Intragroup serotyping of meningococci

The method for obtaining antisera to meningococci of different serotypes are described and the scheme for the preparation of serotyping is presented, as well as the method for the preparation of the determinate fraction of serotype 2. Antisera to typing antigens 1, 2, 2-7, 2-10, 4, 5, 6, 8 (1) have been obtained, their specificity tested in parallel experiments with American and French typing sera. When typing meningococci, the use of antisera to purified protein antigen 2 is recommended.     

Dynamics of adenylate cyclase desensitization during long-term exposure to the hormone

The dependence of adrenal gland adenylate cyclase desensitization on the dose of in vivo injected ACTH, the time of occurrence and duration of the enzyme refractory period and the dependence of desensitization on the number of ACTH injections were analyzed. The experiments were carried out on guinea pigs injected with prolonged action preparations of ACTH (4 and 6 units) daily for 1-6 days. Intramuscular injections of ACTH caused adenylate cyclase refraction to the repeated action of the hormone. The effect of desensitization was the most conspicuous within the first few hours after hormone injection. The decrease of adenylate cyclase sensitivity and the duration of this effect were found to depend on the ACTH dose as well as on the number of injections. It has been shown for the first time that a single in vivo injection of 0.9% NaCl causes short-term desensitization of adenylate cyclase to the repeated action of much higher doses of ACTH in vitro, presumably due to endogenous ACTH release in response to weak stress exposure. The periodicity of changes in adenylate cyclase sensitivity upon prolonged hormone administration is discussed. Sensitization of the enzyme upon daily short-term exposure to physiological doses of ACTH (administration of 0.9% NaCl for 6 days) was revealed.     

Use of spin-labelled substrate analogs for a comparative study of microsomal cytochrome P-450 and P-448

The previously described, iodine-labeled alkylating stable nitroxyl radicals located at different distances between the N-O. group and the iodine atom were used for a comparative study of the structure of microsomal cytochromes P-450 and P-448 active centers. The radicals were shown to change the optical spectra of Fe3+ located in the active site of the enzyme that are similar to those induced by cytochrome P-450 substrates. Some differences in the type of the radicals binding to control, phenobarbital- and 3-methylcholanthrene-induced microsomes were revealed. The alkylating radical substrate analogs covalently bound to microsomal cytochrome P-450 in the vicinity of the active center, resulting in the inhibition of oxidation of type I and II substrates (e. g., aniline and naphthalene). The value of the spectral binding constant (Ks) for naphthalene in the presence of the radical covalently bound to the cytochrome P-450 active center showed a tendency to increase. Using the ESR technique, the interaction between Fe3+ and the radical localized in the active site of cytochrome P-450 was demonstrated. The contribution of Fe3+ to the relaxation of the radicals covalently bound to cytochrome P-450 was evaluated from the values of the spin label ESR spectra saturation curves at 77K. The distances between the N-O. group of these radicals and Fe3+ in the enzyme active center for the three types of microsomes were determined. The data obtained point to structural peculiarities of the active center of cytochrome P-450, depending on the microsomal type.     

The structure of O-specific polysaccharide from Yersinia enterocolitica serotype O:6.31 lipopolysaccharide

The serologically active O-specific polysaccharide has been isolated from the lipopolysaccharide of Yersinia enterocolitica, serovar O: 6.31. Using methylation, partial acid hydrolysis and 13C NMR spectroscopy, the main structural moiety of the O-specific polysaccharide is shown to be the following disaccharide repeating unit: (Formula: see text).     

Effect of postnatal development on calcium currents and slow charge movement in mammalian skeletal muscle

Single- (whole-cell patch) and two-electrode voltage-clamp techniques were used to measure transient (Ifast) and sustained (Islow) calcium currents, linear capacitance, and slow, voltage-dependent charge movements in freshly dissociated fibers of the flexor digitorum brevis (FDB) muscle of rats of various postnatal ages. Peak Ifast was largest in FDB fibers of neonatal (1-5 d) rats, having a magnitude in 10 mM external Ca of 1.4 +/- 0.9 pA/pF (mean +/- SD; current normalized by linear fiber capacitance). Peak Ifast was smaller in FDB fibers of older animals, and by approximately 3 wk postnatal, it was so small as to be unmeasurable. By contrast, the magnitudes of Islow and charge movement increased substantially during postnatal development. Peak Islow was 3.6 +/- 2.5 pA/pF in FDB fibers of 1-5-d rats and increased to 16.4 +/- 6.5 pA/pF in 45-50-d-old rats; for these same two age groups, Qmax, the total mobile charge measurable as charge movement, was 6.0 +/- 1.7 and 23.8 +/- 4.0 nC/microF, respectively. As both Islow and charge movement are thought to arise in the transverse-tubular system, linear capacitance normalized by the area of fiber surface was determined as an indirect measure of the membrane area of the t-system relative to that of the fiber surface. This parameter increased from 1.5 +/- 0.2 microF/cm2 in 2-d fibers to 2.9 +/- 0.4 microF/cm2 in 44-d fibers. The increases in peak Islow, Qmax, and normalized linear capacitance all had similar time courses. Although the function of Islow is unknown, the substantial postnatal increase in its magnitude suggests that it plays an important role in the physiology of skeletal muscle.     

A new class of cardiotonic steroids]

A series of 23-oxosteroid derivatives have been synthesized and tested for their inhibiting Na+, K(+)-dependent ATPase from rat brain in the 1 x 10(-6)-1 x 10(-4) M concentrations. Natural 23-oxogenins from sea star Asterias amurensis and synthetic monoesters showed the inhibiting activity upto 50-55%. These compounds caused heart contraction in frogs at the level of the known cardiotonic strophanthin G, and inotropic activity on isolated heart of mollusk Spisula sachalinensis.     

Structural studies on O-specific polysaccharides of lipopolysaccharides from Yersinia enterocolitica serovars O:5 and O:5,27

Lipopolysaccharides of Yersinia enterocolitica serovars O:5 and O:5,27 were shown to have a similar sugar composition, consisting of L-rhamnose, D-glucose, D-galactose, D- and L-glycero-D-manno-heptose, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, 3-deoxy-D-manno-octulosonate and D-threo-pent-2-ulose (D-xylulose). Partial hydrolysis of lipopolysaccharides with acetic acid produced rhamnans with the following repeating unit: ----3)-L-Rha rho(alpha 1----3)-L-Rha rho(alpha 1----3)-L-Rha rho(beta 1----. 13C-NMR and methylation studies of the lipopolysaccharides gave the following structure for the repeating unit of the two O-specific polysaccharides: ----3)-L-Rha rho(alpha 1----3)-L-Rha rho(alpha 1----3)-L-Rha rho(beta 1----. (formula; see text)     

Selective alkylation of G24 residue in tRNAPhe

Alkylation of E. coli tRNAPhe with 4-(N-2-chloroethyl-N-methylamino) benzyl-5'-phosphamide of oligonucleotide d(pAACCA) was studied. G24 residue located near the sequence C17GGDA21 partially complementary to the oligonucleotide moiety of the reagent was shown to be alkylated. Oligonucleotide d(pAACCA) inhibited the alkylation. Association constant of oligonucleotide derivative with tRNAPhe (10(3) M-1) was evaluated from the dependence of the extent of tRNA modification on the concentration of the reagent. The reported method for selective alkylation of tRNA may be used for preparing photoaffinity derivatives of tRNA bearing an arylazidogroups in desired position.     

Interaction between plasma lipoproteins and bilayer lipid membranes. The role of surface charge

Interactions of planar BLM with different thickness and surface charge were analysed theoretically. Drawing together of the membranes is accompanied with the appearance of intramembrane potential jumps which may cause destruction and breakdown of the membranes. The theory is extrapolated to the interaction between spherical lipoprotein particles and planar BLM. Experimentally calculated (by means of ESR) surface charges of lipoproteins of low density (LLD) (--0,3 . 10(-2) C/m2) and lipoproteins of high density (LHD) (--2 . 10(-2) C/m2) enabled calculation of the interaction energy between the particles and BLM as well as of the values of intramembrane potential jumps. The latter cause local reconstructions of the membranes in the contact region and fusion of the particles with them. The earlier obtained experimental data were proved by the finding that LHD adsorption as compared with LLD is impeded due to the existence of a high energetic barrier. These peculiarities of the particles manifested during their interactions with BLM seem to be one of the factors responsible for atherogenic function of LLD and antiatherogenic one of LHD.     

Molecular evolution of voltage-sensitive ion channel genes: on the origins of electrical excitability

We have analyzed nucleic acid and amino acid sequence alignments of a variety of voltage-sensitive ion channels, using several methods for phylogenetic tree reconstruction. Ancient duplications within this family gave rise to three distantly related groups, one consisting of the Na+ and Ca++ channels, another the K+ channels, and a third including the cyclic nucleotide-binding channels. A series of gene duplications produced at least seven mammalian homologues of the Drosophila Shaker K+ channel; clones of only three of these genes are available from all three mammalian species examined (mouse, rat, and human), pointing to specific genes that have yet to be recovered in one or another of these species. The Shaw-related K+ channels and the Na+ channel family have also undergone considerable expansion in mammals, relative to flies. These expansions presumably reflect the needs of the high degree of physiological and neuronal complexity of mammals. Analysis of the separate domains of the four-domain channels (Ca++ and Na+) supports their having evolved by two sequential gene duplications and implies the historical existence of a functional two-domain channel.