Rigor mortis

Immediately after death, the muscle is soft, limp, and dry and can be reversibly extended by using a low load (5-15 kPa). Cadaveric rigidity (rigor mortis) occurs after a few hours. The muscle can then be extended only by using a heavy load ( 200 kPa) and becomes moist or wet. Rigor can occur in various stages of contraction or stretching. It subsides after some time and the muscle can be easily extended, but irreversibly. Meat with a more or less tender consistency is formed from the muscle. This process is caused by complicated proteolytic reactions, which are discussed in 12.4.3. 

Element fresh tissue Element fresh tissue 

Cessation of blood circulation ends the O2 supply to muscle. Anaerobic conditions start to develop. The energy-rich phosphates, such as creatine phosphate, ATP and ADP, are degraded. The glycolysis process, which is pH and temperature dependent and which is influenced by the presence of glycogen, is the sole remaining energy source. The lactic acid formed remains in the muscle, thereby decreasing the muscle pH from 6.5 to less than 5.8. 

Animal species Concentration (pg/g) Distribution of soluble iron (%)  

The onset of rigor mortis occurs in beef muscle within 10-24 h in pork, 4-18 h and in chicken, 2-4 h. 

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Rigor ll a muscle condition in which muscle fibers, depleted of ATP and phosphocreatine, develop a state of extreme rigidity and cannot be easily extended. (In death, this state is called rigor mortis, the rigor of death.) From what you have learned about muscle contraction, explain the state of rigor in molecular terms. 

A decrease in the concentration of ATP in the sarcoplasm (eg, by excessive usage during the cycle of con-traction-relaxation or by diminished formation, such as might occur in ischemia) has two major effects (1) The Ca ATPase (Ca + pump) in the sarcoplasmic reticulum ceases to maintain the low concentration of Ca + in the sarcoplasm. Thus, the Interaction of the myosin heads with F-actin is promoted. (2) The ATP-depen-dent detachment of myosin heads from F-actin cannot occur, and rigidity (contracmre) sets in. The condition of rigor mortis, following death, is an extension of these events. 

In the absence of ATP, myosin crossbridges are unable to release the actin. As a result, the sarcomeres, and therefore the muscle, remain contracted. This phenomenon is referred to as rigor mortis. Following death, the concentration of intracellular calcium increases. This calcium allows the... 

Tenderness. The contractile state of the muscle after rigor mortis is a major factor in meat tenderness, which is affected by post-mortem conditions creating differences in tenderness. Ageing of fresh pork can be used to improve tenderness. The process is based on a continuous weakening of the structural elements by different endogenous muscle peptidases along with an improved palatability (Taylor et al., 1995). 

Postmortem findings include dark-tarry blood discharge from body orifices, absence of rigor mortis, hemorrhage of the mucous membranes, bloating, and rapid decomposition of the carcass. 

Postmortem examination in fatal cases has shown immediate onset of extreme rigor mortis in the muscles of the thighs and legs, edema and intraalveolar hemorrhage in the lungs, cerebral edema, and liver and kidney damage. The risk of serious intoxication is increased during hot weather. ... 

How We Become a Stiff When a higher vertebrate dies, its muscles stiffen as they are deprived of ATP, a state called rigor mortis. Explain the molecular basis of the rigor state. 

Varetto, L. and Curto, O. (2005). Long persistence of rigor mortis at constant low temperature. Forensic Sci. Int. 147, 31-34. 

Proteases allowed biochemists to see how a cilium would work without nexin linkers. What would removal of the linkers do Perhaps the cilium would work just fine without them, or perhaps it would go into rigor mortis as it did when the dynein arms were removed. 

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