bluuebunny/crossref_metadata_2025 huggingface dataset:
Site‐Specific Acid–Base Properties of Tenoxicam
Authors: Kóczián Kristóf , Völgyi Gergely , Kökösi József , Noszál Béla
Published: September 2007

The Hammett approach, as a new deductive tool, was introduced to characterize the otherwise inaccessible minor protonation pathway of tenoxicam (1), the non‐steroidal anti‐inflammatory drug. A total of eight compounds, constituting a systematic series of side chain‐substituted analogues of tenoxicam and piroxicam (2), were synthesized and studied in terms of acidbase properties and Hammett constants to identify the ideal replacement of the unprotonated pyridin‐2‐yl group, a key moiety in both molecules. Hammett constants of the phenyl substituents have been found to be in a linear correlation with the experimental log K values of the enolate sites, the basic moiety of the extended conjugated system in this family of piroxicam derivatives. Then, a similar correlation was observed for the analogous tenoxicam derivatives. After identifying the 2‐aza Hammett constant of the pyridin‐2‐yl group and the corresponding log K value, the site‐specific acid–base properties of tenoxicam could be quantitated. This novel method is assessed to be a fine‐tuning tool to find the ideal substituent by using analogue‐based deductive method to obtain site‐specific constants of the minor protonation/deprotonation pathway in drugs and biomolecules. The tenoxicam microconstant values indicate that the enolate moiety is of extremely low basicity (reflected by the $ \log \it k^{\rm{O}} $=3.70 and $ \log \it k_{\rm{N}}^{\rm{O}} $=1.09 values), which can, however, be interpreted in terms of the peculiar ring system and the overwhelming electron‐withdrawing effects of the adjacent heteroatoms. A diagram depicting the pH‐dependent distribution of 1 microspecies is also presented.
Myricananone and Myricananadiol: Two New Cyclic ‘Diarylheptanoids’ from the Roots of Myrica nana
Authors: Yu Ya‐Fang , Lu Qing , Guo Li , Mei Ren‐Qiang , Liang Heng‐Xing , Luo Du‐Qiang , Cheng Yong‐Xian
Published: September 2007

Two new cyclic ‘diarylheptanoids’, myricananone (1) and myricananadiol (2), were isolated from the roots of Myrica nana, together with the known compounds myricanol (3), myricanone (4), and porson (5). Their structures were determined by spectroscopic methods, including 1D‐ and 2D‐NMR as well as HR‐ESI‐MS analyses.
Chiral Recognition of Zolmitriptan by Modified Cyclodextrins
Authors: Kumar Vydyula Pavan , Kumar Perepogu Arun , Suryanarayana Iragavarapu , Nageswar Yadavalli Venkata Durga , Rao Kakulapati Rama
Published: September 2007

The two pyrrolidinylidenesulfamido‐modified β‐cyclodextrins (β‐CDs) 3 and 4 were prepared and studied for chiral discrimination of the enantiomers (R)‐ and (S)‐1 of zolmitriptan. The pyrrolidinylidenesulfamido spacer improved the chiral discrimination and binding abilities of these modified cyclodextrins. The hosts 3 and 4 showed higher selectivity for (S)‐1. The association constants (Table) and enantioselectivity factors were calculated for the complexes of (R)‐ and (S)‐1 with the β‐CDs 2–4. The formation of host⋅guest complexes was confirmed by 1H‐NMR studies.
Experimental and Density‐Functional‐Theory (DFT) Studies on the DNA‐Binding Trend and Spectral Properties of the Ruthenium Complexes [Ru(4,7‐dmp)(bdip)]2+ and [Ru(bpy)2(bdip)]2+ (4,7‐dmp=4,7‐Dimethyl‐1,10‐phenanthroline, bdip=2‐(1,3‐Benzodioxol‐4‐yl)‐1H‐imidazo[4,5‐f] [1,10]phenanthroline, bpy=2,2′‐bipyridine)
Authors: Tan Li‐Feng , Zhang Sheng , Chao Hui , Zheng Kang‐Cheng , Wang Fang , Xiao Yue , Ji Liang‐Nian
Published: September 2007

The new ligand bdip (=2‐(1,3‐benzodioxol‐4‐yl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline) and its RuII complexes [Ru(4,7‐dmp)2(bdip)]2+ (1; 4,7‐dmp=4,7‐dimethyl‐1,10‐phenanthroline) and [Ru(bpy)2(bdip)]2+ (2; bpy=2,2′‐bipyridine) were synthesized and characterized by elemental analysis, MS, 1H‐NMR, and cyclic voltammetry. The DNA‐binding properties of 1 and 2 to calf‐thymus DNA (CT‐DNA) were investigated by different spectrophotometric methods and viscosity measurements as well as by equilibrium dialysis and circular‐dichroism (CD) spectroscopy. The results suggest that both complexes bind to DNA through intercalation, and that the ancillary ligands of (polypyridine)ruthenium(II) complexes have significant effects on the spectral properties and DNA‐binding behavior of the complexes. Theoretical studies for these complexes were also carried out by the density‐functional‐theory (DFT) method. The trend in the DNA‐binding affinity and some electrochemical and spectral properties of the complexes were confirmed by the DFT calculations.
Estimation of seasonal crop water consumption in a vineyard using Bowen ratio‐energy balance method
Authors: Zhang B. Z. , Kang S. Z. , Zhang L. , Du T. S. , Li S. E , Yang X. Y.
Published: September 2007

Information about seasonal crop water consumption is useful to develop the appropriate irrigation scheme. Measurements of energy balance components using the Bowen ratio method were made for a complete growing season at a vineyard in the arid region of northwest China. Vine in the experiment was furrow‐irrigated using a trellis system. The measured evapotranspiration was compared with estimates using the soil water balance method. It is shown that the Bowen ratio method provided accurate estimates of evapotranspiration from the vineyard and this requires that the Bowen ratio system is appropriately installed. The energy balance components showed typical diurnal pattern with peaks that occurred around the midday, except for the ground heat flux which delayed its peak by 2–3 h. The sensible heat flux was greater than the latent heat flux and followed the net radiation closely. The ratio of the latent heat flux to net radiation was low in the early growing season and increased over time. Under the limited irrigation experienced in the vineyard, the latent heat flux was controlled by available soil moisture and the total evapotranspiration in the growing season was 253 mm. The seasonal progression of the crop coefficient is similar to that reported in the literature, with the maximum occurring during the month of September. The crop coefficient can be estimated as a non‐linear function of day of year (DOY) and used to estimate evapotranspiration from vineyards in the region. Copyright © 2007 John Wiley & Sons, Ltd.
Estimating finite difference block equivalent hydraulic conductivity for numerically solving the Richards' equation
Authors: Feng Chih‐Yung , Lee Tim Hau , Lee Wen Sen , Chen Chu‐Hui
Published: September 2007

A method is proposed for calculating the equivalent hydraulic conductivity (EHC) within a finite difference block (FDB). Application of the constant‐flux assumption of Darcy's Law, the EHC equals to the integration of effective hydraulic conductivity (Kw) as a function of pressure head (hw) divided by the head difference at the ends of the FDB. Error analysis show that the constant‐flux (CF) EHC estimates are better than those computed by the commonly used arithmetic‐mean (AM), geometric‐mean (GM), and harmonic‐mean (HM) techniques. CF EHC results are even more superior at larger interblock head difference situations.

Simulations of water infiltration experiments show that simulations using the CF EHC or AM or GM weighting technique have only slight difference while applying the Neumann type boundary condition at the ground surface. In case of the Dirichlet type boundary condition, however, the CF EHC is superior to the other two in correctly estimating the depth of infiltration while enlarging the grid size. Therefore, it is recommended to adopt the CF EHC with a larger grid size to the more stable and more efficient results. Copyright © 2007 John Wiley & Sons, Ltd.
Evaluation of snow models in terrestrial biosphere models using ground observation and satellite data: impact on terrestrial ecosystem processes
Authors: Ichii Kazuhito , White Michael A. , Votava Petr , Michaelis Andrew , Nemani Ramakrishna R.
Published: September 2007

Snow is important for water management, and an important component of the terrestrial biosphere and climate system. In this study, the snow models included in the Biome‐BGC and Terrestrial Observation and Prediction System (TOPS) terrestrial biosphere models are compared against ground and satellite observations over the Columbia River Basin in the US and Canada and the impacts of differences in snow models on simulated terrestrial ecosystem processes are analysed. First, a point‐based comparison of ground observations against model and satellite estimates of snow dynamics are conducted. Next, model and satellite snow estimates for the entire Columbia River Basin are compared. Then, using two different TOPS simulations, the default TOPS model (TOPS with TOPS snow model) and the TOPS model with the Biome‐BGC snow model, the impacts of snow model selection on runoff and gross primary production (GPP) are investigated. TOPS snow model predictions were consistent with ground and satellite estimates of seasonal and interannual variations in snow cover, snow water equivalent, and snow season length; however, in the Biome‐BGC snow model, the snow pack melted too early, leading to extensive underpredictions of snow season length and snow covered area. These biases led to earlier simulated peak runoff and reductions in summer GPP, underscoring the need for accurate snow models within terrestrial ecosystem models. Copyright © 2007 John Wiley & Sons, Ltd.
The application of electrical conductivity as a tracer for hydrograph separation in urban catchments
Authors: Pellerin Brian A. , Wollheim Wilfred M. , Feng Xiahong , Vörösmarty Charles J.
Published: September 2007

Two‐component hydrograph separation was performed on 19 low‐to‐moderate intensity rainfall events in a 4·1‐km2 urban watershed to infer the relative and absolute contribution of surface runoff (e.g. new water) to stormflow generation between 2001 and 2003. The electrical conductivity (EC) of water was used as a continuous and inexpensive tracer, with order of magnitude differences in precipitation (12–46 µS/cm) and pre‐event streamwater EC values (520–1297 µS/cm). While new water accounted for most of the increased discharge during storms (61–117%), the contribution of new water to total discharge during events was typically lower (18–78%) and negatively correlated with antecedent stream discharge (r2 = 0·55, p < 0·01). The amount of new water was positively correlated with total rainfall (r2 = 0·77), but hydrograph separation results suggest that less than half (9–46%) of the total rainfall on impervious surfaces is rapidly routed to the stream channel as new water. Comparison of hydrograph separation results using non‐conservative tracers (EC and Si) and a conservative isotopic tracer (δD) for two events showed similar results and highlighted the potential application of EC as an inexpensive, high frequency tracer for hydrograph separation studies in urban catchments. The use of a simple tracer‐based approach may help hydrologists and watershed managers to better understand impervious surface runoff, stormflow generation and non‐point‐source pollutant loading to urban streams. Copyright © 2007 John Wiley & Sons, Ltd.
Cyclin D1/cdk4 can interact with E2F4/DP1 and disrupts its DNA‐binding capacity
Authors: Scimè Anthony , Li Lili , Ciavarra Gianni , Whyte Peter
Published: September 2007

The E2F family of transcription factors regulate the expression of many growth‐related genes in a cell cycle‐dependent manner. These transcription factors can activate or, in conjunction with an Rb‐related protein, repress transcription. E2F transcriptional activity is regulated at several different levels that are each linked to cell cycle progression. In many cell types, E2F4 and E2F5 are the predominant E2F species during G0 and early G1 and function primarily as repressors of E2F‐regulated genes. In this study, co‐immunoprecipitation techniques were used to demonstrate that cyclins D1, D2, and D3 are capable of interacting with E2F4, E2F5, and DP1. Overexpression of cyclin D1/cdk4 reduced E2F4‐mediated transcription in a simple reporter gene assay and electrophoretic mobility shift analyses using nuclear extracts from transfected cells indicated that cyclin D1/cdk4 disrupts the DNA‐binding ability of E2F4. Cell cycle analysis following stimulation of serum‐starved 3T3 cells indicated that E2F4 undergoes changes in its phosphorylation pattern coincident with the synthesis of cyclin D1. Examination of a series of E2F4 deletion mutants indicated that a cyclin D1‐binding site located close to the carboxyl terminus of E2F4 was critical for the disruption of DNA binding by cyclin D1/cdk4. These data support a model in which E2F4 DNA binding is abolished during mid‐G1 at the same time when E2F interactions with pRb‐related proteins are disrupted by cyclin D1/cdk4. J. Cell. Physiol. 214: 568–581, 2008. © 2007 Wiley‐Liss, Inc.
The MAP kinase JNK‐1 of Caenorhabditis elegans: Location, activation, and influences over temperature‐dependent insulin‐like signaling, stress responses, and fitness
Authors: Wolf Marc , Nunes Frank , Henkel Arne , Heinick Alexander , Paul Rüdiger J.
Published: September 2007

The mitogen‐activated protein kinase (MAPK) pathways and insulin‐like signaling play pivotal roles in cellular stress response. Using an anti‐phospho‐SAPK/JNK antibody and a daf‐16::GFP‐based reporter assay, the present study shows in Caenorhabditis elegans that ambient temperature (1–37°C) specifically influences the activation (phosphorylation) of the MAP kinase JNK‐1 as well as the nuclear translocation of DAF‐16, the main downstream target of insulin‐like signaling. Activated JNK‐1 was detected only in neuronal cells, and JNK‐1 was found to be controlled by the MAPK JKK‐1 under heat stress. Comparative analyses on the wildtype and a jnk‐1 deletion mutant revealed a promoting influence of JNK‐1 on both nuclear DAF‐16 translocations and DAF‐16 target gene (superoxide dismutase 3, sod‐3) expressions within peripheral, non‐neuronal tissue. Consequently, the mutant exhibited a reduced thermal tolerance and reproductive fitness at higher temperatures. These results provide evidence of indirect interactions between neuronal MAPK and peripheral insulin‐like signaling in response to environmental stimuli (temperature, H2O2). J. Cell. Physiol. 214: 721–729, 2008. © 2007 Wiley‐Liss, Inc.
The Multi‐PDZ domain protein MUPP1 as a lipid raft‐associated scaffolding protein controlling the acrosome reaction in mammalian spermatozoa
Authors: Ackermann Frauke , Zitranski Nele , Heydecke Diana , Wilhelm Beate , Gudermann Thomas , Boekhoff Ingrid
Published: September 2007

The success of acrosomal exocytosis, a complex process with a variety of interrelated steps, relies on the coordinated interaction of participating signaling molecules. Since scaffolding proteins are known to spatially organize sequential signaling pathways, we examined whether the Multi‐PDZ domain protein MUPP1, recently identified in mammalian spermatozoa, is functionally active in controlling acrosomal secretion in mammalian sperm cells. To address this question, permeabilized mouse sperm were loaded with inhibitory antibodies against MUPP1 as well as with a photosensitive Ca2+ chelator which allows a controlled release of acrosomal Ca2+. The results revealed that MUPP1 controls initial tethering and docking of the acrosomal vesicle, whereas syntaxin 2, a t‐SNARE protein also expressed in the acrosomal cap of mammalian spermatozoa, appears to take part in the final process of acrosomal fusion. Interestingly, using immunogold electron microscopy, it was found that MUPP1 is detectable in the region of the periacrosomal membrane. Furthermore, in isolated detergent‐insoluble glycolipid‐enriched membrane domains from epididymal spermatozoa, MUPP1 was found to show a striking association with the Triton X‐100 insoluble membrane fraction, which did not change significantly upon sperm capacitation or partial chemical extraction of cholesterol. This evidence points to a role of MUPP1 as a membrane raft‐associated molecular organizer, and suggests that mammalian spermatozoa may use a scaffolding protein and distinct membrane subdomains to spatially organize components involved in the process of acrosomal exocytosis. J. Cell. Physiol. 214: 757–768, 2008. © 2007 Wiley‐Liss, Inc.
Gene expression fluctuations in murine hematopoietic stem cells with cell cycle progression
Authors: Dooner Gerri J. , Colvin Gerald A. , Dooner Mark S. , Johnson Kevin W. , Quesenberry Peter J.
Published: September 2007

Evolving data suggest that marrow hematopoietic stem cells show reversible changes in homing, engraftment, and differentiation phenotype with cell cycle progression. Furthermore, marrow stem cells are a cycling population. Traditional concepts hold that the system is hierarchical, but the information on the lability of phenotype with cycle progression suggests a model in which stem cells are on a reversible continuum. Here we have investigated mRNA expression in murine lineage negative stem cell antigen‐1 positive stem cells of a variety of cell surface epitopes and transcription regulators associated with stem cell identity or regulation. At isolation these stem cells expressed almost all cell surface markers, and transcription factors studied, including receptors for G‐CSF, GM‐CSF, and IL‐7. When these stem cells were induced to transit cell cycle in vitro by exposure to interleukin‐3 (IL‐3), Il‐6, IL‐11, and steel factor some (CD34, CD45R c‐kit, Gata‐1, Gata‐2, Ikaros, and Fog) showed stable expression over time, despite previously documented alterations in phenotype, while others showed variation of expression between and within experiments. These latter included Sca‐1, Mac‐1, c‐fms, and c‐mpl. Tal‐1, endoglin, and CD4. These studies indicate that defined marrow stem cells express a wide variety of genes at isolation and with cytokine induced cell cycle transit show marked and reversible phenotype lability. Altogether, the phenotypic plasticity of gene expression for murine stem cells indicates a continuum model of stem cell regulation and extends the model to reversible expression with cell cycle transit of mRNA for cytokine receptors and stem cell markers. J. Cell. Physiol. 214: 786–795, 2008. © 2007 Wiley‐Liss, Inc.
DNA damage and cellular differentiation: More questions than responses
Authors: Simonatto Marta , Latella Lucia , Puri Pier Lorenzo
Published: September 2007

Studies on DNA damage responses in proliferating cells have revealed the relationship between sensing and repair of the DNA lesions and the regulation of the cell cycle, leading to the discovery and molecular characterization of the DNA damage‐activated cell cycle checkpoints. Much less is known about the DNA damage response in progenitors of differentiated cells, in which cell cycle arrest is a critical signal to trigger the differentiation program, and in terminally differentiated cells, which are typically post‐mitotic. How DNA lesions are detected, processed and repaired in these cells, the functional impact of DNA damage on transcription of differentiation‐specific genes, how these events are coordinated at the molecular level, the consequence of defective DNA damage response on tissue‐specific functions and its potential relationship with age‐related diseases are currently open questions. In particular the biological complexity inherent to the global genome reprogramming of tissue progenitors, such as embryonic or adult stem cells, suggests the importance of an accurate DNA damage response at the transcription level in these cells to ensure the genomic integrity of regenerating tissues. J. Cell. Physiol. 213:642–648. © 2007 Wiley‐Liss, Inc.
Batch cultures of Penicillium camembertii on glucose and amino acids—model for growth and ammonium production
Authors: Ayati Fadila , Aziza Majda , Maachi Rachida , Amrane Abdeltif
Published: September 2007

BACKGROUND: Three groups of amino acids were previously characterized based on their ability to be assimilated as carbon source by Penicillium camembertii. To describe the diauxic growth recorded on glucose and amino acids from the second group, such as arginine, an unstructured model was previously developed, based on the sequential consumption of both carbon substrates, glucose, followed after its exhaustion, by arginine. The model was modified to describe also the behaviour recorded during growth on other amino acids.

RESULTS: The growth model involved the carbon substrate consumption (Verlhust model) and the biomass on carbon substrate yield. Glucose was therefore considered during P. camembertii growth on nitrogen source amino acids (lysine—first group); and amino acid consumption was considered during growth on carbon source amino acids (glutamate—third group), with glucose being dissimilated only for energy supply. The excess nitrogen from amino acids was released as ammonium; the linking of this production to growth was found to increase with the ability of the amino acid to be assimilated as carbon source by P. camembertii.

CONCLUSION: The various metabolic behaviours recorded during P. camembertii growth on amino acids, in the presence of a primary carbon source such as glucose, were proved to be satisfactorily described by the model, showing the robustness of the model. Copyright © 2007 Society of Chemical Industry
Organoiridium complexes for hydrogen isotope exchange labeling
Authors: Heys J. Richard
Published: September 2007

An account of the development of organoiridium‐catalyzed hydrogen isotope exchange methods is given for the regioselective labeling of compounds from isotopic hydrogen gas, and their current status. The concept arose out of organometallic chemistry studies of C–H bond activation that revealed the ability of certain metal centers to interact with specific C–H bonds of molecules adjacent to coordinating heteroatoms. Initial success in labeling of model compounds with [Ir(H)2(acetone)2(PPh3)2]BF4 and deuterium gas provided the stimulus for further investigations into modified catalysts, their use with tritium, and applications to the labeling of a wide variety of more complex compounds. Over time, development of mechanistic models and accumulation of empirical data have grown sufficient to permit the prediction of applicability and regioselectivity based on compound structure. Continuing development of new organoiridium catalysts is broadening the range of compound types that can be labeled. Copyright © 2007 John Wiley & Sons, Ltd.
The history of the International Isotope Society
Authors: Susan Alexander B.
Published: September 2007

The author traces back to the late nineteen fifties the history of events preceding the current activities of the International Isotope Society (IIS) founded in 1986. The obvious conclusions are that there was a need for regular scientific meetings focused on topics such as the synthesis of isotopes, isotopically labelled and their applications. The various existing chemical and technical societies could not cover in their meetings such topics as efficiently as the IIS did. The Kansas City 1982 and 1985 first two unofficial meetings lead to the formation of the IIS in 1986 and then to a series of other regular symposia as 1988 (Innsbruck, Austria), 1991 (Toronto, Canada), 1994 (Strasbourg, France), 1997 (Philadelphia, USA), 2000 (Dresden, Germany), 2003 (Boston, USA), 2006 (Edinburgh, United Kingdom) and then in 2009 (Chicago, USA). The IIS also carries out its activities in yearly local Chapter meetings in the US, UK, Central Europe, Romania, Russia and China. At the same time, according to its Mission stated in the IIS Constitution (available in the www.intl.isotope‐soc.org website) the IIS also encourages the continuation of the independent meetings called the International Conferences of Isotopes; the activities of an international Low Level Waste IIS committee; the publication of the IIS Newsletter and maintenance of its website); organizing various workshops and short courses; and last but not least gives its support to the Journal of Labeled Compounds and Radiopharmaceutical by contributing papers and pro‐bono work on the Editorial as well as on the Advisory Board of the Journal. Copyright © 2007 John Wiley & Sons, Ltd.
[11C]Carbon monoxide, a versatile and useful precursor in labelling chemistry for PET‐ligand development
Authors: Långström Bengt , Itsenko Oleksiy , Rahman Obaidur
Published: September 2007

In this review the recent progress in the development of suitable precursors for 11C‐labelling is discussed. Especially the last few years' advancement of the use of [11C] carbon monoxide as a versatile and useful precursor in labelling chemistry is presented. The development is set in perspective of its potential in applying molecular imaging tools in drug and tracer development.The possibility of exploring small tracer libraries utilizing the microdosing concept is explored. Copyright © 2007 John Wiley & Sons, Ltd.
Neuro MR: Protocols
Authors: Mikulis David J. , Roberts Timothy P.L.
Published: September 2007

Clinical MRI depends on a symbiosis between MR physics and clinical requirements. The imaging solutions are based on a balance between the “palette” of available image contrasts derived from nuclear spin physics and tissue biophysics, and clinical determinants such as the anticipated pathology and efficient use of imaging time. Imaging is therefore optimized to maximize diagnostic sensitivity and specificity through the development of protocols organized along the lines of major disease categories. In the other part of this two‐part review, the primary determinants of image contrast, including T1, T2, and T2*, were highlighted. The development of pulse sequences designed to optimize each of these image contrasts was discussed and the impact of technological innovation (parallel imaging and high‐field systems) on the manner in which these sequences could be modified to improve clinical efficacy was further emphasized. The scope of that discussion was broadened to include the application of: 1) water diffusion imaging used primarily for detection of pathologies that restrict the free movement of water in the tissues and for defining fiber tracts in the brain; 2) the intravenous administration of exogenous contrast agents (gadolinium‐diethylene triamine pentaacetic acid [GdDTPA]) for assessment of blood‐brain‐barrier (BBB) defects and brain blood flow; and 3) MR spectroscopy (MRS) for assessment of brain metabolites. The goal of this part is to discuss how these acquisitions are combined into specific protocols that can effectively detect and characterize, or in keeping with our artistic analogy, “paint” each of the major diseases affecting the central nervous system (CNS). This work concludes with a discussion of image artifacts and pitfalls in image interpretation, which, in spite our best efforts to minimize or eliminate them, continue to occur. Much of the ensuing discussion is based on our own institutional experience. Protocols, therefore, do not necessarily match those from other institutions due to variability in clinical emphasis, MR instruments, and available software. An attempt was made to focus on basic clinical sequences that are available on most modern MR systems, with protocols employing generally accepted clinical imaging philosophies. J. Magn. Reson. Imaging 2007;26:838–847. © 2007 Wiley‐Liss, Inc.
Simultaneous myocardial and fat suppression in magnetic resonance myocardial delayed enhancement imaging
Authors: Foo Thomas K.F. , Slavin Glenn S. , Bluemke David A. , Montequin Marcela , Hood Maureen N. , Ho Vincent B.
Published: September 2007

Purpose

To develop a method for fat suppression in myocardial delayed enhancement (MDE) studies that achieves effective signal intensity reduction in fat but does not perturb myocardial signal suppression.

Materials and Methods

A new approach to fat suppression that uses a spectrally‐selective inversion‐recovery (SPEC‐IR) tip‐up radio frequency (RF) pulse following the conventional nonselective IR RF pulse together with a second SPEC‐IR RF pulse is proposed. The tip‐up pulse restores the fat longitudinal magnetization after the nonselective IR pulse and allows the fat magnetization to recover more fully toward its equilibrium value, providing for better fat suppression by the second SPEC‐IR RF pulse. This new approach was validated in phantom studies and in five patients.

Results

Effective fat suppression was achieved using the proposed technique with minimal impact on normal myocardial signal suppression. Mean fat suppression achieved using this approach was 67% ± 8%, as measured in the chest wall immediately opposite the heart.

Conclusion

The results indicate this modular‐type approach optimizes fat suppression in myocardial delayed enhancement studies but does not perturb the basic IR pulse sequence or change basic acquisition parameters. J. Magn. Reson. Imaging 2007;26:927–933. © 2007 Wiley‐Liss, Inc.
Comparison of region‐of‐interest analysis with three different histogram analysis methods in the determination of perfusion metrics in patients with brain gliomas
Authors: Young Robert , Babb James , Law Meng , Pollack Erica , Johnson Glyn
Published: September 2007

Purpose

To compare routine ROI analysis and three different histogram analyses in the grading of glial neoplasms. The hypothesis is that histogram methods can provide a robust and objective technique for quantifying perfusion data in brain gliomas. Current region‐of‐interest (ROI)‐based methods for the analysis of dynamic susceptibility contrast perfusion magnetic resonance imaging (DSC MRI) data are operator‐dependent.

Materials and Methods

A total of 92 patients underwent conventional and DSC MRI. Multiple histogram metrics were obtained for cerebral blood flow (CBF), cerebral blood volume (CBV), and relative CBV (rCBV) maps using tumoral (T), peritumoral (P), and total tumoral (TT) analysis. Results were compared to histopathologic grades. Statistical analysis included Mann‐Whitney (MW) tests, Spearman rank correlation coefficients, logistic regression, and McNemar tests.

Results

The maximum value of rCBV (rCBVmax) showed highly significant correlation with glioma grade (r = 0.734, P < 0.001). The strongest histogram correlations (P < 0.0001) occurred with rCBVT SD (r = 0.718), rCBVP SD25 (r = 0.724) and rCBVTT SD50 (r = 0.685). Multiple rCBVT, rCBVP, and rCBVTT histogram metrics showed significant correlations. CBF and CBV histogram metrics were less strongly correlated with glioma grade than rCBV histogram metrics.

Conclusion

Histogram analysis of perfusion MR provides prediction of glioma grade, with peritumoral metrics outperforming tumoral and total tumoral metrics. Further refinement may lead to automated methods for perfusion data analysis. J. Magn. Reson. Imaging 2007;26:1053–1063. © 2007 Wiley‐Liss, Inc.
Quantification of physiological and hemodynamic indices using T1 dynamic contrast‐enhanced MRI in intracranial mass lesions
Authors: Singh Anup , Haris Mohammad , Rathore Divya , Purwar Ankur , Sarma Manoj , Bayu Getaneh , Husain Nuzhat , Rathore Ram K. Singh , Gupta Rakesh K.
Published: September 2007

Purpose

To estimate precontrast tissue parameter (T10) using fast spin echo (FSE) and to quantify physiological and hemodynamic parameters with leakage correction using T1‐weighted dynamic contrast‐enhanced (DCE) perfusion imaging.

Materials and Methods

Voxel‐wise T10 computation was performed followed by the analysis of T1‐weighted DCE perfusion data for the conversion of signal intensity time curve to concentration time curve, estimation of hemodynamic and physiological perfusion indices, and a method for leakage correction. Validations of accuracy of the computations have also been carried out.

Results

The computed T10 and hemodynamic perfusion indices in normal white and gray matter were in good agreement with the literature values. Physiological perfusion indices in these regions were found negligible, validating computations. Cerebral blood volume (CBV) values change negligibly over the length of concentration time curve in white matter, gray matter, and lesion (CBVcorrected), while CBVuncorrected (lesion) shows linear increase over time.

Conclusion

T1‐weighted DCE perfusion data along with FSE‐based T1 estimation can be used for an accurate estimation of hemodynamic and physiological perfusion indices. J. Magn. Reson. Imaging 2007;26:871–880. © 2007 Wiley‐Liss, Inc.
Least‐squares chemical shift separation for 13C metabolic imaging
Authors: Reeder Scott B. , Brittain Jean H. , Grist Thomas M. , Yen Yi‐Fen
Published: September 2007

Purpose

To describe a new least‐squares chemical shift (LSCSI) method for separation of chemical species with widely spaced peaks in a sparse spectrum. The ability to account for species with multiple peaks is addressed.

Materials and Methods

This method is applied to imaging of 13C‐labeled pyruvate and its metabolites alanine, pyruvate, and lactate. The method relies on a priori knowledge of the resonant frequencies of the different chemical species, as well as the relative signal from the two pyruvate peaks, one of which lies near the alanine peak. With this information a least‐squares method was utilized for separation of signal from the three metabolites, facilitating tremendous reductions in the amount of data required to decompose the different chemical species. Optimization of echo spacing for maximum noise performance of the signal separation is also described.

Results

Imaging an enriched 13C phantom at 3.0T, the LSCSI method demonstrates excellent metabolite separation, very similar to echo planar spectroscopic imaging (EPSI), while only using 1/16th as much data.

Conclusion

This approach may be advantageous for in vivo hyperpolarized 13C metabolic applications for reduced scan time compared with EPSI. J. Magn. Reson. Imaging 2007;26:1145–1152. © 2007 Wiley‐Liss, Inc.
Three‐dimensional delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) for in vivo evaluation of reparative cartilage after matrix‐associated autologous chondrocyte transplantation at 3.0T: Preliminary results
Authors: Trattnig Siegfried , Marlovits Stefan , Gebetsroither Simone , Szomolanyi Pavol , Welsch Goetz H. , Salomonowitz Erich , Watanabe Atsuya , Deimling Michael , Mamisch Tallal Charles
Published: September 2007

Purpose

To use a 3D gradient‐echo (GRE) sequence with two flip angles for delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) to evaluate relative glycosaminoglycan content of repair tissue after matrix‐associated autologous chondrocyte transplantation (MACT).

Materials and Methods

In a phantom study, T1‐mapping based on a 3D‐GRE sequence with different flip angle combinations was compared with a standard inversion recovery (IR) sequence at 3.0T. Fifteen patients were examined after MACT in the knee at “3–13 months” (group I) and “19–42 months” (group II). The δ relaxation rate (δR1) calculated for repair tissue and normal hyaline cartilage was measured and mean values were compared in different postoperative intervals using analysis of variance.

Results

The flip angle combination 35/10° provided the best agreement with IR sequence for short and long T1 values. The mean δR1 for repair tissue was 2.49 versus 1.04 at the intact control site in group I and 1.90 compared with 0.81 in group II. Differences from repair tissue to control sites showed statistically significance for both groups; no significant difference was found between groups.

Conclusion

The 3D dual flip angle dGEMRIC technique optimized for cartilage imaging is comparable to standard T1 IR technique for T1 mapping. Furthermore, the preliminary in vivo study demonstrates the feasibility of the technique in the evaluation of MACT patients. J. Magn. Reson. Imaging 2007;26:974–982. © 2007 Wiley‐Liss, Inc.
Absolute quantification of cerebral blood flow in normal volunteers: Correlation between Xe‐133 SPECT and dynamic susceptibility contrast MRI
Authors: Knutsson Linda , Börjesson Siv , Larsson Elna‐Marie , Risberg Jarl , Gustafson Lars , Passant Ulla , Ståhlberg Freddy , Wirestam Ronnie
Published: September 2007

Purpose

To compare absolute cerebral blood flow (CBF) estimates obtained by dynamic susceptibility contrast MRI (DSC‐MRI) and Xe‐133 SPECT.

Materials and Methods

CBF was measured in 20 healthy volunteers using DSC‐MRI at 3T and Xe‐133 SPECT. DSC‐MRI was accomplished by gradient‐echo EPI and CBF was calculated using a time‐shift‐insensitive deconvolution algorithm and regional arterial input functions (AIFs). To improve the reproducibility of AIF registration the time integral was rescaled by use of a venous output function. In the Xe‐133 SPECT experiment, Xe‐133 gas was inhaled over 8 minutes and CBF was calculated using a biexponential analysis.

Results

The average whole‐brain CBF estimates obtained by DSC‐MRI and Xe‐133 SPECT were 85 ± 23 mL/(min 100 g) and 40 ± 8 mL/(min 100 g), respectively (mean ± SD, n = 20). The linear CBF relationship between the two modalities showed a correlation coefficient of r = 0.76 and was described by the equation CBF(MRI) = 2.4 · CBF(Xe)−7.9 (CBF in units of mL/(min 100 g)).

Conclusion

A reasonable positive linear correlation between MRI‐based and SPECT‐based CBF estimates was observed after AIF time‐integral correction. The use of DSC‐MRI typically results in overestimated absolute perfusion estimates and the present study indicates that this trend is further enhanced by the use of high magnetic field strength (3T). J. Magn. Reson. Imaging 2007;26:913–920. © 2007 Wiley‐Liss, Inc.
Measurement of cerebral blood volume in humans using hyperoxic MRI contrast
Authors: Bulte Daniel , Chiarelli Peter , Wise Richard , Jezzard Peter
Published: September 2007

Purpose

To develop a new method of measuring quantitative regional cerebral blood volume (CBV) using epochs of hyperoxia as an intravenous contrast agent with T2*‐weighted MRI.

Materials and Methods

Images were acquired from six subjects (four male, two female, mean age 29 ± 3.7 years) using a sequence combining pulsed arterial spin labeling interleaved with a gradient echo echo‐planar imaging (EPI) blood oxygenation level‐dependent (BOLD) sequence at 3T. The hyperoxia paradigm lasted 28 minutes consisting of 4 minutes of normoxia, two 6‐minute blocks of hyperoxia separated by 6 minutes of normoxia. During the hyperoxic blocks the subjects were delivered a fractional oxygen concentration of 0.5.

Results

The mean CBV was calculated to be 3.77 ± 1.05 mL/100 g globally, 3.93 ± 0.90 mL/100 g in gray matter (GM), and 2.52 ± 0.78 mL/100 g in white matter (WM). The mean GM/WM ratio was thus found to be 1.56. These values are comparable to those obtained in other studies.

Conclusion

The hyperoxia technique for measuring CBV may be particularly useful for patient groups where an injected bolus of contrast agent is contraindicated. As more functional studies are employing epochs of inspired gases for calibration purposes, this method is easily incorporated into existing paradigms to produce a noninvasive, repeatable, easily tolerated, and quantitative measurement of regional CBV. J. Magn. Reson. Imaging 2007;26:894–899. © 2007 Wiley‐Liss, Inc.
Intracranial time‐of‐flight MR angiography at 7T with comparison to 3T
Authors: von Morze Cornelius , Xu Duan , Purcell Derk D. , Hess Christopher P. , Mukherjee Pratik , Saloner David , Kelley Douglas A.C. , Vigneron Daniel B.
Published: September 2007

Purpose

To establish the feasibility of intracranial time‐of‐flight (TOF) MR angiography (MRA) at 7T using phased array coils and to compare its performance to 3T.

Materials and Methods

In an initial study, five normal volunteers were scanned at 7T and 3T using eight‐channel coils and standard acquisition parameters from a clinical TOF protocol. In a second study three additional studies were performed at 7T and 3T using empirically optimized 7T parameters. Contrast‐to‐noise (CNR) values were measured for major vessel segments.

Results

All measurements documented CNR increases at 7T, with a mean increase of 83% in the initial study and 88% in the second study. The CNR values achieved using the latter protocol were similar to the values obtained in the initial study, despite the 42% reduction expected due to the higher spatial resolution. CNR in the smaller peripheral vessels was increased dramatically, resulting in excellent visualization at high resolution.

Conclusion

TOF MRA at 7T demonstrated improved visualization of the intracranial vasculature, particularly the smaller peripheral vessels, and may benefit studies of small aneurysms, atherosclerosis, vasospasm, and vasculitis. J. Magn. Reson. Imaging 2007;26:900–904. © 2007 Wiley‐Liss, Inc.
Bleomycin‐induced lung injury assessed noninvasively and in spontaneously breathing rats by proton MRI
Authors: Karmouty‐Quintana Harry , Cannet Catherine , Zurbruegg Stefan , Blé François‐Xavier , Fozard John R. , Page Clive P. , Beckmann Nicolau
Published: September 2007

Purpose

To apply proton magnetic resonance imaging (MRI) techniques to assess noninvasively and in spontaneously breathing rats, structural changes following a single intratracheal administration of bleomycin (BLM).

Materials and Methods

Rats were scanned by MRI prior to BLM or vehicle administration and at six hours, 24 hours, week 1, and at weeks 2, 3, 6, and 8 after treatment. Bronchoalveolar lavage (BAL) fluid and histological analyses were performed at 24 hours, and at weeks 1 and 8 (histology only).

Results

Prominent MRI fluid signals were detected in the lungs of BLM‐treated rats one week after challenge. These signals correlated with increased inflammatory parameters in BAL fluid and with marked perivascular and parenchymal infiltration with inflammatory cells in histological slices. At week 2 the MRI signals due to edema resolved, but nevertheless an increase in MRI signal intensity from the lung parenchyma was apparent. In some areas of the right lung the MRI signal intensity in the parenchyma decreased between weeks 2 and 8. These observations were in line with histology demonstrating collagen deposition and atelectasis (hallmarks of fibrosis) at week 1 and a partial recovery of the lung parenchyma at week 8.

Conclusion

The data demonstrate the ability of proton MRI to detect BLM‐induced lung fibrosis as well as the acute inflammatory response caused by the agent. J. Magn. Reson. Imaging 2007;26:941–949. © 2007 Wiley‐Liss, Inc.
Accuracy and reliability of MRI vs. laboratory measurements in an ex vivo porcine model of arthritic cartilage loss
Authors: Jaremko Jacob L. , Maciejewski Conrad M. , Cheng Rita W.T. , Ronsky Janet L. , Thompson Richard B. , Lambert Robert G.W. , Dhillon Sukhvinder S.
Published: September 2007

Purpose

To quantify the accuracy of magnetic resonance imaging (MRI) measurement of change in cartilage volume due to thin linear excisions, simulating arthritic cartilage losses, by comparison with laboratory volume measurements in an ex vivo porcine model.

Materials and Methods

We scanned 15 porcine patellae by T1‐weighted spoiled gradient echo (SPGR) MRI at baseline and after excision of up to three thin layers of articular cartilage. Excised fragment volume was determined from density and weight. Postexcision scans were “fused” to the baseline scan by three‐dimensional (3D) registration. This allowed automated recalculation of the remaining cartilage volume within a baseline region of interest (ROI) following each excision. We compared MRI estimates of change in cartilage volume to direct laboratory measurement of fragment volume.

Results

Our 38 excised fragments averaged 0.16 mL, or ∼7% of cartilage volume. MRI and laboratory estimates of total cartilage volume loss differed by 1.6% ± 13.2% (mean, coefficient of variation [CV]). Accuracy was ±0.1 mL for 95% of scans.

Conclusion

MRI estimates of small changes in porcine patellar cartilage volume were unbiased, reliable, and accurate to 0.1 mL. Despite a proportionately high error in the very thin fragments tested, achievement of similar accuracy in vivo would be adequate to detect approximately two years of osteoarthritic cartilage loss. J. Magn. Reson. Imaging 2007;26:992–1000. © 2007 Wiley‐Liss, Inc.
Assessment of microvascular density, extracellular volume fraction, and radiobiological hypoxia in human melanoma xenografts by dynamic contrast‐enhanced MRI
Authors: Vestvik Ida K. , Egeland Tormod A.M. , Gaustad Jon‐Vidar , Mathiesen Berit , Rofstad Einar K.
Published: September 2007

Purpose

To investigate whether gadopentetate dimeglumine (Gd‐DTPA)‐based dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) may be a useful method for assessing fraction of radiobiologically hypoxic cells in tumors.

Materials and Methods

A‐07 and R‐18 human melanoma xenografts were used as preclinical tumor models. DCE‐MRI was performed at a voxel size of 0.23 × 0.47 × 2.0 mm3. Tumor images of E · F (E is the initial extraction fraction of Gd‐DTPA and F is blood perfusion) and λ (the partition coefficient of Gd‐DTPA) were produced by subjecting DCE‐MRI series to Kety analysis. Microvascular density and extracellular volume fraction (ECVF) were determined by analysis of histological preparations. The fraction of radiobiologically hypoxic cells was measured by the paired survival curve method.

Results

E · F correlated with microvascular density, and λ correlated with ECVF. The fraction of hypoxic cells was ∼6.5‐fold higher in R‐18 tumors than in A‐07 tumors, consistent with the observation that A‐07 tumors showed higher values for E · F and microvascular density and lower cell density (i.e., higher values for λ and ECVF) than R‐18 tumors.

Conclusion

E · F and λ images obtained by Kety analysis of DCE‐MRI series contain information that may be utilized to estimate the extent of radiobiological hypoxia in tumors. J. Magn. Reson. Imaging 2007;26:1033–1042. © 2007 Wiley‐Liss, Inc.
Multisite fMRI reproducibility of a motor task using identical MR systems
Authors: Costafreda Sergi G. , Brammer Michael J. , Vêncio Ricardo Z.N. , Mourão Maria L. , Portela Luiz A.P. , de Castro Claudio Campi , Giampietro Vincent P. , Amaro Edson
Published: September 2007

Purpose

To estimate between‐scanner functional MRI (fMRI) reproducibility in a multisite study.

Materials and Methods

A total of five identical 1.5T MR systems were used to repeatedly scan five subjects while performing a finger tapping task. A two‐way (scanners, subjects) random effects analysis of variance (ANOVA) was used to estimate between‐scanner and between‐subject variability on two outcome variables: task‐related mean blood oxygenation level dependent (BOLD) signal change and volume of activation within a motor region‐of‐interest (ROI).

Results

Between‐scanner variability of fMRI data accounted for a small proportion of the total variation in the BOLD signal change (8.34%, P = 0.114) and volume of activation (5.46%, P = 0.203). Between‐subject variation accounted for more than half of the total variation for both measurements (57.17% and 54.46%, respectively, P < 0.01).

Conclusion

These results support the feasibility of multisite studies using identical scanner systems. J. Magn. Reson. Imaging 2007;26:1122–1126. © 2007 Wiley‐Liss, Inc.