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51.
Claude Penel Thomas Gaspar Michèle Crèvecoeur Claire Kevers Hubert Greppin 《Physiologia plantarum》1990,79(2):250-254
Ca2+ and Mn2+ activate the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) by root microsomes of Vicia lens as they do in other similar systems. The preparation of microsomes in the presence of Mn2+ greatly increases their ability to convert ACC into ethylene, without addition of Mn2+ in the reaction mixture. Ca2+ does not have this property. The effect could not be attributed to Mn2+ entrapping into membrane vesicles (sonication followed by repelleting had no effect) but, possibly, in part to Mn2+ -mediated binding to microsomes of a soluble factor favouring the conversion of ACC to C2 H4 . Although no direct correlation could be established in vitro between ethylene-forming-enzyme (EFE) and peroxidase activities, some soluble peroxidases might be this soluble factor. Mn2+ favoured attachment to membranes of some peroxidase activity from the soluble fraction and from commercial HRP and lipoxygenase. This binding effect of Mn2+ cannot be readily distinguished from its role in the generation of a chain of free radicals and in redox mechanisms. 相似文献
52.
In Vivo and In Vitro Evidence for the Biosynthesis of Testosterone in the Telencephalon of the Female Frog 总被引:5,自引:2,他引:3
Ayikoe G. Mensah-Nyagan Jean-Luc Do-Rego Marc Feuilloley Albert Marcual Catherine Lange †Georges Pelletier Hubert Vaudry 《Journal of neurochemistry》1996,67(1):413-422
Abstract: Neurons and glial cells are capable of synthesizing various steroid hormones, but biosynthesis of testosterone in the CNS has never been reported. The aim of the present study was to demonstrate the synthesis of testosterone in the frog brain. The presence of 17β-hydroxysteroid dehydrogenase (17β-HSD)-like immunoreactivity was detected in a population of glial cells located in the telencephalon. Reversed-phase HPLC analysis of brain tissue extracts combined with radioimmunoassay detection revealed the presence of substantial amounts of testosterone and 5α-dihydrotestosterone (5α-DHT) in the telencephalon where 17β-HSD-positive cells were visualized. In male frogs, castration totally suppressed testosterone and 5α-DHT in the blood and in the rhombencephalon but did not affect the concentration of these two steroids in the telencephalon. Chemical characterization of testosterone in female frog telencephalon extracts was performed by coupling HPLC analysis with gas chromatography-mass spectrometry. Using the pulse-chase technique with [3 H]pregnenolone as a precursor, the formation of a series of metabolites was observed, including dehydroepiandrosterone, androstenedione, testosterone, 5α-DHT, and estradiol. These data demonstrate the existence of an active form of 17β-HSD in the frog telencephalon, which is likely involved in testosterone biosynthesis within the brain. 相似文献
53.
Olivier Cohen Christine Cans Jean Louis Gilardi Hubert Roth Marie-Ange Mermet Pierre Jalbert Jacques Demongeot Martine Cuillel 《Human genetics》1996,97(5):659-667
Reciprocal translocations (rcp) are among the most common constitutional chromosomal aberrations in man. Using a European
database of 1574 families carrying autosomal rcp, a cartographic study was done on the breakpoints involved. The breakpoints
are non-randomly distributed along the different chromosomes, indicating “hot spots”. Breakpoints of rcp that result in descendants
that are unbalanced chromosomally at birth are more frequent in a distal position on chromosomal arms, and 65% of them are
localised in R-bands. Among the R-bands, bands rich in GC islands and poor in Alu repetitive sequences are more frequently
the site of breakpoints, as well as bands that include a fragile site. This result suggests that the variation in degree of
methylation in GC islands could be involved in chromosomal breakage and hence in chromosomal rearrangements.
Received: 10 April 1995 / Revised: 1 July 1995 相似文献
54.
J.Michael Conlon Nicolas Chartrel Jerome Leprince Charles Suaudeau Jean Costentin Hubert Vaudry 《Peptides》1996,17(8):1291-1296
A peptide derived from the posttranslational processing of proenkephalin A was isolated from an extract of the brain of the European green frog Rana ridibunda and its primary structure established as: Tyr-Gly-Gly-Phe-Met-Arg-Arg-Val-Gly-Arg10-Pro-Glu-Trp-Trp-Gln-Asp-Tyr-Gln-Lys-Arg20-Tyr-Gly-Gly-Phe-Met. The structure was confirmed by chemical synthesis. The peptide represents an amphibian equivalent of bovine adrenal peptide E [preproenkephalin A (206–230)-peptide] but the sequence contains two amino acid substitutions (Met15 → Gln and Leu25 → Met) compared with the mammalian peptide. The data support previous hypotheses that the Leu-enkephalin sequence is not present in preproenkephalin A of amphibians. Intracerebroventricular injections of frog peptide E (10 and 100 ng) in mice had no significant effect on horizontal locomotor activity. The peptide, in doses up to 1 μg, had no effect on latency of escape jumping in the hot plate test and the peptide (100 ng) did not modify responses (paw licking, rearing, and escape jumping) in morphine-treated mice. 相似文献
55.
In the short day plant Chenopodium rubrum and the long day plant Nicotiana tabacum cv. Havana 425, adenylate kinase (EC 2.7.4.3) occurs as a family of isoforms, with at least two members localized in the chloroplast representing the main isoforms. In this work, isoforms were separated by anion exchange chromatography and relative isoform activities were compared between vegetative plants and plants induced to flowering. In both species examined, a light regime leading to floral induction resulted in a significant decrease in the activity of one chloroplast isoform. This decrease modified considerably the relative distribution of isoform activities, especially that between the two chloroplast activities. 相似文献
56.
ChimpanzeesPan troglodytes in Kibale National Park, Uganda occasionally swallow entire leaves ofRubia cordifolia (Rubiaceae) without chewing them. The leaves are subsequently egested with minimal damage and no sign of any significant
digestion. Similar behavior reported elsewhere has been proposed to have medicinal effects. Here we test the hypothesis that
chemical components in swallowed leaves have negative effects on intestinal nematodes. We used anin vitro assay to detect the effects of methanol extracts ofR. cordifolia leaves on nematodes,Strongyloides spp., cultured from feces. Control extracts were distilled water, methanol solution, and methanol extracts of food items
that were chewed, rather than swallowed, by chimpanzees. Effects of experimental or control solutions were assayed by nematode
motility. There was no difference in nematode motility among control and experimental extracts. This study therefore did not
support the hypothesis of pharmacological self-medication via leaf swallowing. 相似文献
57.
A protein binds the selenocysteine insertion element in the 3'-UTR of mammalian selenoprotein mRNAs. 总被引:6,自引:0,他引:6
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Several gene products are involved in co-translational insertion of selenocysteine by the tRNA(Sec). In addition, a stem-loop structure in the mRNAs coding for selenoproteins is essential to mediate the selection of the proper selenocysteine UGA codon. Interestingly, in eukaryotic selenoprotein mRNAs, this stem-loop structure, the selenocysteine insertion sequence (SECIS) element, resides in the 3'-untranslated region, far downstream of the UGA codon. In view of unravelling the underlying complex mechanism, we have attempted to detect RNA-binding proteins with specificity for the SECIS element. Using mobility shift assays, we could show that a protein, present in different types of mammalian cell extracts, possesses the capacity of binding the SECIS element of the selenoprotein glutathione peroxidase (GPx) mRNA. We have termed this protein SBP, for Secis Binding Protein. Competition experiments attested that the binding is highly specific and UV cross-linking indicated that the protein has an apparent molecular weight in the range of 60-65 kDa. Finally, some data suggest that the SECIS elements in the mRNAs of GPx and another selenoprotein, type I iodothyronine 5' deiodinase, recognize the same SBP protein. This constitutes the first report of the existence of a 3' UTR binding protein possibly involved in the eukaryotic selenocysteine insertion mechanism. 相似文献
58.
Bienvenu Thierry Hubert Dominique Fonknechten Nuria Dusser Daniel Kaplan Jean Claude Beldjord Cherif 《Human genetics》1994,94(1):65-68
Human Genetics - Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). Analysis of DNA from a pancreatic sufficient patient by means of... 相似文献
59.
Rinkel Monique Hubert Jean-Claude Roux Brigitte Lett Marie-Claire 《Current microbiology》1994,29(5):249-254
AKlebsiella pneumoniae strain having mobilization helper potential has been isolated from the river Rhine. Analysis of the transconjugants resulting from the mobilization of nonconjugative pBR-type plasmids and RSF1010 derivatives showed that the transfer-helper capacity of theK. pneumoniae strain is related to the presence of a Tn3-like transposable element, Tn5403. This element has been identified and localized in a plasmid. 相似文献
60.
Fourier transform infrared (FTIR) spectroscopy for identifying Lactobacillus species 总被引:3,自引:0,他引:3
Abstract Fourier Transform infrared (FTIR) spectroscopy can be used to identify microorganisms. This study describes the influence of culture conditions on FTIR spectra and the discrimination of Lactobacillus species found in breweries. Fifty three Lactobacillus strains were analysed by FTIR spectroscopy and identification at the species level was correct for 94% of the strains, and at the strain level for 91% of the strains. 相似文献