首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 8 毫秒
1.
2.
Abdominal motor unit activity during respiratory and nonrespiratory tasks   总被引:1,自引:0,他引:1  
Abdominalmuscles serve multiple roles, but the functional organization of theirmotoneurons remains unclear. To gain insight, we recorded single motorunit potentials from the internal oblique (IO) and transversusabdominis (TA) muscles of three standing subjects during quietbreathing, a leg lift, and an expiratory threshold load. Inspiratoryairflow, recorded from a pneumotachometer, provided tidal volumes andrespiratory cycle timing. Fine wires, implanted under ultrasonicimaging, detected single motor unit potentials that were visuallydistinguished by their spike morphology. From the number of spikes,firing profiles, times of occurrence in the respiratory cycle, andtheir onset, instantaneous, mean, and peak firing frequencies wededuced that 1) breathing patterns varied across tasks, 2) differentmotor units were recruited for each task with essentially no overlap,3) their firing displayed prominentexpiratory activity during each task, and4) the recruitment levels anddischarge patterns of IO and TA were different. We conclude that the IOand TA motor pools receive a strong central respiratory drive, yet eachpool receives its own distinct, task-dependent synapticinput.

  相似文献   

3.
As the majority of back pain is thought to be mechanical in origin, quantitative tests designed to assess spinal mechanics may provide information about its etiology and treatment. This paper describes the application of structural vibration testing in the spine, its reliability and ability to discriminate between different structural states. In each of five cadaveric pigs, tri-axial accelerometers were fixed to the spinouses of L1-5 and short-duration vibrations (0-2000Hz) were applied to the L3 spinous exclusively. The frequency response function (FRF) of each sensor axis was calculated and the process repeated. Additional FRF data were obtained after the creation of multiple structural alterations including joining of adjacent vertebrae and scalpel transections of each lumbar disc. To assess the reliability of structural vibration testing, the intra-class correlation coefficient was calculated for FRFs obtained from each structural state in each specimen. To determine if structural vibration testing could distinguish between different structural states, correlation coefficients were calculated between FRFs from each structural state and a baseline condition. Most intra-class correlation coefficients (3740) were in the excellent range (>0.75), while FRF data from each structural state were found to be significantly different from that of the baseline state (p<0.05). These results indicate that structural vibration testing can be used to obtain reliable FRFs that are sensitive to alterations in the spine's structure. In the future, we hope to refine this technique to obtain specific diagnoses of, and/or assess therapies for, common spinal disorders.  相似文献   

4.
5.
In this study we analyzed the breath-by-breath activity of single motor units in the diaphragm slip of allobarbital-anesthetized cats during quiet breathing and during continuous positive- and negative-pressure breathing. Our objective was to determine whether single motor units, on the basis of their activities, can be separated into discrete subpopulations or whether they fall on a continuum analogous to that of motor units of hindlimb muscles. The firing profiles of each unit were characterized for each pressure level by the onset and peak firing frequencies, onset latency, duration of firing, number of impulses per breath, and minimal frequency, when appropriate. Units with shorter onset latencies had higher peak frequencies, longer firing durations, and increased firing frequencies than did units with longer onset latencies. These comparative relationships persisted even though the activity of every motor unit was altered during pressure breathing. During positive-pressure breathing onset latencies were lengthened, and durations of firing were shortened with little change in onset or peak frequencies. Late units might be silenced. During negative-pressure breathing onset latencies were shortened, and durations of firing were lengthened, sufficiently in some cases to fill the expiratory pause. In addition, previously inactive units were recruited late in inspiration for short, relatively high frequency bursts during inspiration. The results support the concept that the phrenic motoneuron pool is comprised of three discrete subpopulations.  相似文献   

6.
At early stages of neuromuscular development, motor unit territory is expanded, with each muscle fibre being supplied by several axons. During postnatal development, some synapses are eliminated, motor unit size decreases, and the adult distribution of motor unit sizes emerges. This process depends on activity, since it proceeds more rapidly when the nerve is activated and is slower when activity is reduced. Here we studied whether, in addition to influencing the rate of retraction of motor unit territory, activity during the critical period of development affects the final outcome of the distribution of motor unit sizes. The sciatic nerve of 8- to 12-day-old rats was stimulated daily. One week later the tension of the extensor digitorum longus muscle and that of its individual motor units was recorded. The sizes of individual motor units were calculated and compared with those from animals that received no stimulation. The distribution of motor unit sizes from stimulated muscles was not significantly different from those from control muscles. Therefore, we conclude that although activity increases the rate at which motor units attain their adult size, it does not influence the final outcome of motor unit size distribution.  相似文献   

7.
8.
Based on literature analysis of 308 angiosperm species inventoried from a 50-hectare forest plot on Barro Colorado Island, Panama, 40 species were selected and 80 samples (two samples for every species; leaf + twig and stembark samples) were collected for investigation of their medicinal/pharmaceutical potential. Extracts of these 80 samples were tested in bioassay systems to assess cancer chemoprevention (eight assays), antiplasmodial, cytotoxicity, and anti-HIV activities. Details of bioassay techniques are described. Of the 40 species, 12 (30%) showed activity in one or more of the 11 bioassay systems used. These active species areBombacopsis (= Pachira) quinata, Calophyllum longifolium, Casearia commersoniana, Lozania pittieri, Maclura tinctoria, Mouriri myrtilloides, Olmedia aspera (= Trophis caucana), Pseudobombax septenatum, Spondias radlkoferi, Stylogyne standleyi, Turpinia occidentalis, andVochysia ferruginea. Because literature data on the chemistry ofBombacopsis (= Pachira) quinata, Lozan ia pittieri, Mouriri myrtilloides, Olmedia aspera (= Trophis caucana), Pseudobombax septenatum, andStylogyne standleyi, are lacking, and similar data on the other six species are deficient, further fractionation and isolation work on these active species potentially may yield novel, biologically active structures. This study demonstrates that a plot-based selection of plant species for evaluation of their potential medicinal/ pharmaceutical value has merit in achieving such a goal, and should be used in a program on plant drug discovery.  相似文献   

9.
This study has begun to test the hypothesis that aspects of hand/object shape are represented in the discharge of primary motor cortex (M1) neurons. Two monkeys were trained in a visually cued reach-to-grasp task, in which object properties and grasp forces were systematically varied. Behavioral analyses show that the reach and grasp force production were constant across the objects. The discharge of M1 neurons was highly modulated during the reach and grasp. Multiple linear regressions models revealed that the M1 discharge was highly dependent on the object grasped, with object class, volume, orientation and grasp force as significant predictors. These findings are interpreted as evidence that the CNS controls the hand as a unit.  相似文献   

10.
We constructed cross-correlograms (CCGs) of action potentials of pairs of motor units (MUs) of human soleus, triceps brachii, and the first and second dorsal interosseous muscles. During voluntary muscle contraction, a pronounced peak in the zero bin was found in 21 out of 126 pairs investigated with the aid of the CCG; this indicates that the number of coincidental firings exceeded chance. The width of the peak did not exceed 5 msec (synchronization for a brief interval, i.e., short-term synchronization). When motoneurons of the soleus muscle were activated by vibration, correlations were found in 12 out 89 pairs of MUs investigated. On the CCGs of action potentials of MU pairs in two muscles (the first and second dorsal interosseous muscles), such correlations were found in four out of 10 pairs investigated. In all of these cases, the ratio of above-change coincidences relative to the total number of MU discharges was small, from 3.0 to 6.1%. Synchronization within a brief time interval can be considered a result of simultaneous creation of EPSPs in motoneourons reached by endings of a single pre-motor nerve fiber. In some pairs of MUs, long term synchronization (clustering) occurred, ie., synchronization lasting several tens of milliseconds. The long-term synchronization can be considered a manifestation of fatigue accompanying tremor.Institute for Problems of Information Transmission, Russian Academy of Sciences, Moscow. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 691–698, November–December, 1991.  相似文献   

11.
The review briefs the optical trap method, a modern experimental tool based on the recently discovered ability of light to trap and hold micron and submicron particles in a focused beam. The physical principle underlying the optical trap and the opportunities that it provides for studying the molecular nature of biological motility are considered. Several studies into the physical characteristics and functions of single motor protein molecules performed using the optical trap and recording nanometer displacements and piconewton forces are analyzed.  相似文献   

12.
13.
Whole body vibration (WBV) has been suggested to elicit reflex muscle contractions but this has never been verified. We recorded from 32 single motor units (MU) in the vastus lateralis of 7 healthy subjects (34 ± 15.4 yr) during five 1-min bouts of WBV (30 Hz, 3 mm peak to peak), and the vibration waveform was also recorded. Recruitment thresholds were recorded from 38 MUs before and after WBV. The phase angle distribution of all MUs during WBV was nonuniform (P < 0.001) and displayed a prominent peak phase angle of firing. There was a strong linear relationship (r = -0.68, P < 0.001) between the change in recruitment threshold after WBV and average recruitment threshold; the lowest threshold MUs increased recruitment threshold (P = 0.008) while reductions were observed in the higher threshold units (P = 0.031). We investigated one possible cause of changed thresholds. Presynaptic inhibition in the soleus was measured in 8 healthy subjects (29 ± 4.6 yr). A total of 30 H-reflexes (stimulation intensity 30% Mmax) were recorded before and after WBV: 15 conditioned by prior stimulation (60 ms) of the antagonist and 15 unconditioned. There were no significant changes in the relationship between the conditioned and unconditioned responses. The consistent phase angle at which each MU fired during WBV indicates the presence of reflex muscle activity similar to the tonic vibration reflex. The varying response in high- and low-threshold MUs may be due to the different contributions of the mono- and polysynaptic pathways but not presynaptic inhibition.  相似文献   

14.

Objectives:

To evaluate the effects of performing battling rope exercise with and without the addition of whole-body vibration (WBV) on muscle activity of the leg, trunk, and upper body.

Methods:

Twenty-eight recreationally active university students completed 20-s of battling rope undulation for 6 separate conditions: 1) alternating arm motion no WBV -Alt_NoWBV; 2) alternating arm motion 30 Hz low amplitude WBV -Alt_30 Hz-L; 3) alternating arm motion 50 Hz high amplitude -Alt_50 Hz-H; 4) double arm motion no WBV -Double_NoWBV; 5) double arm motion 30Hz low amplitude WBV -Double_30Hz-L; 6) double arm motion 50 `Hz high amplitude -Double_50 Hz-H. Electromyography (EMG) was measured for the gastrocnemius medialis (GM), vastus medialis oblique (VMO), vastus lateralis (VL), rectus abdominis (RA), multifidus (MF), biceps brachii (BB), and triceps brachii (TB) muscles.

Results:

The double arm motion during undulation resulted in greater (p<0.05) muscle activity in the VMO, VL, RA, and MF muscles while the GM was more active during the alternating arm motion. WBV at 50Hz increased EMG in all muscles measured vs NoWBV and the 30 Hz condition.

Conclusion:

These results are the first to demonstrate that the exercise stimulus of performing battling rope exercise can be augmented by completing the exercise while being exposed to WBV from a ground-based platform.  相似文献   

15.
DNA mechanics as a tool to probe helicase and translocase activity   总被引:1,自引:0,他引:1  
Helicases and translocases are proteins that use the energy derived from ATP hydrolysis to move along or pump nucleic acid substrates. Single molecule manipulation has proved to be a powerful tool to investigate the mechanochemistry of these motors. Here we first describe the basic mechanical properties of DNA unraveled by single molecule manipulation techniques. Then we demonstrate how the knowledge of these properties has been used to design single molecule assays to address the enzymatic mechanisms of different translocases. We report on four single molecule manipulation systems addressing the mechanism of different helicases using specifically designed DNA substrates: UvrD enzyme activity detection on a stretched nicked DNA molecule, HCV NS3 helicase unwinding of a RNA hairpin under tension, the observation of RecBCD helicase/nuclease forward and backward motion, and T7 gp4 helicase mediated opening of a synthetic DNA replication fork. We then discuss experiments on two dsDNA translocases: the RuvAB motor studied on its natural substrate, the Holliday junction, and the chromosome-segregation motor FtsK, showing its unusual coupling to DNA supercoiling.  相似文献   

16.
17.
18.
Maintenance of airway patency during breathing involves complex interactions between pharyngeal dilator muscles. The few previous studies of geniohyoid activity using multiunit electromyography (EMG) have suggested that geniohyoid shows predominantly inspiratory phasic activity. This study aimed to quantify geniohyoid respiration-related activity with single motor unit (SMU) EMG recordings. Six healthy subjects of normal body mass index were studied. Intramuscular EMG recordings of geniohyoid activity were made with a monopolar needle with subjects in supine and seated positions. The depth of the geniohyoid was identified by ultrasound, and the electrode position was confirmed with maneuvers to isolate activity in geniohyoid and genioglossus. Activity was recorded at 85 sites in the geniohyoid during quiet breathing (45 supine and 40 seated). When subjects were supine, 33 sites (73%) showed no activity during breathing and 10 (22%) showed tonic activity. In addition, one site showed a tonic SMU with increased expiratory discharge, and one site in another subject had one unit with expiratory phasic activity. When subjects were seated, 27 sites (68%) in the geniohyoid showed no activity, 12 sites (30%) showed tonic activity that was not respiration related, and one unit at one site showed phasic expiratory activity. The average peak discharge frequency of geniohyoid motor units was 16.2 ± 3.1 impulses/s during the "geniohyoid maneuver," which was the first part of a swallow. In contrast to previous findings, the geniohyoid shows some tonic activity but minimal respiration-related activity in healthy subjects in quiet breathing. The geniohyoid has little active role in airway stability under these conditions.  相似文献   

19.
A secondary analysis of longitudinal and cohort studies was carried out to quantitatively investigate the motor activity pattern, recorded through actigraphy, during the first six hours of nocturnal sleep. The first study was of longitudinal nature. Ten healthy participants (four females) were monitored three times, at baseline (T1) when they were infants (mean age 7.10 ± 0.32 months), at the first follow-up examination (T2) around 4 months later (mean age 11.20 ± 0.63 months) and at the second follow-up (T3) around three years later, when they were preschoolers (mean age 4.68 ± 0.14 years). At T1, T2 and T3 each participant wore the actigraph Basic Mini-Motionlogger (Ambulatory Monitoring, Inc., Ardsley, NY, USA) over at least two consecutive nycthemeral cycles, with the aim to measure the mean hourly motor activity count. Seven- and 11-month-old infants had a higher level of motor activity over the night compared to preschoolers. Furthermore, motor activity increased as the night progressed, with a pronounced increment at both T1 and T2, while at T3 such an increase was less marked. The second study was cross-sectional and aimed to explore the motor activity pattern, using actigraphy, during the first six hours of nocturnal sleep in multiple-age healthy groups, from infancy to adulthood. We assigned participants to eight groups according to age: 20 (five females) aged around 10 months old (mean age 10.65 ± 0.67 months); 13 (nine females) aged around 4 years (mean age 4.38 ± 0.51 years); 21 (10 females) aged around 10 years (mean age 9.67 ± 0.91 years); 21 (nine females) aged around 20 years (mean age 19.33 ± 2.44 years); 20 (10 females) aged around 30 years (mean age 29.80 ± 1.99 years); 20 (15 females) aged around 40 years (mean age 40.70 ± 1.26 years); 20 (11 females) aged around 50 years (mean age 50.15 ± 2.80 years) and 20 (nine females) aged around 60 years (mean age 59.25 ± 3.23 years). The participants aged between 10 and 60 years wore the actigraph Basic Mini-Motionlogger over seven consecutive nycthemeral cycles (infants and preschoolers wore the actigraph over at least two consecutive nycthemeral cycles), with the aim to measure the mean hourly motor activity count. The results indicated a significantly higher motor activity count in 10-month-old infants compared to all the remaining age groups. Moreover, the pattern of motor activity of 10-month-old infants was different from that of all other groups, with the highest motor activity counts from the second to the sixth hour of sleep. Considered as a whole, the results of both studies converge regarding the high motor activity detected among infants, which could be explained by the presence of a maturational process that has not yet been fully completed at this stage of life. In both studies, only the motor activity of infants was above the cutoff level established for normal adults, highlighting the need to establish a specific cutoff value for infants.  相似文献   

20.
Epilepsy is one of the most common neurological disorders and is characterized by recurrent seizures. We use theoretical neuroscience tools to study brain dynamics during seizures. We derive and simulate a computational model of a network of hippocampal neuronal populations. Each population within the network is based on a model that has been shown to replicate the electrophysiological dynamics observed during seizures. The results provide insights into possible mechanisms for seizure spread. We observe that epileptiform activity remains localized to a pathological region when a global connectivity parameter is less than a critical value. After establishing the critical value for seizure spread, we explored how to correct the effect by altering particular synaptic gains. The spreading of seizures is quantified using numerical methods for seizure detection. The results from this study provide a new avenue of exploration for seizure control.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号