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  • 1
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method has been developed for the quantification of 2-hydroxyethylated cysteine resulting as adduct in blood proteins after human exposure to ethylene oxide, by reversed-phase HPLC with fluorometric detection. The specific adduct is analysed in albumin and in globin. After isolation of albumin and globin from blood, acid hydrolysis of the protein and precolumn derivatisation of the digest with 9-fluorenylmethoxycarbonylchloride, the levels of derivatised S-hydroxyethylcysteine are analysed by RP-HPLC and fluorescence detection, with a detection limit of 8 nmol/g protein. Background levels of S-hydroxyethylcysteine were quantified in both albumin and globin, under special consideration of the glutathione transferase GSTT1 and GSTM1 polymorphisms. GSTT1 polymorphism had a marked influence on the physiological background alkylation of cysteine. While S-hydroxyethylcysteine levels in “non-conjugators” were between 15 and 50 nmol/g albumin, “low conjugators” displayed levels between 8 and 21 nmol/g albumin, and “high conjugators” did not show levels above the detection limit. The human GSTM1 polymorphism had no apparent effect on background levels of blood protein 2-hydroxyethylation.
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  • 2
    ISSN: 1423-0127
    Keywords: Hepatitis B surface protein ; Genomic variability ; Escape mutation ; Liver transplantation ; Hepatitis B virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Variations in the major surface proteins (HBsAg) of hepatitis B virus (HBV) have been implicated in the high rate of reinfection in HBV-infected recipients of orthotopic liver transplantations (OLT). Sera from 6 OLT patients positive for HBsAg and from 3 recipients negative for it prior to transplantation were analyzed over several years, and 39 HBsAg sequences were compared. Despite anti-HBs immunoprophylaxis resulting in the disappearance of HBsAg, HBV DNA was detectable by a sensitive nested PCR in almost all sera. In 1 patient, a significant temporary shift in HBV subtypes was observed, indicating a mixed infection or the presence of multiple HBV populations in this patient; this was also true for other patients. Amino acid substitutions compared to wild-type HBV subtypes in 7 patients and variations within patients in 5 patients were detectable over time; the ‘escape mutation’ at amino acid position 145 was detected in 2 patients. Our data suggest that the high rate of reinfection in OLT recipients seems not to be associated with specific sequence variations in the major HBs gene, but shows a remarkable inter- and intraindividual variability. Obviously, no correlation between heterogeneity in this gene and clinical outcome was present.
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  • 3
    ISSN: 1423-0445
    Keywords: Key words. defense allocation — hydroxamic acids — leaf age — optimal defense theory — rye —Secale cereale— Poaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. The among-leaves allocation of DIBOA, a hydroxamic acid associated with plant resistance, in the shoot of rye (Secale cereale) was evaluated over the vegetative development of the plant. The appropriateness of using the concentration of secondary metabolites, DIBOA in this case, as the parameter to evaluate defense allocation in plants is discussed. Both biological and statistical arguments are put forward to suggest that allocation of chemical defenses should refer to absolute content and not to concentration. Results showed that leaf age was significantly linked to leaf concentration of DIBOA, young leaves having higher concentrations. In contrast, leaf content of DIBOA, our proposed currency of allocation, was not significantly higher in younger leaves. Furthermore, a regression analysis showed that the DIBOA content of leaves was better explained by the leaf relative biomass (proportion of shoot biomass) than by leaf biomass itself. It is suggested that, rather than leaf age, leaf relative biomass is the major factor determining DIBOA allocation in rye shoots. It is proposed that studies addressing within-plant defense allocation should use chemical defense content as the currency, emphasizing the major factors driving this process and its underlying mechanisms. Likewise, it is proposed that studies aiming at characterizing optimal patterns of plant defense should use chemical defense concentration as the currency, and be accompanied by evaluations of the actual resistance against herbivores of the plant parts analyzed, together with the effect on plant fitness.
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  • 4
    ISSN: 1423-0445
    Keywords: Key words. defense - induced defense - herbivory - aphids - Rhopalosiphum padi - wild wheat - Triticum uniaristatum - Poaceae - hydroxamic acids - costs of defense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. We characterized the induction of hydroxamic acids (Hx) by aphid infestation in the wild wheat Triticum uniaristatum by addressing the following questions: i) Do different leaves have similar responses to aphid damage?, ii) Is the Hx induction localized or systemic?, iii) How long does the induction last?, and iv) Is the degree of damage related to the magnitude of induced Hx? Based on earlier results on this wheat/aphid system (lack of costs of Hx induction) we expected to find the plant exhibiting cost-saving patterns of response to herbivory. Aphid infestation in the primary leaf led to induced levels of Hx, but no differences in Hx levels were found after infestation of the secondary leaf. Induction of Hx was restricted to the infested leaf (primary leaf). Induced Hx levels exhibited by the primary leaf at the end of aphid infestation were not observed 2 days later. Finally, different aphid densities (between 10 and 40 aphids per leaf) did not produce significant differences in Hx levels in infested primary leaves. Characteristics of Hx induction by aphid infestation in T. uniaristatum partially support the expected cost-saving patterns in the allocation of induced defenses.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 351 (1995), S. 345-351 
    ISSN: 1434-601X
    Keywords: 12.38.-t ; 12.38.Lg ; 14.65.-q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The concept of QCD sum rules is extended to bound states composed of particles with finite mass such as scalar quarks or strange quarks. It turns out that mass corrections become important in this context. The number of relevant corrections is analyzed in a systematic discussion of the IR- and UV-divergencies, leading in general to a finite number of corrections. The results are demonstrated for a system of two massless quarks and two heavy scalar quarks.
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  • 6
    ISSN: 1434-601X
    Keywords: PACS:12.38.Lg Other nonperturbative calculations – 14.20.Dh Protons and neutrons – 13.85.Qk Inclusive production with identified leptons, photons, or other nonhadronic particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The product of an axialvector and a scalar current and its relation to the chiral-odd distribution function h 1 is discussed in the framework of the renormalon approach. Using a bag-model calculation for h 1, we calculate its intrinsic uncertainty due to renormalon poles. The result is given as a function of Bjorken-x as well as for the first moments separately.
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  • 7
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
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  • 8
    ISSN: 1573-5060
    Keywords: aphids ; cereal breeding ; DIBOA ; Diuraphis noxia ; hydroxamic acids ; pest resistance ; Poaceae ; Schizaphis graminum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Hydroxamic acids are secondary metabolites typical of Poaceae that play a role in cereal resistance against pests and pathogens. The content of the hydroxamic acid aglucones DIBOA (2,4-dihydroxy-1,4-benzoxazin-3-one) and DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) was evaluated in wild Poaceae belonging to the tribes Triticeae (genera Hordeum and Elymus) and Aveneae (genera Deschampsia and Phalaris). The concentration of DIBOA in seedling extracts of the wild barleys Hordeum chilense, H. brevisubulatum subsp. violaceum and H. bulbosum was negatively correlated with parameters related to performance of the cereal aphids Schizaphis graminum and Diuraphis noxia. The relevance of the results obtained for breeding programs aimed at increasing cereal resistance against aphids is discussed.
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  • 9
    ISSN: 1573-1561
    Keywords: Defoliation ; regrowth ; induced responses ; chemical defense ; hydroxamic acids ; rye ; Secale cereale ; Poaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effect of defoliation and consecutive defoliation (condefoliation) of rye seedlings on the allocation patterns of biomass and hydroxamic acids (Hx) was evaluated five days after treatment. Growth of condefoliated seedlings was lower than that of defoliated and nondefoliated ones. Concentration of Hx decreased in shoots of condefoliated seedlings compared to nondefoliated ones, while concentration of Hx in root exudates increased. Allocation of Hx to roots and root exudates increased at the expense of allocation to the shoots in condefoliated seedlings. The ratio of Hx-aglucone to Hx-glucoside was higher in shoots of defoliated and condefoliated seedlings. The decrease in quantity of defense in shoots was accompanied by an increase in its quality, given that aglucones are more toxic than glucosides. The increase in concentration of Hx—an allelopathic compound also involved in mineral uptake by roots—in root exudates of condefoliated seedlings was suggested to lead to an advantage in the acquisition of resources for the regeneration of lost biomass.
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  • 10
    ISSN: 1573-1561
    Keywords: Liolaemus lizards ; conspecific chemical recognition ; tongue-flick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Experimental tests were conducted to determine whether females and males of the tree-dwelling lizard Liolaemus tenuis (Tropiduridae) show intraspecific chemical recognition during breeding and postreproductive seasons. Animals were individually maintained in plastic enclosures for one week. Thereafter, the number of tongue-flicks that a lizard performed in the enclosure of a male, a female, its own home enclosure, and a control (unused) enclosure were recorded. In both seasons, males and females made fewer tongue-flicks in their home enclosures than in any other one, indicating a recognition of a familiar place, probably a chemical self-recognition. Conspecific chemical recognition was season dependent. During the post-reproductive season, lizards tongue-flicked at similar rates in conspecific and control enclosures, while during the breeding season enclosures of females elicited more tongue-flicks by both sexes, and the overall tongue-flick rates were higher than in the postreproductive season. Results are discussed within the context of the social system of the species.
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