Vol. 1 No. 3 September 1996

Volume 1 (1996) pp 213-224
Title TRANSPORT THROUGH PORES IN PETP MEMBRANES - A MODEL FOR BIOLOGICAL SYSTEMS?
Authors C. L. Bashford
Abstract Movement of ions, water and non-electrolytes has been measured through narrow pores etched in polyethyleneterephthalate (PETP) membranes previously "tracked" by bombardment with heavy ions. Pore size estimated from flow of water, ions and non-electrolytes is in reasonable agreement with that obtained by a polymer exclusion assay. Flow of ions through narrow pores exhibits characteristic features: i) rapid switching between high- and low- conducting states; ii) selectivity between different ions; iii) inhibition by protons or divalent cations with order of efficacy H+>Zn2+>Ca2+> Mg2+. Ion current and selectivity are reduced when the carboxyl groups lining the pore are methylated. The characteristic features of ion flow in narrow pores arise from the nature of the flow of ions close to a surface bearing fixed charges of the opposite sign.
Address and Contact Information Department of Cellular and Molecular Sciences, Division of Biochemistry, St. George's Hospital Medical School, Cranmer Terrace , London, SW 17 ORE, UK
E-mail: l.bashford@sghms.ac.uk Tel: (+44 181) 725 58 07
[Rozmiar: 1332 bajtów]

Volume 1 (1996) pp 225-143
Title PREPARATION OF NEURONAL NETS FOR VISUALIZATION
Authors M.J. Katkowska
Abstract There is a great variety of techniques for complete neurone visualization currently available. Each of them has some advantages and disadvantages. The selection one of them depends upon the requirements of the situation. One of the most useful techniques for observing individual neurones has bee the Golgi method with its variations. This method has been extended from the light microscopic to the ultrastructural level. The correlation of the neural structure and function was advanced with the technique of intracellular injection of the fluorescent dues. Investigations of the cross-correlations between morphology, electrophysiology and immunohistochemistry of neurones have significantly advanced current knowledge of the complex organization of at least some parts of the nervous system. Some crucial parameters including the selection of the dyes, the injection technique and tissue processing as well as the appropriate immunohistochemical fluorescent markers are discussed. Cell reconstruction techniques also are monitored.
Address and Contact Information Department of Animal Physiology, Institute of Biology and Environmental Protection, N. Copernicus University, 87-100 Torun, POLAND
E-mail: katkow@biol.uni.torun.pl Tel: (+48 56) 14 451 Fax: (+4856) 14 478
[Rozmiar: 1332 bajtów]

Volume 1 (1996) pp 245-257
Title INVOLVEMENT OF INTERFACIAL INSTABILITY IN MORPHOLOGICAL CHANGES OF SOME MEMBRANE-BOUND BODIES
Authors W.T.Coakley
Abstract Systems consisting of single membranes or of interacting membranes with an intervening aqueous layer can be modelled as interfacial regions. Treatments of the stability of thin fluid films against bending and squeezing waves give guidance on the behaviour of such regions. Evidence of bending wave instability on erythrocyte membranes when the spectrin component of the membrane skeleton is denatured is presented. There are two alternative outcomes of such instability. In one case a regular surface wave grows on the rim of the erythrocyte at rates of the order of 3 s-1 and vesicles pinch from the wave crests. In the second outcome the cell rounds up and the membrane partially internalises a discoid volume of suspending phase. The rim of that volume becomes unstable and sends vesicles into the cell. The outcome (internalisation or externalisation of membrane) can be controlled experimentally by altering the surface charge or the transmembrane potential or by exposure to amphiphilic drugs. When two interacting membranes of normal erythrocytes at room temperature adhere in the presence of adhesion-inducing polymers or of lectins two distinct adhesion outcomes are also possible. In the case parallel membranes form a continuous seam. In the second outcome localised regions of close contact formed at regular intervals along the membrane surface are separated by regions of larder normal separation. The characteristic lateral spacing of contact regions changes with different modifiers of the membrane interaction profile in a manner consistent with interfacial instability theory.
Address and Contact Information School of Pure and Applied Biology, University of Wales Cardiff, CF1 3TL, UK
E-mail: sabwtc@cardiff.ac.uk Tel: (+44 1222) 87 42 87 Fax: (+441222) 87 43 05
[Rozmiar: 1332 bajtów]

Volume 1 (1996) pp 259-271
Title FRACTAL ANALYSIS OF DENDRITIC TREE OF TRANSIENT AMACRINE CELL OF GOLD FISH RETINA VERSUS DIFFUSION LIMITED AGGREGATE (DLA)
Authors M.B.A.Djamgoz1, Z.J.Grzywna2*, M.Krasowska2, and S.Vallerga3,4
Abstract Three different methods i.e. IRRM (increasing radius and rings method), BCM (box counting method) and IAM (increasing angle method) have been used in fractal analysis of both, dendritic tree of transient amacrine cell of gold fish retina, and the DLA of the same mass. Advantages and drawbacks of the methods have been listed and analysed. The studies have shown that different methods covered different aspects of the complex nature of investigated sets, especially if they are spatially oriented. Some biophysical interpretation of different fractal dimensions of amacrine dendritic tree and comparison with DLA have been shown. It has also been postulated that DLA could be homeomorphic with the amacrine tree of the same mass.
Address and Contact Information 1Imperial College of Science, Technology and Medicine, Department of Biology, Neurobiology Group, London SW7 2BB, UK
2Silesian Technical University, Department of Physical and Polymer Chemistry, M. Strzody 9, 44-100 Gliwice, POLAND
3Instituto di Cibernetica e Biofisica del Cosiglio Nazionale delle Recherche, 16146 Genova, ITALY
4International Marine Centre, 09072 Oristano, ITALY
[Rozmiar: 1332 bajtów]

Volume 1 (1996) pp 273-289
Title DIFFUSION-REACTION APPROACH APPLIED TO THE IONIC WAVE PROPAGATION THROUGH BIOMEMBRANE CHANNELS
Authors A. Gadomski
Abstract A one-dimensional diffusion-reaction equation for the probability of finding of a random walker (ion) in a space-time domain (protein channel) is proposed to a model the process of ionic wave propagation through membranes. The diffusion process stands here for a kind of kinetic hindrance or perturbation because it is assumed to be very slow. The chemical reaction, in turn, proceeds in an usual way rather, but is presumed to be considered in the fractal-like chemical reaction kinetics regime. The damped pendulum theory is effectively applied to get the solution to the problem studied. This solution has been found to reflect the Kohlrausch-Williams-Watts behaviour characteristic of the slow relaxation kinetics, e.g. in spin glasses or fragile liquids. As a quite specific result, the Weibull function stated in the work of Liebovitch and Sullivan, and describing the channel kinetics in cultured mouse hippocampal neurones has been gained.
Address and Contact Information Department of Theoretical Physics, Technical University for Technology and Agriculture, Kaliskiego Street 7, Building 2.7, 85796 Bydgoszcz, POLAND
E-mail: agad@mail.atr.bydgoszcz.pl Tel: (+48 52) 43 86 43 Fax: (+48 52) 43 86 16
[Rozmiar: 1332 bajtów]

Volume 1 (1996) pp 291-301
Title ON THE CROWD MODELS FOR THE PATCH-CLAMP DATA
Authors Z.J.Grzywna1*, Z. Siwy1** and C.L.Bashford2***
Abstract Patch clamp data of PETP track-etched membranes have been analysed by the crowd model based on three i.e. regular, exponential and delayed maps of the logistic family. The same data were worked out for all equations, indicating expressive difference between theoretical predictions of the models with constant coefficients and experimental data. The differences disappeared for suitably chosen time dependent coefficients. Some possibilities of relating the functional forms of the logistic coefficients to the "dynamical structure" of a membrane as well as "the memory" of a system have also been discussed.
Address and Contact Information 1Department of Physical Chemistry and Technology of Polymers, Silesian Technical University, Strzody 9, 44-100 Gliwice, POLAND
2Department of Cellular and Molecular Sciences, St. George's Hospital Medical School, University of London, Cranmer Terrace, SW17 ORE, UK
* E-mail: grzywna@zeus.polsl.gliwice.pl Tel. and fax: (+48 32) 37 17 22
** E-mail: siwy@zeus.polsl.gliwice.pl Tel. and fax: (+48 32) 37 17 22
*** E-mail: sgbc360@sghms.ac.uk Tel: (+44) 181 725 58 07 Fax: (+44) 181 725 29 92
[Rozmiar: 1332 bajtów]

Volume 1 (1996) pp 303-309
Title THE MEASUREMENT OF LUMINANCE OF LIGHT REFLECTED FROM THE HUMAN IRIS
Authors T. Kleszczewski *, A.Swiecicki and A.Kostrzewska
Abstract The authors developed a method of measuring the light luminance reflected from the human iris. The distribution of white and monochromatic light luminance reflected from the iris was measured in a group of people. The image of the iris was obtained by means of a slit lamp equipped with its own light source and a built-in video camera. The eye was illuminated by white and monochromatic light with the wavelenght of 486, 551, 589 and 656 nm. Experiments were conducted with the exclusion of all other light sources. The obtained image was saved in a computer by means of a Video Blaster FS 200 video card in a file with bmp extension. An original computer program has been written to calculate the luminance value for particular parts of the image.
Address and Contact Information Department of Biophysics Medical School, Mickiewicza 2A, 15-230 Bialystok, POLAND
* Corresponding author: E-mail: kleszczt@cksr.ac.bialystok.pl Tel: (+48 85) 424 797
[Rozmiar: 1332 bajtów]

Volume 1 (1996) pp 311-324
Title RATCHETS, MOLECULAR MOTORS, AND NOISE-INDUCED TRANSPORT
Authors J.Luczka
Abstract The Feynman ratchet and pawl machine is presented to illustrate some implications of the Second Law of thermodynamics and to demonstrate how the useful work can be extracted from fluctuations. Molecular motors moving along microtubules and responsible for transporting vesicles, organelles and other substances in cells are described in terms of Brownian ratchets driven by nonequilibrium fluctuations of the ATP cycles. Models of non-thermal fluctuations are presented and used for showing the noise-induced transport phenomena in spatially periodic structures.
Address and Contact Information Department of Theoretical Physics, Silesian University, 40-007 Katowice, POLAND
E-mail: luczka@us.edu.pl Tel. and fax (+48 32) 588 431
[Rozmiar: 1332 bajtów]

Volume 1 (1996) pp 325-336
Title VOLTAGE ACTIVATED ION CHANNELS FORMED BY A SYNTHETIC ALPHA HELICAL PEPTIDE:-DETERMINATION OF CHANNEL STOICHIOMETRY AND MOLECULAR MODELLING OF PEPTIDE CONFORMATION
Authors I.R.Mellor1*, I.D.Kerr2, M.S.P.Sansom2, M.Sukumar3 and P.Balaram3
Abstract We designed and synthesised an 18 residue peptide (MS 18) similar to the channel forming fungal antibiotic alamethicin. MS 18 formed ion channels in lipid bilayers exhibiting a low discrete conductance level of 55 pS and brief openings to many other conductance levels. Channel formation was markedly depended on transbilayer voltage with macroscopic conductance increasing exponentially beyond an activation voltage. The activation voltage was higher for lower concentrations of peptide. The relationship between conductance, voltage and peptide concentration was used to calculate the mean number of peptide monomers forming the MS 18 channel. This gave an estimate of 4 MS 18 monomers per channel. Molecular modelling of MS 18 revealed a predominantly alpha-helical structure.
Address and Contact Information 1Department of Life Sciences, University of Notthingham, University Park, Nottingham, NG7 2RD, UK.
2Laboratory of Molecular Biophysics, University of Oxford, The Rex Richard's Building, South Parks Road, Oxford, OX 3QU, UK
3Molecular Biophysics Unit, Indian Institute of Science 560 012, India
* Corresponding author
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Volume 1 (1996) pp 337-351
Title VOLTAGE-GATED POTASSIUM CHANNELS IN T LYMPHOCYTES-PHYSIOLOGICAL ROLE AND CHANGES IN CHANNEL EXPRESSION IN DISEASES
Authors A. Teisseyre
Abstract Voltage-gated potassium channels (KV) are predominating and most widely studied ion channels in T lymphocytes (TL). Patch-clamp studies provide evidence that three different types of KV channels, termed n, n' and l, are present in human and in mouse TL. This review focuses on: 1) studies on biophysical properties of the three channel types, 2) role of KV channels in TL cell function. Available data demonstrate that the activity of KV channels in TL is required for: i. setting the Tl resting membrane potential, ii. cell mitogenesis, iii. volume regulation. Blockade of KV channels effectively blocks both mitogenesis and volume regulation of T cells, 3) changes of KV channel expression in diseases. Results of patch-clamp studies provide evidence that expression of TL KV channels is significantly altered in autoimmune diseases and in chronic renal failure. Autoimmune diseases are linked to an abnormally high expression of the l type KV channels, which arises in parallel with the onset of autoimmunity, in mouse double- negative (DN-CD4-CD8-) TL. In chronic renal failure, a significant increase in the whole-cell potassium conductance (gKV), probably also due to altered channel expression, appears in human TL. The rise in the gKV value parallels the onset of the disease. Moreover, long-term therapy of uremic patients with recombinant human Erythropoietin is linked to a significant desrease in the gKV value towards the level of control TL. Altogether, the data demonstrate that patch-clamp studies on the KV channels may provide a valuable tool delineating the role of the channels in TL cell-function and the pathogenesis of the diseases.
Address and Contact Information Department of Biophysics, Wroclaw University of Medicine, Chalubinskiego 10, 50-368 Wroclaw, Poland
[Rozmiar: 1332 bajtów]