Autonomy of differentiation in avian branchial somites and the influence of adjacent tissues

Development ◽  
1987 ◽  
Vol 100 (3) ◽  
pp. 449-462 ◽  
Author(s):  
T. Kenny-Mobbs ◽  
P. Thorogood
Keyword(s):  
Chorioallantoic Membrane ◽  
Growth Conditions ◽  
Explant Culture ◽  
Developmental Pathways ◽  
Morphological Evidence ◽  
Growth Environment ◽  
Enzymatic Dissociation ◽  
Time Migration ◽  
Recombination Experiments ◽  
Do So

This study investigates the differentiative abilities of avian brachial somites at stages of development before, during and after the migration of somitic cells into the wing primordium. These somites are the source of cells that migrate into the forelimbs and there give rise exclusively, and totally, to the skeletal muscle lineage of the wing and yet show no morphological evidence of commitment to that fate when they leave the somites. The aim of the study was to see if the brachial somitic cells are committed to particular developmental pathways at these stages. The brachial somites were isolated from HH stage-12, -15 and -18 chick embryos, either by microdissection or enzymatic dissociation, and grown in organ culture, in explant culture on different substrata or on the chorioallantoic membrane (CAM) of host chicks, either alone or in combination with adjacent tissues. Myogenesis and chondrogenesis occurred in all stage-18 enzymatically separated somites, regardless of the growth environment. Myogenesis was reduced in stage-15 somites and unobservable in stage-12 somites; however, recombination of stage-12 somites with epithelium or neural tube increased the incidence of myogenesis at this stage. The incidence of chondrogenesis was also less in the younger explants. Unlike its effect on myogenic expression, recombination with epithelium resulted in a dramatic decrease in chondrogenesis in both stage-12 and -15 somites. The recombination experiments suggest that conditions that maintain the normal spatial relationships within isolated somites permit expression of a preexisting specification to a particular fate. They also show that the overlying epithelium can inhibit chondrogenesis in these somites. Overall, the results suggest that by the time migration of somitic cells into wing regions is finishing, brachial somitic cells have become stabilized in their ability to undergo both myogenesis and chondrogenesis for they will do so under a variety of growth conditions and independently of adjacent tissues. However, immediately before (stage 12) and shortly after (stage 15) the onset of migration, both myogenic and chondrogenic expression by brachial somitic cells are still under the influence of interactions with adjacent tissues.

NMR methods for in-situ biofilm metabolism studies: spatial and temporal resolved measurements

2005 ◽  
Vol 52 (7) ◽  
pp. 7-12 ◽  
Author(s):  
P.D. Majors ◽  
J.S. McLean ◽  
J.K. Fredrickson ◽  
R.A. Wind
Keyword(s):  
Magnetic Resonance ◽  
Cell Metabolism ◽  
Shewanella Oneidensis ◽  
Growth Conditions ◽  
Magnetic Resonance Images ◽  
Ex Situ ◽  
Adherent Cell ◽  
Growth Environment ◽  
Environment Control

We are developing novel nuclear magnetic resonance (NMR) microscopy, spectroscopy and combined NMR/optical techniques for the study of biofilms under known, controlled growth conditions. Objectives include: time and depth-resolved metabolite concentrations with isotropic spatial resolution on the order of 10 microns, metabolic pathways and flux rates, mass transport and ultimately their correlation with gene expression by optical microscopy in biofilms. We describe the implementation of ex-situ grown biofilms to improve growth environment control and NMR analysis. In-situ NMR depth resolved metabolite profiling techniques are introduced and demonstrated for a Shewanella oneidensis strain MR-1 biofilm. Finally, initial combined confocal fluorescence and magnetic resonance images are shown for a GFP-labeled Shewanella biofilm. These methods are equally applicable to other biofilm systems of interest; thus they may provide a significant contribution toward the understanding of adherent cell metabolism.

scholarly journals When Unity Is Strength: The Strategies Used by Chlamydomonas to Survive Environmental Stresses

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1307 ◽  
Author(s):  
Félix de Carpentier ◽  
Stéphane D. Lemaire ◽  
Antoine Danon
Keyword(s):  
Environmental Conditions ◽  
Wide Spectrum ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Mild Stress ◽  
Unicellular Alga ◽  
Unicellular Organism ◽  
Unicellular Green Alga ◽  
Scientific Fields ◽  
Do So

The unicellular green alga Chlamydomonas reinhardtii is a valuable model system to study a wide spectrum of scientific fields, including responses to environmental conditions. Most studies are performed under optimal growth conditions or under mild stress. However, when environmental conditions become harsher, the behavior of this unicellular alga is less well known. In this review we will show that despite being a unicellular organism, Chlamydomonas can survive very severe environmental conditions. To do so, and depending on the intensity of the stress, the strategies used by Chlamydomonas can range from acclimation to the formation of multicellular structures, or involve programmed cell death.

scholarly journals An interpretable flux-based machine learning model of drug interactions across metabolic space and time

2021 ◽  
Author(s):  
Carolina H Chung ◽  
Sriram Chandrasekaran
Keyword(s):  
Machine Learning ◽  
Combination Therapy ◽  
Drug Interactions ◽  
Growth Conditions ◽  
Drug Combinations ◽  
Time Interval ◽  
Therapy Outcomes ◽  
Data Types ◽  
Growth Environment ◽  
Therapy Design

Drug combinations are a promising strategy to counter antibiotic resistance. However, current experimental and computational approaches do not account for the entire complexity involved in combination therapy design, such as the effect of the growth environment, drug order, and time interval. To address these limitations, we present an approach that uses genome-scale metabolic modeling and machine learning to explain and guide combination therapy design. Our approach (a) accommodates diverse data types, (b) accurately predicts drug interactions in various growth conditions, (c) accounts for time- and order-specific interactions, and (d) identifies mechanistic factors driving drug interactions. The entropy in bacterial stress response, time between treatments, and gluconeogenesis activation were the most predictive features of combination therapy outcomes across time scales and growth conditions. Analysis of the vast landscape of condition-specific drug interactions revealed promising new drug combinations and a tradeoff in the efficacy between simultaneous and sequential combination therapies.

scholarly journals Dependency of hydration and growth conditions on the mechanical properties of oral biofilms

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Pattem ◽  
M. Davrandi ◽  
S. Aguayo ◽  
B. Slak ◽  
R. Maev ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bacterial Diversity ◽  
Time Lapse ◽  
Growth Conditions ◽  
New Combination ◽  
Growth Media ◽  
Phenotypic Properties ◽  
Growth Environment ◽  
Oral Biofilms ◽  
The Impact

AbstractWithin the oral cavity, dental biofilms experience dynamic environments, in part due to changes in dietary content, frequency of intake and health conditions. This can impact bacterial diversity and morpho-mechanical properties. While phenotypic properties of oral biofilms are closely related to their composition, these can readily change according to dynamic variations in the growth environment and nutrient availability. Understanding the interlink between phenotypic properties, variable growth conditions, and community characterization is an essential requirement to develop structure–property relationships in oral-biofilms. In this study, the impact of two distinct growth media types with increasing richness on the properties of oral biofilms was assessed through a new combination of in-vitro time-lapse biophysical methods with microbiological assays. Oral biofilms grown in the enriched media composition presented a decrease in their pH, an increase in soluble EPS production, and a severe reduction in bacterial diversity. Additionally, enriched media conditions presented an increase in biofilm volumetric changes (upon hydration) as well as a reduction in elastic modulus upon indentation. With hydration time considered a major factor contributing to changes in biofilm mechanical properties, we have shown that it is less associated than media richness. Future investigations can now use this time-lapse approach, with a clearer focus on the extracellular matrix of oral biofilms dictating their morpho-mechanical properties.

Impurity Effects in the Growth of 4H-SiC Crystals by Physical Vapor Transport

1999 ◽  
Vol 572 ◽  
Author(s):  
V. Balakrishna ◽  
G. Augustine ◽  
R. H. Hopkins
Keyword(s):  
Electronic Device ◽  
Defect Density ◽  
Growth Parameters ◽  
Large Diameter ◽  
Growth Conditions ◽  
High Resistivity ◽  
Growth Surface ◽  
Second Phase ◽  
Impurity Effects ◽  
Growth Environment

ABSTRACTSiC is an important wide bandgap semiconductor material for high temperature and high power electronic device applications. Purity improvements in the growth environment has resulted in a two-fold benefit during growth: (a) minimized inconsistencies in the background doping resulting in high resistivity (>5000 ohm-cm) wafer yield increase from 10–15% to 70-85%, and (b) decrease in micropipe formation. Growth parameters play an important role in determining the perfection and properties of the SiC crystals, and are extremely critical in the growth of large diameter crystals. Several aspects of growth are vital in obtaining highly perfect, large diameter crystals, such as: (i) optimized furnace design, (ii) high purity growth environment, and (iii) carefully controlled growth conditions. Although significant reduction in micropipe density has been achieved by improvements in the growth process, more stringent device requirements mandate further reduction in the defect density. In-depth understanding of the mechanisms of micropipe formation is essential in order to devise approaches to eliminate them. Experiments have been performed to understand the role of growth conditions and ambient purity on crystal perfection by intentionally introducing arrays of impurity sites on one half of the growth surface. Results clearly suggest that presence of impurities or second phase inclusions during start or during growth can result in the nucleation of micropipes. Insights obtained from these studies were instrumental in the growth of ultra-low micropipe density (less than 2 micropipes cm−2 ) in 1.5 inch diameter boules.

Impact of growth environment and physiological state on metal immobilization byPseudomonas aeruginosaPAO1

2010 ◽  
Vol 56 (7) ◽  
pp. 527-538 ◽  
Author(s):  
Ryan C. Hunter ◽  
Vernon R. Phoenix ◽  
Anuradha Saxena ◽  
Terry J. Beveridge
Keyword(s):  
Metal Binding ◽  
Physiological State ◽  
Growth Conditions ◽  
Spectrophotometric Analysis ◽  
Cell Physiology ◽  
Growth Environment ◽  
Bacterial Surface ◽  
Metal Interactions ◽  
Metal Immobilization ◽  
In Cells

Environmental growth conditions and cell physiology have the potential to influence bacterial surface–metal interactions in both planktonic and biofilm systems. Here, Pseudomonas aeruginosa was studied to determine the influence of these factors (pH, redox potential, and active respiration) on surface electrostatics and metal immobilization. Acid–base titrations revealed a decrease in ionizable ligands at pKa5 (putative carboxyls) in cells grown below pH 6.2 and in cells grown anaerobically relative to cells grown under oxic and circumneutral pH conditions. This observation correlates with Western immunoblotting assays that revealed a reduction in carboxylated B-band lipopolysaccharide in these cells. Furthermore, spectrophotometric analysis revealed a decrease in zinc, copper, and iron immobilization in these cells, suggesting that lipopolysaccharide modification in response to environmental stimuli influences metal binding. The effect of active versus inactive metabolism on metal adsorption was also examined using respiration inhibitors carbonyl cyanide m-chlorophenylhydrazone and sodium azide. Cells treated with these compounds bound more zinc, copper, and iron than untreated controls, suggesting proton extrusion through respiration competes with metal cations for reactive groups on the cell surface. Accumulation of gold did not show the same trend, and transmission electron microscopy studies confirmed it was not a surface-mediated process. These results suggest that variations in growth environment and cell physiology influence metal accumulation by bacterial cell surfaces and may help to explain discontinuous accumulation of metal observed throughout microbial communities.

scholarly journals Growth Conditions Regulate the Requirements for Caulobacter Chromosome Segregation

2008 ◽  
Vol 191 (3) ◽  
pp. 1097-1100 ◽  
Author(s):  
Conrad W. Shebelut ◽  
Rasmus B. Jensen ◽  
Zemer Gitai
Keyword(s):  
Actin Cytoskeleton ◽  
Small Molecule ◽  
Chromosome Segregation ◽  
Growth Conditions ◽  
Small Molecule Inhibitor ◽  
Dependent Effect ◽  
Growth Environment ◽  
Molecule Inhibitor

ABSTRACT Growth environments are important metabolic and developmental regulators. Here we demonstrate a growth environment-dependent effect on Caulobacter chromosome segregation of a small-molecule inhibitor of the MreB bacterial actin cytoskeleton. Our results also implicate ParAB as important segregation determinants, suggesting that multiple distinct mechanisms can mediate Caulobacter chromosome segregation and that their relative contributions can be environmentally regulated.

Growth of SiC Boules with Low Boron Concentration

2006 ◽  
Vol 527-529 ◽  
pp. 47-50 ◽  
Author(s):  
Mark A. Fanton ◽  
R.L. Cavalero ◽  
R.G Ray ◽  
B.E. Weiland ◽  
W.J. Everson ◽  
...  
Keyword(s):  
High Purity ◽  
Pyrolytic Graphite ◽  
Growth Conditions ◽  
Hydrogen Gas ◽  
Boron Diffusion ◽  
Growth Environment ◽  
Carbide Coatings ◽  
Cell Components ◽  
Site Competition ◽  
Graphite Growth

The effects of growth conditions, diffusion barrier coatings, and hot zone materials on B incorporation in 6H-SiC crystals grown by physical vapor transport (PVT) were evaluated. Development of high purity source material with a B concentration less than 1.8x1015 atoms/cm3, was critical to the growth of boules with a B concentration less than 3.0x1016 atoms/cm3. Application of refractory metal carbide coatings to commercial graphite to serve as boron diffusion barriers and the use of very high purity pyrolytic graphite components ultimately led to the growth of SiC boules with boron concentrations as low as 2.4x1015 atoms/cm3. The effect of growth temperature and pressure were closely examined over a range from 2100°C to 2300°C and 5 to 13.5 Torr. This range of growth conditions and growth rates had no effect on B incorporation. Attempts to alter the gas phase stoichiometry through addition of hydrogen gas to the growth environment also had no impact on B incorporation. These results are explained by considering site competition effects and the ability of B to diffuse through the graphite growth cell components.

scholarly journals A minimalistic resource allocation model to explain ubiquitous increase in protein expression with growth rate

2015 ◽  
Author(s):  
Uri Barenholz ◽  
Leeat Keren ◽  
Eran Segal ◽  
Ron Milo
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
Growth Conditions ◽  
Cellular Growth ◽  
Biological Research ◽  
Base Line ◽  
Allocation Model ◽  
Growth Environment ◽  
Active Regulation

Most proteins show changes in level across growth conditions. Many of these changes seem to be coordinated with the specific growth rate rather than the growth environment or the protein function. Although cellular growth rates, gene expression levels and gene regulation have been at the center of biological research for decades, there are only a few models giving a base line prediction of the dependence of the proteome fraction occupied by a gene with the specific growth rate. We present a simple model that predicts a widely coordinated increase in the fraction of many proteins out of the proteome, proportionally with the growth rate. The model reveals how passive redistribution of resources, due to active regulation of only a few proteins, can have proteome wide effects that are quantitatively predictable. Our model provides a potential explanation for why and how such a coordinated response of a large fraction of the proteome to the specific growth rate arises under different environmental conditions. The simplicity of our model can also be useful by serving as a baseline null hypothesis in the search for active regulation. We exemplify the usage of the model by analyzing the relationship between growth rate and proteome composition for the model microorganism E.coli as reflected in two recent proteomics data sets spanning various growth conditions. We find that the fraction out of the proteome of a large number of proteins, and from different cellular processes, increases proportionally with the growth rate. Notably, ribosomal proteins, which have been previously reported to increase in fraction with growth rate, are only a small part of this group of proteins. We suggest that, although the fractions of many proteins change with the growth rate, such changes could be part of a global effect, not requiring specific cellular control mechanisms.

Growth of Micropipe-Free Single Crystal Silicon Carbide (SiC) Ingots Via Physical Vapor Transport (PVT)

2006 ◽  
Vol 527-529 ◽  
pp. 39-42 ◽  
Author(s):  
C. Basceri ◽  
I. Khlebnikov ◽  
Y. Khlebnikov ◽  
P. Muzykov ◽  
M. Sharma ◽  
...  
Keyword(s):  
Single Crystal Silicon ◽  
Growth Conditions ◽  
Substrate Material ◽  
Growth Stages ◽  
Crystal Silicon ◽  
Growth Technique ◽  
Growth Environment ◽  
Bulk Growth ◽  
The Past

The move towards commercialization of SiC based devices places increasing demands on the quality of the substrate material. While the industry has steadily decreased the micropipe (MP) levels in commercial SiC substrates over the past years, the achievement of wafers that are entirely free of MPs marks an important milestone in commercialization of SiC based devices. We present the results of a study for controlling the nucleation and propagation of MP defects in SiC ingots grown via PVT. Our studies confirm that during bulk growth of SiC, foreign polytype nucleation such as 3C-polytype occurs at the initial stages of growth (nucleation period) and/or during subsequent growth in the presence of facets. Results in this investigation suggest that polytype instability during crystal growth adversely impacts the MP density. Based on this key concept, growth conditions for nucleation and growth stages were optimized. These conditions were subsequently implemented in an innovative PVT growth environment to achieve a growth technique with highly effective polytype control. Under continuously modulated growth conditions, MPs induced by seed material and/or formed during the growth were eliminated. 2-inch and 3-inch diameter MP-free (zero MP density) conducting 4H-SiC ingots were obtained.

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