Properties of the slow excitatory postsynaptic potential in mammalian sympathetic ganglion cells

Two types of slow excitatory postsynaptic potentials (EPSPs) with different properties were found in neurons of the rabbit superior cervical sympathetic ganglion. In our group of neurons slow EPSPs increased during artificial hyperpolarization and decreased during depolarization of the membrane. The input resistance of the cells fell or remained unchanged during the development of slow EPSPs. In the second group of cells slow EPSPs increased during depolarization and decreased during hyperpolarization. The reversal potential of these responses, determined by extrapolation, was –78.9±3.6 mV. Depolarization responses to activation of muscarinic cholinergic receptors by acetylcholine or carbachol developed in 53% of neurons with an increase in input resistance and had a reversal potential of –83.2±6.7 mV. It is suggested that in cells of the first group the ionic mechanism of the slow EPSPs is similar to that of the fast EPSPs, whereas in cells of the second group its main component is a decrease in the potassium conductance of the membrane.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 4, pp. 371–379, July–August, 1981.     

Genetic structure of Staphylococcus epidermidis strain No. 17 possessing penicillinase and bacteriocinogenic activity]

The studies on the genetic structure of Staphylococcus epidermidis, strain 17 showed that this strain possessed a factor of bactericinogenicity of the one type, which was an extrachromosomal element not bound with penicillinase activity. The loss of the bacteriocinogenicity factor spontaneously or under the effect of acridine orange at a temperature of 37 degrees C was not observed. Passages of the strain at a temperature of 44 degrees C for 5 days and acridine orange proved to be the most effective eliminating factors. The loss of the bacteriocinogenicity plasmid did not result in changing any biochemical properties of the strain but was accompanied by a loss of the immunity to bacteriocin of the initial strain. The study of the growth regularities of the initial strain and its variant deprived of the bacteriocinogenicity plasmid showed that multiplication of the cells in the presence of the plasmid practically started without the latent period.     

Different families of double-stranded conformations of DNA as revealed by computer calculations

An algorithm has been developed that permits one to find all possible conformations of the sugar-phosphate backbone for any given disposition of DNA base pairs. For each of the conformations thus obtained, the energy of the helix was calculated by the method of atom-atom potentials. Several isolated regions in the space of the bases′ parameters (Arnott's parameters) have been found for energetically favorable helical structures. Two parameters, the distance of a base pair from the helix axis, D, and the windling angle, τ, allow one to subdivide possible conformations into the families of closely related forms. Two regions (ravines) on the (D, τ) map correspond to the know A and B families. In the B family a continuous transition has been obtained in which the double helix undergoes increasing winding, while the base pairs are moving toward the major (nonglycosidic) groove. Interrelationships between the variables, characterizing the spatial structure of the double helix, D, τ, TL and χ, when going along the bottom of the B ravine, were also obtained. Besides the Known A and B families, several new ones were found to be energetically possible. Among these the strongly underwound helices with the negative D values, as well as the forms with the C4-C5 angle in a trans position, should be mentioned. Biological roles of the different double-stranded conformations, in particular, in protein-nuclei acid interaction are discussed.     

The mutagenic effect of different types of irradiation on the sex cells of male mice. VIII. Frequency of development of reciprocal translocations in the spermatogonia of mice subjected to chronic gamma-irradiation]

The frequency of reciprocal translocations in mice spermatogonia after the exposure to chronic gamma-irradiation at doses of 100, 200, 300, 600, 920 r, at the dose rate of 4,2 r/day was investigated. It was shown that the mutation frequency increased insignificantly with the increase of the radiation dose (y =0,8+0.0011x). The comparison of the data obtained with earlier results revealed no changes in the yield of translocations at the reduction of the dose rate from 10 r/day to 4,2 r/day. The investigation of the genetic radiosensitivity of mice spermatogonia after a chronic gamma-irradiation showed a tendency to increase in their radioresistance.     

Studies on the mechanism of the changes in serum and liver gamma-glutamyl transpeptidase activity. I. Experimental extrahepatic cholestasis in rabbits.

Serum, liver and renal gamma-glutamyl transpeptidase (GGT) activities were studied in four groups of rabbits: controls, rabbits with obstructive extrahepatic cholestasis, rabbits with obstructive anuria, and animals with combined obstructive extrahepatic cholestasis and obstructive anuria. Serum GGT was essentially increased in rabbits with obstructive extrahepatic cholestasis, showing peak values in the combined cholestasis + obstructive anuria group, and practically normal values in animals with anuria. Liver GGT was increased in both cholestasis groups, but the increase was less prominent than the increase in serum GGT and there was no correlation between them. In both anuric groups renal GGT was reduced, probably as a result of inhibited enzyme synthesis secondary to the altered conditions for adequate renal function. The results obtained are suggestive of a probable renal involvement in the formation of the serum GGT activity level.     

SOI-nanowire biosensor for detection of D-NFATc1 protein

The nanowire (NW) detection is one of the fast-acting and high-sensitive methods, which can recognize potentially relevant protein molecules. A NW-biosensor based on the silicon-on-insulator (SOI)-structures has been used for biospecific label-free real time detection of the NFATc1 (D-NFATc1) oncomarker. For this purpose, SOI-nanowires (NWs) were modified with aptamers against NFATc1 used as molecular probes. It was shown that using this biosensor it is possible to reach sensitivity of 10^?15 M. This sensitivity was comparable to that of the NW-biosensor with immobilized antibodies used as macromolecular probes. The results demonstrate that approaches used in this study are promising for development of sensor elements for high-sensitive diagnostics of diseases.     

Biodegradation kinetics of poly(3-hydroxybutyrate)-based biopolymer systems

The aim of this study was to evaluate and to compare the long-term kinetics curves of biodegradation of poly(3-hydroxybutyrate) (PHB), its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and a PHB/polylactic acid composite. The total weight loss and the change of average viscosity molecular weight were used as the parameters reflecting the biodegradation degree. The rate of biodegradation was analyzed in vitro in the presence of lipase and in vivo after film implantation in animal tissues. The morphology of the PHB film surface was studied by the atomic force microscopy technique. It was shown that PHB biodegradation involves both polymer hydrolysis and its enzymatic biodegradation. The results obtained in this study can be used for the development of various PHB-based medical devices.     

Optical surface plasmon resonance biosensors in molecular fishing

An optical biosensor employing surface plasmon resonance (SPR; SPR-biosensor) is a highly efficient instrument applicable for direct real time registration of molecular interactions without additional use of any labels or coupled processes. As an independent approach it is especially effective in analysis of various ligand receptor interactions. SPR-biosensors are used for validation of studies on intermolecular interactions in complex biological systems (affinity profiling of various groups of proteins, etc.). Recently, potential application of the SPR-biosensor for molecular fishing (direct affinity binding of target molecules from complex biological mixtures on the optical biosensor surface followed by their elution for identification by LCMS/MS) has been demonstrated. Using SPR-biosensors in such studies it is possible to solve the following tasks: (a) SPR-based selection of immobilization conditions required for the most effective affinity separation of a particular biological sample; (b) SPR-based molecular fishing for subsequent protein identification by mass spectrometry; (c) SPR-based validation of the interaction of identified proteins with immobilized ligand. This review considers practical application of the SPR technology in the context of recent studies performed in the Institute of Biomedical Chemistry on molecular fishing of real biological objects.     

Packing of the transmembrane helices of Na,K-ATPase: direct contact between beta-subunit and H8 segment of alpha-subunit revealed by oxidative cross-linking

Spatial relationships among the transmembrane (TM) segments of alpha- and beta-subunits of the Na,K-ATPase molecule have been investigated using oxidative induction of disulfide bonds. The catalytic alpha-subunit contains 10 TM alpha-helices (H1-H10) with 9 Cys residues located within or close to the membrane moiety. There is one Cys residue in the single TM segment of beta-subunit (Hbeta). Previously, the cross-linking products containing the beta-subunit and two fragments of alpha-subunit (the N-terminal containing H1-H2 helices and the C-terminal containing H7-H10 helices) have been identified in experiments with membrane-bound or detergent-solubilized preparations of the membrane moiety of trypsin-digested Na,K-ATPase [Sarvazyan, N. A., Modyanov, N. N., and Askari, A. (1995) J. Biol. Chem. 270, 26528-26532 and Sarvazyan, N. A., Ivanov, A., Modyanov, N. N., and Askari, A. (1997) J. Biol. Chem. 272, 7855-7858]. Here, we have shown that Cu(2+)-phenanthroline treatment of digitonin-solubilized preparation provides the most efficient formation of intersubunit cross-linked product that is predominantly a dimer of beta-subunit and a 22-kDa C-terminal alpha-fragment containing H7-H10 helices. This cross-linked product was isolated and subjected to CNBr cleavage. The resulting fragments were electrophoretically separated and sequenced. A 17-kDa peptide composed of Ile853-Met942 alpha-fragment and Ala5-Met56 beta-fragment was identified as a product of intersubunit disulfide cross-link between Cys44 of Hbeta and either Cys911 or Cys930, located in H8. This provides the first direct experimental evidence of the juxtaposition of Hbeta and H8 within the Na,K-ATPase molecule. The second detected cross-linked product was composed of alpha-fragments Lys947-Met963 and Tyr974-Tyr1016 linked by induced disulfide bridge between Cys964 (H9) and Cys983 (H10). The spatial proximity of these Cys residues defines the mutual orientation of H9 and H10 helices of alpha-subunit.