Uncovering the Ediacaran phosphorus cycle.

Phosphorus is a limiting nutrient that is thought to control oceanic oxygen levels to a large extent1-3. A possible increase in marine phosphorus concentrations during the Ediacaran Period (about 635-539 million years ago) has been proposed as a driver for increasing oxygen levels4-6. However, little is known about the nature and evolution of phosphorus cycling during this time4. Here we use carbonate-associated phosphate (CAP) from six globally distributed sections to reconstruct oceanic phosphorus concentrations during a large negative carbon-isotope excursion-the Shuram excursion (SE)-which co-occurred with global oceanic oxygenation7-9. Our data suggest pulsed increases in oceanic phosphorus concentrations during the falling and rising limbs of the SE. Using a quantitative biogeochemical model, we propose that this observation could be explained by carbon dioxide and phosphorus release from marine organic-matter oxidation primarily by sulfate, with further phosphorus release from carbon-dioxide-driven weathering on land. Collectively, this may have resulted in elevated organic-pyrite burial and ocean oxygenation. Our CAP data also seem to suggest equivalent oceanic phosphorus concentrations under maximum and minimum extents of ocean anoxia across the SE. This observation may reflect decoupled phosphorus and ocean anoxia cycles, as opposed to their coupled nature in the modern ocean. Our findings point to external stimuli such as sulfate weathering rather than internal oceanic phosphorus-oxygen cycling alone as a possible control on oceanic oxygenation in the Ediacaran. In turn, this may help explain the prolonged rise of atmospheric oxygen levels.

Compensatory remodeling of a septo-hippocampal GABAergic network in the triple transgenic Alzheimer's mouse model.

BACKGROUND: Alzheimer's disease (AD) is characterized by a progressive loss of memory that cannot be efficiently managed by currently available AD therapeutics. So far, most treatments for AD that have the potential to improve memory target neural circuits to protect their integrity. However, the vulnerable neural circuits and their dynamic remodeling during AD progression remain largely undefined. METHODS: Circuit-based approaches, including anterograde and retrograde tracing, slice electrophysiology, and fiber photometry, were used to investigate the dynamic structural and functional remodeling of a GABAergic circuit projected from the medial septum (MS) to the dentate gyrus (DG) in 3xTg-AD mice during AD progression. RESULTS: We identified a long-distance GABAergic circuit that couples highly connected MS and DG GABAergic neurons during spatial memory encoding. Furthermore, we found hyperactivity of DG interneurons during early AD, which persisted into late AD stages. Interestingly, MS GABAergic projections developed a series of adaptive strategies to combat DG interneuron hyperactivity. During early-stage AD, MS-DG GABAergic projections exhibit increased inhibitory synaptic strength onto DG interneurons to inhibit their activities. During late-stage AD, MS-DG GABAergic projections form higher anatomical connectivity with DG interneurons and exhibit aberrant outgrowth to increase the inhibition onto DG interneurons. CONCLUSION: We report the structural and functional remodeling of the MS-DG GABAergic circuit during disease progression in 3xTg-AD mice. Dynamic MS-DG GABAergic circuit remodeling represents a compensatory mechanism to combat DG interneuron hyperactivity induced by reduced GABA transmission.

The gold standard program (GSP) for smoking cessation: a cohort study of its effectiveness among smokers with and without cancer.

BACKGROUND: Smoking cessation treatment is an important prognostic factor for survival after a cancer diagnosis, especially for tobacco-related cancers. After being diagnosed with lung cancer, approximately 50% of patients continue smoking or frequently relapse after a quit attempt. Given the importance of smoking cessation treatment for cancer survivors, the objective was to compare the effectiveness of a 6-week intensive smoking cessation intervention, the Gold Standard Program (GSP), among cancer survivors compared with smokers without cancer. Second, we compared successful quitting among socioeconomically disadvantaged cancer survivors with that among nondisadvantaged cancer survivors. MATERIALS AND METHODS: This was a cohort study based on 38,345 smokers from the Danish Smoking Cessation Database (2006-2016). Linkage to the National Patient Register was used to identify cancer survivors undergoing the GSP after being diagnosed with cancer (except nonmelanoma skin cancer). Linkage to the Danish Civil Registration System was used to identify participants who died, went missing, or emigrated before the follow-up. Logistic regression models were applied to evaluate effectiveness. RESULTS AND CONCLUSION: Six percent (2438) of the included smokers were cancer survivors at the time they undertook the GSP. Their 6-month successful quitting showed no difference compared to that of smokers without cancer, neither before nor after adjustment; 35% versus 37% in crude rates and an aOR of 1.13 (95% CI: 0.97-1.32). Likewise, the results for disadvantaged compared to nondisadvantaged cancer survivors were not significantly different (32% versus 33% and an adjusted aOR of 0.87 (95% CI 0.69-1.11)). Overall, an intensive smoking cessation program seems effective in helping both people without cancer and cancer survivors become successful quitters.

Lung cancer registries in Denmark, Finland, Norway and Sweden: a comparison and proposal for harmonization.

BACKGROUND: Lung cancer is the leading cause of cancer-related death in all Nordic countries which, though similar in demographics and healthcare systems, have noticeable differences in lung cancer survival. Historically, Denmark and Finland have had higher lung cancer incidences and lower survival than Norway and Sweden. All four countries have national cancer registries. Data in these registries are often compared, but their full potential as a source of learning across the Nordic countries is impeded by differences between the registries. In this paper, we describe and compare the Nordic registries on lung cancer-specific data and discuss how a more harmonized registration practice could increase their usefulness as a source for mutual learning and quality improvements. METHODS: We describe and compare the characteristics of data on lung cancer cases from registries in Denmark, Finland, Norway and Sweden. Moreover, we compare the results from the latest annual reports and specify how data may be acquired from the registries for research. RESULTS: Denmark has a separate clinical lung cancer registry with more detailed data than the other Nordic countries. Finland and Norway report lung cancer survival as relative survival, whereas Denmark and Sweden report overall survival. The Danish Lung Cancer Registry and the Swedish Cancer Registry do not receive data from the Cause of Death registries in contrast to the Finnish Cancer Registry and the Cancer Registry of Norway. CONCLUSION: The lung cancer registries in Denmark, Finland, Norway and Sweden have high level of completeness. However, several important differences between the registries may bias comparative analyses.

Trends in survival of epithelial ovarian/tubal cancer by histology and socioeconomic status in Denmark 1996-2017.

OBJECTIVES: To examine time trends in ovarian/tubal cancer relative survival, excess mortality, and all-cause mortality for different histological types and levels of socioeconomic position. METHODS: Women with ovarian/tubal cancer diagnosed 1996-2017 were identified in the Danish Cancer Registry (n = 11,755). Age-standardized 5-year relative survival over time was estimated by histology, socioeconomic status, and stage. Furthermore, 5-year excess mortality rate ratios (EMRR) according to calendar time for all categories of histology and socioeconomic status were calculated using a Poisson regression model. Finally, all-cause mortality by histology and socioeconomic status was estimated in multivariate Cox proportional hazards regression models. RESULTS: Statistically significant improvements in 5-year relative survival occurred for all histological types over time except mucinous tumors (5-year EMRR, localized: 0.92 (95% CI: 0.71-1.16); advanced: 0.96 (95% CI: 0.85-1.08). Increase in relative survival over time and corresponding decrease in excess mortality was observed for all categories of socioeconomic status except for women with localized disease in the lowest income group (5-year EMRR = 0.91 (95% CI:0.76-1.10)). The impact of histology and socioeconomic status on all-cause mortality depended on time since diagnosis. Among the socioeconomic factors, especially low educational level and living alone were associated with increased all-cause mortality, particularly in the first year after diagnosis. CONCLUSIONS: Ovarian/tubal cancer survival generally increased over time across histological types and socioeconomic factors. However, the lack of improvement for mucinous tumors needs further research. Additionally, the results for women with low income and education shows that continued focus on social equality in survival is necessary.

Impact of comorbidity on renal cell carcinoma prognosis: a nationwide cohort study.

BACKGROUND: Presence of comorbid diseases at time of cancer diagnosis may affect prognosis. We evaluated the impact of comorbidity on survival of patients diagnosed with renal cell carcinoma (RCC), overall and among younger (<70 years) and older (≥70 years) patients. METHODS: We established a nationwide register-based cohort of 7894 patients aged ≥18 years diagnosed with RCC in Denmark between 2006 and 2017. We computed 1- and 5-year overall survival and hazard ratios (HRs) for death according to the Charlson Comorbidity Index (CCI) score. RESULTS: Survival decreased with increasing CCI score despite an overall increase in survival over time. The 5-year survival rate of patients with no comorbidity increased from 57% among those diagnosed in 2006-2008 to 69% among those diagnosed in 2012-2014. During the same periods, the survival rate increased from 46% to 62% among patients with a CCI score of 1-2 and from 39% to 44% for those with a CCI score of ≥3. Patients with CCI scores of 1-2 and ≥3 had higher mortality rates than patients with no registered comorbidity (HR 1.15, 95% CI 1.06-1.24 and HR 1.56, 95% CI 1.40-1.73). Patterns were similar for older and younger patients. Particularly, diagnoses of liver disease (HR 2.09, 95% CI 1.53-2.84 and HR 4.01, 95% CI 2.44-6.56) and dementia (HR 2.16, 95% CI 1.34-3.48) increased mortality. CONCLUSION: Comorbidity decreased the survival of patients with RCC, irrespective of age, despite an overall increasing survival over time. These results highlight the importance of focusing on comorbidity in this group of patients.

Early indicators of primary brain tumours: a population-based study with 10 years' follow-up.

BACKGROUND AND PURPOSE: To improve diagnoses of primary brain tumours, knowledge about early indicators is needed. Nationwide Danish health registries were used to conduct a population-based case-control study including all persons diagnosed with a primary brain tumour between 2005 and 2014 in Denmark. METHODS: All 5135 adults diagnosed with a primary brain tumour in the Danish Cancer Registry were matched to 19 572 general population comparisons from the Danish Civil Registration System. Conditional logistic regression analyses were applied to estimate age- and multivariable-adjusted odds ratios (ORs) for the occurrence of a primary brain tumour up to 10 years after hospital diagnoses or prescription of medications related to nervous system diseases and mental and behavioural disorders. RESULTS: Increased odds for primary brain tumour after nervous system diseases and mental and behavioural disorders manifested up to 10 years before tumour diagnosis were found. Increased odds were seen especially for hospital contacts for inflammatory nervous system diseases [OR 11.3; 95% confidence interval (CI) 6.5-19.7], epilepsy (OR 9.0; 95% CI 7.6-10.7) and antiepileptic medications (OR 3.6; 95% CI 3.2-4.0), whilst antidementia medications provided a strong, protective association for primary brain tumours (OR 0.5; 95% CI 0.3-0.8). CONCLUSIONS: Sub-groups of patients diagnosed with or being prescribed certain medications targeting nervous system diseases and mental and behavioural disorders may be at increased risk of being diagnosed with a primary brain tumour. Further studies should disentangle the potential underlying common pathogenetic pathways. The results are important for the development of systematic clinical approaches to ensure early diagnosis of primary brain tumours.

The influence of socioeconomic position on adjuvant treatment of stage III colon cancer: a systematic review and meta-analysis.

BACKGROUND: Patients with colon cancer (CC) with low socioeconomic position (SEP) have a worse survival than patients with high SEP. We investigated the association between different socioeconomic indicators and the steps in the treatment trajectory leading to initiation of adjuvant chemotherapy (ACT) for patients with stage III CC. MATERIALS AND METHODS: A systematic review and meta-analyses were conducted in accordance with the MOOSE checklist. MEDLINE and EMBASE were searched for eligible studies. Meta-analyses were performed on the separate socioeconomic indicators with the random-effects model. The heterogeneity across studies was assessed by the Q and the I 2 statistic. RESULTS: In total, 27 observational studies were included. SEP was measured by insurance, income, poverty, employment, education, or an index on an area or individual level. SEP, regardless of indicator, was negatively associated with the steps in the treatment trajectory leading to initiation of ACT among patients with resected stage III CC. The meta-analyses showed that patients with low SEP had a significantly lower odds of receiving ACT and increased odds of delayed treatment start, whereas SEP had no impact on the choice of therapy: combination or single-agent therapy. CONCLUSION: SEP was associated with less initiation of and higher risk for delayed initiation of ACT. Our findings suggest there is a social disparity in receipt of ACT in patients with stage III CC.

Sustaining better care for patients undergoing emergency laparotomy.

Emergency laparotomy is associated with high mortality. Implementation of an evidence-based care bundle has been shown to improve patient outcomes. A quality improvement project to implement a six-component care bundle was undertaken between July 2015 and May 2018. As part of this project, we worked with 27 hospitals in the Emergency Laparotomy Collaborative. Previous pilot implementation of the same bundle in our hospital between December 2012 and July 2013 had shown marked improvement, maintained until April 2014, but then deterioration. Understanding the reasons for this deterioration informed our work to re-implement the bundle and sustain improvement. A cohort of 930 consecutive patients requiring emergency laparotomy between October 2014 and April 2019 were included. Baseline data were collected between October 2014 and June 2015, and the bundle was re-implemented in July 2015. Thirty-day mortality decreased from 11% in the baseline group to 7.3% after bundle implementation. Hospital length of stay decreased from 19.5 to 17.9 days. Full bundle compliance improved from < 60% to > 80% for all patients, with improvement in application of all individual bundle components. This study provides further evidence that outcomes for high-risk surgical patients can be improved with an evidence-based care bundle, but attention must be paid to maintaining bundle compliance. Issues around sustaining improvement must be considered from project initiation.

Does losing a parent early influence the education you obtain? A nationwide cohort study in Denmark.

BACKGROUND: Health inequalities are rooted in education and we investigate the association between early parental death and attainment across the educational spectrum. METHODS: Using total population data on Danes born between 1982 and 2000 (n = 1 043 813), we assess incidence rate ratios (RRs) by gender for attainment of each educational level (basic school, high school or vocational training, bachelor degree or professional programme, and university graduate degree) according to loss of a parent before the age of 18 years. We adjust for family income, education and psychiatric illness and examine parent's gender, cause of death and child's age at time of death as potential moderators. RESULTS: Bereaved people had significantly lower attainment rates than non-bereaved people: basic school (RR = 0.95; 95% CI: 0.93-0.97 for men and 0.96; 0.94-0.98 for women), high school or vocational training (0.78; 0.76-0.80 for men and 0.82; 0.80-0.84 for women), bachelor degree or professional programme (0.74; 0.70-0.79 for men and 0.83; 0.79-0.86 for women) and university graduate degree (0.77; 0.68-0.86 for men and 0.77; 0.69-0.86 for women). Parent's gender, cause of death and child's age at the death did not modify the associations. CONCLUSIONS: As education impacts population health, support for bereaved school children may be more important than realized.

Adaptive Beamforming Applied to OFDM Systems.

This work proposes an adaptive beamforming scheme applied to time domain, pre-FFT (Fast Fourier Transformation), Orthogonal Frequency-Division Multiplexing (OFDM) systems. This scheme improves the performance and the capacity of OFDM systems, using a supervised adaptive algorithm, with frequency domain multiplexed pilots of the OFDM system as a reference. The simplicity of the proposed structure, as well as the method used to obtain reference signals for the adaptive beamforming, are essential aspects that distinguish this paper from other publications. Details on the operation of the proposed scheme, as well as the performance curves, are presented in this manuscript. The proposal investigated here allows a significant reduction in the guard interval of the OFDM system, thereby increasing its robustness or transmission capacity.

Who are the cancer survivors? A nationwide study in Denmark, 1943-2010.

BACKGROUND: No nationwide studies on social position and prevalence of comorbidity among cancer survivors exist. METHODS: We performed a nationwide prevalence study defining persons diagnosed with cancer 1943-2010 and alive on the census date 1 January 2011 as cancer survivors. Comorbidity was compared by social position with the non-cancer population. RESULTS: Cancer survivors composed 4% of the Danish population. Somatic comorbidity was more likely among survivors (OR 1.59, 95% CI 1.57-1.60) and associated with higher age, male sex, short education, and living alone among survivors. CONCLUSIONS: Among cancer survivors, comorbidity is common and highly associated with social position.

Screening for carcinoma in situ in the contralateral testicle in patients with testicular cancer: a population-based study.

BACKGROUND: Screening programmes for contralateral carcinoma in situ (CIS) testis in patients with unilateral germ-cell cancer (GCC) have never been evaluated. We investigated the effect of screening for contralateral CIS in a large nation-wide, population-based study. PATIENTS AND METHODS: A contralateral single-site biopsy was offered to 4130 patients in whom GCC had been diagnosed in 1984-2007 (screened cohort); 462 patients in whom GCC was diagnosed in 1984-1988 comprised the unscreened cohort. Cases with CIS were offered radiotherapy. Initially CIS-negative biopsies in patients with metachronous GCC were revised according to today's standards. Risk for metachronous GCC was estimated using cumulative incidence and the Cox proportional hazards model. RESULTS: In the screened cohort, contralateral CIS was found in 181 (4.4%) patients. The cumulative incidence of metachronous GCC after 20 years was 1.9% in the screened cohort and 3.1% in the unscreened cohort (P = 0.097), hazard ratio (HR) for the unscreened cohort: 1.59 (P = 0.144). Expert revision with contemporary methodology of CIS-negative biopsy samples from patients with metachronous cancer revealed CIS in 17 out of 45 (38%) cases. Decreased risks for metachronous GCC were related to older age at diagnosis (HR 0.52 per 10 years, P < 0.001) and chemotherapy (HR 0.35, P = 0.002). Limitations include the small number of patients in the unscreened cohort and the retrospective study design. CONCLUSIONS: Our evaluation of a national population-based screening programme for contralateral CIS in patients with testicular cancer showed no significant difference in the risk for metachronous GCC between a screened and an unscreened cohort. Single-site biopsy including modern immunohistochemistry does not identify all cases of CIS.

Postoperative morbidity survey, mortality and length of stay following emergency laparotomy.

Thirty-day mortality following emergency laparotomy is high, and greater amongst elderly patients. Studies systematically describing peri-operative complications are sparse, and heterogeneous. We used the postoperative morbidity survey to describe the type and frequency of complications, and their relationship with outcomes for 144 patients: 114 < 80 years old, and 30 ≥ 80 years old. Cumulative postoperative morbidity survey scores and patterns of morbidity were similar (p = 0.454); however, 28-day mortality was higher in the elderly (10/30 (33.3%) vs. 11/114 (9.6%), p = 0.008), and hospital stay was longer (median (IQR [range]) 17 (13-35 [6-62]) days vs. 11 (7-21 [2-159]) days, p = 0.006). Regression analysis indicated that cardiovascular, haematological, renal and wound complications were associated with longer hospital stay, and that cardiovascular complications predicted mortality. The postoperative morbidity survey system enabled structured mapping of the number and type of complications, and their relationship with outcome, following emergency laparotomy. These results indicate that rather than a greater propensity to complications following surgery, it was the failure to tolerate these that increased mortality in the elderly.

Arise the systems physician.

Healthcare in Australia faces significant challenges. Variations in care, suboptimal safety and reliability, fragmentation of care and unsustainable cost increases are compounded by substantial overuse and underuse of clinical interventions. These problems arise not from intentional actions of individual clinicians, but from deficiencies in the design, operations and governance of systems of care. Physicians play an important role in optimising systems of care and, in doing so, must rely on enhanced skills in a range of domains. These include: how to evaluate and improve quality and safety of clinical processes; analyse and interpret clinical and administrative data in ways that can be used to enhance care delivery; build and lead cohesive multidisciplinary teams capable of solving operational defects and inefficient workarounds; and implement new and effective innovations in clinical service delivery. While clinical skills are essential in individual patient care, skills that improve systems of care targeting whole patient populations will become increasingly desirable and recognised as core skills.

Entropy as a Window Into Behavioral Phase Transitions: Unveiling Contextual Dynamics in Affordance-Based Reaching.

Prior work has demonstrated the presence of hysteresis effects in the control of affordance-guided behavior, in that behavioral transitions around a critical action boundary vary with directions of change in said action boundary. To date, research on this topic has overlooked the influence of the global context on these phenomena. We employ an affordance-based reaching task, whereby participants were asked to move a target to a goal by passing through one of two apertures (size variable or size constant). It was found that the direction of change in the size of the variable aperture influenced the point of behavioral transitions, and this effect interacted with the location of a given goal. In addition, we considered fluctuations in the entropy of participants' reach trajectories as a window into the nature of the behavioral phase transitions. Differences in the structure of entropy were found depending on the direction of change in the size variable aperture. These results are discussed in light of a dynamical systems approach, and recommendations for future work are made.

Exploring Alternatives for Marine Toxicity Testing: Initial Evaluation of Fish Embryo and Mysid Tests.

Current regulations require that toxicity assessments be performed using standardized toxicity testing methods, often using fish. Recent legislation in both the European Union and United States has mandated that toxicity testing alternatives implement the 3Rs of animal research (replacement, reduction, and refinement) whenever possible. There have been advances in the development of alternatives for freshwater assessments, but there is a lack of analogous developments for marine assessments. One potential alternative testing method is the fish embryo toxicity (FET) test, which uses fish embryos rather than older fish. In the present study, FET methods were applied to two marine model organisms, the sheepshead minnow and the inland silverside. Another potential alternative is the mysid shrimp survival and growth test, which uses an invertebrate model. The primary objective of the present study was to compare the sensitivity of these three potential alternative testing methods to two standardized fish-based tests using 3,4-dichloroaniline (DCA), a common reference toxicant. A secondary objective was to characterize the ontogeny of sheepshead minnows and inland silversides. This provided a temporal and visual guide that can be used to identify appropriately staged embryos for inclusion in FET tests and delineate key developmental events (e.g., somite development, eyespot formation, etc.). Comparison of the testing strategies for assessing DCA indicated that: (1) the standardized fish tests possessed comparable sensitivity to each other; (2) the mysid shrimp tests possessed comparable sensitivity to the standardized fish tests; (3) the sheepshead minnow and inland silverside FET tests were the least sensitive testing strategies employed; and (4) inclusion of sublethal endpoints (i.e., hatchability and pericardial edema) in the marine FETs increased their sensitivity. Environ Toxicol Chem 2024;43:1285-1299. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Sex-specific expression of distinct serotonin receptors mediates stress vulnerability of adult hippocampal neural stem cells in mice.

Women are more vulnerable to stress and have a higher likelihood of developing mood disorders. The serotonin (5HT) system has been highly implicated in stress response and mood regulation. However, sex-dependent mechanisms underlying serotonergic regulation of stress vulnerability remain poorly understood. Here, we report that adult hippocampal neural stem cells (NSCs) of the Ascl1 lineage (Ascl1-NSCs) in female mice express functional 5HT1A receptors (5HT1ARs), and selective deletion of 5HT1ARs in Ascl1-NSCs decreases the Ascl1-NSC pool only in females. Mechanistically, 5HT1AR deletion in Ascl1-NSCs of females leads to 5HT-induced depolarization mediated by upregulation of 5HT7Rs. Furthermore, repeated restraint stress (RRS) impairs Ascl1-NSC maintenance through a 5HT1AR-mediated mechanism. By contrast, Ascl1-NSCs in males express 5HT7R receptors (5HT7Rs) that are downregulated by RRS, thus maintaining the Ascl1-NSC pool. These findings suggest that sex-specific expression of distinct 5HTRs and their differential interactions with stress may underlie sex differences in stress vulnerability.

Tryptophan End-Tagging Confers Antifungal Activity on a Tick-Derived Peptide by Triggering Reactive Oxygen Species Production.

WHO has identified several Candida species including Candida albicans as critical priority fungal pathogens due to greater infection prevalence and formation of recalcitrant biofilms. Novel antifungal agents are urgently needed, and antimicrobial peptides (AMPs) are being considered as potential alternatives, but inactivity in physiological salt environments, serum, and plasma often limits further therapeutic development. Tryptophan end-tagging is a strategy to overcome these limitations and is thought to selectively enhance membrane permeabilization in both fungal and bacterial plasma membranes. Here, we show that C-terminal tryptophan end-tagging of the tick-derived peptide Os-C transforms an inactive peptide into Os-C(W5), an antifungal peptide capable of preventing the formation of C. albicans biofilms. Mechanistic insight is provided by circular dichroism spectroscopy and molecular dynamics simulations, which demonstrate that tryptophan end-tagging alters the secondary structure of Os-C, while the latter reveals that end-tagging reduces interactions with, and insertion into, a model C. albicans membrane but promotes peptide aggregation on its surface. Interestingly, this leads to the induction of reactive oxygen species production rather than membrane permeabilization, and consequently, oxidative stress leads to cell wall damage. Os-C(W5) does not induce the hemolysis of human erythrocytes. Reduced cell adhesion and viability contribute to decreased biofilm extracellular matrix formation which, although reduced, is retained in the serum-containing medium. In this study, tryptophan end-tagging was identified as a promising strategy for enhancing the antifungal activity, including the biofilm inhibitory activity of Os-C against C. albicans in physiological salt environments.

QSAR Reveals Decreased Lipophilicity of Polar Residues Determines the Selectivity of Antimicrobial Peptide Activity.

Antimicrobial resistance has increased rapidly, causing daunting morbidity and mortality rates worldwide. Antimicrobial peptides (AMPs) have emerged as promising alternatives to traditional antibiotics due to their broad range of targets and low tendency to elicit resistance. However, potent antimicrobial activity is often accompanied by excessive cytotoxicity toward host cells, leading to a halt in AMP therapeutic development. Here, we present multivariate analyses that correlate 28 peptide properties to the activity and toxicity of 46 diverse African-derived AMPs and identify the negative lipophilicity of polar residues as an essential physiochemical property for selective antimicrobial activity. Twenty-seven active AMPs are identified, of which the majority are of scorpion or frog origin. Of these, thirteen are novel with no previously reported activities. Principal component analysis and quantitative structure-activity relationships (QSAR) reveal that overall hydrophobicity, lipophilicity, and residue side chain surface area affect the antimicrobial and cytotoxic activity of an AMP. This has been well documented previously, but the present QSAR analysis additionally reveals that a decrease in the lipophilicity, contributed by those amino acids classified as polar, confers selectivity for a peptide to pathogen over mammalian cells. Furthermore, an increase in overall peptide charge aids selectivity toward Gram-negative bacteria and fungi, while selectivity toward Gram-positive bacteria is obtained through an increased number of small lipophilic residues. Finally, a conservative increase in peptide size in terms of sequence length and molecular weight also contributes to improved activity without affecting toxicity. Our findings suggest a novel approach for the rational design or modification of existing AMPs to increase pathogen selectivity and enhance therapeutic potential.