A cyclic-AMP-gated conductance in cochlear hair cells.

The patch clamp technique was used to record cAMP-dependent currents of the guinea pig cochlear hair cell plasma membrane. Data obtained indicate that the channels passing this current are moderately selective for monovalent cations and are effectively blocked by L-cis-diltiazem and reversibly blocked by 1 mM Mg2+ or Ca2+. The single-channel unit conductance estimated in the absence of divalent cations is about 16 pS.

Apoptosis of murine BW 5147 thymoma cells induced by dexamethasone and gamma-irradiation.

The mode and the kinetics of the death of T-thymoma cells upon dexamethasone treatment and gamma-irradiation (10Gy) have been studied using flow cytometry and biochemical analysis. It has been shown that the hormone and gamma-irradiation induce cell death by apoptosis. In both cases the cells are initially blocked in G2/M and die only after overcoming the blockage and cytokinesis.

Experimental and theoretical study of energetics of complex formation between nucleic acid bases and the bases with amide group.

A number of nucleic acid base pairs and complexes between the bases and the amide group of acrylamide have been studied experimentally by using mass spectrometry and theoretically by the method of atom-atom potential function calculations. It has been found from temperature dependencies of peak intensities in mass spectra of m2.2.

Comparison of structures of dry and wet hen egg-white lysozyme molecule at 1.8 A resolution.

A high resolution structure of hen egg-white lysozyme containing 36 +/- 1 mol H2O per mol of protein has been obtained using triclinic (P1) crystals cross-linked with glutaraldehyde. Analysis of dehydration-induced structural changes has revealed displacement in relative position of domains and numerous small displacements in positions of individual atoms with r.m.

Fluorescence study of the conformational properties of myoglobin structure. 3. pH-dependent changes in porphyrin and tryptophan fluorescence of the complex of sperm whale apomyoglobin with protoporphyrin IX; the role of the porphyrin macrocycle and iron in formation of native myoglobin structure.

The porphyrin and tryptophan fluorescence of sperm whale apomyoglobin complexed with protoporphyrin IX has been studied in the pH range 2-13. It has been shown that the fluorescence and absorption spectra of protoporphyrin incorporated into the heme crevice remain constant in the pH range 5.5-10.

Fluorescence study of the conformational properties of myoglobin structure. 2. pH- and ligand-induced conformational changes in ferric- and ferrousmyoglobins.

Tryptophanyl fluorescence of high-spin and low-spin complexes of sperm whale ferric- and ferrousmyoglobins, met-, azide- and cyanomyoglobins and deoxy-, oxy- and carboxymyoglobins has been studied in the pH range 2.5-13. The pH-dependent fluorescence of sperm whale metmyoglobin acylated at the N-terminal alpha-amino group by methylisothiocyanate and of bovine metmyoglobin, which contains invariant Trp7 and Trp14 but lacks Tyr151, have also been examined.

Fluorescence study of the conformational properties of myoglobin structure. 1. pH-dependent changes of tryptophanyl fluorescence in intact and chemically modified sperm whale apomyoglobins.

The pH-dependent fluorescence of intact sperm whale apomyoglobin (apo-Mb) containing two tryptophans at positions 7 and 14, and of apo-Mb derivatives modified on Trp7 by 2-hydroxy-5-nitrobenzyl bromide (Koshland reagent) and o-nitrophenylsulphenyl chloride, has been studied. The fluorescence of apomyoglobins modified at His residues by iodoacetamide and bromoacetate, and at the N-terminal alpha-NH2 group by methylisothiocyanate, has also been investigated. The individual fluorescent properties of both tryptophans and their contributions to the total spectrum of apo-Mb have been resolved within the pH range 2-12.

Study of potassium deficiency in cardiac muscle: quantitative X-ray microanalysis and cryotechniques.

An imbalance of potassium in cardiac muscle causes an alteration of heart function. The distribution and concentration of potassium in rat papillary heart muscle was studied using cryofixation and X-ray microanalysis. Freeze-dried cryosections and sections of freeze-dried, embedded tissue were analysed.

Theoretical analysis of an ultrasonic interferometer for precise measurements at high pressures.

Expressions making it possible to calculate the transmission coefficient of an ultrasonic interferometer, its Q factor and errors of interferometric measurements are presented. These expressions are obtained on the basis of a one-dimensional model which takes into account the non-ideal reflection of acoustic waves from the transducers, diffraction losses and electromechanical properties of transducers. Fixed path ultrasonic interferometers which are widely used for high precision measurements of ultrasound absorption and velocity in liquids, include air-backed transducers.

Specific modification of Escherichia coli RNA polymerase with monomercury derivative of fluorescein acetate.

The method of specific modification of RNA polymerase with a monomercuric fluorescein derivative, fluorescein-monomercuriacetate (FMMA), is proposed. Under an appropriate condition of modification, FMMA is capable of mercaptid bonding with one of the alpha-subunits. It is shown that covalent modification with FMMA does not affect the kinetic parameters (KB and k2) of RNA synthesis nor does it lead to the inhibition of the overall RNA synthesis.

Calcium-regulated interactions of human alpha-lactalbumin with bee venom melittin.

Affinity chromatography, fluorescence and circular dichroism spectroscopy methods have been used to study the interaction of melittin, a 26-residue peptide from bee venom, with Ca2(+)-binding alpha-lactalbumin from human milk. It has been revealed that melittin binds to the apo- and acidic states of alpha-lactalbumin while the presence of Ca2+ makes the interaction essentially weaker. The association constant for the complex of melittin with apo-alpha-lactalbumin determined from spectropolarimetric melittin-titration data is 2 X 10(7) M-1.

Ion channel redox model.

Na(+)- and Ca2(+)-channel blockers behave as electron donors in reactions with excited dye radicals, while agonists of these channels behave as electron acceptors in the same reactions. The opposite redox characteristics of channel blockers and agonists may reflect their opposite action on the channels. The observed regularities of channel-modulator reactions with free radicals, as well as, the ability of many proteins to influence long-range electron transfer, are the basis for a model of channel function and regulation by various agents in which labile electrons in the channel-forming protein acts as electric field sensors.

Noncovalent complex between domain AB and domains CD*EF of parvalbumin.

The interaction between domain AB and domains CD*EF of pike parvalbumin III has been studied by intrinsic fluorescence spectroscopy. In the presence of Ca2+ ions, parvalbumin fragment 38-108 containing two calcium binding sites interacts with the short peptide 1-37 with association constant 10(5.3 +/- 0.

Possible mechanism for the influence of weak magnetic fields on biological systems.

A physical mechanism is suggested for a resonant interaction of weak magnetic fields with biological systems. An ion inside a Ca(2+)-binding protein is approximated by a charged oscillator. A shift in the probability of ion transition between different vibrational energy levels occurs when a combination of static and alternating magnetic fields is applied.

A continuum model of contraction waves and protoplasm streaming in strands of Physarum plasmodium.

We present a mathematical model for continuously distributed mechanochemical autooscillations (autowaves) in a protoplasmic strand of Physarum polycephalum. The model is based on a hypothesis of local positive feedback between deformation and contraction of the contractile apparatus. This feedback is mediated through a cell regulatory system whose kinetics involves coupling to mechanical strain.

Analysis of some metabolic conditions promoting selective sensitivity of tumor cells to peroxidative stress.

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.

Actin in synaptic cytoskeleton during long-term potentiation in hippocampal slices.

Potentiated hippocampal synapses were found to be characterized by specific changes of the cytoskeleton in the postsynaptic spine. Aggregated bundles of actin filaments in the potentiated spines were revealed by decoration with myosin subfragment-1.

Alterations in the cytoskeleton of the goldfish Mauthner cells under various pharmacological treatments.

The ultrastructural changes in the cytoskeleton of the goldfish Mauthner cells (M-cells) at various functional states induced by intracerebral microinjections of biologically active substances were studied. Under the action of kainic acid, a structural analog of the excitatory neurotransmitter of glutamate, the density of the cytoplasmic matrix increased. Cytotoxin II from the cobra toxin, which blocks acetylcholine transmission, had an opposite effect upon the M-cell cytoskeleton.

Structural and chemical changes in the cytoskeleton of the goldfish Mauthner cells after vestibular stimulation.

The ultrastructure and protein content of goldfish Mauthner cells (M-cells) at different functional states induced by natural vestibular stimulations were studied. 2-h stimulation, usually causing a fatiguing of the fishes, was found to be accompanied by ultrastructural changes within M-cells and a decreased content of cytoskeletal proteins. After training by short stimulations resulting in a long-term adaptation of the fishes, the ultrastructure and protein content of M-cells could not be distinguished qualitatively and quantitatively from those of non-adapted fishes.

Spectrokinetic characteristics of two types of fluorescence of refractive granules in native individual cells from ascitic tumours.

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.

Resistance of single tumor cells and their intracellular compartments to lipid peroxidation.

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.

The role of receptors in radiation hormesis.

The response of the receptor of plant origin, phytochrome and the receptor of rat lung cytoplasmic membrane adenylate cyclase to chronic, growth- and development-stimulating low-dose gamma-radiation (0.36 and 0.036 cGy/day) has been studied.

Electrical activity of the hippocampus of rats with the central administration of GABA agonists and antagonists.

The frequency spectra of the electrograms of the dorsal hippocampus with intraventricular administration of GABA, muscimol, baclofen, bicuculline, and picrotoxin, were studied in chronic experiments on 24 awake freely-moving rats. The data obtained are in accord with the existing notion regarding the interactions of agonists and antagonists with GABA receptors. The possibility of their participation in the formation and/or modulation of the total electrical activity of the hippocampus is discussed.