Dense granules

Elastase release from dense granules is monitored with a nonfluorescent substrate containing a coumarin derivative. When the substrate is cleaved, fluorescent aminomethylcoumarin is released. 

Platelets adherent to collagen change shape and spread out on the subendothelium. They release the contents of their storage granules (the dense granules and the alpha granules) secretion is also stimulated by thrombin. 

In mouse glioma cells, many kinds of changes in cell organelles after exposure to 5 x 10 5 M mercuric chloride in vitro could be found [ 144]. Nuclei showed pyknotic and irregular shapes mitochondria lost their normal cristae and abnormal electron-dense areas were present within the matrix polyribosomes were dispersed. Numerous electron-dense granules and vacuolations were seen in the cytoplasm, especially around the Golgi region,... 

After administration of mercuric chloride to adult rat kidneys, several changes were found, for example, pars recta of the proximal tubular segment showing fragmentation and disruption of the plasma membrane, basophilic staining, vesiculation and disruption of endoplasmic reticulum and other cytoplasmic membranes, mitochondrial swelling, loss of mitochondrial dense granules and condensation of nuclear chromatin [223-225]. 

It was also observed in earlier studies that mitochondria not only accumulate Ca2+ as an alternative to phosphorylation of ADP (Ca2+ uptake uncouples phosphorylation from electron transport), but could also accumulate much larger amounts of Ca2+ if phosphate was also taken up, resulting in precipitation of Ca2+ within the matrix as insoluble hydroxyapatite, visible as electron-dense granules by EM. An unusual feature of these hydroxyapatite deposits is that they fail to become crystalline and remain amorphous even over protracted periods of time. Their presence in mitochondria in a number of disease conditions underlines the role for mitochondria as a sort of safety device, which can enable the cell to survive, if only for a limited period of time, situations of cytoplasmic Ca2+ overload. 

Dense granule storage pool deficiency Deficiency of dense granules in megakaryocytes and platelets... 

Figure 18-1 Thin section of mitochondria of a cultured kidney cell from a chicken embryo. The small, dark, dense granules within the mitochondria are probably calcium phosphate. Courtesy of Judie Walton.

In addition to bacterialike mitochondrial ribosomes and small circular molecules of DNA, mitochondria may contain variable numbers of dense granules of calcium phosphate, either Ca3(P04)2 or hydroxylapa-tite (Fig. 8-34),4/18 as well as of phospholipoprotein.4... 

Fig. 2. Postembedding technique. Section through part of a tissue cyst of the protozoan parasite Toxoplasma gondii immunostained with a rat monoclonal antibody (CC2) which recognizes a molecule located in the cyst wall (CW) and in dense granules within the parasite (for details, see ref. 2). N, nucleus PG, polysaccharide granules. Three-step protocol rat monoclonal followed by rabbit antirat Ig and visualized with goat antirabbit Ig conjugated to 10-nm gold. Bar is 0.5 pm.

Increase in the rate of liquid feed addition and in its solids or binder content generally produces larger, stronger and more dense granules. There is, of course, an upper limit to the liquid feed rate set by increasing cohesion of bed particles and a tendency for the bed to slump or defluidize. 

The alga Chlamydomonas reinhardtii contains cytoplasmic vacuoles that are often filled with dense granules. Purified granules contained PolyP complexed with calcium and... 

The interaction of Entamoeba histolytica with collagen induces the intracellular formation and the release of electron-dense granules containing collagenase activity, which is important for pathogenicity of this parasite. Purified granules are a complex of mainly cationic proteins, which contains numerous proteolytic activities, actin, and small molecules such as P , PP and cations (Leon et al., 1997). It is not improbable that such granules also contain some quantities of PolyP. 

C. M. Hensgens, H. Santos, C. Zhang, W. H. Kruizinga and T. A. Hansen (1996). Electron-dense granules in Desulfovibrio gigas do not consist of inorganic triphosphate but of a glucose pentakis(diphosphate). Eur. J. Biochem., 242, 327-331. 

G. Leon, C. Fiori, P. Das, M. Moreno, R. Tovar, J. L. Sanchez-Salas and M. L. Munoz (1997). Electron probe analysis and biochemical characterization of electron-dense granules secreted by Entamoeba histolytica. Mol. Biochem. Parasitol., 85, 233-242. 

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