Schistosoma mansoni: differences in acetylcholine, dopamine, and serotonin control of circular and longitudinal parasite muscles

The physiological and pharmacological properties of circular and longitudinal somatic musculature in adult male Schistosoma mansoni were compared using cut muscle sections. Carbachol reduced tone in both circular and longitudinal muscle, but was without effect on circular muscle bathed in high Mg2+, indicating that cholinergic receptors were not associated with circular muscle membrane. 5-Hydroxytryptamine (5-HT) induced rhythmic contractile activity in both sets of muscle. It decreased muscle tone in circular muscle but increased the tone of longitudinal muscle. Metergoline blocked 5-HT effects on both sets of muscle. 5-HT continued to be effective on both sets of muscle bathed in high-Mg2+ medium, indicating that serotonergic receptors were present on both circular and longitudinal muscle membranes. Dopamine decreased both circular and longitudinal muscle tone. Its effects on circular muscle were still present after exposure to high Mg2+, but its effects on the longitudinal muscle were significantly reduced, leading to the conclusion that dopaminergic sites were probably associated with circular muscle membrane but not that of longitudinal muscle. Also, spiroperidol blocked stimulus responsiveness of the circular muscle but not that of the longitudinal muscle. From these studies it appears that there are significant physiological and pharmacological differences between circular and longitudinal muscles in the adult male schistosome.     

Pressure pain sensitivity and hardness along human normal and sensitized muscle

The spatial distribution of pressure sensitivity and muscle hardness was examined on normal muscle tissue and muscle tissue after induction of delayed onset muscle soreness (DOMS). The pressure sensitivity and muscle hardness were assessed at nine sites on the tibialis muscle from the proximal to distal tendon on two separate days. In total 37 healthy volunteers participated in three experiments. In the first experiment pressure pain threshold (PPT) and pressure pain tolerance (PPTO) were assessed. Decreased PPT and PPTO were found on day 2, 7 days after day 1. Proximal and distal stimulation sites were harder compared to muscle belly sites. In a second experiment two different probe sizes were used. Variation in PPT between the nine sites was found for the large probe with muscle belly being less sensitive to pressure stimulation compared to proximal and distal sites. The most proximal stimulation site was harder compared to muscle belly sites. In a third experiment PPT and muscle hardness were assessed before and 48?h after eccentric exercise. PPT at two muscle belly sites was significantly decreased during DOMS. No specific sites were harder during DOMS, the average muscle hardness across sites was however significantly increased. Decreased PPT and increased muscle hardness did not correlate. In conclusion, within subjects the pressure sensitivity varies along the musculoskeletal unit. In DOMS, specific muscle belly sites were more sensitive to pressure stimulation. Muscle–tendon sites were harder compared to muscle belly sites.     

Mechanical analysis of Drosophila indirect flight and jump muscles

The genetic advantages of Drosophila make it a very appealing choice for investigating muscle development, muscle physiology and muscle protein structure and function. To take full advantage of this model organism, it has been vital to develop isolated Drosophila muscle preparations that can be mechanically evaluated. We describe techniques to isolate, prepare and mechanically analyze skinned muscle fibers from two Drosophila muscle types, the indirect flight muscle and the jump muscle. The function of the indirect flight muscle is similar to vertebrate cardiac muscle, to generate power in an oscillatory manner. The indirect flight muscle is ideal for evaluating the influence of protein mutations on muscle and cross-bridge stiffness, oscillatory power, and deriving cross-bridge rate constants. Jump muscle physiology and structure are more similar to skeletal vertebrate muscle than indirect flight muscle, and it is ideal for measuring maximum shortening velocity, force-velocity characteristics and steady-state power generation.     

Pressure pain sensitivity and hardness along human normal and sensitized muscle

The spatial distribution of pressure sensitivity and muscle hardness was examined on normal muscle tissue and muscle tissue after induction of delayed onset muscle soreness (DOMS). The pressure sensitivity and muscle hardness were assessed at nine sites on the tibialis muscle from the proximal to distal tendon on two separate days. In total 37 healthy volunteers participated in three experiments. In the first experiment pressure pain threshold (PPT) and pressure pain tolerance (PPTO) were assessed. Decreased PPT and PPTO were found on day 2, 7 days after day 1. Proximal and distal stimulation sites were harder compared to muscle belly sites. In a second experiment two different probe sizes were used. Variation in PPT between the nine sites was found for the large probe with muscle belly being less sensitive to pressure stimulation compared to proximal and distal sites. The most proximal stimulation site was harder compared to muscle belly sites. In a third experiment PPT and muscle hardness were assessed before and 48 h after eccentric exercise. PPT at two muscle belly sites was significantly decreased during DOMS. No specific sites were harder during DOMS, the average muscle hardness across sites was however significantly increased. Decreased PPT and increased muscle hardness did not correlate. In conclusion, within subjects the pressure sensitivity varies along the musculoskeletal unit. In DOMS, specific muscle belly sites were more sensitive to pressure stimulation. Muscle-tendon sites were harder compared to muscle belly sites.     

Thiol protease and cathepsin D activities in selected tissues and cultured cells from normal and dystrophic mice

Thiol protease and cathepsin D activities were studied in extracts from hindlimb muscle of 60-day-old normal and dystrophic mice, strain 129 ReJ, and from cultured normal and dystrophic cells. Total thiol protease activity in dystrophic muscle extracts was 3.5 times higher than in normal muscle extracts, while cathepsin D, activity was 2.2 times greater in dystrophic muscle compared with normal muscle. Activation (pH 4.5, 30 degrees C) of latent thiol protease activity in extracts of muscle occurred concomitant with the inactivation or dissociation of endogenous protease inhibitors. Thiol protease assays revealed a higher ratio of active to inactive protease activity in extracts from dystrophic muscle than from normal muscle. Cultured myoblasts (L69/1) were found to contain 30-fold more thiol protease(s) and 6-fold more cathepsin D activity than whole muscle. Cells established from dystrophic muscle and grown in culture for periods up to 6 months were more responsive to thiol protease activation conditions than similar cultures derived from normal muscle. From data on the rate and extent of thiol protease activation in extracts from dystrophic cells and hindlimb muscle compared with normal tissue, it appears that cells and tissues from dystrophic mice contain a lower level of protease inhibitors than cells and tissues from normal mice.     

Density and hydration of fresh and fixed human skeletal muscle

The maximum tetanic tension of skeletal muscle (P(0)) is often estimated based on calculation of physiological cross-sectional area (PCSA). PCSA depends on muscle volume, pennation angle, and fiber length. Studies documenting PCSA in fixed human muscles usually compute muscle volume by dividing muscle mass by density. These studies use a density value of 1.0597 g/cm(3), which was originally based on unfixed rabbit and canine muscle tissue. Due to the dehydration effects of different fixation methods, the variable hydration that occurs when fixed tissue is stored in buffered saline, and the potential for species-specific muscle density, this value may be incorrect and an accurate value for fixed human muscle density is needed. To obtain an accurate density and water content values, 4% formaldehyde-fixed (n=54) and 37% formaldehyde-fixed (n=54) cadaveric human muscle samples were divided into 6 groups (0, 6, 12, 18, 24, or 30 h) for hydration in phosphate buffered saline (PBS). Measurements of volume, water content, and mass were made enabling calculation of muscle density. Additionally, water content was measured in living muscle (n=4) to determine the appropriate hydration time in PBS. Comparisons among groups demonstrated a significant increase in muscle water content and muscle volume over time, reaching living tissue levels after 24h, but, interestingly, the hydration process did not affect muscle density. These data yield a density value (mean+/-SE) of 1.112+/-0.006 g/cm(3) in 4% formaldehyde-fixed muscle and 1.055+/-0.006 g/cm(3) in 37% formaldehyde-fixed muscle. These results indicate that the use of inappropriate hydration times or density values can produce PCSA errors of 5-10%.     

骨骼肌卫星细胞的特性及其增殖与分化的调控

成体骨骼肌细胞的数量基本保持恒定,骨骼肌的再生主要依赖肌卫星细胞的增殖与分化。骨骼肌卫星细胞是能够被激活、进而分化为肌细胞的一类成肌细胞。现对肌卫星细胞的发生、体外培养以及增殖与分化的调控进行综述,并对能否通过激活肌卫星细胞的增殖来实现肌肉组织生长的调控进行探讨。     

Regenerative activity of muscle tissue and thymus status in young and old mdx mice with muscle injury and wound xenoplasty

Responses of the skeletal muscle tissue and thymus to muscle injury (complete transection) and wound xenoplasty with the minced muscle tissue of newborn rats (tissue therapy) were studied in mdx mice aged 12–16 and 40–48 weeks. The muscle tissue of mdx mice has genetic defects causing chronic dystrophic processes in it. The muscle tissue of young mdx mice proved to retain a relatively high capacity for regeneration. Under conditions of tissue therapy of the wound, the formation of muscle fibers from muscle cells of the graft and active regeneration of muscle fibers in the recipient mice were observed, and no structural defects were detected in the thymus. The capacity of posttraumatic regeneration in old mdx mice was lower. The xenogenic graft was undergoing resorption, thereby suppressing regeneration of muscle fibers and causing further tissue destruction in the injured muscle. The thymus parenchyma was subject to degenerative changes such as the formation of gaps, hemorrhagic foci, and increased numbers of macrophages and mast cells.     

Differential influence of peripheral and systemic sex steroids on skeletal muscle quality in pre- and postmenopausal women

Aging is associated with gradual decline of skeletal muscle strength and mass often leading to diminished muscle quality. This phenomenon is known as sarcopenia and affects about 30% of the over 60-year-old population. Androgens act as anabolic agents regulating muscle mass and improving muscle performance. The role of female sex steroids as well as the ability of skeletal muscle tissue to locally produce sex steroids has been less extensively studied. We show that despite the extensive systemic deficit of sex steroid hormones in postmenopausal compared to premenopausal women, the hormone content of skeletal muscle does not follow the same trend. In contrast to the systemic levels, muscle tissue of post- and premenopausal women had similar concentrations of dehydroepiandrosterone and androstenedione, while the concentrations of estradiol and testosterone were significantly higher in muscle of the postmenopausal women. The presence of steroidogenetic enzymes in muscle tissue indicates that the elevated postmenopausal steroid levels in skeletal muscle are because of local steroidogenesis. The circulating sex steroids were associated with better muscle quality while the muscle concentrations reflected the amount of infiltrated fat within muscle tissue. We conclude that systemically delivered and peripherally produced sex steroids have distinct roles in the regulation of neuromuscular characteristics during aging.     

Ursolic acid increases skeletal muscle and brown fat and decreases diet-induced obesity, glucose intolerance and fatty liver disease

Skeletal muscle Akt activity stimulates muscle growth and imparts resistance to obesity, glucose intolerance and fatty liver disease. We recently found that ursolic acid increases skeletal muscle Akt activity and stimulates muscle growth in non-obese mice. Here, we tested the hypothesis that ursolic acid might increase skeletal muscle Akt activity in a mouse model of diet-induced obesity. We studied mice that consumed a high fat diet lacking or containing ursolic acid. In skeletal muscle, ursolic acid increased Akt activity, as well as downstream mRNAs that promote glucose utilization (hexokinase-II), blood vessel recruitment (Vegfa) and autocrine/paracrine IGF-I signaling (Igf1). As a result, ursolic acid increased skeletal muscle mass, fast and slow muscle fiber size, grip strength and exercise capacity. Interestingly, ursolic acid also increased brown fat, a tissue that shares developmental origins with skeletal muscle. Consistent with increased skeletal muscle and brown fat, ursolic acid increased energy expenditure, leading to reduced obesity, improved glucose tolerance and decreased hepatic steatosis. These data support a model in which ursolic acid reduces obesity, glucose intolerance and fatty liver disease by increasing skeletal muscle and brown fat, and suggest ursolic acid as a potential therapeutic approach for obesity and obesity-related illness.     

Power and control muscles of cicada song: structural and contractile heterogeneity

Sound production in cicadas is powered by a pair of large muscles whose contractions cause buckling of cuticular tymbals and thereby create sound pulses. Sound is modulated by control muscles that alter the stiffness of the tymbals or change the shape of the abdominal resonance chamber. Muscle ultrastructure and contractile properties were characterized for the tymbal muscle and two control muscles, the ventral longitudinal muscle and the tymbal tensor, of the periodical cicada Magicicada septendecim. The tymbal muscle is a fast muscle that is innervated by a single motoraxon. The control muscles are an order of magnitude less massive than the tymbal muscles, but their innervation patterns were considerably more complex. The tensor muscle is innervated by two axons, each of which evokes rather slow twitches, and the ventral muscle is innervated by at least six axons, some of which produce fast and the others slow contractions. Muscle contraction kinetics correlated well with ultrastructure. Fibers of the tymbal muscle and the portions of the ventral muscle thought to be fast were richly supplied with transverse tubules (T-tubules) and sarcoplasmic reticulum (SR); slow portions of the ventral muscle and the tensor muscle had relatively little SR.Abbreviations SR sarcoplasmic reticulum - TTS transverse tubular system - VLM ventral longitudinal muscle     

Non-uniform muscle adaptations to eccentric exercise and the implications for training and sport

Due to the variations in morphological and architectural characteristics of fibers within a skeletal muscle, regions of a muscle may be differently affected by eccentric exercise. Although eccentric exercise may be beneficial for increasing muscle mass and can be beneficial for the treatment of tendinopathies, the non-uniform effect of eccentric exercise results in regional muscle damage and as a consequence, non-uniform changes in muscle activation. This regional muscle weakness can contribute to muscle strength imbalances and may potentially alter the load distribution on joint structures, increasing the risk of injury. In this brief review, the non-uniform effects of eccentric exercise are reviewed and their implications for training and sport are considered.     

Relationship between myoglobin and succinate dehydrogenase in mouse soleus and plantaris muscle fibres

Summary This report describes a quantitative histochemical study of myoglobin in skeletal muscle fibres. The muscle fibres were classified as fast or slow on the basis of their quantitative myofibrillar ATPase histochemistry. A large range of myoglobin absorbance values was found among fast skeletal muscle fibres. This range was relatively small among slow fibres. The concentrations of myoglobin and the activities of succinate dehydrogenase in individual muscle fibres in serial sections are weakly correlated in both the mouse soleus and plantaris muscle. The myoglobin concentration is higher in fast and slow oxidative soleus muscle fibres and the succinate dehydrogenase activity in these fibres is lower than in oxidative plantaris muscle fibres in the same range of cross-sectional area.     

The effect of caffeine on calcium efflux and calcium translocation in skeletal and visceral muscle.

1. KCl-induced depolarization resulted in a large stimulation of the 45Ca efflux from both cockroach skeletal muscle and rat ileal smooth muscle. 2. Caffeine (10 mM) induced a large stimulation of 45Ca efflux from skeletal muscle, but a fall in the efflux from ileal muscle, especially if the efflux was previously stimulated by KCl depolarization. 3. Caffeine inhibited calcium uptake by skeletal muscle mitochondria and sarcoplasmic reticulum, was without effect on ileal muscle mitochondria, but significantly increased caclium binding by ileal muscle membrane vesicular preparations. 4. The induction of contractures and stimulation of 45Ca efflux in skeletal muscle by caffeine are clearly related to inhibition of intracellular calcium binding by the sarcoplasmic reticulum and mitochondria. 5. The relaxation of ileal muscle by caffeine and the inhibition of fibre calcium efflux correlate well with caffeine enhancement of intracellular calcium binding. These experiments suggest that the membrane vesicular compartment may be the main agency centrally involved in fibre calcium regulation in this muscle during the contraction-relaxation cycle.     

Numbers of muscle nuclei and myosatellite cell nuclei in red and white axial muscle during growth of the carp (Cyprinus carpio)

We determined the percentages of muscle fibie nuclei and satellite nuclei over a growth range of carp ( Cyprinus carpio ), as the increase in the number of muscle fibre nuclei is an important aspect of the increase in muscle mass, and myosatellite cells are believed to be the source of new muscle fibre nuclei. In white as well as in red axial muscle the percentage of the nuclei present in muscle that are muscle nuclei (muscle fibre nuclei+myosatellite nuclei) remained constant during growth (54 and 32% respectively). The difference in the percentage of non-muscle nuclei between white and red axial muscle is mainly caused by the higher content of endothelial nuclei in red axial muscle.
In white axial muscle the DNA/protein ratio (nucleus/sarcoplasm ratio) decreased between 3 and 15 cm S.l. In red axial muscle we found a continuous decrease in DNA/protein ratio over the entire investigated size range (3–50 cm s.l.). This may be related to a longer occurrence of hyperplasia in red than in white axial muscle.
In both fibre types the percentage of muscle nuclei being myosatellite nuclei decreased with increasing length, In white axial muscle it decreased from about 5% in carp of 5 cm s.l. to less than 1% in carp of 20 cm S.L.; for red muscle these values were 11 and 3% respectively.
For white axial muscle we calculated that, especially in larger fish, the myosatellite ceils alone cannot account for the increase in the number of muscle fibre nuclei during growth. The percentage of proliferating nuclei in muscle tissue, measured by the uptake of 5-bromo-2'-deoxy-uridine, is high enough to account for the total increase in nuclei. So indirect evidence is available that another cell type present in the muscle tissue may also be involved in the formation of additional muscle fibre nuclei.     

Somatic and intramuscular distribution of muscle spindles and their relation to muscular angiotypes

The distribution pattern of muscle spindles in the skeletal musculature has been reviewed in a large number of muscles (using the literature data especially from cat and man), and the relation of spindle content to muscle mass was quantitatively examined in 36 cat and 140 human muscles. In both species, the number of spindles increases with increasing muscle mass in a power law fashion of the form y=bx+a, whereby y denotes the logarithm of spindle content within a muscle, and x is the logarithm of muscle mass. For the cat, slope b and intercept a were estimated as 0.39 and 1.53, and for man as 0.48 and 1.33, respectively. The results show that the spindle content of a muscle may be related to its mass, confirming a similar analysis made previously by Banks and Stacey (Mechano receptors, Plenum Press, New York, 1988, pp. 263-269) in a different data set. With regard to the histological profile of muscle fibers, (as it is already well documented by many groups) muscle spindles tend to be located in deeper muscle regions where oxidative fibers predominate, and are far scarcer in superficial and flat muscle regions where glycolytic fibers predominate. These discrete muscle regions differ also in the properties of the vessel tree supplying them, for which the term oxidative and glycolytic "angiotype" has been used. The results from these three aspects of analysis (relation to muscle mass, relation to muscle regions with high oxidative index and relation to muscle regions with dense vascular supply) were combined with histological findings showing that spindles may be in systematic anatomical contact to intramuscular vessels. Based on these data a hypothesis is proposed according to which, both the number and intramuscular placement of muscle spindles are related to the oxidative angiotype supplying the muscle territories rich in oxidative fibers. The hypothesis is discussed.     

Normal Muscle Oxygen Consumption and Fatigability in Sickle Cell Patients Despite Reduced Microvascular Oxygenation and Hemorheological Abnormalities

Background/Aim

Although it has been hypothesized that muscle metabolism and fatigability could be impaired in sickle cell patients, no study has addressed this issue.

Methods

We compared muscle metabolism and function (muscle microvascular oxygenation, microvascular blood flow, muscle oxygen consumption and muscle microvascular oxygenation variability, which reflects vasomotion activity, maximal muscle force and local muscle fatigability) and the hemorheological profile at rest between 16 healthy subjects (AA), 20 sickle cell-hemoglobin C disease (SC) patients and 16 sickle cell anemia (SS) patients.

Results

Muscle microvascular oxygenation was reduced in SS patients compared to the SC and AA groups and this reduction was not related to hemorhelogical abnormalities. No difference was observed between the three groups for oxygen consumption and vasomotion activity. Muscle microvascular blood flow was higher in SS patients compared to the AA group, and tended to be higher compared to the SC group. Multivariate analysis revealed that muscle oxygen consumption was independently associated with muscle microvascular blood flow in the two sickle cell groups (SC and SS). Finally, despite reduced muscle force in sickle cell patients, their local muscle fatigability was similar to that of the healthy subjects.

Conclusions

Sickle cell patients have normal resting muscle oxygen consumption and fatigability despite hemorheological alterations and, for SS patients only, reduced muscle microvascular oxygenation and increased microvascular blood flow. Two alternative mechanisms can be proposed for SS patients: 1) the increased muscle microvascular blood flow is a way to compensate for the lower muscle microvascular oxygenation to maintain muscle oxygen consumption to normal values or 2) the reduced microvascular oxygenation coupled with a normal resting muscle oxygen consumption could indicate that there is slight hypoxia within the muscle which is not sufficient to limit mitochondrial respiration but increases muscle microvascular blood flow.     

Variations of the Contractile Apparatus in Smooth and Striated Muscles : X-ray diffraction studies at rest and in contraction

Structural information is presented for three muscle systems—mammalian smooth muscle at rest and partially active, living toad striated muscle at rest and contracting, and glycerinated rabbit psoas muscle under various conditions of pH and ionic environment. In the smooth muscle no evidence of organized myosin filaments has been found. In the striated muscle the myosin-to-actin distance can vary widely, according to sarcomere length and to muscle treatment, both at rest and during contraction. In the discussion it is suggested that muscle should be considered as a colloidal system and that there need not necessarily be any chemical bonding (cross-linking) involved in the contractile process.     

中国壮侗语族人群的肌肉分布及其与年龄的关系

为了解壮侗语族族群肌肉分布特点以及探讨随年龄增长壮侗语族族群各个部位肌肉量变化的基本特点,使用人体脂肪测量仪采用生物电阻抗法在海南、贵州、广西、云南、湖南五个省、自治区测量了壮侗语族13个族群的身体肌肉量。总样本量为5098例(男性为2126例,女性为2972例)。采用握力计测量了2685例男性和3793例女性的左手、右手握力。研究发现,壮侗语族族群男性、女性肌肉量总体评价接近标准,上下肢肌肉量判断属于标准水平。男性、女性均为躯干肌肉量最大,下肢肌肉量次之,上肢肌肉量最小。男性总肌肉量、四肢肌肉量、躯干肌肉量都大于女性。男性3个年龄组间总肌肉量、躯干肌肉量、上肢肌肉量、右下肢肌肉量的差异具有统计学意义,而左下肢肌肉量彼此接近;女性3个年龄组间总肌肉量、四肢肌肉量、躯干肌肉量差异均具有统计学意义。男性除左下肢肌肉量外,其余5项肌肉量指标均与年龄呈显著负相关关系;女性总肌肉量、躯干肌肉量与年龄呈显著负相关,但四肢肌肉量与年龄无显著负相关。壮侗语族族群肌肉量少于北方族群,具有中国南方族群的特点。在南方族群中,壮侗语族族群男性肌肉量中等,女性肌肉量略多一些。