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Biomedical subjects

K Ishimura

Publications and source records attributed to K Ishimura.

At least 127 records · Page 7Linked to original sources
PubMed1981

Freeze-fracture images on filipin-sterol complexes in the thyroid follicle epithelial cell of mice with special regard to absence of cholesterol at the site of micropinocytosis.

In order to clarify the distribution of cholesterol in the plasma- and cyto-membranes of the thyroid follicle cell, freeze-fracture images of the filipin-treated tissues of normal and TSH-treated mice were observed. The filipin-sterol complexes, 25 to 30 nm protuberances or pits are distributed densely and almost homogeneously on the fractured plasma membrane, though the small depressions showing aggregates of intramembrane particles lack the complexes. Each depression corresponds to the coated pit, which might be an initial site for micropinocytosis of the luminal colloid. The limiting membranes of all the large colloid droplets reabsorbed are generally very rich in the complexes, but some small regions on the limiting membrane of the droplet are less in their density. The membranes of the rough endoplasmic reticulum, of the nucleus and of the Golgi apparatus are almost free from the complexes, though small clusters consisting of 2-5 complexes are rarely scattered. In thin sections, the membranes which are rich in the filipin-sterol complexes become obscure in their fine structure after treatment with filipin for 12-24 h.

Animals↗
PubMed1980

Freeze-fracture images of exocytosis and endocytosis in anterior pituitary cells of rabbits and mice.

Freeze-fracture images of exocytosis and endocytosis were studied in various kinds of secretory cells of the anterior pituitary of mice and rabbits. Exocytotic figures are frequently observed in thin section of the anterior pituitary cells. In freeze-fracture images, small elevated membrane areas without membrane particles are often seen on the PF of the plasma membrane of the secretory cells. There is a secretory granule in the cytoplasm just beneath the particle-free membrane area, and limiting membrane of the granule is also devoid of the membrane particles at the part facing the plasma membrane. The fusion of membranes for exocytosis may occur at this particle-free area. The limiting membrane of the granule which is continuous with the plasma membrane is almost always coated after release of the granule core. This invagination of coated membrane may be an initiation site for the membrane retrieval after exocytosis. In freeze-fracture images, this depressed region with an accumulation of the membrane particles is observed on the PF of the plasma membrane. This particle-rich depressed region is thought to correspond to the coated area of the plasma membrane observed in thin section. It is thought that the membrane retrieval by pinocytosis initiates at the particle-rich depressed region of the plasma membrane.

Animals↗
PubMed1979

Development of cell-to-cell relationships in the thyroid gland of the chick embryo.

Thyroid glands of 7 to 21 day-old chick embryos were examined by electron microscopy using freeze-fracture and thin-section preparations. The primitive follicle lumen first appears between two adjacent epithelial cells in 8 day-old embryos, and is formed in the region of a focal tight junction (macula occludens). The focal tight junction develops into the zonula occludens when the primitive follicle lumen first forms. The zonula occludens is, at first, composed of 4.6 +/- 2.45 strands, but with increasing embryonic age the number of strands increases to 5.9 +/- 1.41 in 13 day-old, and 8.0 +/- 1.75 in 19 day-old embryos. Thyroglobulin stored within the embryonic gland lumina is isolated from the mesenchymal tissue even at the first appearance of these follicle cavities. Well developed gap junctions already occur in the thyroid gland of the 7 day-old embryo, so that an intimate relationship and communication between these cells already exists at the time of their functional differentiation.

Animals↗
PubMed1978

Freeze-etching images of capillary endothelial pores in the liver, thyroid and adrenal of the mouse.

The capillary endothelial pores of perfusion-fixed and immersion-fixed liver, thyroid and adrenal of mice were observed using freeze-etching preparations. In liver sinusoids, endothelial pores are heterogeneous in size and range from 50-100 nm. When the pores are classified into three types according to their size, small pores up to 100 nm in diameter represent 69.8%, intermediate pores measuring 100-500 nm 27.6% and large pores exceeding 500nm 2.6% of all pores in number. The endothelial pores of the thyroid blood capillaries are fairly homogeneous in size (70-90 nm), corresponding to the small type pores in the liver. In both adrenal cortex and medulla, the capillary endothelial pores measure 40-50 nm in diameter, showing small and intermediate types. In the adrenal cortex the former occupy 80.6% of all pores and the latter 19.4%. No larger type pores are recognized in the adrenal gland. These findings are not affected by different fixation methods, either perfusion or immersion.

Adrenal Glands↗
PubMed1978

Freeze-etching observation on the development of intercellular junctions of the duodenal epithelial cells in the chick embryo.

Development of intercellular junctions in duodenal epithelium in the chick embryo was studied by electron microscopy using the thin-section and freeze-fracture techniques. Incomplete tight junctions are already seen in 6 and 7 day old embryos at the apical portion of the lateral plasma membrance, and consist of 1-7 strands, their mean depth measuring 0.2 micron. This corresponds to a "very leaky type" (CLAUDE and GOODENOUGH) of tight junction. Ridges on the PF are discontinuous and rarely cross or link. The tight junctions extend basally at the place where more than three epithelial cells are in contact. On the lateral plasma membrane, particle-aggregates suggesting primitive gap junctions are already recognized. Some are dense aggregations of 3-5 membrane-particles with a halo free of the particles and others are rather loose aggregations of 5-10 particles with an indistinct halo. In 9 day old embryos, the ridges of the tight junction become more discontinuous, although the frequency of the linkage of the neighboring ridges increases. The compartments bounded by the tight junctional strands are angular. These strands become continuous and the facets surrounded by them are roundish in 12 day old embryos. The presumptive immature gap junctions show a characteristic polygonal pattern in 9 day old embryos and gradually increase in size. Mature tight junctions and typical gap junctions of 0.3-0.4 micron diameter are seen after 18 days of incubation. The strands number 6-8 and the depth of the tight junction measures about 0.4 micron in 18 day old embryos. In the chick embryo duodenal epithelium, the tight and gap junctions develop independently from each other without any direct interaction between them.

Animals↗
PubMed1978

Freeze-fracture images of the zonula occludens in the mouse oviduct epithelium.

Freeze-fracture images of zonulae occludentes of the oviduct epithelium of adult mice were observed in the electron microscope. The structure of zonulae occludentes varies depending on the types of oviduct epithelial cells. Those between two secretory cells consist of 5--14 (9.2 +/- 2.0) strands interposed between the luminal and the lateral plasma membrane. The strands run irregularly making well developed anastomoses with one another. The tight junction between two ciliated cells consists of 4--14 (8.5 +/- 2.3) strands. Among them the upper 3--9 strands are unique in shape. The strands run regularly, compactly and parallel to the luminal surface and to each other with a few anastomoses. The distance between the adjacent strands is about 40 nm. Under this characteristic part several strands are very loosely distributed and run irregularly. The pattern of the strands in the zonula occludens between a secretory cell and a ciliated one resembles that between adjacent ciliated cells. The junction consists of 4--13 (8.3 +/- 2.0) strands. The characteristically dense and parallel arrangement of the strands demonstrated in this study is presumed to be related to the ciliary movement. All the zonulae occludentes in the mouse oviduct epithelium are "very tight" in type. No large gap junctions are seen in the mouse oviduct epithelium.

Animals↗
PubMed1977

[In vivo cytogenetic studies of 10-chloro-11b-(2-fluorophenyl)-7-(2-hydroxyethyl)-2, 3, 5, 11b-tetrahydrooxazolo-(3, 2-d) (1, 4) benzodiazepine-6(7H)-one (MS-4101) on rat bone marrow cells (author's transl)].

Chromosome aberrations induced by MS-4101, diazepam, and nitrazepam were studied in Sprague-Dawley rats. Female rats were administered orally via stomach tube daily doses of 200, 500 and 2000 mg/kg of MS-4101, 200 and 500mg/kg of diazepam, 40 and 200mg/kg of nitrazepam and 20 and 50 mg/kg of cylcophosphamide as the positive control for one, 5 and 10 days. In this study, we used bone marrow cells derived from rat femur at 6 or 24 hours after the last drug administration. No significant chromosome aberrations were seen in the treated groups with MS-4101, diazepam, and nitrazepam when compared with the nontreated control. The increase of structural aberration on gap and break was observed in the group of cyclophosphamide as the positive control. These findings indicate that MS-4101, and diazepam and nitrazepam as similar comparative drugs, do not have the potential of induction of chromosome aberrations in rat bone marrow cells.

Animals↗
PubMed1976

Freeze-etching studies on ultrastructural changes of endothelial cells in the thyroid of normal, TSH-treated and thyradin-treated mice.

Freeze-etching images of the capillary endothelium in the thyroid of normal, TSH-treated and Thyradin (powdered thyroid)-treated mice were examined. Numerous pores represent vesicular stomata or fenestrations. The number of the pores and their population density are increased in TSH-treated mice, and decreased in Thyradin-treated animals. In addition, the width of the parajunctional zone and of the flat ray free from endothelial pores is smaller in TSH-treated mice and larger in Thyradin-treated animals. These facts indicate that the number of endothelial pores changes according to the functional activity of the gland.

Animals↗
PubMed1976

Freeze-etching observations on the characteristic arrangement of intramembranous particles in the apical plasma membrane of the thyroid follicular cell in TSH-treated mice.

Thyroid glands of normal, TSH-treated and Thyradin (powdered thyroid)-treated mice were examined by means of the freeze-etching method. Intramembranous particles on the PF (= A face) face of the apical plasma membrane often form aggregates especially in TSH-treated mice. Each aggregate, about 200 nm in diameter, and consisting of 15-25 large particles, corresponds to a depression of the apical cytoplasm, and the particles sometimes form rosettes. Particle-aggregates are very rare in the apical plasma membrane of the thyroid follicular cell of the Thyradin-treated animal. In the cytoplasm just beneath the particle-aggregate no secretory granules, reabsorbed colloid droplets or other special structures are found. From these facts, the aggregate is considered closely related to an initial site for the micropinocytosis of the luminal colloid.

Animals↗
PubMedDate not supplied

Efficacy of thyrotropin-releasing hormone in the treatment of cerebellar ataxia.

We report a 9-year-old girl with cerebellar ataxia in whom the administration of thyrotropin-releasing hormone was effective in the treatment of a prolonged neurologic deficit. Ataxia persisted 18 months after its acute onset of unknown origin. Concentrations of homovanillic acid and 5-hydroxy-indoleacetic acid in the cerebrospinal fluid were measured repeatedly. Changes in the 5-hydroxy-indoleacetic/homovanillic acid ratio were observed, suggesting that thyrotropin-releasing hormone improved symptoms by influencing serotonin metabolism in the central nervous system.

Cerebellar Ataxia↗