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.

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.

scholarly journals The Envelope of Intracellular African Swine Fever Virus Is Composed of a Single Lipid Bilayer

2008 ◽  
Vol 82 (16) ◽  
pp. 7905-7912 ◽  
Author(s):  
Philippa C. Hawes ◽  
Christopher L. Netherton ◽  
Thomas E. Wileman ◽  
Paul Monaghan
Keyword(s):  
High Pressure ◽  
Lipid Bilayer ◽  
Lipid Membrane ◽  
African Swine Fever Virus ◽  
African Swine Fever ◽  
Viral Envelope ◽  
Fever Virus ◽  
Chemical Fixation ◽  
High Pressure Freezing ◽  
Ultrastructural Studies

ABSTRACTAfrican swine fever virus (ASFV) is a member of a family of large nucleocytoplasmic DNA viruses that include poxviruses, iridoviruses, and phycodnaviruses. Previous ultrastructural studies of ASFV using chemical fixation and cryosectioning for electron microscopy (EM) have produced uncertainty over whether the inner viral envelope is composed of a single or double lipid bilayer. In this study we prepared ASFV-infected cells for EM using chemical fixation, cryosectioning, and high-pressure freezing. The appearance of the intracellular viral envelope was determined and compared to that of mitochondrial membranes in each sample. The best resolution of membrane structure was obtained with samples prepared by high-pressure freezing, and images suggested that the envelope of ASFV consisted of a single lipid membrane. It was less easy to interpret virus structure in chemically fixed or cryosectioned material, and in the latter case the virus envelope could be interpreted as having two membranes. Comparison of membrane widths in all three preparations indicated that the intracellular viral envelope of ASFV was not significantly different from the outer mitochondrial membrane (P< 0.05). The results support the hypothesis that the intracellular ASFV viral envelope is composed of a single lipid bilayer.

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.

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