Distinguishing vulnerability and resilience to posttraumatic stress disorder evaluating traumatic experiences, genetic risk and electronic health records

What distinguishes vulnerability and resilience to posttraumatic stress disorder (PTSD) remains unclear. Levering traumatic experiences reporting, genetic data, and electronic health records (EHR), we investigated and predicted the clinical comorbidities (co-phenome) of PTSD vulnerability and resilience in the UK Biobank (UKB) and All of Us Research Program (AoU), respectively. In 60,354 trauma-exposed UKB participants, we defined PTSD vulnerability and resilience considering PTSD symptoms, trauma burden, and polygenic risk scores. EHR-based phenome-wide association studies (PheWAS) were conducted to dissect the co-phenomes of PTSD vulnerability and resilience. Significant diagnostic endpoints were applied as weights, yielding a phenotypic risk score (PheRS) to conduct PheWAS of PTSD vulnerability and resilience PheRS in up to 95,761 AoU participants. EHR-based PheWAS revealed three significant phenotypes positively associated with PTSD vulnerability (top association "Sleep disorders") and five outcomes inversely associated with PTSD resilience (top association "Irritable Bowel Syndrome"). In the AoU cohort, PheRS analysis showed a partial inverse relationship between vulnerability and resilience with distinct comorbid associations. While PheRSvulnerability associations were linked to multiple phenotypes, PheRSresilience showed inverse relationships with eye conditions. Our study unveils phenotypic differences in PTSD vulnerability and resilience, highlighting that these concepts are not simply the absence and presence of PTSD.

Multi-ancestry study of the genetics of problematic alcohol use in over 1 million individuals

Problematic alcohol use (PAU), a trait that combines alcohol use disorder and alcohol-related problems assessed with a questionnaire, is a leading cause of death and morbidity worldwide. Here we conducted a large cross-ancestry meta-analysis of PAU in 1,079,947 individuals (European, N = 903,147; African, N = 122,571; Latin American, N = 38,962; East Asian, N = 13,551; and South Asian, N = 1,716 ancestries). We observed a high degree of cross-ancestral similarity in the genetic architecture of PAU and identified 110 independent risk variants in within- and cross-ancestry analyses. Cross-ancestry fine mapping improved the identification of likely causal variants. Prioritizing genes through gene expression and chromatin interaction in brain tissues identified multiple genes associated with PAU. We identified existing medications for potential pharmacological studies by a computational drug repurposing analysis. Cross-ancestry polygenic risk scores showed better performance of association in independent samples than single-ancestry polygenic risk scores. Genetic correlations between PAU and other traits were observed in multiple ancestries, with other substance use traits having the highest correlations. This study advances our knowledge of the genetic etiology of PAU, and these findings may bring possible clinical applicability of genetics insights-together with neuroscience, biology and data science-closer.

Diversity and Scale: Genetic Architecture of 2,068 Traits in the VA Million Veteran Program

Genome-wide association studies (GWAS) have underrepresented individuals from non-European populations, impeding progress in characterizing the genetic architecture and consequences of health and disease traits. To address this, we present a population-stratified phenome-wide GWAS followed by a multi-population meta-analysis for 2,068 traits derived from electronic health records of 635,969 participants in the Million Veteran Program (MVP), a longitudinal cohort study of diverse U.S. Veterans genetically similar to the respective African (121,177), Admixed American (59,048), East Asian (6,702), and European (449,042) superpopulations defined by the 1000 Genomes Project. We identified 38,270 independent variants associating with one or more traits at experiment-wide P < 4.6 × 10 - 11 significance; fine-mapping 6,318 signals identified from 613 traits to single-variant resolution. Among these, a third (2,069) of the associations were found only among participants genetically similar to non-European reference populations, demonstrating the importance of expanding diversity in genetic studies. Our work provides a comprehensive atlas of phenome-wide genetic associations for future studies dissecting the architecture of complex traits in diverse populations.

The Associations of Racial Discrimination and Neighborhood Disadvantage With World Assumptions Among Black, Latine, and Asian Young Adults

The theory of shattered assumptions proposes that experiencing traumatic events can change how people view themselves and the world. Most adults experience a traumatic event during their lifetime, and some subsequently develop post-traumatic stress disorder (PTSD). However, the current conceptualization of trauma (i.e., Criterion A PTSD) may be too narrow to adequately capture the range of potentially traumatizing events that People of Color experience, including racial discrimination and neighborhood disadvantage. This study investigated the association of racial discrimination and neighborhood disadvantage with core beliefs about the world being safe and predictable (i.e., world assumptions) among a sample of Black, Latine, and Asian young adults. Multi-step analyses of covariance tested associations between racial discrimination and neighborhood disadvantage with world assumptions and whether these held in the context of other traumatic exposures. Results indicated that racial discrimination negatively impacted world assumptions among Asian young adults only and this effect remained in the context of trauma. In addition, low neighborhood support negatively impacted world assumptions across all racial groups and neighborhood violence negatively impacted world assumptions among Latine young adults only; however, this effect did not remain in the context of trauma. This study indicates it is worthwhile to consider other adverse events in the conceptualization of trauma, such as racial discrimination and neighborhood disadvantage, that may impact world assumptions and contribute to subsequent post-trauma psychopathology.

Multi-ancestry study of the genetics of problematic alcohol use in >1 million individuals

Problematic alcohol use (PAU) is a leading cause of death and disability worldwide. To improve our understanding of the genetics of PAU, we conducted a large cross-ancestry meta-analysis of PAU in 1,079,947 individuals. We observed a high degree of cross-ancestral similarity in the genetic architecture of PAU and identified 110 independent risk variants in within- and cross-ancestry analyses. Cross-ancestry fine-mapping improved the identification of likely causal variants. Prioritizing genes through gene expression and/or chromatin interaction in brain tissues identified multiple genes associated with PAU. We identified existing medications for potential pharmacological studies by drug repurposing analysis. Cross-ancestry polygenic risk scores (PRS) showed better performance in independent sample than single-ancestry PRS. Genetic correlations between PAU and other traits were observed in multiple ancestries, with other substance use traits having the highest correlations. The analysis of diverse ancestries contributed significantly to the findings, and fills an important gap in the literature.

Epidemiologic and Genetic Associations of Endometriosis With Depression, Anxiety, and Eating Disorders

IMPORTANCE

Endometriosis is a common chronic gynecologic pathology with a large negative impact on women's health. Beyond severe physical symptoms, endometriosis is also associated with several psychiatric comorbidities, including depression and anxiety.

OBJECTIVE

To investigate whether pleiotropy contributes to the association of endometriosis with depression, anxiety, and eating disorders.

DESIGN, SETTING, AND PARTICIPANTS

This genetic association study was performed between September 13, 2021, and June 24, 2022, in 202 276 unrelated female participants. Genotypic and phenotypic information from the UK Biobank was combined with genome-wide association statistics available from the Psychiatric Genomics Consortium (11 countries), the Million Veteran Program (US), the FinnGen study (Finland), and the CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology) consortium (5 countries).

MAIN OUTCOMES AND MEASURES

The main outcomes were the phenotypic and genetic associations of endometriosis with anxiety, depression, and eating disorders.

RESULTS

A total of 8276 women with endometriosis (mean [SD] age, 53.1 [7.9] years) and 194 000 female controls (mean [SD] age, 56.7 [7.9] years) were included in the study. In a multivariate regression analysis accounting for age, body mass index, socioeconomic status, chronic pain-related phenotypes, irritable bowel syndrome, and psychiatric comorbidities, endometriosis was associated with increased odds of depression (odds ratio [OR], 3.61; 95% CI, 3.32-3.92), eating disorders (OR, 2.94; 95% CI, 1.96-4.41), and anxiety (OR, 2.61; 95% CI, 2.30-2.97). These associations were supported by consistent genetic correlations (rg) (depression rg, 0.36, P = 1.5 × 10-9; anxiety rg, 0.33, P = 1.17 × 10-5; and eating disorders rg, 0.61, P = .02). With the application of a 1-sample mendelian randomization, the genetic liabilities to depression and anxiety were associated with increased odds of endometriosis (depression: OR, 1.09; 95% CI, 1.08-1.11; anxiety: OR, 1.39; 95% CI, 1.13-1.65). A genome-wide analysis of pleiotropic associations shared between endometriosis and psychiatric disorders identified 1 locus, DGKB rs12666606, with evidence of pleiotropy between endometriosis and depression after multiple testing correction (z = -9.46 for endometriosis, z = 8.10 for depression, P = 5.56 × 10-8; false discovery rate q = 4.95 × 10-4).

CONCLUSIONS AND RELEVANCE

These findings highlight that endometriosis is associated with women's mental health through pleiotropic mechanisms. To our knowledge, this is the first large-scale study to provide genetic and phenotypic evidence of the processes underlying the psychiatric comorbidities of endometriosis.

Factor structure of the posttraumatic stress disorder checklist (PCL-17) in 279,897 million veteran program participants

The Million Veteran Program (MVP) uses the posttraumatic stress disorder symptoms (PTSD) Checklist 17 (PCL-17) self-report to assess PTSD. Existing literature suggests that the five-factor dysphoric arousal model best represents the PTSD symptom clusters; this can be tested within MVP, one of the largest samples collected with suitable data. We compared factor models within MVP across genetically defined subsamples (ancestry [European, African, admixed American, and East Asian], sex) via multi-group confirmatory factor analyses in a sample of 279,897 participants. The five-factor dysphoric arousal model best fit the PCL-17 data, consistent with previous findings. The factor structure could also be imposed across all groups tested. Verifying the factor structure provides a framework for future phenotypic and genotypic analyses within MVP and other samples.

Paradoxical age-related improvement in mental health in U.S. military veterans: Results from the national health and resilience in veterans study

OBJECTIVE

To determine whether a seemingly "paradoxical" trend whereby mental health improves as a function of age despite declining physical and cognitive health occurs in U.S. military veterans, who are older, and have higher rates of trauma exposure and psychiatric morbidities relative to non-veterans.

METHODS

Using data from a nationally representative, cross-sectional sample of 4069 U.S. veterans, polynomial regression analyses were conducted to examine changes in self-reported physical, cognitive, and mental health of veterans representing the full age spectrum.

RESULTS

Physical health scores were consistently average and stable until around age 80 when they declined. In contrast, cognitive and mental health scores were markedly lower in young veterans and then increased linearly and positively well into late-life.

CONCLUSIONS

While greater age is associated with relative stability and late-life decline in physical health in U.S. veterans, mental and cognitive health steadily improve until much later in life. Results may help inform age-specific prevention and treatment efforts to promote healthy aging in this population.

Coffee and energy drink use patterns in college freshmen: associations with adverse health behaviors and risk factors

Background

Public health concern over college students mixing caffeine-containing energy drinks (EDs) and alcohol has contributed to an array of ED-focused research studies. One review found consistent associations between ED use and heavy/problem drinking as well as other drug use and risky behaviors (Nutr Rev 72:87–97, 2014). The extent to which similar patterns exist for other sources of caffeine is not known. The present study examined associations between coffee and ED consumption and alcohol, tobacco and other drug use; alcohol use problems; and parental substance abuse and mental health problems in a sample of college freshmen.

Methods

Subjects were N = 1986 freshmen at an urban university who completed an on-line survey about demographics; caffeine; alcohol, tobacco and other drug use; and family history. The sample was 61% female and 53% White. Chi-square analyses and multivariable binary or ordinal logistic regression were used to compare substance use, problem alcohol behavior, and familial risk measures across 3 caffeine use groups: ED (with or without Coffee) (ED + Co; N = 350); Coffee but no ED (Co; N = 761); and neither coffee nor ED (NoCE; N = 875) use.

Results

After adjusting for gender and race, the 3 caffeine use groups differed on 8 of 9 symptoms for alcohol dependence. In all cases, the ED + Co group was most likely to endorse the symptom, followed by the Co group and finally the NoCE group (all p < .002). A similar pattern was found for: use 6+ times of 5 other classes of drugs (all p < .05); extent of personal and peer smoking (all p < .001); and paternal problems with alcohol, drugs and anxiety/depression as well as maternal alcohol problems and depression/anxiety (p < .04).

Conclusions

The response pattern was ubiquitous, with ED + Co most likely, Co intermediate, and NoCE least likely to endorse a broad range of substance use, problem alcohol behaviors, and familial risk factors. The finding that the Co group differed from both the ED + Co and NoCE groups on 8 measures and from the NoCE group on one additional measure underscores the importance of looking at coffee in addition to EDs when considering associations between caffeine and other risky behaviors.

Genetically regulated multi-omics study for symptom clusters of posttraumatic stress disorder highlights pleiotropy with hematologic and cardio-metabolic traits

Posttraumatic stress disorder (PTSD) is a psychiatric disorder that may arise in response to severe traumatic event and is diagnosed based on three main symptom clusters (reexperiencing, avoidance, and hyperarousal) per the Diagnostic Manual of Mental Disorders (version DSM-IV-TR). In this study, we characterized the biological heterogeneity of PTSD symptom clusters by performing a multi-omics investigation integrating genetically regulated gene, splicing, and protein expression in dorsolateral prefrontal cortex tissue within a sample of US veterans enrolled in the Million Veteran Program (N total = 186,689). We identified 30 genes in 19 regions across the three PTSD symptom clusters. We found nine genes to have cell-type specific expression, and over-representation of miRNA-families - miR-148, 30, and 8. Gene-drug target prioritization approach highlighted cyclooxygenase and acetylcholine compounds. Next, we tested molecular-profile based phenome-wide impact of identified genes with respect to 1678 phenotypes derived from the Electronic Health Records of the Vanderbilt University biorepository (N = 70,439). Lastly, we tested for local genetic correlation across PTSD symptom clusters which highlighted metabolic (e.g., obesity, diabetes, vascular health) and laboratory traits (e.g., neutrophil, eosinophil, tau protein, creatinine kinase). Overall, this study finds comprehensive genomic evidence including clinical and regulatory profiles between PTSD, hematologic and cardiometabolic traits, that support comorbidities observed in epidemiologic studies of PTSD.

Resilience to traumatic stress in U.S. military veterans: Application of a novel classification approach in a nationally representative sample

Resilience has been of particular interest to researchers and clinicians focused on response to trauma. In the current study, we employed a novel, discrepancy-based psychiatric resilience (DBPR) analytic approach to operationalizing resilience and examined its relation to potentially protective psychosocial factors in a nationally representative sample of U.S. veterans (N = 2704). Cumulative lifetime trauma burden, severity of PTSD symptoms, and protective factors such as personality characteristics (e.g., conscientiousness), protective psychosocial characteristics (e.g., purpose in life), and social connectedness (e.g., secure attachment style) were assessed. PTSD Checklist (PCL) scores were regressed onto cumulative trauma burden for the entire sample and a predicted PCL score was generated for each veteran. Resilience was operationalized as a lower actual relative to predicted PCL score. Results of a relative importance analysis revealed that somatic symptoms (22.5% relative variance explained [RVE]), emotional stability (22.4% RVE), and a secure attachment style (14.1%) explained the majority of the variance in resilience scores. These results demonstrate the utility of a DBPR approach to operationalizing resilience in U.S. military veterans. They also identify potentially modifiable psychosocial factors that may be bolstered in prevention and treatment efforts designed to mitigate the negative effects of trauma and promote resilience in this population.

Interpersonal Trauma Exposure and Depression in Young Adults: Considering the Role of World Assumptions

The transition to young adulthood confers heightened risk for depression, and exposure to interpersonal trauma (IPT) can magnify this risk. However, not all IPT-exposed young adults develop depressive symptoms, and not all young adults with depressive symptoms report past IPT, suggesting a need to identify moderators of the IPT-depression link. This study investigated whether four different world assumptions-core beliefs about the nature of the world-moderated the association between IPT exposure and depressive symptoms in college students (N = 1,084, M age = 19.5, 74.1% female). Participants self-reported IPT exposure, depressive symptoms, and world assumptions via an online survey. We predicted that the IPT-depressive symptom association would be weaker among young adults with more positive assumptions about the safety of the world, trustworthiness of people, predictability of people, and controllability of events, versus those with more negative world assumptions in these domains. Hierarchical regression results supported this prediction with respect to one world assumption type: more positive beliefs about the world's safety significantly attenuated the relation between past IPT exposure and present depressive symptoms, ΔF(1, 1061) = 9.54, ΔR2 = 0.01, p = .002. The IPT-depressive symptom link was over 3 times as strong for young adults with weak "world-is-safe" assumptions, versus those with strong "world-is-safe" assumptions. No other world assumption types emerged as moderators. Lay theories of the world's safety may represent a basic, survival-oriented belief with implications for depressive symptoms following safety threats, such as IPT. Addressing "world-is-safe" assumptions may enhance depression prevention efforts for IPT-exposed young adults.

Measurement invariance of the World Assumptions Questionnaire across race/ethnic group, sex, and sexual orientation

OBJECTIVE

The World Assumptions Questionnaire (WAQ) was developed to assess optimism and assumptions about the world, which often shift after traumatic events. However, no known study has investigated whether the WAQ holds similar meaning across demographic groups. The objective of this study was to investigate measurement invariance of the WAQ across race/ethnic group, sex, and sexual orientation.

METHOD

Participants consisted of 1,181 college students (75% female; 25% Black, 13% Latinx, 18% Asian, 45% White; 90% heterosexual) who completed an online survey on stress, personality, substance use, and mental health. We investigated a unidimensional and the 4-factor structure of the WAQ using confirmatory factor analysis, and configural, metric, and scalar invariance using multigroup confirmatory factor analysis.

RESULTS

After dropping 3 items, a 4-factor structure fit the data well (comparative fit index = .92; root mean square error of approximation =.05; 95% confidence interval [.045, .054]; standardized root mean square residual = .06). Mean WAQ scores were higher for participants with probable posttraumatic stress disorder on 2 of the 4 factors. We also identified multiple items that were not invariant across race/ethnic group, sex, and sexual orientation. However, after invariant items were removed, evidence of configural, scalar, and metric invariance was found.

CONCLUSIONS

This study replicated the 4-factor structure, mapping onto the 4 WAQ subscales, and indicated that a unidimensional measure of world assumptions should not be used. After making the adjustments recommended herein, the WAQ can be used to investigate differences across race/ethnic group, sex, and sexual orientation. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Sex-stratified gene-by-environment genome-wide interaction study of trauma, posttraumatic-stress, and suicidality

Epidemiologic studies recognize that trauma and posttraumatic stress are associated with heightened suicidal behavior severity, yet examination of these associations from a genetic perspective is limited. We performed a multivariate gene-by-environment genome-wide interaction study (GEWIS) of suicidality in 123,633 individuals using a covariance matrix based on 26 environments related to traumatic experiences, posttraumatic stress, social support, and socioeconomic status. We discovered five suicidality risk loci, including the male-associated rs2367967 (CWC22), which replicated in an independent cohort. All GEWIS-significant loci exhibited interaction effects where at least 5% of the sample had environmental profiles conferring opposite SNP effects from the majority. We identified PTSD as a primary driving environment for GxE at suicidality risk loci. The male suicidality GEWIS was enriched for three middle-temporal-gyrus inhibitory neuron transcriptomic profiles: SCUBE- and PVALB-expressing cells (β = 0.028, p = 3.74 × 10-4), OPRM1-expressing cells (β = 0.030, p = 0.001), and SPAG17-expressing cells (β = 0.029, p = 9.80 × 10-4). Combined with gene-based analyses (CNTN5 p association  = 2.38 × 10-9, p interaction  = 1.51 × 10-3; PSMD14 p association  = 2.04 × 10-7, p interaction  = 7.76 × 10-6; HEPACAM p association  = 2.43 × 10-6, p interaction  = 3.82 × 10-7) including information about brain chromatin interaction profiles (UBE2E3 in male neuron p = 1.07 × 10-5), our GEWIS points to extracellular matrix biology and synaptic plasticity as biological interactors with the effects of potentially modifiable lifetime traumatic experiences on genetic risk for suicidality. Characterization of molecular basis for the effects of traumatic experience and posttraumatic stress on risk of suicidal behaviors may help to identify novel targets for which more effective treatments can be developed for use in high-risk populations.

Characterizing the effect of background selection on the polygenicity of brain-related traits

BACKGROUND

Genome-wide association studies (GWAS) have demonstrated that psychopathology phenotypes are affected by many risk alleles with small effect (polygenicity). It is unclear how ubiquitously evolutionary pressures influence the genetic architecture of these traits.

METHODS

We partitioned SNP heritability to assess the contribution of background (BGS) and positive selection, Neanderthal local ancestry, functional significance, and genotype networks in 75 brain-related traits (8411 ≤ N ≤ 1,131,181, mean N = 205,289). We applied binary annotations by dichotomizing each measure based on top 2%, 1%, and 0.5% of all scores genome-wide. Effect size distribution features were calculated using GENESIS. We tested the relationship between effect size distribution descriptive statistics and natural selection. In a subset of traits, we explore the inclusion of diagnostic heterogeneity (e.g., number of diagnostic combinations and total symptoms) in the tested relationship.

RESULTS

SNP-heritability was enriched (false discovery rate q < 0.05) for loci with elevated BGS (7 phenotypes) and in genic (34 phenotypes) and loss-of-function (LoF)-intolerant regions (67 phenotypes). These effects were strongest in GWAS of schizophrenia (1.90-fold BGS, 1.16-fold genic, and 1.92-fold LoF), educational attainment (1.86-fold BGS, 1.12-fold genic, and 1.79-fold LoF), and cognitive performance (2.29-fold BGS, 1.12-fold genic, and 1.79-fold LoF). BGS (top 2%) significantly predicted effect size variance for trait-associated loci (σ² parameter) in 75 brain-related traits (β = 4.39 × 10^-5, p = 1.43 × 10^-5, model r² = 0.548). Considering the number of DSM-5 diagnostic combinations per psychiatric disorder improved model fit (σ² ~ B_Top2% × Genic × diagnostic combinations; model r² = 0.661).

CONCLUSIONS

Brain-related phenotypes with larger variance in risk locus effect sizes are associated with loci under BGS. We show exploratory results suggesting that diagnostic complexity may also contribute to the increased polygenicity of psychiatric disorders.

The impact of world assumptions on the association between discrimination and internalizing and substance use outcomes

This study investigated whether core beliefs about the world being safe and predictable (i.e. world assumptions) mediated the association between discrimination and internalizing and substance use problems among individuals from marginalized groups. Path analyses tested mediating effects of four types of world assumptions on the association between discrimination (race-, gender-, and sexual orientation-based) and anxiety, depression, alcohol and cannabis problems in college students (N = 1,181, age_mean = 19.50, SD = 1.67). Limited support for mediation by world assumptions was found: among Asian students, race-based discrimination indirectly impacted anxiety symptoms through low perceived controllability of events. Direct effects across groups and discrimination types were also found.

Genetic and Environmental Predictors of Adolescent PTSD Symptom Trajectories Following a Natural Disaster

: Genes, environmental factors, and their interplay affect posttrauma symptoms. Although environmental predictors of the longitudinal course of posttraumatic stress disorder (PTSD) symptoms are documented, there remains a need to incorporate genetic risk into these models, especially in youth who are underrepresented in genetic studies. In an epidemiologic sample tornado-exposed adolescents (n = 707, 51% female, Mage = 14.54 years), trajectories of PTSD symptoms were examined at baseline and at 4-months and 12-months following baseline. This study aimed to determine if rare genetic variation in genes previously found in the sample to be related to PTSD diagnosis at baseline (MPHOSPH9, LGALS13, SLC2A2), environmental factors (disaster severity, social support), or their interplay were associated with symptom trajectories. A series of mixed effects models were conducted. Symptoms decreased over the three time points. Elevated tornado severity was associated with elevated baseline symptoms. Elevated recreational support was associated with lower baseline symptoms and attenuated improvement over time. Greater LGLAS13 variants attenuated symptom improvement over time. An interaction between MPHOSPH9 variants and tornado severity was associated with elevated baseline symptoms, but not change over time. Findings suggest the importance of rare genetic variation and environmental factors on the longitudinal course of PTSD symptoms following natural disaster trauma exposure.

The role of drinking motives and perceived controllability of events in the association between college women's sexual assault victimization and binge drinking

Women with a history of sexual assault are at elevated risk for engaging in binge drinking. The aims of the current study are to investigate two types of drinking motives (coping and social) that potentially underlie the sexual assault-binge drinking link in a sample of female college drinkers (N = 691; 37.6% sexual assault prevalence), and to determine the extent to which the relationships between sexual assault history and each type of drinking motive depend on women's assumptions about the controllability of events. Conditional process analysis results indicated that women who experienced sexual assault (vs. those who did not) were more likely to report both coping and social drinking motives, which in turn, were both positively associated with increased binge drinking. Consistent with our hypothesis, results showed the relationship between sexual assault history and coping drinking motives was moderated by perceived controllability of events. Specifically, sexual assault victims reported high coping motives regardless of controllability of events. Nonvictims only reported high coping motives when their perceived controllability of events was low - comparable to coping motives of victims. This integrative approach affords a more comprehensive understanding of the context in which college women's binge drinking occurs, and offers insight into processes that could be targeted in interventions.

The Nomological Network of a Behavioral Distress Tolerance Task in Veterans

There is a relative lack of research on distress tolerance (DT) in veteran samples. The aims of the study were to (a) evaluate convergent and discriminant validity of a behavioral measure of DT compared to theoretically similar (i.e., self-report DT, negative urgency) and dissimilar (i.e., risk-taking) constructs and (b) evaluate the concurrent validity of DT in relation to posttraumatic stress disorder (PTSD) and depressive symptoms in a veteran sample. A sample of U.S. veterans who served after the September 11, 2001 terror attacks (N = 306, 89.9% male; M age 30.2 years, SD = 4.5, range: 21-40 years) completed self-report and behavioral measures of DT, risk-taking, impulsivity, and depressive symptoms, and completed a clinical interview for PTSD. Results of a multitrait-multimethod matrix found significant yet minimal shared variance, r2 = .01-.03, ps = .002-.055, between the self-report and behavioral measures of DT. We used a series of multiple regressions to examine the relative contribution of the behavioral and self-report DT measures in the prediction of PTSD and depressive symptoms. Self-reported, but not behavioral, DT accounted for unique variance in PTSD, r2 = .12, p < .001, and depressive symptoms, r2 = .23, p < .001. Participants with PTSD or higher scores on measures of depression were more likely to report greater increases in frustration and irritability after completing the behavioral task. Results indicate that DT is not a unidimensional construct and must be considered in the context of specific emotions (e.g., tolerance of irritability vs. fear) and contexts (e.g., behavioral, affective).

Anxiety Sensitivity and Distress Tolerance Typologies and Relations to Posttraumatic Stress Disorder: A Cluster Analytic Approach

A growing literature suggests a relationship between a high anxiety sensitivity (AS; the fear of anxiety and its related consequences)/low distress tolerance (DT; the capacity tolerate internal negative states) profile and posttraumatic stress disorder (PTSD) symptoms. However, specific profiles have not been identified or examined specifically in veteran samples. Thus, the aims of the present study were to establish empirically derived profiles created from response patterns on the Anxiety Sensitivity Index and Distress Tolerance Scale and to examine associations with PTSD symptom clusters among a sample of combat-exposed veterans (N = 250). A cluster analytic approach was utilized to identify AS/DT profiles, and a series of MANOVAs with post hoc analyses was conducted to examine the relationship between each AS/DT profile and each PTSD symptom cluster. Results indicated a three-cluster solution including a high AS/low DT "at risk" profile, a low AS/high DT "resilient" profile, and an average AS/DT "intermediate" profile. The at-risk profile was associated with significantly greater symptoms in each PTSD cluster (i.e., hyperarousal, avoidance, re-experiencing) when compared to the other two profiles. The at-risk profile was also associated with greater depressive symptoms and lower self-reported resilience. These findings extend the previous literature by identifying a high AS/low DT "at risk" profile and its associations with PTSD symptoms, underscoring the potential utility in targeting these affect-regulation constructs for clinical intervention.

Profiles of psychosocial adversity and their associations with health risk behaviors and mental health outcomes in young adults

Adverse psychosocial experiences operate simultaneously to affect mental health and behavior. The current study used mixture modeling to identify subgroups of young adults based on experiences of four types of psychosocial adversity and characterize their associations with depression, anxiety, world assumptions, substance use, and sexual risk behavior. Sexual assault, physical assault, and discrimination (interpersonal adversity) showed similar patterns within each group but diverged from neighborhood disadvantage in two groups. Groups characterized by higher interpersonal adversity reported the most negative health outcomes. Findings highlight variations in the co-occurrence of adverse experiences and differential links to risky health behaviors and mental health.

Predictors and mental health outcomes of potentially traumatic event exposure

The aims were two-fold: to examine prevalence and correlates of lifetime potentially traumatic event (PTE) exposure and to explore the relationships between PTE exposure and mental health outcomes (i.e., trauma related distress, alcohol use quantity and frequency, depression symptoms, and anxiety symptoms) within a large sample of college freshmen. 6120 participants, consisting of three cohorts of incoming freshman at a large southeastern university, completed an online assessment battery measuring a multitude of factors including PTEs, personality, relationships (i.e., parental and peer), and mental health. The majority (81.8%) of participants endorsed experiencing at least one PTE within their lifetime and 39.0% reported at least one interpersonal trauma (i.e., physical assault, sexual assault, other unwanted or uncomfortable sexual situation). The average number of PTE categories endorsed was 1.71 (SD=1.30), and 8.7% of participants reported experiencing four or more separate PTE categories pre-college entry. Female gender and peer deviance were consistently associated with PTE exposure and symptoms of psychopathology. Furthermore, a history of interpersonal PTE exposure was associated with increased alcohol use (i.e., frequency and quantity), trauma related distress, depressive symptoms, and anxiety symptoms. The data demonstrate high prevalence PTE exposure among young adults and the clinical significance of a PTE history.

Potentially traumatic events, personality, and risky sexual behavior in undergraduate college students

OBJECTIVE

Impulsivity and extraversion have demonstrated associations with risky sexual behavior (RSB) and potentially traumatic events (PTEs). In addition, interpersonal trauma appears to be associated with RSB, but research on the relationship between RSB and noninterpersonal PTEs (e.g., accidental) is lacking. The current study aims to investigate the relationships between personality (i.e., impulsivity, extraversion), RSB and multiple types of PTEs (i.e., accidental, physical, or sexual).

METHOD

Personality and demographic characteristics were assessed during participants' (N = 970) first semester of college, past-12 month PTEs and RSB were assessed during the second semester of participants' junior year. Multiple linear regression was used to examine the relationship between PTEs, personality factors, and RSB. Analyses were also conducted to examine the potential mediating effect of interpersonal PTEs on the relationship between personality and RSB.

RESULTS

Impulsivity and extraversion were significantly positively associated with RSB. Both physical and sexual PTEs, but not accidental PTEs, were also significantly positively associated with RSB. Sexual PTEs significantly mediated the relationship between impulsivity and RSB.

CONCLUSIONS

This is the first study to date to simultaneously examine the relationship between personality, RSB, and types of PTEs in a large sample of young adults. Exposure to interpersonal trauma appears to be a salient factor in the relationship between personality, specifically impulsivity, and RSB. These results indicate that college students may benefit from education regarding the potential negative outcomes of RSB, and that individuals with a history of interpersonal PTEs may be at increased risk for sexual risk taking. (PsycINFO Database Record

Potentially Traumatic Events, Posttraumatic Stress Disorder, and Depression among Adults in Puerto Rico

The aims of the current study were to examine the prevalence of potentially traumatic events (PTEs), posttraumatic stress disorder (PTSD; data available in males only), and depressive symptoms in a Puerto Rican sample of 678 adult caretakers (50% female) of twins participating in the Puerto Rican Infant Twin Study. The World Health Organization Composite International Diagnostic Interview version 3.0 (CIDI 3.0) was utilized to assess rates of PTEs, PTSD, and depression among male participants while an abbreviated version of the CIDI 3.0 and the Mood and Feelings Questionnaire were administered to females to assess PTEs and depressive symptoms. Significantly more males than females reported exposure to a PTE (76.6% vs. 44.2%, χ(2) = 64.44, p < 0.001). In males, endorsement of multiple PTEs was associated with increased level of PTSD symptomatology (β = 0.33, p < 0.001). With regard to depression, a similar dose-response relationship was found in both males and females, with depressive symptoms increasing as number of PTEs increased (βs = 0.15, 0.16, ps < 0.05). Exposure to an attack with a weapon was significantly associated with increased depression symptoms in both males and females (βs = 0.24, 0.20, ps < 0.01, respectively). These findings highlight the need for identification of putative risk and resilience factors among PTE-exposed individuals in Puerto Rico.

Induced-anxiety differentially disrupts working memory in generalized anxiety disorder

BACKGROUND

Anxiety is characterized by a bias towards threatening information, anxious apprehension, and disrupted concentration. Previous research in healthy subjects suggests that working memory (WM) is disrupted by induced anxiety, but that increased task-demand reduces anxiety and WM is preserved. However, it is unknown if patients with generalized anxiety disorder (GAD) can similarly normalize their performance on difficult WM tasks while reducing their anxiety. Increased threat-related bias and impoverished top-down control in trait anxiety suggests that patients may not reap the same cognitive and emotional benefits from demanding tasks that those low in anxiety. Here we examine this possibility using a WM task of varying difficulty.

METHODS

GAD patients (N = 30) and healthy controls (N = 30) performed an n-back task (no-load, 1-back, 2-back, and 3-back) while at risk for shock (threat) or safe from shock (safe). Anxiety was measured via startle reflex and self-report.

RESULTS

As predicted, healthy controls' performance was impaired under threat during low-load tasks and facilitated during high-load tasks. In contrast, GAD patients' performance was impaired under threat regardless of WM load. Anxiety was reduced as cognitive load increased in both groups.

CONCLUSIONS

The divergence of emotion regulation (reduction) and performance (persistent impairment) in the patient but not the control group, suggests that different top-down mechanisms may be operating to reduce anxiety. Continued WM disruption in patients indicates that attentional resources are allocated to emotion regulation instead of goal-directed behavior. Implications for our understanding of cognitive disruption in patients, and related therapeutic interventions are discussed.

Longitudinal investigation of interpersonal trauma exposure and alcohol use trajectories

BACKGROUND

The current longitudinal study examined associations between interpersonal potentially traumatic events (PTEs; i.e., sexual or physical assault) and changes in alcohol consumption among incoming college students.

METHODS

1197 students (68% female) participating in a university-wide research study were included in analyses. Assessments were administered at three time-points and included measures of alcohol use, PTEs (Life Events Checklist), and a screener for possible PTSD symptoms (abbreviated Primary Care PTSD Screen). Linear growth curve models were fit to the three repeated measures of alcohol quantity and frequency to determine the role of pre-college and college-onset interpersonal PTEs and possible PTSD symptoms on patterns of alcohol use.

RESULTS

Pre-college interpersonal PTE was associated with greater baseline alcohol use for female but not male students. College-onset interpersonal PTE predicted greater alcohol use at concurrent and future assessments for women but not men, beyond the effects of pre-college PTE. Pre-college possible PTSD symptoms did not predict baseline or change in alcohol use.

CONCLUSIONS

There may be a stronger and longer-lasting impact of interpersonal PTE for college women compared to men on alcohol phenotypes, although replication in studies oversampling men endorsing interpersonal PTE is needed.

Recent advances in the genetics of emotion regulation: a review

Recent attention has been given to the role of emotion regulation in the development and maintenance of psychopathology, and the psychosocial literature on emotion regulation has been growing rapidly over the past decade. However, knowledge about the genetic etiology of emotion regulation facets has been slower to develop. The present paper aims to briefly introduce the various constructs that fall under the umbrella of emotion regulation; provide an overview of behavioral genetic methods; summarize the empirical studies of emotion regulation twin studies; introduce molecular genetic methods; review the recent molecular genetic studies on emotion regulation; and provide future directions for research.

Caretaker mental health and family environment factors are associated with adolescent psychiatric problems in a Vietnamese sample

Little is known about risk factors for adolescent mental health in Vietnam. The present study investigated the relationship between caretaker mental health and adolescent mental health in a cross-sectional Vietnamese sample. Primary caretakers completed measures of their own mental distress and general health status using the Self-Reporting Questionnaire-20 (SRQ-20) as well as reports of adolescent mental health using the parent version of the Strengths and Difficulties Questionnaire (SDQ). Multivariate regression models were used to examine the relationships between the caretaker and adolescent health variables. The demographic factors of age, sex, ethnicity, religious affiliation, and household wealth status demonstrated significant relationships with SDQ subscale scores. Caretaker mental health was positively associated with adolescent mental health, and this association remained significant even after accounting for other relevant demographic variables and caretaker general health status. Understanding correlates of adolescent mental health difficulties may help identify youth and families at risk for developing psychiatric problems and inform mental health interventions in Vietnam.

Site specific nematode management-development and success in cotton production in the United States

Variability in edaphic factors such as clay content, organic matter, and nutrient availability within individual fields is a major obstacle confronting cotton producers. Adaptation of geospatial technologies such global positioning systems (GPS), yield monitors, autosteering, and the automated on-and-off technology required for site-specific nematicide application has provided growers with additional tools for managing nematodes. Multiple trials in several states were conducted to evaluate this technology in cotton. In a field infested with Meloidogyne spp., both shallow (0 to 0.3 m) and deep (0 to 0.91 m) apparent electrical conductivity (ECa) readings were highly correlated with sand content. Populations of Meloidogyne spp. were present when shallow and deep EC values were less than 30 and 90 mS/m, respectively. Across three years of trials in production fields in which verification strips (adjacent nematicide treated and untreated rows across all soil zones) were established to evaluate crop response to nematicide application, deep EC values from 27.4-m wide transects of verification strips were more predictive of yield response to application of 1,3-dichloropropene than were shallow EC values in one location and both ECa values equally effective at predicting responses at the second location. In 2006, yields from entire verification strips across three soil zones in four production fields showed that nematicide response was greatest in areas with the lowest EC values indicating highest content of sand. In 2008 in Ashley and Mississippi Counties, AR, nematicide treatment by soil zone resulted in 36% and 42% reductions in the amount of nematicide applied relative to whole-field application. In 2007 in Bamberg County, SC, there was a strong positive correlation between increasing population densities of Meloidogyne incognita and increasing sand content. Trials conducted during 2007 and 2009 in South Carolina against Hoplolaimus columbus showed a stepwise response to increasing rates of aldicarb in zone 1 but not in zones 2 and 3. Site-specific application of nematicides has been shown to be a viable option for producers as a potential management tool against several nematode pathogens of cotton.

Sustained anxiety increases amygdala-dorsomedial prefrontal coupling: a mechanism for maintaining an anxious state in healthy adults

BACKGROUND

Neuroimaging research has traditionally explored fear and anxiety in response to discrete threat cues (e.g., during fear conditioning). However, anxiety is a sustained aversive state that can persist in the absence of discrete threats. Little is known about mechanisms that maintain anxiety states over a prolonged period. Here, we used a robust translational paradigm (threat of shock) to induce sustained anxiety. Recent translational work has implicated an amygdala-prefrontal cortex (PFC) circuit in the maintenance of anxiety in rodents. To explore the functional homologues of this circuitry in humans, we used a novel paradigm to examine the impact of sustained anticipatory anxiety on amygdala-PFC intrinsic connectivity.

METHODS

Task-independent fMRI data were collected in healthy participants during long-duration periods of shock anticipation and safety. We examined intrinsic functional connectivity.

RESULTS

Our study involved 20 healthy participants. During sustained anxiety, amygdala activity was positively coupled with dorsomedial PFC (DMPFC) activity. High trait anxiety was associated with increased amygdala-DMPFC coupling. In addition, induced anxiety was associated with positive coupling between regions involved in defensive responding, and decreased coupling between regions involved in emotional control and the default mode network.

LIMITATIONS

Inferences regarding anxious pathology should be made with caution because this study was conducted in healthy participants.

CONCLUSION

Findings suggest that anticipatory anxiety increases intrinsic amygdala-DMPFC coupling and that the DMPFC may serve as a functional homologue for the rodent prefrontal regions by sustaining anxiety. Future research may use this defensive neural context to identify biomarkers of risk for anxious pathology and target these circuits for therapeutic intervention.

Spontaneous fast gamma activity in the septal hippocampal region correlates with spatial learning in humans

Hippocampal neuronal populations exhibit multiple kinds of activity patterns, from the dominant theta rhythm during active exploration to high-frequency ripple-like activity during periods of relative inactivity. In animals, evidence is rapidly accruing that these high-frequency ripple activity patterns subserve retention of spatial learning performance. In a translational effort to address the possible function of offline hippocampal processes in humans, we measured spontaneous gamma activity during an awake rest period within a virtual spatial learning context. Whole-head magnetoencephalographic (MEG) recordings were taken while healthy participants (N=24) quietly rested (eyes open) between encoding and retrieval phases of a hippocampal-dependent virtual Morris water maze task. Results are that fast gamma activity (80-140 Hz) in the septal or posterior region of the hippocampus (bilaterally) was positively correlated across participants with subsequent within-session spatial learning rate. Fast gamma did not predict initial retrieval performance following rest, failing to provide evidence of a direct link between spontaneous high-frequency activity patterns during awake rest and consolidation of previous spatial memories. The findings nevertheless are consistent with a prospective role for offline human hippocampal processes in spatial learning and indicate that higher spontaneous gamma activity in the septal hippocampal region is related to faster updating of spatial knowledge in familiar virtual surroundings.

The role of serotonin in the neurocircuitry of negative affective bias: serotonergic modulation of the dorsal medial prefrontal-amygdala 'aversive amplification' circuit

Serotonergic medications can mitigate the negative affective biases in disorders such as depression or anxiety, but the neural mechanism by which this occurs is largely unknown. In line with recent advances demonstrating that negative affective biases may be driven by specific medial prefrontal-amygdala circuitry, we asked whether serotonin manipulation can alter affective processing within a key dorsal medial prefrontal-amygdala circuit: the putative human homologue of the rodent prelimbic-amygdala circuit or 'aversive amplification' circuit. In a double-blind, placebo-controlled crossover pharmaco-fMRI design, subjects (N=19) performed a forced-choice face identification task with word distractors in an fMRI scanner over two separate sessions. On one session subjects received dietary depletion of the serotonin precursor tryptophan while on the other session they received a balanced placebo control diet. Results showed that dorsal medial prefrontal responding was elevated in response to fearful relative to happy faces under depletion but not placebo. This negative bias under depletion was accompanied by a corresponding increase in positive dorsal medial prefrontal-amygdala functional connectivity. We therefore conclude that serotonin depletion engages a prefrontal-amygdala circuit during the processing of fearful relative to happy face stimuli. This same 'aversive amplification' circuit is also engaged during anxiety induced by shock anticipation. As such, serotonergic projections may inhibit engagement of the 'aversive amplification' circuit and dysfunction in this projection may contribute to the negative affective bias in mood and anxiety disorders. These findings thus provide a promising explanation for the role of serotonin and serotonergic medications in the neurocircuitry of negative affective bias.

Passive avoidance is linked to impaired fear extinction in humans

Conventional wisdom dictates we must face our fears to conquer them. This idea is embodied in exposure-based treatments for anxiety disorders, where the intent of exposure is to reverse a history of avoidant behavior that is thought to fuel a patient's irrational fears. We tested in humans the relationship between fear and avoidance by combining Pavlovian differential fear conditioning with a novel task for quantifying spontaneous passive avoidant behavior. During self-guided navigation in virtual reality following de novo fear conditioning, we observed participants keeping their distance from the feared object. At the individual level, passive avoidant behavior was highly associated with maladaptive fear expression (fear-potentiated startle) during late extinction training, indicating that extinction learning was impaired following a brief episode of avoidance. Avoidant behavior, however, was not related to initial acquired fear, raising doubt about a straightforward link between physiological fear and behavioral avoidance. We conclude that a deeper understanding of what motivates avoidance may offer a target for early intervention, before fears transition from the rational to the irrational.

Distinct contributions of human hippocampal theta to spatial cognition and anxiety

Current views of the hippocampus assign this structure, and its prominent theta rhythms, a key role in both cognition and affect. We studied this duality of function in humans, where no direct evidence exists. Whole-head magnetoencephalographic (MEG) data were recorded to measure theta activity while healthy participants (N = 25) navigated two virtual Morris water mazes, one in which they risked receiving aversive shocks without warning to induce anxiety and one in which they were safe from shocks. Results showed that threat of shock elevated anxiety level and enhanced navigation performance as compared to the safe condition. MEG source analyses revealed that improved navigation performance during threat was preferentially associated with increased left septal (posterior) hippocampal theta (specifically 4-8 Hz activity), replicating previous research that emphasizes a predominant role of the septal third of the hippocampus in spatial cognition. Moreover, increased self-reported anxiety during threat was preferentially associated with increased left temporal (anterior) hippocampal theta (specifically 2-6 Hz activity), consistent with this region's involvement in mediating conditioned and innate fear. Supporting contemporary theory, these findings highlight simultaneous involvement of the human hippocampus in spatial cognition and anxiety, and clarify their distinct correlates.

Depressed mood enhances anxiety to unpredictable threat

BACKGROUND

Depression and anxiety disorders (ADs) are highly co-morbid, but the reason for this co-morbidity is unclear. One possibility is that they predispose one another. An informative way to examine interactions between disorders without the confounds present in patient populations is to manipulate the psychological processes thought to underlie the pathological states in healthy individuals. In this study we therefore asked whether a model of the sad mood in depression can enhance psychophysiological responses (startle) to a model of the anxiety in ADs. We predicted that sad mood would increase anxious anxiety-potentiated startle responses.

METHOD

In a between-subjects design, participants (n=36) completed either a sad mood induction procedure (MIP; n=18) or a neutral MIP (n=18). Startle responses were assessed during short-duration predictable electric shock conditions (fear-potentiated startle) or long-duration unpredictable threat of shock conditions (anxiety-potentiated startle).

RESULTS

Induced sadness enhanced anxiety- but not fear-potentiated startle.

CONCLUSIONS

This study provides support for the hypothesis that sadness can increase anxious responding measured by the affective startle response. This, taken together with prior evidence that ADs can contribute to depression, provides initial experimental support for the proposition that ADs and depression are frequently co-morbid because they may be mutually reinforcing.

Vertical Distribution of Rotylenchulus reniformis in Cotton Fields

The possible impact of Rotylenchulus reniformis below plow depth was evaluated by measuring the vertical distribution of R. reniformis and soil texture in 20 symptomatic fields on 17 farms across six states. The mean nematode population density per field, 0 to 122 cm deep, ranged from 0.4 to 63 nematodes/g soil, and in 15 fields more than half of the R. reniformis present were below 30.5 cm, which is the greatest depth usually plowed by farmers or sampled by consultants. In 11 fields measured, root density was greatest in the top 15 cm of soil; however, roots consistently penetrated 92 to 122 cm deep by midseason, and in five fields in Texas and Louisiana the ratio of nematodes to root-length density within soil increased with depth. Repeated sampling during the year in Texas indicated that up to 20% of the nematodes in soil below 60 cm in the fall survived the winter. Differences between Baermann funnel and sugar flotation extraction methods were not important when compared with field-to-field differences in nematode populations and field-specific vertical distribution patterns. The results support the interpretation that R. reniformis below plow depth can significantly impact diagnosis and treatment of cotton fields infested with R. reniformis.

Survey of crop losses in response to phytoparasitic nematodes in the United States for 1994

Previous reports of crop losses to plant-parasitic nematodes have relied on published results of survey data based on certain commodities, including tobacco, peanuts, cotton, and soybean. Reports on crop-loss assessment by land-grant universities and many commodity groups generally are no longer available, with the exception of the University of Georgia, the Beltwide Cotton Conference, and selected groups concerned with soybean. The Society of Nematologists Extension Committee contacted extension personnel in 49 U.S. states for information on estimated crop losses caused by plant-parasitic nematodes in major crops for the year 1994. Included in this paper are survey results from 35 states on various crops including corn, cotton, soybean, peanut, wheat, rice, sugarcane, sorghum, tobacco, numerous vegetable crops, fruit and nut crops, and golf greens. The data are reported systematically by state and include the estimated loss, hectarage of production, source of information, nematode species or taxon when available, and crop value. The major genera of phytoparasitic nematodes reported to cause crop losses were Heterodera, Hoplolaimus, Meloidogyne, Pratylenchus, Rotylenchulus, and Xiphinema.

Interactions Between Calonectria crotalariae and Heterodera glycines on Soybean

The interactions of Heterodera glycines at four egg inoculum levels (0, 100, 1,000, and 10,000 per pot) and three cyst levels (0, 100, and 200 per pot) and Calonectria crotalariae at 500, 5,000, and 50,000 microsclerotia per pot were evaluated on soybean. At the two lowest nematode egg levels, the presence of C. crotalariae did not affect nematode reproduction. At 10,000 eggs per pot, however, nematode reproduction was increased significantly at each microsclerotial level. The increase in nematode reproduction was stepwise at 500 and 5,000 microsclerotia per pot but declined at 50,000 microsclerotia per pot. Similar results were obtained when cysts rather than eggs were used as nematode inoculum. The nematode x fungus interaction significantly affected 60-day plant growth parameters of both Lee 74 and Centennial soybean. The nematode x fungus interaction was antagonistic to plant roots and significantly influenced root injury ratings. The presence of C. crotalariae in tissues of stock plants or plants used as race differentials did not alter the analysis of this population as race 3.

Dynamic bandwidth allocation in a network

Recently protocols have been introduced which enable us to integrate periodic traffic (voice or video) and aperiodic traffic (data) and to extend the size of local area networks without any loss in speed and capacity. One of these, the DRAMA protocol, is based on broadband technology and allows for dynamic allocation of bandwidth to clusters of nodes in the total network. In this paper we propose a distributed algorithm to allocate bandwidth in a fair manner, where we have defined fair to mean that every node in the network, regardless of its location, should have the same expected access delay to the net. We show by means of simulation that the algorithm is stable and within a few percentage points of the optimal solution. Stability is measured in terms of the time it takes the system to return to near optimal distribution of the bandwidth after strong disturbances. The algorithm is shown to handle total reallocation of the resources within O(100ms).

Influence of Calonectria crotalariae on Reproduction of Heterodera glycines on Soybean

Calonectria crotalariae enhanced root penetration of Lee 74 (susceptible) and Centennial (resistant) soybeans by juveniles of race 3 of Heterodera glycines. Numbers of cysts in and on the roots of Lee 74 increased during the first 30 days in the presence of the fungus. Percentage of root infection by the fungus increased at 40 days in Lee 74 in the presence of the nematode. Numbers of cysts in soil at 80 and 120 days after inoculation with both organisms accounted for the significantly increased nematode population levels on Lee 74. In the presence of the fungus on the resistant cultivar, significantly increased levels of cysts were recovered from soil at 120 days. Fungus infection of Centennial roots also infected with the nematode increased from 58 to 86% at 120 days. An inoculum timing study in which Lee 74 was infested with the nematode and fungus individually, sequentially, and in combination at days 0 and 35 indicated that enhanced nematode reproduction was related more to early plant-fungus than to early plant-fungus-nematode interaction(s).