Contractile vacuole

Doberstein, S.K., Baines, I.C., Wiegand, G., Kom, E.D., Pollard, T.D. (1993). Inhibition of contractile vacuole function in vivo by antibodies against myosin-I. Nature 365, 841-843. 

Several mechanisms have evolved to prevent this catastrophe. In bacteria and plants, the plasma membrane is surrounded by a nonexpandable cell wall of sufficient rigidity and strength to resist osmotic pressure and prevent osmotic lysis. Certain freshwater protists that live in a highly hypotonic medium have an organelle (contractile vacuole) that pumps water out of the cell. In multicellular animals, blood plasma and interstitial fluid (the extracellular fluid of tissues) are maintained at an osmolarity close to that of the cytosol. The high concentration of albumin and other proteins in blood plasma contributes to its osmolarity. Cells also actively pump out ions such as Na+ into the interstitial fluid to stay in osmotic balance with their surroundings. 

A Mostly freshwater forms without central capsule reproduction either by equal division or by biflagellate spores one or more nuclei contractile vacuole in freshwater forms with little power of amoeboid movement, either with or without silicious skeleton... 

B Marine forms with central capsule often of large size reproduction by division one or more nuclei no contractile vacuole with... 

Contractile Vacuole (pulsating vacuole) A vesicular reservoir in protozoa in which water and waste products collect and are discharged to the outside by means of a contraction of the vacuole. 

In response to the entry of water, protozoans maintain their normal cell volume by extruding water from contractile vacuoles. 

For labeling the plasma membrane, a series of styryl dyes with different spectral properties is available (17). FM4-64, FM2-10, and FMl S have been tested for the use with Dictyostelium. For the combination with GFP-tagged proteins, FM4-64 offers the advantage of being excitable at the same wavelength (488 or 491 nm), and easily separated from GFP by its emission peak above 700 nm (14). All these styryl dyes label first the plasma membrane and then redistribute within a few minutes to membranes of the contractile vacuole system and of endosomes. Therefore, they should be added to the cells immediately before imaging of the plasma membrane is attempted. Since cells tend to round up as the dyes are integrated into the lipid layer of the membrane, concentrations should be kept at the lowest limit. 

Heuser, J., Zhu, Q., and Clarke, M. (1993) Proton pumps populate the contractile vacuoles of Dictyostelium amoebae. J. Cell Biol. 121,1311-1327... 

Montalvetd A, Rohloff P, Docampo R. A funcdonal aquaporin colocalizes with the vacuolar proton pyrophosphatase to acidocalcisomes and the contractile vacuole complex of Trypanosoma cruzi. J Biol Chem 2004 279 38673-38682. 

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