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General Physiology and Biophysics


Volume 27, 2008, No. 3

Content:


  RAGE upregulation and nuclear factor-κB activation associated with ageing rat cardiomyocyte dysfunction
Z. Gao 1), C. Yang, Y. Wang, P. Wang, H. Chen, X. Zhang, R. Liu, W. Li, X. Qin, X. Liang, C. Hai

1)Department of Toxicology, The Fourth Military Medical University, Xi'an 710032, China. cx-hai@fmmu.edu.cn.


Evidence suggests that ageing is a major risk factor for cardiac dysfunction. Interactions between advanced glycation endproducts (AGEs) and the receptor for AGEs (RAGE) are known to cause chronic cellular activation, including activation of nuclear factor-κB (NF-κB), which has been implicated as a causal factor in the ageing process. To assess whether cardiomyocyte contractile function and the interaction of AGEs with RAGE in the heart are altered in ageing, 25- and 2-month-old male rats were compared. Mechanical properties were assessed in ventricular myocytes using an edge-detection system, including peak twitch amplitude (PTA), time-to-PTA (TPS), time-to-75% relengthening (TR75) and maximal velocity of shortening/relengthening (±dL/dt) in ventricular myocytes. AGEs were detected by using a fluorescence assay. The expression of RAGE and NF-κB was assessed through a Western blot analysis. Compared with young myocytes, aged myocytes displayed a prolonged TR75 at 1 Hz. With increasing stimulus frequency (from 2 to 4 Hz), aged myocytes' PTA was significantly reduced relative to young myocytes. Aged rat hearts displayed high level of AGEs, RAGE upregulation and NF-κB activation. These findings demonstrate impaired cardiomyocyte relaxation and reduced tolerance to increased stimulus frequency in aged rats, which might be associated with enhanced AGEs, RAGE expression, and NF-κB activation.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 152-158.

 
  Multiple treatments with SRIH-14 or octreotide affect adrenal zona glomerulosa in adult male rats
S. Trifunović 1), V. Ajdžanović, B. Šošić-Jurjević, B. Filipović, N. Nestorović, M. Sekulić, V. Milosević

1)Institute for Biological Research ", Siniša Stanković", Bulevar Despota Stefana 142, 11060 Belgrade, Serbia. lanat@ibiss.bg.ac.yu.


Somatostatin analogues are currently used to treat various disorders such as hypersecretion and different neuroendocrine tumors. In this study we examined the effects on the adrenal cortex of somatostatin (SRIH-14) and octreotide administered subcutaneously twice daily for 5 days to adult male rats. Control rats received saline under the same regime. After sacrifice, the adrenal glands were removed and examined morphometrically using the M42 multipurpose test system. Blood samples were prepared for biochemical tests. Both SRIH-14 and octreotide induced morphofunctional changes in adrenal zona glomerulosa. We found significant decreases (p < 0.05) in the absolute cell and nuclear volumes of zona glomerulosa in both experimental groups in comparison to the control. The serum aldosterone level was 11% lower (p < 0.05) in the SRIH-14 and 13% (p < 0.05) lower in the octreotide-treated group in comparison with the control group. Morphometric parameters of zona fasciculata and zona reticulata and corticosterone levels were not altered significantly (p > 0.05) in either treated group. It may therefore be concluded that both SRIH-14 and octreotide affected zona glomerulosa in the same manner by decreasing morphofunctional characteristics.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 159-163.

 
  In vitro labelling of mouse embryonic stem cells with SPIO nanoparticles
J. Krejčí 1), J. Pacherník, A. Hampl, P. Dvořák

1)Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Královopolská 135, 612 65 Brno, Czech Republic. krejci@ibp.cz.


Labelling of mammalian cells with superparamagnetic iron oxide (SPIO) nanoparticles enables to monitor their fate in vivo using magnetic resonance imaging (MRI). However, the question remains whether or not SPIO nanoparticles affect the phenotype of labelled cells. In the present study, the effects of SPIO nanoparticles from two producers on the growth and differentiation of mouse embryonic stem (ES) cells in vitro were investigated. Our observations have shown that SPIO nanoparticles have no effect on the self-renewal of ES cells. Subsequently, we studied the effect of SPIO on the formation of embryoid bodies and neural differentiation of ES cell in monolayer culture. The cavitation of embryoid bodies was partially inhibited and neural differentiation was supported regardless the type of SPIO nanoparticles used. Thus for the first time we documented the effects of SPIO nanoparticles on ES cells and their differentiation.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 164-173.

 
  Transient outward potassium current in rabbit atrium is depressed after short-time rapid atrial pacing but recovers after a longer pacing period
R. Laszlo 1), C. Eick, M. Schwiebert, B. Schreiner, H. Weig, S. Weretka, J. Schreieck

1)Department of Cardiology, University of Tübingen, Otfried-Müller-Strasse 10, D-72076 Tübingen, Germany. roman.laszlo@med.uni-tuebingen.de.


In rabbit, after short-time rapid atrial pacing (RAP), atrial ion currents are reduced similarly as in human chronic atrial fibrillation (AF). Using the rabbit model, time-course of transient outward potassium current (Ito) remodeling due to RAP was studied. RAP (600 bpm) was applied via an atrial lead for 0 (control), 24 and 120 h, n = 4 animals/group. Using patch clamp technique in whole-cell mode, current densities and biophysical properties were measured in isolated atrial myocytes. After 24 h of RAP, a reduction of peak Ito (mean ± SEM, test potential +50 mV, +37°C) was observed (60.3 ± 5.4 pA/pF (control, n = 20) vs. 28.0 ± 2.5 pA/pF (24 h, n = 21)). Inactivation of Ito was slower after 24 h, other biophysical properties were unaltered. However, Ito recovered after 120 h: 51.7 ± 4.5 pA/pF (n = 26, p = n.s. vs. control). Inactivation tended to also recover to initial values but was still different to control. Early Ito remodeling due to RAP in rabbits seems to be more complex than previously thought: a time course of Ito remodeling with swayings has to be considered when using the rabbit model of RAP in order to study early remodeling or rather its therapeutic manipulation.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 174-178.

 
  Does rooibos tea (Aspalathus linearis) support regeneration of rat liver after intoxication by carbon tetrachloride?
O. Uličná 1), O. Vančová, I. Waczulíková, P. Božek, P. Janega, P. Babál, S. Líšková, M. Greksák

1)Laboratory of Pharmacobiochemistry, Third Department of Internal Medicine, Faculty of Medicine, Comenius University, Bratislava, Slovakia..


This study evaluates the effect of rooibos tea (RT, Aspalathus linearis) on biochemical and histological parameters during rat liver regeneration after intoxication by carbon tetrachloride (CCl4). From the 10th week, when the administration of CCl4 was terminated, the liver tissue began to regenerate. Seven days later in the regeneration phase, the animals treated by RT during whole period of the experiment, and those which drunk RT only during the regeneration period, exhibited a trend for decrease in the activity of alanine aminotransferase and significant decrease in the activity of aspartate aminotransferase and in total bilirubin content when compared with the water-drinking group. At the same time, the concentration of plasma albumin was elevated and that of tissue malondialdehyde decreased in the both groups drinking RT. After 42 days of regeneration, all biochemical parameters in all three groups reached the level of control healthy animals. In both groups treated with RT, the extent of fibrotic tissue was lower than in the group which received water. We conclude that RT can be recommended not only for the prevention but also as a co-adjuvant for the therapy of liver diseases.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 179-186.

 
  Uranyl acetate modulates gene expression and protein levels of the type 2, but not type 1 inositol 1,4,5-trisphosphate receptors in mouse kidney
K. Ondrias 1), M. Sirova, L. Kubovcakova, O. Krizanova

1)Institute of Molecular Physiology and Genetics, Centre of Excellence for Cardiovascular Research, Slovak Academy of Sciences, Bratislava, Slovakia. umfgkriz@savba.sk.


Nephrotoxic effect of uranium is already well documented. Nevertheless, little is known about the effect of uranium on calcium homeostasis and calcium transport systems. Calcium released from endoplasmic reticulum through special calcium release channels – inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs) – serves as a main source of cytosolic calcium signaling in the majority of cell types. To contribute to understanding mechanism of toxicity of the uranyl acetate (UA), we focused on modulation of the gene expression, protein levels and activity of IP3 receptor's intracellular calcium channels by UA in mouse kidney. We have found that UA did not affect mRNA and protein levels of the type 1 IP3Rs, but increased mRNA and also protein levels of the type 2 IP3 receptors in kidney. Nevertheless, IP3-induced calcium release was decreased by addition of UA. We assume that decreased activity of IP3 receptors due to the acute exposure to UA results in feedback, which triggers activation of IP3R2 expression. Thus, inhibition of calcium release and increased levels of the type 2 IP3 receptors might participate, at least partially, in UA-induced nephrotoxicity.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 187-193.

 
  Modelisation of the contribution of the Na/Ca exchanger to cell membrane potential and intracellular ion concentrations
S. Bahlouli 1), F. Hamdache, H. Riane

1)Laboratoire de Physique des Plasmas, Matériaux Conducteurs et leurs Applications, Département de Physique, USTO'MB, BP 1505, Al Menouer Oran, Algeria. ba_samia@hotmail.com.


Modelisation plays a significant role in the study of ion transfer through the cell membrane and in the comprehension of cellular excitability. We were interested in the selective ion transfers through the KCa, Nav, Cav channels and the Na/Ca exchanger (NCX). The membrane behaves like an electric circuit because of the existence of ion gradients maintained by the cell. The non-linearity of this circuit gives rise to complex oscillations of the membrane potential. By application of the finite difference method (FDM) and the concept of percolation we studied the role of the NCX in the regulation of the intracellular Ca2+ concentration and the oscillations of the membrane potential. The fractal representation of the distribution of active channels allows us to follow the diffusion of intracellular Ca2+ ions. These calculations show that the hyperpolarization and the change in the burst duration of the membrane potential are primarily due to the NCX.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 194-202.

 
  Short-term effects of thalidomide analogs on hepatic glycogen and nitric oxide in endotoxin-challenged rats
E. Fernández-Martínez 1), I. Wens-Flores, M. Moreno, M. Ortiz, P. Muriel, V. Pérez-Álvarez

1)Centro de Investigación en Biología de la Reproducción, Área Académica de Medicina, I.C.Sa.-Universidad Autónoma del Estado de Hidalgo, Hidalgo, Mexico. efernan@uaeh.reduaeh.mx.


Hepatic glycogen metabolism is altered by nitric oxide (NO) during endotoxic shock. Thalidomide analogs immunomodulate the endotoxin-induced cytokines which regulate the NO release. We analyzed the short-term effects of some thalidomide analogs on the hepatic glycogen store and on the plasma and hepatic NO in an acute model of endotoxic challenge in rat. An endotoxin dose selection was performed. Rats received vehicle, thalidomide or analogs orally and, two hours after last dose, they were injected with endotoxin (5 mg/kg). Animals were sacrificed 2 h after challenge. Liver glycogen was quantified by the anthrone technique. Plasma and hepatic NO was determined by Griess reagent and HPLC. Hepatic interferon-γ, a NO co-inducer, was measured by ELISA. Endotoxin caused inverse dose-dependent effects on plasma NO and on glycogen.Thalidomide analogs showed short-term regulatory effects on glycogen, some of them increased it. Plasma NO was almost unaffected by analogs but hepatic NO was strikingly modulated. Analogs slightly up-regulated the liver interferon-γ and two of them increased it significantly. Thalidomide analogs may be used as a pharmacological tool due to their short-term regulatory effects on glycogen and NO during endotoxic shock. Drugs that increase glycogen may improve liver injury in early sepsis.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 203-210.

 
  Overexpression of P-glycoprotein in L1210/VCR cells is associated with changes in several endoplasmic reticulum proteins that may be partially responsible for the lack of thapsigargin sensitivity
M. Šereš 1), E. Poláková, O. Krizanova, S. Hudecová, S. Klymenko, A. Breier, Z. Sulová

1)Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlárska 5, 833 34 Bratislava, Slovakia. umfgzden@savba.sk.


L1210/VCR cells, which express an abundant amount of P-glycoprotein (P-gp), were found to be resistant to thapsigargin – an inhibitor of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA). In the current paper, we have studied the possible differences among L1210 and L1210/VCR cells in expression of endoplasmic reticulum proteins involved in the regulation of calcium homeostasis and calcium-dependent processes. Amounts of mRNA encoding both calcium release channels (ryanodine receptor channels – RyR and IP3-receptor channels – IP3R) were found to be at similar levels in sensitive and resistant cells. However, mRNAs encoding IP3R1 or 2 were decreased in resistant cells cultivated in the presence of VCR (1.08 µmol/l), while mRNA encoding RyR remained unchanged. The amount of mRNA for SERCA2 was decreased in resistant cells when compared with sensitive cells. This decrease was more pronounced when resistant cells were cultivated in the presence of vincristine (VCR). Calnexin was found to be less expressed at the protein level in resistant as in sensitive cells. The level of mRNA encoding calnexin was decreased only when resistant cells were cultivated in the presence of VCR. Calnexin was found to be associated with immature P-gp in resistant cells. Thus, differences exist between sensitive and resistant cells in the expression of endoplasmic reticulum proteins involved in the control of intracellular calcium homeostasis or calcium-dependent processes. These changes may be at least partially responsible for the lack of sensitivity of resistant cells to thapsigargin.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 211-221.

 
  Rats with monosodium glutamate-induced obesity and insulin resistance exhibit low expression of Gαi2 G-protein
M. Baculikova 1), R. Fiala, D. Jezova, L. Macho, S. Zorad

1)Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlárska 3, 833 06 Bratislava, Slovakia. miroslava.baculikova@savba.sk.


In order to test the potential role of inhibitory G-proteins in mechanisms of insulin resistance in adipose tissue of obese animals we determined the content of Gαi1 and Gαi2 proteins and an extent of protein tyrosine phosphorylation in epididymal fat tissue cell membranes using immunoblot. Monosodium glutamate-induced obese rats displayed adipose tissue hypertrophy, elevated levels of insulin, leptin and slightly elevated serum glucose. We found significantly decreased protein content of Gαi2 in adipose tissue plasma membranes of obese rats. This was in accordance with lower protein tyrosine phosphorylation noticed in adipose tissue cell homogenate of glutamate-treated animals. Our results confirm the role of Gαi2 in development of insulin resistance by crosstalk between the reduced level of inhibitory G-protein and insulin receptor mediated most likely by activation of phosphotyrosine protein dephosphorylation.

General Physiology and Biophysics. Volume 27, 2008, No. 3: 222-226.