Motoneuron firing and isomyosin type of muscle fibres in prior polio

In patients with prior polio there was an excessive use of remaining motor units and an absence of type II muscle fibres in the tibialis anterior (TA). In the present study, eight subjects with prior polio with more than 90% type I fibres in the TA were examined. The aim was to elucidate whether the...

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Bibliographic Details
Published in:Journal of neurology, neurosurgery and psychiatry neurosurgery and psychiatry, 1989-10, Vol.52 (10), p.1141-1148
Main Authors: Borg, K, Borg, J, Dhoot, G, Edström, L, Grimby, L, Thornell, L E
Format: Article
Language:English
Subjects:
Adult
Aged
Biological and medical sciences
Female
Human viral diseases
Humans
Infectious diseases
Male
Medical sciences
Middle Aged
Motor Neurons - physiology
Muscles - pathology
Muscles - physiopathology
Myosins - physiology
Poliomyelitis - pathology
Poliomyelitis - physiopathology
Viral diseases
Viral diseases of the nervous system
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Summary:In patients with prior polio there was an excessive use of remaining motor units and an absence of type II muscle fibres in the tibialis anterior (TA). In the present study, eight subjects with prior polio with more than 90% type I fibres in the TA were examined. The aim was to elucidate whether the lack of type II muscle fibres was due to a selective loss of motoneurons with high threshold and high axonal conduction velocity or due to a muscle fibre transition from type II to type I. There was no decrease of the proportion of motoneurons with high threshold and high axonal conduction velocity. Monoclonal antibodies against fast and slow myosin heavy chains (MHC) were used as histochemical markers and many muscle fibres of type I according to ATPase stainability showed a binding of both anti-fast and anti-slow MHC. It is suggested that the type I muscle fibre dominance in prior polio subjects with excessive use of TA during walking is due to a muscle fibre transition from type II to type I and not to a loss of one class of motor units.
ISSN:0022-3050
1468-330X
DOI:10.1136/jnnp.52.10.1141