R.A. Nilan

Lund University, Lund, Skåne, Sweden

Are you R.A. Nilan?

Claim your profile

Publications (114)364.91 Total impact

  • C. F. Konzak · H. J. Curtis · N. Delihas · R. A. Nilan

    No preview · Article · Jan 2011 · Genome
  • Source

    Full-text · Article · Jul 2010 · Hereditas

  • No preview · Article · Jan 1992 · Crop Science
  • S. E. Ullrich · C. E. Muir · R. A. Nilan

    No preview · Article · Jan 1991 · Crop Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: The in vitro synthesized sodium azide mutagenic metabolite (azidoalanine) produced single-strand breaks and proteinase K-sensitive sites in isolated, germinating barley embryos. In contrast with sodium azide, the efficiency of DNA damage induction was lower, and both types of DNA lesions were totally or partially repaired in the course of subsequent 24 h incubation of the embryos. The mutagenic azide metabolite did not inhibit DNA replication, while azide did so even at doses which are not highly mutagenic. The metabolite labelled with 14C at the amino acid residue was taken up with a similar efficiency both into barley embryos germinating for 2 days and into cells of Salmonella typhimurium TA100. The majority of the radioactivity was incorporated into proteins, less into RNA and a negligible amount into DNA.
    No preview · Article · Dec 1987 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
  • M L Crispi · S E Ullrich · R A Nilan
    [Show abstract] [Hide abstract]
    ABSTRACT: The partial sterility found in several advanced generation, sodium azide-induced lines of spring barley (Hordeum vulgare L.) was investigated. Plants of mutant lines were reciprocally crossed with plants of their untreated mother lines. Spike sterility was measured in the selfed offspring of the plants crossed and in F1 and F2 progeny. Pollen sterility and endosperm development were analyzed in the selfed offspring of the plants crossed. Results indicated that the sterility was inherited in the mutant lines and was not caused by translocations, inversions, endosperm lethals, embryo-endosperm lethals, or major gene mutations. Furthermore, the sterility was not cytoplasmically inherited, and was essentially eliminated in the F1 and F2 of crosses between partially sterile lines and their fertile parents. Results suggest that the sterility may be caused by an environmental interaction with deleterious, homozygous recessive, minor gene mutations that were in the heterozygous condition when the mutant lines were originally selected.
    No preview · Article · Jul 1987 · Theoretical and Applied Genetics
  • W.M. Owais · R.C. Ronald · A Kleinhofs · R.A. Nilan
    [Show abstract] [Hide abstract]
    ABSTRACT: The L- and D-isomers of azidoalanine (azide metabolite) have been chemically synthesized with 60% yield using corresponding N-(tert-butoxycarbonyl)-serine as starting materials. The mutagenic properties of synthesized L-azidoalanine are very similar to those of azide and in vivo synthesized azidoalanine. Synthetic D-azidoalanine shows very low mutagenic activity on Salmonella typhimurium TA1530 strain compared to that of the L-isomer. Thus a stereoselective process is involved in azidoalanine mutagenicity. The data presented in this study suggest that further biochemical activation is required for L-azidoalanine to produce its mutagenic activity.
    No preview · Article · Dec 1986 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
  • S. E. Ullrich · C. E. Muir · R. A. Nilan

    No preview · Article · Jan 1986 · Crop Science
  • S. E. Ullrich · C. E. Muir · R. A. Nilan

    No preview · Article · Jan 1986 · Crop Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: DNA damage induced in germinating barley embryos by mutagenic and sublethal doses (0.1–2 mM, 2 h) of sodium azide, applied at pH 3, was measured by alkaline elution. Isolated nuclei were lysed at a high pH with either 2% SDS or 2 M NaCl on polyvinyl chloride filters and digested with proteinase K or with Micrococcus luteus endonuclease prior to elution. The azide treatments resulted in a dose-dependent increase of proteinase K-sensitive sites and an appearance of Micrococcus luteus endonuclease-sensitive sites. These sites were detected as DNA single-strand breaks after digestion of the DNA with either one or both of the enzymes. The two types of lesion were additive and occurred in a ratio of about 1:1. The additive effect suggested independent origin for the two types of lesion. Breaks independent of proteinase K digestion appeared only when DNA was analysed 24 h after the action of azide. The nature and significance of these DNA lesions are discussed.
    No preview · Article · May 1985 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
  • S. E. Ullrich · R. A. Nilan · A. J. Lejuene · C. E. Muir

    No preview · Article · Jan 1985 · Crop Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: The role of the enzyme O-acetylserine (thiol)-lyase ( (adding hydrogen sulfide), EC in the conversion of azide to a mutagenic metabolite was investigated. Barley O-acetylserine (thiol)-lyase was purified to homogeneity by gel filtration, anion-exchange chromatography, isoelectric focusing and discontinuous nondenaturing polyacrylamide gel electrophoresis. The purified enzyme was able to produce a product from azide and O-acetylserine which increased the frequency of reversions to histidine independence in Salmonella typhimurium TA1530. This demonstrated the role of O-acetylserine (thiol)-lyase in the synthesis of the azide metabolite in barley. The pathway by which the azide metabolite is synthesized was further investigated by comparing the kinetic properties of barley and bacterial O-acetylserine (thiol)-lyase. The kinetic properties of the barley and bacterial enzyme were similar. The results obtained suggested that azide metabolite biosynthesis in barley and bacteria is identical and that azide and sulfide use the same catalytic site on the enzyme. The kinetic data strongly suggest that the product of the initial enzymatic reaction is β-azidoalanine.
    No preview · Article · Nov 1983 · Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology
  • [Show abstract] [Hide abstract]
    ABSTRACT: A mutagenic azide metabolite was purified from the medium in which Salmonella typhimurium cells were grown in the presence of azide. This metabolite was identified to be azidoalanine based on infrared and mass spectroscopy and elemental analysis. This compound appeared to be identical to the mutagenic compound synthesized in vitro from azide and O-acetylserine by partially purified O-acetylserine sulfhydrylase. The metabolite (azidoalanine) mutagenic efficiency and spectrum in S. typhimurium was similar to that of inorganic azide. The compounds 2-azidoethylamine, 2-bromoethylamine, 3-bromopropionic acid and N-(azidomethyl) phthalimide were also mutagenic with a similar spectrum to azide and azidoalanine, but with lower efficiency. The compounds 3-azidopropylamine, 4-azidobutylamine, 3-chloroalanine and ethylamine were only weakly or nonmutagenic. Numerous other chloro, bromo and azido phthalimide derivatives tested were nonmutagenic. It is suggested that the lack of azide mutagenicity (and perhaps carcinogenicity) in mammalian cells may be due to their inability to convert azide to azidoalanine.
    No preview · Article · Oct 1983 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
  • P Arenaz · R.A. Nilan · A Kleinhofs
    [Show abstract] [Hide abstract]
    ABSTRACT: The mutagenicity of sodium azide in both higher plants and bacteria is well documented. However, in mammalian cells, research on the effects of azide on gene mutations has produced conflicting results. Furthermore, no research has been conducted on the effects of azide and its proximal mutagen (mutagenic metabolite) on DNA single-strand breaks. Experiments were designed to overcome this lack of information on azide mutagenicity and to evaluate the potential hazard of azide exposure to man. Chinese hamster V79 cells were treated with either azide or its proximal mutagen(s) for 2 or 6 h, respectively, and analyzed by alkaline elution for single-strand breaks. The data showed that neither azide nor the proximal mutagen(s) induced single-strand DNA breaks or DNA-protein cross-links. Therefore it appears that neither azide nor its proximal mutagen(s) interact directly with DNA and this suggests that azide may be an indirect-acting mutagen. Furthermore, this lack of interaction with DNA may account for azide's lack of carcinogenicity.
    No preview · Article · Apr 1983 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
  • J.L. Rosichan · W.M. Owais · A Kleinhofs · R.A. Nilan
    [Show abstract] [Hide abstract]
    ABSTRACT: The ability of Arabidopsis, Drosophila and Neurospora to convert azide to its mutagenic metabolite was investigated. Cultures of these organisms all contained significant levels of O-acetylserine sulfhydrylase activity. Extracts from each organism produced a product from O-acetylserine and azide in vitro which was mutagenic in Salmonella typhimurium TA1530.
    No preview · Article · Apr 1983 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
  • R. A. Nilan · A. J. Lejeune · C. E. Muir · S. E. Ullrich

    No preview · Article · Jan 1983 · Crop Science
  • T. K. Blake · S. E. Ullrich · R. A. Nilan
    [Show abstract] [Hide abstract]
    ABSTRACT: The hordein storage proteins of barley (Hordeum vulgare L.) are of intense interest due to their genetic diversity and prominence and impact on the industrial and agricultural uses of the seed. Two major hordein loci have been previously mapped on chromosome 5 (Hor-1 and Hor-2 encoding the C and B hordeins, respectively). A third major locus, Hor-3, which codes for D hordein, has been located in the centromeric region of chromosome 5, probably on the long arm. Two allelic variants with apparent molecular weights of 83,000 and 91,000 and similar isoelectric points of 8.0 comprise the products of this locus in the barley varieties ‘Advance’ and ‘Triple Awned Lemma’. The D hordein examined is similar in molecular weight and isoelectric point to the high molecular weight (HMW) glutenin proteins encoded by the 1B chromosome of wheat (Triticum aestivum L.)
    No preview · Article · Dec 1982 · Theoretical and Applied Genetics
  • E DONALDSON · R.A. Nilan · C.F. Konzak
    [Show abstract] [Hide abstract]
    ABSTRACT: The influence of concentrations of oxygen and radiation-induced oxygen sensitive sites on their rates of reactions in barley seeds was investigated.Himalaya (C.I. 620) barley seeds were adjusted to 9.9% water content irradiated with 60Co gamma rays and soaked at 0°C in distilled water bubbled with oxygen and nitrogen gas mixtures containing 0.0, 12.5, 25, 50 and 100% oxygen. Treatment effects were measured as M1 seedling injury.In one experiment, irradiated seeds were initially soaked in oxygen-saturate water, then transferred to O2-free water (nitrogen soaking) at selected time intervals. An increase in oxygen enhancement (OE) as measured by seedling injury is obtained with increased O2-soaking duration. A measure of the reaction rate between O2 and O2-sensitive sites (OSS) is thus obtained. This reaction is radiation exposure dependent. A reverse experiment (initial nitrogen soaking with transfer to O2 soaking at selected intervals) gives a measure of the lifetime of the OSS in water (quenching reaction).The same experimental plan is followed in two other experiments where the oxygen concentration in the gas phase of the soaking solution (OC) is variable. These experiments provide a measure of the influence of OC on the OE and OSS quenching reactions. A single radiation exposure was used. These results are demonstrated in four figures and numerical results and “reaction rates” are in two tables.The quenching reactions were independent of radiation exposure and OC. At low to intermediate OC the quenching reactions terminated the O2-OSS reaction. At 100% OC the O2-OSS reaction was two to three times faster and started three times sooner than the quenching reaction.
    No preview · Article · Feb 1982 · Environmental and Experimental Botany
  • W M Owais · A Kleinhofs · R.A. Nilan
    [Show abstract] [Hide abstract]
    ABSTRACT: Cell-free extracts of Salmonella typhimurium synthesize a mutagenic azide metabolite from sodium azide and O-acetylserine. S. typhimurium mutant DW379 (O-acetylserine sulfhydrylase-deficient) extracts were neither able to carry out this reaction not produce the mutagenic azide metabolite in vivo. The in vitro reaction was inhibited by sulfide but not by L-cysteine. The catalytic activity responsible for the mutagenic metabolite synthesis was stable to brief heating up to 55 degrees C and had a pH optimum between 7-7.4. These results suggest that the enzyme O-acetylserine sulfhydrylase catalyzes the reaction of azide with O-acetylserine to form a mutagenic azide metabolite.
    No preview · Article · Jan 1982 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
  • R. A. Nilan · A. Kleinhofs · C. F. Konzak
    [Show abstract] [Hide abstract]
    ABSTRACT: New knowledge of the mechanism of mutation induction and the nature of mutations in eukaryotes continues to be developed from experiments involving sodium azide. Azide is a potent mutagen in bacteria and in higher plants but it is weakly mutagenic and not carcinogenic in mammalian systems. It was determined that azide acted through a promutagen or organic metabolite both in barley and bacterial cells. This metabolite has been isolated and characterized. During the past year, considerable progress has been made in understanding the pathway by which the metabolite is synthesized in barley and bacteria. It can be synthesized in vitro both in bacteria and barley and some additional knowledge of the structure of the metabolite is being revealed through chemical synthesis of the metabolite. Additional information concerning the lack of azide mutagenicity in mammalian cells has been developed through the detailed studies of the action of azide and its metabolite from bacteria and barley on sister-chromatid exchanges in mammalian cells. Neither azide nor its metabolites of bacteria and barley are particularly effective, and to date no metabolite has been detected in mammalian cells. Azide-induced mutants in barley have been utilized in barley improvement, in probing the pathways of a number of biochemical and physiological processes and in understanding the structure of gene loci and the nature of mutations induced.
    No preview · Article · Oct 1981