Nuclear Magnetic Resonance Studies of Living Muscle

Bratton, C. B.; Hopkins, A. L.; Weinberg, J.W.

doi:10.1126/science.147.3659.738

Cited by 184 publications

(67 citation statements)

References 12 publications

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“…The assumptions made in this paper are in accord with results of nuclear magnetic resonance measurements that indicate a reduced freedom of motion of water in muscle and an increase in freedom in contraction (9)(10)(11)(12). The theory is also in accord with my contention that muscle contraction is "contraction," that is, the shortening of elongated particles, fibers.…”

supporting

confidence: 77%

The Mechanism of Muscle Contraction

Szent‐Györgyi

1974

Proc. Natl. Acad. Sci. U.S.A.

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Muscular contraction is essentially the shortening of the S2 subunits of heavy meromyosin, integrated to macroscopic motion by the thick and thin filaments.According to our present knowledge the main contractile proteins of muscle are myosin and actin which, in vitro, form the complex actomyosin (AM). The actin filaments, in muscle, have attached to them tropomyosin and troponin. The slender myosin molecule is about 1400 A long and is built of two fragments, the "light" and "heavy" meromyosin (LMM and HMM). The latter consists of a long and thin "stalk" (subfragment 2, S2) and a globular "head" (subfragment 1, Si). The HMM S2 is actually a double spiral of two polypeptide fibers attached at one end to the LMM, each peptide carrying a globule, SIat the other (1).AM is strongly hydrophilic. Threads prepared from it contain 97% water. At a proper ionic concentration its micelles show two major changes under influence of ATP: they contract and become completely hydrophobic, anhydrous. Thus, under influence of ATP, suspensions of AM "superprecipitate," while threads contract. If the micelles within the threads have a random orientation, then their contraction causes the thread to contract in all directions, that is, shrink, become shorter and thinner. If the micelles are arranged parallel to the axis, then, under influence of ATP, the threads become shorter and thicker without losing volume, behaving thus similarly to contracting muscle.There are reasons to believe that these changes, shortening and dehydration, reflect the elementary changes taking place in contracting muscle. The analogy between muscle and AM was brought still closer by the development of glycerination and the introduction of the psoas fiber (2), and the demonstration that rigor mortis is essentially a lack of ATP (3). It was natural to expect that muscle would be found to be a bundle of AM threads built of micelles, ordered parallel to the axis.It came as a shock when the electron microscope revealed muscle to consist of "thick" myosin and "thin" actin filaments, which did not shorten on contraction, but only slid alongside one another. Initially no connection was seen between the two. Later, H. E. Huxley (4) showed them to be connected by "bridges." It is generally believed that these bridges are the HMM S2-s of the myosin molecules, which attach themselves, in contracting muscle, to the "actin" of the thin filaments. H. E. Huxley believes that the sliding and In all these studies the hydration and dehydration were completely disregarded. The first question on this line has to be: which of the components of muscle is responsible for the binding and release of the great quantities of water? Actin cannot be, because very little actin is needed to make AM hydrate and dehydrate under influence of ATP. Nor can LMM be made responsible, because it does not interact with actin or ATP, and it is this interaction that induces the changes in hydration. This leaves us with HMM, and within the HMM only the helical HMM S2 could be expected to bind a gr...

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supporting

confidence: 77%

The Mechanism of Muscle Contraction

Szent‐Györgyi

1974

Proc. Natl. Acad. Sci. U.S.A.

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“…In particular, signal intensity changes due to increases in the relaxation time (T2) of tissue water can be measured to indicate exercise-induced activity of muscles. 40 This phenomenon was originally described in 1965, when Bratton et al 8 reported an increase in the T2 of isolated frog skeletal muscle following stimulated isometric contractions. Subsequently, Fleckenstein et al 31 reported the first similar phenomenon in living human subjects and, as a consequence, Fisher et al 29 suggested that this prolongation in T2 relaxation time could be used as a quantitative measurement for muscle activity.…”

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confidence: 99%

Muscle Functional MRI as an Imaging Tool to Evaluate Muscle Activity

Cagnie¹,

Elliott²,

O’Leary³

et al. 2011

Journal of Orthopaedic & Sports Physical Therapy

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Synopsis Muscle functional magnetic resonance imaging (mfMRI) is an innovative technique that offers a noninvasive method to quantify changes in muscle physiology following the performance of exercise. The mfMRI technique is based on signal intensity changes due to increases in the relaxation time of tissue water. In contemporary practice, mfMRI has proven to be an excellent tool for assessing the extent of muscle activation following the performance of a task and for the evaluation of neuromuscular adaptations as a result of therapeutic interventions. This article focuses on the underlying mechanisms and methods of mfMRI, discusses the validity and advantages of the method, and provides an overview of studies in which mfMRI is used to evaluate the effect of exercise and exercise training on muscle activity in both experimental and clinical studies. J Orthop Sports Phys Ther 2011;41(11):896–903, Epub 4 September 2011. doi:10.2519/jospt.2011.3586

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“…Already in 1965, proton NMR relaxation times of living frog muscle were published [13], and in 1968 the first whole-body spectrum of a rat was taken [14]. In the 1960s and 1970s a very large amount of work was published on relaxation, diffusion, and chemical exchange of water in cells and tissues of all sorts.…”

Section: Resistive Electromagnets the Beginning Of Analytical Nmrmentioning

confidence: 99%

Ultra-High Field NMR and MRI—The Role of Magnet Technology to Increase Sensitivity and Specificity

Moser

Laistler

Schmitt³

et al. 2017

Front. Phys.

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"History, of course, is difficult to write, if for no other reason, than that it has so many players and so many authors." -P. J. Keating (former Australian Prime Minister)Starting with post-war developments in nuclear magnetic resonance (NMR) a race for stronger and stronger magnetic fields has begun in the 1950s to overcome the inherently low sensitivity of this promising method. Further challenges were larger magnet bores to accommodate small animals and eventually humans. Initially, resistive electromagnets with small pole distances, or sample volumes, and field strengths up to 2.35 T (or 100 MHz 1 H frequency) were used in applications in physics, chemistry, and material science. This was followed by stronger and more stable (Nb-Ti based) superconducting magnet technology typically implemented first for small-bore systems in analytical chemistry, biochemistry and structural biology, and eventually allowing larger horizontal-bore magnets with diameters large enough to fit small laboratory animals. By the end of the 1970s, first low-field resistive magnets big enough to accommodate humans were developed and superconducting whole-body systems followed. Currently, cutting-edge analytical NMR systems are available at proton frequencies up to 1 GHz (23.5 T) based on Nb 3 Sn at 1.9 K. A new 1.2 GHz system (28 T) at 1.9 K, operating in persistent mode but using a combination of low and high temperature multi-filament superconductors is to be released. Preclinical instruments range from small-bore animal systems with typically 600-800 MHz (14.1-18.8 T) up to 900 MHz (21 T) at 1.9 K. Human whole-body MRI systems currently operate up to 10.5 T. Hybrid combined superconducting and resistive electromagnets with even higher field strength of 45 T dc and 100 T pulsed, are available for material research, of course with smaller free bore diameters. This rather costly development toward higher and higher field strength is a consequence of the inherently low and, thus, urgently needed sensitivity in all NMR experiments. This review particularly describes and compares the developments in superconducting magnet technology and, thus, sensitivity in three Moser et al.UHF MR-Magnet Technology fields of research: analytical NMR, biomedical and preclinical research, and human MRI and MRS, highlighting important steps and innovations. In addition, we summarize our knowledge on safety issues. An outlook into even stronger magnetic fields using different superconducting materials and/or hybrid magnet designs is presented.

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Nuclear Magnetic Resonance Studies of Living Muscle

Cited by 184 publications

References 12 publications

The Mechanism of Muscle Contraction

The Mechanism of Muscle Contraction

Muscle Functional MRI as an Imaging Tool to Evaluate Muscle Activity

Ultra-High Field NMR and MRI—The Role of Magnet Technology to Increase Sensitivity and Specificity

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