Electron microscopic observations on gels with the aid of a modified freeze-etching technique

2007 ◽  
Vol 44 (1) ◽  
pp. 25-34 ◽  
Author(s):  
W. F. Geymayer
Keyword(s):  
Electron Microscopic ◽  
Etching Technique ◽  
Freeze Etching

A New Multiple Specimen Table for Freeze-Etching

1973 ◽  
Vol 31 ◽  
pp. 94-95
Author(s):  
S. K. Paik ◽  
J. R. Allen
Keyword(s):  
Electron Microscopy ◽  
Vacuum Chamber ◽  
Microscopic Image ◽  
Electron Microscopic ◽  
Etching Technique ◽  
Electron Microscopic Image ◽  
Freeze Etching ◽  
Freeze Fixation ◽  
Etched Surface

Considerable progress in freeze etching technique has been made during the last ten years. The purpose of this technique is the preparation of replicas for electron microscopy. The technique consists of four steps. After (a) freeze-fixation, (b) the specimen surface is fractured with a cooled microtome knife in the vacuum chamber, (c) etched by low temperature sublimation, and (d) a replica of the etched surface is produced by evaporation of platinum and carbon.The electron microscopic image obtained with a freeze-etched replica is highly dependent upon the quality of the replìcas. This quality is very easily affected by the thickness of the evaporated layer and the angle of shadowing.

scholarly journals FINE STRUCTURE IN FROZEN-ETCHED YEAST CELLS

1963 ◽  
Vol 17 (3) ◽  
pp. 609-628 ◽  
Author(s):  
H. Moor ◽  
K. Mühlethaler
Keyword(s):  
Special Kind ◽  
Microscopic Investigation ◽  
Electron Microscopic Investigation ◽  
Yeast Cells ◽  
Chemical Fixation ◽  
Membrane Structures ◽  
Electron Microscopic ◽  
Etching Technique ◽  
Cross Sectional ◽  
Freeze Etching

The freeze-etching technique, which is a special kind of freeze-drying, allows electron microscopic investigation of cells and tissues in the frozen state. In regard to yeast cells (Saccharomyces cerevisiae) a freeze-fixation technique has been developed which does not kill the object. The electron micrographs therefore are considered to impart an image of high fidelity. The cutting of the frozen object, which actually consists of a fine splintering, produces not only cross-sectional views (cross-fractures) of the structures but also surface views of the membranes and organelles. Many surface structures are described which have not been shown by the usual sectioning techniques. The cytoplasmic membrane contains hexagonal arrangements of particles which are apparently involved in the production of the glucan fibrils of the cell wall. Alterations of the distribution of nuclear pores are shown in cells of different ages. Freeze-etching enables a clear distinction of endoplasmic reticulum and vacuoles in yeast cells. The membranes of the vesicular systems are covered by ribosomes arranged in circular patterns. The mitochondrial envelope shows small perforations which could allow the exchange of macromolecules. The storage granules consist of concentric layers of lipid, presumably phosphatide. A Golgi apparatus has been detected which may be involved in the storage of lipid. The structure of the unit membrane and the membrane structures of all organelles as revealed by chemical fixation are confirmed in principle. Glycogen agglomerations are identified in the ground plasm of older cells. Insight into artifacts introduced by common chemical fixation and embedding techniques is obtained and discussed.

Structures Formed by Cryoprotective Agents Used in Freezc-Etching

1971 ◽  
Vol 29 ◽  
pp. 448-449
Author(s):  
G. G. Cocks ◽  
C. E. Cluthe
Keyword(s):  
Aqueous Solution ◽  
Polyethylene Oxide ◽  
Liquid Nitrogen Temperature ◽  
Ice Crystals ◽  
Etching Technique ◽  
Structural Constituent ◽  
Cryoprotective Agents ◽  
Quick Freezing ◽  
Freeze Etching ◽  
Fractured Surface

The freeze etching technique is potentially useful for examining dilute solutions or suspensions of macromolecular materials. Quick freezing of aqueous solutions in Freon or propane at or near liquid nitrogen temperature produces relatively large ice crystals and these crystals may damage the structures to be examined. Cryoprotective agents may reduce damage to the specimem, hut their use often results in the formation of a different set of specimem artifacts.In a study of the structure of polyethylene oxide gels glycerol and sucrose were used as cryoprotective agents. The experiments reported here show some of the structures which can appear when these cryoprotective agents are used.Figure 1 shows a fractured surface of a frozen 25% aqueous solution of sucrose. The branches of dendritic ice crystals surrounded hy ice-sucrose eutectic can be seen. When this fractured surface is etched the ice in the dendrites sublimes giving the type of structure shown in Figure 2. The ice-sucrose eutectic etches much more slowly. It is the smooth continuous structural constituent surrounding the branches of the dendrites.

Recent progress in the freeze-etching technique

1971 ◽  
Vol 261 (837) ◽  
pp. 121-131 ◽  
Keyword(s):  
High Vacuum ◽  
Molecular Size ◽  
Etching Technique ◽  
Structural Distortions ◽  
Shadow Casting ◽  
Structural Details ◽  
Freeze Etching ◽  
The One ◽  
Insight Into ◽  
Made In

The freeze-etching technique must be improved if structures at the molecular size level are to be seen. The limitations of the technique are discussed here together with the progress made in alleviating them. The vitrification of living specimens is limited by the fact that very high freezing rates are needed. The critical freezing rate can be lowered on the one hand by the introduction of antifreeze agents, on the other hand by the application of high hydrostatic pressure. The fracture process may cause structural distortions in the fracture face of the frozen specimen. The ‘double-replica’ method allows one to evaluate such artefacts and provides an insight into the way that membranes split. During etching there exists the danger of contaminating the fracture faces with condensable gases. Because of specimen temperatures below —110 °C, special care has to be taken in eliminating water vapour from the high vacuum. An improvement in coating freeze-etched specimens has resulted from the application of electron guns for evaporation of the highest melting-point metals. If heat transfer from gun to specimen is reduced to a minimum, Pt, Ir, Ta, W and C can be used for shadow casting. Best results are obtained with Pt-C and Ta-W . With the help of decoration effects Pt-C shadow castings give the most information about the fine structural details of the specimen.

Fine Structure of Swarmers of Cladophora and Chaetomorpha

1971 ◽  
Vol 9 (3) ◽  
pp. 581-601
Author(s):  
D. G. ROBINSON ◽  
R. D. PRESTON
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Spatial Arrangement ◽  
Cell Wall Synthesis ◽  
Fibrous Layer ◽  
Etching Technique ◽  
Freeze Etching

Naked swarmers of both Cladophora rupestris and Chaetomorpha melagonium have been examined by the freeze-etching technique. The swarmers of Cladophora, collected just after settling, reveal several layers of granules external to the plasmalemma and internal to the so-called ‘fibrous-layer’. Chaetomorpha swarmers collected just before settling show extrusion of vesicles through the plasmalemma. The structures associated with the membranes are discussed in relation to known features of these swarmers already observed by sectioning. The role of granules in the synthesis of cell wall microfibrils is strengthened though the spatial arrangement of the granules seen in this investigation does not completely fulfil the ‘ordered granule’ hypothesis. Description of, and comments on, features related to cell wall synthesis, particularly the Golgi and vacuolar systems, are given.

scholarly journals Preservation of alveolar type II pneumocyte lamellar bodies for electron microscopic studies.

1979 ◽  
Vol 27 (5) ◽  
pp. 989-996 ◽  
Author(s):  
A J Collet
Keyword(s):  
Uranyl Acetate ◽  
Alkaline Solutions ◽  
Alveolar Type ◽  
Morphological Aspect ◽  
Type Ii ◽  
Lamellar Bodies ◽  
Electron Microscopic ◽  
Type Ii Pneumocyte ◽  
Microscopic Studies ◽  
Freeze Etching

Simultaneous fixation with glutaraldehyde and osmium tetroxide, followed by an uranyl acetate (UA) treatment before dehydration and embedding (Hirsch and Fedorko 1968) ensures a very good preservation of lamellar bodies (LB's) as well as of the cellular membranes in type II pneumocyte. The uranyl acetate treatment appeared to be the most efficient step of the procedure. The morphological aspect of lamellar bodies after such a preparation was similar to that observed after freeze-etching of lipid retaining methods. Moreover, the Hirsch-Fedorko procedure is very simple and can easily be used for routine ultrastructural and radioautographic studies. On the other hand, it appeared that the uranyl acetate phospholipid "complex" is very sensitive to the pH of chemical solutions used after sectioning. The "complex" is variously dissolved by alkaline solutions, photographic developers or stains. The best preservation of ultrastructure was obtained with neutral or acidic developers and acidic stains.

scholarly journals AN ANALYSIS OF MEMBRANE SURFACE STRUCTURE BY THE FREEZE-ETCHING TECHNIQUE

1976 ◽  
Vol 9 (1) ◽  
pp. 39a-45
Author(s):  
S. SENO ◽  
N. OTSUKA ◽  
NAGAYASU OTSUKA ◽  
SHIGETO KANDA ◽  
JUNZO SASAKI
Keyword(s):  
Surface Structure ◽  
Membrane Surface ◽  
Etching Technique ◽  
Freeze Etching
Sign in / Sign up

Export Citation Format

Share Document