Daily in vivo neuromuscular stimulation effects on immobilized rat hindlimb muscles

1982 ◽  
Vol 53 (4) ◽  
pp. 960-966 ◽  
Author(s):  
P. F. Gardiner ◽  
M. A. Lapointe
Keyword(s):  
Relaxation Times ◽  
Plaster Cast ◽  
Daily Regimen ◽  
Cross Sectional ◽  
Time To Peak ◽  
Hindlimb Muscles ◽  
Twitch Characteristics ◽  
Gastrocnemius Muscles ◽  
Fast Twitch

The purpose of the investigation was to determine the effects of a daily regimen of near-maximal contractions, produced via in vivo electrical stimulation of peripheral nerve, on functional and histochemical properties of rat hindlimb muscles immobilized for 28 days in a plaster cast. Rats had knee and ankle joints of one hindlimb immobilized; then while anesthetized, half of the group was subjected to a daily regimen of 480 semifused tetanic contractions (50 Hz) via fine-wire electrodes chronically implanted around the sciatic nerve. Immobilization caused significant decreases in soleus and gastrocnemius muscle weights, fiber cross-sectional areas, and twitch and tetanic strength measured in situ. In addition, immobilized soleus muscles had faster time to peak tension (TPT) and higher proportions of fast-twitch fibers, whereas immobilized gastrocnemius muscles demonstrated faster half-relaxation times (RT1/2) and total twitch durations (TPT plus RT1/2). The only significant effects of the imposed contractions were evident in the gastrocnemius in which stimulation prevented the shortening of RT1/2 and total twitch duration and resulted in significantly higher relative tensions at 50 Hz and higher fatigue resistance. Muscle activity of this type imposed on immobilized muscle is ineffective in attenuating atrophy but can, in fast muscle such as gastrocnemius, prevent changes in twitch characteristics resulting from immobilization, as well as augment contractile responses during semifused and fatiguing contractions.

Muscle growth, cell number, type and morphometry in single and twin fetal lambs during mid to late gestation

2000 ◽  
Vol 12 (6) ◽  
pp. 319 ◽  
Author(s):  
S. A. McCoard ◽  
W. C. McNabb ◽  
S. W. Peterson ◽  
S. N. McCutcheon ◽  
P. M. Harris
Keyword(s):  
Muscle Mass ◽  
Litter Size ◽  
Muscle Growth ◽  
Cell Number ◽  
Late Gestation ◽  
Postnatal Life ◽  
Cross Sectional ◽  
Hindlimb Muscles ◽  
Full Complement ◽  
Gastrocnemius Muscles

Muscle growth, myofibre number, type and morphometry were studied in large hindlimb muscles of single and twin fetal lambs during mid to late gestation. Placental insufficiency, evident by lower total placentome weight and number per fetus, resulted in reduced fetal weights from 100 to 140 days gestation in twins compared with singletons (at 140 days: 5016 108 g v. 5750 246 g, respectively; P<0.05). However, competition between littermates did not consistently reduce muscle mass (15–22%) until 140 days gestation. Apparent myofibre number increased with age, indicating that the full complement of myofibres in some large hindlimb muscles may be achieved during early postnatal life. Litter size did not impact on apparent myofibre number in the semitendinosus, plantaris or gastrocnemius muscles. However, a transient effect on myofibre number in the adductor femoris muscle was observed from 80–120 days gestation. The phenotypic maturation of myofibres was unaffected by increasing litter size. Smaller muscle mass in twins was associated with smaller myofibre cross-sectional area in the semitendinosus, adductor femoris and gastrocnemius muscles at 140 days gestation. A similar trend was observed for the plantaris muscle. These results indicate that while competition between littermates for nutrients in late gestation can impact on both fetal and muscle mass, the fetus has the capacity to buffer against the effects of restricted nutrient supply on myofibre hyperplasia and phenotypic maturation, but myofibre hypertrophy is compromised.

Effect of inactivity and passive stretch on protein turnover in phasic and postural rat muscles

1986 ◽  
Vol 61 (1) ◽  
pp. 173-179 ◽  
Author(s):  
P. Loughna ◽  
G. Goldspink ◽  
D. F. Goldspink
Keyword(s):  
Soleus Muscle ◽  
Muscle Length ◽  
Protein Breakdown ◽  
Fractional Rate ◽  
Hindlimb Muscles ◽  
Synthetic Rate ◽  
Suspension Model ◽  
Fast Twitch ◽  
Passive Stretch

A state of hypokinesia and hypodynamia has been induced in the hindlimb muscles of the rat (100 g) using a suspension model. The ensuing muscle atrophy was assessed by reference to muscles in fully mobile control animals, which were either fed ad libitum or fed the same lower food intake of the suspended animals. Over a total of 7 days of suspension the slow-twitch postural soleus muscle underwent a much greater atrophy than the fast-twitch phasic extensor digitorum longus. Changes with respect to the position of the suspended foot, and hence muscle length, necessitate caution in comparing the extent of the atrophy between different muscle types. After 3 days of inactivity the atrophy of the soleus muscle was explained by a 21% decrease in the fractional rate of synthesis (measured in vivo) and a 100% increase in the rate of protein breakdown. The reduction in the synthetic rate was associated with a net loss (23%) of RNA and hence muscle ribosomes. In contrast when this inactive soleus muscle was permanently stretched the RNA content (44%) and protein synthetic rate increased (59%) markedly above control values. Although protein breakdown remained elevated in this stretched muscle, the extent of the atrophy in response to hypokinesia and hypodynamia was greatly reduced.

Chronic stimulation modifies the isotonic shortening velocity of denervated rat slow-twitch muscle

1986 ◽  
Vol 228 (1250) ◽  
pp. 43-58 ◽  
Keyword(s):  
Time Course ◽  
Relaxation Times ◽  
Maximum Velocity ◽  
Fast Muscle ◽  
Shortening Velocity ◽  
Time To Peak ◽  
Slow Twitch Muscle ◽  
Isometric Twitch ◽  
Denervated Muscles

Rat soleus muscles were denervated and stimulated in vivo for periods of up to 104 days. Stimuli used were trains of 1 ms pulses at 100 Hz delivered for periods of 1 s; trains were repeated every 10-100 s. In a majority of animals the tension of the muscles was maintained at about 10% of normal, equivalent to muscles denervated but unstimulated for 20 days. At the longest periods the stimulated muscles developed ten times more tension than ones that were denervated but not stimulated. In denervated and denervated-stimulated muscles twitch contraction and relaxation times were prolonged, compared with controls, for up to 3 weeks. Thereafter both sets showed a speeding of the isometric twitch that was greater in the stimulated muscles. At the longest periods the twitch was as short as that of a denervated fast muscle. Stimulation did not affect contralateral denervated muscles. Twitch: tetanus ratios remained high despite stimulation, and muscles showed little post-tetanic potentiation. Tension developed more rapidly in the tetani of the stimulated muscles, even allowing for larger final values. Maximum velocity of shortening was increased in many of the stimulated muscles, and there was a proportional flattening of the force-velocity curve, i.e. a/P 0 increased. Maximum velocity and a/P 0 increased reciprocally with twitch time to peak, so that those muscles that had twitches most changed by stimulation also had their isotonic properties modified to the greatest extent. Even at the longest period of stimulation, twitch time course and tetanic tension were not converted to those of normal fast muscle.

Fast-twitch muscle unit properties in different rat medial gastrocnemius muscle compartments

1996 ◽  
Vol 75 (6) ◽  
pp. 2243-2254 ◽  
Author(s):  
C. J. DeRuiter ◽  
A. De Haan ◽  
A. J. Sargeant
Keyword(s):  
Force Production ◽  
Medial Gastrocnemius ◽  
Type I ◽  
Nerve Branch ◽  
Cross Sectional ◽  
Entire Area ◽  
Distal Muscle ◽  
Muscle Compartment ◽  
Fast Twitch

1. The effect of muscle unit (MU) localization on physiological properties was investigated within the fast-twitch fatigue-resistant (FR) and fast-fatigable (FF) MU populations of rat medial gastrocnemius (MG) muscle. Single MG MUs were functionally isolated by microdissection of the ventral roots. FR and FF MU properties of the most proximal and distal muscle compartments were compared. The most proximal and distal compartment are subvolumes of the MG innervated by the most proximal and distal primary nerve branch, respectively. A subsample of the isolated units was glycogen depleted and muscle cross sections were stained for glycogen and myosin-adenosinetriphosphatase. 2. It was shown that proximal FF and FR units reached optimum length for force production at shorter muscle lengths compared with the distal FR and FF units. 3. The fast MUs of the proximal compartment had small territories that were located close to and/or within the mixed region (containing type I, IIA, IIX, and IIB fibers) of the muscle. The fast MUs of the distal compartment had greater territories that were located in the more superficial muscle part (containing only type IIX and IIB fibers) and in some cases spanned the entire area of the distal muscle compartment. 4. FR and FF MUs consisted of muscle fibers identified histochemically as type IIX and IIB, respectively. 5. Within each of the FR and FF MU populations, MUs that were located in the most proximal muscle compartment were more resistant to fatigue compared with the units located in the most distal compartment. 6. Cross-sectional fiber areas were smaller for the proximal FR and FF fibers, but specific force did not differ among units. Consequently, when account was taken of the innervation ratio, the proximal FR and FF units produced less force than distal units of the same type. Tetanic forces were 87 +/- 27 (SD) mN (proximal FR), 154 +/- 53 (SD) mN (distal FR), 142 +/- 25 (SD) mN (proximal FF), and 229 +/- 86 (SD) mN (distal FF). 7. The present findings suggest that with increasing demand placed on rat MG during in vivo locomotion, recruitment is likely to proceed from proximal to distal muscle parts within the FR and FF MU populations.

Contractile properties of transplanted extensor digitorum longus muscles of cats

1980 ◽  
Vol 238 (3) ◽  
pp. C120-C126 ◽  
Author(s):  
J. A. Faulkner ◽  
J. H. Niemeyer ◽  
L. C. Maxwell ◽  
T. P. White
Keyword(s):  
Time Course ◽  
Extensor Digitorum Longus ◽  
Autologous Transplantation ◽  
Relaxation Times ◽  
Contractile Properties ◽  
Extensor Digitorum ◽  
Cross Sectional ◽  
Control Value ◽  
Time To Peak ◽  
Significant Difference

Following autologous transplantation of whole extensor digitorum longus (EDL) muscles of cats into the EDL site, we investigated the degree and time course of restoration of contractile properties of autografts toward control values. Isometric and isotonic contractile properties of 66 autografted EDL muscles were measured in situ from 40 to 440 days following transplantation. The control value for maximum tetanus tension (P0) was 27 N. The mean P0 for the autografts increased from 2% of control 40 days after transplantation to 26% 440 days after transplantation. When P0 was normalized per square centimeter of muscle fiber cross-sectional area, no significant difference was observed between the P0 of autografts (28 N/cm2) and controls. Compared to controls, autografts 40-179 days following transplantation had slower time to peak twitch tensions, half-relaxation times, and maximum velocities of shortening and smaller twitch-tetanus tension ratios. Between 180 and 440 days after transplantation, values for autografts approached control values. Autografts fatigued more than twice as rapidly as controls.

A gene for speed: contractile properties of isolated whole EDL muscle from an α-actinin-3 knockout mouse

2008 ◽  
Vol 295 (4) ◽  
pp. C897-C904 ◽  
Author(s):  
S. Chan ◽  
J. T. Seto ◽  
D. G. MacArthur ◽  
N. Yang ◽  
K. N. North ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Mechanical Stability ◽  
Relaxation Times ◽  
Endurance Performance ◽  
Contractile Properties ◽  
Actin Binding ◽  
Power Performance ◽  
Cross Sectional ◽  
Edl Muscle ◽  
Fast Twitch

The actin-binding protein α-actinin-3 is one of the two isoforms of α-actinin that are found in the Z-discs of skeletal muscle. α-Actinin-3 is exclusively expressed in fast glycolytic muscle fibers. Homozygosity for a common polymorphism in the ACTN3 gene results in complete deficiency of α-actinin-3 in about 1 billion individuals worldwide. Recent genetic studies suggest that the absence of α-actinin-3 is detrimental to sprint and power performance in elite athletes and in the general population. In contrast, α-actinin-3 deficiency appears to be beneficial for endurance athletes. To determine the effect of α-actinin-3 deficiency on the contractile properties of skeletal muscle, we studied isolated extensor digitorum longus (fast-twitch) muscles from a specially developed α-actinin-3 knockout (KO) mouse. α-Actinin-3-deficient muscles showed similar levels of damage to wild-type (WT) muscles following lengthening contractions of 20% strain, suggesting that the presence or absence of α-actinin-3 does not significantly influence the mechanical stability of the sarcomere in the mouse. α-Actinin-3 deficiency does not result in any change in myosin heavy chain expression. However, compared with α-actinin-3-positive muscles, α-actinin-3-deficient muscles displayed longer twitch half-relaxation times, better recovery from fatigue, smaller cross-sectional areas, and lower twitch-to-tetanus ratios. We conclude that α-actinin-3 deficiency results in fast-twitch, glycolytic fibers developing slower-twitch, more oxidative properties. These changes in the contractile properties of fast-twitch skeletal muscle from α-actinin-3-deficient individuals would be detrimental to optimal sprint and power performance, but beneficial for endurance performance.

Developmental changes in hindlimb muscles and diaphragm of sheep

1992 ◽  
Vol 263 (4) ◽  
pp. R900-R908 ◽  
Author(s):  
D. I. Finkelstein ◽  
P. Andrianakis ◽  
A. R. Luff ◽  
D. W. Walker
Keyword(s):  
Relaxation Times ◽  
Developmental Changes ◽  
Medial Gastrocnemius ◽  
Neural Drive ◽  
Fetal Sheep ◽  
Heavy Chains ◽  
Hindlimb Muscles ◽  
Contraction Times ◽  
Contraction And Relaxation ◽  
Fast Twitch

In this study, plasma thyroxine, contractile and histochemical (adenosinetriphosphatase and NADH) characteristics of soleus (SOL), medial gastrocnemius (MG), and extensor digitorum longus (EDL) were examined in 140-day-gestation fetal sheep and in 2-, 5-, and 30-day-old lambs and adult ewes. Electrophoretic separation of myosin heavy chains was also done on all muscles and the diaphragm. There were no differences in the twitch contraction and relaxation times of MG and EDL at the different ages; in contrast SOL contraction times were significantly shorter in the fetus and newborn than in the adult. Fast glycolytic fibers first appeared in EDL, MG, and diaphragm at 5, 30, and 5 days after birth, respectively. The proportion of slow oxidative fibers decreased after birth and with postnatal development in EDL, whereas they increased in MG and diaphragm. Plasma thyroxine concentrations were higher in the fetus and day-old lambs than in 2-, 5-, and 30-day-old lambs or adult sheep. It is suggested that contractile specialization of the fast-twitch diaphragm, MG, and EDL is largely achieved in utero and is probably mediated by thyroid hormone. In contrast, SOL changed postnatally, probably influenced by the altered neural drive.

Preserved contractile function despite atrophic remodeling in unloaded rat hearts

2001 ◽  
Vol 281 (3) ◽  
pp. H1131-H1136 ◽  
Author(s):  
Denise C. Welsh ◽  
Konstantina Dipla ◽  
Patrick H. McNulty ◽  
Anbin Mu ◽  
Kaie M. Ojamaa ◽  
...  
Keyword(s):  
Contractile Function ◽  
Cardiac Contractility ◽  
Relaxation Times ◽  
Work Capacity ◽  
Papillary Muscles ◽  
Direct Stimulation ◽  
Cross Sectional ◽  
Time To Peak ◽  
Rat Hearts ◽  
Contraction And Relaxation

The present study was designed to determine whether myocardial atrophy is necessarily associated with changes in cardiac contractility. Myocardial unloading of normal hearts was produced via heterotopic transplantation in rats. Contractions of isolated myocytes (1.2 mM Ca2+; 37°C) were assessed during field stimulation (0.5, 1.0, and 2.0 Hz), and papillary muscle contractions were assessed during direct stimulation (2.0 mM Ca2+; 37°C; 0.5 Hz). Hemodynamic unloading was associated with a 41% decrease in median myocyte volume and proportional decreases in myocyte length and width. Nevertheless, atrophic myocytes had normal fractional shortening, time to peak contraction, and relaxation times. Despite decreases in absolute maximal force generation (Fmax), there were no differences in Fmax/ area in papillary muscles isolated from unloaded transplanted hearts. Therefore, atrophic remodeling after unloading is associated with intact contractile function in isolated myocytes and papillary muscles when contractile indexes are normalized to account for reductions in cell length and cross-sectional area, respectively. Nevertheless, in the absence of compensatory increases in contractile function, reductions in myocardial mass will lead to impaired overall work capacity.

Biochemical and physiological changes in overloaded rat fast- and slow-twitch ankle extensors

1985 ◽  
Vol 59 (2) ◽  
pp. 639-646 ◽  
Author(s):  
R. R. Roy ◽  
K. M. Baldwin ◽  
T. P. Martin ◽  
S. P. Chimarusti ◽  
V. R. Edgerton
Keyword(s):  
Fiber Type ◽  
Relaxation Times ◽  
Glycogen Metabolism ◽  
Medial Gastrocnemius ◽  
Cross Sectional ◽  
Muscle Region ◽  
Type Composition ◽  
Contraction Times ◽  
Slow Twitch ◽  
Fast Twitch

The rat soleus (SOL) or medial gastrocnemius (MG) were chronically overloaded by removing their major synergists bilaterally. After 12–14 wks the overloaded SOL (OS) and overloaded MG (OMG) muscles had approximately 50% greater cross-sectional areas (CSA) than the controls. Maximum twitch (Pt) and tetanic (Po) tensions were approximately 46% larger in the OS compared with the normal SOL. The OMG produced 10 and 37% higher Pt and Po, respectively. Specific tension (Po/CSA) was not altered in either group (P greater than 0.05). Contraction times and half-relaxation times were unchanged. Myofibrillar and myosin ATPase specific activities indicated a shift toward that resembling a slower muscle in both the OS and the red portion but not the white portion of the OMG. Generally, markers of glycogen metabolism were reduced (P less than 0.05) in the same muscle areas that showed reduced ATPase activity. These biochemical results were consistent with the apparent histochemical conversion of fibers from fast-twitch, glycolytic----fast-twitch, oxidative-glycolytic----slow-twitch, oxidative types in these muscle areas. These results suggest that overloading either a fast- or slow-twitch plantarflexor results in an increase in muscle mass and maximum tension and in metabolic shifts that generally resemble those observed in a slower muscle. Further, the degree of adaptation appears to be related to the initial fiber type composition of the muscle and/or of the muscle region.

scholarly journals Blood flow and glucose uptake in denervated, insulin-resistant muscles

1998 ◽  
Vol 274 (2) ◽  
pp. R311-R317 ◽  
Author(s):  
Jiri Turinsky ◽  
Alice Damrau-Abney ◽  
Daniel J. Loegering
Keyword(s):  
Insulin Resistance ◽  
Blood Flow ◽  
Soleus Muscle ◽  
Internal Control ◽  
Muscle Blood Flow ◽  
Insulin Resistant ◽  
Denervated Muscles ◽  
Gastrocnemius Muscles ◽  
Fast Twitch

To investigate whether changes in blood flow contribute to the insulin resistance in denervated muscles, basal and insulin-stimulated 2-deoxy-d-glucose (2-DG) uptake in vivo and blood flow were measured in soleus (slow twitch), plantaris (fast twitch), and gastrocnemius (fast twitch) muscles at 1 and 3 days after a right hindlimb denervation in the rat. Muscles of the contralateral sham hindlimb served as an internal control. Sham plantaris and gastrocnemius muscles showed 32 and 60% lower basal 2-DG uptake, 46 and 66% lower insulin-stimulated 2-DG uptake, and 79 and 81% lower blood flow, respectively, compared with sham soleus muscle. At 1 day after denervation, soleus, plantaris, and gastrocnemius muscles exhibited an 80, 64, and 42% decrease in insulin-stimulated 2-DG uptake, respectively, in the presence of 63, 323, and 304% higher blood flow, respectively. At 3 days after denervation, soleus muscle showed a 60% decrease in basal 2-DG uptake, complete unresponsiveness to insulin, and an 86% decrease in blood flow. In contrast, the denervated plantaris and gastrocnemius muscles exhibited a 262 and 105% increase in basal 2-DG uptake, respectively, no change in insulin-stimulated 2-DG uptake, and no change in blood flow compared with corresponding contralateral sham muscles. The results demonstrate that muscle blood flow is influenced by muscle fiber population and time after denervation and that changes in blood flow do not contribute to the insulin resistance in the denervated muscles.

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