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Biomedical subjects

K Isono

Publications and source records attributed to K Isono.

At least 19 recordsLinked to original sources
PubMed1995

Tautomycin: an inhibitor of protein phosphatases 1 and 2A but not a tumor promoter on mouse skin and in rat glandular stomach.

Tautomycin isolated from Streptomyces spiroverticillatus is an inhibitor of protein phosphatases 1 and 2A. Tautomycin induced hyperphosphorylation of cytokeratin peptides in human keratinocytes (PHK 16-I cells) 30 times less strongly than did okadaic acid. Repeated applications of tautomycin (30 micrograms, 40 nmol/application) did not induce tumor promotion in a two-stage carcinogenesis experiment on mouse skin initiated with 7,12-dimethylbenz[a]anthracene, whereas okadaic acid (1 microgram, 1.2 nmol/application) as a control induced tumor promotion strongly. As for mucosa of rat glandular stomach, tautomycin induced ornithine decarboxylase 4 h after intubation into the stomach. The tumor-promoting activity of tautomycin was next studied in the glandular stomach initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Administration of tautomycin in the diet (1 mg rat-1 day-1), from week 9 to week 52 of the experiment, inhibited rather than enhanced tumor development in the glandular stomach initiated with MNNG. The percentages of tumor-bearing rats of the groups treated with MNNG plus tautomycin, MNNG alone, and tautomycin alone were 20.0%, 40.6%, and 0% respectively in week 52. The reason for the absence of tumor-promoting activity of tautomycin was studied in relation to tumor necrosis factor alpha (TNF alpha), an endogenous tumor promoter. We found that tautomycin neither enhanced TNF alpha mRNA expression in mouse skin nor induced TNF alpha release in a human stomach cancer cell line (KATO III cells), whereas okadaic acid did both. These results indicate that not all inhibitors of protein phosphatases are tumor promoters, and suggest that tumor promotion of the okadaic acid class of compounds is mediated by TNF alpha.

Animals↗
PubMed1995

Enhancement of the antitumor effect by combined use of high-energy shock waves and ATX-70.

The antitumor effects of high-energy shock waves (HESW) in combination with ATX-70 [a gallium-porphyrin complex, 2,4-bis(1-decyloxyethyl)-Ga(III)-1,3,5,8-tetramethylporphyrin++ +-6, 7-dipropionyl diaspartic acid [sequence: see text] were investigated. In vitro, the cell damage to mouse MH134 hepatoma after HESW treatment was enhanced by adding ATX-70. In vivo, HESW and ATX-70 combination therapy inhibited cell growth. However, neither HESW treatment alone nor ATX-70 treatment alone inhibited cell growth. These results imply that the antitumor effects of HESW and ATX-70 combined therapy are caused by activation of ATX-70 by HESW.

Animals↗
PubMed1995

Molecular characterization of a tandem repeat, Afa family, and its distribution among Triticeae.

We have characterized a so-called D genome specific repetitive DNA sequence (pAs1) of Aegilops squarrosa L. (2n = 14, genome DD) with respect to its DNA sequence and its distribution among Triticeae species. The clone consisted of three units of a repetitive DNA sequence of 336 or 337 base pairs, and was AT rich (65.2%). DNA analyses revealed the presence of the pAs1-like sequences in other genomes of Triticeae species, although the repetition was greatly (as much as 100-fold) variable among the genomes. The repetitive sequences from 10 diploid species were amplified using PCR with specific primers, and the sequential variability was analyzed by the digestion pattern obtained with five restriction enzymes. Since the AfaI site was the most conservatively present in the unit of the repetitive sequences, we named them "Afa family." The analysis clearly displayed the variation of the repetitive sequences regardless of the uniformity of the size of the amplified product. These results indicated that plural amplification events of these repetitive sequences happened independently in the genome evolution of Triticeae.

Base Sequence↗
PubMed1995

Role of recruited neutrophils in interleukin-8 production in dog trachea after stimulation with Pseudomonas in vivo.

Cell-free supernatant of Pseudomonas aeruginosa (PA) recruits neutrophils into the airways indirectly by inducing the production of chemotactic factors, including interleukin-8 (IL-8). PA products stimulate IL-8 expression selectively in surface airway epithelium, gland ducts, serous cells, and recruited neutrophils. To examine the relative contribution of neutrophils in IL-8 release in the airway lumen, we studied the effect of inhibition of neutrophil recruitment on IL-8 concentration in tracheal fluid after introduction of PA supernatant into the dog trachea in vivo. Tracheal superfusion with PA supernatant caused neutrophil recruitment and increased the IL-8 concentration in the tracheal lumen; NPC 15669 inhibited both effects. To study whether migration of neutrophils into the airway lumen per se induces their expression of IL-8, we compared effects of local introduction of IL-8 and of PA supernatant into the trachea on IL-8 expression in neutrophils recruited into the trachea. PA supernatant, but not exogenous IL-8 alone, induced IL-8 mRNA expression in neutrophils recruited into the trachea. To determine what product(s) of PA stimulate IL-8 expression in neutrophils, we examined neutrophils isolated from peripheral blood. PA supernatant induced IL-8 production in neutrophils, an effect reproduced by PA lipopolysaccharide and inhibited by polymyxin B. These results suggest that neutrophils recruited into the airway lumen play a major role in local IL-8 production in airways in response to bacteria such as PA, depending on the presence of stimuli such as lipopolysaccharide.

Animals↗
PubMed1994

Cloning and characterization of the ribosomal protein genes in the spc operon of a prokaryotic endosymbiont of the pea aphid, Acyrthosiphon kondoi.

To correlate a prokaryotic endosymbiont in the pea aphid, Acyrthosiphon kondoi, with the endosymbionts in related aphid species as well as with free-living bacteria and subcellular organelles, and to study the mode of its gene expression within aphid cells, we have cloned and characterized the genes encoding ribosomal proteins S3, L16, L29, S17, L14, L24, L5, S14, S8, L6, L18, S5, L30, L15 and secretion protein Y (Sec Y) from the S10 and spc ribosomal protein gene operons of this endosymbiont. The organization of these genes is identical to that in Escherichia coli, and their nucleotide sequences are highly similar (87% identity) to the corresponding E. coli genes. They are much less similar to the corresponding chloroplast and mitochondrial genes. The guanine plus cytosine G+C content of the genes of the A. kondoi endosymbiont is much higher than those of the endosymbionts in related aphid species reported so far. It appears either that the A. kondoi endosymbiont is derived from an ancestral bacterium different from those in other aphids or that its G+C content increased in a relatively short time after the evolutionary divergence of its host.

Amino Acid Sequence↗
PubMed1993

Combination of immunosuppressive drugs for organ transplantation.

Several novel immunosuppressive agents have been developed in recent years. They exhibited not only remarkable immunosuppressive potency but also side effects. They are still short of the final goal in terms of immunosuppression for organ transplantation. Combination treatment is more effective and safer to use, and it will prevail in the future.

Amylases↗
PubMed1992

Efficient large-scale sequencing of the Escherichia coli genome: implementation of a transposon- and PCR-based strategy for the analysis of ordered lambda phage clones.

We have developed a strategy for efficient sequence analysis of the genome of E. coli K-12 using insertions of a Tn5-derived mini-transposon into overlapping ordered lambda phage clones to provide universal primer-binding sites, and PCR amplification of DNA segments adjacent to the insertions. Transposon-containing clones were selected by blue plaque formation on a dnaBamber lacZamber E. coli strain. Insertion points every 0.5-1 kb were identified by 'analytical PCR' and segments between the transposon inserts and phage arms were amplified by 'preparative PCR' using one biotinylated and one non-biotinylated primer. Single strands of amplified DNA fragments were coupled to Streptoavidin-coated paramagnetic beads (Dynabeads M280) through their biotin tails, purified magnetically, and used as templates for fluorescence-based automatic nucleotide sequencing.

Bacteriophage lambda↗
PubMed1992

Elevated expression of the ornithine decarboxylase gene in human esophageal cancer.

The mechanisms involved in sustaining the high levels of ornithine decarboxylase (ODC) activity in human cancers are not well defined. We examined the level of expression of ODC mRNA together with ODC activity in surgically excised human cancers, including esophagus, stomach, colon, and liver tumors, the objective being to determine whether the ODC mRNA level correlates with enhancement of ODC activity in these cancers. Among these tumors, the esophageal cancers had the highest ODC activity (120 +/- 43.9 pmol of CO2/h/mg of protein), compared with the stomach (37.6 +/- 13.7), colon (22.8 +/- 5.9), and liver (10.2 +/- 5.6) cancers. A remarkable increase in ODC mRNA was seen in all of the esophageal cancers. The ratio of ODC mRNA in the tumors, relative to the paired normal tissues, was 14.6 +/- 3.7. Some increase was noted in some of the stomach (2.9 +/- 0.9) and colon (2.1 +/- 0.9) cancers, but there was no increase in the liver tumors (0.9 +/- 0.2). A significant correlation was noted between ODC activity and mRNA expression in cancerous and noncancerous tissues of the esophagus, stomach, and colon, thereby suggesting that increased steady-state mRNA may be responsible for the high ODC activity in these tumors. Southern blot analysis of the DNA from the esophageal cancers revealed no amplification or significant rearrangement of the gene. Mechanisms sustaining high ODC mRNA levels in esophageal cancers may be an enhancement of the promoter activity of this gene or stabilization of the mRNA.

Blotting, Northern↗
PubMed1992

Molecular cloning and characterization of the gene encoding mouse melanoma antigen by cDNA library transfection.

We have isolated a cDNA (H52) of 2.8-kb-long encoding an 80-kDa mouse melanoma Ag that is defined by a syngeneic anti-B16 melanoma mAb with an ability to block anti-melanoma cytotoxic T cell responses. H52 transfectants were brightly stained with the antibody, and the 80-kDa molecule was immunoprecipitated from the transfectants. Northern blot analysis showed that this transcript was detected in mouse melanoma cells of C57BL/6 and DBA/2 origin, C1300 A/J neuroblastoma, L cell (C3H) and EL-4 T lymphoma (C57BL/6), faintly in BW5147 (AKR) T lymphoma, but not in other tumors, such as S913 fibrosarcoma (C57BL/10), NIH3T3, 70 Z/3 pre-B lymphoma, and P3U1 plasmacytoma (BALB/c). Since the transcripts were not found in normal C57BL/6 tissues of fetus, newborn, and adult origin, the H52 expression is associated with transforming phenotypes. However, no tissue- or cell type-specific expression was observed. Nucleotide sequence analysis has clearly demonstrated that H52 cDNA encodes the full length of the env gene and long terminal repeat region of endogenous ecotropic murine leukemia provirus of AKV-type, which is defective in C57BL/6. The H52 envelope protein has several amino acid changes compared to those of AKV, one of which is in the env 14 peptide region preferentially associated with MHC molecule, suggesting the possible reason for the difference of antibody reactivity even in H52-positive tumors. We also demonstrate that CTL against H52 transfectant kills B16 melanoma. Thus, the above results are direct evidence that even the endogenous self molecule, when constitutively expressed, does act as a tumor Ag.

Amino Acid Sequence↗
PubMed1992

Systematic sequencing of the Escherichia coli genome: analysis of the 0-2.4 min region.

A contiguous 111,402-nucleotide sequence corresponding to the 0 to 2.4 min region of the E. coli chromosome was determined as a first step to complete structural analysis of the genome. The resulting sequence was used to predict open reading frames and to search for sequence similarity against the PIR protein database. A number of novel genes were found whose predicted protein sequences showed significant homology with known proteins from various organisms, including several clusters of genes similar to those involved in fatty acid metabolism in bacteria (e.g., betT, baiF) and higher organisms, iron transport (sfuA, B, C) in Serratia marcescens, and symbiotic nitrogen fixation or electron transport (fixA, B, C, X) in Azorhizobium caulinodans. In addition, several genes and IS elements that had been mapped but not sequenced (e.g., leuA, B, C, D) were identified. We estimate that about 90 genes are represented in this region of the chromosome with little spacer.

Bacterial Proteins↗
PubMed1992

Physical dissection and characterization of chromosomes V and VIII of Saccharomyces cerevisiae.

Chromosomes V and VIII of S. cerevisiae were dissected and ordered clone banks were constructed and characterized. Each bank contains almost the entire chromosome from the left to the right telomere except for a small gap in each case. The size of the banks constructed is in good agreement with the physical length of these chromosomes, 580 kb, estimated by pulsed-field gel electrophoresis. The remaining gap in the ordered clone bank of chromosome V was found to be only 1.6 kb in length and to contain a 1.5 kb-long portion of one of the two Ty elements located in tandem. The gap in the bank of chromosome VIII was 6.4 kb in length and contained four copies of the CUP1 gene. A genomic restriction map analysis of the corresponding region of chromosome VIII revealed that a unit of about 2 kb in length harbouring the CUP1 gene was repeated ten times in strain DC5 rho degrees which was used for the bank construction. A 588.5 kb-long high resolution physical map for chromosome V and a 585.6 kb-long one for chromosome VIII have thus been established.

Bacteriophage lambda↗
PubMed1992

Isoflavonoids, genistein, psi-tectorigenin, and orobol, increase cytoplasmic free calcium in isolated rat hepatocytes.

Isoflavonoid compounds, genistein, psi-tectorigenin and orobol have been implicated as inhibitors of tyrosine-specific protein kinase and phosphatidylinositol turnover. These compounds have been frequently used as a pharmacological tool to assess signal transduction pathways in various cell systems. In the course of analyzing signaling pathways in rat hepatocytes, we obtained an unexpected finding that these compounds transiently increase cytoplasmic free calcium. Since the Ca2+ mobilizing effect was observed in 1 microM calcium containing buffer, the source of the Ca2+ may be intracellular stores. Thus, when interpreting data obtained using these compounds, caution is needed.

Aequorin↗
PubMed1992

Cell-cell interaction in graft rejection responses: induction of anti-allo-class I H-2 tolerance is prevented by immune responses against allo-class II H-2 antigens coexpressed on tolerogen.

The intravenous sensitization of C57BL/6 (B6) mice with class I H-2-disparate B6-C-H-2bm1 (bm1) spleen cells results in almost complete abrogation of anti-bm1 CD8+ helper (proliferative and interleukin 2-producing) T cell (Th) activities. Although an appreciable portion of CD8+ cytotoxic T lymphocyte (CTL) precursors themselves remained after this regimen, such a residual CTL activity was eliminated after the engrafting of bm1 grafts, and these grafts exhibited prolonged survival. In contrast, the intravenous sensitization with (bm1 x B6-C-H-2bm12 [bm12])F1 cells instead of bm1 cells failed to induce the prolongation of bm1 graft survival as well as bm12 and (bm1 x bm12)F1 graft survival. In the (bm1 x bm12)F1-presensitized B6 mice before as well as after the engrafting of bm1 grafts, anti-bm1 CTL responses that were comparable to or slightly stronger than those observed in unpresensitized mice were induced in the absence of anti-bm1 Th activities. bm1 graft survival was also prolonged by intravenous presensitization with a mixture of bm1 and bm12 cells but not with a mixture of bm1 and (bm1 x bm12)F1 cells. The capacity of CD4+ T cells to reject bm12 grafts was eliminated by intravenous presensitization with antigen-presenting cell (APC)-depleted bm12 spleen cells. However, intravenous presensitization with APC-depleted (bm1 x bm12)F1 cells failed to induce the prolongation of bm1 graft survival under conditions in which appreciably prolonged bm12 graft survival was induced. More surprisingly, bm1 graft survival was not prolonged even when the (bm1 x bm12)F1 cell presensitization was performed in CD4+ T cell-depleted B6 mice. This contrasted with the fact that conventional class I-disparate grafts capable of activating self Ia-restricted CD4+ as well as allo-class I-reactive CD8+ Th exhibited prolonged survival in CD4+ T cell-depleted, class I-disparate cell-presensitized mice. These results indicate that: (a) intravenous presensitization with class I- and II-disparate cells fails to reduce anti-allo-class I rejection responses that would otherwise be eliminated using only class I-disparate cells; (b) such failure is generated according to the coexpression of both classes of alloantigens on a single cell as tolerogen; and (c) allo-class II antigens coexpressed on tolerogen function to activate CD4+ as well as non-CD4+ Th leading to the generation of anti-class I effector T cell responses.

Animals↗
PubMed1992

p53 gene mutations in gastric and esophageal cancers.

The presence of point mutation of the p53 gene in exons 5, 6, 7, and 8 was examined in 10 cases of gastric adenocarcinoma and 5 cases of esophageal squamous cell carcinoma by polymerase chain reaction and direct nucleotide sequencing. Mutations of the p53 gene were found in 5 cases of gastric cancer and 4 cases of esophageal cancer. The mutations in the stomach cancers consisted of four missence mutations (exons 5 and 8) and one frame shift (exon 7). In the esophageal cancers, three missence mutations (exons 6, 7, and 8) and one point mutation within the splice donor site of intron 5 were found. Of the seven missence mutations in the two cancers, five showed the transition from G to A and two from G to T. All these changes occurred in the highly conserved region of the p53 protein. These results suggest that mutations of the p53 gene are genetic events in the pathogenesis of gastric adenocarcinoma and esophageal squamous cell carcinoma.

Adult↗