A comparison of three cryotechniques (freeze-drying, cryosubstitution, cryosectioning) of specimen preparation for immunolabelling of bacterial antigens of Coxiella burnetii

1994 ◽  
Vol 52 ◽  
pp. 140-141
Author(s):  
T. F. McCaul ◽  
R. J. Gould
Keyword(s):  
Coxiella Burnetii ◽  
Freeze Drying ◽  
Stress Proteins ◽  
Cultured Cells ◽  
High Specificity ◽  
Specimen Preparation ◽  
Bacterial Antigens ◽  
Structural Preservation ◽  
Nuclear Ribonucleoprotein ◽  
Cellular Components

Immuno-electron microscopy has allowed the selective localisation of molecules with high resolution and high specificity. Cryopreparatory methods have provided better retention of antigenicity suitable for precise immunolabelling together with optimal structural preservation of cellular components. Cryosubstitution and cryoultramicrotomy have widely been exploited for immunolabelling. Molecular Distillation Dryer (MDD), a form of freeze-drying technique, has recently been used for immunolabelling of Plasmodium falciparum stress proteins and nuclear ribonucleoprotein particles in cultured cells. In the present study, we report the comparison of all three cryotechniques in the immunolabelling of bacterial antigens of Coxiella burnetii.The highly infectious C. burnetii was prefixed in 3% glutaraldehyde (66 mM cacodylate buffer, pH 6.8 ). The cells were then pre-embedded in 2% low-temperature agarose on Durapore hydrophilic membrane prior to cryofixation using a LifeCell CF100 metal-mirror system. A 1% glutaraldehyde in 100% methanol was used as a medium for cryosubstitution in a Reichert CS Auto Cryosubstitution apparatus.

High-Resolution Scanning Electron Microscopy of Biological Specimens

1988 ◽  
Vol 46 ◽  
pp. 186-187
Author(s):  
M. Müller ◽  
R. Hermann
Keyword(s):  
High Resolution ◽  
Freeze Drying ◽  
Room Temperature ◽  
Structural Information ◽  
Freeze Substitution ◽  
Critical Point Drying ◽  
Sem Study ◽  
Major Factors ◽  
Structural Preservation ◽  
Preparation Techniques

Three major factors must be concomitantly assessed in order to extract relevant structural information from the surface of biological material at high resolution (2-3nm).Procedures based on chemical fixation and dehydration in graded solvent series seem inappropriate when aiming for TEM-like resolution. Cells inevitably shrink up to 30-70% of their initial volume during gehydration; important surface components e.g. glycoproteins may be lost. These problems may be circumvented by preparation techniques based on cryofixation. Freezedrying and freeze-substitution followed by critical point drying yields improved structural preservation in TEM. An appropriate preservation of dimensional integrity may be achieved by freeze-drying at - 85° C. The sample shrinks and may partially collapse as it is warmed to room temperature for subsequent SEM study. Observations at low temperatures are therefore a necessary prerequisite for high fidelity SEM. Compromises however have been unavoidable up until now. Aldehyde prefixation is frequently needed prior to freeze drying, rendering the sample resistant to treatment with distilled water.

scholarly journals A comprehensive approach for artifact-free sample preparation and assessment of mitochondrial morphology in tissue and cultured cells

2021 ◽  
Author(s):  
Antentor Hinton ◽  
Prasanna Katti ◽  
Trace A. Christensen ◽  
Margaret Mungai ◽  
Jianqiang Shao ◽  
...  
Keyword(s):  
Structural Changes ◽  
Cultured Cells ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Morphology ◽  
Specimen Preparation ◽  
Preparation Methods ◽  
Cellular Environment ◽  
Stress Changes ◽  
Precise Relationship ◽  
And Function

Mitochondrial dynamics and morphology (fission, fusion, and the formation of nanotunnels) are very sensitive to the cellular environment and may be adversely affected by oxidative stress, changes in calcium levels, and hypoxia. Investigating the precise relationship between the organelle structure and function requires methods that can adequately preserve the structure while providing accurate, quantitative measurements of mitochondrial morphological attributes. Here, we demonstrate a practical approach for preserving and measuring fine structural changes in two-dimensional electron micrographs, obtained using transmission electron microscopy, highlighting the specific advantages of this technique. Additionally, this study defines a set of quantifiable metrics that can be applied to measure mitochondrial architecture and other organellar structures. Finally, we validated specimen preparation methods that avoid the introduction of morphological artifacts in mitochondrial appearance that do not require whole-animal perfusion.

scholarly journals Microtrabecular lattice of the cytoplasmic ground substance. Artifact or reality.

1979 ◽  
Vol 82 (1) ◽  
pp. 114-139 ◽  
Author(s):  
J J Wolosewick ◽  
K R Porter
Keyword(s):  
Critical Point ◽  
Osmium Tetroxide ◽  
Prolonged Exposure ◽  
Cultured Cells ◽  
Lattice Structure ◽  
Model Systems ◽  
Ground Substance ◽  
Specimen Preparation ◽  
Critical Point Drying ◽  
Cytoplasmic Ground Substance

The cytoplasmic ground substance of cultured cells prepared for high voltage transmission electron microscopy (glutaraldehyde/osmium fixed, alcohol or acetone dehydrated, critical-point dried) consists of slender (3-6 nm Diam) strands--the microtrabeculae (55)--that form an irregular three-dimensional lattice (the microtrabecular lattice). The microtrabeculae interconnect the membranous and nonmembranous organelles and are confluent with the cortices of the cytoplast. The lattice is found in all portions of the cytoplast of all cultured cells examined. The possibility that the lattice structure is an artifact of specimen preparation has been tested by (a) subjecting whole cultured cells (WI-38, NRK, chick embryo fibroblasts) to various chemical (aldehydes, osmium tetroxide) and nonchemical (freezing) fixation schedules, (b) examination of model systems (erythrocytes, protein solutions), (c) substantiating the relaibility of critical-point drying, and (d) comparing images of whole cells with conventionally prepared (plastic-embedded) cells. The lattice structure is preserved by chemical and nonchemical fixation, though alterations in ultrastructure can occur especially after prolonged exposure to osmium tetroxide. The critical-point method for drying specimens appears to be reliable as is the freeze-drying method. The discrepancies between images of plastic-embedded and sectioned cells, and images of whole, critical-point dried cells appear to be related, in part, to the electron-scattering properties of the embedding resin. The described observations indicate that the microtrabecular lattice seen in electron micrographs closely represents the nonrandom structure of the cytoplasmic ground substance of living cultured cells.

P5379Modification with CREKA improves cell retention of myocardial ischemia reperfusion

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
J Chen ◽  
Y N Song ◽  
Z Y Huang
Keyword(s):  
Stem Cells ◽  
Functional Recovery ◽  
Cellular Therapy ◽  
Tissue Injury ◽  
Ischemia Reperfusion ◽  
High Specificity ◽  
Homing Peptide ◽  
Structural Preservation

Abstract Background Poor cell homing limits efficacy of cardiac cellular therapy. The cysteine–arginine–glutamic acid–lysine–alanine (CREKA) homing peptide binds with high specificity to fibrin which is involved in repair of tissue injury. Purpose We assessed if CREKA-modified stem cells had enhanced fibrin-mediated homing ability resulting in better functional recovery and structural preservation in a rat myocardial injury model. Methods CREKA-modified mesenchymal stem cells (CREKA-MSCs) were obtained via membrane fusion with CREKA-modified liposomes. The fibrin targeting ability of CREKA-MSCs was examined both in vitro and in vivo. Results Under both static and flow conditions in vitro, CREKA significantly enhanced MSCs binding ability to fibrin clots. CREKA-MSCs showed much more higher accumulation than unmodified MSCs in injured rat myocardium, colocalizing with fibrin and resulting in better cardiac function. Stem cell-CREKA-fibrin targeting system Conclusions Modification of MSCs with the homing peptide CREKA favored their migration and retention in the infarcted area, resulting in better structural preservation and functional recovery. Fibrin is therefore a novel target for enhancing homing of transplanted cells to injured myocardium and the fibrin-targeting delivery system represents a generalizable platform technology for regenerative medicine.

scholarly journals Heat shock alters nuclear ribonucleoprotein assembly in Drosophila cells.

1983 ◽  
Vol 3 (2) ◽  
pp. 161-171 ◽  
Author(s):  
S Mayrand ◽  
T Pederson
Keyword(s):  
Heat Shock ◽  
Mammalian Cells ◽  
Cultured Cells ◽  
Particle Structure ◽  
Nuclear Maturation ◽  
Shock Response ◽  
Nuclear Rna ◽  
Nuclear Ribonucleoprotein ◽  
Drosophila Cells

Heterogeneous nuclear RNA is normally complexed with a specific set of proteins, forming ribonucleoprotein particles termed hnRNP. These particles are likely to be involved in mRNA processing. We have found that the structure of hnRNP is profoundly altered during the heat shock response in Drosophila cultured cells. Although hnRNA continues to be synthesized at a near-normal rate during heat shock, its assembly into hnRNP is incomplete, as evidenced by a greatly decreased protein content of the particles in Cs2SO4 density gradients. RNA-protein cross-linking conducted in vivo (Mayrand and Pederson, Proc. Natl. Acad. Sci. U.S.A. 78:2208-2212, 1981) also reveals that hnRNA made during heat shock is complexed with greatly reduced amounts of protein. The block of hnRNP assembly occurs immediately upon heat shock, even before the onset of heat shock protein synthesis. Additional experiments reveal that hnRNP assembled normally at 25 degrees C subsequently disassembles during heat shock. The capacity for normal hnRNP assembly is gradually restored after heat-shocked cells are returned to 25 degrees C. Heat-shocked mammalian cells also show a similar block in hnRNP assembly. We suggest that incomplete assembly of hnRNP during heat shock leads to abortive processing of most mRNA precursors and favors the processing or export (or both) of others whose pathway of nuclear maturation is less dependent on, or even independent of, normal hnRNP particle structure. This hypothesis is compatible with a large number of previous observations.

scholarly journals Critical Role for Molecular Iron in Coxiella burnetii Replication and Viability

mSphere ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Savannah E. Sanchez ◽  
Anders Omsland
Keyword(s):  
Host Cell ◽  
Coxiella Burnetii ◽  
Cultured Cells ◽  
Critical Role ◽  
Host Cells ◽  
Physiological Adaptation ◽  
Iron Starvation ◽  
Iron Storage ◽  
Content Type ◽  
Forms Of Iron

ABSTRACT Coxiella burnetii, the causative agent of Query (Q) fever in humans, is a highly infectious obligate intracellular bacterium. Following uptake into a host cell, C. burnetii replicates within a phagolysosome-derived compartment referred to as the Coxiella-containing vacuole (CCV). During infection, C. burnetii exhibits tropism for tissues related to iron storage and recycling (e.g., the liver and splenic red pulp), suggesting that pathogen physiology is linked to host iron metabolism. Iron has been described to have a limited role in C. burnetii virulence regulation, despite evidence that C. burnetii-infected host cells increase expression of transferrin receptors, thereby suggesting that active iron acquisition by the bacterium occurs upon infection. Through the use of host cell-free culture, C. burnetii was separated from the host cell in order to directly assess the role of different forms of iron in C. burnetii replication and viability, and therefore virulence. Results indicate that C. burnetii tolerates molecular iron over a broad concentration range (i.e., ∼0.001 to 1 mM) and undergoes gross loss of viability upon iron starvation. C. burnetii protein synthesis and energy metabolism, however, occur nearly uninhibited under iron concentrations not permissive to replication. Despite the apparent absence of genes related to acquisition of host-associated iron-containing proteins, C. burnetii replication is supported by hemoglobin, transferrin, and ferritin, likely due to release of iron from such proteins under acidic conditions. Moreover, chelation of host iron pools inhibited pathogen replication during infection of cultured cells. IMPORTANCE Host organisms restrict the availability of iron to invading pathogens in order to reduce pathogen replication. To counteract the host’s response to infection, bacteria can rely on redundant mechanisms to obtain biologically diverse forms of iron during infection. C. burnetii appears specifically dependent on molecular iron for replication and viability and exhibits a response to iron akin to bacteria that colonize iron-rich environments. Physiological adaptation of C. burnetii to the unique acidic and degradative environment of the CCV is consistent with access of this pathogen to molecular iron.

Ultrastructure of Epicuticular Wax in Canola

1989 ◽  
Vol 44 (7-8) ◽  
pp. 705-711 ◽  
Author(s):  
K. L. Conn ◽  
J. P. Tewari
Keyword(s):  
Freeze Drying ◽  
Brassica Campestris ◽  
Amorphous Layer ◽  
Epicuticular Wax ◽  
Drying Methods ◽  
Specimen Preparation ◽  
Drying Method ◽  
Air Drying ◽  
Species Specific ◽  
Wax Crystals

Ultrastructure of the epicuticular wax of four commercially grown Canadian cultivars of canola (Brassica campestris cvs. Tobin and Candle, B. napus cvs. Altex and Westar) was investigated. Freeze-drying and air-drying methods of specimen preparation for scanning electron microscopy were compared. The freeze-drying method resulted in disruption and possible washing away of wax crystals, whereas there was no visible damage with the air-drying method. The freeze-drying method provided evidence for an amorphous layer of wax beneath the wax crystals. Ultrastructure of wax in the four cultivars was generally similar. All cultivars had an evenly distributed layer of wax crystals superimposed on an amorphous layer of wax. Some trends such as density of wax on leaves and siliques appeared to be species-specific, whereas density of wax on stems did not. There appeared to be at least three types of wax crystals present. These included plate-like, filamentous, and rod-like crystals. The rods were present singly or in blocks.

scholarly journals Molecular Characterization of a Novel, Widespread Nuclear Protein That Colocalizes with Spliceosome Components

1998 ◽  
Vol 9 (1) ◽  
pp. 143-160 ◽  
Author(s):  
Marion S. Schmidt-Zachmann ◽  
Sylvia Knecht ◽  
Angela Krämer
Keyword(s):  
Molecular Characterization ◽  
Nuclear Protein ◽  
Cultured Cells ◽  
Splicing Factors ◽  
Nuclear Speckles ◽  
Sm Proteins ◽  
Small Nuclear Ribonucleoprotein ◽  
Ribonucleoprotein Particles ◽  
Nuclear Ribonucleoprotein

We report the identification and molecular characterization of a novel type of constitutive nuclear protein that is present in diverse vertebrate species, from Xenopus laevis to human. The cDNA-deduced amino acid sequence of the Xenopus protein defines a polypeptide of a calculated mass of 146.2 kDa and a isoelectric point of 6.8, with a conspicuous domain enriched in the dipeptide TP (threonine-proline) near its amino terminus. Immunolocalization studies in cultured cells and tissues sections of different origin revealed an exclusive nuclear localization of the protein. The protein is diffusely distributed in the nucleoplasm but concentrated in nuclear speckles, which represent a subnuclear compartment enriched in small nuclear ribonucleoprotein particles and other splicing factors, as confirmed by colocalization with certain splicing factors and Sm proteins. During mitosis, when transcription and splicing are downregulated, the protein is released from the nuclear speckles and transiently dispersed throughout the cytoplasm. Biochemical experiments have shown that the protein is recovered in a ∼12S complex, and gel filtration studies confirm that the protein is part of a large particle. Immunoprecipitation and Western blot analysis of chromatographic fractions enriched in human U2 small nuclear ribonucleoprotein particles of distinct sizes (12S, 15S, and 17S), reflecting their variable association with splicing factors SF3a and SF3b, strongly suggests that the 146-kDa protein reported here is a constituent of the SF3b complex.

A dramatic pH-dependent alteration in ANP receptor density: a note for using cultured cells

1993 ◽  
Vol 264 (5) ◽  
pp. C1345-C1349 ◽  
Author(s):  
T. Katafuchi ◽  
H. Hagiwara ◽  
T. Ito ◽  
S. Hirose
Keyword(s):  
Cultured Cells ◽  
Culture Media ◽  
Buffer System ◽  
Batch Cultures ◽  
Ph Values ◽  
Bovine Endothelial Cells ◽  
Number Of Binding Sites ◽  
The Media ◽  
Anp Receptors ◽  
Cellular Components

Culture media tend to become acidic when rapidly growing cells are cultured under batch conditions using a CO2/HCO3- buffer system. The effects of this inherent lowering of pH on cellular makeup of cultured cells, which have long been ignored, were examined by monitoring the pH and number of the atrial natriuretic peptide (ANP) receptors expressed on the cultured bovine endothelial cells. The Eagle's minimum essential medium was adjusted to three different pH values of 7.0, 7.4, and 7.7 and used for 48-h batch cultures. After this 48-h incubation, the pH values of the media were found to be 7.0, 7.1, and 7.4, respectively. These pH shifts had unexpectedly strong influences on the ANP receptor levels without affecting the affinity. Cells maintained in the slightly higher pH medium had a trace amount of the receptor (< 10 sites/cell), while those in the lower pH environment exhibited a large number of binding sites (40,000 sites/cell). Similar situations might occur in other cellular components and in other types of cells, and therefore, such possibilities should be kept in mind when cultured cell systems are used.

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