Functional characteristics of canine costal and crural diaphragm

1988 ◽  
Vol 65 (5) ◽  
pp. 2253-2260 ◽  
Author(s):  
G. A. Farkas ◽  
D. F. Rochester
Keyword(s):  
Contractile Properties ◽  
Force Frequency ◽  
Cross Sectional ◽  
Volume Functional ◽  
Generating Capacity ◽  
Residual Capacity ◽  
Crural Diaphragm ◽  
Muscle Cross Sectional Area

We estimated the in situ force-generating capacity of the costal and crural portions of the canine diaphragm by relating in vitro contractile properties and diaphragmatic dimensions to in situ lengths. Piezoelectric crystals were implanted on right costal and left crural diaphragms of anesthetized dogs, via midline laparatomy. With the abdomen reclosed, diaphragm lengths were recorded at five lung volumes. Contractile properties of excised muscle bundles were then measured. In vitro force-frequency and length-tension characteristics of the costal and crural diaphragms were virtually identical; their optimal force values were 2.15 and 2.22 kg/cm2, respectively. In situ, at residual volume, functional residual capacity (FRC), and total lung capacity the costal diaphragm lay at 102, 95, and 60% of optimal length (Lo), whereas the crural diaphragm lay at 88, 84, and 66% of Lo. Muscle cross-sectional area was 40% greater in costal than in crural diaphragms. Considering in situ lengths, cross-sectional areas, and in vitro length-tension characteristics at FRC, the costal diaphragm could exert 60% more force than the crural diaphragm.

Adaptability of the hamster diaphragm to exercise and/or emphysema

1982 ◽  
Vol 53 (5) ◽  
pp. 1263-1272 ◽  
Author(s):  
G. A. Farkas ◽  
C. Roussos
Keyword(s):  
Contractile Properties ◽  
Force Frequency ◽  
Control Groups ◽  
Optimal Length ◽  
Time To Peak ◽  
Residual Capacity ◽  
Vitro Analysis ◽  
Tetanic Tension ◽  
In Vitro Analysis

In vitro contractile properties of the diaphragm were measured in four groups of inbred adult hamsters (greater than 40wk), randomly divided into sedentary control (SC), exercise control (EC), sedentary emphysematous (SE), and exercise emphysematous (EE) groups. Emphysema was induced by a single endotracheal instillation of elastase. Exercise consisted of running 1 h/day, 7 days/wk for 20 wk. Functional residual capacity (FRC), measured by means of a pressure box, was approximately 2.5 times greater in both emphysematous groups compared with control groups. Small diaphragmatic bundles were then isolated and subjected to in vitro analysis of isometric contractile properties. No differences were observed among the four groups in time to peak tension, half-relaxation time, and shape of the force-frequency curve. The diaphragmatic length-tension curve of emphysematous animals was displaced toward the left; maximal tetanic tension was similar in all groups, while optimal length (Lo), defined as the length at which maximal twitch tension occurred, was significantly shorter in both emphysematous groups. The Lo was negatively correlated with the FRC. Exercise tended to increase the in vitro endurance of the diaphragm bundles in control animals only. Diaphragms from both emphysematous groups, however, did show the greatest resistance to fatigue. It is concluded that 1) daily running for 1 h does not influence the diaphragmatic contractile properties in the hamster, but fatigue was reduced; 2) the load of chronic emphysema decreased the hamster's diaphragm fatiguability; and 3) the diaphragms of emphysematous hamsters chronically adapt by decreasing diaphragmatic length in proportion to the degree of hyperinflation and thus probably continue to operate at an Lo.

Effects of body position and lung volume on in situ operating length of canine diaphragm

1990 ◽  
Vol 69 (5) ◽  
pp. 1702-1708 ◽  
Author(s):  
S. S. Margulies ◽  
G. A. Farkas ◽  
J. R. Rodarte
Keyword(s):  
Lung Volume ◽  
Body Position ◽  
Vertical Gradient ◽  
Postoperative Recovery ◽  
Optimal Force ◽  
Residual Capacity ◽  
Crural Diaphragm

The performance of the diaphragm is influenced by its in situ length relative to its optimal force-generating length (Lo). Lead markers were sutured to the abdominal surface of the diaphragm along bundles of the left ventral, middle, and dorsal regions of the costal diaphragm and the left crural diaphragm of six beagle dogs. After 2-3 wk postoperative recovery, the dogs were anesthetized, paralyzed, and scanned prone and supine in the Dynamic Spatial Reconstructor (DSR) at a total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV). The location of each marker was digitized from the reconstructed DSR images, and in situ lengths were determined. After an overdose of anesthetic had been administered to the dogs, each marked diaphragm bundle was removed, mounted in a 37 degrees C in vitro chamber, and adjusted to Lo (maximum tetanic force). The operating length of the diaphragm, or in situ length expressed as percent Lo, varied from region to region at the lung volumes studied; variability was least at RV and increased with increasing lung volume. At FRC, all regions of the diaphragm was shorter in the prone posture compared with the supine, but there was no clear gravity-dependent vertical gradient of in situ length in either posture. Because in vitro length-tension characteristics were similar for all diaphragm regions, regional in vivo length differences indicate that the diaphragm's potential to generate maximal force is nonuniform.

Expression of airway contractile properties and acetylcholinesterase activity in swine

1989 ◽  
Vol 67 (1) ◽  
pp. 174-180 ◽  
Author(s):  
T. M. Murphy ◽  
R. W. Mitchell ◽  
J. S. Blake ◽  
M. M. Mack ◽  
E. A. Kelly ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Acetylcholinesterase Activity ◽  
Contractile Properties ◽  
Tracheal Smooth Muscle ◽  
Cholinesterase Inhibition ◽  
Maximal Response ◽  
Response Curves ◽  
Cross Sectional

We studied the effect of maturation on contractile properties of tracheal smooth muscle from seventeen 2-wk-old swine (2ws) and fifteen 10-wk-old swine (10ws) in situ and in vitro. The response to parasympathetic stimulation was studied in situ in isometrically fixed segments. Contraction was elicited at lower frequencies [half-maximal response to electrical stimulation (ES50) = 6.7 +/- 0.05 Hz] in 2ws than in 10ws (ES50 = 9.1 +/- 0.4 Hz; P less than 0.01). Despite substantial differences in morphometrically normalized cross-sectional area in 2ws (0.012 +/- 0.003 cm2) and 10ws (0.028 +/- 0.001 cm2; P less than 0.01), maximal active tension elicited by parasympathetic stimulation was similar (12.4 +/- 3.2 g/cm in 2ws vs. 13.3 +/- 2.3 g/cm in 10ws; P = NS). In separate in vitro studies in 25 tracheal smooth muscle strips from 10 swine, concentration-response curves generated with potassium-substituted Krebs solution (KCl) were similar in 2ws and 10ws. In 58 other strips (10 swine), maximal active force elicited with acetylcholine (ACh) in 2ws was significantly greater than for 10ws (P less than 0.001). Removal of the epithelium had no effect. However, cholinesterase inhibition with 10(-7) M physostigmine augmented the response to ACh in 10ws (P less than 0.02) but not 2ws. We demonstrate increased force generation and sensitivity to vagal stimulation in 2ws vs. 10ws, which corresponds to increased reactivity to ACh in vitro. The relative hyperresponsiveness in 2ws is specific for cholinergic response and is attenuated at least in part by maturation of the activity of acetylcholinesterase enzyme.

Specific Force of the Rat Extraocular Muscles, Levator and Superior Rectus, Measured In Situ

2001 ◽  
Vol 85 (3) ◽  
pp. 1027-1032 ◽  
Author(s):  
Bartley R. Frueh ◽  
Paul Gregorevic ◽  
David A. Williams ◽  
Gordon S. Lynch
Keyword(s):  
Skeletal Muscles ◽  
Muscle Length ◽  
Extraocular Muscles ◽  
Specific Force ◽  
Sectional Area ◽  
Cross Sectional ◽  
Superior Rectus ◽  
Muscle Cross Sectional Area

Extraocular muscles are characterized by their faster rates of contraction and their higher resistance to fatigue relative to limb skeletal muscles. Another often reported characteristic of extraocular muscles is that they generate lower specific forces ( sP o, force per muscle cross-sectional area, kN/m2) than limb skeletal muscles. To investigate this perplexing issue, the isometric contractile properties of the levator palpebrae superioris (levator) and superior rectus muscles of the rat were examined in situ with nerve and blood supply intact. The extraocular muscles were attached to a force transducer, and the cranial nerves exposed for direct stimulation. After determination of optimal muscle length ( L o) and stimulation voltage, a full frequency-force relationship was established for each muscle. Maximum isometric tetanic force ( P o) for the levator and superior rectus muscles was 177 ± 13 and 280 ± 10 mN (mean ± SE), respectively. For the calculation of specific force, a number of rat levator and superior rectus muscles were stored in a 20% nitric acid-based solution to isolate individual muscle fibers. Muscle fiber lengths ( L f) were expressed as a percentage of overall muscle length, allowing a mean L f to L o ratio to be used in the estimation of muscle cross-sectional area. Mean L f: L owas determined to be 0.38 for the levator muscle and 0.45 for the superior rectus muscle. The sP o for the rat levator and superior rectus muscles measured in situ was 275 and 280 kN/m2, respectively. These values are within the range of sP o values commonly reported for rat skeletal muscles. Furthermore P o and sP o for the rat levator and superior rectus muscles measured in situ were significantly higher ( P < 0.001) than P oand sP o for these muscles measured in vitro. The results indicate that the force output of intact extraocular muscles differs greatly depending on the mode of testing. Although in vitro evaluation of extraocular muscle contractility will continue to reveal important information about this group of understudied muscles, the lower sP o values of these preparations should be recognized as being significantly less than their true potential. We conclude that extraocular muscles are not intrinsically weaker than skeletal muscles.

Contractile properties of intercostal muscles and their functional significance

1985 ◽  
Vol 59 (2) ◽  
pp. 528-535 ◽  
Author(s):  
G. A. Farkas ◽  
M. Decramer ◽  
D. F. Rochester ◽  
A. De Troyer
Keyword(s):  
Length Change ◽  
Contractile Properties ◽  
Functional Coupling ◽  
Force Frequency ◽  
Active Length ◽  
Residual Capacity ◽  
Measured Length ◽  
The Right

To have some insight into the functional coupling between the parasternal intercostals (PS) and the diaphragm (DPM), we have examined the isometric contractile properties of bundles from canine PS and DPM muscles. Bundles of external (EXT) and internal (INT) interosseous intercostals were studied for comparison. In addition we have related sonometrically measured length of the intercostals in vivo at supine functional residual capacity (FRC) to in vitro optimal force-producing length (Lo). We found that 1) intercostal twitch speed is significantly faster than DPM, thus displacing their relative force-frequency curve to the right of that of the DPM; 2) the ascending limb of the active length-tension curve of all intercostals lies below the DPM curve; i.e., at 85% Lo, PS force is 46% of maximal force (Po), whereas DPM force is still 87% Po; 3) for any given length change beyond Lo, all intercostals generate greater passive tension than the DPM; 4) Po is greater for the intercostals than the DPM; and 5) at supine FRC, both EXT and INT in dogs are nearly operating at Lo, whereas the PS are operating at a length greater than Lo. We conclude that 1) PS produce less force than DPM during breathing efforts involving low- (10–20 Hz) stimulation frequencies, but they generate more force than DPM when high- (greater than 50 Hz) stimulation frequencies are required; and 2) the pressure-generating ability of the PS is better preserved than that of the DPM with increases in lung volume.

Contractile properties of expiratory abdominal muscles: effect of elastase-induced emphysema

1987 ◽  
Vol 62 (6) ◽  
pp. 2314-2319 ◽  
Author(s):  
J. S. Arnold ◽  
A. J. Thomas ◽  
S. G. Kelsen
Keyword(s):  
Relaxation Time ◽  
Contractile Function ◽  
Isometric Tension ◽  
Contractile Properties ◽  
Abdominal Muscles ◽  
Force Frequency ◽  
Contraction Time ◽  
Transverse Abdominis ◽  
External Oblique

The present study examined the intrinsic contractile properties and endurance of the transverse abdominis and external oblique abdominal expiratory muscles in adult hamsters and compared their performance with the diaphragm. Experiments were performed in vitro on isolated bundles of muscle stimulated electrically. In control animals peak twitch tension was similar in the two muscles. In contrast, the twitch contraction time and one-half relaxation time of the transverse abdominis were significantly greater than that of the external oblique. The isometric tension generated over a range of stimulus frequencies (i.e., the force-frequency relationship) was a greater percent of the maximum value in response to subtetanizing frequencies (10–40 Hz) in the transverse abdominis than in the external oblique. For both abdominal muscles, however, the tension generated over this range of stimulus frequencies was less than that of the diaphragm. The endurance of the transverse abdominis during repeated contractions was significantly greater than that of the external oblique but similar to the diaphragm. The effect of chronic hyperinflation produced by elastase-induced emphysema on the contractile function of the two muscles was assessed in a second group of adult hamsters. In emphysematous animals peak twitch tension, contraction time, and one-half relaxation time of the twitch and force-frequency curves of muscles from emphysematous animals were similar to values obtained in control animals for both the external oblique and transverse abdominis. However, the endurance of both the transverse abdominis and external oblique muscles was greater in emphysematous than control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

An in sita Model for Simultaneous Assessment of Inhibition of Demineralization and Enhancement of Remineralization

1992 ◽  
Vol 71 (3_suppl) ◽  
pp. 804-810 ◽  
Author(s):  
J.D.B. Featherstone ◽  
D.T. Zero
Keyword(s):  
Tooth Enamel ◽  
Dental Health ◽  
Oral Care ◽  
Protective Effects ◽  
Cross Sectional ◽  
Food Component ◽  
Whole Saliva ◽  
Salivary Function

In situ models to assess the ability of oral care products or food components to enhance remineralization and/or inhibit demineralization of tooth enamel or roots must be very carefully designed to minimize the confounding effects of the many variables involved. Controlling these variables as closely as possible is essential if meaningful answers are to be obtained from the models. We have developed an in situ model which combines the experience of several groups. Detailed screening of subjects is essential. Selection criteria should include good general health, good dental health, mandibular partial denture, at least eight natural teeth, no active caries lesions, known fluoride history, normal salivary function, and no medications that affect salivary function. Each subject carries a sound enamel slab and an enamel slab with a pre-formed caries-like lesion (demineralized in vitro) in his/her denture on each side of the mouth for test periods of two or four weeks. The demineralization challenge is controlled by extra-oral immersion of the appliances in sucrose daily. Daily product exposure or daily food component exposure is used as desired. Compliance indicators and a diet diary are included. Whole saliva flow rate (unstimulated), plaque acidogenicity, and salivary fluoride are monitored during the test periods. At the end of the test period, the test slabs are assessed for mineral change, after being sectioned, by means of cross-sectional microhardness or microradiography. The mineral loss or gain (ΔM, μm × vol%), compared with adjacent control sections retained in the lab, is calculated as change in ΔZ (μm × vol%), namely, ΔM = ΔZTEST - ΔZ.CONTROL. In this model, demineralization occurs in sound enamel and in the pre-formed lesions in the absence of fluoride or other protective agents. The model has the potential to be able to differentiate among fluoride delivery systems and to assess the caries-protective effects of agents other than fluoride by use of small groups of subjects.

Functional significance of compensatory overloaded rat fast muscle

1982 ◽  
Vol 52 (2) ◽  
pp. 473-478 ◽  
Author(s):  
R. R. Roy ◽  
I. D. Meadows ◽  
K. M. Baldwin ◽  
V. R. Edgerton
Keyword(s):  
Biochemical Properties ◽  
Slow Muscle ◽  
Repetitive Stimulation ◽  
Contractile Properties ◽  
Sectional Area ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Time To Peak ◽  
Isometric Twitch

Chronic overload of a skeletal muscle by removing its synergists produces hypertrophy and marked changes in its metabolic and biochemical properties. In this study alterations in the contractile properties of the plantaris 12–14 wk after bilateral removal of the soleus and gastrocnemius were investigated. In situ isometric and isotonic contractile properties of overloaded plantaris (OP), normal plantaris (NP), and normal soleus (NS) were tested at 33 +/- 1 degree C. Op were 97% heavier than NP and produced 43 and 46% higher twitch (Pt) and tetanic (Po) tensions. However, NP produced more tension per cross-sectional area than OP (mean 26.2 vs. 21.6 N/cm2; P less than 0.001). Isometric twitch time to peak tension (TPT) and half-relaxation time (1/2RT) were significantly longer in OP (mean 36.4 vs. 32.5 ms and 23.9 vs. 18.4 ms). Mean maximum shortening velocity (Vmax, mm/s per 1,000 sarcomeres) were 34.1 for NP and 18.1 for OP (P less than 0.001). The degree of conversion toward the Vmax of NS was 74% compared with only 19 and 14% for TPT and 1/2RT. OP produced a higher proportion of Po at a given stimulation frequency than NP and showed less fatigue than NP after repetitive stimulation. Chronic overload of the fast plantaris modified to varying degrees the contractile properties studied toward that resembling a slow muscle. Although the maximum tension of OP was markedly enhanced it was not in proportion to the increase in muscle mass.

Changes in the human muscle force-velocity relationship in response to resistance training and subsequent detraining

2005 ◽  
Vol 99 (1) ◽  
pp. 87-94 ◽  
Author(s):  
Lars L. Andersen ◽  
Jesper L. Andersen ◽  
S. Peter Magnusson ◽  
Charlotte Suetta ◽  
Jørgen L. Madsen ◽  
...  
Keyword(s):  
Resistance Training ◽  
Knee Extension ◽  
Limb Movement ◽  
Cross Sectional Area ◽  
Contractile Properties ◽  
Type I ◽  
Maximal Velocity ◽  
Sectional Area ◽  
Cross Sectional ◽  
Muscle Cross Sectional Area

Previous studies show that cessation of resistance training, commonly known as “detraining,” is associated with strength loss, decreased neural drive, and muscular atrophy. Detraining may also increase the expression of fast muscle myosin heavy chain (MHC) isoforms. The present study examined the effect of detraining subsequent to resistance training on contractile performance during slow-to-medium velocity isokinetic muscle contraction vs. performance of maximal velocity “unloaded” limb movement (i.e., no external loading of the limb). Maximal knee extensor strength was measured in an isokinetic dynamometer at 30 and 240°/s, and performance of maximal velocity limb movement was measured with a goniometer during maximal unloaded knee extension. Muscle cross-sectional area was determined with MRI. Electromyographic signals were measured in the quadriceps and hamstring muscles. Twitch contractions were evoked in the passive vastus lateralis muscle. MHC isoform composition was determined with SDS-PAGE. Isokinetic muscle strength increased 18% ( P < 0.01) and 10% ( P < 0.05) at slow and medium velocities, respectively, along with gains in muscle cross-sectional area and increased electromyogram in response to 3 mo of resistance training. After 3 mo of detraining these gains were lost, whereas in contrast maximal unloaded knee extension velocity and power increased 14% ( P < 0.05) and 44% ( P < 0.05), respectively. Additionally, faster muscle twitch contractile properties along with an increased and decreased amount of MHC type II and MHC type I isoforms, respectively, were observed. In conclusion, detraining subsequent to resistance training increases maximal unloaded movement speed and power in previously untrained subjects. A phenotypic shift toward faster muscle MHC isoforms (I → IIA → IIX) and faster electrically evoked muscle contractile properties in response to detraining may explain the present results.

Developmental changes in diaphragm contractile properties

1993 ◽  
Vol 75 (2) ◽  
pp. 522-526 ◽  
Author(s):  
B. J. Moore ◽  
H. A. Feldman ◽  
M. B. Reid
Keyword(s):  
Force Production ◽  
Respiratory Muscles ◽  
Contractile Properties ◽  
Stimulus Parameter ◽  
Direct Stimulation ◽  
Cross Sectional ◽  
Tetanic Force ◽  
Effective Excitation ◽  
Maximal Tetanic Force

The contractile properties of pre- and early postnatal respiratory muscles are incompletely understood. We examined the effects of development on isometric contractile properties, with an emphasis on properties at 37 degrees C. One-day-old (n = 10), 3-wk-old (n = 10), and adult (n = 10) rabbits were studied. Isometric contractile properties of costal diaphragm strips were measured in vitro by using direct stimulation. Twitch and maximal, i.e., fused, tetanic force production increased with strip dimension and with age. Maximal tetanic force developed per unit cross-sectional area (stress) was significantly decreased in muscle from 1-day olds, whereas it was greatest in muscle from 3-wk olds. Twitch stress was similar in all three groups. Only when the stimulus duration was prolonged did twitch and fused tetanic force achieve maximal values values for the 1-day-old and 3-wk-old strips, suggesting less effective excitation-contraction coupling in those muscles. We conclude that immature rabbit diaphragm has unique isometric contractile properties and stimulus parameter requirements that cannot be deduced from studies using mature diaphragm.

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