STUDIES ON THE MODE OF ACTION OF EXCESS OF VITAMIN A

Rabbit erythrocytes have been haemolysed by treatment with vitamin A alcohol and the sequence of changes in the fine structure of the cells during lysis has been investigated by phase contrast microscopy of intact cells and electron microscopy of thin sections. The initial effect of the vitamin, which occurs within 1 minute, is the production of cells of bizarre appearance which have a greatly increased surface area relative to untreated cells. Large indentations appear in the surfaces of the cells, and vacuoles are formed from the indentations by a process that resembles micropinocytosis. The cells then become spherical and loss of haemoglobin begins as breaks appear in the membranes of some cells; finally, ghosts are produced that are no longer spherical but still contain numerous vacuoles. These observations support the thesis that one site of action of vitamin A is at lipoprotein membranes.

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LEBENDNACHWEIS VON EINZELELEMENTEN DES ENDOPLASMATISCHEN RETIKULUMS

The Journal of Cell Biology ◽

10.1083/jcb.27.2.433 ◽

1965 ◽

Vol 27 (2) ◽

pp. 433-440 ◽

Cited By ~ 10

Author(s):

Manfred Girbardt

Keyword(s):

Electron Microscopy ◽

Phase Contrast ◽

Preparation Technique ◽

Phase Contrast Microscopy ◽

Membrane Systems ◽

Thin Sections ◽

Living State ◽

Contrast Microscopy ◽

Cell Components ◽

A Cell

By means of a special selective preparation technique, it is possible to investigate in thin sections, by electron microscopy, areas of a cell that have been observed in the living state, by phase-contrast microscopy, up to the time of fixation. Structures recorded in the living state can thus be compared to structures seen in electron micrographs. In cells of the fungus Polystictus versicolor, aggregates of membrane systems as well as single cisternae with a diameter of approximately 200 to 300 A can be detected with phase optics. It can be shown, by calculation, that these structures, which are far below the limit of resolution of the light optical system, give enough contrast to be discernible by phase optics. Thus a basis is provided for observing the dynamics of membrane systems which perhaps may contribute to the analysis of the functional significance of these cell components.

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Compound sensilla in monogenean skin parasites

Parasitology ◽

10.1017/s0031182000031164 ◽

1969 ◽

Vol 59 (3) ◽

pp. 625-636 ◽

Cited By ~ 43

Author(s):

Kathleen M. Lyons

Keyword(s):

Fine Structure ◽

Electron Microscope ◽

Phase Contrast ◽

The Other ◽

Phase Contrast Microscopy ◽

Sense Organs ◽

Dense Membrane ◽

Contrast Microscopy ◽

Membrane Bound

The fine structure of two kinds of compound presumed sense organs from the heads of three skin parasitic monogeneans Gyrodactylus sp. Entobdella soleae (larva only) and Acanthocotyle elegans is described. One kind of compound receptor consists of a number of associated sensilla, each ending in a single cilium (the spike sensilla of Gyrodactylus and the cone sensilla of E. soleae oncomiracidium).The other kind of compound organ is made up of one or a few neurones only, each of which bears many cilia (pit organs of E. soleae oncomiracidium and feeding organ sensilla of Acanthocotyle elegans). The spike sensilla of Gyrodactylus have also been studied using a Cambridge Instrument Co. Stereoscan electron microscope and by phase-contrast microscopy. The ciliary endings of all these sense organs are highly modified and have lost the 9 + 2 structure, being packed with many fibres. The fibre arrangement in the cilia of the cone sensillae of E. soleae oncomiracidium and the feeding organ sensilla of A. elegans has been compared with that in the ciliary endings of other invertebrate mechano- and chemoreceptors. The possibility that the spike sensilla of Gyrodactylus may be chemoreceptors has been discussed but it is considered premature to attempt to assign functions to the other sense organs studied. Electron dense membrane-bound inclusions occurring specifically in the nerves supplying the spike sensilla of Gyrodactylus may be neurosecretory.

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