Biomedical subjects

M Tamai

Publications and source records attributed to M Tamai.

At least 127 records · Page 7Linked to original sources

PubMed1996

Autosomal dominant cone-rod dystrophy associated with mutations in codon 244 (Asn244His) and codon 184 (Tyr184Ser) of the peripherin/RDS gene.

OBJECTIVE: To characterize clinical findings associated with mutations in codon 244 (Asn244His) and codon 184 (Tyr184Ser) of the peripherin/RDS gene. DESIGN: Case reports with clinical features and results of fluorescein angiography, electroretinography, kinetic visual field testing, and DNA analysis. SETTING: University medical center. PATIENTS: Four affected members of two Japanese families with autosomal dominant cone-rod dystrophy associated with transversion mutations in codon 244 (Asn244His) and codon (Tyr184Ser) of the peripherin/RDS gene. RESULTS: Characteristic features included the initial symptoms of decreased visual acuity, macular degeneration, central or paracentral scotoma, cone-mediated electroretinographic responses that were more impaired than rod-mediated responses, and pigmentary degeneration in the midperipheral retina in the late stage. These phenotypic features corresponded to cone-rod dystrophy type 2a by the classification of Szlyk and associates. CONCLUSIONS: The Asn244His and Tyr184Ser mutations in the peripherin/RDS gene cause con-rod dystrophy type 2a. These findings imply that a mutation in codon 244 or codon 184 of the peripherin/RDS gene affects the functions and/or structural stability of cones and rods.

Adult↗

PubMed1996

Variable expressivity in a Japanese family with autosomal dominant retinitis pigmentosa closely linked to chromosome 19q.

OBJECTIVE: To describe the clinical features of a Japanese family with autosomal dominant retinitis pigmentosa, the locus of which has been mapped on chromosome 19q. DESIGN: Ophthalmologic testing, including visual acuity, slit-lamp biomicroscopy, and fundus examinations, for all family members examined. Selected members underwent kinetic visual field testing, electroretinography, and fluorescein angiography. PATIENTS: Eleven symptomatic members, two asymptomatic obligate carriers, and nine nonaffected members in four generations of a single family with autosomal dominant retinitis pigmentosa. RESULTS: Asymptomatic carriers showed mildly affected fundus and fluorescein angiographic images. Visual field testing disclosed restricted central and midperipheral fields. Electroretinograms disclosed reduced amplitudes of rod-isolated responses in both of these family members, indicating functional abnormalities. CONCLUSION: Marked variability in expressivity of the retinitis pigmentosa phenotype was found in a family with autosomal dominant retinitis pigmentosa linked to chromosome 19q.

Aged↗

PubMed1996

Melanin-laden macrophages in cerebrospinal fluid in Vogt-Koyanagi-Harada syndrome.

OBJECTIVE: To identify basophilic granules in the cytoplasm of macrophages in cerebrospinal fluid (CSF) smears from patients with Vogt-Koyanagi-Harada (VKH) syndrome as melanin pigment. DESIGN: Morphological and immunocytochemical studies were performed on CSF smears obtained from 7 patients with VKH syndrome. Specimens were stained with May-Grünwald and evaluated by a silver impregnation method (Fontana-Masson staining). For immunocyto-chemical study, the smear was reacted with mouse anti-human melanoma cell (HMB-45) monoclonal antibody. RESULTS: Basophilic granules were detected in the cytoplasm of macrophages in CSF cell smears obtained from 6 of 7 patients with VKH syndrome in the early stages (within 25 days). Using the silver impregnation method, these basophilic granules were strongly stained black. Moreover, they were identified as melanin by positive immunocytochemical staining. The total number of cells containing cytoplasmic granules ranged from 3 to 8 per 10,000 total cells in CSF. In contrast, no cells containing cytoplasmic granules were found in control CSF cell smears from patients with viral, bacterial, or noninflammatory diseases. CONCLUSION: The identification of melanin-laden macrophages in the CSF of patients with VKH syndrome suggests that these cells are responsible for pleocytosis in the immunopathologic process of VKH syndrome.

Adult↗

PubMed1996

The properties of retinal pigment epithelial cells in proliferative vitreoretinopathy compared with cultured retinal pigment epithelial cells.

Retinal pigment epithelial (RPE) cells, which proliferate and dedifferentiate under several pathological conditions, and cultured RPE cells have been considered a good model for comparison. In this investigation, we compared the properties of RPE cells in proliferative vitreoretinopathy with that of cultured human RPE cells. mRNAs of RPE cells from patients with proliferative vitreoretinopathy and from cultured human RPE cells were extracted, and reverse transcriptase-polymerase chain reaction was performed. We also examined cells that were aspirated from bare RPE surface from a patient with a giant retinal tear. We amplified the interleukin-6 gene in the proliferative membranes and cultured RPE cells. We also amplified the tyrosinase gene in seven of eight proliferative membranes, as well as tyrosinase-related proteins and cellular retinaldehyde-binding protein genes, but not the tyrosinase gene in cultured RPE cells. The cells aspirated from bare RPE surface showed reduced activity for expressing interleukin-6 and tyrosinase genes. The dedifferentiation characteristics of cultured RPE cells were different, in that they were less active than RPE cells in proliferative membranes for expressing the genes of melanogenesis, which are essential for pigment cells. Interleukin-6 and genes that were related to melanogenesis were expressed in the proliferative membranes and may play an important role in the generation of proliferative vitreoretinopathy.

Actins↗

PubMed1996

Tamoxifen circumvents the multidrug resistance in fresh human gastrointestinal cancer cells.

The resistance to doxorubicin (DOX) is mainly due to the effect of P-glycoprotein encoded by the multidrug resistance-1 (mdr1) gene. Tamoxifen (TAM) has been shown to circumvent multidrug resistance in P-glycoprotein-expressing cell lines. In the present study, we clarified the augmentation of DOX sensitivity by TAM using MTT assay in highly purified fresh human tumor cells obtained from 85 cancer patients. Moreover, the correlation between DOX sensitivity and P-glycoprotein expression was assessed by flow cytometry. DOX sensitivity was decreased in proportion to P-glycoprotein expression. The cytotoxicity of DOX was increased by TAM in tumor cells possessing low DOX sensitivity. Moreover, there was a significant correlation between the effect of TAM on cytotoxicity and P-glycoprotein expression. The concentration of DOX in tumor cells was increased in combined exposure of TAM with DOX, compared with the exposure of DOX alone. Thus, TAM might be able to circumvent DOX-resistance for treatment in cancer patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

Portsite and intraabdominal metastases of unsuspected gallbladder carcinoma after laparoscopic cholecystectomy: report of a case.

We herein report a rare case of portsite metastasis of gallbladder carcinoma which occurred after laparoscopic cholecystectomy. A 64-year-old man underwent laparoscopic cholecystectomy at another hospital for symptomatic cholecystolithiasis. The histological examination revealed an adenocarcinoma of the gallbladder infiltrating the entire wall. Despite the physician's advice the patient refused any additional treatment. Thirteen months after surgery he visited our hospital because of a palpable mass at the scar of the right trocar incision. The nodule was removed and histological examination confirmed metastasis from the gallbladder carcinoma.

Abdominal Neoplasms↗

PubMed1996

A comparative study of the polymerase chain reaction and local antibody production in acute retinal necrosis syndrome and cytomegalovirus retinitis.

BACKGROUND: It has been thought that herpes viruses may play an important role in acute retinal necrosis syndrome (herpes simplex and varicella-zoster viruses) as well as in cytomegalovirus retinitis and it would be useful to know the specificity of the methods for detecting the viruses. METHODS: Amplification of the herpetic viral genome DNA by polymerase chain reaction (PCR) in aqueous and vitreous humor was compared with Goldmann-Witmer coefficients against herpetic antigens in five patients with acute retinal necrosis syndrome and in two patients with cytomegalovirus retinitis, using vitreous samples to determine the specificity of these diagnostic methods. RESULTS: The varicella-zoster virus genome DNA was amplified by PCR in four of the five patients with acute retinal necrosis syndrome, and cytomegalovirus genome DNA was enhanced in both patients with cytomegalovirus retinitis. Four patients who exhibited the varicella-zoster viral genome showed marked increase of the Goldmann-Witmer coefficient against varicella-zoster virus. Conversely, the two patients with cytomegalovirus retinitis showed no remarkable changes among the antigens. CONCLUSION: Our results showed that the amplification of the viral genome DNA in the samples by PCR is specific in both diseases, and that the increased level of local antibody production also is specific in varicella-zoster retinitis. In cytomegalovirus retinitis, however, antibody production against cytomegalovirus does not show increase of the Goldmann-Witmer coefficient.

Aged↗

PubMed1996

Autosomal dominant cone-rod dystrophy associated with a Val200Glu mutation of the peripherin/RDS gene.

OBJECTIVE: Mutations of the peripherin/RDS gene have been reported in several kinds of retinal dystrophy, and they show a variety of manifestations. The authors identified a novel Val200Glu mutation of the peripherin/RDS gene in a Japanese family with autosomal dominant cone-rod dystrophy (CRD). This report describes a genotype-phenotype correlation of the Val200Glu mutation. PATIENTS AND METHODS: Fifteen members of one Japanese family with autosomal dominant CRD were screened for mutations in the peripherin/RDS and ROM 1 genes. Clinical features were identified by visual acuity, visual field testing, fundus examination, and electroretinography. RESULTS: A Val200Glu mutation was found in all of the affected family members examined and was segregated with the disease. No patient had a mutation in the ROM 1 gene. Phenotypic characteristics of each affected member in this family showed intrafamilial similarity. Characteristic features included cone function more severely impaired than rod function and degenerative change in the macular region associated with peripheral retinal degeneration. CONCLUSION: The mutation at codon 200 of the peripherin/RDS gene causes both cone and rod degeneration. The Val200Glu mutation results in a type of autosomal dominant CRD.

Adult↗

PubMed1996

Production of IL-6 by T cells from the femoral head of patients with rapidly destructive coxopathy (RDC).

RDC is a syndrome with unknown etiology that causes rapid destruction of a hip joint. We have investigated the production of osteoclast-activating cytokines (IL-6, IL-1alpha and tumour necrosis factor-alpha (TNF-alpha)), interferon-gamma (IFN-gamma) and IL-8 by T cells in the affected joint. The level of IL-6 produced by the T cell lines (TCL) established from the femoral head was significantly higher than that from patients' or healthy donors' peripheral blood mononuclear cells (PBMC). IL-6 production by the TCL from synovial membrane or from patients' PBMC was also significantly higher than that from healthy donors' PBMC. IL-1alpha production by the TCL from the femoral head was significantly higher than any of the other groups when all the TCL were used for the analysis. TNF-alpha production was highest in the TCL from patients' PBMC. The levels of IFN-gamma or IL-8 were not significantly different among these four groups. The plasma levels of all these cytokines except for IFN-gamma, that was rather lower, in RDC patients were not significantly different from those in osteoarthrosis or trauma patients, or healthy donors. These results suggest that T cells at the affected femoral head, and also synovial membrane to some extent, are involved in bone resorption through the production of IL-6 and probably IL-1alpha in patients with RDC.

Aged↗

PubMed1996

Allosteric modulation of GABAA receptors in acutely dissociated neurons of the suprachiasmatic nucleus.

The gamma-aminobutyric acid (GABA)-induced response was investigated in acutely dissociated suprachiasmatic nucleus (SCN) neurons of 11- to 14-day-old rats, under the voltage-clamp condition of nystatin-perforated patch recording. At a holding potential of -40 mV, application of GABA induced inward currents in a concentration-dependent manner. Pentobarbital and 5 beta-pregnan-3 alpha-ol-20-one (pregnanolone) similarly induced inward currents. GABA-induced inward currents were suppressed in a concentration-dependent manner by pretreating neurons with a GABAA receptor antagonist, bicuculline. Bicuculline (3 x 10(-6) M) shifted the concentration-response curve of GABA to the left in a competitive manner. Reversal potential of the GABA response (EGABA) was -3.4 +/- 0.7 mV, close to the theoretical Cl- equilibrium potential of -4.1 mV. Pretreating SCN neurons with diazepam, pentobarbital, and pregnanolone enhanced the 3 x 10(-6) M GABA response. Diazepam (3 x 10(-8) M), pentobarbital (3 x 10(-5) M), and pregnanolone (10(-7) M) shifted the concentration-response curve of GABA to the left without changing the maximal amplitude of GABA responses. EGABA in the presence of diazepam, pentobarbital, or pregnanolone was the same as that in their absence. These results show that the GABA response in acutely dissociated SCN neurons is mediated by the GABAA receptor. Because the GABAA receptor of SCN neurons is allosterically augmented by diazepam, pentobarbital, and pregnanolone, similarly as in other regions of the central nervous system, the present study opens up ways to functionally modulate the GABAA receptors in SCN.

Allosteric Regulation↗

PubMed1996

A retinal pigment epithelium-derived cell line from transgenic mouse harboring temperature-sensitive simian virus 40 large T-antigen gene.

We established a retinal pigment epithelium-derived cell line from transgenic mouse harboring temperature-sensitive simian virus 40 T-antigen gene (tsSV40T) and examined its characteristics. We enucleated both eyes from a 2-month-old transgenic mouse and removed the retinal pigment epithelial (RPE) cells and neuroretinal cells. After cloning the RPE cells, we obtained a cell line (RPET). RPET cells grew well at 33 degrees C but not at 37 degrees C, expressing on the temperature-sensitive character of tsSV40T, and maintained characters of RPE cells such as T1-tyrosinase production, phagocytosis of rod outer segments, and presence of cytokeratin, microvilli on the cell surface and lysosome-like granules around the Golgi apparatus in the cytoplasm. Conditioned medium (CM) from a culture of neuroretinal cells harboring tsSV40T was essentially required for growth. The factor(s) in CM was heat-and acid labile, but was resistant to trypsin digestion. In the presence of 3% CM, epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) and strong effects on RPET cells, whereas insulin, insulin-like growth factor I (IGF-I), and IGF-II had moderate growth effects. Interestingly, none of these growth factors stimulated the RPET cells in the absence of CM. EHS-Matrix had growth effect, whereas laminin, collagen types I and IV, and fibronectin had no marked growth effects on RPET cells. RPET cells were morphologically changed on a laminin-coated dish. They could not spread on the coated dish, and the majority of the cells floated. But when the floating cells were transferred to non-coated dishes, they immediately attached themselves. These results suggest that RPET cells are a good model for for finding novel growth factor(s) and for investigating the mechanism of cell-laminin attachment.

Animals↗

PubMed1996

Heterogeneity and uniqueness of ornithine aminotransferase mutations found in Japanese gyrate atrophy patients.

PURPOSE: To identify mutations in ornithine aminotransferase (OAT) in seven Japanese families with gyrate atrophy (GA), an autosomal recessive chorioretinal degeneration of the eye caused by a generalized biochemical deficiency in OAT; mutations in the OAT gene have shown a high degree of molecular heterogeneity. METHODS: DNA was prepared from patients' fibroblasts and analyzed by polymerase-chain-reaction amplification of the OAT gene sequence, denaturing gradient gel electrophoresis, and direct sequencing for identification of the mutations. RESULTS: Eight different mutations were identified in seven unrelated Japanese GA patients with hyperornithinemia, confirming the high genetic heterogeneity of this disease. Five of these mutations were new, including one causing a pyridoxine-responsive disease, and all eight mutations have been found only in Japanese GA patients. Consistent with some similarity between the Japanese and Finnish populations in genetic isolation and homogeneity, there was a preponderance of homozygous mutations (five out of seven patients) as was previously reported for 16 Finnish GA pedigrees. CONCLUSION: The eight Japanese OAT mutations represent a group of heterogenous mutations unique to a specific population pool.

Amino Acid Sequence↗

PubMed1996

Postnatal developmental expression of glutamine and related amino acids in the rat retinas.

PURPOSE: To evaluate postnatal developmental changes in the amounts of retinal glutamate, glutamine and GABA, and in the distribution of retinal glutamine in the rat. METHODS: Free amino acids were extracted from rat retinas of different postnatal stages, and the concentrations of glutamate, glutamine and GABA were determined by HPLC. Also, anti-glutamine antibody was raised and an immunocytochemistry was performed with paraffin-embedded retinal sections in parallel with free amino acid analyses. RESULTS: Glutamate occurred in high concentrations at the birth and showed a stable pool, while glutamine and GABA remained low until postnatal day 3 or 5, and gradually increased in the developing rat retinas. Glutamine immunolabeling was observed in the retinal pigment epithelium and in a subpopulation of presumed amacrine cells in the early postnatal days. It was also found in Muller cells and in some ganglion cells or displaced amacrine cells in the ganglion cells layer. Glutamine immunolabeling was transiently observed also in horizontal cells. Finally, the immunolabeling was dominant in the inner and outer plexiform layers in the adult retinas. CONCLUSIONS: Postnatal developmental increase in the levels of glutamine and GABA might be dependent on the maturation of neurons or glial cells that possess the activity of the key enzymes of each amino acid. It was suggested that an expression of glutamine immunolabeling can be a marker of neurons that utilize glutamine as a precursor for glutamate or GABA, and of Müller cell maturations in postnatal early stage of the retina, while it changes to demonstrate the locations of glutamine cycle in the retina with adult characteristics.

Animals↗

PubMed1996

Ultrastructure of hyaluronic acid and collagen in the human vitreous.

The ultrastructure of hyaluronic acid (HA) and collagen in the human vitreous was investigated. After fixation with 4% glutaraldehyde and 0.1% cetylpyridinium chloride (CPC), sectioned blocks of retina and attached vitreous body were stained with 500 ppm ruthenium red (RR) in 1.25% glutaraldehyde, postfixed with 500 ppm RR in 2% OsO4, and embedded in Epon 812. In addition, collagen II immunostaining was done. Collagen fibrils were coated with amorphous material believed to be HA. No amorphous material was seen in the fibrils in the cortical areas adjacent to the retina, but the amount of material gradually increased toward the center of the vitreous body. By using anticollagen II antibody, we showed the presence of collagen II, often oriented perpendicular to the surface. The central vitreous demonstrated some dense materials that were collagen fibrils packed into bundles of parallel fibrils. In summary, collagen fibrils contained little HA in the cortical areas adjacent to the retina, but they were packed into bundles of parallel fibrils in the central vitreous.

Collagen↗

PubMed1996

Changes in GABA metabolism in streptozotocin-induced diabetic rat retinas.

We examined the pathogenesis of reduced amplitude in electroretinogram (ERG) oscillatory potentials (OPs) in diabetes, in relation to possible changes in the metabolisms involving retinal amino acid neurotransmitters. With use of streptozotocin diabetic rats, flash ERGs were recorded and quantitative analyses of retinal free amino acids were performed. Immunocytochemical localizations of retinal glycine and GABA were examined. In addition, activities of glutamic acid decarboxylase (GAD) and GABA transaminase (GABA-T) were measured. Our results revealed that the amplitudes of OP 1 and OP 2 decreased, and retinal glycine and GABA content significantly increased in the diabetic rats. An increased immunoreactivity of GABA was observed in Müller cells in the diabetic rat retinas, while no apparent changes were found in glycine immunoreactivity. Finally, increased activations of GAD with reduced activities of GABA-T were observed in the diabetic rat retinas. Thus, reduced amplitudes of OPs were associated with changes in content, localization, and enzyme activities related to GABA in the retinas, implying that changes in GABA metabolism can be a candidate for the pathogenesis of the abnormal OPs in diabetes.

4-Aminobutyrate Transaminase↗

PubMed1996

Localization of proline-like immunoreactivity in young rat retinal neurons.

PURPOSE: To localize proline in the rat retina. METHOD: We prepared antibodies raised against proline coupled to bovine serum albumin (BSA) with glutaraldehyde. To confirm the specificity of the antiserum, crossreactivity with other amino acids was determined using an immunodot procedure. Rat eyes were enucleated on postnatal day 21. Immunohistochemistry was performed on semi-thin sections using gold-labelled secondary antibodies and a silver-enhancement technique. RESULTS: Immunodots revealed that the antiserum was specific for proline. Amino acids from retinal extracts were separated on gel, transferred to BSA-glutaraldehyde treated filters, and stained with antibodies to determine if our antibody reacted only with proline. Staining was most intense on postnatal day 21 and disappeared in the adult retina. In addition to Muller cells, horizontal cells, amacrine cells, and some cells in the ganglion cell layer were labelled. CONCLUSIONS: Antibodies raised against proline revealed a transient immunoreactivity in young rat neurons. Our findings strongly indicate that the retina may express a high level of proline in the developmental stages. This result may provide a clue for clarifying the role of proline in the retina.

Animals↗

PubMed1996

Accumulation of gamma-aminobutyric acid in diabetic rat retinal Müller cells evidenced by electron microscopic immunocytochemistry.

PURPOSE: To evaluate possible changes in the distribution of gamma-aminobutyric acid (GABA) in diabetic rat retinas. METHODS: GABA distributions in the normal control and diabetic rat retinas were determined by a quantitative immunogold electron microscopic immunocytochemistry with anti-GABA antibody. GABA immunoreactivities (GABA-IR) in the retinas were visualized as bound gold colloidal particles in electron microscopy, and the average densities were calculated in each layer or in each kind of cells. The amounts of GABA-IR were statistically compared between normal control and diabetic rat retinas. RESULTS: In the normal control rat retinas, the amounts of GABA-IR was most abundant in the inner portion of the inner nuclear layer, followed by the inner plexiform layer. GABA-IR in amacrine cells ranged from the background level to the highest throughout the retina. Although the distribution pattern of GABA-IR in the diabetic rat retinas was similar to that of the normal control, GABA-IR increased significantly in the inner segment, the outer nuclear layer, and the outer plexiform layer (P < 0.05, by the analysis of variance), and in Müller cells (P < 0.001, by Mann-Whitney's U-test) of the diabetic rat retinas. However, pathologic accumulation of GABA-IR was not demonstrated in amacrine cells of the diabetic rat retinas. CONCLUSIONS: These results supported the accumulation of GABA in diabetic rat retinal Müller cells evidenced by light microscopic immunocytochemistry previously. It was suggested that GABA accumulation represents one of the functional deterioration of Müller cells in diabetic rat retinas.

Animals↗

PubMed1996

Light-evoked changes of glycine-like immunoreactivity in the rat retina.

Glycine is an important inhibitory neurotransmitter in the vertebrate retina. Although many reports of glycine localization by the immunocytochemical method have been published, none has distinguished the neurotransmitter function of glycine from metabolic change. If glycine is the neurotransmitter, it seems that it must be affected or released by stimulation. We evaluated the possibility that glycine in retinal synapses changes with light stimulation. Glycine-like immunoreactivity was found by light microscopy to be present mainly in the inner plexiform layer and amacrine cells. In the inner plexiform layer these immunoreactive products decreased after illumination. The distribution of glycine-like immunoreactivity in the rat retina was also investigated after embedding anti-rabbit IgG-gold colloidal particles (GCP). In the dark-adapted eyes, glycine-like immunoreactivity was marked in the inner plexiform layer (27.8 +/- 5.7 GCP/microns2) and amacrine cells (33.5 +/- 5.5 GCP/microns2). This immunoreactive product significantly decreased only in the inner plexiform layer after illumination (15.5 +/- 4.5 GCP/microns2). These changes in immunoreactivity may reflect the release of endogenous glycine. Our results provide evidence for the role of glycine as a retinal neurotransmitter.

Animals↗