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.

Effects of thyroidectomy on development of skeletal muscle in fetal sheep

1991 ◽  
Vol 261 (5) ◽  
pp. R1300-R1306 ◽  
Author(s):  
D. I. Finkelstein ◽  
P. Andrianakis ◽  
A. R. Luff ◽  
D. Walker
Keyword(s):  
Skeletal Muscle ◽  
Thyroid Gland ◽  
Extensor Digitorum Longus ◽  
Relaxation Times ◽  
Medial Gastrocnemius ◽  
Fetal Sheep ◽  
Twitch Contraction ◽  
Slow Twitch ◽  
Contraction And Relaxation ◽  
Fast Twitch

The influence of the thyroid gland on the functional and histochemical development of fast- and slow-twitch skeletal muscle of fetal sheep has been studied in euthyroid fetal sheep (n = 6) and athyroid fetuses (n = 4) surgically thyroid-ectomized at 70-75 days of gestation. Two fast-twitch muscles, the medial gastrocnemius and extensor digitorum longus, and the slow-twitch soleus muscle were studied at the fetal age of 140 days gestation. The athyroid fetuses had significantly slower twitch contraction and relaxation times in both the medial gastrocnemius and extensor digitorum longus muscles compared with the euthyroid fetuses. Twitch contraction and relaxation times of the soleus were not different in the two groups. Thyroidectomy resulted in an increase in the proportion of fast (type II) muscle fibers and myosin, as shown histochemically and by gel electrophoresis of heavy-chain myosins. These results indicate that the functional maturation of the fast-twitch muscles of sheep is influenced by the presence of an intact thyroid gland from at least 70 days of gestation. In contrast, the slow-twitch soleus muscle fiber diameter and twitch contraction and relaxation times were not different in the two groups.

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.

Adaptation of fibers in fast-twitch muscles of rats to spaceflight and hindlimb suspension

1992 ◽  
Vol 73 (2) ◽  
pp. S58-S65 ◽  
Author(s):  
B. Jiang ◽  
Y. Ohira ◽  
R. R. Roy ◽  
Q. Nguyen ◽  
E. I. Ilyina-Kakueva ◽  
...  
Keyword(s):  
Cross Sections ◽  
Medial Gastrocnemius ◽  
Hindlimb Suspension ◽  
Cross Sectional ◽  
Heavy Chains ◽  
Fast Myosin ◽  
Glycerophosphate Dehydrogenase ◽  
Close Relationship ◽  
Fast Myosin Heavy Chain ◽  
Fast Twitch

The adaptation of single fibers in medial gastrocnemius (MG), a fast-twitch extensor, and tibialis anterior (TA), a fast-twitch flexor, was studied after 14 days of spaceflight (COSMOS 2044) or hindlimb suspension. Cross-sectional area (CSA) and succinate dehydrogenase (SDH), alpha-glycerophosphate dehydrogenase (GPD), and myofibrillar adenosinetriphosphatase (ATPase) activities were determined in fibers identified in frozen serial cross sections. Fibers were categorized as light, dark, or intermediate on the basis of myosin ATPase staining and alkaline preincubation and immunohistochemically as reacting with slow, fast, or both slow and fast myosin heavy chain monoclonal antibodies. Because there was a close relationship between these two means of categorizing fibers, all fibers were categorized on the basis of the immunohistochemical reaction. The percentage of slow- and fast-twitch fibers of the MG and TA were unchanged in either group. Mean fiber size of all fibers, irrespective of type, was unaffected in either muscle after flight or suspension. The fibers that expressed both fast and slow myosin heavy chains were smaller than control in the MG of both experimental groups. Compared with control, the SDH and total SDH activities in the MG were significantly less in suspended rats, with the fast-twitch fibers showing the largest difference. The ATPase activity in the MG was higher in flight than in control or suspended rats. There were no significant effects of flight on fibers of the TA. In contrast, the TA in suspended rats had higher GPD activities than either control or flight rats.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of human thenar motor-unit properties studied by intraneural motor-axon stimulation and spike-triggered averaging

1990 ◽  
Vol 64 (4) ◽  
pp. 1347-1351 ◽  
Author(s):  
C. K. Thomas ◽  
B. Bigland-Ritchie ◽  
G. Westling ◽  
R. S. Johansson
Keyword(s):  
Relaxation Times ◽  
Motor Units ◽  
Motor Axon ◽  
Mean Values ◽  
Spike Triggered Averaging ◽  
Contraction Times ◽  
Human Motor ◽  
Force Components ◽  
Contraction And Relaxation ◽  
Resultant Forces

1. Measurements of twitch contractile properties of human motor units recorded by spike-triggered averaging may be distorted by partial fusion between twitches, because motor units seldom fire at rates below 8-10 Hz. The effects of this fusion were examined by comparing the responses of 27 human thenar motor units when their motor axons were stimulated at 1, 8, and 10 Hz. 2. Resultant forces were calculated from the abduction and flexion force components, together with various contraction and relaxation rate indexes as reported previously. Values for single twitches were compared to measurements made from the unfused force fluctuations ("apparent twitches") of the same units recorded during 8 and 10 Hz stimulation. 3. For all units, stimulation at 8 and 10 Hz caused partial twitch fusion. At 10 Hz, mean values for "apparent twitch" forces, contraction times (CT), and one-half relaxation times (1/2RT) were reduced to 44, 76, and 52% of the corresponding values measured from separate twitches evoked by 1 Hz stimulation. Similar but smaller reductions were seen at 8 Hz. 4. Slow units, with initial twitch CT greater than 60 ms, showed significantly more distortion of all "apparent twitch" parameters when stimulated at both 8 and 10 Hz, compared to fast units (less than 50 ms). 5. The potentiated abduction force component data were compared with abduction forces obtained previously by spike-triggered averaging from the same muscle group. Mean force obtained by spike-triggered averaging ("STA twitch" force: 21 mN) was significantly larger than that measured in abduction in response to either 1 or 10 Hz motor-axon stimulation (14 mN, 6 mN, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Guinea pig soleus and gastrocnemius electromyograms at varying speeds, grades, and loads

1982 ◽  
Vol 52 (2) ◽  
pp. 451-457 ◽  
Author(s):  
K. R. Gardiner ◽  
P. F. Gardiner ◽  
V. R. Edgerton
Keyword(s):  
Guinea Pig ◽  
Work Load ◽  
Burst Duration ◽  
Lateral Gastrocnemius ◽  
Biochemical Alterations ◽  
Hindlimb Muscles ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Grade Increase ◽  
Emg Electrodes

The purpose of the study was to describe changes that occur in the usage of fast-twitch and slow-twitch guinea pig hindlimb muscles, as estimated using chronically implanted electromyogram (EMG) electrodes, during voluntary locomotion under various conditions. Guinea pigs, in which fine wire electrodes were implanted in soleus (SOL) and lateral gastrocnemius (LG) muscles, were exercised at various speeds (13.4, 26.8, 40.2 m/min), grades (0–30%) and in some conditions loads (50–150 g) on a motor-driven treadmill. Bipolar EMG signals were rectified-averaged (RA-EMG) and analyzed for burst duration, amplitude, and the integral of each burst (IEMG). For each condition and muscle, total IEMG/min (IEMG/step x steps/min) was calculated and expressed as a percent of the maximum IEMG recorded. With increasing speed at 0% grade, the ratio of LG to SOL IEMG, each expressed as percent of maximum, remained constant at about 0.82. An increased stepping rate of 150 (at 13.4 m/min) to 225 (at 40.2 m/min) steps/min was accompanied by a 37% decrease in burst duration in LG and SOL. When the treadmill belt speed was increased from 13.4 to 4.02 m/min at 30% grade, the LG/SOL ratio increased from 0.83 to 1.03, whereas burst duration decreased by 49% (SOL) and 51% (LG). Soleus IEMG did not change significantly with increases in speed or grade; LG IEMG increased significantly with speed at 10% grade and with grade increase at the highest speed (40.2 m/min). These data provide some insight into how modifications of work load on a treadmill affect overall muscle activity and may assist in the interpretation of training-induced muscle biochemical alterations previously noted by other investigators.

Recurrent inhibition to and from motoneurons innervating the flexor digitorum and flexor hallucis longus muscles of the cat

1990 ◽  
Vol 63 (3) ◽  
pp. 395-403 ◽  
Author(s):  
T. M. Hamm
Keyword(s):  
Tibialis Anterior ◽  
Recurrent Inhibition ◽  
Medial Gastrocnemius ◽  
Flexor Hallucis Longus ◽  
Flexor Digitorum Longus ◽  
Lateral Gastrocnemius ◽  
Hindlimb Muscles ◽  
Inhibitory Postsynaptic Potentials ◽  
Flexor Digitorum ◽  
Stimulation Of

1. Recurrent inhibitory postsynaptic potentials (IPSPs) to and from motoneurons innervating the flexor digitorum longus (FDL) and flexor hallucis longus (FHL) muscles of the cat were investigated to determine whether recurrent inhibitory projections involving these motoneurons are similar--as would be consistent with the Ia and anatomic synergism of FDL and FHL--or are dissimilar, as are the activities of these muscles during locomotion (O'Donovan et al. 1982). 2. Composite recurrent IPSPs were recorded in several species of motoneurons innervating hindlimb muscles in response to stimulation of a number of muscle nerves in cats allowed to become unanesthetized after ischemic decapitation. 3. No recurrent IPSPs from stimulation of the FDL nerve were observed in motoneurons innervating FDL, FHL, lateral gastrocnemius-soleus (LG-S), medial gastrocnemius (MG), plantaris (Pl), tibialis anterior (TA), or extensor digitorum longus (EDL). 4. The recurrent IPSPs produced by stimulation of FHL were larger and found more frequently in LG-S than in FDL motoneurons. Recurrent inhibition from FHL was also greater in Pl than in FDL motoneurons. 5. The recurrent IPSPs produced by stimulation of LG-S, PL, and MG were larger in FHL than in FDL motoneurons, and those from LG-S and MG were found more frequently in FHL than in FDL motoneurons. 6. Stimulation of the TA nerve produces recurrent IPSPs in FDL but not in FHL motoneurons. A few FDL and FHL cells (6 of 23 and 9 of 34, respectively) received small (less than 0.5 mV) recurrent IPSPs from stimulation of the EDL nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effects of ovariectomy and hindlimb unloading on skeletal muscle

1998 ◽  
Vol 85 (4) ◽  
pp. 1316-1321 ◽  
Author(s):  
Jonathan S. Fisher ◽  
Eileen M. Hasser ◽  
Marybeth Brown
Keyword(s):  
Skeletal Muscle ◽  
Body Weight ◽  
Muscle Growth ◽  
Relaxation Times ◽  
Hindlimb Unloading ◽  
Female Rats ◽  
Time To Peak ◽  
Skeletal Muscle Contraction ◽  
Contraction Times ◽  
Main Effects

Female rats (7–8 mo old, n = 40) were randomly placed into the intact control (Int) and ovariectomized control (Ovx) groups. Two weeks after ovariectomy, animals were further divided into intact 2-wk hindlimb unloaded (Int-HU) and ovariectomized hindlimb unloaded (Ovx-HU). We hypothesized that there would be greater hindlimb unloading-related atrophy in Ovx than in Int rats. In situ contractile tests were performed on soleus (Sol), plantaris (Plan), peroneus longus (Per), and extensor digitorum longus (EDL) muscles. Body weight and Sol mass were ∼22% larger in Ovx than in Int group and ∼18% smaller in both HU groups than in Int rats (Ovx × HU interaction, P < 0.05), and there was a similar trend in Plan muscle ( P< 0.07). There were main effects ( P< 0.05) for both ovariectomy (growth) and hindlimb unloading (atrophy) on gastrocnemius mass. Mass of the Per and EDL muscles was unaffected by either ovariectomy or hindlimb unloading. Time to peak twitch tension for EDL and one-half relaxation times for Sol, Plan, Per, and EDL muscles were faster ( P< 0.05) in Ovx than in Int animals. The results suggest that 1) ovariectomy led to similar increases of ∼20% in body weight and plantar flexor mass; 2) hindlimb unloading may have prevented ovariectomy-related muscle growth; 3) greater atrophy may have occurred in Sol and Plan of Ovx animals compared with controls; and 4) removal of ovarian hormonal influence decreased skeletal muscle contraction times.

Repeated force production and metabolites in two medial gastrocnemius muscle compartments of the rat

1995 ◽  
Vol 79 (6) ◽  
pp. 1855-1861 ◽  
Author(s):  
C. J. De Ruiter ◽  
A. De Haan ◽  
A. J. Sargeant
Keyword(s):  
Blood Flow ◽  
Motor Nerve ◽  
Force Production ◽  
Oxidative Capacity ◽  
Medial Gastrocnemius ◽  
Train Duration ◽  
Functional Consequences ◽  
Force Recovery ◽  
The Difference ◽  
Fast Twitch

The most proximal and distal motor nerve branches in the rat medial gastrocnemius innervate discrete muscle compartments dominated by fast-twitch oxidative and fast-twitch glycolytic fibers, respectively. The functional consequences of the difference in oxidative capacity between these compartments were investigated. Wistar rats were anesthetized with pentobarbital sodium (90 mg/kg ip). Changes in force of both compartments during 21 isometric contractions (train duration 200 ms, stimulation frequency 120 Hz, 3 s between contractions) were studied in situ with and without blood flow. Without blood flow, force and phosphocreatine declined to a greater extent in the proximal than the distal compartment compared with the run with intact flow. After the protocol without blood flow, when flow was restored, the time constants for force recovery (which were closely associated to the recovery of phosphocreatine) were 37 +/- 7 (SD) (proximal compartment) and 148 +/- 20 s (distal compartment). It was concluded that the proximal compartment had a four times higher oxidative capacity and, therefore, a superior ability for repeated force production.

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