Studies on the nitrosation of thiols in relation to vasodilatory action

A kinetic study of the nitrosation of L-cysteine, L-cysteine methyl and ethyl esters, N-acetyl-L-cysteine and glutathione by isopropyl nitrite in acid solution at 25 C was undertaken. The thiols exhibited identical rate laws and in all cases the observed rate constant was reduced by added isopropyl alcohol. The results were found to be consistent with the mechanism in which a rapid reversible acid-catalysed hydrolysis of isopropyl nitrite occurs to give nitrous acid, which then in its protonated form effects nitrosation. The third-order rate constant for the nitrosation of the thiols by isopropyl nitrite and the equilibrium constant for the formation of isopropyl nitrite were found to be in good agreement with the literature values obtained by direct measurement. A similar kinetic study of the nitrosation of L-cysteine, L-cysteine methyl and ethyl esters, N-acetyl-L-cysteine, thioglycolic acid and glutathione by various alkyl nitrites, in water at 25 C , in the pH range 6-13 was undertaken. The pH dependence of the rate constant is consistent with a mechanism involving a direct nitrosation by alkyl nitrites with the thiolate anion (RS(^-)) of the thiol. A quantitative kinetic analysis yielded macroscopic and microscopic pKa values for RSH ionisation in good agreement with the literature values. One exception is L-cysteine where the microscopic, pKp, value (for NH(_2)RSH → NH(_2)RS(^-)) differs significantly from the literature value. In the case of simple alkyl nitrites (ethyl, isopropyl, isoamyl and t-butyl nitrites) steric effects appear to be the major influence in reactivity whereas electron-withdrawing substituents in the β-position greatly enhanced the rate constant. The results were found to satisfy Taft's equation and thus a correlation between structure and reactivity of the alkyl nitrites with the thiols was established. This work shows that at least in vitro a direct and rapid reaction occurs between alkyl nitrites and thiols at pH values likely to be encountered in vivo. This confirms that such reactions could occur in vivo and could be an important feature of the chain of events occurring during the vasodilatory action of alkyl nitrites. Finally a preliminary investigation of the reaction of glyceryl trinitrate with cysteine, in oxygen and oxygen-free nitrogen atmosphere, in the pH range 6-13 was undertaken. In this case no evidence was found for the formation of S-nitrosocysteine or nitric oxide from glyceryl trinitrate in the presence or absence of cysteine. Thus the results could not confirm the hypothesis that glyceryl trinitrate owes its vasodilatory action to the formation of the intermediate, S-nitrosocysteine, from the reaction of nitric oxide (formed from glyceryl trinitrate) and cysteine

Monitoring serum insulin-like growth factor-I (IGF-I), IGF binding protein-3 (IGFBP-3), IGF-I/IGFBP-3 molar ratio and leptin during growth hormone treatment for disordered growth

OBJECTIVE: Serum IGF-I levels are monitored during GH replacement treatment in adults with GH defi- ciency (GHD) to guide GH dose adjustment and to minimize occurrence of GH-related side-effects. This is not routine practice in children treated with GH. The aim of this study was to evaluate changes in (1) serum IGF-I, IGFBP-3 and IGF-I/IGFBP-3 molar ratio, and (2) serum leptin, an indirect marker of GH response, during the first year of GH treatment in children with disordered growth. DESIGN: An observational prospective longitudinal study with serial measurements at five time points during the first year of GH treatment was carried out. Each patient served as his/her own control. PATIENTS The study included 31 patients, grouped as (1) GHD (n=20) and (2) non-GHD (Turner syndrome n=7; Noonan syndrome n=4), who had not previously received GH treatment. MEASUREMENTS: Serum IGF-I, IGFBP-3 and leptin levels were measured before treatment and after 6 weeks, 3 months, 6 months and 12 months of GH treatment, with a mean dose of 0.5 IU/kg/wk in GHD and 0.7 IU/kg/wk in non-GHD groups. IGF-I, IGFBP-3 and the calculated IGF-I/IGFBP-3 molar ratio were expressed as SD scores using reference values from the local population. RESULTS: In the GHD group, IGF-I SDS before treatment was lower compared with the non-GHD (-5.4 ± 2.5 vs. -1.8 ± 1.0; P < 0.001). IGF-I (-1.8 SDS ± 2.2) and IGFBP-3 (-1.1 SDS ± 0.6) levels and their molar ratios were highest at 6 weeks and remained relatively constant thereafter. In the non-GHD group, IGF-I levels increased throughout the year and were maximum at 12 months (0.3 SDS ± 1.4) while IGFBP-3 (1.1 SDS ± 0.9) and IGF-I/IGFBP-3 molar ratio peaked at 6 months. In both groups, IGF-I SDS and IGF-I/IGFBP-3 during treatment correlated with the dose of GH expressed as IU/m2/week (r-values 0.77 to 0.89; P = 0.005) but not as IU/kg/week. Serum leptin levels decreased significantly during GH treatment in the GHD (median before treatment 4.0 g/l; median after 12 months treatment 2.4 g/l; P = 0.02) but not the non-GHD (median before treatment 3.0 g/l; median after 12 months treatment 2.6 g/l). In the GHD group, serum leptin before treatment correlated with 12 month change in height SDS (r = 0.70, P = 0.02). CONCLUSIONS: The pattern of IGF-I, IGFBP-3 and their molar ratio during the first year of GH treatment differed between the GHD and non-GHD groups. Calculation of GH dose by surface area may be preferable to calculating by body weight. As a GH dose-dependent increase in serum IGF-I and IGF-I/IGFBP-3 may be associated with adverse effects, serum IGF-I and IGFBP-3 should be monitored routinely during longterm GH treatment. Serum leptin was the only variable that correlated with first year growth response in GHD

Barrier inhomogeneities of Al/p-In2Te3 thin film Schottky diodes

The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of p-In2Te3/Al thin films Schottky diodes papered by Flash Evaporation technique were measured in the temperature range 303-335 K have been interpreted on the basis of the assumption of a Gaussian distribution of barrier heights (φbo) due to barrier height inhomogeneities that prevail at the interface. It has been found that the occurrence of Gaussian distribution of BHs is responsible for the decrease of the apparent BH (φbo) and increase of the ideality factor (η). The inhomogeneities are considered to have a Gaussian distribution with a mean barrier height of (φbm) and standard deviation (σs) at zero-bias. Furthermore, the activation energy value (φb) at T = 0 and Richardson constant (A**) value was obtained as 0.587 eV and 3.09 Acm– 2 K– 1 by means of usual Richardson plots. Hence, it has been concluded that the temperature dependence of the I-V characteristics of p-In2Te3/Al Schottky Diodes can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the BHs. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2790

Magnetron sputtered Al-ZnO Thin films for photovoltaic applications

The optimization process of the RF magnetron sputtered Al - doped ZnO (AZO) thin films was carried out by studying its structural, optical, electrical, and morphological properties at different RF power and different working pressures for its use as a front-contact for the copper indium diselenide (CIS) based thin film solar cell. The structural study suggests that the preferred orientation of grains along the ( 002) plane having a hexagonal structure of the grains. The optical and electrical properties suggest that the films show an average transmission of 85 % and a resistivity of the order of 10-4 Wcm. The morphology analysis suggests the formation of packed grains having a homogeneous surface. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2210

Laser Induced Damage Studies on Al2O3, SiO2, and MgF2 Thin Films for Anti-Reflection Coating Application in High Power Laser Diode

The laser diode facet damage is one of the impeding factors of the high-power laser diode operation. To overcome this restriction laser diode facet coating can be utilized. During the high power operation of the laser diode, it is observed that the single layer anti reflection (AR) coating at the front facet shows optical damage while the multilayer high reflective coating at the back facet remains undamaged. To determine the “damage threshold” of the materials used for AR coating, an e-beam evaporated Al2O3, MgF2, and SiO2 single layer thin films on GaAs substrate have been optimized for the wavelength ~ 1060 nm. The diode pumped Q-switched Neodymium Yttrium Aluminum Garnet (Nd:YAG) laser (1064 nm) was used to da-mage the samples. The damage on the sample was observed under the microscope. The effective damage radius on the samples was 150 m and average continuous wave laser induced damage threshold was found 10 W. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3101

Design and evaluation of sustained release matrix tablets of levofloxacin for effective treatment of microbial infections

The objective of present work was to formulate and evaluate sustained release matrix tablets of levofloxacin for treating microbial infections effectively. Levofloxacin is the active component of the racemate ofloxacin, and used for treating a variety of clinical conditions such as lower respiratory tract infections, acute sinusitis, uncomplicated skin and soft-tissue infections and complicated urinary tract infections. Different formulations were prepared by wet granulation method using various release rate controlling hydrophilic polymers. The formulations were evaluated for hardness, weight variation, friability and drug content uniformity. The in vitro release of drug from the formulations was studied in pH 1.2 acidic buffer and pH 6.8 phosphate buffer, and it was found that the prepared tablets were able to sustain the release of the drug. The release of levofloxacin from the tablets was diffusion controlled and the release mechanism was non-Fickian. For conclusion, the developed formulations may reduce the dosing intervals, reduce the dose related side effects and increase the drug’s efficacy for treating infections.Keywords: Matrix tablets, levofloxacin, HPMC, guar gum, xantham gum, locust bean gum, Amorphophallus starch

All-Solid-Thin Film Electrochromic Devices Consisting of Layers ITO / NiO / ZrO2 / WO3 / ITO

We have prepared an all-solid-thin film electrochromic device (ECD), consisting of layers ITO / NiO / ZrO2 / WO3 / ITO using the PVD method. The WO3 is used as an electrochromic layer, NiO as an ion-storage layer, and ZrO2 as a solid electrolyte layer in the all-solid-thin film ECD. The optical transmittance varied between 3-59 %. The device shows the coloration and bleaching time of 120 s and 2 s, respectively, with a good memory effect and desirable cycle-life. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3101

Laser scribing optimization of RF magnetron sputtered molybdenum thin films

The optimization process of laser scribing of back contacts is carried out by varying different parameters of laser and thickness of Molybdenum (Mo) thin-films. Mo thin films were deposited by RF magnetron sputtering on the organically cleaned soda lime glass substrate. The thickness of Mo was in the range of 60 nm to 800 nm. For the scribing process the laser power and the laser pulse frequency were varied. Different thickness of Mo shows the different scribe behavior. The optimized process provides a successful isolative laser scribing, having a minimum scribe line width, of Mo layer on glass substrate without any presence of walls, ridges, or collars in scribed areas. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/929

Identification of Patient Safety Improvement Targets in Successful Vascular and Endovascular Procedures: Analysis of 251 hours of Complex Arterial Surgery

AbstractObjectivesTo investigate failures in patient safety for patients undergoing vascular and endovascular procedures to guide future quality and safety interventions.DesignSingle centre prospective observational study.Methods66 procedures (17 thoracoabdominal and 23 abdominal aortic aneurysms, 4 carotid and 22 limb procedures) were observed prospectively over a 9-month period (251 h operating time) by two trained observers. Event logs were recorded for each procedure. Two blinded experts identified and independently categorised failures into 22 types (using a validated category tool) and severity (5-point scale). Data are expressed as median (range). Statistical analysis was performed using Mann–Whitney U, Kruskal–Wallis and Spearman’s Rank tests.Results1145 failures were identified with good inter-assessor reliability (Cronbach’s alpha 0.844). The commonest failure types related to equipment (including unavailability, configuration and other failures) (269/1145 [23.5%]) and communication (240/1145 [21.0%]). A comparatively lower number of technical and psychomotor failures were identified (103 [9.0%]). The number of failures correlated with procedure duration (rho = 0.695, p < 0.001) but not anatomical site of the procedure or pathology of the disease process. Failure rate was higher in patients undergoing combined surgical/endovascular procedures compared to open surgery (median 5.7/h [IQR 4.2–8.1] vs 3.0/h [2.5–3.5]; p < 0.001). The severity of failures was similar (1.5/5 [1–2] vs 1/5 [1–2] respectively; p = 0.095). For combined procedures, failure rates were significantly higher during the endovascular phase (9.6/h [7.5–13.7]) compared to the non-endovascular phase (3.0/h [1.0–5.0]; p < 0.001).ConclusionsFailures in patient safety are common during complex arterial procedures. Few failures were severe, although minor failures during critical stages and accumulation of multiple minor failures may potentially be important. Failures occurred especially during the endovascular phase and were often related to equipment or communication aspects. Interventions to improve procedural safety and quality of care should primarily target these specific areas

Surfactant Free Synthesis and Study of Vanadium Pentoxide Nanostructure

The varied oxidation state and layered structure are two importance features of vanadium pentoxide which makes it more special. Here, vanadium pentoxide nanostructure has been synthesized by a surfactant free and ecofriendly method using ammonium vanadate as a precursor salt. Synthesized nanostructure were characterized using X-ray diffraction method (XRD), Energy Dispersive X-Ray Analysis (EDAX), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy to study its structural, compositional, morphology, vibrational modes and optical behavior. XRD and FTIR confirm the orthorhombic phase of the vanadium pentoxide with a layered structure of irregular plates as observed from the SEM micrograph. Moreover, the band gap of material is 2.13 eV as evaluated from UV-Visible data