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.

Normalization of force generated by canine airway smooth muscles

1991 ◽  
Vol 260 (6) ◽  
pp. L522-L529 ◽  
Author(s):  
H. Jiang ◽  
A. J. Halayko ◽  
K. Rao ◽  
P. Cunningham ◽  
N. L. Stephens
Keyword(s):  
Smooth Muscle ◽  
Cross Section ◽  
Cross Sections ◽  
Smooth Muscles ◽  
Muscle Cells ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Muscle Stress ◽  
Total Tissue

A variety of normalizations have been employed to compare maximal isometric force (Po) produced by smooth muscles at different locations and stages of maturation. Because these procedures have not always been based on rigorous principles, confusion has resulted. To obtain a less ambiguous index of force production, we measured in vitro Po from mongrel canine tracheal (TSM) and bronchial (BSM) smooth muscle with an electromagnetic lever and normalized it to force per unit cross-sectional area of whole tissue (tissue stress), to force per unit cross-sectional area of muscle in the cross section of total tissue (muscle stress), and to force per fractional unit of myosin in the tissue cross section (myosin stress). Proportion of myosin in cross-sectional area of tissue was deduced from data obtained by sodium dodecyl sulfate gel electrophoresis of crude muscle extracts. For TSM, tissue stress was 1.499 X 10(5) N/m2 +/- 0.1 (SE), whereas it was only 0.351 X 10(5) N/m2 +/- 0.05 (SE) for BSM, representing a 4.27-fold difference (P less than 0.01). There was a 1.60-fold difference (P less than 0.05) in muscle stress, which was correlated to the morphometric finding that 79 +/- 1.4% (SE) of the tracheal strip cross section was muscle, whereas only 30 +/- 1.0% (SE) of bronchial tissue was occupied by muscle. Average myosin content was the same in smooth muscle cells of TSM and BSM, indicating that total amount of myosin in tissue cross sections was essentially a function of proportional area of muscle cells in total tissue cross sections.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Form follows function: how muscle shape is regulated by work

2000 ◽  
Vol 88 (3) ◽  
pp. 1127-1132 ◽  
Author(s):  
Brenda Russell ◽  
Delara Motlagh ◽  
William W. Ashley
Keyword(s):  
Muscle Cell ◽  
Cell Shape ◽  
Force Production ◽  
Cardiac Cells ◽  
Cross Sectional Area ◽  
Dynamic Responses ◽  
Mechanical Activity ◽  
Sectional Area ◽  
Cross Sectional ◽  
A Cell

What determines the shape, size, and force output of cardiac and skeletal muscle? Chicago architect Louis Sullivan (1856–1924), father of the skyscraper, observed that “form follows function.” This is as true for the structural elements of a striated muscle cell as it is for the architectural features of a building. Function is a critical evolutionary determinant, not form. To survive, the animal has evolved muscles with the capacity for dynamic responses to altered functional demand. For example, work against an increased load leads to increased mass and cross-sectional area (hypertrophy), which is directly proportional to an increased potential for force production. Thus a cell has the capacity to alter its shape as well as its volume in response to a need for altered force production. Muscle function relies primarily on an organized assembly of contractile and other sarcomeric proteins. From analysis of homogenized cells and molecular and biochemical assays, we have learned about transcription, translation, and posttranslational processes that underlie protein synthesis but still have done little in addressing the important questions of shape or regional cell growth. Skeletal muscles only grow in length as the bones grow; therefore, most studies of adult hypertrophy really only involve increased cross-sectional area. The heart chamber, however, can extend in both longitudinal and transverse directions, and cardiac cells can grow in length and width. We know little about the regulation of these directional processes that appear as a cell gets larger with hypertrophy or smaller with atrophy. This review gives a brief overview of the regulation of cell shape and the composition and aggregation of contractile proteins into filaments, the sarcomere, and myofibrils. We examine how mechanical activity regulates the turnover and exchange of contraction proteins. Finally, we suggest what kinds of experiments are needed to answer these fundamental questions about the regulation of muscle cell shape.

Relevance of classification by size to topographical differences in bronchial smooth muscle response

1993 ◽  
Vol 75 (5) ◽  
pp. 2013-2021 ◽  
Author(s):  
P. Chitano ◽  
S. B. Sigurdsson ◽  
A. J. Halayko ◽  
N. L. Stephens
Keyword(s):  
Smooth Muscle ◽  
Electrical Field Stimulation ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Muscle Response ◽  
Bronchial Responsiveness ◽  
Sixth Generation ◽  
Significant Difference ◽  
And Control

To investigate heterogeneity of airway smooth muscle response, we studied strips of large and small branches from third- to sixth-generation bronchi obtained from ragweed antigen-sensitized and control dogs. The response to electrical field stimulation and carbamylcholine chloride was greater in strips from larger branches of the same generation when expressed as "tissue stress" (force per unit cross-sectional area of the whole tissue), whereas no difference emerged with use of the more appropriate "smooth muscle stress" (force per unit cross-sectional area of the muscle tissue). The response to histamine was significantly higher in small branches than in large ones, and histamine sensitivity [mean effective concentration (EC50)] was 7.79 x 10(-6) [geometric standard error of the mean (GSEM) 1.20] and 1.49 x 10(-5) M (GSEM 1.14), respectively (P < 0.01). Strips from control and sensitized animals at each site and strips from different generations did not show any significant difference. When we clustered our preparations according to dimensions, the response to histamine was significantly higher in small bronchi than in large ones and histamine EC50 was 8.95 x 10(-6) (GSEM 1.17) and 1.57 x 10(-5) M (GSEM 1.18), respectively (P < 0.05). We conclude that evaluation of muscle response in different tissues requires appropriate normalization. Furthermore, classification into generations is inadequate to study bronchial responsiveness, inasmuch as major differences originate from airway size.

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.

Conservation of bronchiolar wall area during constriction and dilation of human airways

1997 ◽  
Vol 82 (3) ◽  
pp. 954-958 ◽  
Author(s):  
R. W. Mitchell ◽  
E. Rühlmann ◽  
H. Magnussen ◽  
N. M. Muñoz ◽  
A. R. Leff ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Contraction ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Wall Area ◽  
Total Cross Sectional Area ◽  
Human Airways ◽  
Contraction And Relaxation

Mitchell, R. W., E. Rühlmann, H. Magnussen, N. M. Muñoz, A. R. Leff, and K. F. Rabe. Conservation of bronchiolar wall area during constriction and dilation of human airways. J. Appl. Physiol. 82(3): 954–958, 1997.—We assessed the effect of smooth muscle contraction and relaxation on airway lumen subtended by the internal perimeter ( A i) and total cross-sectional area ( A o) of human bronchial explants in the absence of the potential lung tethering forces of alveolar tissue to test the hypothesis that bronchoconstriction results in a comparable change of A iand A o. Luminal area (i.e., A i) and A owere measured by using computerized videomicrometry, and bronchial wall area was calculated accordingly. Images on videotape were captured; areas were outlined, and data were expressed as internal pixel number by using imaging software. Bronchial rings were dissected in 1.0- to 1.5-mm sections from macroscopically unaffected areas of lungs from patients undergoing resection for carcinoma, placed in microplate wells containing buffered saline, and allowed to equilibrate for 1 h. Baseline, A o[5.21 ± 0.354 (SE) mm2], and A i(0.604 ± 0.057 mm2) were measured before contraction of the airway smooth muscle (ASM) with carbachol. Mean A inarrowed by 0.257 ± 0.052 mm2in response to 10 μM carbachol ( P = 0.001 vs. baseline). Similarly, A onarrowed by 0.272 ± 0.110 mm2in response to carbachol ( P = 0.038 vs. baseline; P = 0.849 vs. change in A i). Similar parallel changes in cross-sectional area for A iand A owere observed for relaxation of ASM from inherent tone of other bronchial rings in response to 10 μM isoproterenol. We demonstrate a unique characteristic of human ASM; i.e., both luminal and total cross-sectional area of human airways change similarly on contraction and relaxation in vitro, resulting in a conservation of bronchiolar wall area with bronchoconstriction and dilation.

scholarly journals Force: velocity relationship in single isolated toad stomach smooth muscle cells.

1987 ◽  
Vol 89 (5) ◽  
pp. 771-789 ◽  
Author(s):  
D M Warshaw
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Striated Muscle ◽  
Muscle Cells ◽  
Length Change ◽  
Force Transducer ◽  
Cell Length ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Cross Bridges

The relationship between force and shortening velocity (F:V) in muscle is believed to reflect both the mechanics of the myosin cross-bridge and the kinetics of its interaction with actin. To date, the F:V for smooth muscle cells has been inferred from F:V data obtained in multicellular tissue preparations. Therefore, to determine F:V in an intact single smooth muscle cell, cells were isolated from the toad (Bufo marinus) stomach muscularis and attached to a force transducer and length displacement device. Cells were electrically stimulated at 20 degrees C and generated 143 mN/mm2 of active force per muscle cross-sectional area. At the peak of contraction, cells were subjected to sudden changes in force (dF = 0.10-0.90 Fmax) and then maintained at the new force level. The force change resulted in a length response in which the cell length (Lcell) rapidly decreased during the force step and then decreased monotonically with a time constant between 75 and 600 ms. The initial length change that coincided with the force step was analyzed and an active cellular compliance of 1.9% cell length was estimated. The maintained force and resultant shortening velocity (V) were fitted to the Hill hyperbola with constants a/Fmax of 0.268 and b of 0.163 Lcell/s. Vmax was also determined by a procedure in which the cell length was slackened and the time of unloaded shortening was recorded (slack test). From the slack test, Vmax was estimated as 0.583 Lcell/s, in agreement with the F:V data. The F:V data were analyzed within the framework of the Huxley model (Huxley. 1957. Progress in Biophysics and Biophysical Chemistry. 7:255-318) for contraction and interpreted to indicate that in smooth muscle, as compared with fast striated muscle, there may exist a greater percentage of attached force-generating cross-bridges.

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.

Isometric tension and myofilamental cross-sectional area in striated muscle

1962 ◽  
Vol 202 (5) ◽  
pp. 824-826 ◽  
Author(s):  
Einar Helander ◽  
Carl-Axel Thulin
Keyword(s):  
Striated Muscle ◽  
Protein Composition ◽  
Isometric Tension ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Experimental Conditions ◽  
Cross Sectional ◽  
Total N ◽  
Calf Muscles

Isometric tension in tetanically stimulated calf muscles was examined in vivo in 3 rabbits and 18 cats. In two cats the gastrocnemius and soleus muscles were studied separately. After determination of the isometric tension the muscles were dissected and their water content, total N content, and protein composition were analyzed. On this basis it was possible to calculate that part of the cross-sectional area of the muscle fibers which consisted of myofilaments. The recorded maximum isometric tension was related to the myofilamental cross-sectional area. Under the given experimental conditions, the calf muscles developed a tension of 108 ± 5 g/mm2 cross-sectional area. Higher values resulted from tests of individual calf muscles than from combined muscles.

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