Biomedical subjects

K Takai

Publications and source records attributed to K Takai.

At least 73 records · Page 4Linked to original sources

PubMed2000

Internal carotid artery aneurysm visualized during successful endovascular treatment of carotid embolism.

We herein present a case of an internal carotid artery embolism associated with a hidden internal carotid artery aneurysm. The aneurysm was visualized during successful endovascular treatment of the carotid embolism. In retrospect, the aneurysm was at risk of rupture during the procedure. In the endovascular treatment of cerebral embolism, the possibility that aneurysms are hidden by emboli must be borne in mind. Care should be taken not to injure unidentified arterial walls while advancing a catheter blindly.

Aneurysm↗

PubMed2000

[Transformation of severe aplastic anemia to myelodysplastic syndrome with monosomy 7 in a patient who achieved transfusion independence after immunosuppressive therapy].

A 72-year-old woman was given a diagnosis of severe aplastic anemia, and treated with anabolic steroid and cyclosporin A starting in October 1996. Because this treatment was ineffective, anti-thymocyte globulin (ATG) therapy was started in September 1997. In May 1998, chromosome analysis revealed transformation to myelodysplastic syndrome (MDS), refractory anemia with excess of blasts with monosomy 7 in 60% of metaphase cells. The patient showed gradual hematologic improvement and became transfusion independent. Despite progression to acute myeloid leukemia (FAB-M6) with monosomy 7 in 100% of metaphase cells in December 1998, the hemoglobin level recovered to 13.2 g/dl. In May 1999 the blasts increased rapidly and transformation to acute myelomonocytic leukemia (FAB-M4) was diagnosed. The patient was treated with low-dose Ara-C and aclarubicin with no improvement and died in August 1999. This case demonstrated the transformation of severe aplastic anemia to acute myeloid leukemia via MDS with monosomy 7 associated with transfusion independence after immunosuppressive therapy. These findings suggested a close relationship between aplastic anemia and hypoplastic MDS and the possibility of hematologic improvement based on the growth advantage of abnormal clones.

Aged↗

PubMed2000

Expression of adhesion molecules in childhood B-lineage-cell neoplasms.

We analyzed the expression pattern of adhesion molecules including beta 1-integrins (CD49c, CD49d, CD49e, CD49f), beta 2-integrins (CD11a, CD11b, CD11c), CD44, and CD54 in 141 children with B-cell precursor acute lymphoblastic leukemia (pre-B ALL) and in 21 children with B-cell ALL/non-Hodgkin's lymphoma (B-ALL/NHL). The frequencies of CD11a, CD49f, and CD44 expression were significantly higher in CD34+ pre-B ALL than in CD34- pre-B ALL. Although CD49d, CD49e, and CD44 were less frequently expressed in B-ALL/NHL than in pre-B ALL, the expression of CD11a and CD54 were more frequent in B-ALL/NHL. In pre-B ALL, expression of CD11a positively correlated with that of CD11b (P < .05) and CD54 (P < .01), and CD49c positively correlated with CD49f (P < .01). Of the clinical parameters of patients with pre-B ALL, expression of CD11a was associated with a low leukocyte count (P < .05). The presence of CD54 on the cell surface was an independent factor indicating a poor prognosis. The estimated 5-year event-free survival was 42.3% for CD54+ (n = 31) compared with 70.3% for CD54- patients (n = 38) (P < .05). These findings demonstrated that expression of adhesion molecules is dependent on the phenotype of B-lineage cells and that the expression of some of these molecules has clinical significance.

Antigens, CD↗

PubMed2000

[Angioimmunoblastic T-cell lymphoma associated with hemophagocytic syndrome at onset and relapse].

A 66-year-old woman was admitted with high fever, systemic lymphadenopathy, hepatosplenomegaly and pancytopenia. Bone marrow aspiration showed infiltration of atypical lymphoid cells and hemophagocytic histiocytes. The findings of lymph node biopsy were compatible with angioimmunoblastic T-cell lymphoma (AILD). A diagnosis of lymphoma-associated hemophagocytic syndrome (LAHS) was made. Treatment with the THP-COP regimen achieved clinical remission except for mild splenomegaly, but relapse of LAHS was confirmed two years after diagnosis. The patient's condition deteriorated rapidly, and she died of multi-organ failure one month later. Autopsy revealed extended, diffuse infiltration of lymphoma cells in almost all organs. Numerous macrophages showing phagocytosis of erythrocytes and nucleated cells were found in the adrenal glands, lungs, bone marrow, spleen and liver. Epstein-Barr virus genomes were not detected by in situ hybridization, but cytotoxic molecules were immunostained with TIA-1 and granzyme B in the lymphoma cells. Elevated serum levels of sIL-2R, IFN-gamma, IL-6 and M-CSF were found at the onset and relapse of lymphoma. Overproduction of these cytokines was considered to have contributed to the pathogenesis of HPS.

Aged↗

PubMed1999

The stem hairpin loop structure of p2Sp1 RNA is required for RNA-cleaving activity.

We studied the hairpin-loop structure of an RNA fragment (GUUUCGUACAAAC) (R13) with the sequence corresponding to the self-cleavage domain in the precursor of an RNA molecule from bacteriophage T4-infected Escherichia coli cells (p2Sp1 RNA). In order to determine the influence of the hairpin-loop structure on these sequence-specific cleavage reactions, we have synthesized oligoribonucleotides containing hairpin-loop, double-helical stem-loop, and single-stranded RNA structures. The cleavage was affected by the hairpin-loop structure. Furthermore, the helix-stem, which retains the thermodynamically extrastable stem hairpin-loop structures, is also important for the cleavage activity. However, the thermodynamically extrastable helix-stem structure reduced the cleavage activity of the adjacent UA and CA sequences at the helix-stem site. For the cleavage reactions of the RNA cleavage products, the R6 (ACAAAC), R7 (GUUUCGU), and R9 (GUUUCGUAC) mers from the parent RNA, R13 (GUUUCGUACAAAC), a very slight amount of cleavage product (2%) from the RNA 9 was observed, but no reaction occurred for the R6 and R7. We also describe the influences of the sequences (UA and CA) on the cleavage activity.

Base Sequence↗

PubMed1999

Sequence-specific inhibition of a transcription factor by circular dumbbell DNA oligonucleotides.

The inhibition of specific transcription regulatory proteins is a new approach to control gene expression. The transcriptional activities of DNA-binding proteins can be inhibited by the use of double-stranded oligonucleotides that compete for the binding to their specific target sequences in promoters and enhancers. We used nicked (NDODN-kappaB) and circular (CDODN-kappaB) dumbbell DNA oligonucleotides containing a NF-kappaB binding site to analyze the inhibition of the NF-kappaB-dependent activation of the human immunodeficiency virus type-1 (HIV-1) enhancer. The dumbbell DNA oligonucleotides are stable, short segments of double-stranded DNA with closed nucleotide loops on each end, which confer resistance to exonucleases. The dumbbell and other oligonucleotides (decoys) with the NF-kappaB sequence were found to compete with the native strand for NF-kappaB binding. The circular dumbbell and double-stranded phosphorothioate oligonucleotides competed with the native strand for binding to the NF-kappaB binding proteins, while the nicked NF-kappaB dumbbell was a less effective competitor. In Jurkat T-cells, the dumbbell and other oligonucleotides were tested for their ability to block the activation of the plasmid HIV-NL4-3 Luc. The CDODN-kappaB strongly inhibits the specific transcriptional regulatory proteins, as compared with the NDODN-kappaB and the double stranded phosphodiester oligonucleotides. On the other hand, the double stranded phosphorothioate oligonucleotides could also block this activation, but the effect was non-specific. The circular (CDODN) dumbbell oligonucleotides may efficiently compete for the binding of specific transcription factors within cells, thus providing anti-HIV-1 or other therapeutic effects.

Binding Sites↗

PubMed1999

Inhibition of HIV-1 replication by a two-strand system (FTFOs) targeted to the polypurine tract.

Reverse transcription of HIV-1 vRNA into the double-stranded DNA provirus involves initiation of plus-strand DNA synthesis at the polypurine tract (PPT) by reverse transcriptase (RT). The PPT is highly conserved among the known human immunodeficiency virus (HIV-1) strains and is a possible target for triplex formation. We show the effects of triple-helix formation by assays of primer extension inhibition in vitro, using a two-strand system (foldback triplex-forming oligonucleotides (FTFOs)) targeted to the PPT of HIV-1. The two-stranded composition of a triple-helix is thermodynamically and kinetically superior to the three-strand system. The FTFOs inhibited the RT activity in a sequence-specific manner, i.e. the triplex actually formed at the PPT and blocked the RT. The FTFOs containing the phosphorothioate groups at the antisense sequences showed greater 3'-exonuclease resistance. In HIV-1-infected MOLT-4 cells, the FTFOs containing the phosphorothioate groups at the antisense sequence sites and guanosine rich parts within the third Hoogsteen base-pairing sequence inhibit the replication of HIV-1 more effectively than the antisense oligonucleotides, indicating sequence-specific inhibition of HIV-1 replication.

Anti-HIV Agents↗

PubMed1999

Specific inhibition of human telomerase activity by transfection reagent, FuGENE6-antisense phosphorothioate oligonucleotide complex in HeLa cells.

Human telomerase might be associated with malignant tumor development and could be a highly selective target for antitumor drug design. Antisense phosphodiester (ODNs) and phosphorothioate (S-ODNs) oligonucleotides were investigated for their abilities to inhibit telomerase activity in the HeLa cell line. The ODNs and S-ODNs were designed to be complementary to nucleotides within the RNA active site of telomerase. As a transfection reagent, FuGENE6 was used to enhance the cellular uptake of oligonucleotides in cell cultures. The results showed that S-ODN-3 (19-mer) encapsulated with FuGENE6 clearly inhibited the telomerase activity in HeLa cells, and the inhibitory efficiency increased with an increase in the S-ODN-3. However, free S-ODN-3 showed no inhibitory activity. On the other hand, ODN-3 encapsulated with FuGENE6 had no detectable inhibitory activity. The encapsulated S-ODNs exhibited higher inhibitory activities than the free S-ODNs, and showed sequence specific inhibition. Thus, the activities of the S-ODNs were effectively enhanced by using the transfection reagent. The transfection reagent, FuGENE6, may thus be a potentially useful delivery vehicle for oligonucleotide-based therapeutics and transgenes, and is appropriate for use in vitro and in vivo.

Enzyme Activation↗

PubMed1999

Inhibition of restriction endonuclease cleavage by triple helix formation with RNA and 2'-O-methyl RNA oligonucleotides containing 8-oxo-adenosine in place of cytidine.

The ability of homopyrimidine oligoribonucleotides (RNA) and oligo-2'-O-methyl-ribonucleotides (2'-O-methyl RNA) containing 8-oxo-adenosine (AOH) and 8-oxo-2'-O-methyl (AmOH) adenosine to form stable, triple-helical structures with sequences containing the recognition site for the class II-S restriction enzyme, Ksp632-I, was studied as a function of pH. The AOH- and AmOH-substituted RNA and 2'-O-methyl RNA oligonucleotides were shown to bind within the physiological pH range in a pH-independent fashion, without a compromise in specificity. The substitutions of three cytidine residues with AOH showed higher endonuclease inhibition than the substitution of either one or two cytidine residues with AOH. In particular, the 2'-O-methyl RNA oligonucleotide with only one cytidine substituted with AmOH showed higher endonuclease inhibition than the homopyrimidine RNA and 2'-O-methyl RNA oligonucleotides and the RNA oligonucleotides containing either one or two AOH moieties. Furthermore, the AmOH-substituted 2'-O-methyl RNA oligonucleotides were stable (53%) after an incubation in 10% fetal bovine serum for 8 h, whereas the RNA oligonucleotides were completely degraded. Increased resistance to nucleases is observed with the introduction of 2'-O-methylnucleosides. This stabilization should help us to design much more efficient third strand homopyrimidine oligomer and antisense nucleic acid-based antiviral therapies, which could be used as tools in cellular biology.

Adenosine↗

PubMed1999

In vitro codon-reading specificities of unmodified tRNA molecules with different anticodons on the sequence background of Escherichia coli tRNASer.

The codon-reading properties of wobble-position variants of the unmodified form of Escherichia coli tRNASer1 (the UGA anticodon) were measured in a cell-free translation system. Two variants, with the AGA and CGA anticodons, each exclusively read a single codon, UCU and UCG, respectively. The only case of efficient wobbling occurred with the variant with the GGA anticodon, which reads the UCU codon in addition to the UCC codon. Surprisingly, this wobble reading is more efficient than the Watson-Crick reading by the variant with the AGA anticodon. Furthermore, we prepared tRNA variants with AA, UC, and CU, instead of GA, in the second and third positions and measured their relative efficiencies in the reading of codons starting with UU, GA, and AG, respectively. The specificity concerning the wobble position is essentially the same as that in the case of the codons starting with UC.

Amino Acid Sequence↗

PubMed1999

A single uridine modification at the wobble position of an artificial tRNA enhances wobbling in an Escherichia coli cell-free translation system.

5-Methoxyuridine was introduced into the first position of the anticodon of the unmodified form of tRNA(1Ser) from Escherichia coli. The codon reading efficiencies of this tRNA (tRNA(5-methoxyuridine UGA)) relative to those of the unmodified counterpart (tRNA(UGA)) were measured in a cell-free translation system. tRNA(5-methoxyuridine UGA) was more efficient than tRNA(UGA) in the reading of the UCU and UCG codons and was less efficient in the reading of the UCA codon. Thus, the single modification of U to 5-methoxyuridine can enhance the wobble readings.

Amino Acid Sequence↗

PubMed1999

Altered pharmacokinetics of a novel anticancer drug, UCN-01, caused by specific high affinity binding to alpha1-acid glycoprotein in humans.

The large species difference in the pharmacokinetics/pharmacodynamics of 7-hydroxystaurosporine (UCN-01) can be partially explained by the high affinity binding of UCN-01 to human alpha1-acid glycoprotein (AGP) (Fuse et al, Cancer Res., 58: 3248-3253, 1998). To confirm whether its binding to human AGP actually changes the in vivo pharmacokinetics, we have studied the alteration in its pharmacokinetics after simultaneous administration of human AGP to rats: (a) the protein binding of UCN-01 was evaluated by chasing its dissociation from proteins using dextran-coated charcoal. The UCN-01 remaining 0.1 h after adding dextran-coated charcoal to human plasma or AGP was approximately 80%, although the values for other specimens, except monkey plasma (approximately 20%), were <1%, indicating that the dissociation from human AGP was specifically slower than from other proteins; and (b) the pharmacokinetics of UCN-01 simultaneously administered with human AGP has been determined. The plasma concentrations after i.v. administration of UCN-O1 with equimolar human AGP were much higher than those after administration of UCN-01 alone. The steady-state distribution volume and the systemic clearance were reduced to about 1/100 and 1/200, respectively. Human AGP thus reduced the distribution and elimination of UCN-01 substantially. On the other hand, dog AGP, which has a low binding affinity for UCN-01, did not change the pharmacokinetics of UCN-01 so much. Furthermore, human AGP markedly reduced the hepatic extraction ratio of UCN-01 from 0.510 to 0.0326. Also, human AGP (10 microM) completely inhibited the initial uptake of UCN-01 (1 microM) into isolated rat hepatocytes, whereas the uptake of UCN-01 was unchanged in the presence of human serum albumin (10 microM). In conclusion, the high degree of binding of UCN-01 to human AGP causes a reduction in the distribution and clearance, resulting in high plasma concentrations in humans.

Alkaloids↗

PubMed1999

Modified nucleosides in the first positions of the anticodons of tRNA(Leu)4 and tRNA(Leu)5 from Escherichia coli.

Minor leucine tRNA species, tRNA(Leu)4 and tRNA(Leu)5, from Escherichia coli B have been reported to recognize leucine codons UUA and UUG [Goldman, E., Holmes, W. M., and Hatfield, G. W. (1979) J. Mol. Biol. 129, 567-585]. In the present study, these two tRNA(Leu) species were purified from E. coli A19, and the nucleotide sequences were determined by a post-labeling method. tRNA(Leu)5 was found to correspond to the tRNA gene reported as su degrees6 tRNA [Yoshimura, M., Inokuchi, H., and Ozeki, H. (1984) J. Mol. Biol. 177, 627-644]. The first letter of the anticodon was identified to be 2'-O-methylcytidine (Cm). tRNA(Leu)4 was identified as the minor leucine tRNA that has been sequenced previously (tRNA(Leu)UUR) [Yamaizumi, Z., Kuchino, Y., Harada, F., Nishimura, S., and McCloskey, J. A. (1980) J. Biol. Chem. 255, 2220-2225]. There was an unidentified modified nucleoside (N*) in the first position of the anticodon of tRNA(Leu)4. Nucleoside N* was isolated to homogeneity (1 A260 unit). By 1H NMR spectroscopy, nucleoside N was found to be a 2'-O-methyluridine derivative with a substituent having a -CH2NH2+CH2COO- moiety in position 5 of the uracil ring. On the basis of these NMR analyses together with mass spectrometry, the chemical structure of nucleoside N* was determined as 5-carboxymethylaminomethyl-2'-O-methyluridine (cmnm5Um). Nucleoside N* was thus found to be a novel type of naturally occurring modified uridine. Because of the conformational rigidity of Cm and cmnm5Um in the first position of the anticodon, these tRNA(Leu) species recognize the leucine codons UUA++ and UUG correctly, but never recognize the phenylalanine codons UUU and UUC.

Anticodon↗

PubMed1999

Lineage switch in childhood leukemia with monosomy 7 and reverse of lineage switch in severe combined immunodeficient mice.

Morphophenotypic lineage switches occur in a small percentage of those with acute leukemia, and the underlying mechanisms are not clear. In this study, we attempted to induce a lineage switch in acute myelocytic leukemia (AML) with monosomy 7, whose lineage had switched from acute T-lymphocytic leukemia (T-ALL) during chemotherapy, in severe combined immunodeficient (SCID) mice. Although the transplanted myeloid cells were engrafted in SCID mice without cytokine administration, T-ALL developed in SCID mice treated with recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. Analysis of the nucleotide sequences of the rearranged T-cell receptor gamma-chain (TCR-gamma) gene revealed that this lineage switch resulted from the selection of the T-lineage subclone in SCID mice, which had expanded at onset. In addition, we found that the T-lineage and myeloid cells belonged to the distinct subclones, which were different in TCR-gamma gene rearrangements, but were derived from a common clone with an identical N-ras gene mutation for both subclones. In in vitro cultures, only the myeloid subclone grew; the T-lineage subclone failed to grow even in the presence of recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. These results suggested that the initial diagnostic T-lymphoid subclone, whose growth was dependent on these cytokines and the hematopoietic microenvironment, emerged from a bipotential T-lymphoid/myeloid leukemic stem cell, and further genetic event(s) induced the myeloid subclone, which grew independently of these cytokines and the microenvironment.

Acute Disease↗

PubMed1999

Thrombotic microangiopathy associated with reactivation of human herpesvirus-6 following high-dose chemotherapy with autologous bone marrow transplantation in young children.

Thrombotic microangiopathy (TMA) is a serious complication of BMT. Several factors are important in the etiology of TMA, such as cyclosporin A, GVHD, irradiation, intensive conditioning chemotherapy and infection, which cause damage to vascular endothelial cells leading to activation of these cells. We describe two young children with TMA following high-dose chemotherapy with autologous BMT. Development of TMA was accompanied by reactivation of HHV-6, which was identified by both an increase in the copy number of HHV-6 DNA in the peripheral blood and a significant increase in antibody titers to HHV-6. Thus, it was suggested that reactivation of HHV-6 together with high-dose chemotherapy played an important role in the pathogenesis of TMA in these patients. Since HHV-6 is known to infect vascular endothelial cells, and CMV which is virologically closely related to HHV-6, has been reported to be a pathogen that causes TMA, infection with HHV-6 of vascular endothelial cells may induce TMA via damage and activation of these cells.

Bone Marrow Transplantation↗

PubMed1999

Genetic diversity of archaea in deep-sea hydrothermal vent environments.

Molecular phylogenetic analysis of naturally occurring archaeal communities in deep-sea hydrothermal vent environments was carried out by PCR-mediated small subunit rRNA gene (SSU rDNA) sequencing. As determined through partial sequencing of rDNA clones amplified with archaea-specific primers, the archaeal populations in deep-sea hydrothermal vent environments showed a great genetic diversity, and most members of these populations appeared to be uncultivated and unidentified organisms. In the phylogenetic analysis, a number of rDNA sequences obtained from deep-sea hydrothermal vents were placed in deep lineages of the crenarchaeotic phylum prior to the divergence of cultivated thermophilic members of the crenarchaeota or between thermophilic members of the euryarchaeota and members of the methanogen-halophile clade. Whole cell in situ hybridization analysis suggested that some microorganisms of novel phylotypes predicted by molecular phylogenetic analysis were likely present in deep-sea hydrothermal vent environments. These findings expand our view of the genetic diversity of archaea in deep-sea hydrothermal vent environments and of the phylogenetic organization of archaea.

Adaptation, Physiological↗

PubMed1999

Properties of circular dumbbell RNA/DNA chimeric oligonucleotides containing antisense phosphodiester oligonucleotides.

We have designed a new class of oligonucleotides, "dumbbell RNA/DNA chimeric phosphodiesters", containing two alkyl loop structures with RNA/DNA base pairs (sense (RNA) and antisense (DNA) in the double helical stem. The reaction of nicked (NDRDON) and circular (CDRDON) dumbbell RNA/DNA chimeric oligonucleotides with RNaseH gave the corresponding antisense phosphodiester oligonucleotide together with the sense RNA cleavage products. The liberated antisense phosphodiester oligodeoxynucleotide was bound to the target 35mer RNA, which gave 35mer RNA cleavage products by treatment with RNaseH. The circular dumbbell RNA/DNA chimeric oligonucleotide showed more nuclease resistance than the linear antisense phosphodiester oligodeoxynucleotide(anti-ODN) and the nicked dumbbell RNA/DNA chimeric oligonucleotide.

Base Pairing↗

PubMed1999

Phosphorothioate G3T4G3 motifs inhibits the early stage of HIV-1 infection.

It is well known that G-rich phosphorothioate oligonucleotides (G-rich PS) bind to the V3 loop of HIV-1 gp120 and inhibit HIV-1 infection. In this study, we investigated the inhibitory mechanism of a new type of G-rich PS (PS-G3T4G3) on the replication cycle of HIV-1. PS-G3T4G3 inhibits both cell to cell and cell free infections. Binding and entry assays revealed that the inhibitory step of PS-G3T4G3 occurs at the early stage of HIV-1 infection. V3 loop-specific mAb test showed that PS-G3T4G3 binds to the V3 loop and prevents its interaction with chemokine receptors. These results suggest that PS-G3T4G3 may be a novel candidate for an HIV-1 inhibitor.

Base Composition↗