| adhesion of salmonella typhimurium to porcine intestinal epithelial surfaces: identification and characterization of two phenotypes. | salmonella typhimurium 798 is known to persistently colonize swine. a key step required to initiate colonization of intestines is adhesion of the organism to the intestinal epithelium. however, s. typhimurium 798 initially failed to attach to porcine enterocytes in vitro. an enrichment procedure was used to select adhesive s. typhimurium, and when cells of one colony type were grown in tryptone phosphate broth they were adhesive. cells from a colony with a different morphology were not adhesive. ... | 1992 | 1639489 |
| construction of stable lamb-shiga toxin b subunit hybrids: analysis of expression in salmonella typhimurium aroa strains and stimulation of b subunit-specific mucosal and serum antibody responses. | the complete shiga toxin b subunit and two n-terminal segments of the b subunit have been inserted into a cell surface exposed loop of the lamb protein, and expression of the hybrid proteins from three different promoter systems, i.e., (i) an in vitro-inducible tac promoter that provides high-level expression, (ii) the iron-regulated aerobactin promoter presumably induced in vivo under the iron-limiting conditions of the intestinal mucosal environment, and (iii) a synthetic, modified beta-lactam ... | 1992 | 1639503 |
| infection of macrophages with legionella pneumophila induces phosphorylation of a 76-kilodalton protein. | infection of peritoneal macrophages from susceptible a/j mice with legionella pneumophila induced phosphorylation of a 76-kda protein. the phosphorylation occurred when macrophages were infected with a virulent strain of l. pneumophila but did not occur when they were infected with an avirulent strain or with other bacteria such as either pseudomonas aeruginosa or salmonella typhimurium. also, no phosphorylation of this protein was observed when macrophages were stimulated with either lipopolysa ... | 1992 | 1639515 |
| morphological pathway of flagellar assembly in salmonella typhimurium. | the process of flagellar assembly was investigated in salmonella typhimurium. seven types of flagellar precursors produced by various flagellar mutants were purified by cscl density gradient protocol. they were characterized morphologically by electron microscopy, and biochemically by two-dimensional gel electrophoresis. the ms ring is formed in the absence of any other flagellar components, including the switch complex and the putative export apparatus. four proteins previously identified as ro ... | 1992 | 1640458 |
| conformational switching in the flagellar filament of salmonella typhimurium. | the flagellar filament of the mutant salmonella typhimurium strain sjw814 is straight, and has a right-handed twist like the filament of sjw1655. three-dimensional reconstructions from electron micrographs of ice-embedded filaments reveal a flagellin subunit that has the same domain organization as that of sjw1655. both show slight changes from the domain organization of the subunits from sjw1660, which possesses a straight, left-handed filament. this points to the possible role of changes in su ... | 1992 | 1640459 |
| short-term dietary lipid manipulation does not affect survival in two models of murine sepsis. | dietary lipid manipulation has been shown to have various effects on the immune system, depending on the amount of fat, degree of saturation, and type of fat used. in this study we investigated the role of different sources of fat at different levels on the survival of mice in two models of peritonitis, one with pseudomonas aeruginosa and the other with salmonella typhimurium. cf1 mice were pair-fed diets with 5% or 40% of total calories as fat. the source of fat used was coconut oil, oleic acid ... | 1992 | 1640632 |
| outer membranes of gram-negative bacteria are permeable to steroid probes. | the permeability of bacterial outer membranes was assayed by coupling the influx of highly hydrophobic probes, 3-oxosteroids, with their subsequent oxidation catalysed by 3-oxosteroid delta 1-dehydrogenase, expressed from a gene cloned from pseudomonas testosteroni. in salmonella typhimurium producing wild-type lipopolysaccharide, the permeability coefficients for uncharged steroids were 0.45 to 1 x 10(-5) cm s-1, and the diffusion appeared to occur mainly through the lipid bilayer domains of th ... | 1992 | 1640833 |
| tetracycline resistance genes in kenyan hospital isolates of salmonella typhimurium. | all 97 strains of salmonella typhimurium isolated from patients at a hospital in nairobi, kenya, during 1988-90 were resistant to tetracycline. the minimum inhibitory concentration (mic) showed a large distribution range from 1 microgram/ml to 128 micrograms/ml. the strains were heterogeneous with respect to plasmid content, but initially all strains possessed, in addition to other plasmids, a large 60-, 63- or 65-mda plasmid. the tetracycline resistance genes were characterized using oligonucle ... | 1992 | 1642850 |
| oxidation of aflatoxins and sterigmatocystin by human liver microsomes: significance of aflatoxin q1 as a detoxication product of aflatoxin b1. | aflatoxin q1 8,9-oxide was synthesized and found to yield lower levels of n7-guanyl adducts than obtained from aflatoxin b1 8,9-oxide when mixed with calf thymus dna or salmonella typhimurium ta 98 cells. however, when s. typhimurium ta 98 was treated with the (analogous) epoxides of aflatoxin b1, aflatoxin g1, aflatoxin q1, or sterigmatocystin, the ratios of revertants to n7-guanyl dna adducts were similar. aflatoxin q1 and aflatoxin b1 8,9-oxide (trapped here as the glutathione conjugate) are ... | 1992 | 1643250 |
| dimethylchrysene diol epoxides: mutagenicity in salmonella typhimurium, tumorigenicity in newborn mice, and reactivity with deoxyadenosine in dna. | in contrast to 5-methylchrysene and 5,9-dimethylchrysene, 5,6-dimethylchrysene and 5,7-dimethylchrysene are weak tumor initiators on mouse skin. in order to investigate the basis for this, we have evaluated the mutagenic activities toward salmonella typhimurium ta 100 and reactivity with dna of (+/-)-anti-1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-5,6-dimethyl-ch rys ene (anti-5,6-dimec-1,2-diol 3,4-epoxide) and anti-5,7- and anti-5,9-dimec-1,2-diol 3,4-epoxide. the tumorigenic activities of ant ... | 1992 | 1643255 |
| mutations in the arac gene of salmonella typhimurium lt2 which affect both activator and auto-regulatory functions of the arac protein. | the arac gene encodes a regulatory protein, arac, that acts as both an activator and a repressor of transcription of the genes involved in the transport and catabolism of l-arabinose in salmonella typhimurium lt2. five arac mutants which have altered regulatory properties were characterized. all are point mutations which would result in amino acid substitutions near the c terminus of arac. each mutation results in altered activator and auto-regulatory arac function in vivo. in vitro dna-binding ... | 1992 | 1644312 |
| absence of mutagenic activity in salmonella and of clastogenic activity in cho cells of caramel colours i, ii, iii and iv. | a total of 15 caramel colours were examined for genotoxic activity using the salmonella typhimurium plate incorporation assay (ames test). five bacterial strains, ta1535, ta1537, ta1538, ta98 and ta100 were used in all the plate incorporation tests. caramel colours can be divided into four classes, classification depending on the preparative method used. in this study, representatives of all four classes of caramel colour were tested for genotoxic potential in the ames test, some of the caramel ... | 1992 | 1644380 |
| assessment of the genotoxic potential of caramel colour i in four short-term tests. | a battery of three short-term tests in vitro and one in vivo was used to determine the genotoxicity of caramel colour i. the results of the bacterial mutation assay, using five strains of salmonella typhimurium, and the mouse micronucleus assay in vivo showed no evidence of genotoxic activity. results from both the cytogenetics assay in vitro, using cho cells, and the mouse lymphoma assay indicated that there was some genotoxic activity associated with caramel colour i but only in the absence of ... | 1992 | 1644381 |
| a new plasmidic cefotaximase from patients infected with salmonella typhimurium. | salmonella typhimurium strains resistant to most beta-lactams, co-trimoxazole, tobramycin and gentamicin were isolated from patients in two hospitals in buenos aires, argentina, beginning in august 1990. the patients were suffering from meningitis, septicaemia or enteritis. therapy including ampicillin, ceftriaxone and gentamicin failed. the strains produced a plasmidic (pmvp-4) extended broad-spectrum beta-lactamase which is more active against cefotaxime than against ceftazidime (vmax for cefo ... | 1992 | 1644493 |
| the role of a stress-response protein in salmonella typhimurium virulence. | we recently described the use of selective transposon mutagenesis to generate a series of avirulent mutants of a pathogenic strain of salmonella typhimurium. cloning and sequencing of the insertion sites from two of these mutants reveals that both have identical locations within an open reading frame that is highly homologous to a gene, htra, encoding a heat-shock protein in escherichia coli. dna sequence analysis of s. typhimurium htra reveals the presence of a gene capable of encoding a protei ... | 1991 | 1645840 |
| salmonella typhimurium mutants defective in flagellar filament regrowth and sequence similarity of flii to f0f1, vacuolar, and archaebacterial atpase subunits. | many flagellar proteins are exported by a flagellum-specific export pathway. in an initial attempt to characterize the apparatus responsible for the process, we designed a simple assay to screen for mutants with export defects. temperature-sensitive flagellar mutants of salmonella typhimurium were grown at the permissive temperature (30 degrees c), shifted to the restrictive temperature (42 degrees c), and inspected in a light microscope. with the exception of switch mutants, they were fully mot ... | 1991 | 1646201 |
| [surveillance study on bacteriological etiology of 8371 children with diarrhea]. | the results of stool cultures from 8371 children of 0-13 years old with diarrhea during the years of january 1981 to december 1989 in shanghai area are reported. 2906 strains of enteropathogenic bacteria were isolated, with total detection rate of 34.72%. shigella were still the most common pathogens in 1981-1984, and campylobacter jejuni took second place, whereas from 1985 on campylobacter exceeded shigella as the first pathogenic bacteria of children's diarrhea. except in 1987 and 1988 shigel ... | 1991 | 1647837 |
| the outer membrane permeability-increasing action of deacylpolymyxins. | the outer membrane permeability-increasing action of deacylpolymyxins was compared to the well-known potent action of polymyxin b nonapeptide (pmbn). deacylpolymyxin b (dapb), prepared by treating polymyxin b with polymyxin acylase, was found to be a slightly more effective permeabilizer than pmbn. as low a dapb concentration as 1 microgram/ml sensitized escherichia coli to the probe antibiotics (rifampin, fusidic acid, erythromycin, clindamycin, novobiocin) by factors 30-100 and salmonella typh ... | 1991 | 1648055 |
| comparison of the 5' flanking regions of the salmonella typhimurium and escherichia coli glgc genes, encoding adp glucose pyrophosphorylases. | | 1991 | 1648207 |
| genetic evidence that genes fdhd and fdhe do not control synthesis of formate dehydrogenase-n in escherichia coli k-12. | enterobacteria synthesize two formate dehydrogenases, formate dehydrogenase-n (encoded by fdnghi) and formate dehydrogenase h (encoded by fdhf). previous work has identified two rha-linked salmonella typhimurium genes, fdnb and fdnc, which are required primarily for formate dehydrogenase-n activity. analogous mutants, termed fdhd and fdhe, have been isolated in escherichia coli. we used gene fusions between fdng, the structural gene for the large subunit of formate dehydrogenase-n, and lacz, the ... | 1991 | 1648557 |
| reca-dependent increased precise excision of tn10 in salmonella typhimurium. | uv irradiation induced the precise excision of tn10 inserted in met, trp or srl in a salmonella typhimurium strain; mitomycin c was also found to induce the frequency of precise excision of tn10 from srl or met. precise excision of tn10 was not increased by either uv or mitomycin c in a reca mutant. similarly, a reca mutant derived from a uvrd strain showed a drastic reduction in the high spontaneous levels of precise excision of tn10 of this strain. these results indicate that reca is involved ... | 1991 | 1648666 |
| precise excision of tn10 in salmonella typhimurium: effects of mutations in the pola, dam, muth and mutb genes and of methionine or ethionine in the plating medium. | precise excision of tn10 occurs at significantly elevated frequencies in cultures of the pola7 mutant strain of salmonella typhimurium, is further increased in pola7 dam-1 and pola7 mutb strains and decreased in a pola7 muth background. the numbers of precise excision events occurring in pola7 strains are also significantly increased when methionine (20 micrograms/ml or less) is present in the medium but decreased when ethionine (again, 20 micrograms/ml or less) is present. when both amino prese ... | 1991 | 1648667 |
| specificity of protective immunity induced by porin from salmonella typhimurium. | the specificity of protective immunity against salmonella typhimurium in mice immunized with porins from s. typhimurium, salmonella enteritidis and escherichia coli was studied. high levels of protection against s. typhimurium-infection were achieved in mice immunized with porins from s. typhimurium but not from s. enteritidis and e. coli. however, our serological studies demonstrated that porins from s. typhimurium, s. enteritidis and e. coli had antigenic cross-reactivity with each another; in ... | 1991 | 1649959 |
| inducible ph homeostasis and the acid tolerance response of salmonella typhimurium. | the acid tolerance response (atr) is an adaptive system triggered at external ph (pho) values of 5.5 to 6.0 that will protect cells from more severe acid stress (j. foster and h. hall, j. bacteriol. 172:771-778, 1990). correlations between the internal ph (phi) of adapted versus unadapted cells at pho of 3.3 indicate that the atr system produces an inducible ph-homeostatic function. this function serves to maintain the phi above 5 to 5.5. below this range, cells rapidly lose viability. developme ... | 1991 | 1650345 |
| selective cloning of genes encoding rnase h from salmonella typhimurium, saccharomyces cerevisiae and escherichia coli rnh mutant. | we have cloned genes encoding rnase h from escherichia coli rnh mutants, salmonella typhimurium and saccharomyces cerevisiae. selection was accomplished by suppression of the temperature-sensitive growth phenotype of escherichia coli strains containing the rnh-339::cat and either recb270 (ts) or recc271 (ts) mutations. rnases h from e. coli and s. typhimurium contained 155 amino acid residues and differed at only 11 positions. the s. cerevisiae and e. coli rnases h were about 30% homologous. a c ... | 1991 | 1650910 |
| altering the conserved nucleotide binding motif in the salmonella typhimurium muts mismatch repair protein affects both its atpase and mismatch binding activities. | the salmonella typhimurium and escherichia coli muts protein is one of several methyl-directed mismatch repair proteins that act together to correct replication errors. muts is homologous to the streptococcus pneumoniae hexa mismatch repair protein and to the duc1 and rep1 proteins of human and mouse. homology between the deduced amino acid sequence of both muts and hexa, and the type a nucleotide binding site consensus sequence, suggested that atp binding and hydrolysis play a role in their mis ... | 1991 | 1651234 |
| alteration in the electrophoretic mobility of ompc due to variations in the ammonium persulfate concentration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. | studies on salmonella typhi and salmonella typhimurium outer membrane proteins have shown that the relative position of ompc porin in sodium dodecyl sulfate.polyacrylamide gel electrophoresis undergoes an important shift when the concentration of ammonium persulfate in the running gel is increased from 6 to 12 mm. the apparent molecular mass at these concentrations was estimated to be 34 and 40 kda, respectively. under similar electrophoretic conditions the apparent molecular mass estimated for ... | 1991 | 1653699 |
| interspecific recombination between escherichia coli and salmonella typhimurium occurs by the recabcd pathway. | interspecific recombination in conjugation between escherichia coli and salmonella typhimurium is several orders of magnitude lower than intraspecies recombination and is dependent on the reca function. this low efficiency is due to a 20% divergence in the dna sequence. the methyl-directed (mut h,l,s dependent) mismatch repair system appears to control the fidelity of homologous recombination; inactivating one of the mut functions increases the interspecies recombination at least by 10(3)-fold. ... | 1991 | 1655049 |
| molecular characterization of flgm, a gene encoding a negative regulator of flagellin synthesis in salmonella typhimurium. | the expression of flagellin in salmonella typhimurium is coupled to the assembly of complete flagella. mutations which disrupt this coupling define a gene, flgm, which represses the expression of the flagellin genes in strains with mutations in the basal body, switch, or hook flagellar gene (k. l. gillen and k. t. hughes, j. bacteriol. 173:2301-2310, 1991). complementation studies demonstrated that the flgm gene is contained within a 600-bp cloned dna fragment. sequence analysis revealed that th ... | 1991 | 1655712 |
| sugar transport by the bacterial phosphotransferase system. structural and thermodynamic domains of enzyme i of salmonella typhimurium. | enzyme i, the first in the sequence of phosphocarrier proteins of the bacterial phosphoenolpyruvate:glycose phosphotransferase system, is a potential critical point for regulating sugar uptake. the thermal stability of enzyme i was studied by high sensitivity differential scanning calorimetry. at ph 7.5, thermal unfolding of the protein exhibits two peaks with maxima (tm) at 47.6 and 55.1 degrees c, indicating that the protein comprises two cooperative unfolding structures. interaction between t ... | 1991 | 1655788 |
| crystallization and preliminary x-ray diffraction study of the ligand-binding domain of the bacterial chemotaxis-mediating aspartate receptor of salmonella typhimurium. | the periplasmic domain of the aspartate chemotaxis receptor from salmonella typhimurium has been crystallized in the presence and absence of bound aspartate. both crystal forms were grown by precipitation with lithium sulfate and diffract to 1.8 a resolution. the aspartate receptor structure is believed to be prototypical of a large class of receptors including those for polypeptide growth factor hormones as well as those for small chemotaxis-affector molecules such as aspartate and serine. | 1991 | 1656050 |
| increased susceptibility to beta-lactam antibiotics and decreased porin content caused by envb mutations of salmonella typhimurium. | isogenic derivatives carrying envb6, envb9, or envb+ alleles were obtained from a strain of salmonella typhimurium that was partially resistant to mecillinam, a beta-lactam antibiotic specific for penicillin-binding protein 2 (pbp 2). testing of the isogenic strains with several antibacterial agents demonstrated that envb mutations either increased resistance (mecillinam) or did not affect the response (imipemen) to beta-lactams that act primarily on pbp 2, while susceptibilities to beta-lactams ... | 1991 | 1656857 |
| cloning and characterization of the l-rhamnose regulon in salmonella typhimurium lt2. | a salmonella typhimurium lt2 cosmid library was constructed, and a 46-kb recombinant plasmid was isolated that could complement an escherichia coli rha mutant. subsequent subcloning generated a 13.6-kb clai restriction fragment that contained a functional regulatory element. by complementation analyses using different subclones, the approximate physical locations of rhat, rhac1, rhac2, rhab, rhaa, and rhad were determined. the nucleotide sequence spanning the rhab and rhac2 genes was determined. | 1991 | 1657713 |
| cloning, characterization, and dna sequence of the rfalk region for lipopolysaccharide synthesis in salmonella typhimurium lt2. | we have cloned and sequenced the rfal and rfak genes for lipopolysaccharide synthesis in salmonella typhimurium lt2 on a 4.28-kb hindiii fragment from the previously described r' factor pkz3 (s. k. kadam, a. rehemtulla, and k. e. sanderson, j. bacteriol. 161:277-284, 1985). rfal is thought to encode a component of the o-antigen ligase, and rfak is believed to encode the n-acetylglucosamine transferase. the genes were identified by the loss of complementation of prototype rfal and rfak mutations ... | 1991 | 1657881 |
| the salmonella typhimurium virulence plasmid encodes a positive regulator of a plasmid-encoded virulence gene. | the 90-kb virulence plasmid of salmonella typhimurium is necessary for invasion beyond the peyer's patches to the mesenteric lymph nodes and spleens of orally inoculated mice. two tn5 insertions located on the left side of a previously identified 14-kb virulence region (p. a. gulig and r. curtiss iii, infect. immun. 58:3262-3271, 1988) and mapping 272 bp from each other exhibited opposite effects on splenic infection of mice after oral inoculation. spvr23::tn5 decreased splenic infection by 1,00 ... | 1991 | 1657882 |
| functional complementation between chromosomal and plasmid mutagenic dna repair genes in bacteria. | the umudc operons of escherichia coli and salmonella typhimurium and the analogous plasmid operons mucab and impcab have been previously characterized in terms of their roles in dna repair and induced mutagenesis by radiation and many chemicals. the interrelationships of these mutagenic dna repair operons were examined in vivo in functional tests of interchangeability of operon subunits in conferring uv resistance and uv mutability phenotypes to wild-type s. typhimurium and umu mutants of e. col ... | 1991 | 1658597 |
| turmeric (curcuma longa)-induced reduction in urinary mutagens. | rats were fed turmeric at various levels in the diet for up to 3 months and then exposed to benzo[a]pyrene (b[a]p) or 3-methylcholanthrene (3-mc) by ip injection. urinary mutagens were detected using the salmonella typhimurium assay. turmeric fed at 0.5% and above inhibited b[a]p- and 3-mc-mediated mutagenicity. turmeric did not adversely affect the food intake, or weight gain of the rats and no histological changes were detected. these findings are significant in view of the widespread exposure ... | 1991 | 1660015 |
| three-dimensional structures of the ligand-binding domain of the bacterial aspartate receptor with and without a ligand. | the three-dimensional structure of an active, disulfide cross-linked dimer of the ligand-binding domain of the salmonella typhimurium aspartate receptor and that of an aspartate complex have been determined by x-ray crystallographic methods at 2.4 and 2.0 angstrom (a) resolution, respectively. a single subunit is a four-alpha-helix bundle with two long amino-terminal and carboxyl-terminal helices and two shorter helices that form a cylinder 20 a in diameter and more than 70 a long. the two subun ... | 1991 | 1660187 |
| characterization of lip expression in salmonella typhimurium: analysis of lip::lac operon fusions. | strains of salmonella typhimurium which have an auxotrophic requirement for lipoic acid were isolated by mutagenesis with the transposable element mu dj. the chromosomal location of these insertion mutations was determined to be at 14 map units by bacteriophage p22-mediated cotransduction. the lip gene is transcribed in the clockwise direction relative to the s. typhimurium genetic map. strains with lip::lac operon fusions were used to characterize the transcriptional activity of the lip promote ... | 1991 | 1663151 |
| tn5 mutagenesis of the salmonella typhimurium 100 kb plasmid: definition of new virulence regions. | in this study, the 100 kb plasmid of salmonella typhimurium, which is known to contribute to the pathogenicity of the organism, was tagged with the transposon tn5 to define regions of the plasmid contributing to overall virulence. eleven randomly selected vir::tn5 plasmids carried by the plasmid-free s. typhimurium strain ws1321 were physically mapped and then examined in mice for subcutaneous ld50 value, ability to induce splenomegaly, and ability to grow to high numbers in the spleens of infec ... | 1991 | 1665537 |
| salmonella typhimurium dt 193. | | 1991 | 1669816 |
| salmonella typhimurium dt 193. | | 1991 | 1669857 |
| survival of bacteriophage 1 of the salmonella typhimurium phage typing scheme in 4 different types of sterile soil. | the survival of bacteriophage 1 of the salmonella typhimurium phage typing scheme was studied in four different types of sterile soil at 4.20 and 37 degrees c. the longevity of the phage was generally short, not exceeding 36 days and depended on the temperature and the type of soil. | 1991 | 1670055 |
| bacteriological and immunological aspects of conventional and germfree mice infected with salmonella typhimurium. | bacterial invasiveness and immunological responses were studied in germfree (gf) and conventional (cv) mice infected with salmonella typhimurium. bacterial counts of homogenates prepared from liver and spleen showed that the colony forming units (cfu) increased rapidly in gf mice and reached lethal proportions (10(9) cell per organ) by day 6. in cv mice, these counts increased to about 10(4.5) log cell per organ by day 6 and then declined slowly. an increase in serotype-specific igm and igg leve ... | 1991 | 1670260 |
| evaluation of cysteine 283 and glutamic acid 284 in the coenzyme binding site of salmonella typhimurium glutamate dehydrogenase by site-directed mutagenesis and reaction with the nucleotide analogue 2-[4-bromo-2,3-dioxobutyl)thio)-1,n6-ethenoadenosine 2',5'-bisphosphate. | nadp(+)-specific glutamate dehydrogenase of salmonella typhimurium was previously shown to react irreversibly at the coenzyme site with the nucleotide analogue 2-((4-bromo-2,3-dioxobutyl)thio)-1,n6-ethenoadenosine 2',5'-bisphosphate (2-bdb-t epsilon a 2',5'-dp) yielding a partially active enzyme, and inactivation was attributed to modification of the peptide leu282-cys-glu-ile-lys286 (bansal, a., dayton, m.a., zalkin, h., and colman, r.f. (1989) j. biol. chem. 264, 9827-9835). three mutant enzym ... | 1991 | 1672312 |
| terbium(iii) luminescence study of the spatial relationship of tryptophan residues to the two metal ion binding sites of escherichia coli glutamine synthetase. | the luminescence of tb(iii) was used to explore the topography of the metal ion sites of escherichia coli glutamine synthetase and the relationship between these sites and tryptophan residues of the enzyme. by irradiation of tryptophan residues at 295 nm and measurement of the resulting tb(iii) luminescence at 544 nm, a biphasic curve was obtained upon titrating apoenzyme with tb(iii) indicating sequential binding of tb(iii) ions to the two binding sites of glutamine synthetase. the luminescence ... | 1991 | 1672821 |
| site-directed mutagenesis of the beta subunit of tryptophan synthase from salmonella typhimurium. role of active site glutamic acid 350. | to investigate the functional role of glutamic acid 350 in the active site of the beta subunit of tryptophan synthase from salmonella typhimurium, we have replaced this residue by glutamine or alanine by use of site-directed mutagenesis. the mutant alpha 2 beta 2 complexes were expressed, purified, crystallized, and characterized by spectroscopic and kinetic studies with several substrates. we find large alterations in the substrate and reaction specificity of each mutant form of the alpha 2 bet ... | 1991 | 1673461 |
| use of ciprofloxacin to control a salmonella outbreak in a long-stay psychiatric hospital. | an outbreak of diarrhoea due to salmonella virchow phage type 8 occurred in a major block of a large psychiatric hospital. the two other major blocks of the hospital remained unaffected. no source of infection was identified and the epidemiological investigations pointed to cross-infection as the mode of transmission. infection control measures were implemented at an early stage but a total of 55 patients and four members of staff were affected. the disease was self-limiting and of short duratio ... | 1991 | 1675645 |
| sweet's syndrome associated with salmonella typhimurium infection. | a 41-year-old woman presented with the typical clinical and pathohistological features of acute febrile neutrophilic dermatosis (afnd). the disease had been preceded by diarrhoea and vomiting for 2 weeks. stool cultures proved positive for salmonella typhimurium infection. antibiotic therapy and tapering oral steroids led to a complete remission of skin lesions within 2 weeks. to our knowledge, this is the first report of sweet's syndrome associated with salmonellosis. | 1991 | 1676226 |
| type 1 fimbriae of salmonella enteritidis. | salmonella enteritidis was previously shown to produce fimbriae composed of 14,000-molecular-weight (mr) fimbrin monomers (j. feutrier, w. w. kay, and t. j. trust, j. bacteriol. 168:221-227, 1986). another distinct fimbrial structure, comprising 21,000-mr fimbrin monomers, has now been identified. these fimbriae are simply designated as sef 14 and sef 21, respectively (for s. enteritidis fimbriae and the mr [in thousands] of the fimbrin monomer). a simple method for the purification of both stru ... | 1991 | 1677356 |
| a genotoxicological study of hexachlorobenzene and pentachloroanisole. | the potential mutagenic activity of hexachlorobenzene (hcb) and pentachloroanisole (pca) was investigated. no genotoxicity after application on salmonella typhimurium (ames test), escherichia coli, and human peripheral blood lymphocytes in vitro was observed. | 1991 | 1677498 |
| agaritine does not mediate the mutagenicity of the edible mushroom agaricus bisporus. | ethanolic extracts of the edible mushroom agaricus bisporus displayed a direct-acting mutagenic response in various salmonella typhimurium strains, ta104 being clearly the most sensitive. incorporation of an activation system derived from the liver of mice, hamsters or aroclor 1254-induced rats failed to increase the mutagenic response. the mutagenic response of ethanolic extracts from various types of mushroom, containing different levels of agaritine (range 0.3-6.5 g/kg fresh weight), was very ... | 1991 | 1679191 |
| proteus mirabilis flagella and mr/p fimbriae: isolation, purification, n-terminal analysis, and serum antibody response following experimental urinary tract infection. | urinary tract infection with proteus mirabilis may lead to serious complications, including cystitis, acute pyelonephritis, fever, bacteremia, and death. in addition to the production of hemolysin and the enzyme urease, fimbriae and flagellum-mediated motility have been postulated as virulence factors for this species. we purified mannose-resistant/proteuslike (mr/p) fimbriae and flagella from strains cft322 and hu2450, respectively. electron microscopy revealed highly concentrated preparations ... | 1991 | 1680106 |
| mycobacterial heat-shock proteins as carrier molecules. | we have previously shown that the priming of mice with live mycobacterium tuberculosis var. bovis (bacillus calmette-guérin, bcg) and immunization with the repetitive malaria synthetic peptide (nanp)40 conjugated to purified protein derivative (ppd), led to the induction of high and long-lasting titers of anti-peptide igg antibodies, overcoming the requirement of adjuvants and the genetic restriction of the antibody response to the peptide (lussow et al., proc. natl. acad. sci. usa 1990. 87:2960 ... | 1991 | 1680693 |
| inability of plasmodium vinckei-immune spleen cells to transfer protection to recipient mice exposed to vaccine 'vectors' or heterologous species of plasmodium. | mice can be immunized to plasmodium vinckei by repeated infections followed by cure. such immunity is dependent on cd4 t cells and an architecturally modified spleen, but has little requirement for antibody. thus, athymic mice can be exposed to p. vinckei and cured, but do not develop immunity. they are resistant to challenge with parasites, however, if they are then given spleen cells from euthymic immunized animals. such immune spleen cells, however, cannot transfer resistance to normal mice w ... | 1991 | 1683480 |
| survival of bacteria under dry conditions; from a viewpoint of nosocomial infection. | the viability of non-sporing bacteria in a dry state was examined. the number of viable cells was determined at various time intervals, after inoculation onto cotton lint and a glass plate. viable cells of mycobacterium bovis were detected more than 2 months after inoculation, and this was the most resistant species to dry conditions among the bacteria tested. in the case of the gram-positive cocci tested and one species of gram-negative rods, acinetobacter calcoaceticus var. anitratus, the viab ... | 1991 | 1685507 |
| slime capsule and fimbriae on salmonella typhimurium var. cop.--electron microscopic study. | on salmonella typhimurium var. cop. we found, under special culture conditions, on the same cell simultaneously fimbriae and mucoid material which was histochemically identified as an acid mucopolysaccharide. membrane vesicles or invaginations of the cytoplasmic membrane are mentioned as a possible place of the slime production and the function of the glycocalyx is discussed regarding tenacity, as a diffusion barrier and attachment factor. | 1991 | 1685610 |
| dna strand breaks induced in cultured human and rodent cells by chlorohydroxyfuranones--mutagens isolated from drinking water. | chlorohydroxyfuranones, by-products of chlorine disinfection and drinking water contaminants, are shown to produce dna strand breaks in human and rodent cells. one chlorohydroxyfuranone, 3-chloro-4-dichloromethyl-5-hydroxy-2[5h]-furanone (mx), a potent bacterial mutagen, induces 232 +/- 89 dna strand breaks.(cell-microm)-1 in human ccrf-cem cells over a concentration range of 4.4 to 220 microm. this constitutes a dna damage potency comparable to dimethylsulfate (dms). by comparison, 3,4-dichloro ... | 1991 | 1686674 |
| analysis of rat lymphocyte activation of benzo[a]pyrene, 2-acetylaminofluorene, and several of their metabolites to mutagenic and dna-damaging species in vitro. | rat lymphocytes are a potentially useful and convenient cell system for monitoring the genotoxic effects of chemicals in vivo, but little is known about the ability of these cells to metabolize promutagens to genotoxic species. in this study, fischer 344 rat lymphocytes were treated in vitro with benzo[a]pyrene (bap), 2-acetylaminofluorene (2-aaf), and several of their metabolites, and dna damage was measured using nucleoid sedimentation analysis. of the bap derivatives, bap 4,5-oxide and bap 7, ... | 1991 | 1686675 |
| distribution of alginate gene sequences in the pseudomonas rrna homology group i-azomonas-azotobacter lineage of superfamily b procaryotes. | chromosomal dna from group i pseudomonas species, azotobacter vinelandii, azomonas macrocytogens, xanthomonas campestris, serpens flexibilis, and three enteric bacteria was screened for sequences homologous to four pseudomonas aeruginosa alginate (alg) genes (alga, pmm, algd, and algr1). all the group i pseudomonas species tested (including alginate producers and nonproducers) contained sequences homologous to all the p. aeruginosa alg genes used as probes, with the exception of p. stutzeri, whi ... | 1990 | 1689562 |
| 1,n6-ethenoadenosine formation, mutagenicity and murine tumor induction as indicators of the generation of an electrophilic epoxide metabolite of the closely related carcinogens ethyl carbamate (urethane) and vinyl carbamate. | previous studies from this laboratory showed that (i) vinyl carbamate (vc) was much more carcinogenic than ethyl carbamate (ec) and that both carbamates induced the same spectrum of tumors in mice and rats, (ii) adducts of [14c]- or [3h]1,n6-ethenoadenosine and [14c]- or [3h]3,n4-ethenocytidine e were formed in the hepatic rna of infant male b6c3f1 mice administered [1-14c]ethyl or [1,2-3h]ethyl ec and (iii) vc formed much more of the 1,n6-ethenoadenosine (epsilon ado) adduct in the hepatic rna ... | 1990 | 1690091 |
| salmonella lipopolysaccharide in synovial cells from patients with reactive arthritis. | synovial cells from nine patients with reactive arthritis following salmonella enteritidis or salmonella typhimurium infection were examined for salmonella antigens. extensive bacterial cultures of the synovial fluid were negative. eight synovial-fluid cell samples stained positively on immunofluorescence with rabbit antisera against heat-killed s enteritidis or s typhimurium or with monoclonal antibodies specific for the causative salmonella lipopolysaccharide (lps). synovial tissue from the ni ... | 1990 | 1690327 |
| lamb (maltoporin) of salmonella typhimurium: isolation, purification and comparison of sugar binding with lamb of escherichia coli. | lamb (maltoporin) of salmonella typhimurium was found to be more strongly associated with the murein than ompf. it was purified in one step using a hydroxyapatite (htp) column. reconstitution of the pure protein with lipid bilayer membrane showed that lamb of s. typhimurium formed small ion-permeable channels with a single channel conductance of about 90 ps in 1 m kcl and some preference for cations over anions. the conductance concentration curve was linear, which suggested that lamb of s. typh ... | 1990 | 1693746 |
| bacteria-infected fibroblasts have enhanced susceptibility to the cytotoxic action of tumor necrosis factor. | the susceptibility of bacteria-infected fibroblasts to the cytotoxic action of tumor necrosis factor was investigated. l cells infected with shigella flexneri, salmonella typhimurium, or listeria monocytogenes, had an enhanced susceptibility to the cytotoxic activity of tnf-alpha. this enhanced susceptibility was dependent upon the challenge dose of bacteria, the concentration of tnf, and upon the exposure time of bacteria-infected cells to tnf. l cells infected with s. flexneri were susceptible ... | 1990 | 1694886 |
| carbohydrates inhibit the potentiating effect of bacteria, endotoxin and virus on basophil histamine release. | histamine release caused by calcium ionophore a23187 and anti-ige was examined in leukocyte suspensions from 8 healthy individuals. staphylococcus aureus, lipopolysaccharide (lps) from salmonella typhimurium and influenza a virus were found to enhance the histamine release but did not release histamine per se. the potentiation of mediator release depends on a non-transient signal since the potentiating effect was also obtained by preincubation of the cells with lps followed by wash-out and stimu ... | 1990 | 1695460 |
| [direct-action mutagens in exhausts of vehicles with diesel engines]. | the genotoxic activity of exhausts from one-shaft gas-turbine gte-5 engine (30 kw) and a standard d-54a diesel (40 kw) have been studied. thus, the extracts of soot from gte-5 and d-54a induced reversions in salmonella typhimurium both with and without metabolic activation: furthermore, extracts of soot from gte-5 demonstrated a higher mutagenic activity. the direct mutagenic effect of the exhausts depended neither on the presence of bp nor on the other polycyclic aromatic hydrocarbons (pahs). m ... | 1990 | 1696198 |
| assessment of the mutagenic potential of ethanol auto engine exhaust gases by the salmonella typhimurium microsomal mutagenesis assay, using a direct exposure method. | the mutagenic activity of the new brazilian fuel, ethanol, was determined by employing the salmonella typhimurium microsomal mutagenesis assay (ta97, ta98, ta100, ta102, and ta104) and a direct exposure method. this methodology was first used to determine the mutagenic activity of gasoline, revealing mutagenic activity of base-pair substitution without any need for metabolic activation, indicating the presence of direct-action mutagens. experiments with ethanol suggest an indirect mutagenic acti ... | 1990 | 1697535 |
| macrophage activation by leptospiral lipopolysaccharide. | leptospiral lipopolysaccharides (lpss) extracted from leptospira interrogans serovars copenhageni and hebdomadis were tested for the ability to induce macrophage activation. in-vitro analysis showed that each leptospiral lps was a potent activator to macrophages. after stimulation with the lpss, interleukin-1 (il-1) secretion, interferon (ifn) production and chemiluminescence (cl) response were induced. intravenous high-dose injection of the leptospiral lpss induced various lesions such as necro ... | 1990 | 1698063 |
| inflammatory effects of salmonella typhimurium porins. | the inflammatory activity of porins purified from salmonella typhimurium has been investigated. porins (0.3 to 30 micrograms) injected into the rat paw induced a dose-related edema that was not due to lipopolysaccharide contamination and did not appear to be dependent on the activation of the complement system. the edema induced by 30 micrograms of porins was comparable to that caused by 1 mg of carrageenin and was inhibited by indomethacin (5 mg/kg) and dexamethasone (0.1 mg/kg). porins (1 to 1 ... | 1990 | 1698175 |
| oral salmonella: malaria circumsporozoite recombinants induce specific cd8+ cytotoxic t cells. | oral immunization with an attenuated salmonella typhimurium recombinant containing the full-length plasmodium berghei circumsporozoite (cs) gene induces protective immunity against p. berghei sporozoite challenge in the absence of antibody. we found that this immunity was mediated through the induction of specific cd8+ t cells since in vivo elimination of cd8+ cells abrogated protection. in vitro studies revealed that this salmonella-p. berghei cs recombinant induced class i-restricted cd8+ cyto ... | 1990 | 1698908 |
| bacteria and endotoxin enhance basophil histamine release and potentiation is abolished by carbohydrates. | histamine release caused by anti-ige, specific antigens and calcium ionophore a23187 was examined in leukocyte suspensions from healthy individuals and patients allergic to house dust mite and birch pollen. staphylococcus aureus and lps from salmonella typhimurium were found to cause a synergistic enhancement of the release. the potentiation of mediator release by the bacteria and the endotoxin depends on a binding to the basophilocyte, followed by a non-transient event, since the potentiating e ... | 1990 | 1700887 |
| sequence of the pcka gene of escherichia coli k-12: relevance to genetic and allosteric regulation and homology of e. coli phosphoenolpyruvate carboxykinase with the enzymes from trypanosoma brucei and saccharomyces cerevisiae. | the sequence of the pcka gene coding for phosphoenolpyruvate carboxykinase in escherichia coli k-12 and previous molecular weight determinations indicate that this allosteric enzyme is a monomer of mr 51,316. the protein is homologous to atp-dependent phosphoenolpyruvate carboxykinases from trypanosoma brucei and saccharomyces cerevisiae. a potential atp binding site was conserved in all three sequences. a potential binding site for the allosteric activator, calcium, identified in the e. coli en ... | 1990 | 1701430 |
| efficient recognition by rat t cell clones of an epitope of mycobacterial hsp 65 inserted in escherichia coli outer membrane protein phoe. | phoe is a pore-forming protein, abundantly expressed in the escherichia coli outer membrane. previous investigations have shown the possibility of inserting antigenic determinants in cell surface-exposed regions of phoe by recombinant dna techniques without disturbing the biogenesis and the functioning of the protein. this method proved to be successful for foot-and-mouth disease virus b cell determinants. we have now shown for the first time that phoe can also be used as a carrier molecule for ... | 1990 | 1702727 |
| identification and characterization of dppa, an escherichia coli gene encoding a periplasmic dipeptide transport protein. | we describe the isolation and analysis of an escherichia coli gene, dppa, and its role in dipeptide transport. dppa maps near min 79 and encodes a protein (dppa) that has regions of amino acid similarity with a peptide-binding protein from salmonella typhimurium (oppa). like oppa, dppa is found in the periplasmic space and thus is most likely a dipeptide-binding protein. insertional inactivation of dppa results in the inability of a proline auxotroph to utilize pro-gly as a proline source. dppa- ... | 1991 | 1702779 |
| metabolic activation of nitropyrenes and diesel particulate extracts. | the aim of this research was to investigate the possible risks of genotoxicity associated with human exposure to diesel engine emissions. we sought to identify and evaluate the critical components of such emissions by using a variety of short-term biological systems. adducts formed between benzo[a]pyrene and dna in several short-term test systems have been thoroughly investigated. although benzo[a]pyrene has long been used as an index of the potential carcinogenicity of polycyclic aromatic hydro ... | 1990 | 1702973 |
| the chromosomal integration site of the streptomyces element psam2 overlaps a putative trna gene conserved among actinomycetes. | the psam2 element of streptomyces ambofaciens integrates site-specifically in the genome of different streptomyces species by recombination between a 58 bp sequence common to the plasmid (attp) and the chromosome (attb). southern hybridization analysis showed that sequences similar to the psam2 attb site were found in other actinomycetes (mycobacterium, nocardia, micromonospora) as well as unrelated bacteria (bacillus circulans, escherichia coli, clostridium botulinum, bordetella pertussis, and ... | 1990 | 1703270 |
| sequence analysis and expression of the salmonella typhimurium asr operon encoding production of hydrogen sulfide from sulfite. | a chromosomal locus of salmonella typhimurium which complements s. typhimurium asr (anaerobic sulfite reduction) mutants and confers on escherichia coli the ability to produce hydrogen sulfide from sulfite was recently cloned (c. j. huang and e. l. barrett, j. bacteriol. 172:4100-4102, 1990). the dna sequence and the transcription start site have been determined. analysis of the sequence and gene products revealed a functional operon containing three genes which have been designated asra, asrb, ... | 1991 | 1704886 |
| structural determination of a directly mutagenic amino-nitrobiphenyl as the s9 metabolite of 2,4,2',4'-tetranitrobiphenyl in salmonella typhimurium ta98. | in order to elucidate the mechanisms of mutagenic activation of nitrobiphenyls by mammalian activation systems, 2,4,2',4'-tetranitrobiphenyl was incubated with s9 and its mutagenic metabolites were separated by sio2 and al2o3 column chromatography. the most mutagenic diamino-dinitrobiphenyl was isolated from the reaction mixture of 2,4,2',4'-tetranitrobiphenyl with s9 mix at 37 degrees c for 48 h, and its mutability was 4646 revertants/50 ng in salmonella typhimurium ta98 without s9 mix. the dea ... | 1991 | 1706069 |
| dual transcriptional initiation sites from the pyrc promoter control expression of the gene in salmonella typhimurium. | expression of the salmonella typhimurium pyrc gene encoding dihydroorotase is negatively regulated by ctp and stimulated by gtp. this regulation does not occur at the level of transcription initiation but appears to involve translation attenuation of the transcripts. alterations of specific bases in a region of hyphenated dyad symmetry located in the leader established that base pairing in the 5' terminal region of the pyrc leader transcript is required for normal regulation of dihydroorotase sy ... | 1991 | 1706467 |
| negative autoregulation of cysb in salmonella typhimurium: in vitro interactions of cysb protein with the cysb promoter. | cysb protein positively regulates genes of the salmonella typhimurium cysteine regulon and negatively autoregulates cysb. the cysb promoter was characterized by primer extension of cellular rna, which gave products identifying a major in vivo transcription start site located 95 bp upstream of the cysb start codon and two minor sites located 9 and 10 bp downstream of the major site. gel shift binding studies and dnase i footprinting experiments showed that cysb protein binds to the cysb promoter ... | 1991 | 1706701 |
| molecular cloning, characterization, and nucleotide sequence of the rfc gene, which encodes an o-antigen polymerase of salmonella typhimurium. | the rfc gene of salmonella typhimurium was located in a 1.75-kb hindiii fragment and restored wild-type lipopolysaccharide synthesis ability to both an older rfc point mutant and new rfc::is10 mutants. dna sequencing of the hindiii fragment revealed an open reading frame which could encode a protein of 407 amino acids with an mr of 47,472 and also revealed potential translation signals. modulator codons accounted for 12.5% of the total codon content, providing a possible explanation for the nond ... | 1991 | 1707412 |
| the possible role of probiotics as dietary antimutagen. | possible antimutagenic actions of probiotics--mainly lactic acid bacteria--were examined using in vitro and in vivo test systems. in the ames test with salmonella typhimurium ta1538 beef extract and nitrosated beef extract were used as mutagens. l. casei showed high antimutagenic activity on mutagenicity induced by nitrosated beef extract only without s9 mix, whereas omniflora (a lyophilized preparation of lactobacilli and e. coli) and its cell-free culture broth exhibited antimutagenic action o ... | 1991 | 1708108 |
| energy dependence of o-antigen synthesis in salmonella typhimurium. | the uncoupler 2,4-dinitrophenol prevents in vivo synthesis of o antigen in salmonella typhimurium by inhibiting the first reaction of the pathway, formation of galactosyl-pyrophosphoryl-undecaprenol. inhibition was observed only in intact cells; dinitrophenol had no effect on activity of the synthase enzyme in isolated membrane fractions. in vivo inhibition could not be explained by changes in intracellular nucleotide pools or a shift in the equilibrium of the reaction and appeared to be specifi ... | 1991 | 1708761 |
| evidence for energy-dependent transposition of core lipopolysaccharide across the inner membrane of salmonella typhimurium. | the uncoupler 2,4-dinitrophenol blocks the final step of lipopolysaccharide assembly--transfer of o antigen from undecaprenyl pyrophosphate to core lipopolysaccharide--in intact salmonella typhimurium but not in isolated membrane fractions. the o-antigen ligase enzyme is not inhibited by dinitrophenol in vitro, and core lipopolysaccharide synthesized in the presence of uncoupler in vivo is functional as acceptor of o antigen in vitro. the evidence strongly suggests that maintenance of proton mot ... | 1991 | 1708762 |
| primed neutrophils injure rat lung through a platelet-activating factor-dependent mechanism. | bacterial lipopolysaccharide (lps) promotes transient lung neutrophil sequestration. these lps-primed neutrophils, when stimulated by an n-formyl peptide (fnlp), promote lung injury. we hypothesized that lps-primed, fnlp-stimulated neutrophils promote lung injury through a platelet-activating factor (paf)-dependent mechanism. rats were pretreated with either saline or web2170, a paf receptor antagonist (10 mg/kg po). one hour after pretreatment, rats were administered intraperitoneal lps (salmon ... | 1991 | 1710005 |
| intervening sequences (ivss) in the 23s ribosomal rna genes of pathogenic yersinia enterocolitica strains. the ivss in y. enterocolitica and salmonella typhimurium have a common origin. | the 23s ribosomal rna (rrna) was shown to be in two fragments in pathogenic yersinia enterocolitica. the cleavage site in the structural gene of the 23s rrna was occupied by an intervening sequence (ivs) of about 100 nucleotides, analogous to ivss found in salmonellae (burgin et al., 1990). nucleotide sequences of ivss of several y. enterocolitica strains revealed that the ivss of the highly virulent y. enterocolitica serotypes strains, and the ivs of salmonella typhimurium were about 90% simila ... | 1991 | 1710756 |
| error-prone ef-tu reduces in vivo enzyme activity and cellular growth rate. | mutations in salmonella typhimurium encoding error-prone ef-tu (tufa8, tufb103) enhance translational error levels and also cause a reduced growth rate. the relative changes in error level and growth rate are inversely related and dependent on the status of the two tuf genes. possible causes of the reduced growth rate were investigated. several important parameters with the potential to alter growth rate (the ef-tu-ribosome interaction, the in vivo elongation rate and the processivity of transla ... | 1991 | 1710757 |
| interspecies compatibility of selenoprotein biosynthesis in enterobacteriaceae. | several species of enterobacteriaceae were investigated for their ability to synthesize selenium-containing macromolecules. seleniated trna species as well as seleniated polypeptides were formed by all organisms tested. two selenopolypeptides could be identified in most of the organisms which correspond to the 80 kda and 110 kda subunits of the anaerobically induced formate dehydrogenase isoenzymes of e. coli. in those organisms possessing both isoenzymes, their synthesis was induced in a mutual ... | 1991 | 1710885 |
| eric sequences: a novel family of repetitive elements in the genomes of escherichia coli, salmonella typhimurium and other enterobacteria. | we describe a family of highly conserved, enterobacterial repetitive intergenic consensus (eric) sequences, 14 of which have been identified in escherichia coli and salmonella typhimurium and a further three in other enterobacterial species (yersinia pseudotuberculosis, klebsiella pneumoniae and vibrio cholerae). eric sequences are 126 bp long and appear to be restricted to transcribed regions of the genome, either in intergenic regions of polycistronic operons or in untranslated regions upstrea ... | 1991 | 1713281 |
| immunogenicity of foreign peptide epitopes expressed in bacterial envelope proteins. | we have used two bacterial proteins from escherichia coli to express heterologous peptides. both proteins are situated in the e. coli cell envelope but have different properties: lamb is an integral outer membrane protein, and male a soluble periplasmic protein. the peptides were expressed as genetic inserts within "permissive sites" of these recipient proteins, i.e. sites which allow the insertion of foreign peptides without affecting the biological properties of the host protein. in this paper ... | 1990 | 1714094 |
| selection of the same major t cell determinants of influenza nucleoprotein after vaccination or exposure to infectious virus. | in the present study, we have compared the t cell antigenic determinants on nucleoprotein (np) of influenza a/nt/60/68 virus recognized by balb/c mice (h-2d) after vaccination using several different vehicles with the determinants recognized after exposure to infectious virus. mice were immunized s.c. with: 1) purified recombinant np with three different adjuvants--alum, saponin, or cfa; 2) whole inactivated a/okuda virus in pbs or saponin; or 3) live attenuated salmonella typhimurium aroa- vect ... | 1991 | 1715366 |
| structure-activity relationships of a series of antitumoral 5,8-quinazolinediones in mutagenicity studies. | four antitumoral 5,8-quinazolinediones were examined for their ability to induce mutation in salmonella typhimurium. each compound was tested at several concentrations in 4 strains. relationships were established between the structure of the quinones and their mutagenic activities. the mutagenicity was influenced by (i) the nature of the substituent(s) of the quinonic moiety: the methoxyquinone had no mutagenic properties and the aziridinylquinones were mutagenic in the 4 strains with or without ... | 1991 | 1715513 |
| direct expression of bordetella pertussis filamentous hemagglutinin in escherichia coli and salmonella typhimurium aroa. | nonfused (i.e., nonhybrid) filamentous hemagglutinin (fha) of bordetella pertussis was efficiently expressed in escherichia coli k-12 and salmonella typhimurium aroa at levels higher than those found in wild-type b. pertussis when the upstream signals of the gene were replaced and the translation initiation region was engineered to optimize translational efficiency. inclusion of part of the c-terminal fha open reading frame, whose translation product does not appear to be part of the major secre ... | 1991 | 1716615 |
| evolution of the ferric enterobactin receptor in gram-negative bacteria. | using sodium dodecyl sulfate-polyacrylamide gel electrophoresis of iron-deficient and replete cell envelopes, 59fe-siderophore uptake studies, and western immunoblots and cytofluorimetric analyses with monoclonal antibodies (mabs), we surveyed a panel of gram-negative bacteria to identify outer membrane proteins that are structurally related to the escherichia coli k-12 ferric enterobactin receptor, fepa. antibodies within the panel identified fepa epitopes that are conserved among the majority ... | 1991 | 1717434 |
| synthesis and mutagenicity of trans-dihydrodiol metabolites of benzo[b]naphtho[2,1-d]thiophene. | the syntheses of potentially important metabolites of benzo[b]naphtho[2,1-d]thiophene ([2,1]bnt)--trans-1,2-dihydroxy-1,2-dihydrobenzo[b]naphtho[2,1- d]thiophene ([2,1]bnt-1,2-diol) and trans-3,4-dihydroxy-3,4-dihydrobenzo[b]naphtho[2,1-d]thiophene ([2,1]bnt-3,4-diol)--are described. the syntheses involved preparation of the appropriate 1-(3-benzo[b]-thiopheneyl)-2-(methoxyphenyl)ethylenes followed by photocyclization to methoxy-[2,1]bnts, hydrolysis to hydroxy-[2,1]bnts, oxidation to [2,1]bnt-d ... | 1990 | 1718470 |
| cloning and nucleotide sequence of the gene (cita) encoding a citrate carrier from salmonella typhimurium. | a cryptic citrate transport gene (cita) from salmonella typhimurium chromosome was cloned and its nucleotide sequence was determined. the cloned plasmid conferred citrate-utilizing ability on wild-type escherichia coli, which cannot grow on citrate as the sole source of carbon. the resultant e. coli transformant was able to transport citrate. a 1,302-base-pair open reading frame with a preceding ribosomal binding site was found in the cloned dna fragment. the 434-amino-acid protein that could be ... | 1991 | 1718953 |
| antimutagenic and antitumorigenic activities of nordihydroguaiaretic acid. | nordihydroguaiaretic acid (ndga), which occurs in the resinous exudates of many plants is used as an antioxidant in fats and oils. in this study we show that ndga inhibited the mutagenicity of methyl methanesulfonate, benzo[a]pyrene (bp), 2-aminofluorene, and aflatoxin b1 in salmonella typhimurium strain ta100 or ta98 in the absence and presence of rat hepatic microsomal activation system. the addition of ndga during and after nitrosation of methylurea (mu) resulted in a dose-dependent inhibitio ... | 1991 | 1719406 |
| lack of mutagenicity of ochratoxin a and b, citrinin, patulin and cnestine in salmonella typhimurium ta102. | the aspergillus mycotoxins ochratoxin a and b, citrinin and patulin as well as combinations of ochratoxin a and citrinin did not induce reverse mutations in salmonella typhimurium strain ta102. therefore there is no indication for the induction of oxidative damage or crosslinks. the same is true for cnestine, a compound extracted from the plant cnestis glabra. | 1991 | 1719413 |
| chlamydia trachomatis major outer membrane protein epitopes expressed as fusions with lamb in an attenuated aro a strain of salmonella typhimurium; their application as potential immunogens. | the major outer-membrane protein (momp) of chlamydia trachomatis is the focus of attention for chlamydial vaccine design, particularly those serovar- and subspecies-specific epitopes which provoke neutralizing immune responses. selected surface-exposed b-cell epitopes of momp, incorporating b-subspecies specificities, were expressed as fusions with lamb, an inducible outer-membrane transport protein of escherichia coli. these recombinant chlamydial-lamb proteins were correctly transported to the ... | 1991 | 1720166 |
| a microplate version of the sos/umu-test for rapid detection of genotoxins and genotoxic potentials of environmental samples. | the umu-microtest is a miniaturized automated short-term test version proposed for screening of umuc-dependent mutagenic potentials of chemicals relevant to environmental pollution, river water and industrial waste water. the test is based on the sos/umu-test and has been modified in order to allow extensive testing of environmental samples. genetically engineered salmonella typhimurium (ta1535/psk1002) are incubated on a microplate rotor in a sloping position for 2 h with the test samples, foll ... | 1991 | 1720196 |