Role of stretch reflex in voluntary movements. [of human foot

NASA Technical Reports Server (NTRS)

Gottlieb, G. L.; Agarwal, G. C.

1975-01-01

The stretch reflex is often described as a spinal servomechanism, a device for assisting in the regulation of muscle length. Observation of the EMG response to mechanical interruption of voluntary movements fails to demonstrate a significant role for spinal reflexes at 40 msec latency. Two functional responses with latencies of 120 msec and 200 msec, implying supraspinal mediation, are observed.

The differential role of motor cortex in stretch reflex modulation induced by changes in environmental mechanics and verbal instruction.

PubMed

Shemmell, Jonathan; An, Je Hi; Perreault, Eric J

2009-10-21

The motor cortex assumes an increasingly important role in higher mammals relative to that in lower mammals. This is true to such an extent that the human motor cortex is deeply involved in reflex regulation and it is common to speak of "transcortical reflex loops." Such loops appear to add flexibility to the human stretch reflex, once considered to be immutable, allowing it to adapt across a range of functional tasks. However, the purpose of this adaptation remains unclear. A common proposal is that stretch reflexes contribute to the regulation of limb stability; increased reflex sensitivity during tasks performed in unstable environments supports this hypothesis. Alternatively, before movement onset, stretch reflexes can assist an imposed stretch, opposite to what would be expected from a stabilizing response. Here we show that stretch reflex modulation in tasks that require changes in limb stability is mediated by motor cortical pathways, and that these differ from pathways contributing to reflex modulation that depend on how the subject is instructed to react to an imposed perturbation. By timing muscle stretches such that the modulated portion of the reflex occurred within a cortical silent period induced by transcranial magnetic stimulation, we abolished the increase in reflex sensitivity observed when individuals stabilized arm posture within a compliant environment. Conversely, reflex modulation caused by altered task instruction was unaffected by cortical silence. These results demonstrate that task-dependent changes in reflex function can be mediated through multiple neural pathways and that these pathways have task-specific roles.

The differential role of motor cortex in the stretch reflex modulation induced by changes in environmental mechanics and verbal instruction

PubMed Central

Shemmell, Jonathan; An, Je Hi; Perreault, Eric J.

2009-01-01

The motor cortex assumes an increasingly important role in higher mammals relative to that in lower mammals. This is true to such an extent that the human motor cortex is deeply involved in reflex regulation and it is common to speak of “transcortical reflex loops”. Such loops appear to add flexibility to the human stretch reflex, once considered to be immutable, allowing it to adapt across a range of functional tasks. However, the purpose of this adaptation remains unclear. A common proposal is that stretch reflexes contribute to the regulation of limb stability; increased reflex sensitivity during tasks performed in unstable environments supports this hypothesis. Alternatively, prior to movement onset, stretch reflexes can assist an imposed stretch, opposite to what would be expected from a stabilizing response. Here we show that stretch reflex modulation in tasks that require changes in limb stability is mediated by motor cortical pathways, and that these differ from pathways contributing to reflex modulation that depends on how the subject is instructed to react to an imposed perturbation. By timing muscle stretches such that the modulated portion of the reflex occurred within a cortical silent period induced by transcranial magnetic stimulation, we abolished the increase in reflex sensitivity observed when individuals stabilized arm posture within a compliant environment. Conversely, reflex modulation caused by altered task instruction was unaffected by cortical silence. These results demonstrate that task-dependent changes in reflex function can be mediated through multiple neural pathways and that these pathways have task specific roles. PMID:19846713

Robotic investigation on effect of stretch reflex and crossed inhibitory response on bipedal hopping

PubMed Central

Rosendo, Andre; Ikemoto, Shuhei; Shimizu, Masahiro; Hosoda, Koh

2018-01-01

To maintain balance during dynamic locomotion, the effects of proprioceptive sensory feedback control (e.g. reflexive control) should not be ignored because of its simple sensation and fast reaction time. Scientists have identified the pathways of reflexes; however, it is difficult to investigate their effects during locomotion because locomotion is controlled by a complex neural system and current technology does not allow us to change the control pathways in living humans. To understand these effects, we construct a musculoskeletal bipedal robot, which has similar body structure and dynamics to those of a human. By conducting experiments on this robot, we investigate the effects of reflexes (stretch reflex and crossed inhibitory response) on posture during hopping, a simple and representative bouncing gait with complex dynamics. Through over 300 hopping trials, we confirm that both the stretch reflex and crossed response can contribute to reducing the lateral inclination during hopping. These reflexive pathways do not use any prior knowledge of the dynamic information of the body such as its inclination. Beyond improving the understanding of the human neural system, this study provides roboticists with biomimetic ideas for robot locomotion control. PMID:29593088

Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) with chronic cough and preserved muscle stretch reflexes: evidence for selective sparing of afferent Ia fibres.

PubMed

Infante, Jon; García, Antonio; Serrano-Cárdenas, Karla M; González-Aguado, Rocío; Gazulla, José; de Lucas, Enrique M; Berciano, José

2018-06-01

The aim of this study was to describe five patients with cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS) with chronic cough and preserved limb muscle stretch reflexes. All five patients were in the seventh decade of age, their gait imbalance having been initiated in the fifth decade. In four patients cough antedated gait imbalance between 15 and 29 years; cough was spasmodic and triggered by variable factors. Established clinical picture included severe hypopallesthesia predominating in the lower limbs with postural imbalance, and variable degree of cerebellar axial and appendicular ataxia, dysarthria and horizontal gaze-evoked nystagmus. Upper- and lower-limb tendon jerks were preserved, whereas jaw jerk was absent. Vestibular function testing showed bilateral impairment of the vestibulo-ocular reflex. Nerve conduction studies demonstrated normal motor conduction parameters and absence or severe attenuation of sensory nerve action potentials. Somatosensory evoked potentials were absent or severely attenuated. Biceps and femoral T-reflex recordings were normal, while masseter reflex was absent or attenuated. Sympathetic skin responses were normal. Cranial MRI showed vermian and hemispheric cerebellar atrophy predominating in lobules VI, VII and VIIa. We conclude that spasmodic cough may be an integral part of the clinical picture in CANVAS, antedating the appearance of imbalance in several decades and that sparing of muscle spindle afferents (Ia fibres) is probably the pathophysiological basis of normoreflexia.

Effects of Bed Rest on Conduction Velocity of the Triceps Surae Stretch Reflex and Postural Control

NASA Technical Reports Server (NTRS)

Reschke, M. F.; Wood, S. J.; Cerisano, J. M.; Kofman, I. S.; Fisher, E. A.; Esteves, J. T.; Taylor, L. C.; DeDios, Y. E.; Harm, D. L.

2011-01-01

Despite rigorous exercise and nutritional management during space missions, astronauts returning from microgravity exhibit neuromuscular deficits and a significant loss in muscle mass in the postural muscles of the lower leg. Similar changes in the postural muscles occur in subjects participating in long-duration bed rest studies. These adaptive muscle changes manifest as a reduction in reflex conduction velocity during head-down bed rest. Because the stretch reflex encompasses both the peripheral (muscle spindle and nerve axon) and central (spinal synapse) components involved in adaptation to calf muscle unloading, it may be used to provide feedback on the general condition of neuromuscular function, and might be used to evaluate the effectiveness of countermeasures aimed at preserving muscle mass and function during periods of unloading. Stretch reflexes were measured on 18 control subjects who spent 60 to 90 days in continuous 6 deg head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 degrees at a peak velocity of about 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender. Computerized posturography was also conducted on these same subjects before and after bed rest as part of the standard measures. Peak-to-peak sway was measured during Sensory Organization Tests (SOTs) to evaluate changes in the ability to effectively use or suppress visual, vestibular, and proprioceptive information for postural control. Although no gender differences were found, a significant increase in reflex latency and a significant decrease in CV were observed during the bed

Group II muscle afferents probably contribute to the medium latency soleus stretch reflex during walking in humans

PubMed Central

Grey, Michael J; Ladouceur, Michel; Andersen, Jacob B; Nielsen, Jens Bo; Sinkjær, Thomas

2001-01-01

The objective of this study was to determine which afferents contribute to the medium latency response of the soleus stretch reflex resulting from an unexpected perturbation during human walking. Fourteen healthy subjects walked on a treadmill at approximately 3.5 km h−1 with the left ankle attached to a portable stretching device. The soleus stretch reflex was elicited by applying small amplitude (∼8 deg) dorsiflexion perturbations 200 ms after heel contact. Short and medium latency responses were observed with latencies of 55 ± 5 and 78 ± 6 ms, respectively. The short latency response was velocity sensitive (P < 0.001), while the medium latency response was not (P = 0.725). Nerve cooling increased the delay of the medium latency component to a greater extent than that of the short latency component (P < 0.005). Ischaemia strongly decreased the short latency component (P = 0.004), whereas the medium latency component was unchanged (P = 0.437). Two hours after the ingestion of tizanidine, an α2-adrenergic receptor agonist known to selectively depress the transmission in the group II afferent pathway, the medium latency reflex was strongly depressed (P = 0.007), whereas the short latency component was unchanged (P = 0.653). An ankle block with lidocaine hydrochloride was performed to suppress the cutaneous afferents of the foot and ankle. Neither the short (P = 0.453) nor medium (P = 0.310) latency reflexes were changed. Our results support the hypothesis that, during walking the medium latency component of the stretch reflex resulting from an unexpected perturbation is contributed to by group II muscle afferents. PMID:11483721

Effect of thumb anaesthesia on weight perception, muscle activity and the stretch reflex in man.

PubMed Central

Marsden, C D; Rothwell, J C; Traub, M M

1979-01-01

1. We have confirmed the results of Gandevia & McCloskey (1977) on the effect of thumb anaesthesia on perception of weights lifted by the thumb. Weights lifted by flexion feel heavier and weights lifted by extension feel lighter. 2. The change in size of the long-latency stretch reflex in flexor pollicis longus or extensor pollicis longus after thumb anaesthesia cannot explain the effect on weight perception by removal or augmentation of the background servo assistance to muscular contraction. 3. During smooth thumb flexion, thumb anaesthesia increases e.m.g. activity in flexor pollicis longus and extensor pollicis longus for any given opposing torque. 4. During smooth thumb extension the opposite occurs: e.m.g. activity in both extensor and flexor pollicis longus decreases. 5. Clamping the thumb at the proximal phalanx to limit movement solely to the interphalangeal joint reduces or abolishes the effect of anaesthesia on both weight perception and e.m.g. activity during both flexion or extension tasks. 6. Gandevia & McCloskey's findings on the distorting effects of thumb anaesthesia on weight perception cannot be used to support the hypothesis of an efferent monitoring system of the sense of effort. Our results emphasize the close functional relationship between cutaneous and joint afferent information and motor control. PMID:512948

Spasticity Measurement Based on Tonic Stretch Reflex Threshold in Children with Cerebral Palsy Using the PediAnklebot.

PubMed

Germanotta, Marco; Taborri, Juri; Rossi, Stefano; Frascarelli, Flaminia; Palermo, Eduardo; Cappa, Paolo; Castelli, Enrico; Petrarca, Maurizio

2017-01-01

Nowadays, objective measures are becoming prominent in spasticity assessment, to overcome limitations of clinical scales. Among others, Tonic Stretch Reflex Threshold (TSRT) showed promising results. Previous studies demonstrated the validity and reliability of TSRT in spasticity assessment at elbow and ankle joints in adults. Purposes of the present study were to assess: (i) the feasibility of measuring TSRT to evaluate spasticity at the ankle joint in children with Cerebral Palsy (CP), and (ii) the correlation between objective measures and clinical scores. A mechatronic device, the pediAnklebot, was used to impose 50 passive stretches to the ankle of 10 children with CP and 3 healthy children, to elicit muscles response at 5 different velocities. Surface electromyography, angles, and angular velocities were recorded to compute dynamic stretch reflex threshold; TSRT was computed with a linear regression through angles and angular velocities. TSRTs for the most affected side of children with CP resulted into the biomechanical range (95.7 ± 12.9° and 86.7 ± 17.4° for Medial and Lateral Gastrocnemius, and 75.9 ± 12.5° for Tibialis Anterior). In three patients, the stretch reflex was not elicited in the less affected side. TSRTs were outside the biomechanical range in healthy children. However, no correlation was found between clinical scores and TSRT values. Here, we demonstrated the capability of TSRT to discriminate between spastic and non-spastic muscles, while no significant outcomes were found for the dorsiflexor muscle.

Hip proprioceptors preferentially modulate reflexes of the leg in human spinal cord injury

PubMed Central

Onushko, Tanya; Hyngstrom, Allison

2013-01-01

Stretch-sensitive afferent feedback from hip muscles has been shown to trigger long-lasting, multijoint reflex responses in people with chronic spinal cord injury (SCI). These reflexes could have important implications for control of leg movements during functional activities, such as walking. Because the control of leg movement relies on reflex regulation at all joints of the limb, we sought to determine whether stretch of hip muscles modulates reflex activity at the knee and ankle and, conversely, whether knee and ankle stretch afferents affect hip-triggered reflexes. A custom-built servomotor apparatus was used to stretch the hip muscles in nine chronic SCI subjects by oscillating the legs about the hip joint bilaterally from 10° of extension to 40° flexion. To test whether stretch-related feedback from the knee or ankle would be affected by hip movement, patellar tendon percussions and Achilles tendon vibration were delivered when the hip was either extending or flexing. Surface electromyograms (EMGs) and joint torques were recorded from both legs. Patellar tendon percussions and Achilles tendon vibration both elicited reflex responses local to the knee or ankle, respectively, and did not influence reflex responses observed at the hip. Rather, the movement direction of the hip modulated the reflex responses local to the joint. The patellar tendon reflex amplitude was larger when the perturbation was delivered during hip extension compared with hip flexion. The response to Achilles vibration was modulated by hip movement, with an increased tonic component during hip flexion compared with extension. These results demonstrate that hip-mediated sensory signals modulate activity in distal muscles of the leg and appear to play a unique role in modulation of spastic muscle activity throughout the leg in SCI. PMID:23615544

Development of Device to Evoke Stretch Reflexes by Use of Electromagnetic Force for the Rehabilitation of the Hemiplegic Upper Limb after Stroke

NASA Astrophysics Data System (ADS)

Hayashi, Ryota; Ishimine, Tomoyasu; Kawahira, Kazumi; Yu, Yong; Tsujio, Showzow

In this research, we focus on the method of rehabilitation with stretch reflexes for the hemiplegic upper limb in stroke patients. We propose a new device which utilizes electromagnetic force to evoke stretch reflexes. The device can exert an assisting force safely, because the electromagnetic force is non contact force. In this paper, we develop a support system applying the proposed device for the functional recovery training of the hemiplegic upper limb. The results obtained from several clinical tests with and without our support system are compared. Then we discuss the validity of our support system.

Electromechanical analogs of human reflexes.

PubMed

Littman, M G; Liker, M; Stubbeman, W; Russakow, J; McGee, C; Gelfand, J; Call, B J

1989-01-01

The conclusion to be drawn from our modeling is that the combined stretch and tendon reflexes alone can endow artificial muscle with a springlike feel as well as give it a baseline tone. In response to questions that motor physiologists often ask as to what variables the system controls, the answer here is clear: the stretch and tendon reflexes act together to maintain both a tension set-point and a length set-point, but in so doing they also give the system a springlike feel because of the existence of a servo error. The main goal of our studies is to understand the integration of reflexes, and thus far we have only begun to explore the two lowest-level spinal reflexes. We are in the process of expanding this work by developing a much more refined arm explicitly modeled after the human arm. This new arm is to be activated by a minimum of 10 muscles, each of which is reflexively driven, and it will allow us to explore the integration of higher-level reflex action such as automatic inhibition of antagonists and facilitation of synergists.

Effect of peripherally and cortically evoked swallows on jaw reflex responses in anesthetized rabbits.

PubMed

Suzuki, Taku; Yoshihara, Midori; Sakai, Shogo; Tsuji, Kojun; Nagoya, Kouta; Magara, Jin; Tsujimura, Takanori; Inoue, Makoto

2018-05-03

This study aimed to investigate whether the jaw-opening (JOR) and jaw-closing reflexes (JCR) are modulated during not only peripherally, but also centrally, evoked swallowing. Experiments were carried out on 24 adult male Japanese white rabbits. JORs were evoked by trigeminal stimulation at 1 Hz for 30 sec. In the middle 10 sec, either the superior laryngeal nerve (SLN) or cortical swallowing area (Cx) was simultaneously stimulated to evoke swallowing. The peak-to-peak JOR amplitude was reduced during the middle and late 10-sec periods (i.e., during and after SLN or Cx stimulation), and the reduction was dependent on the current intensity of SLN/Cx stimulation: greater SLN/Cx stimulus current resulted in greater JOR inhibition. The reduction rate was significantly greater during Cx stimulation than during SLN stimulation. The amplitude returned to baseline 2 min after 10-sec SLN/Cx stimulation. The effect of co-stimulation of SLN and Cx was significantly greater than that of SLN stimulation alone. There were no significant differences in any parameters of the JCR between conditions. These results clearly showed that JOR responses were significantly suppressed, not only during peripherally evoked swallowing but also during centrally evoked swallowing, and that the inhibitory effect is likely to be larger during centrally compared with peripherally evoked swallowing. The functional implications of these results are discussed. Copyright © 2018. Published by Elsevier B.V.

Bruxism: Is There an Indication for Muscle-Stretching Exercises?

PubMed

Gouw, Simone; de Wijer, Anton; Creugers, Nico Hj; Kalaykova, Stanimira I

Bruxism is a common phenomenon involving repetitive activation of the masticatory muscles. Muscle-stretching exercises are a recommended part of several international guidelines for musculoskeletal disorders and may be effective in management of the jaw muscle activity that gives rise to bruxism. However, most studies of muscle-stretching exercises have mainly focused on their influence on performance (eg, range of motion, coordination, and muscle strength) of the limb or trunk muscles of healthy individuals or individuals with sports-related injuries. Very few have investigated stretching of the human masticatory muscles and none muscle-stretching exercises in the management of (sleep) bruxism. This article reviews the literature on muscle-stretching exercises and their potential role in the management of sleep bruxism or its consequences in the musculoskeletal system.

Interaction between descending input and thoracic reflexes for joint coordination in cockroach: I. descending influence on thoracic sensory reflexes.

PubMed

Mu, Laiyong; Ritzmann, Roy E

2008-03-01

Tethered cockroaches turn from unilateral antennal contact using asymmetrical movements of mesothoracic (T2) legs (Mu and Ritzmann in J Comp Physiol A 191:1037-1054, 2005). During the turn, the leg on the inside of the turn (the inside T2 leg) has distinctly different motor patterns from those in straight walking. One possible neural mechanism for the transformation from walking to inside leg turning could be that the descending commands alter a few critical reflexes that start a cascade of physical changes in leg movement or posture, leading to further alterations. This hypothesis has two implications: first, the descending activities must be able to influence thoracic reflexes. Second, one should be able to initiate the turning motor pattern without descending signals by mimicking a point farther down in the reflex cascade. We addressed the first implication in this paper by experiments on chordotonal organ reflexes. The activity of depressor muscle (Ds) and slow extensor tibia muscle (SETi) was excited and inhibited by stretching and relaxing the femoral chordotonal organ. However, the Ds responses were altered after eliminating the descending activity, while the SETi responses remain similar. The inhibition to Ds activity by stretching the coxal chordotonal organ was also altered after eliminating the descending activity.

Simultaneous characterizations of reflex and nonreflex dynamic and static changes in spastic hemiparesis

PubMed Central

Chung, Sun G.; Ren, Yupeng; Liu, Lin; Roth, Elliot J.; Rymer, W. Zev

2013-01-01

This study characterizes tonic and phasic stretch reflex and stiffness and viscosity changes associated with spastic hemiparesis. Perturbations were applied to the ankle of 27 hemiparetic and 36 healthy subjects under relaxed or active contracting conditions. A nonlinear delay differential equation model characterized phasic and tonic stretch reflex gains, elastic stiffness, and viscous damping. Tendon reflex was characterized with reflex gain and threshold. Reflexively, tonic reflex gain was increased in spastic ankles at rest (P < 0.038) and was not regulated with muscle contraction, indicating impaired tonic stretch reflex. Phasic-reflex gain in spastic plantar flexors was higher and increased faster with plantar flexor contraction (P < 0.012) than controls (P < 0.023) and higher in dorsi-flexors at lower torques (P < 0.038), primarily because of its increase at rest (P = 0.045), indicating exaggerated phasic stretch reflex especially in more spastic plantar flexors, which showed higher phasic stretch reflex gain than dorsi-flexors (P < 0.032). Spasticity was associated with increased tendon reflex gain (P = 0.002) and decreased threshold (P < 0.001). Mechanically, stiffness in spastic ankles was higher than that in controls across plantar flexion/dorsi-flexion torque levels (P < 0.032), and the more spastic plantar flexors were stiffer than dorsi-flexors at comparable torques (P < 0.031). Increased stiffness in spastic ankles was mainly due to passive stiffness increase (P < 0.001), indicating increased connective tissues/shortened fascicles. Viscous damping in spastic ankles was increased across the plantar flexion torque levels and at lower dorsi-flexion torques, reflecting increased passive viscous damping (P = 0.033). The more spastic plantar flexors showed higher viscous damping than dorsi-flexors at comparable torque levels (P < 0.047). Simultaneous characterizations of reflex and nonreflex changes in spastic hemiparesis may help to evaluate and treat

Stretch Reflex as a Simple Measure to Evaluate the Efficacy of Potential Flight Countermeasures Using the Bed Rest Environment

NASA Technical Reports Server (NTRS)

Cerisano, J. M.; Reschke, M. F.; Kofman, I. S.; Fisher, E. A.; Harm, D. L.

2010-01-01

INTRODUCTION: Spaceflight is acknowledged to have significant effects on the major postural muscles. However, it has been difficult to separate the effects of ascending somatosensory changes caused by the unloading of these muscles during flight from changes in sensorimotor function caused by a descending vestibulo-cerebellar response to microgravity. It is hypothesized that bed rest is an adequate model to investigate postural muscle unloading given that spaceflight and bed rest may produce similar results in both nerve axon and muscle tissue. METHODS: To investigate this hypothesis, stretch reflexes were measured on 18 subjects who spent 60 to 90 days in continuous 6 head-down bed rest. Using a motorized system capable of rotating the foot around the ankle joint (dorsiflexion) through an angle of 10 deg at a peak velocity of approximately 250 deg/sec, a stretch reflex was recorded from the subject's left triceps surae muscle group. Using surface electromyography, about 300 reflex responses were obtained and ensemble-averaged on 3 separate days before bed rest, 3 to 4 times in bed, and 3 times after bed rest. The averaged responses for each test day were examined for reflex latency and conduction velocity (CV) across gender and compared with spaceflight data. RESULTS: Although no gender differences were found, bed rest induced changes in reflex latency and CV similar to the ones observed during spaceflight. Also, a relationship between CV and loss of muscle strength in the lower leg was observed for most bed rest subjects. CONCLUSION: Even though bed rest (limb unloading) alone may not mimic all of the synaptic and muscle tissue loss that is observed as a result of spaceflight, it can serve as a working analog of flight for the evaluation of potential countermeasures that may be beneficial in mitigating unwanted changes in the major postural muscles that are observed post flight.

Anatomically remote muscle contraction facilitates patellar tendon reflex reinforcement while mental activity does not: a within-participants experimental trial.

PubMed

Passmore, Steven R; Bruno, Paul A

2012-09-07

The Jendrassik maneuver (JM) is a remote facilitation muscular contraction shown to affect amplitude and temporal components of the human stretch reflex. Conflicting theoretical models exist regarding the neurological mechanism related to its ability to reinforce reflex parameters. One mechanism involves the gamma motoneurons of the fusimotor system, which are subject to both physical and mental activity. A second mechanism describes reduced alpha motoneuron presynaptic inhibition, which is not subject to mental activity. In the current study, we determined if mental activity could be used to create a reflex facilitation comparable to a remote muscle contraction. Using a within-participants design, we investigated the relative effect of the JM and a successfully employed mental task (Stroop task) on the amplitude and temporal components of the patellar tendon reflex. We found that the addition of mental activity had no influence on the patellar tendon reflex parameters measured, while the JM provided facilitation (increased reflex amplitude, decreased total reflex time). The findings from this study support the view that the mechanism for the JM is a reduction in presynaptic inhibition of alpha motoneurons as it is influenced by physical and not mental activity.

Evidence from the use of vibration during procaine nerve block that the spindle group II fibres contribute excitation to the tonic stretch reflex of the decerebrate cat

PubMed Central

McGrath, G. J.; Matthews, P. B. C.

1973-01-01

1. Experiments have been performed to test the hypothesis that the group II fibres from the secondary endings of the muscle spindle provide an excitatory contribution to the tonic stretch reflex of the decerebrate cat. They have consisted of studying the effect of fusimotor paralysis by procaine, applied to the muscle nerve, on the reflex response to the combined stimuli of stretch (5-9 mm at 5 mm/sec) and of high-frequency vibration (100-150 Hz, 150 μm). 2. The reflex response to the combined stimuli was found to be paralysed in two distinct stages which paralleled those of the ordinary stretch reflex described earlier. The two phases of paralysis may be attributed to an early paralysis of the γ efferents followed by a later paralysis of the Ia afferents and α motor fibres. However, the Ia discharges elicited by the combined stimuli, unlike those elicited by simple stretch, should have remained unchanged on γ efferent paralysis since the Ia firing frequency may be presumed to have been clamped at the vibration frequency by the occurrence of one-to-one `driving'. The early reduction of the response to the combined stimuli may thus be attributed to the removal of a stretchevoked autogenetic excitatory input other than that long known to be provided by the Ia pathway. This supports the view that the spindle group II fibres have such an action, since their firing will be appropriately reduced on γ efferent paralysis by removal of their pre-existing fusimotor bias; there is no evidence for the existence of any other group of fibres with the right properties. 3. Recording of compound action potentials and of single units confirmed the great sensitivity of the γ efferents to procaine but showed that the group II fibres were nearly as resistant as the Ia fibres and α motor fibres. 4. The reliability of one-to-one driving of the Ia discharges by the vibration was tested in control experiments in which the reflex was elicited by an asymmetrical vibratory waveform

Muscle afferent potential (`A-wave') in the surface electromyogram of a phasic stretch reflex in normal humans

PubMed Central

Clarke, Alex. M.; Michie, Patricia T.; Glue, Leonard C. T.

1972-01-01

The experiments reported in this paper tested the hypothesis that the afferent potential elicited by a tendon tap in an isometrically recorded phasic stretch reflex can be detected in the surface EMG of normal humans when appropriate techniques are used. These techniques involved (1) training the subjects to relax mentally and physically so that the EMG was silent before and immediately after the diphasic MAP which reflects a highly synchronous discharge of afferent impulses from low threshold muscle stretch receptors after a tendon tap, and (2) using a data retrieval computer to summate stimulus-locked potentials in the EMG over a series of 16 samples using taps of uniform peak force and duration on the Achilles tendon to elicit the tendon jerk in the calf muscles. A discrete, diphasic potential (`A-wave') was recorded from EMG electrodes placed on the surface of the skin over the medial gastrocnemius muscle. The `A-wave' afferent potential had the opposite polarity to the corresponding efferent MAP. Under control conditions of relaxation the `A-wave' had a latency after the onset of the tap of 2 msec, the peak to peak amplitude was of the order of 5 μV and the duration was in the range of 6 to 10 msec. Further experiments were conducted to show that the `A-wave' (1) was not an artefact of the instrumentation used, (2) had a threshold at low intensities of stimulation, and (3) could be reliably augmented by using a Jendrassik manoeuvre compared with the potential observed during control (relaxation) conditions. The results support the conclusion that the `A-wave' emanates from the pool of muscle spindles which discharges impulses along group Ia nerve fibres in response to the phasic stretch stimulus because the primary ending of the spindles is known to initiate the stretch reflex and the spindles can be sensitized by fusimotor impulses so that their threshold is lowered as a result of a Jendrassik manoeuvre. The finding has important implications for the

Tonic vibration reflex in spasticity, Parkinson's disease, and normal subjects

PubMed Central

Burke, David; Andrews, Colin J.; Lance, James W.

1972-01-01

The tonic vibration reflex (TVR) has been studied in the quadriceps and triceps surae muscles of 34 spastic, 15 Parkinsonism, and 10 normal subjects. The TVR of spasticity develops rapidly, reaching a plateau level within 2-4 sec of the onset of vibration. The tonic contraction was often preceded by a phasic spike which appeared to be a vibration-induced equivalent of the tendon jerk. The initial phasic spike was usually followed by a silent period, and induced clonus in some patients. No correlation was found between the shape of the TVR and the site of the lesion in the central nervous system. The TVR of normal subjects and patients with Parkinsonism developed slowly, starting some seconds after the onset of vibration, and reaching a plateau level in 20-60 sec. A phasic spike was recorded occasionally in these subjects, but the subsequent tonic contraction followed the usual time course. Muscle stretch increased the quadriceps TVR of all subjects, including those with spasticity in whom the quadriceps stretch reflex decreased with increasing stretch. It is suggested that this difference between the tonic vibration reflex and the tonic stretch reflex arises from the selective activation of spindle primary endings by vibration, while both the primary and the secondary endings are responsive to muscle stretch. The TVR could be potentiated by reinforcement in some subjects. Potentiation outlasted the reinforcing manoeuvre, and was most apparent at short muscle lengths. As muscle stretch increased, thus producing a larger TVR, the degree of potentiation decreased. It is therefore suggested that the effects of reinforcement result at least partially from the activation of the fusimotor system. Since reinforcement potentiated the TVR of patients with spinal spasticity in whom a prominent clasp-knife phenomenon could be demonstrated, it is suggested that the effects of reinforcement are mediated by a descending pathway that traverses the anterior quadrant of the spinal

Soleus H-reflex gain in humans walking and running under simulated reduced gravity

PubMed Central

Ferris, Daniel P; Aagaard, Per; Simonsen, Erik B; Farley, Claire T; Dyhre-Poulsen, Poul

2001-01-01

The Hoffmann (H-) reflex is an electrical analogue of the monosynaptic stretch reflex, elicited by bypassing the muscle spindle and directly stimulating the afferent nerve. Studying H-reflex modulation provides insight into how the nervous system centrally modulates stretch reflex responses. A common measure of H-reflex gain is the slope of the relationship between H-reflex amplitude and EMG amplitude. To examine soleus H-reflex gain across a range of EMG levels during human locomotion, we used simulated reduced gravity to reduce muscle activity. We hypothesised that H-reflex gain would be independent of gravity level. We recorded EMG from eight subjects walking (1.25 m s−1) and running (3.0 m s−1) at four gravity levels (1.0, 0.75, 0.5 and 0.25 G (Earth gravity)). We normalised the stimulus M-wave and resulting H-reflex to the maximal M-wave amplitude (Mmax) elicited throughout the stride to correct for movement of stimulus and recording electrodes relative to nerve and muscle fibres. Peak soleus EMG amplitude decreased by ≈30% for walking and for running over the fourfold change in gravity. As hypothesised, slopes of linear regressions fitted to H-reflex versus EMG data were independent of gravity for walking and running (ANOVA, P > 0.8). The slopes were also independent of gait (P > 0.6), contrary to previous studies. Walking had a greater y-intercept (19.9%Mmax) than running (-2.5%Mmax; P < 0.001). At all levels of EMG, walking H-reflex amplitudes were higher than running H-reflex amplitudes by a constant amount. We conclude that the nervous system adjusts H-reflex threshold but not H-reflex gain between walking and running. These findings provide insight into potential neural mechanisms responsible for spinal modulation of the stretch reflex during human locomotion. PMID:11136869

Soleus H-reflex gain in humans walking and running under simulated reduced gravity

NASA Technical Reports Server (NTRS)

Ferris, D. P.; Aagaard, P.; Simonsen, E. B.; Farley, C. T.; Dyhre-Poulsen, P.

2001-01-01

The Hoffmann (H-) reflex is an electrical analogue of the monosynaptic stretch reflex, elicited by bypassing the muscle spindle and directly stimulating the afferent nerve. Studying H-reflex modulation provides insight into how the nervous system centrally modulates stretch reflex responses.A common measure of H-reflex gain is the slope of the relationship between H-reflex amplitude and EMG amplitude. To examine soleus H-reflex gain across a range of EMG levels during human locomotion, we used simulated reduced gravity to reduce muscle activity. We hypothesised that H-reflex gain would be independent of gravity level.We recorded EMG from eight subjects walking (1.25 m s-1) and running (3.0 m s-1) at four gravity levels (1.0, 0.75, 0.5 and 0.25 G (Earth gravity)). We normalised the stimulus M-wave and resulting H-reflex to the maximal M-wave amplitude (Mmax) elicited throughout the stride to correct for movement of stimulus and recording electrodes relative to nerve and muscle fibres. Peak soleus EMG amplitude decreased by 30% for walking and for running over the fourfold change in gravity. As hypothesised, slopes of linear regressions fitted to H-reflex versus EMG data were independent of gravity for walking and running (ANOVA, P > 0.8). The slopes were also independent of gait (P > 0.6), contrary to previous studies. Walking had a greater y-intercept (19.9% Mmax) than running (-2.5% Mmax; P < 0.001). At all levels of EMG, walking H-reflex amplitudes were higher than running H-reflex amplitudes by a constant amount. We conclude that the nervous system adjusts H-reflex threshold but not H-reflex gain between walking and running. These findings provide insight into potential neural mechanisms responsible for spinal modulation of the stretch reflex during human locomotion.

Disturbed jaw behavior in whiplash-associated disorders during rhythmic jaw movements.

PubMed

Häggman-Henrikson, B; Zafar, H; Eriksson, P-O

2002-11-01

As shown previously, "functional jaw movements" are the result of coordinated activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital, and cervical spine joints. In this study, the effect of neck trauma on natural jaw function was evaluated in 12 individuals suffering from whiplash-associated disorders (WAD). Spatiotemporal characteristics of mandibular and concomitant head movements were evaluated for three different modes of rhythmic jaw activities: self-paced continuous maximal jaw-opening/-closing movements, paced continuous maximal jaw-opening/-closing movements at 50 cycles/minute, and unilateral chewing. Compared with healthy subjects, the WAD group showed smaller magnitude and altered coordination pattern (a change in temporal relations) of mandibular and head movements. In conclusion, these results show that neck trauma can derange integrated jaw and neck behavior, and underline the functional coupling between the jaw and head-neck motor systems.

Jaw and Order

ERIC Educational Resources Information Center

Mooshammer, Christine; Hoole, Philip; Geumann, Anja

2007-01-01

It is well-accepted that the jaw plays an active role in influencing vowel height. The general aim of the current study is to further investigate the extent to which the jaw is active in producing consonantal distinctions, with specific focus on coronal consonants. Therefore, tongue tip and jaw positions are compared for the German coronal…

[Effect of preconditioning of thermopaste application at Shenque (CV 8) on stretch reflex induced by procedure for prolapse and hemorrhoids in patients with hemorrhoids].

PubMed

Li, Jun; Wen, Yong; Yue, Chao-Chi; Li, Ya-Ling

2013-08-01

To observe clinical effect, feasibility and security of preconditioning of thermopaste application at Shenque (CV 8) for relieving stretch reflex induced by procedure for prolapse and hemorrhoids (PPH). A total of 100 cases of mixed hemorrhoids (stage III and IV) patients were randomized into 1.0 h, 0.5 h, 0 h and control (no application) groups (n = 25 in each group) according to a random number table. Thermopaste was applied to Shenque (CV 8) 1.0 h and 0.5 h before PPH or conducted simultaneously with PPH. The mean arterial pressure, heart rate, blood oxygen saturation of patients before and after anastomose operation, and the incidence of adverse reactions within 24 hours after the procedure were monitored and recorded. The patient's pain degree was assessed by using visual analogue scale. After the preconditioning, of the 25 patients in the 0.5 h group (0.5 h G), 14 experienced marked improvement (in the stretch reflex during PPH), 10 had an improvement, and 1 was invalid, respectively. The markedly effective rate and the total effective rate were 56% and 96%, respectively. The therapeutic effects for inhibiting stretch reflect being from the better to the poorer were 0.5 h G > 1.0 h G > 0 h G >NG. The heart rate and blood pressure from more stable to lesser stable were 0.5 h G> 1.0 h G > 0 h G > NG. The patients' pain reaction during operation and their adverse effects of nausea, vomiting, abdominal distention and abdominal pain, etc. occurred during operation also presented the same tendency in the 4 groups. Thermopaste application to Shenque (CV 8) can effectively prevent and control visceral reflex in patients undergoing PPH, which effect is significantly better when conducted 0.5 hour before the operation.

Tissue engineering the mechanosensory circuit of the stretch reflex arc: sensory neuron innervation of intrafusal muscle fibers.

PubMed

Rumsey, John W; Das, Mainak; Bhalkikar, Abhijeet; Stancescu, Maria; Hickman, James J

2010-11-01

The sensory circuit of the stretch reflex arc, composed of specialized intrafusal muscle fibers and type Ia proprioceptive sensory neurons, converts mechanical information regarding muscle length and stretch to electrical action potentials and relays them to the central nervous system. Utilizing a non-biological substrate, surface patterning photolithography and a serum-free medium formulation a co-culture system was developed that facilitated functional interactions between intrafusal muscle fibers and sensory neurons. The presence of annulospiral wrappings (ASWs) and flower-spray endings (FSEs), both physiologically relevant morphologies in sensory neuron-intrafusal fiber interactions, were demonstrated and quantified using immunocytochemistry. Furthermore, two proposed components of the mammalian mechanosensory transduction system, BNaC1 and PICK1, were both identified at the ASWs and FSEs. To verify functionality of the mechanoreceptor elements the system was integrated with a MEMS cantilever device, and Ca(2+) currents were imaged along the length of an axon innervating an intrafusal fiber when stretched by cantilever deflection. This system provides a platform for examining the role of this mechanosensory complex in the pathology of myotonic and muscular dystrophies, peripheral neuropathy, and spasticity inducing diseases like Parkinson's. These studies will also assist in engineering fine motor control for prosthetic devices by improving our understanding of mechanosensitive feedback. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Trigeminal Proprioception Evoked by Strong Stretching of the Mechanoreceptors in Müller's Muscle Induces Reflex Contraction of the Orbital Orbicularis Oculi Slow-Twitch Muscle Fibers.

PubMed

Matsuo, Kiyoshi; Ban, Ryokuya; Ban, Midori; Yuzuriha, Shunsuke

2014-01-01

The mixed orbicularis oculi muscle lacks an intramuscular proprioceptive system such as muscle spindles, to induce reflex contraction of its slow-twitch fibers. We evaluated whether the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction of the slow-twitch fibers of the orbicularis oculi in addition to those of the levator and frontalis muscles. We evaluated in patients with aponeurosis-disinserted blepharoptosis whether strong stretching of the mechanoreceptors in Müller's muscle from upgaze with unilateral lid load induced reflex contraction of the orbicularis oculi slow-twitch fibers and whether anesthesia of Müller's muscle precluded the contraction. We compared the electromyographic responses of the bilateral orbicularis oculi muscles to unilateral intraoperative direct stimulation of the trigeminal proprioceptive nerve with those to unilateral transcutaneous electrical stimulation of the supraorbital nerve. Upgaze with a unilateral 3-g lid load induced reflex contraction of the bilateral orbicularis oculi muscles with ipsilateral dominance. Anesthesia of Müller's muscle precluded the reflex contraction. The orbicularis oculi reflex evoked by stimulation of the trigeminal proprioceptive nerve differed from that by electrical stimulation of the supraorbital nerve in terms of the intensity of current required to induce the reflex, the absence of R1, and duration. The mechanoreceptors in Müller's muscle functions as an extramuscular proprioceptive system to induce reflex contraction of the orbital orbicularis oculi slow-twitch fibers. Whereas reflex contraction of the pretarsal orbicularis fast-twitch fibers functions in spontaneous or reflex blinking, that of the orbital orbicularis oculi slow-twitch fibers may factor in grimacing and blepharospasm.

Trigeminal Proprioception Evoked by Strong Stretching of the Mechanoreceptors in Müller's Muscle Induces Reflex Contraction of the Orbital Orbicularis Oculi Slow-Twitch Muscle Fibers

PubMed Central

Ban, Ryokuya; Ban, Midori; Yuzuriha, Shunsuke

2014-01-01

Objective: The mixed orbicularis oculi muscle lacks an intramuscular proprioceptive system such as muscle spindles, to induce reflex contraction of its slow-twitch fibers. We evaluated whether the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction of the slow-twitch fibers of the orbicularis oculi in addition to those of the levator and frontalis muscles. Methods: We evaluated in patients with aponeurosis-disinserted blepharoptosis whether strong stretching of the mechanoreceptors in Müller's muscle from upgaze with unilateral lid load induced reflex contraction of the orbicularis oculi slow-twitch fibers and whether anesthesia of Müller's muscle precluded the contraction. We compared the electromyographic responses of the bilateral orbicularis oculi muscles to unilateral intraoperative direct stimulation of the trigeminal proprioceptive nerve with those to unilateral transcutaneous electrical stimulation of the supraorbital nerve. Results: Upgaze with a unilateral 3-g lid load induced reflex contraction of the bilateral orbicularis oculi muscles with ipsilateral dominance. Anesthesia of Müller's muscle precluded the reflex contraction. The orbicularis oculi reflex evoked by stimulation of the trigeminal proprioceptive nerve differed from that by electrical stimulation of the supraorbital nerve in terms of the intensity of current required to induce the reflex, the absence of R1, and duration. Conclusions: The mechanoreceptors in Müller's muscle functions as an extramuscular proprioceptive system to induce reflex contraction of the orbital orbicularis oculi slow-twitch fibers. Whereas reflex contraction of the pretarsal orbicularis fast-twitch fibers functions in spontaneous or reflex blinking, that of the orbital orbicularis oculi slow-twitch fibers may factor in grimacing and blepharospasm. PMID:25210572

Activation Dependence of Stretch Activation in Mouse Skinned Myocardium: Implications for Ventricular Function

PubMed Central

Stelzer, Julian E.; Larsson, Lars; Fitzsimons, Daniel P.; Moss, Richard L.

2006-01-01

Recent evidence suggests that ventricular ejection is partly powered by a delayed development of force, i.e., stretch activation, in regions of the ventricular wall due to stretch resulting from torsional twist of the ventricle around the apex-to-base axis. Given the potential importance of stretch activation in cardiac function, we characterized the stretch activation response and its Ca2+ dependence in murine skinned myocardium at 22°C in solutions of varying Ca2+ concentrations. Stretch activation was induced by suddenly imposing a stretch of 0.5–2.5% of initial length to the isometrically contracting muscle and then holding the muscle at the new length. The force response to stretch was multiphasic: force initially increased in proportion to the amount of stretch, reached a peak, and then declined to a minimum before redeveloping to a new steady level. This last phase of the response is the delayed force characteristic of myocardial stretch activation and is presumably due to increased attachment of cross-bridges as a consequence of stretch. The amplitude and rate of stretch activation varied with Ca2+ concentration and more specifically with the level of isometric force prior to the stretch. Since myocardial force is regulated both by Ca2+ binding to troponin-C and cross-bridge binding to thin filaments, we explored the role of cross-bridge binding in the stretch activation response using NEM-S1, a strong-binding, non-force–generating derivative of myosin subfragment 1. NEM-S1 treatment at submaximal Ca2+-activated isometric forces significantly accelerated the rate of the stretch activation response and reduced its amplitude. These data show that the rate and amplitude of myocardial stretch activation vary with the level of activation and that stretch activation involves cooperative binding of cross-bridges to the thin filament. Such a mechanism would contribute to increased systolic ejection in response to increased delivery of activator Ca2+ during

Avian reflex and electroencephalogram responses in different states of consciousness.

PubMed

Sandercock, Dale A; Auckburally, Adam; Flaherty, Derek; Sandilands, Victoria; McKeegan, Dorothy E F

2014-06-22

Defining states of clinical consciousness in animals is important in veterinary anaesthesia and in studies of euthanasia and welfare assessment at slaughter. The aim of this study was to validate readily observable reflex responses in relation to different conscious states, as confirmed by EEG analysis, in two species of birds under laboratory conditions (35-week-old layer hens (n=12) and 11-week-old turkeys (n=10)). We evaluated clinical reflexes and characterised electroencephalograph (EEG) activity (as a measure of brain function) using spectral analyses in four different clinical states of consciousness: conscious (fully awake), semi-conscious (sedated), unconscious-optimal (general anaesthesia), unconscious-sub optimal (deep hypnotic state), as well as assessment immediately following euthanasia. Jaw or neck muscle tone was the most reliable reflex measure distinguishing between conscious and unconscious states. Pupillary reflex was consistently observed until respiratory arrest. Nictitating membrane reflex persisted for a short time (<1 min) after respiratory arrest and brain death (isoelectric EEG). The results confirm that the nictitating membrane reflex is a conservative measure of death in poultry. Using spectral analyses of the EEG waveforms it was possible to readily distinguish between the different states of clinical consciousness. In all cases, when birds progressed from a conscious to unconscious state; total spectral power (PTOT) significantly increased, whereas median (F50) and spectral edge (F95) frequencies significantly decreased. This study demonstrates that EEG analysis can differentiate between clinical states (and loss of brain function at death) in birds and provides a unique integration of reflex responses and EEG activity. Copyright © 2014 Elsevier Inc. All rights reserved.

Supraspinal control of spinal reflex responses to body bending during different behaviours in lampreys

PubMed Central

Hsu, Li‐Ju; Zelenin, Pavel V.; Orlovsky, Grigori N.

2016-01-01

Key points Spinal reflexes are substantial components of the motor control system in all vertebrates and centrally driven reflex modifications are essential to many behaviours, but little is known about the neuronal mechanisms underlying these modifications.To study this issue, we took advantage of an in vitro brainstem–spinal cord preparation of the lamprey (a lower vertebrate), in which spinal reflex responses to spinal cord bending (caused by signals from spinal stretch receptor neurons) can be evoked during different types of fictive behaviour.Our results demonstrate that reflexes observed during fast forward swimming are reversed during escape behaviours, with the reflex reversal presumably caused by supraspinal commands transmitted by a population of reticulospinal neurons.NMDA receptors are involved in the formation of these commands, which are addressed primarily to the ipsilateral spinal networks.In the present study the neuronal mechanisms underlying reflex reversal have been characterized for the first time. Abstract Spinal reflexes can be modified during different motor behaviours. However, our knowledge about the neuronal mechanisms underlying these modifications in vertebrates is scarce. In the lamprey, a lower vertebrate, body bending causes activation of intraspinal stretch receptor neurons (SRNs) resulting in spinal reflexes: activation of motoneurons (MNs) with bending towards either the contralateral or ipsilateral side (a convex or concave response, respectively). The present study had two main aims: (i) to investigate how these spinal reflexes are modified during different motor behaviours, and (ii) to reveal reticulospinal neurons (RSNs) transmitting commands for the reflex modification. For this purpose in in vitro brainstem–spinal cord preparation, RSNs and reflex responses to bending were recorded during different fictive behaviours evoked by supraspinal commands. We found that during fast forward swimming MNs exhibited convex responses

STRETCH-DEPENDENT SENSITIZATION OF POST-JUNCTIONAL NEURAL EFFECTORS IN COLONIC MUSCLES

PubMed Central

Won, Kyung-Jong; Sanders, Kenton M.; Ward, Sean M.

2012-01-01

Background The colon undergoes distension-induced changes in motor activity as luminal contents or feces increases wall pressure. Input from enteric motor neurons regulates motility. Here we examined stretch-dependent responses in circular muscle strips of murine colon. Methods Length-ramps (6–31μm s−1) were applied in the axis of the circular muscle layer in a controlled manner until 5 mN isometric force was reached. Key Results Length-ramps produced transient membrane potential hyperpolarizations and attenuation of action potential (AP) complexes. Responses were reproducible when ramps were applied every 30s. Stretch-dependent hyperpolarization was blocked by TTX, suggesting AP-dependent release of inhibitory neurotransmitter(s). Atropine did not potentiate stretch-induced hyperpolarizations, but increased compliance of the circular layer. L-NNA inhibited stretch-dependent hyperpolarization and decreased muscle compliance, suggesting release of NO mediates stretch-dependent inhibition. Control membrane potential was restored by the NO donor SNP. Stretch-dependent hyperpolarizations were blocked by L-methionine, an inhibitor of stretch-dependent K+ (SDK) channels in colonic muscles. Loss of ICC, elicited by Kit neutralizing antibody, also inhibited responses to stretch. In presence of L-NNA and apamin, stretch responses became excitatory and were characterized by membrane depolarization and increased AP firing. A neurokinin-1 receptor antagonist inhibited this stretch-dependent increase in excitability. Conclusions & Inferences Our data show that stretch-dependent responses in colonic muscles require tonic firing of enteric inhibitory neurons, but reflex activation of neurons does not appear to be necessary. NO causes activation of SDK channels, and stretch of muscles further activates these channels, explaining the inhibitory response to stretch in colonic muscle strips. PMID:23279087

Short-term locomotor adaptation to a robotic ankle exoskeleton does not alter soleus Hoffmann reflex amplitude.

PubMed

Kao, Pei-Chun; Lewis, Cara L; Ferris, Daniel P

2010-07-26

To improve design of robotic lower limb exoskeletons for gait rehabilitation, it is critical to identify neural mechanisms that govern locomotor adaptation to robotic assistance. Previously, we demonstrated soleus muscle recruitment decreased by approximately 35% when walking with a pneumatically-powered ankle exoskeleton providing plantar flexor torque under soleus proportional myoelectric control. Since a substantial portion of soleus activation during walking results from the stretch reflex, increased reflex inhibition is one potential mechanism for reducing soleus recruitment when walking with exoskeleton assistance. This is clinically relevant because many neurologically impaired populations have hyperactive stretch reflexes and training to reduce the reflexes could lead to substantial improvements in their motor ability. The purpose of this study was to quantify soleus Hoffmann (H-) reflex responses during powered versus unpowered walking. We tested soleus H-reflex responses in neurologically intact subjects (n=8) that had trained walking with the soleus controlled robotic ankle exoskeleton. Soleus H-reflex was tested at the mid and late stance while subjects walked with the exoskeleton on the treadmill at 1.25 m/s, first without power (first unpowered), then with power (powered), and finally without power again (second unpowered). We also collected joint kinematics and electromyography. When the robotic plantar flexor torque was provided, subjects walked with lower soleus electromyographic (EMG) activation (27-48%) and had concomitant reductions in H-reflex amplitude (12-24%) compared to the first unpowered condition. The H-reflex amplitude in proportion to the background soleus EMG during powered walking was not significantly different from the two unpowered conditions. These findings suggest that the nervous system does not inhibit the soleus H-reflex in response to short-term adaption to exoskeleton assistance. Future studies should determine if the

Short-term locomotor adaptation to a robotic ankle exoskeleton does not alter soleus Hoffmann reflex amplitude

PubMed Central

2010-01-01

Background To improve design of robotic lower limb exoskeletons for gait rehabilitation, it is critical to identify neural mechanisms that govern locomotor adaptation to robotic assistance. Previously, we demonstrated soleus muscle recruitment decreased by ~35% when walking with a pneumatically-powered ankle exoskeleton providing plantar flexor torque under soleus proportional myoelectric control. Since a substantial portion of soleus activation during walking results from the stretch reflex, increased reflex inhibition is one potential mechanism for reducing soleus recruitment when walking with exoskeleton assistance. This is clinically relevant because many neurologically impaired populations have hyperactive stretch reflexes and training to reduce the reflexes could lead to substantial improvements in their motor ability. The purpose of this study was to quantify soleus Hoffmann (H-) reflex responses during powered versus unpowered walking. Methods We tested soleus H-reflex responses in neurologically intact subjects (n=8) that had trained walking with the soleus controlled robotic ankle exoskeleton. Soleus H-reflex was tested at the mid and late stance while subjects walked with the exoskeleton on the treadmill at 1.25 m/s, first without power (first unpowered), then with power (powered), and finally without power again (second unpowered). We also collected joint kinematics and electromyography. Results When the robotic plantar flexor torque was provided, subjects walked with lower soleus electromyographic (EMG) activation (27-48%) and had concomitant reductions in H-reflex amplitude (12-24%) compared to the first unpowered condition. The H-reflex amplitude in proportion to the background soleus EMG during powered walking was not significantly different from the two unpowered conditions. Conclusion These findings suggest that the nervous system does not inhibit the soleus H-reflex in response to short-term adaption to exoskeleton assistance. Future studies

Exercise leads to faster postural reflexes, improved balance and mobility, and fewer falls in older persons with chronic stroke.

PubMed

Marigold, Daniel S; Eng, Janice J; Dawson, Andrew S; Inglis, J Timothy; Harris, Jocelyn E; Gylfadóttir, Sif

2005-03-01

To determine the effect of two different community-based group exercise programs on functional balance, mobility, postural reflexes, and falls in older adults with chronic stroke. A randomized, clinical trial. Community center. Sixty-one community-dwelling older adults with chronic stroke. Participants were randomly assigned to an agility (n=30) or stretching/weight-shifting (n=31) exercise group. Both groups exercised three times a week for 10 weeks. Participants were assessed before, immediately after, and 1 month after the intervention for Berg Balance, Timed Up and Go, step reaction time, Activities-specific Balance Confidence, and Nottingham Health Profile. Testing of standing postural reflexes and induced falls evoked by a translating platform was also performed. In addition, falls in the community were tracked for 1 year from the start of the interventions. Although exercise led to improvements in all clinical outcome measures for both groups, the agility group demonstrated greater improvement in step reaction time and paretic rectus femoris postural reflex onset latency than the stretching/weight-shifting group. In addition, the agility group experienced fewer induced falls on the platform. Group exercise programs that include agility or stretching/weight shifting exercises improve postural reflexes, functional balance, and mobility and may lead to a reduction of falls in older adults with stroke.

Increased long-latency reflex activity as a sufficient explanation for childhood hypertonic dystonia: a neuromorphic emulation study

NASA Astrophysics Data System (ADS)

Sohn, Won J.; Niu, Chuanxin M.; Sanger, Terence D.

2015-06-01

Objective. Childhood dystonia is a movement disorder that interferes with daily movements and can have a devastating effect on quality of life for children and their families. Although injury to basal ganglia is associated with dystonia, the neurophysiological mechanisms leading to the clinical manifestations of dystonia are not understood. Previous work suggested that long-latency stretch reflex (LLSR) is hyperactive in children with hypertonia due to secondary dystonia. We hypothesize that abnormal activity in motor cortices may cause an increase in the LLSR leading to hypertonia. Approach. We modeled two possibilities of hyperactive LLSR by either creating a tonic involuntary drive to cortex, or increasing the synaptic gain in cortical neurons. Both models are emulated using programmable very-large-scale-integrated-circuit hardware to test their sufficiency for producing dystonic symptoms. The emulation includes a joint with two Hill-type muscles, realistic muscle spindles, and 2,304 Izhikevich-type spiking neurons. The muscles are regulated by a monosynaptic spinal pathway with 32 ms delay and a long-latency pathway with 64 ms loop-delay representing transcortical/supra-spinal connections. Main results. When the limb is passively stretched, both models produce involuntary resistance with increased antagonist EMG responses similar to human data; also the muscle relaxation is delayed similar to human data. Both models predict reduced range of motion in voluntary movements. Significance. Although our model is a highly simplified and limited representation of reflex pathways, it shows that increased activity of the LLSR is by itself sufficient to cause many of the features of hypertonic dystonia.

Influence of botulinum toxin on rabbit jaw muscle activity and anatomy.

PubMed

Korfage, J A M; Wang, Jeffrey; Lie, S H J T J; Langenbach, Geerling E J

2012-05-01

Muscles can adapt their fiber properties to accommodate to new conditions. We investigated the extent to which a decrease in muscle activation can cause an adaptation of fiber properties in synergistic and antagonistic jaw muscles. Three months after the injection of botulinum toxin type A in one masseter (anterior or posterior) muscle changes in fiber type composition and fiber cross-sectional areas in jaw muscles were studied at the microscopic level. The injected masseter showed a steep increase in myosin type IIX fibers, whereas fast fibers decreased by about 50% in size. Depending on the injection site, both synergistic and antagonistic muscles showed a significant increase in the size of their fast IIA fibers, sometimes combined with an increased number of IIX fibers. Silencing the activity in the masseter not only causes changes in the fibers of the injected muscle but also leads to changes in other jaw muscles. Copyright © 2012 Wiley Periodicals, Inc.

Noxious stimuli do not determine reflex cardiorespiratory effects in anesthetized rabbits.

PubMed

Raimondi, G; Legramante, J M; Iellamo, F; Frisardi, G; Cassarino, S; Peruzzi, G

1996-12-01

The main purpose of this study is to examine whether the stimulation of an exclusively pain-sensing receptive field (dental pulp) could determine cardiorespiratory effects in animals in which the cortical integration of the peripheral information is abolished by deep anesthesia. In 15 anesthetized (alpha-chloralose and urethan) rabbits, low (3-Hz)- and high-frequency (100-Hz) electrical dental pulp stimulation was performed. Because this stimulation caused dynamic and static reflex contractions of the digastric muscles leading to jaw opening jaw-opening reflex (JOR); an indirect sign of algoceptive fiber activation], experimentally induced direct dynamic and static contractions of the digastric muscle were also performed. The low- and high-frequency stimulation of the dental pulp determined cardiovascular [systolic arterial pressure (SAP): -21.7 +/- 4.6 and 10.8 +/- 4.7 mmHg, respectively] and respiratory [pulmonary ventilation (VE): 145.1 +/- 44.9 and 109.3 +/- 28.4 ml/min, respectively] reflex responses similar to those observed during experimentally induced dynamic (SAP: -17.5 +/- 4.2 mmHg; VE: 228.0 +/- 58.5 ml/min) and static (SAP: 5.8 +/- 1.5 mmHg; VE: 148.0 +/- 75.3 ml/min) muscular contractions. The elimination of digastric muscular contraction (JOR) obtained by muscular paralysis did away with the cardiovascular changes induced by dental pulp stimulation, the effectiveness of which in stimulating dental pulp receptors has been shown by recording trigeminal-evoked potentials in six additional rabbits. The main conclusion was that, in deeply anesthetized animals, an algesic stimulus is unable to determine cardiorespiratory effects, which appear to be exclusively linked to the stimulation of ergoreceptors induced by muscular contraction.

NASA/MSFC Large Stretch Press Study

NASA Technical Reports Server (NTRS)

Choate, M. W.; Nealson, W. P.; Jay, G. C.; Buss, W. D.

1985-01-01

The purpose of this study was to: A. assess and document the advantages/disadvantages of a government agency investment in a large stretch form press on the order of 5000 tons capacity (per jaw); B. develop a procurement specification for the press; and C. provide trade study data that will permit an optimum site location. Tasks were separated into four major elements: cost study, user survey, site selection, and press design/procurement specification.

Comparison of stretch reflex responses evoked during drop jumping in highly skilled atheles versus untrained subjects.

PubMed

Judge, L W; Burke, J R

2015-06-01

The purpose of the study was to describe changes in the excitability of the stretch reflex response (SRR) during different drop jumps as a function of training background and as an adaptation to a preseason sport-specific resistance training program. Twelve collegiate field event athletes (discus, hammer, javelin, shot put, and weight; 9 males and 3 females) and 12 college-aged control subjects performed the following three jumps: (1) countermovement jump (CMJ); (2) countermovement drop jump; and (3) bounce-drop jump (BDJ). Neuromechanical changes in the performance of drop jumps by athletes were measured during the sport-specific resistance training program. Pre-post testing of drop jump performance by control subjects was included for comparison. For each jump trial, ground reaction forces (GRF), electromyograms (EMG) and cinematographic data were collected. There were no training adaptations. However, jump heights were greater for the athletes than the controls among the different jumps with the jump heights for all subjects being less during the BDJ than CMJ and CDJ. In athletes only, there was a differential modulation of the SRR from the gastrocnemius muscle with different levels of background muscle activity for the CDJ and BDJ. There were changes in excitability of SRR from the gastrocnemius muscle as a function of training background. Interrelated neuromechanical mechanisms to include landing biomechanics, intrinsic musculotendinous tissue properties of the ankle, and centrally regulated motor commands may underlie the facilitation of the SRR from the gastrocnemius muscle in athletes as compared to controls.

Postural stability and the influence of concurrent muscle activation--Beneficial effects of jaw and fist clenching.

PubMed

Ringhof, Steffen; Leibold, Timo; Hellmann, Daniel; Stein, Thorsten

2015-10-01

Recent studies reported on the potential benefits of submaximum clenching of the jaw on human postural control in upright unperturbed stance. However, it remained unclear whether these effects might also be observed among active controls. The purpose of the present study, therefore, was to comparatively examine the influence of concurrent muscle activation in terms of submaximum clenching of the jaw and submaximum clenching of the fists on postural stability. Posturographic analyses were conducted with 17 healthy young adults on firm and foam surfaces while either clenching the jaw (JAW) or clenching the fists (FIST), whereas habitual standing served as the control condition (CON). Both submaximum tasks were performed at 25% maximum voluntary contraction, assessed, and visualized in real time by means of electromyography. Statistical analyses revealed that center of pressure (COP) displacements were significantly reduced during JAW and FIST, but with no differences between both concurrent clenching activities. Further, a significant increase in COP displacements was observed for the foam as compared to the firm condition. The results showed that concurrent muscle activation significantly improved postural stability compared with habitual standing, and thus emphasize the beneficial effects of jaw and fist clenching for static postural control. It is suggested that concurrent activities contribute to the facilitation of human motor excitability, finally increasing the neural drive to the distal muscles. Future studies should evaluate whether elderly or patients with compromised postural control might benefit from these physiological responses, e.g., in the form of a reduced risk of falling. Copyright © 2015 Elsevier B.V. All rights reserved.

Cutaneous inputs from the back abolish locomotor-like activity and reduce spastic-like activity in the adult cat following complete spinal cord injury

PubMed Central

Frigon, Alain; Thibaudier, Yann; Johnson, Michael D.; Heckman, C.J.; Hurteau, Marie-France

2012-01-01

Spasticity is a condition that can include increased muscle tone, clonus, spasms, and hyperreflexia. In this study, we report the effect of manually stimulating the dorsal lumbosacral skin on spontaneous locomotor-like activity and on a variety of reflex responses in 5 decerebrate chronic spinal cats treated with clonidine. Cats were spinalized 1 month before the terminal experiment. Stretch reflexes were evoked by stretching the left triceps surae muscles. Crossed reflexes were elicited by electrically stimulating the right tibial or superficial peroneal nerves. Windup of reflex responses was evoked by electrically stimulating the left tibial or superficial peroneal nerves. We found that pinching the skin of the back abolished spontaneous locomotor-like activity. We also found that back pinch abolished the rhythmic activity observed during reflex testing without eliminating the reflex responses. Some of the rhythmic episodes of activity observed during reflex testing were consistent with clonus with an oscillation frequency greater than 3 Hz. Pinching the skin of the back effectively abolished rhythmic activity occurring spontaneously or evoked during reflex testing, irrespective of oscillation frequency. The results are consistent with the hypothesis that locomotion and clonus are produced by common central pattern-generators. Stimulating the skin of the back could prove helpful in managing undesired rhythmic activity in spinal cord-injured humans. PMID:22487200

Operant conditioning of the soleus H-reflex does not induce long-term changes in the gastrocnemius H-reflexes and does not disturb normal locomotion in humans.

PubMed

Makihara, Yukiko; Segal, Richard L; Wolpaw, Jonathan R; Thompson, Aiko K

2014-09-15

In normal animals, operant conditioning of the spinal stretch reflex or the H-reflex has lesser effects on synergist muscle reflexes. In rats and people with incomplete spinal cord injury (SCI), soleus H-reflex operant conditioning can improve locomotion. We studied in normal humans the impact of soleus H-reflex down-conditioning on medial (MG) and lateral gastrocnemius (LG) H-reflexes and on locomotion. Subjects completed 6 baseline and 30 conditioning sessions. During conditioning trials, the subject was encouraged to decrease soleus H-reflex size with the aid of visual feedback. Every sixth session, MG and LG H-reflexes were measured. Locomotion was assessed before and after conditioning. In successfully conditioned subjects, the soleus H-reflex decreased 27.2%. This was the sum of within-session (task dependent) adaptation (13.2%) and across-session (long term) change (14%). The MG H-reflex decreased 14.5%, due mainly to task-dependent adaptation (13.4%). The LG H-reflex showed no task-dependent adaptation or long-term change. No consistent changes were detected across subjects in locomotor H-reflexes, EMG activity, joint angles, or step symmetry. Thus, in normal humans, soleus H-reflex down-conditioning does not induce long-term changes in MG/LG H-reflexes and does not change locomotion. In these subjects, task-dependent adaptation of the soleus H-reflex is greater than it is in people with SCI, whereas long-term change is less. This difference from results in people with SCI is consistent with the fact that long-term change is beneficial in people with SCI, since it improves locomotion. In contrast, in normal subjects, long-term change is not beneficial and may necessitate compensatory plasticity to preserve satisfactory locomotion. Copyright © 2014 the American Physiological Society.

Tremor in the tension developed isometrically by soleus during the tonic vibration reflex in the decerebrate cat.

PubMed Central

Cussons, P D; Matthews, P B; Muir, R B

1979-01-01

1. Irregularities in the development of tension during the tonic vibration reflex of the soleus muscle of the decerebrate cat have been analysed into their frequency components. The reflex was recorded isometrically and elicited by longitudinal vibration, normally at 150 Hz. The amplitude of vibration was set so as to elicit a maximal reflex response, suggesting 1:1 driving of the majority of the Ia afferents at the frequency of vibration. 2. The resulting power spectrum regularly showed a well marked tremor peak separated by a trough from any slow irregularities. The predominant frequency of this tremor varied from 4 to 11 Hz in different preparations, with a mean of 7.4 Hz; on average, frequencies within 1.7 Hz on either side contained over half the power of the predominant frequency. Altering the frequency of vibration did not alter the distribution of tremor frequencies. 3. The root mean square value of the tension irregularities, over the range 4-14 Hz, varied from 12 to 110 mN in different preparations (median value, 23 mN); this was superimposed on mean active reflex tensions varying from 2 to 10 N. 4. The 'tremor' due to a single motor unit was estimated from spectral analysis of tetanic contractions of the whole muscle and decreased with increasing frequency of activation. Comparison of the single unit values with the tremor seen during vibration in the same preparations showed that equivalent amounts of tremor to the latter could typically have been produced by the continued synchronous contraction of about five 'average' motor units firing at the predominant tremor frequency. 5. When a tonic stretch reflex was present its tremor frequencies did not differ consistently from those of the tonic vibration reflex. On average, the tremor was smaller for the stretch reflex than for the tonic vibration reflex; the difference was usually slight and might have been related to the stretch refex tension being smaller. 6. Evidence was obtained that the tremor was not

F response and H reflex analysis of physiological unity of gravity and antigravity muscles in man.

PubMed

García, H A; Fisher, M A

1977-01-01

Observational differences between reflex (H reflex) and antidromic (F response) activation of segmental motoneurons by a peripheral electrical stimulus are described. In contrast to H reflexes, the percentage of F responses found after a series of stimuli is directly related to the pick-up field of the recording electrode consistent with this response being due to the variable activation of a small fraction of the available motoneuron pool. Despite the differing physiological mechanisms, both F responses and H reflexes can be used to demonstrate similar relative "central excitatory states" for antigravity muscles (i.e. extensors in the lower extremity and flexors in the upper extremity) and their antagonist gravity muscles. H reflexes were elicited not only in their usual location in certain antigravity muscles but also in unusual locations by length/tension changes in agonist and antagonist groups as well as by passive stretch. The data argue for the physiological unity of similarly acting gravity and antigravity muscles as well as supporting a meaningful role of group II afferents in normal segmental motoneuron pool excitability.

Effects on Hamstring Muscle Extensibility, Muscle Activity, and Balance of Different Stretching Techniques

PubMed Central

Lim, Kyoung-Il; Nam, Hyung-Chun; Jung, Kyoung-Sim

2014-01-01

[Purpose] The purpose of this study was to investigate the effects of two different stretching techniques on range of motion (ROM), muscle activation, and balance. [Subjects] For the present study, 48 adults with hamstring muscle tightness were recruited and randomly divided into three groups: a static stretching group (n=16), a PNF stretching group (n=16), a control group (n=16). [Methods] Both of the stretching techniques were applied to the hamstring once. Active knee extension angle, muscle activation during maximum voluntary isometric contraction (MVC), and static balance were measured before and after the application of each stretching technique. [Results] Both the static stretching and the PNF stretching groups showed significant increases in knee extension angle compared to the control group. However, there were no significant differences in muscle activation or balance between the groups. [Conclusion] Static stretching and PNF stretching techniques improved ROM without decrease in muscle activation, but neither of them exerted statistically significant effects on balance. PMID:24648633

The medial olivocochlear reflex in children during active listening.

PubMed

Smith, Spencer B; Cone, Barbara

2015-08-01

To determine if active listening modulates the strength of the medial olivocochlear (MOC) reflex in children. Click-evoked otoacoustic emissions (CEOAEs) were recorded from the right ear in quiet and in four test conditions: one with contralateral broadband noise (BBN) only, and three with active listening tasks wherein attention was directed to speech embedded in contralateral BBN. Fifteen typically-developing children (ranging in age from 8 to14 years) with normal hearing. CEOAE levels were reduced in every condition with contralateral acoustic stimulus (CAS) when compared to preceding quiet conditions. There was an additional systematic decrease in CEOAE level with increased listening task difficulty, although this effect was very small. These CEOAE level differences were most apparent in the 8-18 ms region after click onset. Active listening may change the strength of the MOC reflex in children, although the effects reported here are very subtle. Further studies are needed to verify that task difficulty modulates the activity of the MOC reflex in children.

Evolution of Muscle Activity Patterns Driving Motions of the Jaw and Hyoid during Chewing in Gnathostomes

PubMed Central

Konow, Nicolai; Herrel, Anthony; Ross, Callum F.; Williams, Susan H.; German, Rebecca Z.; Sanford, Christopher P. J.; Gintof, Chris

2011-01-01

Although chewing has been suggested to be a basal gnathostome trait retained in most major vertebrate lineages, it has not been studied broadly and comparatively across vertebrates. To redress this imbalance, we recorded EMG from muscles powering anteroposterior movement of the hyoid, and dorsoventral movement of the mandibular jaw during chewing. We compared muscle activity patterns (MAP) during chewing in jawed vertebrate taxa belonging to unrelated groups of basal bony fishes and artiodactyl mammals. Our aim was to outline the evolution of coordination in MAP. Comparisons of activity in muscles of the jaw and hyoid that power chewing in closely related artiodactyls using cross-correlation analyses identified reorganizations of jaw and hyoid MAP between herbivores and omnivores. EMG data from basal bony fishes revealed a tighter coordination of jaw and hyoid MAP during chewing than seen in artiodactyls. Across this broad phylogenetic range, there have been major structural reorganizations, including a reduction of the bony hyoid suspension, which is robust in fishes, to the acquisition in a mammalian ancestor of a muscle sling suspending the hyoid. These changes appear to be reflected in a shift in chewing MAP that occurred in an unidentified anamniote stem-lineage. This shift matches observations that, when compared with fishes, the pattern of hyoid motion in tetrapods is reversed and also time-shifted relative to the pattern of jaw movement. PMID:21705368

A Discrete Electromechanical Model for Human Cardiac Tissue: Effects of Stretch-Activated Currents and Stretch Conditions on Restitution Properties and Spiral Wave Dynamics

PubMed Central

Weise, Louis D.; Panfilov, Alexander V.

2013-01-01

We introduce an electromechanical model for human cardiac tissue which couples a biophysical model of cardiac excitation (Tusscher, Noble, Noble, Panfilov, 2006) and tension development (adjusted Niederer, Hunter, Smith, 2006 model) with a discrete elastic mass-lattice model. The equations for the excitation processes are solved with a finite difference approach, and the equations of the mass-lattice model are solved using Verlet integration. This allows the coupled problem to be solved with high numerical resolution. Passive mechanical properties of the mass-lattice model are described by a generalized Hooke's law for finite deformations (Seth material). Active mechanical contraction is initiated by changes of the intracellular calcium concentration, which is a variable of the electrical model. Mechanical deformation feeds back on the electrophysiology via stretch-activated ion channels whose conductivity is controlled by the local stretch of the medium. We apply the model to study how stretch-activated currents affect the action potential shape, restitution properties, and dynamics of spiral waves, under constant stretch, and dynamic stretch caused by active mechanical contraction. We find that stretch conditions substantially affect these properties via stretch-activated currents. In constantly stretched medium, we observe a substantial decrease in conduction velocity, and an increase of action potential duration; whereas, with dynamic stretch, action potential duration is increased only slightly, and the conduction velocity restitution curve becomes biphasic. Moreover, in constantly stretched medium, we find an increase of the core size and period of a spiral wave, but no change in rotation dynamics; in contrast, in the dynamically stretching medium, we observe spiral drift. Our results may be important to understand how altered stretch conditions affect the heart's functioning. PMID:23527160

A discrete electromechanical model for human cardiac tissue: effects of stretch-activated currents and stretch conditions on restitution properties and spiral wave dynamics.

PubMed

Weise, Louis D; Panfilov, Alexander V

2013-01-01

We introduce an electromechanical model for human cardiac tissue which couples a biophysical model of cardiac excitation (Tusscher, Noble, Noble, Panfilov, 2006) and tension development (adjusted Niederer, Hunter, Smith, 2006 model) with a discrete elastic mass-lattice model. The equations for the excitation processes are solved with a finite difference approach, and the equations of the mass-lattice model are solved using Verlet integration. This allows the coupled problem to be solved with high numerical resolution. Passive mechanical properties of the mass-lattice model are described by a generalized Hooke's law for finite deformations (Seth material). Active mechanical contraction is initiated by changes of the intracellular calcium concentration, which is a variable of the electrical model. Mechanical deformation feeds back on the electrophysiology via stretch-activated ion channels whose conductivity is controlled by the local stretch of the medium. We apply the model to study how stretch-activated currents affect the action potential shape, restitution properties, and dynamics of spiral waves, under constant stretch, and dynamic stretch caused by active mechanical contraction. We find that stretch conditions substantially affect these properties via stretch-activated currents. In constantly stretched medium, we observe a substantial decrease in conduction velocity, and an increase of action potential duration; whereas, with dynamic stretch, action potential duration is increased only slightly, and the conduction velocity restitution curve becomes biphasic. Moreover, in constantly stretched medium, we find an increase of the core size and period of a spiral wave, but no change in rotation dynamics; in contrast, in the dynamically stretching medium, we observe spiral drift. Our results may be important to understand how altered stretch conditions affect the heart's functioning.

Vibration parameters affecting vibration-induced reflex muscle activity.

PubMed

Cidem, Muharrem; Karacan, Ilhan; Cakar, Halil Ibrahim; Cidem, Mehmet; Sebik, Oguz; Yilmaz, Gizem; Turker, Kemal Sitki; Karamehmetoglu, Safak Sahir

2017-03-01

To determine vibration parameters affecting the amplitude of the reflex activity of soleus muscle during low-amplitude whole-body vibration (WBV). This study was conducted on 19 participants. Vibration frequencies of 25, 30, 35, 40, 45, and 50 Hz were used. Surface electromyography, collision force between vibration platform and participant's heel measured using a force sensor, and acceleration measured using an accelerometer fixed to the vibration platform were simultaneously recorded. The collision force was the main independent predictor of electromyographic amplitude. The essential parameter of vibration affecting the amplitude of the reflex muscle activity is the collision force.

Evaluation of jaw and neck muscle activities while chewing using EMG-EMG transfer function and EMG-EMG coherence function analyses in healthy subjects.

PubMed

Ishii, Tomohiro; Narita, Noriyuki; Endo, Hiroshi

2016-06-01

This study aims to quantitatively clarify the physiological features in rhythmically coordinated jaw and neck muscle EMG activities while chewing gum using EMG-EMG transfer function and EMG-EMG coherence function analyses in 20 healthy subjects. The chewing side masseter muscle EMG signal was used as the reference signal, while the other jaw (non-chewing side masseter muscle, bilateral anterior temporal muscles, and bilateral anterior digastric muscles) and neck muscle (bilateral sternocleidomastoid muscles) EMG signals were used as the examined signals in EMG-EMG transfer function and EMG-EMG coherence function analyses. Chewing-related jaw and neck muscle activities were aggregated in the first peak of the power spectrum in rhythmic chewing. The gain in the peak frequency represented the power relationships between jaw and neck muscle activities during rhythmic chewing. The phase in the peak frequency represented the temporal relationships between the jaw and neck muscle activities, while the non-chewing side neck muscle presented a broad range of distributions across jaw closing and opening phases. Coherence in the peak frequency represented the synergistic features in bilateral jaw closing muscles and chewing side neck muscle activities. The coherence and phase in non-chewing side neck muscle activities exhibited a significant negative correlation. From above, the bilateral coordination between the jaw and neck muscle activities is estimated while chewing when the non-chewing side neck muscle is synchronously activated with the jaw closing muscles, while the unilateral coordination is estimated when the non-chewing side neck muscle is irregularly activated in the jaw opening phase. Thus, the occurrence of bilateral or unilateral coordinated features in the jaw and neck muscle activities may correspond to the phase characteristics in the non-chewing side neck muscle activities during rhythmical chewing. Considering these novel findings in healthy subjects, EMG

Simultaneous measurement of noise-activated middle-ear muscle reflex and stimulus frequency otoacoustic emissions.

PubMed

Goodman, Shawn S; Keefe, Douglas H

2006-06-01

Otoacoustic emissions serve as a noninvasive probe of the medial olivocochlear (MOC) reflex. Stimulus frequency otoacoustic emissions (SFOAEs) elicited by a low-level probe tone may be the optimal type of emission for studying MOC effects because at low levels, the probe itself does not elicit the MOC reflex [Guinan et al. (2003) J. Assoc. Res. Otolaryngol. 4:521]. Based on anatomical considerations, the MOC reflex activated by ipsilateral acoustic stimulation (mediated by the crossed olivocochlear bundle) is predicted to be stronger than the reflex to contralateral stimulation. Broadband noise is an effective activator of the MOC reflex; however, it is also an effective activator of the middle-ear muscle (MEM) reflex, which can make results difficult to interpret. The MEM reflex may be activated at lower levels than measured clinically, and most previous human studies have not explicitly included measurements to rule out MEM reflex contamination. The current study addressed these issues using a higher-frequency SFOAE probe tone to test for cochlear changes mediated by the MOC reflex, while simultaneously monitoring the MEM reflex using a low-frequency probe tone. Broadband notched noise was presented ipsilaterally at various levels to elicit probe-tone shifts. Measurements are reported for 15 normal-hearing subjects. With the higher-frequency probe near 1.5 kHz, only 20% of subjects showed shifts consistent with an MOC reflex in the absence of an MEM-induced shift. With the higher-frequency probe near 3.5 kHz, up to 40% of subjects showed shifts in the absence of an MEM-induced shift. However, these responses had longer time courses than expected for MOC-induced shifts, and may have been dominated by other cochlear processes, rather than MOC reflex. These results suggest caution in the interpretation of effects observed using ipsilaterally presented acoustic activators intended to excite the MOC reflex.

Reflex effects following selective stimulation of J receptors in the cat.

PubMed Central

Anand, A; Paintal, A S

1980-01-01

1. Experiments carried out on anaesthetized cats showed that increasing blood flow, through the lobes of a lung, by 133% (S.E. 33%) generated an average of 0.75 impulses/sec (S.E. 0.3) in ten almost silent J receptors. Equivalent activity was produced by injecting 12-18 micrograms phenyl diguanide/kg into the right atrium. Such activity caused marked reflex effects, i.e. apnoea, rapid shallow breathing and reduction in the knee jerk. 2. The reflex effects of J receptors were studied after blocking the activity from cardiac receptors by intrapericardial injections of xylocaine. This was necessary because left atrial injections of phenyl diguanide produced reflex respiratory effects and inhibition of the knee jerk. 3. Hypoxia, but not hypercapnia, attenuated the reflex effects of J receptors, apnoea being abolished if the Pa,O2 fell below 35 mmHg. This was a central effect as it occurred in spite of increased activity of J receptors following phenyl diguanide, and effects of hypoxia persisted after cutting both carotid nerves. 4. The only invariable reflex effect of J receptors was a reduction in the total number and the average frequency of phrenic impulses in each breath. The changes in inspiratory time (ti) and expiratory time (te) following apnoea were variable although most frequently both were reduced. In about half the observations the first effect before the apnoea was a reduction in ti, in the other half it was a reduction in te. It was concluded that an input from J receptors inhibits inspiratory and expiratory mechanisms directly. 5. In some cats apnoea and rapid shallow breathing produced by J receptors continued after interrupting their activity by vagotomy and this did not diminish the reduction in ti or te; in other cats it did. The reduction in te was at times quite independent of changes in ti, i.e. pulmonary stretch receptor activity. 6. It was concluded that J receptors must be stimulated during moderate exercise to levels that produce marked

Pulsatile equibiaxial stretch inhibits thrombin-induced RhoA and NF-{kappa}B activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haga, Jason H.; Kaunas, Roland; Radeff-Huang, Julie

2008-07-18

This study investigated interactions between the effects of mechanical stretch and thrombin on RhoA activation in rat aortic smooth muscle cells (RASMC). Equibiaxial, pulsatile stretch, or thrombin produced a significant increase in RhoA activation. Surprisingly, in combination, 30 min of stretch inhibited the ability of thrombin to activate RhoA. NO donors and 8-bromo-cGMP significantly inhibited thrombin-induced RhoA activation. Interestingly, the nitric oxide synthase (NOS) inhibitor L-NAME increased basal RhoA activity, suggesting that NOS activity exerts a tonic inhibition on RhoA. Stretching RASMC increases nitrite production, consistent with the idea that NO contributes to the inhibitory effects of stretch. Thrombin stimulatesmore » MAP kinase and NF-{kappa}B pathways through Rho and these responses were blocked by 8-bromo-cGMP or stretch and restored by L-NAME. These data suggest that stretch, acting through NO and cGMP, can prevent the ability of thrombin to stimulate Rho signaling pathways that contribute to pathophysiological proliferative and inflammatory responses.« less

The medial olivocochlear reflex in children during active listening

PubMed Central

Smith, Spencer B.; Cone, Barbara

2015-01-01

Objective To determine if active listening modulates the strength of the medial olivocochlear (MOC) reflex in children. Design Click-evoked otoacoustic emissions (CEOAEs) were recorded from the right ear in quiet and in four test conditions: one with contralateral broadband noise (BBN) only, and three with active listening tasks wherein attention was directed to speech embedded in contralateral BBN. Study sample Fifteen typically-developing children (ranging in age from 8 to 14 years) with normal hearing. Results CEOAE levels were reduced in every condition with contralateral acoustic stimulus (CAS) when compared to preceding quiet conditions. There was an additional systematic decrease in CEOAE level with increased listening task difficulty, although this effect was very small. These CEOAE level differences were most apparent in the 8–18 ms region after click onset. Conclusions Active listening may change the strength of the MOC reflex in children, although the effects reported here are very subtle. Further studies are needed to verify that task difficulty modulates the activity of the MOC reflex in children. PMID:25735203

Reticular reflex myoclonus: a physiological type of human post-hypoxic myoclonus.

PubMed Central

Hallett, M; Chadwick, D; Adam, J; Marsden, C D

1977-01-01

A patient with post-hypoxic myoclonus, sensitive to therapy with 5-hydroxytryptophan and clonazepam, was subjected to detailed electrophysiological investigation. Brief generalised jerks followed the critical stimulus of muscle stretch. The electroencephalogram showed generalised spikes that were associated with, but not time locked to, the myoclonus. The cranial nerve nuclei were activated upward. Analysis of the findings suggests that the mechanism of the myoclonus is hyperactivity of a reflex mediated in the reticular formation of the medulla oblongata. PMID:301926

Mechanisms of reflex bladder activation by pudendal afferents

PubMed Central

Woock, John P.; Yoo, Paul B.

2011-01-01

Activation of pudendal afferents can evoke bladder contraction or relaxation dependent on the frequency of stimulation, but the mechanisms of reflex bladder excitation evoked by pudendal afferent stimulation are unknown. The objective of this study was to determine the contributions of sympathetic and parasympathetic mechanisms to bladder contractions evoked by stimulation of the dorsal nerve of the penis (DNP) in α-chloralose anesthetized adult male cats. Bladder contractions were evoked by DNP stimulation only above a bladder volume threshold equal to 73 ± 12% of the distension-evoked reflex contraction volume threshold. Bilateral hypogastric nerve transection (to eliminate sympathetic innervation of the bladder) or administration of propranolol (a β-adrenergic antagonist) decreased the stimulation-evoked and distension-evoked volume thresholds by −25% to −39%. Neither hypogastric nerve transection nor propranolol affected contraction magnitude, and robust bladder contractions were still evoked by stimulation at volume thresholds below the distension-evoked volume threshold. As well, inhibition of distention-evoked reflex bladder contractions by 10 Hz stimulation of the DNP was preserved following bilateral hypogastric nerve transection. Administration of phentolamine (an α-adrenergic antagonist) increased stimulation-evoked and distension-evoked volume thresholds by 18%, but again, robust contractions were still evoked by stimulation at volumes below the distension-evoked threshold. These results indicate that sympathetic mechanisms contribute to establishing the volume dependence of reflex contractions but are not critical to the excitatory pudendal to bladder reflex. A strong correlation between the magnitude of stimulation-evoked bladder contractions and bladder volume supports that convergence of pelvic afferents and pudendal afferents is responsible for bladder excitation evoked by pudendal afferents. Further, abolition of stimulation-evoked bladder

Adenosine monophosphate-activated protein kinase activation and suppression of inflammatory response by cell stretching in rabbit synovial fibroblasts.

PubMed

Kunanusornchai, Wanlop; Muanprasat, Chatchai; Chatsudthipong, Varanuj

2016-12-01

Joint mobilization is known to be beneficial in osteoarthritis (OA) patients. This study aimed to investigate the effect of stretching on adenosine monophosphate-activated protein kinase (AMPK) activity and its role in modulating inflammation in rabbit synovial fibroblasts. Uniaxial stretching of isolated rabbit synovial fibroblasts for ten min was performed. Stretching-induced AMPK activation, its underlying mechanism, and its anti-inflammatory effect were investigated using Western blot. Static stretching at 20 % of initial length resulted in AMPK activation characterized by expression of phosphorylated AMPK and phosphorylated acetyl-Co A carboxylase. AMP-activated protein kinase phosphorylation peaked 1 h after stretching and declined toward resting activity. Using cell viability assays, static stretching did not appear to cause cellular damage. Activation of AMPK involves Ca 2+ influx via a mechanosensitive L-type Ca 2+ channel, which subsequently raises intracellular Ca 2+ and activates AMPK via Ca 2+ /calmodulin-dependent protein kinase kinase β (CaMKKβ). Interestingly, stretching suppressed TNFα-induced expression of COX-2, iNOS, and phosphorylated NF-κB. These effects were prevented by pretreatment with compound C, an AMPK inhibitor. These results suggest that mechanical stretching suppressed inflammatory responses in synovial fibroblasts via a L-type Ca 2+ -channel-CaMKKβ-AMPK-dependent pathway which may underlie joint mobilization's ability to alleviate OA symptoms.

The vestibulosympathetic reflex in humans: neural interactions between cardiovascular reflexes

NASA Technical Reports Server (NTRS)

Ray, Chester A.; Monahan, Kevin D.

2002-01-01

1. Over the past 5 years, there has been emerging evidence that the vestibular system regulates sympathetic nerve activity in humans. We have studied this issue in humans by using head-down rotation (HDR) in the prone position. 2. These studies have clearly demonstrated increases in muscle sympathetic nerve activity (MSNA) and calf vascular resistance during HDR. These responses are mediated by engagement of the otolith organs and not the semicircular canals. 3. However, differential activation of sympathetic nerve activity has been observed during HDR. Unlike MSNA, skin sympathetic nerve activity does not increase with HDR. 4. Examination of the vestibulosympathetic reflex with other cardiovascular reflexes (i.e. barorereflexes and skeletal muscle reflexes) has shown an additive interaction for MSNA. 5. The additive interaction between the baroreflexes and vestibulosympathetic reflex suggests that the vestibular system may assist in defending against orthostatic challenges in humans by elevating MSNA beyond that of the baroreflexes. 6. In addition, the further increase in MSNA via otolith stimulation during isometric handgrip, when arterial pressure is elevated markedly, indicates that the vestibulosympathetic reflex is a powerful activator of MSNA and may contribute to blood pressure and flow regulation during dynamic exercise. 7. Future studies will help evaluate the importance of the vestibulosympathetic reflex in clinical conditions associated with orthostatic hypotension.

Choice of biomaterials—Do soft occlusal splints influence jaw-muscle activity during sleep? A preliminary report

NASA Astrophysics Data System (ADS)

Arima, Taro; Takeuchi, Tamiyo; Tomonaga, Akio; Yachida, Wataru; Ohata, Noboru; Svensson, Peter

2012-12-01

AimThe choice of biomaterials for occlusal splints may significantly influence biological outcome. In dentistry, hard acrylic occlusal splints (OS) have been shown to have a temporary and inhibitory effect on jaw-muscle activity, such as tooth clenching and grinding during sleep, i.e., sleep bruxism (SB). Traditionally, this inhibitory effect has been explained by changes in the intraoral condition rather than the specific effects of changes in occlusion. The aim of this preliminary study was to investigate the effect of another type of occlusal surface, such as a soft-material OS in addition to a hard-type OS in terms of changes in jaw-muscle activity during sleep. Materials and methodsSeven healthy subjects (mean ± SD, six men and one woman: 28.9 ± 2.7 year old), participated in this study. A soft-material OS (ethylene vinyl acetate copolymer) was fabricated for each subject and the subjects used the OS for five continuous nights. The EMG activity during sleep was compared to baseline (no OS). Furthermore, the EMG activity during the use of a hard-type OS (Michigan-type OS, acrylic resin), and hard-type OS combined with contingent electrical stimulation (CES) was compared to baseline values. Each session was separated by at least two weeks (washout). Jaw-muscle activity during sleep was recorded with single-channel ambulatory devices (GrindCare, MedoTech, Herlev, Denmark) in all sessions for five nights. ResultsJaw-muscle activity during sleep was 46.6 ± 29.8 EMG events/hour at baseline and significantly decreased during the hard-type OS (17.4 ± 10.5, P = 0.007) and the hard-type OS + CES (10.8 ± 7.1, P = 0.002), but not soft-material OS (36.3 ± 24.5, P = 0.055). Interestingly, the soft-material OS (coefficient of variance = 98.6 ± 35.3%) was associated with greater night-to-night variations than baseline (39.0 ± 11.8%) and the hard-type OS + CES (53.3 ± 13.7%, P < 0.013). ConclusionThe present pilot study in small sample showed that a soft

Brain activity associated with memory and cognitive function during jaw-tapping movement in healthy subjects using functional magnetic resonance imaging.

PubMed

Cho, Seung-Yeon; Shin, Ae-Sook; Na, Byung-Jo; Jahng, Geon-Ho; Park, Seong-Uk; Jung, Woo-Sang; Moon, Sang-Kwan; Park, Jung-Mi

2013-06-01

To determine whether jaw-tapping movement, a classically described as an indication of personal well-being and mental health, stimulates the memory and the cognitive regions of the brain and is associated with improved brain performance. Twelve healthy right-handed female subjects completed the study. Each patient performed a jaw-tapping task and an n-back task during functional magnetic resonance imaging (fMRI). The subjects were trained to carry out the jaw-tapping movement at home twice a day for 4 weeks. The fMRI was repeated when they returned. During the first and second jaw-tapping session, both sides of precentral gyrus and the right middle frontal gyrus (BA 6) were activated. And during the second session of the jaw-tapping task, parts of frontal lobe and temporal lobe related to memory function were more activated. In addition, the total percent task accuracy in n-back task significantly increased after 4 weeks of jawtapping movement. After jaw-tapping training for 4 weeks, brain areas related to memory showed significantly increased blood oxygen level dependent signals. Jaw-tapping movement might be a useful exercise for stimulating the memory and cognitive regions of the brain.

Immediate effect of passive and active stretching on hamstrings flexibility: a single-blinded randomized control trial.

PubMed

Nishikawa, Yuichi; Aizawa, Junya; Kanemura, Naohiko; Takahashi, Tetsuya; Hosomi, Naohisa; Maruyama, Hirofumi; Kimura, Hiroaki; Matsumoto, Masayasu; Takayanagi, Kiyomi

2015-10-01

[Purpose] This study compared the efficacy of passive and active stretching techniques on hamstring flexibility. [Subjects] Fifty-four healthy young subjects were randomly assigned to one of three groups (2 treatment groups and 1 control group). [Methods] Subjects in the passive stretching group had their knees extended by an examiner while lying supine 90° of hip flexion. In the same position, subjects in the active stretching group extended their knees. The groups performed 3 sets of the assigned stretch, with each stretch held for 10 seconds at the point where tightness in the hamstring muscles was felt. Subjects in the control group did not perform stretching. Before and immediately after stretching, hamstring flexibility was assessed by a blinded assessor, using the active knee-extension test. [Results] After stretching, there was a significant improvement in the hamstring flexibilities of the active and passive stretching groups compared with the control group. Furthermore, the passive stretching group showed significantly greater improvement in hamstring flexibility than the active stretching group. [Conclusion] Improvement in hamstring flexibility measured by the active knee-extension test was achieved by both stretching techniques; however, passive stretching was more effective than active stretching at achieving an immediate increase in hamstring flexibility.

Relationships among nocturnal jaw muscle activities, decreased esophageal pH, and sleep positions.

PubMed

Miyawaki, Shouichi; Tanimoto, Yuko; Araki, Yoshiko; Katayama, Akira; Imai, Mikako; Takano-Yamamoto, Teruko

2004-11-01

The purpose of this study was to examine the relationships among nocturnal jaw muscle activities, decreased esophageal pH, and sleep positions. Twelve adult volunteers, including 4 bruxism patients, participated in this study. Portable pH monitoring, electromyography of the temporal muscle, and audio-video recordings were conducted during the night in the subjects' homes. Rhythmic masticatory muscle activity (RMMA) episodes were observed most frequently, with single short-burst episodes the second most frequent. The frequencies of RMMA, single short-burst, and clenching episodes were significantly higher during decreased esophageal pH episodes than those during other times. Both the electromyography and the decreased esophageal pH episodes were most frequently observed in the supine position. These results suggest that most jaw muscle activities, ie, RMMA, single short-burst, and clenching episodes, occur in relation to gastroesophageal reflux mainly in the supine position.

The Cerebellum in Maintenance of a Motor Skill: A Hierarchy of Brain and Spinal Cord Plasticity Underlies H-Reflex Conditioning

ERIC Educational Resources Information Center

Wolpaw, Jonathan R.; Chen, Xiang Yang

2006-01-01

Operant conditioning of the H-reflex, the electrical analog of the spinal stretch reflex, is a simple model of skill acquisition and involves plasticity in the spinal cord. Previous work showed that the cerebellum is essential for down-conditioning the H-reflex. This study asks whether the cerebellum is also essential for maintaining…

Reflexes in cat ankle muscles after landing from falls.

PubMed Central

Prochazka, A; Schofield, P; Westerman, R A; Ziccone, S P

1977-01-01

1. Electrical activity and length of ankle muscles were recorded by telemetry during free fall and landing in cats. 2. After foot contact, there was a delay in onset of stretch of ankle extensors of between 8 and 11 ms. High-speed cinematography showed the delay to be associated with rapid initial dorsiflexion of the toes. 3. Electromyograms (e.m.g.) from lateral gastrocnemius increased in amplitude prior to landing. An early depression of lateral gastrocnemius e.m.g. commenced at 8 ms after foot contact, and was followed by a large peak of activity commencing some 8 ms after the first increase in lateral gastrocnemius length. 4. Local anaesthesia of the plantar cushion did not alter this pattern of response. 5. The early inhibition of lateral gastrocnemius was attributed to the action on lateral gastrocnemius motoneurones of non-cutaneous afferents responding to the initial toe dorsiflexion. Additional autogenetic inhibition may also have contributed. 6. The subsequent peak of e.m.g. was at a latenty consistent with a rapid stretch reflex, and occurred soon enough for the resulting active tension to contribute significantly to the extensor force during body deceleration. PMID:592210

Development of an Intelligent Stretching Device for Ankle Joints With Contracture/Spasticity

DTIC Science & Technology

2001-10-25

percentage corresponded to background dorsi-flexion muscle contraction and 0% was the relaxed state. Next, tendon reflexes were evaluated...the representative cases, joint stiffness was reduced markedly after stretching across the range of muscle contraction (Fig. 5), including both

Pathophysiology of dysarthria in cerebral palsy.

PubMed Central

Neilson, P D; O'Dwyer, N J

1981-01-01

Electromyograms were recorded with hooked-wire electrodes from sixteen lip, tongue and jaw muscles in six normal and seven cerebral palsied adult subjects during a variety of speech and non-speech tasks. The recorded patterns of muscle activity fail to support a number of theories concerning the pathophysiology of dysarthria in cerebral palsy. There was no indication of weakness in individual articulator muscles. There was no evidence of uncontrolled sustained background activity or of abnormal tonic stretch reflex responses in lip or tongue muscles. Primitive or pathological reflexes could not be elicited by orofacial stimulation. No imbalance between positive and negative oral responses was observed. The view that random involuntary movement disrupts essentially normal voluntary control in athetosis was not supported. Each cerebral palsied subject displayed an idiosyncratic pattern of abnormal muscle activity which was reproduced across repetitions of the same phrase, indicating a consistent defect in motor programming. PMID:7334387

Stretch-induced ERK2 phosphorylation requires PLA2 activity in skeletal myotubes.

PubMed

Burkholder, Thomas J

2009-08-14

Mechanical stretch rapidly activates multiple signaling cascades, including phospholipases and kinases, to stimulate protein synthesis and growth. The purpose of this study was to determine whether PLA2 activation contributes to stretch-induced phosphorylation of ERK2 in skeletal muscle myotubes. Myotubes derived from neonatal C57 mice were cultured on silicone membranes and subjected to brief cyclic stretch. Inhibition of PLA2 prevented ERK2 phosphorylation, while inhibition of prostaglandin or leukotriene synthesis did not. ERK2 phosphorylation was also blocked by genistein and PD98059, implicating the canonical raf-MEK-ERK cassette. It appears that PLA2, but not further metabolism of arachidonic acid, is required for stretch-induced activation of ERK2. Exposure to exogenous arachidonic acid had no effect on ERK2 phosphorylation, but exposure to lysophosphatidylcholine, the other metabolite of PLA2, caused a dose-dependent increase in ERK2 phosphorylation. These results suggest that stretch-induced activation of ERK2 may result from an interaction between PLA2 derived lysophosphatidylcholine and membrane receptors.

Stretch-induced ERK2 phosphorylation requires PLA2 activity in skeletal myotubes

PubMed Central

Burkholder, Thomas J.

2009-01-01

Mechanical stretch rapidly activates multiple signaling cascades, including phospholipases and kinases, to stimulate protein synthesis and growth. The purpose of this study was to determine whether PLA2 activation contributes to stretch-induced phosphorylation of ERK2 in skeletal muscle myotubes. Myotubes derived from neonatal C57 mice were cultured on silicone membranes and subjected to brief cyclic stretch. Inhibition of PLA2 prevented ERK2 phosphorylation, while inhibition of prostaglandin or leukotriene synthesis did not. ERK2 phosphorylation was also blocked by genistein and PD98059, implicating the canonical raf-MEK-ERK cassette. It appears that PLA2, but not further metabolism of arachidonic acid, is required for stretch-induced activation of ERK2. Exposure to exogenous arachidonic acid had no effect on ERK2 phosphorylation, but exposure to lysophosphatidylcholine, the other metabolite of PLA2, caused a dose-dependent increase in ERK2 phosphorylation. These results suggest that stretch-induced activation of ERK2 may result from an interaction between PLA2 derived lysophosphatidylcholine and membrane receptors. PMID:19524551

Active shortening protects against stretch-induced force deficits in human skeletal muscle

PubMed Central

Saripalli, Anjali L.; Sugg, Kristoffer B.; Brooks, Susan V.

2017-01-01

Skeletal muscle contraction results from molecular interactions of myosin “crossbridges” with adjacent actin filament binding sites. The binding of myosin to actin can be “weak” or “strong,” and only strong binding states contribute to force production. During active shortening, the number of strongly bound crossbridges declines with increasing shortening velocity. Forcibly stretching a muscle that is actively shortening at high velocity results in no apparent negative consequences, whereas stretch of an isometrically (fixed-length) contracting muscle causes ultrastructural damage and a decline in force-generating capability. Our working hypothesis is that stretch-induced damage is uniquely attributable to the population of crossbridges that are strongly bound. We tested the hypothesis that stretch-induced force deficits decline as the prevailing shortening velocity is increased. Experiments were performed on permeabilized segments of individual skeletal muscle fibers obtained from human subjects. Fibers were maximally activated and allowed either to generate maximum isometric force (Fo), or to shorten at velocities that resulted in force maintenance of ≈50% Fo or ≈2% Fo. For each test condition, a rapid stretch equivalent to 0.1 × optimal fiber length was applied. Relative to prestretch Fo, force deficits resulting from stretches applied during force maintenance of 100, ≈50, and ≈2% Fo were 23.2 ± 8.6, 7.8 ± 4.2, and 0.3 ± 3.3%, respectively (means ± SD, n = 20). We conclude that stretch-induced damage declines with increasing shortening velocity, consistent with the working hypothesis that the fraction of strongly bound crossbridges is a causative factor in the susceptibility of skeletal muscle to stretch-induced damage. NEW & NOTEWORTHY Force deficits caused by stretch of contracting muscle are most severe when the stretch is applied during an isometric contraction, but prevented if the muscle is shortening at high velocity when the

Implementation of reflex loops in a biomechanical finite element model.

PubMed

Salin, Dorian; Arnoux, Pierre-Jean; Kayvantash, Kambiz; Behr, Michel

2016-11-01

In the field of biomechanics, the offer of models which are more and more realistic requires to integrate a physiological response, in particular, the controlled muscle bracing and the reflexes. The following work aims to suggest a unique methodology which couples together a sensory and motor loop with a finite element model. Our method is applied to the study of the oscillation of the elbow in the case of a biceps brachial stretch reflex. The results obtained are promising in the purpose of the development of reactive human body models.

Effect of afferent feedback and central motor commands on soleus H-reflex suppression during arm cycling.

PubMed

Hundza, S R; de Ruiter, Geoff C; Klimstra, M; Zehr, E Paul

2012-12-01

Suppression of soleus H-reflex amplitude in stationary legs is seen during rhythmic arm cycling. We examined the influence of various arm-cycling parameters on this interlimb reflex modulation to determine the origin of the effect. We previously showed the suppression to be graded with the frequency of arm cycling but not largely influenced by changes in peripheral input associated with crank length. Here, we more explicitly explored the contribution of afferent feedback related to arm movement on the soleus H-reflex suppression. We explored the influence of load and rate of muscle stretch by manipulating crank-load and arm-muscle vibration during arm cycling. Furthermore, internally driven ("Active") and externally driven ("Passive") arm cycling was compared. Soleus H-reflexes were evoked with tibial nerve stimulation during stationary control and rhythmic arm-cycling conditions, including: 1) six different loads; 2) with and without vibration to arm muscles; and 3) Active and Passive conditions. No significant differences were seen in the level of suppression between the different crank loads or between conditions with and without arm-muscle vibration. Furthermore, in contrast to the clear effect seen during active cycling, passive arm cycling did not significantly suppress the soleus H-reflex amplitude. Current results, in conjunction with previous findings, suggest that the afferent feedback examined in these studies is not the primary source responsible for soleus H-reflex suppression. Instead, it appears that central motor commands (supraspinal or spinal in origin) associated with frequency of arm cycling are relatively more dominant sources.

Dynamic exercise training prevents exercise pressor reflex overactivity in spontaneously hypertensive rats

PubMed Central

Iwamoto, Gary A.; Vongpatanasin, Wanpen; Mitchell, Jere H.; Smith, Scott A.

2015-01-01

Cardiovascular responses to exercise are exaggerated in hypertension. We previously demonstrated that this heightened cardiovascular response to exercise is mediated by an abnormal skeletal muscle exercise pressor reflex (EPR) with important contributions from its mechanically and chemically sensitive components. Exercise training attenuates exercise pressor reflex function in healthy subjects as well as in heart failure rats. However, whether exercise training has similar physiological benefits in hypertension remains to be elucidated. Thus we tested the hypothesis that the EPR overactivity manifest in hypertension is mitigated by exercise training. Changes in mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) in response to muscle contraction, passive muscle stretch, and hindlimb intra-arterial capsaicin administration were examined in untrained normotensive Wistar-Kyoto rats (WKYUT; n = 6), exercise-trained WKY (WKYET; n = 7), untrained spontaneously hypertensive rats (SHRUT; n = 8), and exercise-trained SHR (SHRET; n = 7). Baseline MAP after decerebration was significantly decreased by 3 mo of wheel running in SHRET (104 ± 9 mmHg) compared with SHRUT (125 ± 10 mmHg). As previously reported, the pressor and renal sympathetic responses to muscle contraction, stretch, and capsaicin administration were significantly higher in SHRUT than WKYUT. Exercise training significantly attenuated the enhanced contraction-induced elevations in MAP (SHRUT: 53 ± 11 mmHg; SHRET: 19 ± 3 mmHg) and RSNA (SHRUT: 145 ± 32%; SHRET: 57 ± 11%). Training produced similar attenuating effects in SHR during passive stretch and capsaicin administration. These data demonstrate that the abnormally exaggerated EPR function that develops in hypertensive rats is significantly diminished by exercise training. PMID:26163445

Passive stretch reduces calpain activity through nitric oxide pathway in unloaded soleus muscles.

PubMed

Xu, Peng-Tao; Li, Quan; Sheng, Juan-Juan; Chang, Hui; Song, Zhen; Yu, Zhi-Bin

2012-08-01

Unloading in spaceflight or long-term bed rest induces to pronounced atrophy of anti-gravity skeletal muscles. Passive stretch partially resists unloading-induced atrophy of skeletal muscle, but the mechanism remains elusive. The aims of this study were to investigate the hypotheses that stretch tension might increase protein level of neuronal nitric oxide synthase (nNOS) in unloaded skeletal muscle, and then nNOS-derived NO alleviated atrophy of skeletal muscle by inhibiting calpain activity. The tail-suspended rats were used to unload rat hindlimbs for 2 weeks, at the same time, left soleus muscle was stretched by applying a plaster cast to fix the ankle at 35° dorsiflexion. Stretch partially resisted atrophy and inhibited the decreased protein level and activity of nNOS in unloaded soleus muscles. Unloading increased frequency of calcium sparks and elevated intracellular resting and caffeine-induced Ca(2+) concentration ([Ca(2+)]i) in unloaded soleus muscle fibers. Stretch reduced frequency of calcium sparks and restored intracellular resting and caffeine-induced Ca(2+) concentration to control levels in unloaded soleus muscle fibers. The increased protein level and activity of calpain as well as the higher degradation of desmin induced by unloading were inhibited by stretch in soleus muscles. In conclusion, these results suggest that stretch can preserve the stability of sarcoplasmic reticulum Ca(2+) release channels which prevents the elevated [Ca(2+)]i by means of keeping nNOS activity, and then the enhanced protein level and activity of calpain return to control levels in unloaded soleus muscles. Therefore, stretch can resist in part atrophy of unloaded soleus muscles.

Active shortening protects against stretch-induced force deficits in human skeletal muscle.

PubMed

Saripalli, Anjali L; Sugg, Kristoffer B; Mendias, Christopher L; Brooks, Susan V; Claflin, Dennis R

2017-05-01

Skeletal muscle contraction results from molecular interactions of myosin "crossbridges" with adjacent actin filament binding sites. The binding of myosin to actin can be "weak" or "strong," and only strong binding states contribute to force production. During active shortening, the number of strongly bound crossbridges declines with increasing shortening velocity. Forcibly stretching a muscle that is actively shortening at high velocity results in no apparent negative consequences, whereas stretch of an isometrically (fixed-length) contracting muscle causes ultrastructural damage and a decline in force-generating capability. Our working hypothesis is that stretch-induced damage is uniquely attributable to the population of crossbridges that are strongly bound. We tested the hypothesis that stretch-induced force deficits decline as the prevailing shortening velocity is increased. Experiments were performed on permeabilized segments of individual skeletal muscle fibers obtained from human subjects. Fibers were maximally activated and allowed either to generate maximum isometric force (F o ), or to shorten at velocities that resulted in force maintenance of ≈50% F o or ≈2% F o For each test condition, a rapid stretch equivalent to 0.1 × optimal fiber length was applied. Relative to prestretch F o , force deficits resulting from stretches applied during force maintenance of 100, ≈50, and ≈2% F o were 23.2 ± 8.6, 7.8 ± 4.2, and 0.3 ± 3.3%, respectively (means ± SD, n = 20). We conclude that stretch-induced damage declines with increasing shortening velocity, consistent with the working hypothesis that the fraction of strongly bound crossbridges is a causative factor in the susceptibility of skeletal muscle to stretch-induced damage. NEW & NOTEWORTHY Force deficits caused by stretch of contracting muscle are most severe when the stretch is applied during an isometric contraction, but prevented if the muscle is shortening at high velocity when the stretch

Modulation of jaw muscle spindle afferent activity following intramuscular injections with hypertonic saline.

PubMed

Ro, J Y; Capra, N F

2001-05-01

Transient noxious chemical stimulation of small diameter muscle afferents modulates jaw movement-related responses of caudal brainstem neurons. While it is likely that the effect is mediated from the spindle afferents in the mesencephalic nucleus (Vmes) via the caudally projecting Probst's tract, the mechanisms of pain induced modulations of jaw muscle spindle afferents is not known. In the present study, we tested the hypothesis that jaw muscle nociceptors gain access to muscle spindle afferents in the same muscle via central mechanisms and alter their sensitivity. Thirty-five neurons recorded from the Vmes were characterized as muscle spindle afferents based on their responses to passive jaw movements, muscle palpation, and electrical stimulation of the masseter nerve. Each cell was tested by injecting a small volume (250 microl) of either 5% hypertonic and/or isotonic saline into the receptor-bearing muscle. Twenty-nine units were tested with 5% hypertonic saline, of which 79% (23/29) showed significant modulation of mean firing rates (MFRs) during one or more phases of ramp-and-hold movements. Among the muscle spindle primary-like units (n = 12), MFRs of 4 units were facilitated, five reduced, two showed mixed responses and one unchanged. In secondary-like units (n = 17), MFRs of 9 were facilitated, three reduced and five unchanged. Thirteen units were tested with isotonic saline, of which 77% showed no significant changes of MFRs. Further analysis revealed that the hypertonic saline not only affected the overall output of muscle spindle afferents, but also increased the variability of firing and altered the relationship between afferent signal and muscle length. These results demonstrated that activation of muscle nociceptors significantly affects proprioceptive properties of jaw muscle spindles via central neural mechanisms. The changes can have deleterious effects on oral motor function as well as kinesthetic sensibility.

Altered Neuromodulatory Drive May Contribute to Exaggerated Tonic Vibration Reflexes in Chronic Hemiparetic Stroke

PubMed Central

McPherson, Jacob G.; McPherson, Laura M.; Thompson, Christopher K.; Ellis, Michael D.; Heckman, Charles J.; Dewald, Julius P. A.

2018-01-01

Exaggerated stretch-sensitive reflexes are a common finding in elbow flexors of the contralesional arm in chronic hemiparetic stroke, particularly when muscles are not voluntarily activated prior to stretch. Previous investigations have suggested that this exaggeration could arise either from an abnormal tonic ionotropic drive to motoneuron pools innervating the paretic limbs, which could bring additional motor units near firing threshold, or from an increased influence of descending monoaminergic neuromodulatory pathways, which could depolarize motoneurons and amplify their responses to synaptic inputs. However, previous investigations have been unable to differentiate between these explanations, leaving the source(s) of this excitability increase unclear. Here, we used tonic vibration reflexes (TVRs) during voluntary muscle contractions of increasing magnitude to infer the sources of spinal motor excitability in individuals with chronic hemiparetic stroke. We show that when the paretic and non-paretic elbow flexors are preactivated to the same percentage of maximum prior to vibration, TVRs remain significantly elevated in the paretic arm. We also show that the rate of vibration-induced torque development increases as a function of increasing preactivation in the paretic limb, even though the amplitude of vibration-induced torque remains conspicuously unchanged as preactivation increases. It is highly unlikely that these findings could be explained by a source that is either purely ionotropic or purely neuromodulatory, because matching preactivation should control for the effects of a potential ionotropic drive (and lead to comparable tonic vibration reflex responses between limbs), while a purely monoaminergic mechanism would increase reflex magnitude as a function of preactivation. Thus, our results suggest that increased excitability of motor pools innervating the paretic limb post-stroke is likely to arise from both ionotropic and neuromodulatory mechanisms

Stretch-Induced Hypertrophy Activates NFkB-Mediated VEGF Secretion in Adult Cardiomyocytes

PubMed Central

Leychenko, Anna; Konorev, Eugene; Jijiwa, Mayumi; Matter, Michelle L.

2011-01-01

Hypertension and myocardial infarction are associated with the onset of hypertrophy. Hypertrophy is a compensatory response mechanism to increases in mechanical load due to pressure or volume overload. It is characterized by extracellular matrix remodeling and hypertrophic growth of adult cardiomyocytes. Production of Vascular Endothelial Growth Factor (VEGF), which acts as an angiogenic factor and a modulator of cardiomyocyte function, is regulated by mechanical stretch. Mechanical stretch promotes VEGF secretion in neonatal cardiomyocytes. Whether this effect is retained in adult cells and the molecular mechanism mediating stretch-induced VEGF secretion has not been elucidated. Our objective was to investigate whether cyclic mechanical stretch induces VEGF secretion in adult cardiomyocytes and to identify the molecular mechanism mediating VEGF secretion in these cells. Isolated primary adult rat cardiomyocytes (ARCMs) were subjected to cyclic mechanical stretch at an extension level of 10% at 30 cycles/min that induces hypertrophic responses. Cyclic mechanical stretch induced a 3-fold increase in VEGF secretion in ARCMs compared to non-stretch controls. This increase in stretch-induced VEGF secretion correlated with NFkB activation. Cyclic mechanical stretch-mediated VEGF secretion was blocked by an NFkB peptide inhibitor and expression of a dominant negative mutant IkBα, but not by inhibitors of the MAPK/ERK1/2 or PI3K pathways. Chromatin immunoprecipitation assays demonstrated an interaction of NFkB with the VEGF promoter in stretched primary cardiomyocytes. Moreover, VEGF secretion is increased in the stretched myocardium during pressure overload-induced hypertrophy. These findings are the first to demonstrate that NFkB activation plays a role in mediating VEGF secretion upon cyclic mechanical stretch in adult cardiomyocytes. Signaling by NFkB initiated in response to cyclic mechanical stretch may therefore coordinate the hypertrophic response in adult

Response of soleus Ia afferents to vibration in the presence of the tonic vibration reflex in the decerebrate cat.

PubMed

Clark, F J; Matthews, P B; Muir, R B

1981-02-01

1. Micro-electrode recordings were made from single Ia afferents in the intact nerve to the soleus muscle in the decerebrate cat while the muscle was developing a tonic vibration reflex. This was done in order to test how effectively the afferents were excited by the vibration, and to see if any insecurity in driving might be related to tremor.2. When the amplitude of vibration was 50 mum, and the tonic vibration reflex was reasonably well developed (> 1 N of active tension) all but one of forty-four Ia afferents were driven 1:1 by the vibration. Most were still driven by 30 mum vibration. The vibration, consisting of a train of discrete pulses at 150 Hz, was applied longitudinally in combination with a stretch of 1 mm to make the muscle taut.3. If the reflex was poorly developed (active tension < 1 N) the driving was on average less secure. However, fourteen of eighteen afferents then studied were still driven 1:1 by 50 mum vibration. The lower level of excitation by vibration was thought to be due to a deficiency of spontaneous fusimotor activity, because stroking the cat's tail or other similar gentle manipulation led each of the three misbehaving afferents so tested to be driven securely by 50 mum vibration; at the same time the reflex tension increased.4. Additional, indirect evidence favouring widespread security of Ia driving by 50 mum vibration in the presence of the reflex was obtained by modulating the amplitude of the 150 Hz vibration with a 7-10 Hz square wave and detecting any tension fluctuations at that frequency by spectral analysis. Small degrees of modulation (e.g. < 10%) produced little if any effect, although larger depths of modulation had a powerful action.5. When the amplitude of vibration was reduced to permit insecure driving but still to elicit a reflex response, the fluctuations in Ia firing pattern were unlike those previously seen in the de-efferented muscle. Spectral analysis showed that these firing fluctuations bore a general

Response of soleus Ia afferents to vibration in the presence of the tonic vibration reflex in the decerebrate cat

PubMed Central

Clark, F. J.; Matthews, P. B. C.; Muir, R. B.

1981-01-01

1. Micro-electrode recordings were made from single Ia afferents in the intact nerve to the soleus muscle in the decerebrate cat while the muscle was developing a tonic vibration reflex. This was done in order to test how effectively the afferents were excited by the vibration, and to see if any insecurity in driving might be related to tremor. 2. When the amplitude of vibration was 50 μm, and the tonic vibration reflex was reasonably well developed (> 1 N of active tension) all but one of forty-four Ia afferents were driven 1:1 by the vibration. Most were still driven by 30 μm vibration. The vibration, consisting of a train of discrete pulses at 150 Hz, was applied longitudinally in combination with a stretch of 1 mm to make the muscle taut. 3. If the reflex was poorly developed (active tension < 1 N) the driving was on average less secure. However, fourteen of eighteen afferents then studied were still driven 1:1 by 50 μm vibration. The lower level of excitation by vibration was thought to be due to a deficiency of spontaneous fusimotor activity, because stroking the cat's tail or other similar gentle manipulation led each of the three misbehaving afferents so tested to be driven securely by 50 μm vibration; at the same time the reflex tension increased. 4. Additional, indirect evidence favouring widespread security of Ia driving by 50 μm vibration in the presence of the reflex was obtained by modulating the amplitude of the 150 Hz vibration with a 7-10 Hz square wave and detecting any tension fluctuations at that frequency by spectral analysis. Small degrees of modulation (e.g. < 10%) produced little if any effect, although larger depths of modulation had a powerful action. 5. When the amplitude of vibration was reduced to permit insecure driving but still to elicit a reflex response, the fluctuations in Ia firing pattern were unlike those previously seen in the de-efferented muscle. Spectral analysis showed that these firing fluctuations bore a general

Jaw elevator silent periods in complete denture wearers and dentate individuals.

PubMed

Celebic, A; Valentic-Peruzovic, M; Alajbeg, I Z; Mehulic, K; Knezovic-Zlataric, D

2008-12-01

Functional meaning and underlying mechanisms of jaw elevator silent period (SP) have still not been completely understood. Since complete denture wearers (CDWs) have no periodontal receptors in their jaws, the aim was to examine SPs in CDWs and to compare it with dentate individuals (DIs). Thirty six DIs (skeletal/occlusal Class I) and 24 eugnath CDWs participated. EMG signals were registered using the EMGA-1 apparatus from the left and the right side anterior temporalis (ATM) and masseter muscles (MM). Ten registrations of an open-close-clench (OCC) cycle were obtained for each individual. DIs had the average latency between 12.5 and 12.9 ms and always one single short inhibitory pause (IP) with complete inhibition of motoneurons (20.1-21.1 ms). On the other hand, in CDWs various types of SPs emerged: single or single prolonged SPs, double SPs, SPs with three IPs, periods of depressed muscle activity following the first, or the second IP, SPs with relative inhibition of motoneurons or even in several registrations the SP was missing. Unless more than one IP emerged, complete duration of inhibitory pauses (CDIP) was measured. CDIP varied from 37.17 to 42.49 ms. Average latencies were from 16.22 to 16.76 ms. Based on the results of this study it is obvious that both, the duration and the latencies were significantly longer in CDWs than in DIs (p<0.05), which can be explained by different mechanisms responsible for the muscle reflex behaviour.

Effects of Jaw Clenching and Jaw Alignment Mouthpiece Use on Force Production During Vertical Jump and Isometric Clean Pull.

PubMed

Allen, Charles R; Fu, Yang-Chieh; Cazas-Moreno, Vanessa; Valliant, Melinda W; Gdovin, Jacob R; Williams, Charles C; Garner, John C

2018-01-01

Allen, CR, Fu, Y-C, Cazas-Moreno, V, Valliant, MW, Gdovin, JR, Williams, CC, and Garner, JC. Effects of jaw clenching and jaw alignment mouthpiece use on force production during vertical jump and isometric clean pull. J Strength Cond Res 32(1): 237-243, 2018-This study examined the effects of jaw clenching, a self-adapted, jaw-repositioning mouthpiece on force production during maximum countermovement vertical jump and maximum isometric midthigh clean pull assessments in an attempt to determine any ergogenic effect attributable to clenching, jaw-repositioning mouthpiece use, or the combination of both. Thirty-six male subjects performed vertical jump and isometric clean pull assessments from a force platform under various mouthpiece and clench conditions. A 3 × 2 (mouthpiece × clench) repeated-measures analysis of variance was conducted to analyze each of the following force production variables for both assessments: peak force, normalized peak force, and rate of force development. In addition, jump height was analyzed for the vertical jump. Results revealed improvements in peak force (F1,35 = 15.84, p ≤ 0.001, (Equation is included in full-text article.)= 0.31), normalized peak force (F1,35 = 16.28, p ≤ 0.001, (Equation is included in full-text article.)= 0.32), and rate of force development (F1,35 = 12.89, p = 0.001, (Equation is included in full-text article.)= 0.27) during the isometric clean pull assessment when participants maximally clenched their jaw, regardless of mouthpiece condition. There were no statistically significant differences in jump height, peak force, normalized peak force, or rate of force development during the vertical jump for any treatment condition. This study supports previous research demonstrating that the implementation of remote voluntary contractions such as jaw clenching can lead to concurrent activation potentiation and a resulting ergogenic effect during activities involving and requiring high-force production.

Mechanical stretch induces MMP-2 release and activation in lung endothelium: role of EMMPRIN.

PubMed

Haseneen, Nadia A; Vaday, Gayle G; Zucker, Stanley; Foda, Hussein D

2003-03-01

High-volume mechanical ventilation leads to ventilator-induced lung injury. This type of lung injury is accompanied by an increased release and activation of matrix metalloproteinases (MMPs). To investigate the mechanism leading to the increased MMP release, we systematically studied the effect of mechanical stretch on human microvascular endothelial cells isolated from the lung. We exposed cells grown on collagen 1 BioFlex plates to sinusoidal cyclic stretch at 0.5 Hz using the Flexercell system with 17-18% elongation of cells. After 4 days of cell stretching, conditioned media and cell lysate were collected and analyzed by gelatin, casein, and reverse zymograms as well as Western blotting. RT-PCR of mRNA extracted from stretched cells was performed. Our results show that 1) cyclic stretch led to increased release and activation of MMP-2 and MMP-1; 2) the activation of MMP-2 was accompanied by an increase in membrane type-1 MMP (MT1-MMP) and inhibited by a hydroxamic acid-derived inhibitor of MMPs (Prinomastat, AG3340); and 3) the MMP-2 release and activation were preceded by an increase in production of extracellular MMP inducer (EMMPRIN). These results suggest that cyclic mechanical stretch leads to MMP-2 activation through an MT1-MMP mechanism. EMMPRIN may play an important role in the release and activation of MMPs during lung injury.

Effect of acute stretch injury on action potential and network activity of rat neocortical neurons in culture.

PubMed

Magou, George C; Pfister, Bryan J; Berlin, Joshua R

2015-10-22

The basis for acute seizures following traumatic brain injury (TBI) remains unclear. Animal models of TBI have revealed acute hyperexcitablility in cortical neurons that could underlie seizure activity, but studying initiating events causing hyperexcitability is difficult in these models. In vitro models of stretch injury with cultured cortical neurons, a surrogate for TBI, allow facile investigation of cellular changes after injury but they have only demonstrated post-injury hypoexcitability. The goal of this study was to determine if neuronal hyperexcitability could be triggered by in vitro stretch injury. Controlled uniaxial stretch injury was delivered to a spatially delimited region of a spontaneously active network of cultured rat cortical neurons, yielding a region of stretch-injured neurons and adjacent regions of non-stretched neurons that did not directly experience stretch injury. Spontaneous electrical activity was measured in non-stretched and stretch-injured neurons, and in control neuronal networks not subjected to stretch injury. Non-stretched neurons in stretch-injured cultures displayed a three-fold increase in action potential firing rate and bursting activity 30-60 min post-injury. Stretch-injured neurons, however, displayed dramatically lower rates of action potential firing and bursting. These results demonstrate that acute hyperexcitability can be observed in non-stretched neurons located in regions adjacent to the site of stretch injury, consistent with reports that seizure activity can arise from regions surrounding the site of localized brain injury. Thus, this in vitro procedure for localized neuronal stretch injury may provide a model to study the earliest cellular changes in neuronal function associated with acute post-traumatic seizures. Copyright © 2015. Published by Elsevier B.V.

Deranged jaw-neck motor control in whiplash-associated disorders.

PubMed

Eriksson, Per-Olof; Zafar, Hamayun; Häggman-Henrikson, Birgitta

2004-02-01

Recent findings of simultaneous and well coordinated head-neck movements during single as well as rhythmic jaw opening-closing tasks has led to the conclusion that 'functional jaw movements' are the result of activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital and cervical spine joints. It can therefore be assumed that disease or injury to any of these joint systems would disturb natural jaw function. To test this hypothesis, amplitudes, temporal coordination, and spatiotemporal consistency of concomitant mandibular and head-neck movements during single maximal jaw opening-closing tasks were analysed in 25 individuals suffering from whiplash-associated disorders (WAD) using optoelectronic movement recording technique. In addition, the relative durations for which the head position was equal to, leading ahead of, or lagging behind the mandibular position during the entire jaw opening-closing cycle were determined. Compared with healthy individuals, the WAD group showed smaller amplitudes, and changed temporal coordination between mandibular and head-neck movements. No divergence from healthy individuals was found for the spatiotemporal consistency or for the analysis during the entire jaw opening-closing cycle. These findings in the WAD group of a 'faulty', but yet consistent, jaw-neck behavior may reflect a basic importance of linked control of the jaw and neck sensory-motor systems. In conclusion, the present results suggest that neck injury is associated with deranged control of mandibular and head-neck movements during jaw opening-closing tasks, and therefore might compromise natural jaw function.

Feedback-controlled and programmed stretching of the ankle plantarflexors and dorsiflexors in stroke: effects of a 4-week intervention program.

PubMed

Selles, Ruud W; Li, Xiaoyan; Lin, Fang; Chung, Sun G; Roth, Elliot J; Zhang, Li-Qun

2005-12-01

To investigate the effect of repeated feedback-controlled and programmed "intelligent" stretching of the ankle plantar- and dorsiflexors to treat subjects with ankle spasticity and/or contracture in stroke. Noncontrolled trial. Institutional research center. Subjects with spasticity and/or contracture after stroke. Stretching of the plantar- and dorsiflexors of the ankle 3 times a week for 45 minutes during a 4-week period by using a feedback-controlled and programmed stretching device. Passive and active range of motion (ROM), muscle strength, joint stiffness, joint viscous damping, reflex excitability, comfortable walking speed, and subjective experiences of the subjects. Significant improvements were found in the passive ROM, maximum voluntary contraction, ankle stiffness, and comfortable walking speed. The visual analog scales indicated very positive subjective evaluation in terms of the comfort of stretching and the effect on their involved ankle. Repeated feedback-controlled or intelligent stretching had a positive influence on the joint properties of the ankle with spasticity and/or contracture after stroke. The stretching device may be an effective and safe alternative to manual passive motion treatment by a therapist and has potential to be used to repeatedly and regularly stretch the ankle of subjects with spasticity and/or contracture without daily involvement of clinicians or physical therapists.

Quantitative evaluation of the stretch reflex before and after hydro kinesy therapy in patients affected by spastic paresis.

PubMed

Pagliaro, P; Zamparo, P

1999-04-01

The aim of this study was the quantitative evaluation of the myotatic reflex in a group of 26 patients affected by stationary spastic paresis (6: hemiparesis; 5: paraparesis; 8: tetraparesis; 7: multiple sclerosis) before and after a treatment of hydro-kinesy therapy. The treatment was carried out in an indoor pool containing warm (32 degrees C) sea water and consisted of active and passive motion exercises, coordination exercises and immersion walking. The measured parameters were: (i) the peak input force (FpH) measured by means of an instrumented hammer with which the patellar tendon was hit; and (ii) the peak value of the corresponding reflex force of the quadriceps femoris (FpQ) measured by means of a load cell connected to the subject's ankle. The peak values of the reflex response (FpQ) were found to increase as a function of the intensity of the imposed stimulus and to reach a plateau between 15 and 30 N of FpH. A Student's t test applied to the paired values of FpQ (as measured at plateau conditions) on both the lower limbs, before and after therapy, showed no significant changes due to the treatment in the four groups of subjects. However, if all subjects were grouped regardless the type of illness: 1) the average reflex response of the affected limb (the one characterized before therapy by the higher FpQ values) was found to decrease following the treatment (75.1+/-26.7 N pre therapy and 69.1+/-29.3 N post therapy, p = 0.07, n = 26); and 2) the effect of the treatment was found to be significantly larger (p = 0.04, n = 26) on the affected limb (delta FpQ = 6.07+/-16.5 N) as respect with the contra lateral one (delta FpQ = -0.16+/-12.1 N).

Mechanical stretch endows mesenchymal stem cells stronger angiogenic and anti-apoptotic capacities via NFκB activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Zhuoli; Gan, Xueqi; Fan, Hongyi

Mesenchymal stem cells (MSCs) have been broadly used for tissue regeneration and repair due to their broad differentiation potential and potent paracrine properties such as angiogenic capacity. Strategies to increase their survival rate after transplantation and the angiogenic ability are of priority for the utility of MSCs. In this study, we found that mechanical stretch (10% extension, 30 cycles/min cyclic stretch) preconditioning increase the angiogenic capacity via VEGFA induction. In addition, mechanical stretch also increases the survival rate of mesenchymal stem cells under nutrients deprivation. Consistent with the increase VEGFA expression and resistance to apoptosis, nuclear localization of NFκB activity p65more » increased upon mechanical stretch. Inhibition of NFκB activity by BAY 11-708 blocks the pro-angiogenesis and anti-apoptosis function of mechanical stretch. Taken together, our findings here raise the possibility that mechanical stretch preconditioning might enhance the therapeutic efficacy of mesenchymal stem cells. - Highlights: • Mechanical stretch increases the angiogenic capacity via VEGFA induction in MSCs. • Mechanical stretch increases the survival rate of MSCs under nutrients deprivation. • Mechanical stretch manipulates MSCs via the activation of NFκB.« less

Modeling and Identification of a Realistic Spiking Neural Network and Musculoskeletal Model of the Human Arm, and an Application to the Stretch Reflex.

PubMed

Sreenivasa, Manish; Ayusawa, Ko; Nakamura, Yoshihiko

2016-05-01

This study develops a multi-level neuromuscular model consisting of topological pools of spiking motor, sensory and interneurons controlling a bi-muscular model of the human arm. The spiking output of motor neuron pools were used to drive muscle actions and skeletal movement via neuromuscular junctions. Feedback information from muscle spindles were relayed via monosynaptic excitatory and disynaptic inhibitory connections, to simulate spinal afferent pathways. Subject-specific model parameters were identified from human experiments by using inverse dynamics computations and optimization methods. The identified neuromuscular model was used to simulate the biceps stretch reflex and the results were compared to an independent dataset. The proposed model was able to track the recorded data and produce dynamically consistent neural spiking patterns, muscle forces and movement kinematics under varying conditions of external forces and co-contraction levels. This additional layer of detail in neuromuscular models has important relevance to the research communities of rehabilitation and clinical movement analysis by providing a mathematical approach to studying neuromuscular pathology.

Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ostrow, Lyle W., E-mail: lostrow1@jhmi.edu; Suchyna, Thomas M.; Sachs, Frederick

2011-06-24

Highlights: {yields} Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. {yields} Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca{sup 2+} permeant SACs. {yields} The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. {yields} Stretch-induced ET-1 production depends on a calcium influx. {yields} SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia.more » We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (<20%) of a rubber substrate increased ET-1 secretion, and 4 {mu}M GsMTx-4 (a specific inhibitor of SACs) inhibited secretion by 30%. GsMTx-4 did not alter basal ET-1 levels in the absence of stretch. Decreasing the calcium influx by lowering extracellular calcium also inhibited stretch-induced ET-1 secretion without effecting ET-1 secretion in unstretched controls. Furthermore, inhibiting SACs with the less specific inhibitor streptomycin also inhibited stretch-induced ET-1 secretion. The data can be explained with a simple model in which ET-1 secretion depends on an internal Ca{sup 2+} threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.« less

Abnormal reflex activation of hamstring muscles in dogs with cranial cruciate ligament rupture.

PubMed

Hayes, Graham M; Granger, Nicolas; Langley-Hobbs, Sorrel J; Jeffery, Nick D

2013-06-01

The mechanisms underlying cranial cruciate ligament rupture (CCLR) in dogs are poorly understood. In this study hamstring muscle reflexes in response to cranial tibial translation were analysed to determine whether these active stabilisers of the stifle joint are differently activated in dogs with CCLR compared to control dogs. In a prospective clinical study reflex muscle activity from the lateral and medial hamstring muscles (biceps femoris and semimembranosus) was recorded using surface electrodes in control dogs (n=21) and dogs with CCLR (n=22). These electromyographic recordings were analysed using an algorithm previously validated in humans. The hamstring reflex was reliably and reproducibly recorded in normal dogs. Both a short latency response (SLR, 17.6±2.1ms) and a medium latency response (MLR, 37.7±2.7ms) could be identified. In dogs with unilateral CCLR, the SLR and MLR were not significantly different between the affected and the unaffected limbs, but the MLR latency of both affected and unaffected limbs in CCLR dogs were significantly prolonged compared to controls. In conclusion, the hamstring reflex can be recorded in dogs and the MLR is prolonged in dogs with CCLR. Since both affected and unaffected limbs exhibit prolonged MLR, it is possible that abnormal hamstring reflex activation is a mechanism by which progressive CCL damage may occur. The methodology allows for further investigation of the relationship between neuromuscular imbalance and CCLR or limitations in functional recovery following surgical intervention. Copyright © 2012 Elsevier Ltd. All rights reserved.

Jaw-phonatory coordination in chronic developmental stuttering.

PubMed

Loucks, Torrey M J; De Nil, Luc F; Sasisekaran, Jayanthi

2007-01-01

A deficiency in sensorimotor integration in a person who stutters may be a factor in the pathophysiology of developmental stuttering. To test oral sensorimotor function in adults who stutter, we used a task that requires the coordination of a jaw-opening movement with phonation onset. The task was adapted from previous limb coordination studies, which show that movement coordination depends on intact proprioception. We hypothesized that adult stutterers would show deficient jaw-phonatory coordination relative to control participants. The task required initiation of phonation as a jaw-opening movement passed through a narrow spatial target. Target amplitude and jaw movement speed were varied. The stuttering group showed significantly higher movement error and spatial variability in jaw-phonatory coordination compared to the control group, but group differences in movement velocity or duration were not found. The aberrant jaw-phonatory coordination of the stuttering participants suggests that stuttering is associated with an oral proprioceptive limitation, although, the findings are also consistent with a motor control deficit. As a result of this activity, reader will (1) learn about a hypothesis and evidence supporting the view that a sensorimotor deficit contributes to chronic developmental stuttering and (2) will obtain information about the role of proprioception in multi-articulatory coordination and how it can be tested using an oral-phonatory coordination task.

Functional Morphology of Eunicidan (Polychaeta) Jaws

NASA Astrophysics Data System (ADS)

Clemo, W. C.; Dorgan, K. M.

2016-02-01

Polychaetes exhibit diverse feeding strategies and diets, with some species possessing hardened teeth or jaws of varying complexity. Species in the order Eunicida have complex, rigidly articulated jaws consisting of multiple pairs of maxillae and a pair of mandibles. While all Eunicida possess this general jaw structure, a number of characteristics of the jaw parts vary considerably among families. These differences, described for fossilized and extant species' jaws, were used to infer evolutionary relationships, but current phylogeny shows that jaw structures that are similar among several families are convergent. Little has been done, however, to relate jaw functional morphology and feeding behavior to diet. To explore these relationships, we compared the jaw kinematics of two taxa with similar but evolutionarily convergent jaw structures: Diopatra (Onuphidae) and Lumbrineris (Lumbrineridae). Diopatra species are tube-dwelling and predominantly herbivorous, whereas Lumbrineris species are burrowing carnivores. Jaw kinematics were observed and analyzed by filming individuals biting or feeding and tracking tooth movements in videos. Differences in jaw structure and kinematics between Diopatra and Lumbrineris can be interpreted to be consistent with their differences in diet. Relating jaw morphology to diet would provide insight into early annelid communities by linking fossil teeth (scolecodonts) to the ecological roles of extant species with similar morphologies.

Corrective Jaw Surgery

MedlinePlus Videos and Cool Tools

... Jaw Surgery Download Download the ebook for further information Corrective jaw, or orthognathic surgery is performed by ... your treatment. Correction of Common Dentofacial Deformities ​ ​ The information provided here is not intended as a substitute ...

Effects of Static and Dynamic Stretching on the Isokinetic Peak Torques and Electromyographic Activities of the Antagonist Muscles

PubMed Central

Serefoglu, Abdullah; Sekir, Ufuk; Gür, Hakan; Akova, Bedrettin

2017-01-01

The aim of this study was to investigate if static and dynamic stretching exercises of the knee muscles (quadriceps and hamstring muscles) have any effects on concentric and eccentric isokinetic peak torques and electromyographic amplitudes (EMG) of the antagonist muscles. Twenty healthy male athletes (age between 18-30 years) voluntarily participated in this study. All of the subjects visited the laboratory to complete the following intervention in a randomized order on 5 separate days; (a) non-stretching (control), (b) static stretching of the quadriceps muscles, (c) static stretching of the hamstring muscles, (d) dynamic stretching of the quadriceps muscles, and (e) dynamic stretching of the hamstring muscles. Static stretching exercises either for the quadriceps or the hamstring muscles were carried out at the standing and sitting positions. Subjects performed four successive repetitions of each stretching exercises for 30 seconds in both stretching positions. Similar to static stretching exercises two different stretching modes were designed for dynamic stretching exercises. Concentric and eccentric isokinetic peak torque for the non-stretched antagonist quadriceps or hamstring muscles at angular velocities of 60°/sec and 240°/sec and their concurrent electromyographic (EMG) activities were measured before and immediately after the intervention. Isokinetic peak torques of the non-stretched agonist hamstring and quadriceps muscles did not represent any significant (p > 0.05) differences following static and dynamic stretching of the antagonist quadriceps and hamstring muscles, respectively. Similarly, the EMG activities of the agonist muscles exhibited no significant alterations (p > 0.05) following both stretching exercises of the antagonist muscles. According to the results of the present study it is possible to state that antagonist stretching exercises either in the static or dynamic modes do not affect the isokinetic peak torques and the EMG activities

Stretch-induced uterine myocyte differentiation during rat pregnancy: involvement of caspase activation.

PubMed

Shynlova, Oksana; Dorogin, Anna; Lye, Stephen J

2010-06-01

Proliferation, differentiation, and apoptosis are three major processes by which the pregnant uterus maintains homeostasis to accommodate the growing fetus. We demonstrated previously that caspase activation in the pregnant rat myometrium at midgestation coincides with the transition from uterine hyperplasia to hypertrophy. We hypothesized that this transition was induced by stasis of myometrial blood flow (and subsequent hypoxia/ischaemia insult) resulting from acute myometrial stretch induced by a growing embryo. Therefore, we measured the expression of active caspase 3 and two hypoxia markers (transcription factor HIF1A and pimonidazole hydrochloride) in pregnant rat myometrium. To investigate the effect of gravidity we used unilaterally pregnant rats. Caspase 3 was activated only in the gravid horn of the unilaterally pregnant animals on Gestational Days 12-15. This activation was associated with high levels of HIF1A and pimonidazole immunostaining, which were limited to the circular myometrial layer of the gravid horn, indicative of hypoxia within this tissue. To isolate the effect of myometrial stretch applied by the growing fetus, we inserted an expandable polymer tube (intra-uterine expandable tube [IUET]) into the empty horn of Day 13 and Day 20 unilaterally pregnant rats. Tissue was collected 2, 14, and 24 h later. In the IUET-stretched empty horn, cleaved caspase 3 was activated at midgestation (Day 14), but not at late gestation (Day 21). We speculate that hypoxia resulting from mechanical stretch may activate caspase 3 within the pregnant myometrium only in the context of a specific endocrine environment.

Interaction between vestibulosympathetic and skeletal muscle reflexes on sympathetic activity in humans

NASA Technical Reports Server (NTRS)

Ray, C. A.

2001-01-01

Evidence from animals indicates that skeletal muscle afferents activate the vestibular nuclei and that both vestibular and skeletal muscle afferents have inputs to the ventrolateral medulla. The purpose of the present study was to investigate the interaction between the vestibulosympathetic and skeletal muscle reflexes on muscle sympathetic nerve activity (MSNA) and arterial pressure in humans. MSNA, arterial pressure, and heart rate were measured in 17 healthy subjects in the prone position during three experimental trials. The three trials were 2 min of 1) head-down rotation (HDR) to engage the vestibulosympathetic reflex, 2) isometric handgrip (IHG) at 30% maximal voluntary contraction to activate skeletal muscle afferents, and 3) HDR and IHG performed simultaneously. The order of the three trials was randomized. HDR and IHG performed alone increased total MSNA by 46 +/- 16 and 77 +/- 24 units, respectively (P < 0.01). During the HDR plus IHG trial, MSNA increased 142 +/- 38 units (P < 0.01). This increase was not significantly different from the sum of the individual trials (130 +/- 41 units). This finding was also observed with mean arterial pressure (sum = 21 +/- 2 mmHg and HDR + IHG = 22 +/- 2 mmHg). These findings suggest that there is an additive interaction for MSNA and arterial pressure when the vestibulosympathetic and skeletal muscle reflexes are engaged simultaneously in humans. Therefore, no central modulation exists between these two reflexes with regard to MSNA output in humans.

Static vs. Dynamic Acute Stretching Effect on Quadriceps Muscle Activity during Soccer Instep Kicking

PubMed Central

Amiri-Khorasani, Mohammadtaghi; Kellis, Eleftherios

2013-01-01

The purpose of this study was to compare the effects of static and dynamic stretching on quadriceps muscle activation during maximal soccer instep kicking. The kicking motion of twelve male college soccer players (body height: 174.66 ± 5.01 cm; body mass: 72.83 ± 4.83 kg; age: 18.83 ± 0.75 years) was captured using six synchronized high-speed infra-red cameras whilst electromyography (EMG) signals from vastus medialis (VM), lateralis (VL) and rectus femoris (RF) were recorded before and after static or dynamic stretching. Analysis of variance designs showed a higher increase in knee extension angular velocity (9.65% vs. −1.45%, p < 0.001), RF (37.5% vs. −8.33%, p < 0.001), VM (12% vs. −12%, p < 0.018), and VL EMG activity (20% vs. −6.67%, p < 0.001) after dynamic stretching exercises. Based on these results, it could be suggested that dynamic stretching is probably more effective in increasing quadriceps muscle activity and knee extension angular velocity during the final swing phase of a maximal soccer instep kick than static stretching. PMID:24511339

Surgical desensitisation of the mechanoreceptors in Müller's muscle relieves chronic tension-type headache caused by tonic reflexive contraction of the occipitofrontalis muscle in patients with aponeurotic blepharoptosis.

PubMed

Matsuo, Kiyoshi; Ban, Ryokuya

2013-02-01

Proprioceptively innervated intramuscular connective tissues in Müller's muscle function as exterior mechanoreceptors to induce reflex contraction of the levator and occipitofrontalis muscles. In aponeurotic blepharoptosis, since the levator aponeurosis is disinserted from the tarsus, stretching of the mechanoreceptors in Müller's muscle is increased even on primary gaze to induce phasic and tonic reflexive contraction of the occipitofrontalis muscle. It was hypothesised that in certain patients with aponeurotic blepharoptosis, the presence of tonic reflexive contraction of the occipitofrontalis muscle due to the sensitised mechanoreceptors in Müller's muscle, can cause chronic tension-type headache (CTTH) associated with occipitofrontalis tenderness. To verify this hypothesis, this study evaluated (1) what differentiates patients with CTTH from patients without CTTH, (2) how pharmacological contraction of Müller's smooth muscle fibres as a method for desensitising the mechanoreceptors in Müller's muscle affects electromyographic activity of the frontalis muscle, and (3) how surgical aponeurotic reinsertion to desensitise the mechanoreceptors in Müller's muscle electromyographically or subjectively affects activities of the occipitofrontalis muscle or CTTH. It was found that patients had sustained CTTH when light eyelid closure did not markedly reduce eyebrow elevation. However, pharmacological contraction of Müller's smooth muscle fibres or surgery to desensitise the mechanoreceptor electromyographically reduced the tonic contraction of the occipitofrontalis muscle on primary gaze and subjectively relieved aponeurotic blepharoptosis-associated CTTH. Over-stretching of the mechanoreceptors in Müller's muscle on primary gaze may induce CTTH due to tonic reflexive contraction of the occipitofrontalis muscle. Therefore, surgical desensitisation of the mechanoreceptors in Müller's muscle appears to relieve CTTH.

Calcium and stretch activation modulate power generation in Drosophila flight muscle.

PubMed

Wang, Qian; Zhao, Cuiping; Swank, Douglas M

2011-11-02

Many animals regulate power generation for locomotion by varying the number of muscle fibers used for movement. However, insects with asynchronous flight muscles may regulate the power required for flight by varying the calcium concentration ([Ca(2+)]). In vivo myoplasmic calcium levels in Drosophila flight muscle have been found to vary twofold during flight and to correlate with aerodynamic power generation and wing beat frequency. This mechanism can only be possible if [Ca(2+)] also modulates the flight muscle power output and muscle kinetics to match the aerodynamic requirements. We found that the in vitro power produced by skinned Drosophila asynchronous flight muscle fibers increased with increasing [Ca(2+)]. Positive muscle power generation started at pCa = 5.8 and reached its maximum at pCa = 5.25. A twofold variation in [Ca(2+)] over the steepest portion of this curve resulted in a two- to threefold variation in power generation and a 1.2-fold variation in speed, matching the aerodynamic requirements. To determine the mechanism behind the variation in power, we analyzed the tension response to muscle fiber-lengthening steps at varying levels of [Ca(2+)]. Both calcium-activated and stretch-activated tensions increased with increasing [Ca(2+)]. However, calcium tension saturated at slightly lower [Ca(2+)] than stretch-activated tension, such that as [Ca(2+)] increased from pCa = 5.7 to pCa = 5.4 (the range likely used during flight), stretch- and calcium-activated tension contributed 80% and 20%, respectively, to the total tension increase. This suggests that the response of stretch activation to [Ca(2+)] is the main mechanism by which power is varied during flight. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Experimental muscle pain produces central modulation of proprioceptive signals arising from jaw muscle spindles.

PubMed

Capra, N F; Ro, J Y

2000-05-01

The aim of the present study was to investigate the effects of intramuscular injection with hypertonic saline, a well-established experimental model for muscle pain, on central processing of proprioceptive input from jaw muscle spindle afferents. Fifty-seven cells were recorded from the medial edge of the subnucleus interpolaris (Vi) and the adjacent parvicellular reticular formation from 11 adult cats. These cells were characterized as central units receiving jaw muscle spindle input based on their responses to electrical stimulation of the masseter nerve, muscle palpation and jaw stretch. Forty-five cells, which were successfully tested with 5% hypertonic saline, were categorized as either dynamic-static (DS) (n=25) or static (S) (n=20) neurons based on their responses to different speeds and amplitudes of jaw movement. Seventy-six percent of the cells tested with an ipsilateral injection of hypertonic saline showed a significant modulation of mean firing rates (MFRs) during opening and/or holding phases. The most remarkable saline-induced change was a significant reduction of MFR during the hold phase in S units (100%, 18/18 modulated). Sixty-nine percent of the DS units (11/16 modulated) also showed significant changes in MFRs limited to the hold phase. However, in the DS neurons, the MFRs increased in seven units and decreased in four units. Finally, five DS neurons showed significant changes of MFRs during both opening and holding phases. Injections of isotonic saline into the ipsilateral masseter muscle had little effect, but hypertonic saline injections made into the contralateral masseter muscle produced similar results to ipsilateral injections with hypertonic saline. These results unequivocally demonstrate that intramuscular injection with an algesic substance, sufficient to produce muscle pain, produces significant changes in the proprioceptive properties of the jaw movement-related neurons. Potential mechanisms involved in saline-induced changes in the

Self-aligning lathe chuck jaws

DOEpatents

Not Available

1980-08-26

A lathe chuck jaw for a lathe chuck having a radially moving actuator which radially moves the jaw into and out from the workpiece is described. A jaw base part is rigidly connected to the actuator. A jaw shoe part is rotatably attached to the base part. The shoe part has a workpiece-conforming surface which can hold the workpiece. The rotatable attachment of the shoe part allows it to match the general orientation of the workpiece, including a nonlongitudinal orientation due to a workpiece's imperfect shape.

Self-aligning lathe chuck jaws

DOEpatents

Peterson, William R.

1982-01-01

A lathe chuck jaw for a lathe chuck having a radially moving actuator which radially moves the jaw in to and out from the workpiece. A jaw base part is rigidly connected to the actuator. A jaw shoe part is rotatably attached to the base part. The shoe part has a workpiece-comforming surface which can hold the workpiece. The rotatable attachment of the shoe part allows it to match the general orientation of the workpiece, including a nonlongitudinal orientation due to a workpiece's imperfect shape.

Effects of Static and Dynamic Stretching on the Isokinetic Peak Torques and Electromyographic Activities of the Antagonist Muscles.

PubMed

Serefoglu, Abdullah; Sekir, Ufuk; Gür, Hakan; Akova, Bedrettin

2017-03-01

The aim of this study was to investigate if static and dynamic stretching exercises of the knee muscles (quadriceps and hamstring muscles) have any effects on concentric and eccentric isokinetic peak torques and electromyographic amplitudes (EMG) of the antagonist muscles. Twenty healthy male athletes (age between 18-30 years) voluntarily participated in this study. All of the subjects visited the laboratory to complete the following intervention in a randomized order on 5 separate days; (a) non-stretching (control), (b) static stretching of the quadriceps muscles, (c) static stretching of the hamstring muscles, (d) dynamic stretching of the quadriceps muscles, and (e) dynamic stretching of the hamstring muscles. Static stretching exercises either for the quadriceps or the hamstring muscles were carried out at the standing and sitting positions. Subjects performed four successive repetitions of each stretching exercises for 30 seconds in both stretching positions. Similar to static stretching exercises two different stretching modes were designed for dynamic stretching exercises. Concentric and eccentric isokinetic peak torque for the non-stretched antagonist quadriceps or hamstring muscles at angular velocities of 60°/sec and 240°/sec and their concurrent electromyographic (EMG) activities were measured before and immediately after the intervention. Isokinetic peak torques of the non-stretched agonist hamstring and quadriceps muscles did not represent any significant (p > 0.05) differences following static and dynamic stretching of the antagonist quadriceps and hamstring muscles, respectively. Similarly, the EMG activities of the agonist muscles exhibited no significant alterations (p > 0.05) following both stretching exercises of the antagonist muscles. According to the results of the present study it is possible to state that antagonist stretching exercises either in the static or dynamic modes do not affect the isokinetic peak torques and the EMG activities

Passive versus active stretching of hip flexor muscles in subjects with limited hip extension: a randomized clinical trial.

PubMed

Winters, Michael V; Blake, Charles G; Trost, Jennifer S; Marcello-Brinker, Toni B; Lowe, Lynne M; Garber, Matthew B; Wainner, Robert S

2004-09-01

Active stretching is purported to stretch the shortened muscle and simultaneously strengthen the antagonist muscle. The purpose of this study was to determine whether active and passive stretching results in a difference between groups at improving hip extension range of motion in patients with hip flexor muscle tightness. Thirty-three patients with low back pain and lower-extremity injuries who showed decreased range of motion, presumably due to hip flexor muscle tightness, completed the study. The subjects, who had a mean age of 23.6 years (SD = 5.3, range = 18-25), were randomly assigned to either an active home stretching group or a passive home stretching group. Hip extension range of motion was measured with the subjects in the modified Thomas test position at baseline and 3 and 6 weeks after the start of the study. Range of motion in both groups improved over time, but there were no differences between groups. The results indicate that passive and active stretching are equally effective for increasing range of motion, presumably due to increased flexibility of tight hip flexor muscles. Whether the 2 methods equally improve flexibility of other muscle groups or whether active stretching improves the function of the antagonist muscles is not known. Active and passive stretching both appeared to increase the flexibility of tight hip flexor muscles in patients with musculoskeletal impairments.

Proprioceptive reaction times and long-latency reflexes in humans.

PubMed

Manning, C D; Tolhurst, S A; Bawa, P

2012-08-01

The stretch of upper limb muscles results in two electromyographic (EMG) peaks, M1 and M2. The amplitude of M2 peak can generally be modified by giving prior instruction to the subject on how to react to the applied perturbation. The unresolved question is whether the amplitude modulation results from change in the gain of the reflex pathway contributing to M2, or by superposition of reaction time (RT) activity. The following study attempted to resolve this question by examining the overlap between proprioceptive RT and M2 activities. Subject's right wrist flexors were stretched, and he/she was instructed either (1) not to intervene (passive task) or (2) to react as fast as possible by simultaneously flexing both wrists (active or compensate task). Under passive and active conditions, M1 and M2 were observed from EMG of right wrist flexors, and during the active condition, RT activities were additionally observed from both sides. The onset and offset of M2 (M1(onset), M2(offset)) were measured from the passive averages, while the RT was measured from the averaged EMG response of the left wrist flexors. For between-subject correlations, the data were divided into two sets: (1) subjects with RT shorter than M2(offset) (fast group) and (2) subjects with RT more than 10 ms longer than their M2(offset) (slow group). Modulation during M2 period was large for the fast group, and it was almost zero for the slow group. These results indicate that the superimposition of RT activity mainly contributes to the instruction-dependent modulation of M2 peak.

Jaw tremor as a physiological biomarker of bruxism.

PubMed

Laine, C M; Yavuz, Ş U; D'Amico, J M; Gorassini, M A; Türker, K S; Farina, D

2015-09-01

To determine if sleep bruxism is associated with abnormal physiological tremor of the jaw during a visually-guided bite force control task. Healthy participants and patients with sleep bruxism were given visual feedback of their bite force and asked to trace triangular target trajectories (duration=20s, peak force <35% maximum voluntary force). Bite force control was quantified in terms of the power spectra of force fluctuations, masseter EMG activity, and force-to-EMG coherence. Patients had greater jaw force tremor at ∼8 Hz relative to controls, along with increased masseter EMG activity and force-to-EMG coherence in the same frequency range. Patients also showed lower force-to-EMG coherence at low frequencies (<3 Hz), but greater coherence at high frequencies (20-40 Hz). Finally, patients had greater 6-10 Hz force tremor during periods of descending vs. ascending force, while controls showed no difference in tremor with respect to force dynamics. Patients with bruxism have abnormal jaw tremor when engaged in a visually-guided bite force task. Measurement of jaw tremor may aid in the detection/evaluation of bruxism. In light of previous literature, our results also suggest that bruxism is marked by abnormal or mishandled peripheral feedback from the teeth. Copyright © 2015. Published by Elsevier Ireland Ltd.

Preparatory co-activation of the ankle muscles may prevent ankle inversion injuries

PubMed Central

DeMers, Matthew S.; Hicks, Jennifer L.; Delp, Scott L.

2018-01-01

Ankle inversion sprains are the most frequent acute musculoskeletal injuries occurring in physical activity. Interventions that retrain muscle coordination have helped rehabilitate injured ankles, but it is unclear which muscle coordination strategies, if any, can prevent ankle sprains. The purpose of this study was to determine whether coordinated activity of the ankle muscles could prevent excessive ankle inversion during a simulated landing on a 30-degree incline. We used a set of musculoskeletal simulations to evaluate the efficacy of two strategies for coordinating the ankle evertor and invertor muscles during simulated landing scenarios: planned co-activation and stretch reflex activation with physiologic latency (60-millisecond delay). A full-body musculoskeletal model of landing was used to generate simulations of a subject dropping onto an inclined surface with each coordination condition. Within each condition, the intensity of evertor and invertor co-activity or stretch reflexes were varied systematically. The simulations revealed that strong preparatory co-activation of the ankle evertors and invertors prior to ground contact prevented ankle inversion from exceeding injury thresholds by rapidly generating eversion moments after initial contact. Conversely, stretch reflexes were too slow to generate eversion moments before the simulations reached the threshold for inversion injury. These results suggest that training interventions to protect the ankle should focus on stiffening the ankle with muscle co-activation prior to landing. The musculoskeletal models, controllers, software, and simulation results are freely available online at http://simtk.org/home/ankle-sprains, enabling others to reproduce the results and explore new injury scenarios and interventions. PMID:28057351

Infant reflexes

MedlinePlus

... infants; Tonic neck reflex; Galant reflex; Truncal incurvation; Rooting reflex; Parachute reflex; Grasp reflex ... up if both hands are grasping your fingers. ROOTING REFLEX This reflex occurs when the baby's cheek ...

Successful treatment of open jaw and jaw deviation dystonia with botulinum toxin using a simple intraoral approach.

PubMed

Moscovich, Mariana; Chen, Zhongxing Peng; Rodriguez, Ramon

2015-03-01

Oromandibular dystonia (OMD) is a focal dystonia that involves the mouth, jaw, and/or tongue. It can be classified as idiopathic, tardive dystonia or secondary to other neurological disorders and subdivided into jaw opening, jaw closing, jaw deviation and lip pursing. The muscles involved in jaw opening dystonia are usually the digastrics and lateral pterygoids. It is known that the lateral pterygoids may be approached both internally and externally. The external approach is the most common; however neurologists experienced in treating patients with botulinum toxin can safely and with no extra cost perform the intraoral procedure. We report our experience in the treatment of jaw opening and jaw deviation dystonia using the intraoral injection approach. Eight patients were selected from the University of Florida with a clinical diagnosis of open jaw/jaw deviation dystonia. All of them were injected with onabotulinum toxin A using the internal approach and the clinical global impression scale was applied. The mean age of the patients was 67 (standard deviation [SD] 10.2) years, with a disease duration of 10.2 (SD 7.7) years and the mean distance they traveled to our institution was 448 km (278 miles). After treatment, six patients scored as very much improved in the clinical global impression scale and two patients scored as much improved. Only one patient reported an adverse event of nasal speech following one of the injections that improved after 4 weeks. Botulinum toxin injections for open jaw/jaw deviation dystonia can be safely performed with the intraoral approach without the need of special devices other than electromyography. Copyright © 2014 Elsevier Ltd. All rights reserved.

A novel approach using tendon vibration of the human flexor carpi radialis muscle to study spinal reflexes.

PubMed

Tsang, Kenneth; de Bruin, Hubert; Archambeault, Mark

2008-01-01

Although most muscle spindle investigations have used the cat model and invasive measurement techniques, several investigators have used microneurography to record from the Ia and II fibres in humans during tendon vibration. In these studies the muscle spindle primary endings are stimulated using transverse vibration of the tendon at reflex sub-threshold amplitudes. Others have used low amplitude vibration and the stretch evoked M-wave response to determine reflex properties during both agonist and antagonist voluntary contractions. In the past we have developed a PC based instrument that uses Labview and a linear servomotor to study tendon reflex properties by recording stretch evoked M-wave responses from single tendon taps or electrical stimuli to the afferent nerve. In this paper we describe a further development of this system to provide precise vibrations of the tendon up to 65 Hz with amplitudes up to 4 mm. The resultant M-wave train is extracted from background noise via phase coherent subtractive filtering. Test results from vibrating the human distal flexor carpi radialis tendon at 10 and 30 Hz, for relaxed, slight flexion and slight extension, are also presented.

[Jaws of amphibians and reptiles].

PubMed

Tanimoto, Masahiro

2005-04-01

Big jaws of amphibians and reptiles are mainly treated in this article. In amphibians enlarged skulls are for the big jaw in contrast with human's skulls for the brain. For example, famous fossils of Homo diluvii testis are ones of salamanders in fact. In reptiles, mosasaur jaws and teeth and their ecology are introduced for instance.

Role of positive urethrovesical feedback in vesical evacuation. The concept of a second micturition reflex: the urethrovesical reflex.

PubMed

Shafik, Ahmed; Shafik, Ali A; El-Sibai, Olfat; Ahmed, Ismail

2003-08-01

Upon feeling the urge to urinate, the urinary bladder contracts, the urethral sphincters relax and urine flows through the urethra. These actions are mediated by the micturition reflex. We investigated the hypothesis that vesical contraction is maintained by positive feedback through continuous flow of urine through the urethra, and that the cessation of urine flow aborts detrusor contraction. Normal saline was infused into the urinary bladders of 17 healthy volunteers (age 35.2 years+/-4.2(SD); ten women and seven men) at a rate of 100 ml/min. On urge, which occurred at a mean volume of 408.6 ml+/-28.7 of saline, the subject micturated while the vesical and urethral pressures during voiding were being recorded; residual urine was measured. The test was repeated after anesthetizing the urethra with xylocaine gel or, on another occasion, after applying a bland gel. On micturition, the urine was evacuated as a continuous stream without straining; no residual fluid was collected. After urethral anesthetization, the fluid came out of the urethra in multiple intermittent spurts and only with excessive straining. There was a large amount of residual fluid (184.6 ml+/-28.4). The results of bland gel application showed no significant difference ( P>0.05) from those without gel. Detrusor contraction during micturition is suggested to be maintained by positive urethrovesical feedback elicited by the continued passage of urine through the urethra. This feedback seems to be effected through the urethrovesical reflex, which produces vesical contraction on stimulation of the urethral stretch receptors. Abortion of this reflex by urethral anesthetization resulted in failure of detrusor contraction and excessive straining was needed to achieve bladder evacuation in multiple spurts. The urethrovesical reflex is thus assumed to constitute a second micturition reflex responsible for the continuation of detrusor contraction and urination. The role of this reflex in the pathogenesis of

Moderate-duration static stretch reduces active and passive plantar flexor moment but not Achilles tendon stiffness or active muscle length.

PubMed

Kay, Anthony D; Blazevich, Anthony J

2009-04-01

The effects of static stretch on muscle and tendon mechanical properties and muscle activation were studied in fifteen healthy human volunteers. Peak active and passive moment data were recorded during plantar flexion trials on an isokinetic dynamometer. Electromyography (EMG) monitoring of the triceps surae muscles, real-time motion analysis of the lower leg, and ultrasound imaging of the Achilles-medial gastrocnemius muscle-tendon junction were simultaneously conducted. Subjects performed three 60-s static stretches before being retested 2 min and 30 min poststretch. There were three main findings in the present study. First, peak concentric moment was significantly reduced after stretch; 60% of the deficit recovered 30 min poststretch. This was accompanied by, and correlated with (r = 0.81; P < 0.01) reductions in peak triceps surae EMG amplitude, which was fully recovered at 30 min poststretch. Second, Achilles tendon length was significantly shorter during the concentric contraction after stretch and at 30 min poststretch; however, no change in tendon stiffness was detected. Third, passive joint moment was significantly reduced after stretch, and this was accompanied by significant reductions in medial gastrocnemius passive muscle stiffness; both measures fully recovered by 30 min poststretch. These data indicate that the stretching protocol used in this study induced losses in concentric moment that were accompanied by, and related to, reductions in neuromuscular activity, but they were not associated with alterations in tendon stiffness or shorter muscle operating length. Reductions in passive moment were associated with reductions in muscle stiffness, whereas tendon mechanics were unaffected by the stretch. Importantly, the impact on mechanical properties and neuromuscular activity was minimal at 30 min poststretch.

The Effects of Two Different Stretching Programs on Balance Control and Motor Neuron Excitability

ERIC Educational Resources Information Center

Kaya, Fatih; Biçer, Bilal; Yüktasir, Bekir; Willems, Mark E. T.; Yildiz, Nebil

2018-01-01

We examined the effects of training (4d/wk for 6 wks) with static stretching (SS) or contract-relax proprioceptive neuromuscular facilitation (PNF) on static balance time and motor neuron excitability. Static balance time, H[subscript max]/M[subscript max] ratios and H-reflex recovery curves (HRRC) were measured in 28 healthy subjects (SS: n = 10,…

Nicotine impairs reflex renal nerve and respiratory activity in deoxycorticosterone acetate-salt rats.

PubMed

Whitescarver, S A; Roberts, A M; Stremel, R W; Jimenez, A E; Passmore, J C

1991-02-01

Smoking exacerbates the increase in arterial pressure in hypertension. The effect of nicotine on the baroreceptor-mediated reflex responses of renal nerve activity (RNA), heart rate, and respiratory activity (minute diaphragmatic activity [MDA]) after bolus injections of phenylephrine was compared in deoxycorticosterone acetate (DOCA)-salt sensitive and normotensive rats. Osmotic minipumps that dispensed either nicotine (2.4 mg/kg/day) or saline were implanted in DOCA and normotensive rats for 18 days. Anesthetized DOCA-nicotine, DOCA-saline, control-nicotine, and control-saline rats had mean arterial pressures (MAP) of 117 +/- 3, 110 +/- 9, 90 +/- 3, and 89 +/- 5 mm Hg, respectively. Nicotine decreased the sensitivity (p less than 0.05) of baroreceptor reflex control of RNA (% delta RNA/delta MAP) in the DOCA-nicotine rats (-0.92 +/- 0.08) compared with the DOCA-saline (-1.44 +/- 0.16), control-nicotine (-1.45 +/- 0.08), or control-saline (-1.45 +/- 0.21) rats. The reflex decrease in respiratory activity (% delta MDA/delta MAP x 100) was impaired (p less than 0.01) in both control-nicotine (-24.5 +/- 3.3) and DOCA-nicotine (-18.2 +/- 4.6) rats compared with control-saline (-59.2 +/- 9.1) and DOCA-saline (-52.5 +/- 9.9) rats. The reflex decrease in heart rate (absolute delta HR/delta MAP) in both DOCA-nicotine (1.56 +/- 0.17) and control-nicotine (1.54 +/- 0.24) rats was augmented compared with DOCA-saline and control-saline rats (0.91 +/- 0.12 and 0.97 +/- 0.14).(ABSTRACT TRUNCATED AT 250 WORDS)

X-ray diffraction evidence for myosin-troponin connections and tropomyosin movement during stretch activation of insect flight muscle

PubMed Central

Perz-Edwards, Robert J.; Irving, Thomas C.; Baumann, Bruce A. J.; Gore, David; Hutchinson, Daniel C.; Kržič, Uroš; Porter, Rebecca L.; Ward, Andrew B.; Reedy, Michael K.

2011-01-01

Stretch activation is important in the mechanical properties of vertebrate cardiac muscle and essential to the flight muscles of most insects. Despite decades of investigation, the underlying molecular mechanism of stretch activation is unknown. We investigated the role of recently observed connections between myosin and troponin, called “troponin bridges,” by analyzing real-time X-ray diffraction “movies” from sinusoidally stretch-activated Lethocerus muscles. Observed changes in X-ray reflections arising from myosin heads, actin filaments, troponin, and tropomyosin were consistent with the hypothesis that troponin bridges are the key agent of mechanical signal transduction. The time-resolved sequence of molecular changes suggests a mechanism for stretch activation, in which troponin bridges mechanically tug tropomyosin aside to relieve tropomyosin’s steric blocking of myosin–actin binding. This enables subsequent force production, with cross-bridge targeting further enhanced by stretch-induced lattice compression and thick-filament twisting. Similar linkages may operate in other muscle systems, such as mammalian cardiac muscle, where stretch activation is thought to aid in cardiac ejection. PMID:21148419

Broken or dislocated jaw

MedlinePlus

... broken or dislocated jaw requires prompt medical attention. Emergency symptoms include difficulty breathing or heavy bleeding. ... safety equipment, such as a helmet when playing football, or using ... can prevent or minimize some injuries to the face or jaw.

Stretching of Active Muscle Elicits Chronic Changes in Multiple Strain Risk Factors.

PubMed

Kay, Anthony David; Richmond, Dominic; Talbot, Chris; Mina, Minas; Baross, Anthony William; Blazevich, Anthony John

2016-07-01

The muscle stretch intensity imposed during "flexibility" training influences the magnitude of joint range of motion (ROM) adaptation. Thus, stretching while the muscle is voluntarily activated was hypothesized to provide a greater stimulus than passive stretching. The effect of a 6-wk program of stretch imposed on an isometrically contracting muscle (i.e., qualitatively similar to isokinetic eccentric training) on muscle-tendon mechanics was therefore studied in 13 healthy human volunteers. Before and after the training program, dorsiflexion ROM, passive joint moment, and maximal isometric plantarflexor moment were recorded on an isokinetic dynamometer. Simultaneous real-time motion analysis and ultrasound imaging recorded gastrocnemius medialis muscle and Achilles tendon elongation. Training was performed twice weekly and consisted of five sets of 12 maximal isokinetic eccentric contractions at 10°·s. Significant increases (P < 0.01) in ROM (92.7% [14.7°]), peak passive moment (i.e., stretch tolerance; 136.2%), area under the passive moment curve (i.e., energy storage; 302.6%), and maximal isometric plantarflexor moment (51.3%) were observed after training. Although no change in the slope of the passive moment curve (muscle-tendon stiffness) was detected (-1.5%, P > 0.05), a significant increase in tendon stiffness (31.2%, P < 0.01) and a decrease in passive muscle stiffness (-14.6%, P < 0.05) were observed. The substantial positive adaptation in multiple functional and physiological variables that are cited within the primary etiology of muscle strain injury, including strength, ROM, muscle stiffness, and maximal energy storage, indicate that the stretching of active muscle might influence injury risk in addition to muscle function. The lack of change in muscle-tendon stiffness simultaneous with significant increases in tendon stiffness and decreases in passive muscle stiffness indicates that tissue-specific effects were elicited.

Effects of exercise pressor reflex activation on carotid baroreflex function during exercise in humans

NASA Technical Reports Server (NTRS)

Gallagher, K. M.; Fadel, P. J.; Stromstad, M.; Ide, K.; Smith, S. A.; Querry, R. G.; Raven, P. B.; Secher, N. H.

2001-01-01

1. This investigation was designed to determine the contribution of the exercise pressor reflex to the resetting of the carotid baroreflex during exercise. 2. Ten subjects performed 3.5 min of static one-legged exercise (20 % maximal voluntary contraction) and 7 min dynamic cycling (20 % maximal oxygen uptake) under two conditions: control (no intervention) and with the application of medical anti-shock (MAS) trousers inflated to 100 mmHg (to activate the exercise pressor reflex). Carotid baroreflex function was determined at rest and during exercise using a rapid neck pressure/neck suction technique. 3. During exercise, the application of MAS trousers (MAS condition) increased mean arterial pressure (MAP), plasma noradrenaline concentration (dynamic exercise only) and perceived exertion (dynamic exercise only) when compared to control (P < 0.05). No effect of the MAS condition was evident at rest. The MAS condition had no effect on heart rate (HR), plasma lactate and adrenaline concentrations or oxygen uptake at rest and during exercise. The carotid baroreflex stimulus-response curve was reset upward on the response arm and rightward to a higher operating pressure by control exercise without alterations in gain. Activation of the exercise pressor reflex by MAS trousers further reset carotid baroreflex control of MAP, as indicated by the upward and rightward relocation of the curve. However, carotid baroreflex control of HR was only shifted rightward to higher operating pressures by MAS trousers. The sensitivity of the carotid baroreflex was unaltered by exercise pressor reflex activation. 4. These findings suggest that during dynamic and static exercise the exercise pressor reflex is capable of actively resetting carotid baroreflex control of mean arterial pressure; however, it would appear only to modulate carotid baroreflex control of heart rate.

The stretch-shortening cycle : a model to study naturally occurring neuromuscular fatigue.

PubMed

Nicol, Caroline; Avela, Janne; Komi, Paavo V

2006-01-01

Neuromuscular fatigue has traditionally been examined using isolated forms of either isometric, concentric or eccentric actions. However, none of these actions are naturally occurring in human (or animal) ground locomotion. The basic muscle function is defined as the stretch-shortening cycle (SSC), where the preactivated muscle is first stretched (eccentric action) and then followed by the shortening (concentric) action. As the SSC taxes the skeletal muscles very strongly mechanically, its influence on the reflex activation becomes apparent and very different from the isolated forms of muscle actions mentioned above. The ground contact phases of running, jumping and hopping etc. are examples of the SSC for leg extensor muscles; similar phases can also be found for the upper-body activities. Consequently, it is normal and expected that the fatigue phenomena should be explored during SSC activities. The fatigue responses of repeated SSC actions are very versatile and complex because the fatigue does not depend only on the metabolic loading, which is reportedly different among muscle actions. The complexity of SSC fatigue is well reflected by the recovery patterns of many neuromechanical parameters. The basic pattern of SSC fatigue response (e.g. when using the complete exhaustion model of hopping or jumping) is the bimodality showing an immediate reduction in performance during exercise, quick recovery within 1-2 hours, followed by a secondary reduction, which may often show the lowest values on the second day post-exercise when the symptoms of muscle soreness/damage are also greatest. The full recovery may take 4-8 days depending on the parameter and on the severity of exercise. Each subject may have their own time-dependent bimodality curve. Based on the reviewed literature, it is recommended that the fatigue protocol is 'completely' exhaustive to reduce the important influence of inter-subject variability in the fatigue responses. The bimodality concept is

Stretch-induced contraction in pulmonary arteries.

PubMed

Kulik, T J; Evans, J N; Gamble, W J

1988-12-01

Stretch stimulates contraction of systemic blood vessels, but the response has not been described in pulmonary vessels. To determine whether pulmonary arteries contract when stretched, isolated cylindrical segments of pulmonary arteries were suspended between two parallel wires, stretched, and the active force was generated in response to stretch measured. Eighty-nine percent of segments from small (in situ diameter less than 1,000 microns) feline pulmonary arteries contracted when stretched, and in 65% of these the magnitude of stretch was related to the magnitude of contraction. Large (in situ diameter greater than or equal to 1,000 microns) feline pulmonary arteries did not contract with stretch. Multiple, rapidly repeated stretches resulted in a diminution of active force development. Stretch-induced contraction required external Ca2+ and was abolished by diltiazem (10 microns), but it was not affected by phenoxybenzamine, phentolamine, diethylcarbamazine, or mechanical removal of endothelium. Indomethacin blunted but did not abolish stretch-induced contraction, an effect that may have been nonspecific. This study suggests that stretch can act, probably directly, on smooth muscle in small feline pulmonary arteries to elicit contraction and that it may be a determinant of pulmonary vascular tone. In addition, feline pulmonary arteries are suitable for the in vitro study of stretch-induced contraction.

The Acute Effects of Static Stretching Compared to Dynamic Stretching with and without an Active Warm up on Anaerobic Performance.

PubMed

Kendall, Bradley J

2017-01-01

The Wingate Anaerobic Test (WAnT) has been used in many studies to determine anaerobic performance. However, there has been poor reporting of warm-up protocols and limited consistency between warm-up methods that have been used. With the WAnT being such a commonly-used test, consistency in warm-up methods is essential in order to compare results across studies. Therefore, this study was designed to compare how static stretching, dynamic stretching, and an active warm-up affect WAnT performance. Ten recreationally active participants (5 males, 5 females) with a mean (SD) age of 23.3 (0.7) volunteered for this study. Subjects were randomized to a specific order of five warm-up protocols, which were performed on individual days followed by a WAnT. Peak power, mean power, power drop, and fatigue index were compared for each trial using a repeated measures ANOVA. For peak power, results revealed that warm-up protocol had a significant effect, F (4,36) = 3.90, p = .01, partial η 2 = .302. It was hypothesized that the dynamic stretching would lead to greater peak power than the static stretching protocol. However, results of post hoc analyses failed to detect a significant difference (p =.065). For the other measured variables no significant differences were found. The findings from this study suggest that warm-up protocols may have significantly different impacts on peak power during the WAnT. Additional research should use larger sample sizes and further explore these warm-up protocols. Developing a standardized warm-up protocol for the WAnT may improve consistency between studies.

p38 mitogen-activated protein kinase up-regulates NF-{kappa}B transcriptional activation through RelA phosphorylation during stretch-induced myogenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Guoping; Liu, Dongxu; Liu, Jing

2010-01-01

p38 MAPK and nuclear factor-B (NF-B) signaling pathways play an indispensable role in the control of skeletal myogenesis. The specific contribution of these signaling pathways to the response of myoblast to the mechanical stimulation and the molecular mechanisms underlying this response remain unresolved. Using an established in vitro model, we now show that p38 MAP kinase activity regulates the transcriptional activation of NF-{kappa}B in response to mechanical stimulation of myoblasts. Furthermore, SB203580 blocked stretch-induced NF-{kappa}B activation during myogenesis, not through down-regulation of degradation of I{kappa}B-{alpha}, and consequent translocation of the p65 subunit of NF-{kappa}B to the nucleus. It is likelymore » that stretch-induced NF-{kappa}B activation by phosphorylation of p65 NF-{kappa}B. Moreover, depletion of p38{alpha} using siRNA significantly reduces stretch-induced phosphorylation of RelA and NF-{kappa}B activity. These results provides the first evidence of a cross-talk between p38 MAPK and NF-{kappa}B signaling pathways during stretch-induced myogenesis, with phosphorylation of RelA being one of the effectors of this promyogenic mechanism. The {alpha} isoform of p38MAP kinase regulates the transcriptional activation of NF-{kappa}B following stimulation with cyclic stretch.« less

Stretch and interleukin 1 beta: pro-labour factors with similar mitogen-activated protein kinase effects but differential patterns of transcription factor activation and gene expression.

PubMed

Sooranna, S R; Engineer, N; Liang, Z; Bennett, P R; Johnson, M R

2007-07-01

IL-1beta and stretch increase uterine smooth muscle cell (USMC) prostaglandin H synthase 2 (PGHS-2) and interleukin (IL)-8 mRNA expression in a mitogen-activated protein kinase (MAPK) dependent mechanism. We have tested our hypothesis that stretch and IL-1beta activate different components of the MAPK cascade in USMC and investigated the effects of specific MAPK inhibitors on these components. Further, we have used a Jun N-terminal kinase (JNK) and p38 activator, anisomycin, to compare the effect of differential MAPK activation on the expression of PGHS-2, IL-8 and oxytocin receptor (OTR) mRNA with that seen in response to stretch and IL-1beta. Stretch, IL-1beta and anisomycin activated similar components of the MAPK cascade and specific inhibitors of MAPK altered phosphorylation of MAPK and downstream cascade components as expected. Expression of OTR mRNA was increased by stretch and anisomycin in a MAPK-independent manner. All three stimuli increased PGHS-2 and IL-8 mRNA expression in a MAPK-dependent manner, but while the MAPK inhibitors reduced the IL-1beta-induced activation of activating transcription factor (ATF)-2, liver activating protein (LAP) and c-jun, the stretch-induced increase in LAP was unaffected by MAPK-inhibition and only JNK inhibition appeared to reduce c-jun activation. These observations show that stretch, IL-1beta and anisomycin activate the same components of the MAPK cascade, but differentially activate LAP and liver inhibitory protein (LIP) perhaps accounting for the increase in OTR by stretch and anisomycin but not IL-1beta observed in this study.

Flexible piezoelectric energy harvesting from jaw movements

NASA Astrophysics Data System (ADS)

Delnavaz, Aidin; Voix, Jérémie

2014-10-01

Piezoelectric fiber composites (PFC) represent an interesting subset of smart materials that can function as sensor, actuator and energy converter. Despite their excellent potential for energy harvesting, very few PFC mechanisms have been developed to capture the human body power and convert it into an electric current to power wearable electronic devices. This paper provides a proof of concept for a head-mounted device with a PFC chin strap capable of harvesting energy from jaw movements. An electromechanical model based on the bond graph method is developed to predict the power output of the energy harvesting system. The optimum resistance value of the load and the best stretch ratio in the strap are also determined. A prototype was developed and tested and its performances were compared to the analytical model predictions. The proposed piezoelectric strap mechanism can be added to all types of head-mounted devices to power small-scale electronic devices such as hearing aids, electronic hearing protectors and communication earpieces.

Desensitization of the Mechanoreceptors in Müller's Muscle Reduces the Increased Reflex Contraction of the Orbicularis Oculi Slow-Twitch Fibers in Blepharospasm.

PubMed

Matsuo, Kiyoshi; Ban, Ryokuya; Ban, Midori

2014-01-01

Although the mixed orbicularis oculi muscle lacks the muscle spindles required to induce reflex contraction of its slow-twitch fibers, the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction. We hypothesize that strong stretching of these mechanoreceptors increases reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. We examined a 71-year-old man with right blepharospasm and bilateral aponeurosis-disinserted blepharoptosis to determine whether the patient's blepharospasm was worsened by increased trigeminal proprioceptive evocation via stretching of the mechanoreceptors in Müller's muscle owing to a 60° upward gaze and serrated eyelid closure, and whether local anesthesia of the mechanoreceptors via lidocaine administration to the upper fornix as well as surgical disinsertion of Müller's muscle from the tarsus and fixation of the disinserted aponeurosis to the tarsus decreased trigeminal proprioceptive evocation and improved patient's blepharospasm. Before pharmacological desensitization, 60° upward gaze and serrated eyelid closure exacerbated the patient's blepharospasm. In contrast, these maneuvers did not worsen his blepharospasm following lidocaine administration. One year after surgical desensitization, the blepharospasm had disappeared and a 60° upward gaze did not induce blepharospasm. Strong stretching of the mechanoreceptors in Müller's muscle appeared to increase reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. In addition to botulinum neurotoxin injections into the involuntarily contracted orbicularis oculi muscle and myectomy, surgical desensitization of the mechanoreceptors in Müller's muscle may represent an additional procedure to reduce blepharospasm.

Desensitization of the Mechanoreceptors in Müller's Muscle Reduces the Increased Reflex Contraction of the Orbicularis Oculi Slow-Twitch Fibers in Blepharospasm

PubMed Central

Ban, Ryokuya; Ban, Midori

2014-01-01

Objective: Although the mixed orbicularis oculi muscle lacks the muscle spindles required to induce reflex contraction of its slow-twitch fibers, the mechanoreceptors in Müller's muscle function as extrinsic mechanoreceptors to induce reflex contraction. We hypothesize that strong stretching of these mechanoreceptors increases reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. Methods: We examined a 71-year-old man with right blepharospasm and bilateral aponeurosis-disinserted blepharoptosis to determine whether the patient's blepharospasm was worsened by increased trigeminal proprioceptive evocation via stretching of the mechanoreceptors in Müller's muscle owing to a 60° upward gaze and serrated eyelid closure, and whether local anesthesia of the mechanoreceptors via lidocaine administration to the upper fornix as well as surgical disinsertion of Müller's muscle from the tarsus and fixation of the disinserted aponeurosis to the tarsus decreased trigeminal proprioceptive evocation and improved patient's blepharospasm. Results: Before pharmacological desensitization, 60° upward gaze and serrated eyelid closure exacerbated the patient's blepharospasm. In contrast, these maneuvers did not worsen his blepharospasm following lidocaine administration. One year after surgical desensitization, the blepharospasm had disappeared and a 60° upward gaze did not induce blepharospasm. Conclusions: Strong stretching of the mechanoreceptors in Müller's muscle appeared to increase reflex contraction of the orbicularis oculi slow-twitch muscle fibers, resulting in blepharospasm. In addition to botulinum neurotoxin injections into the involuntarily contracted orbicularis oculi muscle and myectomy, surgical desensitization of the mechanoreceptors in Müller's muscle may represent an additional procedure to reduce blepharospasm. PMID:25328566

Differential effect of central command on aortic and carotid sinus baroreceptor-heart rate reflexes at the onset of spontaneous, fictive motor activity.

PubMed

Matsukawa, Kanji; Ishii, Kei; Kadowaki, Akito; Liang, Nan; Ishida, Tomoko

2012-08-15

Our laboratory has reported that central command blunts the sensitivity of the aortic baroreceptor-heart rate (HR) reflex at the onset of voluntary static exercise in conscious cats and spontaneous contraction in decerebrate cats. The purpose of this study was to examine whether central command attenuates the sensitivity of the carotid sinus baroreceptor-HR reflex at the onset of spontaneous, fictive motor activity in paralyzed, decerebrate cats. We confirmed that aortic nerve (AN)-stimulation-induced bradycardia was markedly blunted to 26 ± 4.4% of the control (21 ± 1.3 beats/min) at the onset of spontaneous motor activity. Although the baroreflex bradycardia by electrical stimulation of the carotid sinus nerve (CSN) was suppressed (P < 0.05) to 86 ± 5.6% of the control (38 ± 1.2 beats/min), the inhibitory effect of spontaneous motor activity was much weaker (P < 0.05) with CSN stimulation than with AN stimulation. The baroreflex bradycardia elicited by brief occlusion of the abdominal aorta was blunted to 36% of the control (36 ± 1.6 beats/min) during spontaneous motor activity, suggesting that central command is able to inhibit the cardiomotor sensitivity of arterial baroreflexes as the net effect. Mechanical stretch of the triceps surae muscle never affected the baroreflex bradycardia elicited by AN or CSN stimulation and by aortic occlusion, suggesting that muscle mechanoreflex did not modify the cardiomotor sensitivity of aortic and carotid sinus baroreflex. Since the inhibitory effect of central command on the carotid baroreflex pathway, associated with spontaneous motor activity, was much weaker compared with the aortic baroreflex pathway, it is concluded that central command does not force a generalized modulation on the whole pathways of arterial baroreflexes but provides selective inhibition for the cardiomotor component of the aortic baroreflex.

Fine morphology of the jaw apparatus of Puncturella noachina (Fissurellidae, Vetigastropoda).

PubMed

Vortsepneva, Elena; Ivanov, Dmitry; Purschke, Günter; Tzetlin, Alexander

2014-07-01

Jaws of various kinds occur in virtually all groups of Mollusca, except for Polyplacophora and Bivalvia. Molluscan jaws are formed by the buccal epithelium and either constitute a single plate, a paired formation or a serial structure. Buccal ectodermal structures in gastropods are rather different. They can be nonrenewable or having final growth, like the hooks in Clione (Gastropoda, Gymnosomata). In this case, they are formed by a single cell. Conversely, they can be renewable during the entire life span and in this case they are formed by a set of cells, like the formation of the radula. The fine structure of the jaws was studied in the gastropod Puncturella noachina. The jaw is situated in the buccal cavity and consists of paired elongated cuticular plates. On the anterior edge of each cuticular plate there are numerous longitudinally oriented rodlets disposed over the entire jaw surface and immersed into a cuticular matrix. The jaw can be divided into four zones situated successively toward the anterior edge: 1) the posterior area: the zone of formation of the thick cuticle covering the entire jaw and forming the electron-dense outer layer of the jaw plate; 2) the zone of rodlet formation; 3) the zone of rodlet arrangement; and 4) the anterior zone: the free scraping edge of the plate, or the erosion zone. In the general pattern of jaw formation, Puncturella noachina resembles Testudinalia tessulata (Patellogastropoda) studied previously. The basis of the jaw is a cuticular plate formed by the activity of the strongly developed microvillar apparatus of the gnathoepithelium. However, the mechanism of renewal of the jaw anterior part in P. noachina is much more complex as its scraping edge consists not just of a thick cuticular matrix rather than of a system of denticles being the projecting endings of rodlets. © 2014 Wiley Periodicals, Inc.

Reflexive aerostructures: increased vehicle survivability

NASA Astrophysics Data System (ADS)

Margraf, Thomas W.; Hemmelgarn, Christopher D.; Barnell, Thomas J.; Franklin, Mark A.

2007-04-01

Aerospace systems stand to benefit significantly from the advancement of reflexive aerostructure technologies for increased vehicle survivability. Cornerstone Research Group Inc. (CRG) is developing lightweight, healable composite systems for use as primary load-bearing aircraft components. The reflexive system is comprised of piezoelectric structural health monitoring systems, localized thermal activation systems, and lightweight, healable composite structures. The reflexive system is designed to mimic the involuntary human response to damage. Upon impact, the structural health monitoring system will identify the location and magnitude of the damage, sending a signal to a discrete thermal activation control system to resistively heat the shape memory polymer (SMP) matrix composite above activation temperature, resulting in localized shape recovery and healing of the damaged areas. CRG has demonstrated SMP composites that can recover 90 percent of flexural yield stress and modulus after postfailure healing. During the development, CRG has overcome issues of discrete activation, structural health monitoring integration, and healable resin systems. This paper will address the challenges associated with development of a reflexive aerostructure, including integration of structural health monitoring, discrete healing, and healable shape memory resin systems.

Neuromuscular performance of lower limbs during voluntary and reflex activity in power- and endurance-trained athletes.

PubMed

Kyröläinen, H; Komi, P V

1994-01-01

Neural, mechanical and muscle factors influence muscle force production. This study was therefore, designed to compare possible differences in the function of the neuromuscular system among differently adapted subjects. A group of 11 power-trained athletes and 10 endurance-trained athletes volunteered as subjects for this study. Maximal voluntary isometric force and the rate of force production of the knee extensor and the plantar flexor muscles were measured. In addition, basic reflex function was measured in the two experimental conditions. The power athletes produced higher voluntary forces (P < 0.01-0.001) with higher rates for force production (P < 0.001) by both muscle groups measured. Unexpectedly, however, no differences were noticed in the electromyogram time curves between the groups. During reflex activity, the endurance group demonstrated higher sensitivity to the mechanical stimuli, i.e. the higher reflex amplitude caused a higher rate of reflex force development, and the reflex amplitude correlated with the averaged angular velocity. The differences in the isometric conditions could be explained by obviously different muscle fibre distribution, by different amounts of muscle mass, by possible differences in the force transmission from individual myofibrils to the skeletal muscle and by specificity of training. In addition, differences in nervous system structure and muscle spindle properties could explain the observed differences in reflex activity between the two groups.

The Acute Effects of Static Stretching Compared to Dynamic Stretching with and without an Active Warm up on Anaerobic Performance

PubMed Central

KENDALL, BRADLEY J.

2017-01-01

The Wingate Anaerobic Test (WAnT) has been used in many studies to determine anaerobic performance. However, there has been poor reporting of warm-up protocols and limited consistency between warm-up methods that have been used. With the WAnT being such a commonly-used test, consistency in warm-up methods is essential in order to compare results across studies. Therefore, this study was designed to compare how static stretching, dynamic stretching, and an active warm-up affect WAnT performance. Ten recreationally active participants (5 males, 5 females) with a mean (SD) age of 23.3 (0.7) volunteered for this study. Subjects were randomized to a specific order of five warm-up protocols, which were performed on individual days followed by a WAnT. Peak power, mean power, power drop, and fatigue index were compared for each trial using a repeated measures ANOVA. For peak power, results revealed that warm-up protocol had a significant effect, F(4,36) = 3.90, p = .01, partial η2 = .302. It was hypothesized that the dynamic stretching would lead to greater peak power than the static stretching protocol. However, results of post hoc analyses failed to detect a significant difference (p =.065). For the other measured variables no significant differences were found. The findings from this study suggest that warm-up protocols may have significantly different impacts on peak power during the WAnT. Additional research should use larger sample sizes and further explore these warm-up protocols. Developing a standardized warm-up protocol for the WAnT may improve consistency between studies. PMID:28479947

Characterization of bulbospongiosus muscle reflexes activated by urethral distension in male rats.

PubMed

Tanahashi, Masayuki; Karicheti, Venkateswarlu; Thor, Karl B; Marson, Lesley

2012-10-01

The urethrogenital reflex (UGR) is used as a surrogate model of the autonomic and somatic nerve and muscle activity that accompanies ejaculation. The UGR is evoked by distension of the urethra and activation of penile afferents. The current study compares two methods of elevating urethral intraluminal pressure in spinalized, anesthetized male Sprague-Dawley rats (n = 60). The first method, penile extension UGR, involves extracting the penis from the foreskin, so that urethral pressure rises due to a natural anatomical flexure in the penis. The second method, penile clamping UGR, involves penile extension UGR with the addition of clamping of the glans penis. Groups of animals were prepared that either received no additional treatment, surgical shams, or received bilateral nerve cuts (4 nerve cut groups): either the pudendal sensory nerve branch (SbPN), the pelvic nerves, the hypogastric nerves, or all three nerves. Penile clamping UGR was characterized by multiple bursts, monitored by electromyography (EMG) of the bulbospongiosus muscle (BSM) accompanied by elevations in urethral pressure. The penile clamping UGR activity declined across multiple trials and eventually resulted in only a single BSM burst, indicating desensitization. In contrast, the penile extension UGR, without penile clamping, evoked only a single BSM EMG burst that showed no desensitization. Thus, the UGR is composed of two BSM patterns: an initial single burst, termed urethrobulbospongiosus (UBS) reflex and a subsequent multiple bursting pattern (termed ejaculation-like response, ELR) that was only induced with penile clamping urethral occlusion. Transection of the SbPN eliminated the ELR in the penile clamping model, but the single UBS reflex remained in both the clamping and extension models. Pelvic nerve (PelN) transection increased the threshold for inducing BSM activation with both methods of occlusion but actually unmasked an ELR in the penile extension method. Hypogastric nerve (HgN) cuts

Ballistic stretching increases flexibility and acute vertical jump height when combined with basketball activity.

PubMed

Woolstenhulme, Mandy T; Griffiths, Christine M; Woolstenhulme, Emily M; Parcell, Allen C

2006-11-01

Stretching is often included as part of a warm-up procedure for basketball activity. However, the efficacy of stretching with respect to sport performance has come into question. We determined the effects of 4 different warm-up protocols followed by 20 minutes of basketball activity on flexibility and vertical jump height. Subjects participated in 6 weeks (2 times per week) of warm-up and basketball activity. The warm-up groups participated in ballistic stretching, static stretching, sprinting, or basketball shooting (control group). We asked 3 questions. First, what effect does 6 weeks of warm-up exercise and basketball play have on both flexibility and vertical jump height? We measured sit and reach and vertical jump height before (week -1) and after (week 7) the 6 weeks. Flexibility increased for the ballistic, static, and sprint groups compared to the control group (p < 0.0001), while vertical jump height did not change for any of the groups. Our second question was what is the acute effect of each warm-up on vertical jump height? We measured vertical jump immediately after the warm-up on 4 separate occasions during the 6 weeks (at weeks 0, 2, 4, and 6). Vertical jump height was not different for any group. Finally, our third question was what is the acute effect of each warm-up on vertical jump height following 20 minutes of basketball play? We measured vertical jump height immediately following 20 minutes of basketball play at weeks 0, 2, 4, and 6. Only the ballistic stretching group demonstrated an acute increase in vertical jump 20 minutes after basketball play (p < 0.05). Coaches should consider using ballistic stretching as a warm-up for basketball play, as it is beneficial to vertical jump performance.

Vestibular control of sympathetic activity. An otolith-sympathetic reflex in humans

NASA Technical Reports Server (NTRS)

Kaufmann, H.; Biaggioni, I.; Voustianiouk, A.; Diedrich, A.; Costa, F.; Clarke, R.; Gizzi, M.; Raphan, T.; Cohen, B.

2002-01-01

It has been proposed that a vestibular reflex originating in the otolith organs and other body graviceptors modulates sympathetic activity during changes in posture with regard to gravity. To test this hypothesis, we selectively stimulated otolith and body graviceptors sinusoidally along different head axes in the coronal plane with off-vertical axis rotation (OVAR) and recorded sympathetic efferent activity in the peroneal nerve (muscle sympathetic nerve activity, MSNA), blood pressure, heart rate, and respiratory rate. All parameters were entrained during OVAR at the frequency of rotation, with MSNA increasing in nose-up positions during forward linear acceleration and decreasing when nose-down. MSNA was correlated closely with blood pressure when subjects were within +/-90 degrees of nose-down positions with a delay of 1.4 s, the normal latency of baroreflex-driven changes in MSNA. Thus, in the nose-down position, MSNA was probably driven by baroreflex afferents. In contrast, when subjects were within +/-45 degrees of the nose-up position, i.e., when positive linear acceleration was maximal along the naso-ocipital axis, MSNA was closely related to gravitational acceleration at a latency of 0.4 s. This delay is too short for MSNA changes to be mediated by the baroreflex, but it is compatible with the delay of a response originating in the vestibular system. We postulate that a vestibulosympathetic reflex, probably originating mainly in the otolith organs, contributes to blood pressure maintenance during forward linear acceleration. Because of its short latency, this reflex may be one of the earliest mechanisms to sustain blood pressure upon standing.

Vestibular control of sympathetic activity. An otolith-sympathetic reflex in humans.

PubMed

Kaufmann, H; Biaggioni, I; Voustianiouk, A; Diedrich, A; Costa, F; Clarke, R; Gizzi, M; Raphan, T; Cohen, B

2002-04-01

It has been proposed that a vestibular reflex originating in the otolith organs and other body graviceptors modulates sympathetic activity during changes in posture with regard to gravity. To test this hypothesis, we selectively stimulated otolith and body graviceptors sinusoidally along different head axes in the coronal plane with off-vertical axis rotation (OVAR) and recorded sympathetic efferent activity in the peroneal nerve (muscle sympathetic nerve activity, MSNA), blood pressure, heart rate, and respiratory rate. All parameters were entrained during OVAR at the frequency of rotation, with MSNA increasing in nose-up positions during forward linear acceleration and decreasing when nose-down. MSNA was correlated closely with blood pressure when subjects were within +/-90 degrees of nose-down positions with a delay of 1.4 s, the normal latency of baroreflex-driven changes in MSNA. Thus, in the nose-down position, MSNA was probably driven by baroreflex afferents. In contrast, when subjects were within +/-45 degrees of the nose-up position, i.e., when positive linear acceleration was maximal along the naso-ocipital axis, MSNA was closely related to gravitational acceleration at a latency of 0.4 s. This delay is too short for MSNA changes to be mediated by the baroreflex, but it is compatible with the delay of a response originating in the vestibular system. We postulate that a vestibulosympathetic reflex, probably originating mainly in the otolith organs, contributes to blood pressure maintenance during forward linear acceleration. Because of its short latency, this reflex may be one of the earliest mechanisms to sustain blood pressure upon standing.

Hypothalamic stimulation and baroceptor reflex interaction on renal nerve activity.

NASA Technical Reports Server (NTRS)

Wilson, M. F.; Ninomiya, I.; Franz, G. N.; Judy, W. V.

1971-01-01

The basal level of mean renal nerve activity (MRNA-0) measured in anesthetized cats was found to be modified by the additive interaction of hypothalamic and baroceptor reflex influences. Data were collected with the four major baroceptor nerves either intact or cut, and with mean aortic pressure (MAP) either clamped with a reservoir or raised with l-epinephrine. With intact baroceptor nerves, MRNA stayed essentially constant at level MRNA-0 for MAP below an initial pressure P1, and fell approximately linearly to zero as MAP was raised to P2. Cutting the baroceptor nerves kept MRNA at MRNA-0 (assumed to represent basal central neural output) independent of MAP. The addition of hypothalamic stimulation produced nearly constant increments in MRNA for all pressure levels up to P2, with complete inhibition at some level above P2. The increments in MRNA depended on frequency and location of the stimulus. A piecewise linear model describes MRNA as a linear combination of hypothalamic, basal central neural, and baroceptor reflex activity.

21 CFR 872.2060 - Jaw tracking device.

Code of Federal Regulations, 2014 CFR

2014-04-01

...) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.2060 Jaw tracking device. (a) Jaw tracking device... Controls Guidance Document: Dental Sonography and Jaw Tracking Devices.” [68 FR 67367, Dec. 2, 2003] ...

Neuronal activity related to spontaneous and capsaicin-induced rhythmical jaw movements in the rat.

PubMed

Ohta, M; Sasamoto, K; Kobayashi, J

1998-02-01

Intraoral capsaicin induced rhythmical jaw movements (RJM) in anesthetized rats. Neurons in the trigeminal spinal nucleus caudalis or the cortico-peduncular (CP) axons were extracellularly recorded. Capsaicin excited dose-dependently most caudalis neurons, which were activated by stimulation of the oral cavity and/or the tooth pulp and activated during spontaneous or induced RJM. Ten of 55 CP axons were antidromically activated by stimulation of the contralateral trigeminal motor nucleus. All antidromic and 29 other CP axons discharged prior to the spontaneous RJM, but most of them did not during capsaicin-induced RJM. These neuronal activities possibly initiate spontaneous RJM although the activities of caudalis neurons are necessary for capsicin-induced RJM.

Piezo Is Essential for Amiloride-Sensitive Stretch-Activated Mechanotransduction in Larval Drosophila Dorsal Bipolar Dendritic Sensory Neurons

PubMed Central

Suslak, Thomas J.; Watson, Sonia; Thompson, Karen J.; Shenton, Fiona C.; Bewick, Guy S.; Armstrong, J. Douglas; Jarman, Andrew P.

2015-01-01

Stretch-activated afferent neurons, such as those of mammalian muscle spindles, are essential for proprioception and motor co-ordination, but the underlying mechanisms of mechanotransduction are poorly understood. The dorsal bipolar dendritic (dbd) sensory neurons are putative stretch receptors in the Drosophila larval body wall. We have developed an in vivo protocol to obtain receptor potential recordings from intact dbd neurons in response to stretch. Receptor potential changes in dbd neurons in response to stretch showed a complex, dynamic profile with similar characteristics to those previously observed for mammalian muscle spindles. These profiles were reproduced by a general in silico model of stretch-activated neurons. This in silico model predicts an essential role for a mechanosensory cation channel (MSC) in all aspects of receptor potential generation. Using pharmacological and genetic techniques, we identified the mechanosensory channel, DmPiezo, in this functional role in dbd neurons, with TRPA1 playing a subsidiary role. We also show that rat muscle spindles exhibit a ruthenium red-sensitive current, but found no expression evidence to suggest that this corresponds to Piezo activity. In summary, we show that the dbd neuron is a stretch receptor and demonstrate that this neuron is a tractable model for investigating mechanisms of mechanotransduction. PMID:26186008

Piezo Is Essential for Amiloride-Sensitive Stretch-Activated Mechanotransduction in Larval Drosophila Dorsal Bipolar Dendritic Sensory Neurons.

PubMed

Suslak, Thomas J; Watson, Sonia; Thompson, Karen J; Shenton, Fiona C; Bewick, Guy S; Armstrong, J Douglas; Jarman, Andrew P

2015-01-01

Stretch-activated afferent neurons, such as those of mammalian muscle spindles, are essential for proprioception and motor co-ordination, but the underlying mechanisms of mechanotransduction are poorly understood. The dorsal bipolar dendritic (dbd) sensory neurons are putative stretch receptors in the Drosophila larval body wall. We have developed an in vivo protocol to obtain receptor potential recordings from intact dbd neurons in response to stretch. Receptor potential changes in dbd neurons in response to stretch showed a complex, dynamic profile with similar characteristics to those previously observed for mammalian muscle spindles. These profiles were reproduced by a general in silico model of stretch-activated neurons. This in silico model predicts an essential role for a mechanosensory cation channel (MSC) in all aspects of receptor potential generation. Using pharmacological and genetic techniques, we identified the mechanosensory channel, DmPiezo, in this functional role in dbd neurons, with TRPA1 playing a subsidiary role. We also show that rat muscle spindles exhibit a ruthenium red-sensitive current, but found no expression evidence to suggest that this corresponds to Piezo activity. In summary, we show that the dbd neuron is a stretch receptor and demonstrate that this neuron is a tractable model for investigating mechanisms of mechanotransduction.

Pulmonary stretch receptor afferents activate excitatory amino acid receptors in the nucleus tractus solitarii in rats.

PubMed

Bonham, A C; Coles, S K; McCrimmon, D R

1993-05-01

1. The goal of the present study was to identify potential neurotransmitter candidates in the Breuer-Hering (BH) reflex pathway, specifically at synapses between the primary afferents and probable second-order neurones (pump cells) within the nucleus tractus solitarii (NTS). We hypothesized that if activation of specific receptors in the NTS is required for production of the BH reflex, then (1) injection of the receptor agonist(s) would mimic the reflex response (apnoea), (2) injection of appropriate antagonists would impair the apnoea produced by either lung inflation or agonist injection, and (3) second-order neurones in the pathway would be excited by either lung inflation or agonists while antagonists would prevent the response to either. 2. Studies were carried out either in spontaneously breathing or in paralysed, thoracotomized and ventilated rats in which either diaphragm EMG or phrenic nerve activity, expired CO2 concentration and arterial pressure were continuously monitored. The BH reflex was physiologically activated by inflating the lungs. 3. Pressure injections (0.03-15 pmol) of selective excitatory amino acid (EAA) receptor agonists, quisqualic acid (Quis) and N-methyl-D-aspartic acid (NMDA) into an area of the NTS shown previously to contain neurones required for production of the BH reflex produced dose-dependent apnoeas that mimicked the response to lung inflation. Injection of substance P (0.03-4 pmol) did not alter baseline respiratory pattern. 4. Injections of the EAA antagonists, kynurenic acid (Kyn; 0.6-240 pmol), 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX) or 6,7-dinitroquinoxaline-2,3-dione (DNQX) into the BH region of the NTS reversibly impaired the apnoea produced by lung inflation. All three antagonists reduced or abolished the apnoeas resulting from injection of Quis or NMDA, and slowed baseline respiratory frequency. In contrast, injections of the highly selective NMDA receptor antagonist, D-2-amino-5-phosphonovaleric acids (AP5), in

Stretching: Does It Help?

ERIC Educational Resources Information Center

Vardiman, Phillip; Carrand, David; Gallagher, Philip M.

2010-01-01

Stretching prior to activity is universally accepted as an important way to improve performance and help prevent injury. Likewise, limited flexibility has been shown to decrease functional ability and predispose a person to injuries. Although this is commonly accepted, appropriate stretching for children and adolescents involved with sports and…

Swiveling Lathe Jaw Concept for Holding Irregular Pieces

NASA Technical Reports Server (NTRS)

David, J.

1966-01-01

Clamp holds irregularly shaped pieces in lathe chuck without damage and eliminates excessive time in selecting optimum mounting. Interchangeable jaws ride in standard jaw slots but swivel so that the jaw face bears evenly against the workpiece regardless of contour. The jaws can be used on both engine and turret lathes.

21 CFR 872.2060 - Jaw tracking device.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Jaw tracking device. 872.2060 Section 872.2060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.2060 Jaw tracking device. (a) Jaw tracking device...

21 CFR 872.2060 - Jaw tracking device.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Jaw tracking device. 872.2060 Section 872.2060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.2060 Jaw tracking device. (a) Jaw tracking device...

21 CFR 872.2060 - Jaw tracking device.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Jaw tracking device. 872.2060 Section 872.2060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.2060 Jaw tracking device. (a) Jaw tracking device...

21 CFR 872.2060 - Jaw tracking device.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Jaw tracking device. 872.2060 Section 872.2060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.2060 Jaw tracking device. (a) Jaw tracking device...

Experimental masseter muscle pain alters jaw-neck motor strategy.

PubMed

Wiesinger, B; Häggman-Henrikson, B; Hellström, F; Wänman, A

2013-08-01

A functional integration between the jaw and neck regions has been demonstrated during normal jaw function. The effect of masseter muscle pain on this integrated motor behaviour in man is unknown. The aim of this study was to investigate the effect of induced masseter muscle pain on jaw-neck movements during a continuous jaw opening-closing task. Sixteen healthy men performed continuous jaw opening-closing movements to a target position, defined as 75% of the maximum jaw opening. Each subject performed two trials without pain (controls) and two trials with masseter muscle pain, induced with hypertonic saline as a single injection. Simultaneous movements of the mandible and the head were registered with a wireless optoelectronic three-dimensional recording system. Differences in movement amplitudes between trials were analysed with Friedman's test and corrected Wilcoxon matched pairs test. The head movement amplitudes were significantly larger during masseter muscle pain trials compared with control. Jaw movement amplitudes did not differ significantly between any of the trials after corrected Wilcoxon tests. The ratio between head and jaw movement amplitudes was significantly larger during the first pain trial compared with control. Experimental masseter muscle pain in humans affected integrated jaw-neck movements by increasing the neck component during continuous jaw opening-closing tasks. The findings indicate that pain can alter the strategy for jaw-neck motor control, which further underlines the functional integration between the jaw and neck regions. This altered strategy may have consequences for development of musculoskeletal pain in the jaw and neck regions. © 2012 European Federation of International Association for the Study of Pain Chapters.

Cross-bridge kinetics of fast and slow fibres of cat jaw and limb muscles: correlations with myosin subunit composition.

PubMed

Hoh, Joseph F Y; Li, Zhao-Bo; Qin, Han; Hsu, Michael K H; Rossmanith, Gunther H

2007-01-01

Mechanical properties of the jaw-closing muscles of the cat are poorly understood. These muscles are known to differ in myosin and fibre type compositions from limb muscles. This work aims to correlate mechanical properties of single fibres in cat jaw and limb muscles with their myosin subunit compositions. The stiffness minimum frequency, f(min), which reflects isometric cross-bridge kinetics, was measured in Ca(2+)-activated glycerinated fast and slow fibres from cat jaw and limb muscles for temperatures ranging between 15 and 30 degrees C by mechanical perturbation analysis. At 15 degrees C, f(min) was 0.5 Hz for limb-slow fibres, 4-6 Hz for jaw-slow fibres, and 10-13 Hz for limb-fast and jaw-fast fibres. The activation energy for f(min) obtained from the slope of the Arrhenius plot for limb-slow fibres was 30-40% higher than values for the other three types of fibres. SDS-PAGE and western blotting using highly specific antibodies verified that limb-fast fibres contained IIA or IIX myosin heavy chain (MyHC). Jaw-fast fibres expressed masticatory MyHC while both jaw-fast and jaw-slow fibres expressed masticatory myosin light chains (MLCs). The nucleotide sequences of the 3' ends of the slow MyHC cDNAs isolated from cat masseter and soleus cDNA libraries showed identical coding and 3'-untranslated regions, suggesting that jaw-slow and limb-slow fibres express the same slow MyHC gene. We conclude that the isometric cross-bridge cycling kinetics of jaw-fast and limb-fast fibres detected by f(min) are indistinguishable in spite of differences in MyHC and light chain compositions. However, jaw-slow fibres, in which the same slow MyHCs are found in combination with MLCs of the jaw type, show enhanced cross-bridge cycling kinetics and reduced activation energy for cross-bridge detachment.

Volitional control of reflex cough

PubMed Central

Bolser, Donald C.; Davenport, Paul W.

2012-01-01

Multiple studies suggest a role for the cerebral cortex in the generation of reflex cough in awake humans. Reflex cough is preceded by detection of an urge to cough; strokes specifically within the cerebral cortex can affect parameters of reflex cough, and reflex cough can be voluntarily suppressed. However, it is not known to what extent healthy, awake humans can volitionally modulate the cough reflex, aside from suppression. The aims of this study were to determine whether conscious humans can volitionally modify their reflexive cough and, if so, to determine what parameters of the cough waveform and corresponding muscle activity can be modified. Twenty adults (18–40 yr, 4 men) volunteered for study participation and gave verbal and written informed consent. Participants were seated and outfitted with a facemask and pneumotacograph, and two surface EMG electrodes were positioned over expiratory muscles. Capsaicin (200 μM) was delivered via dosimeter and one-way (inspiratory) valve attached to a side port between the facemask and pneumotachograph. Cough airflow and surface EMG activity were recorded across tasks including 1) baseline, 2) small cough (cough smaller or softer than normal), 3) long cough (cough longer or louder than normal), and 4) not cough (alternative behavior). All participants coughed in response to 200 μM capsaicin and were able to modify the cough. Variables exhibiting changes include those related to the peak airflow during the expiratory phase. Results demonstrate that it is possible to volitionally modify cough motor output characteristics. PMID:22492938

Soleus and lateral gastrocnemius H-reflexes during standing with unstable footwear.

PubMed

Friesenbichler, Bernd; Lepers, Romuald; Maffiuletti, Nicola A

2015-05-01

Unstable footwear has been shown to increase lower extremity muscle activity, but the reflex response to perturbations induced by this intervention is unknown. Twenty healthy subjects stood in stable and unstable footwear conditions (presented randomly) while H-reflex amplitude and background muscle activity were measured in the soleus and lateral gastrocnemius (LG) muscles. Wearing unstable footwear resulted in larger H-reflexes (normalized to the maximal M-wave) for the LG (+12%; P = 0.025), but not for the soleus (+4%; P > 0.05). Background activity of both muscles was significantly higher in the unstable condition. The H-reflex facilitation observed with unstable footwear was unexpected, as challenging postural conditions usually result in reflex depression. Increased muscle activity, decreased presynaptic inhibition, and/or more forward postural position may have (over-)compensated the expected reflex depression. Differences between LG and soleus H-reflex modulation may be due to diverging motor unit recruitment thresholds. © 2015 Wiley Periodicals, Inc.

The reflex excitation of the soleus muscle of the decerebrate cat caused by vibration applied to its tendon

PubMed Central

Matthews, P. B. C.

1966-01-01

contractile tension per c/s increase in vibration frequency. 6. The primary afferent ending of the muscle spindle is considered to be the receptor whose excitation leads to the reflex response to vibration. The vibration reflex thus appears to be the well-known stretch reflex, elicited by a rather unusual form of stretching. The size of the vibration reflex and its variation with frequency are discussed in relation to the servo theory of muscular contraction. PMID:5921840

Carbachol injection into the pontine reticular formation depresses laryngeal muscle activities and airway reflexes in decerebrate cats.

PubMed

Adachi, Masaaki; Nonaka, Satoshi; Katada, Akihiro; Arakawa, Takuya; Ota, Ryo; Harada, Hirofumi; Takakusaki, Kaoru; Harabuchi, Yasuaki

2010-05-01

To understand the role of cholinoceptive, medial pontine reticular formation (mPRF) neurons in the control of upper airway, pharyngolaryngeal reflexes, we measured activities of intrinsic laryngeal muscles (posterior cricoarytenoid, PCA; thyroarytenoid, TA), diaphragm (DIA), genioglossus (GG) and a neck muscle (trapezius) in unanesthetized, decerebrated, spontaneously breathing cats with and without mPRF carbachol injections. The ethimoidal nerve was electrically stimulated to evoke sneezing, and the superior laryngeal nerve to evoke the laryngeal reflex, swallowing, and coughing. Carbachol reduced the amplitudes of the spontaneous electromyographic activities in the neck, TA, PCA, GG, and DIA to 7%, 30%, 54%, 45% and 71% of control, respectively, reduced the respiratory rate to 53% without changes in expiratory CO(2) concentration; the magnitude of the laryngeal reflex in the TA muscle to 56%; increased its latency by 13%; and reduced the probability of stimulus-induced sneezing, swallowing, and coughing to less than 40%. These changes lasted more than 1h. These data demonstrate that important upper airway reflexes are suppressed by increasing cholinergic neurotransmission in the mPRF. Because acetylcholine release in the mPRF changes in accordance with sleep-wake cycles, the present findings are relevant to the control of upper airway reflexes during various vigilance states. 2010 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

A rhythmic motor pattern activated by circumferential stretch in guinea-pig distal colon.

PubMed

Spencer, Nick J; Hennig, Grant W; Smith, Terence K

2002-12-01

Simultaneous intracellular recordings were made from pairs of circular muscle (CM) cells, at the oral and anal ends of a segment of guinea-pig distal colon, to investigate the neuronal mechanisms underlying faecal pellet propulsion. When a minimum degree of circumferential stretch was applied to sheet preparations of colon, recordings from CM cells revealed either no ongoing junction potentials, or alternatively, small potentials usually < 5 mV in amplitude. Maintained circumferential stretch applied to these preparations evoked an ongoing discharge of excitatory junction potentials (EJPs) at the oral recording site (range: 1-25 mV), which lasted for up to 6 h. The onset of each large oral EJP was time-locked with the onset of an inhibitory junction potential (IJP) at an anal recording electrode, located 2 cm from the oral recording. Similar results were obtained in isolated intact tube preparations of colon, when recordings were made immediately oral and anal of an artificial faecal pellet. The amplitudes of many large (> 5 mV) oral EJPs were linearly related to the amplitudes of anal IJPs occurring 20 mm apart. In the absence of an L-type Ca(2+) channel blocker, action potentials occurred on each large oral EJP. Synchronized discharges of stretch-activated EJPs and IJPs were preserved following pretreatment with capsaicin (10 microM), were unaffected by nifedipine (1 microM) and did not require the mucosa or submucous plexus. EJPs and IJPs were abolished by hexamethonium (300 microM) or tetrodotoxin (1 microM), but persisted in the presence of pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; 10 microM) or an NK(3) tachykinin receptor antagonist (Neurokinin A 4-10; 100 nM to 5 microM). In summary, maintained circumferential stretch of the distal colon activates a population of intrinsic mechanosensory neurons that generate repetitive firing of ascending excitatory and descending inhibitory pathways to CM. These mechanosensory neurons, which may be

A rhythmic motor pattern activated by circumferential stretch in guinea-pig distal colon

PubMed Central

Spencer, Nick J; Hennig, Grant W; Smith, Terence K

2002-01-01

Simultaneous intracellular recordings were made from pairs of circular muscle (CM) cells, at the oral and anal ends of a segment of guinea-pig distal colon, to investigate the neuronal mechanisms underlying faecal pellet propulsion. When a minimum degree of circumferential stretch was applied to sheet preparations of colon, recordings from CM cells revealed either no ongoing junction potentials, or alternatively, small potentials usually < 5 mV in amplitude. Maintained circumferential stretch applied to these preparations evoked an ongoing discharge of excitatory junction potentials (EJPs) at the oral recording site (range: 1-25 mV), which lasted for up to 6 h. The onset of each large oral EJP was time-locked with the onset of an inhibitory junction potential (IJP) at an anal recording electrode, located 2 cm from the oral recording. Similar results were obtained in isolated intact tube preparations of colon, when recordings were made immediately oral and anal of an artificial faecal pellet. The amplitudes of many large (> 5 mV) oral EJPs were linearly related to the amplitudes of anal IJPs occurring 20 mm apart. In the absence of an L-type Ca2+ channel blocker, action potentials occurred on each large oral EJP. Synchronized discharges of stretch-activated EJPs and IJPs were preserved following pretreatment with capsaicin (10 μm), were unaffected by nifedipine (1 μm) and did not require the mucosa or submucous plexus. EJPs and IJPs were abolished by hexamethonium (300 μm) or tetrodotoxin (1 μm), but persisted in the presence of pyridoxal phosphate-6-azophenyl-2′,4′-disulphonic acid (PPADS; 10 μm) or an NK3 tachykinin receptor antagonist (Neurokinin A 4-10; 100 nm to 5 μm). In summary, maintained circumferential stretch of the distal colon activates a population of intrinsic mechanosensory neurons that generate repetitive firing of ascending excitatory and descending inhibitory pathways to CM. These mechanosensory neurons, which may be interneurons, are

Evaluation of neural reflex activation as a mode of action for the acute respiratory effects of ozone.

PubMed

Prueitt, Robyn L; Goodman, Julie E

2016-09-01

Exposure to elevated levels of ozone has been associated with a variety of respiratory-related health endpoints in both epidemiology and controlled human exposure studies, including lung function decrements and airway inflammation. A mode of action (MoA) for these effects has not been established, but it has been proposed that they may occur through ozone-induced activation of neural reflexes. We critically reviewed experimental studies of ozone exposure and neural reflex activation and applied the International Programme on Chemical Safety (IPCS) mode-of-action/human relevance framework to evaluate the biological plausibility and human relevance of this proposed MoA. Based on the currently available experimental data, we found that the proposed MoA of neural reflex activation is biologically plausible for the endpoint of ozone-induced lung function decrements at high ozone exposures, but further studies are needed to fill important data gaps regarding the relevance of this MoA at lower exposures. A role for the proposed MoA in ozone-induced airway inflammation is less plausible, as the evidence is conflicting and is also of unclear relevance given the lack of studies conducted at lower exposures. The evidence suggests a different MoA for ozone-induced inflammation that may still be linked to the key events in the proposed MoA, such that neural reflex activation may have some degree of involvement in modulating ozone-induced neutrophil influx, even if it is not a direct role.

Pre-Activity and Post-Activity Stretching Perceptions and Practices in NCAA Division I Volleyball Programs

ERIC Educational Resources Information Center

Judge, Lawrence W.; Bodey, Kimberly J.; Bellar, David; Bottone, Adam; Wanless, Elizabeth

2010-01-01

The purpose of this study was to determine if NCAA Division I women's volleyball programs were in compliance with suggested current pre- and post-activity stretching protocols. Questionnaires were sent to NCAA division I women's volleyball programs in the United States. Fifty six coaches (23 males & 33 females) participated in the study. Some…

RefleX: X-ray absorption and reflection in active galactic nuclei for arbitrary geometries

NASA Astrophysics Data System (ADS)

Paltani, S.; Ricci, C.

2017-11-01

Reprocessed X-ray radiation carries important information about the structure and physical characteristics of the material surrounding the supermassive black hole (SMBH) in active galactic nuclei (AGN). We report here on a newly developed simulation platform, RefleX, which allows to reproduce absorption and reflection by quasi-arbitrary geometries. We show here the reliability of our approach by comparing the results of our simulations with existing spectral models such as pexrav, MYTorus and BNTorus. RefleX implements both Compton scattering on free electrons and Rayleigh scattering and Compton scattering on bound electrons. We show the effect of bound-electron corrections on a torus geometry simulated like in MYTorus. We release with this paper the RefleX executable, as well as RXTorus, a model that assumes absorption and reflection from a torus with a varying ratio of the minor to major axis of the torus. To allow major flexibility RXTorus is also distributed in three components: absorbed primary emission, scattered radiation and fluorescent lines. RXTorus is provided for different values of the abundance, and with (atomic configuration) or without (free-electron configuration) taking into account Rayleigh scattering and bound electrons. We apply the RXTorus model in both configurations on the XMM-Newton and NuSTAR spectrum of the Compton-thick AGN NGC 424 and find that the models are able to reproduce very well the observations, but that the assumption on the bound or free state of the electrons has significant consequences on the fit parameters. RefleX executable, user manual and example models are available at http://www.astro.unige.ch/reflex. A copy of the RefleX executable is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A31

Developmental axon stretch stimulates neuron growth while maintaining normal electrical activity, intracellular calcium flux, and somatic morphology

PubMed Central

Loverde, Joseph R.; Pfister, Bryan J.

2015-01-01

Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18% applied over 5 min. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25% strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury. PMID:26379492

Does spasticity contribute to walking dysfunction after stroke?

PubMed Central

Ada, L.; Vattanasilp, W.; O'Dwyer, N.; Crosbie, J.

1998-01-01

OBJECTIVES—Clinically, it is assumed that spasticity of the calf muscles interferes with walking after stroke. The aim was to examine this assumption by evaluating the contribution of spasticity in the gastrocnemius muscle to walking dysfunction in an ambulant stroke population several months after stroke.
METHODS—Fourteen stroke patients who were able to walk independently and 15 neurologically normal control subjects were recruited. Both resting and action stretch reflexes of the gastrocnemius muscle were investigated under conditions that simulated walking. Resting tonic stretch reflexes were measured to assess spasticity whereas action tonic stretch reflexes were measured to assess the possible contribution of spasticity to gait dysfunction.
RESULTS—Two thirds of the stroke patients exhibited resting tonic stretch reflexes which indicate spasticity, whereas none of the control subjects did. However, the stroke patients exhibited action tonic stretch reflexes that were of similar magnitude to the control subjects, suggesting that their reflex activity during walking was not different from that of control subjects. Furthermore, there was no evidence that the action stretch reflex in the stroke patients contributed a higher resistance to stretch than the control subjects.
CONCLUSIONS—Whereas most of the stroke patients exhibited spasticity when measured both clinically and physiologically, they did not exhibit an increase in resistance to dorsiflexion due to exaggerated action tonic stretch reflexes. It is concluded that it is unlikely that spasticity causes problems in walking after stroke in ambulant patients. Therefore, it seems inappropriate to routinely reduce or inhibit the reflex response to improve functional movement in stroke rehabilitation. Factors other than spasticity should be considered when analysing walking after stroke, so that appropriate treatment is provided to patients.

 PMID:9598679

Reconsidering reflexivity: introducing the case for intellectual entrepreneurship.

PubMed

Cutcliffe, John R

2003-01-01

In this article, the author reconsiders reflexivity and attempts to examine some unresolved issues by drawing particular attention to the relationship between reflexivity and certain related phenomena/processes: the researcher's a priori knowledge, values, beliefs; empathy within qualitative research; the presence and influence of the researcher's tacit knowledge, and May's "magic" in method. Given the limitations of some reflexive activity identified in this article, the author introduces the case for greater intellectual entrepreneurship within the context of qualitative research. He suggests that excessive emphasis on reflexive activity might inhibit intellectual entrepreneurship. Wherein intellectual entrepreneurship implies a conscious and deliberate attempt on the part of academics to explore the world of ideas boldly; to take more risks in theory development and to move away from being timid researchers.

Appraisal of jaw swellings in a Nigerian tertiary healthcare facility.

PubMed

Lasisi, Taye J; Adisa, Akinyele O; Olusanya, Adeola A

2013-02-01

The mandible and maxilla can be the site of myriads of lesions that may be categorized as neoplastic, cystic, reactive and infective or inflammatory. Literature reviewing jaw swellings in an amalgamated fashion are uncommon, probably because aetiologies for these swellings are varied. However, to appreciate their relative relationship, it is essential to evaluate the clinico-pathologic profile of jaw swellings. The aim of this appraisal is to describe the array of jaw swellings seen at our hospital from 1990 to 2011, to serve as a reference database. Biopsy records of all histologically diagnosed cases of jaw swellings seen at the department of Oral Pathology, University College Hospital between January 1990 and December 2011 were retrieved, coded and inputted into SPSS version 20. Data on prevalence, age, sex, site and histological diagnosis were analysed descriptively for each category of jaw swellings. All patients below 16 years were regarded as children. A total of 638 jaw swellings were recorded in the 22-year study period. The Non Odontogenic Tumours (NOT) were the commonest, accounting for 46.2% of all jaw swellings. Odontogenic Tumours (OT) formed 45% of all adult jaw swelling while it formed 25.2% in children and adolescents. Ameloblastoma was the commonest while the most common NOT was ossifying fibroma (OF). Chronic osteomyelitis of the jaws was about 6 times commoner in adult females than males and mostly involved the mandible. The most common malignant jaw swelling was Burkitts' lymphoma (BL) that was about 7 times more in children than adults. Osteogenic sarcoma was the most common malignancy in adults. Jaw swellings are extensively varied in types and pattern of occurrence. This study has categorized jaw swellings in a simple but comprehensive fashion to allow for easy referencing in local and international data acquisition and epidemiological comparison. Key words:Jaw swellings, odontogenic, Nigeria.

Asymmetric activation of motor cortex controlling human anterior digastric muscles during speech and target-directed jaw movements.

PubMed

Sowman, Paul F; Flavel, Stanley C; McShane, Christie L; Sakuma, Shigemitsu; Miles, Timothy S; Nordstrom, Michael A

2009-07-01

Like most of the cranial muscles involved in speech, the trigeminally innervated anterior digastric muscles are controlled by descending corticobulbar projections from the primary motor cortex (M1) of each hemisphere. We hypothesized that changes in corticobulbar M1 excitability during speech production would show a hemispheric asymmetry favoring the left side, which is the dominant hemisphere for language processing in most strongly right handed subjects. Fifteen volunteers aged 24.5+/-5.3 (SD) yr participated. All subjects were strongly right handed as reported by questionnaire. A surface electromyograph (EMG) was recorded bilaterally from digastrics and jaw movement detected by an accelerometer attached to a lower incisor. Focal transcranial magnetic stimulation (TMS) was used to assess corticomotor excitability of the digastric representation in M1 of both hemispheres during four tasks: 1) static isometric contraction of digastrics; 2) speaking a single word; 3) visually guided, nonspeech jaw movement that matched the jaw kinematics recorded during task 2; and 4) reciting a sentence. Background EMG was well matched in all tasks and jaw kinematics were similar around the time of the TMS pulse for tasks 2-4. TMS resting thresholds and digastric muscle-evoked potential (MEP) size during isometric contraction did not differ for TMS over left versus right M1. MEPs elicited by TMS over left, but not right M1 increased in size during speech and nonspeech jaw movement compared with isometric contraction. We conclude that left corticobulbar M1 is preferentially engaged for descending control of digastric muscles during speech and the performance of a rapid jaw movement to match a target kinematic profile.

Reno-Cerebral Reflex Activates the Renin-Angiotensin System, Promoting Oxidative Stress and Renal Damage After Ischemia-Reperfusion Injury.

PubMed

Cao, Wei; Li, Aiqing; Li, Jiawen; Wu, Chunyi; Cui, Shuang; Zhou, Zhanmei; Liu, Youhua; Wilcox, Christopher S; Hou, Fan Fan

2017-09-01

A kidney-brain interaction has been described in acute kidney injury, but the mechanisms are uncertain. Since we recently described a reno-cerebral reflex, we tested the hypothesis that renal ischemia-reperfusion injury (IRI) activates a sympathetic reflex that interlinks the renal and cerebral renin-angiotensin axis to promote oxidative stress and progression of the injury. Bilateral ischemia-reperfusion activated the intrarenal and cerebral, but not the circulating, renin-angiotensin system (RAS), increased sympathetic activity in the kidney and the cerebral sympathetic regulatory regions, and induced brain inflammation and kidney injury. Selective renal afferent denervation with capsaicin or renal denervation significantly attenuated IRI-induced activation of central RAS and brain inflammation. Central blockade of RAS or oxidative stress by intracerebroventricular (ICV) losartan or tempol reduced the renal ischemic injury score by 65% or 58%, respectively, and selective renal afferent denervation or reduction of sympathetic tone by ICV clonidine decreased the score by 42% or 52%, respectively (all p < 0.05). Ischemia-reperfusion-induced renal damage and dysfunction persisted after controlling blood pressure with hydralazine. This study uncovered a novel reflex pathway between ischemic kidney and the brain that sustains renal oxidative stress and local RAS activation to promote ongoing renal damage. These data suggest that the renal and cerebral renin-angiotensin axes are interlinked by a reno-cerebral sympathetic reflex that is activated by ischemia-reperfusion, which contributes to ischemia-reperfusion-induced brain inflammation and worsening of the acute renal injury. Antioxid. Redox Signal. 27, 415-432.

Biomechanical calculation of human TM joint loading with jaw opening.

PubMed

Kuboki, T; Takenami, Y; Maekawa, K; Shinoda, M; Yamashita, A; Clark, G T

2000-11-01

A three-dimensional, static mathematical calculation of the stomatognathic system was done to predict total temporomandibular joint (TMJ) loading at different levels of jaw opening. The model assumed that muscle forces acting on the mandible could be simulated by a combination of contractile components (CCs) and elastic components (ECs) and that static equilibrium existed within the body of the mandible. The model also imposed the constraint that any generated joint reaction force would act on the centre of the condyle. The results of the model demonstrated that under all conditions of opening and for all values of the elastic modulus selected, the forces between the TMJ condyle and the articular eminence were compressive in nature. The compressive force magnitude increased from 2.7 to 27.6 N incrementally as the jaw opened from 10 to 40 mm. Overall data in this study indicated that the TMJ tissues undergo low levels of compression at open positions up to 40 mm. Finally, the condition of trismus (increased jaw closing activation with opening) was simulated, the joint reaction force at 20 mm opening increased from 7.7 to 64.9 N with only a 20% activation of the closers.

Frequent jaw-face pain in chronic Whiplash-Associated Disorders.

PubMed

Häggman-Henrikson, Birgitta; Grönqvist, Johan; Eriksson, Per-Olof

2011-01-01

Chronic Whiplash-Associated Disorders (WAD) present with frequent pain in the neck, head and shoulder regions but the presence of frequent jaw-face pain is unclear. The aim of the study was to investigate the frequency of jaw-face pain, pain in other regions, and general symptoms in chronic WAD patients. Fifty whiplash-patients and 50 healthy age- and sex-matched controls were examined by questionnaire for pain in the jaw-face, pain in other regions and other symptoms. In contrast to healthy, a majority of the WAD patients (88%) reported frequent pain in the jaw-face, in addition to frequent pain in the neck (100%), shoulders (94%), head (90%) and back (72%). The WAD patients also reported stiffness and numbness in the jaw-face region, and frequent general symptoms such as balance problems, stress and sleep disturbances. The result suggests that frequent pain in the jaw-face can be part of the spectrum of symptoms in chronic WAD.The finding of self-reported numbness in the jaw-face indicates disturbed trigeminal nerve function and merits further investigation. We conclude that assessment of WAD should include pain in the jaw-face region. A multidisciplinary rehabilitation program including dentists, preferably specialized in the area of orofacial pain, should be advocated after whiplash injury.

Myofiber turnover is used to retrofit frog jaw muscles during metamorphosis.

PubMed

Alley, K E

1989-01-01

Metamorphic reorganization of the head in anuran amphibians entails abrupt restructuring of the jaw complex as larval feeding structures are transformed into their adult configurations. In this morphometric study, light microscopy wa used to analyze the larval maturation and metamorphic transfiguration of the adductor jaw muscles in the leopard frog (Rana pipiens). Larval jaw muscles, first established during embryogenesis, continue to grow by fiber addition until prometamorphosis, stage XII. Thereafter, fiber number remains stable but additional muscle growth continues by hypertrophy of the individual fibers until metamorphic climax. During metamorphic stages XIX-XXIII, a complete involution of all larval myofibers occurs. Simultaneously, within the same muscle beds, a second wave of myogenesis produces myoblasts which are the precursors of adult jaw myofibers. New muscle fibers continue to be added to these muscles well after the completion of metamorphosis; however, the total duration of the postmetamorphic myogenic period has not been defined. These observations provide clear evidence that the entir population of primary myofibers used in larval oral activity disappears from the adductor muscle beds and is replaced by a second wave of myogenesis commencing during climax. These findings indicate that the adductor jaw muscles are prepared for adult feeding by a complicated cellular process that retrofits existing muscle beds with a completely new complement of myofibers.

STRETCHING IMPACTS INFLAMMATION RESOLUTION IN CONNECTIVE TISSUE

PubMed Central

Berrueta, Lisbeth; Muskaj, Igla; Olenich, Sara; Butler, Taylor; Badger, Gary J.; Colas, Romain A.; Spite, Matthew; Serhan, Charles N.; Langevin, Helene M.

2016-01-01

Acute inflammation is accompanied from its outset by the release of specialized pro-resolving mediators (SPMs), including resolvins, that orchestrate the resolution of local inflammation. We showed earlier that, in rats with subcutaneous inflammation of the back induced by carrageenan, stretching for 10 minutes twice daily reduced inflammation and improved pain, two weeks after carrageenan injection. In this study, we hypothesized that stretching of connective tissue activates local pro-resolving mechanisms within the tissue in the acute phase of inflammation. In rats injected with carrageenan and randomized to stretch vs. no stretch for 48 hours, stretching reduced inflammatory lesion thickness and neutrophil count, and increased resolvin (RvD1) concentrations within lesions. Furthermore, subcutaneous resolvin injection mimicked the effect of stretching. In ex vivo experiments, stretching of connective tissue reduced the migration of neutrophils and increased tissue RvD1 concentration. These results demonstrate a direct mechanical impact of stretching on inflammation-regulation mechanisms within connective tissue. PMID:26588184

Bisphosphonate Therapy (and Osteonecrosis of the Jaw)

MedlinePlus

... or other invasive dental procedures, a phenomenon called osteonecrosis of the jaw (see Right and note area ... doctors agree that there is an association between osteonecrosis of the jaw and bisphosphonates, although the drugs ...

Electrocorticographic activity over sensorimotor cortex and motor function in awake behaving rats.

PubMed

Boulay, Chadwick B; Chen, Xiang Yang; Wolpaw, Jonathan R

2015-04-01

Sensorimotor cortex exerts both short-term and long-term control over the spinal reflex pathways that serve motor behaviors. Better understanding of this control could offer new possibilities for restoring function after central nervous system trauma or disease. We examined the impact of ongoing sensorimotor cortex (SMC) activity on the largely monosynaptic pathway of the H-reflex, the electrical analog of the spinal stretch reflex. In 41 awake adult rats, we measured soleus electromyographic (EMG) activity, the soleus H-reflex, and electrocorticographic activity over the contralateral SMC while rats were producing steady-state soleus EMG activity. Principal component analysis of electrocorticographic frequency spectra before H-reflex elicitation consistently revealed three frequency bands: μβ (5-30 Hz), low γ (γ1; 40-85 Hz), and high γ (γ2; 100-200 Hz). Ongoing (i.e., background) soleus EMG amplitude correlated negatively with μβ power and positively with γ1 power. In contrast, H-reflex size correlated positively with μβ power and negatively with γ1 power, but only when background soleus EMG amplitude was included in the linear model. These results support the hypothesis that increased SMC activation (indicated by decrease in μβ power and/or increase in γ1 power) simultaneously potentiates the H-reflex by exciting spinal motoneurons and suppresses it by decreasing the efficacy of the afferent input. They may help guide the development of new rehabilitation methods and of brain-computer interfaces that use SMC activity as a substitute for lost or impaired motor outputs. Copyright © 2015 the American Physiological Society.

Self-aligning fixture used in lathe chuck jaw refacing

NASA Technical Reports Server (NTRS)

Linn, C. C.

1965-01-01

Self-aligning tool positions and rigidly holds lathe chuck jaws for refacing and truing of the clamping surface. The jaws clamp the fixture in the manner of clamping a workpiece. The fixture can be modified to accommodate four-jawed checks.

Cyclic stretch induces cyclooxygenase-2 gene expression in vascular endothelial cells via activation of nuclear factor kappa-{beta}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Haige; Hiroi, Toyoko; Hansen, Baranda S.

2009-11-27

Vascular endothelial cells respond to biomechanical forces, such as cyclic stretch and shear stress, by altering gene expression. Since endothelial-derived prostanoids, such as prostacyclin and thromboxane A{sub 2}, are key mediators of endothelial function, we investigated the effects of cyclic stretch on the expression of genes in human umbilical vein endothelial cells controlling prostanoid synthesis: cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), prostacyclin synthase (PGIS) and thromboxane A{sub 2} synthase (TXAS). COX-2 and TXAS mRNAs were upregulated by cyclic stretch for 24 h. In contrast, PGIS mRNA was decreased and stretch had no effect on COX-1 mRNA expression. We further show that stretch-inducedmore » upregulation of COX-2 is mediated by activation of the NF-{kappa}{beta} signaling pathway.« less

Immediate Effects of Proprioceptive Neuromuscular Facilitation Stretching Programs Compared With Passive Stretching Programs for Hamstring Flexibility: A Critically Appraised Topic.

PubMed

Hill, Kristian J; Robinson, Kendall P; Cuchna, Jennifer W; Hoch, Matthew C

2017-11-01

Clinical Scenario: Increasing hamstring flexibility through clinical stretching interventions may be an effective means to prevent hamstring injuries. However the most effective method to increase hamstring flexibility has yet to be determined. For a healthy individual, are proprioceptive neuromuscular facilitation (PNF) stretching programs more effective in immediately improving hamstring flexibility when compared with static stretching programs? Summary of Key Findings: A thorough literature search returned 195 possible studies; 5 studies met the inclusion criteria and were included. Current evidence supports the use of PNF stretching or static stretching programs for increasing hamstring flexibility. However, neither program demonstrated superior effectiveness when examining immediate increases in hamstring flexibility. Clinical Bottom Line: There were consistent findings from multiple low-quality studies that indicate there is no difference in the immediate improvements in hamstring flexibility when comparing PNF stretching programs to static stretching programs in physically active adults. Strength of Recommendation: Grade B evidence exists that PNF and static stretching programs equally increase hamstring flexibility immediately following the stretching program.

Mitochondrial reactive oxygen species activate the slow force response to stretch in feline myocardium

PubMed Central

Caldiz, Claudia I; Garciarena, Carolina D; Dulce, Raúl A; Novaretto, Leonardo P; Yeves, Alejandra M; Ennis, Irene L; Cingolani, Horacio E; Chiappe de Cingolani, Gladys; Pérez, Néstor G

2007-01-01

When the length of the myocardium is increased, a biphasic response to stretch occurs involving an initial rapid increase in force followed by a delayed slow increase called the slow force response (SFR). Confirming previous findings involving angiotensin II in the SFR, it was blunted by AT1 receptor blockade (losartan). The SFR was accompanied by an increase in reactive oxygen species (ROS) of ∼30% and in intracellular Na+ concentration ([Na+]i) of ∼2.5 mmol l−1 over basal detected by H2DCFDA and SBFI fluorescence, respectively. Abolition of ROS by 2-mercapto-propionyl-glycine (MPG) and EUK8 suppressed the increase in [Na+]i and the SFR, which were also blunted by Na+/H+ exchanger (NHE-1) inhibition (HOE642). NADPH oxidase inhibition (apocynin or DPI) or blockade of the ATP-sensitive mitochondrial potassium channels (5HD or glybenclamide) suppressed both the SFR and the increase in [Na+]i after stretch, suggesting that endogenous angiotensin II activated NADPH oxidase leading to ROS release by the ATP-sensitive mitochondrial potassium channels, which promoted NHE-1 activation. Supporting the notion of ROS-mediated NHE-1 activation, stretch increased the ERK1/2 and p90rsk kinases phosphorylation, effect that was cancelled by losartan. In agreement, the SFR was cancelled by inhibiting the ERK1/2 signalling pathway with PD98059. Angiotensin II at a dose that mimics the SFR (1 nmol l−1) induced an increase in ·O2− production of ∼30–40% detected by lucigenin in cardiac slices, an effect that was blunted by losartan, MPG, apocynin, 5HD and glybenclamide. Taken together the data suggest a pivotal role of mitochondrial ROS in the genesis of the SFR to stretch. PMID:17823205

The relationships among jaw-muscle fiber architecture, jaw morphology, and feeding behavior in extant apes and modern humans.

PubMed

Taylor, Andrea B; Vinyard, Christopher J

2013-05-01

The jaw-closing muscles are responsible for generating many of the forces and movements associated with feeding. Muscle physiologic cross-sectional area (PCSA) and fiber length are two architectural parameters that heavily influence muscle function. While there have been numerous comparative studies of hominoid and hominin craniodental and mandibular morphology, little is known about hominoid jaw-muscle fiber architecture. We present novel data on masseter and temporalis internal muscle architecture for small- and large-bodied hominoids. Hominoid scaling patterns are evaluated and compared with representative New- (Cebus) and Old-World (Macaca) monkeys. Variation in hominoid jaw-muscle fiber architecture is related to both absolute size and allometry. PCSAs scale close to isometry relative to jaw length in anthropoids, but likely with positive allometry in hominoids. Thus, large-bodied apes may be capable of generating both absolutely and relatively greater muscle forces compared with smaller-bodied apes and monkeys. Compared with extant apes, modern humans exhibit a reduction in masseter PCSA relative to condyle-M1 length but retain relatively long fibers, suggesting humans may have sacrificed relative masseter muscle force during chewing without appreciably altering muscle excursion/contraction velocity. Lastly, craniometric estimates of PCSAs underestimate hominoid masseter and temporalis PCSAs by more than 50% in gorillas, and overestimate masseter PCSA by as much as 30% in humans. These findings underscore the difficulty of accurately estimating jaw-muscle fiber architecture from craniometric measures and suggest models of fossil hominin and hominoid bite forces will be improved by incorporating architectural data in estimating jaw-muscle forces. Copyright © 2013 Wiley Periodicals, Inc.

Stretch marks

MedlinePlus

Stretch marks can appear when there is rapid stretching of the skin. The marks appear as parallel ... often disappear after the cause of the skin stretching is gone. Avoiding rapid weight gain helps reduce ...

Jaw-Dropping: Functional Variation in the Digastric Muscle in Bats.

PubMed

Curtis, Abigail A; Santana, Sharlene E

2018-02-01

Diet and feeding behavior in mammals is strongly linked to the morphology of their feeding apparatus. Cranio-muscular morphology determines how wide, forcefully, and quickly the jaw can be opened or closed, which limits the size and material properties of the foods that a mammal can eat. Most studies of feeding performance in mammals have focused on skull form and jaw muscles involved in generating bite force, but few explore how jaw abduction is related to feeding performance. In this study, we explored how the morphology of the digastric muscle, the primary jaw abducting muscle in mammals, and its jaw lever mechanics are related to diet in morphologically diverse noctilionoid bats. Results showed that insectivorous bats have strong digastric muscles associated with proportionally long jaws, which suggests these species can open their jaws quickly and powerfully during prey capture and chewing. Short snouted frugivorous bats exhibit traits that would enable them to open their jaws proportionally wider to accommodate the large fruits that they commonly feed on. Our results support the hypothesis that digastric muscle and jaw morphology are correlated with diet in bats, and that our results may also apply to other groups of mammals. Anat Rec, 301:279-290, 2018. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Additively manufactured sub-periosteal jaw implants.

PubMed

Mommaerts, M Y

2017-07-01

Severe bone atrophy jeopardizes the success of endosseous implants. This technical note aims to present the innovative concept of additively manufactured sub-periosteal jaw implants (AMSJIs). Digital datasets of the patient's jaws and wax trial in occlusion are used to segment the bone and dental arches, for the design of a sub-periosteal frame and abutments in the optimal location related to the dental arch and for the design of the suprastructure. The implants and suprastructure are three-dimensionally (3D) printed in titanium alloy. The provisional denture is 3D-printed in polymer. AMSJIs offer an alternative approach for patients with extreme jaw bone atrophy. This report refers to the use of this technique for full maxillary rehabilitation, but partial defects in either jaw and extended post-resection defects may also be approached using the same technique. This customized, prosthesis-driven reverse-engineering approach avoids bone grafting and provides immediate functional restoration with one surgical session. Copyright © 2017 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Intravital imaging of mouse urothelium reveals activation of extracellular signal-regulated kinase by stretch-induced intravesical release of ATP.

PubMed

Sano, Takeshi; Kobayashi, Takashi; Negoro, Hiromitsu; Sengiku, Atsushi; Hiratsuka, Takuya; Kamioka, Yuji; Liou, Louis S; Ogawa, Osamu; Matsuda, Michiyuki

2016-11-01

To better understand the roles played by signaling molecules in the bladder, we established a protocol of intravital imaging of the bladder of mice expressing a Förster/fluorescence resonance energy transfer (FRET) biosensor for extracellular signal-regulated kinase (ERK), which plays critical roles not only in cell growth but also stress responses. With an upright two-photon excitation microscope and a vacuum-stabilized imaging window, cellular ERK activity was visualized in the whole bladder wall, from adventitia to urothelium. We found that bladder distention caused by elevated intravesical pressure (IVP) activated ERK in the urothelium, but not in the detrusor smooth muscle. When bladder distension was prevented, high IVP failed to activate ERK, suggesting that mechanical stretch, but not the high IVP, caused ERK activation. To delineate its molecular mechanism, the stretch-induced ERK activation was reproduced in an hTERT-immortalized human urothelial cell line (TRT-HU1) in vitro. We found that uniaxial stretch raised the ATP concentration in the culture medium and that inhibition of ATP signaling by apyrase or suramin suppressed the stretch-induced ERK activation in TRT-HU1 cells. In agreement with this in vitro observation, pretreatment with apyrase or suramin suppressed the high IVP-induced urothelial ERK activation in vivo. Thus, we propose that mechanical stretch induces intravesical secretion of ATP and thereby activates ERK in the urothelium. Our method of intravital imaging of the bladder of FRET biosensor-expressing mice should open a pathway for the future association of physiological stimuli with the activities of intracellular signaling networks. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Actinomyces osteomyelitis in bisphosphonate-related osteonecrosis of the jaw (BRONJ): the missing link?

PubMed

De Ceulaer, J; Tacconelli, E; Vandecasteele, S J

2014-11-01

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a rare complication of bisphosphonate treatment characterized by the development of exposed, necrotic bone in the jaw with inflammatory signs. The pathogenesis of BRONJ is not yet fully understood. This review analyzes the evidence supporting the hypothesis that BRONJ may be considered as a bisphosphonate-induced Actinomyces infection of the jaw according to the modified Koch's postulates. The main arguments relies on the following factors: (1) the high prevalence of isolation of Actinomyces from bone BRONJ lesions (73.2 % in retrospective series); (2) the similar pathological appearance of BRONJ and Actinomyces osteomyelitis in most studies, although BRONJ lesions without inflammation have been reported; (3) the high incidence of events that disrupt the normal mucosal barrier as a necessary trigger to develop BRONJ in bisphosphonate-exposed patients; (4) the predilection of bisphosphonate-induced osteonecrosis for the bones of the jaws; and (5) the favorable response of BRONJ on treatment that is active on Actinomyces. If BRONJ confirms to be a bisphosphonate-induced Actinomyces osteomyelitis of the jaw, this has major consequences for the prevention and treatment of this condition.

Researching Reflexively With Patients and Families: Two Studies Using Video-Reflexive Ethnography to Collaborate With Patients and Families in Patient Safety Research.

PubMed

Collier, Aileen; Wyer, Mary

2016-06-01

Patient safety research has to date offered few opportunities for patients and families to be actively involved in the research process. This article describes our collaboration with patients and families in two separate studies, involving end-of-life care and infection control in acute care. We used the collaborative methodology of video-reflexive ethnography, which has been primarily used with clinicians, to involve patients and families as active participants and collaborators in our research. The purpose of this article is to share our experiences and findings that iterative researcher reflexivity in the field was critical to the progress and success of each study. We present and analyze the complexities of reflexivity-in-the-field through a framework of multilayered reflexivity. We share our lessons here for other researchers seeking to actively involve patients and families in patient safety research using collaborative visual methods. © The Author(s) 2015.

The virtual craniofacial patient: 3D jaw modeling and animation.

PubMed

Enciso, Reyes; Memon, Ahmed; Fidaleo, Douglas A; Neumann, Ulrich; Mah, James

2003-01-01

In this paper, we present new developments in the area of 3D human jaw modeling and animation. CT (Computed Tomography) scans have traditionally been used to evaluate patients with dental implants, assess tumors, cysts, fractures and surgical procedures. More recently this data has been utilized to generate models. Researchers have reported semi-automatic techniques to segment and model the human jaw from CT images and manually segment the jaw from MRI images. Recently opto-electronic and ultrasonic-based systems (JMA from Zebris) have been developed to record mandibular position and movement. In this research project we introduce: (1) automatic patient-specific three-dimensional jaw modeling from CT data and (2) three-dimensional jaw motion simulation using jaw tracking data from the JMA system (Zebris).

CURRENT CONCEPTS IN MUSCLE STRETCHING FOR EXERCISE AND REHABILITATION

PubMed Central

2012-01-01

Stretching is a common activity used by athletes, older adults, rehabilitation patients, and anyone participating in a fitness program. While the benefits of stretching are known, controversy remains about the best type of stretching for a particular goal or outcome. The purpose of this clinical commentary is to discuss the current concepts of muscle stretching interventions and summarize the evidence related to stretching as used in both exercise and rehabilitation. PMID:22319684

Hamstring Stiffness Returns More Rapidly After Static Stretching Than Range of Motion, Stretch Tolerance, and Isometric Peak Torque.

PubMed

Hatano, Genki; Suzuki, Shigeyuki; Matsuo, Shingo; Kataura, Satoshi; Yokoi, Kazuaki; Fukaya, Taizan; Fujiwara, Mitsuhiro; Asai, Yuji; Iwata, Masahiro

2017-12-18

Hamstring injuries are common, and lack of hamstring flexibility may predispose to injury. Static stretching increases range of motion (ROM) but also results in reduced muscle strength after stretching. The effects of stretching on the hamstring muscles and the duration of these effects remain unclear. To determine the effects of static stretching on the hamstrings and the duration of these effects. Randomized crossover study. University laboratory. Twenty-four healthy volunteers. We measured the torque-angle relationship (ROM, passive torque (PT) at the onset of pain, and passive stiffness) and isometric muscle force using an isokinetic dynamometer. After a 60-minute rest, the ROM of the dynamometer was set at maximum tolerable intensity; this position was maintained for 300 seconds while static passive torque (SPT) was measured continuously. We remeasured the torque-angle relationship and isometric muscle force after rest periods of 10, 20, and 30 minutes. Change in SPT during stretching; changes in ROM, PT at the onset of pain, passive stiffness, and isometric muscle force before stretching compared with 10, 20, and 30 minutes after stretching. SPT decreased significantly during stretching. Passive stiffness decreased significantly 10 and 20 minutes after stretching, but there was no significant pre- vs. post-stretching difference after 30 minutes. PT at the onset of pain and ROM increased significantly after stretching at all rest intervals, while isometric muscle force decreased significantly after all rest intervals. The effect of static stretching on passive stiffness of the hamstrings was not maintained as long as the changes in ROM, stretch tolerance, and isometric muscle force. Therefore, frequent stretching is necessary to improve the viscoelasticity of the muscle-tendon unit. Muscle force was decreased for 30 minutes after stretching; this should be considered prior to activities requiring maximal muscle strength.

Plasma endotoxin activity in Eastern grey kangaroos (Macropus giganteus) with lumpy jaw disease

PubMed Central

SOTOHIRA, Yukari; SUZUKI, Kazuyuki; OTSUKA, Marina; TSUCHIYA, Masakazu; SHIMAMORI, Toshio; NISHI, Yasunobu; TSUKANO, Kenji; ASAKAWA, Mitsuhiko

2017-01-01

Progressive pyogranulomatous osteomyelitis involving the mandible or maxilla of captive macropods, referred to as “Lumpy jaw disease (LJD)”, is one of the most significant causes of illness and death in captive macropods. The aim of the present study was to evaluate the relationship between the severity of LJD and plasma endotoxin activity in kangaroos. Plasma samples obtained from moderate (n=24) and severe LJD (n=12), and healthy kangaroos (n=46), were diluted 1:20 in endotoxin-free water and heated to 80°C for 10 min. Plasma endotoxin activity was measured using the Limulus amebocyte lysate (LAL)-kinetic turbidimetric (KT) assay. Plasma endotoxin activity was higher in kangaroos with severe LJD (0.199 ± 0.157 EU/ml) than in those with moderate LJD (0.051 ± 0.012 EU/ml, P<0.001) and healthy controls (0.057 ± 0.028 EU/ml, P<0.001). Our results suggest that the severity of LJD in captive macropods may be related to the plasma endotoxin activity. PMID:28484148

Plasma endotoxin activity in Eastern grey kangaroos (Macropus giganteus) with lumpy jaw disease.

PubMed

Sotohira, Yukari; Suzuki, Kazuyuki; Otsuka, Marina; Tsuchiya, Masakazu; Shimamori, Toshio; Nishi, Yasunobu; Tsukano, Kenji; Asakawa, Mitsuhiko

2017-06-29

Progressive pyogranulomatous osteomyelitis involving the mandible or maxilla of captive macropods, referred to as "Lumpy jaw disease (LJD)", is one of the most significant causes of illness and death in captive macropods. The aim of the present study was to evaluate the relationship between the severity of LJD and plasma endotoxin activity in kangaroos. Plasma samples obtained from moderate (n=24) and severe LJD (n=12), and healthy kangaroos (n=46), were diluted 1:20 in endotoxin-free water and heated to 80°C for 10 min. Plasma endotoxin activity was measured using the Limulus amebocyte lysate (LAL)-kinetic turbidimetric (KT) assay. Plasma endotoxin activity was higher in kangaroos with severe LJD (0.199 ± 0.157 EU/ml) than in those with moderate LJD (0.051 ± 0.012 EU/ml, P<0.001) and healthy controls (0.057 ± 0.028 EU/ml, P<0.001). Our results suggest that the severity of LJD in captive macropods may be related to the plasma endotoxin activity.

Increased excitability of spinal pain reflexes and altered frequency-dependent modulation in the dopamine D3-receptor knockout mouse.

PubMed

Keeler, Benjamin E; Baran, Christine A; Brewer, Kori L; Clemens, Stefan

2012-12-01

Frequency-dependent modulation and dopamine (DA) receptors strongly modulate neural circuits in the spinal cord. Of the five known DA receptor subtypes, the D3 receptor has the highest affinity to DA, and D3-mediated actions are mainly inhibitory. Using an animal model of spinal sensorimotor dysfunction, the D3 receptor knockout mouse (D3KO), we investigated the physiological consequences of D3 receptor dysfunction on pain-associated signaling pathways in the spinal cord, the initial integration site for the processing of pain signaling. In the D3KO spinal cord, inhibitory actions of DA on the proprioceptive monosynaptic stretch reflex are converted from depression to facilitation, but its effects on longer-latency and pain-associated reflex responses and the effects of FM have not been studied. Using behavioral approaches in vivo, we found that D3KO animals exhibit reduced paw withdrawal latencies to thermal pain stimulation (Hargreaves' test) over wild type (WT) controls. Electrophysiological and pharmacological approaches in the isolated spinal cord in vitro showed that constant current stimulation of dorsal roots at a pain-associated frequency was associated with a significant reduction in the frequency-dependent modulation of longer-latency reflex (LLRs) responses but not monosynaptic stretch reflexes (MSRs) in D3KO. Application of the D1 and D2 receptor agonists and the voltage-gated calcium-channel ligand, pregabalin, but not DA, was able to restore the frequency-dependent modulation of the LLR in D3KO to WT levels. Thus we demonstrate that nociception-associated LLRs and proprioceptive MSRs are differentially modulated by frequency, dopaminergics and the Ca(2+) channel ligand, pregabalin. Our data suggest a role for the DA D3 receptor in pain modulation and identify the D3KO as a possible model for increased nociception. Copyright © 2012 Elsevier Inc. All rights reserved.

A mechanical stretch induces contractile activation in unstimulated developing rat skeletal muscle in vitro

PubMed Central

Mutungi, Gabriel; Edman, K A P; Ranatunga, K W

2003-01-01

The effects of a stretch-release cycle (≈25 % of the resting muscle fibre length, Lo) on both tension and [Ca2+]i in small, unstimulated, intact muscle fibre bundles isolated from adult and neonatal rats were investigated at 20 °C. The results show that the effects of the length change depended on the age of the rats. Thus, the length change produced three effects in the neonatal rat muscle fibre bundles, but only a single effect in the adult ones. In the neonatal fibre bundles, the length change led to an increase in resting muscle tension and to a transient increase in [Ca2+]i. The stretch-release cycle was then followed by a twitch-like tension response. In the adult fibre bundles, only the increase in resting tension was seen and both the transient increase in [Ca2+]i and the stretch-induced twitch-like tension response were absent. The amplitude of the twitch-like tension response was affected by both 2,3-butanedione monoxime and sarcomere length in the same manner as active twitch tension, suggesting that it arose from actively cycling crossbridges. It was also reversibly abolished by 25 mM K+, 1 μM tetrodotoxin and 1.5 mM lidocaine (lignocaine), and was significantly depressed (P < 0.001) by lowering [Ca2+]o. These findings suggest that a rapid stretch in neonatal rats induces a propagated impulse that leads to an increase in [Ca2+]i, and that abolishing the action potential abolishes the stretch-induced twitch-like tension response. In 5- to 7-day-old rats, the twitch-like tension response was ≈50 % of the isometric twitch. It then decreased progressively with age and was virtually absent by the time the rats were 21 days old. Interestingly, this is the same period over which rat muscles differentiate from their neonatal to their adult types. PMID:12813148

Patterning of somatosympathetic reflexes

NASA Technical Reports Server (NTRS)

Kerman, I. A.; Yates, B. J.

1999-01-01

In a previous study, we reported that vestibular nerve stimulation in the cat elicits a specific pattern of sympathetic nerve activation, such that responses are particularly large in the renal nerve. This patterning of vestibulosympathetic reflexes was the same in anesthetized and decerebrate preparations. In the present study, we report that inputs from skin and muscle also elicit a specific patterning of sympathetic outflow, which is distinct from that produced by vestibular stimulation. Renal, superior mesenteric, and lumbar colonic nerves respond most strongly to forelimb and hindlimb nerve stimulation (approximately 60% of maximal nerve activation), whereas external carotid and hypogastric nerves were least sensitive to these inputs (approximately 20% of maximal nerve activation). In contrast to vestibulosympathetic reflexes, the expression of responses to skin and muscle afferent activation differs in decerebrate and anesthetized animals. In baroreceptor-intact animals, somatosympathetic responses were strongly attenuated (to <20% of control in every nerve) by increasing blood pressure levels to >150 mmHg. These findings demonstrate that different types of somatic inputs elicit specific patterns of sympathetic nerve activation, presumably generated through distinct neural circuits.

Morphometric assessment of pterosaur jaw disparity

NASA Astrophysics Data System (ADS)

Navarro, Charlie A.; Martin-Silverstone, Elizabeth; Stubbs, Thomas L.

2018-04-01

Pterosaurs were a successful group of Mesozoic flying reptiles. They were the first vertebrate group to achieve powered flight and varied enormously in morphology and ecology, occupying a variety of niches and developing specialized feeding strategies. Ecomorphological principles suggest this variation should be reflected by great morphological diversity in the lower jaw, given that the mandible served as the primary apparatus for prey acquisition. Here we present the first study of mandibular shape disparity in pterosaurs and aim to characterize major aspects of variation. We use a combination of geometric morphometric approaches, incorporating both outline analysis using elliptical Fourier analysis and semi-landmark approaches. Our results show that morphological convergence is prevalent and many pterosaurs, belonging to diverse dietary groups and subclades, overlap in morphospace and possessed relatively simple `rod-shaped' jaws. There is no clear trend of size distributions in pterosaur mandibular morphospace, and larger forms are widely distributed. Additionally, there is limited functional signal within pterosaur lower jaw morphospace. Instead, the development of a large anterior ventral crest represents the major component of disparity. This suggests that a socio-sexual trait was a key driver for innovation in pterosaur lower jaw shape.

Morphometric assessment of pterosaur jaw disparity.

PubMed

Navarro, Charlie A; Martin-Silverstone, Elizabeth; Stubbs, Thomas L

2018-04-01

Pterosaurs were a successful group of Mesozoic flying reptiles. They were the first vertebrate group to achieve powered flight and varied enormously in morphology and ecology, occupying a variety of niches and developing specialized feeding strategies. Ecomorphological principles suggest this variation should be reflected by great morphological diversity in the lower jaw, given that the mandible served as the primary apparatus for prey acquisition. Here we present the first study of mandibular shape disparity in pterosaurs and aim to characterize major aspects of variation. We use a combination of geometric morphometric approaches, incorporating both outline analysis using elliptical Fourier analysis and semi-landmark approaches. Our results show that morphological convergence is prevalent and many pterosaurs, belonging to diverse dietary groups and subclades, overlap in morphospace and possessed relatively simple 'rod-shaped' jaws. There is no clear trend of size distributions in pterosaur mandibular morphospace, and larger forms are widely distributed. Additionally, there is limited functional signal within pterosaur lower jaw morphospace. Instead, the development of a large anterior ventral crest represents the major component of disparity. This suggests that a socio-sexual trait was a key driver for innovation in pterosaur lower jaw shape.

Morphometric assessment of pterosaur jaw disparity

PubMed Central

Navarro, Charlie A.; Martin-Silverstone, Elizabeth

2018-01-01

Pterosaurs were a successful group of Mesozoic flying reptiles. They were the first vertebrate group to achieve powered flight and varied enormously in morphology and ecology, occupying a variety of niches and developing specialized feeding strategies. Ecomorphological principles suggest this variation should be reflected by great morphological diversity in the lower jaw, given that the mandible served as the primary apparatus for prey acquisition. Here we present the first study of mandibular shape disparity in pterosaurs and aim to characterize major aspects of variation. We use a combination of geometric morphometric approaches, incorporating both outline analysis using elliptical Fourier analysis and semi-landmark approaches. Our results show that morphological convergence is prevalent and many pterosaurs, belonging to diverse dietary groups and subclades, overlap in morphospace and possessed relatively simple ‘rod-shaped’ jaws. There is no clear trend of size distributions in pterosaur mandibular morphospace, and larger forms are widely distributed. Additionally, there is limited functional signal within pterosaur lower jaw morphospace. Instead, the development of a large anterior ventral crest represents the major component of disparity. This suggests that a socio-sexual trait was a key driver for innovation in pterosaur lower jaw shape. PMID:29765665

History-dependence of muscle slack length following contraction and stretch in the human vastus lateralis.

PubMed

Stubbs, Peter W; Walsh, Lee D; D'Souza, Arkiev; Héroux, Martin E; Bolsterlee, Bart; Gandevia, Simon C; Herbert, Robert D

2018-06-01

In reduced muscle preparations, the slack length and passive stiffness of muscle fibres have been shown to be influenced by previous muscle contraction or stretch. In human muscles, such behaviours have been inferred from measures of muscle force, joint stiffness and reflex magnitudes and latencies. Using ultrasound imaging, we directly observed that isometric contraction of the vastus lateralis muscle at short lengths reduces the slack lengths of the muscle-tendon unit and muscle fascicles. The effect is apparent 60 s after the contraction. These observations imply that muscle contraction at short lengths causes the formation of bonds which reduce the effective length of structures that generate passive tension in muscles. In reduced muscle preparations, stretch and muscle contraction change the properties of relaxed muscle fibres. In humans, effects of stretch and contraction on properties of relaxed muscles have been inferred from measurements of time taken to develop force, joint stiffness and reflex latencies. The current study used ultrasound imaging to directly observe the effects of stretch and contraction on muscle-tendon slack length and fascicle slack length of the human vastus lateralis muscle in vivo. The muscle was conditioned by (a) strong isometric contractions at long muscle-tendon lengths, (b) strong isometric contractions at short muscle-tendon lengths, (c) weak isometric contractions at long muscle-tendon lengths and (d) slow stretches. One minute after conditioning, ultrasound images were acquired from the relaxed muscle as it was slowly lengthened through its physiological range. The ultrasound image sequences were used to identify muscle-tendon slack angles and fascicle slack lengths. Contraction at short muscle-tendon lengths caused a mean 13.5 degree (95% CI 11.8-15.0 degree) shift in the muscle-tendon slack angle towards shorter muscle-tendon lengths, and a mean 5 mm (95% CI 2-8 mm) reduction in fascicle slack length, compared to the

Modulation of H-Reflex Depression with Paired-Pulse Stimulation in Healthy Active Humans.

PubMed

Oza, Preeti D; Dudley-Javoroski, Shauna; Shields, Richard K

2017-01-01

Depression of the Hoffman reflex (H-reflex) is used to examine spinal control mechanisms during exercise, fatigue, and vibration and in response to training. H-reflex depression protocols frequently use trains of stimuli; this is time-consuming and prevents instantaneous assessment of motor neuronal excitability. The purpose of this study was to determine if paired-pulse H-reflex depression is reproducible and whether paired-pulse stimulation adequately estimates the depression induced by the more traditional ten-pulse train. H-reflexes were elicited via ten-pulse trains at 0.1, 0.2, 1, 2, and 5 Hz in ten neurologically intact individuals on two separate days. We measured the depression elicited by the second pulse (H2) and the mean depression elicited by pulses 2-10 (Hmean). H2 was consistent at all frequencies on both days ( r 2 = 0.97, p < 0.05, and ICC (3,1) = 0.81). H2 did not differ from Hmean ( p > 0.05). The results indicate that paired-pulse H-reflex depression has high between-day reliability and yields depression estimates that are comparable to those obtained via ten-pulse trains. Paired-pulse H-reflex depression may be especially useful for studies that require rapid assessment of motor neuronal excitability, such as during exercise, fatigue, and vibration, or to establish recovery curves following inhibition.

Introduction to the JAWS Program

NASA Technical Reports Server (NTRS)

Mccarthy, John

1987-01-01

The JAWS Project is the Joint Airport Weather Studies project conceived in 1980 jointly between the National Center for Atmospheric Research and the Univ. of Chicago. The objectives of the program are threefold: (1) Basic scientific characterization of the microbursts and the statistics of microbursts occurrence; (2) Detection and warning, using the Low Level Wind Shear Alert System (LLWSAS) operation and performance; and (3) Doppler radar and airborne systems. These goals and the operation of the JAWS system in general are discussed in detail.

The evolutionary origin of jaw yaw in mammals

PubMed Central

Grossnickle, David M.

2017-01-01

Theria comprises all but three living mammalian genera and is one of the most ecologically pervasive clades on Earth. Yet, the origin and early history of therians and their close relatives (i.e., cladotherians) remains surprisingly enigmatic. A critical biological function that can be compared among early mammal groups is mastication. Morphometrics and modeling analyses of the jaws of Mesozoic mammals indicate that cladotherians evolved musculoskeletal anatomies that increase mechanical advantage during jaw rotation around a dorsoventrally-oriented axis (i.e., yaw) while decreasing the mechanical advantage of jaw rotation around a mediolaterally-oriented axis (i.e., pitch). These changes parallel molar transformations in early cladotherians that indicate their chewing cycles included significant transverse movement, likely produced via yaw rotation. Thus, I hypothesize that cladotherian molar morphologies and musculoskeletal jaw anatomies evolved concurrently with increased yaw rotation of the jaw during chewing cycles. The increased transverse movement resulting from yaw rotation may have been a crucial evolutionary prerequisite for the functionally versatile tribosphenic molar morphology, which underlies the molars of all therians and is retained by many extant clades. PMID:28322334

Being reflexive in qualitative grounded theory: discussion and application of a model of reflexivity.

PubMed

Engward, Hilary; Davis, Geraldine

2015-07-01

A discussion of the meaning of reflexivity in research with the presentation of examples of how a model of reflexivity was used in a grounded theory research project. Reflexivity requires the researcher to make transparent the decisions they make in the research process and is therefore important in developing quality in nursing research. The importance of being reflexive is highlighted in the literature in relation to nursing research, however, practical guidance as to how to go about doing research reflexively is not always clearly articulated. This is a discussion paper. The concept of reflexivity in research is explored using the Alvesson and Skoldberg model of reflexivity and practical examples of how a researcher developed reflexivity in a grounded theory project are presented. Nurse researchers are encouraged to explore and apply the concept of reflexivity in their research practices to develop transparency in the research process and to increase robustness in their research. The Alvesson and Skoldberg model is of value in applying reflexivity in qualitative nursing research, particularly in grounded theory research. Being reflexive requires the researcher to be completely open about decisions that are made in the research process. The Alvesson and Skolberg model of reflexivity is a useful model that can enhance reflexivity in the research process. It can be a useful practical tool to develop reflexivity in grounded theory research. © 2015 John Wiley & Sons Ltd.

Cessation of cyclic stretch induces atrophy of C2C12 myotubes.

PubMed

Soltow, Quinlyn A; Zeanah, Elizabeth H; Lira, Vitor A; Criswell, David S

2013-05-03

Cyclic stretch of differentiated myotubes mimics the loading pattern of mature skeletal muscle. We tested a cell culture model of disuse atrophy by the cessation of repetitive bouts of cyclic stretch in differentiated C2C12 myotubes. Myotubes were subjected to cyclic strain (12%, 0.7 Hz, 1 h/d) on collagen-I-coated Bioflex plates using a computer-controlled vacuum stretch apparatus (Flexcell Int.) for 2 (2dSTR) or 5 (5dSTR) consecutive days. Control cultures were maintained in the Bioflex plates without cyclic stretch for 2d or 5d. Additionally, some cultures were stretched for 2 d followed by cessation of stretch for 3d (2dSTR3dCES). Cyclic stretching (5dSTR) increased myotube diameter and overall myotube area by ~2-fold (P<0.05) compared to non-stretched controls, while cessation of stretch (2dSTR3dCES) resulted in ~80% smaller myotubes than 5dSTR cells, and 40-50% smaller than non-stretched controls (P<0.05). Further, the calpain-dependent cleavage products of αII-spectrin (150 kDa) and talin increased (3.5-fold and 2.2-fold, respectively; P<0.05) in 2dSTR3dCES myotubes, compared to non-stretched controls. The 1h cyclic stretching protocol acutely increased the phosphorylation of Akt (+4.5-fold; P<0.05) and its downstream targets, FOXO3a (+4.2-fold; P<0.05) and GSK-3β (+1.8-fold; P<0.05), which returned to baseline by 48 h after cessation of stretch. Additionally, nitric oxide production increased during stretch and co-treatment with the NOS inhibitor, l-NAME, inhibited the effects of stretch and cessation of stretch. We conclude that cessation of cyclic stretching causes myotube atrophy by activating calpains and decreasing activation of Akt. Stretch-induced myotube growth, as well as activation of atrophy signaling with cessation of stretch, are dependent on NOS activity. Copyright © 2013 Elsevier Inc. All rights reserved.

Stretched Loops

NASA Image and Video Library

2017-03-16

When an active region rotated over to the edge of the sun, it presented us with a nice profile view of its elongated loops stretching and swaying above it (Mar. 8-9, 2017). These loops are actually charged particles (made visible in extreme ultraviolet light) swirling along the magnetic field lines of the active region. The video covers about 30 hours of activity. Also of note is a darker twisting mass of plasma to the left of the active region being pulled and spun about by magnetic forces. Video is available at http://photojournal.jpl.nasa.gov/catalog/PIA21562

Multiple developmental mechanisms regulate species-specific jaw size

PubMed Central

Fish, Jennifer L.; Sklar, Rachel S.; Woronowicz, Katherine C.; Schneider, Richard A.

2014-01-01

Variation in jaw size during evolution has been crucial for the adaptive radiation of vertebrates, yet variation in jaw size during development is often associated with disease. To test the hypothesis that early developmental events regulating neural crest (NC) progenitors contribute to species-specific differences in size, we investigated mechanisms through which two avian species, duck and quail, achieve their remarkably different jaw size. At early stages, duck exhibit an anterior shift in brain regionalization yielding a shorter, broader, midbrain. We find no significant difference in the total number of pre-migratory NC; however, duck concentrate their pre-migratory NC in the midbrain, which contributes to an increase in size of the post-migratory NC population allocated to the mandibular arch. Subsequent differences in proliferation lead to a progressive increase in size of the duck mandibular arch relative to that of quail. To test the role of pre-migratory NC progenitor number in regulating jaw size, we reduced and augmented NC progenitors. In contrast to previous reports of regeneration by NC precursors, we find that neural fold extirpation results in a loss of NC precursors. Despite this reduction in their numbers, post-migratory NC progenitors compensate, producing a symmetric and normal-sized jaw. Our results suggest that evolutionary modification of multiple aspects of NC cell biology, including NC allocation within the jaw primordia and NC-mediated proliferation, have been important to the evolution of jaw size. Furthermore, our finding of NC post-migratory compensatory mechanisms potentially extends the developmental time frame for treatments of disease or injury associated with NC progenitor loss. PMID:24449843

Stretching & Flexibility: An Interactive Encyclopedia of Stretching. [CD-ROM].

ERIC Educational Resources Information Center

2002

This CD-ROM offers 140 different stretches in full-motion video sequences. It focuses on the proper techniques for overall physical fitness, injury prevention and rehabilitation, and 23 different sports (e.g., golf, running, soccer, skiing, climbing, football, and baseball). Topics include stretching for sports; stretching awareness and education…

The effects of ramp stretches on active contractions in intact mammalian fast and slow muscle fibres.

PubMed

Mutungi, G; Ranatunga, K W

2001-01-01

The effects of a ramp stretch (amplitude <6% muscle fibre length (L0), speed < 13L0 s(-1)) on twitch tension and twitch tension re-development were examined in intact mammalian (rat) fast and slow muscle fibre bundles. The experiments were done in vitro at 20 degrees C and at an initial sarcomere length of 2.68 microm. In both fibre types, a stretch applied during the rising phase of the twitch response (including the time of stimulation) increased the re-developed twitch tension (15-35%). A stretch applied before the stimulus had little or no effect on the twitch myogram in fast muscle fibres, but it increased the twitch tension (approximately 5%) in slow muscle fibres. A similar stretch had little or no effect on tetanic tension in either muscle fibre type. In general, the results indicate that the contractile-activation mechanism may be stretch sensitive and this is particularly pronounced in slow muscle fibres. Recorded at a high sampling rate and examined at an appropriate time scale, the transitory tension response to a stretch rose in at least two phases; an initial rapid tension rise to a break (break point tension, P1a) followed by a slower tension rise (apparent P2a) to a peak reached at the end of the stretch. Plotted against stretch velocity, P1a tension increased in direct proportion to stretch velocity (viscous-like) whereas, P2a tension (calculated as peak tension minus P1a tension) increased with stretch velocity to a plateau (visco-elastic). Examined at the peak of a twitch, P1a tension had a slope (viscosity coefficient) of 1.8 kN m(-2) per L0 s(-1) in fast fibres and 4.7 kN m(-2) per L0 s(-1) in slow muscle fibres. In the same preparations, P2a tension had a relaxation time of 8 ms in the fast muscle fibres and 25 ms in the slow muscle fibres. The amplitudes of both tension components scaled with the instantaneous twitch tension in qualitatively the same way as the instantaneous fibre stiffness. These fast/slow fibre type differences probably

Jaw-muscle fiber architecture in tufted capuchins favors generating relatively large muscle forces without compromising jaw gape.

PubMed

Taylor, Andrea B; Vinyard, Christopher J

2009-12-01

Tufted capuchins (sensu lato) are renowned for their dietary flexibility and capacity to exploit hard and tough objects. Cebus apella differs from other capuchins in displaying a suite of craniodental features that have been functionally and adaptively linked to their feeding behavior, particularly the generation and dissipation of relatively large jaw forces. We compared fiber architecture of the masseter and temporalis muscles between C. apella (n=12) and two "untufted" capuchins (C. capucinus, n=3; C. albifrons, n=5). These three species share broadly similar diets, but tufted capuchins occasionally exploit mechanically challenging tissues. We tested the hypothesis that tufted capuchins exhibit architectural properties of their jaw muscles that facilitate relatively large forces including relatively greater physiologic cross-sectional areas (PCSA), more pinnate fibers, and lower ratios of mass to tetanic tension (Mass/P(0)). Results show some evidence supporting these predictions, as C. apella has relatively greater superficial masseter and temporalis PCSAs, significantly so only for the temporalis following Bonferroni adjustment. Capuchins did not differ in pinnation angle or Mass/P(0). As an architectural trade-off between maximizing muscle force and muscle excursion/contraction velocity, we also tested the hypothesis that C. apella exhibits relatively shorter muscle fibers. Contrary to our prediction, there are no significant differences in relative fiber lengths between tufted and untufted capuchins. Therefore, we attribute the relatively greater PCSAs in tufted capuchins primarily to their larger muscle masses. These findings suggest that relatively large jaw-muscle PCSAs can be added to the suite of masticatory features that have been functionally linked to the exploitation of a more resistant diet by C. apella. By enlarging jaw-muscle mass to increase PCSA, rather than reducing fiber lengths and increasing pinnation, tufted capuchins appear to have

Vastus Medialis Hoffmann Reflex Excitability Is Associated With Pain Level, Self-Reported Function, and Chronicity in Women With Patellofemoral Pain.

PubMed

de Oliveira Silva, Danilo; Magalhães, Fernando Henrique; Faria, Nathálie Clara; Ferrari, Deisi; Pazzinatto, Marcella Ferraz; Pappas, Evangelos; de Azevedo, Fábio Mícolis

2017-01-01

To determine the association between the amplitude of vastus medialis (VM) Hoffmann reflex (H-reflex) and pain level, self-reported physical function, and chronicity of pain in women with patellofemoral pain (PFP). Cross-sectional study. Laboratory of biomechanics and motor control. Women diagnosed with PFP (N=15) aged 18 to 35 years. Not applicable. Data on worst pain level during the previous month, self-reported physical function, and symptom duration (chronicity) were collected from the participants. Maximum evoked responses were obtained by electrical stimulation applied to the femoral nerve and peak-to-peak amplitudes of normalized maximal H-reflexes (maximal Hoffmann reflex/maximal motor wave ratios) of the VM were calculated. A Pearson product-moment correlation matrix (r) was used to explore the relations between the amplitude of VM H-reflex and worst pain during the previous month, self-reported function, and chronicity of pain. Strong negative correlations were found between the amplitude of VM H-reflex and worst pain in the previous month (r=-.71; P=.003) and chronicity (r=-.74; P=.001). A strong positive correlation was found between the amplitude of VM H-reflex and self-reported physical function (r=.62; P=.012). The strong and significant relations reported in this study suggest that women with PFP showing greater VM H-reflex excitability tend to have lower pain, better physical function, and more recent symptoms. Therefore, rehabilitation strategies designed to increase the excitability of the monosynaptic stretch reflex should be considered in the treatment of women with PFP if their effectiveness is demonstrated in future studies. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Unilateral Plantar Flexors Static-Stretching Effects on Ipsilateral and Contralateral Jump Measures

PubMed Central

da Silva, Josinaldo Jarbas; Behm, David George; Gomes, Willy Andrade; Silva, Fernando Henrique Domingues de Oliveira; Soares, Enrico Gori; Serpa, Érica Paes; Vilela Junior, Guanis de Barros; Lopes, Charles Ricardo; Marchetti, Paulo Henrique

2015-01-01

The aim of this study was to evaluate the acute effects of unilateral ankle plantar flexors static-stretching (SS) on the passive range of movement (ROM) of the stretched limb, surface electromyography (sEMG) and single-leg bounce drop jump (SBDJ) performance measures of the ipsilateral stretched and contralateral non-stretched lower limbs. Seventeen young men (24 ± 5 years) performed SBDJ before and after (stretched limb: immediately post-stretch, 10 and 20 minutes and non-stretched limb: immediately post-stretch) unilateral ankle plantar flexor SS (6 sets of 45s/15s, 70-90% point of discomfort). SBDJ performance measures included jump height, impulse, time to reach peak force, contact time as well as the sEMG integral (IEMG) and pre-activation (IEMGpre-activation) of the gastrocnemius lateralis. Ankle dorsiflexion passive ROM increased in the stretched limb after the SS (pre-test: 21 ± 4° and post-test: 26.5 ± 5°, p < 0.001). Post-stretching decreases were observed with peak force (p = 0.029), IEMG (P<0.001), and IEMGpre-activation (p = 0.015) in the stretched limb; as well as impulse (p = 0.03), and jump height (p = 0.032) in the non-stretched limb. In conclusion, SS effectively increased passive ankle ROM of the stretched limb, and transiently (less than 10 minutes) decreased muscle peak force and pre-activation. The decrease of jump height and impulse for the non-stretched limb suggests a SS-induced central nervous system inhibitory effect. Key points When considering whether or not to SS prior to athletic activities, one must consider the potential positive effects of increased ankle dorsiflexion motion with the potential deleterious effects of power and muscle activity during a simple jumping task or as part of the rehabilitation process. Since decreased jump performance measures can persist for 10 minutes in the stretched leg, the timing of SS prior to performance must be taken into consideration. Athletes, fitness enthusiasts and therapists should

A Randomized Trial on the Effect of Bone Tissue on Vibration-induced Muscle Strength Gain and Vibration-induced Reflex Muscle Activity

PubMed Central

Cidem, Muharrem; Karacan, İlhan; Diraçoğlu, Demirhan; Yıldız, Aysel; Küçük, Suat Hayri; Uludağ, Murat; Gün, Kerem; Özkaya, Murat; Karamehmetoğlu, Şafak Sahir

2014-01-01

Background: Whole-body vibration (WBV) induces reflex muscle activity and leads to increased muscle strength. However, little is known about the physiological mechanisms underlying the effects of whole-body vibration on muscular performance. Tonic vibration reflex is the most commonly cited mechanism to explain the effects of whole-body vibration on muscular performance, although there is no conclusive evidence that tonic vibration reflex occurs. The bone myoregulation reflex is another neurological mechanism used to explain the effects of vibration on muscular performance. Bone myoregulation reflex is defined as a reflex mechanism in which osteocytes exposed to cyclic mechanical loading induce muscle activity. Aims: The aim of this study was to assess whether bone tissue affected vibration-induced reflex muscle activity and vibration-induced muscle strength gain. Study Design: A prospective, randomised, controlled, double-blind, parallel-group clinical trial. Methods: Thirty-four participants were randomised into two groups. High-magnitude whole-body vibration was applied in the exercise group, whereas low-magnitude whole-body vibration exercises were applied in the control group throughout 20 sessions. Hip bone mineral density, isokinetic muscle strength, and plasma sclerostin levels were measured. The surface electromyography data were processed to obtain the Root Mean Squares, which were normalised by maximal voluntarily contraction. Results: In the exercise group, muscle strength increased in the right and left knee flexors (23.9%, p=0.004 and 27.5%, p<0.0001, respectively). However, no significant change was observed in the knee extensor muscle strength. There was no significant change in the knee muscle strength in the control group. The vibration-induced corrected Root Mean Squares of the semitendinosus muscle was decreased by 2.8 times (p=0.005) in the exercise group, whereas there was no change in the control group. Sclerostin index was decreased by 15

A Randomized Trial on the Effect of Bone Tissue on Vibration-induced Muscle Strength Gain and Vibration-induced Reflex Muscle Activity.

PubMed

Cidem, Muharrem; Karacan, Ilhan; Diraçoğlu, Demirhan; Yıldız, Aysel; Küçük, Suat Hayri; Uludağ, Murat; Gün, Kerem; Ozkaya, Murat; Karamehmetoğlu, Safak Sahir

2014-03-01

Whole-body vibration (WBV) induces reflex muscle activity and leads to increased muscle strength. However, little is known about the physiological mechanisms underlying the effects of whole-body vibration on muscular performance. Tonic vibration reflex is the most commonly cited mechanism to explain the effects of whole-body vibration on muscular performance, although there is no conclusive evidence that tonic vibration reflex occurs. The bone myoregulation reflex is another neurological mechanism used to explain the effects of vibration on muscular performance. Bone myoregulation reflex is defined as a reflex mechanism in which osteocytes exposed to cyclic mechanical loading induce muscle activity. The aim of this study was to assess whether bone tissue affected vibration-induced reflex muscle activity and vibration-induced muscle strength gain. A prospective, randomised, controlled, double-blind, parallel-group clinical trial. Thirty-four participants were randomised into two groups. High-magnitude whole-body vibration was applied in the exercise group, whereas low-magnitude whole-body vibration exercises were applied in the control group throughout 20 sessions. Hip bone mineral density, isokinetic muscle strength, and plasma sclerostin levels were measured. The surface electromyography data were processed to obtain the Root Mean Squares, which were normalised by maximal voluntarily contraction. In the exercise group, muscle strength increased in the right and left knee flexors (23.9%, p=0.004 and 27.5%, p<0.0001, respectively). However, no significant change was observed in the knee extensor muscle strength. There was no significant change in the knee muscle strength in the control group. The vibration-induced corrected Root Mean Squares of the semitendinosus muscle was decreased by 2.8 times (p=0.005) in the exercise group, whereas there was no change in the control group. Sclerostin index was decreased by 15.2% (p=0.031) in the exercise group and increased by

Specification of jaw identity by the Hand2 transcription factor

PubMed Central

Funato, Noriko; Kokubo, Hiroki; Nakamura, Masataka; Yanagisawa, Hiromi; Saga, Yumiko

2016-01-01

Acquisition of the lower jaw (mandible) was evolutionarily important for jawed vertebrates. In humans, syndromic craniofacial malformations often accompany jaw anomalies. The basic helix-loop-helix transcription factor Hand2, which is conserved among jawed vertebrates, is expressed in the neural crest in the mandibular process but not in the maxillary process of the first branchial arch. Here, we provide evidence that Hand2 is sufficient for upper jaw (maxilla)-to-mandible transformation by regulating the expression of homeobox transcription factors in mice. Altered Hand2 expression in the neural crest transformed the maxillae into mandibles with duplicated Meckel’s cartilage, which resulted in an absence of the secondary palate. In Hand2-overexpressing mutants, non-Hox homeobox transcription factors were dysregulated. These results suggest that Hand2 regulates mandibular development through downstream genes of Hand2 and is therefore a major determinant of jaw identity. Hand2 may have influenced the evolutionary acquisition of the mandible and secondary palate. PMID:27329940

Jaw muscles in older overdenture patients.

PubMed

Newton, James P; McManus, Frank C; Menhenick, Stephen

2004-03-01

To determine, using computer tomography (CT), whether the retention of a small number of teeth in the older adult used to support overdentures could affect the cross-sectional area (CSA) and X-ray density of two jaw closing muscles. Cross-sectional study of a group of older patients subdivided into dentate, edentulous and those wearing overdentures supported by two to five teeth. The sample consisted of 24 subjects aged 55-68 years. CSA and X-ray density of two jaw closing muscles, masseter and medial pterygoid were measured and evaluated using CT. There were no significant differences between left and right jaw muscles, but the CSA of the masseter muscles were significantly larger than the medial pterygoid muscles. The CSA of the masseter and medial pterygoid muscles was significantly smaller in edentulous subjects compared with dentate subjects but no significant difference was observed between subjects wearing overdentures and those with a natural dentition. No significant differences were observed with the X-ray density between different muscles or dental states. The retention of a small number of teeth in the older adult used to support overdentures appears to sustain the CSA of two jaw closing muscles and therefore could enhance these patients' masticatory ability compared with those who were edentulous.

Heterogeneous conservation of Dlx paralog co-expression in jawed vertebrates.

PubMed

Debiais-Thibaud, Mélanie; Metcalfe, Cushla J; Pollack, Jacob; Germon, Isabelle; Ekker, Marc; Depew, Michael; Laurenti, Patrick; Borday-Birraux, Véronique; Casane, Didier

2013-01-01

The Dlx gene family encodes transcription factors involved in the development of a wide variety of morphological innovations that first evolved at the origins of vertebrates or of the jawed vertebrates. This gene family expanded with the two rounds of genome duplications that occurred before jawed vertebrates diversified. It includes at least three bigene pairs sharing conserved regulatory sequences in tetrapods and teleost fish, but has been only partially characterized in chondrichthyans, the third major group of jawed vertebrates. Here we take advantage of developmental and molecular tools applied to the shark Scyliorhinus canicula to fill in the gap and provide an overview of the evolution of the Dlx family in the jawed vertebrates. These results are analyzed in the theoretical framework of the DDC (Duplication-Degeneration-Complementation) model. The genomic organisation of the catshark Dlx genes is similar to that previously described for tetrapods. Conserved non-coding elements identified in bony fish were also identified in catshark Dlx clusters and showed regulatory activity in transgenic zebrafish. Gene expression patterns in the catshark showed that there are some expression sites with high conservation of the expressed paralog(s) and other expression sites with events of paralog sub-functionalization during jawed vertebrate diversification, resulting in a wide variety of evolutionary scenarios within this gene family. Dlx gene expression patterns in the catshark show that there has been little neo-functionalization in Dlx genes over gnathostome evolution. In most cases, one tandem duplication and two rounds of vertebrate genome duplication have led to at least six Dlx coding sequences with redundant expression patterns followed by some instances of paralog sub-functionalization. Regulatory constraints such as shared enhancers, and functional constraints including gene pleiotropy, may have contributed to the evolutionary inertia leading to high

Lewis lung carcinoma regulation of mechanical stretch-induced protein synthesis in cultured myotubes.

PubMed

Gao, Song; Carson, James A

2016-01-01

Mechanical stretch can activate muscle and myotube protein synthesis through mammalian target of rapamycin complex 1 (mTORC1) signaling. While it has been established that tumor-derived cachectic factors can induce myotube wasting, the effect of this catabolic environment on myotube mechanical signaling has not been determined. We investigated whether media containing cachectic factors derived from Lewis lung carcinoma (LLC) can regulate the stretch induction of myotube protein synthesis. C2C12 myotubes preincubated in control or LLC-derived media were chronically stretched. Protein synthesis regulation by anabolic and catabolic signaling was then examined. In the control condition, stretch increased mTORC1 activity and protein synthesis. The LLC treatment decreased basal mTORC1 activity and protein synthesis and attenuated the stretch induction of protein synthesis. LLC media increased STAT3 and AMP-activated protein kinase phosphorylation in myotubes, independent of stretch. Both stretch and LLC independently increased ERK1/2, p38, and NF-κB phosphorylation. In LLC-treated myotubes, the inhibition of ERK1/2 and p38 rescued the stretch induction of protein synthesis. Interestingly, either leukemia inhibitory factor or glycoprotein 130 antibody administration caused further inhibition of mTORC1 signaling and protein synthesis in stretched myotubes. AMP-activated protein kinase inhibition increased basal mTORC1 signaling activity and protein synthesis in LLC-treated myotubes, but did not restore the stretch induction of protein synthesis. These results demonstrate that LLC-derived cachectic factors can dissociate stretch-induced signaling from protein synthesis through ERK1/2 and p38 signaling, and that glycoprotein 130 signaling is associated with the basal stretch response in myotubes. Copyright © 2016 the American Physiological Society.

NK1 receptor activation in rat rostral ventrolateral medulla selectively attenuates somato-sympathetic reflex while antagonism attenuates sympathetic chemoreflex.

PubMed

Makeham, John M; Goodchild, Ann K; Pilowsky, Paul M

2005-06-01

The effects of activation and blockade of the neurokinin 1 (NK1) receptor in the rostral ventrolateral medulla (RVLM) on arterial blood pressure (ABP), splanchnic sympathetic nerve activity (sSNA), phrenic nerve activity, the somato-sympathetic reflex, baroreflex, and chemoreflex were studied in urethane-anesthetized and artificially ventilated Sprague-Dawley rats. Bilateral microinjection of either the stable substance P analog (pGlu5, MePhe8, Sar9)SP(5-11) (DiMe-SP) or the highly selective NK1 agonist [Sar9, Met (O(2))11]SP into the RVLM resulted in an increase in ABP, sSNA, and heart rate and an abolition of phrenic nerve activity. The effects of [Sar9, Met (O(2))11]SP were blocked by the selective nonpeptide NK1 receptor antagonist WIN 51708. NK1 receptor activation also dramatically attenuated the somato-sympathetic reflex elicited by tibial nerve stimulation, while leaving the baroreflex and chemoreflex unaffected. This effect was again blocked by WIN 51708. NK1 receptor antagonism in the RVLM, with WIN 51708 significantly attenuated the sympathoexcitatory response to hypoxia but had no effect on baseline respiratory function. Our findings suggest that substance P and the NK1 receptor play a significant role in the cardiorespiratory reflexes integrated within the RVLM.

Masseter muscular weakness affects temporomandibular synovitis induced by jaw opening in growing rats.

PubMed

Ozaki, Miho; Kaneko, Sawa; Soma, Kunimichi

2008-09-01

To evaluate the influence of impaired masseter function during growth on the development of temporomandibular synovitis. Sixteen 3-week-old male Wistar rats were classified into four groups. The first group served as control; and in the second group, jaw opening was forced for 3 hours when the rats were 9 weeks old. In the third and fourth groups, the masseter muscles were bilaterally resected at 3 weeks of age, and the rats in the fourth group were additionally forced to open their jaw at 9 weeks of age. All rats were sacrificed at 9 weeks. Temporomandibular joint (TMJ) tissue samples were processed for histology, and evaluated for cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expressions by immunohistochemistry to examine the inflammatory changes in the synovial membrane. The control group showed noninflammatory changes. In the jaw-opening group, vascular dilation and weak COX-2 immunoreactivity were induced by jaw opening in the synovium. In the masseter-resection group, the masseter-resected rats exhibited moderate synovial changes while in the resection with opening group, the masseter-resected rats revealed more significant inflammatory changes including synovial hyperplasia, dilated vasculature, fibrin deposits, and intense immunoreactivity for COX-2 and iNOS, all caused by jaw opening. These results suggest that masseter activity in the growth period is an important factor in the induction of temporomandibular synovitis.

The role of the superior laryngeal nerve in esophageal reflexes

PubMed Central

Medda, B. K.; Jadcherla, S.; Shaker, R.

2012-01-01

The aim of this study was to determine the role of the superior laryngeal nerve (SLN) in the following esophageal reflexes: esophago-upper esophageal sphincter (UES) contractile reflex (EUCR), esophago-lower esophageal sphincter (LES) relaxation reflex (ELIR), secondary peristalsis, pharyngeal swallowing, and belch. Cats (N = 43) were decerebrated and instrumented to record EMG of the cricopharyngeus, thyrohyoideus, geniohyoideus, and cricothyroideus; esophageal pressure; and motility of LES. Reflexes were activated by stimulation of the esophagus via slow balloon or rapid air distension at 1 to 16 cm distal to the UES. Slow balloon distension consistently activated EUCR and ELIR from all areas of the esophagus, but the distal esophagus was more sensitive than the proximal esophagus. Transection of SLN or proximal recurrent laryngeal nerves (RLN) blocked EUCR and ELIR generated from the cervical esophagus. Distal RLN transection blocked EUCR from the distal cervical esophagus. Slow distension of all areas of the esophagus except the most proximal few centimeters activated secondary peristalsis, and SLN transection had no effect on secondary peristalsis. Slow distension of all areas of the esophagus inconsistently activated pharyngeal swallows, and SLN transection blocked generation of pharyngeal swallows from all levels of the esophagus. Slow distension of the esophagus inconsistently activated belching, but rapid air distension consistently activated belching from all areas of the esophagus. SLN transection did not block initiation of belch but blocked one aspect of belch, i.e., inhibition of cricopharyngeus EMG. Vagotomy blocked all aspects of belch generated from all areas of esophagus and blocked all responses of all reflexes not blocked by SLN or RLN transection. In conclusion, the SLN mediates all aspects of the pharyngeal swallow, no portion of the secondary peristalsis, and the EUCR and ELIR generated from the proximal esophagus. Considering that SLN is not

Hoffmann-reflex is delayed during 6 degree head-down tilt with balanced traction

NASA Technical Reports Server (NTRS)

Haruna, Y.; Styf, J. R.; Kahan, N.; Hargens, A. R.

1999-01-01

BACKGROUND: Increased spinal height due to the lack of of axial compression on spinal structures in microgravity may stretch the spinal cord, cauda equina, nerve roots, and paraspinal tissues. HYPOTHESIS: Exposure to simulated microgravity causes dysfunction of nerve roots so that the synaptic portion of the Achilles tendon reflex is delayed. METHODS: Six healthy male subjects were randomly divided into two groups with three in each group. The subjects in the first group underwent horizontal bed rest (HBR) for three days. After a two week interval they underwent bed rest in a position of head-down tilt with balanced traction (HDT). So that each subject could serve as his own control, the second group was treated identically but in opposite order. Bilateral F waves and H-reflexes were measured daily (18:30-20:30) on all subjects placed in a prone position. RESULTS: By means of ANOVA, differences between HDT and HBR were observed only in M-latency and F-ratio, not in F-latency, central latency, and H-latency. Differences during the course of the bed rest were observed in M-latency and H-latency only. Tibial H latency was significantly lengthened in HDT group on day 2 and 3, although no significant difference between HDT and HBR was observed. CONCLUSION: The monosynaptic reflex assessed by H-reflex was delayed during 6 degree HDT with traction. The exact mechanism of this delay and whether the change was due to lengthening of the lower part of the vertebrae remain to be clarified.

Mechanical stretch triggers rapid epithelial cell division through Piezo1.

PubMed

Gudipaty, S A; Lindblom, J; Loftus, P D; Redd, M J; Edes, K; Davey, C F; Krishnegowda, V; Rosenblatt, J

2017-03-02

Despite acting as a barrier for the organs they encase, epithelial cells turn over at some of the fastest rates in the body. However, epithelial cell division must be tightly linked to cell death to preserve barrier function and prevent tumour formation. How does the number of dying cells match those dividing to maintain constant numbers? When epithelial cells become too crowded, they activate the stretch-activated channel Piezo1 to trigger extrusion of cells that later die. However, it is unclear how epithelial cell division is controlled to balance cell death at the steady state. Here we show that mammalian epithelial cell division occurs in regions of low cell density where cells are stretched. By experimentally stretching epithelia, we find that mechanical stretch itself rapidly stimulates cell division through activation of the Piezo1 channel. To stimulate cell division, stretch triggers cells that are paused in early G2 phase to activate calcium-dependent phosphorylation of ERK1/2, thereby activating the cyclin B transcription that is necessary to drive cells into mitosis. Although both epithelial cell division and cell extrusion require Piezo1 at the steady state, the type of mechanical force controls the outcome: stretch induces cell division, whereas crowding induces extrusion. How Piezo1-dependent calcium transients activate two opposing processes may depend on where and how Piezo1 is activated, as it accumulates in different subcellular sites with increasing cell density. In sparse epithelial regions in which cells divide, Piezo1 localizes to the plasma membrane and cytoplasm, whereas in dense regions in which cells extrude, it forms large cytoplasmic aggregates. Because Piezo1 senses both mechanical crowding and stretch, it may act as a homeostatic sensor to control epithelial cell numbers, triggering extrusion and apoptosis in crowded regions and cell division in sparse regions.

Epidemiology of the sarcomas of the jaws in a Peruvian population

PubMed Central

Sacsaquispe-Contreras, Sonia J.; Morales-Vadillo, Rafael; Sánchez Lihón, Juvenal

2012-01-01

Objective: Analysis of the clinical characteristics of patients with Sarcomas of the Jaws treated in the “Instituto Nacional de Enfermedades Neoplasicas. Dr. Eduardo Caceres Graziani” from 1952-2007. Study Design: Review of 155 clinical records of patients with Sarcomas of the Jaws and record of age, gender, size, location, clinical symptoms and signs, histopathological diagnoses and type of treatment. The data obtained were analyzed by means of Student’s statistical t-test, Fisher and Friedman’s test. Results: Analysis of 155 Sarcomas of the Jaws. The average age of patients was 36.8 years old (range: 1-80 years); the female gender was the most frequent (52.9%); the average tumor size was 5.5 cm; in upper jaw 54.84% occurred and 45.16% in the lower jaw; the predominant sign was facial asymmetry (87.74%) and the predominant symptom: pain (63.23%). The most frequent diagnosis was Osteosarcoma 50.3% followed by Chondrosarcoma 18%. Surgery plus radiation therapy was the treatment type of choice with 21.94% of cases. Conclusion: The results of this study demonstrate the delayed diagnosis and facial asymmetry and pain appear as the most important events for the diagnosis of Sarcomas of the Jaws. Key words: Sarcoma, jaw, jaw neoplasms, mouth neoplasms. PMID:22143684

[Size of lower jaw as an early indicator of skeletal class III development].

PubMed

Stojanović, Zdenka; Nikodijević, Angelina; Udovicić, Bozidar; Milić, Jasmina; Nikolić, Predrag

2008-08-01

Malocclusion of skeletal class III is a complex abnormality, with a characteristic sagital position of the lower jaw in front of the upper one. A higher level of prognatism of the lower jaw in relation to the upper one can be the consequence of its excessive length. The aim of this study was to find the differences in the length of the lower jaw in the children with skeletal class III and the children with normal sagital interjaw relation (skeletal class I) in the period of mixed dentition. After clinical and x-ray diagnostics, profile tele-x-rays of the head were analyzed in 60 examinees with mixed dentition, aged from 6 to 12 years. The examinees were divided into two groups: group 1--the children with skeletal class III and group 2--the children with skeletal class I. The length of the lower jaw, upper jaw and cranial base were measured. The proportional relations between the lengths measured within each group were established and the level of difference in the lengths measured and their proportions between the groups were estimated. No significant difference between the groups was found in the body length, ramus and the total length of the lower jaw. Proportional relation between the body length and the length of the lower jaw ramus and proportional relation between the forward cranial base and the lower jaw body were not significantly different. A significant difference was found in proportional relations of the total length of the lower jaw with the total lengths of cranial base and the upper jaw and proportional relation of the length of the lower and upper jaw body. Of all the analyzed parameters, the following were selected as the early indicators of the development of skeletal class III on the lower jaw: greater total length of the lower jaw, proportional to the total lengths of cranial base and theupper jaw, as well as greater length of the lower jaw body, proportional to the length of the upper jaw body.

Evolutionary Trends in the Jaw Adductor Mechanics of Ornithischian Dinosaurs.

PubMed

Nabavizadeh, Ali

2016-03-01

Jaw mechanics in ornithischian dinosaurs have been widely studied for well over a century. Most of these studies, however, use only one or few taxa within a given ornithischian clade as a model for feeding mechanics across the entire clade. In this study, mandibular mechanical advantages among 52 ornithischian genera spanning all subclades are calculated using 2D lever arm methods. These lever arm calculations estimate the effect of jaw shape and difference in adductor muscle line of action on relative bite forces along the jaw. Results show major instances of overlap between taxa in tooth positions at which there was highest mechanical advantage. A relatively low bite force is seen across the tooth row among thyreophorans (e.g., stegosaurs and ankylosaurs), with variation among taxa. A convergent transition occurs from a more evenly distributed bite force along the jaw in basal ornithopods and basal marginocephalians to a strong distal bite force in hadrosaurids and ceratopsids, respectively. Accordingly, adductor muscle vector angles show repeated trends from a mid-range caudodorsal orientation in basal ornithischians to a decrease in vector angles indicating more caudally oriented jaw movements in derived taxa (e.g., derived thyreophorans, basal ornithopods, lambeosaurines, pachycephalosaurs, and derived ceratopsids). Analyses of hypothetical jaw morphologies were also performed, indicating that both the coronoid process and lowered jaw joint increase moment arm length therefore increasing mechanical advantage of the jaw apparatus. Adaptive trends in craniomandibular anatomy show that ornithischians evolved more complex feeding apparatuses within different clades as well as morphological convergences between clades. © 2016 Wiley Periodicals, Inc.

Metabolic alterations induced in cultured skeletal muscle by stretch-relaxation activity

NASA Technical Reports Server (NTRS)

Hatfaludy, Sophia; Shansky, Janet; Vandenburgh, Herman H.

1989-01-01

Muscle cells differentiated in vitro are repetitively stretched and relaxed in order to determine the presence of short- and long-term alterations occurring in glucose uptake and lactate efflux that are similar to the metabolic alterations occurring in stimulated organ-cultured muscle and in vivo skeletal muscle during the active state. It is observed that whereas mechanical stimulation increases these metabolic parameters within 4-6 h of starting activity, unstimulated basal rates in control cultures also increase during this period of time, and by 8 h, their rates have reached or exceeded the rates in continuously stimulated cells. Measurements of these parameters in media of different compositions show that activity-induced long-term alterations in the parameters occur independently of growth factors in serium and embryo extracts.

Biocatalysis: Unmasked by stretching

NASA Astrophysics Data System (ADS)

Kharlampieva, Eugenia; Tsukruk, Vladimir V.

2009-09-01

The biocatalytic activity of enzyme-loaded responsive layer-by-layer films can be switched on and off by simple mechanical stretching. Soft materials could thus be used to trigger biochemical reactions under mechanical action, with potential therapeutic applications.

Analysis of feeding function and jaw stability in bedridden elderly.

PubMed

Tamura, Fumiyo; Mizukami, Miki; Ayano, Rika; Mukai, Yoshiharu

2002-01-01

The purpose of this study was to analyze the relationship between jaw stability and the feeding function of 53 bedridden elderly dysphagic patients. Investigations included a questionnaire on daily life activities and meals, oral examinations, functional tests for feeding ability, and assessments of feeding function during the meal. The results of intraoral examination of this patient population for jaw stability revealed that 34.0% of individuals had posterior support for occlusion regardless of whether they had natural teeth or dentures. Thus, the number classified as having mandibular stability (ST) was 18 and that with no mandibular stability (NST) was 35. In a Repetitive Saliva Swallowing Test (RSST), 83.3% of the NST group and 40.0% of the ST group were unable to swallow more than 3 times within 30 seconds. In a water swallowing test, 91.4% of the NST of group was unable to swallow 15 mL of water by a single swallow, while 40.0% of ST group was capable. The results suggest that jaw stabilization by occlusion with the posterior teeth or dental prosthetics is important to feeding function, particularly swallowing.

Flexion Reflex Can Interrupt and Reset the Swimming Rhythm.

PubMed

Elson, Matthew S; Berkowitz, Ari

2016-03-02

The spinal cord can generate the hip flexor nerve activity underlying leg withdrawal (flexion reflex) and the rhythmic, alternating hip flexor and extensor activities underlying locomotion and scratching, even in the absence of brain inputs and movement-related sensory feedback. It has been hypothesized that a common set of spinal interneurons mediates flexion reflex and the flexion components of locomotion and scratching. Leg cutaneous stimuli that evoke flexion reflex can alter the timing of (i.e., reset) cat walking and turtle scratching rhythms; in addition, reflex responses to leg cutaneous stimuli can be modified during cat and human walking and turtle scratching. Both of these effects depend on the phase (flexion or extension) of the rhythm in which the stimuli occur. However, similar interactions between leg flexion reflex and swimming have not been reported. We show here that a tap to the foot interrupted and reset the rhythm of forward swimming in spinal, immobilized turtles if the tap occurred during the swim hip extensor phase. In addition, the hip flexor nerve response to an electrical foot stimulus was reduced or eliminated during the swim hip extensor phase. These two phase-dependent effects of flexion reflex on the swim rhythm and vice versa together demonstrate that the flexion reflex spinal circuit shares key components with or has strong interactions with the swimming spinal network, as has been shown previously for cat walking and turtle scratching. Therefore, leg flexion reflex circuits likely share key spinal interneurons with locomotion and scratching networks across limbed vertebrates generally. The spinal cord can generate leg withdrawal (flexion reflex), locomotion, and scratching in limbed vertebrates. It has been hypothesized that there is a common set of spinal cord neurons that produce hip flexion during flexion reflex, locomotion, and scratching based on evidence from studies of cat and human walking and turtle scratching. We show

Lip line changes in Class III facial asymmetry patients after orthodontic camouflage treatment, one-jaw surgery, and two-jaw surgery: A preliminary study.

PubMed

Lee, Gung-Chol; Yoo, Jo-Kwang; Kim, Seong-Hun; Moon, Cheol-Hyun

2017-03-01

To evaluate the effects of orthodontic camouflage treatment (OCT), one-jaw surgery, and two-jaw surgery on the correction of lip line cant (LLC) and to examine factors affecting the correction of LLC in Class III craniofacial asymmetry patients. A sample of 30 Class III craniofacial asymmetry patients was divided into OCT (n = 10), one-jaw surgery (n = 10), and two-jaw surgery (n = 10) groups such that the pretreatment LLC was similar in each group. Pretreatment and posttreatment cone-beam computed tomography scans were used to measure dental and skeletal parameters and LLC. Pretreatment and posttreatment measurements were compared within groups and between groups. Pearson's correlation tests and multiple regression analyses were performed to investigate factors affecting the amount and rate of LLC correction. The average LLC correction was 1.00° in the one-jaw surgery group, and in the two-jaw surgery group, it was 1.71°. In the OCT group it was -0.04°, which differed statistically significantly from the LLC correction in the other two groups. The amount and rate of LLC correction could be explained by settling of skeletal discrepancies or LLC at pretreatment with goodness of fit percentages of approximately 82% and 41%, respectively. Orthognathic surgery resulted in significant correction of LLC in Class III craniofacial asymmetry patients, while OCT did not.

Aural Acoustic Stapedius-Muscle Reflex Threshold Procedures to Test Human Infants and Adults.

PubMed

Keefe, Douglas H; Feeney, M Patrick; Hunter, Lisa L; Fitzpatrick, Denis F

2017-02-01

Power-based procedures are described to measure acoustic stapedius-muscle reflex threshold and supra-threshold responses in human adult and infant ears at frequencies from 0.2 to 8 kHz. The stimulus set included five clicks in which four pulsed activators were placed between each pair of clicks, with each stimulus set separated from the next by 0.79 s to allow for reflex decay. Each click response was used to detect the presence of reflex effects across frequency that were elicited by a pulsed broadband-noise or tonal activator in the ipsilateral or contralateral test ear. Acoustic reflex shifts were quantified in terms of the difference in absorbed sound power between the initial baseline click and the later four clicks in each set. Acoustic reflex shifts were measured over a 40-dB range of pulsed activators, and the acoustic reflex threshold was objectively calculated using a maximum 10 likelihood procedure. To illustrate the principles underlying these new reflex tests, reflex shifts in absorbed sound power and absorbance are presented for data acquired in an adult ear with normal hearing and in two infant ears in the initial and follow-up newborn hearing screening exams, one with normal hearing and the other with a conductive hearing loss. The use of absorbed sound power was helpful in classifying an acoustic reflex shift as present or absent. The resulting reflex tests are in use in a large study of wideband clinical diagnosis and monitoring of middle-ear and cochlear function in infant and adult ears.

Indirect Estimates of Jaw Muscle Tension in Children with Suspected Hypertonia, Children with Suspected Hypotonia, and Matched Controls

ERIC Educational Resources Information Center

Connaghan, Kathryn P.; Moore, Christopher A.

2013-01-01

Purpose: In this study, the authors compared indirect estimates of jaw-muscle tension in children with suspected muscle-tone abnormalities with age- and gender-matched controls. Method: Jaw movement and muscle activation were measured in children (ages 3 years, 11 months, to 10 years) with suspected muscle-tone abnormalities (Down syndrome or…

Reduced IL-10 production in fetal type II epithelial cells exposed to mechanical stretch is mediated via activation of IL-6-SOCS3 signaling pathway.

PubMed

Hokenson, Michael A; Wang, Yulian; Hawwa, Renda L; Huang, Zheping; Sharma, Surendra; Sanchez-Esteban, Juan

2013-01-01

An imbalance between pro-inflammatory and anti-inflammatory cytokines is a key factor in the lung injury of premature infants exposed to mechanical ventilation. Previous studies have shown that lung cells exposed to stretch produces reduced amounts of the anti-inflammatory cytokine IL-10. The objective of these studies was to analyze the signaling mechanisms responsible for the decreased IL-10 production in fetal type II cells exposed to mechanical stretch. Fetal mouse type II epithelial cells isolated at embryonic day 18 were exposed to 20% stretch to simulate lung injury. We show that IL-10 receptor gene expression increased with gestational age. Mechanical stretch decreased not only IL-10 receptor gene expression but also IL-10 secretion. In contrast, mechanical stretch increased release of IL-6. We then investigated IL-10 signaling pathway-associated proteins and found that in wild-type cells, mechanical stretch decreased activation of JAK1 and TYK2 and increased STAT3 and SOCS3 activation. However, opposite effects were found in cells isolated from IL-10 knockout mice. Reduction in IL-6 secretion by stretch was observed in cells isolated from IL-10 null mice. To support the idea that stretch-induced SOCS3 expression via IL-6 leads to reduced IL-10 expression, siRNA-mediated inhibition of SOCS3 restored IL-10 secretion in cells exposed to stretch and decreased IL-6 secretion. Taken together, these studies suggest that the inhibitory effect of mechanical stretch on IL-10 secretion is mediated via activation of IL-6-STAT3-SOCS3 signaling pathway. SOCS3 could be a therapeutic target to increase IL-10 production in lung cells exposed to mechanical injury.

Vesicular glutamate transporter 1 (VGLUT1)- and VGLUT2-immunopositive axon terminals on the rat jaw-closing and jaw-opening motoneurons.

PubMed

Park, Sook Kyung; Ko, Sang Jin; Paik, Sang Kyoo; Rah, Jong-Cheol; Lee, Kea Joo; Bae, Yong Chul

2018-02-23

To provide information on the glutamatergic synapses on the trigeminal motoneurons, which may be important for understanding the mechanism of control of jaw movements, we investigated the distribution of vesicular glutamate transporter (VGLUT)1-immunopositive (+) and VGLUT2 + axon terminals (boutons) on the rat jaw-closing (JC) and jaw-opening (JO) motoneurons, and their morphological determinants of synaptic strength by retrograde tracing, electron microscopic immunohistochemistry, and quantitative ultrastructural analysis. We found that (1) the large majority of VGLUT + boutons on JC and JO motoneurons were VGLUT2+, (2) the density of VGLUT1 + boutons terminating on JC motoneurons was significantly higher than that on JO motoneurons, (3) the density of VGLUT1 + boutons terminating on non-primary dendrites of JC motoneurons was significantly higher than that on somata or primary dendrites, whereas the density of VGLUT2 + boutons was not significantly different between JC and JO motoneurons and among various compartments of the postsynaptic neurons, and (4) the bouton volume, mitochondrial volume, and active zone area of the VGLUT1 + boutons forming synapses on JC motoneurons were significantly bigger than those of VGLUT2 + boutons. These findings suggest that JC and JO motoneurons receive glutamatergic input primarily from VGLUT2-expressing intrinsic neurons (premotoneurons), and may be controlled differently by neurons in the trigeminal mesencephalic nucleus and by glutamatergic premotoneurons.

Electromyographic reflexes evoked in human flexor carpi radialis by tendon vibration.

PubMed

Cody, F W; Goodwin, C N; Richardson, H C

1990-10-01

The rectified, electromyographic (EMG) reflexes evoked in the voluntarily contracting flexor carpi radialis (FCR) muscle by vibration of its tendon were studied in healthy human subjects. Responses comprised a prominent, transient, short-latency (SL, 20-25 ms) increase in EMG, attributed to Ia mono- and/or oligo-synaptic action, followed by a series of less pronounced troughs and peaks of activity. Evidence of continuing Ia mono- or oligo-synaptic action was indicated by (i) the presence of small subpeaks, at vibration frequency, superimposed upon the excitatory components and (ii) the occurrence of a separate reduction in EMG, of consistent latency (ca. 30 ms), after cessation of stimulation. Progressively shortening the train of vibration from 29 cycles (at 145 Hz) to a single cycle significantly reduced net, excitatory reflex activity. Gradually increasing the level (10-50% maximum) of pre-existing voluntary contraction on top of which reflexes were elicited, by moderately prolonged (29 cycles) trains of vibration, resulted in small increases, in absolute terms, in SL peaks and in later, excitatory EMG activity. Excitatory reflexes, when normalised for pre-stimulus EMG, however, declined in an approximately hyperbolic manner with increasing background activity over this range. Thus, effective "automatic gain compensation" does not operate for vibration reflexes in FCR.

Stretch Marks

MedlinePlus

... stretch marks. This isn't true with regular tanning or tanning beds , though: Stretch marks are less likely to ... up looking more obvious. Plus, the sun and tanning beds do more harm than good when it ...

The trigeminocardiac reflex – a comparison with the diving reflex in humans

PubMed Central

Lemaitre, Frederic; Schaller, Bernhard

2015-01-01

The trigeminocardiac reflex (TCR) has previously been described in the literature as a reflexive response of bradycardia, hypotension, and gastric hypermotility seen upon mechanical stimulation in the distribution of the trigeminal nerve. The diving reflex (DR) in humans is characterized by breath-holding, slowing of the heart rate, reduction of limb blood flow and a gradual rise in the mean arterial blood pressure. Although the two reflexes share many similarities, their relationship and especially their functional purpose in humans have yet to be fully elucidated. In the present review, we have tried to integrate and elaborate these two phenomena into a unified physiological concept. Assuming that the TCR and the DR are closely linked functionally and phylogenetically, we have also highlighted the significance of these reflexes in humans. PMID:25995761

Stretch Garment Dermatitis

PubMed Central

Mihan, Richard; Ayres, Samuel

1968-01-01

A disease of the skin, not hitherto described, is caused by pressure or tension on the skin from the wearing of tight-fitting stretch garments such as “stretch bras,” “stretch girdles” and “stretch socks.” The condition is not due to chemical sensitization of fabrics, dyes or other additives but is of mechanical origin. The eruption may assume various clinical forms and may be characterized by a nondescript erythematous and eczematous appearance or may consist of an exaggeration, in the areas covered by the stretch garment, of already existing dermatosis such as lichen planus, psoriasis, acne vulgaris, discoid lupus erythematosus or atopic dermatitis. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5. PMID:5639939

Reflexive composites: self-healing composite structures

NASA Astrophysics Data System (ADS)

Margraf, Thomas W., Jr.; Barnell, Thomas J.; Havens, Ernie; Hemmelgarn, Christopher D.

2008-03-01

Cornerstone Research Group Inc. has developed reflexive composites achieving increased vehicle survivability through integrated structural awareness and responsiveness to damage. Reflexive composites can sense damage through integrated piezoelectric sensing networks and respond to damage by heating discrete locations to activate the healable polymer matrix in areas of damage. The polymer matrix is a modified thermoset shape memory polymer that heals based on phenomena known as reptation. In theory, the reptation healing phenomena should occur in microseconds; however, during experimentation, it has been observed that to maximize healing and restore up to 85 % of mechanical properties a healing cycle of at least three minutes is required. This paper will focus on work conducted to determine the healing mechanisms at work in CRG's reflexive composites, the optimal healing cycles, and an explanation of the difference between the reptation model and actual healing times.

Fate of tenogenic differentiation potential of human bone marrow stromal cells by uniaxial stretching affected by stretch-activated calcium channel agonist gadolinium

PubMed Central

Balaji Raghavendran, Hanumantha Rao; Pingguan-Murphy, Belinda; Abbas, Azlina A.; Merican, Azhar M.; Kamarul, Tunku

2017-01-01

The role for mechanical stimulation in the control of cell fate has been previously proposed, suggesting that there may be a role of mechanical conditioning in directing mesenchymal stromal cells (MSCs) towards specific lineage for tissue engineering applications. Although previous studies have reported that calcium signalling is involved in regulating many cellular processes in many cell types, its role in managing cellular responses to tensile loading (mechanotransduction) of MSCs has not been fully elucidated. In order to establish this, we disrupted calcium signalling by blocking stretch-activated calcium channel (SACC) in human MSCs (hMSCs) in vitro. Passaged-2 hMSCs were exposed to cyclic tensile loading (1 Hz + 8% for 6, 24, 48, and 72 hours) in the presence of the SACC blocker, gadolinium. Analyses include image observations of immunochemistry and immunofluorescence staining from extracellular matrix (ECM) production, and measuring related tenogenic and apoptosis gene marker expression. Uniaxial tensile loading increased the expression of tenogenic markers and ECM production. However, exposure to strain in the presence of 20 μM gadolinium reduced the induction of almost all tenogenic markers and ECM staining, suggesting that SACC acts as a mechanosensor in strain-induced hMSC tenogenic differentiation process. Although cell death was observed in prolonged stretching, it did not appear to be apoptosis mediated. In conclusion, the knowledge gained in this study by elucidating the role of calcium in MSC mechanotransduction processes, and that in prolonged stretching results in non-apoptosis mediated cell death may be potential useful for regenerative medicine applications. PMID:28654695

Ankle-Dorsiflexion Range of Motion After Ankle Self-Stretching Using a Strap

PubMed Central

Jeon, In-cheol; Kwon, Oh-yun; Yi, Chung-Hwi; Cynn, Heon-Seock; Hwang, Ui-jae

2015-01-01

Context  A variety of ankle self-stretching exercises have been recommended to improve ankle-dorsiflexion range of motion (DFROM) in individuals with limited ankle dorsiflexion. A strap can be applied to stabilize the talus and facilitate anterior glide of the distal tibia at the talocrural joint during ankle self-stretching exercises. Novel ankle self-stretching using a strap (SSS) may be a useful method of improving ankle DFROM. Objective  To compare the effects of 2 ankle-stretching techniques (static stretching versus SSS) on ankle DFROM. Design  Randomized controlled clinical trial. Setting  University research laboratory. Patients or Other Participants  Thirty-two participants with limited active dorsiflexion (<20°) while sitting (14 women and 18 men) were recruited. Main Outcome Measure(s)  The participants performed 2 ankle self-stretching techniques (static stretching and SSS) for 3 weeks. Active DFROM (ADFROM), passive DFROM (PDFROM), and the lunge angle were measured. An independent t test was used to compare the improvements in these values before and after the 2 stretching interventions. The level of statistical significance was set at α = .05. Results  Active DFROM and PDFROM were greater in both stretching groups after the 3-week interventions. However, ADFROM, PDFROM, and the lunge angle were greater in the SSS group than in the static-stretching group (P < .05). Conclusions  Ankle SSS is recommended to improve ADFROM, PDFROM, and the lunge angle in individuals with limited DFROM. PMID:26633750

The effects of passive stretching plus vibration on strength and activation of the plantar flexors.

PubMed

Miller, Jonathan D; Herda, Trent J; Trevino, Michael A; Mosier, Eric M

2016-09-01

This study examined the effects of passive stretching only (PS+CON) and passive stretching with the addition of continuous vibration (VIB) during post-passive stretching tests (PS+VIB) on peak torque (PT), percent voluntary inactivation (%VI), single stimulus twitch torque (TTSINGLE), and doublet stimuli twitch torque (TTDOUBLET) of the plantar flexors at a short (20° plantar flexion (PF)) and long muscle length (15° dorsiflexion (DF)). Fourteen healthy men (age = 22 ± 3 years) performed isometric maximal voluntary contractions at PF and DF, and passive range of motion (PROM) assessments before and after 8 × 30-s passive stretches without (PS+CON) or with VIB (PS+VIB) administered continuously throughout post-passive stretching tests. The passive properties of the muscle tendon unit were assessed pre- and post-passive stretching via PROM, passive torque (PASSTQ), and musculotendinous stiffness (MTS) measurements. PT, TTSINGLE, and TTDOUBLET decreased, whereas, %VI increased following passive stretching at PF and DF (P < 0.05) with no significant differences between PS+CON and PS+VIB. PASSTQ and MTS decreased while PROM increased post-passive stretching during both trials (P < 0.05). The stretching-induced force/torque deficit and increases in %VI were evident following passive stretching at short and long muscle lengths. Although not statistically significant, effect size calculations suggested large and moderate differences in the absolute changes in PT (Cohen's d = 1.14) and %VI (Cohen's d = 0.54) from pre- to post-passive stretching between treatments, with PS+VIB having greater decreases of PT and higher %VI than PS+CON. The decrement in PT following passive stretching may be primarily neural in origin.

Acoustic Reflex Testing in Neonatal Hearing Screening and Subsequent Audiological Evaluation.

PubMed

Jacob-Corteletti, Lilian Cássia Bórnia; Araújo, Eliene Silva; Duarte, Josilene Luciene; Zucki, Fernanda; Alvarenga, Kátia de Freitas

2018-06-18

The aims of the study were to examine the acoustic reflex screening and threshold in healthy neonates and those at risk of hearing loss and to determine the effect of birth weight and gestational age on acoustic stapedial reflex (ASR). We assessed 18 healthy neonates (Group I) and 16 with at least 1 risk factor for hearing loss (Group II); all of them passed the transient evoked otoacoustic emission test that assessed neonatal hearing. The test battery included an acoustic reflex screening with activators of 0.5, 1, 2, and 4 kHz and broadband noise and an acoustic reflex threshold test with all of them, except for the broadband noise activator. In the evaluated neonates, the main risk factors were the gestational age at birth and a low birth weight; hence, these were further analyzed. The lower the gestational age at birth and birth weight, the less likely that an acoustic reflex would be elicited by pure-tone activators. This effect was significant at the frequencies of 0.5, 1, and 2 kHz for gestational age at birth and at the frequencies of 1 and 2 kHz for birth weight. When the broadband noise stimulus was used, a response was elicited in all neonates in both groups. When the pure-tone stimulus was used, the Group II showed the highest acoustic reflex thresholds and the highest percentage of cases with an absent ASR. The ASR threshold varied from 50 to 100 dB HL in both groups. Group II presented higher mean ASR thresholds than Group I, this difference being significant at frequencies of 1, 2, and 4 kHz. Birth weight and gestational age at birth were related to the elicitation of the acoustic reflex. Neonates with these risk factors for hearing impairment were less likely to exhibit the acoustic reflex and had higher thresholds.

Surface EMG crosstalk during phasic involuntary muscle activation in the nociceptive withdrawal reflex.

PubMed

Frahm, Ken S; Jensen, Michael B; Farina, Dario; Andersen, Ole K

2012-08-01

The human nociceptive withdrawal reflex is typically assessed using surface electromyography (sEMG). Based on sEMG, the reflex receptive field (RRF) can be mapped. However, EMG crosstalk can cause erroneous results in the RRF determination. Single differential (SD) vs. double differential (DD) surface EMG were evaluated. Different electrode areas and inter-electrode-distances (IED) were evaluated. The reflexes were elicited by electrical stimulation of the sole of the foot. EMG was obtained from both tibialis anterior (TA) and soleus (SOL) using both surface and intramuscular EMG (iEMG). The amount of crosstalk was significantly higher in SD recordings than in DD recordings (P < 0.05). Crosstalk increased when electrode measuring area increased (P < 0.05) and when IED increased (P < 0.05). Reflex detection sensitivity decreases with increasing measuring area and increasing IED. These results stress that for determination of RRF and similar tasks, DD recordings should be applied. Copyright © 2012 Wiley Periodicals, Inc.

Reduced IL-10 Production in Fetal Type II Epithelial Cells Exposed to Mechanical Stretch Is Mediated via Activation of IL-6-SOCS3 Signaling Pathway

PubMed Central

Hawwa, Renda L.; Huang, Zheping; Sharma, Surendra; Sanchez-Esteban, Juan

2013-01-01

An imbalance between pro-inflammatory and anti-inflammatory cytokines is a key factor in the lung injury of premature infants exposed to mechanical ventilation. Previous studies have shown that lung cells exposed to stretch produces reduced amounts of the anti-inflammatory cytokine IL-10. The objective of these studies was to analyze the signaling mechanisms responsible for the decreased IL-10 production in fetal type II cells exposed to mechanical stretch. Fetal mouse type II epithelial cells isolated at embryonic day 18 were exposed to 20% stretch to simulate lung injury. We show that IL-10 receptor gene expression increased with gestational age. Mechanical stretch decreased not only IL-10 receptor gene expression but also IL-10 secretion. In contrast, mechanical stretch increased release of IL-6. We then investigated IL-10 signaling pathway-associated proteins and found that in wild-type cells, mechanical stretch decreased activation of JAK1 and TYK2 and increased STAT3 and SOCS3 activation. However, opposite effects were found in cells isolated from IL-10 knockout mice. Reduction in IL-6 secretion by stretch was observed in cells isolated from IL-10 null mice. To support the idea that stretch-induced SOCS3 expression via IL-6 leads to reduced IL-10 expression, siRNA-mediated inhibition of SOCS3 restored IL-10 secretion in cells exposed to stretch and decreased IL-6 secretion. Taken together, these studies suggest that the inhibitory effect of mechanical stretch on IL-10 secretion is mediated via activation of IL-6-STAT3-SOCS3 signaling pathway. SOCS3 could be a therapeutic target to increase IL-10 production in lung cells exposed to mechanical injury. PMID:23527226

TRPV2 Channels Contribute to Stretch-Activated Cation Currents and Myogenic Constriction in Retinal Arterioles.

PubMed

McGahon, Mary K; Fernández, José A; Dash, Durga P; McKee, Jon; Simpson, David A; Zholos, Alex V; McGeown, J Graham; Curtis, Tim M

2016-10-01

Activation of the transient receptor potential channels, TRPC6, TRPM4, and TRPP1 (PKD2), has been shown to contribute to the myogenic constriction of cerebral arteries. In the present study we sought to determine the potential role of various mechanosensitive TRP channels to myogenic signaling in arterioles of the rat retina. Rat retinal arterioles were isolated for RT-PCR, Fura-2 Ca2+ microfluorimetry, patch-clamp electrophysiology, and pressure myography studies. In some experiments, confocal immunolabeling of wholemount preparations was used to examine the localization of specific mechanosensitive TRP channels in retinal vascular smooth muscle cells (VSMCs). Reverse transcription-polymerase chain reaction analysis demonstrated mRNA expression for TRPC1, M7, V1, V2, V4, and P1, but not TRPC6 or M4, in isolated retinal arterioles. Immunolabeling revealed plasma membrane, cytosolic and nuclear expression of TRPC1, M7, V1, V2, V4, and P1 in retinal VSMCs. Hypoosmotic stretch-induced Ca2+ influx in retinal VSMCs was reversed by the TRPV2 inhibitor tranilast and the nonselective TRPP1/V2 antagonist amiloride. Inhibitors of TRPC1, M7, V1, and V4 had no effect. Hypoosmotic stretch-activated cation currents were similar in Na+ and Cs+ containing solutions suggesting no contribution by TRPP1 channels. Direct plasma membrane stretch triggered cation current activity that was blocked by tranilast and specific TRPV2 pore-blocking antibodies and mimicked by the TRPV2 activator, Δ9-tetrahydrocannabinol. Preincubation of retinal arterioles with TRPV2 blocking antibodies prevented the development of myogenic tone. Our results suggest that retinal VSMCs express a range of mechanosensitive TRP channels, but only TRPV2 appears to contribute to myogenic signaling in this vascular bed.

Get up and Stretch

ERIC Educational Resources Information Center

Crupi, Jeffrey

2004-01-01

Daily stretching has many benefits for one's body. It can relieve stress and tension, it increases flexibility and it can help prevent injuries. There are many stretching exercises that a teacher can do with his or her students to help promote daily stretching routines. In this article, the author presents several stretching exercises and some…

Brush in the bath of active particles: Anomalous stretching of chains and distribution of particles

NASA Astrophysics Data System (ADS)

Li, Hui-shu; Zhang, Bo-kai; Li, Jian; Tian, Wen-de; Chen, Kang

2015-12-01

The interaction between polymer brush and colloidal particles has been intensively studied in the last two decades. Here, we consider a flat chain-grafted substrate immersed in a bath of active particles. Simulations show that an increase in the self-propelling force causes an increase in the number of particles that penetrate into the brush. Anomalously, the particle density inside the main body of the brush eventually becomes higher than that outside the brush at very large self-propelling force. The grafted chains are further stretched due to the steric repulsion from the intruded particles. Upon the increase of the self-propelling force, distinct stretching behaviors of the chains were observed for low and high grafting densities. Surprisingly, we find a weak descent of the average end-to-end distance of chains at high grafting density and very large force which is reminiscent of the compression effect of a chain in the active bath.

SU-F-E-19: A Novel Method for TrueBeam Jaw Calibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corns, R; Zhao, Y; Huang, V

2016-06-15

Purpose: A simple jaw calibration method is proposed for Varian TrueBeam using an EPID-Encoder combination that gives accurate fields sizes and a homogeneous junction dose. This benefits clinical applications such as mono-isocentric half-beam block breast cancer or head and neck cancer treatment with junction/field matching. Methods: We use EPID imager with pixel size 0.392 mm × 0.392 mm to determine the radiation jaw position as measured from radio-opaque markers aligned with the crosshair. We acquire two images with different symmetric field sizes and record each individual jaw encoder values. A linear relationship between each jaw’s position and its encoder valuemore » is established, from which we predict the encoder values that produce the jaw positions required by TrueBeam’s calibration procedure. During TrueBeam’s jaw calibration procedure, we move the jaw with the pendant to set the jaw into position using the predicted encoder value. The overall accuracy is under 0.1 mm. Results: Our in-house software analyses images and provides sub-pixel accuracy to determine field centre and radiation edges (50% dose of the profile). We verified the TrueBeam encoder provides a reliable linear relationship for each individual jaw position (R{sup 2}>0.9999) from which the encoder values necessary to set jaw calibration points (1 cm and 19 cm) are predicted. Junction matching dose inhomogeneities were improved from >±20% to <±6% using this new calibration protocol. However, one technical challenge exists for junction matching, if the collimator walkout is large. Conclusion: Our new TrueBeam jaw calibration method can systematically calibrate the jaws to crosshair within sub-pixel accuracy and provides both good junction doses and field sizes. This method does not compensate for a larger collimator walkout, but can be used as the underlying foundation for addressing the walkout issue.« less

Pediatric jaw fractures: indications for open reduction.

PubMed

Krausen, A S; Samuel, M

1979-01-01

Jaw fractures in children are generally managed without major surgical intervention. Closed reduction usually is sufficient to restore normal anatomy and function. The one inviolate principle is early treatment. During the past three years, four pediatric jaw fractures that required open reduction were treated. This mode of treatment was necessitated by the limitations imposed by pediatric dental anatomy and by the type of fractures encountered. In at least 24 months of follow-up, no dental problems have been seen.

Lung vagal afferent activity in rats with bleomycin-induced lung fibrosis.

PubMed

Schelegle, E S; Walby, W F; Mansoor, J K; Chen, A T

2001-05-01

Bleomycin treatment in rats results in pulmonary fibrosis that is characterized by a rapid shallow breathing pattern, a decrease in quasi-static lung compliance and a blunting of the Hering-Breuer Inflation Reflex. We examined the impulse activity of pulmonary vagal afferents in anesthetized, mechanically ventilated rats with bleomycin-induced lung fibrosis during the ventilator cycle and static lung inflations/deflations and following the injection of capsaicin into the right atrium. Bleomycin enhanced volume sensitivity of slowly adapting stretch receptors (SARs), while it blunted the sensitivity of these receptors to increasing transpulmonary pressure. Bleomycin treatment increased the inspiratory activity, while it decreased the expiratory activity of rapidly adapting stretch receptors (RARs). Pulmonary C-fiber impulse activity did not appear to be affected by bleomycin treatment. We conclude that the fibrosis-related shift in discharge profile and enhanced volume sensitivity of SARs combined with the increased inspiratory activity of RARs contributes to the observed rapid shallow breathing of bleomycin-induced lung fibrosis.

Independently evolved upper jaw protrusion mechanisms show convergent hydrodynamic function in teleost fishes.

PubMed

Staab, Katie Lynn; Holzman, Roi; Hernandez, L Patricia; Wainwright, Peter C

2012-05-01

A protrusible upper jaw has independently evolved multiple times within teleosts and has been implicated in the success of two groups in particular: Acanthomorpha and Cypriniformes. We use digital particle image velocimetry (DPIV) to compare suction feeding flow dynamics in a representative of each of these clades: goldfish and bluegill. Using DPIV, we contrast the spatial pattern of flow, the temporal relationship between flow and head kinematics, and the contribution of jaw protrusion to the forces exerted on prey. As expected, the spatial patterns of flow were similar in the two species. However, goldfish were slower to reach maximal kinematic excursions, and were more flexible in the relative timing of jaw protrusion, other jaw movements and suction flows. Goldfish were also able to sustain flow speeds for a prolonged period of time as compared with bluegill, in part because goldfish generate lower peak flow speeds. In both species, jaw protrusion increased the force exerted on the prey. However, slower jaw protrusion in goldfish resulted in less augmentation of suction forces. This difference in force exerted on prey corresponds with differences in trophic niches and feeding behavior of the two species. The bluegill uses powerful suction to capture insect larvae whereas the goldfish uses winnowing to sort through detritus and sediment. The kinethmoid of goldfish may permit jaw protrusion that is independent of lower jaw movement, which could explain the ability of goldfish to decouple suction flows (due to buccal expansion) from upper jaw protrusion. Nevertheless, our results show that jaw protrusion allows both species to augment the force exerted on prey, suggesting that this is a fundamental benefit of jaw protrusion to suction feeders.

Active and passive controls of Jeffrey nanofluid flow over a nonlinear stretching surface

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Aziz, Arsalan; Muhammad, Taseer; Alsaedi, Ahmed

This communication explores magnetohydrodynamic (MHD) boundary-layer flow of Jeffrey nanofluid over a nonlinear stretching surface with active and passive controls of nanoparticles. A nonlinear stretching surface generates the flow. Effects of thermophoresis and Brownian diffusion are considered. Jeffrey fluid is electrically conducted subject to non-uniform magnetic field. Low magnetic Reynolds number and boundary-layer approximations have been considered in mathematical modelling. The phenomena of impulsing the particles away from the surface in combination with non-zero mass flux condition is known as the condition of zero mass flux. Convergent series solutions for the nonlinear governing system are established through optimal homotopy analysis method (OHAM). Graphs have been sketched in order to analyze that how the temperature and concentration distributions are affected by distinct physical flow parameters. Skin friction coefficient and local Nusselt and Sherwood numbers are also computed and analyzed. Our findings show that the temperature and concentration distributions are increasing functions of Hartman number and thermophoresis parameter.

Oxygen-conserving reflexes of the brain: the current molecular knowledge.

PubMed

Schaller, B; Cornelius, J F; Sandu, N; Ottaviani, G; Perez-Pinzon, M A

2009-04-01

The trigemino-cardiac reflex (TCR) may be classified as a sub-phenomenon in the group of the so-called 'oxygen-conserving reflexes'. Within seconds after the initiation of such a reflex, there is neither a powerful and differentiated activation of the sympathetic system with subsequent elevation in regional cerebral blood flow (CBF) with no changes in the cerebral metabolic rate of oxygen (CMRO(2)) or in the cerebral metabolic rate of glucose (CMRglc). Such an increase in regional CBF without a change of CMRO(2) or CMRglc provides the brain with oxygen rapidly and efficiently and gives substantial evidence that the TCR is an oxygen-conserving reflex. This system, which mediates reflex protection projects via currently undefined pathways from the rostral ventrolateral medulla oblongata to the upper brainstem and/or thalamus which finally engage a small population of neurons in the cortex. This cortical centre appears to be dedicated to reflexively transduce a neuronal signal into cerebral vasodilatation and synchronization of electrocortical activity. Sympathetic excitation is mediated by cortical-spinal projection to spinal pre-ganglionic sympathetic neurons whereas bradycardia is mediated via projections to cardiovagal motor medullary neurons. The integrated reflex response serves to redistribute blood from viscera to brain in response to a challenge to cerebral metabolism, but seems also to initiate a preconditioning mechanism. Better and more detailed knowledge of the cascades, transmitters and molecules engaged in such endogenous (neuro) protection may provide new insights into novel therapeutic options for a range of disorders characterized by neuronal death and into cortical organization of the brain.

Does induced masseter muscle pain affect integrated jaw-neck movements similarly in men and women?

PubMed

Wiesinger, Birgitta; Häggman-Henrikson, Birgitta; Hellström, Fredrik; Englund, Erling; Wänman, Anders

2016-12-01

Normal jaw opening-closing involves simultaneous jaw and head-neck movements. We previously showed that, in men, integrated jaw-neck movements during jaw function are altered by induced masseter muscle pain. The aim of this study was to investigate possible sex-related differences in integrated jaw-neck movements following experimental masseter muscle pain. We evaluated head-neck and jaw movements in 22 healthy women and 16 healthy men in a jaw opening-closing task. The participants performed one control trial and one trial with masseter muscle pain induced by injection of hypertonic saline. Jaw and head movements were registered using a three-dimensional optoelectronic recording system. There were no significant sex-related differences in jaw and head movement amplitudes. Head movement amplitudes were significantly greater in the pain trials for both men and women. The proportional involvement of the neck motor system during jaw movements increased in pain trials for 13 of 16 men and for 18 of 22 women. Thus, acute pain may alter integrated jaw-neck movements, although, given the similarities between men and women, this interaction between acute pain and motor behaviour does not explain sex differences in musculoskeletal pain in the jaw and neck regions. © 2016 Eur J Oral Sci.

Intralimb and Interlimb Cutaneous Reflexes during Locomotion in the Intact Cat.

PubMed

Hurteau, Marie-France; Thibaudier, Yann; Dambreville, Charline; Danner, Simon M; Rybak, Ilya A; Frigon, Alain

2018-04-25

When the foot contacts an obstacle during locomotion, cutaneous inputs activate spinal circuits to ensure dynamic balance and forward progression. In quadrupeds, this requires coordinated reflex responses between the four limbs. Here, we investigated the patterns and phasic modulation of cutaneous reflexes in forelimb and hindlimb muscles evoked by inputs from all four limbs. Five female cats were implanted to record muscle activity and to stimulate the superficial peroneal and superficial radial nerves during locomotion. Stimulating these nerves evoked short-, mid-, and longer-latency excitatory and/or inhibitory responses in all four limbs that were phase-dependent. The largest responses were generally observed during the peak activity of the muscle. Cutaneous reflexes during mid-swing were consistent with flexion of the homonymous limb and accompanied by modification of the stance phases of the other three limbs, by coactivating flexors and extensors and/or by delaying push-off. Cutaneous reflexes during mid-stance were consistent with stabilizing the homonymous limb by delaying and then facilitating its push-off and modifying the support phases of the homolateral and diagonal limbs, characterized by coactivating flexors and extensors, reinforcing extensor activity and/or delaying push-off. The shortest latencies of homolateral and diagonal responses were consistent with fast-conducting disynaptic or trisynaptic pathways. Descending homolateral and diagonal pathways from the forelimbs to the hindlimbs had a higher probability of eliciting responses compared with ascending pathways from the hindlimbs to the forelimbs. Thus, in quadrupeds, intralimb and interlimb reflexes activated by cutaneous inputs ensure dynamic coordination of the four limbs, producing a whole-body response. SIGNIFICANCE STATEMENT The skin contains receptors that, when activated, send inputs to spinal circuits, signaling a perturbation. Rapid responses, or reflexes, in muscles of the

Reflexive Language and Ethnic Minority Activism in Hong Kong: A Trajectory-Based Analysis

ERIC Educational Resources Information Center

Pérez-Milans, Miguel; Soto, Carlos

2016-01-01

This article engages with Archer's call to further research on reflexivity and social change under conditions of late modernity (2007, 2010, 2012) from the perspective of existing work on reflexive discourse in the language disciplines (Silverstein 1976, Lucy 1993). Drawing from a linguistic ethnography of the networked trajectories of a group of…

M1/70 attenuates blood-borne neutrophil oxidants, activation, and myofiber damage following stretch injury.

PubMed

Brickson, S; Ji, L L; Schell, K; Olabisi, R; St Pierre Schneider, B; Best, T M

2003-09-01

The purpose of this study was to determine the role of the CD11b-dependent respiratory burst in neutrophil oxidant generation and activation, interleukin-8 (IL-8) production, and myofiber damage after muscle stretch injury by using the monoclonal antibody M1/70 to block this pathway. Twelve male New Zealand White rabbits were randomly assigned to a treatment group: M1/70 (n = 6), IgG isotype control (n = 3), or saline control (n = 3). After intravenous injection of the assigned agent under gas anesthesia, a standardized single-stretch injury was created in the right tibialis anterior, whereas the left tibialis anterior underwent a sham surgery. Blood-borne neutrophil oxidant generation and CD11b receptor density and plasma IL-8 levels were measured pre- and 24 h postinjury. Damage was assessed histologically at the hematoma site by counting torn myofibers. M1/70 group demonstrated decreased blood-borne neutrophil oxidant generation (P < 0.05) and CD11b receptor density (P < 0.05), an increase in plasma IL-8 concentration (P < 0.01), and less torn myofibers (P < 0.01) compared with IgG isotype or saline control groups. These data indicate that 1). CD11b-dependent respiratory burst is a major source of oxidants produced by the neutrophil, and that treatment with M1/70 2). attenuates neutrophil activation status, 3). increases plasma IL-8 concentration, and 4). minimizes myofiber damage 24 h postmuscle stretch injury.

FEFsem neuronal response during combined volitional and reflexive pursuit.

PubMed

Bakst, Leah; Fleuriet, Jérome; Mustari, Michael J

2017-05-01

Although much is known about volitional and reflexive smooth eye movements individually, much less is known about how they are coordinated. It is hypothesized that separate cortico-ponto-cerebellar loops subserve these different types of smooth eye movements. Specifically, the MT-MST-DLPN pathway is thought to be critical for ocular following eye movements, whereas the FEF-NRTP pathway is understood to be vital for volitional smooth pursuit. However, the role that these loops play in combined volitional and reflexive behavior is unknown. We used a large, textured background moving in conjunction with a small target spot to investigate the eye movements evoked by a combined volitional and reflexive pursuit task. We also assessed the activity of neurons in the smooth eye movement subregion of the frontal eye field (FEFsem). We hypothesized that the pursuit system would show less contribution from the volitional pathway in this task, owing to the increased involvement of the reflexive pathway. In accordance with this hypothesis, a majority of FEFsem neurons (63%) were less active during pursuit maintenance in a combined volitional and reflexive pursuit task than during purely volitional pursuit. Interestingly and surprisingly, the neuronal response to the addition of the large-field motion was highly correlated with the neuronal response to a target blink. This suggests that FEFsem neuronal responses to these different perturbations-whether the addition or subtraction of retinal input-may be related. We conjecture that these findings are due to changing weights of both the volitional and reflexive pathways, as well as retinal and extraretinal signals.

FEFsem neuronal response during combined volitional and reflexive pursuit

PubMed Central

Bakst, Leah; Fleuriet, Jérome; Mustari, Michael J.

2017-01-01

Although much is known about volitional and reflexive smooth eye movements individually, much less is known about how they are coordinated. It is hypothesized that separate cortico-ponto-cerebellar loops subserve these different types of smooth eye movements. Specifically, the MT-MST-DLPN pathway is thought to be critical for ocular following eye movements, whereas the FEF-NRTP pathway is understood to be vital for volitional smooth pursuit. However, the role that these loops play in combined volitional and reflexive behavior is unknown. We used a large, textured background moving in conjunction with a small target spot to investigate the eye movements evoked by a combined volitional and reflexive pursuit task. We also assessed the activity of neurons in the smooth eye movement subregion of the frontal eye field (FEFsem). We hypothesized that the pursuit system would show less contribution from the volitional pathway in this task, owing to the increased involvement of the reflexive pathway. In accordance with this hypothesis, a majority of FEFsem neurons (63%) were less active during pursuit maintenance in a combined volitional and reflexive pursuit task than during purely volitional pursuit. Interestingly and surprisingly, the neuronal response to the addition of the large-field motion was highly correlated with the neuronal response to a target blink. This suggests that FEFsem neuronal responses to these different perturbations—whether the addition or subtraction of retinal input—may be related. We conjecture that these findings are due to changing weights of both the volitional and reflexive pathways, as well as retinal and extraretinal signals. PMID:28538993

Motor-Evoked Pain Increases Force Variability in Chronic Jaw Pain.

PubMed

Wang, Wei-En; Roy, Arnab; Misra, Gaurav; Archer, Derek B; Ribeiro-Dasilva, Margarete C; Fillingim, Roger B; Coombes, Stephen A

2018-06-01

Musculoskeletal pain changes how people move. Although experimental pain is associated with increases in the variability of motor output, it is not clear whether motor-evoked pain in clinical conditions is also associated with increases in variability. In the current study, we measured jaw force production during a visually guided force paradigm in which individuals with chronic jaw pain and control subjects produced force at 2% of their maximum voluntary contraction (low target force level) and at 15% of their maximum voluntary contraction (high target force level). State measures of pain were collected before and after each trial. Trait measures of pain intensity and pain interference, self-report measures of jaw function, and measures of depression, anxiety, and fatigue were also collected. We showed that the chronic jaw pain group exhibited greater force variability compared with controls irrespective of the force level, whereas the accuracy of force production did not differ between groups. Furthermore, predictors of force variability shifted from trait measures of pain intensity and pain interference at the low force level to state measures of pain intensity at the high force level. Our observations show that motor-evoked jaw pain is associated with increases in force variability that are predicted by a combination of trait measures and state measures of pain intensity and pain interference. Chronic jaw pain is characterized by increases in variability during force production, which can be predicted by pain intensity and pain interference. This report could help clinicians better understand the long-term consequences of chronic jaw pain on the motor system. Copyright © 2018 The American Pain Society. Published by Elsevier Inc. All rights reserved.

Olfactory-corporeal reflex: description of a new reflex and its role in the erectile process.

PubMed

Shafik, A

1997-01-01

The dog approaches the bitch and smells the vulva. The relationship which seems to exist between a special smell in the bitch and sexual arousal in the male dog was investigated. 12 male dogs and 25 bitches were studied. The bitches were divided into five equal groups, each representing 1 of the 5 phases of the estrous cycle. A vaginal swab that soaked in the bitches' vaginal secretions was divided into two pieces: one was sent for estradiol and progesterone determination, and the other was smelt by the male dog. The responses of the intracorporeal pressure (IP) and the electromyographic activity of the bulbo- and ischiocavernosus (BC, IC) muscles of the male dog to the smelling of bitch's vaginal odor were assessed. The pressure response was also determined 10 min and 1 h after either the nasal mucosa or the corporeal tissue was anesthetized. Elevated IP was recorded in 12 of 12, 10 of 12 and 8 of 12 dogs smelling vaginal swabs of bitches in metestrus (p < 0.001), estrus (p < 0.001), and diestrus (p < 0.01), respectively. No pressure response occurred when the vaginal swab was smelt while the nasal mucosa or the corporeal tissue was anesthetized. The BC and IC muscles exhibited no response to smelling of the vaginal swab of bitches in any phase of the estrous cycle. The results were reproducible. The study showed that the IP increased with smelling of vaginal secretions containing high progesterone levels, whereas estradiol-17 beta did not effect IP elevations. The higher the progesterone level, the greater the IP. The increased IP is not due to BC and IC muscle contraction. It is postulated that a reflex relationship exists between IP elevation and olfactory stimulation. This reflex response was reproducible and was not evoked when the two arms of the reflex were anesthetized. We call this reflex 'olfactory-corporeal reflex'. This reflex seems to prime the male dog for sexual intercourse.

Reflex regulation during sustained and intermittent submaximal contractions in humans

PubMed Central

Duchateau, Jacques; Balestra, Costantino; Carpentier, Alain; Hainaut, Karl

2002-01-01

To investigate whether the intensity and duration of a sustained contraction influences reflex regulation, we compared sustained fatiguing contractions at 25 % and 50 % of maximal voluntary contraction (MVC) force in the human abductor pollicis brevis (APB) muscle. Because the activation of motoneurones during fatigue may be reflexively controlled by the metabolic status of the muscle, we also compared reflex activities during sustained and intermittent (6 s contraction, 4 s rest) contractions at 25 % MVC for an identical duration. The short-latency Hoffmann(H) reflex and the long-latency reflex (LLR) were recorded during voluntary contractions, before, during and after the fatigue tests, with each response normalised to the compound muscle action potential (M-wave). The results showed that fatigue during sustained contractions was inversely related to the intensity, and hence the duration, of the effort. The MVC force and associated surface electromyogram (EMG) declined by 26.2 % and 35.2 %, respectively, after the sustained contraction at 50 % MVC, and by 34.2 % and 44.2 % after the sustained contraction at 25 % MVC. Although the average EMG increased progressively with time during the two sustained fatiguing contractions, the amplitudes of the H and LLR reflexes decreased significantly. Combined with previous data (Duchateau & Hainaut, 1993), the results show that the effect on the H reflex is independent of the intensity of the sustained contraction, whereas the decline in the LLR is closely related to the duration of the contraction. Because there were no changes in the intermittent test at 25 % MVC, the results indicate that the net excitatory spinal and supraspinal reflex-mediated input to the motoneurone pool is reduced. This decline in excitation to the motoneurones, however, can be temporarily compensated by an enhancement of the central drive. PMID:12068054

Masticatory motor patterns in ungulates: a quantitative assessment of jaw-muscle coordination in goats, alpacas and horses.

PubMed

Williams, Susan H; Vinyard, Christopher J; Wall, Christine E; Hylander, William L

2007-04-01

We investigated patterns of jaw-muscle coordination during rhythmic mastication in three species of ungulates displaying the marked transverse jaw movements typical of many large mammalian herbivores. In order to quantify consistent motor patterns during chewing, electromyograms were recorded from the superficial masseter, deep masseter, posterior temporalis and medial pterygoid muscles of goats, alpacas and horses. Timing differences between muscle pairs were evaluated in the context of an evolutionary model of jaw-muscle function. In this model, the closing and food reduction phases of mastication are primarily controlled by two distinct muscle groups, triplet I (balancing-side superficial masseter and medial pterygoid and working-side posterior temporalis) and triplet II (working-side superficial masseter and medial pterygoid and balancing-side posterior temporalis), and the asynchronous activity of the working- and balancing-side deep masseters. The three species differ in the extent to which the jaw muscles are coordinated as triplet I and triplet II. Alpacas, and to a lesser extent, goats, exhibit the triplet pattern whereas horses do not. In contrast, all three species show marked asynchrony of the working-side and balancing-side deep masseters, with jaw closing initiated by the working-side muscle and the balancing-side muscle firing much later during closing. However, goats differ from alpacas and horses in the timing of the balancing-side deep masseter relative to the triplet II muscles. This study highlights interspecific differences in the coordination of jaw muscles to influence transverse jaw movements and the production of bite force in herbivorous ungulates.

Single Canonical Model of Reflexive Memory and Spatial Attention

PubMed Central

Patel, Saumil S.; Red, Stuart; Lin, Eric; Sereno, Anne B.

2015-01-01

Many neurons in the dorsal and ventral visual stream have the property that after a brief visual stimulus presentation in their receptive field, the spiking activity in these neurons persists above their baseline levels for several seconds. This maintained activity is not always correlated with the monkey’s task and its origin is unknown. We have previously proposed a simple neural network model, based on shape selective neurons in monkey lateral intraparietal cortex, which predicts the valence and time course of reflexive (bottom-up) spatial attention. In the same simple model, we demonstrate here that passive maintained activity or short-term memory of specific visual events can result without need for an external or top-down modulatory signal. Mutual inhibition and neuronal adaptation play distinct roles in reflexive attention and memory. This modest 4-cell model provides the first simple and unified physiologically plausible mechanism of reflexive spatial attention and passive short-term memory processes. PMID:26493949

Spectral characteristics of speech with fixed jaw displacements

NASA Astrophysics Data System (ADS)

Solomon, Nancy P.; Makashay, Matthew J.; Munson, Benjamin

2004-05-01

During speech, movements of the mandible and the tongue are interdependent. For some research purposes, the mandible may be constrained to ensure independent tongue motion. To examine specific spectral characteristics of speech with different jaw positions, ten normal adults produced sentences with multiple instances of /t/, /s/, /squflg/, /i/, /ai/, and /squflgi/. Talkers produced stimuli with the jaw free to vary, and while gently biting on 2- and 5-mm bite blocks unilaterally. Spectral moments of /s/ and /squflg/ frication and /t/ bursts differed such that mean spectral energy decreased, and diffuseness and skewness increased with bite blocks. The specific size of the bite block had minimal effect on these results, which were most consistent for /s/. Formant analysis for the vocoids revealed lower F2 frequency in /i/ and at the end of the transition in /ai/ when bite blocks were used; F2 slope for diphthongs was not sensitive to differences in jaw position. Two potential explanations for these results involve the physical presence of the bite blocks in the lateral oral cavity, and the oromotor system's ability to compensate for fixed jaw displacements. [Work supported by NIDCD R03-DC06096.

Dynamic stretching and golf swing performance.

PubMed

Moran, K A; McGrath, T; Marshall, B M; Wallace, E S

2009-02-01

The aim of the present study was to examine the effect of dynamic stretching, static stretching and no stretching, as part of a general warm-up, on golf swing performance with a five-iron. Measures of performance were taken 0 min, 5 min, 15 min and 30 min after stretching. Dynamic stretching produced significantly greater club head speeds than both static stretching (Delta=1.9m.s (-1); p=0.000) and no stretching (Delta=1.7 m.s (-1); p=0.000), and greater ball speeds than both static stretching (Delta=3.5m.s (-1); p=0.003) and no stretching (Delta=3.3m.s (-1); p=0.001). Dynamic stretching produced significantly straighter swing-paths than both static stretching (Delta=-0.61 degrees , p=0.000) and no stretching (Delta=-0.72 degrees , p=0.01). Dynamic stretching also produced more central impact points than the static stretch (Delta=0.7 cm, p=0.001). For the club face angle, there was no effect of either stretch or time. For all of the variables measured, there was no significant difference between the static stretch and no stretch conditions. All of the results were unaffected by the time of measurement after stretching. The results indicate that dynamic stretching should be used as part of a general warm-up in golf.

Reflex effects on components of synchronized renal sympathetic nerve activity.

PubMed

DiBona, G F; Jones, S Y

1998-09-01

The effects of peripheral thermal receptor stimulation (tail in hot water, n = 8, anesthetized) and cardiac baroreceptor stimulation (volume loading, n = 8, conscious) on components of synchronized renal sympathetic nerve activity (RSNA) were examined in rats. The peak height and peak frequency of synchronized RSNA were determined. The renal sympathoexcitatory response to peripheral thermal receptor stimulation was associated with an increase in the peak height. The renal sympathoinhibitory response to cardiac baroreceptor stimulation was associated with a decrease in the peak height. Although heart rate was significantly increased with peripheral thermal receptor stimulation and significantly decreased with cardiac baroreceptor stimulation, peak frequency was unchanged. As peak height reflects the number of active fibers, reflex increases and decreases in synchronized RSNA are mediated by parallel increases and decreases in the number of active renal nerve fibers rather than changes in the centrally based rhythm or peak frequency. The increase in the number of active renal nerve fibers produced by peripheral thermal receptor stimulation reflects the engagement of a unique group of silent renal sympathetic nerve fibers with a characteristic response pattern to stimulation of arterial baroreceptors, peripheral and central chemoreceptors, and peripheral thermal receptors.

Stretching Safely and Effectively

MedlinePlus

... shown that stretching immediately before an event weakens hamstring strength. Instead of static stretching, try performing a " ... If you play soccer, for instance, stretch your hamstrings as you're more vulnerable to hamstring strains. ...

Changes in spinal reflex excitability associated with motor sequence learning.

PubMed

Lungu, Ovidiu; Frigon, Alain; Piché, Mathieu; Rainville, Pierre; Rossignol, Serge; Doyon, Julien

2010-05-01

There is ample evidence that motor sequence learning is mediated by changes in brain activity. Yet the question of whether this form of learning elicits changes detectable at the spinal cord level has not been addressed. To date, studies in humans have revealed that spinal reflex activity may be altered during the acquisition of various motor skills, but a link between motor sequence learning and changes in spinal excitability has not been demonstrated. To address this issue, we studied the modulation of H-reflex amplitude evoked in the flexor carpi radialis muscle of 14 healthy individuals between blocks of movements that involved the implicit acquisition of a sequence versus other movements that did not require learning. Each participant performed the task in three conditions: "sequence"-externally triggered, repeating and sequential movements, "random"-similar movements, but performed in an arbitrary order, and "simple"- involving alternating movements in a left-right or up-down direction only. When controlling for background muscular activity, H-reflex amplitude was significantly more reduced in the sequence (43.8 +/- 1.47%. mean +/- SE) compared with the random (38.2 +/- 1.60%) and simple (31.5 +/- 1.82%) conditions, while the M-response was not different across conditions. Furthermore, H-reflex changes were observed from the beginning of the learning process up to when subjects reached asymptotic performance on the motor task. Changes also persisted for >60 s after motor activity ceased. Such findings suggest that the excitability in some spinal reflex circuits is altered during the implicit learning process of a new motor sequence.

An Ancient Gene Network Is Co-opted for Teeth on Old and New Jaws

PubMed Central

Fraser, Gareth J; Hulsey, C. Darrin; Bloomquist, Ryan F; Uyesugi, Kristine; Manley, Nancy R; Streelman, J. Todd

2009-01-01

Vertebrate dentitions originated in the posterior pharynx of jawless fishes more than half a billion years ago. As gnathostomes (jawed vertebrates) evolved, teeth developed on oral jaws and helped to establish the dominance of this lineage on land and in the sea. The advent of oral jaws was facilitated, in part, by absence of hox gene expression in the first, most anterior, pharyngeal arch. Much later in evolutionary time, teleost fishes evolved a novel toothed jaw in the pharynx, the location of the first vertebrate teeth. To examine the evolutionary modularity of dentitions, we asked whether oral and pharyngeal teeth develop using common or independent gene regulatory pathways. First, we showed that tooth number is correlated on oral and pharyngeal jaws across species of cichlid fishes from Lake Malawi (East Africa), suggestive of common regulatory mechanisms for tooth initiation. Surprisingly, we found that cichlid pharyngeal dentitions develop in a region of dense hox gene expression. Thus, regulation of tooth number is conserved, despite distinct developmental environments of oral and pharyngeal jaws; pharyngeal jaws occupy hox-positive, endodermal sites, and oral jaws develop in hox-negative regions with ectodermal cell contributions. Next, we studied the expression of a dental gene network for tooth initiation, most genes of which are similarly deployed across the two disparate jaw sites. This collection of genes includes members of the ectodysplasin pathway, eda and edar, expressed identically during the patterning of oral and pharyngeal teeth. Taken together, these data suggest that pharyngeal teeth of jawless vertebrates utilized an ancient gene network before the origin of oral jaws, oral teeth, and ectodermal appendages. The first vertebrate dentition likely appeared in a hox-positive, endodermal environment and expressed a genetic program including ectodysplasin pathway genes. This ancient regulatory circuit was co-opted and modified for teeth in oral

Synovial sarcoma of the jaw in a dog.

PubMed

Griffith, J W; Frey, R A; Sharkey, F E

1987-05-01

A case of synovial sarcoma of the jaw with pulmonary metastasis is described in a dog. It appears to be a rare or underdiagnosed neoplasm in animals and not previously reported in the jaw. Its diagnostic microscopic features are the biphasic cellular pattern and cleft formations. It may otherwise resemble haemangiopericytoma, malignant fibrous histiocytoma, reticulum cell sarcoma, fibrosarcoma, or giant-cell tumour of soft tissue.

The Relation Between Stretching Typology and Stretching Duration: The Effects on Range of Motion.

PubMed

Thomas, Ewan; Bianco, Antonino; Paoli, Antonio; Palma, Antonio

2018-04-01

Different stretching strategies and protocols are widely used to improve flexibility or maintain health, acting on the muscle tendon-unit, in order to improve the range of motion (ROM) of the joints. This review aims to evaluate the current body of literature in order to understand the relation between stretching typology and ROM, and secondly to evaluate if a relation exists between stretching volume (either as a single training session, weekly training and weekly frequency) and ROM, after long-term stretching. Twenty-three articles were considered eligible and included in the quantitative synthesis. All stretching typologies showed ROM improvements over a long-term period, however the static protocols showed significant gains (p<0.05) when compared to the ballistic or PNF protocols. Time spent stretching per week seems fundamental to elicit range of movement improvements when stretches are applied for at least or more than 5 min, whereas the time spent stretching within a single session does not seem to have significant effects for ROM gains. Weekly frequency is positively associated to ROM. Evaluated data indicates that performing stretching at least 5 days a week for at least 5 min per week using static stretching may be beneficial to promote ROM improvements. © Georg Thieme Verlag KG Stuttgart · New York.

The characters of Palaeozoic jawed vertebrates

PubMed Central

Brazeau, Martin D; Friedman, Matt

2014-01-01

Newly discovered fossils from the Silurian and Devonian periods are beginning to challenge embedded perceptions about the origin and early diversification of jawed vertebrates (gnathostomes). Nevertheless, an explicit cladistic framework for the relationships of these fossils relative to the principal crown lineages of the jawed vertebrates (osteichthyans: bony fishes and tetrapods; chondrichthyans: sharks, batoids, and chimaeras) remains elusive. We critically review the systematics and character distributions of early gnathostomes and provide a clearly stated hierarchy of synapomorphies covering the jaw-bearing stem gnathostomes and osteichthyan and chondrichthyan stem groups. We show that character lists, designed to support the monophyly of putative groups, tend to overstate their strength and lack cladistic corroboration. By contrast, synapomorphic hierarchies are more open to refutation and must explicitly confront conflicting evidence. Our proposed synapomorphy scheme is used to evaluate the status of the problematic fossil groups Acanthodii and Placodermi, and suggest profitable avenues for future research. We interpret placoderms as a paraphyletic array of stem-group gnathostomes, and suggest what we regard as two equally plausible placements of acanthodians: exclusively on the chondrichthyan stem, or distributed on both the chondrichthyan and osteichthyan stems. PMID:25750460

Protective role of aerodigestive reflexes against aspiration: study on subjects with impaired and preserved reflexes.

PubMed

Dua, Kulwinder; Surapaneni, Sri Naveen; Kuribayashi, Shiko; Hafeezullah, Mohammed; Shaker, Reza

2011-06-01

Direct evidence to support the airway protective function of aerodigestive reflexes triggered by pharyngeal stimulation was previously demonstrated by abolishing these reflexes by topical pharyngeal anesthesia in normal subjects. Studies have also shown that these reflexes deteriorate in cigarette smokers. Aim of this study was to determine the influence of defective pharyngeal aerodigestive reflexes on airway protection in cigarette smokers. Pharyngoglottal Closure reflex; PGCR, Pharyngo-UES Contractile reflex; PUCR, and Reflexive Pharyngeal Swallow; RPS were studied in 15 healthy non-smokers (24.2±3.3 SD y, 7 males) and 15 healthy chronic smokers (27.3±8.1, 7 males). To elicit these reflexes and to evaluate aspiration, colored water was perfused into the hypopharynx at the rate of 1 mL/min. Maximum volume of water that can safely dwell in the hypopharynx before spilling into the larynx (Hypopharyngeal Safe Volume; HPSV) and the threshold volume to elicit PGCR, PUCR, and RPS were determined in smokers and results compared with non-smokers. At baseline, RPS was elicited in all non-smokers (100%) and in only 3 of 15 smokers (20%; P<.001). None of the non-smokers showed evidence of laryngeal spillage of water, whereas 12 of 15 smokers with absent RPS had laryngeal spillage. Pharyngeal anesthesia abolished RPS reflex in all non-smokers resulting in laryngeal spillage. The HPSV was 0.61±0.06 mL and 0.76±0.06 mL in non-smokers and smokers respectively (P=.1). Deteriorated reflexive pharyngeal swallow in chronic cigarette smokers predispose them to risks of aspiration and similarly, abolishing this reflex in non-smokers also results in laryngeal spillage. These observations directly demonstrate the airway protective function of RPS. Copyright © 2011 AGA Institute. Published by Elsevier Inc. All rights reserved.

Surgical treatment of jaw osteonecrosis in "Krokodil" drug addicted patients.

PubMed

Poghosyan, Yuri M; Hakobyan, Koryun A; Poghosyan, Anna Yu; Avetisyan, Eduard K

2014-12-01

Retrospective study of jaw osteonecrosis treatment in patients using the "Krokodil" drug from 2009 to 2013. On the territory of the former USSR countries there is widespread use of a self-produced drug called "Krokodil". Codeine containing analgesics ("Sedalgin", "Pentalgin" etc), red phosphorus (from match boxes) and other easily acquired chemical components are used for synthesis of this drug, which used intravenously. Jaw osteonecrosis develops as a complication in patients who use "Krokodil". The main feature of this disease is jawbone exposure in the oral cavity. Surgery is the main method for the treatment of jaw osteonecrosis in patients using "Krokodil". 40 "Krokodil" drug addict patients with jaw osteonecrosis were treated. Involvement of maxilla was found in 11 patients (27.5%), mandible in 21 (52.5%), both jaws in 8 (20%) patients. 35 Lesions were found in 29 mandibles and 21 lesions in 19 maxillas. Main factors of treatment success are: cessation of "Krokodil" use in the pre- (minimum 1 month) and postoperative period and osteonecrosis area resection of a minimum of 0.5 cm beyond the visible borders of osteonecrosis towards the healthy tissues. Surgery was not delayed until sequestrum formation. In the mandible marginal or segmental resection (with or without TMJ exarticulation) was performed. After surgery recurrence of disease was seen in 8 (23%) cases in the mandible, with no cases of recurrence in the maxilla. According to our experience in this case series, surgery is the main method for the treatment of jaw osteonecrosis in patients using "Krokodil". Cessation of drug use and jaw resection minimize the rate of recurrences in such patients. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Small vertical changes in jaw relation affect motor unit recruitment in the masseter.

PubMed

Terebesi, S; Giannakopoulos, N N; Brüstle, F; Hellmann, D; Türp, J C; Schindler, H J

2016-04-01

Strategies for recruitment of masseter muscle motor units (MUs), provoked by constant bite force, for different vertical jaw relations have not previously been investigated. The objective of this study was to analyse the effect of small changes in vertical jaw relation on MU recruitment behaviour in different regions of the masseter during feedback-controlled submaximum biting tasks. Twenty healthy subjects (mean age: 24·6 ± 2·4 years) were involved in the investigation. Intra-muscular electromyographic (EMG) activity of the right masseter was recorded in different regions of the muscle. MUs were identified by the use of decomposition software, and root-mean-square (RMS) values were calculated for each experimental condition. Six hundred and eleven decomposed MUs with significantly (P < 0·001) different jaw relation-specific recruitment behaviour were organised into localised MU task groups. MUs with different task specificity in seven examined tasks were observed. The RMS EMG values obtained from the different recording sites were also significantly (P < 0·01) different between tasks. Overall MU recruitment was significantly (P < 0·05) greater in the deep masseter than in the superficial muscle. The number of recruited MUs and the RMS EMG values decreased significantly (P < 0·01) with increasing jaw separation. This investigation revealed differential MU recruitment behaviour in discrete subvolumes of the masseter in response to small changes in vertical jaw relations. These fine-motor skills might be responsible for its excellent functional adaptability and might also explain the successful management of temporomandibular disorder patients by somatic intervention, in particular by the use of oral splints. © 2015 John Wiley & Sons Ltd.

Pain and Disability in the Jaw and Neck Region following Whiplash Trauma.

PubMed

Häggman-Henrikson, B; Lampa, E; Marklund, S; Wänman, A

2016-09-01

The relationship between whiplash trauma and chronic orofacial pain is unclear, especially with regard to the time elapsed from trauma to development of orofacial pain. The aim was to analyze prevalence of jaw pain and disability, as well as the relationship between pain and disability in the jaw and neck regions in the early nonchronic stage after whiplash trauma. In this case-control study, 70 individuals (40 women, 30 men, mean age 35.5 y) who visited an emergency department with neck pain following a car accident were examined within 3 wk of trauma (group 1) and compared with 70 individuals (42 women, 28 men, mean age 33.8 y), who declined to attend a clinical examination but agreed to fill in questionnaires (group 2). The 2 case groups were compared with a matched control group of 70 individuals (42 women, 28 men, mean age 37.6 y) without a history of neck trauma. All participants completed questionnaires regarding jaw pain and dysfunction, rating pain intensity in jaw and neck regions on the Numerical Rating Scale, the Neck Disability Index, and Jaw Disability Checklist. Compared with controls, individuals with a recent whiplash trauma reported more jaw pain and dysfunction. Furthermore, there was a moderate positive correlation between jaw and neck pain ratings for group 1 (r = 0.61, P < 0.0001) and group 2 (r = 0.59, P < 0.0001). In the logistic regression analysis, cases showed higher odds ratios (range, 6.1 to 40.8) for jaw and neck pain and disability compared with controls. Taken together, the results show that individuals with a recent whiplash trauma report more jaw pain and disability compared with controls without a history of neck trauma. Furthermore, the correlation between jaw and neck pain intensity implies that intensity of neck pain in the acute stage after whiplash trauma might be a possible risk factor also for development of chronic orofacial pain. © International & American Associations for Dental Research 2016.

Gene expression of stretch-activated channels and mechanoelectric feedback in the heart.

PubMed

Kelly, D; Mackenzie, L; Hunter, P; Smaill, B; Saint, D A

2006-07-01

1. Mechanoelectric feedback (MEF) in the heart is the process by which mechanical forces on the myocardium can change its electrical properties. Mechanoelectric feedback has been demonstrated in many animal models, ranging from isolated cells, through isolated hearts to whole animals. In humans, MEF has been demonstrated directly in both the atria and the ventricles. It seems likely that MEF provides either the trigger or the substrate for some types of clinically important arrhythmias. 2. Mechanoelectric feedback may arise because of the presence of stretch-sensitive (or mechano-sensitive) ion channels in the cell membrane of the cardiac myocytes. Two types have been demonstrated: (i) a non-specific cation channel (stretch-activated channel (SAC); conductance of approximately 25 pS); and (ii) a potassium channel with a conductance of approximately 100 pS. The gene coding for the SAC has not yet been identified. The gene for the potassium channel is likely to be TREK, a member of the tandem pore potassium channel gene family. We have recorded stretch-sensitive potassium channels in rat isolated myocytes that have the properties of TREK channels expressed in heterologous systems. 3. It has been shown that TREK mRNA is expressed heterogeneously in the rat ventricular wall, with 17-fold more expression in endocardial compared with epicardial cells. This difference is reflected in the TREK currents recorded from endocardial and epicardial cells using whole-cell patch-clamp techniques, although the difference in current density was less pronounced (approximately threefold). Consistent with this, we show here that when the ventricle is stretched by inflation of an intraventricular balloon in a Langendorff perfused rat isolated heart, action potential shortening was more pronounced in the endocardium (30% shortening at 40 mmHg) compared with that in the epicardium (10% shortening at the same pressure). 4. Computer models of the mechanics of the (pig) heart show pronounced

Jaw1/LRMP has a role in maintaining nuclear shape via interaction with SUN proteins.

PubMed

Kozono, Takuma; Tadahira, Kazuko; Okumura, Wataru; Itai, Nao; Tamura-Nakano, Miwa; Dohi, Taeko; Tonozuka, Takashi; Nishikawa, Atsushi

2018-06-06

Jaw1/LRMP is characterized as a type II integral membrane protein that is localized to endoplasmic reticulum (ER), however, its physiological functions have been poorly understood. An alignment of amino acid sequence of Jaw1 with KASH proteins, outer nuclear membrane proteins, revealed that Jaw1 has a partial homology to the KASH domain. Here, we show that the function of Jaw1 is to maintain nuclear shape in mouse melanoma cell line. The siRNA-mediated knockdown of Jaw1 caused a severe defect in nuclear shape, and the defect was rescued by ectopic expression of siRNA-resistant Jaw1. Since co-immunoprecipitation assay indicates that Jaw1 interacts with SUN proteins that are inner nuclear proteins and microtubules, this study suggests that Jaw1 has a role in maintaining nuclear shape via interactions with SUN proteins and microtubules.

Sweating response to passive stretch of the calf muscle during activation of forearm muscle metaboreceptors in heated humans.

PubMed

Amano, Tatsuro; Ichinose, Masashi; Nishiyasu, Takeshi; Inoue, Yoshimitsu; Koga, Shunsaku; Miwa, Mikio; Kondo, Narihiko

2014-05-15

Activation of muscle metaboreceptors and mechanoreceptors has been shown to independently influence the sweating response, while their integrative control effects remain unclear. We examined the sweating response when the two muscle receptors are concurrently activated in different limbs, as well as the blood pressure response. In total, 27 young males performed passive calf muscle stretches (muscle mechanoreceptor activation) for 30 s in a semisupine position with and without postisometric handgrip exercise muscle ischemia (PEMI, muscle metaboreceptor activation) at exercise intensities of 35 and 50% of maximum voluntary contraction (MVC) under hot conditions (ambient temperature, 35°C, relative humidity, 50%). Passive calf muscle stretching alone increased the mean sweating rate significantly on the forehead, chest, and thigh (SRmean) and mean arterial blood pressure (MAP), but not the heart rate (HR), from prestretching levels by 0.04 ± 0.01 mg·cm(2)·min(-1), 4.0 ± 1.3 mmHg (P < 0.05), and -1.0 ± 0.5 beats/min (P > 0.05), respectively. The SRmean and MAP during PEMI were significantly higher than those at rest. The passive calf muscle stretch during PEMI increased MAP significantly by 3.4 ± 1.0 and 2.0 ± 0.7 mmHg for 35 and 50% of MVC, respectively (P < 0.05), but not that of SRmean or HR at either exercise intensity. These results suggest that sweating and blood pressure responses to concurrent activation of the two muscle receptors in different limbs differ and that the influence of calf muscle mechanoreceptor activation alone on the sweating response disappears during forearm muscle metaboreceptor activation. Copyright © 2014 the American Physiological Society.

Stretch-Oriented Polyimide Films

NASA Technical Reports Server (NTRS)

Hinkley, Jeffrey A.; Klinedinst, D.; Feuz, L.

2000-01-01

Two thermoplastic polyimides - one amorphous, the other crystallizable -- were subjected to isothermal stretching just above their glass transition temperatures. Room-temperature strengths in the stretch direction were greatly improved and, moduli increased up to 3.6-fold. Optimum stretching conditions were determined.

Postactivation potentiation can counteract declines in force and power that occur after stretching.

PubMed

Kümmel, J; Kramer, A; Cronin, N J; Gruber, M

2017-12-01

Stretching can decrease a muscle's maximal force, whereas short but intense muscle contractions can increase it. We hypothesized that when combined, postactivation potentiation induced by reactive jumps would counteract stretch-induced decrements in drop jump (DJ) performance. Moreover, we measured changes in muscle twitch forces and ankle joint stiffness (K A nkle ) to examine underlying mechanisms. Twenty subjects completed three DJs and 10 electrically evoked muscle twitches of the triceps surae subsequent to four different conditioning activities and control. The conditioning activities were 10 hops, 20s of static stretching of the triceps surae muscle, 20s of stretching followed by 10 hops, and vice versa. After 10 hops, twitch peak torque (TPT) was 20% and jump height 5% higher compared with control with no differences in K A nkle . After stretching, TPT and jump height were both 9% and K A nkle 6% lower. When hops and stretching were combined as conditioning activities, jump height was not different compared with control but significantly higher (11% and 8%) compared with stretching. TPTs were 16% higher compared with control when the hops were performed after stretching and 9% higher compared with the reverse order. K A nkle was significantly lower when stretching was performed after the hops (6%) compared with control, but no significant difference was observed when hops were performed after stretching. These results demonstrate that conditioning hops can counteract stretch-related declines in DJ performance. Furthermore, the differences in TPTs and K A nkle between combined conditioning protocols indicate that the order of conditioning tasks might play an important role at the muscle-tendon level. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effects of pirfenidone on increased cough reflex sensitivity in guinea pigs.

PubMed

Okazaki, Akihito; Ohkura, Noriyuki; Fujimura, Masaki; Katayama, Nobuyuki; Kasahara, Kazuo

2013-10-01

Pirfenidone, an antifibrotic drug with anti-inflammatory and antioxidant effects, delays fibrosis in idiopathic pulmonary fibrosis (IPF). Patients with IPF have a greater cough reflex sensitivity to inhaled capsaicin than healthy people, and cough is an independent predictor of IPF disease progression; however, the effects of pirfenidone on cough reflex sensitivity are unknown. After challenge with an aerosolized antigen in actively sensitized guinea pigs, pirfenidone was administered intraperitoneally, and the cough reflex sensitivity was measured at 48 h after the challenge. Bronchoalveolar lavage (BAL) was performed, and the tracheal tissue was collected. Pirfenidone suppressed the capsaicin-induced increase in cough reflex sensitivity in a dose-dependent manner. Additionally, increased levels of prostaglandin E2, substance P, and leukotriene B4, but not histamine, in the BAL fluid were dose dependently suppressed by pirfenidone. The decrease in neutral endopeptidase activity in the tracheal tissue was also alleviated by pirfenidone treatment. The total number of cells and components in the BAL fluid was not influenced. These results suggest that pirfenidone ameliorates isolated cough based on increased cough reflex sensitivity associated with allergic airway diseases, and potentially relieve chronic cough in IPF patients who often have increased cough reflex sensitivity. Prospective studies on cough-relieving effects of pirfenidone in patients with IPF are therefore warranted. Copyright © 2013 Elsevier Ltd. All rights reserved.

Digital impression and jaw relation record for the fabrication of CAD/CAM custom tray.

PubMed

Kanazawa, Manabu; Iwaki, Maiko; Arakida, Toshio; Minakuchi, Shunsuke

2018-03-16

This article describes the protocol of a digital impression technique to make an impression and recording of the jaw relationship of edentulous patients for the fabrication of CAD/CAM custom tray using computer-aided design and manufacturing (CAD/CAM) technology. Scan the maxillary and mandibular edentulous jaws using an intraoral scanner. Scan the silicone jig with the maxillary and mandibular jaws while keeping the jig between the jaws. Import the standard tessellation language data of the maxillary and mandibular jaws and jig to make a jaw relation record and fabricate custom trays (CAD/CAM trays) using a rapid prototyping system. Make a definitive impression of the maxillary and mandibular jaws using the CAD/CAM trays. Digitalization of the complete denture fabrication process can simplify the complicated treatment and laboratory process of conventional methods In addition, the proposed method enables quality control regardless of the operator's experience and technique. Copyright © 2018. Published by Elsevier Ltd.

Masticatory jaw movement of Exaeretodon argentinus (Therapsida: Cynodontia) inferred from its dental microwear

PubMed Central

Yamada, Eisuke; Kubo, Mugino O.

2017-01-01

Dental microwear of four postcanine teeth of Exaeretodon argentinus was analyzed using both two dimensional (2D) and three dimensional (3D) methods to infer their masticatory jaw movements. Results of both methods were congruent, showing that linear microwear features (scratches) were well aligned and mostly directed to the antero-posterior direction in all four teeth examined. These findings support the palinal masticatory jaw movement, which was inferred in previous studies based on the observation of gross morphology of wear facets. In contrast, the lack of detection of lateral scratches confirmed the absence of the lateral jaw movement that was also proposed by a previous study. Considering previous microwear studies on cynodonts, palinal jaw movements observed in Exaeretodon evolved within cynognathian cynodonts from the fully orthal jaw movement of its basal member. Although there are currently only three studies of dental microwear of non-mammalian cynodonts including the present study, microwear analysis is a useful tool for the reconstruction of masticatory jaw movement and its future application to various cynodonts will shed light on the evolutionary process of jaw movement towards the mammalian condition in more detail. PMID:29186178

Kinematic analysis of jaw function in children following traumatic brain injury.

PubMed

Loh, E W L; Goozée, J V; Murdoch, B E

2005-07-01

To investigate jaw movements in children following traumatic brain injury (TBI) during speech using electromagnetic articulography (EMA). Jaw movements of two non-dysarthric children (aged 12.75 and 13.08 years) who had sustained a TBI were recorded using the AG-100 EMA system (Carstens Medizineletronik) during word-initial consonant productions. Mean quantitative kinematic parameters and coefficient of variation (variability) values were calculated and individually compared to the mean values obtained by a group of six control children (mean age 12.57 years, SD 1.52). The two children with TBI exhibited word-initial consonant jaw movement durations that were comparable to the control children, with sub-clinical reductions in speed being offset by reduced distances. Differences were observed between the two children in jaw kinematic variability, with one child exhibiting increased variability, while the other child demonstrated reduced or comparable variability compared to the control group. Possible sub-clinical impairments of jaw movement for speech were exhibited by two children who had sustained a TBI, providing insight into the consequences of TBI on speech motor control development.

Towards Practical Reflexivity in Online Discussion Groups

ERIC Educational Resources Information Center

Sarja, Anneli; Janhonen, Sirpa; Havukainen, Pirjo; Vesterinen, Anne

2018-01-01

This paper continues the discussion about student-driven, interactive learning activities in higher education. Using object-oriented activity theory, the article explores the relational aspects of reflexive practice as demonstrated in five online discussions groups to develop students' conceptual understanding. The purpose of the research is to…

Developmental evidence for serial homology of the vertebrate jaw and gill arch skeleton

PubMed Central

Gillis, J. Andrew; Modrell, Melinda S.; Baker, Clare V. H.

2013-01-01

Gegenbaur’s classical hypothesis of jaw-gill arch serial homology is widely cited, but remains unsupported by either paleontological evidence (e.g. a series of fossils reflecting the stepwise transformation of a gill arch into a jaw) or developmental genetic data (e.g. shared molecular mechanisms underlying segment identity in the mandibular, hyoid and gill arch endoskeletons). Here we show that nested expression of Dlx genes – the “Dlx code” that specifies upper and lower jaw identity in mammals and teleosts – is a primitive feature of the mandibular, hyoid and gill arches of jawed vertebrates. Using fate-mapping techniques, we demonstrate that the principal dorsal and ventral endoskeletal segments of the jaw, hyoid and gill arches of the skate Leucoraja erinacea derive from molecularly equivalent mesenchymal domains of combinatorial Dlx gene expression. Our data suggest that vertebrate jaw, hyoid and gill arch cartilages are serially homologous, and were primitively patterned dorsoventrally by a common Dlx blueprint. PMID:23385581

Oxygen-conserving reflexes of the brain: the current molecular knowledge

PubMed Central

Schaller, B; Cornelius, J F; Sandu, N; Ottaviani, G; Perez-Pinzon, M A

2009-01-01

Abstract The trigemino-cardiac reflex (TCR) may be classified as a sub-phenomenon in the group of the so-called ‘oxygen-conserving reflexes’. Within seconds after the initiation of such a reflex, there is neither a powerful and differentiated activation of the sympathetic system with subsequent elevation in regional cerebral blood flow (CBF) with no changes in the cerebral metabolic rate of oxygen (CMRO2) or in the cerebral metabolic rate of glucose (CMRglc). Such an increase in regional CBF without a change of CMRO2 or CMRglc provides the brain with oxygen rapidly and efficiently and gives substantial evidence that the TCR is an oxygen-conserving reflex. This system, which mediates reflex protection projects via currently undefined pathways from the rostral ventrolateral medulla oblongata to the upper brainstem and/or thalamus which finally engage a small population of neurons in the cortex. This cortical centre appears to be dedicated to reflexively transduce a neuronal signal into cerebral vasodilatation and synchronization of electrocortical activity. Sympathetic excitation is mediated by cortical-spinal projection to spinal pre-ganglionic sympathetic neurons whereas bradycardia is mediated via projections to cardiovagal motor medullary neurons. The integrated reflex response serves to redistribute blood from viscera to brain in response to a challenge to cerebral metabolism, but seems also to initiate a preconditioning mechanism. Better and more detailed knowledge of the cascades, transmitters and molecules engaged in such endogenous (neuro) protection may provide new insights into novel therapeutic options for a range of disorders characterized by neuronal death and into cortical organization of the brain. PMID:19438971

Hypothyroidism impairs somatovisceral reflexes involved in micturition of female rabbits.

PubMed

Sánchez-García, Octavio; López-Juárez, Rhode; Rodríguez-Castelán, Julia; Corona-Quintanilla, Dora L; Martínez-Gómez, Margarita; Cuevas-Romero, Estela; Castelán, Francisco

2018-04-17

To determine the impact of hypothyroidism on the bladder and urethral functions as well as in the activation of the pubococcygeous (Pcm) and bulbospongiosus (Bsm) during micturition. Age-matched control and methimazole-induced hypothyroid female rabbits were used to simultaneously record cystometrograms, urethral pressure, and the reflex activation of Pcm and Bsm during the induced micturition. Urodynamic and urethral variables were measured. Activation or no activation of the Pcm and Bsm during the storage and voiding phases of micturition were categorized as 1 or 0. Significant differences (P ≤ 0.05) between control and hypothyroid groups were determined with unpaired Student-t or Mann-Whitney tests. One-month induced hypothyroidism increased the residual volume and threshold pressure while the opposite was true for the voided volume, maximal pressure, and voiding efficiency. Urethral pressure was also affected as supported by a notorious augmentation of the urethral resistance, among other changes in the rest of measured variables. Hypothyroidism also affected the reflex activation of the Pcm in the voiding phase of micturition. Our findings demonstrate hypothyroidism impairs the bladder and, urethral functions, and reflex activation of Pcm and Bsm affecting the micturition in female rabbits. © 2018 Wiley Periodicals, Inc.

[Reflex seizures, cinema and television].

PubMed

Olivares-Romero, Jesús

2015-12-16

In movies and television series are few references to seizures or reflex epilepsy even though in real life are an important subgroup of total epileptic syndromes. It has performed a search on the topic, identified 25 films in which they appear reflex seizures. Most seizures observed are tonic-clonic and visual stimuli are the most numerous, corresponding all with flashing lights. The emotions are the main stimuli in higher level processes. In most cases it is not possible to know if a character suffers a reflex epilepsy or suffer reflex seizures in the context of another epileptic syndrome. The main conclusion is that, in the movies, the reflex seizures are merely a visual reinforcing and anecdotal element without significant influence on the plot.

Acute Effects of Hamstring Stretching on Sagittal Spinal Curvatures and Pelvic Tilt

PubMed Central

López-Miñarro, Pedro A.; Muyor, José M.; Belmonte, Felipe; Alacid, Fernando

2012-01-01

The aim of this study was to determine acute effects of hamstring stretching in thoracic and lumbar spinal curvatures and pelvic tilt. Fifty-five adults (29.24 ± 7.41 years) were recruited for this study. Subjects performed a hamstring stretching protocol consisting of four exercises. The session consisted of 3 sets of each exercise and subjects held the position for 20 seconds with a 30-second rest period between sets and exercises. Thoracic and lumbar spinal angles and pelvic tilt were measured with a SpinalMouse in relaxed standing, sit-and-reach test and Macrae & Wright position. Hamstring extensibility was determined by active straight leg raise test and sit-and-reach score. All measures were performed before and immediately after the hamstring stretching protocol. Active straight leg raise angle and sitand-reach score significantly improved immediately after the stretching protocol (p<0.001). Greater anterior pelvic tilt (p<0.001) and lumbar flexion (p<0.05) and a smaller thoracic kyphosis in the sit-and-reach (p<0.001) were found after the stretching protocol. However, stretching produced no significant change on spinal curvatures or pelvic tilt in standing and maximal trunk flexion with knees flexed. In conclusion, static stretching of the hamstring is associated to an immediate change in the sagittal spinal curvatures and pelvic position when performing trunk flexion with knees extended, so that allowing for greater lumbar flexion and anterior pelvic tilt and lower thoracic kyphosis. Hamstring stretching is recommended prior to sport activities involving trunk flexion with the knees straight. PMID:23486214

Effects of Static Stretching and Playing Soccer on Knee Laxity.

PubMed

Baumgart, Christian; Gokeler, Alli; Donath, Lars; Hoppe, Matthias W; Freiwald, Jürgen

2015-11-01

This study investigated exercise-induced effects of static stretching and playing soccer on anterior tibial translation (ATT) of the knee joint. Randomized controlled trial. University biomechanics laboratory. Thirty-one athletes were randomly assigned into a stretching (26.9 ± 6.2 years, 1.77 ± 0.09 m, 67.9 ± 10.7 kg) and a control group (27.9 ± 7.4 years, 1.75 ± 0.08 m, 72.0 ± 14.9 kg). Thirty-one amateur soccer players in an additional soccer group (25.1 ± 5.6 years, 1.74 ± 0.10 m, 71.8 ± 14.8 kg). All participants had no history of knee injury requiring surgery and any previous knee ligament or cartilage injury. The stretching group performed 4 different static stretching exercises with a duration of 2 × 20 seconds interspersed with breaks of 10 seconds. The soccer group completed a 90-minute soccer-specific training program. The control group did not perform any physical activity for approximately 30 minutes. Anterior tibial translation was measured with the KT-1000 knee arthrometer at forces of 67 N, 89 N, and maximal manual force (Max) before and after the intervention. There was a significant increase in ATT after static stretching and playing soccer at all applied forces. Maximal manual testing revealed a mean increase of ATT after static stretching of 2.1 ± 1.6 mm (P < 0.0005) and after playing soccer of 1.0 ± 1.5 mm (P = 0.001). The ATT increase after static stretching at 67 and 89 N is significantly higher than in controls. At maximum manual testing, significant differences were evident between all groups. Static stretching and playing soccer increase ATT and may consequently influence mechanical factors of the anterior cruciate ligament. The ATT increase after static stretching was greater than after playing soccer. The observed increase in ATT after static stretching and playing soccer may be associated with changes in kinesthetic perception and sensorimotor control, activation of muscles, joint stability, overall performance, and higher

Control of respiration in fish, amphibians and reptiles.

PubMed

Taylor, E W; Leite, C A C; McKenzie, D J; Wang, T

2010-05-01

Fish and amphibians utilise a suction/force pump to ventilate gills or lungs, with the respiratory muscles innervated by cranial nerves, while reptiles have a thoracic, aspiratory pump innervated by spinal nerves. However, fish can recruit a hypobranchial pump for active jaw occlusion during hypoxia, using feeding muscles innervated by anterior spinal nerves. This same pump is used to ventilate the air-breathing organ in air-breathing fishes. Some reptiles retain a buccal force pump for use during hypoxia or exercise. All vertebrates have respiratory rhythm generators (RRG) located in the brainstem. In cyclostomes and possibly jawed fishes, this may comprise elements of the trigeminal nucleus, though in the latter group RRG neurons have been located in the reticular formation. In air-breathing fishes and amphibians, there may be separate RRG for gill and lung ventilation. There is some evidence for multiple RRG in reptiles. Both amphibians and reptiles show episodic breathing patterns that may be centrally generated, though they do respond to changes in oxygen supply. Fish and larval amphibians have chemoreceptors sensitive to oxygen partial pressure located on the gills. Hypoxia induces increased ventilation and a reflex bradycardia and may trigger aquatic surface respiration or air-breathing, though these latter activities also respond to behavioural cues. Adult amphibians and reptiles have peripheral chemoreceptors located on the carotid arteries and central chemoreceptors sensitive to blood carbon dioxide levels. Lung perfusion may be regulated by cardiac shunting and lung ventilation stimulates lung stretch receptors.

Comparison of single bout effects of bicycle training versus locomotor training on paired reflex depression of the soleus H-reflex after motor incomplete spinal cord injury.

PubMed

Phadke, Chetan P; Flynn, Sheryl M; Thompson, Floyd J; Behrman, Andrea L; Trimble, Mark H; Kukulka, Carl G

2009-07-01

To examine paired reflex depression changes post 20-minute bout each of 2 training environments: stationary bicycle ergometer training (bicycle training) and treadmill with body weight support and manual assistance (locomotor training). Pretest-posttest repeated-measures. Locomotor laboratory. Motor incomplete SCI (n=12; mean, 44+/-16y); noninjured subjects (n=11; mean, 30.8+/-8.3y). All subjects received each type of training on 2 separate days. Paired reflex depression at different interstimulus intervals (10 s, 1 s, 500 ms, 200 ms, and 100 ms) was measured before and after both types of training. (1) Depression was significantly less post-SCI compared with noninjured subjects at all interstimulus intervals and (2) post-SCI at 100-millisecond interstimulus interval: reflex depression significantly increased postbicycle training in all SCI subjects and in the chronic and spastic subgroups (P<.05). Phase-dependent regulation of reflex excitability, essential to normal locomotion, coordinated by pre- and postsynaptic inhibitory processes (convergent action of descending and segmental inputs onto spinal circuits) is impaired post-SCI. Paired reflex depression provides a quantitative assay of inhibitory processes contributing to phase-dependent changes in reflex excitability. Because bicycle training normalized reflex depression, we propose that bicycling may have a potential role in walking rehabilitation, and future studies should examine the long-term effects on subclinical measures of reflex activity and its relationship to functional outcomes.

A Vibrating Jaw Crusher with Auteresonant Electric Motor Drive of Swinging Movement

NASA Astrophysics Data System (ADS)

Zagrivniy, E. A.; Poddubniy, D. A.

2018-01-01

The article relates to a vibrating jaw crusher with pendulum vibrating exciter auteresonant electric motor drive and with elastic element rational force distribution, with limited peak-to-peak swing. Its design and its math model are presented. Also disclosed is the operating principle of a vibrating jaw crusher and the control algorithm for controlling the crushing jaw for maintaining the operating mode at resonant frequency.

The proprioceptive reflex control of the intercostal muscles during their voluntary activation

PubMed Central

Davis, J. Newsom; Sears, T. A.

1970-01-01

1. A quantitative study has been made of the reflex effects of sudden changes in mechanical load on contracting human intercostal muscles during willed breathing movements involving the chest wall. Averaging techniques were applied to recordings of electromyogram (EMG) and lung volume, and to other parameters of breathing. 2. Load changes were effected for brief periods (10-150 msec) at any predetermined lung volume by sudden connexion of the airway to a pressure source variable between ± 80 cm H2O so that respiratory movement could be either assisted or opposed. In some experiments airway resistance was suddenly reduced by porting from a high to a low resistance external airway. 3. Contracting inspiratory and expiratory intercostal muscles showed a `silent period' with unloading which is attributed to the sudden withdrawal from intercostal motoneurones of monosynaptic excitation of muscle spindle origin. 4. For both inspiratory and expiratory intercostal muscles the typical immediate effect of an increase in load was an inhibitory response (IR) with a latency of about 22 msec followed by an excitatory response (ER) with a latency of 50-60 msec. 5. It was established using brief duration stimuli (< 40 msec) that the IR depended on mechanical events associated with the onset of stimulation, whereas stimuli greater than 40 msec in duration were required to evoke the ER. 6. For constant expiratory flow rate and a constant load, the ER of expiratory intercostal muscles increased as lung volume decreased within the limits set by maximal activation of the motoneurone pool as residual volume was approached. 7. The ER to a constant load increased directly with the expiratory flow rate at which the load applied, also within limits set by maximal activation of the motoneurone pool. 8. For a given load, the ER during phonation was greater than that occurring at a similar expiratory flow rate without phonation when the resistance of the phonating larynx was mimicked by an

Stretching position can affect levator scapular muscle activity, length, and cervical range of motion in people with a shortened levator scapulae.

PubMed

Jeong, Hyo-Jung; Cynn, Heon-Seock; Yi, Chung-Hwi; Yoon, Jang-Whon; Lee, Ji-Hyun; Yoon, Tae-Lim; Kim, Bo-Been

2017-07-01

Levator scapulae (LS) muscle stretching exercises are a common method of lengthening a shortened muscle; however, the appropriate stretching position for lengthening the LS in people with a shortened LS remains unclear. The purpose of this study was to compare the effects of different stretching exercise positions on the LS and introduce effective stretching exercise methods to clinicians. Twenty-four university students (12 men, 12 women) with a shortened LS were recruited. LS muscle activity, LS index (LSI), and cervical range of motion (ROM) were measured pre (baseline) and post three different stretching exercise positions (sitting, quadruped, and prone). The LSI and cervical ROM exceeded the minimal detectable change and had significant changes. The LSI was greater in the sitting position than at the baseline (p = 0.01), quadruped position (p < 0.01); the LSI in the prone position presented a higher increase than the quadruped position (p = 0.01). The cervical ROM increased in the sitting position when compared to the baseline (p < 0.01) and quadruped position (p < 0.01). Stretching the LS in the sitting position was the most effective exercise for improving LS muscle length and cervical ROM. Copyright © 2017 Elsevier Ltd. All rights reserved.

The frequency of buccopalpebral reflex in Parkinson disease.

PubMed

Eser, Hülya; Ünal, Yasemin; Kutlu, Gülnihal; Öcal, Ruhsen; İnan, Levent Ertuğrul

2016-11-17

This study aimed to define the frequency of a primitive reflex, the buccopalpebral reflex (BPR), and its association with the clinical situation in patients with Parkinson disease. Between May 2010 and May 2011, 222 patients, 115 with Parkinson disease and 107 patients without any sign of neurodegenerative disease, were included in the study. All included patients were examined for BPR and snout reflex and were also evaluated with the Mini Mental State Examination. All patients with Parkinson disease were classified with the Unified Parkinson's Disease Rating Scale (UPDRS) and the Hoehn and Yahr Score to determine their clinical severity. Sixteen patients with Parkinson disease (13.9%) had a BPR (+) and 4 patients in the control group (3.7%) (P < 0.001). The UPDRS score, UPDRS daily life activities score, and UPDRS motor system score were all higher in the group with BPR (+). All patients with a BPR also had a positive snout reflex. BPR is more frequent in patients with Parkinson disease than in patients without a neurodegenerative disease.

Bouncing on Mars and the Moon-the role of gravity on neuromuscular control: correlation of muscle activity and rate of force development.

PubMed

Ritzmann, Ramona; Freyler, Kathrin; Krause, Anne; Gollhofer, Albert

2016-11-01

On our astronomical neighbors Mars and the Moon, bouncing movements are the preferred locomotor techniques. During bouncing, the stretch-shortening cycle describes the muscular activation pattern. This study aimed to identify gravity-dependent changes in kinematic and neuromuscular characteristics in the stretch-shortening cycle. Hence, neuromuscular control of limb muscles as well as correlations between the muscles' pre-activation, reflex components, and force output were assessed in lunar, Martian, and Earth gravity. During parabolic flights, peak force (F max ), ground-contact-time, rate of force development (RFD), height, and impulse were measured. Electromyographic (EMG) activities in the m. soleus (SOL) and gastrocnemius medialis (GM) were assessed before (PRE) and during bounces for the reflex phases short-, medium-, and long-latency response (SLR, MLR, LLR). With gradually decreasing gravitation, F max , RFD, and impulse were reduced, whereas ground-contact time and height increased. Concomitantly, EMG_GM decreased for PRE, SLR, MLR, and LLR, and in EMG_SOL in SLR, MLR, and LLR. For SLR and MLR, F max and RFD were positively correlated to EMG_SOL. For PRE and LLR, RFD and F max were positively correlated to EMG_GM. Findings emphasize that biomechanically relevant kinematic adaptations in response to gravity variation were accompanied by muscle- and phase-specific modulations in neural control. Gravitational variation is anticipated and compensated for by gravity-adjusted muscle activities. Importantly, the pre-activation and reflex phases were differently affected: in SLR and MLR, SOL is assumed to contribute to the decline in force output with a decreasing load, and, complementary in PRE and LLR, GM seems to be of major importance for force generation. Copyright © 2016 the American Physiological Society.

The Reflexes of the Fundus Oculi

PubMed Central

Ballantyne, A. J.

1940-01-01

The fundus reflexes reveal, in a manner not yet completely understood, the texture and contour of the reflecting surfaces and the condition of the underlying tissues. In this way they may play an important part in the biomicroscopy of the eye. The physiological reflexes are seen at their best in the eyes of young subjects, in well-pigmented eyes, with undilated pupils and with emmetropic refraction. Their absence during the first two decades, or their presence after the forties, their occurrence in one eye only, their appearance, disappearance or change of character should suggest the possibility of some pathological state. The investigation and interpretation of the reflexes are notably assisted by comparing the appearances seen with long and short wave lights such as those of the sodium and mercury vapour lamps, in addition to the usual ophthalmoscopic lights. Most of the surface reflexes disappear in the light of the sodium lamp, sometimes revealing important changes in the deeper layers of the retina and choroid. The physiological reflexes, chiefly formed on the surface of the internal limiting membrane, take the forms of the familiar watered silk or patchy reflexes, the peri-macular halo, the fan reflex in the macular depression and the reflex from the foveal pit. The watered silk or patchy reflexes often show a delicate striation which follows the pattern of the nerve-fibre layer, or there may be a granular or criss-cross texture. Reflexes which entirely lack these indications of “texture” should be considered as possibly pathological. This applies to the “beaten metal” reflexes and to those formed on the so-called hyaloid membrane. The occurrence of physiological reflexes in linear form is doubtful, and the only admittedly physiological punctate reflexes are the so-called Gunn's dots. Surface reflexes which are broken up into small points or flakes are pathological, and are most frequently seen in the central area of the fundus in cases of pigmentary

Reflex regulation of airway sympathetic nerves in guinea-pigs

PubMed Central

Oh, Eun Joo; Mazzone, Stuart B; Canning, Brendan J; Weinreich, Daniel

2006-01-01

Sympathetic nerves innervate the airways of most species but their reflex regulation has been essentially unstudied. Here we demonstrate sympathetic nerve-mediated reflex relaxation of airway smooth muscle measured in situ in the guinea-pig trachea. Retrograde tracing, immunohistochemistry and electrophysiological analysis identified a population of substance P-containing capsaicin-sensitive spinal afferent neurones in the upper thoracic (T1–T4) dorsal root ganglia (DRG) that innervate the airways and lung. After bilateral vagotomy, atropine pretreatment and precontraction of the trachealis with histamine, nebulized capsaicin (10–60 μm) evoked a 63 ± 7% reversal of the histamine-induced contraction of the trachealis. Either the β-adrenoceptor antagonist propranolol (2 μm, administered directly to the trachea) or bilateral sympathetic nerve denervation of the trachea essentially abolished these reflexes (10 ± 9% and 6 ± 4% relaxations, respectively), suggesting that they were mediated primarily, if not exclusively, by sympathetic adrenergic nerve activation. Cutting the upper thoracic dorsal roots carrying the central processes of airway spinal afferents also markedly blocked the relaxations (9 ± 5% relaxation). Comparable inhibitory effects were observed following intravenous pretreatment with neurokinin receptor antagonists (3 ± 7% relaxations). These reflexes were not accompanied by consistent changes in heart rate or blood pressure. By contrast, stimulating the rostral cut ends of the cervical vagus nerves also evoked a sympathetic adrenergic nerve-mediated relaxation that were accompanied by marked alterations in blood pressure. The results indicate that the capsaicin-induced reflex-mediated relaxation of airway smooth muscle following vagotomy is mediated by sequential activation of tachykinin-containing spinal afferent and sympathetic efferent nerves innervating airways. This sympathetic nerve-mediated response may serve to oppose airway

Ca{sup 2+} influx and ATP release mediated by mechanical stretch in human lung fibroblasts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murata, Naohiko; Ito, Satoru, E-mail: itori@med.nagoya-u.ac.jp; Furuya, Kishio

Highlights: • Uniaxial stretching activates Ca{sup 2+} signaling in human lung fibroblasts. • Stretch-induced intracellular Ca{sup 2+} elevation is mainly via Ca{sup 2+} influx. • Mechanical strain enhances ATP release from fibroblasts. • Stretch-induced Ca{sup 2+} influx is not mediated by released ATP or actin cytoskeleton. - Abstract: One cause of progressive pulmonary fibrosis is dysregulated wound healing after lung inflammation or damage in patients with idiopathic pulmonary fibrosis and severe acute respiratory distress syndrome. The mechanical forces are considered to regulate pulmonary fibrosis via activation of lung fibroblasts. In this study, the effects of mechanical stretch on the intracellularmore » Ca{sup 2+} concentration ([Ca{sup 2+}]{sub i}) and ATP release were investigated in primary human lung fibroblasts. Uniaxial stretch (10–30% in strain) was applied to fibroblasts cultured in a silicone chamber coated with type I collagen using a stretching apparatus. Following stretching and subsequent unloading, [Ca{sup 2+}]{sub i} transiently increased in a strain-dependent manner. Hypotonic stress, which causes plasma membrane stretching, also transiently increased the [Ca{sup 2+}]{sub i}. The stretch-induced [Ca{sup 2+}]{sub i} elevation was attenuated in Ca{sup 2+}-free solution. In contrast, the increase of [Ca{sup 2+}]{sub i} by a 20% stretch was not inhibited by the inhibitor of stretch-activated channels GsMTx-4, Gd{sup 3+}, ruthenium red, or cytochalasin D. Cyclic stretching induced significant ATP releases from fibroblasts. However, the stretch-induced [Ca{sup 2+}]{sub i} elevation was not inhibited by ATP diphosphohydrolase apyrase or a purinergic receptor antagonist suramin. Taken together, mechanical stretch induces Ca{sup 2+} influx independently of conventional stretch-sensitive ion channels, the actin cytoskeleton, and released ATP.« less

EMG and peak force responses to PNF stretching and the relationship between stretching-induced force deficits and bilateral deficits

PubMed Central

Cengiz, Asim

2015-01-01

[Purpose] The aim of the present study was to investigate the possibility of an interaction between stretching induced deficit (SFD) and bilateral deficits (BLD) during maximal voluntary isometric hand flexion under PNF stretch and no-stretch conditions through measurement of EMG and force production. [Subjects and Methods] Ten physically active male Caucasian students (age, 24.1±2.38 years; body mass, 79.48±11.40 kg; height, 174.15±0.8 cm) volunteered to participate in this study. EMG and force measurements of the subjects were recorded during either unilateral or bilateral 3-second maximal voluntary isometric hand flexion (MVC) against a force transducer. The paired sample t-test was used to examine the significance of differences among several conditions. Pearson product-moment correlation was used to evaluate the associations between different parameters. [Results] Stretching-induced deficits correlated with bilateral deficits in both force (r=0.85) and iEMG (r=0.89). PNF stretching caused significant decrements in the bilateral and unilateral conditions for both the right and left sides. [Conclusion] Since both force and iEMG decreases were observed in most measurements; it suggests there is a neural mechanism behinnd both the BLD and the SFD. PMID:25931696

Orientation-specific responses to sustained uniaxial stretching in focal adhesion growth and turnover

PubMed Central

Chen, Yun; Pasapera, Ana M.; Koretsky, Alan P.; Waterman, Clare M.

2013-01-01

Cells are mechanosensitive to extracellular matrix (ECM) deformation, which can be caused by muscle contraction or changes in hydrostatic pressure. Focal adhesions (FAs) mediate the linkage between the cell and the ECM and initiate mechanically stimulated signaling events. We developed a stretching apparatus in which cells grown on fibronectin-coated elastic substrates can be stretched and imaged live to study how FAs dynamically respond to ECM deformation. Human bone osteosarcoma epithelial cell line U2OS was transfected with GFP-paxillin as an FA marker and subjected to sustained uniaxial stretching. Two responses at different timescales were observed: rapid FA growth within seconds after stretching, and delayed FA disassembly and loss of cell polarity that occurred over tens of minutes. Rapid FA growth occurred in all cells; however, delayed responses to stretch occurred in an orientation-specific manner, specifically in cells with their long axes perpendicular to the stretching direction, but not in cells with their long axes parallel to stretch. Pharmacological treatments demonstrated that FA kinase (FAK) promotes but Src inhibits rapid FA growth, whereas FAK, Src, and calpain 2 all contribute to delayed FA disassembly and loss of polarity in cells perpendicular to stretching. Immunostaining for phospho-FAK after stretching revealed that FAK activation was maximal at 5 s after stretching, specifically in FAs oriented perpendicular to stretch. We hypothesize that orientation-specific activation of strain/stress-sensitive proteins in FAs upstream to FAK and Src promote orientation-specific responses in FA growth and disassembly that mediate polarity rearrangement in response to sustained stretch. PMID:23754369

[H reflex in patients with spastic quadriplegia].

PubMed

Miyama, Sahoko; Arimoto, Kiyoshi; Kimiya, Satoshi

2009-01-01

Hoffmann reflex (H reflex) is an electrically elicited spinal monosynaptic reflex. H reflex was examined in 18 patients with spastic quadriplegia who had perinatal or postnatal problems. H reflex was elicitable in 11 patients for the abductor pollicis brevis (61.1%), 10 for the abductor digiti minimi (55.6%) and 16 for the abductor hallucis (88.9%). Because the abductor pollicis brevis and the abductor digiti minimi do not exhibit H reflex in normal subjects, it was suggested that the excitability of alpha motor neurons innervating these muscles was increased. H reflex was not detected for the extensor digitorum brevis in any patients, indicating the difference in the excitability among alpha motor neurons. In some patients, H reflex did not disappear under supramaximal stimuli. We conclude that the mechanism of evolution of H reflex in patients with spastic quadriplegia is different from that in normal subjects.

[Odontogenic and nonodontogenic jaw cysts: experience in 25 cases].

PubMed

Ağir, Hakan; Sen, Cenk; Işil, Eda; Unal, Ciğdem; Ustündağ, Emre; Keskin, Gürkan

2008-01-01

We retrospectively evaluated the patients with jaw cysts treated at our center. The study included 25 patients (14 males, 11 females; mean age 33+/-19 years; range 7 to 69 years) who underwent surgery for odontogenic or nonodontogenic jaw cysts. The most common presentation was a swelling in the jaw with or without dental problems. Involvement was in the mandible in 18 patients, and in the maxilla in seven patients. The lesions consisted of eight radicular, six dentigerous, two nasoalveolar, two globulomaxillary cysts, and three keratocysts. Four patients had gingival, nasopalatine, residual, and median mandibular cysts, respectively. Marsupialization, curettage, extensive burring, enucleation, or marginal resection were performed depending on pre- and intraoperative findings. The defects were repaired with a corticocancellous iliac bone block graft in three patients and cancellous iliac bone chips in five patients. During a mean follow-up of 14 months (range 12 to 46 months), recurrence was seen in only one patient with a keratocyst. A good preoperative assessment, complete removal of the cystic lesion, and close radiographic follow-up are essential for a successful outcome in jaw cysts. In selected cases, reconstruction of the defects with autogenous corticocancellous iliac bone graft yields highly satisfactory results.

Effect of cervicolabyrinthine impulsation on the spinal reflex apparatus

NASA Technical Reports Server (NTRS)

Yarotskiy, A. I.

1980-01-01

In view of the fact that the convergence effect of vestibular impulsation may both stimulate and inhibit intra and intersystemic coordination of physiological processes, an attempt was made to define the physiological effect on the spinal reflex apparatus of the convergence of cervicolabyrinthine impulsation on a model of the unconditioned motor reflex as a mechanism of the common final pathway conditioning the formation and realization of a focused beneficial result of human motor activities. More than 100 persons subjected to rolling effect and angular acceleration during complexly coordinated muscular loading were divided according to typical variants of the functional structure of the patella reflex in an experiment requiring 30 rapid counterclockwise head revolutions at 2/sec with synchronous recording of a 20 item series of patella reflex acts. A knee jerk coefficient was used in calculations. In 85 percent of the cases 2 patellar reflexograms show typical braking and release of knee reflex and 1 shows an extreme local variant. The diagnostic and prognostic value of these tests is suggested for determining adaptive possibilities of functional systems in respect to acceleration and proprioceptive stimuli.

Association between patterns of jaw motor activity during sleep and clinical signs and symptoms of sleep bruxism.

PubMed

Yoshida, Yuya; Suganuma, Takeshi; Takaba, Masayuki; Ono, Yasuhiro; Abe, Yuka; Yoshizawa, Shuichiro; Sakai, Takuro; Yoshizawa, Ayako; Nakamura, Hirotaka; Kawana, Fusae; Baba, Kazuyoshi

2017-08-01

The aim of this study was to investigate the association between patterns of jaw motor activity during sleep and clinical signs and symptoms of sleep bruxism. A total of 35 university students and staff members participated in this study after providing informed consent. All participants were divided into either a sleep bruxism group (n = 21) or a control group (n = 14), based on the following clinical diagnostic criteria: (1) reports of tooth-grinding sounds for at least two nights a week during the preceding 6 months by their sleep partner; (2) presence of tooth attrition with exposed dentin; (3) reports of morning masticatory muscle fatigue or tenderness; and (4) presence of masseter muscle hypertrophy. Video-polysomnography was performed in the sleep laboratory for two nights. Sleep bruxism episodes were measured using masseter electromyography, visually inspected and then categorized into phasic or tonic episodes. Phasic episodes were categorized further into episodes with or without grinding sounds as evaluated by audio signals. Sleep bruxism subjects with reported grinding sounds had a significantly higher total number of phasic episodes with grinding sounds than subjects without reported grinding sounds or controls (Kruskal-Wallis/Steel-Dwass tests; P < 0.05). Similarly, sleep bruxism subjects with tooth attrition exhibited significantly longer phasic burst durations than those without or controls (Kruskal-Wallis/Steel-Dwass tests; P < 0.05). Furthermore, sleep bruxism subjects with morning masticatory muscle fatigue or tenderness exhibited significantly longer tonic burst durations than those without or controls (Kruskal-Wallis/Steel-Dwass tests; P < 0.05). These results suggest that each clinical sign and symptom of sleep bruxism represents different aspects of jaw motor activity during sleep. © 2016 European Sleep Research Society.

Influence of the stretch wrapping process on the mechanical behavior of a stretch film

NASA Astrophysics Data System (ADS)

Klein, Daniel; Stommel, Markus; Zimmer, Johannes

2018-05-01

Lightweight construction is an ongoing task in packaging development. Consequently, the stability of packages during transport is gaining importance. This study contributes to the optimization of lightweight packaging concepts regarding their stability. A very widespread packaging concept is the distribution of goods on a pallet whereas a Polyethylene (PE) stretch film stabilizes the lightweight structure during the shipment. Usually, a stretch wrapping machine applies this stretch film to the pallet. The objective of this study is to support packaging development with a method that predicts the result of the wrapping process, based on the mechanical characterization of the stretch film. This result is not only defined by the amount of stretch film, its spatial distribution on the pallet and its internal stresses that result in a containment force. More accurate, this contribution also considers the influence of the deformation history of the stretch film during the wrapping process. By focusing on similarities of stretch wrappers rather than on differences, the influence of generalized process parameters on stretch film mechanics and thereby on pallet stability can be determined experimentally. For a practical use, the predictive method is accumulated in an analytic model of the wrapping process that can be verified experimentally. This paves the way for experimental and numerical approaches regarding the optimization of pallet stability.

The speech focus position effect on jaw-finger coordination in a pointing task.

PubMed

Rochet-Capellan, Amélie; Laboissière, Rafael; Galván, Arturo; Schwartz, Jean-Luc

2008-12-01

This article investigates jaw-finger coordination in a task involving pointing to a target while naming it with a CVCV (e.g., /papa/) versus CVCV (e.g., /papa/) word. According to the authors' working hypothesis, the pointing apex (gesture extremum) would be synchronized with the apex of the jaw-opening gesture corresponding to the stressed syllable. Jaw and finger motions were recorded using Optotrak (Northern Digital, Waterloo, Ontario, Canada). The effects of stress position on jaw-finger coordination were tested across different target positions (near vs. far) and different consonants in the target word (/t/ vs. /p/). Twenty native Portuguese Brazilian speakers participated in the experiment (all conditions). Jaw response starts earlier, and finger-target alignment period is longer for CVCV words than for CVCV ones. The apex of the jaw-opening gesture for the stressed syllable appears synchronized with the onset of the finger-target alignment period (corresponding to the pointing apex) for CVCV words and with the offset of that period for CVCV words. For both stress conditions, the stressed syllable occurs within the finger-target alignment period because of tight finger-jaw coordination. This result is interpreted as evidence for an anchoring of the speech deictic site (part of speech that shows) in the pointing gesture.

Electronic speckle-pattern interferometry (ESPI) applied to the study of mechanical behavior of human jaws

NASA Astrophysics Data System (ADS)

Roman, Juan F.; Moreno de las Cuevas, Vincente; Salgueiro, Jose R.; Suarez, David; Fernandez, Paula; Gallas, Mercedes; Blanchard, Alain

1996-01-01

The study of the mechanical behavior of the human jaw during chewing is helpful in several specific medical fields that cover the maxillo-facial area. In this work, electronic speckle pattern interferometry has been applied to study dead jaw bones under external stress which simulates the deformations induced during chewing. Fringes obtained after subtraction of two images of the jaw, the image of the relaxed jaw and that of the jaw under stress, give us information about the most stressed zones. The interferometric analysis proposed here is attractive as it can be done in real time with the jaw under progressive stress. Image processing can be applied for improving the quality of fringes. This research can be of help in orthognathic surgery, for example in diagnosis and treatment of fractured jaws, in oral surgery, and in orthodontics because it would help us to know the stress dispersion when we insert an osseointegrated implant or place an orthodontic appliance, respectively. Studying fragments of human jaw some results about its elasticity and flexibility were obtained.

Acute Effects of Static Stretching, Dynamic Exercises, and High Volume Upper Extremity Plyometric Activity on Tennis Serve Performance

PubMed Central

Gelen, Ertugrul; Dede, Muhittin; Bingul, Bergun Meric; Bulgan, Cigdem; Aydin, Mensure

2012-01-01

The purpose of this study was to compare the acute effects of static stretching; dynamic exercises and high volume upper extremity plyometric activity on tennis serve performance. Twenty-six elite young tennis players (15.1 ± 4.2 years, 167.9 ± 5.8 cm and 61.6 ± 8.1 kg) performed 4 different warm-up (WU) routines in a random order on non-consecutive days. The WU methods consisted of traditional WU (jogging, rally and serve practice) (TRAD); traditional WU and static stretching (TRSS); traditional WU and dynamic exercise (TRDE); and traditional WU and high volume upper extremity plyometric activity (TRPLYP). Following each WU session, subjects were tested on a tennis serve ball speed test. TRAD, TRSS, TRDE and TRPLYO were compared by repeated measurement analyses of variance and post-hoc comparisons. In this study a 1 to 3 percent increase in tennis serve ball speed was recorded in TRDE and TRPLYO when compared to TRAD (p< 0.05). However, no significant change in ball speed performance between TRSS and TRAD. (p> 0.05). ICCs for ball speed showed strong reliability (0.82 to 0.93) for the ball speed measurements.The results of this study indicate that dynamic and high volume upper extremity plyometric WU activities are likely beneficial to serve speed of elite junior tennis players. Key points After the traditional warm up in tennis, static stretching has no effect on serve speed. Tennis players should perform dynamic exercises and/or high volume upper extremity plyometric activities to improve their athletic performance. PMID:24150068

Building Finite Element Models to Investigate Zebrafish Jaw Biomechanics.

PubMed

Brunt, Lucy H; Roddy, Karen A; Rayfield, Emily J; Hammond, Chrissy L

2016-12-03

Skeletal morphogenesis occurs through tightly regulated cell behaviors during development; many cell types alter their behavior in response to mechanical strain. Skeletal joints are subjected to dynamic mechanical loading. Finite element analysis (FEA) is a computational method, frequently used in engineering that can predict how a material or structure will respond to mechanical input. By dividing a whole system (in this case the zebrafish jaw skeleton) into a mesh of smaller 'finite elements', FEA can be used to calculate the mechanical response of the structure to external loads. The results can be visualized in many ways including as a 'heat map' showing the position of maximum and minimum principal strains (a positive principal strain indicates tension while a negative indicates compression. The maximum and minimum refer the largest and smallest strain). These can be used to identify which regions of the jaw and therefore which cells are likely to be under particularly high tensional or compressional loads during jaw movement and can therefore be used to identify relationships between mechanical strain and cell behavior. This protocol describes the steps to generate Finite Element models from confocal image data on the musculoskeletal system, using the zebrafish lower jaw as a practical example. The protocol leads the reader through a series of steps: 1) staining of the musculoskeletal components, 2) imaging the musculoskeletal components, 3) building a 3 dimensional (3D) surface, 4) generating a mesh of Finite Elements, 5) solving the FEA and finally 6) validating the results by comparison to real displacements seen in movements of the fish jaw.

Effects of robot-guided passive stretching and active movement training of ankle and mobility impairments in stroke.

PubMed

Waldman, Genna; Yang, Chung-Yong; Ren, Yupeng; Liu, Lin; Guo, Xin; Harvey, Richard L; Roth, Elliot J; Zhang, Li-Qun

2013-01-01

To investigate the effects of controlled passive stretching and active movement training using a portable rehabilitation robot on stroke survivors with ankle and mobility impairment. Twenty-four patients at least 3 months post stroke were assigned to receive 6 week training using the portable robot in a research laboratory (robot group) or an instructed exercise program at home (control group). All patients underwent clinical and biomechanical evaluations in the laboratory at pre-evaluation, post-evaluation, and 6-week follow-up. Subjects in the robot group improved significantly more than that in the control group in reduction in spasticity measured by modified Ashworth scale, mobility by Stroke Rehabilitation Assessment of Movement (STREAM), the balance by Berg balance score, dorsiflexion passive range of motion, dorsiflexion strength, and load bearing on the affected limb during gait after 6-week training. Both groups improved in the STREAM, dorsiflexion active range of motion and dorsiflexor strength after the training, which were retained in the follow-up evaluation. Robot-assisted passive stretching and active movement training is effective in improving motor function and mobility post stroke.

[Osteonecrosis of the jaws and bisphosphonates].

PubMed

Junod, A F; Carrel, J-P; Richter, M; Vogt-Ferrier, N

2005-11-02

Widely prescribed, bisphosphonates inhibit bone resorption. They are not metabolised and have long half-lives. Two cases of osteonecrosis of the jaws have recently been attributed to bisphosphonates at the University Hospital of Geneva. The recent literature reveals more than a hundred similar cases throughout the world. Bone exposure appears spontaneously or after dental care. Treatment of the osteonecrosis is controversial and cure very difficult. This pathology is usually seen in patients on chemotherapy, steroids and i.v. bisphosphonates, but is sometimes seen with low-dose p.o. bisphosphonates. In view of the strong association between bisphosphonate therapy and osteonecrosis of the jaw, specialists have recommended dental and oral evaluation during bisphosphonate therapy as well as for several years after drug discontinuation.

Physiologic Development of Tongue-Jaw Coordination from Childhood to Adulthood

ERIC Educational Resources Information Center

Cheng, Hei Yan; Murdoch, Bruce E.; Goozee, Justine V.; Scott, Dion

2007-01-01

Purpose: This investigation aimed to examine the development of tongue-jaw coordination during speech from childhood to adolescence. Method: Electromagnetic articulography was used to track tongue and jaw motion in 48 children and adults (aged 6-38 years) during productions of /t/ and /k/ embedded in sentences. Results: The coordinative…

Deflation-activated receptors, not classical inflation-activated receptors, mediate the Hering-Breuer deflation reflex.

PubMed

Yu, Jerry

2016-11-01

Many airway sensory units respond to both lung inflation and deflation. Whether those responses to opposite stimuli come from one sensor (one-sensor theory) or more than one sensor (multiple-sensor theory) is debatable. One-sensor theory is commonly presumed in the literature. This article proposes a multiple-sensor theory in which a sensory unit contains different sensors for sensing different forces. Two major types of mechanical sensors operate in the lung: inflation- and deflation-activated receptors (DARs). Inflation-activated sensors can be further divided into slowly adapting receptors (SARs) and rapidly adapting receptors (RARs). Many SAR and RAR units also respond to lung deflation because they contain DARs. Pure DARs, which respond to lung deflation only, are rare in large animals but are easily identified in small animals. Lung deflation-induced reflex effects previously attributed to RARs should be assigned to DARs (including pure DARs and DARs associated with SARs and RARs) if the multiple-sensor theory is accepted. Thus, based on the information, it is proposed that activation of DARs can attenuate lung deflation, shorten expiratory time, increase respiratory rate, evoke inspiration, and cause airway secretion and dyspnea.

Sensory feedback from the urethra evokes state-dependent lower urinary tract reflexes in rat.

PubMed

Danziger, Zachary C; Grill, Warren M

2017-08-15

The lower urinary tract is regulated by reflexes responsible for maintaining continence and producing efficient voiding. It is unclear how sensory information from the bladder and urethra engages differential, state-dependent reflexes to either maintain continence or promote voiding. Using a new in vivo experimental approach, we quantified how sensory information from the bladder and urethra are integrated to switch reflex responses to urethral sensory feedback from maintaining continence to producing voiding. The results demonstrate how sensory information regulates state-dependent reflexes in the lower urinary tract and contribute to our understanding of the pathophysiology of urinary retention and incontinence where sensory feedback may engage these reflexes inappropriately. Lower urinary tract reflexes are mediated by peripheral afferents from the bladder (primarily in the pelvic nerve) and the urethra (in the pudendal and pelvic nerves) to maintain continence or initiate micturition. If fluid enters the urethra at low bladder volumes, reflexes relax the bladder and evoke external urethral sphincter (EUS) contraction (guarding reflex) to maintain continence. Conversely, urethral flow at high bladder volumes, excites the bladder (micturition reflex) and relaxes the EUS (augmenting reflex). We conducted measurements in a urethane-anaesthetized in vivo rat preparation to characterize systematically the reflexes evoked by fluid flow through the urethra. We used a novel preparation to manipulate sensory feedback from the bladder and urethra independently by controlling bladder volume and urethral flow. We found a distinct bladder volume threshold (74% of bladder capacity) above which flow-evoked bladder contractions were 252% larger and evoked phasic EUS activation 2.6 times as often as responses below threshold, clearly demonstrating a discrete transition between continence (guarding) and micturition (augmenting) reflexes. Below this threshold urethral flow evoked

The Effectiveness of PNF Versus Static Stretching on Increasing Hip-Flexion Range of Motion.

PubMed

Lempke, Landon; Wilkinson, Rebecca; Murray, Caitlin; Stanek, Justin

2018-05-22

Clinical Scenario: Stretching is applied for the purposes of injury prevention, increasing joint range of motion (ROM), and increasing muscle extensibility. Many researchers have investigated various methods and techniques to determine the most effective way to increase joint ROM and muscle extensibility. Despite the numerous studies conducted, controversy still remains within clinical practice and the literature regarding the best methods and techniques for stretching. Focused Clinical Question: Is proprioceptive neuromuscular facilitation (PNF) stretching more effective than static stretching for increasing hamstring muscle extensibility through increased hip ROM or increased knee extension angle (KEA) in a physically active population? Summary of Key Findings: Five studies met the inclusion criteria and were included. All 5 studies were randomized control trials examining mobility of the hamstring group. The studies measured hamstring ROM in a variety of ways. Three studies measured active KEA, 1 study measured passive KEA, and 1 study measured hip ROM via the single-leg raise test. Of the 5 studies, 1 study found greater improvements using PNF over static stretching for increasing hip flexion, and the remaining 4 studies found no significant difference between PNF stretching and static stretching in increasing muscle extensibility, active KEA, or hip ROM. Clinical Bottom Line: PNF stretching was not demonstrated to be more effective at increasing hamstring extensibility compared to static stretching. The literature reviewed suggests both are effective methods for increasing hip-flexion ROM. Strength of Recommendation: Using level 2 evidence and higher, the results show both static and PNF stretching effectively increase ROM; however, one does not appear to be more effective than the other.

Short Durations of Static Stretching when Combined with Dynamic Stretching do not Impair Repeated Sprints and Agility

PubMed Central

Wong, Del P.; Chaouachi, Anis; Lau, Patrick W.C.; Behm, David G.

2011-01-01

This study aimed to compare the effect of different static stretching durations followed by dynamic stretching on repeated sprint ability (RSA) and change of direction (COD). Twenty-five participants performed the RSA and COD tests in a randomized order. After a 5 min aerobic warm up, participants performed one of the three static stretching protocols of 30 s, 60 s or 90 s total duration (3 stretches x 10 s, 20 s or 30 s). Three dynamic stretching exercises of 30 s duration were then performed (90 s total). Sit-and-reach flexibility tests were conducted before the aerobic warm up, after the combined static and dynamic stretching, and post- RSA/COD test. The duration of static stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit-and-reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). However there were no significant differences in RSA and COD performance between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. Furthermore, the short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. Key points The duration of combined static and dynamic stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit and reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). No significant differences in RSA and COD between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. The short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. PMID:24149890

Short Durations of Static Stretching when Combined with Dynamic Stretching do not Impair Repeated Sprints and Agility.

PubMed

Wong, Del P; Chaouachi, Anis; Lau, Patrick W C; Behm, David G

2011-01-01

This study aimed to compare the effect of different static stretching durations followed by dynamic stretching on repeated sprint ability (RSA) and change of direction (COD). Twenty-five participants performed the RSA and COD tests in a randomized order. After a 5 min aerobic warm up, participants performed one of the three static stretching protocols of 30 s, 60 s or 90 s total duration (3 stretches x 10 s, 20 s or 30 s). Three dynamic stretching exercises of 30 s duration were then performed (90 s total). Sit-and-reach flexibility tests were conducted before the aerobic warm up, after the combined static and dynamic stretching, and post- RSA/COD test. The duration of static stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit-and-reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). However there were no significant differences in RSA and COD performance between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. Furthermore, the short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. Key pointsThe duration of combined static and dynamic stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit and reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001).No significant differences in RSA and COD between the 3 stretching conditions.The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects.The short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments.

Comparative jaw muscle anatomy in kangaroos, wallabies, and rat-kangaroos (marsupialia: macropodoidea).

PubMed

Warburton, Natalie Marina

2009-06-01

The jaw muscles were studied in seven genera of macropodoid marsupials with diets ranging from mainly fungi in Potorous to grass in Macropus. Relative size, attachments, and lamination within the jaw adductor muscles varied between macropodoid species. Among macropodine species, the jaw adductor muscle proportions vary with feeding type. The relative mass of the masseter is roughly consistent, but grazers and mixed-feeders (Macropus and Lagostrophus) had relatively larger medial pterygoids and smaller temporalis muscles than the browsers (Dendrolagus, Dorcopsulus, and Setonix). Grazing macropods show similar jaw muscle proportions to "ungulate-grinding" type placental mammals. The internal architecture of the jaw muscles also varies between grazing and browsing macropods, most significantly, the anatomy of the medial pterygoid muscle. Potoroines have distinctly different jaw muscle proportions to macropodines. The masseter muscle group, in particular, the superficial masseter is enlarged, while the temporalis group is relatively reduced. Lagostrophus fasciatus is anatomically distinct from other macropods with respect to its masticatory muscle anatomy, including enlarged superficial medial pterygoid and deep temporalis muscles, an anteriorly inflected masseteric process, and the shape of the mandibular condyle. The enlarged triangular pterygoid process of the sphenoid bone, in particular, is distinctive of Lagsotrophus. (c) 2009 Wiley-Liss, Inc.

Role of stag beetle jaw bending and torsion in grip on rivals.

PubMed

Goyens, Jana; Dirckx, Joris; Piessen, Maxim; Aerts, Peter

2016-01-01

In aggressive battles, the extremely large male stag beetle jaws have to withstand strongly elevated bite forces. We found several adaptations of the male Cyclommatus metallifer jaw morphology for enhanced robustness that conspecific females lack. As a result, males improve their grip on opponents and they maintain their safety factor (5.2-7.2) at the same level as that of females (6.8), despite their strongly elevated bite muscle force (3.9 times stronger). Males have a higher second moment of area and torsion constant than females, owing to an enhanced cross-sectional area and shape. These parameters also increase faster with increasing bending moment towards the jaw base in males than in females. Male jaws are more bending resistant against the bite reaction force than against perpendicular forces (which remain lower in battles). Because of the triangular cross section of the male jaw base, it twists more easily than it bends. This torsional flexibility creates a safety system against overload that, at the same time, secures a firm grip on rivals. We found no structural mechanical function of the large teeth halfway along the male jaws. Therefore, it appears that the main purpose of these teeth is a further improvement of grip on rivals. © 2016 The Author(s).

Role of stag beetle jaw bending and torsion in grip on rivals

PubMed Central

Goyens, Jana; Dirckx, Joris; Piessen, Maxim; Aerts, Peter

2016-01-01

In aggressive battles, the extremely large male stag beetle jaws have to withstand strongly elevated bite forces. We found several adaptations of the male Cyclommatus metallifer jaw morphology for enhanced robustness that conspecific females lack. As a result, males improve their grip on opponents and they maintain their safety factor (5.2–7.2) at the same level as that of females (6.8), despite their strongly elevated bite muscle force (3.9 times stronger). Males have a higher second moment of area and torsion constant than females, owing to an enhanced cross-sectional area and shape. These parameters also increase faster with increasing bending moment towards the jaw base in males than in females. Male jaws are more bending resistant against the bite reaction force than against perpendicular forces (which remain lower in battles). Because of the triangular cross section of the male jaw base, it twists more easily than it bends. This torsional flexibility creates a safety system against overload that, at the same time, secures a firm grip on rivals. We found no structural mechanical function of the large teeth halfway along the male jaws. Therefore, it appears that the main purpose of these teeth is a further improvement of grip on rivals. PMID:26763329

Pulmonary atelectasis during low stretch ventilation: "open lung" versus "lung rest" strategy.

PubMed

Fanelli, Vito; Mascia, Luciana; Puntorieri, Valeria; Assenzio, Barbara; Elia, Vincenzo; Fornaro, Giancarlo; Martin, Erica L; Bosco, Martino; Delsedime, Luisa; Fiore, Tommaso; Grasso, Salvatore; Ranieri, V Marco

2009-03-01

Limiting tidal volume (VT) may minimize ventilator-induced lung injury (VILI). However, atelectasis induced by low VT ventilation may cause ultrastructural evidence of cell disruption. Apoptosis seems to be involved as protective mechanisms from VILI through the involvement of mitogen-activated protein kinases (MAPKs). We examined the hypothesis that atelectasis may influence the response to protective ventilation through MAPKs. Prospective randomized study. University animal laboratory. Adult male 129/Sv mice. Isolated, nonperfused lungs were randomized to VILI: VT of 20 mL/kg and positive end-expiratory pressure (PEEP) zero; low stretch/lung rest: VT of 6 mL/kg and 8-10 cm H2O of PEEP; low stretch/open lung: VT of 6 mL/kg, two recruitment maneuvers and 14-16 cm H2O of PEEP. Ventilator settings were adjusted using the stress index. Both low stretch strategies equally blunted the VILI-induced derangement of respiratory mechanics (static volume-pressure curve), lung histology (hematoxylin and eosin), and inflammatory mediators (interleukin-6, macrophage inflammatory protein-2 [enzyme-linked immunosorbent assay], and inhibitor of nuclear factor-kB[Western blot]). VILI caused nuclear swelling and membrane disruption of pulmonary cells (electron microscopy). Few pulmonary cells with chromatin condensation and fragmentation were seen during both low stretch strategies. However, although cell thickness during low stretch/open lung was uniform, low stretch/lung rest demonstrated thickening of epithelial cells and plasma membrane bleb formation. Compared with the low stretch/open lung, low stretch/lung rest caused a significant decrease in apoptotic cells (terminal deoxynucleotidyl transferase mediated deoxyuridine-triphosphatase nick end-labeling) and tissue expression of caspase-3 (Western blot). Both low stretch strategies attenuated the activation of MAPKs. Such reduction was larger during low stretch/open lung than during low stretch/lung rest (p < 0.001). Low stretch

Nociception-specific blink reflex: pharmacology in healthy volunteers.

PubMed

Marin, J C A; Gantenbein, A R; Paemeleire, K; Kaube, H; Goadsby, P J

2015-01-01

The physiology and pharmacology of activation or perception of activation of pain-coding trigeminovascular afferents in humans is fundamental to understanding the biology of headache and developing new treatments. The blink reflex was elicited using a concentric electrode and recorded in four separate sessions, at baseline and two minutes after administration of ramped doses of diazepam (final dose 0.07 mg/kg), fentanyl (final dose 1.11 μg/kg), ketamine (final dose 0.084 mg/kg) and 0.9 % saline solution. The AUC (area under the curve, μV*ms) and the latency (ms) of the ipsi- and contralateral R2 component of the blink reflex were calculated by PC-based offline analysis. Immediately after each block of blink reflex recordings certain psychometric parameters were assessed. There was an effect due to DRUG on the ipsilateral (F 3,60 = 7.3, P < 0.001) AUC as well as on the contralateral (F 3,60 = 6.02, P < 0.001) AUC across the study. A significant decrement in comparison to placebo was observed only for diazepam, affecting the ipsilateral AUC. The scores of alertness, calmness, contentedness, reaction time and precision were not affected by the DRUG across the sessions. Previous studies suggest central, rather than peripheral changes in nociceptive trigeminal transmission in migraine. This study demonstrates a robust effect of benzodiazepine receptor modulation of the nociception specific blink reflex (nBR) without any μ-opiate or glutamate NMDA receptor component. The nociception specific blink reflex offers a reproducible, quantifiable method of assessment of trigeminal nociceptive system in humans that can be used to dissect pharmacology relevant to primary headache disorders.

Long-latency reflexes account for limb biomechanics through several supraspinal pathways

PubMed Central

Kurtzer, Isaac L.

2015-01-01

Accurate control of body posture is enforced by a multitude of corrective actions operating over a range of time scales. The earliest correction is the short-latency reflex (SLR) which occurs between 20–45 ms following a sudden displacement of the limb and is generated entirely by spinal circuits. In contrast, voluntary reactions are generated by a highly distributed network but at a significantly longer delay after stimulus onset (greater than 100 ms). Between these two epochs is the long-latency reflex (LLR) (around 50–100 ms) which acts more rapidly than voluntary reactions but shares some supraspinal pathways and functional capabilities. In particular, the LLR accounts for the arm’s biomechanical properties rather than only responding to local muscle stretch like the SLR. This paper will review how the LLR accounts for the arm’s biomechanical properties and the supraspinal pathways supporting this ability. Relevant experimental paradigms include clinical studies, non-invasive brain stimulation, neural recordings in monkeys, and human behavioral studies. The sum of this effort indicates that primary motor cortex and reticular formation (RF) contribute to the LLR either by generating or scaling its structured response appropriate for the arm’s biomechanics whereas the cerebellum scales the magnitude of the feedback response. Additional putative pathways are discussed as well as potential research lines. PMID:25688187

Introversion and individual differences in middle ear acoustic reflex function.

PubMed

Bar-Haim, Yair

2002-10-01

A growing body of psychophysiological evidence points to the possibility that individual differences in early auditory processing may contribute to social withdrawal and introverted tendencies. The present study assessed the response characteristics of the acoustic reflex arc of introverted-withdrawn and extraverted-sociable individuals. Introverts displayed a greater incidence of abnormal middle ear acoustic reflexes and lower acoustic reflex amplitudes than extraverts. These findings were strongest for stimuli presented at a frequency of 2000 Hz. Results are discussed in light of the controversy concerning the anatomic loci (peripheral vs. central neuronal activity) of the individual differences between introverts and extraverts in early auditory processing. Copyright 2002 Elsevier Science B.V.

Reflexive contraction of the levator palpebrae superioris muscle to involuntarily sustain the effective eyelid retraction through the transverse trigeminal proprioceptive nerve on the proximal Mueller's muscle: verification with evoked electromyography.

PubMed

Ban, Ryokuya; Matsuo, Kiyoshi; Osada, Yoshiro; Ban, Midori; Yuzuriha, Shunsuke

2010-01-01

We have proposed a hypothetical mechanism to involuntarily sustain the effective eyelid retraction, which consists of not only voluntary but also reflexive contractions of the levator palpebrae superior muscle (LPSM). Voluntary contraction of fast-twitch fibres of the LPSM stretches the mechanoreceptors in Mueller's muscle to evoke trigeminal proprioception, which induces continuous reflexive contraction of slow-twitch fibres of the LPSM through the trigeminal proprioceptive nerve fibres innervating the mechanoreceptors in Mueller's muscle via the oculomotor neurons, as a tonic trigemino-oculomotor reflex. In the common skeletal mixed muscles, electrical stimulation of the proprioceptive nerve, which apparently connects the mechanoreceptors in muscle spindles to the motoneurons, induces the electromyographic response as the Hoffmann reflex. To verify the presence of the trigemino-oculomotor reflex, we confirmed whether intra-operative electrical simulation of the transverse trigeminal proprioceptive nerve on the proximal Mueller's muscle evokes an electromyographic response in the LPSM under general anaesthesia in 12 patients. An ipsilateral, phasic, short-latency response (latency: 2.8+/-0.3 ms) was induced in the ipsilateral LPSM in 10 of 12 subjects. As successful induction of the short-latency response in the ipsilateral LPSM corresponds to the Hoffmann reflex in the common skeletal mixed muscles, the present study is the first electromyographic verification of the presence of the monosynaptic trigemino-oculomotor reflex to induce reflexive contraction of the LPSM. The presence of the trigemino-oculomotor reflex may elucidate the unexplainable blepharoptosis due to surgery, trauma and tumour, all of which may damage the trigeminal proprioceptive nerve fibres to impair the trigemino-oculomotor reflex. Copyright (c) 2008. Published by Elsevier Ltd.

[Developing team reflexivity as a learning and working tool for medical teams].

PubMed

Riskin, Arieh; Bamberger, Peter

2014-01-01

Team reflexivity is a collective activity in which team members review their previous work, and develop ideas on how to modify their work behavior in order to achieve better future results. It is an important learning tool and a key factor in explaining the varying effectiveness of teams. Team reflexivity encompasses both self-awareness and agency, and includes three main activities: reflection, planning, and adaptation. The model of briefing-debriefing cycles promotes team reflexivity. Its key elements include: Pre-action briefing--setting objectives, roles, and strategies the mission, as well as proposing adaptations based on what was previously learnt from similar procedures; Post-action debriefing--reflecting on the procedure performed and reviewing the extent to which objectives were met, and what can be learnt for future tasks. Given the widespread attention to team-based work systems and organizational learning, efforts should be made toward ntroducing team reflexivity in health administration systems. Implementation could be difficult because most teams in hospitals are short-lived action teams formed for a particular event, with limited time and opportunity to consciously reflect upon their actions. But it is precisely in these contexts that reflexive processes have the most to offer instead of the natural impulsive collective logics. Team reflexivity suggests a potential solution to the major problems of iatorgenesis--avoidable medical errors, as it forces all team members to participate in a reflexive process together. Briefing-debriefing technology was studied mainly in surgical teams and was shown to enhance team-based learning and to improve quality-related outcomes and safety.

A randomized controlled comparison of stretching procedures for posterior shoulder tightness.

PubMed

McClure, Philip; Balaicuis, Jenna; Heiland, David; Broersma, Mary Ellen; Thorndike, Cheryl K; Wood, April

2007-03-01

Randomized controlled trial, To compare changes in shoulder internal rotation range of motion (ROM), for 2 stretching exercises, the "cross-body stretch" and the "sleeper stretch," in individuals with posterior shoulder tightness. Recently, some authors have expressed the belief that the sleeper stretch is better than the cross-body stretch to address glenohumeral posterior tightness because the scapula is stabilized. Fifty-four asymptomatic subjects (20 males, 34 females) participated in the study. The control group (n=24) consisted of subjects with a between-shoulder difference in internal rotation ROM of less than 10 degrees, whereas those subjects with more than a 10 degrees difference were randomly assigned to 1 of 2 intervention groups, the sleeper stretch group (n=15) or the cross-body stretch group (n=15). Shoulder internal rotation ROM, with the arm abducted to 90 degrees and scapula motion prevented, was measured before and after a 4-week intervention period. Subjects in the control group were asked not to engage in any new stretching activities, while subjects in the 2 stretching groups were asked to perform stretching exercises on the more limited side only, once daily for 5 repetitions, holding each stretch for 30 seconds. The improvements in internal rotation ROM for the subjects in the cross-body stretch group (mean +/- SD, 20.0 degrees +/- 12.9 degrees) were significantly greater than for the subjects in the control group (5.9 degrees +/- 9.4 degrees, P = .009). The gains in the sleeper stretch group (12.4 degrees +/- 10.4 degrees) were not significant compared to those of the control group (P = .586) and those of the cross-body stretch group (P = .148). The cross-body stretch in individuals with limited shoulder internal rotation ROM appears to be more effective than no stretching in controls without internal rotation asymmetry to improve shoulder internal rotation ROM. While the improvement in internal rotation from the cross-body stretch was

Description of the lower jaws of Baculites from the Upper Cretaceous U.S. Western Interior

NASA Astrophysics Data System (ADS)

Larson, Neal L.; Landman, Neil H.

2017-03-01

We report the discovery of lower jaws of Baculites (Ammonoidea) from the Upper Cretaceous U.S. Western Interior. In the lower Campanian Smoky Hill Chalk Member of the Niobrara Chalk of Kansas, most of the jaws occur as isolated elements. Based on their age, they probably belong to Baculites sp. (smooth). They conform to the description of rugaptychus, and are ornamented with coarse rugae on their ventral side. One specimen is preserved inside a small fecal pellet that was probably produced by a fish. Another specimen occurs inside in a crushed body chamber near the aperture and is probably in situ. Three small structures are present immediately behind the jaw and may represent the remains of the gills. In the lower Maastrichtian Pierre Shale of Wyoming, two specimens of Baculites grandis contain lower jaws inside their body chambers, and are probably in situ. In both specimens, the jaws are oriented at an acute angle to the long axis of the shell, with their anterior ends pointing toward the dorsum. One of the jaws is folded into a U-shape, which probably approximates the shape of the jaw during life. Based on the measurements of the jaws and the shape of the shell, the jaws could not have touched the sides of the shell even if they were splayed out, implying that they could not have effectively served as opercula. Instead, in combination with the upper jaws and radula, they constituted the buccal apparatus that collected and conveyed food to the esophagus.

An examination of the degrees of freedom of human jaw motion in speech and mastication.

PubMed

Ostry, D J; Vatikiotis-Bateson, E; Gribble, P L

1997-12-01

The kinematics of human jaw movements were assessed in terms of the three orientation angles and three positions that characterize the motion of the jaw as a rigid body. The analysis focused on the identification of the jaw's independent movement dimensions, and was based on an examination of jaw motion paths that were plotted in various combinations of linear and angular coordinate frames. Overall, both behaviors were characterized by independent motion in four degrees of freedom. In general, when jaw movements were plotted to show orientation in the sagittal plane as a function of horizontal position, relatively straight paths were observed. In speech, the slopes and intercepts of these paths varied depending on the phonetic material. The vertical position of the jaw was observed to shift up or down so as to displace the overall form of the sagittal plane motion path of the jaw. Yaw movements were small but independent of pitch, and vertical and horizontal position. In mastication, the slope and intercept of the relationship between pitch and horizontal position were affected by the type of food and its size. However, the range of variation was less than that observed in speech. When vertical jaw position was plotted as a function of horizontal position, the basic form of the path of the jaw was maintained but could be shifted vertically. In general, larger bolus diameters were associated with lower jaw positions throughout the movement. The timing of pitch and yaw motion differed. The most common pattern involved changes in pitch angle during jaw opening followed by a phase predominated by lateral motion (yaw). Thus, in both behaviors there was evidence of independent motion in pitch, yaw, horizontal position, and vertical position. This is consistent with the idea that motions in these degrees of freedom are independently controlled.

Effect of different head-neck-jaw postures on cervicocephalic kinesthetic sense.

PubMed

Zafar, H; Alghadir, A H; Iqbal, Z A

2017-12-01

To investigate the effect of different induced head-neck-jaw postures on head-neck relocation error among healthy subjects. 30 healthy adult male subjects participated in this study. Cervicocephalic kinesthetic sense was measured while standing, habitual sitting, habitual sitting with clenched jaw and habitual sitting with forward head posture during right rotation, left rotation, flexion and extension using kinesthetic sensibility test. Head-neck relocation error was least while standing, followed by habitual sitting, habitual sitting with forward head posture and habitual sitting with jaw clenched. However, there was no significant difference in error between different tested postures during all the movements. To the best of our knowledge, this is the first study to see the effect of different induced head-neck-jaw postures on head-neck position sense among healthy subjects. Assuming a posture for a short duration of time doesn't affect head-neck relocation error in normal healthy subjects.

On the Second Language Acquisition of Spanish Reflexive Passives and Reflexive Impersonals by French- and English-Speaking Adults

ERIC Educational Resources Information Center

Tremblay, Annie

2006-01-01

This study, a partial replication of Bruhn de Garavito (1999a; 1999b), investigates the second language (L2) acquisition of Spanish reflexive passives and reflexive impersonals by French- and English-speaking adults at an advanced level of proficiency. The L2 acquisition of Spanish reflexive passives and reflexive impersonals by native French and…

Restoring walking after spinal cord injury: operant conditioning of spinal reflexes can help.

PubMed

Thompson, Aiko K; Wolpaw, Jonathan R

2015-04-01

People with incomplete spinal cord injury (SCI) frequently suffer motor disabilities due to spasticity and poor muscle control, even after conventional therapy. Abnormal spinal reflex activity often contributes to these problems. Operant conditioning of spinal reflexes, which can target plasticity to specific reflex pathways, can enhance recovery. In rats in which a right lateral column lesion had weakened right stance and produced an asymmetrical gait, up-conditioning of the right soleus H-reflex, which increased muscle spindle afferent excitation of soleus, strengthened right stance and eliminated the asymmetry. In people with hyperreflexia due to incomplete SCI, down-conditioning of the soleus H-reflex improved walking speed and symmetry. Furthermore, modulation of electromyographic activity during walking improved bilaterally, indicating that a protocol that targets plasticity to a specific pathway can trigger widespread plasticity that improves recovery far beyond that attributable to the change in the targeted pathway. These improvements were apparent to people in their daily lives. They reported walking faster and farther, and noted less spasticity and better balance. Operant conditioning protocols could be developed to modify other spinal reflexes or corticospinal connections; and could be combined with other therapies to enhance recovery in people with SCI or other neuromuscular disorders. © The Author(s) 2014.

Alendronate-associated osteonecrosis of the jaws: A review of the main topics

PubMed Central

Paiva-Fonseca, Felipe; Santos-Silva, Alan R.; Della-Coletta, Ricardo; Vargas, Pablo A.

2014-01-01

Bisphosphonates is a group of inorganic pyrophosphates analogues that suppress bone resorption by inducing osteoclast inactivation, being frequently used for management of diseases affecting bone metabolism, bone metastases and bone tumors. However, since 2003 many cases describing the presence of necrotic bone exposures in the jaws have been described in patients receiving these drugs, what represent a significant complication of bisphosphonates treatment. The overall incidence of bisphosphonate-related osteonecrosis of the jaws is low, ranging from 0.7% to 12%, mainly observed in those patients receiving intravenously treatment. Osteonecrosis of the jaws associated to oral bisphosphonate, particularly alendronate, has also been reported by a number of authors. Considering that alendronate is one of the most used drugs worldwide, specially for treatment of osteoporosis, a better understanding of osteonecrosis of the jaws related to its use and how to manage these patients is extremely important. Therefore, in the current manuscript the authors aim to review the most important topics related to this pathological presentation. Key words:Bisphosphonates, alendronate, bisphosphonate-related osteonecrosis of the jaws, osteonecrosis. PMID:23986020

Favouring Reflexivity in Technology-Enhanced Learning Systems: Towards Smart Uses of Traces

ERIC Educational Resources Information Center

George, Sébastien; Michel, Christine; Ollagnier-Beldame, Magali

2016-01-01

During learning activities, reflexive processes allow learners to realise what they have done, understand why, decide on new actions and gain motivation. They help learners to regulate their actions by themselves, that is, to develop metacognitive regulation skills. Computer environments can support reflexive processes to support human learning,…

Neurodevelopmental Reflex Testing in Neonatal Rat Pups.

PubMed

Nguyen, Antoinette T; Armstrong, Edward A; Yager, Jerome Y

2017-04-24

Neurodevelopmental reflex testing is commonly used in clinical practice to assess the maturation of the nervous system. Neurodevelopmental reflexes are also referred to as primitive reflexes. They are sensitive and consistent with later outcomes. Abnormal reflexes are described as an absence, persistence, reappearance, or latency of reflexes, which are predictive indices of infants that are at high risk for neurodevelopmental disorders. Animal models of neurodevelopmental disabilities, such as cerebral palsy, often display aberrant developmental reflexes, as would be observed in human infants. The techniques described assess a variety of neurodevelopmental reflexes in neonatal rats. Neurodevelopmental reflex testing offers the investigator a testing method that is not otherwise available in such young animals. The methodology presented here aims to assist investigators in examining developmental milestones in neonatal rats as a method of detecting early-onset brain injury and/or determining the effectiveness of therapeutic interventions. The methodology presented here aims to provide a general guideline for investigators.

The role of the antigravity musculature during quiet standing in man.

PubMed

Soames, R W; Atha, J

1981-01-01

The view that postural regulation is achieved by controlling the destabilising effects of gravity through myotatic reflex activity was examined using surface electromyography. Forty seconds of recordings were made of myograms from eighteen muscles in each of a sample of nine young adults. It was observed that antigravity muscular activity in standing is generally low and often absent, and that the myograms from the muscles of the right and left sides of the body differed appreciably, the two sides rarely working together. Some sudden and united bursts of antigravity muscle activity could be observed. These might well have been stretch reflex induced, but they were transient and rare. It is concluded that the view that postural control in quiet standing is continuously mediated in a simple way by stretch reflex mechanisms is probably not valid, and that other mechanisms for controlling posture remain to be identified.

Leveraging Researcher Reflexivity to Consider a Classroom Event over Time: Reflexive Discourse Analysis of "What Counts"

ERIC Educational Resources Information Center

Anderson, Kate T.

2017-01-01

This article presents a reflexive and critical discourse analysis of classroom events that grew out of a cross-cultural partnership with a secondary school teacher in Singapore. I aim to illuminate how differences between researcher and teacher assumptions about what participation in classroom activities should look like came into high relief when…

Postmating sexual selection and the enigmatic jawed genitalia of Callosobruchus subinnotatus

PubMed Central

Rönn, Johanna Liljestrand; Schilthuizen, Menno; Arnqvist, Göran

2017-01-01

ABSTRACT Insect genitalia exhibit rapid divergent evolution. Truly extraordinary structures have evolved in some groups, presumably as a result of postmating sexual selection. To increase our understanding of this phenomenon, we studied the function of one such structure. The male genitalia of Callosobruchus subinnotatus (Coleoptera: Bruchinae) contain a pair of jaw-like structures with unknown function. Here, we used phenotypic engineering to ablate the teeth on these jaws. We then experimentally assessed the effects of ablation of the genital jaws on mating duration, ejaculate weight, male fertilization success and female fecundity, using a double-mating experimental design. We predicted that copulatory wounding in females should be positively related to male fertilization success; however, we found no significant correlation between genital tract scarring in females and male fertilization success. Male fertilization success was, however, positively related to the amount of ejaculate transferred by males and negatively related to female ejaculate dumping. Ablation of male genital jaws did not affect male relative fertilization success but resulted in a reduction in female egg production. Our results suggest that postmating sexual selection in males indeed favors these genital jaws, not primarily through an elevated relative success in sperm competition but by increasing female egg production. PMID:28583926

Zoledronate Effects on Systemic and Jaw Osteopenias in Ovariectomized Periostin-Deficient Mice

PubMed Central

Bonnet, Nicolas; Lesclous, Philippe; Saffar, Jean Louis; Ferrari, Serge

2013-01-01

Osteoporosis and periodontal disease (PD) are frequently associated in the elderly, both concurring to the loss of jaw alveolar bone and finally of teeth. Bisphosphonates improve alveolar bone loss but have also been associated with osteonecrosis of the jaw (ONJ), particularly using oncological doses of zoledronate. The effects and therapeutic margin of zoledronate on jaw bone therefore remain uncertain. We reappraised the efficacy and safety of Zoledronate (Zol) in ovariectomized (OVX) periostin (Postn)-deficient mice, a unique genetic model of systemic and jaw osteopenia. Compared to vehicle, Zol 1M (100 µg/kg/month) and Zol 1W (100 µg/kg/week) for 3 months both significantly improved femur BMD, trabecular bone volume on tissue volume (BV/TV) and cortical bone volume in both OVX Postn+/+ and Postn−/− (all p<0.01). Zol 1M and Zol 1W also improved jaw alveolar and basal BV/TV, although the highest dose (Zol 1W) was less efficient, particularly in Postn−/−. Zol decreased osteoclast number and bone formation indices, i.e. MAR, MPm/BPm and BFR, independently in Postn−/− and Postn+/+, both in the long bones and in deep jaw alveolar bone, without differences between Zol doses. Zol 1M and Zol 1W did not reactivate inflammation nor increase fibrous tissue in the bone marrow of the jaw, whereas the distance between the root and the enamel of the incisor (DRI) remained high in Postn−/− vs Postn+/+ confirming latent inflammation and lack of crestal alveolar bone. Zol 1W and Zol 1M decreased osteocyte numbers in Postn−/− and Postn+/+ mandible, and Zol 1W increased the number of empty lacunae in Postn−/−, however no areas of necrotic bone were observed. These results demonstrate that zoledronate improves jaw osteopenia and suggest that in Postn−/− mice, zoledronate is not sufficient to induce bone necrosis. PMID:23505553

Activity of calcium activated protease in skeletal muscles and its changes in atrophy and stretch

NASA Technical Reports Server (NTRS)

Ellis, S.; Nagainis, P. A.

1984-01-01

The reduction of protein content in skeletal muscle undergoing disuse-induced atrophy is correlated with accelerated rates of protein degradation and reduced rates of protein synthesis (Goldspink, 1977). It is not known in what manner myofibers are partially disassembled during disuse atrophy to fibers of smaller diameter; nor is it known which proteases are responsible for this morphological change in contractile protein mass. Dayton and colleagues (1975) have suggested that the Ca(2+)-activated protease (CaP) may initiate myofibril degradation. The discovery of a form of CaP that is activatable by nano-molar concentrations of Ca(2+) indicates that CaP activity may be regulated by physiological concentrations of Ca(2+) (Mellgren, 1980). The enhancement of proteolysis by the Ca(2+) ionophore A23187, reported by Etlinger (1979), is consistent with a significant role for CaP in protein degradation. It was of interest, therefore, to measure the levels of CaP activity and the CaP inhibitor in extracts obtained from skeletal muscles of rat and chicken limbs undergoing disuse atrophy or stretch hypertrophy, respectively.

Stretch-dependent slow force response in isolated rabbit myocardium is Na+ dependent.

PubMed

von Lewinski, Dirk; Stumme, Burkhard; Maier, Lars S; Luers, Claus; Bers, Donald M; Pieske, Burkert

2003-03-15

Stretch induces functional and trophic effects in mammalian myocardium via various signal transduction pathways. We tested stretch signal transduction on immediate and slow force response (SFR) in rabbit myocardium. Experiments were performed in isolated right ventricular muscles from adult rabbit hearts (37 degrees C, 1 Hz stimulation rate, bicarbonate-buffer). Muscles were rapidly stretched from 88% of optimal length (L88) to near optimal length (L98) for functional analysis. The resulting immediate and slow increases in twitch force (first phase and SFR, respectively) were assessed at reduced [Na+]o or without and with blockade of stretch activated ion channels (SACs), angiotensin-II (AT1) receptors, endothelin-A (ET(A)) receptors, Na+/H+-exchange (NHE1), reverse mode Na+/Ca2+-exchange (NCX), or Na+/K+-ATPase. The effects of stretch on sarcoplasmic reticulum Ca2+-load were characterized using rapid cooling contractures (RCCs). Intracellular pH was measured in BCECF-AM loaded muscles, and action potential duration (APD) was assessed using floating electrodes. On average, force increased to 216+/-8% of the pre-stretch value during the immediate phase, followed by a further increase to 273+/-10% during the SFR (n=81). RCCs significantly increased during SFR, whereas pH and APD did not change. Neither inhibition of SACs, AT1, or ET(A) receptors affected the stretch-dependent immediate phase nor SFR. In contrast, SFR was reduced by NHE inhibition and almost completely abolished by reduced [Na+]o or inhibition of reverse-mode NCX, whereas increased SFR was seen after raising [Na+]i by Na+/K+-ATPase inhibition. The data demonstrate the existence of a delayed, Na+- and Ca2+-dependent but pH and APD independent SFR to stretch in rabbit myocardium. This inotropic response appears to be independent of autocrine/paracrine AT1 or ET(A) receptor activation, but mediated through stretch-induced activation of NHE and reverse mode NCX.

Pharmacological modifications of the stretch-induced effects on ventricular fibrillation in perfused rabbit hearts.

PubMed

Chorro, Francisco J; Trapero, Isabel; Such-Miquel, Luis; Pelechano, Francisca; Mainar, Luis; Cánoves, Joaquín; Tormos, Alvaro; Alberola, Antonio; Hove-Madsen, Leif; Cinca, Juan; Such, Luis

2009-11-01

Stretch induces modifications in myocardial electrical and mechanical activity. Besides the effects of substances that block the stretch-activated channels, other substances could modulate the effects of stretch through different mechanisms that affect Ca(2+) handling by myocytes. Thirty-six Langendorff-perfused rabbit hearts were used to analyze the effects of the Na(+)/Ca(2+) exchanger blocker KB-R7943, propranolol, and the adenosine A(2) receptor antagonist SCH-58261 on the acceleration of ventricular fibrillation (VF) produced by acute myocardial stretching. VF recordings were obtained with two epicardial multiple electrodes before, during, and after local stretching in four experimental series: control (n = 9), KB-R7943 (1 microM, n = 9), propranolol (1 microM, n = 9), and SCH-58261 (1 microM, n = 9). Both the Na(+)/Ca(2+) exchanger blocker KB-R7943 and propranolol induced a significant reduction (P < 0.001 and P < 0.05, respectively) in the dominant frequency increments produced by stretching with respect to the control and SCH-58261 series (control = 49.9%, SCH-58261 = 52.1%, KB-R7943 = 9.5%, and propranolol = 12.5%). The median of the activation intervals, the functional refractory period, and the wavelength of the activation process during VF decreased significantly under stretch in the control and SCH-58261 series, whereas no significant variations were observed in the propranolol and KB-R7943 series, with the exception of a slight but significant decrease in the median of the fibrillation intervals in the KB-R7943 series. KB-R7943 and propranolol induced a significant reduction in the activation maps complexity increment produced by stretch with respect to the control and SCH-58261 series. In conclusion, the electrophysiological effects responsible for stretch-induced VF acceleration in the rabbit heart are reduced by the Na(+)/Ca(2+) exchanger blocker KB-R7943 and by propranolol but not by the adenosine A(2) receptor antagonist SCH-58261.

Effect of therapeutic jaw exercise on temporomandibular disorders in individuals with chronic whiplash-associated disorders.

PubMed

Klobas, Luciano; Axelsson, Susanna; Tegelberg, Ake

2006-11-01

The aim of this study was to investigate the effect of a specific therapeutic jaw exercise on the temporomandibular disorders of patients with chronic whiplash-associated disorders. Ninety-four consecutive patients with whiplash-related conditions were referred to and accepted for a treatment period at a center for functional evaluation and rehabilitation during 2001-2002. The patients followed a program of physical therapy, occupational therapy, and pain management. At the start of their stay, they were examined by a physician specialized in rehabilitation medicine and also by a dentist who performed a functional examination of the stomatognathic system. Of the 93 patients who accepted participation in the study, 55 were diagnosed with temporomandibular disorders and chronic whiplash-associated disorders in accordance with the inclusion criteria. They were randomized into a jaw exercise group (n = 25), who performed specific therapeutic jaw exercises, and a control group (n = 30). Both groups undertook the whiplash rehabilitation program at the center. There were no inter- or intra-group differences in symptoms and signs of temporomandibular disorders at baseline, nor at the 3-week and 6-month follow-ups, except for an increase of maximum active mouth-opening capacity in the control group. In conclusion, the therapeutic jaw exercises, in addition to the regular whiplash rehabilitation program, did not reduce symptoms and signs of temporomandibular disorders in patients with chronic whiplash-associated disorders.

Role of Ca2+ signaling in initiation of stretch-induced apoptosis in neonatal heart cells.

PubMed

Liao, Xu Dong; Tang, Ai Hui; Chen, Quan; Jin, Hai Jing; Wu, Cai Hong; Chen, Lan-Ying; Wang, Shi Qiang

2003-10-17

Abnormal mechanical load, as seen in hypertension, is found to induce heart cell apoptosis, yet the signaling link between cell stretch and apoptotic pathways is not known. Using an in vitro stretch model mimicking diastolic pressure stress, here we show that Ca(2+) signaling participates essentially in the early stage of stretch-induced apoptosis. In neonatal rat cardiomyocytes, the moderate 20% stretch resulted in tonic elevation of intracellular free Ca(2+) ([Ca(2+)](i)). Buffering [Ca(2+)](i) by EGTA-AM, suppressing ryanodine-sensitive Ca(2+) release, and blocking L-type Ca(2+) channels all prevented the stretch-induced apoptosis as assessed by phosphatidylserine exposure and nuclear fragmentation. Notably, Ca(2+) suppression also prevented known stretch-activated apoptotic events, including caspase-3/-9 activation, mitochondrial membrane potential corruption, and reactive oxygen species production, suggesting that Ca(2+) signaling is the upstream of these events. Since [Ca(2+)](i) did not change without activating mechanosensitive Ca(2+) entry, we conclude that stretch-induced Ca(2+) entry, via the Ca(2+)-induced Ca(2+) release mechanism, plays an important role in initiating apoptotic signaling during mechanical stress.

Effect of different head-neck-jaw postures on cervicocephalic kinesthetic sense

PubMed Central

Zafar, Hamayun; Alghadir, Ahmad H.; Iqbal, Zaheen A.

2017-01-01

Objectives: To investigate the effect of different induced head-neck-jaw postures on head-neck relocation error among healthy subjects. Methods: 30 healthy adult male subjects participated in this study. Cervicocephalic kinesthetic sense was measured while standing, habitual sitting, habitual sitting with clenched jaw and habitual sitting with forward head posture during right rotation, left rotation, flexion and extension using kinesthetic sensibility test. Results: Head-neck relocation error was least while standing, followed by habitual sitting, habitual sitting with forward head posture and habitual sitting with jaw clenched. However, there was no significant difference in error between different tested postures during all the movements. Conclusions: To the best of our knowledge, this is the first study to see the effect of different induced head-neck-jaw postures on head-neck position sense among healthy subjects. Assuming a posture for a short duration of time doesn’t affect head-neck relocation error in normal healthy subjects. PMID:29199196

Stretch-activated TRPV2 channels: Role in mediating cardiopathies.

PubMed

Aguettaz, Elizabeth; Bois, Patrick; Cognard, Christian; Sebille, Stéphane

2017-11-01

Transient receptor potential vanilloid type 2, TRPV2, is a calcium-permeable cation channel belonging to the TRPV channel family. Although this channel has been first characterized as a noxious heat sensor, its mechanosensor property recently gained importance in various physiological functions. TRPV2 has been described as a stretch-mediated channel and a regulator of calcium homeostasis in several cell types and has been shown to be involved in the stretch-dependent responses in cardiomyocytes. Hence, several studies in the last years support the idea that TRPV2 play a key role in the function and structure of the heart, being involved in the cardiac compensatory mechanisms in response to pathologic or exercise-induced stress. We present here an overview of the current literature and concepts of TRPV2 channels involvement (i) in the mechanical coupling mechanisms in heart and (ii) in the mechanisms that lead to cardiomyopathies. All these studies lead us to think that TRPV2 may also be an important cardiac drug target based on its major physiological roles in heart. Copyright © 2017 Elsevier Ltd. All rights reserved.

Brainstem mechanisms underlying the cough reflex and its regulation.

PubMed

Mutolo, Donatella

2017-09-01

Cough is a very important airway protective reflex. Cough-related inputs are conveyed to the caudal nucleus tractus solitarii (cNTS) that projects to the brainstem respiratory network. The latter is reconfigured to generate the cough motor pattern. A high degree of modulation is exerted on second-order neurons and the brainstem respiratory network by sensory inputs and higher brain areas. Two medullary structures proved to have key functions in cough production and to be strategic sites of action for centrally active drugs: the cNTS and the caudal ventral respiratory group (cVRG). Drugs microinjected into these medullary structures caused downregulation or upregulation of the cough reflex. The results suggest that inhibition and disinhibition are prominent regulatory mechanisms of this reflex and that both the cNTS and the cVRG are essential in the generation of the entire cough motor pattern. Studies on the basic neural mechanisms subserving the cough reflex may provide hints for novel therapeutic approaches. Different proposals for further investigations are advanced. Copyright © 2017 Elsevier B.V. All rights reserved.

Stretching and Young Children: Should We or Shouldn't We?

ERIC Educational Resources Information Center

Mally, Kristi K.

2006-01-01

The purpose of this article is to continue the discussion of "should we or shouldn't we?" Specifically, this article addresses whether or not young children need to spend time participating in static stretching activities during physical education class. Is it a worthwhile use of already limited time to ask young children to stretch? Do they need…

Contribution of the maculo-ocular reflex to gaze stability in the rabbit.

PubMed

Pettorossi, V E; Errico, P; Santarelli, R M

1991-01-01

The contribution of the maculo-ocular reflex to gaze stability was studied in 10 pigmented rabbits by rolling the animals at various angles of sagittal inclination of the rotation and/or longitudinal animal axes. At low frequencies (0.005-0.01 Hz) of sinusoidal stimulation the vestibulo-ocular reflex (VOR) was due to macular activation, while at intermediate and high frequencies it was mainly due to ampullar activation. The following results were obtained: 1) maculo-ocular reflex gain decreased as a function of the cosine of the angle between the rotation axis and the earth's horizontal plane. No change in gain was observed when longitudinal animal axis alone was inclined. 2) At 0 degrees of rotation axis and with the animal's longitudinal axis inclination also set at 0 degrees, the maculo-ocular reflex was oriented about 20 degrees forward and upward with respect to the earth's vertical axis. This orientation remained constant with sagittal inclinations of the rotation and/or longitudinal animal axes ranging from approximately 5 degrees upward to 30 degrees downward. When the longitudinal animal axis was inclined beyond these limits, the eye trajectory tended to follow the axis inclination. In the upside down position, the maculo-ocular reflex was anticompensatory, oblique and fixed with respect to orbital coordinates. 3) Ampullo-ocular reflex gain did not change with inclinations of the rotation and/or longitudinal animal axes. The ocular responses were consistently oriented to the stimulus plane. At intermediate frequencies the eye movement trajectory was elliptic because of directional differences between the ampullo- and maculo-ocular reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Targeted ablation of cardiac sympathetic neurons reduces resting, reflex and exercise-induced sympathetic activation in conscious rats.

PubMed

Lujan, Heidi L; Palani, Gurunanthan; Chen, Ying; Peduzzi, Jean D; Dicarlo, Stephen E

2009-05-01

Cholera toxin B subunit conjugated to saporin (SAP, a ribosomal inactivating protein that binds to and inactivates ribosomes) was injected in both stellate ganglia to evaluate the physiological response to targeted ablation of cardiac sympathetic neurons. Resting cardiac sympathetic activity (cardiac sympathetic tonus), exercise-induced sympathetic activity (heart rate responses to graded exercise), and reflex sympathetic activity (heart rate responses to graded doses of sodium nitroprusside, SNP) were determined in 18 adult conscious Sprague-Dawley male rats. Rats were randomly divided into the following three groups (n = 6/group): 1) control (no injection), 2) bilateral stellate ganglia injection of unconjugated cholera toxin B (CTB), and 3) bilateral stellate ganglia injection of cholera toxin B conjugated to SAP (CTB-SAP). CTB-SAP rats, compared with control and CTB rats, had reduced cardiac sympathetic tonus and reduced heart rate responses to graded exercise and graded doses of SNP. Furthermore, the number of stained neurons in the stellate ganglia and spinal cord (segments T(1)-T(4)) was reduced in CTB-SAP rats. Thus CTB-SAP retrogradely transported from the stellate ganglia is effective at ablating cardiac sympathetic neurons and reducing resting, exercise, and reflex sympathetic activity. Additional studies are required to further characterize the physiological responses to this procedure as well as determine if this new approach is safe and efficacious for the treatment of conditions associated with excess sympathetic activity (e.g., autonomic dysreflexia, hypertension, heart failure, and ventricular arrhythmias).

Neuroprotective effect of gadolinium: a stretch-activated calcium channel blocker in mouse model of ischemia-reperfusion injury.

PubMed

Gulati, Puja; Muthuraman, Arunachalam; Jaggi, Amteshwar S; Singh, Nirmal

2013-03-01

The present study was designed to investigate the potential of gadolinium, a stretch-activated calcium channel blocker in ischemic reperfusion (I/R)-induced brain injury in mice. Bilateral carotid artery occlusion of 12 min followed by reperfusion for 24 h was given to induce cerebral injury in male Swiss mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using Morris water maze test and motor incoordination was evaluated using rota-rod, lateral push, and inclined beam walking tests. In addition, total calcium, thiobarbituric acid reactive substance (TBARS), reduced glutathione (GSH), and acetylcholinesterase (AChE) activity were also estimated in brain tissue. I/R injury produced a significant increase in cerebral infarct size. A significant loss of memory along with impairment of motor performance was also noted. Furthermore, I/R injury also produced a significant increase in levels of TBARS, total calcium, AChE activity, and a decrease in GSH levels. Pretreatment of gadolinium significantly attenuated I/R-induced infarct size, behavioral and biochemical changes. On the basis of the present findings, we can suggest that opening of stretch-activated calcium channel may play a critical role in ischemic reperfusion-induced brain injury and that gadolinium has neuroprotective potential in I/R-induced injury.

Description of the chimaerid jaw and its phylogenetic origins.

PubMed

Grogan, Eileen D; Lund, Richard; Didier, Dominique

1999-01-01

Anatomical delineation of the holocephalan palatoquadrate has proven to be difficult and, so, has been an extensively debated topic as it relates to the evolutionary derivation of jaws, modes of jaw suspension, and the interrelationships of the hondrichthyes (Elasmobranchii and Holocephali). Embryological analyses of the chimaerid jaw and cranium are presented to provide an anatomical description of the palatoquadrate in modern chimaerids. The palatoquadrate fuses, anteriorly, to the nasal capsule early in development. This marks the first point of contact between the mandibular arch and cranium. Orbitonasal canal foramina delineate the dorsal palatoquadrate margin. The posteriormost margin is marked by fusion of the upper jaw with trabecular and parachordal cartilages in the region of the efferent eudobranchial artery foramen and by a suborbitally positioned basitrabecular cartilage. This basitrabecula generates a subocular shelf as it fuses medially to the parachordal cartilage and posteriorly to the postorbital wall and cranial otic process. The results of these analyses are related to morphological studies of Paleozoic chondrichthyan fishes, particularly the autodiastylic paraselachians that represent morphological intermediates to selachians and holocephalans. The paraselachian basitrabecular, which was mechanically fundamental to stabilizing the free autodiastylic upper jaw and a hyoid operculum, is shown to correlate with the suborbital basitrabecular of today's chimaerids. Further analyses of both extant and fossil data permit us to conclude that the primordial chondrichthyan palatoquadrate did not extend posteriorly to include a palatoquadrate-derived otic process. Rather, the posteriormost extent of this element is primitively found within the limits of the orbit and is demarcated by the highly conserved basitrabecular element. The collective analyses support autodiastyly as the ancestral condition from which all fundamental suspensorial states are

Caspase-12 is involved in stretch-induced apoptosis mediated endoplasmic reticulum stress.

PubMed

Zhang, Qiang; Liu, Jianing; Chen, Shulan; Liu, Jing; Liu, Lijuan; Liu, Guirong; Wang, Fang; Jiang, Wenxin; Zhang, Caixia; Wang, Shuangyu; Yuan, Xiao

2016-04-01

It is well recognized that mandibular growth, which is caused by a variety of functional appliances, is considered to be the result of both neuromuscular and skeletal adaptations. Accumulating evidence has demonstrated that apoptosis plays an important role in the adaptation of skeletal muscle function. However, the underlying mechanism of apoptosis that is induced by stretch continues to be incompletely understood. Endoplasmic reticulum stress (ERS), a newly defined signaling pathway, initiates apoptosis. This study seeks to determine if caspase-12 is involved in stretch-induced apoptosis mediated endoplasmic reticulum stress in myoblast and its underlying mechanism. Apoptosis was assessed by Hochest staining, DAPI staining and annexin V binding and PI staining. ER chaperones, such as GRP78, CHOP and caspase-12, were determined by reverse transcription polymerase chain reaction (RT-PCR) and Western blot. Furthermore, caspase-12 inhibitor was used to value the mechanism of the caspase-12 pathway. Apoptosis of myoblast, which is subjected to cyclic stretch, was observed in a time-dependent manner. We found that GRP78 mRNA and protein were significantly increased and CHOP and caspase-12 were activated in myoblast that was exposed to cyclic stretch. Caspase-12 inhibition reduced stretch-induced apoptosis, and caspase-12 activated caspase-3 to induce apoptosis. We concluded that caspase-12 played an important role in stretch-induced apoptosis that is associated by endoplasmic reticulum stress by activating caspase-3.

Phylotranscriptomic consolidation of the jawed vertebrate timetree.

PubMed

Irisarri, Iker; Baurain, Denis; Brinkmann, Henner; Delsuc, Frédéric; Sire, Jean-Yves; Kupfer, Alexander; Petersen, Jörn; Jarek, Michael; Meyer, Axel; Vences, Miguel; Philippe, Hervé

2017-09-01

Phylogenomics is extremely powerful but introduces new challenges as no agreement exists on "standards" for data selection, curation and tree inference. We use jawed vertebrates (Gnathostomata) as model to address these issues. Despite considerable efforts in resolving their evolutionary history and macroevolution, few studies have included a full phylogenetic diversity of gnathostomes and some relationships remain controversial. We tested a novel bioinformatic pipeline to assemble large and accurate phylogenomic datasets from RNA sequencing and find this phylotranscriptomic approach successful and highly cost-effective. Increased sequencing effort up to ca. 10Gbp allows recovering more genes, but shallower sequencing (1.5Gbp) is sufficient to obtain thousands of full-length orthologous transcripts. We reconstruct a robust and strongly supported timetree of jawed vertebrates using 7,189 nuclear genes from 100 taxa, including 23 new transcriptomes from previously unsampled key species. Gene jackknifing of genomic data corroborates the robustness of our tree and allows calculating genome-wide divergence times by overcoming gene sampling bias. Mitochondrial genomes prove insufficient to resolve the deepest relationships because of limited signal and among-lineage rate heterogeneity. Our analyses emphasize the importance of large curated nuclear datasets to increase the accuracy of phylogenomics and provide a reference framework for the evolutionary history of jawed vertebrates.

Interlimb Reflexes Induced by Electrical Stimulation of Cutaneous Nerves after Spinal Cord Injury

PubMed Central

Butler, Jane E.; Godfrey, Sharlene; Thomas, Christine K.

2016-01-01

Whether interlimb reflexes emerge only after a severe insult to the human spinal cord is controversial. Here the aim was to examine interlimb reflexes at rest in participants with chronic (>1 year) spinal cord injury (SCI, n = 17) and able-bodied control participants (n = 5). Cutaneous reflexes were evoked by delivering up to 30 trains of stimuli to either the superficial peroneal nerve on the dorsum of the foot or the radial nerve at the wrist (5 pulses, 300 Hz, approximately every 30 s). Participants were instructed to relax the test muscles prior to the delivery of the stimuli. Electromyographic activity was recorded bilaterally in proximal and distal arm and leg muscles. Superficial peroneal nerve stimulation evoked interlimb reflexes in ipsilateral and contralateral arm and contralateral leg muscles of SCI and control participants. Radial nerve stimulation evoked interlimb reflexes in the ipsilateral leg and contralateral arm muscles of control and SCI participants but only contralateral leg muscles of control participants. Interlimb reflexes evoked by superficial peroneal nerve stimulation were longer in latency and duration, and larger in magnitude in SCI participants. Interlimb reflex properties were similar for both SCI and control groups for radial nerve stimulation. Ascending interlimb reflexes tended to occur with a higher incidence in participants with SCI, while descending interlimb reflexes occurred with a higher incidence in able-bodied participants. However, the overall incidence of interlimb reflexes in SCI and neurologically intact participants was similar which suggests that the neural circuitry underlying these reflexes does not necessarily develop after central nervous system injury. PMID:27049521

The Dynamics of the Stapedial Acoustic Reflex.

NASA Astrophysics Data System (ADS)

Moss, Sherrin Mary

Available from UMI in association with The British Library. This thesis aims to separate the neural and muscular components of the stapedial acoustic reflex, both anatomically and physiologically. It aims to present an hypothesis to account for the differences between ipsilateral and contralateral reflex characteristics which have so far been unexplained, and achieve a greater understanding of the mechanisms underlying the reflex dynamics. A technique enabling faithful reproduction of the time course of the reflex is used throughout the experimental work. The technique measures tympanic membrane displacement as a result of reflex stapedius muscle contraction. The recorded response can be directly related to the mechanics of the middle ear and stapedius muscle contraction. Some development of the technique is undertaken by the author. A model of the reflex neural arc and stapedius muscle dynamics is evolved that is based upon a second order system. The model is unique in that it includes a latency in the ipsilateral negative feedback loop. Oscillations commonly observed on reflex responses are seen to be produced because of the inclusion of a latency in the feedback loop. The model demonstrates and explains the complex relationships between neural and muscle dynamic parameters observed in the experimental work. This more comprehensive understanding of the interaction between the stapedius dynamics and the neural arc of the reflex would not usually have been possible using human subjects, coupled with a non-invasive measurement technique. Evidence from the experimental work revealed the ipsilateral reflex to have, on average, a 5 dB lower threshold than the contralateral reflex. The oscillatory charcteristics, and the steady state response, of the contralateral reflex are also seen to be significantly different from those of the ipsilateral reflex. An hypothesis to account for the experimental observations is proposed. It is propounded that chemical neurotransmitters

Effects of aging and sarcopenia on tongue pressure and jaw-opening force.