Information characteristics of neuronal and synaptic plasticity

Informational losses in neuronal nets(NN) with plastic elements were estimated. These losses are related with 1) transition from "complicated" decoding when from the modification state of such elements information of the whole set of recorded elements is extracted to "simple" decoding natural of NN functioning when information is extracted independently for individual events; 2) uncertainty concerning NN structure, if at decoding in one of the modification states the neuron reactivity totally or the weight of plastic synapse equals zero. After the transition from complicated to simple decoding these losses for gradual plasticity are so great that NN with such plasticity has no advantages in informational capacity as compared to the binary one. These losses are absent for plasticity of Olbus type. They are relatively high for neuronal plasticity of Hebb type. For Hebb synapses their value essentially depends on the net parameters.     

Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections

A method of rapid freezing in supercooled Freon 22 (monochlorodifluoromethane) followed by cryoultramicrotomy is described and shown to yield ultrathin sections in which both the cellular ultrastructure and the distribution of diffusible ions across the cell membrane are preserved and intracellular compartmentalization of diffusabler ions can be quantitated. Quantitative electron probe analysis (Shuman, H., A.V. Somlyo, and A.P. Somlyo. 1976. Ultramicros. 1:317-339.) of freeze-dried ultrathin cryto sections was found to provide a valid measure of the composition of cells and cellular organelles and was used to determine the ionic composition of the in situ terminal cisternae of the sarcoplasmic reticulum (SR), the distribution of CI in skeletal muscle, and the effects of hypertonic solutions on the subcellular composition if striated muscle. There was no evidence of sequestered CI in the terminal cisternae of resting muscles, although calcium (66mmol/kg dry wt +/- 4.6 SE) was detected. The values of [C1](i) determined with small (50-100 nm) diameter probes over cytoplasm excluding organelles over nuclei or terminal cisternae were not significantly different. Mitochondria partially excluded C1, with a cytoplasmic/ mitochondrial Ci ratio of 2.4 +/- 0.88 SD. The elemental concentrations (mmol/kg dry wt +/- SD) of muscle fibers measured with 0.5-9-μm diameter electron probes in normal frog striated muscle were: P, 302 +/- 4.3; S, 189 +/- 2.9;C1, 24 +/- 1.1;K, 404 +/- 4.3, and Mg, 39 +/- 2.1. It is concluded that: (a) in normal muscle the "excess CI" measured with previous bulk chemical analyses and flux studies is not compartmentalized in the SR or in other cellular organelles, and (b) the cytoplasmic C1 in low [K](0) solutions exceeds that predicted by a passive electrochemical distribution. Hypertonic 2.2 X NaCl, 2.5 X sucrose, or 2.2 X Na isethionate produced: (a) swollen vacuoles, frequently paired, adjacent to the Z lines and containing significantly higher than cytoplasmic concentrations of Na and Cl or S (isethionate), but no detectable Ca, and (b) granules of Ca, Mg, and P = approximately (6 Ca + 1 Mg)/6P in the longitudinal SR. It is concluded that hypertonicity produces compartmentalized domains of extracellular solutes within the muscle fibers and translocates Ca into the longitudinal tubules.     

Plant virus infection development as affected by heavy metal stress

The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants.     

Rheological of blood and oxygen transport in long-term adaptation to muscular load

The blood viscosity became reduced after a long-term muscular adaptation in dogs. The main adaptation mechanism is associated with an autoregulated haemodilution and improvement of the red blood cells' microrheology (deformities and aggregation). The findings suggest that reduction in the haemodilution and the blood oxygen capacity are accompanied by a heightened efficiency of the oxygen transport. A sufficient correlation exists between the blood fluidity parameters and the oxygen balance in the body. Value of the optimum haematocrit in oxygen transport, is discussed.     

Effect of Plasma and Cellular Factors on the Aggregation of Erythrocytes from Different Age Populations

Microrheologic properties (aggregation and deformability) were examined in young (upper fraction) and old (bottom fraction) erythrocytes separated by density gradient centrifugation at 30000 g. A significant difference in microrheologic properties of the young and old erythrocytes was revieled. Erythrocyte aggregation was studied in the plasma and serum. Aggregation of the young and old cells in plasma was higher than in serum, which points to the importance of the presence of fibrinogen in the aggregation medium. The study of aggregation kinetics showed that the absence of fibrinogen in the medium produced an insignificant effect on the rate of aggregate formation, but it dramatically affected the degree of aggregation (12 and 88% difference between aggregate number in the plasma and serum, respectively). In young erythrocytes, the difference of the degree of aggregation and kinetics of aggregate formation in the plasma and serum was not so pronounced (32 and 43%, respectively). Analysis of correlations between aggregation and deformation of the young and old erythrocytes revealed more pronounced interrelations of these parameters in the plasma compared to serum, indicating an important role of fibrinogen for the manifestation of microrheologic properties of erythrocytes. These interrelations were most pronounced during aggregate formation, which supported the bridging theory of aggregation.     

Red blood cell aggredation: mechanisms, adrenergic regulation

Red blood cell aggregation is a complex multiple-factor process and exerts a substantial effect on realization of basic blood function: oxygen transport. Insufficient knowledge about mechanisms of erythrocyte aggregation in normal conditions and, especially, in pathological conditions, complicates the control and correction of possible negative consequences of this process. On addition, red blood cell aggregation process is a suitable model for the elucidation of basic patterns of intercellular interactions. The paper presents contemporary data on mechanisms of erythrocyte aggregation and contribution of plasma and membrane erythrocyte properties to this process. Currently available data on intracellular signal pathways are discussed.     

L1 (LINE-1) retrotransposable elements provide a "fossil" record of the phylogenetic history of murid rodents

The single most difficult problem in phylogenetic analysis is deciding whether a shared taxonomic character is due to common ancestry or one that appeared independently due to convergence, parallelism, or reversion to an ancestral state. Mammalian L1 retrotransposons undergo periodic amplifications in which multiple copies of the elements are interspersed in the genome. Because these elements apparently are transmitted only by inheritance and are retained in the genome, a shared L1 amplification event can only be an inherited ancestral character. We propose that L1 amplification events can be an excellent tool for analyzing mammalian evolution and demonstrate here how we addressed several refractory problems in rodent systematics using L1 DNA as a taxonomic character.