High pressure freezing
Springer Online Journal Archives 1860-2000
Summary The effects of high pressure on the ultrastructure of sporangia ofPhytophthora cinnamomi andP. palmivora have been examined by comparing sporangia frozen in a Balzers hyperbaric freezer or pressurized in a French pressure cell with sporangia plunge frozen at ambient pressure. Both freeze fixation methods provided excellent preservation of most cell structures, but one organelle type seen in plunge frozen material, the large peripheral vesicle (LPV), was not observed in high pressure frozen sporangia. Instead, these sporangia contained large irregularly shaped structures which exhibit the patterns of spatial distribution and, forP. cinnamomi, the monoclonal antibody binding characteristic of LPVs. These findings suggest that some factor of the hyperbaric freezing process causes LPVs to be degraded. Sporangia ofP. cinnamomi that had been pressurized in a French pressure cell also exhibited large structures with the spatial distribution and monoclonal antibody binding characteristic of LPVs. The apparent expansion of LPVs that follows from both pressurizing treatments causes considerable passive disruption of sporangial structure. This is the first report of a major disturbance of cell structure from use of the Balzers hyperbaric freezer, and reflects the lability, noted in previous work, of LPVs inPhytophthora.
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