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Fine structure of myonecrosis following adrenalin-induced cerebral vasospasm
Abstract:
Frank necrosis of the media (myonecrosis) which could be confirmed by light microscopy was previously produced by the authors after the injection of adrenalin into the canine chiasmatic cistern. It is the purpose of this paper to report ultrastructural features of myonecrosis following adrenalin-induced cerebral vasospasm. The latter was induced in 10 dogs by a single subarachnoid injection of 0.2 mg/kg of adrenalin. Two dogs died of cerebral vasospasm 3 and 6 days respectively after the experiment, whereas eight other dogs were killed between 2 and 90 days. Microscopically, the circle of Willis showed coagulation necrosis and fibrosis of the media. The fine structure of myonecrosis was characterized by six dynamic changes of vacuolation, dissolution of myofilaments, focal cytoplasmic necrosis, fragmentation, coagulation necrosis and intercellular fibrosis. Despite a simple experimental procedure, the present models disclosed myonecrosis with a marked similarity to humans and contained all of the previously reported ultrastructural features of experimental myonecrosis. It is suggested that sustained contraction of smooth-muscle cells beyond their metabolic capability results in the mechanical destruction of myofilaments.
Insights
Adrenalin-induced cerebral vasospasm causes media myonecrosis in dogs. Ultrastructural analysis revealed dynamic changes, suggesting sustained smooth muscle contraction leads to myofilament destruction.
Area of Science:
- Neurology
- Pathology
- Vascular Biology
Background:
- Cerebral vasospasm is a critical complication of subarachnoid hemorrhage.
- Myonecrosis of the cerebral arteries' media has been observed but requires detailed ultrastructural investigation.
Purpose of the Study:
- To investigate the ultrastructural characteristics of myonecrosis in canine cerebral arteries following adrenalin-induced vasospasm.
- To elucidate the cellular mechanisms underlying myonecrosis in this experimental model.
Main Methods:
- Cerebral vasospasm was induced in 10 dogs via subarachnoid injection of adrenalin (0.2 mg/kg).
- Animals were observed for survival or euthanized at intervals (2–90 days) for histological and ultrastructural analysis of the circle of Willis.
Main Results:
- Microscopically, the media of the circle of Willis exhibited coagulation necrosis and fibrosis.
- Ultrastructural examination revealed six key changes: vacuolation, myofilament dissolution, focal cytoplasmic necrosis, fragmentation, coagulation necrosis, and intercellular fibrosis.
- The observed myonecrosis closely resembled human cases.
Conclusions:
- Adrenalin-induced cerebral vasospasm provides a relevant model for studying arterial myonecrosis.
- Sustained contraction of vascular smooth muscle cells beyond their metabolic limits appears to cause mechanical destruction of myofilaments, leading to myonecrosis.