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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 404 (2000), S. 120-120 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sir Leonard Hayflick makes some good points about ageing and ageing research in his Millennium Essay (Nature 403, 365; 2000). I agree that “humans, and the pet and zoo animals that we choose to protect, are the only ...
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 9 (1962), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. Production of a “vitamin B22-like compound” by Tetrahymena pyriformis mating type II, variety 1, and 3 other tetrahymenids was demonstrated. The compound produced by T. pyriformis was nutritionally active for Escherichia coli and Lactobacillus leichmannii and inert for Ochromonas malhamensis and Euglena gracilis, despite use of a variety of the standard methods for liberating bound B12. By dry-weight it is present in 1 part in 30 million. Its chromatographic and electrophoretic properties are described.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 37 (1990), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Tetrahymena setosa has a nutritional requirement for micro amounts of sterol, a requirement which is also satisfied by relatively large amounts of either intact phospholipids or a mixture of unsaturated fatty acids normally found in these ciliates. Three microsomal fatty acyl-CoA desaturases have been isolated from T. setosa and partially characterized. These enzymes which can account for the formation of the majority of the ciliate's unsaturated fatty acids, include: a Δ9, a Δ12 and a Δ6 desaturase which catalyze the transformation of stearoyl-CoA to oleic acid, of oleoyl-CoA to linoleic acid and of linoleoyl-CoA to ϒ-linolenic acid, respectively. The stearoyl CoA desaturase required NAD (or NADP), ATP and free CoA; the Δ6 and Δ12 desaturases required NADP, but not ATP or CoA. Cellular levels of the three desaturases were highest in mid-logarithmic phase cells and lowest in stationary phase cells. In order to determine if there was a relationship between the sterol requirement and the ability of the organism to desaturate, T. setosa was grown in a synthetic medium supplemented with either cholesterol or a phospholipid which permits growth in the absence of cholesterol, or with both phospholipid and cholesterol. Cells grown with phospholipid alone had only half as much stearoyl-CoA and oleoyl-CoA desaturase activity as cells of identical culture age grown either on cholesterol alone or on cholesterol plus phospholipid.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 45 (1998), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Paramecium tetraurelia contains high concentrations of ethanolamine sphingolipids, especially in its ciliary membrane. Three ethanolamine sphingophospholipids with different long chain bases (dihydrosphingosine, sphingosine and phytosphingosine), and their phosphonyl analogs, were previously identified and characterized. In the present study, radiolabeling experiments on lag- and log-phase cells were performed to investigate the extent of sphingolipid biosynthetic capacities of the ciliate. Long chain bases of sphingolipids are formed by an initial condensation reaction of serine with a fatty-coenzyme A. Thus, radiolabeled palmitic acid, stearic acid and serine were used as precursor compounds in these experiments. The results indicated that (1) sphingolipid precursors were incorporated into every major lipid fraction. (2) ethanolamine sphingophosphonolipids accumulated faster than the ethanolamine sphingophospholipids, (3) in contrast to these sphingolipids, the glycerolipid, phosphatidyethanolamine. accumulated faster than its phosphono analog, and (4) palmitic acid, but not stearic acid, was incorporated into the long chain bases of ethanolamine sphingophospho- and sphingophosphonolipids. consistent with an earlier report demonstrating that these lipids contain only C,g long chain bases. Since P. tetraurelia takes up serine and other water-soluble substrates very slowly, and catabolizes fatty acids rapidly, label is randomized in intact cells. Thus, cell-free protocols provide useful experimental systems for studies of sphingolipid biosynthesis than do intact organisms, when the uptake of precursor substrates are slow.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 9 (1962), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. In a chemically-defined medium Tetrahymena setifera HZ-1 required a sterol, an alcohol, eleven amino acids, a purine, a pyrimidine, and six B-complex vitamins. The sterol requirement was met by a variety of 3β-OH, C27-C29 sterols including cholesterol and stigmasterol, but not by precursors of cholesterol which precede desmosterol or Δ7-cholestenol. Some combinations of long-chain fatty acids with a synthetic dipalmitoyl phosphorylethanolamine partly substituted for sterol. Ethyl and methyl alcohols (but not a variety of other alcohols and organic acids) satisfied the alcohol requirement.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 8 (1961), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Tetrahymena paravorax RP was cultured axenically in a medium of known chemical composition (within the limits of contemporary standards of chemical purity). In this medium, it required 12 amino acids, 6 B-complex vitamins, a purine, a pyrimidine, and inorganic salts. A sterol or sterol ester was necessary for optimal growth. Plant and animal 3 β-OH sterols with saturated and unsaturated ring systems, and with a variety of side chain structures, were active. Several methylated sterols suggested as intermediates in cholesterol synthesis were inhibitory.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 8 (1961), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Glaucoma chaitoni. A has been grown in a medium free from protein. Twelve amino acids, seven B-vita-mins, a purine and pyrimidine were essential. Long-chain unsaturated fatty acids and their triglycerides, synthetic phosphatides, and carbohydrates were stimulatory. Oleic acid- containing lipids were best. The significance of the phosphatide activity and the applicability of the results of this work to problems in tissue cell and bacterial cultivation are discussed.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 6 (1959), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. Differences in temperature-tolerance, generation time, nutritional requirements, osmoresistance, pigment production, and sensitivity to high hydrogen or hydroxyl ion concentration have been observed among varieties, and among mating types within varieties of Tetrahymena pyriformis. The usefulness of these differences to taxonomists and geneticists is discussed.The nutrition of a temperature-tolerant strain, mating type II, variety 1, was given special attention and a chemicallydefined medium devised to support rapid growth at 35d̀ C. At 40d̀, growth in this medium failed, but was good in a crude medium. Temperature factors are suggested. Permeability of this ciliate, as inferred by utilization of nucleotides, was high.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 45 (1998), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Changes in the fatty acid composition of the membrane lipids of the marine ciliate. Parauronema acutum were studied in ciliates harvested from early logarithmic, decelerating logarithmic and stationary phase culture. The relative amounts of 18:1 (9) and 18:2 (9, 12) decreases in both the phospholipid and the neutral sphingolipid fractions with increasing culture age. The content of 18:4 (6, 9, 12, 15), 20:5 (5, 8, 11, 14, 17) and 22:6 (4, 7, 10, 13, 16, 19) in these same lipids increases with culture age. While P. acutum was isolated as a marine ciliate and is usually grown in a medium containing 2.8% NaCl concentration, it actually grows well over NaCl concentration of 1% to 3% and will grow suboptimally without added NaCl. NaCl concentrations above 3% are inhibitory, although suboptimal growth occurs at 5% NaCl concentration. Lipids obtained from ciliates grown at either 1.5% or 2.8% NaCl have essentially identical FAME profiles. Lipids obtained from ciliates grown at either higher or lower concentrations of NaCl show marked changes in FAME profile. In both cases 18:2 (9, 12) content greatly increases while the content of 18 and 20 carbon highly unsaturated fatly acids, particularly 22:6 (4, 7, 10, 13, 16, 19), decreases.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 47 (2000), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . The neutral lipids and their fatty acids and the sterol fractions of the marine ciliated protozoon, Parauronema acutum, were characterized. The neutral lipids consisted of triglycerides (30%), sterols (29%), free fatty acids (24%), steryl esters (9%), and diglycerides (8%) and small amounts of fatty alcohols. The fatty acid profiles of these lipids were very similar although quantitative differences were detected. Saturated fatty acids, primarily 14: 0, 16: 0, and 18: 0 constituted 20-30% of the total. Unsaturated fatty acids containing one to three double bonds, primarily 18: 1(9), 18: 2 (9,12), 18: 3 (9, 12, 15) and 20: 3 (11, 14, 17), constituted 35–50% of the total. Highly unsaturated fatty acids, 18: 4 (6, 9, 12, 15), 20: 5 (5, 8, 11, 14, 17) and 22: 6 (4, 7, 10, 16, 19), constituted 16–25% of the total. The fatty alcohols consisted of 14: 0 (2%), 16: 0 (66%), 18: 0 (3%), 20: 0 (8%), and 22: 0 (21%). The sterols of Parauronema acutum consisted of cholesterol (53%), campesterol (32%), desmosterol (7%), and β-sitosterol (8%).
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