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Fiber Cross-sectional Area (fiber + cross-sectional_area)
Selected AbstractsGrowth Hormone Administration and Exercise Effects on Muscle Fiber Type and Diameter in Moderately Frail Older PeopleJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 7 2001James V. Hennessey MD OBJECTIVE: Reduced muscle mass and strength are characteristic findings of growth hormone deficiency (GHD) and aging. We evaluated measures of muscle strength, muscle fiber type, and cross sectional area in response to treatment with recombinant human growth hormone (rhGH) with or without a structured resistance exercise program in frail older subjects. DESIGN: Placebo-controlled, randomized, double blind trial. SETTING: Outpatient clinical research center at an urban university-affiliated teaching hospital. PARTICIPANTS: Thirty-one consenting older subjects (mean age 71.3 ± 4.5 years) recruited as a subset of a larger project evaluating rhGH and exercise in older people, who underwent 62 quadricep-muscle biopsies. INTERVENTION: Random assignment to a 6-month course of one of four protocols: rhGH administered subcutaneously daily at bedtime, rhGH and a structured resistance exercise program, structured resistance exercise with placebo injections, or placebo injections only. MEASUREMENTS: Muscle biopsy specimens were obtained from the vastus lateralis muscle. Isokinetic dynamometry strength tests were used to monitor individual progress and to adjust the weights used in the exercise program. Serum insulin-like growth factor-I (IGF-I) was measured and body composition was measured using a Hologic QDR 1000W dual X-ray densitometer. RESULTS: The administration of rhGH resulted in significant increase in circulating IGF-I levels in the individuals receiving rhGH treatment. Muscle strength increased significantly in both the rhGH/exercise (+55.6%, P = .0004) as well as the exercise alone (+47.8%, P = .0005) groups. There was a significant increase in the proportion of type 2 fibers between baseline and six months in the combined rhGH treated subjects versus those not receiving rhGH (P = .027). CONCLUSIONS: Our results are encouraging in that they suggest an effect of growth hormone on a specific aging-correlated deficit. IGF-I was increased by administrating rhGH and muscle strength was increased by exercise. The administration of rhGH to frail older individuals in this study resulted in significant changes in the proportions of fiber types. Whether changes in fiber cross-sectional area or absolute number occur with long-term growth hormone administration requires further study. [source] Regional differences in fiber characteristics in the rat temporalis muscleJOURNAL OF ANATOMY, Issue 6 2008E. Tanaka Abstract The behavioral differences in muscle use are related to the fiber type composition of the muscles among other variables. The aim of this study was to examine the degree of heterogeneity in the fiber type composition in the rat temporalis muscle. The temporalis muscle was taken from 10-week-old Wistar strain male rats (n = 5). Fiber types were classified by immunohistochemical staining according to their myosin heavy chain content. The anterior temporalis revealed an obvious regional difference of the fiber type distribution, whereas the posterior temporalis was homogeneous. The deep anterior temporalis showed a predominant proportion of type IIA fibers and was the only muscle portion displaying slow type fibers (< 10%). The other two muscle portions, the superficial anterior and posterior temporalis, did not differ significantly from each other and contained mainly type IIB fibers. Moreover, the deep anterior temporalis was the only muscle portion showing slow type fibers (< 10%). In the deep portion, type IIX fibers revealed the largest cross-sectional area (1943.1 ± 613.7 µm2), which was significantly (P < 0.01) larger than those of type IIA and I + IIA fibers. The cross-sectional area of type IIB fibers was the largest in the remaining two muscle portions and was significantly (P < 0.01) larger than that of type IIX fibers. In conclusion, temporalis muscle in rats showed an obvious heterogeneity of fiber type composition and fiber cross-sectional area, which suggests multiple functions of this muscle. [source] Slow-tonic muscle fibers and their potential innervation in the turtle, Pseudemys (Trachemys) scripta elegansJOURNAL OF MORPHOLOGY, Issue 1 2005Robert J. Callister Abstract A description is provided of the ratio of slow-tonic vs. slow- and fast-twitch fibers for five muscles in the adult turtle, Pseudemys (Trachemys) scripta elegans. The cross-sectional area of each fiber type and an estimation of the relative (weighted) cross-sectional area occupied by the different fiber types are also provided. Two hindlimb muscles (flexor digitorum longus, FDL; external gastrocnemius, EG) were selected on the basis of their suitability for future motor-unit studies. Three neck muscles (the fourth head of testo-cervicis, TeC4; the fourth head of retrahens capitus collique, RCCQ4; transversalis cervicis, TrC) were chosen for their progressively decreasing oxidative capacity. Serial sections were stained for myosin adenosine triphosphatase (ATPase), NADH-diaphorase, and alpha-glycerophosphate dehydrogenase (,-GPDH). Conventional fiber-type classification was then performed using indirect markers for contraction speed and oxidative (aerobic) vs. glycolytic (anaerobic) metabolism: i.e., slow oxidative (SO, including slow-twitch and possibly slow-tonic fibers), fast-twitch, oxidative-glycolytic (FOG), and fast-twitch glycolytic (Fg) fibers. Slow-tonic fibers in the SO class were then revealed by directing the monoclonal antibody, ALD-58 (raised against the slow-tonic fiber myosin heavy chain of chicken anterior latissimus dorsi), to additional muscle cross sections. All five of the tested muscles contained the four fiber types, with the ATPase-stained fibers including both slow-tonic and slow-twitch fibers. The extreme distributions of SO fibers were in the predominately glycolytic TrC vs. the predominately oxidative TeC4 muscle (TrC,SO, 9%; FOG, 20%; Fg, 71% vs. TeC4,SO, 58%: FOG, 16%; Fg, 25%). Across the five muscles, the relative prevalence of slow-tonic fibers (4,47%) paralleled that of the SO fibers (9,58%). TeC4 had the highest prevalence of slow-tonic fibers (47%). The test muscles exhibited varying degrees of regional concentration of each fiber type, with the distribution of slow-tonic fibers paralleling that of the SO fibers. In the five test muscles, fiber cross-sectional area was usually ranked Fg > FOG > SO, and slow-twitch always > slow-tonic. In terms of weighted cross-sectional area, which provides a coarse-grain measure of each fiber type's potential contribution to whole muscle force, all five muscles exhibited a higher Fg and lower SO contribution to cross-sectional area than suggested by their corresponding fiber-type prevalence. This was also the case for the slow-twitch vs. slow-tonic fibers. We conclude that slow-tonic fibers are widespread in turtle muscle. The weighted cross-sectional area evidence suggested, however, that their contribution to force generation is minor except in highly oxidative muscles, with a special functional role, like TeC4. There is discussion of: 1) the relationship between the present results and previous work on homologous neck and hindlimb muscles in other nonmammalian species, and 2) the potential motoneuronal innervation of slow-tonic fibers in turtle hindlimb muscles. J. Morphol. © 2005 Wiley-Liss, Inc. [source] Muscle fiber properties and thermal stability of intramuscular connective tissue in porcine M. semimembranosusJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2009Liisa Voutila Abstract BACKGROUND: Strips can be easily peeled from raw destructured pork (M. semimembranosus, SM muscle) by hand but in normal meat these strips break. In general, destructured meat is pale in color. Porcine SM muscles have thick muscle fibers which could predispose them to destructuration. This study investigated whether the onset and peak temperatures of thermal shrinkage (To and Tp) of intramuscular connective tissue from SM muscles were associated with muscle fiber thickness, capillary density or extracellular space. We also investigated whether these muscle fiber properties of destructured muscles differed from those of normal muscles. RESULTS: The destructured and normal muscles were similar in muscle fiber cross-sectional area, capillary density, extracellular space and sarcomere length. To correlated negatively with sarcomere length. The water content of differential scanning calorimetry samples consisting of intramuscular connective tissue was higher in destructured muscles than in normal muscles. CONCLUSION: Muscle fiber properties (muscle fiber cross-sectional area and sarcomere length) and capillary density are similar in destructured and normal SM muscles. To and Tp of intramuscular connective tissue are similar in destructured and normal muscles. Muscle fiber properties show no association with the thermal shrinkage properties of intramuscular connective tissue. Copyright © 2009 Society of Chemical Industry [source] | ||||||||||