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Biomedical subjects

Akira Hirata

Publications and source records attributed to Akira Hirata.

67 records · Page 4Linked to original sources
PubMed2003

New infusion cannula for prevention of retinal damage by infusion air during vitrectomy.

PURPOSE: Postoperative visual field defects are sometimes found after macular hole surgery. We have previously shown that damage to the retina by air infusion from an infusion cannula is a causative factor. To minimize such damage, we modified the infusion cannula and examined its effects experimentally. METHODS: An infusion cannula with a closed tip and openings on four sides was created. Experimentally, a vitrectomy was performed in rabbit eyes using this new infusion cannula or a conventional cannula. After fluid-air exchange at an air pressure of 40 mmHg, eyes were removed and processed for histologic examination. The areas of the retinal damage caused by air infusion were evaluated. RESULTS: The area of retinal damage created by the new cannula was reduced significantly when compared with damage from conventional cannula use. CONCLUSION: This new cannula, designed for the purpose of scattering the air infusion, can reduce retinal damage, which leads to less frequent postoperative visual field defects.

Air↗
PubMed2003

Probable sporadic Creutzfeldt-Jakob disease with valine homozygosity at codon 129 and bilateral middle cerebellar peduncle lesions.

We describe a 67-year-old Japanese man with probable sporadic Creutzfeldt-Jakob disease (CJD) who had valine homozygosity at codon 129, a rarity in the Japanese. T2-weighted magnetic resonance imaging (MRI) detected high-intensity lesions in the bilateral middle cerebellar peduncles and basal ganglia as well as cerebellar and cortical atrophy. He developed cerebellar ataxia and subsequent mental deterioration, myoclonus, and periodic synchronous discharge as shown in an electroencephalogram. Cerebrospinal fluid examination showed a high level of neuron-specific enolase and a positive immunoassay for the 14-3-3 protein. He died of pneumonia 10 months after the initial symptoms appeared. Whether or not the genetic polymorphism increased his susceptibility to sporadic CJD is not clear because valine homozygosity at codon 129 is less than 1% in the normal Japanese population. Although there is no convincing evidence in the present case, the MRI findings of cerebellar peduncle changes, which are rare in CJD, suggest a kind of degeneration, demyelination, or both.

Aged↗
PubMed2002

Intrathecal administration of nerve growth factor delays GAP 43 expression and early phase regeneration of adult rat peripheral nerve.

Whether nerve growth factor (NGF) promotes peripheral nerve regeneration in vivo, in particular in adults, is controversial. We therefore examined the effect of exogenous NGF on nerve regeneration and the expression of GAP 43 (growth-associated protein 43) in adult rats. NGF was infused intrathecally via an osmotic mini-pump, while control rats received artificial cerebrospinal fluid. Two days after the infusion was initiated, the right sciatic nerves were transected or crushed, and the animals allowed to survive for 3 to 11 days. The right DRG, the right proximal stump of the transected sciatic nerve, and the posterior horn of the spinal cord were examined by Western blotting, immunohistochemistry, and electron microscopy. GAP 43 immunoreactivity in the NGF-treated animals was significantly lower than in the aCSF-treated controls. Electron microscopy showed that the number of myelinated and unmyelinated axons decreased significantly in the NGF-treated rats as compared with the controls. These findings are indicative that exogenous NGF delayed GAP 43 induction and the early phase of peripheral nerve regeneration and supports the hypothesis that the loss of NGF supply from peripheral targets via retrograde transport caused by axotomy serves as a signal for DRG neurons to invoke regenerative responses. NGF administered intrathecally may delay the neurons' perception of the reduction of the endogenous NGF, causing a delay in conversion of DRG neurons from the normal physiological condition to regrowth state.

Animals↗
PubMed2002

ZD1839 (Iressa) induces antiangiogenic effects through inhibition of epidermal growth factor receptor tyrosine kinase.

Epidermal growth factor receptor (EGFR) tyrosine kinase is a potential target for anticancer therapy. ZD1839 (Iressa) is a selective inhibitor of EGFR tyrosine kinase. In this study, we investigated the question as to whether the antitumor effect of ZD1839 is partly attributable to antiangiogenic activity and the potential mechanisms involved. Both ZD1839 and SU5416 [a vascular endothelial growth factor (VEGF)-receptor tyrosine kinase inhibitor] inhibited the migration of human umbilical vein endothelial cell cocultivated with EGF-stimulated cancer cells. ZD1839 also inhibited EGF-induced migration and the formation of tube-like structures by human microvascular endothelial cells. Moreover, ZD1839 almost completely blocked EGF-induced neovascularization of mice cornea, and SU5416 partially blocked neovascularization. In contrast, ZD1839 did not inhibit VEGF-induced angiogenesis. However, EGF-induced up-regulation of the angiogenic factors, VEGF and IL-8, was almost completely blocked by ZD1839. The antitumor effects of ZD1839 could, therefore, be mediated in part by the inhibition of tumor angiogenesis through direct effects on microvascular endothelial cells that express EGFR and also through reduced production of proangiogenic factors by tumor cells.

Angiogenesis Inhibitors↗
PubMed2002

Coinduction of nitric oxide synthase and arginine metabolic enzymes in endotoxin-induced uveitis rats.

The regulation of expression of the arginine-recycling enzymes and arginase isoforms in association with inducible nitric oxide synthase (iNOS) in the eye of endotoxin-induced uveitis (EIU) rats is investigated. An animal model of EIU was created in Wistar rats by intravitreal injection of lipopolysaccharide (LPS). mRNAs for argininosuccinate synthase (AS) and arginase I as well as for iNOS, measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), were induced in the eye of EIU rats. iNOS mRNA increased markedly 3 hr after injection, reached a maximum at 6-12 hr, and then decreased at 24 hr. AS mRNA remained little change at 3 hr and increased maximally at 6 hr (by about 3.3-fold), whereas arginase I mRNA increased later and reached a maximum at 12 hr (by about 4.2-fold). iNOS, AS, and arginase I proteins were also induced. AL and arginase II mRNAs remained little changed. In immunohistochemical analysis, iNOS, AS and arginase I were almost colocalized in infiltrated inflammatory cells in the vitreous, iris, ciliary body and inner layers of the retina. In conclusion, AS and arginase I are coinduced with iNOS in infiltrated inflammatory cells in the eyes of EIU rats, and may regulate NO production by changing intracellular concentration of arginine.

Animals↗
PubMed2002

Expression of dystroglycan and the laminin-alpha 2 chain in the rat peripheral nerve during development.

In Schwann cells, the transmembrane glycoprotein beta-dystroglycan comprises the dystroglycan complex, together with the extracellular glycoprotein alpha-dystroglycan, which binds laminin-2 (alpha 2/beta 1/gamma 1), a major component of the Schwann cell basal lamina. To provide clues to the biological functions of the interaction of the dystroglycan complex with laminin-2 in peripheral nerves, we investigated the expression of beta-dystroglycan and the laminin-alpha 2 chain in rat sciatic nerve during development by immunoblot, immunofluorescence, and immunoelectron microscopic studies. The expression of beta-dystroglycan and the laminin-alpha 2 chain in the rat sciatic nerve was low and not confined to the Schwann cell outer membrane from embryonic day 18 to birth, when there was only an immature basal lamina assembly and no compact myelin formation by Schwann cells. However, the expression of these proteins increased markedly and became clearly localized to the Schwann cell outer membrane between birth and postnatal day 7, when both basal lamina assembly and compact myelin formation by Schwann cells progressed rapidly. From postnatal day 7 to adult, there was no remarkable change in the expression of these proteins. Our results support the hypothesis that the dystroglycan complex functions as an adhesion apparatus, binding the Schwann cell outer membrane with the basal lamina, and suggest that the dystroglycan complex plays a role in Schwann cell myelination through its interaction with laminin-2.

Aging↗
PubMed2002

Intraocular infiltration of adult T-cell leukemia.

PURPOSE: To report a case of adult T-cell leukemia (ATL) with unilateral dense vitreous opacities that benefited from vitrectomy. DESIGN: Interventional case report. METHODS: Diagnostic vitrectomy was performed on a 59-year-old man with ATL who had vitreous opacity in the right eye. RESULTS: White infiltration of the retina was noted after vitrectomy. Cytologic examination of the vitreous specimen obtained during surgery revealed infiltration of ATL cells into the vitreous and retina. After vitrectomy and additional chemotherapy, visual acuity improved in the right eye from 20/100 to 25/20. CONCLUSION: Infiltration of the vitreous and retina by ATL is rare. Diagnostic vitrectomy is effective for treatment and visual improvement.

Drug Therapy↗
PubMed2002

Characterization of denitrifying phosphate-accumulating organisms cultivated under different electron acceptor conditions using polymerase chain reaction-denaturing gradient gel electrophoresis assay.

To investigate the characteristics and the microbial diversity of denitrifying phosphate-accumulating organisms (DNPAOs) that are capable of conducting enhanced biological phosphorus removal (EBPR) using nitrate as electron acceptor, three sequencing batch reactors were operated under three different electron acceptor conditions, i.e., only oxygen, oxygen together with nitrate and only nitrate. Based on the chemical analysis concerning the biochemical transformation of each reactor, it was found that phosphate-accumulating organisms responsible for EBPR consisted of at least three populations including DNPAOs, and that the microbial community structure was changed according to the electron acceptor conditions. Also, the sludge cultivated with oxygen together with nitrate showed a drastic increase in the amount of phosphorus uptake under anoxic conditions, which suggested that a proportion of DNPAOs capable of utilizing nitrate under aerobic conditions were present. On the other hand, the change in microbial community structure depending on the type of electron acceptor was demonstrated by the analysis of the results of denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 16S ribosomal DNA fragments. It was found that the bacteria commonly contained in all the reactors were Rhodocyclus sp. (96% identity) and Dechlorimonas sp. (97% identity) that belonged to the beta subclass of Proteobacteria on the basis of the analysis of the sequence excised from DGGE bands and the determination of phylogenetic affiliation. However, only the presence of Rhodocyclus sp. in all the reactors was demonstrated by fluorescent in situ hybridization analysis.

Bacteria↗
PubMed2002

Human T-cell leukemia virus type 2 (HTLV-2) Tax protein transforms a rat fibroblast cell line but less efficiently than HTLV-1 Tax.

Human T-cell leukemia virus type 1 (HTLV-1) and HTLV-2 are retroviruses with similar biological properties. Whereas HTLV-1 is the causative agent of an aggressive T-cell leukemia, HTLV-2 has been associated with only a few cases of lymphoproliferative disorders. Tax1 and Tax2 are the transcriptional activators of HTLV-1 and HTLV-2, respectively. Here we show that Tax2 transformed a Rat-1 fibroblast cell line to form colonies in soft agar, but the size and number of the colonies were lower than those of Tax1. Use of a chimeric Tax protein showed that the C-terminal amino acids 300 to 353 were responsible for the high transforming activity of Tax1. Activation of cellular genes by Tax1 through transcription factor NF-kappa B is reportedly essential for the transformation of Rat-1 cells. Tax2 also activated the transcription through NF-kappa B in Rat-1 cells, and such activity was equivalent to that induced by Tax1. Thus, the high transforming activity of Tax1 is mediated by mechanisms other than NF-kappa B activation. Our results showed that Tax2 has a lower transforming activity than Tax1 and suggest that the high transforming activity of Tax1 is involved in the leukemogenic property of HTLV-1.

Amino Acid Sequence↗
PubMed2002

Motor dominant neuropathy in Sjögren's syndrome: report of two cases.

Most of the peripheral neuropathies in Sjögren's syndrome (SS) are sensory- or autonomic-dominant. In this report, we present two cases of a rare type of neuropathy, motor dominant neuropathy, in SS. One showed signs similar to those of Guillain-Barré syndrome, and the other showed signs characteristic of chronic inflammatory demyelinating polyradiculoneuropathy. These patients received i.v. immunoglobulin therapy. To our knowledge, this is the first report indicating that i.v. immunoglobulin has beneficial effects on motor dominant neuropathy in SS.

Aged↗
PubMed2002

Amyloid deposition in ocular tissues of patients with familial amyloidotic polyneuropathy (FAP).

It is known that the severity of ocular symptoms does not always correlate with the systemic symptoms in patients with familial amyloidotic polyneuropathy (FAP ATTR V30M). The ocular tissues may have their own TTR metabolic system. The aim of this study is to clarify the distribution of amyloid deposition in the ocular tissues and to investigate the relationship between ocular symptoms and histopathological changes. We analyzed histopathologically 9 autopsied eyes taken from 3 Japanese and 6 Swedish patients with FAP ATTR V30M. Localization of amyloid deposition varied among the different cases, but there were some tendencies in the distribution. The degree of amyloid deposition in the ocular tissues was not always correlated with the duration of the disease. The frequency of amyloid deposition in the conjunctiva, iris, trabecular meshwork and vitreous body were 88.9%, 44.4%, 11.1% and 11.1% respectively in the 9 patients. These frequencies in the histopathological changes correlated with the frequencies in the clinical ocular manifestations as previously reported.

Adult↗
PubMedDate not supplied

Vitreous fluid levels of beta-amyloid((1-42)) and tau in patients with retinal diseases.

PURPOSE: A decrease in beta-amyloid(1-42) (Abeta42) and an increase in tau in the cerebrospinal fluid are reported to be characteristic phenomena in Alzheimer's disease patients. To test the idea that Abeta42 and tau contribute to the development of retinal diseases, we measured Abeta42 and tau concentrations in the vitreous fluid from patients with macular hole (n = 13), diabetic retinopathy (n = 15), or glaucoma concurrent with other ocular diseases (n = 8). METHODS: Vitreous samples were collected from patients who underwent vitrectomy, and sensitive and specific enzyme-linked immunosorbent assays were used to determine the concentrations of Abeta42 and tau. RESULTS: By comparison with the levels in the control macular-hole patients (33.9 +/- 7.1 pg/ml for Abeta42; 3.3 +/- 3.2 pg/ml for tau), there was a significant decrease in the Abeta42 level and a significant increase in the tau level in patients with diabetic retinopathy (1.8 +/- 1.9 pg/ml for Abeta42, P = 0.002; 153.7 +/- 71.6 pg/ml for tau, P = 0.041) or glaucoma concurrent with other ocular diseases (2.8 +/- 1.8 pg/ml for Abeta42, P = 0.006; 113.6 +/- 43.1 pg/ml for tau, P = 0.023). CONCLUSIONS: Our findings indicate the possibility of a role for Abeta42 and tau in the pathogenesis of some retinal diseases.

Aged↗