Cell Structure and Protein Synthesis

1959 ◽  
pp. 460-465
Author(s):  
R. KHESIN
Keyword(s):  
Protein Synthesis ◽  
Cell Structure

scholarly journals Cytochalasin releases mRNA from the cytoskeletal framework and inhibits protein synthesis.

1986 ◽  
Vol 6 (5) ◽  
pp. 1650-1662 ◽  
Author(s):  
D A Ornelles ◽  
E G Fey ◽  
S Penman
Keyword(s):  
Protein Synthesis ◽  
Hela Cells ◽  
Cell Structure ◽  
Cytochalasin D ◽  
Reversible Inhibitor ◽  
Dependent Manner ◽  
Inhibitor Of Protein Synthesis ◽  
Cytoskeletal Elements ◽  
Mrna Binding

Cytochalasin D was shown to be a reversible inhibitor of protein synthesis in HeLa cells. The inhibition was detectable at drug levels typically used to perturb cell structure and increased in a dose-dependent manner. The drug also released mRNA from the cytoskeletal framework in direct proportion to the inhibition of protein synthesis. The released mRNA was unaltered in its translatability as measured in vitro but was no longer translated in the cytochalasin-treated HeLa cells. The residual protein synthesis occurred on polyribosomes that were reduced in amount but displayed a normal sedimentation distribution. The results support the hypothesis that mRNA binding to the cytoskeletal framework is necessary although not sufficient for translation. Analysis of the cytoskeletal framework, which binds the polyribosomes, revealed no alterations in composition or amount of protein as a result of treatment with cytochalasin D. Electron microscopy with embedment-free sections shows the framework in great detail. The micrographs revealed the profound reorganization effected by the drug but did not indicate substantial disaggregation of the cytoskeletal elements.

Cytochalasin releases mRNA from the cytoskeletal framework and inhibits protein synthesis

1986 ◽  
Vol 6 (5) ◽  
pp. 1650-1662
Author(s):  
D A Ornelles ◽  
E G Fey ◽  
S Penman
Keyword(s):  
Protein Synthesis ◽  
Hela Cells ◽  
Cell Structure ◽  
Cytochalasin D ◽  
Reversible Inhibitor ◽  
Dependent Manner ◽  
Inhibitor Of Protein Synthesis ◽  
Cytoskeletal Elements ◽  
Mrna Binding

Cytochalasin D was shown to be a reversible inhibitor of protein synthesis in HeLa cells. The inhibition was detectable at drug levels typically used to perturb cell structure and increased in a dose-dependent manner. The drug also released mRNA from the cytoskeletal framework in direct proportion to the inhibition of protein synthesis. The released mRNA was unaltered in its translatability as measured in vitro but was no longer translated in the cytochalasin-treated HeLa cells. The residual protein synthesis occurred on polyribosomes that were reduced in amount but displayed a normal sedimentation distribution. The results support the hypothesis that mRNA binding to the cytoskeletal framework is necessary although not sufficient for translation. Analysis of the cytoskeletal framework, which binds the polyribosomes, revealed no alterations in composition or amount of protein as a result of treatment with cytochalasin D. Electron microscopy with embedment-free sections shows the framework in great detail. The micrographs revealed the profound reorganization effected by the drug but did not indicate substantial disaggregation of the cytoskeletal elements.

Synthesis of protein and nucleic acid in enucleate cytoplasm

1958 ◽  
Vol 148 (932) ◽  
pp. 332-339 ◽  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Cell Structure ◽  
Genetic Material ◽  
Amino Acid Uptake ◽  
Amoeba Proteus ◽  
Cytoplasmic Process ◽  
Nuclear Fraction ◽  
Acid Uptake

It is now well established that the formation of the individual proteins is controlled by the nuclear genetic material. The question which immediately arises is: are the proteins synthesized in the nucleus? If the liver of a rat which has been injected with a labelled amino acid is homogenized and if the cellular components are separated by the usual fractionation techniques, the microsome fraction contains the most radioactive proteins, and the nuclei are not especially active. Moreover, if the incorporation is carried out in the homogenate in vitro , the presence of the nuclear fraction has no effect on the amino acid uptake by the microsomal proteins (Siekevitz 1952; Keller, Zamecnik & Loftfield 1954; Hultin 1950, 1955). Since the microsomes are pieces of a major cytoplasmic structure (Bernhard, Gautier & Rouiller 1954; Palade & Siekevitz 1956), it would seem that protein synthesis is a cytoplasmic process. Experiments with homogenates are not entirely convincing, however, because the destruction of the cell structure might change the distribution of certain constituents among the fractions; it is known, for instance, that a considerable part of the nuclear proteins are released in the medium used for fractionation (Stern & Mirsky 1954). A direct way to find out whether cytoplasmic proteins are synthesized in the nucleus or in the cytoplasm is to study the capacity for protein synthesis of non-nucleate cytoplasm, or better to compare a nucleus-free fragment of cytoplasm with a fragment of the same cytoplasm containing the nucleus. Two very different unicellular organisms have been used for studies of this type by Brachet (1954 b , 1956; Brachet & Chantrenne 1956); Amoeba proteus and a green alga Acetabularia mediterranea . Both can be cut into nucleate and enucleate parts which will survive for a considerable time.

scholarly journals Symposium 20 - PABMB: Teaching biochemistry in a connected world: How Apps-Embedded Assessment can contribute to learning outcomes mapping

2015 ◽  
Vol 13 ◽  
pp. 42
Author(s):  
Eduardo Galembeck
Keyword(s):  
Protein Synthesis ◽  
Learning Outcomes ◽  
Metabolic Pathways ◽  
Educational Software ◽  
Cell Structure ◽  
Formative Assessments ◽  
Map Learning ◽  
Embedded Assessment ◽  
Preliminary Results ◽  
Usage Data

Symposium 20 - PABMB: Teaching biochemistry in a connected world Chair: Miguel Castanho, Universidade de Lisboa, PortugalAbstract:Apps can be designed to provide usage data, and most of them do. These usage data are usually used to map users interests and to deliver more effective ads that are more likely to result in clicks, and sales. We have applied some of these metrics to understand how it can be used to map students’ behavior using educational software. We tested both Google Analytics, and a system we have developed to map learning outcomes and students engagement. Embedded assessment were implemented in app used to teach: 1) Metabolic Pathways; 2) Protein Synthesis, 3) Cell Structure, and 4) Concepts from techniques used in a Biochemistry Lab course. Our preliminary results show that this approach provides valuable information about class outcomes that can be used for both summative and formative assessments.

Homochirality as the Signature of Extra-Terrestrial Life

1997 ◽  
Vol 161 ◽  
pp. 505-510
Author(s):  
Alexandra J. MacDermott ◽  
Laurence D. Barron ◽  
Andrè Brack ◽  
Thomas Buhse ◽  
John R. Cronin ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Optical Rotation ◽  
Physical Origin ◽  
Natural Choice ◽  
Rosetta Mission ◽  
Terrestrial Life ◽  
Subsurface Layers ◽  
Solar System Bodies ◽  
Origin Of Homochirality

AbstractThe most characteristic hallmark of life is its homochirality: all biomolecules are usually of one hand, e.g. on Earth life uses only L-amino acids for protein synthesis and not their D mirror images. We therefore suggest that a search for extra-terrestrial life can be approached as a Search for Extra- Terrestrial Homochirality (SETH). The natural choice for a SETH instrument is optical rotation, and we describe a novel miniaturized space polarimeter, called the SETH Cigar, which could be used to detect optical rotation as the homochiral signature of life on other planets. Moving parts are avoided by replacing the normal rotating polarizer by multiple fixed polarizers at different angles as in the eye of the bee. We believe that homochirality may be found in the subsurface layers on Mars as a relic of extinct life, and on other solar system bodies as a sign of advanced pre-biotic chemistry. We discuss the chiral GC-MS planned for the Roland lander of the Rosetta mission to a comet and conclude with theories of the physical origin of homochirality.

High-pressure freezing of cells in suspension for low-voltage scanning electron microscopy (LVSEM)

1991 ◽  
Vol 49 ◽  
pp. 64-65
Author(s):  
Marek Malecki ◽  
James Pawley ◽  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Low Voltage ◽  
Culture Media ◽  
Cell Structure ◽  
Freeze Substitution ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Culture Media ◽  
Voltage Scanning

The ultrastructure of cells suspended in physiological fluids or cell culture media can only be studied if the living processes are stopped while the cells remain in suspension. Attachment of living cells to carrier surfaces to facilitate further processing for electron microscopy produces a rapid reorganization of cell structure eradicating most traces of the structures present when the cells were in suspension. The structure of cells in suspension can be immobilized by either chemical fixation or, much faster, by rapid freezing (cryo-immobilization). The fixation speed is particularly important in studies of cell surface reorganization over time. High pressure freezing provides conditions where specimens up to 500μm thick can be frozen in milliseconds without ice crystal damage. This volume is sufficient for cells to remain in suspension until frozen. However, special procedures are needed to assure that the unattached cells are not lost during subsequent processing for LVSEM or HVEM using freeze-substitution or freeze drying. We recently developed such a procedure.

Cell structure properties during in situ creep experiments in the H.V.E.M.

1978 ◽  
Vol 36 (1) ◽  
pp. 574-575
Author(s):  
D. Caillard ◽  
J.L. Martin
Keyword(s):  
Tensile Axis ◽  
Cell Structure ◽  
Image Intensifier ◽  
Foil Thickness ◽  
Average Cell Size ◽  
Average Cell ◽  
Voltage Electron ◽  
Steady Stage ◽  
Stationary Creep

The behaviour of the dislocation substructure during the steady stage regime of creep, as well as its contribution to the creep rate, are poorly known. In particular, the stability of the subboundaries has been questioned recently, on the basis of experimental observations |1||2| and theoretical estimates |1||3|. In situ deformation experiments in the high voltage electron microscope are well adapted to the direct observation of this behaviour. We report here recent results on dislocation and subboundary properties during stationary creep of an aluminium polycristal at 200°C.During a macroscopic creep test at 200°C, a cell substructure is developed with an average cell size of a few microns. Microsamples are cut out of these specimens |4| with the same tensile axis, and then further deformed in the microscope at the same temperature and stain rate. At 1 MeV, one or a few cells can be observed in the foil thickness |5|. Low electron fluxes and an image intensifier were used to reduce radiation damage effects.

High-pressure freezing and freeze substitution of plant tissue

1992 ◽  
Vol 50 (1) ◽  
pp. 748-749
Author(s):  
William P. Sharp ◽  
Robert W. Roberson
Keyword(s):  
High Pressure ◽  
Cell Structure ◽  
Leaf Tissue ◽  
Freeze Substitution ◽  
Crystal Formation ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Components ◽  
Cold Metal ◽  
Brome Grass

The aim of ultrastructural investigation is to analyze cell architecture and relate a functional role(s) to cell components. It is known that aqueous chemical fixation requires seconds to minutes to penetrate and stabilize cell structure which may result in structural artifacts. The use of ultralow temperatures to fix and prepare specimens, however, leads to a much improved preservation of the cell’s living state. A critical limitation of conventional cryofixation methods (i.e., propane-jet freezing, cold-metal slamming, plunge-freezing) is that only a 10 to 40 μm thick surface layer of cells can be frozen without distorting ice crystal formation. This problem can be allayed by freezing samples under about 2100 bar of hydrostatic pressure which suppresses the formation of ice nuclei and their rate of growth. Thus, 0.6 mm thick samples with a total volume of 1 mm3 can be frozen without ice crystal damage. The purpose of this study is to describe the cellular details and identify potential artifacts in root tissue of barley (Hordeum vulgari L.) and leaf tissue of brome grass (Bromus mollis L.) fixed and prepared by high-pressure freezing (HPF) and freeze substitution (FS) techniques.

Structural integrity after cold storage of human epidermal model in hypothermosol: A correlative ultrastructural and fluorescent assay

1994 ◽  
Vol 52 ◽  
pp. 270-271
Author(s):  
Henry H. Eichelberger ◽  
John G. Baust ◽  
Robert G. Van Buskirk
Keyword(s):  
Cold Storage ◽  
Structural Integrity ◽  
Culture Media ◽  
Cell Structure ◽  
Natural State ◽  
Sodium Cacodylate ◽  
Ruthenium Tetroxide ◽  
Cacodylate Buffer ◽  
Before And After

For research in cell differentiation and in vitro toxicology it is essential to provide a natural state of cell structure as a benchmark for interpreting results. Hypothermosol (Cryomedical Sciences, Rockville, MD) has proven useful in insuring the viability of synthetic human epidermis during cold-storage and in maintaining the epidermis’ ability to continue to differentiate following warming.Human epidermal equivalent, EpiDerm (MatTek Corporation, Ashland, MA) consisting of fully differentiated stratified human epidermal cells were grown on a microporous membrane. EpiDerm samples were fixed before and after cold-storage (4°C) for 5 days in Hypothermosol or skin culture media (MatTek Corporation) and allowed to recover for 7 days at 37°C. EpiDerm samples were fixed 1 hour in 2.5% glutaraldehyde in sodium cacodylate buffer (pH 7.2). A secondary fixation with 0.2% ruthenium tetroxide (Polysciences, Inc., Warrington, PA) in sodium cacodylate was carried out for 3 hours at 4°C. Other samples were similarly fixed, but with 1% Osmium tetroxide in place of ruthenium tetroxide. Samples were dehydrated through a graded acetone series, infiltrated with Spurrs resin (Polysciences Inc.) and polymerized at 70°C.

Confocal microscopy of the cytoskeleton in living plant cells following microinjection of fluorescent probes

1993 ◽  
Vol 51 ◽  
pp. 130-131
Author(s):  
Ann Cleary
Keyword(s):  
Cell Division ◽  
Fluorescent Probes ◽  
Actin Filaments ◽  
Intracellular Transport ◽  
Cell Structure ◽  
Plant Cells ◽  
Cell Plate ◽  
Cell Cortex ◽  
Living Plant ◽  
Rhodamine Phalloidin

Microinjection of fluorescent probes into living plant cells reveals new aspects of cell structure and function. Microtubules and actin filaments are dynamic components of the cytoskeleton and are involved in cell growth, division and intracellular transport. To date, cytoskeletal probes used in microinjection studies have included rhodamine-phalloidin for labelling actin filaments and fluorescently labelled animal tubulin for incorporation into microtubules. From a recent study of Tradescantia stamen hair cells it appears that actin may have a role in defining the plane of cell division. Unlike microtubules, actin is present in the cell cortex and delimits the division site throughout mitosis. Herein, I shall describe actin, its arrangement and putative role in cell plate placement, in another material, living cells of Tradescantia leaf epidermis.The epidermis is peeled from the abaxial surface of young leaves usually without disruption to cytoplasmic streaming or cell division. The peel is stuck to the base of a well slide using 0.1% polyethylenimine and bathed in a solution of 1% mannitol +/− 1 mM probenecid.

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