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Development and inhibition of the target phenomenon in tenotomized rat muscle
Abstract:
The sequence of development of the target phenomenon in tenotomized gastrocnemius muscle was studied: the presence of target fibres was preceded by the occurrence of contraction bands and of "moth eaten" appearance of the fibres. This phenomenon was far more pronounced and occurred earlier in type II than in type I fibres. This target phenomenon and the contraction artefacts could be inhibited in the tenotomized muscles by simultaneous neurotomy or immobilization of the muscle with a plaster cast. Delayed denervation inhibited also the target phenomenon, if performed less than 5 days after the tenotomy. These series of experiments seem to indicate that the target phenomenon occurs in more irritable muscle fibres and that muscular activity is needed for its development.
Insights
Muscle activity is crucial for developing target fibers, a phenomenon more pronounced in type II fibers after tenotomy. This process, involving contraction bands, can be prevented by neurotomy or immobilization.
Area of Science:
- Muscle physiology
- Histopathology
- Denervation studies
Background:
- The target phenomenon is a specific histopathological change observed in muscle fibers.
- Understanding the factors influencing its development is key to muscle pathology research.
Purpose of the Study:
- To investigate the sequence of events leading to the target phenomenon in tenotomized gastrocnemius muscle.
- To determine the role of muscle activity and innervation in the development of target fibers.
Main Methods:
- Histological examination of gastrocnemius muscle samples following tenotomy.
- Comparison of changes in type I and type II muscle fibers.
- Intervention with neurotomy and muscle immobilization (plaster cast).
- Evaluation of delayed denervation effects.
Main Results:
- Target fibers were preceded by contraction bands and "moth eaten" fiber appearance.
- These changes were more pronounced and occurred earlier in type II than type I fibers.
- Simultaneous neurotomy or immobilization inhibited the target phenomenon and contraction artifacts.
- Delayed denervation within 5 days post-tenotomy also inhibited the target phenomenon.
Conclusions:
- The target phenomenon appears to occur in more irritable muscle fibers.
- Muscular activity is essential for the development of the target phenomenon.
- Innervation and muscle activity are critical factors in the manifestation of these muscle fiber changes.