Wild-type and food-vacuole-less Tetrahymena thermophila *1Model for iron uptake and utilization in animal cells

Suhr-Jessen, Peter; Rasmussen, Leif

doi:10.1016/0014-4827(82)90280-4

Cited by 6 publications

(6 citation statements)

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“…The gradually formed hydroxo iron (111) gels are also different, whitish in the presence of phosphates, reddish in their absence. Vacuoleless cells fail to grow under these conditions (Suhr-Jessen and Rasmussen, 1982;unpublished data).…”

Section: Resultsmentioning

confidence: 99%

“…Recently we grew food-vacuole-forming 7: thermophila at neutral pH and found that 10 p M Fe(1II) in the absence of citrate was toxic, while 1,000 pM Fe(II1) in the presence of citrate promoted growth (Suhr-Jessen and Rasmussen, 1982). Shortly after the formation of a food vacuole, the pH within the vacuole drops to about 3 (Nilsson, 1977;Fok et al, 1982).…”

Section: Discussionmentioning

confidence: 99%

“…4C). Food-vacuoleless 2: thermophila are unable to utilize oligomeric chloro hydroxo Fe(III), while vacuole formers grow in 2 pM Fe(II1) (Suhr-Jessen and Rasmussen, 1982). Thus the food vacuole is more efficient in uptake of dissolved Fe(II1) than the plasma membrane.…”

Section: Discussionmentioning

confidence: 99%

“…This combined with the use of mutants with temperature-sensitive capacity for food vacuole formation allows an assessment of the role of the different cellular uptake mechanisms (Rasmussen and Orias, 1976;Orias and Rasmussen, 1977;Suhr-Jessen and Rasmussen, 1982;Rasmussen et al, 1984). Here we examine the Fe(II1) requirement and toxicity in the presence and absence of iron chelators.…”

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confidence: 99%

“…Uptake of ferritin and tris-acetylacetonato-Fe(lll) is independent of food vacuole formation and seems to occur by micropinocytosis and by plasma membrane translocation, respectively.The synthetic nutrient medium for the ciliate Tetrahyrnena offers excellent opportunities for studies on the interrelations between components of the medium and their effects on the cells. This combined with the use of mutants with temperature-sensitive capacity for food vacuole formation allows an assessment of the role of the different cellular uptake mechanisms (Rasmussen and Orias, 1976;Orias and Rasmussen, 1977;Suhr-Jessen and Rasmussen, 1982;Rasmussen et al, 1984). Here we examine the Fe(II1) requirement and toxicity in the presence and absence of iron chelators.…”

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confidence: 99%

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Utilization of iron complexes in an animal cell

Rasmussen

Toftlund²,

Suhr-Jessen

1985

Journal Cellular Physiology

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The ciliate protozoan Tetrahymena thermophila was grown in synthetic nutrient medium in the absence of the iron chelator citrate. Utilization and toxicity of various iron compounds or complexes in iron-starved cells were assessed from the number of cell doublings obtained within a standard time. The compounds tested included complexes formed between ortho-phosphates and two forms of ferric hydroxides, native and cationized ferritin, and tris-acetylacetonato Fe(III). The ferric hydroxo ortho-phosphate particles are toxic and can be removed from the medium by Millipore filtration. Uptake of ferritin and tris-acetylacetonato-Fe(III) is independent of food vacuole formation and seems to occur by micropinocytosis and by plasma membrane translocation, respectively.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Utilization of iron complexes in an animal cell

Rasmussen

Toftlund²,

Suhr-Jessen

1985

Journal Cellular Physiology

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Utilization of phosphate compounds for growth ofTetrahymena

Rasmussen¹,

Toftlund²,

Florín-Christensen

et al. 1985

Experientia

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Experientia 41 (1985), Birkh//user Verlag, CH-4010 Basel/Switzerland Adult specimens of Procambarus were anesthetized by cooling. Abdomens were perfused with 4% paraformaldehyde-4% glutaraldehyde in phosphate buffer (pH = 7.3, 4~ Abdominal ganglia were removed, immersed in fixative (overnight), postfixed in OsO4 (2%, 2 h), dehydrated through an ethanol series, stained 'en bloc' with uranyl acetate and finally embedded in araldite. Thin sections of ventral areas of ganglia were stained on grids with lead citrate. Transmission electron microscopy of neuron perikarya reveals the presence of modified double-walled endocytotic vesicles (300-700 nm). They are formed by apposed neuronal and glial membranes which enclose small extrusions of the glial cytoplasm ( fig. 1). The external membrane is of neuronal origin, whilst the internal one is glial. These two membranes are separated by a narrow cleft of 10 nm as in a normal neuron-glia interface 1~'2. These membranes do not show in general gap-like junctions, but can bear neuronal subsurface cisternae. In some cases, a thin lamina of dense neuronal cytoplasm underlies endocytotic figures. Free double-walled vesicles are frequently observed in neuron cell bodies (figs 2 and 3). Their content shows the same density as glial cytoplasm and is lighter than neuron mitochondrial matrix or neuronal cytoplasm. These vesicles are interpreted as modified endocytotic vesicles moving to internal cytoplasm. Both endocytotic vesicles and internalized double-walled vesicles are found in most of the neuron cell bodies, irrespective of their size or situation in the ganglia. They are not found in glia/axon pairs or in neuropile. The presence of gap-like junctions 11, and the observed modified endocytosis suggest that the neuronal microenvironment concept is no longer applicable to the intercellular space between perikarya of abdominal neurons of crayfish and associated peri-1591 neuronal glia cells. Gap-like junctions could allow the glia-toneuron transfer of small proteins up to 1000-1500 dalton ~3. Larger free cytoplasmic macromolecules could be transferred through endocytosis of glial cytoplasmic extrusions. In this case, some coupled mechanism to free the content of the double walled vesicles and to transport it to destination is probably needed 14.1 Varon, S.S., and Somjen, G.G., Neurosci. Res. Prog. Bull. 17 (1979) 1. 2 Gainer, H., Tasaki, I., and Lasek, R.J., J. Cell Biol. 74 (1977) For the chemotaxis assays polycarbonate filters (8 Ilm pore size, Nuclepore, Concorezzo, Milan, Italy) were coated with gelatin as described 18. The cells were trypsinized (2 min, 0.025 % trypsin, 0.1% EDTA in PBS), suspended in serum-containing culture medium to inactivate the enzyme, centrifuged, washed with medium without serum and resuspended in this medium. 2.5-3 x 105 cells/m119 were placed in the upper compartment of Boyden chambers (0.8 ml), while the lower compartment (0.2 ml) contained the molecules to be tested for their chemotactic activity, in serum-flee culture medium (c = 200 nM). Medi...

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Phosphate compounds as iron chelators in animal cell cultures

Rasmussen

Toftlund

1986

In Vitro Cell Dev Biol

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We have studied the capacity of a number of phosphate compounds to act in the double role as a phosphate source and a detoxifier of ferric chloride hydroxo compounds, i.e. as Fe(III) chelators. The tested compounds were: orthophosphate, trimetaphosphate, alpha-glycerophosphate, beta-glycerophosphate, phytic acid, and phosphorylcholine; the test organism the ciliate protozoon Tetrahymena thermophila, an animal cell; and the nutrient medium was synthetic, consisting solely of low-molecular-weight compounds. We assessed growth rates of cells in two experimental series. First, phosphate-starved cells were exposed to the tested phosphate compound as the only phosphate source and the ferric chloride concentrations were varied stepwise from 0 to 1000 microM. Second, we offered the cells orthophosphate as a phosphate source and selected phosphate compounds as chelators. The cell growth results allow the following conclusions: orthophosphate, trimetaphosphate, alpha-glycerophosphate, and beta-glycerophosphate are excellent phosphate sources; trimetaphosphate, alpha-glycerophosphate, beta-glycerophosphate, and phytic acid are excellent Fe(III) chelators; of the tested compounds trimetaphosphate, alpha-glycerophosphate, and beta-glycerophosphate are excellent in the double role as a phosphate source and a ferric chloride hydroxo detoxifier, i.e. as a Fe(III) chelator.

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Wild-type and food-vacuole-less Tetrahymena thermophila *1Model for iron uptake and utilization in animal cells

Cited by 6 publications

References 10 publications

Utilization of iron complexes in an animal cell

Utilization of iron complexes in an animal cell

Utilization of phosphate compounds for growth ofTetrahymena

Phosphate compounds as iron chelators in animal cell cultures

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