Contractile tissues

CRITICAL ASSESSMENT OF THE METHOD The Purkinje fiber is a non-contractile tissue, which facilitates electrode positioning and stability. In comparison to the papillary muscle or the monophasic action potential in the intact heart, drug-induced effects on the action potential duration are considerably larger. Whereas this is not necessarily a disadvantage, the model has been viewed as possibly being too sensitive for drug-induced effects on repolarization. 

In contrast to the Purkinje fiber, the papillary muscle is a contractile tissue lending it also for the measurement of contractile force, together with the action potential configuration. Since effects on the inotropic state of the myocardium can also affect the action potential, this is a useful secondary measurement to have to interpret possible drug-induced effects. However, the contraction of the muscle makes the placement of the electrode more difficult and changes in the contractile function can lead to loss of the electrode placement in the course of a study. 

The force generated by a muscle is proportional to the contraction time. The longer the contraction time, the greater the force development up to the point of maximum tension. Slower contraction leads to greater force production because more time is allowed for the tension produced in contractile elements to be transferred through the noncontractile components to the tendon. This is the force-time relationship. Tension in the tendon will reach the maximum tension developed by the contractile tissues only if the active contraction process is of adequate (even up to 300 msec) duration [Sukop and Nelson, 1974). 

Determination of CK activity CK catalyzes the reversible N-phosphorylation of creatine to form creatine phosphate by Mg -ATP/Mg -ADP complexes and thus is an important enzyme regulator of high-energy phosphate production and utilization within contractile tissues. CK occurs predominantly... 

For details concerning changes in the fine structure of mitochondria of contractile tissues, the reader is referred to the following heart muscle mitochondria (Kisch, 1956 Munn, 1969 Warshaw, 1969 Mackler et al., 1971), skeletal muscle (Allen and Pepe, 1965), and insect flight muscle (Brosemer et al., 1963 Bucher, 1965 Herold, 1965 Gregory et al., 1967 Kleinow et al., 1971 Sacktor and Shimada, 1972). 

Sartoii, S., Bofflto, M., Seraflni, R, Caporale, A., SUvestri, A., Bemardi, E., Sassi, M.R, Boccafoschi, R, CiardeUi, G., 2013. Synthesis and structure-property relationship of polyester-urethanes and their evalnation for the regeneration of contractile tissues. Reactive and Functional Polymers 73,1366-1376. 

In the event that there is a localized infarct, the effected cylinders can be represented by a segment of normal contractile tissue (obeying Carlson s equation) and a segment of abnormal (non-contractile) tissue with only elastic properties. Using this description, Watts (1976) has shown that the individual cylinder equivalent cricuit is modified as illustrated in Figure 12 where ... 

Clark, J.F., M.L. Field, and R. Ventura-Clapier, An introduction to the cellular creatine kinase system in contractile tissue, in Creatine and Creatine Phosphate Scientific and Clinical Perspectives, M.A. Conway and J.F. Clark, Eds. Academic Ftess, San Diego, CA, 996, pp. 51-64. 

Fig. 1 Cross-sectional histological view of the vastus lateralis from a control animal (right), and a BTX-A treated animal receiving six injections in a six months treatment period. Note the loss of contractile tissue (dark) and the increase in fat Oight) in the experimental (lelit) compared to the control muscle...

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