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  • 1
    Electronic Resource
    Electronic Resource
    A procedure for quantification of cytokinins as free bases involving scintillation proximity immunoassay (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 95 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cytokinins occur in a diversity of forms and determination of their individual levels requires extensive purification. However, determination of the total level of each major base in free, riboside and nucleotide forms would often be adequate. Hence, a methanolysis procedure which releases cytokinin bases from 9-ribosyl derivatives was developed and applied to plant extracts. A simple procedure, involving low pressure column chromatography, for purification of the cytokinin bases in treated extracts, and a scintillation proximity immunoassay for their quantification, were developed. The total level of each cytokinin base [N6-(2-isopentenyl)adenine, zeatin and dihydrozeatin] in free and ribosylated forms determined by these methods is reported for several plant tissues and the results are compared with those obtained after additional purification by HPLC. Values for zeatin were not changed by HPLC but isopentenyl-adenine and dihydrozeatin levels were usually reduced indicating the presence of unknown compounds which cross-react in the immunoassay. Modifications to the above purification method to quantify O-glucosyl cytokinins are also described.The methods described facilitate the quantification of the total amount of each cytokinin base in forms closely associated with cytokinin action, and the detection of cytokinin biosynthesis by labelled precursor incorporation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00813.x
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  • 2
    Electronic Resource
    Electronic Resource
    Betel nut residues in archaeological samples of human teeth from the Mariana Islands (1996)
    Springer
    Cellular and molecular life sciences 52 (1996), S. 281-285 
    Details
    ISSN: 1420-9071
    Keywords: Archaeological residues ; Areca catechu L. ; betel nut ; teeth ; tetrahydropyridine alkaloids ; arecaidine ; guvacine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two tetrahydropyridine alkaloids, arecaidine and guvacine that are characteristic of betel nut (Areca catechu L.) have been detected in the deliberately stained labial surface of female teeth excavation on Rota, Mariana Islands. This was accomplished using selected ion monitoring techniques in conjunction with gas chromatography/electron impact-mass spectrometry. These alkaloids were not present on the buccal surface of the teeth and indicate the use of betel nut to effect the staining.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01920724
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature conditional cAMP-requiring mutant strains ofChlamydomonas reinhardtii arrest in G1 and are rescued by added cAMP (1996)
    Springer
    Protoplasma 192 (1996), S. 159-167 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01273888
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  • 4
    Electronic Resource
    Electronic Resource
    Inhibitors of cytokinin metabolism III. The inhibition of cytokininN-glucosylation in radish cotyledons (1991)
    Springer
    Journal of plant growth regulation 10 (1991), S. 179-185 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Cytokinins are deactivated in radish cotyledons by conversion to 7- and 9-glucosides. In a search for inhibitors of this metabolism, the following compounds were found to be effective: (a) 6-benzylamino-2-(2-hydroxyethylamino)-9-methylpurine; (b) 3-isobutyl-1-methylxanthine; (c) papaverine; (d) theophylline; (e) caffeine; and (f) theobromine. The order of effectiveness was: (a)〉(b)=(c)〉(d)=(e)=(f). While the methylxanthines (b) and (d) inhibited formation of both 7- and 9-glucosides of 6-benzylaminopurine (BAP) approximately equally, compounds (a) and (c) preferentially inhibited formation of BAP 9-glucoside. Inhibition of BAP glucoside formation by (a) at 1.3 mM elevated the level of free BAP and BAP nucleotide 23- and 94-fold, respectively. While abscisic acid (ABA) suppressed conversion of zeatin riboside to zeatin 7-glucoside in radish cotyledons, it did not inhibit conversion of BAP to glucosides. Hence, ABA probably does not inhibit the glucosylating enzymes directly but rather reduces the availability of free zeatin when zeatin riboside is supplied. Auxins and nutrient supply did not affect conversion of zeatin riboside to zeatin 7-glucoside. Relative to cotyledons developed in light, those developed in darkness had a reduced capacity to convert zeatin riboside to zeatin 7-glucoside. The results presented have identified types of chemical structures which could be developed to provide more effective inhbitors of cytokininN-glucosylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02279331
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  • 5
    Electronic Resource
    Electronic Resource
    Cytokinins of dryZea mays seed: Quantification by radioimmunoassay and gas chromatography-mass spectrometry (1988)
    Springer
    Journal of plant growth regulation 7 (1988), S. 179-196 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The endogenous cytokinins present in dryZea mays seed were determined using both radioimmunoassay and gas chromatography—mass spectrometry. Similar values for bases and ribosides were obtained by the two methods. The cytokinins present in embryo and endosperm were estimated separately using radioimmunoassay; similar levels of cytokinins were found in these two tissues. The major cytokinins detected on a whole-seed basis were dihydrozeatin riboside, O-glucosyldihydrozeatin riboside, zeatin 9-glucoside, zeatin, and the nucleotides of zeatin, dihydrozeatin, and isopentenyladenine. Cytokinin levels in the mature dry seed were considerably lower than cytokinin levels published in the literature for immature seed. Unexpected activity in the radioimmunoassays was detected in the wash from the DEAE cellulose column chromatography step. The compound(s) responsible for this activity did not have the solvent partitioning characteristics of a cytokinin base or riboside. They eluted as a single fraction following high-performance liquid chromatography on a Zorbax C8 column; this fraction showed no activity in theAmaranthus bioassay for cytokinins, but inhibited the activity of authentic zeatin riboside present at an optimal concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02024681
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  • 6
    Electronic Resource
    Electronic Resource
    Inhibitors of cytokinin metabolism II. Inhibition of cytokinin-alanine conjugation in soybean leaves and associated effects on senescence (1989)
    Springer
    Journal of plant growth regulation 8 (1989), S. 327-330 
    Details
    ISSN: 1435-8107
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A group of xanthine derivatives and a novel analog of 6-benzylaminopurine (BAP) were tested for their ability to inhibit conjugation of cytokinin with alanine in soybean leaves. 3-(5-Hexenyl)-1,7-dimethylxanthine was found to be the most effective xanthine derivative. Although it had no senescence-retarding activity when applied alone to soybean leaves, it enhanced the action of BAP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02021826
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  • 7
    Electronic Resource
    Electronic Resource
    Location of double bonds using the formal addition of CCI2 (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 596-599 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A new method for locating double bonds in olefins and fatty acid is described. The CCI2 moiety, derived form chloroform, was added across the double bonds of a series of compounds using a phase-transfer reaction. The resulting adducts were then analysed by gas chromatography/positive-ion electron ionization mass spectrometry. It was found that it is routinely possible to locate a single double bond in a molecule at the microgram level. The method proved, however, to be of no use in locating terminal double bonds or in distinguishing geometrical isomers. It is possible that the method might be extended to di-olefins.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290051206
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