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General Physiology and Biophysics


Volume 30, 2011, No. 2

Content:


  Effect of hypertension and its reverse on serum nitric oxide concentration and vascular permeability in two-kidney one-clip hypertensive rats
Majid Khazaei 1), Mohammad Zarei, Mohammad Sharifi, Ali Pourshanazari

1)Department of Physiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Khazaei@med.mui.ac.ir.


The aim of this study was to evaluate the effect of hypertension and its reverse on serum nitric oxide (NO) concentration and endothelial permeability in two-kidney one-clip (2K1C) hypertensive rats. 28 male Wistar rats were divided into four groups: 1) 2K1C for 12 weeks; 2) sham-clipped for 12 weeks; 3) 2K1C for 12 weeks and unclipped for 12 weeks; 4) sham-clipped for 12 weeks and unclipped for 12 weeks. Blood samples were taken before experiment, 12th week and 24th week (in groups 3 and 4). Coronary vascular and aortic endothelial permeability were determined by extravasation of Evans blue dye method. Serum NO level was significantly lower in hypertensive group compare with sham group (4.21 ± 1.28 vs. 9.47 ± 1.34 µmol/l, respectively). Reversal of hypertension did not improve serum NO concentration in 2K1C group (4.21 ± 1.28 vs. 4.32 ± 1.34 µmol/l). Coronary vascular and aortic endothelial permeability were not different between hypertensive and normotensive groups and reversal of hypertension did not alter endothelial permeability. Lower serum NO concentration in 2K1C hypertensive rats even after reversal of hypertension suggested that in addition to NO, other mechanisms could be involved in surgical reversal of hypertension. Hypertension and its reverse did not change endothelial permeability at least in this model of hypertension.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 115-120.

 
  Temperature behaviour of viscous flow with proteins
Karol Monkos 1)

1)Department of Biophysics, Medical University of Silesia, H. Jordana 19, 41-808 Zabrze 8, Poland. monkos@sum.edu.pl.


The paper presents the results of viscosity determinations on aqueous solutions of different mammalian serum albumins at a wide range of concentrations and at temperatures ranging from 278 K to 318 K. On the basis of these measurements and a modified Arrhenius equation, the functional dependence of the solution activation energy of viscous flow on temperature was established. The analysis of the results obtained shows that the activation energy decreases with increasing temperature according to a square function for solutions, water molecules, and the albumins studied. The rate at which the activation energy decreases with increasing temperature is different for each albumin and mainly depends on its hydrodynamic radius.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 121-129.

 
  Langevin Poisson-Boltzmann equation: point-like ions and water dipoles near a charged surface
Ekaterina Gongadze 1), Ursula van Rienen, Veronika Kralj-Iglič, Aleš Iglič

1)Institute of General Electrical Engineering, University of Rostock, Justus-von-Liebig Weg 2, D-18059 Rostock, Germany.


Water ordering near a charged membrane surface is important for many biological processes such as binding of ligands to a membrane or transport of ions across it. In this work, the mean-field Poisson-Boltzmann theory for point-like ions, describing an electrolyte solution in contact with a planar charged surface, is modified by including the orientational ordering of water. Water molecules are considered as Langevin dipoles, while the number density of water is assumed to be constant everywhere in the electrolyte solution. It is shown that the dielectric permittivity of an electrolyte close to a charged surface is decreased due to the increased orientational ordering of water dipoles. The dielectric permittivity close to the charged surface is additionally decreased due to the finite size of ions and dipoles.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 130-137.

 
  The effects of β-glucan on iron levels and lipid peroxidation in intra-abdominal sepsis in rats
Semra Ozdemir 1), Selmin Toplan, Gamze Tanriverdi, Oguzhan Sunamak

1)Department of Biophysics, Cerrahpasa Medical Faculty, Istanbul University, Kartaltepe mah. N. Sadak sok. Burak apt. No. 22/5, Bakirkoy/Istanbul, Turkey. hsf@istanbul.edu.tr.


Sepsis is defined as a systemic response of organisms to microorganisms and toxins. Sepsis is associated with the enhanced generation of reactive oxygen metabolites, leading to multiple organ dysfunctions. β-glucan is accepted to be one of the most powerful immune response modifiers. The aim of this study was to investigate the putative protective effect of β-glucan on changes of iron and malondialdehyde (MDA) levels in various tissue and blood after experimental sepsis in rats. Sepsis was induced by cecal ligation and perforation (CLP) in 32 male Wistar albino rat. To evaluate this, rats were divided into four groups as sham operated, β-glucan treated sham operated, CLP and β-glucan treated CLP. Sixteen hours after operation, rats were decapitated and MDA and iron levels were measured in the liver, kidney, heart, diaphragm tissues and blood. Also, whole tissue histopathology was evaluated by a light microscope. The results demonstrate that sepsis significantly decreased iron levels of all tissues and blood. The decrease in tissue iron levels and the increase MDA levels demonstrate the role of trace elements and free radicals in sepsis-induced tissue damage. Our results indicate that the given dose of β-glucan was probably insufficient to prevent sepsis-induced organ injury.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 138-144.

 
  Specific volume and compressibility of bilayer lipid membranes with incorporated Na,K-ATPase
Tibor Hianik 1), Peter Rybár, Roland Krivánek, Mária Petríková, Milena Roudna, Hans Apell

1)Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynska dolina F1, 842 48 Bratislava, Slovakia. tibor.hianik@fmph.uniba.sk.


Ultrasound velocimetry and densitometry methods were used to study the interactions of the Na,K-ATPase with the lipid bilayer in large unilamellar liposomes composed of dioleoyl phosphatidylcholine (DOPC). The ultrasound velocity increased and the specific volume of the phospholipids decreased with increasing concentrations of protein. These experiments allowed us to determine the reduced specific apparent compressibility of the lipid bilayer, which decreased by approx. 11% with increasing concentrations of the Na,K-ATPase up to an ATPase/DOPC molar ratio = 2 × 10⁻⁴. Assuming that ATPase induces rigidization of the surrounding lipid molecules one can obtain from the compressibility data that 3.7 to 100 times more lipid molecules are affected by the protein in comparison with annular lipids. However, this is in contradiction with the current theories of the phase transitions in lipid bilayers. It is suggested that another physical mechanisms should be involved for explanation of observed effect.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 145-153.

 
  The influence of protein coding sequences on protein folding rates of all-β proteins
Rui Li 1), Hong Li

1)School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China. ndlihong@imu.edu.cn.


It is currently believed that the protein folding rate is related to the protein structures and its amino acid sequence. However, few studies have been done on the problem that whether the protein folding rate is influenced by its corresponding mRNA sequence. In this paper, we analyzed the possible relationship between the protein folding rates and the corresponding mRNA sequences. The content of guanine and cytosine (GC content) of palindromes in protein coding sequence was introduced as a new parameter and added in the Gromiha’s model of predicting protein folding rates to inspect its effect in protein folding process. The multiple linear regression analysis and jack-knife test show that the new parameter is significant. The linear correlation coefficient between the experimental and the predicted values of the protein folding rates increased significantly from 0.96 to 0.99, and the population variance decreased from 0.50 to 0.24 compared with Gromiha’s results. The results show that the GC content of palindromes in the corresponding protein coding sequence really influences the protein folding rate. Further analysis indicates that this kind of effect mostly comes from the synonymous codon usage and from the information of palindrome structure itself, but not from the translation information from codons to amino acids.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 154-161.

 
  Relationship between extracellular osmolarity, NaCl concentration and cell volume in rat glioma cells
Béatrice Rouzaire-Dubois 1), Gilles Ouanounou, Jean Dubois

1)Laboratoire de Neurobiologie Cellulaire et Moléculaire-FRE 3295, CNRS, Institut de Neurobiologie Alfred Fessard-FRC2118, Gif sur Yvette, F-91198, France. beatrice.rouzaire-dubois@nbcm.cnrs-gif.fr.


The cell volume, which controls numerous cellular functions, is theoretically linearly related with the inverse osmolarity. However, deviations from this law have often been observed. In order to clarify the origin of these deviations we electronically measured the mean cell volume of rat glioma cells under three different experimental conditions, namely: at different osmolarities and constant NaCl concentration; at different NaCl concentrations and constant osmolarity and at different osmolarities caused by changes in NaCl concentration. In each condition, the osmolarity was maintained constant or changed with NaCl or mannitol. We showed that the cell volume was dependent on both the extracellular osmolarity and the NaCl concentration. The relationship between cell volume, osmolarity and NaCl concentration could be described by a new equation that is the product of the Boyle-van’t Hoff law and the Michaelis-Menten equation at a power of 4. Together, these results suggest that in hyponatriemia, the cell volume deviates from the Boyle-van’t Hoff law because either the activity of aquaporin 1, expressed in glioma cells, is decreased or the reduced NaCl influx decreases the osmotically obliged influx of water.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 162-166.

 
  Stimulatory effect of 17β-estradiol on osteogenic differentiation potential of rat adipose tissue-derived stem cells
Dilek Taskiran 1), Vedat Evren

1)Department of Physiology, Ege University School of Medicine, Bornova-Izmir, Turkey. dilek.taskiran@ege.edu.tr.


Adipose tissue-derived stem cells (ADSCs) are considered as a potential cell source for regenerative medicine and tissue engineering. Although ADSCs have greater proliferation capacity than bone marrow stem cells (BMSCs), lower differentiation ability of these cells limits their utility in experimental and clinical studies. The purpose of this study was to investigate whether 17β-estradiol (E2) has a stimulatory effect on osteogenic differentiation potential of ADSCs in vitro. ADSCs were isolated from visceral adipose tissues of rats and treated with different concentrations of E2 in osteogenic medium (OM) for 21 days. The differences in osteogenic differentiation potential of the cultures were assessed by von Kossa staining, measurement of alkaline phosphatase (ALP) activity and calcium levels. ADSCs cultured in OM supplemented with E2 showed greater bone-like nodule formation and mineral deposition in comparing with the cells grown in OM. In addition, ALP activity and calcium levels also were significantly higher in the cultures exposed to E2 than the cells treated only with OM (p < 0.005, n = 5). Our results suggest that E2 may stimulate the osteogenic differentiation of ADSCs and therefore, can be used as an inducing agent to improve the efficiency of these cells in in vitro and in vivo studies.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 167-174.

 
  Microscopic second harmonic generation (SHG) from tilt-placed collagen fibrils
Ying Chang 1), Huajiang Wei, Ying Jin, Hanping Liu, Xiaoyuan Deng

1)MOE Key Laboratory of Laser Life Science, South China Normal University, Guangzhou 510631, China. yingchang_1984@yahoo.cn.


We report a theoretical study of second-harmonic generation (SHG) from the collagen fibrils which have a tilt angle Φ between their axes with the plane of the polarization angle α of the linearly polarized focused light. The effects of Φ as well as α on SHG emission have been investigated. Our results show that the total strength of SHG electrical field (E) and power (P) reach their maximal values as Φ locates at a certain angle, here it is around 27° under all demonstrated α. When Φ < 27°, E and P gradually increase to their maximal value, while when Φ > 27°, they quickly drops. Specially, E and P are almost undetectable when Φ ≥ 45°. Also, Φ influences the distribution pattern of E, P and their parallel (E2ω,p, P2ω,p) and perpendicular (E2ω,s, P2ω,s) components, such as the number of emission lobes and shape. α has unevenly impact on E and P, the far deviation of α from x axis induce much great decrease of E and P. α = 45° has special influence on the distribution pattern of E2ω,s, E, P2ω,s as well as P compared to those of α = 0° and 90°.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 175-185.

 
  Estimation of thickness of concentration boundary layers by osmotic volume flux determination
Jolanta Jasik-Ślęzak 1), Kornelia Olszówka, Andrzej Ślęzak

1)Department of Public Health, Częstochowa University of Technology, Armia Krajowa al. 36b, 42 200 Częstochowa, Poland. ajslezak@zim.pcz.pl.


The estimation method of the concentration boundary layers thicknesses (δ) in a single-membrane system containing non-electrolytic binary or ternary solutions was devised using the Kedem-Katchalsky formalism. A square equation used in this method contains membrane transport (Lp, σ, ω) and solution (D, C) parameters as well as a volume osmotic flux (Jv). These values can be determined in a series of independent experiments. Calculated values δ are nonlinearly dependent on the concentrations of investigated solutions and the membrane system configuration. These nonlinearities are the effect of a competition between spontaneously occurring diffusion and natural convection. The mathematical model based on Kedem-Katchalsky equations and a concentration Rayleigh number (RC) was presented. On the basis of this model we introduce the dimensionless parameter, called by us a Katchalsky number (Ka), modifies RC of membrane transport. The critical value of this number well describes a moment of transition from the state of diffusion into convective diffusion membrane transport.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 186-195.

 
  Chemically mimicked hypoxia modulates gene expression and protein levels of the sodium calcium exchanger in HEK 293 cell line via HIF-1α
Sona Hudecova 1), Lubomira Lencesova, Lucia Csaderova, Marta Sirova, Dana Cholujova, Martin Cagala, Juraj Kopacek, Dušan Dobrota, Silvia Pastorekova, Olga Krizanova

1)Institute of Molecular Physiology and Genetics, Center of Excellence for Cardiovascular Research, Slovak Academy of Sciences, Vlarska 5, 833 34 Bratislava, Slovak Republic. olga.krizanova@savba.sk.


Up to now a little is known about the effect of hypoxia on the sodium calcium exchanger type 1 (NCX1) expression and function. Therefore, we studied how dimethyloxallyl glycine (DMOG), an activator and stabilizer of the hypoxia-inducible factor (HIF)-1α, could affect expression of the NCX1 in HEK 293 cell line. We also tried to determine whether this activation can result in the induction of apoptosis in HEK 293 cells. We have found that DMOG treatment for 3 hours significantly increased gene expression and also protein levels of the NCX1. This increase was accompanied by a decrease in intracellular pH. Wash-out of DMOG did not result in reduction of the NCX1 mRNA and protein to original – control levels, although pH returned to physiological values. Using luciferase reporter assay we observed increase in the NCX1 promoter activity after DMOG treatment and using wild-type mouse embryonic fibroblast (MEF)-HIF-1+/+ and HIF-1-deficient MEF-HIF-1–/– cells we have clearly shown that in the promoter region, HIF-1α is involved in DMOG induced upregulation of the NCX1. Moreover, we also showed that an increase in the NCX1 mRNA due to the apoptosis induction is not regulated by HIF-1α.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 196-206.

 
  Red wine polyphenols correct vascular function injured by chronic carbon tetrachloride intoxication
Soňa Čačányiová 1), Oľga Pecháňová, Pavel Babál, Andrea Černá, Pavol Janega, Ramaroson Andriantsitohaina

1)Institute of Normal and Pathological Physiology, Centre of Excellence for Cardiovascular Research, Centre of Experimental Medicine, Sienkiewiczova 1, 813 71 Bratislava, Slovak Republic. Sona.cacanyiova@savba.sk.


The aim of the study was to evaluate the effect of red wine polyphenols extract Provinols™ on the development of cardiovascular injury in the model of carbon tetrachloride (CCl4) intoxication. We followed the thoracic aorta vasoactivity and left ventricle nitric oxide (NO) synthase activity in male Wistar rats. In the preventive experiment lasting for 12 weeks the control group, the group receiving CCl4 (0.5 ml/kg) two times a week subcutaneously, the group receiving Provinols™ (30 mg/kg/day) in drinking water and the group receiving CCl4+Provinols™ was used. In the recovery experiment, the initial 12 weeks of CCl4 treatment were followed by 3 weeks of spontaneous recovery or recovery with Provinols™. CCl4-intoxication resulted in the injury of vasoactivity which was demonstrated by the inhibition of acetylcholine-induced relaxation as well as noradrenaline-induced contraction. In the preventive as well as recovery experiment administration of polyphenols refreshed endothelium-dependent relaxant response and normalized inhibited contraction to adrenergic stimuli. Provinols™ treatment significantly increased NO-synthase activity in all groups. The results revealed beneficial effects of red wine polyphenols on vascular function injured by chronic CCl4 intoxication. The correction of endothelial function seems to be attributed to the activation of NO pathway by polyphenols.

General Physiology and Biophysics. Volume 30, 2011, No. 2: 207-213.