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General Physiology and Biophysics

Volume 25, 2006, No. 2


  Effect of the pyridoindole antioxidant stobadine on the cardiac Na+,K+-ATPase in rats with streptozotocin-induced diabetes
J Vlkovičová 1), V Javorková, M Stefek, Z Kyselova, A Gajdošíková, N Vrbjar

1)Institute for Heart Research, Department of Biochemistry, Slovak Academy of Sciences, Dúbravská cesta 9, P.O.Box 104, 840 05 Bratislava 45, Slovakia.

In the present study we examined the effect of dietary supplementation with the pyridoindole antioxidant stobadine on functional properties of the cardiac Na+,K+-ATPase in diabetic rats. Diabetes lasting sixteen weeks which was induced by a single i.v. dose of streptozotocin (55 mg·kg-1) was followed by decrease in the enzyme activity. Evaluation of kinetic parameters revealed a statistically significant decrease in the maximum velocity (Vmax) (32% for ATP-activation, 33% for Na+-activation), indicating a diabetes-induced diminution of the number of active enzyme molecules in cardiac sarcolemma. The ATP-binding properties of the enzyme were not affected by diabetes as suggested by statistically insignificant changes in the value of Michaelis-Menten constant, KM (ATP). On the other hand, the affinity to sodium decreased as suggested by 54% increase in the KM (Na+) value. This impairment in the affinity of the Na+-binding site together with decreased number of active Na+,K+-ATPase molecules are probably responsible for the deteriorated enzyme function in hearts of diabetic animals. Administration of stobadine to diabetic rats dramatically improved the function of cardiac Na+,K+-ATPase with regard to Na+-handling, as documented by statistically significant elevation of Vmax by 66 and 47% decrease in KM (Na+). Our data suggest that stobadine may prevent the diabetes-induced deterioration of cardiac Na+,K+-ATPase, thus enabling to preserve its normal function in regulation of intracellular homeostasis of Na+ and K+ ions.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 111-124.

  Theoretical search for the growth-temperature relationship in plants
S Lewicka 1), M Pietruszka

1)Faculty of Biology and Environmental Protection, University of Silesia, Jagiellonska 28, 40 032 Katowice, Poland.

In this article we deal with the definition of a new phenomenological model with physical bases for the response of short-term cell expansion growth to temperature. Although the interest on both the biomechanical bases of elongation growth and on temperature responses has a long lasting development in plant biology and biophysics, yet the question of the mode of actions of temperature is a very relevant and still open one. The purpose of our paper was not to deal with all the complexity of the possible effects of temperature on a growing cell but to concentrate on two more focused questions: i) whether it is possible to specify an optimal temperature for growth responses all along development by defining some phenomenological equations for temperature response, ii) can we learn something from that on the temperature dependence of the cell wall expansion process using a minimal analytical modelling? To answer both questions we introduce (by extending Lockhart approach) the notion of temperature by simple thermodynamical reasoning. Assuming incompressibility of water (by the constant molar density n/V ) we also accounted for the role of osmosis and consequently – the role of water uptake in growing cell. This approach allowed us (by comparing theoretical solutions and experimental results) not only to determine the specific (resonance) temperature (or corresponding absorption energy kBT*) of the optimal growth but also draw conclusions about the cell wall extensibility dependence on temperature and its evolution in time. A straightforward application of our method to determine optimum growth temperature for different plant species in a greenhouse practice (as its simple implication) can also be recommended.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 125-136.

  Effect of nitric oxide synthases inhibitors on exogenous irritant-induced bronchial hyper-reactivity in guinea pigs
M Antošová 1), A Strapková, G Nosáľová, J Mokrý

1)Department of Pharmacology, Jessenius Faculty of Medicine, Comenius University, Sklabinská 26, 037 53 Martin, Slovakia.

Nitric oxide (NO) is an important endogenous mediator involved in many biological functions in both physiological and pathological conditions. Many of studies suggest that high level of NO may play a role in the pathogenesis of various diseases including respiratory diseases with bronchial hyper-reactivity (BHR). The aim of our study was to examine the relationship between NO production and BHR. The reactivity of tracheal and lung tissue smooth muscle to histamine and acetylcholine was measured in vitro in male guinea pigs pre-treated with NO synthase (NOS) inhibitors. The drugs were administered in vivo during either 3 or 17 days. Furthermore, the animals were exposed in vivo to the toluene vapours after administration of agents. NOS inhibitors showed mainly beneficial effect in the presented study. They decreased the hyper-reactivity of the tracheal and lung tissue smooth muscle evoked by toluene. The decrease was dependent on the duration of their administration and on the type of inhibitor. Short-term administration of inhibitors was more effective than long-term one. A more significant effect was recorded after the pre-treatment with non-selective inhibitor L-NAME. The results showed possible participation of constitutive forms of NOS in the BHR.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 137-147.

  Phosphatidic acid osmotically destabilizes lysosomes through increased permeability to K+ and H+
Y Yi 1), X Wang, G Zhang, T Fu

1)Hunan Agricultural University, Changsha, P. R. China.

Lysosomal destabilization is a critical event not only for the organelle but also for living cells. However, what factors can affect lysosomal stability is not fully studied. In this work, the effects of phosphatidic acid (PA) on the lysosomal integrity were investigated. Through the measurements of lysosomal β-hexosaminidase free activity, intralysosomal pH, leakage of lysosomal protons and lysosomal latency loss in hypotonic sucrose medium, we established that PA could increase the lysosomal permeability to K+ and H+, and enhance the lysosomal osmotic sensitivity. Treatment of lysosomes with PA promoted entry of K+ into the organelle via K+/H+ exchange, which could produce osmotic stresses and osmotically destabilize the lysosomes. In addition, PA-induced increase in the lysosomal osmotic sensitivity caused the lysosomes to become more liable to destabilization in osmotic shocks. The results suggest that PA may play a role in the lysosomal destabilization.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 149-160.

  Complexity analysis of electrocardiographic signals
I Neacsu 1), D Creanga, F Tufescu

1)University Al. I. Cuza, Faculty of Biology, 20A Bd. Carol I, Iasi, Romania.

Two types of electrocardiographic data series were investigated using appropriate tests based on a selection of semi-quantitative analysis algorithms. Distribution histograms, power spectra, auto-correlation functions, state-space portraits, Lyapunov exponents and wavelet transformations were applied to electrocardiograms of normal and stressed subjects. Statistical analysis using the Student's t-test revealed significant and non-significant alterations in stress-loaded cases compared to normal ones. Higher levels of adrenaline may account for a more complex dynamics (deterministic chaos) revealed in the stressed subjects.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 161-176.

  Effects of static and 50 Hz alternating electric fields on superoxide dismutase activity and TBARS levels in guinea pigs
G Güler 1), N Seyhan, A Aricioğlu

1)Department of Biophysics, Medical Faculty, Gazi University, Ankara, Turkey.

The toxic oxygen free radicals are extremely reactive and can cause considerable damage to biomolecules, such as RNA, enzymes, membranes, proteins, and lipids, which may in turn lead to various pathological consequences. Lipid peroxidation, evaluated by determination of thiobarbituric acid reactive substances (TBARS) is the free radical-induced oxidation of polyunsaturated fatty acids. Normally, the oxygen free radicals are neutralized by highly efficient systems in the body. These include antioxidant enzymes like superoxide dismutase (SOD). In a healthy subject, there is a balance between free radicals and levels of antioxidants. The aim of this study was to determine lipid peroxidation and SOD levels in plasma, liver, lung and kidney tissues exposed to different intensities, directions and exposure periods of static and 50 Hz alternating electric fields. Electric field intensities ranging from 0.3 kV/m to 1.8 kV/m were applied in vertical or horizontal direction in exposure periods of 1, 3, 5, 7, and 10 days. The increase in SOD and TBARS levels of plasma, liver, lung, and kidney tissues was found to depend significantly on the type of electric field and the exposure period.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 177-193.

  Effect of BQ-123 and nitric oxide inhibition on liver in rats after renal ischemia-reperfusion injury
M Emre 1), H Erdogan, E Fadillioglu

1)Department of Physiology, Medical Faculty of Inonu University, 44280 Malatya, Turkey.

Ischemia-reperfusion (I/R) injury induces an inflammatory response and production of oxygen-derived reactive species which affect many organs including heart, brain, kidney and gastrointestinal tract. The aim of this study was to assess the hepatic changes after renal I/R injury. Male Sprague Dawley rats were subjected to either sham operation or treatment with L-NAME, L-arginine and BQ-123 during 30 min renal ischemia and 2 h reperfusion injury. Hepatic superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px) activities, and thiobarbituric acid-reactive substances (TBARS) and nitric oxide (NO) levels were evaluated to show hepatic response to renal I/R injury. Catalase and SOD activities showed significant differences between the control and the other groups after I/R. On the other hand, GSH-Px activity did not show any significant changes between the control and the other experimental groups mentioned under above conditions. Meanwhile, levels of TBARS were not different between the control and the other experimental groups, whereas NO level showed changes between the control and experimental groups except the one to which endothelin receptor antagonist agent (BQ-123) subjected. Experimental period may not be enough to determine the changes in GSH-Px activity and level of TBARS. However, catalase and SOD activities decreased in experimental groups treated by chemical agents. NO level decreased in chemicalagent-applied experimental groups but not in the group to which endothelin receptor antagonist BQ-123 was applied alone.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 195-206.

  Reduction of gaseous microembolism during aortic valve replacement using a dynamic bubble trap
M Schönburg 1), T Ziegelhoeffer, B Kraus, A Mühling, M Heidt, U Taborski, T Gerriets, M Roth, S Hein, S Urbanek, W Klövekorn

1)Department of Thoracic and Cardiovascular Surgery, Kerckhoff-Clinic, Benekestrasse 2–8, 61231 Bad Nauheim, Germany.

Serious postoperative psycho-neurological dysfunction is at least partially attributed to the occurrence of gaseous microbubbles in the arterial line of extracorporeal circulation (ECC). Therefore, we investigated in a prospective randomized double blind study whether the usage of dynamic bubble trap (DBT) will reduce microbubble load of patients undergoing aortic valve replacement. Patients (n = 41) were divided into group I (GI, n = 22) with DBT introduced into the arterial line of ECC and group II (GII, n = 19) with placebo-DBT instead. Doppler ultrasonography was used for detection of microbubbles before and after DBT, and for detection of high intensity transient signals (HITS) within the middle cerebral artery. The recording time during ECC was divided into period 1 (P1, until aortic clamp removal) and period 2 (P2, clamp removal until the end of ECC). A significant reduction of microbubble load was found in GI only (p < 0.0001 for ECC; p < 0.0001 for P1; p < 0.0025 for P2). A significant difference in number of HITS between the groups was observed in P1 only (p < 0.002 left middle cerebral artery, p < 0.005 right middle cerebral artery), since in P2 the trapped air in left chamber can go to the supraaortal vessels without passing ECC. In conclusion the use of DBT cannot substitute careful venting after aortic declamping. Nevertheless, reduction of HITS in the cross-clamped period of ECC justifies the use of DBT in patients undergoing open chamber surgery.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 207-214.

  Resveratrol, a natural phenolic compound may reduce carbonylation proteins induced by peroxynitrite in blood platelets
B Olas 1), P Nowak, M Ponczek, B Wachowicz

1)Department of General Biochemistry, Institute of Biochemistry, University of Lodz, Banacha 12/16, 90-237 Lodz, Poland.

Resveratrol (3,4’,5-trihydroxystilbene) has a very broad range of biological properties, including antiplatelet and antioxidative activity. We investigated in vitro the effect of resveratrol on carbonylation of proteins (indicators of oxidative stress) in blood platelets treated with peroxynitrite (ONOO-), a strong biological oxidant and inflammatory mediator. We observed that carbonylation of proteins induced by ONOO- (0.1 mmol/l), in the presence of resveratrol (0.25–0.1 mmol/l) is reduced. Resveratrol may scavenge ONOO-, and may be useful in the prevention of ONOO--related diseases, such as inflammatory and cardiovascular diseases.

General Physiology and Biophysics. Volume 25, 2006, No. 2: 215-222.