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Biomedical subjects

I Koizuka

Publications and source records attributed to I Koizuka.

At least 19 recordsLinked to original sources
PubMed2001

Effects on the optokinetic system of midline lesions in the pretectum of monkeys.

The nucleus of the optic tract (NOT), an important visuo-motor relay between the retina and preoculomotor structures, is responsible for mediating horizontal optokinetic nystagmus (OKN) in monkeys, cats, rabbits and rats. In addition to its projection to the vestibular nuclei, the NOT has a prominent projection to the contralateral NOT via the posterior commissure. In order to evaluate the role of the commissural fibers between the NOTs in OKN, we cut the posterior commissure in three Macaca fuscata. The animals viewed the OKN stripes under three conditions: right eye viewing, left eye viewing, and both eyes viewing. OKN was recorded in response to counter-clockwise and clockwise stimulation at stimulus velocities of 30 degrees/s, 60 degrees/s and 90 degrees/s. After control data were gathered, the posterior commissure was transected with an operating knife. Before the animal was sacrificed, biocytin, an anterograde tracer, was injected into the left NOT in order to confirm that all of the commissural fibers had been cut. Although the midline lesions decreased the initial rapid rise and steady state OKN slow-phase velocity in all three animals, there were no directional differences observed during monocular clockwise or counter-clockwise visual stimulation to either eye. In two of the three animals, there were no significant differences in the time-constants of optokinetic after nystagmus (OKAN) after the lesion. In the remaining animal, the time-constants decreased at stimulus velocities of 30 degrees/s and 60 degrees/s. In conclusion, gain reduction in the rapid rise and steady state slow-phase velocity of OKN can be explained by removal of an excitatory signal mediated by commissural fibers to inhibitory interneurons in the contralateral NOT. However, interrupting the commissural fibers had no effect on the velocity storage mechanism, because the time-constants of OKAN mostly remained largely unchanged by the lesion.

Animals↗
PubMed2000

Nuclear expression of the p16CDKN2 gene product during senescence of human pharyngeal epithelial cells.

OBJECTIVE: It has been proposed that a gene mapping to human chromosome 9p21 plays a critical role in cellular senescence. CDKN2 is a tumor suppressor gene on chromosome 9p21. It encodes a nuclear protein, p16, which inhibits the D-type cyclin/cyclin-dependent kinase complexes that phosphorylate the retinoblastoma protein, thus blocking cell cycle progression through G1. The purpose of this study was to determine whether nuclear p16 expression is altered during the senescence of human pharyngeal epithelial cells (HPECs) m vitro. METHODS: An immunocytochemical study was performed to examine a panel of cultured HPECs with a finite lifespan for the nuclear p16 expression. All HPEC cultures were also subjected to a histochemical assay that identifies senescent cells by their positive beta-galactosidase activity. RESULTS: Nuclear p16 was undetectable when HPECs were initially cultured in serum-free low-calcium medium. However, nuclear p16 was clearly detected when the cultured HPECs exhibited beta-galactosidase activity in the same medium. CONCLUSION: These results suggest that immunocytochemically detectable amounts of nuclear p16 are associated with senescence of HPECs in vitro.

Calcium↗
PubMed2000

Effect of adaptive plasticity of linear vestibulo-ocular reflex upon angular vestibulo-ocular reflex.

OBJECTIVE: The vestibulo-ocular reflex (VOR) produces compensatory eye movements during head movements. The VOR consists of the angular VOR and the linear VOR. The VOR is under adaptive control that corrects VOR performance when visual-vestibular mismatch arises during head movements. Most experiments concerning plasticity of the VOR have used the angular VOR. So far, there has been no investigation on the effect of adaptive plasticity of the linear VOR on the angular VOR. In this study, using a linear sled, we tested the hypothesis that the angular VOR is altered by changes in the linear VOR. METHODS: To modify the linear VOR, we used an adaptation paradigm. Eight subjects were translated sinusoidally at 0.125 Hz and 0.16 g peak acceleration along their inter-aural axis for 40 min, while viewing earth-fixed vertical stripes on the wall while wearing the binocular magnifying lenses. Six of the eight subjects showed an increase in linear VOR sensitivity after adaptation. Each of the six subjects who showed an increase in linear VOR sensitivity after adaptation also showed an increased angular VOR gain at 0.125 Hz. CONCLUSION: These results suggest that the linear VOR and the angular VOR share common neural pathways in such a way that a change in the synaptic efficacy of one pathway is accompanied by a commensurate change in the other.

Adaptation, Physiological↗
PubMed2000

Absence of nuclear p16 from Epstein-Barr virus-associated undifferentiated nasopharyngeal carcinomas.

OBJECTIVE: Epstein-Barr virus (EBV) is detected in the majority of undifferentiated nasopharyngeal carcinomas (UNPCs, World Health Organization type III). However, the exact mechanism involved in the carcinogenesis of EBV-associated UNPCs remains to be elucidated. An important unresolved question is: how is the normal cell cycle deregulated during EBV-associated UNPC development? The p16CDKN2 gene encodes a nuclear protein, p16, which inhibits the D-type cyclin/cyclin-dependent kinase complexes that phosphorylate the retinoblastoma gene product (pRb), thus blocking G1 cell cycle progression. The objective of this study was to determine whether p16 absence is involved in the development of EBV-associated UNPCs. METHODS: We performed immunohistochemistry to detect p16 and pRb and in situ hybridization to detect EBV-encoded small RNA (EBER) in UNPCs from 28 patients. RESULTS: No p16 was detected in 23 of 28 UNPCs (82.1%), whereas pRb was expressed in all those examined and EBER was detected in 22 of 28 (78.6%). The absence of p16 was associated with the presence of EBER in UNPCs (P < .0001): none of the 22 EBER+ UNPCs expressed p16, whereas 5 of 6 EBER- UNPCs did. CONCLUSION: Our data suggest that loss of p16-related cell cycle regulation plays an important role in the development of EBV-associated UNPCs.

Carcinoma↗
PubMed2000

[Endoscopic sinus surgery in flowing water].

A balloon has been developed that completely fills the choana, preventing water from leaking into the pharynx even when the water is entering into the nasal cavity at a rate of 1000 ml per minute. The balloon enables endoscopic sinus surgery (ESS) to be safely performed in "flowing water". This surgical technique is similar to that used in transurethral resections of the prostate because the tip of the endoscope is kept clean, and blood, debris and resected tissues are continuously removed by the water flow. In addition, the water pressure helps to suppress bleeding. This technique enables ESS to be performed with greater ease and efficiency. We have performed ESS in flowing water on 38 patients with chronic sinusitis under local anaesthesia. No complications, such as water leakage into the pharynx, were encountered, and only a few patients felt discomfort from the insertion of the balloon. Even if the balloon had burst, an emergency could have been easily prevented by withdrawing the endoscope from the nasal cavity and stopping the flow of water. Ultrasonography (USG) was used to examine the water-filled nasal cavity during surgery (SSD-2000 and Micro Tip Radial (ASU-101); Aloka, Ltd., Japan). Using USG, the middle turbinate, the inferior turbinate and the nasal septum could be visualized in a single coronal image. When the sensor was in the posterior ethmoid sinus, the orbit and its optic nerve could also be visualized. Since this surgery is performed under local anesthesia, eye movements can rapidly alter the position of the optic nerve. Thus, visualization of the optic nerve's exact position is extremely important. Unfortunately, USG is not very useful for localizing structures and guiding the surgeon to distant tumors or cysts located behind thick bones, since ultrasound can not penetrate hard masses or bones. In this situation, navigation systems are more reliable than USG. Nevertheless, USG is often useful for depicting surgical sites, especially during a crisis, if the medial wall of the orbit is thin or if the skull base has been broken, exposing the dura. USG can also provide early warning of an impending complication. USG also has several practical advantages over navigation systems: the cost of USG is much lower, preparation for surgery is unnecessary, visual information can be obtained in real time, and measurement accuracy (estimated to be about 2 mm for navigation systems) is not a consideration. Thus, USG can be easily used to avoid complications in most surgeries for chronic sinusitis. Flowing water also allows the nasal eavity to be completely washed and sterilized at the end of the surgery. This not only prevents post-operative infection, but enables sinus function to be more quickly recovered. In addition, the pressure from the balloon also prevents post-operative nasal hemorrhaging. This allows patients to be safely discharged from the hospital at an earlier time. The balloon can also be used for non-surgical purposes. For example, emergent epistaxis can be easily stopped by the insertion of this balloon, even if the doctor is not an otorhinolaryngologist. In addition, the balloon's soft pressure allows it to be left in the nose for long periods without any complications. We conclude that this simple balloon, which we have named the "Noda Balloon", is extremely useful for nasal treatments.

Adolescent↗
PubMed2000

[Effects of calcium on HPV16 gene transcription in cultured laryngeal epithelial cells].

Human papillomavirus (HPV) gene transcription is closely linked to the differentiation status of infected epithelial cells. A variety of physiological agents, including calcium, regulates the differentiation of cultured epithelial cells. The expression of cytokeratin No.13 (CK13) can be used as a marker for differentiation in cultured laryngeal epithelial cells (HLEC cells). The purpose of this study is to examine the effects of calcium on CK13 expression and HPV16 gene transcription in HLEC cells. We analyzed two types of HPV16-containing HLEC cells: HPV 16-immortalized HLEC cells (HLEC16 cells) and HPV16-positive (infected) cultured laryngeal papilloma cells (HLP16 cells). In the HLEC16 cells, the viral genes were integrated into the host cell chromosomes, while the HLP16 cells contained extra-chromosomal viral genes. The effects of increasing calcium concentrations on CK13 expression were then evaluated using immunocytochemistry. Both the HLP16 and the HLEC16 cells responded to an increased calcium concentration by inducing CK13 expression. In HLP16 and HLEC16 cells, the CK13 expression was undetectable at low calcium concentrations (0.1 mM) but became clearly detectable at high calcium concentrations (1.0 mM). The level of viral RNA was elevated in HLP16 cells with added calcium (1.0 mM) but was similar in HLEC16 cells grown in either low (0.1 mM) or high (1.0 mM) calcium concentrations. These results suggest that a calcium-induced differentiation results in the up-regulation of HPV16 gene transcription in HLP16 cells. The integration of viral gene into the host cell chromosomes may be an important determinant for the differentiation-independent transcription of HPV16 genes.

Calcium↗
PubMed2000

Characteristics of secondary phase post-rotatory nystagmus following off-vertical axis rotation in humans.

The nystagmus following yaw earth-vertical axis rotation often reverses direction, a phenomenon known as the "secondary phase". The purpose of this study was to examine the existence and the spatial and temporal properties of the secondary phase of post-rotatory nystagmus following off-vertical axis rotation (OVAR). Eleven normal human subjects were rotated at 120 or 180 degrees/s about an off-vertical axis and stopped in the left ear down or right ear down lateral position. Horizontal and vertical eye positions were recorded with a scleral search coil, and horizontal and vertical slow component eye velocities were computed. Our results indicate that (a) there is a robust secondary phase nystagmus following OVAR, and (b) the direction of the secondary phase nystagmus tends to align with earth-horizontal. These results can be explained by a minor modification of an existing VOR model that has been shown to produce secondary phase responses.

Adult↗
PubMed1999

A pitch glide activates an intermediate response between auditory N1 and mismatch negativity.

Pitch glides of a continuous tone elicit auditory N1-like responses. However, their characteristics have not well been investigated, and it remained unclear whether the response is an auditory true N1 or the mismatch negativity (MMN). We found here that a rapid pitch glide activates almost the same response as a true N1. On the contrary, as the rate of the pitch glide decreases, the response continuously varies the characteristics from true N1 to MMN. This suggests that there would exist intermediate responses between auditory N1 and MMN.

Acoustic Stimulation↗
PubMed1999

Rotation vector analysis of eye movement in three dimensions with an infrared CCD camera.

We have developed a new technique for analyzing the rotation vector of eye movement in three dimensions with an infrared CCD camera based on the following four assumptions; i) the eye rotates on a point; ii) the pupil edge is a circle; iii) the distance from the center of eye rotation to pupil circle remains unchanged despite the rotation; iv) the image of the eye by the CCD camera is projected onto a plane which is perpendicular to the camera axis. After taking digital images of voluntary circular eye movements, we first constructed a three-dimensional frame of reference fixed on the orbita of the subject wearing a goggle equipped with an infrared CCD camera, and determined the space coordinates of the center of eye rotation, the center of the pupil, and an iris freckle. We then took digital images of the eye movements during a saccade or vestibulo-ocular reflex (VOR) and analyzed the axis and angle of the eye movements by the trajectories of the center of the pupil and the iris freckle. Finally, Listing's plane of saccade and the gain and the phase of VOR were obtained. The suitability of this technique is examined.

Adult↗
PubMed1998

Ipsilateral dominance of human olfactory activated centers estimated from event-related magnetic fields measured by 122-channel whole-head neuromagnetometer using odorant stimuli synchronized with respirations.

The aim of this study was to measure and analyze olfactory event-related magnetic fields using a whole-cortex biomagnetometer (122-channel SQUID gradiometer). Amyl-acetate gas (approx. 1%) was administered for 300 msec into either the right or left nostril in synchronization with respiration using a mask and an optical fiber sensor. Clear olfactory event-related magnetic fields were asymmetrically obtained on both sides of the forehead in all six subjects. The generators of olfactory magnetic fields were estimated at two regions located fairly asymmetrivally near the bilateral frontal deep areas. The goodness-of-fit was better for the two-dipole model than the one-dipole model in all experiments. In almost all subjects the latency and intensity of ipsilateral olfactory magnetoencephalography (MEG) responses were shorter and larger than those of the contralateral responses, respectively. These results suggest that the olfactory MEG responses on the ipsilateral side are generally larger and more dominant than those on the contralateral side in the human olfactory system.

Brain Mapping↗
PubMed1998

Auditory evoked off-response: its source distribution is different from that of on-response.

Offset auditory responses were investigated by electroencephalography mainly in the 1970s, but since then no particular attention has been paid to them. Among the studies using magnetoencephalography (MEG) devices there are, to our knowledge, only three studies of the auditory off-response, and no significant variance has ever been observed between the source locations of on- and off-responses elicited from pure tones. We measured auditory evoked magnetic fields (AEFs) to various frequency pure tone stimulation in 5 healthy subjects with a 122-channel helmet-shaped magnetometer, and compared the distributions of the source locations of auditory N100m-Off (magnetic off-response around 100 ms) with those of N100m-On. Their spatial distributions were quite close to each other, and yet they were significantly different.

Acoustic Stimulation↗
PubMed1998

Objective tinnitus caused by an aberrant internal carotid artery.

We report the case of a 29 year-old woman who complained of pulsatile tinnitus and impaired hearing. On otoscopic examination, her right tympanic membrane was observed to be in contact with a mass in the middle ear cavity, with the formation of a meniscus at the point of contact. Using a high-sensitivity microphone inserted into the external auditory canal, we recorded pulsatile tinnitus that was synchronous with the electrocardiogram. Magnetic resonance angiography revealed that the middle ear mass was an aberrant internal carotid artery coursing through the hypotympanum.

Adult↗
PubMed1998

[Clinical features in patients with delayed endolymphatic hydrops].

We report clinical features in patients with delayed endolymphatic hydrops (DEH) with juvenile unilateral deafness. Among 23 patients with DEH, 15 cases were diagnosed as ipsilateral DEH and 8 cases as contralateral DEH. The distribution of onset age showed two peaks at ages of < 30 years and > 40 years. In 80% of the ipsilateral DEH cases, the onset of episodic vertigo was at younger ages. On the other hand, in 75% of the contralateral DEH cases, the onset of fluctuation hearing loss of the contralateral ear was at older ages. Ispilateral DEH and Meniere's disease may show different pathophysiologies. The incidence of dominant negative summating potential in the better-hearing ear was 20% in the ispilateral DEH cases and 60% in the contralateral DEH cases. It is suggested that endolymphatic hydrops is in the better-hearing ear of contralateral DEH.

Adult↗
PubMed1997

Micro-magnetic resonance imaging of the inner ear in the guinea pig.

We applied a magnetic resonance microscopy at 7.05 T with a gradient coil unit to image the fine structure of the guinea pig cochlea. First, a three-dimensional MR image of the surface of the cochlea was obtained to select the location of cross-sectional images. Then, cross-sectional images of the basal turn, the second turn and the apical turn of the cochlea were obtained. Based upon the different protein concentrations of the endolymph vs the perilymph, the scala vestibuli, scala tympani and the cochlear duct could be clearly distinguished. This allowed a determination of the location of both the basilar membrane and Reissner's membrane. We raise the possibility that MRM may become useful in the diagnosis of endolymphatic hydrops (Meniere's disease).

Animals↗
PubMed1997

Plasticity of responses to off-vertical axis rotation.

This study assessed whether a change in the magnitude of the angular vestibulo-ocular reflex (VOR) influences the magnitude of the linear VOR, thereby suggesting a common gain element for these reflexes. The responses to linear acceleration using yaw off-vertical axis rotation (OVAR) at 30 degrees tilt were recorded before and after an adaptation protocol designed to increase the angular VOR gain. Subjects included eight asymptomatic healthy young individuals. Eye movements, recorded with electro-oculography, were analyzed to yield gain of the horizontal angular VOR and the magnitude of the modulation and bias components of the response to OVAR. Results indicated that there was no consistent influence of angular VOR gain on the eye movement response to OVAR. Since previous studies have shown that responses to earth horizontal axis rotation are influenced consistently by angular VOR gain, our study suggests that high intensity otolithic stimulation is required to observe changes in the linear VOR following modification of the angular VOR.

Acceleration↗
PubMed1997

[A case report of bilateral perilymph fistula in an adult, with literature review].

Adult bilateral perilymph fistula (PLF) is rare. We report a case of a 55-year-old man who suffered from sudden bilateral hearing loss after blowing his nose. On the first day, he also had bilateral tinnitus but no vertigo. However, he gradually developed vertigo, and nystagmus to the left side began to appear in the following days. Exploratory bilateral tympanotomies were performed and perilymph fistulas were observed at the round window niche in both ears. The round windows were obliterated with fascia of the temporal muscles. After the operation no changes were found in both sides on a pure tone audiogram even at a one-year follow-up. The literature was reviewed and several features were statistically analyzed. In the adult bilateral PLF group, the proportion of the cases in which the cause of PLF was clear was significantly higher than that in the adult unilateral PLF group, but the other clinical features were almost the same. The results suggest that in adults the occurrence of bilateral and unilateral PLF could depend on the level of pressure applied to the middle or inner ear. On the other hand, in the child PLF group, the ratio of bilateral involvement was considerably higher than that in the adult PLF group, and in most cases the PLF was associated with middle and/or inner ear malformations. Healing in the child bilateral PLF group was poor than that in the adult PLF group. Those results suggest that the etiology of bilateral PLF in children may be considerably different from that of adult PLF.

Age Factors↗
PubMed1997

[Clinical features and utricular dysfunction in patients with benign paroxysmal positional vertigo].

We report the clinical features in patients with benign paroxysmal positional vertigo (BPPV), who met the following criteria; (1) a history of brief episodes of positional vertigo, and (2) a characteristic torsional paroxysmal positional nystagmus that was observed visually. The mean age of onset was 55 years. There was no sex predominance. In most patients, positional vertigo disappeared within 2 months. We then used the eccentric rotatory test to examine the patients otolithic function. In the eccentric rotatory test, a patient is rotated around an axis located behind his head (eccentric rotation, ECR). We have demonstrated that the enhancement of vestibulo-ocular reflex (VOR) gain in ECR can be used as an index of the utricular function. Enhancement of VOR gain was observed in ECR to the lower ear in positional vertigo, but not to the uppermost ear. The findings suggest an imbalance in utricular function in patients with BPPV. Otoconia dislodged from the deranged utricle may be a source of canalolithiasis/cupulolithiasis.

Adult↗