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Biomedical subjects

K Yagasaki

Publications and source records attributed to K Yagasaki.

At least 19 recordsLinked to original sources
PubMed1992

Fundus albipunctatus associated with cone dystrophy.

We describe five unrelated patients in whom the typical signs of fundus albipunctatus were accompanied by colour vision defects, bull's eye or similar macular lesions, and severely diminished full-field cone electroretinograms indicating widespread damage to cones outside the macula. All patients had noticed night blindness from childhood. Signs of retinitis punctata albescens, a disease of similar appearance but with characteristics resembling retinitis pigmentosa, were absent. We cannot be sure whether these patients represent a process of fundus albipunctatus or a distinct disease entity or a casual combination of fundus albipunctatus and cone dystrophy.

Adult↗
PubMed1991

Electroretinographic monitoring of retinal function during eye surgery.

We performed a pilot study of electroretinographic monitoring of retinal function during eye surgery performed with local anesthesia. A contact lens with a built-in light-emitting diode was sterilized and used as both a stimulus source and a recording electrode for 30-Hz flicker electroretinograms. Each recording required 7 seconds, during which the operating light (but not the room light) was switched off. Electroretinograms recorded during surgery on 10 patients with minimal retinal abnormality were evaluated for the effects of light adaptation caused by regular exposure to an operating light source or operating microscope. The fluctuations of the amplitude and peak time were small, indicating that this technique can be used to monitor retinal function during eye surgery. Some results during retinal and vitreous surgeries are shown.

Contact Lenses↗
PubMed1990

Effects of dietary methionine and glycine on serum lipoprotein profiles and fecal sterol excretion in normal and hepatoma-bearing rats.

The effects of concurrent addition of methionine (Met) and glycine (Gly) to a 20% casein diet on serum lipoprotein profiles and fecal sterol excretion were studied in male Donryu rats with or without subcutaneous implantation of an ascites hepatoma line of AH109A cells. The hepatoma-bearing rats fed on the 20% casein diet had a notable elevation in the very-low-density lipoprotein + low-density lipoprotein (VLDL + LDL)-cholesterol (Ch) level with a slight but significant decrease in high-density lipoprotein (HDL)-Ch level when compared to the hepatoma-free (normal) rats fed on the same diet. The dietary addition of 1.2% Met and 2.5% Gly in combination suppressed the hepatoma-induced elevation in the (VLDL + LDL)-Ch level with a prevention of the hepatoma-induced decrease in the HDL-Ch level. The addition of the two amino acids also lowered significantly the (VLDL + LDL)-Ch level without affecting the HDL-Ch level in tumor-free rats. Fecal excretion of both neutral and acidic sterols were reduced with growth of the hepatoma. The dietary addition of Met and Gly exerted no or little influence on neutral sterol excretion in both the tumor-free and -bearing states, but it enhanced acidic sterol excretion into feces in both states, especially in the hepatoma-bearing state at the last stage of feeding. These results suggest that the excretion and catabolism of Ch might be impaired in hepatoma-bearing rats with growth of the tumor, and that the supplemental Met and Gly in combination might enhance Ch catabolism by stimulating either synthesis or conjugation of bile acids, leading to a reduction of the (VLDL + LDL)-Ch level in the normal and hepatoma-bearing states.

Animals↗
PubMed1990

Effects of dietary supplemented amino acids on endogenous hypercholesterolemia in rats.

Effects of additions of amino acids to a 20% casein diet on serum cholesterol (Ch) were studied in hypothyroid and hepatoma-bearing rats with endogenous hypercholesterolemia as well as in normal rats. In normal Wistar rats, methionine (Met) was hypercholesterolemic at the "nutritional" level (0.2-0.4%), but hypocholesterolemic at the "excess" level (1.2-2.4%). In Wistar rats with hypothyroidism induced by thiouracil, the addition of excess (1.2%) Met to the 20% casein diet reduced an endogenous hypercholesterolemia due to hypothyroidism by suppressing an elevation in (VLDL + LDL)-Ch with no significant influence on HDL-Ch. In Donryu rats received a subcutaneous implantation of AH109A cells (an ascites hepatoma line), either 1.2% Met, 1.2% cystine (Cys), or 1.2% Met and 2.5% glycine (Gly) in combination improved a hepatoma-induced hypercholesterolemia and abnormal serum lipoprotein profiles by suppressing a hepatoma-induced increase in (VLDL + LDL)-Ch. From Ch turnover studies in hepatoma-bearing rats, an impaired catabolism of Ch in the liver was suggested to be one cause for the hepatoma-induced elevation in (VLDL + LDL)-Ch. One of the dietary manipulations. met and Gly in combination (Met + Gly), was found to improve the impaired Ch catabolism, this leading to a reduction of the (VLDL + LDL)-Ch level by Met + Gly in hepatoma-bearing rats.

Amino Acids↗
PubMed1990

[Modification of an automated perimeter for dark- and light-adapted perimetry].

A modified automated projection static perimeter which can measure thresholds with lights of three different wavelengths in light-adapted as well as in dark adapted state is described. With the modifications described, this instrument can evaluate relative states of rod and cone mechanisms respectively within the visual field range of 72 degrees. These modifications also enable dark-adapted two-color static perimetry quantitatively across the visual field including profile measurement. Results obtained from normal subjects with these techniques permit assessment of the sensitivity in dark and light and also determination of photoreceptor mediation in the dark. These techniques can evaluate rod and cone dysfunctions separately unlike other retinal function tests, and may show that different mechanisms even in one clinical entity of retinal dystrophies, as well as retinal degenerations, can be demonstrated.

Adaptation, Ocular↗
PubMed1989

Cone-rod dystrophy. Phenotypic diversity by retinal function testing.

Three patterns of visual dysfunction were identified in patients with autosomal recessive or simplex cone-rod dystrophy using rod and cone electroretinography and light- and dark-adapted static threshold perimetry. In the first pattern, there was a central rod and cone scotoma with eccentric fixation, mild peripheral retinal dysfunction equally affecting rod and cone systems, and slow progression. The second pattern, which was relatively more severe, also showed a central rod and cone scotoma and eccentric fixation; however, there was more cone than rod dysfunction detected by electroretinography, and function was lost in the peripheral visual field before it was lost in the midperipheral field. A third pattern, which was rapidly progressive, showed central unsteady fixation and no measurable cone function. Patches of rod function were retained in the central and inferotemporal regions of the visual field. Most of the patients studied fit within the three patterns and the patterns were consistent within families.

Adolescent↗
PubMed1989

Interocular asymmetry of visual function in heterozygotes of X-linked retinitis pigmentosa.

Heterozygotes of X-linked retinitis pigmentosa were studied with full field rod and cone electroretinography and light adapted kinetic perimetry. Twelve parameters from the electroretinograms (ERGs) and two parameters from the kinetic visual fields of both eyes of 22 heterozygotes were measured and statistical comparisons made with results from female control subjects. Rod and cone ERG amplitude parameters were significantly lower and cone timing delayed in the heterozygotes. Most of the ERG parameters that were abnormal in measured value also showed significantly greater interocular differences compared with controls. Kinetic visual fields with both V-4e and I-4e test targets were smaller in heterozygotes than in controls. Only with the I-4e target, however, were interocular differences significantly larger in the heterozygotes. For the I-4e target and many of the ERG parameters, using the interocular difference in conjunction with the measured parameter value from a single eye significantly increased the efficacy of discrimination between heterozygotes and controls; for some ERG parameters, the interocular difference alone provided the best separation of the two groups.

Adolescent↗
PubMed1989

Bull's-eye maculopathy and negative electroretinogram.

The authors studied four patients with a bull's-eye maculopathy and otherwise normal fundus. A single-flash electroretinogram (ERG) with an intense white light stimulus in the dark showed a normal a-wave but reduced b-wave amplitude (negative ERG). Other findings common to all four patients were initially normal visual acuity, subsequent progressive decrease in visual acuity, mild to moderate deficiency of color vision, normal peripheral visual field, relatively well preserved cone ERG, normal 30-Hz flicker ERG, normal EOG, near emmetropia and selective involvement in males. Cone dystrophy, retinitis pigmentosa, congenital retinoschisis, congenital stationary night blindness, and Batten's disease were excluded. The correlation between this disease and benign concentric annular macular dystrophy is discussed.

Adult↗
PubMed1988

Rod and cone psychophysics and electroretinography: methods for comparison in retinal degenerations.

Methods have been developed to compare full field rod and cone electroretinograms with results of rod and cone static perimetric measurements across the visual field. In a limited number of patients with retinal degeneration, including two subtypes of retinitis pigmentosa, there were close relationships between electroretinographic and psychophysical parameters. Maximum b-wave amplitude and visual field area were highly correlated, as were electroretinographic and perimetric measures of sensitivity loss. Future application of the methods to large numbers of patients with typical retinitis pigmentosa may help elucidate different mechanisms of retinal degeneration.

Adult↗
PubMed1987

On- and off-responses in photopic electroretinogram in complete and incomplete types of congenital stationary night blindness.

The on- and off-responses of photopic electroretinogram (ERG) were recorded by rectangular light stimuli in 13 patients with complete type and 9 patients with incomplete type of congenital stationary night blindness. The positive on-response (b-wave) was significantly smaller in both types than in normal subjects (P less than 0.001). The rapid off-response was normal in complete type patients, but was significantly smaller in incomplete type patients than in normal subjects (P less than 0.001). Since the rapid off-response mainly reflects the decay of the late receptor potential of the cones, incomplete type patients may have a visual disturbance in the cone itself. Normal rapid off-response with abnormal on-response in complete type patients suggests the existence of a photopic visual disturbance in the middle retinal layer. These results strongly suggest that these two types of congenital stationary night blindness have a different pathogenesis in the photopic visual pathway.

Adolescent↗
PubMed1986

Local macular ERG in patients with Best's disease.

We examined a pair of siblings, a 10-year-old girl (case 1) and a 12-year-old girl (case 2), with Best's disease. The visual acuity was nearly normal in both patients. The central visual field measured with auto-plot tangent screen revealed a small relative paracentral scotoma only in the left eye of case 2. We failed to detect any abnormality in photopic and scotopic electroretinogram (ERG) recorded with Ganzfeld stimuli and the electrooculogram light rise was absent in both patients. Local macular ERG was recorded under a fundus monitor by infrared television fundus camera with test spots of 5, 10, and 15 degrees in diameter. The center of the stimulus spot was always on the fovea during the recording. The local macular ERG was absent in both patients. Our results of local macular ERG may indicate disturbance of the central portion of the retina.

Child↗
PubMed1986

Two cases of retinal degeneration with an unusual form of electroretinogram.

An unusual form of retinal degeneration is reported in 15-year-old girl and 11-year-old girl with different pedigrees, which resembles the cases reported by Gouras and associates (1983). The subjective symptoms in these patients included decreased visual acuity, photophobia, anomalous color vision and night blindness. Electroretinograms (ERGs) in these two patients were identical in substance and revealed drastic alterations in both photopic and scotopic functions. The stimulus versus intensity response curve in a single-flash ERG showed an unusual form. This peculiar supernormal response was elicited by bright stimuli although the stimulus threshold was extremely elevated.

Adolescent↗
PubMed1986

Congenital stationary night blindness with negative electroretinogram. A new classification.

An analysis of 64 patients with congenital stationary night blindness showed that all had essentially normal fundi. Electroretinography (ERG) showed a normal a wave with extremely reduced b wave (negative type) when recorded with a single bright white stimulus in the dark. We classified these patients into two groups based on the evaluation of rod ERG and/or psychophysical dark adaptation measured with an 11 degree test target at 15 degrees in the upper part of the retina. One group (35 patients) lacked rod function (complete type). Nine patients could not be classified. No pedigree showed a complete and incomplete type in one family. Differences between the two groups in refractive error, photopic function, and oscillatory potentials in the ERG suggest a different pathogenesis. Our analysis may provide a new classification of congenital stationary night blindness with a negative ERG.

Adolescent↗
PubMed1986

Effects of dietary methionine, cystine, and glycine on endogenous hypercholesterolemia in hepatoma-bearing rats.

The effects on hypercholesterolemia of dietary additions of cystine (Cys), methionine (Met), glycine (Gly), and a combination of Met and Gly to a 20% casein diet were studied in male Donryu rats subcutaneously implanted with an ascites hepatoma line of AH109A cells. The hepatoma-bearing rats fed the 20% casein diet lapsed into both endogenous hypertriglyceridemia and hypercholesterolemia when compared to hepatoma-free (normal) rats fed the same diet. The hypercholesterolemia was due to an elevation (3.2 fold) in the very low-density lipoprotein plus low-density lipoprotein (VLDL + LDL)-cholesterol (Ch) level. The high-density lipoprotein (HDL)-Ch level was slightly but significantly decreased. These lipoprotein changes in hepatoma-bearing rats resulted in a marked (4.5 fold) increase in the atherogenic index (AI, (VLDL + LDL)-Ch/HDL-Ch) in comparison with that of tumor-free rats. The dietary additions of 1.2% Met, 1.2% Cys, and a combination of 1.2% Met and 2.5% Gly significantly suppressed the hepatoma-induced increase in (VLDL + LDL)-Ch with no influence on the hepatoma-induced decrease in HDL-Ch, leading to a noticeable fall in AI. These results indicate that hepatoma-bearing rats are useful as an endogenously hyperlipidemic model and that some dietary amino acids are capable of improving hepatoma-induced hypercholesterolemia and abnormal serum lipoprotein profiles.

Animals↗
PubMed1986

Oscillatory potentials and pattern electroretinogram: are they related?

The possible relationship between the pattern electroretinogram (ERG) and oscillatory potentials was investigated in two patients with night blindness. One patient had congenital stationary night blindness of Schubert-Bornschein type, and the other had Oguchi's disease. Both had normal visual acuity, normal mass photopic (cone) ERG and normal local macular ERG. In each patient, scotopic (rod) ERG after 20-minute dark adaptation was nonrecordable and the single bright flash ERG was of the negative type. The difference between the ERG pattern of the two patients was found in the oscillatory potentials. The patient with congenital stationary night blindness showed no oscillatory potentials, whereas the patient with Oguchi's disease had good oscillatory potentials. The pattern ERG in both patients was normal. Based on the data of these two patients, it was thought that the pattern ERG is not closely related to the oscillatory potentials and may have different mechanisms of generation.

Electroretinography↗