Biomedical subjects

M Tamai

Publications and source records attributed to M Tamai.

At least 19 recordsLinked to original sources

PubMed2001

Expression of tyrosinase-related protein 2/DOPAchrome tautomerase in the retinoblastoma.

Tyrosinase-related protein 2 (TRP-2), also known as DOPAchrome tautomerase, is an enzyme in melanin biosynthesis and may play an important role in detoxification of a metabolite derived from DOPA. TRP-2 is expressed in melanocytes of neural crest origin and retinal pigment epithelium (RPE), derived from the optic cup. TRP-2 has been established as an early differentiation marker for melanoblasts and RPE. It is therefore of significance to study the regulation of TRP-2/DOPAchrome tautomerase expression. Here we show that TRP-2 mRNA is expressed in Y79 human retinoblastoma cell line, derived from a primitive multipotential retinal cell. Retinoblastoma is the common primary intraocular tumor of childhood. Basal expression levels in Y79 retinoblastoma cells of TRP-2 mRNA and protein are comparable to those in melanoma cells, whereas mRNA for tyrosinase, the rate-limiting enzyme in melanogenesis, is undetectable in retinoblastoma cells. Transient transfection assays showed that the TRP-2 gene promoter efficiently directs the reporter gene expression in retinoblastoma cells as it does in melanoma cells. Moreover, the expression of TRP-2 mRNA was induced by retinoic acid in retinoblastoma cells but not noticeably affected by forskolin, a cAMP-elevating reagent, whereas in melanoma cells its expression was induced by forskolin but not by retinoic acid. These results suggest a difference in the regulation of TRP-2 expression between retinoblastoma and melanoma cells. Moreover, TRP-2 mRNA is expressed in the excised retinoblastoma specimens, as assessed by RT-PCR. The present study shows unexpected features of TRP-2 and may enhance our understanding of the pathophysiology of retinoblastoma.

Colforsin↗

PubMed2001

Neurohistochemical analysis of regeneration in rat peripheral nerve after end-to-side neurorrhaphy.

We investigated the regenerative capacity of motor nerves repaired by end-to-side or end-to-end neurorrhaphy, using choline-acetyltransferase (ChAT) activity measurement or histological analysis. The right medial gastrocnemius nerves (MGNs) of 62 male Fisher strain rats were transected and divided into three groups. In group 1, the distal ends of the MGN were coapted to the side of the lateral gastrocnemius nerve, using a Y-shaped silicone tube in end-to-side neurorrhaphy. In group 2, the nerve ends were reconnected by the traditional end-to-end technique. In group 3, the nerve ends were separated and remained unrepaired. The MGNs were sampled 1, 2, and 3 months postoperatively for histological examinations and ChAT activity measurement. The medial gastrocnemius muscle (MGM) was also sampled for histological evaluations. Axonal regeneration of MGN and the recovery of MGM to nearly normal histology and weight were observed in groups 1 and 2 3 months postoperatively. Although there were no significant differences in ChAT values between groups 1 and 2, the values were significantly larger than that of group 3 3 months postoperatively. These findings suggested that end-to-side neurorrhaphy would be an alternative treatment for peripheral nerve injury in certain clinical situations.

Animals↗

PubMed2001

Device for the removal of button batteries.

OBJECTIVE: There is an increasing number of accidents by erroneous ingestion of button batteries in recent years; the batteries arouse the interest of infants because of their attractive shape and luster. The batteries remaining in the gastrointestinal tract and discharging electric current over a long period of time may induce ulceration or perforation, thus must be carefully considered the selection of appropriate treatment. METHODS: We remove erroneously ingested button batteries with two tubes with ferrite magnets nearly the same size as the button batteries themselves. PATIENTS: Four cases of erroneous ingestion of button batteries. RESULTS: We easily removed button batteries from the stomach within 5 minutes in all cases with two magnet-attached tubes. CONCLUSION: We present this battery removal device together with a literature review, because it seems convenient and useful.

Equipment Design↗

PubMed2001

Induction of adrenomedullin by hypoxia in cultured retinal pigment epithelial cells.

PURPOSE: To explore the effects of hypoxia on the production and secretion of adrenomedullin (ADM) and endothelin (ET)-1 in human retinal pigment epithelial (RPE) cells. METHODS: RPE cells were cultured under normoxic or hypoxic (1% O2) conditions. Expression of ADM and ET-1 was examined by Northern blot analysis and radioimmunoassay. Effects of ADM and ET-1 on the number of RPE cells were examined by modified 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS: ADM mRNA expression levels and immunoreactive ADM levels in the medium were increased by hypoxia in all three human RPE cell lines (ARPE-19, D407, and F-0202). Immunoreactive ET was detected in the cultured media of D407 cells and ARPE-19 cells and identified as ET-1 by reversed-phase high performance liquid chromatography. Hypoxia treatment for 48 hours increased immunoreactive ET levels approximately 1.3-fold in the cultured media of D407, but not ARPE-19 cells. Hypoxia decreased the number of ARPE-19 cells and F-0202 cells, and the treatment with ADM ameliorated the hypoxia-induced decrease in the cell number. In contrast, exogenously added ET-1 had no significant effects on the number of ARPE-19 cells under normoxia and hypoxia. CONCLUSIONS: Hypoxia increased the expression of ADM in all three human RPE cell lines, whereas the induction of ET-1 by hypoxia was found only in D407 cells. ADM induced by hypoxia may have protective roles against hypoxic cell damage in RPE cells.

Adrenomedullin↗

PubMed2001

[Grading of light perception and hand movement utilizing a novel device called the low vision evaluator].

PURPOSE: There has been no device for grading very low visual function expressed as light perception or hand movement up to the present. It is necessary to evaluate even slight effects of modern and classical therapies during the follow-up period. The goal of this study was to invent a novel device for grading such low visual function. METHODS: Sixty-two patients with a visual acuity of counting fingers or worse due to various diseases were examined. The device, which we call the Low Vision Evaluator, has a pair of goggles equipped with two white light-emitting diodes. Nine variations of stimulus for light intensity (1, 10, 100 cd/m2 or 10, 100, 1,000 cd/m2) and duration (0.1, 0.3, 1 second) can be delivered in a random sequence. Patients were asked to push a button whenever they saw a stimulus. Response of patients to the stimuli was recorded. RESULTS AND CONCLUSIONS: The visual function of light perception and hand movement could be reproducibly assessed by this method. The method represents a valuable new tool for evaluating low visual function.

Adult↗

PubMed2000

Expression of the Varicella Zoster Virus Thymidine Kinase and Cytokines in Patients with Acute Retinal Necrosis Syndrome.

Purpose: Acute retinal necrosis (ARN) is caused by varicella zoster virus (VZV) infection. In this study, we investigated the activity of this virus and expressions of some cytokines.Patients and Methods: The expressionof VZV thymidine kinase and some cytokines were investigated by reverse transcriptase-polymerase chain reaction (RT-PCR) in 9 eyes of 8 patients with ARN.Results: Thymidine kinase expression was observed in all samples except one. Several cytokines, such as interferon (IFN) gamma, tumor necrosis factor (TNF)alpha, interleukin (IL)-1 beta, IL-6, and transforming growth factor (TGF)beta 1 were observed in the samples. Among these cytokines, a statistically significant expression of IFNgamma was observed in the samples of ARN, when compared to those of proliferative vitreoretinopathy (PVR) or other uveitis. The expression of IFNgamma also decreased during successive follow-ups.Conclusion: These cytokines may play an important role in the immune response in ARN.

Journal Article↗

PubMed2000

Structural organization of the human microphthalmia-associated transcription factor gene containing four alternative promoters.

Microphthalmia-associated transcription factor (MITF) affects the development of many types of cells, including melanocytes and retinal pigment epithelium (RPE). MITF consists of at least three isoforms, MITF-A, MITF-H and MITF-M, differing at their amino-termini and expression patterns. Here, we characterize the structural organization of the human MITF gene. The gene contains at least four isoform-specific first exons, exons 1A, 1H, 1B and 1M in the 5' to 3' direction, each of which encodes the unique amino-terminus of a given isoform, including newly identified MITF-B. The 5'-flanking regions of these isoform-specific exons are termed promoters A, H, B and M, respectively, which showed different promoter activities, as judged by transient transfection assay. Promoter A directs the expression of a reporter gene in RPE, cervical cancer and melanoma cells, whereas promoter M is functional only in melanoma cells. Promoter H showed the significant activity in RPE and cervical cancer cells but not in melanoma cells. In contrast, the 1.7 kb 5'-flanking region of exon 1B showed no noticeable promoter activity in these cell lines. Therefore, alternative promoters provide the MITF gene with the diversity in transcriptional regulation and the capability of generating structurally different protein isoforms.

Amino Acid Sequence↗

PubMed2000

The SCG10-related gene family in the developing rat retina: persistent expression of SCLIP and stathmin in mature ganglion cell layer.

Neuronal growth-associated proteins (GAPs), such as GAP-43 and SCG10, are thought to play crucial roles in both axonal and dendritic outgrowth during neural development and regeneration, although the underlying mechanisms remain largely unknown. The recent finding that SCG10 is a microtubule regulator and also the identification of RB3 and SCLIP as two new SCG10-related members prompted us to investigate the roles of SCG10-related family in neural development, using the retina as a model system. We determined the temporal expression and the spatial distribution of SCG10-related mRNAs in the developing rat retina. Semiquantitative analysis by RT-PCR revealed that in prenatal retina, levels of SCG10 and stathmin mRNAs were higher than those of RB3 and SCLIP. In the postnatal retina, the level of SCLIP increased, whereas the level of RB3 remained low. In situ hybridization revealed that GAP-43 and all of the SCG10-related family mRNAs were present in the retinal ganglion cells (RGCs) at all stages of retinal development, and that stathmin mRNA was present in mitotic neuroblastic cells. Differential expression of SCG10 and other members of the family became more evident as retinal development proceeded; SCG10 and RB3 expression were relatively specific in the RGCs and amacrine cells, whereas SCLIP was also evident in bipolar and horizontal cells. Stathmin mRNA was highly expressed both in the RGCs and other interneurons. These results indicate that multiple SCG10-related proteins are expressed in single neurons including RGCs, and suggest that these nGAPs play similar but distinct roles in differentiation and functional maintenance of retinal neurons.

Animals↗

PubMed2000

Macular degeneration associated with aberrant expansion of trinucleotide repeat of the SCA7 gene in 2 Japanese families.

OBJECTIVE: To evaluate the macular function of Japanese patients with a trinucleotide repeat expansion in the spinocerebellar ataxia type 7 (SCA7) gene. METHODS: Ophthalmic findings in patients whose DNA analysis revealed expanded alleles of the trinucleotide repeat in the SCA7 gene were evaluated. RESULTS: Trinucleotide repeat was expanded from 40 to 48 in affected patients (control subjects, 12 repeats). Affected patients were characterized by different degrees of visual acuity decrease (0.09-0.9), a tritan axis color vision, a coarse granular appearance of the macular region on scanning laser ophthalmoscopy, depression of multifocal electroretinograms, and macular degeneration. However, pigmentary changes were not observed in the retina. The trinucleotide repeat was longer and the onset of macular dysfunction was earlier in the younger generation. One patient in a family manifested decreased visual acuity 10 years preceding other neurologic signs. CONCLUSIONS AND CLINICAL RELEVANCE: Patients with SCA7 mutations showed macular dysfunction or degeneration with expansion of CAG repeat in the SCA7 gene. However, the lesions were less pigmented than those previously reported. Patients also showed ophthalmologic anticipation, which has not been reported for the ocular changes in other patients who have trinucleotide repeat expansion of the responsible genes.

Adult↗

PubMed2000

Increased expression of adrenomedullin mRNA in the tissues of intraocular and orbital tumors.

PURPOSE: To explore the possible involvement of adrenomedullin in the pathophysiology of intraocular and orbital tumors. METHODS: Competitive reverse transcription-polymerase chain reaction was used to determine adrenomedullin mRNA levels in the tissues from 40 consecutive patients (40 eyes) undergoing vitrectomy, orbital tissue biopsy, or enucleation for various ocular diseases, including intraocular (n = 4) and orbital (n = 3) tumors, proliferative vitreoretinopathy (n = 8), proliferative diabetic retinopathy (n = 8), age-related macular degeneration (n = 4), preretinal macular fibrosis (n = 9), and acute retinal necrosis (n = 4). RESULTS: Adrenomedullin mRNA levels in the tissues obtained from patients with intraocular or orbital tumors were significantly higher than those of patients with proliferative vitreoretinopathy (P <.05), proliferative diabetic retinopathy (P <.05), preretinal macular fibrosis (P <.005), and acute retinal necrosis (P <.01). CONCLUSION: Adrenomedullin may play a role in the pathophysiology of intraocular and orbital tumors.

Adrenomedullin↗

PubMed2000

Spontaneous improvement in a case of C1q nephropathy.

A 17-year-old girl showed mild proteinuria accompanied by hematuria and mild hypocomplementemia. A light microscopic study of the first renal biopsy specimen showed diffuse mild to moderate mesangial proliferation and thickening of the glomerular basement membrane (GBM). An immunofluorescence study showed dominant positive staining (3+) of IgG and C1q in the glomerular mesangium and capillary loop. Staining for C3 and fibrinogen was weak or 1+. Staining for IgA and IgM was negative. Electron-dense deposits were present in the mesangial area and also in the subepithelial, subendothelial, and intramembranous space. Urinary findings improved after dipyridamole treatment. The second renal biopsy, which was performed 5 years later, showed histological improvements, and various pictures of washing-out of deposits were also noted in an electron microscopic study. However, dominant positive staining for IgG and C1q was persistent in an immunofluorescence study. The glomerulopathy of this case belongs in the criteria of neither membranoproliferative glomerulonephritis nor lupus nephritis but could be designated as C1q nephropathy. This is the first report of a histological improvement in C1q nephropathy.

Adolescent↗

PubMed2000

Long-lasting binding of IT-066 to human histamine H2 receptor.

Based on animal models, IT-066, a histamine H2-receptor antagonist, is reported to possess potent and long-lasting antagonisms on histamine H2 receptor (H2R) -mediated effects. However, no reports have been published concerning its interaction with the human H2R. The aim of this study is to characterize its interaction with human H2R. Chinese hamster ovary cell lines stably expressing human H2Rs were obtained. The effects of IT-066, famotidine, and ranitidine on tiotidine binding and histamine-stimulated cAMP production were analyzed. IT-066 inhibited [3H]tiotidine binding and histamine-stimulated cAMP production more potently than famotidine or ranitidine. In addition, preincubation with 10(-5) M IT-066, but not with 10(-5) M famotidine or 10(-4) M ranitidine, had marked inhibitory effects long after extensive washing. Paraformaldehyde fixation of the cells blunted inhibition of [3H]tiotidine binding induced by preincubation with IT-066, but not that by preincubation with famotidine or ranitidine. IT-066 has potent and long-lasting antagonisms on human H2R. At least one of the IT-066 binding sites is not shared by famotidine, ranitidine, or tiotidine and is affected by paraformaldehyde fixation.

Animals↗

PubMed2000

Magnetic resonance imaging of a non-pigmented adenoma of the ciliary epithelium.

PURPOSE: A non-pigmented adenoma of the ciliary epithelium is rare. No good documentation has been reported in which magnetic resonance imaging (MRI), histological examination, and immunohistological evaluation have all been conducted. We showed how this tumor differed from ciliary body melanoma. METHODS: We evaluated the ciliary body tumor by MRI, histological examination, and immunohistochemical examination. The data was compared with previously reported cases. RESULT: The tumor was classified as an adenoma of the non-pigmented ciliary epithelium with extracellular pools of hyaluronidase-sensitive mucopolysaccharide. The MRI appearance of the vitreous in our patient showed hyperintensity on T1, isointensity on T2 and marked enhancement with gadolinium. None of 3 other reported patients exhibited the same signals. CONCLUSION: MRI appearance is most variable in adenomas and no microscopical diagnosis can be based on that. Our patient showed isointensity on T2 with marked enhancement by gadolinium when compared to malignant melanoma.

Adenoma↗

PubMed2000

Quantitative analysis of neural distribution in human coracoacromial ligaments.

This study investigated sensory nerve distribution in 27 human coracoacromial ligaments by immunohistochemical methods using antiprotein gene product 9.5 antibody and anticalcitonin gene related peptide antibody. Mean nerve densities were compared among three areas (acromion side, center, and coracoid side) in two groups (patients with rotator cuff tears and patients with shoulder dislocations). In all three areas of both groups, many nerve fibers immunoreactive to antiprotein gene product 9.5 antibody were observed in the periligamentous bursal tissue. However, in the ligament parenchyma, nerve fibers immunoreactive to antiprotein gene product 9.5 antibody were recognized only around blood vessels. Nerve fibers immunoreactive to anticalcitonin gene related peptide antibody were recognized in the periligamentous bursal tissue. However, in the ligament parenchyma, there were no nerve fibers immunoreactive to anticalcitonin gene related peptide antibody. Nerve density of the rotator cuff tear group, as revealed by both immunostainings, showed a significant increase compared with that of the shoulder dislocation group in all three areas. The results of this study show that it is possible the increase in sensory nociceptive nerve fibers in the coracoacromial ligaments may be one of the causes for pain in patients with rotator cuff tears.

Acromion↗

PubMed2000

Variable R1 region in varicella zoster virus in fulminant type of acute retinal necrosis syndrome.

BACKGROUND/AIMS: Varicella zoster virus (VZV) is a causative agent in acute retinal necrosis (ARN) syndrome. However, in spite of aggressive antiviral therapy, clinical characteristics among patients have varied. Different viral strains were examined to determine their respective role in producing clinical characteristics. The viral strains were also compared with those of previously reported ones. METHODS: To differentiate VZV strains R1 and R5, variable regions of VZV were amplified by nested polymerase chain reaction (PCR) in 11 eyes of 10 patients. Sequence analysis was also performed. RESULTS: Four cases had strains diverted only at the tip of the 3' end of the R1 variable region, similar to that of the H-N3 strain, which was previously reported. Conversely, other cases were diverted to other regions. Interestingly, some of the latter cases showed multiple PCR products in the R1 region that were generated by the truncation of either the 5' or 3' R1 region. Final visual acuities of these patients were less than 0.2. The former cases showed final visual acuities more than 0.4. Only two variants were from the R5 region. No patient had the same viral strain as the European Dumas type. CONCLUSION: These results showed that variable VZV strains participated in ARN. Using PCR of the R1 variable region, it was estimated that patients with a more fulminant type of ARN may have diverse viruses with extensive replication in the affected eyes.

Adolescent↗

PubMed2000

Effect of epidermal growth factor on sodium-dependent L-alanine transport in LLC-PK1 cells.

We evaluated the role of epidermal growth factor (EGF) in the regulation of L-alanine transport in LLC-PK1 renal epithelia. After 2 h of incubation, EGF had no significant effect on L-alanine uptake by LLC-PK1 cells. However, prolonged (16 h) incubation with 2 and 20 ng/ml of EGF resulted in significant increases in sodium-dependent L-alanine uptake as compared with controls. Treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA; 20 ng/ ml) caused a marked increase in sodium-dependent L-alanine uptake after both 2 and 16 h of incubation, and the treatment with TPA (20 ng/ml) EGF (20 ng/ml) for 16 h resulted in significant acceleration of the TPA-stimulated increase in L-alanine uptake by LLC-PK1 cells. Coincubation with H-7 (20 microM) inhibited both EGF- and TPA-stimulated increases in L-alanine uptake, and genistein (20 microg/ml) blocked the stimulatory effect of EGF in L-alanine transport to the control level. Furthermore, coincubation with cycloheximide (20 microg/ml) for 16 h inhibited both EGF- and TPA-stimulated increases in L-alanine transport to a great extent. The sodium- independent L-alanine uptake was not affected by treatment with either EGF or TPA. These results suggest that the activation of protein kinase C through tyrosine kinase activation plays a role in the EGF effect of stimulating L-alanine transport in LLC-PK1 cells and that the effect is mainly due to increased protein de novo synthesis which occurs after protein kinase C activation.

Alanine↗

PubMed2000

Ultrasound biomicroscopic analysis of the human ciliary body after 1 and 2% pilocarpine instillation.

We examined ciliary body thickness (CBT) of 11 human eyes after 1% followed by 2% pilocarpine instillation using ultrasound biomicroscopy. The examination revealed that CBT decreased in 2 eyes after 1% pilocarpine treatment but increased after 2% pilocarpine. In the eyes with decreased CBT by 1% pilocarpine, the pretreatment ciliary bodies were thicker and the changing rate of CBT induced by 2% pilocarpine, although not decreased, was also smaller than that in CBT-increased eyes. These findings showed that the ciliary body was under relatively strong stimulus of endogenous acetylcholine and has subsensitivity to both 1 and 2% pilocarpine in CBT-decreased eyes. Configurative changes in CBT-decreased eyes may be explained by the localization of different muscarinic receptor subtypes in different portions of the ciliary muscle.

Adult↗

PubMed2000

Effective treatment with topical cyclosporin A of a patient with Cogan syndrome.

The purpose of this report is to describe the effective treatment of severe anterior segment inflammation due to Cogan syndrome through the use of topical administration of cyclosporin A. A 47-year-old female patient had been experiencing headaches and difficulties with her vision. Subsequent examination revealed the sudden onset of bilateral conjunctival injection and swelling of bilateral auricles. Despite the multiple treatment (systemic and topical corticosteroid and antibiotic therapy), necrotizing scleritis had appeared bilaterally and the scleral wall was thinning. Topical administration of 1% cyclosporin A was applied to both eyes 4 times a day. After 2 months of this therapy, the epithelial tissue covered the necrotizing tissue and her symptom of ocular pain was relieved and her corrected visual acuity was improved. This is the first case exhibiting that topical cyclosporin A is an effective treatment for severe anterior segment inflammation associated with Cogan syndrome.

Administration, Topical↗