Tick-host interaction: a synthesis of current concepts

Ixodid ticks are recognized world-wide as major vectors of arboviruses, rickettsiae, spirochaetes and parasitic protozoa of man and domestic animals. Some ticks also inject a debilitating, sometimes fatal, paralytic toxin in their saliva. All these factors are transmitted via the salivary glands and mouthparts of the feeding tick. Tick feeding is a prolonged and complex process. Major developmental events occurring within the tick during feeding, as well as extensive tick-host interactions, all influence the likelihood of pathogen transmission. In this review, Reuben Kaufman discusses the sequence and complexity of these interactions.     

Chemical mutagenesis of the mouse genome: an overview

The careful comparison of the phenotypic variations generated by different alleles at a given locus, including of course, those alleles with a deleterious effect, is often an important source of information for the understanding of gene functions. In fact, every time it is possible to match a specific alteration observed at the genomic level with a particular pathology, it is possible to establish a relationship between a gene and its function. When considered from this point of view, the production of new mutations by experimental mutagenesis appears as an alternative to the strategy of in vitro gene invalidation by homologous recombination in embryonic stem (ES) cells, with the advantage that experimental mutagenesis does not require any previous knowledge of the gene structure at the molecular level. Homologous recombination in ES cells is a gene driven approach, in which mutant alleles are produced for those genes that we already know. Experimental mutagenesis, on the contrary, is a phenotype driven approach, in which unknown genes are identified based on phenotypic changes. Also, while homologous recombination in ES cells requires a rather sophisticated technology, mutagenesis is simple to achieve but relies greatly on the efficiency of the mutagenic treatment as well as on the use of an accurate protocol for phenotyping. In this review, we will address a few comments about the different techniques that can be used for the induction of point mutations in the mouse germ line with special emphasis on chemical mutagenesis. We will also discuss the limitations of experimental mutagenesis and the necessity to look for alternative ways for the discovery of new genes and gene functions in the mouse.     

Chemical diversity of several Betulaceae species: comparison of phenolics and terpenoids in northern birch stems

 Phenolics and terpenoids characteristic for silver birch (Betula pendula Roth) were screened in current-growth twigs of seedlings (1-growing-season-old individuals) and current-growth twigs of saplings (3 to 5-year-old individuals) of several birch species. Seedlings were grown in a greenhouse for 1 growing season. Saplings were field cultivated or wild-stand individuals. Chemicals were methanol-extracted, purified and HPLC-diode array detector-, gas chromatograph-flame ionizaton detector- and gas chromatograph-mass selective-analyzed. Species-specific qualitative and quantitative variation of secondary chemicals in birch stems were considerable and dependent on the age of the individual. The chemical diversity and amount were lower in seedlings than in saplings. In saplings, (+)-catechin and its derivatives were found in nearly all species, while arylbutanoids (±rhododendrol glucosides), an arylheptanoid (platyphylloside) and dammaraneterpenoids (papyriferic acid, deacetylpapyriferic acid and pendulic acid) showed a more restricted distribution. The chemicals analyzed in birch stems are a useful tool for recognition of species. Received: 18 September 1995 / Accepted: 19 December 1995     

Metabolism of plastid terpenoids: in vitro inhibition of phytoene synthesis by phenethyl pyrophosphate derivatives

The inhibition of partially purified phytoene synthetase activity from Capsicum annuum chromoplasts was investigated using aminophenethyl pyrophosphate and azidophenethyl pyrophosphate. These compounds were effective inhibitors of phytoene synthesis and kinetic analysis showed that they were competitive with respect to the substrate isopentenyl pyrophosphate. These data were strengthened by the ability of azidophenethyl pyrophosphate to photoinactivate irreversibly the activity of the enzyme complex. These results suggest that the primary targets of these analogs are at the level of isopentenyl pyrophosphate isomerase and geranylgeranyl pyrophosphate synthetase.     

Adaptive management: a synthesis of current understanding and effective application

Summary Adaptive management (AM) remains a commonly cited, yet frequently misunderstood, management approach. The aim of AM is to improve environmental management through ‘learning by doing’ and understand the impact of incomplete knowledge, but AM more commonly consists of ad hoc changes in managing environmental resources in the absence of adequate planning and monitoring. Here, we trace and review the development of AM, the central roles of consultation, collaboration and of monitoring, and of quantitative models and simulations. We identify a series of formalized, structured steps included in one AM cycle and review how current AM programs build upon such cycles. We conclude that the best AM outcomes require rigorous and formalized approaches to planning, collaboration, modelling and evaluation. Finally, simulating potential outcomes of an AM cycle in the presence of existing uncertainty can help to identify management strategies that are most likely to succeed in relation to clearly articulated goals.     

Addition of terpenoids to pear ester plus acetic acid increases catches of codling moth (Lepidoptera: Tortricidae)

Field studies were conducted to evaluate new kairomone blends in combination with pear ester (E,Z)‐2,4‐ethyl decadienoate (PE) and acetic acid (AA) for their attraction of male and female codling moth, Cydia pomonella (L.), in apple, Malus domestica Borkhausen. The addition of decanal to either AA or PE alone significantly increased total and female moth catches. However, the addition of decanal did not improve the attraction of PE + AA. The addition of either the pyranoid (PyrLOX) or furanoid (FurLOX) linalool oxide but not linalool (LOL) increased moth catches with PE but did not increase catches with PE + AA. Similarly, the addition of PyrLOX plus decanal did not improve PE + AA. The addition of (E)‐4,8‐dimethyl‐1,3,7‐nonatriene (DMNT) to either AA, PE + AA or PE + AA+decanal did not significantly increase moth catches. However, the addition of PyrLOX to traps with PE + AA and DMNT (4‐component lure) significantly increased moth catches compared with PE + AA alone or any of the ternary blends of these volatiles. Females accounted for 60%–80% of the total catch with this 4‐component lure. The 4‐component blend with PyrLOX was a more attractive lure than similar blends that substituted LOL, or a binary blend of LOL and FurLOX for PyrLOX. The 4‐component blend caught nearly fourfold more total and female moths than the purported attractant N‐butyl sulphide when it was used in combination with PE + AA. These results indicate that significant improvements in monitoring, mating disruption and mass trapping of codling moth are possible. Further studies are needed to assess the new attractive blend's effectiveness in combination with sex pheromone lures and to evaluate whether other host plant volatiles can be added or substitute for DMNT or LOX when used in combination with PE + AA.     

"Rheumatoid Arthritis": A balanced overview of current research

This is a brief review of the third volume of the series edited by AN Theofilopoulos, "Current Directions in Autoimmunity". This hard-cover volume comprises 282 pages, 46 figures and 14 tables. The book has a cover price of 196 Swiss Francs, or 255 Deutschmarks, or 170.50 US dollars.     

Psoralen plus near-ultraviolet light: a possible new method for measuring DNA repair synthesis

A new method is proposed to inhibit semiconservative DNA synthesis in cultured cells while DNA repair synthesis is being measured. The cells are treated with the DNA-crosslinking agent Trioxalen (4,5,8-trimethylpsoralen) plus near-ultraviolet light, and consequently 99.5% inhibition of replicative DNA synthesis is achieved. Additional DNA-damaging agents induce thymidine incorporation into the double-stranded regions of the DNA. The new method gave results very similar to those obtained with the benzoylated naphthoylated DEAE (BND) cellulose method using three human fibroblast strains, of which one had deficient capacity for DNA repair synthesis following treatment with gamma rays and methyl methanesulfonate. The advantages of the new method are simplicity and rapidity, as well as the high extent to which replicative DNA synthesis is inhibited.     

Genome browsing with Ensembl: a practical overview.

A wealth of gene information is accruing in public databases. Genome browsers such as Ensembl are needed to organize and depict this information in the context of the genome. Ensembl provides an open source gene set based on experimental evidence for over 30 species, the majority of which are vertebrates. Genes and annotation are accessible through the Ensembl browser (http://www.ensembl.org), and through direct queries of its databases using the Perl API (Application Programme Interface), MySQL or BioMart.