Structure,molecular evolution and maintenance of copy number of extended repeated structures in the X-heterochromatin of Drosophila melanogaster

The 60 kb repeats located in the distal heterochromatin of the X chromosome of Drosophila melanogaster were cloned in overlapping cosmids. These regions, designated as SCLRs, comprised the following types of repeated elements Stellate genes, which are known to be involved in spermatogenesis; copia-like retrotransposons; LINE elements, including amplified Type rDNA insertions; and rDNA fragments. The following steps in SCLR formation were hypothesized: insertion of mobile elements into the rDNA and Stellate gene clusters: internal tandem duplication events; recombination between the rDNA cluster and Stellate tandem repeat; and amplification of the whole SCLR structure. There are about nine SCLR copies per haploid genome, but there is approximately a twofold variation in copy number between fly stocks. The SCLR copy number differences between closely related stocks are suggested to be the result of unequal sister chromatid exchange (USCE). The restricted variation in SCLR copy number between unrelated stocks and the absence of chromosomes free of SCLRs suggests that natural selection is active in copy number maintenance.     

Embryonic stem cells derived from morulae,inner cell mass,and blastocysts of mink: Comparisons of their pluripotencies

A characterization of cell lines that we derived from morulae (three lines), blastocysts (two lines), and the inner cell mass (ICM) is given. The karyotype of all the lines was normal; the genotype of four lines was XX, and four lines were genotypically XY. The pluripotencies and commitment status of the derived lines were estimated. First, there were not less than two-thirds of cells in the populations of the lines derived from morulae and the lCM with both Xs active; 70–100% of cells of the blastocyst-derived lines had one of the Xs in an inactive state. The activity of glucose-6-phosphate dehydrogenase (G6PD) in the lines (genotype XX) derived from morulae and ICM was found to be twofold higher than in lines with genotype XY, and G6PD activity was the same in the blastocyst-derived XX lines and XY lines. Second, when injected intraperitoneally into athymic mice, morulae- and ICM-derived cells gave rise to simple and complex embryoid bodies (EB) resembling to typical “cystic” mouse EBs. Third, when injected subcutaneously to athymic mice, the ICM- or morula-derived cells gave rise to typical teratomas containing derivatives of the three germ layers and components of organogenesis. Comparisons of cell lines of different derivations demonstrated that the pluripotencies of the ES cells derived from morulae or the ICM are higher than those of blastocyst derivation. © 1993 Wiley-Liss, Inc.     

Against Culture: Development, Politics, and Religion in Indian Alaska

Against Culture: Development, Politics, and Religion in Indian Alaska. Kirk Dombrowski. Lincoln: University of Nebraska Press, 2001. 247 pp.     

The potential applications of cyanobacterial photosynthesis for clean technologies

Natural photosynthesis may be adapted to advantage in the development of clean energy technologies. Efficient biocatalysts that can be used in solar energy conversion technologies are the cyanobacteria. Photobioreactors incorporating cyanobacteria have been used to demonstrate (a) the production of hydrogen gas, (b) the assimilation of CO₂ with the production of algal biomass, (c) the excretion of ammonium, and (d) the removal of nitrate and phosphate from contaminated waters.Abbreviations Chl chlorophyll - DW dry weight - MSX L-methionine-D-L-sulphoximine - PAR photosynthetically active radiation - PU polyurethane - PV polyvinyl - PVC polyvinylchloride     

Action of surfactants on egg lecithin liposomes

The lytic action of several homologous series of surfactants including N-acyl derivatives of the Na-salt of amino acids on the egg lecithin multilamellar liposomes was examined. The affinity for the lipid membrane and the solubilising capacity of the agents were estimated. The contribution of a CH₂ group and that of the polar head group of surfactants to the free energy of the agent's binding to the membrane were evaluated. The results obtained indicate that the contribution of a CH₂ group to the free binding energy depends on the nature of the surfactants' head group. This dependence is attributed to either various localisation of the agent's molecules in the lipid bilayer or to different properties of the agent's hydrocarbon tails. The contributions of the head groups of the surfactants are assumed to reflect the affinity of these head groups for the lecithin polar head group at the membrane interface. The results obtained indicate some degree of specificity involved in the interactions of the head groups.     

Structural studies on the immunodominant group of lipid A from lipopolysaccharide of Yersinia pseudotuberculosis.

Lipid A isolated from lipopolysaccharide of Yersinia pseudotuberculosis was used for immunization of rabbits to afford antisera to lipid A with titers of 1:640 in the passive hemolysis test. Exhaustion of immune serume with sheep erythrocytes decreased antibody titers up to 1:160. Authentic samples of 2-(DL-3-hydroxytetradecanoyl)amino-2-deoxy-D-glucose 6-phosphate, 2-tetradecanoylamino-2-deoxy-D-glucose 6-phosphate and 2-acetamido-2-deoxy-D-glucose 6-phosphate have been synthesized in order to carry out a comparative study of inhibitory activity of these compounds and lipid A using a system of lipid A and antiserum to lipid A. As a result, the immunodominant moiety of the lipid A of Y. pseudotuberculosis proved to contain a D-glucosamine residue acylated with 3-hydroxytetradecanoic acid at the amino group. The nature of the fatty acid acylating the amino group of glucosamine does not play an important role in the structure of immunodominant moiety of lipid A.     

Possibility of analytical application of the partition in aqueous biphasic polymeric systems technique

The partition behaviour of a number of ionic and nonionic surface-active substances in the dextran-polyethylene glycol system was examined. The strictly linear dependence of the logarithm of the partition coefficient on the alkyl chain length for a homologous series of nonionic surfactants provides a measure of the difference in the relative hydrophobicity between the two phases of the system, in terms of the free energy of transfer of a CH₂ group from the bottom phase to the top phase of the system. This difference is found to be altered in the presence of NaCl or KCl depending on the salt concentration. It is concluded that the influence of the salt composition of the system on the distributed solutes' behaviour may be due to the effect of the ions on the hydrophobicity difference between the phases.The partition of ionic amphiphiles is found to be dependent on the relative hydrophobicity of the compounds as well as on their charge. It is shown that at salt concentrations up to about 0.1 M NaCl the charged solute partition is determined by its charge as well as its relative hydrophobicity, in the presence of 0.1–0.2 M NaCl the substance distribution is highly dependent on its charge and slightly on its lipophility. At the salt concentrations above 0.2 M the solute partition is determined just by its hydrophobic character and seems to be totally independent of its charge. It is concluded that the partition technique can be used for analytical purposes. The method seems to be unique in providing quantitative information on the amphiphilic surface properties of the solutes being partitioned.     

The myriapodological legacy of Victor Ivanovich Motschoulsky (1810–1871)

The little that remains of Motschoulsky’s myriapodological legacy in the collection of Moscow’s Zoological Museum proves to be of very limited value. Only one species of Diplopoda described by Motschoulsky, the Caucasian Hirudisoma roseum (Victor, 1839), is still in use, yet requiring a neotype designation, whereas the remaining few myriapod names he proposed are either nomina dubia or nomina nuda. The former include Scolopendra pentagramma Motschoulsky, 1866 (Chilopoda, Scolopendromorpha, Scolopendridae) and Strongylosoma carinulatum Motschoulsky, 1866 (Diplopoda, Polydesmida, Paradoxosomatidae), both from Japan, as well as Julus costulatus Motschoulsky, 1851 (Diplopoda, Callipodida, Schizopetalidae?), from Montenegro, because their type material is either inadequate or missing.     

The genetic diversity and phylogeny of green microalgae in the genus Choricystis (Trebouxiophyceae,Chlorophyta) in Lake Baikal

Limnology - Green microalgae are of the utmost importance to aquatic ecosystems globally, as they are primary producers and major food sources for many organisms. Microalgae of the genus...     

Perfect Narrowband Absorber Based on Patterned Graphene-Silica Multilayer Hyperbolic Metamaterials

Plasmonics - Graphene-based hyperbolic metamaterials are well known for their optical anisotropy, high absorption of electromagnetic radiation, and low energy loss. We proposed a novel multilayer...