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At least 613 records · Page 34Linked to original sources
PubMed1998

Histaminergic influence on vestibular stimulation-induced locus coeruleus inhibition in rats.

In previous reports we have shown that caloric stimulation (CS) of the vestibular apparatus inhibits locus coeruleus (LC)-noradrenergic neuronal activity in urethane-anaesthetized rats. The present study examined the effect of neural histamine depletion by alpha-fluoromethylhistidine (alpha-FMH) on CS-induced LC inhibition. In alpha-FMH treated rats, LC neuronal inhibition caused by CS was still observed. This finding indicates that the central histaminergic neuron system does not participate in the CS-induced LC-noradrenergic inhibition. It is suggested that the noradrenergic neuron system is involved in the development of vestibulo-autonomic response, independent of the histaminergic neuron system.

Animals↗
PubMed1989

[Mechanisms of development of the dome in the semicircular canals of birds. I. Cellular secretion].

A study of the crista ampullaris of the vestibular apparatus was carried out in chicken embryos. The study group included embryos between stages 24 and 39 of Hamburger-Hamilton. This study elucidates the relationship of the cupula with respect to the epithelium of the crista ampullaris. With electron microscopic examination, the rough endoplasmic reticulum of the crista epithelial sustentacular cells at developmental stage of 31 H-H, demonstrated dilatations containing secretory material. Vesicles, with adhering ribosomes appear to be formed from these dilatations. At later stages of development, the vesicular material took on the characteristics of the fibrillary material composing the cupula. In some cells, secretory vesicles are seen near the apical border of these cells, where they apparently secrete vesicular contents into the endolymphatic space, contributing to the formation of the cupula.

Animals↗
PubMed2007

Dan is required for normal morphogenesis and patterning in the developing chick inner ear.

During vertebrate inner ear development, compartmentalization of the auditory and vestibular apparatuses along two axes depends on the patterning of transcription factors expressed in a region-specific manner. Although most of the patterning is regulated by extrinsic signals, it is not known how Nkx5.1 and Msx1 are patterned. We focus on Dan, the founding member of the Cerberus/Dan gene family that encodes BMP antagonists, and describe its function in morphogenesis and patterning. First, we confirmed that Dan is expressed in the dorso-medial region of the otic vesicle that corresponds to the presumptive endolymphatic duct and sac (ed/es). Second, we used siRNA knockdown to demonstrate that depletion of Dan induced both a severe reduction in the size of the ed/es and moderate deformities of the semicircular canals and cochlear duct. Depletion of Dan also caused suppression of Nkx5.1 in the dorso-lateral region, suppression of Msx1 in the dorso-medial region, and ectopic induction of Nkx5.1 and Msx1 in the ventro-medial region. Most of these phenotypes also appeared following misexpression of the constitutively active form of BMP receptor type Ib. Thus, Dan is required for the normal morphogenesis of the inner ear and, by inhibiting BMP signaling, for the patterning of the transcription factors Nkx5.1 and Msx1.

Animals↗
PubMed2001

Development of the vertebrate inner ear.

The inner ear, also called the membranous labyrinth, contains the cochlea, which is responsible for the sense of hearing, and the vestibular apparatus, which is necessary for the sense of balance and gravity. The inner ear arises in the embryo from placodes, which are epithelial thickenings of the cranial ectoderm symmetrically located on either side of hindbrain rhombomeres 5 and 6. Placode formation in mice is first visible at the 12-somite stage and is controlled by surrounding tissues, the paraxial mesoderm and neural ectoderm. Diffusible molecules such as growth factors play an important role in this process. The activity of several genes confers the identity to the placodal cells. Subsequent cellular proliferation processes under influences from the adjacent hindbrain cause the inner ear epithelium to invaginate and form a vesicle called the otocyst. Combinatorial expression of several genes and diffusible factors secreted from the vesicle epithelium and hindbrain control specification of distinct inner ear compartments. Transplantation studies and inner ear in vitro cultures show that each of these compartments is already committed to develop unique inner ear structures. Later developmental periods are principally characterized by intrinsic differentiation processes. In particular, sensory patches differentiate into fully functional sensory epithelia, and the semicircular canals along with the cochlear duct are elaborated and ossified.

Animals↗
PubMed2003

Direct interaction of serotonin type 3 receptor ligands with recombinant and native alpha 9 alpha 10-containing nicotinic cholinergic receptors.

In the present work, we characterized the effects of serotonin type 3 receptor ligands on recombinant and native alpha 9 alpha 10-containing nicotinic acetylcholine receptors (nAChRs). Our results indicate that the recombinant alpha 9 alpha 10 nAChR shares striking pharmacological properties with 5-HT(3) ligand-gated ion channels. Thus, 5-HT(3) receptor antagonists block ACh-evoked currents in alpha 9 alpha 10-injected Xenopus laevis oocytes with a rank order of potency of tropisetron (IC(50), 70.1 +/- 0.9 nM) > ondansetron (IC(50), 0.6 +/- 0.1 microM) = MDL 72222 (IC(50), 0.7 +/- 0.1 microM). Although serotonin does not elicit responses in alpha 9 alpha 10-injected oocytes, it blocks recombinant alpha 9 alpha 10 receptors in a noncompetitive and voltage-dependent manner (IC(50), 5.4 +/- 0.6 microM). On the other hand, we demonstrate an in vivo correlate of these properties of the recombinant receptor, with those of the alpha 9 alpha 10-containing nAChR of frog saccular hair cells. The possibility that the biogenic amine serotonin might act as a neuromodulator of the cholinergic efferent transmission in the vestibular apparatus and in the organ of Corti is discussed.

Animals↗
PubMed1975

Ocular motor dysfunction in total and hemicerebellectomized monkeys.

Studies of ocular motor function in monkeys undergoing either total or hemicerebellectomies has revealed the following abnormalities which can be attributed to cerebellar dysfunction: 1. Loss of smooth pursuit movements 2. Gaze-fixation nystagmus 3. Loss of inhibitory input on the vestibular apparatus reflected in a decreased latency and prolonged response to caloric stimuli. It is intimated that the role of the hemicerebellum deals with ipsilateral tone and its effect on eye movements.

Animals↗
PubMed1981

Trampoline training injuries--one hundred and ninety-five cases.

In 198 people 201 trampoline injuries are analysed. All except three adults were re-examined, following an observation period of one to four years. School children (145) represented the major part of the 195 persons re-examined. Handling the large trampoline injured 21 of the 145 school children and six children at clubs. Injuries of a permanent nature were found in 49 of the 195 who were re-examined. The biomechanics and physiology of trampoline jumping is evaluated. Mismatch of a multitude of sensory impulses (visual, tactile, others) with impulses from the vestibular apparatus converging towards the orientation centres of the brain, may result in disorientation and then in the inadequate motor reactions actually seen at the time of the trampoline accidents. A G-induced split second loss of consciousness is another possible explanation of the trampoline accident. More secure procedures than trampolining as a school-sport and recreational activity are recommended.

Adolescent↗
PubMed2003

Vestibular activation by bone conducted sound.

OBJECTIVE: To examine the properties and potential clinical uses of myogenic potentials to bone conducted sound. METHODS: Myogenic potentials were recorded from normal volunteers, using bone conducted tone bursts of 7 ms duration and 250-2000 Hz frequencies delivered over the mastoid processes by a B 71 clinical bone vibrator. Biphasic positive-negative (p1n1) responses were recorded from both sternocleidomastoid (SCM) muscles using averaged unrectified EMG. The best location for stimulus delivery, optimum stimulus frequency, stimulus thresholds, and the effect of aging on evoked response amplitudes and thresholds were systematically examined. Subjects with specific lesions were studied. Vestibular evoked myogenic potentials (VEMP) to air conducted 0.1 ms clicks, 7 ms/250-2000 Hz tones, and forehead taps were measured for comparison. RESULTS: Bone conducted sound evoked short latency p1n1 responses in both SCM muscles. Ipsilateral responses occurred earlier and were usually larger. Mean (SD) p1 and n1 latencies were 13.6 (1.8) and 22.3 (1.2) ms ipsilaterally and 14.9 (2.1) and 23.7 (2.7) ms contralaterally. Stimuli of 250 Hz delivered over the mastoid process, posterosuperior to the external acoustic meatus, yielded the largest amplitude responses. Like VEMP in response to air conducted clicks and tones, p1n1 responses were absent ipsilaterally in subjects with selective vestibular neurectomy and preserved in those with severe sensorineural hearing loss. However, p1n1 responses were preserved in conductive hearing loss, whereas VEMP to air conducted sound were abolished or attenuated. Bone conducted response thresholds were 97.5 (3.9) dB SPL/30.5 dB HL, significantly lower than thresholds to air conducted clicks (131.7 (4.9) dB SPL/86.7 dB HL) and tones (114.0 (5.3) dB SPL/106 dB HL). CONCLUSIONS: Bone conducted sound evokes p1n1 responses (bone conducted VEMP) which are a useful measure of vestibular function, especially in the presence of conductive hearing loss. For a given perceptual intensity, bone conducted sound activates the vestibular apparatus more effectively than air conducted sound.

Adult↗
PubMed1995

Medical examinations for pilots.

High altitude is an environment that is alien to man. Stressors associated with the mechanics of flight include motion and acceleration forces applied in three vectors and in degrees that are foreign to the human vestibular apparatus. Furthermore, the work patterns of a pilot can interfere with lifestyle and circadian rhythms. Therefore medical fitness is an important consideration in determining an individual's suitability to exercise a pilot's licence. The medical standards applied depend on the type of aircraft flown and the duties expected of a pilot. There are three broad categories of pilot. In ascending order of stringency of medical standards these are the private pilot, the professional pilot and the military pilot.

Aerospace Medicine↗
PubMed1984

Effects of deuterium oxide and galvanic vestibular stimulation on visual cortical cell function.

/he spontaneous and evoked unit activities of complex visual cortical cells were recorded from Brodmann's area 18 in immobilized, unanesthetized cats before, during, and after stimulation of the vestibular system. The vestibular system was stimulated by intravenous injection of deuterium oxide (D2O)--a noted nystagmogenic agent (14)--or by direct galvanic stimulation of the labyrinth. Measures of the receptive-field areas, poststimulus time histograms, directional preferences, and the optimal speed of the light bar stimulating the cell were obtained before and after the application of D2O. Directional preferences were determined in a novel manner, using a method derived from a hierarchical clustering technique (19). Data were collected and analyzed from a) visual cortical cells in cats with intact labyrinths, b) visual cortical cells in cats following bilateral labrinthectomies, and c) nonvisual cortical cells in cats with intact labyrinths. In cats with intact labyrinths, D2O changed the optimal length of the light bar that was able to stimulate the cortical cell as well as the path on which it evoked the response of the cell. Both values, which constitute the receptive field of the cell, changed approximately proportionately. This effect usually lasts for less than 4.5 h. The other cellular characteristics were also altered by the D2O. Galvanic stimulation of the labyrinth resembles, in its effects, the injection of D2O. In labyrinth-intact cats, the time course of area 18 spontaneous activity dramatically increased 30 min or more after D2O was administered. It peaked 2-3 h later and still had not returned to preinjection levels even 7 h after the D2O administration. In bilaterally labyrinthectomized cats, the spontaneous activity of the visual cells (and the other cellular characteristics studied) did not change following D2O administration. In nonvisual cells from labyrinth-intact cats, the spontaneous activity demonstrated a slight but significant decrease over time after D2O injection. (The other measures, however, did not change.) In pilot studies (about 2 wk prior to the electrophysiological experiments), the cats were injected with D2O. Within 8-10 min afterward, signs of positional nystagmus commenced; and within 30 min, problems in maintaining balance were noted. This continued for 7-8 h before disappearing. In the labyrinthectomized animals, such effects were not observed. These results, therefore, add support to other evidence that suggests that D2O works directly through the vestibular apparatus to produce the effects it does (and not through interference with certain cellular processes).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1977

Vestibulotixoci effect of alkylating agents.

The vestibular sensory epithelia from 3 patients treated with cytotoxic drugs were studied with a surface specimen technique, 2 cases had been treated with cyclophosphamide and 1 with melphalan. In all 3 cases there was some slight degeneration affecting the cristae ampullares. The macula utriculi showed no signs of degeneration. The degeneration affecting the cristae is probably too slight to produce any serious symptoms from the vestibular apparatus.

Adult↗
PubMed1985

Impairment of the chick's grip and balance by streptomycin. A preliminary study.

Chicks were injected daily with streptomycin (400 or 1,200 mg/kg). Damage to the vestibular apparatus was accompanied by steadily impaired abilities of chicks to tighten their grips as evidenced by reduced torque and by slippage of their feet on the perch. As compensation, intoxicated chicks adjusted their footing with cautious, deliberate movements. They always stood erectly and stiffly on the perch; they were unable to roost. They also experienced difficulties in balancing. While symptoms were qualitatively similar at both dosages, their onset came earlier and with greater severity at 1,200 mg/kg. Control chicks steadily increased their torque and displayed normal balance during the course of the experiment.

Animals↗
PubMed1988

Pica as an index of motion sickness in rats.

Rats eat kaolin after treatment with poisons or rotation. Thus, eating of nonnutritive substances such as kaolin, so-called pica, is an illness-response behavior of rats analogous to vomiting in humans. For use of rotation-induced pica as a behavioral index of motion sickness in rats we examined what kind of rotation was effective for inducing pica in rats and whether the vestibular apparatus was necessary for its induction. Rats ate much kaolin after double rotation with continuously changing centrifugal and angular accelerations, but little after single rotation with no accelerative changes. However, even double rotation failed to induce pica in bilaterally labyrinthectomized rats. Thus, rotation-induced pica in rats was induced in the same way as motion sickness in humans, suggesting that it resulted from motion sickness in rats. We conclude that pica can be used as a behavioral index of motion sickness in rats.

Animals↗
PubMedDate not supplied

Organ culture of the mammalian and avian embryo otocyst.

The use of a chemically defined medium supplemented with serum has proved most suitable for the growth of the isolated embryonic otocyst in vitro. Complete differentiation of the cochlear duct and of the vestibular apparatus ensued and is described. The system is reliable for organ cultures of both the avian and mammalian otocyst and for the study of various lesions affecting the inner ear and middle ear.

Animals↗