bluuebunny/crossref_metadata_2025 huggingface dataset:
Apodization and Phase Information in Fourier Transform Spectroscopy
Authors: Codding Edward G. , Horlick Gary
Published: September 2005

This paper presents, in a qualitative and practical manner, several aspects of apodization and the utilization of phase information in Fourier transform spectroscopy. For completeness, examples are presented which illustrate the effects on spectra of applying the more common apodizations. The calculation of phase information is formulated, and the type of information available in phase spectra is discussed and illustrated. The use of phase information in phase correction is discussed, and several examples are presented which illustrate the necessity of employing phase correction in conjunction with certain apodizations. Several unique apodizing functions are illustrated, including a sawtooth function which is quite useful for resolution enhancement. Finally, examples of instrumental and self-apodization are presented.
Generation of Simulated Mass Spectra of Small Organic Molecules by Computerized Pattern Recognition Techniques
Authors: Schechter Joseph , Jurs Peter C.
Published: September 2005

An empirical method employing computerized pattern recognition techniques has been applied to the generation of simulated mass spectra of small organic molecules. Molecular structures are represented in computer-compatible form through the use of a fragmentation code which assigns code designations to specific groups of atoms and/or bonds within the molecules. Using such descriptions of molecules, pattern classifiers have been developed to predict the presence or absence of mass spectral peaks in each of 60 nominal m/e positions and to give a measure of the intensity of peaks in 11 of these. Information in the molecular descriptor lists which correlates with the appearance of specific peaks is shown to be present in relatively few of the descriptors developed. To test the complete system, a number of entire mass spectra were developed; in this test, 93% of the classifications were made correctly.
Laboratory Computer for the High Speed Analysis of High and Low Alloy Steel
Authors: Strieker Friedrich , Friedhoff Paul , Heinen Manfred , Brauner Jochen
Published: September 2005

The evaluation of data is presented for routine work in an x-ray fluorescence analysis spectral laboratory. The plotting of calibration and correction curves for x-ray fluorescence analysis of steels with high and low alloy content is described.
A Flexible Computer Program for Evaluation of Data Obtained via the Walsh Atomic Absorption Method
Authors: Bankston Donald C. , Goldsmith Roger A.
Published: September 2005

A single computer program, for use in especially highly precise and accurate applications of the Walsh atomic absorption method, is designed to allow an analyst the freedoms (1) to determine the concentrations of up to 11 elements in an unrestricted number of samples; (2) to use up to 40 differently named standards and/or series of standards simultaneously, with or without a dilution option; (3) to fit any standard curve and associate it with either one equation or two; (4) to make the equation of all or part of any standard curve a polynomial of either first or second degree; and (5) to have standard curve equation coefficients and/or coordinates of certain points on the standard curve printed out in easily readable form. The concentration of a given element of interest, in any sample, is treated as a variable with random properties. Up to 26 estimates of this concentration can be made, and, from them, the program computes the mean, standard deviation, coefficient of variation, and both 95 and 99% confidence limits about the mean.
Trace Metals Analysis in Petroleum Products by Atomic Absorption
Authors: Vigler M. S. , Gaylor V. F.
Published: September 2005

To provide information for customers who have regional environmental obligations, it was necessary to develop an analytical procedure to analyze for 25 metals in the range from 1 ppb to greater than 5 ppm in petroleum products. Atomic absorption is employed to determine 23 of the elements, namely: Al, Sb, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Pb, Mg, Mn, Mo, Ni, Na, Si, Sn, Ti, V, and Zn. The general procedure is to ash the appropriate amount of sample by absorbing liquid samples on magnesium sulfonate ash aid (Conostan, Conoash M) or potassium sulfonate. Add 5 drops of H2SO4, heat to white fumes, fire, and ash at 650°C. The sulfonated ash is dissolved in dilute acid to provide the aspiration solution. Recovery studies on aluminum, antimony, beryllium, cadmium, and lead in the microgram per gram range are presented.
A Programmed Cell Instrument for Digital Raman Difference Spectroscopy
Authors: Amy Jon W. , Chrisman Ray W. , Lundeen James W. , Ridley Thomas Y. , Sprowles Jolyon C. , Tobias R. Stuart
Published: September 2005

An instrument for digital Raman difference spectroscopy which uses a programmed sample carrier for automated alternate positioning of reference and sample cells in the laser beam is described. Conventional single photon counting equipment is employed with its attendant advantages over dc analog methods. Signal processing is done with a digital computer. There are relatively few limitations on the types of sample cells which may be used. Applications to studies of dilute aqueous solutions of biological molecules, particularly, are discussed.
Ultraviolet Determination of Polystyrene in Paper Products
Authors: Spagnolo F.
Published: September 2005

A quantitative method for determining polystyrene in paper sheets was developed. Polystyrene is determined by refluxing the sample with chloroform and ultraviolet measurement of the polymer in the extract. The percentage recovery was compared to the values obtained by a gravimetric procedure using hot chloroform extraction in a Soxhlet apparatus. The values obtained by both methods were found to be in good agreement.
The Influence of Matrix Anion on Characteristics of the Arc Plasma and on Spectrochemical Determinations
Authors: Rybarova Ž. , Todorović M. , Vukanović V.
Published: September 2005

The influence of the matrix anion in CdO and CdCl2 was studied. Radial distributions of temperature and electron density in the arc plasma were measured. For CdCl2 matrix, a higher arc temperature and electron density as well as higher radial gradients of these values have been observed. Spectral line intensities (with background corrections) of trace elements were investigated in both matrices. Elements evaporate faster from chloride matrix. This causes in the beginning an intensity increase of lines compared with CdO matrix. But in determinations with exposure time long enough to ensure complete vaporization of traces from oxide matrix, an enhancement of integral line intensities of traces in CdO, compared with CdCl2 matrix, has been observed.
Determination of Microgram Quantities of Thallium in Aluminum-, Iron-, and Nickel-Base Alloys
Authors: Burke Keith E.
Published: September 2005

Chemical techniques are required for the determination of trace constituents in commercial nickel and its alloys. An adequate method does not exist for the determination of microgram quantities of thallium; therefore, an extraction-atomic absorption method has been developed. Trace quantities of thallium in nickel are quantitatively extracted from a 10% hydrochloric acid solution containing 2% ascorbic acid and 9% potassium iodide by a 5% solution of tri- n-octylphosphine oxide in 4-methylpentane-2-one (MIBK). The MIBK extract containing the thallium is then nebulized directly into the atomic absorption flame. The concentration range for the determination of thallium in MIBK is an order of magnitude lower than for aqueous media. The proposed analytical technique is accurate and rapid and has a precision (σ) of ±0.15 ppm at the 2.00 ppm level. The limit of detection is 0.1 ppm of thallium. The method is also applicable to aluminum- and iron-base alloys. The solvent extraction procedure used to isolate thallium has also been validated for antimony, bismuth, lead, and tin and can also be applied to the determination of cadmium, copper, indium, and zinc.
A Remote Operation Quadrupole Mass Spectrometer Using a Custom Radio-Frequency Link Approach
Authors: Tashbar Philip W. , Nisen Daniel B. , Moore W. Walding
Published: September 2005

A commercial quadrupole mass spectrometer (residual gas analyzer, RGA) system has been modified to operate at large separations of its electronics console and sensing head. The methods implemented have made practical applications, as well as operation, of such a system possible for the first time. This advance was stimulated by a need for placing sensors at remote (45 or 60 m) chamber locations for space simulation testing of orbital flight spacecraft. Emphasis is placed on instrument functional requirements and describing the hardware changes and adjustment techniques necessary to assure operation at the extended cable lengths.
Infrared Absorption (435 to 250 cm−1) and Ultraviolet Emission Analyses of Selected Sulfides and Sulfosalts: A Correlative Study
Authors: Liese Homer C.
Published: September 2005

Selected sulfides and sulfosalts were investigated first by ir absorption (435 to 250 cm−1) analysis and then by uv spectrochemical analysis. Results revealed that many of the absorption bands were diagnostic, and that some could be correlated with compositional variations.
Comparison of Three Photochemical-Fluorimetric Methods for Determination of Chloroquine
Authors: Lukasiewicz R. J. , Fitzgerald J. M.
Published: September 2005

Chloroquine [7-chloro-4-(4-diethylamino-1-methylbutylamino)quinoline] is both fluorescent and photochemically unstable. The primary photoproduct was also found to be both photoactive and fluorescent. Three fluorimetric methods for measurement of original chloroquine concentration were evaluated: (1) digital integration of the fluorescence decay signal from chloroquine (380 nm); (2) digital integration of the fluorescence increase due to the photoproduct (480 nm); (3) analog recording of product fluorescence as a function of exposure time. The digital methods gave better precision (0.6%) and limit of detection (0.1 ppb) by one and two orders of magnitude, respectively. Sensitivity using integration of native chloroquine fluorescence was better by an order of magnitude than that for integration of photoproduct signal and is therefore the method of choice. The analog method was much less sensitive than either digital procedure. The photochemical conversion of chloroquine to intermediate (fluorescent) and final (nonfluorescent) products was studied. Oxygen increases the photochemical quantum yields and decreases fluorescence quantum yields, but satisfactory analytical data are obtained with air-saturated solutions. Speed of analysis and limits of detection exceed previously reported methods.
Laser-Excited Resonance Raman Spectra of Small Molecules and Ions—A Review
Authors: Kiefer W.
Published: September 2005

Laser-excited resonance Raman spectra of molecular vibrations in the gaseous, liquid, and solid state are reviewed. A short summary of the recently developed Raman techniques for absorbing materials is also given. A bibliography is added in an appendix which covers the literature of laser-excited resonance Raman spectra of molecular vibrations of more complicated molecules, mostly of biological interest.
Crystals for Stellar Spectrometers
Authors: Alexandropoulos N. G. , Cohen Gabrielle G.
Published: September 2005

The principles of crystal evaluation as they apply to the special problems of x-ray astronomy are presented. A number of crystals were evaluated, and the energy dependence of the diffraction properties of (002) PET, (111) Ge, (101) ADP, (001) KAP, and (001) RAP are reported.
Computerized Treatment of Ultraviolet and Visible Absorption Spectra
Authors: Känzig Herbert , Lorenz Regula , Wild Urs P.
Published: September 2005

A versatile double beam ultraviolet and visible spectrophotometer, which uses a small digital computer to collect optical absorption spectra, has been developed in our laboratories. Digital data are stored on paper tape. This work describes the subsequent data treatment on a large computer. Subroutines for wavelength calibration, data smoothing, and data presentation have been written. Spectra obtained in different or overlapping regions with various concentrations may be combined to a single plot of molar absorption coefficients. The data analysis is based on statistical concepts. The standard deviation of the reduced data is calculated and also plotted. This represents a measure of the precision of the recorded data, information which is not easily obtained from commercial spectrometers. Details of the software system with examples of its performance are also presented.
Low Temperature and High Pressure Far Infrared Spectra of Condensed Phases: I. Mono- and Dimethylcyclohexanes
Authors: Lauer James L. , Peterkin M. E.
Published: September 2005

The infrared spectra (60 to 400 cm−1 and 800 to 1100 cm−1) of methylcyclohexane and of all the dimethylcyclohexanes except the 1,1-isomer were obtained with a Michelson interferometer at temperatures between ambient and −150°C and—in the latter wavenumber region—compared with spectra gathered earlier on the same materials maintained in a diamond anvil cell under pressures ranging from ambient to about 40 kb. Most of the spectral bands changed similarly with increasing pressure or decreasing temperature, but there were exceptions ascribable to conformational changes. The intensities of bands associated with analogous modes of vibration varied similarly in these isomers; i.e., they either increased or decreased so that, conversely, this behavior could be used in their assignment to conformational modes. The frequency shifts of corresponding bands between cis and trans isomers were in the same direction for the 1,2- and 1,4-isomers, but opposite for the 1,3-isomers, reflecting the greater stability of the trans isomers in the former case, but of the cis isomer in the latter.
Rapid Analysis of Chrome Ores, Chrome-Magnesia, and Magnesia-Chrome Materials by X-Ray Fluorescence
Authors: Banerjee Subrata , Olsen B. G.
Published: September 2005

A rapid x-ray fluorescence method has been developed for analysis of chrome ores, chrome-magnesia, and magnesia-chrome materials by fusion of the powdered samples with sodium hexametaphosphate and lanthanum oxide. Three NBS standards, one British standard and a few in-house wet chemically analyzed samples were run for SiO2, Fe2O3, Al2O3, CaO, MgO, and Cr2O3 for standardizing the method. Linear regression equations were applied for determining the best fit line. Relative standard deviations were 3% or less except for CaO (5.4%) because of its usually very low concentration.
Comparison of Five Ionization Methods for Producing Mass Spectra of Typical Organophosphorus Pesticides
Authors: Busch Kenneth L. , Bursey Maurice M. , Hass J. Ronald , Sovocool G. Wayne
Published: September 2005

Positive ion mass spectra obtained by conventional electron impact and by methane chemical ionization were compared with the negative ion mass spectra of 16 typical organophosphorus pesticides using methane, a methane-oxygen mixture, and oxygen as enhancement/reagent gases. In the negative ion spectra, phosphate and phenate anions typically carry a large fraction of the ion current. Displacement of chlorine by oxygen is noted in some cases, and migration of aryl groups from oxygen to sulfur is occasionally noted. Ion-molecule reactions between two species derived from sample molecules have been observed. The sensitivity of the negative ion techniques for the pesticides examined is greater than conventional electron impact or methane positive chemical ionization techniques, and can be up to 800 times more sensitive for some compounds.
Resolution Enhancement in Raman Spectroscopy Using Polarization Data
Authors: Krishnan K. , Bulkin B. J.
Published: September 2005

Because overlapping Raman bands will, in general, have different depolarization ratios, it is possible to resolve such bands by means of a computer subtraction of the Ivh spectrum, scaled by an appropriate constant, from the Ivv spectrum. Several examples are given which illustrate both the capabilities and the limitations of the technique.
Pulsed-Laser Mode Competition with a Na-Colored Intracavity Flame
Authors: van Dijk C. A. , Alkemade C. Th. J. , Zeegers P. J. Th.
Published: September 2005

A mode competition effect is observed with a Na-colored H2-O2-Ar flame located inside the cavity of a pulsed tunable dye laser tuned near one of the D-lines. When the Na-concentration is sufficiently high, laser action in the dominant mode is temporarily suppressed and develops in an adjacent mode. Meantime, the saturation of the Na-vapor progresses and, ultimately, laser action in the dominant mode is restored. This explanation is supported by semiquantitative computer simulation.
Uniform Depth Profiling in X-ray Photoelectron Spectroscopy (Electron Spectroscopy for Chemical Analysis)
Authors: Bradley L. , Bosworth Y. M. , Briggs D. , Gibson V. A. , Oldman R. J. , Evans A. C. , Franks J.
Published: September 2005

The difficulties of nonuniform ion etching which hamper depth profiling by X-ray photoelectron spectroscopy (XPS) have been overcome by use of a mechanically scanned saddle-field ion source. The system and its calibration for uniformity are described, and its performance is illustrated by the depth profile of a Si3N4/SiO2/Si metal nitride oxide silicon device. This also allows the potential advantages of XPS profiling over Auger electron spectroscopy profiling to be discussed.
Infrared and Raman Spectra of Bis-β-Diketonates of Palladium (II)
Authors: Bulkin Bernard J. , Rose Rose K.
Published: September 2005

Infrared and Raman data are reported for four palladium-β-diketonates, including the bis-acetylacetonate, bis-1-phenyl-1,3-butanedionato trans chelate, as well as the cis and trans isomers of 1- p-octyloxyphenyl-1,3-butanedionato chelates. The data indicate that a straightforward application of local symmetry selection rules for the —PdO4— subunit is adequate to explain the low frequency infrared and Raman spectra.
The Temperature Dependence of an Absorption Feature in the Vicinity of the Long Wavelength Transmission Cutoff in ZnSe
Authors: Castle P. M. , Toth V. A.
Published: September 2005

The temperature dependence of the infrared absorption spectrum of ZnSe was measured by using a variable temperature, liquid nitrogen cooled, absorption cell interfaced with a Fourier transform infrared spectrometer. Absorption difference spectra were obtained as a function of temperature by using the on-board computing facilities of the spectrometer coupled with its data storage capabilities. The temperature dependence of the absorption feature, which extends from about 450 to 800 cm −1, is shown to be consistent with a two phonon interaction as have been previously suggested.
Computational Procedures for Characterization of High Voltage Spark Sources
Authors: Scheeline Alexander , Klueppel R. J. , Coleman David M. , Walters John P.
Published: September 2005

Equations and a calculation procedure for modeling the operation of an electronic, adjustable-waveform and other types of high voltage spark sources are presented. The equations return time-dependent capacitor voltage and charging current and the calculation procedure returns complete break patterns. Comparisons between laboratory and computed results indicate the calculations predict experiment with accuracy in the 1 to 5% relative error range. This is sufficient to make the calculation procedure useful for characterization of research or production spark sources.
Infrared Intensity Measurements by Band Contour Analysis
Authors: Van Haverbeke L. , Brown C. W. , Herman M. A.
Published: September 2005

A spectroscopic band profile that can be used for asymmetric as well as for symmetric bands is proposed. The meaning of the asymmetry parameter is discussed, and the applications of this profile in infrared intensity determinations are examined.
Inductively Coupled Plasma-Atomic Emission Spectrometry: Analysis of Biological Materials and Soils for Major, Trace, and Ultra-Trace Elements
Authors: Dahlquist R. L. , Knoll J. W.
Published: September 2005

An inductively coupled plasma sustained in flowing argon and a permanently aligned all-glass coaxial pneumatic nebulizer are employed in the atomic emission mode with a direct-reading poly-chromator for simultaneous multielement determinations. The inductively coupled plasma is shown to be remarkably free from matrix and interelement effects by application for the determination of major (Na, K, P, Ca, and Mg) and trace (Fe, Cu, Zn, Mn, Pb, Cd, Co, Cr, Ni, V, Ti, Al, Sr, and Ba) elements in reference biologic materials and soil extracts. Wet-digestion and several dry-ashing sample preparation procedures are evaluated. Accuracy, precision, and sensitivity compare favorably with other multielement instrumental techniques (neutron activation analysis, energy dispersive x-ray fluorescence, solution-rotating disk atomic emission spectrometry) and with flame atomic absorption spectrometry. The directness of the method reported here is illustrated by use of one set of system operating conditions with one set of synthetic reference solutions used to establish a single calibration curve for each element.
Early Enhanced Expression of Interferon-Inducible Protein-10 (CXCL-10) and Other Chemokines Predicts Adverse Outcome in Severe Acute Respiratory Syndrome
Authors: Tang Nelson Leung-Sang , Chan Paul Kay-Sheung , Wong Chun-Kwok , To Ka-Fai , Wu Alan Ka-Lun , Sung Ying-Man , Hui David Shu-Cheong , Sung Joseph Jao-Yiu , Lam Christopher Wai-Kei
Published: September 2005

Background: Exaggerated activation of cytokines/chemokines has been proposed as a factor in adverse outcome of severe acute respiratory syndrome (SARS). Previous studies on chemokines have included only small numbers of patients, and the utility of plasma chemokines as prognostic indicators is unclear.

Methods: We studied 255 archival plasma samples collected during the first or second week after disease onset. The chemokines interferon-inducible protein-10 (IP-10), monokine induced by interferon-γ (MIG), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and regulated upon activation normal T cell expressed and secreted (RANTES) were measured by cytometric bead array with a 4-color FACSCalibur flow cytometer. Reverse transcription and real-time quantitative PCR and immunohistochemical staining were performed to analyze the production of IP-10 in lung tissue at autopsy. Conditional logistic regression was used to identify independent predictors for adverse disease outcome.

Results: Increases in IP-10, MIG, and IL-8 during the first week after onset of fever were associated with adverse outcome (intensive care unit admission or death) in the univariate analysis. During the second week, only MIG concentration was associated with prognosis. After adjusting for other risk factors, plasma IP-10 concentration at the first week remained as an independent prognostic factor, with an odds ratio for adverse outcome of 1.52 (95% confidence interval, 1.05–2.55) per fold increase in plasma IP-10 concentration above the median. During the second week, chemokines provided little independent prognostic information. IP-10 was increased in lung tissue from patients who died of SARS.

Conclusions: Increased plasma IP-10 during the first week of SARS symptoms is an independent predictor of outcome. Chemokine activation may be an early event in SARS, and an exaggerated host response may produce complications.
Hyperhomocysteinemia and arteriosclerosis: historical perspectives
Authors: McCully Kilmer S.
Published: September 2005

Early concepts of the origin of arteriosclerosis were introduced in the 19th century by Rokitansky and Virchow, who described mural thrombosis, inflammatory damage to arterial intima, increased intimal permeability to plasma, mucoid degeneration of arterial wall, deposition of plasma lipids in plaques, and fibrosis and calcification of plaques. Experimental production of arteriosclerosis by feeding animal foods to rabbits was attributed to protein intoxication by Ignatowsky in 1908 and to dietary cholesterol by Anitschkow in 1913. Newburgh confirmed the protein hypothesis in 1915–1925 but failed to identify which amino acid produced plaques because methionine (1922) and homocysteine (1932) had not yet been discovered. Cases of homocystinuria from inherited deficiency of cystathionine synthase were found to be associated with thrombosis and vascular disease in 1964. The index case of methionine synthase deficiency (cobalamin C disease) was found by McCully in 1969 to be associated with arteriosclerosis, leading to the homocysteine theory of arteriosclerosis. The theory explains experimental arteriosclerosis by deficiency of vitamin B
Homocysteine and vascular disease in diabetes: a double hit?
Authors: Huijberts Maya S. P. , Becker Annemarie , Stehouwer Coen D. A.
Published: September 2005

Cardiovascular disease is a major problem in diabetes, and risk factors presumably unrelated to diabetes, such as hyperhomocysteinaemia, may be related to the development of cardiovascular complications in diabetic individuals. Plasma homocysteine levels are usually normal in diabetes, although both lower and higher levels have been reported. Homocysteine levels in diabetes are modulated by hyperfiltration and renal dysfunction, as well as low folate status. Insulin resistance does not appear to be a major determinant of plasma homocysteine level. Hyperhomocysteinaemia has been associated with microalbuminuria and retinopathy in type 1 and type 2 diabetes. In patients with type 2 diabetes, plasma homocysteine concentration is a significant predictor of cardiovascular events and death. This relation seems to be stronger in subjects with diabetes than without. The underlying pathophysiological mechanism of this increased vascular risk remains unexplained, but may be related to worsening of endothelial dysfunction and/or structural vessel properties induced by oxidative stress. Because homocysteine and diabetes have apparent synergistic detrimental vascular effects, patients with diabetes are candidates for screening and treatment with folic acid until the results of ongoing clinical trials are available.
Hyperhomocysteinaemia in chronic kidney disease: focus on transmethylation
Authors: van Guldener Coen , Stam Frank , Stehouwer Coen D. A.
Published: September 2005

Hyperhomocysteinaemia almost invariably occurs in patients with end-stage renal disease (ESRD), but there is debate whether, within the group of ESRD patients, higher or lower plasma homocysteine concentrations are related to an increased risk of vascular disease. Homocysteine is thought to be vasculotoxic in high concentrations, but it may also lead to elevated levels of its precursor, S-adenosylhomocysteine (AdoHcy), which is a potent inhibitor of the transmethylation pathway, in which S-adenosylmethionine (AdoMet) donates its methyl group to a variety of acceptors. Impairment of this transmethylation pathway in ESRD patients has been suggested by high AdoHcy levels, decreased AdoMet/AdoHcy ratios, decreased protein repair requiring methyltransferases, and by DNA hypomethylation. Stable isotope techniques using labelled methionine have indeed demonstrated a decreased whole body transmethylation flux in ESRD patients. These studies have also shown that folic acid treatment is capable of restoring transmethylation rates to normal values. The remaining hyperhomocysteinaemia after folic acid treatment in ESRD is probably due to a persistent impairment of homocysteine clearance through transsulphuration. DNA hypomethylation with its concurrent alterations in gene expression is largely improved by folate treatment. The adverse effects of hyperhomocysteinaemia in ESRD may thus be related to impaired transmethylation. Normalisation of plasma homocysteine does not seem to be required to restore transmethylation to normal levels in ESRD patients.
Evaluation of the technical performance of novel holotranscobalamin (holoTC) assays in a multicenter European demonstration project
Authors: Morkbak Anne L. , Heimdal Randi M. , Emmens Kathleen , Molloy Anne , Hvas Anne-Mette , Schneede Joern , Clarke Robert , Scott John M. , Ueland Per M. , Nexo Ebba
Published: September 2005

A commercially available holotranscobalamin (holo-TC) radioimmunoassay (RIA) (Axis-Shield, Dundee, Scotland) was evaluated in four laboratories and compared with a holoTC ELISA run in one laboratory. The performance of the holoTC RIA assay was comparable in three of the four participating laboratories. The results from these three laboratories, involving at least 20 initial runs of “low”, “medium” and “high” serum-based controls (mean holoTC concentrations 34, 60 and 110pmol/L, respectively) yielded an intra-laboratory imprecision of 6–10%. No systematic inter-laboratory deviations were observed on runs involving 72 patient samples (holoTC concentration range 10–160pmol/L). A fourth laboratory demonstrated higher assay imprecision for control samples and systematic deviation of results for the patient samples. Measurement of holoTC by ELISA showed an imprecision of 4–5%, and slightly higher mean values for the controls (mean holoTC concentrations 40, 70 and 114pmol/L, respectively). Comparable results were obtained for the patient samples. The long-term intra-laboratory imprecision was 12% for the holoTC RIA and 6% for the ELISA. In conclusion, it would be prudent to check the calibration and precision prior to starting to use these holoTC assays in research or clinical practice. The results obtained using the holoTC RIA were similar to those obtained using the holoTC ELISA assay.
Betaine: a key modulator of one-carbon metabolism and homocysteine status
Authors: Ueland Per Magne , Holm Pål I. , Hustad Steinar
Published: September 2005

Betaine serves as a methyl donor in a reaction converting homocysteine to methionine, catalysed by the enzyme betaine-homocysteine methyltransferase. It has been used for years to lower the concentration of plasma total homocysteine (tHcy) in patients with homocystinuria, and has recently been shown to reduce fasting and in particular post-methionine load (PML) tHcy in healthy subjects.

Betaine exists in plasma at concentrations of about 30μmol/L; it varies 10-fold (from 9 to 90μmol/L) between individuals, but the intra-individual variability is small. Major determinants are choline, dimethylglycine and folate in plasma, folic acid intake and gender.

Recent studies have demonstrated that plasma betaine is a stronger determinant of PML tHcy than are vitamin B

To conclude, betaine status is a component of an individual's biochemical make-up with ramifications to one-carbon metabolism. Betaine status should be investigated in pathologies related to altered metabolism of homocysteine and folate, including cardiovascular disease, cancer and neural tube defects.
Molecular targeting by homocysteine: a mechanism for vascular pathogenesis
Authors: Jacobsen Donald W. , Catanescu Otilia , DiBello Patricia M. , Barbato John C.
Published: September 2005

Hyperhomocysteinemia is an independent risk factor for cardiovascular disease. Although there is a growing body of evidence that homocysteine plays a causal role in atherogenesis, specific mechanisms to explain the underlying pathology have remained elusive. This review focuses on chemistry unique to the homocysteine molecule to explain its inherent cytotoxicity. Thus, the high pKa of the sulfhydryl group (pKa=10.0) of homocysteine underlies its ability to form stable disulfide bonds with protein cysteine residues, and in the process, alters or impairs the function of the protein. Albumin, fibronectin, transthyretin, annexin II, and factor V have now been identified as molecular targets for homocysteine, and in the case of albumin, the mechanism of targeting has been elucidated.
Anti-inflammatory compound resveratrol suppresses homocysteine formation in stimulated human peripheral blood mononuclear cells in vitro
Authors: Schroecksnadel Katharina , Winkler Christiana , Wirleitner Barbara , Schennach Harald , Weiss Günter , Fuchs Dietmar
Published: September 2005

Inflammation, immune activation and oxidative stress play a major role in the pathogenesis of cardiovascular disorders. In addition to markers of inflammation, moderate hyperhomocysteinemia is an independent risk factor for cardiovascular disease, and there is a link between the activation of immunocompetent cells and the enhanced formation of homocysteine in vitro. Likewise, anti-inflammatory drugs and nutrients rich in antioxidant vitamins are able to reduce cardiovascular risk and to slow down the atherogenic process. Resveratrol, a phenolic antioxidant synthesized in grapes and vegetables and present in wine, has also been supposed to be beneficial for the prevention of cardiovascular events. Apart from its strong antioxidant properties, resveratrol has also been demonstrated to act as an anti-inflammatory agent. In this study the influence of resveratrol on the production of homocysteine by stimulated human peripheral blood mononuclear cells (PBMCs) was investigated. Results were compared to earlier described effects of the anti-inflammatory compounds aspirin and salicylic acid and of the lipid-lowering drug atorvastatin. Stimulation of PBMCs with the mitogens concanavalin A and phytohemagglutinin induced significantly higher homocysteine accumulation in supernatants compared with unstimulated cells. Treatment with 10–100μM resveratrol suppressed homocysteine formation in a dose-dependent manner. Resveratrol did not influence the release of homocysteine from resting PBMCs. The data suggest that resveratrol may prevent homocysteine accumulation in the blood by suppressing immune activation cascades and the proliferation of mitogen-driven T-cells. The effect of resveratrol to down-regulate the release of homo-cysteine was comparable to the decline of neopterin concentrations in the same experiments. The suppressive effect of resveratrol was very similar to results obtained earlier with aspirin, salicylic acid and atorvastatin; however, it appeared that doses of compounds needed to reduce homocysteine levels to 50% of stimulated cells were always slightly lower than those necessary to achieve the same effect on neopterin concentrations. The influence of resveratrol and of all the other compounds on homocysteine production appears to be independent of any direct effect on homocysteine biochemistry.
Homocysteine and B vitamins in mild cognitive impairment and dementia
Authors: Quadri Pierluigi , Fragiacomo Claudia , Pezzati Rita , Zanda Enrica , Tettamanti Mauro , Lucca Ugo
Published: September 2005

Elderly subjects with mild cognitive impairment have a high risk for conversion to Alzheimer's disease or are already in a preclinical dementia stage. By cross-sectionally comparing subjects in prodromal and early phases of dementia with non-demented controls, we tested the hypothesis whether low serum vitamin B
Homocysteine, type 2 diabetes mellitus, and cognitive performance: The Maine-Syracuse Study
Authors: Robbins Michael A. , Elias Merrill F. , Budge Marc M. , Brennan Suzanne L. , Elias Penelope K.
Published: September 2005

Type 2 diabetes mellitus and higher total plasma homocysteine concentrations are each associated with an increased incidence of cardiovascular disease and with diminished cognitive performance. Relations between homocysteine concentrations and cardiovascular disease incidence are stronger in the presence of type 2 diabetes mellitus. Therefore, we hypothesized that relations between homocysteine concentrations and cognitive performance would be stronger in the presence of type 2 diabetes. We related homocysteine concentrations and cognitive performance on the Mini-Mental State Examination in 817 dementia- and stroke-free participants of the Maine-Syracuse Study, 90 of whom were classified with type 2 diabetes mellitus. Regardless of statistical adjustment for age, sex, gender, vitamin co-factors (folate, vitamin B
Measurement of asymmetric dimethylarginine in plasma: methodological considerations and clinical relevance
Authors: Teerlink Tom
Published: September 2005

Asymmetric dimethylarginine (ADMA) is a potent inhibitor of nitric oxide synthase and is regarded as a novel risk factor for cardiovascular disease. The metabolic pathways of ADMA and homocysteine are strongly intertwined. First, during synthesis of ADMA, two equivalents of homocysteine are formed. Second, homocysteine has been shown to inhibit the ADMA-degrading enzyme dimethylarginine dimethylaminohydrolase. Finally, homocysteine, either directly or by increasing oxidative stress, may promote release of free ADMA by accelerating protein degradation. Currently used techniques for the quantification of ADMA in plasma are mostly based on liquid chromatography with fluorimetric or mass spectrometric detection. Plasma ADMA has a very narrow concentration distribution, with an inter-individual coefficient of variation of approximately 12%, and even slightly elevated ADMA concentrations are associated with increased cardiovascular disease risk. Therefore, to generate useful results in clinical research, high precision of the assay used for the quantification of ADMA assay is a matter of prime importance. Assays with a high coefficient of variation may lead to low statistical power in clinical trials and to a severe underestimation of the strength of associations in epidemiological studies.
Concentrations of homocysteine, related metabolites and asymmetric dimethylarginine in preeclamptic women with poor nutritional status
Authors: Herrmann Wolfgang , Isber Sonia , Obeid Rima , Herrmann Markus , Jouma Muhidien
Published: September 2005

Background: Hyperhomocysteinemia, a proxy measure for the nutritional status of the B vitamins, may be involved in the etiology of preeclampsia via inducing endothelial dysfunction. Asymmetric dimethylarginine (ADMA) is an inhibitor of NO-synthase that may adversely affect the endothelium.

Materials and methods: We investigated serum concentrations of folate, vitamin B

Results: Higher concentrations of Hcy, cystathionine and methylmalonic acid (MMA) were closely linked to a lower status of the B vitamins. Higher concentrations of Hcy and cystathionine were observed in the preeclamptic group than in the matched controls (median Hcy 9.3 vs. 6.0μmol/L; median cystathionine 284 vs. 232nmol/L). Serum folate was significantly lower in patients than in controls (16.4 vs. 36.0nmol/L). Folate supplementation was less likely to be used in preeclamptic women. Concentrations of MMA were elevated in patients and controls and did not differ significantly between the two groups. Median plasma concentrations of ADMA were significantly lower in asymptomatic women than in those who developed preeclampsia before the 37th week of gestation (0.61 vs. 0.68μmol/L).

Conclusions: Elevated serum concentrations of Hcy, cystathionine and MMA indicate poor status of the B vitamins during pregnancy. The adverse effect of Hcy on endothelial function might be related to ADMA in early-onset preeclampsia. More emphasis should be placed on increasing the intake of B vitamins in pregnant women from developing countries.
Interactions between folate and aging for carcinogenesis
Authors: Choi Sang-Woon , Friso Simonetta
Published: September 2005

Inadequate folate intake and aging are each strongly implicated as important risk factors for certain cancers. Since both folate depletion and aging are strongly associated with hyperhomocysteinemia, genomic DNA hypomethylation, and increased uracil misincorporation into DNA, it appears that each of them enhances carcinogenesis by inducing a derangement of one-carbon metabolism that supplies one-carbons to biological methylation reactions and nucleotide synthesis. Recent studies have demonstrated that inadequate dietary folate and aging may interact and synergistically disturb the normal homeostasis of one-carbon metabolism, thereby provoking subsequent biochemical and molecular aberrations, including alterations in critical gene expression related to carcinogenesis. These studies have further indicated that modest folate supplementation may reverse or partially ameliorate those adverse effects induced by folate depletion and aging.
Parental Perspectives on Hospital Staff Members' Acts of Kindness and Commemoration After a Child's Death
Authors: Macdonald Mary Ellen , Liben Stephen , Carnevale Franco A. , Rennick Janet E. , Wolf Susan L. , Meloche Donald , Cohen S. Robin
Published: September 2005

Objectives. Acts of kindness and commemoration by staff members often follow the death of a patient. Acts include attending funerals, sending sympathy cards, sending cards on birthdays/anniversaries, telephoning/visiting family homes, and attending memorial services. This study explores the significance of these acts for bereaved parents.

Methods. Twelve parents whose children died in the ICU of a tertiary care pediatric hospital were interviewed, to explore their experiences of the death. Investigators reviewed transcripts and observational field notes. Multidisciplinary team triangulation was used to corroborate themes, with cross-case analysis.

Results. Three themes emerged regarding parental experiences of staff members' acts, ie, (1) parents placed great importance on the hospital's memorial service and on staff members' presence at the service; (2) parents found it difficult to return to the hospital after the child's death but all attended the memorial service, finding some closure in the return; and (3) parents appreciated receiving cards and greatly valued staff members' efforts to telephone/visit and to attend the funeral. Months later, parents remembered positively which staff members engaged in which activities. Conversely, parents expressed disappointment when staff members did not engage in these activities and/or were absent from memorial/funeral services.

Conclusions. Efforts to support families and to commemorate deceased children are appreciated by bereaved parents. Staff members' absences at commemorative events and a lack of supportive acts are noticed and regretted by families. Staff members and program administrators should attempt to arrange workloads to ensure meaningful contact between staff members and parents during the bereavement period.
Impaired Trophic Interactions Between the Cerebellum and the Cerebrum Among Preterm Infants
Authors: Limperopoulos Catherine , Soul Janet S. , Haidar Haissam , Huppi Petra S. , Bassan Haim , Warfield Simon K. , Robertson Richard L. , Moore Marianne , Akins Patricia , Volpe Joseph J. , du Plessis Adré J.
Published: September 2005

Background. Advanced neuroimaging techniques have brought increasing recognition of cerebellar injury among premature infants. The developmental relationship between early brain injury and effects on the cerebrum and cerebellum remains unclear.

Objectives. To examine whether cerebral parenchymal brain lesions among preterm infants are associated with subsequent decreases in cerebellar volume and, conversely, whether primary cerebellar injury is associated with decreased cerebral brain volumes, with advanced, 3-dimensional, volumetric MRI at term gestational age equivalent.

Methods. Total cerebellar volumes and cerebellar gray and myelinated white matter volumes were determined through manual outlining for 74 preterm infants with unilateral periventricular hemorrhagic infarction (14 infants), bilateral diffuse periventricular leukomalacia (20 infants), cerebellar hemorrhage (10 infants), or normal term gestational age equivalent MRI findings (30 infants). Total brain and right/left cerebral and cerebellar hemispheric volumes were calculated.

Results. Unilateral cerebral brain injury was associated with significantly decreased volume of the contralateral cerebellar hemisphere. Conversely, unilateral primary cerebellar injury was associated with a contralateral decrease in supratentorial brain volume. Cerebellar gray matter and myelinated white matter volumes were reduced significantly not only among preterm infants with primary cerebellar hemorrhage but also among infants with cerebral parenchymal brain injury.

Conclusions. These data suggest strongly that both reduction in contralateral cerebellar volume with unilateral cerebral parenchymal injury and reduction in total cerebellar volume with bilateral cerebral lesions are related to trophic transsynaptic effects. Early-life cerebellar injury may contribute importantly to the high rates of cognitive, behavioral, and motor deficits reported for premature infants.
Longitudinal Neurodevelopmental Evaluation of Children With Opsoclonus-Ataxia
Authors: Mitchell Wendy G. , Brumm Virdette L. , Azen Colleen G. , Patterson Kirsten E. , Aller Sonia K. , Rodriguez Jenny
Published: September 2005

Objective.We previously reported on children with opsoclonus-ataxia and found pervasive neurodevelopmental deficits, years after onset, without a clear relationship to treatment modality or timing of treatment. A significant negative correlation of functional status with age at testing raised a question of whether opsoclonus-ataxia is a progressive encephalopathy. We attempted to answer this question with serial testing. In addition, we examined the relationship between clinical course and developmental outcome.

Methods.Thirteen of 17 children with opsoclonus-ataxia, all with neuroblastoma, who were previously reported were reevaluated a second time 2 to 4 years after the initial assessment. One subject who lived out of state was partially reevaluated and is included. Five new subjects (2 with neuroblastoma and 3 without) were also enrolled. Each was evaluated twice at a minimum interval of 1 year between sessions. Intercurrent medical course was recorded, emphasizing medication and relapse history. Cognitive, adaptive behavior, academic, speech and language, and motor abilities were assessed.

Results.For the group as a whole, overall standardized, age-adjusted cognitive scores improved. Generally, younger subjects' cognitive and adaptive behavior scores improved more than older subjects. Although all subjects had gains in speech, language, and motor function, some progressed at a slow pace, and in some instances, standard scores dropped. There was a striking influence of clinical course. Although initial presentation was severe and all subjects required high doses of corticosteroids or corticotropin, 5 had a monophasic course and were able to be weaned from treatment without relapses. Fourteen had multiple relapses over the years, generally with reduction of medication or intercurrent illnesses. Of the 5 children with monophasic course, 4 are currently functioning in the average range with a full-scale IQ of ≥90 and age-appropriate academic and adaptive skills.

Conclusions.The results continue to raise concern that opsoclonus-ataxia is sometimes a progressive encephalopathy. A minority of children with opsoclonus-ataxia have a monophasic course. Despite initial severity of symptoms, these children may have a more benign prognosis. For the majority of children with opsoclonus-ataxia, the course includes multiple relapses and requires prolonged treatment. Developmental sequelae are significant in these children with chronic course.