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Results for “VESTIBULAR APPARATUS”

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At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

[Vestibular apparatus study of the toad, Xenopus laevis, and rats under prolonged weightlessness].

Fertilized eggs of the clawed toad Xenopus laevis were placed aboard of orbital laboratory of "Salut-6" spacecraft where they developed for 20 days at temperature 15 degrees C. The larvae were fixed in weightlessness. Light and electronmicroscopic studies revealed undisturbed structure on the saccular and utricular maculae and otolith membranes. Some ultrastructural abnormalities were found in the inner ear of adult rats after 20 days of weightlessness ("Kosmos-936").

Animals↗
PubMedDate not supplied

[Reaction of the human vestibular apparatus to periodic effects of the ship-rocking type].

Reactions of the semicircular canals to periodic effects of the ship rolling type have been studied, using a mathematical model. The data obtained give evidence that during the above effects linear combinations of reactions of all semicircular canals may describe changes in the angular velocity of man's movement in an absolute (static) space. Besides, the common segment of the vertical semicircular canals (the common limb) allows a more accurate description of time changes in angular velocity. The mathematical model has demonstrated the dependence of absolute angular velocity as approximated by the semicircular canals from head orientation as related to the body. In addition to general discussions about rolling effects on the semicircular canals, the paper presents calculations of such reactions as applied to a specific object, i. e. a medium-size trawler.

Biomechanical Phenomena↗
PubMedDate not supplied

Auditory and temporal bone abnormalities in CHARGE association.

CHARGE association is a recently described cluster of congenital defects including ocular coloboma, heart disease, choanal atresia, retarded development and/or CNS abnormalities, genital hypoplasia, and ear anomalies. Although congenital hearing loss has been reported in CHARGE association, no information regarding the underlying temporal bone disease is available in the literature to date. The authors evaluated four patients with multiple anomalies consistent with CHARGE syndrome. Two surviving patients have bilateral severe hearing loss on auditory brain stem response testing. Two patients did not survive, and their temporal bones were obtained at autopsy for histologic examination. All four temporal bones showed severe middle ear defects including ossicular deformities, absence of the stapedius muscle, absence of the oval window, aberrant course of the facial nerve, and dehiscence of the facial nerve canal. In the more severely affected case, a Mondini-type malformation of the cochlea was present, together with multiple anomalies of the vestibular apparatus. Vestibular defects also occurred in the other case; however, the cochleae were found to be normally developed.

Abnormalities, Multiple↗
PubMed1981

The immotile-cilia syndrome. Functional and ultrastructural alterations.

Literature was critically reviewed on the grounds of the ultrastructural and clinical observations made on three subjects carriers of Kartagener's syndrome. The relationship between the various ultrastructural aspects (lack of dynein arms and casual orientation of the central microtubular doublet) and the clinical evidence elicited in all the sites lined with ciliated epithelia (auditory apparatus, vestibular apparatus, genital organs and central nervous system). Attribution of the genesis of situs viscerum inversus to lack of ciliar motion was brought up for discussion again.

Adolescent↗
PubMed1974

The role of gravity in the phylogeny of structure and function in animal sensors of spatial orientation, and their predicted action in weightlessness.

The evolution of the structural, functional and cytochemical organization of the gravity receptor which determines a body position in the gravitational field of the earth by means of muscular regulation was traced both invertebrates and vertebrates, using electron microscopic and histochemical methods. In the course of evolution of vertebrates, the specialized gravity receptor-statocyst which, as a rule, consists of primary sensory cells and supplies otoliths, is formed. In vertebrates, there exists a vestibular apparatus made up of secondary sensory cells and also having otoliths. The receptor cells, both of statocysts and the vestibular apparatus, are supplied with special antennas (kinocilia and stereocilia). Deviation of the antennas stimulated by displacement of the otoliths resulting from locomotor activity of animals leads to excitation of the receptor cells. When exposed to a modified gravitational field (linear accelerations of 10 g, for 3 min), the receptor cells of the vestibular apparatus, in all classes of vertebrates, show progressive changes in RNA content and protein synthesis (increase followed by decrease) which return to normal only after 12 days. Thus, immediate transfer of animals and man from acceleration to weightlessness appears to be a reason for movement disease. The above consideration showed the need for an experiment in which an animal (with its vestibular apparatus) which had not undergone previous accelerations, would be exposed to weightlessness. Frog embryos, Rana temporaria, at the stage preceding the organogenesis, when the vestibular apparatus and other organs were lacking, were chosen as a suitable subject. Frog embryos at the stage of an early gastrula were placed in a special container Emkon aboard the Soyuz 10 spacecraft. After short accelerations, they were exposed to weightlessness for 44 hours. The embryos were allowed to continue to develop to the stage of early tail bud. The experimental embryos showed normally developed acoustic vesicles and vestibular ganglia. Clear differentiation of the receptor cells with antennas (kinocilia and stereocilia) was found in the acoustic vesicles. Thus, in weightlessness, vestibular apparatus develops just as well as in the gravitational field of the earth. However, only a much longer stay in weightlessness conditions will indicate whether there are any changes in the structural, cytochemical and functional organization of vestibular apparatus. The similarity in the structural, functional and cytochemical organization of the gravity receptor in vertebrates and invertebrates appears to allow the prediction of the behaviour of the gravity receptor as a whole, and of its receptor elements, both in normal and changed gravitational fields. The first attempts were carried out only on the vestibular apparatus of vertebrates.

Acetylcholinesterase↗