Human activities shape global patterns of decomposition rates in rivers.

Rivers and streams contribute to global carbon cycling by decomposing immense quantities of terrestrial plant matter. However, decomposition rates are highly variable and large-scale patterns and drivers of this process remain poorly understood. Using a cellulose-based assay to reflect the primary constituent of plant detritus, we generated a predictive model (81% variance explained) for cellulose decomposition rates across 514 globally distributed streams. A large number of variables were important for predicting decomposition, highlighting the complexity of this process at the global scale. Predicted cellulose decomposition rates, when combined with genus-level litter quality attributes, explain published leaf litter decomposition rates with high accuracy (70% variance explained). Our global map provides estimates of rates across vast understudied areas of Earth and reveals rapid decomposition across continental-scale areas dominated by human activities.

Root canal instrumentation efficacy of non-fused and fused primary molar roots: a micro-computed tomography study.

PURPOSE: Pulpectomy may be indicated in restorable primary teeth exhibiting irreversible pulpitis or pulpal necrosis. The purpose of this study was to compare the cleaning and shaping efficacy of NiTi systems (Reciproc® Blue and MTwo®) with manual stainless-steel instrumentation in primary molars using micro-CT analysis. METHODS: Fifty-seven maxillary second primary molars were scanned using micro-CT. Teeth with three divergent roots were divided randomly (n = 15) according to instrument type (K file, MTwo®, and Reciproc® Blue). Teeth with root fusion were instrumented manually as a separate group (n = 12). Pre- and post-instrumentation micro-CT images were superimposed, and the instrumentation area (IA) and procedural complications were recorded. RESULTS: No statistically significant differences in IA between file systems was observed in the non-fused teeth. The mean IA of fused roots was significantly lower than in the non-fused distobuccal (p = 0.003) and palatal (p < 0.001) roots. The root segment had a significant effect on IA (p < 0.001) and the highest mean IA was observed in the apical third. Manual instrumentation had fewer procedural complications compared with rotary systems. CONCLUSION: No differences were determined in the cleaning and shaping effectiveness of all systems in non-fused teeth. Uninstrumented areas (> 60%) occurred in both non-fused and fused primary teeth with fewer procedural complications observed after manual instrumentation.

Precipitation and temperature drive continental-scale patterns in stream invertebrate production.

Secondary production, the growth of new heterotrophic biomass, is a key process in aquatic and terrestrial ecosystems that has been carefully measured in many flowing water ecosystems. We combine structural equation modeling with the first worldwide dataset on annual secondary production of stream invertebrate communities to reveal core pathways linking air temperature and precipitation to secondary production. In the United States, where the most extensive set of secondary production estimates and covariate data were available, we show that precipitation-mediated, low-stream flow events have a strong negative effect on secondary production. At larger scales (United States, Europe, Central America, and Pacific), we demonstrate the significance of a positive two-step pathway from air to water temperature to increasing secondary production. Our results provide insights into the potential effects of climate change on secondary production and demonstrate a modeling framework that can be applied across ecosystems.

Psychoneurometric assessment of dispositional liabilities for suicidal behavior: phenotypic and etiological associations.

BACKGROUND: Can core genetic liabilities for suicidal behavior be indexed using psychological and neural indicators combined? The current work addressed this question by examining phenotypic and genetic associations of two biobehavioral traits, threat sensitivity (THT) and disinhibition (DIS) - operationalized as psychoneurometric variables (i.e., composites of psychological-scale and neurophysiological measures) - with suicidal behaviors in a sample of adult twins. METHODS: Participants were 444 identical and fraternal twins recruited from an urban community. THT was assessed using a psychological-scale measure of fear/fearlessness combined with physiological indicators of reactivity to aversive pictures, and DIS was assessed using scale measures of disinhibitory tendencies combined with indicators of brain response from lab performance tasks. Suicidality was assessed using items from structured interview and questionnaire protocols. RESULTS: THT and DIS each contributed uniquely to prediction of suicidality when assessed psychoneurometrically (i.e., as composites of scale and neurophysiological indicators). In addition, these traits predicted suicidality interactively, with participants high on both reporting the greatest degree of suicidal behaviors. Biometric (twin-modeling) analyses revealed that a high percentage of the predictive association for each psychoneurometric trait (83% for THT, 68% for DIS) was attributable to genetic variance in common with suicidality. CONCLUSIONS: Findings indicate that psychoneurometric assessments of biobehavioral traits index genetic liability for suicidal behavior, and as such, can serve as innovative targets for research on core biological processes contributing to severe psychopathology, including suicidal proclivities and actions.

Genetic and environmental overlap between borderline personality disorder traits and psychopathy: evidence for promotive effects of factor 2 and protective effects of factor 1.

BACKGROUND: Previous studies have reported strong genetic and environmental overlap between antisocial-externalizing (factor 2; F2) features of psychopathy and borderline personality disorder (BPD) tendencies. However, this line of research has yet to examine etiological associations of affective-interpersonal (factor 1, F1) features of psychopathy with BPD tendencies. METHOD: The current study investigated differential phenotypic and genetic overlap of psychopathy factors 1 and 2 with BPD tendencies in a sample of over 250 male and female community-recruited adult twin pairs. RESULTS: Consistent with previous research, biometric analyses revealed strong genetic and non-shared environmental correlations of F2 with BPD tendencies, suggesting that common genetic and non-shared environmental factors contribute to both phenotypes. In contrast, negative genetic and non-shared environmental correlations were observed between F1 and BPD tendencies, indicating that the genetic factors underlying F1 serve as protective factors against BPD. No gender differences emerged in the analyses. CONCLUSIONS: These findings provide further insight into associations of psychopathic features - F1 as well as F2 - and BPD tendencies. Implications for treatment and intervention are discussed, along with how psychopathic traits may differentially influence the manifestation of BPD tendencies.

Differentiating psychopathy from antisocial personality disorder: a triarchic model perspective.

BACKGROUND: The triarchic model of psychopathy characterizes the disorder in terms of three distinguishable phenotypic facets: disinhibition, meanness and boldness. The present study sought to (1) inform current debates regarding the role of boldness in the definition of psychopathy and (2) clarify boundaries between psychopathy and antisocial personality disorder (ASPD). METHOD: This study evaluated the degree to which facets of the triarchic model are represented in the most widely used clinical inventory for psychopathy, the Psychopathy Checklist - Revised (PCL-R), in comparison with ASPD as defined by DSM-IV criteria. Adult male offenders from two distinct correctional settings (n = 157 and 169) were investigated to ensure replicability of findings across samples exhibiting high base rates of psychopathy and antisocial behavior. RESULTS: We found evidence for convergent and discriminant validity of the three triarchic facets in predicting symptomatic components of psychopathy as assessed by the PCL-R. Additionally, and crucially vis-à-vis current debates in the field, we found that boldness contributed incrementally (over and above disinhibition and meanness) to prediction of PCL-R psychopathy, in particular its interpersonal style component, but not ASPD. CONCLUSIONS: The three distinct facets of the triarchic model of psychopathy are represented clearly and distinctly in the PCL-R, with boldness through its interpersonal facet, but not in DSM-defined ASPD. Our findings suggest that boldness is central to diagnostic conceptions of psychopathy and distinguishes psychopathy from the more prevalent diagnosis of ASPD.

Genetic and environmental risk factors in males for self-report externalizing traits in mid-adolescence and criminal behavior through young adulthood.

BACKGROUND: Externalizing traits or behaviors are typically assessed by self-report scales or criminal records. Few genetically informative studies have used both methods to determine whether they assess the same genetic or environmental risk factors. METHOD: We examined 442 male Swedish twin pairs with self-reported externalizing behaviors at age 16­17 years [externalizing traits (EXT), self-reported delinquency (SRD), impulsivity (IMP), grandiosity (GRD) and callousness (CLS)] and criminal behavior (CB) from the National Suspect Registry from age 13 to 25 years. Multivariate structural equation modeling was conducted with Mx. RESULTS: The best-fit model contained one genetic, one shared environmental and two non-shared environmental common factors, and variable specific genetic and non-shared environmental factors. The risk for CB was influenced substantially by both genetic (a2=0.48) and familial­environmental factors (c2=0.22). About one-third of the genetic risk for CB but all of the shared environmental risk was indexed by the self-report measures. The degree to which the individual measures reflected genetic versus familial­environmental risks for CB varied widely. GRD and CLS were correlated with CB mainly through common genetic risk factors. SRD and CB covaried largely because of shared familial­environmental factors. For EXT and IMP, observed correlations with CB resulted in about equal parts from shared genetic and shared familial­environmental factors. CONCLUSIONS: In adolescence, measures of grandiose and callous temperament best tap the genetic liability to CB.Measures of antisocial behaviors better index familial­environmental risks for CB. A substantial proportion of the genetic risk to CB was not well reflected in any of the self-report measures.

Reduced cortical call to arms differentiates psychopathy from antisocial personality disorder.

BACKGROUND: Psychopathy and antisocial personality disorder (ASPD) are both characterized by impulsive, externalizing behaviors. Researchers have argued, however, that psychopathy is distinguished from ASPD by the presence of interpersonal-affective features that reflect an underlying deficit in emotional sensitivity. No study to date has tested for differential relations of these disorders with the brain's natural orienting response to sudden aversive events. Method Electroencephalography was used to assess cortical reactivity to abrupt noise probes presented during the viewing of pleasant, neutral and unpleasant pictures in 140 incarcerated males diagnosed using the Psychopathy Checklist - Revised and DSM-IV criteria for ASPD. The primary dependent measure was the P3 event-related potential response to the noise probes. RESULTS: Psychopaths showed significantly smaller amplitude of P3 response to noise probes across trials of all types compared with non-psychopaths. Follow-up analyses revealed that this overall reduction was attributable specifically to the affective-interpersonal features of psychopathy. By contrast, no group difference in general amplitude of probe P3 was evident for ASPD versus non-ASPD participants. CONCLUSIONS: The findings demonstrate a reduced cortical orienting response to abrupt aversive stimuli in participants exhibiting features of psychopathy that are distinct from ASPD. The specificity of the observed effect fits with the idea that these distinctive features of psychopathy reflect a deficit in defensive reactivity, or mobilization of the brain's defensive system, in the context of threat cues.

Delineating physiologic defensive reactivity in the domain of self-report: phenotypic and etiologic structure of dispositional fear.

BACKGROUND: Individual differences in fear and fearlessness have been investigated at their extremes in relation to markedly different forms of psychopathology--anxiety disorders and psychopathy, respectively. A documented neural substrate of fear-related traits and disorders is defensive reactivity as reflected in aversive startle potentiation (ASP). METHOD: The current study extended prior work by characterizing, in a sample of adult twins from the community (n = 2511), the phenotypic and etiologic structure of self-report measures of fear and fearlessness known to be associated with ASP. RESULTS: Analyses revealed a hierarchical structure to the trait fear domain, with an overarching, bipolar fear/fearlessness dimension saturating each measure in this domain, and subfactors labeled 'distress,' 'stimulation seeking' and 'sociability' accounting for additional variance in particular measures. The structure of genetic and non-shared environmental associations among the measures closely mirrored the phenotypic structure of the domain. CONCLUSIONS: The findings have implications for proposals to reconceptualize psychopathology in neurobiological terms.

Clarifying domains of internalizing psychopathology using neurophysiology.

Current initiatives such as the National Institute of Mental Health's Research Domain Criteria project aim to reorganize classification of mental disorders along neurobiological lines. Here, we describe how consideration of findings from psychiatric research employing two physiological measures with distinct neural substrates--the startle blink reflex and the error-related negativity (ERN)--can help to clarify relations among disorders entailing salient anxiety or depressive symptomatology. Specifically, findings across various studies and reviews reveal distinct patterns of association for both the startle blink reflex and the ERN with three key domains of psychopathology: (1) Fear (or phobic) disorders (distinguished by increased startle to unpleasant stimuli, but normal-range ERN). (2) Non-phobic anxiety disorders and negative affect (associated with increased ERN, increased startle across all types of emotional stimuli and increased baseline startle) and, more tentatively (3) Major depression (for which patterns of response for both startle and ERN appear to vary, as a function of severity and distinct symptomatology). Findings from this review point to distinct neurobiological indicators of key psychopathology domains that have been previously demarcated using personality and diagnostic data. Notably, these indicators exhibit more specificity in their relations with these three domains than has been seen in quantitative-dimensional models. Implications of these findings are discussed.

Iron deficiency anemia, beta-thalassemia minor, and anemia of chronic disease: a morphologic reappraisal.

We observed increased numbers of an infrequently referenced poikilocyte, the prekeratocyte, in iron deficiency anemia (IDA) compared with beta-thalassemia minor and anemia of chronic disease (ACD) and, therefore, chose to quantify these cells and other morphologic features in these anemias. Prekeratocytes were observed in 31 (78%) of 40 IDAs vs 11 (37%) of 30 beta-thalassemias (P = .001) and 5 (13%) of 40 ACDs (P < .001) and averaged 0.78 per 1,000 RBCs in IDA vs 0.21 in beta-thalassemia (P < .001) and 0.075 in ACD (P < .001). Pencil cells also were more commonly seen and more numerous in IDAs than in beta-thalassemia or ACD. Target cells were present in most IDAs and thalassemia and in similar numbers. Basophilic stippling was seen in only 5 (17%) of the beta-thalassemias. Our results lend quantitative support to prekeratocytes and pencil cells as morphologic features favoring the diagnosis of IDA but fail to support the diagnostic usefulness of target cells and basophilic stippling in discriminating IDA and beta-thalassemia minor.

Long-lasting modulation of the induction of LTD and LTP in rat hippocampal CA1 by behavioural stress and environmental enrichment.

Behavioural experience (e.g. chronic stress, environmental enrichment) can have long-lasting effects on cognitive functions. Because activity-dependent persistent changes in synaptic strength are believed to mediate memory processes in brain areas such as hippocampus, we tested whether behaviour has also long-lasting effects on synaptic plasticity by examining the induction of long-term potentiation (LTP) and long-term depression (LTD) in slices of hippocampal CA1 obtained from rats either 7-9 months after social defeat (behavioural stress) or 3-5 weeks after 5-week exposure to environmental enrichment. Compared with age-matched controls, defeated rats showed markedly reduced LTP. LTP was even completely impaired but LTD was enhanced in defeated and, subsequently, individually housed (during the 7-9-month period after defeat) rats. However, increasing stimulus intensity during 100-Hz stimulation resulted in significant LTP. This suggests that the threshold for LTP induction is still raised and that for LTD lowered several months after a short stressful experience. Both LTD and LTP were enhanced in environmentally enriched rats, 3-5 weeks after enrichment, as compared with age-matched controls. Because enrichment reduced paired-pulse facilitation, an increase in presynaptic release, facilitating both LTD and LTP induction, might contribute to enhanced synaptic changes. Consistently, enrichment reduced the number of 100-Hz stimuli required for inducing LTP. But enrichment may also actually enhance the range of synaptic modification. Repeated LTP and LTD induction produced larger synaptic changes in enriched than in control rats. These data reveal that exposure to very different behavioural experiences can produce long-lasting effects on the susceptibility to synaptic plasticity, involving pre- and postsynaptic processes.

Modern approaches to the investigation of vitamin B12 deficiency.

The classic workup of a patient for possible PA is revisited in light of the vanishing Schilling test. The vagaries of testing for B12 and blocking antibodies are reexamined. The advantages and disadvantages of newer tests such as MMA and serum gastrin levels are catalogued. At this juncture in the evolution of new test strategies, there is a considerable controversy regarding the significance of high MMA levels in the face of normal B12 levels, particularly in the elderly. Hopefully, this controversy will soon be resolved and the newer crop of tests will be proven and accepted in the workplace. Still, the words of Alexander Pope spring to mind: "Be not the first by whom the new are tried, Nor yet the last to lay the old aside."

Psychopathy, antisocial personality, and suicide risk.

H. Cleckley (1976) maintained that psychopaths are relatively immune to suicide, but substantial evidence exists for a relationship between antisocial deviance and suicidal acts. This study was the first to explicitly examine suicidal history among psychopathic individuals as defined by R. D. Hare's (1991) Psychopathy Checklist--Revised (PCL-R). Male prison inmates (N = 313) were assessed using the PCL-R and DSM-III-R and DSM-IV criteria (American Psychiatric Association, 1987, 1994) for antisocial personality disorder (APD), and they completed A. Tellegen's (1982) Multidimensional Personality Questionnaire (MPQ). Presence or absence of prior suicide attempts was coded from structured interview and prison file records. Suicide history was significantly related to PCL-R Factor 2 (which reflects chronic antisocial deviance) and to APD diagnosis but was unrelated to PCL-R Factor 1, which encompasses affective and interpersonal features of psychopathy. Higher order MPQ dimensions of Negative Emotionality and low Constraint were found to account for the relationship between history of suicidal attempts and antisocial deviance, indicating that temperament traits may represent a common vulnerability for both.

Alcohol affects emotion through cognition.

Determining how, cognition and emotion interact is pivotal to an understanding of human behavior and its disorders. Available data suggest that changes in emotional reactivity and behavior associated with drinking are intertwined with alcohol's effects on cognitive processing. In the study reported here, we demonstrated that alcohol dampens anticipatory fear and response inhibition in human participants not by directly suppressing subcortical emotion centers, as posited by traditional tension-reduction theories, but instead by impairing cognitive-processing capacity. During intoxication, reductions in fear response (assessed via startle potentiation) occurred only under dual-stimulus conditions, and coincided with reduced attentional processing of threat cues as evidenced by brain response (assessed via P3 event-related potentials). The results are consistent with higher cortical mediation of alcohol 's effects on fear, and illustrate more broadly how disruption of a cognitive process can lead to alterations in emotional reactivity and adaptive behavior.

The psychopath as observer: emotion and attention in picture processing.

This study extended prior work showing abnormal affect-startle modulation in psychopaths. Male prisoners viewed specific categories of pleasant (erotic or thrilling) and unpleasant (victim or direct threat) slide pictures, along with neutral pictures. Acoustic startle probes were presented early (300 and 800 ms) and late (1,800, 3,000, and 4,500 ms) in the viewing interval. At later times, nonpsychopaths showed moderate and strong reflex potentiation for victim and threat scenes, respectively. For psychopaths, startle was inhibited during victim scenes and only weakly potentiated during threat. Psychopaths also showed more reliable blink inhibition across pleasant contents than nonpsychopaths and greater heart rate orienting to affective pictures overall. These results indicate a heightened aversion threshold in psychopaths. In addition, deficient reflex modulation at early times suggested a weakness in initial stimulus evaluation among psychopaths.

A startle-probe methodology for investigating the effects of active avoidance on negative emotional reactivity.

This study introduces a new methodology for investigating the impact of active avoidance and behavioral control on defensive emotional reactivity using the startle reflex. A between-groups yoked design was devised that permitted manipulation of participants' perception of control over an aversive event (loud noise) while precisely controlling motor activity and noxious stimulation. Startle responses to tactile (airpuff) probes were compared during threat/performance trials and neutral trials. Results conclusively demonstrated cross-modal startle potentiation in the context of a continuous motor performance task. Also, consistent with prior research, heart rate increased with perceived control. However, behavioral control per se did not appear to mitigate defensive emotion as indexed by startle potentiation. These findings indicate that other parameters may mediate the efficacy of active coping in addition to control, and that the startle probe paradigm can provide a valuable tool for investigating these parameters in future research.

Alcohol and fear-potentiated startle: the role of competing cognitive demands in the stress-reducing effects of intoxication.

Effects of alcohol and cognitive demands on reactions to threat were examined using startle response potentiation to index negative emotion. Men and women received nonalcoholic or alcoholic beverages prior to a series of trial blocks, signaled by light cues indicating that shocks might be delivered ("threat" blocks) or that none would occur ("safe" blocks). Within half of the blocks, participants intermittently viewed pleasant photographic slides. Alcohol attenuated overall startle reactivity, but robust fear potentiation (larger startle magnitudes and shorter latencies during threat versus safe blocks) did not differ by beverage condition. Decomposition of the Beverage x Threat x Slide interaction revealed significant fear potentiation in all conditions, except the one in which alcohol was combined with slides. Thus, dampening of stress response by alcohol may depend on diminished ability to process competing cognitive demands.