Contractile properties of the shortening rat diaphragm in vitro

1987 ◽  
Vol 62 (3) ◽  
pp. 1111-1116 ◽  
Author(s):  
I. A. Mardini ◽  
R. J. McCarter
Keyword(s):  
Isometric Tension ◽  
Contractile Properties ◽  
Rat Diaphragm ◽  
Experimental Conditions ◽  
Diaphragmatic Fatigue ◽  
Definition Of ◽  
Diaphragm In Vitro ◽  
The Relationship ◽  
Frequency Of Stimulation

Diaphragmatic fatigue has been defined in terms of the failure of the muscle to continue to generate a given level of tension. Appropriate shortening of the diaphragm is, however, just as important for adequate ventilation. In this study we have examined in vitro the contractile properties of the rat diaphragm under afterloaded isotonic conditions and the effect of fatigue on the ability of the diaphragm to shorten. Shortening of the muscle strips was found to depend on size of afterload, frequency of stimulation, duration of stimulation, and initial length of the muscle. The afterloaded isotonic length-tension relationship coincided with the relationship between length and active isometric tension only for relatively small afterloads. Fatigue of the muscle strips, induced by isometric or afterloaded isotonic contractions, was associated with a decline in the extent of shortening as well as a decrease in active isometric tension. Ability to shorten and ability to develop isometric tension did not decrease to the same extent under all conditions. We conclude that active shortening, as well as active isometric tension, is decreased by muscular fatigue and that changes in these properties can be different depending on experimental conditions. The results suggest that the definition of diaphragmatic fatigue should be expanded to include the ability of the muscle to shorten by an appropriate amount. The results also suggest that measurement of isometric performance may not provide a complete estimate of the overall performance of the fatigued diaphragm.

Fatigue of the mammalian diaphragm in vitro

1982 ◽  
Vol 53 (2) ◽  
pp. 440-447 ◽  
Author(s):  
S. G. Kelsen ◽  
M. L. Nochomovitz
Keyword(s):  
Duty Cycle ◽  
Phrenic Nerve ◽  
Isometric Tension ◽  
Neural Element ◽  
Sprague Dawley ◽  
Fatigue Process ◽  
Diaphragmatic Muscle ◽  
Diaphragmatic Fatigue ◽  
Diaphragm In Vitro

Diaphragm fatigue was studied in innervated diaphragm strips from 63 Sprague-Dawley rats. The experiments examined 1) the effect on the rate of diaphragmatic fatigue of increases in the diaphragm's duty cycle, i.e., the ratio of the period of diaphragmatic contraction (Ti) to the duration of a cycle of contraction and rest (Ttot) and 2) the possibility that impaired neural transmission contributed to the fatigue process. Alterations in the duty cycle of the diaphragm were simulated by varying the pattern of electrical stimuli applied cyclically to the phrenic nerve. Fatigue was assessed from the rate of fall of isometric tension when the muscle was made to contract 90 times/min. The contribution of neural element fatigue was assessed by comparing the tension during phrenic nerve stimulation to the tension developed when the muscle was stimulated directly. Increasing the duty cycle (Ti/Ttot) from 25 to 50 to 75% increased the rate of diaphragmatic fatigue progressively. Holding Ti/Ttot constant at 75%, while varying Ti and Ttot, did not affect the rate of fatigue. Increases in duty cycle appear to increase the rate of fatigue by increasing the number of times the contractile process was activated. In fatigued muscle strips diaphragmatic tension was greater in directly stimulated muscle than in muscle strips activated via the phrenic nerve. The results indicate that 1) when the breathing action of the diaphragm is simulated in vitro, increases in duty cycle accelerate the fatigue process and 2) failure of transmission of phrenic impulses to diaphragmatic muscle cells contributes to the fall in tension during fatigue.

scholarly journals Action of Insulin on Transport of l-Alanine into Rat Diaphragm in Vitro

1973 ◽  
Vol 248 (18) ◽  
pp. 6450-6455
Author(s):  
Thomas R. Riggs ◽  
K. Janet McKirahan
Keyword(s):  
Rat Diaphragm ◽  
Diaphragm In Vitro

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)

scholarly journals Dephosphorylation of Nucleoside Triphosphates by Rat Diaphragm in vitro.

1957 ◽  
Vol 11 ◽  
pp. 1078-1079 ◽  
Author(s):  
Aa. Rye Alertsen ◽  
O. Walaas ◽  
E. Walaas ◽  
K. E. Almin ◽  
Arne Magnéli ◽  
...  
Keyword(s):  
Rat Diaphragm ◽  
Nucleoside Triphosphates ◽  
Diaphragm In Vitro

Rapid incorporation of [14C]-glucose into a glucan-peptide complex of the rat diaphragm in vitro

1960 ◽  
Vol 40 ◽  
pp. 562-563 ◽  
Author(s):  
Otto Walaas ◽  
Borgar Borrebæk ◽  
Tore Kristiansen ◽  
Eva Walaas
Keyword(s):  
Rat Diaphragm ◽  
Peptide Complex ◽  
Diaphragm In Vitro ◽  
Rapid Incorporation

Theophylline minimally alters contractile properties of canine diaphragm in vitro

1990 ◽  
Vol 69 (4) ◽  
pp. 1390-1396 ◽  
Author(s):  
E. Derom ◽  
S. Janssens ◽  
V. De Bock ◽  
M. Decramer
Keyword(s):  
High Frequency ◽  
Force Production ◽  
Contractile Properties ◽  
Diaphragm Muscle ◽  
Muscle Bundle ◽  
Time To Peak ◽  
Diaphragm In Vitro ◽  
Tetanic Tension

We examined the effects of theophylline on contractile properties and high-frequency fatigue of canine diaphragm in vitro. Eighteen diaphragm muscle bundles were obtained from 10 anesthetized dogs and equilibrated in oxygenated Krebs solution to 100, 200, or 300 mg/l theophylline. These bundles were compared with 18 matched control bundles from the contralateral hemidiaphragm. No statistically significant differences in twitch tension, tetanic tension, twitch-to-tetanus ratio, time to peak tension, or half-relaxation time were observed. Concentrations of 300 mg/l theophylline, however, significantly (P less than 0.05) increased force production at 10 Hz by 32%. A similar tendency was present at lower concentrations and exhibited a clear dose-response behavior. High-frequency fatigue was similar in control and theophylline-treated bundles. We conclude that supratherapeutic in vitro concentrations of theophylline do not increase maximal tetanic tension and do not protect against muscle fatigue but potentiate relative force production at low stimulation frequencies. This relatively small effect cannot be explained by poor diffusion of the drug in the muscle bundle, because theophylline concentrations in the muscle bath and in the muscle bundle were virtually identical. Moreover, it remains unclear whether this potentially beneficial effect can be achieved at in vivo attainable serum concentrations.

THE WATER AND ELECTROLYTE METABOLISM OF RAT DIAPHRAGM IN VITRO

1956 ◽  
Vol 34 (1) ◽  
pp. 1069-1083 ◽  
Author(s):  
R. H. Rixon ◽  
J. A. F. Stevenson
Keyword(s):  
Intracellular Water ◽  
Diaphragm Muscle ◽  
Optimal Conditions ◽  
Rat Diaphragm ◽  
Concentration Gradients ◽  
Hypoxic Conditions ◽  
Diaphragm In Vitro ◽  
Sodium And Potassium

The distribution of water and of sodium and potassium between the cell and synthetic environments has been studied in rat diaphragm muscle. It has been found that: (1) the amount of intracellular water is markedly increased at 0 °C. in oxygen and at 37 °C. in nitrogen compared to that of tissue at 37 °C. in oxygen, in media up to 0.75 osmolar; (2) optimal conditions of temperature and oxygen are necessary to prevent or reduce the uptake of water; (3) swelling at reduced temperatures and under hypoxic conditions is related to the oxygen uptake; (4) the loss of tissue solids during incubation does not have any significant effect on the calculation of the total tissue and intracellular water; (5) the concentration of total sodium and potassium in the tissue, in vivo and in vitro at optimal conditions is slightly in excess of that in the plasma water or incubating medium—this is believed not to represent an active hypertonicity; (6) concomitant with the uptake of water there are marked redistributions of sodium and potassium, the gain of sodium being greater than the loss of potassium. It is concluded that the swelling of tissue cells under conditions that inhibit oxidative metabolism is primarily due to the redistribution of electrolytes and that the natural distribution of water in muscle is determined by active maintenance of the concentration gradients of sodium and potassium across the cell membrane.

pH of isolated resting skeletal muscle and its relation to potassium content

1963 ◽  
Vol 204 (6) ◽  
pp. 1048-1054 ◽  
Author(s):  
Ronald B. Miller ◽  
Ian Tyson ◽  
Arnold S. Relman
Keyword(s):  
Skeletal Muscle ◽  
Intracellular Ph ◽  
Potassium Content ◽  
Ion Concentration ◽  
Detectable Effect ◽  
Rat Diaphragm ◽  
Intracellular Acidosis ◽  
Experimental Conditions ◽  
Hydrogen Ion Concentration

Intracellular pH of isolated rat diaphragm was measured with both a C14-DMO method and a tissue CO2 technique. The values for intracellular pH by each method, although slightly different, changed in parallel under most experimental conditions. Acute, severe potassium depletion in vitro had no detectable effect on intracellular pH, nor did prior depletion in vivo followed by incubation in a potassium-free bath. This was true whether or not the potassium-depleted muscle was exposed to normal or elevated extracellular levels of bicarbonate, and was unaffected by the presence of cationic amino acids in the bath. Acute repletion of previously potassium-depleted muscle resulted in a small rise in cell pH, but this was no greater than that produced by loading normal tissues with potassium. It is concluded that under the conditions of these experiments there is no evidence of intracellular acidosis in potassium-depleted skeletal muscle. Rat diaphragm can lose up to half its potassium content in vitro without detectable increase in hydrogen ion concentration.

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