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Biomedical subjects

Akira Hirata

Publications and source records attributed to Akira Hirata.

At least 37 records · Page 2Linked to original sources
PubMed2005

Expression of a chondroitin sulfate proteoglycan, versican (PG-M), during development of rat cornea.

PURPOSE: To understand the role of chondroitin sulfate proteoglycans during the development of rat cornea, expression of chondroitin sulfate and versican (PG-M) was studied. METHODS: Chondroitin sulfate and keratan sulfate in rat cornea were analyzed by immunohistochemical techniques. Reverse transcription polymerase chain reaction (RT-PCR) for chondroitin sulfate proteoglycans was performed. Versican expression was studied by RT-PCR, immunohistochemical, and dot blot analyses. Expression of hyaluronan was evaluated histochemically using biotinylated hyaluronan binding protein. RESULTS: Chondroitin sulfate was abundant in rat cornea at postnatal day 1 (P1) and became undetectable at P14. RT-PCR analysis showed that versican mRNA was highly expressed at P1 but was little expressed at P42. mRNAs for other chondroitin sulfate proteoglycans including biglycan, aggrecan, and decorin did not change much between P1 and P42. Expression for all versican splicing isoforms (V0-V3) was detectable from P1 through P14 but was undetectable after P21. mRNA for V0, the largest form with many chondroitin sulfate binding sites, decreased markedly in early stages from P1 to P14, whereas mRNA for V3, the shortest form with no chondroitin sulfate binding site, increased. mRNAs for middle-sized forms, V1 and V2, remained little changed during these periods. Immunohistochemical and dot blot analyses showed that versican is highly expressed at early stages of development and little expressed at adulthood. Similarly, hyaluronan, a versican-bound glycosaminoglycan, was highly expressed at early stages and little expressed at adulthood. CONCLUSIONS: Versican and hyaluronan, which can form a large molecular complex, may play an important role in the early phase of corneal development.

Aging↗
PubMed2005

A case of Chandler's syndrome revealed by ultrastructural studies of the trabecular meshwork.

PURPOSE: To investigate ultrastructural changes in the aqueous outflow route and discuss the mechanisms associated with intraocular pressure (IOP) elevation in a patient with presumably early stage Chandler's syndrome. METHODS: A 47-year-old man underwent trabeculectomy because of elevated IOP. A specimen obtained during surgery was studied by transmission electron microscopy. RESULTS: Electron microscopy showed the presence of a monolayer composed of corneal endothelium-like cells and thick basement membrane-like material. Neovascularization was also observed in the corneoscleral trabeculum. CONCLUSIONS: Our results indicate that several mechanisms, including the formation of basement membrane-like tissue, infiltration of inflammatory cells and neovascularization, might contribute to the elevation of IOP in Chandler's syndrome. These may occur even when there is no history of conspicuous inflammatory reaction in the anterior ocular segments.

Aqueous Humor↗
PubMed2005

Characterization of denitrifying polyphosphate-accumulating organisms in activated sludge based on nitrite reductase gene.

Nitrite reductase gene (nirS) fragments in the activated sludge obtained from a sequencing batch reactor (SBR) under anaerobic-aerobic condition were cloned and classified by restriction fragment length polymorphism (RFLP) analysis, and representative fragments were sequenced. One of the nirS clones was approximately 70% of all nirS clones in anaerobic/aerobic (existing oxygen and nitrate) cycle operation in which a large amount of anoxic phosphate uptake was observed. Although the activated sludge samples analyzed might contain bacteria that did not accumulate polyphosphate, it was likely that this nirS fragment sequence was that from denitrifying polyphosphate-accumulating organisms (DNPAOs) which can utilize both oxygen and nitrate as electron acceptors. The sequence was similar to the nirS sequences of Thauera mechernichensis (83% similarity) and Azoarcus tolulyticus (83% similarity) both of which belong to the Rhodocyclus group.

Genes, Bacterial↗
PubMed2004

Significance of cell electrokinetic properties determined by soft-particle analysis in bacterial adhesion onto a solid surface.

The influence of extracellular polymeric substances (EPSs) on bacterial cell electrokinetic properties and on cell adhesion onto glass beads in connection with bacterial cell electrokinetic properties was investigated using 12 heterotrophic bacterial strains. Bacterial cell surface properties such as the softness 1/lambda and charge density ZN were determined by Ohshima's soft-particle analysis using the measured electrophoretic mobility as a function of ionic strength. In 10 of 12 strains, when EPSs covering the cell surface were removed, the softness of the cell decreased, indicating that EPS adsorption enhanced the ease of liquid fluid in the ion-penetrable layer on the cell surface. On the other hand, the negative charge density of the cell surface increased for 9 of 12 strains, suggesting that EPSs covering the cell surface decreased the negative charge density of the cell surface layer. In addition, the characteristics of bacterial cell adhesion onto glass beads were evaluated by the packed-bed method and the data were interpreted to indicate cell adhesiveness. As a result, the efficiency of cell adhesion onto glass beads increased as negative cell surface potential psi0 decreased, whereas there seemed to be no correlation between zeta potential and cell adhesiveness. Cell surface potential psi0, which was derived by taking the bacterial polymer layer with EPSs into consideration, provided a more detailed understanding of the electrokinetic properties of bacterial cells.

Bacteria↗
PubMed2004

Engineering of the pH optimum of Bacillus cereus beta-amylase: conversion of the pH optimum from a bacterial type to a higher-plant type.

The optimum pH of Bacillus cereus beta-amylase (BCB, pH 6.7) differs from that of soybean beta-amylase (SBA, pH 5.4) due to the substitution of a few amino acid residues near the catalytic base residue (Glu 380 in SBA and Glu 367 in BCB). To explore the mechanism for controlling the optimum pH of beta-amylase, five mutants of BCB (Y164E, Y164F, Y164H, Y164Q, and Y164Q/T47M/Y164E/T328N) were constructed and characterized with respect to enzymatic properties and X-ray structural crystal analysis. The optimum pH of the four single mutants shifted to 4.2-4.8, approximately 2 pH units and approximately 1 pH unit lower than those of BCB and SBA, respectively, and their k(cat) values decreased to 41-3% of that of the wild-type enzyme. The X-ray crystal analysis of the enzyme-maltose complexes showed that Glu 367 of the wild type is surrounded by two water molecules (W1 and W2) that are not found in SBA. W1 is hydrogen-bonded to both side chains of Glu 367 and Tyr 164. The mutation of Tyr 164 to Glu and Phe resulted in the disruption of the hydrogen bond between Tyr 164 Oeta and W1 and the introduction of two additional water molecules near position 164. In contrast, the triple mutant of BCB with a slightly decreased pH optimum at pH 6.0 has no water molecules (W1 and W2) around Glu 367. These results suggested that a water-mediated hydrogen bond network (Glu 367...W1...Tyr 164...Thr 328) is the primary requisite for the increased pH optimum of wild-type BCB. This strategy is completely different from that of SBA, in which a hydrogen bond network (Glu 380...Thr 340...Glu 178) reduces the optimum pH in a hydrophobic environment.

Asparagine↗
PubMed2004

Expression of amoA mRNA in wastewater treatment processes examined by competitive RT-PCR.

The expression of ammonia monooxygenase encoding mRNA (amoA mRNA) in a wastewater treatment process was analyzed in an attempt to propose an effective target for the monitoring of nitrifying bacteria in engineered systems or natural environments. The quick response (1-2 h) of amoA mRNA transcription to the recovery of ammonia oxidation activity induced by the sudden exposure to ammonia was observed in a short-time batch-mode incubation whereas the amount of amoA DNA did not markedly change during the incubation under any conditions. In the continuous feeding-operation, amoA mRNA level dynamically changed in response to the change in the surrounding environmental conditions and increase in ammonia oxidation rate. Although, amoA mRNA level did not quickly respond to the decrease in ammonia oxidation activity, it decreases over long time scales. These results suggest that the profiles of amoA mRNA expression can be used as an indicator of the ammonia oxidation activity.

Ammonia↗
PubMed2004

Design of 16S rRNA-targeted oligonucleotide probes and microbial community analysis in the denitrification process of a saline industrial wastewater treatment system.

Three 16S rRNA-targeted oligonucleotide probes, namely, PSMg437 targeting several members of the genus Pseudomonas, Hlm474 targeting several members of the genus Halomonas, and Clw844 targeting several members of the genus Colwellia, were designed. The microbial community structure and nitrogen removal ability of nitrate-containing saline wastewater treatment systems with anaerobic packed bed and fluidized bed were monitored. Direct cell counting using fluorescence in situ hybridization (FISH) images revealed that various phylogenetic groups were evenly distributed in the anaerobic packed bed whereas members of the genus Halomonas were dominant particularly in the anaerobic fluidized bed. These results suggest that the microbial communities produced by different flow conditions correlated with denitrification ability in saline industrial wastewater treatment systems.

Bioreactors↗
PubMed2004

Elevated erythropoietin in vitreous with ischemic retinal diseases.

The aim of the current study was to measure the concentrations of erythropoietin in the vitreous fluid and analyze its association with vascular endothelial growth factor (VEGF) in ischemic vitreoretinal diseases. Vitreous fluid samples were collected from patients with proliferative diabetic retinopathy, branch retinal vein occlusion and idiopathic macular hole. Concentrations of erythropoietin and VEGF in vitreous fluid were significantly elevated in patients with proliferative diabetic retinopathy and branch retinal vein occlusion as compared to patients with macular hole. There were no differences in serum concentrations of erythropoietin and VEGF among patient groups. There was significant correlation between erythropoietin and VEGF concentrations in vitreous fluid. Erythropoietin was up-regulated in ischemic disorders and may act as an endogenous neuroprotective factor against ischemic retinal disorders.

Aged↗
PubMed2004

Ruptured internal limiting membrane associated with blunt trauma revealed by indocyanine green staining.

PURPOSE: Description of cases of traumatic macular hole that appeared concomitant with a ruptured internal limiting membrane (ILM) that was apparent during vitrectomy only after staining with indocyanine green (ICG). METHODS: Vitrectomy with ILM peeling was performed on a 20-year-old man and a 13-year-old boy for treatment of traumatic macular holes. RESULTS: During vitrectomy, the ILM was found to be ruptured along the area of an identified macular hole only after ICG staining. After the vitrectomy, the macular holes were closed and visual acuity improved. However, visual field defect associated with apparent inner-layer retinal damage remained. CONCLUSION: Blunt trauma can cause severe inner-layer retinal damage with rupture of the ILM as well as frank macular hole formation and choroidal rupture.

Adolescent↗
PubMed2004

Morphological damage in rabbit retina caused by subretinal injection of indocyanine green.

PURPOSE: To investigate the effects of subretinal indocyanine green (ICG) on retinal morphology in rabbit eyes. METHODS: Retinal bleb detachments were produced by injections of ICG at dosages of 25 mg/ml, 5 mg/ml, and 0.5 mg/ml or with an injection of balanced salt solution (BSS) into the subretinal space of albino rabbit eyes. Morphological change was assessed by light and transmission electron microscopy from the viewpoint of dose and time. Some sections were also probed with the TUNEL technique to detect apoptotic cells. RESULTS: At 14 days after subretinal injection of BSS and 0.5 mg/ml ICG, the structure of the retina was well preserved. However, injections of 5 mg/ml or 25 mg/ml caused thinning of the retina, especially loss of the outer retinal layer. In eyes injected with 5 mg/ml ICG, the photoreceptors began disappearing within 3 days after the injection and over time showed the development of retinal atrophy. TUNEL-positive cells appeared abundantly in the photoreceptor layers 1 and 3 days after the injection of 5 mg/ml ICG. Transmission electron microscopy confirmed apoptosis in the photoreceptors. CONCLUSION: These data indicate that subretinal ICG induces apparent morphological damage of the retina in a dose-dependent manner.

Animals↗
PubMed2004

PDZ domain-binding motif of human T-cell leukemia virus type 1 Tax oncoprotein augments the transforming activity in a rat fibroblast cell line.

While human T-cell leukemia virus type 1 (HTLV-1) is associated with the development of adult T-cell leukemia (ATL), HTLV-2 has not been reported to be associated with such malignant leukemias. HTLV-1 Tax1 oncoprotein transforms a rat fibroblast cell line (Rat-1) to form multiple large colonies in soft agar, and this activity is much greater than that of HTLV-2 Tax2. We have demonstrated here that the increased number of transformed colonies induced by Tax1 relative to Tax2 was mediated by a PDZ domain-binding motif (PBM) in Tax1, which is absent in Tax2. Tax1 PBM mediated the interaction of Tax1 with the discs large (Dlg) tumor suppressor containing PDZ domains, and the interaction correlated well with the transforming activities of Tax1 and the mutants. Through this interaction, Tax1 altered the subcellular localization of Dlg from the detergent-soluble to the detergent-insoluble fraction in a fibroblast cell line as well as in HTLV-1-infected T-cell lines. These results suggest that the interaction of Tax1 with PDZ domain protein(s) is critically involved in the transforming activity of Tax1, the activity of which may be a crucial factor in malignant transformation of HTLV-1-infected cells in vivo.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Therapeutic factors causing hallucination in Parkinson's disease patients, especially those given selegiline.

Selegiline protects nigral dopaminergic neurons and is recommended for the treatment of patients in the early stage of Parkinson's disease (PD). We treated 112 PD patients and noted that those given selegiline had a high incidence of hallucination. Our objective was to determine which clinical therapeutic factors cause such hallucinations. The Kruskal-Wallis and chi-square test showed that in 94 patients, the severity of the hallucinations was significantly related to the duration of illness, Hoehn and Yahr stage, doses of levodopa and cabergoline, whether or not selegiline was used, and whether or not medication for constipation was required. In addition, patients who were treated with a low dose of levodopa (< or =300 mg/day), who had a low Hoehn and Yahr stage, and a short duration of illness (< or =8 years) together with a high dose of selegiline or cabergoline also tended to have hallucinations. MRI findings were not related to the incidence of hallucination. When selegiline is given to patients who have PD of long duration and a high Hoehn and Yahr stage, and who already are receiving levodopa and a dopamine agonist, the doses of levodopa and the dopamine agonists given, as well as the presence of constipation, may be related to the incidence of hallucination.

Adult↗
PubMed2004

Monitoring the microbial population dynamics at the start-up stage of wastewater treatment reactor by terminal restriction fragment length polymorphism analysis based on 16S rDNA and rRNA gene sequences.

The microbial population dynamics at the start-up stage of a wastewater treatment reactor was investigated using terminal restriction fragment length polymorphism (T-RFLP) analysis based on 16S rDNA and rRNA gene sequences. The results of fragment peaks suggested that the number and activity of nitrifying bacteria increased in association with the start of nitrification, and the relative ratios of 16S rRNA of these bacteria changed prior to those of the 16S rDNA. Furthermore, multidimensional scaling (MDS) analysis revealed that the 16S rRNA exhibited wider dispersion than the 16S rDNA at the start-up stage, indicating that the diversity of 16S rRNA in the microbial communities was strongly affected by environmental changes.

Journal Article↗
PubMed2004

A case of vitreous amyloidosis without systemic symptoms in familial amyloidotic polyneuropathy.

We describe a case of vitreous amyloidosis without systemic symptoms in familial amyloidotic polyneuropathy (FAP) associated with Val30Met transthyretin mutation. A healthy 74-year-old woman noticed left blurred vision and floaters in 1992. Severe vitreous opacities were identified in the left eye. The patient displayed no systemic symptoms, and Congo red staining of the biopsy samples of the stomach and duodenum revealed no amyloid deposition. A diagnosis of FAP was confirmed following genetic investigation. Vitrectomy and cataract surgery was performed with intraocular lens implantation in April 1998. Histopathological examination of the vitreous material revealed amyloid fibrils. Intraocular pressure (IOP) gradually elevated and cupping of the optic disc enlarged. Trabeculectomy was performed in February 2000, but postoperative IOP was again elevated and a needling procedure was performed in March 2000. No postoperative recurrence of vitreous opacity has been reported and IOP has remained well controlled. In the present case, ocular manifestations were the only symptoms of FAP and systemic symptoms have not developed, after more than 12 years. FAP should be suspected as the cause in cases of vitreous opacities in patients from areas with endemic foci of FAP.

Aged↗
PubMed2004

Direct inhibition of EGF receptor activation in vascular endothelial cells by gefitinib ('Iressa', ZD1839).

The development of gefitinib ('Iressa', ZD1839) by targeting the EGFR tyrosine kinase is a recent therapeutic highlight. We have reported that gefitinib is antiangiogenic in vitro, as well as in vivo. In this study, we asked if the anti-angiogenic action of gefitinib is due to a direct effect on activation of vascular endothelial cells by EGF. EGF, as well as VEGF, caused pronounced angiogenesis in an avascular area of the mouse cornea, and i.p. administration of gefitinib almost completely blocked the response to EGF, but not to VEGF. Immunohistochemical analysis demonstrated phosphorylation of EGFR by EGF in the neovasculature, and gefitinib markedly reduced this effect. Gefitinib also inhibited downstream activation of ERK 1/2 via EGFR in cultured microvascular endothelial (HMVE) cells. These findings suggest that the anti-angiogenic effect of gefitinib in the vascular endothelial cells of neo-vasculature is partly attributable to direct inhibition of EGFR activation, and that endothelial cells in malignant tumors play a critical role in the cancer therapeutic efficacy of gefitinib.

Antineoplastic Agents↗