The Current Situation in Chemical Stabilization of Biological Materials

1972 ◽  
Vol 30 ◽  
pp. 132-133
Author(s):  
John H. Luft
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Molecular Level ◽  
Cross Linking ◽  
Chemical Stabilization ◽  
Specimen Preparation ◽  
Sufficient Condition ◽  
Radio Telescopes

With information processing devices such as radio telescopes, microscopes or hi-fi systems, the quality of the output often is limited by distortion or noise introduced at the input stage of the device. This analogy can be extended usefully to specimen preparation for the electron microscope; fixation, which initiates the processing sequence, is the single most important step and, unfortunately, is the least well understood. Although there is an abundance of fixation mixtures recommended in the light microscopy literature, osmium tetroxide and glutaraldehyde are favored for electron microscopy. These fixatives react vigorously with proteins at the molecular level. There is clear evidence for the cross-linking of proteins both by osmium tetroxide and glutaraldehyde and cross-linking may be a necessary if not sufficient condition to define fixatives as a class.

The ionic strength dependence of chromatin folding

1978 ◽  
Vol 36 (2) ◽  
pp. 220-221
Author(s):  
F. Thoma ◽  
TH. Koller
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Ionic Strength ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Carbon Supports ◽  
Ionic Strength Dependence ◽  
Chromatin Folding ◽  
Strength Dependence ◽  
Preparation Techniques

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.

The External Morphology of the Eggs of Culex (Culex) saltanensis (Diptera: Culicidae) Under Scanning Electron Microscopy

2020 ◽  
Author(s):  
J R Santos-Mallet ◽  
T D Balthazar ◽  
A A Oliveira ◽  
W A Marques ◽  
A Q Bastos ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Optical Microscopy ◽  
Osmium Tetroxide ◽  
Neotropical Region ◽  
External Morphology ◽  
Metal Supports ◽  
Scanning Electron

Abstract The aim of the present study was to describe the morphology of the eggs of Culex (Culex) saltanensis Dyar that occurs in the Neotropical region. Eggs of the Cx. (Cux.) saltanensis were collected at the Mata Atlântica FIOCRUZ campus, fixed in 1% osmium tetroxide, prepared for mounting on metal supports, observed under a scanning electron microscope, and described morphologically. The eggs had a coniform shape with a length of approximately 0.5 mm (505–510 µm) and a width in the median portion of 117 µm (113–123 µm). Upper portion is lined with tubers of irregular shape and varying sizes (0.64–1.31 µm), located on a cross-linked matrix forming bands observed under optical microscopy. The micropyle is encased in a necklace of approximately 6.6-µm plates arranged in a flower-like shape. Comparing Cx. (Cux.) saltanensis eggs with several species of different genera, important divergent characteristics can be observed. However, this study points to the need for new descriptions of eggs of species belonging to the same subgenus in order to analyze if there will be differences between them. Culex (Cux.) saltanensis eggs have particular characteristics not observed in eggs of other Culicidae genera.

A Fully Automated System for the Preparation of Samples for Cryo-Electron Microscopy

2010 ◽  
Author(s):  
Zachary J. Thompson ◽  
Kevin L. Johnson ◽  
Nicolas Overby ◽  
Jessica I. Chidi ◽  
William K. Pryor ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Environmental Control ◽  
Human Interaction ◽  
Automated System ◽  
Specimen Preparation ◽  
Cryo Electron Microscopy ◽  
Early Testing ◽  
High Humidity Environment ◽  
Fully Automated System

The preparation of specimens for cryo-electron microscopy is currently a labor and time intensive process, and the quality of resulting samples is highly dependent on both environmental and procedural factors. Specimens must be applied to sample grids in a high-humidity environment, frozen in liquid ethane, and stored in liquid nitrogen. The combination of cryogenic temperatures and humidity-control mandates the segregation of the humidity-controlled environment from the cryogenic environment. Several devices which automate portions of the specimen preparation process are currently in use; however, these systems still require significant human interaction in order to create viable samples. This paper describes a fully automated system for specimen preparation. The resulting system removes the need for human input during specimen preparation, improves process control, and provides similar levels of environmental control. Early testing shows that the resulting system is capable of manipulating samples in an autonomous manner while providing performance similar to existing systems.

scholarly journals A Review Of The Development Of Scanning Electron Microscopy At High Chamber Pressure

1997 ◽  
Vol 5 (1) ◽  
pp. 14-15
Author(s):  
Vivian Robinson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Chamber Pressure ◽  
Natural State ◽  
Specimen Preparation ◽  
Electron Microscopes ◽  
Reproducible Manner ◽  
Scanning Electron

Ever since electron microscopes were developed, it has been the goal of microscopists to observe specimens in their natural state, free from artefacts which can often be introduced through specimen preparation. For most biological specimens, that includes the presence of water. With a pressure of 10-4 torr or lower required to operate a scanning electron microscope (SEM), liquid water, which required a pressure of above 5 torr, was clearly a problem.Although several attempts had been made to examine hydrated specimens in a SEM, the first published results of water imaged in a stable and reproducible manner in the SEM, were presented at the Eighth International Congress on Electron Microscopy in Canberra in 1974 (Robinson, 1974).

Wide Field Electron Microscopy: The Sublimation of Epon-Araldite

1973 ◽  
Vol 31 ◽  
pp. 366-367
Author(s):  
Grace C. H. Yang ◽  
A. B. Morrison
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Specimen Preparation ◽  
Wide Field ◽  
Electron Micrograph ◽  
Field Electron ◽  
Field Electron Microscopy ◽  
Scanning Range

To emphasize the best feature of this technique, the term “wide field” is used throughout the text instead of the usual “scanning range magnification” or “low magnification”. Wide field electron microscopy presently is not being fully utilized in many laboratories, perhaps because the quality of the electron micrograph obtained is not worthy of the supposedly long and tedious specimen preparation. We report here that the quality of the wide field electron micrograph can be greatly enhanced by using the old “sublimation trick” for the methacrylate section.Two kinds of embedment formula were tested: Luft's Epon (mixture A:B= 6;4), and Mollenhauer's Epon-Araldite mixture 1. Only the Epon-Araldite showed the “foot print” of the electron beam (fig. 1).

Energy Filtering in Electron Microscopy and Electron Diffraction

1973 ◽  
Vol 31 ◽  
pp. 282-283
Author(s):  
R. Castaing
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Energy Loss ◽  
Energy Filtering ◽  
Electrostatic Mirror

Energy filtering has proved to be a most valuable tool in electron microscopy. By the simple introduction of a dispersive device in the column of the electron microscope, it is possible to select quite easily, for the production of the image, those of the electrons which have suffered, when crossing the specimen, a given amount of energy loss. A simple filtering device, comprising two 90° magnetic deflections separated by a reflection on an electrostatic mirror, makes possible to select a 1 eV energy bandwidth in the energy loss spectrum of 100 keV electrons without disturbing the quality of the image ; the chosen energy loss may go from zero (quasi-elastic images) up to several hundredths of electron-volts.

Instrumentation and Computation

1990 ◽  
Vol 48 (1) ◽  
pp. 2-3
Author(s):  
P.B. Hirsch
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Materials Science ◽  
Image Interpretation ◽  
Specimen Preparation ◽  
Scanning Tunnelling Microscope ◽  
Transmission Electron ◽  
Wide Range ◽  
Electron Microscopes ◽  
Types Of Information

The benefit to society arising from developments in instrumentation and computation can be judged primarily by the advances in knowledge and understanding generated by their application in different branches of science, covered in the other papers in this symposium. Without advances in instrumentation none of these advances is possible; developments in instrumentation and in image interpretation are therefore fundamental to and precede scientific advances in fields in which knowledge of structure is important. There is little doubt that the revolutionary first step was the development of the transmission electron microscope (TEM) in 1931 by Ernst Ruska; a second was the development of the scanning electron microscope (SEM); and the third the introduction of the scanning tunnelling microscope (STM) for high resolution surface imaging, by Binnig and Rohrer.The TEM and SEM have undergone continuous developments over the last 50 years or so, and have had a far-reaching impact in a wide range of disciplines; the STM is a relative newcomer but no doubt it too will have an increasing impact in furthering our understanding of solids and surfaces in particular. Once the basic instruments became available subsequent developments have been driven by the demands of the scientific disciplines in which these instruments have been applied. Many of the new developments in instrumentation and interpretation have been pioneered by the users themselves, and these in turn have led to modifications in commercial instruments to make such advances in technique available to the user community as a whole. Other developments have been initiated directly by the manufacturers as a result of a perceived need. There has been and continues to be a close interaction between the developers of hardware (not only of electron microscopes but also of ancillary equipment, e.g. microanalysis attachments, image processing equipment, specialist specimen stages, and specimen preparation facilities) and the users, leading to extensions in the range of applications and the types of information which can be obtained by electron microscopy. The following examples from the developments of electron microscopy in Materials Science illustrate these interactions and the particular advances arising from specific developments:

A technique for preparing Beauveria spp. for scanning electron microscopy

1980 ◽  
Vol 58 (15) ◽  
pp. 1700-1703 ◽  
Author(s):  
E. C. Quattlebaum ◽  
G. R. Carner
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Freeze Drying ◽  
Osmium Tetroxide ◽  
Air Drying ◽  
Preparation Methods ◽  
Critical Point Drying ◽  
Scanning Electron

Vapor fixation for 96 h with 1% osmium tetroxide (OsO4) and 3–4 days air drying produced distortion-free specimens of Beauveria spp. for examination with the scanning electron microscope. A combination of 4 h OsO4 vapor fixation and freeze-drying also reduced disruption satisfactorily but specimens were not as well preserved as with the first method. Preparation methods that were ineffective in preventing collapse of hydrophilic structures were Cling Free® sprayed on specimens prior to examination, freeze-drying, critical-point drying (of unfixed material), and vapor fixation with glutaraldehyde.

scholarly journals Electron Microscopy of Retinal Photoreceptors

1960 ◽  
Vol 7 (3) ◽  
pp. 493-497 ◽  
Author(s):  
Arnaldo Lasansky ◽  
Eduardo de Robertis
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Electron Microscope ◽  
Outer Segment ◽  
Osmium Tetroxide ◽  
The Other ◽  
Rod Outer Segments ◽  
Outer Segments ◽  
Retinal Photoreceptors ◽  
L1 And L2

The fine structure of the cone and rod outer segments of the toad was studied under the electron microscope after fixation in osmium tetroxide and fixation in formaldehyde followed by chromation. In the OsO4-fixed specimens, the rod outer segment appears to be built of a stack of lobulated flattened sacs, each of which is made of two membranes of about 40 A separated by an innerspace of about 30 A. The distance between the rod sacs is about 50 A. The sacs in the cone outer segment are originated by the folding of a continuous membrane. The thickness of the membranes and width of the spaces between the cone sacs is the same as in rod, but the sac innerspace is slightly narrower in the cone (∼ 20 A). After fixation in formaldehyde and chromation, two different dense lines (l1 and l2) separated by spaces of less density appear. One of the lines, l1, has a thickness of 70 A and is less dense than the other, l2, which is 30 A thick. The correlation of the patterns obtained with both fixatives is considered and two possible interpretations are given. The possibility that l2 is related to a soluble phospholipid component is discussed. It is suggested that the outer segments have a paracrystallin organization similar to that found in myelin.

The Effect of Electron Microscopy on Pathological Diagnosis of Neoplasm

1990 ◽  
Vol 48 (3) ◽  
pp. 248-249
Author(s):  
Xiaojun Zhou ◽  
Taihe Zhang
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Frozen Section ◽  
Protein A ◽  
Functional Classification ◽  
Lead Citrate ◽  
Thin Sections ◽  
Tumor Tissues ◽  
Frozen Section Diagnosis

Although electron microscopy (EM) has contributed enormously to an understanding of the structural intricacies of tumor cells, the usefulness of EM in pathological diagnoses of neoplasms has not been readily appreciated by general pathologists. In the present study, 223 tumors submitted for EM diagnosis were analyzed in an attempt to gain further information concerning the contribution of EM to tumor diagnosis.223 neoplasms were submitted to EM for their final diagnoses when histopathological diagnoses were obscure, which represented about of the total number of surgical tumor specimens. Most specimens were taken at the time of frozen section diagnosis and a small number of tissues were originally fixed informaldehyde. All of tissues were fixed with buffered glutaradehyde, postfixed with osmium tetroxide and embedded in Epon 812. Ultrasections were made after semith in sections were examined to verify that representative tumor tissues were present. Thin sections were stained with uranium acetate and lead citrate, and examined under JEM-1200 EX electron microscope. In selected cases, mainly with neuroendocrine tumors, nickel grid-mounted sections were subjected to post embedding immunoelectron microscopy (IEM) using protein A-gold for more detailed functional classification. Protein A-gold probes were prepared as Wang and co-workers described.

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