Genetic liability for gastrointestinal inflammation disorders and association with gastrointestinal symptoms in children with and without autism

Children with autism spectrum disorder (ASD) have a greater prevalence of gastrointestinal (GI) symptoms than children without ASD. We tested whether polygenic scores for each of three GI disorders (ulcerative colitis, inflammatory bowel disease, and Crohn's disease) were related to GI symptoms in children with and without ASD. Using genotyping data (564 ASD cases and 715 controls) and external genome-wide association study summary statistics, we computed GI polygenic scores for ulcerative colitis (UC-PGS), inflammatory bowel disease (IDB-PGS), and Crohn's disease (CD-PGS). Multivariable logistic regression models, adjusted for genetic ancestry, were used to estimate associations between each GI-PGS and (1) ASD case-control status, and (2) specific GI symptoms in neurotypical children and separately in ASD children. In children without ASD, polygenic scores for ulcerative colitis were significantly associated with experiencing any GI symptom (adjusted odds ratio (aOR) = 1.36, 95% confidence interval (CI) = 1.03-1.81, p = 0.03) and diarrhea specifically (aOR = 5.35, 95% CI = 1.77-26.20, p = 0.01). Among children without ASD, IBD-PGS, and Crohn's PGS were significantly associated with diarrhea (aOR = 3.55, 95% CI = 1.25-12.34, p = 0.02) and loose stools alternating with constipation (aOR = 2.57, 95% CI = 1.13-6.55, p = 0.03), respectively. However, the three PGS were not associated with GI symptoms in the ASD case group. Furthermore, polygenic scores for ulcerative colitis significantly interacted with ASD status on presentation of any GI symptom within a European ancestry subset (aOR = 0.42, 95% CI = 0.19-0.88, p = 0.02). Genetic risk factors for some GI symptoms differ between children with and without ASD. Furthermore, our finding that increased genetic risks for GI inflammatory disorders are associated with GI symptoms in children without ASD informs future work on the early detection of GI disorders.

S1P lyase inhibition prevents lung injury following high pressure-controlled mechanical ventilation in aging mice

Ventilator-induced Lung Injury (VILI) is characterized by hypoxia, inflammatory cytokine influx, loss of alveolar barrier integrity, and decreased lung compliance. Aging influences lung structure and function and is a predictive factor in the severity of VILI; however, the mechanisms of aging that influence the progression or increased susceptibility remain unknown. Aging impacts immune system function and may increase inflammation in healthy individuals. Recent studies suggest that the bioactive sphingolipid mediator sphingosine-1-phosphate (S1P) and the enzyme that degrades it S1P lyase (SPL) may be involved in lung pathologies including acute lung injury. It is unknown whether aging influences S1P and SPL expression that have been implicated in lung inflammation, injury, and cell apoptosis. We hypothesized that aging and injurious mechanical ventilation synergistically impair S1P levels and enhance S1P lyase (SPL) expression that amplifies alveolar barrier damage and diminishes pulmonary function. Young (2-3 mo) and old (20-25 mo) C57BL/6 mice were mechanically ventilated for 2 h using pressure-controlled mechanical ventilation (PCMV) at 45 cmH2O and 35 cmH2O, respectively. We assessed the impact of aging and PCMV on several indications of acute lung injury, immune cell recruitment, S1P levels and SPL activity. Furthermore, we evaluated the protective effects of inhibiting SPL by tetrahydroxybutylimidazol (THI) administration on the negative outcomes associated with aging and mechanical injury. PCMV exacerbated lung injury in old mice and increased neutrophil influx that was further exacerbated due to aging. SPL expression increased in the young and old ventilated mice and the old nonventilated group. THI treatment reduced several of the indicators of lung injury and resulted in elevated S1P levels in lung tissue and plasma from mice that were injured from mechanical ventilation. CD80 and CD206 activation markers of alveolar and interstitial macrophages were also influenced by THI. SPL inhibition may be a viable therapeutic approach for patients requiring mechanical ventilation by preventing or regulating the exaggerated inflammatory response and reducing lung injury.

Providers' perspectives on the clinical utility of pharmacogenomic testing in pediatric patients

Aim: To assess providers' knowledge, attitudes, perceptions, and experiences related to pharmacogenomic (PGx) testing in pediatric patients. Materials & methods: An electronic survey was sent to multidisciplinary healthcare providers at a pediatric hospital. Results: Of 261 respondents, 71.3% were slightly or not at all familiar with PGx, despite 50.2% reporting prior PGx education or training. Most providers, apart from psychiatry, perceived PGx to be at least moderately useful to inform clinical decisions. However, only 26.4% of providers had recent PGx testing experience. Unfamiliarity with PGx and uncertainty about the clinical value of testing were common perceived challenges. Conclusion: Low PGx familiarity among pediatric providers suggests additional education and electronic resources are needed for PGx examples in which data support testing in children.

Gastrointestinal Symptoms in 2- to 5-Year-Old Children in the Study to Explore Early Development

Gastrointestinal symptoms (GIS) are commonly reported in children with autism spectrum disorder (ASD). This multi-site study evaluated the prevalence of GIS in preschool-aged children with ASD/(n = 672), with other developmental delays (DD)/(n = 938), and children in the general population (POP)/(n = 851). After adjusting for covariates, children in the ASD group were over 3 times more likely to have parent-reported GIS than the POP group, and almost 2 times more likely than the DD group. Children with GIS from all groups had more behavioral and sleep problems. Within the ASD group, children with developmental regression had more GIS than those without; however, there were no differences in autism severity scores between children with and without GIS. These findings have implications for clinical management.

Insect swarms can be bound together by repulsive forces

The cohesion of insect swarms has been attributed to the fact that the resultant internal interactions of the swarming insects produce, on the average, a centrally attractive force that acts on each individual. Here it is shown how insect swarms can also be bound together by centrally forces that on the average are repulsive (outwardly directed from the swarm centres). This is predicted to arise when velocity statistics are heterogeneous (position-dependent). Evidence for repulsive forces is found in laboratory swarms of Chironomus riparius midges. In homogeneous swarms, the net inward acceleration balances the tendency of diffusion (stochastic noise) to transport individuals away from the centre of the swarm. In heterogenous swarms, turbophoresis --the tendency for individuals to migrate in the direction of decreasing kinetic energy-- is operating. The new finding adds to the growing realization that insect swarms are analogous to self-gravitating systems. By acting in opposition to central attraction (gravity), the effects of heterogeneous velocities (energies) are analogous to the effects of dark energy. The emergence of resultant forces from collective behaviours would not be possible if individual flight patterns were themselves unstable. It is shown how individuals reduce the potential for the loose of flight control by minimizing the influence of jerks to which they are subjected.

0123 Sleep Duration and Cognitive Performance on the Stroop Color-Word Task and Simple Reaction Time Task

Introduction

Studies examining sleep factors and cognition suggest that sleep impacts cognitive performance in college students. The focus of the current study was to examine normal sleep patterns in college-aged students and how their sleep affected their cognitive performance.

Methods

Participants were 51 undergraduate students (18 males), average age M=20.25 (SD=1.78) years, who wore actigraph watches to measure their sleep. After one week, participants completed the Multidimensional Assessment of Fatigue (MAF) to assess fatigue and performed a series of cognitive tasks on the computer, including the Stroop Color-Word test. Participants responded to the color of the word presented on the screen instead of the word itself. Stimuli where the color and word did not match were considered incongruent stimuli. Participants also performed a simple reaction time task, where they reacted to an “X” stimulus on the screen.

Results

Mean sleep efficiency was 82.55% (SD=5.70), mean sleep duration was 6.59 hours (SD=79.19 minutes), and the mean MAF score was 21.17 (SD= 7.64). A Pearson correlation indicated a significant negative association between sleep duration and Stroop congruent errors r(49) = -.467, p = .001. Furthermore, a Pearson correlation indicated a significant positive association between sleep duration and incongruent reaction time, r(49)= .290, p= .039 and a significant positive association between sleep duration and simple reaction time, r(49)= .277, p= .049. MAF scores were positively correlated with simple reaction times, r(49)= .376, p=.008. Sleep efficiency was not correlated with any of the cognitive measures.

Conclusion

As expected, participants’ sleep was short and inefficient. Results were expected in that participants made fewer errors with increased sleep, but, unexpectedly, reaction times also increased with more sleep. Fatigue may have played a role in this relationship. It is important to continue this research in order to learn more about sleep factors and cognitive function in college students.

Support

None

Randomized, Placebo-Controlled Trial of Ferrous Sulfate to Treat Insomnia in Children With Autism Spectrum Disorders

BACKGROUND

Insomnia and low iron stores are common in children with autism spectrum disorders, and low iron stores have been associated with sleep disturbance.

METHODS

We performed a randomized placebo-controlled trial of oral ferrous sulfate to treat insomnia in children with autism spectrum disorders and low normal ferritin levels. Twenty participants who met inclusion criteria and whose insomnia did not respond to sleep education were randomized to 3 mg/kg/day of ferrous sulfate (n = 9) or placebo (n = 11) for three months.

RESULTS

Iron supplementation was well tolerated, and no serious adverse events were reported. Iron supplementation improved iron status (+18.4 ng/mL active versus -1.6 ng/mL placebo, P = 0.044) but did not significantly improve the primary outcome measures of sleep onset latency (-11.0 minutes versus placebo, 95% confidence interval -28.4 to 6.4 minutes, P = 0.22) and wake time after sleep onset (-7.7 minutes versus placebo, 95% confidence interval -22.1 to 6.6 min, P = 0.29) as measured by actigraphy. Iron supplementation was associated with improvement in the overall severity score from the Sleep Clinical Global Impression Scale (-1.5 points versus placebo, P = 0.047). Changes in measures of daytime behavior did not differ between groups.

CONCLUSION

This trial demonstrated no improvement in primary outcome measures of insomnia in subjects treated with ferrous sulfate compared with placebo. Interpretation was limited by low enrollment.

Langevin dynamics encapsulate the microscopic and emergent macroscopic properties of midge swarms

In contrast to bird flocks, fish schools and animal herds, midge swarms maintain cohesion but do not possess global order. High-speed imaging techniques are now revealing that these swarms have surprising properties. Here, I show that simple models found on the Langevin equation are consistent with this wealth of recent observations. The models predict correctly that large accelerations, exceeding 10 g, will be common and they predict correctly the coexistence of core condensed phases surrounded by dilute vapour phases. The models also provide new insights into the influence of environmental conditions on swarm dynamics. They predict that correlations between midges increase the strength of the effective force binding the swarm together. This may explain why such correlations are absent in laboratory swarms but present in natural swarms which contend with the wind and other disturbances. Finally, the models predict that swarms have fluid-like macroscopic mechanical properties and will slosh rather than slide back and forth after being abruptly displaced. This prediction offers a promising avenue for future experimentation that goes beyond current quasi-static testing which has revealed solid-like responses.

Sleep Problems in 2- to 5-Year-Olds With Autism Spectrum Disorder and Other Developmental Delays

: media-1vid110.1542/5984243260001PEDS-VA_2018-0492Video Abstract BACKGROUND: Sleep problems can impact daytime behavior, quality of life, and overall health. We compared sleep habits in young children with autism spectrum disorder (ASD) and other developmental delays and disorders and in children from the general population (POP).

METHODS

We included 2- to 5-year-old children whose parent completed all items on the Children's Sleep Habits Questionnaire (CSHQ) in a multisite case-control study: 522 children with ASD; 228 children with other developmental delays and disorders with autism spectrum disorder characteristics (DD w/ASD); 534 children with other developmental delays and disorders without autism spectrum disorder characteristics (DD w/o ASD); and 703 POP. Multivariable analysis of variance compared CSHQ mean total score (TS) and subscale scores between groups. Logistic regression analysis examined group differences by using TS cutoffs of 41 and 48. Analyses were adjusted for covariates.

RESULTS

Mean CSHQ TS for children in each group: ASD (48.5); DD w/ASD (50.4); DD w/o ASD (44.4); and POP (43.3). Differences between children with ASD and both children with DD w/o ASD and POP were statistically significant. Using a TS cutoff of 48, the proportion of children with sleep problems was significantly higher in children in the ASD group versus DD w/o ASD and POP groups (adjusted odds ratios [95% confidence intervals]: 2.12 [1.57 to 2.87] and 2.37 [1.75 to 3.22], respectively).

CONCLUSIONS

Sleep problems are more than twice as common in young children with ASD and DD w/ASD. Screening for sleep problems is important in young children to facilitate provision of appropriate interventions.

Sleep Difficulties and Medications in Children With Autism Spectrum Disorders: A Registry Study

OBJECTIVES

Sleep difficulties are common in children with autism spectrum disorders, with wide-ranging effects on the child's daytime behavior. We reviewed data within our Autism Speaks Autism Treatment Network Registry to determine the prevalence of sleep difficulties and patterns of medication use.

METHODS

Data from 1518 children ages 4 to 10 years were analyzed to determine the number of children documented to have sleep difficulties by parent-completed questionnaires and clinician-completed forms and how these findings related to the use of sleep medications.

RESULTS

The Children's Sleep Habits Questionnaire total score was ≥41 (associated with clinically significant sleep problems in past research) in 71% of children. The prevalence of sleep diagnoses was less frequent (30% of children aged 4-10 years; P < .0001). Medications for sleep were prescribed in 46% of 4- to 10-year-olds given a sleep diagnosis. The most common medication used for sleep was melatonin followed by α-agonists, with a variety of other medications taken for sleep (anticonvulsants, antidepressants, atypical antipsychotics, and benzodiazepines). Children taking medications for sleep had worse daytime behavior and pediatric quality of life than children not taking sleep medications.

CONCLUSIONS

Parent concerns about sleep may not be reflected in the information gathered during a clinic visit, supporting the need to develop screening practice pathways for sleep in autism spectrum disorders. Furthermore, many medications taken for sleep have adverse effects, supporting the need for evidence-based interventions in this population.

Extending Lévy search theory from one to higher dimensions: Lévy walking favours the blind

A diverse range of organisms, including T cells, E. coli, honeybees, sharks, turtles, bony fish, jellyfish, wandering albatrosses and even human hunter-gatherers have movement patterns that can be approximated by Lévy walks (LW; sometimes called Lévy flights in the biological and ecological literature). These observations lend support to the 'Lévy flight foraging hypothesis' which asserts that natural selection should have led to adaptations for Lévy flight foraging, because Lévy flights can optimize search efficiencies. The hypothesis stems from a rigorous theory of one-dimensional searching and from simulation data for two-dimensional searching. The potential effectiveness of three-dimensional Lévy searches has not been examined but is central to a proper understanding of marine predators and T cells which have provided the most compelling empirical evidence for LW. Here I extend Lévy search theory from one to three dimensions. The new theory predicts that three-dimensional Lévy searching can be advantageous but only when targets are large compared with the perceptual range of the searchers, i.e. only when foragers are effectively blind and need to come into contact with a target to establish its presence. This may explain why effective blindness is a common factor among three-dimensional Lévy walkers.

Complementary and alternative medicine use in a large pediatric autism sample

BACKGROUND AND OBJECTIVE

Children and adolescents with autism spectrum disorder (ASD) often use complementary and alternative medicine (CAM), usually along with other medical care. This study aimed to determine associations of ASD diagnostic category, co-existing conditions, and use of medications with use of CAM.

METHODS

We used the Autism Speaks Autism Treatment Network patient registry, which collects information on CAM use, medical conditions, and psychotropic medication at enrollment. CAM was categorized as special diets versus "other" CAM; ASD was defined as autism, pervasive developmental disorder (PDD), or Asperger's. Gastrointestinal symptoms, seizure disorders, sleep problems, and medication use were determined from parent report. Child Behavior Checklist (CBCL) scores were used to measure behavioral symptoms. Logistic regression was used to determine associations of diagnostic category, other medical conditions, and medication use with CAM treatments, controlling for demographic characteristics.

RESULTS

Of 3413 subjects in the registry as of April 2011, 3173 had complete data on CAM use: 896 (28%) reported any use; 548 (17%), special diets; and 643 (20%), other CAM. Higher rates of CAM use were associated with gastrointestinal symptoms (odds ratio [OR] = 1.88), seizures (OR = 1.58), and CBCL total score >70 (OR = 1.29). Children with PDD (OR = 0.62), Asperger's (OR = 0.66), or using medications (0.69) had lower rates.

CONCLUSIONS

Children with ASD use more CAM when they have co-existing gastrointestinal symptoms, seizure disorders, and behavior problems. This study suggests the importance of asking about CAM use in children with ASD, especially those with complex symptoms.

Incorporating sweeps and ejections into Lagrangian stochastic models of spore trajectories within plant canopy turbulence: modeled contact distributions are heavy-tailed

ABSTRACT The turbulent dispersal of fungal spores within plant canopies is very different from that within atmospheric boundary-layers and closely analogous to dispersal within turbulent mixing-layers. The process is dominated by the presence of large coherent flow structures, high-velocity downdrafts (sweeps) and updrafts (ejections), that punctuate otherwise quiescent flow. Turbulent dispersion within plant canopies is best predicted by Lagrangian stochastic (particle-tracking) models because other approaches (e.g., diffusion models and similarity theory) are either inappropriate or invalid. Nonetheless, attempts to construct such models have not been wholly successful. Accounting for sweeps and ejections has substantially worsened rather than improved model agreement with experimental dispersion data. Here we show how this long-standing difficulty with the formulation of Lagrangian stochastic models can be overcome. The new model is shown to be in good agreement with data from a carefully controlled, well-documented wind-tunnel study of scalar dispersion within plant canopy turbulence. Equally good agreement with this data is obtained using Thomson's (1987) Gaussian model. This bolsters confidence in the application of this simple model to the prediction of spore dispersal within plant canopy turbulence. Contact distributions-the probability distribution function for the distance of viable fungal spore movement until deposition-are predicted to have "heavy" inverse power-law tails. It is known that heavy-tailed contact distributions also characterize the dispersal of spores which pass through the canopy turbulence and enter into the overlying atmospheric boundary-layer. Plant disease epidemics due to the airborne dispersal of fungal spores are therefore predicted to develop as accelerating waves over a vast range of scales-from the within field scale to intercontinental scales. This prediction is consistent with recent analyses of field and historical data for rusts in wheat. Such plant disease epidemics are shown to be governed by space-fractional diffusion equations and by Lévy flights.

Distinguishing between Lévy walks and strong alternative models

Lévy walks are a widely used but contentious model of animal movement patterns. They are contentious because they have been wrongly ascribed to some animal species through use of incorrect statistical methods and because they have not been adequately compared against strong alternative models, such as composite correlated random walks. This lack of comparison has been partly because the strong alternative models do not have simple likelihood functions. Here I show that power-spectra and the distribution of the first significant digits (the leading non-zero digits) of the step lengths can distinguish between Lévy walks and composite correlated random walks. Using these diagnostic tools, I bolster previous claims that honey bees use a movement strategy that can be approximated by Lévy walks when searching for their hive or for a food source.

Fitness-maximizing foragers can use information about patch quality to decide how to search for and within patches: optimal Levy walk searching patterns from optimal foraging theory

Optimal foraging theory shows how fitness-maximizing foragers can use information about patch quality to decide how to search within patches. It is amply supported by empirical studies. Nonetheless, the theory largely ignores the fact that foragers may need to search for patches as well as for the targets within them. Here, using an exact but simple mathematical argument, it is shown how foragers can use information about patch quality to facilitate the execution of Lévy walk movement patterns with μ = 2 at inter-patch scales. These movement patterns are advantageous when searching for patches that are not depleted or rejected once visited but instead remain profitable. The analytical results are verified by the results of numerical simulations. The findings bring forth an innovative theoretical synthesis of searching for and within patches and, suggest that foragers' memories may be adaptive under spatially heterogeneous reward schedules.

Exponential and power-law contact distributions represent different atmospheric conditions

It is well known that the dynamics of plant disease epidemics are very sensitive to the functional form of the contact distribution?the probability distribution function for the distance of viable fungal spore movement until deposition. Epidemics can take the form of a constant-velocity travelling wave when the contact distribution is exponentially bounded. Fat-tailed contact distributions, on the other hand, lead to epidemic spreads that accelerate over time. Some empirical data for contact distributions can be well represented by negative exponentials while other data are better represented by fat-tailed inverse power laws. Here we present data from numerical simulations that suggest that negative exponentials and inverse power laws are not competing candidate forms of the contact distribution but are instead representative of different atmospheric conditions. Contact distributions for atmospheric boundary-layers with stabilities ranging from strongly convective (a hot windless day time scenario) to stable stratification (a cold windy night time scenario) but without precipitation events are calculated using well-established state-of-the-art Lagrangian stochastic (particle tracking) dispersal models. Contact distributions are found to be well represented by exponentials for strongly convective conditions; a -3/2 inverse power law for convective boundary-layers with wind shear; and by a -2/3 inverse power law for stably stratified conditions.

Truncated Lévy walks are expected beyond the scale of data collection when correlated random walks embody observed movement patterns

Translating observations taken at small spatio-temporal scales into expected patterns at greater scales is a major challenge in spatial ecology because there is typically insufficient relevant information. Here, it is shown that truncated Lévy walks are the most conservative, maximally non-committal description of movement patterns beyond the scale of data collection when correlated random walks characterize observed movements and when there is partial information about landscape and behavioural heterogeneity. This provides a new conceptual basis for Lévy walks that is divorced from optimal searching theory and free from the difficulties with discerning their presence in empirical data.

Sleep and autism spectrum disorders

Sleep disorders are common in children with autism spectrum disorders and have a significant effect on daytime function and parental stress. The cornerstone of treatment is to establish the cause of the sleep concern, which is often multifactorial. Identifying and treating sleep disorders may result not only in more consolidated sleep, more rapid time to fall asleep, and avoidance of night waking but also favorably affect daytime behavior and parental stress. Targeting effective treatment strategies is dependent on understanding the underlying causes of sleep problems in children with Autism spectrum disorders, therefore further research is paramount.

Chemotaxis can provide biological organisms with good solutions to the travelling salesman problem

The ability to find good solutions to the traveling salesman problem can benefit some biological organisms. Bacterial infection would, for instance, be eradicated most promptly if cells of the immune system minimized the total distance they traveled when moving between bacteria. Similarly, foragers would maximize their net energy gain if the distance that they traveled between multiple dispersed prey items was minimized. The traveling salesman problem is one of the most intensively studied problems in combinatorial optimization. There are no efficient algorithms for even solving the problem approximately (within a guaranteed constant factor from the optimum) because the problem is nondeterministic polynomial time complete. The best approximate algorithms can typically find solutions within 1%-2% of the optimal, but these are computationally intensive and can not be implemented by biological organisms. Biological organisms could, in principle, implement the less efficient greedy nearest-neighbor algorithm, i.e., always move to the nearest surviving target. Implementation of this strategy does, however, require quite sophisticated cognitive abilities and prior knowledge of the target locations. Here, with the aid of numerical simulations, it is shown that biological organisms can simply use chemotaxis to solve, or at worst provide good solutions (comparable to those found by the greedy algorithm) to, the traveling salesman problem when the targets are sources of a chemoattractant and are modest in number (n < 10). This applies to neutrophils and macrophages in microbial defense and to some predators.

Maze-solving by chemotaxis

Here, we report on numerical simulations showing that chemotaxis will take a body through a maze via the shortest possible route to the source of a chemoattractant. This is a robust finding that does not depend on the geometrical makeup of the maze. The predictions are supported by recent experimental studies which have shown that by moving down gradients in pH , a droplet of organic solvent can find the shortest of multiple possible paths through a maze to an acid-soaked exit. They are also consistent with numerical and experimental evidence that plant-parasitic nematodes take the shortest route through the labyrinth of air-filled pores within soil to preferred host plants that produce volatile chemoattractants. The predictions support the view that maze-solving is a robust property of chemotaxis and is not specific to particular kinds of maze or to the fractal structure of air-filled channels within soils.

The Lévy flight paradigm: random search patterns and mechanisms

Over recent years there has been an accumulation of evidence from a variety of experimental, theoretical, and field studies that many organisms use a movement strategy approximated by Lévy flights when they are searching for resources. Lévy flights are random movements that can maximize the efficiency of resource searches in uncertain environments. This is a highly significant finding because it suggests that Lévy flights provide a rigorous mathematical basis for separating out evolved, innate behaviors from environmental influences. We discuss recent developments in random-search theory, as well as the many different experimental and data collection initiatives that have investigated search strategies. Methods for trajectory construction and robust data analysis procedures are presented. The key to prediction and understanding does, however, lie in the elucidation of mechanisms underlying the observed patterns. We discuss candidate neurological, olfactory, and learning mechanisms for the emergence of Lévy flight patterns in some organisms, and note that convergence of behaviors along such different evolutionary pathways is not surprising given the energetic efficiencies that Lévy flight movement patterns confer.

Optimising the success of random destructive searches: Lévy walks can outperform ballistic motions

We re-evaluate the long standing and widely held belief that ballistic movements (i.e. straight-lines movements) outperform Lévy walks when searching for targets that once located are not revisited. The belief stems from the results of analyses of one-dimensional searches, analyses which have not accounted for the fact that target numbers can be continually depleted during the search process. This is a crucial oversight because continual depletion promotes the searching efficiencies of some Lévy walks above that of ballistic motion. The continual depletion effect is not so important for two- and three-dimensional searches. Nevertheless, we show that Lévy walks and ballistic movements can be equally or almost equally effective when searching within two- and three-dimensional environments for randomly and sparsely distributed targets or when searching for targets that are occasionally concealed. We also show that Lévy walks are advantageous when searching for targets that can occasionally evade capture. These situations represent common predator-prey interactions in which predators are involved in 'imperfect destructive' searches. Our model suggests that accounting for coevolutionary arms races at the predator-prey detection/reaction scales can explain to some extent Lévy walk searching patterns of predators at larger scales. This result provides new insights into the Lévy walk movement patterns of some destructive foragers.

Does a 'turbophoretic' effect account for layer concentrations of insects migrating in the stable night-time atmosphere?

Large migrating insects, such as noctuid moths and acridoid grasshoppers, flying within the stable nocturnal boundary layer commonly become concentrated into horizontal layers. These layers frequently occur near the top of the surface temperature inversion where warm fast-moving airflows provide good conditions for downwind migration. On some occasions, a layer may coincide with a higher altitude temperature maximum such as a subsidence inversion, while on others, it may seem unrelated to any obvious feature in the vertical profile of meteorological variables. Insects within the layers are frequently orientated, either downwind or at an angle to the wind, but the mechanisms involved in both layer formation and common orientation have remained elusive. Here, we show through the results of numerical simulations that if insects are treated as neutrally buoyant particles, they tend to be advected by vertical gusts (through the 'turbophoretic' mechanism) into layers in the atmosphere where the turbulent kinetic energy has local minima. These locations typically coincide with local maxima in the wind speed and/or air temperature, and they may also provide cues for orientation. However, the degree of layering predicted by this model is very much weaker than that observed in the field. We have therefore hypothesized that insects behave in a way that amplifies the turbophoretic effect by initiating climbs or descents in response to vertical gusts. New simulations incorporating this behaviour demonstrated the formation of layers that closely mimic field observations, both in the degree of concentration in layers and the rate at which they form.

Deterministic walks with inverse-square power-law scaling are an emergent property of predators that use chemotaxis to locate randomly distributed prey

The results of numerical simulations indicate that deterministic walks with inverse-square power-law scaling are a robust emergent property of predators that use chemotaxis to locate randomly and sparsely distributed stationary prey items. It is suggested that chemotactic destructive foraging accounts for the apparent Lévy flight movement patterns of Oxyrrhis marina microzooplankton in still water containing prey items. This challenges the view that these organisms are executing an innate optimal Lévy flight searching strategy. Crucial for the emergence of inverse-square power-law scaling is the tendency of chemotaxis to occasionally cause predators to miss the nearest prey item, an occurrence which would not arise if prey were located through the employment of a reliable cognitive map or if prey location were visually cued and perfect.

The epidemiology of autism spectrum disorders

Autism spectrum disorders (ASDs) are complex, lifelong, neurodevelopmental conditions of largely unknown cause. They are much more common than previously believed, second in frequency only to mental retardation among the serious developmental disorders. Although a heritable component has been demonstrated in ASD etiology, putative risk genes have yet to be identified. Environmental risk factors may also play a role, perhaps via complex gene-environment interactions, but no specific exposures with significant population effects are known. A number of endogenous biomarkers associated with autism risk have been investigated, and these may help identify significant biologic pathways that, in turn, will aid in the discovery of specific genes and exposures. Future epidemiologic research should focus on expanding population-based descriptive data on ASDs, exploring candidate risk factors in large well-designed studies incorporating both genetic and environmental exposure data and addressing possible etiologic heterogeneity in studies that can stratify case groups and consider alternate endophenotypes.

Appetitive flight patterns of male Agrotis segetum moths over landscape scales

An analysis is presented of the first harmonic radar studies of pheromone-plume locating flights of male Agrotis segetum moths over distances of up to 500 m. Upon release most moths flew in a direction having a downwind component. The first significant changes in flight orientations occur in the immediate vicinity of a pheromone source. Moths that were initially flying downwind change course and start flying crosswind whilst those that initially flew crosswind change course and start flying upwind. It is shown that such behaviour is consistent with the adoption of an effective plume-location strategy, and conditions are identified when downwind flights would be more advantageous than crosswind ones. Additionally, some of the complex flight patterns that can arise at later times are shown to be compatible with the adoption of an optimal biased scale-free (Lévy-flight) searching strategy. It is found that disruptive doses of sex pheromone can have a marked influence upon male moth flight patterns.

Bone morphogenetic protein type 2 receptor gene therapy attenuates hypoxic pulmonary hypertension

Idiopathic pulmonary arterial hypertension (PAH) is characterized by proliferation of pulmonary vascular endothelial and smooth muscle cells causing increased vascular resistance and right heart failure. Mutations in the bone morphogenetic protein receptor type 2 (BMPR2) are believed to cause the familial form of the disease. Reduced expression of BMPR2 is also noted in secondary PAH. Recent advances in the therapy of PAH have improved quality of life and survival, but many patients continue to do poorly. The possibility of treating PAH via improving BMPR2 signaling is thus a rational consideration. Such an approach could be synergistic with or additive to current treatments. We developed adenoviral vectors containing the BMPR2 gene. Transfection of cells in vitro resulted in upregulation of SMAD signaling and reduced cell proliferation. Targeted delivery of vector to the pulmonary vascular endothelium of rats substantially reduced the pulmonary hypertensive response to chronic hypoxia, as reflected by reductions in pulmonary artery and right ventricular pressures, right ventricular hypertrophy, and muscularization of distal pulmonary arterioles. These data provide further evidence for a role for BMPR2 in PAH and provide a rationale for the development of therapies aimed at improving BMPR2 signaling.

Ballooning dispersal in arthropod taxa with convergent behaviours: dynamic properties of ballooning silk in turbulent flows

We present a new model of ballooning behaviour in arthropods in which draglines are regarded as being extendible and completely flexible. Our numerical simulations reveal that silk draglines within turbulent flows can become twisted and stretched into highly contorted shapes. Ballooners are therefore predicted to have little control over their aerodynamic drag and their dispersal within the atmospheric boundary layer. Dragline length is crucial only at lift-off. This prediction runs counter to that of Humphrey who suggested that the length of rigid draglines can be used to control dispersal. In contrast with Humphrey's model, the new model accounts naturally for the large distances travelled by some ballooners.

In vitro susceptibility to the pro-apoptotic effects of TIMP-3 gene delivery translates to greater in vivo efficacy versus gene delivery for TIMPs-1 or -2

Matrix metalloproteinases (MMPs) are essential for extracellular matrix (ECM) breakdown and repair, and have been implicated in the development of metastases. TIMP-3 was initially identified as a potent inhibitor of MMPs, however it also has several properties that are unique and not related to its ability to abrogate MMPs. We studied the effects of overexpression of tissue inhibitor of metalloproteinases-3 (TIMP-3) on lung cancer cells and explored the mechanisms involved in apoptosis-induction in susceptible cells and subsequently, the therapeutic effect in vivo. Overexpression of TIMP-3 resulted in apoptosis of A549 lung cancer cells and AdCMVTIMP3 up-regulated the expression of p53, Fas ligand, TNFR1 and TNFR2 on these cells. Adenoviral delivery of TIMP-3 gene inhibited the growth of pre-established A549 tumours in Balb/c nude mice, and was associated with a greater therapeutic effect than either TIMP-1 or -2 gene delivery. There was no evidence of increased hepatic toxicity following the delivery of TIMP-3 either from intra-tumoural or intravenous injection. Thus, at least in cells showing in vitro susceptibility, TIMP-3 gene therapy offers a therapeutic advantage over TIMPs 1 and 2. These findings establish the potential of adenoviral gene delivery of TIMP3 as a therapeutic agent for selected lung cancers.

White blood cell left shift in a neonate: a case of mistaken identity

We present a full-term male infant who presented with tachypnea and an increased band count on his complete blood count (CBC) with an immature to total neutrophil (I:T) ratio of 0.6 raising suspicion of early onset sepsis. A blood culture was drawn and he was started on appropriate antibiotics. The patient's clinical condition rapidly improved; however, the white cell count 'left shift' persisted. When a detailed family history was obtained, it was discovered that the father, paternal uncle and the grandfather had been diagnosed with Pelger-Huet anomaly (PHA). As the urine, blood and CSF cultures were all negative in this now well-appearing infant, the left shift on the CBC was believed to be due to inheritance of the PHA. We present this case to emphasize that even in this age of sophisticated laboratory evaluation, a good clinical history, including family history, and clinical evaluation, are essential for accurate diagnosis.

Scale-free movement patterns arising from olfactory-driven foraging

The scale-free movement patterns of some foragers has aroused considerable excitement because they are known to optimize the success of random searches when target sites are randomly and sparsely distributed. Here it is shown that scale-free movement patterns can arise from a naive response of foragers to scent concentrations within turbulent plume structures.

Anisotropy of acceleration in turbulent flows

Third-order Lagrangian stochastic models for the evolution of fluid-particle hyperaccelerations (material derivatives of Lagrangian accelerations) are shown to account naturally for the anisotropy of acceleration variances in low-Reynolds-number turbulent flows and for their dependency upon the energy-containing scales of motion. Model predictions are shown to be in close accord with the results of direct numerical simulations for a turbulent channel flow and with previously acquired simulation data for a homogeneous turbulent shear flow.

Stokes number effects in Lagrangian stochastic models of dispersed two-phase flows

The statistical properties of fluid velocities along particle trajectories in turbulent flows have a conditional dependency upon particle velocity. It is shown that the formulation of Lagrangian stochastic (LS) models for particle trajectories in terms of the well-mixed condition for these conditional velocity statistics is exactly analogous to the formulation of second-order LS models for fluid-particle trajectories. The particle aerodynamic response time is shown to be incorporated at second order, which together with the Lagrangian timescale introduced at first order, defines the Stokes number. Reynolds-number effects can be incorporated at third order. The corresponding Fokker-Planck equation is shown to be identical to that advocated by Pozorski and Minier [Phys. Rev. E 59 (1999) 855], who included the fluid velocities "seen" by a particle in the probability density function (pdf) formalism of Reeks and co-workers as a means of circumventing the closure problem (prescribing a closure for the particle flux induced by the fluid) associated with that approach. It is demonstrated that the neglect of Stokes-number effects accounts, in part, for the tendency of first-order LS models to underpredict particle deposition velocities in the diffusion-impaction regime.

Superstatistical mechanics of tracer-particle motions in turbulence

The Lagrangian stochastic model of Reynolds [Phys. Fluids 15, L1-4 (2003)]] for the accelerations of fluid particles in turbulence is shown to predict precisely the observed Reynolds-number dependency of the distribution of Lagrangian accelerations and the exponents characterizing the observed extended self-similarity scaling of the Lagrangian velocity structure functions. Departures from superstatistics of the log-normal kind are accounted for and their impact upon model predictions is quantified.

Interleukin-1beta and tumour necrosis factor-alpha increase microvascular leakage in the guinea pig trachea

OBJECTIVE

Airway microvascular leakage is considered to be an important component of airway inflammation in asthma. In the present study we examined the effect of interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNFalpha) on airway microvascular leakage in vivo.

METHODOLOGY

Tracheal Evans blue extravasation was examined in an isolated tracheal segment, in anaesthetized mechanically ventilated guinea pigs. Baseline tracheal microvascular leakage was measured in five animals. As a control group for aerosol challenge, the isolated tracheal segment (n = 5) underwent saline aerosol challenge. To test whether a combination of IL-1beta (10 ng/mL) and TNFalpha (100 ng/mL) induced Evans blue extravasation, the trachea was exposed to an aerosol of these cytokines (n = 5). As a positive control the tracheal segment was challenged with histamine aerosol (5 x 10(-2) mol) (n = 3). All aerosol challenges were for 1 min.

RESULTS

TNFalpha and IL-1beta aerosol challenge significantly increased Evans blue extravasation (28.9 +/- 1.6 microg/g wet tissue, mean +/- SE) compared to saline challenge (13.8 +/- 3.0 microg/g; P < 0.05). Tracheal dye extravasation without aerosol challenge, was not significantly different from saline-challenged animals (17.5 +/- 2.9 and 13.8 +/- 3.0 microg/g, respectively). Histamine significantly increased Evans blue extravasation (50.1 +/- 4.8 microg/g; P < 0.05) compared to saline challenge.

CONCLUSION

Pro-inflammatory cytokines, TNFalpha and IL-1beta are able to induce significant microvascular leakage in the guinea pig trachea.

Effects of periodicity on flow and dispersion through closely packed fixed beds of spheres

A lattice-Boltzmann formulation is used to investigate the effects of "periodicity" (geometry) on fluid flow and tracer-particle dispersion through fixed beds of spheres comprising of closely packed layers. In the "period-1" arrangement, spheres in the adjacent layers contact at their poles while the "period-2" and "period-3" arrangements correspond to hexagonal and faced-centered cubic close packing. For all three packing arrangements, there is a transition with increasing Reynolds number from a power law to a log-normal distribution of kinetic energies and, velocity and vorticity become more closely aligned giving rise to helical tracer-particle trajectories. It is suggested that these flow characteristics, unlike the stability of flow and the distribution of helicity, are largely insensitive to geometry, even when the geometry creates direct channels through the pack bed orientated along the gradient in applied pressure. For steady flows and strongly turbulent flows, such channels are predicted to provide direct routes for dispersion through a packed bed, while for weakly turbulent flows they influence dispersion primarily by destabilizing the flow and thereby promoting dispersion throughout a bed. The dispersion of tracer-particles released from a source located on or close to a "stagnation streamline" is predicted to be faster than ballistic in the near field and the transition to long-time Fickian diffusion is predicted to be distinguished by a regime of subdiffusion.

Effects of endothelin-1 on K(+) currents from rat ventricular myocytes

It has been suggested that the positive inotropic effect of the vasoactive peptide hormone, endothelin-1 (ET-1), involves inhibition of cardiac K(+) currents. In order to identify the K(+) currents modulated by ET-1, the outward K(+) currents of isolated rat ventricular myocytes were investigated using whole-cell patch-clamp recording techniques. Outward currents were elicited by depolarisation to +40 mV for 200 ms from the holding potential of -60 mV. Currents activated rapidly, reaching a peak (I(pk)) of 1310 +/- 115 pA and subsequently inactivating to an outward current level of 1063 +/- 122 pA at the end of the voltage-pulse (I(late)) (n = 11). ET-1 (20 nM) reduced I(pk) by 247.6 +/- 60.7 pA (n = 11, P < 0.01) and reduced I(late) by 323.2 +/- 43.9 pA (P < 0.001). The effects of ET-1 were abolished in the presence of the nonselective ET receptor antagonist, PD 142893 (10 microM, n = 5). Outward currents were considerably reduced and the effects of ET-1 were not observed when K(+) was replaced with Cs(+) in the experimental solutions; this indicates that ET-1 modulated K(+)-selective currents. A double-pulse protocol was used to investigate the inactivation of the currents. The voltage-dependent inactivation of the currents from potentials positive to -80 mV was fitted by a Boltzmann equation revealing the existence of an inactivating transient outward component (I(to)) and a noninactivating steady-state component (I(ss)). ET-1 markedly inhibited I(ss) by 43.0 +/- 3.8% (P < 0.001, n = 7) and shifted the voltage-dependent inactivation of I(to) by +3.3 +/- 1.2 mV (P < 0.05). Although ET-1 had little effect on the onset of inactivation of the currents elicited from a conditioning potential of -70 mV, the time-independent noninactivating component of the currents was markedly inhibited. In conclusion, the predominant effect of ET-1 was to inhibit a noninactivating steady-state background K(+) current (I(ss)). These results are consistent with the hypothesis that I(ss) inhibition contributes to the inotropic effects of ET-1.

Tachykinin-induced bronchoconstriction in sheep is NK-1 receptor mediated and exhibits tachyphylaxis

OBJECTIVE

Tachykinins are mediators of airway hyper-reactivity and inflammation. There is in vitro evidence that ovine responses to tachykinins correlate closely to human responses. This study was designed to characterize the effect of intravenously administered tachykinins on sheep lung resistance in vivo to determine the effect of dose timing on reproducibility of responses and the induction of tachyphylaxis. We then used this information to help further characterize the response with several pharmacological agents.

METHODOLOGY

Substance P (SP) was administered by infusion to conscious merino ewes and lung resistance (RL) was measured. Infusions were given at 30, 60, 120 min and 24 h intervals. The effect of various agents on the response to SP was then assessed.

RESULTS

Substance P led to a transient increase in RL, mean (+/- SEM) 754.8 (+/- 139)% of baseline, with marked tachyphylaxis at 30, 60 and 120 min. Phosphoramidon increased the peak response to 1151.5 +/- 196%. Atropine and CP 96 345 abolished the response to SP, while indomethacin, sodium cromoglycate and pyrilamine had no significant effect. Substance P had a greater effect on RL than did neurokinin A.

CONCLUSIONS

Substance P increases RL in sheep via a cholinergic mechanism which is mediated by NK-1 receptors, and is subject to tachyphylaxis. These findings have implications for the design of studies using the ovine model in the evaluation of tachykinin antagonists as potential therapeutic agents.

Nicotinic agonists stimulate acetylcholine release from mouse interpeduncular nucleus: a function mediated by a different nAChR than dopamine release from striatum

Acetylcholine release stimulated by nicotinic agonists was measured as radioactivity released from perfused synaptosomes prepared from mouse interpeduncular nucleus (IPN) that had been loaded with [(3)H]choline. Agonist-stimulated release was dependent upon external calcium and over 90% of released radioactivity was acetylcholine. The release process was characterized by dose response curves for 13 agonists and inhibition curves for six antagonists. alpha-Conotoxin MII did not inhibit this release, while alpha-conotoxin AuIB inhibited 50% of agonist-stimulated release. Comparison of this process with [(3)H]dopamine release from mouse striatal synaptosomes indicated that different forms of nicotinic acetylcholine receptors (nAChRs) may mediate these processes. This was confirmed by assays using mice homozygous for the beta 2 subunit null mutation. The deletion of the beta 2 subunit had no effect on agonist-stimulated acetylcholine release, but abolished agonist-stimulated release of dopamine from striatal synaptosomes. Mice heterozygous for the beta 2 subunit null mutation showed decreased dopamine release evoked by L-nicotine with no apparent change in EC(50) value, as well as similar decreases in both transient and persistent phases of release with no changes in desensitization rates.

On the Formulation of Lagrangian Stochastic Models for Heavy-Particle Trajectories

The modeling approach of B. L. Sawford and F. H. Guest ("8th Symposium of Turbulence and Diffusion; San Diego, CA," pp. 96-99. Am. Meteorol. Soc., Boston, MA, 1990) is extended to encompass the formulation of Lagrangian stochastic models for fluid velocities along heavy-particle trajectories in inhomogeneous turbulent flows. The approach ensures consistency with prescribed Eulerian fluid velocity statistics. Models are formulated and then used in conjuction with the equations of motion for heavy particles to simulate the trajectories of heavy particles in vertical turbulent pipe flow. Model predictions for particle-velocity statistics, particle deposition velocities, and mean particle concentrations are shown to be in good agreement with experimental results. In contrast with "eddy-interaction" models but in accord with the results of direct numerical simulations, the models predict a buildup of mean particle concentration within the viscous sublayer at y(+) approximately 0.2. It is suggested that Lagrangian stochastic models for fluid-particle motions provide a good description of fluid velocities along the trajectories of heavy particles, when Lagrangian timescales are appropriately modified. Copyright 2000 Academic Press.

Modulation of the synaptic Ca2+ current in salamander photoreceptors by polyunsaturated fatty acids and retinoids

Synaptic transmission between retinal photoreceptors and second-order neurones is controlled by an L-type Ca2+ conductance (gCa) in the photoreceptor inner segment. Modulation of this conductance therefore influences the flow of visual information to higher centres. Possible modulation of gCa by retinal factors was investigated using patch clamp and Ca2+ imaging. No significant modulation of gCa by retinal neurotransmitters nor by intracellular signalling pathways was found. gCa was inhibited by retinoids (all-trans retinal) and by polyunsaturated fatty acids (PUFAs) such as arachidonic acid and docosahexaenoic acid, which are known to be released in the retina by exposure to light. Some PUFAs tested are physiological substrates for the cyclo-oxygenase, lipoxygenase and epoxygenase pathways, but specific inhibitors of these pathways had no effect on the inhibition of gCa. Treatments designed to activate or inhibit G-protein-coupled pathways or protein kinases A and C similarly had no effect on the inhibition by PUFAs nor on gCa itself. Inhibitors of phosphatases 1 and 2A were also largely ineffective. The inhibition by PUFAs is, however, dependent on membrane potential, suggesting that it arises from a direct interaction of fatty acids with the Ca2+ channel. The effect was not use or frequency dependent, suggesting that the effect does not depend on channel gating state. Control by retinoids and by PUFAs may be an important mechanism by which the Ca2+ conductance, and consequently the transmission of the visual signal, is modulated at the first retinal synapse.