Biomedical subjects

K Sakamoto

Publications and source records attributed to K Sakamoto.

At least 289 records · Page 16Linked to original sources

PubMed1997

The photogenotoxicity of titanium dioxide particles.

We employed a series of in vitro genotoxicity assays--a single cell gel (SCG) assay with mouse lymphoma L5178Y cells, a microbial mutation assay with Salmonella typhimurium, a mammalian cell mutation assay with L5178Y cells, and a chromosomal aberration assay with Chinese hamster CHL/IU cells--to evaluate the photogenotoxicity of titanium dioxide (TiO2) particles. Without UV/visible light irradiation, TiO2 particles exhibited no or weak genotoxicity. With irradiation, however, TiO2 particles exhibited significant genotoxicity in the SCG and chromosomal aberration assays. Therefore, we concluded that TiO2 particles are photogenotoxic.

Animals↗

PubMed1997

Cleavage effect of oligoribonucleotides substituted at the cleavage sites with modified pyrimidine- and purine-nucleosides.

The precursor of an RNA molecule from T4-infected E. coli cells (p2Spl RNA) has the capacity to cleave itself at specific positions [UpA (139-140) and CpA (170-171)], within a putative loop and stem structure. This sequence-specific cleavage requires at least a monovalent cation and non-ionic detergents. In order to determine the influence of the pyrimidine and purine bases on these sequence-specific cleavage reactions, we studied the cleavage reactions of hairpin loop RNAs substituted at the cleavage sites with modified pyrimidine- and purine-nucleosides. The cleavage was affected by the 2'-hydroxyl groups and the bases of the pyrimidines, and the 6-amino group of the purine.

Base Composition↗

PubMed1997

Leukemia inhibitory factor induces apoptosis and proliferation of human carcinoma cells through different oncogene pathways.

Leukemia inhibitory factor (LIF) affects the growth of carcinoma cells, and we thus analyzed its underlying mechanisms. Carcinoma cells constitutively express LIF mRNA, and 23 lines (92.0%) and all (100%) of 25 lines express LIF receptor mRNAs of LIFRbeta and gp130, respectively. Exogenous addition of LIF promoted significant cell proliferation in 4 lines (MCF-7, ZR-75-1, Hs-700T and Panc-1) and suppressed cell growth in 3 lines (AZ-521, GBK-1 and HT-29). LIF significantly induced an immediate early response of genes c-fos and junB 3 hr after stimulation, but not of c-jun during the process of proliferation of MCF-7 and Hs-700T cells, with maximum levels at 30-60 min. The cell-cycle-related gene cyclin E was also induced in MCF-7 and Hs-700T cells, whereas cyclinA, cdk2, c-myc, c-myb and p53 mRNAs were not induced. On the other hand, LIF inhibited growth and increased the rate of cell death of AZ-521 and GBK-1 cells. LIF increased the number of TUNEL-positive cells in AZ-521 cells and DNA fragmentation in AZ-521 and GBK-1 cells. LIF induced apoptosis related genes c-myc and ICE during suppression of cell growth, but p53, p21, c-fos, cyclin A and cyclin E were not induced. Our results suggest that LIF is linked to cell proliferation and apoptosis in some human carcinoma cell lines. It is considered that this is related to differences in signal transduction and induction of oncogenes.

Apoptosis↗

PubMed1997

Probing the ubiquinone reduction site of mitochondrial complex I using novel cationic inhibitors.

A wide variety of N-methylpyridinium and quinolinium cationic inhibitors of mitochondrial complex I was synthesized to develop potent and specific inhibitors acting selectively at one of the two proposed ubiquinone binding sites of this enzyme (Gluck, M. R., Krueger, M. J., Ramsay, R. R., Sablin, S. O., Singer, T. P., and Nicklas, W. J. (1994) J. Biol. Chem. 269, 3167-3174). N-Methyl-2-n-dodecyl-3-methylquinolinium (MQ18) inhibited electron transfer of complex I at under microM order regardless of whether exogenous or endogenous ubiquinone was used as an electron acceptor. The presence of tetraphenylboron (TPB-) potentiated the inhibition by MQ18 in a different way depending upon the molar ratio of TPB- to MQ18. In the presence of a catalytic amount of TPB-, the inhibitory potency of MQ18 was remarkably enhanced, and the extent of inhibition was almost complete. The presence of equimolar TPB- partially reactivated the enzyme activity, and the inhibition was saturated at an incomplete level (approximately 50%). These results are explained by the proposed dual binding sites model for ubiquinone (cited above). The inhibition behavior of MQ18 for proton pumping activity was similar to that for electron transfer activity. The good correlation of the inhibition behavior for the two activities indicates that both ubiquinone binding sites contribute to redox-driven proton pumping. On the other hand, N-methyl-4-[2-methyl-3-(p-tert-butylphenyl)]propylpyridinium (MP6) without TPB- brought about approximately 50% inhibition at 5 microM, but the inhibition reached a plateau at this level over a wide range of concentrations. Almost complete inhibition was readily obtained at low concentrations of MP6 in the presence of TPB-. Thus MP6 appears to be a selective inhibitor of one of the two ubiquinone binding sites. With a combined use of MP6 and 2,3-diethoxy-5-methyl-6-geranyl-1,4-benzoquinone, we also provided kinetic evidence for the existence of two ubiquinone binding sites.

1-Methyl-4-phenylpyridinium↗

PubMed1997

Group II phospholipase A2 is increased in peritoneal and pleural effusions in patients with various types of cancer.

Serum levels of group II phospholipase A2 (PLA2) have been reported to be associated with stage of disease in cancer patients. These levels are also related to the malignant potential in tissues, and are an important prognostic factor. We radioimmunoassayed group II PLA2 levels in pleural and peritoneal effusions from patients with various cancers. We also investigated the production of group II PLA2 in cells in effusions from cancer patients by Northern blotting, immunocytochemistry and in situ hybridization. Immunoreactive group II PLA2 levels were significantly higher in effusions from 47 patients with various cancers, compared with those in sera and cirrhotic ascites. There was no significant correlation between group II PLA2 levels in effusions and those in sera. Group II PLA2 mRNA was expressed at a high level in cells from effusions, by Northern blot analysis, but not in those cells from blood. The localization of group II PLA2 protein and mRNA was intense in carcinoma cells and CD68-positive macrophages, determined by immunocytochemistry and in situ hybridization. In addition, IL-6 and IL-8 levels were significantly higher in effusions, in comparison with those in sera from patients, suggesting that cancer cells and macrophages produce group II PLA2 by IL-6. These group II PLA2 levels are apparently significantly increased in effusions, and the carcinoma cells and macrophages produce group II PLA2, as noted in effusions from patients with various cancers.

Adult↗

PubMed1997

Identification of a chick homologue of Fringe and C-Fringe 1: involvement in the neurogenesis and the somitogenesis.

In Drosophila, Serrate plays an important role to the wing margin formation. A putative secretory protein, Fringe, is indispensable for the wing margin formation inducing Serrate and other genes. Recently, Xenopus homologues of Fringe were identified and one of them, lunatic Fringe (X-lFng), was demonstrated to be involved in mesoderm induction. We have identified two chick Fringe homologous genes by reverse transcription-polymerase chain reaction and cDNA library screening. One of them, C-Fringe 1, showed sequence similarity to X-lFng. In situ hybridization study of C-Fringe 1 has demonstrated its expression in the developing nervous system and in the presomitic mesoderm. The hindbrain and spinal cord showed the distinct stripe pattern expression which was complementary to that of C-Serrate, indicating the correlation between them in vertebrate.

Amino Acid Sequence↗

PubMed1997

Genomic organization and characterization of the gene encoding bovine prostaglandin F2alpha receptor.

We isolated genomic clones for bovine prostaglandin (PG) F2alpha receptor by the standard plaque hybridization method, using the cDNA fragments of bovine PGF2alpha receptor (PGF2alphaR) as probe DNAs. The coding regions of this receptor gene were interspersed by a large intron sequence (33 kb) at the splice junction in the sixth transmembrane domain. The 5'-RACE experiments revealed two alternative transcription start points (tsp), indicating the existence of two potential promoter regions. The major promoter, which was named promoter region A, was located upstream of exon 1 and lacked the typical TATA sequence and CAAT box but had three GC boxes with an overall high GC content. Another putative promoter, region B, was found upstream of exon 2 and had both a TATA-like sequence and a CAAT-like box with several potential binding sites for transcription factors. Southern blot analysis indicated that a single copy gene in the haploid genome encodes PGF2alphaR. Promoter activities of these two putative promoter regions were assayed in the bovine luteal cells, and one of them (promoter region A) was activated by phorbol 12-myristate 13-acetate (TPA) treatment.

Amino Acid Sequence↗

PubMed1997

Effects of bovine serum proteins in culture medium on post-warming survival of bovine blastocysts developed in vitro.

Experiments were conducted to investigate the factors affecting the survival of bovine blastocysts produced in vitro after cryopreservation by vitrification. Zygotes were obtained by in vitro maturation and fertilization of oocytes. Embryos used in this study were developed in vitro at Day 7 and 8 (Day 0 = insemination day) in modified synthetic oviduct fluid medium supplemented with calf serum or BSA. Embryos were cryopreserved in a two-step protocol consisting of exposure to 10% ethylene glycol for 5 min, followed by the original vitrification solution (designated as VS) consisting of 40% (v/v) ethylene glycol, 6% (w/v) polyethylene glycol and 0.5 M sucrose in phosphate-buffered saline for 1 min. After warming, embryos were cultured in modified TCM-199 for an in vitro survival assay. The highest survival rate was obtained from the warmed embryos developed at Day 7 in medium supplemented with BSA (82.6%), and there were significant differences between results with calf scrum and BSA treatment (42.4 and 70.7%, respectively; P < 0.01). However, there were no significant differences in the cell numbers of embryos among the treatments. These results suggest that the survival of embryos developed in medium with BSA is superior to that of embryos developed in medium containing calf serum, although the cell numbers of the embryos developed under both media were similar.

Journal Article↗

PubMed1997

Immunological studies of SK2 hybridoma cells microencapsulated with alginate-poly(L)lysine-alginate (APA) membrane following allogeneic transplantation.

Microencapsulation of living cells or tissues has been proposed to prevent their immune destruction following transplantation. In this study, we examined whether SK2 hybridoma cells microencapsulated in an alginate-poly(L)lysine-alginate (APA) membrane (APA-SK2 cells) were immunoisolated from the allogeneic host's immune system using a cytotoxicity test. The APA membrane inhibited the activation of the host's cellular immune response, but did not prevent the production of cytotoxic antibodies against entrapped SK2 cells following allogeneic transplantation. However, the APA-SK2 cells remained vital in SK2 cell-immunized mice as well as in intact mice. We considered that complement regulatory factors which were present on cell membrane and had species-specific restriction blocked the complement-mediated cell lysis on allogeneic transplantation, since APA-SK2 cells were destroyed by rabbit anti-SK2 cell antiserum. Our results demonstrated that APA membrane could inhibit cell-cell contact between entrapped cells and the host's lymphocytes, but could not completely protect the entrapped cells from xenogeneic humoral immunity.

Adoptive Transfer↗

PubMed1997

A dual effect of 1-methyl-4-phenylpyridinium (MPP+)-analogs on the respiratory chain of bovine heart mitochondria.

We examined effects of several compounds, structurally related to 1-methyl-4-phenylpyridinium (MPP+), on the NADH-dependent respiration of bovine heart submitochondrial particles. 1-Methyl-4-(3 '-trimethylammoniophenyl)pyridinium (analog 8) as well as MPP+ completely inhibited O2 consumption, reduction of ubiquinone-10, and reduction of cytochrome b in a dose-dependent manner. The production of superoxide (O2-) induced by MPP+ or analog 8 was to the same extent as that by rotenone, an inhibitor of complex I of the mitochondrial respiratory chain. Rotenone had no additive effect on the maximal production of O2- induced by MPP+ or analog 8, suggesting that the production was mediated by the same way as rotenone. 1-Methyl-4-(4'-nitrophenyl) pyridinium (analog 1) induced about 20-fold more production of O2 than MPP+ and the production was additively increased by rotenone. Analog 1 only partially inhibited rotenone-sensitive O2 consumption. Paraquat induced the production of O2- as much as analog 1. Paraquat, however, did not inhibit rotenone-sensitive O2 consumption or reduction of cytochrome b. These results suggest that MPP+ and its analogs interact with the mitochondrial respiratory chain at two sites, the substrate side of the rotenone-binding site and the rotenone-binding site. The analogs may be reduced to produce O2- at the former site and inhibit the respiratory chain at the latter site.

Animals↗

PubMed1997

Effect of combination treatment of 15 cGy total body irradiation and OK-432 on spontaneous lung metastasis and mitogenic response of splenocytes in mice.

We investigated whether the combination treatment of 15 cGy total body irradiation (TBI) and a streptococcal preparation, OK-432, synergistically suppresses spontaneous lung metastasis and augments phytohemagglutinin (PHA) and concanavalin A (Con A) responses of splenocytes in WHT/Ht mice. TBI with 15 cGy was carried out 20 days after subcutaneous injection of squamous cell carcinoma cells into a hind leg. Lung colony number was counted 40 days after tumor injection. For PHA and Con A responses, mice were killed 4 hr after 15 cGy TBI. The combination treatment of 15 cGy TBI and OK-432 was most effective when OK-432 was administered 2 days before 15 cGy TBI. The combination treatment decreased the lung colony number to 29.9% of the control number. OK-432 slightly increased the PHA and Con A responses, and 15 cGy TBI did not increase them. However, when these two were combined, the PHA and Con A responses were significantly increased to 393% and 278% of the control levels, respectively. It was suggested that TBI and OK-432 acted synergistically in suppressing the lung metastasis and mitogenic response of splenocytes.

Animals↗

PubMed1997

IL-6 and soluble IL-6 receptor levels change differently after surgery both in the blood and in the operative field.

To investigate alterations in post-operative levels of IL-6 and soluble IL-6 receptor (sIL-6R), we examined their levels in serum and samples of drainage fluids from 26 patients who underwent thoracoabdominal surgery. Serum IL-6 levels reached the maximum within the first post-operative day and decreased thereafter. The IL-6 levels in the drainage fluid were much higher than in the serum (458 +/- 101-fold; mean +/- SEM) in the early post-operative phase. A large quantity of sIL-6R levels was present in blood samples. The time course of serum sIL-6R levels in 26 patients showed no significant change. sIL-6R concentrations in the drainage fluid were significantly lower than in serum (4.5 +/- 1.1-fold; mean +/- SEM) in the early post-operative phase. We propose that IL-6 is produced in the operative field and enters the peripheral blood stream to induce elevation of serum IL-6. On the other hand, sIL-6R levels in the operative field are lower than in the serum, and the serum sIL-6R levels are not influenced by surgical trauma. These data suggest that sIL-6R is being constantly produced in areas other than the operative field, while sIL-6R level is reduced by consumption in the operative field. Mechanisms to cope with surgical stress, involving sIL-6R together with its ligand IL-6 may thus exist.

Aged↗

PubMed1997

Closure of a gastric tube-tracheal fistula by transposition of a pedicled sternocleidomastoid muscle flap.

We treated a 65-year-old man presenting with a gastric tube-tracheal fistula, who had undergone subtotal esophagectomy. The radiological and endoscopical findings demonstrated a 4-mm gastric tube-tracheal fistula located just above the sternum. Conservative treatment using a flexible fiberscope and/or gastrofiberscope, including factor XIII with fibrinogen (Beriplast P, Tisseel, and Borheal), alpha-cyanoacrylate (Aron-alpha-A), n-butyl-2-cyanoacrylate (histoacryl), and human antihemolytic factor XIII (Fibrogammin P) in addition to total parenteral nutrition with no oral intake did not result in closure of the fistula. The fistula was therefore transected and closed through an upper median sternotomy and right partial intercostal incision followed by transposition of the sternocleidomastoid muscle flap between the gastric tube and trachea. The postoperative course was uneventful.

Aged↗

PubMed1997

Acute suppurative perithyroiditis: MR findings.

We report the MR findings in two cases of acute suppurative perithyroiditis. MR has the advantages over other imaging modalities of being able to distinguish areas of inflammation from adjacent normal tissue and of allowing imaging in planes which more accurately demonstrate the extent of the lesion. MR imaging is one of the most useful methods to evaluate this entity.

Acute Disease↗

PubMed1997

Correlation of lesions in the hippocampal region noted on MR images with clinical features.

The purpose of our work was to compare the MR imaging findings of obvious hippocampal and/or juxtahippocampal lesions with corresponding clinical features. Magnetic resonance images of 63 patients with obvious lesions in the hippocampal and/or juxtahippocampal regions were reviewed and their findings were correlated with patients' clinical characteristics. Based on the MR and clinical findings, the patients were divided into four groups: (a) 26 patients with space occupying lesions or suspected vascular malformation frequently causing symptomatic temporal epilepsy; (b) 14 with hippocampal infarcts, which when left-sided or bilateral caused amnesia; (c) 11 with encephalitis and 5 with old temporal contusion usually accompanied by both amnesia and epilepsy; and (d) 7 with temporal atrophy and progressive dementia of subacute onset. Magnetic resonance imaging allows precise localization and evaluation of the clinical correlates of hippocampal and juxtahippocampal lesions, which frequently caused symptomatic temporal epilepsy and/or amnesic syndrome.

Adolescent↗

PubMed1997

CT and MR imaging of craniopharyngioma.

We reviewed imaging findings of CT and MR imaging in 20 cases of surgically confirmed craniopharyngioma in an attempt to determine their relation to patterns of tumor extent. The relationship between these patterns and the frequency of preoperative CT diagnosis and MR imaging diagnosis according to the surgical diagnosis were determined. The CT technique was superior to MR imaging in the detection of calcification. The MR imaging technique was superior to CT for determining tumor extent and provided valuable information about the relationships of the tumor to surrounding structures. Thus, CT and MR imaging have complementary roles in the diagnosis of craniopharyngiomas. In cases of possible craniopharyngioma, noncontrast sagittal T1-weighted images may enable the identification of the normal pituitary, possibly leading to the correct diagnosis.

Adolescent↗

PubMed1997

Intervention of somatic mutational events in vivo by a germline defect at the adenine phosphoribosyltransferase locus.

Both germline and somatic mutations are known to affect phenotypes of human cells in vivo. In previous studies, we cloned mutant peripheral blood T cells from germline heterozygous humans for adenine phosphoribosyltransferase (APRT) (EC 2.4.2.7) deficiency and found that approximately 1.3 x 10-4 peripheral T cells had undergone in vivo somatic mutations. Loss of heterozygosity (LOH) was the major cause of the mutations at the APRT locus since approximately 80% of the mutant T cell clones exhibited loss of normal alleles. In the present study, we identified three heterozygous individuals for APRT deficiency (representing two separate families), in whom none of the somatic mutant cells exhibited LOH at the APRT locus. The germline mutant APRT alleles of these heterozygotes from two unrelated families had the same gross DNA abnormalities detectable by Southern blotting. None of the germline mutant APRT alleles so far reported had such gross DNA abnormalities. The data suggest that the germline mutation unique to these heterozygous individuals is associated with the abrogation of LOH in somatic cells. The absence of LOH at a different locus has already been reported in vitro in an established cell line but the present study describes the first such event in vivo in human individuals.

Adenine Phosphoribosyltransferase↗

PubMed1997

The Arg192 isoform of paraoxonase with low sarin-hydrolyzing activity is dominant in the Japanese.

The high-density-lipoprotein-associated enzyme paraoxonase, which has a role in the detoxification of organophosphorus compounds, is known to be polymorphic in humans. The Arg192 isoform of paraoxonase hydrolyzes paraoxon more rapidly than the Gln192 isoform. However, with respect to the hydrolysis of toxic nerve agents, such as diazoxon, soman, and sarin, the Arg192 isoform displays a lower activity than the other isoform. To evaluate the possibility that the genetic polymorphism was involved in the aggravated extent of human injury in the sarin gas poisoning incident in the Tokyo subway in March 1995, we investigated the prevalance of this polymorphism in the Japanese population. We found that the Arg192 allele is more common in the Japanese (allele frequency: 0.66) than in people of other races (ranging 0.24-0.31). In the Japanese, 135 out of the 326 subjects (41.4%) investigated were homozygous for the Arg192 allele, which shows a very low hydrolysis activity for sarin. Thus, there seems to be a racial difference in vulnerability to toxic nerve agents, such as sarin. The dominance of the Arg192 allele in the Japanese population probably worsened the tragedy of March 1995 in the Tokyo subway.

Alleles↗