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21.
Anna Swierzko Lore Brade Elisabeth C. Höffgen Helmut Brade 《FEMS immunology and medical microbiology》1993,7(3):265-270
Abstract Rabbit polyclonal antibodies against the lipopolysaccharide (LPS) of the Rd1 P− mutant strain R7 of Salmonella minnesota were serologically characterized using R7 LPS, dephosphorylated LPS, deacylated LPS, deacylated, dephosphorylated and reduced LPS, and synthetic partial structures. The latter comprised partial structures of the core region of Rd1 P− LPS bound to the β 1 → 6-linked glucosamine disaccharide with two amide-linked 3-hydroxytetradecanoic acid residues or artificial glycoconjugates comprised of the synthetic oligosaccharides coupled to bovine serum albumin. Using a passive hemolysis and an enzyme immunoassay, absorption and inhibition experiments, the antibody specificities present could be determined. One group of antibodies required components of the core region and the phosphorylated glucosamine disaccharide of the lipid A moiety for binding. The majority of phosphate-independent antibodies was directed against the trisaccharide l -glycero-α- d -manno-heptopyranose(1 → 3)- l -glycero-α- d -manno-heptopyranose(1 → 5)3-deoxy- d -manno-octulosonic acid. Antibodies against the 1 → 3- and 1 → 7-linked heptose disaccharides and against a single heptose were also detected, however, with low titers. No antibodies were found which required the presence of fatty acids. 相似文献
22.
S. Chatfield M. Roberts P. Londono I. Cropley G. Douce G. Dougan 《FEMS immunology and medical microbiology》1993,7(1):1-7
Abstract Safe, live attenuated Salmonella strains can be produced by introducing defined non-reverting mutations into the chromosome. Such rationally attenuated strains have proved to be excellent oral vaccines in several animal species and can therefore be considered as candidate vaccines against invasive salmonellosis in both animals and man. A panel of attenuating lesions is now available from which it is possible to tailor the level of attenuation and hence produce strains with different immunogenic properties. Because of the spectrum of immune responses produced by such Salmonella vaccine strains they have been utilised extensively as vectors for delivering heterologous antigens to the mammalian immune system. We have focussed on the development of a single dose oral tetanus vaccine based on attenuated Salmonella strains expressing a non-toxic, immunogenic protein derived from tetanus toxin (fragment C). Several different expression systems have been used for fragment C and candidate vaccine strains have been constructed that are capable of protecting orally immunised mice against a lethal challenge with tetanus toxin. An oral tetanus vaccine may help to reduce the mortality rate from tetanus in the developing world by overcoming the problems associated with the implementation of vaccine programmes using the current parenteral vaccine. 相似文献
23.
Marie-Thérèse Château Herisoa Rabesandratana René Caravano 《FEMS immunology and medical microbiology》1996,13(1):19-28
Abstract The nature and the localization of the oxidative response triggered by different stimuli in either differentiated U937 cells and peripheral blood-derived human monocytes was investigated using luminometric and cytofluorometric techniques. Differentiated U937 cells essentially produced extracellular superoxide anion (O2 •− ), whatever the stimulus used. Monocytes, however, responded to Salmonella typhimurium , phorbol esters, and opsonized zymosan by an intracellular, an extracellular, and both an intra- and extracellular production of oxygen species, respectively. Furthermore, H2 O2 but not O2 •− was detected in the extracellular oxidative response of monocytes. Using differentiated U937 cells, luminol was found to be as efficient as lucigenin in the detection of extracellular O2 •− , providing sufficient concentrations of extracellular horseradish peroxidase were present. However, both azide and histidine inhibited the lucigenin-enhanced chemiluminescence, suggesting an initial and transient production of singlet oxygen differentiated U937 cells. Taken together these results strongly suggest that, when stimulated, differentiated U937 cells directly excrete O2 •− in the extracellular medium while, within monocytes, O2 •− is rapidly dismutated in H2 O2 which can eventually diffuse outside the cell. Such differences in the oxidative response between the two cell types could be explained by the lack of total closure of the phagosome, only observed in differentiated U937 cells. 相似文献
24.
Takehiko Nohmi Masami Yamada Michiko Matsui Keiko Matsui Masahiko Watanabe Toshio Sofuni 《Molecular & general genetics : MGG》1995,247(1):7-16
Expression of the umuDC operon is required for UV and most chemical mutagenesis in Escherichia coli. The closely related species Salmonella typhimurium has two sets of umuDC-like operons, umuDC
ST on the chromosome and samAB on a 60-MDa cryptic plasmid. The roles of theumuDC-like operons in chemically induced frameshift mutagenesis of the hisD3052 allele of S. typhimurium were investigated. Introduction of a pBR322-derived plasmid carrying umuDCST increased the rate of reversion of hisD3052, following treatment with 1-nitropyrene (1-NP) or 1,8-dinitropyrene (1,-8DNP) tenfold and fivefold, respectively, whereas it did not substantially increase the rate of reversion induced by other frameshift mutagens, i.e. 2-nitrofluorene (2NF) and 2-amino- 3-methyldipyrido[1,2-a:3 ,2-d]imi-dazole (Glu-P-1). Introduction of a pBR322-derived plasmid carrying samAB did not increase the incidence of reversion of hisD3052 observed with any of the mutagens examined. Deletion of umuDC
STSubstantially lowered the reversion rate induced by l-NP or 1,8-DNP, but it did not affect reversion induced by 2-NF, Glu-P-1 or N-hydroxyacetylaminofluorene (N-OH-AAF). Deletion of samAB had little impact on reversion incidence induced by any of the five frameshift mutagens. DNA amplification using the polymerase chain reaction technique followed by restriction enzyme analysis using BssHII, suggested that the mutations induced by the five frameshift mutagens were all CG deletions at the CGCGCGCG sequence in hisD3052. These results suggest that umuDCST, but not samAB, is involved in the -2 frameshift mutagenesis induced by l-NP and 1,8-DNP at the repetitive CG sequence, whereas neither operon participates in induction of the same type of mutations by 2-NF, Glu-P-1 or N-OH-AAF. 相似文献
25.
The possible B-cell epitopes of the outer membrane porin OmpC ofSalmonella typhi have been identified, using the primary structure of the protein, by means of multiple sequence alignment and the known molecular
structure of two other porins. From the analysis, 8 regions were identified as immunodominant and these were ranked based
on antigenic index and the ratio of the number of nonconserved residues to the fragment length. Model building of the top
two ranked regions show the tendency to form loop structures supporting the possibility of these being candidate epitopes. 相似文献
26.
27.
Although bacterial species display wide variation in their overall GC contents, the genes within a particular species' genome
are relatively similar in base composition. As a result, sequences that are novel to a bacterial genome—i.e., DNA introduced
through recent horizontal transfer—often bear unusual sequence characteristics and can be distinguished from ancestral DNA.
At the time of introgression, horizontally transferred genes reflect the base composition of the donor genome; but, over time,
these sequences will ameliorate to reflect the DNA composition of the new genome because the introgressed genes are subject
to the same mutational processes affecting all genes in the recipient genome. This process of amelioration is evident in a
large group of genes involved in host-cell invasion by enteric bacteria and can be modeled to predict the amount of time required
after transfer for foreign DNA to resemble native DNA. Furthermore, models of amelioration can be used to estimate the time
of introgression of foreign genes in a chromosome. Applying this approach to a 1.43-megabase continuous sequence, we have
calculated that the entire Escherichia coli chromosome contains more than 600 kb of horizontally transferred, protein-coding DNA. Estimates of amelioration times indicate
that this DNA has accumulated at a rate of 31 kb per million years, which is on the order of the amount of variant DNA introduced
by point mutations. This rate predicts that the E. coli and Salmonella enterica lineages have each gained and lost more than 3 megabases of novel DNA since their divergence.
Received: 7 July 1996 / Accepted: 27 September 1996 相似文献
28.
29.
The effect of inhibitors and uncouplers on the osmotic shock-sensitive transport systems for glutamine and galactose (by the β-methyl galactoside permease) was compared to their effect on the osmotic shock-resistant proline and galactose permease systems in cytochrome-deficient cells of Salmonella typhimurium SASY28. Both osmotic shock-sensitive and -resistant systems were sensitive to uncouplers and to inhibitors of the membrane-bound Ca2+, Mg2+-activated adenosine triphosphatase. This suggests that uptake by both types of systems is energized in these cells by an electrochemical gradient of protons formed by ATP hydrolysis through the ATPase. 相似文献
30.
Four naturally occurring compounds, indole-3-carbinol (I3C), apigenin (Api), ellagic acid (EA) and tannic acid (TA), were tested for their inhibitory effects against 1-nitropyrene- (1-NP) or 1,6-dinitropyrene (1,6-DNP)-induced genotoxicity in Salmonella tester strains and Chinese hamster ovary (CHO) cells. Api and TA strongly inhibited the bacterial mutagenesis induced by nitropyrenes, while 13C and EA had little or no effect. For example, in TA98, 0.2 μmole Api resulted in 48% and 56% inhibition of the mutagenicity induced by 4 nmole 1-NP and 0.035 nmole 1,6-DNP, respectively. With an equal dose, expected, a good correlation was observed between the antimutagenicity of nitropyrenes and their inhibitory effect on nitroreductase activity. This indicated that one of the possible antimutagenic mechanisms of Api or TA was to inactivate the metabolism of nitropyrenes. Two biological end-points, cytotoxicity and sister-chromatid exchange (SCEs), were used to screen the antigenotoxic effects of these compounds in CHO cells. At the sub-cytotoxic dose, 13C, Api and TA all protected against the cytotoxicity induced by 1-NP and 1,6-DNP, but only TA and Api gave a significant reduction of the frequency of SCEs. Moreover, this reduction was found to be highly dose-dependent. 相似文献