Use of a new index to study relaxation in a vascular model of anaphylactic shock

1993 ◽  
Vol 74 (6) ◽  
pp. 2621-2626 ◽  
Author(s):  
X. Liu ◽  
H. Jiang ◽  
N. L. Stephens
Keyword(s):  
Saphenous Vein ◽  
Anaphylactic Shock ◽  
Muscle Activation ◽  
Muscle Relaxation ◽  
Contractile Element ◽  
Time Index ◽  
Muscle Shortening ◽  
Cross Bridges ◽  
And Control ◽  
Relaxation Index

We have reported increased smooth muscle shortening ability in ragweed pollen-sensitized saphenous vein (SSV). This may account for the vascular hyperreactivity of anaphylactic shock. We have now investigated relaxation in SSV. Because isotonic relaxation is load and initial contractile element length dependent, we developed an adjusted half-relaxation time index, which was independent of these variables. Muscle activation state was monitored by measuring maximum unloaded velocity. The relaxation index showed no difference between SSV and control saphenous vein after 2.5, 10, and 15 s of electrical stimulation; however, after 1 s of stimulation it was prolonged significantly in SSV. We concluded that the cross bridges activating early in contraction demonstrated prolonged relaxation. Activation state during muscle relaxation spontaneously increased toward the end of relaxation, coincident with a slowing in isotonic re-elongation rate. This was seen only in muscles relaxing from 15 s of stimulation. Our results indicate that 1) the relaxation properties of early cycling (1 s) cross bridges are altered after sensitization; and 2) toward the end of isotonic relaxation, cross-bridge cycling rate increases spontaneously, a phenomenon not previously reported. We speculate that the rapid re-elongation in late relaxation may reactivate muscle.

Relaxation of smooth muscle

1994 ◽  
Vol 72 (11) ◽  
pp. 1345-1350 ◽  
Author(s):  
N. L. Stephens ◽  
H. Jiang
Keyword(s):  
Smooth Muscle ◽  
Muscle Relaxation ◽  
Late Phase ◽  
Contractile Element ◽  
Smooth Muscle Relaxation ◽  
Shortening Velocity ◽  
Cycling Rate ◽  
Cross Bridge ◽  
Cross Bridges ◽  
And Control

We have demonstrated that in dogs antigen sensitization results in alterations of contractile properties. These changes could account for the hyperresponsiveness reported in asthma. The failure of the muscle to relax could be another important factor responsible for maintaining high airway resistance. We therefore developed an index of isotonic relaxation, t1/2,CE (half time for relaxation that is independent of muscle load and initial contractile element length), for evaluation of the relaxation process. Because the maximum shortening velocity at 2 s but not at 10 s was greater in sensitized bronchial smooth muscle than that in controls, studies of relaxation were also undertaken at these two times. The mean half-relaxation time indicated by t1/2,CE showed no difference between sensitized and control muscles after 10 s of stimulation (8.38 ± 0.92 vs. 7.78 ± 0.93 s, means ± SE); however, it was prolonged significantly in the sensitized muscle only stimulated for 1 s (12.74 ± 2.5 s, mean ± SE) compared with the control (6.98 ± 1.01 s). During the late phase of isotonic relaxation, both groups showed an unexpected spontaneous increase in zero-load shortening velocity, which is an index of cross-bridge cycling rate. We conclude that (i) both contraction and relaxation properties of early normally cycling cross bridges are altered after sensitization and these changes may account for the hyperresponsiveness observed in asthmatics and (ii) the cross-bridge cycling rate increases spontaneously during isotonic relaxation, probably as a result of reactivation of the contractile mechanism.Key words: smooth muscle relaxation, isotonic relaxation, spontaneous activation in late relaxation, mechanisms for airway hyperresponsiveness, new index of muscle relaxation.

Shortening deactivation: quantifying a critical component of cyclical muscle contraction

2021 ◽  
Author(s):  
Amy K. Loya ◽  
Sarah K. Van Houten ◽  
Bernadette M. Glasheen ◽  
Douglas M. Swank
Keyword(s):  
Power Output ◽  
Muscle Activation ◽  
Muscle Relaxation ◽  
Length Change ◽  
Isometric Tension ◽  
Energetic Cost ◽  
Muscle Shortening ◽  
Shortening Deactivation ◽  
Muscle Types ◽  
Flight Muscles

A muscle undergoing cyclical contractions requires fast and efficient muscle activation and relaxation to generate high power with relatively low energetic cost. To enhance activation and increase force levels during shortening, some muscle types have evolved stretch activation (SA), a delayed increased in force following rapid muscle lengthening. SA's complementary phenomenon is shortening deactivation (SD), a delayed decrease in force following muscle shortening. SD increases muscle relaxation, which decreases resistance to subsequent muscle lengthening. While it might be just as important to cyclical power output, SD has received less investigation than SA. To enable mechanistic investigations into SD and quantitatively compare it to SA, we developed a protocol to elicit SA and SD from Drosophila and Lethocerus indirect flight muscles (IFM) and Drosophila jump muscle. When normalized to isometric tension, Drosophila IFM exhibited a 118% SD tension decrease, Lethocerus IFM dropped by 97%, and Drosophila jump muscle decreased by 37%. The same order was found for normalized SA tension: Drosophila IFM increased by 233%, Lethocerus IFM by 76%, and Drosophila jump muscle by only 11%. SD occurred slightly earlier than SA, relative to the respective length change, for both IFMs; but SD was exceedingly earlier than SA for jump muscle. Our results suggest SA and SD evolved to enable highly efficient IFM cyclical power generation and may be caused by the same mechanism. However, jump muscle SA and SD mechanisms are likely different, and may have evolved for a role other than to increase the power output of cyclical contractions.

Controlled Evaluation of Muscle Relaxation in the Ventilated Neonate

PEDIATRICS ◽  
1981 ◽  
Vol 67 (5) ◽  
pp. 641-646
Author(s):  
N. N. Finer ◽  
P. M. Tomney
Keyword(s):  
Birth Weight ◽  
Intracranial Pressure ◽  
Low Birth Weight ◽  
Muscle Relaxation ◽  
Control Period ◽  
Pancuronium Bromide ◽  
Intracranial Pressure Elevation ◽  
Controlled Evaluation ◽  
And Control ◽  
Inspiratory Oxygen

To assess the effects of muscle relaxation on the critically ill ventilated neonate, pancuronium bromide was administered for a 12-hour period to ten low-birth-weight neonates (960 to 2,000 gm) of 26 to 34 weeks gestation, all of whom required mechanical ventilation and were studied within 48 hours of birth (six to 39 hours). The infants were also studied for a 12-hour period during which no pancuronium bromide was administered. During both study periods, the order of which was randomized, heart rate, blood pressure, Po2, and intracranial pressure were continuously measured. The amounts of handling during the pancuronium and control periods were similar. The results revealed a significantly greater duration of hypoxia (P02 < 50 torr) (56.1 vs 23.6 minutes, P < .001) and hyperoxia (Po2 > 70 torr) during the control period (92.5 vs 13 minutes, P < .001). Durations of intracranial pressure elevation 10 cm H2O above the infant's baseline were significantly less during paralysis (6.7 vs 58.8 minutes, P < .001) as were spikes of intracranial pressure to greater than 25 cm H2O (1.6 vs 24.4, P < .05). There was no significant improvement in blood gas values, fractional inspiratory oxygen, or ventilator settings during muscle relaxation. Pancuronium reduced periods of nonoptimal oxygenation and elevated intracranial pressure and may therefore help to decrease adverse sequelae for the low-birth-weight, ventilated neonate.

Effect of endurance training on muscle activation and force sensation

1995 ◽  
Vol 73 (12) ◽  
pp. 1765-1773 ◽  
Author(s):  
E. Cafarelli ◽  
F. Liebesman ◽  
J. Kroon
Keyword(s):  
Endurance Training ◽  
Muscle Activation ◽  
Vastus Lateralis ◽  
Endurance Performance ◽  
Motor Units ◽  
Control Group ◽  
Reduction In Force ◽  
Leg Cycling ◽  
Before And After ◽  
And Control

One of the consequences of endurance training is a reduction in force sensation in trained muscles at any exercise intensity. To study the central and peripheral contributions to this adaptation, we trained six male subjects with single-leg cycling at 60% [Formula: see text] peak (30 min/day × 3 days/week × 8 weeks); six others were matched controls. Measurements were made during separate 20-min, single-leg rides at 70% pre-training [Formula: see text] peak, with trained (TR), untrained (UT), and control (CT) legs, before and after training. No pre–post differences were observed in the control group. [Formula: see text] peak increased 18% (p < 0.05) in the TR leg and 6% (p < 0.05) in the UT leg of the trained subjects. Force sensation was significantly less in both the TR (70%; p < 0.05) and UT (50%; p < 0.05) legs during 20 min of single-leg cycling after training. Vastus lateralis EMG, plasma lactate, and heart rate were all significantly (p < 0.05) lower when cycling with either the TR or UT leg, which were both lower than when cycling with the CT leg, at the end of each 20-min ride. These data reflect an intramuscular environment that is better adapted to endurance performance by virtue of both central and peripheral mechanisms. Thus, there is less need to recruit additional motor units to maintain the same power output, and this reduced motor outflow leads to a decline in force sensation.Key words: kinesthesia, proprioception, electromyography, single-leg training, endurance training.

Development of a soft cable-driven hand exoskeleton for assisted rehabilitation training

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Dawen Xu ◽  
Qingcong Wu ◽  
Yanghui Zhu
Keyword(s):  
Muscle Activation ◽  
Control Strategies ◽  
Motor Dysfunction ◽  
Force Transmission ◽  
Content Type ◽  
Rehabilitation Training ◽  
Local Structures ◽  
Hand Exoskeleton ◽  
And Control

Purpose Hand motor dysfunction has seriously reduced people’s quality of life. The purpose of this paper is to solve this problem; different soft exoskeleton robots have been developed because of their good application prospects in assistance. In this paper, a new soft hand exoskeleton is designed to help people conduct rehabilitation training. Design/methodology/approach The proposed soft exoskeleton is an under-actuated cable-driven mechanism, which optimizes the force transmission path and many local structures. Specifically, the path of force transmission is optimized and cables are wound around cam-shaped spools to prevent cables lose during fingers movement. Besides, a pre-tightening system is presented to adjust the preload force of the cable-tube. Moreover, a passive brake mechanism is proposed to prevent the cables from falling off the spools when the remote side is relaxed. Findings Finally, three control strategies are proposed to assist in rehabilitation training. Results show that the average correlation coefficient of trajectory tracking is 90.99% and this exoskeleton could provide steady clamping force up to 35 N, which could meet the demands of activities in daily living. Surface electromyography (sEMG)-based intention recognition method is presented to complete assistance and experiments are conducted to prove the effectiveness of the assisted grasping method by monitoring muscle activation, finger angle and interactive force. Research limitations/implications However, the system should be further optimized in terms of hardware and control to reduce delays. In addition, more clinical trials should be conducted to evaluate the effect of the proposed rehabilitation strategies. Social implications May improve the ability of hemiplegic patients to live independently. Originality/value A novel under-actuated soft hand exoskeleton structure is proposed, and an sEMG-based auxiliary grasping control strategy is presented to help hemiplegic patients conduct rehabilitation training.

Vanadate oxidation activates contraction in skinned smooth muscle without myosin light chain phosphorylation

1997 ◽  
Vol 272 (1) ◽  
pp. C278-C288 ◽  
Author(s):  
M. J. Lalli ◽  
K. Obara ◽  
R. J. Paul
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Muscle Activation ◽  
Isometric Force ◽  
Total Force ◽  
Shortening Velocity ◽  
Irreversible Damage ◽  
Initial Control ◽  
High Concentrations ◽  
Cross Bridges

Phosphorylation of the myosin regulatory light chain (LC20-P1) is the major route of smooth muscle activation. However, after prior exposure to vanadate, permeabilized guinea pig taenia coli smooth muscle contracts in the absence of LC20-P1. We characterized the vanadate-induced contraction and investigated the mechanism of this novel activation pathway. Addition of vanadate to a control contracture (6.6 microM Ca2+) inhibits force (effective dose for 50% response was approximately 100 microM). In contrast, preincubation with high concentrations of vanadate (threshold at 1-2 mM) elicited a contraction on subsequent transfer of the fiber to a vanadate-free, Ca(2+)-free solution. Maximum isometric force of approximately 60% of control was obtained in fibers preincubated in 4 mM vanadate for 10 min. Addition of Ca2+ to a vanadate-induced contracture increased force, but the total force never exceeded the initial control. After maximal thiophosphorylation of LC20 with adenosine 5'-O-(3-thiotriphosphate), treatment with vanadate did not increase force. Unloaded shortening velocity (Vmax) was similar in Ca2+ and vanadate contractures and was additive. After thiophosphorylation, preincubation in vanadate had no effect on Vmax, suggesting that vanadate affected the number of activated bridges and not cycle rate. Vanadate mechanisms likely involve oxidation, since preincubation with 4 mM vanadate and 25 mM dithiothreitol (DTT) did not produce force. DTT could reverse a vanadate-induced contracture in 30-60 min. Subsequently, fibers demonstrated control contraction/relaxation cycles. Thus vanadate treatment did not cause irreversible damage, such as the extraction of proteins. Potential oxidation sites are proteins at 17 kDa and between 30 and 40 kDa, which were not alkylated by N-ethylmaleimide if they were treated in the presence of vanadate or in the rigor state. Vanadate-induced contractures are likely mediated by a reversible oxidation that activates cross bridges similarly to that of LC20-Pi and may play an important role in oxidant injury.

In vivo loads on airway smooth muscle: the role of noncontractile airway structures

1992 ◽  
Vol 70 (4) ◽  
pp. 602-606 ◽  
Author(s):  
Philip Robinson ◽  
Mitsushi Okazawa ◽  
Tony Bai ◽  
Peter Paré
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Activation ◽  
Muscle Length ◽  
Tracheal Cartilage ◽  
Elastic Load ◽  
Muscle Shortening ◽  
Trachealis Muscle

The degree of airway smooth muscle contraction and shortening that occurs in vivo is modified by many factors, including those that influence the degree of muscle activation, the resting muscle length, and the loads against which the muscle contracts. Canine trachealis muscle will shorten up to 70% of starting length from optimal length in vitro but will only shorten by around 30% in vivo. This limitation of shortening may be a result of the muscle shortening against an elastic load such as could be applied by tracheal cartilage. Limitation of airway smooth muscle shortening in smaller airways may be the result of contraction against an elastic load, such as could be applied by lung parenchymal recoil. Measurement of the elastic loads applied by the tracheal cartilage to the trachealis muscle and by lung parenchymal recoil to smooth muscle of smaller airways were performed in canine preparations. In both experiments the calculated elastic loads applied by the cartilage and the parenchymal recoil explained in part the limitation of maximal active shortening and airway narrowing observed. We conclude that the elastic loads provided by surrounding structures are important in determining the degree of airway smooth muscle shortening and the resultant airway narrowing.Key words: elastic loads, tracheal cartilage, airway smooth muscle shortening.

scholarly journals Spring-like leg behaviour, musculoskeletal mechanics and control in maximum and submaximum height human hopping

2011 ◽  
Vol 366 (1570) ◽  
pp. 1516-1529 ◽  
Author(s):  
Maarten F. Bobbert ◽  
L. J. Richard Casius
Keyword(s):  
Energy Expenditure ◽  
Muscle Activation ◽  
Mechanical Energy ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Centre Of Mass ◽  
Leg Stiffness ◽  
Reaction Forces ◽  
And Control ◽  
The Relationship

The purpose of this study was to understand how humans regulate their ‘leg stiffness’ in hopping, and to determine whether this regulation is intended to minimize energy expenditure. ‘Leg stiffness’ is the slope of the relationship between ground reaction force and displacement of the centre of mass (CM). Variations in leg stiffness were achieved in six subjects by having them hop at maximum and submaximum heights at a frequency of 1.7 Hz. Kinematics, ground reaction forces and electromyograms were measured. Leg stiffness decreased with hopping height, from 350 N m −1 kg −1 at 26 cm to 150 N m −1 kg −1 at 14 cm. Subjects reduced hopping height primarily by reducing the amplitude of muscle activation. Experimental results were reproduced with a model of the musculoskeletal system comprising four body segments and nine Hill-type muscles, with muscle stimulation STIM( t ) as only input. Correspondence between simulated hops and experimental hops was poor when STIM( t ) was optimized to minimize mechanical energy expenditure, but good when an objective function was used that penalized jerk of CM motion, suggesting that hopping subjects are not minimizing energy expenditure. Instead, we speculated, subjects are using a simple control strategy that results in smooth movements and a decrease in leg stiffness with hopping height.

scholarly journals Experimental evaluation of allergenic properties of Bisphenol-5

2020 ◽  
Vol 27 ◽  
pp. 00063
Author(s):  
R. M. Ahmadullin ◽  
R. S. Muhammadiev ◽  
L. R. Valiullin
Keyword(s):  
Experimental Study ◽  
Anaphylactic Shock ◽  
The Body ◽  
Laboratory Animals ◽  
Preclinical Studies ◽  
Test Drug ◽  
Experimental Conditions ◽  
Negative Effect ◽  
And Control ◽  
Respiratory Movements

The paper presents the results of preclinical studies of the allergenic properties of a new drug bisphenol-5, which has pronounced anti-radical activity. An experimental study of the antioxidant was carried out in doses of 2, 5, 20 mg/kg in guinea pigs and rabbits. It was shown that bisphenol-5 is not able to cause a general anaphylaxis reaction (anaphylactic shock). By the method of skin applications, the absence of allergenic effects of the drug in animals was found. During the formulation of conjunctival tests in experimental and control animals, signs of hypersensitivity, both immediate and delayed, were not observed with respect to the test drug. Changes in body temperature, pulse rate, and the number of respiratory movements as a result of clinical studies of the state of the animal organism after applying bisphenol-5 were also not recorded. Thus, the drug Besphenol-5 in the studied doses and under the selected experimental conditions does not have a negative effect on the body of laboratory animals and does not have allergenic properties.

scholarly journals A QUASI-EXPERIMENTAL PRE-TEST-POST TEST GROUP DESIGN TO ASSESS THE EFFECTIVENESS OF JACOBSON’S PROGRESSIVE MUSCLE RELAXATION EXERCISE ON BLOOD PRESSURE AMONG PATIENT WITH HYPERTENSION IN SACRED HEART HOSPITAL AT THOOTHUKUDI

2021 ◽  
Vol 8 (3) ◽  
Author(s):  
Mr. Israel Jeba Prabu prabhu ◽  
Dr. C.P Sharma sharma
Keyword(s):  
Blood Pressure ◽  
Muscle Relaxation ◽  
Demographic Variables ◽  
Progressive Muscle Relaxation ◽  
Control Group ◽  
Post Test ◽  
Relaxation Exercise ◽  
And Control ◽  
Experimental Group ◽  
Test Level

The objectives of the study were to 1. determine the pre-test and post-test level of blood pressure among patients with Hypertension in experimental and control group.2. assess the efficacy of Jacobson’s progressive muscle relaxation exercise on blood pressure among patients with Hypertension in experimental group.3. Associate the selected socio demographic variables with the level of blood pressure in experimental group. Hypothesis H0: There will not be a significant difference between pre and post test level of blood pressure after Jacobson’s progressive muscle relaxation exercise among patient with Hypertension in experimental and control group. H1: There will be a significant decrease in the level of blood pressure after Jacobson’s progressive muscle relaxation exercise among patient with Hypertension in experimental group. H2:There will be significant association between post test levels of blood pressure with selected demographic variables in experimental group. H01: There will not be significant association between post test levels of blood pressure with selected demographic variables in experimental group. Review of literature was organised based on review related to Jacobson’s progressive muscle relaxation and Jacobson’s progressive muscle relaxation on blood pressure. The tool was validated by experts and found to be valid for the study. Sampling Technique: Sample was selected by using non probability convenience sampling method. Results: the data was tabulated, analyzed and interpreted by using descriptive and inferential statistics. After the detailed analysis this study leads to following conclusions, longer day of intervention shows significant decrease in the level of blood pressure. Major findings show that there is significant decrease in the level of blood pressure after Jacobson’s progressive muscle relaxation exercise among patient with Hypertension in experimental group. It was statistically significant at (P<0.001). Hence the sta

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