Assessing genetic diversity of some Anthurium andraeanum Hort. cut-flower cultivars using RAPD Markers

Randomly amplified polymorphic DNA (RAPD) markers fingerprinting were used to assess the level of genetic variations among 24 cut-flower Anthurium andraeanum Hort. cultivars. Eight decamer primersproduced a total of 98 reproducible PCR bands that were used to calculate the Nei and Li’s genetic distance (GDNL) coefficients amongst the cultivars. GDNL values ranged from 0.018 to 0.163 with an average of 0.09 (representing an average genetic similarity of 91.34%). This significantly low average genetic distance among the various cultivars indicated that genetic variation among the cultivars was low. A dendrogram, produced using unweighted pair group method using arithmetic averages (UPGMA), grouped the cultivars into four main clusters. Cultivar ‘Antartica’ was genetically distinct from all the others. ‘Midori’ and ‘Bourgogne’ together formed a cluster whereas the remaining 21 cultivars grouped into two clusters and were closely related to each other. Clusters did not relate to cultivar provenance or origin and were independent of floral colour and spathe category. Finding correlations between these morphological traits to RAPD markers would necessitate extensive primer screening. Nevertheless, RAPD markers fingerprinting allowed a rapid assessment of the level of genetic variation that would otherwise be difficult to evaluate using the limited number of morphological markers present among these closely related  anthurium cultivars

Evaluation of genetic diversity between 27 banana cultivars (Musa spp.) in Mauritius using RAPD markers

Cultivated bananas (Musa spp.) are mostly diploid or triploid cultivars with various combinations of the A and B genomes inherited from their diploid ancestors Musa acuminata Colla. and Musa balbisianaColla. respectively. Random amplified polymorphic DNA (RAPD) markers were used to establish the relatedness of 27 accessions in the Mauritian Musa germplasm. 15 decamer primers produced a total of115 reproducible amplification products, of which 96 were polymorphic. Computation of the genetic distances shows that similarities ranged from 0.3 to 1.0 with an average of 0.51. With a few exceptions,cluster analysis differentiated pure A containing cultivars from those containing at least one B genome. This paper answers long standing questions on the taxonomic placement of the cultivar ‘BananeRouge’ by providing the basis for its classification within the homogenomic A cultivars. The results presented here also contribute to narrowing the gaps in our current understanding of the migration path of bananas and the emergence of secondary centers of diversity

B cell responses to a peptide epitope. VI. The kinetics of antigen recognition modulates B cell-mediated recruitment of T helper subsets

The ability of Ag-primed B cells to recruit distinct Th subsets was examined using two analogous synthetic peptides, G41CT3 and G28CT3, as model Ags. With sequence differences at only two positions, these peptides were identical both with respect to fine specificity of Abs induced and ability to prime T cells. Lymph node cell populations primed with peptide G41CT3, when challenged with the homologous Ag, yielded predominantly Th2 cytokines. In contrast, a challenge with the heterologous Ag, G28CT3, resulted in a markedly increased production of Th1 cytokines. These distinctions derived from altered APC function of Ag-primed B cells due to differential kinetics of recognition of the two Ags by surface Ig receptors, as confirmed by binding studies with a panel of anti-G41CT3 mAbs. A concentration-dependent circular dichroism study revealed differences in the nature of intermolecular associations for these two peptides. Furthermore, the on-rate of peptide G28CT3 binding to Ab also increased with increasing peptide concentration, implying a dependence on intermolecular interactions. This, in turn, correlated well with the ability of peptide G28CT3 to preferentially activate either Th1 or Th2 cells. Thus, the relative proportion of Th1 vs Th2 cells recruited by Ag-primed B cells is governed by the on-rate of Ag binding to surface Ig receptors, with higher on-rates promoting Th1 recruitment. Further, even subtle changes in solution behavior of an Ag can markedly influence the kinetics of recognition by B cells

B cell responses to a peptide epitope. X. Epitope selection in a primary response is thermodynamically regulated

We examine the etiological basis of hierarchical immunodominance of B cell epitopes on a multideterminant Ag. A model T-dependant immunogen, containing a single immunodominant B cell epitope, was used. The primary IgM response to this peptide included Abs directed against diverse determinants presented by the peptide. Interestingly, affinity of individual monomeric IgM Abs segregated around epitope recognized and was independent of their clonal origins. Furthermore, affinity of Abs directed against the immunodominant epitope were markedly higher than that of the alternate specificities. These studies suggested that the affinity of an epitope-specific primary response, and variations therein, may be determined by the chemical composition of epitope. This inference was supported by thermodynamic analyses of monomer IgM binding to Ag, which revealed that this interaction occurs at the expense of unfavorable entropy changes. Permissible binding required compensation by net enthalpic changes. Finally, the correlation between chemical composition of an epitope, the resultant affinity of the early primary humoral response, and its eventual influence on relative immunogenicity could be experimentally verified. This was achieved by examining the effect of various amino-terminal substitutions on immunogenicity of a, hitherto cryptic, amino-terminal determinant. Such experiments permitted delineation of a hierarchy of individual amino acid residues based on their influence; which correlated well with calculated Gibbs-free energy changes that individual residue side chains were expected to contribute in a binding interaction. Thus, maturation of a T-dependant humoral response is initiated by a step that is under thermodynamic control

B cell responses to a peptide epitope. V. Kinetic regulation of repertoire discrimination and antibody optimization for epitope

The influence of imposing various conformational constraints on immune responses to a model epitope within a synthetic peptide immunogen was examined in mice. Although overall immunogenicity was affected, the model epitope (sequence DPAF) remained the predominant recognition site regardless of the conformation in which it was presented. A comparison of anti-DPAF mAbs obtained in response to two analogue peptides, PS1CT3 and CysCT3, in which the DPAF segment was either unconstrained or held within a cyclic loop, respectively, revealed a significant homology in the paratope composition. At one level a subset of anti-PS1CT3 and anti-CysCT3 mAbs was found to share a common heavy chain variable region. In addition, nucleotide sequence homology comparisons of both heavy and light chain variable regions identified the presence of anti-PS1CT3 and anti-CysCT3 mAbs that collectively appeared to derive from a common progenitor, but with nonidentical somatic mutations. Interestingly, however, no bias toward homologous Ag could be discerned on measurement of relative affinities of the mAbs for the two peptides. In contrast, mAb binding on-rates clearly discriminated between peptides representing the homologous vs the heterologous confomer of the DPAF epitope. Thus, it would appear that the kinetics of Ag recognition dominate over equilibrium binding criteria both in epitope-driven repertoire selection and Ab maturation in a humoral response

Fucosylated chondroitin sulfates from the body wall of the sea cucumber <i>Holothuria forskali</i>. Conformation, selectin binding and biological activity

Fucosylated chondroitin sulfate (fCS) extracted from the sea cucumber Holothuria forskali is composed of the following repeating trisaccharide unit: →3)GalNAcβ4,6S(1→4) [FucαX(1→3)]GlcAβ(1→, where X stands for different sulfation patterns of fucose (X = 3,4S (46%), 2,4S (39%), and 4S (15%)). As revealed by NMR and molecular dynamics simulations, the fCS repeating unit adopts a conformation similar to that of the Lex blood group determinant, bringing several sulfate groups into close proximity and creating large negative patches distributed along the helical skeleton of the CS backbone. This may explain the high affinity of fCS oligosaccharides for L- and P-selectins as determined by microarray binding of fCS oligosaccharides prepared by Cu2+-catalyzed Fenton-type and photochemical depolymerization. No binding to E-selectin was observed. fCS poly- and oligosaccharides display low cytotoxicity in vitro, inhibit human neutrophil elastase activity, and inhibit the migration of neutrophils through an endothelial cell layer in vitro. Although the polysaccharide showed some anti-coagulant activity, small oligosaccharide fCS fragments had much reduced anticoagulant properties, with activity mainly via heparin cofactor II. The fCS polysaccharides showed prekallikrein activation comparable with dextran sulfate, whereas the fCS oligosaccharides caused almost no effect. The H. forskali fCS oligosaccharides were also tested in a mouse peritoneal inflammation model, where they caused a reduction in neutrophil infiltration. Overall, the data presented support the action of fCS as an inhibitor of selectin interactions, which play vital roles in inflammation and metastasis progression. Future studies of fCS-selectin interaction using fCS fragments or their mimetics may open new avenues for therapeutic intervention

Macro-, micro-and re-entrant shape forming of sheets of alloy Ti-6A1-4V

Experiments involving macro-, micro-and re-entrant shape forming in superplastic Ti-6A1-4V alloy sheets of initial thickness 1.6 mm are described. Macroforming followed by microforming into grooves of different geometry as well as re-entrant shape cum micro-forming could be completed successfully. The rate of forming into a wider groove was greater than into a narrower groove but microforming and the filling of corner radii of grooves required considerably more pressure and time than macroforming. For the chosen geometries, at the end of the macroforming stage there was a significant thickness gradient which led to a highly non-uniform thickness distribution after microforming. The effects of the geometry of the dies and the changes in the experimental conditions have also been discussed

Kinetics & Mechanism of Oxidation of Diaryl Sulphoxides by Cr(VI)

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Interleukin-1 derived synthetic peptide as an added co-adjuvant in vaccine formulations

A synthetic peptide containing the immunostimulatory and receptor binding sequences of human IL-1β was synthesized and tested for its immunoadjuvant properties. Using a commercially available hepatitis B vaccine as model antigen we found that added peptide enhanced both total and protective antibody responses in high and low responder strains of mice but was unable to overcome non-responsiveness in a third strain. Increased antibody response to antigen in the responder strains was not accompanied by any significant alteration in IgG isotype composition. These results suggest that this peptide may prove useful as a co-adjuvant in vaccines