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Biomedical subjects

Yozo Miyake

Publications and source records attributed to Yozo Miyake.

At least 19 recordsLinked to original sources
PubMed2006

Complement factor H polymorphisms in Japanese population with age-related macular degeneration.

PURPOSE: To study the frequency of five haplotypes previously reported in the complement factor H (CFH) gene for Japanese patients with age-related macular degeneration (AMD). METHODS: Genomic DNA was isolated from peripheral blood samples taken from 96 Japanese AMD patients and 89 age-matched controls. All patients were diagnosed as having exudative (wet-type) AMD. The amplified polymerase chain reaction (PCR) products of CFH exons 2, 9, and 13, and intron 6 were analyzed by temperature gradient capillary electrophoresis (TGCE) and by direct sequencing. The haplotypes were identified, and their frequencies were calculated and compared with reported results. RESULTS: Five haplotypes were identified in the Japanese population including four already reported in the American population. The frequencies of these haplotypes were significantly different between Japanese and American in both control and case groups. The haplotype containing Y402H, which was previously reported to be associated with AMD, was only 4% in the control and case population, with a p value of 0.802. However, two other haplotypes were found as risk factors, which gave an increased likelihood of AMD of 1.9 and 2.5 fold (95% CI 1.12-3.69 and 1.42-6.38). One protective haplotype that decreased the likelihood of AMD by 1.6 fold (95% CI 0.26-0.67) was identified. CONCLUSIONS: The frequencies for five haplotypes previously identified were analyzed in a Japanese population with AMD. Four previously found haplotypes were identified and one additional haplotype was found. The frequencies of each haplotype were significantly different from that in found Americans affected with AMD. Two of the haplotypes were identified as risk factors and one was considered protective.

Aged↗
PubMed2006

Recording rod ON and OFF responses in ERG and multifocal ERG.

The 5 Hz rectangle stimulus was generally used to record cone ON and OFF response. In this study, the feasibility and recording conditions of recording rod ON and OFF responses in electroretinograms (ERG) and multifocal electroretinograms (mf-ERG) were described, and the character and influence factors of these responses were observed. The result demonstrated that the rod ON and OFF responses of ERG can be recorded with sawtooth rapid-on and rapid-off stimulus. There is a small positive wave in downhill of negative wave in rod OFF response. Rod ON response of mf-ERG can be recorded with simulated rapid-on stimulus. We speculated that the simulated rapid-ON, sawtooth rapid-on and rapid-off stimulus can be an useful tool to investigate retinal disease and have certain clinical values.

Adult↗
PubMed2006

Novel mutations in the OPA1 gene and associated clinical features in Japanese patients with optic atrophy.

PURPOSE: Autosomal dominant optic atrophy (ADOA) is characterized by symmetrical bilateral optic atrophy associated with reduced corrected visual acuity (VA), central or centrocecal scotoma, and color vision disturbances. The disease is genetically heterogeneous, and the OPA1 gene has been identified as the only causative gene. The aims of this study were to identify and report mutations in the OPA1 gene in Japanese patients with ADOA and to describe the clinical features associated with the mutations. DESIGN: Molecular genetic study and observational case reports. PARTICIPANTS: Nine unrelated Japanese families with optic atrophy and 8 isolated cases of optic atrophy. METHODS: Genomic DNA was extracted from peripheral leukocytes, and all exons containing the open reading frame of the OPA1 gene and the flanking intron splice sites were sequenced directly. Complete ophthalmologic examinations were performed. MAIN OUTCOME MEASURES: Direct sequencing of the OPA1 gene and clinical evaluations including VA, visual field, color vision, and disc appearance. RESULTS: Ten different heterozygous mutations, including 6 novel mutations, were detected in the OPA1 gene. The identified mutations included 5 deletions/insertions (c.2061delA, c.2098_2103delCTTAAA, c.2538insT, c.2591insC, and c.2708_2711delTTAG), 4 nonsense mutations (c.112C>T [p.R38X], c.181C>T [p.Q61X], c.946A>T [p.R316X], and c.2713C>T [p.R905X]), and 1 missense mutation (c.1635C>A [p.S545R]). The most common mutation in Caucasians (c.2708_2711delTTAG) was found in 3 unrelated families, suggesting that it is a mutational hot spot. We detected an OPA1 mutation in 8 of 9 familial cases of optic atrophy and in 4 of 8 cases that were initially considered to be sporadic from the patients' family histories. Examinations of family members of 2 sporadic probands revealed the existence of other family members with the OPA1 mutations whose phenotype was very mild or within normal limits. This indicates that patients with ADOA sometimes seem to be sporadic because of the extensive variation in the phenotype or, alternatively, a low penetrance of ADOA. CONCLUSIONS: OPA1 gene mutations are causative in most familial cases of ADOA in Japanese. Sporadic cases of optic atrophy frequently may be caused by OPA1 mutations in the Japanese population. Molecular genetic examinations are useful in determining the hereditary patterns in some cases of optic atrophy.

Adult↗
PubMed2006

Selective amplitude reduction of the PhNR after macular hole surgery: ganglion cell damage related to ICG-assisted ILM peeling and gas tamponade.

PURPOSE: The photopic negative response (PhNR) is a negative component of the photopic electroretinogram (ERG) that is observed after the b-wave and is thought to originate mainly from the activity of ganglion cells and their axons. The purpose of this study was to determine whether there are subclinical functional changes in the inner retina after macular hole surgery, by recording the PhNR before and after surgery. METHODS: In addition to the routine ophthalmic examinations, photopic ERGs were recorded in 16 eyes with an idiopathic macular hole, before and 3 months after surgery. Photopic ERGs were elicited by white Ganzfeld flashes on a rod-suppressing blue background. The amplitude of the PhNR and the a- and b-waves of the photopic ERGs before and after surgery were compared. PhNRs were also recorded in 14 eyes with epiretinal membrane, before and after surgery. RESULTS: Macular holes were closed and visual acuities were improved without any serious complications in all eyes with a macular hole. The amplitude of the PhNR was significantly reduced after surgery (P < 0.05), whereas the amplitude of the photopic a- and b-waves were not significantly altered. For eyes with an epiretinal membrane, the mean amplitude of the PhNR was slightly decreased after the surgery, but the degree of reduction was only one half of that after macular hole surgery. CONCLUSIONS: These results suggest that there are some functional impairments in the inner retina after macular hole surgery, even though the patients did not show any reduction on subjective visual tests. The PhNR can be a useful clinical test to assess the inner retinal function objectively, before and after vitreoretinal surgery.

Adaptation, Ocular↗
PubMed2006

[Recording rod ON and OFF responses in ERG and multifocal ERG].

PURPOSE: To investigate feasibility and recording conditions of recording rod on and off responses in electroretinograms (ERG) and multifocal electroretinograms (mf-ERG), and observe character and influence factors of these responses. METHODS: ERG responses were recorded using the rectangle stimulus, sawtooth rapid-on and rapid-off stimulus in normal subjects after dark adaptation. Flash frequency and flash intensities varied to obtain appropriate recording conditions for clinical use. Mf-ERG responses were recorded in using simulated rectangle stimulus, saw tooth rapid-on and rapid-off stimulus. RESULTS: A large positive wave was found in ERG of rectangle stimulus and rapid-on stimulus. Increasing flash frequency decreased response amplitudes, however, the latency time changed little. A small negative wave with 80 ms latency time was found in ERG of rapid-off stimulus, and a very small positive wave with 75 ms latency time was found in the downhill of the negative wave. Increasing flash frequency increased latency time of the negative wave, but decreased the amplitude of the small positive wave. Oscillatory wave-like waves were found in the responses when flash frequency increased to 3 Hz. A large negative wave following a positive wave was found in mf-ERG of simulated rapid-off stimulus, which was difference from the wave of simulated rectangle stimulus and rapid-on stimulus. CONCLUSIONS: Rod on and off responses of ERG can be recorded with sawtooth rapid-on and rapid-off stimulus. There is a small positive wave in downhill of negative wave in rod off response. Rod on response of mf-ERG can be recorded with simulated rapid-on stimulus. The flash frequency of 0.5-1 Hz and small flash intensity were suggested to appropriate conditions for recording rod on and off responses in ERG. The simulated rapid-on, sawtooth rapid-on and rapid-off stimulus can be used to investigate retinal disease.

Adult↗
PubMed2005

Contribution of retinal neurons to d-wave of primate photopic electroretinograms.

The purpose of this study was to determine the contribution of different types of retinal neurons to the d-wave of the primate electroretinogram using pharmacological agents. NMDA + TTX was used to suppress inner retinal activity, and APB and PDA to block the activity of the ON- and OFF-pathways, respectively. Results indicated that the inner retinal neurons had a small but certain contribution to the d-wave. The initial rapid phase of the d-wave originates from the activity of the cone OFF-pathway nearly exclusively, and the later slow phase is shaped by the cone photoreceptors. The cone ON-pathway acts in a direction opposite to that of the other components.

Aminobutyrates↗
PubMed2005

Physiological function of S-cone system is not enhanced in rd7 mice.

The rd7mouse is a mutant mouse with a relatively late development of retinal degeneration. Earlier studies have shown that rd7 mice have a distinctive pattern of retinal dysplasia with an increased number of cone cells, particularly those with S (short wavelength)-opsin immunoreactivity. These alterations of the rd7 retina are caused by a mutation in the photoreceptor cell-specific nuclear receptor gene, Nr2e3, which is involved in the signaling pathway regulating photoreceptor cell differentiation, cell maintenance, and cell-cell interactions. The purpose of this study was to determine the physiological properties of the rd7 retina using electroretinographic (ERG) techniques. We found that the maximal a-wave amplitude of the ERG in rd7 mice was already reduced to half of the congenic controls at 6 weeks of age with normal phototransduction sensitivity. The photopic ERGs of rd7 mice were not supernormal, and the amplitudes of the S-cone ERGs were not significantly different from those recorded in controls. These results suggested that even though the number of cones expressing S-opsin is increased, the physiological function of the S-cone system is not enhanced in rd7 mice.

Animals↗
PubMed2005

Effect of plasmin on laminin and fibronectin during plasmin-assisted vitrectomy.

OBJECTIVE: To determine whether plasmin will cleave the laminin and fibronectin located at the vitreoretinal junction during plasmin-assisted vitrectomy. METHODS: Western blot analyses were performed with antilaminin or anti-fibronectin antibodies on the internal limiting membranes collected from patients with macular holes or cystoid macular edema who underwent vitrectomy with or without plasmin. The results were compared with the results of in vitro experiments in which commercially available laminin and fibronectin were exposed to commercially available plasmin. RESULTS: In all eyes treated with plasmin, a posterior vitreous detachment was not present before surgery but was created easily with a minimal suction of less than 100 mm Hg during vitrectomy. Western blot analyses showed that the laminin and fibronectin in the internal limiting membrane exposed to plasmin during vitrectomy were degraded to several fragments of lower molecular weights, including a fragment of approximately 13,000 Da for laminin and a fragment of approximately 30,000 Da for fibronectin. These lower-molecular-weight fragments also appeared in the in vitro experiments. CONCLUSION: The laminin and fibronectin at the vitreoretinal junction are degraded during plasmin-assisted vitrectomy. CLINICAL RELEVANCE: These findings provide evidence for the efficacy of using plasmin to create a posterior vitreous detachment during vitreoretinal surgery.

Basement Membrane↗
PubMed2005

Novel mutation in RLBP1 gene in a Japanese patient with retinitis punctata albescens.

PURPOSE: To report a novel mutation in the RLBP1 gene and optical coherence tomographic findings in a Japanese patient with retinitis punctata albescens. DESIGN: Observational case report. METHODS: The RLBP1 gene was analyzed by direct genomic sequencing. A complete ophthalmologic examination was performed. RESULTS: Compound heterozygous mutations in the RLBP1 gene were identified in the patient. The mutations were a novel missense Arg103Trp mutation and a missense Arg234Trp mutation, the causative mutation of Bothnia dystrophy. The patient's fundi showed numerous white dots with diffuse retinal mottling and bilateral macular degeneration. Her visual function deteriorated progressively during 12-year follow-up. Optical coherence tomography demonstrated decreased retinal thickness, especially the photoreceptor layer. CONCLUSION: A novel mutation in RLBP1 gene was found in a Japanese patient with retinitis punctata albescens. Degenerative changes of the outer retina were detected by optical coherence tomography.

Adolescent↗
PubMed2005

Macular hole development in fellow eyes of patients with unilateral macular hole.

PURPOSE: To determine the incidence of developing an idiopathic full-thickness macular hole in fellow eyes that have vitreofoveal attachments and perifoveal vitreous detachment in patients with unilateral idiopathic macular hole. DESIGN: Retrospective cross-sectional observational study. METHODS: The fellow eyes of 201 patients with full-thickness macular holes were examined by optical coherence tomography (OCT). A subset of 58 fellow eyes with vitreofoveal attachments and perifoveal vitreous detachment was observed during follow-up, and the changes in the vitreofoveal attachment within 24 months from the initial OCT examination were investigated. RESULTS: In the 58 eyes, the vitreofoveal relationship changed in 27 eyes. Among the 27 eyes, three eyes developed a full-thickness macular hole, and the other 24 eyes developed a posterior vitreous detachment only over the fovea or a complete posterior vitreous detachment without macular hole formation. The vitreofoveal relationship did not change in 31 eyes during the 24-month period. CONCLUSION: From an analysis of the changes in the vitreoretinal relationship identified by OCT, three (11%) of 27 fellow eyes in patients with unilateral idiopathic macular hole developed a full-thickness macular hole.

Aged↗
PubMed2005

Abnormalities caused by carbohydrate alterations in Ibeta6-N-acetylglucosaminyltransferase-deficient mice.

Ibeta6-N-acetylglucosaminyltransferase (IGnT) catalyzes the branching of poly-N-acetyllactosamine carbohydrate chains. In both humans and mice, three spliced forms of IGnT have been identified, and a common exon is present in all of them. We generated mice deficient in the common exon to understand the physiological function of poly-N-acetyllactosamine branching. IGnT activity was abolished in the stomach, kidney, bone marrow, and cerebellum of the deficient mice, while a low level of the activity persisted in the small intestine. Immunohistochemical analysis confirmed the loss of I antigen from the lung, stomach, and kidney. The deficient mice had reduced spontaneous locomotive activity. The number of peripheral blood lymphocytes was also reduced and renal function decreased in the deficient mice. Furthermore, in aged mice, vacuolization occurred in the kidney, and epidermoid cysts were frequently formed. However, cataracts did not develop earlier in the deficient mice. Decreased levels of lysosomal proteins, LAMP-2 and synaptotagmin VII, were found in the kidney of the deficient mice and correlated with renal abnormalities.

Animals↗
PubMed2005

Cone and rod dysfunction in fundus albipunctatus with RDH5 mutation: an electrophysiological study.

PURPOSE: A prior study showed that some patients with fundus albipunctatus (FA) have severely reduced full-field cone ERGs. The purpose of this study was to investigate the frequency of cone dysfunction and to determine the cause of the reduced full-field cone ERGs in patients with FA and whether the rod system is affected in patients with FA. METHODS: Sixteen consecutive patients with FA (from 1993 to 2003; eight males, eight females; mean age, 25.4 years) with an RDH5 gene mutation were studied. The amplitudes and implicit times of the standard cone ERGs in the patients with FA were compared to those obtained from normal subjects (n = 55). The a-waves of cone ERGs were also elicited by a bright flash and were fitted to a mathematical model of the a-wave. Rod ERG responses were elicited by dim blue flashes after 3 hours of dark adaptation. RESULTS: The amplitude of the b-wave of the cone ERG in the FA group varied considerably from within the normal limits to markedly decreased. Six of 16 patients with FA had b-wave amplitudes that were smaller than the lowest limit of the control subjects. The degree of cone dysfunction tended to be more severe in older patients. The analysis of the cone a-wave demonstrated that R(m) (maximal response amplitude) in the patients with FA with reduced standard cone ERGs was significantly smaller than that in control subjects. Rod ERGs were also reduced in the patients with FA who had reduced cone ERGs. CONCLUSIONS: In patients with FA, 38% had extensive cone dysfunction. The reduced full-field cone ERGs were mainly due to the loss of cone photoreceptors, and the rod system was also affected in some patients.

Adolescent↗
PubMed2005

Functional analysis of the effect of forced activation of STAT3 on M1 mouse leukemia cells.

M1 mouse myeloid leukemia cells exhibit growth arrest and differentiation to monocytes/macrophages in response to leukemia inhibitory factor (LIF) stimulation. Although recent studies have demonstrated that STAT3 plays a central role in this process, it is unknown whether STAT3 activation alone is sufficient. To address this issue, we have established M1/STAT3ER cells, where STAT3 is selectively activated by 4-hydroxytamoxifen (4HT). 4HT stimulation did not have any effect on growth and morphology of M1/ STAT3ER cells, and did not induce the down-regulation of mRNA of c-myc and c-myb, which is necessary for M1 cell differentiation. On the other hand, mRNA of jun-B, IRF1 and p19 was increased by 4HT. DNA precipitation assay indicated that both stimulation of LIF and 4HT similarly activated STAT3ER. Introduction of a constitutive active MAP kinase kinase (MEK1) into M1/STAT3ER cells did not induce differentiation either. Together, our present data suggest that signaling other than the activation of STAT3 and MEK1 may be necessary for M1 cell-growth arrest and differentiation, while a set of early genes of LIF are induced by only STAT3 activation.

Animals↗