Estrogen Deficiency Minimally Affects Diaphragm and Leg Muscle Functions in Female mdx Mice

A new strain of mice, which had arisen by mutation from a dystrophic mouse colony was designated ‘mdx’, because the genetic defect, which manifests itself in brief periods of muscle destruction followed by episodes of muscle regeneration appears to be X-linked. Further studies of histopathological changes in muscle from ‘mdx’ mice at the light microscopic or electron microscopic levels have been published, but only one preliminary study has been on the tibialis anterior (TA) of ‘mdx’ mice less than four weeks old. Lesions in the ‘mdx’ mice vary between different muscles, and centronucleation of fibers in all muscles studied so far appears to be especially prominent in older mice. Lesions in young ‘mdx’ mice have not been studied extensively, and the results appear to be at variance with one another. The degenerative and regenerative aspects of the lesions in the TA of 23 to 26-day-old ‘mdx’ mice appear to vary quantitatively.

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Regenerating myofibers in tibialis anterior muscles of young ‘MDX’ mice

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127943 ◽

1987 ◽

Vol 45 ◽

pp. 726-727

Author(s):

H. D. Geissinge ◽

L.D. Rhodes

Keyword(s):

Muscular Dystrophy ◽

Mouse Model ◽

Tibialis Anterior ◽

Physiological Activity ◽

Mdx Mice ◽

Mode Of Inheritance

A recently discovered mouse model (‘mdx’) for muscular dystrophy in man may be of considerable interest, since the disease in ‘mdx’ mice is inherited by the same mode of inheritance (X-linked) as the human Duchenne (DMD) muscular dystrophy. Unlike DMD, which results in a situation in which the continual muscle destruction cannot keep up with abortive regenerative attempts of the musculature, and the sufferers of the disease die early, the disease in ‘mdx’ mice appears to be transient, and the mice do not die as a result of it. In fact, it has been reported that the severely damaged Tibialis anterior (TA) muscles of ‘mdx’ mice seem to display exceptionally good regenerative powers at 4-6 weeks, so much so, that these muscles are able to regenerate spontaneously up to their previous levels of physiological activity.

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Cardiovascular and Metabolic Responses to Electrical Stimulation-Induced Leg Exercise in Spinal Cord Injury

Methods of Information in Medicine ◽

10.1055/s-0038-1636852 ◽

1997 ◽

Vol 36 (04/05) ◽

pp. 372-375 ◽

Cited By ~ 9

Author(s):

J. R. Sutton ◽

A. J. Thomas ◽

G. M. Davis

Keyword(s):

Spinal Cord ◽

Heart Rate ◽

Spinal Cord Injury ◽

Cardiac Output ◽

Electrical Stimulation ◽

Knee Flexion ◽

Flexion Extension ◽

Cord Injury ◽

Leg Exercise ◽

Leg Muscle

Abstract:Electrical stimulation-induced leg muscle contractions provide a useful model for examining the role of leg muscle neural afferents during low-intensity exercise in persons with spinal cord-injury and their able-bodied cohorts. Eight persons with paraplegia (SCI) and 8 non-disabled subjects (CONTROL) performed passive knee flexion/extension (PAS), electrical stimulation-induced knee flexion/extension (ES) and voluntary knee flexion/extension (VOL) on an isokinetic dynamometer. In CONTROLS, exercise heart rate was significantly increased during ES (94 ± 6 bpm) and VOL (85 ± 4 bpm) over PAS (69 ± 4 bpm), but no changes were observed in SCI individuals. Stroke volume was significantly augmented in SCI during ES (59 ± 5 ml) compared to PAS (46 ± 4 ml). The results of this study suggest that, in able-bodied humans, Group III and IV leg muscle afferents contribute to increased cardiac output during exercise primarily via augmented heart rate. In contrast, SCI achieve raised cardiac output during ES leg exercise via increased venous return in the absence of any change in heart rate.

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