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21.
Restriction cleavage maps of the DNAs of Streptococcus pneumoniae bacteriophages containing protein covalently bound to their 5'' ends 总被引:6,自引:0,他引:6
Rubens López Concepción Ronda Pedro García Cristina Escarmís Ernesto García 《Molecular & general genetics : MGG》1984,197(1):67-74
Summary Several pneumococcal bacteriophages showing a morphology similar to that previously described for Cp-1 (Ronda et al. 1981) have been isolated and purified from throat samples taken from healthy children. Three of these phages (Cp-5, Cp-7 and Cp-9) have been studied in detail and compared to Cp-1. The four phages differed in several respects, e.g. size, structural polypeptides, restriction enzyme cleavage patterns, etc. The DNA of Cp-5, Cp-7 and Cp-9 showed protease-sensitive transfecting activity. This, together with the results obtained by electrophoretic analyses as well as by isotopic labelling of these DNAs with [-32P] ATP and polynucleotide kinase indicated that all these new phages have a protein covalently linked to the 5 ends of their DNAs as in the case of Cp-1 (García et al. 1983). Restriction enzyme cleavage maps of Cp-1, Cp-5, Cp-7 and Cp-9 have been constructed. 相似文献
22.
Cristina Rinaldi-Garaci Enrico Garaci Vera Del Gobbo Cartesio Favalli Teresa Jezzi Allan L. Goldstein 《Cellular immunology》1983,80(1):57-65
The effects of thymosin-α1 on the stimulation of specific release of prostaglandin E2 (PGE2) from splenic lymphocytes and thymocytes were studied. Experiments were also performed to study in parallel the absolute levels of thymosin-α1 in the blood and the induction of serum FTS activity and of azathioprine sensitivity of spleen cells from adult thymectomized (ATx) mice. A significant difference in the release of PGE2 between normal splenocytes and splenocytes from ATx mice was observed. Thymosin-α1 at certain concentrations was able to stimulate PGE2 release from lymphocytes of ATx mice while inhibiting release in lymphocytes of normal mice. Also, thymocytes were stimulated to release PGE2 after incubation with α1 in a manner similar to that seen in spleen cells of ATx mice. Approximately the same concentration of α1 was found to also correct the low azathioprine sensitivity of splenocytes from ATx mice. Determinations of FTS-like activity in the blood and the pharmacokinetics of α1 after administration of this synthetic molecule show a clear dissociation. A maximum peak of α1 activity was obtained after 1 hr, while maximal FTS-like activity was observed after 24 hr. The inhibition of the induction by α1 of FTS-like activity and of Thy 1.2 antigen by indomethacin suggests that the action of α1 requires prostaglandin biosynthesis. 相似文献
23.
Sandro Cavicchi Daniela Guerra Vanna Natali Cristina Pezzoli Gianfranco Giorgi 《Journal of evolutionary biology》1989,2(4):235-251
From a laboratory stock of Drosophila melanogaster (Oregon), reared for more than 20 years at 18° C, a new population was derived and maintained at 28° C for 8 years. The chromosomal and cytoplasmic contribution to genetic divergence between the two populations was estimated. Six body traits and reproductive fitness were taken into account. The third chromosome is responsible for the adaptive difference for temperature between the two lines. Temperature-selected genes which control body size are located on the second and third chromosomes, although the contribution of each chromosome depends on the environment in which the flies develop. The correlation between the chromosomal and cytoplasmic contributions to different traits and fitness, changes with temperature. At 28° C the correlation between fitness and each body trait is proportional to the response to selection exhibited by each of them, but this is not true at 18° C. Body size has, therefore, an adaptive significance in relation to temperature, which is expressed only in the environment where selection occurs. Cytoplasmic genes affect almost all characters to an extent similar to that of chromosomal genes. Inter-chromosomal and nucleo-cytoplasmic interactions are present and also change with temperature. In general, genes selected in a given environment produce greater phenotypic changes in that environment than in another. The population that experienced both temperatures is fitter in both environments, suggesting that the capacity to adapt to warm temperatures depends on genes other than those which are involved in the adaptation to cold. 相似文献
24.
Dr. María Cristina Maldonado Ana María Strasser de Saad Danley Callieri 《Current microbiology》1989,18(5):303-306
Several recent reports have described large numbers of monoclonal antibodies that cross-react with toxins A and B ofClostridium difficile; this suggests that the toxins share major epitopes. Our results show that monoclonal antibodies (MAb) against other antigens bind nonspecifically to both toxins. Therefore, we believe that the cross-reacting MAb bind by this manner and not by a true immune reaction. 相似文献
25.
Pier Giorgio Borasio Carla Biondi Maria Enrica Ferretti Elena Fabbri Maria Cristina Pareschi 《Neurochemical research》1989,14(12):1181-1186
Agonists modulation of Mg2+-dependent adenylate cyclase activity has been studied in guinea-pig superior cervical ganglion crude membrane preparations. In the absence of receptors ligands, Mg2+ stimulates the enzyme in a concentration-dependent manner. The dose-activation curve shows heterogeneity and two components with higher and lower apparent affinity states, are extrapolated. In the presence ofD-Ala2-met-enkephalinamide only one component is present and the apparent affinity of the ganglionic adenylate cyclase system for the divalent cation as well as Vmax are inhibited. On the contrary, prostaglandin E2 increases affinity and Vmax values of the lower and, to a lesser extent, of the higher Km component. When the two drugs are tested in combination, not only the inhibitory effect of the opiate is overcome, but a large increase of the apparent affinities and Vmax values for both components is obtained, suggesting the involvement of the Mg2+-regulated subunits of the adenylate cyclase system in the supra-additive stimulation mechanism of the enzyme. 相似文献
26.
The protective effect of zinc against slight teratogenical action, exerted by low cadmium concentrations, was evaluated inBufo arenarum embryos treated simultaneously with both cations or preincubated with Zn before Cd treatment. Data on survival, malformations, and delay in development pointed out that Zn could prevent the-deleterous effects of Cd in previous and simultaneous treatments with that heavy metal. 相似文献
27.
Figueiredo A. Cristina Almendra M. João Barroso José G. Scheffer Johannes J. C. 《Biotechnology letters》1996,18(8):863-868
The transformation capacity of Achillea millefolium L. ssp. millefolium (yarrow) cell suspension cultures was investigated using geraniol (50mg/l) and borneol, menthol, thymol and farnesols (25mg/l) as substrates. Apart from converting these substrates into several biotransformation products, the cell suspension cultures were also able to glycosylate both the substrates and the biotransformation products. aa]Key Words bb]Achillea millefolium L. ssp. millefolium bb]Yarrow bb]Compositae bb]Biotransformation bb]Glycosylation bb]Geraniol bb]Borneol bb]Menthol bb]Thymol bb]Farnesols 相似文献
28.
We have investigated the substrate subsite recognition requirement of the xyloglucan endo-transglycosylase/xyloglucan-specific endo-(14)--d-glucanase (NXET) from the cotyledons of nasturtium seedlings. Seed xyloglucans are composed almost entirely of the Glc4 subunits XXXG, XLXG, XXLG and XLLG, where G represents an unsubstituted glucose residue, X a xylose-substituted glucose residue and L a galactosyl-xylose-substituted glucose residue. Thus in the xyloglucan sequence shown below, the xylose (Xyl) residues at the backbone glucose (Glc) residues numbered — 3,— 2, + 2 and + 3 may be galactose-substituted, and NXET cleaves between the unsubstituted glucose at — 1 and the xylose-substituted glucose at + 1, which never carries a galactosyl substituent. We have isolated the xyloglucan oligosaccharides XXXGXXXG and XLLGXLLG from NXET digests of tamarind seed xyloglucan, have modified them enzymatically using a pure xyloglucan oligosaccharide-specific -xylosidase from nasturtium seeds to give GXXGXXXG and GLLGXLLG, and have identified and compared the products of NXET action on XXXGXXXG, GXXGXXXG, XLLGXLLG and GLLGXLLG. We have also compared the molar proportions of XXXG, XLXG, XXLG and XLLG in native tamarind and nasturtium seed xyloglucans with those in NXET digests of these polysaccharides. Using these and existing data we have demonstrated that NXET action does not require xylosesubstitution at glucose residues — 4, — 2, + 1 and + 3 and that xylose substitution at + 2, is a requirement. There may also be a requirement for xylose substitution at — 3. We have demonstrated also that galactosyl substitution of a xylose residue at + 1 prevents, and at — 2 modifies, chain-cleavage. A partial model for the minimum substrate binding requirement of NXET is proposed.Abbreviations G
unsubstituted glucose residue
- X
xylose-substituted glucose residue
- L
galactosylxylose-substituted glucose residue
- F
fucosyl-galactosylxylose-substituted glucose residue
- Gal
galactose
- Glc
glucose
- HPAE
high-performance anion-exchange chromatography
- NXET
nasturtium xyloglucan endo-transglycosylase or xyloglucan-specific endo-(14)--d-glucanase
- Xyl
xylose
This work was funded jointly by Unilever UK and the Department of Trade and Industry (UK) via the LINK initiative Agro-Food Quality. 相似文献
29.
Cristina Elena Canteros Laura Rodero Maria Cristina Rivas Graciela Davel 《Mycopathologia》1996,136(1):21-23
A rapid method to evidence urease activity is described. Urea hydrolysis and consequent production ammonia are detected by a chemical reaction producing a blue phenol compound (indophenol blue). Three hundred and three yeast were tested. Out of 107 urease-positive organisms detected by Christensen's Urea Agar Test (CUAT) 102 were positive by our method. No false negatives were observed by this method when testing 87 Cryptococcus strains. Ths practical screening test for presumptive identification of Cryptococcus neoformans is simple, unaffected by pH changes and requires 15 minutes to be performed. 相似文献
30.
Jose Pontón Fernando L. Hernando Maria Dolores Moragues Pedro L. Barea Mara Gerloni Stefania Conti Paola Fisicaro Cristina Cantelli Luciano Polonelli 《Mycopathologia》1996,133(2):89-94
The presence of heat shock mannoproteins (HSMPs) reactive with sIgA was demonstrated in several C. albicans strains. The subculture of the C. albicans isolated from mucosal surfaces on Sabouraud's dextrose agar at 25 °C switched off the HSMP expression. A re-expression of the HSMPs was obtained in the same medium by shifting the temperature of incubation to 37 °C. However, expression of HSMPs in two strains isolated from deep infections was maintained during several subcultures on Sabouraud's dextrose agar at 25 °C. A glycoprotein of 200 kDa seemed to be the main HSMP reacting with vaginal sIgA. The data presented in this study suggest that factors other than temperature can influence the expression of C. albicans HSMPs and therefore these antigens should be referred as stress mannoproteins.Abbreviations HSMPs
heat shock mannoproteins
- MAb
monoclonal antibody
- sIgA
secretory IgA 相似文献