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Biomedical subjects

A Kikuchi

Publications and source records attributed to A Kikuchi.

At least 397 records · Page 22Linked to original sources
PubMed1988

Semi-quantitative immunohistochemical studies on Thy-1 antigen expressed by thymic myoid cells.

Thy-1 antigen expression in the rat thymic myoid cell line R615B2 (Thy-1(+] and R613Ad (Thy-1(-] was studied with a semi-quantitative immunohistochemical assay without disrupting the cell cultures. With this assay, the quantity of Thy-1 antigen on R615B2 cells was detected separately in the cytoplasm and on the cell surface by the use of appropriate fixatives such as chilled ethanol and methanol + 0.3% H2O2. Extracellular Thy-1 antigen was also found in the culture supernatant of R615B2 cells. More than half of extracellular Thy-1 antigen remained in the supernatant even after 100,000 X g centrifugation. No form of Thy-1 antigen was detected at significant levels in R613Ad cells.

Animals↗
PubMed1988

Defects in muscle fiber growth in fatal infantile cytochrome c oxidase deficiency.

In addition to numerous ragged-red fibers in the muscle from a female infant with fetal infantile cytochrome c oxidase deficiency, the muscle fibers were small in caliber with electron microscopic characteristics of immaturity; the satellite cells were significantly increased in number to 31.3% as compared with those in controls, 8.4 +/- 1.6% (p less than 0.001). In the culture system, the biopsied muscle showed markedly reduced growth despite the presence of numerous satellite cells which are known to act as myoblasts in muscle regeneration, and formed fewer numbers of myotubes containing poorly organized myofibrils and mitochondria with no cytochrome c oxidase activity. A defect in myogenesis and a paucity in repair process in severe form may account for the progressive course and a fatal outcome.

Biopsy↗
PubMed1987

Intrinsic DNA-dependent ATPase activity of reverse gyrase.

Reverse gyrase is a type I DNA topoisomerase that promotes positive supercoiling of closed-circular double-stranded DNA through an ATP-dependent reaction, and it was purified from an archaebacterium, Sulfolobus. When ATP is replaced by UTP, GTP, or CTP, this enzyme just relaxes the negatively supercoiled closed-circular double-stranded DNA. We found that reverse gyrase hydrolyzes ATP through a double-stranded DNA-dependent reaction. The superhelicity of the DNA did not affect the ATPase activity. However, reverse gyrase does not hydrolyze UTP, GTP, or CTP. Therefore, any of the four nucleotide 5'-triphosphates acts as an effector for the topoisomerase activity of reverse gyrase, but only ATP supports the positive supercoiling of closed-circular double-stranded DNA, through the energy released on its hydrolysis. Single-stranded DNA was a much more potent cofactor for the ATPase activity of the enzyme than double-stranded DNA, and it acted as a potent inhibitor for the topoisomerase activity on double-stranded DNA. These results indicate that reverse gyrase has higher affinity to single-stranded DNA than to double-stranded DNA, which suggests a cellular function of the enzyme.

Adenosine Triphosphatases↗
PubMed1987

Modes of inhibitory action of protein kinase C in the chemotactic peptide-induced formation of inositol phosphates in differentiated human leukemic (HL-60) cells.

Using the [3H]inositol-labeled plasma membranes isolated from the differentiated human leukemic (HL-60) cells, the mode of inhibitory action of the Ca2+/phospholipid-dependent enzyme protein kinase C in the chemotactic peptide, fMet-Leu-Phe (fMLP)-induced, phospholipase C-mediated hydrolysis of phosphoinositides was investigated. In this cell-free membrane system, fMLP in the presence of GTP plus Ca2+, GTP in the presence of Ca2+, or Ca2+ alone could induce the formation of inositol bis- and trisphosphate (IP2 and IP3, respectively). When the intact cells were pre-treated with 12-O-tetradecanoylphorbol-13-acetate, the fMLP- and GTP-induced formation of IP2 and IP3 was markedly reduced but the Ca2+-induced reactions were not reduced in the isolated membranes. This result suggests that protein kinase C impairs the coupling of the GTP-binding protein to the phospholipase C. In another experiment, preincubation of the isolated membranes with pure rat brain protein kinase C inhibited the fMLP-induced formation of IP2, but did not inhibit the GTP- or Ca2+-induced reaction. Under the same conditions, protein kinase C did not inhibit the fMLP-, GTP-, or Ca2+-induced formation of IP3. This result suggests that protein kinase C impairs additionally the coupling of the fMLP receptor to the GTP-binding protein leading to the formation of IP2. The reason for the failure of protein kinase C to inhibit the fMLP-induced formation of IP3 in the cell-free membrane system is unknown, but several possible mechanisms are discussed.

2,3-Diphosphoglycerate↗
PubMed1987

Further evidence for importance of the subunit combination of silk fibroin in its efficient secretion from the posterior silk gland cells.

A locus responsible for the Nd-s mutation of the silkworm, Bombyx mori, has been mapped very close to or within the fibroin light (L) chain gene on the 14th chromosome (Takei, F., K. Kimura, S. Mizuno, T. Yamamoto, and K. Shimura, 1984, Jpn. J. Genet., 59:307-313). A strain of B. mori carrying the homozygous Nd-sD mutation (Nd-sD/Nd-sD; Nd-sD is allelic to Nd-s) secretes less than 0.3% of fibroin into the lumen of the posterior silk gland compared with a strain carrying the homozygous wild-type alleles (+/+). The small amount of fibroin that is secreted in the Nd-sD/Nd-sD strain consists of the heavy (H) chain only and lacks the L chain, although the L chain mRNA and the proteins that are cross-reactable with the anti-L chain serum are present in the posterior silk gland cells. In the hybrid silkworm, Nd-sD/+, the H chain derived from either the Nd-sD or + allele forms disulfide linkage with the L chain derived from the + allele and these fibroins are secreted into the lumen with an equal efficiency, but the L chain derived from the Nd-sD allele remains in the cell unbound to the H chain. Some evidence suggesting structural abnormality of the L chain derived from the Nd-sD allele is presented. These results, together with the previous results on the effect of the H chain gene-linked Nd(2) mutation (Takei, F., F. Oyama, K. Kimura, A. Hyodo, S. Mizuno, and K. Shimura, 1984, J. Cell Biol., 99:2005-2010), strongly suggest that the H-L subunit combination of silk fibroin is important for its efficient secretion.

Alleles↗
PubMed1986

Direct evidence for involvement of a guanine nucleotide-binding protein in chemotactic peptide-stimulated formation of inositol bisphosphate and trisphosphate in differentiated human leukemic (HL-60) cells. Reconstitution with Gi or Go of the plasma membranes ADP-ribosylated by pertussis toxin.

fMet-Leu-Phe (fMLP) stimulated the formation of inositol bis- and trisphosphate in the [3H]inositol-labeled plasma membranes from the human leukemic (HL-60) cells differentiated to neutrophil-like cells by dibutyryl cyclic AMP. The stimulatory effect of fMLP was completely dependent on the simultaneous presence of GTP and Ca2+. The fMLP-stimulated formation of the phosphorylated inositols was markedly reduced by the prior ADP-ribosylation of the membranes with pertussis toxin. This toxin ADP-ribosylated a Mr approximately 40,000 protein, presumably the alpha subunit of Gi and/or Go, in the membranes. Reconstitution of the membranes ADP-ribosylated by pertussis toxin with Gi or Go purified from rat brain restored the fMLP-stimulated formation of the phosphorylated inositols. The efficiency of the rat brain Gi and Go in this capacity was roughly equal. The rat brain Gi or Go ADP-ribosylated beforehand by pertussis toxin was inactive in this reconstitution. These results indicate that both rat brain Gi and Go have the potency to couple functionally the fMLP receptor to the phospholipase C-mediated polyphosphoinositide hydrolysis and suggest that Gi or Go may be involved in the mechanism of signal transduction from the fMLP receptor to this reaction in the differentiated HL-60 cells.

Adenosine Diphosphate Ribose↗
PubMed1986

Possible involvement of protein kinase C and calcium ion in growth factor-induced expression of c-myc oncogene in Swiss 3T3 fibroblasts.

The addition of platelet-derived growth factor and fibroblast growth factor to quiescent cultures of Swiss 3T3 fibroblasts rapidly induced protein kinase C activation and Ca2+ mobilization and afterwards markedly increased c-myc mRNA levels. 1-Oleoyl-2-acetylglycerol, a membrane-permeable synthetic diacylglycerol, and 12-O-tetradecanoylphorbol 13-acetate, a tumor-promoting phorbol ester, stimulated protein kinase C activation without Ca2+ mobilization. Inversely, Ca2+ ionophores, A23187 and ionomycin, elicited Ca2+ mobilization without protein kinase C activation. Both protein kinase C-activating and Ca2+-mobilizing agents were able to increase c-myc mRNA levels in an additive manner. Prolonged treatment of the cells with phorbol 12,13-dibutyrate, another protein kinase C-activating phorbol ester, led to the down-regulation and complete disappearance of protein kinase C. In these cells, 1-oleoyl-2-acetylglycerol and 12-O-tetradecanoylphorbol 13-acetate did not increase c-myc mRNA levels, but platelet-derived growth factor, fibroblast growth factor, and the Ca2+ ionophores, all of which still induced Ca2+ mobilization, stimulated the increase of c-myc mRNA levels. These results strongly suggest that both protein kinase C and Ca2+ may be involved in platelet-derived growth factor- as well as fibroblast growth factor-induced expression of the c-myc oncogene in Swiss 3T3 cells.

Animals↗
PubMed1986

Hereditary peroneal muscular atrophy in the mouse: an experimental model for congenital contractures (arthrogryposis).

A new mutant, peroneal muscular atrophy (pma) mouse in CF#1 strain has an autosomal recessively inherited equinovarus (club foot deformity) of the hind legs because of the absence of the common peroneal nerve branch of the sciatic nerve. We found the peroneal muscles were hypoplastic with histochemical and electron microscopic characteristics of fetal muscle. The anterior horn cells in the spinal cord were not reduced in number and they appeared to be normal. The density and size of the myelinated fibers in the anterior spinal roots of L3, L4, and L5 and the sciatic nerve in the affected side were not different from those in the unaffected. Therefore, the absence of the common peroneal nerve in the pma mouse is thought to result from the misdirection of these nerve bundles into other peripheral nerves. As the anomalous condition was present at birth with no progression, the pma mouse may be an experimental model for the study of arthrogryposis multiplex congenita or club foot deformity, and may lead to the understanding of the muscle and nerve interaction during development.

Animals↗
PubMed1986

[Possible modes of action of growth factors and tumor promoters in the activation of the c-myc gene in Swiss 3T3 fibroblasts].

It has been suggested that the c-myc gene may play an important role in the regulation of cell proliferation. We have investigated the transmembrane signaling mechanisms of various growth factors and tumor promoters in Swiss 3T3 fibroblasts and have examined the causal relationship between these mechanisms and c-myc gene activation. Platelet-derived growth factor and FGF (fibroblast growth factor) induced the activation of diglyceride-protein kinase C and Ca2+ systems through phosphoinositide turnover, resulting in the activation of the c-myc gene. Epidermal growth factor did not activate these two systems but stimulated gene activation. Prostaglandin E1 elicited Ca2+ mobilization and cyclic AMP generation followed by c-myc gene activation. In contrast to these growth factors, tumor-promoting phorbol esters induced the direct activation of protein kinase C which led to c-myc gene expression. Bile acids, which are known to be colon tumor promoters, were inactive by themselves but enhanced FGF-induced diglyceride formation and thereby potentiated protein kinase C activation. It has not yet been examined whether bile acids potentiate FGF-induced activation of the c-myc gene. The growth factors described above and the phorbol esters stimulated DNA synthesis in the presence of insulin, whereas the bile acids potentiated FGF-induced DNA synthesis. These results strongly suggest that three messenger systems, diglyceride, Ca2+ and cyclic AMP, may be involved in c-myc gene activation which may be implicated in DNA synthesis in Swiss 3T3 cells.

Animals↗
PubMed1986

Inhibition of chemotactic peptide-induced phosphoinositide hydrolysis by phorbol esters through the activation of protein kinase C in differentiated human leukemia (HL-60) cells.

Phorbol-12,13-dibutyrate (PDBU), a tumor-promoting and protein kinase C-activating phorbol ester, inhibited formylmethionylleucyl-phenylalanine-induced generation of inositol mono-, bis-, and tris-phosphates from the hydrolysis of phosphoinositides in human leukemia (HL-60) cells, which had been differentiated to polymorphonuclear leukocyte-like cells by pretreatment with dibutyryl cyclic adenosine 3':5'-monophosphate. PDBU did not alter the binding of formylmethionylleucyl-phenylalanine to the cells. Other protein kinase C-activating substances such as 12-O-tetradecanoylphorbol-13-acetate and 1-oleoyl-2-acetyl-glycerol could substitute for PDBU, but 4 alpha-phorbol-12,13-didecanoate, which is inactive for both tumor promotion and protein kinase C activation, was ineffective in this capacity. Prolonged treatment of the cells with PDBU resulted in the down-regulation and decrease of protein kinase C activity to the level of 30-40% of that in the control cells. In the down-regulated cells, formylmethionylleucylphenylalanine still induced generation of the phosphorylated inositols to the same extent as that in the control cells, but the inhibition of this reaction by PDBU was reduced to 30-50% as compared with that in the control cells. These results strongly suggest that tumor-promoting phorbol esters inhibit the agonist-induced phosphoinositide hydrolysis through the activation of protein kinase C in the differentiated HL-60 cells.

Cell Differentiation↗
PubMed1986

Formation of a phorbol ester-binding fragment from protein kinase C by proteolytic digestion.

When washed human platelets were disrupted by sonication in the presence of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, both the catalytic and [3H]phorbol-12,13-dibutyrate (PDBu)-binding activities of protein kinase C were recovered in the soluble fraction and were not separable from each other upon several column chromatographies. Platelet protein kinase C required diacylglycerol, Ca2+, and phospholipid for its activation and showed a molecular weight of about 87,000 as estimated by gel filtration analysis. However, when platelets were first incubated with 2 microM Ca2+-ionophore A23187 for 5 min at 37 degrees C in the medium containing 3 mM CaCl2 and then disrupted under the same conditions, the catalytic and [3H]phorbol-12,13-dibutyrate-binding activities were separately recovered in the soluble and particulate fractions, respectively; moreover, the catalytic activity recovered in the soluble fraction became independent of diacylglycerol, Ca2+, and phospholipid, and showed a molecular weight of about 50,000 as estimated by gel filtration analysis. The kinetic properties of this Mr 50,000 enzyme were similar to those of the catalytic fragment of rat brain protein kinase C described previously. In a cell-free system, digestion with trypsin of protein kinase C highly purified from rat brain caused the generation of a fragment which had no catalytic activity but showed full [3H]phorbol-12,13-dibutyrate-binding activity. The molecular weight of this fragment was estimated to be about 35,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results indicate that protein kinase C consists of at least two functionally different domains, a hydrophobic phorbol ester- or diacylglycerol-binding and hydrophilic catalytic domains.

Binding Sites↗