scholarly journals The Regulation of Autophagy in Eukaryotic Cells: Do All Roads Pass through Atg1?

Autophagy ◽  
2006 ◽  
Vol 2 (2) ◽  
pp. 146-148 ◽  
Author(s):  
Joseph S. Stephan ◽  
Paul K. Herman
Keyword(s):  
Eukaryotic Cells ◽  
Pass Through

scholarly journals Soil Pollution from Micro- and Nanoplastic Debris: A Hidden and Unknown Biohazard

2020 ◽  
Vol 12 (18) ◽  
pp. 7255 ◽  
Author(s):  
Shamina Imran Pathan ◽  
Paola Arfaioli ◽  
Tommaso Bardelli ◽  
Maria Teresa Ceccherini ◽  
Paolo Nannipieri ◽  
...  
Keyword(s):  
Physical Properties ◽  
Molecular Techniques ◽  
Ecological Effect ◽  
Eukaryotic Cells ◽  
Ecological Functions ◽  
Plastic Debris ◽  
Chemical Structures ◽  
Pass Through ◽  
Nano Size

The fate, properties and determination of microplastics (MPs) and nanoplastics (NPs) in soil are poorly known. In fact, most of the 300 million tons of plastics produced each year ends up in the environment and the soil acts as a log-term sink for these plastic debris. Therefore, the aim of this review is to discuss MP and NP pollution in soil as well as highlighting the knowledge gaps that are mainly related to the complexity of the soil ecosystem. The fate of MPs and NPs in soil is strongly determined by physical properties of plastics, whereas negligible effect is exerted by their chemical structures. The degradative processes of plastic, termed ageing, besides generating micro-and nano-size debris, can induce marked changes in their chemical and physical properties with relevant effects on their reactivity. Further, these processes could cause the release of toxic oligomeric and monomeric constituents from plastics, as well as toxic additives, which may enter in the food chain, representing a possible hazard to human health and potentially affecting the fauna and flora in the environment. In relation to their persistence in soil, the list of soil-inhabiting, plastic-eating bacteria, fungi and insect is increasing daily. One of the main ecological functions attributable to MPs is related to their function as vectors for microorganisms through the soil. However, the main ecological effect of NPs (limited to the fraction size < than 50 nm) is their capacity to pass through the membrane of both prokaryotic and eukaryotic cells. Soil biota, particularly earthworms and collembola, can be both MPs and NPs carriers through soil profile. The use of molecular techniques, especially omics approaches, can gain insights into the effects of MPs and NPs on composition and activity of microbial communities inhabiting the soil and into those living on MPs surface and in the gut of the soil plastic-ingesting fauna.

Importance of Picoplankton in Lake Superior

1986 ◽  
Vol 43 (1) ◽  
pp. 235-240 ◽  
Author(s):  
Gary L. Fahnenstiel ◽  
Linda Sicko-Goad ◽  
Donald Scavia ◽  
Eugene F. Stoermer
Keyword(s):  
Primary Production ◽  
Lake Superior ◽  
Size Class ◽  
Eukaryotic Cells ◽  
Size Fractionation ◽  
Mean Size ◽  
Total Primary Production ◽  
Chroococcoid Cyanobacteria ◽  
Pass Through ◽  
Track Autoradiography

In Lake Superior, approximately 50% of total primary production is attributable to phytoplankton that pass through a 3-μm screen. The <3-μm size class is dominated by eukaryotic flagellates, nonmotile eukaryotic cells (1 μm), and chroococcoid cyanobacteria. Approximately 20% of total primary production is attributable to orange autofluorescent chroococcoid cyanobacteria (mean size = 0.7 μm) as determined by size fractionation and track autoradiography. These small prokaryotes exhibited abundances of 42 000 and 56 000 cells∙ml−1, maximum photosynthetic rates of 7 and 6 fg∙cell−1∙h−1, and growth rates of 1.5 and 0.8∙d−1 in the epilimnion and hypolimnion, respectively. A significant portion of this picoplankton (<1 μm) production may be consumed by heterotrophic protozoans in a "microbial loop."

Instrumentation for detecting channelling radiation in the high-voltage electron microscope

1983 ◽  
Vol 41 ◽  
pp. 318-319
Author(s):  
J. H. Butler ◽  
C. J. Humphreys
Keyword(s):  
Monochromatic Light ◽  
Incident Beam ◽  
Laboratory Frame ◽  
Relativistic Electrons ◽  
Voltage Electron ◽  
Dipole Emission ◽  
Sinusoidal Oscillations ◽  
Pass Through ◽  
Incident Beam Energy ◽  
Increasing Function

Electromagnetic radiation is emitted when fast (relativistic) electrons pass through crystal targets which are oriented in a preferential (channelling) direction with respect to the incident beam. In the classical sense, the electrons perform sinusoidal oscillations as they propagate through the crystal (as illustrated in Fig. 1 for the case of planar channelling). When viewed in the electron rest frame, this motion, a result of successive Bragg reflections, gives rise to familiar dipole emission. In the laboratory frame, the radiation is seen to be of a higher energy (because of the Doppler shift) and is also compressed into a narrower cone of emission (due to the relativistic “searchlight” effect). The energy and yield of this monochromatic light is a continuously increasing function of the incident beam energy and, for beam energies of 1 MeV and higher, it occurs in the x-ray and γ-ray regions of the spectrum. Consequently, much interest has been expressed in regard to the use of this phenomenon as the basis for fabricating a coherent, tunable radiation source.

Radiation Damage, Contrast and Statistics in High Resolution Biological Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 260-261
Author(s):  
Robert M. Glaeser
Keyword(s):  
High Resolution ◽  
Particle Flux ◽  
Unit Area ◽  
Signal To Noise ◽  
Resolution Image ◽  
High Resolution Image ◽  
Pass Through ◽  
Counting Statistics ◽  
The Relationship ◽  
Picture Element

It is well known that a large flux of electrons must pass through a specimen in order to obtain a high resolution image while a smaller particle flux is satisfactory for a low resolution image. The minimum particle flux that is required depends upon the contrast in the image and the signal-to-noise (S/N) ratio at which the data are considered acceptable. For a given S/N associated with statistical fluxtuations, the relationship between contrast and “counting statistics” is s131_eqn1, where C = contrast; r2 is the area of a picture element corresponding to the resolution, r; N is the number of electrons incident per unit area of the specimen; f is the fraction of electrons that contribute to formation of the image, relative to the total number of electrons incident upon the object.

A New High Intensity Grid Cap for RCA-EMU-3 Electron Microscopes

1968 ◽  
Vol 26 ◽  
pp. 316-317
Author(s):  
George Christov ◽  
Bolivar J. Lloyd
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
High Voltage ◽  
High Intensity ◽  
Electron Gun ◽  
Tungsten Filament ◽  
Fluorescent Screen ◽  
Electron Microscopes ◽  
Pass Through ◽  
Ground Potential

A new high intensity grid cap has been designed for the RCA-EMU-3 electron microscope. Various parameters of the new grid cap were investigated to determine its characteristics. The increase in illumination produced provides ease of focusing on the fluorescent screen at magnifications from 1500 to 50,000 times using an accelerating voltage of 50 KV.The EMU-3 type electron gun assembly consists of a V-shaped tungsten filament for a cathode with a thin metal threaded cathode shield and an anode with a central aperture to permit the beam to course the length of the column. The cathode shield is negatively biased at a potential of several hundred volts with respect to the filament. The electron beam is formed by electrons emitted from the tip of the filament which pass through an aperture of 0.1 inch diameter in the cap and then it is accelerated by the negative high voltage through a 0.625 inch diameter aperture in the anode which is at ground potential.

High resolution spot scan imaging of frozen, hydrated actin bundles with 400kV electrons

1992 ◽  
Vol 50 (1) ◽  
pp. 512-513
Author(s):  
J. Jakana ◽  
M.F. Schmid ◽  
P. Matsudaira ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Binding Proteins ◽  
Actin Binding ◽  
Eukaryotic Cells ◽  
Dimensional Structure ◽  
Structural Basis ◽  
Actin Bundle ◽  
Actin Bundles ◽  
3 Dimensional ◽  
Macromolecular Assembly

Actin is a protein found in all eukaryotic cells. In its polymerized form, the cells use it for motility, cytokinesis and for cytoskeletal support. An example of this latter class is the actin bundle in the acrosomal process from the Limulus sperm. The different functions actin performs seem to arise from its interaction with the actin binding proteins. A 3-dimensional structure of this macromolecular assembly is essential to provide a structural basis for understanding this interaction in relationship to its development and functions.

Structure of clathrin cages and coats in ice

1986 ◽  
Vol 44 ◽  
pp. 94-97
Author(s):  
G.P.A. Vigers ◽  
R.A. Crowther ◽  
B.M.F. Pearse
Keyword(s):  
Electron Microscopy ◽  
Heavy Chain ◽  
Outer Part ◽  
Coated Vesicles ◽  
Eukaryotic Cells ◽  
Coat Proteins ◽  
Terminal Domain ◽  
Clathrin Heavy Chain ◽  
Membrane Components

Clathrin forms the polyhedral cage of coated vesicles, which mediate the transfer of selected membrane components within eukaryotic cells. Clathrin cages and coated vesicles have been extensively studied by electron microscopy of negatively stained preparations and shadowed specimens. From these studies the gross morphology of the outer part of the polyhedral coat has been established and some features of the packing of clathrin trimers into the coat have also been described. However these previous studies have not revealed any internal details about the position of the terminal domain of the clathrin heavy chain, the location of the 100kd-50kd accessory coat proteins or the interactions of the coat with the enclosed membrane.

The Hierarchic Order of Intermediate Filament Structure and Assembly

1985 ◽  
Vol 43 ◽  
pp. 722-725
Author(s):  
U. Aebi ◽  
E.C. Glavaris ◽  
R. Eichner
Keyword(s):  
Tissue Specificity ◽  
Structural Model ◽  
Eukaryotic Cells ◽  
Cdna Sequencing ◽  
Filament Structure ◽  
Keratin Filaments ◽  
Isoelectric Points ◽  
Immunological Crossreactivity

Five different classes of intermediate-sized filaments (IFs) have been identified in differentiated eukaryotic cells: vimentin in mesenchymal cells, desmin in muscle cells, neurofilaments in nerve cells, glial filaments in glial cells and keratin filaments in epithelial cells. Despite their tissue specificity, all IFs share several common attributes, including immunological crossreactivity, similar morphology (e.g. about 10 nm diameter - hence ‘10-nm filaments’) and the ability to reassemble in vitro from denatured subunits into filaments virtually indistinguishable from those observed in vivo. Further more, despite their proteinchemical heterogeneity (their MWs range from 40 kDa to 200 kDa and their isoelectric points from about 5 to 8), protein and cDNA sequencing of several IF polypeptides (for refs, see 1,2) have provided the framework for a common structural model of all IF subunits.

Immunocytochemical localization of p65 with one-nanometer gold particles following silver development

1989 ◽  
Vol 47 ◽  
pp. 1042-1043
Author(s):  
Richard W. Burry ◽  
Diane M. Hayes
Keyword(s):  
Plasma Membrane ◽  
Bovine Serum Albumin ◽  
Calf Serum ◽  
Specific Protein ◽  
Immunocytochemical Localization ◽  
Electron Microscopic ◽  
Gold Particles ◽  
Pass Through ◽  
Label Distribution ◽  
Phosphate Buffered Saline

Electron microscopic (EM) immunocytochemistry localization of the neuron specific protein p65 could show which organelles contain this antigen. Antibodies (Ab) labeled with horseradish peroxidase (HRP) followed by chromogen development show a broad diffuse label distribution within cells and restricting identification of organelles. Particulate label (e.g. 10 nm colloidal gold) is highly desirable but not practical because penetration into cells requires destroying the plasma membrane. We report pre-embedding immunocytochemistry with a particulate marker, 1 nm gold, that will pass through membranes treated with saponin, a mild detergent.Cell cultures of the rat cerebellum were fixed in buffered 4% paraformaldehyde and 0.1% glutaraldehyde (Glut.). The buffer for all incubations and rinses was phosphate buffered saline with: 1% calf serum, 0.2% saponin, 0.1% gelatin, 50 mM glycine 1 mg/ml bovine serum albumin, and (not in the HRP labeled cultures) 0.02% sodium azide. The monoclonal #48 to p65 was used with three label systems: HRP, 1 nm avidin gold with IntenSE M development, and 1 nm avidin gold with Danscher development.

Is there an electron wind?

1990 ◽  
Vol 48 (4) ◽  
pp. 798-799
Author(s):  
L. D. Marks ◽  
J. P. Zhang
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Zone Axis ◽  
Electron Holography ◽  
Electron Wave ◽  
Small Particles ◽  
Resolution Electron ◽  
Pass Through ◽  
Electron Wind ◽  
Inelastic Scatter

A not uncommon question in electron microscopy is what happens to the momentum transferred by the electron beam to a crystal. If the beam passes through a crystal and is preferentially diffracted in one direction, is the momentum ’lost’ by the beam transferred to the crystal? Newton’s third law implies that this must be the case. Some experimental observations also indicate that this is the case; for instance, with small particles if the particles are supported on the top surface of a film they often do not line up on the zone axis, but if they are on the bottom they do. However, if momentum is transferred to the crystal, then surely we are dealing with inelastic scattering, not elastic scattering and is not the scattering probability different? In addition, normally we consider inelastic scatter as incoherent, and therefore the part of the electron wave that is inelastically scattered will not coherently interfere with the part of the wave that is scattered; but, electron holography and high resolution electron microscopy work so the wave passing through a specimen must be coherent with the wave that does not pass through the specimen.

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