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  • Articles: DFG German National Licenses  (2)
  • Adenylate cyclase  (1)
  • Betaine  (1)
  • 1
    ISSN: 1615-6102
    Keywords: Adenylate cyclase ; Cell cycle ; Chlamydomonas reinhardtii ; Cyclic AMP ; Cyclic nucleotide phosphodiesterase ; Mutant strains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three independent isolates ofChlamydomonas, selected for caffeine resistance, were found to arrest in G1 phase, as determined by quantitative fluorescence measurements of DNA, when grown at a non-permissive temperature. This cell cycle arrest correlated with lowered levels of cAMP and of adenylate cyclase activity. The arrested cells could be rescued by added cAMP but not AMP, hence the defect was not one of general purine metabolism. Back-crosses to wild type revealed that the phenotypes observed result from a combination of three separable mutations. It is clear that the mutations define functions that are more stringently required for cell division than for growth since the mutant strains are able to grow up to fifteen times normal size while blocked at the non-permissive temperature. The possible interaction of cAMP dependent events with division is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-136X
    Keywords: Key words Methylamines ; Elasmobranchs ; Nuclear magnetic resonance ; Trimethylamine oxide ; Betaine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Methylamines are frequently present in high concentrations in biological samples, but their separation and quantification are difficult. Data presented show that methylamines commonly occurring in biological material can be uniquely identified and quantified by proton nuclear magnetic resonance spectroscopy by recording spectra at both neutral and acid pH. Use of a high sensitivity probe permits this analysis even in the presence of high water concentrations, allowing accurate quantification with minimum preparative technique. The method was tested on tissues of the dogfish. Trimethylamine oxide was found in amounts ranging from 42 mmol kg−1 fresh weight in liver, up to 115 mmol kg−1 fresh weight in heart. Betaine was found to range from 10 mmol kg−1 fresh weight in liver to 49 mmol kg−1 fresh weight in brain. Creatine was not found in heart or liver, but was present in body wall muscle and in brain. Further analysis using high-performance liquid chromatography allowed determination of urea/methylamine ratios, which ranged from 1.9 in liver to 3.7 in body wall muscle.
    Type of Medium: Electronic Resource
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