Multilevel Twin Models: Geographical Region as a Third Level Variable.

The classical twin model can be reparametrized as an equivalent multilevel model. The multilevel parameterization has underexplored advantages, such as the possibility to include higher-level clustering variables in which lower levels are nested. When this higher-level clustering is not modeled, its variance is captured by the common environmental variance component. In this paper we illustrate the application of a 3-level multilevel model to twin data by analyzing the regional clustering of 7-year-old children's height in the Netherlands. Our findings show that 1.8%, of the phenotypic variance in children's height is attributable to regional clustering, which is 7% of the variance explained by between-family or common environmental components. Since regional clustering may represent ancestry, we also investigate the effect of region after correcting for genetic principal components, in a subsample of participants with genome-wide SNP data. After correction, region no longer explained variation in height. Our results suggest that the phenotypic variance explained by region might represent ancestry effects on height.

The state of tranquility: subjective perception is shaped by contextual modulation of auditory connectivity.

In this study, we investigated brain mechanisms for the generation of subjective experience from objective sensory inputs. Our experimental construct was subjective tranquility. Tranquility is a mental state more likely to occur in the presence of objective sensory inputs that arise from natural features in the environment. We used functional magnetic resonance imaging to examine the neural response to scenes that were visually distinct (beach images vs. freeway images) and experienced as tranquil (beach) or non-tranquil (freeway). Both sets of scenes had the same auditory component because waves breaking on a beach and vehicles moving on a freeway can produce similar auditory spectral and temporal characteristics, perceived as a constant roar. Compared with scenes experienced as non-tranquil, we found that subjectively tranquil scenes were associated with significantly greater effective connectivity between the auditory cortex and medial prefrontal cortex, a region implicated in the evaluation of mental states. Similarly enhanced connectivity was also observed between the auditory cortex and posterior cingulate gyrus, temporoparietal cortex and thalamus. These findings demonstrate that visual context can modulate connectivity of the auditory cortex with regions implicated in the generation of subjective states. Importantly, this effect arises under conditions of identical auditory input. Hence, the same sound may be associated with different percepts reflecting varying connectivity between the auditory cortex and other brain regions. This suggests that subjective experience is more closely linked to the connectivity state of the auditory cortex than to its basic sensory inputs.

Nonadditive effects of leaf litter species diversity on breakdown dynamics in a detritus-based stream.

Since species loss is predicted to be nonrandom, it is important to understand the manner in which those species that we anticipate losing interact with other species to affect ecosystem function. We tested whether litter species diversity, measured as richness and composition, affects breakdown dynamics in a detritus-based stream. Using full-factorial analyses of single- and mixed-species leaf packs (15 possible combinations of four dominant litter species; red maple [Acer rubrum], tulip poplar [Liriodendron tulipifera], chestnut oak [Quercus prinus], and rhododendron [Rhododendron maximum]), we tested for single-species presence/absence (additive) or species interaction (nonadditive) effects on leaf pack breakdown rates, changes in litter chemistry, and microbial and macroinvertebrate biomass. Overall, we found significant nonadditive effects of litter species diversity on leaf pack breakdown rates, which were explained both by richness and composition. Leaf packs containing higher litter species richness had faster breakdown rates, and antagonistic effects of litter species composition were observed when any two or three of the four litter species were mixed. Less-consistent results were obtained with respect to changes in litter chemistry and microbial and macroinvertebrate biomass. Our results suggest that loss of litter species diversity will decrease species interactions involved in regulating ecosystem function. To that end, loss of species such as eastern hemlock (Tsuga canadensis) accompanied by predicted changes in riparian tree species composition in the southeastern United States could have nonadditive effects on litter breakdown at the landscape scale.

Urinary Claudin-2 Measurements as a Predictor of Necrotizing Enterocolitis: A Pilot Study.

BACKGROUND: Necrotizing Enterocolitis (NEC) affects 5-10% of NICU patients where initially patients may have only nonspecific clinical findings. A noninvasive tool for detection would aid in diagnosis. Increased urinary claudins have been associated with active adult inflammatory bowel disease. METHODS: Institutional Review Board approval was obtained. Neonatal intestinal tissue samples were obtained from patients with and without NEC. Immunofluorescence analysis of claudin-2 was performed on the intestinal tissue. Thirty two urine samples were collected from 6 NICU patients. Proteins were extracted and urinary claudin-2 expression was measured using Western Blot Analysis. All sample concentrations were normalized to urinary creatinine. Differences were analyzed with ANOVA or Student's T-test. Findings were correlated to the patient's clinical status. RESULTS: Neonatal intestinal immunofluorescence analysis revealed that claudin-2 is present in healthy intestinal epithelium and is decreased in NEC intestinal tissue (p=0.0001). Of the six patients evaluated, three patients had NEC. All 3 patients with NEC had spikes in urinary claudin-2 levels (p<0.001, p<0.001, p 0.0598 respectively). Spikes did not appear to correlate with other etiologies of neonatal sepsis, medication use or need for mechanical ventilation. Levels during active NEC were almost twice that of NEC-free periods (p<0.0001). CONCLUSION: A tool for early detection would facilitate early intervention and potential prevention of severe NEC. Preliminary findings indicate that urinary claudin-2 may represent a potential biomarker for NEC worth further investigation.

Toxin-Producing Anabaena flos-aquae Induces Settling of Chlamydomonas reinhardtii, a Competing Motile Alga.

Toxin production is an adaptation that allows cyanobacteria in resource-limiting environments to ameliorate the effects of herbivory and competition with other phototrophs. We demonstrate that the cyanobacterial toxins anatoxin-a and microcystin-LR paralyze the motile green alga Chlamydomonas reinhardtii. In addition, both purified toxins and cyanobacterial extracellular products containing these toxins cause the alga to settle faster than in nontoxic media. In microcosm experiments, the presence of either the cyanobacterium or its extracellular products induce settling in the alga, similar to the response observed with the addition of both anatoxin-a and microcystin-LR. The cyanobacterial production of paralyzing toxins represents a novel mechanism for phytoplankton settling. This prokaryotic/eukaryotic chemical interaction may create a competitor-free zone for cyanobacteria in lake environments, predicating optimal conditions for a toxic cyanobacterial bloom.

Outbreaks of the winter moth on Sitka Spruce in Scotland are not influenced by nutrient deficiencies of trees, tree budburst, or pupal predation.

Since the early 1980s, the winter moth, Operophtera brumata L. (Lepidoptera: Geometridae) has emerged as a serious pest of Sitka Spruce, Picea sitchensis Bong. plantations in southern Scotland. Outbreaks are characterised by susceptible sites within plantations which can occur immediately adjacent to resistant sites. We investigated the level of some nutrients in the trees, the date of budburst of the trees, and the numbers of some potential predators of winter moth pupae. None could satisfactorily explain outbreak patterns. Although foliage analysis demonstrated that many trees were marginal or deficient in phosphorus, nitrogen and potassium, these deficiencies were not related to the susceptibility of a site. Within sites, the numbers and weights of O. brumata were positively related to phosphorus content and negatively related to calcium content of foliage. Other evidence suggests, however, that these correlations may not represent direct effects of phosphorus and calcium on larval growth and survival. Date of budburst, which commonly determines susceptibility of deciduous hosts to O. brumata, was unrelated to density, and pupal predators were more, not less, abundant in susceptible sites. Although it is difficult to distinguish between factors that initiate outbreaks and those that maintain them, these data suggest that nutrient deficiencies of trees, budburst date, and the distribution of pupal predators of the winter moth cannot explain patterns of outbreak of the winter moth on spruce.

The functional and psychological status of patients with amyotrophic lateral sclerosis: some implications for rehabilitation.

Amyotrophic lateral sclerosis (ALS), known as motor neurone disease (MND) in Britain, poses special problems in rehabilitation by virtue of its nature, trajectory and the age of patients with the disease. Many practical difficulties of ALS are well known, but there has been little research on the psychological parameters of the disease. This study of 181 ALS patients, from a national register in England and Wales, indicates that, contrary to some previous research, psychological distress (measured by the General Health Questionnaire) is widespread among patients at all stages of the disease. Severity of functional impairment is significantly related to psychological distress, but explains only a small part of the variance. Rehabilitation in relation to ALS must take account of the high incidence of psychological difficulties, as well as the considerable functional problems associated with the disease.

Stress improves selective attention towards emotionally neutral left ear stimuli.

Research concerning the impact of psychological stress on visual selective attention has produced mixed results. The current paper describes two experiments which utilise a novel auditory oddball paradigm to test the impact of psychological stress on auditory selective attention. Participants had to report the location of emotionally-neutral auditory stimuli, while ignoring task-irrelevant changes in their content. The results of the first experiment, in which speech stimuli were presented, suggested that stress improves the ability to selectively attend to left, but not right ear stimuli. When this experiment was repeated using tonal stimuli the same result was evident, but only for female participants. Females were also found to experience greater levels of distraction in general across the two experiments. These findings support the goal-shielding theory which suggests that stress improves selective attention by reducing the attentional resources available to process task-irrelevant information. The study also demonstrates, for the first time, that this goal-shielding effect extends to auditory perception.

Neural basis of auditory expectation within temporal cortex.

Predictive coding frameworks of perception propose that neural networks form predictions of expected input and generate prediction errors when the external input does not match expectation. We therefore investigated the processing of unexpected sounds and silence in the auditory cortex using fMRI. Unexpected sounds, when compared to expected sounds, evoked greater activation in large areas of the left temporal and insular cortices. Additionally the left middle temporal gyrus exhibited greater activation to unexpected events in general, whether sounds or silence, when compared to the corresponding expected events. These findings support predictive coding models of perception, which suggest that regions of the temporal cortex function to integrate sensory information with predictive signals during auditory perception.

Auditory hallucinations: expectation-perception model.

In this paper, we aimed to present a hypothesis that would explain the mechanism of auditory hallucinations, one of the main symptoms of schizophrenia. We propose that auditory hallucinations arise from abnormalities in the predictive coding which underlies normal perception, specifically, from the absence or attenuation of prediction error. The suggested deficiencies in processing prediction error could arise from (1) abnormal modulation of thalamus by prefrontal cortex, (2) absence or impaired transmission of external input, (3) dysfunction of the auditory and association cortex, (4) neurotransmitter dysfunction and abnormal connectivity, and (5) hyperactivity activity in auditory cortex and broad prior probability. If there is no prediction error, the initially vague prior probability develops into an explicit percept in the absence of external input, as a result of a recursive pathological exchange between auditory and prefrontal cortex. Unlike existing explanations of auditory hallucinations, we propose concrete mechanisms which underlie the imbalance between perceptual expectation and external input. Impaired processing of prediction error is reflected in reduced mismatch negativity and increased tendency to report non-existing meaningful language stimuli in white noise, shown by those suffering from auditory hallucinations. We believe that the expectation-perception model of auditory hallucinations offers a comprehensive explanation of the underpinnings of auditory hallucinations in both patients and those not diagnosed with mental illness. Therefore, our hypothesis has the potential to fill the gaps in the existing knowledge about this distressing phenomenon and contribute to improved effectiveness of treatments, targeting specific mechanisms.

Correlated cerebral events between physically and sensory isolated pairs of subjects exposed to yoked circumcerebral magnetic fields.

In three different experiments pairs of unrelated people sitting in two different rooms were exposed simultaneously to different rates of circumcerebral rotations of weak, complex magnetic fields in order to produce "dynamic similarity". Quantitative electroencephalographic (QEEG) measurements were taken for one member of each pair in one room while the other sat in a closed chamber in another room and intermittently observed 5Hz, 8Hz, 10Hz, or 15Hz flashing lights. Reliable increases in QEEG power within specific frequencies over the right parietal region were observed during the similar-frequency light flashes when the shared temporal-spatial complexity of the circumcerebral rotating fields was based on 100ms, the average duration of normal microstates. The development of this experimental procedure could facilitate rational understanding of this class of "coincidence" phenomena.

Auditory hallucinations in those populations that do not suffer from schizophrenia.

The following article discusses the phenomenon of auditory hallucinations in those who do not suffer from schizophrenia. Research has shown the occurrence of auditory hallucinations in the general population to such an extent that they cannot be said to be pathognomonic of psychiatric illness. In addition, it has long been known that certain hallucinatory experiences occur in health, such as hypnagogic and hypnopompic hallucinations. However, there are fundamental differences in the characteristics of these experiences. In the psychiatric population, these tend to be frequent, intrusive, and distressing. In contrast, in the nonclinical population, these are often predominantly positive and nonthreatening. The exact mechanism for the occurrence of auditory hallucinations is not yet known, but it is hoped that through the study of those in health, the mechanisms that underpin pathophysiologic processes in clinical conditions also can be elucidated.

Neural activity in speech-sensitive auditory cortex during silence.

That auditory hallucinations are voices heard in the absence of external stimuli implies the existence of endogenous neural activity within the auditory cortex responsible for their perception. Further, auditory hallucinations occur across a range of healthy and disease states that include reduced arousal, hypnosis, drug intoxication, delirium, and psychosis. This suggests that, even in health, the auditory cortex has a propensity to spontaneously "activate" during silence. Here we report the findings of a functional MRI study, designed to examine baseline activity in speech-sensitive auditory regions. During silence, we show that functionally defined speech-sensitive auditory cortex is characterized by intermittent episodes of significantly increased activity in a large proportion (in some cases >30%) of its volume. Bilateral increases in activity are associated with foci of spontaneous activation in the left primary and association auditory cortices and anterior cingulate cortex. We suggest that, within auditory regions, endogenous activity is modulated by anterior cingulate cortex, resulting in spontaneous activation during silence. Hence, an aspect of the brain's "default mode" resembles a (preprepared) substrate for the development of auditory hallucinations. These observations may help explain why such hallucinations are ubiquitous.

Elevational trends in defense chemistry, vegetation, and reproduction in Sanguinaria canadensis.

Evaluation of biotic interactions along geographic gradients reveals that pressure on plant populations by herbivores and pathogens increases as latitude decreases, and is accompanied by a parallel increase in the number and toxicity of alkaloid-bearing plants. We compared rhizome alkaloid content with plant reproductive and vegetative characters in Sanguinaria canadensis (Papaveraceae) along an elevational gradient over two growing seasons to ascertain 1) if alkaloid production in bloodroot varies among populations and systematically with elevation, and 2) if there exists a correlation between isoquinoline alkaloid, vegetative and reproductive production. In general, alkaloid content in bloodroot rhizomes declines with elevation, increases with rhizome water content, varies by site, and fluctuates seasonally with plant growth and reproduction. Alkaloid content was positively correlated with vegetative and reproductive effort with few exceptions. Analysis of total protopine and benzophenanthridine alkaloid concentrations revealed generally similar patterns as those of individual alkaloid concentrations, although significant differences did appear between individual alkaloid concentrations.

Environmental and genotypic influences on isoquinoline alkaloid content in Sanguinaria canadensis.

In a common garden, we investigated genetic and environmental influences on alkaloid production using Sanguinaria canadensis as a model. Nutrient and shade regimes were applied to replicated clones over one growing season, and induction of alkaloid production in bloodroot was tested on a whole-plant basis using jasmonic acid as an elicitor. Alkaloid concentrations increased with decreasing light intensity and fertilizer levels. Induction was not achieved by foliar application of jasmonic acid. Genetic influences represented by clone effects may be indicated by variation in alkaloid concentration by clone, but this experimental design did not allow us to distinguish genetic from pre-experiment environmental influences on the rhizomes.

Green algal extracellular products regulate antialgal toxin production in a cyanobacterium.

Many bacterial genes and virulence factors are regulated by interbacterial and/or host-parasite chemical signals. We demonstrate that toxin production by a free-living freshwater cyanobacterium is regulated in part by the presence of extracellular products of a eukaryotic green alga. In growth experiments, extracellular products made by the cyanobacterium Anabaena flos-aquae contained both anatoxin and microcystin, and significantly reduced the yield of Chlamydomonas reinhardtii, a green alga. Based on experiments in which we added purified toxins to C. reinhardtii cultures, we believe that microcystin was responsible for the growth reduction. A. flos-aquae produced anatoxin constitutively when grown alone, but anatoxin concentration increased in the presence of C. reinhardtii elicitors. Microcystin accumulation depended on the growth phase; however, high concentrations of C. reinhardtii extracellular products completely inhibited microcystin accumulation. Our results demonstrate that cyanobacterial toxin production may be regulated by complex growth phase-dependent and environmental chemical cues, and suggest that secreted chemicals can mediate the outcome of competition between the cyanobacterium A. flos-aquae and the green alga C. reinhardtii.

Algal extracellular products suppress Anabaena flos-aquae heterocyst spacing.

Intra- and interspecific chemical signals allow bacteria to respond to environmental conditions by regulating gene transcription. In cyanobacteria, gene products and the presence of fixed nitrogen regulate heterocyst frequency. In this paper, we describe a chemical made by a green alga, Chlamydomonas reinhardtii, that suppresses heterocyst formation in the co-occurring cyanobacterium, Anabaena flos-aquae. Cyanobacterial heterocyst frequencies were reduced in the presence of water-soluble, proteinase- and heat-resistant molecules greater than 15 kDa in molecular size. Green algal cells in all phases of growth made the suppressor. Ammonium and nitrate concentrations in the medium did not correlate with this change in phenotype. In addition, growth rate was not enhanced by the extracellular products. Therefore, C. reinhardtii extracellular products acted as a heterocyst inhibitor, not as a fixed nitrogen source. Chemical interactions between green algae and cyanobacteria influence heterocyst formation, an important consideration in understanding the outcome of competition between these organisms and the dynamics of phytoplankton communities.

Leaf phenolic inhibition of gypsy moth nuclear polyhedrosis virus Role of polyhedral inclusion body aggregation.

Bioassays with nuclear polyhedrosis virus (NPV) administered to gypsy moth larvae on leaf disks from various tree species reveal strong viral inhibition by some tree species. Phenolic extracts from inhibitory tree leaves cause virus polyhedral inclusion bodies (PIBs) to form large aggregations. However, aggregated PIBs treated with leaf extracts and administered to larvae on laboratory diet (without phenolics) retain virulence. Our results suggest that leaf phenolics, especially hydrolyzable tannins, inhibit NPV infection, but may not act via aggregations formed in the foregut.

Estimating the relative roles of top-down and bottom-up forces on insect herbivore populations: a classic study revisited.

Although most ecologists agree that both top-down and bottom-up forces (predation and resource limitation, respectively) act in concert to influence populations of herbivores, it has proven difficult to estimate the relative contributions of such forces in terrestrial systems. Using a combination of time-series analysis of population counts recorded over 16 years and experimental data, we present the first estimates of the relative roles of top-down and bottom-up forces on the population dynamics of two terrestrial insect herbivores on the English oak (Quercus robur). Data suggest that temporal variation in winter moth, Operophtera brumata, density is dominated by time-lagged effects of pupal predators. By comparison, spatial variation in O. brumata density is dominated by host-plant quality. Overall, top-down forces explain 34.2% of population variance, bottom-up forces explain 17.2% of population variance, and 48.6% remains unexplained. In contrast, populations of the green oak tortrix, Tortrix viridana, appear dominated by bottom-up forces. Resource limitation, expressed as intraspecific competition among larvae for oak leaves, explains 29.4% of population variance. Host quality effects explain an additional 5.7% of population variance. We detected no major top-down effects on T. viridana populations. An unknown factor causing a linear decline in T. viridana populations over the 16-year study period accounts for most of the remaining unexplained variance. We discuss the observed differences between the insect species and the utility of time-series analysis as a tool in assessing the relative importance of top-down and bottom-up forces on herbivore populations.

Rickettsia associated with male-killing in a buprestid beetle.

Many populations of the buprestid leaf-mining beetle, Brachys tessellatus, from central South Carolina, USA, show highly skewed sex ratios, ranging from 1.3 to 6.0 females per male. We have identified a Rickettsia bacterium that is associated with sex ratio distortion (SRD) and selective killing of male embryos in B. tessellatus. Molecular assays of infection by this bacterium are highly associated with SRD within families, and treatment with an antibiotic (tetracycline) increases the number of male eggs that hatch and develop. The 16S rDNA sequence indicates that this is a novel Rickettsia, most closely related to Rickettsia bellii (a tick-associated bacterium) and a pea-aphid Rickettsia. It is also related to a Rickettsial bacterium that causes male-killing in an unrelated ladybird beetle species. Low levels of parthenogenesis are also observed in this system (about 10% of females) and may be the result of selection due to male rarity, or a direct result of infection by the Rickettsia.