bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Lignan and two Eudesmanes from Lepidozia vitrea
Authors: Ma Bin , Guo Huai‐Fang , Lou Hong‐Xiang 
Published: January 2007

AbstractA new lignan, 1, was isolated from Lepidozia vitrea, together with two known eudesmane terpenoids, 2 and 3, as well as 7,8‐dihydroxycoumarin (4). Their structures were elucidated on the basis of extensive 1D‐ and 2D‐NMR as well as MS analyses.
Five New Steroidal Glycosides from Caralluma dalzielii
Authors: Oyama Masayoshi , Iliya Ibrahim , Tanaka Toshiyuki , Iinuma Munekazu 
Published: January 2007

AbstractFive new pregnane glycosides, caradalzielosides A–E (1–5), were isolated from the aerial parts of Caralluma dalzielii. Their structures were elucidated by extensive 1D‐ and 2D‐NMR spectroscopic analysis as well as by HR‐FAB‐MS experiments.
Reactions of Methyl Diazoacetate with (E)‐ and (Z)‐1,2‐Bis(trifluoromethyl)ethene‐1,2‐dicarbonitrile: Novel and Unanticipated Pathways
Authors: Huisgen Rolf , Mlostoń Grzegorz , Pöchlauer Peter , Fišera Lubor , Giera Henry 
Published: January 2007

AbstractThe cycloadditions of methyl diazoacetate to 2,3‐bis(trifluoromethyl)fumaronitrile ((E)‐BTE) and 2,3‐bis(trifluoromethyl)maleonitrile ((Z)‐BTE) furnish the 4,5‐dihydro‐1H‐pyrazoles 13. The retention of dipolarophile configuration proceeds for (E)‐BTE with > 99.93% and for (Z)‐BTE with > 99.8% (CDCl3, 25°), suggesting concertedness. Base catalysis (1,4‐diazabicyclo[2.2.2]octane (DABCO), proton sponge) converts the cycloadducts, trans‐13 and cis‐13, to a 94 : 6 equilibrium mixture (CDCl3, r.t.); the first step is N‐deprotonation, since reaction with methyl fluorosulfonate affords the 4,5‐dihydro‐1‐methyl‐1H‐pyrazoles. Competing with the cis/trans isomerization of 13 is the formation of a bis(dehydrofluoro) dimer (two diastereoisomers), the structure of which was elucidated by IR, 19F‐NMR, and 13C‐NMR spectroscopy. The reaction slows when DABCO is bound by HF, but F− as base keeps the conversion to 22 going and binds HF. The diazo group in 22 suggests a common intermediate for cis/trans isomerization of 13 and conversion to 22: reversible ring opening of N‐deprotonated 13 provides 18, a derivative of methyl diazoacetate with a carbanionic substituent. Mechanistic comparison with the reaction of diazomethane and dimethyl 2,3‐dicyanofumarate, a related tetra‐acceptor‐ethylene, brings to light unanticipated divergencies.
Muscle MRI in inherited neuromuscular disorders: Past, present, and future
Authors: Mercuri Eugenio , Pichiecchio Anna , Allsop Joanna , Messina Sonia , Pane Marika , Muntoni Francesco 
Published: January 2007

AbstractInterest in muscle MRI has been largely stimulated in the last few years by the recognition of an increasing number of genetic defects in the field of inherited neuromuscular disorders. Muscle ultrasound (US) and computed tomography (CT) have been used to detect the presence of muscle involvement in patients affected by these disorders, but until recently the use of muscle MRI has been, with a few exceptions, limited to detecting inflammatory forms. The aim of this review is to illustrate how muscle MRI, in combination with clinical evaluation, can contribute to the selection of appropriate genetic tests and more generally in the differential diagnosis of genetically distinct forms of neuromuscular disorders. Possible future applications of muscle MRI are also discussed. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Structural and functional assessment of trabecular and cortical bone by micro magnetic resonance imaging
Authors: Wehrli Felix W. 
Published: January 2007

AbstractOsteoporosis is a multifactorial disorder of bone mineral homeostasis affecting the elderly. It is a major public health issue with significant socioeconomic consequences. Recent findings suggest that bone loss—the key manifestation of the disease—is accompanied by architectural deterioration, both affecting the bone's mechanical competence and susceptibility to fracture. This article reviews the potential of quantitative micro MRI (μ‐MRI), including a discussion of the technical requirements for image acquisition, processing, and analysis for assessing the architectural implications of osteoporosis and as a means to monitor the response to treatment. With current technology, the resolution achievable in clinically acceptable scan times and necessary signal‐to‐noise ratio (SNR) is comparable to trabecular thickness. This limited spatial resolution regime demands processing and analysis algorithms designed to operate under such limiting conditions. It is shown that three different classes of structural parameters can be distinguished, characterizing scale, topology, and orientation. There is considerable evidence that osteoporotic bone loss affects all three classes but that topological changes, resulting from conversion of trabecular plates to rods, with the latter's eventual disconnection, are particularly prominent. Clinical applications discussed can be divided into those dealing with assessment of osteoporotic fracture risk as opposed to the study of the effect of disease progression and regression in response to treatment. Current data suggest that noninvasive assessment of cortical and trabecular bone (TB) architecture by μ‐MRI may provide new surrogate endpoints to assess the efficacy of intervention in osteoporosis treatment and prevention. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Collagen structure: The molecular source of the tendon magic angle effect
Authors: Fullerton Gary D. , Rahal Andrés 
Published: January 2007

AbstractThis review of tendon/collagen structure shows that the orientational variation in MRI signals from tendon, which is referred to as the “magic angle” (MA) effect, is caused by irreducible separation of charges on the main chain of the collagen molecule. These charges are held apart in a vacuum by stereotactic restriction of protein folding due in large part to a high concentration of hydroxyproline ring residues in the amino acids of mammalian collagen. The elevated protein electrostatic energy is reduced in water by the large dielectric constant of the highly polar solvent (κ ∼ 80). The water molecules serve as dielectric molecules that are bound by an energy that is nearly equivalent to the electrostatic energy between the neighboring positive and negative charge pairs in a vacuum. These highly immobilized water molecules and secondary molecules in the hydrogen‐bonded water network are confined to the transverse plane of the tendon. Orientational restriction causes residual dipole coupling, which is directly responsible for the frequency and phase shifts observed in orientational MRI (OMRI) described by the MA effect. Reference to a wide range of biophysical measurements shows that native hydration is a monolayer on collagen hm = 1.6 g/g, which divides into two components consisting of primary hydration on polar surfaces hpp = 0.8 g/g and secondary hydration hs = 0.8 g/g bridging over hydrophobic surface regions. Primary hydration further divides into side‐chain hydration hpsc = 0.54 g/g and main‐chain hydration hpmc = 0.263 g/g. The main‐chain fraction consists of water that bridges between charges on the main chain and is responsible for almost all of the enthalpy of melting ΔH = 70 J/g‐dry mass. Main‐chain water bridges consist of one extremely immobilized Ramachandran water bridge per tripeptide hRa = 0.0658 g/g and one double water bridge per tripeptide hdwb = 0.1974 g/g, with three water molecules that are sufficiently slowed to act as the spin‐lattice relaxation sink for the entire tendon. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Frontiers in musculoskeletal MRI: Articular cartilage
Authors: Kneeland J. Bruce , Reddy Ravinder 
Published: January 2007

AbstractThe techniques and uses of MRI in current clinical practice, primarily as a means to detect morphologic abnormalities, are reviewed. Ongoing development of techniques that can improve morphologic assessment including techniques to increase spatial and contrast resolution is discussed, as are methods to measure cartilage volumes and thickness. Finally, several of the more widely studied techniques used to probe loss of the macromolecular structure of cartilage prior to the development of macroscopic defects are presented and compared. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Ultra‐high‐field MRI of the musculoskeletal system at 7.0T
Authors: Regatte Ravinder R. , Schweitzer Mark E. 
Published: January 2007

AbstractHigh‐field (3T) and ultra‐high‐field (UHF, 7T and above) systems are increasingly being used to explore potential musculoskeletal applications because they provide a high intrinsic signal‐to‐noise ratio (SNR), potentially higher resolution (spatial and temporal), and improved contrast. However, imaging at 7T and above presents certain challenges, such as homogeneous radiofrequency (RF) coil design, increased chemical shift artifacts, susceptibility artifacts, RF energy deposition, and changes in relaxation times compared to more typical clinical scanners (1.5 and 3T). Despite these issues, MRI at 7T likely will provide some excellent opportunities for high‐resolution morphologic imaging and forays into functional imaging of musculoskeletal systems. In this review we address some of these issues and also demonstrate the feasibility of acquiring high‐resolution in vivo images of the musculoskeletal system in healthy human volunteers at 7.0T. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Applications of magnetic resonance elastography to healthy and pathologic skeletal muscle
Authors: Ringleb Stacie I. , Bensamoun Sabine F. , Chen Qingshan , Manduca Armando , An Kai‐Nan , Ehman Richard L. 
Published: January 2007

AbstractMagnetic resonance elastography (MRE) is capable of noninvasively quantifying the mechanical properties of skeletal muscles in vivo. This information can be clinically useful to understand the effects of pathologies on the mechanical properties of muscle and to quantify the effects of treatment. Advances in inversion algorithms quantify muscle anisotropy in two‐dimensional (2D) and three‐dimensional (3D) imaging. Databases of the shear stiffness of skeletal muscle have been presented in the relaxed and contracted states in the upper extremity (biceps brachii, flexor digitorum profundus, and upper trapezius), distal leg muscles (tibialis anterior, medial gastrocnemius, lateral gastrocnemius, and trapezius), and proximal leg muscles (vastus lateralis, vastus medialis, and sartorius). MRE measurements have successfully validated a mathematical model of skeletal muscle behavior in the biceps brachii, correlated to electromyographic data in the distal leg muscles and quantified the effects of pathologies on the distal and proximal leg muscles. Future research efforts should be directed toward improving one‐dimensional (1D) and 3D MRE data acquisition and image processing, tracking the effects of treatment on pathologic muscle and correlating the shear stiffness with clinical measurements. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Balanced SSFP imaging of the musculoskeletal system
Authors: Gold Garry E. , Hargreaves Brian A. , Reeder Scott B. , Block Walter F. , Kijowski Richard , Vasanawala Shreyas S. , Kornaat Peter R. , Bammer Roland , Newbould Rexford , Bangerter Neal K. , Beaulieu Christopher F. 
Published: January 2007

AbstractMagnetic resonance imaging (MRI), with its unique ability to image and characterize soft tissue noninvasively, has emerged as one of the most accurate imaging methods available to diagnose bone and joint pathology. Currently, most evaluation of musculoskeletal pathology is done with two‐dimensional acquisition techniques such as fast spin echo (FSE) imaging. The development of three‐dimensional fast imaging methods based on balanced steady‐state free precession (SSFP) shows great promise to improve MRI of the musculoskeletal system. These methods may allow acquisition of fluid sensitive isotropic data that can be reformatted into arbitrary planes for improved detection and visualization of pathology. Sensitivity to fluid and fat suppression are important issues in these techniques to improve delineation of cartilage contours, for detection of marrow edema and derangement of other joint structures. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Magnetic resonance imaging of entheses using ultrashort TE (UTE) pulse sequences
Authors: Benjamin Michael , Bydder Graeme M 
Published: January 2007

AbstractThe attachment of tendons, ligaments, and joint capsule to bone (entheses) is reviewed and new options for visualizing key components of entheses provided by ultrashort TE (UTE) pulse sequences are described. Many features of entheses are adapted to the dispersion of stress at the boundary between tendons/ligaments and bone. Of particular interest is fibrocartilage, which has mechanical properties different from those of both “pure” tendon/ligament and bone. Features typical of entheses can also be seen at sites where tendons or ligaments are in contact with (but not attached to) bone, and the concept of a “functional enthesis” has been developed to emphasize the similarities. The enthesis concept has also been broadened to include the idea of an “enthesis organ” in which many tissues play a role in dissipating stress concentration. UTE pulse sequences can specifically identify the calcified and uncalcified fibrocartilage tissue components of entheses and differentiate these from fibrous connective tissue and bone. These tissues cannot be separately visualized at entheses with conventional pulse sequences. Entheses are involved in overuse syndromes and seronegative spondyloarthropathies (SpA) and there are important issues related to tissue repair and healing following surgery. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
The magic angle effect: A source of artifact, determinant of image contrast, and technique for imaging
Authors: Bydder Mark , Rahal Andres , Fullerton Gary D. , Bydder Graeme M. 
Published: January 2007

AbstractThis review provides a formalism for understanding magic angle effects in clinical studies. It involves consideration of the fiber‐to‐field angle for linear structures such as tendons, ligaments, and peripheral nerves, disc‐like and circular structures such as menisci and labra, as well as complex three‐dimensional structures. There may be one or more fiber types with different orientations within each of these tissues. The orientation of these fibers to B0 is crucial in determining their magic angle effect. Tissues may show a variety of appearances depending on their baseline T2, as well as the increase in T2 produced by the magic angle effect. The appearances are affected by TE, which affects both the general tissue signal level and the change in signal produced by the magic angle effect, fiber‐to‐slice orientation, and partial volume effects. Deliberate positioning of structures and tissues at particular orientations to B0 can be used to increase the signal from tissues such as tendons and ligaments and so allow them to be imaged with conventional sequences. The technique can also be used to produce contrast between tissues with fibers that have different orientations to B0. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Magnetic resonance imaging with ultrashort TE (UTE) PULSE sequences: Technical considerations
Authors: Tyler Damian J. , Robson Matthew D. , Henkelman R. Mark , Young Ian R. , Bydder Graeme M. 
Published: January 2007

AbstractIt is now possible to detect signals from tissues and tissue components with short T2s, such as cortical bone, using ultrashort TE (UTE) pulse sequences. The background to the use of these sequences is reviewed with particular emphasis on MR system issues. Tissue properties are discussed, and tissues are divided into those with a majority and those with a minority of short T2 components. UTE pulse sequences and their variants are described and clinical applications are illustrated. System design requirements for sequences of this type, including gradient performance, RF switching, and data‐processing issues, are outlined. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Low‐field musculoskeletal MRI
Authors: Ghazinoor Shaya , Crues John V. , Crowley Chris 
Published: January 2007

AbstractSince it was first introduced in the field of medical imaging in the early 1980s, MRI has become essential for the diagnosis and treatment of musculoskeletal conditions. Most imaging in the United States is performed on high‐field (>1.0T), whole‐body scanners. However, for reasons discussed below, imaging at low (<0.5T) and medium (0.5–1.0T) field strengths using small, low‐cost, easily installed scanners in imaging centers and physicians' offices is gaining increasing popularity. Such scanners can be very useful for imaging the upper and lower extremities, from the shoulder to the fingers and the hips to the toes. In this review we provide an overview of the different available extremity scanners and their advantages and disadvantages, briefly review the literature regarding their use, and discuss our experience in using low‐field extremity scanners to evaluate joints. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Study of order and dynamic processes in tendon by NMR and MRI
Authors: Navon G. , Eliav U. , Demco D.E. , Blümich B. 
Published: January 2007

AbstractTendons are composed of a parallel arrangement of densely packed collagen fibrils that results in unique biomechanical properties of strength and flexibility. In the present review we discuss several advanced magnetic resonance spectroscopy (MRS) and imaging (MRI) techniques that have allowed us to better understand the biophysical properties of tendons and ligaments. The methods include multiple quantum and T2 filtering combined with NMR and MRI techniques. It is shown in detail how these techniques can be used to extract a number of useful parameters: 1) the 1H‐1H and 1H‐2H dipolar interactions; 2) the proton exchange rates between water and collagen, and between water molecules; 3) the distribution of fibril orientations; and 4) the anisotropy of diffusion. It is shown that relaxation data as a function of angular dependence can be obtained in vivo using mobile NMR sensors. Finally, this article describes how double quantum filtered (DQF) MRI can be used to image and monitor the healing process in injured tendons. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Developments in dynamic MR elastography for in vitro biomechanical assessment of hyaline cartilage under high‐frequency cyclical shear
Authors: Lopez Orlando , Amrami Kimberly K. , Manduca Armando , Rossman Phillip J. , Ehman Richard L. 
Published: January 2007

AbstractThe design, construction, and evaluation of a customized dynamic magnetic resonance elastography (MRE) technique for biomechanical assessment of hyaline cartilage in vitro are described. For quantification of the dynamic shear properties of hyaline cartilage by dynamic MRE, mechanical excitation and motion sensitization were performed at frequencies in the kilohertz range. A custom electromechanical actuator and a z‐axis gradient coil were used to generate and image shear waves throughout cartilage at 1000–10,000 Hz. A radiofrequency (RF) coil was also constructed for high‐resolution imaging. The technique was validated at 4000 and 6000 Hz by quantifying differences in shear stiffness between soft (∼200 kPa) and stiff (∼300 kPa) layers of 5‐mm‐thick bilayered phantoms. The technique was then used to quantify the dynamic shear properties of bovine and shark hyaline cartilage samples at frequencies up to 9000 Hz. The results demonstrate that one can obtain high‐resolution shear stiffness measurements of hyaline cartilage and small, stiff, multilayered phantoms at high frequencies by generating robust mechanical excitations and using large magnetic field gradients. Dynamic MRE can potentially be used to directly quantify the dynamic shear properties of hyaline and articular cartilage, as well as other cartilaginous materials and engineered constructs. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Pathophysiology of the intervertebral disc and the challenges for MRI
Authors: Urban Jill P.G. , Winlove C. Peter 
Published: January 2007

AbstractThrough its ability to make relatively noninvasive and repeatable measurements, MRI has a great deal to offer, not only to clinical diagnosis of intervertebral disc disorders but also as a tool for basic research into disc physiology and the etiology of disc degeneration. In this brief review we outline the structure of the disc, the composition and organization of its macromolecules, and the changes that occur during disc degeneration, attempting to summarize features that have been or could become targets of MRI characterization. It is important to recognize, however, the fundamental limitation that most of the changes so far observed in MRI are consequences of alterations in cellular metabolism that occurred months to years previously and provide little insight into the current functional status of the tissue. There is therefore a need to develop MR techniques that directly characterize cellular activity and factors such as nutrient delivery on which it is critically dependent. We therefore briefly review cellular energy metabolism and nutrient transport into the avascular disc and consider the ability of MRI to reveal information about such processes. As a corollary of this discussion we also consider the constraints that the unusual transport properties of the disc impose on the delivery of contrast agents to the disc, since an understanding of these limitations is central to interpretation of the resulting images. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Response to Preoperative Chemoembolization Correlates with Outcome After Liver Transplantation in Patients with Hepatocellular Carcinoma
Authors: Millonig Gunda , Graziadei Ivo W. , Freund Martin C. , Jaschke Werner , Stadlmann Sylvia , Ladurner Ruth , Margreiter Raimund , Vogel Wolfgang 
Published: January 2007

Abstract

Patients with small hepatocellular carcinoma (HCC) can be cured by liver transplantation (LT). However, many patients drop out during the waiting time as a result of tumor progression. We prospectively investigated the effect of transarterial chemoembolization on long-term survival of 116 patients with HCC listed for LT. Intention-to-treat analysis revealed that patients with either complete or partial response to therapy (no vital tumor or devascularization of ≥30%, respectively) as assessed by computed tomographic scan before LT had far better 1-, 2-, and 5-year survival rates (100, 93.2, and 85.7%; and 93.8, 83.6, and 66.2%, respectively) compared with those with no response or with tumor progression (82.4, 50.7, and 19.3%). Posttransplant survival analysis showed a marked survival benefit according to transarterial chemoembolization response: patients with complete or partial response had 1-, 2-, and 5-year survival rates of 89.1, 85.1, and 85.1%, and 88.6, 77.4, and 63.9%, respectively, compared with 68.6, 51.4, and 51.4% for patients whose disease did not respond to therapy. Subgroup analysis, however, showed that these benefits were only seen in patients whose disease met the Milan criteria, but not in disease exceeding the Milan criteria but fitting the expanded University of California at San Francisco criteria. These patients were also more likely to drop out as a result of tumor progression while waiting for LT (dropout rate 12.1 vs. 2.9%) and to develop recurrent HCC (21.6 vs. 7.6%). Downstaged patients did even worse, with a dropout rate of 26.7% and a 5-year survival rate of only 25%. In conclusion, the response to preoperative chemoembolization may predict long-term outcome after LT. Liver Transpl 13:272–279, 2007. © 2007 AASLD.