Effect of testosterone of the proliferation of satellite cells in extensor digitorum longus muscle. An in vivo and in vitro study

1992 ◽  
Vol 76 (2) ◽  
pp. 220-220
Author(s):  
Joubert Yolaine ◽  
Alameddine Hala ◽  
Tobin Christine
Keyword(s):  
Satellite Cells ◽  
Extensor Digitorum Longus ◽  
In Vitro Study ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Vitro Study ◽  
Longus Muscle

scholarly journals The effect of tendon compliance on in vitro/in vivo estimations of sarcomere length

1995 ◽  
Vol 198 (2) ◽  
pp. 503-506
Author(s):  
R James ◽  
I Young ◽  
J Altringham
Keyword(s):  
Extensor Digitorum Longus ◽  
Sarcomere Length ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Worst Case ◽  
Longus Muscle ◽  
Tendon Compliance

The errors likely to result from using excised rigor muscles to determine in vivo sarcomere length ranges were calculated for mouse extensor digitorum longus muscle (EDL). This muscle was chosen because its very long tendon makes it particularly susceptible to errors arising from tendon compliance. By placing dissected limbs into different locomotory stances, and allowing them to go into rigor, the range of sarcomere lengths over which muscles operate in vivo can be determined, but it is subject to errors due to tendon compliance. A tendon compliance of 0.24 GPa and a muscle rigor stress of 35 kPa were determined, and these were used to correct the estimates of in vivo sarcomere length, under worst case conditions. The error introduced was very small: a reduction in sarcomere length of less than 0.5 %.

Potentiation of in vitro concentric work in mouse fast muscle

1998 ◽  
Vol 84 (1) ◽  
pp. 236-243 ◽  
Author(s):  
R. W. Grange ◽  
R. Vandenboom ◽  
J. Xeni ◽  
M. E. Houston
Keyword(s):  
Extensor Digitorum Longus ◽  
Conditioning Stimulus ◽  
Muscle Length ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Fast Muscle ◽  
Phosphate Content ◽  
Longus Muscle

Grange, R. W., R. Vandenboom, J. Xeni, and M. E. Houston.Potentiation of in vitro concentric work in mouse fast muscle. J. Appl. Physiol. 84(1): 236–243, 1998.—Phosphorylation of myosin regulatory light chain (R-LC) is associated with potentiated work and power during twitch afterloaded contractions in mouse extensor digitorum longus muscle [R. W. Grange, C. R. Cory, R. Vandenboom, and M. E. Houston. Am. J. Physiol. 269 ( Cell Physiol. 38): C713–C724, 1995]. We now describe the association between R-LC phosphorylation and potentiated concentric work when the extensor digitorum longus muscle is rhythmically shortened and lengthened to simulate contractions in vivo. Work output (at 25°C) was characterized at sine frequencies of 3, 5, 7, 10, and 15 Hz at excursions of 0.6, 1.2, and 1.6 mm (∼5, 9, and 13% optimal muscle length) at a low level of R-LC phosphorylation. Muscles stimulated during the sine function with a single twitch at specific times before or after the longest muscle length yielded maximal concentric work near the longest muscle length at a sine frequency of 7 Hz (e.g., excursion ∼9% optimal muscle length = 1.6 J/kg). Power increased linearly between sine frequencies of 3 and 15 Hz at all excursions (maximum ∼29 W). After a 5-Hz 20-s conditioning stimulus and coincident with a 3.7-fold increase in R-LC phosphate content (e.g., from 0.19 to 0.70 mol phosphate/mol R-LC), work at the three excursions and a sine frequency of 7 Hz was potentiated a mean of 25, 44, and 50% ( P < 0.05), respectively. The potentiated work during rhythmic contractions is consistent with enhanced interaction between actin and myosin in the force-generating states. On the basis of observations in skinned skeletal muscle fibers (H. L. Sweeney and J. T. Stull. Proc. Natl. Acad. Sci. USA 87: 414–418, 1990), this enhancement could result from increased phosphate incorporation by the myosin R-LC. Under the assumption that the predominant effect of the conditioning stimulus was to increase R-LC phosphate content, our data suggest that a similar mechanism may be evident in intact muscle.

scholarly journals The influence of electrical stimulation in vitro on protein synthesis and other metabolic parameters of rat extensor digitorum longus muscle

1970 ◽  
Vol 118 (2) ◽  
pp. 209-220 ◽  
Author(s):  
Virginia M. Pain ◽  
K. L. Manchester
Keyword(s):  
Amino Acids ◽  
Electrical Stimulation ◽  
Amino Acid ◽  
Extensor Digitorum Longus ◽  
Glucose Consumption ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Longus Muscle

1. Apparatus is described in which rat extensor digitorum longus muscle can be incubated in buffer under conditions of light tension and be subject to contractures induced by electrical stimulation in vitro. Under these conditions the tissue retains its weight, its content of potassium and size of the extracellular space at values similar to those in vivo. 2. Though uptake of glucose was enhanced on addition of insulin, there was little increase in glucose consumption on stimulation. Breakdown of glycogen and enhancement of lactate output were found on stimulation. 3. Incorporation into protein of several labelled amino acids was diminished during stimulation. Accumulation of [14C]leucine was enhanced whereas that of glycine was decreased. 4. There were no very consistent changes in the content of free unlabelled amino acids during incubation with or without stimulation. Comparison of actual amino acid concentrations in tissue and incubation mixture with accumulation of 14C-labelled amino acid indicated that full equilibration of the cell pool of amino amino acids with the medium is slow. 5. Substantial oxidation of several 14C-labelled acids was observed. 6. The ATP content of the tissue declined a little during incubation and somewhat faster after a period of stimulation. 7. The results are discussed in relation to the way in which exercise can induce muscle hypertrophy.

scholarly journals The influence of passive stretch on the growth and protein turnover of the denervated extensor digitorum longus muscle

1978 ◽  
Vol 174 (2) ◽  
pp. 595-602 ◽  
Author(s):  
David F. Goldspink
Keyword(s):  
Protein Synthesis ◽  
Extensor Digitorum Longus ◽  
Similar Rate ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Denervated Muscle ◽  
Longus Muscle ◽  
Induced Changes ◽  
Passive Stretch

At 7 days after cutting the sciatic nerve, the extensor digitorum longus muscle was smaller and contained less protein than its innervated control. Correlating with these changes was the finding of elevated rates of protein degradation (measured in vitro) in the denervated tissue. However, at this time, rates of protein synthesis (measured in vitro) and nucleic acid concentrations were also higher in the denervated tissue, changes more usually associated with an active muscle rather than a disused one. These anabolic trends have, at least in part, been explained by the possible greater exposure of the denervated extensor digitorum longus to passive stretch. When immobilized under a maintained influence of stretch the denervated muscle grew to a greater extent. Although this stretch-induced growth appeared to occur predominantly through a stimulation of protein synthesis, it was opposed by smaller increases in degradative rates. Nucleic acids increased at a similar rate to the increase in muscle mass when a continuous influence of stretch was imposed on the denervated tissue. In contrast, immobilization of the denervated extensor digitorum longus in a shortened unstretched state reversed most of the stretch-induced changes; that is, the muscle became even smaller, with protein synthesis decreasing to a greater extent than breakdown after the removal of passive stretch. The present investigation suggests that stretch will promote protein synthesis and hence growth of the extensor digitorum longus even in the absence of an intact nerve supply. However, some factor(s), in addition to passive stretch, must contribute to the anabolic trends in this denervated muscle.

Alterations in intramuscular connective tissue after limb casting affect contraction-induced muscle injury

1995 ◽  
Vol 78 (3) ◽  
pp. 1065-1069 ◽  
Author(s):  
T. K. Lapier ◽  
H. W. Burton ◽  
R. Almon ◽  
F. Cerny
Keyword(s):  
Connective Tissue ◽  
Muscle Injury ◽  
Extensor Digitorum Longus ◽  
Plantar Flexion ◽  
Extensor Digitorum ◽  
Control Group ◽  
Longus Muscle ◽  
Limb Immobilization

This study examined the effect of alterations in rat intramuscular connective tissue (CT), secondary to limb immobilization, on the muscle's susceptibility to contraction-induced injury. Hindlimbs were casted for 3 wk with the extensor digitorum longus muscle fixed in a shortened (IM-SP) or lengthened position (IM-LP). An age-matched control group remained uncasted. Extensor digitorum longus muscles were injured in vivo by using a motorized foot pedal that repeatedly flexed and extended the foot while the muscle was electrically stimulated during plantar flexion. Four hours postinjury, maximum isometric tetanic force (Po) was measured in vitro and was used as a functional index of muscle injury. Muscles were fixed, sectioned, and stained for later analysis. Intramuscular CT concentration, expressed as the ratio of CT area to muscle fiber area, was significantly higher in both IM-SP (0.153 +/- 0.003) and IM-LP (0.174 +/- 0.003) groups compared with controls (0.104 +/- 0.003). Po values of injured muscles both IM-LP and IM-SP were higher than the injured controls' Po of 9.41 +/- 0.63 N/cm2 (P < 0.05). Injured IM-LP muscle forces were significantly higher than those of IM-SP. This study demonstrated that limb immobilization increases intramuscular CT concentration, which is accompanied by attenuation of muscle injury. We conclude that remodeling of intramuscular CT affects the muscle's resistance to contraction-induced injury.

scholarly journals Differential effects of acute changes in cell Ca2+ concentration on myofibrillar and non-myofibrillar protein breakdown in the rat extensor digitorum longus muscle in vitro. Assessment by production of tyrosine and Nτ-methylhistidine

1987 ◽  
Vol 241 (1) ◽  
pp. 121-127 ◽  
Author(s):  
M N Goodman
Keyword(s):  
Extensor Digitorum Longus ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Ionophore A23187 ◽  
Myofibrillar Proteins ◽  
Rat Muscle ◽  
Longus Muscle ◽  
Acute Changes ◽  
Tissue Contents

The influence of Ca2+ on myofibrillar proteolysis was evaluated in the isolated extensor digitorum longus muscle incubated in vitro with agents previously shown to increase the intracellular concentration of Ca2+. Myofibrillar proteolysis was evaluated by measuring the release of N tau-methylhistidine, and total proteolysis was evaluated by measuring tyrosine release by incubated muscles after the inhibition of protein synthesis with cycloheximide. Incubated muscles released measurable quantities of N tau-methylhistidine, and muscle contents of the amino acids remained stable over 2 h of incubation. The release of N tau-methylhistidine by incubated muscles was similar to its release by perfused rat muscle in response to brief starvation, indicating the integrity of the incubated muscles. Ca2+ ionophore A23187, dibucaine, procaine, caffeine and elevated K+ concentration increased lactate release by incubated muscles and decreased tissue contents of ATP and phosphocreatine to varying degrees, indicating the metabolic effectiveness of the agents tested. Only A23187 and dibucaine increased total cell Ca2+, and they increased tyrosine release. Caffeine and elevated [K+] increased neither cell Ca2+ nor tyrosine release; however, only A23187 and dibucaine increased tyrosine release significantly. On the other hand, these agents were without effect on myofibrillar proteolysis as assessed by N tau-methylhistidine release by incubated muscles and changes in tissue contents of the amino acid. In fact, some of the agents tested tended to decrease myofibrillar proteolysis slightly. These results indicate that acute elevation of intracellular Ca2+ is associated with increased breakdown of non-myofibrillar but not myofibrillar proteins. Because of this, the role of elevated Ca2+ in muscle atrophy in certain pathological states is questioned. The data also indicate that the breakdown of myofibrillar and non-myofibrillar proteins in muscle is regulated independently and by different pathways, a conclusion reached in previous studies with perfused rat muscle.

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