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Biomedical subjects

A Flock

Publications and source records attributed to A Flock.

At least 73 records · Page 4Linked to original sources
PubMed1979

Pathological actin in vestibular hair cells of the waltzing guinea pig.

Vestibular type 1 hair cells in the waltzing guinea pig contain needle-shaped inclusion bodies which grow in an uncontrolled fashion associated with the destruction of the cell. The needles are shown to be composed by filaments of actin, a protein identified in the electron microscope by its ability to bind subfragment 1 of myosin. Whereas actin filaments in stereocilia are oriented down towards the cell body, filaments in the needles point up towards the cuticular plate. The hereditary lesion appears to be associated with a defective control of polymerization of actin into filaments.

Actins↗
PubMed1978

Cupular movement and nerve impulse response in the isolated semicircular canal.

The aim of the study was to record nerve impulse responses to controlled displacements of the cupula and relate these to observations of cupular motion. The preparation was the skate semicircular canal, isolated and maintained in a chamber. The canal was cut and tied tightly to an oil-filled tube driven by a 1 microliter syringe. In some experiments dye was used to make the face of the cupula visible. Small volume displacements (0.02 microliter) caused a billowing of the central portion of the cupula, whereas for repeated large displacements (0.1 microliter) the top of the cupula moved along the roof of the ampulla. Displacements of the latter amount were close to saturation in the characteristic functions (spike rate versus volume displacement) of nerve firing. It seems that the discharge rate of tonically responding units in the skate crista ampullaris rather faithfully record the force acting on the cupula. The motion of the base of the cupula rather than its tip appears to be the relevant parameter in setting the level of excitation in the sensory cells within the physiological range of stimulation. Such a mode of operation would ensure the highest sensitivity of the sense organ.

Animals↗
PubMed1977

Freeze-fracturing of the auditory basilar papilla in the lizard Calotes versicolor.

Membrane-associated structures were studied in the cells of the basilar papilla, the hearing organ of a lizard, Calotes versicolor, by means of freeze-fracture. Zonulae occludents of an intermediate to tight type were found to join the apical membranes of sensory and supporting cells. Gap junctions were frequently observed between neighboring supporting cells. The size and shape of the gap junctions varied considerably. Their distribution was as follows: small junctions were seen apically, large ones basally. This finding suggests the existence of electrical coupling among the supporting cells. Only afferent synapses have been described in this organ. Aggregates of particles were found in the pre- as well as the post-synaptic membranes, similar to those described at synapses in the central nervous system.

Animals↗
PubMed1977

Actin filaments in sensory hairs of inner ear receptor cells.

Receptor cells in the ear are excited through the bending of sensory hairs which project in a bundle from their surface. The individual stereocilia of a bundle contain filaments about 5 nm in diameter. The identity of these filaments has been investigated in the crista ampullaris of the frog and guinea pig by a technique of decoration with subfragment-1 of myosin (S-1). After demembranation with Triton X-100 and incubation with S-1, "arrowhead" formation was observed along the filaments of the stereocilia and their rootlets and also along filaments in the cuticular plate inside the receptor cell. The distance between attached S-1 was 35 nm and arrowheads pointed in towards the cell soma. It is concluded that the filaments of stereocilia are composed of actin.

Actin Cytoskeleton↗
PubMed1976

Innervation of skin glands in the frog.

A comparative study was undertaken on the innervation of mucous and granular glands in frog skin. Results obtained by the Falck-Hillarp fluorescence technique and cholinesterase staining indicated that both types of glands receive exclusively adrenergic innervation. Electron microscopy was used to investigate the innervation pattern at the ultrastructural level. The distribution of nerve terminals was found to differ in the two types of glands. In the mucous gland, terminals were found at a distance of about 0.5 mum from the basement membrane but never within the gland parenchyma. In the granular gland, the terminals were located between smooth muscle cells and also in direct contact with the secretory epithelium but never outside the basement membrane.

Adrenergic Fibers↗
PubMed1976

Non-innervated sense organs of the lateral line: development in the regenerating tail of the salamander Ambystoma mexicanum.

New lateral organs (neuromasts) are formed in regenerating tails of the larvae of a urodele, the axolotl (Ambystoma mexicanum), even in the absence of the lateral line nerve, as confirmed by electron microscopic examination. The non-innervated organs are similar to normal innervated organs. The hair cells are polarized in opposite directions, and despite the lack of nerve endings, contain synaptic bodies, which in normal innervated organs are found in relation to afferent boutons.

Ambystoma↗
PubMed1976

Inhibition by efferent nerve fibres: action on hair cells and afferent synaptic transmission in the lateral line canal organ of the burbot Lota lota.

1. Intracellular recordings were made from morphologically identified hair cells in the lateral line canal organs of the burbot Lota lota. 2. I.p.s.p.s were recorded from hair cells when the efferent fibres were excited by electrical stimulation of the lateral line nerve. The i.p.s.p.s were abolished when the fish was injected with immobilizing concentration of Flaxedil which is known to block the efferent synapses. 3. The i.p.s.p.s are accompanied by a decrease in the resistance of the hair cell membrane and an increase in the intracellular receptor potential. 4. Spontaneous and mechanically evoked e.p.s.p.s which were recorded intracellularly from the post-synaptic afferent nerve terminals were reduced in amplitude for the duration of the i.p.s.p.

Animals↗
PubMed1973

The post-synaptic action of efferent fibres in the lateral line organ of the burbot Lota lota.

1. The post-synaptic action of efferent fibres on lateral line organs in the burbot was investigated with extracellular electrodes.2. Selective excitation of efferent fibres or stimulation of the lateral line nerve causes a negative efferent potential in the epithelium, an increase in the microphonic potential, and inhibition of afferent nerve impulses.3. Stimulation of the lateral line nerve causes antidromic impulses in the afferent fibres in addition to exciting the efferent fibres. However, stimulation of the lateral line nerve has no post-synaptic influence on lateral line organs when the efferent synapses are selectively blocked by gallamine.4. The influence of efferent stimulation on the microphonic potential is greater at large amplitudes of mechanical stimulation than at low.5. The similarities between the effects of efferent stimulation in the lateral line organ and in the cochlea suggest similar synaptic mechanisms.

Action Potentials↗