The potential-dependent K+ channel in molluscan neurones is organized in a cluster of elementary channels

Single potential-dependent K⁺ channels were studied using the patch-voltage-clamp method. Two types of channel with identical, but oppositely directed, potential dependences were found. The channels of the first type (slow channels) are assumed to be responsible for the outward rectification. The properties of the channels of the second type (fast channels) are similar to those of the K⁺ channels in neurone soma which create the fast transient currents. The kinetic characteristics of both types of channel are presented. The conductances of slow and fast K⁺ channels are approx. 30 and 40 pS, respectively, at zero membrane potential and a K⁺ concentration of 50 mmol/l at the inner side of the membrane. The following sequence of channel selectivity with respect to monovalent cations was found: $\text{Tl}{}^{\mathrm{+}}\text{>}\text{K}{}^{\mathrm{+}}\text{>}\text{Rb}{}^{\mathrm{+}}\text{?}\text{Cs}{}^{\mathrm{+}}\text{?}\text{Li}{}^{\mathrm{+}}\text{?}\text{Na}{}^{\mathrm{+}}$. The probability of the channel open state monotonically decreases with free Ca²⁺ concentration at the inside membrane surface for both types of channel. It was found that the channels have discrete and multiple conductance substrates. It is supposed that a unitary K⁺ channel consists of approx. 16 elementary ones with conductances of approx. 2 pS (slow channels) and approx. 2.5 pS (fast channels) at zero potential. At + 100 mV the elementary conductances are equal to approx. 4 and 5.5. pS, respectively. Thus, according to this assumption, the unitary channel is a cluster of elementary channels.     

Single Cl− channels in molluscan neurones: Multiplicity of the conductance states

Summary Properties of the single Cl^– channels were studied in excised patches of surface membrane from molluscan neurones using single-channel recording technique. These channels are controlled by Ca²⁺ and K⁺ acting on cytoplasmic and outer membrane surfaces, respectively, and by the membrane potential. The channels display about 16 intermediate conductance sublevels, each of them being multiples of 12.5 pS. The upper level of the channel conductance is about 200 pS. The channel behavior is consistent with an aggregation of channel-forming subunits into a cluster.     

Discrete parameters of current oscillation in single ion channels

Using the patch-voltage-clamp method it was shown that oscillations of an open channel are fast current transitions between 64 multiple sublevels. Average values of elementary conductance step (gamma) and substate lifetime (tau el) were determined for different kinds of ionic channels. The values of gamma lie in the range from 1.5 to 6 pS, and tau el--in the range from 0.15 to 0.5 ms. The channel transitions between the substates are highly cooperative processes. The data are regarded in terms of the hypothesis about clustery organization of ionic channels.     

The Raman Spectroscopy,XRD, SEM,and AFM Study of Arabinogalactan Sulfates Obtained Using Sulfamic Acid

The structure of sodium salts of arabinogalactan (AG) sulfates obtained by sulfating AG of larch wood with a sulfamic acid–urea mixture in 1,4-dioxane was studied by the methods of Raman spectroscopy, X-ray diffraction (XRD) phase analysis, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The introduction of sulfate groups into the structure of arabinogalactan was confirmed by the appearance in the Raman spectra of new absorption bands related to the deformation vibrations δ (SO₃) at 420 cm^–1 and δ (О=S=O) at 588 cm^–1, stretching vibrations ν (C–O–S) at 822 cm^–1, symmetrical stretching vibrations ν_s (O=S=O) at 1076 cm^–1, and asymmetric stretching vibrations of ν_as (O=S=O) at 1269 cm^–1. According to the XRD data, the amorphization of arabinogalactan structure occurs during the sulfation process. The SEM method revealed a significant difference in the morphology of the sulfated and starting arabinogalactan. The starting AG consists of particles of predominantly globular shape with a size of 10 to 90 μm; arabinogalactan sulfates, of particles of various shapes with sizes of 1–8 μm. According to the AFM, the surface of sulfated arabinogalactan film consists of rather homogeneous spherical particles about 70 nm in size. The root-mean-square value of the surface roughness is 33 nm. The surface of sulfated AG film does not contain impurities.     

Cells resistant to toxic concentrations of manganese have increased ability to repair DNA

Manganese (Mn) is crucially important for vital activity of cells and has many biological functions. Nevertheless, high doses of Mn taken up by an organism over a long period may cause neurodegenerative diseases such as manganism and Parkinsonism. The molecular mechanisms of this Mn toxicity are still poorly studied. It is now believed that Mn-induced pathophysiological neural processes are multifaceted and affect several metabolic pathways. In particular, Mn ions might affect the processes of DNA replication and repair. To test this possibility, we obtained an SKOV-3 cell line resistant to the toxic action of Mn ions. We found that these cells are characterized by the activation of poly(ADP-ribose)polymerase, which leads to increased ability to repair DNA. Thus, the model used here supports the suggestion that at least one cause of Mn cytotoxicity might be disorders of the processes involved in DNA replication and repair.     

Multifractal analysis of K+ channel activity

The Multifractal version of the Detrended Fluctuation Analysis was used for the study of non-stationary dwell time series of Ca²⁺-activated K⁺ channels (K_Ca channels) in cultured kidney Vero cells and of voltage-dependent K⁺ channels (K_v channels) in mollusc (Lymnaea stagnalis) neurons. The data obtained can briefly be summarized as follows: (i) The generalized fluctuation function F _q (l) strongly depends on the index (order) q; for monofractal time series, such dependence is nonexistent; (ii) The relationship between the scaling exponent τ commonly employed in standard multifractal analysis and q is characterized by two slopes and a transitory region, whereas monofractal processes are characterized by the linear dependence; (iii) The relationship between the singularity spectrum f(h) and the Hurst exponent h is bell-shaped, while in the case of monofractal processes it is represented by a single point f(h) = 1. Random mixing of the time series resulted in the narrowing of the spectrum f(h) and a shift of f(h) towards the value more characteristic of stochastic (monofractal) processes (h ～ 0.5). It is concluded that the activities of both K_Ca channels in kidney Vero cells and of K_V channels in mollusc (Lymnaea stagnalis) neurons can be characterized as multifractal processes.     

The genetic-demographic approach in anthropological research. X. The dynamics of the sex-age structure of Khakass populations]

Social-economic remakings in Siberia are reflected in the economy of a rural inhabitant and the sex-age structure of the Khakass populations. The age average of the population increased from 26.7 years in 1954 up to 31.2 years in 1980. It has been established that the effectively reproductive size of a population (Ne) which takes into account its historical extent serves as a satisfactory estimate of the veritable (not single, instantaneous) size of a population.     

A genetic-demographic approach in anthropological research. VI. The methodological aspects of collecting, storing and analyzing large blocks of genealogical and biodemographic data

A new method of collection and presentation of the genealogical data in nontraditional (nongraphic) way is proposed. The collection of genealogical data within a population is organized through the family lists presented in perforated cards. The quick and correct identification of any population member realizes by colour tab indexes. The principles of arrangement and algorithms of organization of population tab card system are described.     

The genetic-demographic approach in anthropological research. XI. The structure of the reproductive behavior of Khakass families]

A detailed analysis of chronological intervals typical of reproduction process has been carried out in rural Khakassian populations to reveal the mechanisms of natural selection and gene drift. It is shown that the process of reproduction is connected with cultural traditions and economical activity of a population under study. The main characteristics of reproductive family behavior (the whole number of children and sex ratio, birth interval ect.) play a very important role in family and kin relationships, age, sex and marriage-migration structure of the population.