Acid vacuole

Tunicates (ascidians or sea-squirts) are invertebrate marine organisms, which can accumulate vanadium at concentrations approaching 350 mM (the concentration of vanadium in seawater is 10 8 M). This vanadium is taken up as V(V) from seawater (Figure 17.16), reduced to oxidation state III or IV and stored in a soluble form in the blood cells within acidic vacuoles at concentrations a million fold higher than in their external surroundings. 

All of the previous studies with cell suspension cultures of C. roseus have led to the conclusion that not all of the cells in suspension produce alkaloids, i.e., that some differentiation occurs. Neumann and co-workers at Halle 149) used fluorescence and electron microscopy to show that, like the intact plants, indole alkaloid accumulation occurs in the vacuoles of particular cells. Yet there appears to be no ultrastructural difference between these cells and those which do not produce alkaloids. It had been suggested earlier that basic alkaloids were accumulated by some kind of ion trap mechanism in acidic vacuoles (750). Indeed, a substantial pH difference was observed between those vacuoles which do accumulate alkaloids (pH 3) and those which do not (pH 5). It was concluded that the tonoplast of the alkaloid cells seemed to be highly permeable to the neutral form of the alkaloids, but only slightly permeable to the protonated forms. Cell lines which did not exhibit a difference in their vacuolar pH did not accumulate alkaloids. 

Different antimalarials selectively kill the parasite s different developmental forms. The mechanism of action is known for some of them pyrimethamine and dapsone inhibit dihydrofolate reductase (p. 273), as does chlorguanide (proguanil) via its active metabolite. The sulfonamide sulfadoxine inhibits synthesis of dihydrofolic acid (p. 272). Chlo-roquine and quinine accumulate within the acidic vacuoles of blood schizonts and inhibit polymerization of heme, the latter substance being toxic for the schizonts. 

U. Pick and M. Weiss (1991). Polyphosphate hydrolysis within acidic vacuoles in responce to amino-induced alkaline stress in the halotolerant alga Dunaliella salina. Plant. Physiol, 97, 1234—1240. 

After binding, T. cruzi enters host cells via an acidic vacuole, which fuses with lysosomes [818,844-846]. The parasitophorous vacuole formed in this way is later disrupted in order to release the trypanosomes into the cytosol. 7ra j-sialidase activity seems to be required for the latter step, as it desialylates the highly sialylated lysosomal... 

Aluminium, generally supposed to be biological inert, can, when solubilized in the acidic vacuoles of plants, show mild toxicity. 

In recent years, the ECL cell has achieved prominence as the target for gastrin s hyperplastic effect on the endocrine cell population in the stomach. ECL cells are easily identified due to their histamine, acidic vacuole, and HDC content. 

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