Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

A collagen-alkaline phosphatase conjugate membrane: enzymatic kinetics in-vitro stability

Collagen-alkaline phosphatase membranes have been prepared, and their enzymatic kinetics and in-vitro stability analyzed. Collagen-alkaline phosphatase dispersions were prepared by complexation in aqueous alkaline solution and cast into membranes by controlled dehydration. These membranes were then crosslinked in glutaraldehyde solution, washed thoroughly, and dried. Crosslinking in glutaraldehyde confers increased stability of catalytic activity to these collagen-enzyme membranes, especially when compared to uncrosslinked collagen-alkaline phosphatase membranes assayed in a similar fashion. Crosslinking in glutaraldehyde also appears to inhibit gross leaching of the soluble enzyme from the carrier matrix. Apparent intrinsic kinetic properties of the collagen-alkaline phosphatase conjugate were analyzed in membranes of various thickness in order to determine the effect of internal diffusion resistances on the kinetics of the immobilized enzyme. The apparent Michaelis constant of the immobilized enzyme decreased as a function of decreasing membrane thickness, reaching an observed apparent Michaelis constant of 1.6mM at a membrane thickness of 0.2 mm. Extrapolation of the apparent Michaelis constant to zero membrane thickness, using a linear plot of the natural logarithm of the apparent Michaelis constant versus membrane thickness, allowed estimation of the true Michaelis constant of the immobilized enzyme. The estimated value for the true Michaelis constant of the collagen-alkaline phosphatase complex was 0.7mM. This value agrees closely with reported values for several purified mammalian alkaline phosphatase. The apparent Michaelis constant for the 0.2mm collagen-enzyme membrane agrees closely with the Michaelis constant reported for an alkaline phosphate purified from chondrocyte matrix vesicles. The intrinsic maximum reaction velocity (V(m)) of the collagen-enzyme complex was estimated b plotting the observed reaction rate as a function of decreasing membrane thickness and extrapolating such plots, at various substrate concentrations, to the limiting case of zero membrane thickness. The maximum reaction velocity was obtained by the common intercept of these plots as they approached zero membrane thickness.     

Structural basis of a conserved idiotope expressed by an autoreactive human B cell lymphoma. Evidence that a VH CDR3 mutation alters idiotypy and specificity

Our laboratory has previously investigated the relationship of autoimmune disease and B cell neoplasia in a patient with a diffuse, well differentiated splenic B cell lymphoma and associated autoimmune hemolysis due to an anti-Pr2 antibody. EBV-immortalized B cell clones, established from this lymphoma, were shown to secrete the same pathologic anti-Pr2 antibody. The antiidiotypic mAb, RI.1, defined a private Id (IdRI.1) of the anti-Pr2 antibody that was related to the Ag-binding site and was expressed by both the lymphoma and derived cell lines. This unique Id was expressed by the majority of splenic tumor B cells and also was conserved over a period of 4 yr. In this report, the structural basis of IdRI.1 expression was investigated by analysis of Id- variants isolated by flow microfluorimetry using RI.1. Six Id- cell lines that secrete IgM kappa but lack Pr2 specificity were generated from an Id+ cell line, LS2. These lines were shown to be related to LS2 and the lymphoma by karyotype and by restriction fragment analysis of Ig gene rearrangements. Shared and unshared nucleotide substitutions in the VH and VL regions of the six independent clones were used to construct a genealogic tree relating the Id- clonal members to a common Id+ precursor. The tree illustrates that the base changes occurred sequentially, suggesting that they were introduced by somatic point mutation. Only one VH CDR3 bp difference from the LS2 nucleic acid sequence is common to all Id- sequences, resulting in an amino acid substitution of cysteine 108 to tyrosine. Taken together, these findings suggest that both the expression of IdRI.1 and Ag binding are affected by a single mutation localized to the D region of the anti-Pr2 antibody.     

Identification of T-cell epitopes on E2 protein of rubella virus, as recognized by human T-cell lines and clones.

T-cell epitopes on the E2 protein of rubella virus were studied by using 15 overlapping synthetic peptides covering the E2 protein sequence. The most frequently recognized epitopes on E2 were E2-4 (residues 54 to 74), with 5 of 10 tested T-cell lines responding to it. Two CD4+ cytotoxic T-cell cloned isolated from one T-cell line responded strongly in proliferation assays with peptide E2-4 and were cytotoxic to target cells presenting the E2-4 determinant. Truncated peptides contained within the E2-4 peptide sequence were used to define the T-cell determinants. Results indicated that amino acid residues 54 to 65 were directly involved. Human cell lines with different HLA phenotypes were tested for the capacity to present the antigenic determinants. The results suggested that recognition of peptide E2-4 by T-cell clones was associated with HLA DR7.