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    Asymmetric dimethylarginine in experimental breast cancer; action of Vitamin C and E
    (Pakistan Medical Assoc, 2015) Erbas, Hakan; Turksever, Aylin; Aydogdu, Nurettin; Cakir, Erol
    Objective: To investigate the arginase-nitric oxide synthase paradox through asymmetric dimethylarginine, symmetric dimethylarginine and nitric oxide levels, and to see the effect of antioxidant vitamins on this mechanism of cancer action. Methods: The animal-based study was conducted at Trakya University, Turkey, in 2008, and comprised mice that were divided into five equal groups. Group 1 had healthy controls, while in the other four groups breast cancer was induced. Group 2 received saline solution, group 3 received 200 mg/kg/day vitamin C (tumour +vit C), group 4 received 300 mg/kg/day vitamin E (tumour +vitE) and group 5 received both 200 mg/kg/day vitamin C and 300 mg/kg/day vitamin E (tumour +vit C+vit E) for 15 days intra-peritoneally. Arginine, asymmetric dimethylarginine, symmetric dimethylarginine and nitric oxide levels were determined in each group. Results: The 50 mice in the study were divided into five groups of 10(20%) each. Plasma arginine levels were significantly decreased, asymmetric dimethylarginine and symmetric dimethylarginine levels were increased, while plasma nitric oxide level was significantly decreased in group 2. There was no statistically significant difference in treatment groups for all parameters (p>0.05 each). Conclusion: Understanding of the mechanism may help to develop new anti-cancer agents.
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    The effect of melatonin on protein oxidation and nitric oxide in the brain tissue of hypoxic neonatal rats
    (Elsevier, 2007) Eskiocak, Sevgi; Tutunculer, Filiz; Basaran, Umit Nusret; Taskiran, Ali; Cakir, Erol
    Melatonin is a potent antioxidant agent that can scavenge oxy- and nitroradicals generated under hypoxic conditions in the brain. In this study, we investigated the effect of melatonin on protein oxidation and nitric oxide (NO) during hypoxia. Seven-day-old Sprague-Dawley newborn rats were divided into three groups. Hypoxic (n = 9) and melatonin (n = 11) groups were subjected to 2 h of hypoxic exposure (a humidity mixture of gases consisting of 92% nitrogen and 8% oxygen). Melatonin (at a dose of 10 mg/kg) was administrated 30 min before the onset hypoxia and then at 24th and 48th hours after the end of the hypoxic exposure. Control (n = 10) and hypoxic groups received the isotonic sodium chloride according to the same schedule. The brain tissue concentration of advanced oxidation protein products (AOPP) and protein thiol (P-SH) was used as an index of protein oxidation. In our study, although AOPP and NO increased significantly, the levels of P-SH decreased in the hypoxic group. The level of AOPP was declined by melatonin treatment. However, perturbed thiol status could not be recovered by melatonin treatment. There was no relationship between the levels of NO and protein oxidation markers. These results indicate that exogenous melatonin could prevent AOPP, but that it is inadequate in recovering perturbed thiol status. Therefore, melatonin alone was observed to be an incomplete treatment to prevent protein oxidation in hypoxia-induced brain damage. (c) 2006 Elsevier B.V. All rights reserved.
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    The Effect of N-acetylcysteine on Brain Tissue of Rats Fed with High-Cholesterol Diet
    (Walter De Gruyter Gmbh, 2008) Eskiocak, Sevgi; Altaner, Semsi; Bayir, Serpil; Cakir, Erol
    Objectives: The effect of N-acetylcysteine in rats fed a high-cholesterol diet on oxidative stress in the plasma and brain tissue of rats was investigated. Methods: The animals were maintained on a basal diet (control, n=10) or a high-cholesterol diet (1 % w/w) for eight weeks. The rats fed high-cholesterol diet were separated to three group; high-cholesterol diet (n=10), low N-acetylcysteine (n=10) and high N-acetylcysteine groups (n=9). Low and high N-acetylcysteine groups received N-acetylcysteine at a dose of 50 and 100 mg/kg/day respectively via intraperitoneally for eight weeks. Malondialdehyde, glutathione, nitric oxide, cholesterol and triglyceride levels were analyzed in the samples. The results were analyzed by Kruskal-Wallis variance analysis and then a Mann-Whitney U test. Results: When N-acetylcysteine was administered at a low dose, lipid peroxidation products in the brain significantly decreased compared with the high-cholesterol group, while glutathione content enhanced. On the other hand, when N-acetylcysteine was administered at a high dose, lipid peroxidation products in the brain and plasma significantly increased compared with the control group. Conclusions: These results suggest that N-acetylcysteine has a dual effect. If the N-acetylcysteine dose was carefully selected, N-acetylcysteine may have a neuroprotective effect against oxidative stress and hypercholesterolemia.