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  • Springer  (39)
  • Oxford University Press  (3)
  • American Physical Society (APS)
  • 1995-1999  (42)
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  • 1
    Electronic Resource
    Electronic Resource
    Isochorismate hydroxymutase from a cell-suspension culture of Galium mollugo L. (1997)
    Springer
    Planta 202 (1997), S. 206-210 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Anthraquinone biosynthesis ; Galium ; Isochorismate hydroxymutase ; Rubiaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Isochorismate hydroxymutase (i.e. isochorismate synthase, EC 5.4.99.6) was purified from an anthraquinone-producing cell-suspension culture of Galium mollugo L. Although attempts to stabilize the labile enzyme met with little success, a substantial increase in enzyme activity was observed in the presence of glycine betaine (500 mM). Column chromatography on solid supports other than diethylaminoethyl (DEAE)-Sephacel, Phenylsepharose Cl-4B or Cibacron Blue 3G-A did not give active enzyme preparations. In spite of these drawbacks the enzyme was purified 573-fold. Enzyme activity depended strictly on the presence of Mg2+. Kinetic data for chorismate in the forward reaction (K m = 807 μM, V max = 6.2 pkat · mg−1) and for isochorismate in the reverse reaction (K m = 675 μM, V max = 5.9 pkat · mg−1) were determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050120
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  • 2
    Electronic Resource
    Electronic Resource
    A Microtomographic System for the Nondestructive Evaluation of Bone Architecture (1996)
    Springer
    Calcified tissue international 58 (1996), S. 24-29 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Microtomography — Computed tomography — Bone structure — Bone strength — Osteoporosis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Microtomography (micro-computed-tomography, μ-CT) is a method to image and quantify trabecular bone. It has the capability to address the role of trabecular architecture on the mechanical properties of bone and to study trabecular bone remodeling. The system described in this work is based on a compact fan-beam type tomograph that can work in spiral scanning or multislice mode. An X-ray tube with a microfocus is used as a source, a CCD-array as a detector. Samples with diameters from a few millimeters to a maximum of 14 mm can be measured, typically, bone biopsies with a diameter of 8 mm and a length of approximately 10 mm are measured. Spatial resolution is 28 μm. Usually the volume of interest contains 4 × 4 × 4 mm3 and is represented in 14 × 14 × 14 μm3 voxels. 3D stereological indices are extracted according to the standard definitions used in histomorphometry. Triangular surface representation is effected with an extended marching cube algorithm and forms a convenient basis for finite element analysis. Microtomographic measurements may be employed to ``calibrate'' lower-dose, lower-resolution images in vivo as well as to nondestructively assess unprocessed surgical bone biopsy specimens. These specimens remain intact for mechanical or histological testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900006
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  • 3
    Electronic Resource
    Electronic Resource
    Chemical ozone loss in the Arctic vortex in the winter 1995–96: HALOE measurements in conjunction with other observations (1998)
    Springer
    Annales geophysicae 17 (1998), S. 101-114 
    Details
    ISSN: 0992-7689
    Keywords: Chemical ozone loss (Arctic vortex 1995–96; halogen chemistry)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Severe chemical ozone loss has been detected in the Arctic in the winter and spring of 1995–96 by a variety of methods. Extreme reductions in column ozone due to halogen catalysed chemistry were derived from measurements of the Halogen Occultation Experiment (HALOE) on board the Upper Atmosphere Research Satellite in the Arctic vortex. Here, we discuss further aspects of the HALOE observations in the Arctic over this period. Potential problems, both in the data themselves and in the methodology of the data analysis are considered and the reason for the differences between the Arctic ozone losses deduced from HALOE data version 17 and 18 is analysed. Moreover, it is shown that HALOE measurements in the Arctic in winter and spring 1995–96 compare well with observations by other ground-based and satellite instruments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-0101-x
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  • 4
    Electronic Resource
    Electronic Resource
    Microbial production of specifically ring-13C-labelled 4-hydroxybenzoic acid (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 985-988 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract When transformed with a recombinant vector carrying the ubiC gene (encoding chorismate pyruvate-lyase, EC 4.1.3.27) the triple mutant (Phe−, Trp−, Tyr−) Klebsiella pneumoniae 62-1 excretes 4-hydroxybenzoic acid instead of chorismic acid. The recombinant strain can be used to produce in high yield specifically ring-labelled 4-hydroxybenzoic acid from isotopically labelled glucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166913
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  • 5
    Electronic Resource
    Electronic Resource
    Growth rate-dependent expression of phenol-assimilation pathways in Alcaligenes eutrophus JMP 134–the influence of formate as an auxiliary energy source on phenol conversion characteristics (1996)
    Springer
    Applied microbiology and biotechnology 46 (1996), S. 156-162 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Alcaligenes eutrophus JMP 134 was continuously (carbon-source-limited) grown on phenol to determine the maximum growth rates (μmax) as a function of the phenol assimilation pathways expressed. During growth on phenol as the sole source of carbon and energy, an almost exclusive expression of the ortho cleavage pathway (catechol 1,2-dioxygenase) was observed at initially low growth rates. This allowed a μmax of 0.28 h-1. The induction of the meta cleavage pathway (catechol 2,3-dioxygenase), which appeared at around 0.25 h-1, resulted in a further increase in the growth rate to 0.40 h-1 after the enzyme activities of this pathway had been correspondingly expressed. Hence, two maximum growth rates, one for the ortho and one for the meta cleavage pathway, exist for the growth of A. eutrophus JMP 134 on phenol. Growth on phenol was stimulated by formate, which served as an auxiliary energy source in this strain. The simultaneous utilization of phenol and formate at a molar ratio of 1:5.2 resulted in an increase of the yield coefficient from about 0.75 g dry mass/g phenol to 1.25 g/g. Furthermore, formate exerted a pronounced effect on the growth rate. At a molar ratio of phenol to formate of 1:4.2, the growth rate was increased to 0.42 h-1, despite the exclusive induction of the ortho cleavage pathway. The meta cleavage pathway was expressed during growth on this substrate mixture at about 0.4 h-1. However, this did not enable a significant increase of the growth rate beyond 0.4 h-1. This is attributed to an exhaustion of the capacity for formate oxidation at this rate. The results are discussed with respect to energy production capabilities when phenol is assimilated as an energy-deficient heterotrophic substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050798
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  • 6
    Electronic Resource
    Electronic Resource
    Isolation and characterization of a thermophilic bacillus strain, that degrades phenol and cresols as sole carbon source at 70 °C (1996)
    Springer
    Applied microbiology and biotechnology 46 (1996), S. 593-596 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A phenol-degrading thermophilic bacterium, designated Bacillus sp. A2, was isolated from a water and mud sample from a hot spring in Iceland. The aerobic isolate grew optimally on phenol at 65 °C. At 70 °C, 85% of the optimal growth rate was still observed. No growth was observed at 40 °C and 75 °C. Bacillus sp. A2 is a gram-positive spore-forming rod. According to 16S rDNA analysis Bacillus sp. A2 is closely related to Bacillus stearothermophilus, Bacillus kaustophilus and Bacillus thermoleovorans. Bacillus sp. A2 degraded phenol completely in concentrations up to 5 mM. In addition, all three isomers of cresol were utilized as sole carbon and energy sources. The degradation of phenols proceeds via the meta-cleavage pathway and the enzymes involved in its degradation are constitutively expressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050866
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  • 7
    Electronic Resource
    Electronic Resource
    Substrate inhibition under stationary growth conditions – nutristat experiments with Ralstonia eutropha JMP 134 during growth on phenol and 2,4-dichlorophenoxyacetate (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 648-655 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Ralstonia eutropha (formerly Alcaligenes eutrophus) JMP 134 was continuously grown on phenol and 2,4-dichlorophenoxyacetate at elevated levels of stationary substrate concentration by using the nutristat principle in order to study the physiological impact exerted by these toxic substrates. Growth at stationary concentrations of both the substrates resulted in the reduction of growth efficiency and growth rate. The growth yield data revealed a pronounced dependence on the substrate concentration, and the growth yield increasingly diminished with rising substrate concentration. Inhibition was more pronounced with 2,4-dichlorophenoxyacetate, which reduced the growth yield coefficient by 50% at a substrate concentration of 0.1–0.25 mM. The same effect was obtained with phenol at about 5 mM. The growth rate profile had two distinct phases: after an initially strong reduction, the rate levelled-off at higher substrate concentrations. Standardizing the inhibition profiles, by taking into account the maximum effect after extrapolating the data to zero growth yield, revealed an almost identical pattern with both substrates, indicating some common mechanism. The growth yield data show that an increased amount of energy is required for both growth and maintenance. Homeostatic work was increased by a factor of 8 at 75% inhibition; growth collapsed once this amount of energy was no longer available. The effects are discussed with respect to the properties of these substrates functioning as potential uncouplers of energy conservation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051110
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  • 8
    Electronic Resource
    Electronic Resource
    Prevalence of Trabecular Microcallus Formation in the Vertebral Body and the Femoral Neck (1997)
    Springer
    Calcified tissue international 60 (1997), S. 479 -484 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Trabecular microcallus formation — Vertebra — Femur — Histomorphometry — Bone density — Osteoporosis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Trabecular microcallus formation (TMF) has been described previously in the human vertebra and femur, but the difference in TMF prevalence at these two sites has not been studied and the role of TMF remains controversial. In this study, the 4th lumbar vertebra (L4) and right proximal femur were removed from 27 male and 23 female cadavers. A 2 cm cube cut from the center of L4 and a 1 cm-thick slice cut from the femoral neck were cleaned, defatted, and dried. The apparent density of the L4 cubes was determined as dry weight/bulk bone volume. Using a dissecting microscope at low magnification (4–60×), TMF were identified and counted in both the vertebral and femoral samples. A 8 mm diameter core was then cut from the center of the L4 cubes in the vertical direction, and selected histomorphometric parameters of the core were evaluated with an X-ray microcomputed tomography system (μ-CT). There was a significantly greater prevalence of TMF in vertebral cubes (82%) than in the femoral slices (11%) (P 〈 0.001). TMF prevalence did not differ significantly between males and females, but the mean number of TMF in the vertebra was significantly (P 〈 0.05) greater in females (15.0/vertebra) than in males (7.7/vertebra). In the vertebra, the majority of the observed TMF were in vertical trabeculae. Subjects over 60 years old had a higher TMF prevalence than those under 60 years old (P 〈 0.01). TMF numbers increased with decreasing apparent density (P 〈 0.05), whereas no significant correlations were found between TMF and bone volume (BV/TV), trabecular number (Tb.N), or trabecular thickness (Tb.Th) as assessed by μ-CT. In two fractured vertebra, very few TMFs (2 and 4, respectively) were observed. These results demonstrated that the occurrence of TMF is strongly related to the anatomical site, probably due to differences in the applied loads and the trabecular structure between sites. The results were consistent with the hypothesis that TMF is a mechanism acting to maintain bone strength, but further studies are needed to clarify this important issue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900266
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  • 9
    Electronic Resource
    Electronic Resource
    Validity and reproducibility of benthic cover estimates made during broadscale surveys of coral reefs by manta tow (1999)
    Springer
    Coral reefs 18 (1999), S. 353-356 
    Details
    ISSN: 1432-0975
    Keywords: Key words Coral Reef ; Manta tow ; Survey ; Benthic video ; Observer ; Comparisons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  There is limited information on the validity and reproducibility of estimates of benthic cover from manta tow surveys. To address this, benthic cover estimates from the same reef area were compared (i) among observers and (ii) with an independent assessment using under-water video. Benthic cover was classified into 11 categories. There was generally unbiased agreement within one cover category, both among observers (89%) and for comparisons between manta tow and video (86%). While estimates of dead coral cover were reproducible, they were not valid because the concordance between observer estimates and video estimates was not greater than would be expected by chance. Manta tow estimates of the cover of sand and rubble were biased in that they consistently overestimated sand and rubble cover in comparison with estimates from video. The results indicate that manta towing is generally effective for the broadscale estimation of live coral cover, providing observers receive adequate training.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003380050212
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  • 10
    Electronic Resource
    Electronic Resource
    Interindividual variation in the enzymatic 15-keto-reduction of 13,14-dihydro-15-keto-prostaglandin E1 in human liver and in human erythrocytes (1997)
    Springer
    European journal of clinical pharmacology 52 (1997), S. 147-153 
    Details
    ISSN: 1432-1041
    Keywords: Key wordsProstaglandin E1 ; Carbonyl reductase; 13 ; 14-dihydro-15-keto-PGE1 ; 13 ; 14-dihydro-PGE1 ; human ; liver ; erythrocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The therapeutic response to PGE1 is highly variable, and a contribution by variable formation of its active tertiary metabolite PGE0 is in question. Hence, the objective of this study was to assess the person-to-person variation of the reduction of the inactive intermediate metabolite 15-KD PGE1 by human liver and human erythrocytes in forming the active metabolite PGE0. Methods: Source of enzyme was lysed erythrocytes from 29 donors, and a bank of 37 donor livers including specimens from 15 children. Tritium-labelled 13,14-dihydro-15-keto-prostaglandin E1 (15-KD PGE1) was used at low nanomolar concentrations and found to be converted almost exclusively to the more polar compound 13,14-dihydro-prostaglandin E1 (PGE0) by an NADPH-dependent carbonyl reductase. The identity of the product PGE0 was established by comparison of its chromatographic and mass spectral characteristics with authentic PGE0. Results: Lysed erythrocytes had readily measurable enzymatic activity; differences between the preparations from 29 subjects were very small with only a twofold range of variation. In contrast to lysed erythrocytes, intact erythrocytes did not catalyse the reaction so that the erythrocyte activity should be medically immaterial. 15-KD PGE1 15-ketoreductase activity of liver cytosol averaged 61.1 fmol · min−1 · mg−1 protein in preparations from 37 human livers. Individual activities varied over an almost tenfold range, with indications of a non-normal distribution. Kinetic studies of selected specimens showed substantially different Vmax values but indistinguishable k M values, suggesting that the individual variation in 15-KD PGE1 15-ketoreduction is the result of differences in enzyme concentration rather than of structural enzyme variations. The activity in 15 livers from children was significantly lower than in those from adults. Inhibition data suggest that both the liver and the erythrocyte enzymes belong to the class of carbonyl reductases. Conclusions: The variations in hepatic enzyme activity may be expected to affect the transformation of 15-KD PGE1 to the active metabolite PGE0 in vivo. The clinical significance remains to be explored.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050264
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