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  • Vallee, B L  (9)
  • 1995-1999  (9)
  • Linguistics  (9)
  • Natural Sciences  (9)
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  • 1995-1999  (9)
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  • 1
    Online Resource
    Online Resource
    Potentiation of the bioavailability of daidzin by an extract of Radix puerariae.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 9 ( 1996-04-30), p. 4284-4288
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 9 ( 1996-04-30), p. 4284-4288
    Abstract: The dose effect of pure daidzin on the suppression of ethanol intake in Syrian golden hamsters was compared with that of crude daidzin contained in a methanol extract of Radix puerariae (RP). EC50 values estimated from the graded dose-response curves for pure daidzin and RP extract daidzin are 23 and 2.3 mg per hamster per day, respectively. Apparently the antidipsotropic activity of the RP extract cannot be accounted for solely by its daidzin content (22 mg/g). In addition to daidzin, six other isoflavones were identified in the RP extract and quantified--namely, puerarin (160 mg per g of extract), genistin (3.7 mg/g), daidzein (2.6 mg/g), daidzein-4',7-diglucoside (1.2 mg/g), genistein (0.2 mg/g), and formononetin (0.16 mg/g). None of these, administered either alone or combined, contributes in any significant way to the antidipsotropic activity of the extract. Plasma daidzin concentration-time curves determined in hamsters administered various doses of pure daidzin or RP extract by i.p.injection indicate that the crude extract daidzin has approximately 10 times greater bioavailability than the pure compound. Reconstruction of the dose-response effects for pure and crude daidzin using bioavailable daidzin rather than administered dose gives a single curve. Synthetic daidzin added to the RP extract acquires the bioavailability of the endogenous daidzin that exists naturally in the extract. These results show that (i) daidzin is the major active principle in methanol extracts of RP, and (ii) additional constituents in the methanol extract of RP assist uptake of daidzin in golden hamsters.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.9.4284
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Daidzin suppresses ethanol consumption by Syrian golden hamsters without blocking acetaldehyde metabolism.
    Proceedings of the National Academy of Sciences ; 1995
    In:  Proceedings of the National Academy of Sciences Vol. 92, No. 19 ( 1995-09-12), p. 8990-8993
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 92, No. 19 ( 1995-09-12), p. 8990-8993
    Abstract: Daidzin is a potent, selective, and reversible inhibitor of human mitochondrial aldehyde dehydrogenase (ALDH) that suppresses free-choice ethanol intake by Syrian golden hamsters. Other ALDH inhibitors, such as disulfiram (Antabuse) and calcium citrate carbimide (Temposil), have also been shown to suppress ethanol intake of laboratory animals and are thought to act by inhibiting the metabolism of acetaldehyde produced from ingested ethanol. To determine whether or not daidzin inhibits acetaldehyde metabolism in vivo, plasma acetaldehyde in daidzin-treated hamsters was measured after the administration of a test dose of ethanol. Daidzin treatment (150 mg/kg per day i.p. for 6 days) significantly suppresses ( 〉 70%) hamster ethanol intake but does not affect overall acetaldehyde metabolism. In contrast, after administration of the same ethanol dose, plasma acetaldehyde concentration in disulfiram-treated hamsters reaches 0.9 mM, 70 times higher than that of the control. In vitro, daidzin suppresses hamster liver mitochondria-catalyzed acetaldehyde oxidation very potently with an IC50 value of 0.4 microM, which is substantially lower than the daidzin concentration (70 microM) found in the liver mitochondria of daidzin-treated hamsters. These results indicate that (i) the action of daidzin differs from that proposed for the classic, broad-acting ALDH inhibitors (e.g., disulfiram), and (ii) the daidzin-sensitive mitochondrial ALDH is not the one and only enzyme that is essential for acetaldehyde metabolism in golden hamsters.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.92.19.8990
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1995
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Characterization of mouse angiogenin-related protein: implications for functional studies on angiogenin.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 9 ( 1996-04-30), p. 4331-4335
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 9 ( 1996-04-30), p. 4331-4335
    Abstract: Angiogenin-related protein (Angrp), the putative product of a recently discovered mouse gene, shares 78% sequence identity with mouse angiogenin (Ang). In the present study, the relationship of Angrp to Ang has been investigated by producing both proteins in bacteria and comparing their functional properties. We find that mouse Ang is potently angiogenic, but Angrp is not, even when assayed at relatively high doses. A deficiency in catalytic capacity, which is essential for the biological activity of Ang, does not appear to underlie Angrp's lack of angiogenicity. In fact, Angrp has somewhat greater ribonucleolytic activity toward tRNA and dinucleotide substrates than does Ang. Instead, an inability to bind cellular receptors is implicated since Angrp does not inhibit Ang-induced angiogenesis. Poor conservation of the Ang receptor recognition sequence 58-69 in Angrp most likely contributes to this defect. However, other substitutions must also influence receptor binding since an Angrp quadruple mutant that is identical to Ang in this segment still lacks both angiogenic activity and the capacity to inhibit Ang. The functional differences between Ang and Angrp, together with evidence presented herein that Angrp is regulated differently than Ang, suggest that the roles of the two proteins in vivo may be quite distinct.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.9.4331
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Crystal structure of bovine angiogenin at 1.5-A resolution.
    Proceedings of the National Academy of Sciences ; 1995
    In:  Proceedings of the National Academy of Sciences Vol. 92, No. 7 ( 1995-03-28), p. 2949-2953
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 92, No. 7 ( 1995-03-28), p. 2949-2953
    Abstract: The capacity of angiogenin (Ang) to induce blood vessel growth is critically dependent on its ribonucleolytic activity. Crystallography and mutagenesis of human Ang have previously shown that its pyrimidine binding site is obstructed by Gln-117, implying that a conformational change is a key part of the mechanism of Ang action. The 1.5-A-resolution crystal structure of bovine Ang, in which glutamic acid is substituted for Gln-117, now confirms that a blocked active site is characteristic of these proteins. Indeed, the inactive conformation of bovine Ang is stabilized by a more extensive set of interactions than is that of human Ang. The three-dimensional structure of the putative receptor binding site is also well conserved in the two proteins. The Arg-Gly-Asp segment of this site in bovine Ang, which is replaced by Arg-Glu-Asn in human Ang, does not have a conformation typical of an integrin recognition site.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.92.7.2949
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1995
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Cell cycle regulation of metallothionein in human colonic cancer cells.
    Proceedings of the National Academy of Sciences ; 1995
    In:  Proceedings of the National Academy of Sciences Vol. 92, No. 2 ( 1995-01-17), p. 579-583
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 92, No. 2 ( 1995-01-17), p. 579-583
    Abstract: Elevated levels of metallothionein (MT) found in rapidly growing tissues such as neonatal liver and various types of human tumors have suggested a role for MT in cell proliferation. To further explore this possibility we investigated the concentration of MT in human colonic cancer (HT-29) cells at different stages of proliferation by means of immunocytochemistry and competitive binding. MT is increased in subconfluent proliferating cells relative to growth-inhibited confluent cells, much as it is in growing tissues. Cycling cells synchronized with compactin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, revealed an oscillation of cytoplasmic MT that reached a maximum in successive late G1 phases and at the G1/S transition. Individual phase of the cell cycle were assessed by [3H] thymidine incorporation and by immunofluorescence employing an antibody that detects a nuclear antigen associated with proliferation. An enzyme-linked immunosorbent assay was used to quantify the relative amounts of MT in homogenate supernatants of HT-29 cells. A 2- to 3-fold increase in MT in actively proliferating cells and the regulation of the protein during the mitotic cell cycle point to a physiological role for MT in cellular proliferation and suggest that it may also serve as a proliferation marker.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.92.2.579
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1995
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    A combined kinetic and modeling study of the catalytic center subsites of human angiogenin.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 2 ( 1996-01-23), p. 804-808
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 2 ( 1996-01-23), p. 804-808
    Abstract: Kinetic analysis and molecular modeling have been used to map the ribonucleolytic center of angiogenin (Ang). Pyrimidine nucleotides were found to interact very weakly with Ang, consistent with the inaccessible B1 pyrimidine binding site revealed by x-ray crystallography. Ang also lacks an effective phosphate binding site on the 5' side of B1. Although the B2 site that preferentially binds purines on the 3' side of B1 is also weak, its associated phosphate subsites make substantial contributions: both 3',5'-ADP and 5'-ADP have Ki values 6-fold lower than for 5'-AMP, and adding a 3'-phosphate to the substrate CpA increases Kcat/Km by 9-fold. Thus Ang has a functional P2 site on the 3' side of B2 and a site for a second phosphate on the 5' side of B2. Modeling of an Ang-d(ApTpApA) complex suggested that Arg-5 forms part of the P2 site and that a 2'-phosphate might bind more tightly than a 3'-phosphate. Both predictions were confirmed kinetically. The subsite map obtained by this combined approach indicated that 5'-diphosphoadenosine 2'-phosphate might be a more potent inhibitor than any of the nucleotides tested thus far. Indeed, its Ki value of 150 microM is 50-fold lower than that for the best nucleotide previously reported and 400-fold lower than the Km for the best dinucleotide substrate. This compound may serve as a suitable starting point for the eventual design of tight-binding inhibitors of Ang as antiangiogenic agents for human therapy.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.2.804
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    X-ray absorption fine structure as a monitor of zinc coordination sites during oogenesis of Xenopus laevis.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 8 ( 1996-04-16), p. 3227-3231
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 8 ( 1996-04-16), p. 3227-3231
    Abstract: The x-ray absorption fine structure (XAFS) zinc K-edge steps for intact stages I,II and V,VI Xenopus laevis oocytes demonstrate that the zinc concentration is about 3 and 1 mM, respectively. However, the chi(k) function for the early stage oocytes differs markedly from that for the late one. Analysis of the XAFS data for stage I,II oocytes indicates that zinc is bound to 2.0 +/- 0.5 sulfur atoms at an average coordination distance of 2.29 +/- 0.02 angstroms and 2.0 +/- 0.5 nitrogen or oxygen (N/O) atoms at 2.02 +/- 0.02 angstroms. In marked contrast, in stage V,VI oocytes, zinc is bound to 4.1 +/- 0.4 N/O atoms at an average distance of 1.98 +/- 0.01 angstroms. Our previous studies demonstrated that 90% of the zinc in stage VI oocytes is sequestered within yolk platelets, associated with a single molecule, lipovitellin, the proteolytically processed product of vitellogenin. XAFS analysis of yolk platelets, lipovitellin, and vitellogenin demonstrates that zinc is bound to 4.0 +/- 0.5 N/O ligands at an average distance of 1.98 +/- 0.01 angstroms in each case, identical to that of stage V,VI oocytes. The higher shell contributions in the Fourier transforms indicate that two of the N/O zinc ligands are His in both stage V,VI and I,II oocytes. The results show that in stage I,II oocytes, there is a high concentration of a zinc protein whose zinc coordination site likely is composed of (His)2(Cys)2, such as, e.g., TFIIIA. As the oocytes develop, the predominant zinc species becomes one that exhibits the (His)2(N/0)2 zinc site found in lipovitellin. Hence, the ligands to the zinc atoms in intact oocytes and the changes that take place as a function of oogenesis and after their fertilization, during embryogenesis, now can be examined and explored.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.8.3227
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 8
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    Online Resource
    The C-terminal region of human angiogenin has a dual role in enzymatic activity.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 8 ( 1996-04-16), p. 3243-3247
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 8 ( 1996-04-16), p. 3243-3247
    Abstract: The ribonucleolytic activity of angiogenin (Ang) is essential to Ang's capacity to induce blood vessel formation. Previous x-ray diffraction and mutagenesis results have shown that the active site of the human protein is obstructed by Gln-117 and imply that the C-terminal region of Ang must undergo a conformational rearrangement to allow substrate binding and catalysis. As a first step toward structural characterization of this conformational change, additional site-directed mutagenesis and kinetic analysis have been used to examine the intramolecular interactions that stabilize the inactive conformation of the protein. Two residues of this region, Ile-119 and Phe-120, are found to make hydrophobic interactions with the remainder of the protein and thereby help to keep Gln-117 in its obstructive position. Furthermore, the suppression of activity by the intramolecular interactions of Ile-119 and Phe-120 is counterbalanced by an effect of the adjacent residues, Arg-121, Arg-122, and Pro-123 which do not appear to form contacts with the rest of the protein structure. They contribute to enzymatic activity, probably by constituting a peripheral subsite for binding polymeric substrates. The results reveal the nature of the conformational change in human Ang and assign a key role to the C-terminal region both in this process and, presumably, in the regulation of human Ang function.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.8.3243
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 9
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    Online Resource
    Angiogenin antagonists prevent tumor growth in vivo.
    Proceedings of the National Academy of Sciences ; 1995
    In:  Proceedings of the National Academy of Sciences Vol. 92, No. 2 ( 1995-01-17), p. 442-446
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 92, No. 2 ( 1995-01-17), p. 442-446
    Abstract: A noncytotoxic neutralizing monoclonal antibody (mAb), 26-2F, to human angiogenin (Ang), a potent inducer of neovascularization, has been reported to prevent or delay the establishment of HT-29 human tumor xenografts in athymic mice. In the present study the tumor model was modified to increase sensitivity to Ang antagonists to facilitate further investigations and comparisons of their capacity to inhibit tumor growth. An increase in the percentage of tumor-free mice from 10-25% to 65% is observed in this modified model after treatment with mAb 26-2F. An additional neutralizing mAb, 36u, that interacts with a different epitope on Ang similarly prevents the appearance of tumors, both alone and in combination with mAb 26-2F. In those tumors that develop in mice treated with these agents, the number of vascular elements is reduced. Actin, an Ang antagonist that unlike the mAbs binds both human and mouse Ang, also prevents the establishment of tumors while exhibiting no toxic effects at daily doses 〉 50 times the molar amount of circulating mouse Ang. Ang antagonists also inhibit the appearance of tumors derived from two other Ang-secreting human tumor cell lines--i.e., A549 lung adenocarcinoma and HT-1080 fibrosarcoma. These results demonstrate that inhibition of the action of Ang is an effective therapeutic approach for the treatment of malignant disease.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.92.2.442
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1995
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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