PubMed Health⌕ Search

Biomedical subjects

J Gybels

Publications and source records attributed to J Gybels.

6 recordsLinked to original sources
PubMed1992

Further evidence for myelinated as well as unmyelinated fibre damage in a rat model of neuropathic pain.

A mononeuropathy, produced by ligation of the sciatic nerve in rats, has recently been proposed as an animal model of experimental pain and pain-related disorders (hyperalgesia and allodynia). We investigated quantitatively the morphological changes in myelinated and unmyelinated fibres of the sciatic nerves 2 weeks after ligation in rats exhibiting allodynia to thermal stimulation. There was a marked reduction in the number of large myelinated fibres distal to the ligature (711 +/- 34 compared with 5315 +/- 230 in normal nerves). We also found a significant loss of small myelinated fibres (2429 +/- 109 compared with 3197 +/- 308 in normal nerves), the remaining fibres of this type showing pathological properties. Finally, ultrastructural evidence of damage to unmyelinated fibres was found. The typical pattern of large clusters of normal unmyelinated axons was no longer present within most regions of the nerve. There was a significant reduction in the size of the unmyelinated fibres (0.41 micron +/- 0.15 compared with 0.71 micron +/- 0.08 in normal nerves), together with a twofold increase in their number per cluster. Hypotheses about the mechanism of thermal allodynia in this pain model therefore must take into account the fact that all fibre classes show pathological changes.

Animals↗
PubMed1979

Percutaneous epidural dorsal cord stimulation in multiple sclerosis.

The effectiveness of percutaneous epidural stimulation has been evaluated in 11 patients with multiple sclerosis. Trial stimulation was performed at the thoracic level and lasted for 4 to 10 days. Evaluation was accomplished before the start and at regular intervals during and after the treatment. The scoring systems of the Standard Neurological Examination and of the Disability Status Scale of Kurtzke were used for evaluation of the neurological status. In addition, functionally useful changes were assessed by a physical therapist using a disability scoring technique designed at the National Multiple Sclerosis Centre at Melsbroek. Visual and somatosensory evoked potentials were also recorded at regular intervals. Six out of 11 patients claimed a subjective improvement following stimulation. But only four patients had better scoring results in the quantitative neurological testing, and for only two patients was this objective improvements functionally useful.

Activities of Daily Living↗
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↗