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Muscle Hypertrophy (muscle + hypertrophy)
Kinds of Muscle Hypertrophy Selected AbstractsGreater growth hormone and insulin response in women than in men during repeated bouts of sprint exerciseACTA PHYSIOLOGICA, Issue 2 2009M. Esbjörnsson Abstract Aim:, In a previous study, sprint training has been shown to increase muscle cross-sectional area in women but not in men [Eur J Appl Physiol Occup Physiol 74 (1996) 375]. We hypothesized that sprint exercise induces a different hormonal response in women than in men. Such a difference may contribute to explaining the observed gender difference in training response. Method:, Metabolic and hormonal response to three 30-s sprints with 20-min rest between the sprints was studied in 18 physically active men and women. Results:, Accumulation of blood lactate [interaction term gender (g) × time (t): P = 0.022], and plasma ammonia (g × t: P < 0.001) after sprint exercise was greater in men. Serum insulin increased after sprint exercise more so in women than in men (g × t: P = 0.020), while plasma glucose increased in men, but not in women (g × t: P < 0.001). Serum growth hormone (GH) increased in both women and men reaching similar peak levels, but with different time courses. In women the peak serum GH level was observed after sprint 1, whereas in men the peak was observed after sprint 3 (g × t; P < 0.001). Serum testosterone tended to decrease in men and increase in women (g × t: P = 0.065). Serum cortisol increased approx. 10,15% after sprint exercise, independent of gender (time: P = 0.005). Conclusion:, Women elicited a greater response of serum GH and insulin to sprint exercise. This may contribute to explaining the earlier observed muscle hypertrophy in women in response to sprint training. [source] The adaptive responses in several mediators linked with hypertrophy and atrophy of skeletal muscle after lower limb unloading in humansACTA PHYSIOLOGICA, Issue 2 2009K. Sakuma Abstract Aim:, To determine the adaptive changes in several molecules regulating muscle hypertrophy and atrophy after unloading, we examined whether unilateral lower limb suspension changes the mRNA and protein levels of SRF-linked (RhoA, RhoGDI, STARS and SRF), myostatin-linked (myostatin, Smad2, Smad3 and FLRG) and Foxo-linked (P-Akt, Foxo1, Foxo3a and Atrogin-1) mediators. Methods:, A single lower limb of each of eight healthy men was suspended for 20 days. Biopsy specimens were obtained from the vastus lateralis muscle pre- and post-suspension. Results:, The volume of the vastus lateralis muscle was significantly decreased after unloading. The amount of RhoA, RhoGDI or SRF protein in the muscle was not significantly changed post-suspension. An RT-PCR semiquantitative analysis showed increased levels of myostatin mRNA but not Smad2, Smad3 or FLRG mRNA. Unloading did not elicit significant changes in the amount of p-Smad3 or myostatin protein in the muscle. The amount of p-Akt protein was markedly reduced in the unloaded muscle. Lower limb suspension did not influence the expression pattern of Foxo1, Foxo3a or Atrogin-1. Conclusion:, Unloading inducing a mild degree of muscle atrophy may decrease p-Akt and increase myostatin but not SRF-linked mediators. [source] The expression patterns of Pax7 in satellite cells during overload-induced rat adult skeletal muscle hypertrophyACTA PHYSIOLOGICA, Issue 4 2009M. Ishido Abstract Aim:, Activated satellite cells (SCs) have the ability to reacquire a quiescent, undifferentiated state. Pax7 plays a crucial role in allowing activated SCs to undergo self-renewal. Because the increase in the SC population is induced during overload-induced skeletal muscle hypertrophy, it is possible that Pax7-regulated SC self-renewal is involved in the modulation of the SC population during the functional overload of skeletal muscles. However, the characteristics of the expression patterns of Pax7 in SCs during the functional overload of adult skeletal muscles are poorly understood. Methods:, Using immunohistochemical approaches, we examined the temporal and spatial expression patterns of Pax7 expressed in SCs during the functional overloading of rat skeletal muscles. Results:, The time course of Pax7 expression in SCs was similar to that of the expression of the differentiation regulatory factor myogenin during the early stage of functional overload. However, the percentage of SCs that expressed Pax7 was markedly higher than that of the SCs that expressed myogenin. Coexpression of Pax7 and myogenin was not detected in SCs. In addition, the expression of cyclin-dependent kinase inhibitor p21, which regulates cell cycle arrest and differentiation, was not detected in Pax7-positive SCs. Conclusion:, These results suggest that Pax7-regulated self-renewal of SCs may be induced during the early stage of functional overload and may contribute to modulating the SC population in hypertrophied muscles. Furthermore, it was suggested that the numbers of SCs which underwent self-renewal may be higher than that of SCs which were provided as the additional myonuclei for hypertrophying myofibres. [source] Changes in skeletal muscle size, fibre-type composition and capillary supply after chronic venous occlusion in ratsACTA PHYSIOLOGICA, Issue 4 2008S. Kawada Abstract Aim:, We have previously shown that surgical occlusion of some veins from skeletal muscle results in muscle hypertrophy without mechanical overloading in the rat. The present study investigated the changes in muscle-fibre composition and capillary supply in hypertrophied muscles after venous occlusion in the rat hindlimb. Methods:, Sixteen male Wistar rats were randomly assigned into two groups: (i) sham operated (sham-operated group; n = 7); (ii) venous occluded for 2 weeks (2-week-occluded group; n = 9). At the end of the experimental period, specimens of the plantaris muscle were dissected from the hindlimbs and subjected to biochemical and histochemical analyses. Results:, Two weeks after the occlusion, both the wet weight of plantaris muscle relative to body weight and absolute muscle weight showed significant increases in the 2-week-occluded group (,15%) when compared with those in the sham-operated group. The concentrations of muscle glycogen and lactate were higher in the 2-week-occluded group, whereas staining intensity of muscle lipid droplets was lower in the 2-week-occluded group than those in the sham-operated group. The percentage of type I muscle fibre decreased, whereas that of type IIb fibre increased in the 2-week-occluded group when compared with the sham-operated group. Although the expression of vascular endothelial growth factor-188 mRNA increased, the number of capillaries around the muscle fibres tended to decrease (P = 0.07). Conclusion:, Chronic venous occlusion causes skeletal muscle hypertrophy with fibre-type transition towards faster types and changes in contents of muscle metabolites. [source] Alterations of M-cadherin, neural cell adhesion molecule and , -catenin expression in satellite cells during overload-induced skeletal muscle hypertrophyACTA PHYSIOLOGICA, Issue 3 2006M. Ishido Abstract Aim:, Neural cell adhesion molecule (NCAM) and M-cadherin are cell adhesion molecules expressed on the surface of skeletal muscle satellite cell (SC). During myogenic morphogenesis, M-cadherin participates in mediating terminal differentiation and fusion of myoblasts by forming a complex with , -catenin and that NCAM contributes to myotube formation by fusion of myoblasts. Hypertrophy and hyperplasia of functionally overloaded skeletal muscle results from the fusion with SCs into the existing myofibres or new myofibre formation by SC,SC fusion. However, the alterations of NCAM, M-cadherin and , -catenin expressions in SCs in response to functional overload have not been investigated. Methods:, Using immunohistochemical approaches, we examined the temporal and spatial expression patterns of these factors expressed in SCs during the functional overload of skeletal muscles. Results:, Myofibres with SCs showing NCAM+/M-cadherin,, NCAM+/M-cadherin+ or NCAM,/M-cadherin+ were detected in overloaded muscles. The percentage changes of myofibres with SCs showing NCAM+/M-cadherin,, NCAM+/M-cadherin+ or NCAM,/M-cadherin+ were elevated in day-3 post-overloaded muscles, and then only the percentage changes of myofibres with SCs showing NCAM,/M-cadherin+ were significantly increased in day-7 post-overload muscles (P < 0.05). Both , -catenin and M-cadherin were co-localized throughout quiescent, proliferation and differentiation stages of SCs. Conclusion:, These results suggested that the expressions of NCAM, M-cadherin and , -catenin in SCs may be controlled by distinct regulatory mechanisms during functional overload, and that interactions among NCAM, M-cadherin and , -catenin in SCs may play important roles to contribute to overload-induced muscle hypertrophy via fusion with each other or into the existing myofibres of SCs. [source] Effects of Botulinum Toxin Type A on Contouring of the Lower FaceDERMATOLOGIC SURGERY, Issue 5 2005Seong Wook Choe MD background. Masseteric muscle hypertrophy is an uncommon condition represented as a swelling of the masseter muscle. Recent reports have demonstrated the successful use of botulinum in the treatment of masseteric hypertrophy. objective. This study was a prospective trial to evaluate the effectiveness of botulinum toxin type A (Botox) in the treatment of masseteric muscle hypertrophy according to doses of 10, 20, and 30 U. materials and methods. Twenty-two patients were referred to the dermatologic clinic for the management of masseteric muscle hypertrophy. Ultrasonographic measurements of the thickness of the masseter muscle were performed, and clinical photographs were taken before treatment and 1, 2, 3, 4, 6, and 9 months after the treatment. results. The median values of percentage reduction of muscle mass were 10.3%, 16.5%, 23.7%, 24.7%, 21.6%, 16.5% in the 10 U group; 11.9%, 18.8%, 24.8%, 27.7%, 26.7%, and 21.8% in the 20 U group; and 12.0%, 19.4%, 25.0%, 27.8%, 37.8%, and 24.1% in the 30 U group. conclusion. The adequate dose of botulinum toxin type A for treatment of masseteric muscle hypertrophy should be above 20 U. The effect of botulinum toxin type A is maintained for at least 9 months as the treatment of masseteric muscle hypertrophy. [source] Muscle, tendon, and somatotropin responses to the restriction of muscle blood flow induced by KAATSU-walk trainingEQUINE VETERINARY JOURNAL, Issue S36 2006T. ABE Summary Objective: The efficacy of KAATSU training has been demonstrated in human athletes, both as a therapeutic method as well as a training aid. The purpose of this study was to investigate the effects of slow walk training combined with restriction of muscle blood flow (KAATSU) on muscle and tendon size. Methods: Six healthy, unfit Standardbred mares performed walking (240 m/min for 10 min and then 5 min recovery) with KAATSU, and 6 mares performed walking without KAATSU. A specially designed elastic cuff1 was placed at the most proximal position of the forelegs and inflated to a pressure of 200,230 mmHg throughout the walking and recovery sessions. The training was conducted once a day, 6 days/week for 2 weeks. Skeletal muscle thickness and tendon thickness were measured using B-mode ultrasound at baseline and after 2 weeks of training. Venous blood samples were obtained before the first acute exercise and 5, 15 and 60 min afterwards. Serum somatotropin concentration was determined using a commercially available equine-specific ELISA kit. Results: The acute increase in plasma somatotropin was 40% greater (P<0.05) in the KAATSU-walk group than in the Control-walk group 5 min after exercise and remained elevated (P<0.05) at 15 and 60 min post exercise compared with the Control-walk group. After 2 weeks of training, muscle thickness increased (P<0.05) 3.5% in the KAATSU-walk group but did not change in the Control-walk group (0.7%). Tendon thickness did not change (P>0.05) in either group. Conclusions: These data demonstrate that KAATSU training can induce muscle hypertrophy in horses and suggest that KAATSU training may provide significant therapeutic/rehabilitative value in horses, as has been shown in man. [source] Effect of amino acid and glucose administration following exercise on the turnover of muscle protein in the hindlimb femoral region of ThoroughbredsEQUINE VETERINARY JOURNAL, Issue S36 2006A. MATSUI Summary Reasons for performing study: In man, muscle protein synthesis is accelerated by administering amino acids (AA) and glucose (Glu), because increased availability of amino acids and increased insulin secretion, is known to have a protein anabolic effect. However, in the horse, the effect on muscle hypertrophy of such nutrition management following exercise is unknown. Objectives: To determine the effect of AA and Glu administration following exercise on muscle protein turnover in horses. We hypothesise that administration of AA and Glu after exercise effects muscle hypertrophy in horses, as already shown in man and other animals. Methods: Measurements of the rate of synthesis (Rs) and rate of degradation (Rd) of muscle protein in the hindlimb femoral region of thoroughbred horses were conducted using the isotope dilution method to assess the differences between the artery and iliac vein. Six adult Thoroughbreds received a continuous infusion of L-[ring- 2H5]-phenylalanine during the study, the stable period for plasma isotope concentrations (60 min), resting periods (60 min), treadmill exercise (15 min) and recovery period (240 min). All horses were given 4 solutions (saline [Cont], 10% AA [10-AA], 10% Glu [10-Glu] and a mixture with 10% AA and 10% Glu [10-Mix]) over 120 min after exercise, and the Rs and Rd of muscle protein in the hindlimb measured. Results: The average Rs during the 75,120 min following administration of 10-Mix was significantly greater than for the other solutions (P<0.05). The second most effective solution was 10-AA, and there was no change in Rs after 10-Glu. Conclusions: Administration of AA following exercise accelerated Rs in the hindlimb femoral region, and this effect was enhanced when combined with glucose, because of increasing insulin secretion or a decreased requirement for AA for energy. Potential relevance: Further studies are required regarding the effect on muscle hypertrophy of supplementing amino acids and glucose in the feed of exercising horses. [source] Angiotensin-Converting Enzyme Genotype Affects the Response of Human Skeletal Muscle to Functional OverloadEXPERIMENTAL PHYSIOLOGY, Issue 5 2000Jonathan Folland The response to strength training varies widely between individuals and is considerably influenced by genetic variables, which until now, have remained unidentified. The deletion (D), rather than the insertion (I), variant of the human angiotensin-converting enzyme (ACE) genotype is an important factor in the hypertrophic response of cardiac muscle to exercise and could also be involved in skeletal muscle hypertrophy , an important factor in the response to functional overload. Subjects were 33 healthy male volunteers with no experience of strength training. We examined the effect of ACE genotype upon changes in strength of quadriceps muscles in response to 9 weeks of specific strength training (isometric or dynamic). There was a significant interaction between ACE genotype and isometric training with greater strength gains shown by subjects with the D allele (mean ± S.E.M.: II, 9.0 ± 1.7%; ID, 17.6 ± 2.2%; DD, 14.9 ± 1.3%, ANOVA, P 0.05). A consistent genotype and training interaction (ID DD II) was observed across all of the strength measures, and both types of training. ACE genotype is the first genetic factor to be identified in the response of skeletal muscle to strength training. The association of the ACE I/D polymorphism with the responses of cardiac and skeletal muscle to functional overload indicates that they may share a common mechanism. These findings suggest a novel mechanism, involving the renin-angiotensin system, in the response of skeletal muscle to functional overload and may have implications for the management of conditions such as muscle wasting disorders, prolonged bed rest, ageing and rehabilitation, where muscle weakness may limit function. [source] Basement membrane thickening and clinical features of children with asthmaALLERGY, Issue 6 2007E. S. Kim Background:, Asthma is a chronic inflammatory disease, characterized by airway inflammation, bronchial hyper-responsiveness, and airway obstruction. Although asthma induces partially reversible airway obstruction, obstruction can sometimes become irreversible. This may be a consequence of airway remodeling, which includes a number of structural changes, such as epithelial detachment, basement membrane (BM) thickening, smooth muscle hypertrophy, and new vessel formation. This study evaluated children with asthma for the presence of BM thickening. Methods:, Eighteen children with asthma and 24 control subjects underwent flexible bronchoscopy with endobronchial biopsy. Light microscopy was used to measure BM thickness in paraffin-embedded biopsy sections. The association between BM thickening and age, sex, duration of asthma, asthma severity, FEV1, FEV1/FVC, FEF25,75%, methacholine PC20, eosinophil count, and presence of atopy was examined. Results:, Basement membrane thickness was greater in subjects with asthma (8.3 ± 1.4 ,M) than in control subjects (6.8 ± 1.3 ,M, P = 0.0008). Multiple regression analysis revealed that sex, FEV1/FVC, total IgE, and atopy (IgE for Dermatophagoides pteronyssinus >0.34 kUA/l) were significant predictive factors for BM thickness. There was no significant association between BM thickness and age, duration of asthma, FEV1, FEF25,75%, methacholine PC20, eosinophil count, or asthma severity. Conclusions:, Basement membrane thickening has been known to be present in children with asthma. In addition, we report an association between BM thickness and sex, FEV1/FVC, total IgE, and the presence of IgE specific to D. pteronyssinus. [source] Genetic variability in the myostatin gene does not explain the muscle hypertrophy and clinical penetrance in myotonia congenitaMUSCLE AND NERVE, Issue 3 2010Viviane P. Muniz MS No abstract is available for this article. [source] Regulation of STARS and its downstream targets suggest a novel pathway involved in human skeletal muscle hypertrophy and atrophyTHE JOURNAL OF PHYSIOLOGY, Issue 8 2009Séverine Lamon Skeletal muscle atrophy is a severe consequence of ageing, neurological disorders and chronic disease. Identifying the intracellular signalling pathways controlling changes in skeletal muscle size and function is vital for the future development of potential therapeutic interventions. Striated activator of Rho signalling (STARS), an actin-binding protein, has been implicated in rodent cardiac hypertrophy; however its role in human skeletal muscle has not been determined. This study aimed to establish if STARS, as well as its downstream signalling targets, RhoA, myocardin-related transcription factors A and B (MRTF-A/B) and serum response factor (SRF), were increased and decreased respectively, in human quadriceps muscle biopsies taken after 8 weeks of both hypertrophy-stimulating resistance training and atrophy-stimulating de-training. The mRNA levels of the SRF target genes involved in muscle structure, function and growth, such as ,-actin, myosin heavy chain IIa (MHCIIa) and insulin-like growth factor-1 (IGF-1), were also measured. Following resistance training, STARS, MRTF-A, MRTF-B, SRF, ,-actin, MHCIIa and IGF-1 mRNA, as well as RhoA and nuclear SRF protein levels were all significantly increased by between 1.25- and 3.6-fold. Following the de-training period all measured targets, except for RhoA, which remained elevated, returned to base-line. Our results show that the STARS signalling pathway is responsive to changes in skeletal muscle loading and appears to play a role in both human skeletal muscle hypertrophy and atrophy. [source] East Friesian sheep carry a Myostatin allele known to cause muscle hypertrophy in other breedsANIMAL GENETICS, Issue 4 2010C. W. Bignell No abstract is available for this article. [source] The RYR1 g.1843C>T mutation is associated with the effect of the IGF2 intron3-g.3072G>A mutation on muscle hypertrophyANIMAL GENETICS, Issue 1 2007A. Stinckens Summary Muscle growth is a complex phenomenon regulated by many factors, whereby net growth results from the combined action of synthesis and turnover. In pigs, two quantitative trait nucleotides (QTN) are known to have an important influence on muscle growth and fat deposition: one QTN is located in the ryanodine receptor 1 (RYR1) gene (RYR1 g.1843C>T) and the other, a paternally expressed QTN, is in the insulin-like growth factor 2 (IGF2) gene (IGF2 intron3-g.3072G>A). The mutation in IGF2 abrogates in vitro interaction with a repressor, which leads to a threefold increase of IGF2 expression in post-natal muscle. The family of the calpains, a family of Ca2+ -sensitive muscle endopeptidases, and their specific inhibitor calpastatin play an important role in post-natal protein degradation, also influencing muscle and carcass traits. This study investigated the possible interactions between the genotypes of the RYR1 and IGF2 QTN on IGF2 expression. Samples were taken from several muscles and from pigs at several ages, and messenger RNA expression levels were measured using a real-time quantification assay. IGF2 expression in m. longissimus dorsi of animals with mutations in both IGF2 and RYR1 was significantly lower than in animals that inherited the IGF2 mutation but were homozygous wildtype for RYR1. [source] Postnatal changes in the expression of genes located in the callipyge region in sheep skeletal muscleANIMAL GENETICS, Issue 6 2006A. C. Perkins Summary The expression of five genes surrounding the callipyge (CLPG) mutation was analysed in skeletal muscles from lambs at one prenatal and two postnatal ages that coincide with the onset and establishment of muscle hypertrophy. Genotype-specific changes in transcript abundance were detected for paternal allele-specific DLK1 and PEG11 (the official symbol of the latter is RTL1) and the maternal allele-specific MEG3, PEG11AS and MEG8 when the mutation was inherited in cis. There were differences in the temporal and muscle-specific effects on expression between the maternal allele-specific genes and paternal allele-specific genes. Maternal inheritance of the CLPG allele had a significant effect on the expression of MEG3 and MEG8 at prenatal and postnatal ages, whereas paternal inheritance of DLK1 and PEG11 only affected postnatal expression. Genotype-specific changes in PEG11AS expression were detected only in prenatal muscle. Maternal inheritance of the mutation caused similar changes in MEG3 and MEG8 expression in the semimembranosus, which undergoes hypertrophy, and the supraspinatus, which does not hypertrophy. Paternal inheritance of the mutation caused changes in PEG11 expression in both muscles, although the magnitude of expression in semimembranosus was more than 100-fold greater than in supraspinatus. DLK1 expression was upregulated in callipyge animals at both postnatal ages in the semimembranosus, but there was no effect of genotype on DLK1 expression in the supraspinatus at any age. Increased DLK1 expression was likely the primary cause of muscle hypertrophy, but a contribution of PEG11 to the phenotype cannot be ruled out based on gene expression. [source] Mechano-biology of skeletal muscle hypertrophy and regeneration: Possible mechanism of stretch-induced activation of resident myogenic stem cellsANIMAL SCIENCE JOURNAL, Issue 1 2010Ryuichi TATSUMI ABSTRACT In undamaged postnatal muscle fibers with normal contraction and relaxation activities, quiescent satellite cells of resident myogenic stem cells are interposed between the overlying external lamina and the sarcolemma of a subjacent mature muscle fiber. When muscle is injured, exercised, overused or mechanically stretched, these cells are activated to enter the cell proliferation cycle, divide, differentiate, and fuse with the adjacent muscle fiber, and are responsible for regeneration and work-induced hypertrophy of muscle fibers. Therefore, a mechanism must exist to translate mechanical changes in muscle tissue into chemical signals that can activate satellite cells. Recent studies of satellite cells or single muscle fibers in culture and in vivo demonstrated the essential role of hepatocyte growth factor (HGF) and nitric oxide (NO) radical in the activation pathway. These experiments have also reported that mechanically stretching satellite cells or living skeletal muscles triggers the activation by rapid release of HGF from its extracellular tethering and the subsequent presentation to the receptor c-met. HGF release has been shown to rely on calcium-calmodulin formation and NO radical production in satellite cells and/or muscle fibers in response to the mechanical perturbation, and depend on the subsequent up-regulation of matrix metalloproteinase (MMP) activity. These results indicate that the activation mechanism is a cascade of events including calcium ion influx, calcium-calmodulin formation, NO synthase activation, NO radical production, MMP activation, HGF release and binding to c-met. Better understanding of ,mechano-biology' on the satellite cell activation is essential for designing procedures that could enhance muscle growth and repair activities in meat-animal agriculture and also in neuromuscular disease and aging in humans. [source] Whole-body high-field MRI shows no skeletal muscle degeneration in young patients with recessive myotonia congenitaACTA NEUROLOGICA SCANDINAVICA, Issue 2 2010C. Kornblum Kornblum C, Lutterbey GG, Czermin B, Reimann J, von Kleist-Retzow J-C, Jurkat-Rott K, Wattjes MP. Whole-body high-field MRI shows no skeletal muscle degeneration in young patients with recessive myotonia congenita. Acta Neurol Scand: 2010: 121: 131,135. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Background,,, Muscle magnetic resonance imaging (MRI) is the most sensitive method in the detection of dystrophic and non-dystrophic abnormalities within striated muscles. We hypothesized that in severe myotonia congenita type Becker muscle stiffness, prolonged transient weakness and muscle hypertrophy might finally result in morphologic skeletal muscle alterations reflected by MRI signal changes. Aim of the study,,, To assess dystrophic and/or non-dystrophic alterations such as fatty or connective tissue replacement and muscle edema in patients with severe recessive myotonia congenita. Methods,,, We studied three seriously affected patients with myotonia congenita type Becker using multisequence whole-body high-field MRI. All patients had molecular genetic testing of the muscle chloride channel gene (CLCN1). Results,,, Molecular genetic analyses demonstrated recessive CLCN1 mutations in all patients. Two related patients were compound heterozygous for two novel CLCN1 mutations, Q160H and L657P. None of the patients showed skeletal muscle signal changes indicative of fatty muscle degeneration or edema. Two patients showed muscle bulk hypertrophy of thighs and calves in line with the clinical appearance. Conclusions,,, We conclude that (i) chloride channel dysfunction alone does not result in skeletal muscle morphologic changes even in advanced stages of myotonia congenita, and (ii) MRI skeletal muscle alterations in myotonic dystrophy must be clear consequences of the dystrophic disease process. [source] A congenital dermal sinus presenting the muscle fasciculation and hypertrophyACTA NEUROLOGICA SCANDINAVICA, Issue 5 2001M. Takahashi Objective, To report unique and unknown clinical features of muscle fasciculation and muscle hypertrophy in a case of congenital dermal sinus. Patients, A 16-year-old girl presented with continuous fasciculation, often cramp, and hypertrophy of the left calf muscle. The radiography showed spina bifida of L4, L5 and S1. MRI revealed dermal sinus tract from the skin dimple of the back to the dura mater, and connected to the intradural inclusion tumor. At surgery the inclusion tumor contained many short hairs, and the cauda equina were severely adherent. Microdissection of the tumor and the adhesion was performed. At 2 years after surgery fasciculation decreased but continued; however, painful cramps of the calf muscle do not occur. Conclusions, Short hairs of dermoid and the adherence might be irritative to the cauda equina. The hyperactivity of the stimulated motor neuron may cause the muscle fasciculation leading to hypertrophy of the calf muscle. [source] Novel role for ,-adrenergic signalling in skeletal muscle growth, development and regenerationCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2010James G Ryall Summary 1. In adult mammals, skeletal muscle mass is maintained through a precise balance of protein synthesis and protein degradation, whereas during development cellular (not protein) turnover predominates. When protein balance is shifted towards synthesis, skeletal muscle hypertrophy ensues. In contrast, increased protein degradation leads to skeletal muscle atrophy. Insulin-like growth factor (IGF)-I is among the best documented of the growth factors and regulates skeletal muscle mass by increasing protein synthesis and decreasing protein degradation. However, an IGF-I-independent growth pathway has been identified that involves the activation of ,-adrenoceptors and subsequent skeletal muscle growth, development and hypertrophy. 2. Although the importance of ,-adrenergic signalling in the heart has been well documented and continues to receive significant attention, it is only more recently that we have started to appreciate the importance of this signalling pathway in skeletal muscle structure and function. Studies have identified an important role for ,-adrenoceptors in myogenesis and work from our laboratory has identified a novel role for ,-adrenoceptors in regulating skeletal muscle regeneration after myotoxic injury. In addition, new data suggest that ,-adrenoceptors are markedly upregulated during differentiation of C2C12 cells. 3. It is now clear that ,-adrenoceptors play an important role in regulating skeletal muscle structure and function. Importantly, a clearer understanding of the pathways regulating skeletal muscle mass may lead to the identification of novel therapeutic targets for the treatment of muscle wasting disorders, including sarcopenia, cancer cachexia and the muscular dystrophies. [source] Comparative effects of resistance training on peak isometric torque, muscle hypertrophy, voluntary activation and surface EMG between young and elderly womenCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 2 2007Jack Cannon Summary We compared the effect of a 10-week resistance training program on peak isometric torque, muscle hypertrophy, voluntary activation and electromyogram signal amplitude (EMG) of the knee extensors between young and elderly women. Nine young women (YW; range 20,30 years) and eight elderly women (EW; 64,78 years) performed three sets of ten repetitions at 75% 1 repetition maximum for the bilateral leg extension and bilateral leg curl 3 days per week for 10 weeks. Peak isometric torque, EMG and voluntary activation were assessed before, during, and after the training period, while knee extensor lean muscle cross-sectional area (LCSA) and lean muscle volume (LMV) were assessed before and after the training period only. Similar increases in peak isometric torque (16% and 18%), LCSA (13% and 12%), LMV (10% and 9%) and EMG (19% and 21%) were observed between YW and EW, respectively, at the completion of training (P<0·05), while the increase in voluntary activation in YW (1·9%) and EW (2·1%) was not significant (P>0·05). These findings provide evidence to indicate that participation in regular resistance exercise can have significant neuromuscular benefits in women independent of age. The lack of change in voluntary activation following resistance training in both age groups despite the increase in EMG may be related to differences between measurements in their ability to detect resistance training-induced changes in motor unit activity. However, it is possible that neural adaptation did not occur and that the increase in EMG was due to peripheral adaptations. [source] | |||||||||||||