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Biomedical subjects

J Van Hees

Publications and source records attributed to J Van Hees.

32 records · Page 2Linked to original sources
PubMed1988

Painful muscle spasms complicating algodystrophy: central or peripheral disease?

A 21 year old female patient developed Südeck's atrophy of the right foot secondary to a chronic Achilles tendinitis. The condition was complicated by the occurrence of painful muscle spasms in the right leg and incontinence of urine. The spasms had characteristics of both a tonic ambulatory foot response and a spinal flexor reflex. The movements disappeared during sleep. Regional anaesthesia of the right leg made the spasms disappear both in and outside the region of anaesthesia. Backaveraging of the EEG showed the involuntary spasms to be preceded by a cortical potential similar to a readiness potential, indicating a cortical potential similar to a readiness potential, indicating a cortical component in the pathophysiology of the muscle spasms complicating Südeck's atrophy.

Adult↗
PubMed1986

Transfer factor therapy in multiple sclerosis: a three-year prospective double-blind clinical trial.

One hundred five patients with MS were divided into three groups matched for age, sex, and disability, and treated with either placebo, transfer factor prepared from leukocytes of random donors, or transfer factor from leukocytes of family members living with the patients. There were no differences in the three treatment groups for changes in disability, activities of daily living, or evoked potentials. Eighteen months of transfer factor therapy had no effect on gamma-interferon production or natural killer cell activities.

Activities of Daily Living↗
PubMed1985

Histochemical changes of substance P, FRAP, serotonin and succinic dehydrogenase in the spinal cord of rats with adjuvant arthritis.

Various histochemical changes were found in spinal segments L4-L5 of rats with adjuvant arthritis, predominantly 30 days after inoculation. A slight to marked increase of substance P immunoreactivity occurred in laminae I, II and X. FRAP activity was enhanced in lamina II. Serotonin immunoreactivity was heavier in laminae I, VIII and IX in a few animals. The intensity of the histoenzymological reaction for succinic dehydrogenase increased in certain laminae VIII and X neurons. At day 15 of the disease the increase of substance P and FRAP activities was chiefly restricted to the medial portion of the superficial dorsal horn. There was a significant positive correlation between the scratching behaviour of arthritic rats and the substance P immunoreactivity in laminae X and I. If one accepts that scratching is pain-related, the data are consistent with a possible role of substance P in the chronic pain associated with adjuvant arthritis. They leave undetermined the significance of the other histochemical changes.

Acid Phosphatase↗
PubMed1984

Suppression of C-fibre discharges upon repeated heat stimulation may explain characteristics of concomitant pain sensations.

Nociceptors with unmyelinated axons were recorded from the superficial radial nerves of 7 volunteers. A sequence of uniform radiant heat stimuli of 18 s duration, starting from an individually adjusted adapting temperature were used to raise the skin surface temperature by 6 degrees C to a painful level (41-43 degrees C). These stimuli followed each other at 3 different interstimulus intervals of 35 s, 70 s and 105 s, occurring in a random order. The subjects were asked to track the time course of the stimulus-evoked sensation by manipulating the length of a light bar. Adaptation and stimulus temperatures were chosen to induce sensations of heat and/or pain. All nociceptors studied responded to these stimuli with a phasic response of 3-5 s duration, often followed by a low frequency tonic discharge, lasting as long as the stimulus. No discharges were seen in interstimulus periods. Discharge rates during the phasic responses were linearly related to interval duration, whereas tonic discharges were not influenced by the preceding interval. In parallel readings of pain responses were lower up to the 10th second of the stimulus after short rather than after long intervals. These results indicate that the suppression of C-fibre nociceptor discharges during repetitive stimulation may explain concomitant reductions in the magnitude of human pain sensations.

Adult↗
PubMed1984

ERPs associated with decisions based on slowly increasing warm and painful stimuli.

The event-related potential (ERP), produced by subjects who were experiencing a gradually increasing heat stimulus, was recorded 3.5 sec before and 1 sec after a motor response. Subjects responded when the stimulus was 'just warm,' 'just at prickling pain' or 'above the temperature of just prickling pain.' Two control procedures mimicked the readiness potential (RP) and motor potential (MP) experiments. The results showed that the steadily rising negative MP was modified to a positive wave before the decision of 'warm.' During the 'pain' and 'above pain' conditions, the pre-decision slow wave was less negative than the MP but less positive than that of the 'warm' condition. A temperature control condition confirmed that rising temperature alone did not produce these results. Principal components analysis confirmed these differences by producing factors which were interpreted as representing the ERPs of the conditions of 'warm,' 'pain,' 'above pain,' RP and MP. It was evident from pilot studies that uncontrolled electrical activity from the skin potential response (SPR) was contaminating the results. SPR forced all ERP curves in the positive direction and several attempts to eliminate the SPR from the ERP data failed. While the SPR was produced differentially across conditions and across the experimental session, the smaller the variability in the electro-oculogram (EOG) recorded from above and below the orbits, the smaller was the SPR contamination that we recorded in the ERP. Therefore, we selected subjects for this experiment who showed a stable orbital EOG.

Adult↗
PubMed1984

Nociceptor discharges and sensations due to prolonged noxious mechanical stimulation--a paradox.

Forceps were used to induce controlled squeeze stimuli to small skin folds of the dorsal surface of the hand of human volunteers. Psychophysical and microneurographic experiments were performed to characterize sensations and afferent input induced by stimuli exerting a constant force during a period of 120 s. The psychophysical data showed that forces greater than 4 N exerted on forceps faces of 30 mm2 elicited pain, which had two main characteristics: (a) stronger stimuli evoked a stronger pain response, (b) pain had a tendency to increase throughout the 120-s stimulus duration. In contrast, discharges of polymodal C-fibre nociceptors showed an initial high frequency dynamic discharge followed by adaptation. It was found that the ratio of C-fibre activity to activity in myelinated SA-fibres provided a better correlate of the time course of the stimulus-induced pain sensations than C-fibre activity alone. Possible reasons for the mismatch between nociceptor input and pain sensations are discussed.

Afferent Pathways↗
PubMed1981

C nociceptor activity in human nerve during painful and non painful skin stimulation.

Percutaneous recordings from more than one hundred single C fibres have been performed in the radial nerve of conscious human subjects. All these fibres belong to the poly-modal C nociceptor group, being excited by mechanical and thermal and also by chemical stimulation. Conduction velocities showed a monophasic distribution with a mean value of 0.86 m/s (SD: 0.17). The mechanical threshold, measured with von Frey hairs, varied between 2.3 and 13.1 g. The receptive field was circular or elliptical; for 33 units the mean axes were 6 mm and 7 mm. Mechanically evoked C fibre discharge even up to more than 10 spikes/s was not necessarily accompanied by pain sensation. Nettle sting evoked an irregular C fibre discharge (maximum 10 spikes/s) accompanied by a pricking and burning sensation; the sensation of itch which was sometimes reported, was not correlated with the discharge frequency. C fibre activation by a chemical irritant (paint remover) also evoked an irregular discharge (maximum 3 to 6 spikes/s), accompanied by pricking and burning pain sensation. The C threshold for radiant heat usually lay below the subject's pain threshold. Increasing skin temperature produced increasing neural firing rate. The mean spike frequency rarely exceeded two spikes/s even with stimuli evoking strong heat pain. The occurrence of subjective heat pain response could be as well predicted from th C fibre spike frequency as from the skin temperature. It is concluded that nociceptive C input provoked by thermal or chemical stimuli correlates well with pain sensation. However, similar C input provided by mechanical stimulation which activates also A beta mechanoreceptors, did not necessarily produce pain sensation.

Adult↗
PubMed1980

Latencies of chemically evoked discharges in human cutaneous nociceptors and of the concurrent subjective sensations.

Percutaneous recordings from single nociceptive A delta- and C-fibers have been performed from the superficial radial nerves of conscious human subjects. Nociceptors were tested with a chemical irritant substance, which induced a burning sensation when applied to the intact skin. A comparison of the onset of spike discharges in nociceptors and the onset of the subjective burning sensation indicated that under the conditions of our experiments summation of input from nociceptors is needed in order to induce pain sensations. In particular, our results indicate spatial summation.

Adult↗
PubMed1979

A comparison between the discharges of human nociceptive nerve fibres and the subject's ratings of his sensations.

1. Impulses in cutaneous nerve fibres were recorded percutaneously with tungsten micro-electrodes from the superficial radial nerve of adult human subjects. 2. Eight units studied had conduction velocities below 1.5 m/sec, and thus belong to the class of C fibres. On the basis of their responsiveness to mechanical and to thermal stimuli the units were classified as 'polymodal nociceptors'. 3. Units were tested with 12 sec heat pulses starting from a base line temperature of 43.0-43.5 degrees C. Heat stimuli reaching three different maximal levels were applied in randomized order, the subjects being blind with respect to stimulus size. Each of the eight units studied was tested with more tha 20 stimuli and with four of them were 80-125 stimulus repetitions. 4. After each stimulus the subjects had to rate his sensations on a six-point rating scale extending from 'just noticeable' to 'very hot, painful'. 5. Discrimination between the three stimulus levels by the integtated spike discharges and by the ratings of the subject was compared using the P(A) measure of the Signal Detection Theory. It was found that both the neurophysiological and the psychophysical measurements provided about equal discrimination. 6. In addition it has been found that spike discharges and ratings share a common variance beyond their common dependence on the stimulus level. Among the factors contributing to this interdependence a 'temporal position effect' was the most significant. 7. In spite of this interdependence between discharge rates and subjective ratings, the latter gave a better estimation of the stimulus size than of the discharge rates of the individual C fibre under study. 8. It was concluded that the polymodal C-nociceptors might be instrumental for the quantitative aspects of heat pain sensation. The hypothesis was derived from the present results that, under the conditions of cour experiments, the loss of information in the course of central processing might be about equal to the gain by the parallel processing in a population of nociceptors excited by a stimulus.

Action Potentials↗
PubMedDate not supplied

[Vectorial competence of Glossina tachinoides Westwood and Glossina palpalis gambiensis Vanderplank infected by Trypanosoma brucei brucei EATRO 1125].

The vectorial competence (VC) of teneral (less than 32 h) Glossina tachinoides Westwood and G. palpalis gambiensis Vanderplank, fed simultaneously on a guinea-pig infected with Trypanosoma brucei brucei EATRO 1125, was assessed. Statistical analysis of the experimental results revealed that female G. tachinoides had a significantly higher midgut infection rate than males. Such a sex-related difference was not observed in G. p. gambiensis. Male G. p. gambiensis had higher midgut infection rates than male G. tachinoides. The metacyclic index did not differ between both subspecies, although G. p. gambiensis showed relatively more metacyclic infections than G. tachinoides. A global VC of 0.0242 and 0.0483 was found for G. tachinoides and G. p. gambiensis, respectively. VC did not differ significantly either between sexes or between the two species. However, G. tachinoides more rapidly infected the feeding host than G. p. gambiensis. In all infected flies, the procyclic index value was superior to the metacylic index value, suggesting that the infection is established by an ascending origin. Both large and slender parts of the salivary glands were constantly infected. Longitudinally dividing trypomastigotes of unequal length have been observed in the alimentary canal of the flies.

Animals↗