamma secreting cells, due not only to a diminished proportion of IFN-gamma secreting NK cells, but also to a reduced percentage of T cells secreting IFN-gamma. The results indicate that IFN-gamma is secreted in response to respiratory infection with F. tularensis LVS, and that NK cells are the early responders responsible for IFN-gamma secretion.     

Structural basis for SH2D1A mutations in X-linked lymphoproliferative disease

X-linked lymphoproliferative disease (XLP) is a rare and severe immune deficiency, characterized by abnormal immune responses to the Epstein-Barr virus. Recently, the gene responsible for XLP, SH2D1A, has been identified and shown to code for a small cytoplasmic protein with an SH2 domain that interacts with SLAM and 2B4, two receptorial molecules involved in signal transduction in T and NK cells, respectively. A variety of SH2D1A gene mutations have been reported thus far in XLP males. Here we describe a single-strand conformation polymorphism assay for mutation analysis in XLP. Four novel patients with SH2D1A mutations are described. These mutants, and the others previously reported in the literature, have been included in a Registry (SH2D1Abase) that is fully accessible on the World Wide Web. A three-dimensional model of the SH2 domain of the SH2D1A protein has been developed, based on homology with other SH2 domains. The structural consequences of disease-causing SH2D1A mutations are discussed.     

Lethal presentation of mosaic tetrasomy 12p (Pallister-Killian) syndrome

A lethally malformed neonate with mosaic tetrasomy 12p is presented. This is the third reported case of mosaic tetrasomy 12p to have died in the neonatal period. These three babies have shown a consistent phenotype characterized by dysmorphic facies and large diaphragmatic hernia. Mosaic tetrasomy 12p is usually not detectable from lymphocyte investigation, indicating that chromosome studies from cultured fibroblasts should be undertaken in neonates with multiple malformations which include a diaphragmatic defect.     

Incidence and levels of fumonisin contamination in Colombian corn and corn products

A survey was conducted to determine the levels of fumonisins B1 and B2 in corn and corn-based products available in Colombia for human and animal consumption. A total of 120 samples were analyzed by acetonitrile-water extraction, cleanup with a strong-anion-exchange column, and liquid chromatography with o-phthaldialdehyde-2-mercaptoethanol derivatization and fluorescence detection. The samples of corn and corn-based products for animal intake were taken at different feed manufacturing plants, whereas the samples used for human foods where purchased from local retail stores. The number of positive samples for fumonisin B1 was 20.0% higher in corn and corn-based products for animal intake (75.0%) than in corn and corn-based products for human consumption (55.0%). The levels of fumonisin B1 were also higher in corn and corn-based products for animal intake (mean = 694 μg/kg; range = 32–2964 μg/kg), than in corn and corn-based products for human intake (mean = 218 μg/kg; range = 24–2170 μg/ kg). The incidence and levels of fumonisin B2 were lower than those for fumonisin B1. Corn and corn-based products for animal consumption had an incidence of fumonisin B2 of 58.3%, with a mean value of 283 μg/kg, and a range of 44–987 μg/kg. The incidence of fumonisin B2 in corn-based products for human intake was 35.0%, with a mean value of 118 μg/kg and a range of 21–833 μg/kg. The highest incidence and levels of fumonisins were found in samples of hominy feed, with concentrations ranging from 86 to 2964 μg/kg fumonisin B1 and 57 to 987 μg/kg fumonisin B2.     

Immunocytochemical detection of lignin-related epitopes in cell walls in bryophytes and the charalean alga Nitella

Lignins are complex phenolic heteropolymers present in xylem and sclerenchyma cell walls in tracheophytes. The occurrence of lignin-like polymers in bryophytes is controversial. In this study two polyclonal antibodies against homoguaiacyl (G) and guaiacyl/syringyl (GS) synthetic lignin-like polymers that selectively labelled lignified cell walls in tracheophytes also bound to cell walls in bryophytes, the GS antibody usually giving a stronger labelling than the G antibody. In contrast to tracheophytes, the antibody binding in liverworts and mosses was not tissue-specific. In the hornworts Megaceros flagellaris and M. fuegiensis the pseudoelaters and spores were labelled more intensely than the other cell types with the GS antibody. The cell walls in Nitella were labelled with both antibodies but no binding was observed in Coleochaete. The results suggest that the ability to incorporate G or GS moieties in cell walls is a plesiomorphy (primitive character) of the land plant clade.     

Structures of bulged three-way DNA junctions.

We have studied a series of three-way DNA junctions containing unpaired bases on one strand at the branch-point of the junctions. The global conformation of the arms of the junctions has been analysed by means of polyacrylamide gel electrophoresis, as a function of conditions. We find that in the absence of added metal ions, all the results for all the junctions can be accounted for by extended structures, with the largest angle being that between the arms defined by the strand containing the extra bases. Upon addition of magnesium (II) or hexamine cobalt (III) ions, the electrophoretic patterns change markedly, indicative of ion-dependent folding transitions for some of the junctions. For the junction lacking the unpaired bases, the three inter-arm angles appear to be quite similar, suggesting an extended structure. However, the addition of unpaired bases permits the three-way junction to adopt a significantly different structure, in which one angle becomes smaller than the other two. These species also exhibit marked protection against osmium addition to thymine bases at the point of strand exchange. These results are consistent with a model in which two of the helical arms undergo coaxial stacking in the presence of magnesium ions, with the third arm defining an angle that depends upon the number of unpaired bases.