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111.
Yaīr Reisner Gabriel Gachelin Philippe Dubois Jean-François Nicolas Nathan Sharon François Jacob 《Developmental biology》1977,61(1):20-27
Peanut agglutinin (PNA), a lectin specific for terminal d-galactosyl residues, was found to react with embryonal carcinoma cells, but not with their differentiated derivatives. Receptors for PNA were detectable at the surface of all cells of the quasinullipotent F9 line and on only 50% of the multipotent PCC3/A/1 line. The fraction of the PCC3/A/1 population which expresses the F9 antigen was found to be included in the subpopulation carrying the PNA receptors. PNA+ and PNA? subpopulations of PCC3/A/1 were separated by a PNA-mediated reversible agglutination of PNA+ cells with rabbit erythrocytes. These subpopulations were essentially F9+ and F9?, respectively. 相似文献
112.
The purpose of this study was to employ the Salmonella/microsomal assay (Ames test) to investigate the mutagenic potential of a thermostable exotoxin of Bacillus thuringiensis subsp. morrisoni. Bacteria are ideal for the detection of infrequently occurring point mutations because the large number of organisms (200 to 400 million bacteria per plate) exposed to the mutagen at any one time increases the possibility of observing a random mutational event. The exotoxin used in this study was produced using the shaker flask fermentation procedure with mineral casein broth. A Petri dish method of bioassay using fresh bovine feces was used to determine the efficacy of the exotoxin against horn flies. The LD50 was found to be 5.35 μl/g of feces. Five bacterial tester strains were identified and characterized for the genetic markers described by Ames et al. (B. N. Ames et al., 1975, Mutat. Res., 31, 347–364). Appropriate doses of the B. thuringiensis supernatant, solvent or positive control were added to agar plates. The supernatant was tested at five dose levels against all five strains of bacteria. Controls of bacteria only were included for spontaneous reversions. All treatments were performed in triplicate. The numbers of revertant colonies from each set of triplicate plates were averaged and the standard deviation calculated and compared to that found with the solvent control. The negative controls, positive controls, and sterility controls all fulfilled requirements for determination of a valid test. No detectable mutagenic activity was found for the thermostable exotoxin of B. thuringiensis morrisoni. 相似文献
113.
Oryza sativa L. var. bahia coleoptile cell walls show sufficient autolytic activity for the release into the surrounding medium of amounts up to 60 μg of sugars per mg of dry weight of cell wall. The products released elute in Bio-gel P.2 as mono- and polysaccharides with glucose as the sole component. The polysaccharide component releases tri- and tetrasaccharides on treatment with a glucanase specific for β (1–3) (1–4) linkages in the same proportion as that of the mixed glucan of the cell wall. This supports the hypothesis that the polysaccharide component originates from the cell wall glucan and that autolysis is therefore related to the processes of the loss of rigidity of the cell wall. Nojirimycin (a specific glucanase inhibitor and inhibitor of auxin-induced elongation) decreases autolytic activity of the cell walls, reducing it to 30% of its normal value. Bio-gel P. 2 elution of the products released in autolysis in the presence of nojirimycin shows that only the monosaccharide fraction was affected. 相似文献
114.
Role of pancreatic enzymes in the intraluminal transport and ileal absorption of vitamin B 12 (Cb 1)
J P Nicolas G Marcoullis 《Comptes rendus des séances de la Société de biologie et de ses filiales》1980,174(4):548-563
The present paper outlines the classical concepts of transport and absorption of vitamin B12 and discusses findings which provide new insight into the important role of pancreatic enzymes in the absorption of the vitamin B12. In vivo experiments with healthy subjects and patients with exocrine pancreatic insufficiency demonstrate that the pancreatic enzymes do not activate "the precursor" intrinsic factor molecule but solely dissociate vitamin from the inactive R type proteins with a consequent coupling to the biologically active intrinsic factor. 相似文献
115.
Some diversity and niche amplitude parameters were applied to rangeland pastures of the Central Iberian Peninsula and to their succession stages after the periodical ploughing typical of the traditional management of these areas. Four different slopes within a large area of undulating terrain were selected for the monitoring of succession as they contained the characteristical geomorphological pattern of the area (denudation, transport and accumulation sectors).If we consider the total entropy theorem, H (E.P.)=H(E)+H(P/E), the total entropy of the slope H(E.P) and the entropy of species H(E) increase as succession progresses. As the value of the entropy of the sampling plots conditioned by the species H(P/E) is affected by the number of plots utilized, we employed the expression A=H(P/E)/log2 number of plots, similar to Pielou's index for niche amplitude, W=H(P/E)/H(P).This values decreases with succession, indicating that plant species tend to occupy more definite sectors along the slope. The number of low entropy species H(P/E)
i or specialist species, confined to narrow sectors also increases. When computed separately within the different sectors niche amplitude results in small values for the low slope regions (accumulation sector). This effect becomes more pronounced when succession advances.
Nous remercions le Conseil d'Administration de La Paranza, propriétaire du Castillo de Vañuelas, et particulièrement Mrs. C. Hernandez-Ros et J. A. Léon-Vrquijò, pour les faeilités qu'ils ont données à cette équipe durant la réalisation de ce travail. 相似文献
116.
Importance of neurophysin dimer and of tyrosine-49 in the binding of neurohypophyseal peptides 总被引:1,自引:0,他引:1
P Nicolas J Wolff M Camier C Di Bello P Cohen 《The Journal of biological chemistry》1978,253(8):2633-2639
117.
Genetic and biochemical consequences of thymidylate stress 总被引:8,自引:0,他引:8
We have examined the genetic and biochemical consequences of thymidylate stress in haploid and diploid strains of the simple eukaryote Saccharomyces cerevisiae (Bakers' yeast). Previously we reported that inhibition of dTMP biosynthesis causes "thymineless death" and is highly recombinagenic, but apparently not mutagenic, at the nuclear level; however, it is mutagenic for mitochondria. Concurrent provision of dTMP abolishes these effects. Conversely, excess dTMP is highly mutagenic for nuclear genes. It is likely that DNA strand breaks are responsible for the recombinagenic effects of thymidylate deprivation; such breaks could be produced by reiterative uracil incorporation and excision in DNA repair patches. In our experiments, thymidylate stress was produced both by starving dTMP auxotrophs for the required nucleotide and also by blocking de novo synthesis of thymidylate by various antimetabolites. We found that the antifolate methotrexate is a potent inducer of mitotic recombination (both gene conversion and mitotic crossing-over). This suggests that the gene amplification associated with methotrexate resistance in mammalian cells could arise, in part, by unequal sister-chromatid exchange induced by thymidylate stress. In addition, several sulfa drugs, which impede de novo folate biosynthesis, also have considerable recombinagenic activity. 相似文献
118.
J González-Cabrero R de Nicolas L Hernando J Egido 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(12):4162-4166
We have recently described that patients with IgA nephropathy present high serum levels of anti-BSA idiotypic antibodies that were well correlated with the existence of hematuria. Furthermore, these Id were found in circulating and renal deposited immune complexes. In the present work, we examined the expression of surface idiotypic determinants on PBL by flow cytometry and their in vitro production, using as reagent anti-idiotypic antibodies previously well characterized. The presence of cross-reactive Id-bearing cells was observed in 5 out of 6 patients studied, with frequencies ranging from 3 to 12% of lymphocytes. After 7 days of culture, the spontaneous synthesis of idiotypic antibodies by PBL was found elevated in 6 out of 13 (46%) patients. A major Id cell expression and production was noted in patients with active disease as defined by hematuria. The preincubation of PBL with 20 and 50 micrograms of anti-idiotypic antibodies/2 x 10(6) cells for 3 days induced a significant inhibition of cross-reactive Id production in a dose-dependent fashion, with a degree of suppression between 12 and 50% in five out of six patients studied. In the above assays, as negative controls, we used the anti-Id antibodies previously adsorbed on an Id-Sepharose column. On the whole, these results suggest that patients with IgA nephropathy present dysfunctions in the Id-Anti-Id network that could play an important role in the pathogenesis of this disease. 相似文献
119.
Nucleotide sequence of xylE from the TOL pDK1 plasmid and structural comparison with isofunctional catechol-2,3-dioxygenase genes from TOL, pWW0 and NAH7.
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Detailed restriction and nucleotide sequence analysis of the Pseudomonas putida TOL plasmid pDK1 xylE gene revealed significant homology with isofunctional xylE (81.5%) and nahH (78.0%) genes from the TOL pWW0 and NAH7 plasmids. The highest degrees of nucleotide and apparent amino acid conservation (82.2 and 86.4%, respectively) among all three genes were found to exist within a region comprising 264 nucleotides encoding the C terminus. A comparison of localized regions revealed significantly greater homology between xylEpWW0 and xylEpDK1 within the C-terminal region, whereas xylEpWW0 and nahH showed greater similarity at the N terminus. The possibility that xylEpWW0 may represent a genetic hybrid of xylEpDK1 and nahH is discussed. 相似文献
120.