bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vivo quantitation of metabolite concentrations in the brain by means of proton MRS
Authors: Henriksen Ole 
Published: March 2007

AbstractMRS offers unique possibilities for non‐invasive studies of biochemistry in the human brain in vivo. A growing body of evidence suggests that proton MRS may contribute to the clinical evaluation of a number of pathologies including ischaemia, tumours, epilepsy, metabolic and neuropaediatric disorders. In most cases results are expressed as ratios between metabolite signals obtained at certain experimental conditions. Presenting the results as metabolite signal ratios may lead to misinterpretation because such alterations can be due to changes in the content of either one of the metabolites or both, or may simply be due to changes in relaxation behaviour. Absolute quantitation of metabolite concentrations is therefore warranted. A number of studies using single volume proton MRS indicate that absolute quantitation of metabolite concentration is possible with respect to N‐acetyl aspartate (NAA), total creatine, choline containing compounds, (Cho) and inositols (Ins). Internal standards (unsaturated water signal) as well as external standards have been used for signal calibration. Quality control with respect to signal linearity with concentration or with size of selected volume, selection efficiency, outer volume depression and signal contamination is essential for validation of the measurements. Furthermore, corrections for the influence of relaxation behaviour are necessary. The results published so far indicate that the concentrations of NAA, total creatine, Cho and Ins in mmoles (kg wet weight)−1 range between 8.2 and 17.2, (mean 10.2), 5.9 and 11.6 (mean 7.2), 1.1 and 2.0 (mean 1.5) and 3.9 and 8.1 (mean 6.1), respectively. So far only a limited number of clinical studies has been published including studies of acute stroke, multiple sclerosis and Alzheimer's disease. The results are promising and encourage further exploitation of the utility of quantitative proton MRS in clinical practise.
The design of macrocyclic ligands for monitoring magnesium in tissue by 31P NMR
Authors: Haveren Jacco Van , Deleon Linda , Ramasamy Ravichandran , Westrenen Jeroen Van , Dean Sherry A. 
Published: March 2007

AbstractA series of ligands based upon 1,4,7‐triazacyclononane, containing variable numbers of acetate vs methylene‐phosphonate ester or methylenephosphinate sidechains, has been synthesized and characterized as possible 31P NMR probes for monitoring [Mg2+ ]free. The diacetate monophosphinate and diacetate monophosphonate ester mixed ligands proved to have conditional (dissociation) constants at pH 7.4 in an appropriate range for measuring typical levels of intracellular [Mg2+ ]free and binding selectivities for Mg2+ over Ca2+ that ranged from 1.4 to 6.8. The 31P resonances of these ligands were well downfield of typical tissue phosphate metabolite resonances, and addition of Mg2+ to any one of these ligands resulted in well‐resolved resonances for HL and MgL (where L = ligand), in slow chemical exchange. The chemical shift differences between the HL and MgL species varied from 2.1 to 2.6 ppm for three different ligands. The conditional Mg2+‐L binding constants were sensitive to pH in the physiological range, due to protonation of a single macrocyclic nitrogen at high pH (log K1 values ranged from 10 to 12). However, given conditions that allow an independent assessment of pH (i.e., from the 31P chemical shift of Pi), we show that accurate KD values can be estimated from the known thermodynamic stability constants (KMgL) and ligand protonation constants (K1). This makes these ligands potentially useful for monitoring [Mg2+ ]free by 31P NMR over a variety of solution conditions, even during conditions when the pH may be changing.
A fast method for in vivo lactate imaging
Authors: Reese T. , Norris D. G. , Leibfritz D. 
Published: March 2007

AbstractA robust method for fast lactate imaging is presented using a combination of a lactate editing sequence and a one‐shot imaging experiment. The lactate editing method is based on manipulation of the phase of the lactate CH3 signal via J‐modulation. This is applied as a preparation experiment to the U‐FLARE imaging sequence. Phantom experiments are presented in which the quality of water and lipid suppression is established. Edited lactate images with a spatial resolution of 3 m̈L and total measuring time of 15.8 min are shown. These were obtained from a hemispherical ischemia in the gerbil brain. The images are compared with diffusion‐weighted water images.
T1 and T2 relaxation times of the major 1H‐containing metabolites in rat brain after focal ischemia
Authors: Toorn Annette Van Der , Dijkhuizen Rick M. , Tulleken Cees A. F. , Nicolay Klaas 
Published: March 2007

AbstractThe relaxation properties of water and metabolites were measured in rat brain following the occlusion of the middle cerebral artery (MCA) with localized 1H MRS. The PRESS sequence was employed to select volumes of 39 m̈L in the ischemic and the contralateral hemisphere. T1 and T2 relaxation times and peak intensities of water, choline containing compounds (Cho), creatine and phosphocreatine (Cre) and N‐acetyl aspartate (NAA) in both hemispheres were determined at 3‐6 h, 1 day and 3 or 4 days after occlusion. Lactate in the ischemic hemisphere was also quantified. The relaxation properties and peak intensities of NAA, Cre and Cho remained unchanged in the ischemic volume during the first 3‐6 h of ischemia as compared to the contralateral volume. Water T1 was slightly increased in the ischemic volume. After 24 h the T1 and T2 of water and Cre and the T1 of Cho had increased significantly in the ischemic volume, while the peak intensities of Cho, Cre and NAA were reduced. It appears therefore that tissue changes which occur in the early phase of ischemia have no significant effects on the relaxation behaviour of the metabolites. However, ischemic brain damage affects the relaxation behaviour and concentration of the metabolites and water at later stages.
Characteristic metabolic profiles revealed by 1H NMR spectroscopy for three types of human brain and nervous system tumours
Authors: Florian Catarina L. , Preece Nicholas E. , Bhakoo Kishore K. , Williams Stephen R. , Noble Mark 
Published: March 2007

AbstractCell culture techniques, high‐resolution in vitro 1H NMR spectroscopy, and chromatographic analyses were used to compare the properties of three types of human brain and nervous system tumours. Cell lines were immunocytochemically characterized at all stages in culture with specific antibodies. Intracellular metabolites present in cell extracts were analysed by 1H NMR spectroscopy and by high performance liquid chromatography (HPLC). The spectra from meningiomas, neuroblastomas, and glioblastomas displayed, in addition to similarities — including the presence of signals from leucine, isoleucine, valine, threonine, lactate, acetate, glutamate, choline‐containing compounds and glycine — certain distinguishing metabolic features. Spectra from meningiomas featured relatively high signals from alanine. Intense signals from creatine were present in neuroblastoma spectra, while in spectra from glioblastoma they were not detectable. We found statistically significant differences by 1H NMR spectroscopy in the amounts of alanine, glutamate, creatine, phosphorylcholine and threonine among the types of tumours examined. HPLC determinations confirmed that there were also other metabolites specific to a type of tumour, such as taurine, γ‐aminobutyric acid, and serine. We suggest that these findings have potential relevance for the development of non‐invasive diagnosis of tumour lineage by 1H NMR spectroscopy in vivo.
Signal profile measurements for evaluation of the volume‐selection performance of ISIS
Authors: Ljungberg Maria , Starck Göran , Forssell‐Aronsson Eva , Alpsten Magne , Ekholm Sven 
Published: March 2007

AbstractHigh‐resolution signal profiles obtained with a test phantom were used in this study to evaluate the volume‐selection performance of an implementation of ISIS (Image Selected In vivo Spectroscopy). The phantom simulated the brain with regard to volume and loading of coil. A remotely controlled, movable signal source inside the phantom was filled with orthophosphoric acid. Signal profiles of the volume of interest (VOI) were measured in three perpendicular directions. Special interest was focused on the transition zones, the position of the profiles, and the effects of off‐resonance and T1 smearing. The transition zones were on average 5.6 mm wide and the full width at half maximum (FWHM) was 35 mm for a VOI of 40 × 40 times; 40 mm3. The positions of the centre of the signal profiles were x = 3.2, y=‐0.7 and z=3.3mm off‐centre. The deviation of the volume position could be explained by off‐resonance effects during imaging and spectroscopy. These data illustrate the importance of detailed knowledge of the volume‐selection performance when attempting precision measurements using image‐guided in vivo MRS.
The application of porous‐media theory to the investigation of time‐dependent diffusion in in vivo systems
Authors: Helmer Karl G. , Dardzinski Bernard J. , Sotak Christopher H. 
Published: March 2007

AbstractRecent developments in solid‐boundary porous‐media theory have shown that useful structural information can be extracted from the time‐dependent diffusion coefficient, D(t), of the fluid filling the interstitial space. This theoretical framework provides a basis from which to understand the results from diffusion experiments performed in other types of systems (e.g. biological). Structural information about porous media can be obtained from the short‐time behavior of D(t) in the form of the ratio of the surface area to pore volume, S/V. The long‐time behavior of D(t) in porous media provides an indirect measure of the macroscopic structure. In this case, the longtime diffusion coefficient, Deff, reflects the tortuosity, T, of the medium; a property of both the connectivity of the diffusion paths and the volume fraction of the sample. Measurements of D(t) were performed in RIF‐1 tumors, using both spectroscopy and imaging, and the data were used to calculate S/V and T. The results were compared with histological sections in order to correlate S/V and T with differences in tissue structure (i.e. necrotic vs non‐necrotic tumor tissue). Based on spectroscopic measurements, there is a trend towards decreasing S/V and T with increasing tumor volume, consistent with the interpretation that water in necrotic tissue is experiencing relatively fewer restricting barriers (as compared to non‐necrotic tumor tissue). Based on D(t) maps generated from RIF‐1 tumors, Deff, and hence T appears to be much more sensitive than S/V in differentiating between necrotic and non‐necrotic tissue. In addition to characterizing diseased tissue, S/V and particularly T appear to be sensitive to structural changes that would accompany tumor treatment and should therefore provide a useful tool for monitoring the progress of therapeutic interventions.
Molecular diffusion, tissue microdynamics and microstructure
Authors: Bihan Denis Le 
Published: March 2007

AbstractDiffusion NMR is the only method available today that noninvasively provides information on molecular displacements over distances comparable to cell dimensions. This information can be used to infer tissue microstructure and microdynamics. However, data may be fairly difficult to interpret in biological tissues which differ markedly from the theoretical “infinite isotrope medium”, as many factors may affect the NMR signal. The object of this paper is to analyze the expected effects of temperature, restriction, hindrance, membrane permeability, anisotropy and tissue inhomogeneity on the diffusion measurements. Powerful methods, such as q‐space imaging, diffusion tensor imaging and diffusion spectroscopy of metabolites further enhance the specificity of the information obtained from diffusion NMR experiments.
Isolation and identification of the five major sesquiterpene hydrocarbons of ginger
Authors: Van Beek Teris A. , Lelyveld Gerrit P. 
Published: March 2007

AbstractForty‐eight different ginger oils from nine countries spanning four continents have been investigated by dual capillary gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). All oils were found to contain the same five major sesquiterpene hydrocarbons. Two of them were isolated in one step from an Indian oil by an efficient reversed phase high performance liquid chromatographic (RP‐HPLC) separation. The other three were isolated by a combination of RP‐HPLC and preparative capillary GC. They were identified by UV, MS, 1H NMR and 13C NMR as α‐zingiberene (1), β‐bisabolene (2), (E,E)‐α‐farnesene (3), β‐sesquiphellandrene (4) and ar‐curcumene (5). The reported absence of some of these compounds in earlier studies could in many cases be explained by unsatisfactory separations, misidentifications and confusion in the nomenclature.
A blind comparison of simple bench‐top bioassays and human tumour cell cytotoxicities as antitumor prescreens
Authors: Anderson J. E. , Goetz C. M. , McLaughlin J. L. , Suffness M. 
Published: March 2007

AbstractSimple bench‐top bioassays involving brine shrimp lethality, Lemna frond proliferation, and the inhibition of crown gall tumours on potato discs, as well as the human tumour cell lines A‐549 lung carcinoma, MCF‐7 breast carcinoma and HT‐29 colon adenocarcinoma, were compared for their accuracy to detect known in vivo (P‐388) active antitumour agents supplied by the National Cancer Institute. The potato disc assay was the best and showed excellent correlation to in vivo activity (p=0.008). The brine shrimp assay (p = 0.033) proved to be superior or equally as accurate as the in vitro human solid tumour cell lines (p = 0.033‐0.334). The Lemna assay (p = 0.708) showed the poorest correlation. The brine shrimp and potato disc assays are suggested as convenient in‐house prescreens to existing cytotoxicity or antitumour assays.
Analysis and distribution of swainsonine and related polyhydroxyindolizidine alkaloids by thin layer chromatography
Authors: Molyneux Russell J. , James Lynn F. , Panter Kip E. , Ralphs Michael H. 
Published: March 2007

AbstractA spray reagent which is sensitive and specific for polyhydroxyindolizidine glycosidase inhibitors such as swainsonine and castanospermine has been developed for their visualization on thin layer chromatographic plates. The method involves treatment of the plates with a sequential system consisting of 10% acetic anhydride in benzene, followed by Ehrlich's reagent. This technique has been used to follow the isolation and purification of minor alkaloidal constituents from Astragalus lentiginosus and Castanospermum australe. The occurrence of swainsonine and its N‐oxide in a number of Astragalus and Oxytropis species has been investigated. Species previously incriminated as locoweeds on the basis of field observations were all shown to contain the alkaloid and it was also found to occur in additional species. The highest levels of swainsonine were found in the seeds and pods, with lesser amounts in the leaves and stems, and none detectable in the roots.
Strategy for the isolation and identification of coumarins with calcium antagonistic properties from the roots of Angelica archangelica
Authors: Härmälä P. , Vuorela H. , Hiltunen R. , Nyiredy Sz. , Sticher O. , Törnquist K. , Kaltia S. 
Published: March 2007

AbstractFifteen coumarins, 2′‐angeloyl‐3′‐isovaleryl vaginate (4), archangelicin (3), oxypeucedanin hydrate (8), bergapten (5), byakangelicin angelate (15), imperatorin (11), isoimperatorin (6), isopimpinellin (13), 8‐[2‐(3‐methylbutroxy)‐3‐hydroxy‐3‐methylbutoxy]psoralen (12), osthol (1), ostruthol (9), oxypeucedanin (7), phellopterin (14), psoralen (2) and xanthotoxin (10), have been isolated from a chloroform extract of the roots of Angelica archangelica L. subsp. archangelica (Apiaceae). 2, 4, 12, and 15 are reported for the first time from A. archangelica L. The isolation was carried out using medium pressure liquid chromatography (MPLC) using the normal phase mode and then subsequently using a combination of the reversed and normal phase techniques. The eluents were optimized by thin layer chromatography and high performance liquid chromatography preassays according to the “PRISMA” system, and then transferred without modification of the solvent selectivity to preparative MPLC separations. The structures of the compounds were elucidated by a combination of spectroscopic methods. The isolation was carried out from a chloroform extract which in earlier tests had exhibited calcium blocking activity on the uptake of 45Ca2+ in clonal rat pituitary GH4C1 cells. The calcium antagonistic activity of the isolated compounds was then tested using the same method as for the extracts. All the coumarins tested exhibited calcium antagonistic activity. Archangelicin showed activity significantly higher than that of verapamil in this test system.
The quantitative analysis of seed proteins from peas using high performance liquid chromatography
Authors: Chambers Stephen J. , Bacon James R. , Lambert Nigel 
Published: March 2007

AbstractHydroxyapatite chromatography is frequently employed in the purification of pea seed proteins. By scaling down the procedure and interfacing it to a high performance liquid chromatographic (HPLC) system a method has been developed for the quantitative analysis of seed proteins not only from pea but potentially many other seeds. Under appropriate conditions three peaks were eluted from the column after first washing with a saline buffer. The peaks were shown by SDS‐polyacryamide gel electrophoresis to correspond to albumin, legumin and vicilin respectively. The technique provides results of a high degree of accuracy. Protein compositions were determined for six commercial pea varieties, with each analysis taking one hour and requiring less than one milligram of protein extract. Multiple loadings of the same sample indicated a very high level of reproducibility. The HPLC method revealed significantly higher levels of albumin compared with published values, and demonstrated the unreliability of fractionating globulins and albumins on the basis of solubility. The merits of this technique relative to alternative methods are discussed.
A kinetic method for assay of plant peroxidase and catalase activities by chemiluminescence
Authors: Frébort Ivo , Haviger Antonín , Jílek Milan 
Published: March 2007

AbstractA chemiluminescent method for the simultaneous assay of peroxidase and catalase activities and chemical traps and quenchers of free radicals in natural samples, based on the additions of peroxidase standards, is presented. The method was standardized with horseradish peroxidase and beef liver catalase. The theoretical basis, mathematical treatment and computer processing of the method are described. The technique was used to analyse 25 samples of various common fruits and vegetables. The levels of peroxidase activity thus determined were compared with those obtained using the guaiacol method and were found to be in good agreement. The relationship between the shape of the chemiluminescent curves and the proportions of peroxidase and catalase activities and traps and quenchers are discussed.
Separation and identification of flavone, flavonol, isoflavone and flavanone aglycones by capillary column gas chromatography
Authors: Koupai‐Abyazani Mohammed R. , Creaser Colin S. , Stephenson G. Richard 
Published: March 2007

AbstractA rapid and sensitive capillary column gas chromatographic method for the separation and identification of trimethylsilyl derivatives of flavonoid aglycones is reported. Well‐resolved, sharp and symmetrical peaks were obtained for a wide range of flavone, flavonol, isoflavone and flavanone aglycones with a variety of substitution patterns. Chromatographic behaviour and the effects of the number, position and type of the substituents on the retention times of these compounds have been defined.
Mass spectrometry of underivatized naturally occurring glycosides
Authors: Wolfender Jean‐Luc , Maillard Marc , Marston Andrew , Hostettmann Kurt 
Published: March 2007

AbstractMass spectrometry is essential for the structure determination of naturally occurring glycosides. Molecular weight and sugar sequence information can be obtained. Development of “soft” ionization techniques has allowed a direct mass spectrometric investigation of underivatized glycosides. Numerous different and complementary methods of ionization have been used for their study. For a given compound, the choice of a particular technique is crucial in order to obtain the structural information needed. A brief survey of these ionization techniques is given, together with examples of their use in major classes of plant glycosides.
Reversed phase thin layer chromatographic methods for separation of cytokinins
Authors: Letham D. S. , Singh S. , Willcocks D. A. 
Published: March 2007

AbstractSilica gel layers were impregnated with a range of hydrophobic products. Only two such materials, liquid paraffin and the silicone fluid dimethylpolysiloxane, yielded thin layers which separated cytokinins effectively by reversed phase chromatography. The chromatographic behaviour of numerous cytokinins on these layers using a number of solvents is reported. The use of the layers and of integrated normal phase‐reversed phase thin layer chromatographic systems to separate cytokinins in crude extracts is discussed.
Macrocyclic trichothecenes from brazilian Baccharis species: From microanalysis to large‐scale isolation
Authors: Jarvis Bruce B. 
Published: March 2007

AbstractTwo Brazilian species of Baccharis, B. megapotamica and B. coridifolia, have been shown to contain a number of macrocyclic trichothecene antibiotics, some of which are identical to those produced by the common soil fungi Myrothecium. A number of different materials and methods have been used in a large‐scale (1800 kg) isolation procedure and in the chemical analysis of plant material, inter alia ferric gel precipitation, fractionation using polyethyleneimine impregnated silica gel and countercurrent chromatography.
The determination of the petroselinic acid content of coriander (Coriandrum sativum) oil by capillary gas chromatography
Authors: Griffiths D. Wynne , Robertson Graeme W. , Millam Stephen , Holmes Amanda C. 
Published: March 2007

AbstractA rapid capillary gas chromatographic method has been developed for screening coriander fruits for petroselinic acid content. The method also permits determination of the concentrations of the other major long‐chain fatty acids present in coriander oil and allows an estimate of the total oil content of the sample to be determined. The method is applicable at the single fruit level and the results of analysing the constituent husk and embryo fractions have shown significant differences between their fatty acid compositions.