Analysis of the functional role in behavior of the neuromediator receptor by antisense knockdown of its gene expression

Now available nucleotide sequences of neurotransmitter receptor genes enable to apply oligonucleotides targeted to mRNAs of these genes for highly selective inactivation of their expression (antisense-knockdown) and for function determination of single receptor subtype by this experimental approach. The antisense-knockdown may be of special importance in case of receptor families members of which are pharmacologically similar. Advantages of the antisense technology for investigation into the brain neurotransmitter receptor function in regulation of behaviour, are discussed.     

New hepatitis B virus of cranes that has an unexpected broad host range

All hepadnaviruses known so far have a very limited host range, restricted to their natural hosts and a few closely related species. This is thought to be due mainly to sequence divergence in the large envelope protein and species-specific differences in host components essential for virus propagation. Here we report an infection of cranes with a novel hepadnavirus, designated CHBV, that has an unexpectedly broad host range and is only distantly evolutionarily related to avihepadnaviruses of related hosts. Direct DNA sequencing of amplified CHBV DNA as well a sequencing of cloned viral genomes revealed that CHBV is most closely related to, although distinct from, Ross' goose hepatitis B virus (RGHBV) and slightly less closely related to duck hepatitis B virus (DHBV). Phylogenetically, cranes are very distant from geese and ducks and are most closely related to herons and storks. Naturally occurring hepadnaviruses in the last two species are highly divergent in sequence from RGHBV and DHBV and do not infect ducks or do so only marginally. In contrast, CHBV from crane sera and recombinant CHBV produced from LMH cells infected primary duck hepatocytes almost as efficiently as DHBV did. This is the first report of a rather broad host range of an avihepadnavirus. Our data imply either usage of similar or identical entry pathways and receptors by DHBV and CHBV, unusual host and virus adaptation mechanisms, or divergent evolution of the host genomes and cellular components required for virus propagation.     

The Localization of Precursor Cells for Larval and Adult Hemopoietic Cells of Xenopus Laevis in two Regions of Embryos

For determination of the localization of lymphoid and erythroid precursor cells in embryos of Xenopus laevis , diploid-triploid chimeras were produced either by joining embryos antero-posteriorly or by orthotopic grafting of various tissues into N ieuwkoop -F aber st. 22–23 tailbud embryos. The sources of the hemopoietic cells were determined in the chimeric animals at various stages by microspectrophotometry of F eulgen -stained cells. Analyses of chimeras produced by joining embryos antero-posteriorly at different levels showed that the precursor cells that contribute to the hemopoietic cells are localized in the posterior half to three quarters. Orthotopic grafting of ventral or dorsal tissues revealed that the precursor cells that contribute to hemopoietic cells in early larvae are mostly localized in the ventral blood island (VBI) mesoderm, whereas those for late larvae and adults are localized both in the dorso-lateral plate (DLP) mesoderm comprising the prospective mesonephros and in the VBI mesoderm. Reciprocal heterotopic grafting of VBI- and DLP mesoderms showed that the two compartments differ in their capacities to differentiate into hemopoietic cells. It is proposed that the VBI-derived cells migrating towards the primary lymphoid organs constitute the transient hemopoietic population of early larvae, and the importance of the mesonephric region for definitive hemopoiesis is pointed out.     

Role of cytoplasmic proteins in cold shock injury of Amoeba

Strains of Amoeba have been used to study the mechanisms of cellular injury induced by rapid cooling (cold shock). Cell viability was found to depend on the time and temperature of cold exposure, on the rate of cooling and on the morphology of the cells prior to chilling. All strains underwent a granuloplasmic contraction following undercooling to ?10 °C, although its extent varied; strains most damaged by cold shock exhibited the most violent cytoplasmic contractions. Cryomicroscopy demonstrated that the cellular contraction occurred upon rewarming, not during cooling. Cells damaged by cold shock were osmotically responsive, demonstrating that irreversible damage to the plasmalemma does not account for the phenomenon.Several compounds protected Amoeba against cold shock injury, glycerol and glucose being the most effective. With glycerol an optimum rate of cooling was observed upon cooling to ?10 °C, at both faster and slower cooling rates damage increased.The state of cellular actin in control cells and following cold shock was monitored by the DNase 1 inhibition assay and by electron microscopy. A comparatively “cold shock resistant” strain of A. proteus was found to contain less total actin per unit cellular protein than the more “sensitive” Amoeba sp. strain Bor. In the Bor strain a cold-induced aggregation of cytoplasmic filaments was evident in electron micrographs, presumably a crosslinking of preexisting F-actin.     

Effect of the methods of sterilization on the quality of nutrient media and on the level of antibiotic production]

It was shown that conditions for heat sterilization of nutrient media for biosynthesis of antibiotics had an impact on their biochemical composition and activity of a fermentation broth in production of penicillin and erythromycin. The temperature of 120 degrees C and the time of 25 minutes proved to be optimal for sterilization of the media in regard to both preservation of their biochemical composition and providing of the maximum antibiotic productivity on the one hand and maintenance of the sterility during the fermentation process on the other hand.     

Relative numerousness judgements in crows and pigeons in the urgent comparison of stimuli earlier linked to different amounts of reinforcement]

The ability of pigeons (Colomba livia, L.) and crows (Corvus corone cornix, L.) was studied to realize urgent numerousness judgement of reinforcement consisting of discrete elements (wheat grains and meal worm larvae, respectively). In the process of preliminary training the birds mastered the information about the conformity of the feeder colour with the definite number (1-9 for pigeons and 5-12 for crows) of reinforcement units at isolated presentation of feeders. In test at presentation of pairs formed from these feeders, pigeons and crows chose the stimulus connected with a greater quantity of reinforcement. In the range of 1-8 units the precision of choice in pigeons depended on absolute and relative differences between comparing values. In crows in the range of 6-12 this dependence was not revealed. The ability to solve the given test is considered as one of manifestations of elementary reasoning.     

Analysis of DNA from human adenovirus type 6 with restriction endonucleases HindIII, BglIII and BamHI

The genome of the type 6 human adenovirus has three restriction sites for R.BamHI, thirteen for R.HindIII and ten for R.BglII. The terminal fragments of DNA cleaved by each of the enzymes have been determined by means of terminal nucleotidyl transferase and by analysis of the DNA-terminal protein complex. The sequence of the cleaved fragments has been determined by partial cleavage of DNA, simultaneous digestion of DNA with various combinations of enzymes and secondary digestion of individual isolated fragments with other enzymes. The following order of the cleaved fragments in the adenovirus type 6 genome has been found (the figures in brackets are the weights in mega-daltons): for R.BamHI-B(7.1)-D(3.0)-C(4.05)-A(8.5); for R.HindIII-F(1.7)-C1(2.14)-A(3.44)-M(0.046)-I(1.24)-J(0.77)-D(2.1)-E(1.96)-B(3.18)-H(1.36)-L(0.18)-C2(2.14)-G(1.44)-K(0.16); for R.BglII-E(2.07)-B(3.58)-A(4.8)-C(3.36)-I(0.78)-D(3.25)-G(1.37)-J(0.21)-F(1.85)-K(0.17)-H(0.94).