Immature event-related alpha dynamics in children compared with the young adults during inhibition shown by day-night stroop task

Introduction: Inhibitory control develops gradually from infancy to childhood and improves further during adolescence as the brain matures. Related previous studies showed the indispensable role of task-related alpha power during inhibition both in children and young adults. Nonetheless, none of the studies have been able to investigate the direct differences in brain responses between children and young adults when confronted with a stimulus that should be inhibited. Because, unlike event-related designs, task-related designs involve continuous tasks over a certain period, which precludes the possibility of making such a comparison. Accordingly, by employing event-related design, the present study first time in the literature, aimed to analyze the event-related alpha phase locking and event-related alpha synchronization/ desynchronization to differentiate the inhibitory processes in children compared to young adults. Methods: Twenty children between the ages of 6 to 7 years and 20 healthy young adult subjects between the ages of 18 to 30 years were included in the study. Day-night Stroop task was applied to all subjects during 18-channel EEG recordings. Event-related time-frequency analysis was performed with the complex Morlet Wavelet Transform for the alpha frequency band (8–13 Hz). Event related spectral perturbation (ERSP) in three different time windows (0–200 ms, 200–400 ms, 400–600 ms) and Event-related phase locking in the early time window (0–400 ms) was calculated. Results: The children had increased alpha power in early and late time windows but decreased alpha phase locking in the early time windows compared to young adults. There were also topological differences between groups; while young adults had increased alpha phase-locking in frontal and parietal electrode sites, children had increased occipital alpha power and phase locking. Discussion: The shift in event-related alpha power observed from posterior to anterior regions with age may suggest a progressive maturation of the frontal areas involved in inhibitory processes from childhood to adulthood. The results of the present study showed that children and young adults had different EEG oscillatory dynamics during inhibitory processes at alpha frequency range

Immature event-related alpha dynamics in children compared with the young adults during inhibition shown by day-night stroop task

IntroductionInhibitory control develops gradually from infancy to childhood and improves further during adolescence as the brain matures. Related previous studies showed the indispensable role of task-related alpha power during inhibition both in children and young adults. Nonetheless, none of the studies have been able to investigate the direct differences in brain responses between children and young adults when confronted with a stimulus that should be inhibited. Because, unlike event-related designs, task-related designs involve continuous tasks over a certain period, which precludes the possibility of making such a comparison. Accordingly, by employing event-related design, the present study first time in the literature, aimed to analyze the event-related alpha phase locking and event-related alpha synchronization/ desynchronization to differentiate the inhibitory processes in children compared to young adults.MethodsTwenty children between the ages of 6 to 7  years and 20 healthy young adult subjects between the ages of 18 to 30  years were included in the study. Day-night Stroop task was applied to all subjects during 18-channel EEG recordings. Event-related time-frequency analysis was performed with the complex Morlet Wavelet Transform for the alpha frequency band (8–13  Hz). Event related spectral perturbation (ERSP) in three different time windows (0–200  ms, 200–400  ms, 400–600  ms) and Event-related phase locking in the early time window (0–400  ms) was calculated.ResultsThe children had increased alpha power in early and late time windows but decreased alpha phase locking in the early time windows compared to young adults. There were also topological differences between groups; while young adults had increased alpha phase-locking in frontal and parietal electrode sites, children had increased occipital alpha power and phase locking.DiscussionThe shift in event-related alpha power observed from posterior to anterior regions with age may suggest a progressive maturation of the frontal areas involved in inhibitory processes from childhood to adulthood. The results of the present study showed that children and young adults had different EEG oscillatory dynamics during inhibitory processes at alpha frequency range

Serisin bazlı polimerik yara örtüsü hazırlanması ve biyomalzeme özelliklerinin incelenmesi.

In this study, it was aimed to produce sericine/collagen composite membranes and to investigate their properties as a wound dressing. Different membrane compositions were prepared by casting and solvent evaporation method. After initial studies for optimization of ratios, membrane groups at two different thicknesses were prepared for each selected ratio and cross-linked with 3 % (w/v) glutaraldehyde (GTA). Considering the wound dressing requirements, equilibrium degree of swelling (EDS), water vapor transmission rate (WVTR), oxygen permeability, mechanical properties, in situ degradation, microbial penetration and cytotoxicity of membranes were examined. The EDS of membranes had a range of 14.91 to 4.37 (g/g) and increased significantly with the presence of sericin. There was no obvious relationship between the sericin ratio of membranes and WVTR, but the increase in membrane thickness decreased WVTR significantly. Thin and sericin containing membranes had statistically better oxygen permeabilities. Sericin deteriorated the tensile strength and elongation of membranes statistically. Cross-linked groups were resistant to hydrolytic degradation through 4 weeks of incubations. None of the membranes were penetrable to bacteria owing to their dense structure. For cytotoxicity studies, 3T3 fibroblasts and keratinocytes were seeded on membranes separately, and analyzed with MTT assays, and light microscopy and scanning electron microscopy (SEM). As regards to MTT assay, keratinocytes proliferated significantly on membranes and reached to high confluence within 7 days. Similarly, fibroblasts also showed high proliferation on membranes. Light microscopy and SEM analysis showed that both cells could attach, grow and spread on membranes. Also, cells gained their characteristic morphology after 1 day and formed flattened structure within 7 days.M.S. - Master of Scienc

The anticancer activity of doxorubicin-loaded levan-functionalized gold nanoparticles synthesized by laser ablation

Bu çalışmada, altın nanoparçacıklar (AuNP'ler), deiyonize suda nano-atımlı Nd-YAG lazer ışınlamasına maruz bırakıldıktan sonra sentezlenmiş (PLAL) ve doksorubisin (DOX) konjuge levan kaplı AuNP komplekslerinin MCF-7 meme kanseri hücrelerine antikanser etkinliğini değerlendirmek için levan polisakkariti ile işlevselleştirilmiştir. Fizikokimyasal test sonuçlarına göre, levan miktarındaki artışlar kolloidal stabiliteyi ve ilaç kapsülleme etkinliğini (DEE) önemli ölçüde arttırmıştır. En yüksek levan miktarına (10 mg/mL levan) sahip 10L-AuNP grubu için DEE %92,21 ± 0,56 olarak hesaplanmıştır. 48 saatlik MTT testleriyle incelenen konsantrasyonlarda sadece levan, kaplı olmayan AuNP'ler ve 10L-AuNP'nin sitotoksik olmadığı (> %80 hücre canlılığı) bulunmuştur. 10L-AuNP'nin daha yüksek DOX yüklemelerinde (25, 50 ve 100 μg/mL), hücre canlılığı, serbest DOX ile karşılaştırıldığında önemli ölçüde azalmıştır. Sonuç olarak, bu nanoparçacık kompleksleri, gelecekteki çalışmalarda DOX gibi kanser ilaçları ve ayrıca diğer ilaçlar için de etkili ilaç dağıtım araçları olarak önerilebilir.Here, gold nanoparticles (AuNPs) were synthesized upon exposure to nano-pulsed Nd-YAG laser irradiation in de-ionized water (PLAL) and functionalized with levan polysaccharide for assessing the anticancer efficacy of doxorubicin (DOX)-conjugated levan-capped AuNPs complexes to MCF-7 breast cancer cells. According to the physicochemical test results, the increments in levan amount enhanced the colloidal stability and the drug encapsulation efficiency (DEE) significantly. For the 10L-AuNP group having the highest levan amount (10 mg/ mL levan), DEE was calculated as 92.21 ± 0.56%. The lean levan, uncapped AuNPs, and 10L-AuNP were found non-cytotoxic (>80% cell viability) in the studied concentrations with 48 h MTT assays. At higher DOX loadings (25, 50, and 100 μg/mL) of 10L-AuNP, the cell viability reduced significantly compared to free DOX. Overall, these nanoparticle complexes could be proposed as potent drug delivery vehicles for cancer drugs such as DOX, as well as other drugs in the prospective studies

Deri doku mühendisliği uygulamaları için biyoetkin ajan yüklü iki katmanlı doku iskeleleri üretilmesi ve karakterizasyonu.

In this study, it was aimed to fabricate tissue scaffolds from different biological polymers (collagen, silk fibroin and sericin) for skin tissue engineering applications. For this purpose, bilayered scaffolds composed of epidermal (collagen/sericin films) and dermal (collagen sponges, collagen matrices or silk fibroin matrices) layers were produced with different biomaterial fabrication methods. Casting and solvent evaporation (film), lyophilization/freeze-drying (sponge) and dry/wet electro-spinning (micro/nanofibrous matrices) methods were used to obtain the scaffolds. Different sizes (10-55nm) of gold nanoparticles (AuNPs) with spherical shapes were synthesized and one size group (37 nm) was incorporated into dermal layers. Collagen based scaffolds were cross-linked with glutaraldehyde and silk fibroin based ones were treated with ethanol to increase the aqueous stability. The suitability of these scaffolds to skin tissue engineering applications was evaluated by means of physicochemical characterization, in vitro biocompatibility, antibacterial assessment, intra-dermal irritation, skin sensitization, genotoxicity and in vivo rat skin wound healing tests. The resistance of collagen based scaffolds to hydrolytic and enzymatic degradation was enhanced significantly after cross-linking, on the contrary collagen nanofibrous scaffolds had tendency to degrade quickly. Especially silk fibroin based scaffolds had the lowest degradation levels. Based on water swelling, silk fibroin based scaffolds and collagen sponge groups were similar (10-30 g/g) due to their similar porosities (70-80%) and pore size distributions (10-200 µm). However, water swelling of collagen nanofibrous scaffolds was lower (3 g/g) in comparison due to their low porosity (10%) and small pore sizes (0-8 µm). The water vapor transmission rates of bilayered scaffolds were statistically similar (about 1300-1400 g/m2/day) and they were confirmed to have good oxygen permeability, which was attributed to collagen/sericin film. Tensile strength of collagen based scaffolds enhanced significantly after cross-linking. AuNPs incorporation into collagen based scaffolds did not have a significant effect on tensile strength values. Yet, AuNPs incorporation significantly increased tensile strength of silk fibroin based scaffolds. Also, tensile strength decreased dramatically when the testing was done in wet conditions. On the other hand, elongation at break of all the wet scaffolds were improved significantly reaching to even above 100% values. Elastic modulus of all the scaffolds increased significantly after cross-linking indicating increased hardness, on the contrary elastic modulus decreased significantly in wet conditions as they became more extensible and softer in aqueous environment. The cytotoxic effect of AuNPs on keratinocyte and fibroblasts were size and dose dependent. None of the scaffolds (epidermal and dermal layers) had a cytotoxic effect (cell viability > 85%) on L929 fibroblasts. Cell seeding tests showed that, fibroblasts and keratinocytes attached and gained their natural morphology (spread or polygonal) in 1 day and proliferated on the scaffolds during 3 days incubation period according to SEM analysis. Antibacterial assessment tests based on the agar disc diffusion method provided strong evidence that AuNPs fabricated in this study had an antibacterial potential against S. Aureus. Also, the OD measurement and SEM analysis showed that S. Epidermidis could not attach onto scaffolds containing AuNPs compared to control without AuNPs. In vivo tests results showed that all the groups had significantly better wound contraction than untreated controls on post-operative 14th day. Early stage re-epithelization started to form in collagen based and silk fibroin based scaffold groups, with low inflammation, and high fibrosis and granulation tissue formation compared to MatridermTM. Also, the groups containing honey or AuNPs started to recover their mechanical properties much quicker than MatridermTM according to biomechanical tests. All these results suggested that all the groups, especially the groups containing honey or AuNPS have equal or slightly better in vivo healing effect than MatridermTM. According to animal toxicology evaluation and genotoxicity tests on BLCS-AuX, there were no adverse skin reactions (irritation or sensitization) or genotoxicity. As a conclusion, it could be suggested that all of these bilayered skin substitutes, especially the groups containing bioactive agents (honey or AuNPs) could be very valuable skin substitute materials for use in the management of skin wounds.Ph.D. - Doctoral Progra

The relationship between oil prices and economic growth: Panel data analysis for OPEC and oil-imported countries

Dünya ekonomileri için yarattığı uzun dönemli makroekonomik etkiler nedeniyle petrol fiyatları ile ekonomik büyüme arasındaki ilişkiler çok sayıda araştırmaya konu olmuştur. Dolayısıyla bu çalışmada, petrol fiyatları ile ekonomik büyüme arasındaki ilişkiler 1980–2011 döneminde OPEC ve petrol ithalatçısı ülkeler için panel veri analizleri kullanılarak araştırılmıştır. Analiz sonuçları, petrol fiyatları ile ekonomik büyüme arasında hem eşbütünleşme ve hem de nedensellik ilişkisi olduğunu göstermiştir. İlaveten, OPEC ülkelerinde petrol fiyatlarındaki artışın iktisadi büyümeyi tetiklediği, ithalatçı ülkelerde ise fiyatlardaki yükselişlerin büyüme sürecini olumsuz etkilediği gözlenmiştir.The relationship between oil price and economic growth is the subject of many studies because oil price creates long-term macroeconomic impacts for the World economies. Therefore in this paper, the relationship between oil price and economic growth is investigated by using panel data analysis over the period of 1980–2011 for OPEC and oil-imported countries. The results of panel data analysis show that there is a both cointegration and causality relationship between the oil price and economic growth. In additon, it is observed that an increase in oil price triggers the economic growth in OPEC countries; in oil-imported countries, however, a rise in price affect the economic growth process adversely