Biomedical subjects

Arata Horii

Publications and source records attributed to Arata Horii.

27 records · Page 2Linked to original sources

PubMed2003

Long-term effects of permanent vestibular lesions on hippocampal spatial firing.

The hippocampus is thought to be important for spatial representation processes that depend on the integration of both self-movement and allocentric cues. The vestibular system is a particularly important source of self-movement information that may contribute to this spatial representation. To test the hypothesis that the vestibular system provides self-movement information to the hippocampus, rats were given either a bilateral labyrinthectomy (n = 6) or a sham surgery (n = 6), and at least 60 d after surgery hippocampal CA1 neurons were recorded extracellularly while the animals foraged freely in an open arena. Recorded cells were classified as complex spiking (n = 80) or noncomplex spiking (n = 33) neurons, and their spatial firing fields (place fields) were examined. The most striking effect of the lesion was that it appeared to completely abolish location-related firing. The results of this and previous studies provide converging evidence demonstrating that vestibular information is processed by the hippocampus. The disruption of the vestibular input to the hippocampus may interfere with the reconciliation of internal self-movement signals with the changes to the external sensory inputs that occur as a result of that movement. This would disrupt the ability of the animal to integrate allocentric and egocentric information into a coherent representation of space.

Analysis of Variance↗

PubMed2003

Steroid effects on vestibular compensation in human.

Vestibular neuritis (VN) rapidly damages unilateral vestibular periphery, inducing severe balance disorders. In most cases, such vestibular imbalance is gradually restored to within the normal level after clinical therapies. This successive clinical recovery occurs due to regeneration of vestibular periphery and/or accomplishment of central vestibular compensation. We experienced 36 patients with VN treated at our hospital, including cases in our previous preliminary report. To elucidate effects of steroid therapy both on the recovery of peripheral function and on the adaptation of central vestibular compensation, we examined caloric test and several questionnaires with two randomly divided groups, 18 steroid-treated and 18 nonsteroid-treated patients, over two years after the onset. These examinations revealed that steroid-treated patients had a tendency of better canal improvements (13/18, 72%) than nonsteroid-treated ones (10/18, 55.6%). However, there was no significant difference between these two groups. In cases with persistent canal paresis, steroid-treated patients (n = 5) reduced handicaps in their everyday life due to the dizziness induced by head and/or body movements and the disturbance of their mood, more effectively than those with nonsteroid therapy (n = 8). These findings suggest that steroid therapy with VN could be effective on not only vestibular periphery but central vestibular system, to restore the balance.

Activities of Daily Living↗

PubMed2003

Magnetic resonance imaging of pleomorphic adenoma arising from the external auditory canal.

Pleomorphic adenoma arising from the external auditory canal is a very rare neoplasm, and there has been no report on magnetic resonance (MR) imaging of pleomorphic adenoma of the external auditory canal. We report here a case of 65-year-old male with this tumour, measuring 12 mm in a diameter. Histopathology was confirmed from the specimen obtained at the surgical excision. MR revealed that the tumour had a well-defined margin showing hypointensity on T1-weighted images and hyperintensity on T2-weighted images relative to the parotid gland. The tumour was well enhanced by contrast material. No invasion to the surrounding tissue was observed. These MR findings were compatible with pleomorphic adenoma of the salivary gland origin. In treating pleomorphic adenoma of the external auditory canal, complete surgical excision is essential for the prevention of recurrence. It can be concluded that MR imaging is helpful for making a differential diagnosis of external auditory canal tumours and selection of adequate treatment.

Adenoma, Pleomorphic↗

PubMed2003

Bilateral peripheral vestibular lesions produce long-term changes in spatial learning in the rat.

In order to investigate whether bilateral peripheral vestibular lesions cause long-term impairment of spatial learning, rats were tested in a reference memory radial arm maze learning task at least 5 weeks following a bilateral labyrinthectomy (BL) or sham control lesion. All control rats reached criterion (i.e., 1 error or less, averaged across 7 trials for 3 consecutive days of training) but only 4 of the 8 BL rats had reached criterion by day 21 of the training sessions. The control rats reached criterion more quickly than the lesioned rats (Control, 7.0 +/- 0.63 days, Lesioned, 15.8 +/- 1.4 days, t10= 5.84, p < 0.0001). This difference resulted from the greater number of errors made by the BL animals. However, the latency to respond was comparable as a result of the increased locomotor activity of the BL group (i.e., 'hyperkinesis), and the overall rate of acquisition of the task, as indicated by analysis of the exponential decrease in errors over the entire training period, was not significantly different between the 2 groups. The results of this study demonstrate that BL in rats produces long-term changes in performance in a spatial reference memory task, which are not simply due to the inability to move but may relate to the way that the brain uses vestibular information to create spatial representations and determines behavioural strategies on the basis of these representations.

Animals↗

PubMed2002

Application of real-time quantitative polymerase chain reaction to quantification of glutamate receptor gene expression in the vestibular brainstem and cerebellum.

Reverse transcription-polymerase chain reaction (RT-PCR) is a powerful tool to detect specific gene expression from a small amount of tissue, which is superior to the traditional RNA assays such as Northern blotting and in situ hybridization (ISH) in terms of sensitivity. However, conventional RT-PCR is not suitable for quantification due to its exponential nature. Recently, a real-time quantitative PCR method has been developed to overcome the weak points of RT-PCR, e.g. quantification. Here we describe the use of real-time quantitative PCR using a fluorescent TaqMan probe, to study the regional differences in expression of glutamate receptor subunit/subtype genes (NR1, NR2A, GluR2, KA2, mGluR1, mGluR7) in the central vestibular system including the vestibular nucleus complex, inferior olive and cerebellar flocculus. We found that real-time quantitative PCR yielded similar results to other techniques such as ISH but offered several advantages in terms of relative speed and ability to detect low levels of gene expression. We suggest that real-time quantitative PCR is a useful method to study gene expression for other neurotransmitter receptors in the vestibular brainstem and cerebellum, and is also expected to be more accurate to assess the changes in gene expression following any treatment.

Animals↗

PubMed2002

Quantitative changes in mRNA expression of glutamate receptors in the rat peripheral and central vestibular systems following hypergravity.

In order to investigate the mechanisms responsible for adaptation to altered gravity, we assessed the changes in mRNA expression of glutamate receptors in vestibular ganglion cells, medial vestibular nucleus, spinal vestibular nucleus/lateral vestibular nucleus, cerebellar flocculus, and uvula/nodulus from rats exposed to hypergravity for 2 h to 1 week using real-time quantitative RT-PCR methods. The mRNA expression of GluR2 and NR1 receptors in the uvula/nodulus and NR1 receptors in the medial vestibular nucleus increased in animals exposed to 2 h of hypergravity, and it decreased gradually to the control level. The mRNA expression of GluR2 receptors in vestibular ganglion cells decreased in animals exposed to 1 week of hypergravity. Neither the metabotropic glutamate receptor 1 nor delta2 glutamate receptor in flocculus and uvula/nodulus was affected by a hypergravity load for 2 h to 1 week. It is suggested that the animals adapted to the hypergravity by enhancing the cerebellar inhibition of the vestibular nucleus neurons through activation of the NR1 and GluR2 receptors on the Purkinje cells in uvula/nodulus especially at the early phase following hypergravity. In the later phase following hypergravity, the animals adapted to the hypergravity by reducing the neurotransmission between the vestibular hair cells and the primary vestibular neurons via down-regulation of the postsynaptic GluR2 receptors in the vestibular periphery.

Animals↗

PubMed2002

Changes in fos expression in the rat brainstem after bilateral labyrinthectomy.

In order to elucidate the role of the vestibulocerebellar neural circuits during two-stage bilateral labyrinthectomy (BL) we examined Fos-like immunoreactive (-LIR) neurons as a marker of neural activation in the rat brainstem after BL and the projections of these neurons into the vestibulocerebellum using retrograde tracing and immunohistochemical techniques. Simultaneous BL did not show any Fos expression in the medial vestibular nucleus (MVe). However, with an interval of > 6 h between the two stages of BL, Fos-LIR neurons were induced in the ipsilateral (ipsi-) MVe of the side operated on second, partially projecting into the ipsi-vestibulocerebellum. A previous study demonstrated that some of the unilateral labyrinthectomy-induced Fos-LIR neurons in the ipsi-MVe projected into the ipsi-vestibulocerebellum and inhibited the contra-MVe neurons, resulting in the restoration of the right-left balance. Taken together with our present data, it is suggested that some of the labyrinthectomy-induced Fos expression in the ipsi-MVe is representative of a switch-on signal for the vestibulo-cerebello-vestibular inhibitory neural circuits, which remain turned off after symmetrical lesions such as simultaneous BL but are turned on after severe asymmetrical lesions in order to restore the balance.

Adaptation, Physiological↗

PubMed2002

[Changes in plasma inner ear hormones after endolymphatic sac drainage and steroid-instillation surgery (EDSS)].

We treated 33 cases of intractable Meniere's disease with endolymphatic sac drainage and steroid-instillation surgery (EDSS), attaining good long-term results in vertigo and hearing. To elucidate how EDSS affects the diseased inner ear, we examined changes in plasma inner ear hormones after EDSS. Among inner ear hormones, plasma vasopressin was significantly decreased after EDSS compared to after mastoidectomy. In cases with good long-term results in vertigo and hearing, postoperative plasma vasopressin remained lower over the long term than in cases with poor results. In cases with negative glycerol test results one year after surgery, postoperative plasma vasopressin also remained significantly lower over the long term than in cases with positive results. Previous studies reported that vestibular neurons projected into hypothalamic supraoptic and paraventricular nuclei and that changes in the inner ear pressure were related to plasma vasopressin. Taken together with present findings, this suggests that EDSS may reduce plasma vasopressin through modification of the diseased inner ear environment, resulting in improved inner ear function.

Aldosterone↗

PubMedDate not supplied

Horizontal canal type BPPV: bilaterally affected case treated with canal plugging and Lempert's maneuver.

A 54-year-old woman complained of positional vertigo. During 3 months' observation, the patient showed mostly geotropic or apogeotropic nystagmus due to right canalolithiasis or cupulolithiasis, however, she sometimes showed nystagmus which suggested left horizontal canalolithiasis. We suspected that she suffered from bilateral horizontal canal type benign paroxysmal positional vertigo (BPPV) and performed Lempert's maneuver for both directions, however, they were ineffective. She underwent canal plugging for right horizontal canal. After surgery she showed no positional nystagmus of right horizontal canal origin. However, apogeotropic nystagmus of the left horizontal canal origin was still observed. This nystagmus changed to geotropic nystagmus and finally disappeared following Lempert's maneuver for the left side. Bilateral horizontal canal BPPV is difficult to be resolved, probably because physical treatment for one side would move debris to the cupula in the other canal. Canal plugging combined with Lempert's maneuver to the other side is one treatment option for intractable bilateral horizontal canal BPPV.

Electronystagmography↗