Fibrinogen does not relate to cardiovascular or muscle manifestations in COPD: cross-sectional data from the ERICA study.

Cardiovascular and skeletal muscle manifestations constitute important comorbidities in COPD, with systemic inflammation proposed as a common mechanistic link. Fibrinogen has prognostic role in COPD. We aimed to determine whether aortic stiffness and quadriceps weakness are linked in COPD, and whether they are associated with the systemic inflammatory mediator-fibrinogen. Aortic pulse wave velocity (aPWV), quadriceps maximal volitional contraction (QMVC) force and fibrinogen were measured in 729 patients with stable, Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages II-IV COPD. The cardiovascular and muscular manifestations exist independently (P=0.22, χ2). Fibrinogen was not associated with aPWV or QMVC (P=0.628 and P=0.621, respectively), making inflammation, as measured by plasma fibrinogen, an unlikely common aetiological factor.

Co-design workshops with families experiencing multiple and interacting adversities including parental mental health, substance use, domestic violence, and poverty: intervention principles and insights from mothers, fathers, and young people.

BACKGROUND: Clustering and co-occurring of family adversities, including mental health problems, substance use, domestic violence and abuse, as well as poverty can increase health and behavioural risks for children, which persist throughout the life course. Yet, interventions that acknowledge and account for the complex interactive nature of such risks are limited. This study aimed to develop intervention principles based on reflections from mothers, fathers, and young people who experience multiple and interacting adversities. These principles will show how family members perceive an intervention may bring about positive change and highlight key insights into design and delivery. METHODS: A series of six co-design workshops with mothers, fathers, and young people who experienced multiple and interacting adversities (n = 41) were iteratively conducted across two regions in England (London and North-East) by four researchers. Workshop content and co-design activities were informed by advisory groups. Data from facilitator notes and activities were analysed thematically, resulting in a set of intervention principles. RESULTS: The intervention principles highlighted that: (1) to reduce isolation and loneliness parents and young people wanted to be connected to services, resources, and peer support networks within their local community, particularly by a knowledgeable and friendly community worker; (2) to address feelings of being misunderstood, parents and young people wanted the development of specialised trauma informed training for practitioners and to have the space to build trusting, gradual, and non-stigmatising relationships with practitioners; and (3) to address the needs and strengths of individual family members, mothers, fathers, and young people wanted separate, tailored, and confidential support. CONCLUSIONS: The current study has important implications for practice in supporting families that experience multiple and interacting adversities. The intervention principles from this study share common characteristics with other intervention models currently on offer in the United Kingdom, including social prescribing, but go beyond these to holistically consider the whole families' needs, environments, and circumstances. There should be particular focus on the child's as well as the mothers' and fathers' needs, independently of the family unit. Further refinement and piloting of the developing intervention are needed.

Families can experience multiple difficulties. These difficulties include parental mental health problems, alcohol and drug use, domestic violence, and poverty. These difficulties can impact the wellbeing of both parents and children. Currently, support that is provided to families rarely accounts for these complex and multiple difficulties. This study aimed to gather insights from mothers, fathers, and young people about how to best support families who experience multiple difficulties at the same time. We ran six workshops with community groups of mothers, fathers, and young people from London and North East England. We learned that: (1) Parents and young people wanted to be connected to services, resources and peer support networks within their local community. (2) Parents and young people wanted to build trusting, gradual, and non-stigmatising relationships with practitioners. (3) Parents and young people wanted support that was personalised to their own needs and that focused on their strengths. This research contributes key ideas for supporting families, which will be used alongside other studies to develop new ways of supporting families. The next steps will be to complete and test the developing support model, by delivering it to families and measuring how well it works.

Cost-effectiveness of the children and young People's health partnership (CYPHP) model of integrated care versus enhanced usual care: analysis of a pragmatic cluster randomised controlled trial in South London.

Background: Integration of paediatric health services across primary and secondary care holds great promise for the management of chronic conditions, yet limited evidence exists on its cost-effectiveness. This paper reports the results of the economic evaluation of the Children and Young People's Health Partnership (CYPHP) aimed at integrating care for children with common chronic conditions (asthma, eczema, and constipation). Methods: Cost-effectiveness, cost-utility and cost-benefit analyses were conducted alongside a pragmatic cluster randomised controlled trial involving 97,970 children in 70 general practices in South London, including 1,731 participants with asthma, eczema and or constipation with self-reported health-related quality of life measures. Analyses considered the National Health Service (NHS)/Personal Social Service (PSS) and societal perspectives, and time horizons of 6 and 12-months. Costs included intervention delivery, health service use (primary and secondary care), referrals to social services, and time lost from work and school. Health outcomes were measured through the Paediatric Quality of Life Inventory, the Child Health Utility 9-Dimensions, and monetarised benefit combining Quality-Adjusted Life Years (QALYs) for children and parental mental well-being. Results present incremental cost-effectiveness ratios (ICERs), compared to a willingness to pay threshold (WTP) of £20,000-30,000/QALY, and net monetary benefit (NMB), with deterministic sensitivity analyses. Findings: At 6 months, from the NHS/PSS perspective, CYPHP is not cost-effective (ICER = £721,000/QALY), and this result holds at 12 months (ICER = £45,586/QALY). However, under the societal perspective CYPHP falls within WTP thresholds (ICER = £22,966/QALY), with a probability of being cost-effective between 0.4 and 0.6 at £20,000/QALY and £30,000/QALY, respectively. The cost-benefit analysis yields a positive NMB of CYPHP at 12 months £109 under the societal perspective, with similar probabilistic results. Interpretation: CYPHP was not cost-effective at 6 months or under the NHS/PSS perspective. Trends towards cost-effectiveness are observed once a longer time horizon and a more inclusive perspective on effects is considered. Further research beyond 12 months is needed as the model becomes firmly embedded into the paediatric healthcare delivery system. Funding: This research was funded by Guy's and St Thomas' Charity, Lambeth and Southwark Clinical Commissioning Groups. The funders had no role in the writing of the manuscript, decision to submit it for publication, or any other process involved in the research.

"They had clothes on their back and they had food in their stomach, but they didn't have me": The contribution of parental mental health problems, substance use, and domestic violence and abuse on young people and parents.

BACKGROUND: The parental risk factors of mental health problems, substance use, and domestic violence and abuse each individually negatively impacts children's health and developmental outcomes. Few studies have considered the lived experience and support needs of parents and children in the real-world situation where these common risks cluster. OBJECTIVE: This study explores parents' and young people's lived experiences of the clustering of parental mental health problems, parental substance use, and domestic violence and abuse. METHODS: Semi-structured interviews were conducted with 18 mothers, 6 fathers, and 7 young people with experiences of these parental risk factors. Transcribed interviews were analysed using reflexive thematic analysis. RESULTS: Four themes were developed, 1) cumulative adversity, 2) the impact of syndemic risk, 3) families navigating risk, and 4) family support. Parents and young people described family situations of stress wherein they experienced cumulative impact of multiple parental risk factors. Parents sought to navigate stressors and parent in positive ways under challenging conditions, often impeded by their own childhood trauma and diminished confidence. Parents and young people spoke of the need for, and benefits of having, support; both as a family and as individuals, to successfully address this trio of parental risks and the related impact. CONCLUSIONS: This study highlights the high level of stress families experience and the efforts they go to mitigate risk. Services and interventions need to reflect the complexity of multiple needs and consider both the whole family and individuals when providing support.

TSHR is the main causative locus in autosomal recessively inherited thyroid dysgenesis.

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder and results in mental retardation if untreated. Eighty-five percent of CH cases are due to disruptions in thyroid organogenesis and are mostly sporadic, but about 2% of thyroid dysgenesis is familial, indicating the involvement of genetic factors in the aetiology of the disease. In this study, we aimed to investigate the Mendelian (single-gene) causes of non-syndromic and non-goitrous congenital hypothyroidism (CHNG) in consanguineous or multi-case families. Here we report the results of the second part (n=105) of our large cohort (n=244), representing the largest such cohort in the literature, and interpret the overall results of the whole cohort. Additionally, 50 sporadic cases with thyroid dysgenesis and 400 unaffected control subjects were included in the study. In familial cases, first, we performed potential linkage analysis of four known genes causing CHNG (TSHR, PAX8, TSHB, and NKX2-5) using microsatellite markers and then examined the presence of mutations in these genes by direct sequencing. In addition, in silico analyses of the predicted structural effects of TSHR mutations were performed and related to the mutation specific disease phenotype. We detected eight new TSHR mutations and a PAX8 mutation but no mutations in TSHB and NKX2-5. None of the biallelic TSHR mutations detected in familial cases were present in the cohort of 50 sporadic cases. Genotype/phenotype relationships were established between TSHR mutations and resulting clinical presentations. Here we conclude that TSHR mutations are the main detectable cause of autosomal recessively inherited thyroid dysgenesis. We also outline a new genetic testing strategy for the investigation of suspected autosomal recessive non-goitrous CH.

Tumor risks and genotype-phenotype-proteotype analysis in 358 patients with germline mutations in SDHB and SDHD.

Succinate dehydrogenase B (SDHB) and D (SDHD) subunit gene mutations predispose to adrenal and extraadrenal pheochromocytomas, head and neck paragangliomas (HNPGL), and other tumor types. We report tumor risks in 358 patients with SDHB (n=295) and SDHD (n=63) mutations. Risks of HNPGL and pheochromocytoma in SDHB mutation carriers were 29% and 52%, respectively, at age 60 years and 71% and 29%, respectively, in SDHD mutation carriers. Risks of malignant pheochromocytoma and renal tumors (14% at age 70 years) were higher in SDHB mutation carriers; 55 different mutations (including a novel recurrent exon 1 deletion) were identified. No clear genotype-phenotype correlations were detected for SDHB mutations. However, SDHD mutations predicted to result in loss of expression or a truncated or unstable protein were associated with a significantly increased risk of pheochromocytoma compared to missense mutations that were not predicted to impair protein stability (most such cases had the common p.Pro81Leu mutation). Analysis of the largest cohort of SDHB/D mutation carriers has enhanced estimates of penetrance and tumor risk and supports in silicon protein structure prediction analysis for functional assessment of mutations. The differing effect of the SDHD p.Pro81Leu on HNPGL and pheochromocytoma risks suggests differing mechanisms of tumorigenesis in SDH-associated HNPGL and pheochromocytoma.

Naturally occurring mutations alter the stability of polycystin-1 polycystic kidney disease (PKD) domains.

Mutations in polycystin-1 (PC1) can cause autosomal dominant polycystic kidney disease, which is a leading cause of renal failure. The available evidence suggests that PC1 acts as a mechanosensor, receiving signals from the primary cilia, neighboring cells, and extracellular matrix. PC1 is a large membrane protein that has a long N-terminal extracellular region (about 3000 amino acids) with a multimodular structure including 16 Ig-like polycystic kidney disease (PKD) domains, which are targeted by many naturally occurring missense mutations. Nothing is known about the effects of these mutations on the biophysical properties of PKD domains. Here we investigate the effects of several naturally occurring mutations on the mechanical stability of the first PKD domain of human PC1 (HuPKDd1). We found that several missense mutations alter the mechanical unfolding pathways of HuPKDd1, resulting in distinct mechanical phenotypes. Moreover, we found that these mutations also alter the thermodynamic stability of a structurally homologous archaeal PKD domain. Based on these findings, we hypothesize that missense mutations may cause autosomal dominant polycystic kidney disease by altering the stability of the PC1 ectodomain, thereby perturbing its ability to sense mechanical signals.

Novel TSHR mutations in consanguineous families with congenital nongoitrous hypothyroidism.

OBJECTIVE: Nonsyndromic autosomal recessively inherited nongoitrous congenital hypothyroidism (CHNG) can be caused by mutations in TSHR, PAX8, TSHB and NKX2-5. We aimed to investigate mutational frequencies of these genes and genotype/phenotype correlations in consanguineous families with CHNG. DESIGN: Because consanguinity in individuals with a presumptive genetic condition is often an indicator of an autosomal recessive inheritance and allows firmer correlations to be established between genotype and phenotype, we planned to execute our study in consanguineous families. PATIENTS: Hundred and thirty-nine children with CHNG phenotype born to consanguineous families. MEASUREMENTS: First, we investigated cases for evidence of linkage to the four known CHNG genes by microsatellite marker analysis. Mutation analysis by direct sequencing was then performed in those cases in whom linkage to the relevant candidate gene could not be excluded. In addition, in silico analysis of the predicted structural effects of TSHR mutations was performed and related to the mutation-specific disease phenotype. RESULTS: Homozygous germline TSHR mutations were detected in six families (5%), but no mutations were detected in PAX8, TSHB and NKX2-5. Four of TSHR mutations had not previously been described. Genotype-phenotype correlations were established and found to be related to the predicted structural effects of the mutations. CONCLUSIONS: Known causative genes account for the development of CHNG only in a minority of cases, and our cohort should provide a powerful resource to identify novel causative genes and to delineate the extent of locus heterogeneity in autosomal recessively inherited CHNG.

Mechanical unfolding of proteins: insights into biology, structure and folding.

Since user-friendly atomic force microscopes came onto the market a few years ago, scientists have explored the response of many proteins to applied force. This field has now matured beyond the phenomenological with exciting recent developments, particularly with regards to research into biological questions. For example, detailed mechanistic studies have suggested how mechanically active proteins perform their functions. Also, in vitro forced unfolding has been compared with in vivo protein import and degradation. Additionally, investigations have been carried out that probe the relationship between protein structure and response to applied force, an area that has benefited significantly from synergy between experiments and simulations. Finally, recent technological developments offer exciting new avenues for experimental studies.

Discussion and documentation of future care: a before-and-after study examining the impact of an alternative approach to recording treatment decisions on advance care planning in an acute hospital.

OBJECTIVE: To determine whether discussion and documentation of decisions about future care was improved following the introduction of a new approach to recording treatment decisions: the Universal Form of Treatment Options (UFTO). METHODS: Retrospective review of the medical records of patients who died within 90 days of admission to oncology or respiratory medicine wards over two 3-month periods, preimplementation and postimplementation of the UFTO. A sample size of 70 per group was required to provide 80% power to observe a change from 15% to 35% in discussion or documentation of advance care planning (ACP), using a two-sided test at the 5% significance level. RESULTS: On the oncology ward, introduction of the UFTO was associated with a statistically significant increase in cardiopulmonary resuscitation decisions documented for patients (pre-UFTO 52% to post-UFTO 77%, p=0.01) and an increase in discussions regarding ACP (pre-UFTO 27%, post-UFTO 49%, p=0.03). There were no demonstrable changes in practice on the respiratory ward. Only one patient came into hospital with a formal ACP document. CONCLUSIONS: Despite patients' proximity to the end-of-life, there was limited documentation of ACP and almost no evidence of formalised ACP. The introduction of the UFTO was associated with a change in practice on the oncology ward but this was not observed for respiratory patients. A new approach to recording treatment decisions may contribute to improving discussion and documentation about future care but further work is needed to ensure that all patients' preferences for treatment and care at the end-of-life are known.

Structural bioinformatics mutation analysis reveals genotype-phenotype correlations in von Hippel-Lindau disease and suggests molecular mechanisms of tumorigenesis.

Mutations in the VHL gene lead to von Hippel-Lindau (VHL) disease, a clinically heterogeneous cancer syndrome. Here, we use software and database tools to understand and predict the phenotypes associated with missense mutations in the VHL gene product, pVHL. The protein product pVHL is known to interact with elongin B, elongin C, and the HIF substrate. By analyzing known and predicted interaction sites and predictions of thermodynamic stability change upon mutation, we generate new hypotheses regarding the molecular etiology of renal cell carcinoma (RCC) and pheochromocytoma (PCC) in VHL disease. We find that the molecular causes of RCC and PCC appear to be decoupled. RCC may arise through two distinct mechanisms: disruption of HIF interactions or binding at the elongin B interface. PCC is triggered by mutations which disrupt interactions at the elongin C binding site. These findings have important implications for VHL disease and for nonfamilial RCC, because most cases of clear cell RCC are linked with VHL inactivation. Additionally, predicting effects of genetic variation will be critical as genetic sequencing accelerates; the analytical strategy presented here may elucidate other systems as further data on genetic variation become available.

Identifying risk factors for L'Hermitte's sign after IMRT for head and neck cancer.

BACKGROUND: L'Hermitte's sign (LS) after chemoradiotherapy for head and neck cancer appears related to higher spinal cord doses. IMRT plans limit spinal cord dose, but the incidence of LS remains high. METHODS: One hundred seventeen patients treated with TomoTherapy™ between 2008 and 2015 prospectively completed a side-effect questionnaire (VoxTox Trial Registration: UK CRN ID 13716). Baseline patient and treatment data were collected. Radiotherapy plans were analysed; mean and maximum spinal cord dose and volumes receiving 10, 20, 30 and 40 Gy were recorded. Dose variation across the cord was examined. These data were included in a logistic regression model. RESULTS: Forty two patients (35.9%) reported LS symptoms. Concurrent weekly cisplatin did not increase LS risk (p = 0.70, OR = 1.23 {95% CI 0.51-2.34}). Of 13 diabetic participants (9 taking metformin), only 1 developed LS (p = 0.025, OR = 0.13 {95% CI 0.051-3.27}). A refined binary logistic regression model showed that patients receiving unilateral radiation (p = 0.019, OR = 2.06 {95% CI 0.15-0.84}) were more likely to develop LS. Higher V40Gy (p = 0.047, OR = 1.06 {95% CI 1.00-1.12}), and younger age (mean age 56.6 vs 59.7, p = 0.060, OR = 0.96 {95% CI 0.92-1.00}) were associated with elevated risk of LS, with borderline significance. CONCLUSIONS: In this cohort, concomitant cisplatin did not increase risk, and LS incidence was lower in diabetic patients. Patient age and dose gradients across the spinal cord may be important factors.

Surrogate Markers of Cardiovascular Risk and Chronic Obstructive Pulmonary Disease: A Large Case-Controlled Study.

Cardiovascular disease is a common comorbidity and cause of mortality in chronic obstructive pulmonary disease. A better understanding of mechanisms of cardiovascular risk in chronic obstructive pulmonary disease patients is needed to improve clinical outcomes. We hypothesized that such patients have increased arterial stiffness, wave reflections, and subclinical atherosclerosis compared with controls and that these findings would be independent of smoking status and other confounding factors. A total of 458 patients with a diagnosis of chronic obstructive pulmonary disease and 1657 controls (43% were current or ex-smokers) with no airflow limitation were matched for age, sex, and body mass index. All individuals underwent assessments of carotid-femoral (aortic) pulse wave velocity, augmentation index, and carotid intima-media thickness. The mean age of the cohort was 67±8 years and 58% were men. Patients with chronic obstructive pulmonary disease had increased aortic pulse wave velocity (9.95±2.54 versus 9.27±2.41 m/s; P<0.001), augmentation index (28±10% versus 25±10%; P<0.001), and carotid intima-media thickness (0.83±0.19 versus 0.74±0.14 mm; P<0.001) compared with controls. Chronic obstructive pulmonary disease was associated with increased levels of each vascular biomarker independently of physiological confounders, smoking, and other cardiovascular risk factors. In this large case-controlled study, chronic obstructive pulmonary disease was associated with increased arterial stiffness, wave reflections, and subclinical atherosclerosis, independently of traditional cardiovascular risk factors. These findings suggest that the cardiovascular burden observed in this condition may be mediated through these mechanisms and supports the concept that chronic obstructive pulmonary disease is an independent risk factor for cardiovascular disease.

A structural bioinformatics approach to the analysis of nonsynonymous single nucleotide polymorphisms (nsSNPs) and their relation to disease.

The prediction of the effects of nonsynonymous single nucleotide polymorphisms (nsSNPs) on function depends critically on exploiting all information available on the three-dimensional structures of proteins. We describe software and databases for the analysis of nsSNPs that allow a user to move from SNP to sequence to structure to function. In both structure prediction and the analysis of the effects of nsSNPs, we exploit information about protein evolution, in particular, that derived from investigations on the relation of sequence to structure gained from the study of amino acid substitutions in divergent evolution. The techniques developed in our laboratory have allowed fast and automated sequence-structure homology recognition to identify templates and to perform comparative modeling; as well as simple, robust, and generally applicable algorithms to assess the likely impact of amino acid substitutions on structure and interactions. We describe our strategy for approaching the relationship between SNPs and disease, and the results of benchmarking our approach -- human proteins of known structure and recognized mutation.

The INVEST project: investigating the use of evidence synthesis in the design and analysis of clinical trials.

BACKGROUND: When designing and analysing clinical trials, using previous relevant information, perhaps in the form of evidence syntheses, can reduce research waste. We conducted the INVEST (INVestigating the use of Evidence Synthesis in the design and analysis of clinical Trials) survey to summarise the current use of evidence synthesis in trial design and analysis, to capture opinions of trialists and methodologists on such use, and to understand any barriers. METHODS: Our sampling frame was all delegates attending the International Clinical Trials Methodology Conference in November 2015. Respondents were asked to indicate (1) their views on the use of evidence synthesis in trial design and analysis, (2) their own use during the past 10 years and (3) the three greatest barriers to use in practice. RESULTS: Of approximately 638 attendees of the conference, 106 (17%) completed the survey, half of whom were statisticians. Support was generally high for using a description of previous evidence, a systematic review or a meta-analysis in trial design. Generally, respondents did not seem to be using evidence syntheses as often as they felt they should. For example, only 50% (42/84 relevant respondents) had used a meta-analysis to inform whether a trial is needed compared with 74% (62/84) indicating that this is desirable. Only 6% (5/81 relevant respondents) had used a value of information analysis to inform sample size calculations versus 22% (18/81) indicating support for this. Surprisingly large numbers of participants indicated support for, and previous use of, evidence syntheses in trial analysis. For example, 79% (79/100) of respondents indicated that external information about the treatment effect should be used to inform aspects of the analysis. The greatest perceived barrier to using evidence synthesis methods in trial design or analysis was time constraints, followed by a belief that the new trial was the first in the area. CONCLUSIONS: Evidence syntheses can be resource-intensive, but their use in informing the design, conduct and analysis of clinical trials is widely considered desirable. We advocate additional research, training and investment in resources dedicated to ways in which evidence syntheses can be undertaken more efficiently, offering the potential for cost savings in the long term.

Applying physical science techniques and CERN technology to an unsolved problem in radiation treatment for cancer: the multidisciplinary 'VoxTox' research programme.

The VoxTox research programme has applied expertise from the physical sciences to the problem of radiotherapy toxicity, bringing together expertise from engineering, mathematics, high energy physics (including the Large Hadron Collider), medical physics and radiation oncology. In our initial cohort of 109 men treated with curative radiotherapy for prostate cancer, daily image guidance computed tomography (CT) scans have been used to calculate delivered dose to the rectum, as distinct from planned dose, using an automated approach. Clinical toxicity data have been collected, allowing us to address the hypothesis that delivered dose provides a better predictor of toxicity than planned dose.

The remarkable mechanical strength of polycystin-1 supports a direct role in mechanotransduction.

Polycystin-1 is a large membrane-associated protein that interacts with polycystin-2 in the primary cilia of renal epithelial cells to form a mechanosensitive ion channel. Bending of the cilia induces calcium flow into the cells, mediated by the polycystin complex. Antibodies to polycystin-1 and polycystin-2 abolish this activation. Based on this, it has been suggested that the extracellular region of polycystin-1, which has a number of putative binding domains, may act as a mechanosensor. A large proportion of the extracellular region of polycystin-1 consists of beta-sandwich PKD domains in tandem array. We use atomic force microscopy to investigate the mechanical properties of the PKD domains of polycystin-1. We show that these domains, despite having a low thermodynamic stability, exhibit a remarkable mechanical strength, similar to that of immunoglobulin domains in the giant muscle protein titin. In agreement with the experimental results molecular dynamics simulations performed at low constant force show that the first PKD domain of polycystin (PKDd1) has a similar unfolding time as titin I27, under the same conditions. The simulations suggest that the basis for this mechanical stability is the formation of a force-stabilised intermediate. Our results suggest that these domains will remain folded under external force supporting the hypothesis that polycystin-1 could act as a mechanosensor, detecting changes in fluid flow in the kidney tubule.

Accumulated dose to the rectum, measured using dose-volume histograms and dose-surface maps, is different from planned dose in all patients treated with radiotherapy for prostate cancer.

OBJECTIVE: We sought to calculate accumulated dose (DA) to the rectum in patients treated with radiotherapy for prostate cancer. We were particularly interested in whether dose-surface maps (DSMs) provide additional information to dose-volume histograms (DVHs). METHODS: Manual rectal contours were obtained for kilovoltage and daily megavoltage CT scans for 10 participants from the VoxTox study (380 scans). Daily delivered dose recalculation was performed using a ray-tracing algorithm. Delivered DVHs were summated to create accumulated DVHs. The rectum was considered as a cylinder, cut and unfolded to produce daily delivered DSMs; these were summated to produce accumulated DSMs. RESULTS: Accumulated dose-volumes were different from planned in all participants. For one participant, all DA levels were higher and all volumes were larger than planned. For four participants, all DA levels were lower and all volumes were smaller than planned. For each of these four participants, ≥1% of pixels on the accumulated DSM received ≥5 Gy more than had been planned. CONCLUSION: Differences between accumulated and planned dose-volumes were seen in all participants. DSMs were able to identify differences between DA and planned dose that could not be appreciated from the DVHs. Further work is needed to extract the dose data embedded in the DSMs. These will be correlated with toxicity as part of the VoxTox Programme. ADVANCES IN KNOWLEDGE: DSMs are able to identify differences between DA and planned dose that cannot be appreciated from DVHs alone and should be incorporated into future studies investigating links between DA and toxicity.

Non-native interactions are critical for mechanical strength in PKD domains.

Experimental observation has led to the commonly held view that native state protein topology is the principle determinant of mechanical strength. However, the PKD domains of polycystin-1 challenge this assumption: they are stronger than predicted from their native structure. Molecular dynamics simulations suggest that force induces rearrangement to an intermediate structure, with nonnative hydrogen bonds, that resists unfolding. Here we test this hypothesis directly by introducing mutations designed to prevent formation of these nonnative interactions. We find that these mutations, which only moderately destabilize the native state, reduce the mechanical stability dramatically. The results demonstrate that nonnative interactions impart significant mechanical stability, necessary for the mechanosensor function of polycystin-1. Remarkably, such nonnative interactions result from force-induced conformational change: the PKD domain is strengthened by the application of force.

Atomic force microscopy: mechanical unfolding of proteins.

Mechanical unfolding of proteins using atomic force microscopy is becoming a routine biophysical technique. Mechanistic investigations in this rapidly evolving field are beginning to resolve the factors that contribute to the behaviour of biological macromolecules under force. Here we describe the force-mode apparatus, the experimental set-up, tractable systems of study, and the analysis of the resultant force data. Finally we summarise some of the recent achievements and limitations of this technique.