Analysis Tools
cardiovascular system
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• following infusion of the beta-adrenergic agonist isoproterenol for 3 days at 30 mg kg-1 day-1, homozygotes display normal induction of myocardial hypertrophy with a similar (30%) increase in the heart-to-body weight ratio relative to heterozygous control mice
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• pacemaker cells in mice older than 3 months exhibit fewer extensions compared with wild-type cells
• the node in mice older than 3 months is more compact than in wild-type mice
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• stress-induced at 5.5 and 8 months
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• long pauses and intercurrent periods of normal sinus rhythm upon stress at 5.5 and 8 months
• stress-induced pauses increase with age
• however, no block is observed
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• at 5.5 and 8 months, exercised mice exhibit sinus bradycardia and abnormal sinoatrial node conduction unlike wild-type mice
• in response to mental stress and catecholamines, mice a blunted increase in heart rate compared with wild-type mice
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muscle
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• pacemaker cells in mice older than 3 months exhibit fewer extensions compared with wild-type cells
• the node in mice older than 3 months is more compact than in wild-type mice
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• following cardiotoxin injection into the hindlimbs, adult homozygotes display delayed and less efficient skeletal muscle regeneration relative to heterozygous control mice
• at 5 and 10 days after cardiotoxin injection, the muscle architecture appears more disorganized in homozygous than in heterozygous mutants, with new myotubes remaining small or intermediate in size
• despite the kinetic differences in muscle regeneration, lesions are essentially repaired in both groups of mice at 20 days after muscle injury
• in vitro, adult satellite cells isolated from skeletal muscle of homozygous mutant mice are able to undergo myotube formation; however, their differentiation is retarded relative to that observed in heterozygous satellite cells
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homeostasis/metabolism
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• at 5.5 and 8 months, exercised mice exhibit sinus bradycardia and abnormal sinoatrial node conduction unlike wild-type mice
• in response to mental stress and catecholamines, mice a blunted increase in heart rate compared with wild-type mice
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