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Biomedical subjects

M Magnusson

Publications and source records attributed to M Magnusson.

At least 163 records · Page 9Linked to original sources
PubMed1988

Clinical aspects of eye tracking test.

The eye tracking test is today a well established part of clinical otoneurological examination. In the present paper some applications of the test in evaluating of the level of lesion within the vestibular system are reviewed.

Central Nervous System Diseases↗
PubMed1988

Presentation of a posturographic test with loading of the proprioceptive system.

Postural control is maintained by sensory feedback from visual, vestibular and somatosensory receptors. Recently several methods for evaluating postural control have been devised, utilizing an imposed perturbation. Most of these methods use stimuli which simultaneously affect more than one of the sensory feedback loops. In the present paper a posturographic technique is presented with specific loading of the proprioceptive system, using a computer controlled vibratory stimulus and computerized analysis of the results.

Central Nervous System Diseases↗
PubMed1988

Pharmacological treatment of vertigo.

A review of the treatment of vestibular disorders with drugs is presented. In animal experiments, administration of certain drugs, e.g. alcohol, barbiturates and chlorpromazine, retards the vestibular compensation, while others, e.g. caffeine, amphetamine and ACTH, accelerate the compensation. In compensated animals, some drugs produce overcompensation and some decompensation. A double-blind, randomized trial of the effect of scopolamine and dimenhydrinate in patients with vertigo of varying origin showed, as compared with placebo, that these drugs did not significantly alleviate the vestibular imbalance. The reason for the poor efficacy of the treatment may have been overcompensation of vestibular function loss and adverse effects caused by the drugs. Care should be taken that the drugs used do not retard the vestibular compensation caused by the central nervous system.

Animals↗
PubMed1987

An identification technique for the spike artefact of saccadic eye movements.

Many subjects have a negative spike in the beginning of a saccade in electro-oculographic signals. The amplitude of the spike depends on the location of the electrodes. The spike distorts the saccades and causes errors in the parameters. The saccade spike can assist in the identification of small saccades. A syntactic technique based on formal languages and parsing is presented which looks for spikes from the electro-oculographic signal. For calculation of the algorithm, saccades from the photoelectric signal have been concurrently recorded and compared with the electro-oculographic signal.

Algorithms↗
PubMed1987

Analysis of dimycocerosates of glycosylphenolphthiocerols in the identification of some clinically significant mycobacteria.

Extracts of representative mycobacteria were examined by thin-layer chromatography for glycosylphenolphthiocerol dimycocerosates. The glycolipid typical of Mycobacterium bovis was also found in Mycobacterium africanum and Mycobacterium microti, but it was absent in Mycobacterium bovis AN 5. Mycobacterium gastri strains contained a glycolipid which was chromatographically similar to that in Mycobacterium kansasii. Representatives of Mycobacterium marinum produced a distinct glycolipid type, and one strain had major amounts of a more polar variant. The sugar moieties of purified lipids, including that from Mycobacterium leprae, were identified by thin-layer chromatography of methyl glycosides in acid methanolysates.

Chromatography, Thin Layer↗
PubMed1987

An ergonomic study of work methods and physical disorders among professional butchers.

Butchers considered that the back and the upper extremities were subjected to high loads from their work. Of the 92% with reported physical disorders, 80% had pains or complaints from more than one body area. Most frequent were disorders of the back and shoulders. 50% of the butchers had been on sick leave due to their disorders. By ergonomic analysis of the work, several work tasks which caused high loads on those body parts in which disorders had occurred were identified. The high loads were found to have the following main causes, which occurred together in many work situations: (1) Exertion of high forces when cutting the meat. (2) Frequent and heavy manual materials handling. (3) Inappropriate working postures. It appeared from the study that the workload on the butchers was unnecessarily high and that it could be the main reason for the high frequency of disorders amongst them. The strain on them was to a large extent caused by bad working postures, which could be improved by introducing improved equipment. The equipment should be such that the working-height may be adjusted both to the individual and for the task performed.

Journal Article↗
PubMed1987

Investigation of optimal table height and surface angle in meatcutting.

Butchers have a high frequency of occupational disorders or pain localised to their hands, shoulders, low back and neck, compared with other occupational groups. It is likely that the disorders are caused by high loadings of these parts of the body during work. The high loadings have been found to be caused by high resistance when cutting, inappropriate working postures and by manual handling of material. To improve the butchers' working conditions by providing means for appropriate working postures, cutting tables with adjustable height and surface angle were constructed and tested. Evaluations were made during work in the laboratory and in the industry. The aim of these tests was to find the optimal height of the table for each butcher and to find out if a tilted surface would improve the working postures and be accepted by the butchers. The evaluations were made by biomechanical calculations from photos, ergonomic analysis of videotapes taken during the tests and by using ranking scales. The results show that (1) one optimal height of the table was not to be found, meaning a height resulting in a posture that causes no load on both back and shoulders at the same time; (2) a table height of 17 to 22 cm below elbow height resulted in low loadings on both the low back and the shoulders and was ranked as the most comfortable height; (3) tilting of the surface 5 degrees to 10 degrees was accepted by the butchers and ergonomically favourable; (4) the possibility of altering the table height during the workday was perceived as unloading since the load could be shifted between different parts of the body.

Journal Article↗
PubMed1987

Hemodynamic effects of loud noise before and after central sympathetic nervous stimulation.

The hemodynamic effects of loud noise after central alpha 2-adrenoceptor stimulation were studied in 13 patients with mild (WHO 1) essential hypertension. The patients were randomized (double-blind) to treatment with either placebo or guanfacine 1-2 mg for four weeks and then crossed over and treated for another four weeks. All patients were exposed to a loud broad-band noise (105 dBA for 30 min) and all were studied both on placebo and guanfacine. Guanfacine significantly reduced the resting blood pressure from 141/92 to 134/88 mmHg (p less than 0.01) as well as heart rate at rest from 63 to 58 beats/min (p less than 0.05). Noise stimulation caused a significant increase in blood pressure and resistance in the placebo-treated group, while cardiac output decreased significantly. Pretreatment for one month with the central alpha 2-adrenoceptor stimulating agent guanfacine did not block the noise-induced pressor response nor the increase in peripheral resistance. A significant decrease in stroke volume was observed and cardiac output also tended to decrease in this group. It could be concluded that loud noise is a potent pressor stimulus which causes vasoconstriction and that the blood pressure response during noise could not be blocked by the centrally acting antihypertensive agent guanfacine. Since noise causes vasoconstriction it also induces an increased tone in the small arteries and, if the noise stimulus is sufficiently strong and repeated for a long time, it might cause structural changes in the resistance vessels and permanent arterial hypertension in humans.

Adrenergic alpha-Agonists↗
PubMed1987

Neural activity, alertness and visual orientation in intact and unilaterally labyrinthectomized rabbits.

Electrical brain activity and eye movements were recorded in 10 intact and 6 unilaterally labyrinthectomized rabbits, each with implanted electrodes. The frequency of optokinetic nystagmus (OKN) and a 10-second aggregate of theta waves in the dorsal hippocampus were determined after exposure of the animals to sound, vibration and optokinetic stimulation. Each stimulus used caused significant increases in OKN and theta activity. Vibratory stimuli caused stronger increases in OKN and theta activity than did sound stimuli. Not only was OKN significantly reduced after unilateral labyrinthectomy (UL), but alerting the rabbit with sound or vibration failed to restore the responses to normal, and hippocampal EEG responses to sound, vibration or optokinetic stimulus were significantly reduced. The findings indicate that a visual orientation reflex is normally improved by simultaneous sensory stimulation. Reduced response to stimuli after UL affects not only orientational reflexes but other sensory responses as well, and is accompanied by a reduced state of alertness.

Acoustic Stimulation↗
PubMed1987

Evaluation of optokinetic nystagmus in differentiating between peripheral vestibular and infratentorial lesions.

Optokinetic nystagmus (OKN) was studied in ten patients with vestibular neuritis, and in seventeen patients with unilateral and thirteen patients with bilateral infratentorial lesions and compared with OKN in fifty healthy subjects. Mean and maximum slow phase velocity of OKN was calculated as well as the asymmetry of responses. The efficiency of the different variables in OKN, in discriminating between different lesion sites, was tested in a linear discriminant function analysis. Slow phase velocity of OKN could satisfactorily separate patients with infratentorial lesions from healthy subjects or subjects with vestibular neuritis. Asymmetry of OKN did not contribute further to the correct diagnosis.

Adolescent↗