Plant sensitivity to low intensity 105 GHz electromagnetic radiation

Exposing seedlings of the flax, Linum usitatissimum L., to a variety of weak environmental stresses followed by a 2 day calcium deprivation, triggers the common response of production of epidermal meristems (actively dividing groups of cells) in the hypocotyl, which is the part of the stem between the root and the cotyledons (the pre-existing leaves in the embryo). This production reaches a plateau of 10-20 meristems after a month in the case of mechanical stimulation and cold shock. Recently, we have shown that radiation from a global system for mobile communication (GSM) telephone also triggers production of meristems with a plateau of around six meristems. Here, we show that a single 2 h exposure to radiation emitted at 105 GHz at non-thermal levels by a Gunn oscillator induces meristem production with kinetics similar to that induced by weak environmental stimuli and radiation from GSM telephone.     

The FAR protein family of the nematode Caenorhabditis elegans. Differential lipid binding properties,structural characteristics,and developmental regulation

Parasitic nematodes of humans and plants secrete a structurally novel type of fatty acid- and retinol-binding protein, FAR, into the tissues they occupy. These proteins may interfere with intercellular lipid signaling to manipulate the defense reactions of the host or acquire essential lipids for the parasites. The genome of the nematode Caenorhabditis elegans encodes eight FAR-like proteins (Ce-FAR-1 to -8). These fall into three discrete groups as indicated by phylogenetic sequence comparisons and intron positions, the proteins from parasitic nematodes falling into group A. Recombinant Ce-FAR-1 to -7 were produced in Escherichia coli and tested for lipid binding in fluorescence-based assays. Ce-FAR-1 to -6 bound DAUDA (11-((5-dimethylaminonaphthalene-1-sulfonyl)amino)undecanoic acid), cis-parinaric acid, and retinol with dissociation constants in the micromolar range, whereas Ce-FAR-7 bound the latter two lipids relatively poorly. Each protein produced a characteristic shift in peak fluorescence emission of DAUDA, and one (Ce-FAR-5) produced a shift greater than has been observed previously for any lipid-binding protein. Selected Ce-FAR proteins were analyzed by circular dichroism (CD) and differential scanning calorimetry, were found to be helix-rich, and exhibited high thermal stability (transition midpoint, 82.7 degrees C). CD and secondary structure predictions, however, both indicated that Ce-FAR-7 possesses substantially less helix than the other FAR proteins. The genes encoding the Ce-FAR proteins were found to be transcribed differentially through the life cycle of C. elegans, such that Ce-far-4 was transcribed at highest levels in the fourth larval stage, and Ce-far-3 and -7 predominated in males.     

Down-regulation of Rac activity during beta 2 integrin-mediated adhesion of human neutrophils

In human neutrophils, beta2 integrin engagement mediated a decrease in GTP-bound Rac1 and Rac2. Pretreatment of neutrophils with LY294002 or PP1 (inhibiting phosphatidylinositol 3-kinase (PI 3-kinase) and Src kinases, respectively) partly reversed the beta2 integrin-induced down-regulation of Rac activities. In contrast, beta2 integrins induced stimulation of Cdc42 that was independent of Src family members. The PI 3-kinase dependence of the beta2 integrin-mediated decrease in GTP-bound Rac could be explained by an enhanced Rac-GAP activity, since this activity was blocked by LY204002, whereas PP1 only had a minor effect. The fact that only Rac1 but not Rac2 (the dominating Rac) redistributed to the detergent-insoluble fraction and that it was independent of GTP loading excludes the possibility that down-regulation of Rac activities was due to depletion of GTP-bound Rac from the detergent-soluble fraction. The beta2 integrin-triggered relocalization of Rac1 to the cytoskeleton was enabled by a PI 3-kinase-induced dissociation of Rac1 from LyGDI. The dissociations of Rac1 and Rac2 from LyGDI also explained the PI 3-kinase-dependent translocations of Rac GTPases to the plasma membrane. However, these accumulations of Rac in the membrane, as well as that of p47phox and p67phox, were also regulated by Src tyrosine kinases. Inasmuch as Rac GTPases are part of the NADPH oxidase and the respiratory burst is elicited in neutrophils adherent by beta2 integrins, our results indicate that activation of the NADPH oxidase does not depend on the levels of Rac-GTP but instead requires a beta2 integrin-induced targeting of the Rac GTPases as well as p47phox and p67phox to the plasma membrane.     

The naphthoquinol oxidizing cytochrome bc1 complex of the hyperthermophilic knallgasbacterium Aquifex aeolicus: properties and phylogenetic relationships

Phylogenetic analysis of constituent proteins of Rieske/cytochrome b complexes [Schütz et al. (2000) J. Mol. Biol. 300, 663-675] indicated that the respective enzyme from the hyperthermophile Aquifex (A.) aeolicus is closely related to proteobacterial counterparts, in disagreement with positioning of its parent species on small subunit rRNA trees. An assessment of the details and possible reasons for this discrepancy necessitates a thorough understanding of the biochemical and biophysical properties of the enzyme in addition to the bioinformatic data. The cytochrome bc(1) complex from A. aeolicus, which is part of the "Knallgasreaction" pathway, was therefore studied in membranes and in detergent-solubilized, isolated complex. Hemes b(L) (E(m,7) = -190 mV; g(z)= 3.7), b(H) (E(m,7) = -60 mV; g(z )= 3.45), and c(1) (E(m,7) = +160 mV; g(z )= 3.55) were identified by EPR and optical spectroscopy in combination with electrochemical methods. Two electrochemically distinct (E(m,7) = +95 mV; E(m,7) = +210 mV) Rieske centers were detected in membranes, and the +210 mV species was shown to correspond to the Rieske center of the cyt bc(1) complex. The gene coding for this latter Rieske protein was heterologously expressed in Escherichia coli, and the resulting protein was characterized in detail. The pool quinone of A. aeolicus was determined to be naphthoquinone. The redox poises of the individual electron-transfer steps are compared to those of other Rieske/cyt b complexes. The Aquifex enzyme was found to represent the only extant naphthoquinol oxidizing true cyt bc(1) complex described so far. An improved scenario for the phylogenetic positioning of the Aquifex cyt bc(1) complex is proposed.     

Two splice variants of the Wilms' tumor 1 gene have distinct functions during sex determination and nephron formation

Alternative splicing of Wt1 results in the insertion or omission of the three amino acids KTS between zinc fingers 3 and 4. In vitro experiments suggest distinct molecular functions for + and -KTS isoforms. We have generated mouse strains in which specific isoforms have been removed. Heterozygous mice with a reduction of +KTS levels develop glomerulosclerosis and represent a model for Frasier syndrome. Homozygous mutants of both strains die after birth due to kidney defects. Strikingly, mice lacking +KTS isoforms show a complete XY sex reversal due to a dramatic reduction of Sry expression levels. Our data demonstrate distinct functions for the two splice variants and place the +KTS variants as important regulators for Sry in the sex determination pathway.     

Epidemic dengue/dengue hemorrhagic fever as a public health, social and economic problem in the 21st century

Dengue fever/dengue hemorrhagic fever is now one of the most important public health problems in tropical developing countries and also has major economic and societal consequences.     

Attenuation markers of a candidate dengue type 2 vaccine virus, strain 16681 (PDK-53), are defined by mutations in the 5' noncoding region and nonstructural proteins 1 and 3

The genome of a candidate dengue type 2 (DEN-2) vaccine virus, strain PDK-53, differs from its DEN-2 16681 parent by nine nucleotides. Using infectious cDNA clones, we constructed 18 recombinant 16681/PDK-53 viruses to analyze four 16681-to-PDK-53 mutations, including 5' noncoding region (5'NC)-57 C-to-T, premembrane (prM)-29 Asp-to-Val (the only mutation that occurs in the structural proteins), nonstructural protein 1 (NS1)-53 Gly-to-Asp, and NS3-250 Glu-to-Val. The viruses were studied for plaque size, growth rate, and temperature sensitivity in LLC-MK(2) cells, growth rate in C6/36 cells, and neurovirulence in newborn mice. All of the viruses replicated to peak titers of 10(7.3) PFU/ml or greater in LLC-MK(2) cells. The crippled replication of PDK-53 virus in C6/36 cells and its attenuation for mice were determined primarily by the 5'NC-57-T and NS1-53-Asp mutations. The temperature sensitivity of PDK-53 virus was attributed to the NS1-53-Asp and NS3-250-Val mutations. The 5'NC-57, NS1-53, and NS3-250 loci all contributed to the small-plaque phenotype of PDK-53 virus. Reversions at two or three of these loci in PDK-53 virus were required to reconstitute the phenotypic characteristics of the parental 16681 virus. The prM-29 locus had little or no effect on viral phenotype. Sequence analyses showed that PDK-53 virus is genetically identical to PDK-45 virus. Restriction of the three major genetic determinants of attenuation markers to nonstructural genomic regions makes the PDK-53 virus genotype attractive for the development of chimeric DEN virus vaccine candidates.     

Nickel absorption and distribution from rat small intestine In situ

The aim of this work was to study the absorption of nickel chloride in rats by means of the intestinal perfusion in situ technique at nickel concentrations of 1, 5, 10, 25, and 100 mg/L. Active transport and facilitated diffusion seem to play an important role in the intestinal absorption of nickel at concentrations≤10 mg/L. At higher concentrations, the absorption rate would be limited by saturation of the carriers. The distribution of the absorbed nickel was studied by intestinal perfusion of a 10-mg Ni/L solution for 30 or 60 min. Both in concentration and amount, the jejunum showed the higher values of absorbed nickel, followed by the kidneys and liver. When all of the collected organs (brain, heart, liver, lungs, spleen, kidneys, and testicles) and blood, but not the small intestine, are analyzed following a 60-min perfusion, it was found that 1% of the initial concentration had passed through the intestinal barrier.