ISSN:
1434-4726
Keywords:
Kryotome sections
;
Fluorescence
;
Guinea pig
;
Inner ear
;
Tetracycline
;
Transport
;
Kryotom-Sektion
;
Fluoreszenz
;
Meerschweinchen
;
Innenohr
;
Tetracylin
;
Transport
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Description / Table of Contents:
Zusammenfassung An 31 ohrgesunden Meerschweinchen wurde Tetracyclin in gelöster Form in das Mittelohr appliziert. Dabei wurden entweder nur die beiden Fensternischen oder die gesamte Paukenhöhle gefüllt. Die gefrorenen Köpfe wurden im Kryotom geschnitten und im UV-Licht betrachtet. Auf diese Weise konnte das Tetracyclin im Innenohr nachgewiesen werden. Durch das Einfrieren des Kopfes wurden die Flüssigkeitsräume von Innenohr und Gehirn weder bei der Applikation noch bei der Auswertung eröffnet. Das Tetracyclin gelangt vor allem über das runde Fenster ins Innenohr. Außerdem kann es auch über das ovale Fenster in das Vestibulum eindringen. Als weitere Zugangswege kommen die Diffusion durch die knöcherne Labyrinthkapsel sowie der Transport über labyrinthdurchquerende Gefäße in Betracht. Von der ersten Windung der Scala tympani gelangt das Tetracyclin relativ schnell über den Aquaeductus cochleae in den Subarachnoidalraum.
Notes:
Summary In 31 young healthy guinea pigs a 2% solution of tetracycline was introduced into the middle ear under urethane anesthesia. In one group tetracycline was filled in the tympanic cavity. In the other it was applied only to the round and oval windows. The solution was removed from the specimens after various periods of contact and the cochlea immediately frozen with liquid air. The head was then frozen, severed and mounted on the cryotome. The specimens were illuminated with ultraviolet light under the operating microscope. The distribution pattern of the tetracycline was determined in the following manner: Every 5 μm parallel to the modiolus a section of the labyrinth was cut away and the fluorescent face of the remaining specimen was examined and photographed. The results of each animal were recorded in diagram-form (Fig. 1). In this way, the liquid-spaces of the labyrinth and the brain remain closed throughout the application and evaluation phases of the experiment, and changes of pressure or direction of flow are excluded. In both test series the perilymph of the tympanic scale of the first coil showed a distinct fluorescence after every period of application. In the first series, in which the whole bulla was filled, tetracycline was detected after 10 min: (1) in all the scales of the first turn, (2) in the vestibule, (3) in the utricule and (4) in the two upper coils (Fig. 2a). After 30 min of application, fluorescence appeared in the whole cochlea and in the perilymphatic duct up to the subarachnoidal space (Fig. 2b). After 60 min the substance had diffused throughout all the lymphatic spaces of the inner ear, including the endolymphatic duct and sac (Fig. 2c). In addition, all the experiments of this series revealed the presence of tetracycline in the bony structure of the cochlea (Fig. 4a). The tangential cut through this structure showed a high concentration of tetracycline in its blood vessels (Fig. 5). In the second series, where tetracycline was applied only to the niches, a more sharply differentiated picture appeared. After 10 min fluorescence was observed in the first turn of the scala tympani and in the vestibule (Fig. 3a). After 1 h the substance had only penetrated the first quarter of the first coil, whereas it had already reached the subarachnoidal space via the perilymphatic duct (Fig. 3c). After 2 h the fluorescence appeared in addition in the endolymphatic duct and sac, in the utricule, and it had diffused both longitudinally and transversally throughout the first coil, but not beyond the beginning of the second coil (Fig. 3d). In contrast to the first series, no significant penetration of the bony capsule could be observed (Fig. 4b). These findings lead to the following conclusions: 1. Low molecular substances reach the inner ear fluids very quickly through the round window membrane as well as through the stapes footplate and the cochlear bone. 2. The transport of low molecular substances to the inner ear is facilitated by blood vessels in its bony capsule. 3. The different invasion of the cochlea and the perilymphatic duct in the second series of experiments speaks for a drainage of the perilymph from the scala tympani into the subarachnoidal space.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00455557
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