Fine structure in freeze-etched allium cepa L. root tips

doi:10.1016/S0022-5320(64)80072-1

Journal of Ultrastructure Research

Volume 11, Issues 5–6, December 1964, Pages 401-411

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Allium cepa root tips were freeze-etched with results indicating that the technique can be applied advantageously to ultrastructural studies in the multicellular tissues of higher plants. The picture of cell and membrane structure which emerges, confirms in most respects the picture observed after chemical fixation and positive staining. In addition, freeze-etching permitted determination of pore size and revealed surface structures not seen in normally sectioned preparations.

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Cited by (54)

Molecular cytochemistry of freeze-fractured cells: Freeze-etching, fracture-label, fracture-permeation, and label-fracture
1987, Advances in Molecular and Cell Biology
This chapter describes three alternative techniques for the cytochemical characterization of the components (membrane associated or not) that are exposed by freeze-fracture. The first, fracture-label permits the labeling of plasma and intracellular membranes (as well as cytoplasms and nucleoplasms) after freeze-fracture. The second, fracture-permeation explores the compactness of cytoplasmic and nucleoplasmic matrices in glutaraldehyde fixed cells. The third, label-fracture relates directly the surface labeling of a membrane to its freeze-fracture morphology. Freeze-fracture splits and exposes plasma membranes and intracellular membranes; in addition, cross-fracture exposes components of both cytoplasms and nucleoplasms. As conventional freeze-fracture is performed under vacuum, the molecules it exposes cannot be labeled because the specimens are frozen and inaccessible inside a vacuum chamber. Freeze-fracture is revealing itself as the least damaging method to expose receptors and antigens for labeling. Its random course ensures the steric availability of plasma and intracellular membranes, of cytoplasm and nucleoplasm components, as well as of extracellular matrices.
Detection of microdomains in biomembranes An appraisal of recent developments in freeze-fracture cytochemistry
1983, BBA - Reviews on Biomembranes
Quantitative freeze-fracture study of plasmalemma and nuclear envelope of Zea mays root cells during early germination
1982, Journal of Ultrasructure Research
Descriptive and quantitative observations of the plasmalemma and nuclear envelope of freeze-fractured root cells are reported for quiescent and early germinating maize embryos.
The numerical density of particles exposed on the extracellular fracture faces of the plasmalemma increases significantly between 12 and 24 hr of germination while it remains unchanged on the protoplasmic fracture faces. The plasmalemma is significantly thicker after 24 hr of germination probably due partially to its enrichment in particles.
Between 24 and 72 hr of germination there is a significant increase in the density of nucleopores. The fine structure of the nucleopores changes between 4 and 24 hr of germination. The first 24 hr of germination are also characterized by a spectacular rise in the density of particles of the two nuclear membranes.
The results are discussed with respect to germination, particularly that of the maize embryo in which several cellular and molecular aspects have already been studied.
Morphometry of nuclear pore complexes in thyroid cells during hyperplasia and involution
1981, Molecular and Cellular Endocrinology
Nuclear pore complexes were analyzed in freeze-fractured replicas of thyroid follicular cells of C₃H mice in different physiological states. Thyroid stimulation induced a rapid and simultaneous increase of the nuclear surface and volume and of the total number of pore complexes. The numerical density (N_a) of pore complexes increased at the 6th day of stimulation, but after that time the proportion of cells with an increased N_a was always higher than the proportion of ³H-labelled nuclei. During thyroid involution, all the nuclear parameters, including the N_a, returned to normal values.
These results indicate that the total number of pore complexes and their N_a are correlated with the cellular activity rather than with the cell cycle. They also suggest that 2 different mechanisms are involved in the generation of pore complexes: first, an addition of new memranes with a low density of pore complexes; later, a formation of new pore complexes in preexisting membranes. However, during involution, parts of the nuclear membranes and pore complexes in the remaining parts disappear synchronously.
In freeze-fractured thyroid nuclear membranes, 2 neighbouring pore complexes were always separated by a distance of 105 nm. Clusters of pore complexes were not observed. A comparison of the distances between pore complexes and between randomly generated points never showed any significant differences indicating that pore complexes were randomly distributed.
Structure of inner membranes in rat heart muscle mitochondria as revealed by means of freeze-fracturing
1978, Journal of Ultrasructure Research
The freeze-fracture technique was applied under conditions that made it possible to observe structural components in mitochondria with dimensions as small as 40 to 50 Å. Three different types of membranes were identified in rat heart muscle mitochondria: two structurally different membranes located at the surface of the mitochondria and the inner membranes forming the cristae. The latter membranes, which are analyzed in this paper, differed structurally from the two surface membranes. The inner membranes were 165 Å thick (minimum width measured) and consisted of a dense three-dimensional aggregation of particles with no indications of the existence of any lipid bilayers extending between the particles in the interior of the membranes. The distribution of particle dimensions showed that the dimensions 90–100 and 120–140 Å dominated. Many particles showed a characteristic shape, for instance, with square-shaped faces. A fairly large fraction of the membrane particles were rod-shaped, with a maximum length of 500 Å. The most common lengths of these particles were 120–200 Å. The matrix surface of the inner membranes was fairly smooth partially due to a rather dense arrangement of particles that faced the matrix with flat surfaces. Many of these particles exposed square-shaped faces at this surface. In order to account for the smoothness of the matrix surface it was furthermore assumed that, at this surface, lipid molecules filled in the spaces between the particles like mortar in a brick wall. The threedimensional arrangement of closely packed particles that was observed agrees with the observations made by Sjöstrand and Barajas (1968, J. Ultrastruct. Res. 25, 121) on material prepared according to the low denaturation techniques. The thickness of the inner membranes exceeds somewhat that measured on the latter material. This difference can be accounted for by the different conditions under which the measurements were made. Earlier work in which the freezefracturing technique was applied mostly concerned the innermost surface membrane which has erroneously been assumed to be identical to the inner membranes of the cristae.
Freeze-fracture replication in biological research: Development, current practice and future prospects
1977, Micron (1969)

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¹: Postdoctoral Fellow, National Science Foundation. Present address: Department of Botany, University of California, Berkeley 4, California, U.S.A.

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Fine structure in freeze-etched allium cepa L. root tips

J. Ultrastruct. Res.

Am. J. Botany

Science

Circulation

J. Cell Biol.

J. Ultrastruct. Res.

Z. Schweiz. Forstv. Beih.