Biomedical subjects

T Noguchi

Publications and source records attributed to T Noguchi.

At least 109 records · Page 6Linked to original sources

PubMed2001

The relation of oxidative DNA damage to hypertension and other cardiovascular risk factors in Tanzania.

OBJECTIVES: To clarify the mechanism of involvement of oxidative stress in hypertensives, we investigated the relationship between the marker of oxidative DNA damage, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), and cardiovascular risk factors, such as hypertension and serum glycosylated hemoglobin (HbA1c), among Tanzanians aged 46-58 years who were not on antihypertensive medication. DESIGN AND METHODS: Sixty subjects (males/females, 28/ 32) were selected randomly from the subjects who completed a 24h urine collection in our epidemiological study at Dar es Salaam, Tanzania in 1998. The subjects were divided into two groups, hypertensive subjects (systolic blood pressure (SBP) > or = 140 mmHg and/or diastolic blood pressure (DBP) > or =90 mmHg) and normotensive subjects (SBP < 140 mmHg and DBP < 90 mmHg) or hyperglycemic subjects (HbA1c > or = 6.0%) and normoglycemic subjects (HbA1c < 6.0%). Biological markers from urine and blood were analyzed centrally in the WHO Collaborating Center. RESULTS: The mean levels of HbA1c and 8-OHdG were significantly higher in the hypertensive subjects than in the normotensive subjects (P < 0.05). Urinary 8-OHdG was significantly higher in hyperglycemic subjects than in normoglycemic subjects. HbA1c was positively correlated with the 24-h urinary 8-OHdG excretions (r= 0.698, P < 0.0001). CONCLUSIONS: These findings suggest oxidative DNA damage is increased in hypertensive subjects, and there is a positive correlation between the level of blood glucose estimated as HbA1c and oxidative DNA damage. Hyperglycemia related to insulin resistance in hypertension in Tanzania is associated with increased urinary 8-OHdG.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

Effects of mutation in hepatitis C virus nonstructural protein 5A on interferon resistance mediated by inhibition of PKR kinase activity in mammalian cells.

The IFN-induced double-stranded RNA (dsRNA)-activated protein kinase PKR is one of the key molecules in the antiviral effects of IFN. To clarify the effects of hepatitis C virus nonstructural protein 5A (NS5A) on antiviral activity of IFN, in particular on PKR kinase activity, in mammalian cells, we established inducible NS5A-expressing cell lines derived from human osteosarcoma (Saos-2). The cells expressing NS5A derived from an IFN-resistant clone (NS5A-lb) that interacted with endogenous PKR in vitro, showed a suppressive effect on IFN function as determined by interference with vesicular stomatitis virus (VSV) infection, whereas NS5A (NS5A-2a) from an IFN-sensitive clone did not block the antiviral effect of IFN. A mutant with deletion of the IFN sensitivity determining region (ISDR) in NS5A-1b (NS5A-AISDR) also interacted with PKR and suppressed its activity in vitro. However, neither NS5A-2a nor the C-terminal truncated mutant of NS5A-1b (NS5A-deltaC) blocked PKR activity. These observations confirmed the previous report that the inhibitory effect of NS5A on IFN activity is mediated at least in part by the repression of PKR. In addition, we showed that IFN sensitivity was determined not only by the ISDR but that the involvement of the C-terminal region of NS5A-1b is important for the suppression of PKR activity.

Amino Acid Sequence↗

PubMed2001

Inhibition of the motility and growth of B16F10 mouse melanoma cells by dominant negative mutants of Dok-1.

Dok-1 (p62(Dok)) is a multiple-site docking protein that acts downstream of receptor and nonreceptor tyrosine kinases. Although it has been proposed to contribute to the control of cell growth and migration through association with the Ras GTPase-activating protein and the adapter protein Nck, the role of Dok-1 remains largely unknown. The functions of Dok-1 have now been investigated by the generation of two different COOH-terminal truncation mutants of this protein: one (DokPH+PTB) containing the pleckstrin homology and phosphotyrosine-binding domains, and the other (DokPH) composed only of the pleckstrin homology domain. Both of these mutant proteins were shown to act in a dominant negative manner. Overexpression of each of the mutants in highly metastatic B16F10 mouse melanoma cells thus both inhibited the tyrosine phosphorylation of endogenous Dok-1 induced by cell adhesion as well as reduced the association of the endogenous protein with cellular membranes and the cytoskeleton. Overexpression of DokPH+PTB in these cells also markedly reduced both the rates of cell spreading, migration, and growth as well as the extent of Ras activation. The effects of DokPH on these processes were less pronounced than were those of DokPH+PTB, indicating the importance of the phosphotyrosine-binding domain. These results suggest that at least in B16F10 cells, Dok-1 positively regulates not only cell spreading and migration but also cell growth and Ras activity.

Animals↗

PubMed2001

Differential regulation of IGFBP-2 and IGFBP-5 gene expression by vitamin A status in Japanese quail.

To investigate the involvement of the insulin-like growth factor (IGF) system in vitamin A (VA)-supported growth, we examined the effects of VA status on IGF binding protein (IGFBP)-2 and -5 gene expression in Japanese quail. VA deficiency caused a reduction in IGFBP-2 mRNA only in lung, without effect in other tissues. However, the expression of IGFBP-5 mRNA was more sensitive to the change of VA status. IGFBP-5 mRNA levels were significantly reduced by VA depletion in a tissue-specific manner, which preceded the decrease in body weight. A single injection of retinoic acid or retinol to VA-deficient quail did not affect the levels of IGFBP-2 mRNA, but it rapidly induced the expression of IGFBP-5 mRNAs in some tissues. These results are the first to show that gene expression of some IGFBPs in vivo are under the control of VA status and suggest a possible involvement of the IGF system in mediating the physiological actions of VA in the growth of Japanese quail.

Aging↗

PubMed2001

Activation of PKC decreases myocardial O2 consumption and increases contractile efficiency in rats.

The effect of protein kinase C (PKC) activation on cardiac mechanoenergetics is not fully understood. To address this issue, we determined the effects of the PKC activator phorbol 12-myristate 13-acetate (PMA) on isolated rat hearts. Hearts were exposed to PMA with or without pretreatment with the PKC inhibitor chelerythrine. Contractile efficiency was assessed as the reciprocal of the slope of the linear myocardial O2 consumption (VO2) pressure-volume area (PVA) relation. PMA decreased contractility (Emax; -30 +/- 8%; P < 0.05) and increased coronary perfusion pressure (+58 +/- 11%; P < 0.01) without altering left ventricular end-diastolic pressure. Concomitantly, PMA decreased PVA-independent VO2 [nonmechanical energy expenditure for excitation-contraction (E-C) coupling and basal metabolism] by 28 +/- 8% (P < 0.05) and markedly increased contractile efficiency (+41 +/- 8%; P < 0.05) in a manner independent of the coronary vascular resistance. Basal metabolism was not affected by PMA. Chelerythrine abolished the PMA-induced vasoconstriction, negative inotropy, decreased PVA-independent VO2, and increased contractile efficiency. We conclude that PKC-mediated phosphorylation of regulatory proteins reduces VO2 via effects on both the contractile machinery and the E-C coupling.

Alkaloids↗

PubMed2001

A comparison of DNA copy number changes detected by comparative genomic hybridization in malignancies of the liver, biliary tract and pancreas.

Tumors arising from the liver, biliary tract and pancreas, which originate in the foregut and are in close anatomical proximity to each other, sometimes show similar histological features. No studies have focused on genetic similarities and differences between tumors of these organs. To elucidate the similarities and differences in DNA copy number alterations between tumors of these organs, we applied comparative genomic hybridization (CGH) to cancers of the liver (31 cases), biliary tract (42 cases) and pancreas (27 cases). Some alterations were common to tumors of all three organs, and some were preferential in certain types of tumor. Gains of 1q and 8q and losses of 8p and 17p were common to all tumors. In contrast, 13q14 and 16q losses were detected exclusively in hepatocellular carcinomas (HCCs; p < 0.01). The incidence of 17q21 gain and 5q loss was higher in biliary tract cancers than in the other two types (p < 0.05). Pancreatic cancers exhibited higher incidence of 5q14-q23 gain and 19p loss than tumors of other organs (p < 0.01). Gains of 7p, 7q, 12p and 20q and losses of 3p, 6q, 9p and 18q were frequent in both biliary tract and pancreatic cancers but rare in HCCs (p < 0.05). The present results suggest that although genes located at 1q, 8p, 8q and 17p are frequently involved in HCC, biliary tract and pancreatic cancer, at least some of the genes implicated in carcinogenesis are different between these three types. It is also suggested that CGH analysis is useful as a potential adjunct for the diagnosis and management of these tumors of organs that are anatomically close to one another.

Aged↗

PubMed2001

Low metacarpal bone density, tooth loss, and periodontal disease in Japanese women.

The relationship between periodontitis and systemic bone mineral density in Japanese women is undetermined. We tested the hypothesis that periodontitis was more frequent in women with low metacarpal bone mineral density (m-BMD). Subjects were 190 Japanese women (89 premenopausal, 101 post-menopausal). Periodontal status was evaluated according to the Community Periodontal Index of Treatment Need (CPITN). M-BMD was measured by computed x-ray densitometry. The proportion of subjects with periodontitis (CPITN > or = 3) increased as m-BMD decreased in pre-menopausal (18.2%, 36.9%, and 66.6% in the normal, borderline, and very low m-BMD groups, p < 0.02) and post-menopausal women (41.5%, 54.8%, 60%, and 68.4% in the normal, borderline, low, and very low m-BMD groups, p < 0.05). Among post-menopausal women, those with very low m-BMD had fewer teeth present than women with normal m-BMD (19.9+/-7.2 vs. 25.1+/-4.1, p < 0.01). These results indicate that m-BMD loss is associated with periodontitis in Japanese women, and with tooth loss after menopause.

Adult↗

PubMed2001

Up-regulation of upstream stimulatory factors by protein malnutrition and its possible role in regulation of the IGF-binding protein-1 gene.

Protein malnutrition drastically induces the expression of the IGF-binding protein-1 (IGFBP-1) gene. We have previously shown that the region between -77 and -112 bp upstream of the rat IGFBP-1 gene contributes to the response of this gene to amino acid limitation. In an attempt to elucidate the basis of the responsiveness of this putative amino acid response unit (AARU), we searched the nucleus of the rat liver for a trans-acting factor whose binding to AARU was dependent on protein nutrition. Liver nuclear extracts of rats fed a protein-free diet and of those fed a control diet were compared by EMSA using the AARU as probe. One of the protein-probe complexes underwent a drastic increase after dietary protein deprivation. Assays using specific antibodies and several competitor oligonucleotides led to identification of the protein composing the complex as upstream stimulatory factor-1 (USF) and USF-2. The binding site of the USF proteins in the AARU turned out to be a CACGGG sequence that was homologous to the consensus USF-binding sequence (E box; CANNTG). Further, Western blot analyses showed that a protein-free diet caused significant increases in USF-1 and USF-2 levels. Thus, elevated expression of the IGFBP-1 gene under protein malnutrition can be attributable to increased binding of USF to its promoter, which results from increased USF levels. The data suggest that the changes in these ubiquitously distributed transcription factors play an important role in the nutritional regulation of expression of mammalian genes.

Animals↗

PubMed2001

Reorganization of actin cytoskeleton at the growing end of the cleavage furrow of Xenopus egg during cytokinesis.

We studied reorganization of actin-myosin cytoskeleton at the growing ends of the cleavage furrow of Xenopus eggs in order to understand how the contractile ring is formed during cytokinesis. Reorganization of F-actin structures during the furrow formation was demonstrated by rhodamine-phalloidin staining of the cleavage furrow and by time-lapse scanning with laser scanning microscopy of F-actin structures in the cleavage furrow of live eggs to which rhodamine-G-actin had been injected. Actin filaments assemble to form small clusters that we call 'F-actin patches' at the growing end of the furrow. In live recordings, we observed emergence and rapid growth of F-actin patches in the furrow region. These patches then align in tandem, elongate and fuse with each other to form short F-actin bundles. The short bundles then form long F-actin bundles that compose the contractile ring. During the furrow formation, a cortical movement towards the division plane occurs at the growing ends of the furrow, as shown by monitoring wheatgerm agglutinin-conjugated fluorescent beads attached to the egg surface. As a result, wheatgerm agglutinin-binding sites accumulate and form 'bleb-like' structures on the surface of the furrow region. The F-actin patch forms and grows underneath this structure. The slope of F-actin accumulation in the interior region of the furrow exceeds that of accumulation of the cortex transported by the cortical movement. In addition, rhodamine-G-actin microinjected at the growing end is immediately incorporated into the F-actin patches. These data, together with the rapid growth of F-actin patches in the live image, suggest that actin polymerization occurs in the contractile ring formation. Distribution of myosin II in the cleavage furrow was also examined by immunofluorescence microscopy. Myosin II assembles as spots at the growing end underneath the bleb-like structure. It was suggested that myosin is transported and accumulates as spots by way of the cortical movement. F-actin accumulates at the position of the myosin spot a little later as the F-actin patches. The myosin spots and the F-actin patches are then simultaneously reorganized to form the contractile ring bundles

Actin Cytoskeleton↗

PubMed2001

Contractile ring formation in Xenopus egg and fission yeast.

How actin filaments (F-actin) and myosin II (myosin) assemble to form the contractile ring was investigated with fission yeast and Xenopus egg. In fission yeast cells, an aster-like structure composed of F-actin cables is formed at the medial cortex of the cell during prophase to metaphase, and a single F-actin cable(s) extends from this structure, which seems to be a structural basis of the contractile ring. In early mitosis, myosin localizes as dots in the medial cortex independently of F-actin. Then they fuse with each other and are packed into a thin contractile ring. At the growing ends of the cleavage furrow of Xenopus eggs, F-actin at first assembles to form patches. Next they fuse with each other to form short F-actin bundles. The short bundles then form long bundles. Myosin seems to be transported by the cortical movement to the growing end and assembles there as spots earlier than F-actin. Actin polymerization into the patches is likely to occur after accumulation of myosin. The myosin spots and the F-actin patches are simultaneously reorganized to form the contractile ring bundles. The idea that a Ca signal triggers cleavage furrow formation was tested with Xenopus eggs during the first cleavage. We could not detect any Ca signals such as a Ca wave, Ca puffs or even Ca blips at the growing end of the cleavage furrow. Furthermore, cleavages are not affected by Ca-chelators injected into the eggs at concentrations sufficient to suppress the Ca waves. Thus we conclude that formation of the contractile ring is not induced by a Ca signal at the growing end of the cleavage furrow.

Actins↗

PubMed2001

A novel ATP regeneration system using polyphosphate-AMP phosphotransferase and polyphosphate kinase.

Polyphosphate-AMP phosphotransferase (PAP) and polyphosphate kinase (PPK) were used for designing a novel ATP regeneration system, named the PAP-PPK ATP regeneration system. PAP is an enzyme that catalyzes the phospho-conversion of AMP to ADP, and PPK catalyzes ATP formation from ADP. Both enzymes use inorganic polyphosphate [poly(P)] as a phosphate donor. In the PAP-PPK ATP regeneration system, ATP was continuously synthesized from AMP by the coupling reaction of PAP and PPK using poly(P). Poly(P) is a cheap material compared to acetyl phosphate, phosphoenol pyruvate and creatine phosphate, which are phosphate donors used for conventional ATP regeneration systems. To achieve efficient synthesis of ATP from AMP, an excessive amount of poly(P) should be added to the reaction solution because both PAP and PPK consume poly(P) as a phosphate donor. Using this ATP generation reaction, we constructed the PAP-PPK ATP regeneration system with acetyl-CoA synthase and succeeded in synthesizing acetyl-CoA from CoA, acetate and AMP. Since too much poly(P) may chelate MG2+ and inhibit enzyme activity, the Mg2+ concentration was optimized to 24 mM in the presence of 30 mM poly(P) in the reaction. In this reaction, ATP was regenerated 39.8 times from AMP, and 99.5% of CoA was converted to acetyl-CoA. In addition, since the PAP-PPK ATP regeneration system can regenerate GTP from GMP, it could also be used as a GTP regeneration system.

Journal Article↗

PubMed2001

Novel method for enzymatic synthesis of CMP-NeuAc.

A novel method for synthesizing CMP-NeuAc was established. We first confirmed that the putative neuA gene of Haemophilus influenzae, identified by its whole genome sequence project, indeed encodes CMP-NeuAc synthetase (EC 2.7.7.43). The enzyme requires CTP as a cytidylyl donor for cytidylylation of NeuAc. The enzyme was coupled with an enzymatic CTP-generating system from CMP and inorganic polyphosphate as a sole phospho-donor driven by the combination of polyphosphate kinase and CMP kinase, where phosphorylation of CMP is done by the combined activity expressed by both enzymes, and subsequent phosphorylation of CDP by polyphosphate kinase itself occurred efficiently. When CMP-NeuAc synthetase of H. influenzae, polyphosphate kinase, and CMP kinase were added to the reaction mixture containing equimolar concentrations (15 mM) of CMP and NeuAc, and polyphosphate (150 mM in terms of phosphate), CMP-NeuAc was synthesized up to 10 mM in 67% yield.

Cytidine Monophosphate↗

PubMed2001

Regulation of hydroxyindole-O-methyltransferase gene expression in Japanese quail (Coturnix coturnix japonica).

Hydroxyindole-O-methyltrasferase (HIOMT) plays an important role as the final enzyme in the synthesis of melatonin. In this study, the expression of the HIOMT gene in Japanese quail was investigated with respect to tissue distribution and the effects of light and vitamin A deficiency. HIOMT mRNA in the pineal gland and eye had a clear daily rhythm with peak values in daytime. The testis also contained a detectable amount of HIOMT mRNA, which did not display a rhythmic change over a 24-h period. When birds were rendered vitamin A deficient through feeding with a vitamin A-free diet, the daily rhythm of the HIOMT gene almost disappeared in both the pineal gland and eye due to increases in the nighttime values. Our previous observations and these results suggest that vitamin A and a photo-signal are required to maintain the rhythmic expression of the HIOMT gene as well as the arylalkylamine N-acetyltransferase gene.

Acetylserotonin O-Methyltransferase↗

PubMed2001

A new type of allantoinase in amphibian liver.

Allantoinase and allantoicase are known to form a complex in amphibian liver. In this study, a new type of allantoinase that did not form a complex with allantoicase was found in the amphibian liver. Purified enzyme had a molecular mass of about 44 kDa both in SDS-PAGE and gel-filtrations. The enzyme cross-reacted with anti-sardine allantoinase polyclonal antibody, and it weakly cross-reacted with anti-bullfrog allantoinase polyclonal antibody.

Amidohydrolases↗

PubMed2001

Natto mucilage containing poly-gamma-glutamic acid increases soluble calcium in the rat small intestine.

We prepared natto (fermented soybeans) mucilage containing poly-gamma-glutamic acid (gamma-PGA) from commercial natto. The effect of natto mucilage on calcium (Ca) solubility in vitro and in vivo was investigated. Ca solubility in vitro increased with an increase in the amount of natto mucilage, due to inhibition of the formation of an insoluble complex of Ca with phosphate by natto mucilage. Rats were fed with 5 g of soybean protein isolate, natto, mucilage-free natto, or natto mucilage diet for 1.5 h. Small intestinal contents were collected 2.5 h after ingestion. In the lower half of the small intestine, both the amount and the percentage of soluble Ca of intestinal contents were significantly higher (P < 0.001) in rats fed with natto mucilage diet than in those fed with the other diets. Natto mucilage also increased Ca solubility in vivo. These results suggested that gamma-PGA is responsible for the increasing effect of natto mucilage on Ca solubility.

Animals↗

PubMed2001

Effects of vitamin E and sesamin on hypertension and cerebral thrombogenesis in stroke-prone spontaneously hypertensive rats.

The preventive effects of sesamin, a lignan from sesame oil, and vitamin E on hypertension and thrombosis were examined using stroke-prone spontaneously hypertensive rats (SHRSP). At 5 weeks of age the animals were separated into four groups: (i) a control group; (ii) a vitamin E group, which was given a 1,000 mg alpha-tocopherol/kg diet; (iii) a sesamin group, given a 1,000 mg sesamin/kg diet; and (iv) a vitamin E plus sesamin group, given a 1,000 mg alpha-tocopherol plus 1,000 mg sesamin/kg diet for 5 weeks from 5 to 10 weeks of age. Resting blood pressure was measured by the tail-cuff method once weekly. A closed cranial window was created and platelet-rich thrombi were induced in vivo using a helium-neon laser technique. The number of laser pulses required for formation of an occlusive thrombus was used as an index of thrombotic tendency. In control rats, systolic blood pressure and the amount of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) became significantly elevated with age. However, the elevation in blood pressure and 8-OHdG were significantly suppressed in rats administrated vitamin E, sesamin, or vitamin E plus sesamin. At 10 weeks, the number of laser pulses required to induce an occlusive thrombus in arterioles of the control group was significantly lower than in the other groups (p<0.05). These results indicate that chronic ingestion of vitamin E and sesamin attenuated each of elevation in blood pressure, oxidative stress and thrombotic tendency, suggesting that these treatments might be beneficial in the prevention of hypertension and stroke.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

Chromosomal imbalances in gastric cancer. Correlation with histologic subtypes and tumor progression.

DNA copy number changes were analyzed by comparative genomic hybridization (CGH) in 38 gastric carcinomas and correlated with tumor histologic type and progression. Gains of copy numbers were observed in all tumors, affecting all chromosomes except chromosome 16. The average number of copy number gains was 7 (range, 1-13), most frequently located on chromosomes 11, 12, 15, 17, and 20 in 45% to 97% of tumors. High-level amplifications were found on chromosomes 12, 15, 17, and 20; the latter was affected most frequently (66%). Loss of DNA copy numbers was detected in 14 tumors affecting 7 chromosomes. No statistically significant differences in the frequency and pattern of chromosomal imbalances were observed in tumor histologic type (Lauren classification) and grade of differentiation, as well as the prognostic parameters depth of invasion (pT) and lymph node involvement (pN). Our results indicate that in gastric cancer there is no specific recurrent pattern of DNA aberrations to be correlated with tumor histologic type or stage. However, CGH analysis could reveal new, recurrent genetic changes in gastric cancer affecting chromosomes sites that harbor genes known to participate in tumorigenesis and progression of several human malignant neoplasms.

Carcinoma↗

PubMed2001

Tissue inhibitor of metalloproteinases 1 and 2 directly stimulate the bone-resorbing activity of isolated mature osteoclasts.

Tissue inhibitor metalloproteinases 1 (TIMP-1) and 2 have been reported to inhibit bone resorption. However, here, we report the direct action of both TIMP-1 and TIMP-2 on isolated rabbit mature osteoclasts to stimulate their bone-resorbing activity at significantly lower concentrations (approximately ng/ml) than those (approximately microg/ml) required for the inhibition of bone resorption. The cell population used in this study consisted of a mature osteoclast population with >95% purity. TIMP-1 (approximately 50 ng/ml) and TIMP-2 (approximately 8-10 ng/ml) increased the pit area excavated by the isolated mature osteoclasts. The stimulatory effects of TIMPs were abolished by simultaneous addition of anti-TIMP antibodies. At higher concentrations, the stimulation of bone resorption decreased reversely to the control level. The magnitude of the stimulatory effect of TIMP-2 was more than that of TIMP-1. Metalloproteinase inhibitors such as BE16627B and R94138 could not replace TIMPs with respect to the bone-resorbing activity, suggesting that the osteoclast-stimulating activity of TIMPs was independent of the inhibitory activity on matrix metalloproteinases (MMPs). TIMPs stimulated tyrosine phosphorylation of cellular proteins in the isolated mature osteoclasts. Both herbimycin A, an inhibitor of tyrosine kinases, and PD98059 and U0126, inhibitors of mitogen-activated protein kinase (MAPK), completely blocked the TIMP-induced stimulation of osteoclastic bone-resorbing activity. On the plasma membrane of osteoclasts, some TIMP-2-binding proteins were detected by a cross-linking experiment. These findings show that TIMPs directly stimulate the bone-resorbing activity of isolated mature osteoclasts at their physiological concentrations and that the stimulatory action of TIMPs is likely to be independent of their activities as inhibitors of MMPs.

Acetamides↗