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Biomedical subjects

K Kaga

Publications and source records attributed to K Kaga.

At least 19 recordsLinked to original sources
PubMed2003

Myelin-deficiency in the cochlear nerve of the 'bt' mutant hamster.

In a previous report, we showed abnormal auditory evoked potentials in the mutant hamster, 'black tremor (bt)', with significantly prolonged wave latencies of auditory brainstem responses and prolonged N1 latencies of compound action potentials, but normal cochlear microphonics. In this report, we present the results of morphological studies supporting the results of our electrophysiological studies of the auditory pathway in bt. Observation by transmission electron microscopy revealed an abnormal myelin sheath surrounding the spiral ganglion cells, and a thinner compact myelin sheath surrounding the axons in bt than in normal hamsters. The bt hamster has a myelin deficiency not only in the brainstem, but also in the cochlear nerve.

Animals↗
PubMed2003

Time-intensity trade of bilaterally bone-conducted sounds in normal hearing subjects.

OBJECTIVE AND METHODS: In an effort to examine the rules by which information of bilaterally applied bone-conducted signals arising from interaural time differences (ITD) and interaural intensity differences (IID) is combined, data were measured for continuous 500 Hz narrow-band noise at 60 dBHL in 30 normal-hearing subjects using a centering method. Time-intensity trading functions were obtained by means of a sound image shifted towards one side by presenting an ITD, and shifted back to a centered sound image by varying the IID in the same ear. ITD values were varied from -600 to +600 microseconds at 200 microseconds steps, where negative values indicate delays to the right ear. RESULTS: Time-intensity trading functions in response to bone-conducted signals showed significantly lower discrimination thresholds across IIDs, when compared to a control group with applied air-conducted signals. These findings can be interpreted as a constructive interference effect related to the intimate mechanism of bilateral bone conduction, where interaural time differences play a major role. CONCLUSION: Time-intensity trade of bilaterally bone-conducted sounds in normal-hearing subjects is the highly sensitive. The high speed of sound through the skull may be the main reason for the high sensitivity of time-intensity trading.

Adult↗
PubMed2001

Transfection of young guinea pig vestibular cells in vitro with an adenovirus vector.

This study shows distributions of lacZ-positive cells in the vestibular labyrinthine explants of young guinea pigs with mature ears. When adenovirus lacZ vectors were administered to the vestibular labyrinth following removal of the otoconial membrane, lacZ-positive cells were observed in the mesothelial cells in the perilymphatic space, in the sensory and supporting cells in the utricle and ampulla, and in the transitional and dark cells in the ampulla. When the otoconial membrane was preserved, lacZ-positive cells were not distributed in the utricular sensory epithelium. These findings suggest that adenovirus vectors can transform a variety of vestibular epithelial cells, but that it is difficult for adenovirus vectors to pass through the otoconial membrane.

Adenoviridae↗
PubMed2001

Retrospective and prospective coding for predicted reward in the sensory thalamus.

Reward is important for shaping goal-directed behaviour. After stimulus-reward associative learning, an organism can assess the motivational value of the incoming stimuli on the basis of past experience (retrospective processing), and predict forthcoming rewarding events (prospective processing). The traditional role of the sensory thalamus is to relay current sensory information to cortex. Here we find that non-primary thalamic neurons respond to reward-related events in two ways. The early, phasic responses occurred shortly after the onset of the stimuli and depended on the sensory modality. Their magnitudes resisted extinction and correlated with the learning experience. The late responses gradually increased during the cue and delay periods, and peaked just before delivery of the reward. These responses were independent of sensory modality and were modulated by the value and timing of the reward. These observations provide new evidence that single thalamic neurons can code for the acquired significance of sensory stimuli in the early responses (retrospective coding) and predict upcoming reward value in the late responses (prospective coding).

Animals↗
PubMed2001

Morphological changes of vestibular ganglion cells in human fetuses and in pediatric patients.

The temporal bone histopathology of human vestibular ganglion cells of fetuses and pediatric patients was studied. In the first study, we traced the morphological changes in vestibular ganglion cells in human fetuses ranging from 13 weeks to 39 weeks of gestational age by using 13 temporal bone serial sections. Vestibular ganglion cells had reached histological maturity by the 24th week of gestation and the volume of vestibular ganglion cell cytoplasm increased until the 39th week of gestation. In the second study, the temporal bone serial sections of seven neonates, eight infants and five children were investigated to reveal pathological changes in vestibular ganglion cells. Morphological changes in vestibular ganglion cells in human fetuses were revealed. Vestibular ganglion cells were changed pathologically by intracranial disease and variety etiology affecting the inner ear, because these are located in the internal auditory canal between the brain and labyrinth.

Child↗
PubMed2001

Expression of NeuroD and TrkB in developing and aged mouse olfactory epithelium.

To better understand the roles of NeuroD, a member of the basic helix-loop-helix transcription factor family, during the differentiation of olfactory receptor neurons, we studied the expression of NeuroD in developing and aging mouse olfactory epithelium (OE). During embryonic period, NeuroD expression is confined in the basal compartment of OE. During neonatal period, NeuroD expression is detected in the middle compartment and in the basal compartment of OE. In the adult, the number of NeuroD expressing cells in the basal compartment significantly decreased, while the NeuroD-positive cells in the middle compartment was maintained throughout lifetime. This dual phase expression pattern of NeuroD suggests multiple roles of NeuroD in the neurogenesis of ORNs.

Aging↗
PubMed2001

Identification of dual specificity phosphatases induced by olfactory bulbectomy in rat olfactory neuroepithelium.

Dual specificity protein tyrosine phosphatases (dsPTPs) are a subfamily of protein tyrosine phosphatases implicated in the regulation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK), and p38 mitogen-activated protein kinases (MAPKs) which are target enzymes activated by a wide range of cell-surface stimuli. Like these kinases, a class of dsPTP has been implicated in cell differentiation, regeneration, and apoptosis. In order to isolate dsPTPs which might play an important role in neuronal regeneration and apoptosis in olfactory neuroepithelium, we subcloned DNA fragments amplified by reverse transcription-polymerase chain reaction (RT-PCR), using degenerate oligonucleotide primers based on the conserved amino acid regions within the catalytic domain of dsPTPs, from rat olfactory epithelial RNA 1 and 4 h after an olfactory bulbectomy. The PCR products were subcloned into the pCRII vector, and 23 clones were chosen for further characterization. The sequence of these 23 individual clones revealed that two clones were identical to the rat dsPTP, MKP-3, and the other 21 clones were identical to the rat dsPTP, MKP-1. By Northern analysis, the MKP-1 transcript was induced and peaked 4 h following a bulbectomy. Similar results were obtained with the MKP-3 transcript. These results suggest that MKP-1 and MKP-3 may be involved in the early steps of apoptosis in vivo in rat olfactory neuroepithelium.

Animals↗
PubMed2001

Auditory brainstem response and temporal bone pathology findings in a brain-dead infant.

The criteria for assessing adult brain death have been already established, but those for infant brain death have not been yet established in Japan. We report auditory brainstem response (ABR) and postmortem pathology of the temporal bone and brain of a brain-dead 9-month-old female. During the comatose state, her ABR showed only waves I and II bilaterally. Autopsy revealed the presence of a left cerebellar astrocytoma, herniation and anoxic encephalopathy. The pathological examination of the temporal bone revealed the destruction of the inner ear particularly on the left side. In the auditory pathway of brain-dead patients, degeneration occurs first in the cerebrum, followed by the cochlear nerve. Thus, ABR is one of the useful means to assess brain death even in infants.

Astrocytoma↗
PubMed2001

Blunt chest trauma with deep pulmonary laceration.

BACKGROUND: Deep pulmonary laceration (DPL) is rare and its survival rate is low. The present study focused on the prognostic factors of DPL. METHODS: The present study concerned 17 DPL patients treated in Tokai University Hospital between 1988 and 1998. The prognostic factors of DPL were compared with systolic blood pressure (SBP), PaO2, and the volume of intrathoracic blood loss. Characteristic findings of initial chest roentgenograms of DPL were investigated. RESULTS: Eleven patients were saved and 6 patients died. An SBP of less than 80 mm Hg on arrival at the hospital and a blood loss of more than 1,000 mL through the chest tube within 2 hours after arrival were poor prognostic factors. Hypoxemia on arrival was not a poor prognostic factor. Chest roentgenograms showed macular infiltrative shadow with moderate lung collapse and deviation of the mediastinal shadow toward the unaffected side. Selective bronchial occlusion with a Univent prevented suffocation by intrabronchial blood. CONCLUSIONS: Two poor prognostic factors of DPL are SBP less than 80 mm Hg on arrival and blood loss of more than 1,000 mL through the chest tube within 2 hours after arrival.

Accidents, Traffic↗
PubMed2001

Bone-conducted vestibular evoked myogenic potentials in patients with congenital atresia of the external auditory canal.

OBJECTIVE: The purpose of this study was to determine whether vestibular evoked myogenic potentials from the sternocleidomastoid muscle in response to bone-conducted clicks and short tone-bursts can be used to assess vestibular apparatus function in patients with conductive hearing problems, particularly bilateral external auditory canal atresia. DESIGN: Evoked-potential responses to bone-conducted auditory stimuli were recorded from the sternocleidomastoid muscle of 15 patients (11 male and four female, aged 4--20 years) with congenital bilateral atresia of the external auditory canal, with or without the middle ear anomalies. SETTING: This study was conducted in the outpatient clinic of the Tokyo University Hospital, Department of Otolaryngology, University of Tokyo. INTERVENTION: Diagnostic. OUTCOME MEASURES: Bone-conducted vestibular evoked myogenic potentials in response to clicks and short tone-bursts were recorded with surface electrodes over both sternocleidomastoids in each patient. RESULTS: In all patients, bone-conducted clicks and short tone-bursts evoked larger biphasic responses from the sternocleidomastoid ipsilateral to the stimulated ear. Short tone-bursts evoked vestibular evoked myogenic potentials with higher amplitude and better waveform morphology than clicks at the same subjective intensity. CONCLUSION: Loud auditory stimuli delivered by bone conduction can evoke myogenic potentials from the sternocleidomastoid. This method is a noninvasive, rapid, and convenient test for investigating the vestibular system function in patients with bilateral external auditory canal atresia, with or without the middle ear anomalies.

Adolescent↗
PubMed2001

Electrophysiological measures of auditory function in the neurofilament-deficient mutant quail (Quv).

Auditory pathway electrophysiological studies were performed on the mutant quail 'Quv'. This mutation is known to result in neurofilament deficiencies of both the peripheral and central nervous systems. Auditory evoked brainstem responses (ABRs), electrocochleograms (EcochGs) and middle latency responses (MLRs) were evaluated. ABRs in Quv quails demonstrated markedly altered waveforms exhibiting longer latencies, absence of the later peaks and lower amplitudes. The EcochG showed normal cochlear microphonics with no obvious abnormalities in amplitude or latency and normal latencies for peak N1. Quv quails had a mild threshold elevation with a normal latency for the first peak of the ABR (P1). The Quv MLRs showed no significant differences in amplitude but they revealed a latency prolongation for peaks N0, Pa and Na relative to the controls. We have discovered abnormal findings of auditory evoked potentials in the neurofilament-deficient quail (Quv). We suggest that the smaller axonal size and axonal hypotrophy due to altered neurofilament expression underlies these abnormal auditory evoked potential responses.

Acoustic Stimulation↗
PubMed2001

Auditory nerve fiber differences in the normal and neurofilament deficient Japanese quail.

A primary axonal disease affecting the central and peripheral nervous system was discovered in a mutant strain of the Japanese quail, named quiver (Quv). We have previously demonstrated altered auditory evoked potentials in the neurofilament (NF) deficient quail. In this current study we attempt to find relationships between the auditory evoked potential results and the histo-pathological abnormalities of the auditory neurons. No abnormalities in the external auditory meatus and tympanic cavity were observed in either Quv or control quails and the ganglion cell bodies and their nuclei appeared normal by light microscopy. The myelin staining pattern was found to be similar in both strains with hematoxylin and eosin and Klüver-Barrera staining. The frequency histograms of fiber and axonal diameters of myelinated fibers showed an unimodal pattern in both strains. In Quv quails myelinated fibers and their axoplasm were smaller in diameter than in controls resulting in smaller neural tissue mass. In electron microscopic observation the axons of the Quv quail were composed of mitochondria and microtubules and smooth endoplasmic reticuli. In Quv quail electron micrographs of cochlear nerve myelinated fibers NFs were not seen in the axons and the neuronal cell bodies. Our current findings indicate that the previously reported reduction of conduction velocity of auditory evoked potentials may be due to smaller fiber and/or axonal diameter. The g-ratio, myelin thickness and fiber circularity were found to be the same for both strains. In conclusion, loss of axonal cytoskeletal elements (NFs) correlates well with our electrophysiological findings. Reduced conduction velocity and severely distorted auditory evoked potentials in NF deficient quails seem to be primarily due to axonal hypotrophy.

Animals↗
PubMed2001

Frequency sensitivity range of the saccule to bone-conducted stimuli measured by vestibular evoked myogenic potentials.

Vestibular evoked myogenic potentials (VEMPs) occurring in cervical muscles after intense sound stimulation conducted by air or bone are thought to be a polysynaptic response of otolith-vestibular nerve origin. We report the results of an experiment to investigate whether acoustic stimulation of the saccule by bone conduction produces VEMPs in which response amplitudes are somewhat sensitive to stimulus frequency, as appears to be the case with air-conducted stimuli. Prior to this we investigated the effect of stimulation repetition rate on bone-conducted VEMPs (B-VEMPs) at stimulus frequencies of 200 and 400 Hz with five different repetition rates (5, 10, 20, 40, and 80 Hz). B-VEMPs were recorded from 12 normal hearing subjects in response to bone-conducted 70 dB (normal hearing level), 10-ms tone bursts (rise/fall time=1 ms and plateau time=8 ms) at frequencies of 100, 200, 400, 800, 1600 and 3200 Hz. Our study showed that B-VEMP amplitudes were highest at 10 Hz but decreased as the repetition rate increased. B-VEMP response amplitudes were found to be maximal for stimulus frequencies from 200 to 400 Hz. This response may contribute to the perception of loud sounds.

Acoustic Stimulation↗
PubMed2001

The effect of sternocleidomastoid electrode location on vestibular evoked myogenic potential.

OBJECTIVE: The purpose of this study was to investigate the effect of a sternocleidomastoid (SCM) electrode array on the vestibular evoked myogenic potential (VEMP) and the most optimal recording site for clinical use. METHODS: Fifteen normal adults (10 men and 5 women, aged 18 to 38 years) were tested. We placed electrodes at four different locations over the SCM muscle: the upper part of the SCM muscle at the level of mandibular angle, the middle part of the muscle, and immediately above sternal and clavicular origins of the SCM muscle. Sound evoked myogenic potentials in response to monoaurally delivered short tone-bursts (500 Hz at 95 dBnHL, rise/fall time=1 ms and plateau=2 ms) were recorded with surface electrodes over the isometrically contracting SCM muscle. RESULTS: On the clavicle, the upper and middle parts of SCM from all subjects, air-conducted short tone burst evoked biphasic responses (p13-n23). VEMPs recorded at the upper part of the muscle showed the largest amplitude, followed by that at the middle part. However, the latency of the first peaks (p13-n23) was not constant in the upper part. Recording from the middle part of SCM muscle were more consistent. CONCLUSION: Our findings suggest that the middle part of the SCM muscle is the optimal location for recording vestibular evoked myogenic potential.

Adolescent↗
PubMed2001

Metastasis of cervical esophageal carcinoma to the temporal bone--a study of the temporal bone histology.

A 49-year-old male developed left abducens nerve palsy as a result of metastatic spread of carcinoma of the cervical esophagus to Rouviere's node and infiltration of the petrous portion of the left temporal bone. Postmortem temporal bone histology revealed that cancer cells had invaded the greater superficial petrosal nerve (GPN), lesser superficial petrosal nerve, tensor tympani muscle (TTM) and the skin covering the anterior wall of the left external auditory meatus. These findings suggest that the carcinoma metastasized from the cervical esophagus to Rouviere's node and directly invaded the middle cranial fossa and then the temporal bone, and further infiltrated the middle ear via perineural invasion.

Carcinoma, Squamous Cell↗
PubMed2001

Bone-conducted sound lateralization of interaural time difference and interaural intensity difference in children and a young adult with bilateral microtia and atresia of the ears.

Bone-conducted sound lateralization tests to determine interaural time difference (ITD) and interaural intensity difference (IID) were conducted by means of a self-recording apparatus in 20 children and a young adult with bilateral microtia and atresia of the ear. This apparatus changes ITD automatically from 0 to 2,000 micros at 50 micros/s and IID from 1 to 40 dB at 1 dB's. When ITD exceeds approximately 200 micros/s and IID exceeds 5 dB in normal subjects the sounds are recognized separately. The test stimulus was a continuous narrow-band noise at 500 Hz and 30 dB SL applied to the right and left mastoids through bone vibrators. In the patients with bilateral atresia of the ears, ITD results revealed approximately normal thresholds of discrimination in half the patients and IID results revealed threshold elevation in only 10%. It is noted that bone-conducted sound lateralization abilities of ITD or IID are maintained in many of these patients.

Adolescent↗
PubMed2001

Analysis of optokinetic nystagmus in patients with lesions on the left unilateral parietal lobe or the entire left hemisphere.

Optokinetic nystagmus (OKN) was studied by computer analysis in nine patients with lesions on the left unilateral parietal lobe (group A) and in five patients with lesions on the entire left hemisphere (group B), as confirmed by CAT or MRI scans. OKN stimulation and recordings were evaluated based on the optokinetic pattern (OKP). In group A, there was no directional preponderance. However, in group B, the Electronystagmography recordings showed typical asymmetry of OKP. This asymmetry was revealed by a low amplitude and a significantly impaired slow-phase eye velocity of the right OKP. Asymmetry of OKP resulted from the impaired slow-phase eye velocity of the contralateral OKN to the damaged hemisphere because of a slight change in fast-phase eye velocity.

Adolescent↗