The Osmoregulatory System of the Amoeba, Acanthamoeba Castellanii

1972 ◽  
Vol 57 (1) ◽  
pp. 55-76
Author(s):  
R. A. PAL
Keyword(s):  
Plasma Membrane ◽  
Polyethylene Glycol ◽  
Ethylene Glycol ◽  
Surface Membrane ◽  
Acanthamoeba Castellanii ◽  
Sodium Sulphate ◽  
The Body ◽  
Contractile Vacuole ◽  
Body Volume ◽  
Food Vacuoles

1. It is estimated that Acanthamoeba castellanii eliminates a volume of water equal to its body volume in about 15-30 min. About 7% of the vacuolar discharge enters the body by means other than osmosis through the surface membrane. Food vacuoles fusing with the contractile vacuole do not significantly affect the rate of output. 2. Vacuolar output declines with the age of culture so that during the stationary phase of growth it is about half of that during early log phase of growth. 3. The rate of output of the contractile vacuole decreases with an increase of concentration of a non-penetrating solute in the external medium and shows a rectilinear relationship up to 0.07 M concentration. A low residual output after 0.07 M may be due to food vacuoles and pinocytic vacuoles. 4. On the basis of vacuolar output the excess internal osmotic pressure and permeability constant of water has been estimated as 0.07 M non-electrolyte and 0.04µm min-1 atm.-1 respectively. 5. On the basis of vacuolar behaviour it is concluded that the relative permeabilities of the plasma membrane to different solutes follows this order: methyl alcohol > ethylene glycol > urea > glycerol. On certain assumptions the permeability of the plasma membrane to ethylene glycol has been estimated provisionally as 0.107 x 10-16 mol/sec/µm2/mol/l. 6. Vacuolar behaviour suggests that sodium chloride, sodium nitrate, sodium sulphate and potassium chloride, but not magnesium chloride and calcium chloride, pass into the cell freely. 7. Growth of populations of A. castellanii is almost normal in polyethylene glycol 600 up to 0.07 M concentration but in higher concentrations it is low. There are some indications of an increase in volume of A . castellanii in cultures of polyethylene glycol 600 up to 0.07 M concentration, but not in higher concentrations. For amoebae cultured in media containing polyethylene glycol 600 the rate of output of the contractile vacuole declines sharply with an increase of polyethylene glycol 600 up to 0.07 M concentration and then more gradually.

scholarly journals Amoeba chironomi, nov. sp., Parasitic in the Alimentary Tract of the Larva of a Chironomus

Parasitology ◽  
1909 ◽  
Vol 2 (1-2) ◽  
pp. 32-41 ◽  
Author(s):  
Annie Porter
Keyword(s):  
Digestive Tract ◽  
Alimentary Tract ◽  
Cross Infection ◽  
The Body ◽  
Entire Length ◽  
Contractile Vacuole ◽  
Iris Diaphragm ◽  
Highly Sensitive ◽  
Food Vacuoles ◽  
Well Differentiated

Amoeba chironomi, nov. sp., is distributed through practically the entire length of the digestive tract of the larva of Chironomus.The body of A. chironomi varies from 15μ, to 18μ in length and from 10μ. to 12μ in breadth. The single pseudopodium may reach 15μ in length; one pseudopodium only is usually present.Ectoplasm and endoplasm are well differentiated. A nucleus and a contractile vacuole are present. Food vacuoles are rare. The contractile vacuole resembles an iris diaphragm, consisting of a series of fine, curved, radiating canaliculi, opening into a central space. The excretory products are faintly reddish in colour. The presence of a contractile vacuole is uncommon in parasitic Amoebae.The nucleus is poor in chromatin. A nucleolus is present.A. chironomi is highly sensitive to the degree of concentration of the medium in which it lives. Very slight increase in density causes the organism to encyst.Encystment occurs in the rectum of the host, and the cysts are voided with the faeces. The cysts are from 12μ. to 20μ long and from 9μ broad. The process of encystment is rapid.The method of cross-infection of the host is probably a “casual” one, viz. by the mouth.

scholarly journals Phagotrophy and Two New Structures in the Malaria Parasite Plasmodium berghei

1959 ◽  
Vol 6 (1) ◽  
pp. 103-112 ◽  
Author(s):  
Maria A. Rudzinska ◽  
William Trager
Keyword(s):  
Plasma Membrane ◽  
Plasmodium Berghei ◽  
Food Vacuole ◽  
The Body ◽  
Host Cells ◽  
Butyl Methacrylate ◽  
Host Cytoplasm ◽  
Mitochondrial Functions ◽  
Food Vacuoles ◽  
Almost All

Blood collected from rats infected with Plasmodium berghei was centrifuged and the pellet was fixed for 1 hour in 1 per cent buffered OsO4 with 4.9 per cent sucrose. The material was embedded in n-butyl methacrylate and the resulting blocks sectioned for electron microscopy. The parasites were found to contain, in almost all sections, oval bodies of the same density and structure as the host cytoplasm. Continuity between these bodies and the host cytoplasm was found in a number of electron micrographs, showing that the bodies are formed by invagination of the double plasma membrane of the parasite. In this way the host cell is incorporated by phagotrophy into food vacuoles within the parasite. Hematin, the residue of hemoglobin digestion, was never observed inside the food vacuole but in small vesicles lying around it and sometimes connected with it. The vesicles are pinched off from the food vacuole proper and are the site of hemoglobin digestion. The active double limiting membrane is responsible not only for the formation of food vacuoles but also for the presence of two new structures. One is composed of two to six concentric double wavy membranes originating from the plasma membrane. Since no typical mitochondria were found in P. berghei, it is assumed that the concentric structure performs mitochondrial functions. The other structure appears as a sausage-shaped vacuole surrounded by two membranes of the same thickness, density, and spacing as the limiting membrane of the body. The cytoplasm of the parasite is rich in vesicles of endoplasmic reticulum and Palade's small particles. Its nucleus is of low density and encased in a double membrane. The host cells (reticulocytes) have mitochondria with numerous cristae mitochondriales. In many infected and intact reticulocytes ferritin was found in vacuoles, mitochondria, canaliculi, or scattered in the cytoplasm.

scholarly journals The Physiology of Contractile Vacuoles

1934 ◽  
Vol 11 (4) ◽  
pp. 364-381
Author(s):  
J. A. KITCHING
Keyword(s):  
Fresh Water ◽  
Sea Water ◽  
Tap Water ◽  
Marine Species ◽  
The Body ◽  
Contractile Vacuole ◽  
Body Volume ◽  
Water Value ◽  
Contractile Vacuoles ◽  
Sustained Increase

1. The rate of output of fluid from the contractile vacuole of a fresh-water Peritrich Ciliate was decreased to a new steady value immediately the organism was placed in a mixture of tap water and sea water. The rate of output returned to its original value immediately the organism was replaced in tap water. The contractile vacuole was stopped when the organism was treated with a mixture containing more than 12 per cent, of sea water. 2. Transference of various species of marine Peritricha from 100 per cent, sea water to mixtures of sea water and tap water led to an immediate increase of the body volume to a new and generally steady value. Return of the organism to 100 per cent, sea water led to an immediate decrease of the body volume to its original value or less. 3. Marine Peritricha showed little change in rate of output when treated with concentrations of sea water between 100 and 75 per cent. In more dilute mixtures the rate of output was immediately increased, and then generally fell off slightly to a new steady value which was still considerably above the original (100 per cent. sea water) value. The maximum sustained increase was approximately x 80. Return of the organism to 100 per cent, sea water led to an immediate return of the rate of output to approximately its original value. 4. When individuals of some marine species were placed in very dilute concentrations of sea water, the pellicle was frequently raised up in blisters by the formation of drops of fluid underneath it, and the contractile vacuole stopped. 5. Evidence is brought forward to suggest that in the lower concentrations of sea water marine forms lost salts. 6. The contractile vacuole probably acts as an osmotic controller in fresh-water Protozoa. Its function in those marine Protozoa in which it occurs remains obscure.

The Physiology of Contractile Vacuoles

1948 ◽  
Vol 25 (4) ◽  
pp. 421-436
Author(s):  
J. A. KITCHING
Keyword(s):  
Osmotic Pressure ◽  
Sea Water ◽  
External Medium ◽  
External Solution ◽  
Pond Water ◽  
The Body ◽  
Contractile Vacuole ◽  
Effect Of Temperature ◽  
Body Volume ◽  
Sucrose Solutions

1. On transfer from sea water to dilute sea water, the marine peritrich ciliate Vorticella marina swells more rapidly at higher temperatures. 2. It is concluded that the permeability of the surface of V. marina to water is influenced by temperature, with a Q10 of very roughly 2·5-3·2. 3. The body volume of the fresh-water peritrich ciliate Carchesium aselli is maintained approximately constant when the organism is transferred to solutions of sucrose of concentrations up to about 0·04 M; in higher concentrations the organism shrinks. 4. The rate of output of the contractile vacuole of C. aselli decreases with increasing concentrations of sucrose in the external medium; the rate of output is very low in 0·05 M-sucrose. 5. From a consideration of the effects of sucrose solutions on the body volume and on the rate of vacuolar output it is concluded that the initial osmotic pressure of C. aselli normally exceeds that of the external pond water by about 0·04-0·05 M non-electrolyte. 6. The internal osmotic pressure of C. aselli is not materially increased by increase of temperature. 7. It is concluded that the increase in rate of vacuolar output, which accompanies increase of temperature, counterbalances an increased rate of osmotic uptake of water from the external medium, and that this increased rate of uptake is due to an effect of temperature on the permeability of the surface through which the water enters. 8. The rate of vacuolar output is temporarily much increased when C. aselli, which has been equilibrated in solutions of ethylene glycol, is returned to pond water. 9. It is suggested that the temperature and the osmotic pressure of the external solution largely determine the osmotic stress which is imposed on the organism, and that they thus influence the state of hydration of the protoplasm; in turn this may be supposed to determine the activity of the contractile vacuole.

The Physiology of Contractile Vacuoles

1948 ◽  
Vol 25 (4) ◽  
pp. 406-420
Author(s):  
J. A. KITCHING
Keyword(s):  
Fresh Water ◽  
High Temperatures ◽  
Normal Level ◽  
Contractile Vacuole ◽  
High Rate ◽  
Body Volume ◽  
Slow Decline ◽  
Food Vacuoles ◽  
Contractile Vacuoles

1. The rate of output of the contractile vacuole in a fresh-water peritrich ciliate (Carchesium aselli) varies with temperature with a Q10 of about 2·5-3·2, or a µ of about 17,000, over the range 0-30° C. 2. There is a slow decline in output during exposure for several hours to high temperatures (25-30° C.). At still higher temperatures (34° C.) a high rate of output is maintained for a few minutes, but swelling and death rapidly ensue. 3. The frequency of uptake of food vacuoles also varies with temperature, increasing from 0 to about 24° C., but decreasing at higher temperatures. At about 0° C. and at temperatures above about 30° C. no food vacuoles are taken up and the adoral cilia remain extended and motionless. 4. No change in body volume could be detected during exposure to high temperatures (25-30° C.) for two or more hours, even though the rate of vacuolar output was increased to three or four times its normal level at 15° C. It is concluded that the rate of uptake of water from the outside medium must have been increased correspondingly. 5. It is suggested that temperature affects the permeability of the organism to water, and that the rate of vacuolar output is adjusted accordingly, although on the evidence so far presented other explanations are possible.

Turnover of Plasma Membrane During Phagocytosis

1972 ◽  
Vol 11 (2) ◽  
pp. 569-579
Author(s):  
R. J. GOODALL ◽  
Y. F. LAI ◽  
J. E. THOMPSON
Keyword(s):  
Plasma Membrane ◽  
Cytoplasmic Membrane ◽  
De Novo ◽  
Surface Membrane ◽  
Acanthamoeba Castellanii ◽  
De Novo Synthesis ◽  
Cellular Membranes ◽  
Latex Beads ◽  
Specific Radio ◽  
Preferential Synthesis

Levels of radioactive glycine and glycerol incorporated into the plasma membrane of Acanthamoeba castellanii during phagocytosis were determined in order to elucidate how surface membrane expended during this process is replaced. The amoebae were allowed to ingest latex beads in the presence of the labelled membrane precursors and plasma membrane was then isolated and analysed for the presence of radioactivity. The isolated membrane fragments were found to be quite highly labelled. In order to ascertain whether this represented preferential synthesis of plasma membrane in response to phagocytosis, the specific radio-activities of the isolated membrane fractions were compared with those of corresponding particulate homogenates, which were composites of all cellular membranes. Enrichment values calculated in this manner proved to be essentially similar for both phagocytosing and non-phagocytosing amoebae. This indicates that de novo synthesis of plasma membrane is not essential for phagocytosis and in turn suggests that pre-existing cytoplasmic membrane is used to replace surface membrane consumed during ingestion. Presumably the incorporation of membrane precursors that was observed represents molecular turnover that occurs irrespective of phagocytosis.

The Physiology of Contractile Vacuoles

1951 ◽  
Vol 28 (2) ◽  
pp. 203-214
Author(s):  
J. A. KITCHING
Keyword(s):  
Ethylene Glycol ◽  
Osmotic Pressure ◽  
Sea Water ◽  
Tap Water ◽  
Good Evidence ◽  
The Body ◽  
Body Volume ◽  
Dilute Solution ◽  
High Level ◽  
Osmoregulatory Mechanism

1. Evidence from osmotic experiments indicates that the amount of osmotically inactive material in the suctorian Podophrya is small, and that the internal osmotic pressure of the cytoplasm is approximately that of a 0-04 M solution of non-electrolyte. 2. When the internal osmotic pressure of Podophrya is raised to an abnormally high level by equilibration with a solution of ethylene glycol or with dilute sea water, and the organism is then transferred to tap water, the rate of vacuolar output is temporarily raised far above its normal value. The body swells only slightly. This is taken as good evidence for osmoregulation. 3. When Podophrya is placed in a dilute solution of sucrose the rate of vacuolar output (relative to the original rate in tap water) decreases rectilinearly with the concentration of sucrose used, reaching zero at about 0.04M. This is as would be required for good osmoregulation. 4. There is a slight lag in the response of the contractile vacuole to a change of medium. It is suggested that this delay in adjustment of the osmoregulatory mechanism must result in a slight change of body volume, which could be the basis for the control of vacuolar output.

Interaction between intracellular vacuoles and the cell surface analysed by finite aperture theory interference reflection microscopy

1982 ◽  
Vol 54 (1) ◽  
pp. 287-298
Author(s):  
D. Gingell ◽  
I. Todd ◽  
N. Owens
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Surface Membrane ◽  
Contractile Vacuole ◽  
Contractile Mechanism ◽  
Cell Surface Membrane ◽  
Minimal Thickness ◽  
Finite Aperture ◽  
Mechanical Consequence

Using finite aperture theory we have shown that localized very dark areas in the interference reflection images of Dictyostelium discoideum amoebae are due to the close intracellular approach of vesicles and tubular elements of the contractile vacuole system to the plasma membrane adjacent to the substratum. Vesicles interacting in this way become locally deformed to the planar contour of the substratum and are separated from the cell surface membrane by a constant approximately less than 0.1 micron of cytoplasm. Lamellar processes formed by these cells on very adhesive surfaces have identical dimensions. This minimal thickness may be a mechanical consequence of a contractile mechanism which pulls membranes together.

scholarly journals The Physiology Of Contractile Vacuoles

1936 ◽  
Vol 13 (1) ◽  
pp. 11-27
Author(s):  
J. A. KITCHING
Keyword(s):  
Cell Membrane ◽  
Body Surface ◽  
Salt Concentration ◽  
Sea Water ◽  
Cane Sugar ◽  
The Body ◽  
Contractile Vacuole ◽  
Body Volume ◽  
Oxidative Process ◽  
Low Concentrations

1. There was no change in the body volume of marine Peritricha subjected to reductions in the salt concentration of the medium, so long as the osmotic pressure of the medium was kept constant by the addition of urea, glycerol, or cane-sugar. In mixtures of isotonic non-electrolytes with sea water the rate of vacuolar output was decreased--more so in the case of urea than of glycerol. It is concluded that the cell membrane is relatively impermeable to urea, glycerol, and cane-sugar, and also to neutral salts. 2. Excretory substances could not be produced in sufficient quantity to attract water into the contractile vacuole by osmosis at the rate observed. The process of diastole therefore involves "secretion" of water by the vacuolar walls. 3. Cyanide and sulphide in very low concentrations rapidly caused a great reduction in the rate of output of the contractile vacuole of marine Peritricha. In the case of cyanide this effect was rapidly reversible. Alcohols and urethane only decreased the rate of vacuolar output when present in much higher concentrations. It is suggested that possibly vacuolar activity depends directly on an oxidative process. 4. When marine Peritricha were transferred from dilute sea water to dilute sea water of the same concentration+cyanide M/200 or M/500 (the pH being carefully controlled), the contractile vacuole was completely or almost completely stopped, and the body increased in volume. When the organism was transferred back to dilute sea water of the same concentration without cyanide, the contractile vacuole became active again and the body decreased in volume until a new steady value was attained which was rather below the value in dilute sea water before cyanide treatment. 5. The increase in body volume consequent on treatment with cyanide was greater the more dilute was the sea water. For sea water of concentrations of 100-75 per cent, no swelling was detectable when the organism was treated with cyanide. 6. The rate of output of the contractile vacuole is sufficiently great to account for the decrease in body volume during recovery from cyanide. 7. The permeability of the body surface to water is estimated as 0.05-0.10 cubic micra per square micron per atmosphere per minute.

The Physiology of Contractile Vacuoles

1954 ◽  
Vol 31 (1) ◽  
pp. 68-75
Author(s):  
J. A. KITCHING
Keyword(s):  
The Body ◽  
Contractile Vacuole ◽  
Body Volume ◽  
Sudden Increase ◽  
Small Decrease ◽  
Partial Restoration ◽  
Contractile Vacuoles

1. A study has been made of the effects of sudden changes of temperature on the contractile vacuole of the suctorian Discophrya piriformis Guilcher. 2. A sudden increase of temperature from below 15° C. by 5° or more causes a temporary fall in the rate of output, followed by a rise to a new level higher than the original. During the depression in activity the body swells slightly. 3. The vacuolar frequency increases immediately but briefly when the temperature is raised, falls steeply when the depression sets in, and when secretion is re-established rises again to a level above the original. 4. A sudden fall in temperature causes an immediate decrease in vacuolar frequency, followed by a partial restoration. The rate of output falls rather more slowly and remains low. In several cases a small decrease in body volume was observed. 5. It is suggested that the contractile vacuole is really contractile. 6. The observations on vacuolar frequency described in this paper are interpreted in terms of an inherent vacuolar rhythm which is modified by temperature and which is partially linked with rate of secretion.

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