bluuebunny/crossref_metadata_2025 huggingface dataset:
An Ultraviolet (242 nm Excitation) Resonance Raman Study of Live Bacteria and Bacterial Components
Authors: Dalterio R. A. , Nelson W. H. , Britt D. , Sperry J. F.
Published: July 2005

Ultraviolet-excited (242 nm) resonance Raman spectra have been obtained for the first time for five types of bacteria: Escherichia coli, Pseudomonas fluorescens, Staphylococcus epidermidis, Bacillus subtilis, and Enterobacter cloacae. Detailed, highly reproducible spectra show substantial differences in both the intensities and the energies of peaks, which suggests that such spectra provide unique “fingerprints” reflecting the unique combinations of chemotaxonomic markers present in each type of organism. Many of the spectral features excited by 242-nm radiation probably arise from cellular RNA, DNA, and the amino acids tyrosine and tryptophan. Background fluorescence has been shown to be negligible.
The Use of FT-IR to Characterize Photosensitive Thermosets
Authors: Snyder Randy W. , Yandrasits Michael , Gotro Jeffrey T.
Published: July 2005

Photosensitive polymers are used extensively in the electronics industry to pattern line channels on silicon chips, ceramic substrates, and circuit boards. The photolytic process often requires an ultraviolet light exposure and subsequent bake to produce the required properties, prior to solvent development operations. An in situ FT-IR method was developed to assess the cross-linking reaction induced by UV exposure and investigate the effect of temperature on the overall reaction. The method employs a commercially available heated sample cell holder and an in-house fabricated fiber optic exposure tool. The UV-induced cure reaction was monitored as a function of time. The effect of bake temperature after exposure was also monitored.
The Influence of Solvents on the Fluorescence Background in Raman Spectroscopy
Authors: Higuchi Sciichiro , Yu Er Jie , Tanaka Shigeyuki
Published: July 2005

For the purpose of reducing the fluorescence background induced by the laser irradiation in the measurements of Raman spectra, the influence of solvents on the background intensities for three polycyclic aromatic compounds was examined, where the experiments were conducted with typical solvents. It was demonstrated that the behaviors of the fluorescence background against the laser irradiation time were quite different according to the solvents, and that the behaviors could be classified roughly into the three categories. It was proved that when suitable solvents were used, the background intensities could be reduced sufficiently, even for the fluorescent samples such as those treated here; thus, the clear observation of Raman spectra is obtained. As an example of the solvent influence on the Raman spectra, the results of measurements for three separate cases were shown for 1-nitropyrene. The three cases are as follows: first, the Raman bands are masked almost completely by the strong background (solvent: 1,1,2,2-tetrachloroethane); second, though the spectrum can be obtained, its S/N ratio is low because of the relatively large background (solvent: acetonitrile); third, a clear spectrum with excellent S/N ratio can be obtained because the background intensity is low enough (solvent: carbon tetrachloride).
Feasibility of Quantitative UV Resonance Raman Spectroscopy with a KrF Excimer Laser
Authors: Lin Liang-Tsair , Mann Charles K. , Vickers Thomas J.
Published: July 2005

The feasibility of quantitative resonance Raman spectroscopy with a KrF excimer laser providing primary radiation at 249 nm has been examined. The instrumentation is described, and results are reported for measurements with a photomultiplier detector and scanning monochromator. Considerations affecting the success of the internal standardization are described. A least-squares fitting procedure is employed for quantifying the overlapped analyte and internal standard spectral lines. Instrumental detection limits of 2.2, 1.2, and 1.0 mg/L are reported for anthracene, 9-methylanthracene, and 2-methylanthracene, respectively, for spectra obtained with 120 laser pulses per step. Detection limits in the low ppb range are projected for a system employing an intensified diode array detector.
Background Correction in Multicomponent Spectroscopic Analysis Using Target Transformation Factor Analysis
Authors: Gemperline Paul J. , Boyette Stacey E. , Tyndall Kimberly
Published: July 2005

A principal components regression (PCR) is used to construct a calibration matrix for multicomponent spectroscopic analysis which corrects for background absorption due to variable concentrations of unknown species in a sample matrix. Mixed standards are used in the method, and spectra of the pure background components are not needed. The background correction capability of the method is demonstrated with the use of the UV spectra of aqueous standards prepared from cobalt (II) nitrate and nickel (II) nitrate. Known concentrations of chromium (III) nitrate were added to simulate a background which gave rise to relative concentration errors as high as 70% without the background correction capabilities of the method. With the background correction capabilities of the method, the relative concentration errors were reduced to less than one percent. Preliminary results are presented from an application of PCR to determine the concentration of two active ingredients in a pharmaceutical product in the presence of weakly absorbing tablet excipient materials.
Absolute Light Scattering Calibration of the Stopped-Flow Spectrophotometer with Application to the Kinetics of Formation of Monodispersed Colloidal Hematite
Authors: Hsu Wan Peter , Patel Ramesh C. , Matijevic Egon
Published: July 2005

A calibration method based on absolute intensities of scattered light from colloidal silica was developed to standardize the stopped-flow temperature jump spectrophotometer (SFTJ). The need for such calibration was exemplified by the study of the temperature effect on the Rayleigh ratio changes during the formation of solid iron (hydrous) oxides.
Resonant Two-Photon Ionization in Biomolecules Using Laser Desorption in Supersonic Beam-Mass Spectrometry
Authors: Tembreull Roger , Lubman David M.
Published: July 2005

Resonant two-photon ionization (R2PI) has been demonstrated for several classes of biomolecules in a supersonic jet. These thermally labile and nonvolatile species have been vaporized with pulsed laser desorption, with the use of a CO2 laser from a ceramic surface with subsequent entrapment in a jet expansion. R2PI is then demonstrated in a time-of-flight mass spectrometer (TOFMS) with the use of ultraviolet laser radiation at either 280 or 266 nm. The 280-nm wavelength is found to be a fairly general tool for exciting the π-π* transition of the molecules under study, viz., metabolites of catecholamines, indoleamines, and tyrosine near their respective origin regions. The resulting mass spectra exhibit soft ionization where either molecular ions or minimal fragmentation is produced. At frequencies of much higher energy than that of the origin, fragmentation becomes increasingly difficult to prevent.
Raman Measurements in the Presence of Fluorescence
Authors: Mann Charles K. , Vickers Thomas J.
Published: July 2005

A method for eliminating the direct effects of fluorescence on Raman spectra is described. It is based upon the differences in widths of Raman and fluorescence peaks and is intended for applications of Raman measurements in chemical analysis. It involves only calculations that are carried out after the measurement has been made and does not require any instrumental enhancement beyond that normally used for Raman measurements. The extent of improvement that can be expected is shown, and the conditions under which its limits are reached are indicated. A technique involving an empirical correction is described which allows extension of these limits in certain cases.
Diffuse Reflectance FT-IR Analysis of Rosin Flux-Metal Oxide Interactions
Authors: Snyder Randy W.
Published: July 2005

The use of diffuse reflectance Fourier transform-infrared spectroscopy for the analysis of rosin flux residues on metal oxide powders, after exposure to high-temperature soldering conditions, is examined. The flux is shown to solvate some metal ions to form metal-carboxylate salt complexes. The ability of nonactivated rosin flux to remove possible corrosion products of copper-tin/lead solder joint areas is discussed.
A New Baseline Correction Algorithm Using Objective Criteria
Authors: Liu Juwhan , Koenig Jack L.
Published: July 2005

A baseline correction algorithm using a least-squares procedure is developed. Linear or quadratic types of baselines are obtained through successive fitting and rejection of data points on a statistical basis. After the entire spectrum or a subsection is fitted to a least-squares line, the standard error of estimate is utilized as a criterion to determine if the fluctuation of each data point about the line can be thought of as the baseline fluctuation. Comments on various baseline correction procedures are also made.
The Spectropus™ System: Remote Sampling Accessories for Reflectance, Emission, and Transmission Analysis Using Fourier Transform Infrared Spectroscopy
Authors: Powell G. L. , Milosevic M. , Lucania J. , Harrick N. J.
Published: July 2005

The Spectropus™ system,‡ a versatile optical sampling system for performing infrared spectroscopic analyses on remotely located samples with little regard to their size and with spectral quality and sampling rates comparable to, or better than, those achievable with spectrometer sample compartment accessories, is described. The Spectropus™ uses a “glass-tube beam-line” optical transfer system for delivering the collimated beam of an FT-IR spectrometer to one of several dedicated accessories, complete with its own detector, that may be located several meters distance from the spectrometer. The accessories include the barrel ellipsoid diffuse reflectance and emission accessory, the grazing-incidence external reflection accessory, and the gas analysis accessory. One system described here supports up to four accessories in laboratory air and another supports two accessories in two different glove boxes. Application examples include the monitoring of the formation of LiOH and LiOD on LiH and LiD in glove boxes as a result of moisture corrosion; the analysis of ink stains on paper; the analysis of inks, parylene films, and oil stains on metals; the analysis, with monolayer resolution, of oxides on aluminum foil and on uranium being oxidized in air; the analysis of wood and of graphite-epoxy composites, including the rapid sequential determination of diffuse reflectance and emission spectra from one point on one sample; and sub-part-per-million gas analyses using an evacuated cell reference spectrum that is free of pressurization stress artifacts.
Evolving Factor Analysis for Frequency-Domain Lifetime Resolution of Fluorescence Spectra
Authors: Millican David W. , McGown Linda B.
Published: July 2005

Evolving factor analysis (EFA) is a new approach to the resolution of individual component spectra on the basis of fluorescence lifetime differences. Phase-resolved fluorescence spectra collected at several excitation modulation frequencies are well suited to EFA resolution because the frequency-response curve of phase-resolved intensity for each lifetime component has a single, unique maximum. Unlike other self-modeling spectral matrix resolution methods, EFA has no fundamental limitation upon the number of components that can be resolved. In this work, the resolution of two-component and three-component mixtures of polycyclic aromatic hydrocarbons is demonstrated.
Optical Determination of the Temperature of Transparent Microparticles
Authors: Vehring R. , Schweiger G.
Published: July 2005

We present a noncontact temperature-sensing method for microdroplets of water, which relies on temperature dependence of the OH stretching band of the spontaneous Raman spectrum. Temperatures of freely moving evaporating droplets with mean particle diameters of approximately 35 µm have been measured with an accuracy of ±1°C in the range from 10 to 65°C. The method allows the observation of droplet cooling during the initial unsteady phase of evaporation.
Locally Weighted Regression in Diffuse Near-Infrared Transmittance Spectroscopy
Authors: Næs Tormod , Isaksson Tomas
Published: July 2005

This paper presents an application of locally weighted regression (LWR) in diffuse near-infrared transmittance spectroscopy. The data are from beef and pork samples. The LWR method is based on the idea that a nonlinearity can be approximated by local linear equations. Different weight functions (for the samples) as well as different distance measures for “closeness” are tested. The LWR is compared to principal component regression and partial least-squares regression. The LWR with weighted principal components is shown to give the best results. The improvements with respect to linear regression are up to 15% of the prediction errors.
Current Sensitivity of Plasma Voltage and Emission Line Intensities in a Planar Magnetron Glow Discharge Device
Authors: McCaig Lori , Sacks Richard
Published: July 2005

A coaxial arrangement of a ring-shaped ceramic magnet and a disk-shaped rare-earth magnet is used to trap plasma electrons in circular orbits near the surface of the planar cathode. This configuration results in the formation of a ring-shaped plasma which is stable at all pressures in the range 0.0007 Torr to over 10 Torr. A model is presented which describes the sensitivities of plasma emission intensities to the discharge current for atoms and ions of both the plasma gas and the sputtered flux of cathodic material. The model is based on the number of electron collisions needed to generate the radiating species. Experimental data for the species Ar, Ar+, Cu, and Cu+ are compared to the model.
Batch Injection Analysis Using Fiber-Optic Fluorometric Detection
Authors: Wang J. , Rayson G. D. , Taha Z.
Published: July 2005

Fluorometric detection of analytes using batch injection analysis (BIA) has been investigated. BIA involves the injection of microliter samples toward a nearby detector which is immersed in a large-volume, nonflowing, blank solution. The characteristics and advantages of employing fiber-optic fluorometric detection for BIA are described. Similar to analogous flow injection measurements, batch injection fluorometric analysis offers high speed, reproducibility and simplicity, while eliminating the need for pumps, valves, and associated tubings. With injection rates at 120–500 samples/h, there is no observable carryover, and the precision is typically 2–3% (RSD).
Analysis of Aerosol Particles by Resonance Raman Scattering Technique
Authors: Fung K. H. , Tang I. N.
Published: July 2005

An analytical technique for aerosol samples which utilizes the resonance Raman effect is described. The aerosol particles were generated at 50 kHz by a vibrating orifice. The nominal particle size was 45 µm in diameter. The visible lines (4579, 4765, 4880, and 5145 Å) of a continuous argon-ion laser were used as the excitation source. Within the coverage of the laser wavelengths, effects of pre-resonance, resonance, and post-resonance Raman scattering were studied. Under the resonance condition, the enhancement of p-nitrosodimethylaniline is 5.5 × 104 when compared to that of nitrate ions. The corresponding concentration of detection limit is 10−6 molar.
Near-Infrared Analysis of Chemical Constituents and Physical Characteristics of Polymers
Authors: Zhu Chu , Hieftje Gary M.
Published: July 2005

The polybutylene terephthalate (PBT) concentration and intrinsic viscosity of polycarbonate (PC) polymer blends were determined by means of near-infrared (NIR) reflectance and absorption spectrometry coupled with multiple regression analysis. The cross-search method was used in the selection of analytical wavelengths, whereas the correctness of the determinations was confirmed by cross validation. The correlation coefficients between the reference and NIR-determined values for the reflectance and absorption techniques were 0.979 and 0.955, respectively. The apparent number of orthogonal degrees of freedom in the polymer standards was affected by the number of samples employed in the NIR regression analysis.
Effects of Data Sampling Rate on Pattern Recognition Analysis of FT-IR Interferograms
Authors: Small Gary W. , Carpenter Scott E.
Published: July 2005

Fourier transform infrared (FT-IR) data of pure and mixture samples of benzene and nitrobenzene are used to investigate and improve methods for interferogram-based qualitative analyses. For use in dedicated monitoring applications, the methodology employed is based on the application of pattern recognition analysis to short, digitally filtered interferogram segments. In the work described here, the impact of the interferogram data sampling rate on the analysis is studied. The results of this study indicate that optimal pattern recognition prediction performance is achieved by use of linear discriminants developed from faster sampled interferogram data. These findings suggest that improved performance can be obtained in FT-IR monitoring applications through the use of spectrometer designs based on a decreased interferogram scan length, coupled with faster sampling electronics.
Polarization-Modulation Emission FT-IR Measurement of Thin Organic Films on Metal Surfaces
Authors: Tochigi Kenji , Momose Hideto , Misawa Yutaka , Suzuki Takaya
Published: July 2005

A polarization-modulation technique has been combined with Fourier transform infrared (FT-IR) spectrometry to eliminate the large background radiation which interferes with the infrared emission from thin organic films on metal surfaces. A step scan and a continuous scan interferometer which were combined with a photoelastic modulator were also studied, and the step scan system was found to be stabler and have a better S/N. The spectrum of a 12-nm perfluoropolyether film was obtained at 120°C by this system.
Characteristics of a Kilowatt-Plus Helium Microwave-Induced Plasma Utilizing 2- and 3-cm-Depth TM010 Resonator Cavities
Authors: Wu Mingin , Carnahan Jon W.
Published: July 2005

A kilowatt-plus microwave-induced plasma (KiP-MIP) system was modified for better analytical performance. Modifications included the use of a redesigned plasma torch and a new plasma resonator cavity. The use of the redesigned plasma torch improved the detection of aqueous chloride by 2 orders of magnitude. With the redesigned plasma torch, the performance of the KiP-MIP utilizing the original 3-cm-depth and 2-cm-depth resonator cavities were studied. Results indicated that the KiP-MIP with the 2-cm-depth resonator cavity exhibited better characteristics in terms of plasma energy coupling, excitation characteristics, and determination of aqueous chloride.
Chemically Prepared Silver/Alumina Substrate for Surface-Enhanced Raman Scattering
Authors: Li Ying-Sing , Wang Yu
Published: July 2005

A new silver-coated alumina/glass substrate was prepared by a chemical reduction method at room temperature. The substrate was found to exhibit strong surface-enhanced scatterings for crystal violet (CV), p-nitrophenol (PNP), p-nitrobenzoic acid (PNBA), and pyrene. Optimization of silver deposition time was achieved by using CV as an analyte. Lower limits of detection were determined for these compounds to demonstrate the analytical potential of the new substrate. Enhancement factors of ∼106 and ∼107 were determined from comparisons of the surface-enhanced Raman scattering (SERS) intensities of mono-molecular layers with the normal Raman intensities for PNP and PNBS, respectively. Three different methods of sample applications were adapted and tested. The reusability of the substrates was tested by recording the surface-enhanced resonance Raman scattering (SERRS) spectra of CV at different conditions.
An Evaluation of the Variable-Exit-Angle Ultrasoft X-Ray Fluorescence Technique as Applied to Ni/Fe Thin-Film Multilayers
Authors: Scimeca T. , Andermann G.
Published: July 2005

The variable-exit-angle ultrasoft x-ray fluorescence technique has been evaluated for Ni/Fe thin-film multilayers. The theoretical and experimental agreement is reasonable. The experimental results demonstrate that on these Ni/Fe samples quantitative information can be obtained in the presence of surface contamination.
Effect of l-Carnitine on Acetyl-CoA Content and Activity of Blood Platelets in Healthy and Diabetic Persons
Authors: Michno Anna , Raszeja-Specht Anna , Jankowska-Kulawy Agnieszka , Pawełczyk Tadeusz , Szutowicz Andrzej
Published: July 2005

Background: Excessive blood platelet activity contributes to vascular complications in diabetic persons. Increased acetyl-CoA in platelets from diabetic persons has been suggested to be a cause of this hyperactivity. We therefore investigated whether l-carnitine, which up-regulates metabolism of acetyl-CoA in muscles and brain, may affect platelet function in healthy and diabetic individuals.

Methods: We obtained platelets from healthy and diabetic persons and measured acetyl-CoA concentrations, malonyl dialdehyde (MDA) synthesis, and platelet aggregation in the absence and presence of l-carnitine. Activities of selected enzymes involved in glucose and acetyl-CoA metabolism were also assessed.

Results: Fasting glucose, fructosamine, and hemoglobin A1c were present in significantly higher amounts in the blood of diabetic patients than in healthy individuals. Activities of carnitine acetyltransferase, glucose-6-phosphate dehydrogenase, oxoglutarate dehydrogenase, and fatty acid synthase were 17%–62% higher in platelets from diabetic patients. Mitochondrial acetyl-CoA was increased by 98% in platelets from diabetic patients, MDA synthesis was increased by 73%, and platelet aggregation by 60%. l-Carnitine had no or only a slight effect on these indices in platelets from healthy individuals, but in platelets from diabetic patients, l-carnitine caused a 99% increase in acetyl-CoA in the cytoplasmic compartment along with increases in MDA synthesis and platelet aggregation.

Conclusions: Excessive platelet activity in persons with diabetes may result from increased acetyl-CoA, which apparently increases synthesis of lipid activators of platelet function. l-Carnitine may aggravate platelet hyperactivity in diabetic persons by increasing the provision of surplus acetyl-CoA to the cytoplasmic compartment.
Identification and Quantification of 8 Sulfonylureas with Clinical Toxicology Interest by Liquid Chromatography–Ion-Trap Tandem Mass Spectrometry and Library Searching
Authors: Hoizey Guillaume , Lamiable Denis , Trenque Thierry , Robinet Arnaud , Binet Laurent , Kaltenbach Matthieu L , Havet Sandrine , Millart Hervé
Published: July 2005

Background: Identification of sulfonylureas in blood may be useful in the evaluation of hypoglycemic crises of unknown origin. The aim of the present study was to develop a highly selective liquid chromatography–electrospray tandem mass spectrometry (MS-MS) method using an ion-trap detector for rapid screening, identification, and quantification of sulfonylureas in human plasma.

Methods: After standard liquid–liquid extraction with glisoxepide as an internal standard, 8 sulfonylureas (glibenclamide, glipizide, gliclazide, glibornuride, glimepiride, carbutamide, chlorpropamide, and tolbutamide) were eluted from a C18 column within 10 min with an isocratic mobile phase. Drugs were identified and quantified in full-scan MS-MS mode by use of a homemade MS-MS library. We used the assay in 134 cases of hypoglycemic crises of unknown origin.

Results: No ion suppression effect was noted for the analytes at their specific retention-time windows. For all drugs, assay validation showed good linearity (r2 >0.990) and acceptable imprecision and recovery based on commonly used criteria of acceptance. The mean extraction recoveries were 63%–87% for 5 sulfonylureas but <45% for 3 (carbutamide, chlorpropamide, and tolbutamide). Nevertheless, the high sensitivity of the MS instrument made possible detection and quantification of all 8 drugs at subtherapeutic to toxic concentrations with good precision. Sulfonylureas were found in 9 hypoglycemic patients.

Conclusion: The described assay method allows accurate, rapid identification and quantification of 8 sulfonylureas in human plasma and can be used for specific diagnosis of factitious hypoglycemia caused by ingestion of these drugs.
Molecular Control of Physiological and Pathological T-Cell Recruitment after Mouse Spinal Cord Injury
Authors: Jones T. Bucky , Hart Ronald P. , Popovich Phillip G.
Published: July 2005

The intraspinal cues that orchestrate T-cell migration and activation after spinal contusion injury were characterized using B10.PL (wild-type) and transgenic (Tg) mice with a T-cell repertoire biased toward recognition of myelin basic protein (MBP). Previously, we showed that these strains exhibit distinct anatomical and behavioral phenotypes. In Tg mice, MBP-reactive T-cells are activated by spinal cord injury (SCI), causing more severe axonal injury, demyelination, and functional impairment than is found in non-Tg wild-type mice (B10.PL). Conversely, despite a robust SCI-induced T-cell response in B10.PL mice, no overt T-cell-mediated pathology was evident. Here, we show that chronic intraspinal T-cell accumulation in B10.PL and Tg mice is associated with a dramatic and sustained increase in CXCL10/IP-10 and CCL5/RANTES mRNA expression. However, in Tg mice, chemokine mRNA were enhanced 2- to 17-fold higher than in B10.PL mice and were associated with accelerated intraspinal T-cell influx and enhanced CNS macrophage activation throughout the spinal cord. These data suggest common molecular pathways for initiating T-cell responses after SCI in mice; however, if T-cell reactions are biased against MBP, molecular and cellular determinants of neuroinflammation are magnified in parallel with exacerbation of neuropathology and functional impairment.
Selective Disruption of Nucleus Accumbens Gating Mechanisms in Rats Behaviorally Sensitized to Methamphetamine
Authors: Brady Anne Marie , Glick Stanley D. , O'Donnell Patricio
Published: July 2005

Behavioral sensitization of psychostimulant-induced locomotor activity in rats has been proposed as a model of addiction and is accompanied by neuroadaptations in the nucleus accumbens and related circuits. Here, we usedin vivointracellular recordings to examine electrophysiological properties of accumbens neurons from animals that did or did not exhibit behavioral sensitization after repeated methamphetamine (5.0 mg/kg; 5 d). Although spontaneous activity of accumbens neurons was virtually unchanged, multiple synaptic interactions controlling membrane potential states were disrupted in sensitized animals. For example, stimulation of the ventral tegmental area attenuated accumbens responses to prefrontal cortex activation in nonsensitized and saline-treated animals, but not in sensitized animals. Acute methamphetamine (0.5 mg/kg) abolished accumbens up and down states in nonsensitized and saline-treated animals, suggesting a disruption of normal information processing in this area. However, acute methamphetamine failed to affect this pattern in accumbens neurons from sensitized animals. These results suggest that both acute and repeated methamphetamine administration can disrupt synaptic interactions in the nucleus accumbens; however, the nature of these alterations depends critically on the extent of behavioral sensitization. It is speculated that the response to acute methamphetamine in nonsensitized and saline-treated animals may be functionally adaptive, whereas the neuroadaptations observed in sensitized animals may be maladaptive and detrimental to accumbens information processing.
Physiological Role for Casein Kinase 1 in Glutamatergic Synaptic Transmission
Authors: Chergui Karima , Svenningsson Per , Greengard Paul
Published: July 2005

Casein kinase 1 (CK1) is a highly conserved serine/threonine kinase, present in virtually all cell types, in which it phosphorylates a wide variety of substrates. So far, no role has been found for this ubiquitous protein kinase in the physiology of nerve cells. In the present study, we show that CK1 regulates fast synaptic transmission mediated by glutamate, the major excitatory neurotransmitter in the brain. Through the use of CK1 inhibitors, we present evidence that activation of CK1 decreases NMDA receptor activity in the striatum via a mechanism that involves activation by this kinase of protein phosphatase 1 and/or 2A and resultant increased dephosphorylation of NMDA receptors. Indeed, inhibition of CK1 increases NMDA-mediated EPSCs in medium spiny striatal neurons. This effect is associated with an increased phosphorylation of the NR1 and NR2B subunits of the NMDA receptor and is occluded by the phosphatase inhibitor okadaic acid. The mGluR1, but not mGluR5, subclass of metabotropic glutamate receptors uses CK1 to inhibit NMDA-mediated synaptic currents. These results provide the first evidence for a role of CK1 in the regulation of synaptic transmission in the brain.
Rat Adrenal Chromaffin Cells Are Neonatal CO2Sensors
Authors: Muñoz-Cabello Ana M. , Toledo-Aral Juan J. , López-Barneo José , Echevarría Miriam
Published: July 2005

We studied the participation of adrenal medulla (AM) chromaffin cells in hypercapnic chemotransduction. Using amperometric recordings, we measured catecholamine (CAT) secretion from cells in AM slices of neonatal and adult rats perfused with solutions bubbled with different concentrations of CO2. The secretory activity augmented from 1.74 ± 0.19 pC/min at 5% CO2to 6.36 ± 0.77 pC/min at 10% CO2. This response to CO2was dose dependent and appeared without changes in extracellular pH, although it was paralleled by a drop in intracellular pH. Responsiveness to hypercapnia was higher in neonatal than in adult slices. The secretory response to hypercapnia required extracellular Ca2+influx. Both the CO2-induced internal pH drop and increase in CAT secretion were markedly diminished by methazolamide (2 μm), a membrane-permeant carbonic anhydrase (CA) inhibitor. We detected the presence of two CA isoforms (CAI and CAII) in neonatal AM slices byin situhybridization and real-time PCR. The expression of these enzymes decreased in adult AM together with the disappearance of responsiveness to CO2. In patch-clamped chromaffin cells, hypercapnia elicited a depolarizing receptor potential, which led to action potential firing, extracellular Ca2+influx, and CAT secretion. This receptor potential (inhibited by methazolamide) was primarily attributable to activation of a resting cationic conductance. In addition, voltage-gated K+current amplitude was also decreased by high CO2. The CO2-sensing properties of chromaffin cells may be of physiologic relevance, particularly for the adaptation of neonates to extrauterine life, before complete maturation of peripheral and central chemoreceptors.
State-Dependent Alterations in Hippocampal Oscillations in Serotonin 1A Receptor-Deficient Mice
Authors: Gordon Joshua A. , Lacefield Clay O. , Kentros Clifford G. , Hen Rene
Published: July 2005

Mice lacking the serotonin 1A receptor (5-HT1AR) show increased levels of anxiety-related behavior across multiple tests and background strains. Tissue-specific rescue experiments, lesion studies, and neurophysiological findings all point toward the hippocampus as a potential mediator of the phenotype. Serotonin, acting through 5-HT1ARs, can suppress hippocampal theta-frequency oscillations, suggesting that theta oscillations might be increased in the knock-outs. To test this hypothesis, local field potential recordings were obtained from the hippocampus of awake, behaving knock-outs and wild-type littermates. The magnitude of theta oscillations was increased in the knock-outs, specifically in the anxiety-provoking elevated plus maze and not in a familiar environment or during rapid eye movement sleep. Theta power correlated with the fraction of time spent in the open arms, an anxiety-related behavioral variable. These results suggest a possible role for the hippocampus, and theta oscillations in particular, in the expression of anxiety in 5-HT1AR-deficient mice.
Modeling Cooperative Volume Signaling in a Plexus of Nitric Oxide Synthase-Expressing Neurons
Authors: Philippides Andrew , Ott Swidbert R. , Husbands Philip , Lovick Thelma A. , O'Shea Michael
Published: July 2005

In vertebrate and invertebrate brains, nitric oxide (NO) synthase (NOS) is frequently expressed in extensive meshworks (plexuses) of exceedingly fine fibers. In this paper, we investigate the functional implications of this morphology by modeling NO diffusion in fiber systems of varying fineness and dispersal. Because size severely limits the signaling ability of an NO-producing fiber, the predominance of fine fibers seems paradoxical. Our modeling reveals, however, that cooperation between many fibers of low individual efficacy can generate an extensive and strong volume signal. Importantly, the signal produced by such a system of cooperating dispersed fibers is significantly more homogeneous in both space and time than that produced by fewer larger sources. Signals generated by plexuses of fine fibers are also better centered on the active region and less dependent on their particular branching morphology. We conclude that an ultrafine plexus is configured to target a volume of the brain with a homogeneous volume signal. Moreover, by translating only persistent regional activity into an effective NO volume signal, dispersed sources integrate neural activity over both space and time. In the mammalian cerebral cortex, for example, the NOS plexus would preferentially translate persistent regional increases in neural activity into a signal that targets blood vessels residing in the same region of the cortex, resulting in an increased regional blood flow. We propose that the fineness-dependent properties of volume signals may in part account for the presence of similar NOS plexus morphologies in distantly related animals.
Mitochondrial Nitric Oxide Mediates Decreased Vulnerability of Hippocampal Neurons from Immature Animals to NMDA
Authors: Marks Jeremy D. , Boriboun Chan , Wang Janice
Published: July 2005

Mitochondrial membrane potential (ΔΨm)-dependent Ca2+uptake plays a central role in neurodegeneration after NMDA receptor activation. NMDA-induced ΔΨmdissipation increases during postnatal development, coincident with increasing vulnerability to NMDA. NMDA receptor activation also produces nitric oxide (NO), which can inhibit mitochondrial respiration, dissipating ΔΨm. Because ΔΨmdissipation reduces mitochondrial Ca2+uptake, we hypothesized that NO mediates the NMDA-induced ΔΨmdissipation in immature neurons, underlying their decreased vulnerability to excitotoxicity. Using hippocampal neurons cultured from 5- and 19-d-old rats, we measured NMDA-induced changes in [Ca2+]cytosol, ΔΨm, NO, and [Ca2+]mito. In postnatal day 5 (P5) neurons, NMDA mildly dissipated ΔΨmin a NO synthase (NOS)-dependent manner and increased NO. The NMDA-induced NO increase was abolished with carbonyl cyanide 4-(trifluoromethoxy)phenyl-hydrazone and regulated by [Ca2+]mito. Mitochondrial Ca2+uptake inhibition prevented the NO increase, whereas inhibition of mitochondrial Ca2+extrusion increased it. Consistent with this mitochondrial regulation, NOS and cytochrome oxidase immunoreactivity demonstrated mitochondrial localization of NOS. Furthermore, NOS blockade increased mitochondrial Ca2+uptake during NMDA. Finally, at physiologic O2tensions (3% O2), NMDA had little effect on survival of P5 neurons, but NOS blockade during NMDA markedly worsened survival, demonstrating marked neuroprotection by mitochondrial NO. In P19 neurons, NMDA dissipated ΔΨmin an NO-insensitive manner. NMDA-induced NO production was not regulated by ΔΨm, and NOS immunoreactivity was cytosolic, without mitochondrial localization. NOS blockade also protected P19 neurons from NMDA. These data demonstrate that mitochondrial NOS mediates much of the decreased vulnerability to NMDA in immature hippocampal neurons and that cytosolic NOS contributes to NMDA toxicity in mature neurons.
Expression of Mutant NMDA Receptors in Dopamine D1Receptor-Containing Cells Prevents Cocaine Sensitization and Decreases Cocaine Preference
Authors: Heusner Carrie L. , Palmiter Richard D.
Published: July 2005

The interaction of dopamine and glutamate in limbic brain regions mediates behaviors associated with psychostimulants, which act in part to increase dopamine signaling at both D1receptors (D1Rs) and D2receptors. Many addictive behaviors are a result of learned associations, and NMDA receptor activation has been shown to be important for these behaviors. We hypothesized that if NMDA receptor activation in dopamine receptor-containing cells is required for the addictive properties of psychostimulants, then mice with reduced NMDA receptor activity in D1R-containing cells would have attenuated long-term behavioral changes to these drugs. We generated a mouse line in which D1R-containing cells express an NR1 NMDA receptor subunit containing a mutation in the pore that reduces calcium flux. Mice expressing the mutant NMDA receptors in D1R-containing cells have normal basal activity and display similar increases in locomotor activity when treated with acute amphetamine or cocaine. However, the mutant mice fail to display locomotor sensitization to repeated cocaine administration. In addition, these mice also have a decreased ability to form a conditioned place preference to cocaine. These data suggest that intact NMDA receptor signaling in D1R-containing cells is required for the manifestation of behaviors associated with repeated drug exposure.
Tyrosine 394 Is Phosphorylated in Alzheimer's Paired Helical Filament Tau and in Fetal Tau with c-Abl as the Candidate Tyrosine Kinase
Authors: Derkinderen Pascal , Scales Timothy M. E. , Hanger Diane P. , Leung Kit-Yi , Byers Helen L. , Ward Malcolm A. , Lenz Christof , Price Caroline , Bird Ian N. , Perera Timothy , Kellie Stuart , Williamson Ritchie , Noble Wendy , Van Etten Richard A. , Leroy Karelle , Brion Jean-Pierre , Reynolds C. Hugh , Anderton Brian H.
Published: July 2005

Tau is a major microtubule-associated protein of axons and is also the principal component of the paired helical filaments (PHFs) that comprise the neurofibrillary tangles found in Alzheimer's disease and other tauopathies. Besides phosphorylation of tau on serine and threonine residues in both normal tau and tau from neurofibrillary tangles, Tyr-18 was reported to be a site of phosphorylation by the Src-family kinase Fyn. We examined whether tyrosine residues other than Tyr-18 are phosphorylated in tau and whether other tyrosine kinases might phosphorylate tau. Using mass spectrometry, we positively identified phosphorylated Tyr-394 in PHF-tau from an Alzheimer brain and in human fetal brain tau. When wild-type human tau was transfected into fibroblasts or neuroblastoma cells, treatment with pervanadate caused tau to become phosphorylated on tyrosine by endogenous kinases. By replacing each of the five tyrosines in tau with phenylalanine, we identified Tyr-394 as the major site of tyrosine phosphorylation in tau. Tyrosine phosphorylation of tau was inhibited by PP2 (4-amino-5-(4-chlorophenyl-7-(t-butyl)pyrazolo[3,4-d]pyrimidine), which is known to inhibit Src-family kinases and c-Abl. Cotransfection of tau and kinases showed that Tyr-18 was the major site for Fyn phosphorylation, but Tyr-394 was the main residue for Abl.In vitro, Abl phosphorylated tau directly. Abl could be coprecipitated with tau and was present in pretangle neurons in brain sections from Alzheimer cases. These results show that phosphorylation of tau on Tyr-394 is a physiological event that is potentially part of a signal relay and suggest that Abl could have a pathogenic role in Alzheimer's disease.
Discharge of Identified Orexin/Hypocretin Neurons across the Sleep-Waking Cycle
Authors: Lee Maan Gee , Hassani Oum K. , Jones Barbara E.
Published: July 2005

Although maintained by multiple arousal systems, wakefulness falters if orexin (hypocretin), orexin receptors, or orexin neurons are deficient; narcolepsy results with hypersomnolence or sudden onset of rapid eye movement sleep [or paradoxical sleep (PS)] and loss of muscle tonus. To learn how orexin neurons maintain wakefulness, we recorded neurons in head-fixed rats across the sleep-waking cycle and then labeled them with Neurobiotin to identify them by immunohistochemistry. We show that identified orexin neurons discharge during active waking, when postural muscle tone is high in association with movement, decrease discharge during quiet waking in absence of movement, and virtually cease firing during sleep, when postural muscle tone is low or absent. During PS, they remain relatively silent in association with postural muscle atonia and most often despite phasic muscular twitches. They increase firing before the end of PS and thereby herald by several seconds the return of waking and muscle tone. The orexin neurons would thus stimulate arousal, while antagonizing sleep and muscle atonia.
Different Functional Types of Bipolar Cells Use Different Gap-Junctional Proteins
Authors: Lin Bin , Jakobs Tatjana C. , Masland Richard H.
Published: July 2005

Rod signals are transmitted to ON retinal ganglion cells by means of gap junctions between AII amacrine cells and ON bipolars. The AII amacrine cells are known to express connexin36 (Cx36), but previous studies of Cx36 in ON cone bipolars have been ambiguous. Here, we studied bipolar cells in a transgenic mouse line that expresses high levels of green fluorescent protein (GFP) in one type of ON cone bipolar cell. We found strong Cx36 immunostaining in the axon terminals of the GFP-labeled type 357 bipolar cells in both vertical sections and whole mounts of the retina. This finding was confirmed by single-cell immunostaining and single-cell reverse transcription-PCR (RT-PCR). As reported previously (Maxeiner et al., 2005), Cx45 was found in some ON bipolar cells, but RT-PCR showed Cx36 and not Cx45 to be expressed by the type 357 bipolar cells. Some of the remaining GFP-negative bipolar cells expressed Cx45 but not Cx36. It appears that different types of ON cone bipolar cells express different connexins at their gap junctions with AII amacrine cells.
Evaluating the Operations Underlying Multisensory Integration in the Cat Superior Colliculus
Authors: Stanford Terrence R. , Quessy Stephan , Stein Barry E.
Published: July 2005

It is well established that superior colliculus (SC) multisensory neurons integrate cues from different senses; however, the mechanisms responsible for producing multisensory responses are poorly understood. Previous studies have shown that spatially congruent cues from different modalities (e.g., auditory and visual) yield enhanced responses and that the greatest relative enhancements occur for combinations of the least effective modality-specific stimuli. Although these phenomena are well documented, little is known about the mechanisms that underlie them, because no study has systematically examined the operation that multisensory neurons perform on their modality-specific inputs. The goal of this study was to evaluate the computations that multisensory neurons perform in combining the influences of stimuli from two modalities. The extracellular activities of single neurons in the SC of the cat were recorded in response to visual, auditory, and bimodal visual-auditory stimulation. Each neuron was tested across a range of stimulus intensities and multisensory responses evaluated against the null hypothesis of simple summation of unisensory influences. We found that the multisensory response could be superadditive, additive, or subadditive but that the computation was strongly dictated by the efficacies of the modality-specific stimulus components. Superadditivity was most common within a restricted range of near-threshold stimulus efficacies, whereas for the majority of stimuli, response magnitudes were consistent with the linear summation of modality-specific influences. In addition to providing a constraint for developing models of multisensory integration, the relationship between response mode and stimulus efficacy emphasizes the importance of considering stimulus parameters when inducing or interpreting multisensory phenomena.
Highly Efficient Sex Chromosome Interchanges Produced By I-CreI Expression in Drosophila
Authors: Maggert Keith A , Golic Kent G
Published: July 2005

The homing endonuclease I-CreI recognizes a site in the gene encoding the 23S rRNA of Chlamydomonas reinhardtii. A very similar sequence is present in the 28S rRNA genes that are located on the X and Y chromosomes of Drosophila melanogaster. In this work we show that I-CreI expression in Drosophila is capable of causing induced DNA damage and eliciting cell cycle arrest. Expression also caused recombination between the X and Y chromosomes in the heterochromatic regions where the rDNA is located, presumably as a result of a high frequency of double-strand breaks in these regions. Approximately 20% of the offspring of males expressing I-CreI showed exceptional inheritance of X- and Y-linked markers, consistent with chromosome exchange at rDNA loci. Cytogenetic analysis confirmed the structures of many of these products. Exchange between the X and Y chromosomes can be induced in males and females to produce derivative-altered Y chromosomes, attached-XY, and attached-X chromosomes. This method has advantages over the traditional use of X rays for generating X-Y interchanges because it is very frequent and it generates predictable products.
Epistatic Interactions Among Herbicide Resistances in Arabidopsis thaliana: The Fitness Cost of Multiresistance
Authors: Roux Fabrice , Camilleri Christine , Giancola Sandra , Brunel Dominique , Reboud Xavier
Published: July 2005

The type of interactions among deleterious mutations is considered to be crucial in numerous areas of evolutionary biology, including the evolution of sex and recombination, the evolution of ploidy, the evolution of selfing, and the conservation of small populations. Because the herbicide resistance genes could be viewed as slightly deleterious mutations in the absence of the pesticide selection pressure, the epistatic interactions among three herbicide resistance genes (acetolactate synthase CSR, cellulose synthase IXR1, and auxin-induced AXR1 target genes) were estimated in both the homozygous and the heterozygous states, giving 27 genotype combinations in the model plant Arabidopsis thaliana. By analyzing eight quantitative traits in a segregating population for the three herbicide resistances in the absence of herbicide, we found that most interactions in both the homozygous and the heterozygous states were best explained by multiplicative effects (each additional resistance gene causes a comparable reduction in fitness) rather than by synergistic effects (each additional resistance gene causes a disproportionate fitness reduction). Dominance coefficients of the herbicide resistance cost ranged from partial dominance to underdominance, with a mean dominance coefficient of 0.07. It was suggested that the csr1-1, ixr1-2, and axr1-3 resistance alleles are nearly fully recessive for the fitness cost. More interestingly, the dominance of a specific resistance gene in the absence of herbicide varied according to, first, the presence of the other resistance genes and, second, the quantitative trait analyzed. These results and their implications for multiresistance evolution are discussed in relation to the maintenance of polymorphism at resistance loci in a heterogeneous environment.