bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic exercise imaging with an MR‐compatible stationary cycle within the general electric open magnet
Authors: Cheng Christopher P. , Schwandt Douglas F. , Topp Eric L. , Anderson James H. , Herfkens Robert J. , Taylor Charles A. 
Published: February 2003

AbstractMany cases of muscular ischemia do not manifest without increased metabolic demand. Hence, diagnosis of intermittent claudication often requires inducing physiologic challenge, such as by exercise. Cine phase‐contrast MRI can concurrently acquire cross‐sectional vascular anatomy and through‐plane blood velocities, enabling blood flow rate quantification. An MR‐compatible stationary cycle was designed, constructed, and tested for flow quantification in large arteries during lower‐limb exercise in a General Electric Signa SP 0.5 T open magnet. The cycle demonstrated smooth cycling during image acquisition, has freewheeling capability, is adjustable for subject size and strength, and can quantify workload. A healthy 59‐year‐old male was imaged at the supraceliac and infrarenal levels of the abdominal aorta at rest and during exercise. An exercise workload of 47.9 W was achieved. His heart rate increased from 52 to 78 bpm, supraceliac flow increased from 1.7 to 3.7 L/min, and infrarenal flow increased from 0.4 to 3.2 L/min from rest to exercise. Magn Reson Med 49:581–585, 2003. © 2003 Wiley‐Liss, Inc.
Effects of hematocrit and oxygen saturation level on blood spin‐lattice relaxation
Authors: Silvennoinen M. Johanna , Kettunen Mikko I. , Kauppinen Risto A. 
Published: February 2003

AbstractIn the present study blood T1 was determined as a function of hematocrit and oxygen saturation. T1 showed a significant linear dependency on both of these parameters. In addition, oxygen dissolved in blood plasma in hyperoxygenated blood resulted in relaxation enhancement, comparable in size to that due to the change in oxygenation state of hemoglobin. As blood T1 is a key factor for quantification of flow with arterial spin labeling methods, the influence of T1 variation in the physiological range of hematocrit and oxygen saturation to flow determination is discussed. Magn Reson Med 49:568–571, 2003. © 2003 Wiley‐Liss, Inc.
Reduced k‐space encoding for dual‐contrast TrueFISP imaging
Authors: Merrifield Robert , Keegan Jennifer , Firmin David , Yang Guang‐Zhong 
Published: February 2003

AbstractDual‐contrast TrueFISP imaging relies on the use of two RF pulses with different RF flip‐angles for enhancing image contrast and performing automatic tissue classification based on multispectrum clustering. The original technique, however, involves an extended imaging time, which limits its clinical application. The purpose of this study is to compare the applicability of two reduced k‐space sampling techniques, reduced imaging using generalized series reconstruction (RIGR) and key‐hole imaging, for minimizing the imaging time required. The performance of both approaches was evaluated theoretically and practically using 3D cine datasets acquired from eight asymptomatic subjects. Magn Reson Med 49:595–598, 2003. © 2003 Wiley‐Liss, Inc.
Albumin‐binding MR blood pool agents as MRI contrast agents in an intracranial mouse glioma model
Authors: Adzamli Kofi , Yablonskiy Dmitriy A. , Chicoine Michael R. , Won Eun Kyung , Galen Karen P. , Zahner Michael C. , Woolsey Thomas A. , Ackerman Joseph J.H. 
Published: February 2003

AbstractIntravenous MRI contrast agents are commonly used to improve the detection of intracranial tumors and other central nervous system (CNS) lesions for diagnosis and treatment planning. Two small‐molecule, albumin‐binding blood pool contrast agents (MP‐2269 and MS‐325) of potential clinical significance were evaluated at 1.5 Tesla in a mouse glioma model and compared with an extracellular contrast agent (OptiMARK). Tumor image contrast was significantly enhanced and long‐lived following administration of 30 μmole/kg of the blood pool agents: specifically, contrast enhancement peaked slowly at 25–30 min following administration, remained constant for >3 hr, and returned to baseline within 20 hr. Comparable but “transient” enhancement was achieved using 100 μmole/kg OptiMARK: specifically, contrast enhancement peaked rapidly at 2–5 min following administration and then declined over 40 min. The blood pool contrast agents demonstrated an approximately threefold increased dose‐effectiveness and a lengthened window of tumor contrast enhancement in comparison to commonly available extracellular contrast agents. This demonstrates the potential of alternative contrast‐enhanced (CE) MRI examination protocols for tumor detection. Magn Reson Med 49:586–590, 2003. © 2003 Wiley‐Liss, Inc.
Fast method for correcting image misregistration due to organ motion in time‐series MRI data
Authors: Gupta Sandeep N. , Solaiyappan Meiyappan , Beache Garth M. , Arai Andrew E. , Foo Thomas K.F. 
Published: February 2003

AbstractTime‐series MRI data often suffers from image misalignment due to patient movement and respiratory and other physiologic motion during the acquisition process. It is necessary that this misalignment be corrected prior to any automated quantitative analysis. In this article a fast and automated technique for removing in‐plane misalignment from time‐series MRI data is presented. The method is computationally efficient, robust, and fine‐tuned for the clinical setting. The method was implemented and tested on data from 21 human subjects, including myocardial perfusion imaging, renal perfusion imaging, and blood‐oxygen level‐dependent cardiac T imaging. In these applications 10‐fold or better reduction in image misalignment is reported. The improvement after registration on representative time–intensity curves is shown. Although the method currently corrects translation motion using image center of mass, the mathematical framework of our approach may be extended to correct rotation and other higher‐order displacements. Magn Reson Med 49:506–514, 2003. © 2003 Wiley‐Liss, Inc.
Computing oxygen‐enhanced ventilation maps using correlation analysis
Authors: Mai Vu M. , Tutton Sean , Prasad Pottumarthi V. , Chen Qun , Li Wei , Chen Chi , Liu Benjamin , Polzin Jason , Kurucay Saban , Edelman Robert R. 
Published: February 2003

AbstractCorrelation maps of oxygen‐enhanced ventilation were obtained in nine healthy volunteers using complete and selected image series. The complete series included all images acquired with the subjects alternately inhaling room air and 100% oxygen. The selected series were the subsets of the complete series and included only co‐registered images that showed matched diaphragmatic position at maximal expiration. Cross‐correlation was computed between the time response function of each pixel and the input function representing the alternation between periods of room air and 100% oxygen inhalation. The confidence level for the correlation analysis was set to 0.01. Pulmonary parenchymal anatomy was consistently reproduced throughout the lung, even in anterior slices where published data have reported correlation problems. The overall average correlation coefficient was 0.66 ± 0.07 for the complete series and 0.75 ± 0.08 for the selected series. It was concluded that correlation analysis could be used to reconstruct qualitative oxygen‐enhanced ventilation maps. Magn Reson Med 49:591–594, 2003. © 2003 Wiley‐Liss, Inc.
Effects of equilibrium exchange on diffusion‐weighted NMR signals: The diffusigraphic “shutter‐speed”
Authors: Lee Jing‐Huei , Springer Charles S. 
Published: February 2003

AbstractA general picture is presented of the implications for diffusion‐weighted NMR signals of the parsimonious two‐site‐exchange (2SX) paradigm. In particular, it is shown that the diffusigraphic “shutter‐speed,” τ−1 ≡ |q2(DA – DB)|, is a useful concept. The “wave‐number” q has its standard definition (given in the text), and DA and DB are the apparent diffusion coefficients (ADCs) of molecules in the two “sites,” A and B, if there is no exchange between them. At low gradient strengths (center of q‐space), τ−1 is less than rate constants for intercompartmental water molecule exchange in most tissue cases. Thus, the exchange reaction appears fast. However, q is increased during the course of most experiments and, as it is, the shutter‐speed becomes “faster” and the exchange reaction, the kinetics of which do not change, appears to slow down. This causes a multiexponential behavior in the diffusion‐weighting dimension, b, which also has its standard definition. This picture is found to be in substantial agreement with a number of different experimental observations. It is applied here to literature 1H2O data from a yeast cell suspension and from the human and the rat brain. Since the equilibrium transcytolemmal water exchange reaction appears to be in the fast‐exchange‐limit at small b, the initial slope represents the weighted‐average of the ADCs of intra‐ and extracellular water. Of course, in tissue the former is in the significant majority. Furthermore, a consideration of reasonable values for the other 2SX parameters suggests that, for resting brain tissue, the intracellular water ADC may be larger than the extracellular water ADC. There are some independent inferences of this, which would have ramifications for many applications of diffusion‐weighted MRI. Magn Reson Med 49:450–458, 2003. Published 2003 Wiley‐Liss, Inc.
Rapid combined T1 and T2 mapping using gradient recalled acquisition in the steady state
Authors: Deoni Sean C.L. , Rutt Brian K. , Peters Terry M. 
Published: February 2003

AbstractA novel, fully 3D, high‐resolution T1 and T2 relaxation time mapping method is presented. The method is based on steady‐state imaging with T1 and T2 information derived from either spoiling or fully refocusing the transverse magnetization following each excitation pulse. T1 is extracted from a pair of spoiled gradient recalled echo (SPGR) images acquired at optimized flip angles. This T1 information is combined with two refocused steady‐state free precession (SSFP) images to determine T2. T1 and T2 accuracy was evaluated against inversion recovery (IR) and spin‐echo (SE) results, respectively. Error within the T1 and T2 maps, determined from both phantom and in vivo measurements, is approximately 7% for T1 between 300 and 2000 ms and 7% for T2 between 30 and 150 ms. The efficiency of the method, defined as the signal‐to‐noise ratio (SNR) of the final map per voxel volume per square root scan time, was evaluated against alternative mapping methods. With an efficiency of three times that of multipoint IR and three times that of multiecho SE, our combined approach represents the most efficient of those examined. Acquisition time for a whole brain T1 map (25 × 25 × 10 cm) is less than 8 min with 1 mm3 isotropic voxels. An additional 7 min is required for an identically sized T2 map and postprocessing time is less than 1 min on a 1 GHz PIII PC. The method therefore permits real‐time clinical acquisition and display of whole brain T1 and T2 maps for the first time. Magn Reson Med 49:515–526, 2003. © 2003 Wiley‐Liss, Inc.
A simple measure of flow disorder and wall shear stress in phase contrast MRI
Authors: Pipe James G. 
Published: February 2003

AbstractA method for estimating the standard deviation of velocity within a voxel is proposed. This estimate is based on data collected using a phase‐contrast MRI technique. Simulations are presented to characterize the estimate and in vivo data are shown. Several different uses of the estimate are proposed, including obtaining a measure of wall shear stress, aiding in data combination from different phase‐contrast MRI datasets, and mitigation of flow void artifacts. Magn Reson Med 49:543–550, 2003. © 2003 Wiley‐Liss, Inc.
Deletion of Two-Component Regulatory Systems Increases the Virulence of
Mycobacterium tuberculosis
Authors: Parish Tanya , Smith Debbie A. , Kendall Sharon , Casali Nicola , Bancroft Gregory J. , Stoker Neil G. 
Published: February 2003

ABSTRACT

Two-component regulatory signal transduction systems are widely distributed among bacteria and enable the organisms to make coordinated changes in gene expression in response to a variety of environmental stimuli. The genome sequence of
Mycobacterium tuberculosis
contains 11 complete two-component systems, four isolated homologous regulators, and three isolated homologous sensors. We have constructed defined mutations in six of these genes and measured virulence in a SCID mouse model. Mice infected with four of the mutants (deletions of
devR
,
tcrXY
,
trcS
, and
kdpDE
) died more rapidly than those infected with wild-type bacteria. The other two mutants (
narL
and
Rv3220c
) showed no change compared to the wild-type H37Rv strain. The most hypervirulent mutant (
devR
Δ) also grew more rapidly in the acute stage of infection in immunocompetent mice and in gamma interferon-activated macrophages. These results define a novel class of genes in this pathogen whose presence slows down its multiplication in vivo or increases its susceptibility to host killing mechanisms. Thus,
M. tuberculosis
actively maintains a balance between its own survival and that of the host.
Inhalational Poisoning by Botulinum Toxin and Inhalation Vaccination with Its Heavy-Chain Component
Authors: Park Jong-Beak , Simpson Lance L. 
Published: February 2003

ABSTRACTBotulinum toxin is the etiologic agent responsible for the disease botulism, which is characterized by peripheral neuromuscular blockade. Botulism is ordinarily encountered as a form of oral poisoning. The toxin is absorbed from the lumen of the gut to reach the general circulation and is then distributed to peripheral cholinergic nerve endings. However, there is a widespread presumption that botulinum toxin can also act as an inhalation poison, which would require that it be absorbed from the airway. Experiments have been done to show that both pure toxin and progenitor toxin (a complex with auxiliary proteins) are inhalation poisons. Interestingly, the data indicate that auxiliary proteins are not necessary to protect the toxin or to facilitate its absorption. When studied on rat primary alveolar epithelial cells or on immortalized human pulmonary adenocarcinoma (Calu-3) cells, botulinum toxin displayed both specific binding and transcytosis. The rate of transport was greater in the apical-to-basolateral direction than in the basolateral-to-apical direction. Transcytosis was energy dependent, and it was blocked by serotype-specific antibody. The results demonstrated that the holotoxin was not essential for the process of binding and transcytosis. Both in vivo and in vitro experiments showed that the heavy-chain component of the toxin was transported across epithelial monolayers, which indicates that the structural determinants governing binding and transcytosis are found in this fragment. The heavy chain was not toxic, and therefore it was tested for utility as an inhalation vaccine against the parent molecule. This fragment was shown to evoke complete protection against toxin doses of at least 104times the 50% lethal dose.
Rho GTPase Is Activated by Cytotoxic Necrotizing Factor 1 in Peripheral Blood T Lymphocytes: Potential Cytotoxicity for Intestinal Epithelial Cells
Authors: Brest Patrick , Mograbi Baharia , Hofman Véronique , Loubat Agnès , Rossi Bernard , Auberger Patrick , Hofman Paul 
Published: February 2003

ABSTRACTSome strains ofEscherichia colirelated to acute cystitis or colitis produce a toxin named cytotoxic necrotizing factor 1 (CNF-1). CNF-1 mediates its effects on epithelial cells or phagocytes via the permanent activation of small GTP-binding proteins, caused by the toxin-induced deamidation of Glu63of p21 Rho. The behavior of peripheral blood T lymphocytes during the acute phase of bacterial colitis has been poorly investigated. Our study was conducted to test whether (i) peripheral blood T lymphocytes can be activated by CNF-1 and (ii) CNF-1-activated T lymphocytes are cytotoxic against intestinal epithelial cells. Activation of T lymphocytes by CNF-1 was assessed by electrophoresis, flow cytometry, confocal microscopy, and electron microscopy studies. Assays for migration and adherence of CNF-1-treated T lymphocytes were performed in Transwell chambers with T84 intestinal epithelial cells grown on polycarbonate semipermeable filters. CNF-1 induced a decrease in the electrophoretic mobility of the GTP-binding protein Rho in treated T lymphocytes. CNF-1 provoked an increase in the content of actin stress fibers and pseudopodia in T lymphocytes. Several adherence molecules were clustered into cytoplasmic projections in CNF-1-treated T lymphocytes and adherence of such lymphocytes on the basolateral pole of T84 was increased, resulting in cytotoxicity toward epithelial cells. Such enhanced adherence in response to CNF-1 was dependent on p42-44MAPkinase activation of T lymphocytes. Taken together, these results suggest that CNF-1, by acting on T lymphocytes, may increase in an important fashion the virulence of certain strains ofE. coliagainst the intestinal epithelia.
Polymorphic Membrane Protein H Has Evolved in Parallel with the Three Disease-Causing Groups ofChlamydia trachomatis
Authors: Stothard Diane R. , Toth Gregory A. , Batteiger Byron E. 
Published: February 2003

ABSTRACTChlamydia trachomatisis a human pathogen causing trachoma, urogenital disease, and lymphogranuloma venereum (LGV). A family of nine polymorphic membrane protein genes (pmpAtopmpI), resembling autotransporter proteins, has recently been discovered inC. trachomatis. pmpgenes are large and predicted to be outer membrane proteins. We hypothesized that they would contain useful nucleotide sequence variability for epidemiologic studies. Since sequence information is available only for serovars D and L2, we sought to determine the amount of diversity within an individualpmpgene among serovars. We used restriction fragment length polymorphism (RFLP) analysis as a primary screen to assess the amount of sequence divergence among thepmpgenes for serovars A to L3 ofC. trachomatis. RFLP analysis showed little variation for some of the genes, such aspmpA, but substantial variation in others, such aspmpI. pmpHandpmpEyielded RFLP patterns that clustered the 15 serovars into ocular, urogenital, and LGV groups, and both proteins have been localized to the outer membrane. Therefore, we chose to sequencepmpE,pmpH, andpmpIfrom each of the 15 serovars. Evolutionary analysis showed three distinct divergence patterns. PmpI was least variable, resulting in an ambiguous evolutionary pattern. PmpE showed a high degree of diversity in the ocular strains compared to the other strains. Finally, the evolution of PmpH shows three groups that reflect disease groups, suggesting this protein may play a role in pathogenesis.
Expression of Truncated Internalin A Is Involved in Impaired Internalization of Some
Listeria monocytogenes
Isolates Carried Asymptomatically by Humans
Authors: Olier Maïwenn , Pierre Fabrice , Rousseaux Sandrine , Lemaître Jean-Paul , Rousset André , Piveteau Pascal , Guzzo Jean 
Published: February 2003

ABSTRACT

Fourteen human carriage
Listeria monocytogenes
isolates were compared to sporadic and epidemic-associated human strains in order to ascertain the pathogenic behavior of these unrecognized asymptomatic strains. Experimental infection of 14-day-old chick embryos revealed that the majority of the carriage strains were attenuated for virulence. Of the 10 attenuated carriage strains, 5 were affected in their invasion capacities in vitro. Western blot analysis with antibody directed against InlA, the surface protein implicated in the internalization in host cells, allowed correlation between the ability of the carriage strains to enter Caco-2 cells and InlA expression. Indeed, these five carriage strains produced truncated forms of InlA. Four of the five truncated forms of InlA had an apparent molecular mass of 47 kDa. In order to assess the existence of a genetic lineage, partial sequences of
inlA
gene of these four strains were compared and revealed that they had a high degree of sequence conservation at the gene (99.86%) and amino acid (100%) levels. Comparison of their nucleotide sequences with that of the corresponding segment of
inlA
from EGD-e and Scott A strains, taken as epidemic references, showed more divergence. Taken together, these observations suggest the presence of specific traits that characterize
L. monocytogenes
strains isolated during asymptomatic carriage. Some of these traits could provide some explanations about the determinants that make them unable to cause systemic human infection.
Nitric Oxide Partially ControlsCoxiella burnetiiPhase II Infection in Mouse Primary Macrophages
Authors: Zamboni Dario S. , Rabinovitch Michel 
Published: February 2003

ABSTRACTIn most primary or continuous cell cultures infected with the Q-fever agentCoxiella burnetii, bacteria are typically sheltered in phagolysosome-like, large replicative vacuoles (LRVs). We recently reported that only a small proportion of mouse peritoneal macrophages (PMΦ) infected with a nonvirulent, phase II strain ofC. burnetiideveloped LRVs and that their relative bacterial load increased only slowly. In the majority of infected PMΦ, the bacteria were confined to the small vesicles. We show here that nitric oxide (NO) induced by the bacteria partially accounts for the restricted development of LRVs in primary macrophages. Thus, (i) PMΦ and bone marrow-derived macrophages (BMMΦ) challenged with phase IIC. burnetiiproduced significant amounts of NO; (ii) the NO synthase inhibitors aminoguanidine andN-methyl-l-arginine reduced the production of NO and increased the frequency of LRVs (although the relative bacterial loads of individual LRVs did not change, the estimated loads per well increased appreciably); (iii) gamma interferon (IFN-γ) or the NO donor sodium nitroprusside, added to BMMΦ prior to or after infection, reduced the development and the relative bacterial loads of LRVs and lowered the yield of viable bacteria recovered from the cultures; and (iv) these effects of IFN-γ may not be entirely dependent on the production of NO since IFN-γ also controlled the infection in macrophages from inducible NO synthase knockout mice. It remains to be determined whether NO reduced the development of LRVs by acting directly on the bacteria; by acting on the traffic, fusion, or fission of cell vesicles; or by a combination of these mechanisms.