Although recent work has shown that both deterministic and stochastic processes are important in structuring microbial communities, the factors that affect the relative contributions of niche and neutral processes are poorly understood. The macrobiological literature indicates that ecological disturbances can influence assembly processes. Thus, we sampled bacterial communities at 4 and 16 weeks following a wildfire and used null deviation analysis to examine the role that time since disturbance has in community assembly. Fire dramatically altered bacterial community structure and diversity as well as soil chemistry for both time-points. Community structure shifted between 4 and 16 weeks for both burned and unburned communities. Community assembly in burned sites 4 weeks after fire was significantly more stochastic than in unburned sites. After 16 weeks, however, burned communities were significantly less stochastic than unburned communities. Thus, we propose a three-phase model featuring shifts in the relative importance of niche and neutral processes as a function of time since disturbance. Because neutral processes are characterized by a decoupling between environmental parameters and community structure, we hypothesize that a better understanding of community assembly may be important in determining where and when detailed studies of community composition are valuable for predicting ecosystem function.

Prognostic/epidemiologic study, level IV.

Purpose Patients with severe sepsis who experience rapid, early deterioration and death are of particular concern. Our objective was to identify predictors of early death in Emergency Department (ED) patients with severe sepsis. Methods Secondary analysis of two prospective studies of adult ED patients with severe sepsis. The primary outcome was early death, defined as death within 24 hours of triage. Results Out of 410 severe sepsis admissions, 20 patients experienced early death. These patients demonstrated significantly higher initial lactate (7.3 versus 3.3 mmol/L, p < 0.001) and modified SOFA (mSOFA) scores (10 vs 6, p<.001), were less likely to normalize their lactate (p<0.001), had lower initial pH (p<0.001), and more frequently had early positive blood cultures (p=0.021). Multivariable logistic regression identified initial serum lactate level (OR 1.19, 95% CI 1.06–1.35) and mSOFA score (OR 1.17, 95% CI 1.00–1.36) as independent predictors of early death. A repeat lactate ≥ 5 mmol/L had a sensitivity of 55% and specificity of 89% for early death. There were no significant treatment differences between groups. Conclusion Initial serum lactate and mSOFA score were independent predictors of mortality within 24 hours of ED admission in patients with severe sepsis.

Drugs, notably SSRIs, that elevate brain extracellular 5-HT (5-HT Ext ) are antidepressants. Unfortunately, most patients fail to remit. Multipronged clinical evidence suggests that elevating 5-HT Ext beyond the SSRI effect enhances antidepressant efficacy, but previous such drug strategies had prohibitive limitations. In humans, adjunct treatment with the 5-HT precursor 5-hydroxytryptophan (5-HTP) elevates 5-HT Ext beyond the SSRI effect. Small pilot trials suggest that adjunct 5-HTP can confer antidepressant response in treatment-resistant depression (TRD). However, sustained, stable 5-HT Ext elevation is required for antidepressant effect; therefore, the rapid absorption and elimination of standard 5-HTP immediate release (IR) likely curtail 5-HTP IR's antidepressant potential. Slow-release (SR) drug delivery can crucially improve efficacy and safety of rapidly absorbed and eliminated compounds. Here we tested in mice the hypothesis that SR delivery will substantially improve 5-HTP's drug properties, by minimizing adverse effects and securing sustained 5-HT Ext elevation beyond the SSRI effect. We modeled 5-HTP SR with minipumps, 5-HTP IR with injections, and chronic SSRI with dietary fluoxetine. We tested adjunct 5-HTP SR in wild-type mice and in mice with low brain 5-HT owing to expression of a mutant form of the brain 5-HT synthesis enzyme, tryptophan hydroxylase 2. In both lines of mice, adjunct 5-HTP SR synergized with SSRI to elevate 5-HT Ext beyond the SSRI effect. We observed no adverse effect. Adjunct 5-HTP IR could not produce this therapy-like profile, producing transient 5-HT Ext spikes and marked adverse effects. Integrated with a body of clinical data, our mouse data suggest that an adjunct 5-HTP SR drug could safely and effectively elevate 5-HT Ext beyond the SSRI effect and represent a novel treatment for TRD.

Rationale Escitalopram is a superior antidepressant to racemic citalopram. It has been hypothesized that binding of R-citalopram to the serotonin transporter (SERT) antagonizes escitalopram binding to and inhibition of the SERT, curtailing the elevation of extracellular 5-hydroxytryptamine (5-HTExt), and antidepressant efficacy. Further, it has been suggested that a putative allosteric binding site is important for binding of escitalopram to the primary, orthosteric, site, and for R-citalopram’s inhibition hereof. Objectives Primary: Investigate at the human (h)SERT, at clinical relevant doses, whether R-citalopram antagonizes escitalopram-induced 5-HTExt elevation. Secondary: Investigate whether abolishing the putative allosteric site affects escitalopram-induced 5-HTExt elevation and/or modulates the effect of R-citalopram. Methods Recombinant technology; in vivo microdialysis; receptor binding; pharmacokinetics; 5-HT sensitive behaviors (tail suspension, marble burying). Results We generated mice expressing either the wild-type human SERT (hSERTWT) or hSERT carrying amino acid substitutions (A505V, L506F, I507L, S574T and I575T) collectively abolishing the putative allosteric site (hSERTALI/VFL+SI/TT). One mg/kg escitalopram yielded clinical relevant plasma levels and brain levels consistent with therapeutic SERT occupancy. Importantly, escitalopram-induced 5-HTExt elevation was not decreased by R-citalopram co-treatment. Further, escitalopram-induced 5-HTExt elevation was not affected by loss of the allosteric site. The behavioral effects of the clinically relevant escitalopram dose were small, tending to be enhanced by R-citalopram co-administration. Conclusions We find no evidence that R-citalopram directly antagonizes escitalopram or that the putative allosteric site is important for hSERT inhibition by escitalopram. Our findings points to mechanisms for R-citalopram antagonism of escitalopram’s antidepressant action other than direct antagonistic binding interactions at the hSERT.

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Study Objective: We developed a novel, quick, easy to use electrocardiogram (ECG) screening criterion (Seamens’ Sign) for left ventricular hypertrophy (LVH). This new criterion was defined as the presence of QRS complexes touching or overlapping in two contiguous precordial leads. Methods: This study was a retrospective chart review of 2184 patient records. The primary outcome was whether Seamens’ Sign was noninferior in confirming LVH compared to other common criteria. Test characteristics were calculated for each of the LVH criteria. Inter-rater agreement was assessed on a random sample using Cohen’s Kappa. Results: Median age was 63, 52% of patients were male and there was a 35% prevalence of LVH by transthoracic echocardiogram (TTE). Nine percent were positive for LVH on ECG based on Seamens’ Sign. Seamens’ Sign had a specificity of 0.92. Tests assessing noninferiority indicated Seamens’ Sign was non-inferior to all criteria (p < 0.001) except for Cornell criterion for women (p = 0.98). Seamens’ Sign had 90% (0.81-1.00) inter-rater agreement, the highest of all criteria in this study. Conclusion: When compared to both the Sokolow-Lyon criteria and the Cornell criterion for men, Seamens’ Sign is noninferior in ruling in LVH on ECG. Additionally, Seamens’ Sign has higher inter-rater agreement compared to both Sokolow-Lyon criteria as well as the Cornell criteria for men and women, perhaps related to its ease of use.