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Dive into the research topics where Yahya Guvenc is active.

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Featured researches published by Yahya Guvenc.


Journal of Neurosurgery | 2016

Neuroprotective effects of thymoquinone against spinal cord ischemia-reperfusion injury by attenuation of inflammation, oxidative stress, and apoptosis

Emre Cemal Gokce; Ramazan Kahveci; Aysun Gokce; Berker Cemil; Nurkan Aksoy; Mustafa F. Sargon; Ucler Kisa; Bulent Erdogan; Yahya Guvenc; Fatih Alagoz; Ozan Kahveci

OBJECTIVE Ischemia-reperfusion (I/R) injury of the spinal cord following thoracoabdominal aortic surgery remains the most devastating complication, with a life-changing impact on the patient. Thymoquinone (TQ), the main constituent of the volatile oil from Nigella sativa seeds, is reported to possess strong antioxidant, antiinflammatory, and antiapoptotic properties. This study investigated the effects of TQ administration following I/R injury to the spinal cord. METHODS Thirty-two rats were randomly allocated into 4 groups. Group 1 underwent only laparotomy. For Group 2, aortic clip occlusion was introduced to produce I/R injury. Group 3 was given 30 mg/kg of methylprednisolone intraperitoneally immediately after the I/R injury. Group 4 was given 10 mg/kg of TQ intraperitoneally for 7 days before induction of spinal cord I/R injury, and administration was continued until the animal was euthanized. Locomotor function (Basso, Beattie, and Bresnahan scale and inclined plane test) was assessed at 24 hours postischemia. Spinal cord tissue samples were harvested to analyze tissue concentrations of malondialdehyde, nitric oxide, tumor necrosis factor-α, interleukin-1, superoxide dismutase, glutathione-peroxidase, catalase, and caspase-3. In addition, histological and ultrastructural evaluations were performed. RESULTS Thymoquinone treatment improved neurological outcome, which was supported by decreased levels of oxidative products (malondialdehyde and nitric oxide) and proinflammatory cytokines (tumor necrosis factor-α and interleukin-1), increased activities of antioxidant enzymes (superoxide dismutase, glutathione-peroxidase, and catalase), as well as reduction of motor neuron apoptosis. Light microscopy and electron microscopy results also showed preservation of tissue structure in the treatment group. CONCLUSIONS As shown by functional, biochemical, histological, and ultrastructural analysis, TQ exhibits an important protective effect against I/R injury of the spinal cord.


Turkish journal of trauma & emergency surgery | 2015

Outcomes and demostration of cranial firearm injuries: A multicenter retrospective study.

Kadir Çınar; Mehmet Seçer; Fatih Alagoz; Murat Ulutaş; Ozhan Merzuk Uckun; Ali Erdem Yildirim; Ahmet Gurhan Gurcay; Yahya Guvenc; Haydar Celik; Fırat Narin

BACKGROUND Cranial firearm injuries (CFAI) are associated with significant morbidity and mortality.This study was aimed to determine the factors affecting mortality of CFAI cases managed in our institution by a retrospective analysis of CT scans and clinical data. METHODS This multicenter retrospective study examined two hundred and nineteen patients presenting to neurosurgery clinics after CFAI between January 2012 and November 2014. Age, sex, Glasgow Coma Score (GCS), CT findings, and mortality and morbidity rates of the patients were analyzed to determine the factors affecting mortality. RESULTS Mean age of the study population was 24.19±12.25 years, 85.8% of them were male. The most common CT findings were fracture (100%), intracranial hemorrhage (61.2%), and an intracranially located foreign body (44.3%). A cranial operation was performed in 64.8% of the victims. Mean GCS on admission was 8±3.9, which increased in survivors (p<0.05). CONCLUSION CFAIs are associated with increased mortality and morbidity. We determined that many factors affected morbidity and mortality rates, and patient age, presence of intracranial hemorrhage, GCS, and treatment protocols were significantly associated with mortality.


Turkish Neurosurgery | 2014

Biochemical and histopathological effects of catechin on experimental peripheral nerve injuries.

Ali Erdem Yildirim; Ali Dalgic; Denizhan Divanlioglu; Rifat Akdag; Cetinalp Ne; Fatih Alagoz; Helvacioglu F; Take G; Yahya Guvenc; Koksal I; Ahmet Deniz Belen

AIM Catechin is a type of polyphenol, along with epicatechin, epigallocatechin, and epigallocatechin-gallate (EGCG). This study aims to investigate the effect of EGCG, a major metabolite of catechin, which is the principle bioactive compound in green tea, on rats with peripheral nerve injury. MATERIAL AND METHODS A total of 74 rats were divided into six groups, namely the control, the trauma, the normal saline, a 25mg/kg EGCG, a 50mg/kg EGCG and a daily consumption group (10mg/kg EGCG was given intraperitoneally for 14 days before the trauma). Except the first group, the other groups underwent a 1-minute sciatic nerve compression by clip with 50gr/cm2 pressure. Nerve samples were obtained at 28 day after trauma for the biochemical and histopathological analysis. RESULTS Our study showed that the Daily consumption, 25mg/kg EGCG and 50mg/kg EGCG groups demonstrated statistically significant decreased lipid peroxidation levels and particularly daily consumption, and the 25mg/kg EGCG group showed a favourable reduction of degeneration and edema histologically. CONCLUSION This study shows that Catechin and its derivatives have a protective effect on peripheral nerve injury.


Turkish Neurosurgery | 2013

The effects of levetiracetam on neural tube development in the early stage of chick embryos.

Yahya Guvenc; Ali Dalgic; Deniz Billur; Derya Karaoglu; Sevim Aydin; Ergun Daglioglu; Cagatay Ozdol; Osman Arikan Nacar; Ali Erdem Yildirim; Deniz Belen

AIM This study aimed to investigate the effects of a new generation antiepileptic agent, levetiracetam, on the neural tube development in a chick embryo model that corresponds to the first month of vertebral development in mammals. MATERIAL AND METHODS Forty-five Atabey® breed fertilized chicken eggs with no specific pathogens were randomly divided into 5 groups. All of the eggs were incubated at 37.8±2°C and 60±5 % relative humidity in an incubator. Group A was control group. The other eggs were applied physiological saline and drugs at a volume of 10 μL by the in ovo method at the 28th hour of the incubation period. Group B was given distilled water; Group C, physiological saline; Group D, Levetiracetam (L8668) at a dose equivalent to the treatment dose for humans (10 mg/ kg), and Group E, Levetiracetam (L8668) at a dose of 10 times the treatment dose. The embryos in all of the groups were removed from the shells at the 48th hour and morphologically and histologically evaluated. RESULTS Of the 45 embryos incubated, neural tubes of 41 were closed and the embryos displayed normal development. CONCLUSION Levetiracetam, at a dose equivalent to human treatment dose and 10 times the treatment dose, was shown not to cause neural tube defects in chick embryos.


Turkish Neurosurgery | 2015

Metamizole Sodium Induces Neural Tube Defects in a Chick Embryo Model.

Yahya Guvenc; Deniz Billur; Sevim Aydin; Ersin Ozeren; Adnan Demirci; Fatih Alagoz; Ali Dalgic; Deniz Belen

AIM The aim of this study was to investigate the effects of metamizole sodium on neural tube development in the early stage chick embryo model that complies with the first month of embryonic development in mammals. MATERIAL AND METHODS A total of 40 fertilized chicken eggs were divided into 4 equal groups. The eggs were incubated in the incubator at a temperature of 37.8±2°C with 60±5% humidity. Group A was the control, Group B was administered physiological saline, Group C was administered 30 mg/kg metamizole sodium (based on the therapeutic index range of it used in humans) and Group D was administered 90 mg/kg metamizole sodium. All embryos were removed from the egg at the 48th hour and morphologically and histologically examined. RESULTS Normal development was seen and the neural tube was closed in 17 embryos in Groups A and B. A neural tube defect was seen in 2 embryos in group A and in 1 embryo in group B. A neural tube closure defect was seen in all embryos in group C and 9 embryos in group D. There was 1 dead embryo in Group D. CONCLUSION Metamizole sodium was seen to produce a neural tube defect in the chicken embyro model.


Turkish Neurosurgery | 2016

Efficacy of Lumboperitoneal Shunting in Patients with Normal Pressure Hydrocephalus.

Mehmet Akif Bayar; Ayhan Tekiner; Haydar Celik; Ali Yilmaz; Guner Menekse; Timur Yildirim; Fatih Alagoz; Yahya Guvenc; Yavuz Erdem

AIM To evaluate the effectiveness of lumboperitoneal (LP) shunt procedures in the treatment of normal pressure hydrocephalus (NPH). MATERIAL AND METHODS A medical record review was conducted to obtain demographic, clinical, laboratory data, as well as pre-, intra, -postoperative details of 65 patients who underwent LP shunt surgery for NPH between January 1, 2001 and January 1, 2014 in the Neurosurgery Clinics of Ankara Training and Research Hospital and Ankara Numune Hospital. RESULTS At the 3rd month after LP shunt surgery, headache was resolved in almost all patients. At the end of first year, while statistically significant improvements were noted in the Modified Rankin Scale Scores and Mini-Mental State Examination Scores, gait disturbance, urinary incontinence and cognitive functions were improved by 86%, 72% and 65% of the patients, respectively. CONCLUSION LP shunt surgery is associated with a lower rate of complication in comparison to ventriculoperitoneal shunt surgery and is an effective procedure in the treatment of NPH.


Turkish Neurosurgery | 2015

The Biochemical, Histopathological and Clinical Comparison of the Neuroprotective Effects of Subcutaneous Adalimumab and Intravenous Methylprednisolone in an Experimental Compressive Spinal Cord Trauma Model

Haydar Celik; Mete Karatay; Yavuz Erdem; Ali Erdem Yildirim; İdris Sertbaş; Eylem Karatay; Halil Kul; Yahya Guvenc; Ismet Koksal; Menekse G; Fatih Alagoz; Huseyin Hayri Kertmen; Muzaffer Caydere

AIM To evaluate the neuroprotective effects of adalimumab in an experimental spinal cord injury model and compare them with those of the widely-used methylprednisolone. MATERIAL AND METHODS Forty male Wistar rats were divided into 5 as the sham, trauma, adalimumab, methylprednisolone, and adalimumab+methylprednisolone groups. Only laminectomy was performed in the sham group. Laminectomy and trauma was performed to the trauma group but no treatment was given. A single dose of 40 mg/kg subcutaneous adalimumab was administered after the laminectomy and trauma to group 3. A single dose of intravenous 30 mg/kg methylprednisolone was administered right after laminectomy and trauma to group 4. Single doses of 40 mg/kg adalimumab and 30 mg/kg methylprednisolone were administered together after laminectomy and trauma to group 5. Serum malondialdehyde (MDA), TNF-α, IL-1β and IL-6 levels were measured and sections were obtained for histopathological study at the end of the 7 < sup > th < /sup > day. RESULTS MDA, TNF-α, IL-1β and IL-6 levels in serum were significantly decreased in the adalimumab group with clinical and histopathological improvement not less than the methylprednisolone group. The serum MDA levels were similar when the two drugs were given together or separately but there was a statistically quite significant decrease in TNF-α, IL-1β and IL-6 levels with concurrent use. Statistically significantly better results were obtained on histopathological evaluation with the use of both drugs together. CONCLUSION This study revealed that adalimumab is as effective as methylprednisolone in compressive spinal cord injury in rats.


Turkish Neurosurgery | 2015

Analysis of Traumatic Acute Subdural Hematomas: Outcomes and Predictive Factors In a Single Center Experience.

Fatih Alagoz; Ali Erdem Yildirim; Mert Sahinoglu; Murat Korkmaz; Mehmet Seçer; Haydar Celik; Cihat Yel; Yahya Guvenc; Ozhan Merzuk Uckun; Firat Narin; Ergun Daglioglu; Ahmet Deniz Belen

AIM In the present study, we evaluated the association of the Glasgow Coma Scale (GCS) score and amount of blood loss with mortality in patients presenting with traumatic acute subdural hematoma (ASDH). MATERIAL AND METHODS This retrospective study was performed on 99 patients who were operated for traumatic acute subdural hematoma (ASDH) without any systemic association at a single center. Epidural hematoma was reported to be the most common additional pathology. Age, sex, mechanism of trauma, time interval between onset of trauma and admission to the emergency ward, associated problems, thickness of hematoma and Glasgow Coma Scale (GCS) score at the time of admission and on discharge were all studied. RESULTS The GCS score was inversely proportional to the thickness of hematoma and interval between onset of trauma and surgery (p < 0.05). Although the mortality rate was reported to be high in traffic accidents, the rate was low in patients with head trauma only (p < 0.05). The mortality rate was high in patients with associated pathologies (p < 0.05). Lost patients were reported to be older patients with more extensive ASDH or those who presented earlier with a low GCS (p < 0.05). CONCLUSION ASDH is associated with high mortality. GCS score and the thickness of the ASDH are important predictors of mortality. Age, additional trauma, and interval between trauma and hospital admission are major predictive factors for mortality.


British Journal of Neurosurgery | 2015

The effect of flurbiprofen on the development of anencephaly in early stage chicken embryos

Ersin Özeren; Uygur Er; Yahya Guvenc; Adnan Demirci; Ata Türker Arikok; Engin Şenveli; Rüçhan Behzat Ergün

Abstract Objective. The study investigated the effect of flurbiprofen on the development of anencephaly in early stage chicken embryos. Material and methods. We looked at four groups with a total of 36 embryos. There was a control group, a normal saline group, a normal-dose group and a high-dose group with ten, ten, eight and eight eggs with embryo respectively. Results. Two embryos in the control group, studied with light microscopy at 48 h, were consistent with 28–29 hours’ incubation in the Hamburger–Hamilton System. They had open neural tubes. The other embryos in this group were considered normal. One embryo in the normal saline group was on the occlusion stage at 48 h. One embryo showed an open neural tube. They were compatible with 28–29 hours’ incubation in the Hamburger–Hamilton system. The remaining eight embryos showed normal development. In the normal dose group, one embryo showed underdevelopment of the embryonic disc and the embryo was dead. In four embryos, the neural tubes were open. One cranial malformation was found that was complicated with anencephaly in one embryo. In two embryos the neural tubes were closed, as they showed normal development, and they reached their expected stages according to the Hamburger–Hamilton classification. There was no malformation or growth retardation. Four experimental embryos were anencephalic in the high dose group, and three embryos had open neural tubes. One embryo exhibited both anencephaly and a neural tube closure defect. None of the embryos in this group showed normal development. Conclusions. Even the usual therapeutic doses of flurbiprofen increased the risk of neural tube defect. Flurbiprofen was found to significantly increase the risk of anencephaly. The provision of improved technical materials and studies with larger sample sizes will reveal the stage of morphological disruption during the development of embryos.


Journal of Craniofacial Surgery | 2010

Cranial ossifying fibroma causing visual disorder.

Askin Esen Hasturk; Yahya Guvenc; Erkan Kaptanoglu

Fibrous lesions of the head and the maxillofacial region are generally slow-developing benign tumors that may aggressively take course in clinical terms. These locally destructive lesions show a high recurrence rates unless they are removed gross totally. Sarcomatoid degeneration is also reported to develop in recurring lesions. Difficulties in the diagnosis, classification, and treatment make this entity complex for several years. These tumors are frequently seen among children and young adults. The maxilla and the mandibula are the 2 most common sites that the tumor originates. In our article, we discuss a 59-year-old man whose condition was diagnosed as an ossified fibroma revealing craniofacial extension. Accompanied by literature findings, it has been underlined that, as well as with the pathologic criteria, clinical features and radiologic images should be evaluated together for a specific diagnosis in fibrous lesions.

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Mete Karatay

Yeni Yüzyıl University

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