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Dive into the research topics where Tolga Guvenc is active.

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Featured researches published by Tolga Guvenc.


Journal of Pineal Research | 2005

Morphological, stereological and radiological changes in pinealectomized chicken cervical vertebrae.

Mehmet Turgut; Süleyman Kaplan; Ahmet Tuncay Turgut; Hüseyin Aslan; Tolga Guvenc; Emre Cullu; Serpil Erdogan

Abstract:  Considerable evidence supports the hypothesis that melatonin plays an important role in osteogenesis. We carried out an experiment to investigate histological and radiological changes in the cervical vertebrae of pinealectomized chickens. Thirty new‐hatched chicks were divided into two groups: pinealectomized group (n = 15) and nonpinealectomized control (n = 15). Surgical pinealectomies were performed in Hybro broiler chickens at the age of 3 days. At 8 wk, one animal from each group was examined using computed tomography scanner to obtain density histograms of four consecutive vertebrae between the 4th and 7th cervical vertebral segments of chickens. At the end of the study, all animals were killed for subsequent measurement of bone mineral density (BMD) and macroscopic, radiographic and histopathological evaluation of specimens. We found that the profile of the density histogram in nonpinealectomized control group showed a spike profile for the vertebral body, indicating an increase in the amount of higher density tissues in this region, while a plateau‐shaped profile was obtained for the vertebral body in pinealectomy group, indicating the presence of heterogenous bone tissue. Accordingly, the mean value of BMD in pinealectomy group was significantly lower at the vertebral body in chickens compared with control subjects (P < 0.001). At the end of the experiment, almost all of the chickens in pinealectomy group developed a scoliotic curvature and the mean weight and length of the cervical vertebral bodies of the pinealectomized chickens were significantly lower than those of control group (P < 0.001). Although the numerical density of osteocytes and osteoblasts in pinealectomy group was significantly higher than that from the control group, total number of osteocytes but not osteoblasts in cervical vetrebrae from pinealectomized animals was significantly lower than that from nonpinealectomized control animals (P < 0.05). In conclusion, the results of the current study demonstrated for the first time pinealectomy‐induced histomorphometrical changes in chicken vertebral column using stereological methods, suggesting that pineal gland/melatonin may have an osteoinductive effect on bone formation, but further studies are needed to elucidate the relationship of our findings with some disorders such as postmenopausal and/or senile osteoporosis.


Parasitology International | 2008

Seroprevalence of equine babesiosis in the Black Sea region of Turkey

Mustafa Açici; Sinasi Umur; Tolga Guvenc; H. Hilal Arslan; Mithat Kurt

The prevalence of Theileria equi and Babesia caballi was determined in equid blood samples in five provinces of the Black Sea region of Turkey by using the indirect fluorescent antibody test (IFAT). Of 153 samples, 53 (34.6%) and 33 (21.5%) were seropositive to B. caballi and T. equi, respectively. In addition, 8 (5.2%) of samples were seropositive to both T. equi and B. caballi. Anti T. equi and B. caballi antibodies were detected in all five regions. The prevalence of B. caballi was higher than T. equi in all counties. Antibodies to T. equi and B. caballi were detected in horses of all ages, and there were no significant differences among age groups. Out of 84 horses, 32 (38.0%) were positive for B. caballi infection and 20 (23.8%) were positive for T. equi infection. Five horses (5.6%) were found to be seropositive to both B. caballi and T. equi. Of 38 donkeys, 14 (36.8%) were found to be positive for B. caballi infection and 5 (13.1%) positive for T. equi infection. In addition, 2 (5.2%) samples were seropositive for both T. equi and B. caballi infections. Out of 31 mules, 8 (25.8%) were positive for B. caballi infection and 8 (25 8%) positive for T. equi infection. One (3.2%) sample was seropositive for both T. equi and B. caballi infections. Of all the animals in this study, only 3 horses were infected by Rhipicephalus turanicus and Hyalomma detritum, and no haemoparasites were detected by microscopic examination.


International Journal of Antimicrobial Agents | 2012

Efficacy of tigecycline/colistin combination in a pneumonia model caused by extensively drug-resistant Acinetobacter baumannii

Esmeray Mutlu Yilmaz; Mustafa Sunbul; Abdurrahman Aksoy; Hava Yilmaz; Akif Koray Guney; Tolga Guvenc

Due to increasing drug resistance, available antimicrobial options are limited in the treatment of Acinetobacter baumannii infections. Particularly in cases caused by extensively drug-resistant (XDR) A. baumannii, combination regimens must also be taken into consideration. In this study, the efficacies of tigecycline, colistin and tigecycline/colistin combination on bacterial counts in lung tissue were investigated in a rat pneumonia model. One A. baumannii strain resistant to all antimicrobial agents except tigecycline and colistin was selected for the study. In vivo studies revealed a >3 log reduction in bacterial counts in the tigecycline, colistin and combination groups at 24 h and 48 h compared with the control group. No significant differences were determined between colistin, tigecycline and combination groups (P>0.05). On the other hand, differences between treatment groups and the control group were statistically significant (P=0.01). A greater reduction in bacterial counts was observed at 48 h compared with 24 h in the tigecycline group than in the colistin group (P=0.038 and P=0.139, respectively); the most significant decrease between 24 h and 48 h was observed in the combination group (P=0.014). Despite detection of in vitro synergistic activity in this study, no statistically significant differences were found between colistin, tigecycline and combination treatments in terms of efficacy on bacterial counts in lung tissue. In the treatment of infections with a high mortality rate such as pneumonia caused by XDR A. baumannii, combining tigecycline with colistin during the first 48 h and continuing treatment with one of these agents seems a rational approach.


Journal of Maternal-fetal & Neonatal Medicine | 2012

The effect of resveratrol on blood pressure in a rat model of preeclampsia

Ozlem Moraloglu; Yaprak Engin-Üstün; Esra Tonguc; Turgut Var; Ömer Lütfü Tapisiz; Hakan Ergün; Tolga Guvenc; Ayhan Gacar

Objective: To examine the hypothesis that resveratrol administration could result in blood pressure and blood flow decrease in a rat preeclampsia model. Materials and Methods: Desoxycorticosterone acetate (DOCA) was used to produce hypertension. The Wistar albino rats were divided randomly into three groups: control (n = 12), DOCA injected (n = 11), and DOCA injected and resveratrol treated (n = 13). Rats were sacrificed on gestational day 16–20. The systolic blood pressure was measured by the tail-cuff method. Urine protein was expressed as protein/creatinine. Laser Doppler measurements of the blood flow were made in one placenta, the left kidney and both parietal lobes of brain. Placentas were examined by light microscopy. Results: DOCA injected group exhibited significant differences in blood pressure and protein/creatinine. Mean blood pressure in DOCA-treated rats was 130.1 ± 12.9 mmHg at baseline and 148.4 ± 20.1 mmHg at the time of euthanization (p = 0.044). Resveratrol did not significantly affect blood pressure, placental and renal blood flows. There were also no significant differences in placental pathology parameters among the three groups. Conclusion: The present study demonstrated that resveratrol did not decrease blood pressure, and did not result in a significant response in blood flows and placental pathology parameters.


Experimental Lung Research | 2012

Infliximab attenuates activated charcoal and polyethylene glycol aspiration-induced lung injury in rats

Aygül Güzel; Mithat Günaydin; Ahmet Guzel; Hasan Alacam; Naci Murat; Ayhan Gacar; Tolga Guvenc

ABSTRACT Aspiration is a serious complication of gastrointestinal (GI) decontamination procedure. Studies have shown that tumor necrosis factor-α (TNF-α) blockers have beneficial effects on lung injury. Therefore, the authors investigated the attenuation by infliximab (INF) on activated charcoal (AC)- and polyethylene glycol (PEG)-induced lung injury in rat model. Forty-two male Sprague-Dawley rats were allotted into 1 of 6 groups: saline (NS), activated charcoal (AC), polyethylene glycol (PEG), NS+INF treated, AC+INF treated, and PEG+INF treated. All materials were aspirated into the lungs at a volume of 1 mL/kg. Before aspiration, the rats were injected subcutaneously with INF. Seven days later, both lungs and serum specimens in all groups were evaluated histopathologically, immunohistochemically, and biochemically. Following aspiration of AC and PEG, evident histopathological changes were assigned in the lung tissue that were associated with increased expression of inducible nitric oxide synthase (iNOS), increased serum levels of oxidative stress markers (malondialdehyde [MDA], surfactant protein-D [SP-D], TNF-α), and decreased antioxidant enzyme (glutathione peroxidase [GSH-Px]) activities. INF treatment significantly decreased the elevated serum MDA and TNF-α levels and increased serum GSH-Px levels. Furthermore, the current results show that there is a significant reduction in the activity of iNOS in lung tissue and increased serum SP-D levels of AC and PEG aspiration-induced lung injury with INF treatment. These findings suggest that INF attenuates lung inflammation and prevents GI decontamination agent–induced lung injury in rats.


Journal of Veterinary Science | 2007

Mammary fibroadenoma in a lamb.

M. Yavuz Gülbahar; Tolga Guvenc; Murat Yarim; Yonca B. Kabak; Yuksel Sozgen

A fibroadenoma was diagnosed in the left udder of a 3-month-old female Chios lamb. No recurrence was observed after surgery. Grossly, the tumor had a whitish-gray lobular appearance, and the lobules were interlaced with thin septa. Microscopically, the tumor was composed of proliferating fibroepithelial tissue, including differentiated ducts lined by whorls and interlacing bundles of abundant loose fibrovascular stroma. Immunohistochemistry revealed the ductal epithelium to be positive for pancytokeratin (AE1/AE3) and loose fibrovascular stroma was positive for vimentin and basal cells covering the ductal epithelium of alpha-smooth-muscle actin. Immunostaining for the estrogen and progesterone receptors was negative. A diagnosis of mammary fibroadenoma was made based on the histological and immunohistochemical findings.


Angiology | 2017

Platelet-to-Lymphocyte Ratio Predicts Contrast-Induced Acute Kidney Injury in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention:

Yalcin Velibey; Ahmet Öz; Ozan Tanik; Tolga Guvenc; Koray Kalenderoğlu; Ayça Gümüşdağ; Evliya Akdeniz; Mehmet Bozbay; Ahmet İlker Tekkeşin; Özge Güzelburç; Mert İlker Hayıroğlu; Ahmet Taha Alper; Murat Ugur; Mehmet Eren

We aimed to investigate the relationship between platelet-to-lymphocyte ratio (PLR) and contrast-induced acute kidney injury (CI-AKI) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI). A total of 2563 patients diagnosed with STEMI and underwent primary pPCI were retrospectively included in the study. Levels of PLR and creatinine were measured before and at 72 hours after pPCI. Patients were divided into 2 groups: non-CI-AKI group and CI-AKI group. Contrast-induced acute kidney injury occurred in 6.4% of the overall study population. Patients in the CI-AKI group had significantly higher PLR than those in the non-CI-AKI group (169.18 ± 81.01 vs 149.49 ± 74.54, P < .001). In logistic regression analysis, PLR was an independent predictor of CI-AKI (odds ratio [OR]: 1.774, 95% CI: 1.243-2.532, P = .002), along with age, use of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker prior to the procedure, preprocedural creatinine level, amount of contrast material used during the procedure, and hypertension. Increased PLR levels are independently associated with a greater risk of CI-AKI in patients undergoing primary PCI for STEMI.


Journal of Veterinary Science | 2011

The expressions of HSP70 and αB-crystallin in myocarditis associated with foot-and-mouth disease virus in lambs.

Mustafa Yavuz Gulbahar; Yonca Betil Kabak; M.O. Karayigit; Murat Yarim; Tolga Guvenc; Unal Parlak

This study describes the expression of heat shock protein70 (HSP70) and alpha-basic-crystallin (α-BC) and their association with apoptosis and some related adaptor proteins in the pathogenesis of foot-and-mouth disease virus (FMDV)-induced myocarditis in lambs. HSP70 was generally overexpressed in the myocardial tissues and inflammatory cells of FMDV-induced myocarditis with differential accumulation and localization in same hearts when compared to non-foot-and-mouth disease control hearts. α-BC immunolabeling showed coarse aggregations in the Z line of the cardiomyocytes in FMDV-infected hearts in contrast to control hearts. Overall, the results of this study show that the anti-apoptotic proteins, HSP70 and α-BC, were overexpressed with increased apoptosis in FMDV-infected heart tissues. Both proteins failed to protect the cardiomyocytes from apoptosis as defense mechanisms to the FMDV during the infection, suggesting that the virus is able to increase apoptosis via both downregulation and/or upregulation of these anti-apoptotic proteins.


Biotechnic & Histochemistry | 2015

Immunohistochemical detection of autophagy-related microtubule-associated protein 1 light chain 3 (LC3) in the cerebellums of dogs naturally infected with canine distemper virus.

Yonca Betil Kabak; Mahmut Sözmen; Murat Yarim; Tolga Guvenc; Mo Karayigit; Mustafa Yavuz Gulbahar

We investigated the expression of microtubule-associated protein 1 light chain 3 (LC3) protein in the cerebellums of dogs infected with canine distemper virus (CDV) using immunohistochemistry to detect autophagy. The cerebellums of 20 dogs infected with CDV were used. Specimens showing demyelination of white matter were considered to have an acute infection, whereas specimens showing signs of severe perivascular cuffing and demyelination of white matter were classified as having chronic CDV. Cerebellar sections were immunostained with CDV and LC3 antibodies. The cytoplasm of Purkinje cells, granular layer cells, motor neurons in large cerebellar ganglia and some neurons in white matter were positive for the LC3 antibody in both the control and CDV-infected dogs. In the infected cerebellums, however, white matter was immunostained more intensely, particularly the neurons and gemistocytic astrocytes in the demyelinated areas, compared to controls. Autophagy also was demonstrated in CDV-positive cells using double immunofluorescence staining. Our findings indicate that increased autophagy in the cerebellum of dogs naturally infected with CDV may play a role in transferring the virus from cell to cell.


Journal of Thoracic Disease | 2014

The evaluation of different treatment protocols for trauma-induced lung injury in rats

Hızır Ufuk Akdemir; Aygül Güzel; Celal Kati; Latif Duran; Hasan Alacam; Ayhan Gacar; Tolga Guvenc; Naci Murat; Bülent Şişman

BACKGROUND Lung contusion is an important factor that affects mortality and morbidity of lung injury after blunt chest trauma (BCT). The present study aims to evaluate the effectiveness of different treatment regimens on BCT-induced lung injury. METHODS A total of 35 Sprague Dawley rats were divided into five experimental groups (n=7): sham, control; BCT; BCT + MP, BCT group treated with methylprednisolone (MP; 30 mg/kg on first day and 3 mg/kg/d on the following days); BCT + Q, BCT group treated with quercetin (Q; 50 mg/kg/d for seven days); and BCT + MP + Q, BCT group treated with the same doses of MP and Q. Serum Clara Cell Protein-16 (CC-16), thiobarbituric acid reactive substances (TBARS), and superoxide dismutase (SOD) levels were analyzed to determine histopathological changes in the lung tissues. RESULTS Elevated serum CC-16 and TBARS levels and reduced serum SOD levels were found in the BCT group compared to the Sham group. There was a significant change in the serum CC-16 levels in the BCT + MP group compared to the Sham group. Serum TBARS levels were significantly lower in the BCT + MP and BCT + Q group compared to the BCT group. The combined therapy regimen yielded significantly decreased CC-16 levels and increased serum SOD levels compared to the individual treatment groups. Serum TBARS levels did not significantly differ between the BCT + MP + Q group and the other treatment groups. Compared to the BCT + MP + Q group, the BCT + MP group showed significantly lower alveolar edema (AED) and alveolar exudate (AEX) scores, while the BCT + Q group showed significantly lower peribronchial inflammatory cell infiltration (PICI) and AED scores. CONCLUSIONS The combined usage of quercetin and low dose MP treatment after initial high dose MP at the early stage of lung injury after BCT is more effective.

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Murat Yarim

Ondokuz Mayıs University

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Ayhan Gacar

Ondokuz Mayıs University

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Recai Tunca

Adnan Menderes University

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Ömer Kozan

Dokuz Eylül University

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Hasan Alacam

Ondokuz Mayıs University

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