Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Reyhan Bayrak is active.

Publication


Featured researches published by Reyhan Bayrak.


Nephrology Dialysis Transplantation | 2008

Nigella sativa protects against ischaemia/reperfusion injury in rat kidneys

Omer Bayrak; Nuket Bavbek; Omer Faruk Karatas; Reyhan Bayrak; Ferhat Catal; Ersin Cimentepe; Ali Akbas; Erol Yildirim; Dogan Unal; Ali Akcay

BACKGROUND Renal ischaemia followed by reperfusion leads to acute renal failure in both native kidneys and renal allografts, which is a complex pathophysiologic process involving hypoxia and free radical (FR) damage. The oil of Nigella sativa (NSO) has been subjected to considerable pharmacological investigations that have revealed its antioxidant activity in different conditions. But there is no previously reported study about its effect on ischaemia/reperfusion (I/R) injury of kidneys. The aim of this study was to investigate the possible effects of NSO in I/R-induced renal injury in rats. METHODS Thirty healthy male Wistar albino rats were randomly assigned to one of the following groups: control, sham, I/R, NSO+I/R, I/R+NSO and NSO. I/R, NSO+I/R and I/R+NSO rats were subjected to bilateral renal ischaemia followed by reperfusion and then all the rats were killed and kidney function tests, serum and tissue oxidants and antioxidants were determined and histopathological examinations were performed. RESULTS Pre- and post-treatment with NSO produced reduction in serum levels of blood urea nitrogen (BUN) and creatinine caused by I/R and significantly improved serum enzymatic activities of superoxide dismutase (SOD) and glutathion peroxidase (GSH-Px) and also tissue enzymatic activities of catalase (CAT), SOD and GSH-Px. NSO treatment resulted in lower total oxidant status (TOS) and higher total antioxidant capacity (TAC) levels and also significant reduction in serum and tissue malondialdehyde (MDA), nitric oxide (NO) and protein carbonyl content (PCC) that were increased by renal I/R injury. The kidneys of untreated ischaemic rats had a higher histopathological score, while treatment with NSO nearly preserved the normal morphology of the kidney. CONCLUSIONS In view of previous observations and our data, with the potent FR scavenger and antioxidant properties, NSO seems to be a highly promising agent for protecting tissues from oxidative damage and preventing organ damage due to renal I/R.


American Journal of Nephrology | 2008

Nigella sativa Oil for Prevention of Chronic Cyclosporine Nephrotoxicity: An Experimental Model

Ebru Uz; Omer Bayrak; Efkan Uz; Arif Kaya; Reyhan Bayrak; Burak Uz; Faruk Turgut; Nuket Bavbek; Mehmet Kanbay; Ali Akcay

Nephrotoxicity is the main secondary effect of cyclosporine A (CsA) treatment. The antioxidant action of Nigella sativa oil (NSO) may explain the protective effect of these agents against various hepatotoxic and nephrotoxic models in vivo and in vitro. This study was designed to investigate the possible protective effects of NSO, in prevention of chronic CsA-induced nephrotoxicity in rats. Animals were randomly divided into four experimental groups: the control group received sunflower oil, the other groups were treated with CsA (25 mg/kg/day b.w. orally) or NSO (2 ml/kg orally) or CsA + NSO, respectively. Urine and serum creatinine levels, tissue superoxide dismutase, glutathione peroxidase and catalase enzyme activities, and nitric oxide and malondialdehyde levels were measured, and histological examination was performed. In our study, CsA caused a significant deterioration in the renal function, morphology and gave rise to severe oxidative stress in the kidney. NSO significantly improved the functional and histological parameters and attenuated the oxidative stress induced by CsA. In conclusion, our study demonstrated for the first time that NSO protects kidney tissue against oxygen free radicals, preventing renal dysfunction and morphological abnormalities associated with chronic CsA administration.


Diagnostic Pathology | 2012

The value of CDX2 and cytokeratins 7 and 20 expression in differentiating colorectal adenocarcinomas from extraintestinal gastrointestinal adenocarcinomas: cytokeratin 7-/20+ phenotype is more specific than CDX2 antibody

Reyhan Bayrak; Hacer Haltas; Sibel Yenidunya

AbstractBackground/ObjectiveMetastatic adenocarcinoma from an unknown primary site is a common clinical problem. Determining the cytokeratin (CK) 7/CK20 pattern of tumors is one of the most helpful procedures for this purpose since the CK7-/CK20+ pattern is typical of colorectal adenocarcinomas. CDX2, a critical nuclear transcription factor for intestinal development, is expressed in intestinal epithelium and adenocarcinomas. In the present study, we compared the sensitivity and specificity of CDX2 expression and the CK7-/CK20+ phenotype in differentiating colorectal adenocarcinomas from pancreatic and gastric adenocarcinomas.MethodsCK7/CK20 staining pattern and CDX2 expression were evaluated in 118 cases of colorectal, 59 cases of gastric, and 32 cases of pancreatic adenocarcinomas. The sensitivity, specificity, and positive and negative predictive values of the CK7-/CK20+ phenotype and of CDX2 expression were analyzed.ResultsThe CK7-/CK20+ immunophenotype was expressed by 75 of 118 (64%) colorectal and 3 of 59 (5%) gastric tumors and was not observed in any pancreatic adenocarcinomas. The CK7+/CK20+ immunophenotype was expressed in 24/118 (20%) of colon, 28/59 (48%) of gastric and 7/32 (22%) of pancreatic adenocarcinomas. The CK7+/CK20- expression pattern was observed in only 2% (2 of 118) of colorectal carcinomas. CDX2 was expressed in 114 of 118 (97%) colorectal, 36 of 59 (61%) gastric, and 5 of 32(16%) pancreatic adenocarcinomas. There was no significant association between CDX2 expression and tumor differentiation in colorectal carcinomas. In gastric carcinomas, CDX2 expression was more common in intestinal type tumors than in diffuse type carcinomas. The CK7-/CK20+ phenotype showed a specificity of 96.7% in predicting colorectal adenocarcinomas, which was superior to that of CDX2 expression. CDX2 expression at both cut-off levels (> 5% and > 50%) had a higher sensitivity (96.6% and 78%) than the CK phenotype.ConclusionsBoth the CK7-/CK20+ phenotype and expression of the antibody CDX2 are highly specific and sensitive markers of colorectal origin. CDX2 expression should be a useful adjunct for the diagnosis of intestinal adenocarcinomas, particularly when better established markers such as CK7 and CK20 yield equivocal results. The CK7-/CK20+ phenotype is superior in its specificity and positive predictive value and might be preferred.Virtual slidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/4851011866354821


Pathology Research and Practice | 2011

Cytokeratin 7 and cytokeratin 20 expression in colorectal adenocarcinomas

Reyhan Bayrak; Sibel Yenidunya; Hacer Haltas

Cytokeratin 7 (CK7) and cytokeratin 20 (CK20) are low molecular weight cytokeratins. The expressions of CK7 and CK20 have been studied in various primary and metastatic carcinomas. Their expression patterns may help to distinguish the site of origin of metastatic carcinomas. We investigated the expressions of CK7 and CK20 in 196 cases of colorectal carcinoma. Paraffin sections of 196 colonic adenocarcinomas were randomly selected, retrieved, and immunostained for CK7 and CK20 with a standard avidin-biotin complex method. CK7 was expressed in 34/196 (17.3%) and CK20 in 159/196 (81.1) cases of colorectal adenocarcinoma. CK7-/CK20+ had the greatest proportion (65.8%) in colorectal carcinomas. The CK7+/CK20+ immunophenotype was identified in 30/196 (15.3%), CK7-/CK20- in 33/196 (16.9%), and CK7+/CK20- in 4/196 (2%) colon adenocarcinomas. The CK7 and CK20 expression patterns were different in colorectal carcinomas according to histological grade, location of the tumor, and lymph node metastasis. CK20 positivity was more common in low grade carcinomas than in high grade carcinomas (85.1% versus 47.6%) and in rectal and sigmoid carcinomas than in proximal colon carcinomas (88.2% versus 63.2% and 88.9% versus 63.2%, respectively). Furthermore, CK7 expression was more common in tumors with lymph node metastasis than in non-metastatic tumors (25.3% versus 11%). In conclusion, a considerable number of colorectal carcinomas showed reactivity to CK7 (17.3%) or no reactivity to CK20 (18.9%). Therefore, CK7 positivity or CK20 negativity does not rule out a colorectal origin of metastatic carcinoma.


Molecular and Cellular Biochemistry | 2006

Erdosteine against acetaminophen induced Renal toxicity

Bunyamin Isik; Reyhan Bayrak; Ali Akcay; Sadik Sogut

Acetaminophen (APAP) induced toxicities have been a major problem in clinical practice. The aim of the present study was to demonstrate a possible protective role of erdosteine, a mucolytic agent having antioxidant properties via its active metabolites, on APAP induced renal damage in rats. Female Wistar Albino rats were divided into groups including control, erdosteine (150 mg/kg, oral), APAP (1 g/kg, oral) APAP+erdosteine (150 mg/kg, oral) and APAP+erdosteine (300 mg/kg, oral). APAP treatment caused lipid peroxidation as well as high NO level in renal tissue. Also, APAP treated rats had decreased activities of CAT and GSH-Px, but not SOD. In addition, tubular epithelial degeneration, vacuolization and cell desquamation were clearly observed in the APAP treated rats. The cellular debris in the proximal tubules and cortical interstitial congestions were prominent in the kidneys of APAP treated rats. BUN and creatinine levels were increased after APAP administration. All these pathological changes were reversed after erdosteine treatments. Erdosteine treated APAP groups showed milder tubular degeneration, epithelial vacuolization in the proximal tubules, lesser cellular desquamation and better morphology when compared with APAP groups. In conclusion, erdosteine may be a choice of preventive treatment against APAP induced nephrotoxicity.


American Journal of Nephrology | 2008

Oral β-Glucan Protects Kidney against Ischemia/Reperfusion Injury in Rats

Omer Bayrak; Faruk Turgut; Omer Faruk Karatas; Ersin Cimentepe; Reyhan Bayrak; Ferhat Catal; Omer Atıs; Ali Akcay; Dogan Unal

Background: Ischemia-reperfusion (I/R) injury is one of the leading causes of acute renal failure. β-(1→3)-Glucans are glucose polymers with a variety of stimulatory effects on the immune system. We designed this study to determine the possible protective effect of the orally administered soluble β-glucan against I/R injury. Methods: 30 rats were randomly divided into 5 experimental groups (control, sham operated, β-glucan, I/R and I/R+β-glucan groups, n = 6 each). β-Glucan was administered orally to 6 rats of the β-glucan and I/R+β-glucan groups. The rats were subjected to bilateral renal ischemia followed by reperfusion in the I/R and I/R+β-glucan groups. All of the rats were then sacrificed and kidney function tests, serum and tissue oxidants and antioxidants were evaluated. Results: The serum urea and cystatin C levels were significantly higher in the I/R group compared to the I/R+β-glucan group (p < 0.01). The serum and tissue antioxidant markers (SOD, GSH-Px) were significantly lower in the I/R group than the I/R+β-glucan group (p < 0.01). The serum oxidant markers (NO and PC) were significantly higher in the I/R group than the I/R+β-glucan group (p < 0.01). Conclusion: Based on the present data, we conclude that increased antioxidants and decreased oxidants modulated by β-glucan attenuated the renal I/R injury.


Renal Failure | 2009

The effect of dietary ginger (Zingiber officinals Rosc) on renal ischemia/reperfusion injury in rat kidneys.

Ebru Uz; Omer Faruk Karatas; Emin Mete; Reyhan Bayrak; Omer Bayrak; Ali Fuat Atmaca; Omer Atıs; Mehmet Erol Yildirim; Ali Akcay

Oxidative stress has been considered as one of the possible mechanisms of ischemia/ reperfusion (I/R) injury in the kidney. The aim of this study was to analyze the possible protective effect of dietary ginger (Zingiber officinals Rosc), a free radical scavenger, on renal I/R injury in rats. The protective effect of ginger against the damage inflicted by reactive oxygen species (ROS) during renal I/R was investigated in Wistar albino rats using histopathological and biochemical parameters. Thirty rats were randomly divided into five experimental groups (i.e., control, sham-operated, ginger, I/R, and I/R + ginger groups, n = 6 each). The ginger and I/R + ginger groups were fed on the test diet containing 5% ginger. The rats were subjected to bilateral renal ischemia followed by reperfusion in I/R and I/R + ginger groups. At the end of the reperfusion period, rats were sacrificed, and kidney function tests, serum and tissue oxidants and antioxidants, and renal morphology were evaluated. Serum urea, creatinine, and cystatin C (CYC) levels were significantly elevated in the ischemia group, but these levels remained unchanged in the ginger + I/R group compared to the I/R group. Reduction of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) enzyme activity was significantly improved by the treatment with ginger compared to I/R group. Administration of ginger resulted in significant reduction levels of tissue malondialdehyde (MDA), NO, protein carbonyl contents (PCC) in the ginger + I/R group compared with the I/R group. Ginger supplementation in the diet before I/R injury resulted in higher total antioxidant capacity (TAC) and lower total oxidant status (TOS) levels than I/R group. The ginger supplemented diet prior to I/R process demonstrated marked reduction of the histological features of renal injury. The findings imply that ROS play a causal role in I/R-induced renal injury, and ginger exerts renoprotective effects probably by the radical scavenging and antioxidant activities.


Diagnostic Pathology | 2011

Predictive value of pathological and immunohistochemical parameters for axillary lymph node metastasis in breast carcinoma

Sibel Yenidunya; Reyhan Bayrak; Hacer Haltas

Background/ObjectiveWhile several prognostic factors have been identified in breast carcinoma, the clinical outcome remains hard to predict for individual patients. Better predictive markers are needed to help guide difficult treatment decisions. Axillary lymph node metastasis (ALNM) is one of the most important prognostic determinants in breast carcinoma; however, the reasons why tumors vary in their capability to result in axillary metastasis remain unclear. Identifying breast carcinoma patients at risk for ALNM would improve treatment planning. This study aimed to identify the factors associated with ALNM in breast carcinoma, with particular emphasis on basal-like phenotype.MethodsBreast carcinoma patients (n = 210) who underwent breast conserving surgery and axillary lymph node dissection (ALND) (level I and II) or modified radical mastectomy were included in this study. Pathological and immunohistochemical data including individual receptor/gene status was collected for analysis. The basal phenotype status was ascertained using the basal cytokeratin markers CK5, CK14, CK17 and EGFR.ResultsALNM was found in 55% (n = 116) of the patients. On univariate analysis, multicentric disease, large tumor size (>2 cm), vascular and lymphatic invasion, epithelial hyperplasia, necrosis, in situ carcinoma and perineural invasion were associated with higher risk for ALNM, whereas CK5, CK14, EGFR positivity and basal-like tumor type were associated with lower risk. On multivariate analysis, CK5 positivity (OR 0.003, 95%CI 0.000-0.23, p = 0.009) and lymphatic/vascular invasion (OR 17.94, 95%CI 4.78-67.30, p < 0.001) were found to be independent predictors.ConclusionsAlthough the value of complete ALND has been questioned in invasive breast cancer patients, treatment decisions for breast carcinoma have been influenced by many parameters, including lymph node status. Since histopathologic characteristics and expression of biological markers varies among the same histologic subtypes of breast carcinoma, specific clinical and histopathologic features of the primary tumor and ALN status like sentinel node might be used to tailor the loco-regional and systemic treatment in different clinical settings.


Drug and Chemical Toxicology | 2011

Effects of erdosteine on cyclosporine-A–induced hepatotoxicity in rats

Elife Erarslan; Fuat Ekiz; Burak Uz; Cemile Koca; Ummuhani Ozel Turkcu; Reyhan Bayrak; Tuncay Delibasi

Cyclosporine A (CsA) is a potent immunosuppressive agent used for organ transplantations and various autoimmune disorders. However, hepatotoxicity due to CsA remains one of the major side effects. The use of antioxidants reduces the adverse effects of CsA. The aim of this study was to determine the protective effects of erdosteine on CsA-induced liver injury through tissue oxidant/antioxidant parameters and to evaluate light microscopic alterations in rat-liver tissues. Rats were randomly divided into four experimental groups: The control group received sunflower oil (2 mL/kg/day, per orally; p.o.), while the other groups were treated with CsA (25 mg/kg/day, p.o.) or erdosteine (10 mg/kg/day, p.o.) or CsA+erdosteine, respectively. Serum aspartate aminotransferase and alanine aminotransferase levels, tissue malondialdehyde and nitric oxide levels, and superoxide dismutase, glutathione peroxidase and catalase enzyme activities were measured. Histological examination was performed. CsA caused a significant deterioration in the hepatic function tests, morphology, and gave rise to severe oxidative stress in the liver. Erdostein significantly improved the functional and histological parameters and attenuated the oxidative stresss induced by CsA. Erdostein protects liver tissue against oxygen free radicals and prevents hepatic dysfunction and morphological abnormalities associated with chronic CsA administration.


Diagnostic Pathology | 2012

Invasive lobular carcinoma with extracellular mucin as a distinct variant of lobular carcinoma: a case report

Hacer Haltas; Reyhan Bayrak; Sibel Yenidunya; Dilek Kosehan; Meral Sen; Kayihan Akin

The differences between invasive lobular and ductal carcinomas affect the diagnostic and therapeutic management for patients with breast cancer. In most cases, this can be accomplished because of distinct histomorphologic features. However, occasionally, this task may become quite difficult, in particular when dealing with the variants of infiltrating lobular carcinoma. Lobular carcinoma has been considered a variant of mucin-secreting carcinoma with only intracytoplasmic mucin. The presence of extracellular mucin is a feature of ductal carcinoma. Herein is presented a case of lobular carcinoma with extracellular and intracellular mucin in a 43-year-old female patient, and confirmed by immunohistochemistry. Up to the present, infiltrating lobular carcinoma displaying extracellular mucin has not been described in the literature except two case.Virtual slidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1839906067716744

Collaboration


Dive into the Reyhan Bayrak's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Omer Faruk Karatas

Erzurum Technical University

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge