scholarly journals Active Segregation Dynamics in the Living Cell

2021 ◽  
Author(s):  
Ajay Bansal ◽  
Amit Das ◽  
Madan Rao
Keyword(s):  
Living Cell ◽  
Growth Dynamics ◽  
Phase Segregation ◽  
Active Phase ◽  
Theoretical Work ◽  
Special Focus ◽  
Nonequilibrium Phase ◽  
Phase Ordering ◽  
The Many ◽  
Membrane Components

In this paper, we bring together our efforts in identifying and understanding nonequilibrium phase segregation driven by active processes in the living cell, with special focus on the segregation of cell membrane components driven by active contractile stresses arising from cortical actomyosin. This also has implications for active segregation dynamics in membraneless regions within the cytoplasm and nucleus (3d). We formulate an active version of the Flory-Huggins theory that incorporates a contribution from fluctuating active stresses. Apart from knitting together some of our past theoretical work in a comprehensive narrative, we highlight some new results, and establish a cor- respondence with recent studies on Active Model B/B+. We point to the many unusual aspects of the dynamics of active phase segregation, such as (i) anomalous growth dynamics, (ii) coarsening accompanied by propulsion and coalescence of domains that exhibit nonreciprocal effects, (iii) seg- regation into mesoscale domains, (iv) emergence of a nonequilibrium phase segregated steady state characterised by strong macroscopic fluctuations (fluctuation dominated phase ordering (FDPO)), and (v) mesoscale segregation even above the equilibrium Tc. Apart from its implications for actively driven segregation of binary fluids, these ideas are at the heart of an Active Emulsion description of the lateral organisation of molecules on the plasma membrane of living cells, whose full molecular elaboration appears elsewhere.

Increasing the Validity of Cross-Cultural Assessments: Use of Improved Methods for Test Adaptations 1Laboratory of Psychometric and Evaluative Research Report No.275. Amherst, MA: University of Massachusetts, School of Education. Paper presented at the 23rd International Congress of Applied Psychology, Madrid, 1994.

1995 ◽  
Vol 11 (3) ◽  
pp. 147-157 ◽  
Author(s):  
Ronald K. Hambleton ◽  
Anil Kanjee
Keyword(s):  
Cross Cultural ◽  
Research Report ◽  
Special Focus ◽  
School Of Education ◽  
Language And Culture ◽  
Evaluative Research ◽  
University Of Massachusetts ◽  
The Many ◽  
Educational Tests ◽  
Improved Methods

Translating or adapting psychological and educational tests from one language and culture to other languages and cultures has been a common practice for almost a hundred years, beginning with Binet's test of intelligence. Despite the long history and the many good reasons for adapting tests, proper methods for conducting test adaptations and establishing score equivalence are not well known by psychologists. The purpose of this paper is to focus attention on judgmental and statistical methods and procedures for adapting tests with special focus on procedures for identifying poorly adapted items. When these methods are correctly applied, the validity of any cross-cultural uses of the adapted test should be increased.

The Council

2020 ◽  
pp. 117-149
Author(s):  
Vivien A. Schmidt
Keyword(s):  
Member State ◽  
Public Perceptions ◽  
European Council ◽  
Special Focus ◽  
Member States ◽  
The Third ◽  
The Many ◽  
Mutual Accountability ◽  
Two Sides ◽  
Input Legitimacy

Chapter 5 discusses the pathway to legitimacy of the European Council (and the Council), with a special focus on Germany’s predominance through “one size fits one” rules. The chapter begins with an analysis of the Council’s particular sources of power and grounds for throughput legitimacy in Eurozone governance. It questions member-state leaders’ assumptions about their representativeness (input legitimacy), then asks if they meet the requirements of deliberative mutual accountability (throughput legitimacy) or even whether Germany fits the criteria expected of a benevolent hegemon. Next the chapter discusses the Janus-faced public perceptions of Council crisis governance. These are divided between views of the Council as an unaccountable (German) dictatorship or as a mutually accountable deliberative body (in the shadow of Germany). This part first presents the Council as an unaccountable dictatorship by detailing the ways in which Germany was predominant on its own and/or in tandem with a weaker France. It then counters with a discussion of the Council as a mutually accountable deliberative body, by charting not only the many instances in which member states agreed with German preferences but also where Germany acquiesced to those of other member states. The chapter ends with an examination of the actions of the Council (in particular the Eurogroup of Finance Ministers) and the Troika (IMF, Commission, and ECB) with regard to the program countries. This can be seen as two sides of the same coin: harsh dictatorship (especially the third Greek bailout) or deliberative authoritarianism (eg, Ireland, Portugal, Cyprus and Greece in the second bailout).

scholarly journals Angular momentum transport in accretion disks: a hydrodynamical perspective

2019 ◽  
Vol 82 ◽  
pp. 391-413 ◽  
Author(s):  
S. Fromang ◽  
G. Lesur
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Dynamical Evolution ◽  
Theoretical Work ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Recent Developments ◽  
The Many ◽  
The Universe

The radial transport of angular momentum in accretion disk is a fundamental process in the universe. It governs the dynamical evolution of accretion disks and has implications for various issues ranging from the formation of planets to the growth of supermassive black holes. While the importance of magnetic fields for this problem has long been demonstrated, the existence of a source of transport solely hydrodynamical in nature has proven more difficult to establish and to quantify. In recent years, a combination of results coming from experiments, theoretical work and numerical simulations has dramatically improved our understanding of hydrodynamically mediated angular momentum transport in accretion disk. Here, based on these recent developments, we review the hydrodynamical processes that might contribute to transporting angular momentum radially in accretion disks and highlight the many questions that are still to be answered.

scholarly journals The endocytic pathways of Dictyostelium discoideum

2019 ◽  
Vol 63 (8-9-10) ◽  
pp. 461-471 ◽  
Author(s):  
James H. Vines ◽  
Jason S. King
Keyword(s):  
Immune System ◽  
Maturation Process ◽  
Cellular Functions ◽  
Social Amoeba ◽  
The Social ◽  
Evolutionary Context ◽  
The Many ◽  
Membrane Components ◽  
Mammalian Immune System ◽  
Endocytic Pathways

The formation and processing of vesicles from the cell surface serves many important cellular functions ranging from nutrient acquisition to regulating the turnover of membrane components and signalling. In this article, we summarise the endocytic pathways of the social amoeba Dictyostelium from the clathrin-dependent and independent internalisation of surface components to the engulfment of bacteria or fluid by phagocytosis and macropinocytosis respectively. Due to similarities with the professional phagocytes of the mammalian immune system Dictyostelium has been extensively used to investigate the complex remodelling and trafficking events that occur as phagosomes and macropinosomes transit through the cell. Here we discuss what is known about this maturation process in order to kill any potential pathogens and obtain nutrients for growth. Finally, we aim to put these studies in evolutionary context and highlight some of the many questions that remain in our understanding of these complex and important pathways.

scholarly journals Evaluating neuronal and glial growth on electrospun polarized matrices: bridging the gap in percussive spinal cord injuries

2007 ◽  
Vol 3 (2) ◽  
pp. 119-126 ◽  
Author(s):  
Woon N. Chow ◽  
David G. Simpson ◽  
John W. Bigbee ◽  
Raymond J. Colello
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injuries ◽  
Growth Dynamics ◽  
Axonal Guidance ◽  
Directional Growth ◽  
Fiber Alignment ◽  
The Matrix ◽  
The Many ◽  
Spinal Cord Repair ◽  
Potential Use

AbstractOne of the many obstacles to spinal cord repair following trauma is the formation of a cyst that impedes axonal regeneration. Accordingly, we examined the potential use of electrospinning to engineer an implantable polarized matrix for axonal guidance. Polydioxanone, a resorbable material, was electrospun to fabricate matrices possessing either aligned or randomly oriented fibers. To assess the extent to which fiber alignment influences directional neuritic outgrowth, rat dorsal root ganglia (DRGs) were cultured on these matrices for 10 days. Using confocal microscopy, neurites displayed a directional growth that mimicked the fiber alignment of the underlying matrix. Because these matrices are generated from a material that degrades with time, we next determined whether a glial substrate might provide a more stable interface between the resorbable matrix and the outgrowing axons. Astrocytes seeded onto either aligned or random matrices displayed a directional growth pattern similar to that of the underlying matrix. Moreover, these glia-seeded matrices, once co-cultured with DRGs, conferred the matrix alignment to and enhanced outgrowth exuberance of the extending neurites. These experiments demonstrate the potential for electrospinning to generate an aligned matrix that influences both the directionality and growth dynamics of DRG neurites.

scholarly journals Cellular Factors Implicated in Filovirus Entry

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Suchita Bhattacharyya ◽  
Thomas J. Hope
Keyword(s):  
Tyrosine Kinases ◽  
Treatment Strategies ◽  
Cytoskeletal Proteins ◽  
Biological Weapons ◽  
Future Research ◽  
Special Focus ◽  
Common Receptor ◽  
Cellular Factors ◽  
Niemann Pick ◽  
Membrane Components

Although filoviral infections are still occurring in different parts of the world, there are no effective preventive or treatment strategies currently available against them. Not only do filoviruses cause a deadly infection, but they also have the potential of being used as biological weapons. This makes it imperative to comprehensively study these viruses in order to devise effective strategies to prevent the occurrence of these infections. Entry is the foremost step in the filoviral replication cycle and different studies have reported the involvement of a myriad of cellular factors including plasma membrane components, cytoskeletal proteins, endosomal components, and cytosolic factors in this process. Signaling molecules such as the TAM family of receptor tyrosine kinases comprising of Tyro3, Axl, and Mer have also been implicated as putative entry factors. Additionally, filoviruses are suggested to bind to a common receptor and recent studies have proposed T-cell immunoglobulin and mucin domain 1 (TIM-1) and Niemann-Pick C1 (NPC1) as potential receptor candidates. This paper summarizes the existing literature on filoviral entry with a special focus on cellular factors involved in this process and also highlights some fundamental questions. Future research aimed at answering these questions could be very useful in designing novel antiviral therapeutics.

scholarly journals Notes

1933 ◽  
Vol 112 (779) ◽  
pp. 477-479
Keyword(s):  
Osmotic Pressure ◽  
Recent Work ◽  
Living Cell ◽  
Biological Theory ◽  
Freezing Point ◽  
Living Cells ◽  
Hen’S Egg ◽  
Chemical Complex ◽  
The Difference ◽  
The Many

Recent work on the osmotic pressure of the hen’s egg has introduced a sense of uncertainty as to the value of the many comparisons which have been made between osmotic pressures of the blood, body fluids, and surrounding media. The uncertainty pertains not to theory but to a simple matter of fact and, as this involves that most fundamental datum for biological theory—viz., the state of the water in the living cell—there is urgent need to have it cleared up. The fact in dispute is the freezing point of the yolk and white of the bird’s egg. Atkins in 1909 by measurements, obviously made with the greatest care, found “no difference between the freezing point of white and yolk of the same egg and a mixture of white and yolk gave the same depression.” Atkins (1909) used the ordinary Beckmann technique and so, too, did Straub (1929) twenty years later, but with a surprisingly different result for he found a constant difference between white and yolk of the hen’s egg amounting on the average to —0·15° C. A. V. Hill (1930) confirmed Straub’s (1929) finding by a different method. He compared the fall in temperature caused by evaporation with that of water and from the difference calculated the osmotic pressure. Howard (1932) using the Beckmann method again found no difference in the freezing point of white and yolk. In these measurements the yolk was puddled by stirring so that at sometime or another the structure was broken down. Yolk is not only a chemical complex but it is alive, gross mechanical disturbance might, therefore, have the effect it usually has on living cells and cause chemical breakdown with consequent fall of the freezing point. Hale’s experiments were designed to explore this possibility by observing directly the freezing point of intact yolk and white.

scholarly journals The Many Forms and Functions of Long Term Plasticity at GABAergic Synapses

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Arianna Maffei
Keyword(s):  
Synaptic Plasticity ◽  
Neural Circuits ◽  
Dynamic Range ◽  
Theoretical Work ◽  
Long Term Potentiation ◽  
Inhibitory Neurons ◽  
Gabaergic Synapses ◽  
The Many ◽  
And Function

On February 12th 1973, Bliss and Lomo submitted their findings on activity-dependent plasticity of glutamatergic synapses. After this groundbreaking discovery, long-term potentiation (LTP) and depression (LTD) gained center stage in the study of learning, memory, and experience-dependent refinement of neural circuits. While LTP and LTD are extensively studied and their relevance to brain function is widely accepted, new experimental and theoretical work recently demonstrates that brain development and function relies on additional forms of plasticity, some of which occur at nonglutamatergic synapses. The strength of GABAergic synapses is modulated by activity, and new functions for inhibitory synaptic plasticity are emerging. Together with excitatory neurons, inhibitory neurons shape the excitability and dynamic range of neural circuits. Thus, the understanding of inhibitory synaptic plasticity is crucial to fully comprehend the physiology of brain circuits. Here, I will review recent findings about plasticity at GABAergic synapses and discuss how it may contribute to circuit function.

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