Computer models of the electrophysiological properties of the heart]

Computer models of the heart can improve the understanding of the electrophysiological processes in healthy and diseased heart. They become more and more important for detailed diagnosis of arrhythmias and for optimization of therapy. Models of myocardium cells known today are described--they are based on the properties of all relevant ion channels in the cell membrane. Then it is demonstrated, how many cells can be joined to form a cell patch and how finally the complete heart can be modelled. A simpler approach is using a so called cellular automation that allows for a significant reduction of calculation time while sacrificing some accordance to reality. Adaptive cellular automations allow for a fast simulation with acceptable accuracy. Using them some results were gained for the simulation of typical arrhythmias, in the field of validation using an animal model and for therapy planning with RF-ablation.     

Amyloid-like fibrils in elastin-related polypeptides: structural characterization and elastic properties

We report on the structural characterization of amyloid-like fibrils, self-assembled from synthetic polypentapeptides poly(ValGlyGlyLeuGly), whose monomeric sequence is a recurring, simple building block of elastin. This polymer adopts a beta-sheet structure as revealed by circular dichroism and Fourier transform infrared spectroscopy. Furthermore, Thioflavin-T and Congo red birefringence assays confirm the presence of amyloid-like structures. To analyze the supramolecular assembly and elastic properties of the fibrils, we employed atomic force microsocopy and spectroscopy, measuring also the elasticity of mature elastin for a comparative analysis. In the case of fibrils we estimated a Young's modulus ranging from 3.5 to 7 MPa, whereas for elastin it is around 1 MPa. The possibility to section individual fibrils with nanometric control by the AFM tip, realizing biomolecular gaps in the 100 nm range, is also demonstrated. These results are expected to open interesting perspectives for the fabrication of protein-inspired nanostructures with specific physical and chemical properties for applications in biotechnology and tissue engineering.     

Nucleotide sequence heterogeneity of the RNA from a natural population of foot-and-mouth-disease virus

The genomic RNA from isolates of foot-and-mouth-disease virus (FMDV) of serological types O or C obtained during epizootic outbreaks have been analysed by two-dimensional gel electrophoresis of the T1 RNase-generated oligonucleotides (T1 fingerprinting). Among virus isolates that are closely related serologically, 4-12 oligonucleotide changes were detected constitute the genome, the variations affect 0.7%-2.2% positions in FMDV RNA. Higher nucleotide-sequence divergence exists between the genomic RNAs from serologically unrelated viruses, while a 100-fold lower RNA sequence heterogeneity has been detected by analysis of individual clones derived from one viral isolate. Oligonucleotide mapping indicates that the variant oligonucleotides are scattered throughout the FMDV genome. We suggest that extensive genetic variability at many RNA sites is the basis for the antigenic diversity of FMDV.     

Study of the structural polypeptides of Chilo suppressalis iridescent virus (Iridovirus type 6)]

We report a procedure for the purification of Chilo iridescent virus (Iridovirus type 6), an evaluation of the purification procedure, and the results of analyses of the virion proteins by acrylamide gel electrophoresis. Purity was evaluated in three ways, i.e., by analysis of purified virions from artificial mixtures of infected and labeled uninfected larvae, electrophoresis at neutral pH, and electron-microscopic examination. Analysis of the polypeptides of purified CIV gave the following results: (i) after solubilization with SDS-B-mercaptoethanol, 16 polypeptides could be resolved in Coomassie brillant blue-stained electrophoretograms with molecular weights ranging from 18,000 to 115,000; (ii) after solubilization with SDS-urea, 26 polypeptides could be resolved with molecular weights ranging from 10,000 to 230,000 daltons.     

A study of the heterogeneous 37s ribonucleic acid induced by foot-and-mouth-disease virus

1. The 37s RNA induced in baby-hamster kidney cells by infection with foot-and-mouth-disease virus was examined on sucrose gradients and by filtration through Sepharose 4B. 2. The RNA sedimented faster (37s) and as a broader band than the 35s RNA from purified virus. 3. Treatment with deoxyribonuclease, Pronase or amylase did not alter the sedimentation profile of the 37s RNA. 4. Treatment of individual fractions of the RNA with phenol, dimethyl sulphoxide or methylCellosolve did not decrease the sedimentation rate of the faster-sedimenting molecules. 5. Sedimentation in sucrose gradients of different ionic strengths or containing EDTA had no effect on the heterogeneous nature of the profile. 6. On filtration through Sepharose 4B columns, the 37s virus-induced RNA was eluted before viral RNA. 7. Only 20% of the rapidly sedimenting RNA was incorporated into complete virus particles.     

Synthesis and processing of precursor polypeptides to murine mammary tumor virus structural proteins.

Biosynthesis of murine mammary tumor virus (MuMTV) proteins was studied in the chronically MuMTV-infected epithelial cell line MuMT-73 by using monospecific antisera to the major MuMTV core protein p27 and the major envelope glycoprotein gp47. In pulse-labeling experiments using [35S]methionine, monospecific antisera to p27 precipitated a 75,000-molecular-weight protein as the major intracellular component. Analysis of the same cellular extracts with monospecific antisera to gp47 revealed that the gp47 precursor was a 70,000-dalton protein. After chase periods, there was a loss of label from the precursors and a concomitant increase of labeled extracellular mature viral proteins. The glycoprotein precursor incorporated labeled glucosamine and seemed to be processed more rapidly than the p27 precursor. Considerable amounts of apparently nonvirion-associated gp47 and glycoprotein precursor could be detected in the extracellular culture fluid.     

Three structural polypeptides coded for by minite virus of mice, a parvovirus.

Purified full and empty virions of minute virus of mice were separated on CsCl gradients, and their polypeptides were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The empty particle contains two polypeptides, A (83,300 daltons) and B (64,300 daltons), which are 15 to 18% and 82 to 85%, respectively, of the virion mass. The full particle contains the single-stranded DNA genome, proteins A and B, and a third polypeptide, C (61,400 daltons). Again A is 15 to 18% of the protein mass, but the amounts of B and C vary inversely in different preparations of full particles. These polypeptides comprise greater than 99.6% of the protein in either virion, and their molecular weights and molar ratios are independent of the species of host cell on which the virus is propagated, They are not found in uninfected cells, and no protein component of uninfected cells copurifies with either virion under our conditions. Pulse-chase experiments show that the three proteins are synthesized only after virus infection and are therefore probably virus coded. Sequential harvesting from the nuclei of cells infected under one cycle growth conditions shows an increase in the proportion of C in full particles as infection progresses, suggesting that C is derived from B in a late maturation step.     

The electrophysiological properties of the conduction pathways of the stellate ganglion in the cat in postnatal ontogeny]

In new-born, 10-, and 20-day-old kittens and in adult cats, the stellate ganglia branches contained both continuous and synaptically interrupted fibres. In the course of postnatal ontogenesis, the average conduction velocity of excitation and average amplitude of the responses increased. In new-born and 10-day old kittens, these are C-fibres. Apart from the latter, A delta and B fibres appeared in 20-day old kittens. In adult cats, two subgroups of all types of the fibres appeared. Since the 10-day age, synaptically interrupted responses have been recorded in anastomoses and inferior cardiac nerve following stimulation of cranial and caudal branches of the subclavian loop, the responses being conducted in both directions in adult cats.     

Antiarrhythmic and electrophysiological properties of etmozin and its diethylamine analog]

Effects of antiarrhythmic drug etmosin and its diethylamine analogue (etmosin DAA) were compared in dogs with the ventricular rhythm disturbances induced by coronary artery ligation according to Harris' method. As demonstrated, both drugs stopped ventricular rhythm disturbances, but etmosin DAA had a more rapid and prolonged effect. Electrophysiological properties of etmosin and etmosin DAA were studied by the method of potential fixation on trabeculae of frog atria. Both drugs proved to reduce rapid sodium inflow, etmosin DAA acting more intensively and longer. Taking into account the high antiarrhythmic activity of etmosin DAA it is believed that this drug had good prospects for further investigation.     

Preparative isolation of basic structural proteins of the influenza virus]

The schemes for preparative electrophoretic isolation and purification of major proteins from influenza virus are described. The viral envelope protein, hemagglutinin, two of its subunits, internal M and NP proteins of influenza viruses A/FPV/Rostock (H7N1), A/PR/8/34 (H1N1) and X-31 (H3N2) were obtained in preparative amounts and characterized by amino acid and N-terminus analyses.     

The structural and functional properties of light and dark mouse hepatocytes]

The morphofunctional analysis of the light and dark hepatocytes of mouse C3HA line has shown that the dark cells have increased electronic density of hyaloplasm in contrast to the light ones. The light hepatocytes predominate among tetra- and octaploid cells. Both cell types are able to incorporate [3H] uridine and [3H] thymidine. Mitosis are met among the light hepatocytes only.     

Biochemical properties of oncornavirus polypeptides

The major structural polypeptides of avian and mammalian oncornaviruses display a variety of unique physical and chemical properties. Techniques were designed to emphasize certain qualities of the individual proteins and glycoproteins which facilitate their identification in complex mixtures.     

Investigation of the electrophysiological properties of enniatins

Enniatins are cyclohexadepsipeptides produced by various species of the genus Fusarium, and are known to have ionophoric, antibiotic, and in vitro hypolipidaemic properties. With the patch clamp technique in the inside-out mode it could be shown that enniatin easily incorporates into the cell membrane in which it forms cation-selective pores. This feature is characterized by unitary transitions to conductance levels typical for channels, ion selectivity, rectification, conductivity in the pS range, and block. A model of vertically stacked enniatin molecules that form sandwich complexes is suggested. Like gramicidin enniatin is a passive channel. Single channel properties for the isomers enniatin A1, B, and B1 differed from each other. This implies an influence of the substituted moieties on the complexation of cations. Electrical activity was followed by changes in intracellular ion concentrations, which are consistent with depolarization of the membrane resting potential, shortening of action potential duration, and reduced contractility.