scholarly journals Formation of Water-Free Cavity in the Process of Nafion Swelling in a Cell of Limited Volume; Effect of Polymer Fibers Unwinding

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2888
Author(s):  
Barry W. Ninham ◽  
Polina N. Bolotskova ◽  
Sergey V. Gudkov ◽  
Yulchi Juraev ◽  
Mariya S. Kiryanova ◽  
...  
Keyword(s):  
Colloidal Particles ◽  
Temporal Dynamics ◽  
Polymer Surface ◽  
Volume Effect ◽  
Polymer Fibers ◽  
Exclusion Zone ◽  
Limited Volume ◽  
Water Pretreatment ◽  
A Cell ◽  
Cell Window

When Nafion swells in water, colloidal particles are repelled from the polymer surface; this effect is called the formation exclusion zone (EZ), and the EZ size amounts to several hundred microns. However, still no one has investigated the EZ formation in a cell whose dimension is close to the EZ size. It was also shown that, upon swelling in water, Nafion fibers “unwind” into the water bulk. In the case of a cell of limited volume, unwound fibers abut against the cell windows, and water is completely pushed out from the region between the polymer and the cell window, resulting in a cavity appearance. The temporal dynamics of the collapse of this cavity was studied depending on the cell size. It is shown that the cavity formation occurs due to long-range forces between polymer strands. It turned out that this scenario depends on the isotopic composition of the water, ionic additives and water pretreatment. The role of nanobubbles in the formation and collapse of the cavity were analyzed. The results obtained allowed us to conclude that the EZ formation is precisely due to the unwinding of polymer fibers into the liquid bulk.

scholarly journals Stimulus-Specific Distinctions in Spatial and Temporal Dynamics of Stress-Activated Protein Kinase Kinase Kinases Revealed by a Fluorescence Resonance Energy Transfer Biosensor

2009 ◽  
Vol 29 (22) ◽  
pp. 6117-6127 ◽  
Author(s):  
Taichiro Tomida ◽  
Mutsuhiro Takekawa ◽  
Pauline O'Grady ◽  
Haruo Saito
Keyword(s):  
Energy Transfer ◽  
Protein Kinase ◽  
Fluorescence Resonance Energy Transfer ◽  
Cell Population ◽  
Temporal Dynamics ◽  
Single Cells ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
A Cell ◽  
Fluorescence Resonance

ABSTRACT The stress-activated protein kinases (SAPKs), namely, p38 and JNK, are members of the mitogen-activated protein kinase family and are important determinants of cell fate when cells are exposed to environmental stresses such as UV and osmostress. SAPKs are activated by SAPK kinases (SAP2Ks), which are in turn activated by various SAP2K kinases (SAP3Ks). Because conventional methods, such as immunoblotting using phospho-specific antibodies, measure the average activity of SAP3Ks in a cell population, the intracellular dynamics of SAP3K activity are largely unknown. Here, we developed a reporter of SAP3K activity toward the MKK6 SAP2K, based on fluorescence resonance energy transfer, that can uncover the dynamic behavior of SAP3K activation in cells. Using this reporter, we demonstrated that SAP3K activation occurs either synchronously or asynchronously among a cell population and in different cellular compartments in single cells, depending on the type of stress applied. In particular, SAP3Ks are activated by epidermal growth factor and osmostress on the plasma membrane, by anisomycin and UV in the cytoplasm, and by etoposide in the nucleus. These observations revealed previously unknown heterogeneity in SAPK responses and supplied answers to the question of the cellular location in which various stresses induce stimulus-specific SAPK responses.

scholarly journals Assessment of the Effects of Stretch-Injury on Primary Rat Microglia

2020 ◽  
Author(s):  
Mike Shaughness ◽  
Kimberly Byrnes
Keyword(s):  
Time Course ◽  
Cell Injury ◽  
Mechanical Stretch ◽  
Course Evaluation ◽  
Cell Diameter ◽  
Exclusion Zone ◽  
Post Injury ◽  
Stretch Injury ◽  
Arginase 1 ◽  
A Cell

Abstract Background: Mechanical stretch-injury is a prominent force involved in the etiology of traumatic brain injury (TBI). It is known to directly cause damage and dysfunction in neurons, astrocytes, and endothelial cells. However, the deleterious effects of stretch-injury on microglia, the brain’s primary immunocompetent cell, are currently unknown. Methods: The Cell Injury Controller II (CICII), a validated model of cellular neurotrauma, was used to induce a mechanical stretch-injury in primary rat microglia. Statistical analysis utilized student t-test and one and two way-ANOVAs with Tukey’s and Sidak’s multiple comparisons, respectively. Results: Cells exposed to stretch-injury showed no signs of membrane permeability, necrosis, or apoptosis, as measured by media derived lactate dehydrogenase (LDH) and cleaved-caspase 3 immunocytochemistry, respectively. Interestingly, injured cells displayed a functional deficit in production nitric oxide (NO), identified by media assay and immunocytochemistry, at 6, 12, 18, and 48 hours post-injury. Furthermore, gene expression analysis revealed the expression of inflammatory cytokines IL-6 and IL-10 and enzyme arginase-1 was significantly down-regulated at 12 hours post-injury. Time course evaluation of migration, using a cell exclusion zone assay, showed stretch-injured cells display decreased migration into the exclusion zone at 48 and 72 hours post-stretch. Lastly, coinciding with the functional immune deficits, was a significant change in morphology, with process length decreasing and cell diameter increasing following an injury at 12 hours. Conclusions: Taken together, the data demonstrate that stretch-injury produces significant alterations in microglial function, which may have marked impact on their response to injury or their interaction with other cells.

Technique for Bilateral Intracranial Implantation of Cells in Monkeys Using an Automated Delivery System

2000 ◽  
Vol 9 (5) ◽  
pp. 595-607 ◽  
Author(s):  
Krys S. Bankiewicz ◽  
John Bringas ◽  
Phillip Pivirotto ◽  
Ethan Kutzscher ◽  
Dea Nagy ◽  
...  
Keyword(s):  
Side Effects ◽  
Mass Effect ◽  
Volume Effect ◽  
Tissue Mass ◽  
Routine Manner ◽  
Clinical Complications ◽  
Mri Scans ◽  
A Cell ◽  
Magnetic Resonance Imaging Mri ◽  
Automated Delivery

Intracerebral grafting combined with gene transfer may provide a powerful technique for local delivery of therapeutic agents into the CNS. The present study was undertaken to: (i) develop a reliable and reproducible automated cell implantation system, (ii) determine optimal implantation parameters of cells into the striatum, (iii) determine upper safe limits of cellular implantation into the neostriatum of monkeys. Autologous fibroblasts were infused into six sites of the striatum in nonhuman primates (Macaca mulatta, n = 11). Twenty-six-gauge cannulae were inserted vertically through cortical entry sites into the striatum (two sites in the caudate nucleus and four sites in the putamen) at predefined coordinates based on magnetic resonance imaging (MRI). The cannulae were guided by an electronically operated, hydraulic micropositioner and withdrawn at controlled rates, while cells (5, 10, 20, 40, or 80 μl/site) were infused simultaneously. Varying infusion rates and cell concentrations were also evaluated. Visualization and evaluation of graft placement were performed using contrast MRI at 3–5 days postsurgery. Animals were monitored for signs of clinical complications and sacrificed 2 weeks following surgery. Postimplantation MRI revealed a tissue mass effect of the implant with shifting of midline, edema, and infiltration of the white tracts at 40 and 80 μl/site. In addition, these animals developed transient hemiparesis contralateral to the implant site. MRI of animals grafted with 20 μl/site exhibited columnar-shaped implants and evidence of infiltration into white matter tracts possibly due to a volume effect. No clinical side effects were seen in this group. At 14 days postsurgery, MRI scans showed consistent columnar grafts (measuring approximately 5 mm in height) throughout the striatum in animals implanted with 5 or 10 μl/site. No signs of clinical side effects were associated with these volumes and postmortem histological examination confirmed MRI observations. Optimal surgical parameters for delivery of cells into the striatum consist of a graft volume of 10 μl/site, an infusion rate of 1.6 μl/min, a cell concentration of 2.0 × 105 cells/μl, and a cannula withdrawal rate of 0.75 mm/min. These results show that infusion of cells into the striatum can be done in a safe and routine manner.

Self-Pulsing and Chaos in an Extended-Cavity Diode Laser with Intracavity Atomic Absorber

1998 ◽  
Vol 08 (09) ◽  
pp. 1801-1809
Author(s):  
F. di Teodoro ◽  
E. Cerboneschi ◽  
D. Hennequin ◽  
E. Arimondo
Keyword(s):  
Diode Laser ◽  
Temporal Dynamics ◽  
Optical Feedback ◽  
Diode Lasers ◽  
External Cavity ◽  
High Dimensional ◽  
Cesium Vapor ◽  
A Cell ◽  
Extended Cavity ◽  
Low Dimensional

An experimental investigation of the temporal dynamics of a diode laser subject to optical feedback from an external cavity containing a cell filled with cesium vapor has been performed. Peculiar dynamic regimes, such as self-pulsing, low-dimensional, and high-dimensional chaos, characterized by a new time scale, much longer than the time scales of all instabilities taking place in diode lasers under standard feedback conditions, have been identified.

scholarly journals Horizontal gene transfer by natural transformation promotes both genetic and epigenetic inheritance of traits

2019 ◽  
Author(s):  
Ankur B. Dalia ◽  
Triana N. Dalia
Keyword(s):  
Antibiotic Resistance ◽  
Gene Transfer ◽  
Horizontal Gene Transfer ◽  
Dna Sequences ◽  
Natural Transformation ◽  
Temporal Dynamics ◽  
Epigenetic Inheritance ◽  
Major Mechanism ◽  
A Cell ◽  
Dna 2

AbstractNatural transformation (NT) is a major mechanism of horizontal gene transfer in microbial species that promotes the spread of antibiotic resistance determinants and virulence factors. Here, we develop a cell biological approach to characterize the spatial and temporal dynamics of homologous recombination during NT inVibrio cholerae. Our results directly demonstrate (1) that transforming DNA efficiently integrates into the genome as single-stranded DNA, (2) that the resulting heteroduplexes are resolved by chromosome replication and segregation, and (3) that integrated DNA is rapidly expressed prior to cell division. We show that the combination of these properties results in the epigenetic transfer of gene products within transformed populations, which can support the transgenerational epigenetic inheritance of antibiotic resistance in bothV. choleraeandStreptococcus pneumoniae. Thus, beyond the genetic acquisition of novel DNA sequences, NT can also promote the epigenetic inheritance of traits during this conserved mechanism of horizontal gene transfer.

scholarly journals The role of single occupancy effects on integrase dynamics in a cell-free system

2016 ◽  
Author(s):  
Georgios Artavanis ◽  
Victoria Hsiao ◽  
Clarmyra A. Hayes ◽  
Richard M. Murray
Keyword(s):  
Binding Sites ◽  
Temporal Dynamics ◽  
Regulatory Elements ◽  
Enzyme Concentration ◽  
Boolean Logic ◽  
Free System ◽  
Phage Integrase ◽  
Memory Modules ◽  
Number Of Binding Sites ◽  
A Cell

AbstractPhage integrase-based circuits are an alternative approach to relying on transcriptional and translational repression for biomolecular circuits. Previous research has shown that circuits based on integrases can perform a variety of functions, including counters, Boolean logic operators, memory modules and temporal event detectors. It is therefore essential to develop a principled theoretical and experimental framework for the design, implementation and study of such circuits. One of the fundamental questions that such a framework should address concerns the functionality limitations and temporal dynamics of the integrases as regulatory elements. Here, we test the functionality of several large serine integrases from a recently published library in a cell-free transcription-translation (TX-TL) platform. Additionally, we use a combination of experimental data and models to investigate integrase dynamics as a function of enzyme concentration and number of binding sites.We report that sequestration of integrase molecules, either in the form of monomers or dimers, by the integrase's own binding sites dominates integrase dynamics, and that the delay in the activation of the reporter is negatively correlated with integrase plasmid concentration. We have validated our sequestration hypothesis by building a model with MATLAB’s SimBiology toolbox, and running simulations with various integrase and binding sites concentrations. The simulation results qualitatively match the experimental results, and offer further insights into the system.

Membrane-based pretreatment to mitigate variations in desalination plants

2018 ◽  
Vol 77 (12) ◽  
pp. 2858-2866 ◽  
Author(s):  
J. Arevalo ◽  
R. Sandin ◽  
M. D. Kennedy ◽  
S. G. Salinas Rodriguez ◽  
F. Rogalla ◽  
...  
Keyword(s):  
Pilot Plant ◽  
Colloidal Particles ◽  
High Water ◽  
Stable Operation ◽  
High Concentration ◽  
Chemical Cleaning ◽  
Membrane Performance ◽  
Water Pretreatment ◽  
Cleaning Procedures ◽  
Desalination Plants

Abstract The main source of potable water in high water-stress areas is commonly produced in brackish and seawater desalination plants. Owing to the presence of high concentration of suspended solids, organic matter and colloidal particles in raw water, pretreatment processes are needed for a stable operation of desalination plants. A submerged membrane ultrafiltration pilot plant has been operated as pretreatment of complex brackish surface water to study the filtration performance. The results show the membrane performance, chemical reagent requirements, water quality and cleaning procedures efficiency of an ultrafiltration pilot plant used as pretreatment for a reverse osmosis system. Alternative chemical cleaning procedures have been satisfactorily implemented, which maximize permeability recovery and allow a stable operation.

scholarly journals Negative Feedback Facilitates Temperature Robustness in Biomolecular Circuit Dynamics

2014 ◽  
Author(s):  
Shaunak Sen ◽  
Richard M Murray
Keyword(s):  
Temperature Dependence ◽  
Negative Feedback ◽  
Reaction Rate ◽  
Temporal Dynamics ◽  
Effect Of Temperature ◽  
Translation System ◽  
Degradation Mechanisms ◽  
First Order ◽  
A Cell ◽  
Transcriptional Feedback

Temporal dynamics in many biomolecular circuits can change with temperature because of the temperature dependence of underlying reaction rate parameters. It is generally unclear what circuit mechanisms can inherently facilitate robustness in the dynamics to variations in temperature. Here, we address this issue using a combination of mathematical models and experimental measurements in a cell-free transcription-translation system. We find that negative transcriptional feedback can reduce the effect of temperature variation on circuit dynamics. Further, we find that effective negative feedback due to first-order degradation mechanisms can also enable such a temperature robustness effect. Finally, we estimate temperature dependence of key parameters mediating such negative feedback mechanisms. These results should be useful in the design of temperature robust circuit dynamics.

scholarly journals A cell cycle-coordinated nuclear compartment for Polymerase II transcription encompasses the earliest gene expression before global genome activation

2018 ◽  
Author(s):  
Yavor Hadzhiev ◽  
Haseeb K. Qureshi ◽  
Lucy Wheatley ◽  
Ledean Cooper ◽  
Aleksandra Jasiulewicz ◽  
...  
Keyword(s):  
Gene Expression ◽  
Temporal Dynamics ◽  
Nuclear Compartment ◽  
Cell Cycles ◽  
Regulatory Architecture ◽  
4D Imaging ◽  
Zygotic Gene ◽  
A Cell ◽  
Spatio Temporal ◽  
Genome Activation

AbstractMost metazoan embryos commence development with rapid cleavages without zygotic gene expression and their genome activation is delayed until the mid-blastula transition (MBT). However, a set of genes escape global repression during the extremely fast cell cycles, which lack gap phases and their transcription is activated before the MBT. Here we describe the formation and the spatio-temporal dynamics of a distinct transcription compartment, which encompasses the earliest detectable transcription during the first wave of genome activation. Simultaneous 4D imaging of expression of pri-miR430 and zinc finger genes by a novel, native transcription imaging approach reveals a pair of shared transcription compartments regulated by homolog chromosome organisation. These nuclear compartments carry the majority of nascent RNAs and transcriptionally active Polymerase II, are depleted of compact chromatin and represent the main sites for detectable transcription before MBT. We demonstrate that transcription occurs in the S-phase of the cleavage cycles and that the gradual slowing of these cell cycles are permissive to transcription before global genome activation. We propose that the demonstrated transcription compartment is part of the regulatory architecture of nucleus organisation, and provides a transcriptionally competent, supporting environment to facilitate early escape from the general nuclear repression before global genome activation.

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