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101.
《Somatosensory & motor research》2013,30(4):254-261
AbstractPurpose:?Localized mechanical vibration, applied directly to a muscle, is known to have powerful, duration-dependent effects on the muscle spindle’s reflex arc. Here, the conditioning of the function of the spindle reflex arc via vibration was examined with considerations for use as a non-invasive, sensorimotor research tool.Methods:?Muscle spindle function was examined with patellar tendon taps prior to and following exposure to muscle vibration applied to the quadriceps femoris for acute (<5?s) and prolonged (20?min) durations. Surface electromyography (sEMG), torque, and accelerometry signals were obtained during the taps to quantify various measures of reflex magnitude and latency.Results:?Our findings suggest that acute vibration had no effect on normalized reflex torque or sEMG amplitude (p?>?0.05), but increased total reflex latency (p?=?0.022). Alternatively, prolonged vibration reduced normalized reflex torque and sEMG amplitude (p?<?0.001), and increased reflex latency (p?<?0.001).Conclusions:?Our findings support the use of prolonged vibration as a practical means to decrease the function of the muscle spindle’s reflex arc. Overall, this suppressive effect was evident in the majority of subjects, but the extent was variable. This approach could potentially be used to help delineate the muscle spindle’s role in various sensory or motor tasks in which more direct measures are not feasible. Acute vibration, however, did not potentiate muscle spindle function as hypothesized. Rather, our results suggest that acute vibration increased total reflex latency. Accordingly, potential mechanical and neurophysiological mechanisms are discussed. 相似文献
102.
Chiara Zoppirolli Hans-Christer Holmberg Barbara Pellegrini Diego Quaglia Lorenzo Bortolan Federico Schena 《Journal of electromyography and kinesiology》2013,23(6):1512-1519
This investigation was designed to evaluate the effectiveness of stretch–shortening cycling (SSCEFF) in upper-limb extensor muscles while cross-country skiing using the double-poling technique (DP). To this end, SSCEFF was analyzed in relation to DP velocity and performance. Eleven elite cross-country skiers performed an incremental test to determine maximal DP velocity (Vmax). Thereafter, cycle characteristics, elbow joint kinematics and poling forces were monitored on a treadmill while skiing at two sub-maximal and racing velocity (85% of Vmax). The average EMG activities of the triceps brachii and latissimus dorsi muscles were determined during the flexion and extension sub-phases of the poling cycle (EMGFLEX, EMGEXT), as well as prior to pole plant (EMGPRE). SSCEFF was defined as the ratio of aEMGFLEX to aEMGEXT. EMGPRE and EMGFLEX increased with velocity for both muscles (P < 0.01), as did SSCEFF (from 0.9 ± 0.3 to 1.3 ± 0.5 for the triceps brachii and from 0.9 ± 0.4 to 1.5 ± 0.5 for the latissimus dorsi) and poling force (from 253 ± 33 to 290 ± 36 N; P < 0.05). Furthermore, SSCEFF was positively correlated to Vmax, to EMGPRE and EMGFLEX (P < 0.05). The neuromuscular adaptations made at higher velocities, when more poling force must be applied to the ground, exert a major influence on the DP performance of elite cross-country skiers. 相似文献
103.
Background
The expression of myocardin, a cardiac-restricted gene, increases during environmental stress. How mechanical stretch affects the regulation of myocardin in vascular smooth muscle cells (VSMCs) is not fully understood. We identify the mechanisms and pathways through which mechanical stretch induces myocardin expression in VSMCs.Results
Rat VSMCs grown on a flexible membrane base were stretched to 20% of maximum elongation, at 60 cycles per min. An in vivo model of aorta-caval shunt in adult rats was also used to investigate myocardin expression. Cyclic stretch significantly increased myocardin and angiotensin II (AngII) expression after 18 and 6 h of stretch. Addition of extracellular signal-regulated kinases (ERK) pathway inhibitor (PD98059), ERK small interfering RNA (siRNA), and AngII receptor blocker (ARB; losartan) before stretch inhibited the expression of myocardin protein. Gel shift assay showed that myocardin-DNA binding activity increased after stretch. PD98059, ERK siRNA and ARB abolished the binding activity induced by stretch. Stretch increased while myocardin-mutant plasmid, PD98059, and ARB abolished the promoter activity. Protein synthesis by measuring [3H]proline incorporation into the cells increased after cyclic stretch, which represented hypertrophic change of VSMCs. An in vivo model of aorta-caval shunt also demonstrated increased myocardin protein expression in the aorta. Confocal microscopy showed increased VSMC size 24 h after cyclic stretch and VSMC hypertrophy after creation of aorta-caval shunt for 3 days.Conclusions
Cyclic stretch enhanced myocardin expression mediated by AngII through the ERK pathway in cultured rat VSMCs. These findings suggest that myocardin plays a role in stretch-induced VSMC hypertrophy. 相似文献104.
Gliboff S 《Journal of the history of biology》2007,40(2):259-294
The German paleontologist H. G. Bronn is best remembered for his 1860 translation and critique of Darwin’s Origin of Species, and for supposedly twisting Darwinian evolution into conformity with German idealistic morphology. This analysis of Bronn’s
writings shows, however, that far from being mired in an outmoded idealism that confined organic change to predetermined developmental
pathways, Bronn had worked throughout the 1840s and 1850s on a new, historical approach to life. He had been moving from the
study of plant and animal forms in the abstract towards placing them into geological and biogeographical context, analyzing
patterns of progress and adaptation, explaining species diversity and individual variation, and applying biological insights
to practical problems such as artificial breeding. Even though Bronn never fully accepted the idea of species transformation,
he saw Darwin’s theory as a bold new move toward his own goal of establishing a comprehensive, historical science of life,
and he presented it as such in his translation and commentary. Thus Darwin’s ideas gained a quick and generally favorable
hearing in Germany not because of their easy assimilability into an older tradition, but because of their appeal to the innovative
Bronn. 相似文献
105.
Until now the reproducibility of the short latency stretch reflex of the internal rotator muscles of the glenohumeral joint has not been identified. Twenty-three healthy male participants performed three sets of external shoulder rotation stretches with various pre-activation levels on two different dates of measurement to assess test–retest reliability. All stretches were applied with a dynamometer acceleration of 104°/s2 and a velocity of 150°/s. Electromyographical response was measured via surface EMG. Reflex latencies showed a pre-activation effect (ƞ2 = 0,355). ICC ranged from 0,735 to 0,909 indicating an overall “good” relative reliability. SRD 95% lay between ±7,0 to ±12,3 ms. The reflex gain showed overall poor test–retest reproducibility. The chosen methodological approach presented a suitable test protocol for shoulder muscles stretch reflex latency evaluation. A proof-of-concept study to validate the presented methodical approach in shoulder involvement including subjects with clinically relevant conditions is recommended. 相似文献
106.
Luis C. Barrio Francois Clarac Washington Buño 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(3):313-321
Summary Electrophysiological experiments showed that a tetrodotoxin (TTX) sensitive slowly inactivating Na+ current contributed to the excitability of the sensory neuron (SN1) that innervates the slow receptor muscle in the abdominal muscle receptor (MR1) of crayfish, Procambarus clarkii. Following either tetraethylammonium (TEA) blockage of the K+ delayed rectifier currents or exposure to high temperature, a depolarizing plateau potential was evoked by the slow Na+ current. Ca++ substitution by other divalent cations had no effect on the plateau potential, demonstrating that Ca++ is not involved in plateau potential genesis. Simultaneous intrasomatic and extraaxonic recordings coupled with 4-aminopyridine (4-AP) exposure indicated that the slowly inactivating Na+ current is primarily somatic, and does not contribute significantly to spiking.Abbreviations
4-AP
4-aminopyridine
-
HAP
hyperpolarizing after-potential
-
MR1
slowly adapting muscle receptor organ
-
SR1
sensory neuron of MR1
-
TEA
tetraethylammonium
-
TTX
tetrodotoxin 相似文献
107.
Summary Non-encapsulated, fine beaded nerve endings were found histologically on some muscle fibres in a number of limb muscles in newts and axolotls. They were present in newt muscles that had been chronically de-efferented, and in which no efferent activity survived, and were therefore likely to be sensory. They were located only on muscle fibres on or near the outside surface of the muscle. These small-diameter muscle fibres were characterised histochemically by low lipid, SDH and phosphorylase content; ultrastructurally by low glycogen content, and relatively large myofilaments poorly delimited by a sparse SR. There were many of this type (Type 1) that did not support sensory endings. A few endings occurred on another larger-diameter type of fibre (Type 2) whose properties were opposite to those listed above for Type 1. There was virtually no specialization of muscle fibre structure beneath the sensory endings.Physiological experiments involving ramp-and-hold and sinusoidal stretch applied to the muscle whilst recording single-unit afferent responses in m.ext. dig. III of axolotls showed unit responses very similar to those known from muscle spindles, particularly those of the frog.We are grateful to the M.R.C. for an equipment grant (to R.M.A.P.R.), and to Mrs. Janis Taberner for her technical help. Part of this work was done during the tenure of a Nuffield-NRC Lectureship (Q.B.) which is gratefully acknowledged, as is financial support by Prof. J.R. Nussall during a visit to the University of Alberta at Edmonton. 相似文献
108.
J. M. Drummond D. L. Macmillan 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,183(5):583-601
Using extracellular and intracellular stimulation, recording and dye-filling, we identified and studied the superficial extensor
motor neurons of the crayfish, Cherax destructor. Functional associations of each neuron were characterised by recording its responses to sensory and abdominal cord inputs,
its extensor muscle innervation pattern and its relationships with other neurons. Two clear associations were found among
the six neurons of each segment. A medium-sized excitor (no. 3), that innervates a substantial percentage of extensor muscle
fibres, and the largest excitor (no. 6), recruited during peak, excitation, were inhibited by input from unknown interneurons
that excited the common inhibitor (no. 5). Likewise, these excitors received excitatory input when the inhibitor was silent.
Another medium-sized neuron (no. 4) that innervates many muscle fibres was co-active with one of the small excitors (no. 2).
The two medium-sized neurons were never active at the same time, and these two groupings may be determined by pre-motor interneurons.
The implications of these findings for our understanding of motor control in this system are discussed.
Accepted: 21 June 1998 相似文献
109.
Cell swelling has been shown to increase the permeability of the plasma membrane to ions such as K+, Na+, Ca2+ or Cl– in many types of cells. In cardiac cells, swelling has been reported to increase Cl– conductance, but whether cation-selective currents are activated by swelling is not known. Low Cl– or Cl–-free solutions were used to study the presence of such currents. Lowering the osmolarity of the extracellular medium from 299 to 219 mOsm resulted in cell swelling and concurrent activation of a cation-selective whole-cell current. When cell-attached patches were formed on swollen cells, opening of bursting single channel currents were observed in 18% of the patches studied. Ion substitution experiments indicated that the channel discriminated poorly among monovalent cations, and was impermeable to Cl–. The channel was permeable to Ca2+. In symmetrical 140 mM K+, the current-voltage relation was linear with a single channel conductance of 36 ± 3 pS. Depolarization increased channel open probability. Interestingly, depending on the membrane patch studied, application of negative pressure to the pipette caused either an increase or a decrease in the open probability of the channel already activated by swelling. Thus, the sensitivity to tension of the swelling-activated channel was different from those of previously reported stretch-activated channels. These findings suggest that nonselective cation channels exist in rat atrial cells and may be involved in swelling-induced changes in cell function.Dr. Kim is an Established Investigator of the American Heart Association. 相似文献
110.