Ultrastructure of the Zoosporangia of Albugo ipomoeae-panduratae as Revealed by Conventional Chemical Fixation and High Pressure Freezing Followed by Freeze Substitution

Mycologia ◽  
2003 ◽  
Vol 95 (1) ◽  
pp. 1 ◽  
Author(s):  
Charles W. Mims ◽  
Elizabeth A. Richardson
Keyword(s):  
High Pressure ◽  
Freeze Substitution ◽  
Chemical Fixation ◽  
High Pressure Freezing

Cryo-SEM and TEM of High Pressure Frozen Cells - Some Technical Contributions

2001 ◽  
Vol 7 (S2) ◽  
pp. 728-729
Author(s):  
Paul Walther
Keyword(s):  
High Pressure ◽  
Physiological State ◽  
Electron Microscopic Observation ◽  
Freeze Substitution ◽  
Chemical Fixation ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Electron Microscopic ◽  
Biological Specimen ◽  
Freeze Fracturing

Imaging of fast frozen samples is the most direct approach for electron microscopy of biological specimen in a defined physiological state. It prevents chemical fixation and drying artifacts. High pressure freezing allows for ice-crystal-free cryo-fixation of tissue pieces up to a thickness of 200 urn and a diameter of 2 mm without prefixation. Such a frozen disc, however, is not directly amenable to electron microscopic observation: The structures of interest have to be made amenable to the electron beam, and the structures of interest must produce enough contrast to be recognized in the electron microscope. This can be achieved by freeze fracturing, cryo-sectioning or freeze substitution.The figures show high pressure frozen bakers yeast saccharomyces cerevisiae in the cryo-SEM (Figures 1 and 2) and after freeze substitution in the TEM (Figure 3). For high pressure freezing either a Bal-Tec HPM 010 (Princ. of Liechtenstein; Figures 1 and 2), or a Wohlwend HPF (Wohlwend GmbH, Sennwald, Switzerland; Figure 3) were used.

High Pressure Freezing and Freeze Substitution of Primitive Agglutinated Foraminifera

1998 ◽  
Vol 4 (S2) ◽  
pp. 1136-1137
Author(s):  
Susan T. Goldstein ◽  
Elizabeth A. Richardson
Keyword(s):  
High Pressure ◽  
Freeze Substitution ◽  
Florida Keys ◽  
Carbonate Sediments ◽  
Chemical Fixation ◽  
High Pressure Freezing ◽  
Fine Grained ◽  
Ultrastructural Studies ◽  
Large Size ◽  
Sexual Generation

Freeze substitution techniques can provide exceptional fixation of many types of small biological materials. Ultrastructural studies on the Foraminiferida (marine rhizopods) traditionally have used standard chemical fixation protocols. The relatively large size (-25 μm - several cm) and the presence of a mineralized shell in most taxa precludes the application of many cryo-techniques. High pressure freezing, however, provides a method for freezing organisms as large as many of the smaller foraminifera often without extensive ice damage. Gamonts (sexual generation) from three representatives of the suborder Astrorhizina ﹛Myxotheca sp., Cribrothalammina alba, and Hyperammina sp.) were selected because they are among the most primitive foraminifera and have only very finely agglutinated shells with non-mineralized, organic cements. Myxotheca sp. and C. alba were originally collected from salt marsh environments on Sapelo Island, Georgia, and Hyperammina sp. was isolated from fine-grained carbonate sediments of the Florida Keys.

scholarly journals Cartilage ultrastructure after high pressure freezing, freeze substitution, and low temperature embedding. I. Chondrocyte ultrastructure--implications for the theories of mineralization and vascular invasion.

1984 ◽  
Vol 98 (1) ◽  
pp. 267-276 ◽  
Author(s):  
E B Hunziker ◽  
W Herrmann ◽  
R K Schenk ◽  
M Mueller ◽  
H Moor
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Vascular Invasion ◽  
Freeze Substitution ◽  
Electron Microscopic Examination ◽  
Cartilage Tissue ◽  
Chemical Fixation ◽  
High Pressure Freezing ◽  
Electron Microscopic ◽  
Cell Destruction

Electron microscopic examination of epiphyseal cartilage tissue processed by high pressure freezing, freeze substitution, and low temperature embedding revealed a substantial improvement in the preservation quality of intracellular organelles by comparison with the results obtained under conventional chemical fixation conditions. Furthermore, all cells throughout the epiphyseal plate, including the terminal chondrocyte adjacent to the region of vascular invasion, were found to be structurally integral. A zone of degenerating cells consistently observed in cartilage tissue processed under conventional chemical fixation conditions was not apparent. Hence, it would appear that cell destruction in this region occurs during chemical processing and is not a feature of cartilage tissue in the native state. Since these cells are situated in a region where tissue calcification is taking place, the implication is that the onset and progression of cartilage calcification are, at least partially, controlled by the chondrocytes themselves. The observation that the terminal cell adjacent to the zone of vascular invasion is viable has important implications in relation to the theory of vascular invasion. This may now require reconceptualization to accommodate the possibility that active cell destruction may be a precondition for vascular invasion.

Jet freezing of cells and tissues with and without cryoprotectants

1993 ◽  
Vol 51 ◽  
pp. 106-107
Author(s):  
M.V. Parthasarathy ◽  
Carole Daugherty ◽  
T. Müller
Keyword(s):  
High Pressure ◽  
Biological Samples ◽  
Plant Cells ◽  
Freeze Substitution ◽  
Chemical Fixation ◽  
High Pressure Freezing ◽  
High Quality ◽  
The Past ◽  
Copper Specimen ◽  
Cell Structures

For the past several years cryofixation/freeze-substitution techniques have become valuable alternatives to chemical fixation of biological specimens. The superiority of cryofixation in preserving labile cell structures has been documented in several studies. Commercially available jet freezers and the BAL-TEC HPM010 high pressure freezer have extended high quality cryofixation from monolayer cells to cells relatively deep inside tissues. High pressure freezing can theoretically freeze biological materials of 0.5 mm thickness without the use of cryoprotectants and propane jet freezing is reported to freeze biological samples up to 40 μm in thickness without cryoprotection. Although high pressure freezing is the obvious method of choice for freezing large biological samples, its high cost combined with its apparent inability to consistently preserve microfilaments in some plant cells has prompted us to explore the capability of jet freezing to yield well frozen samples with and without cryoprotectants.We used the commercially available jet freezer JFD 030 (BAL-TEC) to obtain our results. Tightly pelleted cells sandwiched between 0.1 mm thick copper specimen carriers normally froze well without any cryoprotectants, after propane jet freezing (Figs. 1-2).

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