Altered ivermectin pharmacology and defective visual system in <Emphasis Type="Italic">Drosophila</Emphasis> mutants for histamine receptor HCLB

The Drosophila gene hclB encodes a histamine-gated chloride channel, which can be activated by the neurotoxin ivermectin when expressed in vitro. We have identified two novel hclB mutants, carrying either a missense mutation (P293S, allele hclB ^T1 ) or a putative null mutation (W111*, allele hclB ^T2 ), as well as a novel splice form of the gene. In survival studies, hclB ^T1 mutants were more sensitive to ivermectin than wild-type, whereas hclB ^T2 were more resistant. Electroretinogram recordings from the two mutants exhibited enlarged peak amplitudes of the transient components, indicating altered synaptic transmission between retinal photoneurons and their target cells. Ivermectin treatment severely affected or completely suppressed these transient components in an allele-specific manner. This suppression of synaptic signals by ivermectin was dose-dependent. These results identify HCLB as an important in vivo target for ivermectin in Drosophila melanogaster, and demonstrate the involvement of this protein in the visual pathway. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

Acellular pertussis vaccine

Protective, immunogenic, toxic, and sensitizing properties of acellular pertussis vaccine (aPV) developed according to original technology were studied, aPV had marked protective activity which lasted more than 2 years. Sera of mice immunized by aPV also possess protective properties, and they were more prominent than in sera of mice immunized by pertussis bacteria suspension (PS). Immune sera to aPV neutralized cytopathogenic effect of pertussis toxin (PT) on ovarian Chinese hamster cells in 1:250 dilution, whereas neutralizing activity of sera to PS was very low. Level of antibodies to PT was higher in rabbits immunized, according to schedules and dosage recommended for children, by aPV than by PS. High immunogenicity of aPV was proved also by levels of IgG to PT in sera of mice immunized three times by aPV in human dosage. During experiments on mice and guinea pigs aPV had mild toxicity, did not induce autoimmune process, did not have anaphylactogenic properties compared with bacterial suspension characterized by high anaphylactogenic activity. Histamine-sensitizing abilityof aPVwas 40 times lower than that of PS. Assessment of pyrogenic properties of aPV and PS performed on rabbits showed that aPV was 1,000 times less pyrogenic than PS. Obtained results demonstrate high protective and immunogenic properties of domestic acellular pertussis vaccine and its low toxic and sensitizing characteristics.     

N-(Aryl)-4-(azolylethyl)thiazole-5-carboxamides: novel potent inhibitors of VEGF receptors I and II

Novel potent derivatives of N-(aryl)-4-(azolylethyl)thiazole-5-carboxamides are described as inhibitors of vascular endothelial growth factor receptor II (VEGFR-2). Several compounds display VEGFR-2 inhibitory activity reaching IC(50)<100 nM in both enzymatic and cellular assays. The compounds also inhibit the related tyrosine kinase, VEGFR-1. By controlling the substitution pattern on the 5-carboxamido pharmacophore, both dual and specific VEGFR-2 thiazoles were identified.     

Antimalarial effects in mice of orally administered peptidyl cysteine protease inhibitors.

The Plasmodium falciparum cysteine protease falcipain is required for the degradation of hemoglobin by erythrocytic malaria parasites. In prior studies, peptidyl inhibitors of falcipain blocked hemoglobin degradation and development by cultured parasites and one of these compounds, when administered parenterally, cured Plasmodium vinckei-infected mice. We now report an evaluation of orally administered peptidyl inhibitors of falcipain in a mouse malaria model. In studies with a fluoromethyl ketone, orally administered morpholine urea-phenylalanine-homophenylalanine-fluoromethyl ketone delayed the progression of murine malaria. In studies of a new series of vinyl sulfones, a set of related compounds demonstrated marked inhibition of falcipain and of parasite biological activities in vitro. One of these compounds, N-methyl piperazine urea-leucine-homophenylalanine-2-naphthalene vinyl sulfone, cured about 40% of mice when administered orally twice-a-day for four days. Our results suggest that peptidyl inhibitors of falcipain have promise as antimalarial chemotherapeutic agents.     

Synthesis and primary evaluation of the hepatoprotective properties of novel pyrimidine derivatives

Based on the active ingredient of the drug Ximedon (1,2-dihydro-4,6-dimethyl-1-N-(2-hydroxyethyl)pyrimidone-2, referred below to as pyrimidine (I), novel derivatives containing biogenic acids: succinic, L-ascorbic, para-aminobenzoic, nicotinic, and L-2-amino-4-(methylthio)butanoic (L-methionine) acids have been synthesized. The parameters of acute toxicity (LD₅₀) have been studied. The antitoxic effect of the compounds upon the injury by the hepatotropic poison carbon tetrachloride has been examined as the primary evaluation of their hepatoprotective properties. It has been found that, according to toxicological safety, the compounds synthesized belong to classes III and IV (moderately and little toxic compounds). The conjugates of pyrimidine (I) with ascorbic acid and methionine (LD₅₀ more than 5400 mg/kg) are least toxic. Pyrimidine (I) and its derivatives possess the antitoxic activity upon acute poisoning with carbon tetrachloride; the combined injection of carbon tetrachloride with pyrimidine (I) or its derivatives leads to an increase in the survival of animals and the normalization of the integral functional parameters, weight and body temperature, which decrease upon toxic injury. In addition, pyrimidine (I) and some of its derivatives (conjugates with L-ascorbic, succinic, para-aminobenzoic, and nicotinic acids) decrease the weight coefficients of the liver and kidneys (the organ-to-body-weight ratio) and the activity of transaminases, the markers of hepatic cytolysis, which increase upon toxic injury with carbon tetrachloride. The area of the pathological injury of the liver by steatosis and necrosis decreases by the action of pyrimidine (I) and its novel derivatives (conjugates with L-ascorbic, succinic, and nicotinic acids) two to three times. Advantages of pyrimidine (I) and its novel derivatives over the hepatoprotective drug Thiotriazolin have been revealed.     

Seasonal variations in the diversity and abundance of diazotrophic communities across soils

The nitrogen (N)-fixing community is a key functional community in soil, as it replenishes the pool of biologically available N that is lost to the atmosphere via anaerobic ammonium oxidation and denitrification. We characterized the structure and dynamic changes in diazotrophic communities, based on the nifH gene, across eight different representative Dutch soils during one complete growing season, to evaluate the amplitude of the natural variation in abundance and diversity, and identify possible relationships with abiotic factors. Overall, our results indicate that soil type is the main factor influencing the N-fixing communities, which were more abundant and diverse in the clay soils (n=4) than in the sandy soils (n=4). On average, the amplitude of variation in community size as well as the range-weighted richness were also found to be higher in the clay soils. These results indicate that N-fixing communities associated with sandy and clay soil show a distinct amplitude of variation under field conditions, and suggest that the diazotrophic communities associated with clay soil might be more sensitive to fluctuations associated with the season and agricultural practices. Moreover, soil characteristics such as ammonium content, pH and texture most strongly correlated with the variations observed in the diversity, size and structure of N-fixing communities, whose relative importance was determined across a temporal and spatial scale.     

Ultrasensitivity by Molecular Titration in Spatially Propagating Enzymatic Reactions

Delineating design principles of biological systems by reconstitution of purified components offers a platform to gauge the influence of critical physicochemical parameters on minimal biological systems of reduced complexity. Here we unravel the effect of strong reversible inhibitors on the spatiotemporal propagation of enzymatic reactions in a confined environment in vitro. We use micropatterned, enzyme-laden agarose gels which are stamped on polyacrylamide films containing immobilized substrates and reversible inhibitors. Quantitative fluorescence imaging combined with detailed numerical simulations of the reaction-diffusion process reveal that a shallow gradient of enzyme is converted into a steep product gradient by addition of strong inhibitors, consistent with a mathematical model of molecular titration. The results confirm that ultrasensitive and threshold effects at the molecular level can convert a graded input signal to a steep spatial response at macroscopic length scales.     

Surface Modification of Melamine-Formaldehyde (MF-R) Macroparticles in Complex Plasma

The surface modification of melamine-formaldehyde (MF-R) macroparticles (4.12 ± 0.09 μm in diameter) in dc glow discharges in neon, argon, and an argon–oxygen mixture (90% Ar, 10% O₂) was studied experimentally. The macroparticles were treated in the discharge plasma for 10, 20, 40, and 60 min. The macroparticles were placed in ordered plasma–dust structures and then extracted from them. The results of atomic force microscopy of the surface profile are presented. Quantitative data on destruction of the surface layer and aspects of its modification are discussed. The amount of substance removed from the particle surface for the exposure time was calculated using the fractal analysis method.