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S Iwagami

Publications and source records attributed to S Iwagami.

29 records · Page 2Linked to original sources
PubMed1990

Enhancement of bradykinin-induced prostacyclin synthesis in porcine aortic endothelial cells by pertussis toxin. Possible implication of lipocortin I.

Bradykinin-stimulated prostacyclin synthesis in porcine aortic endothelial cells was enhanced by pretreatment of the cells with pertussis toxin or islet-activating protein (IAP) for 5 hr or longer. Although ADP-ribosylation of a protein with a molecular weight of 41-42 kD in the cell membranes was completed by 3 hr after the addition of IAP into the incubation medium, there was good correlation between enhancement of bradykinin-induced prostacyclin synthesis and ADP-ribosylation of the IAP substrate over a wide range of IAP concentrations. Furthermore, even if IAP was removed from the incubation medium at 3 hr, bradykinin-induced prostaglandin synthesis at 24 hr was still potentiated. Cycloheximide and actinomycin D enhanced bradykinin-induced prostacyclin synthesis and apparently blocked the effect of IAP. Since this result suggested the involvement of an inhibitor protein(s) of prostacyclin synthesis in the IAP effect, we studied the effect of IAP on the level of lipocortin I which is known to inhibit phospholipase A2. Western and Northern blot analyses revealed that IAP decreased the amounts of protein and mRNA of lipocortin I. These results suggest that the enhancement of bradykinin-induced prostacyclin synthesis by IAP is associated with a decrease in the level of lipocortin I.

Adenosine Diphosphate Ribose↗
PubMed1990

The role of lipocortin I in macrophage-mediated immunosuppression in tumor-bearing mice.

The soluble mediators and/or mechanisms involved in immunosuppression in tumor-bearing hosts are not well characterized, although macrophages have long been recognized as major participants. We have investigated the role of lipocortin I, a phospholipid-binding protein, in macrophage-mediated immunosuppression in tumor-bearing mice. Proliferation of splenic lymphocytes in response to the mitogens (PHA, Con A, LPS, and PWM) was severely suppressed in tumor (Sqc-NH-1 carcinoma)-bearing mice. This immunosuppression was associated with a decrease in T and B lymphocytes and an increase in macrophages in these spleens. Mac-2+ macrophages were found only in spleens from tumor-bearing mice. Splenic macrophages from tumor-bearing, but not normal, mice were responsible for this immunosuppression, as revealed by negative and positive selection experiments. The levels of lipocortin I mRNA expression were markedly increased in peripheral blood cells from tumor-bearing mice as compared with those from normal mice. Lipocortin I mRNA was strongly induced in splenic mononuclear cells from tumor-bearing mice. Furthermore, these cells displayed increased expression of lipocortin I protein, as judged by Western blot analysis with polyclonal anti-lipocortin I serum. Some nonimmune organs such as the heart, submaxillary gland, muscle, and bladder also displayed increased levels of lipocortin I mRNA expression in tumor-bearing mice. Mac-2+ macrophages among the splenic mononuclear cells in tumor-bearing mice expressed lipocortin I mRNA, as judged by negative and positive selection experiments. Most of these Mac-2+ macrophages also had Mac-1 and Mac-3 Ag. Lipocortin I protein was increased in the serum of tumor-bearing mice as compared with normal mice. The culture supernatants of splenic cells from tumor-bearing mice suppressed the mitogenic responses of splenic cells from normal mice, and addition of anti-lipocortin I antiserum inhibited this suppression. Furthermore, recombinant mouse lipocortin I suppressed mitogenic responses of splenic cells from normal mice. In summary, Mac-2+ macrophage-derived lipocortin I was largely involved in immunosuppression in tumor-bearing mice.

Animals↗
PubMed1990

Constitutive expression of interleukin-7 mRNA and production of IL-7 by a cloned murine thymic stromal cell line.

Mouse interleukin-7 (IL-7) cDNA was cloned from mouse thymic stromal cell clone MRL 104.8a using a polymerase chain reaction (PCR) technique and expressed in COS-7 cells. The resulting recombinant interleukin-7 (rIL-7) supported the proliferation of mouse antigen-specific helper T cell (Th) clone 9-16 in the absence of IL-2 and antigen as well as mouse pre-B cell line DW34. It was also found that high levels of the mRNA for IL-7 were constitutively expressed in the MRL104.8a cells, and a potent amount of IL-7 was produced in its culture supernatant. These results provide the evidence for constitutive expression of IL-7 mRNA and for production of IL-7 by thymic stromal cells that have a critical role in intrathymic T cell development. The results are discussed in the context of the functional and molecular relationship between IL-7 and the previously described cytokines produced by thymic stromal cells.

Animals↗
PubMed1988

Evolutionary dynamics of tryptophan tRNAs in Mycoplasma capricolum.

Mycoplasma capricolum uses two tryptophan codons, the "universal" nonsense codon UGA and the universal codon UGG. The bacterium contains two tryptophan tRNAs, one with anticodon UCA, (U: 2'-O-methyl U derivative), and the other with CCA (5'-C: partially 2'-O-methylated). tRNAUCA would translate codons UGA and probably UGG by wobbling. tRNACCA is much less charged by tryptophan in the cells than tRNAUCA, and the intracellular amount of tRNACCA is 5-10 times lower than that of tRNAUCA. The genes for these two tRNAs are separated by a terminator-like structure in a single operon. In vitro transcription experiments suggest that the predominance of tRNAUCA over tRNACCA results from the attenuation of transcription by this terminator-like structure.

Base Sequence↗
PubMed1985

UGA is read as tryptophan in Mycoplasma capricolum.

UGA is a nonsense or termination (opal) codon throughout prokaryotes and eukaryotes. However, mitochondria use not only UGG but also UGA as a tryptophan codon. Here, we show that UGA also codes for tryptophan in Mycoplasma capricolum, a wall-less bacterium having a genome only 20-25% the size of the Escherichia coli genome. This conclusion is based on the following evidence. First, the nucleotide sequence of the S3 and L16 ribosomal protein genes from M. capricolum includes UGA codons in the reading frames; they appear at positions corresponding to tryptophan in E. coli S3 and L16. Second, a tRNATrp gene and its product tRNA found in M. capricolum have the anticodon sequence 5' U-C-A 3', which can form a complementary base-pairing interaction with UGA.

Biological Evolution↗
PubMed1983

[Estimation of drug-metabolizing enzyme activities by measuring urinary metabolites of aspirin].

The effect of the inducers of drug-metabolizing enzymes on the urinary excretion of aspirin metabolites in rats was studied. As to the inducer, rats were administered polychlorinated biphenyls (KC-500: 10, 50, and 100 mg/kg b.w.), phenobarbital (80 mg/kg b.w.), or 3-methylcholanthrene (25 mg/kg) intraperitoneally once a day for three days. The rats were orally administered aspirin (50 mg/kg) on the second-10th day after the pre-treatment with each inducer, and the urine were collected respectively. Aspirin metabolites (salicylic acid, salicyluric acid, and gentisic acid) in the urine were simultaneously determined with high-performance liquid chromatography and the liver microsomal cytochrome P-450 was determined. The results obtained were as follows. Excretion rate of total gentisic acid and salicylate glucuronide in the urine collected for first 6 hours were increased significantly by the pre-treatment with KC-500 or phenobarbital. In the pre-treated rats with various dose of KC-500, positive correlation was observed between the amount of liver microsomal cytochrome P-450 and the urinary excretion rate of gentisic acid (p less than 0.001). Salicylic acid hydroxylating activity of liver microsome was increased in the rats pretreated with KC-500, phenobarbital, or 3-methylcholanthrene. These results show that the increased urinary excretion of total gentisic acid and salicylate glucuronide may be due to the induction of drug-metabolizing enzymes in the liver. Therefore, it may be expected that these two aspirin metabolites are good indicators for the estimation of the activities of drug-metabolizing enzymes in vivo.

Animals↗
PubMed1976

[Induction of mouse and rat liver microsomal enzymes by polychlorinated biphenyls and its relations to the PCB levels in the tissue].

Kanechlor (KC)-300, 400, 500, and 600 consisting of polychlorinated biphenyls (PCB) containing 43, 48, 55, and 61% chlorine respectively, were administered in a single dose of 100 mg/kg to mice and rats. The effect of PCB was investigated by determining pentobarbital sleeping time, liver microsomal hemoprotein contents, PCB level and gaschromatography (GC) pattern in tissue. Pentobarbital sleeping time was prolonged 2 to 4 times longer than that of control level after 3 to 4 hr of KC treatment in both ICR and ddN strain mice and KC-300 was the most effective. Forty-eight hr after treatment, however, this sleeping time was half that of the control. Sleeping time in ICR strain mice returned to control level 8 days after the treatment with KC-300 and KC-500, but the decrease in sleeping time continued in ddN mice. Conversely, the prolongation of sleeping time in rats was only 20% the control level at 3 hr after KC-300 treatment, but the shortening of sleeping time was more marked than in mice. Both the prolongation of sleeping time in mice treated with KC-300 and the shortening of sleeping time in rats treated wiht KC-500 were more rapidly effected when an oral dose rather than when a intraperitoneal one was given. Induction of liver microsomal cytochrome P-450 level was maximum in rats treated with KC-600 and increase of hemoprotein level and shortening of sleeping time were proportional to the chlorine content of PCB. The CO-difference spectrum of microsomes from rats treated with KC had an absorbance maximum at 448 nm. Direct relationship between storage of PCB in adipose tissue and the induced effect by KC has also been demonstrated in rats. PCB level in the liver of rats was higher for about 8 hr after KC-500 treatment given orally and was lower than the PCB level in adipose tissue after 8 hr. The GC-pattern of PCB stored in tissues was different from that of standard KC, indicating that all components were not metabolized at the same rate and that the components of the KC with the longer retention time were metabolized to a lesser degree than those with the shorter retention time.

Adipose Tissue↗
PubMedDate not supplied

Analysis of TCRAV and TCRBV repertoires in healthy individuals by microplate hybridization assay.

We have developed an adaptor ligation PCR-based microplate hybridization assay (MHA) for analysis of T cell receptor alpha chain variable region (TCRAV) and T cell receptor beta chain variable region (TCRBV) repertoires. Forty three TCRAV and thirty eight TCRBV-specific probes were immobilized onto microplate wells in water-soluble carbodiimide. After hybridization of 5'-biotinylated PCR products, quantitative ELISA was carried out and followed by automated colorimetric reading. The conditions for immobilization and hybridization were optimized using representative TCRBV-specific probes. The sensitivity of MHA allows us to detect as low as 40 pg of biotinylated PCR products. The frequencies of individual V segments obtained by MHA were consistent with those obtained by FACS analysis and reverse dot blot assays. Analysis of the entire TCRAV and TCRBV repertoires could be done using a single 96-well plate, and completed in less than 6 h. Simplicity and reproducibility of this method make it suitable for routine laboratory use. The expression of TCRAV and TCRBV segments was next studied in peripheral blood mononuclear cells (PBMC) of 14 healthy donors using the newly developed MHA method. TCRAV8S1, TCRAV23S1, TCRBV2S1, TCRBV3S1, TCRBV4S1, and TCRBV6S5 were highly expressed in PBMC. Further, the TCRAV repertoires among individuals were less variable compared to the TCRBV repertoires. Interestingly, considerable variations in the expression levels of BV3S1, BV4S1, and BV17S1 were observed among individuals. One polymorphic site was found at the coding region of BV4S1, and there were two alleles. These results suggest that variable expression among individuals may be associated with unknown allelic polymorphism in coding and/or regulatory regions of these TCRBV segments, or with disparity in HLA genes.

Flow Cytometry↗
PubMedDate not supplied

Development of a syngenic brain-tumor model resistant to chloroethyl-nitrosourea using a methylguanine DNA methyltransferase cDNA.

Chloroethyl-nitrosourea (CENU) is one of the most potent chemotherapeutic agents for brain tumors. However, acquired resistance to this drug has become a serious problem in the treatment of brain tumor patients. The main mechanism of the resistance is a recruitment of the O6-methylguanine-DNA- methyltransferase (MGMT) in tumor cells. Many approaches, including treatment with enzyme-depletions, antibodies, antisenses, and a ribozyme, have been reported to successfully overcome the resistance. In order to evaluate these approaches properly, we designed a syngenic rat brain-tumor model resistant to CENU. The 9L rat gliosarcoma cells were retrovirally transduced with MGMT cDNA and stereotactically implanted into the brain parenchyma. In this model, rats inoculated with resistant cells died significantly earlier than did rats with control cells after treatment with CENU. Because of the limited intracranial space, the animals presented a restricted survival. Since the survival was sensitive and reproducible, this system may have a role in the evaluation of approaches to drug-resistant brain-tumors.

Animals↗