A new flexible model for maintenance and feeding expenses that improves description of individual growth in insects

Metabolic theories in ecology interpret ecological patterns at different levels through the lens of metabolism, typically applying allometric scaling to describe energy use. This requires a sound theory for individual metabolism. Common mechanistic growth models, such as 'von Bertalanffy', 'dynamic energy budgets' and the 'ontogenetic growth model' lack some potentially important aspects, especially regarding regulation of somatic maintenance. We develop a model for ontogenetic growth of animals, applicable to ad libitum and food limited conditions, based on an energy balance that expresses growth as the net result of assimilation and metabolic costs for maintenance, feeding and food processing. The most important contribution is the division of maintenance into a 'non-negotiable' and a 'negotiable' part, potentially resulting in hyperallometric scaling of maintenance and downregulated maintenance under food restriction. The model can also account for effects of body composition and type of growth at the cellular level. Common mechanistic growth models often fail to fully capture growth of insects. However, our model was able to capture empirical growth patterns observed in house crickets.

Food webs coupled in space: Consumer foraging movement affects both stocks and fluxes

The exchange of material and individuals between neighbouring food webs is ubiquitous and affects ecosystem functioning. Here, we explore animal foraging movement between adjacent, heterogeneous habitats and its effect on a suite of interconnected ecosystem functions. Combining dynamic food web models with nutrient-recycling models, we study foraging across habitats that differ in fertility and plant diversity. We found that net foraging movement flowed from high to low fertility or high to low diversity and boosted stocks and flows across the whole loop of ecosystem functions, including biomass, detritus, and nutrients, in the recipient habitat. Contrary to common assumptions, however, the largest flows were often between the highest and intermediate fertility habitats rather than highest and lowest. The effect of consumer influx on ecosystem functions was similar to the effect of increasing fertility. Unlike fertility, however, consumer influx caused a shift towards highly predator-dominated biomass distributions, especially in habitats that were unable to support predators in the absence of consumer foraging. This shift resulted from both direct and indirect effects propagated through the interconnected ecosystem functions. Only by considering both stocks and fluxes across the whole loop of ecosystem functions do we uncover the mechanisms driving our results. In conclusion, the outcome of animal foraging movements will differ from that of dispersal and diffusion. Together we show how considering active types of animal movement and the interconnectedness of ecosystem functions can aid our understanding of the patchy landscapes of the Anthropocene. This article is protected by copyright. All rights reserved.

Conceptual data systems architecture principles for information systems

Information systems alignment with enterprise evolution affects the performance of enterprises. The systems conceptual and data quality, development time and sustainable life cycle management, are issues for enterprise competitiveness. The ability to directly generate enterprise information systems from models has been thought of as a solution to improve on these issues. Model-driven systems have been a research topic for decades. Fundamental principles for a proven model-driven information systems architecture are outlined in this article. Architectural foundation is a separation of user communities conceptual domain from the information technical domain. The users domain is modeled as an information system model in three layers, conceptual data logic model, interface model and user community model. The technical domain is a platform, allowing the modeling and execution of such a model. These principles have been applied in practice and proven viable. Two platforms and applications, which adhere to these principles, are briefly described.

Beyond body size—new traits for new heights in trait-based modelling of predator-prey dynamics

Food webs map feeding interactions among species, providing a valuable tool for understanding and predicting community dynamics. Using species’ body sizes is a promising avenue for parameterizing food-web models, but such approaches have not yet been able to fully recover observed community dynamics. Such discrepancies suggest that traits other than body size also play important roles. For example, differences in species’ use of microhabitat or non-consumptive effects of intraguild predators may affect dynamics in ways not captured by body size. In Laubmeier et al. (2018), we developed a dynamic food-web model incorporating microhabitat and non-consumptive predator effects in addition to body size, and used simulations to suggest an optimal sampling design of a mesocosm experiment to test the model. Here, we perform the mesocosm experiment to generate empirical time-series of insect herbivore and predator abundance dynamics. We minimize least squares error between the model and time-series to determine parameter values of four alternative models, which differ in terms of including vs excluding microhabitat use and non-consumptive predator-predator effects. We use both statistical and expert-knowledge criteria to compare the models and find including both microhabitat use and non-consumptive predator-predator effects best explains observed aphid and predator population dynamics, followed by the model including microhabitat alone. This ranking suggests that microhabitat plays a larger role in driving population dynamics than non-consumptive predator-predator effects, although both are clearly important. Our results illustrate the importance of additional traits alongside body size in driving trophic interactions. They also point to the need to consider trophic interactions and population dynamics in a wider community context, where non-trophic impacts can dramatically modify the interplay between multiple predators and prey. Overall, we demonstrate the potential for utilizing traits beyond body size to improve trait-based models and the value of iterative cycling between theory, data and experiment to hone current insights into how traits affect food-web dynamics.

High Mortality from Major Vascular Trauma in Traffic Accidents: A Population-Based Study

BACKGROUND AND AIMS

Injuries involving major arteries are an important cause of mortality and morbidity, most often from road traffic accidents. Our aim was to study the outcome of major vascular trauma from traffic accidents in an entire population, including patients who die at the scene and those who reach hospital alive.

MATERIALS AND METHODS

This was a retrospective analysis of all patients who sustained major vascular trauma in traffic accidents in Iceland from 2000 to 2011. Patient demographics, mechanism, and location of vascular injury and treatment were registered. Injury scores were calculated and overall survival estimated.

RESULTS

There were 62 individuals (mean age 44 years, 79% males) with 95 major vascular traumas, giving an incidence of 1.69/100,000 inhabitants (95% confidence interval: 1.27-2.21). A total of 33 died at the scene and 8 during transportation to hospital but 21 (34%) reached hospital alive. Most patients who succumbed had thoracic major vascular traumas (76%) or abdominal major vascular traumas (23%). Mean new injury severity score for the 21 admitted patients was 44. A total of 18 were operated with vascular repair, 3 with endovascular stent graft insertion. The mean hospital stay for discharged patients was 34 days. Altogether, 15 of the 62 patients (24%) survived to discharge from hospital, with a 5-year survival of 86% for discharged patients.

CONCLUSION

Every other patient with major vascular trauma following traffic accidents died at the scene and a further 13% died during transportation to hospital, most of whom sustained major vascular trauma to the thoracic aorta. However, one-third of the patients reached hospital alive and 71% of them survived to discharge, with excellent long-term survival.

Circulating plasma microRNAs as biomarkers for iron status in blood donors

OBJECTIVES

To investigate whether microRNAs can serve as biomarkers for iron status in blood donors.

BACKGROUND

Serum ferritin is a widely used biochemical test for detecting iron deficiency, but it has its limitations. Certain microRNAs (miRNAs) reportedly have a role in regulating iron homeostasis. Circulating miRNAs have been reported as potential biomarkers for various conditions but have not yet been studied in iron deficiency.

METHODS

Participating blood donors were divided into two groups: high ferritin (HF) (>150 µg L^-1 ) and low ferritin (LF) (<15 µg L^-1 ). MiRNA analysis was performed by an miRNA profiling service (Exiqon) using commercial qPCR assays. The study had two phases: (i) a pilot study (20 participants) where 179 miRNAs were analysed and (ii) a confirmation study (50 participants) of 13 selected miRNAs.

RESULTS

Mean serum ferritin was 13·8 µg L^-1 in the LF arm compared to 231 µg L^-1 in the HF group (P < 0·001). Hepcidin plasma levels were higher in the HF arm (P < 0·001), whereas soluble transferrin receptor 1 was higher in the LF group (P < 0·001). In the pilot study, samples did not separate according to study group on unsupervised analysis. When directly comparing HF vs LF groups, 17 miRNAs were differentially expressed (P < 0·05, t-test) but did not pass correction for multiple testing. The confirmation study of 13 selected miRNAs verified these findings as no miRNA was significantly different between the study groups.

CONCLUSION

In this study, circulating plasma miRNAs did not emerge as promising biomarkers for iron status in healthy individuals. However, in the future, alternative detection methods such as next-generation sequencing might indicate miRNAs that correlate with iron stores.

Ecosystem function in predator-prey food webs-confronting dynamic models with empirical data

Most ecosystem functions and related services involve species interactions across trophic levels, for example, pollination and biological pest control. Despite this, our understanding of ecosystem function in multitrophic communities is poor, and research has been limited to either manipulation in small communities or statistical descriptions in larger ones. Recent advances in food web ecology may allow us to overcome the trade-off between mechanistic insight and ecological realism. Molecular tools now simplify the detection of feeding interactions, and trait-based approaches allow the application of dynamic food web models to real ecosystems. We performed the first test of an allometric food web model's ability to replicate temporally nonaggregated abundance data from the field and to provide mechanistic insight into the function of predation. We aimed to reproduce and explore the drivers of the population dynamics of the aphid herbivore Rhopalosiphum padi observed in ten Swedish barley fields. We used a dynamic food web model, taking observed interactions and abundances of predators and alternative prey as input data, allowing us to examine the role of predation in aphid population control. The inverse problem methods were used for simultaneous model fit optimization and model parameterization. The model captured >70% of the variation in aphid abundance in five of ten fields, supporting the model-embodied hypothesis that body size can be an important determinant of predation in the arthropod community. We further demonstrate how in-depth model analysis can disentangle the likely drivers of function, such as the community's abundance and trait composition. Analysing the variability in model performance revealed knowledge gaps, such as the source of episodic aphid mortality, and general method development needs that, if addressed, would further increase model success and enable stronger inference about ecosystem function. The results demonstrate that confronting dynamic food web models with abundance data from the field is a viable approach to evaluate ecological theory and to aid our understanding of function in real ecosystems. However, to realize the full potential of food web models, in ecosystem function research and beyond, trait-based parameterization must be refined and extended to include more traits than body size.

High Redundancy as well as Complementary Prey Choice Characterize Generalist Predator Food Webs in Agroecosystems

Food web structure influences ecosystem functioning and the strength and stability of associated ecosystem services. With their broad diet, generalist predators represent key nodes in the structure of many food webs and they contribute substantially to ecosystem services such as biological pest control. However, until recently it has been difficult to empirically assess food web structure with generalist predators. We utilized DNA-based molecular gut-content analyses to assess the prey use of a set of generalist invertebrate predator species common in temperate agricultural fields. We investigated the degree of specialization of predator-prey food webs at two key stages of the cropping season and analysed the link temperature of different trophic links, to identify non-random predation. We found a low level of specialization in our food webs, and identified warm and cool links which may result from active prey choice or avoidance. We also found a within-season variation in interaction strength between predators and aphid pests which differed among predator species. Our results show a high time-specific functional redundancy of the predator community, but also suggest temporally complementary prey choice due to within-season succession of some predator species.

Rare and Common Variants Conferring Risk of Tooth Agenesis

We present association results from a large genome-wide association study of tooth agenesis (TA) as well as selective TA, including 1,944 subjects with congenitally missing teeth, excluding third molars, and 338,554 controls, all of European ancestry. We also tested the association of previously identified risk variants, for timing of tooth eruption and orofacial clefts, with TA. We report associations between TA and 9 novel risk variants. Five of these variants associate with selective TA, including a variant conferring risk of orofacial clefts. These results contribute to a deeper understanding of the genetic architecture of tooth development and disease. The few variants previously associated with TA were uncovered through candidate gene studies guided by mouse knockouts. Knowing the etiology and clinical features of TA is important for planning oral rehabilitation that often involves an interdisciplinary approach.

Pharmacokinetics and Pharmacodynamics of Melagatran, a Novel Synthetic LMW Thrombin Inhibitor, in Patients with Acute DVT

Forty-eight patients with acute proximal deep vein thrombosis (DVT) were randomised to intravenous infusions for 4 to 6 days with melagatran, a novel synthetic low molecular weight thrombin inhibitor, or unfractionated heparin adjusted by the activated partial thromboplastin time (APTT). The aim of the study was to investigate the pharmacokinetics, pharmacodynamics and the safety of melagatran therapy at three different doses. Steady-state plasma concentrations were rapidly achieved and maintained throughout the infusion period. The mean plasma concentrations in the low, medium and high dose groups were 0.17, 0.31 and 0.53 μmol/l, respectively. The prolongation of APTT was stable during the melagatran infusions and correlated to the plasma concentration. Phlebographically verified regression of thrombus size measured as decrease in Marder score was seen after 4 to 6 days in 8 of 12 patients, 6 of 12 patients and 5 of 11 patients in the low, medium and high dose groups of melagatran and in 5 of the heparin-treated patients. In the low dose group with melagatran, thrombus extension was seen in one patient. At the dose levels studied, melagatran was well tolerated with no clinically significant bleeding problems, suggesting that melagatran could safely be given to patients suffering from DVT.

Morphological determinants of signal carrier frequency in katydids (Orthoptera): a comparative analysis using biophysical evidence of wing vibration

Male katydids produce mating calls by stridulation using specialized structures on the forewings. The right wing (RW) bears a scraper connected to a drum-like cell known as the mirror and a left wing (LW) that overlaps the RW and bears a serrated vein on the ventral side, the stridulatory file. Sound is generated with the scraper sweeping across the file, producing vibrations that are amplified by the mirror. Using this sound generator, katydids exploit a range of song carrier frequencies (CF) unsurpassed by any other insect group, with species singing as low as 600 Hz and others as high as 150 kHz. Sound generator size has been shown to scale negatively with CF, but such observations derive from studies based on few species, without phylogenetic control, and/or using only the RW mirror length. We carried out a phylogenetic comparative analysis involving 94 species of katydids to study the relationship between LW and RW components of the sound generator and the CF of the male's mating call, while taking into account body size and phylogenetic relationships. The results showed that CF negatively scaled with all morphological measures, but was most strongly related to components of the sound generation system (file, LW and RW mirrors). Interestingly, the LW mirror (reduced and nonfunctional) predicted CF more accurately than the RW mirror, and body size is not a reliable CF predictor. Mathematical models were verified on known species for predicting CF in species for which sound is unknown (e.g. fossils or museum specimens).

Conditions for Eltonian Pyramids in Lotka-Volterra Food Chains

In ecological communities consumers (excluding parasites and parasitoids) are in general larger and less numerous than their resource. This results in a well-known observation known as 'Eltonian pyramids' or the 'pyramid of numbers', and metabolic arguments suggest that this pattern is independent of the number of trophic levels in a system. At the same time, Lotka-Volterra (LV) consumer-resource models are a frequently used tool to study many questions in community ecology, but their capacity to produce Eltonian pyramids has not been formally analysed. Here, I address this knowledge gap by investigating if and when LV food chain models give rise to Eltonian pyramids. I show that Eltonian pyramids are difficult to reproduce without density-dependent mortality in the consumers, unless biologically plausible relationships between mortality rate and interaction strength are taken into account.

Functional identity and diversity of animals predict ecosystem functioning better than species-based indices

Drastic biodiversity declines have raised concerns about the deterioration of ecosystem functions and have motivated much recent research on the relationship between species diversity and ecosystem functioning. A functional trait framework has been proposed to improve the mechanistic understanding of this relationship, but this has rarely been tested for organisms other than plants. We analysed eight datasets, including five animal groups, to examine how well a trait-based approach, compared with a more traditional taxonomic approach, predicts seven ecosystem functions below- and above-ground. Trait-based indices consistently provided greater explanatory power than species richness or abundance. The frequency distributions of single or multiple traits in the community were the best predictors of ecosystem functioning. This implies that the ecosystem functions we investigated were underpinned by the combination of trait identities (i.e. single-trait indices) and trait complementarity (i.e. multi-trait indices) in the communities. Our study provides new insights into the general mechanisms that link biodiversity to ecosystem functioning in natural animal communities and suggests that the observed responses were due to the identity and dominance patterns of the trait composition rather than the number or abundance of species per se.

Symptoms and side effects in chronic non-cancer pain patients: clinical implications and development of new assessment tools

OBJECTIVE

To improve a 41-item screening tool evaluated in our previous study by making it more simple and convenient to patients and at the same time maintain the level of information and the sensitivity.

METHODS

In a prospective, two-period questionnaire study, patients suffering from chronic pain of non-cancer origin for more than 6 months, were asked to fill in two questionnaires: QSSE-41 or QSSE-33 and SF-36. The first part of the study (QSSE-41) included an age- and sex-matched control group.

RESULTS

A total of 67 patients were included in QSSE-41 and 60 patients in QSSE-33. In QSSE-41, the mean number of symptoms reported by the patient group (12.3) was significantly higher than those reported by the controls (6.8) (P < 0.001). Out of the total number of symptoms, 40.3% were reported to be side effects caused by analgesics, and out of those 61.3% were reported as acceptable and 38.7% as unacceptable side effects. In the QSSE-33, the mean number of symptoms reported by the patient group was 13.6. Out of the total number of symptoms, 46.3% were reported to be side effects caused by analgesics, and out of those 56.4% were reported as acceptable and 43.6% as unacceptable side effects.

CONCLUSIONS

This new and shorter screening tool QSSE-33 may substitute the original QSSE-41 and in clinical use, contribute substantially to a more comprehensive and detailed understanding of symptoms/side effects and may consequently lead to improved therapies.

Cortical activation changes and improved motor function in stroke patients after focal spasticity therapy--an interventional study applying repeated fMRI

Background

Impaired dominant hand function in stroke patients is a common clinical problem. Functional improvement after focal spasticity therapy is well documented but knowledge about central correlates is sparse. Brain activity was therefore followed during therapy with repeated functional magnetic resonance imaging (fMRI). The purpose was to analyse motor function and central nervous system (CNS) correlates in response to a standardized motor task in stroke patients after a comprehensive focal spasticity therapy.

Methods

Six consecutive first-time chronic stroke patients [4 women; mean age (SD) 66 (10) years] with right-sided hand paresis and spasticity were studied. Peripheral effects after focal spasticity management including intramuscular botulinum toxin type A (BoNT-A) injections were assessed on 3 occasions (baseline, 6 and 12 weeks) with functional tests. Brain effects were assessed on the same occasions by fMRI blood oxygen level dependent (BOLD) technique during a standardized motor task focusing on the motor and pre-motor cortex (Brodmann areas, BA4a, BA4p & BA6). For reference 10 healthy individuals [5 women; mean age (SD) of 51(8) years], were studied twice with ≥ 6 weeks interval.

Results

After therapy there was a significant reduction in spasticity and functional improvement in 5 of 6 patients. In response to the motor task there was a ~1.5 - 3% increase in brain activity in the motor and pre-motor cortex. At baseline, this increase was larger in the non-injured (ipsilateral) than in the contralateral hemisphere. Compared with healthy subjects the patients showed a significantly (2–4.5 times) higher brain activity, especially on the ipsilateral side. After therapy, there was a larger decrease in the ipsilateral and a minor decrease in the contralateral response, i.e. a clear lateralization of left-to-right in a normalizing direction in all areas.

Conclusions

Comprehensive focal spasticity management was also in this study associated with brain reorganization in a “normalizing” left/right lateralization direction in addition to improved motor function. Furthermore, quantification of BOLD intensity in specified BAs showed reduced neuronal “over-activity” in the injured brain after therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-015-0306-4) contains supplementary material, which is available to authorized users.

Functional and structural alterations in the cingulate motor area relate to decreased fronto-striatal coupling in major depressive disorder with psychomotor disturbances

Psychomotor disturbances are a classic feature of major depressive disorders. These can manifest as lack of facial expressions and decreased speech production, reduced body posture and mobility, and slowed voluntary movement. The neural correlates of psychomotor disturbances in depression are poorly understood but it has been suggested that outputs from the cingulate motor area (CMA) to striatal motor regions, including the putamen, could be involved. We used functional and structural magnetic resonance imaging to conduct a region-of-interest analysis to test the hypotheses that neural activation patterns related to motor production and gray matter volumes in the CMA would be different between depressed subjects displaying psychomotor disturbances (n = 13) and matched healthy controls (n = 13). In addition, we conducted a psychophysiological interaction analysis to assess the functional coupling related to self-paced finger-tapping between the caudal CMA and the posterior putamen in patients compared to controls. We found a cluster of increased neural activation, adjacent to a cluster of decreased gray matter volume in the caudal CMA in patients compared to controls. The functional coupling between the left caudal CMA and the left putamen during finger-tapping task performance was additionally decreased in patients compared to controls. In addition, the strength of the functional coupling between the left caudal CMA and the left putamen was negatively correlated with the severity of psychomotor disturbances in the patient group. In conclusion, we found converging evidence for involvement of the caudal CMA and putamen in the generation of psychomotor disturbances in depression.

The neural correlates of self-paced finger tapping in bipolar depression with motor retardation

OBJECTIVE

Motor retardation is a characteristic feature of bipolar depression, and is also a core feature of Parkinson's disease. Within the framework of the functional deafferentiation theory in Parkinson's disease, we hypothesised that motor retardation in bipolar depression is mediated by disrupted subcortical activation, leading to decreased activation of cortical motor areas during finger tapping.

METHODS

We used functional magnetic resonance imaging to investigate neural activity during self-paced finger tapping to elucidate whether brain regions that mediate preparation, control and execution of movement are activated differently in subjects with bipolar depression (n = 9) compared to healthy controls (n = 12).

RESULTS

An uncorrected whole-brain analysis revealed significant group differences in dorsolateral and ventromedial prefrontal cortex. Corrected analyses showed non-significant differences in patients compared to controls: decreased and less widespread activation of the left putamen and left pallidum; increased activity in the left thalamus and supplementary motor area; decreased activation in the left lateral pre- and primary motor cortices; absence of activation in the pre-supplementary motor area; activation of the bilateral rostral cingulate motor area.

CONCLUSION

Both movement preparation and execution may be affected in motor retardation, and the activity in the whole left-side motor circuit is altered during self-initiated motor performance in bipolar depression.

Clinical trial: marine lipid suppositories as laxatives

Cod-liver oil and other marine products containing polyunsaturated fatty acids have anti-inflammatory, anti-bacterial and anti-viral effects and may be useful in the treatment of various inflammatory and infectious diseases. We developed suppositories and ointment with 30% free fatty acid (FFA) extract from omega-3 fish oil. Our purpose was to evaluate the safety of marine lipid suppositories and ointment in healthy volunteers and to explore the laxative effect of the suppositories. Thirty healthy volunteers were randomized either to a study group administrating 30% FFA suppositories and applying 30% FFA ointment to the perianal region twice per day for two weeks, or to a control group using placebo suppositories and ointment in a double blinded manner. Results: No serious toxic effects or irritation were observed. In the study group 93% felt the urge to defecate after administration of the suppositories as compared to 37% in the control group (P = 0.001). Subsequently 90% in the study group defecated, compared to 33% in the control group (P = 0.001). Conclusion: The marine lipid suppositories and ointment were well tolerated with no significant toxic side effects observed during the study period. The suppositories have a distinct laxative effect and we aim to explore this effect in further clinical trials.

Thinner cortex in the frontal lobes in mentally disordered offenders

Antisocial and violent behaviour have been associated with both structural and functional brain abnormalities in the frontal and the temporal lobes. The aim of the present study was to assess cortical thickness in offenders undergoing forensic psychiatric assessments, one group with psychopathy (PSY, n=7) and one group with autism spectrum disorder (ASD, n=7) compared to each other as well as to a reference group consisting of healthy non-criminal subjects (RG, n=12). A second aim was to assess correlation between scores on a psychopathy checklist (PCL-SV) and cortical thickness. Magnetic resonance imaging (MRI) and surface-based cortical segmentation were used to calculate cortical thickness. Analyses used both regions of interest and statistical maps. When the two groups of offenders were compared, there were no differences in cortical thickness, but the PSY group had thinner cortex in the temporal lobes and in the whole right hemisphere compared to RG. There were no differences in cortical thickness between the ASD group and RG. Across subjects there was a negative correlation between PCL-SV scores and cortical thickness in the temporal lobes and the whole right hemisphere. The findings indicate that thinner cortex in the temporal lobes is present in psychopathic offenders and that these regions are important for the expression of psychopathy. However, whether thinner temporal cortex is a cause or a consequence of the antisocial behaviour is still unknown.

Species-rich ecosystems are vulnerable to cascading extinctions in an increasingly variable world

Global warming leads to increased intensity and frequency of weather extremes. Such increased environmental variability might in turn result in increased variation in the demographic rates of interacting species with potentially important consequences for the dynamics of food webs. Using a theoretical approach, we here explore the response of food webs to a highly variable environment. We investigate how species richness and correlation in the responses of species to environmental fluctuations affect the risk of extinction cascades. We find that the risk of extinction cascades increases with increasing species richness, especially when correlation among species is low. Initial extinctions of primary producer species unleash bottom-up extinction cascades, especially in webs with specialist consumers. In this sense, species-rich ecosystems are less robust to increasing levels of environmental variability than species-poor ones. Our study thus suggests that highly species-rich ecosystems such as coral reefs and tropical rainforests might be particularly vulnerable to increased climate variability.

The dimensionality of between-person differences in white matter microstructure in old age

Between-person differences in white matter microstructure may partly generalize across the brain and partly play out differently for distinct tracts. We used diffusion-tensor imaging and structural equation modeling to investigate this issue in a sample of 260 adults aged 60-87 years. Mean fractional anisotropy and mean diffusivity of seven white matter tracts in each hemisphere were quantified. Results showed good fit of a model positing that individual differences in white matter microstructure are structured according to tracts. A general factor, although accounting for variance in the measures, did not adequately represent the individual differences. This indicates the presence of a substantial amount of tract-specific individual differences in white matter microstructure. In addition, individual differences are to a varying degree shared between tracts, indicating that general factors also affect white matter microstructure. Age-related differences in white matter microstructure were present for all tracts. Correlations among tract factors did not generally increase as a function of age, suggesting that aging is not a process with homogenous effects on white matter microstructure across the brain. These findings highlight the need for future research to examine whether relations between white matter microstructure and diverse outcomes are specific or general.

Symptoms and side effects in chronic non-cancer pain: patient report vs. systematic assessment

BACKGROUND

relieving distressing symptoms and managing the side effects of analgesics are essential in order to improve quality of life and functional capacity in chronic non-cancer pain patients. A quick, reliable and valid tool for assessing symptoms and side effects is needed in order to optimize treatment. We aimed to investigate the symptoms reported by chronic non-cancer pain patients after open-ended questioning vs. a systematic assessment using a list of symptoms, and to assess whether the patients could distinguish between the symptoms and the side effects induced by analgesics.

METHODS

patients treated with either opioids and/or adjuvant analgesics were asked to report their symptoms spontaneously, followed by a 41-item investigator-developed symptom checklist. A control group also filled in the checklist.

RESULTS

a total of 62 patients and 64 controls participated in the study. The numbers of symptoms reported by the patients (9.9 ± 5.9) were significantly higher than those reported by the controls (3.2 ± 3.9) (P<0.001). In the patient group, the number of spontaneously reported symptoms (1.3 ± 1.4) was significantly lower than the symptoms reported when using the symptom checklist (9.9 ± 5.9) (P<0.001). The six most frequently symptoms reported by the patients were: (1) Fatigue; (2) Memory deficits; (3) Dry mouth; (4) Concentration deficits; (5) Sweating; and (6) Weight gain. Out of the six most frequently reported symptoms, the share of side effects due to analgesics was: (1) Dry mouth (42%); (2) Sweating (34%); (3) Weight gain (29%); (4) Memory deficits (24%); (5) Fatigue (19%); and (6) Concentration deficits (19%).

CONCLUSION

the number of symptoms reported using systematic assessment was eightfold higher than those reported voluntarily. Fatigue, cognitive dysfunction, dry mouth, sweating and weight gain were the most frequently reported. The patients reported the side effects of their analgesics to contribute substantially to the reported symptoms.

Interaction strength, food web topology and the relative importance of species in food webs

1. We established complex marine communities, consisting of over 100 species, in large subtidal experimental mesocosms. We measured the strength of direct interactions and the net strength of direct and indirect interactions between the species in those communities, using a combination of theoretical and empirical approaches. 2. Theoretical predictions of interaction strength were derived from the interaction coefficient matrix, which was parameterised using allometric predator-prey relationships. Empirical estimates of interaction strength were quantified using the ln-ratio, which measures the change in biomass density of species A in the presence and absence of species B. 3. We observed that highly connected species tend to have weak direct effects and net effects in our experimental food webs, whether we calculate interaction strength theoretically or empirically. 4. We found a significant correlation between our theoretical predictions and empirical estimates of direct effects and net effects. The net effects correlation was much stronger, indicating that our experimental communities were dominated by a mixture of direct and indirect effects. 5. Re-calculation of the theoretical predictions of net effects after randomising predator and prey body masses did not affect the negative relationship with connectance. 6. These results suggest that food web topology, which in this system is constrained by body mass, is overwhelmingly important for the magnitude of direct and indirect interactions and hence species importance in the face of biodiversity declines.

Parallel imaging: is GRAPPA a useful acquisition tool for MR imaging intended for volumetric brain analysis?

Background

The work presented here investigates parallel imaging applied to T1-weighted high resolution imaging for use in longitudinal volumetric clinical studies involving Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI) patients. This was in an effort to shorten acquisition times to minimise the risk of motion artefacts caused by patient discomfort and disorientation. The principle question is, "Can parallel imaging be used to acquire images at 1.5 T of sufficient quality to allow volumetric analysis of patient brains?"

Methods

Optimisation studies were performed on a young healthy volunteer and the selected protocol (including the use of two different parallel imaging acceleration factors) was then tested on a cohort of 15 elderly volunteers including MCI and AD patients. In addition to automatic brain segmentation, hippocampus volumes were manually outlined and measured in all patients. The 15 patients were scanned on a second occasion approximately one week later using the same protocol and evaluated in the same manner to test repeatability of measurement using images acquired with the GRAPPA parallel imaging technique applied to the MPRAGE sequence.

Results

Intraclass correlation tests show that almost perfect agreement between repeated measurements of both segmented brain parenchyma fraction and regional measurement of hippocampi. The protocol is suitable for both global and regional volumetric measurement dementia patients.

Conclusion

In summary, these results indicate that parallel imaging can be used without detrimental effect to brain tissue segmentation and volumetric measurement and should be considered for both clinical and research studies where longitudinal measurements of brain tissue volumes are of interest.

Food web structure and interaction strength pave the way for vulnerability to extinction

This paper focuses on how food web structure and interactions among species affects the vulnerability, due to environmental variability, to extinction of species at different positions in model food webs. Vulnerability is here not measured by a traditional extinction threshold but is instead inspired by the IUCN criteria for endangered species: an observed rapid decline in population abundance. Using model webs influenced by stochasticity with zero autocorrelation, we investigate the ecological determinants of species vulnerability, i.e. the trophic interactions between species and food web structure and how these interact with the risk of sudden drops in abundance of species. We find that (i) producers fulfil the criterion of vulnerable species more frequently than other species, (ii) food web structure is related to vulnerability, and (iii) the vulnerability of species is greater when involved in a strong trophic interaction than when not. We note that our result on the relationship between extinction risk and trophic position of species contradict previous suggestions and argue that the main reason for the discrepancy probably is due to the fact that we study the vulnerability to environmental stochasticity and not extinction risk due to overexploitation, habitat destruction or interactions with introduced species. Thus, we suggest that the vulnerability of species to environmental stochasticity may be differently related to trophic position than the vulnerability of species to other factors. Earlier research on species extinctions has looked for intrinsic traits of species that correlate with increased vulnerability to extinction. However, to fully understand the extinction process we must also consider that species interactions may affect vulnerability and that not all extinctions are the result of long, gradual reductions in species abundances. Under environmental stochasticity (which importance frequently is assumed to increase as a result of climate change) and direct and indirect interactions with other species some extinctions may occur rapidly and apparently unexpectedly. To identify the first declines of population abundances that may escalate and lead to extinctions as early as possible, we need to recognize which species are at greatest risk of entering such dangerous routes and under what circumstances. This new perspective may contribute to our understanding of the processes leading to extinction of populations and eventually species. This is especially urgent in the light of the current biodiversity crisis where a large fraction of the world's biodiversity is threatened.

CONSUMER–RESOURCE BODY-SIZE RELATIONSHIPS IN NATURAL FOOD WEBS

It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-'resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.

The effects of tobacco smoking and rheumatoid factor seropositivity on disease activity and joint damage in early rheumatoid arthritis

OBJECTIVE

To study the effect of tobacco smoking and rheumatoid factor (RF) isotypes on disease activity and joint damage in early rheumatoid arthritis (RA).

METHODS

One hundred early RA patients were followed prospectively for 2 yr. They were evaluated at recruitment and at 6 and 24 months. Sociodemographic information included smoking history, and radiographs of hands and feet were obtained. RF was monitored by IgM- and IgA-specific RF enzyme-linked immunosorbent assay and by agglutination, and serial measurements were also obtained for C-reactive protein. The influence of tobacco smoking and RF positivity on disease outcome was evaluated using multivariate analysis. Covariates for the regression analysis included sex, age, coffee consumption and IgA-RF positivity.

RESULTS

A gradient of increase in disease activity was observed from never smokers to former smokers to current smokers during the 2 yr of observation, defined by number of swollen joints (SJC), tender joints (TJC) and visual analogue scale for pain (P<0.001, P=0.02 and P=0.005, respectively), but smoking status did not influence radiological progression. Ever smokers were more often IgA RF positive (P<0.05). IgA RF-positive patients had more active disease (SJC P=0.002, TJC P=0.01) and showed more radiological progression (P<0.0001) compared with IgA RF-negative patients. Of the RF-positive patients 22% had elevated IgM RF without IgA RF and these patients showed similar disease activity and radiological joint progression to the RF-negative patients. None of these associations were explained by possible confounders.

CONCLUSION

Tobacco smoking has an adverse effect on patients with early RA and this is possibly immunologically mediated. IgM RF does not predict poorer prognosis in RA unless it is associated with a concomitant elevation of IgA RF.

Using community viability analysis to identify fragile systems and keystone species

Owing to interdependences among species in ecological communities, the loss of one species can trigger a cascade of secondary extinctions with potentially dramatic effects on the functioning and stability of the community. It is, therefore, important to assess the risk and likely extent of secondary extinctions. Community viability analysis is a new technique that can be used to accomplish this goal. The analysis can also be used to identify fragile community structures and keystone species and, hence, to provide guidelines for conservation priorities. Here, we describe the principles underlying community viability analysis and review its contributions to our understanding of the response of ecological communities to species loss.