Morphology of rigor--shortened bovine muscle and the effect of trypsin on pre- and postrigor myofibrils.
Bovine semitendinosus muscles were sampled immediately after death, after 24 hr postmortem with storage at 2 degrees , 16 degrees , or 37 degrees C, and after 312 hr postmortem with storage at 2 degrees and 16 degrees C. A biopsy technique was used to prevent shortening during glutaraldehyde fixation. Postfixation in osmium tetroxide was followed by embedding in an Epon-Araldite mixture. Bovine muscle was supercontracted after 24 hr storage at 27deg; but was only slightly contracted after storage at 16 degrees for 24 hr. Muscle held at 37 degrees for 24 hr was slightly less supercontracted than the 2 degrees muscle. Striking similarities existed between muscles stored at 16 degrees and at 2 degrees C for 312 hr. Both were slightly shortened with narrowed I bands and an area of increased density, probably due to overlap of thin filaments in the middle of the A band. Postmortem shortening was accompanied by banding-pattern changes similar to those predicted for contracting muscle by Huxley and Hanson's sliding filament model. Treatment of myofibrils with 0.05% trypsin resulted in a rapid loss of Z lines and, in supercontracted myofibrils, caused a return of the banding pattern of resting muscle.
D000818:Animals; D002417:Cattle; D003643:Death; D005260:Female; D006652:Histological Techniques; D008854:Microscopy, Electron; D008962:Models, Theoretical; D009119:Muscle Contraction; D009132:Muscles / Q000166:cytology*; D009210:Myofibrils / Q000187:drug effects*; D014357:Trypsin / Q000494:pharmacology*
D014357:Trypsin