Diurnal patterns of water use in Eucalyptus victrix indicate pronounced desiccation-rehydration cycles despite unlimited water supply

Knowledge about nocturnal transpiration (E(night)) of trees is increasing and its impact on regional water and carbon balance has been recognized. Most of this knowledge has been generated in temperate or equatorial regions. Yet, little is known about E(night) and tree water use (Q) in semi-arid regions. We investigated the influence of atmospheric conditions on daytime (Q(day)) and nighttime water transport (Q(night)) of Eucalyptus victrix L.A.S. Johnson & K.D. Hill growing over shallow groundwater (not >1.5 m in depth) in semi-arid tropical Australia. We recorded Q(day) and Q(night) at different tree heights in conjunction with measurements of stomatal conductance (g(s)) and partitioned E(night) from refilling processes. Q of average-sized trees (200-400 mm diameter) was 1000-3000 l month(-1), but increased exponentially with diameter such that large trees (>500 mm diameter) used up to 8000 l month(-1). Q was remarkably stable across seasons. Water flux densities (J(s)) varied significantly at different tree heights during day and night. We show that g(s) remained significantly different from zero and E(night) was always greater than zero due to vapor pressure deficits (D) that remained >1.5 kPa at night throughout the year. Q(night) reached a maximum of 50% of Q(day) and was >0.03 mm h(-1) averaged across seasons. Refilling began during afternoon hours and continued well into the night. Q(night) eventually stabilized and closely tracked D(night). Coupling of Q(night) and D(night) was particularly strong during the wet season (R2?=?0.95). We suggest that these trees have developed the capacity to withstand a pronounced desiccation-rehydration cycle in a semi-arid environment. Such a cycle has important implications for local and regional hydrological budgets of semi-arid landscapes, as large nighttime water fluxes must be included in any accounting.     

Semiochemicals of the common bed bug,Cimex lectularius L. (Hemiptera: Cimicidae), and their potential for use in monitoring and control

The recent resurgence of the common bed bug, Cimex lectularius L., has driven an increase in research into the biology and behaviour of this pest. Current control is reliant on the application of insecticides, but, owing to the development of insecticide resistance, there is a need for new tools and techniques. Semiochemicals (behaviour‐ and physiology‐modifying chemicals) could be exploited for management of bed bugs. The aim of this review was to evaluate studies undertaken in bed bug chemical ecology to date, with particular reference to how the research could be exploited for monitoring and control. Bed bugs, like many other insects, have a complex olfactory system. Recent studies have characterised the olfactory sensilla, located on the terminal segment of the antennae, to functional classes by electrophysiological screening. Behavioural studies have revealed the presence of an alarm pheromone and potential airborne aggregation semiochemicals, but it is not yet understood if bed bugs use a sex pheromone during mating. Host location cues have been investigated, and carbon dioxide has been found to be highly attractive both in laboratory and in field studies. Recent field trials have tested blends of other potential kairomones, which have been shown to have an additive effect when used in a heated bed bug trap with carbon dioxide. The trap, which combines heat and kairomones, is the only trap currently available with proven efficacy in the field. In order for semiochemicals to be useful for bed bug management, an increased knowledge and understanding of the biology, behaviour and chemical ecology of this insect is essential. Copyright © 2010 Society of Chemical Industry     

Decomposition and nitrogen release of understorey plant residues in biological and integrated apple orchards under field conditions in New Zealand

In grassed-down apple orchards in New Zealand, the understorey vegetation is usually mown and the plant residues are returned to the orchard floors as a source of nutrients. It is, therefore, important to determine the decomposition pattern and the rate of N release from understorey plant residues. In this study, the decomposition and N release of surface-placed understorey plant residues were determined in the field and compared across treatments of grassed-down biological (BFP) and integrated fruit production (IFP) orchards in two different locations (Lincoln and Clyde) in New Zealand using the litterbag technique. At Lincoln, the field experiment was a randomised complete block design with three different treatments (two BFPs, one IFP) each with three replicates; while at Clyde, the field experiment consisted of non-replicated apple orchard plots with three treatments (two IFPs, one BFP). A comparison was also made between surface-placed and soil-buried understorey plant residues in a BFP orchard at one location. Samples of understorey plant residues collected from orchard mowings in the respective treatments were returned to the same treatment plot in litterbags and retrieved at intervals of 90 days for 360-450 days. Results showed that the single exponential decay model, Y=A₀ e^-kt, accounted significantly (PА.001) for 97-99% of the variation in the decomposition and N release patterns, which ranged from 6.0᎒^-3-9.6᎒^-3 day^-1 and 7.0᎒^-3-13.0᎒^-3 day^-1, respectively. Half-lives for C and N of residues were approximately 70-120 days and 50-110 days, respectively. Soil-buried plant residues showed more rapid decomposition and N release compared with those of surface-placed plant residues (80% vs. 54% in 90 days). In general, plant residue decomposition and N release were significantly more rapid in IFP than in BFP treatments (13.0᎒^-3 vs 7.0᎒^-3 day^-1 for N release). Overall, differences in plant residue decomposition and N release rates related to understorey plant residue quality and treeline management practices rather than the orchard system as a whole.     

Effects of Soil Matric Suction on Retention and Percolation of Bacillus Subtilis in Intact Soil Cores

Bacillus subtilis endospores (resistant to rifampicin) irrigated on the surface of intact soil cores (20 cm diameter × 8 cm length) which were equilibrated under selected suctions, i.e. 0, 0.5, 2, 5, 10 kPa, were then percolated by saturated water flow. The bacterial retention and percolation percentage were significantly correlated with the suctions. The higher retention with higher suction was explained by micropore storage, attachment to static air-water interface (AWI), and irreversible adsorption to soil particles. The bacterial percolation was mainly controlled by initial replacement of pore water storage, and following reversible detachment process. Another sensitivity experiment with four replicates using lincomycin-resistant B. subtilis at 0 and 0.5 kPa suctions revealed that small increase (0 to 0.5 kPa) in soil matric suction incurred a substantial higher level of bacterial retention. Based on our experimental results, soil matric suction was proposed as a comprehensive parameter to monitor bacterial transport and fate for animal waste disposal (irrigation) and subsurface bioremediation.     

Do psychological and physiological stressors alter the acute pain response to castration and tail docking in lambs?

Objective To investigate whether events that may be stressful to young lambs, including simulated infection or social isolation, modulate pain experienced by lambs following castration and tail docking (C/D). Study design Randomised, controlled, prospective study. Animals Fifty male lambs born to 46 second‐parity Mule ewes. Methods Lambs were allocated randomly to one of four groups, experiencing either a potential stressor or handling on day 2 after birth, followed by C/D or handling only on day 3. Quantitative sensory testing (QST) data [mechanical nociceptive thresholds (MNT), Semmes Weinstein filaments (SW), response to cold] and serum cortisol concentration were measured at time points after application of treatments to lambs on days 2 and 3 after birth. The treatment groups were LPS, injection of bacterial lipopolysaccharide IV on day 2, C/D on day 3; ISOL, isolation from the dam for 10 minutes on day 2, C/D on day 3; CAST, handling only on day 2, C/D on day 3; CONT, handled only on days 2 and 3. Results Castration and tail docking caused transient hypoalgesia as measured by MNT and SW. Simulated infection and isolation caused hyperalgesia 3 hours after application, indicated by a reduction in MNT, however they did not alter the pain response to C/D compared to lambs in the CAST group. Injection of LPS and C/D caused increased serum cortisol concentration. The magnitude of the cortisol response to C/D was not altered by prior exposure to either LPS or isolation. Conclusions and clinical relevance LPS and isolation did not modulate the response to C/D but did cause hyperalgesia. This highlights the importance of flock health management and husbandry techniques to reduce the incidence of either systemic infection or psychological stressors in young lambs.     

Association of QRS duration and survival in dogs with dilated cardiomyopathy: A retrospective study of 266 clinical cases

ObjectiveThe purpose of this study was to investigate the prognostic value of QRS duration in dogs with dilated cardiomyopathy (DCM) by studying its relationship with survival time.MethodsThe medical records of dogs diagnosed with DCM were retrospectively searched for good quality ECG tracings. The QRS duration was measured from the ECG tracing and two different models were used: binary variable (dogs were divided into 2 groups based on a QRS duration of <60 ms or ≥60 ms) and continuous variable. The survival times were analysed by the Kaplan-Meier method and Cox’s proportional hazard model.Results266 dogs met the inclusion and exclusion criteria. A QRS duration ≥60 ms was associated with a reduced survival time compared to those with a QRS duration <60 ms (Hazard Ratio of 1.34, 95% CI 1.05–1.71, P = 0.02). When considered as a continuous variable the Hazard Ratio was 1.015 for each increase in QRS duration of 1 ms (95% CI 1.006–1.024, p = 0.001).Dogs with a QRS duration < 60 ms had a median survival time (IQ range) of 25 weeks (97-65) and dogs with a QRS duration ≥60 ms had a median survival time (IQ range) of 13 weeks (3–34).ConclusionThe measurement of QRS duration is relatively simple to perform from a surface ECG recording. A duration ≥60 ms is associated with shorter survival times in dogs with DCM, which may provide practitioners with additional prognostic information.     

Tryptophan-accelerated electron flow through proteins

Energy flow in biological structures often requires submillisecond charge transport over long molecular distances. Kinetics modeling suggests that charge-transfer rates can be greatly enhanced by multistep electron tunneling in which redox-active amino acid side chains act as intermediate donors or acceptors. We report transient optical and infrared spectroscopic experiments that quantify the extent to which an intervening tryptophan residue can facilitate electron transfer between distant metal redox centers in a mutant Pseudomonas aeruginosa azurin. Cu(I) oxidation by a photoexcited Re(I)-diimine at position 124 on a histidine(124)-glycine(123)-tryptophan(122)-methionine(121) beta strand occurs in a few nanoseconds, fully two orders of magnitude faster than documented for single-step electron tunneling at a 19 angstrom donor-acceptor distance.     

How a DNA polymerase clamp loader opens a sliding clamp

Processive chromosomal replication relies on sliding DNA clamps, which are loaded onto DNA by pentameric clamp loader complexes belonging to the AAA+ family of adenosine triphosphatases (ATPases). We present structures for the ATP-bound state of the clamp loader complex from bacteriophage T4, bound to an open clamp and primer-template DNA. The clamp loader traps a spiral conformation of the open clamp so that both the loader and the clamp match the helical symmetry of DNA. One structure reveals that ATP has been hydrolyzed in one subunit and suggests that clamp closure and ejection of the loader involves disruption of the ATP-dependent match in symmetry. The structures explain how synergy among the loader, the clamp, and DNA can trigger ATP hydrolysis and release of the closed clamp on DNA.