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A FREY-WYSSLING

Publications and source records attributed to A FREY-WYSSLING.

18 recordsLinked to original sources
PubMed1961

A new freezing-ultramicrotome.

The difficulties in sectioning frozen biological objects for electron microscopic investigations are overcome by Steere's freezing-etching method. In order to test this method and to open up a wide field of application, the new freezing-ultramicrotome has been designed. The apparatus consists of the combination of an ultramicrotome with freezing-drying and shadow-casting installations in the same vacuum container. The preliminary results show, on the one hand, the practicability of all preparational steps and, on the other, that it is possible to resolve internal structures of cell organelles and even macromolecular patterns.

Desiccation↗
PubMed1960

Stained pectin as seen in the electron microscope.

This paper describes electron microscopic studies on the distribution of pectin within young plant cells. Dark-grown onion roots, from 1 to 3 mm. in length, were used. In order to make the pectic substances selectively dense to electrons, they were first reacted with basic hydroxylamine. This treatment produces pectic hydroxamic acids, which in turn were treated with ferric ion to form insoluble complexes. The tissue was imbedded, sectioned, and then observed by electron microscopy. Dense deposits of iron were found in the region of the middle lamella and in a second area near the surface of the primary wall. Transverse walls of varying maturity were noted. The pectin of the more frequent, immature cross-walls, leads directly into the inner reacting layer of the axillary (longitudinal) wall. The pectin of the more mature transverse walls becomes, on the other hand, intimately associated with the middle lamella pectin of the axillary wall. It is shown that the pectin of the middle lamella represents the hot water-soluble portion of the pectic substance, while the internal layer of the axillary wall and the transverse wall pectin represent the so called residual fraction. Hot versene extraction removes essentially all electron-dense material.

Cell Wall↗
PubMed1959

[Development and structure of proplastids].

In this study the proplastid development in embryonic cells is described for the apical meristem of Elodea canadensis, embryo sacs from Lilies, and Begonia leaf buds. The formation of these cell organelles originates with submicroscopical particles which consist of a homogeneous stroma with a surrounding double membrane. When these proplastids reach an average size of 1 micro, the inner layer of the membrane begins to invaginate into the stroma. This process is comparable to tubuli formation in mitochondria. Under growth conditions with sufficient exposure to light, the development of the grana and stroma lamellae proceeds without interruption. If the plants are kept in the dark, small vesicles are formed which accumulate in the prolamellar body of the proplastids. After illumination these elementary vesicles merge to form membranes which evolve into grana and stroma lamellae. The structural similarity of the early proplastid stages with the mitochondria seems to indicate that there exists some phylogenetic relationship between the two cell organelles.

Light↗