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Biomedical subjects

J Noth

Publications and source records attributed to J Noth.

At least 91 records · Page 5Linked to original sources
PubMed1991

Evidence that low-threshold muscle afferents evoke long-latency stretch reflexes in human hand muscles.

1. The aim of the present study was to identify the type of spinal afferents involved in the generation of the long-latency response in intrinsic human hand muscles. Position-controlled extensions were imposed on the index finger or on the wrist of healthy subjects who were exerting a steady voluntary flexion force at the relevant joint. Averaged surface electromyographic (EMG) responses of the first dorsal interosseus muscle (FDI) or of the wrist flexors were evaluated with respect to latency and size. 2. Small transient angular displacements of the index finger (1 degree, as measured at the metacarpophalangeal joint), which are supposed to excite primary rather than secondary afferents, evoked two clearly discernible EMG responses with mean latencies of 32.3 ms (M1 response) and 54.7 ms (M2 response), respectively. The size of the M2 response exceeded the size of the M1 response by 60%. In the wrist flexors, transient stretch (1 degree) gave rise to a large M1 response (latency 22.8 ms) and a small, inconstent M2 response. 3. Small-amplitude vibration of the index finger elicited EMG responses in the FDI that were qualitatively and quantitatively similar to those seen in response to small transient stretches of the index finger. This was also true for fast ramp-and-hold stretches (stretch velocity 400 degrees/s, amplitude 5 degrees), whereas slow ramp-and-hold stretches (125 degrees/s, 5 degrees) elicited predominantly M2 responses. 4. In the FDI, the mechanical threshold of the M1 and M2 response to the transient angular displacement was approximately 0.15 degrees, with a tendency for the M2 response to appear at a lower threshold.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

[Musical hallucinations in hearing loss in the aged].

An 83-year-old woman experienced the abrupt onset of musical hallucinations. She had had long-standing progressive hearing loss due to otosclerosis. The clinical, psychopathological and pathogenetic aspects of this syndrome are discussed by means of a review of the literature.

Aged↗
PubMed1990

[Neurologic and psychiatric disorders in vinyl chloride disease].

A literature review and an own case observation of neurological and psychiatrical disturbances in vinyl chloride disease are presented. In acute vinyl chloride intoxication, patients complain of vertigo, nausea and headache. At higher concentrations, vinyl chloride exerts a narcotic effect. In patients with chronic occupational exposure, neurological disturbances include sensory-motor polyneuropathy, trigeminal sensory neuropathy, slight pyramidal signs and cerebellar and extrapyramidal motor disorders. Psychiatric disturbances present as neurasthenic or depressive syndromes. Sleep disorders and disorders of sexual functions are frequently encountered. Pathological EEG alterations can be found in a high proportion of patients. The long term course and prognosis of the neurological and psychiatrical disorders in vinyl chloride disease are obscure. In an own case, a slight sensory polyneuropathy, bilateral hyposmia, a marked neurasthenic syndrome, typical EEG changes and computed tomography signs of cerebral atrophy were found in a 56-years-old patient as late as 16 years after the exposure to vinyl chloride.

Adult↗
PubMed1989

[The Charles Bonnet syndrome].

The Charles Bonnet syndrome represents an organic hallucinosis characterized by the appearance of visual hallucinations in otherwise sane elderly people. As a specific organic factor, a reduced visual acuity due to ophthalmologic disorder can be found in the majority of patients. Clinical, psychopathological and pathogenetic aspects of the Charles Bonnet syndrome are discussed by the means of a review of 46 cases reported in the literature (including an own case observation).

Aged↗
PubMed1989

Achromobacter xylosoxidans corneal ulcer in a therapeutic soft contact lens wearer.

Achromobacter xylosoxidans is an opportunistic organism that is usually seen in immunocompromised or immunosuppressed patients. It is an aerobic gram-negative rod, often confused with other more commonly seen gram-negative bacteria such as Pseudomonas aeruginosa. The organism is usually sensitive to extended spectrum penicillins such as carbenicillin and usually resistant to aminoglycosides and first generation cephalosporins. We wish to describe a corneal ulcer from A. xylosoxidans that developed in a patient wearing a therapeutic soft contact lens. The patient did not have a preexisting microbial keratitis and was not receiving corticosteroid therapy.

Aged↗
PubMed1988

Reconsideration of the concept of enhanced static fusimotor drive in rigidity in patients with Parkinson's disease.

The electromyographic responses elicited in the first dorsal interosseus muscle by small muscle stretches or by electrical stimulation of the median nerve were investigated in parkinsonian patients and in age-matched healthy subjects. Stimuli were applied during a steady level of contraction in the intrinsic hand muscle. This ensured comparable levels of excitability in the alpha-motoneurone pool in patients and normals. It was found that the normal short-latency stretch reflex was almost absent in rigid patients, while responses to electrical stimulation of low-threshold nerve fibres were of equal size in both groups. This result suggests that there is a change in fusimotor control of muscle spindles in Parkinson's rigidity without alteration of the central gain of the Ia-transmitted stretch reflex.

Electric Stimulation↗
PubMed1988

Language functions in Huntington's disease.

A comprehensive language test battery (Aachen Aphasia Test) was administered to 45 patients in the early, middle or later stages of Huntington's disease (HD) and to 20 control subjects. In spontaneous speech, many HD patients exhibited a loss of conversational initiative. Dysarthria was a common finding. Reading skills were found to be impaired mainly as a consequence of dysarthria; some HD patients displayed visual dyslexia. In addition to the characteristic disturbances of writing skills due to the choreiform movement disorder, the writing of HD patients with advanced dementia indicated constructional dysgraphia, characterized by frequent omissions, perseverations and substitutions. HD patients exhibited no evidence of word-finding difficulty or other semantic deficits in spontaneous speech. There was, however, a marked impairment in visual confrontation naming, with a significant rise in naming error rate as the disease progressed in severity. In most instances, the inappropriate names referred to an object visually similar to the target object, suggesting that visual misperception is the major cause of the naming disorder in HD. Syntactical structure of spontaneous speech was typically reduced to short, simple sentence construction. Verbal stereotypes were only rarely encountered and occurred late in the course of the disease. Tests of language comprehension reflected the general degree of dementia. It is concluded that there are no primary language changes in HD. Instead, a variety of language impairments develop secondary to other neurological and neuropsychological changes.

Adult↗
PubMed1987

Medium and long latency EMG responses in leg muscles: Parkinson's disease.

Short, medium, and long latency EMG responses to muscle stretch from triceps surae and anterior tibialis muscles were recorded in normals and in 33 patients with Parkinson's disease. The latencies of all EMG responses except short latency were normal in patients with Parkinson's disease. The integrals of the medium latency responses in the stretched triceps surae muscle were significantly increased in patients. This result indicates a modulatory influence of the basal ganglia on medium latency EMG responses.

Adult↗
PubMed1987

Long latency EMG responses in hand and leg muscles: cerebellar disorders.

Electromyographic responses to stretches of hand muscles (first dorsal interosseus) and leg muscles (triceps surae, tibialis anterior) were investigated in patients with cerebellar disorders of different locations. Stimuli consisted of short dorsiflexions of the index finger during background force and in tilting (toe up) of a movable platform on which the subject stood. The most important findings were increased long latency responses in upper and lower extremities. For hand muscles it was the late part of the long latency complex, which was increased. For leg muscles it was the long latency response in the anterior tibialis muscle, the antagonist of the stretched triceps surae. The medium latency response in the triceps surae was unaffected. Latencies of the early segmental reflexes and the long latency responses were normal except for cases with peripheral neuropathy (moderate increase in latency of all EMG responses) and diseases affecting both the peripheral nerves and the dorsal columns (for example Friedreich's ataxia). The latter leads to a pronounced delay of the short latency response and a massive delay of the long latency complex in the first dorsal interosseus and of the long latency response in the anterior tibialis muscle.

Atrophy↗
PubMed1986

Long loop reflexes: concepts and consequences.

New experimental results on long latency reflexes in human limb muscles were presented by neurophysiologists and clinicians with great experience in this field. The scope of presentations reached from the pattern of long latency reflexes in leg muscles during stance and the modifications in various motor disorders to the firing behavior of single motor units during torque perturbations of the elbow and to the role of habituation in long latency reflexes. Finally, the effect of stereoencephalotomy on long latency reflexes in normals and patients with parkinsonian tremor was reviewed.

Animals↗
PubMed1985

Long-loop reflexes in small hand muscles studied in normal subjects and in patients with Huntington's disease.

Long-latency electromyographic (EMG) responses of the first dorsal interosseus muscle were evoked by short displacements of the index finger in healthy subjects and in patients with Huntington's disease (HD). In all 20 healthy subjects the early spinal response (mean latency 31.5 ms) was followed by a reproducible later reflex response with a mean latency of 56.5 ms. The activity pattern of single motor units of the stretched muscle was similar to that of the surface EMG. Thus all single motor units tested could be active during either the first or second response phase, but never in both in a given trial. Of the 50 patients with HD, the late EMG response was missing completely in all but 7, but the early spinal component was almost identical to that of the control group. Double stretches at an interval of 25 ms evoked two similar EMG responses in these patients, proving that the motoneuron pool is still excitable during the time at which the second response would have appeared in healthy subjects. The reflex responses of the thenar muscles evoked by electrical stimulation of the median nerve were examined during a voluntary opposing contraction of the thumb in both groups of subjects. In normal subjects, two EMG responses could be distinguished with latencies similar to those of the mechanically elicited responses. Patients with HD again lacked the second response, although the first spinal response was always present. The results are discussed with respect to different proposals concerning the origin of long-latency responses in human muscles. At least for distal hand muscles, the results suggest that the long-latency responses are long-loop reflexes.

Adolescent↗
PubMed1984

Long latency reflex force of human finger muscles in response to imposed sinusoidal movements.

Reflex stiffness of the flexing human index finger was studied using sinusoidal movements at 3-16 Hz. The Nyquist stiffness diagram indicates the presence of a 'presonance' at around 4 Hz, its 'C' shape after correction for the mechanical properties of the relaxed finger is consistent with the involvement of a stretch reflex in its generation. This contention was supported by the presence of negative friction around 4 Hz and the disappearance of the modulation of the stiffness curve after afferent ischaemic block. Correction for the mechanical properties of active muscle, measured after afferent block, permitted the isolation of the reflex component of stiffness. The circular form of the Nyquist diagram indicates a relatively flat frequency response for the reflex over the range tested, and its radius gives a measure of reflex gain. The low value of the frequency at which the frictional force is minimal, suggests the involvement of a reflex of longer than spinal latency. This is discussed in relation to mechanisms of tremor genesis and the interaction of spinal and long latency reflexes in distal hand muscles.

Biomechanical Phenomena↗