Mechanisms Underlying Stabilization of Temporally Summated Muscle Contractions in the Lobster (Panulirus) Pyloric System

2001 ◽  
Vol 85 (1) ◽  
pp. 254-268 ◽  
Author(s):  
Lee G. Morris ◽  
Scott L. Hooper
Keyword(s):  
Muscle Contraction ◽  
Duty Cycle ◽  
Motor Nerve ◽  
Cycle Period ◽  
Neural Basis ◽  
Regime Changes ◽  
Relative Contribution ◽  
Duty Cycles ◽  
Dilator Muscle ◽  
S Period

Muscles are the final effectors of behavior. The neural basis of behavior therefore cannot be completely understood without a description of the transfer function between neural output and muscle contraction. To this end, we have been studying muscle contraction in the well-investigated lobster pyloric system. We report here the mechanisms underlying stabilization of temporally summating contractions of the very slow dorsal dilator muscle in response to motor nerve stimulation with trains of rhythmic shock bursts at a physiological intraburst spike frequency (60 Hz), physiological cycle periods (0.5–2 s), and duty cycles from 0.1 to 0.8. For temporal summation to stabilize, the rise and relaxation amplitudes of the phasic contractions each burst induces must equalize as the rhythmic train continues. Stabilization could occur by changes in rise duration, rise slope, plateau duration, and/or relaxation slope. We demonstrate a generally applicable method for quantifying the relative contribution changes in these characteristics make to contraction stabilization. Our data show that all characteristics change as contractions stabilize, but their relative contribution differs depending on stimulation cycle period and duty cycle. The contribution of changes in rise duration did not depend on period or duty cycle for the 1-, 1.5-, and 2-s period regimes, contributing ∼30% in all cases; but for the 0.5-s period regime, changes in rise duration increased from contributing 25% to contributing 50% as duty cycle increased from 0.1 to 0.8. At all cycle periods decreases in rise slope contributed little to stabilization at small duty cycles but increased to contributing ∼80% at high duty cycles. The contribution of changes in plateau duration decreased in all cases as duty cycle increased; but this decrease was greater in long cycle period regimes. The contribution of changes in relaxation slope also decreased in all cases as duty cycle increased; but for this characteristic, the decrease was greatest in fast cycle period regimes, and in these regimes at high duty cycles these changes opposed contraction stabilization. Exponential fits to contraction relaxations showed that relaxation time constant increased with total contraction amplitude; this increase presumably underlies the decreased relaxation slope magnitude seen in high duty cycle, fast cycle period regimes. These data show that changes in no single contraction characteristic can account for contraction stabilization in this muscle and suggest that predicting muscle response in other systems in which slow muscles are driven by rapidly varying neuronal inputs may be similarly complex.

scholarly journals Comparison of extraocular and intraocular pressure transducers for measurement of transient intraocular pressure fluctuations using continuous wireless telemetry

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jessica V. Jasien ◽  
Ye Emma Zohner ◽  
Sonia Kuhn Asif ◽  
Lindsay A. Rhodes ◽  
Brian C. Samuels ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Duty Cycle ◽  
Rhesus Macaques ◽  
Pressure Fluctuations ◽  
Linear Mixed Effects ◽  
Pressure Transducers ◽  
Duty Cycles ◽  
Fluctuation Frequency ◽  
S Period ◽  
Optimal Approach

AbstractThe optimal approach for continuous measurement of intraocular pressure (IOP), including pressure transducer location and measurement frequency, is currently unknown. This study assessed the capability of extraocular (EO) and intraocular (IO) pressure transducers, using different IOP sampling rates and duty cycles, to characterize IOP dynamics. Transient IOP fluctuations were measured and quantified in 7 eyes of 4 male rhesus macaques (NHPs) using the Konigsberg EO system (continuous at 500 Hz), 12 eyes of 8 NHPs with the Stellar EO system and 16 eyes of 12 NHPs with the Stellar IO system (both measure at 200 Hz for 15 s of every 150 s period). IOP transducers were calibrated bi-weekly via anterior chamber manometry. Linear mixed effects models assessed the differences in the hourly transient IOP impulse, and transient IOP fluctuation frequency and magnitude between systems and transducer placements (EO versus IO). All systems measured 8000–12,000 and 5000–6500 transient IOP fluctuations per hour > 0.6 mmHg, representing 8–16% and 4–8% of the total IOP energy the eye must withstand during waking and sleeping hours, respectively. Differences between sampling frequency/duty cycle and transducer placement were statistically significant (p < 0.05) but the effect sizes were small and clinically insignificant. IOP dynamics can be accurately captured by sampling IOP at 200 Hz on a 10% duty cycle using either IO or EO transducers.

scholarly journals Differential effects of respiratory and electrical stimulation-induced dilator muscle contraction on mechanical properties of the pharynx in the pig

2016 ◽  
Vol 121 (3) ◽  
pp. 606-614 ◽  
Author(s):  
A. Brodsky ◽  
Y. Dotan ◽  
M. Samri ◽  
A. R. Schwartz ◽  
A. Oliven
Keyword(s):  
Electrical Stimulation ◽  
Muscle Contraction ◽  
Emg Activity ◽  
Tongue Muscle ◽  
Relative Contribution ◽  
Dilator Muscle ◽  
Pressure Area ◽  
Relationship Of ◽  
Respiratory Stimulation

Respiratory stimulation (RS) during sleep often fails to discontinue flow limitation, whereas electrical stimulation (ES) of the hypoglossus (HG) nerve frequently prevents obstruction. The present work compares the effects of RS and HG-ES on pharyngeal mechanics and the relative contribution of tongue muscles and thoracic forces to pharyngeal patency. We determined the pressure-area relationship of the collapsible segment of the pharynx in anesthetized pigs under the following three conditions: baseline (BL), RS induced by partial obstruction of the tracheostomy tube, and HG-ES. Parameters were obtained also after transection of the neck muscles and the trachea (NMT) and after additional bilateral HG transection (HGT). In addition, we measured the force produced by in situ isolated geniohyoid (GH) during RS and HG-ES. Intense RS was recognized by large negative intrathoracic pressures and triggered high phasic genioglossus and GH EMG activity. GH contraction produced during maximal RS less than a quarter of the force obtained during HG-ES. The major finding of the study was that RS and ES differed in the mechanism by which they stabilized the pharynx: RS lowered the pressure-area slope, i.e., reduced pharyngeal compliance (14.1 ± 2.9 to 9.2 ± 1.9 mm2/cmH2O, P < 0.01). HG-ES shifted the slope toward lower pressures, i.e., lowered the calculated extraluminal pressure (17.4 ± 5.8 to 9.2 ± 7.4 cmH2O, P < 0.01). Changes during RS and HG-ES were not affected by NMT, but the effect of RS decreased significantly after HGT. In conclusion, HG-ES and RS affect the pharyngeal site of collapse differently. Tongue muscle contraction contributes to pharyngeal stiffening during RS.

scholarly journals Wi-Fi Coexistence with Duty Cycled LTE-U

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Yimin Pang ◽  
Alireza Babaei ◽  
Jennifer Andreoli-Fang ◽  
Belal Hamzeh
Keyword(s):  
Duty Cycle ◽  
Monte Carlo Analysis ◽  
Cycle Period ◽  
Distributed Coordination ◽  
Time Sharing ◽  
Performance Loss ◽  
Duty Cycles ◽  
Shared Channel ◽  
The Difference ◽  
Coordination Function

Coexistence of Wi-Fi and LTE-Unlicensed (LTE-U) technologies has drawn significant concern in industry. In this paper, we investigate the Wi-Fi performance in the presence of duty cycle based LTE-U transmission on the same channel. More specifically, one LTE-U cell and one Wi-Fi basic service set (BSS) coexist by allowing LTE-U devices to transmit their signals only in predetermined duty cycles. Wi-Fi stations, on the other hand, simply contend the shared channel using the distributed coordination function (DCF) protocol without cooperation with the LTE-U system or prior knowledge about the duty cycle period or duty cycle of LTE-U transmission. We define the fairness of the above scheme as the difference between Wi-Fi performance loss ratio (considering a defined reference performance) and the LTE-U duty cycle (or function of LTE-U duty cycle). Depending on the interference to noise ratio (INR) being above or below −62 dbm, we classify the LTE-U interference as strong or weak and establish mathematical models accordingly. The average throughput and average service time of Wi-Fi are both formulated as functions of Wi-Fi and LTE-U system parameters using probability theory. Lastly, we use the Monte Carlo analysis to demonstrate the fairness of Wi-Fi and LTE-U air time sharing.

Acoustic-Reflex Dynamics for Pulsed Signals

1978 ◽  
Vol 21 (2) ◽  
pp. 295-308
Author(s):  
Terry L. Wiley ◽  
Raymond S. Karlovich
Keyword(s):  
Duty Cycle ◽  
Acoustic Impedance ◽  
Normal Hearing ◽  
Broadband Noise ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Acoustic Reflex ◽  
Stapedius Muscle ◽  
Duty Cycles

Contralateral acoustic-reflex measurements were taken for 10 normal-hearing subjects using a pulsed broadband noise as the reflex-activating signal. Acoustic impedance was measured at selected times during the on (response maximum) and off (response minimum) portions of the pulsed activator over a 2-min interval as a function of activator period and duty cycle. Major findings were that response maxima increased as a function of time for longer duty cycles and that response minima increased as a function of time for all duty cycles. It is hypothesized that these findings are attributable to the recovery characteristics of the stapedius muscle. An explanation of portions of the results from previous temporary threshold shift experiments on the basis of acoustic-reflex dynamics is proposed.

scholarly journals Effects of acetylcholine and nitric oxide on forearm blood flow at rest and after a single muscle contraction

1998 ◽  
Vol 85 (6) ◽  
pp. 2249-2254 ◽  
Author(s):  
R. W. Brock ◽  
M. E. Tschakovsky ◽  
J. K. Shoemaker ◽  
J. R. Halliwill ◽  
M. J. Joyner ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Muscle Contraction ◽  
Forearm Blood Flow ◽  
Mechanical Effect ◽  
Voluntary Contraction ◽  
Single Muscle ◽  
Cuff Inflation ◽  
S Period ◽  
Echo Doppler Ultrasound

We tested the hypothesis that ACh or nitric oxide (NO) might be involved in the vasodilation that accompanies a single contraction of the forearm. Eight adults (3 women and 5 men) completed single 1-s-duration contractions of the forearm to raise and lower a weight equivalent to ∼20% maximal voluntary contraction through a distance of 5 cm. In a second protocol, each subject had a cuff, placed completely about the forearm, inflated to 120 mmHg for a 1-s period, then released as a simulation of the mechanical effect of muscle contraction. Three conditions were studied, always in this order: 1) control, with intra-arterial infusion of saline; 2) after muscarinic blockade with atropine; and 3) after NO synthase inhibition with N G-monomethyl-l-arginine (l-NMMA) plus atropine. Forearm blood flow (FBF), measured by combined pulsed and echo Doppler ultrasound, was reduced at rest with l-NMMA-atropine compared with the other two conditions. After the single contraction, there were no effects of atropine, butl-NMMA reduced the peak FBF and the total postcontraction hyperemia. After the single cuff inflation, atropine had no effects, whereasl-NMMA caused changes similar to those seen after contraction, reducing the peak FBF and the total hyperemia. The observation thatl-NMMA reduced FBF in response to both cuff inflation and a brief contraction indicates that NO from the vascular endothelium might modulate the basal level of vascular tone and the mechanical component of the hyperemia with exercise. It is unlikely that ACh and NO from the endothelium are involved in the dilator response to a single muscle contraction.

ATP concentrations and muscle tension increase linearly with muscle contraction

2003 ◽  
Vol 95 (2) ◽  
pp. 577-583 ◽  
Author(s):  
Jianhua Li ◽  
Nicholas C. King ◽  
Lawrence I. Sinoway
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Muscle Contraction ◽  
Motor Nerve ◽  
Muscle Tension ◽  
Nerve Fibers ◽  
Ventral Root ◽  
Ventral Roots ◽  
Root Stimulation ◽  
Stimulation Of

Previous studies have suggested that activation of ATP-sensitive P2X receptors in skeletal muscle play a role in mediating the exercise pressor reflex (Li J and Sinoway LI. Am J Physiol Heart Circ Physiol 283: H2636–H2643, 2002). To determine the role ATP plays in this reflex, it is necessary to examine whether muscle interstitial ATP (ATPi) concentrations rise with muscle contraction. Accordingly, in this study, muscle contraction was evoked by electrical stimulation of the L7 and S1 ventral roots of the spinal cord in 12 decerebrate cats. Muscle ATPi was collected from microdialysis probes inserted in the muscle. ATP concentrations were determined by the HPLC method. Electrical stimulation of the ventral roots at 3 and 5 Hz increased mean arterial pressure by 13 ± 2 and 16 ± 3 mmHg ( P < 0.05), respectively, and it increased ATP concentration in contracting muscle by 150% ( P < 0.05) and 200% ( P < 0.05), respectively. ATP measured in the opposite control limb did not rise with ventral root stimulation. Section of the L7 and S1 dorsal roots did not affect the ATPi seen with 5-Hz ventral root stimulation. Finally, ventral roots stimulation sufficient to drive motor nerve fibers did not increase ATP in previously paralyzed cats. Thus ATPi is not largely released from sympathetic or motor nerves and does not require an intact afferent reflex pathway. We conclude that ATPi is due to the release of ATP from contracting skeletal muscle cells.

The development of a representative multidimensional transient duty cycle for in-service switcher locomotives

2021 ◽  
pp. 095440972110418
Author(s):  
Mohamed A Hegazi ◽  
Andreas Hoffrichter ◽  
Jeffrey L Andrews ◽  
Gordon Lovegrove
Keyword(s):  
Duty Cycle ◽  
Electric Propulsion ◽  
Clustering Algorithm ◽  
Power Level ◽  
Time Data ◽  
Major Drawback ◽  
Model Based Clustering ◽  
Engine Efficiency ◽  
Duty Cycles ◽  
Acceleration And Deceleration

Switcher locomotives operate in railway yards where they shunt railcars and assemble trains. Shunting railcars requires frequent aggressive acceleration and deceleration events in order for the locomotive to push or pull railcars onto specific tracks. As a result, switcher locomotives rarely sustain tractive power for any significant period of time. Given that all switchers in North America rely on diesel-electric propulsion; the result is rapid and frequent transitions in engine power leading to a very low engine efficiency and high levels of emissions. Any attempt to quantify or remedy these issues will face a lack of a representative profile or test cycle. A locomotive duty cycle is a breakdown of time spent at each power level of the locomotive’s engine. A major drawback of current duty cycles is that they only account for steady power. Such cycles are not representative of real switcher locomotive operation. This paper presents a real-world transient duty cycle for switcher locomotives that accounts for the rapid power transitions and is argued to be more statistically representative of actual operations. The methodology adopted relies on real-time data collection, microtrip based trip segmentation, and a finite mixture model-based clustering algorithm. Measurements were collected on a EMD 16-645 GP9 locomotive. The duty cycle developed herein is representative of switching operations in Southern Railway of British Columbia’s New Westminster Yard as an example of the methodology which can be repeated in other cases as well.

The central nervous origin of the swimming motor pattern in embryos of Xenopus laevis

1982 ◽  
Vol 99 (1) ◽  
pp. 185-196 ◽  
Author(s):  
J. A. Kahn ◽  
A. Roberts
Keyword(s):  
Motor Activity ◽  
Similar Pattern ◽  
Sensory Feedback ◽  
Motor Nerve ◽  
Motor Pattern ◽  
Cycle Period ◽  
Phase Lag ◽  
Nerve Activity ◽  
Rhythmic Motor ◽  
Swimming Pattern

Rhythmic motor nerve activity was recorded in stage 37/38 Xenopus embryos paralysed with curare. The activity was similar to the swimming motor pattern in the following ways: cycle period (40–125 ms), alternation of activity on either side of a segment, rostro-caudal phase lag. Episodes of rhythmic motor activity could be evoked by stimuli that evoke swimming and inhibited by stimuli that normally inhibit swimming. On this basis we conclude that the swimming motor pattern is generated by a central nervous mechanism and is not dependent on sensory feedback. In addition to the swimming pattern, another pattern of motor activity (‘synchrony’) was sometimes recorded in curarized embryos. In this, the rhythmic bursts on either side of a segment occurred in synchrony, and the rhythm period (20–50 ms) was half that in swimming. This was probably not an artifact of curarization as there were indications of a similar pattern in uncurarized embryos. Its function remains unclear.

scholarly journals Assessment of Effects of Laser Light Combining Three Wavelengths (450, 520 and 640 nm) on Temperature Increase and Depth of Tissue Lesions in an Ex Vivo Study

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5340
Author(s):  
Kamil Jurczyszyn ◽  
Witold Trzeciakowski ◽  
Zdzisław Woźniak ◽  
Piotr Ziółkowski ◽  
Mateusz Trafalski
Keyword(s):  
Duty Cycle ◽  
Temperature Increase ◽  
Ex Vivo ◽  
Visible Spectrum ◽  
Maximum Temperature ◽  
Lesion Depth ◽  
Single Beam ◽  
Duty Cycles ◽  
Rate Of Increase

Background: Lasers are widely used in medicine in soft and hard tissue surgeries and biostimulation. Studies found in literature typically compare the effects of single-wavelength lasers on tissues or cell cultures. In our study, we used a diode laser capable of emitting three components of visible light (640 nm, red; 520 nm, green; 450 nm, blue) and combining them in a single beam. The aim of the study was to assess the effects of laser radiation in the visible spectrum on tissue in vitro, depending on the wavelength and pulse width. Methods: All irradiations were performed using the same output power (1.5 W). We used various duty cycles: 10, 50, 80 and 100% with 100 Hz frequency. Maximum superficial temperature, rate of temperature increase and lesion depth were investigated. Results: Maximum superficial temperature was observed for 450 + 520 nm irradiation (100% duty cycle). The highest rate of increase of temperature was noted for 450 + 520 nm (100% duty cycle). Maximum lesion depth was observed in case of three-wavelength irradiation (450 + 520 + 640 nm) for 100, 80 and 50% duty cycles. Conclusions: The synergistic effect of two-wavelength (450 + 520 nm) irradiation was observed in case of maximum temperature measurement. The deepest depth of lesion was noted after three-wavelength irradiation (450 + 520 + 640 nm).

Diaphragmatic blood flow in the dog

1986 ◽  
Vol 60 (2) ◽  
pp. 554-561 ◽  
Author(s):  
H. Bark ◽  
S. M. Scharf
Keyword(s):  
Blood Flow ◽  
Duty Cycle ◽  
Stimulus Frequency ◽  
Phase Flow ◽  
Transdiaphragmatic Pressure ◽  
Relaxation Phase ◽  
Duty Cycles ◽  
Tension Time ◽  
Phrenic Artery ◽  
Electromagnetic Flow Probe

In anesthetized mongrel dogs we measured the blood flow in the left phrenic artery (Qdi), using an electromagnetic flow probe, before and during supramaximal phrenic nerve stimulation (pacing). This was done at constant respiratory rate (24/min) but at three different stimulation frequencies at a duty cycle of 0.4 (20, 50, and 100 Hz) and at three different duty cycles at a stimulation frequency of 50 Hz (duty cycle = 0.2, 0.4, and 0.8). Qdi was unchanged during diaphragm contraction until transdiaphragmatic pressure (Pdi) was greater than approximately 11 cmH2O, whereafter it began to decrease, reaching zero at Pdi approximately 20 cmH2O. Thus, when Pdi was greater than 21 cmH2O, all flow occurred during relaxation. Qdi averaged over the entire respiratory cycle (Qt) was less at duty cycle = 0.8 than under the other conditions. This was because of decreasing length of relaxation phase rather than a difference of relaxation phase flow (Qr), which was maximal during all conditions of phrenic stimulation. During pacing-induced fatigue, Qt actually rose slightly as Pdi fell. This was due to an increase in contraction phase flow while Qr remained constant. The relationship between Qt and tension-time index was not unique but varied according to the different combinations of duty cycle and stimulus frequency.

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