Preservation of in vitro muscle fiber function in dermatomyositis and inclusion body myositis: a single fiber study

Five patients with untreated dermatomyositis, five with inclusion body myositis, and 16 healthy elderly volunteer subjects (controls) underwent open (dermatomyositis and inclusion body myositis) or percutaneous (controls) muscle biopsy. Biopsied muscles included deltoid, biceps and vastus lateralis. Chemically skinned single muscle fibers were activated with Ca(+2); the slack test was performed to determine maximal unloaded shortening velocity (Vo). Parameters measured include single fiber cross sectional area, maximal force, specific force and Vo. 429 Type I and 94 Type IIA fibers were studied. Cross sectional area and maximal force were greater in inclusion body myositis than dermatomyositis or control for Type I and IIA fibers. Specific force of Type I fibers was similar in inclusion body myositis and dermatomyositis but greater than in controls. Vo was greater in Type I, but not IIA, fibers in dermatomyositis compared with inclusion body myositis and controls. The force and velocity generating capacity of single muscle fibers is preserved in patients with dermatomyositis and inclusion body myositis suggesting that dysfunction of the contractile proteins does not contribute to clinical muscle weakness.

[1]  D G Moisescu,et al.  Calcium and strontium concentration changes within skinned muscle preparations following a change in the external bathing solution. , 1978, The Journal of physiology.

[2]  D. Costill,et al.  Effect of swim taper on whole muscle and single muscle fiber contractile properties. , 2001, Medicine and science in sports and exercise.

[3]  L. Larsson,et al.  A technique for studies of the contractile apparatus in single human muscle fibre segments obtained by percutaneous biopsy. , 1992, Acta physiologica Scandinavica.

[4]  U. K. Laemmli,et al.  Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4 , 1970, Nature.

[5]  K. Edman.  The velocity of unloaded shortening and its relation to sarcomere length and isometric force in vertebrate muscle fibres. , 1979, The Journal of physiology.

[6]  D. Maughan,et al.  Swelling of skinned muscle fibers of the frog. Experimental observations. , 1977, Biophysical journal.

[7]  M. Johnson,et al.  Data on fibre size in thirty-six human muscles. An autopsy study. , 1973, Journal of the neurological sciences.

[8]  L. Larsson,et al.  Maximum velocity of shortening in relation to myosin isoform composition in single fibres from human skeletal muscles. , 1993, The Journal of physiology.

[9]  L. Larsson,et al.  Contractile properties in single muscle fibres from chronically overused motor units in relation to motoneuron firing properties in prior polio patients , 1995, Journal of the Neurological Sciences.

[10]  R. Moss.  Sarcomere length‐tension relations of frog skinned muscle fibres during calcium activation at short lengths. , 1979, The Journal of physiology.

[11]  V R Edgerton,et al.  Myosin heavy chain isoforms of human muscle after short-term spaceflight. , 1995, Journal of applied physiology.

[12]  Robert C. Griggs,et al.  Unicorns, dragons, polymyositis, and other mythological beasts , 2003 .

[13]  W. Frontera,et al.  Skeletal muscle fiber quality in older men and women. , 2000, American journal of physiology. Cell physiology.

[14]  W. Frontera,et al.  Contractile properties of single muscle fibers in myotonic dystrophy , 2000, Muscle & nerve.

[15]  P. Gallagher,et al.  Reduction in hybrid single muscle fiber proportions with resistance training in humans. , 2001, Journal of applied physiology.

[16]  W. Frontera,et al.  Skeletal muscle fiber function and rate of disease progression in amyotrophic lateral sclerosis , 2002, Muscle & nerve.

[17]  M. Johnson,et al.  Data on the distribution of fibre types in thirty-six human muscles. An autopsy study. , 1973, Journal of the neurological sciences.

[18]  W. V. van Venrooij,et al.  Polymyositis , 2003, Neurology.

[19]  K. Borg,et al.  Sporadic inclusion body myositis: morphology, regeneration, and cytoskeletal structure of muscle fibres , 2004, Journal of Neurology, Neurosurgery & Psychiatry.

[20]  W. Evans,et al.  Suction applied to a muscle biopsy maximizes sample size. , 1982, Medicine and science in sports and exercise.