bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent development of monolithic materials as matrices in microcolumn separation systems
Authors: Zhu Guijie , Zhang Lihua , Yuan Huiming , Liang Zhen , Zhang Weibing , Zhang Yukui 
Published: March 2007

AbstractThis review summarizes the development of monolithic materials, including both organic and inorganic polymers, according mainly to the papers published in the past two years. Due to their good permeability, fast mass transfer, high stability, and their ease of modification, such materials have been widely used in microcolumn separation systems, not only as stationary phases for CEC and capillary HPLC, but also as substances for sample concentration and enzyme reactor. All the research results demonstrate that monolithic materials in microseparation systems can be expected to play an increasingly important role in the analysis of complex samples.
Vinylogous Amadori rearrangement: Implications in food and biological systems
Authors: Yaylayan Varoujan A. , Locas Carolina P. 
Published: March 2007

AbstractThe 4‐hydroxy‐alkenals are important lipid peroxidation products and are known to play a major role both in the development of degenerative diseases in biological systems and off‐flavors, or rancidity in food systems. The 4‐hydroxy‐alkenals can also be formed in nonlipid systems from 2‐deoxy‐sugar moieties such as 2‐deoxy‐ribose. FTIR spectroscopic evidence was provided for such a transformation catalyzed by amino acids through monitoring the decrease in intensity of the aldehydic band centered at 1716 cm–1 of the open form of 2‐deoxy‐ribose and increase in the intensity of the formed conjugated aldehydic band centered at 1672 cm–1. Furthermore, 4‐hydroxy‐alkenals can react with nitrogen nucleophiles such as amino acids and proteins to form Schiff base adducts that are able to undergo vinylogous Amadori rearrangement (vARP) and subsequently cyclize to generate a pyrrole moiety. This cyclization is prevented in the case of secondary amino acids such as proline to form a stable vinylogous Amadori rearrangement product (vARP). Monitoring this reaction of proline with 4‐hydroxy‐2‐nonenal (HNE) has indicated that within 15 min at 28°C the 1685 cm–1 band of HNE completely disappears and that at 50°C, vARP is formed within 5 min, as indicated by the formation of a characteristic band at 1709 cm–1.
Maillard reaction products enriched food extract reduce the expression of myofibroblast phenotype markers
Authors: Ruhs Stefanie , Nass Norbert , Somoza Veronika , Friess Ulrich , Schinzel Reinhard , Silber Rolf‐Edgar , Simm Andreas 
Published: March 2007

AbstractAdvanced glycation end products (AGE) are associated with a wide range of degenerative diseases. The present investigation aimed at analysing the influence of AGE containing nutritional extracts on cardiac fibroblasts (CFs) as the major cell type responsible for cardiac fibrosis. Mice CFs were treated with bread crust extract (BCE) which contained significant amounts of a variety of AGE modifications. BCE treatment with up to 30 mg/mL did not impair cell viability. Furthermore, BCE induced a moderate elevation of reactive oxygen species (ROS) production and activation of redox sensitive pathways like the p42/44MAPK, p38MAPK and NF‐κB but did not alter Akt kinase phosphorylation. Expression of smooth muscle α‐actin and tropomyosin‐1, which represent markers for myofibroblast differentiation, was reduced after bread crust treatment. These data suggest a putative antifibrotic effect of melanoidin‐rich food.
Parameters for the evaluation of the thermal damage and nutraceutical potential of lupin‐based ingredients and food products
Authors: Arnoldi Anna , Resta Donatella , Brambilla Francesca , Boschin Giovanna , D'Agostina Alessandra , Sirtori Elena , O'Kane Francesca 
Published: March 2007

AbstractFoods based on sweet lupin proteins are gaining attention from industry and consumers because of their possible role in the prevention of cardiovascular disease. When promoting lupin‐based foods for inclusion in a daily diet, the thermal damage suffered during processing is of relevance to the bioactive and nutritional quality of the food product. N‐(2‐furoylmethyl)‐L‐lysine (furosine) quantification demonstrates that currently available sweet lupin protein isolates have a thermal damage comparable to or lower than other traditional food ingredients, and are a good source of lysine in non‐dairy products. In lupin‐based foods claiming to have cholesterol‐lowering potential, shotgun proteomics offers itself as a fast and effective screening method for assessing the biological availability of active peptides. Such a method is readily applicable to other legume‐enriched food products.
Formation of 5‐hydroxymethyl‐2‐furfural (HMF) and 5‐hydroxymethyl‐2‐furoic acid during roasting of coffee
Authors: Murkovic Michael , Bornik Maria‐Anna 
Published: March 2007

AbstractThe formation of 5‐hydroxymethyl‐2‐furfural (HMF) and 5‐hydroxymethyl‐2‐furoic acid (HMFA) during roasting of coffee was studied. At 240°C the maximum concentration of HMF occurs after 3 min with a quick degradation up to 10 min when most of the HMF has disappeared again. Similar to 5‐hydroxymethyl‐furfural, HMFA is formed in coffee but not in a model system consisting of sucrose, alanine with or without chlorogenic acid. It was shown that HMFA is produced from different precursors than HMF namely glyceraldehyde and pyruvate. The comparison of the laboratory scale roasting with industrial roasting showed that 5‐hydroxymethyl‐furfural decreases with a higher degree of roasting whereas HMFA did not change. In the laboratory scale experiments, the highest concentration of 5‐hydroxymethyl‐furfural in coffee (909 μg/g) was obtained after 3 min and the maximum concentration of HMFA after 4 min (150 μg/g). Industrially roasted coffee contained up to 350 μg/g 5‐hydroxymethyl‐furfural and 140 μg/g HMFA.
Measurement of perfusion rate in human melanoma xenografts by contrast‐enhanced magnetic resonance imaging
Authors: Lyng Heidi , Dahle Gro A. , Kaalhus Olav , Skretting Arne , Rofstad Einar K. 
Published: March 2007

AbstractReliable methods based on MRI for measurement of the perfusion rate in human tumors are highly warranted. Tumors of two amelanotic human melanoma xenograft lines were subjected to dynamic 1H MRI after i.v. administration of gado‐pentetate dimeglumine (Gd‐DTPA). The aim was to investigate to what extent different perfusion parameters determined from the Gd‐DTPA kinetics, i.e., the initial uptake rate, the maximal uptake, the decay rate, and the perfusion rate calculated by use of the Kety equation, can be used as a reliable estimate of tumor perfusion rate. Each parameter was calculated in dual; one calculation was based on relative signal intensity increase (RSII) in T1‐weighted MR images and the other on Gd‐DTPA concentration determined from the images. The perfusion parameters were compared with the perfusion rates determined from measurement of tumor uptake of 86Rb or [14C]iodoantipyrine. The results showed that reliable estimates of tumor perfusion rate can be achieved from analysis of Gd‐DTPA kinetics by use of the Kety equation. Gd‐DTPA kinetics based on concentration might be used to achieve reliable estimates of absolute tumor perfusion rate, whereas reliable estimates of the relative perfusion rate might also be achieved from Gd‐DTPA kinetics based on RSII. The initial uptake rate, the maximal uptake, and the decay rate of Gd‐DTPA, however, are not reliable estimates of tumor perfusion rate, mainly because these parameters are highly influenced by the tumor extracellular volume fraction in addition to the perfusion rate.
Dynamic k‐space filling for bolus chase 3D MR digital subtraction angiography
Authors: Lee Howard M. , Wang Yi 
Published: March 2007

AbstractA bolus chase three‐dimensional (3D) MR digital subtraction angiography (MRDSA) technique was implemented using dynamic k‐space filling. This technique permits rapid 3D arterial imaging of the entire lower extremity at multiple stations using a single intravenous injection. Image acquisition at the first (most proximal) station starts from the edge of k‐space and ends in the center of k‐space (edge‐center order). Image acquisition for middle stations starts from the edge of k‐space, arrives at the center of k‐space at the middle of data acquisition, and ends at the edge of k‐space (edge‐center‐edge order). Image acquisition for the last station starts from the center of k‐space and ends at the edge of k‐space (center‐edge order). This dynamic k‐space filling minimizes contrast dose and motion artifacts. Bolus chase 3D MRDSA was performed on four normal volunteers and three patients using a multiple‐phase 3D fast gradient‐echo sequence, 25‐ml gadolinium dose, and a prototype stepping table. Total bolus chase 3D acquisition time was 46 s. Mask subtraction using both complex and magnitude subtraction was performed. Complex subtraction was found to be necessary for proper delineation of arteries below the aortic bifurcation. Diagnostic results were consistently obtained for all subjects.
Signal undershoots following visual stimulation: A comparison of gradient and spin‐echo BOLD sequences
Authors: Jones Richard A. , Schirmer Timo , Lipinski Bernadette , Elbel Gregor K. , Auer Dorothee P. 
Published: March 2007

AbstractGradient‐echo (GRE) and spin‐echo (SE) EPI BOLD sequences were used to quantitate the effect of visual stimulation. Both sequences showed a positive BOLD response during stimulation and a negative BOLD response in the interstimulation intervals. The relaxation rate changes during stimulation were larger for the GRE sequence than for the SE sequence, whereas in the interstimulation intervals they were not significantly different. In both cases, the ratio of the GRE/SE relaxation rate changes were consistent with BOLD effects in larger vessels despite the well‐known lower sensitivity of the SE sequence to the extravascular component of the BOLD effect in larger vessels. The most probable explanation of this result is that a significant fraction of the observed changes originated from the intravascular component of the BOLD effect. The SE sequence depicted smaller areas of activation than the GRE sequence with more than 85% of the pixels being depicted as significant by the SE sequence being also significant in the GRE activation maps. However, for the reverse comparison, an overlap of only 35% was observed, with many of the strongly correlated GRE pixels showing weak correlations in the corresponding SE activation image. Our results, together with the fact that signal undershoots have not been observed by groups using MR sequences that measure absolute flow changes for similar stimulation paradigms, suggest that the undershoot may be due to alterations in the blood volume and/or hematocrit during stimulation that normalize at a slower rate than the changes in blood flow after the cessation of the stimulation, leading to a poststimulation signal undershoot.
Gadolinium‐bearing red cells as blood pool MRI contrast agents
Authors: Johnson Kevin M. , Tao Jing Zang , Kennan Richard P. , Gore John C. 
Published: March 2007

AbstractHuman and rat red blood cells (RBCs) were loaded with gadolinium DTPA dimeglumine using an osmotic pulse technique to create a blood pool contrast agent for MRI. The resulting packed red cells contained 30.9 ± 3.3 (1 SD) mmol Gd/literfor humans and 24.7 ± 3.5 (1 SD) mmol Gd/liter for rats. Longitudinal relaxation rate constant of human RBCs increased from 2.0 ± 0.1 to 145.6 ± 36.2 s−1; the transverse relaxation rate constant increased from 6.8 ± 1.2 to 562 ± 410 s−1. For rat RBCs, R1 increased from 1.45 ± 0.15 to 84.8 ± 23.9 s−1; R2 increased from 7.1 ± O.64 to 247 ± 158 s−1. Affinity for oxygen was slightly reduced (control P50 = 22.3 ± 2.3 versus experimental P50 = 27.3 ± 1.3, P < 0.01), as was mechanical de‐formability. No drop in relaxivities was seen after 5 days of storage. The apparent volume of distribution was 0.0164 ± 0.003 liter/kg, biologic half‐life 4.38 ± 0.34 h, and total plasma clearance 0.003 ± 0.0006 liter/kg/h. Compared with Gd‐DTPA “free” in the plasma, tissue enhancement from RBCs was initially lower but was much prolonged. Preparation is simple enough to be reproduced by most laboratories.
A new semiautomated, three‐dimensional technique allowing precise quantification of total and regional cerebellar volume using MRI
Authors: Luft Andreas R. , Skalej Martin , Welte Dorothea , Kolb Rupert , Biirk Katrin , Schulz Jorg B. , Klockgether Thomas , Voigt Karsten 
Published: March 2007

AbstractA new method was developed to measure total and regional cerebellar volumes using MRI. Previously, the volumes of the cerebellum and its substructure had been studied planimetri‐cally. The new method uses three‐dimensional semiautomated volumetry with focus on reliability and performance. The method consists of a manual presegmentation using landmark‐adjusted planes followed by region‐growing segmentation and calculation of volume. The cerebellum is partitioned into 11 regions defined by planes, which are adjusted for internal cerebellar landmarks (three radial regions inside the vermis that extend into the medial hemisphere (one‐fourth of the transverse diameter of the hemisphere); one region in the lateral hemisphere (remaining three‐fourths)). Forty‐six healthy volunteers were examined and the effects of age, gender, and symmetry were estimated. Shrinkage in the vermis (especially anterior superior compartment) was marked. Age effects diminished laterally and were not observed in the lateral hemisphere. Age effects on the total cerebellar volume were marginal. Effects of gender and symmetry were nonsignificant. Technique and results are discussed and related to methods and findings of others.
The effect of sample freezing on proton magic‐angle spinning NMR spectra of biological tissue
Authors: Middleton David A. , Bradley Daniel P. , Connor Susan C. , Mullins Paul G. , Reid David G. 
Published: March 2007

AbstractMagic‐angle spinning (MAS) has recently been shown to enhance spectral resolution in NMR examinations of intact biological tissue ex vivo. This work demonstrates that freezing certain tissue samples before examination by 1H MAS NMR can have a marked effect on their spectra. Spectra of rat kidney after freezing in liquid nitrogen, compared with spectra before freezing, showed a significant increase in signal intensities from alanine (>100%), glutamine (>40%), and glycine (>100%), and a decrease in signals assigned to lipids and other macromolecules. Some resonances‐such as from leucine, valine, isoleucine, and aspartate‐only became visible after freezing the tissue. These observations suggest that low temperature storage of tissue necropsies or biopsies might affect the results of a MAS NMR analysis, possibly resulting in the misinterpretation of metabolite changes to pathogen or disease effects.
Three‐dimensional 87Rb imaging of isolated pig hearts: Effects of regional ischemia
Authors: Kupriyanov Valery V. , Shen Jie , Kuzio Bozena , Sun Jiankang , Deslauriers Roxanne 
Published: March 2007

AbstractThe aim of this work was to investigate whether 1) Rb uptake is reduced in ischemic myocardium, and 2) 87Rb three‐dimensional (3D) imaging can detect the ischemic area. Hearts of domestic pigs (n = 8, 20–30 kg) were perfused retrogradely with Krebs‐Henseleit buffer in a 7‐T, 40‐cm horizontal bore magnet interfaced with Bruker MSLX spectrometer. Control (C) and ischemic (I) (45 min ligation of the left anterior descending coronary artery (LAD)) hearts were loaded with Rb+ by perfusion with a Rb+‐containing solution (2–4.7 mM, 30–100% of K+ substitution) for 35 min and 87Rb (C) or 31P (ischemic area in I) spectra were acquired. After mechanical arrest with 0.6–0.9 mM lidocaine, 87Rb images (7 min each, 1 cm3 resolution) were acquired (30–40 min) in the presence of Rb+‐containing perfusate. Subsequently, the hearts were stained with Evans blue (EB) and samples taken for measurements of Rb+ content. In the Group C, distribution of Rb+ in the left ventricle and the intensities of the 3D 87Rb images were uniform. In the ischemic area (Group I), verified by the lack of EB staining and changes in 31P spectra, the images showed a reduced intensity, which corresponded to decreased Rb+ content (33 ± 11% of the normal). Thus, 87Rb imaging reveals damaged cells detecting reduced Rb+ content in the ischemic area.
Detecting natural abundance carbon signal of NAA metabolite within 12‐cm3 localized volume of human brain using 1H‐{13C} NMR spectroscopy
Authors: Chen Wei , Adriany Gregor , Zhu Xiao‐Hong , Gruetter Rolf , Ugurbil Kamil 
Published: March 2007

AbstractNMR spectroscopy has been applied extensively to study metabolism noninvasively in the human brain and other tissues. However, it usually suffers from poor signal‐to‐noise ratio due to low NMR sensitivity and low metabolite concentrations. In this study, the technique of proton‐observe‐carbon‐edited (POCE) NMR spectroscopy combined with a single‐shot localization sequence was used to detect the natural abundance carbon signal of the amino acid N‐acetyl aspartate from a 12‐cm3 localized volume in the occipital lobe of humans at 4 T. The results suggest that NMR spectroscopy is sensitive enough to detect signals from low concentration metabolites (<60 nmol/g) from small volumes in the human brain within several minutes of data acquisition. This reveals that in vivo NMR spectroscopy is a promising technique for detecting small metabolite changes and low traces of 13C isotopic labeling for dynamic metabolism studies aimed at investigating physiological and pathological questions.
Targeting of ultrasmall superparamagnetic iron oxide (USPIO) particles to tumor cells in Vivo by using transferrin receptor pathways
Authors: Kresse Mayk , Wagner Susanne , Pfefferer Detlev , Lawaczeck Rüdiger , Elste Volker , Semmler Wolfhard 
Published: March 2007

AbstractHuman transferrin was covalently coupled to ultrasmall superparamagnetic iron oxide (USPIO) particles, and the trans‐ferrin‐USPIO obtained was investigated in vivo in experimental SMT/2A tumor‐bearing rats (rat mammary carcinoma). Physicochemical characterization showed an overall size of 36 nm (DLS) with a core size of 5 nm (TEM). Relaxivities were R,1 = 23.6 and R2 = 52.1 liter/mmol · s (0.47 T). Bound transferrin was 280 μg/mg of iron. Pharmacokinetic investigations revealed a half‐life of 17 min in normal rats. The MR evaluation of tumor signal intensity over time showed a 40% (range 25–55%) signal reduction 150 min after injection with the reduction persisting for at least 8 h. Control experiments using the parent USPIO compound or USPIO labeled with a nonspecific human serum albumin (HSA‐USPIO) showed a change of only 10% (range 5–15%) in tumor signal intensity over time. The results demonstrate that a combination of the USPIO relaxivity properties with the specificity of transferrin‐medi‐ated endocytosis allows in vivo detection of tumors by MR imaging.
A 16‐element phased‐array head coil
Authors: Porter Jay R. , Wright Steven M. , Reykowski Arne 
Published: March 2007

AbstractVolume‐array coils offer increased signal‐to‐noise ratio (SNR) over standard volume coils near the array elements while preserving the SNR at the center of the volume. As the number of array elements is increased, the SNR advantage as well as the complexity of actually constructing the array increases also. In this study, a 16‐channel receive‐only array for imaging of the brain is demonstrated and compared to a circularly polarized (CP) head coil of similar shape and diameter. The array was formed from a 2 × 8 grid of square elements placed on a cylindrical form. Mutual coupling was minimized by a combination of overlapping element placement and current‐reducing matching networks. Simultaneous data acquisition from the 16 individual elements was performed using a four‐channel receiver system with each channel time domain multiplexed by a factor of 4. Theoretical and experimental comparisons between the array and a standard CP head coil show that the array offers an increase in SNR of nearly a factor of 3 near its surface while maintaining a comparable SNR to that of the CP head coil in the center of the region of interest.
Quantification of myocardial perhsion by MRI after coronary occlusion
Authors: Vallée Jean‐Paul M. , Sostman H. Dirk , Macfall James R. , Degrado Timothy R. , Zhang Jian , Sebbag Laurent , Cobb Fred R. , Wheeler Ted , Hedlund Larry W. , Turkington Timothy G. , Spritzer Charles E. , Coleman R. Edward 
Published: March 2007

AbstractThe objectives of this study were to define the relationship between the first order constant of Gd‐DTPA transfer (K1) and the myocardial blood flow (MBF) at rest and to compare it with an equivalent relationship obtained for positron emission tomography (PET). In a canine model of permanent coronary occlusion (n = 4), myocardial and blood time concentration curves obtained by 13N‐ammonia PET and Gd‐DTPA‐enhanced MRI were fitted by a one‐compartment model to determine K1. A linear relationship was observed between MRIderived K1 and MBF measured by microspheres (K1 = 0.88 × flow −0.015, R = 0.95), which compares favorably with the equivalent relationship derived from PET (K1 = 0.74 × flow +0.16, R = 0.88). The results of this preliminary study suggest that, at rest and distal to a permanently occluded coronary artery, myocardial perfusion quantification by MRI is possible and can challenge PET.
Integrated MRI assessment of regional function and perfusion in canine myocardial infarction
Authors: Kraitchman Dara L. , Young Alistair A. , Bloomgarden Daniel C. , Fayad Zahi A. , Dougherty Lawrence , Ferrari Victor A. , Boston Raymond C. , Axel Leon 
Published: March 2007

AbstractA single integrated examination using regional measurements of perfusion from contrast‐enhanced MRI and three‐dimensional (3D) strain from tissue‐tagged MRI was developed to differentiate infarcted myocardium from adjacent tissue with functional abnormalities. Ten dogs were studied at baseline and 10 days after a 2‐hour occlusion of the left anterior descending coronary artery (LAD). Strain was determined using a 3D finite element model. Two‐dimensional measurements of hypoenhancing regions were highly correlated with myocardial viability (r = 0.96). Signal intensity versus time curves obtained from contrast‐enhanced MRI were used for quantitative perfusion analysis. The remote and adjacent noninfarcted tissue of the dogs with LAD occlusion, as well as the infarcted tissue, exhibited abnormal deformation patterns as compared to normal dogs positive predictive value (PPV) of strain determination of infarction = (66%). Integration of contrast‐enhanced MRI results with 3D strain analysis enabled the delineation of the myocardial infarction (PPV = 100%) from functionally compromised myocardium. This integrated cardiac examination shows promise for noninvasive serial assessment of potentially jeopardized noninfarcted myocardium to study the process of infarct remodeling and expansion.
Comparing individual signal‐averaged spectra
Authors: Spencer Richard G. S. 
Published: March 2007

AbstractIt is demonstrated here that individual signal‐averaged NMR spectra can be compared statistically in a rigorous fashion. This is accomplished by considering the ensemble of single acquisitions, which are summed to produce spectra. Applications of this concept include assessment of the statistical significance of apparent metabolite variations in control preparations and quantitative comparison of signals obtained during the fast response period in functional MRI.