PubMed Health⌕ Search

Biomedical subjects

G F Dohlman

Publications and source records attributed to G F Dohlman.

15 recordsLinked to original sources
PubMed1980

Mechanism of the Ménière attack.

A survey of experimental evidence showing the influence of an increase in potassium concentration in the perilymph on cochlear and vestibular nerve branches is discussed. Informations have indicated that a concentration lower than 20--30 mM produced an increase in action potential frequency in nerve preparations and that a low potassium concentration in animal experiments produced an ipsilateral nystagmus. Increasing the concentration of potassium in the endolymph to values not over the normal endolymph concentration, blocked the conduction of action potentials in the vestibular nerve branches resulting in a reversible contralateral nystagmus. From these results it may be concluded that all objective symptoms of a Ménière attack can be experimentally reproduced by one single factor: the potassium concentration in the perilymph. The known ruptures in the distended walls in a hydrops, with a diffusion of endolymph potassium into the perilymph surrounding the nerve branches to the vestibular and cochlear areas have consequently been assumed to produce the basis for Ménière attacks.

Action Potentials↗
PubMed1980

Further remarks on the mechanism producing the symptoms of Ménière's disease.

The characteristic symptoms of a Ménière attack--low-tone hearing loss; and nystagmus of long duration, often beating in an ipsilateral direction, eventually changing to a contralateral direction, with a return to normal function between attacks--have all been reproduced in animal experiments by increasing the potassium concentration of the interstitial fluid surrounding the afferent nerve branches from the sensory areas of the inner ear. Several recent experiments of other investigators have shown that a low potassium concentration may increase the action potential frequency. This would explain an ipsilateral nystagmus. Raising the concentration further depresses the action potential frequency, resulting in a contralateral nystagmus. Furthermore, there is evidence indicating that cochlear microphonics might not be affected by increases in the potassium concentration. This seems to indicate that the nerves, and not the hair cells, are engaged in the production of those symptoms dependent on potassium increase. The clinical signs of a similar reaction of the cochlear hair cells in Ménière's cases seem to support the assumption of a similar cause. All the objective symptoms of a Ménière attack, thus, seem to comply with the experimental findings of an endolymphatic potassium contamination of the perilymph spaces around the afferent nerve branches.

Action Potentials↗
PubMed1976

Experiments on the mechanism of Ménière attacks.

The pattern of response decline following semicircular canal stimulation corresponds to a mechanical process. This process is the elastic recoil of the hairs of the sensory cells. The response decline is the same, whether the endolymph-cupula system is patent or mechanically maintained in a displaced position. The role of the bending of the entire cupula as the principle factor is excluded for the response and its decline. Repeated endolymph displacements immediately after each decline of response always result in an equal response and its decline. This rules out the depletion of a chemical mediator as a cause for the response decline. Indentations of the sidewalks of the ampulla result in reactions suggesting that the ampulla is filled with a loose gel secreted by the planum semilunatum cells.

Action Potentials↗
PubMed1973

Experiments on fluid movements through the labyrinthine membranous walls.

Methods were selected and tested for studying the flux of water through the labyrinthine walls. Mannitol which does not pass through the walls was used in isotonic concentration in the endolymphatic space, and various concentrations of mannitol solutions in the perilymph space created a concentration gradient which resulted in a flux of water through the membranous wall. This is a first step in investigating the flux of solutes and solvent through these walls of the labyrinth as a basis for studying substances which chronically increase the colloid osmotic pressure due to their difficulty in passing the walls.

Animals↗