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Takao Imai

Publications and source records attributed to Takao Imai.

17 recordsLinked to original sources
PubMed2006

Benign paroxysmal positional vertigo due to a simultaneous involvement of both horizontal and posterior semicircular canals.

From April 2001 to November 2003, we investigated 8 patients with benign paroxysmal positional vertigo (BPPV) that was suspected to simultaneously affect both the horizontal and posterior semicircular canals (HSCC and PSCC). These cases showed typical vertical-torsional nystagmus induced by the Dix-Hallpike maneuver, followed by a horizontal nystagmus. They also showed a direction-changing geotropic or apogeotropic positional nystagmus triggered by lateral head rotations in the supine position. Using the three-dimensional analysis of the positional nystagmus, the rotation axis of the positional nystagmus had a component perpendicular to the plane of PSCC and another component perpendicular to the plane of HSCC. All these findings suggest that BPPV in these patients was a combination of posterior and horizontal canal BPPV. The observation of a vertical-torsional positional nystagmus should prompt the specialist to perform not only the canalith repositioning procedure, but also to execute lateral head turns in the supine position.

Adult↗
PubMed2006

Natural history of benign paroxysmal positional vertigo and efficacy of Epley and Lempert maneuvers.

We assessed the efficacy of Epley maneuver in patients with posterior canal benign paroxysmal positional vertigo (P-BPPV) and Lempert maneuver in patients with horizontal canal BPPV (H-BPPV). In patients with P-BPPV, positional vertigo in patients treated by Epley maneuver was significantly resolved more quickly than that in untreated patients. But in patients with H-BPPV, there were no significant differences of time course in remission of positional vertigo between untreated patients and patients treated by Lempert maneuver. Among the untreated patients, the positional vertigo in patients with H-BPPV was significantly resolved more quickly than that in patients with P-BPPV. Epley maneuver was effective for the treatment of patients with P-BPPV, whereas the efficacy of Lempert maneuver for the treatment of patients with H-BPPV was limited. The natural courses in remission of positional vertigo in untreated patients with H-BPPV showed significantly faster resolution than that in patients with P-BPPV.

Adolescent↗
PubMed2006

Three-dimensional analysis of benign paroxysmal positional nystagmus in a patient with anterior semicircular canal variant.

OBJECTIVE: To show the positional nystagmus in a patient who had suffered from benign paroxysmal positional vertigo (BPPV) that was thought to be caused by involvement of the anterior semicircular canal (ASCC) (A-BPPV). STUDY DESIGN: Retrospective case report. SETTING: City hospital. PATIENT: The present study reports a rare case of A-BPPV in a 41-year-old woman. CASE REPORT: The patient is 41-year-old woman who developed a positional vertigo after playing volleyball on March 22, 2005 and consulted our hospital the next day. When left Dix-Hallpike maneuver was performed, she showed a positional nystagmus of which fast phase direction of the torsional component was clockwise while that of the vertical component was downward. We plotted the slow phase eye velocity of the positional nystagmus during the left Dix-Hallpike maneuver on three-dimensional coordinates that showed the axis of the positional nystagmus to be perpendicular to the plane of the right ASCC. CONCLUSION: These results suggested that the patient was suffering from A-BPPV.

Adult↗
PubMed2005

Hzf protein regulates dendritic localization and BDNF-induced translation of type 1 inositol 1,4,5-trisphosphate receptor mRNA.

The localization of certain mRNAs to dendrites and their local translation in synaptic regions are proposed to be involved in certain aspects of synaptic plasticity. A cis-acting element within the 3' untranslated region (3' UTR) of the targeted mRNAs, which is bound by a trans-acting RNA-binding protein, controls the dendritic mRNA localization. Here, we identified hematopoietic zinc finger (Hzf) as a trans-acting factor that regulates the dendritic mRNA localization of the type 1 inositol 1,4,5-trisphosphate receptor (IP(3)RI), a dendritically localized mRNA in cerebellar Purkinje cells, via binding to the 3' UTR. In Hzf-deficient mice, the dendritic localization of IP(3)RI mRNA and brain-derived neurotrophic factor-induced IP(3)RI protein synthesis in the cerebellum were impaired. These findings suggest that Hzf is an RNA-binding protein that controls the dendritic mRNA localization and activity-dependent translation of IP(3)RI, and may be involved in some aspects of synaptic plasticity.

3' Untranslated Regions↗
PubMed2005

Function of RNA-binding protein Musashi-1 in stem cells.

Musashi is an evolutionarily conserved family of RNA-binding proteins that is preferentially expressed in the nervous system. The first member of the Musashi family was identified in Drosophila. This protein plays an essential role in regulating the asymmetric cell division of ectodermal precursor cells known as sensory organ precursor cells through the translational regulation of target mRNA. In the CNS of Drosophila larvae, however, Musashi is expressed in proliferating neuroblasts and likely has a different function. Its probable mammalian homologue, Musashi-1, is a neural RNA-binding protein that is strongly expressed in fetal and adult neural stem cells (NSCs). Mammalian Musashi-1 augments Notch signaling through the translational repression of its target mRNA, m-Numb, thereby contributing to the self-renewal of NSCs. In addition to its functions in NSCs, the role of mammalian Musashi-1 protein in epithelial stem cells, including intestinal and mammary gland stem cells, is attracting increasing interest.

Animals↗
PubMed2005

Comparing the accuracy of video-oculography and the scleral search coil system in human eye movement analysis.

The measurement of eye movements in three dimensions is an important tool to investigate the human vestibular and oculomotor system. The primary methods for three dimensional eye movement measurement are the scleral search coil system (SSCS) and video-oculography (VOG). In the present study, we compare the accuracy of VOG with that of SSCS using an artificial eye. We then analyzed the Y (pitch) and Z (yaw) component of human eye movements during saccades, smooth pursuit and optokinetic nystagmus, and the X (roll) component of human eye movement during the torsional vestibulo-ocular reflex induced by rotation in normal subjects, using simultaneous VOG and SSCS measures. The coefficients of the linear relationship between the angle of a simulated eyeball and the angle measured by both VOG and SSCS was almost unity with y-intercepts close to zero for torsional (X), vertical (Y) and horizontal (Z) movements, indicating that the in vitro accuracy of VOG was similar to that of SSCS. The average difference between VOG and SSCS was 0.56 degrees , 0.78 degrees and 0.18 degrees for the X, Y and Z components of human eye movements, respectively. Both the in vitro and in vivo comparisons demonstrate that VOG has accuracy comparable to SSCS, and is a reliable method for measurement of three dimensions (3D) human eye movements.

Adult↗
PubMed2004

Dynamics of the vestibulo-ocular reflex in patients with the horizontal semicircular canal variant of benign paroxysmal positional vertigo.

OBJECTIVE: Two types of direction-changing positional nystagmus, the geotropic and apogeotropic variants, are observed in patients with the horizontal semicircular canal (HSCC) type of benign paroxysmal positional vertigo (H-BPPV). In this study, we assessed the dynamics of the vestibulo-ocular reflex (VOR) of the HSCC in patients with H-BPPV. MATERIAL AND METHODS: Patients were rotated about the earth-vertical axis at frequencies of 0.1, 0.3, 0.5, 0.7 and 1.0 Hz with a maximum angular velocity of 50 degrees/s. Eye movements were recorded on a video imaging system using an infrared charge-coupled device (CCD) camera, and our new technique for analyzing the rotation vector of eye movements in three dimensions was used. RESULTS: In the patients with geotropic positional nystagmus, there were no differences in VOR gain between rotation to the affected and unaffected sides at frequencies of 0.1-1.0 Hz. Although no differences in VOR gain at frequencies of 0.3-1.0 Hz were noticed in patients with apogeotropic positional nystagmus, the VOR gain at 0.1 Hz was significantly smaller on rotation to the affected compared to the unaffected side. CONCLUSION: The results indicate that cupulolithiasis in the HSCC affected the dynamics of the HSCC-ocular reflex at 0.1 Hz, but not at higher frequencies, and that canalolithiasis in the HSCC does not change the VOR gain of the HSCC at any frequency. It is suggested that cupulolithiasis causes transient impairment of HSCC function by means of its mechanical restriction of movements of the cupula.

Adult↗
PubMed2004

Vertical canal function in normal subjects and patients with benign paroxysmal positional vertigo.

OBJECTIVES: To assess the dynamics of the vertical semicircular canal (VSCC)-ocular reflex in normal subjects and then to compare their gain in VSCC-ocular reflex with that of patients with benign paroxysmal positional vertigo (BPPV). MATERIAL AND METHODS: Subjects were sinusoidally rotated around the earth-vertical axis with their head tilted 60 degrees backward and turned 45 degrees to the right or left side from the sagittal plane at frequencies of 0.1, 0.3, 0.5, 0.7 and 1.0 Hz with a maximum angular velocity of 50 degrees/s. Head rotation to the right side on the right anterior semicircular canal (SCC)-left posterior SCC plane or to the left side on the left anterior SCC-right posterior SCC plane stimulated the pair of VSCCs. Eye movements were recorded on a video imaging system with an infrared charge-coupled device camera, using our new technique for analyzing the rotation vector of eye movements in three dimensions. RESULTS: The mean gains in left posterior SCC-ocular reflex in normal subjects ranged from 0.44 at 0.1 Hz to 0.79 at 1.0 Hz, while the mean gains in right anterior SCC-ocular reflex ranged from 0.45 at 0.1 Hz to 0.73 at 1.0 Hz. The mean gains in right posterior SCC-ocular reflex in normal subjects ranged from 0.53 at 0.1 Hz to 0.89 at 1.0 Hz, while the mean gains in left anterior SCC-ocular reflex ranged from 0.53 at 0.1 Hz to 0.88 at 1.0 Hz. Thus, the gains in VSCC-ocular reflex did not differ among the four VSCCs in normal subjects. Similarly, vestibulo-ocular reflex (VOR) gains of the four VSCCs in patients with right- or left-sided BPPV were almost the same at all frequencies compared to those of normal subjects. CONCLUSION: In patients with BPPV, gains in VOR in the four VSCCs were not changed in comparison with those of normal subjects. It is suggested that the mass of free-floating otoconial debris associated with canalolithiasis was too small compared to that of the endolymph to change the canal dynamics.

Adult↗
PubMed2003

Origin of higher affinity to RNA of the N-terminal RNA-binding domain than that of the C-terminal one of a mouse neural protein, musashi1, as revealed by comparison of their structures, modes of interaction, surface electrostatic potentials, and backbone dynamics.

Musashi1 is an RNA-binding protein abundantly expressed in the developing mouse central nervous system. Its restricted expression in neural precursor cells suggests that it is involved in maintenance of the character of progenitor cells. Musashi1 contains two ribonucleoprotein-type RNA-binding domains (RBDs), RBD1 and RBD2, the affinity to RNA of RBD1 being much higher than that of RBD2. We previously reported the structure and mode of interaction with RNA of RBD2. Here, we have determined the structure and mode of interaction with RNA of RBD1. We have also analyzed the surface electrostatic potential and backbone dynamics of both RBDs. The two RBDs exhibit the same ribo-nucleoprotein-type fold and commonly make contact with RNA on the beta-sheet side. On the other hand, there is a remarkable difference in surface electrostatic potential, the beta-sheet of RBD1 being positively charged, which is favorable for binding negatively charged RNA, but that of RBD2 being almost neutral. There is also a difference in backbone dynamics, the central portion of the beta-sheet of RBD1 being flexible, but that of RBD2 not being flexible. The flexibility of RBD1 may be utilized in the recognition process to facilitate an induced fit. Thus, comparative studies have revealed the origin of the higher affinity of RBD1 than that of RBD2 and indicated that the affinity of an RBD to RNA is not governed by its fold alone but is also determined by its surface electrostatic potential and/or backbone dynamics. The biological role of RBD2 with lower affinity is also discussed.

Animals↗
PubMed2003

A new rotational test for vertical semicircular canal function.

OBJECTIVE: We developed a new rotating chair in order to assess the function of the vertical semicircular canal (VSCC) by analyzing VSCC-induced post-rotatory nystagmus (PRN). METHODS: We examined 14 healthy subjects, wearing goggles equipped with an infrared CCD camera, and sitting on a chair which was designed to stimulate a pair of the VSCCs by tilting the head 60 degrees backward with a 45 degrees rotation to the left or right side from the sagital plane. The time constant (TC) or maximal slow phase eye velocity (MSPEV) of the vertical component of four kinds of PRN were analyzed in four corresponding rotatory conditions, and used as functional index of the corresponding VSCC. RESULTS: The mean values of MSPEV in both anterior semicircular canal (ASCC) and posterior semicircular canal (PSCC)-induced PRN tended to be lower (P<0.10) than those induced by the lateral semicircular canal (LSCC). The result suggests that the threshold to the angular velocity in the VSCC is lower than that in the LSCC. The mean values of TC in both ASCC and PSCC-induced PRN were significantly lower (P<0.05) than those induced by the LSCC. CONCLUSION: The significant reduction of TC in VSCC-induced PRN compared with LSCC-induced PRN indicates that VSCC function is less affected by velocity storage mechanisms than LSCC function. The rotational test with respect to the VSCC can be used as a tool for assessing vertical canal function.

Adult↗
PubMed2002

Musashi: a translational regulator of cell fate.

Transcription is thought to have a major role in the regulation of cell fate; the importance of translational regulation in this process has been less certain. Recent findings demonstrate that translational regulation contributes to cell-fate specification. The evolutionarily conserved, neural RNA-binding protein Musashi, for example, controls neural cell fate. The protein functions in maintenance of the stem-cell state, differentiation, and tumorigenesis by repressing translation of particular mRNAs. In mammals it might play an important role in activating Notch signalling by repressing translation of the Notch inhibitor m-Numb.

Animals↗
PubMed2002

Regulation of tau RNA maturation by thyroid hormone is mediated by the neural RNA-binding protein musashi-1.

The tau gene encodes a microtubule-associated protein expressed by neuronal and glial cells. Abnormal deposits of Tau protein are characteristic of several neurodegenerative disorders. Additionally, mutations affecting tau pre-mRNA alternative splicing of exon 10 are associated with frontotemporal dementia and Parkinsonism linked to chromosome 17. In rodents, this process is developmentally regulated by thyroid hormone (T3) causing the predominance of exon 10-containing transcripts. Here we demonstrate that musashi-1 (msi-1) gene is induced by T3 during rat brain development and in N2a cells. T3 increases msi-1 mRNA level in an actinomycin D-sensitive, cycloheximide-resistant fashion without affecting its half-life, which suggests a transcriptional effect. Both ectopic Msi-1 expression and T3 treatment increased the proportion of exon 10-containing tau transcripts. Furthermore, antisense msi-1 expression inhibited T3 action. Our results show that msi-1 mediates the posttranscriptional regulation of tau expression by T3.

Animals↗
PubMed2002

Effects of caloric vestibular stimulation on head and trunk movements during walking.

The effects of vestibular stimulation on head and trunk movements were investigated during human walking (4.0 km/h). Vestibular stimulation was produced by irrigating an external auditory meatus with 4 degrees C ice water for 10 s. Using a 3-D motion analysis system, the linear (medial/lateral and vertical) translations and angular (yaw, pitch and roll) rotations were determined at the head, thorax, pelvis, knee, and foot. After caloric stimulation, waking trajectory deviated toward the stimulated side during dizziness. In addition, the amplitude of medial/lateral (M/L) linear translation and yaw rotation were significantly increased by caloric stimulation, especially at the head and thorax, whereas changes in vertical translation and pitch and roll rotations were not significant. The compensatory coordination (i.e., the yaw rotation to oppose the M/L linear translation) of the head was precisely maintained both before and after caloric stimulations, but it was decreased at the thorax and pelvis after stimulation. Our results suggested that vestibular sensory information, probably via the horizontal semicircular canals, contributes predominantly to the regulation of dynamic head and trunk movements in the M/L direction.

Adult↗
PubMed2002

Three-dimensional analysis of human locomotion in normal subjects and patients with vestibular deficiency.

The purpose of this study was to clarify the role of the vestibular system in human locomotion. The subjects were nine healthy controls, nine patients with unilateral vestibular deficiency (UVD) and nine patients with bilateral vestibular deficiency (BVD). The UVD subjects were Ménière's disease patients who were being treated with administration of gentamicin into the tympanic cavity. BVD subjects were hearing-impaired individuals who showed no response to the ice-water caloric test. A total of 13 markers were attached to the head, trunk (C7), hip and foot in order to measure translational and rotational motions with the aid of a video image processing system. All subjects were instructed to restrict their stride length to approximately 80 cm while walking on a treadmill and watching a visual target. However, walking speed varied depending on the ability of the subject to maintain body equilibrium. The results showed that walking speed and step frequency were significantly lower for the UVD and BVD groups than for the normal group. Analysis of head movements in the sagittal plane showed a counteracting motion between pitch rotations and vertical translation as previously reported. We also found head counteracting motions between yaw rotation and lateral translation in the horizontal plane. These mechanisms are thought to help stabilize the gaze during walking. When the head fixation point was calculated by projecting the naso-occipital axis line during walking, the head counteracting motion was found to assist the vestibulo-ocular reflex in stabilizing the gaze. In addition, normal subjects seemed to use head stabilization as a space strategy in order to minimize head yaw movement. In contrast, UVD and BVD subjects adopted head stabilization as a trunk strategy.

Case-Control Studies↗
PubMedDate not supplied

Three-dimensional eye rotation axis analysis of benign paroxysmal positioning nystagmus.

We have developed a new technique for analyzing the rotation vector of eye movement with an infrared CCD camera [Imai et al.: Acta Otolaryngol 1999;119:24-28]. We used this technique to analyze the eye rotation axis of benign paroxysmal positioning nystagmus (BPPN) that was induced by the Dix-Hallpike maneuver in 14 patients with benign paroxysmal positioning vertigo (BPPV). Eye rotation axes of BPPN in 8 patients were closely perpendicular to the posterior canal of the undermost ear in the provocative head position. Under the hypothesis that BPPN is due to a mechanical stimulation of the posterior canal by canalolithiasis, this finding suggested that the posterior canal of the undermost ear is the lesion. On the other hand, eye rotation axes of BPPN in the other 6 patients were closely aligned with the naso-occipital axis. It is suggested that canalolithiasis induces endolymphatic flow in both posterior and anterior canals via the common crus and the summation of the eye movements induced by stimulation of both the posterior and anterior canals rotates the eye along the naso-occipital axis.

Adult↗
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↗