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Zoznam článkov

General Physiology and Biophysics


Volume 25, 2006, No. 1

Content:


  Is the ApoE polymorphism associated with dilated cardiomyopathy?
D Jurkovicova 1), E Goncalvesova, B Sedlakova, S Hudecova, J Fabian, O Krizanova

1)Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlárska 5, 833 34 Bratislava 37, Slovakia. dana.jurkovicova@savba.sk.


Apolipoprotein E (ApoE) is 34 kDa protein involved in the modulation of cholesterol transport and homeostasis. Polymorphism of the ApoE gene has been implicated in many chronic cardiovascular and neuronal diseases. ApoE ε4 allele has been reported to be associated with increased risk of cardiovascular diseases such as myocardial infarction, hypertension, coronary heart disease, etc. Fifty patients with the end-stage dilated cardiomyopathy (DCM) and advanced congestive heart failure were examined in our study. For evaluation of ApoE polymorphism, novel approach of fast screening of ApoE gene polymorphism by combination of PCR and blotting (CVD StripAssay) was used. Individual genotypes were correlated with basic cardiologic clinical parameters. The reported frequency of this allele in Caucasian population is 14.7 %. Our results showed that in patients with DCM frequency of the ApoE ε4 allele is 40 %. Frequency of the genotype ε2/4 was 58 % and ε3/4 was 22 %. Comparison with control Caucasian groups monitored by others clearly revealed that frequency of ε4 alelle is increased in patients with advanced stages of DCM. This observation suggests association of ApoE polymorphism with severe form of DCM. Physiological consequences of this observation remain to be clarified.

General Physiology and Biophysics. Volume 25, 2006, No. 1: 3-10.

 
  Time dependent effects of dexamethasone on serum insulin level and insulin receptors in rat liver and erythrocytes
G Korićanac 1), E Isenović, V Stojanović-Šušulić, D Mišković, Z Žakula, N Ribarac-Stepić

1)Department of Molecular Biology and Endocrinology, „Vinča“ Institute of Nuclear Sciences, P.O.Box 522, 11001 Belgrade, Serbia and Montenegro. gogi@vin.bg.ac.yu.


The effects of glucocorticoid excess on regulation of insulin receptors were investigated in dexamethasone-treated rats. Glucocorticoid excess was produced by administration of dexamethasone (0.5 mg/100 g b.w.) 30 min, 4, 12, 18, 24, 42 or 70 h before experiments. This treatment caused time-dependent changes of glucose and insulin concentration in blood, as well as in amounts of specific insulin binding and insulin receptors of liver cells and erythrocytes. The time intervals in which dexamethasone produced the increase in insulin concentration were accompanied with decrease in insulin binding to receptors in membranes of liver cells, while significant changes in insulin binding to receptors of erythrocytes were not observed under the same experimental conditions. The effect is maximal 18 and 42 h after dexamethasone treatment that increase insulin blood level by about 85% and 60%, respectively. Receptor analysis revealed that changes in specific binding of insulin could be due to significant changes in amount of binding sites on cell surface rather than to mild alteration in receptor affinity. These findings suggest that besides the changes in insulin level, the alterations in insulin receptor number and affinity may play a major role in the states of altered insulin sensitivity which accompany glucocorticoid excess.

General Physiology and Biophysics. Volume 25, 2006, No. 1: 11-24.

 
  Changes in the expression and/or activation of regulatory proteins in rat hearts adapted to chronic hypoxia
M Strnisková 1), T Ravingerová, J Neckář, F Kolář, S Pastoreková, M Barančík

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


Chronic intermittent high altitude (IHA) hypoxia results in long-term adaptation protecting the heart against acute ischemia/reperfusion injury; however, molecular mechanisms of this phenomenon are not completely elucidated so far. The present study was aimed at investigation of a modulating effect of IHA hypoxia on the expression and/or activation of selected regulatory proteins, with particular emphasis on differential responses in the right ventricle (RV) and left ventricle (LV). Adult male Wistar rats were exposed to IHA hypoxia of 7000 m simulated in a hypobaric chamber (8 h/day, 25 exposures), and protein contents and activities in myocardial fractions were determined by Western blot analysis. In markedly hypertrophic RV of hypoxic rats, gelatinolytic activity of MMP-2 and protein levels of carbonic anhydrase IX (a marker of hypoxia) were significantly enhanced. Study of mitogen-activated protein kinases (MAPKs) revealed no differences in the contents of total p38-MAPK in both ventricles between the IHA and normoxic control rats, whereas activation of p38-MAPK was decreased in the RV and moderately increased in the LV of IHA rats as compared to controls. Extracellular signal regulated kinase-2 (ERK-2) was partially up-regulated in the RV of IHA rats, and, in addition, expression of acidic fibroblast growth factor (aFGF), a potential activator of ERK cascade, was also significantly increased. In contrast, expression of ERKs in the LV as well as their activities in both ventricles, were not affected by IHA hypoxia. Differential effects of IHA hypoxia on c-Jun-N-terminal protein kinases (JNKs) in the RV and LV were also observed. As compared with the controls, total content of JNKs was increased in the RV of the IHA rats, while expression of JNKs in the LV was down-regulated. IHA hypoxia changed neither total levels of Akt kinase in both RV and LV, nor Akt kinase activity in the RV. However, increased levels of activated phospho-Akt kinase were found in the LV of IHA rats. The results demonstrate that adaptation of rat hearts to chronic IHA hypoxia is associated with disctinct changes in the levels and/or activation of several regulatory proteins in two ventricles. The latter could be attributed to both myocardial remodeling and cardioprotection induced by chronic hypoxia.

General Physiology and Biophysics. Volume 25, 2006, No. 1: 25-41.

 
  Blockade of AT1 receptors by losartan did not affect renin gene expression in kidney medulla
K Tybitanclová 1), Ľ Szabová, M Grima, C Ingert, B Železná, Š Zórad

1)Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlárska 3, 833 06 Bratislava 37, Slovakia. katarina.tybitanclova@savba.sk.


This study was designed to determine particular changes in the renin gene expression and activity in renal cortex and medulla after AT1 receptor blockade. It was found that two-week-treatment with AT1 blocker losartan induced an increase in tissue renin activity in both parts of kidney causing subsequent elevation of plasma renin activity. Renin mRNA in losartan-treated rats was increased only in cortex, suggesting cortex origin of elevated renin activity in medulla. Medullary renin mRNA indicated local synthesis of renin within the whole kidney and supported the idea of the presence of tissue renin-angiotensin system. Our results show that gene expression of renin in kidney medulla is insensitive to AT1 receptor blockade and this points out that the regulation of kidney renin-angiotensin system probably differs from that in cortex.

General Physiology and Biophysics. Volume 25, 2006, No. 1: 43-51.

 
  Mechanistic equations for membrane transport of multicomponent solutions
G Suchanek 1)

1)Institute of Physics, Świetokrzyska Academy 15, 25-406 Kielce, Poland. suchaneg@pu.kielce.pl.


In the present article, mechanistic equations for membrane transport of N+1-component solutions have been derived. The major specific investigation result is the introduction – for ternary solutions – of two diffusion coefficients ωd1 and ωd2 for solutes, as well as two cross coefficients ωd12 and ωd21 for these solutes. The latter parameters may be treated as coefficients of interdiffusion. The expansion of the description of substance transport to include the N+1-component solutions does not formulate any additional physical phenomena other than those which are formulated by the transport equations for three-component solutions.

General Physiology and Biophysics. Volume 25, 2006, No. 1: 53-63.

 
  Effect of valproic acid and antiapoptotic cytokines on differentiation and apoptosis induction of human leukemia cells
M Řezáčová 1), J Vávrová, D Vokurková, D Záškodová

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


This work compares effect of histondeacetylase inhibitor, valproic acid (VA), on proliferation, differentiation and apoptosis induction in two human leukemic cell lines: HL-60 (human promyleocytic leukemia, p53 negative) and MOLT-4 (human T-lymphocyte leukemia, p53 wild type). Incubation with VA caused decrease in percentage of cells in S phase of cell cycle. The decrease was more intensive in HL-60 cells, where the cells in S phase were absent 6 days after the beginning of incubation with VA (4 mmol/l). 3-day-long incubation of HL-60 cells with 4 mmol/l VA caused differentiation of these cells, marked by increase in CD11b and co-stimulatory/adhesion molecule CD86, and induction of a significant apoptosis. Annexin V positive cells lost the CD11b antigen. 3-day-long incubation of MOLT-4 cells with VA (1–2 mmol/l) inhibited proliferation and decreased percentage of cells in S phase of the cell cycle. 90% of MOLT-4 cells are CD7 positive. This CD7 positivity is not changed during apoptosis induction (detected as Annexin V positivity). On the other hand, CD4 marker expression decreases after incubation with 1–2 mmol/l VA, but during apoptosis induction by 4 mmol/l VA, most of the apoptotic Annexin V positive cells were also CD4 positive. Using a clonogenic survival assay EC50 for 3-day-long incubation with VA was determined. For HL-60 cells, the established EC50 was 1.84 mmol/l, for MOLT-4 cells it was 1.76 mmol/l. Ability of VA to induce differentiation in HL-60 cells thus does not affect final cell killing. However, the elimination of the cells was considerably affected by presence of hematopoietic growth factors. 14-day-long incubation of HL-60 cells with VA in conditioned medium (source of IL-3, SCF, G-CSF) caused increase in EC50 to 4 mmol/l, while in MOLT-4 cells (cultivation without conditioned medium), the EC50 decreased to 0.63 mmol/l.

General Physiology and Biophysics. Volume 25, 2006, No. 1: 65-79.

 
  Effect of pentoxifylline on endothelaemia and hypothalamic-pituitary-adrenocortical axis activation in female rats under stress exposure
V Kristova 1), A Kiss, Z Pirnik, M Kriska, D Jezova

1)Department of Pharmacology, Faculty of Medicine, Comenius University, Sasinkova 4, 813 72 Bratislava 1, Slovakia. viera.kristova@fmed.uniba.sk.


Endothelial dysfunction may belong to negative consequences of stress exposure accompanied by activation of several stress systems including the hypothalamic-pituitary-adrenocortical (HPA) axis. The present experiments were aimed at testing the hypotheses that i) immobilization (IMO) stress results in sustained increase in endothelaemia for 24 h and that ii) pentoxifylline, a drug with endothelium protective properties, attenuates the rise in endothelaemia and HPA axis activation in female rats as shown previously in males. Circulating endothelial cells increased immediately after the IMO for 2 h, returned back to control levels at 12 h and increased again at 24 h. Stress-induced rise in adrenocorticotropic hormone (ACTH) and corticosterone levels was particularly high immediately after the IMO. Pretreatment with pentoxifylline (20 mg/kg subcutaneously for 7 days) attenuated the rise in endothelaemia and adrenal corticosterone measured at 24 h following IMO. Plasma levels of ACTH and proopiomelanocortin gene expression in the anterior pituitary were not affected by pentoxifylline treatment. The present results indicate that IMO stress in female rats induces a biphasic rise in endothelaemia early at the time of stress exposure and than 24 h thereafter. Based on these data and our previous study we can conclude that intensive stress has a negative influence on endothelial cells in both sexes and no gender differences seem to be present in the protective action of pentoxifylline.

General Physiology and Biophysics. Volume 25, 2006, No. 1: 81-89.

 
  Inhibition of rat brain ecto-atpase activity by various drugs
A Horvat 1), T Orlić, A Banjac, T Momić, S Petrović, M Demajo

1)Laboratory for Molecular Biology and Endocrinology, „Vinča“ Institute of Nuclear Sciences, P.O.Box 522, 11001 Belgrade, Serbia and Montenegro. ahorvat@vin.bg.ac.yu.


The in vitro effect of digoxin, verapamil, propranolol, carbamazepine, diazepam and promethazine were investigated on the ecto-ATPase activity of synaptosomal plasma membranes from the rat brain. ATP hydrolyzing activities of the enzyme were not affected by digoxin while the use of all other drugs resulted in significant and dose-dependent ihibition in ATP hydrolysis. According to values of IC50 and Kiapp, the order of inhibitory potency of the drugs applied was: diazepam > promethazine > verapamil > propranolol >> carbamazepine. Kinetic analysis of the nature of the ATPase inhibition revealed that it resulted from a direct action of drugs on the enzyme protein. The aim of the present study was to determine the potential neuromodulatory side effects of the drugs investigated. The results achieved indicated that all investigated drugs, except digoxin, may modulate neuronal activities via the purinergic receptors P2 by increasing extracellular concentrations of ATP as a consequence of inhibition of the ecto-ATPase activity. Our findings indicate that it may be useful to take into consideration the possible side effects of the investigated drugs, when they are used in treatment of different pathologies, particularly in the treatment of epilepsy by carbamazepine and diazepam.

General Physiology and Biophysics. Volume 25, 2006, No. 1: 91-105.