bluuebunny/crossref_metadata_2025 huggingface dataset:
Lactate‐dehydrogenase‐based biosensors for glyoxylate and NADH determination: A novel principle of analyte recyling
Authors: Schubert Florian , Scheller Frieder , Krasteva Nikolina G.
Published: February 2006

Two types of bienzyme electrodes based on the oxidation of glyoxylate to oxalate by NAD+ in the presence of lactate dehydrogenase (LDH) are described. The enzymes were entrapped in gelatin membranes and combined with an oxygen probe. A sequence sensor using LDH coupled with oxalate oxidase is useful for the determination of glyoxylate between 1 × 10−5 and 2.5 × 10−3 M. The sensor performance was optimized with respect to pH and cofactor concentration. As a novel approach to internal analyte recycling in biosensors, the LDH‐catalyzed recycling of NADH/NAD+ during the parallel oxidation of glyoxylate and reduction of pyruvate is utilized in a sensor for highly sensitive NADH measurement. Lactate monooxygenase was coupled as an auxiliary enzyme to indicate the lactate formed from pyruvate. The calibration curve of the proposed sensor is linear between 7 × 10−6 and 1.8 × 10−3 M NADH in the absence of glyoxylate (i.e., without analyte recycling) and between 3 × 10−8 and 2 × 10−6 M in the presence of glyoxylate (i.e., with analyte recycling).
Electrochemical cell design and experimental procedures for measuring electrode reaction kinetics at low and variable temperatures
Authors: Mu Xi Hai , Schultz Franklin A.
Published: February 2006

An electrochemical cell is described for measuring electrode reaction kinetics at low and variable temperatures in nonaqueous solvents. The cell contains a working electrode of conventional size (at which the standard heterogeneous electron transfer rate constant is determined by cyclic voltammetry) and a microelectrode (at which the diffusion coefficient is measured by steady‐state microelectrode voltammetry). Uncompensated solution resistance is minimized by a combination of close placement of the reference electrode salt bridge tip and the working electrode surface and instrumental positive feedback. Cell performance is evaluated by an examination of ferrocene oxidation and manganese(III) (tetraphenylporphyrin) chloride reduction at temperatures between 229 and 298 K. Comparison of the responses from these reversible and quasi‐reversible redox couples in the same solution demonstrates that the effects of uncompensated solution resistance are absent from the experimental measurements and that increases in the cyclic voltammetric peak potential separation with sweep rate are due entirely to the kinetics of the Mn(III)/Mn(II) electrode reaction.
Electrochemical NO2 gas sensors: Model and mechanism for the electroreduction of NO2
Authors: Chang Si‐Chung , Stetter Joseph R.
Published: February 2006

Two types of sensing devices have been studied in order to elucidate the mechanism of response of amperometric gas sensors. A high‐surface‐area electrode (HSAE) sensor produces fast electrode reactions, and the steady‐state sensor signals are controlled either by permeation or by the supply of analyte to the sensor. For low‐surface‐area electrode (LSAE) sensors, a kinetically controlled signal is observed. A mechanism that involves a “chemically” induced changes in the gold electrode surface oxide coverage is proposed, and the activation energy for NO2 reduction at a gold electrocatalyst is calculated. A general model of sensor response is proposed that can describe the behavior of the steady‐state response for both HSAE and LSAE sensors.
Polarography of penem carbapenem antibiotics and the azetidinone intermediate
Authors: Bersier Pierre M. , Bersier Jacques , Sedelmeier Gottfried , Hungerbühler Ernst
Published: February 2006

Various penems, structurally closely related carbapenems, and the intermediate 4‐acetoxyazetidin‐2‐one were studied by direct current sampled dc, differential pulse polarography (DPP), cyclic voltammetry, and ac tensammetry. Optimum pH ranges for the determination of 4‐acetoxyazetidin‐2‐one and the various penems are discussed. In Britton—Robinson buffer (BRP) penems exhibit (pH 3) one stable reduction wave, which can be exploited analytically. Carbapenems exhibit stability problems in BRP (pH 3). They can be determined after conversion by hydrolysis into a stable imine form. Useful linear concentration ranges are 10 to 140 μg/mL for 4‐acetoxyazetidin‐2‐one and 20 to 170 and 0.5 to 70 μg/mL for penems using dc polarography and DPP, respectively. The precision of the proposed analytical methods is acceptable, with relative standard deviations around 2.5% for the assay of 4‐acetoxyazetidin‐2‐one and 2.5 and 2–5% for the penem and carbapenem, respectively.
Poly(ester‐sulfonic acid)‐coated mercury film electrodes for anodic stripping voltammetry
Authors: Wang Joseph , Taha Ziad
Published: February 2006

The antifouling properties of poly(ester‐sulfonic acid) coatings are explored for stripping voltammetric measurements of trace metals in the presence of organic surfactants. Up to at least 100 mg/L of gelatin, Triton X‐100, albumin, or humic acid does not affect the stripping response of heavy metals. A relative standard deviation of 4% is obtained for 20 successive measurements of 5 × 10−7 M lead in the presence of 50 mg/L Triton X‐100. Experimental variables, including film thickness, rotation speed, analyte, and surfactant concentrations, are explored. Potential for speciation work and assays of clinical samples is also indicated. The resistance to surfactant interferences, coupled with the simple coating procedure, good mechanical stability, and low cost, make poly(ester‐sulfonic acid) coatings very attractive for anodic stripping voltammetry.
The electrochemical determination of free CuO in YBaCuO superconductor materials
Authors: Gruner Wolfgang , Stahlberg Rudi , Brainina Khjena Z. , Akselrod Nadeshda L. , Kamyshov Valentin M.
Published: February 2006

Using a carbon paste electroactive electrode (CPEE), the mechanism of cathodic and anodic electrochemical processes on several copper oxide compounds in 0.1–1.0 mol/L hydrochloric acid media has been investigated. It is shown that the cathodic reaction of CuO is much more sensitive under selected conditions than that of other copper‐containing phases, which results in the variation of the preparation procedure of YBaCuO superconducting materials. A quantitative analysis is thus possible to determine the free CuO with a content of 0.5–10 wt% YBa2Cu3O7‐x with about 10–20% relative standard deviation. The cathodic reduction reaction by chemical—electrochemical mechanisms or by solid state conversion is also discussed.
Development of a computerized electrochemical system for stripping voltammetry
Authors: Hernández‐Brito J. J. , Cardona‐Castellano P. , Pérez‐Peña J. , Gelado‐Caballero Ma. D.
Published: February 2006

A computer‐controlled electrochemical system has been developed to determine heavy metal using stripping voltammetry. The system consists of a potentiostat (which we have designed and developed), a polarographic static mercury electrode (303A, PAR), an analog‐digital conversion board (DT2801‐A), a personal computer, and an HP7440 plotter. The potentiostat runs between −2.0 to +2.0 V with multirange current selection between ±50 nA and ±100 μA. There are various outlet channels with different time constants and noise levels. The fastest channel can detect processes on the order of 200 μs with a noise level of ±2.0 nA, while for 30 ms processes the noise is ±100 pA. The software developed controls the sequences of potentials, acquires and stores the currents, and plots them at its convenience. The system has been tested successfully in the determination of different metals using anodic and cathodic stripping voltammetry with different types of waveforms.
Uncertainty in the potential of a reference interface in liquid/liquid measurements
Authors: Vanýsek Petr
Published: February 2006

Electrochemical research on interfaces between two immiscible electrolytes often relies on establishing the so‐called reference interface. This interface is formed by two immiscible solvents, each with a dissolved electrolyte. The electrolytes are chosen such that the two solvents share one common ion. The potential of the interface is then determined by a calculation. In this study, it is shown that this ionsensitive interface does not always have the commonly accepted potential value. Reasons for this and corrective actions are given.
Polarographic estimation of conjugated enes
Authors: Husain Sajid , Sastry G. S. R. , Prasad P. Ravi , Sarma G. V. R.
Published: February 2006

A polarographic method for the estimation of styrene, isoprene, and 1,3‐cyclohexadiene using 0.02 M tetrabutyl ammonium iodide in N,N‐dimethylformamide as supporting electrolyte has been developed. The method is useful for the quality assurance of conjugated enes as well as for determining trace quantities of these compounds in industrial products such as polymers, elastomers, or adhesives.
An instrument for alternating current voltammetry featuring a digital phase‐sensitive detector: Application to flow‐injection analysis using ac amperometry
Authors: Curran David J. , Gelbert Mark B. , Kingsley Edward D.
Published: February 2006

An instrument, which incorporates a lock‐in amplifier based on a digital phase sensitive detector, has been designed and constructed for ac electrochemical measurements of solutions containing low concentrations of analyte. The performance of the lock‐in amplifier was characterized experimentally. Phase angle resolution is better than 0.01°, and signal capture ratios up to about 80,000 can be attained. An up/down counter replaces the multiplier of the typical analog phase‐sensitive detector. Provision was made to sum the net count over a preselected number of cycles of the reference signal to improve the sensitivity and signal‐to‐noise ratio of the phase‐sensitive detector. The lock‐in amplifier output can be read on a recorder via a digital‐to‐analog converter or sent to a computer. Overall instrument performance is demonstrated using ac amperometry at a carbon paste electrode and flow injection techniques to determine o‐dianisidine. Peak currents corresponding to a solution concentration of 6 nM in the detector were successfully measured.
A clay‐modified electrode for ion‐exchange voltammetry
Authors: Wielgos Todd , Fitch Alanah
Published: February 2006

Clay modified electrodes are characterized and optimized for their analytical use in ion‐exchange voltammetry using Ru(NH3) as a test ion. The effect of electrolyte concentration on the conductivity of the film, the time for signal development, the amount of clay coating, and rinsing procedures are investigated. The linear range of the clay‐modified electrode was found to be four orders of magnitude, and 100 pmol of the complex were sensed.
Study of electrochemical reduction of selenium (+4) using square wave voltammetry
Authors: Zelić Marina , Branica Marko
Published: February 2006

The electrochemical reduction of selenium (+ 4) on hanging mercury drop electrode (HMDE) has been studied using square wave voltammetry (SWV). The product of the first, very complex electrode reaction can be further reduced in a process characterized by reactant and product adsorption. The height of the stripping peak increases up to four times with the addition of Cu2+ ions, although the electrode reaction becomes less reversible. The square wave cathodic stripping peak currents are an order of magnitude higher than the corresponding differential pulse values, but the detection limit (3 × 10−10 mol/L) is practically the same for both techniques. The concentration of selenium (+ 4) in rainwater samples has been determined.
The construction of two long‐optical‐path spectroelectrochemical cells
Authors: Shi Minglian , Gao Xiaoxia
Published: February 2006

The construction and operation of two novel, long‐optical‐path‐length spectroelectrochemical cells are described. In addition to giving a sensitive optical response, the cells are more convenient to use than conventional designs. Model systems are used to demonstrate that the cell with a gold foil working electrode functions well at positive potentials while the pure mercury working electrode is particularly attractive for studies in negative potential ranges.
Voltammetric determination of thiram following adsorptive accumulation on a rotating gold disk electrode
Authors: Sevilla M. Teresa , Procopio Jesús Rodriguez , Pinilla Jose M. , Hernandez Lucas
Published: February 2006

The oxidation of thiram was studied by cyclic voltammetry on a rotating gold disk electrode. The oxidation process involves the adsorption of thiram. The limit of detection obtained was 0.04 μg/mL and the method was applied to thiram determination in formulations. The spontaneous adsorption of thiram on the rotating gold disk electrode produces a substantial enhancement of the voltammetric signal. This effect can be exploited as an effective accumulation step prior to the voltammetric measurement. The best results are obtained thiram solutions adjusted to pH 1 with phosphoric‐acetic acid buffer, an accumulation potential of 0.0 V, and a scan rate of 400 mV/s for the voltammetric step. Under these conditions, the detection limit was 0.3 ng/mL after 10 minutes of accumulation. The method was applied to the determination of thiram in water with good results.
Amperometric investigation of nickel and cobalt complexes with cephalexin
Authors: Kapetanović V. , Sužnjević D. , Veselinović D.
Published: February 2006

Cephalexin complexes with Ni(II) and Co(II) ions have been studied polarographically in an aqueous medium with a pH of 7–7.5, and an ionic strength of 0.2. It is shown that Ni(II) and Co(II) ions and cephalexin form [NiCEF]+ and [CoCEF]+ complexes under the experimental conditions cited. The stoichiometric composition of the complexes and the stability constants, log K′ = 3.16 for Ni(II)‐cephalexin and log K′ = 3.09 for Co(II) cephalexin, were determined by the Leden method.
Flow‐injection analysis with immobilized oxidase/peroxidase enzymes and fluoride electrode detection
Authors: Matuszewski Wojciech , Trojanowicz Marek , Meyerhoff Mark E.
Published: February 2006

Various 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

Dielectric 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

A 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

The 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.
Electroanalytical techniques for drug analysis
Authors: Patriarche G. J. , Zhang Hao
Published: February 2006

An overview on pharmaceuticals treated by electroanalytical techniques is presented. The review covers the period between 1987 and 1990 and includes more than 100 references. It includes the use of mercury and solid modified electrodes. Recent trends are discussed. The coverage is not exhaustive.
Second‐generation automated voltammetric cell
Authors: Yarnitzky Chaim N.
Published: February 2006

A 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

The 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

The 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

New 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

A 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

Hydroxide 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

A 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

A 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

An 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

The 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

The 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

The 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

Stereological 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

Lipoprotein 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

The 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

The 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.
Covalent labeling of the cocaine‐sensitive catecholamine transporter
Authors: Howard B. D. , Cho A. K. , Zhang M.‐b. , Koide M. , Lin S.
Published: February 2006

Xylamine is an alkylating agent that is a substrate for and specific irreversible inhibitor of the cocaine‐sensitive catecholamine transporter that functions in catecholamine reuptake into neurons and PC12 cells. [3H]xylamine prominently labels nine PC12 proteins; the relative xylamine‐alkylation of a Mr 54,000 protein was decreased by cocaine and increased in the case of a PC12 variant, B9, which is deficient in catecholamine transport. [3H]xylamine labels no such protein in another transport variant, MPT1. We propose that this Mr 54,000 protein (1) is a component of the catecholamine transporter, (2) is present in B9 cells but in a conformation that reduces transporter activity and makes alkylation by xylamine more likely, and (3) is absent in MPT1 cells. Nerve growth factor treatment restores transporter activity in B9 cells but not in other transporter‐deficient variants.
Mechanisms of [3H] γ‐aminobutyric acid release by chromaffin cells in primary culture
Authors: Oset‐Gasque M. J. , Castro E. , González M. P.
Published: February 2006

The basal and evoked [3H] γ‐aminobutyric acid (GABA) release from chromaffin cells in primary cultures was studied and compared with that of [3H]NA. [3H]GABA was found to be released, in a dose‐dependent fashion, by different secretagogues known to induce noradrenaline (NA) release, that is, the cholinergic agonist nicotine, high‐potassium chloride, veratridine, and calcium ionophores. In general, there was a parallelism between percentages of release of both [3H]GABA and [3H]NA, although in all circumstances the former were lower. The nicotine‐and high‐potassium‐evoked [3H]GABA release was absolutely calcium dependent, thus indicating the existence of a exocytotic‐like mechanism, whereas in the veratridine‐induced release, a calcium‐independent component was also detected. This latter component was sodium dependent, as it showed an absolute requirement for extracellular sodium and was enhanced by ouabain. Moreover, it was inhibited by known GABA uptake inhibitors, which indicate that this component of [3H]GABA release induced by veratridine could be due to GABA outflow through the membrane carrier. The above results, together with that obtained from studies about subcellular localization of [3H]GABA taken up by chromaffin cells, seem to support the existence of two mechanisms for [3H]GABA release by chromaffin cells: one calcium‐dependent, exocytotic‐like, and another calcium‐independent and sodium‐dependent, possibly mediated by the GABA carrier. Both processes could have a functional role on the regulation of extracellular GABA levels and so in the control of catecholamine release by chromaffin cells.
Quantitative brain autoradiography of [9, 10‐3H]palmitic acid incorporation into brain lipids
Authors: Noronha J. G. , Bell J. M. , Rapoport S. I.
Published: February 2006

The distribution of radioactivity within brain metabolic compartments was examined following the intravenous injection of [9,10‐3H]palmitate into awake rats. Brain radioactivity reached a maximum value by 15 min after [9,10‐3H]palmitate injection and remained unchanged for at least 4 hr. Regional differences in radioactivity could be determined with high resolution by quantitative autoradiography, at the level of cell layers within the hippocampus and cerebral cortex, and between striosomes of the caudate nucleus. Regional brain radioactivities were converted to normalized regional radioactivities (k) by dividing them by the integrated plasma fatty acid radioactivity (integrated over the time course of the experiment). These values reflected incorporation mainly into brain phospholipids; radioactivity due to nonlipid components was minimal. Indeed, about 85% of brain radioactivity was within lipids between 5 min and 4 hr postinjection, the remainder being equally divided between protein‐associated pellet and aqueous‐soluble metabolites. The major lipids labeled were phospholipids, particularly phosphatidylcholine, which contained about 75% of phospholipid radioactivity. The results show that [9,10‐3H]palmitate can be used to examine incorporation of plasma palmitate into individual brain regions via quantitative autoradiography. Furthermore, the tracer is a rather selective marker for phosphatidylcholine and can be used to examine turnover and synthesis of this phospholipid. [9,10‐3H]palmitate has advantages over [U‐14C]palmitate for autoradiographic studies of incorporation; following the 14C‐tracer, significant label even at 4 hr after injection is in nonlipid compartments (glutamate and aspartate), and the long path length of 14C limits resolution at the cell layer level.
Changes with aging in the levels of amino acids in rat CNS structural elements: IV. Methionine and basic amino acids
Authors: Banay‐Schwartz M. , Lajtha A. , Palkovits M.
Published: February 2006

This paper reports the distribution of methionine, histidine, lysine, arginine, and ornithine in 53 discrete brain areas of 3‐and 29‐month‐old male Fischer 344 rats microdissected by the punch technique. Like that of the other amino acids we reported in previous papers of this series, the distribution of methionine and the basic amino acids was regionally highly heterogeneous. The ratios of levels in the areas of highest concentrations to levels in the areas of lowest concentration varied from 10 to 15 for these amino acids, except that it was 23 for arginine. This heterogeneity is also illustrated by the finding that in some areas arginine was more than 5% of the total amino acid content and in others was less than 0.5%.

The distribution of methionine differed from that of the basic amino acids, which were high in hypothalamic areas and low in the limbic system.

With aging, methionine and basic amino acids, like the other amino acids studied in this series, mainly decreased in level, although in a few cases increases could be seen. Significant decreases were noted more than five times as often as increases.
Iron‐dependent peroxidation of rat brain: A regional study
Authors: Subbarao K. V. , Richardson J. S.
Published: February 2006

Iron has been shown to initiate a variety of free radical reactions in biological systems. The present study examined the in vitro susceptibility of homogenates prepared from different regions of rat brain to iron‐induced peroxidation. Among the regions studied, basal thiobarbituric acid‐reactive product (TBAR) formation is highest in the cerebellum and amygdala, intermediate in the cortex, hippocampus, and neo‐stratium, and lowest in the hypothalamus, midbrain, and brainstem. In the presence of 200 μM FeCl3, there is a 20–25‐fold increase in the net TBAR formation in all regions, with TBAR formation in the cerebellum and amygdala being significantly higher than in the midbrain and brainstem. Time‐course and dose‐response studies of iron‐induced peroxidation showed that the cerebellum and amygdala are the most susceptible regions with respect to concentration of iron and duration of the incubation time, whereas the midbrain and brainstem are the least affected areas. Following low‐speed (1,000g) centrifugation of brain part homogenates, TBAR formation in the supernatant fractions is quite uniform across regions, while the pellet fractions give the same regional variations as the whole homogenates. TBAR formation in both fractions is increased 20–30‐fold in the presence of 200 μM iron. Brain tissue TBAR formation induced by 200 μM iron is inhibited by the iron chelator desferrioxamine (IC50 = 600μM), by Tris buffer pH = 8.0 (2.5 mM Tris gives 50% inhibition by trapping hydroxyl radicals), and by high concentrations of the cyclooxygenase inhibitor indomethacin (IC50 = 1.2 mM).
Effect of lithium on tachykinins, calcitonin gene‐related peptide, and neuropeptide Y in rat brain
Authors: Mathé A. A. , Jousisto‐Hanson J. , Stenfors C. , Theodorsson E.
Published: February 2006

The effects of lithium on brain regional concentrations of substance P (SP)‐, neurokinin A (NKA)‐, calcitonin gene‐related peptide (CGRP)‐ and neuropeptide Y (NPY)‐like immunoreactivities (‐LI) were studied in rat. In the pilot study, rats were divided into three groups that were administered vehicle, or 1 or 4 mEq/kg lithium sulphate, respectively, intraperitoneally once/day for 9 days. In the second experiment, rats were divided into three groups receiving vehicle, or 1 or 2 mEq/kg lithium sulphate, respectively, intraperitoneally twice/day for 9 days. After sacrifice by focused microwave irradiation, brains were dissected, weighed, and frozen. Peptides were extracted and measured in extract aliquots by specific radioimmunoassays. Marked regional differences (P<.001) were found for each of the peptides measured. In the pilot study the higher lithium dose, 4 mEq/kg, significantly raised neuropeptide levels. However, animals receiving this dose also showed signs of toxicity. In the second experiment, lithium increased SP‐LI concentrations in striatum and hypothalamus (72 and 29%, P's<.001 and .05). NKA‐LI was also elevated in striatum (44%, P<.01). CGRP‐LI, in parallel to SP‐LI, was increased in striatum and hypothalamus (58 and 78%, P's <.05 and .01). In contrast, lithium decreased CGRP‐LI in the pituitary gland (56%, P < .01). NPY‐LI was increased in striatum, and frontal and occipital cortex (30, 66, and 60%, respectively; P's < .01, .01, and .05). In conclusion, lithium, in doses equivalent to those used clinically, has a significant effect on SP‐, NKA‐, CGRP‐, and NPY‐LI concentrations in several brain structures, most prominently in the striatum. These findings raise the possibility that lithium's effects on neuropeptides are specific and may represent one of its mechanisms of action on mood and motor behavior.
Calcitonin gene‐related peptide identifies spinal motoneurons in vitro
Authors: Juurlink B. H. J. , Munoz D. G. , Devon R. M.
Published: February 2006

Cell dissociation of E6 chick spinal cord followed by isolation of larger low‐density cells by using a discontinuous density metrizamide gradient resulted in the obtention of a motoneuron‐enriched fraction of cells. These cells were cultured in the presence of horse serum and muscle extract for a period of 8 days and examined for the presence of calcitonin gene‐related peptide. More than 90% of such cells were positive for calcitonin gene‐related peptide. When E14 spinal cord was examined, calcitonin gene‐related peptide was present only in the axons of primary sensory neurons and in the somas of motoneurons in the ventral horns. It is concluded that more than 90% of the neurons in our cultures are motoneurons.