Effects of blood‐flow‐restricted resistance training on muscle function in a 74‐year‐old male with sporadic inclusion body myositis: a case report

Sporadic inclusion body myositis (sIBM) is a systemic disease that is characterized by substantial skeletal muscle weakness and muscle inflammation, leading to impaired physical function. The objective was to investigate the effect of low‐load resistance exercise with concurrent partial blood flow restriction to the working muscles (blood‐flow‐restricted (BFR) training) in a patient with sIBM. The training consisted of 12 weeks of lower extremity BFR training with low training loads (~25‐RM). The patient was tested for mechanical muscle function and functional capacity before and after 6 and 12 weeks of training. Maximal horizontal gait speed increased by 19%, which was accompanied by 38–92% improvements in mechanical muscle function (maximal isometric strength, rate of force development and muscle power). In conclusion, BFR training was well tolerated by the patient with sIBM and led to substantial improvements in mechanical muscle function and gait speed.     

End‐exercise ΔHHb/ΔVO2 and post‐exercise local oxygen availability in relation to exercise intensity

Increased local blood supply is thought to be one of the mechanisms underlying oxidative adaptations to interval training regimes. The relationship of exercise intensity with local blood supply and oxygen availability has not been sufficiently evaluated yet. The aim of this study was to examine the effect of six different intensities (40–90% peak oxygen uptake, VO_2peak) on relative changes in oxygenated, deoxygenated and total haemoglobin (ΔO₂Hb, ΔHHb, ΔTHb) concentration after exercise as well as end‐exercise ΔHHb/ΔVO₂ as a marker for microvascular O₂ distribution. Seventeen male subjects performed an experimental protocol consisting of 3 min cycling bouts at each exercise intensity in randomized order, separated by 5 min rests. ΔO₂Hb and ΔHHb were monitored with near‐infrared spectroscopy of the vastus lateralis muscle, and VO₂ was assessed. ΔHHb/ΔVO₂ increased significantly from 40% to 60% VO₂peak and decreased from 60% to 90% VO₂peak. Post‐exercise ΔTHb and ΔO₂Hb showed an overshoot in relation to pre‐exercise values, which was equal after 40–60% VO_2peak and rose significantly thereafter. A plateau was reached following exercise at ≥80% VO_2peak. The results suggest that there is an increasing mismatch of local O₂ delivery and utilization during exercise up to 60% VO_2peak. This insufficient local O₂ distribution is progressively improved above that intensity. Further, exercise intensities of ≥80% VO_2peak induce highest local post‐exercise O₂ availability. These effects are likely due to improved microvascular perfusion by enhanced vasodilation, which could be mediated by higher lactate production and the accompanying acidosis.     

Non‐adrenergic non‐cholinergic inhibition of gastrointestinal smooth muscle and its intracellular mechanism(s)

Relaxation of gastrointestinal smooth muscle caused by release of non‐adrenergic non‐cholinergic (NANC) transmitters from enteric nerves occurs in several physiologic digestive reflexes. Likely candidate NANC inhibitory agents include nitric oxide (NO), adenosine triphosphate (ATP), vasoactive intestinal peptide (VIP), pituitary adenylate cyclase‐activating peptide (PACAP), carbon monoxide (CO), protease‐activated receptors (PARs), hydrogen sulfide (H₂S), neurotensin (NT) and beta‐nicotinamide adenine dinucleotide (β‐NAD). Multiple NANC transmitters work in concert, are pharmacologically coupled and are closely coordinated. Individual contribution varies regionally in the gastrointestinal tract and between species. NANC inhibition of gastrointestinal smooth muscle involves several intracellular mechanisms, including increase of cyclic guanosine monophosphate (cGMP), increase of cyclic adenosine monophosphate (cAMP) and hyperpolarization of the cell membrane via direct or indirect activation of potassium ion (K⁺) channels.     

Effect of chemical immobilization of SDF‐1α into muscle‐derived scaffolds on angiogenesis and muscle progenitor recruitment

The availability of three‐dimensional bioactive scaffolds with enhanced angiogenic capacity that have the capability to recruit tissue specific resident progenitors is of great importance for the regeneration of impaired skeletal muscle. Here, we have investigated whether introduction of chemoattractant factors to tissue specific extracellular matrix promotes cellular behaviour in vitro as well as muscle progenitor recruitment and vascularization in vivo. We developed an interconnective macroporous sponge from decellularized skeletal muscle with maintained biochemical traits of the intact muscle. SDF‐1α, a potent cell homing factor involved in muscle repair, was physically adsorbed or chemically immobilized in these muscle‐derived sponges. The immobilized sponges showed significantly higher SDF‐1α conjugation efficiency along with improved metabolism and infiltration of muscle‐derived stem cells in vitro, and thus generated uniform cellular constructs. In vivo, femoral muscle implantation in rats revealed a negligible immune response in all scaffold groups. We observed enhanced engraftment, neovascularization, and infiltration of CXCR4⁺ cells in the immobilized‐SDF‐1α sponge compared with nonimmobilized controls. Although Pax7⁺ cells identified adjacent to the immobilized‐SDF‐1α implantation site, other factors appear to be necessary for efficient penetration of Pax7⁺ cells into the sponge. These findings suggest that immobilization of cell homing factors via chemical mediators can result in recruitment of cells to the microenvironment with subsequent improvement in angiogenesis.     

Effect of self‐administered stretching on NIRS‐measured oxygenation dynamics

This study determined human skeletal muscle oxygenation dynamics during and after a single bout of self‐administered stretching (SAS) of the plantar flexors. Nine healthy recreationally fit men (n = 7; age = 25·7 years) and women (n = 2; age = 23·5 years) performed two protocols: (i) one bout of SAS for 4 min and (ii) one bout of moderate intensity cycling for 4 min. We used near infrared spectroscopy to measure changes in muscle deoxygenated haemoglobin–myoglobin ([HHb]) and blood volume ([Hb_tot]) of gastrocnemius medialis muscle before, during and after stretching. The SAS caused an increase (P<0·05) in [HHb] during stretching between 60 and 240 s relative to baseline, but not at 30 s. No significant difference was found for [Hb_tot] at any time interval during SAS. Furthermore, the increase in local blood flow (suggested by [Hb_tot] changes) was found to be significantly increased relative to baseline at 1, 5 and 10 min after SAS, thus providing novel evidence for a poststretch hyperaemia. No significant interaction for [HHb] was found between stretching and cycling conditions, suggesting that the metabolic disturbance during stretching closely resembles moderate intensity exercise. These findings suggest that a single self‐administered stretch for 60 s can produce a substantial microcirculatory event and that blood flow may be enhanced for up to 10 min after stretching.     

In vitro effects of the cyclooxygenase inhibitor indomethacin and of the phospholipase‐C inhibitor U‐73122 on carbachol‐induced contractions of porcine detrusor muscle

Prostaglandin synthetase inhibitors belong to one substance class additionally used in the treatment of bladder dysfunctions associated with involuntary bladder contractions. However, the mechanism of action of non‐steroidal anti‐inflammatory drugs (NSAIDs) on the detrusor muscle is not clear. In this study, it was examined in vitro whether the NSAID indomethacin exhibited an inhibitory effect on carbachol‐induced contractions of the porcine detrusor muscle. Additionally, the inhibitory effect of the phospholipase‐C inhibitor U‐73122 on carbachol‐induced contractions of the porcine detrusor muscle was investigated. Experiments were performed on the muscle strips of the porcine detrusor muscle suspended in a tissue bath. Effects of indomethacin at 10^?6 and 10^?5 m on the maximum carbachol‐induced contraction and on the carbachol–response curve were investigated. Additionally, the inhibitory influence of U‐73122 at a concentration of 10^?5.5 m on the carbachol–response curve was investigated. Pretreatment with indomethacin at both concentrations did not result in a significant reduction in the maximum contraction compared with the control. In the experiments in which carbachol concentration‐response curves were generated, indomethacin exhibited at both concentrations a very small but significant change at carbachol concentrations of 10^?8 and 10^?7.5 m . In the experiments with U‐73122, a significant change was found in the concentration–response curve of carbachol at all concentrations of carbachol from 10^?6.5 to 10^?4 m . The mean maximum carbachol‐induced contraction was 141.8 ± 6.8% after incubation with U‐73122 and 166.0 ± 6.4% in the control group (P < 0.05). Indomethacin did not inhibit the carbachol‐induced contractions of the porcine detrusor muscle. The cyclooxygenase does not play a significant role in the carbachol‐induced bladder contraction of the porcine detrusor muscle. The inhibitory action of the phospholipase‐C inhibitor U‐73122 on the carbachol‐induced contraction was significant, but small. The results point to an inferior role of this pathway.     

Fabrication of scaffold‐free contractile skeletal muscle tissue using magnetite‐incorporated myogenic C2C12 cells

We have fabricated a functional skeletal muscle tissue using magnetite‐incorporated myogenic cell line C2C12 and a magnetic field. Magnetite‐incorporated C2C12 cells were patterned linearly on a monolayer of fibroblast NIH3T3 cells, using a magnetic field concentrator. After induction of differentiation, the C2C12 cells fused and formed multi‐nucleated myotubes. The 3T3 layer became detached in a sheet‐like manner after cultivation in differentiation medium for 5–8 days. When two separate collagen films were placed on a culture dish as tendon structures, a cylindrical construct was formed. Histological observation of the fabricated cylindrical tissue revealed the presence of multinucleate cells within it. Immunofluorescence staining of the construct showed the presence of sarcomere structures within the construct. Western blot analysis showed that muscle proteins were expressed in the construct. When the construct was stimulated with electric pulses, it exhibited active tension of approximately 1 µ N. These results demonstrate that functional skeletal muscle tissue was formed through magnetic force‐based tissue engineering. This is the first report of fabrication of skeletal muscle tissue with active tension‐generating capability using magnetic force‐based tissue engineering. The scaffold‐free skeletal muscle tissue engineering technique presented in this study will be useful for regenerative medicine, drug screening or use as a bio‐actuator. Copyright © 2010 John Wiley & Sons, Ltd.     

The susceptibility of the knee extensors to eccentric exercise‐induced muscle damage is not affected by leg dominance but by exercise order

The aims of this study were first to compare the response of dominant and non‐dominant legs to eccentric exercise and second, to examine whether there is an effect of exercise order on the magnitude of symptoms associated with intense eccentric protocols. Eighteen young men performed three sets of 30 maximal eccentric isokinetic (60° s^?1) contractions of the knee extensors (range of motion, ROM: 0°–100°, 0 = full extension) using either dominant or non‐dominant leg. They repeated a similar eccentric bout using the contralateral leg 6 weeks later. The sequence of leg's use was allocated to create equally balanced groups. Four indirect markers of muscle damage including subjective pain intensity, maximal isometric strength, muscle stiffness and plasma creatine kinase (CK) activity were measured before and 24 h after exercise. All markers changed significantly following the eccentric bout performed either by dominant or non‐dominant legs, but no significant difference was observed between legs. Interestingly, the comparison between the first and second eccentric bouts revealed that muscle soreness (?42%, P<0·001), CK activity (?62%, P<0·05) and strength loss (?54%, P<0·01) were significantly lower after the second bout. This study suggests that leg dominance does not influence the magnitude of exercise‐induced muscle damage and supports for the first time the existence of a contralateral protection against exercise‐induced muscle damage in the lower limbs.     

Potential induction of rat muscle‐derived stem cells to neural‐like cells by retinoic acid

Several recent studies have demonstrated that stem cell differentiation can be generated by derivatives of retinoic acid. In this study we chose retinoic acid (RA) for inducing neural differentiation of rat muscle‐derived stem cells (rMDSCs). rMDSCs were pre‐induced with 10 ng/ml basic fibroblast growth factor (bFGF) and then treated with 2 μM RA. After stimulation, RA induced rMDSCs to have a neural‐like morphology after 1–7 days of in vitro differentiation. In the results of immunocytochemistry, rMDSC treated with RA showed abundant positive cells against the neuronal markers neuronal‐specific enolase (NSE) and tubulin‐βIII (Tuj1). Also, 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase (CNPase)‐positive cells were observed, indicating oligodendrocyte lineage cells. However, positive cells against glial fibrillary acidic protein (GFAP), marker of astrocytes, were not detected. The mRNA profile of these cells included higher expression of NSE compared with those of non‐treated cells in real‐time PCR. From the data in this work, we suggest that rMDSCs can trans‐differentiate into a neural‐like phenotype under the RA conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Ultrasound Findings of Delayed‐Onset Muscle Soreness

The purpose of this series was to retrospectively characterize the ultrasound findings of delayed‐onset muscle soreness (DOMS). The Institutional Review Board approved our study, and informed consent was waived. A retrospective search of radiology reports using the key phrase “delayed‐onset muscle soreness” and key word “DOMS” from 2001 to 2015 and teaching files was completed to identify cases. The sonograms were reviewed by 3 fellowship‐trained musculoskeletal radiologists by consensus. Sonograms were retrospectively characterized with respect to echogenicity (hypoechoic, isoechoic, or hyperechoic), distribution of muscle involvement, and intramuscular pattern (focal versus diffuse and well defined versus poorly defined). Images were also reviewed for muscle enlargement, fluid collection, muscle fiber disruption, and increased flow on color or power Doppler imaging. There were a total of 6 patients identified (5 male and 1 female). The average age was 22 years (range, 7–44 years). Of the 6 patients, there were a total of 11 affected muscles in 7 extremities (1 bilateral case). The involved muscles were in the upper extremity: triceps brachii in 27% (3 of 11), biceps brachii in 18% (2 of 11), brachialis in 18% (2 of 11), brachioradialis in 18% (2 of 11), infraspinatus in 9% (1 of 11), and deltoid in 9% (1 of 11). On ultrasound imaging, the abnormal muscle was hyperechoic in 100% (11 of 11), well defined in 73% (8 of 11), poorly defined in 27% (3 of 11), diffuse in 73% (8 of 11), and focal in 27% (3 of 11). Increased muscle size was found in 82% (9 of 11) and minimal hyperemia in 87.5% (7 of 8). The ultrasound findings of DOMS include hyperechoic involvement of an upper extremity muscle, most commonly appearing well defined and diffuse with increased muscle size and minimal hyperemia.     

Effects of eccentric jaw exercise on temporal summation in jaw‐closing muscles of healthy subjects

Eccentric jaw exercises has been known to cause muscle soreness but no studies have so far examined to what extent temporal summation mechanisms within the exercised muscles are changed. The purpose of the present study was to investigate the effects of an eccentric biting exercise on the temporal summation, mechanical pressure sensitivity and jaw muscle activity. A total of 15 healthy men participated in a two‐session‐experiment: In one session, they performed 30 min controlled eccentric jaw exercise and the other session served as a no‐exercise control. Soreness sensations at rest and during maximal biting, pressure pain thresholds (PPTs) and electromyographic (EMG) activity during maximal jaw biting were recorded before (baseline), immediately after (Post‐task), and 1 day after the exercise (1‐day‐after). The temporal summation ratio using intra‐muscular electrical stimulation of the masseter was investigated at baseline and at 1‐day‐after. The eccentric jaw exercise was associated with significant increases in soreness sensation and decreased PPTs at Post‐task and at 1‐day‐after. The EMG activity and biting force did not change. The summation ratio was significantly decreased at 1‐day‐after in both sessions. The present findings demonstrate that eccentric jaw exercise does not induce detectable changes in temporal summation. However, the summation ratio may have clinical utility to differentiate the location of sensitization.     

Angiogenic gene‐modified myoblasts promote vascularization during repair of skeletal muscle defects

Vascularization is thought to be a principle obstacle in the reconstruction of skeletal muscle defects. Long‐term survival of reconstructed skeletal muscle is dependent on good vascularization. In this study, we upregulated angiogenic gene expression in myoblasts in an attempt to promote vascularization during repair of skeletal muscle defects. Skeletal myoblasts were isolated and expanded from newborn male Sprague–Dawley (SD) rats. The cells were transfected with human vascular endothelial growth factor 165 (VEGF‐165) or human stromal cell‐derived factor 1 (SDF‐1), using Lipofectamine? 2000 transfection reagent, prior to seeding onto calf collagen scaffolds. Gene and protein overexpression was verified by ELISA, RT–PCR and western blot analysis. Cell‐seeded scaffolds were transplanted into back muscle defects in female SD rats. At weeks 2, 4 and 8 after transplantation, Y chromosome detection was used to observe the survival of growth factor‐producing cells within the scaffolds in vivo. Capillary density was investigated using microvessel density detection, haematoxylin and eosin (H&E) staining and immunohistochemical staining. We found that vascularization was enhanced by transfected myoblasts compared with non‐transfected myoblasts. In addition, VEGF‐165 and SDF‐1 had a synergistic effect on vascularization during repair of skeletal muscle defects in vivo. In conclusion, we have combined myoblast‐seeded collagen sponge with gene therapy, resulting in a promising approach for the construction of well‐vascularized skeletal muscle. Copyright © 2013 John Wiley & Sons, Ltd.     

Endothelium‐dependent and endothelium‐independent effects of 1‐nitro‐2‐propylbenzene on rat aorta

A group of nitro compounds contains a benzene ring in a short aliphatic chain with the NO₂ group, property that supposedly favors its vasodilator profile. In this study, we evaluated in isolated rat aorta the effects of 1‐nitro‐2‐propylbenzene (NPB), a nitro compound containing the NO₂ in the aromatic ring. In aorta precontracted with KCl, NPB (1‐3000 μm ) induced full endothelium‐independent relaxation. In endothelium‐intact preparations, phenylephrine‐induced contractions were fully relaxed by NPB, effect unaltered by N(ω)‐nitro‐L‐arginine methyl ester (L‐NAME) or 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ). In the concentration range of 30–300 μm , NPB slightly but significantly potentiated the phenylephrine‐induced contraction. Such potentiation was unaltered by the thromboxane‐prostanoid receptor antagonist seratrodast, but was abolished by endothelium removal or by preincubation of endothelium‐intact preparations with L‐NAME, ODQ or by ruthenium red and HC‐030031, blockers of subtype 1 of ankyrin transient receptor potential (TRPA₁) channels. Verapamil exacerbated the potentiating effect of NPB. The potentiating effect was undetectable in preparations precontracted by 9,11‐dideoxy‐11α,9α‐epoxymethanoprostaglandin F2α (U‐46619). Relaxation was reduced by ruthenium red while it was enhanced by HC‐030031. In conclusion, NPB has vasodilator properties but with a mechanism of action distinct from its analogues. Contrary to other nitro compounds, its relaxing effects did not involve recruitment of the guanylyl cyclase pathway. NPB has also endothelium‐dependent potentiating properties on phenylephrine‐induced contractions, a phenomenon that putatively required a role of endothelial TRPA₁ channels. The present findings reinforce the notion that the functional group NO₂ in the aliphatic chain of these nitro compounds determines favorably their vasodilator properties.     

Aggregated low‐density lipoprotein induce impairment of the cytoskeleton dynamics through urokinase‐type plasminogen activator/urokinase‐type plasminogen activator receptor in human vascular smooth muscle cell

Summary. Background: Urokinase‐type plasminogen activator (UPA) regulates vascular smooth muscle cell (VSMC) functions relevant in vascular remodeling by facilitating proteolysis at the cell surface and inducing cell signaling pathways. Our previous results demonstrated that aggregated low‐density lipoprotein (agLDL) impair cytoskeleton dynamics, a key event contributing to VSMC behavior during progression of atherosclerotic plaques. Objectives: To investigate whether mechanisms underlying inhibition of cytoskeleton dynamics in lipid‐loaded VSMC occurs through a UPA‐mediated process. Methods: Adhesion assay was performed in lipid‐loaded human VSMC after 16‐h exposition to agLDL (100 μg mL^?1). Protein subcellular localization and actin‐fiber formation were assessed by confocal microscopy. For analysis of protein expression western blots were carried out. Co‐immunoprecipitates of UPAR were examined by one‐dimensional‐ or two‐dimensional electrophoresis (1‐DE or 2‐DE), mass spectrometry MALDI‐TOF and western blot. Results: agLDL induced UPA subcellular delocalization and significantly decreased UPA levels during attachment of VSMC. UPA (enhanced endogenous‐expression or exogenous added) acting as a urokinase‐type plasminogen activator receptor (UPAR)‐ligand restored actin‐cytoskeleton organization and adhesion capacity of lipid‐loaded cells to control levels. UPAR co‐immunoprecipitated with the unphosphorylated form of myosin regulatory light chain (MRLC) in lipid‐loaded cells. The detrimental effects of agLDL on MRLC phosphorylation were reversed by high levels of UPA. The UPA effects on VSMC exposed to agLDL involved FAK phosphorylation. Conclusions: The detrimental effects of atherogenic LDL on VSMC are mediated by a decrease and delocalization of the UPA–UPAR interaction that result in an impairment of cytoskeleton dynamics and adhesion capacity affecting cell phenotype and function.