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Fixation induces differential polarized translocations of organelles in hyphae of Saprolegnia ferax
Author(s) -
Kaminskyj Susan G. W.,
Jackson Sandra L.,
Heath I. Brent
Publication year - 1992
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1992.tb03226.x
Subject(s) - organelle , fixative , biology , cytoplasm , hypha , biophysics , tonicity , fixation (population genetics) , microbiology and biotechnology , ultrastructure , vesicle , paraformaldehyde , vacuole , anatomy , chemistry , biochemistry , membrane , organic chemistry , gene
SUMMARY Saprolegnia hyphal tips were examined during fixation, and living or freeze‐substituted tips were quantitatively compared with those fixed in commonly employed formulations of paraformaldehyde and glutaraldehyde. Treating hyphae with fixatives induced extensive longitudinal translocations of the cytoplasm and organelles, usually beginning with contractions toward the tip. These translocations were minimal in the extreme apex (~10 μm) and more extensive subapically. Hypertonic media or hypotonic buffers seldom or never induced translocations, respectively; in contrast, hypotonic buffers containing detergents or the Ca 2+ ‐ionophore, A23187, frequently induced contractions. All fixations caused net nucleus movement away from the tip, with the amount of displacement depending on the pre‐fixation distance from the tip. Similarly, all fixations moved the most‐apical of saltatory vesicles away from the tip, but the total number in the apex increased or decreased depending on the fixative used. The patterns of these results suggest that nucleus and vesicle distribution controls may be related (with respect to most‐apical organelles) but also at least partially independent (with respect to organelle populations in hyphal tips). Hyphal diameter was reduced by some, but not all fixations; this variability did not correlate with displacements of either organelle, nor with fixative osmotic pressure. Evidently fixative‐induced changes are more complex and systematic in highly polarized tip‐growing cells than previously reported in other, less polarized, cell types. These results also suggest that hyphae contain multiple and complex organelle distribution and hyphal diameter control systems which can be readily altered, often subtly, by fixation protocols commonly and uncritically employed in immunocytochemical and ultrastructural analyses, and that fixation can cause serious cellular reorganization.