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Biomedical subjects

M Takumida

Publications and source records attributed to M Takumida.

At least 91 records · Page 5Linked to original sources
PubMed1984

Development of the utricular macula in the mouse.

There have been many studies reporting on the development of the utricular macula using transmission electron microscopy. This study demonstrates the morphological development of the utricular macula in the mouse using scanning electron microscopy. Utricular maculae from CBA/CBA mice were studied from the 11.5th gestational day to 2 weeks after birth. Between the 11.5th and 12.5th gestational day there are numerous microvilli and a primary cilium on the surface of the otocyst. Sensory hairs appear on the 13.5th gestational day. The kinocilium and stereocilia are short and the latter of almost equal in length. The polarity of the kinocilium is first noticed after the 16.5th gestational day. The formation of otoconia starts on the 14.5th gestational day. They are shaped like a dumb-bell and are oval and columnar. Otoconia with a hexagonal form are recognized after the 16.5th gestational day.

Acoustic Maculae↗
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Localization of nitric oxide synthase isoforms (NOS I, II and III) in the vestibular end organs of the guinea pig.

The localization of nitric oxide (NO) synthase (NOS) isoforms was investigated in the vestibular organ of the pigmented guinea pig by indirect immunohistochemistry. The cytoplasm of both type I and type II vestibular sensory cells as well as vestibular ganglion cells showed both NOS I and III immunoreactivity, whereas there was no reactivity in their nuclei and sensory hairs. The afferent nerve chalices were usually not stained. NOS III staining was also observed in the nerve fibers contacting type II cells and in the subepithelial tissue. The endothelial lining of the blood vessels displayed reactivity for NOS III. The cytoplasm of fluid transporting cells showed weak staining for NOS I and moderate staining for NOS III. Immunostaining for NOS II did not display any reactivity in general. These findings may suggest that NO is a mediator of neurotransmission in the vestibular system in sensory cells and ganglia. NO in the fluid transporting cells may play an important role for maintaining the endolymph and ion homeostasis, and NOS III in vascular endothelial cells implies regulatory effects of NO on vascular wall tonus and vestibular blood supply.

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Calcium mobilization in isolated epithelial cells of the endolymphatic sac.

Endolymphatic sac epithelial cells were isolated from the endolymphatic sac of the guinea pig by enzymatic and mechanical dissociation. The intracellular free calcium ion concentrations ([Ca2+]i) of the isolated cells were determined using the Ca(2+)-sensitive dye fura-2. The isolated cells were classified into two types, i.e. light and dark cells. In the resting state, [Ca2+]i in the cells was variable in both types of cells. In the presence of 200 microM ATP, there was a rapid rise in [Ca2+]i. These findings suggest that endolymphatic sac epithelial cells may have receptor-mediated Ca channels which may play an important role for a nerve-mediated local feedback system of the endolymphatic sac to regulate homeostasis of endolymph volume, pressure and electrolyte balance.

Animals↗
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Possible involvement of free radicals in lipopolysaccharide-induced labyrinthitis in the guinea pig: a morphological and functional investigation.

Intratympanic injection of bacterial lipopolysaccharide impaired caloric responses and caused severe and widespread morphological damage to vestibular end organs and the endolymphatic sac in the guinea pig. These effects could be blocked with N-nitro-L-arginine methylester, a competitive inhibitor of nitric oxide synthase, with superoxide dismutase, an O2 scavenger, with dexamethasone, and with ebselen, a scavenger of peroxynitrite. These observations indicate that enhanced nitric oxide and superoxide production, resulting in formation of peroxynitrite, is probably an important factor responsible for the pathological damage to vestibuli. If this is so, we may have found a way to study vestibular pathogenesis in inner ear disease.

Animals↗
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Lipopolysaccharide-induced expression of reactive oxygen species and peroxynitrite in the guinea pig vestibular organ.

The purpose of this study was to investigate the occurrence of reactive oxygen species and peroxynitrite in the vestibular organ of the guinea pig following inoculation with bacterial lipopolysaccharide (LPS). The animals were injected transtympanically with 1 mg of LPS 24 h after the intraperitoneal injection of 0.1 mg LPS. Forty-eight hours after the inoculation, varying degrees of degeneration of the vestibular end organs were observed. Immunohistochemical study revealed immunoreactivity to xanthine oxidase (which generates O-2) in the vestibular organ after inoculation with LPS. Immunohistochemical investigation with a specific antinitrotyrosine antibody also showed intense staining of sensory epithelium, fluid transporting cells and the endolymphatic sac, suggesting formation of peroxynitrite in the vestibular organ through the reaction of NO with O-2. On the basis of these data, it can be concluded that NO together with O-2, which form more reactive peroxynitrite, may be the most important pathogenic agents in LPS-induced labyrinthitis in the guinea pig.

Animals↗
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Free radicals in the guinea pig inner ear following gentamicin exposure.

The purpose of this study was to investigate the occurrence of free radicals, nitric oxide (NO), superoxide (O-2) and peroxynitrite, in the inner ear of the guinea pig following intratympanic injection with 5 mg of gentamicin (GM). Forty-eight hours after GM injection, varying degrees of degeneration of the inner ear were observed. Immunohistochemical study revealed immunoreactivity to NO synthase II (which generates NO) and to xanthine oxidase (which generates O-2) in both the vestibular organ and the organ of Corti. Immunohistochemical investigation, using a specific antinitrotyrosine antibody, also showed intense staining, suggesting formation of peroxynitrite in the inner ear through the reaction of NO with O-2. Scanning electron-microscopic study showed that the ototoxic effects could be blocked with N-nitro-L-arginine methylester, a competitive inhibitor of NO synthase, with superoxide dismutase, an O-2 scavenger, and with ebselen, a scavenger of peroxynitrite. On the basis of these findings, it can be concluded that NO together with O-2, which form more reactive peroxynitrite, play an important role in GM ototoxicity in the guinea pig.

Animals↗
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Influence of elastase and hyaluronidase on the ciliary interconnecting systems in frog vestibular sensory cells.

Bullfrog vestibular end organs were incubated in frog Ringer's solution, hyaluronidase and elastase. When assessed by scanning electron microscopy, long-time incubation in frog Ringer's solution caused damage to side links. Elastase caused severe damage to tip links with a slight alteration to side links. The glycocalyx of the hair cells decreased after incubation in elastase or hyaluronidase. Electrophysiological measurements showed a remarkable decrease in compound action potentials after the elastase treatment, while no change was observed after the long-time incubation in frog Ringer's solution or hyaluronidase. The results are in agreement with the hypothesis that tip links are involved in mechanotransduction, and side links keep the cilia arranged in a bundle.

Actin Cytoskeleton↗
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Isolated vestibular sensory cells in the guinea pig.

Vestibular sensory cells were isolated from the utricular macula or cristae ampullares of the guinea pig by enzymatic and mechanical dissociation. The isolated cells were classified into three types: flask-shaped type I sensory cells, rod-shaped type II sensory cells and round-shaped supporting cells. The cilia of type I sensory cells in the crista ampullaris were longer than those in the corresponding cell type in the utricular macula, while no morphological differences of the cell bodies were noted between crista ampullaris and utricular macula. Isolated living vestibular cells have a motile capacity. After exposure to a hypo-osmotic medium, the type I sensory cells showed tilting of the hair bundle. This change in shape may be closely related to the active mechanical transduction control.

Animals↗
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Effect of glycerol on the guinea pig inner ear after removal of the endolymphatic sac.

The effects of glycerol were investigated in guinea pigs in which the endolymphatic sac (ES) and duct (ED) had been obliterated unilaterally. Twenty-four hours after obliteration of the right ES and ED, glycerol was injected intraperitoneally. One to two hours after administration of glycerol, collapse or folding of Reissner's membrane was observed in the operated cochlea. No remarkable change was found in the nonoperated ear. The lumen of the ES of the nonoperated ear collapsed with intraluminal stainable substance within 1 h. The volume of the stainable substance increased with time and could still be seen 4 h after the injection of glycerol. Twenty-four hours after the injection of glycerol, the configuration of the ES was normal again. In addition, the animals showed marked unilateral (operated side) vestibular dysfunction after injection of glycerol. These findings suggest that the ES also has a secretory capacity and plays an important role in inner ear fluid volume and pressure regulation.

Animals↗
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Cytoskeletal basis for contractility of outer hair cells in the normal adult human organ of Corti: comparisons with vestibular hair cells.

The present study is the first consecutive analysis of the adult normal human organ of Corti and vestibular hair cells with regard to the expression of F-actin, actin-associated proteins (alpha-actinin, alpha- and beta-spectrins, vinculin and tropomyosin), beta-tubulin and the calcium-binding protein synaptophysin. The expression of these cytoskeletal and their associated proteins in man is largely similar to, although not identical with, that previously described for several other mammalian species. However, a few very unusual staining patterns were found. In several long outer hair cells a rod of F-actin extended from the infracuticular area to the cell nucleus. Fluorescence for tropomyosin occurred both in the cuticular plates of the outer and inner hair cells, and in the area of close apposition between the base of the outer hair cell and the apical part of Deiter's cell. In contrast, the vestibular hair cells showed immunoreactivity for tropomyosin only in the cuticular plates.

Actinin↗
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Three-dimensional organization of cytoskeletons in the vestibular sensory cells.

The cytoskeletal organization of the guinea pig vestibular sensory cells was investigated employing the saponin perfusion method using scanning electron microscopy as well as immunohistochemical technique. The intermediate filaments were demonstrated in the sensory cells. They were usually seen surrounding the nucleus and extending through the cytoplasm which connected the nuclear membrane to the plasma membrane, cuticular plate or other cytoorganelles. These findings may suggest that the intermediate filaments provide mechanical support to the cell and its nucleus. Microtubules were found mainly in the supranuclear portion of the cells and run parallel to the main axis of the cell body, which is directly connected to the cuticular plate. These findings may suggest that the microtubules provide mechanical support to the cell and may be closely related to the sensory cell transduction system. The actin filaments were densely packed in the site of the cuticular plate. They also distributed throughout the cytoplasm, which appeared as a dense network in the periphery region. These findings support the idea that the actin filaments could be responsible for sensory cell transduction as well as to give mechanical strength to the surface of the cell and enable the cell to change its shape and move.

Actins↗
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Attenuation of aminoglycoside ototoxicity by glutathione.

Aminoglycoside antibiotics are commonly used for the treatment of serious gram-negative infections despite a high incidence of associated ototoxicity. Attempts to elucidate the mechanisms of toxicity or prevent the adverse effects have previously been unsuccessful. Recently, the damaging effects of aminoglycosides on the inner ear have been shown to be caused by a metabolite of the drug, implying an enzymatic conversion of the parent compound. Glutathione has been suggested to be closely related to the detoxification mechanisms of this metabolite. This study revealed the possible attenuation of aminoglycoside ototoxicity by glutathione. Guinea pigs were given amikacin alone or amikacin with prior intramuscular injection of glutathione. The pretreatment of glutathione significantly reduced the damage of outer hair cells of the organ of Corti. This may indicate that glutathione reduces the aminoglycoside ototoxicity and can be favorably applied in clinical use.

Amikacin↗
PubMedDate not supplied

Polychromatic labeling of otoconia for the investigation of calcium turnover.

The calcium ion turnover into otoconia of adult guinea pigs was investigated by the use of different fluorochromes, i.e. tetracycline (TC), calcein (Cal) and alizarin complexone (AC). The administration of all fluorochromes induced yellow (TC), green (Cal) and red (AC) fluorescence on the outer surface of otoconia, respectively. Sequential polychromatic labeling with AC followed by TC induced only red fluorescence after 1 week administration of TC, combined fluorescence after 2 weeks administration of TC and only yellow fluorescence after more than 3 weeks of administration of TC. The otoconia labeled with both AC and TC showed red fluorescence on the side faces of otoconia and yellow fluorescence on the terminal faces. These results may indicate the existence of a dynamic exchange of calcium ions in the otoconia and this exchange is mainly restricted to the terminal faces. The sequential polychromatic labeling may thus be of great use for the further investigation of the calcium dynamics of otoconia.

Acoustic Maculae↗
PubMedDate not supplied

Electron probe X-ray microanalysis of otoconia in the guinea pig inner ear.

By using the electron probe X-ray microanalysis technique, the elemental composition of otoconia was analyzed in the normal adult pigmented guinea pig. In the X-ray spectra of otoconia, the most abundant element was Ca, but significant peaks for P, S, Cl and K were also detected. The comparison of the elemental composition in the utricular and saccular otoconia did not show any significant difference. Regression analysis revealed that the concentrations of Ca and K are related by a linear function in both the utricular and saccular otoconia. Analysis of otoconia of different sizes showed that there were no differences in Ca concentration in small, normal and large otoconia. The comparison of other elemental compositions revealed that P, S, Cl and K in the central part of saccular small otoconia showed higher concentrations than those of normal or large otoconia. P, S, Cl and K in the utricular small otoconia showed relatively higher concentrations. These findings may indicate that the small otoconia are immature or newly generated.

Animals↗
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Effect of streptomycin on the otoconial layer of the guinea pig.

The effects of streptomycin on the otoconial layer of the adult guinea pig were investigated using scanning electron microscopy. Administration of streptomycin induced a reduction of otoconia with formation of giant otoconia. These phenomena reached their maximum 4 weeks after the cessation of streptomycin intoxication in the utricle and between 2 and 6 weeks after in the saccule. Otoconia began to recover in the utricle 4 weeks and in the saccule 6 weeks after the cessation of streptomycin intoxication with an increasing number of small otoconia. Eight or 10 weeks after the cessation of streptomycin intoxication, the otoconial layer has completely recovered in both the utricle and saccule.

Animals↗