- Volume 133, Issue 6, 1987
Volume 133, Issue 6, 1987
- Biochemistry
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Purification and Characterization of Extracellular Glucosyltransferase from Streptococcus mutans Serotype b (Subspecies rattus)
Summary: An extracellular glucosyltransferase (GT-S) synthesizing water-soluble glucan was purified from the culture supernatant of Streptococcus mutans BHT (serotype b, subsp. rattus) by DEAE-Sepharose chromatography and preparative isoelectric focusing. The M r of the enzyme was 155000 and the pI was 4·5. The GT-S had a specific activity of 10·2 i.u. (mg protein)−1, an optimum pH of 6·0 and a Km value of 0·8 mm for sucrose, and was activated twofold by dextran T10. The GT-S was immunologically partially identical with the corresponding enzymes in crude preparations from serotypes c, e and f. The glucan synthesized de novo from sucrose by the GT-S was water-soluble and consisted of 29 mol% of non-reducing terminal, 49 mol% of 1,6-α-linked, 11 mol% of 1,3-α-linked and 11 mol% of 1,3,6-α-branched glucose residues.
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Composition of the Lipopolysaccharide from Different Capsular Serotype Strains of Haemophilus influenzae
More LessSummary: Lipopolysaccharide (LPS) from all six serotype strains of Haemophilus influenzae was similar in composition. The oligosaccharide, of each LPS, was composed of glucose, galactose, heptose and 2-keto-3-deoxyoctonic acid. The lipid A was composed of glucosamine, phosphate and the fatty acids 14:0 and 3-OH 14:0. Each LPS also contained ethanolamine and ethanolamine phosphate, and the oligosaccharides from two strains additionally contained small amounts of glucosamine. Although the LPS was similar in composition, different serotypes had quantitative differences, especially in the galactose content, which correlated with the antigenic specificity of their homologous antisera and with their mobility on SDS-polyacrylamide gel electrophoresis (SDS-PAGE). A survey by SDS-PAGE showed that LPS from strains of the serotypes a, c and d was characteristically of lower Mr than the LPS from most (80%) serotype b strains.
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Inorganic Pyrophosphatase Activity in Cell-free Extracts of Ureaplasma urealyticum
More LessSummary: Cell-free extracts of Ureaplasma urealyticum strains Pi and T960 (CX8) (serovars 6 and 8, respectively) metabolized inorganic pyrophosphate (PPi). The inorganic pyrophosphatase (PPase) activity was greatest with Mg2+ as cofactor, but Mn2+ acted as a poor substitute. The PPases of the two serovars differed electrophoretically. Although the highest PPase activity was obtained using PPi as substrate, the enzyme could also utilize to a lesser degree both tripolyphosphate and trimetaphosphate. No activity was observed against β-glycerophosphate, naphthyl phosphates, glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-bisphosphate, thiamin pyrophosphate, phosphoribosylpyrophosphate, ADP or ATP. Acid- and alkaline-phosphatase activities were observed with naphthyl phosphates as substrates, but they did not have the same electrophoretic mobility on gels as the PPase activity. U. urealyticum PPase was inhibited by oxidized glutathione, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, phenyl-glyoxal, p-chloromercuribenzoic acid, Mn2+, Zn2+ and Ca2+. Neither reduced glutathione, l-cysteine nor Co2+ enhanced activity. PPi can act as a substrate or regulator of certain metabolic reactions, and PPi metabolism can function in bacterial bioenergetics; its role in ureaplasmas is presently unclear.
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Extracellular Acid and Alkaline Proteases from Candida olea
G. Nelson and T. W. YoungSummary: Candida olea 148 secreted a single acid protease when cultured at acidic pH. In unbuffered medium, the culture pH eventually became alkaline and a single alkaline protease was produced. This was the only proteolytic enzyme produced when the organism was grown in buffered medium at alkaline pH. Both proteolytic enzymes were purified to homogeneity (as assessed by SDS-PAGE). The Mr of the acid protease was 30900, the isoelectric point 4·5; optimum activity against haemoglobin was at 42 °C and pH 3·3. This enzyme was inactivated at temperatures above 46 °C and was inhibited by pepstatin and diazoacetyl-norleucine methyl ester but was insensitive to inhibition by either 1,2-epoxy-3-(p-nitrophenoxy)-propane or compounds known to inhibit serine, thiol or metallo proteases. The acid protease contained 11% carbohydrate. The alkaline protease had an M r of 23400 and an isoelectric point of 5·4. The activity of this enzyme using azocoll as substrate was optimal at 40°C in the range pH 8·0-9·0. This enzyme was inactivated at temperatures above 42°C and was inhibited by phenylmethyl-sulphonyl fluoride and irreversibly inactivated by EDTA. The enzyme was also partially inhibited by DTT but was insensitive to either pepstatin or p-chloromercuribenzoic acid.
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Differential Translational Efficiency of the mRNAs Isolated from Derepressed and Glucose Repressed Saccharomyces cerevisiae
More LessSummary: Carbon catabolite derepression induced changes in the pool of yeast mRNAs translatable in a protein-synthesizing reticulocyte system. Competition experiments with globin mRNA showed that the mRNA population obtained from derepressed cells possessed a higher translational efficiency than mRNA from repressed cells. The mRNAs that could account for the high translational efficiency of the derepressed mRNA were not detected in cells growing in glucose-rich medium. Analysis of protein synthesis in the presence of 7-methylguanosine 5′-phosphate indicated that the initiation factors recognizing the 5′-terminal structure of capped messengers interacted with lower affinity with the repressed than with some specific derepressed mRNAs.
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Involvement of a Conidial Endoglucanase and a Plasma-membrane-bound β-Glucosidase in the Induction of Endoglucanase Synthesis by Cellulose in Trichoderma reesei
More LessSummary: The induction of endo-1,4-β-glucanase synthesis by Trichoderma reesei QM 9414 was investigated in conidia, mycelia and protoplasts. Cellulose induced endoglucanase synthesis only in conidia, but not in glucose-grown mycelia or protoplasts. Cellooligosaccharides and sophorose induced endoglucanase synthesis in mycelia, conidia and protoplasts. Only conidia exhibited detectable basal endoglucanase levels, whereas β-glucosidase activity was found in conidia, mycelia and protoplasts. The β-glucosidase was inhibited in vitro by nojirimycin and glucono-δ-lactone. Addition of either of these inhibitors to the induction medium blocked de novo synthesis of endo-1,4 β-glucanase with cellulose (conidia) or cellooligosaccharides (protoplasts and mycelia) as inducer, whereas induction by sophorose remained unaffected. The results are consistent with the assumption that basal constitutive levels of endoglucanase and β-glucosidase are involved in the induction of cellulase synthesis by cellulose in T. reesei.
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Selective Inactivation of an Extra-cytoplasmic Acid Phosphatase of Yeast-like Cells of Sporothrix schenckii by Sodium Fluoride
More LessSummary: Suspensions of intact, yeast-like cells of Sporothrix schenckii exhibited an acid phosphatase (EC 3.1.3.2) activity against p-nitrophenyl phosphate of about 5 IU (g dry wt)−1, without recourse to membrane perturbation. This extra-cytoplasmic acid phosphatase was reversibly and competitively inhibited by orthophosphate (K i=2 mm at pH 5) but unaffected by l(+)-tartrate (in contradistinction to some of the cytoplasmic acid phosphatases of the same organism). Inactivation by NaF of the extra-cytoplasmic isoenzyme was irreversible and followed first order kinetics; sensitivity to NaF was decreased by the presence of citrate, phosphate or substrate. Neither Km (0·3 mm at pH 5) nor V max for this enzyme in acetate buffer was greatly affected by pH in the range 3-5 but the first order rate constant for inactivation by NaF was strongly dependent on pH (maximum at pH 3·5). Crude cell-free extracts of yeast cells had nine electrophoretically distinct acid phosphatase activity bands and, on the basis of the pattern of inhibitors, the extra-cytoplasmic activity was identified as Y-I, an isoenzyme that barely penetrates standard polyacrylamide gel electropherograms. Additional evidence for the assignment came from selective inactivation of this isoenzyme by short treatments of intact cells with NaF under conditions that did not allow penetration of the plasma membrane by the inhibitor and did not kill the cells.
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Glycollate Inhibition of Growth of Pseudomonas aeruginosa on Lactate Medium
More LessSummary: Glycollate inhibited growth of Pseudomonas aeruginosa in media containing either pyruvate or lactate as carbon sources. Glycollamide, but not glyoxylate, showed similar effects. Spontaneous mutants (L/G strains) were isolated that were able to grow on lactate medium in the presence of glycollate: their growth in pyruvate medium was still inhibited by glycollate. Synthesis of membrane-bound NAD+-independent D(−)- and L(+)-lactate dehydrogenases (iLDHs) was inducible by D- or L-lactate in the parent strain but was constitutive in the L/G strains. Glycollate inhibited induction of the synthesis of iLDHs in the parent strain growing in succinate medium but had no effect under the same conditions on strain L/G1. Glycollate was a competitive inhibitor of L(+)-iLDH (K i = 11 mM). No differences were found in the kinetic properties of L(+)-iLDH in cell-free extracts from strain L/G1 and the parent organism. Glycollate appears to inhibit growth on lactate medium predominantly through prevention of lactate induction of iLDH synthesis.
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13C Nuclear Magnetic Resonance Study of Biosynthesis of Glucosylglycerol by a Cyanobacterium under Osmotic Stress
More LessSummary: 13C nuclear magnetic resonance spectroscopy was used to study the biosynthesis and turnover of O-α-Dglucopyranosyl-(1→2)-glycerol (glucosylglycerol) in the marine cyanobacterium Synechococcus N100 during osmotic shock. There was a rapid increase in the level of this heteroside following hyperosmotic shock, with most of the solute being synthesized from extracellular carbon via photosynthetic CO2 fixation. However, changes in the 13C labelling patterns during the time course of the response suggested that up to 10% of the newly synthesized material may be derived from intracellular carbon. No increase in glucosylglycerol was observed when cells were subjected to hyperosmotic shock in the dark. These experiments indicated that a good yield of highly 13C-enriched glucosylglycerol, which could serve as a source of labelled glucose and glycerol, could be obtained simply and quickly by subjecting this cyanobacterium to hyperosmotic stress in the presence of 90% 13C-enriched bicarbonate.
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Adaptation of the Membrane Fatty Acid Composition by Growth in the Presence of n-Alkanols Influences Glycosyltransferase Expression in Streptococcus salivarius
More LessSummary: Growth of Streptococcus salivarius ATCC 25975 in the presence of n-alkanols in the series methanol to decan-1-ol led to a decrease in the unsaturated to saturated fatty acid ratio. Each member of the set of n-alkanols which was examined over a range of concentrations possessed a point at which extracellular glucosyltransferase (GTF) production was minimal; increasing the concentration of the n-alkanol past this point stimulated GTF production. This effect was greatest with hexan-1 -ol although it was observed to a lesser extent with pentan-1 -ol and heptan-1-ol. Reduced cell-associated fructosyltransferase activity was observed with increasing concentrations of each n-alkanol. Growth in the presence of 25 mM-propan-1-ol gave rise to a fatty acid profile in which 55% of the fatty acids were of an odd chain length. S. salivarius ATCC 25975 was shown to be able to utilize ethanol in a similar manner to propan-1-ol by growing it in the presence of 400 mM-[14C]ethanol. Analysis of the membrane lipids at the stationary phase of growth indicated that 17·6 % of the carbon of the fatty acids was derived from ethanol. A leaky adh mutant, S. salivarius MJ 37501, was isolated. The leaky nature of the mutant enabled it to incorporate reduced levels of odd-chain-length fatty acids into its membrane lipids when grown in the presence of 100 mM-propan-1-ol, but not when grown in the presence of 25 mM-propan-1-ol. S. salivarius ATCC 25975 therefore metabolized propan-1-ol (and ethanol) via a constitutive alcohol dehydrogenase.
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Uptake of Ca2+ Driven by the Membrane Potential in Energy-depleted Yeast Cells
More LessSummary: The time-course of 45Ca2+ influx into yeast cells was measured under non-steady-state conditions obtained by preincubating the cells in a Ca2+-free medium containing glucose and buffer. Two components were distinguished: a saturable component which reached a steady-state after about 40 s of 45Ca2+ uptake and a linear increase in cellular 45Ca2+ starting after 60-90s. Using differential extraction methods it was determined that after 20s of uptake, 45Ca2+ was localized in the cytoplasmic pool and in bound form with no 45Ca2+ in the vacuole. After 3 min most of the cellular 45Ca2+ was concentrated in the vacuole and in bound form. The initial rate of 45Ca2+ uptake under non-steady-state conditions thus measured 45Ca2+ transport across the plasma membrane without interference by vacuolar uptake. The effect of membrane potential (δψ) on this transport was investigated in cells depleted of ATP. A high δψ was produced by preincubating the cells with trifluoperazine (TFP) and subsequently washing the cells free from TFP. Substantial 45Ca2+ influx was measured in the absence of metabolic energy in cells with a high δψ. Below a threshold value of −69·5 mV the logarithms of the initial rate of 45Ca2+ influx and of the steady-state level of the first component were linear with respect to δψ. It is suggested that 45Ca2+ influx across the plasma membrane is mediated by channels which open when δψ is below a threshold value. The results indicated that Ca2+ influx across the plasma membrane was driven electrophoretically by δψ.
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- Development And Structure
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Isolation of Motile Variants from Gas-vacuolate Strains of Ancylobacter aquaticus
More LessSummary: Flagellate variants were selected from most of the nonmotile, gas-vacuolate strains of Ancylobacter aquaticus under study. The number and location of flagella on the cells were variable. Flagellins produced by five independently isolated strains of A. aquaticus were serologically related. Variants of strain M1 selected for their motility did not produce gas vesicles; however, gas-vacuolate, nonmotile clones arose in these motile variants at a frequency of about 10−2. Formation of flagella has also been found in ‘Renobacter vacuolatum’ and another heterotrophic gas-vacuolate bacterium that has not yet been identified.
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- Ecology
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Behaviour of Fungi Antagonistic to Sclerotinia sclerotiorum on Plant Tissue Segments
More LessSummary: To assess the ability of fungi antagonistic to Sclerotinia sclerotiorum to inhibit the formation of sclerotia and to grow through plant tissue from cut surfaces, a plant-tissue-based system has been developed using celery, lettuce and tomato segments. Pythium oligandrum consistently showed no ability to grow through plant tissue or prevent sclerotium formation whereas Gliocladium roseum and three isolates of Trichoderma harzianum showed significant ability to grow through plant tissue and significantly decreased the production of sclerotia. Treatment of the plant tissue with G. roseum or T. harzianum 24 h before, or at the same time as, application of S. sclerotiorum gave significantly greater inhibition of sclerotium formation than did treatment 24 h after application of S. sclerotiorum. Of the fungi tested, G. roseum had the greatest ability to grow through the tissue and T. harzianum WT6 the greatest ability to inhibit sclerotium formation.
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- Genetics And Molecular Biology
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Isolation of Amidase-negative Mutants of Pseudomonas aeruginosa Using Glycollamide as a Selective Agent
More LessSummary: A positive selection is described for isolating amidase-negative mutants from Pseudomonas aeruginosa strains. The method is based on the conversion, via amidase activity, of glycollamide to glycollate which is growth inhibitory. Three types of mutant were isolated on lactate medium containing glycollamide: (i) mutants in which amidase activity was reduced or absent; (ii) double mutants that were amidase-negative and resistant to glycollate inhibition of growth; and (iii) glycollate-resistant mutants. By raising glycollamide concentrations in the selection medium, amidase-negative mutants were obtained from strains producing altered amidases with low specific acetamidase and glycollamidase activities. Glycollamide has wider applicability than fluoroacetamide as a selective agent for obtaining amidase-negative mutants.
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Nucleotide Sequence of the Immunity and Lysis Region of the ColE9-J Plasmid
More LessSummary: We have determined the nucleotide sequence of a 1500 bp fragment of the ColE9-J plasmid which encodes colicin E9 immunity and colicin E5 immunity and contains two lys genes. Open reading frames corresponding to the four genes have been located and their position confirmed by transposon mutagenesis of sub-clones of the ColE9-J plasmid. The E9imm gene shows 69% homology at both the nucleotide and the amino acid level to the previously sequenced E2 imm gene. The E5imm gene shows little homology to any other E colicin immunity gene which has been sequenced. The lys gene distal to the 3′ end of the E5imm gene shows considerable sequence homology to all other previously sequenced E colicin lys genes. The lys gene distal to the 3′ end of the E9imm gene is identical to the pColE2 and pColE3 lys genes for the first 59 nucleotides but encodes a much smaller gene product than any other lys gene which has been sequenced. The two lys genes sequenced here are exceptions to Shepherd's rule concerning the number of RNY codons in the three possible reading frames.
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Nucleotide Sequence and Functional Analysis of the Two nifH Copies of Rhizobium ORS571
More LessSummary: In Rhizobium ORS571, which is able to form both root and stem nodules on the tropical plant Sesbania rostrata and to grow in the free-living state at the expense of N2, two copies of the nifH gene, which codes for the nitrogenase Fe-protein, were characterized. One copy, nifH1, was localized in the nifHDK operon; the other, nifH2, was localized elsewhere. nifH1 and nifH2 differed in only six nucleotides and both encoded a polypeptide of 296 amino acids with a single change at position 282, a serine in nifH1 and a threonine in nifH2 At position 102, arginine in the sequence Gly-Arg-Gly-Val-Ile-Thr might, as in Rhodospirillum rubrum, be the site of ‘switch-off’ inactivation. Compared with other nifH genes, the highest SAB was found with Bradyrhizobium japonicum and Rhizobium sp. (Parasponia). A sequence identical (nifH1) or very similar (nifH2) to the nif consensus sequence was found upstream from the initiation codon. Homology with sequences upstream from Klebsiella pneumoniae nif promoters, which affect nifA-mediated activation, was also found in both cases. From mutants carrying either a single nifH1 or nifH2 deletion, or a double nifH1-nifH2 deletion, it appeared that both genes were functional ex planta and in Planta and that no other nifH copy seemed to be present in ORS571. The optimal expression of nifH1 and of nifH2 might depend on different physiological conditions.
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Isolation and Characterization of a Generalized Transducing Phage for the Marine Luminous Bacterium Vibrio fischeri MJ-1
More LessSummary: A marine bacteriophage active against the marine luminous bacterium Vibrio fischeri MJ-1 was isolated from offshore waters in Ensenada, Baja California, Mexico, and was shown to be active in generalized transduction, transducing 14 of 17 different amino acid auxotrophs to prototrophy. For some of the amino acid auxotrophic markers, such as arginine and methionine, several different mutants could be transduced. The phage grew well at temperatures up to 27 °C, and produced high-titre lysates (1010 p.f.u. ml-1 or higher). Single-step growth analysis showed a latent period of 23 min at 25 °C with a burst size of 100. Phage adsorption was maximum at NaCl concentrations characteristic of the marine environment. No evidence for lysogeny was found.
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Novel Genetic Components Controlling Invertase Production in Saccharomyces cerevisiae
More LessSummary: Low levels of invertase (EC 3.2.1.26) activity were observed in most diploid strains of S. cerevisiae used in this work. There was no effect of mating type on invertase levels, and cell surface was not a limiting factor, because an increase in ploidy did not cause further decrease in specific invertase activity. Finally, some diploids showed the activity expected from the additive effects of different SUC genes, and haploid strains possessing two SUC genes expressed very variable invertase activities depending on the strain. This suggested the existence of one or more additional genes which control the levels of invertase. Genetic analysis of SUC5 strains provided evidence of the existence of a new gene, RPS5 which drastically reduced the specific invertase activity in strains possessing active SUC alleles. The recessive allele of this gene (rps5) allows expression of higher levels of invertase. We suggest that genes similar to RPS5 are responsible for the low levels of invertase activity observed in diploid strains of S. cerevisiae.
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glnA Mutations Conferring Resistance to Methylammonium in Escherichia coli K12
More LessSummary: Cells of Escherichia coli K12 were sensitive to 100 mm-methylammonium when cultured under nitrogen limitation, and resistant when grown with an excess of either NH4C1 or glutamine. Glutamine synthetase activity was required for expression of the methylammonium-sensitive phenotype. Mutants were isolated which were resistant to 100 mm-methylammonium, even when grown under nitrogen limitation. P1 bacteriophage transduction and F′ complementation analysis revealed that the resistance-conferring mutations mapped either inside the glnA structural gene and/or elsewhere in the E. coli chromosome. Glutamine synthetase was purified from the wild-type and from some of the mutant strains. Strains carrying glnA-linked mutations that were solely responsible for the methylammonium-resistant phenotype yielded an altered enzyme, which was less active biosynthetically with either ammonium or methylammonium as substrate. Sensitivity to methylammonium appeared to be due to synthesis of γ-glutamylmethyl-amide by glutamine synthetase, which was synthesized poorly, if at all, by mutants carrying an altered glutamine synthetase enzyme.
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- Immunology
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Flavonoids Protect Against T-2 Mycotoxins both in vitro and in vivo
More LessSummary: Quercetin was able to reduce the cytotoxic effect of T-2 mycotoxin on cultured murine thymocytes. When given to mice immediately before challenge with T-2 mycotoxins, quercetin significantly reduced mortality.
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- Pathogenicity And Medical Microbiology
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Analysis of Sheath and Core Structures of the Axial Filament of Treponema pallidum
More LessSummary: Electron microscopy and SDS-PAGE have been used to analyse the polypeptide and antigenic composition of the sheath and core components of the axial filament of Treponema pallidum. The sheath contains a major 37 kDa polypeptide which was solubilized by a combination of trypsin and urea treatments with concurrent loss of binding of anti-37 kDa monoclonal antibody. These studies also indicated some antigenic heterogeneity within the axial filament population. Trypsin treatment alone removed a number of antigenic determinants from the axial filament but left others intact, suggesting differences in their location within the sheath structure. A second 31·5 kDa polypeptide may also be associated with the sheath. The axial filament core comprises at least two components, an antigenically dominant 33·5 kDa polypeptide and a second of 34 kDa. The structure of the axial filament in T. pallidum and Treponema phagedenis biotype Reiterii was similar, but antigenic cross-reactivity of sheath and core components was incomplete.
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Inter-strain Homology of Pilin Gene Sequences in Neisseria meningitidis Isolates That Express Markedly Different Antigenic Pilus Types
More LessSummary: Neisseria meningitidis isolates examined in this study elaborated one of two pilus types that were antigenically markedly different. Each pilus type reacted either with SM1, a monoclonal antibody that recognizes an epitope common to all gonococcal pili, or with a polyclonal antiserum raised against meningococcal pili that did not react with SM1, but not both. Total genomic DNA from all N. meningitidis isolates analysed, irrespective of pilus type, contained at least one region with extensive homology to a gonococcal pilE probe. Different N. meningitidis strains possessed one of several configurations of genomic pilE-homologous segments. Chromosomal rearrangement of pilE-homologous sequences was associated with P+ to P− pilus phase transition in the strains examined. The arrangement of pilE-homologous segments in total genomic DNA from N. meningitidis isolated from the blood and cerebro-spinal fluid of the same patient was apparently identical.
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Mannose Inhibition as a Significant Marker for Differentiating among Novobiocin-resistant Staphylococci of Relevance in Clinical Microbiology
More LessSummary: A specific method for the identification of Staphylococcus saprophyticus among novobiocin-resistant species isolated from man is described. The test is based on novobiocin resistance, non-fermentation of d-mannose and early inhibition with late secondary growth on glucose/man-nose + novobiocin agar plates. On this medium novobiocin-resistant Staphylococcus cohnii showed a confluent, continuous and homogeneous growth after 24 h which remained unchanged at 48 h whether or not it fermented d-mannose, whereas novobiocin-resistant Staphylococcus xylosus fermented d-mannose. These results are discussed in relation to a possible causal role of PTS enzymes and phosphomannose isomerase deficiency in mannose inhibition.
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Platelet Aggregation by Group B Streptococci
More LessSummary: Forty-six strains of group B streptococci (GBS), including various serotypes and nonserotypable strains, were tested for their ability to induce platelet aggregation in human plateletrich plasma; four strains, all belonging to type III, showed a positive reaction. The characteristics of the reaction were investigated in these four positive strains. Aggregation was dependent on the ratio of bacteria to platelets, being maximal at a ratio of 4·3. Platelet aggregation was inhibited by EDTA (100% inhibition at 3·1 mM), indomethacin (100% inhibition at 10 mM), acetylsalicylic acid (93-100% inhibition at 5·0 mM) and quinacrine (100% inhibition at 0·25 mM). Thus the reaction was cation-dependent and required cyclooxygenase activity. Assays for cytosolic lactate dehydrogenase did not indicate platelet lysis. GBS induced the release of [3H]serotonin, which was maximal (68-78%) at 10 min after the reaction was started. Experiments with gel-filtered platelets suggested that GBS-induced platelet aggregation required both fibrinogen and heat-resistant (56°C, 30 min) serum factors. Type-specific antisera prevented the platelet aggregation activity of heat-killed bacteria, but not of live bacteria. Trypsin digestion of the bacterial cells caused an almost complete loss of the platelet aggregation activity.
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- Physiology And Growth
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Environmental Regulation of Methanol and Formaldehyde Metabolism by Methylophilus methylotrophus
More LessSummary: Methylophilus methylotrophus was grown in continuous culture at different dilution rates under either methanol or oxygen limitation. Methanol dehydrogenase and formate oxidation were repressed by the presence of high concentrations of methanol in the growth medium, whereas hexulose phosphate synthase was constitutive and the glucose-6-phosphate and 6-phospho-gluconate dehydrogenases were regulated only by the growth rate. Chemical analysis and 13C NMR spectroscopy showed that the oxidation of methanol was accompanied by the spillage of 0 to 50% of the input carbon as formaldehyde and dihydroxyacetone, the extent of which reflected the methanol dehydrogenase: hexulose phosphate synthase activity ratio and/or the energy status of the cells. It is concluded that the observed regulation of key enzymes of methanol and formaldehyde metabolism by the growth environment occurs in order to achieve the required in situ rates of energy conservation and carbon flux demanded by the imposed growth rate, and that the spillage of formaldehyde and dihydroxyacetone reflects limitations on metabolism imposed by kinetic and/or metabolite pool effects.
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The Effect of Catalase on Recovery of Heat-injured DNA-repair Mutants of Escherichia coli
More LessSummary: The apparent sensitivity of Escherichia coli K12 to mild heat was increased by recA (def), recB and polA, but not by uvrA, uvrB or recF mutations. However, addition of catalase to the rich plating medium used to assess viability restored counts of heat-injured recA, recB and polA strains to wild-type levels. E. coli p3478 polA was sensitized by heat to a concentration of hydrogen peroxide similar to that measured in autoclaved recovery medium. The apparent heat sensitivity of DNA-repair mutants is thus due to heat-induced sensitivity to the low levels of peroxide present in rich recovery media. It is proposed that DNA damage in heated cells could occur indirectly by an oxidative mechanism. The increased peroxide sensitivity of heat-injured cells was not due to a decrease in total catalase activity but may be related specifically to inactivation of the inducible catalase/peroxidase (HPI).
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A Mutant of Streptococcus pneumoniae That Exhibits Thermosensitive Penicillin Tolerance and the Paradoxical Effect
More LessSummary: Mutants of Streptococcus pneumoniae that contain active autolysin and yet cannot be induced to lyse during treatment with penicillin (Lyt+Tol+ mutants) have been described. We have now shown that these mutants are temperature dependent (32 °C); at 37 °C these bacteria underwent penicillin-induced lysis. In addition, mutants at the lysis-permissive temperature showed the so-called ‘paradoxical response’ to penicillin. Temperature shift experiments indicated that the change from tolerant to lytic response or vice versa is a fast process. No differences were detected in autolysin specific activity or in the kinetics of inhibition of protein, peptidoglycan and teichoic acid syntheses in cells treated with penicillin at 32 and 37 °C. The results of genetic crosses indicated that the thermosensitivity of penicillin-induced autolysis in the Lyt+Tol+ mutants is not a property of the autolytic enzyme itself. The observations suggest that the thermosensitive process in the mutants represents either a step(s) in autolysin regulation or involves some difference in the structure of the cell walls produced at 32 °C versus 37 °C.
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Long-term Studies of Ciliate-Bacterial Interactions: Use of a Chemostat Fed with Bacteria Grown in a Separate Chemostat
More LessSummary: Two-stage chemostat cascades have been used to study growth of the ciliate Tetrahymena pyriformis on Escherichia coli over extended periods of time. Upward drifts (continuous, slow, uni-directional changes) of ciliate number density and downward drifts of ciliate mean cell size and density of residual bacteria occurred for many generations of ciliates before steady states were obtained. Ciliate chemostats were operated at two different dilution rates. Rates of drift were slower, and drifts persisted longer, both in terms of time and in terms of numbers of generations, in the chemostats operated at the higher dilution rate. Some speculations on the origins of the drifts are presented.
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- Systematics
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Chromosomal DNA Probes for the Identification of Bacteroides Species
More LessSummary: We compared 22 Bacteroides species by DNA-DNA homology studies using the S1 endonuclease method. None of the currently defined species shared more than 30% DNA homology with any other species examined with the exception of B. buccae and B. capillus (which along with B. pentosaceus are now considered a single species), which shared 86% of their DNA sequences. Two clusters showed weak genetic relationships, with DNA homology > 10%. The first cluster included B. corporis, B. disiens, B. bivius, B. intermedius and B. melaninogenicus. The second cluster included B. fragilis, B. eggerthii, B. ovatus, B. thetaiotaomicron and B. uniformis. Five of the oral species, B. asaccharolyticus, B. gingivalis, B. loescheii, B. intermedius and B. melanogenicus, were chosen for study as whole chromosomal probes in dot blot assays. These were tested against 243 clinical strains biochemically identified as Bacteroides species. The DNA probes correctly identified 94% of the clinical strains. DNA probe and biochemical identification was 100% for two of the five species. In contrast, only 86% of the strains biochemically identified as B. intermedius were identified by the DNA probe. The DNA probes gave a species identification to seven strains which could not be biochemically identified.
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BCG Identification by DNA Restriction Fragment Patterns
More LessSummary: Seven daughter strains of BCG were characterized by restriction fragment analysis with the enzymes BstEII, PvuII and BclI. Comparisons of fragment patterns confirmed that BCG is correctly classified as a Mycobacterium bovis variant and suggested that the Swedish strain is most closely related to the original BCG strain.
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Volumes and issues
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Volume 170 (2024)
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Volume 152 (2006)
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Volume 151 (2005)
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Volume 150 (2004)
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Volume 149 (2003)
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Volume 148 (2002)
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Volume 147 (2001)
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Volume 146 (2000)
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Volume 145 (1999)
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Volume 144 (1998)
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Volume 143 (1997)
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Volume 142 (1996)
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Volume 141 (1995)
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Volume 140 (1994)
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Volume 139 (1993)
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Volume 138 (1992)
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Volume 137 (1991)
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Volume 136 (1990)
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Volume 135 (1989)
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Volume 134 (1988)
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Volume 133 (1987)
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Volume 132 (1986)
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Volume 131 (1985)
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Volume 130 (1984)
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Volume 129 (1983)
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Volume 128 (1982)
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Volume 127 (1981)
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Volume 126 (1981)
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Volume 125 (1981)
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Volume 124 (1981)
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Volume 123 (1981)
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Volume 122 (1981)
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Volume 121 (1980)
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Volume 120 (1980)
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Volume 119 (1980)
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Volume 118 (1980)
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Volume 117 (1980)
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Volume 116 (1980)
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Volume 115 (1979)
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Volume 114 (1979)
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Volume 113 (1979)
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Volume 112 (1979)
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Volume 111 (1979)
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Volume 110 (1979)
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Volume 109 (1978)
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Volume 108 (1978)
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Volume 107 (1978)
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Volume 106 (1978)
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Volume 105 (1978)
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Volume 104 (1978)
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Volume 103 (1977)
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Volume 102 (1977)
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Volume 101 (1977)
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Volume 100 (1977)
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Volume 99 (1977)
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Volume 98 (1977)
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Volume 97 (1976)
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Volume 96 (1976)
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Volume 95 (1976)
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Volume 94 (1976)
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Volume 93 (1976)
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Volume 92 (1976)
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Volume 91 (1975)
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Volume 90 (1975)
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Volume 89 (1975)
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Volume 88 (1975)
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Volume 87 (1975)
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Volume 86 (1975)
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Volume 85 (1974)
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Volume 84 (1974)
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Volume 83 (1974)
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Volume 82 (1974)
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Volume 81 (1974)
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Volume 80 (1974)
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Volume 79 (1973)
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Volume 78 (1973)
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Volume 77 (1973)
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Volume 76 (1973)
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Volume 75 (1973)
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Volume 74 (1973)
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Volume 73 (1972)
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Volume 72 (1972)
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Volume 71 (1972)
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Volume 70 (1972)
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Volume 69 (1971)
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Volume 68 (1971)
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Volume 67 (1971)
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Volume 66 (1971)
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Volume 65 (1971)
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Volume 64 (1970)
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Volume 63 (1970)
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Volume 62 (1970)
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Volume 61 (1970)
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Volume 60 (1970)
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Volume 59 (1969)
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Volume 58 (1969)
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Volume 57 (1969)
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Volume 56 (1969)
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Volume 55 (1969)
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Volume 54 (1968)
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Volume 53 (1968)
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Volume 52 (1968)
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Volume 51 (1968)
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Volume 50 (1968)
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Volume 49 (1967)
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Volume 48 (1967)
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Volume 47 (1967)
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Volume 46 (1967)
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Volume 45 (1966)
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Volume 44 (1966)
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Volume 43 (1966)
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Volume 42 (1966)
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Volume 41 (1965)
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Volume 40 (1965)
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Volume 39 (1965)
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Volume 38 (1965)
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Volume 37 (1964)
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Volume 36 (1964)
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Volume 35 (1964)
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Volume 34 (1964)
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Volume 33 (1963)
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Volume 32 (1963)
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Volume 31 (1963)
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Volume 30 (1963)
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Volume 29 (1962)
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Volume 28 (1962)
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Volume 27 (1962)
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Volume 26 (1961)
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Volume 25 (1961)
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Volume 24 (1961)
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Volume 23 (1960)
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Volume 22 (1960)
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Volume 21 (1959)
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Volume 20 (1959)
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Volume 19 (1958)
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Volume 18 (1958)
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Volume 17 (1957)
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Volume 16 (1957)
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Volume 15 (1956)
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Volume 14 (1956)
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Volume 13 (1955)
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Volume 12 (1955)
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Volume 11 (1954)
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Volume 10 (1954)
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Volume 9 (1953)
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Volume 8 (1953)
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Volume 7 (1952)
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Volume 6 (1952)
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Volume 5 (1951)
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Volume 4 (1950)
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Volume 3 (1949)
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Volume 2 (1948)
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Volume 1 (1947)