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Violence is a major public health problem globally, with the highest rates in low- and middle-income countries (LMICs) in the Americas and southern Africa. Parenting programmes in high-income countries can diminish risk for violence, by reducing risk factors such as child aggression and harsh parenting, and increasing protective factors such as child cognitive development and school readiness. However, there is critical need to identify low-cost programmes with replicable benefits that work in real-world LMICs contexts. A three-arm, randomised, single-blind trial evaluated effects of two low-cost, group-based parenting programmes recommended for LMICs (ACT: Raising Safe Kids; DBS: dialogic book-sharing) on child aggression (primary outcome), child development, parenting, maltreatment, and stress. Participants were 369 children with medium-high levels of aggression (mean age 3.1 years at baseline) in poor households. Interventions were implemented in city health and education services in southern Brazil. Maternal reports, filmed observations, child tasks, and hair cortisol were assessed at baseline, 1-month post-intervention, and 8-month follow-up. Intention-to-treat analyses compared each of ACT and DBS with a control group. Three hundred sixty-eight (99.7%) participants completed follow-up assessments 8 months after the interventions. There was no effect of ACT (standardised mean difference, SMD 0.11, 95% CI - 0.05, 0.27) or DBS (SMD 0.05, 95% CI - 0.11, 0.21) on the primary outcome of child aggression. ACT reduced harsh parenting behaviour post-intervention (SMD - 0.23; 95% CI - 0.46, 0.01), but not at follow-up. DBS improved book-sharing practices at both time points (e.g., maternal sensitivity at follow-up SMD 0.33; 95% CI 0.08, 0.57). There were no benefits of either programme for other parenting, child development, or stress outcomes. Two parenting programmes in Brazil had small effects on parenting practices but did not reduce child aggression or several other important risk/protective factors for violence. Effective early interventions that reduce violence in real-world LMIC settings are highly desirable but may be challenging to achieve.

Coagulation factor XIa is a candidate target for anticoagulants that better separate antithrombotic efficacy from bleeding risk. We report a co-crystal structure of the FXIa protease domain with DEF, a human monoclonal antibody that blocks FXIa function and prevents thrombosis in animal models without detectable increased bleeding. The light chain of DEF occludes the FXIa S1 subsite and active site, while the heavy chain provides electrostatic interactions with the surface of FXIa. The structure accounts for the specificity of DEF for FXIa over its zymogen and related proteases, its active-site-dependent binding, and its ability to inhibit substrate cleavage. The inactive FXIa protease domain used to obtain the DEF-FXIa crystal structure reversed anticoagulant activity of DEF in plasma and in vivo and the activity of a small-molecule FXIa active-site inhibitor in vitro. DEF and this reversal agent for FXIa active-site inhibitors may help support clinical development of FXIa-targeting anticoagulants.

Platelets are critical for haemostasis, thrombosis, and inflammatory responses, but the events that lead to mature platelet production remain incompletely understood. The bone marrow has been proposed to be a major site of platelet production, although there is indirect evidence that the lungs might also contribute to platelet biogenesis. Here, by directly imaging the lung microcirculation in mice, we show that a large number of megakaryocytes circulate through the lungs, where they dynamically release platelets. Megakaryocytes that release platelets in the lungs originate from extrapulmonary sites such as the bone marrow; we observed large megakaryocytes migrating out of the bone marrow space. The contribution of the lungs to platelet biogenesis is substantial, accounting for approximately 50% of total platelet production or 10 million platelets per hour. Furthermore, we identified populations of mature and immature megakaryocytes along with haematopoietic progenitors in the extravascular spaces of the lungs. Under conditions of thrombocytopenia and relative stem cell deficiency in the bone marrow, these progenitors can migrate out of the lungs, repopulate the bone marrow, completely reconstitute blood platelet counts, and contribute to multiple haematopoietic lineages. These results identify the lungs as a primary site of terminal platelet production and an organ with considerable haematopoietic potential.

The final step of triacylglycerol synthesis is catalyzed by acyl-CoA:diacylglycerol acyltransferases (DGATs). We have previously shown that ApoE-/-Dgat1-/- mice are protected from developing atherosclerosis in association with reduced foam cell formation. However, the role of DGAT1, specifically in myeloid and other hematopoietic cell types, in determining this protective phenotype is unknown. To address this question, we reconstituted the bone marrow of irradiated Ldlr-/-mice with that from wild-type (WT→ Ldlr-/-) and Dgat1-/-(Dgat1-/-→ Ldlr-/-) donor mice. We noted that DGAT1 in the hematopoietic compartment exerts a sex-specific effect on systemic cholesterol homeostasis. However, both male and female Dgat1-/-→ Ldlr-/-mice had higher circulating neutrophil and lower lymphocyte counts than control mice, suggestive of a classical inflammatory phenotype. Moreover, specifically examining the aortae of these mice revealed that Dgat1-/-→ Ldlr-/-mice have atherosclerotic plaques with increased macrophage content. This increase was coupled to a reduced plaque collagen content, leading to a reduced collagen-to-macrophage ratio. Together, these findings point to a difference in the inflammatory contribution to plaque composition between Dgat1-/-→ Ldlr-/-and control mice. By contrast, DGAT1 deficiency did not affect the transcriptional responses of cultured macrophages to lipoprotein treatment in vitro, suggesting that the alterations seen in the plaques of Dgat1-/-→ Ldlr-/-mice in vivo do not reflect a cell intrinsic effect of DGAT1 in macrophages. We conclude that although DGAT1 in the hematopoietic compartment does not impact the overall lipid content of atherosclerotic plaques, it exerts reciprocal effects on inflammation and fibrosis, two processes that control plaque vulnerability.

Functional imaging of proteolytic activity is an emerging strategy to quantify disease and response to therapy at the molecular level. We present a new peptide-based imaging probe technology that advances these goals by exploiting enzymatic activity to deposit probes labelled with near-infrared (NIR) fluorophores or radioisotopes in cell membranes of disease-associated proteolysis. This strategy allows for non-invasive detection of protease activity in vivo and ex vivo by tracking deposited probes in tissues. We demonstrate non-invasive detection of thrombin generation in a murine model of pulmonary embolism using our protease-activated peptide probes in microscopic clots within the lungs with NIR fluorescence optical imaging and positron-emission tomography. Thrombin activity is imaged deep in tissue and tracked predominantly to platelets within the lumen of blood vessels. The modular design of our probes allows for facile investigation of other proteases, and their contributions to disease by tailoring the protease activation and cell-binding elements.

Functional imaging of proteolytic activity is an emerging strategy to quantify disease and response to therapy at the molecular level. We present a new peptide-based imaging probe technology that advances these goals by exploiting enzymatic activity to deposit probes labelled with near-infrared (NIR) fluorophores or radioisotopes in cell membranes of disease-associated proteolysis. This strategy allows for non-invasive detection of protease activity in vivo and ex vivo by tracking deposited probes in tissues. We demonstrate non-invasive detection of thrombin generation in a murine model of pulmonary embolism using our protease-activated peptide probes in microscopic clots within the lungs with NIR fluorescence optical imaging and positron-emission tomography. Thrombin activity is imaged deep in tissue and tracked predominantly to platelets within the lumen of blood vessels. The modular design of our probes allows for facile investigation of other proteases, and their contributions to disease by tailoring the protease activation and cell-binding elements.

Abstract Abstract 1111 Collapse of membrane lipid asymmetry is a hallmark of blood coagulation. TMEM16F of the TMEM16 family that includes TMEM16A/B Ca2+-activated Cl− channels (CaCCs) is linked to Scott Syndrome with deficient Ca2+-dependent lipid scrambling. We generated TMEM16F-knockout mice that exhibit bleeding defects associated with platelet deficiency in Ca2+-dependent phosphatidylserine exposure and procoagulant activity, and lack a Ca2+-activated cation current in the platelet precursor megakaryocytes. TMEM16F channels permeate both monovalent and divalent cations including Ca2+, and exhibit synergistic gating by Ca2+ and voltage. We further pinpointed a residue in the putative pore region important for the cation versus anion selectivity of TMEM16F-SCAN and TMEM16A-CaCC channels. This study thus identifies a novel Ca2+-activated channel permeable to Ca2+ and critical for Ca2+-dependent scramblase activity. Disclosures: No relevant conflicts of interest to declare.

Collapse of membrane lipid asymmetry is a hallmark of blood coagulation. TMEM16F of the TMEM16 family that includes TMEM16A/B Ca(2+)-activated Cl(-) channels (CaCCs) is linked to Scott syndrome with deficient Ca(2+)-dependent lipid scrambling. We generated TMEM16F knockout mice that exhibit bleeding defects and protection in an arterial thrombosis model associated with platelet deficiency in Ca(2+)-dependent phosphatidylserine exposure and procoagulant activity and lack a Ca(2+)-activated cation current in the platelet precursor megakaryocytes. Heterologous expression of TMEM16F generates a small-conductance Ca(2+)-activated nonselective cation (SCAN) current with subpicosiemens single-channel conductance rather than a CaCC. TMEM16F-SCAN channels permeate both monovalent and divalent cations, including Ca(2+), and exhibit synergistic gating by Ca(2+) and voltage. We further pinpointed a residue in the putative pore region important for the cation versus anion selectivity of TMEM16F-SCAN and TMEM16A-CaCC channels. This study thus identifies a Ca(2+)-activated channel permeable to Ca(2+) and critical for Ca(2+)-dependent scramblase activity during blood coagulation. PAPERFLICK:

There is great interest in examining the consequences of the COVID-19 pandemic on adolescent mental health, but most studies were conducted in high-income countries. The identification of overall effects and protective factors is essential to understand the determinants of mental wellbeing in contexts of stress. We aimed to study changes in adolescent mental health during the pandemic and the risk and protective factors associated with these changes in a Brazilian birth cohort. One thousand nine hundred forty nine adolescents from the 2004 Pelotas Birth Cohort were assessed prepandemic (T1, November 2019 to March 2020, mean age 15.69 years) and mid-pandemic (T2, August to December 2021, mean age 17.41 years). Mental health was assessed using the Strengths and Difficulties Questionnaire. Prepandemic and pandemic-related predictors were examined as predictors of change in multivariate latent change scores models. There was a mean increase in adolescent total mental health difficulties (M = 1.071, p <.001), hyperactivity/inattention (M = 0.208, p <.001), emotion symptoms (M = 0.409, p <.001), and peer problems (M = 0.434, p <.001) during the pandemic. This increase was associated with several negative family context variables, including harsh parenting and maternal depressive symptoms at T2. Higher emotion regulation levels protected against increases in adolescent mental health difficulties related to the COVID-19 pandemic. Family-context variables emerged as important risk factors for the deterioration of adolescent mental health during the COVID-19 pandemic. Interventions promoting emotion regulation strategies are a promising approach to protecting adolescent wellbeing in periods of stress. [ABSTRACT FROM AUTHOR]

Questioning is central to the development of scientific and health literacies. In exploring this concept, Tongan science teachers hypothesized that their ability to use and encourage questioning presented challenges in the context of Tongan social and cultural norms. This study set out to develop a peer-to-peer protocol to enable teachers to characterize current practice, and identify barriers and facilitators to the use of questioning in Tongan science classrooms. Participating teachers co-constructed a peer-to-peer observation protocol, collected, anonymized and analyzed observational data to identify current use, enablers and facilitators of questioning in their classrooms. Findings suggest that peer observation and talanoa (collective critical discussion) enabled teachers to characterize and critique their current practice, and increased teacher understanding of the process of questioning and its value in the development of scientific and health literacy. Three hypotheses were developed to explore potential strategies to increase the use questions in Tongan science classrooms.

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