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Biomedical subjects

Y Takaku

Publications and source records attributed to Y Takaku.

At least 19 recordsLinked to original sources
PubMed2001

The process of cell adhesion among dissociated single cells of Hydra: morphological observations.

Ultrastructural observations were made on the initial adhesion process at the adherent region of Hydra endodermal cell pairs brought into contact (following dissociation) using a three-dimensional laser manipulator. Total contact length across the diameter of the adherent region decreased during the period 10-60 min after initial adhesion. However, the mean numbers of closest (<4 nm) and medium (5-25 nm) separation distances between membranes (thought to be important in total cell adhesion) were not significantly different. These data indicate that adherent cell pairs maintain a constant adhesiveness during the first 60 min of the adhesion process, despite membrane rearrangements. The relative length of each separation distance in adherent cell pairs approached that reported previously for intact Hydra. The sums of lengths in both the closest and medium categories (as a proportion of total contact length) increased because the length of cleavages (distances >25 nm) decreased significantly during the same time period. These results suggest that adherent cell pairs undergo rapid, active membrane changes in the adherent region, which might be associated with cell sorting. The possible significance of these changes for active rearrangement are discussed.

Animals↗
PubMed2001

Diurnal changes in retinula cell sensitivities and receptive fields (two-dimensional angular sensitivity functions) in the apposition eyes of Ligia exotica (Crustacea, Isopoda).

The structural organization of the retinula cells in the eye of Ligia exotica changes diurnally. At night, the microvilli elongate, losing the regular and parallel alignment characteristic of the day condition. Crystalline cones and distal rhabdom tips are not pushed into each other during the day, but at night the rhabdoms protrude into the crystalline cones by up to 5 microm. Screening pigment granules in the retinula cells disperse during the night, but migrate radially towards the vicinity of the rhabdom during the day. No such displacements of the pigment granules of either distal or proximal screening pigment cells were observed. The sensitivity of the eye, monitored by electroretinogram (ERG) recordings, changes diurnally: values at midnight are, on average, 10 times those occurring during the day. However, intracellular recordings from single retinula cells (50 during the day and 50 at night) indicate that the difference between night and day sensitivities is only 2.5-fold. Two-dimensional angular sensitivity curves, indicative of a single unit's spatial sensitivity, had considerably less regular outlines at night than during the day. If based on the 50 % sensitivity level, day and night eyes possessed receptive fields of almost identical width (approximately 2 degrees), but if sensitivities below the 50 % limit were included, then receptive fields at night were significantly more extensive. We suggest that the morphological adaptations and diurnal changes in chromophore content seen in the apposition eye of L. exotica allow this animal to improve its photon capture at night while preserving at least some of the spatial resolving power characteristic of the light-adapted state. This would explain why this animal is capable of performing complex escape behaviours in the presence of predators both in bright and in very dim light.

Animals↗
PubMed2000

Initial homotypic cell pair adhesion in regenerating Hydra facilitates subsequent adhesion of homotypic cells.

In Hydra vulgaris at the level of dissociated single cells endodermal cells adhere to each other more readily than to ectodermal cells at the initial adhesion. The time required for adhesion to occur between two adjacent cells is shorter for both endodermal and ectodermal homotypic cell adhesions once the initial adhesion of the first pair of cells has been established. It is confirmed that contact of an aggregated pair with additional homotypic cells facilitates the occurrence of homotypic adhesions; heterotypic adhesions are discouraged. This suggests that adhesion of homotypic cells contributes to an increased readiness for subsequent homotypic cells to adhere.

Animals↗
PubMed1999

Ultrastructural observations of adherent cell pairs in hydra vulgaris

Previous morphological studies of cell sorting in Hydra vulgaris have considered only clusters of cells. Here, we present ultrastructural observations on the adherent region of cell pairs brought into contact (following dissociation) using a three-dimensional laser manipulator. There was a much larger area of close membrane contact between endodermal cell pairs in comparison with ectodermal cell pairs. Separation distances between membranes were categorized into three classes: closest distance (<4 nm); medium distance (5-25 nm); and cleavage (>25 nm). The sum of distances in the closest and medium categories as a proportion of total contact length was significantly greater (P<0.01) for endodermal cells (49.0+/-6.5 %) than for ectodermal cells (26.7+/-4. 4 %). In intact Hydra, this sum of distances was also significantly greater for endodermal cells, indicating that newly adherent cells, even after adhesion for only 10 min, display similar morphological characteristics to cells in intact Hydra. This suggests that close membrane contacts contribute to differential cell adhesion, which may form the basis of the cell sorting process.

Journal Article↗
PubMed1998

Strength distribution in the tibia.

Stress fracture of a tibia is rarely associated with osteoarthros of the knee joint (gonarthrosis), whereas the present authors experienced a case of tibial stress fracture with high level lateral flail. To make an analysis with the statics of an elastic body, the shape of the tibia was read from a roentgenogram with a digitizer. The bend of a tibia was expressed with curvature (the reciprocal with curvature radius); fracture was expected to occur where the curvature was large. From the analysis, the fracture had occurred near one of the maximums of the curvature when the knee side was fixed and a force was applied to the ankle side --walking situation, e.g. The analysis also has indicated that the tibia would be very weak when the ankle side was fixed--skiing situation, e.g.

Aged↗
PubMed1994

Survey of complications of indocyanine green angiography in Japan.

PURPOSE: We evaluated the safety of indocyanine green for use in fundus angiography. METHODS: We sent a questionnaire concerning complications of indocyanine green to 32 institutions in Japan, which were selected on the basis of the client list from the Topcon Company, which manufactures the indocyanine green fundus camera. RESULTS: Ophthalmologists at 15 institutions responded, reporting a total of 3,774 indocyanine green angiograms performed on 2,820 patients between June 1984 and September 1992. Before angiography, intradermal or intravenous indocyanine green testing, or both was performed at 13 of 15 institutions. For three patients, the decision was made not to proceed with angiography after positive preangiographic testing. The dosage of indocyanine green used for angiography varied from 25 to 75 mg, depending upon the institution. There were 13 cases of adverse reactions (0.34%), ten of which were mild reactions such as nausea, exanthema, urtication, itchiness, and urgency to defecate, and did not require treatment. Also recorded were one case of pain of the vein, which required treatment, and two cases of hypotension. The two hypotensive patients required treatment for shock. CONCLUSIONS: A comparison of frequency of adverse reactions to indocyanine green with the previously reported frequency of such reactions to fluorescein sodium indicated that indocyanine green is a safe as fluorescein for use in angiography.

Aged↗
PubMed1994

Storage and analysis of Goldmann's visual fields with a personal computer.

A method of storing and analyzing Goldmann's visual fields with a personal computer has been developed and applied to cases of retinal detachment. Original two-dimensional analogue data, obtained manually by ophthalmologists, were digitized and transferred to a personal computer. A one-megabyte floppy disk was able to store data of 170 charts. Stored data were easily displayed on the CRT of the computer using two- and three-dimensional graphics. Total and four quadrant areas surrounded by isopter curves were calculated for fellow eyes, diseased eyes and operated eyes. Furthermore, weighted areas with four types of weighting function which attach more importance to the center than the periphery of a visual field were calculated. Power type weighting function was found to give the most significant effect on emphasizing abnormality of eyes with retinal detachment.

Adult↗
PubMed1994

Radiation dosimetry with an electron spin resonance spectrometer.

Radiation dosimetry was undertaken using an electron spin resonance (ESR) spectrometer in students' laboratory work. Sugar was used as a dosimeter element and irradiated with both an X-ray generator (34 kVp, 8 mA) and a 60Co sealed source (3.7 MBq). The ESR system detects unpaired electrons created by the ionizing radiation. The lowest detection limit of the absorption dose was 20 Gy.

Carbohydrates↗
PubMed1992

Daily intakes of 232Th and 238U in Japanese males.

Diet samples were collected by a duplicate portion method from 31 locations in Japan and were analyzed by inductively coupled plasma mass spectrometry. Average daily intakes per adult male were estimated at 1.7 mBq for 232Th and 8.8 mBq for 238U.

Adult↗
PubMed1992

[Effects of aging on fluorescein iris and angle photography in normal subjects].

In the present study we took the fluorescein iris and angle photography of normal eyes and studied them according to different age groups. The range of age in 108 eyes of 92 subjects was from 20 to 93 years. They were free from any systemic diseases or ophthalmic diseases which would cause iris rubeosis. Fluorography was carried out using a Mizuno Trabeculens to determine the leakage points of fluorescence from the iris and the angle. In the angle there were gonio vessels which revealed no leakage of fluorescein. They were observed in 8 of 30 eyes (27%) for subjects in the fifth decade of life or less and in 24 of 78 eyes (31%) for subjects aged 50-90. No significant difference was seen between the two age groups. As to variations of gonio vessels, radial ciliary body vessel was found in 23 eyes, radial iris vessel or trabecular vessel in 10 eyes, and circular ciliary band vessel in 7 eyes. In the pupillary margin no leakage was seen in 30 eyes of 30 cases in the fifth decade of life or less, while leakage was found in 33 of 78 eyes, 42 of 62 cases over the fifth decade of life. In the angle leakage was seen in 4 of 30 eyes, 13 of 30 cases in the fifth decade of life or less, while leakage was observed in 43 of 78 eyes over the fifth decade of life. These results suggested that leakage of fluorescence from the pupillary margin, the angle or both increases with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Measurement of atmospheric radon daughter concentrations at the campus of Fukushima Medical College.

Radon daughter concentrations in outdoor and indoor air were measured at the campus of Fukushima Medical College. Radon daughters in the air were sampled with a flow rate of 20 L/min through a glass fiber filter or a membrane filter, and the decay of activity on the filter was analyzed with two types of technique, i.e., the gross-beta one-count method using a G.M. tube and the alpha spectroscopic method using a semiconductor detector. The present paper describes principles and techniques of the measurement in detail.

Air Pollutants↗
PubMed1983

Dual delivery system for argon laser photocoagulation. Improved techniques of the binocular indirect argon laser photocoagulator.

A dual delivery system provided alternate delivery of the laser beam to the slit lamp and binocular ophthalmoscope. Ophthalmologists may choose between the two systems in accordance with the nature and location of the fundus lesion. A pilot study comparing the rate of laser hit between the slit-lamp photocoagulator and the binocular indirect argon laser photocoagulator (BIALP) showed that accuracy was better with the slit lamp and BIALP when they were operated in the sitting position than with the BIALP operated in the standing position. A photo-electric safety switch was attached to the blocking filter of the BIALP to protect operator's and patient's eyes. The improved machine and techniques increased the efficiency and safety of argon laser photocoagulation. Postoperative use of the BIALP was of particular value. Laser photocoagulation in children's eyes became possible for the first time with the BIALP.

Argon↗
PubMed1981

Gyrate atrophy with hyperornithinaemia: different types of responsiveness to vitamin B6.

Three cases of Japanese patients with gyrate atrophy of the choroid and retina with hyperornithinaemia were studied clinically and biochemically. The types of disease differed in responsiveness to vitamin B6. In-vivo responsiveness to vitamin B6 was correlated with in-vitro data. It is suggested that the in-vitro examination of the influence of pyridoxal phosphate on ornithine ketoacid transaminase activity in cultured fibroblasts may be useful in ascertaining the efficacy of vitamin B6 treatment in gyrate atrophy. In addition the early development of the fundus lesions was observed in one case (case 1), and the ciliary body abnormality and chorioretinal atrophy were noted in another (case 3).

Adolescent↗
PubMed1980

Ornithine ketoacid aminotransferase in the bovine eye.

Ornithine ketoacid aminotransferase in bovine ocular tissues was studied biochemically. The retinal pigment epithelium, ciliary body, iris, and neuroretina showed high specific activity. The cornea and choroid revealed a lower activity. Aqueous humor, lens, vitreous body, and sclera showed no activity. The pH optima of the enzyme in the retinal pigment epithelium and ciliary body were near 8.0.

Animals↗