Biomedical subjects

Takatsune Nishiyama

Publications and source records attributed to Takatsune Nishiyama.

4 recordsLinked to original sources

PubMed2004

New method for detecting misrouted retinofugal fibers in humans with albinism by magnetoencephalography.

In humans with albinism, a large percentage of the ganglion cell axons from the temporal retina decussate abnormally in the chiasm and synapse in the contralateral LGN. The aim of this study was to determine whether the misrouting of the optic fibers can be detected by magnetoencephalography (MEG). Visually evoked magnetic fields (VEFs) were recorded from three patients with albinism. After monocular stimulation, the isofield contour maps of the VEFs showed a single current dipole pattern over the contralateral hemisphere in patients with albinism. These results clearly illustrated the reduced uncrossed retinofugal pathway of patients with albinism.

Adolescent↗

PubMed2003

Characterization of AOC2 gene encoding a copper-binding amine oxidase expressed specifically in retina.

We have previously cloned a human, retina-specific, amine oxidase gene (RAO, gene symbol: AOC2), a member of the copper-binding amine oxidase super family. AOC2 shares sequence identity with the human kidney amine oxidase gene (KAO, gene symbol: AOC1) and the vascular adhesion protein-1 gene (VAP-1, gene symbol: AOC3). For further analysis of AOC2, the sequences surrounding the human AOC2 and the complete mouse and partial rat homologue of AOC2 were cloned for characterization. Real-time quantitative PCR, in situ hybridization, and immunohistochemistry were performed to determine the specific expression of AOC2 in the mouse retina and especially in the retinal ganglion cells. Our results demonstrated that the copper-binding motif and the enzyme active site of AOC1 and AOC3 were both conserved in mouse AOC2. The human and mouse AOC2 was flanked by two genes, the Psme3 gene for PA-28 gamma subunit and, surprisingly, the AOC3 gene. Rat AOC2 contained a stop codon that terminated the peptide length to 127 amino acids. The presence of human and rat AOC pseudogene in this region, in addition to the tandemly positioned two AOC genes, indicates the possibility of successful AOC3 replication to retina-specific AOC2 for human and mouse but unsuccessful for rat.

Amine Oxidase (Copper-Containing)↗

PubMedDate not supplied

Multifocal magnetoencephalogram applied to objective visual field analysis.

PURPOSE: To establish an objective visual field analysis by visual evoked magnetic fields. METHODS: Forty-eight focal areas of the visual field were stimulated by the visual evoked response imaging system (VERIS). The multifocal visual evoked magnetic fields (mfVEFs) of 11 healthy subjects were recorded. The output signals were recorded with VERIS, and the second-order kernel was calculated. The equivalent current dipoles (ECDs) were estimated, and the relative positioning of ECDs was determined by a magnetoencephalography (MEG) system. RESULTS: The mfVEFs consisted of either two- or three-peak waves. Large amplitude mfVEFs were elicited when the stimulus was confined to 6 degrees of the central visual field, but a strong response could not always be obtained between 6 degrees and 12 degrees. All ECDs were estimated to originate in the occipital striate cortex. The ECDs for the upper (lower) field stimulations were estimated to be on the lower (upper) cortex, while those for right (left) field stimulations were on the left (right) cortex. CONCLUSIONS: The locations of mfVEF peak ECDs were correlated with the stimulated visual field and generally matched the cruciform model. In combination with the multifocal technique, MEG can be used for objective visual field analysis.

Adult↗

PubMedDate not supplied

Secondary amyloidosis in a corneal graft.

PURPOSE: To describe a case of secondary amyloidosis that occurred in a corneal graft. METHODS: A 30-year-old Japanese woman had opacities in the corneal graft in her right eye. Slit-lamp microscopy examination demonstrated nodular, subepithelial opacities in the graft. Results of a physical examination and her past medical history were unremarkable, except for a history of a penetrating keratoplasty for keratoconus at the age of 17. Since then, the patient had worn a hard contact lens for over 10 years. The specimen obtained by keratectomy was examined histologically. RESULTS: The histologic examination revealed hyaline, and amorphous materials stained with Congo red, which were dichroic under polarized light. Transmission electron microscopy showed the characteristic fibrillar pattern of amyloid. CONCLUSIONS: This appears to be the first reported case of secondary amyloidosis in a corneal graft. A long-standing history of hard contact lens wear may play a role in the pathogenesis of this rare condition.

Adult↗