Identification and disruption of bacteria associated with sheep scab mites-novel means of control?

Psoroptes ovis mites, which cause psoroptic mange (sheep scab), were investigated to identify potential bacterial targets for endosymbiont control of sheep scab. In addition, transmission of bacteria to the sheep skin was investigated through the characterisation of bacteria present in P. ovis faecal trails and on the fleece environment by internal transcribed spacer (ITS) sequencing. A diverse range of bacteria was identified in addition to a potential endosymbiont candidate, Comamonas sp, which was detected in P. ovis by both ITS PCR and endosymbiont-specific PCR. Disruption of these bacteria within P. ovis, through the use of antibiotics, was explored; with significant reduction in mean mite survival when administered antibiotic diets compared with controls (LR4 = 23.12, P < 0.001). The antibiotic treatments also significantly affected the bacterial density (CFU/mite) within P. ovis, indicating that mite survival may be linked to the bacterial communities that they harbour. Although antibiotics are not suitable for practical application, these results suggest disrupting bacteria associated with P. ovis should be further investigated for novel control.

Wheat bulb fly (Delia coarctata, Fallén, Diptera: Anthomyiidae) larval response to hydroxamic acid constituents of host-plant root exudates.

Wheat bulb fly (WBF, Delia coarctata, Fallén, Diptera: Anthomyiidae) is a pest of commercial importance in wheat, barley and rye, with attacked crops failing to produce full potential yields. Females do not oviposit in association with a host-plant; therefore, prompt location of a suitable host is critical to the survival of the newly hatched larvae. The objective of this study was to conduct choice test bioassays to assess the attraction of WBF larvae to specific chemical constituents of WBF host-plant root exudates, the hydroxamic acids DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) and MBOA (6-methoxy-benzoxazolin-2-one). The larval response to four concentrations of each test compound was assessed in arena bioassays. Analysis using a Rayleigh test of uniformity of the final resting positions of larvae in response to these chemicals indicated attraction. These results go some way to explaining the mechanisms by which WBF larvae locate host plants, giving the potential to develop semiochemical based control strategies.

Behavioural response of wheat bulb fly (Delia coarctata, Diptera: Anthomyiidae) larvae to the primary plant metabolite carbon dioxide.

Wheat bulb fly (WBF) larvae use chemotaxis to orientate towards host-plant root exudates. This study aimed to investigate the role of the primary plant metabolite carbon dioxide (CO2) in host-plant location by WBF. Arena based behavioural experiments were used to identify whether CO2 induced chemotaxis (directional movement in response to a chemical stimulus) or kinesis (non-directional movement in response to a stimulus) from WBF larvae. No chemotactic response was observed when larvae were presented to a point source of CO2. However, elevated levels of CO2 induced kinesis, with both track length and tortuosity (number of twists and turns in the movement path) increasing at elevated CO2 levels of 1000-2000 ppm, demonstrating increased searching behaviour. Soil emission of CO2 was quantified to compare soil levels with those identified as eliciting behavioural effects on the larvae. Samples removed from soil gave a mean CO2 concentration of 557 (±46) ppm, which is lower than the lowest concentration of CO2 found to induce a behavioural response and higher than the lowest CO2 concentration tested, which was found not to alter behaviour. It is proposed that increased CO2 concentrations in the soil act as a behavioural trigger, inducing intensive searching of an area by WBF larvae. This increases the likelihood of finding more host-specific identifiers, such as secondary metabolites when near a potential host-plant.

Impaired long-term potentiation in the prefrontal cortex of Huntington's disease mouse models: rescue by D1 dopamine receptor activation.

BACKGROUND: The introduction of gene testing for Huntington's disease (HD) has enabled the neuropsychiatric and cognitive profiling of human gene carriers prior to the onset of overt motor and cognitive symptoms. Such studies reveal an early decline in working memory and executive function, altered EEG and a loss of striatal dopamine receptors. Working memory is processed in the prefrontal cortex and modulated by extrinsic dopaminergic inputs. OBJECTIVE: We sought to study excitatory synaptic function and plasticity in the medial prefrontal cortex of mouse models of HD. METHODS: We have used 2 mouse models of HD, carrying 89 and 116 CAG repeats (corresponding to a preclinical and symptomatic state, respectively) and performed electrophysiological field recording in coronal slices of the medial prefrontal cortex. RESULTS: We report that short-term synaptic plasticity and long-term potentiation (LTP) are impaired and that the severity of impairment is correlated with the size of the CAG repeat. Remarkably, the deficits in LTP and short-term plasticity are reversed in the presence of a D(1) dopamine receptor agonist (SKF38393). CONCLUSION: In a previous study, we demonstrated that a deficit in long-term depression (LTD) in the perirhinal cortex could also be reversed by a dopamine agonist. These and our current data indicate that inadequate dopaminergic modulation of cortical synaptic function is an early event in HD and may provide a route for the alleviation of cognitive dysfunction.

Role of CO2 in the formation of gold deposits.

Much of global gold production has come from deposits with uneconomic concentrations of base metals, such as copper, lead and zinc. These 'gold-only' deposits are thought to have formed from hot, aqueous fluids rich in carbon dioxide, but only minor significance has been attached to the role of the CO2 in the process of gold transport. This is because chemical bonding between gold ions and CO2 species is not strong, and so it is unlikely that CO2 has a direct role in gold transport. An alternative indirect role for CO2 as a weak acid that buffers pH has also appeared unlikely, because previously inferred pH values for such gold-bearing fluids are variable. Here we show that such calculated pH values are unlikely to record conditions of gold transport, and propose that CO2 may play a critical role during gold transport by buffering the fluid in a pH range where elevated gold concentration can be maintained by complexation with reduced sulphur. Our conclusions, which are supported by geochemical modelling, may provide a platform for new gold exploration methods.

Altered free radical metabolism in acute mountain sickness: implications for dynamic cerebral autoregulation and blood-brain barrier function.

We tested the hypothesis that dynamic cerebral autoregulation (CA) and blood-brain barrier (BBB) function would be compromised in acute mountain sickness (AMS) subsequent to a hypoxia-mediated alteration in systemic free radical metabolism. Eighteen male lowlanders were examined in normoxia (21% O(2)) and following 6 h passive exposure to hypoxia (12% O(2)). Blood flow velocity in the middle cerebral artery (MCAv) and mean arterial blood pressure (MAP) were measured for determination of CA following calculation of transfer function analysis and rate of regulation (RoR). Nine subjects developed clinical AMS (AMS+) and were more hypoxaemic relative to subjects without AMS (AMS-). A more marked increase in the venous concentration of the ascorbate radical (A(*-)), lipid hydroperoxides (LOOH) and increased susceptibility of low-density lipoprotein (LDL) to oxidation was observed during hypoxia in AMS+ (P < 0.05 versus AMS-). Despite a general decline in total nitric oxide (NO) in hypoxia (P < 0.05 versus normoxia), the normoxic baseline plasma and red blood cell (RBC) NO metabolite pool was lower in AMS+ with normalization observed during hypoxia (P < 0.05 versus AMS-). CA was selectively impaired in AMS+ as indicated both by an increase in the low-frequency (0.07-0.20 Hz) transfer function gain and decrease in RoR (P < 0.05 versus AMS-). However, there was no evidence for cerebral hyper-perfusion, BBB disruption or neuronal-parenchymal damage as indicated by a lack of change in MCAv, S100beta and neuron-specific enolase. In conclusion, these findings suggest that AMS is associated with altered redox homeostasis and disordered CA independent of barrier disruption.

3D-printed poly(vinylidene fluoride)/carbon nanotube composites as a tunable, low-cost chemical vapour sensing platform.

We report the production of flexible, highly-conductive poly(vinylidene fluoride) (PVDF) and multi-walled carbon nanotube (MWCNT) composites as filament feedstock for 3D printing. This account further describes, for the first time, fused deposition modelling (FDM) derived 3D-printed objects with chemiresistive properties in response to volatile organic compounds. The typically prohibitive thermal expansion and die swell characteristics of PVDF were minimized by the presence of MWCNTs in the composites enabling straightforward processing and printing. The nanotubes form a dispersed network as characterized by helium ion microscopy, contributing to excellent conductivity (∼3 × 10-2 S cm-1). The printed composites contain little residual metal particulate relative to parts from commercial PLA-nanocomposite material visualized by micro-X-ray computed tomography (µ-CT) and corroborated with thermogravimetric analysis. Printed sensing strips, with MWCNT loadings up to 15% mass, function as reversible vapour sensors with the strongest responses arising with organic compounds capable of readily intercalating and subsequently swelling the PVDF matrix (acetone and ethyl acetate). A direct correlation between MWCNT concentration and resistance change was also observed, with larger responses (up to 161% after 3 minutes) being generated with decreased MWCNT loadings. These findings highlight the utility of FDM printing in generating low-cost sensors that respond strongly and reproducibly to target vapours. Furthermore, the sensors can be easily printed in different geometries, expanding their utility to wearable form factors. The proposed formulation strategy may be tailored to sense diverse sets of vapour classes through structural modification of the polymer backbone and/or functionalization of the nanotubes within the composite.

The effect of low dose recombinant human growth hormone replacement on regional fat distribution, insulin sensitivity, and cardiovascular risk factors in hypopituitary adults.

GH deficiency is associated with increased cardiovascular morbidity, which may be determined by alterations in vascular risk factors. We report the effect of partially treated hypopituitarism and subsequent GH replacement (mean dose, 0.2 IU/kg.week) on putative cardiovascular risk factors in 22 nondiabetic hypopituitary subjects in a 6-month, double blind, controlled study (active/placebo ratio, 11:11). All patients were subsequently treated with GH for a further 6 months. Total fat, percent body fat, and central fat were measured by dual energy x-ray absorptiometry. The hypopituitary patients had increased percent fat (P = 0.03) and central fat (P < 0.01) compared with body mass index-matched controls. Before GH treatment, fasting (total) and specific insulin positively correlated with body mass index (P = 0.02 and P < 0.001, respectively), waist/hip ratio (P = 0.05 and P = 0.01), and central fat (P = 0.03 and P = 0.003). Specific insulin and insulin sensitivity (IS), calculated by homeostatic model of assessment, were related to total fat (P < 0.001 and P = 0.02). GH treatment for 6 months led to a reduction in total fat (P < 0.02), percent fat (P = 0.002), central fat (P = 0.012), waist/hip ratio (P < 0.05), total cholesterol (P = 0.03), and apolipoprotein-B (P = 00001), as well as a decrease in the IS from 36.9% (range, 12-100%) to 25% (range, 2.5-55%; P = 0.0002). This was paralleled by a rise in fasting (total) and specific insulin (P = 0.016 and P = 0.002). The degree of correlation among indices of IS, body composition, and fat distribution increased after GH treatment. Fasting plasma glucose rose significantly, but was within the reference range. During 12 months of GH therapy, a significant increase in serum lipoprotein-(a) was observed (P < 0.05). Although GH has beneficial effects on central adiposity and lipid fractions, it is also associated with a decrease in IS; these effects may vary between individuals.

Interrelationships among three measures of preference for cognitive style based on hemisphere specialization theory.

Right and left cerebral hemisphere and limbic scores derived from the Herrmann Brain Dominance Profile were correlated with left, right, and integrated scores from the Torrance-Reynolds Your Style of Learning and Thinking and four cognitive style scores from the Kolb Learning Style Inventory. Coefficients from 40 students in occupational therapy indicated low moderate positive relationships between like-named hemisphere scores, lack of significant relationships between cognitive style and two independent measures of hemispheric preference, and relative independence of preferred hemisphere mode as well as relative independence between cerebral and limbic systems. The data are interpreted as requiring cautious concern about the validity of these measures by potential users.

Multivariate analyses of cognitive and cognitive style variables based on hemisphere specialization theory predictive of success in a college developmental studies program.

Right and left cerebral hemisphere and limbic scores derived from the Herrmann Brain Dominance Profile, Scholastic Aptitude Test Verbal and Mathematics scores, and High School Grade Point Average were correlated with grades in college developmental courses in reading, English, and mathematics for 146 students. Pearson correlations ranged from -.27 to .42. Multiple correlations with seven predictors ranged from .45 to .55, and from .14 to .37 for the profile scores alone. Discriminant analyses yielded hit-rates (predictive of classification of success and failure/actual classification) of 69%/72% in Reading, 76%/75% in English, and 66%/71% in Mathematics.

The effect of CO2 on the speciation of bromine in low-temperature geological solutions: an XANES study.

CO(2)-rich solutions are common in geological environments. An XANES (X-ray absorption near-edge structure) study of Br in CO(2)-bearing synthetic fluid inclusions has revealed that Br exhibits a strong pre-edge feature at temperatures from 298 to 423 K. Br in CO(2)-free solutions does not show such a feature. The feature becomes smaller and disappears as temperature increases, but reappears when temperature is reduced. The size of the feature increases with increasing X(CO(2)) in the fluid inclusion, where X(CO(2)) is the mole fraction of CO(2) in the solution [n(CO(2))/(n(CO(2)) + n(H(2)(O)) + n(RbBr)); n indicates the number of moles]. The pre-edge feature is similar to that shown by covalently bonded Br, but observed and calculated concentrations of plausible Br-bearing covalent compounds (Br(2), CH(3)Br and HBr) are vanishingly small. An alternative possibility is that CO(2) affects the hydration of Br sufficiently that the charge density changes to favour the 1s-p level transitions that are thought to cause the pre-edge peak. The distance between the first two post-edge maxima in the XANES also decreases with increasing X(CO(2)). This is attributed to a CO(2)-related decrease in the polarity of the solvent. The proposed causes of the observed features are not integrated into existing geochemical models; thus CO(2)-bearing solutions could be predicted poorly by such models, with significant consequences for models of geological processes such as ore-formation and metamorphism.

Effects of kaolin particle film on Myzus persicae (Hemiptera: Aphididae) behaviour and performance.

The emergence of resistance mechanisms to, and revocation of, many insecticides used in the control of the polyphagus aphid pest, Myzus persicae (Sulzer), has increased the pressure to develop novel approaches for the control of the pest in many crops. Kaolin-based particle films provide a physical barrier against insect pests and show considerable potential for controlling M. persicae. We conducted a series of laboratory experiments to investigate the mode of action of kaolin against aphids. The material appeared to have no direct effect on M. persicae; spraying adult aphids with aqueous kaolin suspension had no significant impact on their subsequent survival or reproduction on untreated plants. Similarly, when aphids were placed on kaolin-treated host-plants (Brassica oleracea), their performance (survival, growth rate and reproduction) was not significantly different from aphids on untreated plants. However, when M. persicae were given a choice between kaolin-treated and untreated (or water solvent-treated) leaf areas, both adults and nymphs exhibited a significant preference for non-kaolin-treated host-plant material. Rejection of kaolin-treated plant material occurred very rapidly (within 20 min) and this behavioural effect may be related to the efficacy of kaolin in controlling aphids under field conditions.

Behavioral and electrophysiological response of cabbage seed weevils (Ceutorhynchus assimilis) to conspecific odor.

The responses ofCeutorhynchus assimilis Payk. (Coleoptera, Curculionidae) to the odor of overwintered and new generation weevils were studied using an olfactometer, choice tests in a laboratory cage, field tests using sticky traps baited with live weevils, and by electroantennograms (EAG's). Unmated male weevils and, to a lesser extent, female weevils of the overwintered generation were attracted to the odor of live unmated over-wintered female weevils. New generation weevils exhibited no behavioral response to conspecific odor. Male and female weevils of the overwintered generation exhibited positive EAGs to hexane extracts of overwintered female weevils, whereas EAGs of new-generation weevils of either sex were unresponsive to these extracts. This suggests that the unmated female weevils from the overwintered generation produce a volatile chemical or chemicals that attracts unmated male and female weevils. The new generation of female weevils does not produce this attractive chemical before overwintering, and male and female weevils of this generation can not detect the chemical(s) via their antennal chemoreceptors until they have undergone their overwintering period.

Spinal dysraphism: genetic relation to neural tube malformations.

The families of 207 index patients treated for spinal dysraphism at The Hospital for Sick Children were studied to discover whether the condition was aetiologically related to the classical neural tube malformation--spina bifida cystica and anencephaly. The index patients had all had a tethered conus medullaris and one or more of a variety of anomalies of the spinal cord, vertebrae, or skin overlying the vertebral column. Of 364 sibs of index patients, 9 had an encephaly and 6 spina bifida cystica, a pro-proportion of 4.12%. This approximates to the proportion of sibs affected by neural tube malformations in the London region when the index patients themselves have spina bifida or anencephaly. It is, therefore, appropriate that the mothers of children with spinal dysraphism should be offered prenatal screening for neural tube malformations.

Electroantennogram responses of the cabbage seed weevil,Ceutorhynchus assimilis, to oilseed rape,Brassica napus ssp.Oleifera, volatiles.

Electroantennograms (EAGs) were recorded from male and female cabbage seed weevils (Ceutorhynchus assimilis Payk.) in response to volatiles isolated and identified from the odor of oilseed rape (Brassica napus ssp.oleifera DC. cv. Ariana). Relatively large EAGs were obtained on stimulation with volatiles produced by the oilseed rape crop at the time when seed weevils were actively searching for host plants. Artificial rape odor without certain key volatile compounds was in most cases significantly less stimulatory than odor containing these volatiles. There were significant differences in the EAG response of the sexes ofC. assimilis to the green leaf volatiles of oilseed rape and several terpenes present in rape flower odor. The importance of the qualitative and quantitative composition of host-plant odor in host location byC. assimilis is discussed.

Effect of genetic counselling on the prevalence of Huntington's chorea.

The relative fertility of sons and daughters of patients with Huntington's chorea was found to be a little under 0.5 if they had been told of their risk of transmitting the disease before they had started their families. The effect was much the same in those who had attended the genetic clinic at The Hospital for Sick Children on a single occasion and those who had been told of their risk directly, or indirectly through the patient's spouse or family doctor, by the neurologist who was looking after their affected parent at the National Hospital for Nervous Diseases. If all offspring of patients were informed of their risk the effect on the prevalence of the disorder would be substantial, especially if the mutation rate is low and the reproductive fitness of patients in the past has been close to 1.0. Men and women at risk of developing the disease should not be seen on just one occasion, however: they need continued support by being seen regularly at a special neurological genetic clinic.

Toward development of neem-based repellents against the Scottish Highland biting midge Culicoides impunctatus.

Oil of neem, from the tree Azadirachta indica A. Juss (Meliaceae), was evaluated for repellent and antifeedant activity against Culicoides biting midges (Diptera: Ceratopogonidae), by three complementary methods with serial dilutions. Electroantennograms revealed the sensitivity of Culicoides nubeculosus (Meigen) females to neem > or = 0.10%. Culicoides impunctatus Goetghebuer females were repelled by > or = 1% in a Y-tube olfactometer, Using a membrane feeder for wild-caught parous females of C. impunctatus, the proportion blood-feeding was significantly reduced by topical applications of neem oil > or = 0.10% concentrations, with blood-feeding completely prevented by > or =1%. On the basis of these response data, we developed 2% neem-based formulations for personal protection against biting midges.