Sarcoplasmic muscle physiology

Parvalbumins control the flow of Ca2+ within the muscular sarcoplasm and, thus, play an important role in the muscle physiology (Taylor et al. 2004 Wild and Lehrer... 

Turner WH, Brading AF 1997 Smooth muscle of the bladder in the normal and the diseased state pathophysiology, diagnosis and treatment. Pharmacol Ther 75 77—110 van Breemen C, Chen Q, Laher I 1995 Superficial buffer barrier function of smooth muscle sarcoplasmic reticulum. Trends Pharmacol Sci 16 98-105 Wray S 1993 Uterine contraction and physiological mechanisms of modulation. Am J Physiol 264 C1-C18... 

Eisner You are saying that in these gut smooth muscles the sarcoplasmic reticulum (SR) is not relevant to normal physiological contraction. Earlier, Sue Wray showed that in the uterus SR release wasn t involved in normal contraction (Wray et al 2002, this volume). This is a meeting about the SR. In which smooth muscle is there unequivocal evidence that the SR plays a significant role in contraction ... 

Malignant hyperthermia is a frequently fatal condition that involves severe muscle contraction and hyperthermia. Episodes are triggered by stress and/or specific volatile anesthetics, such as halothane, which cause excessive calcium release from the sarcoplasmic reticulum. The disorder is caused by a mutation in the skeletal muscle ryanodine receptor. The physiological mechanism by which stress triggers malignant hyperthermia is not fully understood. 

Herrmann-Frank, A., Darling, E., and Meissner, G. (1991) Functional characterization of the Ca -gated Ca release channel of vascular smooth muscle sarcoplasmic reticulum. Pflugers Archiv - European Journal of Physiology, 418 353-359. 

Smith, J.S., Imagawa, T., Ma, J., Fill, M., Campbell, K.P., and Coronado, R. (1988) Purified ryanodine receptor from rabbit skeletal muscle is the calcium-release channel of sarcoplasmic reticulum. Journal of General Physiology, 92 1-26. 

The most physiologically important futile cycle results from cell membranes that are leaky. For example, in muscle cells ATP is consumed in pumping calcium ions into the sarcoplasmic reticulum. Leakage of calcium ions from this compartment forces the process to proceed faster than would be necessary if the membrane were totally impermeable to these ions. 

Lipids play an essential role in the structure and function of biological membranes. The concept that the lipid enviroment influences the activity of membrane bound enzymes is now generally accepted. The sarcoplasmic reticulum(SR) of skeletal muscle is an intracellular membranous system with an important physiological role in contraction and relaxation (Hasselbach, 1964 Martonosi, 1971). The Ca2+ transport and (Ca2++ Mg2+)-ATPase activities which exhibit isolated SR preparations have been shown to be dependent on membrane phospholipids (Martonosi, 1968). An involvement of the fatty acid component of phospholipids in the functioning of the Ca2+ pump has also been suggested (Seiler et al., 1970 Seiler Hasselbach,... 

It is possible, of course, to use direct calorimetry, often in combination with the indirect approach (OUR) to investigate the properties of muscle under different physiological conditions and in the diseased state. Chinet s group [70] found that the slow- and fast-twitch skeletal muscle fibres from the murine model of Duchenne muscular dystrophy had a reduced sarcoplasmic energy metabolism as measured by the combined direct and indirect calorimeter [69]. The possibility that this could be due to diminished glucose availability was then examined [71] but was dismissed in favour of decreased oxidative utilisation of glucose and free fatty acids, conceivably due to defective mitochondria. 

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