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Background: Managing the limits of temperature adaptation is relevant both in medicine and in biotechnology. There are numerous scattered publications on the identification of the temperature limits of existence for various organisms and using different methods. Dmitry Petrovich Kharakoz gave a general explanation for many of these experimental results. The hypothesis implied that each cycle of synaptic exocytosis includes reversible phase transitions of lipids of the presynaptic membrane due to the entry and subsequent removal of calcium ions from the synaptic terminal. The correspondence of the times of phase transitions has previously been experimentally shown on isolated lipids in vitro. In order to test the hypothesis of D.P. Kharakoz in vivo, we investigated the influence of the temperature of long-term acclimatization on the temperature of heat and cold shock, as well as on the kinetics of temperature adaptation in zebrafish. Testing the hypothesis included a comparison of our experimental results with the results of other authors obtained on various models from invertebrates to humans., Results: The viability polygon for Danio rerio was determined by the minimum temperature of cold shock (about 6 °C), maximum temperature of heat shock (about 43 °C), and thermopreferendum temperature (about 27 °C). The ratio of the temperature range of cold shock to the temperature range of heat shock was about 1.3. These parameters obtained for Danio rerio describe with good accuracy those for the planarian Girardia tigrina, the ground squirrel Sermophilus undulatus, and for Homo sapiens., Conclusions: The experimental values of the temperatures of cold shock and heat shock and the temperature of the thermal preferendum correspond to the temperatures of phase transitions of the lipid-protein composition of the synaptic membrane between the liquid and solid states. The viability range for zebrafish coincides with the temperature range, over which enzymes function effectively and also coincides with the viability polygons for the vast majority of organisms. The boundaries of the viability polygon are characteristic biological constants. The viability polygon of a particular organism is determined not only by the genome, but also by the physicochemical properties of lipids that make up the membrane structures of synaptic endings. The limits of temperature adaptation of any biological species are determined by the temperature range of the functioning of its nervous system.

We investigated the kinetics of the luminescence induced by reactive oxygen species in planarians during regeneration process. It was found that regeneration is accompanied with changes in the concentration of reactive oxygen species correlating with energy-intensive processes such as oxidative stress, caused by damage to cell membranes in the dissection of the planarian, phagocytosis of dying cells and mitosis of neoblasts. We showed for the first time that there is an opportunity of registering the physiological state of pluripotent stem cells at the level of the organism in vivo.

The microspectral analysis technique was used to identify molecular components of a number of plant and animal cells. This technique allows of performing optical measurements during freezing down to the temperature of liquid nitrogen. Revealed biochemical heterogeneity suggests functional specialization of individual cells within a population. Analysis of the fluorescence quenching revealed temperature intervals in which processes of recrystallization of intracellular water associated with specific pigment-protein complexes take place. A proposed experimental approach may find its application in correlation microscopy and also in cryobiology in order to search after optimal modes for the freezing and thawing of cryopreserved cells.

We analyzed the effects of weak combined magnetic fields, tuned to the cyclotron resonance condition for calcium ions, obtained in different phases of planarian regeneration. We showed that the result of regeneration in 72 hours after decapitation depends on the length of exposure, and the time between decapitation and initiation of a half-hour exposure. The experimental dependence can be explained by a multiplicity of enzymatic targets activated in different phases of the regeneration process.

The values of the parameters of serum-free media (concentration of Na+, amino acids, and carbohydrates, as well as the pH values) have been determined at which the rate of the differentiation of neuroblastoma cells is minimal, and the rate of proliferation is maximal. It was shown that media inducing the differentiation of 70% of cells during the cell cycle provide the maximal time of survival of differentiated cells.

An oxidative stress resistance in Paecilomyces lilacinus strain from Chernobyl Atomic Energy Station (ChAES) as well as in P. lilacinus strains from zones with control level of radioactive pollution has been studied. It was shown that radial growth rate of the colony of the ChAES strain in a range of glucose concentrations 0.002%; 0.2%; 0.5%; 1.0% showed maximum on the medium with 0.2% glucose. It was 1.5 times higher than growth rate of the control strains. Adaptation slowdown reaction has been found as a result of the first 10-30 min H2O2 treatment most profound in the ChAES (No 1941) strain. Under 10(-3) mol/l H2O2 growth of No 1941 resumed with 20% loss in growth rate. Cessation of growth of the control strain (No 10) was observed under these conditions. It has been shown that in the strain from ChAES zone adaptation to low glucose content in the medium (0.2%) was coupled with an increased resistance to oxidative stress.

The effect of hydrogen peroxide ( 10(-9)-10(-1) M) on the mycelial growth of the fungi Alternaria alternata, Cladosporium cladosporioides, Mucor hiemalis, and Paecilomyces lilacinus has been studied. The growth of fungi isolated from habitats with a background level of radioactive contamination was stopped by H2O2 concentrations equal to 10(-3) and 10(-2) M, whereas the growth of fungi that were isolated from habitats with high levels of radioactive contamination was only arrested by 10(-1) M H2O2. The response of the different fungi to hydrogen peroxide was of three types: (1) a constant growth rate of fungal hyphae at H2O2 concentrations between 10(-9) and 10(-4) M and a decrease in this rate at 10(-3) M H2O2, (2) a gradual decrease in the growth rate as the H2O2 concentration was increased, and (3) an increase in the growth rate as the H2O2 concentration was increased from 10(-7) to 10(2)-5 M. The melanin-containing species A. alternata and C. cladosporioides exhibited all three types of growth response to hydrogen peroxide, whereas the light-pigmented species M. hiemalis and P. lilacinus showed only the first type of growth response. A concentration of hydrogen peroxide equal to 10(-1) M was found to be lethal to all of the fungi studied. The most resistant to hydrogen peroxide was found to be the strain A. alternata 56, isolated from the exclusion zone of the Chernobyl Nuclear Power Plant.

X-ray electron probe microanalysis of a Neurospora crassa hyphal preparation revealed a significant heterogeneity of the potassium content in the hyphae. Low-potassium areas were found in a close proximity of the growing tip and in the distal part of the hyphae in the submembrane area of about 1 microm width. The intracellular potassium concentration was shown to change more than 3-5 times from apical to distal regions of the leading hyphae, the potassium contents in the apical part of the hyphae usually being minimal. We suggest that the content of intracellular potassium is determined by the volume occupied by free intracellular water, i.e., by the size of the space available for diffusion of substances, including inorganic ions.

Three types of population growth and development of chemotaxic motile bacteria Escherichia coli on semi-solid nutrient media are investigated: a) stable development - circular symmetrical waves; b) bursts; c) fractal-like self-organization. Experimental investigation of the burst formation is presented. The microscopic analysis of growing, fractal-like structures is carried out, and a mechanism for such structure formation is suggested. It is supposed that fractal-like bacterial structures growth is based on the principle of successively forming multiple micro-bursts. A mathematical model has been suggested to reproduce the experimental results. The structures obtained by numerical modeling of population growth in the parameter space 'substrate concentration - bacterial movement rate' reproduce the corresponding experimental structures in the space 'nutrient concentration in the media - the density of the media'.

To describe electrical phenomena observed in growth of Neurospora crassa hyphae, a theoretical model was developed considering the hypha as a one-dimensional electric cable with non-uniform longitudinal distribution of current sources reflecting the activity of proton pumps. A profile of the density of the pump current along the hypha is proposed, at which the results of simulation quantitatively coincide with the results of physiological experiments. The model values of energy coupling in the growth zones were estimated. The experimental dependence of the elongation rate of regenerating apical hypha fragments on their lengths was determined. Based on the comparison of these experimental results with the results of analysis of the model, the contribution of the axial metabolite transport, from the distal parts of the hypha to the apical part, to the dynamics of the apical cell growth was estimated. The possibility of evaluating the intensity of high-molecular-weight syntheses and/or accumulation of substances in granules was demonstrated. The growth rate of the regenerating hypha fragments was shown to correlate with the electric current flowing into the apical fragment 0.2-mm in length.

Analysis of experimental results and published data within the framework of the suggested mathematical model of ion-osmotic homeostasis revealed the dependence of a variety of cell parameters on temperature. It was shown that the cold-induced drastic increase in the basal concentration of cytoplasmic Ca was determined, on the one hand, by the suppression of transport processes responsible for Ca removal from the cytoplasm, and, on the other hand, by the increase of calcium fluxes, both from the outer medium and from cell organelles. The cold-induced variation in the ratio of permeabilities for Na and K ions was found, which can be due to the activation of different calcium- and potential-dependent channels or by formation of membrane defects. Besides the flow of calcium ions through appropriate selective channels, its delivery into the cytosol through membrane defects actively induced by cell cooling can not be excluded. Formation of nonselective transmembrane channels was promoted by lipid peroxidation and proteolysis induced by an increase in the basal concentration of calcium. The new approaches to protecting the cell from cold injury are discussed.

Low ouabain concentration (1 x 10(-6) M) is shown to decrease intracellular K+ (K+in) and to increase intracellular Na+ (Na+in) in human fibroblast cell cultures. The same ouabain concentration was without effect upon K+in ad Na+in in rodent cultures such as BHK-21, mouse fibroblasts and rat glyoma C6 cells. K+in and Na+in in the mixed cultures of human and BHK-21 fibroblasts or human and mouse fibroblasts were found to be resistant to 1 x 10(-6) M ouabain whereas that of the mixtures of human and rat glyoma C6 cells proved to be ouabain-sensitive. The gap-junction-mediated dye transfer was revealed between human and BHK-21 cells. Such an effect was very small in the human-C6 cell mixed culture. It is concluded that cells with active ion pumps can support the maintenance of K+ and Na+ gradients in cells with inactive pumps, provided that effective ion transport via gap junctions takes place.

An attempt was made to analyze heterogeneity of tumor populations with respect to potential stability of single cells and their intracellular compartments (lipid-containing refractory granules, RG, and cytoplasmic sites) to lipid peroxidation (LP). LP was initiated by a combined action of hypoxia and u.v.-light and measured by the level of fluorescent product of lipid peroxidation (FPLP) well distinguished from other fluorescent components of the cell. Irrespective of the cell growth stage, RG were found to make a major contribution to the total intensity of FPLP of the cell. However, this contribution was minimal (20 to 30%) in exponentially growing ascites tumor cells and maximal (70 to 90%) in the stationary growing ones. It is noteworthy that in both cases the heterogeneous tumor population has cells with a high stability to inhibitory and cytokilling action of LP. We believe that the approach suggested in this work is of potential importance for experimental and clinical practice since it is highly sensitive for detecting FPLP in single cells, which allows one to reveal various subcellular tumor populations and estimate their stability to LP.

Some metabolic parameters enhancing the sensitivity of tumor cells and their lipoprotein refractive granules (RG) to peroxidative stress were investigated during the growth cycle of ascite tumors in vivo. The majority of tumor cells only in the stationary growth phase had the increased sensitivity to peroxidative stress, tested by fluorescence intensivity of peroxidation products. The increase of this intensity correlates well with the decrease of tumor proliferation, the functional activity of mitochondria, the cellular level of ATP and extracellular pH. These metabolic conditions are favourable for increasing the neutral lipid accumulation in the stationary tumor cells, their RG and nuclei, as compared to exponentially growing cells. The sensitivity of tumor cells to peroxidation can be also enhanced with the help of exogenous polyunsaturated fatty acid (PUFA). Based on literature and our own data on Ehrlich ascites carcinoma (EAC), a working hypothesis is proposed to explain the enhanced selective sensitivity of tumor cells to PUFA peroxidation products (PP) suppressing the cell growth (especially in the stationary phase of EAC growth).

The spectrokinetic parameters of two different types of fluorescence of lipid-containing refractory granules (RG1 and RG2) specific to native single cells from rat ovarian tumour and Zaidela ascites hepatoma were studied. With these parameters it was possible for the first time to reveal and estimate the contribution of fluorescent lipid peroxidation products to the total fluorescence band (430-470 nm) of RG1 as well as to reveal another fluorescent component with parameters similar to those of NAD(P)H. The phenomenon of 'photoinflammation' of RG2 fluorescence under UV light, reported previously for lipofuscin granules, was observed in vitro for four retinal derivatives, but only in the absence of their contact with air.

Animal cell cooperation has been studied in a mixed cell culture. Membrane potentials of human embryonic cells and hamster BHK-21 cells were recorded by intracellular microelectrodes. The Na+/K(+)-ATPase inhibitor ouabain (1 x 10(-6) M; 2 h) caused strong depolarisation of the human cells in pure culture. The same treatment reduced only slightly the membrane potential in the hamster cells in pure or mixed cultures, as well as in the human cells in mixed culture. The above data can be explained by effective ion fluxes through heterotypic gap junctions in mixed culture. Thus, in the presence of ouabain the Na+/K(+)-ATPase of hamster cells creates transmembrane differences of the electrochemical potential of ions not only in the hamster cells, but in the human cells as well.

It has been shown that the effect of fluorescence "inflammation" in lipid-containing granules (LCG) within the range of 540-570 nm is due to the presence of retinene derivatives in their composition. Retinene derivatives under investigation (three out of four) gave rise to the effect of "inflammation" only under anaerobic conditions. Manifestation of this effect in vitro correlated with the number of unsaturated double bonds in the aromatic ring.

A mathematical model is proposed which in the limits of a cell unifield self-consistent scheme enables to interpret quantitatively the results of electrophysiological, morphological and bioenergetic measurements. Using the model one can calculate the membrane potential, ionic fluxes, intracellular ionic concentrations, cell volume, as well as the rate of ATP hydrolysis by ionic pump.

Membrane potentials, input resistances, and electric coupling in the apical parts of N. crassa growing hyphae were recorded with the aid of intracellular microelectrodes. It was revealed that the apical cells were always depolarized by 10 to 30 mV as compared to the adjacent proximal cells. The septal pore maintained an electrical resistance of 4 to 6 M omega. The calculated values of the endogenous electrical current passing through the septal pore varied between 0.5 and 1 nA. Electrical isolation of the apical cells resulted in their depolarization from 120-150 mV to 40-60 mV, characteristics of the membrane potential value of N. crassa adult hyphae with completely blocked electrogenic pumps. A simultaneous increase in the input resistance value from 15-20 M omega to 40-80 M omega was observed. The above data can be explained assuming that H+-ATPase activity was greatly lowered in the apical cells. Thus in the intact hyphae with electrically coupled cells energy is transferred from the proximal hyphal compartments to the apical ones.