A model of contractile vacuole

SUMMARYThe electric potential of the contractile vacuole (CV) of Paramecium multimicronucleatum was measured in situ using microelectrodes,one placed in the CV and the other (reference electrode) in the cytosol of a living cell. The CV potential in a mechanically compressed cell increased in a stepwise manner to a maximal value (approximately 80 mV) early in the fluid-filling phase. This stepwise change was caused by the consecutive reattachment to the CV of the radial arms, where the electrogenic sites are located. The current generated by a single arm was approximately 1.3×10-10 A. When cells adapted to a hypotonic solution were exposed to a hypertonic solution, the rate of fluid segregation, RCVC, in the contractile vacuole complex (CVC) diminished at the same time as immunological labelling for V-ATPase disappeared from the radial arms. When the cells were re-exposed to the previous hypotonic solution, the CV potential, which had presumably dropped to near zero after the cell's exposure to the hypertonic solution, gradually returned to its maximum level. This increase in the CV potential occurred in parallel with the recovery of immunological labelling for V-ATPase in the radial arm and the resumption of RCVC or fluid segregation. Concanamycin B, a potent V-ATPase inhibitor, brought about significant decreases in both the CV potential and RCVC. We confirm that (i) the electrogenic site of the radial arm is situated in the decorated spongiome, and (ii) the V-ATPase in the decorated spongiome is electrogenic and is necessary for fluid segregation in the CVC. The CV potential remained at a constant high level(approximately 80 mV), whereas RCVC varied between cells depending on the osmolarity of the adaptation solution. Moreover, the CV potential did not change even though RCVC increased when cells adapted to one osmolarity were exposed to a lower osmolarity, implying that RCVC is not directly correlated with the number of functional V-ATPase complexes present in the CVC.

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Preliminary note on the functions and homologies of the contractile vacuole in plants and animals

Annals and Magazine of Natural History ◽

10.1080/00222938909460296 ◽

1889 ◽

Vol 3 (13) ◽

pp. 64-66 ◽

Cited By ~ 1

Author(s):

Marcus M. Hartog

Keyword(s):

Contractile Vacuole ◽

Preliminary Note

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MICRURGICAL STUDIES IN CELL PHYSIOLOGY

The Journal of General Physiology ◽

10.1085/jgp.10.1.9 ◽

1926 ◽

Vol 10 (1) ◽

pp. 9-21 ◽

Cited By ~ 11

Author(s):

Paul Reznikoff

Keyword(s):

Heavy Metals ◽

Metal Cation ◽

Surface Membrane ◽

The Other ◽

Contractile Vacuole ◽

Toxic Action ◽

Cell Physiology ◽

Relative Toxicity ◽

A Cell

I. Plasmalemma. 1. The order of toxicity of the salts used in these experiments on the surface membrane of a cell, taking as a criterion viability of amebæ immersed in solutions for 1 day, is HgCl2, FeCl3> AlCl3> CuCl2> PbCl2> FeCl2. Using viability for 5 days as a criterion, the order of toxicity is PbCl2> CuCl2> HgCl2> AlCl3> FeCl3> FeCl2. 2. The rate of toxicity is in the order FeCl3> HgCl2> AlCl3> FeCl2> CuCl2> PbCl2. 3. The ability of amebæ to recover from a marked tear of the plasmalemma in the solutions of the salts occurred in the following order: AlCl3> PbCl2> FeCl2> CuCl2> FeCl3> HgCl2. II. Internal Protoplasm. 4. The relative toxicity of the salts on the internal protoplasm, judged by the recovery of the amebæ from large injections and the range over which these salts can cause coagulation of the internal protoplasm, is in the following order: PbCl2> CuCl2> FeCl3> HgCl2> FeCl2> AlCl3. 5. AlCl3 in concentrations between M/32 and M/250 causes a marked temporary enlargement of the contractile vacuole. FeCl2, FeCl3, and CuCl3 produce a slight enlargement of the vacuole. 6. PbCl2, in concentrations used in these experiments, appears to form a different type of combination with the internal protoplasm than do the other salts. III. Permeability. 7. Using the similarity in appearance of the internal protoplasm after injection and after immersion to indicate that the surface is permeable to a substance in which the ameba is immersed, it is concluded that AlCl3 can easily penetrate the intact plasmalemma. CuCl2 also seems to have some penetrating power. None of the other salts studied give visible internal evidence of penetrability into the ameba. IV. Toxicity. 8. The toxic action of the chlorides of the heavy metals used in these experiments, and of aluminum, is exerted principally upon the surface of the cell and is due not only to the action of the metal cation but also to acid which is produced by hydrolysis.

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Identification of Contractile Vacuole Proteins in Trypanosoma cruzi

PLoS ONE ◽

10.1371/journal.pone.0018013 ◽

2011 ◽

Vol 6 (3) ◽

pp. e18013 ◽

Cited By ~ 44

Author(s):

Paul N. Ulrich ◽

Veronica Jimenez ◽

Miyoung Park ◽

Vicente P. Martins ◽

James Atwood ◽

...

Keyword(s):

Trypanosoma Cruzi ◽

Contractile Vacuole

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Dictyostelium discoideum RabS and Rab2 colocalize with the Golgi and contractile vacuole system and regulate osmoregulation

Journal of Biosciences ◽

10.1007/s12038-016-9610-4 ◽

2016 ◽

Vol 41 (2) ◽

pp. 205-217 ◽

Cited By ~ 7

Author(s):

Katherine Maringer ◽

Azure Yarbrough ◽

Sunder Sims-Lucas ◽

Entsar Saheb ◽

Sanaa Jawed ◽

...

Keyword(s):

Dictyostelium Discoideum ◽

Contractile Vacuole

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Contractile Vacuole Complexes in Algae

Proceedings in Life Sciences - Compartments in Algal Cells and Their Interaction ◽

10.1007/978-3-642-69686-2_15 ◽

1984 ◽

pp. 139-146 ◽

Cited By ~ 7

Author(s):

K. Hausmann ◽

D. J. Patterson

Keyword(s):

Contractile Vacuole

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The vacuolar proton pump of Dictyostelium discoideum: molecular cloning and analysis of the 100 kDa subunit

Journal of Cell Science ◽

10.1242/jcs.109.5.1041 ◽

1996 ◽

Vol 109 (5) ◽

pp. 1041-1051 ◽

Cited By ~ 2

Author(s):

T. Liu ◽

M. Clarke

Keyword(s):

Dictyostelium Discoideum ◽

Proton Pump ◽

Single Gene ◽

Consensus Sequence ◽

Amino Acid Sequences ◽

Contractile Vacuole ◽

Proton Pumps ◽

Variable Regions ◽

Endosomal Membranes ◽

Vacuolar Proton Pump

The vacuolar proton pump is a highly-conserved multimeric enzyme that catalyzes the translocation of protons across the membranes of eukaryotic cells. Its largest subunit (95-116 kDa) occurs in tissue and organelle-specific isoforms and thus may be involved in targeting the enzyme or modulating its function. In amoebae of Dictyostelium discoideum, proton pumps with a 100 kDa subunit are found in membranes of the contractile vacuole complex, an osmoregulatory organelle. We cloned the cDNA that encodes this 100 kDa protein and found that its sequence predicts a protein 45% identical (68% similar) to the corresponding mammalian proton pump subunit. Like the mammalian protein, the predicted Dictyostelium sequence contains six possible transmembrane domains and a single consensus sequence for N-linked glycosylation. Southern blot analysis detected only a single gene, which was designated vatM. Using genomic DNA and degenerate oligonucleotides based on conserved regions of the protein as primers, we generated products by polymerase chain reaction that included highly variable regions of this protein family. The cloned products were identical in nucleotide sequence to vatM, arguing that Dictyostelium cells contain only a single isoform of this proton pump subunit. Consistent with this interpretation, the amino acid sequences of peptides derived from a protein associated with endosomal membranes (Adessu et al. (1995) J. Cell Sci. 108, 3331–3337) match the predicted sequence of the protein encoded by vatM. Thus, a single isoform of the 100 kDa proton pump subunit appears to serve in both the contractile vacuole system and the endosomal/lysosomal system of Dictyostelium, arguing that this subunit is not responsible for regulating the differing abundance and function of proton pumps in these two compartments. Gene targeting experiments suggest that this subunit plays important (possibly essential) roles in Dictyostelium cells.

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The Physiology of Contractile Vacuoles

Journal of Experimental Biology ◽

10.1242/jeb.37.1.73 ◽

1960 ◽

Vol 37 (1) ◽

pp. 73-82

Author(s):

J. A. KITCHING ◽

J. E. PADFIELD ◽

M. H. ROGERS

Keyword(s):

Body Surface ◽

Normal Activity ◽

The Body ◽

Contractile Vacuole ◽

Diffusion Constants ◽

Contractile Vacuoles

1. The suctorian Discophrya collini (Root) has been subjected to D2O-H2O mixtures containing up to 99.7% D2O. 2. In 25% D2O or over there is a rapid but temporary shrinkage of the body. This shrinkage is difficult to estimate owing to the wrinkling of the body surface, but amounts to at least 10% in the undiluted (99.7%)D2O. 3. During the period of temporary shrinkage the contractile vacuole ceases activity. Normal activity is resumed when the normal volume is regained. In concentrations of D2O too low to cause shrinkage there is a temporary fall in the rate of vacuolar output. 4. Return to H2O leads to a brief but often very considerable rise in vacuolar output. 5. It is concluded that D2O penetrates less rapidly than H2O. A difference of at least 10% in the diffusion constants in the membrane would be required to explain our results. We cannot exclude this as unreasonable from our data, although an explanation based on differences in the equilibrium properties of D2O and H2O might also be invoked.

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