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PubMed1996

Markedly improved skeletal muscle function with local muscle training in patients with chronic heart failure.

BACKGROUND: Reduced heart pump function and skeletal muscle abnormalities are considered important determinants for the low physical exercise capacity in chronic heart failure. Because of reduced ventricular function, traditional physical rehabilitation may cause underperfusion and low local work intensity, thereby producing suboptimal conditions for skeletal muscle training. HYPOTHESIS: The study was undertaken to determine the effects of local exercise training, designed as one- or two-legged knee extensor training, on exercise capacity in patients with moderate chronic heart failure. Because such exercise models use only about one quarter to half the muscle mass used in cycle ergometer training, the influence of a restricted circulatory capacity should therefore be limited. Further, we aimed to determine whether or not chronic heart failure skeletal musculature abnormalities are counteracted with such training. METHODS: Fourteen patients with chronic heart failure [age 58 +/- 3 years, ejection fraction (EF) 28 +/- 4%] were randomized to two different training protocols three times a week for 8 weeks and compared with a nontraining control group (n = 7, age 62 +/- 3, EF 27 +/- 3%). Group 2L (n = 7) underwent simultaneous two-legged knee extensor training (about 4 kg working muscle) for 15 min at 65-75% of VO2 max of the two-legged kick. Group 1L (n = 7) trained each leg at a time for 15 min of continuous one-legged dynamic knee extensor work with the same training load per muscle mass, that is, at 35% of VO2 max of the two-legged kick (about 2 kg working muscle). Peak VO2 of two-legged knee extensor exercise (l/min), two-legged endurance (W), and strength (Nm) were determined before and after the training period. The activity of citrate synthase (CS) was estimated in tissue samples from the quadriceps femoris muscle. RESULTS: Peak VO2 did not change with training. Two-legged knee extensor endurance exercise capacity increased by an average of 40-50% (p < 0.01) in all training patients in both the 2L and 1L groups, while no change was observed in the control group. Depressed skeletal muscle CS activity increased by 25-35% in both training groups (p < 0.01). Strength increased by 16% in the 2L group after training (p < 0.05), while no change was seen in the 1L and control groups. CONCLUSIONS: Skeletal muscle changes in stable moderate chronic heart failure are not entirely irreversible. A major factor contributing to these changes and to exercise limitation is deconditioning. Local muscle training is efficient and can at least partially improve skeletal muscle function in these patients. Different degrees of local activation, that is, one- or two-legged knee extensor exercise, do not seem to differ in terms of their effect on exercise capacity. Depressed skeletal muscle oxidative capacity adapts to such physical training with increased activity to an extent not different from that for healthy volunteers.

Adaptation, Physiological↗
PubMed1997

Lamprey fructose-1,6-bisphosphate aldolase: characterization of the muscle-type and non-muscle-type isozymes.

To study evolutionary aspects of fructose-1,6-bisphosphate (Fru-1,6-P2) aldolase during deuterostomian evolution, we have purified and characterized aldolases from the muscle and liver of lamprey (Entosphenus japonicus). Aldolase from the skeletal muscle and liver was identified to be the muscle-type isozyme and the non-muscle-type isozyme that was encoded by cDNAs M8 and L3, respectively, as described previously (Zhang, R., Yatsuki, H., Kusakabe, T., Iwabe, Miyata, T., Imai, T., Yoshida, M., and Hori, K., J. Biochem. 117, 545-553, 1995). The muscle-type isozyme has properties similar to vertebrate aldolase A, while the non-muscle-type isozyme shows a similarity to bacterial class I aldolase and vertebrate aldolase C but not to aldolase B, the liver-type aldolase, in terms of kinetic parameters: the Kcat values toward Fru-1,6-P2 and Fru-1-P, the Fru-1,6-P2/Fru-1-P activity ratio, and the Km values toward these substrates. The two enzymes have tetrameric forms with a molecular mass of approximately 160,000 and have similar pH optimum. The muscle-type and non-muscle-type isozymes from the tissues show different electrophoretic mobility; the muscle-type isozyme moves much faster than the non-muscle-type isozyme toward anodic side. The recombinant muscle-type and non-muscle-type aldolases gave similar characteristics as those from the tissues. The results presented in this paper, together with the data presented in the previous paper, strongly suggest that in lamprey it is possible to have two types of aldolase isozymes rather than one or three isozymes.

Amino Acid Sequence↗
PubMed1994

Muscarinic stimulation of arachidonic acid release and prostaglandin synthesis in bovine ciliary muscle: prostaglandins induce cyclic AMP formation and muscle relaxation.

In the present study it is demonstrated that in bovine ciliary muscle, muscarinic stimulation results in: (a) release of 14C-arachidonic acid (14C-AA) and 14C-labeled prostaglandins (PGs) from muscle prelabeled with 14C-AA; (b) release of endogenous PGs, measured by means of radioimmunoassay; (c) enhanced IP3 production and (d) muscle contraction. In addition, PGs, such as PGE2 and PGD2, increased cAMP formation and induced muscle relaxation. The studies on the kinetics of 14C-AA metabolism revealed that incorporation of 14C-AA into glycerolipids and its conversion into PGs by the ciliary muscle were rapid and time-dependent. The amounts of 14C-radioactivity recovered in the major PGs decreased in the following order: PGD2 > PGE2 < PGF2 alpha > 6-keto-PGF1 alpha. The rate of endogenous PGF2 alpha synthesis by iris-ciliary body tissues from different mammalian species was found to be in the following order: ciliary muscle < ciliary processes < sphincter muscle. The EC50s for muscarinic-stimulated release of 14C-AA, 14C-labeled PGs, and endogenous PGF2 alpha and PGE2, and for IP3 production and contraction of the ciliary muscle indicate that CCh is 2-16 times as potent as pilocarpine in eliciting these responses, with the greatest difference being for contraction. The maximal increase in ciliary muscle tension due to CCh was 48% greater than that evoked by pilocarpine. All PGs tested, including PGE2, 17-phenyl trinor PGE2, 11-deoxy PGE1, PGF2 alpha and PGD2 had no effect on IP3 production and contraction in the ciliary muscle. However, PGE2 and PGD2 stimulated cAMP formation and inhibited CCh-induced IP3 production in a dose-dependent manner. In addition, PGE2 and PGD2 induced relaxation in ciliary muscle precontracted by CCh. In presence of indomethacin (1 microM), the CCh-induced contraction was greater than that observed in absence of the cyclo-oxygenase inhibitor. It is suggested that in the ciliary muscle certain PGs, such as PGE2 and PGD2, may function to modulate, via cAMP, the responses to muscarinic stimulation in this tissue.

Animals↗
PubMed1994

The morphology and mechanical properties of endomysium in series-fibred muscles: variations with muscle length.

In the series-fibred muscle architecture commonly found in large muscles of mammals and birds, the intrafasciculary-terminating muscle fibres have no direct tendinous attachments. Contractile force produced in these fibres must be transmitted between adjacent muscle fibres via the endomysial connective tissue which separates them. The endomysium is thus an essential mechanical component in such muscles. Studies of motor end-plate banding patterns and the frequent occurrence of tapering ends of fibres within the fascicles of the bovine sternomandibularis muscle show it to be a series-fibred muscle. Sodium hydroxide digestion of fixed samples of this muscle to remove the myofibrillar apparatus revealed the endomysium to be a disordered planar network of mainly curvilinear collagen fibrils. The orientation distribution of the collagen fibrils in the endomysial network was measured by image analysis of scanning electron micrographs. Analysis of endomysial preparations from muscle fixed at sarcomere lengths between 1-4 microns showed that the orientation distribution of collagen fibrils is quantitatively related to muscle length. At rest sarcomere length the collagen fibril network is not completely random, but has a slight circumferential bias. The orientation distribution shows a progressive shift towards the circumferential direction at short sarcomere lengths and towards the longitudinal direction at long sarcomere lengths. The relationship between the number-weighted mean collagen orientation and sarcomere length was compared to two geometric models of network behaviour, the isoareal and constant shape models. Both fitted the data reasonably, although the constant shape model described the rate of change of mean orientation more closely. From fibrous composites theory, the reinforcement efficiency factor, eta, was calculated from the measured collagen fibril orientation distributions. These calculations predict a non-linearly increasing longitudinal tensile modulus for the endomysium with increasing sarcomere length, in agreement with its known non-linear properties, but confirm that the tensile properties of the endomysium are unsuitable for transmission of tensile force from muscle fibres contracting near rest length. This reinforces a previous interpretation that contractile force is transmitted between neighbouring muscle fibres by trans-laminar shear through the endomysium rather than by in-plane tension.

Animals↗
PubMed1993

Fish muscle structure: fibre types in flatfish and mullet fin muscles using histochemistry and antimyosin antibody labelling.

In studies of the myosin crossbridge interaction with actin in vertebrate muscles, the muscles of bony fish have the unique advantage for ultrastructural work that the A-band has a simple 'crystalline' lattice of myosin filaments. However, the anatomy and physiology of these fish muscles is relatively poorly understood compared with the rabbit, chicken or frog muscles conventionally used for crossbridge studies. Here the fibre types in fish fin muscles have been characterized to allow sensible selection of single fish fibres for ultrastructural studies. The fibre type compositions of the fin muscles of mullet, plaice, sole and turbot were examined by histochemistry and immunohistochemistry using polyclonal antibodies raised against various myosin isoforms: fish slow, fish fast, mammalian fast (type IIA) and chicken tonic myosins. In the mullet, fin muscles were composed of variable proportions of fast and slow fibres. In the three flatfish, the fin muscle showed a zonal arrangement with slow fibres, binding anti-slow myosin antibody, next to the skin (alpha region). The bulk of the muscle, distal to the skin, was a typical fast muscle both histochemically and in its reaction with antibodies (delta region). Between these two regions there may be one (sole) or two (turbot, plaice) intermediate zones (beta and gamma regions) comparable to the pink/intermediate layer of myotomal muscle. In the plaice fin muscle, two kinds of slow fibre could be distinguished immunohistochemically.

Animals↗
PubMed1990

The role of blood flow and/or muscle hypoxia in capillary growth in chronically stimulated fast muscles.

Capillary supply, the proportion of oxidative fibres and blood flow were studied in fast rat muscles (tibialis anterior, TA, and extensor digitorum, EDL) made ischaemic by ligation of the common iliac artery, in chronically stimulated muscles and in ischaemic chronically stimulated muscles. Stimulation was carried out for 6 h/day at 10 Hz (three periods of 2 h with 90-120-min intervals between stimulations) for 10-12 days using electrodes implanted in the vicinity of the lateral popliteal nerve. Blood flow (measured by radioactive microspheres) was 3.62 +/- 0.52 ml.100 g-1.min-1 at rest and 78.4 +/- 14.6 ml.100 g-1.min-1 (mean +/- SEM) during isometric contractions at 4 Hz. Ischaemic muscles had significantly lower blood flow at rest as well as during contractions (72 +/- 14% and 25 +/- 4% of the values in contralateral muscles respectively). Stimulated muscles had significantly higher flow than contralateral control muscles during contractions; stimulated ischaemic muscles had normal blood flow at rest, but the increase in flow during contractions was limited to a similar extent to that in ischaemic muscles alone. Of all anatomically present capillaries (staining for alkaline phosphatase in frozen sections) the capillary/fibre ratio increased by 36% in stimulated tibialis anterior, but was not significantly different from control muscles in stimulated ischaemic TA and was even lower than in control muscles in stimulated ischaemic EDL. The proportion of fast oxidative fibres (estimated on the basis of histochemical staining for myosin ATPase and succinate dehydrogenase) increased from 53.2 +/- 3.2% in normal EDL to 82.0 +/- 2.3% in chronically stimulated EDL and to 100% in chronically stimulated ischaemic muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1981

Muscle aldolase: the stress-dependent modification of catalytic and structural properties by rat muscle lysosomal cathepsin B.

Stress dependent variations in th properties of the rat muscle aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) have been linked to the corresponding changes in the levels of proteolytic activities in rat muscle. Whole-body X-irradiation of rat was shown to result in loss of muscle aldolase activity towards fructose 1,6-bisphosphate by 50% while fructose 1-phosphate activity remained unchanged (Pote, M.S. and Altekar, W. (1980) Ind. J. Biochem, Biophys. 17, 255-262). Incubation of muscle extract of irradiated rat with that from control rat or rabbit muscle aldolase caused similar changes in aldolase activity. The changes are attributed to the action of catheptic enzymes possessing latency characteristics and capable of using aldolase as a substrate; the time course of their increase after irradiation corresponds to that of loss in muscle aldolase activities. Exposure of rats to stress resulted in an increase in the 'free' proteolytic activity, and the concomitant loss of 'bound' activity in muscle lysosomes indicates labilization of lysosomal membrane. The observed degradation of aldolase in vivo by muscle lysosomes is shown to be due to the action of cathepsin B (EC 3.4.22.1) present in the proteolytic enzymes released into cytosol under stress. Inactivation of rabbit muscle aldolase and rat muscle aldolase by rat muscle cathepsin B inhibited by leupeptin, antipain an iodoacetamide, but not be pepstatin. Inactivation is shown to be due to the release of C-terminal tyrosine if aldolase, required for its catalytic activity. Cathepsin B who acts as a rate-limiting enzyme in the degradation of aldolase. Such a proteolytic modification of aldolase in vivo could be relevant not only to the regulation of aldolase activity of glycolysis in muscle but also to the degradation of aldolase during stress conditions related to tissue damage and the maintenance of normal aldolase levels in the blood.

Amino Acids↗
PubMed1981

Interaction between macrophages and aortic smooth muscle cells. Enhancement of cholesterol esterification in smooth muscle cells by media of macrophages incubated with acetylated LDL.

Mouse peritoneal macrophages were cultured for 24 h in Dulbecco-Vogt medium containing 10% calf serum. This medium was replaced with Dulbecco-Vogt medium containing 1% bovine serum albumin to which all subsequent additions were made. Medium changes, accompanied by appropriate additions, were made every 48 or 72 h and the media were used for incubation of aortic smooth muscle cells, prelabeled with [3H]cholesterol. The amount of labeled cholesteryl ester in the smooth muscle cells incubated for 48 h with macrophage media which had been collected 48-144 h after addition of acetylated LDL was increased 3-4 times above that present prior to postincubation. A marked increment in cholesteryl ester mass occurred also after incubation of smooth muscle cells with macrophage media conditioned with acetylated LDL and this effect was shared by maleylated LDL, but not by other negatively charged compounds. The increase in labeled cholesteryl ester in smooth muscle cells was more pronounced with media collected at later time intervals of incubation with macrophages and was evident 8 hr after postincubation. Only the d less than 1.063 fraction of the medium enhanced cholesterol esterification in smooth muscle cells. The acetylated LDL reisolated from macrophage media at d less than 1.063 did not compete with native LDL for degradation by smooth muscle cells. No increase in degradation of 125I-labeled acetylated LDL preincubated with macrophages was observed above that of non-preincubated acetylated LDL. The macrophage medium conditioned with acetylated LDL depressed [14C]acetate incorporation into sterols in smooth muscle cells and this effect was abolished by extraction of the medium with diethyl ether. The ratio of free to total cholesterol in the macrophage media collected after incubation with acetylated LDL increased from 28-70%, and a decrease occurred after incubation with smooth muscle cells. The enhancement of cholesterol esterification could be abolished by addition of high density apolipoprotein/sphingomyelin mixture during incubation with macrophages, even though excretion of free cholesterol into the medium increased 3-fold. It is proposed that when smooth muscle cells are presented with a lipoprotein in which an increase in the free to esterified cholesterol ratio occurred, and which is not recognized by a specific receptor, the enhancement of cellular cholesterol esterification is due mostly to a surface transfer of lipoprotein-free cholesterol. The present results offer another view of the possible interactions between macrophages and smooth muscle cells. A modified lipoprotein, not recognized by smooth muscle cells, is ingested by macrophages, which leads to accumulation of esterified cholesterol. Part of the esterified cholesterol undergoes hydrolysis and is excreted back into the medium, leading to enrichment of the lipoproteins in the medium with free cholesterol. This enrichment with free cholesterol promotes cholesterol esterification in smooth muscle cells.

Acylation↗
PubMed1983

Developmental autonomy of muscle fine structure in muscle lineage cells of ascidian embryos.

We have observed ultrastructural features of muscle differentiation in the muscle lineage cells of cleavage-arrested whole embryos and partial embryos of ascidians. Whole embryos of Ciona intestinalis and Ascidia ceratodes were cleavage-arrested with cytochalasin B at the 8-cell stage and reared to an age equivalent to several hours after hatching; these embryos formed extensive myofilaments which were often further organized into myofibrils of different sizes and densities in the peripheral cytoplasm of the two muscle lineage blastomeres (B4.1 pair). Developing myofibrils in cleavage-arrested embryos resembled the muscle elements observed in normal hatched larvae, but were less uniformly organized. A similar development of myofilaments and myofibrils occurred in the muscle lineage cells of multicellular partial embryos reared to "hatching" age. These partial embryos resulted from the isolated muscle lineage pair (B4.1) of blastomeres of the 8-cell stage (Ciona and Ascidia), and from a muscle lineage blastomere pair (B5.2) isolated at the 16-cell stage (Ascidia). Muscle lineage cells in the partial embryos were readily identified by the dense aggregates of mitochondria in their cytoplasm. Taken together, these results from the two kinds of partial embryo effectively eliminate inductive interactions with embryonic tissues other than mesodermal as a necessary factor in the onset of self-differentiation in muscle lineage cells. The relative complexity of muscle phenotype expressed in cleavage-arrested and partial embryos attests to an unusually strong developmental autonomy in the ascidian muscle lineages. This autonomy lends further support to the theory that a localized and segregated egg cytoplasmic determinant is responsible for larval muscle development in ascidian embryos.

Animals↗
PubMed1995

Influences on the gamma-muscle spindle system from muscle afferents stimulated by increased intramuscular concentrations of bradykinin and 5-HT.

There is evidence that static muscular contractions induce a release of bradykinin (BK) in the working muscle, and that increased concentration of BK and 5-HT in a muscle increases the discharge rate of a subpopulation of group III and group IV muscular afferents. It is also known that activity in group III and IV muscle afferents may activate gamma-motoneurones to both homonymous and heteronymous muscles. The aim of the present study was to investigate whether increased concentration of BK and 5-HT in one muscle may influence the activity in primary and secondary muscle spindle afferents (MSAs) from the chemically affected muscle and from surrounding muscles, via fusimotor reflexes. The experiments were made on six cats anaesthetised with alpha-chloralose. The triceps surae (GS) and the posterior biceps and semitendinosus (PBSt) muscles were subjected to sinusoidal stretches. Simultaneous recordings of 2-11 MSAs from these muscles were made and the mean rate of firing and the modulation for each MSA were determined. Responses of 47 MSAs (26 PBSt and 21 GS) were recorded. The responsiveness of the MSAs to injections of BK (9-100 mg/ml, 0.5-1.0 ml) and 5-HT (25-150 mg/ml, 0.5-1.0 ml) was 89% and 83%, respectively, for injections into the arterial supply of the ipsilateral GS muscle, and 84% and 40% respectively for injections to the contralateral GS muscle. Of 10 secondarŁy MSAs, only one was unresponsive to BK injections, while several MSAs responded to both ipsilateral and contralateral BK injections.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed2006

Wrapping of trunk thoracic extensor muscles influences muscle forces and spinal loads in lifting tasks.

BACKGROUND: An improved assessment of risk of spinal injury during lifting activities depends on an accurate estimation of trunk muscle forces, spinal loads and stability margin which in turn requires, amongst others, an accurate description of trunk muscle geometries. The lines of action of erector spinae muscles are often assumed to be linear despite the curved paths of these muscles in forward flexion postures. METHODS: A novel approach was introduced that allowed for the proper simulation of curved paths for global extensor muscles in our Kinematics-driven finite element model. The lever arms of global muscles at different levels were restrained either to remain the same or decrease only by 10% relative to their respective values in upright posture. Based on our earlier measurements, static lifting tasks at two trunk flexions (40 degrees and 65 degrees ) and three lumbar postures (free style, lordotic and kyphotic) with 180 N in hands were analyzed. FINDINGS: Muscle forces and spinal compression at all levels substantially decreased as the global extensor muscles took curved paths. In contrast, the shear force at lower levels increased. Allowing for a 10% reduction in these lever arms during flexion increased muscle forces and compression forces at all levels. Despite smaller muscle forces, wrapping of global muscles slightly improved the spinal stability. INTERPRETATION: Consideration of global extensor muscles with curved paths and realistic lever arms is important in biomechanical analysis of lifting tasks. Reduction in the erector spinae lever arms during flexion tasks could vary depending on the lumbar posture. Results advocate small flattening of the lumbar curvature in isometric lifts yielding smaller compression and shear forces at the critical L5-S1 level.

Abdominal Muscles↗