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  • pharmacokinetics  (2.025)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 59-68 
    ISSN: 1573-0867
    Schlagwort(e): bicarbonate-extractable potassium ; muriate of potash ; potassium ; potassium chloride ; relative effectiveness ; silicate rock powder ; Triticum aestivum ; Trifolium subterraneum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Granite (silicate) rock dust, a by-product of quarry operations, is being advocated and used as a fertilizer in the wheatbelt of south-western Australia (WA). The dust is insoluble and based on its nutrient element content (1.9% K and 0.3%P and negligible N) it is not expected to be a useful fertilizer. Previous laboratory studies and glasshouse experiments in WA suggest the dust is a slow release K fertilizer. This paper extends the previous studies to consider the dust as an NP or K fertilizer in the year of application in a field experiment on a soil deficient in N, P and K. In addition, the effectiveness of the dust as a K fertilizer was compared with the effectiveness of KCl (muriate of potash), the K fertilizer used in WA at present, in glasshouse experiments using K deficient soils. In the field experiment, compared with NP fertilizer or NPK fertilizer (urea, supplying N; superphosphate, providing P, S, Ca, Cu, Zn and Mo; KCl providing K), the dust had no effect on grain yield of wheat (Triticum aestivum); in fact dust applied at 20 t ha-1, for unknown reasons, reduced yields by about 65% compared to the nil (no fertilizer, no dust) treatment. Relative to the nil treatment, applying NPK fertilizer increased yields about threefold, from 0.54 to 1.79 t ha. The glasshouse experiments showed that, relative to KCl, the dust was from about 0.02 to 14% as effective in K deficient grey sandy soils for producing dried tops of 30-day old wheat plants or 42-day old clover (Trifolium subterraneum) plants. In soils with adequate K (yellow sands, sandy loams or clays, loamy clays, clay loams and clays), neither KCl nor the dust affected yields of 30 to 42-day old wheat or clover plants grown in the glasshouse. In the glasshouse experiments, no yield depressions were measured for the dust applied up to 17 g dust per kg soil (equivalent to 17 t dust ha-1 mixed into the top 10 cm of soil in the field). It is concluded that the dust has no value as a fertilizer.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 117-123 
    ISSN: 1573-0867
    Schlagwort(e): labelled nitrogen ; Lolium perenne ; nitrogen cycling ; root biomass ; straw ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Large amounts of nitrogen (N) fertiliser (150–200 kg N/ha) are currently being applied to perennial ryegrass (Lolium perenneL.) seed crops in New Zealand. Due to increasing requirements for efficient use of N fertilisers and minimising nitrate contamination of the environment, a field experiment was established using 15N-labelled fertiliser to follow the fate of applied N. Urea-15N was applied to a perennial ryegrass seed crop in April (30 kg N/ha), August (30 kg N/ha), September (60 kg N/ha) and October (60 kg N/ha). The urea-15N was applied in solution and watered in to minimise volatilisation loss. At the time of harvest (December), 9% of the applied 15N was in the seed, 29% in the straw, 19% in the roots and 39% in the soil organic matter. Losses of 15N were minimal as the N was applied in several applications, each one at a relatively low rate, and at times when leaching was unlikely to occur. Ryegrass plants used a greater proportion of the N applied in September and October (61–65%) compared with that applied in April (44%). Consequently more N was recovered from the soil in the autumn application (57%) than from the September and October applications (28–44%). The availability of the residual fertiliser N to a subsequent wheat (Triticum aestivum L.) crop was studied in a glasshouse experiment. The residual fertiliser N was present in the soil and ryegrass roots and stubble. The wheat plants only recovered 7–9% of this residual N. Most of the N taken up by the wheat came from the soil organic N pool. Overall, applying a total of 180 kg N/ha to the ryegrass appeared to have minimal direct impact on the environment. In the short term N not used by the ryegrass plants contributed to the soil organic N pool.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Sciences of soils 5 (2000), S. 10-21 
    ISSN: 1432-9492
    Schlagwort(e): Soil temperature ; Triticum aestivum ; Stubble retention ; Nitrogen ; Early growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Early growth and development are often lower when wheat is sown into standing stubble. A study was conducted to determine whether this difference in early growth could be explained by the effects of stubble on soil temperature in the vicinity of the young plant. The roles of nitrogen nutrition and soil strength were also assessed. Three crops were monitored (1990–1992), with the wheat being sown into either standing wheat stubble after a no-till fallow (NT), or into no-tilled plots from which the stubble had been removed by burning (NB). Measurements were made of wheat growth and development, soil and plant N, soil temperature and penetration resistance. The site was on a black earth near Warialda in the northern wheatbelt of New South Wales, Australia. In 1992 wheat was also grown under simulated stubble to isolate the shading and soil temperature effects of stubble from other factors. A significant (P〈0.05) relationship was found between average soil temperature and above ground dry matter (DM) at 65 days after sowing (DAS) but not at 107 DAS. This relationship accounted for differences in DM production at 65 DAS between NT and NB treatments in 1991 and 1992, but not in 1990. In that year the lower DM production in NT plots was associated with poorer N nutrition, and possibly disease. Laboratory incubations indicate that immobilisation of N as stubble decomposed could have contributed to this. Burning stubble produced no immediate increase in soil N availability, so that it is unlikely that N contained in stubble contributed to the difference. Soil strength differences between treatments and phytotoxic effects are unlikely to have contributed to growth differences in this soil.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 100 (2000), S. 789-793 
    ISSN: 1432-2242
    Schlagwort(e): Key words Glutenin ; Triticum aestivum ; Wheat storage proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Low-molecular-weight (LMW) glutenin subunits consist mainly of two domains, one at the N- terminus which contains repeats of short amino-acid motifs, and a non-repetitive one rich in cysteine, at the C- terminal region. In previous reports, polyacrylamide-gel electrophoresis has been used to show that large size variation exists among LMW and HMW glutenin subunits, and it has been suggested that deletions and insertions within the repetitive region are responsible for these variations in length. In this study, PCR-amplification of genomic DNA (Triticum aestivum variety Chinese Spring) was used to isolate three full-length LMW glutenin genes: LMWG-MB1, LMWG-MB2 and LMWG-MB3. The deduced amino-acid sequences show a high similarity between these ORFs, and with those of other LMW glutenin genes. Comparisons indicate that LMWG-MB1 has probably lost a 12-bp fragment through deletion and that LMWG-MB1 and LMWG-MB2 have an insertion of 81 bp within the repetitive domain. The current study has shown direct evidence that insertions and/or deletions provide a mechanistic explanation for the allelic variation, and the resultant evolution, of prolamin genes. Single-base substitutions at identical sites generate stop codons in both LMWG-MB2 and LMWG-MB3 indicating that these clones are pseudogenes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 100 (2000), S. 1085-1094 
    ISSN: 1432-2242
    Schlagwort(e): Key words Wheat ; High-molecular-weight glutenin ; AS-PCR ; Glu-A1 locus ; Null allele ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The present work reports new PCR markers that amplify the complete coding sequence of the specific alleles of the high molecular weight (HMW) glutenin genes. A set of AS-PCR molecular markers was designed which use primers from nucleotide sequences of the Glu-A1 and Glu-D1 genes, making use of the minor diffeences between the sequences of the x1, x2* of Glu-A1, and the x5 and y10 of Glu-D1. These primers were able to distinguish between x2* and the x1 or xNull of Glu-A1. Also x5 was distinguishable from x2, and y10 from y12. The primers amplified the complete coding regions and corresponded to the upstream and downstream flanking positions of Glu-A1 and Glu-D1. Primers designed to amplify the Glu-A1 gene amplified a single product when used with genomic DNA of common wheats and the xNull allele of this gene. This work also describes the cloning and characterisation of the nucleotide sequence of this allele. It possesses the same general structure as x2* and x1 (previously determined) and differs from these alleles in the extension of the coding sequence for a presumptive mature protein with only 384 residues. This is due to the presence of a stop codon (TAA) 1215-bp downstream from the start codon. A further stop codon (TAG), 2280-bp downstream from the starting codon is also found. The open reading frame of xNull and x1 alleles has the same size in bp. Both are larger than x2* which shows two small deletions. The reduced size of the presumptive mature protein encoded by xNull could explain the negative effect of this allele on grain quality.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1432-2242
    Schlagwort(e): Keywords AFLPs ; Bulked segregant analysis ; Marker-assisted selection ; Microsatellites ; Powdery mildew resistance ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Molecular markers were identified in common wheat for the Pm24 locus conferring resistance to different isolates of the powdery mildew pathogen, Erysiphe graminis DM f. sp. tritici (Em. Marchal). Bulked segregant analysis was used to identify amplified fragment length polymorphism (AFLP) markers and microsatellite markers linked to the gene Pm24 in an F2 progeny from the cross Chinese Spring (susceptible)× Chiyacao (resistant). Two AFLP markers XACA/CTA-407 and XACA/CCG-420, and three microsatellite markers Xgwm106, Xgwm337 and Xgwm458, were mapped in coupling phase to the Pm24 locus. The AFLP marker locus XACA/CTA-407 co-segregated with the Pm24 gene, and XACA/CCG-420 mapped 4.5 cM from this gene. Another AFLP marker locus XAAT/CCA-346 co- segregated in repulsion phase with the Pm24 locus. Pm24 was mapped close to the centromere on the short arm of chromosome 1D, contrary to the previously reported location on chromosome 6D. Pm24 segregated independently of gene Pm22, also located on chromosome 1D. An allele of microsatellite locus Xgwm337 located 2.4±1.2 cM from Pm24 was shown to be diagnostic and therefore potentially useful for pyramiding two or more genes for powdery mildew resistance in a single genotype.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 100 (2000), S. 32-38 
    ISSN: 1432-2242
    Schlagwort(e): Key words Waxy (Wx) protein ; Triticum aestivum ; Amylose content ; Starch ; Rapid Visco-Analyzer ; Swelling power ; Noodle quality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Waxy (Wx) protein is a granule-bound starch synthase (GBSS) responsible for amylose production in cereal endosperm. Eight isolines of wheat (Triticum aestivum L.) having different combinations of presence and absence of three Wx proteins, Wx-A1, -B1, and -D1, were produced in order to elucidate the effect of Wx protein deficiencies on the apparent amylose content and starch-pasting properties. An improved SDS gel electrophoresis showed that ’Bai Huo’ (a parental wheat) carried a variant Wx-B1 protein from an allele, Wx-B1e. Thus, wheat lines of types 1, 2, 4, and 6 examined in this study contained a variant Wx-B1 allele and not the standard allele, Wx-B1a. The results from 3 years of experiments using 176 lines derived from two cross-combinations showed that apparent amylose content increased the least in type 8 (waxy) having no Wx proteins and, in ascending order, increased in type 5 (only the Wx-A1 protein is present) 〈type 7 (Wx-D1) 〈type 6 (Wx-B1) 〈type 3 (Wx-A1 and -D1) 〈type 4 (Wx-A1 and -B1) 〈type 2 (Wx-B1 and -D1) 〈type 1 (three Wx proteins). However, Tukey’ s studentized range test did not detect significant differences in some cases. Densitometric analysis suggested that the amylose content was related to the amount of the Wx protein in the eight types. Parameters in the Rapid Visco-Analyzer test and swelling power were correlated to amylose content. Consequently, amylose content and pasting properties of starch were determined to be influenced the most by the lack of the Wx-B1 protein, followed by a lack of Wx-D1, and leastly by the Wx-A1 deficiency, which indicated the presence of differential effects of the three null alleles for the Wx protein.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1432-2242
    Schlagwort(e): Keywords Composite populations ; Triticum aestivum ; Blumeria (Erysiphe) graminis f. sp. tritici ; Residual resistance effects ; Quantitative resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The evolution of adult plant resistance towards powdery mildew (caused by Blumeria graminis f. sp. tritici) was investigated in 11 wheat populations cultivated for 10 years in a French network for dynamic management (DM) of wheat genetic resources. The aims of the study were to compare the evolution of resistance in sites submitted to different powdery mildew pressure and to investigate the implication of specific resistance gene action in adult plant resistance. For this, 7 of the 11 populations were characterized for their composition of specific resistance genes (results presented in a former paper). Even though no population differed significantly from the initial PA0 pool for mean adult plant resistance, divergence appeared among the final populations. The populations with the highest adult plant resistance level originated from sites where powdery mildew pressure is known to be high (Vervins, Le Rheu), whereas populations with the lowest adult plant resistance corresponded to areas with no, or very low, powdery mildew pressure (Toulouse, Montreuil-Bellay). A residual effect of defeated specific resistance genes was hypothesized, as lines accumulating at least two specific resistance genes appeared more resistant. Additional quantitative resistance seemed to be involved in adult plant resistance. DM lines appeared then as an interesting source of variability for resistance towards powdery mildew. Moreover, as these lines had been grown in mixed populations they may be appropriate as components of a composite cultivar.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 100 (2000), S. 519-527 
    ISSN: 1432-2242
    Schlagwort(e): Key words Wheat ; Triticum aestivum ; Physical mapping ; Deletion lines ; RFLP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Extended physical maps of chromosomes 6A, 6B and 6D of common wheat (Triticum aestivum L. em Thell., 2n=6x=42, AABBDD) were constructed with 107 DNA clones and 45 homoeologous group-6 deletion lines. Two-hundred and ten RFLP loci were mapped, including three orthologous loci with each of 34 clones, two orthologous loci with each of 31 clones, one locus with 40 clones, two paralogous loci with one clone, and four loci, including three orthologs and one paralog, with one clone. Fifty five, 74 and 81 loci were mapped in 6A, 6B and 6D, respectively. The linear orders of the mapped orthologous loci in 6A, 6B and 6D appear to be identical and 65 loci were placed on a group-6 consensus physical map. Comparison of the consensus physical map with eight linkage maps of homoeologous group-6 chromosomes from six Triticeaespecies disclosed that the linear orders of the loci on the maps are largely, if not entirely, conserved. The relative distributions of loci on the physical and linkage maps differ markedly, however. On most of the linkage maps, the loci are either distributed relatively evenly or clustered around the centromere. In contrast, approximately 90% of the loci on the three physical maps are located either in the distal one-half or the distal two-thirds of the six chromosome arms and most of the loci are clustered in two or three segments in each chromosome.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 1432-2242
    Schlagwort(e): Key words Composite populations ; Triticum aestivum ; Blumeria (Erysiphe) graminis f. sp. tritici ; Selection ; Drift
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Dynamic management has been proposed as a complementary strategy to gene banks for the conservation of genetic resources. The evolution of frequencies of genes for specific resistance towards powdery mildew (caused by Blumeria graminis f. sp. tritici) in populations of a French network for dynamic management of bread wheat genetic resources was investigated after 10 years of multiplication without human selection. The objective was to determine whether specific resistance gene diversity was maintained in the populations and whether any changes could be attributed to selection due to pathogen pressure. Seven populations, originating from four of the network sites, were characterized and compared to the initial population for six specific resistance gene frequencies detected by nine Blumeria graminis f. sp. tritici isolates. Diversity decreased at the population level, but because of a strong differentiation between the populations, this diversity was maintained at the network level. The comparison of Fst parameters estimated on neutral markers (RFLP) and on resistance gene data revealed that in two of the populations specific resistance genes had been selected by pathogen pressure, whereas evolution in two other populations seemed to be the result of genetic drift. For the three last populations, conclusions were less clear, as one had probably experienced a strong bottleneck and the other two presented intermediate Fst values. A dynamic management network with sites contrasted for pathogen pressure, allowing genetic drift in some populations and selection in others, appeared, at least on the short term, to be a good tool for maintaining the diversity of genes for specific resistance to powdery mildew.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Russian journal of plant physiology 47 (2000), S. 734-739 
    ISSN: 1608-3407
    Schlagwort(e): Triticum aestivum ; bioelectric potentials ; frost resistance ; critical points
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Winter wheat (Triticum aestivum L.) seedlings of three cultivars differing in frost resistance were used to study cooling-induced changes in the bioelectric potential. Measurements were performed with nonfreezing graphite–glycerol electrodes in the regime of monitoring. Upon a gradual change in air temperature from 20 to –15°C at the rates of 20 and 2°C/h, the bioelectric potential underwent abrupt transitions at certain moments, indicating changes in the physiological condition of plants. The time required for the achievement of these critical states, as well as the survival of plants after thawing, depended both on the temperature and the cooling rate. Apparently, these characteristics were related to the dynamics of phase transitions of water. Cultivar-specific features were manifested in the different abilities of plants to maintain free water in a supercooled state. It is supposed that the critical points are related to the cold resistance of colloid systems and to the temperature lethal for plants.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Investigational new drugs 18 (2000), S. 373-381 
    ISSN: 1573-0646
    Schlagwort(e): clinical pharmacology ; dihydropyrimdine dehydrogenase ; eniluracil ; oral 5-FU ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract The pharmacological inactivation of dihydropyrimidine dehydrogenase (DPD)represents one strategy to improve 5-FU therapy, which historically hasbeen associated with unpredictable pharmacological behavior andtoxicity. This is principally due to high interpatientdifferences in the activity of DPD, the enzyme that mediates theinitial and rate-limiting step in 5-FU catabolism. Byinactivating DPD and suppressing the catabolism of 5-FU,eniluracil has dramatically altered the pharmacological profileof 5-FU. The maximum tolerated dose of oral 5-FU given with oraleniluracil (1.0 to 25 mg/m2) is substantially lower thanconventional 5-FU doses. In the presence of eniluracil,bioavailability of 5-FU has increased to approximately 100%, thehalf-life is prolonged to 4 to 6 hours, and systemic clearanceis reduced 〉 20-fold to values comparable the glomerularfiltration rate (46 to 58 mL/min/m2). Renal excretion(∼ 45% to 75%), instead of DPD-related catabolism, is theprincipal route of elimination of oral 5-FU given witheniluracil. Chronic daily administration of oral 5-FU 1.0mg/m2 twice daily with eniluracil 20 mg twice dailyproduces 5-FU steady-state concentrations (8–38 ng/mL) similarto those achieved with protracted intravenous administration onclinically relevant dose-schedules. On a daily × 5regimen, higher 5-FU AUC values are related to neutropenia,whereas elevated 5-FU AUC and steady-state concentrations arerelated to diarrhea when oral 5-FU is given daily with eniluracilon a chronic schedule. The pharmacokinetic behavior of oraleniluracil is similar to that for oral 5-FU. Administration ofeniluracil 10 to 20 mg twice daily completely inactivates DPDactivity both in peripheral blood mononuclear cells and incolorectal tumor tissue, and prolonged inhibition of DPD afterdiscontinuation of eniluracil treatment has been noted. In thepresence of eniluracil, oral administration of 5-FU is feasibleand variation in 5-FU exposure is reduced, with the anticipationof further reduction in variation as dosing guidelines based onrenal function are formulated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    ISSN: 1573-904X
    Schlagwort(e): allometric scaling ; interspecies scaling ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To evaluate (1) allometric scaling of systemic clearance (CL)using unbound drug concentration, (2) the potential usage of brainweight (BRW) correction in allometric scaling of both CL and oralclearance (CL/F). Methods. Human clearance was predicted allometrically (CLu = a ·Wbiv) using unbound plasma concentration for eight Parke-Daviscompounds and 29 drugs from literature sources. When the exponent bivwas higher than 0.85, BRW was incorporated into the allometricrelationship (CLu*BRW = a · Wbiv). This approach was also applied tothe prediction of CLu/F for 10 Parke-Davis compounds. Human oralt1/2, Cmax, AUC, and bioavailability were estimated based onallometrically predicted pharmacokinetic (PK) parameters. Results. Human CL and CL/F were more accurately estimated usingunbound drug concentration and the prediction was further improvedwhen BRW was incorporated into the allometric relationship. ForParke-Davis compounds, the predicted human CL and CL/F werewithin 50-200% and 50-220% of the actual values, respectively. Theestimated human oral t1/2, Cmax, and AUC were within 82-220%,56-240%, and 73-190% of the actual values for all 7 compounds,suggesting that human oral PK parameters of those drugs could bereasonably predicted from animal data. Conclusions. Results from the retrospective analysis indicate thatallometric scaling of free concentration could be applied to orallyadministered drugs to gain knowledge of drug disposition in man, and to helpdecision-making at early stages of drug development.
    Materialart: Digitale Medien
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  • 14
    ISSN: 1573-904X
    Schlagwort(e): pharmacokinetics ; recombinant human interleukin-11 ; absorption ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 15
    ISSN: 1573-904X
    Schlagwort(e): (R,S)-Ifosfamide ; R2-, R3-, S2-, S3-DCE-IFF ; iterative-two stage analysis ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To describe the pharmacokinetics of R- andS-Ifosfamide (IFF), and their respective 2 and 3 N-dechloroethylated (DCE)metabolites (R2-, R3-, S2, S3-DCE-IFF) in cancer patients. Methods. (R,S)-IFF was administered (1.5 g/m2)daily for 5 days in 13 cancer patients. Plasma and urine samples were collectedand analyzed using an enantioselective GC-MS method. An average of 97observations per patient were simultaneously fitted using apharmacokinetic-metabolism (PK-MB) model. A population PK analysis was performedusing an iterative 2-stage method (IT2S). Results. Auto-induction of IFF metabolism was observed over the 5day period. Increases were seen in IFF clearance (R: 4 vs 7 L/h; S: 5vs 10 L/h), and in the formation of DCE (R: 7 vs 9%; S: 14 vs 19%)and active metabolites (4-OHM-IFF; R: 71 vs 77%; S: 67 vs 71%). Anovel finding of this analysis was that the renal excretion of the DCEmetabolites was also induced. Conclusions. This population PK-MB model for (R,S)-IFF may beuseful in the optimization of patient care, and gives new insight intothe metabolism of (R,S)-IFF.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Pharmaceutical research 17 (2000), S. 782-787 
    ISSN: 1573-904X
    Schlagwort(e): stealth and remote loading proliposome ; doxorubicin ; pharmacokinetics ; acute toxicity ; anticancer effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The aim of the study was to prepare stealth and remoteloading proliposome (SRP-L) to carry doxorubicin (DXR) and evaluatethe pharmacokinetics, acute toxicity, and anticancer effect of DXRcarried with SRP-L. Methods. SRP-L was transparent solution. When SRP-L was injectedinto 0.9% NaCl aqueous solution containing DXR, liposomes formedand automatically loaded DXR (SRP-L-DXR). The long circulation ofSRP-L-DXR was evaluated using the pharmacokinetics ofSRP-L-DXR, cardiolipin liposomal DXR (CL-DXR) and free DXR (F-DXR).The acute toxicity and anticancer effect of SRP-L-DXR were evaluatedin C57BL/6 mice and murine hystocytoma M5076 tumor model. Results. The average diameter of SRP-L-DXR in pure water was112.9 ± 8.6 (nm) and the encapsulation efficiency of SRP-L-DXRwas 96.5 ± 0.2% in pure water, 95.5 ± 0.1% in 5% glucose and 98.01± 0.6% in 0.9% NaCl. The plasma concentration of SRP-L-DXR wasmuch higher than those of F-DXR and CL-DXR. Compared with thatof F-DXR, the SRP-L-DXR had lower acute toxicity and its anticancereffects depended upon the therapeutic treatment. Conclusions. A novel proliposome (SRP-L) was developed, whichcould automatically load DXR and form SRP-L-DXR with excellentcharacteristics. SRP-L-DXR had lower acute toxicity but was notalways more effective for the treatment of the ascitic M5076 thanF-DXR.
    Materialart: Digitale Medien
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  • 17
    ISSN: 1573-904X
    Schlagwort(e): morphine ; nociceptive effect ; electrical stimulation vocalisation method ; microdialysis ; retrodialysis by drug ; pharmacokinetics ; pharmacodynamics ; modelling ; blood-brain barrier transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To quantify the contribution of distributional processes across the blood-brain barrier (BBB) to the delay in antinociceptive effect of morphine in rats. Methods. Unbound morphine concentrations were monitored in venous blood and in brain extracellular fluid (ECF) using microdialysis (MD) and in arterial blood by regular sampling. Retrodialysis by drug was used for in vivo calibration of the MD probes. Morphine was infused (10 or 40 mg/kg) over 10 min intravenously. Nociception, measured by the electrical stimulation vocalisation method, and blood gas status were determined. Results. The half-life of unbound morphine in striatum was 44 min compared to 30 min in venous and arterial blood (p 〈 0.05). The BBB equilibration of morphine, expressed as the ratio of areas under the curve between striatum and venous blood, was less than unity (0.28 ± 0.09 and 0.22 ± 0.17 for 10 and 40 mg/kg), respectively, indicating active efflux of morphine across the BBB. The concentration-effect relationship exhibited a clear hysterisis with an effect delay half-life of 32 and 5 min based on arterial blood and brain ECF concentrations, respectively. Conclusions. Eighty five percent of the effect delay was caused by morphine transport across the BBB, indicating possible involvement of rate limiting mechanisms at the receptor level or distributional phenomena for the remaining effect delay of 5 min.
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  • 18
    ISSN: 1573-904X
    Schlagwort(e): bioequivalence ; dose proportionality ; mixed effects model ; pharmacokinetics ; power model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The aim of this work was a pragmatic, statistically sound and clinically relevant approach to dose-proportionality analyses that is compatible with common study designs. Methods. Statistical estimation is used to derive a (1-α)% confidence interval (CI) for the ratio of dose-normalized, geometric mean values (Rdnm) of a pharmacokinetic variable (PK). An acceptance interval for Rdnm defining the clinically relevant, dose-proportional region is established a priori. Proportionality is declared if the CI for Rdnm is completely contained within the critical region. The approach is illustrated with mixed-effects models based on a power function of the form PK = β0 • Doseβ1; however, the logic holds for other functional forms. Results. It was observed that the dose-proportional region delineated by a power model depends only on the dose ratio. Furthermore, a dose ratio (ρ1) can be calculated such that the CI lies entirely within the pre-specified critical region. A larger ratio (ρ2) may exist such that the CI lies completely outside that region. The approach supports inferences about the PK response that are not constrained to the exact dose levels studied. Conclusion. The proposed method enhances the information from a clinical dose-proportionality study and helps to standardize decision rules.
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  • 19
    ISSN: 1573-904X
    Schlagwort(e): SK&F 107647 ; peptide ; pharmacokinetics ; hematore gulatory ; adenocarcinoma ; cytokines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To describe the pharmacokinetics of SK&F 107647, a synthetichematoregulatory peptide, in healthy volunteers and in patientswith adenocarcinoma.Methods. SK&F 107647 pharmacokinetics were evaluated in 2dose-escalation studies. Volunteers received SK&F 107647 as single15-minute iv infusion doses of 1, 10, 100, 500, and 1000 μg/kg. Cancerpatients received 2-hour iv infusions of 0.001, 0.01, 0.1 and 1μg/kg once daily for 10 days. Drug concentrations were quantified in plasmaand urine of healthy volunteers and on days 1 and 10 in plasma ofcancer patients receiving the two top dose levels.Results. In volunteers, mean clearance (CL) ranged from 76.7 to 101ml/hour/kg; mean volume of distribution at steady-state (Vss)rangedfrom 175 to 268 ml/kg. Most of the administered dose was renallyexcreted as intact peptide within 24 hours postinfusion. In patients,mean CL was 57.6 ml/hour/kg, mean Vss ranged from 128 to 150ml/kg and terminal half-life from 2.1 to 3.4 hours. There was littleaccumulation of drug. In both studies, linear pharmacokinetics wasobserved. Clearance approached normal glomerular filtration rate(GFR) in volunteers and correlated with creatinine clearance incancer patients.Conclusions. SK&F 107647 exhibits linear pharmacokinetics, a smallVss, and clearance, primarily renal, approaching normal GFR.
    Materialart: Digitale Medien
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  • 20
    ISSN: 1573-904X
    Schlagwort(e): glycyrrhizic acid ; modeling ; enterohepatic cycling ; PBPK ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To analyze the role of the kinetics of glycyrrhizic acid (GD) in its toxicity. A physiologically-based pharmacokinetic (PBPK) model that has been developed for humans. Methods. The kinetics of GD, which is absorbed as glycyrrhetic acid (GA), were described by a human PBPK model, which is based on a rat model. After rat to human extrapolation, the model was validated on plasma concentration data after ingestion of GA and GD solutions or licorice confectionery, and an additional data derived from the literature. Observed interindividual variability in kinetics was quantified by deriving an optimal set of parameters for each individual. Results. The a-priori defined model successfully forecasted GA kinetics in humans, which is characterized by a second absorption peak in the terminal elimination phase. This peak is subscribed to enterohepatic cycling of GA metabolites. The optimized model explained most of the interindividual variance, observed in the clinical study, and adequately described data from the literature. Conclusions. Preclinical information on GD kinetics could be incorporated in the human PBPK model. Model simulations demonstrate that especially in subjects with prolonged gastrointestinal residence times, GA may accumulate after repeated licorice consumption, thus increasing the health risk of this specific subgroup of individuals.
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  • 21
    ISSN: 1573-904X
    Schlagwort(e): luteinising hormone-releasing hormone (LH-RH) antagonist ; cetrorelix ; pharmacokinetics ; population PK/PD-modeling ; testosterone ; rat ; dog
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. Population models for thepharmacokinetic-pharmacodynamic relationship for cetrorelix (CET), a luteinising hormone-releasinghormone (LH-RH) antagonist, and the pharmacodynamic response ontestosterone production were investigated in rats and dogs. Methods. The plasma concentrations of CET and testosterone weredetermined after intravenous and subcutaneous injections. Thepopulation PK/PD-models were developed using P-PHARM software. Results. Absolute bioavailability of cetrorelix was 100% in rats and97% in dogs. In rats, the pharmacokinetics was explained by atwo-compartment model with saturable absorption, while athree-compartment model was used in dogs. Testosterone suppression in both specieswas described by a sigmoid Emax model with maximum effect (Emax)considered as total hormonal suppression. The duration of testosteronesuppression in rats was longer at higher doses. The populationelimination half-lifes after iv-dose were 3.0 h in rats and 9.3 h in dogs.Population mean estimates of IC50 were 1.39 and 1.24 ng/ml in ratsand dogs, respectively. Conclusions. A population pharmacokinetic model was developed toexplain the dissolution rate limited absorption from the injection site.The suppression of testosterone could be described by an indirectinhibitory sigmoid Emax model. In both species 1-2 ng/ml CET inplasma was necessary to suppress testosterone production.
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  • 22
    ISSN: 1573-904X
    Schlagwort(e): methylphenidate ; average bioequivalence ; individual bioequivalence ; human ; pharmacokinetics ; replicated design
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To determine the relative bioavailability of two marketed,immediate-release methylphenidate tablets. The study used a replicatedstudy design to characterize intrasubject variability, and determinebioequivalence using both average and individual bioequivalencecriteria. Methods. A replicated crossover design was employed using 20subjects. Each subject received a single 20 mg dose of the reference tableton two occasions and two doses of the test tablet on two occasions.Blood samples were obtained for 10 hr after dosing, and plasma wasassayed for methylphenidate by GC/MS. Results. The test product was more rapidly dissolved in vitro and morerapidly absorbed in vivo than the reference product. The mean Cmaxand AUC(0 − ∞) differed by 11% and 9%, respectively. Using anaverage bioequivalence criterion, the 90% confidence limits for theLn-transformed Cmax and AUC(0 − ∞), comparing the two replicatesof the test to the reference product, fell within the acceptable range of80–125%. Using an individual bioequivalence criterion the test productfailed to demonstrate equivalence in Cmax to the reference product. Conclusions. The test and reference tablets were bioequivalent usingan average bioequivalence criterion. The intrasubject variability of thegeneric product was greater and the subject-by-formulation interactionvariance was borderline high. For these reasons, the test tablets werenot individually bioequivalent to the reference tablets.
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  • 23
    ISSN: 1573-904X
    Schlagwort(e): 1,4-dihydropyridine calcium channel antagonist ; (+)-[3H]PN 200-110 ; senescence-accelerated prone mouse ; brain concentration ; pharmacokinetics ; in vivo receptor binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To characterize the in vivo specific binding andpharmacokinetics of a 1,4-dihydropyridine (DHP) calcium channel antagonist, PN200-110, in the senescent brain, using senescence-accelerated pronemice (SAMP8) and senescence-resistant mice (SAMR1). Methods. Blood, brain, and heart samples were taken periodically fromSAMR1 and SAMP8 following intravenous injection of (+)-[3H]PN200-110, and the concentration of (+)-[3H]PN 200-110 in the plasmaand tissues was determined. In addition, the in vivo specific bindingof (+)-[3H]PN 200-110 in the brains of SAMR1 and SAMP8 wasmeasured periodically after intravenous injection of the radioligand. Results. There was very little significant difference between SAMR1and SAMP8 in terms of the half-life (t1/2), total body clearance (CLtot),steady-state volume of distribution (Vdss), and AUC for the plasmaconcentration of (+)-[3H]PN 200-110 after intravenous injection ofthe radioligand. The brain concentration (AUCbrain) for (+)-[3H]PN200-110 and the brain/plasma AUC ratio (AUCbrain/AUCplasma) weresignificantly lower in SAMP8 than in SAMR1, and the heartconcentration (AUCheart) and the heart/plasma AUC ratio (AUCheart/AUCplasma)were similar in both strains. Also, the brain/plasma unbound AUCratio (AUCbrain/AUCplasma-free) for (+)-[3H]PN 200-110 wassignificantly lower in SAMP8 than in SAMR1. The in vivo specific binding(AUCspecific binding, maximal number of binding sites: Bmax) of(+)-[3H]PN 200-110 was significantly lower in brain particulate fractionsof SAMP8 than SAMR1. Conclusions. The concentration and in vivo specific binding of(+)-[3H]PN 200-110 was significantly reduced in the senescent brain. Thesimultaneous analysis of the concentrations of centrally acting drugsand the in vivo specific binding in the brain in relation to theirpharmacokinetics may be valuable in evaluating their CNS effects.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Pharmaceutical research 17 (2000), S. 903-905 
    ISSN: 1573-904X
    Schlagwort(e): P-glycoprotein ; hepatic metabolism ; pharmacokinetics ; first-pass metabolism ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Pharmaceutical research 17 (2000), S. 127-134 
    ISSN: 1573-904X
    Schlagwort(e): in-situ head perfusion ; pharmacokinetics ; red blood cells ; water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To develop a viable, single pass rat head perfusion modeluseful for pharmacokinetic studies. Methods. A viable rat head preparation, perfused with MOPS-bufferedRinger's solution, was developed. Radiolabelled markers (red bloodcells, water and sucrose) were injected in a bolus into the internalcarotid artery and collected from the posterior facial vein over 28minutes. The double inverse Gaussian function was used to estimatethe statistical moments of the markers. Results. The viability of the perfusion was up to one hour, with optimalperfusate being 2% bovine serum albumin at 37°C, pH 7.4. Thedistribution volumes for red blood cells, sucrose and water (from all studies,n = 18) were 1.0 ± 0.3ml, 6.4 ± 4.2ml and 18.3 ± 11.9ml, respectively.A high normalised variance for red blood cells (3.1 ± 2.0) suggestsa marked vascular heterogeneity. A higher normalised variance forwater (6.4 ± 3.3) is consistent with additional diffusive/permeabilitylimitations. Conclusions. Analysis of the physiological parameters derived fromthe moments suggested that the kinetics of the markers were consistentwith distribution throughout the head (weight 25g) rather than justthe brain (weight 2g). This model should assist in studying solutepharmacokinetics in the head.
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  • 26
    ISSN: 1573-904X
    Schlagwort(e): α1-acid glycoprotein ; protein binding ; dissociation rate ; species difference ; physiological model ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The extremely low clearance and small distribution volumeof UCN-01 in humans could be partly due to the high degree of bindingto hAGP (1,2). The quantitative effects of hAGP on the pharmacokineticsof UCN-01 at several levels of hAGP and UCN-01 were estimatedin rats given an infusion of hAGP to mimic the clinical situation anda physiological model for analysis was developed. Methods. The plasma concentrations of UCN-01 (72.5–7250 nmol/kgiv) in rats given an infusion of hAGP, 15 or 150 nmol/h/kg, weremeasured by HPLC. Pharmacokinetic analysis under conditionsassuming rapid equilibrium of protein binding and incorporating thedissociation rate was conducted. Results. The Vdss and CLtot of UCN-01 (725 nmol/kg iv) in ratsgiven an infusion of hAGP, 150 nmol/h/kg, fell to about 1/250 and 1/700that in control rats. The Vdss and CLtot following 72.5–7250nmol/kg UCN-01 to rats given 150 nmol/h/kg hAGP were 63.9–688ml/kg and 3.18–32.9 ml/h/kg, respectively, indicating non-linearitydue to saturation of UCN-01 binding. The CLtot estimated by thephysiological model assuming rapid equilibrium of UCN-01 bindingto hAGP, was six times higher than the observed value while the CLtotestimated by the model incorporating koff, measured using DCC, wascomparable with the observed value. Conclusions. These results suggest that the slow dissociation ofUCN-01 from hAGP limits its disposition and elimination.
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  • 27
    ISSN: 1573-904X
    Schlagwort(e): IVIVC ; racemate ; enantiomers ; metoprolol ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To investigate the ability of an IVIVC developedwith a racemate drug as well as each enantiomer in predicting the invivo enantiomer drug performance. Methods. Dissolution of metoprolol extended releasetablets with different release characteristics (e.g., fast (F),moderate (M), and slow (S)) was performed using USP ApparatusI, pH 1.2, 50 rpm. Metoprolol racemate tablets (S, M, and F, 100 mg) and 50mg oral solution were administered to healthy volunteers, blood samples werecollected over 24 (solution) and 48 (tablet) hours and assayed. IVIVC modelsdeveloped were: (1) Racemate-fraction of drug dissolved (FRD) vsRacemate-fraction of drug absorbed (FRA), (2) R-FRD vs R-FRA, and (3) S-FRDvs S-FRA for combinations of formulations (S/M/F, S/M, S/F, and M/F).Enantiomer Cmax and AUC prediction errors (PEs) were estimated for modelevaluation after convolution of in vivo release rates. Results. The R-IVIVC and S-IVIVC accurately predicted theR- and S-metoprolol pharmacokinetic profiles, respectively. The averagedprediciton errors (PE) for the enantiomer Cmax and AUC were less than10% for S/M/F, M/F, and S/F IVIVC models. Racemate-IVIVC (M/F) wasable to predict S-enantiomer with an average %PE of 2.52 for S-Cmaxand 4.3 for S-AUC. However, the racemate-IVIVC was unable to predict theR-enantiomer pharmacokinetic profile. Conclusions. Metoprolol racemate data cannot be used toaccurately predict R-enantiomer drug concentrations. However, the racematedata was predictive of the active stereoisomer.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 226 (2000), S. 11-19 
    ISSN: 1573-5036
    Schlagwort(e): Chlorpropham (CIPC) ; microtubules ; nuclei ; recovery ; roots ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The present ultrastructural investigation on the effects of 50 μM chlorpropham (previously called CIPC) on growing roots of wheat (Triticum aestivum (L.) Thell cv. Vergina) was undertaken to clarify the mechanism of a carbamate herbicide action in plant cells, since the wide range of responses of plant cells to carbamate herbicides is based mainly on immunofluorescence studies. Cells of control roots contained abundant microtubules both in interphase and mitotic arrays. In chlorpropham-treated roots, however, no microtubules could be detected at all, neither in dividing nor in differentiating cells. Cycling cells became binucleate, polyploid or contained incomplete cell walls, the result of inhibition of cytokinesis. In long-term drug treatments (24 h or more) the affected cells entered a new cycle, which, however, did not progress beyond mid-metaphase. The nuclei of binucleate cells initiated prophase synchronously. Small vacuoles and Golgi vesicles were trapped within the nucleoplasm of the multilobed nuclei. In roots recovering from 8 h chlorpropham treatment, cells continued to exhibit polyploid nuclei, intranuclear vacuoles and incomplete walls. Microtubules reappeared but they were sparse and lacked a definite orientation. Preprophase cells did not form normal preprophase bands of microtubules, while mitotic cells occasionally contained microtubules bound to chromosomes and converged to minipoles. It is concluded that chlorpropham disorganized directly microtubules in addition to irreversibly affecting microtubule organizing centres, which failed to further support microtubule arrays.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 226 (2000), S. 275-285 
    ISSN: 1573-5036
    Schlagwort(e): arbuscular mycorrhiza ; Daucus carota ; Glomus mosseae ; Glomus intraradices ; monoxenic culture ; N uptake ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract New information on N uptake and transport of inorganic and organic N in arbuscular mycorrhizal fungi is reviewed here. Hyphae of the arbuscular mycorrhizal fungus Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe (BEG 107) were shown to transport N supplied as 15N-Gly to wheat plants after a 48 h labelling period in semi-hydroponic (Perlite), non-sterile, compartmentalised pot cultures. Of the 15N supplied to hyphae in pot cultures over 48 h, 0.2 and 6% was transported to plants supplied with insufficient N or sufficient N, respectively. The increased 15N uptake at the higher N supply was related to the higher hyphal length density at the higher N supply. These findings were supported by results from in vitro and monoxenic studies. Excised hyphae from four Glomus isolates (BEG 84, 107, 108 and 110) acquired N from both inorganic (15NH4 15NO3, 15NO3 − or 15NH4 +) and organic (15N-Gly and 15N-Glu, except in BEG 84 where amino acid uptake was not tested) sources in vitro during short-term experiments. Confirming these studies under sterile conditions where no bacterial mineralisation of organic N occurred, monoxenic cultures of Glomus intraradices Schenk and Smith were shown to transport N from organic sources (15N-Gly and 15N-Glu) to Ri T-DNA transformed, AM-colonised carrot roots in a long-term experiment. The higher N uptake (also from organic N) by isolates from nutrient poor sites (BEG 108 and 110) compared to that from a conventional agricultural field implied that ecotypic differences occur. Although the arbuscular mycorrhizal isolates used contributed to the acquisition of N from both inorganic and organic sources by the host plants/roots used, this was not enough to increase the N nutritional status of the mycorrhizal compared to non-mycorrhizal hosts.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell, tissue and organ culture 63 (2000), S. 35-40 
    ISSN: 1573-5044
    Schlagwort(e): anther culture ; EDTA ; ferrous ions ; ferric ions ; Hordeum vulgare ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A suitable form of iron supplement in the induction medium was found to be important for further development of induced pollen embryos in barley and wheat cultivars (genotypes), especially those providing few green plants viain vitro androgenesis. Genotypes able to regenerate many green plants were less susceptible to the lack of iron in induction medium. Although Fe-EDTA was found to be a suitable form of iron in the induction medium, androgenesis was also induced on media containing non-chelated iron (Fe2+ and Fe3+ ions). EDTA alone without iron inhibited the androgenic response even in the wheat cv. Florida, a model cultivar for androgenesis in wheat. In all barley cultivars under study including cv. Igri, a model cultivar for androgenesis in barley, EDTA alone caused an almost total suppression of androgenesis.
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  • 31
    ISSN: 1573-5060
    Schlagwort(e): Cheyenne ; polymorphism ; RAPD ; recombinant inbred chromosome line(RICL) RFLP ; STS ; SSR ; Triticum aestivum ; Wichita
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Previously chromosome 3A of wheat (Triticum aestivum L.) was reported to carry genes influencing yield, yield components, plant height, and anthesis date. The objective of current study was to survey various molecular marker systems for their ability to detect polymorphism between wheat cultivars Cheyenne(CNN) and Wichita (WI), particularly for chromosome3A. Seventy-seven `sequence tagged site' (STS), 10simple sequence repeat (SSR), 40 randomly amplified polymorphic DNA (RAPD) markers, and 52 restriction fragment length polymorphism (RFLP) probes for wheat homoeologous group 3 chromosomes, were investigated. Three (3.9%) STS-PCR primer sets amplified polymorphic fragments for the two cultivars, of which one was polymorphic for chromosome 3A. Sixty percent of SSR markers detected polymorphism between CNN and WI of which 50% were polymorphic for chromosome 3A. Twenty percent of RAPD markers detected polymorphism between CNN and WI in general, but none of these detected polymorphism for chromosome 3A. Of the fifty-two RFLP probes, 78.8% detected polymorphism between CNN and WI for group 3 chromosomes with one or more of seven restriction enzymes and 42% of the polymorphic fragements were for chromosome 3A. These high levels of RFLP and SSR polymorphisms between two related wheat cultivars could be used to map and tag genes influencing important agronomic traits. It may also be important to reconsider RFLP as the most suitable marker system at least for anchor maps of closely related wheat cultivars.
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  • 32
    ISSN: 1573-5060
    Schlagwort(e): complementary genes ; hybrid necrosis ; spring wheat ; Triticum aestivum ; winter wheat ; winter × springwheat hybridization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The distribution and allelic expressivity of hybrid necrosis genes (Ne 1 and Ne 2) were studied in 21 winter (mostly exotic) and 43 spring type elite wheat genotypes, by crossing them with two known testers, C 306 (Ne 1-carrier) and HD 2380 (Ne 2-carrier).Ne 1 gene was present in one north-west Himalayan winter wheat landrace, Shoure Local, but absent in the other winter as well as spring wheats. Ne 2 gene was prevalent to a much lower extent in the exotic winter wheat germplasm (31.57%) as compared to the recently developed Indian and Mexican spring wheat semidwarfs (69.80%). This may suggest that breeders have tried to preclude hybrid necrosis by selecting for non-carrier genotypes in the development of exotic winter wheats in contrast to the situation in spring wheats. Based on the degree of expression of hybrid necrosis genes in the F1 hybrids, the carrier genotypes were characterized with respect to the allelic strength of the hybrid necrosis genes. The 27 non-carrier genotypes of the two ecotypes identified in the present study have a greater potential use in future hybridization programmes so as to overcome the problem of hybrid necrosis.
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  • 33
    ISSN: 1573-5060
    Schlagwort(e): allelic variation ; Chinese wheat ; glutenin subunit ; seed storage protein ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Variation in the electrophoretic banding patterns of high-molecular-weight (HMW) glutenin subunits of 274hexaploid wheat (Triticum aestivum) varieties from China was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and 27 different major HMW glutenin subunits were identified. Each variety contained three to five subunits and 29different glutenin subunit patterns were observed in274 Chinese hexaploid wheats. Seventeen alleles were identified based on the comparison of subunits mobility with that previously identified in a set of standard hexaploid wheats. The Chinese hexaploid wheats exhibited allelic variation in HMW glutenin subunit composition and the variation differed from that of Japanese and hexaploid wheats of other countries.
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  • 34
    ISSN: 1573-5060
    Schlagwort(e): bunt infection ; bunt resistance ; frost resistance ; Tilletia caries ; T. foetida ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In order to determine the effects of bunt inoculation on frost resistance and winter hardiness in lines containing resistance genes, the bunt [Tilletia foetida (Wallroth) Liro, T. caries (DC.) Tulasne] susceptibility of wheat lines containing bunt resistance genesBt1 to Bt10 and the effect of the year on the degree of infection were studied over six years from 1991 to 1997 in an artificial inoculation nursery. Uninoculated and artificially inoculated wheat plants were tested for frost resistance in the phytotron in 1995 and in the field in boxes in three years from 1994/95 to 1996/97. The line withBt10 was very resistant, lines with Bt5, Bt6, Bt8 and Bt9 were resistant, the line with Bt4 was moderately resistant, those with Bt2 and Bt3 were moderately susceptible, the line with Bt1 was susceptible and the line with Bt7 was very susceptible to the local bunt population in Hungary. Bunt incidence also varied over years. The frost resistance of the Bt lines was generally lower after bunt inoculation than that of uninoculated plants. The increased frost kill in inoculated plants was not correlated with the extent of varietal susceptibility to bunt. Some lines with resistance, namely those with Bt5 (1.6% infection), Bt8 (0.6%) and Bt10 (0.0%), suffered significantly greater frost kill in the young plant stage as the result of bunt inoculation. By contrast, the Bt7line had excellent frost resistance and winter hardiness but suffered the greatest extent of bunt infection, whereas the Bt6 line had good frost resistance and good bunt resistance.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 222 (2000), S. 25-34 
    ISSN: 1573-5036
    Schlagwort(e): deficiency ; genotypic differences ; iron ; nutrient efficiency ; phytosiderophore ; tolerance ; Triticum aestivum ; Triticum durum ; zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Tolerance to Zn deficiency in wheat germplasm may be inversely related to uptake and transport of Fe to shoots. The present study examined eight bread (Triticum aestivum) and two durum (T. turgidum L. conv. durum) wheat genotypes for their capacity to take up and transport Fe when grown under either Fe or Zn deficiency. Bread wheat genotypes Aroona, Excalibur and Stilleto showed tolerance to Zn and Fe deficiency, while durum wheat genotypes are clearly less tolerant to either deficiency. Roots of bread wheats tolerant to Zn deficiency exuded more phytosiderophores than sensitive bread and durum genotypes. Greater amounts of phytosideophores were exuded by roots grown under Fe than Zn deficiency. A relatively poor relationship existed between phytosiderophore exudation or the Fe uptake rate and relative shoot growth under Fe deficiency. At advanced stages of Zn deficiency, genotypes tolerant to Zn deficiency (Aroona and Stilleto) had a greater rate of Fe uptake than other genotypes. Zinc deficiency depressed the rate of Fe transport to shoots in all genotypes in early stages, while advanced Zn deficiency had the opposite effect. Compared with Zn-sufficient plants, 17-day-old Zn-deficient plants of genotypes tolerant to Zn deficiency had a lower rate of Fe transport to shoots, while genotypes sensitive to Zn deficiency (Durati, Yallaroi) had the Fe transport rate increased by Zn deficiency. A proportion of total amount of Fe taken up that was transported to shoots increased with duration of either Fe or Zn deficiency. It is concluded that greater tolerance to Zn deficiency among wheat genotypes is associated with the increased exudation of phytosiderophores, an increased Fe uptake rate and decreased transport of Fe to shoots.
    Materialart: Digitale Medien
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 112 (2000), S. 23-31 
    ISSN: 1573-5060
    Schlagwort(e): A granules ; B granules ; quantitative analysis ; starch quality ; triploid endosperm ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Two lines of hexaploid wheat were crossed and the basic generations of parent, F1, F2 and back-cross were sown in a controlled-environment chamber. FreshF1 and back-cross grains were generated, so the material could be handled either as the standard set of basic generations on a whole-plant basis, or as an extended set on an embryo or endosperm basis. The experiment was repeated. Mature grains were harvested and the starch particle size distribution was analysed in 3284 grains from 111 plants. Means and variances were partitioned into additive, dominance and interaction components. Grains from cross-pollinations had B-granule contents between parental values, rather than of the maternal parent, indicating an involvement of the grain genotype. Quantitative models based on endosperm genotype gave a better fit to the data than those based on embryo genotype. The difference in starch B-granule content between the parents was largely due to additive genes. Dominant genes were also indicated, with the first dose in the triploid endosperm having a large effect while the second dose had little or none. Non-allelic interactions were significant in the second experiment where the use of more types of backcross made them more detectable. There were also small and significant residual effects of the maternal plant in the first experiment, attributed to the vigour of the F1 mother plant and to the cytoplasm of Sunco. Narrow-sense heritability was low, between 0.05and 0.18 depending on the generation. Transgressive segregation was not found, suggesting that all alleles tending to increase the B-granule content were found in the Sunco parent and none in ME71. There was also no detectable heterosis in this character. The results show that breeding and selection for a low B-granule content should be possible but a further reduction will require new and complementary genes.
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  • 37
    ISSN: 1573-5060
    Schlagwort(e): disease resistance ; doubled haploid ; Fusarium headblight ; genetic analysis ; Fusarium graminearum ; recombinant inbred ; Triticum aestivum ; wheat scab
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The genetic constitution of resistance to Fusarium head blight (FHB, scab) caused by Fusarium graminearum in the Chinese wheat cultivar Sumai 3 and the Japanese cultivar Saikai 165 was investigated using doubled haploid lines (DHLs) and recombinant inbred lines (RILs). Frequency distributions of DHLs derived from two F1 crosses, Sumai 3 (very resistant to resistant; VR-R) / Gamenya (very susceptible; VS) and Sumai 3 / Emblem (VS), fitted well to 1: 2: 1 (resistant: moderately resistant: susceptible) ratios for reaction to FHB in the field. It is suggested that the resistance of Sumai 3 is controlled by two major genes with additive effects. One of the resistance genes may be linked in repulsion to the dominant suppressor B1 for awnedness with recombination values 15.1 ± 3.3% in Sumai 3 /Gamenya and 21.4 ± 4.3% in Sumai 3 / Emblem. Saikai 165 is a Japanese resistant line derived from an F1 Sumai 3 / Asakaze-komugi (moderately resistant; MR). The data for RILs derived from the cross Emblem / Saikai 165, indicates that three resistance genes control the resistance of Saikai 165.
    Materialart: Digitale Medien
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 113 (2000), S. 219-225 
    ISSN: 1573-5060
    Schlagwort(e): deficiency ; genotypic variation ; iron ; nutrient efficiency ; phytosiderophore ; Triticum aestivum ; Triticum durum ; zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Tolerance to Fe deficiency of wheat genotypes exhibiting differential tolerance to Zn deficiency is not known, even though the relationship between Fe nutrition and differential tolerance of wheat genotypes to Zn deficiency has been hypothesised frequently. In the present experiment, eight Triticum aestivum and two T. turigidum L. conv. durum cultivars were grown in nutrient solution deficient in either Znor Fe. Three indices of tolerance to nutrient deficiency were compared: relative [(-nutrient/+nutrient) × 100] shoot growth, shoot dry weight under nutrient deficiency and relative shoot/root dry weight ratio. Genotypes Aroona, Excalibur, Stilleto and Trident were classified as tolerant to both Zn and Fe deficiency, while durum wheats Durati and Yallaroi were sensitive to Zn deficiency and moderate to sensitive to Fe deficiency. Genotypes Excalibur, Stilleto and Trident come from the same breeding programme and have the common parent (line MEC3 =Sonora64//TZPP/YAQUI54) that could have been the donor of the genes for tolerance to Zn deficiency. When Fe-deficient, all wheat genotypes were severely chlorotic but kept producing shoot and root dry matter at a relatively high rate, making the relationship between the relative shoot growth and the relative leaf chlorophyll content poor. This is the first report of wheat genotypes exhibiting multiple tolerance to Zn and Fe deficiencies.
    Materialart: Digitale Medien
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  • 39
    ISSN: 1573-5060
    Schlagwort(e): bread wheat ; breeding and environmental effects ; gene frequency ; geographical distribution ; hybrid necrosis ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Using the Information and Analytical System of Wheat Genetic Resources GRIS 3.2, the peculiarities of distribution of hybrid necrosis genes in bread wheat in different regions of the world were analyzed. Considerable variation in frequencies of the Ne1 and Ne2 genes in regions with different moisture and heat supply was revealed. A significant effect of breeding on frequency dynamics of different genotypes Ne1ne2, ne1Ne2 and ne1ne2 was confirmed.
    Materialart: Digitale Medien
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  • 40
    ISSN: 1573-5087
    Schlagwort(e): abscisic acid ; drought stress ; Triticum aestivum ; wheat germ agglutinin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Expression of wheat germ agglutinin (WGA) gene inthe developing embryos of wheat (Triticumaestivum L. cv. C-306) was studied in relation toabscisic acid (ABA) accumulation under water stressconditions. Imposition of water stress resulted inelevated ABA levels in the embryos at threedevelopmental stages (18, 24 and 30 DPA). On thecontrary, the effect of drought stress on WGAaccumulation was stage dependent with significantincrease in WGA content being observed at only 24 DPA. Our results suggest that apart from ABA, otherfactors which are temporally expressed, are alsoinvolved in regulation of WGA gene expression.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Genetic resources and crop evolution 47 (2000), S. 281-284 
    ISSN: 1573-5109
    Schlagwort(e): agronomic traits ; isozymes ; landrace ; Triticum aestivum ; variation ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A sample of an Argentinean landrace of wheat showed considerable variation in most of the evaluated morphological and agronomic characters. However, analyses with high molecular glutenins and two isozyme systems, known to be highly polymorphic among current cultivars, revealed very little or no variation, respectively. The large difference in the observed variation between morphoagronomic and biochemical characters is discussed.
    Materialart: Digitale Medien
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Fish physiology and biochemistry 23 (2000), S. 225-232 
    ISSN: 1573-5168
    Schlagwort(e): methylisoborneol ; catfish ; cytochrome P450 ; biotransformation ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract 2-Methylisoborneol (MIB) and structurally related terpenoid compounds are responsible for millions of dollars of lost revenue to catfish farmers. In an attempt to determine enzymatic pathways of biotransformation and elimination of MIB, the in vitro metabolism of MIB was examined in the Ulvade strain of channel catfish (Ictalurus punctatus). Although cytochrome P450 (CYP) activities were observed and correlated with expression of specific isoforms (i.e. steroid hydroxylation and CYP3A expression), no metabolites of MIB were observed. To determine whether extrahepatic biotransformation may be occurring the in vivo metabolism and disposition of 14C-MIB was examined in Uvalde, USDA-103 channel catfish, and a channel catfish X blue catfish (Ictalurus furcatus) hybrid species. Confirming in vitro hepatic studies, no metabolites were observed in plasma from animals treated with an intra-arterial dose of 14C-MIB. 14C-MIB elimination was predicted using a two compartment model in each strain of fish. There was no significant difference in terminal half-lives between strains but possible differences in total body clearance and apparent volumes of distribution which may be related to higher lipid content in the hybrids. Results of these studies indicate biotransformation has no involvement in MIB elimination and that other physiological processes may play a more significant role in MIB disposition within Ictalurid fish species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical ecology 26 (2000), S. 2141-2154 
    ISSN: 1573-1561
    Schlagwort(e): Allelopathy ; phenolic acids ; 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one ; DIMBOA ; GC-MS-MS ; wheat ; Triticum aestivum ; weed suppression ; annual ryegrass ; Lolium rigidum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Wheat allelopathy has potential for weed suppression. Allelochemicals were identified in wheat seedlings, and they were exuded from seedlings into agar growth medium. p-Hydroxybenzoic, trans-p-coumaric, cis-p-coumaric, syringic, vanillic, trans-ferulic, and cis-ferulic acids and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) were identified in both the shoots and roots of 17-day-old wheat seedlings and their associated agar growth medium. Wheat accessions with previously identified allelopathic activity tended to contain higher levels of allelochemicals than poorly allelopathic ones. The allelopathic compounds present in the shoots generally also were identified in the roots and in the agar medium. Allelochemicals were distributed differentially in wheat, with roots normally containing higher levels of allelochemicals than the shoots. When the eight allelochemicals were grouped into benzoic acid and cinnamic acid derivatives, DIMBOA, total coumaric, and total ferulic acids, the amount of each group of allelochemicals was correlated between the roots and the shoots. Most of the allelochemicals identified in the shoots and roots could be exuded by the living roots of wheat seedling into the agar growth medium. However, the amounts of allelochemicals in the agar growth medium were not proportional to those in the roots. Results suggest that wheat plants may retain allelochemicals once synthesized. The presence of allelochemicals in the agar growth medium demonstrated that wheat seedlings were able to synthesize and to exude phytotoxic compounds through their root system that could inhibit the root growth of annual ryegrass.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 109-116 
    ISSN: 1573-0867
    Schlagwort(e): labelled nitrogen ; Lolium perenne ; nitrogen cycling ; root biomass ; straw ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A field trial was carried out to compare the transformations and plant uptake of urine N and S in a short-term pasture from within an arable/pasture ley rotation and a long-term pasture. Animal urine labelled with 15N and 35S was applied to microplots at both sites. These microplots were destructively sampled at various time intervals over 12 months and analysed for 15N and 35S. It is known that soil organic matter accumulates under short-term pastures compared with a long-term pasture in which accumulation and degradation are in balance. Consequently, it was hypothesised that immobilization of urine N and S is more intense in the short-term. However, in this study there was considerably less immobilization of 15N and 35S into soil organic forms under short-term pasture than long-term pasture. This was attributable to a greater pasture dry matter response to urine application under the short-term pasture (due to its inherently low N fertility) resulting in a greater plant uptake of 15N and 35S with less 15N and 35S consequently being available for immobilization. At both sites, all of the applied 35S was accounted for through plant uptake and recovery in the soil, but 21–48% of the 15N was unaccounted for and presumed to have been lost through gaseous emissions. It was concluded that accumulation of soil organic N and S under short-term pastures is likely to be attributable to turnover of plant residues (particularly root material) and does not appear to be related to immobilization in urine patches.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell, tissue and organ culture 60 (2000), S. 69-73 
    ISSN: 1573-5044
    Schlagwort(e): cereals ; tissue culture ; Triticum durum ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Fertile, green plants were regenerated from immature inflorescence explants from each of four Canadian wheat cultivars. The cultivars were representative of four classes of Canadian wheat. Explants from immature inflorescences of three size ranges were cultured on two types of media: MSI/MSR, which contains 1650 mg l-1 NH4NO3and sucrose as a carbon source, and BII/BIR, which contains 250 mg l-1 NH4NO3and maltose as a carbon source. Regeneration from all cultivars was significantly better on BII/BIR media than on MSI/MSR media. On BII/BIR media, `AC Karma', `Plenty', and `Fielder' gave the highest number of shoots per 10 explants, where the explants were derived from immature inflorescences 5.1 to 10.0 mm in length. 'Columbus' did not regenerate on MSI/MSR medium, and regenerated poorly on BII/BIR medium. Differences were found between cultivars with regard to the number of regenerant plants produced with the best treatments: `Plenty' produced 16.1 shoots per 10 explants, `AC Karma' 12.4, `Fielder' 6.4, and `Columbus' 2.2.
    Materialart: Digitale Medien
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  • 46
    ISSN: 1573-5060
    Schlagwort(e): biochemical marker ; gene location ; Lophopyrum elongatum ; Puccinia striiformis ; stripe rust ; substitution line ; Triticum aestivum ; yellow rust
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A set of T. aestivum-L. elongatum chromosome substitution lines was tested for yellow rust resistance at the seedling stage. Inheritance of the resistance and esterase-5 (Est-5) variation were studied. The results demonstrated that L.elongatum carried a new gene(s) conferring yellow rust resistance. This gene was dominant and located on chromosome 3E of L. elongatum. The biochemical locus encoding Est-5was also located on chromosome 3E, and co-segregated with theYr gene(s) in the wheat background. The transmission frequencies of chromosome 3E in 3E(3A) × CS, 3E(3B) × CS and 3E(3D) × CS hybrids were scored.None of the hybrids transmitted the alien chromosome at thetheoretical maximum rate, but the transmission frequencies ofchromosome 3E in F2 populations of 3E(3A) × CS and 3E(3D) × CS were significantly higher than in thatof 3E(3B) × CS.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 111 (2000), S. 199-203 
    ISSN: 1573-5060
    Schlagwort(e): Diuraphis noxia (Mordvilko) ; protein ; Russian wheat aphid ; Triticum aestivum ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has become a perennial, serious pest of wheat (Triticum aestivum L.) in the western United States. Current methodologies used to enhance RWA resistance in wheat germplasm could benefit from an understanding of the biochemical mechanisms underlying resistance to RWA. This study was initiated to identify specific polypeptides induced by RWA feeding that may be associated with RWA resistance. The effects of RWA feeding on PI 140207 (a RWA-resistant spring wheat) and Pavon (a RWA-susceptible spring wheat) were examined by visualizing, silver-stained denatured leaf proteins separated by two-dimensional polyacrylamide gel electrophoresis. Comparisons of protein profiles of noninfested and RWA-infested Pavon and PI 140207 revealed a 24-kilodalton-protein complex selectively inhibited in Pavon that persisted in PI 140207during RWA attack. No other significant qualitative or quantitative differences were detected in RWA-induced alterations of protein profiles. These results suggest that RWA feeding selectively inhibit synthesis and accumulation of proteins necessary for normal metabolic functions in susceptible plants.
    Materialart: Digitale Medien
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  • 48
    ISSN: 1573-5036
    Schlagwort(e): plant uptake ; potassium ; potassium starvation ; radiocaesium ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Short term experiments were carried out to investigate the effect of internal tissue potassium concentration on the uptake of radiocaesium by spring wheat (Triticum aestivum cv. Tonic). The results showed that potassium starvation increased Cs influx rates by a factor of 10 compared with non-starved plants. Solution to plant tissue transfer factor (TF) values also increased by around an order of magnitude after potassium starvation treatment. The enhancement of Cs influx rates by potassium starvation could be offset by an increase in external potassium concentration: this effect is minimal at external potassium concentrations greater than approximately 200 μM (8 mg L-1). This reveals that Cs influx into plant roots is subject to control by both internal and external potassium status. The kinetics of Cs uptake by potassium in starved and non-starved plants can be described adequately by the Michaelis-Menten equation. It was shown that potassium starvation substantially reduces the Km value from approximately 28 to 6 μM, which suggests that starvation treatment increases significantly the affinity of plant roots for Cs+. Mechanisms involved in K-Cs interactions during plant uptake are discussed in this paper. Finally, the relevance of such mechanisms as determinants of radiocaesium uptake by plants growing under different ecological conditions is emphasised.
    Materialart: Digitale Medien
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  • 49
    ISSN: 1573-5060
    Schlagwort(e): genetic diversity ; germplasm ; RFLP ; Triticum aestivum ; wheat breeding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A set of 292 accessions of common wheat (Triticum aestivum L.) representing 21 germplasm pools based on geographical or breeding program origins was assayed for RFLP diversity. Thirty cDNA and genomic DNA probes and the HindIII restriction enzyme were employed for RFLP analysis. About 61% of all 233 scored bands were present in 75% or more of the accessions. All but one of the 30 probes revealed polymorphism, and the average number of distinct patterns per probe over all accessions was 9.5.Polymorphic Information Content (PIC) values within a pool varied from 0 to 0.9 and depended on the identities of both the germplasm pool and the probe. Rare banding patterns with a relative frequency of ≤0.2 within a pool were detected. These rare patterns were more likely to occur in pools exhibiting high levels of heterogeneity. The highest level of polymorphism was observed in the Turkish landraces from Southwest Asia. The Eastern U.S. soft red winter wheat germplasm pool was more genetically diverse than the other advanced germplasm pools, and nearly as diverse as the Turkish landrace pool. RFLP-based genetic relationships between germplasm pools generally tracked expectations based on common geographical origin, breeding history and/or shared parentages. The Chinese wheat landraces from Sichuan, Tibet, and Yunnan provinces were distinct from other pools. Similarity matrices for among-pool genetic distance estimates based on either band frequencies or banding pattern frequencies showed good correlation with matrices derived from Nei and Li's mean genetic similarity estimates (r=−0.82** and r=−0.73**, respectively.
    Materialart: Digitale Medien
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  • 50
    ISSN: 1573-5079
    Schlagwort(e): canopy architecture ; canopy photosynthesis ; CO2 enrichment ; global change ; leaf area index ; leaf tip angle ; nitrogen stress ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The response of whole-canopy net CO2 exchange rate (CER) and canopy architecture to CO2 enrichment and N stress during 1996 and 1997 for open-field-grown wheat ecosystem (Triticum aestivum L. cv. Yecora Rojo) are described. Every Control (C) and FACE (F) CO2 treatment (defined as ambient and ambient +200 μmol mol−1, respectively) contained a Low- and High-N treatment. Low-N treatments constituted initial soil content amended with supplemental nitrogen applied at a rate of 70 kg N ha−1 (1996) and 15 kg N ha−1 (1997), whereas High-N treatments were supplemented with 350 kg N ha−1 (1996 and 1997). Elevated CO2 enhanced season-long carbon accumulation by 8% and 16% under Low-N and High-N, respectively. N-stress reduced season-long carbon accumulation 14% under ambient CO2, but by as much as 22% under CO2 enrichment. Averaging both years, green plant area index (GPAI) peaked approximately 76 days after planting at 7.13 for FH, 6.00 for CH, 3.89 for FL, and 3.89 for CL treatments. Leaf tip angle distribution (LTA) indicated that Low-N canopies were more erectophile than those of High-N canopies: 48° for FH, 52° for CH, and 58° for both FL and CL treatments. Temporal trends in canopy greenness indicated a decrease in leaf chlorophyll content from the flag to flag-2 leaves of 25% for FH, 28% for CH, 17% for CL, and 33% for FL during 1997. These results indicate that significant modifications of canopy architecture occurs in response to both CO2 and N-stress. Optimization of canopy architecture may serve as a mechanism to diminish CO2 and N-stress effects on CER.
    Materialart: Digitale Medien
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Chromosome research 8 (2000), S. 671-676 
    ISSN: 1573-6849
    Schlagwort(e): meiotic metaphase I pairing ; recombinant isochromosome ; Triticum aestivum ; Triticum dicoccoides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A recombinant isochromosome i5BLrec of wheat was developed with one arm and the proximal 36% of the other arm of Chinese Spring (CS) origin and the distal 64% of the recombined arm of Triticum turgidum subsp. dicoccoides origin. The i5BLrec} provides an unusual opportunity to analyze the role of the centromere or arm heterozygosity in chromosome prealignment and synapsis during meiosis. In monosomic condition, the i5BLrec formed a ring univalent in 86.8% of the pollen mother cells (PMCs) at meiotic metaphase I. In the disomic condition, the two i5BLrec preferentially paired as a normal bivalent in 74.8% of the PMCs, which differed significantly (p〈0.01) from the normal bivalent pairing of 51% observed in diisosomic 5BL chromosomes of the CS (Di5BLCS) control plants. In plants with one i5BLrec and a normal 5BCS, the long arm of 5BCS paired with the homologous arm of i5BLrec in 54.4% of the PMCs, and 40.4% of the PMCs had a 5BCS univalent and a i5BLrec ring univalent. The implications of the i5BLrec pairing data on the mechanism of Ph1 gene action are discussed.
    Materialart: Digitale Medien
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Chromosome research 8 (2000), S. 501-511 
    ISSN: 1573-6849
    Schlagwort(e): BFB cycle ; chromosome healing ; gametocidal factor ; rye deficiencies ; Secale cereale ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The gametocidal factor on the Aegilops cylindrical chromosome 2Cc was used to induce and analyze the nature of chromosomal rearrangements in rye chromosomes added to wheat. For this purpose we isolated plants disomic for a given rye chromosome and monosomic for 2Cc and analyzed their progenies cytologically. Rearranged rye chromosomes were identified in 7% of the progenies and consisted of rye deficiencies (4.6%), wheat–rye dicentric and rye ring chromosomes (1.8%), and terminal translocations (0.6%). The dicentric and ring chromosomes initiated breakage–fusion–bridge cycles (BFB) that ceased within a few weeks after germination as the result of chromosome healing. Of 56 rye deficiencies identified, after backcrossing and selfing, only 33 were recovered in either homozygous or heterozygous condition covering all rye chromosomes except 7R. The low recovery rate is probably caused by the presence of multiple rearrangements induced in the wheat genome that resulted in poor plant vigor and seed set, low transmission, and an underestimation of the frequency of wheat–rye dicentric chromosomes. Genomic in-situ hybridization (GISH) analysis of the 33 recovered rye deficiencies revealed that 30 resulted from a single break in one chromosome arm followed by the loss of the segment distal to the breakpoint. Only three had a wheat segment attached distal to the breakpoint. Although some of the Gc-induced rye rearrangements were derived from BFB cycles, all of the recovered rye rearrangements were simple in structure. The healing of the broken chromosome ends was achieved either by the de-novo addition of telomeric repeats leading to deficiencies and telocentric chromosomes or by the fusion with other broken ends in the form of stable monocentric terminal translocation chromosomes.
    Materialart: Digitale Medien
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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Pharmaceutical research 17 (2000), S. 1426-1431 
    ISSN: 1573-904X
    Schlagwort(e): eplerenone ; selective aldosterone receptor antagonist ; dog ; pharmacokinetics ; absorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The present study was conducted to characterize the pharmacokinetics of eplerenone (EP), a selective aldosterone receptor antagonist, and its open lactone ring form in the dog. Methods. Pharmacokinetic studies of EP were conducted in dogs following i.v., oral, and rectal dosing (15 mg/kg) and following intragastric, intraduodenal, intrajejunal, and intracolonic dosing (7.5 mg/kg). Results. After oral administration, the systemic availability of EP was 79.2%. Systemic availabilities following administration via other routes were similar to that following oral administration. The half-life and plasma clearance of EP were 2.21 hr and 0.329 l/kg/hr, respectively. Plasma concentrations of the open lactone ring form were lower than EP concentrations regardless of the route of administration. The C-14 AUC in red blood cells was approximately 64% and 68% of the plasma AUC for i.v. and oral doses. Percentages of the dose excreted as total radioactivity in urine and feces were 54.2% and 40.6%, respectively, after i.v. administration, and 40.7% and 52.3%, respectively, after oral administration. The percentages of the dose excreted in urine and feces as EP were 13.7% and 2.5%, respectively, after i.v. administration, and 2.1% and 4.6% after oral administration, respectively. Approximately 11% and 15% of the doses were excreted as the open form following i.v. and oral doses. Conclusions. EP was rapidly and efficiently absorbed throughout the gastrointestinal tract, resulting in a good systemic availability. The drug did not preferentially accumulate in red blood cells. EP was extensively metabolized; however, first-pass metabolism after oral and rectal administration was minimal. EP and its metabolites appear to be highly excreted in the bile.
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  • 54
    ISSN: 1573-904X
    Schlagwort(e): amphotericin B ; liposomes ; pharmacokinetics ; toxicokinetics ; tissue distribution ; toxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. Amphotericin B in small, unilamellar liposomes (AmBisome) is safer and produces higher plasma concentrations than other formulations. Because liposomes may increase and prolong tissue exposures, the potential for drug accumulation or delayed toxicity after chronic AmBisome was investigated. Methods. Rats (174/sex) received intravenous AmBisome (1, 4, or 12 mg/kg), dextrose, or empty liposomes for 91 days with a 30-day recovery. Safety (including clinical and microscopic pathology) and toxicokinetics in plasma and tissues were evaluated. Results. Chemical and histopathologic changes demonstrated that the kidneys and liver were the target organs for chronic AmBisome toxicity. Nephrotoxicity was moderate (urean nitrogen [BUN] ≤51 mg/dl; creatinine unchanged). Liposome-related changes (vacuolated macrophages and hypercholesterolemia) were also observed. Although plasma and tissue accumulation was nonlinear and progressive (clearance and volume decreased, half-life increased with dose and time), most toxic changes occurred early, stabilized by the end of dosing, and reversed during recovery. There were no delayed toxicities. Concentrations in liver and spleen greatly exceeded those in plasma; kidney and lung concentrations were similar to those in plasma. Elimination half-lives were 1-4 weeks in all tissues. Conclusions. Despite nonlinear accumulation, AmBisome revealed predictable hepatic and renal toxicities after 91 days, with no new or delayed effects after prolonged treatment at high doses that resulted in plasma levels 〉200 μg/ml and tissue levels 〉3000 μg/g.
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Pharmaceutical research 17 (2000), S. 1236-1242 
    ISSN: 1573-904X
    Schlagwort(e): aspergillosis ; pharmacokinetics ; amphotericin B ; biodistribution ; liposomes ; cholesterol hemisuccinate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. This study compared the biodistribution of two amphotericin B formulations in normal and Aspergillus infected mice. Amphotericin B cholesterol hemisuccinate vesicles (ABCV) which reduces the toxicity of amphotericin B and thereby enhances its therapeutic efficacy in a murine model of aspergillosis was compared with conventional amphotericin B deoxycholate suspension (AmBDOC). Methods. ABCV (12 mg/kg wt) and AmBDOC (2 mg/kg wt) were intravenously administered to normal and A.fumigatus infected mice. The concentration of amphotericin B in plasma and other organs was determined at different time points. Results. It was observed that ABCV had a significantly different pharmacokinetic profile compared to conventional amphotericin B. In comparison to AmBDOC significantly lower levels of amphotericin B were observed in kidneys and plasma, the major target organs of toxicity. Animals receiving ABCV demonstrated high levels of amphotericin B in liver (38% retention till 48 h) and spleen (2.6% retention till 48 h) in comparison to AmBDOC (7.3% and 0.21% retention in liver and spleen respectively till 48 h). Biodistribution studies of ABCV in infected mice demonstrated that there was a moderate enhancement in levels of amphotericin B in liver, spleen, lungs and kidneys as compared to normal mice and the plasma levels were reduced. However, such observations were not made after AmBDOC administration to infected mice except for kidneys in which there was a marked increase in uptake as compared to normal mice. Conclusions. Our results suggest that prolonged retention of high concentrations of ABCV in reticuloendothelial system organs is the reason for its reduced toxicity. Enhanced localization of the drug at the infected site may lead to improvement in therapeutic efficacy.
    Materialart: Digitale Medien
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  • 56
    ISSN: 1573-904X
    Schlagwort(e): oral absorption ; humans ; dogs ; rats ; interspecies scale-up ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To conduct a retrospective evaluation of using dog as ananimal model to study the fraction of oral dose absorbed (F) of 43drugs in humans and to briefly discuss potential factors that mighthave contributed to the observed differences in absorption. Methods. Mean human and dog absorption data obtained under fastedstate of 43 drugs with markedly different physicochemical andpharmacological properties and with mean F values ranging from 0.015 to1.0 were obtained from the literature. Correlation of F values betweenhumans and dogs was studied. Based on the same references, additionalF data for humans and rats were also obtained for 18 drugs. Results. Among the 43 drugs studied, 22 drugs were virtuallycompletely absorbed in both dogs and humans. However, the overallcorrelation was relatively poor (r2 = 0.5123) as compared to the earlier ratvs. human study on 64 drugs (r2 = 0.975). Several drugs showed muchbetter absorption in dogs than in humans. Marked differences in thenonliner absorption profiles between the two species were found forsome drugs. Also, some drugs had much longer Tmax values andprolonged absorption in humans than in dogs that might be theoreticallypredicted. Data on 18 drugs further support great similarity in F betweenhumans and rats reported earlier from our laboratory. Conclusions. Although dog has been commonly employed as ananimal model for studying oral absorption in drug discovery anddevelopment, the present study suggests that one may need to exercise cautionin the interpretation of data obtained. Exact reasons for the observedinterspecies differences in oral absorption remain to be explored.
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  • 57
    ISSN: 1573-904X
    Schlagwort(e): benzodiazepines ; pharmacokinetics ; EEG ; operational model of agonism ; receptor binding ; muscimol-induced Cl−uptake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. A mechanism-based model is applied to analyse adaptivechanges in the pharmacodynamics of benzodiazepines upon chronictreatment in rats. Methods. The pharmacodynamics of midazolam was studied in ratswhich received a constant rate infusion of the drug for 14 days, resultingin a steady-state concentration of 102 ± 8 ng·ml−1. Vehicle treated ratswere used as controls. Concentration-EEG effect data were analysed onbasis of the operational model of agonism. The results were comparedto data obtained in vitro in a brain synaptoneurosomal preparation. Results. The relationship between midazolam concentration and EEGeffect was non-linear. In midazolam pre-treated rats the maximum EEGeffect was reduced by 51 ± 23 μV from the original value of 109 ±15 μV in vehicle treated group. Analysis of this change on basis ofthe operational model of agonism showed that it can be explained bya change in the parameter tissue maximum (Em) rather than efficacy(τ). In the in vitro studies no changes in density, affinity or functionalityof the benzodiazepine receptor were observed. Conclusions. It is concluded that the observed changes in theconcentration-EEG effect relationship of midazolam upon chronic treatmentare unrelated to changes in benzodiazepine receptor function.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthetica 38 (2000), S. 607-614 
    ISSN: 1573-9058
    Schlagwort(e): chlorophyll fluorescence ; diphenyl carbazide ; donor side ; electron transport ; MnCl2 ; NH2OH ; photosystem ; senescence ; thylakoid protein ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Changes in various components of photosynthetic apparatus during the 6-d dark incubation at 25 °C of detached control and DCMU-treated Triticum aestivum L. leaves were examined. The rate of photosystem 2 (PS2) activity was decreased with increase of the time of dark incubation in control leaves. In contrast to this, DCMU-treated leaves demonstrated high stability by slowing down the inactivation processes. Diphenyl carbazide and NH2OH restored the PS2 activity more in control leaves than in DCMU-treated leaves. Mn2+ failed to restore the PS2 activity in both control and DCMU-treated samples. Similar results were obtained when Fv/Fm was evaluated by chlorophyll fluorescence measurements. The marked loss of PS2 activity in dark incubated control leaves was primarily due to the loss of D1, 33, and 23 kDa extrinsic polypeptides and 28-25 kDa LHCP2 polypeptides.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthetica 37 (2000), S. 519-527 
    ISSN: 1573-9058
    Schlagwort(e): alanine ; aspartate ; glycine ; glycollate ; malate ; nitrate ; serine ; sugars ; Triticum aestivum ; urea ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract 14CO2 uptake in leaves of wheat plants (Triticum aestivum L.) fertilized by urea or Ca(NO3)2 (25 mol m-3) was investigated. The Warburg effect (inhibition of 14CO2 uptake by oxygen) under 0.03 vol. % CO2 concentration was observed only in non-fertilized plants. Under 0.03 vol. % CO2, the Warburg antieffect (stimulation of 14CO2 uptake by oxygen) was detected only in plants fertilized by Ca(NO3)2. Under saturating CO2 concentration (0.30 vol. %), the Warburg antieffect was observed in all variants. Under limitation of ribulose-1,5-bisphosphate carboxylase/oxygenase activity (0.30 vol. % CO2 + 1 vol. % O2), the rate of synthesis of glycollate metabolism products decreased in control and urea-fertilized plants but was enhanced in nitrate-fed plants. Hence, there was an activation of glycollate formation via transketolase reaction in fertilized plants, and the products of nitrate reduction function were oxidants in nitrate-fertilized plants whereas the superoxide radical played this role in urea-fertilized plants.
    Materialart: Digitale Medien
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  • 60
    ISSN: 1573-9058
    Schlagwort(e): net photosynthetic rate ; soil and atmospheric drought ; stomatal conductance ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Yields of wheat in semiarid and arid zones are limited by drought, and water condition is very important at each stage of development. Studies carried out at Loess Plateau in the northwestern part of China indicated that yield of spring wheat (Triticum aestivum L.) cv. Dingxi 81-392 was reduced by 41% when subjected to water stress. The effects of two water regimens on net photosynthetic rate (P N), stomatal conductance (g s), and intercellular CO2 concentration (C i) were investigated at the jointing, booting, anthesis, and grain filling stages. Low soil moisture in comparison to adequate one had invariably reduced P N during the diurnal variations at the four growth stages. P N and g s in both soil moisture regimes was maximally reduced at midday. C i and the stomatal limitation fluctuated remarkably during photosynthesis midday depression processes, especially at the grain filling stage. Hence atmospheric drought at midday was one of the direct causes inducing stomata closure and the g s depression, but it was beneficial for maintaining stable intrinsic water use efficiency. Fluctuation in C i implicated that non-stomatal limitation also plays an important role during the period of photosynthesis midday depression. Consequently stomatal and/or non-stomatal limitation are the possible cause of the midday photosynthesis decline.
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthetica 37 (2000), S. 615-619 
    ISSN: 1573-9058
    Schlagwort(e): carbon based secondary compounds (CBSC) ; isoorientin ; leaf age ; litter ; phenolics ; tricin ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We compared flavonoids in green, mature, and senescing flag leaves of wheat grown under ambient (AC - 370 μmol mol-1) and elevated (EC - 550 μmol mol-1) concentrations of CO2 in a FACE (Free Air CO2 Enrichment) system. The concentrations of flag leaf flavonoids (e.g., isoorientin and tricin) decreased to one third in mature leaves, and the majoritary isoorientin almost disappeared in senescing leaves. Flavonoid concentrations increased in green well-developed flag leaves under EC (46 % isoorientin and 55 % tricin), whereas the differences disappeared in mature and senescing flag leaves. Predictions of changes in litter phenolic concentrations and their effects on decomposition rates under EC based on changes in green leaves need to be revised.
    Materialart: Digitale Medien
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    European journal of plant pathology 106 (2000), S. 837-842 
    ISSN: 1573-8469
    Schlagwort(e): Triticum aestivum ; Septoria nodorum ; Phaeosphaeria nodorum ; epidemiology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The transmission of Stagonospora nodorum from four naturally infected winter wheat seedlots was quantified in controlled environment germination chambers at 9, 13, 17, 21, and 25 °C. Seedlings were harvested when the second leaf began to emerge. Coleoptiles and first seedling leaves were examined for the presence of lesions caused by S. nodorum. First leaves were incubated on Bannon's medium for 2 weeks, after which they were examined for pycnidia of S. nodorum. Transmission to the coleoptile occurred at all temperatures, but decreased from 100% to 72% as temperature increased from 9 to 25 °C. Transmission to the first leaf was less, dropping from 37% to 2% as temperature increased from 9 to 25 °C. At least 44% of infected first leaves were symptomless at all temperatures, with 96% of infected leaves showing no symptoms at 25 °C. Transmission to seedling leaves occurred over a broad temperature range. Under the high densities at which wheat is sown, a significant number of infected seedlings per unit area may originate from relatively low initial seed infection levels and transmission efficiencies.
    Materialart: Digitale Medien
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  • 63
    ISSN: 1573-8221
    Schlagwort(e): acylprolyldipeptide ; GVS-111 ; pharmacokinetics ; blood-brain barrier permeability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Pharmacokinetics of GVS-111, a new acylprolyldipeptide with nootropic properties and its penetration across the blood-brain barrier were studied in rats using HPLC. It was found that the dipeptide is absorbed in the gastrointestinal tract, enters the circulation, and penetrates through the blood-brain barrier in an umodified state.
    Materialart: Digitale Medien
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  • 64
    ISSN: 1573-8264
    Schlagwort(e): carboxylation efficiecy ; carotenoids ; chlorophyll ; growth analysis ; net photosynthetic rate ; photochemical efficiency ; ribulose 1,5-bisphosphate carboxylase/oxygenase ; stomatal conductance ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Wheat plants were grown from sowing to day 18 in 26-dm3 chambers at three different CO2 concentrations: 150 (-CO2), 350 (C, control), 800 (+CO2) μmol mol-1. Afterwards, plants of the three variants were grown at the same natural CO2 concentration. Plant characteristics were measured just before the transfer (0 days after CO2 treatment, DAT), and at 5 – 8 DAT on the 1st leaf, and at 12 – 22 DAT on the 4th leaf. Decreased or increased CO2 concentrations caused acclimations which persisted after transplantation to natural CO2 concentration. At 5 – 8 DAT, stomatal density, stomatal conductance (gs), CO2 saturated net photosynthetic rate (PNsat0), radiation saturated net photosynthetic rate (PNsat1), and carboxylation efficiency (τ) were higher in -CO2 plants and lower in +CO2 plants than in C plants. As compared with C plants, the photochemical efficiency (α) was lower in -CO2 and higher in -CO2 plants, however, chlorophyll (Chl) a, Chl b, Chl a–b and carotenoid contents were lower in both -CO2 and +CO2 plants. On the 4th leaf, which emerged on plant after finishing CO2 treatments, at 12 – 22 DAT, no differences in stomatal density and g, between treatments were observed. In -CO2 plants, pigment content and PNsat0 were higher, α was lower, and PNsat1 and τ were not different from C plants. In contrast, in +CO2 plants, pigment content, PNsat1 and τ were lower, and PNsat0 and α were unchanged. Leaf area, dry mass, and tiller development increased in +CO2 plants and decreased in -CO2 plants. In the interval between 8 and 22 DAT, lower net assimilation rate in +CO2 than in -CO2 plants was observed.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Biologia plantarum 43 (2000), S. 523-528 
    ISSN: 1573-8264
    Schlagwort(e): accumulation ; grains ; lithium ; mobility ; phloem ; potassium ; rubidium ; sodium ; strontium ; Triticum aestivum ; xylem
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The alkali metals cesium, rubidium, lithium and sodium were introduced together with strontium via flaps into leaf laminas or into the stem of maturing, intact winter wheat (Triticum aestivum L. cv. Arina) grown in a field. Long-distance transport of these elements and the influence of the application date and of different application positions were investigated. The phloem-immobile Sr served as a marker for the distribution of the xylem sap in the plants. Dry matter accumulation in the grains and the transpiration per shoot were not markedly affected by the treatments as compared to control plants. The phloem mobility was rather high for Cs and Rb. Li was almost immobile in the phloem (similarly to Sr). An application into the cut stem xylem below the second leaf node contributed more to the contents in the grains than an application into the flag leaf. An earlier feeding date led to a higher accumulation in the grains. The marked losses of the elements applied during maturation (most pronounced for Li) can be explained by leakage in the rain.
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Biologia plantarum 43 (2000), S. 61-66 
    ISSN: 1573-8264
    Schlagwort(e): lipids ; polypeptide pattern ; salt stress ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Wheat seedlings of a salt tolerant cultivar were grown hydroponically in presence and absence of 100 mM NaCl. Roots were harvested, and the plasma membrane (PM) fraction was purified. PM ATPase required a divalent cations for activity (Mg 〉 Mn 〉 Ca 〉 Co 〉 Zn 〉 Ni 〉 Cu), and it was further stimulated by monovalent cations (K 〉 Rb 〉 NH4 〉 Li 〉 choline 〉 Cs). The pH optima were 6.0 and 5.6 in absence and presence of 25 mM KCl, respectively. The enzyme was sensitive to vanadate and DCCD but insensitive to azide, oligomycine and nitrate. The enzyme displayed a high preference for ATP but was also able to hydrolyze other nucleotide tri- and diphosphates. The enzyme activity showed a simple Michaelis-Menten kinetics for the substrate Mg2+-ATP in both control and salt exposed roots. The polypeptide patterns of control and salt stressed PM fractions, detected by SDS-PAGE, were very similar. NaCl substantially reduced the PM ATPase specific activity, whereas it had little effect on the apparent Km for Mg2+-ATP. Since the root PM ATPase of salt sensitive and resistant genotypes responded similarly to salinity stress, it seems unlikely that the mechanism of salt tolerance in wheat is primarily based on differences in PM ATPase characteristics.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Biologia plantarum 43 (2000), S. 309-311 
    ISSN: 1573-8264
    Schlagwort(e): grains ; maturation ; radioisotopes ; transport ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Steam-girdling experiments with detached wheat shoots showed that cesium was eliminated from the xylem sap and loaded into the phloem during acropetal transport. This transfer is important for the accumulation of cesium (especially also of the radiopollutants 134Cs and 137Cs) in maturing wheat grains.
    Materialart: Digitale Medien
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Biologia plantarum 43 (2000), S. 559-562 
    ISSN: 1573-8264
    Schlagwort(e): phenolics ; susceptibility ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Polyphenol oxidase activity was higher in resistant wheat cultivar ACC-8226 than in susceptible cultivar MP-845 in control sets and after inoculation of Alternaria triticina. However, similar polyphenol oxidase isozyme pattern was found in control and inoculated sets of both the cultivars, but the band intensity was higher after inoculation. Three and four peroxidase isozymes were found in ACC-8226 and MP-845, respectively. An extra peroxidase isozyme band was observed in both the cultivars after inoculation. The results suggest an active role of peroxidase and polyphenol oxidase in defence mechanism of wheat plants.
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  • 69
    ISSN: 1573-8264
    Schlagwort(e): ascorbic acid ; ascorbate peroxidase ; active oxygen species ; catalase ; hydroger ; peroxide ; oxidative stress ; superoxide dismutase ; temperature stress ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An experiment was conducted with three wheat (Triticum aestivum L.) genotypes C 306, HD 2285 and HD 2329 (differently susceptible to water and temperature stress) to study the extent of oxidative injury and activities of antioxidant enzymes in relation to heat stress induced by manipulating dates of sowing. Increase in temperature by late sowing significantly decreased leaf relative water content (RWC), ascorbic acid content, and increased H2O2 content and lipid peroxidation in all the genotypes at 8 and 23 d after anthesis. Temperature tolerant genotypes C 306, closely followed by HD 2285 were superior to HD 2329 in maintaining high RWC, ascorbic acid content, and lower H2O2 content and lipid peroxidation (malondialdehyde content) under high temperature (late sowing) at the two stages. Activities of superoxide dismutase and catalase were highest in HD 2285 followed by C 306 and minimum in HD 2329 while ascorbate peroxidase activity was highest in C 306.
    Materialart: Digitale Medien
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  • 70
    ISSN: 1573-8264
    Schlagwort(e): active oxygen species ; catalase ; chloroplast ; glutathione reductase ; lipid peroxidation ; nitrate reductase ; proline ; superoxide dismutase ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We induced an oxidative stress by means of exogenous hydrogen peroxide in two wheat genotypes, C 306 (tolerant to water stress) and Hira (susceptible to water stress), and investigated oxidative injury and changes in antioxidant enzymes activity. H2O2 treatment caused chlorophyll degradation, lipid peroxidation, decreased membrane stability and activity of nitrate reductase. Hydrogen peroxide increased the activity of antioxidant enzymes, glutathione reductase and catalase. These effects increased with increasing H2O2 concentrations. However, no change was observed in the activity of superoxide dismutase and proline accumulation.
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Biologia plantarum 43 (2000), S. 257-262 
    ISSN: 1573-8264
    Schlagwort(e): nitrate assimilation ; Triticum aestivum ; Zn toxicity ; Cu toxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of Zn2- on nitrate reductase (NR, EC 1.6.6.1) activity was studied in botá wheat (Triticum aestivum cv. Oasis) leaves and in the NR enzyme partially purified from wheat leaves. Leaf segments were floated on 0 to 5 mM ZnSO4 solutions (pH 6.0) for 24 h under continuous light. Zn2- at 250 μM decreased NR activity and increased membrane permeability. However, parameters of cellular oxidative damage were scarcely affected by Zn2- treatments. Accordingly, the decrease of NR activity induced by Zn2- was not prevented by benzoate (a scavenger of oxygen radicals). The effect of Zn2- was dependent on leaf age: it decreased NR activity in mature but not in young leaves. Zn2 inhibited the partially purified NR. This inhibition was not reversed by either co- or post-incubation with cysteine, and the amount of -SH groups of the purified NR was not affected by Zn2+ indicating that Zn2- inhibition does not involve key -SH groups of the enzyme. However, o-phenantroline both prevented and reversed Zn2+-induced NR inhibition. We concluded that the effect of Zn2+ on NR activity in vivo is not associated with an increase in active oxygen generation and involves a direct and reversible inhibition of the enzyme.
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  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Risk analysis 19 (1999), S. 711-726 
    ISSN: 1539-6924
    Schlagwort(e): variability ; exposure ; susceptibility ; risk assessment ; pharmacokinetics ; pharmacodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract This paper reviews existing data on the variability in parameters relevant for health risk analyses. We cover both exposure-related parameters and parameters related to individual susceptibility to toxicity. The toxicity/susceptibility data base under construction is part of a longer term research effort to lay the groundwork for quantitative distributional analyses of non-cancer toxic risks. These data are broken down into a variety of parameter types that encompass different portions of the pathway from external exposure to the production of biological responses. The discrete steps in this pathway, as we now conceive them, are: •Contact Rate (Breathing rates per body weight; fish consumption per body weight) •Uptake or Absorption as a Fraction of Intake or Contact Rate •General Systemic Availability Net of First Pass Elimination and Dilution via Distribution Volume (e.g., initial blood concentration per mg/kg of uptake) •Systemic Elimination (half life or clearance) •Active Site Concentration per Systemic Blood or Plasma Concentration •Physiological Parameter Change per Active Site Concentration (expressed as the dose required to make a given percentage change in different people, or the dose required to achieve some proportion of an individual's maximum response to the drug or toxicant) •Functional Reserve Capacity–Change in Baseline Physiological Parameter Needed to Produce a Biological Response or Pass a Criterion of Abnormal Function Comparison of the amounts of variability observed for the different parameter types suggests that appreciable variability is associated with the final step in the process–differences among people in “functional reserve capacity.” This has the implication that relevant information for estimating effective toxic susceptibility distributions may be gleaned by direct studies of the population distributions of key physiological parameters in people that are not exposed to the environmental and occupational toxicants that are thought to perturb those parameters. This is illustrated with some recent observations of the population distributions of Low Density Lipoprotein Cholesterol from the second and third National Health and Nutrition Examination Surveys.
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  • 73
    ISSN: 1539-6924
    Schlagwort(e): MeHg ; pharmacokinetics ; PBPK model ; variability ; risk assessment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract An analysis of the uncertainty in guidelines for the ingestion of methylmercury (MeHg) due to human pharmacokinetic variability was conducted using a physiologically based pharmacokinetic (PBPK) model that describes MeHg kinetics in the pregnant human and fetus. Two alternative derivations of an ingestion guideline for MeHg were considered: the U.S. Environmental Protection Agency reference dose (RfD) of 0.1 μg/kg/day derived from studies of an Iraqi grain poisoning episode, and the Agency for Toxic Substances and Disease Registry chronic oral minimal risk level (MRL) of 0.5 μg/kg/day based on studies of a fish-eating population in the Seychelles Islands. Calculation of an ingestion guideline for MeHg from either of these epidemiological studies requires calculation of a dose conversion factor (DCF) relating a hair mercury concentration to a chronic MeHg ingestion rate. To evaluate the uncertainty in this DCF across the population of U.S. women of child-bearing age, Monte Carlo analyses were performed in which distributions for each of the parameters in the PBPK model were randomly sampled 1000 times. The 1st and 5th percentiles of the resulting distribution of DCFs were a factor of 1.8 and 1.5 below the median, respectively. This estimate of variability is consistent with, but somewhat less than, previous analyses performed with empirical, one-compartment pharmacokinetic models. The use of a consistent factor in both guidelines of 1.5 for pharmacokinetic variability in the DCF, and keeping all other aspects of the derivations unchanged, would result in an RfD of 0.2 μg/kg/day and an MRL of 0.3 μg/kg/day.
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 91 (1999), S. 403-412 
    ISSN: 1570-7458
    Schlagwort(e): aphid ; Diuraphis noxia ; Triticum aestivum ; endosymbiont ; insect-plant interactions ; phloem ; amino acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The feeding behavior of Diuraphis noxia Mordvilko (Homoptera: Aphididae) on susceptible hosts causes both ultrastructural and tissue level damage which may affect phloem composition. Genetic evidence suggests that endosymbiotic bacteria in most aphids overproduce limiting amino acids to benefit hosts but that D. noxia depends less on endosymbionts for these nutrients, possibly due to an enriched diet. To determine whether D. noxia feeding damage results in higher concentrations of essential amino acids, stylet exudates were analyzed from wheat (Triticum aestivum) damaged to different degrees. Comparison of samples from undamaged and damaged susceptible wheat revealed changes in amino acid composition and an increase in levels of essential amino acids, indicating a nutritionally enhanced ingesta. The changes in stylet exudates paralleled changes in leaf exudates, indicating that the effects are systemic. Feeding damage is not observed on a resistant wheat host, var. Halt, and leaf exudates from infested Halt did not show changes in amino acid composition. Mean relative growth of nymphs was significantly lower on Halt than on susceptible Arapahoe, indicating that Halt is a less suitable host. Both varieties show similar amino acid levels in non-infested samples, suggesting that D. noxia infestation does not enhance the phloem environment in Halt. This study provides evidence that aphid feeding can generate a nutritionally enhanced phloem diet.
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 91 (1999), S. 111-114 
    ISSN: 1570-7458
    Schlagwort(e): sieve element ; salivation ; aphid ; plant resistance ; wheat ; Sitobion fragariae ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Extended sieve element salivation (E1 waveform in the electrical penetration graph) is a characteristic activity during early sieve element punctures, particularly in resistant plants. In order to explore a chemically-mediated mechanism of resistance associated with sieve element salivation, we compared the pattern of feeding behaviour of the aphid, Sitobion fragariae (Walker), on two cultivars of the wheat Triticum aestivum L., with different concentrations of hydroxamic acids (Hx). During 24 h of electronic monitoring, aphids dedicated over 50% of the total time to phloem ingestion from the sieve elements. Total time allocated to E1 in the experiment, time to first E1 within the experiment, time allocated to E1 before a sustained phloem ingestion (E2) and the contribution of sieve element salivation to the phloem phase (E1/[E1+E2]) were significantly higher in the high-Hx cultivar. The increased salivation in plants with higher contents of Hx suggests the existence, at least in this system, of a chemically-mediated sieve element constraint.
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  • 76
    ISSN: 1432-1890
    Schlagwort(e): Key words Glomus mosseae ; Hydroponics ; Nitrate uptake ; Root respiration ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Oxygen and CO2 fluxes were measured in hydroponically grown mycorrhizal and non-mycorrhizal Triticum aestivum L. cv. Hano roots. The NO3 – uptake of the plants was used to estimate the amount of root respiration attributable to ion uptake. Plants were grown at 4 mM N and 10 μM P, where a total and viable mycorrhizal root colonisation of 48% and 18%, respectively, by Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe (BEG 107) was observed. The O2 consumption and NO3 – uptake rates were similar and the CO2 release was higher in mycorrhizal than in non-mycorrhizal wheat. This resulted in a significantly higher respiratory quotient (RQ, mol CO2 mol–1 O2) in mycorrhizal (1.27±0.13) than in non-mycorrhizal (0.79±0.05) wheat. As the biomass and N and P concentrations in mycorrhizal and non-mycorrhizal wheat were the same, the higher RQ resulted from the mycorrhizal colonisation and not differences in nutrition per se.
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  • 77
    ISSN: 1432-0789
    Schlagwort(e): Key words Phosphate-solubilizing microorganisms ; Mussoorie rock phosphate ; Vesicular-arbuscular mycorrhizae ; Triticum aestivum ; Nutrient-deficient soils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract  The effect of inoculating wheat (Triticum aestivum L.) with the PO4 3–-solubilizing microorganisms (PSM) Bacillus circulans and Cladosporium herbarum and the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus sp. 88 with or without Mussoorie rock phosphate (MRP) amendment in a nutrient-deficient natural sandy soil was studied. In the sandy soil of low fertility root colonization by VAM fungi was low. Inoculation with Glomus sp. 88 improved root colonization. At maturity, grain and straw yields as well as N and P uptake improved significantly following inoculation with PSM or the VAM fungus. These increases were higher on combined inoculation of PSM and the VAM fungus with MRP amendment. In general, a larger population of PSM was maintained in the rhizosphere of wheat in treatments with VAM fungal inoculation and MRP amendment. The results suggest that combined inoculation with PSM and a VAM fungus along with MRP amendment can improve crop yields in nutrient-deficient soils.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 53 (1999), S. 157-175 
    ISSN: 1573-0867
    Schlagwort(e): Brassica napus ; Cicer arietinum ; current P ; Lens culinaris ; Lupinus albus ; Lupinus angustifolius ; P concentration response ; P content response ; Pisum sativum ; previous P ; sigmoid response ; single superphosphate ; Triticum aestivum ; Vicia faba ; yield response
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Phosphorus (P) is a major deficiency of soils of south-western Australia (WA). The fertilizer P requirements are not known for grain legumes being evaluated for neutral to alkaline, fine textured soils in WA. To rectify this, glasshouse and field experiments were undertaken to compare the responses of several grain legume species, wheat and canola to applications of single superphosphate and the results are reported in this paper. The glasshouse experiments measured responses of dried tops, harvested at 26 to 42 days after sowing, to P that was freshly-applied (current P) and previously-applied (previous P). Responses in the glasshouse were measured using yield, P concentration and P content (P concentration multiplied by yield) of oven dried tops of the following: wheat (Triticum aestivum), canola (Brassica napus), faba bean (Vicia faba), chickpea (Cicer arietinum), lentil (Lens culinaris), field pea (Pisum sativum), albus lupin (Lupinus albus) and narrow leaf lupin (Lupinus angustifolius). Field experiments in 1994 and 1995 compared seed (grain) yield responses of faba bean, chickpea, lentil, albus lupin and wheat to applications of current P. The P was banded (drilled) with the seed while sowing at 5 cm depth. Canola and wheat produced very large yield responses to increasing applications of current P. Responses were much smaller for albus lupin, faba bean and chickpea. Responses for lentil, narrow leaf lupin and field pea, fell in between responses of the small and large seeded species. Similar trends for responses were obtained as measured using yield, P concentration, or P content. For soils treated with previous P, similar trends were observed as for current P, but differences in yield responses between species were much less marked and the response curves tended to become more sigmoid. In the field experiments, grain yield responses to current P of albus lupin and chickpea were less than that for wheat. Relative to wheat, faba bean was the most responsive grain legume to applications of current P, with lentil producing similar responses to wheat in one experiment at a newly cleared, P deficient site.
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  • 79
    ISSN: 1432-1890
    Schlagwort(e): Key words Arbuscular mycorrhiza ; Hordeum vulgare ; Triticum aestivum ; Glomus intraradices ; Mycorrhiza-helper bacteria ; Secondary compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Colonization of Hordeum vulgare L. cv. Salome (barley)and Triticum aestivum L. cv. Caprimus (wheat) roots by the arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith leads to de novo synthesis of isoprenoid cyclohexenone derivatives with blumenin [9-O-(2′-O-β-glucuronosyl)-β-glucopyranoside of 6-(3-hydroxybutyl)-1,1,5-trimethyl-4-cyclohexen-3-one] as the major constituent and to transient accumulation of hydroxycinnamate amides (4-coumaroylagmatine and -putrescine). Accumulation of these compounds in mycorrhizal wheat roots started 2 weeks after sowing together with the onset of arbuscule formation and proceeded with mycorrhizal progression. Highest levels were reached in 3- to 4-week-old secondary roots (root branches of first and higher order) characterized by the formation of vesicles. In the final developmental stages, the fungus produced massive amounts of spores, enclosing the stele of older root parts (older than 5 weeks) characterized by cortical death. In these root parts, the secondary compounds were detected in trace amounts only, indicating that they were located in the cortical tissues. Some rhizosphere bacteria tested, i.e. Agrobacterium rhizogenes, Pseudomonas fluorescens, and Rhizobium leguminosarum, markedly stimulated both fungal root colonization and blumenin accumulation, thus, acting as mycorrhiza-helper bacteria (MHB). Application of blumenin itself strongly inhibited fungal colonization and arbuscule formation at early stages of mycorrhiza development. This was associated with a markedly reduced accumulation of the hydroxycinnamate amides 4-coumaroylputrescine and -agmatine. The results suggest that both the isoprenoid and the phenylpropanoid metabolism are closely linked to the developmental stage and the extent of fungal colonization. Their possible involvement in the regulation of mycorrhiza development is discussed.
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 98 (1999), S. 472-477 
    ISSN: 1432-2242
    Schlagwort(e): Key words QTL ; Ear emergence time ; Plant height ; Recombinant substitution line ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Chromosome 5A of wheat carries major gene loci for agronomic traits including the vernalization requirement (Vrn-A1) and ear morphology (Q). To determine whether the genetic variation for ear emergence time and plant height is attributable to either of these major genes as pleiotropic effects or independent QTL, we combined a RFLP map constructed from 120 recombinant substitution lines derived from a cross between ‘Chinese Spring’ (Cappelle-Desprez 5A) and CS(Triticum spelta 5A) with data collected from field trials over 3 years. For ear emergence time the main effects on flowering time were by Vrn-A1 and QEet.ocs-5A.1, the latter a QTL in the 28.6-cM Xcdo584/Q interval linked to Q by less than 10 cM. The CS(T. spelta 5A) allele at QEet.ocs-5A.1 contributed to an earlier ear emergence time by 2.7–6.0 days, which was approximately equal to the effects of Vrn-A1. For plant height, three QTLs were identified on the long arm and linked in repulsion. The CS(T. spelta 5A) allele at Vrn-A1 or closely linked to Xfba068 contributed to a height reduction of 3.5–6.1 cm, whereas both the Q allele and Qt.ocs-5A.1 allele within the Xcdo1088/Xbcd9 interval from CS(Cappelle-Desprez 5A) produced a shorter plant. When plant height was partitioned into culm length and ear length, the Vrn-A1 allele and CS(Cappelle-Desprez 5A) allele at QCl.ocs-5A.1 within the Xcd1088/Xbcd9 interval were found to contribute to a shorter culm. CS(T. spelta 5A) allele at q was a major determinant of a long ear, together with minor effects at QEl.ocs-5A.1 within the Xcdo1088/Xbcd9 interval.
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  • 81
    ISSN: 1432-2242
    Schlagwort(e): Key words Erysiphe graminis ; Powdery mildew resistance ; QTL ; Triticum aestivum ; Triticum spelta
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Powdery mildew is one of the major diseases of wheat in regions with a maritime or semi-continental climate and can strongly affect grain yield. The attempt to control powdery mildew with major resistance genes (Pm genes) has not provided a durable resistance. Breeding for quantitative resistance to powdery mildew is more promising, but is difficult to select on a phenotypic basis. In this study, we mapped and characterised quantitative trait loci (QTLs) for adult-plant powdery mildew resistance in a segregating population of 226 recombinant inbred lines derived from the cross of the Swiss wheat variety Forno with the Swiss spelt variety Oberkulmer. Forno possibly contains the Pm5 gene and showed good adult-plant resistance in the field. Oberkulmer does not have any known Pm gene and showed a moderate susceptible reaction. Powdery mildew resistance was assessed in field trials at two locations in 1995 and at three locations in 1996. The high heritability (h2=0.97) for powdery mildew resistance suggests that the environmental influence did not affect the resistance phenotype to a great extent. QTL analysis was based on a genetic map containing 182 loci with 23 linkage groups (2469 cM). With the method of composite interval mapping 18 QTLs for powdery mildew resistance were detected, explaining 77% of the phenotypic variance in a simultaneous fit. Two QTLs with major effects were consistent over all five environments. One of them corresponds to the Pm5 locus derived from Forno on chromosome 7B. The other QTL on 5A, was derived from the spelt variety Oberkulmer and did not correspond to any known Pm gene. In addition, five QTLs were consistent over three environments, and six QTLs over two environments. The QTL at the Pm5 locus showed a large effect, although virulent races for Pm5 were present in the mixture of isolates. Molecular markers linked with QTLs for adult-plant resistance offer the possibility of simultaneous marker-assisted selection for major and minor genes.
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  • 82
    ISSN: 1432-2242
    Schlagwort(e): Key words Aegilops tauschii ; Triticum aestivum ; Genetic mapping ; Molecular markers ; Agronomically important genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Aegilops tauschii is the diploid D-genome progenitor of bread wheat (Triticum aestivum L. em Thell, 2n=6x=42, AABBDD). A genetic linkage map of the Ae. tauschii genome was constructed, composed of 546 loci. One hundred and thirty two loci (24%) gave distorted segregation ratios. Sixty nine probes (13%) detected multiple copies in the genome. One hundred and twenty three of the 157 markers shared between the Ae. tauschii genetic and T. aestivum physical maps were colinear. The discrepancy in the order of five markers on the Ae. tauschii 3DS genetic map versus the T. aestivum 3D physical map indicated a possible inversion. Further work is needed to verify the discrepancies in the order of markers on the 4D, 5D and 7D Ae. tauschii genetic maps versus the physical and genetic maps of T. aestivum. Using common markers, 164 agronomically important genes were assigned to specific regions on Ae. tauschii linkage, and T. aestivum physical, maps. This information may be useful for map-based cloning and marker-assisted plant breeding.
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 98 (1999), S. 1171-1182 
    ISSN: 1432-2242
    Schlagwort(e): Key words Lodging ; Morphological traits ; QTL ; Triticum aestivum ; Triticum spelta
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Lodging can strongly affect both the grain yield and the quality of wheat. Lodging represents a quantitative trait and is difficult to assess on a phenotypic basis. Marker-assisted selection (MAS) could therefore become an important tool in breeding for lodging resistance. In this study, we mapped and characterised quantitative trait loci (QTLs) for lodging resistance, as well as morphological traits correlated with lodging, in a segregating population of 226 recombinant inbred lines derived from the cross of the lodging-resistant wheat variety Forno with the susceptible spelt variety Oberkulmer. Lodging, plant height, leaf width, leaf-growth habit, culm stiffness, culm swinging, culm thickness, days to ear emergence and days to flowering were assessed in field trials at two locations in 1996 and at one location in 1997. Additionally, at one location weight and length parameters were also assessed. Plant height and culm stiffness explained 77% of the phenotypic variance of lodging in a multiple regression model over all three environments. QTL analysis of lodging and morphological parameters was based on a genetic map containing 230 loci with 23 linkage groups (2469 cM). With the method of composite interval mapping nine QTLs for lodging resistance were detected, explaining 63% of the phenotypic variance in a simultaneous fit. Seven of these QTLs coincided with QTLs for morphological traits, reflecting the correlations between these traits and lodging. In our population the most efficient way to improve lodging resistance would be by a combination of indirect selection on plant height and culm stiffness together with MAS on the two QTLs for lodging resistance which did not coincide with QTLs for morphological traits.
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 98 (1999), S. 1248-1252 
    ISSN: 1432-2242
    Schlagwort(e): Key words Wheat ; Chromosome sorting ; Chromosome isolation ; Aneuploids ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  We are reporting the successful isolation of wheat chromosome arm 1DS by flow cytometry. A chromosome suspension was prepared for the 1DS ditelosomic line and the normal ‘Chinese Spring’ (CS) by chopping 2-day-old root tip meristems, synchronized by hydroxyurea, in HEPES-magnesium sulfate buffer containing propidium iodide. Chromosomes were analyzed and sorted with a FACS Vantage flow cytometer and cell sorter. An extra peak was observed in the flow karyotype of the ditelosomic line that was absent in ‘CS’. The estimated size of chromosomes from the extra peak matched with the expected size of chromosome 1DS. Chromosomes from the putative 1DS peak were analyzed by both fluorescent microscopy and N-banding analysis. A total of 571 chromosomes from two separate experiments were analyzed, and all were observed to be telosomics except for 2 which were broken. About 82% of these telosomics showed the diagnostic N-band of 1DS, the remaining were unbanded and are probably also 1DS. This strategy can also be used to sort other wheat arms.
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 99 (1999), S. 772-784 
    ISSN: 1432-2242
    Schlagwort(e): Key words Transgenic wheat ; Triticum aestivum ; Tritordeum ; Transgene inheritance ; Marker gene stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The stability and heritability of three marker genes was investigated in a population of twelve independent transgenic cereal lines (six wheat and six tritordeum). Integration patterns, inheritance of structural transgenes and inheritance of expression were analysed in the T0 and T1 generations for all 12 lines. Transmission and expression were analysed in the T2 generation for 9 lines and in the T3 generation for the six wheat lines. Inheritance of integration patterns was highly stable, and transmission of the transgenes and inheritance of their expression followed Mendelian ratios in the majority of lines. A gradual reduction in uidA expression was observed over three generations, which was not accompanied by a similar reduction in bar expression. Some unexpected phenomena associated with transgene inheritance were also observed and are discussed.
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  • 86
    ISSN: 1573-9368
    Schlagwort(e): low molecular weight glutenin promoter ; particle bombardment ; transgene expression ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Transgenic wheat plants from specific cultivars can now be routinely engineered in many laboratories. However, our understanding of the factors controlling transgene expression and stability in wheat compared to other cereals is rather limited. Only a few promoters have been tested in transgenic wheat, and relatively little is known of their relative activities and expression parameters. In the present study, the spatial and temporal properties of one heterologous constitutive promoter and one seed‐specific wheat promoter were investigated. We generated constructs with the reporter gene gusA (β‐glucuronidase) driven by: (a) the constitutive maize ubiquitin‐1 (ubi‐1) promoter, and (b) two different‐sized fragments of the seed‐specific low molecular weight glutenin (LMWG1D1) promoter from wheat. The activities of all three promoter constructs were comparable in endosperm tissue. A detailed analysis of spatial and temporal properties of the promoters is described. Heat shock treatment of transgenic plants carrying the ubi‐1: gusA construct resulted in a significant elevation in the levels of GUS activity. The inheritance of transgene expression levels and stability was evaluated over four generations, as a function of transgene integration patterns and copy number.
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  • 87
    ISSN: 1618-2545
    Schlagwort(e): BLB light ; conidiogenesis ; Fusarium globosum ; subtropical Japan ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The second report ofFusarium globosum is based on strains isolated from wheat in Ishigaki Island, Okinawa, in subtropical Japan. Morphological features of the Japanese isolates are described. These strains show different reactions in conidiogenesis to light conditions. Under continuous BLB light, falcate sporodochial conidia are typically induced, but production of aerial globose conidia is suppressed. In two of the strains, clavate conidia became longer under BLB light. Application of both, complete darkness and continuous BLB light, is recommended as standard light conditions to cultureFusarium isolates.
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  • 88
    ISSN: 1573-0646
    Schlagwort(e): pharmacokinetics ; capecitabine ; 5-fluorouracil ; phase I trials
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract An excretion balance and pharmacokinetic study was conducted in cancer patients with solid tumors who received a single oral dose of capecitabine of 2000 mg including 50 μ Ci of 14C-radiolabelled capecitabine. Blood, urine and fecal samples were collected until radioactive counts had fallen to below 50 dpm/mL in urine, and levels of intact drug and its metabolites were measured in plasma and urine by LC/MS-MS (mass spectrometry) and 19F-NMR (nuclear magnetic resonance) respectively. Based on the results of the 6 eligible patients enrolled, the dose was almost completely recovered in the urine (mean 95.5%, range 86–104% based on radioactivity measurements) over a period of 7 days after drug administration. Of this, 84% (range 71–95) was recovered in the first 12 hours. Over this time period, 2.64% (0.69–7.0) was collected in the feces. Over a collection period of 24–48h, a total of 84.2% (range 80–95) was recovered in the urine as the sum of the parent drug and measured metabolites (5′-DFCR, 5′-DFUR, 5-FU, FUH2, FUPA, FBAL). Based on the radioactivity measurements of drug-related material, absorption is rapid (tmax 0.25–1.5 hours) followed by a rapid biphasic decline. The parent drug is rapidly converted to 5-FU, which is present in low levels due to the rapid metabolism to FBAL, which has the longest half-life. There is a good correlation between the levels of radioactivity in the plasma and the levels of intact drug and the metabolites, suggesting that these represent the most abundant metabolites of capecitabine. The absorption of capecitabine is rapid and almost complete. The excretion of the intact drug and its metabolites is rapid and almost exclusively in the urine.
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  • 89
    ISSN: 1573-0646
    Schlagwort(e): docetaxel ; plasma assay ; clinical trials ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract We have developed a specific and sensitive method aiming atdocetaxel (Taxotere®) determination in plasma of treatedpatients. This involved solid-phase extraction of 1 ml of plasmaonto carboxylic acid (CBA) grafted silica cartridges followed byreversed-phase liquid chromatography with UV detection. The bestselectivity was obtained through the use of C18 Uptisphere® asstationary phase. The low limit of quantitation obtained (LOQ:5 ng/ml) allowed measurements of docetaxel up to 24 hours afterone-hour infusions with low dosages of drug (60 mg/m2). Themethod was applied successfully to monitor docetaxel plasma levelswithin two protocols associating fixed dosages of either methotrexate or gemcitabine with escalating doses of Taxotere®.
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  • 90
    ISSN: 1573-8744
    Schlagwort(e): pharmacokinetics ; pharmacodynamics ; effect compartment model ; indirect response ; sigmoid E max ; tiagabine ; GABA uptake inhibitor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Pharmacological inhibition of GABA uptake transporters provides a mechanism for increasing GABAergic transmission, which may be useful in the treatment of various neurological disorders. The purpose of our investigations was to develop an integrated pharmacokinetic–pharmacodynamic (PK/PD) model for the characterization of the pharmacological effect of tiagabine, R-N-(4,4-di-(3-methylthien-2-yl)but-3-enyl)nipecotic acid, in individual rats in vivo. The tiagabine-induced increase in the amplitude of the EEG 11.5–30 Hz frequency band (β), was used as pharmacodynamic endpoint. Chronically instrumented male Wistar rats were randomly allocated to four groups which received an infusion of 3, 10, or 30 mg kg −1 $$(\bar x \pm SE,{\text{ }}n = 23)$$ $$96 \pm 9$$ ml min -1 kg−1, 1.5ŷ0.1 L kg−1 and 20ŷ0.2 min.A time delay was observed between the occurrence of maximum plasma drug concentrations and maximal response. A physiological PK/PD model has been used to account for this time delay, in which a biophase was postulated to account for tiagabine available to the GABA uptake carriers in the synaptic cleft and the increase in EEG effect was considered an indirect response due to inhibition of GABA uptake carriers. The population values for the pharmacodynamic parameters characterizing the delay in pharmacological response relative to plasma concentrations were keo=0.030 min −1 and kout=81 min−1, respectively. Because of the large difference in these values the PK/PD model was simplified to the effect compartment model. Population estimates $$(\bar x \pm SE)$$ were E0=155 ŷ 6 μV, Emax=100 ŷ 5 μV, EC50=287 ŷ 7 ng ml−1, Hill factor=1.8 ŷ 0.2 and keo=0.030 ŷ 0.002 min −1. The results of this analysis show that for tiagabine the combined “effect compartment-indirect response” model can be simplified to the classical “effect compartment” model.
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 491-512 
    ISSN: 1573-8744
    Schlagwort(e): muscle relaxants ; peripheral elimination ; pharmacokinetics ; peripheral concentrations ; volume of distribution ; pharmacokinetic model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract For anesthetic drugs undergoing nonorgan-based elimination, there is a definite trend towards using pharmacokinetic (PK) models in which elimination can occur from both central (k10 ) and peripheral compartments(k20 ). As the latter cannot be assessed directly, assumptions have to be made regarding its value. The primary purpose of this paper is to evaluate the impact of assuming various degrees of peripheral elimination on the estimation of PK parameters. For doing so, an explanatory model is presented where previously published data from our laboratory on three muscle relaxants, i.e., atracurium, doxacurium, and mivacurium, are used for simulations. The mathematical aspects for this explanatory model as well as for two specific applications are detailed. Our simulations show that muscle relaxants having a short elimination half-life are more affected by the presence of peripheral elimination as their distribution phase occupies the major proportion of their total area under the curve. Changes in the exit site dependent PK parameters (Vdss ) are also mostly significant when k20 is smaller than k10 . Although the physiological processes that determine drug distribution and those affecting peripheral elimination are independent, the two are mathematically tied together in the two-compartment model with both central and peripheral elimination. It follows that, as greater importance is given to k20 , the rate of transfer from the central compartment (k12 ) increases. However, as a result of a proportional increase in the volume of the peripheral compartment, peripheral concentrations remain unchanged whether or not peripheral elimination is assumed. These findings point out the limitations of compartmental analysis when peripheral elimination cannot be measured directly.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 325-328 
    ISSN: 1573-8744
    Schlagwort(e): anesthetic techniques ; continuous infusion ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We have previously described a method of rapidly obtaining a specified steady-state plasma concentration of an intravenous drug within precise limits. However the method is limited to drugs whose disposition may be characterized by an open two-compartment system. In this paper, we illustrate how the method can be extended to drugs whose disposition may be characterized by a mammillary model with any number of compartments. Refinements of our previous technique are also described.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 93
    ISSN: 1573-8744
    Schlagwort(e): psoriasis ; hu1124 ; CD11a ; CD3-positive lymphocytes ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The pharmacokinetics of hu1124, a human anti-CD11a antibody, were investigated in human subjects with psoriasis. CD11a is a subunit of LFA-1, a cell surface molecule involved in T cell mediated immune responses. Subjects received a single dose of 0.03, 0.1, 0.3, 0.6, 1, 2, 3, or 10 mg/kg of hu1124 intravenously over 1–3 hr. Blood samples were collected at selected times from 60 min to 72 days after administration. Plasma samples were assayed for hu1124 by ELISA, and pharmacokinetic analyses were performed on the drug plasma concentrations. As the dose of hu1124 was increased, the clearance decreased from 322 ml/day per kg at 0.1 mg/kg to 6.6 ml/day per kg at 10 mg/kg of hu1124. The plasma hu1124 concentration–time profile suggested that the clearance of hu1124 was saturable above 10 μg/ml. In addition, treatment with hu1124 caused a rapid reduction in the level of CD11a expression on CD3-positive lymphocytes (T cells) to about 25% of pretreatment levels. Regardless of the hu1124 dose administered, cell surface CD11a remained at this reduced level as long as hu1124 was detectable (〉0.025 μg/ml) in the plasma. When hu1124 levels fell below 3 μg/ml, the drug was rapidly cleared from the circulation and expression of CD11a returned to normal within 7–10 days thereafter. In vitro, half-maximal binding of hu1124 to lymphocytes was achieved at about 0.1 μg/ml and saturation required more than 10 μg/ml. One of the receptor-mediated pharmacokinetic/pharmacodynamic models which was developed describes the dynamic interaction of hu1124 binding to CD11a, resulting in the removal of hu1124 from the circulation and reduction of cell surface CD11a. The model accounts for the continually changing number of CD11a molecules available for removing hu1124 from the circulation based on prior exposure of cells expressing CD11a to hu1124. In addition, the model also accounts for saturation of CD11a molecules by hu1124 at drug concentrations of approximately 10 μg/ml, thereby reducing the clearance rate of hu1124 with increasing dose.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 531-554 
    ISSN: 1573-8744
    Schlagwort(e): drug–drug interactions ; NPML ; experimental design ; pharmacodynamic variability ; pharmacokinetics ; entropy ; covariate ; second stage model ; controlled trial
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Population approaches are appealing methods for detecting then assessing drug–drug interactions mainly because they can cope with sparse data and quantify the interindividual pharmacokinetic (PK) and pharmacodynamic (PD) variability. Unfortunately these methods sometime fail to detect interactions expected on biochemical and/or pharmacological basis and the reasons of these false negatives are somewhat unclear. The aim of this paper is firstly to propose a strategy to detect and assess PD drug–drug interactions when performing the analysis with a nonparametric population approach, then to evaluate the influence of some design variates (i.e., number of subjects, individual measurements) and of the PD interindividual variability level on the performances of the suggested strategy. Two interacting drugs A and B are considered, the drug B being supposed to exhibit by itself a pharmacological action of no interest in this work but increasing the A effect. Concentrations of A and B after concomitant administration are simulated as well as the effect under various combinations of design variates and PD variability levels in the context of a controlled trial. Replications of simulated data are then analyzed by the NPML method, the concentration of the drug B being included as a covariate. In a first step, no model relating the latter to each PD parameter is specified and the NPML results are then proceeded graphically, and also by examining the expected reductions of variance and entropy of the estimated PD parameter distribution provided by the covariate. In a further step, a simple second stage model suggested by the graphic approach is introduced, the fixed effect and its associated variance are estimated and a statistical test is then performed to compare this fixed effect to a given value. The performances of our strategy are also compared to those of a non-population-based approach method commonly used for detecting interactions. Our results illustrate the relevance of our strategy in a case where the concentration of one of the two drugs can be included as a covariate and show that an existing interaction can be detected more often than with a usual approach. The prominent role of the interindividual PD variability level and of the two controlled factors is also shown.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 329-338 
    ISSN: 1573-8744
    Schlagwort(e): propofol ; anaesthesia ; pharmacokinetics ; compartment models ; effect compartment models
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Conventional compartmental pharmacokinetic analysis may provide inaccurate prediction of drug concentrations after rapid iv administration. To examine this, compartment and effect compartment analysis was applied to measured arterial and brain concentrations of propofol in sheep after iv administration at a range of doses and dose rates. Although arterial and brain concentrations were reasonably well fitted to compartmental and effect compartment models for individual doses and dose rates, the structure and parameters of all models differed with changes in both dose and rate of administration. There were large discrepancies between predicted and measured arterial and brain concentrations when these models were used to predict drug concentrations across doses and dose rates. These data support the limitations of this type of modeling in the setting of rapid propofol administration.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 513-529 
    ISSN: 1573-8744
    Schlagwort(e): desmopressin ; indirect-response modeling ; overhydration ; pharmacokinetics ; pharmacodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The objective of the present study was to investigate the pharmacokinetics (PK) and pharmacodynamics (PD) of desmopressin in healthy male subjects at different levels of overhydration. Also, we examined if an indirect-response model could be related to renal physiology and the pharmacological action of desmopressin. Eight healthy male subjects participated in this open, randomized crossover study with three periods. Each subject was orally water loaded (0 to 20ml·kg −1 body weight) on 3 study days in order to achieve three different levels of hydration. After the initial water load, urine was voided every 15 min and the volumes were measured. To ensure continuous overhydration the subjects replaced their fluid loss with drinking-water. When a steady-state diuresis was achieved after approximately 2 hr, 0.396 μg of desmopressin was administered intravenously as a bolus injection. Blood was sampled and urine was collected at intervals throughout the study day (10 hr). An indirect-response model, where desmopressin was assumed to inhibit the elimination of response, was fit to the urine osmolarity data. There were no statistically significant effects of different levels of hydration, as expressed by urine flow rate at baseline, on the estimates of the PK and PD model parameters. The calculated terminal half-lives of elimination (t1/2 β) ranged between 2.76 and 8.37 hr with an overall mean of 4.36 hr. The overall means of plasma clearance and the volumes of distribution of the central compartment (Vc ) and at steady state (Vss ) were estimated to be 1.34 (SD 0.35) ml·min −1 ·kg −1 , 151 (SD28) ml·kg −1 , and 386 (SD 63) ml·kg −1 , respectively. High urine flow rate, indicating overhydration, produced a diluted urine and thus a low osmolarity at baseline (R0 ). The effect of the urine flow rate on the urine osmolarity at baseline was highly significant (p〈0.0001). The mean values for IC50 and the sigmoidicity factor (γ) were 3.7 (SD 1.2) pg·ml −1 and 13.0 (SD 3.5), respectively. In most cases when there was a high urine flow rate at baseline, the model and the estimated PD parameters could be related to the pharmacological action of desmopressin and renal physiology. Thus, the indirect-response model used in this study offers a mechanistic approach of modeling the effect of desmopressin in overhydrated subjects.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    ISSN: 1573-8744
    Schlagwort(e): prediction interval ; pharmacokinetics ; population analysis ; NONMEM ; inverse regression ; immunosuppressives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Basiliximab is an immunosuppressant chimeric monoclonal antibody directed to the human interleukin-2 receptor α-chain used for prevention of acute rejection episodes in organ transplantation. The minimally effective serum concentration necessary to saturate receptor epitopes in kidney transplant patients is 0.2 μg/ml. To guide dose selection for Phase 3 efficacy trials, a population pharmacostatistical model was fitted to intensively sampled Phase 2 pharmacokinetic data. This served as a basis from which to examine candidate dose regimens with respect to the duration over which receptor-saturating concentrations would be achieved posttransplant. Three prediction methods were assessed: one based on simulations, and two others based on first-order approximation using either inverse regression or inversion of confidence intervals. An 80% prediction interval was generated by each method to evaluate its predictive performance against prospectively collected Phase 3 data in 39 renal transplant patients who received two injections of 20mg basiliximab, one prior to surgery and one on Day 4 posttransplant. All methods provided correct prediction of the duration of receptor-saturating concentration. As anticipated, the best performance was obtained from the simulation method which predicted 30 values in the 80% prediction interval, 19.7–52.7 days. The actually observed 80% interval from the Phase 3 data was 23.7–58.3 days.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 559-575 
    ISSN: 1573-8744
    Schlagwort(e): T-helper cells ; trafficking ; rebound ; corticosteroids ; circadian rhythm ; methylprednisolone ; drug interactions ; pharmacokinetics ; pharmacodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A physiologic pharmacodynamic model was developed to jointly characterize the effects of corticosteroid treatment on adrenal suppression and T-helper cell trafficking during single and multiple dosing in asthmatic patients. Methylprednisolone (MP), cortisol, and T-helper cell concentrations obtained from a previously published study during single day and 6 days of multiple dosing MP treatment were examined. The formation and disposition kinetics of MP were described with a compartmental model. The biorhythmic profile of basal cortisol secretion rate was analyzed using a recent Fourier approach based on circadian harmonics. A three-compartment loop model was proposed to represent three major T-helper cell pools: blood, extravascular site, and lymph nodes. T-helper cell synthesis and degradation rate constants were obtained from the literature. The suppressive effects of cortisol and MP on T-helper cell concentrations were described with a joint additive inhibition function altering the cell migration rate from lymph nodes to blood. The model adequately described both plasma cortisol profiles and T-helper cells in blood after single and multiple doses of MP. The potency of MP for suppression of cortisol secretion was estimated as IC50 = 0.8 ng/ml. The biorhythmic nature of the basal T-helper cells in blood was well described as under the influence of basal circadian cortisol concentrations with IC50 = 79 ng/ml. The model fitted potency of MP for suppression of T-helper cells was IC50 = 4.6 ng/ml. The observed rebound of T-helper cells in blood can also be described by the proposed model. The rhythm and suppression of plasma cortisol and T-helper cells before and during single and multiple dose MP treatment were adequately described by these extended indirect response models.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    ISSN: 1573-904X
    Schlagwort(e): etomidate ; pharmacokinetics ; pharmacodynamics ; rat ; electroencephalogram
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The effect-plasma concentration relationship of etomidate was studied in the rat using electroencephalographic changes as a pharmacodynamic parameter. Methods. Etomidate was infused (50 mg/kg/h) in chronically instrumented rats (n = 6) until isoelectric periods of 5 s or longer were observed in the electroencephalogram (EEG). The EEG was continuously recorded during the experiment and frequent arterial blood samples were taken for determination of etomidate plasma concentrations. The changes observed in the raw EEG signal were quantified using aperiodic analysis in the 2.5−7.5 Hz frequency band. The return of the righting reflex was used as another parameter of anesthesia. Results. A mean dose of 8.58 ± 0.41 mg/kg needed to be infused to reach the end point of 5 s isoelectric EEG. The plasma concentration time profiles were most adequately fitted using a three-exponential model. Systemic clearance, volume of distribution at steady-state and elimination half-life averaged 93 ± 6 ml/min/kg, 4.03 ± 0.24 l/kg and 59.4 ± 10.7 min respectively. The EEG effect-plasma concentration relationship was biphasic exhibiting profound hysteresis. Semi-parametric minimization of this hysteresis revealed an equilibration half-life of 2.65 ± 0.15 min, and the biphasic effect-concentration relationship was characterized nonparametrically by descriptors. The effect-site concentration at the return of the righting reflex was 0.44 ± 0.03 μg/ml. Conclusions. The results of the present study show that the concentration-effect relationship of etomidate can be characterized in individual rats using aperiodic analysis in the 2.5−7.5 Hz frequency band of the EEG. This characterization can be very useful for studying the influence of diseases on the pharmacodynamics of etomidate in vivo.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    ISSN: 1573-904X
    Schlagwort(e): bioequivalence ; neural networks ; prediction ; pharmacokinetics ; verapamil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. The methodology of predicting the pharmacokinetic parameters (AUC, cmax, tmax) and the assessment of their variability in bioequivalence studies has been developed with the use of artificial neural networks. Methods. The data sets included results of 3 distinct bioequivalence studies of oral verapamil products, involving a total of 98 subjects and 312 drug applications. The modeling process involved building feedforward/backpropagation neural networks. Models for pharmacokinetic parameter prediction were also used for the assessment of their variability and for detecting the most influential variables for selected pharmacokinetic parameters. Variables of input neurons based on logistic parameters of the bioequivalence study, clinical-biochemical parameters, and the physical examination of individuals. Results. The average absolute prediction errors of the neural networks for AUC, cmax, and tmax prediction were: 30.54%, 39.56% and 30.74%, respectively. A sensitivity analysis demonstrated that for verapamil the three most influential variables assigned to input neurons were: total protein concentration, aspartate aminotransferase (AST) levels, and heart-rate for AUC, AST levels, total proteins and alanine aminotransferase (ALT) levels, for cmax, and the presence of food, blood pressure, and body-frame for tmax. Conclusions. The developed methodology could supply inclusion or exclusion criteria for subjects to be included in bioequivalence studies.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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