Intranuclear structures containing RNA maturation factors in early vitellogenic oocytes of Rana temporaria

We have examined the distribution of RNA processing factors in the germinal vesicle (GV) of the common frog Rana temporaria during early vitellogenesis by immunostaining on light- and electronmicroscopic levels and by in situ nucleic acid hybridization. Small nuclear RNPs (snRNP) and factor SC35 involved in pre-mRNA splicing occur in lampbrush chromosome loops and numerous granules 1-3 microns in size. These granules are identical to B snurposomes of Xenopus laevis and Notophtalmus viridescens described earlier (Wu et al., 1991). Some of B snurposomes are attached to homologous loops of lampbrush chromosomes. Immunofluorescent study of Cajal bodies/coiled bodies (CB) showed that sometimes CB have B snurposomes attached to their surface. In this case splicing factor SC35 is found in B snurposomes and B-like inclusions in CB matrix. In CB without attached B snurposomes splicing factor SC35 localizes throughout the whole organelle. Staining of GV spreads with antibodies against nucleolar protein NO38 revealed this protein in CB, nucleoli and micronucleoli. Using in situ nucleic acid hybridization and immunofluorescent staining we have found that on GV spreads from hibernating frogs B snurposomes contact nucleoli. Nucleoli contain snRNP. These data suggest that nucleoli may be storage sites of snRNPs during natural inactivation of RNA synthesis. During winter season in Rana temporaria GV nucleoli become compacted and a number of micronucleoli (less than 2 microns) dramatically increases. Analysis of micronucleoli showed that they contain rRNA, protein NO38, trace amount of U3 small nucleolar RNA and do not contain fibrillarin, involved as U3 in pre-rRNA processing. We suggest that decrease of rRNA synthesis during frog hibernation results in transformation of part of nucleoli in micronucleoli.     

Stimulation of Cellular Mechanisms of Potato Antivirus Resistance by the Action of a Preparation Based on <Emphasis Type="Italic">Bacillus subtilis</Emphasis> Bacteria

A comparative study of the antiviral activity of a new biopreparation based on bacteria Bacillus subtilis (strain 47) and commercial biopesticides (beta-protectin, phyto-protectin, frutin) in potato plants of Belarusian selection (Lileya and Scarb) was carried out in vivo and ex vitro. Pretreatment of plants with B. subtilis biopreparation and biopesticides prevents infection by potato X-viruses. The antiviral efficacy of B. subtilis does not depend on the conditions of plant growth and is more effective than biopesticides. Increased potato plant resistance to viral infection was accompanied by an effect leading to an increase in the mass of minitubers and the dry matter content in them. Treatment of potato plants with B. subtilis did not affect the molecular heterogeneity of peroxidase and superoxide dismutase, but it changed the relative activity of their isoforms. Treatment with a bacterial preparation increased the activity of superoxide dismutase when it was applied both to intact plants and those preinfected with virus. The results indicate that pretreatment of potato plants with the B. subtilis drug prevents virus infection, inducing the antiviral resistance of the potato, and is accompanied by a change in the activity of redox enzymes.     

Peculiarities of dopamine receptors on the membrane of spinal cord multipolar neurons of the brook lamprey Lampetra planeri

On isolated multiporal neurons of spinal cord of amniocoete larva of the brook lamprey Lampetra planeri, by the patch-clamp method in configuration "the whole cell", a modulating effect of dopamine on potential-activated Na+ currents was studied. Application of dopamine (10 microM) was shown to produce a complex action on the sodium current amplitude. In some cases a decrease of the amplitude, on average, by 13.5 +/- 2.2% was found, while in others--an increase, on average, by 8.6 +/- 6.1%. The modulation dopamine effect was not accompanied by any changes either of the threshold of the current appearance or of resistance of neuronal cell membranes. Pharmacological analysis with use of dopamine agonist has shown that the agonist of D1-receptors (-)-SKF-38393 (10 microM) decreases the Na+ current amplitude, whereas the agonist of D2-receptors (-)-quinpirole (10 microM) can produce in different cells both an increase, by 30.7 +/- 17.0 %, and a decrease, by 13.2 +/- 3.1%, of the Na+ current amplitude. The obtained data indicate the existence of D1- and D2-receptors on the membrane of multipolar spinal neurons of the amniocoete larva of the brook lamprey. Study of action of antagonists has shown that the antagonist of D1-receptors (+)-SCH-23390 (10 microM) does not affect action of the agonist of D1-receptors (-)-SKF-38393 (10 microM); the antagonist of D2-receptors (-)-sulpiride (10 microM) blocks completely effects both of the agonist of D1-receptors (-)-SKF-38393 (10 microM) and of the agonist of D2-receptors (-)-quinpirole (10 microM). The antagonist of D1-receptors (+)-SCH-23390 (10 microM) produced no effect on action of the agonist of D1-receptors (-)-SKF-38393 (10 microM). The obtained data indicate peculiarities of dopamine receptors of Cyclostomata as compared with those in mammals.     

The crystal structure of NAD(P)H quinone oxidoreductase 1 in complex with its potent inhibitor dicoumarol

NAD(P)H quinone oxidoreductase 1 (NQO1) is a ubiquitous flavoenzyme that catalyzes two-electron reduction of quinones to hydroquinones utilizing NAD(P)H as an electron donor. NQO1 binds and stabilizes several short-lived proteins including the tumor suppressors p53 and p73 and the enzyme ornithine decarboxylase (ODC). Dicoumarol is a widely used potent competitive inhibitor of NQO1 enzymatic activity, which competes with NAD(P)H for binding to NQO1. Dicoumarol also disrupts the binding of NQO1 to p53, p73, and ODC and induces their ubiquitin-independent proteasomal degradation. We report here the crystal structure of human NQO1 in complex with dicoumarol at 2.75 A resolution. We have identified the interactions of dicoumarol with the different residues of NQO1 and the conformational changes imposed upon dicoumarol binding. The most prominent conformational changes that occur in the presence of dicoumarol involve Tyr 128 and Phe 232 that are present on the surface of the NQO1 catalytic pocket. On the basis of the comparison of the NQO1 structure in complex with different NQO1 inhibitors and our previous analysis of NQO1 mutants, we propose that the specific conformation of Tyr 128 and Phe 232 is important for NQO1 interaction with p53 and other client proteins.     

Effect of alginate matrix composition on regrowth of in vitro-derived encapsulated apical microcuttings of hybrid aspen

Effect of alginate matrix composition on regrowth performance of encapsulated microcuttings of hybrid aspen (Populus tremula L. × P. tremuloides Mincx.) was studied. Both high regrowth frequency and viability of explants were registered in all encapsulation mixtures tested. Some ingredients of the matrix (nutrient medium salts, sugars, growth regulators) significantly affected the initial development of the microcuttings. Sucrose appeared to play an important role in the starting stage of the regrowth event.     

Neoglycoconjugates Based on Dendrimer Poly(aminoamides)

Neoglycoconjugates containing 4, 8, 32, and 64 terminal residues of B-disaccharide (B_DI) or N-acetylneuraminic acid (Neu5Ac) attached to poly(aminoamide)-type dendrimers (PAMAMs) were synthesized. The ability of B_DI conjugates to bind natural xenoantibodies (anti-B_DI antibodies) and the ability of Neu5Ac conjugates to inhibit the hemagglutinin-mediated adhesion of influenza virus were studied. The biological activity of PAMAM conjugates turned out to be higher than that of free carbohydrate ligands, but less than that of multivalent glycoconjugates based on other types of synthetic polymeric carriers. A conformational analysis of PAMAM matrices and resulting conjugates was performed to determine the statistical distances between carbohydrate ligands. The computations revealed the tendency of the PAMAM chains toward compaction and formation of dense globules. The process results in a decrease in the distances between the carbohydrate ligands in the conjugates and, hence, could affect the ability of glycoconjugates to efficiently bind the polyvalent carbohydrate-recognizing proteins.     

Glutamate uptake determines pathway specificity of long-term potentiation in the neural circuitry of fear conditioning

Long-term synaptic modifications in afferent inputs to the amygdala underlie fear conditioning in animals. Fear conditioning to a single sensory modality does not generalize to other cues, implying that synaptic modifications in fear conditioning pathways are input specific. The mechanisms of pathway specificity of long-term potentiation (LTP) are poorly understood. Here we show that inhibition of glutamate transporters leads to the loss of input specificity of LTP in the amygdala slices, as assessed by monitoring synaptic responses at two independent inputs converging on a single postsynaptic neuron. Diffusion of glutamate ("spillover") from stimulated synapses, paired with postsynaptic depolarization, is sufficient to induce LTP in the heterosynaptic pathway, whereas an enzymatic glutamate scavenger abolishes this effect. These results establish active glutamate uptake as a crucial mechanism maintaining the pathway specificity of LTP in the neural circuitry of fear conditioning.     

Study of the antigenic structure of hepatitis B virus proteins. I. Synthesis of pre-S fragments of hepatitis B virus proteins and their immunogenicity

Fragments of hepatitis B virus envelope proteins corresponding to the parts of the pre-S domain were synthesised and immobilized on the carriers with low own immunogenicity. The highest stimulation of the antibody production was observed for the antigens immobilized on microspherical carriers or gelatin modified by H-Gly-Tyr-OH. Among peptides used for immunization, pre-S fragment 134-144, conjugated with microspherical carrier, proved to be the most active.