scholarly journals Fluid deformable surfaces

2019 ◽  
Vol 878 ◽  
pp. 1-4 ◽  
Author(s):  
A. Voigt
Keyword(s):  
Lipid Membranes ◽  
Shape Change ◽  
Governing Equations ◽  
Tight Coupling ◽  
Tangential Flow ◽  
Deformable Surfaces ◽  
Bending Elasticity ◽  
Natural Element ◽  
Numerical Tools

Lipid membranes are examples of fluid deformable surfaces, which can be viewed as two-dimensional viscous fluids with bending elasticity. With this solid–fluid duality any shape change contributes to tangential flow and vice versa any tangential flow on a curved surface induces shape deformations. This tight coupling between shape and flow makes curvature a natural element of the governing equations. The modelling and numerical tools outlined in Torres-Sánchez et al. (J. Fluid Mech., vol. 872, 2019, pp. 218–271) open a new field of study by enabling the exploration of the role of curvature in this context.

Role of spectrin in membrane fusion and in shape change of human erythrocyte ghost

1978 ◽  
Vol 36 (2) ◽  
pp. 328-329
Author(s):  
Hideo Hayashi ◽  
Yoshikazu Hirai ◽  
John T. Penniston
Keyword(s):  
Conformational Changes ◽  
Human Erythrocyte ◽  
Shape Change ◽  
Membrane Surface ◽  
Slight Modification ◽  
Active Role ◽  
Main Role ◽  
Bank Blood ◽  
Human Erythrocyte Ghost

Spectrin is a membrane associated protein most of which properties have been tentatively elucidated. A main role of the protein has been assumed to give a supporting structure to inside of the membrane. As reported previously, however, the isolated spectrin molecule underwent self assemble to form such as fibrous, meshwork, dispersed or aggregated arrangements depending upon the buffer suspended and was suggested to play an active role in the membrane conformational changes. In this study, the role of spectrin and actin was examined in terms of the molecular arrangements on the erythrocyte membrane surface with correlation to the functional states of the ghosts.Human erythrocyte ghosts were prepared from either freshly drawn or stocked bank blood by the method of Dodge et al with a slight modification as described before. Anti-spectrin antibody was raised against rabbit by injection of purified spectrin and partially purified.

scholarly journals Role of the extracellular cAMP-adenosine pathway in renal physiology

2001 ◽  
Vol 281 (4) ◽  
pp. F597-F612 ◽  
Author(s):  
Edwin K. Jackson ◽  
Raghvendra K. Dubey
Keyword(s):  
Adenosine Receptors ◽  
Epithelial Transport ◽  
Receptor Activation ◽  
Hormonal Control ◽  
Renal Physiology ◽  
Tight Coupling ◽  
Extracellular Adenosine ◽  
Mediated Effects ◽  
Extracellular Camp

Adenosine exerts physiologically significant receptor-mediated effects on renal function. For example, adenosine participates in the regulation of preglomerular and postglomerular vascular resistances, glomerular filtration rate, renin release, epithelial transport, intrarenal inflammation, and growth of mesangial and vascular smooth muscle cells. It is important, therefore, to understand the mechanisms that generate extracellular adenosine within the kidney. In addition to three “classic” pathways of adenosine biosynthesis, contemporary studies are revealing a novel mechanism for renal adenosine production termed the “extracellular cAMP-adenosine pathway.” The extracellular cAMP-adenosine pathway is defined as the egress of cAMP from cells during activation of adenylyl cyclase, followed by the extracellular conversion of cAMP to adenosine by the serial actions of ecto-phosphodiesterase and ecto-5′-nucleotidase. This mechanism of extracellular adenosine production may provide hormonal control of adenosine levels in the cell-surface biophase in which adenosine receptors reside. Tight coupling of the site of adenosine production to the site of adenosine receptors would permit a low-capacity mechanism of adenosine biosynthesis to have a large impact on adenosine receptor activation. The purposes of this review are to summarize the physiological roles of adenosine in the kidney; to describe the classic pathways of renal adenosine biosynthesis; to review the evidence for the existence of the extracellular cAMP-adenosine pathway; and to describe possible physiological roles of the extracellular cAMP-adenosine pathway, with particular emphasis on the kidney.

scholarly journals Cholesterol provides nonsacrificial protection of membrane lipids from chemical damage at air–water interface

2018 ◽  
Vol 115 (13) ◽  
pp. 3255-3260 ◽  
Author(s):  
Xinxing Zhang ◽  
Kevin M. Barraza ◽  
J. L. Beauchamp
Keyword(s):  
Lipid Membranes ◽  
Membrane Lipids ◽  
Oh Radicals ◽  
Significant Finding ◽  
Water Interface ◽  
Unsaturated Lipids ◽  
Air Water Interface ◽  
Liquid Ordered ◽  
Ester Linkage

The role of cholesterol in bilayer and monolayer lipid membranes has been of great interest. On the biophysical front, cholesterol significantly increases the order of the lipid packing, lowers the membrane permeability, and maintains membrane fluidity by forming liquid-ordered–phase lipid rafts. However, direct observation of any influence on membrane chemistry related to these cholesterol-induced physical properties has been absent. Here we report that the addition of 30 mol % cholesterol to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (POPG) monolayers at the air–water interface greatly reduces the oxidation and ester linkage cleavage chemistries initiated by potent chemicals such as OH radicals and HCl vapor, respectively. These results shed light on the indispensable chemoprotective function of cholesterol in lipid membranes. Another significant finding is that OH oxidation of unsaturated lipids generates Criegee intermediate, which is an important radical involved in many atmospheric processes.

scholarly journals The Pioneers of Parents' Centre: Movers and Shakers for Change in the Philosophies and Practices of Childbirth and Parent Education in New Zealand

2021 ◽  
Author(s):  
◽  
Marie Bell
Keyword(s):  
New Zealand ◽  
Young Children ◽  
Parent Education ◽  
Shape Change ◽  
Structured Interview ◽  
Child Rearing ◽  
The Social ◽  
The 1950S ◽  
Changing Times

<p>This thesis presents the voices of 17 pioneers of the organisation parents' Centre, founded in Wellington, New Zealand, in 1952. They reflect on Parents' Centre's contribution to the welfare and happiness of young children and their parents, and the challenges and satisfactions for them as 'movers and shakers' of an entrenched system. The pioneers, 13 women and 3 men, were a group of professionals and parents educated in the progressive tradition who worked as volunteers to found and develop the organisation. They challenged the well-established and generally respected views of the policymakers of the 1950s about the management of childbirth and parent education for young children. They believed that the education and care of the child from birth to three needed to be brought into line with the progressive principles and practices which had been gaining ground in the schools and pre-schools of New Zealand since the 1920s and which emphasised holistic development, especially the psychological aspects. Using Bronfenbrenner's ecological systems theory I set the study within the social climate of the 1950s to assess the contribution the changing times made to the success of the organisation. I identified the social and economic forces which brought change both in the institutions of society and within every day family life, particularly for young children and their parents. As researcher, I added my voice to their reflections while also playing the role of analyst. The study used an oral history method to record the stories of the participants from a contemporary perspective. My involvement in the organisation over 50 years gave me insider knowledge and a rapport with the people interviewed. Using a loosely structured interview I adopted a collegial method of data gathering. A second interview, two years after the first, informed the pioneers about my use of the interview material and gave opportunities for critical comments on my analysis. It became apparent that under the leadership of Helen Brew, parents' Centre was able to influence change. Analyses of the background of the pioneers and of the educationalists who influenced them in training, career and parenthood show that key influences on the pioneers were lecturers at Wellington and Christchurch Training Colleges and Victoria University of Wellington. The liberal thrust of these educational institutions reinforced similar philosophical elements in the child rearing practices experienced by the pioneers. Overall, the pioneers expressed satisfaction with the philosophies and practice they advocated at that time, their achievements within Parent's Centre, and pride in founding a consumer organisation effective for New Zealand conditions. They saw Parents' Centre as having helped to shape change. This study documents the strategies used by Parents' Centre to spread its message to parents, policy makers and the general public. At the end of the study the pioneers were in agreement that the change in the role of women, particularly as equal breadwinners with men, presented a challenge to the consumer and voluntary aspects of the organisation of Parents' Centre today. Some felt the organisation had lost its radical nature and was at risk of losing the consumer voice. Nonetheless, all the pioneers felt that Parents' Centre still had a part to play in providing effective ante-natal education 'by parents for parents' and a continuing role in working for change in the services in accordance with the needs of parents and children under three.</p>

scholarly journals The Role of Instinct in David Hume's Conception of Human Reason

2020 ◽  
Vol 18 (3) ◽  
pp. 273-288
Author(s):  
James Hill
Keyword(s):  
Human Nature ◽  
Animal Kingdom ◽  
Human Reason ◽  
Mathematical Thought ◽  
Natural Element ◽  
General Relations ◽  
Intellectual Power ◽  
As If ◽  
Experimental Reasoning

This article investigates the role of instinct in Hume's understanding of human reason. It is shown that while in the Treatise Hume makes the strong reductive assertion that reason is ‘nothing but’ an instinct, in the First Enquiry the corresponding statement has been modified in several ways, rendering the relation between instinct and reason more complex. Most importantly, Hume now explicitly recognises that alongside instinctive experimental reasoning, there is a uniquely human intellectual power of intuitive and demonstrative reason that is not itself an instinct. At first sight it may look as if this intellectual reason, that is capable of grasping ‘relations of ideas’, is not even grounded in instinct but is a thoroughly non-natural element in human nature. On closer analysis, however, it is shown that intellectual reason, in its apprehension of ‘abstract’ and general relations, is dependent on language – the use of ‘terms’ – and that language itself is grounded in instinctive associations of ideas. Thus, Hume's overall view is that even the intellect is an outgrowth of instinct and his conception of human nature is, therefore, shown to be fully naturalistic. Yet this naturalism can still make room for the ‘exceptionalism’ of human mathematical thought, which has no counterpart in the animal kingdom where language is lacking.

The role of cholesterol in lipid membranes

1969 ◽  
Vol 173 (1) ◽  
pp. 143-145 ◽  
Author(s):  
J. De Gier ◽  
J.G. Mandersloot ◽  
L.L.M. Van Deenen
Keyword(s):  
Lipid Membranes

Abstract 16440: Cu Transporter ATP7A Protects Against Fibrosis Through Limiting Endothelial to Mesenchymal Transition

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Seock-Won Youn ◽  
Sudhahar Varadarajan ◽  
Archita Das ◽  
Ronald D McKinney ◽  
Tohru Fukai ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Inflammatory Diseases ◽  
Shape Change ◽  
Atherosclerotic Lesion ◽  
Transport Proteins ◽  
Dependent Manner ◽  
Mesenchymal Transition ◽  
Endothelial To Mesenchymal Transition

Background: Endothelial to mesenchymal transition (EndMT) is induced by inflammation and contributes to fibrosis; however, underlying mechanism is poorly understood. Cu plays an important role in physiological processes and pathophysiologies associated with inflammatory diseases. Since excess Cu is toxic, bioavailability of Cu is tightly controlled by Cu exporter ATP7A, which obtains Cu via Cu chaperone, Atox1, and exclude Cu. We reported that Atox1 also functions as a Cu dependent transcription factor. However, role of Cu transport proteins in EndMT is entirely unknown.[[Unable to Display Character: &#8232;]] Results: Here we show that TNFα stimulation for 24hr in HUVEC significantly decreased ATP7A protein (80%) and increased intracellular Cu and Atox1 in nucleus, which was associated with shape change forming EndMT. ATP7A depletion with shRNA in EC significantly reduced EC markers (VE-cadherin and VEGFR2) and increased mesenchymal markers (αSMA, Calponin, SM22α, Collagen I/II). ATP7A siRNA also increased intracellular Cu and nuclear Atox1. These ATP7A knockdown-induced phenotype changes were inhibited by Cu chelators BCS and TTM. Mechanistically, microarray and qPCR based screening revealed that ATP7A knockdown in EC significantly increased miR21 (2.5 fold) and miR125b (1.5 fold) which induce EndMT in a Cu-dependent manner. Of note, promoters of both miR21 and miR125b have Cu dependent transcription factor Atox1 binding sites. Consistent with this, overexpression of Atox1 increased miR21 and miR125b expression as well as promoted EndMT. In vivo, ATP7A mutant (ATP7Amut) mice with reduced Cu export function showed impaired blood flow recovery and reduced arteriogenesis while increased αSMA+ cells and fibrosis in capillary network after ischemic injury. Moreover, ATP7Amut mice crossed with ApoE-/- mice with high fat diet (HFD) induced robust fibrosis and enhanced atherosclerotic lesion vs ApoE-/-/HFD mice.[[Unable to Display Character: &#8232;]] Conclusions: ATP7A protects against fibrosis by preventing EndMT via nuclear Atox1-mediated upregulation of miR21 and miR125b which induce EndMT, in Cu dependent manner. These findings provide the foundation for novel protective role of Cu transport proteins against EndMT- and fibrosis-mediated cardiovascular diseases.

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