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Öğe Cooling and response to hydrogen peroxide in human saphenous vein: role of the endothelium(WILEY, 2005) Sahin, AS; Atalik, KE; Sahin, TK; Dogan, NIn the present work we studied the responses of human saphenous vein to H2O2 and effects of moderate cooling on these responses with analysis of the role of endothelium. H2O2 (10(-7)-10(-2) m) induced concentration-dependent contraction in the intact human saphenous vein strips at both temperatures. At 28 degrees C, the maximal contraction induced by H2O2 was significantly lower than that at 37 degrees C. Compared with intact strips, the sensitivity and the maximal contraction to H2O2 were significantly enhanced in endothelium-denuded strips at 37 and 28 degrees C. However, pD(2) values and maximal contractions were not significantly different in endothelium-denuded strips at different temperatures. Pretreatment with N-G-nitro-L-arginine methyl ester (L-NAME) increased significantly the maximal contraction and sensitivity to H2O2 at 37 and 28 degrees C. The contractions increased by L-NAME were restored by the pre-incubation Of L-arginine (10(-3) m) at every temperature studied. The contractile responses of intact human saphenous veins to H2O2 were reduced significantly by 10(-5) m indomethacin at both temperatures. Our results suggest that H2O2-induced contraction of human saphenous vein are mediated by its direct effect on the smooth muscle and by the generation of products of the cyclooxygenase pathway from the endothelium. Signalling pathways of these contractile effects are the same at 3 7 and 28 degrees C. Under normal temperature conditions, the contraction to H2O2 is possibly modulated by endothelial nitric oxide. Cooling reduces the contraction to H2O2 by increasing release of nitric oxide.Öğe The effect of bupivacaine on compound action potential parameters of sciatic nerve fibers(TAYLOR & FRANCIS LTD, 2004) Dalkilic, N; Bariskaner, H; Dogan, N; Demirel, I; Ilhan, BThe aim of this study was to document the effects of the local anesthetic agent bupivacaine on individual fibers of peripheral nerve. To accomplish this objective, compound action potentials (CAPs) were recorded from isolated frog sciatic nerves treated with bupivacaine for seven individual concentration levels. Numerical and fast Fourier transform (FFT) analysis were performed on these recordings. The areas, latency periods, maximum and minimum derivatives, and power spectrums of the CAPs were computed. The results show that the area and the absolute values of maximum and minimum derivatives decrease linearly as bupivacaine concentration increases. The power spectrum of the CAPs, which resides in the 0-1000 Hz interval, initially shifts to higher frequencies then returns to lower frequency region again with increasing bupivacaine concentration. Due to this result, it is thought that bupivacaine inhibits nerve fibers in a dose-dependent manner. It primarily affects the fibers having the least myelin sheets (motor fibers), then it begins to depress the fast conducting (neurosensorial) fibers as the bupivacaine concentration increases, and finally blocks the unmyelinated C-fibers.Öğe Effects of magnesium sulfate on Na+,K+-ATPase and intracranial pressure level after cerebral ischemia(JOHN LIBBEY EUROTEXT LTD, 2004) Ustun, ME; Bariskaner, H; Yosunkaya, A; Gurbilek, M; Dogan, NIn the present study, the effects of magnesium sulfate on Na+,K+-ATPase levels and intracranial pressure (ICP) after cerebral ischemia in rabbits were studied. Thirty New Zealand rabbits were divided into three groups. Group I was the control group. In group 2 (untreated group) cerebral ischemia was produced by clamping bilateral common carotid arteries for 60 min but in group 3 magnesium sulfate was administered 100 mg/kg i.v. 10 min after opening the clamps. In group 1, ICP recordings were obtained 5, 60 and 120 min after craniectomy. In groups 2 and 3, ICP recordings were obtained 5 min after craniectomy but before clamping, 60 min after clamping and 60 min after opening the clamps. After taking ICP recordings, brain cortices were resected and Na+,K+-ATPase activity was determined by subtracting the enzyme activity in the presence of ouabain from the total activity in the absence of ouabain method. There was a significant difference between Na+,K+-ATPase levels of ;group 1 and group 2 (P < 0.05). There was no significant difference in Na+,K+-ATPase levels between group 1 and 3 (P > 0.05), also preischemic ICP values were same in all groups (P > 0.05). Preischemic and postischemic ICP values were significantly different between groups 1 and 2 (P < 0.05), also postischemic (120 min) ICP values were significantly different between group 2 and group 3 (P < 0.05). ICP values correlate well with Na+,K+-ATPase level. These results demonstrate that cerebral ischemia leads to a decrease of ATPase level in the brain and magnesium sulfate suppresses the decrease of Na+,K+-ATPase, also magnesium sulfate treatment improves the ICP changes.Öğe The relaxant effects of alfentanil and remifentanil on noradrenaline-treated rat aorta(VSP BV, 2003) Tuncer, S; Bariskaner, H; Dogan, NBackground and objective: In this in vitro study on rat thoracic aorta, the effects of indomethacin (a prostaglandin synthesis inhibitor), propranolol (a beta adrenergic receptor blocker), tetraethylammonium (TEA) (a calcium-actived potassium channel blocker), glibenclamide (an ATP-dependent potassium channel blocker) and naloxone (an opioid receptor antagonist) on the responses induced by alfentanil and rernifentanil were investigated. Methods: Aortas isolated from rats were cut into spiral strips 12 mm in length, 3 mm wide. Strips were mounted in organ baths at 37degreesC continuously gassed with 95% and 5% CO2. The responses of the drugs were recorded isometrically on polygraph. Results: In both groups, strips were precontracted with 10(-6) M noradrenaline (NA). Then alfentanil or remifentanil (10(-8) to 10(-5) M) was administered cumulatively. Both alfentanil and rernifentanil significantly produced relaxation (p < 0.05). Indomethacin, propranolol, TEA, glibenclamide and naloxone did not significantly modify responses of the opioids. The rank order of potencies of these drugs was alfentanil > remifentanil. Conclusion: Prostaglandins, beta adrenergic receptors, potassium channels and opioid receptors have no role in the responses induced by alfentanil and remifentanil.Öğe The role of K+ ions on the response to carbachol of calf coronary artery and cardiac vein during cooling(PROUS SCIENCE, SA, 2001) Atalik, KE; Sahin, AS; Ulusoy, HB; Dogan, NThe role of K+ ions on the vasoconstrictions induced by carbachol during cooling (28 degreesC) in the endothelium of a denuded calf coronary artery and cardiac vein (noncutaneous vessel) was studied. Carbachol (10(-9) - 3 X 10(-4)M) induced concentration-dependent contractions at both 37 degreesC and 28 degreesC. The sensitivity, but not the maximal response, of carbachol (10(-9) - 3 x 10(-4) M) was significantly lower at 28 degreesC than at 37 degreesC. Cooling to 28 degreesC after treatment with tetraethylammonium (TEA, 10(-3) M) or ouabain (10(-5) M), or after incubation in K+-free medium, increased the sensitivity to carbachol in both preparations. The results suggest a role for K+ ions in the cooling-induced changes of noncutaneous vessels. (C) 2001 Prous Science. All rights reserved.Öğe Warming and response to contractile agents in calf cardiac vein: Role of the Ca2+, K-Ca(2+), and Na+ ion channel blockers(PROUS SCIENCE, SAU-THOMSON REUTERS, 2005) Atalik, KE; Sahin, AS; Dogan, NThe effects of wartning (to 41 degrees C) oil the serotonin (5-HT, 10(-8)-3 x 10(-3) M)- and carbachol (10(-9)-3 x 10(-4) M)-induced contractions and the role of calcium (Ca2+). potassium (K+), and sodium (Na+) channel blockers, in the warming-induced responses were investigated in the calf cardiac vein. Concentration-response curves to 5-HT and carbachol were isometrically recorded at 37 and 41 degrees C (control). The same procedure was repeated at 41 degrees C in the presence of verapamil (10(-6) M), caffeine (3 x 10(-4) M), tetraethylammonium (TEA, 10(-3) M), flecainide (10(-6) M), and also in the Ca2+-free medium with ethlylene glycol bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA). During warning, the sensitivity, but not the maximum response, was significantly higher. Warming to 41 degrees C after treatment with verapamil or flecainide decreased the sensitivity, whereas treatment with caffine increased the sensitivity significantly. Treatment with TEA (lid not modify the effect of warming. Furthermore, warming to 41 degrees C after incubation in Ca2+-free solutions with EGTA decreased the sensitivity to 5-HT and carbachol. The results of this study suggest the role for Ca2+ and Na+ ions in the warming-induced changes of cardiac vein treated with 5-HT and carbachol. (c) 2005 Prous Science. All right reserved.Öğe Warming and Response to Contractile Agents in Calf Cardiac Vein: Role of the Nitric Oxide(BLACKWELL PUBLISHING LTD, 2003) Atalik, Kısmet Esra; Sahin, AS; Ulusoy, HB; Dogan, NThe effects of warming on the response to various contractile agents of calf cardiac vein were studied using 2.5-mm long cylindrical segments. Concentration-response curves for carbachol (10(-9)-3 x 10(-4) M), 5-hydroxytryptamine (5-HT; 10(-8)-3 x 10(-3)), potassium chloride (KCl; 10(-4)-5 x 10(-2) m) and calcium chloride (CaCl2; 10(-4)-10(-2)) were isometrically recorded at 37 and 41degreesC (warming). During warming the sensitivity, but not the maximal response, of carbachol 5-HT, KCl, and CaCl2 was significantly higher than at 37degreesC. Warming to 41degreesC after treatment with N-G-nitro-L arginine methyl esther (10(-5) m) did not modify the effect of warming. These results suggest that nitric oxide seems to have no role in the warming-induced responses in calf cardiac vein.
