Effects of electrical stimulation and postmortem storage on changes in titin, nebulin, desmin, troponin-T, and muscle ultrastructure in Bos indicus crossbred cattle.
The effects of electrical stimulation (ES) on degradation of titin, nebulin, desmin, and troponin-T (TN-T) and on structural changes in the longissimus muscle (LM) from Brahman x Simmental (B x S) cattle (Bos indicus cross) were determined. The left side of seven B x S beef carcasses was stimulated (200 V, 20 Hz) within 1 h of death, and the right side was the nonstimulated (NS) control. Myofibrils for SDS-PAGE and samples for transmission electron microscopy were prepared from the LM at 0, 1, 3, 7, 14, and 28 d postmortem (PM). The SDS-PAGE results showed that the T1 band of titin was absent by 7 d in two animals, by 14 d in four animals, and by 28 d in one animal in both NS and ES samples. By SDS-PAGE, intact nebulin was gone by 7 d in two animals and by 14 d in five animals, but in blots, nebulin decreased by 7 d and was absent by 14 d in both NS and ES samples. The desmin band could still be seen as a light band at 28 d in Western blots of both NS and ES samples. A decrease in TN-T and a concomitant increase in the 30-kDa polypeptide were observed in both NS and ES samples. Western blots with a monoclonal antibody to TN-T confirmed that TN-T decreased at similar rates in NS and ES samples but showed that the 30-kDa polypeptide was more heavily labeled in ES samples from 7 to 28 d. Contraction nodes were present in O-d ES samples and were still observed in 28-d ES samples. Narrow, intermediate, and wide I-band fractures were seen earlier and at a greater frequency in ES than in NS samples. Overall, ES had no detectable effect on titin, nebulin, desmin, or TN-T degradation but accelerated the appearance and enhanced the frequency of three types of I-band fractures in the LM from Bos indicus crossbred cattle.
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Department of Animal Science, Iowa State University, Ames 50011, USA.
Stromer
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Rouse
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Robson
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RM
D000818:Animals; D015153:Blotting, Western / Q000662:veterinary; D002417:Cattle / Q000033:anatomy & histology*; D064211:Connectin; D003893:Desmin / Q000032:analysis*; D004558:Electric Stimulation; D004591:Electrophoresis, Polyacrylamide Gel / Q000662:veterinary; D005511:Food Handling; D005519:Food Preservation; D006863:Hydrogen-Ion Concentration; D008297:Male; D008854:Microscopy, Electron / Q000662:veterinary; D009124:Muscle Proteins / Q000032:analysis*; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000648:ultrastructure*; D011180:Postmortem Changes; D011494:Protein Kinases / Q000032:analysis*; D013997:Time Factors; D014336:Troponin / Q000032:analysis*; D020107:Troponin T
D064211:Connectin; D003893:Desmin; D009124:Muscle Proteins; D014336:Troponin; D020107:Troponin T; C035620:nebulin; D011494:Protein Kinases