scholarly journals Stochasticity in bacterial division control: Preliminary consequences for protein concentration

2019 ◽  
Author(s):  
Cesar Augusto Nieto Acuna ◽  
Cesar Augusto Vargas Garcia ◽  
Juan Manuel Pedraza
Keyword(s):  
Chromosome Number ◽  
Cell Size ◽  
Protein Concentration ◽  
Occurrence Rate ◽  
Mrna Synthesis ◽  
Bacterial Division ◽  
Cellular Volume ◽  
Constant Rate ◽  
Classical Models ◽  
Protein Number

ABSTRACTThe stochastic nature of protein concentration inside cells can have important consequences in their physiology and population fitness. Classical models of gene expression consider these processes as first-order reactions with little dependence with the cell size. However, the concentrations of the relevant molecules depend directly on the cellular volume. Here we model the cell size dynamics as exponential growth followed by division with occurrence rate proportional to the size. This framework, together with known models of chromosome replication and both protein and mRNA synthesis, lets us predict relationships between cell size and both protein number and concentration. As a main result, we find that protein production strategies (constant rate or rate proportional to either chromosome number, cell size or chromosome number times cell size) can be experimentally distinguished from the correlation between protein concentration and cell size.

Lung endothelial and epithelial permeability after platelet-activating factor

1987 ◽  
Vol 63 (5) ◽  
pp. 1770-1775 ◽  
Author(s):  
R. W. Bolin ◽  
T. R. Martin ◽  
R. K. Albert
Keyword(s):  
Protein Concentration ◽  
Platelet Activating Factor ◽  
Endothelial Permeability ◽  
Dry Weight ◽  
Fluid Filtration ◽  
Vascular Space ◽  
Constant Rate ◽  
Wet Weight ◽  
Pulmonary Arterial ◽  
Intravascular Pressure

We investigated whether platelet-activating factor (PAF) increased epithelial or endothelial permeability in isolated-perfused rabbit lungs. PAF was either injected into the pulmonary artery or instilled into the airway of lungs perfused with Tyrode's solution containing 1% bovine serum albumin. The effect of adding neutrophils or platelets to the perfusate was also tested. Perfusion was maintained 20–40 min after adding PAF and then a fluid filtration coefficient (Kf) was determined to assess vascular permeability. At the end of each experiment, one lung was lavaged, and the lavagate protein concentration (BALP) was determined. Wet weight-to-dry weight ratios (W/D) were determined on the other lung. PAF added to the vascular space increased peak pulmonary arterial pressure (Ppa) from 13.5 +/- 3.1 (mean +/- SE) to 24.2 +/- 3.3 cmH2O (P less than 0.05). The effect was amplified by platelets [Ppa to 70.8 +/- 8.0 cmH2O (P less than 0.05)] but not by neutrophils [Ppa to 22.0 +/- 1.4 cmH2O (P less than 0.05)]. Minimal changes in Ppa were observed after instilling PAF into the airway. The Kf, W/D, and BALP of untreated lungs were not increased by injecting PAF into the vasculature or into the air space. The effect of PAF on Kf, W/D, and BALP was unaltered by adding platelets or neutrophils to the perfusate. PAF increases intravascular pressure (at a constant rate of perfusion) but does not increase epithelial or endothelial permeability in isolated-perfused rabbit lungs.

The influence of cell size and chromosome dosage on cold-hardiness expression in the Triticeae

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 667-671 ◽  
Author(s):  
A. E. Limin ◽  
D. B. Fowler
Keyword(s):  
Chromosome Number ◽  
Cell Size ◽  
Common Wheat ◽  
Ploidy Level ◽  
Guard Cell ◽  
Cold Hardiness ◽  
Gene Dosage ◽  
Large Cell ◽  
Gene Dosage Effect ◽  
Ploidy Levels

The influence of cell size and chromosome dosage on cold-hardiness expression was investigated in members of the tribe Triticeae. Mean leaf guard-cell lengths for ploidy levels of 2x, 4x, 6x, and 8x were found to increase by approximately 10 μm with each addition of two basic (x = 7) genomes, indicating that larger cell size was associated with higher ploidy level. Poor expression of cold hardiness in amphiploids was associated with large cell size. However, comparisons among and within species indicated that ploidy level was not the only factor determining cell size. Significant differences in guard-cell length were observed among common wheat (Triticum aestivum L. em. Thell.) cultivars. Cell size differences among cultivars were found in both hardened and nonhardened common wheat plants and these differences were associated with cultivar cold hardiness (r = 0.95, P ≤ 0.01). The evidence indicated that smaller cell size influenced cold tolerance by amplifying the expression of cold-hardiness genes in cold-acclimated plants, probably by reducing the degree of cell contraction from freeze dehydration. A chromosome (gene) dosage effect that favored the expression of genes from the parent species contributing the higher chromosome number was also shown to play an important role in the expression of cold hardiness in interspecific hybrids and amphiploids. Comparison of related species with similar cell size and chromosome number suggested differences in the effectiveness of cold hardiness conferring genes. Observations made on species from the Triticeae indicate that when cold-hardiness potential is limited at the diploid level, a plant group may expand its cold-hardiness range by "loading up" on existing cold-hardiness genes by means of polyploidy. An increased genetic potential may then be further enhanced by selection for smaller cell size within the polyploid nucleotype. This process appears to have been responsible for the superior cold hardiness of hexaploids within the Triticum genus.Key words: cell size, cold hardiness, gene dosage, Triticeae, evolution, interspecific hybrid, Agropyron.

scholarly journals Multi-phosphorylation reaction and clustering tune Pom1 gradient mid-cell levels according to cell size

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Veneta Gerganova ◽  
Charlotte Floderer ◽  
Anna Archetti ◽  
Laetitia Michon ◽  
Lina Carlini ◽  
...  
Keyword(s):  
Cell Growth ◽  
Cell Size ◽  
Protein Concentration ◽  
Single Cells ◽  
Lateral Diffusion ◽  
Membrane Association ◽  
Allelic Series ◽  
Concentration Gradients ◽  
Mitotic Entry ◽  
Phosphorylation Reaction

Protein concentration gradients pattern developing organisms and single cells. In Schizosaccharomyces pombe rod-shaped cells, Pom1 kinase forms gradients with maxima at cell poles. Pom1 controls the timing of mitotic entry by inhibiting Cdr2, which forms stable membrane-associated nodes at mid-cell. Pom1 gradients rely on membrane association regulated by a phosphorylation-dephosphorylation cycle and lateral diffusion modulated by clustering. Using quantitative PALM imaging, we find individual Pom1 molecules bind the membrane too transiently to diffuse from pole to mid-cell. Instead, we propose they exchange within longer lived clusters forming the functional gradient unit. An allelic series blocking auto-phosphorylation shows that multi-phosphorylation shapes and buffers the gradient to control mid-cell levels, which represent the critical Cdr2-regulating pool. TIRF imaging of this cortical pool demonstrates more Pom1 overlaps with Cdr2 in short than long cells, consistent with Pom1 inhibition of Cdr2 decreasing with cell growth. Thus, the gradients modulate Pom1 mid-cell levels according to cell size.

scholarly journals Modeling Cell Size Regulation: From Single-Cell-Level Statistics to Molecular Mechanisms and Population-Level Effects

2018 ◽  
Vol 47 (1) ◽  
pp. 251-271 ◽  
Author(s):  
Po-Yi Ho ◽  
Jie Lin ◽  
Ariel Amir
Keyword(s):  
Cell Size ◽  
Molecular Mechanisms ◽  
Population Level ◽  
Coarse Grained ◽  
Future Directions ◽  
Size Regulation ◽  
Biologically Relevant ◽  
Level Statistics ◽  
Cycle Regulation ◽  
Protein Number

Most microorganisms regulate their cell size. In this article, we review some of the mathematical formulations of the problem of cell size regulation. We focus on coarse-grained stochastic models and the statistics that they generate. We review the biologically relevant insights obtained from these models. We then describe cell cycle regulation and its molecular implementations, protein number regulation, and population growth, all in relation to size regulation. Finally, we discuss several future directions for developing understanding beyond phenomenological models of cell size regulation.

scholarly journals Increasing cell size remodels the proteome and promotes senescence

2021 ◽  
Author(s):  
Michael C Lanz ◽  
Evgeny Zatulovskiy ◽  
Matthew P Swaffer ◽  
Lichao Zhang ◽  
Shuyuan Zhang ◽  
...  
Keyword(s):  
Cell Size ◽  
Protein Concentration ◽  
Cell Function ◽  
Size Control ◽  
Cell Physiology ◽  
Proliferating Cells ◽  
Size Dependent ◽  
Large Size ◽  
Concentration Changes ◽  
Proteome Changes

Cell size is tightly controlled in healthy tissues, but it is poorly understood how cell size affects cell physiology. To address this, we measured how the proteome changes with cell size. Protein concentration changes are widespread, depend on the DNA-to-cell size ratio, and are predicted by subcellular localization, size-dependent mRNA concentrations, and protein turnover. As proliferating cells grow larger, concentration changes associated with cellular senescence are increasingly pronounced, suggesting that large size may be a cause rather than just a consequence of cell senescence. Consistent with this hypothesis, larger cells are prone to replicative-, DNA damage-, and CDK4/6i-induced senescence. More broadly, our findings show how cell size could impact many aspects of cell physiology through remodeling the proteome, thereby providing a rationale for cell size control to optimize cell function.

scholarly journals Cytological localization of chorionic gonadotropin alpha and placental lactogen mRNAs during development of the human placenta.

1982 ◽  
Vol 93 (1) ◽  
pp. 190-198 ◽  
Author(s):  
M Hoshina ◽  
M Boothby ◽  
I Boime
Keyword(s):  
Chorionic Gonadotropin ◽  
Human Placenta ◽  
First Trimester ◽  
Placental Lactogen ◽  
Mrna Synthesis ◽  
Placental Development ◽  
Trophoblast Differentiation ◽  
Constant Rate ◽  
Alpha Gene ◽  
Cytological Localization

Probes derived from clones bearing cDNAs corresponding to the alpha subunit of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) were used to localize their respective mRNAs cytologically in sections of first trimester and term human placenta. hPL mRNA was exclusively localized to the syncytial layer, hCG alpha mRNA was found in the syncytial layer and also in some differentiating cytotrophoblasts. Hybridization was specific because no signal was observed when labeled pBR322 was hybridized to placental sections or when the placental probes were hybridized to sections of human tonsils. In addition, RNA in placental interstitial cells did not hybridize with hCG alpha and hPL probes. Hybridization with the hCG alpha probe was much greater in first trimester than in term sections, whereas hPL signals were comparable in both first trimester and term placentae. Syncytial formation proceeds through cellular intermediates of cytotrophoblastic origin, and the data suggest that transcription of the hCG alpha gene is initiated before the completion of syncytial formation. In contrast, hPL mRNA synthesis starts later in trophoblast differentiation, likely after the stage of syncytial formation. The data also suggested that hCG alpha mRNA synthesis becomes attenuated but that hPL is transcribed at a rather constant rate during placental development.

Correlation between protein concentration and bacterial cell size can reveal mechanisms of gene expression

2020 ◽  
Vol 17 (4) ◽  
pp. 045002 ◽  
Author(s):  
César Nieto-Acuña ◽  
Juan Carlos Arias-Castro ◽  
César Vargas-García ◽  
Carlos Sánchez ◽  
Juan Manuel Pedraza
Keyword(s):  
Gene Expression ◽  
Cell Size ◽  
Bacterial Cell ◽  
Protein Concentration

scholarly journals Heterogeneity of clonal lymphocytes with regard to bcl-2 protein concentration and cell size.

1997 ◽  
Vol 50 (6) ◽  
pp. 326-328
Author(s):  
T J Bromidge ◽  
D J Howe ◽  
S A Johnson ◽  
S A Rule
Keyword(s):  
Cell Size ◽  
Protein Concentration

scholarly journals PyEcoLib: a python library for simulating E. coli stochastic size dynamics

2020 ◽  
Author(s):  
Camilo Blanco ◽  
Cesar Nieto ◽  
Cesar Vargas ◽  
Juan Pedraza
Keyword(s):  
Cell Size ◽  
Stochastic Dynamics ◽  
Jump Process ◽  
Fixed Number ◽  
Discrete Events ◽  
Continuous Processes ◽  
Continuous Growth ◽  
E Coli ◽  
Bacterial Division ◽  
Arbitrary Precision

Recent studies describe bacterial division as a jump process triggered when it reaches a fixed number of stochastic discrete events at a rate depending on the cell-size. This theoretical approach enabled the computation of stochastic cell-size transient dynamics with arbitrary precision, with the possibility of being coupled to other continuous processes as gene expression. Here we synthesize most of this theory in the tool PyEcoLib, a python-based library to estimate bacterial cell size stochastic dynamics including continuous growth and division events. In this library, we include examples predicting statistical properties seen in experiments.

Conversion of magnetic energy and the width of current sheets

2002 ◽  
Vol 68 (1) ◽  
pp. 53-58
Author(s):  
MANUEL NÚÑEZ
Keyword(s):  
Energy Transfer ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Magnetic Energy ◽  
Plasma Conductivity ◽  
Constant Rate ◽  
Classical Models ◽  
Field Lines ◽  
A Current ◽  
Fast Reconnection

Magnetic reconnection is one of the most efficient ways of transforming magnetic into kinetic and thermal energies. We prove a general identity relating the energy transfer in a neighborhood of a current sheet, where reconnection is assumed to occur. With some reasonable hypotheses regarding the geometry of stream and field lines, we prove that for a constant rate of transformation of magnetic energy, the width of the current sheet must grow with the plasma conductivity. Hence an enhanced diffusivity seems necessary for certain classical models of fast reconnection to work.

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