Alterations in Myofibril Size and Structure During Growth, Exercise, and Changes in Environmental Temperature

Goldspink, G.

doi:10.1002/cphy.cp100118

Cited by 31 publications

(36 citation statements)

References 90 publications

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“…Whether the extra ATP produced by these additional mitochondria is used for altered mechanical functioning at the shorter sarcomere length or whether the ATP is essential for the maintenance of the specialized myotendinous junction and creation of new sarcomeres is unknown. The nuclei, smooth SR, and Golgi complexes were greatly increased here, supporting the concept of a n increase in protein synthesis in this region (Goldspink, 1983).…”

Section: Discussionsupporting

confidence: 82%

“…Recently the membrane has been shown to be highly developed at the myotendinous junction, with numerous folds and villiform processes (Hanek and Bock, 1971;Nakao 1976;Ishikawa et al, 1983;Michna, 1983;Trotter et al, 1983a,b;Tidball 1983Tidball , 1984. Sarcomere addition occurs most readily at the ends of fibers growing in length (Williams and Goldspink, 1978;Goldspink, 1983), and these terminal sarcomeres are of the shortest length (Huxley and Peachey, 1961;Gordon et al, 1966).…”

mentioning

confidence: 99%

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Muscle fiber termination at the tendon in the frog's sartorius: A stereological study

Eisenberg

Milton

1984

Am. J. Anat.

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The force produced within skeletal muscle fibers is transmitted to the bone via a myotendinous junction. This junctional region was examined by light and electron microscopy in the sartorius muscles of three Rana temporaria. The muscle fibers tapered and inserted at an angle of about 25 degrees with the connective tissue fascia near the bone. The composition of the structures within the last 100 microns of the fiber was analyzed morphometrically. The T-system, terminal cisternae, and caveolae were the same as in the central region of the muscle fiber. However, the mitochondrial content was higher and the volume of longitudinal sarcoplasmic reticulum was lower than elsewhere in the fiber. The membrane at the end of the fiber had extensive villiform processes interdigitating with the tendon. The surface area of the membrane around the villiform processes was estimated with point-counting techniques and calculated from the stereological equations appropriate for partially anisotropic structures. The extra membrane involved in the myotendinous junction was about 32 times that of the cross-sectional area of the fiber. Part of this additional membrane contained specialized adherens junctions through which the contractile proteins of the muscle are anchored to collagen. The increased area at the myotendinous junction presumably provides greater mechanical strength than a flat termination. The high values of membrane capacitance and specific resistance measured electrophysiologically at the end of the fiber also can be attributed to the characteristics of the terminal membrane structure.

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Section: Discussionsupporting

confidence: 82%

mentioning

confidence: 99%

Muscle fiber termination at the tendon in the frog's sartorius: A stereological study

Eisenberg

Milton

1984

Am. J. Anat.

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“…In vivo increases in fascicle length are associated with the addition of sarcomeres in series (assuming a fixed sarcomere length) and appear to be strongly influenced by muscle length or stretch (12,46,50). A study by Boakes et al (5) wherein surgery placed the thigh muscles under constant stretch to address a leg-length discrepancy, resulted in a 4-cm femoral lengthening.…”

Section: Discussionmentioning

confidence: 99%

“…To further augment sarcomerogenesis at different muscle lengths are the effects stretch has on muscle. Muscles undergoing different amounts of stretching and shortening have been shown to adapt to their new functional lengths by the addition or removal of sarcomeres in series (12,46,50), with an increase in functional length associated with increased protein synthesis (13).…”

Section: Introductionmentioning

confidence: 99%

Impact of Range of Motion During Ecologically Valid Resistance Training Protocols on Muscle Size, Subcutaneous Fat, and Strength

McMahon

Morse²,

Burden³

et al. 2014

Journal of Strength and Conditioning Research

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The impact of using different resistance training (RT) kinematics, which therefore alters RT mechanics, and their subsequent effect on adaptations remain largely unreported. The aim of this study was to identify the differences to training at a longer (LR) compared with a shorter (SR) range of motion (ROM) and the time course of any changes during detraining. Recreationally active participants in LR (aged 19 ± 2.6 years; n = 8) and SR (aged 19 ± 3.4 years; n = 8) groups undertook 8 weeks of RT and 4 weeks of detraining. Muscle size, architecture, subcutaneous fat, and strength were measured at weeks 0, 8, 10, and 12 (repeated measures). A control group (aged 23 ± 2.4 years; n = 10) was also monitored during this period. Significant (p > 0.05) posttraining differences existed in strength (on average 4 ± 2 vs. 18 ± 2%), distal anatomical cross-sectional area (59 ± 15 vs. 16 ± 10%), fascicle length (23 ± 5 vs. 10 ± 2%), and subcutaneous fat (22 ± 8 vs. 5 ± 2%), with LR exhibiting greater adaptations than SR. Detraining resulted in significant (p > 0.05) deteriorations in all muscle parameters measured in both groups, with the SR group experiencing a more rapid relative loss of postexercise increases in strength than that experienced by the LR group (p > 0.05). Greater morphological and architectural RT adaptations in the LR (owing to higher mechanical stress) result in a more significant increase in strength compared with that of the SR. The practical implications for this body of work follow that LR should be observed in RT where increased muscle strength and size are the objective, because we demonstrate here that ROM should not be compromised for greater external loading.

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“…Unlike vertebrates and some arthropods, in which striated muscle fibers may be altered during ontogeny via expression of different isoforms of MHC (Bárány, 1967;Goldspink, 1968;Goldspink, 1983;Gauthier et al, 1978;Bandman, 1985;Gondret et al, 1996), changes in the ratio of the alkali light chains (Sweeney et al, 1988) or changes in calcium sensitivity via expression of isoforms of troponinT (Fitzhugh and Marden, 1997), squids appear to modify muscle mechanical properties by altering the lengths of the thick filaments. For example, the thick filaments of the obliquely striated transverse muscles of the arms of the oval squid Sepioteuthis lessoniana increase in length during ontogeny, from 2.2 mm in hatchlings to 6.4mm in adults, while the thick filament lengths of the cross-striated transverse muscles of the tentacles decrease from 2.4 mm to 1.2 mm during the same interval (Kier, 1996).…”

Section: Introductionmentioning

confidence: 99%

The ontogeny of muscle structure and locomotory function in the long-finned squidDoryteuthis pealeii

Thompson

Bartol

Baksi

et al. 2010

Journal of Experimental Biology

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SUMMARYUnderstanding the extent to which changes in muscle form and function underlie ontogenetic changes in locomotory behaviors and performance is important in understanding the evolution of musculoskeletal systems and also the ecology of different life stages. We explored ontogenetic changes in the structure, myosin heavy chain (MHC) expression and contractile properties of the circular muscles that provide power for jet locomotion in the long-finned squid Doryteuthis pealeii. The circular muscle fibers of newly hatched paralarvae had different sizes, shapes, thick filament lengths, thin:thick filament ratio, myofilament organization and sarcoplasmic reticulum (SR) distribution than those of adults. Viewed in cross section, most circular muscle cells were roughly triangular or ovoid in shape with a core of mitochondria; however, numerous muscle cells with crescent or other unusual cross-sectional shapes and muscle cells with unequal distributions of mitochondria were present in the paralarvae. The frequency of these muscle cells relative to 'normal' circular muscle cells ranged from 1:6 to 1:10 among the 19 paralarvae we surveyed. The thick filaments of the two types of circular fibers, superficial mitochondria-rich (SMR) and central mitochondria-poor (CMP), differed slightly in length among paralarvae with thick filament lengths of 0.83±0.15 mm and 0.71±0.1 mm for the SMR and CMP fibers, respectively (P 0.05; ANOVA). During ontogeny the thick filament lengths of both the CMP and SMR fibers increased significantly to 1.78±0.27 mm and 3.12±0.56 mm, respectively, in adults (P<0.0001 for both comparisons; ANOVA with Tukey's highly significant difference post hoc tests). When sectioned parallel to their long axes, the SMR and CMP fibers of both paralarvae and adults exhibited the myofilament arrangements typical of obliquely striated muscle cells but the angle of obliquity of the dense bodies was 22.8±2.4 deg. and 4.6±0.87 deg. for paralarvae and adults, respectively. There were also differences in the distribution of the anastomosing network of SR. In paralarvae, the outer and central zones of SR were well developed but the intramyoplasmic zone was greatly reduced in some cells or was scattered non-uniformly across the myoplasm. Whereas in adults the intramyoplasmic SR region was composed primarily of flattened tubules, it was composed primarily of rounded vesicles or tubules when present in the paralarvae. The ontogenetic differences in circular muscle structure were correlated with significant differences in their contractile properties. In brief tetanus at 20°C, the mean unloaded shortening velocity of the paralarval circular muscle preparations was 9.1 L 0 s -1 (where L 0 was the preparation length that generated the peak isometric stress), nearly twice that measured in other studies for the CMP fibers of adults. The mean peak isometric stress was 119±15 mN mm -2 physiological cross section, nearly half that measured for the CMP fibers of adults. Reverse transcriptase-polymerase chain reaction analysis of pa...

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Alterations in Myofibril Size and Structure During Growth, Exercise, and Changes in Environmental Temperature

Cited by 31 publications

References 90 publications

Muscle fiber termination at the tendon in the frog's sartorius: A stereological study

Muscle fiber termination at the tendon in the frog's sartorius: A stereological study

Impact of Range of Motion During Ecologically Valid Resistance Training Protocols on Muscle Size, Subcutaneous Fat, and Strength

The ontogeny of muscle structure and locomotory function in the long-finned squidDoryteuthis pealeii

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