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61.
Jean-Alain Fehrentz Corine Genu-Dellac Muriel Amblard Franclois Winternitz Albert Loffet Jean Martinez 《Journal of peptide science》1995,1(2):124-131
N-Urethane-protected N-carboxyanhydrides (UNCAs) are very reactives. They have been successfully used in peptide synthesis, in both solution and solid phase. We have demonstrated that UNCAs are interesting starting materials for the synthesis of various amino acid derivatives. Chemoselective reduction of UNCAs with sodium borohydride led the corresponding N-protected β amino alcohols. Reaction of UNCAs with Meldrum's acid, followed by cyclisation, yielded enantiomerially pure tetramic acid derivatives. Diastereoselective reduction of tetramic acid derivatives produced (4S,5S)-N-alkoxycarbonyl-4-hydroxy-5-alkylpyrrolidin-2-ones derived from amino acids, which after hydrolysis yielded statine and statine analogues. Tetramic acid derivatives could also be obtained by reaction of UNCAs with benzyl ethyl followed by hydrogenolytic deprotection and decarboxylation. UNCAs also reacted with phosphoranes to produce the ketophosphorane in excellent yields. Subsequent oxidation with oxone or with [bis(acetoxy)-iodol]-benzene produced vicinal tricarbonyl derivatives. These reactions usually proceeded smoothly and with high yields. 相似文献
62.
Iciar Martinez Bent Dreyer Aasta Agersborg Annick Leroux Gilles Boeuf 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》1995,112(4)
Rearing of 1-year-old Arctic charr (Salvelinus alpinus) at 12°C, as well as the administration of 50 or 75 mgT3/kg feed, accelerated the neonatal to adult fast myosin heavy chain transition, but the effect of temperature was more dramatic than the effect of T3 administration. The endogenous plasma levels of T3 in charrs reared at 12°C were higher than those of analogous groups reared at natural temperature, which in the period under study was between 0.5 and 12°C. As in other species, T3 seemed to play a role in the regulation of the neonatal to adult fast myosin isoform transition by down-regulating the levels of the neonatal and increasing the levels of an adult fast myosin heavy chain. Temperature seemed to accelerate this transition at least, but not only, by inducing an increase in the endogenous levels of T3 in the Arctic charr. 相似文献
63.
Members of the rab family of small GTPases are localized to distinct cellular compartments and function as specific regulators of vesicle transport between organelles. Overexpression of rab5, which is associated with early endosomes and the plasma membrane, increases the rate of endocytosis [Bucci et al. (1992) Cell, 70, 715-728]. From sequence alignments and molecular modelling we identified structural elements that might contribute to the definition of the functional specificity of rab5. To test the role of these elements experimentally, we transplanted them onto rab6, which is associated with the Golgi complex. The chimeric proteins were assayed for intracellular localization and stimulation of endocytosis. First, we found that the C-terminus of rab5 could target rab6 to the plasma membrane and early endosomes but it did not confer rab5-like stimulation of endocytosis. Further replacement of other regions revealed that the N-terminus, helix alpha 2/loop 5 and helix alpha 2/loop 7 were all required to functionally convert rab6 into rab5. Reciprocal hybrids of rab5 containing these regions replaced with those of rab6 were inactive, demonstrating that each region is essential for rab5 function. These results indicate that distinct structural elements specify the localization, membrane association and regulatory function of rab5. 相似文献
64.
Murielle Rinaldi-Carmona Francis Barth Michel Haulme David Shire Bernard Calandra Christian Congy Serge Martinez Jeanne Maruani Gervais Nliat Daniel Caput Pascual Ferrara Philippe Soubri Jean Claude Brelire Grard Le Fur 《FEBS letters》1994,350(2-3):240-244
SR141716A is the first selective and orally active antagonist of the brain cannabinoid receptor. This compound displays nanomolar affinity for the central cannabinoid receptor but is not active on the peripheral cannabinoid receptor. In vitro, SR141716A antagonises the inhibitory effects of cannabinoid receptor agonists on both mouse vas deferens contractions and adenylyl cyclase activity in rat brain membranes. After intraperitoneal or oral administration SR141716A antagonises classical pharmacological and behavioural effects of cannabinoid receptor agonists. This compound should prove to be a powerful tool for investigating the in vivo functions of the anandamide/cannabinoid system. 相似文献
65.
Responses of rat submandibular acini to intracellular alkalinization were investigated. Intracellular alkalinization was induced by addition of NH4Cl or methylamines, or by prepulse with Na butyrate. Only partial recovery occurred following Na butyrate prepulse or methylated amine addition, but full recovery was observed following addition of NH4Cl. The latter recovery was DIDS and dimethylamiloride-insensitive but was inhibited by bumetanide or high [K+] and stimulated in Na+ free buffer and by ouabain. Acetylcholine stimulated recovery from NH4Cl- or Na butyrate pre-pulse-induced alkalinization and reduced the extent of alkalinization induced by methylated amines. Acetylcholine-stimulated recovery from NH4Cl-induced alkalinization was mimicked by substance P or ionomycin and was partially Ca2+-dependent. This stimulated recovery was bumetanide-insensitive but was partially sensitive to charybdotoxin. Taken together, these data indicate that in unstimulated cells, recovery from alkalinization induced by NH4Cl occurs by bumetanide-sensitive transport of the NH4+ ion, that DIDS-inhibitable anion transport contributes little to this recovery, and that acetylcholine and other Ca2+-elevating agents accelerate recovery from NH4Cl-induced alkaline challenge by a mechanism insensitive to bumetanide, DIDS, ouabain, and dimethylamiloride but sensitive to extracellular Ca2+ and to charybdotoxin. Partial recovery from alkaline challenge can also occur in the absence of NH4+ ions, and acetylcholine also stimulates this mode of recovery. Together, these data suggest that these cells have little intrinsic ability to recover from intracellular alkalinization and that the NH4+ ion may be a surrogate for K+ in at least two ion transport pathways. © 1994 wiley-Liss, Inc. 相似文献
66.
Leopold J. Anghileri Philippe Maincent Alfredo Cordova Martinez Pierre Thouvenot 《Biological trace element research》1994,46(1-2):103-111
The effects of the interaction between low molecular weight iron complexes (citrate, lactate, and ATP complexes) with ATP and proteins, on the modification of Ehrlich carcinoma cell calcium homeostasis have been studied. In that modification the ferric-ATP complex shows much higher activity than the others. Sodium ATP, by iron translocation from citrate and lactate, increases their activity. This phenomenon implicates ATP as a mediator on the cellular activity of the complexes. Proteins, particularly ferritin, appear to moderately reduce their activity, whereas glutathione and ascorbic acid, acting as lipid peroxidation-inhibitors, show only a slight reduction of the iron complex’s effects on cellular calcium uptake. 相似文献
67.
Carolina Martinez Pulido Indra S. Harry Trevor A. Thorpe 《Plant Cell, Tissue and Organ Culture》1994,39(3):225-230
Three-day-old cotyledonary explants of Pinus canariensis were subjected to 30 induction treatments using half-strength Bornman's medium containing various combinations of N6- benzyladenine, zeatin, kinetin and 2-isopentenyl-adenine. The highest numbers of buds were obtained with 10 M 6-benzyladenine, but both kinetin and zeatin influenced shoot elongation. Shoots were maintained on half-strength Schenk and Hildebrandt medium with 2% sucrose and 0.05% activated charcoal. For rooting, shoots were pulsed for 4 h in a 100 M indole-3-butyric acid aqueous solution (pH 4.2–4.5), and planted in peat:vermiculite:perlite (1:1:1). After 8 weeks, the numbers of rooted shoots were similar for most treatments. Therefore, the bud induction treatments did not significantly influence rooting of adventitious shoots of Canary Island pine. 相似文献
68.
Hepatitis B virus nucleocapsid particles do not cross the hepatocyte nuclear membrane in transgenic mice. 总被引:13,自引:10,他引:3 下载免费PDF全文
Transgenic mice that express the hepatitis B virus core protein were used to examine factors that influence the intracellular localization of nucleocapsid particles in the primary hepatocyte in vivo. In this model, viral nucleocapsid particles are strictly localized to the nucleus of the hepatocyte except when the nuclear membrane dissolves during cell division, at which time they enter the cytoplasm. The cytoplasmic nucleocapsid particles do not reenter the nucleus, however, when the nuclear membrane re-forms after cell division. The data support the notion that nucleocapsid particles can form de novo within the nucleus, and they suggest that performed nucleocapsid particles cannot be transported across the intact nuclear membrane in either direction. The results imply that nucleocapsid disassembly is probably required for entry of the hepadnaviral genome into the nucleus, and they question the role of the intranuclear viral nucleocapsid particle during the viral life cycle. 相似文献
69.
Summary
Coleus blumei cells were immobilized in a column reactor packed withLuffa cylindrica pieces. Medium was fed from the top of the column using a spray system and cells maintained high viability for 52 days. Cell
growth was slower but rosmarinic acid production was better compared to immobilized cells in the shake flasks. 相似文献
70.
G. León M. A. Martinez J. P. Etchegaray M. I. Vera J. Figueroa M. Krauskopf 《World journal of microbiology & biotechnology》1994,10(2):149-153
To obtain specific DNA probes for the identification of the fish pathogen, Renibacterium salmoninarum, a discriminatory recombinant DNA library was constructed using selective fragments of the bacterial genome. Three renibacterial clones, pMAM29, pMAM46 and pMAM77, containing 149, 73, and 154 bp respectively, were isolated and characterized. The specificity of the probes was confirmed by dot-blot and Southern hybridization analyses. Bacterial hybridization experiments revealed that pMAM29 discriminates the R. salmoninarum genome from that of other fish pathogens such as Aeromonas salmonicida, Yersinia ruckeri, Flexibacter columnaris, Lactobacillus piscicola, Vibrio ordalii, Vibrio anguillarum and Aeromonas hydrophila. Thus, this probe may provide a new means to diagnose bacterial kidney disease in asymptomatic fish and ova.The authors are with the instituto de Bioquímica, Universidad Austral de Chile, P.O. Box 567, Valdivia, Chile 相似文献