| Summary: | CHAPTER 1 A brief introduction is given to the structure, biochemistry and electrophysiological and mechanical properties of fish muscle. CHAPTER 2 1. The neuromuscular end plates and preterminal axons of cod, Gadus morhua, fast myotomal muscle were stained for cholinesterase activity. 2. The number of end plates per fibre on superficial fast fibres (17.88 ± 2.13, mean ± 1 S.D.) was significantly higher than that of deep fast fibres (14.79 ± 2.48, P<< 0.001). A small degree of multi-terminal innervation was noted. The end plates showed a great variety in structure and size. 3. Fast muscle contains fibres with a wide range of diameters (20-240 µm). However, no correlation was found between the number of end plates per fibre and fibre diameter. CHAPTER 3 1. The force-velocity characteristics of threads of natural actomyosin, and purified component proteins, from dogfish fast and slow muscle, and rabbit fast skeletal and cardiac muscle have been investigated. 2. Maximum isometric tensions were around 30-70 g cm⁻². The time taken to reach full tension after activation with ATP was 2-8 min. 3. Force-velocity curves obtained could be fitted to a linear form of Hill's equation (1938). In common with intact and skinned fibre studies, points below 0.7 P₀ were found to lie on a straight line. 4. Maximum contraction velocities were around 10⁻² Ls⁻¹, 2-3 orders of magnitude lower than those of intact muscle fibres. 5. The relative velocities of the different thread types do not reflect those of the corresponding muscles, on the basis of measurements on intact fibres, and on measurements of actomyosin/myofibrillar ATPase activities. 6. It is concluded that filament formation, geometry and packing, and not differences in cross bridge cycling rates, largely determine the observed properties of actomyosin threads. CHAPTER 4 A description of the apparatus used to study the isometric and isotonic properties of skinned fibres is given, together with the methods and protocol used in Chapters 5-7. CHAPTER 5 1. The pCa-tension ...
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