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Volumn 36, Issue 5, 2010, Pages 743-751

Using low-intensity pulsed ultrasound to improve muscle healing after laceration injury: An in vitro and in vivo study

Author keywords

Fast twitch; Low intensity pulsed ultrasound; Muscle healing; Muscle laceration injury; Tetanus

Indexed keywords

C2C12 CELLS; CELL LINES; CELL NUMBER; CLINICAL TRIAL; CONTROL GROUPS; DENSITOMETRIC EVALUATION; EVALUATION METHOD; EXPERIMENTAL STUDIES; FAST-TWITCH; GASTROCNEMIUS MUSCLE; HEALING TIME; IN-CELL; IN-VITRO; INJURY MODELS; LEG MUSCLES; LOW-INTENSITY PULSED ULTRASOUND; MUSCLE PROTEINS; MUSCLE REGENERATION; MYOBLAST CELLS; MYOFIBERS; MYOTUBES; STRENGTH DIFFERENCES; SUBCLONES; WESTERN-BLOT ANALYSIS;

EID: 77952322485     PISSN: 03015629     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.ultrasmedbio.2010.02.010     Document Type: Article
Times cited : (59)

References (55)
  • 1
    • 0025372575 scopus 로고
    • Regulation of satellite cells during skeletal muscle growth and development
    • Allen R.E., Rankin L.L. Regulation of satellite cells during skeletal muscle growth and development. Proc Soc Exp Biol Med 1990, 194:81-86.
    • (1990) Proc Soc Exp Biol Med , vol.194 , pp. 81-86
    • Allen, R.E.1    Rankin, L.L.2
  • 2
    • 0026642924 scopus 로고
    • Quadriceps contusion: Hastening the return to play
    • Aronen J.G., Chronister R.O. Quadriceps contusion: Hastening the return to play. Physician Sportsmed 1992, 20:130-136.
    • (1992) Physician Sportsmed , vol.20 , pp. 130-136
    • Aronen, J.G.1    Chronister, R.O.2
  • 3
    • 0002841587 scopus 로고
    • The satellite cell and muscle regeneration
    • McGraw-Hill, Inc,, New York, A.G. Engel, C. Franzini-Armstrong (Eds.)
    • Bischoff R. The satellite cell and muscle regeneration. Myology 1994, 97-118. McGraw-Hill, Inc,, New York. 2nd edition. A.G. Engel, C. Franzini-Armstrong (Eds.).
    • (1994) Myology , pp. 97-118
    • Bischoff, R.1
  • 4
    • 0017184389 scopus 로고
    • A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding
    • Bradford M.M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem 1976, 72:248-254.
    • (1976) Anal Biochem , vol.72 , pp. 248-254
    • Bradford, M.M.1
  • 6
    • 0027501452 scopus 로고
    • Incisional wound healing: A controlled study of low and high dose ultrasound
    • Byl N., McKenzie A.L., Wong T., West T., Hunt T.K. Incisional wound healing: A controlled study of low and high dose ultrasound. J Orthop Sports Phys Ther 1993, 18:619-628.
    • (1993) J Orthop Sports Phys Ther , vol.18 , pp. 619-628
    • Byl, N.1    McKenzie, A.L.2    Wong, T.3    West, T.4    Hunt, T.K.5
  • 7
    • 0020960533 scopus 로고
    • The regeneration of skeletal muscle fibers following injury: A review
    • Carlson B.M., Faulkner J.A. The regeneration of skeletal muscle fibers following injury: A review. Med Sci Sports Exerc 1983, 15:187-196.
    • (1983) Med Sci Sports Exerc , vol.15 , pp. 187-196
    • Carlson, B.M.1    Faulkner, J.A.2
  • 8
    • 11144293690 scopus 로고    scopus 로고
    • Use of antifibrotic agent suramin to improve muscle recovery after strain injury
    • Chan Y.S., Li Y., Foster W., Fu F.H., Huard J. Use of antifibrotic agent suramin to improve muscle recovery after strain injury. Am J Sports Med 2005, 43-51.
    • (2005) Am J Sports Med , pp. 43-51
    • Chan, Y.S.1    Li, Y.2    Foster, W.3    Fu, F.H.4    Huard, J.5
  • 10
    • 0024343241 scopus 로고
    • The significance of membrane changes in the safe and effective use of therapeutic and diagnosis
    • Dinno M.A., Dyson M., Young S.R., Mortimer A.J., Hart J., Crum L. The significance of membrane changes in the safe and effective use of therapeutic and diagnosis. Phys Med Biol 1989, 34:1543-1552.
    • (1989) Phys Med Biol , vol.34 , pp. 1543-1552
    • Dinno, M.A.1    Dyson, M.2    Young, S.R.3    Mortimer, A.J.4    Hart, J.5    Crum, L.6
  • 11
    • 0015828994 scopus 로고
    • Slavetinska. Strengthening of sutured skin wound with ultrasound in experiments on animals
    • Drastichova V., Samohyl J. Slavetinska. Strengthening of sutured skin wound with ultrasound in experiments on animals. Acta Chir Plast 1973, 15:114-119.
    • (1973) Acta Chir Plast , vol.15 , pp. 114-119
    • Drastichova, V.1    Samohyl, J.2
  • 12
    • 0020638987 scopus 로고
    • The stimulation of bone growth by ultrasound
    • Duarte L.R. The stimulation of bone growth by ultrasound. Arch Orthop Trauma Surg 1983, 101:153-159.
    • (1983) Arch Orthop Trauma Surg , vol.101 , pp. 153-159
    • Duarte, L.R.1
  • 13
    • 0025637624 scopus 로고
    • The biomechanical effects of low-intensity ultrasound on healing tendons
    • Enwemeka C.S., Rodriquez O., Mendosa S. The biomechanical effects of low-intensity ultrasound on healing tendons. Ultrasound Med Biol 1990, 16:801-807.
    • (1990) Ultrasound Med Biol , vol.16 , pp. 801-807
    • Enwemeka, C.S.1    Rodriquez, O.2    Mendosa, S.3
  • 14
    • 0029907306 scopus 로고    scopus 로고
    • Growth hormone and the insulin-like growth factor system in myogenesis
    • Florini J.R., Ewton D.Z., Coolican S.A. Growth hormone and the insulin-like growth factor system in myogenesis. Endocr Rev 1996, 17:481-517.
    • (1996) Endocr Rev , vol.17 , pp. 481-517
    • Florini, J.R.1    Ewton, D.Z.2    Coolican, S.A.3
  • 15
    • 0024521838 scopus 로고
    • Effect of growth factors on myogenic differentiation
    • Florini J.R., Magri K.A. Effect of growth factors on myogenic differentiation. Am J Physiol 1989, 256:701-711.
    • (1989) Am J Physiol , vol.256 , pp. 701-711
    • Florini, J.R.1    Magri, K.A.2
  • 16
    • 0023740803 scopus 로고
    • A pilot study: The therapeutic effects of ultrasound following partial rupture of Achilles tendons in male rats
    • Frieder S., Weisberg J., Fleming B. A pilot study: The therapeutic effects of ultrasound following partial rupture of Achilles tendons in male rats. J Orthop Sports Phys Ther 1988, 10:39-46.
    • (1988) J Orthop Sports Phys Ther , vol.10 , pp. 39-46
    • Frieder, S.1    Weisberg, J.2    Fleming, B.3
  • 17
    • 34247103235 scopus 로고    scopus 로고
    • Effect of therapeutic pulsed ultrasound on parameters of oxidative stress in skeletal muscle after injury
    • 482-428
    • Freitas L.S., Freitas T.P., Silveira P.C., Rocha L.G., Pinho R.A., Streck E.L. Effect of therapeutic pulsed ultrasound on parameters of oxidative stress in skeletal muscle after injury. Cell Biol Int 2007, 31. 482-428.
    • (2007) Cell Biol Int , vol.31
    • Freitas, L.S.1    Freitas, T.P.2    Silveira, P.C.3    Rocha, L.G.4    Pinho, R.A.5    Streck, E.L.6
  • 18
    • 0034945607 scopus 로고    scopus 로고
    • The use of antifibrosis agent to improve muscle recovery after laceration
    • Fukushima K., Badlani N., Usas A., Riano F., Fu F., Huard J. The use of antifibrosis agent to improve muscle recovery after laceration. Am J Sports Med 2001, 29:394-402.
    • (2001) Am J Sports Med , vol.29 , pp. 394-402
    • Fukushima, K.1    Badlani, N.2    Usas, A.3    Riano, F.4    Fu, F.5    Huard, J.6
  • 20
    • 0346446642 scopus 로고
    • The stimulation of protein synthesis in human fibroblasts by therapeutic ultrasound
    • Harvey W., Dyson M., Pond J.B. The stimulation of protein synthesis in human fibroblasts by therapeutic ultrasound. Rheum Rehabil 1975, 14:237.
    • (1975) Rheum Rehabil , vol.14 , pp. 237
    • Harvey, W.1    Dyson, M.2    Pond, J.B.3
  • 21
    • 0028214665 scopus 로고
    • Acceleration of tibial fracture healing by non-invasive, low-intensity pulsed ultrasound
    • Heckman J.D., Ryaby J.P., McCabe J., Frey J.J., Kilcoyne R.F. Acceleration of tibial fracture healing by non-invasive, low-intensity pulsed ultrasound. J Bone Joint Surg 1994, 76A:26-34.
    • (1994) J Bone Joint Surg , vol.76 A , pp. 26-34
    • Heckman, J.D.1    Ryaby, J.P.2    McCabe, J.3    Frey, J.J.4    Kilcoyne, R.F.5
  • 22
    • 0026527862 scopus 로고
    • Activation of myogenic precursor cells after muscle injury
    • Hurme T., Kalimo H. Activation of myogenic precursor cells after muscle injury. Med Sci Sports Exerc 1992, 24:197-205.
    • (1992) Med Sci Sports Exerc , vol.24 , pp. 197-205
    • Hurme, T.1    Kalimo, H.2
  • 23
    • 33749264224 scopus 로고    scopus 로고
    • Effects of low-intensity pulsed ultrasound on the differentiation of C2C12 cells
    • Ikeda K., Takayama T., Suzuki N., Shimada K., Otsuka K., Ito K. Effects of low-intensity pulsed ultrasound on the differentiation of C2C12 cells. Life Sci 2006, 79:1936-1943.
    • (2006) Life Sci , vol.79 , pp. 1936-1943
    • Ikeda, K.1    Takayama, T.2    Suzuki, N.3    Shimada, K.4    Otsuka, K.5    Ito, K.6
  • 24
    • 0036143009 scopus 로고    scopus 로고
    • Continuous therapeutic ultrasound accelerates repair of contraction-induced skeletal muscle damage in rats
    • Karnes J.L., Burton H.W. Continuous therapeutic ultrasound accelerates repair of contraction-induced skeletal muscle damage in rats. Arch Phys Med Rehabil 2002, 83:1-4.
    • (2002) Arch Phys Med Rehabil , vol.83 , pp. 1-4
    • Karnes, J.L.1    Burton, H.W.2
  • 27
    • 0022501653 scopus 로고
    • Scintigraphic control of bone-fracture healing under ultrasonic stimulation: An animal experimental study
    • Klug W., Franke W.G., Knoch H.G. Scintigraphic control of bone-fracture healing under ultrasonic stimulation: An animal experimental study. Eur J Nucl Med 1986, 11:494-497.
    • (1986) Eur J Nucl Med , vol.11 , pp. 494-497
    • Klug, W.1    Franke, W.G.2    Knoch, H.G.3
  • 28
    • 69849092303 scopus 로고    scopus 로고
    • Low-intensity pulsed ultrasound stimulates cell proliferation, proteoglycan synthesis and expression of growth factor-related genes in human nucleus pulposus cell line
    • Kobayashi Y., Sakai D., Iwashina T., Iwabuchi S., Mochida J. Low-intensity pulsed ultrasound stimulates cell proliferation, proteoglycan synthesis and expression of growth factor-related genes in human nucleus pulposus cell line. Eur Cell Mater 2009, 17:15-22.
    • (2009) Eur Cell Mater , vol.17 , pp. 15-22
    • Kobayashi, Y.1    Sakai, D.2    Iwashina, T.3    Iwabuchi, S.4    Mochida, J.5
  • 29
    • 0030792575 scopus 로고    scopus 로고
    • Accelerated healing of distal radius fractures with the use of specific, low-intensity ultrasound
    • Kristiansen T.K., Ryaby J.P., McCabe J., Frey J.J., Roe L.R. Accelerated healing of distal radius fractures with the use of specific, low-intensity ultrasound. J Bone Joint Surg [Am] 1997, 79:961-973.
    • (1997) J Bone Joint Surg [Am] , vol.79 , pp. 961-973
    • Kristiansen, T.K.1    Ryaby, J.P.2    McCabe, J.3    Frey, J.J.4    Roe, L.R.5
  • 30
    • 63149136931 scopus 로고    scopus 로고
    • Experimental assessment of calvarial bone defect re-ossification stimulation using low-intensity pulsed ultrasound
    • Lavandier B., Gleizal A., Béra J.C. Experimental assessment of calvarial bone defect re-ossification stimulation using low-intensity pulsed ultrasound. Ultrasound Med Biol 2009, 35:585-594.
    • (2009) Ultrasound Med Biol , vol.35 , pp. 585-594
    • Lavandier, B.1    Gleizal, A.2    Béra, J.C.3
  • 31
    • 0023803882 scopus 로고    scopus 로고
    • Two monoclonal antibodies to actin: One muscle selective and one generally reactive
    • Lessard J. Two monoclonal antibodies to actin: One muscle selective and one generally reactive. Cell Motility and the Cytoskeleton 1998, 10:349-362.
    • (1998) Cell Motility and the Cytoskeleton , vol.10 , pp. 349-362
    • Lessard, J.1
  • 32
  • 33
    • 0000642664 scopus 로고
    • Satellite cell of skeletal muscle fibers
    • Mauro A. Satellite cell of skeletal muscle fibers. J Biophys Biochem Cytol 1961, 9:493-495.
    • (1961) J Biophys Biochem Cytol , vol.9 , pp. 493-495
    • Mauro, A.1
  • 34
    • 0018027371 scopus 로고
    • Histological studies of the effects of ultrasound therapy on surgically split flexor tendons
    • Morcos M.B., Aswad A. Histological studies of the effects of ultrasound therapy on surgically split flexor tendons. Equine Vet J 1987, 10:267.
    • (1987) Equine Vet J , vol.10 , pp. 267
    • Morcos, M.B.1    Aswad, A.2
  • 35
    • 0023749929 scopus 로고
    • The effect of therapeutic ultrasound on calcium uptake in fibroblasts
    • Mortimer A.J., Dyson M. The effect of therapeutic ultrasound on calcium uptake in fibroblasts. Ultrasound Med Biol 1988, 14:499-506.
    • (1988) Ultrasound Med Biol , vol.14 , pp. 499-506
    • Mortimer, A.J.1    Dyson, M.2
  • 36
    • 0025035058 scopus 로고
    • Khan SA, Figueiredo M, Kaufman JJ, Siffert RS. Noninvasive low-intensity pulsed ultrasound accelerates bone healing in the rabbit
    • Pilla A.A., Mont M.A., Nasser P.R. Khan SA, Figueiredo M, Kaufman JJ, Siffert RS. Noninvasive low-intensity pulsed ultrasound accelerates bone healing in the rabbit. J Orthop Trauma 1990, 4:246-253.
    • (1990) J Orthop Trauma , vol.4 , pp. 246-253
    • Pilla, A.A.1    Mont, M.A.2    Nasser, P.R.3
  • 37
    • 0030016957 scopus 로고    scopus 로고
    • Overexpression of the type-1 insulin-like growth factor receptor increases ligand-dependent proliferation and differentiation in bovine skeletal myogenic culture
    • Quinn L.S., Haugk K.L. Overexpression of the type-1 insulin-like growth factor receptor increases ligand-dependent proliferation and differentiation in bovine skeletal myogenic culture. J Cell Physiol 1996, 168:34-41.
    • (1996) J Cell Physiol , vol.168 , pp. 34-41
    • Quinn, L.S.1    Haugk, K.L.2
  • 38
    • 33845410702 scopus 로고    scopus 로고
    • Low-intensity pulsed ultrasound accelerates osteogenesis at bone-tendon healing junction
    • Qin L., Lu H., Fok P., Cheung W., Zheng Y., Lee K., Leung K. Low-intensity pulsed ultrasound accelerates osteogenesis at bone-tendon healing junction. Ultrasound Med Biol 2006, 32:1905-1911.
    • (2006) Ultrasound Med Biol , vol.32 , pp. 1905-1911
    • Qin, L.1    Lu, H.2    Fok, P.3    Cheung, W.4    Zheng, Y.5    Lee, K.6    Leung, K.7
  • 40
    • 0032949629 scopus 로고    scopus 로고
    • Effects of therapeutic ultrasound on the regeneration of skeletal myofibers after experimental muscle injury
    • Rantanen J., Thorsson O., Wollmer P., Hurme T., Kalimo H. Effects of therapeutic ultrasound on the regeneration of skeletal myofibers after experimental muscle injury. Am J Sports Med 1999, 27:54-59.
    • (1999) Am J Sports Med , vol.27 , pp. 54-59
    • Rantanen, J.1    Thorsson, O.2    Wollmer, P.3    Hurme, T.4    Kalimo, H.5
  • 41
    • 0035113549 scopus 로고    scopus 로고
    • Current concepts review. The use of low-intensity ultrasound to accelerate the healing of fracture
    • Rubin C., Bolander M., Ryaby J.P., Hadjiargyrou M. Current concepts review. The use of low-intensity ultrasound to accelerate the healing of fracture. J Bone Joint Surg 2001, 83A:259-270.
    • (2001) J Bone Joint Surg , vol.83 A , pp. 259-270
    • Rubin, C.1    Bolander, M.2    Ryaby, J.P.3    Hadjiargyrou, M.4
  • 42
    • 0021149543 scopus 로고
    • How safe is diagnostic ultrasonography?
    • St.John Brown B. How safe is diagnostic ultrasonography?. Can Med Assoc J 1984, 131:307-311.
    • (1984) Can Med Assoc J , vol.131 , pp. 307-311
    • St.John Brown, B.1
  • 43
    • 0033052563 scopus 로고    scopus 로고
    • Bone defect healing enhanced by ultrasound stimulation: An in vitro tissue culture model
    • Sun J.S., Tsuang Y.H., Lin F.H., Liu H.C., Tsai C.Z., Chang W.H. Bone defect healing enhanced by ultrasound stimulation: An in vitro tissue culture model. J Biomed Mater Res 1999, 46:253-261.
    • (1999) J Biomed Mater Res , vol.46 , pp. 253-261
    • Sun, J.S.1    Tsuang, Y.H.2    Lin, F.H.3    Liu, H.C.4    Tsai, C.Z.5    Chang, W.H.6
  • 44
    • 0027465376 scopus 로고
    • Experimental muscle strain injury: Early functional and structural deficits, and the increased risk for reinjury
    • Taylor D.C., Dalton J.D., Seaber A.V., Garrett W.E. Experimental muscle strain injury: Early functional and structural deficits, and the increased risk for reinjury. Am J Sports Med 1993, 21:190-194.
    • (1993) Am J Sports Med , vol.21 , pp. 190-194
    • Taylor, D.C.1    Dalton, J.D.2    Seaber, A.V.3    Garrett, W.E.4
  • 46
    • 33846631811 scopus 로고    scopus 로고
    • Effects of low-intensity pulsed ultrasound on tendon-bone healing in an intra-articular sheep knee model
    • Walsh W.R., Stephens P., Vizesi F., Bruce W., Huckle J., Yu Y. Effects of low-intensity pulsed ultrasound on tendon-bone healing in an intra-articular sheep knee model. Arthroscopy 2007, 23:197-204.
    • (2007) Arthroscopy , vol.23 , pp. 197-204
    • Walsh, W.R.1    Stephens, P.2    Vizesi, F.3    Bruce, W.4    Huckle, J.5    Yu, Y.6
  • 47
    • 0037219136 scopus 로고    scopus 로고
    • A new direction for ultrasound therapy in sports medicine
    • Warden S.J. A new direction for ultrasound therapy in sports medicine. Sports Med 2003, 33:95-107.
    • (2003) Sports Med , vol.33 , pp. 95-107
    • Warden, S.J.1
  • 48
    • 0018906223 scopus 로고
    • The role of ultrasound-induced cavitation in the ″ in vitro″ stimulation of collagen synthesis in human fibroblasts
    • Webster D.F., Harvey W., Dyson M. The role of ultrasound-induced cavitation in the ″ in vitro″ stimulation of collagen synthesis in human fibroblasts. Ultrasonics 1980, 18:33-37.
    • (1980) Ultrasonics , vol.18 , pp. 33-37
    • Webster, D.F.1    Harvey, W.2    Dyson, M.3
  • 49
    • 0001937888 scopus 로고
    • Surgical applications of ultrasound
    • Churchill Livingstone, New York, W.L. Nyborg, M.C. Ziskin (Eds.)
    • Wells P.N.T. Surgical applications of ultrasound. Biological effects of ultrasound 1985, 157-167. Churchill Livingstone, New York. W.L. Nyborg, M.C. Ziskin (Eds.).
    • (1985) Biological effects of ultrasound , pp. 157-167
    • Wells, P.N.T.1
  • 50
    • 70349208515 scopus 로고    scopus 로고
    • Ultrasound enhances recombinant human BMP-2 induced ectopic bone formation in a rat model
    • Wijdicks C.A., Virdi A.S., Sena K., Sumner D.R., Leven R.M. Ultrasound enhances recombinant human BMP-2 induced ectopic bone formation in a rat model. Ultrasound Med Biol 2009, 35:1629-1637.
    • (2009) Ultrasound Med Biol , vol.35 , pp. 1629-1637
    • Wijdicks, C.A.1    Virdi, A.S.2    Sena, K.3    Sumner, D.R.4    Leven, R.M.5
  • 51
    • 1142309526 scopus 로고    scopus 로고
    • Influence of therapeutic ultrasound on skeletal muscle regeneration following blunt contusion
    • Wilkin L.D., Merrick M.A., Kirby T.E., Devor S.T. Influence of therapeutic ultrasound on skeletal muscle regeneration following blunt contusion. Int J Sports Med 2004, 25:73-77.
    • (2004) Int J Sports Med , vol.25 , pp. 73-77
    • Wilkin, L.D.1    Merrick, M.A.2    Kirby, T.E.3    Devor, S.T.4
  • 52
    • 0030250583 scopus 로고    scopus 로고
    • Lewallen DG, Kinnick RR, Greenleaf JF, Bolander ME. Exposure to low-intensity ultrasound increases aggrecan gene expression in a rat femur fracture model
    • Yang K.H., Parvizi J., Wang S.J. Lewallen DG, Kinnick RR, Greenleaf JF, Bolander ME. Exposure to low-intensity ultrasound increases aggrecan gene expression in a rat femur fracture model. J Orthop Res 1996, 14:802-809.
    • (1996) J Orthop Res , vol.14 , pp. 802-809
    • Yang, K.H.1    Parvizi, J.2    Wang, S.J.3
  • 53
    • 0025638970 scopus 로고
    • Macrophage responsiveness to therapeutic ultrasound
    • Young S.R., Dyson M. Macrophage responsiveness to therapeutic ultrasound. Ultrasound Med Biol 1990, 16:809-816.
    • (1990) Ultrasound Med Biol , vol.16 , pp. 809-816
    • Young, S.R.1    Dyson, M.2
  • 54
    • 0025180234 scopus 로고
    • The effect of therapeutic ultrasound on angiogenesis
    • Young S.R., Dyson M. The effect of therapeutic ultrasound on angiogenesis. Ultrasound Med Biol 1990, 16:261-269.
    • (1990) Ultrasound Med Biol , vol.16 , pp. 261-269
    • Young, S.R.1    Dyson, M.2
  • 55
    • 0002353985 scopus 로고
    • Applications of ultrasound in medicine-Comparison with other modalities
    • Plenum, New York, M.H. Repacholi, M. Grandolfo, A. Rindi (Eds.)
    • Ziskin M.C. Applications of ultrasound in medicine-Comparison with other modalities. Ultrasound: Medical applications, biological effects, and hazard potential 1987, 49-59. Plenum, New York. M.H. Repacholi, M. Grandolfo, A. Rindi (Eds.).
    • (1987) Ultrasound: Medical applications, biological effects, and hazard potential , pp. 49-59
    • Ziskin, M.C.1


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