Physiologie (Bucarest)最新文献

In experiments with the "sleeves" and the whole roots of Zea mays seedings, the idea of the complicated nature of root pressure and an active part of parenchyma cells in water pumping by roots has been confirmed. It has been shown that root pumping activity is summarized by two, principally different constituents--metabolic and osmotic. The metabolic constituent functions exclusively at the expense of the parenchyma cells activity.

In the study of the role of the hydration water in the structure and function of biosystems, one of the major problems is the investigation of the dynamics of hydration water. For this purpose, many papers were reported about relaxation measurements of hydration water by 1HNMR. Most of them were concerned with rotational motion of hydration water. There were few papers dealing with translational motion of hydration water in rigid systems, such as unfrozen water and bound water of protein. The spin-echo or pulse gradient methods are useless in the study of such systems, whereas the self-diffusion coefficient D, the index of translational motion, can be estimated by the spin-locking method. This report is concerned with the study of the translational motion of unfrozen and bound water of solution and powder of protein, respectively, and the measuring of the values of D by spin-locking using of 1HNMR. The coefficient can be obtained by measuring the relaxation time T1 varying the locking power w1. For hydration monolayer in protein solution at -35 degrees C, D values of 10(-9)-10(-10) cm2/sec, and for monolayer in protein powder at room temperature, D values of 10(-10)-10(-11) cm2/sec were obtained. By heat denaturation of the protein, the values were slightly altered, though the rotational motion revealed by T1 measurement appeared not so affected. This difference might derive from the alteration of the protein surface by the unfolding of protein molecule due to the denaturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Calmodulin seems to be strongly involved in the process of transmitter release. By activating a specific proteinkinase system, calmodulin could initiate the phosphorylation of some axolemal or vesicular protein, thus triggering the exocytosis of the synaptic vesicles and the transmitter release. Under these conditions it was to be expected that a calmodulin blocking agent such as trifluoperazine, used in appropriate concentrations for this effect, should block the transmitter release. Contradictory results determined us to reexamine the question under extended experimental conditions. Our data suggest that calmodulin could both activate and block the transmitter release through probably different mechanisms.

The paper deals with the influence of electrolytes on the structure temperature of water. The variations in water structure have been investigated by the method of the states spectra of water, i.e. by the distribution function of the wetting angle of water drops, which evaporate under constant conditions. Some results have been obtained about the mechanism of the action of ions, stabilizing and breaking the water structure, on the stable states in the latter under conditions far away from equilibrium.

Cellular physical interactions are determinant in many and various biological processes: aggregation, adhesion, segregation, contact inhibition, fusion, etc. A real advance concerning the understanding of cellular interactions from a physical point of view has been performed of late, but a great many problems still remain to be clarified. Thus, DLVO theory extrapolated to cell-cell interactions, is unable to describe cellular interactions at very short distances of separation, where other forces play an important role. A sketch of the original form of DLVO theory, its criticism along with the nature and mechanism of the short range repulsive forces (hydration forces) are presented and discussed.

This report focuses on two groups of cationic cancerostatics, anthracycline antibiotics and 1,4-benzoquinone-guanylhydrazone-thiosemicarbazone (ambazone), lining up biophysical and biochemical effects on the level of membranes and membrane constituents. The interaction of both drugs with multilamellar liposomes consisting of phosphatidylcholine used as a simple model membrane system could be ensured by means of steady state and nanosecond time-resolved fluorometric investigations. The biochemical effect on membranes is underlined by the inhibition of the neuraminidase activity of the Sendai virus, modification of the CAMP phosphodiesterase activity of leukemia L 1210 cells of mice and reduction of the lymphocyte blast transformation.

Compression isotherms of astaxanthin (AX; 3,3'-dihydroxy-4,4'-dioxo-beta-carotene) monolayers, recorded at the air/water interface show, on the one hand, the collapse pressure to depend on the subphase pH, indicating the ionisation of AX at high pH values, and on the other hand, the subphase Co2+ ions to have a condensing effect upon the monolayer and to entail the increase of its collapse pressure. The latter effects are assigned to surface complex formation. The interfacial tension at the benzene/water interface (the benzene phase containing AX, the water phase Co2+ ions) exhibit a maximum at a molar ratio AX: Co of about 3.6, pleading for the formation of relatively stable Co(AX)4 type interfacial complex. Geometric model and ligand field considerations show besides the dative type sigma-bond formation, the possibility of both dative and retrodative type pi-bond formation between Co2+ and the AX ligands. Under the working conditions used, the formation of a neutral non-electrolyte type complex of the composition [Co(LH)2L2] is postulated, where LH stands for the neutral AX molecule, L- for its anion.

Investigating the kinetics of K+ efflux, two K+ fractions were found in the muscle exposed to 5.8 M glycerol solution at -12 degrees C. The minor K+ fraction was exchangeable with Na+. The amount of released K+ ions being in the K+/Na+ ion exchange was saturable with increase in the concentration of Na+ ion in the medium. It was 11 mmol K+/kg wet wt., which corresponds to the magnitude of the "medium" K+ fraction found by A. S. Troshin in the muscle by means of isotope technique. The minor K+ fraction was temperature and ouabain dependent. K+ fraction with similar features was found by W. Negendank in human lymphocytes, however, its magnitude was 120 mmol K+/kg w.wt. The ratio of the two magnitudes is equal to the ratio of the total cell surface of the muscle and the lymphocyte of one kg. From this fact, it can be concluded that the 11 mmol K+/kg fraction exchangeable with Na+ is bound directly to the cell membrane or to an unidentified structure near to the membrane surface. The preference of K+ binding at higher temperature is interpreted by the assumption that both K+ and Na+ bind to the binding sites of the 11 mmol/kg fraction with their hydration shells.

Bacterial metabolism can drive various processes with biotechnological significance, like in the case of biosensors for probing organic compounds, or in biofuel cells. Here we present some of our results connected with the construction of a bacterial electrode with Pseudomonas sp. for probing glucose in body fluids, and those related to biofuel cells with anaerobic bacteria (Clostridium sp.). The output of the bioselective electrode linearly indicates glucose concentrations in the 2.5 x 10(-5)-1.25 x 10(-4) M domain, with a sensitivity limit of 10(-5) M. The time constant is 10 min, and it works for more than ten days. The amperometric response of biofuel cells with Clostridium sp. offers the electrical image of the state of the bacterial culture itself, thus being a promising tool for the automated control of the bacterial suspensions used in fermentative reactors.