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General Physiology and Biophysics


Volume 27, 2008, No. 1

Content:


  Serum lipoprotein composition, lecithin cholesterol acyltransferase and tissue lipase activities in pregnant diabetic rats and their offspring receiving enriched n-3 PUFA diet
N. Soulimane-Mokhtari 1), B. Guermouche, M. Saker, S. Merzouk, H. Merzouk, A. Hichami, S. Madani, N. Khan, J. Prost

1)Laboratoire de Physiologie Animale et Biochimie, Département de Biologie, Faculté des Sciences, Université de Tlemcen, Algérie. nassima_amel@yahoo.fr.


The effects of dietary n-3 polyunsaturated fatty acids on lipoprotein concentrations and on lipoprotein lipase (LPL), hepatic triglyceride lipase (HTGL) and lecithin cholesterol acyltransferase (LCAT) activities were studied in streptozotocin-induced diabetic rats during pregnancy and in their macrosomic offspring from birth to adulthood. Pregnant diabetic and control rats were fed Isio-4 diet (vegetable oil) or EPAX diet (concentrated marine omega-3 EPA/DHA oil), the same diets were consumed by pups at weaning. Compared with control rats, diabetic rats showed, during pregnancy, a significant elevation in very low density lipoprotein (VLDL) and low and high density lipoprotein (LDL-HDL1)-triglyceride, cholesterol and apoprotein B100 concentrations and a reduction in apoprotein A-I levels. HTGL activity was high while LPL and LCAT activities were low in these rats. The macrosomic pups of Isio-4-fed diabetic rats showed a significant enhancement in triglyceride and cholesterol levels at birth and during adulthood with a concomitant increase in lipase and LCAT activities. EPAX diet induces a significant diminution of VLDL and LDL-HDL1 in mothers and in their macrosomic pups, accompanied by an increase in cholesterol and apoprotein A-I levels in HDL2–3 fraction. It also restores LPL, HTGL and LCAT activities to normal range. EPAX diet ameliorates considerably lipoprotein disorders in diabetic mothers and in their macrosomic offspring.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 3-11.

 
  Enhanced early after-myocardial infarction concentration of TNF-α subsequently increased circulating and myocardial adrenomedullin in spontaneously hypertensive rats
J. Dřímal 1), V. Knezl, E. Paulovičová, D. Dřímal

1)Institute of Experimental Pharmacology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia. exfadrim@savba.sk.


Both inflammatory cytokine tumor necrosis factor-α (TNF-α) and the cardiac protective peptide adrenomedullin (AM) are increased in cardiac tissues and plasma in patients with myocardial infarction (MI) and chronic heart failure. Recently they have been increasingly recognized as important factors in the pathophysiology of MI and resultant congestive heart failure. Compared with sham-operated spontaneously hypertensive rats (SHR), we investigated myocardial immunoreactivity of TNF-α and AM and also their mutual relations in vivo in SHR+MI. Residual myocardial depression after MI was studied also in isolated perfused hearts. In chronic experiments, 24 and 48 h after permanent ligation of the descending anterior branch of the left coronary artery, we examined hemodynamics, plasma and myocardial peptide levels. Left ventricular function was assessed in isolated perfused hearts subjected to “global ischemia and reperfusion” and after induction of "calcium paradox". Circulating and myocardial TNF-α concentrations increased early after MI in SHR. Studies with global ischemia and calcium paradox in isolated heart showed early myocardial depression and calcium-dependent gradual increase of left-ventricular end-diastolic pressure. In the SHR+MI myocardial AM concentrations were increased 9- and 49-fold after respective 24 h and culminated 48 h following MI. Circulating and myocardial AM was increased in SHR+MI in association with TNFα-induced myocardial depression. The both studied cardiac parameters displayed the beneficial effect of the enhanced myocardial AM concentration.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 12-18.

 
  Model of concentration changes across the synaptic cleft during a single quantum release
A. Skorinkin 1), A. Shaihutdinova, F. Vyskočil

1)Institute of Physics, Kazan State University , Kremliovskaja ul. 18, 420008 Kazan, Russia. askorink@yandex.ru.


A model of concentration changes across the synaptic cleft during a single quantum release is presented that can be used for description and characterization of the kinetic in postsynaptic current development under the influence of different antagonists, modulators, desensitization promoters or complex channel blockers. The model enables the calculation of the relative number of open channels as a function of time for two standard cases – when acetylcholinesterase (AChE) is either active or inhibited. One outcome of the present model is that the variable part of AChE activity is zero at the moment of acetylcholine (Ach) release and then increases. This is in contrast to common view that the activity of AChE at the initial moment of release of quanta is maximal and decreases over the time course of quantum action. However, the model explains why non-quantal ACh leakage from the nerve terminal creating a concentration of approximately 10–8 mol·l–1 in the cleft can escape hydrolysis by intrasynaptically located cholinesterase and reach the subsynaptic membrane. The model can also be used for theoretical considerations of time and amplitude changes during repetitive nerve-evoke quanta release.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 19-24.

 
  The effect of experimental diabetes on the circadian pattern of adenosine deaminase and myeloperoxidase activities in rat liver
C. Uluoglu 1), B. Cimen, G. Ozbey, C. Karasu, D. Durakoglugil, A. Gunes, N. Turkozkan, H. Zengil

1)Department of Pharmacology, Faculty of Medicine, Gazi University, Besevler, 06500 Ankara, Turkey. culuoglu@yahoo.com.


This study investigated time-dependent variations in the activities of adenosine deaminase (ADA), an adenosine-metabolizing enzyme, and myeloperoxidase (MPO), an oxidation reaction-catalyzing enzyme, in control and streptozotocin (STZ)-induced diabetic rat liver. The animals were sacrificed at six different times of day (1, 5, 9, 13, 17 and 21 hours after lights on – HALO). The hepatic activity of ADA did not change depending on the STZ treatment whereas MPO activity was significantly higher in the diabetics than in the controls. Hepatic ADA activity was dependent on the time of sacrifice with the lowest activity at 21 HALO and the highest activity at 5 HALO. Both enzyme activities failed to show any significant interaction between STZ treatment and time of sacrifice, which means that diabetes does not influence the 24 h pattern of these activities. Since MPO, a heme protein localized in the leukocytes, is involved in the killing of microorganisms, increased MPO activity in diabetic rat liver may reflect leukocyte infiltration secondary to diabetes. A reduction in ADA activity during the dark (activity/feeding) period will presumably lead to high concentrations of adenosine in the liver, possibly contributing to changes in some metabolic processes, such as glycogen turnover and oxygen supply.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 25-31.

 
  Preserving effects of melatonin on the levels of glutathione and malondialdehyde in rats exposed to irradiation
Ö. Yıldırım 1), S. Çomoğlu, S. Yardımcı, M. Akmansu, G. Bozkurt, S. Sürücü

1)Department of Biology, Faculty of Sciences, Ankara University, 06100 Tandogan, Ankara, Turkey. yildirim@science.ankara.edu.tr.


In this study we investigated whether pretreatment with melatonin was protective against the injury of the central nervous system (CNS) in rats receiving LD50 whole body irradiation. The wistar rats were randomized into four groups: i) the control group (CG), ii) melatonin-administered group (MG; 1 mg/kg body weight), iii) irradiated group (RG; 6.75 Gy, one dose), and iv) melatonin-administered and irradiated group (MRG). Blood samples were drawn from the rats 24 h after the treatment and plasma glutathione levels were assayed. Plasma glutathione level was significantly higher in RG than CG. The melatonin pretreatment prevented GSH increase induced by irradiation. Lipid peroxidation and glutathione levels of rat cerebral cortex were determined in all groups after 24 h. Cortical malondialdehyde (MDA) was significantly higher in the RG. The melatonin pretreatment prevented cortical MDA increase induced by irradiation. Cortical GSH was significantly lower in RG than the CG. The melatonin pretreatment prevented cortical GSH decrease induced by irradiation. Tissue samples were obtained from cerebral cortex and hypothalamus which also were affected by ionizing irradiation in the CNS and were evaluated with electron microscopy. Histopathological findings showed that LD50 whole body irradiation resulted in damage of the neuronal cells of CNS. The results obtained from this study demonstrated that pretreatment with melatonin prevented the damage that develops in CNS following irradiation. The beneficial effect of melatonin can be related to protection of the CNS from oxidative injury and preventing the decrease in the level of cortical glutathione.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 32-37.

 
  Potassium-chloride promiscuous channels in mitochondrial membranes
K. Ondrias 1), L. Malekova, O. Krizanova

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


Mitochondrial membranes isolated from a rat heart muscle were incorporated into a bilayer lipid membrane (BLM) and channel currents were measured in 250/50 mmol/l KCl cis/trans solutions. The channel currents measured from −40 to +40 mV had various linear voltage-current relationships and K+/Cl permeability ratios at distinct voltage ranges. The channels possessed K+-Cl promiscuous property. Depending on voltage, membrane permeability suddenly switched from K+ over Cl to Cl over K+ and back. The channels had Cl/K+ > 1 permeability at potentials around 0 mV and the permeability was switched to K+/Cl > 1 at more negative and positive potentials. The chloride channel blocker, 5-nitro-2-(phenylpropylamino)-benzoate (NPPB, 5 × 10–5 mol/l), influenced properties of the promiscuous channels – it activated potassium conductance of the channels.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 38-44.

 
  Effects of voltage sensitive dye di-4-ANEPPS on guinea pig and rabbit myocardium
M. Novakova 1), J. Bardonova, I. Provaznik, E. Taborska, H. Bochorakova, H. Paulova, D. Horky

1)Department of Physiology, Faculty of Medicine, Masaryk University, Komenského náměstí 2, 662 43 Brno, Czech Republic. majka@med.muni.cz.


Voltage-sensitive dyes (VSDs) are used to record transient potential changes in various cardiac preparations. In our laboratory, action potentials have been recorded by optical probe using di-4-ANEPPS. In this study, the effects of two different ways of staining were compared in guinea pig and rabbit isolated hearts perfused according to Langendorff: staining either by coronary perfusion with low dye concentration or with concentrated dye as a bolus into the aorta. Staining with low dye concentration lead to its better persistence in the tissue. Electrogram and coronary flow were monitored continuously. During the staining and washout of the dye, prominent electrophysiological changes occurred such as a decrease in spontaneous heart rate, partial atrioventricular block and changes of ST-T segment, accompanied by a decrease in mean coronary flow. No production of hydroxyl radicals was found by HPLC which excluded significant ischemic damage of the myocardium. Good viability of the stained preparation was supported by unchanged electron microscopy. Since in rabbit hearts the VSD-induced arrhythmogenesis was less pronounced, we conclude that the rabbit myocardium is more resistant to the changes triggered by VSD application. It may be due to different properties of the membrane potassium channels in the cardiomyocytes of these two species.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 45-54.

 
  The effects of nitronium ion on nitration, carbonylation and coagulation of human fibrinogen
M. Ponczek 1), P. Nowak, B. Wachowicz

1)Department of General Biochemistry, University of Lodz, Banacha 12/16, 90 273 Lodz, Poland. mponczek@biol.uni.lodz.pl.


The effect of nitronium ion on nitration, carbonylation and coagulation of human fibrinogen (Fg) in vitro was investigated. We observed that nitration of tyrosine, induced by NO2BF4 (0.01 mmol/l), was increased. No changes in carbonylation by NO2BF4 (0.01 mmol/l) were noticed. Mentioned alterations were associated with amplified coagulation of Fg. Higher concentrations of NO2BF4 (1 and 0.1 mmol/l) triggered growth of nitration and carbonylation of Fg, but led to inhibi-tion of polymerization. Slight nitration may be responsible for increase, whereas sizable nitration and oxidation may lead to inhibition of Fg coagulation.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 55-58.

 
  Angiopoietin-like protein 4: development, analytical characterization, and clinical testing of a new ELISA
D. Stejskal 1), M. Karpíšek, H. Reutová, V. Humeňanská, M. Petzel, P. Kušnierová, I. Vařeka, R. Vařeková, P. Stejskal

1)Department of Laboratory Medicine, Šternberk Hospital, Jivavská 20, 785 16 Šternberk, Czech Republic. david.stejskal@nemstbk.cz.


The aim of our work was to develop an assay for the determination of angiopoietin-like protein 4 (Angplt4) in human blood, and to investigate its levels in healthy volunteers and donors suffer from metabolic syndrome. We developed and evaluated the sandwich ELISA method for the quantitative determination of human Angplt4 in serum samples. We conducted also the pilot study on individuals with metabolic syndrome or familiar hypercholesterolemia and healthy probands and measured blood pressure, waist circumference, Angplt4 serum levels, serum cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, insulin, glucose, A-FABP and calculate BMI and QUICKI insulin sensitivity index. In the study on 30 healthy volunteers we demonstrated that sex or age is not the determinant for Angplt4 serum values. Futhermore, we tested 115 individuals with metabolic syndrome and found that probands with metabolic syndrome did not differ in Angplt4 values than healthy individuals from the first study (medians 8.7 vs. 8.1 ng/ml, p = 0.6). Individuals with metabolic syndrome did not differ in sex or age from healthy. Angplt4 values correlated with the HDL-cholesterol (r = −0.25; p < 0.01), FGF-21 (r = 0.23, p < 0.01), glucose (r = 0.17; p = 0.03), uric acid (r = 0.17; p = 0.49), lipocalin-2 (r = 0.23, p < 0.01), triacylglycerols (r = 0.25; p < 0.01) and number or characters of metabolic syndrome (r = 0.21; p < 0.01). No significant correlation was found between serum Angplt4 and BMI, WC or QUICKI. However, we performed stepwise regression and we found that Angplt4 was not an independent marker for metabolic syndrome. The patients from the metabolic syndrome group suffering diabetes mellitus (n = 83) did not differ in serum Angplt4 from the group of healthy patients, too. The pilot study supports the hypothesis about the role of Angplt4 as a new class of lipid metabolism modulator. Their values could be a new key predictors of metabolic syndrome. Further research is necessary to confirm our findings in individuals with dyslipidemia, obesity, coronary artery diseases and different medication in order to assess Angplt4 value as a risk predictor of accelerated atherosclerosis.

General Physiology and Biophysics. Volume 27, 2008, No. 1: 59-63.