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  • 1
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    Stoichiometry: linking elements to biochemicals (2004)
    In:  EPIC3Ecology, 85, pp. 1193-1202
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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    PAPER (OA)
  • 2
    Electronic Resource
    Electronic Resource
    ORNITHINE DECARBOXYLASE ACTIVITY IN DEVELOPING RAT BRAIN (1972)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 19 (1972), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Total ornithine decarboxylase (ODC) (EC 4.1.1.17) activity per rat brain was elevated markedly from 14 days after conception to 12 days postnatum. ODC activity in the brainstem was very low and changed little during postnatal development. Activity in the cerebral hemispheres declined from a high level at birth to the low adult level by 8 days postnatum. Conversely activity in the cerebellum increased markedly from 3 days until 11 days postnatum, then suddenly decreased. Hence, the periods of greatest ODC activity paralleled those of maximal cell proliferation in each brain region. During perinatal brain development ODC activity changed considerably; it declined at about one day prior to term, and then increased rapidly to its highest level of activity at 4 h postnatum. Premature birth by caesarian section or lack of maternal care and nutrition did not affect this early postnatal response. The postnatal burst in ODC activity appears to be unique for brain tissue, since this response did not occur in heart, skeletal muscle or liver.Data from studies in which portions of fractions characterized by high or low enzymatic activity, respectively, were mixed or in which the supernatant enzyme fraction was dialysed are not consistent with the presence of direct inhibitors or activators of the enzyme. In addition, administration of cycloheximide to newborn rats abolished the 4-h postnatal burst in ODC activity. Our results suggest that the increase in ODC activity reflects enzyme synthesis de novo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1972.tb05090.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Purification and partial characterization of two acid phosphatases from rat bone (1979)
    Springer
    Calcified tissue international 27 (1979), S. 219-226 
    Details
    ISSN: 1432-0827
    Keywords: Acid phosphatases ; Bone phosphatases ; ATPase ; Enzyme purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Acid phosphatase activity in homogenized tibiae and femora of suckling rats was extracted with 0.3M KCl and 0.1% Triton X-100. A high-speed supernatant was treated with protamine sulfate, dialyzed, and chromatographed on CM-52 cellulose. All of the acid phosphatase activity was eluted with a sodium acetate buffer and combined ionic strength-pH gradient into two peaks (E1 and E2). Both enzyme peaks were further purified with Sephadex G-200, which resulted in 700- and 1000-fold purification for E2 and E1, respectively. A total of 220 units (µmoles substrate/min) of E2 with a specific activity of 160 units/mg protein has been obtained in one run by this procedure. E1 has a high molecular weight (〉100,000) and shows preference for monophosphate ester substrates, is markedly inhibited by tartrate, and has a pH optimum near 5. E2 has a lower molecular weight (〈40,000) and shows negligible activity with monophosphate esters [except withp-nitrophenyl phosphate (p-NPP)], but high activity with ADP and ATP. E2 is unaffected by tartrate and shows a pH optimum near 6. Both enzymes are competitively inhibited by inorganic phosphate, and E2, but not E1, is markedly inhibited byp-chloromercuribenzoate. Withp-NPP as substrate, E1 and E2 have distinctly different values for Km. E1 appears similar to the high molecular weight acid phosphatases of soft tissues. However, E2 appears to differ from the low molecular weight phosphatases in soft tissues with regard to substrate specificity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441189
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Chromatographic separation of two acid phosphatases from rat bone (1977)
    Springer
    Calcified tissue international 24 (1977), S. 187-190 
    Details
    ISSN: 1432-0827
    Keywords: Column chromatography ; Acidβ-glycerophosphatase ; Acid inorganic pyrophosphatase ; Acid p-nitrophenylphosphatase ; Bone phosphatases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Extracts of tibiae of suckling rats were prepared with 0.3 M KCl containing 0.1% Triton X-100 and were chromatographed with CM-52 cellulose. Most of the acid phosphatase activity determined with p-nitrophenylphosphate (p-NPP) was bound to the cellulose and could be eluted with a sodium acetate buffer gradient in 2 distinct peaks. The major peak, E2, was bound strongly to the cellulose and showed high activity with p-NPP and inorganic pyrophosphate (P-Pi), but only slight activity withβ-glycerophosphate (β-GP) and was unaffected by tartrate. The minor peak, E1, was weakly bound to the adsorbent, showed equal activity with p-NPP andβ-GP, but negligible activity with P-Pi and was completely inhibited by tartrate. These results support earlier evidence suggesting that bone contains at least 2 different acid phosphatases and that the more abundant enzyme may function as a pyrophosphatase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02223314
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Further studies on the separation and identification of two phosphatases with acid optima from rat bone (1981)
    Springer
    Calcified tissue international 33 (1981), S. 261-267 
    Details
    ISSN: 1432-0827
    Keywords: Acid phosphatases ; Acid phosphoprotein phosphatases ; Bone phosphatases ; Enzyme purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Studies were designed to examine the effects of isotonic sucrose and hypertonic KCl on the extraction and properties of phosphatases (acid optima) from long bones of suckling rats. Low-speed supernatants (S) of homogenates in sucrose were dialyzed against sucrose or deionized H2O. Free enzyme was recovered from both retentates by ultracentrifugation before (S1) or after sequential treatment with KCl and Triton X-100 (S2), protamine (S3), and a final dialysis (S4). Activity was measured withp-nitrophenylphosphate (p-NPP), β-glycerophosphate (β-GP), ATP, and casein. S was evaluated for latent enzyme with hypertonic KCl and classic lysing methods. Fractionation of activity in final extracts was accomplished with CM-52 cellulose or electrophoresis. Results showed that: (a) sucrose did not alter the types or properties of enzymes extracted, but did decrease yield of activities; (b) activity in S was increased approximately 20% by lysing methods, 80% by hypertonic KCl, and was unstable unless salt and detergent were present; and (c) chromatography or electrophoresis of S4 resolved only two enzymes: a tartrate-sensitive phosphomonoesterase (E1) responsible for 15% of the total activity in S, and a tartrate-insensitive enzyme (E2) which accounted for 85% of the activity, was unstable in isotonic medium, had high affinity for ATP andp-NPP, and had low affinity for casein and β-GP. It is concluded that sucrose is not necessary for the isolation of total bone acid phosphatase activity, that hypertonic KCl does not negatively affect the properties of the enzymes isolated, and that E1 and E2 show different latencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409447
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of Fe2+ and ascorbic acid on acid phosphatases from rat bone (1982)
    Springer
    Calcified tissue international 34 (1982), S. 54-58 
    Details
    ISSN: 1432-0827
    Keywords: Acid phosphatases ; Acid phosphoprotein phosphatases ; Bone phosphatases ; Ferrous iron ; Ascorbic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effect of ferrous iron (Fe2+) and the reducing agents cysteine, dithiothreitol, and especially ascorbate on acid phosphatase activity was determined in vitro. Activity was extracted from homogenates of suckling rat tibia and femur with hypertonic KCl and Triton X-100, treated with protamine to remove interfering macromolecules, and dialyzed. Tartrate-sensitive and tartrate-resistant activity were separated and partially purified by cation exchange chromatography. At optimum dosage levels, Fe2+ was 100 times more potent than reducing agents in stimulating activity. Hypertonic KCl facilitated the effects of all agents. Fe2+ had no effect on tartrate-sensitive activity (E1), but specifically stimulated the hydrolysis ofβ-glycerophosphate, casein, and especially ATP andp-nitrophenylphosphate (p-NPP) by tartrate-resistant enzyme (E2); other divalent cations were either inhibitory or ineffective over a concentration range of 10−5 to 10−2M. Stimulation of E2 was detectable at 10−6M Fe2+, and the effect was synergistically increased by 10−3M ascorbate. E2 was stimulated maximally at 10−4M Fe2+ + 10−3M ascorbate, but at these concentrations their combined effects were additive. Both stimulated and unstimulated enzyme had identical pH optima (5.8), but the activity of the stimulated enzyme declined more slowly at higher pH values. Hypertonic KCl, Fe2+, or ascorbate reduced one-fourth to one-half the Km of activity withp-NPP substrate, which suggested a direct effect of these substances on E2. It is postulated the Fe2+ may interact with sulfhydryl groups in E2, and that reducing agents and KCl may facilitate this action by (a) maintaining the enzyme in an optimal conformational state, and (b) keeping iron reduced as Fe2+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411209
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  • 7
    Electronic Resource
    Electronic Resource
    Enzyme-linked immunosorbent assay for detection ofPseudomonas aeruginosa H (Flagellar) antigen (1988)
    Springer
    European journal of clinical microbiology & infectious diseases 7 (1988), S. 256-260 
    Details
    ISSN: 1435-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An enzyme-linked immunosorbent assay (ELISA) with goat anti-rabbit IgG conjugated to peroxidase was used to test for the two antigen types ofPseudomonas aeruginosa: b (homogeneous) and a (heterogeneous) which contains the common subantigen (a0) and combinations of subtypes (a, a2 a3 a4). Preparations of b-type flagellar antigen could be distinguished from a-type by using b-adsorbed antisera titers as reciprocals of endpoint dilutions exceeding one million. Extracts from nonflagellated bacteria or purified lipopolysaccharides from the same strain were used as controls, which showed only background activity. Unknown flagellar antigen was determined using both isolated antigen preparations and formalin-killed bacterial cells. The ELISA procedure proved much more sensitive than the slide agglutination procedure: whereas nine of 18 strains tested did not react in the slide agglutination procedure all 18 strains were definitively typed as a or b strains with the ELISA. The ELISA also revealed the presence of a dominant, cross-reacting epitope (a0) in the heterogeneous a-type flagella using either isolated antigen or intact cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01963097
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  • 8
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    When is a biogeochemical model too complex? Objective model reduction for North Atlantic time-series sites (2013)
    Elsevier
    In:  Progress in Oceanography, 116 . pp. 49-65.
    Details
    Publication Date: 2019-07-30
    Description: Highlights • We objectively identify and remove unconstrained parameters from a marine ecosystem model. • Optimal model complexity is identified using three model selection metrics. • As many as 14 of the model’s 30 parameters can be removed, with no significant reduction in model-data misfit. • Optimal model structures and parameters are different at two different North Atlantic locations. • The specialised structures and parameters at each site may be unsuitable for new environments The degree of structural complexity that should be incorporated in marine biogeochemical models is unclear. We know that the marine ecosystem is complex, and that its observed behaviour is attributable to the interaction of a large number of separate processes, but observations are scarce and often insufficient to constrain more than a small number of model parameters. This issue is addressed using a novel algorithm that systematically removes model processes that are not constrained by observations. The algorithm is applied to a one-dimensional, eight component ecosystem-biogeochemistry model at two North Atlantic time-series sites. Between 11 and 14 of the 30 model parameters can be removed at each site with no significant reduction in the model’s ability to fit upper ocean (0–200 m) biogeochemical tracer and productivity data. The statistically optimal model structures and parameters provide estimates of the most likely state variables and fluxes at each site. Differences in these estimates between the two sites indicate that the optimal models are specialised to both the physical environment and the assimilated observations. At each site the heavily reduced models may thus be suitable for diagnostic purposes but may not be sufficiently complex for more general applications, such as in global ocean general circulation models, or for predicting the response of marine systems to environmental change.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.pocean.2013.06.002
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Ocean fertilization: A potential means of geoengineering? (2008)
    Royal Society of London
    In:  Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 366 (1882). pp. 3919-3945.
    Details
    Publication Date: 2020-06-12
    Description: The oceans sequester carbon from the atmosphere partly as a result of biological productivity. Over much of the ocean surface, this productivity is limited by essential nutrients and we discuss whether it is likely that sequestration can be enhanced by supplying limiting nutrients. Various methods of supply have been suggested and we discuss the efficacy of each and the potential side effects that may develop as a result. Our conclusion is that these methods have the potential to enhance sequestration but that the current level of knowledge from the observations and modelling carried out to date does not provide a sound foundation on which to make clear predictions or recommendations. For ocean fertilization to become a viable option to sequester CO 2, we need more extensive and targeted fieldwork and better mathematical models of ocean biogeochemical processes. Models are needed both to interpret field observations and to make reliable predictions about the side effects of large-scale fertilization. They would also be an essential tool with which to verify that sequestration has effectively taken place. There is considerable urgency to address climate change mitigation and this demands that new fieldwork plans are developed rapidly. In contrast to previous experiments, these must focus on the specific objective which is to assess the possibilities of CO 2 sequestration through fertilization. © 2008 The Royal Society.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1098/rsta.2008.0139
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Does excess carbon affect respiration of the rotifer Brachionus calyciflorus Pallas? (2006)
    Wiley
    In:  Freshwater Biology, 51 . pp. 2320-2333.
    Details
    Publication Date: 2017-01-16
    Description: 1. Herbivorous zooplankton maintain a rather constant elemental composition in their body mass as compared with the variability commonly encountered in their food. Furthermore, their high phosphorus (P) and nitrogen (N) content means that they often face an excess of carbon (C) in their diet. Regulation of this surplus of energy may occur via modulation of assimilation efficiency, or postassimilation by increased respiration (CO2) and/or excretion dissolved organic carbon, DOC. Whereas several studies have examined the effect of elemental imbalance in the genus Daphnia, few have examined other zooplankton taxa. 2. We investigated whether the rotifer Brachionus calyciflorus uses increased respiration as a means of stoichiometrically regulating excess dietary C. Growth rate and respiration were measured under different food qualities (C : N and C : P ratios). 3. Both C : N and C : P ratios in food had strong effects on growth rate, demonstrating strong nutrient limitation of rotifer growth when nutrient elements were depleted in the diet and indicating the need for stoichiometric regulation of excess ingested C. 4. Respiration measurements, supported by a stoichiometric model, indicated that excess C was not released as CO2 in B. calyciflorus and that nutrient balance must therefore be maintained by other means such as excretion of DOC or egestion in faecal material.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1365-2427.2006.01653.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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