Role of lipopolysaccharide in antimicrobial and cell penetrating peptide membrane interactions probed by deuterium NMR of whole cells.

Understanding how non-lipid components of bacteria affect antimicrobial peptide (AMP)-induced membrane disruption is important for a comprehensive understanding of AMP mechanisms and informing AMP-based drug development. This study investigates how lipopolysaccharide (LPS) affects membrane disruption by the AMP MSI-78 and compares the results to the effect of TP2, a cell-penetrating peptide that crosses membrane bilayers without permeabilizing them. We destabilize the LPS layer of Escherichia coli (E. coli) cells via chelation of the stabilizing divalent cations. 2H NMR spectra of E. coli demonstrate that EDTA concentrations of 2.5 mM and 9.0 mM alone have very minor effects on lipid acyl chain order. Interestingly, we find that E. coli pre-treated with 9.0 mM EDTA before treatment with MSI-78 are more sensitive to AMP-induced acyl chain disruption, indicating that intact LPS reduces MSI-78-induced membrane disruption in E. coli. Surprisingly, we also found that at the level of 2H NMR, the peptide-induced acyl chain disruption is similar for MSI-78 and TP2, although MSI-78 permeabilizes the bilayer and TP2 does not. Furthermore, LPS disruption appears to protect the bacteria from TP2, although it sensitizes them to MSI-78.

Lower Levels of Classroom Aggression Predict Stronger Relations Between Peer Victimization and Reactive Versus Proactive Aggression.

We examined the concurrent relations of children's reactive and proactive aggression with their experience of peer victimization. Extending previous research, we assessed these relations at both the child and classroom levels. We predicted that reactive aggression would relate positively to peer victimization, proactive aggression would relate negatively to peer victimization, and that these relations would vary with classroom levels of aggression. Participants included 1,291 fourth- and fifth-grade children (681 girls; M age = 10.14 years) and their 72 teachers from 9 schools in one public school district in the Mid-Atlantic United States. Children completed self-report measures of peer victimization and teachers completed measures of aggression for each child in their classrooms. Via two-level regression (level 1 = child; level 2 = classroom), reactive aggression related positively to peer victimization and proactive aggression related negatively to peer victimization. The positive relation between reactive aggression and peer victimization was only significant in classrooms with low levels of reactive aggression. The negative relation between proactive aggression and peer victimization was only significant in classrooms with low levels of proactive aggression. Our hypotheses were supported and offered further evidence for differential relations of reactive and proactive aggression with peer victimization at the child level, while demonstrating the important role of classroom norms for aggression in moderating these relations.

Role of lipopolysaccharide in antimicrobial and cell penetrating peptide membrane interactions probed by deuterium NMR of whole cells.

Understanding how non-lipid components of bacteria affect antimicrobial peptide (AMP)-induced membrane disruption is important for a comprehensive understanding of AMP mechanisms and informing AMP-based drug development. This study investigates how lipopolysaccharide (LPS) affects membrane disruption by the AMP MSI-78 and compares the results to the effect of TP2, a cell-penetrating peptide that crosses membrane bilayers without permeabilizing them. We destabilize the LPS layer of Escherichia coli (E. coli) cells via chelation of the stabilizing divalent cations. 2H NMR spectra of E. coli demonstrate that EDTA concentrations of 2.5 mM and 9.0 mM alone have very minor effects on lipid acyl chain order. Interestingly, we find that E. coli pre-treated with 9.0 mM EDTA before treatment with MSI-78 are more sensitive to AMP-induced acyl chain disruption, indicating that intact LPS reduces MSI-78-induced membrane disruption in E. coli. Surprisingly, we also found that at the level of 2H_NMR, the peptide-induced acyl chain disruption is similar for MSI-78 and TP2, although MSI-78 permeabilizes the bilayer and TP2 does not. Furthermore, LPS disruption appears to protect the bacteria from TP2, although it sensitizes them to MSI-78.

2H NMR Study of Polymer Segmental Dynamics at Varying Cross-Linking in Poly(N-isopropylacrylamide) Microgels.

A microscopic understanding of the internal structure and dynamics of poly(N-isopropylacrylamide) (PNIPAM) chains, in microgel colloids, is developed using deuterium NMR (2H NMR) to study deuterated PNIPAM suspensions as functions of temperature and pressure for four cross-linker molar fractions (f). The PNIPAM polymers were labeled with deuterons at the backbone (d3-PNIPAM) or on side chains (d7-PNIPAM). 2H NMR spectra of the d3-PNIPAM suspensions for all cross-linker molar fractions indicated freely moving chains at low temperature and a nearly immobilized fraction above ∼35 °C. Polymer segments in the collapsed phase of the d3-PNIPAM suspension were more mobile than those in the dry powder. This is direct microscopic evidence that the polymer remains significantly hydrated in the collapsed phase, consistent with strong, indirect evidence from recent light scattering and rheology measurements from our laboratory. However, the observation of a small fraction of immobilized segments in the swollen phase for higher cross-linker molar fraction suggests that, particularly for high levels of cross-linking, some polymer is nonhydrated even in the swollen phase. Finally, variable-pressure NMR (up to 90 MPa) showed a slight increase in transition temperature with pressure for lower cross-linker molar fractions and a larger increase in transition temperature with pressure for higher cross-linker molar fractions. This is consistent with a previously reported dependence of collapse transition enthalpy on cross-linker molar fraction.

Genetic Sequencing of Attwater's Prairie Chicken Avian Poxvirus and Evaluation of Its Potential Role in Reticuloendotheliosis Virus Outbreaks.

Efforts to breed Attwater's prairie chickens (APC; Tympanuchus cupido attwateri) in captivity to supplement wild populations of this endangered bird have been negatively affected by infections with Avipoxvirus and reticuloendotheliosis virus (REV). Because REV can be integrated into the genome of fowlpox virus (FPV) and may be transmitted in that manner, identifying the source of avipox disease in APC is important to mitigate the impact of this virus. Tissue samples from APC were collected from breeding programs in Texas from 2016 to 2020. These samples consisted of 11 skin lesions and three internal organs from a total of 14 different birds that died of unknown causes or were euthanized. Avipoxvirus was detected by PCR and isolation in embryonating chicken eggs in all skin lesion samples but was not detected in internal organs. Using sequence analysis of FPV polymerase and 4b genes, we determined that 10 out of 11 Avipoxvirus detections resided within the fowlpox clade and a single sample resided within the canarypox clade. REV sequences were detected in all FPV positive samples and in all internal organ tissues but were not detected in the sample matching the canarypox clade. Analysis of REV sequences and PCR detection showed the REV infecting APC was consistent with REV-A and had little variability on analysis of the U3 region of the long terminal repeat. The results of this study indicate control of REV in APC breeding colonies may benefit by a vaccination program targeting FPV and REV. However, a commercially available vaccine for REV is not available at this time.

Secuenciación genética de un virus de la viruela aviar de un gallo grande de las praderas Attwater y evaluación de su papel potencial en los brotes del virus de la reticuloendoteliosis. Los esfuerzos para criar gallos de las praderas grandes de Attwater (APC; Tympanuchus cupido attwateri) en cautiverio para complementar las poblaciones silvestres de esta ave en peligro de extinción se han visto afectados negativamente por infecciones con Avipoxvirus y con el virus de la reticuloendoteliosis (REV). Debido a que el virus de la reticuloendoteliosis puede integrarse en el genoma del virus de la viruela del pollo (FPV) y puede transmitirse de esa manera, identificar la fuente del virus pox en gallos de las praderas grandes es importante para mitigar el impacto de este virus. Se recolectaron muestras de tejido de gallos de las praderas grandes de programas de reproducción en Texas entre los años 2016 a 2020. Estas muestras consistieron en 11 lesiones cutáneas y tres órganos internos de un total de 14 aves diferentes que murieron por causas desconocidas o fueron sacrificadas. El Avipoxvirus se detectó mediante PCR y por aislamiento en huevos embrionados de pollo en todas las muestras de lesiones cutáneas, pero no se detectó en los órganos internos. Utilizando el análisis de secuencia de la polimerasa del virus de la viruela del pollo y de los genes 4b, se determinó que diez de las once detecciones de Avipoxvirus residían dentro del clado de la viruela aviar del pollo y una sola muestra residía dentro del clado de la viruela del canario. Se detectaron secuencias del virus de la reticuloendoteliosis en todas las muestras positivas para virus de la viruela de pollo y en todos los tejidos de órganos internos, pero no se detectaron en la muestra que coincidía con el clado de la viruela del canario. El análisis de las secuencias del virus de la reticuloendoteliosis y la detección por PCR mostró que los virus de reticuloendoteliosis que infectan a gallos de las praderas grandes eran compatible con virus de la reticuloendoteliosis A y tenía poca variabilidad en el análisis de la región U3 de la región repetida terminal larga. Los resultados de este estudio indican que el control del virus de la reticuloendoteliosis en colonias reproductoras de gallos de las praderas grandes puede beneficiarse de un programa de vacunación dirigido los virus de la viruela del pollo y de la reticuloendoteliosis. Sin embargo, una vacuna disponible comercialmente contra el virus de la reticuloendoteliosis no está disponible en este momento.

Role of Charge in Lipid Vesicle Binding and Vesicle Surface Saturation by Gaduscidin-1 and Gaduscidin-2.

The histidine-rich antimicrobial peptides Gad-1 and Gad-2, from paralogous genes in cod, provide an opportunity to examine the effect of charge and nonelectrostatic factors on peptide-vesicle interaction and on peptide antimicrobial activity. In this study, the dependence of vesicle ζ-potential on peptide concentration has been used to examine the binding of these peptides to model vesicle surfaces at pH = 5.0, for which the charges of Gad-1 and Gad-2 are +8 and +5, respectively, and at pH = 7.0, where their charges are +3 and +1, respectively. Interpreting the observed ζ-potential behaviors as examples of Langmuir adsorption isotherms, it is possible to infer the equilibrium constant for peptide-vesicle binding, the fraction of the peptide bound at low peptide concentration, and the maximum peptide-to-lipid ratio when the vesicle surface is saturated at high peptide concentration. For both peptides, higher peptide charge is found to be correlated with a lower fraction of the peptide being bound to vesicle surfaces at low peptide concentration and with a smaller maximum bound peptide-to-lipid ratio at high peptide concentration. The equilibrium binding constant, on the other hand, is more strongly correlated with the peptide sequence than with the charge. Gad-1, which has been shown to be more biologically active than Gad-2, displayed a significantly higher equilibrium binding constant. These observations suggest that while the maximum peptide density on the vesicle surface is limited by electrostatic interactions, the free energy of peptide binding, like the observed antimicrobial activities of the Gad peptides, is also sensitive to other peptide factors which might, for example, influence hydrophobic interactions.

Roles of histidine charge and cardiolipin in membrane disruption by antimicrobial peptides Gaduscidin-1 and Gaduscidin-2.

Gad-1 and Gad-2 are helical, histidine-rich antimicrobial peptides (AMPs) from paralogous genes in cod. 15N and 2H solid state nuclear magnetic resonance (NMR) were used to characterize their lipid-bound structures and lipid interactions. Gad-1 was found to position in-plane in POPC: POPG bilayers. Gad-1 displayed greater effects than Gad-2 on lipid acyl chain order of POPE: POPG and POPE: POPG: CL bilayers, in keeping with its greater activity against E. coli. The effect of Gad-1 and Gad-2 on lipid bilayer order was only weakly affected by changes in pH, and hence changes in histidine charge. This was somewhat surprising for Gad-2 as this peptide's biological activity has been shown to be greater at low pH and thus the finding may point to the existence of functional interactions with non-lipid components of bacteria. The incorporation of cardiolipin into POPE: POPG bilayers in such a way as to preserve the overall charge of the bilayers did not alter Gad-1's effects on lipid acyl chain order parameters, which report on motions on the 10-5 s timescale. When cardiolipin and Gad-1 were both present, there were subtle changes on membrane dynamics at other timescales.

Effects of a Growth Mindset of Personality on Emerging Adults' Defender Self-Efficacy, Moral Disengagement, and Perceived Peer Defending.

This study investigated the effects of a brief educational exercise aimed to promote a growth mindset of personality (the belief that personality traits are malleable) on outcomes linked to peer defending. Undergraduates (N = 60) were randomly assigned to complete a learning task designed to foster a growth mindset of personality or to a matching control task. They then read a vignette of a college student victimized by peers and completed paper-and-pencil measures of defender self-efficacy, moral disengagement, and perceived defender behavior, followed by a brief manipulation check. The experimental manipulation was successful, and participants who completed the growth mindset of personality intervention reported higher defender self-efficacy, lower moral disengagement, and higher perceived defending behavior. There was also a significant indirect effect of the experimental manipulation on perceived defending via self-efficacy, suggesting that a growth mindset of personality may influence peer defending through gains in defender self-efficacy. Implications are discussed for bullying prevention, with emphasis on programming for emerging adults at college.

Impact of road proximity on infants and children with bronchopulmonary dysplasia.

INTRODUCTION: Infants born prematurely are at high risk for morbidities, including lung disease (bronchopulmonary dysplasia [BPD]). Little is known regarding environmental factors that can impact outcomes in BPD. We sought to assess the role of traffic-related air pollution (TRAP) on respiratory outcomes in BPD. METHODS: A total of 784 subjects were included from the Johns Hopkins BPD clinic. Caregivers completed questionnaires on environmental exposures and respiratory outcomes (acute care use and chronic symptoms). Distance to the nearest major roadway was derived from subjects' geocoded residential addresses. RESULTS: Approximately half of the subjects (53.8%) lived within 500 m of a major roadway. Subjects who lived within 500 m of a major roadway were more likely to be non-white (P = .006), have a lower estimated household income (P < .001) and live in more densely populated zip codes (P < .001) than those who lived further than 500 m away. For every 1 km increase in distance between residence and roadway, the likelihood of activity limitations decreased by 35% (P = .005). No differences in acute care use were seen with proximity to major roadways. CONCLUSIONS: Proximity to a major roadway was associated with chronic respiratory symptoms, such as activity limitations (eg, dyspnea), and tended to be associated with nighttime symptoms as well. Self-reported minorities and families with lower estimated household incomes may be more likely to be exposed to TRAP. Further research is necessary to define the effects of TRAP versus other sources of indoor and outdoor air pollution as well as to determine the best ways of combatting pollution-related respiratory morbidities.

Structural parameters of soft PNIPAM microgel particles as a function of crosslink density.

HYPOTHESIS: The temperature dependences of hydrodynamic radii in thermo-sensitive microgel suspensions, known as collapse curves, are commonly fitted to the benchmark Flory-Rehner theory but parameters obtained often yield little physical insights. Our study of poly(N-isopropylacrylamide) (PNIPAM) microgel suspensions in water is driven by the hypothesis that fitting to Flory-Rehner theory can yield meaningful parameters that separate into ones that are insensitive to crosslink density or deuteration and ones that are not. EXPERIMENTS: Dynamic light scattering (DLS) and rheology experiments were done on 8 microgel variants, protonated and deuterated PNIPAM for four crosslink densities, synthesized under otherwise identical conditions. FINDINGS: Remarkably, polymer volume fractions in the microgel particle at collapse, ϕcollapse, obtained via rheology, are independent of crosslink density. Along with collapse curves from DLS, this determines the temperature dependence of microgel water and polymer volume fractions. Fitting collapse curves to Flory-Rehner theory yields reference polymer volume fractions, ϕ0, associated with microgel particle elasticity. ϕ0 is much lower than ϕcollapse, and increases with crosslink density. For all microgel sample variants, a crossover temperature, where the elastic contribution to osmotic pressure changes sign, is found to approximate the final temperature after microgel synthesis and also to the free polymer θ temperature.

Preadolescents' Internal Attributions for Negative Peer Experiences: Links to Child and Classroom Peer Victimization and Friendship.

In addition to children's own peer relations, contextual norms for peer relations in classrooms and schools can influence how they perceive their peer interactions, and in some cases, might do so in opposite ways. The current study examined the relations of preadolescents' internal attributions for negative peer experiences with their own peer victimization and reciprocal friendship, as well as their classrooms' norms for peer victimization and reciprocal friendship. A racially diverse sample of 532 boys and girls from 37 fourth- and fifth-grade classrooms completed self-report measures of two internal attributions (characterological and behavioral) and peer nominations for peer victimization and reciprocal friendship. Multilevel multivariate regression was used to test a series of two-level models. Child peer victimization was positively associated with characterological attributions, and classroom peer victimization was negatively related to these attributions. Child reciprocal friendship was negatively associated with characterological and behavioral attributions, and classroom reciprocal friendship was positively related to characterological attributions. Results reveal distinct relations of children's own peer victimization and reciprocal friendship with their internal peer attributions. The findings also highlight the contextualized nature of children's internal peer attributions and provide additional support for the emerging notion of inverse or paradoxical effects of class/school-level variables on children's social cognition. Implications are briefly discussed for both school-based intervention and psychotherapy.

Preadolescents' Daily Peer Victimization and Perceived Social Competence: Moderating Effects of Classroom Aggression.

Few studies have assessed children's daily peer experiences, and even fewer have considered their daily self-perceptions. This daily diary study examined relations between preadolescents' daily reports of peer victimization and perceived social competence, along with moderating effects of classroom aggression. A racially diverse sample of 182 children in 5th grade (105 boys; M age = 10.64 years; 35% White, 31% Black, 17% Hispanic, 17% other or not reported) completed daily measures of peer victimization and perceived social competence, with most children completing measures on 8 school days. Teachers completed measures of aggression for each participating pupil. Four types of peer victimization (verbal victimization, social manipulation, social rebuff, and property attacks) predicted decreased daily perceived social competence. Daily social rebuff predicted decreased daily perceived social competence beyond the effects of the other types of victimization. Classroom aggression moderated the relation of verbal victimization with perceived social competence, such that this relation was significant in classrooms with lower aggression and nonsignificant in classrooms with higher aggression. Results indicate that preadolescents' daily self-perceptions fluctuate with daily victimization by peers, particularly with social rebuff. Findings also suggest that the impact of verbal victimization on children's self-views could be exacerbated in classrooms that better manage peer-to-peer aggression. Accordingly, targeted interventions appear critical for children who continue to experience peer victimization in schools with highly effective aggression prevention programs.

College students' daily coping, mood, and quality of life: Benefits of problem-focused engagement.

In this short communication, we investigated the relations of daily coping, mood, and quality of life in college students (n = 74) over seven consecutive days (n = 510). Specifically, we tested whether four types of daily coping (problem-focused engagement, problem-focused disengagement, emotion-focused engagement, and emotion-focused disengagement) were associated with three aspects of daily functioning (negative mood, positive mood, and quality of life). In a single multilevel multivariate regression model, we examined the day-to-day relations of the four coping strategies with mood and quality of life, while controlling for perceived stress. Results largely supported our hypotheses, such that problem-focused engagement was linked to lower negative mood and higher positive mood and quality of daily life, whereas the three other types of coping were negatively related or unrelated to daily functioning. These findings provide support for the benefits of problem-focused engagement in coping with everyday stressors of life as a college student, and implications for psychotherapy and counselling are discussed.

Unexpected Prevalence of eae-Positive Escherichia coli in the Animas River, Durango, Colorado.

Since 2014, biology students at Fort Lewis College have studied the water quality of the Animas River in Durango, Colorado. Environmental microbiology and molecular biology techniques have been employed to study Escherichia coli isolates from the river and to define characteristics of the bacteria related to public health. E. coli was found in the river, as well as in culverts and tributary creeks that drain into the river within the Durango city limits. Concentrations of E. coli in the river occasionally exceeded the US EPA guideline of 126 CFU per 100 mL for recreational water use. Many of the E. coli isolates were able to be grown at 45 °C, an indication of mammalian origin. Unexpectedly, 8% of the isolates contained the intimin (eae) gene, a virulence gene characteristic of two pathotypes of E. coli, the enterohemorrhagic and enteropathogenic E. coli. Several isolates tested were resistant to multiple antibiotics commonly used in animal and human medicine. Further study is warranted to determine the source of these bacteria entering the Animas River, and to further characterize the possible disease potential of multi-antibiotic resistant and virulence gene-containing isolates found in a semi-rural/urban setting.

Simulation-based Education and Human Factors Training in Postgraduate Medical Education: A Northern Ireland Perspective.

With their potential to improve patient safety, simulation based education (SBE) and human factors training are gaining momentum across the spectrum of medical education. There are ever increasing drivers for their integration, in particular within the postgraduate arena. This article aims to provide an overview of both simulation based education and human factors training. The breadth of terminology can be bewildering and our target audience is novice or developing practitioners and policymakers. We focus particularly on a regional setting where the Northern Ireland Simulation and Human Factors Network (NISHFN) is working to advance the field.

REVIEW OF MORTALITY AND EFFECTIVENESS OF NEONATAL TREATMENT IN CAPTIVE ATTWATER'S PRAIRIE CHICKENS ( TYMPANUCHUS CUPIDO ATTWATERI).

A retrospective study of mortality and neonatal treatment for 975 Attwater's prairie chickens ( Tympanuchus cupido attwateri) was conducted from 2009-2015. Gross necropsy, histopathology, and medical records for chicks less than 8 wk of age at the Houston Zoo were reviewed and summarized. The total mortality rate was 36% ( n = 352). Yolk sac infection was the most common cause of death (21%; n = 73) followed by maladaptation (19%; n = 68), musculoskeletal abnormalities (19%; n = 66), necrotic enteritis (13%; n = 44), and mucoid enteritis (11%; n = 39). Gavage feeding of a highly digestible formula was associated with a higher proportion of necrotic enteritis and a reduced occurrence of both mucoid enteritis and maladaptation. Meloxicam administration had a significantly reduced incidence of mucoid enteritis. Survival past 10 days of age, prevention of neonatal bacterial infection, and supportive treatment with meloxicam are important factors to increase chick survival and improve captive breeding success for Attwater's prairie chickens. Gavage feeding of a diet low in digestible carbohydrates has the potential for reducing disease due to necrotic enteritis in this species.

Effects of Amphipathic Polypeptides on Membrane Organization Inferred from Studies Using Bicellar Lipid Mixtures.

SP-B63-78, a lung surfactant protein fragment, and magainin 2, an antimicrobial peptide, are amphipathic peptides with the same overall charge but different biological functions. Deuterium nuclear magnetic resonance has been used to compare the interactions of these peptides with dispersions of 1,2-dimyristoyl- sn-glycero-3-phophocholine (DMPC)/1,2-dihexanoyl- sn-glycero-3-phophocholine (DHPC) (4:1) and DMPC/1,2-dimyristoyl- sn-glycero-3-phopho-(1'-rac-glycerol) (DMPG)/DHPC (3:1:1), two mixtures of long-chain and short-chain lipids that display bicellar behavior. This study exploited the sensitivity of a bicellar system structural organization to factors that modify partitioning of their lipid components between different environments. In small bicelle particles formed at low temperatures, short-chain components preferentially occupy curved rim environments around bilayer disks of the long-chain components. Changes in chain order and lipid mixing, on heating, can drive transitions to more extended assemblies including a magnetically orientable phase at intermediate temperature. In this work, neither peptide had a substantial effect on the behavior of the zwitterionic DMPC/DHPC mixture. For bicellar mixtures containing the anionic lipid DMPG, the peptide SP-B63-78 lowered the temperature at which magnetically orientable particles coalesced into more extended lamellar structures. SP-B63-78 did not promote partitioning of the zwitterionic and anionic long-chain lipid components into different environments. Magainin 2, on the other hand, was found to promote separation of the anionic lipid, DMPG, and the zwitterionic lipid, DMPC, into different environments for temperatures above 34 °C. The contrast between the effects of these two peptides on the lipid mixtures studied appears to be consistent with their functional roles in biological systems.

The simultaneous assessment of and relations between children's sympathetic and parasympathetic psychophysiology and their reactive and proactive aggression.

The goal of the current study was to examine the link between children's psychophysiology and aggression when both constructs were assessed simultaneously in scenarios designed to provide the opportunity to aggress for either a reactive reason or a proactive reason. Both sympathetic nervous system (SNS) activity (skin conductance) and parasympathetic nervous system (PNS) activity (respiratory sinus arrhythmia or RSA), as well as their interaction, were included as physiological measures. Participants were 35 5th-grade children who were placed in two virtual-peer scenarios; one scenario provided the opportunity to aggress in response to peer provocation (i.e., reactive aggression) and the other scenario provided the opportunity to aggress for instrumental gain (i.e., proactive aggression). Both skin conductance and RSA were assessed at the time that children were given the opportunity to aggress; this simultaneous assessment of psychophysiology and aggression allowed for an examination of in-the-moment relations between the two constructs. For the reactive scenario, RSA moderated the in-the-moment relation between skin conductance and aggression such that the association was positive at low RSA but negative at high RSA. For the proactive scenario, skin conductance negatively predicted aggression in-the-moment, and RSA positively predicted aggression in-the-moment, but their interaction was not a significant predictor of aggression. Theoretical implications for reactive and proactive aggression and underlying physiological processes are discussed.