| urine mutagenicity in workers directly employed in coke production. | mutagenicity and toxicity of urine samples of 30 coke oven workers (group i) and 26 individuals composing a control group (group ii) was estimated using ames test with salmonella typhimurium strains ta 98 and ta 100. urine mutagenicity and toxicity, tested with strain ta 98 and metabolic activation, was significantly higher in group i than in group ii. using the strain ta 100, urine samples of coke oven workers showed only direct toxicity. mutagenic and toxic activity was observed mostly in work ... | 1992 | 1298485 |
| proliferative and t-cell specific interleukin (il-2/il-4) production responses in spleen cells from mice vaccinated with aroa live attenuated salmonella vaccines. | t-cell responses were studied in mice immunized with the salmonella typhimurium aroa sl3261 live attenuated vaccine strain. t-cell responses in the spleen, both in whole cell populations and in nylon wool non-adherent (t-cell enriched) cells, were studied in vitro as proliferation by incorporation of tritiated thymidine and production of t-cell specific cytokines [il-2 (interleukin-2)/il-4]. stimulating antigens included whole salmonella lysates and purified lipopolysaccharide (lps), both untrea ... | 1992 | 1298869 |
| the biological interaction of cis- and trans-urocanic acid and dna. | the potential for the cis and trans isomers of urocanic acid to produce dna damage was measured by assays for dna binding (32p-postlabeling assay), for induction of dna repair (unscheduled dna synthesis assay) and induction of mutations (salmonella typhimurium and escherichia coli plate-incorporation assays). these assays did not detect any evidence of a direct effect of either isomer of urocanic acid on dna over a wide range of concentrations. these results suggest that neither isomer of urocan ... | 1992 | 1300140 |
| butylated hydroxyanisole produces both mutagenic and desmutagenic derivatives under gastric conditions. | dietary butylated hydroxyanisole (bha) has been known to have inconsistent functions on carcinogenesis, both prevention and initiation. we assumed that both functions of bha were introduced by the derivatives formed after the reaction with gastric components such as nitrite in the stomach. we then identified the derivatives produced by incubating bha with sodium nitrite at ph 2.0 or ph 5.0. eight derivatives were detected; 2-tert.-butyl-p-quinone (bq), 3,3'-di-tert.-butyl-biphenyldiquinone-(2,5, ... | 1992 | 1300306 |
| coexpression of the cys e and cys m genes of salmonella typhimurium in mammalian cells: a step towards establishing cysteine biosynthesis in sheep by transgenesis. | the salmonella typhimurium genes for serine acetyltransferase (cys e) and o-acetylserine sulphydrylase b (cys m) were isolated and characterized in order to express these as transgenes in sheep to establish a cysteine biosynthesis pathway and, thereby, to achieve an increased rate of wool growth. comparison of the s. typhimurium and escherichia coli genes showed considerable homology, both at the nucleotide and amino acid sequence levels. the in vitro and in vivo expression studies showed that b ... | 1992 | 1301209 |
| antigen-binding diversity of human hybridoma autoantibodies derived from splenocytes of patients with sle. | the antigen-binding specificity of human hybridoma-derived monoclonal autoantibodies (mab) was analysed with mabs derived from the spleens of two patients with active systemic lupus erythematosus (sle). from one patient 72 mabs (rsp clones) and from the other 173 mabs (rt clones) were obtained. the binding specificity of these mabs was analysed by solid- and fluid-phase elisa against the autoantigens ssdna, dsdna, cardiolipin, smrnp, histones, sm-d and ss-b (la) synthetic peptides, and foreign a ... | 1992 | 1301976 |
| extracellular export of shiga toxin b-subunit/haemolysin a (c-terminus) fusion protein expressed in salmonella typhimurium aroa-mutant and stimulation of b-subunit specific antibody responses in mice. | the shiga toxin b-subunit has been fused to the 23-kd c-terminus of escherichia coli haemolysin a (hlya) and exported from attenuated antigen carrier strain of salmonella typhimurium aroa (sl3261). the expression of the gene fusion under the control of a synthetic modified beta-lactamase promoter (constitutive expression) and under the iron-regulated aerobactin promoter showed that the fusion protein could be stably expressed and exported out of the bacterial cell in significant amounts so long ... | 1992 | 1302285 |
| role of intestinal microflora in metabolism of glutathione conjugates of 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide. | dna adduct formation in the liver of b6c3f1 mice after administration of 1-nitropyrene (1-np) was shown by the 32p-postlabeling technique. the major adduct was not n-(deoxyguanosin-8-yl)-1-aminopyrene, which was easily formed in in vitro nitroreduction of 1-np in the presence of dna, but the major spots migrated to the same position as the in vitro dna adduct spots of k-region epoxides of 1-np (1-np 4,5- and 9,10-oxide). 1-np oxides formed by the oxidative activation of 1-np in the liver were ex ... | 1992 | 1306295 |
| reaction of the nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]adenosine 2',5'-bisphosphate at the coenzyme site of wild-type and mutant nadp(+)-specific glutamate dehydrogenases from salmonella typhimurium. | wild-type glutamate dehydrogenase (ec 1.4.1.4) from salmonella typhimurium reacts at 25 degrees c in 0.1 m phosphate buffer, ph 7, with the nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]-adenosine 2',5'-bisphosphate (2-bdb-ta 2',5'-dp) to give 78% inactivation. protection against inactivation was achieved with nadph, indicating that modification occurred in the region of the coenzyme binding site. after reaction of the enzyme with 2-bdb-ta 2',5'-dp, the dioxo moiety of the bound reagent wa ... | 1992 | 1309291 |
| a method for constructing single-copy lac fusions in salmonella typhimurium and its application to the hema-prfa operon. | this report describes a set of escherichia coli and salmonella typhimurium strains that permits the reversible transfer of lac fusions between a plasmid and either bacterial chromosome. the system relies on homologous recombination in an e. coli recd host for transfer from plasmid to chromosome. this e. coli strain carries the s. typhimurium put operon inserted into trp, and the resulting fusions are of the form trp::put::[kanr-x-lac], where x is the promoter or gene fragment under study. the pu ... | 1992 | 1309519 |
| interdomain salt bridges modulate ligand-induced domain motion of the sulfate receptor protein for active transport. | the refined crystal structure of the liganded form of the salmonella typhimurium sulfate-binding protein, a periplasmic receptor of active transport, is made up of two globular domains bisected by a deep cleft wherein the dehydrated sulfate is completely engulfed and bound by hydrogen bonds and van der waals' forces. two salt bridges (between glu15 and arg174 and between asp68 and arg134) span the cleft opening. to elucidate the role of the inter-domain salt bridges in the ligand-induced domain ... | 1992 | 1309886 |
| a blni restriction map of the salmonella typhimurium lt2 genome. | blni or avrii (5'-cctagg) sites are very rare in the salmonella typhimurium lt2 genome. blni was used to construct a physical map which was correlated with the genetic map by using three methods. first, tn10 carries blni sites, and the extra restriction sites produced by 34 genetically mapped tn10 insertions were physically mapped by using pulsed-field gel electrophoresis. second, six genetically mapped mud-p22 prophage insertions were used to assign blni fragments. integration of mud-p22 introd ... | 1992 | 1311299 |
| a physical map of the salmonella typhimurium lt2 genome made by using xbai analysis. | xbai digestion and pulsed-field gel electrophoresis of the genome of salmonella typhimurium lt2 yields 24 fragments: 23 fragments (total size, 4,807 kb) are from the chromosome, and one fragment (90 kb) is from the virulence plasmid pslt. some of the 23 fragments from the chromosome were located on the linkage map by the use of cloned genes as probes and by analysis of strains which gain an xbai site from the insertion of tn10. twenty-one of the fragments were arranged as a circular physical map ... | 1992 | 1311300 |
| rapid mapping in salmonella typhimurium with mud-p22 prophages. | a new method for mapping mutations in the salmonella typhimurium chromosome is described and applied to the localization of novel regulatory mutations affecting expression of the nirb (nitrite reductase) gene. the mapping technique is also illustrated by the mapping of mutations in genes affecting carbohydrate catabolism and biosynthetic pathways. the new mapping method involves use of the hybrid phage mudp and mudq (together referred to as mud-p22), originally constructed by youderian et al. (g ... | 1992 | 1311301 |
| nitrobenzo[a]pyrene-induced dna amplification in sv40-transformed chinese hamster embryo cells. | nitrobenzo[a]pyrenes (nbaps) are ubiquitous environmental pollutants that produce mutations in salmonella typhimurium and chinese hamster ovary cells. in this study, 1-, 3-, and 6-nbap induced amplification of sv40 dna sequences in an sv40-transformed chinese hamster embryo cell line which is sensitive to dna amplification by various known carcinogens. of the three isomers, 3-nbap produced the highest level of gene amplification, which was 4.8 relative to untreated controls at a dose of 5 microg ... | 1992 | 1311674 |
| identification of a salmonella typhimurium invasion locus by selection for hyperinvasive mutants. | salmonella typhimurium penetrate intestinal epithelial cells during infection. in vitro studies reveal that the availability of oxygen during bacterial growth decreases their capacity to adhere to and enter cultured epithelial cells. to identify s. typhimurium genes involved in epithelial cell entry, mutants were selected that entered hep-2 cells when grown under repressing, aerobic culture conditions. two types of transposons were used to generate bacterial mutations--transposons that disrupt g ... | 1992 | 1311853 |
| localization of the exonuclease and polymerase domains of bacillus subtilis dna polymerase iii. | structural gene mutants were cloned and exploited to identify the major catalytic domains of bacillus subtilis dna polymerase iii (bspoliii), a 162.4-kda [1437 amino acids (aa)] polymerase: 3'-5' exonuclease (exo) required for replicative dna synthesis. analysis of the sequence, mutagenicity, and catalytic behavior of natural and site-directed point mutants of bspoliii unequivocally located the domain involved in exonuclease catalysis within a 155-aa residue segment displaying homology with the ... | 1992 | 1312503 |
| structural relatedness of enteric bacterial porins assessed with monoclonal antibodies to salmonella typhimurium ompd and ompc. | the immunochemistry and structure of enteric bacterial porins are critical to the understanding of the immune response to bacterial infection. we raised 41 monoclonal antibodies (mabs) to salmonella typhimurium ompd and ompc porin trimers and monomers. enzyme-linked immunosorbent assays, immunoprecipitations, and/or western immunoblot techniques indicated that 39 mabs (11 anti-trimer and 28 anti-monomer) in the panel are porin specific and one binds to the lipopolysaccharide; the specificity of ... | 1992 | 1312535 |
| surface presentation of shigella flexneri invasion plasmid antigens requires the products of the spa locus. | an avirulent, invasion plasmid insertion mutant of shigella flexneri 5 (phs1059) was restored to the virulence phenotype by transformation with a partial hindiii library of the wild-type invasion plasmid constructed in pbr322. western immunoblot analysis of phs1059 whole-cell lysates revealed that the synthesis of the invasion plasmid antigens virg, ipaa, ipab, ipac, and ipad was similar to that seen in the corresponding isogenic s. flexneri 5 virulent strain, m90t. ipab and ipac, however, were ... | 1992 | 1312536 |
| a single regulatory gene integrates control of vitamin b12 synthesis and propanediol degradation. | the cob operon of salmonella typhimurium encodes enzymes required for synthesis of adenosyl-cobalamin (vitamin b12). the pdu operon encodes enzymes needed for use of propanediol as a carbon source, including an adenosyl-cobalamin-dependent enzyme, propanediol dehydratase. these two operons both map near min 41 of the s. typhimurium linkage map and are transcribed divergently. here we report that the cob and pdu operons form a single regulon. transcription of this regulon is induced by either gly ... | 1992 | 1312999 |
| the poc locus is required for 1,2-propanediol-dependent transcription of the cobalamin biosynthetic (cob) and propanediol utilization (pdu) genes of salmonella typhimurium. | in this communication we present evidence that indicates that 1,2-propanediol (1,2-pdl) is a positive effector of the transcription of the cobalamin (vitamin b12) biosynthetic (cob) operon and of the 1,2-pdl utilization (pdu) genes. the stimulatory effects of 1,2-pdl were demonstrated using mu d-lac transcriptional fusions to cob and pdu. significantly increased levels of transcription of the cob and pdu operon fusions were measured in cultures grown under both anoxic and highly aerated conditio ... | 1992 | 1313000 |
| mutations in topa interfere with the inducible expression of dna damage response loci in salmonella typhimurium. | strains of salmonella typhimurium deficient in topoisomerase i activity (topa mutants) are uv sensitive and non-mutable (overbye and margolin: j bacteriol 146:170-178, 1981). using lac-operon fusions to dna damage inducible (din) loci we investigated whether these observations could be explained by an inability of topa strains to efficiently induce dna damage responses. mitomycin c (mmc)-induced expression of lac-operon fusions to uvrb and to a second sos locus, din-9, was largely eliminated in ... | 1992 | 1315267 |
| detection of porin antigen in serum for early diagnosis of mouse infections with salmonella typhimurium. | the monoclonal antibodies to porin, an outer membrane protein isolated from salmonella typhimurium and sandwich enzyme linked immunosorbent assay (elisa) has made possible the detection of porin from sera of s. typhimurium-infected mice. the specificity of the monoclonal antibodies was ascertained based on their cross-reactivity with porins isolated from s. typhi, shigella flexneri and escherichia coli and lipopolysaccharide (lps) of s. typhimurium and e. coli. serum samples were found to be pos ... | 1992 | 1315558 |
| early caulobacter crescentus genes flil and flim are required for flagellar gene expression and normal cell division. | the biogenesis of the caulobacter crescentus polar flagellum requires the expression of more than 48 genes, which are organized in a regulatory hierarchy. the flbo locus is near the top of the hierarchy, and consequently strains with mutations in this locus are nonmotile and lack the flagellar basal body complex. in addition to the motility phenotype, mutations in this locus also cause abnormal cell division. complementing clones restore both motility and normal cell division. sequence analysis ... | 1992 | 1315735 |
| in vivo administration of recombinant growth hormone or gamma interferon activities macrophages: enhanced resistance to experimental salmonella typhimurium infection is correlated with generation of reactive oxygen intermediates. | purified and recombinant forms of growth hormone (gh) as well as of recombinant rat gamma interferon (ifn-gamma) enhance the survival of rats deprived of endogenous pituitary gh secretion by hypophysectomy (hx rats) and infected with virulent salmonella typhimurium. macrophages obtained from rats with intact pituitaries (pituitary-intact rats) or hx rats that were treated in vivo with either gh or the closely related hormone prolactin released elevated (p less than 0.05) levels of superoxide ani ... | 1992 | 1316877 |
| dissection of the salmonella typhimurium genome by use of a tn5 derivative carrying rare restriction sites. | a polylinker with rare restriction sites was introduced into a mini-tn5 derivative. these sites include m.xbai-dpni (tctagatctaga), which is rare in most bacterial genomes, swai (atttaaat) and paci (ttaattaa), which are rare in g+c-rich genomes, noti (gcggccgc) and sfii (ggccn5ggcc), which are rare in a+t-rich genomes, and blni (cctagg), spei (actagt), and xbai (tctaga), which are rare in the genomes of many gram-negative bacteria. this tn5(pfm) (pulsed-field mapping) transposon carries resistan ... | 1992 | 1317382 |
| the swi4+ gene of schizosaccharomyces pombe encodes a homologue of mismatch repair enzymes. | the swi4+ gene of schizosaccharomyces pombe is involved in termination of copy-synthesis during mating-type switching. the gene was cloned by functional complementation of a swi4 mutant transformed with a genomic library. determination of the nucleotide sequence revealed an open reading frame of 2979 nucleotides which is interrupted by a 68 bp long intron. the putative swi4 protein shows homology to duc-1 (human), rep-3 (mouse), hexa (streptococcus pneumoniae) and muts (salmonella typhimurium). ... | 1992 | 1317550 |
| the genes required for heme synthesis in salmonella typhimurium include those encoding alternative functions for aerobic and anaerobic coproporphyrinogen oxidation. | insertion mutagenesis has been used to isolate salmonella typhimurium strains that are blocked in the conversion of 5-aminolevulinic acid (ala) to heme. these mutants define the steps of the heme biosynthetic pathway after ala. insertions were recovered at five unlinked loci: hemb, hemcd, and heme, which have been mapped previously in s. typhimurium, and hemg and hemh, which have been described only for escherichia coli. no other simple hem mutants were found. however, double mutants are describ ... | 1992 | 1317844 |
| the comparison of cell-mediated immunity induced by immunization with porin, viable cells and killed cells of salmonella typhimurium. | a marked level of cell-mediated immunity (cmi) to salmonella typhimurium-infection in mice, as determined by acquired resistance, delayed-type hypersensitivity, interleukin-2 production and interferon-gamma production, was induced by immunization with porin or viable cells but not with killed cells of s. typhimurium lt2. when the up-regulation of immune system to each immunogen was studied by comparing increases of ia-bearing macrophages, the immunization with porin or viable cells, but not kill ... | 1992 | 1318491 |
| antibacterial and antiviral activity of camel milk protective proteins. | lysozyme (lz), lactoferrin (lf), lactoperoxidase (lp), immunoglobulin g and secretory immunoglobulin a were extracted from camel milk. the activity of these protective proteins was assayed against lactococcus lactis subsp. cremoris, escherichia coli, staphylococcus aureus, salmonella typhimurium and rotavirus. comparative activities of egg white lz, bovine lz and bovine lf are also presented. the antibacterial activity spectrum of camel milk lz was similar to that of egg white lz, and differed f ... | 1992 | 1319434 |
| starvation-inducible loci of salmonella typhimurium: regulation and roles in starvation-survival. | four starvation-inducible loci (stia, stib, stic, and stie) of salmonella typhimurium have been extensively characterized as to their genetic and physiologic regulation, and their roles in survival during prolonged simultaneous phosphate (p)-, carbon (c)- and nitrogen (n)-starvation (pcn-starvation). strains of s. typhimurium lt-2, isogenic with the exception of lacking either the stia, stib or stic locus, died off more quickly and survived at much reduced levels compared with their wild-type pa ... | 1992 | 1320726 |
| phosphorylation site of ntrc, a protein phosphatase whose covalent intermediate activates transcription. | the ntrc transcription factor is a member of a family of homologous prokaryotic regulatory proteins that participate in the transduction of extracellular and nutritional signals. it has been demonstrated that the phosphate group from a histidine residue of the phosphorylated ntrb protein autokinase is transferred to the ntrc protein. phosphorylation of the ntrc protein is transient and activates its transcriptional enhancement activity. we have investigated the site of phosphorylation of the sal ... | 1992 | 1321122 |
| [mutagenicity tests of suplatast tosilate (ipd-1151t)]. | 1. the reverse mutation test was carried out on suplatast tosilate (ipd-1151t) at dose range of 50-5000 micrograms/plate using salmonella typhimurium strains ta100, ta1535, ta98 ta1538 and ta1537, and escherichia coli strains wp2, wp2uvra. in all tester strains no significant differences were observed in the number of revertant colonies as compared with solvent control in the absence or presence of mammalian metabolic activation system. 2. the chromosomal aberration test on ipd-1151t was carried ... | 1992 | 1321262 |
| alteration of neutrophil function in bcg-treated and non-treated swine after exposure to salmonella typhimurium. | salmonella typhimurium infection in swine causes an enterocolitis followed by a persistent carrier state, but little is known about the mechanisms that allow this organism to colonize and persist in host tissues. neutrophils provide a first line of defense against invading pathogens such as salmonella typhimurium. the purpose of this study was to evaluate porcine neutrophil function after in vivo exposure to salmonella and to determine if the immunomodulator, bacillus calmette guerin (bcg), exer ... | 1992 | 1321531 |
| salmonella typhimurium porins stimulate platelet-activating factor synthesis by human polymorphonuclear neutrophils. | porins, a family of hydrophobic proteins located in the outer membrane of cell-wall of gram-negative bacteria, were shown to stimulate the synthesis and release of platelet-activating factor (paf), a 1-o-alkyl-2-acetyl-sn-glycerol-3-phosphorylcholine mediator of inflammation and endotoxic shock produced by polymorphonuclear neutrophils. paf synthesis was independent either from contamination by lps or generation of tnf. experiments with labeled precursors demonstrated that paf was synthesized vi ... | 1992 | 1321849 |
| electron spin resonance spectroscopy of oxygen radicals generated by synthetic fecapentaene-12 and reduction of fecapentaene mutagenicity to salmonella typhimurium by hydroxyl radical scavenging. | fecapentaenes form a class of potent fecal mutagens and have been suggested to play an initiating role in colon carcinogenesis. although several indications have been found that fecapentaenes may induce oxidative dna damage as well as dna alkylation, the mechanism of genotoxicity remains unknown. in this study, electron spin resonance spectroscopy with several spin traps has been used in order to determine whether reactive oxygen species can be formed by fecapentaene-12 (fp-12). no specific cond ... | 1992 | 1322251 |
| the fifth datta lecture. structural similarities between the aspartate receptor of bacterial chemotaxis and the trp repressor of e. coli. implications for transmembrane signaling. | a high resolution structure of the n-terminal ligand-binding domain of the aspartate receptor which mediates aspartate chemotaxis in salmonella typhimurium has recently been reported. a least-squares superposition of the alpha-amino nitrogen, alpha-carbon, beta-carbon, and alpha-carboxylate carbon of the aspartate bound to the aspartate receptor onto the equivalent atoms in the tryptophan bound to the trp repressor provides evidence for similarity between key parts of the active sites that bind ... | 1992 | 1322324 |
| identification, genetic analysis and dna sequence of a 7.8-kb virulence region of the salmonella typhimurium virulence plasmid. | the 90-kilobase (kb) virulence plasmid of salmonella typhimurium is responsible for invasion from the intestines to mesenteric lymph nodes and spleens of orally inoculated mice. we used tn5 and aminoglycoside phosphotransferase (aph) gene insertion mutagenesis and deletion mutagenesis of a previously identified 14-kb virulence region to reduce this virulence region to 7.8kb. the 7.8-kb virulence region subcloned into a low copy-number vector conferred a wild-type level of splenic infection to vi ... | 1992 | 1322485 |
| an unusual pagc::tnphoa mutation leads to an invasion- and virulence-defective phenotype in salmonellae. | two phenotypes believed to contribute to the pathogenesis of salmonella infections are macrophage survival and invasion of epithelial cells. it was recently observed that the salmonella macrophage survival factor pagc has significant amino acid similarity to the yersinia invasion factor ail. this observation raised the possibilities that macrophage survival is in part determined by the pathway of entry and that pagc confers an entry mechanism that does not trigger the microbicidal activities of ... | 1992 | 1323535 |
| role of is1 in the conversion of virulence (vi) antigen expression in enterobacteriaceae. | when escherichia coli hb101 harbors pwr127, a plasmid comprising the viab gene from citrobacter freundii wr7004 and the cole1-derived packc1, the strain produces the virulence (vi) antigen. vi antigen expression is abolished (vi- phenotype), however, when an is1 or is1-like dna element inserts into the viab region. to determine the sites of is1 insertion, pwr127 dnas extracted from 95 independently isolated vi- strains were analyzed by digestion with the restriction endonuclease psti and agarose ... | 1992 | 1324399 |
| escherichia coli prlc encodes an endopeptidase and is homologous to the salmonella typhimurium opda gene. | mutations at the escherichia coli prlc locus suppress the export defect of certain lamb signal sequence mutations. the salmonella typhimurium opda gene encodes an endoprotease that can participate in the catabolism of certain peptides and is required for normal development of phage p22. plasmids carrying either the wild-type (ptc100 prlc+) or suppressor alleles of prlc complemented all phenotypes associated with an s. typhimurium opda mutation. a plasmid carrying an amber mutation in prlc [prlc3 ... | 1992 | 1325967 |
| mutations that affect the regulation of phs in salmonella typhimurium. | the regulation of phs [production of hydrogen sulphide (h2s)] in salmonella typhimurium is complex. previous studies have shown that expression is dependent upon the presence of reduced sulphur and anaerobiosis and is modulated by carbon source and growth stage. transposon mutagenesis failed to find any potential trans-acting factors effective in the regulation of phs in relation to oxygen. spontaneous mutants capable of expressing phs-lac aerobically were isolated and characterized. these mutat ... | 1992 | 1326591 |
| activity of a plasmid-borne leu-500 promoter depends on the transcription and translation of an adjacent gene. | leu-500 is a chromosomal promoter mutation in salmonella typhimurium that normally causes the promoter to be inactive in the initiation of rna synthesis. but in a strain that has mutations in topa, the gene encoding dna topoisomerase i, the mutant promoter becomes active. we show that the leu-500 promoter can function on a plasmid when it is adjacent to the tetracycline-resistance gene teta. activation of the leu-500 promoter requires that the teta gene is transcribed and translated and that the ... | 1992 | 1326763 |
| preferential utilization of glucose over melibiose, and vice versa, in a pts mutant of salmonella typhimurium. | preferential utilization of glucose and melibiose was investigated in wild type cells and in pts mutant (ptsi-leaky) cells of salmonella typhimurium. a typical diauxic growth and preferential utilization of glucose over melibiose were observed in wild type cells when these two sugars were added as carbon source. similar results were obtained with a pts mutant (sb1476) although utilization of glucose was slow. when cyclic adenosine 3',5'-monophosphate (camp) was added to the culture medium to rel ... | 1992 | 1327563 |
| autogenous regulation of ethanolamine utilization by a transcriptional activator of the eut operon in salmonella typhimurium. | the genes required for use of ethanolamine as a carbon and nitrogen source are encoded by a single operon (eut) whose expression is induced by the simultaneous presence of both ethanolamine and cobalamin (vitamin b12). the action of b12 as an inducer of this operon reflects the fact that this cofactor is required by the degradative enzyme ethanolamine lyase (eutbc). the eutr gene encodes a protein that activates transcription of the eut operon in response to the simultaneous presence of b12 and ... | 1992 | 1328159 |
| mgta and mgtb: prokaryotic p-type atpases that mediate mg2+ influx. | the gram-negative bacterium salmonella typhimurium possesses three distinct mg2+ transport systems, encoded by the cora, mgta, and mgtb loci. the cora transport system is the constitutive mg2+ influx system. it can also mediate mg2+ efflux at very high extracellular mg2+ concentrations. in contrast, the mgta and mgtb mg2+ transport systems are normally expressed only at low extracellular mg2+ concentrations. a strain of s. typhimurium was constructed by mutagenesis which lacks mg2+ transport and ... | 1992 | 1328179 |
| isolation and characterization of the methionine aminopeptidase from porcine liver responsible for the co-translational processing of proteins. | a methionine aminopeptidase that specifically removes methionine residues from peptides with amino-terminal sequences of met-ala-, met-val-, met-ser-, met-gly-, and met-pro- but not met-leu- or met-lys- has been isolated to homogeneity from porcine liver by a procedure involving five chromatographic steps. the enzyme, whose specificity matches that predicted for the entity responsible for the co-translational amino-terminal processing of nascent polypeptide chains, has a measured molecular mass ... | 1992 | 1328207 |
| ribose and glucose-galactose receptors. competitors in bacterial chemotaxis. | the periplasmic ribose and glucose-galactose receptors (binding proteins) of gram-negative bacteria compete for a common inner membrane receptor in bacterial chemotaxis, as well as being the essential primary receptors for their respective membrane transport systems. the high-resolution structures of the periplasmic receptors for ribose (from escherichia coli) and glucose or galactose (from both salmonella typhimurium and e. coli) are compared here to outline some features that may be important ... | 1992 | 1328650 |
| in vitro antibacterial activities of tosufloxacin against and uptake of tosufloxacin by outer membrane mutants of escherichia coli, proteus mirabilis, and salmonella typhimurium. | the antibacterial activities of tosufloxacin and other quinolones against and apparent uptakes of tosufloxacin and other quinolones by outer membrane mutants of escherichia coli, proteus mirabilis, and salmonella typhimurium were studied. the hydrophobicity of tosufloxacin was nearly equal to that of ofloxacin or lower than those of sparfloxacin and nalidixic acid. ompf- and ompc-deficient e. coli and 40-kda porin-deficient p. mirabilis mutants were twofold more susceptible to tosufloxacin and s ... | 1992 | 1329639 |
| certain tryptophan photoproducts are inhibitors of cytochrome p450-dependent mutagenicity. | two photoproducts, derived from uv-irradiation of the amino acid l-tryptophan and with high ah (tcdd) receptor binding affinity, were tested for genotoxic and antimutagenic effects. the two indolo[3,2-b]carbazole derivatives, with the molecular weights of 284 and 312, respectively, were tested in saccharomyces cerevisiae strain d7 for mitotic gene conversion and reverse mutation and in strain rs112 for sister chromatid conversion and gene conversion. no significant (p > 0.05) genotoxic effects w ... | 1992 | 1330548 |
| sequence of the sodium ion pump oxaloacetate decarboxylase from salmonella typhimurium. | a genomic library of salmonella typhimurium dna was constructed in the lambda-phage embl3 and screened by immunoblotting for expression of the oxaloacetate decarboxylase alpha-subunit. after subcloning on plasmids the entire sequence of the oxaloacetate decarboxylase was determined. the genes encoding subunits gamma (oadg), alpha (oada), and beta (oadb) of the decarboxylase are clustered on the chromosome in that order. a typical consensus sequence of a promoter is not found upstream of the oadg ... | 1992 | 1331067 |
| rapid plasmid dna isolation from mucoid gram-negative bacteria. | exopolysaccharides interfere with the isolation and characterization of plasmid dna from gram-negative bacteria. to repress capsular polysaccharide production, bacteria were cultured in medium containing bismuth nitrate and sodium salicylate. rapid removal of other contaminating bacterial surface components was achieved by mild acidic zwitterionic detergent extraction. after treatment, bacterial cells were more readily lysed in alkaline detergents. the resulting plasmid preparations contained vi ... | 1992 | 1333482 |
| active protection of mice against salmonella typhi by immunization with strain-specific porins. | nih mice were immunized with between 2.5 and 30 micrograms of two highly purified porins, 34 kda and 36 kda, isolated from the virulent strain salmonella typhi 9,12, vi:d. of mice immunized with 10 micrograms of porins, 90% were protected against a challenge with up to 500 ld50 (50% lethal doses) of s. typhi 9,12,vi:d and only 30% protection was observed in mice immunized with the same dose of porins but challenged with the heterologous strain salmonella typhimurium. these results demonstrate th ... | 1992 | 1333686 |
| effects of tetanus toxin, salmonella typhimurium porin, and bacterial lipopolysaccharide on platelet aggregation. | endotoxins may interfere with platelet aggregation by interacting with the platelet membrane. the aim of this study was to evaluate the effects of tetanus toxin, salmonella typhimurium porin, and bacterial lipopolysaccharide (lps) on platelet aggregation induced by adp and thrombin in vitro. spontaneous platelet aggregation and platelet aggregation induced by adp and thrombin were measured. our results show that salmonella typhimurium porin and bacterial lps enhanced human and rabbit platelet ag ... | 1992 | 1335019 |
| purification and properties of nadp-dependent glutamate dehydrogenase from ruminococcus flavefaciens fd-1. | glutamate dehydrogenase (gdh) (l-glutamate:nadp+ oxidoreductase, deaminating, ec 1.4.1.4) from the cellulolytic ruminal bacterium ruminococcus flavefaciens has been purified and characterized. the native enzyme and subunit are 280 and 48 kda, respectively, suggesting that the native enzyme is a hexamer. the enzyme requires 0.5 m kcl for optimal activity and has a ph optimum of 6.9 to 7.0. the kms for ammonia, alpha-ketoglutarate, and glutamate are 19, 0.41, and 62 mm, respectively. the sigmoidal ... | 1992 | 1335719 |
| characterization of monoclonal antibodies to the outer membrane protein (ompd) of salmonella typhimurium. | a panel of monoclonal antibodies, seven against the trimeric and seven against the monomeric forms to outer membrane protein d (ompd) of salmonella typhimurium were produced. the specificities of these monoclonal antibodies for the porin proteins of s. typhimurium and their cross-reactions with salmonella porins ompc and ompf were determined by western immunoblotting and enzyme-linked immunosorbent assay. we observed that ompd shared more epitopes and had greater structural similarity with ompc ... | 1992 | 1335826 |
| the catalase-peroxidase of mycobacterium intracellulare: nucleotide sequence analysis and expression in escherichia coli. | the activation of catalase genes in response to oxidative stress may contribute to the intracellular survival of mycobacteria. in this report, the nucleotide sequence of a mycobacterial catalase gene is described. the deduced protein sequence of this mycobacterium intracellulare gene (mi85) was 60% identical to the escherichia coli hydroperoxidase i (hpi) protein, 59% identical to the salmonella typhimurium (hpi) catalase, and 47% identical to a bacillus stearothermophilus peroxidase. the mi85 p ... | 1992 | 1336034 |
| effects of rufloxacin in salmonella typhimurium infection in mice. | this study was undertaken to investigate the efficacy of rufloxacin, a new quinolone which is interesting due to its pharmacokinetics characterized by a long plasma half-life, in the treatment of systemic salmonella infections in the mouse typhoid model. innately susceptible balb/c and resistant cba mice were used to investigate the efficacy of rufloxacin in controlling systemic salmonella infections when given for brief or prolonged periods. the present study shows that rufloxacin is not only v ... | 1992 | 1337552 |
| mutant of salmonella typhimurium lacking the inhibitory function for phagosome-lysosome fusion in murine macrophages. | it has recently been described that salmonella typhimurium is capable of inhibiting phagosome-lysosome fusion in murine macrophages after ingestion. we selected a mutant of s. typhimurium lacking the phagosome-lysosome fusion inhibitory function from a collection of tn5-insertion mutants and examined its relevance to the pathogenesis in mice. the tn5 insertion mutant which has a defect in fusion inhibitory function was found to be significantly sensitive to the intracellular killing by murine ma ... | 1992 | 1338547 |
| horizontal transfer of a phosphatase gene as evidence for mosaic structure of the salmonella genome. | the genomes of escherichia coli and salmonella typhimurium are similar with respect to base composition, chromosome size, and the order, orientation and spacing of genes, but differ with respect to some 29 'loops', regions unique to one species. to evaluate the genetic basis for the structure and organization of the enteric bacterial genomes, we examined the gene encoding a non-specific acid phosphatase (phon) which maps to a loop at 96 min on the s.typhimurium chromosome. we detected atypical b ... | 1992 | 1339343 |
| [epidemiologic markers of salmonella typhimurium and salmonella agona]. | among s. typhimurium and s. agona strains isolated during the period from 1971 to 1987, the biotypes, colicine types and resistance patterns were determined for 734 s. typhimurium and 631 s. agona strains. among 734 s. typhimurium strains 65 biotypes were disclosed with prevalence of biotypes 1a (28.34%), 1b (29.84%) and 9 bi (18.28). concerning s. agona, the biotype 1a represented by 87.16%, was the commonest clone among our strains. although colicine typing added little information to characte ... | 1992 | 1340037 |
| present phage types and antibiotic susceptibility of salmonellae. | a total of 168 strains of salmonella were isolated in the command pathology laboratory (wc) delhi cantt during the year 1990. out of this, 143 were salmonella typhi, 17 salmonella paratyphi a, 7 salmonella typhimurium and 1 salmonella manhattan. the commonest phage type and biotype of salmonella typhi was type e1 and type 1 respectively. the dominant biotype of salmonella paratyphi a was type i. there was a very high degree of multidrug resistance of most of the strains. but all the strains were ... | 1992 | 1344225 |
| virulence of non-type 1-fimbriated and nonfimbriated nonflagellated salmonella typhimurium mutants in murine typhoid fever. | the virulence of salmonella typhimurium mutants that were unable to synthesize type 1 fimbriae was tested in a murine typhoid fever model. nonfimbriated mutants (fim) exhibited a lower 50% lethal dose than a wild-type (fim+) strain and produced significantly higher mortality (fim, 55%; fim+, 37% [p less than 0.002]) in mice that were challenged orally. there was no difference in virulence when the wild-type and mutant strains were injected intraperitoneally into mice. the progress of a short-ter ... | 1992 | 1346124 |
| substitution of glutamic acid 109 by aspartic acid alters the substrate specificity and catalytic activity of the beta-subunit in the tryptophan synthase bienzyme complex from salmonella typhimurium. | in an effort to understand the catalytic mechanism of the tryptophan synthase beta-subunit from salmonella typhimurium, possible functional active site residues have been identified (on the basis of the 3-d crystal structure of the bienzyme complex) and targeted for analysis utilizing site-directed mutagenesis. the chromophoric properties of the pyridoxal 5'-phosphate cofactor provide a particularly convenient and sensitive spectral probe to directly investigate changes in catalytic events which ... | 1992 | 1346502 |
| photolabeling of cher methyltransferase with s-adenosyl-l-methionine (adomet). studies on the adomet binding site. | cher methyltransferase from salmonella typhimurium was directly photolabeled with s-adenosyl-l-[methyl-3h]methionine. the labeled protein was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (sds-page) and then was detected by fluorography. the methylase-s-adenosyl-l-methionine adduct was found to be stable under the experimental conditions employed. labeling was found to be a function of the concentration of enzyme, s-adenosyl-l-methionine (adomet), and the intensity and t ... | 1992 | 1349019 |
| dynamics of non-specific antibacterial activity of the peritoneal cells of mice induced with coxiella burnetii antigen. | it was found that primary immunization with coxiella burnetii antigen increased mouse resistance to salmonella typhimurium infection as evidenced by acceleration of bacterial elimination from the peritoneal cavity and a decrease in lethality of experimental animals. the existence of two rises of bactericidal activity of mouse peritoneal cells was ascertained: the "early" on days 1 and 2, and the "late" on day 14 after c. burnetii administration. the first rise was accompanied by some increase in ... | 1992 | 1350168 |
| isolation and characterization of conditional adherent and non-type 1 fimbriated salmonella typhimurium mutants. | mutations in the genes encoding the type 1 fimbriae of salmonella typhimurium were isolated by selecting for the deletion of tn10 inserted adjacent to the chromosomal fim+ genes and screening for the loss of mannose-sensitive haemagglutination (ha) activity. s. typhimurium strains with tn10 insertions in ahp were hypersensitive to peroxides, and tetracycline-sensitive derivatives of ahp::tn10 mutants displayed two fim mutant phenotypes. the predominant class of fim mutants did not synthesize typ ... | 1992 | 1351241 |
| type 1 pili enhance the invasion of salmonella braenderup and salmonella typhimurium to hela cells. | the relationship between type 1 pili-associated adhesion and invasion to hela cells by salmonella braenderup and s. typhimurium was studied. when the clinical isolates of these strains were grown in l-broth, they showed both type 1 pili formation and mannose-sensitive adhesion to hela cells. on the other hand, the type 1 pili-defective mutants, which were obtained either by repeated subcultures on l-agar plates or by the transposon tn1-insertion mutagenesis of the s. braenderup and s. typhimuriu ... | 1992 | 1355852 |
| the rhizobium leguminosarum biovar phaseoli glnt gene, encoding glutamine synthetase iii. | plasmid pge203 contains the rhizobium leguminosarum biovar phaseoli glnt locus. glutamine synthetase iii (gsiii) was purified from a glutamine auxotrophic strain of klebsiella pneumoniae carrying this plasmid. sequencing of a 2.4-kb fragment containing the glnt locus reveals an open reading frame of 435 amino acids (aa), whose first eight aa are identical to those determined from pure gsiii by direct aa sequencing, thus confirming that glnt indeed codes for gsiii activity. the comparison of the ... | 1992 | 1356885 |
| adhesion of salmonella typhimurium var. copenhagen in the intestines of pigeons. | the attachment of salmonella typhimurium var. copenhagen to the intestinal epithelium of pigeons was studied. after experimental infection, the intestines of both young and adult pigeons were examined in vivo and in vitro. investigations were carried out by electron and immunofluorescence microscopy. attachment of the salmonella strain to duodenal epithelium was established. following repeated washing after inoculation, bacterial cells could be seen by sem and tem in association with the surface ... | 1992 | 1358160 |
| the effect of thymidine on the antibacterial and antiviral activity of zidovudine. | the effect of thymidine and deoxyadenosine on the antiviral and antibacterial effect of zidovudine was studied in human immunodeficiency virus type 1 (hiv-1) escherichia coli and salmonella typhimurium. in quantitative assays, 10 micrograms ml-1 thymidine was shown to increase the 50% inhibitory concentration (ic50) of zidovudine for hiv-1 by approximately 100-fold and to reduce zidovudine (1 microm)-induced protection of c8166 cells from 2.04 to 0.18 log syncytial-forming units. thymidine also ... | 1992 | 1359104 |
| identification of ancillary fim genes affecting fima expression in salmonella typhimurium. | regulation of the gene, fima, encoding the major fimbrial subunit of s. typhimurium s6704 was examined by using a lambda fima-lacz lysogen. transformation of the lambda fima-lacz lysogen with various derivatives of the recombinant plasmid that encodes type 1 fimbrial expression, pisf101, indicated that two regions of this plasmid alter beta-galactosidase production. one plasmid is a deletion resulting in the loss of a 28-kda polypeptide downstream of fima, while the other plasmid encodes a 24- a ... | 1992 | 1360005 |
| morphological and cytoskeletal changes in epithelial cells occur immediately upon interaction with salmonella typhimurium grown under low-oxygen conditions. | salmonella typhimurium grown under oxygen-limiting conditions were found to enter into, elicit actin filament rearrangement in, and effect morphological changes upon hep-2 cells within 15 min after infection. video microscopy revealed that host cell morphological changes associated with entry began within 1 min of productive adherence. polarized caco-2 cell morphology was affected 40 s after infection with low-oxygen-grown s. typhimurium. stationary-phase s. typhimurium did not elicit these phen ... | 1992 | 1360615 |
| radial mass density functions of vitrified helical specimens determined by scanning transmission electron microscopy: their potential use as substitutes for equatorial data. | using stem dark field images, we have determined linear mass densities and radial density profiles of vitrified helical particles. the samples studied are: tmv, rna-free helical polymers of tmv coat protein (tmv-p), salmonella typhimurium bacterial flagellar filaments and escherichia coli pili. the difference between the profiles obtained for tmv and tmv-p shows a maximum at a radius of about 4 nm, corresponding to the rna in tmv. of the peaks that are resolved in x-ray diffraction analysis we c ... | 1992 | 1362014 |
| bacterial flagellar diversity and significance in pathogenesis. | bacterial flagella are structurally diverse, ranging from the thoroughly investigated model examples found in escherichia coli and salmonella typhimurium to the more exotic sheathed flagella of, for example, helicobacter pylori, and the complex multi-flagellin endoflagella found in many spirochaetes. we summarize some of the emerging structural and genetic findings relating to these more novel flagellar types, and outline their possible significance in the pathogenicity of some medically importa ... | 1992 | 1362173 |
| role of t cells, tnf alpha and ifn gamma in recall of immunity to oral challenge with virulent salmonellae in mice vaccinated with live attenuated aro- salmonella vaccines. | the sl3261 salmonella typhimurium aroa live vaccine strain confers solid protection against oral challenge with virulent salmonellae, immunity persisting long after the vaccine has been cleared from the tissues. balb/c mice immunized with sl3261 and later subjected to in vivo depletion of both cd4+ and cd8+ t cells had impaired recall of immunity to oral challenge with the virulent s. typhimurium c5, with increased mortality and higher bacterial loads in the reticuloendothelial system (res). sel ... | 1992 | 1363824 |
| sequences of the envm gene and of two mutated alleles in escherichia coli. | the nucleotide sequence of the escherichia coli envm gene was determined. it codes for a protein of 262 amino acids. the sequences of the e. coli and salmonella typhimurium envm proteins are 98% identical. gene envm is preceded in e. coli by a 43-nucleotide-long structural element, termed 'box c', which occurs in several e. coli operons between structural genes. this sequence element is totally absent in s. typhimurium. gene envm was mapped at coordinate position 1366.8 kb of the physical map of ... | 1992 | 1364817 |
| the tryptophan synthase multienzyme complex: exploring structure-function relationships with x-ray crystallography and mutagenesis. | the bifunctional tryptophan synthase alpha 2 beta 2 complex that catalyzes the final two reactions in tryptophan biosynthesis is a classic example of a multienzyme complex that "channels" a metabolic intermediate (indole) between two active sites. the three-dimensional structure of the alpha 2 beta 2 complex from salmonella typhimurium reveals that the four polypeptide subunits are arranged in an extended alpha beta beta alpha order forming a complex 150 a long. the active sites of the neighbori ... | 1990 | 1366510 |
| development of a piezoelectric immunosensor for the detection of salmonella typhimurium. | a piezoelectric biosensor has been developed for the detection of salmonella typhimurium. the antibody to salmonella was immobilized on the crystal by various immobilization procedures. the best result was obtained when antibody was immobilized on the crystal precoated with a thin layer of polyethyleneimine. the response of the coated crystal for s. typhimurium in a microbial suspension was in the range of 10(5) to 10(9) cells ml-1. the time required for a complete interaction between the crysta ... | 1990 | 1366514 |
| dna sequence of a salmonella-specific dna fragment and the use of oligonucleotide probes for salmonella detection. | hybridization specificity of a 1.8-kb hindiii dna fragment isolated from salmonella typhimurium by a molecular cloning technique was confirmed by colony hybridization with 327 salmonella isolates of various serotypes and 56 non-salmonella isolates including enterobacteriaceae closely related to salmonella, such as escherichia coli, klebsiella, citrobacter and shigella. it was found that this 1.8-kb dna fragment was highly specific for all the salmonella isolates tested. the dna sequence of this ... | 1991 | 1367316 |
| use of the nirb promoter to direct the stable expression of heterologous antigens in salmonella oral vaccine strains: development of a single-dose oral tetanus vaccine. | plasmid ptetnir15, which directs the expression of the non-toxic immunogenic fragment c of tetanus toxin from the anaerobically inducible nirb promoter, was introduced into the salmonella typhimurium aroa arod live oral vaccine strain brd509. the resulting strain, designated brd847, was used to vaccinate orally balb/c mice and was tested for plasmid stability and its ability to protect against a lethal tetanus toxin challenge. ptetnir15 was stably inherited by bacteria growing or persisting in t ... | 1992 | 1368983 |
| role of nalidixic acid in isolation of salmonella typhimurium strains capable of growth at 48 degrees c. | salmonella typhimurium thermotolerant mutants dependent on the presence of nalidixic acid for growth at 48 degrees c were isolated and designated nalidixic acid-dependent, thermotolerant mutants, naldttl. genetic mapping revealed that naldttl alleles map within the gyra gene. when s. typhimurium strain q was plated in the dark on nutrient agar containing nalidixic acid (20 micrograms/ml) as a photosensitizer and briefly exposed to white light or near vu light prior to incubation at 42 degrees c, ... | 1992 | 1369196 |
| a general method to generate dna probes for microorganisms. | we present a method that permits the rapid generation of dna probes for eubacteria. in the procedure the variable regions for the 16s rrna genes are amplified using polymerase chain reaction (pcr) technology and primers based on the conserved regions of these genes. following sequencing of the variable regions, a choice is possible for a probe specific for that organism. no knowledge of the molecular biology of the microorganism is required prior to the application of this approach. the generali ... | 1990 | 1369980 |
| mutagenicity of complex mixtures in salmonella typhimurium. a report of the international programme on chemical safety's collaborative study on complex mixtures. | | 1992 | 1370099 |
| mutagenicity and chemical analysis of sequential organic extracts of airborne particulates. | to obtain insight into the identity of chemicals associated with the mutagenicity of united states national institute of standards and technology (nist) standard reference materials srm 1649 (urban dust) and srm 1650 (diesel particulate), parallel mutagenicity tests and chemical analyses were performed on dichloromethane and sequential organic extracts of these samples. srm 1649 and 1650 were sequentially extracted with five organic solvents of increasing polarity, in order to partition mutageni ... | 1992 | 1370100 |
| design and implementation of a collaborative study of the mutagenicity of complex mixtures in salmonella typhimurium. | in 1987, the international programme on chemical safety (ipcs) in collaboration with the u.s. environmental protection agency (u.s. epa) and the u.s. national institute of standards and technology (u.s. nist) initiated an international collaborative study of the mutagenicity of complex environmental mixtures in the ames salmonella typhimurium mutation assay. the objectives of this study were: (1) to estimate the inter- and intra-laboratory variability associated with the extraction of mixtures f ... | 1992 | 1370107 |
| results of a comparative study on the salmonella pre-incubation and plate incorporation assays using test samples from the ipcs collaborative study. | three complex mixtures (air particles, diesel particles and a coal tar fraction) and two pure compounds (benzo[a]pyrene and 1-nitropyrene) were tested in both the pre-incubation and the plate incorporation assay employing salmonella typhimurium ta98 and ta100. each experiment was conducted independently 2 or 4 times in duplicate in the presence and absence of metabolic activation. the mutagenic activities were calculated by least squares linear regression from the slope of the linear portion of ... | 1992 | 1370112 |
| structural requirements for the induction of the sos repair in bacteria by nitrated polycyclic aromatic hydrocarbons and related chemicals. | the case (computer-automated structure evaluation) methodology was used to investigate the structural basis of the sos-inducing activity of 56 nitrated polycyclic aromatic hydrocarbons (nitroarenes, npah) and the unsubstituted parent pah molecules. based upon the presence and/or absence of structural features, case identified 5 activating (biophores) and 4 inactivating (biophobes) fragments responsible for the sos-inducing activity. based upon these fragments, case correctly calculated the genot ... | 1992 | 1370243 |
| characterization of lipopolysaccharide fractions and their interactions with cells and model membranes. | the role of the length of the o-antigen polysaccharide side chain of bacterial lipopolysaccharide (lps) in biological and model membrane systems was investigated. lps from salmonella typhimurium atcc 14028 was chromatographed on a sephadex g-200 column in the presence of sodium deoxycholate and separated into three fractions on the basis of molecular size. sodium dodecyl sulfate-polyacrylamide gel electrophoresis, western blot (immunoblot), and chemical analyses indicated that these fractions di ... | 1992 | 1370286 |
| substructure of the flagellar basal body of salmonella typhimurium. | the salmonella typhimurium basal body, a part of the flagellar rotary motor, consists of four rings (denoted m, s, p and l) and a coaxial rod. using low-dose electron microscopy and image averaging methods on negatively stained and frozen-hydrated preparations, we examined whole basal body complexes and subcomplexes obtained by dissociation in acid. dissociation occurs in steps, allowing us to obtain images of substructures lacking the m ring, lacking the m and s rings, and lacking the m and s r ... | 1992 | 1370543 |
| the bvgas locus negatively controls motility and synthesis of flagella in bordetella bronchiseptica. | the products of the bvgas locus coordinately regulate the expression of bordetella virulence factors in response to environmental conditions. we have identified a phenotype in bordetella bronchiseptica that is negatively controlled by bvg. environmental signals which decrease (modulate) the expression of bvg-activated genes lead to flagellum production and motility in b. bronchiseptica. wild-type (bvg+) strains are motile and produce peritrichous flagella only in the presence of modulating signa ... | 1992 | 1370665 |
| modulating effect of tanshinones on mutagenic activity of trp-p-1 and benzo[a]pyrene in salmonella typhimurium. | the modulating effects of the chinese medicinal plant 'tan-shen', the radix of salvia miltiorrhiza bunge, on the mutagenic activities of trp-p-1 (3-amino-1,4-dimethyl-5h-pyrido[4,3-b]indole) and b(a)p (benzo[a]pyrene) were investigated using salmonella typhimurium ta98. ether- and hot water-extracted 'tan-shen' enhanced both mutagens at low concentrations, but suppressed them at high concentrations. extracts by ether treatment were more effective than those extracted by hot water. dihydrotanshin ... | 1992 | 1370713 |
| modulation of mutagenic properties in a series of dna-directed alkylating agents by variation of chain length and alkylator reactivity. | four series of aniline mustards linked to a dna-affinic acridine chromophore by alkyl chains of varying length (2-5 carbon atoms) have been studied for their mutagenic properties, as estimated in four strains of salmonella typhimurium and in saccharomyces cerevisiae strain d5. the four series have very different mustard reactivities, as determined by the aniline link group (-o-, -ch2-, -s- or -so2-). some of the derived compounds cause frameshift mutagenesis which can be detected in ta98 and als ... | 1992 | 1370717 |
| formation of genotoxic metabolites from anthraquinone glycosides, present in rubia tinctorum l. | rubia tinctorum l., a medicinal plant used for the treatment of kidney and bladder stones, contains a characteristic spectrum of 9,10-anthraquinone derivatives, which are substituted in only one of the aromatic benzo rings. the majority of the anthraquinones present in the plant itself or in plant extracts are glycosides. we investigated the metabolism of two such glycosides, alizarinprimeveroside (alp) and lucidinprimeveroside (lup). alp given orally to rats was metabolized to alizarin (al) and ... | 1992 | 1370725 |
| amino acid substitutions in naturally occurring variants of ail result in altered invasion activity. | yersinia enterocolitica is the causative agent of a variety of gastrointestinal syndromes ranging from acute enteritis to mesenteric lymphadenitis. in addition, systemic infections resulting in high mortality rates can occur in elderly and immunocompromised patients. more than 50 serotypes of y. enterocolitica have been identified, but only a few of them commonly cause disease in otherwise healthy hosts. those serotypes that cause disease have been divided into two groups, american and non-ameri ... | 1992 | 1370953 |
| mutagenicity of pyrrolizidine alkaloids in the salmonella typhimurium/mammalian microsome system. | the mutagenicity of a series of pyrrolizidine alkaloids, and of extracts from several italian senecio species containing pyrrolizidine alkaloids, including s. inaequidens, s. fuchsii and s. cacaliaster, were tested using the salmonella typhimurium/mammalian microsome system. retrorsine, senecivernine, seneciphylline and the senecio extracts showed a weakly mutagenic activity. | 1992 | 1370983 |
| genotoxicity and cell proliferative activity of a nitrosated oroxylum indicum vent fraction in the pyloric mucosa of rat stomach. | in vivo genotoxic activity and cell proliferative activity were examined in the stomach mucosa of male f344 rats by in vivo short-term methods after oral administration of a nitrosated oroxylum indicum vent (oiv) fraction, which had been found to be mutagenic without s9 mix to salmonella typhimurium ta98 and ta100. administration of the nitrosated oiv fraction at doses of 1 and 2 g/kg body weight induced dose-dependent dna single-strand scission (p less than 0.02), determined by the alkaline elu ... | 1992 | 1371592 |
| collaborative study using the preincubation salmonella typhimurium mutation assay for airborne particulate matter in japan. a trial to minimize interlaboratory variation. | a collaborative study has been performed over a period of 3 years to develop a suitable method for monitoring the mutagenicity of airborne particulate matter. the study was organized with 8 laboratories and performed in the following steps: (1) selection of a suitable technique for each process involved in the mutagenicity monitoring, (2) developing a tentative protocol by combining systematically the selected techniques, (3) evaluation of the protocol by intra- and inter-laboratory studies, (4) ... | 1992 | 1371825 |
| mutagenicity assay for nitroarenes of air pollutants held in leaves of woody plants. | a new method was developed for the detection of mutagenic nitroarenes held in the leaves of woody plants using a small amount of leaves. this method consists of extraction of mutagen from fresh leaves (15-30 g) by ultrasonication with ethyl acetate and purification by elution with benzene on a silica gel column to remove such inhibitory components for mutagenesis as chlorophyll. the mutation assay uses the new salmonella typhimurium strains yg1021 (a nitroreductase-overproducing strain of ta98) ... | 1992 | 1371833 |
| biphenyl and fluorinated derivatives: liver enzyme-mediated mutagenicity detected in salmonella typhimurium and chinese hamster v79 cells. | hepatocarcinogenic polychlorinated and polybrominated biphenyls usually show negative results in in vitro mutagenicity assays. problems in their testing result from their low water solubility and their slow rate of metabolism. we therefore investigated better soluble model compounds, namely biphenyl and its 3 possible monofluorinated derivatives. in the direct test, these compounds proved to be nonmutagenic in salmonella typhimurium ta98 and ta100 (reversion to histidine prototrophy) and in chin ... | 1992 | 1371835 |