Yazar "Sahin, Omer" seçeneğine göre listele

Listeleniyor 1 - 10 / 10
  • [ X ]
    Öğe
    Adverse effect of VEGFR-2 (rs1870377) polymorphism on the clinical course of COVID-19 in females and males in an age-dependent manner
    (Elsevier, 2023) Kocakap, Derya Beyza Sayin; Kaygusuz, Sedat; Aksoy, Emel; Sahin, Omer; Baccioglu, Ayse; Ekici, Aydanur; Kalpaklioglu, Ayse Fusun
    The COVID-19 pandemic has affected people worldwide with varying clinical presentations ranging from mild to severe or fatal, and studies have found that age, gender, and some comorbidities can influence the severity of the disease. It would be valuable to have genetic markers that might help predict the likely outcome of infection. For this objective, genes encoding VEGFR-2 (rs1870377), CCR5D32 (rs333), and TLR3 (rs5743313) were analyzed for polymorphisms in the peripheral blood of 160 COVID-19 patients before COVID-19 vaccine was available in Turkiye. We observed that possession of the VEGFR-2 rs1870377 mutant allele increased the risk of severe/moderate disease in females and subjects >= 65 years of age, but was protective in males <65 years of age. Other significant results were that the CCR5D32 allele was protective against severe disease in subjects >= 65 years of age, while TLR3 rs5743313 polymorphism was found to be protective against severe/moderate illness in males <65 years of age. The VEGFR-2 rs1870377 mutant allele was a risk factor for severe/moderate disease, particularly in females over the age of 65. These findings suggest that genetic polymorphisms have an age-and sex-dependent influence on the severity of COVID-19, and the VEGFR-2 rs1870377 mutant allele could be a potential predictor of disease severity.(c) 2023 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.
  • [ X ]
    Öğe
    Correction: Effects of Short-Time Austenitization on Mechanical Properties and Transformation-Induced Plasticity in Alloyed Austempered Ductile Iron (International Journal of Metalcasting, (2022), 16, 4, (1836-1848), 10.1007/s40962-021-00723-3)
    (Springer Science and Business Media Deutschland GmbH, 2023) Nalcaci, Burak; Sahin, Omer; Okur, Onur; Aydin, Murat; Erdogan, Mehmet
    The original online version of this article was revised. The graphical abstract, Fig. 8, Table 4, and miscellaneous values throughout the text were corrected. © 2023, American Foundry Society.
  • [ X ]
    Öğe
    Differences in autonomic activity in individuals with optimal, normal, and high-normal blood pressure levels
    (Kare Publ, 2010) Dogru, M. Tolga; Simsek, Vedat; Sahin, Omer; Ozer, Nurtac
    Objectives: We investigated differences in autonomic activity in normotensive individuals having optimal, normal and high-normal blood pressure (BP) levels according to the guidelines of the European Society of Hypertension and European Society of Cardiology (ESH/ESC). Study design: The study included 294 normotensive subjects (135 males, 159 females; age range 16 to 75 years) with similar clinical, morphometric, biochemical, electrocardiographic, and echocardiographic features. The subjects were classified into the following BP groups: group 1 (n=113) with optimal BP (<120/80 mmHg); group 2 (n=104) with normal BP (120-129/80-84 mmHg), and group 3 (n=77) with high-normal BP (130-139/85-89 mmHg). All the subjects underwent 24-hour Holter monitoring to obtain heart rate variability (HRV) parameters of 24-hour, daytime, and nighttime periods. Normalized low (LFn) and high (HFn) frequency powers, and logarithmic (Log) values of HRV parameters were also calculated. Results: On 24-hour Holter monitoring, heart rates were similar in three groups. Compared to group 1 and 2, group 3 exhibited significantly higher LF/HF (p<0.001) and LFn (p=0.001) values, and significantly lower HFn (p=0.001), pNN50 (p=0.001), and rMSSD (p=0.005) values. There were no significant differences between the groups with respect to daytime HRV parameters; however, nighttime LF/HF, LFn, and HFn values were significantly different between the groups. Log LF/HF values obtained during the 24-hour and nighttime periods showed significant differences between group 1 and group 3 (for 24 hours, p<0.001; for night, p=0.001) and between group 2 and group 3 (for 24 hours, p<0.001; for night, p=0.009), but group 1 and group 2 did not differ significantly in this respect (p>0.05). Conclusion: These findings suggest that subjects with high-normal BP have increased sympathetic activity and decreased parasympathetic activity, possibly making them more liable to hypertension.
  • Küçük Resim
    Öğe
    Effect of Diurnal Blood Pressure on Endothelial Functions in Essential Hypertensive Patients
    (Elsevier Science Inc, 2013) Sahin, Omer; Ebinc, Haksun; Simsek, Vedat; Tulmac, Murat; Dogru, Mehmet Tolga
    …
  • Küçük Resim
    Öğe
    Effect of Diurnal Blood Pressure on Myocardial Performance Index and Aortic Elasticity Parameters in Essential Hypertensive Patients
    (Elsevier Science Inc, 2013) Sahin, Omer; Ebinc, Haksun; Simsek, Vedat
    …
  • [ X ]
    Öğe
    Effects of Short-Time Austenitization on Mechanical Properties and Transformation-Induced Plasticity in Alloyed Austempered Ductile Iron
    (Springer Science and Business Media Deutschland GmbH, 2022) Nalcaci, Burak; Sahin, Omer; Okur, Onur; Aydin, Murat; Erdogan, Mehmet
    The present study was performed to investigate the influences of short-time austenitization on mechanical properties and transformation-induced plasticity (TRIP) in austempered ductile iron. For this purpose, Cu–Ni–Mo-alloyed ductile iron (DI) were poured into sand molds and subsequently the DI samples were austenitized at 850 °C for the duration of 15–30–60 min followed by holding in a salt bath at an austempering temperature of 260 °C for 90 min. Characterization studies were carried out with dilatometer, image analyses software, tensile test, hardness test, XRD analysis, optical and scanning electron microscopies. Findings revealed that as the austenitization time increased, carbon content of austenite (total of high carbon and blocky) and bainitic ferrite cell size enhanced, and phase volume fractions of transformation products of austenite changed. Within this context, changes in the mechanical properties were discussed. Optimum combination of strength and ductility and maximum TRIP effect were determined in the shortest (15 min)-austenitized sample. Accordingly, it was determined 15 min austenitization led to progression in the mechanical properties as 146 MPa and 2.8 % increment in the tensile strength and total elongation respectively, compared to 45 min austenitized sample. Graphical Abstract: [Figure not available: see fulltext.] © 2021, American Foundry Society.
  • [ X ]
    Öğe
    EFFECTS OF SHORT-TIME AUSTENITIZATION ON MECHANICAL PROPERTIES AND TRANSFORMATION-INDUCED PLASTICITY IN ALLOYED AUSTEMPERED DUCTILE IRON
    (Springer Int Publ Ag, 2022) Nalcaci, Burak; Sahin, Omer; Erdogan, Mehmet; Okur, Onur; Aydin, Murat
    The present study was performed to investigate the influences of short-time austenitization on mechanical properties and transformation-induced plasticity (TRIP) in austempered ductile iron. For this purpose, Cu-Ni-Moalloyed ductile iron (DI) were poured into sand molds and subsequently the DI samples were austenitized at 850 degrees C for the duration of 15-30-60 min followed by holding in a salt bath at an austempering temperature of 260 degrees C for 90 min. Characterization studies were carried out with dilatometer, image analyses software, tensile test, hardness test, XRD analysis, optical and scanning electron microscopies. Findings revealed that as the austenitization time increased, carbon content of austenite (total of high carbon and blocky) and bainitic ferrite cell size enhanced, and phase volume fractions of transformation products of austenite changed. Within this context, changes in the mechanical properties were discussed. Optimum combination of strength and ductility and maximum TRIP effect were determined in the shortest (15 min)-austenitized sample. Accordingly, it was determined 15 min austenitization led to progression in the mechanical properties as 146 MPa and 2.8 % increment in the tensile strength and total elongation respectively, compared to 45 min austenitized sample. [GRAPHICS] .
  • [ X ]
    Öğe
    EFFECTS OF SHORT-TIME AUSTENITIZATION ON MECHANICAL PROPERTIES AND TRANSFORMATION-INDUCED PLASTICITY IN ALLOYED AUSTEMPERED DUCTILE IRON (vol 16, pg 1836, 2021)
    (Springer Int Publ Ag, 2023) Nalcaci, Burak; Sahin, Omer; Erdogan, Mehmet; Okur, Onur; Aydin, Murat
    [Abstract No tAvailable]
  • [ X ]
    Öğe
    Investigation and long-term monitoring of the presence of neutralizing antibody in patients with COVID-19 disease of different clinical severity
    (Wiley, 2022) Kaygusuz, Sedat; Korukluoglu, Gulay; Cosgun, Yasemin; Sahin, Omer; Arslan, Ferhat
    Understanding the immune responses elicited by severe acute respiratory syndrome virus (SARS-CoV-2) infection is critical to public health policy and vaccine development and prevention of reinfections for COVID-19. It is important to know the neutralizing capacity of antibodies and to monitor their persistence. Patients with COVID-19 were divided into four groups (severe-critical, moderate, mild, and asymptomatic) according to their clinical severity. Antibodies against SARS-CoV-2 spike viral surface protein were investigated by ELISA method 3 and 9 months after the onset of the disease. Neutralizing antibody (NAb) response was evaluated by microneutralization test. Patients who received at least two doses of COVID-19 vaccine after illness were enrolled. SARS-CoV-2 immunoglobulin G (IgG) and NAb titers were shown to be strongly correlated with disease severity. Anti-SARS-CoV-2 IgG and NAb levels were found to be compatible with each other. After 9 months of follow-up, both IgG and NAb levels continued unabated in individuals who had the disease. In individuals who received at least two doses of the vaccine, these levels increased, except for severe-critical patients. High levels of anti-SARS-CoV-2 IgG are indicative, as it is difficult to investigate NAb in routine laboratories. At the same time, it can be predicted that this period may be much longer if it continues for at least 9 months and is reinforced with vaccination.
  • [ X ]
    Öğe
    The relationship between serum sex steroid levels and heart rate variability parameters in males and the effect of age
    (Aves, 2010) Dogru, M. Tolga; Basar, M. Murad; Yuvanc, Ercan; Simsek, Vedat; Sahin, Omer
    Objectives: We evaluated the relationships between sex steroid levels and heart rate variability (HRV) parameters. Study design: The study included 114 male subjects (mean age 46.6 +/- 11.3 years) presenting to our department for cardiologic evaluation. Hormonal analysis included serum levels of luteinizing hormone, prolactin, total testosterone (TT), free testosterone, estradiol (E2), and dehydroepiandrosterone sulfate (DHEA-S). Parameters of HRV were derived from 24-hour Holter monitoring. The associations between serum sex steroid levels and HRV parameters were investigated in three age groups (20-39 years; 40-59 years; >60 years). Results: All the participants had normal biochemical results. The three age groups were similar in terms of anthropometric measurements. Among sex steroids analyzed, only serum DHEA-S level was significantly different among the groups (p=0.026), showing a decreasing trend with age. In the evaluation of HRV, all parasympathetic activities decreased (for HFn, pNN50, and rMSDD: p=0.001, p=0.000, and p=0.000, respectively), while only LF/HF among sympathetic activities increased (p=0.000) with age. Partial correlation analysis with control of age and waist circumference showed that TT and DHEA-S were positively correlated with HFn (parasympathetic parameter), and were in negative correlation with LF/HF24 hours and global sympathetic index (GSI) (sympathetic parameters). Serum E2 level was negatively correlated with the parasympathetic parameter of rMSSD, and positively correlated with LF/HF24 hours and GSI. Among serum sex steroids, DHEA-S was the most correlated parameter with autonomic functions. Conclusion: Our results showed positive correlations between androgens and parasympathetic activity and between estradiol and sympathetic activity in men, independent from anthropometric factors.