Effect of hindlimb unloading on rat soleus fiber force, stiffness, and calcium sensitivity

1995 ◽  
Vol 79 (5) ◽  
pp. 1796-1802 ◽  
Author(s):  
K. S. McDonald ◽  
R. H. Fitts
Keyword(s):  
Time Course ◽  
Fiber Diameter ◽  
Isometric Force ◽  
Calcium Sensitivity ◽  
Cross Sectional Area ◽  
Hindlimb Unloading ◽  
Sectional Area ◽  
Cross Sectional ◽  
Control Value ◽  
Cross Bridges

The purpose of this study was to examine the time course of change in soleus muscle fiber peak force (N), tension (Po, kN/m2), elastic modulus (Eo), and force-pCa and stiffness-pCa relationships. After 1, 2, or 3 wk of hindlimb unloading (HU), single fibers were isolated and placed between a motor arm and a transducer, and fiber diameter, peak absolute force, Po, Eo, and force-pCa and stiffness-pCa relationships were characterized. One week of HU resulted in a significant reduction in fiber diameter (68 +/- 2 vs 57 +/- 1 microns), force (3.59 +/- 0.15 vs. 2.19 +/- 0.12 x 10(-4) N), Po (102 +/- 4 vs. 85 +/- 2 kN/m2), and Eo (1.96 +/- 0.12 vs. 1.37 +/- 0.13 x 10(7) N/m2), and 2 wk of HU caused a further decline in fiber diameter (45 +/- 1 microns), force (1.31 +/- 0.06 x 10(-4) N), and Eo (0.96 +/- 0.09 x 10(7) N/m2). Although the mean fiber diameter and absolute force continued to decline through 3 wk of HU, Po recovered to values not significantly different from control. The Po/Eo ratio was significantly increased after 1 (5.5 +/- 0.3 to 7.1 +/- 0.6), 2, and 3 wk of HU, and the 2-wk (9.5 +/- 0.4) and 3-wk (9.4 +/- 0.8) values were significantly greater than the 1-wk values. The force-pCa and stiffness-pCa curves were shifted rightward after 1, 2, and 3 wk of HU. At 1 wk of HU, the Ca2+ sensitivity of isometric force, assessed by Ca2+ concentration required for half-maximal force, was increased from the control value of 1.83 +/- 0.12 to 2.30 +/- 0.10 microM. In conclusion, after HU, the decrease in soleus fiber Po can be explained by a reduction in the number of myofibrillar cross bridges per cross-sectional area. Our working hypothesis is that the loss of contractile protein reduces the number of cross bridges per cross-sectional area and increases the filament lattice spacing. The increased spacing reduces cross-bridge force and stiffness, but Po/Eo increases because of a quantitatively greater effect on stiffness.

Mechanical deficit persists during long-term muscle hypertrophy

1990 ◽  
Vol 69 (3) ◽  
pp. 861-867 ◽  
Author(s):  
S. C. Kandarian ◽  
T. P. White
Keyword(s):  
Isometric Force ◽  
Force Production ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Plantaris Muscle ◽  
Cross Sectional ◽  
Control Value ◽  
Muscle Cross Sectional Area ◽  
Synergistic Muscle

Hypotheses were tested that the deficit in maximum isometric force normalized to muscle cross-sectional area (i.e., specific Po, N/cm2) of hypertrophied muscle would return to control value with time and that the rate and magnitude of adaptation of specific force would not differ between soleus and plantaris muscles. Ablation operations of the gastrocnemius and plantaris muscles or the gastrocnemius and soleus muscles were done to induce hypertrophy of synergistic muscle left intact in female Wistar rats (n = 47) at 5 wk of age. The hypertrophied soleus and plantaris muscles and control muscles from other age-matched rats (n = 22) were studied from days 30 to 240 thereafter. Po was measured in vitro at 25 degrees C in oxygenated Krebs-Ringer bicarbonate. Compared with control values, soleus muscle cross-sectional area increased 41-15% from days 30 to 240 after ablation, whereas Po increased 11 and 15% only at days 60 and 90. Compared with control values, plantaris muscle cross-sectional area increased 52% at day 30, 40% from days 60 through 120, and 15% at day 240. Plantaris muscle Po increased 25% from days 30 to 120 but at day 240 was not different from control value. Changes in muscle architecture were negligible after ablation in both muscles. Specific Po was depressed from 11 to 28% for both muscles at all times. At no time after the ablation of synergistic muscle did the increased muscle cross-sectional area contribute fully to isometric force production.

Normalization of contractile parameters in canine airway smooth muscle: morphological and biochemical

1992 ◽  
Vol 70 (4) ◽  
pp. 635-644 ◽  
Author(s):  
N. L. Stephens ◽  
A. Halayko ◽  
H. Jiang
Keyword(s):  
Smooth Muscle ◽  
Muscle Cell ◽  
Striated Muscle ◽  
Isometric Force ◽  
Smooth Muscles ◽  
Cross Sectional Area ◽  
Unit Weight ◽  
Sectional Area ◽  
Cross Sectional ◽  
Cross Bridges

Asthma research has recently highlighted the importance of correctly normalizing force development for purposes of comparing stiffness properties of smooth muscles between different airways, between airways at different stages of maturity, and between airways from different animal species. This problem does not exist in striated muscle where the entire tissue consists almost entirely of muscle and where cross bridges cycle at the same rate throughout a contraction when load correlation is made. In the bronchus, cross-sectional area of true muscle may constitute only 20–30% of the total tissue cross section, and load-independent cycling rate varies fourfold during the course of a contraction because of the occurrence of normally cycling and latch bridges. These features are responsible for the difficulty in force normalization in smooth muscle. Our studies indicate that normalization with respect to true muscle cell cross-sectional area (derived by quantitative morphometry of appropriate tissue transverse sections) is the most valid. This is only so, however, when it has been proved that the actomyosin content per unit weight of the different muscle tissues is the same.Key words: isometric force, force normalization, muscle cell stress, actomyosin stress.

scholarly journals Soleus fiber force and maximal shortening velocity after non-weight bearing with intermittent activity

1996 ◽  
Vol 80 (3) ◽  
pp. 981-987 ◽  
Author(s):  
J. J. Widrick ◽  
J. J. Bangart ◽  
M. Karhanek ◽  
R. H. Fitts
Keyword(s):  
Isometric Force ◽  
Weight Bearing ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Cross Sectional Area ◽  
Type I ◽  
Sectional Area ◽  
Shortening Velocity ◽  
Adult Rats ◽  
Cross Sectional

This study examined the effectiveness of intermittent weight bearing (IWB) as a countermeasure to non-weight-bearing (NWB)-induced alterations in soleus type I fiber force (in mN), tension (Po; force per fiber cross-sectional area in kN/m-2), and maximal unloaded shortening velocity (Vo, in fiber lengths/s). Adult rats were assigned to one of the following groups: normal weight bearing (WB), 14 days of hindlimb NWB (NWB group), and 14 days of hindlimb NWB with IWB treatments (IWB group). The IWB treatment consisted of four 10-min periods of standing WB each day. Single, chemically permeabilized soleus fiber segments were mounted between a force transducer and position motor and were studied at maximal Ca2+ activation, after which type I fiber myosin heavy-chain composition was confirmed by sodium dodecyl sufate-polyacrylamide gel electrophoresis. NWB resulted in a loss in relative soleus mass (-45%), with type I fibers displaying reductions in diameter (-28%) and peak isometric force (-55%) and an increase in Vo (+33%). In addition, NWB induced a 16% reduction in type I fiber Po, a 41% reduction in type I fiber peak elastic modulus [Eo, defined as (delta force/delta length) x (fiber length/fiber cross-sectional area] and a significant increase in the Po/Eo ratio. In contrast to NWB, IWB reduced the loss of relative soleus mass (by 22%) and attenuated alterations in type I fiber diameter (by 36%), peak force (by 29%), and Vo (by 48%) but had no significant effect on Po, Eo, or Po/Eo. These results indicate that a modest restoration of WB activity during 14 days of NWB is sufficient to attenuate type I fiber atrophy and to partially restore type I peak isometric force and Vo to WB levels. However, the NWB-induced reductions in Po and Eo, which we hypothesize to be due to a decline in the number and stiffness of cross bridges, respectively, are considerably less responsive to this countermeasure treatment.

Tenotomy and repair of latissimus dorsi muscles in rats: implications for transposed muscle grafts

1993 ◽  
Vol 75 (3) ◽  
pp. 1294-1299 ◽  
Author(s):  
V. A. Kadhiresan ◽  
P. J. Guelinckx ◽  
J. A. Faulkner
Keyword(s):  
Muscle Mass ◽  
Latissimus Dorsi ◽  
Cross Sectional Area ◽  
Specific Force ◽  
Sectional Area ◽  
Average Force ◽  
Cross Sectional ◽  
Absolute Power ◽  
Control Value ◽  
Optimum Velocity

The functional properties of latissimus dorsi (LTD) muscles were evaluated 160 to 180 days after tenotomy and repair, when grafts had stabilized. Our hypothesis was that, compared with control LTD muscles, LTD grafts would develop less absolute force and power but that the specific force and normalized power would not differ. Expressed as a percentage of the value for control LTD muscles, values for grafts were 67% for muscle mass, 74% for mean single fiber cross-sectional area, 56% for maximum absolute isometric tetanic force, 64% for maximum absolute average force during shortening, and 70% for maximum absolute power. Compared with control LTD muscles, grafts showed no significant differences either in the number of fibers in the total muscle cross section or in the optimum velocity for the development of power. When force and power of grafts were normalized for total fiber cross-sectional area and mass, respectively, only the value for maximum specific force (84% of control value) was significant. The mechanisms responsible for the decrease in specific force after tenotomy and repair are not known. In contrast to the deficit in maximum specific force, the 30% deficit in maximum absolute power of grafts compared with control LTD muscles was explained completely by the 33% smaller muscle mass.

Effects of prolonged undernutrition on structure and function of the diaphragm

1985 ◽  
Vol 58 (4) ◽  
pp. 1354-1359 ◽  
Author(s):  
S. G. Kelsen ◽  
M. Ference ◽  
S. Kapoor
Keyword(s):  
Body Weight ◽  
Isometric Force ◽  
Dry Weight ◽  
Cross Sectional Area ◽  
Diaphragm Muscle ◽  
Sectional Area ◽  
Cross Sectional ◽  
Muscle Structure ◽  
The Cross

The present study examined the effect of prolonged undernutrition on diaphragmatic structure and force-generating ability. Studies were performed on 58 Syrian hamsters in which the feed was reduced by 33% for a 4-wk period. Sixty animals fed a similar diet ad libitum served as controls. Diaphragm muscle structure was assessed from its mass (wet and dry weight), thickness, fiber composition, and fiber size. Isometric force produced in vitro by isolated muscle strips in response to electrical stimulation of the phrenic nerve was examined over a range of muscle lengths (length-tension relationship). In undernourished animals, body weight decreased 25 +/- 5%. Diaphragm wet and dry weight, muscle thickness, and the cross-sectional area of fast-glycolytic (FG) and fast-oxidative (FO) fibers were significantly less in undernourished than control animals and correlated with reductions in body weight. The cross-sectional area of slow-oxidative (SO) fibers was the same in the two groups. The percentage of FG fibers in undernourished animals was decreased slightly and the percentage of SO fibers increased. Maximum isometric tension was reduced in undernourished animals as compared with controls, but the position and shape of the length-tension relationship was the same in the two groups. Reductions in muscle force appeared to be explained by decreases in muscle mass, since tension corrected for cross-sectional area or tissue weight was the same in the two groups. Therefore muscle mechanical efficiency appeared to be unaffected by undernutrition. These data indicate that prolonged undernutrition causes deleterious changes in diaphragm muscle structure that impair its ability to generate force.

Maximal isometric force and muscle cross‐sectional area of the forearm in fencers

1994 ◽  
Vol 12 (6) ◽  
pp. 567-572 ◽  
Author(s):  
V. Margonato ◽  
G.S. Roi ◽  
C. Cerizza ◽  
G.L. Galdabino
Keyword(s):  
Isometric Force ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Muscle Cross Sectional Area ◽  
Maximal Isometric Force

Myogenic response of rat femoral small arteries in relation to wall structure and [Ca2+]i

2002 ◽  
Vol 283 (1) ◽  
pp. H118-H125 ◽  
Author(s):  
Vladimir V. Matchkov ◽  
Olga S. Tarasova ◽  
Michael J. Mulvany ◽  
Holger Nilsson
Keyword(s):  
Intracellular Calcium ◽  
External Iliac Artery ◽  
Wall Stress ◽  
Calcium Sensitivity ◽  
Contralateral Side ◽  
Cross Sectional Area ◽  
Wall Structure ◽  
Sectional Area ◽  
Cross Sectional ◽  
Small Arteries

The present study investigated the influence of media thickness on myogenic tone and intracellular calcium concentration ([Ca2+]i) in rat skeletal muscle small arteries. A ligature was loosely tied around one external iliac artery of 5-wk-old spontaneously hypertensive rats. At 18 wk of age, femoral artery blood pressure was 102 ± 11 mmHg ( n = 15) on the ligated side and 164 ± 6 mmHg ( n = 15) on the contralateral side. Small arteries feeding the gracilis muscle had a reduced media cross-sectional area and a reduced media-to-lumen ratio on the ligated side, where also the range of myogenic constriction was shifted to lower pressures. However, when expressed as a function of wall stress, diameter responses were nearly identical. [Ca2+]i was higher in vessels from the ligated hindlimb at pressures above 10 mmHg, but vasoconstriction was not accompanied by changes in [Ca2+]i. Thus the myogenic constriction here seems due primarily to changes in intracellular calcium sensitivity, which are determined mainly by the force per cross-sectional area of the wall and therefore altered by changes in vascular structure.

Der Zusammenhang von dynamischen und isometrischen Maximalkraftparametern und Muskelquerschnitt bzw. Muskelvolumen

2014 ◽  
Vol 62 (1) ◽  
Keyword(s):  
Muscle Mass ◽  
Isometric Force ◽  
Body Height ◽  
Strength Test ◽  
Cross Sectional Area ◽  
Morphological Data ◽  
Morphological Parameters ◽  
Sectional Area ◽  
Maximal Strength ◽  
Cross Sectional

The aim of the study was the evaluation of the correlation between maximal strength and muscle mass depending on the kind of analysis which was used. Two different methods of strength evaluation and several morphological parameters were used. 77 male participants (age: 27,2 ± 6,6 years; body height: 179,9 ± 4,0 cm; body weight: 82,5 ± 10,4 kg) joined the study. Maximal strength was tested by measuring the isometric force (MIF) and analysing the one repetition maximum (1RM). The morphological data was captured by magnetic resonance imaging. The volume of the muscle (VOL), the biggest cross sectional area (QSMAX), the cross sectional area of the upper (QS30), middle (QS60) and lower (QS90) third of the scanned area of the arm flexors were examined. After analysing the data for normal distribution with the Kolmogorov-Smirnov-Test, the Pearson product moment correlation was used to quantify the correlation of the parameters. Significance level was set at 1%. The results of the study showed high correlations between the dynamic strength test and the morphological parameters (r = 0,77-0,82; p < 0,01) and moderate correlations between the isometric strength test and the morphological data (r = 0,46-0,53; p < 0,01). In addition, the two different parameters for maximal strength correlated moderately (r = 0,55; p < 0,01). The results of the study show that different morphological parameters can be used to describe the correlation between maximal strength and muscle mass. It should be recognised that the way of measuring maximal strength seems to be a substantial variable, which influences the apparent correlations.

scholarly journals Excitability and contractility of skeletal muscle engineered from primary cultures and cell lines

2001 ◽  
Vol 280 (2) ◽  
pp. C288-C295 ◽  
Author(s):  
Robert G. Dennis ◽  
Paul E. Kosnik ◽  
Mark E. Gilbert ◽  
John A. Faulkner
Keyword(s):  
Skeletal Muscle ◽  
Relaxation Time ◽  
Cell Lines ◽  
Isometric Force ◽  
Cross Sectional Area ◽  
Specific Force ◽  
Sectional Area ◽  
Cross Sectional ◽  
Peak Tension ◽  
Time To Peak

The purpose of this study was to compare the excitability and contractility of three-dimensional skeletal muscle constructs, termed myooids, engineered from C2C12 myoblast and 10T½ fibroblast cell lines, primary muscle cultures from adult C3H mice, and neonatal and adult Sprague-Dawley rats. Myooids were 12 mm long, with diameters of 0.1–1 mm, were excitable by transverse electrical stimulation, and contracted to produce force. After ∼30 days in culture, myooid cross-sectional area, rheobase, chronaxie, resting baseline force, twitch force, time to peak tension, one-half relaxation time, and peak isometric force were measured. Specific force was calculated by dividing peak isometric force by cross-sectional area. The specific force generated by the myooids was 2–8% of that generated by skeletal muscles of control adult rodents. Myooids engineered from C2C12-10T½ cells exhibited greater rheobase, time to peak tension, and one-half relaxation time than myooids engineered from adult rodent cultures, and myooids from C2C12-10T½ and neonatal rat cells had greater resting baseline forces than myooids from adult rodent cultures.

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