Mutagenicity of methyl-, ethyl-, propyl- and butylnitrosourea towards Escherichia coli WP2 strains with varying DNA repair capabilities.

Methyl- (MNUA), ethyl- (ENUA), propyl- (PNUA) and butylnitrosourea (BNUA) have been tested for toxicity and mutation in a liquid suspension assay towards Escherichia coli WP2 and some of its repair deficient derivatives. A comparison of survival rates after nitrosourea exposure between WP2 and WP2 uvrA showed no difference between the two strains but a consistent difference in potency between the various nitrosoureas studied. Toxicity increased in the order MNUA less than PNUA less than ENUA less than BNUA. ENUA and PNUA induced a greater number of trp+ revertants in both strains than did MNUA and BNUA, particularly at low survival rates. None of these differences in biological potency could be accounted for by differences in rates of hydrolysis. ENUA, PNUA and BNUA were non-mutagenic towards WP2 lexA, WP2 recA and WP2 uvrA lexA, whereas MNUA did induce mutations. Ethyl methanesulphonate (EMS) was able to mutate WP2 lexA. These results are discussed in the light of current theories regarding the mechanism of action of these compounds.     

Effect of mutagens, chemotherapeutic agents and defects in DNA repair genes on recombination in F' partial diploid Escherichia coli.

The ability of mutagenic agents, nonmutagenic substances and defects in DNA repair to alter the genotype of F' partial diploid (F30) Escherichia coli was determined. The frequency of auxotrophic mutants and histidine requiring (His-) haploid colonies was increased by mutagen treatment but Hfr colonies were not detected in F30 E. coli even with specific selection techniques. Genotype changes due to nonreciprocal recombination were determined by measuring the frequency of His- homogenotes, eg. F' hisC780, hisI+/hisC780, hisI+, arising from a His+ heterogenote, F' hisC780 hisI+/hisC+, his1903. At least 75% of the recombinants were homozygous for histidine alleles which were present on the F' plasmid (exogenote) of the parental hetergenote rather than for histidine alleles on the chromosome. Mutagens, chemotherapeutic agents which histidine alleles on the chromosome. Mutagens, chemotherapeutic agents which block DNA synthesis and a defective DNA polymerase I gene, polA1, were found to increase the frequency of nonreciprocal recombination. A defect in the ability to excise thymine dimers, uvrC34, did not increase spontaneous nonreciprocal recombination. However, UV irradiation but not methyl methanesulfonate (MMS) induced greater recombination in this excision-repair defective mutant than in DNA-repair-proficient strains. Mutagenic agents, with the exception of ethyl methanesulfonate (EMS), induced greater increases in recombination than the chemotherapeutic agents or the polA1 mutation. EMS, which causes relatively little degradation of DNA, was more mutagenic but less recombinogenic than MMS, a homologous compound ths that inhibition of DNA occurring single-stranded regions in replicative intermediates of the DNA. Mutagens which cause the rapid breakdown of DNA may, in addition, introduce lesions into the genome that increase the number of single-stranded regions thus inducing even higher frequencies of recombination.     

Genetic studies of the lac repressor. III. Additional correlation of mutational sites with specific amino acid residues

The complete results of the analysis of over 5300 independently derived nonsense mutations in the lacI gene are presented. These have been mapped and divided into specific sites. A total of 105 nonsense mutations derived from 90 different codons can be distinguished, of which several are the result of tandem double base changes induced by ultraviolet light. With the aid of results determined in a preceding paper (Miller et al., 1977), the majority of these mutations have been assigned to points in the gene coding for specific residues in the lac repressor. This allows a detailed correlation of the physical and genetic map.Recombination studies have been carried out using mutations at known sites. For crosses involving mutations separated by less than 30 nucleotides (the main object of this study), a significant lack of agreement between distance and recombination frequency has been found.     

Mutagenesis of yeast by hydrazine: dependence upon post-treatment cell division.

Hydrazine was found to be mutagenic for yeast (Saccharomyces cerevisiae) at exposures (concentration × time) ranging over nearly three orders of magnitude. Little or no forward mutation from CAN1 to can1 was detectable upon immediate plating following treatment in neutral buffer suspension. Post-treatment cell division in yeast extract peptone dextrose complex growth medium was required for expression of induced mutation to canavanine resistance. Frequencies of induced mutation rose to levels approximately 10-fold higher than spontaneous levels for exposures between 0.1 and 12.0 min mol/l. Survival remained at 100%. For exposures greater than 80 min mol/l viability and mutation frequency began to decrease sharply. By contrast, single treatments of ethyl methanesulfonate, methyl methanesulfonate, N-methyl-N′-nitro-N-nitro-soguanidine, nitrous acid, hydroxylamine, and ultraviolet light were able to increase mutation frequency with this system upon immediate assay. Further growth-dependent increases in mutation frequency were not observed with HA and UV.Expression of HZ-induced mutation was detectable after treated cells had undergone less than one population doubling in YEPD. Such mutation expression could be blocked by the inhibitors cycloheximide and hydroxyurea, which block protein synthesis and DNA synthesis respectively. Results were similar to those obtained previously with Haemophilus influenzae and similarly suggest that, in this eukaryote, HZ-induced lesions lead to mutation by causing base mispairing at DNA replication rather than by means of an error-prone repair mechanism.     

Two new iridoid glucosides from Mussaenda parviflora and Mussaenda shikokiana

From the leaves of Mussaenda parviflora, two new iridoid glucosides, mussaenoside and shanzhiside methyl ester were isolated and their structures e     

Methyl Oleate Modulates <Emphasis Type="Italic">LIP2</Emphasis> Expression in the Lipolytic Yeast <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis>

Methyl oleate was used as a primary carbon source and as an alternative inducer for the production of an extracellular lipase, Lip2, in Y. lipolytica strain LgX64.81 grown in a 20-l bioreactor. The lipase-encoding gene, LIP2, was investigated during culture on methyl oleate using a pLIP2–LacZ reporter fusion and we provide evidence for the involvement of methyl oleate in its regulation. Revisions requested 7 July 2005; Revisions received 30 August 2005     

Methyl <Emphasis Type="Italic">tert</Emphasis>-butyl Ether and <Emphasis Type="Italic">tert</Emphasis>-butyl Alcohol Degradation by <Emphasis Type="Italic">Fusarium solani</Emphasis>

Fusarium solani degraded methyl tert-butyl ether (MTBE) and other oxygenated compounds from gasoline including tert-butyl alcohol (TBA). The maximum degradation rate of MTBE was 16 mg protein h and 46 mg/g protein h for TBA. The culture transformed 77% of the total carbon to ¹⁴CO₂. The estimated yield for MTBE was 0.18 g dry wt/g MTBE.     

A quinonoid is an intermediate of oxidative deamination reaction catalyzed by Dopa decarboxylase

The reactions of Dopa decarboxylase (DDC) with l- and d-enantiomers of tryptophan methyl ester are described. Although both the enantiomers bind to the active site of the enzyme with similar affinity, their binding modes are different. l-enantiomer binds in an unproductive mode, while d-enantiomer acts as an oxidative deamination substrate. For the first time a quinonoid has been detected as intermediate of this reaction. By using rapid-scanning stopped-flow kinetic technique rate constants for formation and decay of this species have been determined. All these data, besides validating the functional DDC active site model, represent an important step toward the elucidation of the catalytic pathway of oxidative deamination.     

p38 MAPK is involved in CB2 receptor-induced apoptosis of human leukaemia cells

Cannabinoids have been shown to inhibit the growth of a broad spectrum of tumour cells. However, the molecular mechanisms involved in that effect have not been completely elucidated. Here, we investigated the possible involvement of mitogen-activated protein kinases (MAPKs) in CB2 receptor-induced apoptosis of human leukaemia cells. Results show that stimulation of the CB2 receptor leads to p38 MAPK activation and that inhibition of this kinase attenuates CB2 receptor-induced caspase activation and apoptosis. These findings support a role for p38 MAPK in CB2 receptor-induced apoptosis of human leukaemia cells.     

Rosmarinic acid production by <Emphasis Type="Italic">Coleus forskohlii</Emphasis>hairy root cultures

Coleus forskohlii hairy root cultures were found to produce forskolin and rosmarinic acid (RA) as the main metabolites. The growth and RA production by C. forskohlii hairy root cultures in various liquid media were examined. The hairy root cultures showed good growth in hormone-free Murashige and Skoog medium containing 3% (w/v) sucrose (MS medium), and Gamborg B5 medium containing 2% (w/v) sucrose (B5 medium). RA yield reached 4.0 mg (MS medium) and 4.4 mg (B5 medium) after 5 weeks of culture in a 100 ml flask containing 20 ml of each medium. Hairy root growth and RA were also investigated after treatment with various concentrations of yeast extract (YE), salicylic acid (SA) and methyl jasmonic acid (MJA). RA production in a 100 ml flask containing 20 ml B5 medium reached 5.4 mg (1.9 times more than control) with treatment of 0.01 or 1% (w/v) YE, 5.5 mg (2.0 times more than control) with treatment of 0.1 mM SA, and the maximum RA content with 9.5 mg per flask (3.4 times more than control) was obtained in the hairy roots treated with 0.1 mM MJA. These results suggest that MJA is an effective elicitor for production of RA in C. forskohlii hairy root cultures.