Postnatal Muscle Fiber Assembly: Localization of Newly Synthesized Myofibrillar Proteins

Morkin, Eugene

doi:10.1126/science.167.3924.1499

Cited by 77 publications

(49 citation statements)

References 19 publications

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“…Perhaps a return to muscle activity, following long periods of disuse, leads to the peripheral replacement of the lost contractile proteins, including the possible expression of embryonic myosin. This concept is consistent with the addition of newly formed myofibrillar proteins being predominantly at the periphery of fibers undergoing growth (Morkin, 1970;Patterson and Goldspink, 1976).…”

Section: Discussionsupporting

confidence: 64%

Activity-induced fiber regeneration in rat soleus muscle

Wanek

Snow

2000

Anat. Rec.

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In an attempt to understand why muscle recovery is limited following atrophy due to limb immobilization, satellite cell activity and muscle fiber regeneration were analyzed in rat soleus muscles. Adult rat hindlimbs were immobilized in plaster casts for a period of two to ten weeks. Soleus muscles were examined by electron microscopy for evidence of fiber degeneration or regeneration, and to quantify satellite cell nuclei. Immunocytochemical localization of embryonic myosin was used to identify regenerating myofibers. Soleus muscle wet weight to body weight ratios for the casted muscles significantly decreased over the 10-week immobilization period. The casted muscles displayed ultrastructural evidence of minor fiber damage, including myofibrillar atrophy, Z-disc disruption, and abnormal triadic junctions. No ultrastructural evidence of regeneration was seen in the casted animals. The number of satellite cells in the casted muscles significantly decreased from 6.4% to 3.3% by eight to 10 weeks of immobilization. Approximately 1.0% of extrafusal fibers in the control soleus muscles appeared to be regenerating since they expressed embryonic myosin and were of a small diameter, while in casted muscles, only 0.1% of the fibers were embryonic myosin-positive. Following release from immobilization, a reappearance of embryonic myosin-positive fibers was noted within four days of renewed activity. In contrast to control muscles, embryonic myosin-positive fibers in the recovery muscles included both small and large diameter fibers. Subtle changes in functional activity influence muscle damage and subsequent myofiber regeneration. Reduced activity reduces muscle fiber regeneration, while increased activity, as seen by increased hindlimb weight bearing and return to normal activity following immobilization, increase regenerating fibers and also the expression of embryonic myosin in adult fibers.

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Section: Discussionsupporting

confidence: 64%

Activity-induced fiber regeneration in rat soleus muscle

Wanek

Snow

2000

Anat. Rec.

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“…A study done over 25 years ago suggested that newly synthesized myofibrillar proteins were added exclusively to the surface of growing myofibrils (Morkin 1970), an observation consistent with assembly and disassembly occurring at the surface and not in the interior of myofibrils. On the other hand, this mechanism also indicates that the interior of myofibrils would be immortal unless the entire myofibril was turned over, and the implications of such immortality to physiological functioning of the myofibril are unclear.…”

Section: Muscle Protein Turnover and The Rolementioning

confidence: 95%

The calpain system and skeletal muscle growth

Goll¹,

Thompson²,

Taylor³

et al. 1998

Can. J. Anim. Sci.

109

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. 1998. The calpain system and skeletal muscle growth. Can. J. Anim. Sci. 78: 503-512. The first protein of a group of proteins now identified as belonging to the calpain system was purified in 1976. The calpain system presently is known to be constituted of three well-characterized proteins; several lesser studied proteins that have been isolated from invertebrates; and 10 mRNAs, two each in Drosophila and C. elegans and six in vertebrates, that encode proteins, which, based on sequence homology, belong to the calpain family. The three well-characterized proteins in the calpain family include two Ca 2+ -dependent proteolytic enzymes, µ-calpain and m-calpain, and a protein, calpastatin, that has no known activity other than to inhibit the two calpains. A substantial amount of experimental evidence accumulated during the past 25 yr has shown that the calpain system has an important role both in rate of skeletal muscle growth and in rate and extent of postmortem tenderization. Calpastatin seems to be the variable component of the calpain system, and skeletal muscle calpastatin activity is highly related to rate of muscle protein turnover and rate of postmortem tenderization. The current paradigm is that high calpastatin activity: 1) decreases rate of muscle protein turnover and hence is associated with an increased rate of skeletal muscle growth; and 2) decreases calpain activity in postmortem muscle and hence is associated with a lower rate of postmortem tenderization. This article summarizes some of the known properties of the calpain system and discusses the potential importance of the calpain system to animal science.Key words: Calpain, calpastatin, postmortem tenderization, skeletal muscle growth Goll, D. E., Thompson, V. F., Taylor, R. G. et Ouali, A. 1998. Le système des calpaïnes et la croissance des muscles squeletiques. Can. J. Anim. Sci. 78: 503-512. La première protéine d'un groupe désormais identifié comme appartenant au système des calpaïnes a été purifiée en 1976. On sait aujourd'hui que ce système comprend trois protéines bien caractérisées. Plusieurs protéines moins étudiées, isolées chez les invertébrés et 10 ARNm codant pour les protéines,dont deux chacun trouvés chez Drosophila et chez C. elegans et six, chez les vertébrés, appartiendraient également d'après l'homologie séquentielle à la famille des calpaïnes. Les trois protéines bien caractérisées, mentionnées plus haut, comprennent deux enzymes protéolytiques Ca 2+ -dépendantes, la µ-calpaïne et la m-calpaïne, et une protéine, la calpastatine qui semble n'avoir d'autre fonction que d'inhiber l'activité des deux calpaïnes. Un corpus substantiel d'évidence expérimentale accumulé au cours des 25 dernières années révèle que le système des calpaïnes joue un rôle important à la fois à l'égard du taux de croissance des muscules squelettiques et du degré d'attendrissage de la viande postmortem. La calpastatine semble être la composante variable du système et son activité dans les muscles squelettiques est étroitement reliée au taux de renouvellement ...

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“…4 Pressure-overload conditions, such as aortic stenosis and hypertension, result in concentric hypertrophy, which is characterized by an increase in ventricular wall thickness, little or no chamber dilation, and the parallel addition of sarcomeres. 5,6 Conversely, volume-overload conditions, such as mitral regurgitation, promote an eccentric (dilated) form of hypertrophy, which is characterized by relatively little increase in wall thickness, a disproportionately large increase in chamber volume, and the serial addition of sarcomeres. 7,8 The molecular mechanism by which these different hemodynamic loads lead to distinct forms of cardiac hypertrophy is unclear.…”

mentioning

confidence: 99%

Regulation of Cardiomyocyte Mechanotransduction by the Cardiac Cycle

et al. 2001

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Background-Overloading the left ventricle in systole (pressure overload) is associated with a distinct morphological response compared with overload in diastole (volume overload). Methods and Results-We designed a novel computer-controlled experimental system that interfaces biaxially uniform strain with electrical pacing, so that cellular deformation can be imposed during a specified phase of the cardiac cycle. Cardiomyocytes were exposed to strain (4%) during either the first third (systolic phase) or last third (diastolic phase) of the cardiac cycle. Strain imposed during the systolic phase selectively activated p44/42 mitogen-activated protein kinase (MAPK) and MAPK/extracellular signal-regulated protein kinase kinase (MEK1/2, an activator of p44/42 MAPK) compared with strain imposed during the diastolic phase. In contrast, there was no difference in activation of p38 and c-Jun NH 2 -terminal kinases induced by strain imposed during the systolic phase (5.8-and 3.3-fold versus control, nϭ4) compared with the diastolic phase (5.5-and 3.1-fold). Induction of both brain natriuretic peptide (5.8-fold versus control, PϽ0.05, nϭ3) and tenascin-C (7.0-fold, PϽ0.02) mRNA expression by strain imposed during the systolic phase was greater than during the diastolic phase (3.9-and 3.6-fold, respectively).[ 3 H]leucine incorporation induced by strain imposed during the systolic phase (4.0-fold versus control) was greater than during the diastolic phase (2.7-fold, PϽ0.02, nϭ4); a selective inhibitor of MEK1/2 inhibited this difference. Conclusions-Mechanical activation of p44/42 MAPK and MEK1/2, gene expression, and protein synthesis is regulated by the cardiac cycle, suggesting that mechanotransduction at the cellular level may underlie differences between pressure and volume overload of the heart.

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Postnatal Muscle Fiber Assembly: Localization of Newly Synthesized Myofibrillar Proteins

Cited by 77 publications

References 19 publications

Activity-induced fiber regeneration in rat soleus muscle

Activity-induced fiber regeneration in rat soleus muscle

The calpain system and skeletal muscle growth

Regulation of Cardiomyocyte Mechanotransduction by the Cardiac Cycle

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