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General Physiology and Biophysics


Volume 29, 2010, No. 1

Content:


  Mitochondrial complex I in the network of known and unknown facts
Maria Chomova 1), Peter Racay

1)Institute of Medical Biochemistry, Jessenius Faculty of Medicine, Comenius University, Malá Hora 4, 036 01 Martin, Slovakia. maria.chomova@jfmed.uniba.sk.


The mitochondrial respiratory chain consists of five multi‐subunit complexes embedded in the inner mitochondrial membrane. Complex I is the largest and most complicated proton pump of the respiratory chain encoded by both the mitochondrial and nuclear genomes. In this minireview, attention is given to recent knowledge on the structure, catalytic properties, supramolecular organisation of complex I and its possible role in the triggering of apoptosis.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 3-11.

 
  Effects of electrical heterogeneity on transmural reentry during acute global ischemia
Hong Zhang 1), Yin Jin, Zhen Zhang, Lin Yang, Ye Huang

1)School of Electrical Engineering, Xi'an Jiaotong University, 28 West Xianning Road, Xi'an, Shaanxi 710049, P. R. China. maxr@263.net.


Ventricular arrhythmias are commonly observed in patients with ischemia. It is reported that the electrophysiological changes evoked by ischemia are greater in the epicardium than in the endocardium. To investigate the effects of this heterogeneity on transmural reentry, the computer simulation method is used. A two‐dimensional model which can reproduce the endocardial, epicardial and middle cell types, approximate the ischemic characteristics and distribution of the ischemic severity is developed by setting different ratios of the maximum conductance of the rapid and slow inward rectifier potassium currents and considering the three major component conditions of acute ischemia at the ionic level. The results demonstrate that action potentials of the ischemic cells have elevated resting potential, shortened duration, slowed upstroke and declined amplitude. Conduction velocity is much more depressed in the epicardium because of the ischemia‐induced transmural gradient of excitability. The epicardially initiated activation has wider vulnerable window and more possibility to cause unidirectional propagation even reentry. Dispersion of the excitability is proposed to be the underlying mechanism.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 12-22.

 
  Combined treatment of tetrahydrocurcumin and chlorogenic acid exerts potential antihyperglycemic effect on streptozotocin‐nicotinamide‐induced diabetic rats
Krishnamoorthy Karthikesan 1), Leelavinothan Pari, Venugopal Menon

1)Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Annamalai Nagar – 608 002, Tamil Nadu, India. paribalaji@gmail.com.


We have shown that separate dose of tetrahydrocurcumin (THC) at a dose of 80 mg/kg body weight (b.w.) and chlorogenic acid (CGA) at a dose of 5 mg/kg b.w. exerts antidiabetic potential in streptozotocin (STZ) (45 mg/kg b.w.) nicotinamide induced diabetic rats. In the present study we have attempted to compare the antihyperglycemic activity exerted by the combined treatment of THC/CGA with THC and CGA alone treated diabetic rats. After the experimental period of 45 days we observed that supplementation with combined dose of THC/CGA significantly decreased glycosylated hemoglobin (HbA1C) and increased the levels of plasma insulin, C‐peptide, hemoglobin and glycogen which were decreased upon STZ treatment and also significantly reversed the altered activities of gluconeogenic enzymes such as glucose-6-phosphatase, fructose-1,6-bisphosphatase, and of glycolytic enzymes such as glucokinase and hexokinase in the tissues of experimental rats as compared to their individual supplementation. Thus our results substantiate that though THC and CGA alone found to exert hypoglycemic activity the maximum hypoglycemic effect was always observed in diabetic rats treated THC/CGA and this summed effect seems to have a promising value for the development of a potent phytomedicine for diabetes.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 23-30.

 
  Influence of ischemia/reperfusion and modulation of PI3K/Akt kinase pathway on matrix metalloproteinase‐2 in rat hearts
Anna Špániková 1), Monika Ivanová, Jana Matejikova, Tana Ravingerova, Miroslav Barancik

1)Institute for Heart Research, Slovak Academy of Sciences, Dúbravská cesta 9, P.O. Box 104, 840 05 Bratislava, Slovakia. miroslav.barancik@savba.sk.


Matrix metalloproteinases (MMPs) are enzymes that play an important role in degradation and remodeling of extracellular matrix and MMP‐2 has been also shown as a primary mediator of the acute mechanical dysfunction of the heart immediately after ischemia/reperfusion (I/R). The aims of the study were to investigate the influence of I/R on MMP‐2 and to study the effects of wortmannin on modulation of MMP‐2 activities after cycle of short I/R procedures (ischemic preconditioning, IP). Wortmannin is a specific inhibitor of PI3K/Akt kinase pathway activation of which was found to play a role in infarct size limiting mechanisms in the rat heart. In the study isolated Langendorff‐perfused rat hearts subjected to protocols of prolonged (test) I/R and/or IP were used. Wortmannin was infused before and during the reperfusion phase of IP. The levels and activation of proteins were determined by immunoblot assay. The MMP‐2 activities were measured by zymography. We found that ischemia induced time‐dependent activation of tissue pro‐MMP‐2. Strong activation occurred after 15 min ischemia, during prolonged ischemia and following reperfusion the activities of this form of MMP‐2 declined. The specific activities of both 72 and 63 kDa forms of MMP‐2 were increased in perfusates collected during reperfusion after 30 min ischemia and these activities peaked in the first minute of reperfusion. Cycle of short ischemia and reperfusion that led to increased cardiac tolerance against prolonged I/R reduced 72 kDa MMP‐2 activities and induced also an activation of Akt kinase. The application of wortmannin was connected with inhibition of IP‐mediated Akt kinase activation. Moreover, the actions of wortmannin were linked with modulation of MMP‐2 activities. Our results suggest that MMP‐2 may be involved in the responses of rat hearts to ischemia and point to possible relationship between Akt kinase and modulation of MMP‐2 activities in rat hearts.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 31-40.

 
  The effects of the natural antioxidant quercetin and anions of the Hofmeister series on liposomes marked with chlorophyll a
Magdalena Drăguşin 1), Laura Ţugulea, Constanţţa Ganea

1)Department of Biophysics, University of Medicine and Pharmacy Carol Davila, 8 Eroii Sanitari Blvd., 050474, Bucharest, Romania. magdadragusin@yahoo.com.


The unilamellar liposomes of dimyristoylphosphatidylcholine (DMPC), marked with chlorophyll a (Chla), have been chosen as suitable models in studies aimed at determining the effects of natural antioxidant quercetin (QCT) and Hofmeister series anions on lipid bilayers. The variations of steady state fluorescence emission intensity of Chla have been recorded and the values of Chla fluorescence anisotropy, under constant temperature and viscosity, at pH = 7.3‐7.4 have been measured. Two types of experiments have been performed. In the first type of experiment, the concentration of anions was maintained constant and the concentration of QCT was varied (from 0 to 100 µmol/l). In the second type of experiment, the concentration of QCT was constant (30 µmol/l) and the concentration of anions was varied (from 0 to 152 mmol/l). The quenching of Chla fluorescence by QCT pleads in favor of QCT insertion at interface water‐lipid, in the vicinity of the polar heads of lipids from liposomal bilayer at physiological pH and temperature. Fluorescence anisotropy of Chla in liposomes brought more evidences for QCT localizations at lipid/water interface. Chla is sensing a more rigid microenvironment when QCT is added to the lipid bilayer and specific effects of the Hofmeister series anions.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 41-49.

 
  Neuropathy in a rat model of mild diabetes induced by multiple low doses of streptozotocin: effects of the antioxidant stobadine in comparison with a high‐dose α‐lipoic acid treatment
Silvia Skalská 1), Pavol Kučera, Zoltán Goldenberg, Milan Stefek, Zuzana Kyselova, Pavol Jariabka, Alena Gajdošíková, Katarína Klobučníková, Pavel Traubner, Svorad Štolc

1)Institute of Experimental Pharmacology and Toxicology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia. silvia.skalska@yahoo.com.


Hyperglycaemia‐induced oxidative stress makes an important contribution to the aetiology of diabetic neuropathy. The aim of our study was to evaluate the effect of the antioxidant stobadine (STB) in comparison with a treatment by a high‐dose of α‐lipoic acid (ALA), on the neurological consequences of chronic hyperglycaemia in an animal model of diabetes in Wistar rats (16 weeks old), made diabetic by streptozotocin (STZ 3 × 20 mg i.v.). Neuropathy was evaluated electrophysiologically by measuring motor nerve conduction velocity (NCV) in the 4th and 8th week in vivo and motor NCV and resistance to ischaemic conduction failure (RICF) of the sciatic nerve in the 10th week of the experiment in vitro. The therapy with ALA (100 mg/kg i.p., 5 times a week) and STB (25 mg/kg i.p., 5 times a week) had a significant effect on NCV in vivo in the 8th week of the experiment and no effect in the 10th week in vitro. The RICF elevated in diabetic animals was significantly modified by ALA. The effect of the antioxidant STB on NCV was comparable with that of ALA, while RICF was affected only by ALA. We conclude that treatment with appropriate antioxidants might partially prevent nerve dysfunction in diabetic rats.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 50-58.

 
  The effect of radiofrequency radiation on DNA and lipid damage in non‐pregnant and pregnant rabbits and their newborns
Goknur Guler 1), Arin Tomruk, Elcin Ozgur, Nesrin Seyhan

1)Gazi Üniversitesi T&inodot, p Fakültesi Biyofizik AbD, Dekanlık Binası 5. Kat 06510 Besevler, Ankara 06500, Turkey. gozturk@gazi.edu.tr.


The concerns of people on possible adverse health effects of radiofrequency radiation (RFR) generated from mobile phones as well as their supporting transmitters (base stations) have increased markedly. RFR effect on oversensitive people, such as pregnant women and their developing fetuses, and older people is another source of concern that should be considered. In this study, oxidative DNA damage and lipid peroxidation levels in the brain tissue of pregnant and non‐pregnant New Zealand White rabbits and their newborns exposed to RFR were investigated. Thirteen‐month‐old rabbits were studied in four groups as non‐pregnant‐control, non‐pregnant‐RFR exposed, pregnant‐control and pregnant‐RFR exposed. They were exposed to RFR (1800 MHz GSM; 14 V/m as reference level) for 15 min/day during 7 days. Malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels were analyzed. MDA and 8-OHdG levels of non‐pregnant and pregnant‐RFR exposed animals significantly increased with respect to controls (p < 0.001, Mann‐Whitney test). No difference was found in the newborns (p > 0.05, Mann‐Whitney). There exist very few experimental studies on the effects of RFR during pregnancy. It would be beneficial to increase the number of these studies in order to establish international standards for the protection of pregnant women from RFR.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 59-66.

 
  Melatonin modulates hypoxia‐induced changes of rat brain excitability
Dana Maresova 1), Vladimir Riljak, Jan Mares

1)Institute of Physiology, 1st Faculty of Medicine, Charles University in Prague, Albertov 5, 128 00 Prague 2, Czech Republic. vladimir.riljak@lf1.cuni.cz.


The aim of our study was to test the hypothesis, if melatonin pre-treatment (in dose of 100 mg/kg) can influence the changes of brain function after short‐term hypoxia exposition (simulated altitude 9000 m) in young immature rats. Experiments were performed on freely moving 12‐, 25‐ and 35‐day‐old male Wistar rats. One hour prior to hypoxia exposition, animals were pre‐treated with melatonin and 24 hours after hypoxia cortical afterdischarges (ADs) were elicited by repeated stimulation of the right sensorimotor cortex. The duration of evoked ADs and shape of evoked graphoelements was monitored. Short‐term exposure to hypoxic conditions resulted in significantly shorter ADs duration in 12‐day‐old rats after stimulations (except the 2nd one stimulation) compared to control group. Administration of melatonin prolonged the duration of ADs after all stimulations except the 1st one. Analysis of the duration ADs revealed no significant changes, either after the exposition to hypobaric hypoxia or after melatonin administration in 25‐ and 35‐day‐old animals. Effects and mechanisms of melatonin action on the brain seizure susceptibility and the possible beneficial role of that treatment in hypoxic brain damage are discussed.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 67-71.

 
  Effect of S‐adenosylmethionine on liver regeneration induced by partial hepatectomy
Lukáš Kohoutek 1), Zuzana Červinková, Otto Kučera, Tomáš Roušar, Tomáš Garnol, Jiří Šiller, Halka Lotková

1)Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University in Prague, Šimkova 870, 500 38 Hradec Králové, Czech Republic. lotko@lfhk.cuni.cz.


S‐adenosylmethionine (SAMe) is a key metabolite regulating growth, differentiation and death of hepatocytes. Experimentally, exogenous SAMe has been documented to attenuate hepatocarcinogenesis. The aim of our study was to evaluate the effect of SAMe on proliferation of hepatocytes that are not cancerously transformed. Partial 2/3 hepatectomy (PH) was performed in rats, control animals underwent laparotomy. SAMe was injected immediately after the surgery and then at 24 h intervals for two days at 10 or 40 mg/kg. The animals were sacrificed 24, 48 and 72 h after operation and the intensity of liver regeneration was evaluated. SAMe treatment at 10 mg/kg was associated with decrease in the synthesis of liver DNA 48 h after PH, however, it was not reflected in DNA content. SAMe treatment at 40 mg/kg led to the reduction of DNA synthesis 72 h after PH followed by the diminution of DNA content. The results have documented the inhibition of the liver regeneration by SAMe that may be mediated by the suppression of liver fat accumulation. Cell GSH level correlating with the growth rate was not affected by SAMe. Prevention from the decrease in the intracellular content of SAMe, as a factor attenuating regeneration remains to be verified.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 72-78.

 
  Alterations in adipocyte glucose transporter GLUT4 and circulating adiponectin and visfatin in rat adjuvant induced arthritis
Jana Jurčovičová 1), Andrea Štofková, Martina Škurlová, Miroslava Baculíková, Štefan Zórad, Mária Stančíková

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


Rheumatoid arthritis in humans brings about impaired insulin sensitivity and glucose tolerance. Since adipose tissue plays a role in glucose homeostasis, we evaluated the size of adipocytes, the amount of glucose transporter type 4 (GLUT4) in adipocyte plasma membranes, and circulating insulin, glucose, and adipokines affecting glucose metabolism, resistin, adiponectin and visfatin during experimental adjuvant arthritis (AA) in male Lewis rats. AA was induced by a single injection of complete Freund's adjuvans. Adipocyte diameter was assessed microscopically, GLUT4 was measured by Western blotting. Plasma insulin, adiponectin, visfatin were quantitated by RIA, and resistin by ELISA. Arthritic rats showed cachexia, reduced adipocyte size, and downregulated membrane GLUT4 (4065 ± 962 vs. 9911 ± 680 arb. units of optic density, p < 0.01), reduced plasma adiponectin (1.956 ± 0.10 vs. 3.16 ± 0.22 µg/ml, p < 0.001), and enhanced visfatin (1.84 ± 1.05 vs. 1.24 ± 0.1 ng/ml, p < 0.01). Plasma glucose and insulin were unaltered, as were the resistin levels. Conclusion: AA induced cachexia results in reduction of adipocyte size, and paradoxically also in downregulation of GLUT4 in adipocyte membranes. This is supposed to be functionally related to the reduced adiponectin levels. The upregulated visfatin in rat arthritis is a novel finding, and it confirms its role in autoimmunity across the species.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 79-84.

 
  Prophylactic role of curcumin against cyclosporine-induced nephrotoxicity: Histological and immunohistological study
Eman Abdel Fattah 1), Hala Hashem, Fayza Ahmed, Mohammed Ghallab, Ivan Varga, Sefan Polak

1)Department of Histology and Cell Biology, Faculty of Medicine, Zagazig University, Zagazig City, Egypt.


This study aimed to investigate the possible protective role of curcumin against renal damage caused by administration of cyclosporine A (CsA) in adult male rats. For this purpose, 27 adult male albino rats were used and divided into three equal groups. Group I (control group) and group II (CsA‐treated group) received a daily subcutaneous injection of CsA at a dose of 20 mg/kg b.w. Group III (prophylactic group) received a daily oral curcumin at a dose of 15 mg/kg b.w. simultaneously with CsA. After 21 days, all the animals were anaesthetized and the kidneys were rapidly removed and processed to prepare paraffin sections stained with H&E, PAS and Masson's trichrome. In addition, the glutathione S‐transferase (GST) enzyme was detected immunohistochemically. The optical density and the area (in %) of positive GST immunoreactions were measured in the cytoplasm of renal tubules and glomeruli and the data were statistically analyzed. Examination of sections from CsA‐treated group showed renal tubules with vacuolated cytoplasm and others with darkly stained pyknotic nuclei. Apical brush borders of proximal tubules were undefined and PAS positive granules were noticed in their cytoplasm. The renal corpuscles contained shrunken glomeruli with widening of their Bowman's spaces. Inflammatory cellular infiltrate and increase in the collagen fibers were observed between the renal tubules. In prophylactic group, the structure of renal tubules and corpuscles were preserved except few tubular darkly stained pyknotic nuclei. Numerous blood vessels, few cellular infiltration and thin collagen fibers were observed between the renal tubules. Statistical analysis of morphometric data showed significant increase in the optical density of GST immunoreactivity in the cells of renal tubules and glomeruli of CsA‐treated group when compared with the control or prophylactic groups. However, a significant decrease in the area of GST immunoreactivity in sections from prophylactic group was observed when compared with control or CsA‐treated groups. In conclusion, protective effect of curcumin against cyclosporine‐induced nephrotoxicity in rats was proven based on the study of histological changes and GST immunoexpression. This study supposes the possible therapeutic applications of curcumin in CsA‐treated patients.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 85-94.

 
  Generalized phenomenological equation of plant growth
Sylwia Lewicka 1), Mariusz Pietruszka

1)The H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31342 Kraków, Poland. sylwia.lewicka@ifj.edu.pl.


Enlargement is one of the most fundamental activities of plants, and there are many simultaneous processes involved. Several could be temperature‐dependent, like metabolic processes and cell wall sensitivity. A description of plant cell elongation was elaborated by Lockhart in the mid‐60's of the last century in the form of time‐dependent differential equation. However, the main disadvantage of this approach was the missing environmental temperature at which growth takes place, as well as the lack of representation of environmental factors influencing growth, like growth stimulators/inhibitors, external pressure or light. This absence has been merely covered in the series of our recent papers. Consequently, this manuscript attempts to construct a fairly complete, all‐encompassing set of mathematical relationships which describe the basic process of cell/organ extension and the effects of modifying environmental perturbations. The output is provided in a form of composite equation supported by mathematical derivations. Starting with the generalized time‐ and temperature‐dependent growth equation, we involve the action of phytohormones and toxic compounds, and especially of light (photocontrol of plant growth) onto the growth processes. All these external factors (treated as perturbations) are mapped onto the proper terms of temperature modified equation of growth thus giving a new theoretical tool to verify, interpret and draw conclusions concerning data originating from various kinds of plant‐physiological experiments. It seems that this novel approach can provide a starting point for further experimentation especially on the plastic and elastic components of the growth process.

General Physiology and Biophysics. Volume 29, 2010, No. 1: 95-105.