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Öğe Analgesic effect of metformin on hyperalgesia induced by REM sleep deprivation(Wiley, 2023) Gurel, Elif Ezgi; Ozturk, Gulnur; Ozturk, Levent; Tosunoglu, Esra Akbas; Gul, Tugba Kizil; Arslan, Enver[Abstract Not Available]Öğe Arginase activity and nitric oxide levels in patients with obstructive sleep apnea syndrome(Hospital Clinicas, Univ Sao Paulo, 2014) Yuksel, Meral; Okur, Hacer Kuzu; Pelin, Zerrin; Ogunc, Ayliz Velioglu; Ozturk, LeventOBJECTIVE: Obstructive sleep apnea syndrome is characterized by repetitive obstruction of the upper airways, and it is a risk factor for cardiovascular diseases. There have been several studies demonstrating low levels of nitric oxide in patients with obstructive sleep apnea syndrome compared with healthy controls. In this study, we hypothesized that reduced nitric oxide levels would result in high arginase activity. Arginase reacts with L-arginine and produces urea and L-ornithine, whereas L-arginine is a substrate for nitric oxide synthase, which produces nitric oxide. METHODS: The study group consisted of 51 obstructive sleep apnea syndrome patients (M/F: 43/8; mean age 49 +/- 10 years of age) and 15 healthy control subjects (M/F: 13/3; mean age 46 +/- 14 years of age). Obstructive sleep apnea syndrome patients were divided into two subgroups based on the presence or absence of cardiovascular disease. Nitric oxide levels and arginase activity were measured via an enzyme-linked immunosorbent assay of serum samples. RESULTS: Serum nitric oxide levels in the control subjects were higher than in the obstructive sleep apnea patients with and without cardiovascular diseases (p<0.05). Arginase activity was significantly higher (p<0.01) in obstructive sleep apnea syndrome patients without cardiovascular diseases compared with the control group. Obstructive sleep apnea syndrome patients with cardiovascular diseases had higher arginase activity than the controls (p<0.001) and the obstructive sleep apnea syndrome patients without cardiovascular diseases (p<0.05). CONCLUSION: Low nitric oxide levels are associated with high arginase activity. The mechanism of nitric oxide depletion in sleep apnea patients suggests that increased arginase activity might reduce the substrate availability of nitric oxide synthase and thus could reduce nitric oxide levels.Öğe Blood pressure, autonomic stress, and inflammatory markers during sleep deprivation and recovery in healthy men(Turkish Soc Cardiology, 2021) Bozer, Ozge; Kaya, Oktay; Ozturk, Gulnur; Bulut, Erdogan; Zorkun, Cafer; Ozturk, LeventObjective: Recent community-based studies have identified sleep deprivation (SD) as an important modifiable risk factor for hypertension However, the underlying mechanisms linking SD to hypertension remain elusive. Thus, this study investigates blood pressure (BP) responses to cardiac autonomic stress tests in the presence of SD. Furthermore, we analyzed vascular inflammatory biomarkers as a possible underlying factor linking SD to increased BP. Methods: Ten healthy male volunteers (age, 21.6 +/- 1.2 years) underwent repeated autonomic stress tests for three consecutive days (baseline, SD, and recovery). The autonomic stress tests included the Valsalva maneuver, mental arithmetic, isometric handgrip, and cold pressor tests. Each day, resting BPs were measured, venous blood samples were collected for intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and E-selectin measurements, and stress tests were performed between 0900 and 1100. Ambulatory BP was recorded during the entire SD period (24 h). Results: One-night SD abolished BP reactivity to the Valsalva maneuver, isometric hand grip, and cold pressor tests, which returned after recovery sleep. Ambulatory BP monitoring showed that the mean systolic and diastolic BPs were 121.1 +/- 8.5 mm Hg and 72.8 +/- 6.3 mm Hg, respectively, between 0700 and 2300 and 120.3 +/- 9.6 mm Hg and 74.1 +/- 6.1 mm Hg, respectively, between 2300 and 0700 during the SD day (p>0.05 for both). Vascular inflammatory markers seemed unrelated to BP changes. Conclusion: Acute SD altered BP responses to cardiac autonomic stress tests in healthy men without affecting resting BP levels. SD led to a non-dipping pattern in BP oscillation. Collectively, these findings highlight the importance of sleep in regulating BP.Öğe Can obstructive apnea and hypopnea during sleep be differentiated by using electroencephalographic frequency bands? Statistical analysis of receiver-operator curve characteristics(Tubitak Scientific & Technological Research Council Turkey, 2011) Ucar, Erdem; Sut, Necdet; Gulyasar, Tevfik; Umut, Ilhan; Ozturk, LeventAim: To investigate whether electroencephalographic (EEG) frequency bands are applicable in distinguishing abnormal respiratory events such as obstructive apnea and hypopnea in patients with sleep apnea. Materials and methods: The polysomnographic recordings of 20 patients were examined retrospectively. EEG record segments were taken from C4-A1 and C3-A2 channels and were analyzed with software that uses digital signal processing methods, developed by the study team. Percentage values of delta, theta, alpha, and beta frequency bands were evaluated through discriminant and receiver-operator curve (ROC) analysis to distinguish between apneas and hypopneas. Results: For the G4-A1 channel, delta (%) provided the highest discriminative value (AUG = 0.563; P < 0.001); on the other hand, alpha (%) gave the lowest discriminative value (AUG = 0.519; P = 0.041). Likewise, whereas for the C3-A2 channel delta (%) gave the highest discriminative value (AUG = 0.565; P < 0.001), alpha produced the lowest discriminative value (AUG = 0.501; P = 0.943). Conclusion: As a result of discriminant analysis, the accurate classification rate of hypopneas was 44.8% and the accurate classification of obstructive apneas was 63.5%. Of the 4 frequency bands, the most significant was delta. The predictive values were not at significance level.Öğe Cardiopulmonary responses to exercise in moderate-to-severe obstructive sleep apnea(Turkish Assoc Tuberculosis & Thorax, 2005) Ozturk, Levent; Metin, Gokhan; Cuhadaroglu, Caglar; Utkusavas, Ayfer; Tutluoglu, BulentInformation regarding the safety of maximal cardiopulmonary exercise testing (CPET) or the mechanisms of exercise limitation in obstructive sleep apnea (OSA) patients is fairly limited. In the present study, we addressed the problem of exercise capacity in moderate-to-severe OSA patients. Nineteen non-consecutive patients (three female, 16 male) with moderate-to-severe OSA and 11 age and body mass index matched control subjects (four female, seven male) underwent respiratory function tests during pre-exercise resting period and volitionally limited cardiopulmonary exercise testing on an electronically braked cycle ergometer. All participants completed CPET without any complication. Control subjects were exercise limited due to deconditioning. None of the patients revealed mechanical ventilatory limitation to exercise or had evidence of cardiac ischaemia. Five patients had no limitation to exercise. Six patients had low VO2peak, low anaerobic treshold (AT), and low peak O-2 pulse, a pattern consistent with ventricular dysfunction. Six patients had low VO2peak, low AT, and peak heart rate less than 85% predicted. This pattern is consistent with exercise limitation due to peripheral vascular disease. Two patients had low VO2peak, low AT without peak oxygen pulse and peak heart rate abnormalities consistent with deconditioning. We concluded that moderate-to-severe OSA patients have impaired exercise capacity. Exercise limitation seems to originate from cardiovascular reasons namely left ventricular dysfunction and/or peripheral vascular impairment; and finally, maximal CPET can be tolerated by these patient group without serious complications.Öğe Öğe Circadian Physiology and Sleep: Concepts and Definitions(Wiley, 2019) Ozturk, Levent[Abstract Not Available]Öğe Commentary on Viewpoint: REGULATION OF LEPTIN BY HYPOXIA(Amer Physiological Soc, 2008) Ozturk, Levent[Abstract Not Available]Öğe Daytime sleepiness and sleep habits as risk factors of traffic accidents in a group of Turkish public transport drivers(E-Century Publishing Corp, 2014) Ozer, Cahit; Etcibasi, Seref; Ozturk, LeventAim: To explore the association of daytime sleepiness, sleep complaints and sleep habits with self-reported car crashes among public transport drivers. Methods: A cross-sectional descriptive study was carried out on male professional public drivers in two different cities using a validated, self-administered sleep questionnaire which comprised of symptoms suggesting sleep disorders, a subjective report of daytime sleepiness and driving characteristics. The subjects (mean age +/- SD, 40 +/- 11 years) were divided into two groups: (1) accident group and (2) no accident group. Results: Forty nine (15.3%) of the 320 public drivers reported that they had at least one sleepiness related motor vehicle accident and/or near-missed accident (Group 1). The mean age, body mass index and annual distance driven were similar in both groups. Although Group 1 reported less sleep time per night, more witnessed apneas, abnormal sleep, alcohol use and had higher mean Epworth Sleepiness Scale scores than Group 2, multivariate analysis of risk factors revealed that only daytime sleepiness increase the risk of traffic accidents [OR: 1.32 (1.19-1.47)]. Conclusion: These results suggest that self-reported sleepiness is a predictive sign of traffic accidents due to driver sleepiness.Öğe DETECTION OF DRIVER SLEEPINESS AND WARNING THE DRIVER IN REALTIME USING IMAGE PROCESSING AND MACHINE LEARNING TECHNIQUES(Lublin Univ Technology, Poland, 2017) Umut, Ilhan; Aki, Ozan; Ucar, Erdem; Ozturk, LeventThe aim of this study is to design and implement a system that detect driver sleepiness and warn driver in real-time using image processing and machine learning techniques. Viola-Jones detector was used for segmenting face and eye images from the cameraacquired driver video. Left and right eye images were combined into a single image. Thus, an image was obtained in minimum dimensions containing both eyes. Features of these images were extracted by using Gabor filters. These features were used to classifying images for open and closed eyes. Five machine learning algorithms were evaluated with four volunteer's eye image data set obtained from driving simulator. Nearest neighbor IBk algorithm has highest accuracy by 94.76% while J48 decision tree algorithm has fastest classification speed with 91.98% accuracy. J48 decision tree algorithm was recommended for real time running. PERCLOS the ratio of number of closed eyes in one minute period and CLOSDUR the duration of closed eyes were calculated. The driver is warned with the first level alarm when the PERCLOS value is 0.15 or above, and with second level alarm when it is 0.3 or above. In addition, when it is detected that the eyes remain closed for two seconds, the driver is also warned by the second level alarm regardless of the PERCLOS value. Designed and developed real-time application can able to detect driver sleepiness with 24 FPS image processing speed and 90% real time classification accuracy. Driver sleepiness were able to detect and driver was warned successfully in real time when sleepiness level of driver is achieved the defined threshold values.Öğe Diagnostic Value of Gait Analysis in Patients with Lumbar Disc Herniation(Wiley, 2019) Delen, Emre; Ozturk, Gulnur; Karahan, Menekse; Ulucam, Enis; Ozturk, Levent[Abstract Not Available]Öğe Differences in grain zinc are not correlated with root uptake and grain translocation of zinc in wild emmer and durum wheat genotypes(Springer, 2017) Yilmaz, Ozlem; Kazar, Gamze Altintas; Cakmak, Ismail; Ozturk, LeventCereal-based foods fall short of providing adequate dietary zinc (Zn) to human beings. Developing new genotypes with high genetic capacity for root uptake and grain deposition of Zn is an important challenge. There is a large genetic variation for grain Zn concentration among and between wheat species, especially within wild emmer wheat (Triticum turgidum ssp. dicoccoides) that can be exploited in order to understand the physiological mechanisms contributing to grain Zn accumulation. Eight different wild emmer genotypes and two durum wheat (Triticum durum) cultivars were used to investigate root uptake, root-to-shoot translocation and remobilization (i.e., retranslocation) from flag leaves into grains of (ZnSO4)-Zn-65-treated plants. The initial seed Zn concentrations of wild emmer wheat and durum genotypes used in the experiments were different, ranging from 45 to 73 mg kg(-1) and from 35 to 40 mg kg(-1), respectively. Plants were grown in nutrient solution for the experiments investigating root uptake and shoot transport of Zn by using Zn-65 labeled ZnSO4 and in soil medium for the experiments studying shoot and grain Zn concentrations and Zn-65 translocation from flag leaves into grains. The treatment of flag leaves with Zn-65 was realized by immersion of flag leaves into (ZnSO4)-Zn-65 solution for 15 seconds and for 5 times during the anthesis and early milk stages. Wild emmer and durum wheat genotypes expressed highly significant differences in root uptake and root-to-shoot translocation of Zn-65 and translocation of Zn-65 from flag leaves into grains. However, none of these parameters showed a significant correlation either with the initial seed Zn concentrations at sowing or the grain Zn concentrations at harvest. The durum wheat cultivars with higher grain yield had lower concentration of Zn both in seeds at sowing or in grains at harvest, while wild emmer genotypes with lower grain yield capacity had higher concentration of Zn both in seeds at sowing or in grains at harvest. The concentration or content (total amount) of Zn in shoot during the early growth stage also did not correlate with the initial seed Zn concentrations. Differences in grain Zn concentration of wild emmer and cultivated wheats could not be explained by root Zn uptake and Zn translocation from flag leaf into grains during seedling and reproductive growth stages, respectively. It seems that there are additional key factors affecting the expression of genetic variation for grain Zn accumulation.Öğe DNA methylation of the prestin gene and outer hair cell electromotile response of the cochlea in salicylate administration(Tubitak Scientific & Technological Research Council Turkey, 2017) Bulut, Erdogan; Budak, Metin; Ozturk, Levent; Turkmen, Mehmet T.; Uzun, Cem; Sipahi, TammamBackground/aim: Activity of the prestin gene may have a role in the pathogenesis of salicylate-induced ototoxicity. We investigated DNA methylation for prestin gene exon 1 in salicylate-injected guinea pigs. Materials and methods: Fifteen guinea pigs (30 ears) underwent audiological evaluation including 1000 Hz probe-tone tympanometry and a distortion product otoacoustic emission (DPOAE) test. The animals were randomly divided into three groups. Groups 2 (8 ears) and 3 (14 ears) were injected with intramuscular saline and sodium salicylate (200 mg/kg), respectively twice daily for 2 weeks. Group 1 (8 ears) received no injection. DPOAE measurements were performed at baseline; after 1, 2, 4, and 8 h (acute effect); and after 1 and 2 weeks (chronic effect). After audiological measurements, the animals were sacrificed for DNA isolation. Results: While a significant decrease (P < 0.01) was found for the acute effect in all frequencies in Group 3 according to baseline measurements, there was no difference in terms of chronic effect. DNA methylation increased during the acute phase of salicylate administration, whereas it returned to initial levels during the chronic phase. Conclusion: Salicylate-induced changes in DPOAE responses may be related to prestin-gene methylation. These results may have important implications for salicylate ototoxicity.Öğe The effect of 24-hour sleep deprivation on subjective time perception(Elsevier, 2023) Sen, Buket; Kurtaran, Nurcan Erdogan; Ozturk, LeventIn this study, we investigated the effect of 24-h total sleep deprivation on subjective time perception. Twenty-five participants aged 18-35 years (13 female and 12 male) were recruited. Time perception and cognitive assessments were performed twice: after a regular night's sleep and following a 24-h sleep deprivation. The retrospective and prospective tasks were used to measure time perception. In order to prevent order effect, the test orders were randomized. The Stroop test and the Wechsler Memory Scale-III were used to evaluate attention, processing speed, and memory. The repeated measures ANOVA was used to examine gender-by-sleep deprivation interactions on time perception. We found that retrospective time perception was significantly prolonged after sleep deprivation (p < 0.05). Women had a shorter prospective time estimation rate after adequate sleep than men, but this difference disappeared after sleep deprivation. The Stroop test showed improvement in cognitive flexibility after sleep deprivation (p < 0.05), and short-term or working memory appeared unaffected by one night of sleep deprivation. There was a negative correlation between sleepiness rate and working memory function in female subgroup. The results suggest that even short-term sleep deprivation can significantly affect time perception, which may have important implications in critical situations.Öğe The Effect of Exogenous Melatonin on Blood Glucose in A Model of Experimental Chronic Sleep Deprivation(Wiley, 2023) Gul, Tugba Kizil; Kaya, Oktay; Puyan, Fulya Oz; Ozturk, Levent[Abstract Not Available]Öğe The Effect of Ginkgo Biloba on Hyperalgesia Induced by REM Sleep Deprivation(Wiley, 2023) Gurel, Elif Ezgi; Ozturk, Levent; Ozturk, Gulnur; Deger, Ecem Busra; Tosunoglu, Esra Akbas[Abstract Not Available]Öğe The Effect of Metformin on Hyperalgesia Induced by REM Sleep Deprivation(Wiley, 2022) Gurel, Elif Ezgi; Ozturk, Gulnur; Gunduz, Samime Sarli; Tosunoglu, Esra Akbas; Ozturk, Levent[Abstract Not Available]Öğe The Effect of Music on Sleep Latency(Wiley, 2022) Arslan, Enver; Deger, Ecem Busra; Ozturk, Levent[Abstract Not Available]Öğe The Effect of Music on Subjective Time Perception(Wiley, 2019) Gul, Tugba Kizil; Ozturk, Gulnur; Kaya, Oktay; Sen, Burcu; Memi, Gulsun; Ozturk, Levent[Abstract Not Available]Öğe The effect of one-night sleep deprivation on cognitive functions in healthy young adults(Brazilian Assoc Sleep, 2021) Pekcetin, Serkan; Ozturk, Gulnur; Cetin, Buse; Ozturk, LeventIntroduction: The effects of acute sleep deprivation on cognitive function have not been clearly elucidated. The purpose of this study was to evaluate changes in cognitive function in healthy adults after one night of sleep deprivation. Material and Methods: Twenty-one healthy young adults (aged 18-30 years) underwent assessment of cognitive functions before and after one night of total sleep deprivation and an age- and gender-matched control group was assessed before and after a normal night sleep. Cognitive functions were assessed using the Montreal cognitive assessment (MOCA) and trail making test (TMT) parts A and B. Results: General linear model repeated measures demonstrated an insignificant effect for time x group (sleep deprivation) interaction for MOCA, TMT Part A, and TMT Part B scores after one-night sleep deprivation (p>.05 for all). Conclusion: A single night of sleep deprivation, which can be inevitable in modern society, had no significant effect on cognitive performance in healthy adults.
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