scholarly journals ATP Mediates Yeast Cell-Cell Communication

2020 ◽  
Author(s):  
Michael Caplow
Keyword(s):  
Cell Density ◽  
High Cell Density ◽  
Cell Communication ◽  
Growth Stimulation ◽  
High Density ◽  
Mutant Protein ◽  
Chromosome Loss ◽  
Low Density ◽  
High Cell ◽  
In Cells

AbstractYeast secrete ATP in response to glucose, a property with previously unknown functional consequence. In this report, we show that extracellular ATP is a signal for growth of surrounding cells. The ATP signaling behavior was uncovered by finding reduced toxicity of an inducible, dominant-lethal form of alpha tubulin (tub1-828) in cells grown at high, compared to low cell density. Reduced cell death at high cell density resulted because the rate of chromosome loss/cell division was lower (18-fold) in a cultures inoculated with a high density (350,000) compared to a low density (5,000) of cells. The sparing effect of growth at high cell density could be replicated by growing together 3440 cells that express tub1-828, with 2.3 E6 cells that do not express the mutant protein. Toxicity was reduced at high cell density apparently because a secreted signal induces growth, so that the mutant protein is rapidly diluted by synthesis of wild-type α-tubulin. Further, fluorescence-activated cell sorting (FACS) analysis after DNA staining showed that the rate of the G1-G2 transition was faster with cells at high density. ATP replaced the need for high cell density for resistance to tub1-828, and stimulated the transition from G1 to G2 in cells at low density. Cells lacking the enzyme nucleoside diphosphate kinase did not respond to nucleotide stimulation of growth during expression of mutant tubulin, suggesting that NDP kinase has a regulatory role in growth stimulation. This newly discovered quorum sensing response in yeast, mediated by ATP, indicates that yeast decision-making is not entirely autonomous.

scholarly journals The human asialoglycoprotein receptor is a possible binding site for low-density lipoproteins and chylomicron remnants

1991 ◽  
Vol 276 (1) ◽  
pp. 79-87 ◽  
Author(s):  
E Windler ◽  
J Greeve ◽  
B Levkau ◽  
V Kolb-Bachofen ◽  
W Daerr ◽  
...  
Keyword(s):  
Cell Density ◽  
Hepg2 Cells ◽  
High Cell Density ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Asialoglycoprotein Receptor ◽  
Low Density ◽  
High Cell ◽  
Chylomicron Remnants

Binding and internalization of chylomicron remnants from rat mesenteric lymph by HepG2 cells was inhibited by both excess remnants and low-density lipoprotein (LDL) to the same extent. Ligand blots revealed binding of remnants and LDL to the LDL receptor. Measures regulating LDL receptor activity greatly influenced the binding of remnants: ethinyloestradiol, the hydroxymethylglutaryl-CoA reductase inhibitor pravastatin and the absence of LDL all increased binding, whereas high cell density or the presence of LDL decreased binding. Also, asialofetuin, asialomucin, the neoglycoprotein galactosyl-albumin and an antibody against the asialoglycoprotein receptor all decreased substantially the binding of remnants. At high cell density, binding internalization and degradation of chylomicron remnants was inhibited by up to 70-80%, yet binding of LDL was inhibited by no more than 20-30%. In cross-competition studies, the binding of 125I-asialofetuin was efficiently competed for by asialofetuin itself or by the antibody, and also by LDL and remnants, yet remnants displayed an approx. 100-fold higher affinity than LDL. Likewise, remnants of human triacylglycerol-rich lipoproteins and asialofetuin interfered with each others' binding to HepG2 cells or human liver membranes. It is concluded that the LDL receptor mediates the internalization of chylomicron remnants into hepatocytes depending on its activity, according to demand for cholesterol. Additionally, the asialoglycoprotein receptor may contribute to the endocytosis of LDL, but predominantly of chylomicron remnants.

scholarly journals High-density preculture of PBMCs restores defective sensitivity of circulating CD8 T cells to virus- and tumor-derived antigens

Blood ◽  
2015 ◽  
Vol 126 (2) ◽  
pp. 185-194 ◽  
Author(s):  
Julia Wegner ◽  
Stephan Hackenberg ◽  
Claus-Jürgen Scholz ◽  
Sergey Chuvpilo ◽  
Dmitry Tyrsin ◽  
...  
Keyword(s):  
T Cells ◽  
Cell Density ◽  
Cd8 T Cells ◽  
Memory T Cells ◽  
High Cell Density ◽  
High Density ◽  
High Cell ◽  
Key Points ◽  
Cd8 Memory T Cells

Key Points CD8 memory T cells in PBMCs are antigen-hyporesponsive due to loss of priming by tissue-dependent interactions. Preculture at high cell density allows the detection of antiviral and antitumor responses that may be overlooked without this step.

What’s in the Offing?

Bioprinting ◽  
2021 ◽  
pp. 202-218
Author(s):  
Kenneth Douglas
Keyword(s):  
3D Printing ◽  
Cell Density ◽  
Cardiac Tissue ◽  
High Cell Density ◽  
High Density ◽  
High Cell ◽  
Hierarchical Network ◽  
Native Tissue ◽  
Vascular Channels ◽  
Cell Densities

Abstract: This chapter attempts to peer into the possible future of bioprinting to consider two conceivable directions that bioprinting might take while also contemplating what we may be able to learn about bioprinting’s trajectory by reflecting on another biomedical quest—the twentieth-century’s attempt to conquer polio. In one study that might offer a route for bioprinting, a team created bioconstructs with cell densities approaching that of native tissue (about 108 cells/gram). The group used embedded 3D printing to create a branched, hierarchical network of vascular channels within a large, high cell density bioconstruct and perfused media through the channels that they created using fugitive ink. This was to provide nutrient support for the cells. They also built a high-density cardiac construct in which the cells beat synchronously and showed functional contractility. They quantitatively measured the deformation of the cardiac tissue during contraction.

scholarly journals Chemotactic behaviour of Escherichia coli at high cell density

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Remy Colin ◽  
Knut Drescher ◽  
Victor Sourjik
Keyword(s):  
Escherichia Coli ◽  
Cell Density ◽  
Collective Motion ◽  
High Cell Density ◽  
Environmental Gradients ◽  
Model Organism ◽  
High Density ◽  
Intermediate Cell ◽  
High Cell ◽  
Cell Densities

AbstractAt high cell density, swimming bacteria exhibit collective motility patterns, self-organized through physical interactions of a however still debated nature. Although high-density behaviours are frequent in natural situations, it remained unknown how collective motion affects chemotaxis, the main physiological function of motility, which enables bacteria to follow environmental gradients in their habitats. Here, we systematically investigate this question in the model organism Escherichia coli, varying cell density, cell length, and suspension confinement. The characteristics of the collective motion indicate that hydrodynamic interactions between swimmers made the primary contribution to its emergence. We observe that the chemotactic drift is moderately enhanced at intermediate cell densities, peaks, and is then strongly suppressed at higher densities. Numerical simulations reveal that this suppression occurs because the collective motion disturbs the choreography necessary for chemotactic sensing. We suggest that this physical hindrance imposes a fundamental constraint on high-density behaviours of motile bacteria, including swarming and the formation of multicellular aggregates and biofilms.

scholarly journals Chemotactic behaviour ofEscherichia coliat high cell density

2018 ◽  
Author(s):  
Remy Colin ◽  
Knut Drescher ◽  
Victor Sourjik
Keyword(s):  
Cell Density ◽  
Collective Motion ◽  
High Cell Density ◽  
Environmental Gradients ◽  
Model Organism ◽  
High Density ◽  
Intermediate Cell ◽  
High Cell ◽  
Swimming Bacteria ◽  
Cell Densities

AbstractAt high cell density, swimming bacteria exhibit collective motility patterns, self-organized through physical interactions of a however still debated nature. Although high-density behaviours are frequent in natural situations, it remained unknown how collective motion affects chemotaxis, the main physiological function of motility, which enables bacteria to follow environmental gradients in their habitats. Here, we systematically investigate this question in the model organismEscherichia coli, varying cell density, cell length, and suspension confinement. The characteristics of the collective motion indicate that hydrodynamic interactions between swimmers made the primary contribution to its emergence. We observe that the chemotactic drift is moderately enhanced at intermediate cell densities, peaks, and is then strongly suppressed at higher densities. Numerical simulations reveal that this suppression occurs because the collective motion disturbs the choreography necessary for chemotactic sensing. We suggest that this physical hindrance imposes a fundamental constraint on high-density behaviours of motile bacteria, including swarming and the formation of multicellular aggregates and biofilms.

scholarly journals Cell Density Plays a Critical Role in Ex Vivo Expansion of T Cells for Adoptive Immunotherapy

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
Qiangzhong Ma ◽  
Yawen Wang ◽  
Agnes Shuk-Yee Lo ◽  
Erica M. Gomes ◽  
Richard P. Junghans
Keyword(s):  
T Cells ◽  
Cell Density ◽  
T Cell Activation ◽  
Cell Activation ◽  
High Cell Density ◽  
Ex Vivo ◽  
Low Density ◽  
High Cell ◽  
Low Cell Density

The successful ex vivo expansion of a large numbers of T cells is a prerequisite for adoptive immunotherapy. In this study, we found that cell density had important effects on the process of expansion of T cells in vitro. Resting T cells were activated to expand at high cell density but failed to be activated at low cell density. Activated T cells (ATCs) expanded rapidly at high cell density but underwent apoptosis at low cell density. Our studies indicated that low-cell-density related ATC death is mediated by oxidative stress. Antioxidants N-acetylcysteine, catalase, and albumin suppressed elevated reactive oxygen species (ROS) levels in low-density cultures and protected ATCs from apoptosis. The viability of ATCs at low density was preserved by conditioned medium from high-density cultures of ATCs in which the autocrine survival factor was identified as catalase. We also found that costimulatory signal CD28 increases T cell activation at lower cell density, paralleled by an increase in catalase secretion. Our findings highlight the importance of cell density in T cell activation, proliferation, survival and apoptosis and support the importance of maintaining T cells at high density for their successful expansion in vitro.

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