Delineation of the epitope recognized by an antibody specific for N- glycolylneuraminic acid-containing gangliosides

P3 is a mouse monoclonal antibody (mAb) that binds to several NeuGc- containing gangliosides. It also reacts with antigens expressed in human breast tumors (Vazquez et al. (1995) Hybridoma , 14, 551-556). In this work, the binding specificity of P3 has been characterized in more detail using a panel of glycolipids that included several disialylated gangliosides and several chemical derivatives of NeuGc-GM3. The carboxyl group and the nitrogen function of sialic acid were found to play important roles in the antibody binding, whereas the glycerol tail appears to be nonrelevant. Molecular modeling was used to analyze the binding data, including the finding that P3 selectively recognizes the internal NeuGc in GD3. For this purpose, conformational studies of GD3 were performed using molecular dynamics. It was concluded that sialic acid binds the P3 antibody through its upper face (the one on which the carboxyl group is exposed) and the C4-C5 side of the sugar ring, whereas none or very little contact between the galactose residue and the protein is evident. Conformational analysis of GD3 revealed that, despite the large flexibility of the NeuGcalpha8NeuGc linkage, the P3 binding epitope on the external sialic acid is not well exposed for any of the possible conformations this linkage can adopt, whereas the internal sialic acid presents the epitope in a proper way for several of these conformations. As a final result, a coherent picture of the epitope that fits the wide binding data was obtained.      

Evidence for Maternal Transmission of Chloroplast DNA in the Genus Asplenium (Aspleniaceae,Pteridophyta)

Little is known about the mode of transmission of chloroplasts in ferns, despite the importance of such knowledge for molecular phylogenetic and biosystematic studies. Andersson-Kötto (1930, 1931) inferred from crossing experiments that chloroplasts are inherited biparentally in Asplenium scolopendrium L. Here we present evidence from artificial hybridisation that demonstrates maternal inheritance of chloroplast DNA in the genus Asplenium (Aspleniaceae, Pteridophyta) using length variation in a non-coding spacer (trnL_UAA-trnF_GAA) in the chloroplast DNA.     

Cytological variation and evolution withinPelargonium sectionHoarea (Geraniaceae)

Chromosome numbers of 65 species of sect.Hoarea have been determined. These show three basic chromosome numbers, x = 11, 10 and 9. Only a few species are tetraploid. In five species both diploid and tetraploid cytotypes are reported. Several cases of deviations in chromosome numbers and cytological abnormalities were found, most of these being related to the presence of B chromosomes that occur in eight species. Evidence is presented to suggest that the basic chromosome numbers of x = 10 and x = 9 are derived from x = 11 by centric fusion. Although variation in basic chromosome number withinPelargonium has been the subject of detailed study, this is the first time that evidence has been found for a mechanism of change in basic number, that of centric fusion by Robertsonian translocation. For the species of sect.Hoarea with x = 9, where the evidence for Robertsonian translocation is greatest, this process has probably taken place quite recently. In contrast to results from other sections of the genusPelargonium, the three different basic numbers of sect.Hoarea do not contradict its delimitation as a natural taxon.     

A nonlinear method for estimating nucleotide polymorphism from restriction maps

Restriction mapping is used to estimate nucleotide sequence polymorphism when the regions to be studied are too long or too numerous to be sequenced. Restriction mapping is less costly than DNA sequencing, but it does not allow direct measurement of underlying nucleotide polymorphism. It is therefore useful to be able to estimate underlying nucleotide polymorphism from observations of polymorphism in restriction maps, as this offers some of the resolution afforded by DNA sequencing at a reduced cost. Previous estimators of underlying nucleotide polymorphism have assumed that each restriction-enzyme- binding site contains, at most, a single polymorphic nucleotide position (the low-polymorphism-frequency assumption), and this assumption has placed an upper limit on the level of polymorphism that can be resolved by these estimators. The present study documents an estimator which allows relaxation of this assumption. The new estimator more accurately estimates underlying nucleotide polymorphism when the polymorphism level is high enough to falsify the low-polymorphism- frequency assumption. The new estimator therefore yields good results for data sets that are too divergent for analysis by present methods.      

A reappraisal ofPelargonium sect.Ligularia (Geraniaceae)

A study of 33 species ofPelargonium sect.Ligularia reveals four basic chromosome numbers, x = 8, 9, 10, and 11, and variation in chromosome size. From evidence of karyology and hybridization attempts, proposals are made to divide the section into smaller groups and to transfer some species to other sections.     

The biogeochemistry of basic cations in two forest catchments with contrasting lithology in the Czech Republic

The biogeochemistry of Ca, Mg, K, and Nawere investigated in two forested catchments in theCzech Republic, one underlain by leucogranite, theother by serpentinite. High weathering rates at theserpentinite site at Pluhv Bor resultedin Mg²⁺ as the dominant cation on the soilexchange complex and in drainage water. Other basiccations (Ca²⁺, K⁺, Na⁺) showedrelatively low concentrations and outflow instreamwater. The catchment exhibited high basesaturation in mineral soils (>70%), and nearneutral soil and stream pH, despite elevated inputsof acidic deposition. Slow growth of Norway spruceat Pluhv Bor may be caused by K deficiency, Mgoversupply and/or Ni toxicity. In contrast, thegranitic site at Lysina showed low concentrations ofbasic cations on the soil exchange complex and instreamwater. Soil and drainage water at Lysina werehighly impacted by acidic deposition. Soil pH wasextremely acidic (<4.5) throughout the soilprofile, and the base saturation of the mineral soilwas very low (<5%). Supplies of basic cationsfrom atmospheric deposition and soil processes wereless than inputs of SO^2- ₄ on anequivalence basis, resulting in low pH and highconcentrations of total Al in drainage water. Needle yellowing in Norway spruce was possibly theresult of Mg deficiency at Lysina. Because of theirextremely different lithologies, these catchmentsserve as valuable end-members of ecosystemsensitivity to elevated levels of acidicdeposition.     

An Electron Microscope Study of Autoinfection in Neogregarines (Sporozoa, Neogregarinida)

SYNOPSIS. In an electron microscope study of the neogregarine Farinocystis tribolii Weiser 1953 in the fat body of the larvae of the flour beetle Tribolium castaneum , empty oocysts and adjacent sporozoites of the gregarine were found. The empty oocysts contained host cell cytoplasm, a residuum only slightly larger than that in mature oocysts, and some remnants of the oocyst membrane pressed tightly against the inner surface of the wall. Apparently normal sporozoites were found near the empty oocysts and no damaged ones were seen. It is assumed that the sporozoites go on developing in the host, i.e., that autoinfection takes place.     

Alterations of NADPH:protochlorophyllide oxidoreductase quantity and lipid composition in etiolated barley seedlings infected by Barley stripe mosaic virus (BSMV)

To understand the phenomenon by which infection of seed-transmitted Barley stripe mosaic virus (BSMV) alters membrane structures and inhibits protochlorophyllide biosynthesis of dark-grown barley ( Hordeum vulgare L.) plants, we analysed the presence of NADPH:protochlorophyllide oxidoreductase (POR, EC 1.3.1.33) and the galactolipid content and fatty acid composition. The amount of POR in etioplasts of infected leaves, compared with non-infected leaves, was reduced, as measured by immunoelectron microscopy and Western blot. These results are in agreement with the previously described reduction of the ratio of the photoactive 650 nm to non-photoactive 630 nm absorbing protochlorophyllide forms ( Harsányi et al. , 2002 . Physiol. Plant 114 , 149–155). The galactolipid content was lower in infected leaves. Monogalactosyl-diacylglycerol (MGDG) content was reduced to 40% and digalactosyl-diacylglycerol to 55% of control plants on a fresh weight basis. In infected plants, the proportion of linolenic acid decreased in both galactolipids. The lower amount of highly unsaturated fatty acids and the reduced abundance of MGDG correlated well with the previously detected reduction in the membrane ratio of prolamellar body (PLB) to prothylakoid ( Harsányi et al. , 2002 . Physiol. Plant 114 , 149–155). The reduced amount of POR and the above described alterations in the lipid composition resulted in a disturbed structure of PLBs. As a consequence, pigment synthesis and the greening process were inhibited in infected cells, in turn explaining the appearance of chlorotic stripes of BSMV-infected barley leaves. Our results show that BSMV infection can be detected at a very early stage of leaf development.     

Development of EST‐SSRs from the Alpine Lady‐fern,Athyrium distentifolium

The utility of EST‐simple sequence repeats (EST‐SSRs) was evaluated in the fern Athyrium distentifolium. From 1152 frond cDNA clones, 165 microsatellites, including di‐, tri‐, tetra and penta‐nucleotide repeat motifs, were identified. Primer design was possible for 74 of the SSRs; subsequent screening of 10 loci on 186 individuals from six natural populations revealed between two and seven alleles per locus and expected heterozygosity (H_E) estimates ranging from 0.027 to 0.809. Eight of these loci were further examined for cross‐species and cross‐generic amplification in other Woodsiaceae species, and polymorphic products were detected. EST‐derived SSRs provide robust, informative and potentially transferable polymorphic markers suitable for biodiversity research.     

红细胞在钙离子和离子载体A23187作用下的流变特性研究

用新激光衍射法研究了钙离子及离子载体A23187对红细胞流变特性的影响.用不同浓度的钙离子及离子载体A23187分别处理红细胞后,测量其取向指数和小变形指数.结果表明离子载体A23187较细胞外钙离子浓度对红细胞流变特性的影响更大.而且,最大取向指数和最大小变形指数随着钙离子及离子载体A23187浓度的增加而降低.离子载体A23187浓度增加导致红细胞变形能力明显降低.