The Role of Fusion in Ant Chromosome Evolution: Insights from Cytogenetic Analysis Using a Molecular Phylogenetic Approach in the Genus Mycetophylax

Among insect taxa, ants exhibit one of the most variable chromosome numbers ranging from n = 1 to n = 60. This high karyotype diversity is suggested to be correlated to ants diversification. The karyotype evolution of ants is usually understood in terms of Robertsonian rearrangements towards an increase in chromosome numbers. The ant genus Mycetophylax is a small monogynous basal Attini ant (Formicidae: Myrmicinae), endemic to sand dunes along the Brazilian coastlines. A recent taxonomic revision validates three species, Mycetophylax morschi, M. conformis and M. simplex. In this paper, we cytogenetically characterized all species that belongs to the genus and analyzed the karyotypic evolution of Mycetophylax in the context of a molecular phylogeny and ancestral character state reconstruction. M. morschi showed a polymorphic number of chromosomes, with colonies showing 2n = 26 and 2n = 30 chromosomes. M. conformis presented a diploid chromosome number of 30 chromosomes, while M. simplex showed 36 chromosomes. The probabilistic models suggest that the ancestral haploid chromosome number of Mycetophylax was 17 (Likelihood framework) or 18 (Bayesian framework). The analysis also suggested that fusions were responsible for the evolutionary reduction in chromosome numbers of M. conformis and M. morschi karyotypes whereas fission may determines the M. simplex karyotype. These results obtained show the importance of fusions in chromosome changes towards a chromosome number reduction in Formicidae and how a phylogenetic background can be used to reconstruct hypotheses about chromosomes evolution.     

Enrichment of rat tissue lipids with fatty acids that are prostaglandin precursors.

The effects of supplementation of a complete diet with ethyl arachidonate and with ethyl dihomo-gamma-linolenate (20 : 3Omega6) on the fatty acid composition of plasma and tissue lipid classes were studied in normal rats. 2. These prostaglandin precursors were incorporated in varying degrees into all lipid classes of the tissues that were investigated. The largest elevations were seen in plasma and tissue triacylglycerols. Significant increases were also observed in phospholipids, cholesteryl esters and the free fatty acid fraction. 3. Following the feeding of the ester of 20 : 3Omega6, arachiodonate levels also rose in the lipids of some tissues. In others, such as the renal medulla and platelets, and increase in 20 : 3Omega6 content occurred without a rise in 20 : 4. 4. Platelet aggregation is known to be stimulated by 20 : 4 (via active metabolites), but not by 20 : 3Omega6. The ability to modify 20 : 3Omega6 levels selectively in certain tissues is of interest in light of such pharmacologic differences from 20 : 4.     

A micro-method for quantitative determination of acylneuraminic acids from erythrocyte membranes.

A micro-method is presented which enables the fast and exact determination of acid-hydrolyzed acylneuraminic acids in erythrocyte membranes. Erythrocytes from 1 ml of human and rabbit blood containing ACD buffer are, washed and hemolyzed on Millipore filters of pore size 1.2 mu. Acylneuraminic acids are released from the erythrocyte membranes still on the filters under the optimal conditions of 0.1 N HCl at 80 degrees C for 50 min. A prerequisite for the determination of the true amount of acylneuraminic acids using the periodic acid/thiobarbituric acid assay is the small-scale extraction of lipids from the hydrolysate and anion-exchange chromatography of acylneuraminic acids. The values thus obtained must be corrected, as 20% of acylneuraminic acids are destroyed during acid hydrolysis. In samples of human blood from 10 healthy individuals, on an average 223 nmol acylneuraminic acids per ml of packed erythrocytes were found, and in the same amount of rabbit erythrocytes, 1e method for a screening of the acylneuraminic acid content of erythrocyte membranes in hemolytic diseases or of other cell membranes is discussed.     

A COMPARATIVE ELECTRON MICROSCOPICAL STUDY OF RNA FROM DIFFERENT SOURCES

Electron micrographs of ribosomal RNA from Escherichia coli, microsomal RNA from calf, rat, and chick liver, Bacillus cereus RNA and E. coli soluble RNA are presented. Filaments of about 10 A in diameter could be observed in preparations obtained from aqueous solutions of high molecular weight RNA. When ammonium acetate solutions were used a tendency for coiling and aggregation was observed. E. coli soluble RNA appears as small, sometimes elongated particles the smallest diameter being of about 10 A.     

Dynamic proteomics in individual human cells uncovers widespread cell-cycle dependence of nuclear proteins

We examined cell cycle-dependent changes in the proteome of human cells by systematically measuring protein dynamics in individual living cells. We used time-lapse microscopy to measure the dynamics of a random subset of 20 nuclear proteins, each tagged with yellow fluorescent protein (YFP) at its endogenous chromosomal location. We synchronized the cells in silico by aligning protein dynamics in each cell between consecutive divisions. We observed widespread (40%) cell-cycle dependence of nuclear protein levels and detected previously unknown cell cycle-dependent localization changes. This approach to dynamic proteomics can aid in discovery and accurate quantification of the extensive regulation of protein concentration and localization in individual living cells.     

The diagnosis of the sex chromosomes in human tissues

Summary The nuclei in the skin, and in the neutrophils, have been studied in men and women, in relation to a diagnosis of the sex chromosomes in non-dividing nuclei.It has been shown in the skin, that the appearance of chromocenters, which are presumably formed by the X and Y, can vary according to metabolic conditions, but that a determination of the percent of nuclei with different numbers of chromocenters and nucleoli in the young and old spinous cells, gives a characteristic distribution of nuclear types in each of the two sexes.Since such a determination includes cells with individual X and Y chromocenters, it should be possible to detect by this method not only cases that are XX or XY, but also cases with abnormal sex chromosome constitutions.     

A novel 43-kDa glycoprotein is detected in the nucleus of mammalian cells by autoantibodies from dogs with autoimmune disorders

We have characterized a new antibody specificity in a panel of sera from dogs developing systemic lupus erythematosus (SLE) or clinically related autoimmune disorders. This antibody stains in a speckled fashion the nucleus of cells of different mammalian origins. The target antigen is a basic (pI 9.2) nuclear polypeptide with an apparent molecular weight of 43 kDa (p43) which is detected in various mammalian cell nuclei. p43, as studied in HeLa cells, appears to be cell cycle-independent. It is released from nuclei by salts (0.5 M NaCl or 0.25 M ammonium sulfate). Upon subfractionation of nuclear components, p43 is found in the fraction containing HnRNPs and is recovered in immunoprecipitates obtained with 4F4 monoclonal antibody to HnRNP C proteins. Immunoelectron microscopy revealed that p43 is concentrated over the dense chromatin periphery and interchromatin granule clusters. Another important feature of p43 is its ability to specifically bind wheat germ agglutinin lectin but not concanavalin A nor Ulex europaeus I, supporting the notion that p43 is a glycoprotein bearing an N-acetyl-glucosamine moiety. Consistent with this result, a radio-active p43 band is specifically immunoprecipitated by canine anti-p43 autoantibodies from HeLa cells metabolically labeled with [14C]glucosamine. Finally, anti-p43 antibodies do not immunoprecipitate SnRNA, indicating that p43 has no apparent association with SnRNPs.     

Prostaglandin H synthase: protein synthesis-independent regulation in bovine aortic endothelial cells

The objective ofthe present study was to examine whether prostaglandin H synthase(PGHS) can be regulated by pathways independent of de novo synthesis ofPGHS. Incubation of bovine aortic endothelial cells (BAEC) for as shortas 5 min with NaF (40 mM) resulted in a 60% increase in PGHS activity.PGHS activity induced by NaF was unaffected by either 10 µMcycloheximide or 1 µM actinomycin D. Aspirin (25 µM) completelyinhibited resting PGHS activity, and NaF did not induce furtherstimulation. NS-398 (500 nM), a specific PGHS-2 inhibitor, wasineffective. Basic fibroblast growth factor (bFGF) induced asignificant increase in PGHS activity within 30 min and was insensitiveto cycloheximide. The levels of PGHS-1 and PGHS-2 proteins, as measuredby Western blots, were not affected by NaF or bFGF. The tyrosine kinaseinhibitor genistein attenuated PGHS activity that was induced by NaFand bFGF, whereas the tyrosine phosphatase inhibitor, sodiumorthovanadate, augmented these responses. The G protein activators5'-guanylyl imidodiphosphate and guanosine5'-O-(3-thiotriphosphate) inhibited both resting andNaF-induced PGHS activities. These results suggest that, in BAEC,PGHS-1 activity can be regulated by tyrosine kinase and/or Gproteins, independently of de novo protein synthesis.