bluuebunny/crossref_metadata_2025 huggingface dataset:
Does binding of Gd‐DTPA to myocardial tissue contribute to late enhancement in a model of acute myocardial infarction?
Authors: Decking Ulrich K.M. , Pai Vinay M. , Wen Han , Balaban Robert S.
Published: January 2003

The long‐lasting signal enhancement by Gd‐DTPA in areas of myocardial infarction has been conventionally explained by low perfusion and an enhanced Gd distribution volume. To test whether binding of Gd to myocardial constituents is an additional factor contributing to this effect, Gd‐DTPA was allowed to equilibrate between homogenized porcine myocardial tissue and physiological saline. The relaxation rate (1/T1) of homogenate samples (n = 61) increased in proportion (r2 = 0.98) to the Gd concentration (0.025–0.5 mM) of the surrounding medium, with no evidence for augmented uptake. The diffusion‐limited uptake was only slightly more rapid than the subsequent Gd‐release. The amount of Gd released was in line with all of the Gd‐DTPA in the homogenate participating in water proton relaxation. The data from this acute myocardial infarction model do not support the notion that Gd‐DTPA binding in the early stages of myocardial damage contributes to delayed enhancement. Magn Reson Med 49:168–171, 2003. Published 2003 Wiley‐Liss, Inc.
Multiple‐mouse MRI
Authors: Bock Nicholas A. , Konyer Norman B. , Henkelman R. Mark
Published: January 2003

Several theoretical parallel‐imaging approaches are evaluated that seek to improve the efficiency of an MRI experiment involving multiple small samples, such as mice. The best method for our mouse phenotyping application is chosen in terms of efficiency and ease of implementation, and the approach is demonstrated at 1.5 T on a clinical scanner with an array of four shielded birdcage coils with four parallel receivers. Electronic interactions between the receiver channels in the system are quantified and a novel sensitivity‐encoding (SENSE)‐like postprocessing method is described to remove the resulting image ghosts. In parallel imaging with a four‐coil array, the time required for three‐dimensional (3D) high‐resolution imaging of four mice is reduced to one‐fourth the time that it would take to image the mice sequentially. Magn Reson Med 49:158–167, 2003. © 2003 Wiley‐Liss, Inc.
Motion correction in MRI using an apparatus for dynamic angular position tracking (ADAPT)
Authors: Peshkovsky A. , Knuth K.H. , Helpern J.A.
Published: January 2003

Motion during MRI examinations is a serious problem that degrades the quality of the data (images) acquired. Motion can be corrected during the postprocessing of the data; however, this approach is suboptimal and is typically limited to in‐plane or translational motion. An apparatus for dynamic angular position tracking (ADAPT) for prospective angular motion correction has been developed. This application is capable of “tracking” the scanned region of interest by performing dynamic adjustments of orientation of the scanning plane. The operation of the apparatus is based on deuterium MR spectroscopy and does not rely on the use of magnetic field gradients. Orientation‐sensitive deuterium quadrupolar interaction in a single crystal attached to a subject is used to monitor the angular position in magnetic fields. Measurements are performed with an independent spectrometer channel in the background of the MRI scans. This apparatus is very cost‐ and time‐efficient because it utilizes the hardware already available on many spectrometers and can be used in parallel with MRI scans. Potentially, rotations by a fraction of one degree can be easily corrected and the angular position information can be rapidly updated. Magn Reson Med 49:138–143, 2003. © 2003 Wiley‐Liss, Inc.
Determining and visualizing uncertainty in estimates of fiber orientation from diffusion tensor MRI
Authors: Jones Derek K.
Published: January 2003

Diffusion tensor MRI (DT‐MRI) permits determination of the dominant orientation of structured tissue within an image voxel. This has led to the development of 2D graphical methods for representing fiber orientation and DT‐MRI “tractography,” which aims to reconstruct the 3D trajectories of white matter fasciculi. Most contemporary fiber orientation mapping schemes and tractography algorithms employ the directional information contained in the eigenvectors of the diffusion tensor to approximate white matter fiber orientation. However, while the uncertainty associated with every estimate of an eigenvector has long been recognized, no attempts to quantify this uncertainty in vivo have been reported. Here, a method is proposed for determining confidence intervals in fiber orientation from real DT‐MRI data using the bootstrap method. This is used to construct maps of the “cone of uncertainty,” allowing simultaneous viewing of fiber orientation and its uncertainty, and to examine the relationship between orientation uncertainty and tissue anisotropy. Magn Reson Med 49:7–12, 2003. © 2003 Wiley‐Liss, Inc.
Reconstruction after rotational motion
Authors: Atkinson David , Hill Derek L.G.
Published: January 2003

Patient rotational motion during a scan causes the k‐space sampling to be both irregular and undersampled. Conventional regridding requires an estimate of the sampling density at each measured point and is not strictly consistent with sampling theory. Here, a 2D problem is converted to a series of 1D regriddings by exact interpolation along the measured readouts. Each 1D regridding, expressed in matrix form, requires a matrix inversion to gain an exact solution. Undersampled regions make the matrix ill‐conditioned but summing the matrix columns (without inversion) indicates the undersampled regions. The missing data could be reacquired, but in this study it is estimated using a Delaunay triangle‐based linear interpolation on the original 2D data. The matrix conditioning is improved, leading to images with reduced artifacts compared to other regridding schemes. Furthermore, there is no requirement to estimate a density compensation function at each of the measured points. Magn Reson Med 49:183–187, 2003. © 2003 Wiley‐Liss, Inc.
Interventional MRA using actively visualized catheters, TrueFISP, and real‐time image fusion
Authors: Quick Harald H. , Kuehl Hilmar , Kaiser Gernot , Hornscheidt Dirk , Mikolajczyk Krzysztof P. , Aker Stephanie , Debatin Jörg F. , Ladd Mark E.
Published: January 2003

An integrated system for performing interventional magnetic resonance angiography (MRA) with actively visualized instruments and real‐time image fusion was implemented on a 1.5 T scanner. True fast imaging with steady precession (TrueFISP) imaging provided high acquisition speed paired with high signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) for the simultaneous visualization of active instruments and arterial morphology. The system enabled simultaneous image reconstruction and image postprocessing of multiple receiver channels, with subsequent image fusion display in real time. Optional interleaved image acquisition in two planes provided additional important information for biplanar instrument guidance. Various vascular interventions, including selective catheterization and subsequent selective MRA of the abdominal aorta, renal arteries, superior mesenteric artery (SMA), hepatic artery, and aortic arch, were performed on 10 pigs under MR guidance. In terms of instrument contrast, image acquisition, reconstruction, and fusion speed, the setup represents a powerful platform for performing interventional MRA procedures. Magn Reson Med 49:129–137, 2003. © 2003 Wiley‐Liss, Inc.
Measurement of regional lung function in rats using hyperpolarized 3helium dynamic MRI
Authors: Chen Ben T. , Brau Anja C.S. , Johnson G. Allan
Published: January 2003

Dynamic regional lung function was investigated in rats using a radial acquisition cine (RA‐CINE) pulse sequence together with hyperpolarized (HP) 3He gas delivered by a constant flow ventilator. Based on regional differences in the behavior of inspired air, the lung was conceptually divided into two regions (the major airways and the peripheral airspace) for purposes of functional analysis. To measure regional function in the major airways, a large RF flip angle (24°) was applied to reduce 3He magnetization in the peripheral airspace, and signal intensity (SI) was normalized with the projected airway diameter to estimate local airflow. Higher normalized signal intensity was observed in the left branch airway as compared to the right branch airway. To determine regional function in the peripheral airspace, a small RF flip angle (6°) was used. Incremental increases of peripheral SI in successive lung images were consistent with the increase in lung volume. A new “skipping” scanning strategy using dummy frames allows a trade‐off between the number of frames acquired for dynamic information, the RF flip angle, and the penetration depth of 3He magnetization into the lung. This work provides a novel approach to simultaneously assess dynamic regional function and morphology. Magn Reson Med 49:78–88, 2003. © 2003 Wiley‐Liss, Inc.
Imaging of ischemia and infarction in blood‐perfused pig hearts using 87Rb MRI
Authors: Kupriyanov V.V. , Xiang B. , Sun J. , Jilkina O. , Kuzio B.
Published: January 2003

87Rb‐MRI was used to measure Rb+ uptake in blood‐perfused pig hearts during complete occlusion (120 and 70 min) of the left anterior descending artery (LAD) and subsequent reperfusion (120 and 170 min). The Rb+ uptake rate and maximal Rb image intensity during 120‐min occlusion were significantly lower in the ischemic anterior left ventricular (LV) wall (0.35 ± 0.14%/min and 26 ± 4.7%) relative to those in the remote posterior LV wall (2.43 ± 0.33%/min and 98 ± 10%). Reperfusion after 120 and 70 min of occlusion resulted in formation of damaged areas, which had 40 ± 4 and 73 ± 10% of the 87Rb image intensity observed in the remote posterior wall. The infarct sizes determined histologically by triphenyltetrazolium chloride staining were 9.6 ± 3.4 and 5.6 ± 4.6% of the total ventricular mass (LV + RV) in the 120‐ and 70‐min occlusion groups, respectively. The sizes determined by MRI were 13.1 ± 2 and 2.8 ± 4.3% of the total number of pixels, respectively. The Rb+ uptake in the anterior wall during 120‐min occlusion was somewhat lower than that previously observed in crystalloid‐perfused hearts. It is concluded that blood does not interfere with the ability of 87Rb MRI to detect ischemic and infarct areas. Magn Reson Med 49:99–107, 2003. © 2003 Wiley‐Liss, Inc.
Triggered real‐time MRI and cardiac applications
Authors: Nayak Krishna S. , Hu Bob S.
Published: January 2003

Real‐time interactive MRI is becoming the method of choice for many cardiac applications. One current limitation of real‐time techniques is inaccurate slice registration during free‐breathing. A simple “triggered real‐time” imaging approach is proposed which enables the acquisition of synchronized and accurately registered real‐time movie loops during short breathholds. Initial in vivo results demonstrate application to complete 4D ventricular function assessment and fully resolved flow imaging. Magn Reson Med 49:188–192, 2003. © 2003 Wiley‐Liss, Inc.
Detection of [1,6‐13C2]‐glucose metabolism in rat brain by in vivo 1H‐[13C]‐NMR spectroscopy
Authors: de Graaf Robin A. , Brown Peter B. , Mason Graeme F. , Rothman Douglas L. , Behar Kevin L.
Published: January 2003

Localized, water‐suppressed 1H‐[13C]‐NMR spectroscopy was used to detect 13C‐label accumulation in cerebral metabolites following the intravenous infusion of [1,6‐13C2]‐glucose (Glc). The 1H‐[13C]‐NMR method, based on adiabatic RF pulses, 3D image‐selected in vivo spectroscopy (ISIS) localization, and optimal shimming, yielded high‐quality 1H‐[13C]‐NMR spectra with optimal NMR sensitivity. As a result, the 13C labeling of [4‐13C]‐glutamate (Glu) and [4‐13C]‐glutamine (Gln) could be detected from relatively small volumes (100 μL) with a high temporal resolution. The formation of [n‐13C]‐Glu, [n‐13C]‐Gln (n = 2 or 3), [2‐13C]‐aspartate (Asp), [3‐13C]‐Asp, [3‐13C]‐alanine (Ala), and [3‐13C]‐lactate (Lac) was also observed to be reproducible. The 13C‐label incorporation curves of [4‐13C]‐Glu and [4‐13C]‐Gln provided direct information on metabolic pathways. Using a two‐compartment metabolic model, the tricarboxylic acid (TCA) cycle flux was determined as 0.52 ± 0.04 μmol/min/g, while the glutamatergic neurotransmitter flux equaled 0.25 ± 0.05 μmol/min/g, in good correspondence with previously determined values. Magn Reson Med 49:37–46, 2003. © 2003 Wiley‐Liss, Inc.
Performance of a new gadolinium‐based intravascular contrast agent in free‐breathing inversion‐recovery 3D coronary MRA
Authors: Huber Michael E. , Paetsch Ingo , Schnackenburg Bernhard , Bornstedt Axel , Nagel Eike , Fleck Eckart , Boesiger Peter , Maggioni Fabio , Cavagna Friedrich M. , Stuber Matthias
Published: January 2003

In three‐dimensional (3D) coronary magnetic resonance angiography (MRA), the in‐flow contrast between the coronary blood and the surrounding myocardium is attenuated as compared to thin‐slab two‐dimensional (2D) techniques. The application of a gadolinium (Gd)‐based intravascular contrast agent may provide an additional source of signal and contrast by reducing T1blood and supporting the visualization of more distal or branching segments of the coronary arterial tree. In six healthy adults, the left coronary artery (LCA) system was imaged pre‐ and postcontrast with a 0.075‐mmol/kg bodyweight dose of the intravascular contrast agent B‐22956. For imaging, an optimized free‐breathing, navigator‐gated and ‐corrected 3D inversion recovery (IR) sequence was used. For comparison, state‐of‐the‐art baseline 3D coronary MRA with T2 preparation for non‐exogenous contrast enhancement was acquired. The combination of IR 3D coronary MRA, sophisticated navigator technology, and B‐22956 allowed for an extensive visualization of the LCA system. Postcontrast, a significant increase in both the signal‐to‐noise ratio (SNR; 46%, P < 0.05) and contrast‐to‐noise ratio (CNR; 160%, P < 0.01) was observed, while vessel sharpness of the left anterior descending (LAD) artery and the left coronary circumflex (LCX) were improved by 20% (P < 0.05) and 18% (P < 0.05), respectively. Magn Reson Med 49:115–121, 2003. © 2003 Wiley‐Liss, Inc.
Transmit SENSE
Authors: Katscher Ulrich , Börnert Peter , Leussler Christoph , van den Brink Johan S.
Published: January 2003

The idea of using parallel imaging to shorten the acquisition time by the simultaneous use of multiple receive coils can be adapted for the parallel transmission of a spatially‐selective multidimensional RF pulse. As in data acquisition, a multidimensional RF pulse follows a certain k‐space trajectory. Shortening this trajectory shortens the pulse duration. The use of multiple transmit coils, each with its own time‐dependent waveform and spatial sensitivity, can compensate for the missing parts of the excitation k‐space. This results in a maintained spatial definition of the pulse profile, while its duration is reduced. This work introduces the concept of parallel transmission with arbitrarily shaped transmit coils (termed “Transmit SENSE”). Results of numerical studies demonstrate the theoretical feasibility of the approach. The experimental proof of principle is provided on a commercial MR scanner. The lack of multiple independent transmit channels was addressed by combining the excitation patterns from two separate subexperiments with different transmit setups. Shortening multidimensional RF pulses could be an interesting means of making 3D RF pulses feasible even for fast T relaxing species or strong main field inhomogeneities. Other applications might benefit from the ability of Transmit SENSE to improve the spatial resolution of the pulse profile while maintaining the transmit duration. Magn Reson Med 49:144–150, 2003. © 2003 Wiley‐Liss, Inc.
Fast, automated, N‐dimensional phase‐unwrapping algorithm
Authors: Jenkinson Mark
Published: January 2003

This work investigates the general problem of phase unwrapping for arbitrary N‐dimensional phase maps. A cost function‐based approach is outlined that leads to an integer programming problem. To solve this problem, a best‐pair‐first region merging approach is adopted as the optimization method. The algorithm was implemented and tested with 3D MRI medical data for venogram studies, as well as for fMRI applications in EPI unwarping and rapid, automated shimming. Magn Reson Med 49:193–197, 2003. © 2003 Wiley‐Liss, Inc.
Comparison of the dependence of blood R2 and R on oxygen saturation at 1.5 and 4.7 Tesla
Authors: Silvennoinen M.J. , Clingman C.S. , Golay X. , Kauppinen R.A. , van Zijl P.C.M.
Published: January 2003

Gradient‐echo (GRE) blood oxygen level‐dependent (BOLD) effects have both intra‐ and extravascular contributions. To better understand the intravascular contribution in quantitative terms, the spin‐echo (SE) and GRE transverse relaxation rates, R2 and R, of isolated blood were measured as a function of oxygenation in a perfusion system. Over the normal oxygenation saturation range of blood between veins, capillaries, and arteries, the difference between these rates, R′2 = R − R2, ranged from 1.5 to 2.1 Hz at 1.5 T and from 26 to 36 Hz at 4.7 T. The blood data were used to calculate the expected intravascular BOLD effects for physiological oxygenation changes that are typical during visual activation. This modeling showed that intravascular ΔR is caused mainly by R2 relaxation changes, namely 85% and 78% at 1.5T and 4.7T, respectively. The simulations also show that at longer TEs (>70 ms), the intravascular contribution to the percentual BOLD change is smaller at high field than at low field, especially for GRE experiments. At shorter TE values, the opposite is the case. For pure parenchyma, the intravascular BOLD signal changes originate predominantly from venules for all TEs at low field and for short TEs at high field. At longer TEs at high field, the capillary contribution dominates. The possible influence of partial volume contributions with large vessels was also simulated, showing large (two‐ to threefold) increases in the total intravascular BOLD effect for both GRE and SE. Magn Reson Med 49:47–60, 2003. © 2003 Wiley‐Liss, Inc.
On‐ and off‐resonance T1ρ MRI in acute cerebral ischemia of the rat
Authors: Gröhn Olli H.J. , Mäkelä Heidi I. , Lukkarinen Jouko A. , DelaBarre Lance , Lin Joseph , Garwood Michael , Kauppinen Risto A.
Published: January 2003

The ability of on‐resonance T1ρ (T1ρ) and off‐resonance T1ρ (T) measurements to indicate acute cerebral ischemia in a rat model of transient middle cerebral artery (MCA) occlusion was investigated at 4.7 T. T1ρ was determined with B1 fields of 0.4, 0.8, and 1.6 G, and T with five offset frequencies (Δω) ranging from 0–7.5 kHz at B1 of 0.4 G, yielding effective B1 (Beff) from 0.4 to 1.8 G. Diffusion, T1, and T2 were also quantified. Both T1ρ and T acquired with Δo < 2.5 kHz showed positive contrast during the first hours of MCA occlusion in the ischemic tissue delineated by low diffusion. Interestingly, T contrast acquired with Δω > 2.5 kHz was clearly less sensitive to ischemic alterations, and developed with a delayed time course. This discrepancy is thought to be a consequence of the frequency dependency of cross‐relaxation during irradiation with spin‐lock pulses. Magn Reson Med 49:172–176, 2003. © 2003 Wiley‐Liss, Inc.
Co‐registration of acquired MR ventilation and perfusion images—Validation in a porcine model
Authors: Rizi Rahim R. , Saha Punam K. , Wang Binquan , Ferrante Margaret A. , Lipson David , Baumgardner James , Roberts David A.
Published: January 2003

Under controlled imaging conditions, functional, co‐registered ventilation and perfusion images were obtained for quantitative MRI assessment of pulmonary function. Experiments were conducted on 25–35 kg Yorkshire pigs (N = 5) under ketamine/isoflurane anesthesia. Ventilation and perfusion MR images were obtained using laser polarized gas and gadolinium (Gd), respectively. The mutual information‐based technique was used to quantify the initial misregistration between the acquired ventilation and perfusion images, to cope with different intensity characteristics. Means and standard deviations (SDs) of misregistrations for the five subjects, in terms of absolute translation and absolute rotations around each of the three coordinate axes, were computed to evaluate the hypothesis. For qualitative illustrations, plots of mutual information values under absolute translations and rotations around each of the three coordinate axes are presented. This preliminary study shows the feasibility of acquiring functional image data that are spatially co‐registered. This method has potential applications in the quantitative assessment of regional alveolar ventilation and pulmonary perfusion ratio, in both normal and diseased lung. Magn Reson Med 49:13–18, 2003. © 2003 Wiley‐Liss, Inc.
High‐resolution assessment of blood flow in murine RIF‐1 tumors by monitoring uptake of H217O with proton T1ρ‐weighted imaging
Authors: Tailor Dharmesh R. , Poptani Harish , Glickson Jerry D. , Leigh John S. , Reddy Ravinder
Published: January 2003

Perfusion parameters, such as blood flow, are critical properties of tumors related to angiogenesis, drug delivery, radiosensitivity, bioenergetic status, and steady state levels of metabolites, such as lactate, that have been proposed as indices of tumor response to therapy. The existing MR methods for measuring tumor blood flow (TBF) have limitations related to sensitivity, spatial resolution, or dependence on other physiological properties such as vascular permeability. To address many of these difficulties, this study introduces the use of an 17O‐enriched tracer in conjunction with high‐resolution, indirect MRI to measure TBF. To demonstrate the advantages of this technique, relative TBF was measured in subcutaneous RIF‐1 tumors in C3H mice by monitoring the uptake of H217O with a resolution of 0.16 × 0.31 × 3 mm in 13 sec. At this resolution, tumor heterogeneity with respect to blood flow is clearly visible. Measurement of the tracer arterial input function, which is necessary for determination of absolute blood flow, may be facilitated with improved temporal resolution. Magn Reson Med 49:1–6, 2003. © 2003 Wiley‐Liss, Inc.
Viral RNA in nerve tissues of patients with hepatitis C infection and peripheral neuropathy
Authors: De Martino Luisa , Sampaolo Simone , Tucci Celeste , Ambrosone Lucia , Budillon Alberta , Migliaresi Sergio , Di Iorio Giuseppe
Published: January 2003

To assess the presence of viral ribonucleic acid (RNA) in nerve tissues of 15 patients with hepatitis C virus (HCV) infection and peripheral neuropathy with (11) or without (4) mixed cryoglobulinemia, nested reverse transcription–polymerase chain reaction (RT‐PCR) was performed. Amplification of HCV‐RNA was successful in 7 patients with and 3 without mixed cryoglobulinemia. This study demonstrates that the nested RT‐PCR technique is a sensitive method to detect viral RNA in nerve tissue, and offers further evidence that in patients with HCV infection peripheral neuropathy can occur in the absence of mixed cryoglobulinemia. Muscle Nerve 27:102–104, 2003
Two novel mutations in the myophosphorylase gene in a patient with McArdle disease
Authors: Deschauer Marcus , Hertel Kathrin , Zierz Stephan
Published: January 2003

We identified two novel mutations in exon 2 of the myophosphorylase gene in a 33‐year‐old German women with McArdle disease. The patient was compound heterozygous for a novel nonsense mutation at codon 84 changing tyrosine to stop codon (Y84X) and for a novel missense mutation at codon 93 changing arginine to tryptophan (R93W). These mutations are the first to be described in exon 2 and expand the genetic heterogeneity in patients with McArdle disease. Muscle Nerve 27: 105–107, 2003
Predictability of maximum voluntary isometric knee extension force from submaximal contractions in older adults
Authors: Stackhouse Scott K. , Stevens Jennifer E. , Johnson Christopher D. , Snyder‐Mackler Lynn , Binder‐Macleod Stuart A.
Published: January 2003

The purposes of this study were to develop and test a model describing the relationship between the central activation ratio (CAR; a measure of voluntary muscle activation) and percent maximum voluntary contraction (%MVC) force for old adults and to provide a method for more accurate determination of voluntary muscle activation failure. Twenty‐one adults (ages 64–81) performed isometric testing of the quadriceps at 25%, 50%, 75%, and 100% MVC. During each contraction, a 100‐HZ, 120‐ms train of electrical pulses was delivered to the quadriceps muscle to quantify voluntary muscle activation. Similar to a young, healthy population (ages 20–35), a curvilinear relationship existed between the CAR and %MVC force for older adults. Predictions of subjects' MVCs using the linear model of CAR–%MVC force relationship generally demonstrated poor agreement with actual MVCs. Predictions of MVC from submaximal contractions (25%, 50%, and 75%) using a previously identified curvilinear young adult CAR–%MVC relationship were good [ICC (2,1): 0.81, 0.96, and 0.82, respectively]. Similar agreement was obtained from the curvilinear older adult CAR–%MVC relationship. These data suggest that the CAR–%MVC relationship is similar in young and older adult subjects and that curvilinear models of this relationship can predict MVC forces in older adults more accurately. Reexamination of the relationship between the CAR and %MVC force may allow a more accurate determination of how failure of voluntary muscle activation contributes to weakness in old adults. Muscle Nerve 27: 40–45, 2003
Attenuation of stretch‐induced histopathologic changes of skeletal muscles by quinacrine
Authors: Willems Mark E. T. , Stauber William T.
Published: January 2003

Quinacrine is an inhibitor of phospholipase A2, an enzyme thought to be involved in activity‐related injury of skeletal muscles. Histopathologic changes after injury by stretches of activated plantar‐flexor muscles were measured in untreated and quinacrine‐treated rats. On day 4 of treatment (50 mg·kg−1 intraperitoneally for 5 days), 30 stretches were induced by ankle rotation after muscles reached a maximal isometric force. During the stretch protocol, peak stretch forces and isometric force deficits after each stretch [total deficits 56.7 ± 2.8% (untreated rats) and 59.6 ± 1.7% (quinacrine‐treated rats)] were similar for both groups (n = 6 each). Two days after the stretch protocol, histopathologic changes were evaluated using antibody staining on cross‐sections of gastrocnemius medialis muscles. Swollen myofibers devoid of desmin were identified. Similar cells, but not all swollen myofibers, in adjacent sections stained for albumin. Quinacrine reduced the number of desmin‐negative and albumin‐positive cells by 88% (P < 0.05) and 84% (P < 0.05), indicating that it attenuated histopathologic changes that follow stretch injury of activated skeletal muscles. Histopathologic changes following muscle injury or myopathic disease may thus be reduced or even prevented by selective drug intervention, thereby reducing the risk of muscle fibrosis. Muscle Nerve 27: 65–71, 2003
Leukocytoclastic‐vasculitic neuropathy associated with chronic Epstein–Barr virus infection
Authors: Kanai Kazuaki , Kuwabara Satoshi , Mori Masahiro , Arai Kimihito , Yamamoto Takako , Hattori Takamichi
Published: January 2003

We report a patient with leukocytoclastic‐vasculitic neuropathy associated with chronic Epstein–Barr virus (EBV) infection. A 55‐year‐old man had been suffering from chronic progressive axonal polyneuropathy and skin erythema for 3 years. A skin biopsy showed capillary vasculitis with clustered leukocyte fragments. Findings of serum assays, a polymerase chain reaction for EBV‐DNA, and in situ hybridization indicated chronic EBV infection. Immunosuppressive treatment resulted in the gradual lessening of his general and neurologic symptoms. Muscle Nerve 27:113–116, 2003
Depression of spinal motoneurons may underlie weakness associated with severe anemia
Authors: Leis A. Arturo , Stokic Dobrivoje S. , Shepherd Jinna M.
Published: January 2003

A 37‐year‐old woman had a 2‐week history of progressive weakness, muscle hypotonia, and absent or hypoactive deep tendon reflexes. Nerve conduction studies showed diminished H‐reflexes and absent or decreased persistence of F‐waves in all limbs. The patient was admitted to the hospital with a diagnosis of Guillain–Barré syndrome. Laboratory studies revealed severe anemia with a hemoglobin level of 4.1 g/dl and hematocrit of 15.1%. Immediate blood transfusion resulted in a hemoglobin of 13.2 g/dl and hematocrit of 40.2%, associated with rapid neurological recovery (normal stretch reflexes and muscle strength) and normalization of F‐waves and H‐reflexes. This case demonstrates that severe anemia may be associated with signs and symptoms that mimic Guillain–Barré syndrome, both clinically and electrophysiologically. It also suggests that a relative depression of spinal motoneuron excitability may be a possible mechanism for the weakness that is commonly observed in severe anemia. Muscle Nerve 27:108–112, 2003
Effects of superimposed electrical stimulation on perceived discomfort and torque increment size and variability
Authors: Miller Michael , Downham David , Lexell Jan
Published: January 2003

Superimposed electrical stimulation techniques can be used to detect central activation failure (CAF), that is, incomplete central nervous system recruitment or suboptimal activation of motor units. The purpose of this study was to evaluate the effects of two stimulation parameters on perceived discomfort and torque increment size and variability. Discomfort was evaluated using a visual analog scale (0–100 mm) for pain. The rectus femoris muscle of the dominant leg of 24 young healthy men was stimulated during submaximal (80% maximal) voluntary contractions. The size and variability of torque increments and perceived discomfort were assessed following stimulation with: (1) pulse trains (100 HZ, 150 V, 0.2‐ms pulse duration) of different lengths (50 ms and 100 ms); and (2) pulse trains (100 HZ, 100 ms, 150 V) with different pulse durations (0.2 ms and 0.1 ms). Pulse trains of 100 ms generated larger torque increments and produced less variability, but caused more discomfort than pulse trains of 50 ms. Average discomfort ratings for pulse trains of 100 ms were 43.1 mm, and of 50 ms were 53.2 mm. There was no difference in torque increment size or in variability between pulse trains with pulse durations of 0.1 ms and 0.2 ms, whereas discomfort was less for the shorter pulse durations; average discomfort ratings were 53.1 mm and 58.1 mm for pulse durations of 0.1 ms and 0.2 ms, respectively. Thus, the appropriate selection of stimulation parameters can reduce discomfort but maintain the ability to detect CAF. Muscle Nerve 27: 90–98, 2003
Comparison of surgical and electrodiagnostic findings in single root lumbosacral radiculopathies
Authors: Tsao Bryan E. , Levin Kerry H. , Bodner Russ A.
Published: January 2003

To identify the segmental innervation of L‐2–S‐1 muscles, we compared the preoperative electrodiagnostic examinations of 45 patients with single‐level lumbosacral radiculopathies confirmed radiologically and surgically. The electrodiagnostic findings were classified as abnormal only by the needle examination and only if muscles demonstrated active denervation or a marked neurogenic motor unit potential firing pattern. In comparison to other surgical, intraoperative root stimulation, and clinical studies, we found several differences. Overall, there was little overlap among L‐2–4, L‐5, and S‐1 radiculopathies. The tibialis anterior was predominantly L‐5 innervated, the gastrocnemius (medial and lateral head) predominantly S‐1 innervated, and the biceps femoris (short and long head) exclusively S‐1 innervated. The two heads of biceps femoris were not affected in any patients with L‐5 radiculopathy in whom they were examined. These findings help guide both the clinician and surgeon in the diagnosis and treatment of lumbosacral radiculopathies. Muscle Nerve 27: 60–64, 2003
The utility of segmental nerve conduction studies in ulnar mononeuropathy at the elbow
Authors: Azrieli Yevgeny , Weimer Louis , Lovelace Robert , Gooch Clifton
Published: January 2003

Patients with clinical evidence of ulnar mononeuropathy at the elbow may have normal routine motor and sensory nerve conduction studies, suggesting a low sensitivity for these methods. Other, more specialized techniques may have a higher sensitivity, increasing diagnostic yield, and provide more specific localization of the lesion. We compared the sensitivity and specificity of ulnar segmental nerve conduction studies (SgNCS or “inching”) at 2‐cm intervals with those of routine ulnar motor and sensory studies. We studied 21 arms with symptoms or signs of ulnar neuropathy and 25 asymptomatic control arms. SgNCS proved significantly more sensitive than more routine studies in diagnosing ulnar neuropathy at the elbow, with a sensitivity of 81%, whereas motor conduction velocity in a longer (10–14 cm) segment across the elbow was the next most sensitive at 24%. Recording from the first dorsal interosseous muscle did not improve sensitivity when compared with recording from the abductor digiti quinti. Short SgNCS significantly improves detection of ulnar mononeuropathy at the elbow and should be considered when routine studies are negative and clinical suspicion remains high. Muscle Nerve 27: 46–50, 2003
Ryanodine receptor antibodies in myasthenia gravis: Epitope mapping and effect on calcium release in vitro
Authors: Skeie Geir Olve , Mygland Åse , Treves Susan , Gilhus Nils Erik , Aarli Johan Arild , Zorzato Francesco
Published: January 2003

Patients with myasthenia gravis can have antibodies against skeletal muscle ryanodine receptor (Ry1), the sarcoplasmic reticulum calcium‐release channel, which plays a crucial role in excitation–contraction coupling. We have screened a panel of overlapping Ry1 fusion proteins with Ry1 antibody–containing myasthenia gravis sera to identify the main immunogenic region. The pc2 Ry1 fusion protein representing a Ry1 region close to the N‐terminus (residues 799–1172) was identified as the main immunogenic region for the antibodies. The binding kinetics of the Ry1 antibodies to the pc2 Ry1 fusion protein were tested using an optical biosensor. Ry1 antibodies in the IgG fraction from sera of patients with myasthenia gravis bound with high affinity and with a stoichiometry of 1:1. The functional effect of these Ry1 antibodies was tested in an in vitro Ca2+‐release assay. The Ry1 antibodies induced a twofold increase of the half‐maximal concentration for 4‐Cl‐m‐cresol–induced Ca2+ release from terminal cisternae vesicles but had no effect on Vmax. The effect on 4‐Cl‐m‐cresol–induced Ca2+ release was specific, as preincubation of the active IgG fraction with the pc2 Ry1 fusion protein abolished the inhibition. These data suggest that the Ry1 sequence defined by residues 799–1172 is involved in the regulation of Ry1 function, and that this regulation could be functionally affected in vivo in patients with myasthenia gravis. Muscle Nerve 27: 81–89, 2003
Initial semeiology in children with Charcot–Marie–Tooth disease 1A duplication
Authors: Berciano José , García Antonio , Combarros Onofre
Published: January 2003

The aim of this study was to describe the initial signs and symptoms in Charcot–Marie–Tooth disease type 1A (CMT‐1A). Twelve secondary cases with CMT‐1A were serially evaluated. Ages at initial clinical examination ranged between 1 month and 5 years (mean, 2 years) and final ages between 6 and 23 years (mean, 13 years). First signs of the disease were detected at initial or upon serial examinations in all 12 patients at ages ranging between 1 and 10 years (median, 4 years). The most frequent signs were lower limb areflexia in 12, difficulty in heel walking in 8, nerve enlargement in 6, atrophy of intrinsic foot muscles in 6, clawing of toes in 5, pes cavus or cavus varus in 4, shortening of Achilles tendon in 3, peroneal weakness in 1, and stocking hypoesthesia in 1. Only three patients were symptomatic at the initial evaluation. We conclude that initial CMT‐1A signs usually appear in early childhood, although they may be quite subtle and require serial examinations for detection. Lower limb areflexia is the only constant early sign. Muscle Nerve 27: 34–39, 2003
Multifacility ordered median problems on networks: A further analysis
Authors: Kalcsics Jörg , Nickel Stefan , Puerto Justo
Published: January 2003

In this paper, we address the ordered p‐median problem, which includes as special cases most of the classical multifacility location problems discussed in the literature. Finite dominating sets (FDS) are known for particular instances of this problem: p‐median, p‐center, and p‐centdian. We find an FDS for the ordered p‐median problem. This set allows us to gain a better insight into the general FDS structure of network location problems. This FDS is later used to present the first polynomial time algorithm for p‐facility ordered median problems on tree networks. This result is combined with some approximation algorithms to give an O(log M log log M) approximate solution of these problems on general networks, where M is the number of vertices. © 2002 Wiley Periodicals, Inc.
The SONET edge‐partition problem
Authors: Goldschmidt Olivier , Hochbaum Dorit S. , Levin Asaf , Olinick Eli V.
Published: January 2003

Motivated by a problem arising in the design of telecommunications networks using the SONET standard, we consider the problem of covering all edges of a graph using subgraphs that contain at most k edges with the objective of minimizing the total number of vertices in the subgraphs. We show that the problem is 𝒩𝒫‐hard when k ≥ 3 and present a linear‐time

‐approximation algorithm. For even k values, we present an approximation scheme with a reduced ratio but with increased complexity. © 2002 Wiley Periodicals, Inc.
Upgrading trees under diameter and budget constraints
Authors: Chepoi Victor , Noltemeier Hartmut , Vaxès Yann
Published: January 2003

Given a tree T = (V, E) endowed with a length function l and a cost function c, the diameter lowering problem consists in finding the reals 0 ≤ x(e) ≤ l(e), e ∈ E such that the tree obtained from T by decreasing the length of every edge e by x(e) units has a minimal diameter subject to the constraint ∑e∈Ec(e)x(e) ≤ B, where B is the available budget (analogously, one can minimize the cost of lowering subject to a diameter constraint). We present an O(|V|2) algorithm for solving this problem by developing and using algorithms of similar complexity for related eccentricity lowering problems. © 2002 Wiley Periodical, Inc.
Toward faster algorithms for dynamic traffic assignment. I. Parametric quickest‐path trees
Authors: Dial Robert B.
Published: January 2003

Being first in a three‐part series promising a practical solution to the user‐equilibrium dynamic traffic assignment problem, this paper devises a parametric quickest‐path tree algorithm, whose model makes three practical assumptions: (i) the traversal time of an arc i → j is a piecewise linear function of the arrival time at its i‐node; (ii) the traversal time of a path is the sum of its arcs' traversal times; and (iii) the FIFO constraint holds, that is, later departure implies later arrival. The algorithm finds a quickest path, and its associated earliest arrival time, to every node for every desired departure time from the origin. Its parametric approach transforms a min‐path tree for one departure‐time interval into another for the next adjacent interval, whose shared boundary the algorithm determines on the fly. By building relatively few trees, it provides the topology explicitly and the arrival times implicitly of all min‐path trees. Tests show the algorithm running upward of 10 times faster than the conventional brute‐force approach, which explicitly builds a min‐path tree for every departure time. Besides dynamic traffic assignment, other applications for which these findings have utility include traffic control planning, vehicle routing and scheduling, real‐time highway route guidance, etc. © 2002 Wiley Periodicals, Inc.
Social network coordination and graph routing
Authors: Onn Shmuel , Sperber Elisheva
Published: January 2003

We consider the problem of coordinating robots moving on a network. Each robot is autonomous and needs to visit various sites of the network at various times. The sequence of destinations for each robot changes dynamically and unpredictably. Recently, Onn and Tennenholtz showed that the problem can be solved by introducing a social law on the network, which, once obeyed by all robots, enables each to move to any desired destination without collisions and regardless of the actions of other robots, needing neither central coordination nor mutual communication. This social law can be derived from a suitably defined routing of the graph underlying the network. Here, we study the complexity of routing. We provide an effective characterization of 2‐routable graphs, and by establishing a correspondence between hypergraph coloring and graph routing, we show that computing or approximating an optimal routing is generally hard. We also discuss routing in planar graphs, which often underlie robotic networks and show that the correspondence between coloring and routing together with the Four Color Theorem guarantee the existence of small and effectively computable routings in bipartite planar graphs of small radius. The complexity of routing arbitrary planar graphs remains open. © 2002 Wiley Periodicals, Inc.
A note on needle‐ice mound formation in the High Drakensberg, Southern Africa
Authors: Grab Stefan
Published: January 2003

Small needle‐ice mounds are described from the High Drakensberg. They develop infrequently during periods of several days of uninterrupted cold conditions. Ice growth incorporates sediment and stones. An accumulated segregated ice length of >41 cm was measured, with clasts heaved ∼14 cm. During subsequent thaw phases, the ice ablates from the top downwards, forming sediment veneers and cappings. These mounds contribute towards turf exfoliation, thereby exposing sediment to deflation. Copyright © 2002 John Wiley & Sons, Ltd.
Observations on a blockstream in the vicinity of Sani Pass, Lesotho highlands, Southern Africa
Authors: Boelhouwers Jan , Holness Steve , Meiklejohn Ian , Sumner Paul
Published: January 2003

Coarse slope deposits, frequently grading into blockstreams, are common throughout the Lesotho highlands, southern Africa. This paper describes one such blockstream. It is interpreted as a typical lag deposit derived from valley‐wide colluvial mantles, which contains superimposed and incorporated Late‐Pleistocene blocky material. Blocks are largely derived from local scarps but may contain a component of corestones from mobilized regolith. The widespread mantle argues against landscape‐scale glaciation in the Lesotho highlands in the Late Pleistocene. Rather, the environment appears to have been conducive to deep seasonal frost during the period of block production. No unequivocal evidence for permafrost is found. Copyright © 2002 John Wiley & Sons, Ltd.
High‐resolution seismic and ground penetrating radar–geophysical profiling of a thermokarst lake in the western Lena Delta, Northern Siberia
Authors: Schwamborn G. J. , Dix J. K. , Bull J. M. , Rachold V.
Published: January 2003

High‐resolution seismic and ground‐penetrating‐radar (GPR) data have been acquired over Lake Nikolay in the western Lena Delta in order to study the uppermost basin fill and the bordering frozen margins. GPR (100 MHz antenna pair) measurements were completed on the frozen lake and its permafrost margins, while high‐resolution seismic data were acquired from the lake during open‐water conditions in summer using a 1.5–11.5 kHz Chirp profiler. The combined use of the two profiling systems allows stratigraphic profiling in both frozen and unfrozen parts of the lake. Shallow seismic reflection images of the uppermost 4 to 5 m of sediments are compared to GPR sections, which have approximately the same horizontal and vertical resolution. Short sediment cores aid calibrate the geophysical data. Copyright © 2002 John Wiley & Sons, Ltd.
Internal structure and behaviour of a rock glacier in the Arid Andes of Argentina
Authors: Croce Flavia A. , Milana Juan P.
Published: January 2003

This paper reports results of the application of combined refraction and geoelectric geophysical methods to the study of the El Paso rock glacier in the arid Andes of Argentina. The data allow inferences to be made upon the internal structure, and permafrost thickness of the rock glacier. The El Paso rock glacier is located in the arid to hyper‐arid Agua Negra basin. Due to its altitude, it records some of the world's highest global radiation. The active layer thickness was studied using refraction seismic methods. Seasonal monitoring of this layer showed large variations in thickness, being thicker in summer and thinner in winter. Geoelectric methods allowed detection of a wet layer underlying permafrost, thereby providing information about the character of the rock‐glacier base. The maximum inferred thickness of El Paso permafrost was 18.5 m. Three main layers were detected: an upper deposit of dry debris over a debris‐water layer, a debris‐ice‐mixture (i.e. permafrost), and a lower one composed of wet debris. The geophysical results permit a first estimate of the volume of water (6.3 hm3) enclosed in the rock glaciers of this region, indicating that locally, rock glaciers are important water resources. However the incidence of water availability to the arid lowlands is unknown. Copyright © 2002 John Wiley & Sons, Ltd.
Modelling rock avalanches and their relation to permafrost degradation in glacial environments
Authors: Bottino Giannantonio , Chiarle Marta , Joly André , Mortara Giovanni
Published: January 2003

High runout distances characterize landslides falling on glaciers because of (1) low friction offered by ice to sliding and (2) complex rock‐ice interactions that take place during mass motion. Block‐fall models (two (2D) and three dimensional (3D)) were tested on the 1936 Felik landslide (Mount Rosa Massif). Geotechnical parameters were assessed through a back‐analysis aided by field surveys, aerial photo and historical data analysis. Outcomes are verified for two rock‐ice avalanches which ran along the Brenva Glacier (Mount Blanc Massif) in 1920 and 1997. Empirical models show poor precision (75%). 3D numerical models are too complex but 2D ones gave results that pointed out that real runouts exceed predicted ones by 30%, possibly due to fluidization processes. Rock‐ice avalanches require attention because they originate in areas likely destined to experience permafrost degradation and glacier retreat. Copyright © 2002 John Wiley & Sons, Ltd.
Morphometry and environmental characteristics of turf‐banked solifluction lobes, Kluane Range, Yukon Territory, Canada
Authors: Hugenholtz Chris H. , Lewkowicz Antoni G.
Published: January 2003

Measurements of turf‐banked solifluction lobes at a site in the Kluane Range, Yukon Territory, are compared to observations made by L.W. Price of similar features located 50 km to the north in the Ruby Range. Both studies show that a threshold depth of snow is necessary for lobes to develop. The relative importance of solifluction on slopes with different orientations, however, is not congruent. The largest lobes at our site are present on northeast‐facing slopes and the smallest on northwest‐facing slopes. Lobe dimensions increase downslope in association with a greater organic mat thickness, a higher soil fines content, and a reduced late‐summer thaw depth. Riser heights that are large relative to tread length‐to‐width ratios are correlated with a thin organic mat, a thick active layer and a high coarse particle content. The lobe plan‐form, described by the ratio of tread length to tread width, is significantly correlated with only one biophysical variable. Mean and median length‐to‐width ratios are below unity for all aspects at our site and in several other studies, suggesting a common evolutionary form. A cycle of solifluction lobe development is proposed, in which a lobe enlarges to a maximum size that depends on micro‐site environmental characteristics. Copyright © 2002 John Wiley & Sons, Ltd.