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Biomedical subjects

K Hama

Publications and source records attributed to K Hama.

At least 109 records · Page 6Linked to original sources
PubMed1978

A study of the fine structure of the pit organ of the common Japanese sea eel Conger myriaster.

The fine structure of the pit organ of the sea eel has been studied by means of electron microscopy. The sensory epithelium of the pit organ consists of sensory cells and supporting cells. The apical surface of the sensory cell is studded with sensory hairs consisting of a kinocilium and stereocilia. The sensory cells are divided into two groups. In one, the kinocilium points dorsally and in the other the kinocilium points ventrally. The total number of sensory cells in one pit organ is about 100, and the ratio of cells with opposite polarity is about 1:1. On the basis of these structural features, the pit organ is considered to be a mechano-receptor sensitive to the movement of liquid in a dorso-ventral direction. It may also serve as an ion receptor, sensitive to environmental ion concentration. Efferent nerve terminals make rare synaptic contacts on the afferent nerve fiber.

Animals↗
PubMed1978

Fine structure of the Müller cell revealed by high-voltage electron microscopy.

The three-dimensional organization of Müller cells in the retina of various vertebrates was investigated by means of high-voltage electron microscope stereoscopy using 2-5 micrometer-thick Golgi preparations. The alveolar compartments constituted by thin lamellar processes of the Müller cell were seen in the outer and inner nuclear layers. The radial process of the Müller cell has many irregular appendages which attenuate into thin lamellae to invade the neuropile. The functional significance of the characteristic morphological features of the Müller cell is discussed.

Animals↗
PubMed1977

Fine structure of the ordinary lateral line organ. II. The lateral line canal organ of spotted shark, Mustelus manazo.

The lateral line organ of the spotted shark is characterized by its semi-cylindrical shape. Each organ (neuromast) is so closely apposed to the next that the individual neuromasts are almost continuous. The neuromast is composed of receptor cells, supporting cells and mantle cells. The receptor cells bear one kinocilium and up to 40 stereocilia. Bi-directional arrangement of the receptor cells as occurs in teleosts was demonstrated. Afferent and efferent nerve endings were found at the base of the receptor cells. The supporting cells extend from the basal lamina to the free surface. Long microvilli and a cilium-like "ciliary rod" project from the top of each supporting cell. The cell contains relatively few elements of the Golgi apparatus and little rough endoplasmic reticulum, but mitochondria and filaments are abundant. The mantle cell limits the lateral margin of the neuromast. It is distinguished from the supporting cell because of its long crescent-shaped nucleus and scarce, short microvilli. Myelinated nerve fibres are found in the subepithelial connective tissue but not in the epithelium. The fine structure of the shark lateral line organ suggests that this organ is in an intermediated step of evolution between that of lamphrey and teleost.

Animals↗
PubMed1977

Gap junctions between the supporting cells in some acoustico-vestibular receptors.

Extensive gap junctions are found between the supporting cells in acoustico-vestibular receptors (saccular macula of the goldfish; ampullar crista, utricular macula and organ of Corti of the guinea pig). The fine structural details of these gap junctions were examined using lanthanum hydroxide staining and freeze-fracture replicas, as well as conventional thin sections. It was found in the lanthanum treated saccular macula of the goldfish that the gap junction globules consist of five or six subunits surrounding a central 2 nm hole. Similar subunits of the gap junction globule are also found in freeze-fracture replicas of the saccular macula of the goldfish and the ampullar crista of the guinea pig. Possible functions of the extensive gap junctions between supporting cells of these receptors are discussed.

Animals↗
PubMed1977

Fine structure of the afferent synapse of the hair cells in the saccular macula of the goldfish, with special reference to the anastomosing tubules.

The fine structure of the afferent synapse has been studied in the hair cells of the goldfish saccular macula. A spherical dense body which is surrounded by synaptic vesicles is observed in association with the presynaptic membrane. An alternating, parallel arrangement of dense bars and of rows of synaptic vesicles is observed on the presynaptic membrane beneath the dense body. Each row consists of five to six immediately available synaptic vesicles, and five to six such rows of vesicles are observed per synapse. Sometimes anastomosing tubules are found around the dense body. The tubules are formed by direct infolding of the plasma membrane. Many coated vesicles are found at the periphery of the anastomosing tubules. A possible role of the anastomosing tubules in the turnover of the synaptic vesicle membrane is discussed.

Animals↗