scholarly journals Analysis of protrusion dynamics in amoeboid cell motility by means of regularized contour flows

2021 ◽  
Vol 17 (8) ◽  
pp. e1009268
Author(s):  
Daniel Schindler ◽  
Ted Moldenhawer ◽  
Maike Stange ◽  
Valentino Lepro ◽  
Carsten Beta ◽  
...  
Keyword(s):  
Cell Motility ◽  
Cancer Metastasis ◽  
Gaussian Process Regression ◽  
Time Lapse ◽  
Reference Points ◽  
Computational Method ◽  
Growth Time ◽  
Amoeboid Cell ◽  
Wide Range ◽  
Open Source Software Package

Amoeboid cell motility is essential for a wide range of biological processes including wound healing, embryonic morphogenesis, and cancer metastasis. It relies on complex dynamical patterns of cell shape changes that pose long-standing challenges to mathematical modeling and raise a need for automated and reproducible approaches to extract quantitative morphological features from image sequences. Here, we introduce a theoretical framework and a computational method for obtaining smooth representations of the spatiotemporal contour dynamics from stacks of segmented microscopy images. Based on a Gaussian process regression we propose a one-parameter family of regularized contour flows that allows us to continuously track reference points (virtual markers) between successive cell contours. We use this approach to define a coordinate system on the moving cell boundary and to represent different local geometric quantities in this frame of reference. In particular, we introduce the local marker dispersion as a measure to identify localized membrane expansions and provide a fully automated way to extract the properties of such expansions, including their area and growth time. The methods are available as an open-source software package called AmoePy, a Python-based toolbox for analyzing amoeboid cell motility (based on time-lapse microscopy data), including a graphical user interface and detailed documentation. Due to the mathematical rigor of our framework, we envision it to be of use for the development of novel cell motility models. We mainly use experimental data of the social amoeba Dictyostelium discoideum to illustrate and validate our approach.

scholarly journals Epigenetic control via allosteric regulation of mammalian protein arginine methyltransferases

2017 ◽  
Vol 114 (38) ◽  
pp. 10101-10106 ◽  
Author(s):  
Kanishk Jain ◽  
Cyrus Y. Jin ◽  
Steven G. Clarke
Keyword(s):  
Cancer Metastasis ◽  
Gene Activation ◽  
Kinetic Studies ◽  
Arginine Methylation ◽  
Histone H4 ◽  
Protein Arginine Methyltransferases ◽  
Wide Range ◽  
Substrate Concentrations

Arginine methylation on histones is a central player in epigenetics and in gene activation and repression. Protein arginine methyltransferase (PRMT) activity has been implicated in stem cell pluripotency, cancer metastasis, and tumorigenesis. The expression of one of the nine mammalian PRMTs, PRMT5, affects the levels of symmetric dimethylarginine (SDMA) at Arg-3 on histone H4, leading to the repression of genes which are related to disease progression in lymphoma and leukemia. Another PRMT, PRMT7, also affects SDMA levels at the same site despite its unique monomethylating activity and the lack of any evidence for PRMT7-catalyzed histone H4 Arg-3 methylation. We present evidence that PRMT7-mediated monomethylation of histone H4 Arg-17 regulates PRMT5 activity at Arg-3 in the same protein. We analyzed the kinetics of PRMT5 over a wide range of substrate concentrations. Significantly, we discovered that PRMT5 displays positive cooperativity in vitro, suggesting that this enzyme may be allosterically regulated in vivo as well. Most interestingly, monomethylation at Arg-17 in histone H4 not only raised the general activity of PRMT5 with this substrate, but also ameliorated the low activity of PRMT5 at low substrate concentrations. These kinetic studies suggest a biochemical explanation for the interplay between PRMT5- and PRMT7-mediated methylation of the same substrate at different residues and also suggest a general model for regulation of PRMTs. Elucidating the exact relationship between these two enzymes when they methylate two distinct sites of the same substrate may aid in developing therapeutics aimed at reducing PRMT5/7 activity in cancer and other diseases.

Experimental Measurements and CFD Evaluation of the Onset Flow Boiling at Low Pressure and High Subcooling Flow of R-11 Within Vertical Annulus

2014 ◽  
Author(s):  
Y. Bouaichaoui ◽  
R. Kibboua ◽  
M. Matkovič
Keyword(s):  
Heat Flux ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Fluid Model ◽  
Computer Code ◽  
Computational Method ◽  
Subcooled Boiling ◽  
Two Phase ◽  
Local Flow ◽  
Wide Range

The knowledge of the onset of subcooled boiling in forced convective flow at high liquid velocity and subcooling is of importance in thermal hydraulic studies. Measurements were performed under various conditions of mass flux, heat flux, and inlet subcooling, which enabled to study the influence of different boundary conditions on the development of local flow parameters. Also, some measurements have been compared to the predictions by the three-dimensional two-fluid model of subcooled boiling flow carried out with the computer code ANSYS-CFX-13. A computational method based on theoretical studies of steady state two phase forced convection along a test section loop was released. The calculation model covers a wide range of two phase flow conditions. It predicts the heat transfer rates and transitions points such as the Onset of Critical Heat Flux.

scholarly journals Directed migration: Cells navigate by extracellular vesicles

2018 ◽  
Vol 217 (8) ◽  
pp. 2613-2614 ◽  
Author(s):  
Bong Hwan Sung ◽  
Alissa M. Weaver
Keyword(s):  
Cell Motility ◽  
Dictyostelium Discoideum ◽  
Extracellular Vesicles ◽  
Cancer Metastasis ◽  
Chemical Gradient ◽  
Directed Migration ◽  
Cell Biol

Directional cell motility toward a chemical gradient, chemotaxis, is critical during inflammation, embryogenesis, and cancer metastasis. In this issue, Kriebel et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201710170) demonstrate that the key cAMP chemoattractant for Dictyostelium discoideum amoebas is synthesized within and released from extracellular vesicles to promote chemotaxis.

scholarly journals P342 Left atrial contraction longitudinal strain is a volume-independet parameter

2020 ◽  
Vol 21 (Supplement_1) ◽  
Author(s):  
S Unlu ◽  
B Sezenoz ◽  
A Sahinarslan ◽  
T Arinsoy ◽  
A Cengel
Keyword(s):  
Speckle Tracking ◽  
Longitudinal Strain ◽  
Heart Diseases ◽  
Left Ventricular ◽  
Reference Points ◽  
Volume Index ◽  
Valvular Heart Diseases ◽  
Wide Range ◽  
Before And After ◽  
2D Speckle Tracking

Abstract Background The left atrium (LA) is the main contributor of left ventricular (LV) filling. LA volume and volume index are routinely evaluated during echocardiographic assessment as having prognostic value in a wide range of cardiovascular pathologies. Yet, LA volume is easily affected by volume status. Thus, a non-invasive novel parameter such as indices of LA longitudinal strain (LS) have been proposed as alternative measurements. LA strain was shown to be associated with LV filling pressures and it has been suggested to provide prognostic information in patients with heart failure, atrial fibrillation, ischemic and valvular heart diseases. Nevertheless the acute effect of hemodynamic changes on LA LS indices is not well-established due to lack of evidence in healthy subjects and patient populations. The aim of this study is to evaluate the LA mechanics and change in echocardiographic methods used for assessment of LA by examining the end stage kidney patients before and after the hemodialysis (HD). Methods Patients between 18 and 85 years of age, receiving HD for at least 6 months were included. The echocardiographic images were obtained before and after HD. 2D speckle tracking strain analysis was performed for LA in 45 patients. Reference points for analysis are set on the "P" waves. LA reservoir, conduit and contraction phase LS were calculated. The changes in echocardiographic methods before and after hemodialysis were examined. Correlation between volume depletion and change in echocardiographic parameters were calculated. Results 45 patients (47.7 ± 14.7 years of age, 19 women) were included in study. The mean volume of ultrafiltration was 2755.12 ± 845.5 ml . The chamber sizes of LA are decreased after hemodialysis (LA diameter; 4.9 ± 0.8 cm vs. 4.4 ± 0.5 cm p < 0.001, LA area; 27.8 ± 4.0 cm2 vs. 19.6 ± 3.8 cm2 p < 0.001). LA reservoir phase LS measurements (% 44.6 ± 10.8 vs. % 38.15 ± 8.11 p < 0.001) showed significant changes after HD. In contrast LA contraction LS measurements (% -16.6 ± 7.0 vs. % -16.4 ± 7.1 p:0.893) did not differ after HD. The relative change in LA reservoir phase LS (r = 0.74, p:0.001) showed correlation with the ultrafiltrated volume. Conclusion LA contraction LS is a volume independent measurement obtained by 2D speckle tracking. Assessment of LA mechanics with echocardiography would be an easy and repeatable assessment which can guide to describe the cardiac pathophysiology and hemodynamics better. Moreover defining novel volume independent parameters for evaluation of LA would contribute to clinical perspectives of the patients.

Abstract C50: CXCL12-triggered amoeboid cell motility is mediated through a RhoA-directed signaling hub

2013 ◽  
Author(s):  
Meghan M. Wyse ◽  
Andrea L. Nestor-Kalinoski ◽  
Kathryn M. Eisenmann
Keyword(s):  
Cell Motility ◽  
Amoeboid Cell
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