Structure of agarose gels: Mean pore radius

1989 ◽  
Vol 47 ◽  
pp. 884-885
Author(s):  
Gary A. Griess ◽  
Philip Serwer
Keyword(s):  
Osmium Tetroxide ◽  
Pore Radius ◽  
Agarose Gel Electrophoresis ◽  
Gel Structure ◽  
Biophysical Characterization ◽  
Thin Sections ◽  
Agarose Gels ◽  
Transmission Electron ◽  
Self Consistent

To use an agarose gel's sieving for the biophysical characterization of macromolecules and supramolecular complexes, the effective gel's pore radius (PE) is determined as a function of the agarose percentage (A). In previous studies, performed by use of agarose gel electrophoresis, the sieving of spheres of known radius (R) was used, together with two different (unproven) theories of sieving, to obtain PE. The PE values obtained were self-consistent and independent of R. The PE vs. A relationship did not agree with that predicted by a model that represents the gel as straight, randomly-oriented fibers (random fiber model). To test the accuracy of both the empirical PE vs. A relationship and the previously assumed model of gel structure, in the present study thin sections of agarose gels have been examined by use of electron microscopy.Gels of the agarose previously used to quantify sieving (SeaKem LE, Marine Colloids) were cast in the buffer previously used: 0.025 M sodium phosphate, pH 7.4, 0.001M MgCl2. Pieces of gel were fixed with osmium tetroxide, dehydrated and embedded in Epon. Dark gold (120 nm) sections were examined with a JEM-100CX transmission electron microscope. Electron micrographs were captured with a DataTranslation QuickCapture video digitizer and were processed on a Macintosh II computer using the program, Image.4

Observations of thick and thin sections in a field-emission SEM

1994 ◽  
Vol 52 ◽  
pp. 1018-1019
Author(s):  
W. P. Wergin ◽  
S. Roy ◽  
E. F. Erbe ◽  
C. A. Murphy ◽  
C. D. Pooley
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Room Temperature ◽  
Osmium Tetroxide ◽  
Uranyl Acetate ◽  
Chemical Fixation ◽  
Thin Sections ◽  
Transmission Electron ◽  
Conventional Transmission Electron Microscope ◽  
Scanning Electron

Larvae of the nematode, Steinernema carpocapsae Weiser strain All, were cryofixed and freezesubstituted for 3 days in acetone containing 2% osmium tetroxide according to established procedures. Following chemical fixation, the nematodes were brought to room temperature, embedded in Spurr's medium and sectioned for observation with a Hitachi S-4100 field emission scanning electron microscope that was equipped with an Oxford CT 1500 Cryotrans System. Thin sections, about 80 nm thick, similar to those generally used in conventional transmission electron microscope (TEM) studies were mounted on copper grids and stained with uranyl acetate for 30 min and lead citrate for 5 min. Sections about 2 μm thick were also mounted and stained in a similar fashion. The grids were mounted on an Oxford grid holder, inserted into the microscope and onto a cryostage that was operated at ambient temperature. Thick and thin sections of the larvae were evaluated and photographed in the SEM at different accelerating voltages. Figs. 4 and 5 have undergone contrast conversion so that the images would resemble transmitted electron micrographs obtained with a TEM.

Transmission Electron Microscopy of Lipid Vesicles for Drug Delivery: Comparison between Positive and Negative Staining

2010 ◽  
Vol 16 (4) ◽  
pp. 456-461 ◽  
Author(s):  
Valentina Bello ◽  
Giovanni Mattei ◽  
Paolo Mazzoldi ◽  
Nicoletta Vivenza ◽  
Paolo Gasco ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Drug Delivery ◽  
Transmission Electron Microscopy ◽  
Iron Oxide ◽  
Osmium Tetroxide ◽  
Lipid Vesicles ◽  
Negative Staining ◽  
Transmission Electron ◽  
Compositional Characterization

AbstractLipid-containing nanostructures, in the form of solid lipid nanoparticles or iron oxide nanoparticles (NPs) coated with a lipid shell, were used as case studies for assessing and optimizing staining for transmission electron microscopy structural and compositional characterization. These systems are of paramount importance as drug delivery systems or as bio-compatible contrast agents. In particular, we have treated the systems with a negative (phospshotungstic acid) or with a positive (osmium tetroxide) staining agent. For iron-oxide NPs coated with the lipid shell, negative staining was more efficient with respect to the positive one. Nevertheless, in particular cases the combination of the two staining procedures provided more complete morphological and compositional characterization of the particles.

Ultrastructure of lymphatic endothelium

1989 ◽  
Vol 47 ◽  
pp. 924-925
Author(s):  
A. Singh ◽  
D.N. Ezeasor ◽  
N.K. Sidhu
Keyword(s):  
Osmium Tetroxide ◽  
Healthy Adult ◽  
West African ◽  
Lymphatic Endothelium ◽  
Vascular Perfusion ◽  
Thin Sections ◽  
Continuous Layer ◽  
Transmission Electron ◽  
Cacodylate Buffer ◽  
Flocculent Material

Recently, the lymphatics in the caprine hemal nodes have been described. The present study describes some ultrastructural features of the endothelium in the lymphatics of the goat hemal nodes.Hemal nodes located along the aorta, were collected from 15 clinically healthy, adult, West African dwarf goats. The tissues were fixed by either immersion or perfusion methods. For immersion fixation, the nodes were excised, and immersed temporarily in cold 2.5% glutaraldehyde in 0. IM cacodylate buffer, pH 7.3. After 5 min, the nodes were diced into 1-2 mm cubes and further fixed for 2 h in the same fixative. The par-aortic nodes were fixed by vascular perfusion. The two batches of tissues were post-fixed in 2% osmium tetroxide in cacodylate buffer, and further processing was done by conventional methods for transmission electron microscopy. The thin sections were examined and photographed in a Hitachi H-7000 electron microscope.The lymphatic wall comprised a continuous layer of fenestrated endothelial cells. The nuclei were oval and contained heterochromatin. The cytoplasm exhibited fenestrations that were closed by a membrane, and vesicular compartments bound on luminal and/or abluminal aspects by fenestrated membranes(Fig. 1). occasionally lymphocytes(Fig. 2) or erthyrocytes, most probably intransit, occupied these compartments. In material fixed by immersion, most of the vesicles contained flocculent material similar to that contained in the lumen(Fig. 3).

Electron Microscopy as an aid to diagnosis in pediatric hematology/oncology

1989 ◽  
Vol 47 ◽  
pp. 1062-1063
Author(s):  
K. L. Saving ◽  
R. C. Caughey
Keyword(s):  
Electron Microscopy ◽  
Phosphate Buffer ◽  
Osmium Tetroxide ◽  
Uranyl Acetate ◽  
En Bloc ◽  
Thin Sections ◽  
Megakaryoblastic Leukemia ◽  
Pediatric Hematology ◽  
Transmission Electron ◽  
Microscopy Techniques

This presentation is designed to demonstrate how scanning and transmission electron microscopy techniques can be utilized to confirm or support a variety of unusual pediatric hematologic/oncologic disorders. Patients with the following diagnoses will be presented: (1) hereditary pyropoikilocytosis, (2) familial erythrophagocytic lymphohistiocytosis, (3) acute megakaryoblastic leukemia, and (4) pseudo-von Willebrand’s disease.All transmission and scanning electron microscopy samples were fixed in 2.5% glutaraldehyde, rinsed in Millonig’s phosphate buffer, and post-fixed with 1% osmium tetroxide. The transmission samples were then en bloc stained with 0.5% uranyl acetate, rinsed with Walpole ’ s non-phosphate buffer, dehydrated with graded series of ethanols and embedded with Epon 812 epoxy resin. Ultramicrotomy thin sections were stained with uranyl acetate and lead citrate and scanned using a JEOL-JEM 100C, The scanning samples were dehydrated with graded series of ethanols, critical point dried with CO2, gold-coated, and scanned using a JEOL-JSM 35. The peroxidase samples were fixed in 3% glutaraldehyde, incubated in diaminobenzidine (DAB), dehydrated with ethanol, embedded with Epon 812, and scanned without post-staining using a JEOL-JEM 100C.

scholarly journals Characterization of a Latent Virus-Like Infection of Symbiotic Zooxanthellae

2007 ◽  
Vol 73 (9) ◽  
pp. 2976-2981 ◽  
Author(s):  
Jayme Lohr ◽  
Colin B. Munn ◽  
William H. Wilson
Keyword(s):  
Uv Light ◽  
Latent Virus ◽  
Thin Sections ◽  
Virus Like Particles ◽  
Transmission Electron ◽  
Uv Irradiance ◽  
Virus System ◽  
Insight Into

ABSTRACT A latent virus-like agent, which we designated zooxanthella filamentous virus 1 (ZFV1), was isolated from Symbiodinium sp. strain CCMP 2465 and characterized. Transmission electron microscopy and analytical flow cytometry revealed the presence of a new group of distinctive filamentous virus-like particles after exposure of the zooxanthellae to UV light. Examination of thin sections of the zooxanthellae revealed the formation and proliferation of filamentous virus-like particles in the UV-induced cells. Assessment of Symbiodinium sp. cultures was used here as a model to show the effects of UV irradiance and induction of potential latent viruses. The unique host-virus system described here provides insight into the role of latent infections in zooxanthellae through environmentally regulated viral induction mechanisms.

Ultrastructural Changes in Oral Mucosa After Topical Application of Nicotine

1990 ◽  
Vol 48 (3) ◽  
pp. 232-233
Author(s):  
J.E. Laffoon ◽  
M.J. Kremer ◽  
C.A. Squier ◽  
C.A. Lesch
Keyword(s):  
Oral Mucosa ◽  
Osmium Tetroxide ◽  
Ultrastructural Changes ◽  
Epithelial Surface ◽  
Potential Health ◽  
Thin Sections ◽  
Transmission Electron ◽  
Attached Gingiva ◽  
Cacodylate Buffer ◽  
Phosphate Buffered Saline

The potential health risks involved with the use of smokeless tobacco have been well documented. This habit involves the placement of tobacco containing 0.2-8.0% nicotine directly on the oral mucosa. It is possible that such levels of nicotine may have a directly injurious effect; we have examined this using pig oral mucosa, which has a similar oral mucosa to that of man.Biopsies of porcine attached gingiva, buccal (B) and floor of mouth mucosa (FM) were incubated with either 2% or 6% nicotine in phosphate buffered saline (PBS) placed on the epithelial surface at 37°C for 1 or 2 hours. Controls were incubated with PBS at the same pH (7.5%) and osmolarity (450 milliosmoles) as the nicotine solution. The biopsies were prefixed in 2% paraformaldehyde, 2.5% glutaraldehyde, washed with cacodylate buffer, post fixed with 1% solution of osmium tetroxide in cacodylate buffer, dehydrated in graded alcohols, infiltrated, embedded and polymerized in Spurrs epoxy resin. Thin sections were prepared from all specimens and examined in the transmission electron microscope (TEM).

Characterization of beam-induced thinning and shrinkage of semi-thick sections in the HVEM

1990 ◽  
Vol 48 (3) ◽  
pp. 752-753
Author(s):  
J.R. Kremer ◽  
E.T. O'Toole ◽  
G.P. Wray ◽  
D.M. Mastronarde ◽  
S.J. Mitchell ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Colloidal Gold ◽  
Similar Data ◽  
Thin Sections ◽  
Gold Particles ◽  
Dose Rates ◽  
Transmission Electron ◽  
Conventional Transmission Electron Microscope

It is well known that irradiation of plastic sections in a conventional transmission electron microscope (cTEM) causes specimen thinning and distortion. Thinning has been observed in the cTEM using several embedding media, using methods such as shrinkage of ordered paracrystalline structures, and shrinkage of sections coated with colloidal gold markers. The total thinning observed in the cTEM (80kev) is 30-50% for thin sections of epon araldite, but similar data do not exist for the HVEM at 1000 kev. Here we describe beam induced thinning and shrinkage of 0.2um sections in the HVEM.Experiments were performed using 0.2um sections of EPOX 812/Araldite or LX112 with 15 nm and 30 nm gold particles affixed to either surface of the section. The sections were initially tilted to approximately 25° and irradiated with known dose rates. Micrographs were taken at different times between 0-20 minutes then the sections were tilted back to 0° for a reference micrograph.

TEM sample preparation and analysis of single-crystalline Si spheres

1994 ◽  
Vol 52 ◽  
pp. 876-877
Author(s):  
Kim M. Jones
Keyword(s):  
Solar Cell ◽  
Sample Preparation ◽  
Spherical Shape ◽  
Tem Analysis ◽  
Thin Sections ◽  
Transmission Electron ◽  
Sample Preparation Procedure ◽  
Refinement Process ◽  
Main Components

In parallel with the technological advancements in the field of Transmission Electron Microscopy (TEM), numerous innovations in TEM sample preparation have also transpired. Innovations in polishing techniques, ion etching, and ultramicrotomy have not only expanded the types of materials that are being investigated with TEM, but have also improved the quality of the thin sections that are examined. Described in this paper is a sample preparation procedure that was developed in order to prepare small Si spheres for TEM analysis. Metallurgical-grade Si is the starting material used in the productionof the spheres. The Si spheres are the main components in the Spheral Solar Cell technology developed by Texas Instruments. The solar cell configuration is shown schematically in Fig. 1. The spheresaresubjected to a number of refinement steps, for example: denuding, gettering, and annealing in order to achieve a purity that is suitable for solar cell fabrication. TEM characterization of the Si spheres was performed at various stages in the refinement process. The spherical shape and size (ave. dia.=0.75 mm) of the Si pose a challenge for TEM sample preparation.

Investigation of CPE/PVC morphology via STEM

1988 ◽  
Vol 46 ◽  
pp. 932-933
Author(s):  
E. G. Rightor ◽  
E. I. Garcia-Meitin ◽  
D. W. Liou
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Staining Technique ◽  
Light Phase ◽  
Thin Sections ◽  
Chlorinated Polyethylene ◽  
Selective Staining ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Diamond Knife

Microscopic characterization of the phase morphology of poly(vinyl chloride) (PVC) modified with chlorinated polyethylene (CPE) is vital to understanding the blend physical properties. A 2-3 week CPE selective staining technique, developed by Fleischner et al., has been the mainstay for recent TEM investigations of CPE/PVC. Several researchers employing this method have reported a network structure of CPE surrounding primary PVC particles.Rapid electron beam-induced dehydrochlorination of chlorinated polymers prohibits TEM examination of unstained sections. Chemical changes resulting from such dehydrochlorination of polymers was addressed recently by Vesely and Finch. In this study we investigated unstained thin sections, obtained at ambient temperature with a diamond knife, by scanning transmission electron microscopy (STEM) on a JEOL 2000 FX.As the STEM micrographs show (Figs. 1-3), sufficient contrast was available to distinguish CPE (light phase) from the PVC matrix (dark). Differences in initial chlorine concentration and rates of beam-induced mass loss most likely account for the contrast between phases.

Identification of polymer phases in elastomer blends

1992 ◽  
Vol 50 (1) ◽  
pp. 392-393
Author(s):  
P. Sadhukhan
Keyword(s):  
Electron Microscopy ◽  
Polymer Blends ◽  
Osmium Tetroxide ◽  
Standard Specimen ◽  
Liquid Nitrogen Temperature ◽  
Synthetic Polymers ◽  
Specimen Preparation ◽  
Transmission Electron ◽  
Identification And Characterization

Elastomers are composed of natural rubber and synthetic polymers. They are generally blended to produce rubbers with certain “designing properties” Shaffer, et al., 1985), including high resilience, tensile strength and elongation, resistance to tear, flexing, freezing and abrasion and low permanent set. The analytical procedures used for the identification and characterization of these polymer blends range from a simple color or flame test to more sophisticated technique like electron microscopy. Over the years, transmission electron microscopy has become the principal technique of direct visualization and subsequent characterization of phase separation and domains in polymer blends. The standard specimen preparation has been to perform cryo-ultramicrotomy on solid blend materials at liquid nitrogen temperature (Andrews et al., 1967) followed by staining with osmium tetroxide (Kato, 1966) to enhance differential contrast between the polymers in these blends. Without prior knowledge of the chemistry between the polymers and osmium, it is difficult to identify them under the TEM.

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