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Biomedical subjects

T Nakayama

Publications and source records attributed to T Nakayama.

At least 55 records · Page 3Linked to original sources
PubMed2001

An evaluation of screening for lung cancer in Niigata Prefecture, Japan: a population-based case-control study.

Although an annual screening programme for lung cancer has been carried out widely in Japan since 1987, there is insufficient evidence to confirm its efficacy in terms of reducing mortality. In order to evaluate the efficacy of the lung cancer screening which has been widely carried out in Japan since 1987, a case-control study was conducted in Niigata Prefecture, Japan. In the study area, chest X-ray examinations for all participants and sputum cytology for high-risk participants were offered annually. Case subjects, who had died from lung cancer (174), and control subjects matched by sex, year of birth, residence and smoking status (801), who had been alive at the time of diagnosis of the corresponding case, were selected from the National Health Insurance holders. Screening histories of the subjects were compared between cases and matched controls for the identical calendar period before the time of diagnosis of the cases. The odds ratio of death from lung cancer for those screened within 12 months vs those not screened was 0.401 (95% CI: 0.272-0.591) with adjustment by smoking index. Our results suggest that annual lung cancer screening might reduce mortality from lung cancer by approximately 60%.

Adult↗
PubMed2001

The activity and signaling range of mature BMP-4 is regulated by sequential cleavage at two sites within the prodomain of the precursor.

Proteolytic maturation of proBMP-4 is required to generate an active signaling molecule. We show that proBMP-4 is cleaved by furin in a sequential manner. Cleavage at a consensus furin site adjacent to the mature ligand domain allows for subsequent cleavage at an upstream nonconsensus furin site within the prodomain. BMP-4 synthesized from precursor in which the upstream site is noncleavable is less active, signals at a shorter range, and accumulates at lower levels than does BMP-4 cleaved from native precursor. Conversely, BMP-4 cleaved from precursor in which both sites are rapidly cleaved is more active and signals over a greater range. Differential use of the upstream cleavage site could provide for tissue-specific regulation of BMP-4 activity and signaling range.

Amino Acid Sequence↗
PubMed2001

Malonyl-CoA:anthocyanin 5-O-glucoside-6"'-O-malonyltransferase from scarlet sage (Salvia splendens) flowers. Enzyme purification, gene cloning, expression, and characterization.

The orange to blue coloration of flowers in nature is, in most cases, provided by anthocyanins, a class of plant flavonoids, many of which are modified by malonyl group(s). However, the identity of the enzyme catalyzing the malonylation reaction remains to be established. Here, we describe for the first time the purification, characterization, and cDNA cloning of an anthocyanin malonyltransferase from scarlet sage (Salvia splendens) flowers. The purified enzyme (termed Ss5MaT1) was a monomeric 50-kDa protein catalyzing the regiospecific transfer of the malonyl group from malonyl-CoA to the 6"'-hydroxyl group of the 5-glucosyl moiety of anthocyanins. Ss5MaT1 showed a k(cat) value of 7.8 s(-1) at 30 degrees C and pH 7.0 for the malonylation of bisdemalonylsalvianin (pelargonidin 3-(6"-O-caffeyl-beta-glucopyranoside)-5-beta-glucopyranoside) and K(m) values of 101 microm and 57 microm for bisdemalonylsalvianin and malonyl-CoA, respectively. p-Coumaric acid, which mimics an aromatic acyl group linked to the 3-glucosidic moiety of an anthocyanin substrate, was a competitive inhibitor with respect to the substrate. This strongly suggests that the presence of an aromatic acyl group at the 3-glucosidic moiety of anthocyanin is important for substrate recognition by the enzyme. On the basis of the partial amino acid sequences of the purified enzyme, we isolated a cDNA encoding Ss5MaT1. Ss5MaT1 consisted of 462 amino acids and shared motifs that are commonly found among members of a versatile plant acyltransferase family, which was recently shown to include numerous homologs of unknown biochemical functions. Northern blot analysis revealed that the transcripts of Ss5MaT1 were detected in petals, sepals, bracts, and red stems, in accordance with the pigment accumulation patterns. Phylogenetic analysis suggests that the aliphatic and aromatic acylations of anthocyanins are generally catalyzed by subfamily members of the plant acyltransferase family.

Acyltransferases↗
PubMed2001

Hypermethylation of the CD44 gene is associated with progression and metastasis of human prostate cancer.

BACKGROUND: CD44 is a metastasis suppressor gene for prostate cancer and the down-regulation of CD44 and its variants is associated with the progression of prostate cancer. Also, hypermethylation of the CpG islands of the CD44 gene is closely associated with transcriptional inactivation, resulting in the decreased expression of CD44. To clarify the exact role of methylation status of CpG islands of CD44 gene in the progression and metastasis of prostate cancer, we investigated the methylation status of this gene in primary and metastatic human prostate tumors obtained from surgery or autopsy. METHODS: We examined 97 samples from 40 Japanese patients with adenocarcinoma of the prostate. Tumor tissues were obtained from radical prostatectomy specimens from eight patients with stage B, 12 patients with stage C and three patients with stage D1 and at autopsy from 17 hormone-refractory metastatic cases, who had initially responded to the therapy and thereafter relapsed. Distant metastatic tissues were also obtained at autopsy (i.e., liver, lung, kidney, mammary gland, and pelvic lymph nodes) from 10 of 17 hormone-refractory cases. We analyzed the hypermethylation status of CD44 promotor region by PCR using genomic DNAs digested with the m(5)C-sensitive restriction enzyme HpaII. RESULTS: The correlation between the methylation status of CD44 gene and the stage progression of prostate cancer was statistically significant (P = 0.0438). In two of 10 hormone-refractory cases, a comparison of the methylation status of the CD44 gene in metastases to that in primary tumors revealed interfocal heterogeneity of CD44 methylation status. CONCLUSIONS: These results indicate an important role of CD44 methylation in the progression and metastasis of prostate cancer, although the amount of methylational heterogeneity is substantial among metastatic sites within the same patient.

Adenocarcinoma↗
PubMed2001

Ascorbate attenuates atrial pacing-induced peroxynitrite formation and electrical remodeling and decreases the incidence of postoperative atrial fibrillation.

Atrial fibrillation (AF), the most common chronic arrhythmia, increases the risk of stroke and is an independent predictor of mortality. Available pharmacological treatments have limited efficacy. Once initiated, AF tends to self-perpetuate, owing in part to electrophysiological remodeling in the atria; however, the fundamental mechanisms underlying this process are still unclear. We have recently demonstrated that chronic human AF is associated with increased atrial oxidative stress and peroxynitrite formation; we have now tested the hypothesis that these events participate in both pacing-induced atrial electrophysiological remodeling and in the occurrence of AF following cardiac surgery. In chronically instrumented dogs, we found that rapid (400 min(-1)) atrial pacing was associated with attenuation of the atrial effective refractory period (ERP). Treatment with ascorbate, an antioxidant and peroxynitrite decomposition catalyst, did not directly modify the ERP, but attenuated the pacing-induced atrial ERP shortening following 24 to 48 hours of pacing. Biochemical studies revealed that pacing was associated with decreased tissue ascorbate levels and increased protein nitration (a biomarker of peroxynitrite formation). Oral ascorbate supplementation attenuated both of these changes. To evaluate the clinical significance of these observations, supplemental ascorbate was given to 43 patients before, and for 5 days following, cardiac bypass graft surgery. Patients receiving ascorbate had a 16.3% incidence of postoperative AF, compared with 34.9% in control subjects. In combination, these studies suggest that oxidative stress underlies early atrial electrophysiological remodeling and offer novel insight into the etiology and potential treatment of an enigmatic and difficult to control arrhythmia. The full text of this article is available at http://www.circresaha.org.

Aged↗
PubMed2001

Splenomegaly induced by recombinant human granulocyte-colony stimulating factor in rats.

Spontaneous ruptures of the spleen have been observed in donors and patients with malignancy during mobilization of peripheral blood stem cells. Thus, we investigated the morphological and histological alteration of the spleen, and mRNA expression levels and activities of the DNA-synthesizing enzymes thymidylate synthase (TS) and thymidine kinase (TK) in the splenic cells, of rats treated with recombinant human granulocyte-colony stimulating factor (rhG-CSF). Daily injections of rhG-CSF for 5 or 7 days slightly enhanced the splenic weight. Single or 3-day treatment with rhG-CSF markedly enhanced the number of granulocytes in peripheral blood. Expression levels of TS and TK mRNA in the splenic cells were significantly increased 6 hours after rhG-CSF treatment. Early expression of TS and TK mRNA in the splenic cells may indicate a reseeding of hematopoietic cells from the bone marrow. Daily injections with rhG-CSF enhanced the TS and TK activities in the splenic cells. As continuous elevations of DNA-synthesizing enzyme activity and spleno-megaly are suggestive of a possible splenic rupture, the monitoring of peripheral granulocytes and splenic size is necessary during the rhG-CSF treatment.

Animals↗
PubMed2001

Structural and cohesive properties of a C60 monolayer.

We have explored the cohesive property of a monolayer of C (60) molecules (ML- C (60)) by means of total energy calculations with the density-functional theory. The total energy curve calculated for ML- C (60), which is obtained as a function of the lattice constant, has two minima and shows a hysteresis in the compression-tension stroke. These two minima in energy correspond to the different structural phases of ML- C (60): one is a monomer phase and the other is a polymer one. The energy band gap within the framework of the local density approximation varies from 1 eV (semiconducting phase) to 0 eV (metallic phase) with external pressure and without structural transition from the monomer phase to the polymer one.

Carbon↗
PubMed2001

Specificity analysis and mechanism of aurone synthesis catalyzed by aureusidin synthase, a polyphenol oxidase homolog responsible for flower coloration.

Aureusidin synthase, which plays a key role in the yellow coloration of snapdragon flowers, is a homolog of plant polyphenol oxidase (PPO). The enzyme specifically acted on chalcones with a 4-monohydroxy or 3,4-dihydroxy B-ring to produce aurones, for whose production the oxidative cyclization of chalcones must be preceded by 3-oxygenation. However, it exhibited virtually no PPO activity toward non-chalcone phenolics. The enzyme was competitively inhibited by phenylthiourea, a specific PPO inhibitor. These results led us to propose a mechanism of aurone synthesis by aureusidin synthase on the basis of known PPO-catalyzed reactions and conclude that the enzyme is a chalcone-specific PPO specialized for aurone biosynthesis.

Benzofurans↗
PubMed2001

Extrathymic development of V alpha 11 T cells in placenta during pregnancy and their possible physiological role.

The molecular and cellular mechanisms of the feto-maternal immune responses in the placenta in connection with natural abortion remain unclear. In this report we provide evidence that V(alpha11) T cells developed in the placenta may be responsible for the induction of natural abortion. The majority of V(alpha11) TCRs detected during pregnancy showed a consensus motif in the CDR3 region, similar to that of anti-GM3 TCR clones, and were of maternal origin. V(alpha11) TCRs were found in the middle to late stages of gestation due to de novo generation in the placenta, not to migration from the maternal side, as evidenced by the significant increases in the out-of-frame V(alpha11) TCR mRNA and the copy number of circular DNA generated by V(alpha11) gene rearrangements. Furthermore, administration of anti-V(alpha11) Ab to pregnant mice resulted in a significant decrease in the incidence of fetal demise, suggesting that V(alpha11) T cells detected in the placenta develop extrathymically and are involved in natural abortion.

Animals↗
PubMed2001

A functional rhodopsin-green fluorescent protein fusion protein localizes correctly in transgenic Xenopus laevis retinal rods and is expressed in a time-dependent pattern.

To study rhodopsin biosynthesis and transport in vivo, we engineered a fusion protein (rho-GFP) of bovine rhodopsin (rho) and green fluorescent protein (GFP). rho-GFP expressed in COS-1 cells bound 11-cis retinal, generating a pigment with spectral properties of rhodopsin (A(max) at 500 nm) and GFP (A(max) at 488 nm). rho-GFP activated transducin at 50% of the wild-type activity, whereas phosphorylation of rho-GFP by rhodopsin kinase was 10% of wild-type levels. We expressed rho-GFP in the rod photoreceptors of Xenopus laevis using the X. laevis principal opsin promoter. Like rhodopsin, rho-GFP localized to rod outer segments, indicating that rho-GFP was recognized by membrane transport mechanisms. In contrast, a rho-GFP variant lacking the C-terminal outer segment localization signal distributed to both outer and inner segment membranes. Confocal microscopy of transgenic retinas revealed that transgene expression levels varied between cells, an effect that is probably analogous to position-effect variegation. Furthermore, rho-GFP concentrations varied along the length of individual rods, indicating that expression levels varied within single cells on a daily or hourly basis. These results have implications for transgenic models of retinal degeneration and mechanisms of position-effect variegation and demonstrate the utility of rho-GFP as a probe for rhodopsin transport and temporal regulation of promoter function.

Amino Acid Sequence↗
PubMed2001

An antimicrotubule agent, TZT-1027, does not induce neuropathologic alterations which are detected after administration of vincristine or paclitaxel in animal models.

One of the major dose-limiting toxicities induced by antimicrotubule antitumor agents such as vinca alkaloids and taxanes is peripheral neuropathy. The neurotoxicity of TZT-1027 (a dolastatin 10 derivative antimicrotubule agent) was thus assessed using the animal models for antimicrotubule agent-induced neurotoxicity. Rabbits were intravenously given TZT-1027 or vincristine weekly for 5 weeks. In the mouse study, TZT-1027, vincristine or paclitaxel was intravenously given every 2 days and/or weekly. Despite the neuropathologic evidence such as myelinated axonal and fiber degeneration in the peripheral nerves and in the sensory tracts of the spinal cord following the treatment with vincristine or paclitaxel, no drug-induced alteration was observed in the TZT-1027 groups. Although there are reports that some other dolastatin derivatives with antimicrotubule activity showed no neurotoxic potential in humans, the present study represents the first demonstration in experimental animals that a dolastatin derivative has no, or at least a lower, neurotoxic potential compared to other antimicrotubule agents.

Animals↗
PubMed2001

Cloning and rational mutagenesis of kexstatin I, a potent proteinaceous inhibitor of Kex2 proteinase.

Kexstatin I is a potent proteinaceous inhibitor of Kex2 proteinase (EC 3.4.21.61). In the present study we show the molecular cloning, primary structure determination and expression of the gene encoding kexstatin I. We also demonstrate its enhanced activity and specificity for Kex2 proteinase inhibition by rational mutagenesis. The cloned kexstatin I gene encoded a protein of 145 amino acid residues, including the 35-residue signal sequence for secretion. The amino acid sequence showed 52% identity with those of the Streptomyces subtilisin inhibitors (SSIs). Thus kexstatin I is the first SSI-family member that can inhibit Kex2 proteinase. The reactive site of the inhibitor was determined to be -Thr(69)-Lys(70) downward arrowGlu(71)-, where downward arrow indicates the reactive site. Because Kex2 proteinase generally shows the highest affinity for substrates with basic amino acid residues at the P(1) and P(2) sites, conversion of the Thr(69)-Lys(70) segment of the inhibitor into dibasic motifs was expected to result in enhanced inhibitory activities. Thus we constructed kexstatin I mutants, in which the Thr(69)-Lys(70) sequence was replaced by the Thr(69)-Arg(70), Lys(69)-Lys(70) and Lys(69)-Arg(70) sequences using PCR-based mutagenesis, and analysed them kinetically. Among these mutants, the Lys(69)-Arg(70) mutant was the most potent inhibitor. The K(i) for Kex2 proteinase was 3.2x10(-10) M, which was 140-fold lower than that of the inhibitor with the Thr(69)-Lys(70) sequence. Although kexstatin I could also inhibit subtilisin, the enhancement of inhibitory activity upon such mutations was specific for Kex2 proteinase inhibition.

Amino Acid Sequence↗
PubMed2001

Expression and regulation of Na pump isoforms in cultured cerebellar granule cells.

We investigated expression of Na pump isoforms in cultured cerebellar granule cells and measured in situ ion pump activities of the isoforms, to elucidate functions of Na pump isoforms in neurons. The cells expressed three Na pump isoforms (alpha1, alpha2 and alpha3 isoforms), however the alpha1 isoform acted as a main ion pump under basal conditions. The ion pump activity of the alpha3/ alpha2 isoforms increased remarkably after stimulation of the neurons with glutamate, therefore the alpha3/alpha2 isoforms as well as the alpha1 isoform acted as ion pumps after the stimulation. The glutamate effects were mainly mediated by non-NMDA receptors. These results suggest that alpha1 isoform and alpha3/alpha2 isoforms are functionally important under basal conditions and after neuronal excitation, respectively.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2001

Charge inversion of colloidal particles in an aqueous solution: screening by multivalent ions.

We investigate the structure of the electric double layer on charged colloids by Monte Carlo simulations. Using the primitive model of asymmetric electrolytes, the integrated charge distribution function on a spherical colloidal particle are also studied. With high concentrations of divalent ions, numerical results predict charge oscillation and charge inversion phenomena, which the traditional Derjaguin-Landau-Verwey-Overbeek theory cannot reproduce.

Journal Article↗
PubMed2001

Requirement for natural killer T (NKT) cells in the induction of allograft tolerance.

In this study, we investigated the role of Valpha14 natural killer T (NKT) cells in transplant immunity. The ability to reject allografts was not significantly different between wild-type (WT) and Valpha14 NKT cell-deficient mice. However, in models in which tolerance was induced against cardiac allografts by blockade of lymphocyte function-associated antigen-1/intercellular adhesion molecule-1 or CD28/B7 interactions, long-term acceptance of the grafts was observed only in WT but not Valpha14 NKT cell-deficient mice. Adoptive transfer with Valpha14 NKT cells restored long-term acceptance of allografts in Valpha14 NKT cell-deficient mice. The critical role of Valpha14 NKT cells to mediate immunosuppression was also observed in vitro in mixed lymphocyte cultures in which lymphocyte function-associated antigen-1/intercellular adhesion molecule-1 or CD28/B7 interactions were blocked. Experiments using IL-4- or IFN-gamma-deficient mice suggested a critical contribution of IFN-gamma to the Valpha14 NKT cell-mediated allograft acceptance in vivo. These results indicate a critical contribution of Valpha14 NKT cells to the induction of allograft tolerance and provide a useful model to investigate the regulatory role of Valpha14 NKT cells in various immune responses.

Adaptation, Physiological↗
PubMed2001

Inhibition of tumor metastasis by adoptive transfer of IL-12-activated Valpha14 NKT cells.

A unique lymphocyte lineage, the Valpha14 NKT cells, expresses both NK1.1 and an invariant antigen receptor encoded by Valpha14 and Jalpha281 gene segments. Valpha14 NKT cells play crucial roles in various immune responses, including autoimmune diseases, allergic reactions and anti-tumor immunity. Valpha14 NKT cells were demonstrated to be essential for anti-tumor effect of IL-12 in vivo. Here, we report that adoptive transfer of IL-12-activated Valpha14 NKT cells prevents hepatic metastasis of B16 melanoma. The injection of large amounts of IL-2, IL-4, and IFN-gamma, which are cytokines produced by activated Valpha14 NKT cells, exhibited no significant inhibition of the metastasis of this melanoma. The cells prepared from the liver of IL-12-injected mice expressed a potent cytotoxic activity on B16 melanoma cells in vitro. Although the adoptive transfer of IL-12-activated Valpha14 NKT cells prevents hepatic metastasis of B16 melanoma, activated NK cells from IL-12-injected RAG-1-/- mice failed to inhibit the metastasis of this melanoma. Thus, the anti-tumor effect of IL-12 can be replaced by adoptive transfer of IL-12-activated Valpha14 NKT cells but not by IL-12-activated NK cells, suggesting a minor role of NK cells for the IL-12-mediated anti-tumor effect in this experimental system. Moreover, our studies have suggested the involvement of direct cytotoxic mechanisms rather than cytokine-mediated immune responses at the effector phase of the Valpha14 NKT cell-mediated anti-tumor activity.

Adoptive Transfer↗
PubMed2001

Mutations in the NMMHC-A gene cause autosomal dominant macrothrombocytopenia with leukocyte inclusions (May-Hegglin anomaly/Sebastian syndrome).

Macrothrombocytopenia with leukocyte inclusions is a rare autosomal dominant platelet disorder characterized by a triad of giant platelets, thrombocytopenia, and characteristic Döhle body-like leukocyte inclusions. A previous study mapped a locus for the disease on chromosome 22q12.3-q13.2 by genome-wide linkage analysis. In addition, the complete DNA sequence of human chromosome 22 allowed a positional candidate approach, and results here indicate that the gene encoding nonmuscle myosin heavy chain-A, NMMHC-A, is mutated in this disorder. Mutations were found in 6 of 7 Japanese families studied: 3 missense mutations, a nonsense mutation, and a one-base deletion resulting in a premature termination. Immunofluorescence studies revealed that NMMHC-A distribution in neutrophils appeared to mimic the inclusion bodies. These results provide evidence for the involvement of abnormal NMMHC-A in the formation of leukocyte inclusions and also in platelet morphogenesis.

Amino Acid Sequence↗