The relationship between glutathione peroxidase and bioimpedance parameters in nondiabetic hemodialysis patients

There is growing evidence from experimental and clinical studies that oxidative stress is involved in the pathogenesis of malnutrition. This cross‐sectional study aimed to investigate the relationship between glutathione peroxidase (GPx) levels as a marker of antioxidant status and the nutritional status assessed by bioimpedance analysis (BIA). Ninety‐seven nondiabetic stable outpatient uremic adults undergoing chronic hemodialysis (HD) were recruited for this study. Impedance measurements were performed using a multifrequency bioelectrical impedance analyzer after dialysis. GPx levels correlated with intracellular water (ICW) (r = 0.341, P = 0.011), ICW/total body weight (r = 0.320, P = 0.017), lean body mass (r = 0.300, P = 0.026) and total body cell mass (r = 0.339, P = 0.011). When patients were divided into two groups according to mean GPx levels (83.9 U/gr hemoglobin), the patients with higher GPx (GPx > 83.9 U/gr hemoglobin) had higher albumin (P = 0.038), lean body mass (P = 0.026), ICW (P = 0.011), and total body cell mass (P = 0.011) compared with those with lower GPx (GPx ≤ 83.9 U/gr hemoglobin). Furthermore, in the patients with higher GPx, body fat; extracellular water/total body water; illness marker and body fat mass index were lower than other group. In conclusion, our results reveal correlation indicating a relationship between antioxidant status (as measured by GPx) and nutritional status as assessed by BIA in nondiabetic HD patients.     

Hydrophobic microbeads as an alternative pseudo-affinity adsorbent for recombinant human interferon-α via hydrophobic interactions

Hydrophobic interaction chromatography (HIC) is increasingly used for protein purification, separation and other biochemical applications. The aim of this study was to prepare hydrophobic microbeads and to investigate their recombinant human interferon-α (rHuIFN-α) adsorption capability. For this purpose, we had synthesized functional monomer, N-methacryloyl-l-phenylalanine (MAPA), to provide a hydrophobic functionality to the adsorbent. The poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-phenylalanine) [poly(HEMA–MAPA)] microbeads were prepared by suspension copolymerization. microbeads were characterized using FTIR, swelling behavior, and SEM micrographs. Equilibrium swelling ratio of poly(HEMA–MAPA) and poly(HEMA) microbeads were 53.3% and 69.3%, respectively. The specific surface area and average pore diameters determined by BET apparatus were 17.4 m²/g and 47.3 Å for poly(HEMA) microbeads and 18.7 m²/g and 49.8 Å for poly(HEMA–MAPA) microbeads. Adsorption experiments were performed under different conditions. Maximum rHuIFN-α adsorption capacity was found to be 137.6 ± 6.7 mg/g by using poly(HEMA–MAPA) microbeads with a size range of 150–250 μm and containing 327 μmol MAPA/g microbeads. Compared with poly(HEMA–MAPA) microbeads, nonspecific rHuIFN-α adsorption onto plain poly(HEMA) microbeads was very low, about 4.2 ± 2.3 mg/g. To determine the effects of adsorption conditions on possible conformational changes of rHuIFN-α structure, fluorescence spectrophotometry was employed. Repeated adsorption–elution processes showed that these microbeads are suitable for repeatable rHuIFN-α adsorption.     

Vertical distributions of 137Cs, 40K, 232Th and 226Ra in soil samples from Istanbul and its environs, Turkey

Determining the distribution of natural and artificial radionuclides in soil profiles as well as the surface layer of the soil is necessary due to the fact that radionuclides can enter the food chain from deeper soil layers and also contaminate ground water. In the current study, the activity-depth profiles of (137)Cs were determined in soil samples from 20 sites in and around the city of Istanbul. Naturally occurring radionuclides were determined at 12 of the locations. Uncultivated soil samples were taken in six horizontal layers at each location. Activity concentrations were measured with a gamma spectrometer. The impacts of texture, organic matter and pH of the soil on the vertical distribution of the radionuclides were also studied. The average and standard deviations of (137)Cs and (40)K activity concentrations in soil at a depth of 5 cm were found to be 16.46±14.71 and 450.2±239.1 Bq kg(-1), respectively. The activity concentrations of (40)K, (232)Th and (226)Ra were distributed uniformly with regard to soil depth. The depth distribution of (137)Cs generally fitted a linear function. The study revealed that >20 y after the Chernobyl disaster of 1986, 55 % of (137)Cs still remains in the upper 10 cm of soil in the Istanbul environment.     

Common Kinetic Mechanism of Abasic Site Recognition by Structurally Different Apurinic/Apyrimidinic Endonucleases

Apurinic/apyrimidinic (AP) endonucleases Nfo (Escherichia coli) and APE1 (human) represent two conserved structural families of enzymes that cleave AP-site–containing DNA in base excision repair. Nfo and APE1 have completely different structures of the DNA-binding site, catalytically active amino acid residues and catalytic metal ions. Nonetheless, both enzymes induce DNA bending, AP-site backbone eversion into the active-site pocket and extrusion of the nucleotide located opposite the damage. All these stages may depend on local stability of the DNA duplex near the lesion. Here, we analysed effects of natural nucleotides located opposite a lesion on catalytic-complex formation stages and DNA cleavage efficacy. Several model DNA substrates that contain an AP-site analogue [F-site, i.e., (2R,3S)-2-(hydroxymethyl)-3-hydroxytetrahydrofuran] opposite G, A, T or C were used to monitor real-time conformational changes of the tested enzymes during interaction with DNA using changes in the enzymes’ intrinsic fluorescence intensity mainly caused by Trp fluorescence. The extrusion of the nucleotide located opposite F-site was recorded via fluorescence intensity changes of two base analogues. The catalytic rate constant slightly depended on the opposite-nucleotide nature. Thus, structurally different AP endonucleases Nfo and APE1 utilise a common strategy of damage recognition controlled by enzyme conformational transitions after initial DNA binding.     

Overcoming problems in Turkey's renewable energy policy: How can EU contribute?

Fossil fuels cover most of the energy demand in the world, and this creates significant social, economic and environmental problems. Many countries have taken measures to increase the share of renewable energy sources (RES), especially in electricity generation, and the review of literature shows that the success of a country in RES diffusion depends on a comprehensive renewable energy policy which combines political commitment with stable and long-term support measures that stimulate technological innovation. As the largest economy in the world, EU has also taken steps to increase RES usage in electricity generation in member states. Similar to other developing countries, Turkey is learning lessons from EU experiences regarding RES policies, and Turkey is also reforming its legal framework in line with acquis communautaire as a candidate country. As a result, EU has a multiway impact on Turkey's renewable energy policy. An overview of Turkey's renewable energy policy showed that EU has significantly contributed to Turkey in shaping its renewable energy policy, and Turkey should increase cooperation with EU in order to utilize its renewable energy potential.     

Corrélations «texture cristalline-propriétés mécaniques» des plâtres durcis. Étude préliminaire

Résumé Les auteurs analysent les différentes notions à considérer pour conduire une étude rigoureuse des corrélations entre texture cristalline et propriétés mécaniques des platres durcis. Ce sont: 1) les phénomènes découlant de la croissance cristalline proprement dite (mode de germination et de croissance, vitesse de croissance, taille et forme des cristaux, adhérence entre cristaux, croissance cristalline gênée); 2) l'influence de certains phénomènes extérieurs: intervention d'effets mécaniques, utilisation de modificateurs de prise et emploi d'adjuvants solides, phénomènes d'absorption, d'humidification, ou de dessication). Cette étude préliminaire est illustrée par des observations expérimentales de textures et d'évolutions de textures et de propriétés mécaniques en fonction de certains facteurs particuliers étudiés.

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Summary The authors analyze the different notions which have to be taken into account to lead a rigourous study of the correlations between the crystalline texture and the mechanical properties of hardened plasters. These notions are 1) the phenomena dealing with the crystal growth (process of nucleation and growth, rate of growth, size and form of crystals, adhesion between crystals, “bored” crystal growth) and 2) outside phenomena (mechanical effects, use of modifiers and solid additives, adsorption, humidification and drying process). This preliminary study is illustrated by experimental observations on textures and on texture and mechanical properties evolutions versus some particular factors.

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Communication à la III^e Réunion de la Commission ?Gypsum/Plaster? de la RILEM, Budapest, Hongrie, 9–10 Octobre 1974.     

Thermodynamic Analysis of Some Industrial Applications with Variable Ambient Conditions

In this study, the general exergy balance equation of an open system is obtained based on the variable ambient temperature and pressure. Using this result, the mathematical equations regarding both the reversible work given to the system in the electric arc furnace used in steel production and the exergy loss in the rotary burner used in cement production are derived. In obtaining these equations, it is assumed that the ambient temperature has a sinusoidal variation. The effects of varying ambient parameters on calculated exergy values in industrial applications are discussed, and the obtained results are analyzed and demonstrated.