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At least 109 records · Page 6Linked to original sources
PubMed1980

Permanently proliferating rat vascular smooth muscle cell with maintained expression of smooth muscle characteristics, including actin of the vascular smooth muscle type.

Cells of an established clonal line (RVF-SMC) derived from rat vena cava are described by light and electron microscope methods and biochemical analysis of the major proteins. The cells are flat, and they moderately elongate and form monolayers. They are characterized by prominent cables of microfilaments bundles decoratable with antibodies to actin and alpha-actinin. These bundles contain numerous densely stained bodies and are often flanked by typical rows of surface caveolae and vesicles. The cells are rich in intermediate-sized filaments of the vimentin type but do not show detectable amounts of desmin and cytokeratin filaments. Isoelectric focusing and protein chemical studies have revealed actin heterogeneity. In addition to the two cytoplasmic actins, beta and gamma, common to proliferating cells, two smooth muscle-type actins (an acidic alpha-like and a gamma-like) are found. The major (alpha-type) vascular smooth muscle actin accounts for 28% of the total cellular actin. No skeletal muscle or cardiac muscle actin has been detected. The synthesis of large amounts of actin and vimentin and the presence of at least three actins, including alpha-like actin, have also been demonstrated by in vitro translation of isolated poly(A)+ mRNAs. This is, to our knowledge, the first case of expression of smooth muscle-type actin in a permanently growing cell. We conclude that permanent cell growth and proliferation is compatible with the maintained expression of several characteristic cell features of the differentiated vascular smooth muscle cell including the formation of smooth muscle-type actin.

Actins↗
PubMed1993

[A comparative study of the structural state of skeletal muscle and smooth muscle fiber tropomyosin in ghost skeletal muscle fibers by a fluorescent probe method].

The structural state of skeletal muscle and smooth muscle fiber tropomyosins in ghost fibers of skeletal muscles has been studied by means of polarization microfluorimetry. Tropomyosins and F-actin of ghost fibers were labelled with N-(iodoacetyl)-N-(1-naphthyl-5-sulfo)-ethylenediamine (1,5-IA-EDANS) or the phalloidin-rhodamine complex, respectively. It has been found that skeletal tropomyosin bound to ghost muscle fibers is more flexible in comparison with smooth muscle tropomyosin. The flexibility of the thin filaments of the ghost fibers labelled in F-actin by the phalloidin-rhodamine complex and containing smooth muscle tropomyosin is higher than that of the thin filaments containing the bound skeletal muscle protein.

Animals↗
PubMed2001

The lacZ gene under the control of the 7 kb of human dystrophin muscle specific promoter is expressed in cardiac muscle but not in adult skeletal muscle in transgenic mice.

In previous transgenic studies, we reported a 0.9 kb fragment from a mouse dystrophin muscle promoter that contains the regulatory elements required for expression of dystrophin only in the right heart. In this study, to further characterize the regulation of muscle type of promoter, we analyzed promoter activity and tissue specificity using a total 14 kb fragment around the human dystrophin muscular-specific exon 1 in vitro and in vivo. In vitro analysis showed that the lacZ construct of the 7 kb promoter and 7 kb intron 1 was expressed 2.5 times as strong as the lacZ construct of only the 7 kb promoter in C2/4 myotubes. In vivo analysis revealed expression of both constructs in the whole heart, skeletal muscle and vascular smooth muscle in embryos. However, in adults, the expression in skeletal muscle disappeared. We conclude that the 7 kb upstream region and the 7 kb intronic region included responsible elements for the expression in the heart, but not in skeletal muscle in vivo. It is possible that a strong enhancer element for skeletal muscle exists in some other region.

Animals↗
PubMed2006

Nerve growth factor improves the muscle regeneration capacity of muscle stem cells in dystrophic muscle.

Researchers have attempted to use gene- and cell-based therapies to restore dystrophin and alleviate the muscle weakness that results from Duchenne muscular dystrophy (DMD). Our research group has isolated populations of muscle-derived stem cells (MDSCs) from the postnatal skeletal muscle of mice. In comparison with satellite cells, MDSCs display an improved transplantation capacity in dystrophic mdx muscle that we attribute to their ability to undergo long-term proliferation, self-renewal, and multipotent differentiation, including differentiation toward endothelial and neuronal lineages. Here we tested whether the use of nerve growth factor (NGF) improves the transplantation efficiency of MDSCs. We used two methods of in vitro NGF stimulation: retroviral transduction of MDSCs with a CL-NGF vector and direct stimulation of MDSCs with NGF protein. Neither method of NGF treatment changed the marker profile or proliferation behavior of the MDSCs, but direct stimulation with NGF protein significantly reduced the in vitro differentiation ability of the cells. NGF stimulation also significantly enhanced the engraftment efficiency of MDSCs transplanted within the dystrophic muscle of mdx mice, resulting in the regeneration of numerous dystrophin-positive muscle fibers. These findings highlight the importance of NGF as a modulatory molecule, the study of which will broaden our understanding of its biologic role in the regeneration and repair of skeletal muscle by musclederived cells.

Animals↗
PubMed1999

Difficulties in estimating muscle forces from muscle cross-sectional area. An example using the psoas major muscle.

Most biomechanical models use muscle cross-sectional area (CSA) as an indicator of maximum isometric muscle force. In general, there are multiple estimates of CSA for the same muscle. For example, numerous studies have estimated the CSA of the psoas major muscle using different subject populations and positions. However, few studies have combined the available information to obtain an overall estimate of CSA or investigated the effect different subject characteristics may have on CSA. In the present update, nine studies that reported psoas major CSA or physiologic CSA were compared with respect to subject characteristics, methodology, and results. Corrections to cadaveric data were made to adjust physiologic CSA to CSA. Comparison of reported values for living subjects indicated that females have smaller mean CSA than males for the psoas major muscle and that body size does not significantly influence muscle CSA in males. Areas derived from cadaveric data were smaller than similar studies on living subjects, possibly because of subject age, removal of tendinous and fatty components of fascicles, and lack of detailed data for fascicle angles in the supine position. Results indicate that researchers who use muscle CSA in biomechanical models should carefully assess the appropriateness of the data used, particularly in relation to potential sex differences and the influence of postural changes on CSA.

Biomechanical Phenomena↗
PubMed1993

Autografted minced muscle fragments do not affect muscle regeneration in partially excised rat gastrocnemius muscle.

The kinetics of the regeneration process following partial excision or mincing in the rat gastrocnemius muscle was compared using histological and physiological methods. Immediately following injury there was a marked decrease in the distance of shortening (DS) values during isotonic contraction, followed by a progressive increase until 2 weeks after injury. By 85 days the DS values attained those of control muscle during contraction against low loads (up to 50 g), and 80 and 62% of control values at 150 and 250 g, respectively. However, there was no difference in the DS values at 28 and 85 days after injury between muscles that were partially excised or when the removed part of the muscle was minced and placed in the injured site. It is concluded that the enrichment of an injured area of the gastrocnemius muscle with minced autografted muscle does not result in long-term improvement of the functional capacity of the regenerated muscle due to the addition of satellite cells and/or other factors in the minced tissue.

Animals↗
PubMed2006

Partitioning locomotor energy use among and within muscles. Muscle blood flow as a measure of muscle oxygen consumption.

Linking the mechanics and energetics of locomotion in vertebrates has been hampered by a lack of information regarding the energy use of individual skeletal muscles in vivo. Here, we present a review of the available data concerning the relationship between the rates of skeletal muscle blood flow and oxygen consumption (V(O2)). In active muscle, during aerobically supported exercise, there is a linear relationship between these variables, irrespective of the muscle fiber type and intensity of exercise through most of the aerobic exercise range. We conclude that the rate of blood flow is the best available indicator of aerobic metabolic rate in multiple individual muscles or regions of muscles during locomotion. The practical considerations of using the injectable microsphere technique to measure muscle blood flow in this context are discussed.

Animals↗
PubMedDate not supplied

Muscle biopsies show that FES of denervated muscles reverses human muscle degeneration from permanent spinal motoneuron lesion.

This paper presents biopsy analyses in support of the clinical evidence of muscle recovery induced by a new system of life-long functional-electrical-stimulation (FES) training in permanent spinal-motoneuron-denervated human muscle. Not earlier than 1 year after subjects experienced complete conus cauda lesion, their thigh muscles were electrically stimulated at home for several years with large skin surface electrodes and an expressly designed stimulator that delivered much longer impulses than those presently available for clinical use. The poor excitability of long-term denervated muscles was first improved by several months of twitch-contraction training. Then, the muscles were tetanically stimulated against progressively increased loads. Needle biopsies of vastus lateralis from long-term denervated subjects showed severe myofiber atrophy or lipodystrophy beginning 2 years after spinal cord injury (SCI). Muscle biopsies from a group of 3.6- to 13.5-year denervated subjects, who underwent 2.4 to 9.3 years of FES, show that this progressive training almost reverted long-term muscle atrophy/degeneration.

Adult↗
PubMed2001

In muscle-specific lipoprotein lipase-overexpressing mice, muscle triglyceride content is increased without inhibition of insulin-stimulated whole-body and muscle-specific glucose uptake.

In patients with type 2 diabetes, a strong correlation between accumulation of intramuscular triclycerides (TGs) and insulin resistance has been found. The aim of the present study was to determine whether there is a causal relation between intramuscular TG accumulation and insulin sensitivity. Therefore, in mice with muscle-specific overexpression of human lipoprotein lipase (LPL) and control mice, muscle TG content was measured in combination with glucose uptake in vivo, under hyperinsulinemic-euglycemic conditions. Overexpression of LPL in muscle resulted in accumulation of TGs in skeletal muscle (85.5 +/- 33.3 vs. 25.7 +/- 23.1 micromol/g tissue in LPL and control mice, respectively; P < 0.05). During the hyperinsulinemic clamp study, there were no differences in plasma glucose, insulin, and FFA concentrations between the two groups. Moreover, whole-body, as well as skeletal muscle, insulin-mediated glucose uptake did not differ between LPL-overexpressing and wild-type mice. Surprisingly, whole-body glucose oxidation was decreased by approximately 60% (P < 0.05), whereas nonoxidative glucose disposal was increased by approximately 50% (P < 0.05) in LPL-overexpressing versus control mice. In conclusion, overexpression of human LPL in muscle increases intramuscular TG accumulation, but does not affect whole-body or muscle-specific insulin-mediated uptake, findings that argue against a simple causal relation between intramuscular TG content and insulin resistance.

Animals↗
PubMed1998

A novel muscle spindle containing muscle fibres devoid of sensory innervation in the posterior cricoarytenoid muscle of the normal adult guinea pig.

A novel muscle spindle composed of five thin intrafusal muscle fibres and four thick muscle fibres was encountered in the posterior cricoarytenoid muscle of the normal adult guinea pig. Four intrafusal muscle fibres of the five were innervated by the annulospiral type of sensory ending, but lacked a distinct aggregation of equatorial nuclei such as bags and chains. On the other hand, one intrafusal fibre and four thick fibres between the layers of the spindle capsule absolutely lacked sensory innervation and were almost similar in the fine structural features to neighbouring extrafusal fibres. These fibres are considered to fail to receive the sensory innervation in an early stage of development, and to retain an undifferentiated feature of intrafusal fibre in the intracapsular space into adulthood or to follow the course of extrafusal differentiation between the layers of the spindle capsule. It is suggested therefore that this muscle spindle may be primitive.

Animals↗
PubMed2006

Differential expression of smooth muscle myosin, smooth muscle actin, h-caldesmon, and calponin in the diagnosis of myofibroblastic and smooth muscle lesions of skin and soft tissue.

The diagnosis of low-grade and pseudosarcomatous spindle cell lesions of skin and soft tissue can sometimes be problematic; in particular, distinction between fibroblastic, myofibroblastic, and smooth muscle proliferations can occasionally pose difficulties on routine histologic examination. We have applied a panel of immunohistochemical markers to a series of spindle cell lesions of skin and soft tissue to assess the utility of the differential expression of smooth muscle and myofibroblastic-associated markers. Twenty-eight cases of nodular fasciitis, 42 cases of fibromatosis, and 3 cases of myofibroblastic sarcoma were stained with antibodies against smooth muscle actin (SMA), smooth muscle myosin (SMMS), calponin, and high-molecular weight caldesmon (h-caldesmon). For comparison, 12 cases of cutaneous leiomyoma and 8 cases of leiomyosarcomas involving superficial soft tissues and fascia were studied with the same panel of antibodies. Thirty-eight of 42 cases of fibromatosis were positive for SMA, 42/42 cases were positive for calponin, 39/42 cases were negative for SMMS, and all cases were negative for h-caldesmon. All cases of nodular fasciitis were positive for SMA and calponin, and all were negative for h-caldesmon and SMMS. All cases of myofibroblastic sarcoma were positive for SMA and 2/3 cases for calponin, and were negative for SMMS and h-caldesmon. All cases of cutaneous leiomyoma and leiomyosarcoma were positive for all 4 markers tested. Our results demonstrate a remarkably consistent pattern of reactivity of muscle and myofibroblastic-associated markers in lesions predominantly composed of myofibroblastic spindle cells, characterized by positive staining for SMA and calponin and absence of reactivity for SMMS and h-caldesmon. Application of this panel of stains may be of aid in the differential diagnosis of low-grade myofibroblastic lesions such as nodular fasciitis and fibromatosis from smooth muscle tumors of skin and soft tissue. This panel may additionally be of assistance in the diagnosis of myofibroblastic sarcoma.

Actins↗
PubMed1998

Muscle fiber diameter and muscle type distribution following free microvascular muscle transfers: a prospective study.

The histology of free microvascular muscle flaps in 19 patients was studied prospectively. Biopsies were taken during operation, and after 2 and 6 weeks, as well as 3, 6, and 9 months, postoperatively, fixed and stained using the van Gieson method. Fiber diameters were analyzed morphometrically and fiber types defined immunohistochemically using myosin fast antibody. During the nine-month follow-up period, mean muscle fiber diameter decreased significantly (P < 0.01), type-1 fibers atrophied significantly (P < 0.05) compared to type-2 fibers, and the percentage of type-2 fibers increased from a mean of 56% intraoperatively to 73% at 9 months. Fatty change and fibrosis were already present 2 weeks after operation and increased with the duration of follow-up. The decrease in muscle fiber diameter 9 months after free flap transfer correlated with clinical factors such as the delay of reconstructive surgery, recipient site, postoperative infection, and postoperative immobilization. The present results confirm that type-specific atrophy related to denervation appears and indicates that clinical events other than denervation influence the muscle atrophy seen in human free muscle flaps. These findings focus attention on the role of muscle regeneration, reinnervation, and revascularization taking place after free flap transfer.

Adolescent↗
PubMed2004

Experimental muscle pain increases trapezius muscle activity during sustained isometric contractions of arm muscles.

OBJECTIVE: In the present study, the influence of experimental muscle pain on muscle co-ordination and fatigue development during sustained isometric elbow flexion was investigated. METHODS: Conventional surface electromyography (EMG) was recorded from the biceps brachii, brachioradialis, deltoideus and trapezius muscle during isometric elbow flexion at 40% maximum force. Single motor unit (MU) conduction velocity in the biceps brachii was assessed using a high spatial resolution surface EMG technique. Measurements were performed on 15 healthy subjects before, during and after (1) injection of hypertonic (pain condition) and (2) isotonic saline (control) into the biceps brachii. The pain intensity was assessed on a 10 cm visual analogue scale. RESULTS: The experimental results showed in both experimental sessions a fatigue-related increase of the root mean square value of EMG (222+/-164% of the baseline), and a decrease of the median frequency (118+/-16% of the baseline) in all investigated muscles. A maximum pain level of in average 3.2 cm on the visual analogue scale was reached after injection of hypertonic saline during contraction. Differences between painful and control condition were seen in an increased trapezius activity (230+/-141%) during pain. The global EMG activity of the brachioradialis and biceps brachii was unaffected by experimental muscle pain in line with unaffected single MU conduction velocity in the biceps brachii. Differences in endurance time (mean 89.3 and 102.3 s, pain and control, respectively) were not significant. CONCLUSIONS/SIGNIFICANCE: The findings suggest that upper extremity pain could be a possible source for overloading the trapezius muscle and as such is an important factor in occupational settings.

Adult↗
PubMed1986

Muscle morphology and enzymes in proximal and distal muscle groups of lower limb from patients with corticosteroid treated rheumatoid arthritis: the relationship to maximal isokinetic muscle strength.

Abnormal morphological and enzymatic patterns in the lateral vastus muscle have been found in women with corticosteroid treated rheumatoid arthritis. By means of biopsies from the lateral heads of right gastrocnemius muscles, the histology and enzyme activities were compared with those found in right vastus lateralis biopsies. The findings were correlated with isometric and isokinetic strength of the plantar flexors. The relative occurrence of type I fibres in the gastrocnemius muscle was 46.4 +/- 18.7 (SD) %, which is significantly higher than found in the vastus lateralis [35.7 +/- 13.3 (SD) %] (P less than 0.03). The relatively lower percentage of type II fibres in the gastrocnemius muscle was due to a relatively low percentage of type II A fibres [mean 27.9 +/- 16.4 (SD) %] (P less than 0.05). The area of type I fibres in the gastrocnemius muscle was 26.1 X 10(2) +/- 10.0 (SD) micron 2, which is 74% of the mean area for type I fibres found in the vastus lateralis (P less than 0.01). The area of type II fibres in the gastrocnemius was 14.9 X 10(2) +/- 7.1 (SD) micron 2, which is 77% of the mean area for type II fibres found in the vastus lateralis. The isokinetic muscle strength of the plantar flexors in corticosteroid treated patients with rheumatoid arthritis was reduced to less than 50% at all angular velocities when compared with healthy women. The same difference was found in the knee extensors.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2005

Skeletal muscle ATP turnover and muscle fiber conduction velocity are elevated at higher muscle temperatures during maximal power output development in humans.

The effect of temperature on skeletal muscle ATP turnover and muscle fiber conduction velocity (MFCV) was studied during maximal power output development in humans. Eight male subjects performed a 6-s maximal sprint on a mechanically braked cycle ergometer under conditions of normal (N) and elevated muscle temperature (ET). Muscle temperature was passively elevated through the combination of hot water immersion and electric blankets. Anaerobic ATP turnover was calculated from analysis of muscle biopsies obtained before and immediately after exercise. MFCV was measured during exercise using surface electromyography. Preexercise muscle temperature was 34.2 degrees C (SD 0.6) in N and 37.5 degrees C (SD 0.6) in ET. During ET, the rate of ATP turnover for phosphocreatine utilization [temperature coefficient (Q10) = 3.8], glycolysis (Q10 = 1.7), and total anaerobic ATP turnover [Q10 = 2.7; 10.8 (SD 1.9) vs. 14.6 mmol x kg(-1) (dry mass) x s(-1) (SD 2.3)] were greater than during N (P < 0.05). MFCV was also greater in ET than in N [3.79 (SD 0.47) to 5.55 m/s (SD 0.72)]. Maximal power output (Q10 = 2.2) and pedal rate (Q10 = 1.6) were greater in ET compared with N (P < 0.05). The Q10 of maximal and mean power were correlated (P < 0.05; R = 0.82 and 0.85, respectively) with the percentage of myosin heavy chain type IIA. The greater power output obtained with passive heating was achieved through an elevated rate of anaerobic ATP turnover and MFCV, possibly due to a greater effect of temperature on power production of fibers, with a predominance of myosin heavy chain IIA at the contraction frequencies reached.

Adenosine Triphosphate↗
PubMedDate not supplied

Distribution of muscle fibre types in human skeletal muscle fascicles: an autopsy study of three human muscles.

The predominance of type 2 fibres in the periphery of the muscle fascicle is a phenomenon attributed to local factors or to the adaptation of the muscle to functional needs. As the majority of relevant studies has been performed on quadriceps muscle of males, the purpose of this study was to examine other muscles along with quadriceps, in females as well as in males, with parallel morphometric analysis of fibres, in order to determine whether differences in size exist in addition to differences in proportion. Cryostat sections (ATPase, pH 9.4) were studied from 13 quadriceps femoris, 13 biceps brachii and 11 deltoid muscles taken at autopsy from 11 males and 8 females. The number and smallest diameter of type 1 and 2 fibres were counted and the percentage and mean diameter of the two types of fibres were calculated in the interior and the periphery of randomly selected fascicles. We found that: the predominance of type 2 fibres in the periphery is constant in all muscles studied, regardless of sex and age; there is a progressive age-related reduction in the diameter of type 2 fibres.

Adolescent↗