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Öğe Arabidopsis thaliana Ogg1 protein excises 8-hydroxyguanine and 2,6-diamino-4-hydroxy-5-formamidopyrimidine from oxidatively damaged DNA containing multiple lesions(Amer Chemical Soc, 2003) Morales-Ruiz, T; Birincioglu, M; Jaruga, P; Rodriguez, H; Roldan-Arjona, T; Dizdaroglu, MA functional homologue of eukaryotic Ogg1 proteins in the model plant Arabidopsis thaliana has recently been cloned, isolated, and characterized [Garcia-Ortiz, M. V., Ariza, R. R., and RoldanA Arjona, T. (2001) Plant Mol. Biol. 47,795-804]. This enzyme (AtOgg1) exhibits a high degree of sequence similarity in several highly conserved regions with Saccharomyces cerevisiae, Drosophila melanogaster, and human Ogg1 proteins. We investigated the substrate specificity and kinetics of AtOgg1 for excision of modified bases from oxidatively damaged DNA that contained multiple pyrimidine- and purine-derived lesions. Two different DNA substrates prepared by exposure to ionizing radiation in aqueous solution under N2O or air were used for this purpose. Gas chromatography/isotope-dilution mass spectrometry was applied to identify and quantify modified bases in DNA samples. Of the 17 modified bases identified in DNA samples, only 8-hydroxyguanine and 2,6-diamino-4-hydroxy-5-formamidopyrimidine were significantly excised from both DNA substrates. This is in agreement with the substrate specificities of other eukaryotic Ogg1 proteins that had previously been studied under identical conditions. Excision depended on incubation time, enzyme concentration, and substrate concentration and followed Michaelis-Menten kinetics. A significant dependence of excision on the nature of DNA substrate was observed in accord with previous studies on other DNA glycosylases. A comparison of excision kinetics pointed to significant differences between AtOgg1 and other Ogg1 proteins. We also investigated the effect of base-pairing on the excision using double-stranded oligodeoxynucleotides that contained 8-OH-Gua paired with each of the four DNA bases. The activity of AtOgg1 was most effective on the 8-OH-Gua:C pair with some or very low activity on other pairs in agreement with the activity of other Ogg1 proteins. The results unequivocally show that AtOgg1 possesses common substrates with other eukaryotic Ogg1 proteins albeit significant differences between their excision kinetics.Öğe Biomarkers of oxidative DNA damage used to detect genetic changes in tissue-engineered skin(Pergamon-Elsevier Science Ltd, 2002) Rodriguez, H; Birincioglu, M; Jaruga, P; Barker, PE; O'Connell, C; Dizdaroglu, M[Abstract Not Available]Öğe Clarifications and relationships between estrogen and prostaglandins - Reply(Elsevier Science Inc, 2000) Sonmez, AS; Birincioglu, M; Lurie, D[Abstract Not Available]Öğe Comparison of the effects of tibolone and hormone replacement therapy on echocardiographic basic cardiac functions in postmenopausal women: A randomized placebo controlled study.(Elsevier Science Inc, 1997) Taskin, O; Buhur, A; Burak, F; Birincioglu, M; Burak, F; Atmaca, R; Ozdemir, R[Abstract Not Available]Öğe DNA base damage by the antitumor agent 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine)(Amer Chemical Soc, 2003) Birincioglu, M; Jaruga, P; Chowdhury, G; Rodriguez, H; Dizdaroglu, M; Gates, KSTirapazamine is a bioreductively activated DNA-damaging agent that selectively kills the hypoxic cells found in solid tumors. This compound shows clinical promise and is currently being examined in a variety of clinical trials, including several phase III studies. It is well established that DNA is an important cellular target for tirapazamine; however, the structural nature of the DNA damage inflicted by this drug remains poorly understood. As part of an effort to understand the chemical events responsible for the hypoxia-selective cytotoxicity of this drug, the studies reported here are designed to characterize tirapazamine-mediated damage to the genetic information stored in the heterocyclic base residues of double-stranded DNA. Here, we used gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry to characterize and quantify oxidative DNA base damage mediated by tirapazamine. A multiplicity of modified bases including 8,5'-cyclopurine-2'-deoxynucleoside tandem lesions were identified and quantified. The results provide the first detailed insight regarding the structural identity of the DNA base lesions caused by this drug. Interestingly, it appears that the hypoxic conditions under which tirapazamine operates, along with the unique chemical properties of the drug, yield a unique variety of DNA base damage that is dominated by formamidopyrimidine and 5-hydroxy-6-hydropyrimidine lesions. Importantly, the results suggest that tirapazamine may generate a set of poorly repaired, potentially cytotoxic DNA base lesions that block DNA transcription and replication. Overall, the results indicate that DNA base damage may contribute to the biological effects of tirapazamine in vivo.Öğe The effect of carbon dioxide pneumoperitoneum on free radicals(Springer, 2000) Sare, M; Yilmaz, I; Hamamci, D; Birincioglu, M; Özmen, M; Yesilada, ÖBackground: Carbon dioxide is usually preferred as the insufflating agent for laparoscopic surgery because it is readily available, noncombustible, and chemically stable. It is still questionable, however, if CO2 pneumoperitoneum has any effect on free radicals and lipid peroxidation. The purpose of this study was to investigate the possible effects of CO2 pneumoperitoneum on free radicals and lipid peroxidation in the erythrocytes of rats. Methods: Fifty male Sprague-Dawley rats were divided into five equal,groups: controls, a sham-operation group, and three groups of 5, 10, or 15 mmHg pneumoperitoneum with CO2. At the end of the procedure, blood was collected and the erythrocytes were separated from the plasma. The resultant supernatant fractions of erythrocytes were assayed For superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA). Results: SOD activities of the 5 and 10 mmHg pneumoperitoneum groups were significantly lower than those of the sham operation group. SOD activity was greater in the 15 mmHg pneumoperitoneum group than in any of the other groups, and this activity was significantly different from that seen in the 5 and 10 mmHg pneumoperitoneum groups (p < 0.05). No significant changes were observed in the CAT activities of the study,groups (p > 0.05). MDA level was increased in the 5 mmHg pneumoperitoneum group; this result was statistically different from the control and 15 mmHg pneumoperitoneum groups (p < 0.05). No significant differences were found in the CAT activities for the study groups. On the other hand, the SOD activities of the 5 and 10 mmHg pneumoperitoneum groups were significantly lower than those of the sham and the 15 mmHg pneumoperitoneum group (p < 0.05 for all comparisons). Conclusions: These results indicate that CO2 pneumoperitoneum applied with 5-10 mmHg pressure increases the formation of free oxygen radicals by inhibiting SOD activity and that the accumulation of free radicals elevates the level of MDA, a metabolite of Lipid peroxidation. The effect of CO2 pneumoperitoneum on free radicals and lipid peroxidation is pressure-dependent in rats. The mechanism underlying this pressure dependency is still under investigation.Öğe Effects of captopril and losartan on myocardial ischemia-reperfusion induced arrhythmias and necrosis in rats(Academic Press Ltd Elsevier Science Ltd, 2002) Ozer, MK; Sahna, E; Birincioglu, M; Acet, AAngiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type I (AT(1)) receptor blockers improve ischemia-reperfusion induced arrhythmias and infarct size in several animal models. However, the effects of pretreatment with ACEIs or AT, receptor blockers on acute myocardial infarct size and arrhythmias are controversial. Thus, we sought to assess the comparative effects of pretreatment with ACEI captopril and AT(1)-receptor blocker losartan on myocardial infarct size and arrhythmias in a rat model of ischemia-reperfusion. We randomly assigned 92 male Wistar rats for arrhythmias (n = 60) and necrosis (n = 32) experiments. To produce arrhythmia, the left main coronary artery was occluded for 7 min, followed by 7 min of reperfusion and to produce necrosis, the the left main coronary artery was occluded for 30 min, followed by 120 min of reperfusion. Captoptil (3 mg kg(-1)) and losartan (0.2 and 2 mg kg(-1)) were given intravenously 10 min before occlusion. Captopril reduced the incidences of ventricular fibrillation (VF) and mortality associated with irreversible VR whereas the studied doses of losartan did not. Captopril also decreased the number of ventricular beats on reperfusion. Losartan 2 mg kg(-1) reduced both the number of ventricular premature beats and the incidence of ventricular tachycardia (VT) on reperfusion, while losartan at dose of 0.2 mg kg(-1) had no effect on these arrhythmias. Compared to the control group, both captopril and losartan reduced myocardial infarct size in the rat model of ischemia-reperfusion, but this was statistically significant for captopril only. In this experimental model, although captopril did not reduce the incidence of reperfusion-induced VT, it was more effective than the AT(1)-receptor blocker losartan at preventing mortality associated with irreversible VF and to reduce myocardial infarct size in rat model of ischemia-reperfusion. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Effects of captopril on ischaemia-reperfusion-induced arrhythmias in an in vivo rat model(Academic Press Ltd, 1995) Olmez, E; Birincioglu, M; Aksoy, T; Acet, AThe antiarrhythmic effects of captopril, an angiotensin converting enzyme (ACE) inhibitor, were investigated in an in vivo rat model of coronary artery ligation. Captopril (0.3-3 mg kg(-1)) or saline were administered by intravenously 10 min before coronary ischaemia. The left main coronary artery was then occluded for 7 min, followed by 7 min of reperfusion. Captopril caused a marked decrease in mean arterial blood pressure which was transient at 0.3 and 1 mg kg(-1), and at doses of 1 and 3 mg kg(-1), it produced marked bradycardia. The incidence of ventricular tachycardia (VT) on ischaemia was significantly reduced the captopril at a dose of 3 mg kg(-1) only and on reperfusion at doses of 1 and 3 mg kg(-1). At the same doses, captopril significantly reduced the mean duration of ventricular fibrillation (VF) on reperfusion. The incidence of mortality resulting from reperfusion-induced irreversible VF in the control group decreased from 42.9% to 14.3% (NS), 21.4% (NS) and 7.7% (P<0.05) in captopril at 0.3, 1 and 3 mg kg(-1), respectively. Our results indicate that captopril appears to limit the arrhythmias following reperfusion and this may be due in part to the antiischemic effect associated with bradycardia and vasodepression. (C) 1995 The Italian Pharmacological SocietyÖğe Effects of carbon dioxide pneumoperitoneum on free radical formation in lung and liver tissues(Springer, 2002) Sare, M; Hamamci, D; Yilmaz, I; Birincioglu, M; Mentes, BB; Özmen, M; Yesilada, ÖBackground: The purpose of this study was to investigate the possible effects of carbon dioxide (CO2) pneumoperitoneum on free radical formation and lipid peroxidation in the lung and liver tissues of rats. Methods: For this study, 50 male Sprague-Dawley rats were divided into five equal groups: control (group 1); sham operation (group 2): 5, 10, or 15 mmHg (group 3, 4, or 5) pneumoperitoneum with CO2 groups. At the end of the procedures, the rats were killed, and perfusion was performed via vena jugularis with cold Ringer's lactate. After the perfusion procedure, the lung and liver were harvested, and the supernatant fractions of the lungs and livers were assayed for superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA). Results: Both the lung and liver CAT activities were elevated consistently and significantly in the order of the study groups. as compared with the previous groups (p < 0.01 for all comparisons). The lung and liver SOD levels were elevated in groups 4 and 5, as compared with the other groups (p < 0.05). The lung MDA was significantly higher in groups 3 and 4, but not in group 5. Significant elevation in liver MDA was noted only in the 5-mmHg pneumoperitoneum group (p < 0.05). Conclusions: These results indicate that CO2 pneumoperitoneum applied with 5, 10, or 15 mmHg pressure increases the formation of free oxygen radicals, which is counterbalanced by increased SOD and CAT activities of the lung and liver tissues. This effect of CO2 pneumoperitoneum on free radicals and lipid peroxidation appears to be pressure dependent in rats. The mechanism underlying this pressure dependency is still under investigation.Öğe Effects of chronic ethanol consumption on ?-adrenergic-induced contractions and endothelium-dependent relaxations in rat thoracic aorta(Academic Press Ltd, 2000) Sahna, E; Kurcer, Z; Ozturk, F; Cengiz, N; Vardi, N; Birincioglu, M; Olmez, EThe effects of chronic oral administration of ethanol (7.2% daily during 24 weeks) on the contractions induced by phenylephrine (Phe) and the endothelium-dependent relaxation responses to acetylcholine (ACh) were studied in rat thoracic aorta. Ethanol pretreatment significantly attenuated the contractile responses to Phe, resulting in parallel shift of the concentration-response curve to the right. EC50 values of Phe were 64.6 +/- 11.2 and 95.5 +/- 8.5 nmol l(-1) in control and ethanol-fed rats, respectively. On the other hand, either calcium-induced contractions or relaxation responses to ACh and sodium nitroprusside were similar in the vessels of the control and ethanol-treated rats. These results suggest that chronic ethanol ingestion significantly attenuates the alpha(1)-adrenergic-induced contractions but does not affect the relaxation responses mediated by nitric oxide in rat aortic rings. (C) 2000 Academic Press.Öğe The effects of duration of CO2 insufflation and irrigation on peritoneal microcirculation assessed by free radical scavengers and total glutathion levels during operative laparoscopy(Journal Amer Assoc Gynecologic Laparoscopists, 1998) Taskin, O; Buhur, A; Birincioglu, M; Burak, F; Atmaca, R; Yilmaz, I; Wheeler, JMStudy Objective. To investigate the effects of peritoneal exposure to carbon dioxide (CO2) on peritoneal microcirculation and free radical scavenger (FRS) metabolism, and its role in potential adhesion formation after operative laparoscopy. Design. Randomized, controlled study (Canadian Task Force classification I). Setting. University-affiliated hospital. Patients. Twenty-eight women undergoing operative laparoscopy for adnexal masses. Intervention. For each patient, a 1 x I-cm sidewall peritoneal flap was excised at the end of laparoscopy and numbered randomly. Similar flaps obtained from 24 women immediately after entering the abdomen during laparotomy served as controls. Measurements and Main Results. Changes in glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels were studied in homogenized peritoneal tissues. The duration of CO2 exposure and amount of CO2 used were correlated with levels of free radical scavengers and compared with controls. Mean CO2 exposure, amount of CO2 used, and CO2 pressure (15 mm Hg) was similar between low irrigation and irrigated laparoscopy (118.3 +/- 25 and 39.2 +/- 8.81 min and 125 +/- 20 and 44.5 +/- 6.81 min, respectively). The change in FRS levels was significantly correlated with duration and amount of CO2 exposure ( r = -0.92). Levels of GSH-Px, SOD, CAT, and GSH were significantly lower in the CO2 exposure group than in controls (0.57 els of GSH-Px, SOD, CAT; and GSH were significantly lower in the CO2 exposure group than in controls (0.57 mu mol, 1.8 ng, 48.5 mu mol, 1.5 nmol vs 0.8 mu mol, 2.6 +/- 0.4 ng, 79 mu mol, 3.6 nmol, respectively). Conclusion, Exposure to CO2 has adverse effects on peritoneal microcirculation and cell-protective systems, which are proposed mechanisms in adhesion formation. Avoiding long CO2 exposure and copiously irrigating the abdominal cavity throughout surgery may lessen these effects. The potential role of the peritoneal FRS system on postoperative adhesion formation and its relation to estrogen status mandates further studies.Öğe The effects of estrogen/progesterone replacement therapy with or without low-dose testosterone on ischemia-reperfusion induced ventricular arrhythmias in ovariectomized rats.(Elsevier Science Inc, 1997) Taskin, O; Birincioglu, M; Olmez, E; Aksoy, T; Kilic, E; Wheeler, JM[Abstract Not Available]Öğe Effects of misoprostol on bone loss in ovariectomized rats(Elsevier Science Inc, 1999) Sonmez, AS; Birincioglu, M; Özer, MK; Kutlu, R; Chuong, CJThis study was performed to investigate whether misoprostol (prostaglandin Fl analogue) (Cytotec, Searle, England) is effective for restoration of bone loss. Four-month-old parous female Sprague-Dawley rats (n = 30) were subjected either to bilateral ovariectomy (OVX, 24 fats) or to sham surgery (sham, 6 rats), The OVX rats were divided into four groups 60 days after the surgery. Six of them were killed, and dual-energy X-ray absorption (Norland xr-36, Norland Corporation, Fort Atkinson, WI, USA) measurements were performed, called pretreatment OVX group. The remaining groups teach had 6 rats) treated orally with 0 (control), 100, 200 mu g/kg/day misoprostol for 60 days. All rats were killed 60 days after having treatment, and bone loss of the lumbar spine was measured by dual-energy X-ray absorption. The bone mineral density was decreased by 25.4% in control group and 23.6% in pretreatment group compared to sham group, but restored by 86% and 96% in groups treated with 100 and 200 mu g/kg/day misoprostol, respectively. These results suggest that misoprostol restores bone loss in the lumbar spine of OVX rats in a dose-dependent manner. (C) 1999 Elsevier Science Inc. All rights reserved.Öğe Effects of misoprostol on lipoprotein (a) levels of ovariectomized rats(Elsevier Science Inc, 1999) Sonmez, AS; Birincioglu, M; Turkoz, Y; Adam, B; Lurie, D; Chuong, CJObjective: To determine the effects of misoprostol on plasma lipoprotein (a) concentrations of ovariectomized rats. Design: Controlled prospective study. Setting: Animal research laboratory. Animal(s): Four-month-old female Sprague-Dawley rats. Intervention(s): Blood samples were obtained before and 60 days after ovariectomy, and the rats were divided into three groups. Group I (five rats) was treated with vehicle (water); groups II and III (nine and eight rats, respectively) were treated with oral misoprostol at 100 and 200 mu g/kg/d, respectively, for 60 days, after which blood was drawn again. Main Outcome Measure(s): Serum lipoprotein (a) levels. Result(s): The median lipoprotein (a) level before ovariectomy was 10.8 mg/dL (range, 10.6-46.5 mg/dL). Sixty days after ovariectomy, the level increased significantly to 15.9 mg/dL (range, 10.6-36.9 mg/dL). After treatment, there was no change in lipoprotein (a) levels in the vehicle-treated group (range, 16.3-21.1 mg/dL); however, the lipoprotein (a) levels decreased significantly in the group treated with 100 mu g/kg/d of misoprostol, from 15.4 mg/dL to 10.8 mg/dL, and in the group treated with 200 mu g/kg/d of misoprostol, from 17.1 mg/dL to 10.6 mg/dL. Conclusion(s): Misoprostol caused a significant decrease in lipoprotein (a) levels. (Fertil Steril(R) 1999;72: 518-21. (C) 1999 by American Society for Reproductive Medicine.) 518.Öğe The effects of twisted ischaemic adnexa managed by detorsion on ovarian viability and histology: an ischaemia-reperfusion rodent model(Oxford Univ Press, 1998) Taskin, O; Birincioglu, M; Aydin, A; Buhur, A; Burak, F; Yilmaz, I; Wheeler, JMThis prospective controlled follow-up study was designed to examine the effects of adnexal torsion on long-term ovarian histology and radical scavenger (FRS) activity, and subsequent viability following the detorsion of twisted ischaemic adnexa, in a primate centre of a university clinic. Adnexal torsion/occlusion was created by twisting the adnexa three times and fixing on to the side wall or by applying vascular clips in cycling female rats at 70 days of age. Following an ischaemic period of 4 to 36 h, the twisted adnexas were surgically removed and fixed. In the second group of rats, following the above ischaemic periods, the torsion/occlusion were relieved by detwisting or removing the vascular clips. Then the animals were reperfused for a week and adnexas were extirpated. After both ischaemia and reperfusion, the removed adnexas were examined histologically and tissue concentrations of glutathione peroxidase, superoxide dismutase, catalase and glutathione were determined. Regardless of the ischaemia time, all the twisted adnexas were black-bluish in appearance. Despite the gross ischaemic-haemorrhagic features, histological sections revealed negligible changes, with intact ovarian structure similar to controls in 4-24 h groups. Though decreased compared with controls, the change in tissue concentrations of FRS was not significant in 4-24 h groups. Only the 36 h group showed prominent congestion on all sections and a significant decrease in all radical scavenger concentrations studied. While no longterm reperfusion injury was observed histologically in 4-24 h groups, the 36 h group ended with adnexal necrosis. Our findings support the importance of early diagnosis and conservative surgical management (detorsion) in adnexal torsion. Lack of histological changes and unimpaired FRS metabolism are consistent with the recent data that vascular compromise is caused by venous or lymphatic stasis in early torsion and that adnexal integrity is not correlated with gross ischaemic appearance, thus providing evidence of adnexal resistance against ischaemia.Öğe The effects of twisted ischemic adnexa managed by detorsion on ovarian viability and histology: An ischemia-reperfusion rodent model.(Amer Soc Reproductive Medicine, 1997) Taskin, O; Birincioglu, M; Aydin, A; Buhur, A; Burak, F; Wheeler, JM[Abstract Not Available]Öğe Endometrial Na+, K+-ATPase pump function and vasopressin levels during hysteroscopic surgery in patients pretreated with GnRH agonist(Journal Amer Assoc Gynecologic Laparoscopists, 1998) Taskin, O; Buhur, A; Birincioglu, M; Burak, F; Atmaca, R; Yilmaz, I; Wheeler, JMStudy Objective. To investigate the effects of gonadotropin-releasing hormone (GnRH) analog pretreatment on endometrial Na+, K+-adenosine triphosphatase (ATPase) pump function and peripheral blood vasopressin levels, and their role in fluid absorption and mechanisms of hyponatremia in patients undergoing hysteroscopic endometrial ablation. Design. Prospective, randomized, placebo-controlled study (Canadian Task Force classification I). Setting. University-affiliated hospital. Patients. Seventeen women with dysfunctional uterine bleeding. Intervention, Nine women received a GnRH analog and eight received saline approximately 6 to 8 weeks before hysteroscopic ablation by electrosurgery. Measurements and Main Results. Both before randomization and immediately before surgery, endometrial biopsy samples were obtained and numbered consecutively without patient identification. Operative hysteroscopy was performed with glycine 1.5% mixed with 2% alcohol. The amount of irrigant and irrigant deficit; blood levels of albumin and ethanol; hematocrit and hemoglobin; changes in sodium levels; and central venous pressure were compared. The Na+, K+-ATPase pump activity was significantly increased in the GnRH analog group compared with the saline group and correlated with decreased estradiol levels (0.4 +/- 0.08 vs 0.26 +/- 0.06 mu mol/min/ml). Vasopressin levels were significantly lower in the GnRH group (3.2 +/- 0.9 vs 7.6 +/- 1.7 mu mol/L). Mean volume of irrigant used and operating time were similar in both groups. Volume deficit, decrease in protein, and hematocrit were less in GnRH than in the saline group. Blood ethanol levels, decrease in sodium, and irrigant deficit were significantly lower in GnRH group. Conclusion. Pretreatment with GnRH analogs may prevent the adverse effects of estradiol on endometrial Na+, K+-ATPase and creates a protective mechanism against iatrogenic hyponatremia, which is more critical in women than men in case of absorption of irrigating fluid. Moreover, created hypoestrogenism may enhance Na+, K+-ATPase activity in brain as well as endometrium, thus decreasing women's susceptibility to hyponatremic complications and brain damage. Suppressed vasopressin levels may be protective against fluid absorption in GnRH analog-treated patients.Öğe Free radical-induced damage to DNA: Mechanisms and measurement(Elsevier Science Inc, 2002) Dizdaroglu, M; Jaruga, P; Birincioglu, M; Rodriguez, HFree radicals are produced in cells by cellular metabolism and by exogenous agents. These species react with biomolecules in cells, including DNA. The resulting damage to DNA, which is also called oxidative damage to DNA, is implicated in mutagenesis, carcinogenesis, and aging. Mechanisms of damage involve abstractions and addition reactions by free radicals leading to carbon-centered sugar radicals and OH- or H-adduct radicals of heterocyclic bases. Further reactions of these radicals yield numerous products, Various analytical techniques exist for the measurement of oxidative damage to DNA. Techniques that employ gas chromatography (GC) or liquid chromatography (LC) with mass spectrometry (MS) simultaneously measure numerous products, and provide positive identification and accurate quantification. The measurement of multiple products avoids misleading conclusions that might be drawn from the measurement of a single product, because product levels vary depending on reaction conditions and the redox status of cells. In the past, GUMS was used for the measurement of modified sugar and bases, and DNA-protein cross-links. Recently, methodologies using LC/tandem MS (LC/MS/MS) and LC/MS techniques were introduced fur the measurement of modified nucleosides. Artifacts might occur with the use of any of the measurement techniques. The use of proper experimental conditions might avoid artifactual formation of products in DNA. This article reviews mechanistic aspects of oxidative damage to DNA and recent developments in the measurement of this type of damage using chromatographic and mass spectrometric techniques. Published by Elsevier Science, Inc.Öğe Genomic DNA of Nostoc commune (Cyanobacteria) becomes covalently modified during long-term (decades) desiccation but is protected from oxidative damage and degradation(Oxford Univ Press, 2003) Shirkey, B; McMaster, NJ; Smith, SC; Wright, DJ; Rodriguez, H; Jaruga, P; Birincioglu, MGenomic DNA of Nostoc commune ( Cyanobacteria) became covalently modified during decades of desiccation. Amplification of gene loci from desiccated cells required pretreatment of DNA with N-phenacylthiazolium bromide, a reagent that cleaves DNA- and protein-linked advanced glycosylation end-products. DNA from 13 year desiccated cells did not show any higher levels of the commonly studied oxidatively modified DNA damage biomarkers 8-hydroxyguanine, 8-hydroxyadenine and 5-hydroxyuracil, compared to commercially available calf thymus DNA. Different patterns of amplification products were obtained with DNA from desiccated/ rehydrating cells and a liquid culture derived from the dried material, using the same set of primers. In contrast, a reproducible fingerprint was obtained, irrespective of time of rehydration of the DNA, using a primer (5'-GWCWATCGCC-3') based upon a highly iterated palindromic repeat sequence present in the genome. In vitro, the desiccation of cccDNA led to loss of supercoiling, aggregation, loss of resolution during agarose gel electrophoresis and loss of transformation and transfection efficiency. These changes were minimized when DNA was desiccated and stored in the presence of trehalose, a non-reducing disaccharide present in Nostoc colonies. The response of the N. commune genome to desiccation is different from the response of the genomes of cyanobacteria and Deinococcus radiodurans to ionizing radiation.Öğe Irreproducible results: Good for surgeons, bad for scientists - Reply(Elsevier Science Inc, 2000) Sonmez, AS; Birincioglu, M[Abstract Not Available]
