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911.
912.
Liliana Chayet M. Cecilia Rojas Osvaldo CoriClifford A. Bunton Don C. McKenzie 《Bioorganic chemistry》1984,12(4):329-338
Kinetic analysis of the nonenzymic solvolysis of neryl and geranyl pyrophosphate (NPP and GPP, respectively) showed that the dissociation constants of the bis-metallic complexes with Mg2+ and Mn2+ were larger for NPP than for GPP by approximately one order of magnitude. Rate constants for reaction of the bis-metallic complexes were larger for NPP than for GPP. Qualitatively similar behavior was observed with complexes of Co2+. Extents of elimination and cyclization were increased by metal ions. Carbocyclase-catalyzed formation of cyclic monoterpene hydrocarbons in the presence of Mg2+ involved bis-metallic complexes as the “true” substrates. 相似文献
913.
Cecilia Schelin Håkan Wallin James Halpert Bengt Jergil 《Chemico-biological interactions》1984,49(3):269-281
A reconstituted mixed-function oxidase system, containing the major β-naphthoflavone-induced isozyme of rat liver cytochrome P-450 bound benzo[a]pyrene covalently in the presence of NADPH. NADPH-cytochrome P-450 reductase was required for binding and a maximum rate of adduct formation was obtained at 8 units of reductase per nmol cytochrome P-450. Phosphatidylcholine inhibited this reaction. Benzo[a]pyrene was bound to the cytochrome, but not to the reductase, as shown by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Approximately 6 molecules of benzo[a]pyrene bound to each molecule cytochrome P-450 during prolonged incubations. No binding occurred when the β-naphthoflavone-induced isozyme of cytochrome P-450 was replaced by the major isozyme induced by phenobarbital, but both cytochromes incorporated benzo[a]pyrene to approximately the same extent when they were incubated together in the presence of the reductase and NADPH. Metabolically activated benzo[a]pyrene also bound covalently to purified epoxide hydrodrolase, when this enzyme was added to the reconstituted mixed-function oxidase system. 相似文献
914.
Cecilia Gotti Donatella Cabrini Emanuele Sher Prof. Francesco Clementi 《Cell biology and toxicology》1987,3(4):431-440
Neurotoxicity of long-term exposure to lead, aluminum and cadmium has been studied in vitro on the human neuroblastoma cell line IMR32 by measuring cytotoxicity, and the effects on neuronal-specific characteristics such as nitrite outgrowth and expression of cholinergic receptors as parameters of toxicity. Cytotoxicity was highest with cadmium, intermediate with lead and lowest with aluminum exposure. Lead, but not cadmium and aluminum, interfered with neurite growth. The expression of a-bungarotoxin binding sites and muscarinic receptors was markedly increased by cadmium and not affected by aluminum exposure. Lead induced only an increase of toxin binding sites. These in vitro modifications are discussed in relation to the possible use of neuronal cell lines for detecting neurotoxic effects of heavy metals.Abbreviations ACh
acetylcholine
- -Bgtx
-bungarotoxin
- BrdUr
5'-bromodeoxyuridine
- CNS
central nervous system 相似文献
915.
Anna Carmen Borrione Anna Maria Cecilia Zanellato Leopoldo Saggin Manuela Mazzoli Giuseppe Azzarello Saverio Sartore 《Differentiation; research in biological diversity》1988,38(1):49-59
Myosin heavy chain (MHC) composition of chemically-induced rhabdomyosarcoma (RMS) was analyzed by gel electrophoresis and Western blotting using a panel of monoclonal antimyosin antibodies specific for embryonic-, neonatal-, slow- and adult fast-type MHC isoforms. Myosin extracted from tumours and electrophoresed on 6%-sodium dodecyl sulfate (SDS)glycerol gels was found to migrate as three distinct MHC components. These polypeptides were present in different relative amounts in the five RMS studied. Western blotting experiments revealed that variable proportions of embryonic-, slow- and adult fast-, but not neonatal-type, MHC isoforms are consistently expressed in RMS. Indirect and double immunofluorescence procedures applied to cryosections of tumoral tissue showed that: (a) RMS cells were unreactive with antineonatal-type-MHC antibody, (b) the majority of neoplastic, desmin-positive, cells contained embryonic- as well as adult fast-type MHCs and (c) a minority of cells were labelled by anti-slow MHC antibody. The results of this study indicate that there is no obligatory sequence of MHC isoform expression in the molecular transition (emb----neo----adult) which occurs during rat skeletal myogenesis. 相似文献
916.
917.
The role of inositol trisphosphate as a chemical messenger in excitation-contraction coupling is discussed, both in terms of positive and negative results. The evidence presented includes experiments on the effect of inositol trisphosphate in intact and skinned fibers, in calcium release from isolated sarcoplasmic reticulum vesicles, in activation of single calcium release channels incorporated in planar bilayers, and biochemical experiments that have established the presence of all the intermediate steps involved in the metabolism of phosphoinositides, both in intact muscle and in isolated membranes. From these results, it is clear that a role for inositol triphosphate in skeletal muscle function is highly likely; whether this molecule is the physiological messenger in excitation-contraction coupling remains to be established. 相似文献
918.
Aldo Andreani Silvia Burnelli Massimiliano Granaiola Alberto Leoni Alessandra Locatelli Rita Morigi Mirella Rambaldi Lucilla Varoli Laura Landi Cecilia Prata Francesco Vieceli Dalla Sega Cristiana Caliceti Robert H. Shoemaker 《Bioorganic & medicinal chemistry》2010,18(9):3004-3011
This paper reports the synthesis of new derivatives (formed by two indole systems separated by a central moiety) analogous of potent antitumor agents previously described. The activity of the bis-indoles bearing a pyridine core confirms the good result described in the previous paper and compound 4c was chosen for the first in vivo experiment (Hollow Fiber Assay). COMPARE analysis and structure–activity relationships were also considered. Contrary to data reported by other Authors, no correlations were found between antitumor activity and NQO1 induction. 相似文献
919.
Nilanjan Saha Layne T Watson Karen Kafadar Naren Ramakrishnan Alexey Onufriev Shrinivasrao Mane Cecilia Vasquez-Robinet 《Journal of computational biology》2007,14(1):97-112
Earlier work rigorously derived a general probabilistic model for the PCR process that includes as a special case the Velikanov-Kapral model where all nucleotide reaction rates are the same. In this model, the probability of binding of deoxy-nucleoside triphosphate (dNTP) molecules with template strands is derived from the microscopic chemical kinetics. A recursive solution for the probability function of binding of dNTPs is developed for a single cycle and is used to calculate expected yield for a multicycle PCR. The model is able to reproduce important features of the PCR amplification process quantitatively.With a set of favorable reaction conditions, the amplification of the target sequence is fast enough to rapidly outnumber all side products. Furthermore, the final yield of the target sequence in a multicycle PCR run always approaches an asymptotic limit that is less than one. The amplification process itself is highly sensitive to initial concentrations and the reaction rates of addition to the template strand of each type of dNTP in the solution. This paper extends the earlier Saha model with a physics based model of the dependence of the reaction rates on temperature, and estimates parameters in this new model by nonlinear regression. The calibrated model is validated using RT-PCR data. 相似文献
920.
G. Cecilia Toro Christer Wernstedt Carlos Medina Nicols Jaramillo Ulf Hellman Norbel Galanti 《Journal of cellular biochemistry》1992,49(3):266-271
Trypanosoma cruzi presents six histones electrophoretically resolved in three gel systems. Indirect evidence shows that one of these histones, name, corresponds to H4 in other species. We present evidence that histones is H4 by sequencing its amino terminal end. The amino terminal of T. cruzi histone H4, unlike that of other H4s examined thus far is not blocked. Moreover, this protein presents two variants. This partial amino acid sequence of T. cruzi histone H4 differs greatly from homologous sequences of human, yeast, or Tetrahymena. Since the conservatism of the core histones (H2A, H2B, H3, and H4) is clearly illustrated by comparative sequence analyses, the data shown here demonstrates that T. cruzi histone H4 is the most divergent reported. Quantitative analysis of the data suggests that the rate of substitutions in the histone H4 amino terminal sequence varies among different lineages. We postulate a slow-down in the evolutionary rate of histone H4 amino terminal domain in the metazoa branch related perhaps to the appearance of a novel function for this domain. 相似文献