Extensor digitorum longus (EDL) muscles from rats at various intervals after birth were grafted into EDL muscles of adult recipients. Three to twelve months after the operation, host muscles containing the grafts were removed and examined for the presence of muscle spindles in the graft. The aim of the study was to establish when muscle spindles become capable of regeneration during development. Regenerated muscles grafted during the first week after birth were virtually spindleless. Grafts of muscles transplanted 10 and 15 days postnatally contained only 5-8 muscle spindles on average. In contrast, the regenerated grafts originating from muscles of 24- and 28-day-old rats were spindle-rich as in mature muscle grafts; the number of spindles in the transplanted EDL muscles (25.0 +/- 2.3; mean +/- SE) attained values comparable to free standard autografts of these muscles in adult animals. Thus, the critical period after grafting, which also involves the loss of a vascular supply, is considerably longer than the critical period for muscle-spindle survival after nerve injury. Fifteen days after birth, when muscle spindles still survive denervation, only a few regenerated spindles were present in the individual muscle regenerates. We assume that the low resistance of immature spindle capsules to ischaemia accounts for their massive degeneration and abortive spindle regeneration in grafts from 10- to 15-day-old rats.

• MeSH
• Adenosine Triphosphatases metabolism   MeSH
• Muscle, Skeletal growth & development   transplantation   MeSH
• Rats MeSH
• Myofibrils enzymology   MeSH
• Muscle Spindles anatomy & histology   physiology   MeSH
• Regeneration physiology   MeSH
• Muscle Development * MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adenosine Triphosphatases MeSH