Is cell segregation like oil and water: asymptotic versus transitory regime

Segregation of different cell types is a crucial process for the pattern formation in tissues, in particular during embryogenesis. Since the involved cell interactions are complex and difficult to measure individually in experiments, mathematical modelling plays an increasingly important role to unravel the mechanisms governing segregation. The analysis of these theoretical models focuses mainly on the asymptotic behavior at large times, in a steady regime and for large numbers of cells. Most famously, cell-segregation models based on the minimization of the total surface energy, a mechanism also driving the demixing of immiscible fluids, are known to exhibit asymptotically a particular algebraic scaling behavior. However, it is not clear, whether the asymptotic regime of the numerical models is relevant at the spatio-temporal scales of actual biological processes and in-vitro experiments. By developing a mapping between cell-based models and experimental settings, we are able to directly compare previous experimental data to numerical simulations of cell segregation quantitatively. We demonstrate that the experiments are reproduced by the transitory regime of the models rather than the asymptotic one. Our work puts a new perspective on previous model-driven conclusions on cell segregation mechanisms.Comment: 24 pages, 7+4 figure

Myc Regulates Embryonic Vascular Permeability and Remodeling

Previous work has shown that c-Myc is required for adequate vasculogenesis and angiogenesis. To further investigate the contribution of Myc to these processes, we conditionally expressed c-Myc in embryonic endothelial cells using a tetracycline-regulated system. Endothelial Myc overexpression resulted in severe defects in the embryonic vascular system. Myc-expressing embryos undergo widespread edema formation and multiple hemorrhagic lesions. They die between embryonic days 14.5 and 17.5. The changes in vascular permeability are not caused by deficiencies in vascular basement membrane composition or pericyte coverage. However, the overall turnover of endothelial cells is elevated as is revealed by increased levels of both proliferation and apoptosis. Whole-mount immunohistochemical analysis revealed alterations in the architecture of capillary networks. The dermal vasculature of Myc-expressing embryos is characterized by a reduction in vessel branching, which occurs despite upregulation of the proangiogenic factors vascular endothelial growth factor-A and angiopoietin-2. Thus, the net outcome of an excess of vascular endothelial growth factor-A and angiopoietin-2 in the face of an elevated cellular turnover appears to be a defect in vascular integrity. (Circ Res. 2009;104:1151-1159.

VRAC: molecular identification as LRRC8 heteromers with differential functions

Abstract A major player of vertebrate cell volume regulation is the volume-regulated anion channel (VRAC), which conducts halide ions and organic osmolytes to counteract osmotic imbalances. The molecular entity of this channel was unknown until very recently, although its biophysical characteristics and diverse physiological roles have been extensively studied over the last 30 years. On the road to the molecular identification of VRAC, experimental difficulties led to the proposal of a variety of false candidates. In 2014, in a final breakthrough, two groups independently identified LRRC8A as indispensable component of VRAC. LRRC8A is part of the leucine-rich repeat containing 8 family, which is comprised of five members (LRRC8A-E). Of those, LRRC8A is an obligatory subunit of VRAC but it needs at least one of the other family members to mediate the swelling-induced Cl − current I Cl,vol . This review discusses the remarkable journey which led to the molecular identification of VRAC, evidence for LRRC8 proteins forming the VRAC pore and their heteromeric assembly. Furthermore, first major insights on the role of LRRC8 proteins in cancer drug resistance and apoptosis and the role of LRRC8D in cisplatin and taurine transport will be summarized

Effect of Nintedanib on Progression of Systemic Sclerosis-Associated Interstitial Lung Disease Over 100 Weeks: Data From a Randomized Controlled Trial

OBJECTIVE In the SENSCIS trial, participants with systemic sclerosis-associated interstitial lung disease (SSc-ILD) were randomized to receive nintedanib or placebo until the last participant reached week 52 but for 100 weeks or less. Nintedanib reduced the rate of decline in forced vital capacity (FVC) (ml/year) over 52 weeks by 44% (41 ml [95% confidence interval (95% CI): 2.9-79.0]) versus placebo. We investigated the effect of nintedanib over the whole SENSCIS trial. METHODS The annual rate of decline in FVC (ml/year) over the whole trial was assessed descriptively using 1) on-treatment data plus off-treatment data from participants who prematurely discontinued treatment (intent-to-treat analysis) and 2) only on-treatment data to assess the effect of nintedanib in participants who remained on treatment. RESULTS In the intent-to-treat analysis, the adjusted mean (SE) annual rate of decline in FVC over 100 weeks was -54.9 (11.1) and -88.8 (10.9) ml/year in the nintedanib (n = 287) and placebo (n = 288) groups, respectively (difference 34.0 ml/year [95% CI: 3.4-64.5]). In the on-treatment analysis, the adjusted mean (SE) annual rate of decline in FVC over 100 weeks was -55.1 (12.3) and -94.0 (11.7) ml/year in the nintedanib (n = 286) and placebo (n = 288) groups, respectively (difference 38.9 ml/year [95% CI: 5.6-72.1]). The adverse event profile of nintedanib over 100 weeks was consistent with that observed over 52 weeks. CONCLUSION Nintedanib provides a sustained benefit on slowing the progression of SSc-ILD over 100 weeks, with adverse events that are manageable for most patients

Survival analysis for AdVerse events with VarYing follow-up times (SAVVY) -- estimation of adverse event risks

The SAVVY project aims to improve the analyses of adverse event (AE) data in clinical trials through the use of survival techniques appropriately dealing with varying follow-up times and competing events (CEs). Although statistical methodologies have advanced, in AE analyses often the incidence proportion, the incidence density, or a non-parametric Kaplan-Meier estimator (KME) are used, which either ignore censoring or CEs. In an empirical study including randomized clinical trials from several sponsor organisations, these potential sources of bias are investigated. The main aim is to compare the estimators that are typically used in AE analysis to the Aalen-Johansen estimator (AJE) as the gold-standard. Here, one-sample findings are reported, while a companion paper considers consequences when comparing treatment groups. Estimators are compared with descriptive statistics, graphical displays and with a random effects meta-analysis. The influence of different factors on the size of the bias is investigated in a meta-regression. Comparisons are conducted at the maximum follow-up time and at earlier evaluation time points. CEs definition does not only include death before AE but also end of follow-up for AEs due to events possibly related to the disease course or the treatment. Ten sponsor organisations provided 17 trials including 186 types of AEs. The one minus KME was on average about 1.2-fold larger than the AJE. Leading forces influencing bias were the amount of censoring and of CEs. As a consequence, the average bias using the incidence proportion was less than 5%. Assuming constant hazards using incidence densities was hardly an issue provided that CEs were accounted for. There is a need to improve the guidelines of reporting risks of AEs so that the KME and the incidence proportion are replaced by the AJE with an appropriate definition of CEs

On the twist-2 contributions to polarized structure functions and new sum rules

The twist-2 contributions to the polarized structure functions in deep inelastic lepton--hadron scattering are calculated including the exchange of weak bosons and using both the operator product expansion and the covariant parton model. A new relation between two structure functions leading to a sequence of new sum rules is found. The light quark mass corrections to the structure functions are derived in lowest order QCD.Comment: 15 pages Latex, inclding five eps-figures, all compressed by uufile substituting the ps-file available befor

Health-related Quality of Life in the Phase III LUME-Colon 1 Study: Comparison and Interpretation of Results From EORTC QLQ-C30 Analyses

INTRODUCTION: We used European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) data from the LUME-Colon 1 study to illustrate different methods of statistical analysis for health-related quality of life (HRQoL), and compared the results. PATIENTS AND METHODS: Patients were randomized 1:1 to receive nintedanib 200 mg twice daily plus best supportive care (n = 386) or matched placebo plus best supportive care (n = 382). Five methods (mean treatment difference averaged over time, using a mixed-effects growth curve model; mixed-effects models for repeated measurements (MMRM); time-to-deterioration (TTD); status change; and responder analysis) were used to analyze EORTC QLQ-C30 global health status (GHS)/QoL and scores from functional scales. RESULTS: Overall, GHS/QoL and physical functioning deteriorated over time. Mean treatment difference slightly favored nintedanib over placebo for physical functioning (adjusted mean, 2.66; 95% confidence interval [CI], 0.97-4.34) and social functioning (adjusted mean, 2.62; 95% CI, 0.66-4.47). GHS/QoL was numerically better with nintedanib versus placebo (adjusted mean, 1.61; 95% CI, -0.004 to 3.27). MMRM analysis had similar results, with better physical functioning in the nintedanib group at all timepoints. There was no significant delay in GHS/QoL deterioration (10%) and physical functioning (16%) with nintedanib versus placebo (TTD analysis). Status change analysis showed a higher proportion of patients with markedly improved GHS/QoL and physical functioning in the nintedanib versus placebo groups. Responder analysis showed a similar, less pronounced pattern. CONCLUSION: Analyses of EORTC QLQ-C30 data showed that HRQoL was not impaired by treatment with nintedanib versus placebo. Analysis and interpretation of HRQoL endpoints should consider symptom type and severity and course of disease. ispartof: CLINICAL COLORECTAL CANCER vol:18 issue:4 pages:269-+ ispartof: location:United States status: publishe