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Katsuyuki Imai

Publications and source records attributed to Katsuyuki Imai.

14 recordsLinked to original sources
PubMed2006

Distribution of retinylester-storing stellate cells in the arrowtooth halibut, Atheresthes evermanni.

Hepatic stellate cells play a major role in retinylester storage in mammals, but the retinoid-storing state in nonmammalian vertebrates remains to be elucidated. In this study, we examined retinoids and retinoid-storing cells in the arrowtooth halibut, Atheresthes evermanni. High-performance liquid chromatography analyses revealed the highest concentrations of stored retinoids (retinol and retinylester, 6199 nmol/g) in the pyloric cecum, a teleost-specific organ protruding from the intestine adjacent to the pylorus. Considerable amounts of retinoids were also stored in the intestine (3355 nmol/g) and liver (1891 nmol/g), and small amounts in the kidney (102 nmol/g). Very small amounts or no retinoids were detected in the heart, gill, skeletal muscle, and gonads (less than 2 nmol/g). Use of gold chloride staining and fluorescence microscopy to detect retinoid autofluorescence showed that, in the pyloric cecum and intestine, retinoid-storing cells were localized in the lamina propria mucosae. Under electron microscopy, cells containing well-developed lipid droplets, which are common morphological characteristics of the hepatic stellate cells of mammals, were observed in the lamina propria mucosae of the pyloric cecum. Thus, the distribution of stellate cells with retinoid-storing capacity differs between this halibut and mammals, suggesting that the retinoid-storing site has shifted during vertebrate evolution.

Animals↗
PubMed2005

Further application of a two-step heparin affinity chromatography method using divalent cations as eluents: purification and identification of membrane-bound heparin binding proteins from the mitochondrial fraction of HL-60 cells.

Membrane proteins were obtained from the mitochondrial fraction of HL-60 cells by solubilization with octyl glucoside and bound to heparin-gels. Bound proteins were successively eluted with solutions containing increasing concentrations of Mg(2+) in the first and increasing concentrations of Ca(2+) in the second chromatography. After SDS-PAGE and subsequent N-terminal amino acid analysis of proteins on each band, 13 proteins were identified. Fifteen out of the 37 proteins analysed were modified at their N-termini. These results show that this two-step affinity chromatography method using divalent cations as eluents can be applied to a variety of membranes for the isolation of specific proteins.

Amino Acid Sequence↗
PubMed2005

Degradation of extracellular matrix by extrahepatic stellate cells in the intestine of the lamprey, Lampetra japonica.

To investigate the mechanisms involved in the atrophy of the intestines in lampreys (Lampetra japonica) during the spawning migration stage, we examined by morphological methods their intestines with special reference to degradation of extracellular matrix (ECM) components. Stellate cells are known to be distributed not only in the liver (hepatic stellate cells) but also in other organs, such as the pancreas, intestine, lung, and kidney (extrahepatic stellate cells). Hepatic stellate cells are well known to be able to biosynthesize, secrete, and degrade ECM. Therefore, we investigated the cellular and molecular mechanisms involved in the atrophy of the intestines by focusing on these intestinal extrahepatic stellate cells. The cells were found to contain phagocytosed and degraded collagen fibrils, which are one of the ECM components. A positive reaction for trimetaphosphatase (TMPase, a cytochemical marker of lysosomes) was preferentially detected in round or elongated vesicles in the intestinal extrahepatic stellate cells and the deposits of the reaction products coexisted with the degraded collagen fibrils. However, the basement membrane of the intestine, which membrane is also an ECM component, was preserved throughout the spawning migration stage of the lamprey and accumulated as a mass of thick membrane, suggesting the existence of a special mechanism for selective digestion of ECM components. These results indicate that the intestinal extrahepatic stellate cells in Lampetra japonica during its spawning migration stage might play an important mechanistic role in the atrophy of lamprey intestines by phagocytizing collagen fibrils and digesting the phagocytized collagen fibrils in their lysosomes.

Adipocytes↗
PubMed2004

Cell-cell junctions between mammalian (human and rat) hepatic stellate cells.

To investigate intercellular junctions between mammalian hepatic stellate cells, we examined cultured human and rat hepatic stellate cells at the ultrastructural and molecular levels. Intercellular junctions between cultured human stellate cells, which developed irrespective of the type of culture substratum, were detected by transmission electron microscopy. On the basis of their characteristic ultrastructure, these junctions were identified in cultured human hepatic stellate cells as adherens junctions but not as tight junctions, desmosomes, or gap junctions. N-cadherin, alpha-catenin and beta-catenin, and p120ctn were detected by Western blotting in rat stellate cells as molecular components of the intercellular adhesive structures. Immunofluorescence for pan-cadherin, alpha-catenin, and beta-catenin were also detected in cultured human stellate cells. Moreover, pan-cadherin and beta-catenin were co-localized at the contact regions between the cultured human stellate cells. These data suggest that the junctional adhesion between the stellate cells can be formed both in vivo and in vitro. Thus, hepatic stellate cells may participate in the structural organization of the cells in liver lobules through the formation of intercellular adherens junctions. This is the first description of the presence of cell-cell junctions between hepatic stellate cells in mammals at the fine structural and molecular levels.

Animals↗
PubMed2004

Intercellular Adhesive Structures Between Stellate Cells - An Analysis in Cultured Human Hepatic Stellate Cells.

To investigate whether or not hepatic stellate cells can form intercellular junctions with each other, we cultured human stellate cells (LI90) on different kinds of substrata. Intercellular junctions were detected between these cultured stellate cells by transmission electron microscopy (TEM). The molecular components of the intercellular adhesive structures were identified by immunofluorescence microscopy. Immunofluorescence for cadherin and catenins was detected at the adhesion sites between the cultured stellate cells. Thus, the intercellular junctions were indicated to be adherens junctions at the molecular level. The junctions developed in the cultured stellate cells irrespective of the type of substratum. These data suggest that the junctional formation between the stellate cells occurs in vivo as well as in vitro.

Journal Article↗
PubMed2004

Intralobular Distribution of Vitamin A-Storing Lipid Droplets in Hepatic Stellate Cells with Special Reference to Polar Bear and Arctic Fox.

We examined the liver of adult polar bears, arctic foxes, and rats by gold chloride staining, fluorescence microscopy for the detection of autofluorescence of vitamin A, hematoxylin-eosin staining, staining with Masson's trichrome, Ishii and Ishii's silver impregnation, and transmission electron microscopical morphometry. The liver lobules of the arctic animals showed a zonal gradient in the storage of vitamin A. The density (i.e., cell number per area) of hepatic stellate cells was essentially the same among the zones. These results indicate that the hepatic stellate cells of the polar bears and arctic foxes possess heterogeneity of vitamin A-storing capacity in their liver lobules.

Journal Article↗
PubMed2004

3-D structure of extracellular matrix regulates gene expression in cultured hepatic stellate cells to induce process elongation.

HSCs showed myofibroblast-like shapes when cultured on polystyrene surface or on type I collagen-coated surface, whereas HSCs cultured on type I collagen gel were induced to elongate cellular processes, suggesting that HSCs recognize 3-D structure of extracellular type I collagen fibrils and change their morphology and function. In this study we examined the differentially regulated gene expression by extracellular matrix (ECM) components by PCR-differential display (PCR-DD) analysis followed by cloning and FASTA homology search, and identified the mRNA species as a transcription factor SP1, breast cancer resistant protein (BCRP), dystonin, and KAP3B. Regulation of dystonin and KAP3B expression was confirmed by RT-PCR analysis. Thus, cell surface-binding to extracellular interstitial collagen may trigger intracellular signaling and alteration in gene expression, and HSCs not only produce various ECM components but also change their morphology and gene expression in response to ECM components adhering to the cells.

Journal Article↗
PubMed2004

Vitamin A distribution and content in tissues of the lamprey, Lampetra japonica.

Vitamin A (retinol and retinyl ester) distribution and content in tissues of a lamprey (Lampetra japonica) were analyzed by morphological methods, namely, gold chloride staining, fluorescence microscopy to detect specific vitamin A autofluorescence, and electron microscopy, as well as high-performance liquid chromatography (HPLC). Hepatic stellate cells showed an abundance of vitamin A stored in lipid droplets in their cytoplasm. Similar cells storing vitamin A were present in the intestine, kidney, gill, and heart in both female and male lampreys. Morphological data obtained by gold chloride staining method, fluorescence microscopy, transmission electron microscopy, and HPLC quantification of retinol were consistent. The highest level of total retinol measured by HPLC was found in the intestine. The second and third highest concentrations of vitamin A were found in the liver and the kidney, respectively. These vitamin A-storing cells were not epithelial cells, but mesoderm-derived cells. We propose as a hypothesis that these cells belong to the stellate cell system (family) that stores vitamin A and regulates homeostasis of the vitamin in the whole body in the lamprey. Fibroblastic cells in the skin and somatic muscle stored little vitamin A. These results indicate that there is difference in the vitamin A-storing capacity between the splanchnic and intermediate mesoderm-derived cells (stellate cells) and somatic and dorsal mesoderm-derived cells (fibroblasts) in the lamprey. Stellate cells derived from the splanchnic and intermediate mesoderm have high capacity and fibroblasts derived from the somatic and dorsal mesoderm have low capacity for the storage of vitamin A in the lamprey.

Animals↗
PubMed2004

Effects of ascorbic acid and ascorbic acid 2-phosphate, a long-acting vitamin C derivative, on the proliferation and differentiation of human osteoblast-like cells.

In order to investigate the effect of ascorbic acid (AsA) and ascorbic acid 2-phosphate (Asc 2-P), a long-acting vitamin C derivative, on the growth and differentiation of human osteoblast-like cells, we supplemented the culture medium of MG-63 cells with various concentrations (0.25 to 1 mM) of these factors. Asc 2-P significantly stimulated nascent cell growth at all concentrations in the presence of fetal bovine serum (FBS). On the other hand, AsA showed a growth repressive effect depending on its concentration, and that of FBS. Asc 2-P also increased expression of osteoblast differentiation markers, such as collagen synthesis and alkaline phosphatase (ALP) activity. These stimulative activities of Asc 2-P were attenuated by inhibitors of collagen synthesis, indicating that these effects were dependent on collagen synthesis. Electron micrographs of the cells showed the formation of a three-dimensional tissue-like structure endowed with a mature extracellular matrix in the presence of Asc 2-P.

Alkaline Phosphatase↗
PubMed2003

Epimorphin is involved in differentiation of rat hepatic stem-like cells through cell-cell contact.

Epimorphin, a mesenchymal cell surface-associated molecule, is detected on hepatic stellate cells (HSCs) in the liver. Here, we show the involvement of epimorphin in differentiation of rat hepatic stem-like cells (HSLCs) through contact with HSCs. HSLCs, isolated from adult rats, cultured in stellate cell-conditioned medium had no phenotypic and morphological changes, whereas HSLCs co-cultured with HSCs expressed albumin, transferrin, and tyrosine aminotransferase. An anti-epimorphin antibody inhibited hepatocytic differentiation of HSLCs in co-culture. Furthermore, epimorphin induced mRNA expression of albumin, transferrin, tyrosine aminotransferase, and gamma-glutamyl transpeptidase with decrease of c-kit and musashi-1. Morphologically, HSLCs piled up when co-cultured with HSCs, which was dramatically inhibited by an anti-epimorphin antibody. HSLCs contact with epimorphin started piling up, changed their shape from flat to cuboidal, and subsequently developed bile-canaliculi-like structures. In conclusion, epimorphin is a factor that induces differentiation of hepatic stem-like cells through epithelial-mesenchymal cell contact.

Animals↗
PubMed2003

Extracellular matrix-regulated p53 expression and nuclear localization in cultured Detroit 562 cells derived from pharyngeal carcinoma.

Tumor suppressor p53 functions as a transcriptional factor that regulates the cell cycle and apoptosis. A mutated p53 gene can result in decreased sequence-specific DNA binding and transcriptional activity of the p53 protein. In this study, we examined the regulatory role of the extracellular matrix components in p53 expression and nuclear localization in a Detroit 562 cell line derived from a pharyngeal carcinoma. When cultured on a polystyrene surface, type I collagen gel, or Matrigel containing basement membrane components, Detroit 562 cells showed a distinct response to extracellular matrix components morphologically. As shown by Western blotting, Detroit 562 cells cultured on Matrigel displayed an increased expression of p53 protein as well as an elevated nuclear p53 level, as compared with the cells cultured on the polystyrene surface or type I collagen gel. When cultured on Matrigel, nuclear p53-positive cells were exclusively localized to the outer surface layer of the cell clusters, whereas most of the inner cells showed no p53 expression. In Detroit 562 cell clusters on Matrigel, proliferative activities, as evaluated by proliferationcell nuclear antigen staining and bromo-deoxyuridine incorporation assay, were evenly distributed; virtually no apoptotic cells, as evaluated by the fluorescence TUNEL assay, were detected in the cell clusters, suggesting that the peculiar localization of nuclear p53-positive cells was not directly related to cell proliferation or apoptosis. These results indicate that p53 expression and its localization in Detroit cells were modulated by extracellular matrix signals, particularly by the basement membrane components in Matrigel.

Biocompatible Materials↗
PubMed2002

Membrane-bound heparin binding proteins from HL-60 cells purified in a two-step affinity chromatography differentially eluted with divalent cations.

Solubilized membrane proteins from HL-60 cells were separated by two-step affinity chromatography. Proteins eluted with MgCl2 in the first heparin-gel were applied to the second heparin-gel and eluted with CaCl2. The eluted proteins were analysed and purified by electrophoresis. N-terminal amino acid sequences of eight proteins on the characteristic bands were determined. Homology search for the sequences indicated that three microsomal proteins, two nuclear proteins and a glycolytic enzyme were eluted with divalent cations, whereas a nuclear ribonucleoprotein and a membrane-cytoskelton linker protein were not dissociated with divalent cations, but with 2 M NaCl. Heparin affinity chromatography combined with differential elution with divalent cations can be a useful method for separation of membrane proteins.

Amino Acid Sequence↗