WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
Browse
48 results
Search Results
Article Citation - WoS: 37Mechanisms of Cellular Resistance To Imatinib in Human Chronic Myeloid Leukemia Cells(Taylor and Francis Ltd., 2007) Baran, Yusuf; Ural, Ali Uğur; Gündüz, UfukA major advancement in the treatment of chronic myeloid leukemia (CML) has been the development of imatinib, which has shown striking activity in the chronic phase and the accelerated phase, but less so in the blast phase of the disease. Despite high rates of hematologic and cytogenetic responses to therapy, the emergence of resistance to imatinib has been recognized as a major problem in the treatment of patients with CML. Various cellular mechanisms may be involved in the nature of cellular resistance. Increased amount of target, alteration in structure of target proteins, decreased drug uptake and increased detoxification are well-known mechanisms of resistance. On the other hand, in some cases, even if anticancer drugs reach their sites of action, bypassing drug efflux system of the cells, some cells still may survive via the dysregulation of apoptotic signalling. In this study, mechanisms of resistance to imatinib-induced apoptosis in human Meg-01 CML cells were examined. Continuous exposure of cells to step-wise increasing concentrations of imatinib resulted in the selection of 200- and 1000 nM imatinib-resistant sub-lines referred to as Meg-01/IMA-0,2 and Meg-01/1MA-1, respectively. MTT cell proliferation, cell cycle analyses and trypan blue dye exclusion analyses showed that Meg-0l/IMA-1 cells were resistant to imatinib-induced apoptosis as compared to parental sensitive cells. There was an increased expression of BCR/ABL, Bcl-2 and an increase in mitochondrial membrane potential (MMP) detected in resistant cells comparing to parental sensitive cells. There was no mutation detected in imatinib binding site of ABL kinase region. Various diverse mechanisms have been reported for their involvement in the multidrug resistance. In this study, it has been shown that the degree of BCR/ABL expression appears to be directly proportional to the levels of imatinib resistance. In addition, there have been BCR/ABL-independent mechanisms reported for deriving resistance against imatinib. Our results revealed that besides BCR/ABL overexpression, imatinib resistance also depends on the inhibition of apoptosis as a result of up-regulation of anti-apoptotic stimuli and down-regulation of pro-apoptotic stimuli through MMP but does not depend on any mutation on imatinib binding site of ABL kinase.Conference Object Citation - WoS: 7Modeling of Low Temperature Geothermal District Heating Systems(Taylor and Francis Ltd., 2004) Yıldırım, Nurdan; Gökçen, GüldenIn this work, low temperature geothermal district heating systems with heat pumps have been studied and compared with fuel-oil boiler heating systems for intermittent and continuous regimes according to the optimum indoor air temperature and operational cost. Izmir Institute of Technology (IZTECH) Campus is taken as a case study. Various heat pump and boiler configurations are studied to meet required duty. Operational cost analysis for each alternative is conducted. According to the results, for IZTECH Campus the best alternative, which gives the optimum indoor air temperature and the lowest operational cost, is heat pump continuous regime.Conference Object Detection of Urban Change Using Remote Sensing and Gis: Izmir Case(Taylor and Francis Ltd., 2008) Tarhan, Çiğdem; Arkon, Cemal; Çelik, M.; Gümüştekin, Şevket; Tecim, V.This study is an example of how land use changes could be detected via high resolution remotely sensed data. In order to perform "change detection" IKONOS satellite images, belonging to 2001 and 2004, have been used. An automated Graphical User Interface (GUI) has been created for detection of environment. Different image enhancement techniques and a fuzzy inference system have been combined in the GUI. The detection results are classified according to some basic levels such as 20-50% and 70%. Additionally, four different change detection algorithms have been applied which are pixel-based, object based, feature based. These algorithms have been examined according to change detection levels with different image enhancement techniques. At the end of the study, the results have been compared.Article Citation - WoS: 18Citation - Scopus: 19A Suppressed Demand Analysis Method of the Transportation Disadvantaged in Policy Making(Taylor and Francis Ltd., 2009) Duvarcı, Yavuz; Mizokami, ShoshiThis paper proposes a method for estimating transportation supply requirements when the suppressed demand of the transportation disadvantaged (TD) can be calculated and added to existing demand for travel. The underlying assumption is that the travel conditions of these TD groups must be equal to the 'conventional' demand, known as 'full release'. Utilising the modelling approach for TD, suppressed demand analysis, diagnosis of difficulties and equity between conventional and disadvantaged groups were realised, while elaborating special cases for the most vulnerable TD groups (such as elderly and disabled persons) and simultaneously identifying areas of difficulty. From the early virtual results, it is concluded that, for the full release of suppressed trips (only a 5% increase), policy makers must be ready to face some financial burdens, requiring coordination of effort to both standardise these TD groups and reduce the costs incurred by operators.Article Citation - WoS: 16Citation - Scopus: 16Multidrug Resistance Mediated by Mrp1 Gene Overexpression in Breast Cancer Patients(Taylor and Francis Ltd., 2009) Abaan, Ogan Demir; Mutlu, Pelin Kaya; Baran, Yusuf; Atalay, Can; Gündüz, UfukMultidrug resistance (MDR) is a serious handicap towards the effective treatment of breast cancer patients. One of the most prevalent MDR mechanisms is through the overexpression of genes coding the proteins called Multidrug Resistance-associated Proteins (MRPs). The aim of this study was to investigate the expression of MRP1 in tumor tissues from breast cancer patients. In this study, a semi-quantitative RT-PCR approach was utilized. Our results suggest that MRP1 overexpression can mediate MDR in patients. Pre-evaluation of the level of such MDR mediators before chemotherapy can increase the efficacy of the treatment.Article Citation - WoS: 6Citation - Scopus: 6Docetaxel Enhances the Cytotoxic Effects of Imatinib on Philadelphia Positive Human Chronic Myeloid Leukemia Cells(Taylor and Francis Ltd., 2009) Güçlüler, Gözde; Baran, YusufChronic myelogenous leukemia (CML) results from a translocation between chromosomes 9 and 22 which generates BCR/ABL fusion protein and characterized by uncontrolled proliferation of immature white blood cells. Imatinib, a molecularly targeting anticancer agent, is used widely for the treatment of CML and showed significant activity in chronic and accelerated phases but much less in blast crisis phase. The resistance to imatinib especially in blast crisis phase is recognized as a major problem in the treatment of CML patients. Docetaxel is shown to arrest cells in G2/M phase of the cell cycle which makes cells more sensitive to chemo- and radiotherapy. In this study, we aimed to increase chemosensitivity of human K562 CML cells to imatinib in combination with docetaxel. Taken together, our results showed that the combination of imatinib and docetaxel decreased cellular proliferation and increased apoptosis in human K562 chronic myeloid leukemia cells as compared to any agent alone. Imatinib and docetaxel induced apoptosis through caspase-3 enzyme activity and mitochondrial membrane potential.Article Citation - WoS: 18Citation - Scopus: 22Prediction of Lignin and Extractive Content of Pinus Nigra Arnold. Var. Pallasiana Tree Using Near Infrared Spectroscopy and Multivariate Calibration(Taylor and Francis Ltd., 2009) Üner, Birol; Karaman, İbrahim; Tanrıverdi, H.; Özdemir, DurmuşDetermination of quality parameters such as lignin and extractive content of wood samples by wet chemistry analyses takes a long time. Near infrared (NIR) spectroscopy coupled with multivariate calibration offers a fast and nondestructive alternative to obtain reliable results. However, due to the complexity of the spectra obtained from NIR, some wavelength selection is generally required to improve the predictive ability of multivariate calibration methods. Pinus nigra Arnold. Var. pallasiana is the second most growing pine species in Turkey. Even though its rotation period is very high, around 120 years, the forest products industry has widely accepted the use of Pinus nigra because of its ability to grow on a wide range of sites and its suitability to produce desirable products. In this study, 51 samples of Pinus nigra trees were collected and their lignin and extractive content were determined with standard reference (TAPPI) methods. Then, the same samples were scanned with near infrared spectrometer between 1000 and 2500 nm in diffuse reflectance mode. Multivariate calibration models were built with genetic inverse least squares method for both lignin and extractive content using the concentration information obtained from wet standard reference method. Overall, standard error of calibration (SEC) and standard error of prediction (SEP) were ranged between 0.35% (w/w) and 2.4% (w/w).Article Citation - WoS: 13Citation - Scopus: 20Weighing Diverse Theoretical Models on Turkish Maqam Music Against Pitch Measurements: a Comparison of Peaks Automatically Derived From Frequency Histograms With Proposed Scale Tones(Taylor and Francis Ltd., 2009) Bozkurt, Barış; Yarman, Ozan; Karaosmanoğlu, M. Kemal; Akkoç, CanSince the early 20th century, various theories have been advanced in order to mathematically explain and notate modes of Traditional Turkish music known as maqams. In this article, maqam scales according to various theoretical models based on different tunings are compared with pitch measurements obtained from select recordings of master Turkish performers in order to study their level of match with analysed data. Chosen recordings are subjected to a fully computerized sequence of signal processing algorithms for the automatic determination of the set of relative pitches for each maqam scale: f0 estimation, histogram computation, tonic detection + histogram alignment, and peak picking. For nine well-recognized maqams, automatically derived relative pitches are compared with scale tones defined by theoretical models using quantitative distance measures. We analyse and interpret histogram peaks based on these measures to find the theoretical models most conforming with all the recordings, and hence, with the quotidian performance trends influenced by them.Article Citation - WoS: 3Citation - Scopus: 3The Impact of Planimetric Configuration on Structurally Damaged Residential Buildings(Taylor and Francis Ltd., 2009) Kazanasmaz, Zehra TuğçeThis study was conducted to determine a significant relationship between planimetric configuration and vulnerability of hazardous buildings located in seismic zones by developing design and construction efficiency indicators. Case study examples were chosen from residential buildings in Bolu, Düzce and Kaynasli in Turkey, which were damaged by the 1999 earthquakes. Utilizing field survey drawings, efficiency quotients; compactness quotients; construction efficiency ratios; aspect ratios and height-to-base ratios were defined as planimetric configuration indicators. The significant relationship between these aspects and the damage level of buildings were determined through statistical analyses and scatter charts. Planimetric configuration - including building geometry, cantilever projections and layout of columns -was reviewed according to the Turkish Earthquake Code. Findings revealed certain dependencies for efficiency ratios, which would satisfactorily predict the seismic vulnerability of buildings based on planimetric configuration. Researchers in the field of architecture who are engaged in earthquake-resistant design may use the general methodology. In addition, architects and structural engineers can use this approach presented here to evaluate their design.Article Citation - WoS: 28Citation - Scopus: 30Hydrochemical and Isotopic Composition of Tuzla Geothermal Field (canakkale-Turkey) and Its Environmental Impacts(Taylor and Francis Ltd., 2009) Baba, Alper; Yüce, Galip; Deniz, Ozan; Yasin, DidemTuzla is an active geothermal area located in northwestern Turkey, 80 km south of the city of Canakkale and 5 km from the Aegean Coast. Geothermal brine, deriving from this area, contains an abundance of NaCl and a water temperature of 173°C (T1 well at 814 m depth) is typically encountered. The aim of this study was to determine the hydrogeochemical properties of the geothermal brine using both chemical and isotopic data, and to investigate the origin of the geothermal brine in the Tuzla area and the environmental impacts of Tuzla Geothermal Field (TGF). Both geothermal brine and shallow groundwater in the area are of meteoric origin. Isotope results indicate that the hot saline waters (brine) in the Tuzla geothermal field originate from connate water along faults. As the saline water rises to the surface, it mixes with shallow groundwaters in various ratios. In addition, the high sodium (Na) and chloride (Cl) content in the Tuzla Stream, fed from the Tuzla geothermal brine during the dry season, cause an increase in sodium and chloride concentrations in the shallow groundwaters by infiltration into the aquifer. Moreover, salt accumulation on the surface is observed due to the uncontrolled artesian flow of geothermal brine, which adversely affects the salinity of shallow groundwater.