Biomedical subjects

M Tamai

Publications and source records attributed to M Tamai.

At least 91 records · Page 5Linked to original sources

PubMed1999

Analysis of the retinal edema of full-thickness macular holes by scanning laser ophthalmoscopy and optical coherence tomography.

The purpose of this study was to investigate the relationship between the dark area illuminated by scanning laser ophthalmoscopy (SLO) and cystic spaces around macular holes as shown by optical coherence tomography (OCT). SLO allows for two dimensional retinal examination, using short wave length (514 nm, argon) which is useful for the vitreoretinal surface and inner retina; red helium-neon laser (633 nm), which is capable of imaging deeper tissues; and infrared diode laser (780 nm), for choroidal examination. OCT is analogous to ultrasound except that optical rather than acoustic reflectivity is measured. OCT can produce the cross-sectional view of retina. Using SLO (helium-neon laser) and OCT, we examined 8 eyes with full-thickness macular holes. Eight normal eyes served as controls. Cystic spaces were in proportion to dark areas with statistical significance as shown by correlation analysis. Evaluation of the full-thickness macular holes by using both SLO and OCT is highly useful.

Aged↗

PubMed1999

Functional analysis after auto iris pigment epithelial cell transplantation in patients with age-related macular degeneration.

Recent transplantation studies indicate that subretinal space is not always an immunologically privileged site and non-autologous cells may be rejected in patients with exudative age-related macular degeneration (AMD). We performed autologous iris pigment epithelial (IPE) cell transplantation by cell suspension after autologous IPE cell culture in 8 patients with AMD. These patients were followed without immunosuppression between 1.5 and 8 months and the retinal function was analyzed. No cystoid macular edema or fluorescein leakage was observed. Six of the 8 patients improved visual acuity of more than two lines and the other two patients retained preoperative visual acuity. Five patients had increased visual field sensitivity, one patient retained pretransplantation sensitivity, and one patient showed a gradual decrease in sensitivity (one patient was not examined). Although 2 of the 8 patients showed decreased amplitude of flicker electroretinography (ERG) (about 60 to 70% as that of preoperative level), the average improvement of each amplitude of a single white flash (a wave), photopic, or flicker ERG was 123, 102, and 107%, respectively. No proliferative change in the submacular lesion or vitreous cavity was observed after transplantation. From this functional analysis, transplanted autologous IPE may have, in part, an alternative function in regard to the retinal pigment epithelium in the subretinal space.

Aged↗

PubMed1999

Na+,K+-ATPase activity in cultured bovine retinal pigment epithelium.

PURPOSE: To characterize electrogenic Na+,K+-ATPase activity in cultured bovine retinal pigment epithelium (RPE). METHODS: Cultured bovine RPE cells from passages 3 through 5 were dissociated enzymatically. Na+,K+-adenosine triphosphatase (ATPase)-activated currents (Ip) were measured by using a nystatin perforated-patch recording technique under voltage- clamp conditions. In the presence of suitable blockers for known voltage-dependent Na+, K+, and Ca2+ conductances, the Ip was activated in a concentration-dependent manner by adding K to the external solution. RESULTS: The median effective concentration (EC50) and Hill coefficient for external K+ concentration ([K+]o) were 1.06 mM and 2.55, respectively. The Ip showed no significant voltage dependency. A large outward shift of holding current was observed when [Na+]o, was removed. In the presence of [Na+]o, the addition of K+ to the external solution induced Ip, even when the internal solution did not contain Na+, suggesting the existence of a continuous Na+ influx across the plasma membrane in the presence of [Na+]o,. When Na+ was removed from the external and internal solutions, a transient Ip was observed, indicating that the transient Ip was activated by the intracellular residual Na+. The Ip was concentration-dependently suppressed by ouabain. The 50% inhibitory concentration (IC50) value and Hill coefficient for ouabain were 5.98 microM and 1.12, respectively. CONCLUSIONS: The present study is the first to reported the functional properties of electrogenic Na+,K+-ATPase activity in cultured bovine RPE.

Animals↗

PubMed1998

Identification of a novel isoform of microphthalmia-associated transcription factor that is enriched in retinal pigment epithelium.

Mutations at the mouse locus encoding microphthalmia-associated transcription factor (Mitf) affect the development of many cell types, including retinal pigment epithelium (RPE), melanocytes, mast cells, and osteoclasts. Here we have identified a novel Mitf isoform, Mitf-a, and its human homologue MITF-A by cDNA cloning. MITF-A consists of 520 amino acid residues and differs in the amino-terminus from authentic melanocyte-type MITF (MITF-M). MITF-A mRNA is widely expressed and represents a predominant MITF isoform in cultured RPE cells, whereas MITF-M mRNA is exclusively expressed in melanocytes and melanoma cells. In situ hybridization analysis suggested that Mitf-a mRNA is enriched in the prospective RPE of mouse embryo. Moreover, transient cotransfection assays suggested that MITF-A activated transcription of the tyrosinase and tyrosinase-related protein 1 genes. MITF-A/Mitf-a therefore may play an important role in melanogenesis in RPE.

Amino Acid Sequence↗

PubMed1998

Arrestin gene mutations in autosomal recessive retinitis pigmentosa.

OBJECTIVE: To assess the clinical and molecular genetic studies of patients with autosomal recessive retinitis pigmentosa associated with a mutation in the arrestin gene. DESIGN: Results of molecular genetic screening and case reports with DNA analysis and clinical features. SETTING: University medical center. PATIENTS: One hundred twenty anamnestically unrelated patients with autosomal recessive retinitis pigmentosa. METHODS: DNA analysis was performed by single strand conformation polymorphism followed by nucleotide sequencing to search for a mutation in exon 11 of the arrestin gene. Clinical features were characterized by visual acuity slitlamp biomicroscopy, fundus examinations, fluorescein angiography, kinetic visual field testing, and electroretinography. RESULTS: We identified 3 unrelated patients with retinitis pigmentosa associated with a homozygous 1-base-pair deletion mutation in codon 309 of the arrestin gene designated as 1147delA. All 3 patients showed pigmentary retinal degeneration in the midperipheral area with or without macular involvement. Patient 1 had a sibling with Oguchi disease associated with the same mutation. Patient 2 demonstrated pigmentary retinal degeneration associated with a golden-yellow reflex in the peripheral fundus. Patients 1 and 3 showed features of retinitis pigmentosa without the golden-yellow fundus reflex. CONCLUSIONS: Although the arrestin 1147delA has been known as a frequent cause of Oguchi disease, this mutation also may be related to the pathogenesis of autosomal recessive retinitis pigmentosa. This phenomenon may provide evidence of variable expressivity of the mutation in the arrestin gene.

Adult↗

PubMed1998

rim2 (recombination-induced mutation 2) is a new allele of pearl and a mouse model of human Hermansky-Pudlak syndrome (HPS): genetic and physical mapping.

A mouse mutation, rim2, is one of a series of spontaneous mutations that arose from the intra-MHC recombinants between Japanese wild mouse-derived wm7 and laboratory MHC haplotypes. This mutation is single recessive and characterized by diluted coat color and hypo-pigmentation of the eyes. We mapped the rim2 gene close to an old coat color mutation, pearl (pe), on Chromosome (Chr) 13 by the high-density linkage analysis. The pearl mutant is known to have abnormalities similar to Hermansky-Pudlak syndrome (HPS), a human hemorrhagic disorder, characterized by albinism and storage pool deficiency (SPD) of dense granules in platelets. A mating cross of C57BL10/Slc-rim2/rim2 and C57BL/6J-pe/pe showed no complementation of coat color. Additionally, characteristics similar to SPD were also observed in rim2. Thus, rim2 appeared to be a new allele of the pe locus and serves as a mouse model for human HPS. We have made a YAC contig covering the rim2/pe locus toward positional cloning of the causative gene.

Albinism, Oculocutaneous↗

PubMed1998

A new mutation Rim3 resembling Re(den) is mapped close to retinoic acid receptor alpha (Rara) gene on mouse chromosome 11.

A new mouse mutation, recombination-induced mutation 3 (Rim3), arose spontaneously in our mouse facility. This mutation exhibits corneal opacity as well as abnormal skin and hair development resembling rex denuded (Re(den)) and bareskin (Bsk). Large-scale linkage analysis with two kinds of intersubspecific backcrosses revealed that Rim3 is mapped to the distal portion of Chromosome (Chr) 11, in which Re(den) and Bsk have been located, and is very close to the retinoic acid receptor, alpha (Rara). The genes, keratin gene complex-1, acidic, gene 10, 12 (Krt1-10, 12), granulin (Grn), junctional plakoglobin (Jup) and Rara, all of which regulate growth and differentiation of epithelial cells, are genetically excluded as candidate genes for Rim3, but are clustered in the short segment on mouse Chr 11.

Animals↗

PubMed1998

Correlation of varicella-zoster virus copies and final visual acuities of acute retinal necrosis syndrome.

BACKGROUND: Herpes viruses may play an important role in acute retinal necrosis (ARN) syndrome, and raised antibody titer or virus genome have been detected in intraocular fluids of patients with ARN. In spite of aggressive anti-viral therapy, the clinical courses and final visual acuities among these patients have varied. Our purpose was to estimate the amount of virus and compare it to final visual acuity in patients with ARN. METHODS: The number of varicella-zoster virus copies in aqueous and vitreous before and after administration of anti-viral therapy were estimated by polymerase chain reaction (PCR) and by semi-nested PCR in 12 eyes of 11 patients with ARN and were compared with clinical characteristics. RESULTS: Viral genome DNA was amplified in ocular fluids diluted between 10(-3) and 10(-6) in patients whose final visual acuities were 0.3 or less. Conversely, the dilution required was between 10(-1) to 10(-3) in the patients whose final visual acuities were 0.4 or better. The difference was statistically significant. Further, patients in the latter group reacted to the anti-viral drug acyclovir more promptly than did the former patients. CONCLUSION: Our results showed that final visual acuity may partly depend on the number of virus copies in ocular fluids. The number of virus copies tended to be higher in elderly or immunocompromised patients than in others, and the treatment was less efficacious in these patients.

Acyclovir↗

PubMed1998

Ultrasound biomicroscopic analysis of anterior proliferative vitreoretinopathy.

PURPOSE: To report the use of ultrasound biomicroscopy for preoperative assessment of anterior proliferative vitreoretinopathy. METHODS: Case report. In a 35-year-old man with tractional retinal detachment and anterior proliferative vitreoretinopathy, we used ultrasound biomicroscopy with UX-02 (Rion Co Ltd, Tokyo, Japan) to perform the preoperative analysis of the ciliary body, anterior vitreous, and detached peripheral retina. RESULTS: In all meridians, the posterior insertion of the vitreous was drawn anteriorly, creating a retinal trough, and the meridian distance between the anterior and posterior vitreous base insertions was reduced. Retinochoroidal detachment was detected posterior to the anterior vitreous base insertion. Based on these imagings, sclerotomy locations were selected. CONCLUSION: Ultrasound biomicroscopy may be useful to assess anterior proliferative vitreoretinopathy preoperatively and to decide on sclerotomy sites.

Adult↗

PubMed1998

Characterization of the electrogenic Na+ -K+ pump in bipolar cells isolated from carp retina.

The electrogenic Na+ -K+ pump current (Ip) in carp bipolar cells was investigated under voltage-clamp conditions. The Ip was activated in a concentration-dependent manner by adding external K+ (Ko+) and was completely suppressed with 10(-4) M ouabain (EC50=1.23 mM; Hill coefficient=1.36). The Ip was suppressed in a concentration-dependent manner by ouabain (IC50=1.90 mM; Hill coefficient=0.93). The Ip did not show a distinct voltage dependency either with or without Na(o)+. A large outward shift of the holding current was observed by completely removing Na(o)+. In the presence of Na(o)+, a steady Ip was observed even in the absence of internal Na+ (Na(i)+). These results suggest that continuous Na+ influxes exist across the membrane. When external and internal Na+ was removed, a transient Ip was observed (half decay time (t1/2) was 5.0+/-0.6 s), thus indicating that the transient Ip was activated by the residual Na(i)+. In the absence of Na(o)+, the transient Ip was also observed with lower than 8 mM Na(i)+. The t1/2 depended on Na(i)+. However, a steady Ip was observed with 10 mM Na(i)+ or more. The functional properties of the Ip are discussed.

Animals↗

PubMed1998

Characterization of the electrogenic Na+-K+ pump in horizontal cells isolated from the carp retina.

The electrogenic Na+-K+ pump current in horizontal cells acutely dissociated from the carp retina was investigated using a nystatin-perforated patch recording configuration under voltage-clamp conditions. In the presence of suitable blockers for known voltage-dependent Na+, K+ and Ca2+ conductances, the pump current was activated in a concentration-dependent manner by adding K+ ions to external solution. The EC50 value and Hill coefficient for the external K+ concentration were 0.66 mM and 1.39, respectively. The pump current did not show any significant voltage dependency at the physiological potential range between -90 and 20 mV either with or without external Na+ ions. In the presence of 120 mM external Na+ concentration, the addition of 3 mM K+ to the external solution induced a steady outward pump current even when the patch-pipette (internal) solution did not contain Na+. A large outward shift of the holding current was observed by removing external Na+. The result thus suggests that continuous Na+ influxes exist across the plasma membrane in the presence of external Na+. When Na+ was removed from both external and internal solutions, a transient outward pump current was observed by adding K+ to the external solution, thus indicating that the transient pump current was activated by the residual intracellular Na+ ions. The pump current was suppressed by ouabain in a concentration-dependent manner, and the ouabain-sensitive inhibition curve was fitted by two components. The IC50 values of high- and low-sensitive pump currents for ouabain were 20 nM and 10.4 microM, respectively, indicating the existence of at least two isoforms of the pump in the horizontal cells.

Animals↗

PubMed1998

Analysis of urinary 11-dehydrothromboxane B2 in patients with occluded retinal vein using GC/SIM.

We describe variations of 11-dehydrothromboxane B2(11-dehydro-TXB2) levels in human urine samples. Retinal vein occlusion (RVO) is a thrombotic disease in which the retinal vein is blocked by blood aggregations. We considered the possibility that 11-dehydro-TXB2 plays an important role in the formation of RVO. Thus, we determined the 11-dehydro-TXB2 levels in patients with RVO using gas chromatography/selected ion monitoring (GC/SIM) and compared them with those of healthy volunteers. The thromboxane levels in patients with RVO, who did not also have diabetes, were significantly higher than those in healthy volunteers. One cause of RVO may be the variation of thromboxane production. Furthermore, this GC/SIM method can be applied to the prevention and treatment of not only RVO, but also of general thrombosis.

Adult↗

PubMed1998

Arginine vasopressin stimulates phospholipid methylation in cultured rat mesangial cells: possible role for PGE2 production.

Incorporation of [3H-methyl] groups into phospholipids and prostaglandin E2 (PGE2) production in cultured rat mesangial cells were examined in the presence and absence of arginine vasopressin (AVP). In cells stimulated with AVP, a rapid increase in the incorporation of [3H-methyl] group into phospholipids was observed within 1 min after stimulation. The [3H-methyl] group present in the phospholipids began to decline 2.5 min after stimulation. The production of PGE2 increased with AVP treatment, and the decline in methylated phospholipids paralleled the release of PGE2 in AVP-stimulated cells. The inhibition of phospholipid methylation by treatment with adenosyl-S-isobutyl mercaptan (SIBA) resulted in a marked decrease in AVP-stimulated PGE2 production. In order to determine the identity of the methylated phospholipids, [3H-methyl] incorporation into phosphatidylethanolamine derivatives was examined. In AVP-stimulated cells, an increase of [3H-methyl] labeled phosphatidylcholine and lysophosphatidylcholine was observed after stimulation with AVP, followed by an apparent increase of [3H-methyl] labeled lysophosphatidylcholine. These findings indicate that AVP stimulates phospholipid methylation in cultured rat mesangial cells and phosphatidylcholine, synthesized by a transmethylation pathway, may be a source for PGE2 production.

Animals↗

PubMed1998

Dedifferentiation of the retinal pigment epithelium compared to the proliferative membranes of proliferative vitreoretinopathy.

PURPOSE: To examine the gene expression for melanogenesis of retinal pigment epithelial cells during dedifferentiation and to compare the condition to that of eyes obtaining anatomical success after surgery for proliferative vitreoretinopathy. METHODS: Gene expression for melanogenesis was determined by reverse transcriptase-polymerase chain reaction of tyrosinase and tyrosinase-related protein-1 genes in normal and cultured retinal pigment epithelial cells and in proliferative membranes in patients with proliferative vitreoretinopathy. RESULTS: Gene expression for melanogenesis was classified into three types during dedifferentiation of retinal pigment epithelial cells: (1) tyrosinase-related protein-1 gene expression, (2) tyrosinase and tyrosinase-related protein-1 gene expression and (3) no expression of these genes. The expression of these genes were maintained better in mediums with basic fibroblast growth factor than in medium without basic fibroblast growth factor. Of the anatomically unsuccessful patients with proliferative vitreoretinopathy treated by surgery, 76.9% showed both tyrosinase and tyrosinase-related protein-1 gene expression; only 20% of the anatomically successful patients showed the gene expression. CONCLUSIONS: We reported three different conditions of retinal pigment epithelial cells based on gene expression for melanogenesis during dedifferentiation. The different condition of the retinal pigment epithelial cells may have some relationship to the anatomical results for proliferative vitreoretinopathy surgery.

Adolescent↗

PubMed1998

Isomerization of 11-cis-retinol to all-trans-retinol in bovine rod outer segments.

It is known that exogenous 11-cis-retinol inhibits the recovery of photosensitivity of bleached rod outer segments (ROS) and 11-cis-retinol exists in the interphotorecepter matrix. We examined the conversion of 11-cis-retinol with bovine ROS. ROS was incubated with 11-cis-retinol under dim red light. Retinoids were extracted from the reaction mixture with hexane and analyzed by HPLC coupled with a fluorescence spectrophotometer. Isomerization of 11-cis-retinol to all-trans-retinol was observed in the presence of ROS. This isomerization was not suppressed by heat treatment and did not have stereospecificity. In addition, we incubated purified rhodopsin and phospholipids extracted from ROS with 11-cis-retinol. Rhodopsin was found to isomerize 11-cis-retinol to all-trans-retinol as well as ROS, but phospholipids did not. In contrast, the phospholipids inhibited the isomerization of 11-cis-retinol to all-trans-retinol by the purified rhodopsin. Commercially available phospholipids, especially phosphatidylserine, also inhibited the isomerization. Our results suggest that rhodopsin has activity for the isomerization of 11-cis-retinol to all-trans-retinol and may play an important role in the detoxification of 11-cis-retinol in the ROS.

Animals↗

PubMed1998

Values for urinary beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase in normal healthy infants.

BACKGROUND: Measuring urinary beta 2 microglobin (B2M) and N-acetyl-beta-D-glucosaminidase (NAG) excretion is widely used as a valuable clinical tool in assessing renal tubular lesions. However, few data are available on normal values for urinary excretion of B2M and NAG in infancy. METHODS: Urinary B2M and NAG were measured in healthy infants. The logarithmic values of urinary B2M, NAG, B2M/creatinine ratio and NAG/creatinine ratio were distributed almost normally and reference ranges were calculated from the logarithms of the observed values. RESULTS: The levels of urinary B2M and B2M/creatinine ratio were highest in the 1-month-old group, followed by a decrease during the first 3 months. Urinary B2M excretions in the 3-month-old group showed rather lower levels than those of the 12-month-old and 36-month-old groups. Although urinary NAG excretions were almost constant throughout all groups, urinary NAG/creatinine ratio decreased gradually until 3 years of age. CONCLUSIONS: We suggest that these reference ranges are of importance in evaluating tubular damage due to a variety of renal diseases in infancy.

Acetylglucosaminidase↗

PubMed1998

Optic disc edema associated with spinocerebellar degeneration.

A 58-year-old man presented with optic disc edema as a rare association with spinocerebellar degeneration (SCD). The patient also had chronic idiopathic intestinal pseudo-obstruction with hypoalbuminemia. No elevation of intraspinal pressure and no intracranial lesion was observed. The hypoalbuminemia reacted promptly to treatment, whereas the optic disc edema regressed gradually. An association between SCD and optic atrophy has often been described, but to our knowledge this is the first report of SCD in association with optic disc edema.

Fluorescein Angiography↗

PubMed1998

Gene expression of the phosducin-like protein in the retina.

Phosducin, which is expressed abundantly in the retina, mediates phototransduction or signal transduction cascades by interacting with transducin or G-protein beta gamma-subunits. We have reported on the possibility that phosducin is expressed from a multiple gene family and that each phosducin may mediate G-protein-coupled signal transduction cascades. To elucidate new genes that may mediate signal transduction cascades in the retina and that may form a gene family with phosducin, we screened a bovine retinal cDNA library. During the screening, we identified a cDNA that looked the same as the phosducin-like protein of the rat, as reported by other investigators. We examined the gene expression in rat retina using semiquantitative polymerase chain reaction and compared it to that of other organs. One form generated by alternative splicing expressed in the retina was the same as in other tissues, but, interestingly, another form had differing tissue distribution and was expressed abundantly in the retina.

Alternative Splicing↗