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Biomedical subjects

W A Nix

Publications and source records attributed to W A Nix.

At least 37 records · Page 2Linked to original sources
PubMed1990

Relationship between electrical and mechanical properties of motor units.

In six healthy volunteers, the size of the motor unit action potential (MUAP) was related to its contractile behaviour. Electrical activity was determined by measuring amplitude and area of the potential, using the macro electromyography (EMG) technique. The mechanical response was characterised by contraction time, twitch force and relaxation time, recorded with the spike triggered averaging technique. With increasing tension of the whole muscle corresponding to an increasing threshold, the force of single units enlarged exponentially compared to their EMG. There was only a weak relationship between contraction time and electrical activity and none between EMG and relaxation time.

Action Potentials↗
PubMed1990

[Methodology and diagnostic potentialities of macro-EMG. I. Methodology].

Macro-EMG records electrical activity from the whole motor unit (MU) as a parameter of its size. The main component of the recording device is a modified single fiber or concentric needle electrode. Different sized uptake areas allow to record with different selectivities from the MU. The teflon insulated shaft surface allows to record with a defined large blank area unselectively macro-signals from the muscle. The conceptual ideas to use a concentric needle in addition to the single fibre electrode is to simplify the trigger-potential recording, which needs to be selective within the MU. In both instances the EMG apparatus has to provide two channels, one for the trigger and the second for an averaging device to record the macro-EMG. The different techniques use the single fiber or concentric EMG-potential as a trigger to average the associated macro-potential from the raw signals. The electrodes different design allow the whole single-fiber-needle to lie within the MU territory whereas the MU is only touched by the concentric needles tip. This implies different recording situations and results. Anatomically macro-EMG size is varied by the recording site of the muscle. The signal is greater close to the endplate zone and declines to stable values about 20 mm apart. For quantitative measurements within a muscle 20 different potentials have to be evaluated for median amplitude, duration and area.

Electromyography↗
PubMed1990

[Methodology and diagnostic possibilities of macro-EMG. II. Diagnostic possibilities].

The macro-EMG can be recorded with a modified single fiber or concentric needle. The two needles attain different results with smaller potentials values for the concentric needle type. For the single fiber type normal data are given for the EDC and tibialis anterior muscle. These data are compared with previously published results and their statistical evaluation. The concentric needle type can be used for scanning EMG. In addition potential stability can be examined in different parts of the MU using the unblanketing principle. A further novel use for macro-EMG is simultaneous single motor unit twitch recording to compare mechanical and electrical MU activity. In normal muscle the electrical signal is positively correlated with twitch force. In diseased muscle like ALS twitch is dissociated from electrical potential size. Macro-EMG allows to quantify MU size, a prerequisite to follow up dynamic changes in muscle. Improved computer programs in commercially available EMG-machines will help to introduce this method into clinical EMG laboratories as a useful addition to increase the diagnostic yield of EMG.

Electromyography↗
PubMed1990

[Chronic fatigue syndrome--a new disease picture?].

The chronic fatigue syndrome has recently been more frequently diagnosed. Yet it is unknown if this syndrome represents a disease entity of its own or merely a diagnostic label for a miscellaneous group of disorders. Further investigations are needed to find out if the syndrome has an organic or psychosomatic aetiology, or a mixture of both. In the meantime it is the responsibility of the clinician to make this decision in each individual case.

Diagnosis, Differential↗
PubMed1989

[The plasticity of motor units in change of the activity pattern by electric stimulation--electrostimulation and its possible clinical applications].

Motoneuron and muscle fibers interact on the motor unit level, whereby discharge characteristics from the neuron imposed on the muscle seem to play a major role. Within the unit all muscle fibers are biochemically homogeneous and display a high degree of plasticity under different functional demands. To distinguish the existing different units rationals are listed that classify the units by physiological and histochemical parameters. Furthermore the review summarizes the available knowledge on the importance of activity patterns--as a biological principle--involved in the control of phenotypic expression of innervated and denervated muscle. The sequelae are shown of electrical stimulation on innervated and denervated animal muscles. In extent to these findings the consequences are discussed for stimulation procedures that can be imposed on normal and diseased human muscles as a therapeutic tool.

Electric Stimulation Therapy↗
PubMed1988

[Macro-EMG: methodology and problems of determining normal values using the common extensor muscle of the fingers as an example].

The macro-EMG technique registers simultaneously two different potentials from one motor unit. One signal is a single fiber potential, the other an unselective compound recording (macro) of the action potentials of all the muscle fibers within this unit. So motor unit size can be quantified by its electrical activity. Measured data can only be judged upon if normal data are available. These we compiled for the extensor digitorum communis muscle in 83 healthy volunteers. As parameters of the macro-potential amplitude, area and duration were evaluated. It is shown, that amplitude and area are sufficient to characterise a potential. The potential itself is strongly influenced by age and muscle volume. Diagnostic evaluation of the macro-potential is only possible within the context of the results of the single fiber recording and the estimation of fiber density. We found within 105 normal persons a fiber density between 1.2 to 1.9 without a significant dependence on age. With our normal data it is now possible to derive diagnostic conclusions from macro-EMG data.

Adolescent↗
PubMed1987

The effect of isometric short-term electrical stimulation on denervated muscle.

Electrical stimulation was applied daily for 20 minutes to denervated rabbit extensor digitorum longus muscle. One group was stimulated with short tetani, another with 1-Hz frequency, using isometric contractions for both. Tetanic stimulation induced severe fibrosis and is harmful to denervated muscle. One Hertz stimulation retarded denervation-induced fatigue and atrophy, as well as slowing of contraction time.

Animals↗
PubMed1985

Changes of energy metabolism, myosin light chain composition, lactate dehydrogenase isozyme pattern and fibre type distribution of denervated fast-twitch muscle from rabbit after low frequency stimulation.

The influence of low frequency (8-10 Hz) electrical stimulation on denervated fast-twitch muscle from rabbit was investigated. Prolonged direct stimulation of denervated muscle resulted in higher oxidative enzyme activities. Furthermore, single fibre analyses for succinate dehydrogenase showed a more uniform distribution of activity in stimulated-denervated muscle when compared to normal muscle. As was also the case following stimulation of innervated muscle, glycolytic enzymes were decreased in activity and the LDH-isozyme pattern was also shifted towards heart type. No change of the myosin light chain pattern could be observed after 56 days of stimulation.

Animals↗
PubMed1985

Influence of direct low frequency stimulation on contractile properties of denervated fast-twitch rabbit muscle.

A continuous electrical 8 Hz impulse pattern imposed directly via implanted electrodes on denervated fast twitch muscle induced changes in its contractile characteristics. Compared with non-stimulated denervated muscle, stimulated muscle showed slowing of contraction time and improved fatigue resistance. The reaction for succinic dehydrogenase was more intense in the denervated stimulated muscle, indicating an increased capacity of oxidative enzymes. The rate of atrophy was not influenced by stimulation. The 8 Hz frequency pattern is the mediator for these changes in the characteristics of denervated muscles. It demonstrates a comparable effect on innervated muscle. The contralateral normal innervated muscle was also influenced by the electrical stimulation. Contraction time as well as twitch tension were increased. This finding is important when using the normal muscle as intraindividual control.

Animals↗
PubMed1984

[Computer tomographic studies in Wilson disease].

5 patients with proven Wilson's disease had clinical examinations and follow-up scans up to 6 years while being under penicillamine treatment. Severe neurological deficits were associated with marked CT abnormalities. In all other cases clinical condition and CT finding was only loosely correlated. Under therapy, some hypodense areas normalized their attenuation partially or completely. In primarily normal CT's, cupruresis did not induce alterations. As there is no firm correlation between CT findings and clinical involvement the CT examination is of limited value in prognosis.

Adolescent↗
PubMed1983

Electrical stimulation of regenerating nerve and its effect on motor recovery.

The rate of recovery of motor function, after axonotmesis of the motor nerve innervating the soleus muscle in the rabbit, was evaluated. In a chronic study over a period of 4 weeks, contraction parameters and muscle action potentials were recorded. A group of rabbits, whose soleus nerves were stimulated with 4 pps for 24 h daily, was compared with a control group. The electrically stimulated animals showed a faster improvement in motor function and reached their initial values a week earlier than the controls. Electrical stimulation proved to have a positive effect on the regeneration and motor recovery of nerves.

Animals↗
PubMed1982

The effect of low-frequency electrical stimulation on the denervated extensor digitorum longus muscle of the rabbit.

Both extensores digitorum longi (EDL) muscles of rabbits were denervated by crushing the common peroneal nerves. The EDL muscle on one side was directly stimulated at 10-12 Hz via implanted electrodes. This treatment reduced the changes of twitch/tetanus ratios produced by denervation and prevented the slowing of contraction and relaxation that follows denervation. It is concluded that the stimulation reduced the duration of the active state of denervated muscles. These effects of stimulation were reduced after 5 weeks, probably because by that time the slowing effect of low-frequency activity on the fast muscles became apparent.

Animals↗
PubMed1980

[Central nervous system damage after decompression accidents (author's transl)].

An increasing number of decompression accidents can be observed due to increasing popularity of diving and due to ignorance of its dangers. Permanent neurological damage is a frequent consequence of insufficient availability of treatment at the site of the accident. A 39-year-old man with a decompression accident showed the broad neurological symptomatology caused by multitopic lesions of the central nervous system. Apart from well known spinal symptoms manifold cerebral manifestations occurred. Mental and in particular neuropsychological defects could be observed beyond the purely neurological symptomatology.

Brain Diseases↗
PubMedDate not supplied

Reversible esophageal motor dysfunction in botulism.

Two cases of botulism with autonomic and neuromuscular system involvement are presented. In both patients, dryness of the mouth and difficulties in swallowing were predominant symptoms. Esophageal manometry revealed a marked decrease in peristaltic amplitude, which was most pronounced in the upper third of the esophagus. These functional abnormalities returned to normal following recovery from the acute disease.

Adolescent↗