Person: YEGEN, BERRAK
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YEGEN
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BERRAK
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Publication Metadata only Bombesin ameliorates colonic damage in experimental colitis(1999) YEGEN, BERRAK; Güllüoğlu, B. M.; Kurtel, H.; Güllüoğlu, M. G.; Aktan, A. O.; Yeğen, B. C.; Dizdaroğlu, F.; Yalin, R.; Yeğen, B. C.In the present study we investigated the possible therapeutic effects of bombesin on an experimentally induced colitis model in rats. Inflammation of the colon was induced by a single intracolonic administration of 30 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS) at 8 cm from the anus. Immediately after the induction of colitis, some rats were given bombesin (10 microg/kg; subcutaneously) three times a day for 14 days, while another group received vehicle treatment. On day 14, the rats were decapitated and plasma carbonyl content and tissue myeloperoxidase level, as an index of granulocyte infiltration into intestinal tissue, were determined in order to obtain an objective evaluation of colonic injury. In the colitis group, increased macroscopic damage score, elevated MPO level and high plasma carbonyl content, together with the microscopic appearance revealed severe inflammatory changes resembling IBD. Bombesin treatment attenuated the TNBS-induced colonic damage and stimulated histopathologically apparent mucosal proliferation, suggesting that bombesin may play a role in protecting gut integrity.Publication Metadata only Inhibitory effects of gastrin releasing peptide on gastric emptying in rats(ELSEVIER SCIENCE BV, 1996) YEGEN, BERRAK; Yegen, BC; Gurbuz, V; Coskun, T; Bozkurt, A; Kurtel, H; Alican, I; Dockray, GJGastrin-releasing peptide (GRP) has a wide range of biological actions, including stimulation of the frequency of antral contractions and delaying gastric emptying. The present study was designed to evaluate the role of GRP in the control of gastric emptying of liquid test meals in the rat. The emptying of methyl cellulose given by gavage to fasted rats, or of saline given via the fistula to conscious gastric fistula rats was not influenced by the GRP antagonists, NC-8-89 (Leu(13)-psi-(CH2NH)-Leu(14)-bombesin) and 2258U89 ((de-NH2)Phe(19),D-Ala(24),D-Pro(26)psi (CH2NH)Phe(27)(-GRP (19-27)), at 2 mg/kg, s.c. However, both antagonists (0.02, 0.2 and 2 mg/kg) reversed the inhibitory effect of HCl on gastric emptying in gastric fistula rats (P < 0.05-0.001). When peptone was administered after a preload, but not otherwise, the inhibition of emptying was also partly reversed by both antagonists at all doses used (P < 0.05-0.001). Interestingly, the delay in the emptying of hyperosmolal saline compared to saline, was enhanced at a dose of 0.2 mg/kg of both antagonists (P < 0.05 and P < 0.01). Food intake did not change significantly with the two lower doses of antagonists, but was decreased by the highest dose of NC 8-89. We conclude that GRP specifically inhibits gastric emptying of acid and peptone solutions in the conscious rat.Publication Metadata only Pathways mediating CRF-induced inhibition of gastric emptying in rats(1997) YEGEN, BERRAK; Coşkun, T.; Bozkurt, A.; Alican, I.; Ozkutlu, U.; Kurtel, H.; Yegen, B. C.The corticotrophin-releasing factor (CRF) is shown to be released during stress suggesting that CRF has a physiological role in the mediation of central nervous system (CNS) response to stress, including an inhibitory effect on gastric emptying. In the present study, we have examined the pathways by which intracerebroventricularly (i.c.v.) administered CRF and central CRF activation during stress alter the gastric emptying rate of saline (0.14 M), acid (50 mM), peptone (4.5%) and peptone after preload. The emptying rates of all these test meals were significantly (p < 0.05-0.001) delayed with increasing doses of i.c.v. CRF (0.001, 0.003, 0.01, 0.1, 0.3 and 1 nmol/10 microl), when compared with their i.c.v. saline-treated controls. The 1-nmol dose of CRF inhibited the emptying of acid, peptone and peptone after a preload by 43.8%, 64.1% and 81.1%, respectively. Twenty-minute swim stress delayed gastric emptying rate of saline, acid and peptone solutions significantly (p < 0.001) and the CRF receptor antagonist, alpha-helical CRF (8 nmol/10 microl, i.c.v.), applied before the swim stress, abolished the inhibitory effect of stress on the emptying rate of these solutions. Acute intragastric administration of capsaicin (2 mg/rat) and systemic capsaicin (125 mg kg(-1)) treatment facilitated the gastric emptying rate of acid, peptone and peptone after preload significantly, almost abolishing the inhibitory effect of central CRF (p < 0.001). However, either capsaicin treatment had no effect on stress-induced inhibition of the gastric emptying of none of the solutions, except peptone after a preload. Our findings demonstrate that the gastric inhibitory response induced by swimming as a stress-producing stimulus is mediated by the endogenous release of CRF. They also suggest that CRF exerts its CNS actions on the gastrointestinal tract via vago-vagal, capsaicin-sensitive pathways, probably involving the central cholecystokinin (CCK) mechanisms.Publication Metadata only Effect of cold-restraint stress on glutathione and lipid peroxide levels in the liver and glandular stomach of rats(1990) YALÇIN, AHMET SUHA; Yeğen, B.; Dedeoğlu, A.; Aykaç, I.; Oktay, S.; Yalçin, A. S.The effect of starvation and cold-restraint stress on glutathione and lipid peroxide levels in the liver, stomach and plasma of rats was investigated. Hepatic and gastric glutathione levels were significantly decreased in starvation and cold-restraint groups when compared with values obtained from the control group. In both tissues, lipid peroxide levels were significantly decreased after starvation but were not significantly different from control values after cold-restraint treatment. However, when compared with the values obtained from the starvation group there was a significant increase in both hepatic and gastric lipid peroxide levels after cold-restraint. Plasma lipid peroxide levels were slightly decreased in the starvation group and significantly increased in the cold-restraint group. Our results suggest that pathological consequences of stress on different tissues could be due to stimulation of lipid peroxidation.Publication Metadata only NICARDIPINE REDUCES THE LEVELS OF LEUKOTRIENE-C4 AND PROSTAGLANDIN-E2, FOLLOWING DIFFERENT ISCHEMIC PERIODS IN RAT-BRAIN TISSUE(CHURCHILL LIVINGSTONE, 1992) YEGEN, BERRAK; AKTAN, S; AYKUT, C; OKTAY, S; YEGEN, B; ERCAN, SIschemic depolarization of nerve membranes is associated with a rapid influx of calcium into the cell, resulting in production of arachidonic acid (AA) metabolites. These metabolites, particularly leukotriene C4 (LTC4) have a very potent vasoconstrictor effect on cerebral arteries inducing vasogenic edema that may damage the ischemic penumbra. Calcium antagonists are assumed to prevent or reduce metabolic disturbances associated with ischemia. In this study, after developing an experimental animal model simulating the concept of the ischemic penumbra in the rat, the levels of LTC4 and prostaglandin E2 (PGE2) produced in the forebrain following different ischemic periods, such as 4th, 15th, 60th and 240th min were measured by a bioassay method, including 6 rats for each ischemic group. Then the effect of the 1-4 dihydropirine nicardipine (1 mg/kg) on these mediators was investigated by giving it to the rat 30 min before the development of the ischemic model in each corresponding group (n = 6). We showed that nicardipine significantly reduced the high levels of LTC4 and PGE2 in the 4th min and 4th h of cerebral ischemia (p < 0.005, p < 0.0005). So it may be concluded that institution of nicardipine may be helpful in protecting the ischemic penumbra during the early hours of cerebral ischemia.Publication Metadata only THE HYPOTENSIVE EFFECT OF CISAPRIDE IN RAT(ELSEVIER SCIENCE INC, 1994) YEGEN, BERRAK; ONAT, F; YEGEN, B; BERKMAN, K; OKTAY, S1. Cisapride is a prokinetic agent believed to facilitate acetylcholine release from the myenteric plexus of the gut. The aim of the present study was to investigate the effect of cisapride on blood pressure and the effects of muscarinic receptor antagonists on the cisapride-induced blood pressure changes. 2. Cisapride was given i.v. alone or 10 min after muscarinic receptor antagonists. Cisapride given i.v. produced a significant decrease in blood pressure in a dose-related manner. Atropine, AF-DX 116 and 4-DAMP given 10 min before cisapride injection, partially inhibited the hypotensive response to cisapride. In pithed rat, the effect of cisapride on blood pressure remained unaltered. 3. This study indicates that the action of cisapride is not through central mechanisms and part of cisapride's effect is through the cholinergic system.Publication Metadata only GASTRIC LIPID-PEROXIDATION, GLUTATHIONE AND CALCIUM-CHANNEL BLOCKERS IN THE STRESS-INDUCED ULCER MODEL IN RATS(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 1994) YEGEN, BERRAK; ALICAN, I; TOKER, F; ARBAK, S; YEGEN, BC; YALCIN, AS; OKTAY, SThe antiulcer activity of verapamil and its analogues devapamil and gallopamil was studied. All three drugs reduced cold-restraint stress-induced ulcer development. Gallopamil almost abolished gastric ulcers. Verapamil prevented the increase in gastric lipid peroxidation (LP) due to stress. On the other hand, devapamil and gallopamil increased gastric lipid peroxidation and decreased glutathione levels. This effect may be attributed to the increase in oxygen supply due to possible effective vasodilation at gastric mucosa. The second part of this study revealed that stress-induced gastric ulcers in rats rapidly and spontaneously heal and disappear within 24 h. During recovery, gastric LP decreased and glutathione levels increased within 12 h after the withdrawal of stress, preceded by an initial reduction in glutathione. After 72 h, an unexplained increase in gastric LP and a decrease in glutathione were observed. Treatment with verapamil, devapamil and gallopamil promoted healing, gallopamil being again the most effective. Their effects on gastric LP and glutathione levels are in accordance with the results of pretreatment experiments. In conclusion, devapamil and gallopamil are effective antiulcer agents against stress-induced ulcers, but unlike verapamil, antioxidant activity does not seem likely to be among their mechanisms of action.Publication Metadata only Oxidative organ damage in a rat model of thermal injury: the effect of cyclosporin A(1997) YEGEN, BERRAK; Gürbüz, V.; Corak, A.; Yeğen, B. C.; Kurtel, H.; Alican, I.Animal models of thermal trauma implicate oxygen radicals as a causative agent in local wound response, development of burn shock and distant organ injury. It has been proposed that the source of reactive oxygen metabolites could be neutrophils sequestered in systemic organs as a result of the systemic inflammatory reaction to a local burn insult. Recent studies have suggested that cyclosporin A (CsA), a potent immunosuppressive drug, may have effects on neutrophils by modulating the rate of their accumulation during acute inflammatory reactions. This study aimed to assess the role of neutrophils in the early and late phases of burn injury in rats with second-degree skin burn. We also aimed to determine whether CsA has protective effects on organs remote from the thermal injury. The results demonstrate that there is significant neutrophil accumulation in the gastric mucosa, liver and lung tissues during the early phase of a burn injury and that CsA failed to protect these organs. In conclusion, the data of this study suggest that neutrophil accumulation in liver, lung and gastric mucosa following burn injury may be involved in the pathogenesis of remote organ damage. The results also indicate that CsA failed to reduce the severity of damage in these organs, probably due to its own toxic effects.Publication Metadata only Effect of intraluminal temperature on human oesophageal motor function(1998) YEGEN, BERRAK; Özdoǧan O., Saadalla A.J.A., Emironal G., Yeǧen B.Ç., Ulusoy N.B.Oesophageal motor activity is altered by bolus temperature. The effects of sustained cold or warm intraluminal temperature on oesophageal motility have not been documented in detail. Oesophageal manometry was performed in 11 normal subjects after intraluminal room, cold- and warm-water treatments. The intraluminal temperatures were 34.2 ± 0.8, 30.6 ± 1.7 and 39.7 ± 0.9°C respectively during room temperature, cold and warm applications. Low-temperature treatment prolonged the duration of lower oesophageal sphincter relaxation and the duration of oesophageal peristaltic contraction wave compared with the room temperature and warm treatments. Low temperature also attenuated the mean pressure slope of oesophageal contraction waves and resulted in an increased percentage of non-transmitted and simultaneous contractions. The effects of low-temperature application persisted as long as the intraluminal temperature remained constant and there was no adaptation. Cooling oesophageal lumen temperature alters oesophageal motor activity, and this effect is not adaptive.Publication Metadata only CARDIOVASCULAR EFFECTS OF CENTRALLY ACTIVE CHOLINOMIMETICS IN CONSCIOUS AND ANESTHETIZED RATS - THE ROLE OF AMYGDALA(PERGAMON-ELSEVIER SCIENCE LTD, 1995) YEGEN, BERRAK; OZKUTLU, U; COSKUN, T; ONAT, F; YEGEN, BC; OKTAY, SCentral cardiovascular effects of cholinergic agonists depend on the dose, site and mode of administration, species, and to the state of the animal. Intravenous injection of physostigmine and intracerebroventricular injection of carbachol produced presser and tachycardic responses in urethane-anesthetized rats. Both agents also elicited presser responses in conscious rats, but bradycardia occurred in the presence of anesthesia, Additionally, presser responses to physostigmine, but not to carbachol, were significantly exaggerated by urethane anesthesia. These results demonstrate that anesthesia depresses cardiovascular reflexes and the inhibitory control mechanisms on acetylcholine release from the nerve endings involved in cardiovascular regulation. The role of the central nucleus of the amygdala (CNA) was also investigated in this study. The presser effects of intracerebroventricular injection of carbachol were significantly attenuated by electrolytic ablation of the CNA, but heart rate changes were not altered both in anesthetized and conscious rats. These results indicate that the CNA plays a role in cholinergic control of blood pressure, but not in the regulation of heart rate.