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  • 1
    Electronic Resource
    Electronic Resource
    Stability of the Perovskite Compounds in the Ce-Ga-O and Pu-Ga-O Systems (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Cerium oxides are used as surrogates for plutonium oxides because of the similarities in their thermodynamic properties. In this study, the stability limits of both CeGaO3 and PuGaO3 with respect to the partial pressure of oxygen and temperature have been predicted by theoretical calculations. Using the results of the calculations as guidance, mixtures of CeO2 and Ga2O3 have been prepared and thermally treated at 1273, 1473, and 1673 K, in atmosphere of air, argon, or Ar–6% H2. In the samples annealed under low oxygen partial pressures, the CeGaO3 perovskite-type compound was identified. Based on Rietveld structure refinement, the orthorhombic space group (Pnma, 62) was confirmed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00533.x
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  • 2
    Electronic Resource
    Electronic Resource
    Quinolizidine alkaloids in seeds of Lupinus mutabilis (1983)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 31 (1983), S. 934-938 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00119a003
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  • 3
    Electronic Resource
    Electronic Resource
    Cation Disorder and Vacancy Distribution in Nonstoichiometric Magnesium Aluminate Spinel, MgO·xAl2O3 (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Neutron diffractometry and X-ray diffractometry were used to characterize the cation disorder and vacancy distribution in nonstoichiometric spinel, MgO·xAl2O3, where x greaterthan equal to 1.0. Both synthetic and natural samples were examined. Least-squares refinements of integrated intensities for single crystals and Rietveld profile refinements for powders yielded the average scattering “power” from tetrahedral and octahedral sites within the almost-perfect cubic close-packed oxygen sublattice. The cation disorder was calculated assuming models in which the vacancies resided on tetrahedral, octahedral, or both types of sites. No degree of cation disorder was consistent with the tetrahedral vacancy model, and vacancies most likely resided on octahedral sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02242.x
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  • 4
    Electronic Resource
    Electronic Resource
    Diversity and variability of plant secondary metabolism: a mechanistic view (1996)
    Springer
    Entomologia experimentalis et applicata 80 (1996), S. 177-188 
    Details
    ISSN: 1570-7458
    Keywords: structural diversity ; biosynthesis ; intraspecific variation ; secondary plant metabolites ; constitutive defence ; pyrrolizidine alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Based upon a brief historical view, the typical features of plant secondary metabolism and its role in chemical interactions between plants and their environment are discussed. Facts and arguments are presented favouring the hypothesis that secondary metabolism evolved under the selection pressure of a competitive environment. The high ‘degree of chemical freedom’ of secondary metabolism which, in contrast to primary metabolism, allows structural modifications with almost no restrictions, is stressed as mechanistic basis for the generation of chemical diversity. Biochemical and physiological properties of secondary metabolism are in accordance with such a view. It is suggested that the great chemical diversity and intraspecific variability of secondary metabolism is the result of processes of natural selection which act upon highly variable chemical structures. This view is exemplified by the pyrrolizidine alkaloids, a typical class of secondary compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194753
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  • 5
    Electronic Resource
    Electronic Resource
    Storage and metabolism of radioactively labeled pyrrolizidine alkaloids by butterflies and larvae of Mechanitis polymnia (Lepidoptera: Nymphalidae, Ithomiinae) (2000)
    Springer
    Chemoecology 10 (2000), S. 25-32 
    Details
    ISSN: 1423-0445
    Keywords: Key words. pyrrolizidine alkaloids, sequestration, chemical defense, alkaloid metabolism, N-oxidation, Mechanitis polymnia, Ithomiinae, Nymphalidae, Lepidoptera.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. Tracer feeding studies with radioactively labeled pyrrolizidine alkaloids (PAs) were performed to attain experimental information about the specificity and mechanisms of uptake, metabolism and storage of PAs in the alkaloid sequestering ithomiine butterfly Mechanitis polymnia. Adult butterflies easily ingest the tracers offered dissolved in a saturated sugar solution. Feeding of [14C]rinderine (free base) confirmed that M. polymnia is well adapted to sequester and maintain PAs of the lycopsamine type. Approximately 80% of the ingested radioactivity can be recovered in methanol extracts of the butterflies over a period of at least 6 hours. Labeled rinderine is efficiently N-oxidized and transformed into a metabolite of still unknown structure. These two metabolites are formed in almost equal amounts and account for more than 90% of total radioactivity. After four hours the toxic free base is only detectable in traces. Radioactively labeled senecioylretronecine (free base), a PA that often accompanies PAs of the lycopsamine type in plants, is metabolized in a different manner. The toxic free base disappeared as fast as the tertiary rinderine, but the final products which accumulated in a stable ratio after 12 hours were mainly two polar metabolites of unknown structure; senecioylretronecine N-oxide accounts for less than 10% of total PAs. Labeled senecionine a macrocyclic PA, which never has been found in wild caught M. polymnia is only slowly N-oxidized. In females ca 50% of the ingested senecionine is still present as free base after 24 hours, whereas under the same conditions in males this percentage is only ca 20%. This difference in N-oxidation was the only significant sex-specific difference observed in various experiments. Larvae of M. polymnia which feed on Solanum tabacifolium, a plant that does not contain PAs, are able to sequester and partly N-oxidize labeled senecioylretronecine and senecionine. However, the storage is not very efficient; with the two tracers less than 5% of radioactivity remained in the bodies after 24 hours.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000490050004
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  • 6
    Electronic Resource
    Electronic Resource
    Pyrrolizidine alkaloids between plants and insects: A new chapter of an old story (1994)
    Springer
    Chemoecology 5-6 (1994), S. 139-146 
    Details
    ISSN: 1423-0445
    Keywords: biochemistry of plants ; sequestration by insects ; transformation by insects ; pyrrolizidine alkaloids ; alkaloidN-oxides ; Asteraceae ; Senecio ; Lepidoptera ; Arctiidae ; Tyria ; Creatonotos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Among alkaloids the pyrrolizidine alkaloids (PAs) play a unique role in the interactions between plants and adapted insects. InSenecio spp. (Asteraceae) PAs are synthesized in the roots as alkaloidN-oxides which are specifically translocated into shootsvia the phloem-path and channeled to the preferred sites of storage (e.g. inflorescences) where they are stored in the cell vacuoles. In differentSenecio spp. senecionineN-oxide is produced as the common product of biosynthesis, which subsequentlyvia a number of simple but specific reactions is transformed into typical speciesspecific PA-patterns. Insects from diverse taxa sequester PAs for their own defense. Lepidopterans (e.g. arctiids such asTyria jacobaeae andCreatonotos transiens) may hydrolyze plant acquired ester-PAs and convert the resulting necine base into insect-specific PAs by esterification with an acid of their own metabolism. Adapted arctiids and the grasshopperZonocerus take up PAs in the state of the tertiary amine.N-Oxides are reduced in the guts prior to uptake. In the bodies the tertiary PAs are rapidlyN-oxidized by a specific mixed-function oxigenase and are maintained in theN-oxide state. The importance of the reversible interconversion of the nontoxicN-oxide (pro-toxine) into the toxic tertiary alkaloid is discussed as the specific feature of PAs in plant-insect interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01240598
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  • 7
    Electronic Resource
    Electronic Resource
    Tropane and pyrrolizidine alkaloids in the ithomiinesPlacidula euryanassa andMiraleria cymothoe (Lepidoptera: Nymphalidae) (1996)
    Springer
    Chemoecology 7 (1996), S. 61-67 
    Details
    ISSN: 1423-0445
    Keywords: chemical defense ; tropane alkaloids ; pyrrolizidine alkaloids ; lycopsamine ; Ithomiinae ; Placidula euryanassa ; Miraleria cymothoe ; Solanaceae ; Brugmansia suaveolens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Larvae of the ithomiine butterflyPlacidula euryanassa sequester tropane alkaloids (TAs) from the host plantBrugmansia suaveolens and pass them through the pupae to freshly emerged adults. Wild caught adults also show in their tissues, variable amounts of pyrrolidizine alkaloids (PAs), probably sequestered from variable plant sources and subject to dynamics of incorporation, accumulation and utilization of PAs by ithomiine butterflies. The ratio TAs/PAs is also variable between different populations.Miraleria cymothoe, another ithomiine that feeds onB. suaveolens as larvae, does not sequester TAs from the host-plant, but sequesters PAs from plant sources visited by the adult butterflies. The main alkaloid found in both butterflies is lycopsamine, which also is the principal PA found in all genera of Ithomiinae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01239482
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  • 8
    Electronic Resource
    Electronic Resource
    Sequestration of pyrrolizidine alkaloids by larvae ofTellervo zoilus (Lepidoptera: Ithomiinae) and their role in the chemical protection of adults against the spiderNephila maculata (Araneidae) (1996)
    Springer
    Chemoecology 7 (1996), S. 68-73 
    Details
    ISSN: 1423-0445
    Keywords: sequestration of secondary compounds ; chemical defense ; pyrrolizidine alkaloids ; lycopsamine ; Ithomiinae ; Tellervo zoilus ; Danainae ; Euploea core ; Danaus affinis ; Apocynaceae ; Parsonsia straminea ; Araneae ; Nephila maculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Life stages of the primitive Australian ithomiine butterflyTellervo zoilus and its larval hostplant, the apocynaceous vineParsonsia straminea, were quantitatively assayed for pyrrolizidine alkaloids (PAs). PAs were found in all stages, mainly as N-oxides, being most concentrated in larvae and freshly-emerged adults. Although adults feed at various confirmed PA sources this probably does not compensate for losses, as wild-caught adults had considerably lower concentrations of PAs. The main alkaloid present in both freshly-emerged adults and in leaves of the host-plant was lycopsamine (1b), stored by butterflies in the N-oxide form. Its presence in higher proportion, in relation to intermedine (1a), in larvae, pupae and adults ofTellervo in relation to the host-plants suggests the inversion of intermedine to lycopsamine by the insects. No 14-member ring macrocyclic PAs were detected in either food-plant or butterflies. Several other PAs were found in wild-caught adults reflecting visits to other PA sources. PAs were also found in high concentrations in freshly-emerged individuals of the danaineEuploea core bred onParsonsia straminea. Wild-caughtDanaus affinis had high PA levels acquired from adult feeding. Freshly emergedEuploea raised onIschnocarpus frutescens andDanaus raised onIschnostemma carnosum (both PA-free) were preyed on by the orb weaving spiderNephila maculata, and showed no PAs. In all cases where PAs were present, most butterflies were liberated, usually cut out of the web unharmed, byNephila. The spider's response was not closely linked to PA concentration, however, and may also depend on hunger levels and previous experience with PA-containing butterflies. All control and other non-PA containing butterflies were consumed although rejection of some body parts of freshly-emergedDanaus affinis suggests that compounds other than PAs may be involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01239483
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  • 9
    Electronic Resource
    Electronic Resource
    Sequestration of plant pyrrolizidine alkaloids by chrysomelid beetles and selective transfer into the defensive secretions (1991)
    Springer
    Chemoecology 2 (1991), S. 41-48 
    Details
    ISSN: 1423-0445
    Keywords: pyrrolizidine alkaloid N-oxides ; alkaloid sequestration ; defensive secretion ; host plant ; Coleoptera ; Chrysomelidae ; Oreina ; Asteraceae ; Adenostyles alliariae ; Senecio fuchsii ; Petasites paradoxus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Oreina cacaliae andO. speciosissima (Coleoptera, Chrysomelidae) sequester in their elytral and pronotal defensive secretions pyrrolizidine alkaloids (PAs) as Noxides (PA N-oxides). The PA N-oxide patterns found in the beetles and their host plants were evaluated qualitatively and quantitatively by capillary gas chromatography/mass spectrometry (GC-MS). Of the three host plantsAdenostyles alliariae (Asteraceae) is the exclusive source for PA N-oxide sequestration in the defensive secretions of the beetles. With the exception of O-acetylseneciphylline the N-oxides of all PAs ofA. alliariae, i.e. senecionine, seneciphylline, spartioidine, integerrimine, platyphylline and neoplatyphylline were identified in the secretion. PA N-oxides typical ofSenecio fuchsii (Asteraceae) were detected in the bodies of the beetles but not in their secretion. No PAs were found in the leaves of the third host plant,Petasites paradoxus (Asteraceae). The results suggest the existence of two distinctive storage compartments for PA N-oxides in the beetle: (1) the defensive secretion, containing specifically PA N-oxides acquired fromA. alliariae; (2) the body of the beetle, sequestering additionally but less selectively PA N-oxides from other sources,e.g. S. fuchsii or monocrotaline N-oxide fed in the laboratory. The concentration of PA N-oxides in the defensive secretion is in the range of 0.1 to 0.3 mol/1, which is more than 2.5 orders of magnitude higher than that found in the body of the beetle. No significant differences exist in the ability of the two species of beetles to sequester PA N-oxides fromA. alliariae, althoughO. speciosissima, but notO. cacaliae, produces autogenous cardenolides. A negative correlation seems to exist between the concentrations of plant-derived PA N-oxides andde novo synthesized cardenolides in the defensive secretion ofO. speciosissima.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01240665
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  • 10
    Electronic Resource
    Electronic Resource
    Role of mitochondrial glutamate dehydrogenase in the reassimilation of ammonia produced by glycine serine transformation (1980)
    Springer
    Planta 149 (1980), S. 207-208 
    Details
    ISSN: 1432-2048
    Keywords: Ammonia assimilation ; Glutamate dehydrogenase ; Mitochondria ; Photorespiratory ammonia production ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ability of isolated pea-shoot mitochondria conditioned to incorporate ammonia into glutamate to reassimilate endogenously produced ammonia from glycine transformation was investigated. In the presence of 1 mM to 20 mM glycine less than 15% of the ammonia liberated was found to be incorporated into glutamate. Thus, a prominent role of mitochondrial glutamate dehydrogenase in the reassimilation of intramitochondrially produced ammonia can be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380885
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