Home About us Contact
|
Home About us Contact | ||
|
|
||
Quadriceps Muscles (quadriceps + muscle)
Selected AbstractsAMP-activated protein kinase in contraction regulation of skeletal muscle metabolism: necessary and/or sufficient?ACTA PHYSIOLOGICA, Issue 1 2009T. E. Jensen Abstract In skeletal muscle, the contraction-activated heterotrimeric 5,-AMP-activated protein kinase (AMPK) protein is proposed to regulate the balance between anabolic and catabolic processes by increasing substrate uptake and turnover in addition to regulating the transcription of proteins involved in mitochondrial biogenesis and other aspects of promoting an oxidative muscle phenotype. Here, the current knowledge on the expression of AMPK subunits in human quadriceps muscle and evidence from rodent studies suggesting distinct AMPK subunit expression pattern in different muscle types is reviewed. Then, the intensity and time dependence of AMPK activation in human quadriceps and rodent muscle are evaluated. Subsequently, a major part of this review critically examines the evidence supporting a necessary and/or sufficient role of AMPK in a broad spectrum of skeletal muscle contraction-relevant processes. These include glucose uptake, glycogen synthesis, post-exercise insulin sensitivity, fatty acid (FA) uptake, intramuscular triacylglyceride hydrolysis, FA oxidation, suppression of protein synthesis, proteolysis, autophagy and transcriptional regulation of genes relevant to promoting an oxidative phenotype. [source] Congenital hypomyelination neuropathy in a newborn infant: unusual cause of diaphragmatic and vocal cord paralysesJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2002JS Hahn We report a case of congenital hypomyelination neuropathy presenting at birth. The infant had generalized hypotonia and weakness. There was decreased respiratory effort along with a right phrenic nerve and left vocal cord paralyses. Tongue fasciculations were present. Deep tendon reflexes were absent in the upper extremities and hypoactive (1+) in the lower extremities. Magnetic resonance imaging of the head revealed no intracranial abnormalities, including normal cerebral myelination. Nerve conduction study showed absence of motor and sensory action potentials in the hands when the nerves in the upper limbs were stimulated. A motor response could be elicited only in the proximal leg muscles. Needle electromyography study was normal in the proximal limb muscles, but showed active denervation in the distal muscles of the arm and leg. These findings were thought to be consistent with a length-dependent sensorimotor peripheral polyneuropathy of axonal type with greater denervation of the distal muscles. A biopsy of the quadriceps muscle showed mild variability in fiber diameter, but no group typing or group atrophy. The muscle fibers showed no intrinsic abnormalities. Biopsy of the sural nerve showed scattered axons with very thin myelin sheaths. There was also a nearly complete loss of large diameter myelinated fibers. No onion bulb formations were noted. These findings were thought to be consistent with congenital hypomyelination neuropathy with a component of axonopathy. DNA analysis for identification of previously characterized mutations in the genes MPZ, PMP22, and EGR2 was negative. Several attempts at extubation failed and the infant became increasingly ventilator-dependent with increasing episodes of desaturation and hypercapnea. He also developed increasing weakness and decreased movement of all extremities. He underwent surgery at 2 months of age for placement of a gastrostomy tube and a tracheostomy. He was discharged from the hospital on a ventilator at 6 months of age. The infant was 13 months old at the time of submission of this report. Although he appears cognitively normal, he remains profoundly hypotonic and is on a home ventilator. There was no evidence of progressive weakness. Congenital hypomyelination neuropathy is a rare form of neonatal neuropathy that should be considered in the differential diagnosis of a newborn with profound hypotonia and weakness. It appears to be a heterogeneous disorder with some of the cases being caused by specific genetic mutations. [source] Postcontraction changes of muscle architecture in human quadriceps muscleMUSCLE AND NERVE, Issue 4 2004Konrad Mahlfeld MD Abstract Maximal voluntary contraction changes the mechanical properties of skeletal muscle. Using ultrasound, we investigated whether these changes are reflected by changes in muscle architecture in the vastus lateralis muscle of 8 healthy volunteers. The mean pennation angle during the time interval from 3 to 6 min after maximal voluntary contraction (late postcontraction state) was 14.4 ± 1.11° (mean ± SEM) and differed significantly from the precontraction state (16.2 ± 1.39°), but the pennation angle in the early postcontraction state did not change statistically from the precontraction angle. Thus, postcontraction changes of the muscle,tendon interface appeared for 6 min after a maximal contraction, which may be important for biomechanical optimization of force transmission in vivo. Muscle Nerve 29: 597,600, 2004 [source] Neuromuscular Electrical Stimulation As a Possible Means to Prevent Muscle Tissue Wasting in Artificially Ventilated and Sedated Patients in the Intensive Care Unit: A Pilot StudyNEUROMODULATION, Issue 4 2010Raf L.J. Meesen PhD Objective:, The aim of this study was to explore if electrical stimulation could prevent muscle atrophy. Material and Methods:, Patients were hospitalized for postoperative coronary artery bypass graftin, chronic obstructive pulmonary disease, ventilatory failure, or acute cerebro-vascular accident, and were divided into an intervention group or a control group. The intervention group underwent daily 30 minute training with an intermittent neuromuscular electrical stimulation applied to the right quadriceps muscle. Heart rate, respiration rate, systolic and diastolic blood pressure, and oxygen saturation were monitored before, during, and after electrical stimulation. Circumference of both thighs was measured. Results:, The intervention resulted in a significant reduction of muscle atrophy in the stimulated as compared with the non-stimulated limb (p < 0.05), without making any impact on cardiovascular, respiratory and, hemodynamic characteristics. Conclusions:, Muscle atrophy is prevented by intermittent neuromuscular electrical stimulation while this intervention showed no obvious impact on the cardio-respiratory conditions of the patients. [source] Feasibility of Gait Event Detection Using Intramuscular Electromyography in the Child with Cerebral PalsyNEUROMODULATION, Issue 3 2004Richard T. Lauer PhD Abstract The objective of this study was to develop and test the feasibility of a model that employs electromyographic (EMG) signals to predict the occurrence of gait events in the child with cerebral palsy (CP). This model could be the basis of a future functional electrical stimulation (FES) control system to assist gait. Two children were implanted with bifilar intramuscular electrodes into the quadriceps muscle bilaterally. Muscle activity and gait parameters were recorded, and a fuzzy inference system was used to correlate EMG to five distinct gait events. For nine of the 10 gait events evaluated, the model predicted gait events to within 82 ms on average, as referenced to the VICON motion analysis system. For eight of the 10 events, prediction errors were 0.3% or less. Results indicate that EMG from the proximal musculature could be used to predict the occurrence of gait events in these two children with CP. [source] Magnetic resonance angiography of collateral vessels in a murine femoral artery ligation modelNMR IN BIOMEDICINE, Issue 1 2004Shawn Wagner Abstract The in vivo detection of growing collateral vessels following arterial occlusion is difficult in small animals. We have addressed the feasibility of performing high resolution time-of-flight angiograms to monitor the growth of collateral vessels after femoral artery occlusion in mice. We will also present a low-pass quadrature birdcage coil construction with a sufficient signal-to-noise ratio to produce high resolution. After a 4-month recovery period a C57BL/6 mouse with a surgical occlusion of the right femoral artery was used to assess the image quality and time requirements to produce magnetic resonance angiograms sufficient to assess collateral artery development using a two-dimensional gradient echo sequence. At a resolution of 100,×,100,×,100,,m and a matrix size of 256,×,128,×,256 for a 2.56,cm isometric volume, three scans were performed with one, two and four repetitions resulting in signal-to-noise ratios for the femoral artery proximal to the ligation site of 58, 126 and 194, respectively. Five C57BL/6 mice were additionally measured 4 weeks after occlusion using two repetitions and the visual collateral vessels were assessed for number and location: 2.0,±,1.2 in quadriceps muscle, 0.6,±,0.5 in adductor (deep adductor vessel), 0.0,±,0.0 in adductor (surface adductor vessels). The results showed a significant difference, two-sided t -test, p,<,0.05, in number of vessels in all the locations. We have shown that this method can be utilized to elucidate the contribution of collateral vessels to arterial flow. Copyright © 2004 John Wiley & Sons, Ltd. [source] Synovial ablation in a rabbit rheumatoid arthritis model using photodynamic therapyANZ JOURNAL OF SURGERY, Issue 7 2002Andrew D. Beischer Background: At present there is no ideal minimally invasive method for ablating inflamed synovium in joints that has been unresponsive to optimal medical management in patients with rheumatoid arthritis. The aim of this study was to determine whether photodynamic therapy could be used for this purpose. Methods: In a rabbit knee model of rheumatoid arthritis the pharmacokinetics of the photosensitizer Haematoporphyrin Derivative (HpD) into periarticular tissues and blood was measured following intravenous injection of HpD. The second phase of the study was to determine the histological effect of HpD activation by 63 nm light delivered via an intra-articular optic fibre using a dye pumped KTP-YAG laser. The light dose was varied from 0,200 joule/cm2. Results: Pharmacokinetic studies determined that inflamed synovium rapidly accumulated HpD, with peak levels being reached 12 h following intravenous injection. The ratio of HpD uptake into inflamed synovium versus peri-articular quadriceps muscle was found to be 22.8. Histological examination of the treated knees indicated that selective destruction of inflamed synovium was achieved at light doses 100 joules/cm2 and above. No significant effect was observed on normal intra-articular tissues. Conclusion: We have demonstrated that the first generation photosensitizer HpD selectively accumulates within inflamed synovium. Activation of HpD by intra-articular light administration resulted in selective ablation of the inflamed synovium. These findings indicate that PDT offers potential as a new selective, minimally invasive synovectomy technique. [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] Intra- and intermuscular variation in human quadriceps femoris architecture assessed in vivoJOURNAL OF ANATOMY, Issue 3 2006Anthony J. Blazevich Abstract Despite the functional importance of the human quadriceps femoris in movements such as running, jumping, lifting and climbing, and the known effects of muscle architecture on muscle function, no research has fully described the complex architecture of this muscle group. We used ultrasound imaging techniques to measure muscle thickness, fascicle angle and fascicle length at multiple regions of the four quadriceps muscles in vivo in 31 recreationally active, but non-strength-trained adult men and women. Our analyses revealed a reasonable similarity in the superficial quadriceps muscles, which is suggestive of functional similarity (at least during the uni-joint knee extension task) given that they act via a common tendon. The deep vastus intermedius (VI) is architecturally dissimilar and therefore probably serves a different function(s). Architecture varies significantly along the length of the superficial muscles, which has implications for the accuracy of models that assume a constant intramuscular architecture. It might also have consequences for the efficiency of intra- and intermuscular force transmission. Our results provide some evidence that subjects with a given architecture of one superficial muscle, relative to the rest of the subject sample, also have a similar architecture in other superficial muscles. However, this is not necessarily true for vastus lateralis (VL), and was not the case for VI. Therefore, the relative architecture of one muscle cannot confidently be used to estimate the relative architecture of another. To confirm this, we calculated a value of whole quadriceps architecture by four different methods. Regardless of the method used, we found that the absolute or relative architecture of one muscle could not be used as an indicator of whole quadriceps architecture, although vastus medialis, possibly in concert with VL and the anterior portion of VI, could be used to provide a useful snapshot. Importantly, our estimates of whole quadriceps architecture show a gender difference in whole quadriceps muscle thickness, and that muscle thickness is positively correlated with fascicle angle whereas fascicle length is negatively, although weakly, correlated with fascicle angle. These results are supportive of the validity of estimates of whole quadriceps architecture. These data are interpreted with respect to their implications for neural control strategies, region-specific adaptations in muscle size in response to training, and gender-dependent differences in the response to exercise training. [source] Predicting the effect of muscle length on fatigue during electrical stimulationMUSCLE AND NERVE, Issue 4 2009M. Susan Marion PhD Abstract Mathematical models have been developed to predict fatigue during functional electrical stimulation, but the predictive accuracy at different muscle lengths is unknown. The objectives of our study were to: (1) experimentally determine the relationship between knee extension angle (20°, 40°, 65°, and 90°) and fatigue of the quadriceps muscles, and (2) predict that relationship using a mathematical model. A computer-controlled stimulator sent trains of pulses to surface electrodes on the thighs of five subjects while forces were measured at the ankle. A two-component mathematical model was developed. One component accounted for force, and the other accounted for fatigue. The model was fit to the data, and parameters were identified at 90°. The fitted subject-averaged r2 value was 0.89. The model was used to predict fatigue at the remaining angles, and the subject-averaged r2 values were >0.75. Therefore, at least 75% of the variability in the measurements was explained by the model. The force model is explicitly dependent on angle, and the fatigue model is explicitly dependent on force; therefore, the dependence of fatigue on knee angle was implicit. Muscle Nerve, 2009 [source] Classic pyomyositis of the extremities as an unusual manifestation of Blastomyces dermatitidis: a report of two casesMYCOSES, Issue 4 2010Michael Y. Lin Summary Pyomyositis is an infection of skeletal muscle that, by definition, arises intramuscularly rather than secondarily from adjacent infection. It is usually associated with bacterial infection, particularly Staphylcococcus aureus. Fungi are rare causes, and Blastomyces dermatitidis has not been reported previously. In this case series, we report two cases of pyomyositis caused by B. dermatitidis. Cases were prospectively identified through routine clinical care at a single academic referral hospital. Two patients with complaints of muscle pain and subacute cough were treated at our hospital in 2007. Both patients were found to have pyomyositis caused by B. dermatitidis, in the quadriceps muscles in one patient, and in the calf muscle in another , by radiological imaging and fungal culture. Both were also diagnosed with pneumonia caused by B. dermatitidis (presumptive in one, confirmed in the other). There was no evidence of infection of adjacent structures, suggesting that the route of infection was likely direct haematogenous seeding of the muscle. A review of the literature confirmed that although B. dermatitidis has been described as causing axial muscle infection secondary to adjacent infection such as vertebral osteomyelitis, our description of isolated muscle involvement (classic pyomyositis) caused by B. dermatitidis, particularly of the extremity muscles, is unique. We conclude that B. dermatitidis is a potential cause of classic pyomyositis. [source] The Effect of Fatigue on the Timing of Electrical Stimulation-Evoked Muscle Contractions in People with Spinal Cord InjuryNEUROMODULATION, Issue 3 2004Peter J. Sinclair PhD Abstract This study investigated the activation dynamics of electrical stimulation-evoked muscle contractions performed by individuals with spinal cord injury (SCI). The purpose was to determine whether electrical stimulation (ES) firing patterns during cycling exercise should be altered in response to fatigue-induced changes in the time taken for force to rise and fall with ES. Seven individuals with SCI performed isometric contractions and pedaled a motorized cycle ergometer with stimulation applied to the quadriceps muscles. Both exercise conditions were performed for five minutes while the patterns of torque production were recorded. ES-evoked knee extension torque fell by 75% under isometric conditions, and the rate of force rise and decline decreased in proportion to torque (r = 0.91, r = 0.94, respectively). There was no change in the time for torque to rise to 50% of maximum levels. The time for torque to decline did increase slightly, but only during the first minute of exercise. Cycling power output fell approximately 50% during the five minutes of exercise, however, there was no change in the time taken for torque to rise or fall. The magnitude of ES-evoked muscle torques decline substantially with fatigue, however, the overall pattern of torque production remained relatively unchanged. These results suggest there is no need to alter stimulation firing patterns to accommodate fatigue during ES-evoked exercise. [source] Early events of electroporation-mediated intramuscular DNA vaccination potentiate Th1-directed immune responsesTHE JOURNAL OF GENE MEDICINE, Issue 9 2005Eirik Grønevik Abstract Background Application of electrical pulses after DNA injection into muscle increases expression of the encoded genes, and is shown to improve antigen-specific immune responses when used for DNA vaccination. In addition, electroporation causes tissue injury and inflammatory reactions. Together with immune stimulatory motifs in the injected DNA these factors may potentiate the immune response by acting as adjuvants for the antigen. Here, we have examined the role of these factors in promoting the efficiency of DNA vaccination. Methods We injected a plasmid DNA vector containing the gene Ag85B from M. tuberculosis into mouse quadriceps muscles followed by electroporation. Ag85B was under control of a Tet-responsive promoter, and was expressed either immediately or up to 28 days later by administrating doxycycline to the mice. Delayed expression was combined with injection of non-coding DNA or saline with or without electroporation to examine the ability of these factors to enhance the Ag85B-specific antibody response in the blood and cellular responses in the spleen. Blood samples were analysed with ELISA, while the number of Ag85B-specific IFN-,- and IL-4-producing spleenocytes was analysed with ELISpot. Results Delaying Ag85B expression by 5 or 28 days caused lower anti-Ag85B-specific IgG2a levels. In contrast, the IgG1 antibody response was not significantly affected. Injection of non-coding DNA followed by electroporation moderately increased the IgG2a response. Delaying the Ag85B expression by 28 days reduced the average number of Ag85B-specific IFN-,-producing spleenocytes by over 60%. No significant change in the number of IL-4-producing Ag85B-specific spleenocytes was observed. Conclusions These results suggest that DNA and electroporation per se may act as good adjuvants in promoting efficient Th1-directed responses during DNA vaccination. Copyright © 2005 John Wiley & Sons, Ltd. [source] In vivo Remote Delivery of DNA Encoding for Hypoxia-inducible Factor 1 Alpha Reduces Myocardial Infarct SizeCLINICAL AND TRANSLATIONAL SCIENCE, Issue 1 2009Gabor Czibik M.D. Abstract We tested if remote gene delivery of hypoxia-inducible factor 1 alpha (HIF-1,) protected hearts against induced ischemia, hypothesizing that gene delivery into skeletal muscle may lead to secretion of proteins with actions elsewhere. Murine quadriceps muscles were transfected with DNA encoding for human HIF-1,, which resulted in a local, but lasting expression (mRNA and protein, where the latter had nuclear localization). Subjection of isolated hearts to global ischemia and reperfusion 1, 4, and 8 weeks after gene delivery resulted in infarct size reduction (p < 0.05). Supporting that this was due to paracrine effects, HL-1 cells treated with conditioned media from cells transfected with HIF-1, or serum from HIF-1,-treated mice were protected against H2O2 -induced cell death (p < 0.05, respectively). The latter protection was reduced when a heme oxygenase activity blocker was used. Taqman low-density array of 47 HIF-1,-regulated genes at the treatment site showed nine specific upregulations (p < 0.05). Of the corresponding proteins, PDGF-B and adrenomedullin were upregulated in the heart. HIF-1, treatment induced an increased vascularization of the heart and skeletal muscle. In conclusion, remote delivery of DNAfor HIF-1, was cardioprotective, represented by consistent infarct size reduction, which may be due to release of paracrine factors from the transfected muscle. [source] | |||||||||||||