The isolation and characterization of bacteriophages infecting obligately thermophilic strains of Bacillus

Twenty-four thermophilic bacteriophages have been isolated from diverse sources such as compost, soil, silage and rotting straw. Although considerable individual host specificity was observed, the phages were able to infect most of the major taxonomic groups of Bacillus thermophiles. The phages varied considerably in morphology and size; the phage heads were either cylindrical or polyhedral with tails varying in length between 15 and 500 nm. Most of the phages were stable at 50 degrees C for 4-5 h but at 70 degrees C the plaque-forming units decreased by between 10(2)- and 10(7)-fold in 2 h. The DNA of morphologically similar phages was examined by restriction enzyme analysis, and some differences in the DNA fragment patterns were found. Efficiency of plating data indicated that 'B. caldotenax' has a restriction and modification system. These phages may be valuable for the study of the genetics of thermophilic bacilli: transduction of 'B. caldotenax' and 'B. caldovelox' by phage JS017 has been observed.     

Endogenous ABA maintains shoot growth in tomato independently of effects on plant water balance: evidence for an interaction with ethylene

To examine whether the reduced shoot growth of abscisic acid (ABA)-deficient mutants of tomato is independent of effects on plant water balance, flacca and notabilis were grown under controlled-humidity conditions so that their leaf water potentials were equal to or higher than those of well-watered wild-type plants throughout development. Most parameters of shoot growth remained markedly impaired and root growth was also greatly reduced. Additional experiments with flacca showed that shoot growth substantially recovered when wild-type levels of ABA were restored by treatment with exogenous ABA, even though improvement in leaf water potential was prevented. The ability of applied ABA to increase growth was greatest for leaf expansion, which was restored by 75%. The ethylene evolution rate of growing leaves was doubled in flacca compared to the wild type and treatment with silver thiosulphate to inhibit ethylene action partially restored shoot growth. The results demonstrate that normal levels of endogenous ABA are required to maintain shoot development, particularly leaf expansion, in well-watered tomato plants, independently of effects on plant water balance. The impairment of shoot growth caused by ABA deficiency is at least partly attributable to ethylene.     

Endogenous opioid peptides: do they mediate the acute antihypertensive action of clonidine in humans?

The involvement of endogenous opioid peptides in the antihypertensive action of acutely administered clonidine, a centrally acting adrenergic agonist, was studied in humans. Eight hypertensive subjects received clonidine 0.2 mg orally, naloxone 8 mg i.v. followed by a 0.13 mg/min infusion, and both drugs together on separate days. Clonidine resulted in a significant decrease in mean blood pressure, which was not affected by concomitant treatment with naloxone. Naloxone alone or with clonidine caused significant elevations in plasma aldosterone, not mediated by increased plasma renin activity. Plasma beta-endorphin was not increased after clonidine administration. In humans, the antihypertensive effects of acute clonidine administration do not appear to be mediated by the release or action of endogenous opioids.     

Effects of urbanisation on disease prevalence and age structure in blackbird Turdus merula populations

Despite increasing interest in urban ecology most attention has focussed on describing changes in assemblage composition and structure along urbanisation gradients, whilst relatively little research has focussed on the mechanisms behind these changes. Ecological theory predicts that alterations in biotic interactions are particularly likely to arise, especially with regard to disease risk. Here, we report on differences in prevalence of avian malaria and tick infection and intensity in 11 paired urban and rural blackbird Turdus merula populations from across the western Palearctic. We find large and consistent reductions in tick prevalence and intensity in urban areas. There are also large reductions in the prevalence of avian malaria in many, but not all, urban areas. The proportion of first year birds in urban populations is significantly lower than that in rural ones, and across the more natural rural sites southerly populations contain fewer first years than northern ones. These patterns are expected to arise if survival rates are higher in urban areas, and are negatively correlated with latitude.     

A new approach to extending the wheat marker pool by anchored PCR amplification of compound SSRs

A study was undertaken to determine the utility in bread wheat of anchored PCR for the development of single locus SSR markers targeted at compound repeat motifs. In anchored PCR, microsatellite amplification is achieved using a single primer complementary to the flanking sequence, and one which anchors to the repeat junction of the compound SSR. The recovery rate of useable markers was found to be similar (43%) to that reported for conventionally generated SSRs. Thus, anchored PCR can be used to reduce the costs of marker development, since it requires that only half the number of primers be synthesised. Where fluorescence-based platforms are used, marker deployment costs are lower, since only the anchoring primers need to be labelled. In addition, anchored PCR improves the recovery of useful markers, as it allows assays to be generated from microsatellite clones with repeat sequences located close to their ends, a situation where conventional PCR amplification fails as two flanking primers cannot be designed. Strategies to permit the large-scale development of compound SSR markers amplified by anchored PCR are discussed.Communicated by P. Langridge     

Purification of Monoclonal Antibodies Using High Performance Liquid Chromatography (HPLC)

Recent increases in the ability to detect low levels of immunofluorescence have shown the need for highly purified primary immunoreagents. There are now reports of purification of monoclonal antibodies using HPLC with reverse phase columns. In this study we have utilized standard size exclusion HPLC to purify both biotinylated and non-biotinylated monoclonal antibodies from hybridoma culture supernatants. Results indicated that both biotinylated and non-biotinylated monoclonal antibodies retained their antigen binding capacity after purification, and were not different in this capacity from commercially available, affinity purified reagents. These findings indicate that size exclusion HPLC may be used in the purification of biologically active monoclonal antibodies, and suggest that this technique may be used in the large scale production of antibodies and their fragments, in antibody purification from ascites fluid, and in antisera quality control.     

Canalization of Gene Expression and Domain Shifts in the Drosophila Blastoderm by Dynamical Attractors

The variation in the expression patterns of the gap genes in the blastoderm of the fruit fly Drosophila melanogaster reduces over time as a result of cross regulation between these genes, a fact that we have demonstrated in an accompanying article in PLoS Biology (see Manu et al., doi:10.1371/journal.pbio.1000049). This biologically essential process is an example of the phenomenon known as canalization. It has been suggested that the developmental trajectory of a wild-type organism is inherently stable, and that canalization is a manifestation of this property. Although the role of gap genes in the canalization process was established by correctly predicting the response of the system to particular perturbations, the stability of the developmental trajectory remains to be investigated. For many years, it has been speculated that stability against perturbations during development can be described by dynamical systems having attracting sets that drive reductions of volume in phase space. In this paper, we show that both the reduction in variability of gap gene expression as well as shifts in the position of posterior gap gene domains are the result of the actions of attractors in the gap gene dynamical system. Two biologically distinct dynamical regions exist in the early embryo, separated by a bifurcation at 53% egg length. In the anterior region, reduction in variation occurs because of stability induced by point attractors, while in the posterior, the stability of the developmental trajectory arises from a one-dimensional attracting manifold. This manifold also controls a previously characterized anterior shift of posterior region gap domains. Our analysis shows that the complex phenomena of canalization and pattern formation in the Drosophila blastoderm can be understood in terms of the qualitative features of the dynamical system. The result confirms the idea that attractors are important for developmental stability and shows a richer variety of dynamical attractors in developmental systems than has been previously recognized.