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  • Cell multiplication  (1)
  • Chemosensory behaviour  (1)
  • 2-methyl- 1, 2-propanediol aglycone
  • Springer  (2)
  • 1
    ISSN: 1432-136X
    Keywords: Synthetic nutrient medium ; Cell multiplication ; Hemin ; Phospholipids ; Tetrahymena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ciliate Tetrahymena thermophila was grown in a synthetic nutrient medium at various amino acid concentrations. Before the beginning of the experiments the cells were starved for 4 h in a pH buffer. They were inoculated at an initial density of only 250 cells per ml. Under these conditions the cells grew and multiplied at only the two highest amino acid concentrations used. Hemin or phospholipids were found to stimulate cell growth at the lower amino acid concentrations. The mechanism behind this stimulatory effect is unknown, but may be connected with the maintenance of an adequate energy flow under adverse conditions. These additions represent an improvement of the synthetic medium for Tetrahymena.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1430-3418
    Keywords: Concanavalin A receptors ; Recognition ; Chemosensory behaviour ; Tetrahymena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between concanavalin A (ConA) receptors and the chemosensory behaviour of the ciliated protozoan Tetrahymena thermophila was studied using the peptide chemoattractants proteose peptone and fibroblast growth factor. Studies on the chemosensory behaviour in semisolid methylcellulose showed that 50 μg/ml ConA selectively inhibited the persistent element of swimming behaviour by reducing time runs of cells responding to proteose peptone from 12.2±4.5 min to 0.8±0.3 min. Methyl-alpha-D-mannoside, but not methyl-alpha-D-galactoside, abolished the inhibitory effect of ConA, suggesting that mannoside-containing ConA receptors are involved in maintaining a persistent swimming behaviour. Control experiments, carried out in liquids where persistent swimming is less important for cellular behaviour, showed that ConA did not affect proteose-peptone-induced chemoattraction under these conditions as measured by a two-phase assay for chemoattraction. Also, no inhibitory effect of ConA could be found on swimming rates when individual velocities of ConA-treated cells were determined. When tested in liquid chemoattraction assays, ConA was found to be a weak but significant chemoattractant. Studies of the cellular location of ConA receptors on the plasma membrane of starved cells showed an unequal distribution. A preferential clustering of receptors at the anterior end of the cell was observed when determined at high concentrations (100 μg/ml) of fluorescent ConA. Methyl-alpha-D-mannoside but not methyl-alpha-D-galactoside abolished the fluorescent ConA labelling, indicating a preferential clustering of these mannoside-containing receptors at the anterior part of the plasma membrane and cilia. At lower concentrations (25 μg/ml), FITC-ConA produced more general labelling of the entire cell membrane. The results suggest that ConA receptors are necessary for the persistent element of swimming and that binding of ConA to its receptors interferes with processes related to signal transduction rather than by limiting the free movement of cilia required for locomotion. The gradient of receptors seen at high FITC-ConA concentrations may be important for a putative spatial chemosensory mechanism, i.e. chemotaxis.
    Type of Medium: Electronic Resource
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