The relationship between kanamycin ototoxicity and glucose transport

The clinical utility of the aminoglycoside antibiotics is hampered by their well-known capacity to cause labyrinthine and renal damage. The mechanism by which these damages are produced is unknown. Attention was focused on the aminosugar moiety of these antibiotics by the finding of Owada (1962) which demonstrated that 3-aminoglucose is as ototoxic as its parent antibiotic, kanamycin. It is known that aminosugars compete with glucose for transport and that the sensory cells of the cochlea depend on glucose as a primary energy source. The hypothesis that grew out of these considerations was that kanamycin might be causing its ototoxicity by inhibiting glucose transport at one of several sites in the inner ear. To test this hypothesis the ototoxicity of kanamycin was determined in hyperglycemic animals. Hyperglycemia clearly and dramatically protects animals against ototoxicity as evidenced both by electrocochleographical and histological examination.

Detection of an auditory nerve--activating substance

A substance or substances capable of increasing the firing rate of primary auditory fibers is detectable in the perilymph of frogs and guinea pigs subjected to sound stimulation. The increase in firing rate occurs in single units of the frog auditory nerve after perilymph obtained from frogs or guinea pigs during sound stimulation is infused into the frog perilymphatic sac. Perilymph collected from animals maintained in silence failed to cause an increase in firing rate of primary auditory fibers of the frog.

Primary reconstruction by modified cervical island skin flap following resection of oral and pharyngeal cancer

Reconstruction of the intraoral defect following cancer surgery often causes formation of fistula, impairment of lingual movement, and prolonged hospitalization by secondary reconstruction. To reduce such complications, the modified cervical island skin flap method as a one-stage intraoral reconstruction was used in 18 patients. Lateral cervical island flap was used in 15 cases and the median flap in three. This method proved to be successful for 17 patients. One patient who received a preoperative full dose of irradiation developed a fistula. There were two types of healing of the skin flap. The postoperative external appearance and function of the tongue were commendable.

A simple, sensitive method for the quantitation of kanamycin in tissue and biological fluids

A method is described for the quantitative determination of kanamycin in blood, urine, cochlear perilymph and kidney. The method is simple, involving only protein precipitation, chromatographic separation and fluorometric determination following reaction with fluorescamine. The method is sensitive, determining as little as 80--100 ng/ml of kanamycin. The method is reliable, recovering better than 90% of the kanamycin added to the fluids and tissues mentioned. It is also less cumbersome and less expensive than other methods currently used.

A possible involvement of acidic glycosaminoglycans in kanamycin ototoxicity

The content of acidic glycosaminoglycans (AGAG) was determined quantitatively by electrophoretic microanalysis in the cochlea, kidney and brain of the guinea pig. Kanamycin treatment (400 mg/kg body weight/day, i.m., 10 successive days) reduced the content of AGAG markedly in the lateral wall of the membranous cochlea. Furthermore, from the results of the ultrahistochemical and freeze-fracturing study, we propose here an "excretion system for basic aminoglycoside antibiotics" by means of the co-operation of spiral ligament cells and AGAG produced by them. Thus we have tentatively concluded both that kanamycin is excreted via the above mentioned "excretion system" in the lateral wall of the membranous cochlea and that it damages this system to form the circulus vitiosus of its opopoxicity.

Tissue levels of kanamycin in correlation with oto- and nephrotoxicity

The time courses of kanamycin (KM) levels in the perilymph, kidney, liver, brain and blood were observed by a bioassay method in normal guinea pigs and in animals pretreated with KM for 10 successive days. In the kidney and perilymph of the normal guinea pigs, the injected KM became highly concentrated and was eliminated only after a protracted delay. This tendency was much more intensified in kidney and perilymph of the pretreated animals. By contrast, the KM in blood and brain was eliminated rapidly both in the normal and in the pretreated animals. It is concluded that the high accumulation and slow elimination of KM by the inner ear and kidney and, moreover, the enhancement of these phenomena by successive pretreatment are one of the important factors in the origin of oto- and nephrotoxicity.

Neuronal architecture of on and off pathways to ganglion cells in carp retina

Bipolar, amacrine, and ganglion cells of carp retina, stained intracellularly with Procion yellow, can be divided into types a and b, according to the destination of terminals and dendritic trees in the inner plexiform layer (sublamina a and b, respectively). Type a cells showed hyperpolarizing, or off, responses and type b cells depolarizing, or on, responses. Carp thus resembles cat in the basic organization of on and off pathways in the retina.

Experiences with the tracheoesophageal shunt method for vocal rehabilitation after total laryngectomy

The tracheoesophageal (T-E) shunt technique reported by Komorn et al. (1973) was used for vocal rehabilitation in 8 laryngectomized patients including one case of hypopharyngeal cancer. It was proved that this technique was a simple one-stage procedure with a low incidence of complication. Four out of 7 patients, excluding one patient who died of another disease, acquired excellent speech without symptomatic aspiration. Two patients developed fairly good speech. One shunt was closed by aspiration. The shunt constructed by a flap measuring 2 x 4 cm, opened 1 cm below the distal end of the trachea, showed good results. The T-E shunt speech exceeds esophageal speech in duration and intelligibility.

On the periodically aggregated particles on the fracture face of the cochlear hair cell

By means of the freeze-fracture technique, the membrane specialization of the cochlear hair cell of guinea pigs was studied. Periodically aggregated particles were revealed on the PF face of the plasma membrane of the outer hair cell. The particles were around 12 nm in diameter and 10 to 17 nm in center-to-center spacing. Their arragement was hexagonal, orthogonal or parallel. Possible involvement of this structure in the electrical excitability of the membrane was discussed.