Diffusivity estimation for activator–inhibitor models: theory and application to intracellular dynamics of the actin cytoskeleton

A theory for diffusivity estimation for spatially extended activator–inhibitor dynamics modeling the evolution of intracellular signaling networks is developed in the math- ematical framework of stochastic reaction–diffusion systems. In order to account for model uncertainties, we extend the results for parameter estimation for semilinear stochastic partial differential equationsPostprint (published version

How cortical waves drive fission of motile cells

Cytokinesis—the division of a cell into two daughter cells—is a key step in cell growth and proliferation. It typically occurs in synchrony with the cell cycle to ensure that a complete copy of the genetic information is passed on to the next generation of daughter cells. In animal cells, cytokinesis commonly relies on an actomyosin contractile ring that drives equatorial furrowing and separation into the two daughter cells. However, also contractile ring-independent forms of cell division are known that depend on substrate-mediated traction forces. Here, we report evidence of an as yet unknown type of contractile ring-independent cytokinesis that we termed wave-mediated cytofission. It is driven by self-organized cortical actin waves that travel across the ventral membrane of oversized, multinucleated Dictyostelium discoideum cells. Upon collision with the cell border, waves may initiate the formation of protrusions that elongate and eventually pinch off to form separate daughter cells. They are composed of a stable elongated wave segment that is enclosed by a cell membrane and moves in a highly persistent fashion. We rationalize our observations based on a noisy excitable reaction–diffusion model in combination with a dynamic phase field to account for the cell shape and demonstrate that daughter cells emerging from wave-mediated cytofission exhibit a well-controlled size.Postprint (published version

Balanced hydroxyethylstarch (HES 130/0.4) impairs kidney function in-vivo without inflammation

Volume therapy is a standard procedure in daily perioperative care, and there is an ongoing discussion about the benefits of colloid resuscitation with hydroxyethylstarch (HES). In sepsis HES should be avoided due to a higher risk for acute kidney injury (AKI). Results of the usage of HES in patients without sepsis are controversial. Therefore we conducted an animal study to evaluate the impact of 6% HES 130/0.4 on kidney integrity with sepsis or under healthy conditions Sepsis was induced by standardized Colon Ascendens Stent Peritonitis (sCASP). sCASP-group as well as control group (C) remained untreated for 24 h. After 18 h sCASP+HES group (sCASP+VOL) and control+HES (C+VOL) received 50 ml/KG balanced 6% HES (VOL) 130/0.4 over 6h. After 24h kidney function was measured via Inulin- and PAH-Clearance in re-anesthetized rats, and serum urea, creatinine (crea), cystatin C and Neutrophil gelatinase-associated lipocalin (NGAL) as well as histopathology were analysed. In vitro human proximal tubule cells (PTC) were cultured +/- lipopolysaccharid (LPS) and with 0.1–4.0% VOL. Cell viability was measured with XTT-, cell toxicity with LDH-test. sCASP induced severe septic AKI demonstrated divergent results regarding renal function by clearance or creatinine measure focusing on VOL. Soleley HES (C+VOL) deteriorated renal function without sCASP. Histopathology revealed significantly derangements in all HES groups compared to control. In vitro LPS did not worsen the HES induced reduction of cell viability in PTC cells. For the first time, we demonstrated, that application of 50 ml/KG 6% HES 130/0.4 over 6 hours induced AKI without inflammation in vivo. Severity of sCASP induced septic AKI might be no longer susceptible to the way of volume expansio

Treatment With Erythropoietin for Patients With Optic Neuritis: Long-term Follow-up.

BACKGROUND AND OBJECTIVE Erythropoietin (EPO) is a candidate neuroprotective drug. We assessed its long-term safety and efficacy as an adjunct to methylprednisolone in patients with optic neuritis and focused on conversions to multiple sclerosis (MS). METHODS The TONE trial randomized 108 patients with acute optic neuritis but without previously known MS to either 33,000 IU EPO or placebo in conjunction with 1,000 mg methylprednisolone daily for 3 days. After reaching the primary end point at 6 months, we conducted an open-label follow-up 2 years after randomization. RESULTS The follow-up was attended by 83 of 103 initially analyzed patients (81%). There were no previously unreported adverse events. The adjusted treatment difference of peripapillary retinal nerve fiber layer atrophy in relation to the fellow eye at baseline was 1.27 µm (95% CI -6.45 to 8.98, p = 0.74). The adjusted treatment difference in low-contrast letter acuity was 2.87 on the 2.5% Sloan chart score (95% CI -7.92 to 13.65). Vision-related quality of life was similar in both treatment arms (National Eye Institute Visual Functioning Questionnaire median score [IQR]: 94.0 [88.0 to 96.9] in the EPO and 93.4 [89.5 to 97.4] in the placebo group). The rate of multiple sclerosis-free survival was 38% in the placebo and 53% in the EPO group (hazard ratio: 1.67, 95% CI 0.96 to 2.88, p = 0.068). DISCUSSION In line with the results at 6 months, we found neither structural nor functional benefits in the visual system of patients with optic neuritis as a clinically isolated syndrome, 2 years after EPO administration. Although there were fewer early conversions to MS in the EPO group, the difference across the 2-year window was not statistically significant. CLASSIFICATION OF EVIDENCE This study provides Class II evidence that for patients with acute optic neuritis, EPO as an adjunct to methylprednisolone is well tolerated and does not improve long-term visual outcomes. TRIAL REGISTRATION INFORMATION The trial was preregistered before commencement at clinicaltrials.gov (NCT01962571)

Export of malaria proteins requires co-translational processing of the PEXEL motif independent of phosphatidylinositol-3-phosphate binding

Acknowledgements We thank the Red Cross blood bank in Melbourne for human erythrocytes. We thank Svenja Gunther for expression of GBP130 66–196 proteins; Michelle Gazdik and Chris Burns for help in preparing lipids; Lachlan Whitehead (Centre for Dynamic Imaging, Walter and Eliza Hall Institute) for assistance with quantification of export; and David Bocher for help with generation of STEVOR constructs. This work was supported by the National Health and Medical Research Council of Australia (grants 637406, 1010326, 1049811 and 1057960), a Ramaciotti Foundation Establishment Grant (3197/2010), a Victorian State Government Operational Infrastructure Support and Australian Government NHMRC IRIISS, and the Canadian Institutes for Health Research (MOP#130359). J.A.B is an Australian Research Council QEII Fellow, SF was supported by the Research Training Group GRK1459 of the German Research Foundation, and AFC is a Howard Hughes International Scholar.Peer reviewedPublisher PD

Effect of Enzymatic Treatment of Different Starch Sources on the in Vitro Rate and Extent of Starch Digestion

Gelatinized wheat, potato and waxy maize starches were treated enzymatically in order to increase the degree of branching of the amylopectin fraction and thereby change the starch degradation profile towards a higher proportion of slowly digestible starch (SDS). The materials were characterized by single-pulse 1H HR-MAS NMR spectroscopy and in vitro digestion profile according to the Englyst procedure. Using various concentrations and incubation times with branching enzyme (EC 2.4.1.18) without or with additional treatment with the hydrolytic enzymes; β-amylase (EC 3.2.1.2), α-glucosidase (EC 3.2.1.20), or amyloglucosidase (EC 3.2.1.3) the proportion of α-(1–6) linkages was increased by up to a factor of 4.1, 5 and 5.8 in waxy maize, wheat and potato starches, respectively. The proportion of SDS was significantly increased when using hydrolytic enzymes after treatment with branching enzyme but it was only for waxy maize that the proportion of α-(1–6) bonds and the in vitro digestion profile was significantly correlated

NUScon: a community-driven platform for quantitative evaluation of nonuniform sampling in NMR

Although the concepts of nonuniform sampling (NUS) and non-Fourier spectral reconstruction in multidimensional NMR began to emerge 4 decades ago (Bodenhausen and Ernst, 1981; Barna and Laue, 1987), it is only relatively recently that NUS has become more commonplace. Advantages of NUS include the ability to tailor experiments to reduce data collection time and to improve spectral quality, whether through detection of closely spaced peaks (i.e., “resolution”) or peaks of weak intensity (i.e., “sensitivity”). Wider adoption of these methods is the result of improvements in computational performance, a growing abundance and flexibility of software, support from NMR spectrometer vendors, and the increased data sampling demands imposed by higher magnetic fields. However, the identification of best practices still remains a significant and unmet challenge. Unlike the discrete Fourier transform, non-Fourier methods used to reconstruct spectra from NUS data are nonlinear, depend on the complexity and nature of the signals, and lack quantitative or formal theory describing their performance. Seemingly subtle algorithmic differences may lead to significant variabilities in spectral qualities and artifacts. A community-based critical assessment of NUS challenge problems has been initiated, called the “Nonuniform Sampling Contest” (NUScon), with the objective of determining best practices for processing and analyzing NUS experiments. We address this objective by constructing challenges from NMR experiments that we inject with synthetic signals, and we process these challenges using workflows submitted by the community. In the initial rounds of NUScon our aim is to establish objective criteria for evaluating the quality of spectral reconstructions. We present here a software package for performing the quantitative analyses, and we present the results from the first two rounds of NUScon. We discuss the challenges that remain and present a roadmap for continued community-driven development with the ultimate aim of providing best practices in this rapidly evolving field. The NUScon software package and all data from evaluating the challenge problems are hosted on the NMRbox platform

The machinery underlying malaria parasite virulence is conserved between rodent and human malaria parasites

Sequestration of red blood cells infected with the human malaria parasite Plasmodium falciparum in organs such as the brain is considered important for pathogenicity. A similar phenomenon has been observed in mouse models of malaria, using the rodent parasite Plasmodium berghei, but it is unclear whether the P. falciparum proteins known to be involved in this process are conserved in the rodent parasite. Here we identify the P. berghei orthologues of two such key factors of P. falciparum, SBP1 and MAHRP1. Red blood cells infected with P. berghei parasites lacking SBP1 or MAHRP1a fail to bind the endothelial receptor CD36 and show reduced sequestration and virulence in mice. Complementation of the mutant P. berghei parasites with the respective P. falciparum SBP1 and MAHRP1 orthologues restores sequestration and virulence. These findings reveal evolutionary conservation of the machinery underlying sequestration of divergent malaria parasites and support the notion that the P. berghei rodent model is an adequate tool for research on malaria virulence