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M Imada

Publications and source records attributed to M Imada.

At least 55 records · Page 3Linked to original sources
PubMed1988

Fibronectin phosphorylation by ecto-protein kinase.

The presence of membrane-associated, extracellular protein kinase (ecto-protein kinase) and its substrate proteins was examined with serum-free cultures of Swiss 3T3 fibroblast. When cells were incubated with [gamma-32]ATP for 10 min at 37 degrees C, four proteins with apparent molecular weights between 150 and 220 kDa were prominently phosphorylated. These proteins were also radiolabeled by lactoperoxidase catalyzed iodination and were sensitive to mild tryptic digestion, suggesting that they localized on the cell surface or in the extracellular matrix. Phosphorylation of extracellular proteins with [gamma-32P]ATP in intact cell culture is consistent with the existence of ecto-protein kinase. Anti-fibronectin antibody immunoprecipitated one of the phosphoproteins which comigrated with a monomer and a dimer form of fibronectin under reducing and nonreducing conditions of electrophoresis, respectively. The protein had affinity for gelatin as demonstrated by retention with gelatin-conjugated agarose. This protein substrate of ecto-protein kinase was thus concluded to be fibronectin. The sites of phosphorylation by ecto-protein kinase were compared with those of intracellularly phosphorylated fibronectin by the analysis of radiolabeled amino acids and peptides. Ecto-protein kinase phosphorylated fibronectin at serine and threonine residues which were distinct from the sites of intracellular fibronectin phosphorylation.

Adenosine Triphosphate↗
PubMed1988

Macroscopic intestinal colonies of mice as a tool for studying differentiation of multipotential intestinal stem cells.

Macroscopic nodules composed of regenerating intestinal epithelium were developed within an area of the murine jejunum ulcerated by X-irradiation (1700 rads). The authors investigated whether such intestinal nodules were clonal and whether this method was useful as a tool for studying differentiation of intestinal stem cells. For examination of the clonality, intestinal nodules were produced in the jejunum of (C57BL/6 X DS)F1-Pgk-1b/Pgk-1a mice that carried X-chromosome inactivation mosaicism for the phosphoglycerate kinase gene. All intestinal nodules contained only 1 type of phosphoglycerate kinase, suggesting the monoclonal origin of nodules. Histochemical and electron microscopic studies showed the presence of absorptive epithelial, goblet, and entero-endocrine cells in most intestinal nodules, suggesting the multipotentiality of the nodule-forming stem cells. Moreover, villi developed on the top of some intestinal nodules, implicating the potential of the multipotential stem cell to construct the highly organized structure. The result indicates that the intestinal nodule method is useful for investigating differentiation potentials of multipotential intestinal stem cells.

Animals↗
PubMed1987

Scanning electron microscopy of vascular architecture in the gastric mucosa of the golden hamster.

The three-dimensional architectures and the regional differences of the vascular system in the mucosa of the hamster stomach were revealed by scanning electron microscopy of corrosion casts. In the forestomach, the vascular network spreads two-dimensionally in a thin lamina propria. In the corpus and the antrum, the capillaries in the thick lamina propria are well developed, extending three-dimensionally along the gastric pits and glands. In the corpus, the submucosal arteries enter the lamina propria to become ascending capillaries, which project toward the top of the lamina propria and anastomose to create a capillary network beneath the mucosal epithelium. A subepithelial capillary is much wider in diameter than an ascending capillary and is, therefore, a sinusoid capillary. Subepithelial capillaries join descending venules, which are less numerous than the ascending capillaries. Near the gastric lumen, the capillaries in the corpus can be classified into two types: arched type in the cephalic (upper) region and honeycomb type in the caudal (lower) region. In the antrum, the submucosal arterial plexus is less well developed than that in the corpus. The mucosal aspect of the corrosion cast shows many clumps, formed by a unit of capillary network. Functional significances of different vascular architectures in the gastric mucosa of the forestomach, corpus, and antrum are discussed.

Animals↗
PubMed1987

Fetomodulin: marker surface protein of fetal development which is modulatable by cyclic AMP.

A novel cell surface marker of fetal development was identified in both in vivo and in vitro systems of the mouse using monoclonal antibodies against a glycoprotein of an apparent size of 133,000 Da. Two independent clones of hybridomas were isolated by fusing murine myeloma cells, NS-1, with spleen cells of a rat which was immunized with murine 3T3 fibroblast. The analysis of molecular size and tryptic peptides of the immunoprecipitate indicated that fibroblast and putative parietal endoderm cells, which were derived by induced differentiation of F9 embryonal carcinoma cells with retinoic acid and cyclic AMP, expressed apparently the same protein. Undifferentiated F9 cells and F9 cells which were treated with retinoic acid or cyclic AMP alone had little or no immunoprecipitable proteins. Analogously, parietal endoderm of in vivo embryos tested positive for this protein but visceral endoderm and embryonic ectoderm did not. The amount of this surface protein was increased in fibroblast and differentiated F9 cells by elevation of intracellular cyclic AMP concentrations. These results are consonant with a hypothesis that this surface protein plays a role in fetal development via a quantitative modulation by cyclic AMP.

Animals↗
PubMed1986

A 200 kDa surface glycoprotein of human fibroblasts encoded by a gene on chromosome 11 is regulated by cyclic AMP.

A gene mapped to the long arm of human chromosome 11 was previously characterized to code for a cell-surface glycoprotein of an apparent molecular mass of 200 kDa in fibroblasts. We now report that this surface protein is expressed in an increased amount when human fibroblasts or human X Chinese-hamster hybrid cells containing human chromosome 11 are treated with 1 mM dibutyryl cyclic AMP. A detailed analysis of this phenomenon of induction was performed using a long-established, stable cell line of human X Chinese-hamster hybrid cells, J1 clone, which contained human chromosome 11 and expressed the 200 kDa glycoprotein of human origin. It was shown that the 200 kDa protein of J1 cells was inducible with 1 mM dibutyryl cyclic AMP, 10 mM unmodified cyclic AMP, 0.2 mM 8-para-chlorophenylthio cyclic AMP or 1 nM cholera toxin. Induction was potentiated by the addition of a phosphodiesterase inhibitor, Ro 20-1724. These results are consistent with the finding in human fibroblast, confirming that human fibroblasts express a 200 kDa glycoprotein on their surface which is regulated by intracellular concentrations of cyclic AMP. The regulation may be at the level of transcription since the addition of actinomycin D prevented the induction.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗
PubMed1986

Three-dimensional aspects of blood vessels in thyroids from normal, low iodine diet-treated, TSH-treated, and PTU-treated rats.

Three-dimensional images of blood vessels in thyroid glands from normal, low iodine diet-treated, thyroid-stimulating hormone (TSH)-treated and propylthiouracil (PTU)-treated rats were investigated by use of the corrosion-cast method. The vascular casts made by the injection of methacrylate resin were observed with the scanning electron microscope. In normal animals, each follicle is surrounded by a clearly defined basket-like capillary network, which is generally independent of adjacent networks, though a few anastomoses or common capillaries are sometimes seen. In low iodine diet-treated or TSH-treated animals, the capillaries in the basket-like network become markedly dilated and fuse with one another. Though the vascular casts of PTU-treated animals are similar to those of low iodine diet-treated or TSH-treated ones in some aspects, most basket-like networks become distorted and irregular in shape, and the capillaries are heterogeneously dilated and show many buds, branches and anastomoses. We consider that these peculiar changes in the thyroid of the PTU-treated animals are due not only to the elevation of serum TSH but also to other unknown factors. It is clear that the distribution and morphology of the thyroid capillaries are extremely affected and changed by functional states of the gland.

Animals↗
PubMed1986

Identification of 200,000-dalton human cell surface protein encoded by gene mapped to long arm of chromosome 11.

Cell surface proteins and glycoproteins of human and Chinese hamster cells and their hybrid cell clones were analyzed by two-dimensional gel electrophoresis. The J1 clone of human-Chinese hamster hybrid cells contained chromosome 11 as its only human chromosome. The J1 cells expressed a glycoprotein of 200,000 daltons which was shared by human fibroblasts but not by the parental Chinese hamster ovary cells. The 200,000-dalton protein was identified as a cell surface protein by the method of lactoperoxidase-catalyzed iodination. The protein was electrophoretically purified from radioiodinated cultures of human fibroblasts and J1 cells and subjected to the analysis of tryptic peptides by thin-layer electrophoresis followed by chromatography. The protein from both sources gave rise to fingerprints which closely resembled to each other. The results are consistent with a hypothesis that the 200,000-dalton protein of the J1 clone is of human origin. Analysis of segregant clones of J1 cells, which have deletions on human chromosome 11, has further suggested that the gene for this glycoprotein maps to the long arm of chromosome 11. A gene coding for the 200,000-dalton protein has not been previously mapped to this chromosome.

Animals↗
PubMed1986

A laboratory evaluation of two methods for measuring low levels of formaldehyde in indoor air.

Two methods for measuring formaldehyde at ppb levels--the modified pararosaniline (PRA) and the modified chromotropic acid (CTA)--were evaluated in a laboratory study. A dynamic double dilution system was used to generate controlled test atmospheres of formaldehyde by the catalytic depolymerization of trioxane. Impinger samples were collected from the sampling manifold and analyzed accordingly. Both methods demonstrated good precision (3.5% for the PRA and 3.4% for the CTA) but differed in accuracy and collection efficiency. Accuracy was 87.7 +/- 7.5% for the PRA and 92.5 +/- 4.2% for the CTA, while collection efficiency was 91.9 +/- 6.9% and 98.7 +/- 4.7% respectively. These differences were mainly due to the use of 1% NaHSO3 as the absorbing solution in the CTA method. Additionally, the NaHSO3 solution has the advantage of long sample preservation, making the modified CTA the method of choice in most non-industrial indoor air sampling situations.

Air Pollutants, Occupational↗
PubMed1986

Three-dimensional imaging of blood vessels in thyroids from normal and levothyroxine sodium-treated rats.

Three-dimensional images of the microvascular architecture in the thyroid glands of levothyroxine sodium-treated (for 4 weeks) rats were examined by scanning electron microscopy of corrosion casts made by the injection of methacrylate resin. In the experimental animals, each follicle was surrounded by a clearly defined basket-like capillary network generally independent of the adjacent one in the same manner as in normal animals. However, the capillaries were markedly poor in distribution, conspicuously small in diameter, and their anastomoses were clearly decreased as compared with the normal state. The diameters of the capillaries were 3-8 microns in these cases, while those in normal specimens were 5-15 microns. The capillary bed surrounding each follicle occupied about 25% of the follicular surface area, while that in normal cases occupied about 50%. In conclusion, it became clear that the distribution and morphology of the thyroid capillaries are markedly affected and changed by the functional state of the gland.

Animals↗
PubMed1985

Application of rapid freezing followed by freeze-substitution acrolein fixation for cytochemical studies of the rat stomach.

A method involving rapid freezing followed by substitution fixation was developed, using acrolein as a fixative. This was then applied to several cytochemical stainings, and showed well preserved and clear cell structures. Membranes were apparently negatively stained and the ultrastructure of mitochondria, rough endoplasmic reticulum and Golgi apparatus was clearly discernible. The mitochondrial and cytoplasmic matrices were stained rather densely compared with routine chemically fixed preparations, implying a good preservation of matrix substances. Periodic acid-thiocarbohydrazide-silver proteinate staining was applied to the present method. The mucous granules of surface covering epithelial cells indicated fine staining of bipartite structure and the Golgi apparatus of mucous cells showed clear staining differences based on polarity. Postembedding lectin-ferritin and immunocytochemical stainings were applicable to the present preparations and stable stainings of secretory granules were obtained. A low temperature embedding material, Lowicryl K4M, was also examined. The cell preservation of these samples was not as good as those embedded in Epon, but the rough endoplasmic reticulum and Golgi apparatus of chief cells were stained with anti-pepsinogen antibody as were the secretory granules. The present method was also applicable to light microscopy.

Acrolein↗
PubMed1985

Characterization of a human rhabdomyosarcoma cell strain in tissue culture.

A new human rhabdomyosarcoma cell strain, designated KYM-1, has been established from a neck tumor found in a 9-month-old infant. The cultured cells were round and mainly free-floating or in a moniliform pattern with a population doubling time of 75 hours. In stained preparations, the cells were pleomorphic and had a single round or oval nucleus in non-striated cytoplasm. However, the intracellular presence of myogenic markers was clearly shown by enzyme-immunochemical stains. An ultrastructural feature of the KYM-1 cells was the presence of numerous intermediate filaments in the perinuclear area and around the Golgi complexes which were associated with abundant cell organelles and aggregates of glycogen granules. High viscosity of the spent culture medium was attributed to hyaluronic acid, identified by electrophoresis and hyaluronidase digestion, and immunological and biochemical analyses revealed that the increased concentration of plasminogen activator activity found in the culture medium was almost wholly of the tissue plasminogen activator type. The KYM-1 cells also contained high concentrations of alkaline phosphatase activity. Tumorigenicity of the cells was confirmed by heterotransplantation into hamsters treated with anti-thymocyte serum.

Animals↗
PubMed1982

Increase of a surface glycoprotein by cyclic AMP in Chinese hamster ovary cells. Dependence on cell-cell interaction.

Cell surface proteins and glycoproteins of the CHO-K1 clone of Chinese hamster ovary cells were radiolabeled by surface-specific reactions as well as by metabolic incorporation of glycoprotein precursors. After the proteins were separated by two-dimensional gel electrophoresis, they were quantified according to the amount of radioactivity which was associated with individual proteins spots. A glycoprotein of 133,000 daltons (P133-11) wa found to increase severalfold by the elevation of the cytoplasmic level of adenosine 3':5'-cyclic monophosphate. In this paper, we report that the increase of P133-11 was more efficient in dense cultures than in sparse cultures. The use of conditioned medium or frequent medium changes during the treatment with the cyclic nucleotide did not influence the efficiency of the increase of the glycoprotein, indicating that the enrichment or exhaustion of diffusible materials was not responsible for this density-dependent phenomenon. The same conclusion was drawn from an experiment in which the amount of P133-11 was compared between homogeneously plated sparse cultures and cultures containing the same number of cells in the form of colonies with well contacted cells at an average density of 400 cells/colony. The increase of the protein was higher in the latter type of cell cultures. We, therefore, propose that the interaction of surface components upon cell-cell contact plays a role in the expression of P133-11 surface glycoprotein.

Animals↗
PubMed1982

Effects of cyclic AMP on S-100 protein level in C-6 glioma cells.

Dibutyryl cyclic AMP (dbcAMP) markedly elevated S-100 protein level in C-6 glioma cells in vitro. Quantitative analysis by two-dimensional polyacrylamide gel electrophoresis revealed that the elevation was caused by a combination of increased synthesis and reduced degradation of S-100 protein in C-6 cells exposed to dbcAMP. These results suggest that dbcAMP affects both the synthesis and the degradation of S-100 protein in C-6 cells.

Animals↗