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Biomedical subjects

K Ohtsuka

Publications and source records attributed to K Ohtsuka.

At least 253 records · Page 14Linked to original sources
PubMed1981

[Reconstructive operation of Moyamoya disease and its problems (author's transl)].

Cerebrovascular moyamoya disease is a chronic occlusive disease of unknown etiology, 90% of which are found among Japanese. At the 3rd International Symposium on Microsurgical Anastomosis held in 1976, Kikuchi and Kawasawa reported an preventing effect of STA-MCA bypass surgery for ischemic episode of this disease. Thereafter, they proposed a new operation to place temporal muscle on the brain surface, namely Encephalo-Myo Synangiosis (EMS), for the patients lacking suitable recipient artery of middle cerebral artery territory. The authors report clinical experience of eight STA-MCA anastomosis, two STA-MCA anastomosis with EMS and one EMS performed on six cases with moyamoya disease. The follow up period after operation ranged from seven to 18 months. Four patients had excellent results, and one good. One died of subdural hematoma of non-operated side seven months after contralateral bypass procedure. STA-MCA bypass surgery is an effective treatment for moyamoya disease. Also, EMS is expected to be a replaceable surgical procedure for STA-MCA bypass under absence of suitable recipient artery.

Adult↗
PubMedDate not supplied

Effects of superior colliculus inhibition on three-dimensional visual motion processing in the lateral suprasylvian visual area of the cat.

PURPOSE: To determine whether visual inputs from the tectothalamocortical pathway influence three-dimensional motion processing within the lateral suprasylvian (LS) area of the cat. METHODS: Tungsten microelectrodes were used for recording visual-evoked potentials (VEPs) from the LS area of 4 cats. Random dot stereograms were used as visual stimuli. Three-dimensional, motion-triggered VEPs were recorded from the LS area. Each motion sequence consisted of an abrupt onset of motion disparity with a 2 degrees amplitude followed by an abrupt offset and a stationary phase of 900 ms. The velocity of the motion disparity was varied in eight steps from 10 degrees to 400 degrees per second. The onset of motion disparity was used as the trigger for recording the VEPs. Single or multiple injections (two to three) of muscimol were made mainly into the rostral superior colliculus (SC). The amplitudes of the VEPs before and after the muscimol injection were compared. RESULTS: A large negative wave ( N1) with an implicit time of 92.7 +/- 13.5 ms (mean +/- SD, n = 98) was recorded consistently. The amplitude of N1 was significantly larger on stereovision of motion disparity than on either binocular vision of two-dimensional lateral motion or monocular vision, indicating that N1 contains neurons sensitive to motion disparity. The amplitude of N1 was not altered by muscimol injection into the SC at velocities < or =50 degrees/s. On the other hand, the amplitude of N1 was reduced to 66-71% of that observed before muscimol injection at velocities > or =75 degrees/s. CONCLUSIONS: These findings suggest that the LS area processes three-dimensional motion inputs via two parallel pathways, the geniculostriate pathway and the tectothalamocortical pathway, at velocities of motion disparity > or =75 degrees/s, while the three-dimensional motion inputs project to the LS area only via the geniculostriate pathway at velocities of motion disparity < or = 50 degrees/s.

Animals↗
PubMedDate not supplied

Dynamic asymmetries in convergence eye movements under natural viewing conditions.

PURPOSE: To clarify differences in the dynamics of convergence eye movements in response to symmetrical stimuli between the dominant eye and the nondominant eye under natural viewing conditions. METHODS: This study was conducted in 11 normal volunteers (age range, 22-30 years). The subject was seated on a chair, and the head was fixed using a bite-block. The dominant eye was determined with the "hole-in-the-card" test. Horizontal positions of the eyes were recorded using an infrared reflection device. Recordings of right eye movements were subtracted from left eye movements to obtain the vergence response. The fixation target was moved toward the center of both eyes from 50 to 20 cm in front of the face at a constant velocity in five steps (20, 30, 40, 50, and 60 cm/s). The target was moved by a pulse motor controlled by a microcomputer. The dynamic properties of each eye movement and the vergence components were analyzed. RESULTS: At velocities < or =40 cm/s, convergence responses consisted of two components: the fusion-initiating component and the fusion-sustaining component. The fusion-initiating component drove the initial faster dynamic portion of the response, and the fusion-sustaining component maintained the latter slower dynamic portion of the response. The mean peak velocity of the fusion-initiating component was significantly greater in the dominant eye than in the nondominant eye. The mean peak latency of the catch-up component was significantly shorter in the dominant eye than in the nondominant eye. CONCLUSIONS: The present study indicated that the trajectory of convergence eye movement under natural viewing conditions consists of two components, the fusion-initiating component and the fusion-sustaining component, and that the convergence response to symmetric stimuli was asymmetric between the dominant eye and the nondominant eye during the fusion-initiating phase. The neural control system of convergence eye movements preferentially drives the dominant eye during the fusion-initiating phase of the response.

Accommodation, Ocular↗
PubMedDate not supplied

Accommodation and pupilloconstriction areas in the cat midbrain.

The results of our previous studies suggest that the rostral superior colliculus (SC) is involved in the control of accommodation in the cat. The accommodation-related area in the rostral SC projects into the pretectum and the mesencephalic reticular formation (MRF), indicating that these areas may also be involved in the control of accommodation. In this study, we tried to identify cat midbrain areas of accommodation and pupilloconstriction control by systematically mapping microstimulation responses. Three regions were found to evoke the accommodation response: the posterolateral pretectum, including the nucleus of the optic tract and the posterior pretectal nucleus; the posteromedial pretectum, including the nucleus of the posterior commissure (NPC) and adjacent commissural fibers; and the MRF area dorsolateral to the oculomotor nucleus. Pupilloconstriction was evoked by microstimulation of the posteromedial pretectum around the NPC and the anterior pretectum around the olivary pretectal nucleus.

Accommodation, Ocular↗
PubMedDate not supplied

Topographical analysis of motion-triggered visual-evoked potentials in man.

PURPOSE: The middle temporal (MT) area of the cortex of the monkey is involved in visual motion analysis. Previous studies using brain-imaging techniques have shown that the area around the anterior occipital cortex in man is homologous to the area MT of the monkey. In this study, we investigated the cortical components of motion-triggered visual evoked potentials and their topography in the visual cortex of man. METHODS: Visual evoked potentials to the onset of a visual motion stimulus (m-VEPs) were recorded from 5 normal subjects aged 25 to 34 years. A random dot pattern was used as the stimulus for the m-VEPs. The dots moved horizontally to the right and then to the left alternately for 500 milliseconds with interstimulus intervals of 1500 milliseconds. The speed of motion was varied in five steps from 5-25 degrees/s. Fifteen electrodes were placed on the occiput around O(z) at 5-cm intervals. Color contour maps showing the distribution of voltage over the 15 electrodes at latencies ranging from 0-200 milliseconds with a 20-millisecond interval were made for each subject. These were coregistered with three-dimensional magnetic resonance images of the same brain to specify the topography of the main components of the m-VEPs in relation to the sulcal and gyral pattern of the visual cortex. RESULTS: We consistently observed a positive wave with a peak latency of about 100 milliseconds (P100) and a negative wave with a peak latency of about 150 milliseconds (N150) for all subjects. Topographical analysis showed that P100 was dominant in a relatively wide area caudal to O(z), whereas N150 was dominant in a relatively small area posterior to the right anterior occipital sulcus, which included the area corresponding to the area MT in man. CONCLUSIONS: These findings suggest that N150 represents the activity of the area MT in the human visual cortex related to motion perception.

Adult↗
PubMedDate not supplied

Results of transmedial-canthal ethmoidal decompression for severe dysthyroid optic neuropathy.

PURPOSE: To study the effects of ethmoidal wall (one-wall) decompression using a transmedial-canthal approach (transmedial-canthal ethmoidectomy) for the treatment of dysthyroid optic neuropathy. METHODS: The ethmoidal wall and air cells were completely removed using a transmedial-canthal approach in 6 eyes of 4 patients (mean age = 55 years; age range, 46-69 years) with dysthyroid optic neuropathy. Similar surgery was performed on 2 contralateral eyes in 2 of the patients for cosmetic reasons. The preoperative corrected visual acuity in the 6 eyes ranged from hand motion to 20/100. Centrocecal scotomas were detected using automatic static threshold perimetry in the 6 eyes. RESULTS: After transmedial-canthal ethmoidectomy, the corrected visual acuity improved to better than 20/20 in the 6 eyes, and the centrocecal scotomas had almost completely resolved. There were no major complications, such as cerebrospinal fluid leakage or diplopia associated with the surgery. There were no relapses during an average follow-up period of 29 months. CONCLUSIONS: These findings suggest that transmedial-canthal ethmoidectomy is an effective and safe therapy for dysthyroid optic neuropathy.

Aged↗
PubMedDate not supplied

The results of serial dynamic enhanced computed tomography in patients with carotid-cavernous sinus fistulas.

PURPOSE: To assess serial dynamic enhanced computed tomography (serial DE-CT) as a diagnostic tool for carotid-cavernous sinus fistula (CCF). METHODS: Serial DE-CT was performed in seven patients (ages 31-74) with CCF. Contrast material was injected intravenously at a dose of 60 mL with an injection speed of 4 mL per second. Serial axial images of the cavernous sinus were undertaken every 3 seconds using a helical computed tomography system. This relatively low-risk technique provides direct evidence of the arteriovenous shunt in the cavernous sinus. RESULTS: In early imaging after the injection, enhancement of the cavernous sinus on the side of the CCF was noted at the arterial phase in all patients, whereas early enhancement of the cavernous sinus was not observed on the contralateral uninvolved side. CONCLUSIONS: These findings suggest the usefulness of serial DE-CT as a diagnostic tool for the initial diagnosis of both high- and low-flow CCFs.

Adult↗
PubMedDate not supplied

Gene structural analysis and expression of human renal dipeptidase.

Human renal dipeptidase cDNA and genomic DNA were isolated from human kidney cDNA and genomic libraries, respectively. The human renal dipeptidase gene has a total length of approximately 6 kb and consists of ten exons and nine introns. The exons and cDNA each encode the 411 amino acid residues of the precursor protein, including 16 amino acid residues of signal sequence and a hydrophobic carboxyl terminal sequence for the attachment of a phosphatidylinositol glycan. Although the cDNA was slightly different from the cDNA reported by Adachi et al. (1990), the differences observed suggest, by comparison with human genomic DNA, that it may not represent an allelic variant but a cloning artifact. The recombinant human renal dipeptidase was produced on the surface of transfected L929 cells and had the same character as native renal dipeptidase. Northern blotting hybridization analysis showed that renal dipeptidase mRNA is only transcribed in kidney.

Amino Acid Sequence↗