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Biomedical subjects

Y Yamana

Publications and source records attributed to Y Yamana.

At least 19 recordsLinked to original sources
PubMed1988

Reflow of obstructed capillaries in the maculae of humans with diabetic retinopathy, observed by fluorescein angiography.

As diabetic retinopathy progresses, the non-perfused area in the retina gradually enlarges as the capillaries are obstructed. To elucidate the process of capillary obstruction we examined macular capillaries in 104 diabetics, using fluorescein angiography. The follow-up period was three to eight years. We found that some capillaries in the macular were obstructed, then became unobstructed. Reflow of blood into the macula after the obstruction was observed in nine patients (8.7%). The time between obstruction and reflow varied from two months to four years. There were four cases of simple, three of preproliferative, and two of proliferative retinopathy. Reflow in the capillaries was confirmed as occurring at the same position and in vessels with the same diameter as seen before the obstruction. There was no leakage of the fluorescein dye from the capillary where reflow took place. We tentatively conclude that one of the causes of this phenomenon is a functional obstruction.

Adolescent↗
PubMed1987

Effect of argon laser photoradiation on monkey retina treated with hematoporphyrin derivative--fluorescein angiographic and light microscopic study.

To determine the method of treating retinoblastoma by means of argon laser photoradiation and hematoporphyrin derivative (HpD), we gave HpD intravenously at a dose of 2.5 or 5.0 mg per kg to monkeys, and 40 minutes, one day or 3 days after this injection, argon laser photoradiation was performed at 2.0 mm diameter with a 10-minute exposure at intensities of 40, 100 or 200 mW. As photoradiation after HpD injection of 5.0 mg per kg induced severe retinal changes, 2.5 mg per kg was thought to be the dose for clinical application. Photoradiation 3 days after the injection of HpD was found to be the best choice of timing. One hundred to 200 mW intensity of laser beam was considered to be an appropriate range. Without HpD, changes in the retinal pigment epithelium and outer segment of the visual cells of the photoradiated eyes resembled those caused by conventional photocoagulation. Characteristic findings of the photoradiated retina were obstruction of the retinal vessels, fragility of the nerve fiber layer and attenuation of the inner nuclear layer. Photoradiation at a high intensity induced retention of subretinal fluid in the nonphotoradiated area. Therefore, at the time of photoradiation, light should be delivered only to the tumor.

Animals↗
PubMed1986

Photoradiation therapy using argon laser and a hematoporphyrin derivative for retinoblastoma--a preliminary report.

Five children with retinoblastoma were treated using an argon laser photocoagulator and a hematoporphyrin derivative. Fluorescein angiography after the photoradiation revealed hypofluorescence of the tumor, indicating obstruction of the tumor vessels. Histopathologic examination of the tumor from the patient treated with photoradiation therapy and without other treatments revealed that tumor cells were destroyed and angionecrosis took place. It was thought that the tumor smaller than 4 disc diameters might be destroyed by this treatment alone. In the case of a larger tumor, photoradiation therapy plus radiotherapy was necessary, but the dose of radiation could be reduced. The side effects embraced vitreous hemorrhage and retinal damage in the nontumorous part when photoradiation was excessive; use of Goldmann's three-mirror funduscope was indispensable to avoid excessive photoradiation. Based on the present experience the following methods may be recommended: 3 days after intravenous administration of 2.5 mg per kg of the hematoporphyrin derivative, photoradiation is carried out using an argon laser of 2-mm spot size and the intensity of 200 mW for 10 minutes. If the tumor remains viable, repeat the photoradiation with 100 mW intensity plus the hematoporphyrin derivative at one-month intervals.

Argon↗
PubMed1983

Autoradiographic localizations of [35S]-sulfate and [3H]-glucosamine in the hamster ciliary epithelium.

The localization of [35S]-sulfate and [3H]-glucosamine in the hamster non-pigmented ciliary epithelium was studied by light and electron microscopic autoradiography. The radioactivity was concentrated in the Golgi complex of the non-pigmented ciliary epithelium 10 mins after injections of [35S]-sulfate or [3H]-glucosamine. Silver grains of both isotopes covered the cytoplasm 60 mins after the administration and were then associated with the basal infoldings. Radioactivity of [3H]-glucosamine was observed in the basal lamina of the non-pigmented ciliary epithelium and the ciliary zonule; however, the localization of [35S]-sulfate in the basal lamina and the ciliary zonule was not demonstrated. These data lend support to the idea that the non-pigmented ciliary epithelium may synthesize glycosaminoglycans (GAG) and secrete non-sulfated glycosaminoglycans into the posterior chamber.

Animals↗
PubMed1983

Carcinoembryonic antigen and alpha fetoprotein levels in retinoblastoma.

Plasma carcinoembryonic antigen (CEA) and alpha fetoprotein (AFP) levels were analyzed in 22 patients with retinoblastoma. In 13 patients, the titers could be determined both before and after treatment. The plasma CEA level was elevated in 4 to over 2.5 ng ml-1 prior to therapy, and the plasma AFP level was elevated in 4 to over 20 ng ml-1 before treatment. High CEA and AFP levels in all patients at the time of pretreatment were lowered with therapy. In most bilateral cases, conservative treatment had been performed in the contralateral eye after the severely diseased eye had been enucleated. Plasma CEA and AFP levels were gradually decreased during therapy. These levels were elevated with a recurrence and/or bone metastasis.

Carcinoembryonic Antigen↗
PubMed1983

D-scan ultrasonography of orbital lesion.

Ultrasonography has evolved recently into a valuable technique for examining intraocular and orbital lesions. However, ultrasound examinations usually have been performed using A- and B-scan. We report D-scan ultrasonography or orbital lesions that include orbital tumors, endocrine exophthalmos, vascular lesions and inflammatory changes. D-scan ultrasonography is a useful diagnostic method because of the three-dimensional presentation. It serves to pinpoint not only the location of the orbital lesion but also internal reflectivity showing tissue characterization.

Adult↗
PubMed1983

Early signs of diabetic retinopathy by fluorescein angiography.

The initial sign of diabetic retinopathy is considered to be microaneurysm, determined by ophthalmoscopy. To elucidate early vascular changes in diabetes, fluorescein angiography was performed in 272 eyes of 166 patients who had shown no evidence of diabetic retinopathy by ophthalmoscopy. Early retinal vascular changes shown by fluorescein angiography were seen in 181 eyes (66.5%) out of 272 eyes. These angiographic findings embraced dye leakage, dilatation of capillaries, filling defect of capillaries, microaneurysm-like spot dilatation and microaneurysm. Statistical analysis and follow-up studies for 1 to 5 years revealed that, with progression of the disease, the angiographic changes progressed in the following order: dye leakage, dilatation of capillaries, filling defect of capillaries, microaneurysm-like spot dilatation and microaneurysm.

Adult↗
PubMed1983

Diabetic retinopathy and hemoglobin A1.

A prospective study was conducted in 36 diabetic patients to correlate the fasting blood sugar level (FBS) and the levels of hemoglobin A1 (HbA1) with the severity and progression of diabetic retinopathy. During an average follow-up of 12.6 +/- 2.9 months, the FBS and HbA1 levels were determined and progression of diabetic retinopathy assessed by fluorescein fundus angiography. The time-averaged HbA1 and FBS were correlated significantly. The HbA1 levels were significantly augmented in the order of good, fair and poor sugar control groups. The patients with progressive retinopathy had significantly higher FBS and HbA1 levels than the patients whose retinopathy remained unchanged. The correlation between the HbA1 level and the severity of retinopathy was not statistically significant. It was concluded that the combination of HbA1 and FBS levels will be useful for long-term control of diabetes and of progression of retinopathy.

Adult↗
PubMed1983

Falciform retinal fold as sign of familial exudative vitreoretinopathy.

We studied family members of 9 patients with falciform retinal fold, and found a number of cases showing features of familial exudative vitreoretinopathy (FEVR) in the fundi. Retinal fold was also seen in the eye of a cousin of the propositus. Three cases with falciform retinal fold were bilateral and 7 cases were unilateral. Retinal folds were located in the temporal half of the fundis in 11 of the 13 eyes with retinal fold. These 11 eyes showed avascularized zones of retinal vessels with scalloped edges in the periphery; in the 2 remaining eyes the retinal vessels were restricted within the fold. Thirty-one eyes of 18 cases, members of 7 pedigrees, showed features of FEVR. The observed avascularized zones with scalloped pattern of the vessels and vitreoretinal involvements were divided into 3 groups: 23 eyes of stage 1, 6 eyes of stage 2, and 2 eyes of stage 3, respectively. It was, therefore, concluded that falciform retinal fold being located temporally or bilaterally could be one of the signs of FEVR and that FEVR was a disease affecting regression of the hyaloid vascular system and development of the retinal vessels during fetal life. FEVR was classified into 4 groups: type 1, type 2, type 3 and type 4 of falciform retinal fold. The disease may be transmitted as autosomal dominant inheritance.

Adult↗
PubMed1982

Application of fluorescein angiography in retinoblastoma.

Although a slight dilatation of the retinal capillaries is the only significant fluorescein angiographic finding in retinoblastoma when the tumor is less than 0.5 disk diameter in size, microaneurysms become distinct in the tumor after it attains a size of 1 disk diameter. As growth of the tumor progresses, blood vessels within the tumor become thicker and permeability increases; eventually neovascularization occurs. When the tumor exceeds 3 disk diameters in size, the feeder arteries and drainage veins become dilated and tortuous. With healing of the retinoblastoma, light fluorescent stains and thick vessels are no longer demonstrable and the dye is visible in the sclera during later periods. A recurrent tumor is visible as a white fluffy mass in which the fluorescent dye accumulates. Occasionally a thick vessel stemming from the scar can be detected in a recurrent tumor.

Eye Neoplasms↗