The reinnervation of regenerated hair cells in the basilar papilla of chicks after kanamycin ototoxicity.

When newly hatched chicks were injected with kanamycin on 8 successive days, the hair cells were destroyed completely in the area 0.4 to 0.8 mm from the proximal end of the basilar papilla. At this time, and 1 and 7 days following the completion of 10 days of injections, the nerve fibres in the basilar papilla of chicks show no sign of injury. On the first day following 10 days kanamycin administration the regenerated hair cells obtained not only afferent innervation, but also efferent innervation. At 15 days following drug cessation, afferent innervation of the regenerated hair cells was already similar to the controls, and the thresholds measured at this time were significantly better than those at 1 and 7 days. The chalice efferent terminals did not appear until the 60th day of drug cessation. Efferent innervation of the regenerated hair cells also approached maturity at this time. Compared with the half month after the completion of drug injection, the hearing of birds had no evident increase. It was obvious that afferent innervation of the regenerated hair cells was related more to the recovery of hearing than efferent innervation. The regenerated hair cells beginning reinnervation early and maturing were important factors influencing the recovery of the birds' hearing function after kanamycin ototoxicity.

Ontogenesis of rat cochlea. A quantitative study of the organ of Corti.

A systematic quantitative set of data concerning the organ of Corti in developing Sprague-Dawley rats at intervals from 18 days of gestation to 10 days after birth (DAB) is provided in this study. Using phalloidin staining, the total number of inner and outer hair cells, the whole length of cochlea, as well as the diameter of inner and outer hair cells and the intercellular space between inner hair cells were determined in order to analyze the quantitative change of inner and outer hair cells during development and to explore some roles of the factors regulating the growth of cochlea. The results show that: (1) The length of cochlea approached its adult size by 7DAB. (2) The growth of the extreme part of the apex was responsible for the delayed elongation of the cochlea. (3) Growth in the cochlear length mainly results from an increase of cell diameter tempered by a decrease of intercellular space. (4) The adult size of inner and outer hair cells was obtained by 7-14DAB. (5) The final number of inner and outer hair cells was reached at 3DAB and remained constant through adulthood. No significant hair cell overproduction and cell death were observed during ontogenesis of the cochlea. The negligible importance of overproduction and missing hair cells during hair cell differentiation suggest that there is a precise regulation phenomenon for producing the right spatial organization of the organ of Corti.

The alteration of ultrastructure and immunoreactivity of human embryonic organ of Corti tissue culture after exposure to aminoglycoside (neomycin) ototoxicity.

Using electron microscopy and GABA immunohistochemistry we evaluated the effects on human embyronic organ of Corti tissue culture of exposure to the ototoxic aminoglycoside antibiotic neomycin at a dose of 1 mM for 48 to 96 hrs. Neomycin induces the formation of multilamellar myeloid structures. These lesions, found only in the basal coil but both in inner and outer hair cells, were characteristic of the membrane-associated neomycin-induced damage. A large amount of lipofucsin and numerous lipoid vacuoles as well as vesicle-filled mound-like protrusions were also observed after exposure to neomycin. It seems there is no obvious effect on GABAergic innervation.

SEM observation and GABA immunoreactivity of human embryonic organ of Corti tissue culture.

Scanning electronic microscopy (SEM) observation and GABA immunoreactivity of the tissue culture of 6 human embryonic organs of Corti are reported. The normal structural appearance of the hair cells and the facts that there were no bulging of cuticular plates, and cytoplasmic protrusion proved that the hair cells were healthy. After GABA immunostaining, radial bundles, innerspiral bundles, and the ending of inner and outer hair cell regions displayed typical GABA-positive reactivity. The results indicate that the human embryonic organ of Corti is well developed differentiated, and mature at 19 gestational weeks and can continue to grow and differentiate in vitro. The study offers an ideal and important biological model for further research into the human ear.

Human embryonic organ of Corti in tissue culture and NSE expression.

For the first time ever, the cochlear tissue of the human embryo has been successfully grown in vitro in two cases, and neuro-specific enolase (NSE) immunoreactivity was studied in one of these tissues. The outer hair cells were arranged in three rows, and the inner hair cells in one row and in better order than the outer hair cells. After NSE immunostaining, the outer spiral bundle, tunnel fiber, outer hair cells, inner hair cells, and the spiral ganglion cells showed positive staining. This data suggests that the human embryonic cochlea has nearly reached complete maturation by 16 weeks, and that the tissue of the Corti organ can be differentiated and matured in vitro.

[Particle induced X-ray emission for trace element analysis of hairs from patients with cancer].

In this paper, trace element analysis of the hairs from the patients with nasopharyngeal carcinoma (NPC) and osteoma was made using particle induced X-ray emission (PIXE) technique in order to obtain some information on the correlation between trace element and these two tumors. The hair samples of 34 NPC patients were each collected before and three months after radiotherapy (60Co) (group 1). The hair specimens from 34 osteoma patients were collected preoperatively and postoperatively. For comparison, 65 hair samples were collected from 40 normal subjects (group 2) and 25 NPC patients, who had received radiotherapy (60Co) five years before without any recrudescence (group 3). The trace element analysis of all specimens was made by PIXE. The results show that there is a significant difference between groups 1 and 2 (P less than 0.01) but no difference is found between groups 2 and 3 for Mn, Cu, Zn, As etc. content in the hairs. Cu and Zn content in the hairs of the osteoma patients is much lower than that of the normal subjects (P less than 0.01) while for K, Ti and Mn content, the former is higher than the latter. The above experimental results are discussed in detail.