Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)最新文献

Both living cell and central nervous system can be treated as objects similar to artificial neural networks, actively studied now. One can see deep analogies between evolutionary processes in these systems, and correspondences can be established between some phenomena and objects. These are: genome vs. memory, gene vs. symbol, cell type vs. image, mitosis vs. sleep, organism vs. perception state, species vs. language, fertilization vs. attention, meiosis vs. paradoxal sleep. There is reason to study these correspondences on more technical level being based upon network nature of the living cell and nervous system.

It is shown that the reasons for the poor replicability of the nonthermal bioeffects of radiofrequency have the fundamental bases. The efficiency of the living system process is determined by the conversion of electromagnetic energy into Helmholtz free energy. The efficiency dependence on the absorbed power of electromagnetic radiation is quite different in the Wien region (visible light) and in the Rayleigh–Jeans region (radiofrequency). In the Wien region the endergonic and exergonic processes could never be confused. In the Rayleigh–Jeans region the endergonic and exergonic processes could be confused. It gives the poor replicability.

We present a model for the development of chemiluminescence (CL) in autoclaved liquid growth media, as they are used in microbiology for the culturing of microorganisms, or in other related Maillard systems. The model distinguishes between four different stages consisting of sugar fragmentation during heating, autooxidation of highly reducing fragmentation products, radical chain reactions leading to a peroxidation of the media, and finally the formation of excited states, energy transfer reactions and CL emission. The proposed model is also discussed in regard of a recently reported elimination of this CL in growing cultures of microorganisms and possible pathways for this interference are suggested.

The leucocyte surface properties manifest the cell-mediated immunity. The response of the cell-mediated immunity to external magnetic field was examined by observing leucocyte adherence to solid state surfaces. In the presence of antigen, leucocytes taken from cancer patients exhibit decreased adherence in contrast with adherence of leucocytes from healthy humans. After 1 h exposure to a sinusoidal magnetic field of 50 Hz and of 1 mT or 10 mT, adherence of leucocytes taken from cancer patients is strongly increased. The 1 mT magnetic field has stronger effect than the 10 mT field.

In an effort to obtain synthetic analogues of water-oxidizing complex (WOC) of photosystem II (PS II) of plant photosynthesis, a Schiff base manganese and a cobalt complex, employing Niten, a SALEN type ligand, have been prepared. Cyclic and square wave voltammetric measurements have been performed to assess their redox characteristics. Both complexes undergo several reduction processes in cathodic negative potential region at more or less similar potentials. In view of these reductions being independent of the nature of the metal, they are thought to be ligand-localized. Although similar in negative region, a marked difference in the behavior of the complexes is observed in anodic region. While the cobalt complex is electrochemically inactive in the positive potentials up to +1.0 V vs. Ag/AgCl, the manganese complex displays two oxidation waves at +0.25 and +0.5 V vs. Ag/AgCl. The presence of oxidation wave in manganese complex at +0.5 V vs. Ag/AgCl or +0.7 V vs. NHE suggests that this complex can catalyze the oxidation of water and can, thus, simulate the WOC of PS II.

The widespread impact made by technology has raised concerns about the safety of human exposure to electromagnetic radiation in the environment. The brain is especially sensitive to the influence of microwaves. The most effective method for estimation of the organism's functional states is an analysis of electroencephalograms. The statistical and spectral methods are usually used for analysis of animal electrocorticograms. The information obtained in such way is the integrated character and it is sometimes insufficient for identification of the brain state charging caused by various factors, especially microwaves altering the ecological situation. The nonlinear dynamics method is used in our work concurrent with the spectral correlation method for animal electrocorticogram processing. The correlation dimensionality represents a numerical criterion allowing for comparative investigation of various dynamic states of the system. In the process of investigation, it has been found that the nonlinear dynamics method may be used to analyze the electrocorticograms of experimental animal in different functional states being confirmed by increasing parameter of the correlation dimensionality in electrocorticograms of animal irradiated by microwaves or subjected to the introduction of strychnine.

Bacterial ferritin of Azotobacter vinelandii (AvBF) is directly able to pick electrons up for iron release from or transfer them for storage to a platinum electrode in the absence of mediator or other reducer. The ferritin containing the structure of heme-Co²⁺ in part shows weakened activity to electrode and decreases the rate of iron release greatly. A reversible reduction process of the ferritin is observed by the spectral change regularly ranging from 310 to 260 nm under mixed gases containing 98% H₂ and 2% to O₂. The activity of nitrogen fixation from the whole cell of A. vinelandii increases greatly by H₂ reduction with potentials ranging from −397 to −425 mV vs. NHE, indicating two important roles of H₂-uptake reaction of the ferritin in increasing activity of nitrogen fixation and in supplying iron to synthesize nitrogenase.

Upon a carbon paste electrode, fullerene C₆₀ and successively methyl pyropheophorbide-a (chlorin) were casted to prepare a chlorin–fullerene modified carbon paste electrode (CFE). Photocurrents on the CFE were produced by irradiating of visible lights (>510 nm) in an aqueous solution of 0.05 M ethylenediaminetetraacetic acid and 0.1 M Na₂SO₄ at pH 6.7. Larger anodic photocurrent was induced by the CFE than by the carbon paste electrodes modified with either the fullerene or the chlorin. In addition, the photocurrent of the CFE was dependent upon the amount of fullerene casted. The photocurrent action spectra of the CFE (at 300 mV vs. Ag/Ag⁺) showed that photoinduced electron transfer occurred from the excited state of the chlorin to the fullerene and/or from the chlorin to the photoexcited fullerene, and the electron of the fullerene anion radical produced was then shifted to the carbon paste. Upon irradiation of >375 nm lights, the anodic photocurrent of the CFE was enhanced by increase in the illuminated light power and reached 0.03 mA cm⁻² in the present system.

Electrooptical and conductometrical relaxation methods have given a new insight in the molecular mechanisms of the electroporative delivery of drug-like dyes and genes (DNA) to cells and tissues. Key findings are: (1) Membrane electroporation (ME) and hence the electroporative transmembrane transport of macromolecules are facilitated by a higher curvature of the membrane as well as by a gradient of the ionic strength across charged membranes, affecting the spontaneous curvature. (2) The degree of pore formation as the primary field response increases continuously without a threshold field strength, whereas secondary phenomena, such as a dramatic increase in the membrane permeability to drug-like dyes and DNA (also called electropermeabilization), indicate threshold field strength ranges. (3) The transfer of DNA by ME requires surface adsorption and surface insertion of the permeant molecule or part of it. The diffusion coefficient for the translocation of DNA (M_r≈3.5×10⁶) through the electroporated membrane is D_m=6.7×10⁻¹³ cm² s⁻¹ and D_m for the drug-like dye Serva Blue G (M_r≈854) is D_m=2.0×10⁻¹² cm² s⁻¹. The slow electroporative transport of both DNA and drugs across the electroporated membrane reflects highly interactive (electro-) diffusion, involving many small pores coalesced into large, but transiently occluded pores (DNA). The data on mouse B-cells and yeast cells provide directly the flow and permeability coefficients of Serva blue G and plasmid DNA at different electroporation protocols. The physico-chemical theory of ME and electroporative transport in terms of time-dependent flow coefficients has been developed to such a degree that analytical expressions are available to handle curvature and ionic strength effects on ME and transport. The theory presents further useful tools for the optimization of the ME techniques in biotechnology and medicine, in particular in the new field of electroporative delivery of drugs (electrochemotherapy) and of DNA transfer and gene therapy.

The number of reports on the effects induced by radiofrequency (RF) electromagnetic fields and microwave (MW) radiation in various cellular systems is still increasing. Until now no satisfactory mechanism has been proposed to explain the biological effects of these fields. One of the current theories is that heat generation by RF/MW is the cause, in spite of the fact that a great number of studies under isothermal conditions have reported significant cellular changes after exposure to RF/MW. Therefore, this study was undertaken to investigate which effect MW radiation from these fields in combination with a significant change of temperature could have on cell proliferation. The experiments were performed on the same cell line, and with the same exposure system as in a previous work [S. Kwee, P. Raskmark, Changes in cell proliferation due to environmental non-ionizing radiation: 2. Microwave radiation, Bioelectrochem. Bioenerg., 44 (1998), pp. 251–255]. The field was generated by signal simulation of the Global System for Mobile communications (GSM) of 960 MHz. Cell cultures, growing in microtiter plates, were exposed in a specially constructed chamber, a Transverse Electromagnetic (TEM) cell. The Specific Absorption Rate (SAR) value for each cell well was calculated for this exposure system. However, in this study the cells were exposed to the field at a higher or lower temperature than the temperature in the field-free incubator i.e., the temperature in the TEM cell was either 39 or 35±0.1°C. The corresponding sham experiments were performed under exactly the same experimental conditions. The results showed that there was a significant change in cell proliferation in the exposed cells in comparison to the non-exposed (control) cells at both temperatures. On the other hand, no significant change in proliferation rate was found in the sham-exposed cells at both temperatures. This shows that biological effects due to RF/MW cannot be attributed only to a change of temperature. Since the RF/MW induced changes were of the same order of magnitude at both temperatures and also comparable to our previous results under isothermal conditions at 37°C, cellular stress caused by electromagnetic fields could initiate the changes in cell cycle reaction rates. It is widely accepted that certain classes of heat-shock proteins are involved in these stress reactions.