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.      

Expression of platelet membrane glycoproteins and alpha-granule proteins by a human erythroleukemia cell line (HEL)

We demonstrate that HEL, a human erythroleukemic cell line, has numerous megakaryocytic markers which were markedly enhanced following the addition of the inducers dimethyl sulfoxide or 12-O-tetradecanoylphorbol-13-acetate to the culture medium. Ultrastructural and cytochemical studies showed: (i) the presence of organelles morphologically resembling the platelet alpha-granules; and (ii) a peroxidase activity with the same characteristics as that specifically found in platelets. The platelet alpha-granule proteins (von Willebrand factor, platelet factor-4 and beta-thromboglobulin) were immunologically detected in the HEL cell cytoplasm and their amounts increased after induction. Of particular interest was the presence of platelet membrane proteins. A monoclonal antibody specific for glycoprotein Ib bound to HEL cells. Platelet membrane glycoproteins IIb and IIIa were identified on intact cells using specific antibodies in a binding assay or in cell lysates using either crossed immunoelectrophoresis or an immunoblotting procedure following SDS-polyacrylamide gel electrophoresis. Most HEL cells also expressed the platelet alloantigen PIA1. All of the platelet membrane proteins were present in higher amounts after induction. Glycophorin A, specific for the erythroid lineage, was also detected on HEL cells. Thus, while confirming the presence of erythroid markers, our studies provide evidence that the HEL cell line also expresses platelet antigens. As such, HEL cells represent a unique system with which to study the biosynthesis of platelet-specific proteins and glycoproteins.     

The human calcitonin gene is located on the short arm of chromosome 11

By molecular hybridization of human calcitonin cDNA probes to DNA from human-rodent hybrid cells containing identified human chromosomes, we have mapped the human calcitonin gene to the short arm of chromosome 11. This location has been confirmed by in situ hybridization, which further localized the calcitonin gene to region 11p13-15. The significance of this region regarding gene linkage and possible markers for inherited cancers is discussed.     

Regioelectronic factors in metabolic hydroxylation of aliphatic carbon atoms

EHT calculations have been performed on model molecules acting as substrates for mammalian mono-oxygenases. C_α---H bonds are consistently found to have larger overlap populations compared with C_β---H and C_γ---H bonds. It is known on the other hand that metabolic hydroxylation of aliphatic carbon atoms shows a marked regioselectivity for α-carbons. The quantum-mechanical results sustain the view that C---H bonds of relatively high electronic density are preferred target sites for the cytochrome P-450-mediated oxygenation, and that the oxygen atom being activated is transformed into an electrophilic species capable of C---H bond insertion.     

Transferrin binding to K562 cell line : Effect of heme and sodium butyrate induction

Experiments demonstrating the existence of receptors for iron-saturated transferrin on K562 cells are described. Binding of ¹²⁵I-labelled transferrin is rapid, saturable and reversible, and can be specifically inhibited by unlabelled transferrin, but not by other proteins. The number of receptors determined by Scatchard analysis significantly decreased when K562 cells moved from the exponential to the quiescent phase of growth. Induction by hemin or sodium butyrate resulted in a marked reduction of transferrin binding. This phenomenon was due entirely to reduction in the number of receptors and was without effect on the affinity of interaction. The effect of butyrate and hemin on the number of transferrin receptors in other hematopoietic cell lines was investigated. Butyrate on the various cell lines was variable in its effect, whereas hemin constantly elicited a significant reduction in the number of transferrin receptors.