Mutations induced by benzo[a]pyrene diolepoxide at the hprt locus in human T-lymphocytes in vitro

Human T-lymphocytes have been treated with benzo[a]pyrene diolepoxide (BPDE) in vitro and T-cell clones mutated in the hprt gene have been isolated. The mutant frequencies in BPDE-treated T-cell cultures were on average 24-fold higher than those of untreated cultures. Thus, BPDE is a potent inducer of gene mutation in this system. In order to examine which types of mutations are induced by BPDE in human cells, 41 spontaneous and 44 BPDE-induced mutant clones have been characterized using the Southern blot technique. In addition, rearrangements of the T-cell-receptor beta and gamma loci have been used to determine the proportion of isolated clones that are unique, and thus likely to represent independent mutational events. Out of 23 independent spontaneous mutants 4 had large hprt alterations that could be detected on Southern blots. Two of these alterations, deletions of exons 2-6, have been confirmed using PCR of hprt cDNA and direct sequencing of the PCR product. All 33 independent BPDE-induced mutants had normal hprt restriction patterns which indicates that BPDE is mainly a point mutagen in this system.     

Bioconversions in aqueous two-phase systems.

Bioconversions involving enzymes and/or microbial cells in aqueous two-phase systems are reviewed. The partitioning of biocatalysts, substrates, and products is discussed in relation to their size. The efficiency of retaining biocatalysts in aqueous two-phase systems is summarized in relation to other methods of recirculating. The influence of phase components on the activity and the stability of enzymatic biocatalysts is exemplified with penicillin acylase and the cellulolytic enzyme system, and the effect of phase components on biocatalytic living cells is exemplified with the production of alpha-amylase with Bacillus sp. Process design costs in bioconversions in aqueous two-phase systems are briefly summarized.     

Systematics of theLactobacillus population on rat intestinal mucosa with special reference toLactobacillus reuteri

The systematics of theLactobacillus population of the intestines of 88 different rats was studied; 80 rats had been fed on fermented oat-meal soup (Molin et al. 1992). One-hundred-twenty-twoLactobacillus strains from the intestinal mucosa were phenotypically classified together with twenty-eight reference strains ofLactobacillus andLeuconostoc, using 49 unit characters. Data were examined using Jaccard coefficient, and unweighted pair group algorithm with arithmetic averages. Two major and eleven minor clusters were defined at the 76% S_J-similarity level: Cluster 1 included thirty isolates which could not be identified further, but had resemblance to the type strains ofL. jensenii, L. gasseri, L. crispatus, and to some extent toL. acidophilus. Cluster 12 including fifty-four intestinal isolates was identified asL. reuteri; and so was cluster 13 (five isolates). Isolates of the major clusters were found in all parts of the intestines. The genomic homogeneity of theL. reuteri isolates was scrutinized by endonuclease restriction analysis of the chromosomal DNA, and the isolates could be divided into six genomic strains.     

Sexual selection

Competition over mates takes many forms and has far-reaching consequences for many organisms. Recent work suggests that relative reproductive rates of males and females, sperm competition and quality variation among mates affect the strength of sexual selection. Song, other display, body size, visual ornaments and material resource offerings are often sexually selected. There is much empirical evidence of mate choice, and its evolution is clarified by mathematical models. Recent advances in theory also consider costs of choice, effects of deleterious mutations, fast and slow evolution of preferences and preferred traits, and simultaneous preferences for several traits. Contests over mates are important; so is sperm competition, scrambles, endurance rivalry, and coercion. The latter mechanisms have received less attention than mate choice. Sexual selection may explain puzzling aspects of plant pollination biology.     

A comprehensive linkage map of the pig based on a wild pig - Large White intercross

A comprehensive linkage map, including 236 linked markers with a total sex-average map length of about 2300 cM, covering nearly all parts of the pig genome has been established. Linkage groups were assigned to all 18 autosomes, the X chromosome and the X/Y pseudoautosomal region. Several new gene assignments were made including the assignment of linkage group U1 (EAK-HPX) to chromosome 9. The linkage map includes 77 type I loci informative for comparative mapping and 72 in situ mapped markers physically anchoring the linkage groups on chromosomes. A highly significant heterogeneity in recombination rates between sexes was observed with a general tendency towards an excess of female recombination. The average ratio of female to male recombination was estimated at 1–4:1 but this parameter varied between chromosomes as well as between regions within chromosomes. An intriguing finding was that blood group loci were overrepresented at the distal ends of linkage groups.     

Localization and organization of phenol degradation genes ofPseudomonas putida strain H

The genetic organization of the DNA region encoding the phenol degradation pathway ofPseudomonas putida H has been investigated. This strain can utilize phenol or some of its methylated derivatives as its sole source of carbon and energy. The first step in this process is the conversion of phenol into catechol. Catechol is then further metabolized via themeta-cleavage pathway into TCA cycle intermediates. Genes encoding these enzymes are clustered on the plasmid pPGH1. A region of contiguous DNA spanning about 16 kb contains all of the genetic information necessary for inducible phenol degradation. The analysis of mutants generated by insertion of transposons and cassettes indicates that all of the catabolic genes are contained in a single operon. This codes for a multicomponent phenol hydroxylase andmeta-cleavage pathway enzymes. Catabolic genes are subject to positive control by the gene product(s) of a second locus.     

Immunoaffinity column clean-up for the high-performance liquid chromatographic determination of aflatoxins B1, B2, G1, G2, M1 and Q1 in urine

A method for the determination of aflatoxins B₁, B₂, G₁, G₂, M₁ and Q₁ in human urine has been developed. The 10-ml urine samples were automatically cleaned up on immunoaffinity columns and analysed by high-performance liquid chromatography (HPLC), including post-column derivatization with bromine and fluorescence detection. Average aflatoxin recoveries were: B₁ 103%, B₂ 106%, G₁ 98% and G₂ 96% in the range 6.8–73 pg/ml of urine and M₁ 103% and Q₁ 100% in the range 18–97 pg/ml of urine. The relative standard deviations were all between 1% and 21%. The determination limits of aflatoxins in urine were 6.8 pg/ml for B₁, B₂, G₁ and G₂ and 18 pg/ml for M₁ and Q₁.     

Evaluation of mass spectrometric techniques for charaterization of engineered proteins

A simple and versatile method of in vitro site-specific mutagenesis based on polymerase chain reaction (PCR) is described. The complete method required the use of three oligonucleotide primers and two PCRs. The product of the first PCR was used as one of the primers (megaprimer) in the second PCR. Essentially 100% of the final product incorporated the desired mutation. The various aspects of the procedure and its application is described in detail.