bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow‐injection analysis with immobilized oxidase/peroxidase enzymes and fluoride electrode detection
Authors: Matuszewski Wojciech , Trojanowicz Marek , Meyerhoff Mark E. 
Published: February 2006

AbstractVarious flow‐injection analysis arrangements employing immobilized oxidase and peroxidase enzymes in conjunction with fluoride ion‐selective electrode detection are described. Selective measurement of substrates is based on the oxidase‐catalyzed production of hydrogen peroxide. The liberated peroxide is detected via a coupled peroxidase reaction involving a fluoroaromatic reagent added to the carrier stream to yield free fluoride ions. Three specific arrangements are evaluated: (1) both enzymes coimmobilized on a single membrane covering the fluoride electrode detector, (2) both enzymes immobilized on controlled‐pore glass within a flow‐through reactor place before the potentiometric detector, and (3) two separate enzyme reactors placed in series upstream from the electrode. Optimum sensitivity toward model analyte glucose using glucose oxidase is achieved with arrangements based on the immobilized enzyme reactors. With these systems, detection of glucose at concentrations ranging from 0.1 to 10 mM is possible at throughputs of more than 30 samples/h.
Dielectric behavior of PVC membranes plasticized with dioctyl sebacate or o‐nitrophenyl‐octyl ether
Authors: Dulic N. , Horváth L. , Horvai G. , Tóth K. , Pungor E. 
Published: February 2006

AbstractDielectric spectroscopy was employed to study the dielectric behavior of typical ISE membrane plasticizers and their compounds with PVC. Distinctly different patterns are reported with PVC compounds of polar and apolar plasticizers.
Concentration‐step amperometric sensor for uric acid using uricase
Authors: Uchiyama Shunichi , Suzuki Shuichi , Sato Tomohiro 
Published: February 2006

AbstractA novel amperometric method for biochemical substrates consuming oxygen in their enzyme reactions is proposed. This method is based on the measurement of the current peak observed when the sample solution is dropped on the thin membrane dipped in the enzyme solution, which is placed on the oxygen gas‐selective permeable membrane. In order to illustrate the present concept, uric acid was chosen as a measurable species and the response characteristics of the sensor were investigated. The peak current obtained by sample addition was proportional to the concentration of uric acid in the dropped solution, and the method was applied to measure uric acid in human urine. The results obtained were in fairly good agreement with those obtained using a conventional spectrophotometric method.
Electroanalytical determination of diazinon: Direct current and differential pulse polarography and adsorptive stripping voltammetry
Authors: Martínez R. Carabias , Domínguez F. Becerro , Méndez J. Hernández , Martín P. González 
Published: February 2006

AbstractThe polarographic behavior of the pesticide Diazinon was investigated in water/methanol solutions. Two methods are proposed for its determination. The first involves differential pulse polarography with a detection limit of 2.65 × 10−6 M, and the second is based on adsorptive stripping voltammetry at a hanging mercury drop electrode that yields a detection limit of 4.01 × 10−9 M.
Second‐generation automated voltammetric cell
Authors: Yarnitzky Chaim N. 
Published: February 2006

AbstractA new automated polarographic cell is described. The sample solution is pressurized and forced into the cell through a short glass tube. A thin film of the solution is formed on the inside wall of the tube while the nitrogen flows in the center. Equilibrium (and deoxygenation) is achieved very rapidly. Comparison of the thin film cell and the previous nebulizer automated cell clearly shows the advantages of the new device in terms of sample collection efficiency, sample volume, and nitrogen consumption.
Silver deposition at poly(4‐vinylpyridine) films on glassy carbon: Effects of polymer cross‐linking
Authors: Saiki Hiroshi , Shimazu Katsuaki , Kuwana Theodore 
Published: February 2006

AbstractThe effect of increasing the cross‐linking of poly(4‐vinylpyridine) films on glassy carbon substrates for the electrochemical deposition of Ag microparticles has been investigated. Cyclic voltammetric patterns for the deposition and stripping processes are elucidated. The electrochemical potential required for the deposition shifts to more negative values with cross‐linking. These shifts can be attributed to the polymer becoming more compact and to increased electrical resistance. There are two different components to this resistance. One is related linearly to the thickness of the film, while the other is independent of thickness. Both components are, however, related to the degree of cross‐linking. For the first component, the effect may be due to an increase in the resistance for electrolyte transport through the polymer channels constricted by the cross‐linking. The other is attributed to the increased resistance for water and electrolyte penetration from the solution phase into the polymer, whose hydrophobicity is increased by the cross‐linking and, thereby, is unwetted and insulative. Useful information regarding the permeability of the cross‐linked polymer is obtained by using silver as a probe.
Hydrophobic uptake and voltammetry of ergot alkaloids at lipid‐coated electrodes
Authors: Wang Joseph , Ozsoz Mehmet 
Published: February 2006

AbstractThe ergot alkaloids, ergotamine tartarate, ergonovine maleate, and ergocristine, are shown to be effectively partitioned into a lipid layer on a glassy carbon electrode. Such hydrophobic accumulation greatly enhances the sensitivity and selectivity of the subsequent voltammetric scan. A high degree of selectivity is achieved as polar electroactive species (present at large excess) are excluded by the hydrophobic layer. Detection limits of 1 × 10−8 M for ergotamie tartarate, 3 × 10−7 M for ergocristine, and 1 × 10−6 M for ergonovine maleate are attained (3 minute accumulation). Numerous variables affecting the response are explored. Differences in the hydrophobicity of ergot alkaloids account for changes in hydrophobic uptake and, hence, sensitivity. Applicability to selective measurements in untreated urine samples is illustrated.
Membrane ion‐selective electrodes for gold determination in cyanide solutions
Authors: Brzozka Zbigniew 
Published: February 2006

AbstractNew polymeric membrane electrodes based on the ion‐associated species formed by the cyanide of gold with hydrophobic cations, reversible to gold cyanide complex ions, were examined. Most exhibit a linear response with a nearly Nernstian slope over the 10−5 to 10−2 M concentration range of dicyanoaurite. The electrodes have been applied to the determination of gold in various cyanide electroplating baths.
Elimination of interferences in flow‐injection amperometric determination of glucose in blood serum using immobilized glucose oxidase
Authors: Matuszewski Wojciech , Trojanowicz Marek , Lewenstam Andrzej 
Published: February 2006

AbstractA flow‐injection system with anodic amperometric detection for glucose determination in human blood serum samples was optimized by a comparison of various arrangements of enzyme immobilization and the elimination of interferences. The best results were obtained using a compact membrane biosensor in a wall‐jet, flow‐through detector with a platinum disk electrode covered with an evaporated Nafion layer, a polyester membrane with immobilized glucose oxidase, and another protective polyester membrane. In the optimized conditions, a linear response was observed up to 25 mM glucose with a detection limit of 200 μM glucose and a sampling rate of 120 samples/h for a 20 μL sample volume. Results of glucose determination in human serurn were compared with a Beckman Glucose Analyzer 2 and a Kone Dynamic analyzer.
Oxidation of hydroxide to oxygen at an electrode modified with a film containing palladium and iridium oxides
Authors: Cox James A , Jaworski Robert K. , Das Basudev K. 
Published: February 2006

AbstractHydroxide is oxidized to oxygen at 0.7 V versus a saturated calomel electrode in a pH 11 solution at a glassy carbon electrode modified with a film containing palladium and iridium oxide. Although this converts to a value that is among the lowest of the reported overpotentials for this reaction, the utility for large‐scale electrolyses is limited by the need to periodically reactivate the surface with an acid treatment. The reaction, however, has considerable promise for electroanalytical chemistry. Voltammetric working curves in the millimolar range are linear at slow scan rates; at 40 mV/s, the sensitivity is 241 mA/mol. The current is mass transport limited at a rotating disk electrode. A general mechanism, proposed in part on the basis of a Tafel plot, is presented.
Determination of the dissociation potentials of metal complexes by computerized flow‐injection potentiometric stripping analysis
Authors: Fayyad Manar 
Published: February 2006

AbstractA method is described for determining the dissociation potentials of metal complexes using computerized flow‐injection potentiometric stripping analysis (CFIPSA). The dissociation potentials of Bi:NTA and Bi:EDTA complexes are determined at pH 2 by measuring the bismuth(III) concentrations (i.e., the counts in solutions containing the 1:1 complexes at different deposition potentials between −0.15 and −0.90 V vs. Ag/AgCl). Dissociation potentials of −0.35 and −0.50 V vs. Ag/AgCl have been found for Bi:NTA and Bi:EDTA, respectively.
Determination of ciprofloxacin by differential pulse polarography
Authors: O'Dea Philip , García Agustín Costa , Ordieres Arturo J. Miranda , Blanco Paulino Tuñón , Smyth Malcolm R. 
Published: February 2006

AbstractA simple and rapid method for the determination of the antibiotic ciprofloxacin by differential pulse polarography (DPP) has been developed. The changes in the voltammetric behavior of this drug compound with pH was studied, and the most suitable pH for analytical purposes was found to be pH 8.5. The DPP behavior of this compound at this pH exhibited two reduction waves at −1.44 and −1.64 V. The former wave could be used to determine ciprofloxacin between 5 × 10−7 and 3 × 10−5 M. The method was applied to the determination of ciprofloxacin in formulated tablets with a relative standard deviation of less than 0.4%.
A polishable amperometric biosensor for bilirubin
Authors: Wang Joseph , Ozsoz Mebmet 
Published: February 2006

AbstractAn amperometric enzyme electrode for bilirubin based on the incorporation of bilirubin oxidase and horseradish peroxidase within a graphite‐epoxy matrix is reported. The resulting bienzyme electrodes are renewable (by polishing) and offer low‐potential detection of bilirubin. The limit of detection is 4 × 10−6 M and the response is linear up to 1 × 10−4 M. The influence of various experimental variables is described. The surface‐to‐surface reproducibility is 14% (in terms of relative standard deviation). The fabrication scheme is simple and the response times are short. The prospects of using amperometric bilirubin electrodes for diagnostic work are discussed.
A new strategy for analyzing the chronometry of constructed rock features in deserts
Authors: Cerveny Niccole Villa , Kaldenberg Russell , Reed Judyth , Whitley David S. , Simon Joseph , Dorn Ronald I. 
Published: February 2006

AbstractThe western Great Basin contains thousands of constructed rock features, including rock rings, cairns, and alignments. Unlike subtractive geoglyphs, such as the Nasca Lines of Peru, that remove desert pavement, these surface features alter the location and positioning of cobble‐ to bouldersized rocks. The chronology of surface rock features has remained unconstrained by numerical ages because no prior chronometric approach has been able to yield age control. We propose a new strategy for studying these features by analyzing anthropogenic modifications to rock coatings, an approach that permits the use of several dating methods, two of which are assessed here: radiocarbon dating of pedogenic carbonate and rock‐varnish microlaminations. Initial results from Searles Valley, eastern California, suggest that constructed rock features may be as old as early Holocene and terminal Pleistocene. Archaeological surveys of desert areas would be greatly enhanced if they noted altered positions of rock coatings. © 2006 Wiley Periodicals, Inc.
Characterizing anthropic sediments in north European Neolithic settlements: An assessment from Skara Brae, Orkney
Authors: Simpson Ian A. , Guttmann Erika B. , Cluett Jonathan , Shepherd Alexandra 
Published: February 2006

AbstractThe creation of anthropic sediments, traditionally referred to under the blanket term midden, through the utilization of settlement waste materials in domestic settlement construction was first recognized during early excavations at the Orcadian Neolithic site of Skara Brae (V.G. Childe, 1931a; 1931b). Prior to the present study there has been no systematic attempt to identify the nature of these sediments at Skara Brae, whose likely occupation dates between ˜3100 and 2500 B.C., or to assess whether different materials were incorporated into construction or varied with different phases of site formation. The opportunity to begin addressing these issues arose with the location of undisturbed sediment samples held in storage since the last site excavations of 1972–1973 (D.V. Clarke, 1976). Ten thin sections were manufactured from these samples, representing earlier and later phases of Neolithic settlement at Skara Brae. Observations using thin‐section micromorphology, supported by total phosphorus and particle‐size distribution analyses, suggest that both earlier and later settlement phases show accumulation of household waste dominated by fuel residues. These wastes may have been used to help stabilize wind‐blown sand deposits during the later settlement phases. In addition, the use of clay material tempered with household waste is associated with wall construction. Animal manures are only evident in anthropic deposits on the edge of the main settlement site where composting may have been taking place, and there is no evidence for their use in site construction. The authors conclude by drawing attention to possible diverse uses of anthropic sediments in settlement construction at other Neolithic settlements in Orkney. © 2006 Wiley Periodicals, Inc.
Integrating geochemistry and micromorphology to interpret feature use at Dust Cave, a Paleo‐Indian through middle‐archaic site in Northwest Alabama
Authors: Homsey Lara K. , Capo Rosemary C. 
Published: February 2006

AbstractThe authors develop an integrated method using geochemistry and micromorphology to examine the use of archaeological features at Dust Cave, a Paleo‐Indian through Middle Archaic (10,650–3600 cal. B.C.) site in northwest Alabama. Samples analyzed using ICP‐AES for aluminum (Al), barium (Ba), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorous (P), strontium (Sr), sulfur (S), and zinc (Zn) and suggest that cultural features differ chemically from geogenic sediments in several ways: (a) K‐means cluster analyses indicate that features of known origin and suspected features of the same origin cluster together, thereby allowing for a preliminary separation into discrete functionalities; (b) phosphorus serves as an indicator of human occupation intensity; and (c) Sr/Ca and K/P ratios help identify anthropogenic materials. Micromorphological observations allow for a finer subdivision of feature types and help highlight postdepositional processes affecting cave sediments, and interpretation of activity at the site. These findings show that feature diversity and occupation intensity increased through time, peaking during the Middle Archaic. © 2006 Wiley Periodicals, Inc.
Quantitative ultrastructural studies of hepatocytes from fed and starved frogs
Authors: Baic D. , Ladewski B. G. , Frye B. E. 
Published: February 2006

AbstractStereological analysis of liver tissue excised from mature female Rana pipiens starved for 59 days and from a fed control group was conducted both at the light and electron microscopy levels. Average cellular volume decreased by more than a factor of 4 following prolonged fasting. Nuclear volume was not significantly decreased. Mitochondrial volume per cell showed a slight, though not statistically significant, decrease from 540 μm3 to 420 μm3. Rough endoplasmic reticulum decreased in absolute surface area per cell from 13,600 μm2/cell to 3,000 μm2/cell after starvation, but its surface density in the cytoplasm remained relatively constant. Lipid decreased from 650 μm3 per cell to less than 1 μm3 per cell after fasting. Glycogen decreased from 49% of hepatocyte cytoplasmic volume to less than 15%, a decrease in absolute volume from 4,000–240 μm3 per cell. Glycogen changed from the α to the β‐configuration during fasting. Condensed cross‐banded fibers or sheets formed within the rough endoplasmic reticulum cisternae of some fasted animals. The significance of these results relative to the energy metabolism of poikilotherms is discussed.
Low density lipoprotein receptor‐related protein‐2/megalin is expressed in oligodendrocytes in the mouse spinal cord white matter
Authors: Wicher Grzegorz , Larsson Mårten , Svenningsen Åsa Fex , Gyllencreutz Erika , Rask Lars , Aldskogius Håkan 
Published: February 2006

AbstractLipoprotein receptor‐related protein‐2 (LRP2)/megalin is a member of the low density lipoprotein receptor (LDLR) family, and is essential in absorptive epithelia for endocytosis of lipoproteins, low molecular weight proteins, cholesterol and vitamins, as well as in cellular signaling. Previous studies have shown megalin expression in ependymal cells and choroid plexus. We have investigated megalin expression in the spinal cord of postnatal mice with immunohistochemistry and immunoblot. Antibodies recognizing either the cytoplasmic tail (MM6) or the extracellular domain (E11) of megalin labeled oligodendrocytes in the spinal cord white matter, in parallel with myelination. MM6 antibodies, predominantly labeled the nuclei, whereas E11 antibodies labeled the cytoplasm of these cells. MM6 antibodies labeled also nuclei of oligodendrocytes cultured from embryonic mouse spinal cord. Immunoblots of spinal cord showed intact megalin, as well as its carboxyterminal fragment, the part remaining after shedding of the extracellular domain of megalin. Megalin‐immunoreactive oligodendrocytes also expressed presenilin 1, an enzyme responsible for γ‐secretase mediated endodomain cleavage. These findings show that spinal cord oligodendrocytes are phenotypically different from those in the brain, and indicate that megalin translocates signals from the cell membrane to the nucleus of oligodendrocytes during the formation and maintenance of myelin of long spinal cord pathways. © 2006 Wiley‐Liss, Inc.
Role of axons in the regulation of PO biosynthesis by Schwann cells
Authors: Brunden K. R. , Windebank A. J. , Poduslo J. F. 
Published: February 2006

AbstractThe role of axons in the expression of the major myelin glycoprotein, PO, has been investigated using neuron/Schwann cell cultures. These cultures were either nonmyelinating or myelinating due to growth in defined medium or in medium containing serum and chick embryo extract, respectively. The neurons and Schwann cells used in the studies were derived from embryonic day 15 rat dorsal root ganglia (DRG), and the Schwann cells from these ganglia are shown not to synthesize appreciable levels of Po prior to growth in culture. Myelinating cultures of Schwann cells and neurons grown together for 18–21 days synthesize Po that is readily identified by immunoblotting. The nonmyelinating cultures, which do not assemble basal lamina, also synthesize Po that is detectable by either [3H]mannose precursor incorporation or by immunoblotting. The steady‐state level of Po in the nonmyelinating cultures is less than that of the myelinating cultures, and the Po that is synthesized by the former appears to be catabolized shortly after its biosynthesis. Since nonmyelinating Schwann cells synthesize Po when in contact with neurites in vitro, we have examined the ability of such nonmyelinating cells to express the glycoprotein in vivo. Very little steady‐state Po is detected in immunoblots of the adult rat cervical sympathetic trunk (CST), a nerve in which approximately 99% of the axons are nonmyelinated. Similarly, the amounts of [3H]mannose and [3H]amino acids that are incorporated into newly synthesized Po are much lower in the CST than in the adult sciatic nerve. The Schwann cells of the CST are induced to synthesize myelin after growth in serum‐containing medium with embryonic DRG neurites that are devoid of endogenous Schwann cells due to prior treatment with an antimitotic agent. Immunoblot analysis of these cultures reveals a level of Po that is comparable to that of myelinating DRG Schwann cell/neuron cultures. These data indicate that DRG neurites supply a signal that can initiate the synthesis of Po in the absence of basal lamina and myelination. Furthermore, this signal may be reduced or altered in the CST.
Sulfate incorporation into peripheral nerve endoneurial glycolipids after crush and permanent transection injury
Authors: Kohriyama T. , Yu R. K. , Berg C. T. , Poduslo J. F. 
Published: February 2006

AbstractThe sulfation of peripheral nerve glycolipids was examined at 35 days after both crush injury or permanent transection of the adult rat sciatic nerve by in vitro incorporation of [35S]sulfate into endoneurial slices. These experimental models of neuropathy are characterized by the presence and absence of both axonal regeneration and subsequent myelin assembly. Although the sulfo‐glucuronosyl glycosphingolipids (SGGLs) were not detected by α‐napthol reagent after HPTLC separation of the total acidic lipid extract, fluorographic analysis after sulfate incorporation revealed a 4.7‐fold increase in [35S]sulfate in the sulfo‐glucuronosyl paragloboside (SGPG) and a 3.5‐fold increase in the sulfo‐glucuronosyl‐lactosaminosyl paragloboside (SGLPG) after the crush injury compared to permanent transection. These [35S]sulfate‐labeled lipids were identified by comigration after HPTLC separation by immunostaining with specific IgM monoclonal antibodies from a patient with de‐myelinating neuropathy and plasma cell dyscrasia. Enhanced incorporation of sulfate in the crushed nerves was also observed in the sulfatides and in several unknown lipids migrating between GM2 and GM3, between GM1 and GM2, slightly above the origin, and at the origin. Since previous studies (Yao and Poduslo: J Neurochem 50:630–638, 1988) have shown [35S]sulfate incorporation, but not [3H]Gal or [3H]Glc, into sulfatides at 35 days after transection, it is possible that the sulfation observed in the present studies does not represent de novo biosynthesis but rather sulfation of an endogenous pool of glycolipids that results from the nerve injury. The present data suggest that the sulfation reaction for SGGL α biosynthesis is enhanced during axonal regeneration and remyelination; however, the reduced level of incorporation after transection injury, which contains approximately 90% Schwann cells at 35 days post‐transection, suggests that lower concentrations of the SGGLs may also be present in Schwann cell‐related membranes.