bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduction of extracellular dehydroascorbic acid by K562 cells
Authors: Schweinzer Esther , Mao Yulu , Krajnik Paul , Getoff Nicola , Goldenberg Hans 
Published: May 2005

AbstractK562 erythroleukaemic cells produced ascorbate when incubated with dehydroascorbic acid. The reduction depended on the number of cells and on the concentration of dehydroascorbic acid. The observed rate consists of a high affinity (apparent) Km 7 μM, Vmax 3·25 pmol min−1 (106 cells)−1 and a low affinity component, which was non‐saturable up to 1 mM of DHA (rate increase of 0·1 pmol min−1 (106 cells)−1 (1 μM of DHA−1). The rate was dependent on temperature and was stimulated by glucose and inhibited by phloretin, N‐ethylmaleimide, parachloro‐mercuribenzoate and thenoyltrifluoroacetone. Although uptake of DHA proceeded at a higher rate than its extracellular reduction, the generation of extracellular ascorbate from DHA cannot be accounted for by intracellular reduction and the release of ascorbate, since the latter was not linear with time and had an initial rate of approximately 3 pmol min−1 (106 cells−1). At a concentration of DHA of 100 μM this is 25 per cent of the observed reduction.
Interaction between Na ions and the Cl/HCO3 exchanger in basolateral membranes from rat jejunum
Authors: Orsenigo M. N. , Tosco M. , Faelli A. 
Published: May 2005

AbstractThe jejunal basolateral Cl/HCO3 exchanger is modulated by two Na‐dependent regulatory sites located on the inner and outer membrane surfaces. The aim of this work was to focus on the interaction between the anion exchanger and intracellular or extracellular sodium. Uptake studies, performed using basolateral membrane vesicles, provided kinetic parameters as a function of outside or inside Na concentration. The intracellular Na‐sensitive modifier site seems to be primarily involved in the modulation of the Cl/HCO3 exchanger.
Alteration of erythrocyte membrane Na, K‐ATPase in children with borderline or essential hypertension
Authors: Stojadinovic Nataša D. , Petronijević Milan R. , Pavićević Mirjana H. , Mršulja Bogomir B. , Kostić Milosav M. 
Published: May 2005

AbstractThe aim of this study was to evaluate the substrate (ATP) kinetics of erythrocyte membrane Na, K‐ATPase in children with borderline or essential hypertension. Although the activity of Na, K‐ATPase in the presence of in vivo concentrations of ATP was not significantly altered, kinetic studies showed an obvious inhibition of enzyme activity in the erythrocyte membrane of children with borderline or essential hypertension. Hanes plot analysis revealed a decrease of Vmax from 7·19 in erythrocytes from control subjects to 4·93 and 3·33 in those from children with borderline or essential hypertension, respectively. A mean value of the Km decreased from 0·10 in the control to 0·08 and 0·02 in children with borderline or essential hypertension, respectively. The energy status of erythrocytes, estimated by ATP, ADP and AMP levels, ATP/ADP ratio, and adenylate energy charge (AEC) was not significantly changed in the cells from hypertensive children. The use of a free radical‐generating system (FeSO4/ascorbate) in vitro significantly reduced enzyme activity in the control erythrocytes while in those from hypertensive children it was abolished completely. The level of lipid peroxides was considerably higher (+37 per cent) in the plasma, while that of reduced glutathione was significantly lower both in the erythrocytes and the plasma of children with essential hypertension than in healthy children. These results indicate significant alterations of the antioxidant status which could be the cause of the inhibited Na,K‐ATPase activity in erythrocyte membranes from hypertensive children.
Metabolism of glucose and glutamine in lymphocytes from graves' hyperthyroid patients: influence of methimazole treatment
Authors: Werner M. C. , Rosa L. F. B. P. Costa , Romaldini J. H. , Curi R. 
Published: May 2005

AbstractSeveral studies have shown that thyroid hormones are able to influence selected immune responses such as cell mediated immunity, differentiation of B lymphocytes and the activity of NK cells. These hormones can also regulate the metabolism of glucose and glutamine in rat macrophages and their effects seem to occur mainly through the Krebs cycle. Alterations in the hexokinase, citrate synthase, glucose‐6‐phosphate dehydrogenase and glutaminase activities in lymphocytes from patients with Graves' disease, either untreated or on methimazole (MMI) therapy were investigated. Experiments were also done in vitro to determine the activities of these enzymes in normal lymphocytes cultured for 24 h in the presence of MMI, T3 and T4 using concentrations close to the physiological. Changes in the conversion of [U‐14C]‐glucose and [U‐14C]‐glutamine to 14CO2 as caused by the addition of MMI, T3 or T4 to the culture medium were also evaluated. The results indicate that high levels of thyroid hormones might stimulate the metabolism of glucose and glutamine for a short period of time but, if the stimulus is maintained, the utilization of glutamine by lymphocytes is then suppressed. Moreover, MMI does affect lymphocyte metabolism but the significance of this finding for its immunosuppressive effect remains to be examined.
Characterization of γ‐glutamyltranspeptidase in the liver of the frog: 3. Response to freezing and thawing in the freeze‐tolerant wood frogRana sylvatica
Authors: Hemmings Susan J. , Storey Kenneth B. 
Published: May 2005

AbstractThe freeze tolerant wood frogRana sylvaticawas studied to determine the impact of the freezing and thawing of this frog on the activity of γ‐glutamyltranspeptidase in the liver. On exposure to −2·5°C, for 1, 12 and 24 h, frogs were found to be cool, covered with ice crystals and frozen, respectively. Thawing for 24 h at 4°C recovered the frogs completely. A 45 per cent decrease in the liver weight: body weight ratio was notable after 1 h at −2·5°C, suggestive of an early hepatic capacitance response. A glycemic response to freezing was observed: blood glucose levels exhibited a 55 per cent decrease after 1 h at −2·5°C on cooling; a 10·5‐fold increase after 12 h at −2·5°C on the initiation of freezing; and a 22‐fold increase after 24 h at −2·5°C in the fully frozen state. Blood glucose levels remained elevated four‐fold in the thawed state. Plasma insulin levels were increased twofold in the frozen state and 1·8‐fold in the thawed state, while plasma ketone levels were increased 1·8‐fold in the frozen state and 1·5‐fold in the thawed state. Plasma total T3levels were decreased by 22 per cent in the frozen state and normalized on thawing.In homogenates and plasma membranes isolated from the livers ofRana sylvatica, the activity of γ‐glutamyltranspeptidase was found to be elevated at all stages of the freeze–thaw process. After 1, 12 and 24 h at −2·5°C, activities were increased 2·5‐, 2·3‐, 2·4‐fold respectively in the homogenates and 2·5‐, 2·2‐, 2·4‐fold respectively in the plasma membranes. After thawing, activities were still increased 1·9‐fold in both homogenates and plasma membranes. In homogenates prepared from the kidneys ofRana sylvatica, the activity of γ‐glutamyltranspeptidase was increased 1·4‐fold after 1 h at −2·5°C after which it returned to normal. The role of thyroid hormone in producing the increase in γ‐glutamyltranspeptidase in the liver ofRana sylvaticain response to freezing is discussed as is the significance of the enzyme increase in terms of hepatic cytoprotection and freeze tolerance.
Hepatic fatty acid‐supported respiration in rats fed an energy‐dense diet
Authors: Liverini Giovanna , Iossa Susanna , Mollica Maria P. , Lionetti Lillà , Barletta Antonio 
Published: May 2005

AbstractThe energy balance and hepatic fatty acid‐supported respiration were studied in rats fed a control or an energy‐dense diet. In addition, state 3 and 4 respiratory rates as well as ketone body production with palmitoylcarnitine as substrate were determined in isolated mitochondria. Metabolizable energy intake and energy expenditure increased in rats fed an energy‐dense diet, but the gain in body weight and lipid content remained unchanged. No variation occurred in the mitochondrial palmitoylcarnitine utilization rate and ketone body production, but a significant increase in the mitochondrial content of ketone bodies and the serum levels was found in rats fed an energy‐dense diet. Furthermore, we have shown a significant increase in fatty acid‐stimulated respiration in hepatocytes from rats fed an energy‐dense diet. The enhanced hepatic fatty acid utilization as an energy substrate found in rats fed an energy‐dense diet may contribute to reduce the availability of lipids for storage, thus counteracting the development of obesity.
Influence of fibronectin on HIV‐1 infection and capability of binding to platelets
Authors: Pugliese A. , Savarino A. , Cantamessa C. , Torre D. 
Published: May 2005

AbstractWe have previously demonstrated that fibronectin (FN) can bind HIV‐1 envelope proteins, in particular gp120. The aim of the present study was to determine some biological effects of this phenomenon. Pretreating HIV‐1 with human FN increased the infectivity of HIV‐1, when a low concentration of the virus was used. In contrast, an RGD‐containing pentapeptide (Gly‐Arg‐Gly‐Asp‐Ser), which is a fundamental binding site of FN, reduced the infectivity of a suspension of HIV‐1 at high concentrations of the virus. It is likely that FN bridges the cell surface and the virions, while the RGD‐containing pentapeptide may saturate the HIV‐1 binding sites for cell surface receptors. Moreover, gp120 was bound to the FN present on the surface of platelets. The specifity of this binding was confirmed by the inhibition obtained by pretreating platelets with anti‐FN antibodies. The consequence of the surface modifications of the platelets could explain the thrombocytopenia that frequently occurs in patients infected with HIV and suggests also the possibility that platelets could be a vehicle for the virus in the circulation.
The design of calibration in near infra‐red reflectance analysis by clustering
Authors: Næs Tormod 
Published: May 2005

AbstractA procedure for selecting samples to use in multivariate calibration, inspired by a paper by Zemroch, is proposed. The method developed is designed for multicollinear data and is based on cluster analysis. It selects among availabe spectra the samples to submit to chemical analysis and calibration. The method is tested on an example from NIR spectroscopy of biscuit dough pieces.
Estimation in compositional data analysis
Authors: Rayens William S. , Srinivasan Cidambi 
Published: May 2005

AbstractCompositional data arise naturally in several branches of science, including chemistry, geology, biology, medicine, ecology and manufacturing design. In chemistry, these constrained data seem to occur typically when raw data are normalized or when output is obtained from a constrained estimation procedure, such as might be used in a source apportionment problem. It is important not only for chemists to be aware that the usual multivariate statistical techniques are not applicable to constrained data, but also to have access to appropriate techniques as they become available. The currently available methodology is due principally to Aitchison and is based on log–normal models. This paper suggests new parametric and non‐parametric approaches to significantly improve the existing methodology. In the parametric setting, some recent work of Rayens and Srinivasan is extended and a practical regression model is proposed. In the development of the non‐parametric approach, minimum distance methods coupled with multivariate bootstrap techniques are used to obtain point and region estimators.
Slowly converging parafac sequences: Swamps and two‐factor degeneracies
Authors: Mitchell Ben C. , Burdick Donald S. 
Published: May 2005

AbstractThe alternating least squares PARAFAC algorithm is a useful tool for resolving trilinear three‐way data arrays. Occasionally, however, it becomes bogged down for many iterations in the vicinity of a poor quality resolution before moving on to a much superior optimum fit. We investigate this behavior in a simulation study and suggest ways of overcoming the obstacles it presents.
The dorsal sack, the aulix and the diencephalic flexure
Authors: Wilder B. G. 
Published: May 2005

AbstractIn many of the lower vertebrates there is a pouch‐like evagination of the diatela (membranous roof of the diacele, or “third ventricle”) between the epiphysis and the paraphysis. In Ceratodus and in Polyodon it is anteverted and very large. In the green turtle it projects dorsad. Its mammalian representative is crowded caudad by the cerebrum and rests upon the retroverted epiphysis. It is commonly ignored in figures and descriptions, but was shown by Reichert. The speaker, without recognizing its homology, figured it in the New York Medical Journal, 1885, p. 320. It is large in the sheep and long in the cow and horse. The diaplexuses are continued into it.Aulix is the mononym proposed by the speaker in 1882 for the “Sulcus Monroi” of Reichert—a sigmoid groove on the mesal surface of the thalamus just ventrad of the medicommissure and connecting the orifice of the mesocele with the porta (foramen of Monro) at either side. His and C. S. Minot regard it as the diencephalic representative of the “sulcus interzonalis,” the primary furrow between the dorsal and ventral zones of the nervous axis. But recent observations in the neurologic laboratory at Cornell upon embryo kittens render this interpretation somewhat doubtful, and the matter is under investigation.In 1889, in the “Reference Hand‐Book of the Medical Sciences” the speaker called attention to the sharp angle between the prosencephalic and the diencephalic portions of the brain cavities. A recent review of the brains of all vertebrate classes warrants the generalization that a marked diencéphalic flexure occurs in all Reptiles, Birds and Mammals, while in Amphibians and “fishes” it is absent or insignificant.
Low temperature, aerosol‐assisted chemical vapor deposition (AACVD) of CdS, ZnS, and Cd1‐xZnxS using monomeric single‐source precursors: M(SOCCH3)2 TMEDA
Authors: Nyman May , Hampden‐Smith Mark J. , Duesler Eileen N. 
Published: May 2005

Novel, monomeric single‐source precursors for the CVD of metal sulfides, which are widely used in solar cell technology, are described. The Figure shows the molecular structure of M(SOCCH3)TMEDA, where TMEDA = N,N,N,N‐tetramethylethylenediamine, for the Cd and Zn complexes. These compounds allow the lowest deposition temperatures so far reported for highly oriented crystalline, stoichiometric films.magnified image
Voltammetric monitoring of photochemical reactions: The photosubstitution of group VIA hexacarbonyls
Authors: Compton R. G. , Barghout R. , Eklund J. C. , Fisher A. C. 
Published: May 2005

AbstractVoltammetry at an irradiated platinum channel electrode is used to monitor photosubstitution reactions of the Group VIA hexacarbonyls, M(CO)6 (M = Cr,Mo,W), in acetonitrile solution, in which up to three CO ligands are replaced by solvent molecules. It is shown that this methodological approach can be used to suggest reaction mechanisms and to quantify rates of photoreactions, so giving estimates of quantum yields.
Determination of dimethoate in water by cathodic stripping square‐wave voltammetry
Authors: Hernández P. , Ballesteros Y. , Galán F. , Hernández L. 
Published: May 2005

AbstractThis article describes the direct‐determination of the pesticide dimethoate In river water in an alkalin media and accumulaton medium through cathodic stripping voltammetry. By employing an alkaline potential of 30 mV, reduction peak appears at −0.7 V. The detection limit is 1 ng ml−1.
Anodic behavior of some Vinca alkaloids with cytostatic activity: Effect of pH
Authors: Brett A. M. Oliveira , Grazina M. M. M. , Macedo T. R. A. , Raimundo D. 
Published: May 2005

AbstractThe anodic oxidation mechanism of the Vinca alkaloids vinblastine, its semisynthetic derivatives vindesine and 5′‐noranhydrovinblastine, and of vincristine, all with closely similar structures, was studied at a glassy carbon disk electrode in buffered aqueous media using differential pulse and cyclic voltammetry. The effect of pH on the mecharism showed that it is a complex multistep electron transfer with deprotonation steps involved and that the final products, dimers or polymers, adsorb strongly to the electrode, forming an unreactve film on the electrode surface. The electrochemical differential pulse voltammograms showed a correlation between the vinblastine derivatives, whereas vincristine reacts at different potentials. These differences in the anodic oxidation mechanisms of the compounds studied can be related to their neurotoxicity and myelosuppression effects. These effects may be due to the metabolite and/or degradation products of the compounds and result from how they are attached to, or transported across, cellular structures such as cell membranes.
Rapid coulometry of tocopherols in ethanol and chloroform using ferricyanide ion mediator
Authors: Uchiyama Shunichi , Kurokawa Yuichi , Hasebe Yasushi , Suzuki Shuichi 
Published: May 2005

AbstractIn order to estimate the absolute determination method of tocopherols, rapid coulometry has been carried out by using a vapor grown carbon fiber electrode impregnated with ethanol‐water solution containing ferricyanide ion as a mediator. The electrolysis time of 1 × l0−3 M α‐tocopherol in ethanol was below 30 seconds, and its current efficiency was attained to be 100.1% when an ethanol content in pH 4.0 electrolyte is 20%. Four isomers of vitamin E in chloroform were also determined by indirect coulometry in which ferricyanide solution was mixed with sample solution for 10 minutes prior to electrolysis and the current efficiencies of α‐, β‐, γ‐, and δ‐tocopherols were obtained to be 97.6, 100.5, 89.7, and 83.7%, respectively, and the relative standard deviations were below 1%.
Electrochemical oxidation of thiobenzanilide
Authors: Gabriel Jiří , Němec Ivan , Zimová Naďa , Hanuš Vladimír , Waisser Karel 
Published: May 2005

AbstractThe electrochemical oxidation of thiobenzanilide was studied in anhydrous acetonitrile as a model for the enzymatic oxidation of the substance. It has been found that a single electron is exchanged in the presence of 5 × 10−2 M HClO4 The oxidation products were identified as H2S, benzanilide, and 2‐phenylbenzthiazole.
The effect of the nature of the polymer backbone on the stability and the analytical response of polymer‐modified electrodes
Authors: Doherty A. P. , Stanley M. A. , Arana G. , Koning C. E. , Brinkhuis R. H. G. , Vos J. G. 
Published: May 2005

AbstractThe synthesis, characterization, and sensor application of the novel redox polymer [Os(bipy)2(PS)7.5(DMAP)2.5Cl]Cl, where bipy = 2,2′‐bipyridyl, PS = polystyrene, and DMAP = poly[4‐(N‐methyl‐N‐p‐vinylbenzylamino) pyridine], are described. The charge transport properties of electrodes modified with the redox material are investigated using cyclic voltammetry and chronoamperometry. The modified electrode behaves as an efficient electrocatalyst for the outer‐sphere reduction of FeIII, with the cross‐exchange reaction occurring at the surface of the polymer (Sk″) at concentrations less than 1.0 × 10−3 mol dm−3 FeIII, with a change over to the Ste, kinetic regime at higher substrate concentrations. Direct agreement was observed between the kinetic behavior at rotating disk electrodes and in thin‐layer flow cells. Application of the modified electrodes for the determination of iron in pharmaceutical formulations and the long term stability of the electrodes are investigated. The results obtained are compared with those reported for the analogous metallopolymer [Os(bipy)2(PVP)10Cl]Cl, where PVP is poly‐4‐vinylpyridine.
Differential pulse stripping voltammetric determination of thallium with an 8‐hydroxyquinoline‐modified carbon paste electrode
Authors: Cai Qiantao , Khoo Soo Beng 
Published: May 2005

AbstractA carbon paste electrode incorporating 8‐hydroxyquinoline was fabricated to selectively accumulate TlI at open circuit. The accumulated TlI, after reduction to metallic thallium at the electrode surface, was anodically stripped by differential pulse voltammetry. Under optimized conditions, TlI concentrations in the range 1.00 × 10−8 M − 1.00 × 10−5 M gave two linear regions due to different controlling factors for accumulation. A detection limit of 4.90 × 10−9 M (1.00 ppb) was found for a 120‐s accumulation. For 10 determinations of TlI at concentrations of 1.00 × 10−6 M and 1.00 × l0−7 M, relative standard deviations of 2.60% and 3.20% were obtained, respectively. Interferences from BiIII, PbII and CuII could be removed by masking with complexing agents such as sodium diethyldithiocarbamate, EDTA, sodium citrate, etc. A method was developed for thallium speciation and analysis, based on the determination of TlI while masking TlIII with EDTA followed by chemical reduction of TlIII to TlI with hydroxylamine hydrochloride. This method was tested using a synthetic sample containing known concentrations of TlI and TlIII.
Rapid determination of manganese in wastewaters and seawater by stripping potentiometry
Authors: Scollary Geoffrey R. , Chen Guo Nan , Cardwell Terence J. , Vincente‐Beckett Victoria A. 
Published: May 2005

AbstractA rapid stripping potentiometric method for the determination of trace levels of manganese in seawater and industrial waste waters has been developed. The analysis is performed in the presence of oxygen with an analysis time of less than 2.5 min per sample at manganese concentrations lower than 5μg/L. The precision of the method is satisfactory and the results for 5 seawater and waste water samples compare favorably with graphite furnace atomic absorption spectrophotometry.
A study of ethylamine at a gold rotating ring‐disk electrode using pulsed electrochemical detection at the ring
Authors: Dobberpuhl David A. , Johnson Dennis C. 
Published: May 2005

AbstractLinear scan (cyclic) voltammetry at the disk with simultaneous pulsed electrochemical detection (PED) at the ring of a rotated ring‐disk electrode (RRDE) is demonstrated to be applicable for studies of the complex anodic behavior of ethylamine at gold electrodes in 0.10 M NaOH. The oxidation of ethylamine at the disk occurs during positive scans concomitantly with formation of surface oxide (Au → AuOH → AuO). However, the final oxide‐covered surface (AuO) is inert for further ethylamine oxidation. Data obtained at the RRDE demonstrate that the total ethylamine signal at the disk is composed of simultaneous contributions from: oxidative desorption of ethylamine preadsorbed at the oxide‐free Au surface and oxidation of ethylamine transported to the disk simultaneously with oxide formation. Based on ring‐disk data, preadsorbed ethylamine is estimated to correspond to a fractional surface coverage of 0.7 ± 0.1 monolayer for 10 to 60 μM ethylamine. Of this coverage, ca. 75% corresponds to ethylamine coadsorbed reversibly with OH− and 25% to ethylamine adsorbed irreversibly by a mechanism concluded to be chemisorption.