scholarly journals Persistent growth of microtubules at low density

2021 ◽  
pp. mbc.E20-08-0546
Author(s):  
Anton Burakov ◽  
Ivan Vorobjev ◽  
Irina Semenova ◽  
Ann Cowan ◽  
John Carson ◽  
...  
Keyword(s):  
Slow Growth ◽  
Dynamic Instability ◽  
Alternative Hypothesis ◽  
Leading Edge ◽  
Low Density ◽  
Local Regulation ◽  
Density Dependent ◽  
Rac1 Activity ◽  
Dependent Mechanism ◽  
Peripheral Cytoplasm

Microtubules (MTs) often form a polarized array with minus-ends anchored at the centrosome and plus-ends extended towards the cell margins. Plus-ends display behavior known as dynamic instability, – transitions between rapid shortening and slow growth. It is known that dynamic instability is regulated locally to ensure entry of MTs into nascent areas of cytoplasm, but details of this regulation remain largely unknown. Here, we test alternative hypothesis for the local regulation of MT behavior. We used microsurgery to isolate a portion of peripheral cytoplasm from MTs growing from the centrosome, crating cytoplasmic areas locally depleted of MTs. We found that in sparsely populated areas MT plus-ends persistently grew or paused but never shortened. In contrast, plus-ends that entered regions of cytoplasm densely populated with MTs frequently transitioned to shortening. Persistent growth of MTs in sparsely populated areas could not be explained by a local increase in concentration of free tubulin subunits or elevation of Rac1 activity proposed to enhance MT growth at the cell leading edge during locomotion. These observations suggest the existence of a MT-density dependent mechanism regulating MT dynamics that determines dynamic instability of MTs in densely populated areas of the cytoplasm and persistent growth in sparsely populated areas. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text]

Variation in xylem anatomy of selected populations of lodgepole pine

2001 ◽  
Vol 31 (11) ◽  
pp. 2049-2057 ◽  
Author(s):  
Tongli Wang ◽  
Sally N Aitken
Keyword(s):  
Cell Wall ◽  
Wall Thickness ◽  
Slow Growth ◽  
Lodgepole Pine ◽  
High Density ◽  
Cell Wall Thickness ◽  
Fast Growth ◽  
Low Density ◽  
Xylem Anatomy ◽  
Latewood Density

Variation in xylem anatomy among selected populations of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) was examined using digital image analysis based on an annual growth ring (age 10) per tree. Four subpopulations were selected using the following criteria for height growth and wood density: (i) fast growth and high density; (ii) slow growth and high density; (iii) fast growth and low density; and (iv) slow growth and low density. Significant differences were found among subpopulations for several anatomical parameters including tracheid density, lumen size, and cell wall thickness that may affect the economic value and utilization of wood. Principal component analysis indicate that the first four principal components (PCs) were associated with (i) ring area (PC1), (ii) earlywood density (PC2), (iii) latewood density (PC3), and (iv) lumen shape in earlywood (PC4), suggesting that these aspects of wood properties and growth are controlled by different sets of genes. Relative contributions of total number of tracheids, tracheid lumen size, and cell wall thickness to ring area and correlations between cell wall area proportion and X-ray density are discussed.

scholarly journals Density-dependent nerve growth factor regulation of Gs-alpha RNA in pheochromocytoma 12 cells.

1990 ◽  
Vol 10 (6) ◽  
pp. 3277-3279 ◽  
Author(s):  
G Tjaden ◽  
A Aguanno ◽  
R Kumar ◽  
D Benincasa ◽  
R M Gubits ◽  
...  
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
G Protein ◽  
Alpha Subunit ◽  
Low Density ◽  
Dependent Manner ◽  
Nerve Growth ◽  
Density Dependent ◽  
Stimulatory G Protein ◽  
Gs Alpha

Nerve growth factor (NGF) affects levels of the alpha subunit of the stimulatory G protein (Gs-alpha) in pheochromocytoma 12 cells in a bidirectional, density-dependent manner. Cells grown at high density responded to NGF treatment with increased levels of Gs-alpha mRNA and protein. Conversely, in cells grown in low-density cultures, levels of this mRNA were lowered by NGF treatment.

scholarly journals Actomyosin-based Retrograde Flow of Microtubules in the Lamella of Migrating Epithelial Cells Influences Microtubule Dynamic Instability and Turnover and Is Associated with Microtubule Breakage and Treadmilling

1997 ◽  
Vol 139 (2) ◽  
pp. 417-434 ◽  
Author(s):  
Clare M. Waterman-Storer ◽  
E.D. Salmon
Keyword(s):  
Epithelial Cells ◽  
Dynamic Instability ◽  
Leading Edge ◽  
Unknown Origin ◽  
Time Lapse ◽  
Lung Epithelial Cells ◽  
Retrograde Flow ◽  
Microtubule Dynamic ◽  
Lung Epithelial ◽  
Time Lapse Imaging

We have discovered several novel features exhibited by microtubules (MTs) in migrating newt lung epithelial cells by time-lapse imaging of fluorescently labeled, microinjected tubulin. These cells exhibit leading edge ruffling and retrograde flow in the lamella and lamellipodia. The plus ends of lamella MTs persist in growth perpendicular to the leading edge until they reach the base of the lamellipodium, where they oscillate between short phases of growth and shortening. Occasionally “pioneering” MTs grow into the lamellipodium, where microtubule bending and reorientation parallel to the leading edge is associated with retrograde flow. MTs parallel to the leading edge exhibit significantly different dynamics from MTs perpendicular to the cell edge. Both parallel MTs and photoactivated fluorescent marks on perpendicular MTs move rearward at the 0.4 μm/min rate of retrograde flow in the lamella. MT rearward transport persists when MT dynamic instability is inhibited by 100-nM nocodazole but is blocked by inhibition of actomyosin by cytochalasin D or 2,3-butanedione–2-monoxime. Rearward flow appears to cause MT buckling and breaking in the lamella. 80% of free minus ends produced by breakage are stable; the others shorten and pause, leading to MT treadmilling. Free minus ends of unknown origin also depolymerize into the field of view at the lamella. Analysis of MT dynamics at the centrosome shows that these minus ends do not arise by centrosomal ejection and that ∼80% of the MTs in the lamella are not centrosome bound. We propose that actomyosin-based retrograde flow of MTs causes MT breakage, forming quasi-stable noncentrosomal MTs whose turnover is regulated primarily at their minus ends.

Surface pressures and their corrections for the flow past a finite-length plate in supersonic low density flow

1979 ◽  
Vol 95 (1) ◽  
pp. 177-187 ◽  
Author(s):  
S. L. Gai
Keyword(s):  
Experimental Study ◽  
Finite Length ◽  
Leading Edge ◽  
Low Density ◽  
Cold Wall ◽  
Trailing Edge ◽  
Flow Past ◽  
Density Flow ◽  
Recent Method

An experimental study of the flow past a thin finite length plate in a supersonic low density stream is reported. The paper discusses the corrections that are necessary for surface pressures measured under rarefied conditions. It is shown that the recent method of ‘orifice’ corrections due to Harbour & Bienkowski is versatile and reliable to use for both cold wall and insulated wall measurements. For the conditions of the experiment, the flow over the plate was found to be dominated by both leading-edge and trailing-edge interactions.

scholarly journals Expression of the leucocyte common antigen-related (LAR) tyrosine phosphatase is regulated by cell density through functional E-cadherin complexes

2002 ◽  
Vol 365 (2) ◽  
pp. 513-519 ◽  
Author(s):  
Javelle R. SYMONS ◽  
Charles M. LeVEA ◽  
Robert A. MOONEY
Keyword(s):  
Cell Density ◽  
Contact Inhibition ◽  
Mammary Adenocarcinoma ◽  
Low Density ◽  
Common Antigen ◽  
Regulation Of Expression ◽  
Density Dependent ◽  
Protein Levels ◽  
Density Dependent Regulation ◽  
E Cadherin

The leucocyte common antigen-related phosphatase (LAR) has been implicated in receptor tyrosine kinase signalling pathways while also displaying cell-density-dependency and localization to adherens junctions. Whereas physiological substrates for LAR have not been identified unequivocally, β-catenin associates with LAR and is a substrate in vitro. With the implication that LAR may play a role in regulating E-cadherin-dependent cell—cell communication and contact inhibition, the relationship of LAR with E-cadherin was investigated. LAR expression increased with cell density in the human breast cancer cell line MCF-7 and in Ln 3 cells derived from the 13762NF rat mammary adenocarcinoma. LAR protein levels decreased rapidly when cells were replated at a low density after attaining high expression of LAR at high cell density. COS-7 cells displayed comparable density-dependent regulation of LAR expression when transiently expressing exogenous LAR under the control of a constitutively active promoter, indicating that the regulation of expression is not at the level of gene regulation. Disrupting homophilic E-cadherin complexes by chelating extracellular calcium caused a marked decrease in LAR protein levels. Similarly, blocking E-cadherin interactions with saturating amounts of E-cadherin antibody (HECD-1) also led to a rapid and pronounced loss of cellular LAR. In contrast, mimicking cell-surface E-cadherin engagement by plating cells at low density on to dishes coated with HECD-1 resulted in a 2-fold increase in LAR expression compared with controls. These results suggest that density-dependent regulation of LAR expression is mediated by functional E-cadherin and may play a role in density-dependent contact inhibition by regulating tyrosine phosphorylation in E-cadherin complexes.

scholarly journals Modelling GTPase dynamics to understand RhoA-driven cancer cell invasion

2016 ◽  
Vol 44 (6) ◽  
pp. 1695-1700 ◽  
Author(s):  
Joseph H.R. Hetmanski ◽  
Jean-Marc Schwartz ◽  
Patrick T. Caswell
Keyword(s):  
Cell Migration ◽  
Rho Gtpases ◽  
Leading Edge ◽  
Local Environment ◽  
Future Research ◽  
Rhoa Activity ◽  
Rac1 Activity ◽  
Logical Modelling ◽  
Invasive Cell

Metastasis, initially driven by cells migrating and invading through the local environment, leads to most cancer-associated deaths. Cells can use a variety of modes to move in vitro, all of which depend on Rho GTPases at some level. While traditionally it was thought that Rac1 activity drives protrusive lamellipodia at the leading edge of a polarised cell while RhoA drives rear retraction, more recent work in 3D microenvironments has revealed a much more complicated picture of GTPase dynamics. In particular, RhoA activity can dominate the leading edge polymerisation of actin to form filopodial actin-spike protrusions that drive more invasive cell migration. We recently described a potential mechanism to abrogate this pro-invasive localised leading edge Rac1 to RhoA switch via manipulation of a negative feedback loop that was revealed by adopting a logical modelling approach. Both challenging dogma and taking a formal, mathematical approach to understanding signalling involved in motility may be vital to harnessing harmful cell migration and preventing metastasis in future research.

scholarly journals PENGARUH IMPLEMENTASI KEBIJAKAN PERATURAN DAERAH NOMOR 12 TAHUN 2009 TENTANG KAWASAN TANPA ROKOK OLEH SATUAN POLISI PAMONG PRAJA TERHADAP PENEGAKAN DISIPLIN MASYARAKAT DI KAWASAN UMUM KOTA BOGOR

2019 ◽  
Vol 5 (1) ◽  
pp. 1
Author(s):  
Daman Huri ◽  
Denny Hernawan ◽  
G. Goris Seran
Keyword(s):  
Policy Implementation ◽  
Alternative Hypothesis ◽  
Rank Correlation ◽  
Spearman Rank Correlation ◽  
Local Regulation ◽  
The Public ◽  
Public Areas ◽  
Coefficient Corrélation ◽  
The Mean ◽  
Communication Resource

The aim of the research is to analyze the effect of policy implementation of Local Regulation No. 12/2009 concerning Areas Without Cigarettes by Civil Service Police Unit on the enforcement of public discipline in the public areas of Bogor City. The policy implementation is understood in Edward III’s perspective based on four aspects, namely communication, resource, disposition/attitude, and bureaucratic structure. The public discipline uses Elizabeth Hunrlock’s perspective based on three aspects, namely rule/norm, consistence, punishment and reward. The research uses Weight Mean Score formula to count the mean and to describe it. It also uses Spearman Rank Correlation formula based on SPSS version.20 to test a hypothesis concerning the relation of policy implementation to public discipline. The results of the research indicate that the policy implementation gets the mean score 3.28, meaning good enough, and the public discipline gets the mean score 3.65, meaning good. The coefficient correlation of two variables gets value 0.406, categorized as the middle. By t-test, the research gets tcount value 3.688 and ttable (N=71) value 1.666. Therefore, tcount > ttable means that alternative hypothesis is accepted. The coefficient determination indicates 16.4% of contribution of policy implementation to public discipline.Keywords: Areas Without Cigarettes, Policy Implementation, Public Areas, Public Discipline.

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