Biomedical subjects

M Takumida

Publications and source records attributed to M Takumida.

99 records · Page 6Linked to original sources

PubMedDate not supplied

Localization of nitric oxide synthase isoforms (I, II and III) in the endolymphatic sac of the guinea pig.

The localization of nitric oxide (NO) synthase (NOS) isoforms was examined in the endolymphatic sac (ES) of the pigmented guinea pig by indirect immunohistochemistry. The cytoplasm of the epithelial cells in the ES showed both NOS-I and -III immunoreactivity, whereas their nuclei appeared negative. NOS-III staining was also observed in the endothelial lining of the blood vessels. These findings support the hypothesis that NO in the epithelial cells may play an important role for the active intracellular transport of the endolymph and ion. NO may also be crucially involved in the regulation of ES blood flow. Immunostaining for NOS II revealed no reactivity in general, while in lipopolysaccharide-inoculated animals, intense reactivity was found in the cytoplasm of the ES epithelial cells as well as macrophages in the lumen. Thus it has been indicated that NO also may play an important role in the immunodefensive mechanisms in the ES.

Animals↗

PubMedDate not supplied

Three-dimensional structures of the vestibular sensory epithelia.

Vestibular neurosensory epithelia of the guinea pig and the bull frog were investigated by scanning electron microscopy. The crista ampullaris or macula were freeze fractured followed by maceration with 0.1% OsO4 solution for 24-60 h (osmium-DMSO-osmium method). Following this, three-dimensional intracellular structures were observed. The mitochondria which exist in the nerve chalice surrounding the type I cell were various in shape, globular, long and slender. Golgi apparatus, endoplasmic reticulum and thin fibrous structures of the sensory cells or supporting cells were clearly demonstrated. Concerning nervous system, nerve fibre, afferent and efferent nerve endings, further synaptic structures were also observed stereoscopically.

Acoustic Maculae↗

PubMedDate not supplied

Intracellular changes in the endolymphatic sac after labyrinthectomy.

Intracellular changes within the lining epithelium of the murine endolymphatic sac were investigated following surgical labyrinthectomy. The light and the dark epithelial cells reacted differently. Some light cells showed altered morphology after labyrinthectomy. The smooth endoplasmic reticulum formed a tubular network in the apical cytoplasm which was contiguous with the extremely well developed rough endoplasmic reticulum. These light cells also contained numerous granules. Such cell modifications indicated a secretory potential in this type of light cells. The dark cells showed signs of increased activity, with an augmentation of endoplasmic reticulum and an increased electron density of the cytoplasm. The dark cells increased their luminal surface to such an extent that they frequently covered the luminal surface of neighbouring light cells. Our hypothesis is that the dark cells may, in some way, control the function of the light cells and in this way also the absorptive mechanisms of the endolymphatic sac.

Animals↗

PubMedDate not supplied

Stereociliary glycocalyx and interconnections in the guinea pig vestibular organs.

Stereociliary glycocalyx and interconnections in the guinea pig vestibular organs were investigated at the electron microscopic level by using the ruthenium red staining technique. This staining visualized the glycocalyx and ciliary interconnections as well as the contact zone between the sensory hair bundle and the otolithic membrane or the cupula. Glycocalyx was found over the entire length of the stereocilia and the kinocilium of the sensory cells as well as over the entire apical surface of the supporting cells, in the form of a fuzzy filamentous layer. The ciliary structures were found interconnected by different types of connections, such as between the kinocilium and the neighboring stereocilia, and connections between stereocilia. These connections all emerged from the fuzzy layer of the glycocalyx and were also stained identically by ruthenium red, and were therefore considered to be morphologically similar. In addition, the tips of the sensory hairs were firmly attached to the otolithic membrane or the cupula. These findings suggested that the glycocalyx in the cell lining serves as an anchoring structure for the mechanical coupling not only between the ciliary structures, but also between the sensory hair bundle and the otolithic membrane or cupula.

Afferent Pathways↗

PubMedDate not supplied

Geometrical array of the vestibular sensory hair bundle.

The stereometrical arrangement of the sensory hair bundles in vestibular epithelia of the guinea pig was studied with high-resolution scanning electronmicroscopy. Besides the previously known arrangement in tall and short hair bundles, a new morphological criterion dividing the hair bundles into two separate populations is described. Thus the hair bundles can be separated into a loose and a tight type, depending on the interrelationship between the individual stereocilia. The cilia in the loose hair bundle are arranged in longitudinal rows parallel with the cell's plane of polarization, so that the stereocilia increasing stepwise in height are compressed tightly together. The stereocilia in the tight hair bundle type are arranged in equally tall transverse rows in which the cilia are situated directly adjacent to each other. While all the stereocilia are connected by thin filaments along the entire course of their shafts, their bevelled tips are connected by a single tip link to the shaft of the adjacent, taller stereocilium. The tip link morphology differs between the two hair bundle types. It is assumed that these two different types of hair bundles have different mechanical properties, which could indicate a higher degree of selectivity on the hair cell level in the vestibular end organs.

Animals↗

PubMedDate not supplied

Cytochemical identification of secreted carbohydrates in the endolymphatic sac.

Carbohydrate complexes were investigated in the murine endolymphatic sac by means of histochemical techniques in normal untreated animals as well as after ethacrynic acid treatment. The light epithelial cells were classified into three different types: normal, granular and vacuolar. The granular and vacuolar cells were believed to secrete glycoproteins and/or proteoglycans, the presence of which was closely correlated with the component of the precipitate in the lumen of the endolymphatic sac. This finding suggested that the light cells not only absorb endolymph but may also be involved with secretory activity. Such a dual modality in function may have several important implications, since it suggests that the endolymphatic sac has both absorptive and secretory functions.

Animals↗

PubMedDate not supplied

Sensory hair fusion and glycocalyx changes following gentamicin exposure in the guinea pig vestibular organs.

This study demonstrates the mechanism of sensory hair fusion and its relationship to glycocalyx on the hair cells in the vestibular epithelia of gentamicin-treated guinea pigs, using a ruthenium red staining technique. 0.1 ml of a solution containing 50 mg gentamicin sulphate per 1 ml was injected once into the middle ear. After 7 days, various stages of sensory hair degeneration were observed. The glycocalyx was clearly visualized by ruthenium red. The gentamicin-induced hair damage started with a local decrease in or loss of glycocalyx from neighbouring sensory hairs, followed by formation of local attachment areas of membrane sensory hairs. These findings suggest that the glycocalyx of the sensory cell may play an important role in separating the cilia as well as maintaining the organization of the bundle. Therefore, the decrease in or loss of glycocalyx from the hair bundle of sensory cells affected by gentamicin, either directly or secondarily, can be considered as closely related to the fusion of the sensory hairs.

Animals↗

PubMedDate not supplied

Uptake of radioactive sulphur in the endolymphatic sac. An autoradiographic study.

Autoradiographic uptake of labelled sulphur (S35) in the endolymphatic sac was analysed after performing surgical labyrinthectomy and after systemic administration of glycerol and ethacrynic acid. Accumulation of radioactive substance was observed after surgical labyrinthectomy and associated with a deposition of stainable substance in the endolymphatic sac lumen. Increased activity was noted in the epithelial layer after administration of ethacrynic acid, whereas glycerol did not increase radioactivity in the endolymphatic sac despite the deposition of stainable substance therein. This fact was believed to depend on a too short time interval between the injection and the sacrifice of the animals, as well as a weaker concentration of the sulphated compound within the endolymphatic sac. The results suggest that the endolymphatic sac may secrete sulphur-containing substances presumably associated with a deposition of a stainable substance in the endolymphatic sac.

Animals↗

PubMedDate not supplied

Three-dimensional observation of the spiral ganglion cell. Normal structure and pathological changes.

Spiral ganglia of guinea pig and mouse were investigated by scanning electron microscopy (SEM). The cochlea was freeze-fractured and then macerated with 0.1% OsO4 solution for 70-90 h (A-O-D-O method (1]. This allowed three-dimensional observation of the general view of the spiral ganglion and the intracellular structure. Two types of spiral ganglion cell, type I and type II, could be distinguished by the A-O-D-O method. Intracellular membranous structures such as mitochondria, endoplasmic reticulum (ER) and Golgi apparatus were also demonstrated stereoscopically. Furthermore, morphological changes in mouse spiral ganglion cells due to injection of Mycobacterium fortuitum were observed, using SEM. The degenerative process began as swelling of the mitochondria. When Schwann cell became affected, the myelin sheath disappeared and the ganglion cell border became indistinct. This degeneration developed rapidly, suggesting a direct influence of the bacteria on the ganglion cell. Various types of inclusion body with limiting membrane could be demonstrated stereoscopically. As Romand & Romand (4) suggested, these inclusion bodies may be remnants of cellular organellae or various type of lysosomes.

Animals↗