bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing a numerical cellular braided‐stream model with a physical model
Authors: Doeschl‐Wilson Andrea B. , Ashmore Peter E.
Published: April 2005

A. B. Murray and C. Paola (1994, Nature, vol. 371, pp. 54–57; 1997, Earth Surface Processes and Landforms, vol. 22, pp. 1001–1025) proposed a cellular model for braided river dynamics as an exploratory device for investigating the conditions necessary for the occurrence of braiding. The model reproduces a number of the general morphological and dynamic features of braided rivers in a simplified form. Here we test the representation of braided channel morphodynamics in the Murray–Paola model against the known characteristics (mainly from a sequence of high resolution digital elevation models) of a physical model of a braided stream. The overall aim is to further the goals of the exploratory modelling approach by first investigating the capabilities and limitations of the existing model and then by proposing modifications and alternative approaches to modelling of the essential features of braiding. The model confirms the general inferences of Murray and Paola (1997) about model performance. However, the modelled evolution shows little resemblance to the real evolution of the small‐scale laboratory river, although this depends to some extent on the coarseness of the grid used in the model relative to the scale of the topography. The model does not reproduce the bar‐scale topography and dynamics even when the grid scale and amplitude of topography are adapted to be equivalent to the original Murray–Paola results. Strong dependence of the modelled processes on local bed slopes and the tendency for the model to adopt its own intrinsic scale, rather than adapt to the scale of the pre‐existing topography, appear to be the main causes of the differences between numerical model results and the physical model morphology and dynamics. The model performance can be improved by modification of the model equations to more closely represent the water surface but as an exploratory approach hierarchical modelling promises greater success in overcoming the identified shortcomings. Copyright © 2005 John Wiley & Sons, Ltd.
Modelling the hysteresis in the velocity pattern of slow‐moving earth flows: the role of excess pore pressure
Authors: van Asch T. W. J.
Published: April 2005

This paper describes the velocity pattern of a slow‐moving earth flow containing a viscous shear band and a more or less rigid landslide body on top. In the case of small groundwater fluctuations, Bingham's law may describe the velocity of these slow‐moving landslides, with velocity as a linear function of excess shear stress. Many authors have stated that in most cases a non‐linear version of Bingham's law best describes the moving pattern of these earth flows. However, such an exponential relationship fails to describe the hysteresis loop of the velocity, which was found by some authors. These authors showed that the velocity of the investigated earth flows proved to be higher during the rising limb of the groundwater than during the falling limb.

To explain the hysteris loop in the velocity pattern, this paper considers the role of excess pore pressure in the rheological behaviour of earth flows by means of a mechanistic model. It describes changes in lateral internal stresses due to a change in the velocity of the earth flow, which generates excess pore pressure followed by pore pressure dissipation. Model results are compared with a hysteresis in the velocity pattern, which was measured on the Valette landslide complex (French Alps). Copyright © 2005 John Wiley & Sons, Ltd.
Rock fragment distributions and regolith evolution in the Ouachita Mountains, Arkansas, USA
Authors: Phillips Jonathan D. , Luckow Ken , Marion Daniel A. , Adams Kristin R.
Published: April 2005

Rock fragments in the regolith are a persistent property that reflects the combined influences of geologic controls, erosion, deposition, bioturbation, and weathering. The distribution of rock fragments in regoliths of the Ouachita Mountains, Arkansas, shows that sandstone fragments are common in all layers, even if sandstone is absent in parent material. Shale and sandstone fragments are produced at the bedrock weathering front, but the shale weathers rapidly and intact fragments are rare in the solum. Sandstone is weathered from ridgetop outcrops and transported downslope. Some of these fragments are moved downward, by faunalturbation and by transport into pits associated with rotting tree stumps. Upward movement by treethrow is common, resulting in a net concentration of rocks near the surface. However, the highest fragment concentrations are in the lower regolith, indicating active production at the weathering front. The regolith is a dynamic feature, reflecting the influences of vertical and horizontal processes, of active weathering at the bedrock interface, and of surficial sediment movements. The role of trees in redistributing rock fragments suggests that significant regolith mixing occurs over time scales associated with forest vegetation communities, and that forest soils have likely been extensively mixed within Holocene and historic time. Copyright © 2005 John Wiley & Sons, Ltd.
Flow behaviour and runout modelling of a complex debris flow in a clay‐shale basin
Authors: Remaître Alexandre , Malet Jean‐Philippe , Maquaire Olivier , Ancey Christophe , Locat Jacques
Published: April 2005

Identification of debris‐flow hazard areas necessitates the knowledge of the flow thickness and the runout distance. Both have been investigated using a numerical runout model. On the Faucon stream (South French Alps), representative of clay‐shale basins, results of various rheological tests and numerical experiments are presented and discussed. The calibration of the model was undertaken using the results of both geomorphological surveys and sedimentological analyses. Rheological tests using either a parallel‐plate rheometer, a coaxial rheometer, slump tests, and an inclined plane were carried out on several samples. Results have shown that the flow behaviour could be described by an Herschel‐Bulkley constitutive equation. The rheological responses of several natural suspensions collected from surficial deposits (sandstones, moraines, weathered black marls) were also investigated. In order to model the runout of the flow, the model BING was used. The model describes well the influence of each type of sediment on the behaviour (runout distance, deposit thickness) of the flow, although the velocities were significantly overestimated. Different risk scenarios are tested and discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Using on‐nadir spectral reflectance to detect soil surface changes induced by simulated rainfall and wind tunnel abrasion
Authors: Chappell Adrian , Zobeck Ted M. , Brunner Gillian
Published: April 2005

The surface susceptibility to erosion (erodibility) is an important component of soil erosion models. Many studies of wind erosion have shown that even relatively small changes in surface conditions can have a considerable effect on the temporal and spatial variability of dust emissions. One of the main difficulties in measuring erodibility is that it is controlled by a number of highly variable soil factors. Collection of these data is often limited in scale because in situ measurements are labour‐intensive and very time‐consuming. To improve wind erosion model predictions over several spatial and temporal scales simultaneously, there is a requirement for a non‐invasive approach that can be used to rapidly assess changes in the compositional and structural nature of a soil surface in time and space. Spectral reflectance of the soil surface appears to meet these desirable requirements and it is controlled by properties that affect the soil erodibility.

Three soil surfaces were modified using rainfall simulation and wind tunnel abrasion experiments. Observations of those changes were made and recorded using digital images and on‐nadir spectral reflectance. The results showed clear evidence of the information content in the spectral domain that was otherwise difficult to interpret given the complicated interrelationships between soil composition and structure. Changes detected at the soil surface included the presence of a crust produced by rainsplash, the production of loose erodible material covering a rain crust and the selective erosion of the soil surface. The effect of rainsplash and aeolian abrasion was different for each soil tested and crust abrasion was shown to decrease as rainfall intensity increased. The relative contributions of the eroded material from each soil surface to trapped mixtures of material assisted the erodibility assessment. Ordination analyses within each of two important soil types explained significant amounts of the variation in the reflectance of all wavebands by treatments of the soil and hence changes in the soil surface. The results show that soil surface conditions within a soil type are an underestimated source of variation in the characterization of soil surface erodibility and in the remote sensing of soil. Copyright © 2005 John Wiley & Sons, Ltd.
A note on cross‐profile morphology for glacial valleys
Authors: Morgan Frank
Published: April 2005

We provide an improvement to the Hirano–Aniya catenary model for the cross‐profile morphology of a glacial valley. Copyright © 2005 John Wiley & Sons, Ltd.
Response to Morgan's comment
Authors: Hirano M. , Aniya M.
Published: April 2005

We respond to Morgan's comment on our model for cross‐profile morphology for glacial valleys. Copyright © 2005 John Wiley & Sons, Ltd.
Identification of androgen‐responsive genes that are alternatively regulated in androgen‐dependent and androgen‐independent rat prostate tumors
Authors: Pfundt Rolph , Smit Frank , Jansen Corine , Aalders Tilly , Straatman Huub , van der Vliet Walter , Isaacs John , van Kessel Ad Geurts , Schalken Jack
Published: April 2005

The vast majority of androgen‐dependent prostate tumors progress toward incurable, androgen‐independent tumors. The identification of androgen‐responsive genes, which are still actively transcribed in the tumors of patients who have undergone androgen ablation, may shed light on the molecular mechanisms underlying this phenomenon. To address this question, we chose the Dunning R3327 rat model system, in which the progression from androgen‐dependent to ‐independent tumors is represented by several transplantable prostate‐derived tumors. Gene expression profiles were analyzed in normal rat prostates and in the prostates of rats 14 days after castration by use of microarrays containing approximately 5,000 oligonucleotides, together representing more than 4,800 known rat genes. These expression profiles were compared with similarly obtained expression profiles of androgen‐dependent and androgen‐independent rat prostate tumors. By doing so, a series of known and novel prostate cancer–associated androgen‐responsive genes was identified. Within this series, we were able to identify several clusters of genes that are differentially regulated in the various prostate tumors. These genes may serve as (i) novel prognostic identifiers and (ii) novel therapeutic targets. © 2005 Wiley‐Liss, Inc.
Functional evidence of decreased tumorigenicity associated with monochromosome transfer of chromosome 14 in esophageal cancer and the mapping of tumor‐suppressive regions to 14q32
Authors: Ko Josephine Mun Yee , Yau Wing Lung , Chan Pui Ling , Lung Hong Lok , Yang Lichun , Lo Paulisally H. Y. , Tang Johnny C. O. , Srivastava Gopesh , Stanbridge Eric J. , Lung Maria Li
Published: April 2005

Despite the abundant evidence of high allelic loss of chromosome arm 14q in human cancers, tumor‐suppressor genes mapped to this chromosome have yet to be identified. To narrow the search for candidate genes, we performed monochromosome transfer of chromosome 14 into an esophageal carcinoma cell line, SLMT‐1 S1. Statistically significant suppression of the tumorigenic potential of microcell hybrids containing the transferred chromosome 14 provided functional evidence that tumor‐suppressive regions of chromosome 14 are essential for esophageal cancer. Tumor segregants emerging in nude mice during the tumorigenicity assay were analyzed by detailed PCR‐microsatellite typing to identify critical nonrandomly eliminated regions (CRs). A 680‐kb CR mapped to 14q32.13 and an ∼2.2‐Mb CR mapped to 14q32.33 were delineated. Dual‐color BAC FISH analysis of microcell hybrids and tumor segregants verified the selective loss of the 14q32.13 region. In contrast, similar transfers of an intact chromosome 11 into SLMT‐1 S1 did not significantly suppress tumor formation. These functional complementation studies showing the correlation of tumorigenic potential with critical regions of chromosome 14 validated the importance of the 14q32 region in tumor suppression in esophageal cancer. The present study also paved the path for further identification of novel tumor‐suppressor genes that are relevant to the molecular pathogenesis of esophageal cancer. © 2005 Wiley‐Liss, Inc.
Cultures of rat astrocytes challenged with a steady supply of glutamate: New model to study flux distribution in the glutamate–glutamine cycle
Authors: Fonseca Luís L. , Monteiro Miguel A.R. , Alves Paula M. , Carrondo Manuel J.T. , Santos Helena
Published: April 2005

Glutamate metabolism in astrocytes was studied using an experimental setup that simulates the role of neurons (glutamate producers and glutamine consumers) by the addition of glutaminase to the culture medium. Thereby, a steady supply of glutamate was imposed at the expense of glutamine, and the stress intensity was manipulated by changing the glutaminase concentration. Glutamate supply rates in the range 8–23 nmol/min/mg protein were examined for periods of up to 48 h. When the glutamate supply rate exceeded the uptake rate of this amino acid, a transient increase in the extracellular concentration of glutamate was observed. In response to this stress, the fluxes through the glutamate transporter and glutamine synthetase were increased considerably, and the extracellular concentration of glutamate was eventually restored to a low level. The increased levels of glutamine synthetase were demonstrated by immunoblotting analysis. The effect on glutamate metabolism of the transaminase inhibitor, aminooxyacetic acid (AOAA), and of NH4Cl was also investigated. The supply of glutamate caused a concomitant reduction in the levels of phosphocreatine, phosphoethanolamine, and phosphocholine without affecting the ATP pool. Glutamine synthetase was shown to be is a key element in the control of glutamate metabolism in astrocytic cultures. The metabolic fate of glutamate depends greatly on the time of endurance to the challenge: in naive cells, glutamate was primarily metabolized through the transaminase pathway, while in well‐adapted cells glutamate was converted almost exclusively through glutamine synthetase. © 2005 Wiley‐Liss, Inc.
Optic radiation changes after optic neuritis detected by tractography‐based group mapping
Authors: Ciccarelli Olga , Toosy Ahmed T. , Hickman Simon J. , Parker Geoff J.M. , Wheeler‐Kingshott Claudia A.M. , Miller David H. , Thompson Alan J.
Published: April 2005

Postmortem data suggest that trans‐synaptic degeneration occurs in the lateral geniculate nucleus after optic nerve injury. This study investigated in vivo the optic radiations in patients affected by optic neuritis using fast marching tractography (FMT), a diffusion magnetic resonance imaging (MRI) fiber tracking method, and group mapping techniques, which allow statistical comparisons between subjects. Seven patients, 1 year after isolated unilateral optic neuritis, and ten age and gender‐matched controls underwent whole‐brain diffusion tensor MR imaging. The FMT algorithm was used to generate voxel‐scale connectivity (VSC) maps in the optic radiations in each subject in native space. Group maps of the left and right optic radiations were created in the patient and control group in a standardized reference frame using statistical parametric mapping (SPM99). The reconstructed optic radiations in the patient group were localized more laterally in the posterior part of the tracts and more inferiorly than in the control group. Patients showed reduced VSC values in both tracts compared with controls. These findings suggest that the group mapping techniques might be used to assess changes in the optic radiations in patients after an episode of optic neuritis. The changes we have observed may be secondary to the optic nerve damage. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Using automated morphometry to detect associations between ERP latency and structural brain MRI in normal adults
Authors: Cardenas Valerie A. , Chao Linda L. , Blumenfeld Rob , Song Enmin , Meyerhoff Dieter J. , Weiner Michael W. , Studholme Colin
Published: April 2005

Despite the clinical significance of event‐related potential (ERP) latency abnormalities, little attention has focused on the anatomic substrate of latency variability. Volume conduction models do not identify the anatomy responsible for delayed neural transmission between neural sources. To explore the anatomic substrate of ERP latency variability in normal adults using automated measures derived from magnetic resonance imaging (MRI), ERPs were recorded in the visual three‐stimulus oddball task in 59 healthy participants. Latencies of the P3a and P3b components were measured at the vertex. Measures of local anatomic size in the brain were estimated from structural MRI, using tissue segmentation and deformation morphometry. A general linear model was fitted relating latency to measures of local anatomic size, covarying for intracranial vault volume. Longer P3b latencies were related to contractions in thalamus extending superiorly into the corpus callosum, white matter (WM) anterior to the central sulcus on the left and right, left temporal WM, the right anterior limb of the internal capsule extending into the lenticular nucleus, and larger cerebrospinal fluid volumes. There was no evidence for a relationship between gray matter (GM) volumes and P3b latency. Longer P3a latencies were related to contractions in left temporal WM, and left parietal GM and WM near the interhemispheric fissure. P3b latency variability is related chiefly to WM, thalamus, and lenticular nucleus, whereas P3a latency variability is not related as strongly to anatomy. These results imply that the WM connectivity between generators influences P3b latency more than the generators themselves do. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Anterior cingulate cortex: An fMRI analysis of conflict specificity and functional differentiation
Authors: Milham Michael P. , Banich Marie T.
Published: April 2005

In this event‐related functional magnetic resonance imaging (fMRI) study, we provide evidence that the role of the anterior cingulate cortex (ACC) in cognitive control may not be unitary, as the responses of different ACC subregions vary depending upon the nature of task‐irrelevant information. More specifically, using the color‐word Stroop task (congruent, incongruent, and neutral trial types), we examined the degree to which increases in neural activity within ACC are specific to conditions of conflict, as posited by the conflict monitoring theory (Botvinick et al. [1999]: Rev Neurosci 10:49–57; Carter et al. [1998]: Science 280:747–749). Although incongruent and congruent trials both involve two competing sources of color information (color word and ink color), only incongruent trials involve a direct conflict between task‐relevant and task‐irrelevant information. Although the anterior division of the ACC rostral zone exhibited conflict specific increases in neural activity (i.e., incongruent > congruent = neutral), the posterior division exhibited a more generalized pattern, increasing whenever the task‐irrelevant information was color related, regardless of whether it was conflicting (i.e., incongruent and congruent > neutral). Our data thus suggest a possible functional differentiation within the ACC. As such, it is unlikely that the role of the ACC in cognitive control will be able to be accommodated by a single unifying theory. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Rheological and recovery properties of poly(ethylene glycol) diacrylate hydrogels and human adipose tissue
Authors: Patel Parul Natvar , Smith Connie Kathleen , Patrick Charles W.
Published: April 2005

The viscosity and elastic and viscous moduli of poly(ethylene glycol) diacrylate (PEGDA) hydrogels and human abdominal adipose tissue are measured as a function of shear rate and frequency. Results indicate that both materials exhibit shear thinning and are viscoelastic in nature. Rheological tests suggest that the hydrogels become firmer as strain and frequency increase. Adipose tissue, however, begins to fail at higher strains and frequencies. This behavior is confirmed by measuring the complex modulus of both materials as a function of strain. Recovery properties are also measured for each material as a function of deformation. Although PEGDA hydrogels are able to recover up to 78% of their original height after 15% deformation, adipose tissue is not able to recover over the range of deformations tested. The frequencies and strains over which the tests are conducted are those physiologically experienced by the human body. The hydrogels are able to withstand this range of forces and, hence, are appropriate for use as a soft tissue filler material. In addition, the hydrogels swell 38.1% ± 0.9% independent of surface area. The complex modulus of hydrogels of varying polymer concentrations is also measured as a function of strain to determine the effects of changing polymer content. These results indicate that as polymer content increases, the hydrogels become firmer due to the higher number of polymer chains and behave more elastically. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 73A: 313–319, 2005
Effects of bone morphogenetic protein‐2 and hyaluronic acid on the osseointegration of hydroxyapatite‐coated implants: An experimental study in sheep
Authors: Aebli Nikolaus , Stich Hermann , Schawalder Peter , Theis Jean‐Claude , Krebs Jörg
Published: April 2005

Research efforts aim at enhancing early osseointegration of cementless implants to improve early fixation and, thus, reduce the risk of loosening. The aim of the present study was to investigate whether bone morphogenetic protein (BMP) 2 had a positive effect on the osseointegration of hydroxyapatite‐coated implants. Hydroxyapatite (HA) implants (perforated hollow cylinders and solid rods) were coated with BMP‐2 and hyaluronic acid (HY) as the carrier or with HY alone. Uncoated HA implants served as controls. The osseointegration of the implants was evaluated either by light microscopy or by pullout tests after 1, 2, and 4 weeks of unloaded implantation in the cancellous bone of 24 sheep. The BMP‐2 coating significantly increased bone growth into the implant perforations compared with HA‐coated implants at 2 and 4 weeks. Bone‐implant contact and interface shear strength of BMP‐2 implants were lower than HA implants at 2 weeks. At 4 weeks, there was no significant difference in bone‐implant contact and shear strength between BMP‐2 and HA‐coated implants. The BMP‐2 coating enhanced gap healing but had no positive or even an inhibitory effect (at 2 weeks) on bone‐implant contact and interface shear strength. In the clinical situation, a perfect press‐fit implantation cannot be achieved, and BMP‐2 may be beneficial for enhancing bone growth into gaps around cementless implants. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 73A: 295–302, 2005
3D‐Epitope‐Explorer (3DEX): Localization of conformational epitopes within three‐dimensional structures of proteins
Authors: Schreiber Andreas , Humbert Michael , Benz Alexander , Dietrich Ursula
Published: April 2005

Neutralizing antibodies often recognize conformational, discontinuous epitopes. Linear peptides mimicking such conformational epitopes can be selected from phage display peptide libraries by screening with the respective antibodies. However, it is difficult to localize these “mimotopes” within the three‐dimensional (3D) structures of the target proteins. Knowledge of conformational epitopes of neutralizing antibodies would help to design antigens able to elicit protective immune responses. Therefore, we provide here a software that allows to localize linear peptide sequences within 3D structures of proteins. The 3D‐Epitope‐Explorer (3DEX) software allows to map conformational epitopes in 3D protein structures based on an algorithm that takes into account the physicochemical neighborhood of Cα‐ or Cβ‐atoms of individual amino acids. A given amino acid of a peptide sequence is localized within the protein and the software searches within predefined distances for the amino acids neighboring that amino acid in the peptide. Surface exposure of the amino acids can also be taken into consideration. The procedure is then repeated for the remaining amino acids of the peptide. The introduction of a joker function allows to map peptide mimotopes, which do not necessarily have 100% sequence homology to the protein. Using this software we were able to localize mimotopes selected from phage displayed peptide libraries with polyclonal antibodies from HIV‐positive patient plasma within the 3D structure of gp120, the exterior glycoprotein of HIV‐1. We also analyzed two recently published peptide sequences corresponding to known conformational epitopes to further confirm the integrity of 3DEX. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 879–887, 2005
Quantum chemical modeling of CO oxidation by the active site of molybdenum CO dehydrogenase
Authors: Siegbahn Per E. M. , Shestakov Alexander F.
Published: April 2005

The catalytic mechanism of molybdenum containing CO dehydrogenase has been studied using hybrid DFT methods with quite large chemical models. The recent high‐resolution X‐ray structure, showing the surprising presence of copper linked to molybdenum, was used as a starting point. A pathway was initially found with a low barrier for CO bond formation and CO2 release. However, this pathway did not include the formation of any SCO2 species, which had been suggested by experiments with an n‐butylisocyanide inhibitor. When these SCO2 structures were studied they were found to lead to deep minima, making CO2 release much more difficult. A large effort was spent, including investigations of other spin states, varying the number of protons and electrons, adding water, etc., until a plausible pathway for SC bond cleavage was found. In this pathway a water molecule is inserted in between molybdenum and the SCO2 group. Full catalytic cycles, including electron and proton transfers, are constructed both with and without SC bond formation. When these pathways are extended to two full catalytic cycles it can be understood why the formation of the SC bond actually makes catalysis faster, even though the individual step of CO2 release becomes much more difficult. These results agree well with experimental findings. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 888–898, 2005
MR findings in a rare case of sclerosing mesenteritis of the mesocolon
Authors: Ghanem Nadir , Pache Gregor , Bley Thorsten , Kotter Elmar , Langer Mathias
Published: April 2005

Sclerosing mesenteritis is a rare, usually benign disorder of the mesentery. Depending on the predominant tissue component (inflammation, fat, or fibrosis), it is known as mesenteric panniculitis or retractile mesenteritis. We present a rare case of retractile mesenteritis of the mesocolon as a cause of severe abdominal pain. US, CT, and MRI were the imaging modalities used. We emphasize the MR finding of a fibrous capsula in retractile mesenteritis, as this is to our knowledge the first study to describe this entity. This finding may be valuable for establishing a diagnosis of sclerosing mesenteritis, as well as for differentiating this disease from other mesenteric diseases. J. Magn. Reson. Imaging 2005;21:632–636. © 2005 Wiley‐Liss, Inc.
Normal white matter development from infancy to adulthood: Comparing diffusion tensor and high b value diffusion weighted MR images
Authors: Bashat Dafna Ben , Sira Liat Ben , Graif Moshe , Pianka Pazit , Hendler Talma , Cohen Yoram , Assaf Yaniv
Published: April 2005

Purpose

To evaluate the sensitivity of high b value diffusion weight magnetic resonance imaging (DWI) in detecting normal white matter maturation, compare it to conventional diffusion tensor imaging (DTI), and to obtain normative quantitative data using this method.

Materials and Methods

High b value DWI (bmax= 6000 sec/mm2) using q‐space analysis and conventional DTI (b = 1000 sec/mm2) were performed on 36 healthy subjects aged 4 months to 23 years. Fractional‐anisotropy (FA), apparent‐displacement, and apparent‐probability values were measured in all slices and in six regions of interest (ROIs) of large fiber tracks. Values were correlated with each other and with age using regression analysis.

Results

FA, displacement, and probability indices from all slices were highly correlated with each other (r > 0.87,P< 0.0001) and with age (r > 0.82,P< 0.0001). All age‐related changes in the six pre‐determined ROIs were best fitted by mono‐exponential functions. Changes in the splenium extended to a later age when compared with the genu of the corpus‐callosum, while the centrum semi‐ovale demonstrated the latest changes with age.

Conclusions

High b‐value DWI and DTI showed changes in white matter from infancy through adulthood. However, high b‐value detects a signal that is likely to originate mainly from the intra‐axonal water population, and thus may represent different aspects of development and different sensitivity to pathology. J. Magn. Reson. Imaging 2005;21:503–511. © 2005 Wiley‐Liss, Inc.
Combined use of the intravascular blood‐pool agent, gadomer, and carbon dioxide: A novel type of double‐contrast magnetic resonance angiography (MRA)
Authors: Maes Robbert M. , Lewin Jonathan S. , Duerk Jeffrey L. , Wacker Frank K.
Published: April 2005

Purpose

To evaluate the combined use of carbon dioxide (CO2) and a gadolinium‐based blood‐pool agent for magnetic resonance angiography (MRA).

Materials and Methods

After an initial intravenous injection of the blood‐pool agent Gadomer (Schering AG, Germany), repeated transcatheter CO2 injections were performed in the aorta and the renal arteries of two fully‐anesthetized pigs. Real‐time images were acquired using a true fast imaging with steady‐state precession (FISP) sequence.

Results

During the CO2 injections, the Gadomer‐enhanced blood was totally replaced, resulting in an immediate, temporary, total signal loss in the vessel lumen. Susceptibility artifacts during the injections or catheter manipulations rarely occurred.

Conclusion

Due to T1‐shortening, the circulating blood‐pool agent prevents flow artifacts during catheter manipulations because the steady‐state is reached much earlier. Therefore, this double‐contrast MRA method improves catheter conspicuity and might be helpful for guiding and controlling intravascular procedures during interventional MRI. J. Magn. Reson. Imaging 2005;21:645–649. © 2005 Wiley‐Liss, Inc.
Method for improving the accuracy of quantitative cerebral perfusion imaging
Authors: Sakaie Ken E. , Shin Wanyong , Curtin Kenneth R. , McCarthy Richard M. , Cashen Ty A. , Carroll Timothy J.
Published: April 2005

Purpose

To improve the accuracy of dynamic susceptibility contrast (DSC) measurements of cerebral blood flow (CBF) and volume (CBV).

Materials and Methods

In eight volunteers, steady‐state CBV (CBVSS) was measured using TrueFISP readout of inversion recovery (IR) before and after injection of a bolus of contrast. A standard DSC (STD) perfusion measurement was performed by echo‐planar imaging (EPI) during passage of the bolus and subsequently used to calculate the CBF (CBFDSC) and CBV (CBVDSC). The ratio of CBVSS to CBVDSC was used to calibrate measurements of CBV and CBF on a subject‐by‐subject basis.

Results

Agreement of values of CBV (1.77 ± 0.27 mL/100 g in white matter (WM), 3.65 ± 1.04 mL/100 g in gray matter (GM)), and CBF (23.6 ± 2.4 mL/(100 g min) in WM, 57.3 ± 18.2 mL/(100 g min) in GM) with published gold‐standard values shows improvement after calibration. An F‐test comparison of the coefficients of variation of the CBV and CBF showed a significant reduction, with calibration, of the variability of CBV in WM (P < 0.001) and GM (P < 0.03), and of CBF in WM (P < 0.0001).

Conclusion

The addition of a CBVSS measurement to an STD measurement of cerebral perfusion improves the accuracy of CBV and CBF measurements. The method may prove useful for assessing patients suffering from acute stroke. J. Magn. Reson. Imaging 2005;21:512–519. © 2005 Wiley‐Liss, Inc.
Multisite trial of MR flow measurement: Phantom and protocol design
Authors: Summers Paul E. , Holdsworth David W. , Nikolov Hristo N. , Rutt Brian K. , Drangova Maria
Published: April 2005

Purpose

To describe a portable, easily assembled phantom with well‐defined bore geometry together with a series of tests that will form the basis of a standardized quality assurance protocol in a multicenter trial of flow measurement by the MR phase mapping technique.

Materials and Methods

The phantom consists of silicone polymer layers containing parallel straight and stenosed flow channels in one layer and a U‐bend in a second layer, separated by hermetically sealed agarose slabs. The phantom is constructed by casting low melting‐point metal in an aluminum mold precisely milled to the desired geometry, and then using the low melting‐point metal core as a negative around which the silicone is allowed to set. By melting out the metal, the flow channels are established. The milled aluminum mold is reusable, ensuring faithful reproduction of the flow geometry for all phantoms thus produced. The agarose layers provide additional loading and static background signal for background correction. With the use of the described phantom, one can evaluate flow measurement accuracy and repeatability, as well as the influence of several imaging geometry factors: slice offset, in‐plane position, and slice‐flow obliquity.

Results

The new phantom is compact and portable, and is well suited for reassembly. We were able to demonstrate its facility in a battery of tests of interest in evaluating MR flow measurements.

Conclusion

The phantom is a robust standardized test object for use in a multicenter trial. Such a trial, to investigate the performance of MR flow measurement using the phantom and the tests we describe, has been initiated. J. Magn. Reson. Imaging 2005;21:620–631. © 2005 Wiley‐Liss, Inc.
Frequency of malignancy in lesions classified as probably benign after dynamic contrast‐enhanced breast MRI examination
Authors: Sadowski Elizabeth A. , Kelcz Frederick
Published: April 2005

Purpose

To determine the chance of malignancy in lesions classified as “probably benign” by dynamic magnetic resonance imaging (MRI), in a heterogeneous population.

Materials and Methods

Reports from 473 patients, from March 1994 to March 2002, who underwent breast MRI were retrospectively reviewed. A total of 79 patients (17%) had lesions classified as probably benign after the MRI, which required further imaging follow‐up. We evaluated subsequent MRI, mammographic reports, and clinical follow‐up in these patients and established the frequency of malignancy in this group.

Results

MRI classified probably benign lesion were diagnosed in 79 women because of focal or diffuse mild enhancement and benign dynamic enhancement curves in the area of the mammographic abnormality, or because of the presence of microcalcifications on the mammogram, or because of incidental enhancing lesions. Two‐year radiographic and/or clinical follow‐up was available in 68 women. On follow‐up, four women (6%) were diagnosed with cancer between 14 and 18 months after the initial MRI.

Conclusion

Patients with a lesion assessed as probably benign by dynamic contrast enhanced MRI have a higher chance of malignancy than patients with probably benign lesions (Breast Imaging Reporting and Data System category 3, BI‐RADS 3) seen on mammography. These patients should be informed of the increased risk of cancer and be given the option of biopsy or close follow‐up. J. Magn. Reson. Imaging 2005;21:556–564. © 2005 Wiley‐Liss, Inc.
Predicting final infarct size using acute and subacute multiparametric MRI measurements in patients with ischemic stroke
Authors: Lu Mei , Mitsias Panayiotis D. , Ewing James R. , Soltanian‐Zadeh Hamid , Bagher‐Ebadian Hassan , Zhao Qingming , Oja‐Tebbe Nancy , Patel Suresh C. , Chopp Michael
Published: April 2005

Purpose

To identify early MRI characteristics of ischemic stroke that predict final infarct size three months poststroke.

Materials and Methods

Multiparametric MRI (multispin echo T2‐weighted [T2W] imaging, T1‐weighted [T1W] imaging, and diffusion‐weighted imaging [DWI]) was performed acutely (<24 hours), subacutely (three to five days), and at three months. MRI was processed using maps of apparent diffusion coefficient (ADC), T2, and a self‐organizing data analysis (ISODATA) technique. Analyses began with testing for individual MRI parameter effects, followed by multivariable modeling with assessment of predictive ability (R2) on final infarct size.

Results

A total of 45 patients were studied, 15 of whom were treated with tissue plasminogen activator (tPA) before acute MRI. The acute DWI and DWI‐ISODATA mismatch lesion size, and the interactions of ADC, T2, and T2W imaging lesion with tPA remained in the final multivariable model (R2 = 70%). A large acute DWI lesion or DWI < ISODATA lesion independently predicted increase in the final infract size, with predictive ability 68%. Predictive ability increased (R2 = 83%) when subacute MRI parameters were included along with acute DWI, DWI‐ISODATA mismatch, and acute T2W image lesion size by tPA treatment interaction. Subacute DWI > acute DWI lesion size predicted an increased final infarct size (P < 0.01).

Conclusion

Acute‐phase DWI and DWI‐ISODATA mismatch strongly predict the final infarct size. An acute‐to‐subacute DWI lesion size change further increases the predictive ability of the model. J. Magn. Reson. Imaging 2005;21:495–502. © 2005 Wiley‐Liss, Inc.
Rapid measurement of renal artery blood flow with ungated spiral phase‐contrast MRI
Authors: Park Jong B. , Santos Juan M. , Hargreaves Brian A. , Nayak Krishna S. , Sommer Graham , Hu Bob S. , Nishimura Dwight G.
Published: April 2005

Purpose

To verify the potential of ungated spiral phase‐contrast (USPC), which has been shown to provide accurate and reproducible time‐averaged measurements of pulsatile flow, for rapid measurement of renal artery blood flow (RABF) in vivo.

Materials and Methods

The RABF rates of 11 normal human subjects and one patient with renal failure were measured with USPC within six seconds.

Results

Rapid USPC scans produced reproducible RABF measurements (SD ≤ 9%) that agreed with the normal RABF rates known from the literature. The RABF rates of the patient with renal failure were substantially less (<50–65%) than the normal RABF rates.

Conclusion

The results demonstrate that it is now possible to obtain rapid and consistent RABF measurements within six seconds with USPC. J. Magn. Reson. Imaging 2005;21:590–595. © 2005 Wiley‐Liss, Inc.
Gd(ABE‐DTTA)‐enhanced cardiac MRI for the diagnosis of ischemic events in the heart
Authors: Simor Tamás , Gaszner Balázs , Oshinski John N. , Waldrop Sandra M. , Pettigrew Roderic I. , Horváth Iván G. , Hild Gábor , Elgavish Gabriel A.
Published: April 2005

Purpose

To demonstrate that contrast‐enhanced MRI (ceMRI) with the aid of Gd(ABE‐DTTA) is able to detect ischemic events in the heart in a canine ischemia/reperfusion (30/40 minutes) model.

Materials and Methods

ECG‐gated, T1‐weighted MR image sets (four to five slices each) with three‐minute time resolution were collected in transiently LAD‐occluded dogs. Following the acquisition of control image sets, ischemia was started by occluding the LAD. Either Gd(ABE‐DTTA) (N = 6) or Gd(DTPA) (N = 6) was injected, and imaging was continued for 30 minutes of ischemia and 40 minutes of reperfusion. The contrast agent (CA)‐induced MRI signal intensity enhancement (SIE) and contrast were monitored. Microspheres measured myocardial perfusion (MP) to verify areas of ischemia and reperfusion.

Results

SIEs of 86% ± 3% and 97% ± 3% in nonischemic, and 25% ± 5% and 29% ± 8% in ischemic regions were found within three minutes of onset of ischemia with Gd(ABE‐DTTA) and Gd(DTPA), respectively. For the rest of the 30 minutes of ischemia, with Gd(ABE‐DTTA) SIE of 60% ± 3% and 25% ± 5% persisted in the nonischemic and ischemic regions, respectively. With Gd(DTPA), however, SIE in the nonischemic areas decreased rapidly after the first three minutes of ischemia, while SIE in the ischemic areas increased, abolishing contrast. Thus, there was a persistent contrast with Gd(ABE‐DTTA) and a short‐lived contrast with Gd(DTPA) during ischemia. Furthermore, with Gd(ABE‐DTTA) some contrast was still visible in the early reperfusion period.

Conclusion

Gd(ABE‐DTTA) in an ischemia/reperfusion model induces a persistent MRI contrast between regions of normal and ischemic myocardium, and verifies reperfusion. Therefore, it can be used to detect myocardial ischemic events. J. Magn. Reson. Imaging 2005;21:536–545. © 2005 Wiley‐Liss, Inc.
Infection with human T lymphotropic virus type I in organ transplant donors and recipients in Spain
Authors: Toro Carlos , Benito Rafael , Aguilera Antonio , Bassani Sylvina , Rodríguez Carmen , Calderón Enrique , Caballero Estrella , Álvarez Patricia , García Juan , Rodríguez‐Iglesias Manuel , Guelar Ana , Romero Jorge del , Soriano Vincent
Published: April 2005

Human T‐cell lymphotropic virus (HTLV) antibody screening is not recommended uniformly before transplantation in Western countries. In the year 2001, the first cases of HTLV‐I infection acquired through organ transplantation from one asymptomatic carrier were reported in Europe. All three organ recipients developed a subacute myelopathy shortly after transplantation. This report rose the question about whether to implement universal anti‐HTLV screening of all organ donors or selective screening of donors from endemic areas for HTLV‐I infection should be carried out. A national survey was conducted thereafter in which anti‐HTLV antibodies were tested in 1,298 organ transplant donors and 493 potential recipients. None was seropositive for HTLV‐I and only one recipient, a former intravenous (i.v.) drug user, was found to be infected with HTLV‐II. In a different survey, HTLV screening was conducted in 1,079 immigrants and 5 (0.5%) were found to be asymptomatic HTLV‐I carriers. All came from endemic areas for HTLV‐I infection. No cases of HTLV‐II infection were found among immigrants. These results support the current policy of mandatory testing of anti‐HTLV antibodies in Spain only among organ transplant donors coming from HTLV‐I endemic areas or with a highly suspicion of HTLV‐I infection. J. Med. Virol. 76:268–270, 2005. © 2005 Wiley‐Liss, Inc.
Dichotomy in cross‐clade reactivity and neutralization by HIV‐1 sera: Implications for active and passive immunotherapy
Authors: Cavacini Lisa A. , Duval Mark , Patil Ajay , Wood Charles , Mayer Kenneth H. , Ruprecht Ruth M. , Posner Marshall R.
Published: April 2005

The identification of broadly reactive and cross‐clade neutralizing antibodies will facilitate the development of a more universally effective vaccine for human immunodeficiency virus (HIV). Antibodies in sera from individuals infected with Clade B HIV bind native primary viral isolates, and virus binding correlates with neutralization and stable clinical disease. In this study, we quantified cross‐clade antibody reactivity and neutralization by Clades B and C sera. Primary viral isolates were captured by serum IgG bound to anti‐human IgG and quantitated as p24 released by lysis of captured virus. Neutralization was determined using PHA‐stimulated PBMC. Clade B antibodies reacted more frequently with Clade B R5 virus, but positive sera captured quantitatively more X4 virus than R5 and R5X4 virus. Clade B sera reacted less frequently and captured less Clade C virus than Clade B virus. Antibodies in Clade C sera captured Clades B and C isolates with equal frequency and quantity. There was no difference in neutralization of Clade B virus by either group of sera; however, Clade C sera neutralized Clade C virus, whereas Clade B sera were ineffective against Clade C virus. Thus, there are distinct differences in cross‐clade reactivity of and neutralization by antibodies induced in response to Clade C infection compared to Clade B infection. Understanding antibody responses to native virions after Clade C infection and cross clade antibody behavior has implications for understanding pathogenesis and vaccine development. J. Med. Virol. 76:146–152, 2005. © 2005 Wiley‐Liss, Inc.
Nucleotide mutations associated with hepatitis B e antigen negativity
Authors: Sun XiaoHong , Rokuhara Akinori , Tanaka Eiji , Gad Amal , Mutou Hidetomo , Matsumoto Akihiro , Yoshizawa Kaname , Kiyosawa Kendo
Published: April 2005

One hundrded and forty four patients with chronic hepatitis B were tested to identify new mutations associated with hepatitis B e antigen (HBeAg) negativity, using a full genome sequence analysis. All the patients were Chinese and had hepatitis B virus infection of genotype C. Patients with none of the pre‐core or core promoter mutations were significantly (P < 0.001) less common in the group with anti‐HBe (13%) than in the group with HBeAg (56%). The complete nucleotide sequence was determined in four anti‐HBe‐positive patients who had neither pre‐core nor core promoter mutations and in five HBeAg‐positive patients who also had neither of these mutations (the groups were matched for age and sex). Six mutations were found to be significantly more common in the former group than in the latter: G529A (3/4 vs. 0/5), C934A (4/4 vs. 1/5), A1053G (4/4 vs. 1/5), G1915T/A (4/4 vs. 0/5), T2005C/A (4/4 vs. 0/5), and C3026T (3/4 vs. 0/5). Three of the six mutations were significantly more common in the four anti‐HBe‐positive patients who had neither pre‐core nor core promoter mutations, compared to 11 HBeAg‐positive patients who had pre‐core and core promoter mutations, and also compared to 15 anti‐HBe‐positive patients who had pre‐core and core promoter mutations, suggesting further the specificity of these mutations. Of the six mutations, two resulted in amino acid substitution in the polymerase protein, and one is located near the enhancer I region. The results suggest that the six newly discovered mutations are associated with HBeAg negativity. J. Med. Virol. 76:170–175, 2005. © 2005 Wiley‐Liss, Inc.
Contrasting patterns of hepatitis C virus infection in two regions from Tunisia
Authors: Mejri S. , Salah A. Ben , Triki H. , Alaya N. Ben , Djebbi A. , Dellagi K.
Published: April 2005

This report is a population‐based study describing the pattern of hepatitis C virus (HCV) infection in two distinct regions in Tunisia. The study included a total of 11,507 individuals sampled in 1996 from both genders, all age groups, urban and rural settings belonging to 2,973 families. HCV infection was assessed by commercial enzyme immunoassay (EIA) and immunoblot assays and detection of HCV RNA by PCR. HCV genotypes and subtypes were determined by sequencing in the 5′‐untranslated region (UTR) viral genomic region and the INNO‐LiPA HCVII genotyping kit. Genetic relatedness between HCV strains was assessed by sequencing of a portion of the NS5B region. HCV prevalence was significantly higher in the North‐Western region than in the Southern one: 1.7% versus 0.2% (P < 10−3, χ2 = 8,506). There was no difference in positivity according to gender or living in rural or urban settings; the only significant risk factor was advanced age. HCV prevalence among household contacts of HCV positives was not significantly higher than the prevalence in the whole study population. These results indicate a heterogeneity in the geographical distribution of HCV in Tunisia. An increased HCV transmission occurs in the North‐Western region with large predominance of genotype 1b (88%) and low contribution of intrafamilial transmission. J. Med. Virol. 76:185–193, 2005. © 2005 Wiley‐Liss, Inc.