bluuebunny/crossref_metadata_2025 huggingface dataset:
A High-Pressure Inductively Coupled Plasma Torch
Authors: Smith Thomas R. , Denton M. Bonner
Published: July 2005

An inductively coupled plasma (ICP) torch utilizing an extended coolant tube that tapers down to a small exit orifice designed to increase the pressure within the ICP torch is described. This torch design makes use of the advantages associated with higher torch operating pressures (including improved detection limits, increased sensitivity, and better plasma stability), without requiring major modifications to existing commercially available ICP torch box and matching networks. Detection limits obtained with the use of the new torch design are compared with those obtained from several commonly used torch designs using a commercially available torch box and spectrometer. A two- to sevenfold improvement in detection limits is observed through increasing torch operating pressure from 101.325 KPa (760 Torr, or atmospheric pressure) to 120 KPa (900 Torr).
Surface-Enhanced Raman Analysis of Benzo[A]Pyrene-DNA Adducts on Silver-Coated Cellulose Substrates
Authors: Vo-Dinh Tuan , Uziel Mayo , Morrison Alan L.
Published: July 2005

Benzo[a]pyrene-7,8-diol-9,10 epoxide (BPDE)-DNA adducts have been analyzed by surface-enhanced Raman scattering (SERS) spectrometry. BPDE is the ultimate carcinogenic metabolite of benzo[a]pyrene. The SERS measurements were performed with the use of a silver-coated cellulose material as the SERS-active substrate. The acid hydrolyzed products of BPDE-DNA adducts, DNA, and the BP-tetrols were also analyzed by SERS. The results indicate that SERS has great promise as a tool for detecting BPDE-DNA adducts in biological samples.
Estimation of Absolute Number Densities from Shapes of Atomic Fluorescence Curves of Growth
Authors: Smith B. W. , Rutledge M. J. , Winefordner J. D.
Published: July 2005

A general-purpose computer program has been developed to calculate atomic fluorescence curves of growth (COG) for a wide variety of cases and particularly for the experimentally interesting cases where the excitation source spectral bandwidth is not much different from the absorption linewidth in typical flames and plasmas. Calculations over a wide range of the variables which affect the shape of the COG in the high-number-density region show that the point of departure from linearity can be used to predict the absolute number density in the atomizer cell. For resonance atomic fluorescence, the point at which the experimental curve of growth is twofold below the low-density linear asymptote invariably occurs at a k0 L (peak absorption coefficient × absorption pathlength) product of 2 ± 1. Number densities can easily be determined to within an order of magnitude accuracy, even when such variables as source spectral width, collection geometry, and damping parameter are totally unknown. In favorable circumstances, where such variables are well known, accuracies of ±10% may be obtained. The calculated curves of growth are in excellent agreement with several COGs which have been experimentally obtained.
Studies of Energy Transfer and Ionization Processes in a Helium ICP
Authors: Fannin H. B. , Seliskar C. J. , Miller D. C.
Published: July 2005

The spectral consequences of the introduction of varying concentrations of heavy rare gas atoms into a reduced-pressure helium ICP have been examined. A term-dependent quenching of He(I) emission was observed and is consistent with previous work on a kinetic model for this ICP. In addition, the ionization behavior of the added rare gases has been studied, and a simple rule seems to emerge from the results: the first ionization potential of helium represents an upper bound to the plasma energy available (probably through collisional processes) to excite and/or ionize added species. Although spectroscopic temperatures can be calculated from the state population distributions for the added neutral gas atoms, the fact that the values vary with concentration and with the chemical identity of the species betrays the fact that the plasma is not in local thermodynamic equilibrium with respect to neutral atoms. Quite differently, the results for plasma positive ions show the same statistically determined spectroscopic temperatures; thus, it appears that these ions are nearly equilibrated and also suprathermal in population distribution.
Diffuse Reflectance FT-IR Studies of the Adsorption of CO on Rh/Al2O3Catalysts
Authors: Hamadeh Issam M. , Griffiths Peter R.
Published: July 2005

The diffuse reflectance/FT-IR spectrum of CO/Rh/Al2O3system has been investigated in terms of pretreatment of the catalyst, Rh loading, CO pressure (coverage), and coadsorption of CO with oxygen. The widths of all bands were narrowed by Fourier self-deconvolution (FSD), and six types of CO/Rh adsorbed species, including two which have not been assigned previously, have been identified by their C-O stretching frequencies. Species I, assigned to Rh(I)(CO)2, is formed with isolated Rh atoms and/or edge Rh atoms of atomic “rafts” and/or atomic crystallites. Species II is assigned to Rh(O)-CO. Species III' is assigned to [Rh(O)|2CO. Species VI is assigned to [Rh(I)]2CO. Two new species—IIIa, assigned to [Rh(O)]3CO, with underlying Rh atom, and VI', assigned to [Rh(I))2(CO)3—are postulated.
Photoacoustic Spectra of Rare Earth Pentaphosphates
Authors: Strȩk W. , L̸ukowiak E. , Marchewka M. , Ratajczak H.
Published: July 2005

The photoacoustic (PA) spectra of rare earth pentaphosphates of the general formula REP5O14, where RE = Pr, Nd, Ho, Er, Tm, are reported. The photoacoustic bands were identified and compared with the absorption spectra. For quantitative analysis of PA bands of lanthanide (III) ions, the intensity ratio vector is introduced, characterizing the intensity distribution of f-f transitions. It was found that the relative intensities of photoacoustic bands are comparable with the intensities of absorption bands. It is concluded that the nonradiative relaxation mechanism leading to the PA signal is independent of the manifold-to-manifold J-J' radiationless transitions.
The Analysis of Metals at a Distance Using Laser-Induced Breakdown Spectroscopy
Authors: Cremers David A.
Published: July 2005

Laser-Induced Breakdown Spectroscopy (LIBS) has been used to provide a rapid analysis of metals at distances between 0.5 and 2.4 m from the focusing lens and light-collection optics. The laser sparks were generated with the use of pulses from a Nd: YAG laser, and the spark light was collected by the use of a fiber optic cable. The wide acceptance angle of the cable relaxed the constraint that the spark be formed at a precise location for maximum light-collection efficiency and allowed the detection system to be placed remote from the sample. The identification of the main elemental component of eight metals using lines over a 40-nm spectral region was demonstrated by the use of a single laser pulse to record each spectrum. The accuracy and precision of analysis of the minor constituents of steel were determined, and the effect of surface contamination was examined. The application of LIBS to some industrial monitoring situations is discussed.
Infrared Characterization of Uranium Oxide Powders Using a Metal Light Pipe
Authors: Cort B. , Andrew J. F. , Hansen G. J.
Published: July 2005

A light-pipe technique has been used to measure infrared spectra of U02, U3O8, and UO3, in the range 2000 to 450 cm−1. Comparison with transmission spectra found in the literature indicates that the technique is very suitable for characterization of actinide powders and will therefore be a useful tool for future work, especially with hazardous materials such as actinides. The spectra obtained show all features predicted by group theory calculations, and the spectrum for the trioxide exhibits previously unseen features characteristic of uranyl bonds.
Solid-State 13C NMR Characterization of Irradiation-Cross-Linked Natural Rubber
Authors: Patterson Dwight J. , Koenig Jack L.
Published: July 2005

Solid-state 13C NMR was used to characterize the structure changes produced in gamma irradiation in natural rubber. The structure of the irradiated natural rubber was found to be heterogeneous, consisting of a mobile phase and a semi-rigid phase. Cis-trans chain isomerization was detected in the mobile phase of the gamma-irradiated samples. The CP/MAS spectra of the more rigid phase contained resonances due to quaternary carbons arising from cross-links and vinyl end groups caused by main chain scission. The calculated values of β and G( X) agreed with earlier published results. Peroxide-cured natural rubber of an equivalent amount of network density showed a higher amount of trans structure than did the gamma-irradiated natural rubber.
Background Corrections in the Determination of Cd and Pb by Flame AAS in Plant and Soil Samples with High Fe Levels
Authors: Van Der Lee J. J. , Temminghoff E. , Houba V. J. G. , Novozamsky I.
Published: July 2005

Plant leaf digests and soil extracts were analyzed for Cd and Pb by flame AAS in three ways: with deuterium background correction, with the Smith-Hieftje background correction system, and without any background correction. Background correction proved to be necessary for both elements and for both types of material. The two background correction systems gave equal results, provided that Fe concentrations were low. High Fe concentrations caused spectral interference (i.e., structured background), which was overcompensated by the deuterium system. The Smith-Hieftje system, however, produced correct results.
An X-Ray Photoelectron Spectroscopic Study of the Free Surface Segregation of Impurities in Platinum and Palladium
Authors: Paul Alan J. , Sherwood Peter M. A.
Published: July 2005

X-ray photoelectron spectroscopy has been used to observe the free surface segregation of impurities in samples of platinum and palladium. Heating in vacuo to 600°C promoted the surface segregation of silver, gold, and carbon in platinum and the surface segregation of silver and sulfur in palladium. All species segregated in their elemental form. The core level binding energies of the silver and gold segregants were lower than those measured for the corresponding pure metal states.
Compression of Infrared Libraries by Eigenvector Projection
Authors: Harrington P. B. , Isenhour T. L.
Published: July 2005

Different methods of data preprocessing were evaluated for the compression of Fourier transform-infrared spectral libraries by principal component analysis (PCA). The effect of noise on compressed library searches was examined. A PCA compression of an infrared library achieved an 81% reduction in size without any loss in search performance.
Vibrational Analysis of Terephthalate and Terephthalate-D4 Ions
Authors: Boerio F. J. , Roth P. G.
Published: July 2005

Infrared and Raman spectra of the terephthalate and terephthalate-d4 ions have been obtained. Normal coordinate analysis was carried out for both ions by transferring force fields from previous work on aromatic esters and p-nitro-benzoate and then refining all the force constants for the carboxylate groups and the diagonal force constants for the benzene rings by a first-order perturbation technique. An interpretation of the observed spectra has been proposed and selected eigenvectors have been presented.
Human Processor Interface for ICP-AES: Concepts and Implementation
Authors: Karanassios V. , Horlick G.
Published: July 2005

A dual-processor, distributed-intelligence approach to the computerization of an atomic emission spectrometer is presented. One processor handles data acquisition and instrument control and the second processor handles data presentation and user interaction. In particular, a unique human processor interface (HPI) has been developed for user interaction. A key goal in the development of the interface was to make the front-end processor's behavior “instrument-like,” as opposed to making the instrument “computer-like”: that is, to implement an instrument metaphor. This term is derived in concept from the desk-top metaphor: the instrument is mapped onto the screen where it appears as a pictorial representation of the original. In one's mapping the instrument, its dials, its controls, its indicators, and its front panels onto the screen and utilizing a point-and-click syntax in conjunction with a mouse, pull-down menus, and multiple overlapping windows, and by one's treating the entire screen as a menu, operating the instrument becomes an intuitive activity rather than a memorization test. By the clicking of the mouse at any location on this instrument metaphor, multiple levels of overlapping windows appear on the screen that provide additional graphic and text information. In our application, this metaphor is also used as a vehicle for direct instrument control from the computer's screen. In this paper, the distributed-intelligence system is described, the instrument metaphor concept is explained, and its application to ICP-AES instrumentation is illustrated. As part of this application, an extensive, graphically accessible atomic spectroscopy data base, complete with an elaborate help and explain facility, has been developed.
Application of X-Ray-Fluorescence Spectrometry to the Analysis of Ta-Nb-Sn Slags and Associated By-Products
Authors: Balaes A. M. E. , Dixon K. , Wall G. J.
Published: July 2005

This paper describes the development of an accurate, precise, and rapid analytical procedure using x-ray-fluorescence spectrometry for the determination of Nb, Ta, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Zr, and Sn in a wide variety of materials resulting from the processing of Ta-Nb-Sn slags to produce Ta-Nb oxides. The method involves evaporation of all the liquids to dryness, a 1:8 fusion of the solid materials with a flux consisting of Na-Li tetraborate and Na2CO3, and the addition of La oxide as a heavy absorber. With the use of a computer program, residual matrix effects are corrected for by influence-factor calculations.
Fourier Transform IR Spectroscopy Study of the Degradation of Pyromellitic Acid Diester
Authors: Sanchez L. A. , Wedgewood A. R.
Published: July 2005

The degradation of pyromellitic acid diester (PMDE) was studied by transmission Fourier transform IR spectroscopy (FT-IR). Reaction temperatures were varied from room temperature to 280°C, and the effect of temperature upon the observed vibrational modes of PMDE was monitored and analyzed. The formation of both a cyclic and a noncyclic anhydride was observed.
Characterization of a Dual Inductively Coupled Plasma Atomic Emission Source
Authors: Allen G. Mark , Coleman David M.
Published: July 2005

A dual inductively copuled plasma atomic emission spectroscopic system is described. This new analytical discharge segregates the normally integrated processes of sampling and spectral excitation associated with atomic emission sources. A low-power, low-argon-flow, radio-frequency plasma is used as a sampling device to create gaseous species from liquid and solid samples which are subsequently transported to a second plasma for excitation. Design and construction of instrumentation and associated operational parameters are reviewed. Comparisons of the sampling and the excitation plasmas include spatial emission profiles, linear calibration plots, signal-to-background ratios, and analytical detection limits. Use of the dual ICP for direct analysis of particulates (coal fly ash and firebrick) is demonstrated.
The Temperature Dependence of Band Maxima Molar Absorptivities of the Carbon-Halogen Stretching Mode in Tertiary Butyl Chloride, Bromide, and Iodide in the Liquid Phase
Authors: Katon J. E. , Lobo Stanislaus R. , Simpson J. C.
Published: July 2005

The absorbances at the peak maxima of the carbon-halogen stretching mode of t-butyl chloride, bromide, and iodide have been measured as a function of temperature. With the use of corrected concentration and pathlengths, these data have been converted into molar absorptivities at the respective peak maxima. The data have then been analyzed statistically for the purpose of developing a mathematical model for the dependency of molar absorptivity, at these peak maxima, on the absolute temperature. In all three cases, a linear relationship of the form e = XT + Y was found to satisfactorily fit the data. The molar absorptivity of all three band maxima decreases approximately 1% per Kelvin. This result indicates that attempts to apply Beer's law at temperatures other than that used to derive the constants will lead to significant error if the temperatures differ by more than a few degrees.
Energy Level Determination Using Two-Photon (Vacuum Ultraviolet and Visible) Resonance Spectroscopy*
Authors: McCann M. P. , Chen C. H. , Payne M. G.
Published: July 2005

With the use of a Nd:YAG laser and a dye laser, energy levels in argon and krypton have been measured. This technique can examine energy levels in the range of 11.9 eV to 16.4 eV, with the accuracy rivaling methods that employ very long VUV monochromators. The amount of photoionization has been calculated and agrees well with the experiment.
A Study of the Interaction of Phthalate Esters with Chlorine-Containing Polymers
Authors: Dessain Edison C. , Anderson Dennis
Published: July 2005

The infrared spectra of blends of various ortho-phthalate esters with polyvinyl chloride) and vinylidene chloride/(20%)acrylonitrile copolymer were recorded. The data indicate that the lowering of the ester carbonyl absorption frequency is due to a dipole-dipole/complex type interaction between the carbonyl of the ester and the chlorine of the polymer in addition to hydrogen bonding with acidic hydrogens. The lowering of the absorption frequence increases with an increase in the amount of chlorine in the polymer chain.
New Fiber-Optic-Based Instrumentation for the Measurement of Low-Temperature Phosphorescence Intensities and Lifetimes
Authors: Carroll Mary K. , Hieftje Gary M.
Published: July 2005

New fiber-optic instrumentation for phosphorescence-lifetime determinations and for steady-state phosphorescence measurements is shown to perform comparably to conventional instrumentation. The importance of optimal glass formation in the fiber-optic sample cell is considered in some detail. Detection limits for acetophenone, benzophenone, and p-nitrophenol are reported, and phosphorescence lifetimes are measured for several compounds, with values ranging from 2.5 ms to 4.7 s.
Transmission Infrared Spectra of Adsorbed Polymers Using a Dual-Beam FT-IR Instrument
Authors: Tripp C. P. , Hair M. L.
Published: July 2005

A dual-beam FT-IR instrument with optical null has been developed for the study of polymers adsorbed on low-surface-area solids. By the use of narrow-bandpass filters coupled with the dual-beam FT-IR, a sensitivity of 2 × 10−5 absorption units per scan has been achieved. Transmission infrared spectra are shown for poly(ethylene oxide-b-styrene) and didodecyl dimethyl ammonium bromide (DODAB) adsorbed on silicon.
Investigation of β-Cyclodextrin Immobilized at Silica Surfaces by Fluorescence Spectroscopy
Authors: Litwiler Kevin S. , Bright Frank V.
Published: July 2005

Steady-state and frequency-domain fluorescence spectroscopy are used to study the inclusion complexation of six anilinonaphthalene sulfonates (ANSs) with silica-immobilized beta-cyclodextrin (βCD). To fit the experimental data, we compared several modified Lorentzian lifetime distribution models. However, in all cases studied, a simple unimodal Lorentzian distribution best fit the fluorescence decay kinetics. The recovered distribution shapes did not change substantially as the surface was titrated with ANS; however, subtle trends suggest that silica-immobilized βCDs in more hydrophobic environments complex first. Furthermore, the recovered distribution widths (a measure of the environmental heterogeneity) for the silica-immobilized βCD-ANS complexes are always broader than those for ANS-βCD complexes in bulk solution.
Infrared Emission Spectroscopy of Coal Minerals and Their Thermal Transformations
Authors: Vassallo A. M. , Cole-Clarke P. A. , Pang L. S. K. , Palmisano A. J.
Published: July 2005

An infrared (IR) emission cell which is capable of operation up to 1500°C is described. The cell is based on an atomic absorption graphite furnace and is coupled to a Fourier transform infrared spectrometer. The spectrometer has been used to measure the emission spectrum of quartz from 200 to 1400°C, and the changes in the spectrum occurring with temperature can be related to the formation of cristobalite; transitions between low and high forms (alpha and beta forms) can also be monitored. Aragonite has also been analyzed through the temperature range 100 to 600°C, and the aragonite/calcite transition is clearly evident. The transformation of kaolinite to metakaolinite and through to mullite and cristobalite has also been studied with this in situ technique. The formation of mullite is evident in the spectrum at temperatures as low as 900°C, and the formation of cristobalite is clearly seen at 1200°C.
Variable-Temperature Diffuse Reflectance Infrared Studies of Calcium Oxalate Monohydrate
Authors: White Robert L. , Ai Jiu
Published: July 2005

The thermal degradation of calcium oxalate monohydrate is studied by using diffuse reflectance Fourier transform infrared spectroscopy combined with quadrupole mass spectrometry (DRIFTS/MS). DRIFTS/MS results are correlated with thermogravimetric analyses to verify the thermal properties of samples studied. Infrared spectral evidence for CaC2O4H2O dehydration and infrared spectra for three different CaC2O4 phases are given. In addition, the significance of a band at 1085 cm−1 assigned to CO22− which appears during the decomposition of CaC2O4 to CaCO3 is discussed.
Confocal Raman Microspectroscopy: Theory and Application to Thin Polymer Samples
Authors: Tabaksblat Ronald , Meier Robert J. , Kip Bert J.
Published: July 2005

Raman microspectroscopy can be used effectively to study very small samples or to study small areas within a transparent sample. With the application of the technique of confocal microscopy to a Raman microscope, the depth resolution of the instrument can be enhanced considerably. Confocal microscopy uses a pinhole, placed in the back image plane of the microscope objective, to block light from outside the focal plane. In this way the signal from the small volume element one wants to study can be better separated from the signals arising from the surrounding material. In this paper we show that the performance of the confocal Raman microscope can be described satisfactorily by geometrical optics. Furthermore, we have performed measurements to determine the depth resolution of our system for different combinations of objectives and pinholes. Finally, we report on the applications of this technique to different polymer systems, such as multilayer foils, fibers, and fiber composites.
Hyphenated On-The-Spot TG/FT-IR Technique
Authors: Jansen J. A. J. , Van Der Maas J. H. , De Boer A. Posthuma
Published: July 2005

By the coupling of thermogravimetry (TG) and Fourier transform infrared spectroscopy (FT-IR), the thermal behavior of polymeric materials can be elucidated from their mass loss combined with characterization of the evolved components. A hyphenated TG/FT-IR technique is presented, which enables the direct detection and characterization of evolving components in TG experiments, i.e., without transferring these components from the TG to the FT-IR equipment. In this on-the-spot TG/FT-IR technique, the IR beam of the FT-IR spectrometer is led directly into the TG equipment. The IR beam is reflected by a mirror mounted inside the TG equipment and subsequently detected by a standard FT-IR detector. In this way, the evolved components are detected both in gas and condensed phase directly in the TG equipment. The detection limits are in the sub µg/s range. The experimental setup and conditions are presented together with advantages and applications in the field of polymeric research.
Automated Image Analysis for Distortion Compensation in Sequencing Gel Electrophoresis
Authors: Koutny Lance B. , Yeung Edward S.
Published: July 2005

A computerized method is described for correcting systematic distortion of images from slab gel electrophoresis. Such distortions can lead to misinterpretation of the information contained in the gel. The method is useful for data analysis in one-dimension slab gel electrophoresis where the information is manifested in rectangular shaped bands, such as conventional restriction digest or sequencing gels, and the distortions can be adequately described by continuous low-order polynomial functions. The purpose is to eliminate human skill and judgement from the process and to minimize human interaction, which would be useful in any future attempts to automate the analysis of electrophoretic gels.
Optical Considerations for Infrared Reflection Spectroscopic Analysis in the C-H Stretching Region of Monolayer Films at an Aqueous/Metal Interface
Authors: Popenoe Darwin D. , Stole Scott M. , Porter Marc D.
Published: July 2005

This paper describes the optical analysis, construction, testing, and application of a cell for measuring in situ IR reflection spectra in the C-H stretching region of monolayer films of long-chain alkanethiolates on evaporated Au films beneath a thin overlayer (∼1 µm) of aqueous solution. The cell facilitates the interchange of sample (monolayer-coated) and reference substrates—a major improvement over previous designs. This allows the acquisition of an IR reflection spectrum of a monolayer without the application of electrochemical or polarization-modulation methods. The optical properties of the cell are analyzed within the context of classical electromagnetic theory; the effects of angle of incidence, solution layer thickness, and solution composition (H2O and D2O) and the refractive indices of the IR-transparent window material on the observed spectrum are specifically examined. Calculations of both the mean-square electric fields and the reflection spectra for a monolayer of octadecanethiolate on Au are presented. From these results, conditions to achieve high surface detectability are identified, and optically induced alterations in the intensities and shapes of the monolayer spectrum are delineated. Spectra for the same monolayer are measured to test these predictions as well as to assess the practical limitations of the experimental technique.
Analysis of the UV Absorption Band of Cephalosporins
Authors: Vilanova B. , Muñoz F. , Donoso J. , Blanco F. Garcia
Published: July 2005

We studied the absorption spectrum of 7-aminocephalosporanic acid between 312 and 238 nm (32,000–42,000 cm−1) at different pH values. The spectrum was deconvoluted into log-normal curves that showed three different transitions; the first two bands are due to π-π* transitions between the HOMO and LUMO, and from the HOMO to the LUMO + 1, respectively. We also recorded the spectrum of the acid in dioxane/water mixtures and found band I to shift to shorter wavelengths with an increase in the medium polarity. Theoretical calculations allowed us to ascribe this behavior to the fact that the β-lactam nitrogen atom possesses a high electron density in the ground state. As the medium polarity increases, so does the stability of this state, which results in the band being shifted to higher energy values. The theoretical calculations (MNDO) performed yielded 36.8 and 39.8 kK (1 kK = 103 cm−1) for the first two electron transitions, i.e., very close to the experimental values (∼36 and 39 kK).
Surface-Enhanced Raman Spectroscopy at a Silver Electrode as a Real-Time Detector in Flowing Streams
Authors: Pothier Neil J. , Forcé R. Ken
Published: July 2005

An analytical application for Surface-Enhanced Raman Spectroscopy at a silver electrode is described. Real-time SER spectra of adenine and cytosine have been recorded in a 10-µL spectroelectrochemical flow cell under flowing conditions. Charge-coupled-device detection allowed high-quality spectra spanning a ∼1200 cm−1 region to be recorded with integration times of 4 seconds. A low-power He Ne laser was used as a source. SERS at the silver electrode offers rapid time response to adsorption/desorption by appropriate potential modulation. The technique is extremely reproducible and insensitive to temperature and flow rate. The effects of incident photon energy and applied potential on the intensity of the Raman signal are discussed.
Automated On-Line Solid-Phase Extraction Coupled with HPLC for Measurement of 5-Hydroxyindole-3-acetic Acid in Urine
Authors: Mulder Erik J , Oosterloo-Duinkerken Alida , Anderson George M , De Vries Elisabeth GE , Minderaa Ruud B , Kema Ido P
Published: July 2005

Background: Quantification of 5-hydroxyindole-3-acetic acid (5-HIAA) in urine is useful in diagnosing and monitoring of patients with carcinoid tumors and in the study of serotonin (5-hydroxytryptamine) metabolism in various disorders. We describe an automated method that incorporates on-line solid-phase extraction (SPE) and HPLC to measure urinary 5-HIAA.

Methods: Automated prepurification of urine was accomplished with HySphere-resin GP SPE cartridges containing strong hydrophobic polystyrene resin. The analyte (5-HIAA) and internal standard [5-hydroxyindole-3-carboxylic acid (5-HICA)] were eluted from the SPE cartridge, separated by reversed-phase HPLC, and detected fluorometrically with a total cycle time of 20 min. Urinary excretion of 5-HIAA was measured in a group of patients with known and suspected carcinoid tumors (n = 63) and in 20 patients with autism.

Results: The internal standard (5-HICA) and 5-HIAA were recovered in high yields (87.2%–114%). Within- and between-series CVs for the measurement of 5-HIAA in urine ranged from 1.2% to 3.9% and 3.2% to 7.6%, respectively. For urine samples from patients with known or suspected carcinoid tumors, results obtained by the automated method were highly correlated (r = 0.988) with those from an established manual extraction method. For samples from autistic patients, urinary excretion of 5-HIAA was similar to that reported for healthy individuals.

Conclusion: This SPE-HPLC method demonstrated lower imprecision and time per analysis than the manual solvent extraction method.
Abnormal Long-Lasting Synaptic Plasticity and Cognition in Mice Lacking the Mental Retardation GenePak3
Authors: Meng Jinsong , Meng Yanghong , Hanna Amanda , Janus Christopher , Jia Zhengping
Published: July 2005

Mutations in thePak3gene lead to nonsyndromic mental retardation characterized by selective deficits in cognition. However, the underlying mechanisms are yet to be elucidated. We report here that the knock-out mice deficient in the expression of p21-activated kinase 3 (PAK3) exhibit significant abnormalities in synaptic plasticity, specifically hippocampal late-phase long-term potentiation, and deficiencies in learning and memory. A dramatic reduction in the active form of transcription factor cAMP-responsive element-binding protein in the knock-out mice implicates a novel signaling mechanism by which PAK3 and Rho signaling regulate synaptic function and cognition.
Neurocognitive and Psychotiform Behavioral Alterations and Enhanced Hippocampal Long-Term Potentiation in Transgenic Mice Displaying Neuropathological Features of Human α-Mannosidosis
Authors: D'Hooge Rudi , Lüllmann-Rauch Renate , Beckers Tom , Balschun Detlef , Schwake Michael , Reiss Karina , von Figura Kurt , Saftig Paul
Published: July 2005

Mice with α-mannosidase gene inactivation provide an experimental model for α-mannosidosis, a lysosomal storage disease with severe neuropsychological and psychopathological complications. Neurohistological alterations in these mice were similar to those in patients and included vacuolations and axonal spheroids in the CNS and peripheral nervous system. Vacuolation was most prominent and evenly distributed in neuronal perikarya of the hippocampal CA2 and CA3 regions, whereas CA1 and dentate gyrus were weakly or not affected. Field potential recordings from CA1 region in hippocampal slices showed enhanced theta burst-induced long-term potentiation (LTP) in α-mannosidase-deficient mice. Longitudinal assessment in age-matched α-mannosidase-deficient and wild-type littermates, using an extended test battery, demonstrated a neurocognitive and psychotiform profile that may relate to the psychopathological alterations in clinical α-mannosidosis. Brainstem auditory-evoked potentials and basic neuromotor abilities were not impaired and did not deteriorate with age. Exploratory and conflict tests revealed consistent decreases in exploratory activity and emotional blunting in the knock-out group. α-Mannosidosis mice were also impaired in aversively motivated learning and acquisition of signal-shock associations. Acquisition and reversal learning in the water maze task, passive avoidance learning in the step-through procedure, as well as emotional response conditioning in an operant procedure were all impaired. Acquisition or shaping of an appetitive instrumental conditioning task was unchanged. Appetitive odor discrimination learning was only marginally impaired during shaping, whereas both the discrimination and reversal subtasks were normal. We propose that prominent storage and enhanced LTP in hippocampus have contributed to these specific behavioral alterations in α-mannosidase-deficient mice.
Fibroblast Growth Factor 8 Regulates Neocortical Guidance of Area-Specific Thalamic Innervation
Authors: Shimogori Tomomi , Grove Elizabeth A.
Published: July 2005

Thalamic innervation of each neocortical area is vital to cortical function, but the developmental strategies that guide axons to specific areas remain unclear. We took a new approach to determine the contribution of intracortical cues. The cortical patterning molecule fibroblast growth factor 8 (FGF8) was misexpressed in the cortical primordium to rearrange the area map. Thalamic axons faithfully tracked changes in area position and innervated duplicated somatosensory barrel fields induced by an ectopic source of FGF8, indicating that thalamic axons indeed use intracortical positional information. Because cortical layers are generated in temporal order, FGF8 misexpression at different ages could be used to shift regional identity in the subplate and cortical plate either in or out of register. Thalamic axons showed strikingly different responses in the two different conditions, disclosing sources of positional guidance in both subplate and cortical plate. Unexpectedly, axon trajectories indicated that an individual neocortical layer could provide not only laminar but also area-specific guidance. Our findings demonstrate that thalamocortical axons are directed by sequential, positional cues within the cortex and implicate FGF8 as an indirect regulator of thalamocortical innervation.
Voltage-Gated Sodium Channel Nav1.6 Is Modulated by p38 Mitogen-Activated Protein Kinase
Authors: Wittmack Ellen K. , Rush Anthony M. , Hudmon Andy , Waxman Stephen G. , Dib-Hajj Sulayman D.
Published: July 2005

Nav1.6 is the major sodium channel isoform at nodes of Ranvier in myelinated axons and, additionally, is distributed along unmyelinated C-fibers of sensory neurons. Thus, modulation of the sodium current produced by Nav1.6 might significantly impact axonal conduction. Mitogen-activated protein kinases (MAPKs) are expressed in neurons and are activated after injury, for example, after sciatic nerve transection and hypoxia. Although the role of MAPK in signal transduction and in injury-induced regulation of gene expression is well established, the ability of these kinases to phosphorylate and modulate voltage-gated sodium channels has not been reported. Sequence analysis shows that Nav1.6 contains a putative MAP kinase-recognition module in the cytoplasmic loop (L1), which joins domains 1 and 2. We show in this study that sodium channels and p38 MAP kinase colocalize in rat brain tissue and that activated p38α phosphorylates L1 of Nav1.6, specifically at serine 553 (S553),in vitro. None of the other cytoplasmic loops and termini of the channel are phosphorylated by activated p38α in these assays. Activation of p38 in the neuronal ND7/23 cell line transfected with Nav1.6 leads to a significant reduction in the peak Nav1.6 current amplitude, without a detectable effect on gating properties. The substitution of S553 with alanine within L1 of the Nav1.6 channel prevents p38-mediated reduction of Nav1.6 current density. This is the first demonstration of MAPK phosphorylation and modulation of a voltage-gated sodium channel, and this modulation may represent an additional role for MAPK in regulating the neuronal response to injury.
History-Dependent Multiple-Time-Scale Dynamics in a Single-Neuron Model
Authors: Gilboa Gail , Chen Ronen , Brenner Naama
Published: July 2005

History-dependent characteristic time scales in dynamics have been observed at several levels of organization in neural systems. Such dynamics can provide powerful means for computation and memory. At the level of the single neuron, several microscopic mechanisms, including ion channel kinetics, can support multiple-time-scale dynamics. How the temporally complex channel kinetics gives rise to dynamical properties of the neuron is not well understood. Here, we construct a model that captures some features of the connection between these two levels of organization. The model neuron exhibits history-dependent multiple-time-scale dynamics in several effects: first, after stimulation, the recovery time scale is related to the stimulation duration by a power-law scaling; second, temporal patterns of neural activity in response to ongoing stimulation are modulated over time; finally, the characteristic time scale for adaptation after a step change in stimulus depends on the duration of the preceding stimulus. All these effects have been observed experimentally and are not explained by current single-neuron models. The model neuron here presented is composed of an ensemble of ion channels that can wander in a large pool of degenerate inactive states and thus exhibits multiple-time-scale dynamics at the molecular level. Channel inactivation rate depends on recent neural activity, which in turn depends through modulations of the neural response function on the fraction of active channels. This construction produces a model that robustly exhibits nonexponential history-dependent dynamics, in qualitative agreement with experimental results.
Selective Lengthening of the Cell Cycle in the Neurogenic Subpopulation of Neural Progenitor Cells during Mouse Brain Development
Authors: Calegari Federico , Haubensak Wulf , Haffner Christiane , Huttner Wieland B.
Published: July 2005

During embryonic development of the mammalian brain, the average cell-cycle length of progenitor cells in the ventricular zone is known to increase. However, for any given region of the developing cortex and stage of neurogenesis, the length of the cell cycle is thought to be similar in the two coexisting subpopulations of progenitors [i.e., those undergoing (symmetric) proliferative divisions and those undergoing (either asymmetric or symmetric) neuron-generating divisions]. Using cumulative bromodeoxyuridine labeling ofTis21-green fluorescent protein knock-in mouse embryos, in which these two subpopulations of progenitors can be distinguishedin vivo, we now show that at the onset as well as advanced stages of telencephalic neurogenesis, progenitors undergoing neuron-generating divisions are characterized by a significantly longer cell cycle than progenitors undergoing proliferative divisions. In addition, we find that the recently characterized neuronal progenitors dividing at the basal side of the ventricular zone and in the subventricular zone have a longer G2phase than those dividing at the ventricular surface. These findings are consistent with the hypothesis (Calegari and Huttner, 2003) that cell-cycle lengthening can causally contribute to neural progenitors switching from proliferative to neuron-generating divisions and may have important implications for the expansion of somatic stem cells in general.
Netrin-1 Induces Axon Branching in Developing Cortical Neurons by Frequency-Dependent Calcium Signaling Pathways
Authors: Tang Fangjun , Kalil Katherine
Published: July 2005

A single axon can innervate multiple targets by collateral branching. Axon branching is thus essential for establishing CNS connectivity. However, surprisingly little is known about the mechanisms by which branching is regulated. Axons often stop elongating before branches develop and anatomical and molecular data suggest that axon branching occurs independent of axon outgrowth. We found that netrin-1 dramatically increases cortical axon branching. Here, we sought to identify intracellular signaling components involved in netrin-1-induced axon branching. Using live cell imaging of dissociated developing cortical neurons, we show that netrin-1 rapidly increases the frequency of repetitive calcium transients. These transients are often restricted to small regions of the axon. Simultaneous imaging of calcium activity and development of axon branches revealed that Ca2+transients coincide spatially and temporally with protrusion of branches from the axon. Remarkably, fully formed branches with motile growth cones could developde novowithin 20 min. Netrin-1-induced Ca2+transients involve release from intracellular stores and Ca2+signaling is essential for netrin-1-induced axon branching. Using techniques to overexpress or suppress kinase activity, we find that calcium/calmodulin-dependent protein kinase II (CaMKII) and mitogen-activated protein kinase (MAPK) are major downstream targets of the netrin-1 calcium signaling pathway and are required for axon branching. CaMKII, but not MAPK, is also involved in axon outgrowth. The role of CaMKII and MAPKs in axon branching is consistent with the sensitivity of these kinases to changes in the frequency Ca2+transients. Together, these novel findings define calcium signaling mechanisms required for development of new axon branches promoted by a guidance cue.
Ablation of the Inflammatory Enzyme Myeloperoxidase Mitigates Features of Parkinson's Disease in Mice
Authors: Choi Dong-Kug , Pennathur Subramaniam , Perier Celine , Tieu Kim , Teismann Peter , Wu Du-Chu , Jackson-Lewis Vernice , Vila Miquel , Vonsattel Jean-Paul , Heinecke Jay W. , Przedborski Serge
Published: July 2005

Parkinson's disease (PD) is characterized by a loss of ventral midbrain dopaminergic neurons, which can be modeled by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Inflammatory oxidants have emerged as key contributors to PD- and MPTP-related neurodegeneration. Here, we show that myeloperoxidase (MPO), a key oxidant-producing enzyme during inflammation, is upregulated in the ventral midbrain of human PD and MPTP mice. We also show that ventral midbrain dopaminergic neurons of mutant mice deficient in MPO are more resistant to MPTP-induced cytotoxicity than their wild-type littermates. Supporting the oxidative damaging role of MPO in this PD model are the demonstrations that MPO-specific biomarkers 3-chlorotyrosine and hypochlorous acid-modified proteins increase in the brains of MPTP-injected mice. This study demonstrates that MPO participates in the MPTP neurotoxic process and suggests that inhibitors of MPO may provide a protective benefit in PD.
Structural Determinants of α4β2 Nicotinic Acetylcholine Receptor Trafficking
Authors: Ren Xiao-Qin , Cheng Shi-Bin , Treuil Magdalen W. , Mukherjee Jayanta , Rao Jayaraman , Braunewell K. H. , Lindstrom Jon M. , Anand Rene
Published: July 2005

The structural determinants of nicotinic acetylcholine receptor (AChR) trafficking have yet to be fully elucidated. Hydrophobic residues occur within short motifs important for endoplasmic reticulum (ER) export or endocytotic trafficking. Hence, we tested whether highly conserved hydrophobic residues, primarily leucines, in the cytoplasmic domain of the α4β2 AChR subunits were required for cell surface expression of α4β2 AChRs. Mutation of F350, L351, L357, and L358 to alanine in the α4 AChR subunit attenuates cell surface expression of mutant α4β2 AChRs. Mutation of F342, L343, L349, and L350 to alanine at homologous positions in the β2 AChR subunit abolishes cell surface expression of mutant α4β2 AChRs. The hydrophobic nature of the leucine residue is a primary determinant of its function because mutation of L343 to another hydrophobic amino acid, phenylalanine, in the β2 AChR subunit only poorly inhibits trafficking of mutant α4β2 AChR to the cell surface. All mutant α4β2 AChRs exhibit high-affinity binding for [3H]epibatidine. In both tsA201 cells and differentiated SH-SY5Y neural cells, wild-type α4β2 AChRs colocalize with the Golgi marker giantin, whereas mutant α4β2 AChRs fail to do so. The striking difference between mutant α4 versus mutant β2 AChR subunits on cell surface expression of mutant α4β2 AChRs points to a cooperative or regulatory role for the α4 AChR subunit and an obligatory role for the β2 AChR subunit in ER export. Collectively, our results identify, for the first time, residues within AChR subunits that are essential structural determinants of α4β2 AChR ER export.
Loss of Neurons from Laminas I-III of the Spinal Dorsal Horn Is Not Required for Development of Tactile Allodynia in the Spared Nerve Injury Model of Neuropathic Pain
Authors: Polgár Erika , Hughes David I. , Arham Ahmad Z. , Todd Andrew J.
Published: July 2005

It has been proposed that death of inhibitory interneurons in the dorsal horn contributes to the neuropathic pain that follows partial nerve injury. In this study, we have used two approaches to test whether there is neuronal death in the dorsal horn in the spared nerve injury (SNI) model. We performed a stereological analysis of the packing density of neurons in laminas I-III 4 weeks after operation and found no reduction on the ipsilateral side compared with that seen on the contralateral side or in sham-operated or naive rats. In addition, we used two markers of apoptosis, terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) staining and immunocytochemical detection of cleaved (activated) caspase-3. Neither of these methods demonstrated apoptotic neurons in the dorsal spinal cord 1 week after operation. Although TUNEL-positive cells were present throughout the gray and white matter at this stage, they were virtually all labeled with antibody against ionized calcium-binding adapter molecule 1, a marker for microglia. All animals that underwent SNI showed clear signs of tactile allodynia affecting the ipsilateral hindpaw. These results suggest that a significant loss of neurons from the dorsal horn is not necessary for the development of tactile allodynia in the SNI model.
Target-Dependent Use of Coreleased Inhibitory Transmitters at Central Synapses
Authors: Dugué Guillaume P. , Dumoulin Andréa , Triller Antoine , Dieudonné Stéphane
Published: July 2005

Corelease of GABA and glycine by mixed neurons is a prevalent mode of inhibitory transmission in the vertebrate hindbrain. However, little is known of the functional organization of mixed inhibitory networks. Golgi cells, the main inhibitory interneurons of the cerebellar granular layer, have been shown to contain GABA and glycine. We show here that, in the vestibulocerebellum, Golgi cells contact both granule cells and unipolar brush cells, which are excitatory relay interneurons for vestibular afferences. Whereas IPSCs in granule cells are mediated by GABAAreceptors only, Golgi cell inhibition of unipolar brush cells is dominated by glycinergic currents. We further demonstrate that a single Golgi cell can perform pure GABAergic inhibition of granule cells and pure glycinergic inhibition of unipolar brush cells. This specialization results from the differential expression of GABAAand glycine receptors by target cells and not from a segregation of GABA and glycine in presynaptic terminals. Thus, postsynaptic selection of coreleased fast transmitters is used in the CNS to increase the diversity of individual neuronal outputs and achieve target-specific signaling in mixed inhibitory networks.