Cytoplasm particles

Hofmann, I., Casella, M., Schnolzer, M., Schlechter, T., Spring, H., and Franke, W. W. (2006). Identification of the junctional plaque protein plakophilin 3 in cytoplasmic particles containing RNA-binding proteins and the recruitment of plakophilins 1 and 3 to stress granules. Mol. Biol. Cell 17, 1388—1398. 

M. Ottesen and R. Weber, Compt. Rend. Trav. Lab. Carlsberg, 29 417 (1955). Density-Gradient Centrifugation as a means of Separating Cytoplasmic Particles. 

From early observations, De Duve defined lysosomes as cytoplasmic particles that were associated with a range of acid hydrolases (7). At the electron microscope level, membrane-bound vacuoles or compartments were recognized and shown to contain acid hydrolases that were detectable by C5dochemical staining (15). The definitive description of a lysosome (16) includes a membrane-bound organelle compartment that is acidic and... 

D6. de Duve, C., Lysosomes a new group of cytoplasmic particles. In Subcellular Particles (T. Hayaishi, ed.), p. 128. Ronald Press, New York, 1959. 

Endothelial cells from villous mierove.ssels Strong cxprcs.sion of vWf, ACE, UEA lectin, WGA lectin Long life span, higher proliferation than large placental vessels, rod-like cytoplasmic particles Jinga el al, (2000)... 

Lohka. M. J., and Masui, Y. (1984). Roles of cytosol and cytoplasmic particles in nuclear envelope assembly and sperm pronuclear formation in cell free preparations from amphibian eggs. J. Cell Biol. 9si 1222-1230. 

The specimen preparation requirements (namely, purified components in solution as starting material, for attachment to the substrate and freeze-drying) limited the range of STEM studies in the past. Considerable success was obtained with extracellular particles (viruses) and soluble cytoplasmic particles (ribosomes, chaperone proteins, intermediate filaments, dynein, and other structures robust enough to survive purification). 

Thus three types of nucleoproteins containing D-RNA have been described up to now nuclear particles, informosomes (free cytoplasmic particles), and polysome-bound mRNA-proteins. Only the nuclear particles have been obtained in a purified state, and this has made it possible to study their protein composition and structural organization more extensively. Unfortunately, free informosomes and polysome-bound particles have not been characterized to a similar extent due to the difficulties in their isolation. This does not allow one to compare directly these three types of particles and to establish whether they represent the same structural elements or not. To answer this question it will be necessary to characterize the proteins constituting the cytoplasmic particles. 

Another approach to the analysis of mRNA transfer to the ribosomes is the study of cytoplasmic particles containing newly formed cytoplasmic mRNA. Leytin et al. (1971) have found that the material containing newly formed mRNA is somewhat less dense in the CsCl gradient than polysomes formed earlier. For example, while the bulk of polysomes have a buoyant density of 1.55 to 1.56 g/cm, the newly formed material possesses a density of 1.47 to 1.53 g/cm. Newly formed particles comprise only a small fraction of the total material since they cannot be detected by routine UV absorption methods. With more detailed analysis two newly formed components may be observed component A with p = 1.49 g/cm and component B with p = 1.52 g/cm. After long-term incubation, or in the presence of actinomycin D (chase experiment), almost all radioactive material is transferred from A to B peaks to the main peak of the polysomes. Inhibition of protein synthesis by cycloheximide interferes with these polysome transformations, and the label representing newly synthesized material accumulates in component A (p = 1.49 g/cm ). Thus one can suggest that component A converts to B and the latter is transformed into mature polysomes. It was found further than... 

M. Revel and H. H. Hiatt. 1965. A cytoplasmic particle bearing messenger RNA in... 

Kafatos, F. C. 1968. Cytoplasmic particles carrying rapidly labeled RNA in developing insect epidermis. Proc. Nat. Acad. Sci. U.S.A., 59 1251-1258. 

Cytoplasmic Particle-Assodated Poly(ADPR) Polymerase Activity... 

Signal recognition particles (SRPs) Cytoplasmic particles that dock ribosomes on the surface of the endoplasmic reticulum (ER) if the nascent polypeptide is destined to be processed by the ER. The SRP recognizes and binds to a specific N-terminal signal sequence on the nascent polypeptide. 

Novikoff, A.B., Podber, E., Ryan, J., Noe, E. Biochemical heterogeneity of the cytoplasmic particles isolated from rat liver homogenate. J. Histochem. Cytochem. 1, 27-46 (1953)... 

Electron microscopic examination of nuclei prepared in 0.25 M sucrose in the presence of calcium demonstrates clumping of the intranuclear structures. Clumping should warn investigators of the possibility of agglomeration of cytoplasmic material. It is also believed that the effect of DNase on nuclear oxidative phosphorylation constitutes a reliable method of distinguishing nuclear and mitochondrial oxidative phosphorylation. Although this conclusion is probably justified, it can be substantiated only by adequate control studies of the effect of DNase on the oxidative phosphorylation of cytoplasmic particles. 

Blaschko, H. and Welch, A. D., Localization of adrenaline in cytoplasmic particles of the bovine adrenal medulla, Arch. exp. Path. Pharmak. 219, 17 (1953). 

Mammalian Tyrosinase. Another copper-containing tyrosinase has been found in cytoplasmic particles of melanocytes of mammalian skin. This enzyme attacks n-tyrosine, but not D-tyrosine, after a lag period. With dopa as substrate, there is no lag. The product is a polymerized oxidation product, a highly colored melanin. The enzyme is more stable than the plant tyrosinases, and can be assayed both manometrically and by estimation of the product. C Mabeled tyrosine has been used to produce labeled, insoluble melanin. 

The chloroplasts are embedded in the cytoplasm of the cell and are one of a number of cytoplasmic particles that are found in plant cells. There is no general agreement as to the nature of these various cytoplasmic particles (5). The term mitochondria is commonly used to denote one of these fractions, and a great deal of work has been carried out on their physiological role particularly with respect to the localization of enzymes... 

It is inferred in these studies that the chloroplast is the photosynthetic unit and contains all of the enzymes and cofactors essential for reducing carbon dioxide to the carbohydrate level. Because of the known difficulties in obtaining chloroplast preparations free from contamination by mitochondria and other cytoplasmic particles, it would be well to withhold judgment on this question. 

The oxidation of tyrosine to 3,4-dihydroxyphenylalanine (DOPA) is a well-established reaction that occurs enzymatically under the influence of tyrosinase. The presence of tyrosinase has been shown in mammalian tissues, a particularly good source being the Harding-Passey mouse melanoma. " Lemer et determined that the enzymatic activity for tyrosine and DOPA is associated with cytoplasmic particles and that the two activities are not separable. Preparations can be obtained which have a long induction period before the onset of the oxidation of tyrosine and... 

Confirmation that the synthesis of n-ascorbic acid m vwo does in fact proceed via these or very similar routes was obtained in work in which the enzymic oxidation in vitro of L-galactono-7-lactone to L-ascorbic acid by plant mitochondria was demonstrated (Mapson et al., 1954). The enzymes responsible were located entirely within the cytoplasmic particles (mitochondria), and their activity depended on the maintenance of the mitochondria in an intact condition. 

Lysosomes are described as cytoplasmic particles containing numerous acid hydrolases of various specificities. Under normal conditions, the membrane of the granules is impermeable to the substrates of these enzymes however, a variety of chemical or physical agents are able to alter the lysosomal membrane and thus provide the enzymes with free access to the external substrates (Fig. 1). Lysosomes are found in many animal tissues, and increasing evidence is recently being uncovered that they are also present in plants. 

Oxidations by Washed Cytoplasmic Particles op Etiolated Mung Bean... 

Spimn, a. S., and Nemer, M. (1965). Messenger RNA in early sea-urchin embryos Cytoplasmic particles. Science 150, 214-217. 

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