-
Volume 133,
Issue 11,
1987
Volume 133, Issue 11, 1987
- Biochemistry
-
-
-
Methyl Mercaptan Oxidase, a Key Enzyme in the Metabolism of Methylated Sulphur Compounds by Hyphomicrobium EG
More LessSUMMARY: Methyl mercaptan (MM)-oxidase was purified tenfold to near homogeneity from Hyphomicrobium EG grown on dimethyl sulphoxide. The enzyme was a monomer with an Mr value of about 40000-50000. It catalysed the formation of stoicheiometric amounts of formaldehyde, sulphide and H2O2 from MM and O2. It had a K m of 5-10 μm for MM and was strongly inhibited by substrate concentrations above 14 μm, the K i for this inhibition being 42 μm. Ethyl mercaptan and sulphide also served as substrates for the enzyme (K m 18 and 60 μm respectively), whereas methanol was not oxidized. Upon oxidation of these compounds H2O2 was formed. Although sulphide was a substrate for the enzyme, it also acted as a non-competitive inhibitor of MM oxidation (K i 90 μm). Alcohol oxidase (EC 1.1.3.13) purified from Hansenula polymorpha was also found to oxidize MM (K m 110 μm) although at a low rate. The products formed were the same as for MM oxidation by the bacterial enzyme. In contrast to MM-oxidase however, alcohol oxidase was inactive with sulphide and was not inhibited by methyl mercaptan concentrations up to 500 μm.
-
-
-
-
Biosynthesis and Scavenging of Purines by Pathogenic Mycobacteria Including Mycobacterium leprae
More LessSUMMARY: Purine biosynthesis de novo could not be detected in suspensions of Mycobacterium leprae isolated from armadillo tissue. In contrast, non-growing suspensions of other pathogenic mycobacteria, also isolated from infected host tissue did synthesize purines. Rates of synthesis, judged by incorporation of [2-14C]glycine or [3-14C]serine into nucleic acid purines were 600 times higher in M. microli and 110 times higher in M. avium - both isolated from infected mouse tissue - than the lowest possible rate detectable and therefore the highest possible rate in M. leprae. The rate of purine synthesis relative to purine scavenging (judged by comparing incorporation of [3-14C]serine and [8-14C]hypoxanthine into nucleic acid purines in suspensions of mycobacteria) varied only slightly – 4-fold in M. microti and 6-fold in M. avium- whether organisms were harvested from media with or without purines, from media with a low nitrogen content but containing a purine, from mice or even with starved organisms. Thus, the failure of M. leprae to synthesize purines could not be explained as either a result of using non-growing mycobacteria in the incubations with 14C-labelled precursors or as repression or inhibition of synthesis de novo. It appears that M, leprae requires a supply of the purine ring from its environment. Nucleotides, which may be the major source of the purine ring in the intracellular environment, were not taken up directly by M. leprae but could be hydrolysed first to nucleosides and then taken up.
-
-
-
Enzymes for Purine Synthesis and Scavenging in Pathogenic Mycobacteria and Their Distribution in Mycobacterium leprae
More LessSUMMARY: Three enzymes catalysing the synthesis of four intermediates (phosphoribosylglycinamide, phosphoribosylaminoimidazole-succinocarboxamide, phosphoribosylaminoimidazole-carbox-amide and AMP) in the purine biosynthetic pathway were detected in extracts of Mycobacterium microti and M. avium, even when the organisms had been grown in mice. However only one of the three enzymes, adenylosuccinate AMP-lyase (catalysing the synthesis of the last two of the four intermediates listed above) was detected in M. leprae. Phosphoribosyltransferases, which convert adenine, guanine and hypoxanthine to the corresponding nucleoside monophosphates, and adenosine kinase were the major enzymes for purine scavenging in all mycobacteria studied. In contrast to enzymes in the synthetic pathway, evidence for metabolic regulation of the purine-scavenging enzymes was obtained. In particular, 20-80-fold differences in the activities of guanine phosphoribosyltransferase and adenosine kinase were observed when M. microti was grown in media with or without purines, or in mice. In M. leprae, activities of all phosphoribosyltransferases were low in comparison with activities in M. microti and M. avium (specific acitivity <2% when comparisons were made between extracts of host-grown mycobacteria). However, activity of adenosine kinase was higher in host-grown M. leprae than in host-grown M. microti or M. avium.
-
-
-
Comparison of the Phosphatases of Lysobacter enzymogenes with Those of Related Bacteria
More LessSUMMARY: Lysobacter enzymogenes ATCC 29487 (UASM 495) produces an outer-membrane-associated phosphatase and an excreted phosphatase. The cell-associated enzyme was compared to phosphatases of nine other Gram-negative gliding bacteria and to that of Escherichia coli. The other three species of the genus Lysobacter also produce a particulate, cell-associated phosphatase. Antiserum prepared against the phosphatase from the outer membrane of L. enzymogenes effectively precipitated the phosphatases of two other L. enzymogenes strains and the enzymes of L. antibioticus, L. brunescens and L. gummosus. Some inhibition of the enzyme by the antiserum also was observed. No significant reaction could be detected beween the antiserum and the cell-associated phosphatases of species of Cytophaga johnsonae, ‘C. compacta’, Myxococcus xanthus, E. coli and the excreted phosphatase of L. enzymogenes. The results indicate that the four species of the genus Lysobacter are closely related despite their physiological differences and that the outer-membrane-associated phosphatases of these organisms have different structural characteristics than the phosphatases of the other Gramnegative bacteria that were used. Furthermore, differences in the amino acid compositions of the cell-associated and the excreted phosphatase of L. enzymogenes confirm the immunological results and are in agreement with the physical and chemical differences noted between the two enzymes.
-
-
-
Xanthan Lyases - Novel Enzymes Found in Various Bacterial Species
More LessSUMMARY: Xanthan lyases, cleaving the terminal β-mannosidic linkage of the side-chain of the exopolysaccharide xanthan from Xanthomonas campestris, have been obtained from several sources. These include a Bacillus species, a Corynebacterium species and a mixed culture. The lyases were initially associated with endo-β-glucanases cleaving the main chain of xanthan. Partial purification of the enzymes was achieved and the Bacillus preparation was separated by FPLC into material free of endoglucanase and glycosidase activities. The lyase was active on polysaccharides with and without acetate and pyruvate. The optimal size of the substrate appeared to be in the range of degree of polymerization (DP) 25–35, i.e. 5–7 repeat units of the polysaccharide. No activity was found against xanthan modified by reduction of the carboxyl groups or by the addition of amine or hydroxyethyl groups. The combined action of the lyase and the endoglucanase yielded a series of oligosaccharides, each with a side-chain terminating in an unsaturated uronic acid and containing the molar ratio of d-glucose to d-mannose, 2:1.
-
-
-
Purification and Characterization of a 2-Oxoglutarate-linked ATP-independent Deacetoxycephalosporin C Synthase of Streptomyces lactamdurans
More LessSUMMARY: The deacetoxycephalosporin C (DAOC) synthase (expandase) of Streptomyces lactamduranswas highly purified, as shown by SDS-PAGE and isoelectric focusing. The enzyme catalysed the oxidative ring expansion that converts penicillin N into DAOC. The enzyme was very unstable but could be partially stabilized in 25 mm-Tris/HCl, pH 9·0, in the presence of DTT (0·1 mm). The enzyme required 2-oxoglutarate, oxygen and Fe2 +, but did not need ATP, ascorbic acid, Mg2 + or K+. The optimum temperature was between 25 and 30 °C. The DAOC synthase showed a high specificity for the penicillin substrate. Only penicillin N but not isopenicillin N, penicillin G or 6-aminopenicillanic acid served as substrates. 2-Oxoglutarate analogues were not used as substrates although 2-oxobutyrate and 3-oxoadipate inhibited the enzyme by 100% and 56% respectively. The enzyme was strongly inhibited by Cu2 +, Co2 +and Zn2 +. The apparent K m values for penicillin N, 2-oxoglutarate and Fe2 +were 52 μm, 3 μmand 71 μmrespectively. The enzyme was a monomer with a molecular mass of 27000 Da ± 1000.
-
-
-
Adhesion of Oral Streptococci from a Flowing Suspension to Uncoated and Albumin-coated Surfaces
More LessSUMMARY: A flow cell system was developed which allowed the study of bacterial adhesion to solid substrata at well-defined shear rates. In addition, the system enabled the solid surfaces to be coated with a proteinaceous film under exactly the same shear conditions. In this flow cell system, adhesion of three strains of oral streptococci from a phosphate-buffered solution onto three different substrata was studied as a function of time in the absence and presence of a bovine serum albumin (BSA) coating at a shear rate of 21 s-1. To obtain a wide range in surface free energies (γ) representative strains (γb 38-117 mJ m-2) and solid substrata (γs 20-109 mJ m-2) were selected. The number of bacteria adhering was counted microscopically. In the absence of a BSA coating a linear relation was found between the number of bacteria adhering at saturation (n b, s) and the calculated interfacial free energy of adhesion (ΔF adh) for each of the three strains. In the presence of a BSA coating the number of bacteria adhering was greatly decreased in all cases. However, despite the presence of the BSA coating there was still a linear relation between the number of bacteria adhering at saturation and the interfacial free energy of adhesion, calculated on the basis of the surface free energy of the uncoated substrata. It can be concluded that the bare, uncoated substratum still influenced bacterial adhesion in spite of the marked influence of a BSA coating.
-
-
-
The Respiratory Chain of Anaerobically Grown Escherichia coli: Reactions with Nitrite and Oxygen
More LessSUMMARY: The reactions of nitrite and oxygen with the cytochrome d oxidase of Escherichia coli were studied, following growth of cells on glycerol with fumarate as respiratory oxidant. Optical difference spectroscopy was used to investigate the kinetics of product formation during the reaction of the respiratory chain with nitrite. Two kinetically distinct species were formed in the reaction with nitrite; these had spectral features at 438 nm and 630 nm. These observations indicate that the cytochrome d does not contribute significantly to absorbance in the Soret region, and that changes elicited by ligand binding in the Soret region are largely attributable to haemoprotein b-590. Inhibition of respiratory oxidase activity by nitrite was also investigated. The inhibition was competitive with oxygen (K i 0·83 mm, pH 7), which allowed analysis of the reaction of the oxidase with oxygen itself. The reaction with oxygen was cooperative with an apparent number of oxygen-binding sites, n, of 1·26 at pH 7, increasing to 1·72 at pH 6. We propose a model for the oxidase in which there are two ligand-binding sites.
-
-
-
Enzymic Basis for Leakiness of Auxotrophs for Phenylalanine in Pseudomonas aeruginosa
More LessSUMMARY: The dual enzymic routes for phenylalanine biosynthesis that exist in Pseudomonas aeruginosa complicate the isolation of phenylalanine auxotrophs. Mutants blocked in each of the various phenylalanine-pathway steps are essential for full appreciation of the physiological nature and gene-enzyme relationships of this biochemical system. A leaky phenylalanine-requiring mutant of P. aeruginosa (PAT1051) was found to lack the bifunctional P-protein (chorismate mutase-prephenate dehydratase), but retained the monofunctional isozyme species of chorismate mutase (chorismate mutase-F) as well as cyclohexadienyl dehydratase (components of the arogenate ‘overflow’ route to phenylalanine). This is the first mutant of P. aeruginosa shown to be deficient in any enzyme specific for phenylalanine synthesis. It is concluded that although the arogenate pathway has the demonstrated potential to overproduce phenylalanine, the substrate levels normally available to the arogenate pathway in the wild-type are inadequate to satisfy the full metabolic demand for phenylalanine.
-
- Biotechnology
-
-
-
Submerged Fermentation of Penicillium paxilli Biosynthesizing Paxilline, a Process Inhibited by Calcium-induced Sporulation
More LessSUMMARY: A submerged fermentation process for the production of the tremorgenic mycotoxin paxilline by Penicillium paxilli has been developed. The fungus did not sporulate and accumulated paxilline to 1·5% (w/w) in freeze-dried cells within 6 d in a 60 1 stirred fermenter. Induction of extensive differentiation of conidiophores and profuse sporulation by adding 2% (w/v) CaCl2. 2H2O to the medium at batching reduced paxilline yield by 97%. Paxilline biosynthesis occurred when the glucose in the medium had been exhausted, implying that carbon catabolite repression may be involved in the biosynthesis of this alkaloid, even when calcium-induced sporulation inhibits or delays the onset of paxilline biosynthesis. Sporulation-induced inhibition of indole-terpenoid alkaloid biosynthesis in P. paxilli contrasts with the situation in some other penicillia elaborating indole alkaloids and allows disassociation of aspects of secondary metabolite biosynthesis from growth-associated differentiation, which formerly seemed to be linked.
-
-
- Development And Structure
-
-
-
A Comparison of the Adhesion, Coaggregation and Cell-surface Hydrophobicity Properties of Fibrillar and Fimbriate Strains of Streptococcus salivarius
SUMMARY: Fibrillar and fimbriate strains of Streptococcus salivarius were compared for their ability to adhere to buccal epithelial cells and saliva-coated hydroxyapatite beads, and for their ability to coaggregate with Veillonella strains. The fibrillar Lancefield group K strains adhered statistically significantly better to both buccal epithelial cells and saliva-coated hydroxyapatite beads than the fimbriate strains, which lacked the Lancefield group K antigen. After 1 h the fibrillar strains coaggregated statistically significantly better than the fimbriate strains with V. parvula strain VI, but after 24 h, coaggregation both of fibrillar and of fimbriate strains reached approximately 90%. Freshly isolated Veillonella strains all coaggregated with the S. salivarius strains, but the percentage coaggregation varied considerably after 1 h depending on the Veillonella strain. Coaggregation was independent of the presence of Ca2 +. S. salivarius strain HB-V5, a mutant of strain HB that had lost the Veillonella-binding protein, coaggregated weakly with V. parvula strain V1, but coaggregated very well with other wild-type veillonellae, suggesting the presence of an alternative mechanism for Veillonella-binding for strain HB. Fibrillar strains were, therefore, more adhesive to oral surfaces and coaggregated with veillonellae after 1 h better than the fimbriate S. salivarius strains. Both fibrillar and fimbriate strains were highly hydrophobic in the hexadecane-buffer partition assay.
-
-
- Genetics And Molecular Biology
-
-
-
Biochemical and Genetical Analysis of Rhizobium meliloti Mutants Defective in C4-dicarboxylate Transport
More LessSUMMARY: Inhibition studies with free-living cells of Rhizobium meliloti2011 showed that succinate, fumarate and malate are transported via a common transport system. It is an active process that is inducible by succinate. The apparent K m for succinate uptake in free-living cells is 5·3 μm. Seven Tn5-induced mutants that did not grow on succinate, fumarate or malate lacked the C4-dicarboxylate transport system in the free-living state (Detfl-). Five of these mutants (RMS11, RMS16, RMS17, RMS24, RMS118) induced nodules on alfalfa with about half the nitrogen-fixation activity of the wild-type (Fixred). The remaining two mutants (RMS420 and RMS938) gave rise to small, white and ineffective nodules on alfalfa (Fix-). These results correlated with the dicarboxylate transport rates of bacteroids isolated from appropriate nodules: bacteroids isolated from nodules induced by the Fixred mutants transported succinate or malate at about 30-50% of the wild-type rate (Dctsred), whereas bacteroids isolated from nodules induced by Fix-mutants showed no uptake activity (Dcts-). From an R. meliloti 2011 bank three cosmids were identified which complemented different Dctfl- mutants. Complemented Dctfl- mutants could grow again on agar containing succinate or malate. In the case of Fix- mutants complementation resulted in effective nodules. The cosmids pRmSC101 and pRmSC102 complemented the Fix- mutant RMS420. A third cosmid, pRmSC121, complemented the second Fix- mutant RMS938 and nearly all of the Fixred mutants. For the Fix- mutant RMS420 the Tn5 insertion site was found to be located on a 15·3 EcoRI fragment which is also part of the complementing cosmid pRmSC102.
-
-
-
-
Detection and Characterization of IS256, an Insertion Sequence in Staphylococcus aureus
More LessSUMMARY: Resistance to the aminoglycosides gentamicin (Gmr), tobramycin (Tmr) and kanamycin (Kmr) in strains of Staphylococcus aureusisolated in Australia is mediated by the transposon Tn4001. The 1·35 kb inverted repeat of this transposon exhibits many of the characteristics of an insertion sequence and has consequently been designated IS256. Tandem duplication of IS256 contiguous with Tn4001 results in an increase in the level of GmrTmrKmr, thereby implying that the element possesses strong promoter sequences. Both contiguous and independent insertions of IS256 into the staphylococcal chromosome have been observed, the latter suggesting that the element may play a role in molecular rearrangements of the genome.
-
-
-
The aacA-aphD Gentamicin and Kanamycin Resistance Determinant of Tn4001 from Staphylococcus aureus: Expression and Nucleotide Sequence Analysis
More LessSUMMARY: The aacA-aphD aminoglycoside resistance determinant of the Staphylococcus aureus transposon Tn4001, which specifies resistance to gentamicin, tobramycin and kanamycin, has been cloned and shown to express these resistances in Escherichia coli. The determinant encoded a single protein with an apparent size of 59 kDa which specified both aminoglycoside acetyltransferase [AAC(6′)] and aminoglycoside phosphotransferase [APH(2″)] activities. Nucleotide sequence analysis of the determinant showed it to be capable of encoding a 479-amino-acid protein of 56·9 kDa. Analysis of Tn/725 insertion mutants of the determinant indicated that resistance to tobramycin and kanamycin is due to the AAC activity specified by, approximately, the first 170 amino acids of the predicted protein sequence and is consistent with the gentamicin resistance, specified by the APH activity, being encoded within the C-terminal region of the protein. Comparison of the C-terminal end of the predicted amino acid sequence with the reported sequences of 13 APHs and a viomycin phosphotransferase revealed a region which is highly conserved among these phosphotransferases.
-
-
-
Molecular Characterization and Comparison of 38 Virulent and Temperate Bacteriophages of Streptococcus lactis
More LessSUMMARY: Thirty-three virulent and five temperate phages of Streptococcus lactis and Streptococcus cremoris were differentiated into three groups by DNA homology. A complete lack of DNA homology was demonstrated between the phage groups. Within each group, large parts of the phage genomes were homologous except for a few phages. One group consisted of five temperate and two virulent phages suggesting that virulent phages isolated during abnormal fermentations and temperate phages isolated after induction from lactic streptococcal starter cultures may be related to one another. We observed a good correlation between the grouping of phages by DNA homology and by their protein composition since within the same DNA homology group, the protein composition of a phage exhibited some similarities with that of the other phages of the group. Therefore, the DNA homologies seemed to be located, at least, in the region coding for the structural proteins. By immunoblotting. we confirmed the relatedness between the proteins of the phages belonging to the same DNA homology group. The important host range factor in bacterium-phage interactions appeared to be an unreliable criterion in determining phage taxonomy.
-
-
-
Characterization of Bdellovibrio bacteriovorus Bacteriophage MAC-1
More LessSUMMARY: The bacteriophage MAC-1, which specifically infects Bdellovibrio bacteriovorus, was plaque purified and raised to high titre. The phage was purified by NaCl/polyethylene glycol precipitation, followed by two cycles of isopycnic density gradient centrifugation in CsCl. The purified phage exhibited a density of 1·363 g cm-3 and a sedimentation coefficient of 94S. Nucleic acid isolated from purified phage was resistant to hydrolysis under alkaline conditions and to digestion with RNAase, but it was hydrolysed by DNAase, providing evidence that the phage genome is made up of DNA. The lack of hyperchromic effect upon denaturation, hydrolysis of phage DNA by SI nuclease, characteristic fluorescent staining with acridine orange, and resistance to digestion with a variety of restriction endonucleases are consistent with the DNA being single-stranded. A buoyant density of 1·722 g cm-3 and a sedimentation coefficient of 17·9S were obtained for the phage DNA. The molecular mass of phage DNA was determined as 1·58 MDa by agarose gel electrophoresis with single-stranded DNA as standards. Electron microscopy of the DNA showed that the genome is circular in nature. In addition, using Southern blots, the two replicative forms, RFI (supercoiled)and RF2 (circular) have been identified and isolated from infected cell extracts.
-
-
-
Isolation and Genetic Analysis of Operator-constitutive Mutants of the H1 Operon in Salmonella typhimurium
More LessSUMMARY: In phase-2 cells of diphasic Salmonellastrains, expression of H1 is repressed by the H1 repressor, coded for by the rhl gene. A procedure for the isolation of operator-constitutive (H1-Oc )mutants of the H1 operon is described. Using three-factor crosses between an H1-O c H1 strain and H1-O+ H1 strains, where motility recovery via H1-phase (or phase 1) flagellation was used as the selected marker and the H1-O character was the unselected marker, the relative position of the H1-Oc site to the H1 gene was determined. A diphasic H1-Oc strain produced, in phase 2, copolymer filaments composed of H1 and H2 flagellin.
-
-
-
Transcription and Expression of the Exotoxin A Gene of Pseudomonas aeruginosa
More LessSUMMARY: The exotoxin A genes from Pseudomonas aeruginosa strains PA103 and PAO1 have been independently cloned in a pUC9-derived plasmid. In a non-toxigenic mutant of PAO1 as host, the cloned genes directed the synthesis of intact exotoxin A that expressed ADP-ribosyltransferase activity upon treatment with urea and dithiothreitol. Western-blot analysis of culture supernatants identified a polypeptide of 67 kDa, the molecular mass of intact exotoxin A. There was an approximately 15-fold increase in the toxin yield from P. aeruginosa cells carrying a cloned PA103 gene compared to PA103, and a 40-fold increase in the yield of toxin from cells carrying a cloned PAO1 gene compared to PAO1; cells carrying the cloned PA103 gene yielded about four times more toxin than those carrying the cloned PAO1 gene. Toxin expression was correlated with the presence of a transcript that was initiated 88 bp upstream from the translational start site. Little or no messenger RNA from either cloned gene could be detected in an Escherichia coli host, or in a P. aeruginosa host grown in the presence of 0·1 mMFe2 +, a condition that inhibits toxin expression. The nucleotide sequences of two regions, each of approximately 500 bp, near the 5′ and 3′ termini of the structural gene were established. In these regions, the exotoxin A gene from PAO1 has ten base-pair differences compared to the PA103 gene, three in the non-coding region, and seven in the structural gene, four of which should lead to amino-acid differences. No apparent sequence similarities were found between the inferred promoter region of the exotoxin A gene and that of other Pseudomonas genes, nor with the consensus sequence of E. coli promoters.
-
-
-
Genetic Mapping of the Bacitracin Synthetase Gene(s) in Bacillus licheniformis
More LessSUMMARY: The map position of a mutation in the bacitracin synthetase gene(s) in Bacillus licheniformis ATCC 10716 was determined by transduction with phage SP-15. Results indicate that it is linked to the lys and trp loci and is distinct from the known sporulation loci on the chromosome of Bacillus licheniformis. The defect(s) of the enzyme complex were analysed in terms of its ability to bind covalently 14C-labelled amino acid precursors of the bacitracin molecule.
-
-
-
Plasmid Transfer between Strains of Pseudomonas aeruginosa on Membrane Filters Attached to River Stones
More LessSUMMARY: A naturally occurring mercury-resistance, conjugative plasmid, designated pQM1, was isolated from a bacterial population on the surface of stones from a river using Pseudomonas aeruginosa as a recipient. This was a narrow-host-range plasmid [IncP-13; 165 MDa; Tra+, Hgr, fluorescein mercuric acetater, merbrominr, Phi(E79), UVr] confined to some Pseudomonas spp. It was used to demonstrate transfer between bacteria on stones in laboratory microcosm experiments and in situ. Transfer occurred (3·3 × 10-1 to 6·8 × 10-9 per recipient) at all the temperatures used (6-20°C), although frequencies were lower in the cold. Nutrient status also affected transfer frequency, rich conditions promoting transfer. The presence of competing bacteria in the natural epilithon lowered transfer frequencies, but when unscrubbed stones were heat treated, transfer was enhanced, perhaps because of nutrient release from the heated epilithon.
-
Volumes and issues
-
Volume 171 (2025)
-
Volume 170 (2024)
-
Volume 169 (2023)
-
Volume 168 (2022)
-
Volume 167 (2021)
-
Volume 166 (2020)
-
Volume 165 (2019)
-
Volume 164 (2018)
-
Volume 163 (2017)
-
Volume 162 (2016)
-
Volume 161 (2015)
-
Volume 160 (2014)
-
Volume 159 (2013)
-
Volume 158 (2012)
-
Volume 157 (2011)
-
Volume 156 (2010)
-
Volume 155 (2009)
-
Volume 154 (2008)
-
Volume 153 (2007)
-
Volume 152 (2006)
-
Volume 151 (2005)
-
Volume 150 (2004)
-
Volume 149 (2003)
-
Volume 148 (2002)
-
Volume 147 (2001)
-
Volume 146 (2000)
-
Volume 145 (1999)
-
Volume 144 (1998)
-
Volume 143 (1997)
-
Volume 142 (1996)
-
Volume 141 (1995)
-
Volume 140 (1994)
-
Volume 139 (1993)
-
Volume 138 (1992)
-
Volume 137 (1991)
-
Volume 136 (1990)
-
Volume 135 (1989)
-
Volume 134 (1988)
-
Volume 133 (1987)
-
Volume 132 (1986)
-
Volume 131 (1985)
-
Volume 130 (1984)
-
Volume 129 (1983)
-
Volume 128 (1982)
-
Volume 127 (1981)
-
Volume 126 (1981)
-
Volume 125 (1981)
-
Volume 124 (1981)
-
Volume 123 (1981)
-
Volume 122 (1981)
-
Volume 121 (1980)
-
Volume 120 (1980)
-
Volume 119 (1980)
-
Volume 118 (1980)
-
Volume 117 (1980)
-
Volume 116 (1980)
-
Volume 115 (1979)
-
Volume 114 (1979)
-
Volume 113 (1979)
-
Volume 112 (1979)
-
Volume 111 (1979)
-
Volume 110 (1979)
-
Volume 109 (1978)
-
Volume 108 (1978)
-
Volume 107 (1978)
-
Volume 106 (1978)
-
Volume 105 (1978)
-
Volume 104 (1978)
-
Volume 103 (1977)
-
Volume 102 (1977)
-
Volume 101 (1977)
-
Volume 100 (1977)
-
Volume 99 (1977)
-
Volume 98 (1977)
-
Volume 97 (1976)
-
Volume 96 (1976)
-
Volume 95 (1976)
-
Volume 94 (1976)
-
Volume 93 (1976)
-
Volume 92 (1976)
-
Volume 91 (1975)
-
Volume 90 (1975)
-
Volume 89 (1975)
-
Volume 88 (1975)
-
Volume 87 (1975)
-
Volume 86 (1975)
-
Volume 85 (1974)
-
Volume 84 (1974)
-
Volume 83 (1974)
-
Volume 82 (1974)
-
Volume 81 (1974)
-
Volume 80 (1974)
-
Volume 79 (1973)
-
Volume 78 (1973)
-
Volume 77 (1973)
-
Volume 76 (1973)
-
Volume 75 (1973)
-
Volume 74 (1973)
-
Volume 73 (1972)
-
Volume 72 (1972)
-
Volume 71 (1972)
-
Volume 70 (1972)
-
Volume 69 (1971)
-
Volume 68 (1971)
-
Volume 67 (1971)
-
Volume 66 (1971)
-
Volume 65 (1971)
-
Volume 64 (1970)
-
Volume 63 (1970)
-
Volume 62 (1970)
-
Volume 61 (1970)
-
Volume 60 (1970)
-
Volume 59 (1969)
-
Volume 58 (1969)
-
Volume 57 (1969)
-
Volume 56 (1969)
-
Volume 55 (1969)
-
Volume 54 (1968)
-
Volume 53 (1968)
-
Volume 52 (1968)
-
Volume 51 (1968)
-
Volume 50 (1968)
-
Volume 49 (1967)
-
Volume 48 (1967)
-
Volume 47 (1967)
-
Volume 46 (1967)
-
Volume 45 (1966)
-
Volume 44 (1966)
-
Volume 43 (1966)
-
Volume 42 (1966)
-
Volume 41 (1965)
-
Volume 40 (1965)
-
Volume 39 (1965)
-
Volume 38 (1965)
-
Volume 37 (1964)
-
Volume 36 (1964)
-
Volume 35 (1964)
-
Volume 34 (1964)
-
Volume 33 (1963)
-
Volume 32 (1963)
-
Volume 31 (1963)
-
Volume 30 (1963)
-
Volume 29 (1962)
-
Volume 28 (1962)
-
Volume 27 (1962)
-
Volume 26 (1961)
-
Volume 25 (1961)
-
Volume 24 (1961)
-
Volume 23 (1960)
-
Volume 22 (1960)
-
Volume 21 (1959)
-
Volume 20 (1959)
-
Volume 19 (1958)
-
Volume 18 (1958)
-
Volume 17 (1957)
-
Volume 16 (1957)
-
Volume 15 (1956)
-
Volume 14 (1956)
-
Volume 13 (1955)
-
Volume 12 (1955)
-
Volume 11 (1954)
-
Volume 10 (1954)
-
Volume 9 (1953)
-
Volume 8 (1953)
-
Volume 7 (1952)
-
Volume 6 (1952)
-
Volume 5 (1951)
-
Volume 4 (1950)
-
Volume 3 (1949)
-
Volume 2 (1948)
-
Volume 1 (1947)
Most Read This Month
