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R Thalmann

Publications and source records attributed to R Thalmann.

113 records · Page 7Linked to original sources
PubMedDate not supplied

Distribution of cyclic nucleotides in the organ of Corti.

Recent developments in radioimmunoassay technology have made possible measurements of cyclic nucleotides in individual specimens of the organ of Corti and its subdivisions. Steep longitudinal and transverse gradients of glycogen are known to exist in the organ of Corti of the guinea pig, with preferential accumulation in the outer hair cells of the apical turns. However, no significant longitudinal gradient of cyclic AMP was detectable in the organ of Corti, and the concentration of the compound was found to be nearly equal in the inner and outer hair cell layers. This is indirect evidence against the concept that cyclic AMP plays a role as "second messenger" in the control of glycogen metabolism of the organ of Corti. By contrast, the concentration of cyclic GMP was found to be consistently higher in the inner layer than in the outer layer of the organ of Corti, and to increase significantly in basal direction. This trend is remarkably similar to the distribution patterns of acetylcholinesterase, which may be considered as indirect evidence in favor of a possible role of cyclic GMP in the mediation of cholinergic effects.

Acetylcholinesterase↗
PubMedDate not supplied

Gradients of organic substances between fluid compartments of the cochlea.

We have previously demonstrated the presence of steep gradients of amino acids between cochlear endolymph and perilymph of scala vestibuli. However, only recently have we succeeded in developing a sampling technique which is capable of providing amino acid levels in scala tympani which are representative of the in vivo situation under physiological circumstances. This is achieved by sampling perilymph in a closed system, which precludes unphysiological contamination by CSF via the cochlear aqueduct. It is also shown that amino acids which exhibit very steep gradients between CSF and perilymph, such as glycine and alanine, can be used as endogenous markers to assess the degree of artifactual admixture of CSF when perilymph is sampled by conventional techniques in the open system. Moreover, pilot experiments indicate that net production of perilymph is very low when the cochlear aqueduct is blocked.

Amino Acids↗