Mathematical Modeling of Myosin Induced Bistability of Lamellipodial Fragments

For various cell types and for lamellipodial fragments on flat surfaces, externally induced and spontaneous transitions between symmetric nonmoving states and polarized migration have been observed. This behavior is indicative of bistability of the cytoskeleton dynamics. In this work, the Filament Based Lamellipodium Model (FBLM), a two-dimensional, anisotropic, two-phase continuum model for the dynamics of the actin filament network in lamellipodia, is extended by a new description of actin-myosin interaction. For appropriately chosen parameter values, the resulting model has bistable dynamics with stable states showing the qualitative features observed in experiments. This is demonstrated by numerical simulations and by an analysis of a strongly simplified version of the FBLM with rigid filaments and planar lamellipodia at the cell front and rear

Modelling, analysis, and simulation of actin-driven wound healing in cells

Diese Diplomarbeit behandelt die Modellierung, Analyse und Simulation von Wundheilung innerhalb von Zellen, die ein Netzwerk aus Polymerfilamenten, das Lamellipodium genannt wird, nutzen, um Löcher innerhalb der Zelle zu schließen. Diese Löcher können spontan auftreten oder mithilfe einer Mikronadel künstlich erzeugt werden. Das Projekt, in dessen Rahmen die Arbeit verfasst wurde, befasst sich mit der Frage, wie sich diese Arten von Zellen entlang einer Oberfläche vorwärts bewegen. Die Mechanismen, die dieser Vorwärtsbewegung zugrunde liegen, sind schon lange Gegenstand wissenschaftlichen Interesses und haben zu verschiedenen Modellen geführt. Christian Schmeiser, Dietmar Ölz und John Victor Small vom Institut für Molekularbiologie an der Österreichischen Akademie der Wissenschaften geben mit ihrer Arbeit den Rahmen für meine Diplomarbeit vor. Sie gehen davon aus, dass das Lamellipodium aus dünnen Stäben besteht, die miteinander und mit dem Substrat über Proteine verbunden sind, und dass das Lamellipodium von der Zellmembran umhüllt wird. In früheren Arbeiten wurden Gleichungen hergeleitet, die aus dem Einfluss verschiedener Kräfte resultierten, sowie aus Überlegungen in Bezug auf die Lebenszeit der zuvor genannten Proteine. Im ersten Kapitel werde ich einen Überblick über den biologischen Hintergrund geben, auch um die Modellierungsannahmen im zweiten Kapitel hinreichend zu motivieren. Dort wird die stark vereinfachende Annahme gemacht, dass das Lamellipodium radialsymmetrisch sei. Diese Annahme impliziert, dass die Evolution eines einzelnen Filaments, des Referenzfilaments, Information über das gesamte Lamellipodium enthält. Im dritten Kapitel wird ein numerisches Schema hergeleitet, auf dem Simulationen aufgebaut werden können. Diese Simulationen werden in Matlab durchgeführt, wobei ein Code verwendet wird, der von Dietmar Ölz entwickelt wurde, und den ich für meine Zwecke angepasst habe. Die Analyse der Simulationen zeigt, dass bestimmte Modifikationen im Modell notwendig sind, um realistische Ergebnisse zu erhalten. Das letzte Kapitel behandelt die ersten Versuche die komplexere Situation eines Lamellipodiums zu modellieren, das mehrere Richtungen für Filamente zulässt.This diploma thesis is devoted to the modelling, analysis, and simulation of wound healing within cells that use a meshwork of polymer filaments, called lamellipodium, to close a hole within the cell that either appears spontaneously or is created artificially by a microneedle. It is part of a larger project concerned with the question of how these types of cells move along a surface, since the mechanisms are the same in both cases. The mechanisms which facilitate protrusion have been under investigation for some time in the scientific community resulting in various models. The works of Christian Schmeiser, Dietmar Ölz and John Victor Small of the Institute of Molecular Biology at the Österreichische Akademie der Wissenschaften provide a mathematical framework for my diploma thesis. They consider the lamellipodium to consist of a meshwork of thin rods that are connected to each other and the substrate via proteins and enclosed by the cell membrane. In previous works they derived equations of motion resulting from various forces and considerations about the lifetime of the aforementioned proteins. In the first chapter I will provide the biological background which will justify the modelling assumptions in chapter two. A strong assumption will be made about the geometry of the lamellipodium, namely that it is radially symmetric. This assumption implies that only the evolution of a single filament, the reference filament, is necessary to provide information about the evolution of the whole lamellipodium. In chapter three a numerical scheme will be derived which will be used to facilitate simulations. These simulations are done in Matlab, using a code developed by Dietmar Ölz that I have adapted for my purposes. The analysis of the outcome will show that certain modifications of the model will be necessary in order to produce feasible results. The last chapter is devoted to a first attempt in modelling the more complex situation of multiple directions of filaments in a lamellipodium

Elucidating the function of mycorrhizal-induced Kunitz protease inhibitors and characterization of their putative target proteases in Medicago truncatula

Most terrestrial plants live in symbiosis with arbuscular mycorrhizal fungi. In this study, a mycorrhizal-induced gene family of Medicago truncatula encoding putative Kunitz protease inhibitors was functionally characterized by means of biomolecular, biochemical, microscopical and in silico methods. Their putative target proteases were identified among a clan of serine carboxypeptidases. Results suggest that both protein families work functionally together to control mycorrhizal establishment

Anti-SARS-CoV-2 total immunoglobulin and neutralising antibody responses in healthy blood donors throughout the COVID-19 pandemic: a longitudinal observational study.

INTRODUCTION Quantifying antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and neutralising antibodies may help to understand protection at the individual and population levels. Determination of neutralising antibodies using classical virus neutralisation tests (VNT) is considered the gold standard, but they are costly and time-intensive. Enzyme-linked immunosorbent assay (ELISA)-based surrogate VNTs (sVNT) or anti-SARS-CoV-2 spike protein receptor binding domain immunoglobulins (anti-S-RBD Ig) may be suitable alternatives to VNTs. We aimed to (a) explore the correlations between anti-S-RBD Ig, VNT, and sVNT measurements and (b) describe humoral immunity against SARS-CoV-2 after vaccination, natural infection, and vaccine breakthrough infection in healthy blood donors. METHODS We measured total anti-SARS-CoV-2 Ig in 5714 serum samples from 2748 healthy individuals visiting the Swiss Red Cross Blood Donation Centre in Basel from 03/2020 to 04/2022. We used the Elecsys® Anti-SARS-CoV-2 immunoassay (Roche) against the N- and S-receptor binding domain (RBD) proteins. In a subset of 548 samples from 123 donors, we conducted sVNTs against the Wuhan wild-type SARS-CoV-2 (SARS-CoV-2 Neutralizing Antibodies Detection Kit; Adipogen™). In 100 samples from 40 donors, we correlated sVNT and VNTs against the wild-type (D614G WU1) virus. Surveys were sent to the blood donors to collect data on their SARS-CoV-2 infection and vaccination status. Using this data, donors were categorised as "vaccination only", "infection before vaccination", "post-vaccine breakthrough infection", and "natural infection only". RESULTS Our longitudinal observation study cohort consisted of 50.7% males with a median age of 31 years (range 18-75 y). Anti-SARS-CoV-2 N protein positivity rates per month indicate 57.1% (88/154) of the cohort was infected up to 04/2022. No differences in seropositivity were found between sexes, age groups, blood types (AB0 or RhD), and cytomegalovirus serostatus. We observed a high correlation between anti-S-RBD Ig and inhibition percentage (Spearman's ρ = 0.92, Kendall's τ = 0.77, p <0.0001). We determined the sensitivity and specificity for the manufacturers' thresholds for detecting virus-neutralising effects and computed the "best" cut-off based on our real-world data. We categorised 722/1138 (63.5%) donors as vaccination only (82.3%), post-vaccine breakthrough infection (7.8%), infection before vaccination (5.8%), and natural infection only (4.2%). We observed a lower inhibition percentage in the natural infection-only group than in all other vaccinated groups. The infection before vaccination group had higher anti-S-RBD Ig titres after the first vaccine dose than the other vaccinated groups. CONCLUSION In total, 57.1% of healthy blood donors were infected with SARS-CoV-2, but natural infection without evidence of vaccination seems to result in substantially lower neutralising antibody levels. An estimate of antibody neutralisation may be helpful to assess reinfection risk. Total anti-S-RBD Ig correlates with surrogate virus neutralisation test results, a surrogate for neutralisation; therefore, we suggest that total anti-S-RBD Ig may estimate the level of neutralising antibodies. The threshold for protection from an unfavourable clinical outcome must be evaluated in prospective clinical cohorts

Ca2+ release and buffering effects of synthetic hydroxyapatite following bacterial acid challenge

Background Synthetic particulate hydroxyapatite (HAP; Ca-5(PO4)(3)(OH)) is used as ingredient in oral care products but its effects on cariogenic biofilms are not clear yet. The primary mode of action of HAP may be acting as a calcium phosphate reservoir when deposited in oral biofilms and release Ca2+ and (hydrogen) phosphate ions upon bacterial acid challenge. The aim of this in vitro study was to test this hypothesis by investigating release of Ca2+ ions and potential buffering effects from HAP upon bacterial acid challenge in planktonic cultures and biofilms of Streptococcus mutans. Methods Planktonic cultures of S. mutans were grown in BHI broth with 1% sucrose or with additional 5% HAP or 5% silica for up to 48 h. Separately, biofilms of S. mutans were grown in BHI for 72 h in total. After 24 h of this biofilm culture, either BHI alone or BHI with additional 0.5% HAP or 0.5% silica was added. After 48 h, BHI with 1% sucrose was added to allow bacterial acid formation. Ca2+ release was determined colorimetrically and pH measurements were performed using a pH electrode. For statistical analysis, non-parametrical procedures were applied (n >= 10; Mann-Whitney U test; alpha = 0.05). Results Relevant release of Ca2+ was only evident in planktonic cultures or biofilms with HAP but not in both other groups (p <= 0.001). In suspended biofilms with HAP, median pH was 4.77 after 72 h and about 0.5 pH units higher as compared to both other groups (4.28 or 4.32, respectively; p <= 0.001). Conclusions Under the tested conditions, synthetic HAP releases Ca2+ ions upon bacterial acid challenge and may also show some buffering capacity but further studies are needed to investigate whether the concentrations tested here can also be reached clinically in dental biofilms

Die Subanalyse von Rheuma-VOR zeigt den erheblichen Bedarf der rheumatologischen Versorgung auf

Background: Early diagnosis and treatment of inflammatory rheumatic diseases can prevent consequential damage such as permanently limited mobility and joint or organ damage. Simultaneously, there is an increasing deficit in medical care owing to the lack of rheumatological capacity. Rural regions are particularly affected. Objectives: The available unconfirmed diagnoses of the study Rheuma-VOR were analysed regarding another definitive inflammatory rheumatic disease. Materials and methods: The returned questionnaires of the rheumatologists participating in Rheuma-VOR were screened for definitive inflammatory rheumatic diseases other than the required diagnosis of rheumatoid arthritis, psoriatic arthritis or spondyloarthritis. Results: Of 910 unconfirmed diagnoses, in 245 patients another definitive diagnosis could be confirmed. A total of 29.8% of the diagnoses corresponded to degenerative joint changes or chronic pain syndrome, whereas 26.1% involved different forms of inflammatory arthritis. The majority of diagnoses (40.5%) were collagenosis or vasculitis, Discussion: The available data show that a rheumatological presentation was indicated for the majority of patients. Owing to the increasing deficits in medical care a prior selection of the patients is crucial to make optimal use of restricted rheumatological capacities.Hintergrund: Eine frühe Diagnose und Behandlung entzündlich-rheumatischer Erkrankungen kann Folgeschäden wie dauerhafte Einschränkungen der Mobilität und Gelenk- oder Organschäden verhindern. Gleichzeitig besteht ein größer werdendes Versorgungsdefizit aufgrund fehlender rheumatologischer Kapazitäten. Betroffen sind besonders die ländlichen Regionen. Ziel der Arbeit: Die vorliegenden nicht bestätigten Diagnosen der Studie Rheuma-VOR wurden hinsichtlich des Vorliegens einer anderen definitiven entzündlich-rheumatischen Erkrankung analysiert. Material und Methoden: Die eingegangenen Fragebögen der an der Rheuma-VOR-Studie teilnehmenden Rheumatolog:innen wurden nach Vermerken anderer entzündlich-rheumatischer Erkrankungen als der geforderten Diagnose einer rheumatoiden Arthritis, Psoriasis-Arthritis oder Spondyloarthritis gescreent. Ergebnisse: Von 910 „nicht bestätigten“ Diagnosen waren bei 245 Patient:innen andere gestellte Diagnosen auszuwerten. Insgesamt 29,8 % der Diagnosen entsprechen degenerativen Gelenkveränderungen oder chronischen Schmerzsyndromen, bei 26,1 % lagen verschiedene Formen entzündlicher Arthritiden vor. Der Großteil der Diagnosen (40,5 %) entfiel auf Kollagenosen und Vaskulitiden, wobei die Polymyalgia rheumatica mit 20 % am häufigsten diagnostiziert wurde (49 Patient:innen). Diskussion: Die vorliegenden Daten zeigen, dass bei einem Großteil der Patient:innen die rheumatologische Vorstellung indiziert war. Aufgrund der ambulanten Versorgungsdefizite ist eine vorherige Selektion des Patientenguts essenziell, um die eingeschränkten Kapazitäten bestmöglich zu nutzen

Scoliosis: density-equalizing mapping and scientometric analysis

<p>Abstract</p> <p>Background</p> <p>Publications related to scoliosis have increased enormously. A differentiation between publications of major and minor importance has become difficult even for experts. Scientometric data on developments and tendencies in scoliosis research has not been available to date. The aim of the current study was to evaluate the scientific efforts of scoliosis research both quantitatively and qualitatively.</p> <p>Methods</p> <p>Large-scale data analysis, density-equalizing algorithms and scientometric methods were used to evaluate both the quantity and quality of research achievements of scientists studying scoliosis. Density-equalizing algorithms were applied to data retrieved from ISI-Web.</p> <p>Results</p> <p>From 1904 to 2007, 8,186 items pertaining to scoliosis were published and included in the database. The studies were published in 76 countries: the USA, the U.K. and Canada being the most productive centers. The Washington University (St. Louis, Missouri) was identified as the most prolific institution during that period, and orthopedics represented by far the most productive medical discipline. "BRADFORD, DS" is the most productive author (146 items), and "DANSEREAU, J" is the author with the highest scientific impact (h-index of 27).</p> <p>Conclusion</p> <p>Our results suggest that currently established measures of research output (i.e. impact factor, h-index) should be evaluated critically because phenomena, such as self-citation and co-authorship, distort the results and limit the value of the conclusions that may be drawn from these measures. Qualitative statements are just tractable by the comparison of the parameters with respect to multiple linkages. In order to obtain more objective evaluation tools, new measurements need to be developed.</p

Premature stroke and cardiovascular risk in primary Sjögren's syndrome

IntroductionPrimary Sjögren's syndrome (pSS) is associated with an increased prevalence of traditional risk factors and cardiovascular diseases (CVDs). The study aimed to identify specific risk factors for CVD in pSS patients.MethodsPSS patients with and without CVD were compared. All patients fulfilled the EULAR/ACR classification criteria. Patients with CVD presented at least one of the following manifestations: myocardial infarction, transient ischemic attacks, ischemic or hemorrhagic stroke, peripheral artery disease, coronary artery disease, and carotid plaques. Data were collected by a standardized protocol and review of medical records.Results61/312 (19.6%) pSS patients presented with CVD. Traditional risk factors such as hypertension, hypercholesterinemia and diabetes (p &lt; 0.05), pSS manifestations, in particular vasculitis (p = 0.033) and Raynaud's phenomenon (p = 0.018) were associated with CVD. Among patients with ischemic events (28/312, 9%), particularly cerebrovascular disease (n = 12/28, 42.9%), correlations with increased EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) (p = 0.039) and EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI) (p = 0.048) were observed. Age at first cerebrovascular event was 55.2 [48.9–69.6] years. Multivariate analysis confirmed hypertension [odds ratio (OR) 3.7, 95% confidence interval (CI) 1.87–7.18, p &lt; 0.001], hypercholesterinemia (OR 3.1, 95% CI 1.63–5.72, p &lt; 0.001), male gender (OR 0.4, 95% CI 0.17–0.78, p = 0.009), Raynaud's phenomenon (OR 2.5, 95% CI 1.28–4.82, p = 0.007), and CNS involvement (OR 2.7, 95% CI 1.00–7.15, p = 0.048) as independent CVD predictors.ConclusionRaynaud's phenomen as well as vasculitis and high ESSDAI have shown a significant association to CVD. PSS patients with cerebrovascular events were younger than expected. Knowledge about risk factors may help clinicians to identify pSS patients at risk for CVD. After diagnosis of pSS, patients should be screened for risk factors such as hypertension and receive appropriate therapy to prevent or at least reduce sequelae such as infarction. However, further investigations are necessary in order to achieve a reliable risk stratification for these patients

O-GlcNAc transferase regulates collagen deposition and fibrosis resolution in idiopathic pulmonary fibrosis

BackgroundIdiopathic pulmonary fibrosis (IPF) is a chronic pulmonary disease that is characterized by an excessive accumulation of extracellular matrix (ECM) proteins (e.g. collagens) in the parenchyma, which ultimately leads to respiratory failure and death. While current therapies exist to slow the progression, no therapies are available to resolve fibrosis.MethodsWe characterized the O-linked N-Acetylglucosamine (O-GlcNAc) transferase (OGT)/O-GlcNAc axis in IPF using single-cell RNA-sequencing (scRNA-seq) data and human lung sections and isolated fibroblasts from IPF and non-IPF donors. The underlying mechanism(s) of IPF were further investigated using multiple experimental models to modulate collagen expression and accumulation by genetically and pharmacologically targeting OGT. Furthermore, we hone in on the transforming growth factor-beta (TGF-β) effector molecule, Smad3, by co-expressing it with OGT to determine if it is modified and its subsequent effect on Smad3 activation.ResultsWe found that OGT and O-GlcNAc levels are upregulated in patients with IPF compared to non-IPF. We report that the OGT regulates collagen deposition and fibrosis resolution, which is an evolutionarily conserved process demonstrated across multiple species. Co-expression of OGT and Smad3 showed that Smad3 is O-GlcNAc modified. Blocking OGT activity resulted in decreased phosphorylation at Ser-423/425 of Smad3 attenuating the effects of TGF-β1 induced collagen expression/deposition.ConclusionOGT inhibition or knockdown successfully blocked and reversed collagen expression and accumulation, respectively. Smad3 is discovered to be a substrate of OGT and its O-GlcNAc modification(s) directly affects its phosphorylation state. These data identify OGT as a potential target in pulmonary fibrosis resolution, as well as other diseases that might have aberrant ECM/collagen accumulation