Chemically Fueled Dissipative Cross-Linking of Protein Hydrogels Mediated by Protein Unfolding.

Cells assemble dynamic protein-based nanostructures far from equilibrium, such as microtubules, in a process referred to as dissipative assembly. Synthetic analogues have utilized chemical fuels and reaction networks to form transient hydrogels and molecular assemblies from small molecule or synthetic polymer building blocks. Here, we demonstrate dissipative cross-linking of transient protein hydrogels using a redox cycle, which exhibit protein unfolding-dependent lifetimes and mechanical properties. Fast oxidation of cysteine groups on bovine serum albumin by hydrogen peroxide, the chemical fuel, formed transient hydrogels with disulfide bond cross-links that degraded over hours by a slow reductive back reaction. Interestingly, despite increased cross-linking, the hydrogel lifetime decreased as a function of increasing denaturant concentration. Experiments showed that the solvent-accessible cysteine concentration increased with increasing denaturant concentration due to unfolding of secondary structures. The increased cysteine concentration consumed more fuel, which led to less direction oxidation of the reducing agent and affected a shorter hydrogel lifetime. Increased hydrogel stiffness, disulfide cross-linking density, and decreased oxidation of redox-sensitive fluorescent probes at a high denaturant concentration provided evidence supporting the unveiling of additional cysteine cross-linking sites and more rapid consumption of hydrogen peroxide at higher denaturant concentrations. Taken together, the results indicate that the protein secondary structure mediated the transient hydrogel lifetime and mechanical properties by mediating the redox reactions, a feature unique to biomacromolecules that exhibit a higher order structure. While prior works have focused on the effects of the fuel concentration on dissipative assembly of non-biological molecules, this work demonstrates that the protein structure, even in nearly fully denatured proteins, can exert similar control over reaction kinetics, lifetime, and resulting mechanical properties of transient hydrogels.

The H3F3 K36M mutant antibody is a sensitive and specific marker for the diagnosis of chondroblastoma.

AIMS: We recently reported that 95% of chondroblastomas harbour a p.K36M mutation in either H3F3A (chromosome 1) or H3F3B (chromosome 17), with the majority involving H3F3B. The aim of this study was to assess the expression of the K36M-mutated protein by immunohistochemistry in a large group of tumours. METHODS AND RESULTS: One thousand eight hundred and ninety-four tumours, including 85 chondroblastomas and 10 clear-cell chondrosarcomas, were studied; of these, 82 chondroblastomas and one clear-cell chondrosarcoma known to harbour the H3F3 p.K36M mutation expressed the mutated protein. Three chondroblastomas and nine clear-cell chondrosarcomas wild type for H3F3A/H3F3B were negative for p.K36M immunoexpression. The remaining 1799 cases tested, 545 of which were known to be wild type for the H3F3A and H3F3B p.K36M mutations, included 1047 primary bone tumours, and 507 soft tissue and joint tumours. Two hundred and forty-five other tumour types not expected to harbour the mutation were negative for p.K36M immunoexpression. CONCLUSIONS: Our data demonstrate the specificity and sensitivity of this immunomarker, and will be a useful adjunct for reaching a diagnosis of chondroblastoma.

Contributions of Trauma and Economic Insecurity to Psychological Distress in Response to the COVID-19 Pandemic.

Background: Racially minoritized women with limited socioeconomic resources are at increased risk for adverse psychological outcomes in response to the COVID-19 pandemic. Disproportionate rates of trauma exposure and economic insecurity likely heighten risk for these outcomes among socioeconomically vulnerable individuals, but the unique contributions of these factors are poorly understood. As such, we examined trauma and economic factors as predictors of pandemic-related psychological distress and symptoms. Methods: Ninety-six women recruited for a trauma research study (91.7% Black, Mage=38.3 years, SDage=11.8 years) completed measures of trauma exposure, economic insecurity, and several items assessing psychological distress and symptoms related to the COVID-19 pandemic. We examined concern for mental and physical health impacts of COVID-19 as well as changes in self-reported levels of anxiety and anhedonia from the three months prior to the pandemic to the past two weeks. Linear regression analyses were used to assess contributions of trauma exposure and economic insecurity to COVID-19-related distress. Results: Childhood maltreatment and lifetime trauma exposure did not predict COVID-19-related distress; however, financial concern significantly contributed to concern for the physical health impact of COVID-19 (B = .30, p < .05). Food insecurity emerged as the only significant predictor of concern for mental health impact of COVID-19 (B=.91, p < .01). Housing instability was the only significant predictor of COVID-19-related increases in anhedonia (B = -.30, p < .05). Conclusions: Economic insecurity, namely self-reported financial concern, food insecurity, and housing instability, was related to COVID-19-related psychological distress in a sample of predominately Black American women living in under-resourced communities. Findings may help identify populations at risk for COVID-19-related psychological distress and symptoms and develop effective interventions, such as expanding access to nutritious food sources and housing support, for minoritized community members.

H3F3A (Histone 3.3) G34W Immunohistochemistry: A Reliable Marker Defining Benign and Malignant Giant Cell Tumor of Bone.

Giant cell tumor of bone (GCTB) is a locally aggressive subarticular tumor. Having recently reported that H3.3 G34W mutations are characteristic of this tumor type, we have now investigated the sensitivity and specificity of the anti-histone H3.3 G34W rabbit monoclonal antibody in a wide variety of tumors including histologic mimics of GCTB to assess its value as a diagnostic marker. We also determined the incidence of H3.3 G34 mutations in primary malignant bone tumors as assessed by genotype and H3.3 G34W immunostaining. A total of 3163 tumors were tested. Totally, 213/235 GCTB (90.6%) showed nuclear H3.3 p.G34W immunoreactivity. This was not the case for the rare variants, p.G34L, M, and V, which occurred most commonly in the small bones of the hands, patella, and the axial skeleton. If these sites were excluded from the analysis, H3.3 G34W expression was found in 97.8% of GCTB. Malignant bone tumors initially classified as osteosarcomas were the only other lesions (n=11) that showed G34W expression. Notably an additional 2 previously reported osteosarcomas with a p.G34R mutation were not immunoreactive for the antibody. A total of 11/13 of these malignant H3.3-mutant tumors exhibited an osteoclast-rich component: when imaging was available all but one presented at a subarticular site. We propose that subarticular primary malignant bone sarcoma with H3.3 mutations represent true malignant GCTB, even in the absence of a benign GCTB component.

Digital PCR analysis of circulating tumor DNA: a biomarker for chondrosarcoma diagnosis, prognostication, and residual disease detection.

Conventional chondrosarcoma is the most common primary bone tumor in adults. Prognosis corresponds with tumor grade but remains variable, especially for individuals with grade (G) II disease. There are currently no biomarkers available for monitoring or prognostication of chondrosarcoma. Circulating tumor DNA (ctDNA) has recently emerged as a promising biomarker for a broad range of tumor types. To date, little has been done to study the presence of ctDNA and its potential utility in the management of sarcomas, including chondrosarcoma. In this study, we have assessed ctDNA levels in a cohort of 71 patients, 32 with sarcoma, including 29 individuals with central chondrosarcoma (CS) and 39 with locally aggressive and benign bone and soft tissue tumors, using digital PCR. In patients with CS, ctDNA was detected in pretreatment samples in 14/29 patients, which showed clear correlation with tumor grade as demonstrated by the detection of ctDNA in all patients with GIII and dedifferentiated disease (n = 6) and in 8/17 patients with GII disease, but never associated with GI CS. Notably detection of ctDNA preoperatively in GII disease was associated with a poor outcome. A total of 14 patients with CS had ctDNA levels assessed at multiple time points and in most patients there was a clear reduction following surgical removal. This research lays the foundation for larger studies to assess the utility of ctDNA for chondrosarcoma diagnosis, prognostication, early detection of residual disease and monitoring disease progression.

What is the Relationship between Risky Outdoor Play and Health in Children? A Systematic Review.

Risky outdoor play has been associated with promoting children's health and development, but also with injury and death. Risky outdoor play has diminished over time, concurrent with increasing concerns regarding child safety and emphasis on injury prevention. We sought to conduct a systematic review to examine the relationship between risky outdoor play and health in children, in order to inform the debate regarding its benefits and harms. We identified and evaluated 21 relevant papers for quality using the GRADE framework. Included articles addressed the effect on health indicators and behaviours from three types of risky play, as well as risky play supportive environments. The systematic review revealed overall positive effects of risky outdoor play on a variety of health indicators and behaviours, most commonly physical activity, but also social health and behaviours, injuries, and aggression. The review indicated the need for additional "good quality" studies; however, we note that even in the face of the generally exclusionary systematic review process, our findings support the promotion of risky outdoor play for healthy child development. These positive results with the marked reduction in risky outdoor play opportunities in recent generations indicate the need to encourage action to support children's risky outdoor play opportunities. Policy and practice precedents and recommendations for action are discussed.

What Is the Relationship between Outdoor Time and Physical Activity, Sedentary Behaviour, and Physical Fitness in Children? A Systematic Review.

The objective of this systematic review was to examine the relationship between outdoor time and: (1) physical activity, (2) cardiorespiratory fitness, (3) musculoskeletal fitness, (4) sedentary behaviour; or (5) motor skill development in children aged 3-12 years. We identified 28 relevant studies that were assessed for quality using the GRADE framework. The systematic review revealed overall positive effects of outdoor time on physical activity, sedentary behaviour, and cardiorespiratory fitness, although causality could not be assumed due to a lack of RCTs. Motor skill development was unrelated to outdoor time; however, this relationship was only examined in a single study of preschool children. No studies were found that examined associations between outdoor time and musculoskeletal fitness.