Resistance management: the stable zone strategy

The different strategies of insecticide resistance management that have been formulated so far consist of delaying the appearance and spread of resistance genes. In this paper, we propose a strategy that can be used even if resistance genes are already present. This strategy consists of applying insecticides in an area smaller than a certain critical size, so that gene flow from the untreated area, combined with the fitness cost of the resistance genes, prevents its frequency reaching high equilibrium value. A two-locus model was analysed numerically to determine population densities at equilibrium as a function of selection coefficients (insecticide selection, fitness costs of resistance genes and dominances), gene flow and size of the treated area. This model indicates that there is an optimal size for the treated area where a minimal and stable density reach equilibrium, and where resistance genes cannot invade. This resistance management strategy seems applicable to a large variety of field situations, but eventually it may encounter obstacles due to a modifier which reduces the fitness costs of resistance genes.     

Copurification of P6, MRP8, and MRP14 from Human Granulocytes and Separation of Individual Proteins

A method is described for purification of P6, MRP8, and MRP14, three calcium-binding proteins assigned to the S100 protein family. The purification procedure included preparation of human granulocytes, ammonium sulfate precipitation, and anion-exchange chromatography and resulted in the copurification of P6, MRP8, and MRP14. Individual proteins were separated by either preparative isoelectric focusing or preparative SDS–PAGE. The procedure was carried out in the course of 4 days and yielded several milligrams of essentially pure P6, MRP8, and MRP14 in either native or denatured form.     

pH homeostasis and ATP synthesis: studies of two processes that necessitate inward proton translocation in extremely alkaliphilic Bacillus species

Alkaliphilic Bacillus species that are isolated from nonmarine, moderate salt, and moderate temperature environments offer the opportunity to explore strategies that have developed for solving the energetic challenges of aerobic growth at pH values between 10 and 11. Such bacteria share many structural, metabolic, genomic, and regulatory features with nonextremophilic species such as Bacillus subtilis. Comparative studies can therefore illuminate the specific features of gene organization and special features of gene products that are homologs of those found in non-extremophiles, and potentially identify novel gene products of importance in alkaliphily. We have focused our studies on the facultative alkaliphile Bacillus firmus OF4, which is routinely grown on malate-containing medium at either pH 7.5 or 10.5. Current work is directed toward clarification of the characteristics and energetics of membrane-associated proteins that must catalyze inward proton movements. One group of such proteins are the Na⁺/H⁺ antiporters that enable cells to adapt to a sudden upward shift in pH and to maintain a cytoplasmic pH that is 2–2.3 units below the external pH in the most alkaline range of pH for growth. Another is the proton-translocating ATP synthase that catalyzes robust production of ATP under conditions in which the external proton concentration and the bulk chemiosmotic driving force are low. Three gene loci that are candidates for Na⁺/H⁺ antiporter encoding genes with roles in Na⁺- dependent pH homeostasis have been identified. All of them have homologs in B. subtilis, in which pH homeostasis can be carried out with either K⁺ or Na⁺. The physiological importance of one of the B. firmus OF4 loci, nhaC, has been studied by targeted gene disruption, and the same approach is being extended to the others. The atp genes that encode the alkaliphile's F₁F_O-ATP synthase are found to have interesting motifs in areas of putative importance for proton translocation. As an initial step in studies that will probe the importance and possible roles of these motifs, the entire atp operon from B. firmus OF4 has been cloned and functionally expressed in an Escherichia coli mutant that has a full deletion of its atp genes. The transformant does not exhibit growth on succinate, but shows reproducible, modest increases in the aerobic growth yields on glucose as well as membrane ATPase activity that exhibits characteristics of the alkaliphile enzyme. Received: January 22, 1998 / Accepted: February 16, 1998     

Prepared Bed Land Treatment of Soils Containing Diesel and Crude Oil Hydrocarbons

An ex situ, field-scale, prepared bed land treatment unit (LTU) was used to bio-remediate soils containing petroleum hydrocarbons. Two soils were treated in side-by-side units to compare performance: (1) a clayey silt containing crude oil hydrocarbons from releases 30 to 40 years ago and (2) a silty sand containing diesel fuel hydrocarbons from a leak about three years prior to the bioremediation. The effectiveness of the bioremediation in the LTU was evaluated over a period of 18 months. The results indicated that: (1) prepared bed bioremediation reduced the hydrocarbon concentration, mobility, and relative toxicity in the soil with the diesel fuel, and (2) chemical bioavailability appeared to limit bioremediation of the soil containing the crude oil hydrocarbons. Although the soils containing the crude oil hydrocarbons contained an average of 10,000?mg TPH/kg dry soil, these soils had limited hydrocarbon availability, nontoxic conditions, and low potential for chemical migration. For the soils containing the diesel fuel, active prepared bed bioremediation of about 15 weeks was adequate to reach an environmentally acceptable endpoint. At that time, there was little further TPH loss, no Microtox^TM toxicity, and limited hydrocarbon mobility.     

Hydration effects on physiological strain of horses during exercise-heat stress

This study examined the effects ofhyperhydration, exercise-induced dehydration, and oral fluidreplacement on physiological strain of horses during exercise-heatstress. On three occasions, six horses completed a 90-min exerciseprotocol (50% maximal O₂ uptake,34.5°C, 48% relative humidity) divided into two 45-min periods(exercise I andexercise II) with a 15-min recoverybetween exercise bouts. In random order, horses receivedno fluid (NF), 10 liters of water (W), or a carbohydrate-electrolytesolution (CE) 2 h before exercise and between exercise bouts. Compared with NF, preexercise hyperhydration (W and CE) did not alter heart rate, cardiac output (), stroke volume (SV), corebody temperature, sweating rate (SR), or sweating sensitivity duringexercise I. In contrast, afterexercise II, exercise-induceddehydration in NF (decrease in body mass: NF, 5.6 ± 0.8%; W, 1.1 ± 0.4%; CE, 1.0 ± 0.2%) resulted in greater heat storage,with core body temperature ~1.0°C higher compared with W and CE.In exercise II, the greater thermalstrain in NF was associated with significant(P < 0.05) decreases in (10 ± 2%), SV (9 ± 3%), SR, and sweatingsensitivity. We concluded that 1)preexercise hyperhydration provided no thermoregulatory advantage;2) maintenance of euhydration byoral fluid replacement (~85% of sweat fluid loss) during exercise inthe heat was reflected in higher , SV, and SR withdecreased heat storage; and 3) W oran isotonic CE solution was equally effective in reducing physiological strain associated with exercise-induced dehydration and heat stress.

     

In vitro stem elongation of sweet pepper in media containing 24-epi-brassinolide

In vitro regeneration of sweet pepper (Capsicum annuum L. cvs Jupiter and Pimiento Perfection) has been performed via direct organogenesis. The resulting shoot-buds were placed on media containing 24-epi-brassinolide (EBR) 0.1 μM, a plant steroid lactone, in the presence or absence of zeatin 9.1 μM plus GA3 5.2 μM for further stem elongation. Different responses to these treatments were recorded depending upon the protocols used and the genotypes tested. It appears that EBR does not always act directly on stem elongation but may be an elicitor and/or an enhancer of elongation in concert with endogenous and other exogenously added growth regulators. Elongated shoots were easily rooted with alpha-naphtalenacetic acid 0.5 μM (0.1 mgl-1) and transfered to soil, and following acclimation were taken to maturity in the greenhouse. This revised version was published online in June 2006 with corrections to the Cover Date.     

Susceptibility of Paulownia elongata to Agrobacterium and production of transgenic calli and hairy roots by in vitro inoculation

Susceptibility of Paulownia elongata S.Y. Hu (princess tree) to Agrobacterium tumefaciens and A. rhizogenes was demonstrated by inoculating in vitro shoots. Shoots had a gall formation frequency of ≥83% when inoculated with any of three A. tumefaciens strains (542, A281, or C58). Timing of gall appearance and type of callus proliferation differed among A. tumefaciens strains. Rapidly proliferating callus was produced from explants that were inoculated with A. tumefaciens. Hairy roots were produced directly from wound sites on 33% of shoots inoculated with A. rhizogenes strain R1601. Rapidly growing detached roots were produced from explants that were inoculated with A. rhizogenes. Opine analyses demonstrated the expression of foreign genes in proliferating galls/hairy roots shortly after emergence from wound sites and in callus and roots after 12 weeks of in vitro culture. Southern analyses demonstrated the presence of tDNA in long-term callus and root cultures. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Drosophila Gene for Antizyme Requires Ribosomal Frameshifting for Expression and Contains an Intronic Gene for snRNP Sm D3 on the Opposite Strand

Previously, a Drosophila melanogaster sequence with high homology to the sequence for mammalian antizyme (ornithine decarboxylase antizyme) was reported. The present study shows that homology of this coding sequence to its mammalian antizyme counterpart also extends to a 5′ open reading frame (ORF) which encodes the amino-terminal part of antizyme and overlaps the +1 frame (ORF2) that encodes the carboxy-terminal three-quarters of the protein. Ribosomes shift frame from the 5′ ORF to ORF2 with an efficiency regulated by polyamines. At least in mammals, this is part of an autoregulatory circuit. The shift site and 23 of 25 of the flanking nucleotides which are likely important for efficient frameshifting are identical to their mammalian homologs. In the reverse orientation, within one of the introns of the Drosophila antizyme gene, the gene for snRNP Sm D3 is located. Previously, it was shown that two closely linked P-element transposon insertions caused the gutfeeling phenotype of embryonic lethality and aberrant neuronal and muscle cell differentiation. The present work shows that defects in either snRNP Sm D3 or antizyme, or both, are likely causes of the phenotype.