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Bone loss in the lower leg during 35 days of bed rest is predominantly from the cortical compartment
Joern Rittweger, Boštjan Šimunič, Giancarlo Bilancio, Natale Gaspare De Santo, Massimo Cirillo, Gianni Biolo, Rado Pišot, Ola Eiken, Igor B. Mekjavić, Marco Narici, 2009, izvirni znanstveni članek

Opis: Immobilization-induced bone loss is usually greater in the epiphyses than in the diaphyses. The larger fraction of trabecular bone in the epiphyses than in the diaphyses offers an intuitive explanation to account for this phenomenon. However, recent evidence contradicts this notion and suggests that immobilization-induced bone loss from the distal tibia epiphysis is mainly from the cortical compartment. The aim of this study was to establish whether this pattern of bone loss was a general rule during immobilization. Wemonitored various skeletal sites with different tissue composition during 5 weeks of immobilization. Ten healthy male volunteers with mean age of 24.3 years (SD 2.6 years) underwent strict horizontal bed rest. Bone scans were obtained during baseline data collection, at the end of bed rest and after 14 days of recovery by peripheral Quantitative Computed Tomography (pQCT). Sectional images were obtained from the distal tibia epiphysis (at 4% of the tibia's length), from the diaphysis (at 38%), from the proximal metaphysis (at 93%) and from the proximal epiphysis (at 98%), as well as from the distal femur epiphysis (at 4% of the femur's length) and from the patella. Relative bone losses were largest at the patella, where they amounted to - 3.2% (SD 1.8%, p < 0.001) of the baseline values, and smallest at the tibia diaphysis, where they amounted to - 0.7% (SD 1.0%, p = 0.019). The relative losses were generally larger from cortical than from trabecular compartments (p = 0.004), and whilst all skeletal sites depicted such cortical losses, substantial trabecular losses were found only from the proximal tibia epiphysis. Results confirm that the differential losses from the various skeletal sites cannot be explained on the basis of trabecular vs. cortical tissue composition differences, but that endocortical circumference can account for the different amounts of bone loss in the tibia. The present study therefore supports the suggestion of the subendocortical layer as a transitional zone, which can readily be transformed into trabecular bone in response to immobilization. The latter will lead to cortical thinning, a factor that has been associated with the risk of fracture and with osteoarthritis.
Najdeno v: osebi
Ključne besede: space flight, simulated microgravity, osteoporosis, exercise, pQCT
Objavljeno: 15.10.2013; Ogledov: 1882; Prenosov: 31
URL Polno besedilo (0,00 KB)

Effects of inactivity on human muscle glutathione synthesis by a double-tracer and single-biopsy approach
Francesco Agostini, Luciano Dalla Libera, Joern Rittweger, Sara Mazzucco, Mihaela Jurdana, Igor B. Mekjavić, Rado Pišot, Luisa Gorza, Marco Narici, Gianni Biolo, 2010, izvirni znanstveni članek

Opis: Oxidative stress is often associated to inactivity-mediated skeletal muscle atrophy. Glutathione is one of the major antioxidant system stimulated, both at muscular and systemic level, by activation of oxidative processes. We measured changes in glutathione availability, oxidative stress induction and atrophy extent mediated by 35-days of experimental bed rest in vastus lateralis muscle of healthy human volunteers. To assess muscle glutathione synthesis, we applied a novel single-biopsy and double-tracer ([2H2]glycine and [15N]glycine) approach based on evaluation of steady-state precursor incorporation in product. The correlations between the traditional (multiple-samples, one-tracer) and new (one-sample, double-tracer infusion) methods were analyzed in erythrocytes by Passing & Bablok and Altman-Bland tests. Muscle glutathione absolute synthesis rate increased following bed rest from 5.5 1.1 to 11.0 1.5 mmol (kg wet tissue / day)-1 (n=9; p=0.02) while glutathione concentration failed to change significantly. Bed rest induced vastus lateralis muscle atrophy, as assessed by pennation angle changes measured by ultrasonography (from 18.6 1.0 to 15.3 0.9 degrees; p=0.01) and thickness changes (from 2.3 0.2 to 1.9 0.1 cm; p<0.001). Moreover, bed rest increased protein oxidative stress, as measured by muscle protein carbonylation changes (from 0.6 0.1 to 1.00 0.1 Oxy RP-1; p<0.04). In conclusion, we developed in erythrocytes a new minimally-invasive method to determine peptide synthesis rate in human tissues. Application of the new method to skeletal muscle suggests that disuse atrophy is associated to oxidative stress induction as well as to compensatory activation of the glutathione system
Najdeno v: osebi
Ključne besede: Antioxidant system, Muscle damage, Oxidative stress, bed rest, muscle glutathione, stable isotopes
Objavljeno: 15.10.2013; Ogledov: 1944; Prenosov: 47
URL Polno besedilo (0,00 KB)

Whole muscle contractile parameters and thickness loss during 35-day bed rest
Rado Pišot, Marco Narici, Boštjan Šimunič, Maarten D. de Boer, Olivier Seynnes, Mihaela Jurdana, Gianni Biolo, Igor B. Mekjavić, 2008, izvirni znanstveni članek

Opis: Extended exposure to microgravity leads to significant musculoskeletal adaptations. Contractile parameters of four skeletal muscles (biceps brachii-BB, vastus medialis-VM, biceps femoris-BF and gastrocnemius medialis-GM) were measured in ten healthy males (aged 22.3 +/- 2.2 years) during 35 days of horizontal bed rest by a mechanomyography-based method termed 'tensiomyography' (TMG). Two contractile parameters: contraction time (Tc) and maximal displacement (Dm) were individually measured from electrically evoked maximal single twitch TMG response of all four muscles before and after bed rest. Significant changes in Tc were found after bed rest, as shown by an increase in GM muscle Tc by 18% (p < 0.01). Dm values significantly increased (p < 0.01) after bed rest, by 24, 26 and 30% in the VM, BF and GM muscles, respectively. In the GM, the change in Dm significantly correlated with the decrease in muscle thickness (r = -0.70, p < 0.01). In conclusion, bed rest induced changes in both Dm and Tc of the TMG signal; changes in Dm being inversely related to those of muscle thickness. Amongst the investigated muscles, most affected, in terms of atrophy and mechanical alterations, were those of the lower limbs. The observed increase in Dm may be attributed to a decrease in muscle, as well as tendon stiffness, causing larger muscle fibre and non-contractile tissue oscillations following contraction.
Najdeno v: osebi
Ključne besede: Bed rest, skeletal muscle, muscle contraction, muscle thickness, mechanomyography, tensiomiography, ultrasound
Objavljeno: 15.10.2013; Ogledov: 2039; Prenosov: 49
URL Polno besedilo (0,00 KB)
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Effect of 5 weeks horizontal bed rest on human muscle thickness and architecture of weight bearing and non-weight bearing muscles
Maarten D. de Boer, Olivier Seynnes, Pietro di Prampero, Rado Pišot, Igor B. Mekjavić, Gianni Biolo, Marco Narici, 2008, izvirni znanstveni članek

Opis: The aim of the present study was to investigate the changes in thickness, fascicle length (L f) and pennation angle of the antigravity gastrocnemiusmedialis (GM) and vastus lateralis (VL) muscles, and the non-antigravity tibialis anterior (TA) and biceps brachii (BB) muscles measured by ultrasonography in ten healthy males (aged 22.3 +/- 2.2 years) in response to 5 weeks of horizontal bed rest (BR). After BR, muscle thickness decreased by 12.2 +/- 8.8% (P < 0.05) and 8.0 +/- 9.1% (P < 0.005) in the GM and VL, respectively. No changes were observed in the TA and BB muscles. L f and pennation angle decreased by 4.8 +/- 5.0% (P < 0.05) and 14.3 +/- 6.8% (P < 0.005) in the GM and by 5.9 +/- 5.3% (P < 0.05) and 13.5 +/- 16.2% (P < 0.005) in the VL, again without any changes in the TA and BB muscles. The finding that amongst the antigravity muscles of the lower limbs, the GM deteriorated to a greater extent than the VL is possibly related to the differences in relative load that this muscle normally experiences during daily loading. The dissimilar response in antigravity and non-antigravity muscles to unloading likely reflects differences in loading under normal conditions. The significant structural alterations of the GM and VL muscles highlight the rapid remodelling of muscle architecture occurring with disuse.
Najdeno v: osebi
Ključne besede: muscle, disuse, microgravity, atrophy
Objavljeno: 15.10.2013; Ogledov: 1965; Prenosov: 51
URL Polno besedilo (0,00 KB)
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Odziv sestave telesa, mišične togosti in ravnotežja po 35-dnevni odsotnosti gibanja pri mladih in zdravih preiskovancih
Boštjan Šimunič, Joern Rittweger, Gregor Cankar, Mihaela Jurdana, Tadeja Volmut, Tina Šetina, Igor B. Mekjavić, Rado Pišot, 2008, izvirni znanstveni članek

Opis: Uvod: Problemi sedečega načina sodobnega življenja se kažejo v fizioloških odzivih, tako pri starejših kot tudi pri mlajših ljudeh. Cilj raziskave je bilugotoviti odziv morfoloških in skeletno-mišičnih značilnosti ter izgubo funkcionalnih sposobnosti ohranjanja ravnotežja po 35-dnevni popolni gibalni nedejavnosti in zagotovljeni uravnoteženi prehrani glede na njeno sestavo in preiskovančevo telesno težo. Metode: Deset moških preiskovancev (starih 24,32,6 let) je v bolnišničnem okolju preležalo 35 dni v vodoravnem položaju. Fiziološke odzive telesa smo vrednotili z merjenji telesne, maščobne in mišične mase, mineralne vsebnosti sprednje golenske kosti, togosti trebuha dveh funkcionalno različnih glav antigravitacijske mišice in sposobnost ohranjanja ravnotežja. Rezultati: Preiskovanci so v povprečju značilno izgubili 0,97 % (P=0,001) telesne teže, 4,1 % (P=0,009) mišične mase in 1,7 % (P=0,000) mineralne gostote tibialne kosti ter pridobili 1,4 % (P<0,000) maščobne mase. Mišična togost se je značilno zmanjšala od 8. dne ležanja (P=0,006) dalje pri distalni in že od 1. dneva (P=0,007) dalje pri proksimalniglavi notranje stegenske mišice ter se 14. dan po zaključku BR vrnila v izhodiščno stanje le pri distalni glavi. Po zaključku BR in dan kasneje smo ugotovili značilno izgubo ohranjanja ravnotežja za 9,5 % (P=0,006), in 17,4 % (P=0,000), medtem ko 14. dan po zaključku ležanja ni biloveč značilnih razlik. Zaključek: Povzamemo lahko, da z uravnoteženo prehrano lahko omejimo izgubo telesne teže in pridobivanje maščobne mase, vendar ne moremo zmanjšati izgube mišične mase ter mineralne vsebnosti tibialne kosti. Ugotovili smo, da se mišična togost zmanjšuje v dveh časovno zakasnjenih procesih. Sposobnost ohranjanja ravnotežja je zmanjšana v vsaj prvih 24 urah po zaključku ležanja.
Najdeno v: osebi
Ključne besede: popolna gibalna neaktivnost, okoljska fiziologija, tenziomiografija, ravnotežje, morfologija, kostna mineralna vsebnost, mišična togost
Objavljeno: 15.10.2013; Ogledov: 2055; Prenosov: 28
URL Polno besedilo (0,00 KB)

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