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| 2. |
- Leroy, Marie-Josephe, et al.
(författare)
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Characterization of two recombinant PDE3 (cGMP-inhibited cyclic nucleotide phosphodiesterase) isoforms, RcGIP1 and HcGIP2, expressed in NIH 3006 murine fibroblasts and Sf9 insect cells
- 1996
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 35:31, s. 10194-10202
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Tidskriftsartikel (refereegranskat)abstract
- cDNAs encoding PDE3 [cGMP-inhibited cyclic nucleotide phosphodiesterase (cGI PDE)] isoforms, cGIP1 and cGIP2, have been cloned from rat (R) and human (H) cDNA libraries. The deduced amino acid sequences of RcGIP1 and HcGIP2 are very similar in their conserved catalytic domains but differ in their N-terminal regulatory domains [Meacci, E., et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 3721-3725; Taira, M., et al. (1993) J. Biol. Chem. 268, 18573-18579]. cDNAs encoding both rat adipocyte RcGIP1 and human myocardial HcGIP2 (full-length forms and truncated forms lacking much of the putative N-terminal domain) were expressed in NIH 3006 fibroblasts and in Sf9 insect cells. The recombinant proteins exhibited the expected subunit molecular mass, immunologic reactivities, and characteristics of native membrane-associated forms of the enzymes, e.g., high affinity for cAMP (Km), sensitivity to the selective cGI PDE inhibitors OPC 3689 and OPC 3911 and to cGMP. The full-length recombinants were predominantly particulate, whereas the truncated HcGIP2 forms were cytosolic suggesting that N-terminal domains contain structural determinants important for membrane association. Both fibroblast RcGIP1 and authentic adipocyte cGI PDE were phosphorylated in vitro by cAMP-dependent protein kinase; tryptic [32P]peptides released from rat adipocyte 32P-cGI PDE and 32P-RcGIP1 exhibited identical electrophoretic profiles suggesting that the same peptides are phosphorylated in both.
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| 3. |
- Lu, H, et al.
(författare)
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Catalytic reduction of nitric oxide over copper Part III : Influence of water vapour
- 1999
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Ingår i: Journal of Molecular Catalysis A. - 1381-1169 .- 1873-314X. ; 138:2-3, s. 227-236
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on the effect of water vapour on the reduction of NO over copper in the presence of oxygen and isobutene. Reactions were studied at 700 K and at 770 K. Mass spectroscopy (MS) and X-ray photoelectron spectroscopy (XPS) were used to monitor the gas phase composition during reaction and to analyse the catalyst surface, respectively. XPS spectra show that the presence of water vapour influences the Cu oxidation state. At 700 K adsorption of aldehyde is partly blocked by copper oxide resulting in a decrease in the activity of the reaction, although the main mechanism is not changed. At 770 K, water vapour generates an even more oxidised surface, which promotes a complete oxidation of hydrocarbon, the main mechanism of NO reduction is changed, and the activity of the reaction is slightly increased. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 4. |
- Pradier, C.M., et al.
(författare)
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NO reduction by isobutene, in the presence of oxygen, on platinum and copper : a comparative study
- 1996
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 29:1-4, s. 59-65
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Tidskriftsartikel (refereegranskat)abstract
- The reaction of NO, oxygen and isobutene was studied under conditions close to stoichiometric, on a platinum and on a copper disk in order to better understand the role of each metal, free of any support and dispersion effects. The products of the reaction were analysed by mass spectrometry and an XPS characterization of the surface was carried out at different stages of the reaction. A correlation between the catalytic activity for NO conversion and the presence of adsorbed intermediates has been clearly demonstrated on platinum. On copper, a redox cycle of the metal is necessary to activate the catalyst. On platinum, oxygen is necessary to initiate the reaction, clean the surface and form reactive intermediates; the reaction is strongly sensitive to oxygen concentration, whereas on copper, oxygen does not directly participate in the reaction mechanism.
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| 5. |
- Stolte, W.C., et al.
(författare)
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The K-shell Auger decay of atomic oxygen
- 1997
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - 0953-4075. ; 30:20, s. 4489-4497
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Tidskriftsartikel (refereegranskat)abstract
- Relative photoionization cross sections for O+ and O2+ produced by the Auger decay of a 1s hole in atomic oxygen were measured by using synchrotron radiation between 525 and 553 eV. Energies and quantum defects of the members of the two Rydberg series converging to [1s]2s22p4(4P) and [1s]2s22p4(2P) ionization thresholds were determined. In addition, the 2P and 4P ionization thresholds were calculated from the two Rydberg series. The 182 meV resolution of the monochromator allowed a detailed study over both thresholds revealing evidence for post-collision interaction and allowing a comparison of the ionization continuum above both 2P and 4P thresholds with that of the ionization continuum above the Ar L2 and L3 edges. This comparison indicates that the lifetimes of the Ar(2p) and O(1s) hole states are approximately the same.
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| 6. |
- Yuan, XiMing, et al.
(författare)
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The establishment of two cell lines from a mouse uterine cervical carcinoma (U14) and their metastatic phenotype changes
- 1995
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Ingår i: Clinical and Experimental Metastasis. - 0262-0898 .- 1573-7276. ; 13:6, s. 463-73
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the heterogeneity of metastatic potential of murine cervical carcinoma (U14). Two cell lines, P11-90 and L10-90, were established from a pulmonary metastatic substrain (U14AP11) and a lymphatic metastatic substrain (U14AL10), which were selected from U14 in vivo after 11 and 10 passages, respectively. The biologic differences between the two cell lines are as follows. (1) The cells of the P11-90 line grow more rapidly compared with the L10-90 line. From the 40th passage the medium pH was different. (2) The median number of chromosomes in P11-90 and L10-90 was 72 and 64, respectively; the rates of gap aberration were 88% and 78%, respectively. (3) The number of T lymphocytes and T helper lymphocytes in the peripheral blood from hosts with P11-90 were higher than that of hosts transplanted with L10-90, but the number of B lymphocytes in the latter was larger than that in the former. (4) The metastatic potential of each cell line partially decreased compared to the relative tumor substrain, but their organ preference still remained and the transplant locations, axillary or footpad, had a prominent influence on their metastatic behavior. To observe the effects of metastatic target organs on the metastatic phenotypes of tumor cells, as well as to explore a method for the establishment and maintenance of the metastatic organ preference of tumor cells, conditioned medium (CM) from pulmonary or lymphatic node diploid cells was added to the culture medium of P11-90 and L10-90. Two sublines, P + P11-90 and Ln + L10-90, were thus established. Using stereological methods we found that the majority of P + P11-90 cells became larger and their nuclei also increased in size compared with their parental lines, but the majority of Ln + L10-90 cells became smaller in size, though the nuclei were enlarged. The pulmonary metastatic rate and lymphatic metastatic rate of P + P11-90, as well as the lymphatic metastatic rate of Ln + L10-90, were restored dramatically. The results suggest that by taking advantage of the interaction between tumor cells and the CM of host cells the metastatic potential of tumor cell lines can be maintained in vitro. Our work may offer an experimental model for the manipulation of metastasis of cell lines coming from the same parent strain but with different metastatic potentials.(ABSTRACT TRUNCATED AT 400 WORDS)
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| 7. |
- Zhu, J. W., et al.
(författare)
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Reductase specificity and the ratio regulation of E/Z isomers in pheromone biosynthesis of the European corn borer, Ostrinia nubilalis (Lepidoptera Pyralidae)
- 1996
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Ingår i: Insect Biochemistry and Molecular Biology. - : Elsevier BV. - 0965-1748. ; 26:2, s. 171-176
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Tidskriftsartikel (refereegranskat)abstract
- Species specificity of moth sex pheromones is in many cases achieved by means of specific blends rather than by specific components. Two pheromone strains of the European corn borer, Ostrinia nubilalis, use (E)- and (Z)-11-tetradecenyl acetate in different ratios as their pheromone, but show the same ratio of the pheromone precursors (70:30 E/Z-11-tetradecenoic acid). The hypothesis that the ratio of the pheromone components in the two strains and their hybrids is controlled by the specificity of the reductase system, responsible for conversion of acid to the corresponding alcohol precursors, was tested. Deuterium-labeled alcohols, aldehydes and fatty acids corresponding to the two pheromone components were topically applied to the pheromone glands in different ratios and their selective incorporation into pheromone components was determined by gas chromatography with mass selective detection. Acetylation of the (E)- and (Z)-11-tetradecenols was unselective, whereas the corresponding aldehydes and acids were selectively incorporated into the pheromone components. Z strain females selectively metabolized the Z-isomers whereas E strain females converted the E-isomers. The E strain being the most selective of the two strains. Hybrids converted both geometric isomers. The relative conversion rate of both E- and Z-isomers of all tetradecenoic acids with the double bond in positions from 7-12, was also determined. In addition to the Δ11-isomers, the E strain females converted (E)-8-tetradecenoic acid into acetate and the Z strain females converted (E)-12-tetradecenoic acid. None of these substrates occur naturally in the pheromone gland, but (E)-12-tetradecenyl acetate is a pheromone component of the Asian corn borer O. furnacalis. Thus the possibility for conversion of (E)-12-tetradecenoic acid to acetate in the Z strain, as well as the earlier reported conversion of (Z)-11-tetradecenoic acid to acetate in O. furnacalis, suggests that O. furnacalis is closest related to the Z strain of O. nubilalis.
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