Q2. What is the effect of m-calpain on muscle growth?
The hypothesis is that in living muscle, elevation of calpastatin suppresses m-calpain (and perhaps m-calpain), which in turn reduces the rate of protein degradation resulting in an increase in muscle growth.
Q3. What is the effect of suppression of protein degradation on muscle tenderness?
If muscle hypertrophy were caused by reduced protein degradation, the authors would expect increased meat toughness to occur only in hypertrophied muscles whose tenderness is affected by changes in postmortem proteolysis (e.g., longissimus).
Q4. What is the mechanism responsible for the decrease in muscle growth in domestic animals?
suppression of protein degradation seems to be the mechanism that is responsible for differences in the rates of muscle growth in domestic animals (Bohorov, Buttery, Correia, & Soar, 1987; Koohmaraie, Killefer, et al., 1995; Maruyama, Sunde, & Swick, 1978; Reeds, Hay, Dorwood, & Palmer, 1986).
Q5. What is the role of calpain 3 in muscle tissue?
The mutation in calpain 3 that results in limb girdle muscular dystrophy causes loss of catalytic activity of calpain 3 (Ono et al.,1998).
Q6. What is the efficient method to increase muscle growth rate?
3. Decreased protein synthesis and decreased protein degradation, providing decrease in protein degradation is greater than the decrease in synthesis (most efficient method to increase muscle growth rate).
Q7. What is the evidence to support the above proposal?
The best evidence to support the above proposal is the observation that incubation of isolated myofibrils from several rat muscles in a relaxing solution released a small amount of myofilaments that constituted less than 5% of the total myofibrillar proteins (Etlinger, Zad, Fischman, & Rabinowitz, 1975).
Q8. What is the objective of a calpain-mediated approach to increase muscle mass?
If the objective is to increase muscle mass without any regard for meat tenderness (for the production of ground beef or tenderness enhanced products), one can select for animals with high calpastatinactivity.
Q9. What is the hypothesis for the removal of myofilaments?
The Goll et al. (1992) proposal stated that the proteasome complex is a good candidate to degrade the released myofilaments into amino acids.
Q10. What is the way to increase muscle tenderness?
Of all the possible mechanisms of increasing muscle deposition, only the mechanism that involves suppression of protein degradation will result in decreased meat tenderness.
Q11. What is the importance of recognizing that the relative contribution of sarcomere length?
The importance discussed earlier of recognizing that the relative contribution of sarcomere length, postmortem proteolysis, and collagen concentration to ultimate meat tenderness is muscle dependent is supported by the callipyge model.
Q12. What are the objectives of this manuscript?
The objectives of this manuscript are to review the mechanisms of muscle growth, the biochemical basis for meat tenderness, and the relationship between these two important processes.
Q13. How many sheep are very tender at 24 h?
In this example, three of 11 sheep are very tender at 24 h, two acceptable and six tough, so for five of 11 animals extensive tenderization has occurred in the first 24 h.