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Biomedical subjects

T Kuwabara

Publications and source records attributed to T Kuwabara.

At least 361 records · Page 20Linked to original sources
PubMed1975

Lysosomes and melanin granules of the retinal pigment epithelium in a mouse model of the Chediak-Higashi syndrome.

The origin of giant granules in the retinal pigment epithelium of the beige mouse was investigated with electron microscopy and ultrastructural histochemistry. These granules were found to contain melanin and acid phosphatase. Apparently they arise from fusions of primary lysosomes with melanin granules which are already enlarged from multiple fusions among melanosomes. Therefore, the giant granules are not primary lysosomes, nor are they simply enlarged melanin granules as suspected from light microscopic studies. A deficiency of primary lysosomes in the pigment epithelium results, suggesting a defect in intracellular digestion similar to that found in the leukocytes of Chediak-Higashi patients and several animal models. Affected humans probably have defective digestion in their retinal pigment epithelium also; which could impair the renewal process for rod outer segments. Thus, Chediak-Higashi patients may show an increased susceptibility to light damage due not only to hypopigmentation, but to defective intracellular digestion, as well.

Acid Phosphatase↗
PubMed1975

Development of the optic nerve of the rat.

Development of the rat optic nerve is studied electron microscopically. By marked bionecrosis, many neuroepithelial cells of the fissure portion of the optic stalk are eliminated immediately following optic cup formation. A small number of the surviving neuroepithelial cells forms the tubular optic stalk. The wall cells of the stalk elongate and proliferate to become a cluster of cells at the retrobulbar region. These cells differentiate into glia cells, astrocytes first and oligodendroglia cells second. Axons invade into the intercellular spaces of the elongating stalk cells which are differentiating into astrocytes. The invading axons are found first in the space at the basal portion of the stalk cells, or the peripheral zone of the optic nerve. Myelination occurs in the later stage of development. The fine processes of the oligodendroglia cells which surround groups of axons, eliminate the cytoplasm, and become the first myelin membrane.

Animals↗
PubMed1975

Cytologic changes of the retina and pigment epithelium during hibernation.

The pigment epithelium and the retina of hibernating frogs, bats, and ground squirrels are studied electron microscopically and the findings are compared with those of the same animals obtained in normal condition. The smooth endoplasmic reticulum of the pigment epithelial cell becomes sparse and transforms into large tubular structures during the hibernation. No appreciable changes are noted in the rod outer segments of hibernating bats and frogs. However, the cone outer segments of the ground squirrel show striking disappearance during experimental hibernation. Regeneration of the cone outer segments of the squirrel retina is found to be fast when the animals are placed in a normal environment.

Animals↗
PubMed1975

Early cytologic changes of Fraser cataract. An electron microscopic study.

The cataractous lens of the Fraser strain mouse was studied electron microscopically in its early developmental stage. Cytologic abnormalities were found in the cells of the invaginating ectodermal cell of the early optic cup. Morphogenetically degenerating cells were more numerous in this stage. In general, cells of the posterior layer of the developing lens elongated normally. However, they contained great numbers of dilated rough endoplasmic reticulum, vacuoles, and mitochondria, but less amounts of crystalline substance and polysomes. During the further differentiating stage (thirteenth and fourteenth fetal day), apical portions of these cells began to swell and the lens became opaque. The swollen lens cells degenerated after this stage.

Animals↗
PubMed1975

Microperoxisomes in retinal pigment epithelium.

Microperoxisomes were found to be abundant in the retinal pigment epithelium of the human, rhesus monkey, mice, rats, domestic fowl, and frog by ultrastructural histochemistry. They were rare in other cells of the retina and choroid. These organelles had a granular matrix, ranged in diameter from 0.15 mum to 0.30 mum, and were bound by a single tripartite membrane which often maintained slender connections with the smooth endoplasmic reticulum and other microperoxisomes. They exhibited a positive reaction (electron opaque product) following incubation in diaminobenzidine and H2O2 for the demonstration of the peroxidatic activity of catalase (Novikoff et al., J. Histochem. Cytochem. 20: 1006, 1972). The reaction was inhibited by: (1) aminotriazole; (2) dichlorophenol-indophenol; (3) preheating at 95 degrees C.; or (4) elimination of H2O2. Microperoxisomes, like the well-known peroxisomes (microbodies) of liver cells have been inplicated in various aspects of lipid metabolism and the detoxification of H2O2. We demonstrated for the first time that microperoxisomes respond to drug-induced changes in lipid metabolism, as previously shown for peroxisomes. Nafenopin is a recently utilized drug which greatly decreases serum lipids, increases hepatic catalase activity, and induces an increased size and number of hepatic peroxisomes. Black, beige, albino, and obese mutant mice of the C57BL/6J strain treated with nafenopin for several weeks showed a two- to threefold increase in the number of microperoxisomes in the retinal pigment epithelium. Microperoxisomes of the retinal pigment epithelium may be involved in the transport, storage, and rapid turnover of lipids associated with the maintenance of photoreceptor outer segment disc membranes.

Adult↗
PubMed1974

Ocular hazard from picosecond pulses of Nd: YAG laser radiation.

Seven rhesus monkeys (14 eyes) were exposed to 1064-nanometer radiation in single pulses of 25 to 35 picoseconds fromn a mode-locked Nd: YA G laser. Threshold injury resulted from single pulses with a mnean energy of 13 +/- 3 mnicrojoules. Electron microscopy of the retina revealed that damnage was highly localized in the photoreceptor and pigmented epithelial cells at the oluter retina. Membrane disruption, distorted outer segmtzents, and abnormnal melanin granules resembling fetal premelanosomnies were observed.

Animals↗
PubMed1974

Selective destruction of the pigmented epithelium in the ciliary body of the eye.

Perfusion of the internal carotid artery with hypertonic solution selectively destroys most of the pigmented epithelium of the ciliary body of the monkey eye, converts fenestrated endothelium of capillaries to continuous endothelium, and transiently breaks down the blood-aqueous barrier. The nonpigmented epithelium regenerates and the intraocular pressure returns to normal even though the pigmented epithelium is permanently destroyed.

Amides↗