Search results for "muscle spindle"
showing 10 items of 18 documents
Two different pathogenic mechanisms, dying-back axonal neuropathy and pancreatic senescence, are present in the YG8R mouse model of Friedreich ataxia
2016
Frataxin (FXN) deficiency causes Friedreich's ataxia (FRDA), a multisystem disorder with neurological and non-neurological symptoms. FRDA pathophysiology combines developmental and degenerative processes of dorsal root ganglia (DRG), sensory nerves, dorsal columns and other central nervous structures. A dying-back mechanism has been proposed to explain the peripheral neuropathy and neuropathology. In addition, affected individuals have non-neuronal symptoms such as diabetes mellitus or glucose intolerance. To go further in the understanding of the pathogenic mechanisms of neuropathy and diabetes associated with the disease, we have investigated the humanized mouse YG8R model of FRDA. By bio…
Effects of botulinum toxin type A on vibration induced facilitation of motor evoked potentials in spasmodic torticollis.
2004
It has not been clarified if botulinum toxin (BTX) injection leads to muscle spindle dysfunction in man. This study aimed to test the hypothesis that BTX application reduces the facilitation of a magnetic evoked response (MEP).We used the vibration induced facilitation of an MEP of the sternocleidomastoid muscle (SCM) as a surrogate marker for muscle spindle function in 20 healthy subjects and 10 patients with idiopathic rotational torticollis in whom BTX was injected unilaterally.The increase in the amplitude and area of the MEPs in the clinically not affected and untreated SCM of the patients did not differ significantly from the controls. At baseline, the vibration induced increase in th…
Short-latency stretch reflex modulation in response to varying soleus muscle activities.
2002
The current investigation examined the effect of various types of background muscle contractions on the short-latency stretch reflex (SLR) elicited from the soleus muscle while subjects were in a sitting position. A stretch was applied to the calf muscles while they performed an isometric (pre-ISO), shortening (pre-SHO) and lengthening contraction (pre-LEN) with several pre-contraction levels. The ankle was at a 90 degrees tibio-tarsal joint angle when the perturbation was applied. Subjects developed and maintained a given pre-load level, which was maintained at various percentages of the maximum voluntary isometric plantar flexion torque. This was performed at 80 degrees in pre-SHO, 90 deg…
Effects of effort and EMG levels on short-latency stretch reflex modulation after varying background muscle contractions.
2005
It is known that the short-latency stretch reflex (SLSR) is modulated by the background muscle activity when it is elicited at matched torque levels. This study was designed to examine the effects of muscle contraction types before a stretch perturbation on SLSR in the human soleus muscle (SOL) when SLSR was elicited at the same levels of effort and at matched electromyographic (EMG) activity levels. A mechanical stretch perturbation was applied to the calf muscles when the ankle joint reached a ninety degree tibio-tarsal joint angle after the muscles performed an isometric (pre-ISO), shortening (pre-SHO) and lengthening contraction (pre-LEN). Subjects were seated on an ankle ergometer chai…
Continuous, bilateral Achilles' tendon vibration is not detrimental to human walk.
2001
Sensory feedback from the moving limbs contributes to the regulation of animal and human locomotion. However, the question of the specific role of the various modalities is still open. Further, functional loss of leg afferent fibres due to peripheral neuropathy does not always lead to major alteration in the gait pattern. In order to gain further insight on proprioceptive control of human gait, we applied vibratory tendon stimulation, known to recruit spindle primary afferent fibres, to both triceps surae muscles during normal floor walk. This procedure would disturb organisation and execution of walking, especially if spindles fire continuously and subjects are blindfolded. Vibration induc…
Stretch Reflex Responses Following Mechanical Stimulation in Power- and Endurance-Trained Athletes
1994
The basic stretch reflex responses evoked by the mechanical stimuli were investigated among different athletic groups. The tests were performed by a special ankle ergometer, which created dorsiflexion velocities from 25 deg x s-1 to 115 deg x s-1 around the ankle joint. The EMG activity of soleus (SO), gastrocnemius (GA) and tibialis anterior (TA) muscles was recorded with surface electrodes. In all subjects higher angular velocities caused higher stretch reflex responses. The endurance-trained athletes were more sensitive to the used stimuli than the power-trained athletes, because of their shorter latency times (43 +/- 7 ms vs 45 +/- 7 ms, p < 0.001 for the SO muscle and 40 +/- 8 ms vs 43…
Neuromuscular performance of lower limbs during voluntary and reflex activity in power- and endurance-trained athletes.
1994
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. U…
Bilateral reciprocal organisation in man: focus on IA interneurone
1994
The H reflex of flexor carpi radialis and radial-induced reciprocal inhibition were recorded in normal subjects during conditioning stimulation of the contralateral median or radial nerves. It was found that stimulation of the contralateral median nerve enhanced the degree of reciprocal inhibition exerted by the radial nerve on the median nerve, while contralateral radial nerve stimulation reduced the reciprocal inhibition exerted by the extensor on the flexor. In two subjects in which a pure extensor H reflex was recorded specular features were observed following contralateral median and radial stimulation. These findings are considered to be the electrophysiological manifestation of contr…
The fine structure of denervated and reinnervated muscle spindles: morphometric study of intrafusal muscle fibers.
1979
The fine structure of normal, denervated, and reinnervated muscle spindles in lower lumbrical muscles of rats was studied morphometrically at time intervals ranging from 3-14 months. In control spindles, the mean transverse area of mitochondria was estimated to be more than twice as large in nuclear chain than in typical nuclear bag fibers. Following denervation, there was a severe decrease of the mean number and transverse area of mitochondria, and a moderate, but statistically significant decrease of the mean transverse area of intrafusal muscle fibers (IMFs) despite an increase of the number of IMFs. At 12-14 months of reinnervation, changes of the transverse areas of IMFs were statistic…
Ultrastructure of a muscle spindle-analogous receptor organ in the mandible of Oncopeltus fasciatus (Insecta, Heteroptera) with remarks on the homolo…
1985
A non-ciliary muscle receptor organ in the first mandibular retractor muscle of Oncopeltus fasciatus is described. The organ consists of two specialized muscle fibres of the first retractor, which are embedded in a thickened layer of connective tissue. The sensory innervation is supplied by three multiterminal sense cells sending several dendrites to the receptor muscle fibres. ‘Naked’ dendritic terminals are attached to the muscle surface or connective tissue fibrils. The far-reaching analogy of the receptor to the intrafusal chain-fibres of vertebrate muscle spindles is remarkable. The existence of a muscle receptor organ in the first mandibular retractor may serve as an argument in favor…