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Biomedical subjects

Y Satow

Publications and source records attributed to Y Satow.

At least 37 records · Page 2Linked to original sources
PubMed1996

Influence of paternal (252) Cf neutron exposure on abnormal sperm, embryonal lethality, and liver tumorigenesis in the F(1) offspring of mice.

Experiments were conducted to determine whether neutron-induced genetic damage in parental germline cells can lead to development of cancer in the offspring. Seven-week-old C3H male mice were irradiated with (252) Cf neutrons at a dose of 0, 50, 100, or 200 cGy. Two weeks or three months after irradiation, the male mice were mated with virgin 9-week-old C57BL females. Two weeks after irradiation, the irradiated male mice showed an increased incidence of sperm abnormalities, which led to embryo lethalities in a dose-dependent manner when they were mated with unirradiated female mice. Furthermore, liver tumors in male offspring of male mice in the 50 cGy group were significantly increased in 19 of 44 (43.2%) animals, in clear contrast to the unirradiated group (1 of 31; 3.2%) (P < 0.01). In the 100 cGy group, 6 of 39 (15%) mice had lesions. At 3 months after irradiation abnormal sperm and embryonal lethality were not significantly increased. The incidences of liver tumors in male offspring from the 50 cGy, 100 and 200 cGy groups were 6 of 20 (30%), 5 of 22 (23%) and 1 of 19 (5%), respectively, which are not significantly increased compared with the control. It is concluded that increased hepatic tumor risk in the F(1) generation may be caused by genetic transmission of hepatoma-associated trait(s) induced by (252) Cf neutron irradiation.

Animals↗
PubMed1996

No alteration in DNA topoisomerase I gene related to CPT-11 resistance in human lung cancer.

Mutations and reduced expression of DNA topoisomerase I (topo I) gene have been shown to be important in the acquisition of resistance to camptothecin and its analogues in vitro, but their significance has not been verified in vivo. We investigated possible topo I gene mutations and topo I mRNA expression levels in 127 samples obtained from 56 patients with lung tumors, including patients who had developed clinical resistance to topo I inhibitors. No mutations were detected in any of the samples examined and expression levels did not differ significantly between clinically resistant cases and others. However, the topo I mRNA expression level was significantly higher in small cell lung carcinomas than in non-small cell lung carcinomas (P < 0.05). These results suggest that topo I mRNA levels may affect CPT-11 sensitivity in human lung cancer. However, topo I gene mutations and reduced topo I mRNA expression may not be the main mechanism of clinically acquired resistance to camptothecin analogues in vivo.

Adult↗
PubMed1995

Expression of the vascular endothelial growth factor (VEGF) receptor gene, KDR, in hematopoietic cells and inhibitory effect of VEGF on apoptotic cell death caused by ionizing radiation.

Vascular endothelial growth factor (VEGF) has been identified as a peptide growth factor specific for vascular endothelial cells. In this study, we demonstrated the expression of the KDR gene transcript, which encodes a cell surface receptor for VEGF, in normal human hematopoietic stem cells, megakaryocytes, and platelets as well as in human leukemia cell lines, HEL and CMK86. Moreover, we showed the expression of VEGF gene transcript in these normal fresh cells and cell lines. To elucidate biological functions of VEGF on hematopoiesis, we determined whether this growth factor has mitogenic activity to hematopoietic cells or the ability to suppress apoptotic cell death. The liquid culture and colony-formation assay revealed that VEGF suppressed apoptotic cell death of both CMK86 cells and normal hematopoietic stem cells caused by gamma-ray irradiation, although mitogenic activity of VEGF was not detected. The ability of VEGF to suppress apoptotic cell death was independent of the change of cell cycle distribution. These data suggest that VEGF may play an important role in survival or maintenance of hematopoietic stem cells due to the prevention of apoptotic cell death caused by some stresses such as ionizing radiation and that VEGF may give leukemia cells some abilities of resistance against radiotherapy in an autocrine or paracrine manner.

Apoptosis↗
PubMed1995

Crystal structure of Ustilago sphaerogena ribonuclease U2 at 1.8 A resolution.

The crystal structure of purine-specific ribonuclease (RNase) U2 from Ustilago sphaerogena has been solved by the molecular replacement methods using RNase T1 as a search model. The structure, with 114 amino acid residues, 141 water molecules, and a sulfate ion, is refined to an R factor of 0.143 at 1.8 A resolution. As evidenced by the electron densities, residues 49 and 50 are revised to Glu 49 and Asp 50, respectively, and also Asp 45 is identified as a beta-isomerized form to L-isoaspartate with a beta-peptide linkage. RNase U2 consists of a beta-hairpin at residues from 7 to 14, a 4.4-turn alpha-helix from 16 to 32, a central beta-sheet with five strands, and a protruding beta-turn from 74 to 77. As for the catalytic site residues, His 41, Glu 62, and Arg 85 are located as constituents of the central beta-sheet, and Tyr 39 and His 101 are situated at either end of the beta-sheet. The side chains of Tyr 39, Glu 62, Arg 85, and His 101 are hydrogen-bonded to the sulfate ion which marks the RNA phosphate position. Though the side chain of His 41 is pointing away from the sulfate, small conformational adjustments of His 41 enable the side chain to interact with either the phosphate or the ribose group of RNA. The loop region from Tyr 44 to Asp 50 is ascribed to the base recognition site where Glu 49 is involved in adenine recognition. beta-Isomerized Asp 45 suggests that this region is conformationally flexible and alterable.

Amino Acid Sequence↗
PubMed1995

Three-dimensional structures of the Fab fragment of murine N1G9 antibody from the primary immune response and of its complex with (4-hydroxy-3-nitrophenyl)acetate.

The three-dimensional structures of the Fab fragment, in its unliganded and liganded crystals, of mouse anti-(4-hydroxy-3-nitrophenyl)acetate (NP) antibody N1G9 have been determined by the molecular replacement method. The unliganded and NP-liganded structures were refined at 2.4 A resolution to crystallographic R-factors of 0.194 and 0.196, respectively. Antibody N1G9 bears lambda light chains, and is one of the primary immune response antibodies. Fab N1G9 exhibits an elbow angle of 197 degrees in both structures. This large angle is ascribed to the VL-CL interface formed by lambda-chain residues. A hydrophobic pocket surrounded by the complementarity-determining regions except L2 is identified as a hapten-binding site. Between the liganded and unliganded structures, root-mean-square (r.m.s.) positional deviations are 0.42 A for the main-chain atoms, and 0.74 A for all the protein atoms. The major structural differences between these structures are localized in the hapten-binding site, and yield an r.m.s. deviation of 1.03 A for the side-chain atoms. The soaked NP ligand is in van der Waals contact with the aromatic side-chains of Tyr32L and Trp91L of the light chain, and Trp33H and Tyr97H of the heavy chain, and is hydrogen-bonded to the side-chains of Trp96L, His35H, Arg50H, Tyr95H, and Ser100aH. The side-chain of Lys58H is salt-bridged to the NP hydroxyl group. The side-chains of Arg50H, Trp33H, and Tyr97H are shifted toward the NP carboxyl group. The side-chain of Trp33H, whose replacement to Leu increases affinity by tenfold, is sandwiched between the Arg50H and Tyr97H side-chains, and is in cramped contact both with the ligand and with these side-chains. Affinity increases in the maturation of the anti-NP antibodies are ascribable to conformational relief of these cramped contacts through the replacement of Trp33H or through suitable structural alterations in the H3 region.

Animals↗
PubMed1995

Expression of c-Mpl and c-Mpl ligand gene in hematopoietic cells of individuals with and without myeloproliferative disorders and leukemia cell lines.

We examined the expression of c-Mpl (MPL) and c-Mpl ligand (ML) gene in hematopoietic cells in individuals with and without myeloproliferative disorders (MPD) and leukemic cell lines by RT-PCR. The MPL gene transcripts were detected in normal CD34+ cells, platelets, megakaryocytes and monocytes, while the ML gene was expressed in CD34+ cells, megakaryocytes, T cells, monocytes and bone marrow fibroblasts, as well as liver tissue. The ML gene product produced in the bone marrow microenvironment might, in part, be involved in hematopoiesis. The MPL gene expression was detected in platelets and peripheral blood mononuclear cells from the majority of patients with MPD including chronic myelocytic leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). In contrast, the ML gene expression was found in the majority of ET and CML patients, but not in PV or PMF patients. These findings suggest that even in MPD the megakaryocytopoiesis depends on the MPL signal transduction system, and that in ET and CML, the ML production by mononuclear cells in the bone marrow microenvironment might play a part in the higher megakaryocytopoiesis observed in these diseases. Both the MPL and ML gene expression were detected in all the leukemic cell lines tested, suggesting that this cytokine/receptor system is involved in cell growth through autocrine and paracrine systems.

Base Sequence↗
PubMed1995

c-kit point mutation of extracellular domain in patients with myeloproliferative disorders.

c-kit is a tyrosine kinase receptor whose ligand is stem cell factor (SCF). Gene alteration of the c-kit extracellular domain was analysed by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) in 25 patients with myeloproliferative disorders (MPD). In the N-terminal part of the domain, mobility shifts indicating sequence alteration were detected in three of the patients, two primary myelofibrosis (PMF) and one chronic myelogenous leukaemia (CML). The subsequent sequencing revealed the same point mutations at codon 52 causing amino acid substitution (Asp-->Asn). To our knowledge this is the first report with a c-kit point mutation found in human fresh tumour cells.

Adult↗
PubMed1995

Platelet derived growth factor expression, myelofibrosis and chronic myelogenous leukemia.

CML is often associated with myelofibrosis, and fibrosis in the accelerated phase is one of the diagnostic criteria for this accelerated phase. In this review, the mechanism of myelofibrosis associated with CML is discussed with emphasis on the cell origin of the production and release of platelet derived growth factor (PDGF) and its interaction with marrow fibroblasts. In the initial stage of myelofibrosis in chronic phase CML, atypical small megakaryocytes might leak PDGF, possibly PDGF-AB, together with other growth factors. As the clinical phase of the disease progresses to accelerated or blastic phase, a larger quantity of PDGF-AB or PDGF-BB might be secreted from blastic cells with myeloid phenotype. In addition some fibroblasts may be attracted by the PDGF and proliferate, and deposit collagen as well as fibronectin in the bone marrow stroma.

Blast Crisis↗
PubMed1995

Leukemic transformation of primary myelofibrosis: immunophenotype, genotype and growth characteristics of blast cells.

Blast cells from six patients with leukemic transformation of primary myelofibrosis (PMF) were studied by morphology, immunophenotype and genotype as well as response to hematopoietic growth factors. The majority of the patients showed granulocytic or granulo-monocytic blasts, and only one had T lymphoid-monocytic blasts. None of the patients showed rearrangement of Ig or TCR genes, or the existence of the bcr-abl fused gene. A prominent growth response to GM-CSF and IL-3 was evident in all of the patients examined in liquid as well as semisolid cultures. The response to G-CSF was observed in four of the six patients in suspension culture, and in two of three patients in the clonogenic assay. Stem cell factor (SCF) was a weak growth stimulant, however the combination of this factor with GM-CSF or IL-3 was synergistically stimulatory. These results suggest that leukemic transformation of PMF occurs mainly at the level of myeloid stem cell, and that GM-CSF, IL-3, G-CSF and SCF are major growth factors for the blast cells in these cases.

Aged↗
PubMed1994

Structure of the allosteric regulatory enzyme of purine biosynthesis.

Multi-wavelength anomalous diffraction (MAD) has been used to determine the structure of the regulatory enzyme of de novo synthesis of purine nucleotides, glutamine 5-phosphoribosyl-1-pyrophosphate (PRPP) amidotransferase, from Bacillus subtilis. This allosteric enzyme, a 200-kilodalton tetramer, is subject to end product regulation by purine nucleotides. The metalloenzyme from B. subtilis is a paradigm for the higher eukaryotic enzymes, which have been refractory to isolation in stable form. The two folding domains of the polypeptide are correlated with functional domains for glutamine binding and for transfer of ammonia to the substrate PRPP. Eight molecules of the feedback inhibitor adenosine monophosphate (AMP) are bound to the tetrameric enzyme in two types of binding sites: the PRPP catalytic site of each subunit and an unusual regulatory site that is immediately adjacent to each active site but is between subunits. An oxygen-sensitive [4Fe-4S] cluster in each subunit is proposed to regulate protein turnover in vivo and is distant from the catalytic site. Oxygen sensitivity of the cluster is diminished by AMP, which blocks a channel through the protein to the cluster. The structure is representative of both glutamine amidotransferases and phosphoribosyltransferases.

Adenosine Monophosphate↗
PubMed1994

Platelet-derived growth factor expression in accelerated and blastic phase of chronic myelogenous leukaemia with myelofibrosis.

Myelofibrosis is sometimes associated with accelerated and blastic phase of chronic myelogenous leukaemia (CML). In order to investigate the role of platelet derived growth factor (PDGF) in this pathogenesis, expression and production of PDGF was studied in the blast cells from 11 patients. Five patients had myelofibrosis with myeloid blasts, while six patients did not show fibrosis, including three with myeloid blasts and three with lymphoid blasts. PDGF-A chain transcript was expressed in most of the patients. On the other hand, PDGF-B chain transcript was detected in all of the five patients with myeloid blasts and with fibrosis, in one of the three patients with myeloid blasts and without fibrosis, and in none of the three lymphoid crisis patients without fibrosis. In the patients with myeloid blasts and with fibrosis, PDGF protein, PDGF-AB and/or PDGF-BB, was found to be secreted from blast cells. In addition, the PDGF activity in the culture of myeloid blasts from two patients with fibrosis was also growth stimulatory for human marrow fibroblasts. These results suggest that expression and secretion of PDGF-AB or PDGF-BB in blast cells play an important role in the pathogenesis of marrow fibrosis associated with accelerated and blastic phase of CML.

Adult↗
PubMed1992

Crystal structure of an electron-transfer complex between methylamine dehydrogenase and amicyanin.

The crystal structure of the complex between the quinoprotein methylamine dehydrogenase (MADH) and the type I blue copper protein amicyanin, both from Paracoccus denitrificans, has been determined at 2.5-A resolution using molecular replacement. The search model was MADH from Thiobacillus versutus. The amicyanin could be located in an averaged electron density difference map and the model improved by refinement and model building procedures. Nine beta-strands are observed within the amicyanin molecule. The copper atom is located between three antiparallel strands and is about 2.5 A below the protein surface. The major intermolecular interactions occur between amicyanin and the light subunit of MADH where the interface is largely hydrophobic. The copper atom of amicyanin and the redox cofactor of MADH are about 9.4 A apart. One of the copper ligands, His 95, lies between the two redox centers and may facilitate electron transfer between them.

Bacterial Proteins↗
PubMed1992

Chemotactic activities of peripheral blood polymorphonuclear leukocytes and peritoneal exudate polymorphonuclear leukocytes in MRL mice.

Chemotactic responsiveness to fMet-Leu-Phe in concentrations of 10(-8) to 10(-4) M in the Boyden chamber was compared between peritoneal exudate cells (PEC) and polymorphonuclear leukocytes (PMN) isolated from peripheral blood, between MRL/Mp-+/+ (MRL-+/+) and MRL/Mp-lpr/lpr (MRL-lpr/lpr) mice, and between young (6-9 week old) and aged (16-24 week old) mice. Chemotactic responsiveness of PEC did not differ between MRL-+/+ and MRL-lpr/lpr, and young and aged mice. While, PMN showed greater chemotaxis in aged MRL-+/+ mice than that in aged MRL-lpr/lpr mice. These results suggest that chemotactic responsiveness of PMN differ from that of PEC which is assumed to be preactivated by an inflammatory agent injected into the peritoneal cavity to elicit cells. Less responsiveness of PMN to the bacterial origin peptide might relate to the autoimmune disease of this murine model.

Amino Acid Sequence↗
PubMed1991

Detection of HTLV-I antigen in peripheral and cord blood lymphocytes from carrier mothers.

Vertical transmission of human T-cell lymphotropic virus type-I (HTLV-I) from an antibody-positive carrier mother to her infant has been reported, but it is not clear when and by what route such transmission occurs. Peripheral blood and cord blood lymphocytes from 40 antibody-positive carrier mothers were cultured for 2 months and HTLV-I antigen was sought by indirect immunofluorescence. Viral antigen was detected in 28 (70%) samples of peripheral blood lymphocytes and in 2 of cord blood lymphocytes, both from mothers positive for antigen in peripheral blood. From these data it is estimated that transplacental infection occurs at a rate of about 7%.

Adult↗
PubMed1991

Refined crystal structure of the complex of subtilisin BPN' and Streptomyces subtilisin inhibitor at 1.8 A resolution.

The crystal structure of subtilisin BPN' complexed with a proteinaceous inhibitor SSI (Streptomyces subtilisin inhibitor) was refined at 1.8 A resolution to an R-factor of 0.177 with a root-mean-square deviation from ideal bond lengths of 0.014 A. The work finally established that the SSI-subtilisin complex is a Michaelis complex with a distance between the O gamma of active Ser221 and the carbonyl carbon of the scissile peptide bond being an intermediate value between a covalent bond and a van der Waals' contact, 2.7 A. This feature, as well as the geometry of the catalytic triad and the oxyanion hole, is coincident with that found in other highly refined crystal structures of the complex of subtilisin Novo, subtilisin Carlsberg, bovine trypsin or Streptomyces griseus protease B with their proteinaceous inhibitors. The enzyme-inhibitor beta-sheet interaction is composed of two separate parts: that between the P1-P3 residues of SSI and the 125-127 chain segment (the "S1-3 site") of subtilisin and that between the P4-P6 residues of SSI and th 102-104 chain segment (the "S4-6 site") of subtilisin. The latter beta-interaction is unique to subtilisin. In contrast, the beta-sheet interaction previously found in the complex of subtilisin Novo and chymotrypsin inhibitor 2 or in the complex of subtilisin Carlsberg and Eglin C is distinct from the present complex in that the two types of beta-interactions are not separate. As for the flexibility of the molecules comprising the present complex, the following observations were made by comparing the B-factors for free and complexed SSI and comparing those for free and complexed subtilisin BPN'. The rigidification of the component molecules upon complex formation occurs in a very localized region: in SSI, the "primary" and "secondary" contact regions and the flanking region; in subtilisin BPN', the S1-3 and S4-6 sites and the flanking region.

Bacterial Proteins↗
PubMed1991

Molecular recognition at the active site of subtilisin BPN': crystallographic studies using genetically engineered proteinaceous inhibitor SSI (Streptomyces subtilisin inhibitor).

Unlike trypsin-like serine proteases having only one conspicuous binding pocket in the active site, subtilisin BPN' has two such pockets, the S1 and S4 pockets, which accommodate the P1 and P4 residues of ligands (after Schechter and Berger notation) respectively. Using computer graphics, the geometrical nature of the two pockets was carefully examined and strategies for site-directed mutagenesis studies were set up against a protein SSI (Streptomyces subtilisin inhibitor), which is a strong proteinaceous inhibitor (or a substrate analogue) of subtilisin BPN'. It was decided to convert the P1 residue, methionine 73, into lysine (M73K) with or without additional conversion of the P4 residue, methionine 70, into glycine (M70G). The crystal structures of the two complexes of subtilisin BPN', one with the single mutant SSI (M73K) and the other with the double mutant SSI (M73K, M70G) were solved showing that (i) small 'electrostatic induced-fit movement' occurs in the S1 pocket upon introducing the terminal plus charge of the lysine side chain, and (ii) large 'mechanical induced-fit movement' occurs in the S4 pocket upon reducing the size of the P4 side chain from methionine to glycine. In both (i) and (ii), the induced-fit movement occurred in a concerted fashion involving both the enzyme and 'substrate' amino acid residues. The term 'substrate-assisted stabilization' was coined to stress the cooperative nature of the induced-fit movements.

Bacterial Proteins↗