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Biomedical subjects

M Tamai

Publications and source records attributed to M Tamai.

At least 181 records · Page 10Linked to original sources
PubMed1994

[S antigen in retinas of royal college of surgeons rats: time course and retinal pigment epithelium transplant study].

Retinas of Royal College of Surgeons (RCS) rats were investigated immunocytochemically for the distribution of S antigen prior to and during the retinal disease process. RCS retinas onto which retinal pigment epithelium (RPE) had been transplanted were also immunostained with antibody for S antigen. At P2, weak immunostaining for S antigen was seen in neuroepithelium. At P22, the staining pattern outlined the entire photoreceptor layer. At P30, at the beginning of retinal degeneration, immunostaining for S antigen was considerably reduced in the degenerating photoreceptor outer segment. In the RCS retina at P90, immunostaining for S antigen was completely lost. However, retinas with transplanted RPE showed preserved immunocytochemical staining for S antigen at this late stage. These results suggest a loss of production of S antigen in degenerated retinal tissue, and that RPE transplantation helps to preserve S antigen in the RCS rat retina.

Animals↗
PubMed1994

[Dual nature of excitatory amino acids in the vertebrate retina].

Glutamic acid plays an important role as a main excitatory amino acid and also as one of the central metabolites in the central nervous system (CNS). This amino acid also acts as a toxic substance in the vertebrate CNS, including the retina, especially in ischemic conditions. This paper reviews recent advances in retinal research on glutamate metabolism and its relationship with pathogenesis of retinal diseases. Excessive administration of glutamate induces overstimulation of N-methyl-D-aspartate (NMDA) and non-NMDA receptors, and influx of Na+, Cl-, and water to postsynaptic elements, causing lysis and swelling. In hypoxic or ischemic conditions, accumulation of glutamate was observed in most parts of the retina. Morphological and functional changes induced by ischemia could be prevented by preadministration of an antagonist of NMDA receptors. These results suggest that the same pathological mechanism as in the CNS exists in the retina. They also suggest that a new pharmacological approach for treating retinal abnormalities caused by ischemia could be introduced in the ophthalmology clinic in the near future. Abnormality of glutamate dehydrogenase, an important enzyme in the glutamate metabolism, has been reported in patients with spinocerebellar degenerations. Retinal dystrophy was also reported in some of them. Partial deficiency of heat-labile activity of this enzyme has been reported to be profoundly related with those patients with retinal abnormalities. This suggests that not only glutamate itself, but also abnormalities in its metabolic path way might be deeply correlated with the pathogenesis of retinal degeneration.

Animals↗
PubMed1993

Identification and immunohistochemistry of retinol dehydrogenase from bovine retinal pigment epithelium.

We studied the properties of retinol dehydrogenase (11-cis-specific) from bovine retinal pigment epithelium. Detergents caused a loss of retinol dehydrogenase activity; therefore, we added 3 mM NADH as a stabilizer to solubilize this enzyme and partially purified this enzyme using Sepharose CL-6B and hydroxyapatite column chromatography. The partially-purified sample, which contained two major proteins (66 kDa, 33 kDa), had substrate preference to 11-cis and 13-cis-retinal but not to all-trans and 9-cis isomers. Monoclonal anti-33 kDa protein of retinal pigment epithelial crude extract by Western blotting. In addition, we found that monoclonal anti-retinol dehydrogenase antibody bound specifically to retinal pigment epithelium and not to Müller cells or to rod outer segments by immunohistochemical methods.

Alcohol Oxidoreductases↗
PubMed1993

Expression of carcinoembryonic antigen in fresh human gastric cancer cells assessed by flow cytometry.

The expression of carcinoembryonic antigen (CEA) by tumor cells from freshly excised human gastric cancers was investigated using flow cytometry (FCM). Highly purified fresh human cancer cells were obtained from solid tumors in 20 patients and from malignant ascites in 6 patients. Thirteen of the 26 tumors were positive for CEA by FCM. CEA expression was more common in well-differentiated tumors than in poorly differentiated tumors. CEA expression was investigated by both FCM and immunohistochemistry in 9 patients, and the two methods agreed in 8 of them. However, quantitative evaluation of CEA expression could only be performed by FCM and not by immunohistochemical staining. FCM could analyze the expression of CEA not only on the cell membrane but also in the cytoplasm, by using gastric cancer cells with or without Triton X-100 treatment. Thus, this study showed that CEA expression can be determined and evaluated quantitatively by FCM.

Aged↗
PubMed1993

Stargardt's disease/fundus flavimaculatus: psychophysical and electrophysiologic results.

Retinal functions were analyzed psychophysically and electrophysiologically in 73 patients (146 eyes) with Stargardt's disease/fundus flavimaculatus. Patients were classified into types 1, 2, 3, and 4; patients with type 3 were subdivided into 3E and 3L (early and late onset of initial symptoms). Most had visual acuity (VA) of 20/200 or greater at initial testing. VA declined 0.25 octave/year during follow-up (mean, 6.1 years). Four of 16 patients (25%) older than 40 years had VA of 20/200 or less in the stronger eye. Psychophysical tests (flicker profile, central scotoma, dark adaptation) showed variable degrees of abnormalities. Electrophysiological tests showed significant photopic b-wave amplitude decreases, particularly in type 3E (42.2% of normal). The electro-oculogram light peak/dark trough ratio was abnormal in 60 of 132 eyes (45.5%), especially in type 3E (25 of 34 eyes, 73.5%). Visual prognosis and overall visual function varied depending upon disease type, location of retinal lesions, and age of onset. In Type 3E, overall retinal function was poorest and accompanied by the most severe decline of central vision and function in the surrounding macula.

Adolescent↗
PubMed1993

Usefulness of anaerobic threshold for evaluating daily life activity and prescribing exercise to the healthy subjects and patients.

Forty-three subjects were studied as for the relationship between anaerobic threshold (AT) and medical data including individual life style. Age, habit of exercise, and obesity are related to AT, showing a correlation coefficient of 0.533, 0.457 and 0.428, respectively. On the other hand, plasma lipid levels and alcohol are not so strongly related to AT, showing low correlation coefficient of 0.241 and 0.209 respectively. No correlation is found on the other factors such as FBS, Liver and blood pressure etc. Physical active life, commuting time, cumulative exercise hours in a month and work hours in a month are correlated to AT, showing correlation coefficient of 0.799, 0.734, 0.708 and 0.671, respectively, and even "more than once a month" frequency of exercise has affected AT. In conclusion, AT is a useful index for evaluating daily life activity and prescribing exercise regimen.

Activities of Daily Living↗
PubMed1993

Visual outcome after vitrectomy for diabetic retinopathy. A five-year follow-up.

For 5 years after surgery we measured visual acuity in 56 eyes that had undergone pars plana vitrectomy for proliferative diabetic retinopathy. A total of 44.7% eyes maintained improved visual outcome, 19.6% had unchanged visual acuity, and 35.7% were considered failures, as compared to preoperative measurements. Visual results obtained from each patient's visual acuity measured at 3 months, 6 months, 1 year, and 3 years after surgery were statistically compared with that obtained from the visual acuity at 5 years using the chi 2 test. Results showed that visual results recorded at 3 months and 6 months were significantly different from that recorded at the 5-year follow-up (p < 0.02, respectively). We found a tendency for the visual acuity to change during the initial 6 months after surgery and to stabilize by 1 year. Further analysis showed that the initial instability was due to the presence of preoperative retinal detachment. Postoperative visual functions also worsened with complications such as postoperative retinal detachment, glaucoma, and cataract formation.

Adult↗
PubMed1993

An autoreactive T cell clone generated in the autologous mixed lymphocyte reaction in a patient with gastric carcinoma.

Autoreactive T cell clones were established from a patient with early gastric carcinoma and a healthy control in order to investigate the mechanism of suppression of autologous mixed lymphocyte reaction (AMLR) and its significance in immune surveillance against tumor. Clone 3F6 from the gastric carcinoma patient responded to only autologous non-T cells with less reactivity than 4 clones from the control subject. The proliferative response of clone 3F6 to interleukin-2 and immobilized anti-CD3 antibody was also suppressed when compared with the control clones. Autoreactive T cells were able to kill tumor cells and autologous PHA-blasts. The cytotoxic activity of clone 3F6 was also markedly suppressed when compared with the control clones. This data suggests that autoreactive T cells may be impaired in cancer patients and that this immunological disorder might cause the defective immune surveillance against tumors.

Autoimmunity↗
PubMed1993

A multicenter study of typical retinitis pigmentosa in Japan.

A nationwide, multicenter study of typical retinitis pigmentosa was carried out in collaboration with 13 university hospitals throughout Japan. A total of 253 patients, 122 males and 131 females, with a wide range of ages (mean 48 years), were registered during a two-month period in 1989. Determination of inheritance pattern revealed 30.2% autosomal recessive cases, 15.4% autosomal dominant, 0.5% X-linked, and 48.9% simplex, indicating a relative decrease in autosomal recessive cases and a relative increase in simplex cases in recent decades. The age at onset, initial symptom, and visual functions including visual acuity, visual field and electroretinogram showed a marked interindividual variability, but statistical analysis demonstrated that visual defects progressed with increasing age and disease duration. A correlation between the phenotypic variation and the genetic type was observed. This survey of retinitis pigmentosa in Japan provides information for counseling and rehabilitation of patients and encourages basic and clinical research of this genetic disease.

Adolescent↗
PubMed1993

[Experimental research on choroidal circulation. 1. Effect of sectioning or stimulation of the cervical sympathetic nerve upon choroidal blood flow].

Choroidal blood flow (CBF) was continuously measured with a laser doppler flowmeter (LDF) in 32 pentobarbital-anesthetized cats. A rise in intraocular pressure (IOP) caused a decrease in CBF, but when the IOP increase was slight, it induced a CBF increase. A sustained increase of CBF occurred following sectioning of the cervical sympathetic nerve (CSN) in 7 out of 18 eyes, but no noticeable blood flow change was observed in the remaining 11 eyes. Two different vasomotor responses in CBF were observed in response to electrical stimulation of the peripheral cut end of the CSN; one was a decrease and the other an increase. From the present experiments, decrease of CBF elicited by CSN stimulation is considered to be due to an increase in the activity in vasoconstrictor fibers of choroidal capillary blood vessels, but the exact mechanism of the CBF increase is unknown. Slight changes in position of the LDF probe sometimes alter the vasoresponses, suggesting that the site at which CBF was measured is crucial for investigating the effects of dissection or electrical stimulation of the CSN on CBF.

Animals↗
PubMed1993

[Bilateral hyperplasia of the coronoid apophyses. A clinical case].

The authors report on the case of a young patient affected with bilateral hyperplasia of the coronoid apophyses, who presented a serious reduction of the mandibular excursion. Normal mouth opening was re-established by a bilateral osteotomy with endoral removal of the coronoid apophyses.

Adult↗
PubMed1993

Retinal changes in myotonic dystrophy. Clinical and follow-up evaluation.

Retinal changes in myotonic dystrophy include butterfly-shaped pigmentary changes in the macula, reticular pigmentary retinal changes in the midperiphery, and peripheral atrophic polygonal-shaped changes. To assess the prevalence and progressiveness of these changes in a large series, 49 patients with myotonic dystrophy were examined. Of the eyes studied, 26 (26.6%) had butterfly-shaped macular pigmentary changes, 24 (24.5%) had reticular pigmentary retinal changes, and 43 (43.9%) had peripheral atrophic polygonal-shaped changes. Ten patients (18 eyes) had two different types at once. Visual acuity was not severely affected. Electroretinographic examination showed diminished a and b wave amplitudes in eyes with and without retinal changes. Arden ratios on the electrooculogram were normal in 13 of 14 patients tested. During the follow-up period, which exceeded 5 years, 3 of 9 patients had newly developed or enlarged, patterned changes of the pigment epithelium. These results suggest that pigmentary retinal changes in patients with myotonic dystrophy are slowly progressive.

Adolescent↗
PubMed1993

Expression of glial fibrillary acidic protein in rabbit Müller cells after lensectomy-vitrectomy.

PURPOSE: To assess retinal response after lensectomy-vitrectomy, the authors analyzed glial fibrillary acidic protein (GFAP), which retinal glial cells express in several pathologic conditions. METHODS: GFAP expression was examined by means of immunohistochemistry, Western blot analysis, and enzyme-linked immunosorbent assay (ELISA) in rabbit retina after lensectomy-vitrectomy. RESULTS: Müller cells had detectable GFAP immunoreactivity in peripheral retina 3 days after surgery. GFAP immunoreactivity was present in both peripheral and posterior regions 7 days, 14 days, and 6 months after surgery. The authors confirmed that anti-GFAP antibody recognized the 51 kDa protein specifically by Western blot analysis. Time-dependent increase of GFAP in peripheral retina was also obtained by ELISA: CONCLUSIONS: Such progressive GFAP accumulation in Müller cells, which are sensitive to microenvironmental changes, may reflect some underlying retinal response after lensectomy-vitrectomy.

Animals↗
PubMed1993

[Expression of modified nucleoside, 1-methyladenosine in intraocular tumors and the retinas].

1-methyladenosine is one of the modified nucleosides, the levels of which are elevated in urine of patients with malignant tumors. We report herein immunohistological expression of 1-methyl-adenosine in tumor cells and retinas. Eight retinoblastomas, 4 malignant melanomas, two metastatic choroidal tumors, 3 retinal dysplasias, one intraocular hemorrhage and 5 normal eye retinas in human were examined. In addition, 8 experimental rabbit choroidal tumor XV2s, and 5 normal rabbit retinas were examined. 1-Methyladenosine was expressed in almost all malignant tumors and retinas with these tumors, while there was little expression in benign tumor cells, retinas with benign tumor and retinas in normal eyes. Results in rabbits were almost the same as in humans. Examination of expression of 1-methyladenosine is expected to be useful for the histological diagnosis of intraocular tumors.

Adenosine↗
PubMed1992

Defective autologous mixed lymphocyte reaction (AMLR) and killer activity generated in the AMLR in cancer patients.

The autologous mixed lymphocyte reaction (AMLR) and the killer activity generated in the AMLR (AMLR-killer) in the spleen and the peripheral blood of patients with gastric cancer were investigated. The AMLR in cancer patients was suppressed, especially in the spleen, compared to that seen in controls. There was no correlation between AMLR activity and the stage status of the cancer. The cytotoxic activity of AMLR-killer cells against various tumor-cell lines was also suppressed in the spleen, and had a tendency to be suppressed in the peripheral blood of cancer patients. The autologous tumor-killing activity of AMLR-killer cells was developed in cancer patients with high AMLR activity, but was not induced in patients with low AMLR activity. Autotumor killing activity was decreased by the elimination of CD4+ cells, whereas the elimination of CD16+ cells resulted in a marked reduction in cytotoxicity against K562, indicating that the non-specific killer cells which lysed K562 were different from the specific killer cells that lysed autotumor cells. This suggests that AMLR activity is related to the differentiation and proliferation of lymphocytes with specific or non-specific cytotoxic activity and that this activity plays an important role in immune surveillance against tumors.

Adult↗