Hydrostatic pressure effects on vestibular hair cell afferents in fish and crustacea

Following the discovery of a hydrostatic pressure sensor with no associated gas phase in the crab, and the knowledge that several systems of cells in culture show long term alterations to small changes in hydrostatic pressure, we show here that vestibular type II hair cells in a well known model system (the isolated elasmobranch labyrinth), are sensitive to hydrostatic pressure. This new finding for the vertebrate vestibular system may provide an explanation for low levels of resting activity in vertebrate hair cells and explain how fish without swim bladders sense hydrostatic cues. It could have implications for humans using their balancing systems in hypobaric or hyperbaric environments such as in aircraft or during space exploration. Although lacking the piston mechanism thought to operate in crab thread hairs which sense angular acceleration and hydrostatic pressure, the vertebrate system may use larger numbers of sensory cells with resultant improvement in signal to noise ratio. The main properties of the crab hydrostatic pressure sensing system are briefly reviewed and new experimental work on the isolated elasmobranch labyrinth is presented.

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The angular acceleration receptor system of the statocyst of Octopus vulgaris : morphometry, ultrastructure, and neuronal and synaptic organization

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1987.0010 ◽

1987 ◽

Vol 315 (1174) ◽

pp. 305-343 ◽

Cited By ~ 37

Keyword(s):

Hair Cells ◽

Angular Acceleration ◽

Sensory Cells ◽

Octopus Vulgaris ◽

Afferent Neurons ◽

Synaptic Organization ◽

Receptor System ◽

First Order ◽

Small Primary ◽

Primary Sensory Cells

The angular acceleration receptor system (crista/cupula system) of the statocyst of Octopus vulgaris has been thoroughly reinvestigated, and detailed information is presented regarding its morphometry, ultrastructure, and neuronal and synaptic organization. In each of the nine crista sections, some receptor hair cells are primary sensory cells with an axon extending from their base. Also, there are large and small secondary sensory hair cells without axons, which make afferent synapses with large and small first-order afferent neurons. The afferent synapses are of two morphologically distinct types, having either a finger-like or a flat postsynaptic process; both can be seen in the same hair cell. In addition to the afferents, there is a dense plexus of efferent fibres in each crista section, and efferent synapses can be seen at the level of the hair cells and of the neurons. The morphometric analysis of the nine crista sections shows obvious differences between the odd-numbered (C1, C3, C5, C7, C9) and the even-numbered (C2, C4, C6, C8) crista sections: they differ in length, in the number of the small primary sensory cells and in the number of the small first-order afferent neurons. Centrifugal cobalt filling of the three crista nerves revealed a disproportionate innervation of the nine crista sections: the anterior crista nerve innervates section C1 and the first half of section C2, the medial crista nerve innervates the second half of section C2, sections C3, C4, C5, and the first half of section C6, and the posterior crista nerve innervates the second half of section C6, and sections C7, C8 and C9. In each of the three crista nerves, only 25% of the total number of axons are afferent fibres, the remaining 75 % are efferent. To each of the nine crista sections a cupula is attached. In the form and size of the cupulae there is again a conspicuous difference between the odd and the even crista sections: a small widebased cupula is attached to each of the odd crista sections, whereas the even crista sections each have a large narrow-based cupula with a small area of attachment. The results are discussed with reference to their functional consequences.

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The anatomy and ultrastructure of the labyrinth of the lamprey ( Lampetra fluviatilis L.)

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1968.0029 ◽

1968 ◽

Vol 170 (1019) ◽

pp. 113-134 ◽

Cited By ~ 83

Keyword(s):

Hair Cells ◽

Angular Acceleration ◽

Semicircular Canals ◽

Sensory Cells ◽

Open Communication ◽

Lampetra Fluviatilis ◽

Sensory Ending ◽

Sensory Hair Cell ◽

New Type ◽

Anatomy And Ultrastructure

The anatomy of the labyrinth of the lamprey ( Lampetra fluviatilis ) is described. The ampullae of the two semicircular canals are each equipped with a complex three-armed sensory crista. They may be considered homologues of the ampullae of the vertical canals of the gnathostomes. However, the complexity of their cristae encourages the assumption that they may cover a spatial range of responses to angular acceleration which includes responses to accelerations in a horizontal plane controlled in the gnathostomes by the horizontal semi-circular canal. The otolith-bearing end organs are found to be located on a common macular structure. This is subdivided into an anterior horizontal, a vertical, and a posterior horizontal macula, each of which portions carries a characteristic arrangement of sensory cells. On the basis of an electronmicroscopic analysis of the orientation of the hair cells in the three main portions of the macula a revision of the homologies found in the older literature appears to be called for. It is suggested to homologize the anterior horizontal macula with the macula utriculi, the vertical macula with the macula sacculi and the posterior horizontal macula with the macula lagenae of the labyrinth of gnathostome animals. A separate sensory ending in the dorsal part of the labyrinth, the dorsal macula, may be the homologue of the macula neglecta. Ultrastructurally the end organs of the lamprey labyrinth conform with those of the gnathostome labyrinth with the exception of the presence of a new type of sensory hair cell which is equipped with a stiff kinoeilium of extraordinary length accompanied by extremely short stereocilia. This cell is found preponderantly in the vertical macula (macula sacculi). A striated organelle in the cytoplasm of the hair cells appears to be uniquely confined to the labyrinth of the lamprey. Morphologically the lamprey labyrinth differs from all other chordate labyrinths including that of its fellow cyclostome Myxine by the presence of large ciliated chambers in its centre in which long and powerful cilia maintain a permanent pattern of four endolymph vortices. The ciliated chambers are in open communication with the ampullae and with the spaces containing the otolith-bearing maculae. The analysis of the functional significance of the anatomical and ultrastructural findings will be described in a separate paper.

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Fluorocitrate Neural Dystrophy of the Guinea Pig Cochlea

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100115468 ◽

1975 ◽

Vol 33 ◽

pp. 368-369

Author(s):

G.J. Spector ◽

C.D. Carr ◽

I. Kaufman Arenberg ◽

R.H. Maisel

Keyword(s):

Hearing Loss ◽

Hair Cells ◽

Sodium Phosphate ◽

Sensory Cells ◽

Barium Salt ◽

Perfusion Medium ◽

Cochlear Hair Cells ◽

Neural Degeneration ◽

Sodium Phosphate Buffer ◽

Cochlear Neurons

All studies on primary neural degeneration in the cochlea have evaluated the end stages of degeneration or the indiscriminate destruction of both sensory cells and cochlear neurons. We have developed a model which selectively simulates the dystrophic changes denoting cochlear neural degeneration while sparing the cochlear hair cells. Such a model can be used to define more precisely the mechanism of presbycusis or the hearing loss in aging man.Twenty-two pigmented guinea pigs (200-250 gm) were perfused by the perilymphatic route as live preparations using fluorocitrate in various concentrations (15-250 ug/cc) and at different incubation times (5-150 minutes). The barium salt of DL fluorocitrate, (C6H4O7F)2Ba3, was reacted with 1.0N sulfuric acid to precipitate the barium as a sulfate. The perfusion medium was prepared, just prior to use, as follows: sodium phosphate buffer 0.2M, pH 7.4 = 9cc; fluorocitrate = 15-200 mg/cc; and sucrose = 0.2M.

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