scholarly journals Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows

Soft Matter ◽  
2015 ◽  
Vol 11 (23) ◽  
pp. 4658-4668 ◽  
Author(s):  
Amarin G. McDonnell ◽  
Tilvawala C. Gopesh ◽  
Jennifer Lo ◽  
Moira O'Bryan ◽  
Leslie Y. Yeo ◽  
...  
Keyword(s):  
Cell Suspensions ◽  
Extensional Viscosity ◽  
Model Systems ◽  
Extensional Flows ◽  
Induced Changes ◽  
Living Materials

Cell suspensions are model systems for studying properties of living materials. A comparison of theory against microfluidic experiments confirms that particle motility causes extensional viscosity to decrease in “pushers” and increase in “pushers”.

Attachment of Oral Cytophaga Species to Hydroxyapatite-Containing Surfaces

1980 ◽  
Vol 29 (2) ◽  
pp. 768-777 ◽  
Author(s):  
Roger A. Celesk ◽  
Jack London
Keyword(s):  
Ethylenediaminetetraacetic Acid ◽  
Root Surface ◽  
Cell Suspensions ◽  
Model Systems ◽  
Proteinase K ◽  
Resting Cells ◽  
Streptococcus Sanguis ◽  
Number Of Binding Sites ◽  
Attachment Process

Model systems simulating the cementum portion of teeth were used to characterize the attachment process by which certain species of oral Cytophaga initiate the colonization of the tooth root surface in vitro. The adsorption of these bacteria to spheroidal hydroxyapatite beads and mechanically powdered root material followed Langmuir isotherm kinetics. From such data, the number of binding sites per 20 mg of substrate and the affinity constants were evaluated for two strains of Cytophaga sp. Resting cells of the two strains tested adhered relatively tenaciously to hydroxyapatite beads in numbers similar to those observed with cells of Streptococcus sanguis . Attachment of bacteria to the substrates was partially inhibited by (i) coating the substrates with human serum or saliva, (ii) pretreating cell suspensions with proteinase K or phospholipase C or D, or (iii) exposing the cells to temperatures greater than 60°C for 15 min. Treating resting cell suspensions with pronase, neuraminidase, phospholipase A2, or 0.1 M ethylenediaminetetraacetic acid had no effect on the attachment process.

Microfluidic rheology of methylcellulose solutions in hyperbolic contractions and the effect of salt in shear and extensional flows

Soft Matter ◽  
2020 ◽  
Vol 16 (22) ◽  
pp. 5273-5281
Author(s):  
Benjamin L. Micklavzina ◽  
Athena E. Metaxas ◽  
Cari S. Dutcher
Keyword(s):  
Extensional Viscosity ◽  
Extensional Flows

The addition of NaCl to methylcellulose solutions increases the extensional viscosity, which can be measured quantitatively using hyperbolic microfluidic contractions. Fluid stresses during flow can be visualized via birefringence.

scholarly journals Evidence for Carrier-Mediated Transport of Monosaccharides in the Ehrlich Ascites Tumor Cell

1967 ◽  
Vol 50 (7) ◽  
pp. 1907-1928 ◽  
Author(s):  
Alan R. Kolber ◽  
Paul G. LeFevre
Keyword(s):  
Transport Model ◽  
Ehrlich Ascites Tumor Cell ◽  
Tracer Uptake ◽  
Cell Suspensions ◽  
Ehrlich Ascites Tumor ◽  
Model Systems ◽  
Sugar Uptake ◽  
Ascites Tumor ◽  
Carrier Mediated Transport ◽  
Ehrlich Ascites

Evidence for carrier-mediated transport of monosaccharides in the Ehrlich ascites tumor cells was provided through kinetic analysis of data obtained by: (a) studying sugar uptake by dilute cell suspensions with an optical densimetric apparatus, (b) studying sugar uptake by thicker cell suspensions by means of direct chemical analytical methods using packed cell plugs, (c) observing the effects of a competitive inhibitor upon sugar uptake with the chemical analytical method, and (d) measurement of tracer uptake of a high affinity sugar in thick cell suspensions in the absence of net movement. Quantitative application of the data obtained with the above experimental procedures to theoretical model systems derived for both carrier-mediated transport and simple passive diffusion indicated that the results were consonant with predictions for the carrier-mediated transport model, but could not be explained on the basis of uncomplicated diffusion.

scholarly journals Model-based Evaluation of Gene Expression Changes in Response to Leishmania Infection

2019 ◽  
Vol 13 ◽  
pp. 117762501982835 ◽  
Author(s):  
Brendan D Stamper ◽  
Madison Davis ◽  
Sean Scott-Collins ◽  
Julie Tran ◽  
Caryn Ton ◽  
...  
Keyword(s):  
Gene Expression ◽  
Host Response ◽  
Leishmania Species ◽  
Model Systems ◽  
Leishmania Infection ◽  
In Vitro Characterization ◽  
Transcriptional Changes ◽  
Induced Changes

Since the development of high-density microarray technology in the late 1990s, global host gene expression changes in response to various stimuli have been extensively studied. More than a dozen peer-reviewed publications have investigated the effect of Leishmania infection in various models since 2001. This review covers the transcriptional changes in macrophage models induced by various Leishmania species and summarizes the resulting impact these studies have on our understanding of the host response to leishmaniasis in vitro. Characterization of the similarities and differences between various model systems will not only further our understanding of Leishmania-induced changes to macrophage gene expression but also identify potential therapeutic targets in the future.

(9,9-Dialkylfluorene-co-fluorenone) copolymers containing low fluorenone fractions as model systems for degradation-induced changes in polyfluorene-type semiconducting materials

e-Polymers ◽  
2002 ◽  
Vol 2 (1) ◽  
Author(s):  
Patricia Scandiucci de Freitas ◽  
Ullrich Scherf ◽  
Maximilien Collon ◽  
Emil J. W. List
Keyword(s):  
Energy Transfer ◽  
Solid State ◽  
Excitation Energy ◽  
Short Communication ◽  
Excitation Energy Transfer ◽  
Building Blocks ◽  
Model Systems ◽  
Semiconducting Materials ◽  
Optical And Electronic Properties ◽  
Induced Changes

AbstractThis short communication describes synthesis, optical and electronic properties of novel 9,9-dialkylfluorene-co-fluorenone copolymers which function as model systems for degradation-induced changes in polyfluorene-type semiconducting materials. Only very small fractions of incorporated fluorenone building blocks lead to a dramatic change of the solid state properties (photo- and electroluminescence). The results are discussed in terms of intra- vs. intermolecular excitation energy transfer.

scholarly journals Viral Proteomics

2007 ◽  
Vol 71 (2) ◽  
pp. 398-411 ◽  
Author(s):  
Karen L. Maxwell ◽  
Lori Frappier
Keyword(s):  
Viral Infection ◽  
Protein Interactions ◽  
Protein Structures ◽  
Model Systems ◽  
Host Protein ◽  
Regulatory Proteins ◽  
Molecular Processes ◽  
Antiviral Therapies ◽  
Infected Cells ◽  
Induced Changes

SUMMARY Viruses have long been studied not only for their pathology and associated disease but also as model systems for molecular processes and as tools for identifying important cellular regulatory proteins and pathways. Recent advances in mass spectrometry methods coupled with the development of proteomic approaches have greatly facilitated the detection of virion components, protein interactions in infected cells, and virally induced changes in the cellular proteome, resulting in a more comprehensive understanding of viral infection. In addition, a rapidly increasing number of high-resolution structures for viral proteins have provided valuable information on the mechanism of action of these proteins as well as aided in the design and understanding of specific inhibitors that could be used in antiviral therapies. In this paper, we discuss proteomic studies conducted on all eukaryotic viruses and bacteriophages, covering virion composition, viral protein structures, virus-virus and virus-host protein interactions, and changes in the cellular proteome upon viral infection.

scholarly journals A modifier screen identifies regulators of cytoskeletal architecture as mediators of Shroom-dependent changes in tissue morphology

Biology Open ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. bio055640
Author(s):  
Jeffrey D. Hildebrand ◽  
Adam D. Leventry ◽  
Omoregie P. Aideyman ◽  
John C. Majewski ◽  
James A. Haddad ◽  
...  
Keyword(s):  
Cell Morphology ◽  
Cell Shape ◽  
Myosin Ii ◽  
Control Cell ◽  
Rho Kinase ◽  
Model Systems ◽  
Tissue Architecture ◽  
Tissue Morphology ◽  
Cell Architecture ◽  
Induced Changes

ABSTRACTRegulation of cell architecture is critical in the formation of tissues during animal development. The mechanisms that control cell shape must be both dynamic and stable in order to establish and maintain the correct cellular organization. Previous work has identified Shroom family proteins as essential regulators of cell morphology during vertebrate development. Shroom proteins regulate cell architecture by directing the subcellular distribution and activation of Rho-kinase, which results in the localized activation of non-muscle myosin II. Because the Shroom-Rock-myosin II module is conserved in most animal model systems, we have utilized Drosophila melanogaster to further investigate the pathways and components that are required for Shroom to define cell shape and tissue architecture. Using a phenotype-based heterozygous F1 genetic screen for modifiers of Shroom activity, we identified several cytoskeletal and signaling protein that may cooperate with Shroom. We show that two of these proteins, Enabled and Short stop, are required for ShroomA-induced changes in tissue morphology and are apically enriched in response to Shroom expression. While the recruitment of Ena is necessary, it is not sufficient to redefine cell morphology. Additionally, this requirement for Ena appears to be context dependent, as a variant of Shroom that is apically localized, binds to Rock, but lacks the Ena binding site, is still capable of inducing changes in tissue architecture. These data point to important cellular pathways that may regulate contractility or facilitate Shroom-mediated changes in cell and tissue morphology.

Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures

1984 ◽  
Vol 42 ◽  
pp. 268-269
Author(s):  
E. Knapek ◽  
H. Formanek ◽  
G. Lefranc ◽  
I. Dietrich
Keyword(s):  
Low Temperatures ◽  
Carbon Films ◽  
Organic Crystals ◽  
Wide Spread ◽  
Lens System ◽  
Preparation Conditions ◽  
Thin Carbon ◽  
Electron Diffractograms ◽  
Diffraction Patterns ◽  
Induced Changes

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.

Drug Induced Changes in Cell Organelles

1968 ◽  
Vol 26 ◽  
pp. 110-111
Author(s):  
Sarah A. Luse
Keyword(s):  
Clinical Medicine ◽  
Cell Organelles ◽  
Riboflavin Deficiency ◽  
Drug Induced ◽  
New Era ◽  
Health And Disease ◽  
In The Beginning ◽  
Cellular Pathology ◽  
Induced Changes ◽  
The Impact

In the mid-nineteenth century Virchow revolutionized pathology by introduction of the concept of “cellular pathology”. Today, a century later, this term has increasing significance in health and disease. We now are in the beginning of a new era in pathology, one which might well be termed “organelle pathology” or “subcellular pathology”. The impact of lysosomal diseases on clinical medicine exemplifies this role of pathology of organelles in elucidation of disease today.Another aspect of cell organelles of prime importance is their pathologic alteration by drugs, toxins, hormones and malnutrition. The sensitivity of cell organelles to minute alterations in their environment offers an accurate evaluation of the site of action of drugs in the study of both function and toxicity. Examples of mitochondrial lesions include the effect of DDD on the adrenal cortex, riboflavin deficiency on liver cells, elevated blood ammonia on the neuron and some 8-aminoquinolines on myocardium.

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