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Biomedical subjects

M Takumida

Publications and source records attributed to M Takumida.

At least 37 records · Page 2Linked to original sources
PubMed1996

Scanning electron microscopic observation of the statocyst in the crayfish Procambarus clarkii Girard.

The statocyst in the crayfish Procambarus clarkii was investigated using scanning electron microscopy. The statocyst contains static hairs arranged in four group, i.e. lateral, medial, proximal, and distal. All the hairs are the same in basic structure. They differ in length and diameter and in their position with respect to the other hairs in the group and to the statolith. In terms of morphological polarization, the hairs in the lateral and medial groups are polarized toward the center of the crescent, while the hairs in the proximal group are polarized away from the center of the crescent. In the distal group, most hairs are polarized toward the center of the crescent, while some hairs are at random. This morphological polarization may be consistent with that of functional polarization. The statolith overlays the lateral and medial hair groups. The hairs in the distal group do not touch the statolith, whereas the hairs in the proximal group make contact with it from the side. It has been therefore indicated that the lateral, medial and proximal groups could detect gravity and linear acceleration like macular end organs and distal group could detect angular acceleration like semicircular canal in mammals.

Animals↗
PubMed1996

Uptake of tetracycline in otoconia of the guinea pig.

Calcium ion turnover in the otoconia of adult guinea pigs was investigated by observing the uptake of tetracycline. Oral administration of tetracycline resulted in the deposition of tetracycline (fluorescence) on the outer surface of otoconia, indicating the occurrence of dynamic exchange and/or uptake of calcium ions in the otoconia. Prolonged administration of tetracycline induced with fluorescence deposition in the central portion as well as on the surface of the otoconia. These findings suggest the occurrence of neogenesis, regeneration and/or growth of otoconia even in adult animals.

Animals↗
PubMed1996

Incorporation of tetracycline into otoconia of the guinea-pig following streptomycin intoxication.

The effects of streptomycin on the calcium ion turnover into otoconia of adult guinea-pigs investigated by the use of tetracycline. The oral administration of tetracycline induced the deposition of tetracycline (fluorescence) on the outer surface of otoconia indicating the existence of dynamic exchange and/or uptake of calcium ions in the otoconia. The significant finding is that streptomycin specifically interfered with calcium uptake into the otoconia which indicated that the decrease in calcium uptake caused by streptomycin may be closely related to the loss of otoconia as well as to a decrease in the calcium contents of otoconia. The decrease in calcium incorporation into otoconia caused by streptomycin was recovered within 6 weeks after the last injection of streptomycin. The number of otoconia with fluorescence in the central portion as well as their outer surface was increased. It is therefore suggested that the recovery of calcium uptake as well as new otoconial regeneration may play an important role for the recovery from loss of otoconia.

Animals↗
PubMed1996

The effect of gentamicin on cytoskeletons in the vestibular sensory cells: a high-resolution scanning electron microscopic investigation.

The effect of gentamicin on the cytoskeletal organization of guniea pig vestibular sensory cells was investigated employing the saponin perfusion method and scanning electron microscopy. The intermediate filaments and microtubules were noted to have degenerated following gentamicin intoxication. Such degeneration was not linked with primary mitochondrial damage, but closely related to subsequent degeneration of Golgi apparatus and of endoplasmic reticulum. These findings suggest that microtubules and intermediate filaments work closely together to maintain the structural integrity of both the Golgi apparatus and the membrane-bound organelles, which can be altered by ototoxic drugs before the degeneration of membrane-bound organelles.

Animals↗
PubMed1995

Cytoskeletal organization of the vestibular sensory epithelia.

The cytoskeletal organization of the guinea pig vestibular sensory epithelium was investigated by employing the saponin perfusion method and scanning electron microscopy. The skeletal framework of a a cell was found to consist of actin, intermediate filaments and microtubules. The membrane-bound organelles such as nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. were also well documented. This made it possible to investigate the three-dimensional organization of cytoskeletons as well as their complex interaction with various membrane-bound organelles. The intermediate filaments were demonstrated not only in the supporting cells but also in the sensory cells. They are usually seen surrounding the nucleus and extending through the cytoplasm which connects the nuclear membrane to the plasma membrane, cuticular plate, reticular lamina or other cyto-organelles. The intermediate filaments are also closely related to the desmosomes. These findings suggest that the intermediate filaments provide mechanical support to the cell and its nucleus. In the sensory cells, microtubules are found mainly in the supranuclear portion of the cells, running parallel to the main axis of the cell body, which is directly connected to the cuticular plate. These findings suggest that the microtubules provide the cell with mechanical support and may be closely related to the sensory cell transduction system. Inside the supporting cells, the microtubules are closely related to the secretory granules, Golgi apparatus and intermediate filaments, which supports the idea that the microtubules may control the distribution of intermediate filaments, and also play an important role for transport of the secretory granules.

Animals↗
PubMed1995

Otoconia on the vestibular dark cells of the ampullar areas.

Morphological and metabolic differences in the otoconia on vestibular dark cells of the ampullar area before and after streptomycin treatment were studied by scanning electron microscopy and X-ray microanalyser. Young adult pigmented guinea pigs were used in this study. In the control group, distribution of the otoconia showed a regular pattern. In the SM group the otoconia decreased in numbers and the regularity of the distribution pattern seemed to disappear. Calcium content of the otoconia in SM group also decreased. From these findings, it was concluded that SM might affect not only the sensory and supporting cells but also the vestibular dark cells.

Animals↗
PubMed1995

Anatomical and physiological characteristics of the vestibular ganglion of the bull frog.

The spatial distribution of nerve fibers from individual vestibular end organs in the vestibular ganglia (VG) was studied using horseradish peroxidase (HRP). HRP was injected into the cut end of the bull frog ampullary nerve. Stained neural elements were counted on the serial sections. Spatial distribution was also studied by recording ampullary nerve compound action potentials (AP) from VG. The anterior semicircular canal (SC) nerves were distributed in the anterior half of VG. The horizontal SC nerves were also distributed in the anterior half of VG, but tended to be posterior. The posterior SC nerves were found predominantly in the posterior half and antero-dorsal portions. These distribution patterns corresponded well with those confirmed by AP recording. There were a few neural connections between anterior and posterior SC, or horizontal and posterior SC, indicating receptor-receptor fibers.

Action Potentials↗
PubMed1994

Cytoskeletal organization of the vestibular sensory epithelia: saponin perfusion method for observing intracellular structures by scanning electron microscopy.

The cytoskeletal organization of the guinea pig vestibular sensory epithelial cells were investigated by the use of saponin perfusion method using scanning electron microscopy. The skeletal framework of a cell is composed of thin (actin or intermediate filaments) and thick filaments (microtubules). The membrane bound organelles such as nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. were also well demonstrated. This made it possible to investigate the three-dimensional structures of cytoskeletons as well as their complex interactions with various membranes bound organelles. It is therefore suspected that this technique may provide us further information about distribution, topographic relationships, and the functional role of cytoskeletons.

Actin Cytoskeleton↗
PubMed1994

Motile responses of isolated vestibular hair cells.

Vestibular sensory cells were isolated from the utricular macula or crista ampullaris of the guinea pig by enzymatic and mechanical dissociation. Isolated vestibular hair cells, especially type I hair cells, showed an active motile capacity. After exposure to a medium containing high concentration of potassium, or to a hypoosmotic medium, the type I hair cells showed tilting of their hair bundle to about 15 degrees. Given the tight and dense structure of the vestibular epithelium, the changes in shape of the isolated vestibular hair cells may in vivo lead to an influence of the mechano-sensitive stereocilia and modulate stiffness and compliance of the receptor structure as a whole including its cupular or macular relationship. This active mechanical events could be closely related to an active adaptation process.

Animals↗
PubMed1994

Cytoskeletal organization of the vestibular supporting cells. Saponin perfusion method for observing intracellular structures by scanning electron microscopy.

The cytoskeletal organization of the guinea pig vestibular supporting cells was investigated employing the saponin perfusion method using scanning electron microscopy. The skeletal framework of a cell was composed of actin, intermediate filaments and microtubules. The membrane bound organelles such as nucleus mitochondria, endoplasmic reticulum, Golgi apparatus, etc. were also well documented. This made it possible to investigate the three-dimensional organization of cytoskeletons as well as their complex interaction with various membrane bound organelles. The intermediate filaments were usually seen surrounding the nucleus and extending through the cytoplasm which connected the nuclear membrane to the plasma membrane, reticular lamina or other cytoorganelles. The intermediate filaments also closely related to the desmosomes. These findings suggest that the intermediate filaments provide mechanical support to the cell and its nucleus. The microtubules were closely related to the secretory granules, Golgi apparatus and intermediate filaments, which supports the idea that the microtubules may control the distribution of intermediate filaments, and also play an important role for the transport of the secretory granules.

Actins↗
PubMed1993

Glycocalyx and ciliary interconnections in bullfrog vestibular end organs: normal structure and changes after incubation in frog Ringer's solution.

The ultrastructure of ciliary interconnecting systems as well as changes after incubation in frog Ringer's solution of the bullfrog vestibular end organs were investigated by using a scanning electron microscopy. The plasma membrane of the sensory hairs showed rather rough appearance. Side links emerged from the plasma membrane and tightly connected neighboring cilia. The tip links stretched from the tips of the stereocilia to their taller neighbors. These tip links were arranged in a same direction towards the kinocilium. These findings indicate that the side links may keep the cilia arranged in a bundle and the tip links may be involved in sensory cell transduction system. Changes in the surface texture and ciliary interconnecting systems were detected 2 hrs after incubation in frog Ringer's solution. Such changes included an increase in granularity of the surface membrane, fracturing and disappearance of all types of ciliary interconnections, especially side links. The tip links were more durable than side links. This indicates that the physiological studies of bullfrog hair bundle are justified across a 1-hr interval from the time the temporal bones are removed from the animal.

Animals↗
PubMed1992

The effect of endolymphatic sac obliteration on vestibular sensory hair bundles. A high-resolution scanning electron microscopic investigation.

A tannic acid-osmium staining technique and high-resolution scanning electron microscopy were used to demonstrate changes in the glycocalyx and ciliary interconnections of the vestibular sensory cells of guinea pigs after extradural obliteration of the endolymphatic sac and duct. Three months after the obliteration, it was possible to observe degeneration in the glycocalyx and the ciliary interconnections as well as the tip links. These findings suggest that the endolymphatic hydrops causes an endolymphatic ionic imbalance which affects the glycocalyx and ciliary interconnections resulting in further morphological changes of the cilia. The tip links, which are believed to be involved in sensory cell transduction, also seem to be affected.

Animals↗
PubMed1992

The statoconial membrane of the guinea pig utricular macula. Scanning electron microscopic investigation combined with the freeze-fracturing technique.

The superstructure of the guinea pig utricular macula was investigated using scanning electron microscopy combined with the freeze-fracturing technique. The statoconial membrane was composed of the otoconial layer, otolithic membrane and subcupular meshwork. The otolithic membrane consisted of closely arranged filaments with beaded appearance and densely packed globular matrix near the otoconial layer. The subcupular meshwork consisted of long branching filaments cross-bridged to one another. The filaments were continuous with those of the otolithic membrane on one side and with the surface of the epithelium on the other, which fills the space between the otolithic membrane and the macular surface. The otolithic membrane would function as a rigid plate and equally distribute the shear force of the otoconial layer to all the ciliary bundles. The subcupular meshwork may play an important role in transmitting the shear strain of the otolithic membrane to all the ciliary bundles and may also exert an additional dampening effect to prevent unwanted vibration.

Acoustic Maculae↗
PubMed1991

Intermediate filaments in the endolymphatic sac of the guinea pig.

The expression of the five main groups of intermediate filaments and their subgroups, especially cytokeratins, was investigated in the guinea pig endolymphatic sac at the light microscopic level using immunohistochemistry. Immunostaining for cytokeratin (PKK1, PKK2, PKK3) was found in the epithelial cell layer of the sac. Vimentin was seen to stain epithelial cell layer as well as subepithelial tissue. These findings may indicate that the cytokeratins are closely related to the inner ear fluid transport. The coexpression of cytokeratin and vimentin seemed to indicate the dual function of absorption and secretion of the endolymphatic sac epithelial cell to regulate the inner ear fluid homeostasis.

Animals↗
PubMed1991

Carbohydrates of the vestibular end organs. An ultrastructural study using gold-labeled lectins.

The presence of carbohydrates in the glycocalyx of the vestibular end organs of the guinea pig was investigated at the ultrastructural level using lectin-gold solutions. The glycocalyx of both the sensory and the supporting cells has variable sugar components. The glycocalyx of the sensory cells including the ciliary interconnections contains N-acetyl-glucosamine, galactose and mannose. In contrast, the glycocalyx of the supporting cells had a lower amount of N-acetylglucosamine. The ciliary interconnections, which have been considered to be a part of the glycocalyx, have larger amounts of galactose and mannose than the surface glycocalyx. These findings indicate that the sugar components may be closely related to the functional significance of the inner-ear glycocalyx and that the functional properties of the glycocalyx may differ between the sensory and the supporting cells of the vestibular end organs.

Animals↗
PubMed1991

Modulation of the endolymphatic sac function.

A method for inducing a partial dysfunction of the endolymphatic sac and its effect was investigated. Acetazolamide as well as amiloride caused collapse of the lateral intercellular spaces in the endolymphatic sac epithelium and a subsequent mild endolymphatic hydrops. These changes indicate a decreased absorption rate of endolymph in the endolymphatic sac. Colchicine caused a disturbed secretory activity of the sac induced by glycerol. Animals treated with colchicine showed marked signs of inner ear malfunction after additional treatment with glycerol, which might indicate that the secretory activity in the sac is closely related to the regulation of inner ear fluid homeostasis and functional disturbance.

Acetazolamide↗
PubMed1991

Effect of gentamicin on vestibular ganglion.

The morphological changes of the vestibular ganglion induced by gentamicin (GM) were investigated using light, scanning and transmission electron microscopy. The guinea pigs were injected 4 mg of GM into the middle ear for 5 days. The vestibular ganglion was observed up to 4 weeks after the treatment. Three days after the treatment the degenerative change was first noted in the vestibular ganglion. The degenerative process started from the destruction of mitochondrial cristae and vacuolization of the cytoplasm of the Schwann cell. The cytoplasmic organelles in the ganglion cell gradually deteriorated with swelling of the endoplasmic cisterns as well as Golgi apparatus. At the later stage, the myelin sheath around the ganglion cell disappeared and the number of the cells reduced. These changes of the ganglion cell may be due to the direct action of GM.

Animals↗