Hair Cell Nuclei Research Articles

Possible precursors to new hair cells, support cells, and Schwann cells in the ear of a post-embryonic fish

The sources of new hair cells, support cells, and Schwann cells were identified in the statoacoustic end organs of normal post-embryonic fish ( Astronotus ocellatus). S-phase cells, defined as cells that take up 3H-thymidine in preparation for mitosis, and their progeny were visualized using autoradiography. Two types of S-phase cells were found: ‘embryonic-like neuroepithelial’ (NE) cells and ‘basally located S-phase’ (BLS) cell. The NE cells had elongated nuclei and processes extending basally and apically. Thirty minutes after the thymidine injection labeled NE cell nuclei were found between hair cell nuclei and support cell nuclei. After two and four hours survival some labeled NE nuclei were closer to the lumen, where they divided. One labeled support cell was seen after four hours survival and one labeled hair cell after nine hours survival. Significant numbers of labeled support and hair cells were not seen until 24 h survival. These results led us to identify NE cells as the immediate source of new hair cells and support cells. The BLS cells had small nuclei with little surrounding cytoplasm. Shortly after the thymidine injection BLS cells were found between the hair cell nuclei and the basement membrane, and they underwent mitosis in this position. The BLS cells resemble intra-epithelial Schwann cells, except that they are not curved around axonal profiles. We suggest that the BLS cells are Schwann cell precursors.

Hair cell regeneration after acoustic trauma in adult Coturnix quail.

Recovery of hair cells was studied at various times after acoustic trauma in adult quail. An initial loss of hair cells recovered to within 5 percent of the original number of cells. Tritium-labeled thymidine was injected after this acoustic trauma to determine if mitosis played a role in recovery of hair cells. Within 10 days of acoustic trauma, incorporation of [3H]thymidine was seen over the nuclei of hair cells and supporting cells in the region of initial hair cell loss. Thus, hair cell regeneration can occur after embryonic terminal mitosis.

Immunocytochemical localization of choline acetyltransferase-like immunoreactivity in the guinea pig cochlea

The immunocytochemical localization of the enzyme choline acetyltransferase (ChAT) was examined in the guinea pig organ of Corti to determine if both lateral and medial systems of efferents would show immunoreactive labeling for this specific enzyme marker of cholinergic neurons. Cochleae were also examined after lesion of efferents to determine if ChAT-like immunoreactivity is confined to efferents. ChAT-like immunoreactivity was seen in the inner spiral bundle, tunnel spiral bundle and by the bases of inner hair cells corresponding to the lateral system of efferents. ChAT-like immunoreactivity was also seen in crossing fibers and puncta at the bases and by the nuclei of outer hair cells corresponding to the medial system of efferents. With the use of video enhanced contrast microscopy more than 9 ChAT-like immunoreactive puncta at the bases of outer hair cells could be resolved. In cochleae examined 6 weels after ipsilateral lesion of efferents, no ChAT-like immunoreactivity was observed. These results add strong evidence that acetylcholine is a transmitter of both the medial and lateral systems of efferents.

Immediate alterations in the impulse noise exposed organ of Corti of the guinea pig.

Cochlear microphonics and morphological changes in the organ of Corti were examined in guinea pigs exposed to 1 or 10 impulses of 164 dB SPL. Immediately after noise exposure the CM amplitudes of frequencies between 500 and 10000 Hz delcined severly with an accelerating tendency during the next 2 hours. The decrease in CM in two groups differed insignificantly. 10 minutes after impulse exposure, whole-mount specimens showed mainly swollen and translocated nuclei of outer hair cells. After 2 hours we found large quantities of pyknotic nuclei, karyorrhexis, and gaps in the normal OHC pattern. Despite minor numerical differences in injured cells of either group, exposure to 10 impulses caused a greater degree of irreversible alteration. Altogether, altered hair cells were only localized in the basal and lower second turn, and their numbers were relatively small. This stands in contrast to severe decrease of CM from low to high frequencies. Hair cell injury and additional mechanical lesion of the reticular membrane caused many sites of leakage, allowing interchange of endo-and peri-lymph. This effect is considered to be the main cause of functional damage indicated by rapid CM decline.

The effect of high level sound on hearing sensitivity, cochlear sensorineuroepithelium and vasculature of the chinchilla.

Ten young chinchilla were tested for hearing and then exposed for 8 hours to a 110 dB (SPL) broad-band noise. Post-stimulation recovery was assessed daily until permanent threshold shifts were obtained. Cochlear tissues were prepared in order to allow viewing of sensory cells as well as the vascular supply of the cochlea. Findings included inconsistent displacement of the vestibular membrane, poor injection of a contrast medium into vessels, moderate outer hair cell loss and displaced inner hair cell nuclei. Small basal turn cell damage was accompanied by greater than expected losses for high frequency pure tones.

Peripheral auditory tuning for fine frequency analysis by the CF-FM bat,Rhinolophus ferrumequinum

1. The cochlea of the horseshoe bat,Rhinolophus ferrumequinum, was frequency mapped by exposing for 30 min to one or two continuous pure tones of intensities between 70 and 110 dB SPL. The evaluation was made by differentiating between normal and swollen nuclei of the outer hair cells (OHC) of the organ of Corti and by measuring the diameter of the nuclei of the OHC. 2. In control animals the radial diameter of the OHC nuclei varies systematically from a mean of 2.85 μm at the base to 3.2 um at the apex (Fig. 1). 3. All frequencies used for exposure were normalized to the resting frequency (FR), which is the frequency of the pure tone component of the orientation sound in a non-flying bat. The individual FR lay between 82.6 and 83.3 kHz. 4. For analysing the small frequencies between 83.0 to 86.0 kHz in which relevant echoes occur, 3.15 mm length of the basilar membrane is used, about the same length as for the octaves from FR/4 to FR/2 (2.85 mm) and from FR/2 to FR (3.2 mm) (Fig. Ca, b). 5. The discontinuity of the mechanical data at 4.5 mm of the length of the basilar membrane (part I of this paper) coincides with FR and the less pronounced discontinuity at 7.8 mm coincides with FR/2. 6. Location and mechanism of the auditory filter are discussed.

The polytene nucleus of the giant hair cell ofBryonia anthers

The growth of the nuclei and cells that constitute the hairs on the anther ofBryonia dioica has been investigated. The cell at the base of the hair reaches a volume of nearly 106 μm3 just before the flower opens, while the cells distal to it do not grow and have volumes of less than 104 μm3. The nucleus of the basal cell undergoes endopolyploidisation, doubling its DNA every 1.3 days in the early stage of this process, to reach a maximum DNA content of 256 C which is equal to 512 pg of DNA. Nuclei in the distal hair cells do not have more than a 4 C DNA content. The endopolyploid nucleus of the basal cell contains chromosome structures that are polytene. Homologous polytene chromosomes often appear to be paired.

Staining of hair cell nuclei by a fluorescent derivative of hemicholinium-3.

The uptake of terphenyl-HC-3, a fluorescent derivative of hemicholinium-3, by cochlear hair cells was investigated in normal and damaged guinea pig cochleas. The uptake of terphenyl-HC-3 by hair cell nuclei is markedly reduced in Kanamycin and noise-induced cochlear damage. This reduction of terphenyl-HC-3 uptake occurs before the appearance of the classic distortions in the gross morphology of the hair cells resulting from such damage.

Ultrastructure of the hairs of the filamentous green alga Bulbochaete hiloensis (Nordst.) Tiffany: an apoplastidic plant cell with a well developed Golgi apparatus

Bulbochaete hiloensis is a filamentous green alga in the Oedogoniales. It possesses colourless hair cells, the ultrastructure and development of which are unusual in several respects: (1) The initial wall of the hair cell is formed by eversion of a pre-formed pad of cell wall material (Cook, 1962). (2) The hair cells are apoplastidic, even lacking colourless remnants of plastid material. (3) A nucleolus is lacking from young and mature hair cell nuclei, though it is not known whether one is present in the earliest stages. (4) Despite the absence of chloroplasts, starch reserves, and a nucleolus, the ultrastructure of the cytoplasm is characteristic of intensive granulocrine secretory activity. Massed cisternae of rough endoplasmic reticulum and numerous dictyosomes, together with associated transitional and secretory vesicles, are present. Substrate for the biosyntheses in these systems must enter the hairs via plasmodesmata, which exist in the basal wall. The product is probably a mucilage, exported to the exterior through a system of pores which pierce the outer wall of the hair. (5) Microtubules lie in the hair, and in its bulbous base, where some may be interpreted as having a role in anchoring the nucleus. (6) The significance of the apoplastidic and anucleolate condition is discussed.

Microfluorometric quantitation of nuclear proteins and nucleic acids in cabbage root hair cells infected by Plasmodiophora brassicae

Quantitative cytofluorometric measurements of DNA, RNA, histone, total protein and protein-bound lysine and arginine were obtained on nuclei in cabbage root hair cells infected by Plasmodiophora brassicae. Within 6 to 8 h after penetration of the root hair cells, nuclear RNA, total protein and non-histone protein increased markedly, whereas histone declined. Although nuclear DNA decreased slightly as the root hair cells aged from 6 to 27 h, the parasite did not alter the DNA content of infected cells compared to noninfected cells. Losses in total histones upon infection were attributable to decreases in the lysine-rich fraction. Protein-bound arginine was unchanged by infection. Increases in nuclear RNA and protein upon infection were accompanied by enlargement of the nucleolus. Increased numbers of plasmodia within the root hair cell produced limited increases in nuclear RNA and protein.