ISSN:
1432-0878
Keywords:
Endoplasmic reticulum
;
Golgi apparatus
;
Membrane flow
;
Ciliate ultrastructure
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Various differentiating forms of rough and smooth endoplasmic reticulum (ER), as well as a novel type of a Golgi apparatus-equivalent organelle, are described for the ciliate Tetrahymena pyriformis. Ergastoplasmic stackings and dictyosomal configurations have been studied in particular detail since such structures had hitherto been reported not to occur in these ciliate cells. A Tetrahymena cell can contain several hundred dictyosomes, which are frequently formed at the mitochondrial jacket-ER. The following way of secretory flow is suggested for Tetrahymena: Small patches of rough ER (or of the nuclear envelope) loose their ribosomes and become smooth. From such smooth membrane areas vesicles pinch off which are distinct by greater membrane thickness and electron contrast as well as by an intimate association with characteristic granulo-fibrillar aggregates. Such ER-derived vesicles can then conflux, either to give rise to a stream of vesicles with distally increasing sizes, or to produce a localized “pile up” as more or less comprehensive stacks of flattened cisternae in the typical mode of a dictyosome with forming and secreting face polarity. The observations indicate that processes of cytomembrane differentiation and membrane flow take place in ciliate systems. In addition, the coincidence of vesicle pinching off with the appearance of fenestrae in the cisternae has led to new concepts of how pores in cisternae might generally be formed as a consequence of vesicle production.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00455249
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