PubMed Health⌕ Search

Biomedical subjects

I Pyykkö

Publications and source records attributed to I Pyykkö.

At least 199 records · Page 11Linked to original sources
PubMed1984

A reduction of vestibulo-visual integration during transdermally administered scopolamine and dimenhydrinate. A presentation of gain control theory in motion sickness.

The effect of transdermally administered scopolamine (TTS scopolamine) (release rate 5 micrograms/h) and dimenhydrinate (100 mg) was examined on optovestibular nystagmus in 16 volunteers in a randomized double-blind trial. A statistically significant decrease in the optokinetic part of nystagmus was observed during all treatments. Most profound reduction was found during treatment with two TTS scopolamine. The vestibular part was reduced by treatment with two TTS scopolamine, only. The results indicate that scopolamine and dimenhydrinate exert their effect in motion sickness by reducing the vestibular and visual influx and by partly inhibiting the integrative functioning of the vestibular nuclei. In their action, the motion sickness drugs seem to assist the cerebellum by diminishing impulses from various orientation reflexes in order to preserve the functional capacity of the central nervous system. Different symptoms in motion sickness seem to arise when the vestibular gain operates beyond the normal range of the cerebellar control mechanisms.

Dimenhydrinate↗
PubMed1984

Intra-individual variation in oculomotor performance in man.

Peak velocity of saccade, maximum velocity of smooth pursuit, and peak velocity of slow phase of vestibular and optovestibular nystagmus were measured three times daily on three separate days in 6 healthy subjects in order to estimate the intra-individual variation of the results of oculomotor tests. Analysis of variance revealed that the oculomotor performance of the individual subjects varied systematically, depending on whether the tests were performed in the morning, at noon, or late in the afternoon. In particular, the velocity of saccade displayed lowest values in the afternoon. The present results indicate that oculomotor performance may depend on the individual biological rhythm of fatigue; however, it is also possible that eye motor behaviour is coupled to an independent rhythm of motor activity. Circadian rhythmicity of oculomotor performance should be considered in follow-up studies and in examination of patients with reduced vigilance.

Adult↗
PubMed1983

Vibration syndrome and vibration in pedestal grinding.

At one Finnish foundry all the workers had typical symptoms of vibration induced white finger (VWF) after they began using a new type of pedestal grinding machine. The objectives of this study were to establish the severity of the symptoms and the difference in vibration exposure between the new and the old machines. Vibration detection thresholds and grip forces were measured, as well as the vibration in the casting and in the wrist simultaneously. The mean latency for VWF among the grinders was 10.3 months after the change of pedestal grinding machines. All the grinders had numbness in their hands. The vibration detection threshold was significantly higher for the grinders than for their referents. At the same circle speed, the new wheels caused vibration levels up to 12 dB more than the old wheels. The circle speed had a slight influence on the vibration. The vibration levels of light (0.5 kg) casting were up to 25 dB higher than the heavy (5 kg) casting. The use of a pneumatic pressing device decreased the vibration levels in the wrist by 5-10 dB. The increase in vibration, which occurred when the new wheels were taken into use, was too small to explain such a dramatic outbreak of VWF. This led to the conclusion that some other feature such as the impulse character of the vibration also contributed to the effects of vibration.

Adult↗
PubMed1983

Blood pressure, flow, and peripheral resistance of digital arteries in vibration syndrome.

The peripheral circulation was studied in 19 lumberjacks and in 12 control subjects. Twelve of the lumberjacks were free from vascular symptoms and seven had vibration induced white finger (VWF). Using the strain-gauge plethysmographic technique, the digital circulation was examined at rest, during cooling of the upper body, and during heating of the upper body. At rest and during vasodilatation no significant differences were found between the lumberjacks and the controls. During reflexive vasoconstriction, digital blood flow in the upper body was more reduced in lumberjacks with VWF than in control subjects. Furthermore, digital blood pressure of the lumberjacks with VWF fell more than in the control group. The peripheral resistance also increased more, but this difference was not statistically significant. There was no evidence that the exaggerated vasoconstriction of VWF resulted from a narrowing of the lumen of arterioles due to hypertrophy of the vessel wall. The present findings suggest that VWF is produced by the highly sensitive responsiveness of the affected vessel to normal vasoconstrictor stimuli.

Adult↗
PubMed1983

Visually evoked slow eye movements, visual-vestibular interaction, and infratentorial lesions.

The maximum velocity gain of smooth pursuit and optokinetic, vestibular, and optovestibular slow phases was examined in 15 patients with pontine, 10 with medullary, 10 with cerebellar, and 5 with combined cerebello-brain stem disorders. Marked dissociations were observed between smooth pursuit and optokinetic slow phases, especially in medullary disease. A cerebellar deficit enhanced slow phase velocity gain during rotation in darkness, whereas the corresponding gain during rotation in light was normal.

Adolescent↗
PubMed1982

Clonidine in the treatment of vibration-induced white fingers.

The effect of clonidine, a centrally acting drug diminishing the sympathetic activity of peripheral nerves, was examined in a double-blind study of 60 forest workers with vibration-induced white fingers. Clonidine was administered in daily doses of 0.450 mg or 0.100 mg during 30 d. The results were evaluated from a self-administered questionnaire. No significant differences were discerned between the active and placebo groups in respect to either recovery time after an attack or frequency of attacks. Neither did the subjective evaluation of the overall effectiveness of the drug show any differences between the groups. In two subjects clonidine provoked Raynaud's phenomenon, which subsided after the cessation of treatment. The recording of finger pulse plethysmography for two subjects treated with 0.450 mg of clonidine daily revealed comparatively well preserved vascular reflexes, whereas sympathetic mass reflexes such as galvanic skin response were almost absent.

Clinical Trials as Topic↗
PubMed1981

Rapid eye movements reflecting neurological disorders.

The accuracy and velocity of voluntary saccades together with the velocity of fact phases of nystagmus were studied in 26 patients belonging to 4 groups with defined neurological disorders. Patients with speech disorders of the dyspraxia type, indicating the lesion in the left frontal cortex, showed a pronounced decrease in saccadic accuracy in combination with normal saccadic and quick phase velocity. Patients with pontine disorders showed a significant decrease in the peak velocity of saccades and quick phases of nystagmus while the accuracy of the saccades ranged from normal to severely disturbed. Patients with acute meningo-encephalitis showed increases in peak velocity of saccades and of quick phases of nystagmus and the accuracy was somewhat reduced. Patients with a labyrinthine disease showed normal velocity of saccades and of quick phases as well as normal accuracy of saccades.

Acute Disease↗
PubMed1981

Eye-velocity programming in brain-stem disorders.

Eye movements in 30 patients with brain-stem lesions were evaluated with electro-oculography, and the findings were analyzed with regard to the site of the lesion in the brain stem. Eye velocities generally were reduced more severely in pontine than in medullary lesions. In medullary lesions, there even was a slight enhancement of the velocities in the fast component of optokinetic and postrotatory nystagmus. In contrast to the slow-phase velocity of OKN, which often was preserved in medullary lesions, the smooth-pursuit velocity was reduced in lesions at all levels in the brian stem. This indicates that these two types of visually induced eye movements use different mechanisms.

Adolescent↗
PubMed1981

Hand-arm vibration in the aetiology of hearing loss in lumberjacks.

A longitudinal study of hearing loss was conducted among a group of lumberjacks in the years 1972 and 1974--8. The number of subjects increased from 72 in 1972 to 203 in 1978. They were classified according to (1) a history of vibration-induced white finger (VWF), (2) age, (3) duration of exposure, an (4) duration of ear muff usage. The hearing level at 4000 Hz was used to indicate the noise-induced permanent threshold shift (NIPTS). The lumberjacks were exposed, at their present pace of work, to noise, Leq values 96-103 dB(A), and to the vibration of a chain saw (linear acceleration 30-70 ms-2). The chain saws of the early 1960s were more hazardous, with the average noise level of 111 dB(A) and a variation acceleration of 60-180 ms-2. When classified on the basis of age, the lumberjacks with VWF had about a 10 dB greater NIPTS than subjects without VWF. NIPTS increased with the duration of exposure to chain saw noise, but with equal noise exposure the NIPTS was about 10 dB greater in lumberjacks with VWF than without VWF. With the same duration of ear protection the lumberjacks with VWF consistently had about a 10 dB greater NIPTS than those without VWF. The differences in NIPTS were statistically significant. The possible reason for more advanced NIPTS in subjects with VWF is that vibration might operate in both of these disorders through a common mechanism--that is, producing a vasoconstriction in both cochlear and digital blood vessels as a result of sympathetic nervous system activity.

Adult↗
PubMed1980

Vibration-induced decrease in the muscle force in lumberjacks.

Isometric maximal hand grip force was measured with a strain gauge dynamometer in 91 lumberjacks and 31 controls during a 2-min compression-relaxation task. Measurements were carried out on both hands with and without simultaneous vibration exposure. The muscle forces of older subjects were smaller than those of younger men, independent of occupational vibration exposure. The fatigue curves of lumberjacks and control subjects had the same shape. During vibration exposure in the test, the forces diminished in the left hand significantly in the lumberjacks but not in the control subjects. The force level of fatigue curves of the lumberjacks with a history of diminished grip force was lower and decreased more during vibration exposure than in the lumberjacks with a history of normal grip force. The reduction in the hand grip force during vibration exposure in the lumberjacks seemed to be linked to lesions in the peripheral nerves and to activation of a tonic vibration reflex, but probably not to circulation disturbances. The fatigue mechanism seemed to be the same in lumberjacks and control subjects.

Adult↗
PubMed1979

Hand grip forces during chain saw operation and vibration white finger in lumberjacks.

The hand grip forces at the front and rear handles of a chain saw were measured during work, in 89 professional lumberjacks. The symptoms caused by vibration to the upper limbs were compared with the hand grip force (HGF) during work. To allow better comparison between subjects we used the ratio of hand grip force (HGF) to the maximal voluntary compression force (MVC), HGF/MVC expressed as a percentage. The mean HGF during sawing varied from 5 to 12 N in all subjects. The variation in HGF was greater at the front handle than at the rear handle, during sawing. The lumberjacks who had vibration-induced white fingers (VWF), had a higher HGF/MVC in both hands than the lumberjacks without VWF. Those lumberjacks affected by VWF used over 12% of their MVC at work. Subjects without HGF/MVC ratio. The lumberjacks with and without numbness in their hands had equal HGF/MVC ratios.

Adolescent↗
PubMed1979

Blood flow in the contralateral hand during vibration and hand grip contractions of lumberjacks.

Pulse wave changes were examined among 63 professional lumberjacks. The tests were carried out in connection with an annual health examination. A photoelectric plethysmographic method was used to measure pulse wave changes during contralateral muscle work and vibration exposure from a dynamic shaker with a strain-gauge dynamometer. The relative changes in pulse wave amplitude were counted, and the changes were classified as dilatations, constrictions, or constant pulse wave amplitude. Contralateral muscle work caused vasodilatation, but vibration exposure could cause vasoconstrictions in the right hand. Most of the vasospasms were recorded at 60 and 100 Hz. The strongest vasospasms were seen at 200 Hz. The occurrence of vasospasms in the contralateral hand correlated with the severity of white finger symptoms rated according to an index for traumatic vasospastic disease.

Adult↗