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The tridimensional structure of the Golgi apparatus of atrial muscle cells has been studied in thin and thick sections with low- and high-voltage electron microscopes. Cardiac tissue was inpregnated with osmium, stained to demonstrate phosphate activity (i.e., nicotinamide adenine dinucleotide phosphatase or NADPase; thiamine pyrophosphatase or TPPase; cytidine monophosphatase or CMPase) or postfixed and stained with potassium ferrocyanide-reduced osmium. At low power, in thick (3-10 micron) sections, the cisosmiophilic element and the NADPase- and the TPPase-positive saccules each appeared as a continuous irregular ribbon that formed, at the two poles of the nucleus, two conical masses connected to each other by beltlike bands encircling the nucleus. At higher magnifications, the continuous Golgi apparatus showed saccular regions along its length connected by short intersaccular tubular regions. In the saccular regions, the following five superimposed elements formed a stack: (1) the cis-osmiophilic network of anastomosed tubules; (2) a chromophobic, dilated saccule perforated with numerous pores; (3) a thin NADPase-positive saccule showing few pores; (4) a thin TPPase-positive saccule perforated with numerous minute pores; and (5) a CMPase-positive transelement that showed saccular and tubular regions and was often partly separated from the overlying saccule. In the intersaccular tubular regions, membranous tubules connected and bridged saccules of two adjacent saccular regions. Secretory granules usually appeared in this region as dilations of the tubules connected to all elements of the Golgi stack except the cis-osmiophilic element.
The tridimensional structure of the Golgi apparatus of atrial muscle cells has been studied in thin and thick sections with low- and high-voltage electron microscopes. Cardiac tissue was inpregnated with osmium, stained to demonstrate phosphate activity (i.e., nicotinamide adenine dinucleotide phosphatase or NADPase; thiamine pyrophosphatase or TPPase; cytidine monophosphatase or CMPase) or postfixed and stained with potassium ferrocyanide-reduced osmium. At low power, in thick (3-10 micron) sections, the cisosmiophilic element and the NADPase- and the TPPase-positive saccules each appeared as a continuous irregular ribbon that formed, at the two poles of the nucleus, two conical masses connected to each other by beltlike bands encircling the nucleus. At higher magnifications, the continuous Golgi apparatus showed saccular regions along its length connected by short intersaccular tubular regions. In the saccular regions, the following five superimposed elements formed a stack: (1) the cis-osmiophilic network of anastomosed tubules; (2) a chromophobic, dilated saccule perforated with numerous pores; (3) a thin NADPase-positive saccule showing few pores; (4) a thin TPPase-positive saccule perforated with numerous minute pores; and (5) a CMPase-positive transelement that showed saccular and tubular regions and was often partly separated from the overlying saccule. In the intersaccular tubular regions, membranous tubules connected and bridged saccules of two adjacent saccular regions. Secretory granules usually appeared in this region as dilations of the tubules connected to all elements of the Golgi stack except the cis-osmiophilic element.
Immunocytochemistry has made great strides in the morphology of endocrine glands, especially the adenohypophysis, because the localization of hormones can be clearly demonstrated by this method in the microscopic preparations both for light and electron microscopy. In the adenohypophysis, electron microscopic immunocytochemistry is useful for identifying the producer cell of each hormone. The second contribution is its application to the cell biology of secretion mechanisms. The pituitary hormones, their precursors, derivatives, and fragments were artificially synthesized and their antibodies were produced. Using these antibodies the intracellular sites of synthesis, condensation, processing, and sorting were studied under the electron microscope. The ultrastructure of each cell organelle and its alteration due to the changing function was studied. It was proved that the intracisternal granules in the thyroidectomy cells contain thyroid-stimulating hormone (TSH). The trans-Golgi network or GERL contains a peculiar supporting structure, intracisternal skeleton. Transport of secretory granules may be performed in relation to the microtubules, actin, and some related substances. The most frequently observed mode of hormone release in the adenohypophysis is exocytosis. Sometimes multigranular exocytosis occurs. Vesiculation of membrane around the secretory granules often occur inward or outward. The inward vesiculation forms pinocytotic vesicles, through which the membrane material may be retrieved. The outward vesiculation forms vesicle-like fragments of cytoplasm being discarded to the extracellular space. By these mechanisms the surface area of the cell is maintained constantly.
It is uncommon to find acid phosphatase activity in mature secretory granules. This paper demonstrates by light and electron microscope cytochemistry an acid phosphatase in mature secretory granules in the cells of one region of the salivary gland of Bradysia hygida (Diptera, Sciaridae). These secretory granules increase in number during larval development up to the beginning of the pre-pupal period when they undergo massive exocytosis. Biochemical assays show that upon exocytosis of the majority of the granules the total acid phosphatase activity in the granular gland region drops to 10% of the maximum reached before exocytosis. During and after exocytosis, two other acid phosphatases, eletrophoretically different and much weaker in activity, become increasingly detectable in all gland regions. At the same time, in whole mount preparations, numerous tiny acid phosphatase-positive granules (probably secondary lysosomes) become evident in all major cell types of the salivary gland. These results indicate that the S2 region of the salivary gland has mature secretory granules containing an acid phosphatase destined for exocytosis which is different in molecular properties from other acid phosphatases (likely lysosomal) made by the gland.
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