Search PubMed⌕ Search

Biomedical subjects

G Eguchi

Publications and source records attributed to G Eguchi.

At least 91 records · Page 5Linked to original sources
PubMed1986

Transformation of a polygonal cellular pattern during sexual maturation of the avian oviduct epithelium: computer simulation.

A peculiar cellular pattern resembling a checkerboard has been observed on the luminal surface of the oviduct epithelium of an adult Japanese quail. The epithelium is a monolayer cell sheet and consists of two types of columnar cells, ciliated cells (C-cells) and gland cells (G-cells) assembled in alternating blocks. The pattern develops, during sexual maturation, from a kagome-like pattern (in which large C-cells are surrounded by small G-cells) characteristic of the immature oviduct. In the present paper, computer simulations of the pattern transformation from kagome to checkerboard were performed assuming a few properties of individual cells. The adult checkerboard-like pattern is not strictly rectangular, but is deformed toward a honeycomb pattern. In theoretical considerations the assumption that adhesion is stronger between unlike cells than between like cells formed an ideal checkerboard pattern, because all cell boundaries in it are edges along which unlike cells meet. On the other hand, a honeycomb pattern formed after assuming that the boundary length of the cellular pattern is minimized (caused by contraction of bundles of microfilaments running along lateral boundaries of the columnar epithelial cell while keeping contact between neighbouring cells). The actual checkerboard-like pattern was considered to be in a balanced state between the effects of (1) the strong adhesion between unlike cells, and (2) the boundary contraction. Using a computational analysis, this consideration enabled us to obtain a quantitative parameter value for the difference between cell adhesions of unlike cells and of like cells. C-cells divided once during the kagome-checkerboard transformation, while G-cells did not divide. We performed computer simulations starting with the kagome pattern in which all C-cells divided once. The computer program of the boundary shortening procedure we used involved the quantitative parameter value for differential cell adhesion obtained as described above. A checkerboard pattern was successfully generated in the simulation. It is concluded that the strong adhesion between unlike cells and the boundary shortening have important roles in formation and maintenance of the kagome and checkerboard patterns of the avian oviduct epithelium.

Animals↗
PubMed1985

The regeneration of newt limbs deformed in nature.

The regeneration of abnormal limbs from a wild newt population was examined. The abnormalities were: mirror symmetrical reduplications of digit parts, deformed wrists, or limbs with supernumerary digits. Normal regeneration resulted after amputation of the abnormal parts, regardless of the original deformity. The results suggest that the abnormalities are probably the result of local trauma to the limbs.

Animals↗
PubMed1985

Increase in actin contents and elongation of apical projections in retinal pigmented epithelial cells during development of the chicken eye.

The structural and biochemical changes of cytoskeletal components of retinal pigmented epithelial cells were studied during the development of chicken eyes. When the cytoskeletal components of the pigmented epithelial cells from various stages of development were examined by SDS PAGE, actin contents in the cells markedly increased between the 15-d-old and hatching stages. Immunofluorescence microscopy showed that chicken pigmented epithelial cells have two types of actin bundles. One is the circumferential bundle associated with the zonula adherens region as previously reported (Owaribe, K., and H. Masuda, 1982, J. Cell Biol., 95:310-315). The other is the paracrystalline bundle forming the core of the apical projections. The increase in actin contents after the 15-d-old stage is accompanied by the formation and elongation of core filaments of apical projections in the cells. During this period the apical projections extend into extracellular space among outer and inner segments of photoreceptor cells. Accompanying this change is an elongation of the paracrystalline bundles of actin filaments in the core of the projection. By electron microscopy, the bundles decorated with muscle heavy meromyosin showed unidirectional polarity, and had transverse striations with approximately 12-nm intervals, as determined by optical diffraction of electron micrographs. Since the shape of these bundles was not altered in the presence or absence of Ca2+, they seemed not to have villin-like proteins. Unlike the circumferential bundles, the paracrystalline bundles did not contract when exposed to Mg-ATP. These observations indicate that the paracrystalline bundles are structurally and functionally different from the circumferential actin bundles.

Actins↗
PubMed1984

Phenylthiourea enhances Cu cytotoxicity in cell cultures: its mode of action.

PTU markedly enhanced the cytotoxic effects of CuCl2 on chick embryonic PECs cultured in vitro. We investigated this newly discovered effect of PTU and its analogues in relation to the toxic effects of Cu ion. Most PECs maintained in medium containing 0.5 mM PTU were lysed within 4 h by the addition of 0.1 mM CuCl2, which addition killed no PECs in the absence of PTU. The effect of PTU was not specific to PECs. All the cell lines tested, KB, N-18, N-115 and B-16, reacted against exogenous Cu in the presence of PTU as did the PECs. Analogues of PTU had effects on PECs similar to those on PTU in the presence of Cu ion. ANTU had a greater effect than PTU. MTU and TU had less effect than PTU. PTU did not affect the cytolysis induced by the addition of the divalent cations Mn, Co and Zn. About 6-fold the 64Cu-uptake by PECs was scored in the presence of PTU. The relation between this cytotoxic-enhancing effect and other biological activities of PTU are discussed.

Animals↗
PubMed1984

Cell behaviour in a polygonal cell sheet.

Cell monolayers on culture dishes were divided into two groups: tensile monolayers and non-tensile ones. In the development of an epithelium, a non-tensile cell monolayer turns into a tightly bound tensile one. Detection of these states was carried out by using the boundary shortening procedure, a computer-based geometrical method to show how much the polygonal cell boundary contracts. Non-tensile monolayers were divided further into two groups according to their motility: a fluctuating monolayer in which cells move laterally, and a stable monolayer in which cells are immobilized. Quantitative determination of cell motility was performed by analysing time-lapse cellular patterns. These computer-based geometrical analyses enabled us to divide monolayers into three groups: tensile stable monolayers, non-tensile stable monolayers and fluctuating monolayers, and this study therefore gives an insight into the way in which changing conformations of cells may be assayed.

Animals↗
PubMed1982

Degeneration of retinal neuroblasts by chinoform-ferric chelate.

The possible mechanism of neuropathic effect of chinoform was investigated using cultured retinal neuroblasts from chick embryos. Retinal neuroblasts completely degenerated by chinoform-ferric chelate within a day. This change, however,, was not observed with free chinoform or ferric ion alpha-Tocopherol had a potent protective effect on the toxicity of the chelate. From these results, it was concluded that the lipid peroxidation due to ferric ion chelated with chinoform incorporated into the membrane of nerve tissues is the most important step in induction of the neuropathy.

Animals↗
PubMed1982

Microenvironments controlling the transdifferentiation of vertebrate pigmented epithelial cells in in vitro culture.

The transdifferentiation of pigmented epithelial cells in vitro is briefly introduced. Several environmental conditions regulating the process have been demonstrated experimentally. On the basis of these data we have suggested regulatory factors in relation to the mechanisms for the initiation of the transdifferentiation of pigmented epithelial cells, focussing particularly on cell surface functions. Finally, we have presented data which contributes to the establishment of a useful and powerful cell culture system which makes it possible for us to analyse the molecular basis of transdifferentiation.

Animals↗
PubMed1982

Enzymic mechanism of starch breakdown in germinating rice seeds : 11. Ultrastructural changes in scutellar epithelium.

The ultrastructural changes occurring in the scutellar epithelium cells of rice seeds have been studied during germination and early seedling growth. During this time, several prominent structural changes occur, including (a) formation, development, and proliferation of organelles such as mitochondria, rough endoplasmic reticulum, free ribosomes, and Golgi apparatus; (b) folded structural modification of plasmamembranes in later stages; and (c) conspicuous decrease in lipid-storing spherosomes. Glyoxysome-like electron dense particles are detectable but their formation is much less prominent. It is conceivable that all these structural changes are related to the enhancement of the metabolic activities of the epithelial cells including the synthesis of hydrolytic enzymes such as alpha-amylase and their secretion into the endosperm tissues. Some enzyme activities characteristic of mitochondria and glyoxysomes have been determined using the crude scutellar extracts, and the results dealing with the low activities of the glyoxylate cycle enzymes and palmitoyl-coenzyme A oxidase appear to indicate that fatty acid breakdown is possibly via mitochondrial beta-oxidation, although we reserve a definitive conclusion on the glyoxysomes being nonfunctional in fatty acid oxidation in rice seedlings.

Journal Article↗
PubMed1982

Transplantation of the reversed dermis from skin leading to repair of the buccal mucosal epithelium.

Skin grafting or mucosal grafting has been widely applied as the established method to compensate mucosal defects. However, in the grafted skin the epidermis never transformed into the mucosal epithelium; the original nature of the transplant was maintained as skin. The available donor of mucosa is also strictly limited. Therefore, an improvement in method has been much needed in the field of oral surgery. We tried to transplant the dermis freed completely from the epidermis instead of the full-thickness skin, and succeeded in compensation of the mucosal defect. The defects of the buccal mucosa in 30 dogs were repaired, one side with reversed dermis graft (RDG) in which the dermis was turned inside out and sutured onto the bed. On the other side, the ordinary free full-thickness skin graft (FTSG) was carried out as a control. Comparative clinical and histological observations were conducted to analyze the healing processes. In RDG the graft was covered by the surrounding mucosal epithelium to form the mucosal tissue, while the implanted tissue inhibited the wound constricture. Histological examination revealed that the epithelial elements underwent degeneration, presumably through being embedded by the grafting of the dermis inside out. The epithelium covering the dermis graft seems to be nothing but normal oral mucosal epithelium.

Animals↗
PubMed1982

Regeneration of the lens as a phenomenon of cellular transdifferentiation: regulability of the differentiated state of the vertebrate pigment epithelial cell.

The transdifferentiation of pigment epithelial cells in vitro was reviewed on the basis of results in the classic studies of lens regeneration in the newt. It is now known that pigment epithelial cells of avian embryos and human foetuses as well as of the newt can readily transdifferentiate into lens cells, when dissociated and cultured in vitro. The evidence now permits us to postulate that the potential of the pigment epithelial cell population for transdifferentiation is strongly conserved in vertebrates in general. Several environmental conditions controlling the processes have been suggested, and we can now provide an in vitro experimental system which is particularly useful for analysis of the molecular basis of transdifferentiation of the pigment epithelial cell, and its role as the cellular basis of lens regeneration.

Animals↗
PubMed1981

Studies on aspartase. VII. Subunit arrangement of Escherichia coli aspartase.

Aspartase (L-aspartate ammonia-lyase, EC 4.3.1.1) of Escherichia coli is composed of four subunits of seemingly identical molecular weight (Suzuki, S., Yamaguchi, J. And Tokushige, M.(1973) Biochim. Biophys. Acta 321, 369-381). The subunit arrangement of the enzyme was studied by two distinct methods, cross-linking of subunits with a bifunctional reagent, dimethyl suberimidate, and statistical classification of negatively stained electron microscopic images. In the former method, the densitometric patterns of the cross-linked aspartase were analyzed quantitatively after separating each component by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and the results were compared with the theoretical distribution. In the latter method, a number of electron microscopic images were classified into several groups according to their characteristic appearance. The results obtained by these two methods are compatible with the possibility that the enzyme has a tetrameric structure consisting of two pairs of dimers, in which the two pairs of rod-shape subunits meet perpendicularly, being typical of D2 symmetry.

Ammonia-Lyases↗
PubMed1981

Demonstration of contractility of circumferential actin bundles and its morphogenetic significance in pigmented epithelium in vitro and in vivo.

Each pigmented epithelial cell bears circumferential actin bundles at its apical level when the pigmented epithelium is established in eyes in situ or in culture in vitro. Well-differentiated pigmented epithelia in culture were treated with a 50% glycerol solution containing 0.1 M KCl, 5 mM EDTA, and 10 mM sodium phosphate buffer, pH 7.2, for 24 h or more at 4 degrees C. When the glycerinated epithelium was transferred to the ATP solution, each cell constituting the epithelium began to contract. The epithelium was cleaved into many cell groups as a result of contraction of each cell. The periphery of each cell group was lifted to form a cup or vesicle and eventually detached from the substratum. However, those cells that had not adhered tightly and not formed a monolayer epithelium with typical polygonal cellular pattern contracted independently as observed in the glycerinated fibroblasts. Contraction of the glycerinated pigmented epithelial cells was inhibited by N-ethylmaleimide but not by cytochalasin B. ITP and UTP also effected the contraction of the glycerinated cells, but GTP and ADP did not. Ca2+ was not required. This contractile model of pigmented epithelium provides a useful experimental system for analyzing the function of actin in cellular morphogenesis.

Actins↗