The angiotensin-converting enzyme (ACE) I/D and α-actinin 3 (ACTN3) R/X polymorphisms have been suggested to influence variations in skeletal muscle function. This study investigated the association between ACE I/D and ACTN3 R/X polymorphisms and muscle strength and contractile properties in young UK Caucasian men. Measurements of the knee extensor muscles were taken from 79 recreationally active but non-strength-trained males on two occasions. Isometric knee extensor strength was measured using a conventional strength-testing chair. Maximal twitches were electrically evoked by percutaneous stimulation to assess time-topeak tension, half-relaxation time and peak rate of force development. The torque-velocity relationship was measured at four angular velocities (0, 30, 90 and 240 deg s −1 ) using isokinetic dynamometry, and the relative torque at high velocity was calculated (torque at 240 deg sas a percentage of that at 30 deg s −1 ). The ACE I/D and ACTN3 R/X polymorphisms were genotyped from whole blood by polymerase chain reaction. Serum ACE activity was assayed from serum using automated spectrophotometry. Physical characteristics were independent of either genotype. Absolute and relative high-velocity torque were not influenced by ACE or ACTN3 genotypes. Isometric strength and the time course of a maximal twitch were independent of ACE and ACTN3 genotypes. Serum ACE activity was significantly dependent on ACE genotype (P < 0.001), but was not associated with any measure of functional or contractile properties. Knee extensor functional and contractile properties, including high-velocity strength, were not influenced by ACE and ACTN3 polymorphisms in a cohort of UK Caucasian males. Any influence of these individual polymorphisms on human skeletal muscle does not appear to be of sufficient magnitude to influence function in free-living UK Caucasian men. Genetic factors are thought to determine 20-80% of the variation in a number of traits important to athletic performance (MacArthur & North, 2007), for example the relative proportion of fast-and slowtwitch skeletal muscle fibres (Simoneau & Bouchard, 1995; ∼45% due to inherited factors). The annual publication of the human gene map for performance and health-related fitness phenotypes (Rankinen et al. 2006) lists more than 150 genes or genetic regions associated with athletic performance and physical fitness traits. The angiotensin-converting enzyme (ACE) I/D polymorphism (Williams et al. 2005) and α-actinin 3 (ACTN3) R577X polymorphism (Mills et al. 2001) have recently been identified as potential influences contributing to variations in skeletal muscle composition, function and performance.The ACE gene has been the most extensively studied gene in the area of human performance phenotypes. A functional polymorphism of the ACE gene is defined as the presence (insertion, I allele) or absence (deletion, D allele) of a 287-amino-acid base pair Alu repeat sequence within intron 16 of the ACE gene on chromosome 17 (Rigat et al. 1990). The polymorphism results in th...

SynopsisThin sections of the spinal ganglion of the rat were cut and examined with the electron microscope. Two main types of nerve cell are described. Type A with equal electron density of nucleus and cytoplasm. The cytoplasm contains large aggregates of Nissl's substance discretely scattered throughout the cell, mitochondria and osmophilic granules. Type B with a “light” nucleus and a “dark” cytoplasm. The cytoplasm is closely packed and homogeneous so that it is difficult to separate out the various cytoplasmic elements.There is a well-marked nuclear membrane about 500 Å thick and characteristic strawberry nucleolus.The capsular cells are closely applied to the nerve cell with no intervening boundaries. A system of cytoplasmic filaments—the “endoplasmic reticulum”—is present in the intercellular regions.There are nerve fibres with lamellated myelin sheath, axolemma, Schwann cells and Schwann membrane.

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