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Hypothesis: cell volume limits cell divisions

100%
Biliński T., Bartosz G.
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2006
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vol. 53
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issue 4
833-835
EN
Mammalian somatic cells and also cells of the yeast Saccharomyces cerevisiae are capable of undergoing a limited number of divisions. Reaching the division limit is referred to, apparently not very fortunately, as replicative aging. A common feature of S. cerevisiae cells and fibroblasts approaching the limit of cell divisions in vitro is attaining giant volumes. In yeast cells this phenomenon is an inevitable consequence of budding so it is not causally related to aging. Therefore, reaching a critically large cell volume may underlie the limit of cell divisions. A similar phenomenon may limit the number of cell divisions of cultured mammalian cells. The term replicative (generative) aging may be therefore illegitimate.
2
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Heme synthesis in yeast does not require oxygen as an obligatory electron acceptor.

81%
Krawiec Z., Święciło A., Biliński T.
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2000
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vol. 47
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issue 4
1027-2035
EN
In a previous paper (Krawiec, Z., Biliński, T., Schüller, C. & Ruis, H., 2000, Acta Biochim. Polon. 47, 201-207) we have shown that catalase T holoenzyme is synthesized in the absence of oxygen after treatment of anaerobic yeast cultures with 0.3 M. NaCl, or during heat shock. This finding suggests that heme moiety of the enzyme can either be formed de novo in the absence of oxygen, or derives from the preexisting heme pool present in cells used as inoculum. The strain bearing hem1 mutation, resulting in inability to form δ-aminolevulinate (ALA), the first committed precursor of heme, was used in order to form heme-depleted cells used as inocula. The cultures were supplemented with ALA at the end of anaerobic growth prior the stress treatment. The appearance of active catalase T in the stressed cells strongly suggests that heme moiety of catalase T is formed in the absence of oxygen. This finding suggests the necessity to reconsider current opinions concerning mechanisms of heme synthesis and the role of heme as an oxygen sensor.
3
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Reactive oxygen species as second messengers? Induction of the expression of yeast catalase T gene by heat and hyperosmotic stress does not require oxygen.

81%
Krawiec Z., Biliński T., Schüller C., Ruis H.
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2000
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vol. 47
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issue 1
201-207
EN
It is shown that oxygen is not absolutely needed for stress-induced synthesis of catalase T in the yeast Saccharomyces cerevisiae. Yeast cells develop heat resistance after exposure to elevated temperatures in anoxia. The levels of catalase activity and thermotolerance are comparable to those in aerobically stressed cells. While these results obviously do not exclude a stress signaling role of reactive oxygen species in some systems, as postulated by other authors, they suggest that the question of the obligatory requirement for reactive oxygen species in other stress signaling systems should be rigorously re-investigated.
4
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Effect of anaerobiosis and glucose on the content of haem and its precursors in intact yeast cells

80%
Łukaszkiewicz J., Biliński T.
Acta Biochimica Polonica
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1979
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vol. 26
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issue 1-2
161-169
5
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Effect of stress on the life span of the yeast Saccharomyces cerevisiae.

71%
Święciło A., Krawiec Z., Wawryn J., Bartosz G., Biliński T.
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2000
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vol. 47
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issue 2
355-364
EN
A correlation is known to exist in yeast and other organisms between the cellular resistance to stress and the life span. The aim of this study was to examine whether stress treatment does affect the generative life span of yeast cells. Both heat shock (38°C, 30 min) and osmotic stress (0.3 M NaCl, 1 h) applied cyclically were found to increase the mean and maximum life span of Saccharomyces cerevisiae. Both effects were more pronounced in superoxide dismutase-deficient yeast strains (up to 50% prolongation of mean life span and up to 30% prolongation of maximum life span) than in their wild-type counterparts. These data point to the importance of the antioxidant barrier in the stress-induced prolongation of yeast life span.
6
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Yeast as a biosensor for antioxidants: simple growth tests employing a Saccharomyces cerevisiae mutant defective in superoxide dismutase

61%
Żyracka E., Zadrąg R., Kozioł S., Krzepiłko A., Bartosz G., Biliński T.
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EN
Mutants of Saccharomyces cerevisiae devoid of Cu,Zn-superoxide dismutase are hypersensitive to a range of oxidants, hyperbaric oxygen and hyperosmotic media, show lysine and methionine auxotrophy when grown under the atmosphere of air and have a shortened replicative life span when compared to the wild-type strain. Ascorbate and other antioxidants can ameliorate these defects, which may be a basis of simple tests sensing the presence of antioxidants. In particular, tests of growth on solid medium (colony formation) in the absence of methionine and/or lysine, or in the presence of 0.8 M NaCl can be useful for detection and semiquantitative estimation of compounds of antioxidant properties. Hypoxic atmosphere was found to increase the sensitivity of detection of antioxidants. The test of abolishment of lysine auxotrophy showed a concentration dependence of the antioxidant effects of cysteine and N-acetylcysteine which, however, lost their protective action at high concentration, in contrast to glutathione which was effective also at higher concentrations.
7
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Deficiency in superoxide dismutases shortens life span of yeast cells

61%
Wawryn J., Krzepiłko A., Myszka A., Biliński T.
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