Cells vacuoles

In yeasts and other fungi, the vacuole is an important organelle sharing some properties with the mammalian lysosome (an acidic compartment containing a variety of hydrolytic enzymes) and with the plant cell vacuole (responsible for metabolite storage and for cytosolic ion and pH homeostasis) [18,19]. 

Anthocyanins are colored flavonoids that attract animals when a flower is ready for pollination or a fruit is ready to eat. They are glycosides (i.e., the molecule contains a sugar) that range in color from red, pink, and purple to blue depending on the number and placement of substitutes on the B ring (see Fig. 3.7), the presence of acid residues, and the pH of the cell vacuole where they are stored. Without the sugar these molecules are called anthocyanidins. The color of some pigments results from a complex of different anthocyanin and flavone molecules with metal ions. 

Most anionic FITC-labeled fluorochromes microinjected into the cytoplasm are compartmented by the plant cell vacuoles at rates that depend on their molecular size (14,15). 

F) Hepatic 0.025 0.05 (hepatic cell vacuolation, slightly increased liver weights) ... 

The lysosomes are the cell s stomach, serving to break down various cell components. For this purpose, they contain some 40 different types of hydrolases, which are capable of breaking down every type of macromolecule. The marker enzyme of lysosomes is acid phosphatase. The pH optimum of lysosomal enzymes is adjusted to the acid pH value and is also in the range of pH 5. At neutral pH, as in the cytoplasm, lysosomal enzymes only have low levels of activity. This appears to be a mechanism for protecting the cells from digesting themselves in case lysosomal enzymes enter the cytoplasm at any time. In plants and fungi, the cell vacuoles (see p. 43) have the function of lysosomes. 

Heptachlor epoxide is more toxic then heptachlor. The acute oral LD50 for heptachlor epoxide in rodents and rabbits ranged from 39 to 144mg/kg3 After dietary exposure of rats, heptachlor epoxide caused hepatic cell vacuolization at all dose levels (0.5-10 ppm for up to 108 weeks). Degeneration, hepatomegaly, and regeneration were also reported. Like heptachlor, the ability of heptachlor epoxide to induce lethality after acute exposure may involve its ability to interfere with nerve action or release of neurotransmitters and to inhibit the function of the receptor for y-aminobutyric acid. ... 

FIGURE 8.3 In vivo absorptance spectrum for a single anthocyanic cell vacuole in a leaf of Aristotelia serrata. (K.S. Gould, unpublished data.)... 

Returning once again to the questions of function and uses, the old concept of flavonoids being merely the by-products of cellular metabolism, which are simply compartmentalized in solution in the cell vacuole, is well and truly past its use-by date. For a start, studies have revealed that flavonoids are also commonly found on the outer surfaces of leaves and flowers, albeit only the aglycone form. Additionally, flavonoids have been shown over the past few years to be found in the cell wall, the cytoplasm, in oil bodies, and associated with the nucleus and cell proteins, as well as in the vacuole. Even in the vacuole, flavonoids are not necessarily found free in solution. For example, protein-bound flavonoids have been isolated from lisianthus and other flowers in which a structurally specific binding has been identified (in anthocyanic vacuolar inclusions). It is probable that flavonoid location and specific protein binding properties will ultimately prove to relate directly to their function in plants. 

Other herbicides are selectively inactivated by the target crop whilst the weeds that they control either do not metabolise them or they do it so slowly that the weed is killed before it can inactivate the herbicide. There are a number of key plant enzymes that are used in the inactivation of herbicides. Microsomal mixed function oxidases are able to hydroxylate a wide range of herbicides such as bentazone and diclofop-methyl (Figure 2.30). It is often the case that these hydroxylated metabolites are subsequently glucosylated by sugars in the tissue and these conju-gants can be stored in the cell vacuole where they can have no phytotoxic effects. 

Plants use osmotic pressure to achieve mechanical rigidity. The very high solute concentration in the plant cell vacuole draws water into the cell (Fig. 2-13). The resulting osmotic pressure against the cell wall (turgor pressure) stiffens the cell, the tissue, and the plant body. When the lettuce in your salad wilts, it is because loss of water has reduced turgor pressure. Sudden alterations in turgor pressure produce the movement of plant... 

In some cases with crude preparations from higher plants, it has been shown that the cell volume increased highly, and neoplasmic cell vacuolization was observed. As a result of the administration of polysaccharides, the membranes of Ascites cells showed increased permeability to solutes and, consequently, the cell inhibed more water and swelled. 

As most phenols are found as esters or glycosides, knowledge of their location in a cell or tissue is essential. It is typical that such phenols are sequestered or stored in the cell vacuole. This is important since all phenols are weak acids (see Chapter 2) and as such they are relatively toxic even to... 

Although there were some differences on the effects of temperature and pressure according to each particular compound, the free bases of hyoscyamine (1), scopolamine (2), and pseudoephedrine (6) were all found to be highly soluble in supercritical CO,. However, the hydrochloride salts of these compounds were scarcely extracted by pure CO, under any conditions employed. These results were consistent with preliminary evidence indicating that these alkaloids are not extracted from plant materials by pure CO,. This means that the alkaloids in living cells in the plant are not in the form of their free bases but rather as water-soluble salts in the cell vacuole [40]. Therefore, it was necessary to develop a procedure to enhance the solubilities of alkaloidal salts in CO,. 

Vacuoles are large vesicles used in cells. Vacuoles in plant cells store nutrients, metabolites, and waste products, and maintain the shape and structure of the cells. Figure 14.3 shows an example of vesicles interacting with a vacuole [880]. 

Plant cell vacuole Plant cells usually contain one or more membrane-bounded vacuoles. These are used to store nutrients (e.g. sucrose), water, ions and waste products (especially excess nitrogen-containing compounds). Like lysosomes in animal cells, vacuoles have an acidic pH maintained by H+ pumps in the membrane and contain a variety of degradative enzymes. Entry of water into the vacuole causes it to expand, creating hydrostatic pressure (turgor) inside the cell which is balanced by the mechanical resistance of the cell wall. 

Callus cultures derived from Jerusalem artichoke tubers are initially quiescent and have to be induced to divide. The induction of division is accompanied by a transformation in cell structure, which reflects changes in metabolism (e.g., Gamburg et al., 1999). Within an hour of the excision of Jerusalem artichoke tuber explants, ribosomes increase in abundance. They take the form of helices when scattered in the cytoplasm, and spirals when associated with the endoplasmic reticulum, and increase in frequency over time in line with the rate of protein synthesis (Yeoman and Street, 1973). Electron-dense bodies appear soon after in cell vacuoles, and to a lesser extent in the cytoplasm (Bagshaw et al., 1969), while crystal-containing bodies form in cells, which may contain hydrolytic enzymes (Bagshaw et al., 1969 Gerola and Bassi, 1964). Dormant Jerusalem artichoke tuber explants contain a variety of mitochondrial profiles, including distinctive cup-shaped... 

K. J. Indge (1968c). Polyphosphates of the yeast cell vacuole. J. Gen. Microbiol., 51, 447-455. 

Secondary metabolites can accumulate in the same cell and tissue in which they are formed, but intermediates and end-products can also be transported to other locations for further elaboration or accumulation. For example, TAs and nicotine are typically produced near the root apex, but mostly accumulate within leaf cell vacuoles. Even TA biosynthesis itself involves intercellular transport of several pathway intermediates (Fig.7.9A). P-Glucuronidase (GUS) localization in A. belladonna roots transformed with a PMT promoter-GUS fusion showed that PMT expression is restricted to the pericycle.144 Immunolocalization and in situ RNA hybridization also demonstrated the pericycle-specific expression of H6H.145,146 In contrast, TR-I was immunolocalized to the endodermis and outer root cortex, whereas TR-II was found in the pericycle, endodermis, and outer cortex.85 The localization of TR-I to a different cell type than PMT and H6H implies that an intermediate between PMT and TR-I moves from the pericycle to the endodermis (Fig.7.9A). Similarly, an intermediate between TR-I and H6H must move back to the pericycle. The occurrence of PMT in the pericycle provides the enzyme with efficient access to putrescine, ornithine, and arginine unloaded from the phloem. In the same way, scopolamine produced in the pericycle can be readily translocated to the leaves via the adjacent xylem. 

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