Search

Species‐specific uptake and allocation mechanisms for N are scarce, in particular when trees are cultivated in potted soil under more natural conditions than in hydroponic culture. The objective of this study was to compare specific N‐uptake rates for economically and ecologically important tree species in Central European forests: pine (Pinus sylvestris), spruce (Picea abies), oak (Quercus petraea), beech (Fagus sylvatica), lime (Tilia cordata), and ash (Fraxinus excelsior) when they grow in mineral soil from an old fallow site with a pH of 6. We used an 15N‐labeling method to measure tree seedling 15N uptake in potted soils (Humic Cambisol) when both N forms NH$ _4^+ $and NO$ _3^- $were simultaneously present in the soil solution for interspecies comparison and assessment of relationships between specific 15N‐uptake rates and amino acid–accumulation rates or relative growth rates (RGR). The results demonstrate that tree species varied significantly in their capacity to take up NH$ _4^+ $or NO$ _3^- $into roots, stems, or leaves, but indicate only marginal differences in their preference for NH$ _4^+ $or NO$ _3^- $when they grow in mineral soil. The ranking of specific 15N‐uptake rates for NH$ _4^+ $and NO$ _3^- $was oak < beech < spruce < pine < lime < ash. Fine roots of all species had the highest specific 15N‐uptake rates for both N forms, followed by total roots, leaves/needles, and stems. As regards tree seedling species, we found negative relationships between glutamine (Gln)‐accumulation rates in leaves/needles and total 15N‐uptake rates in fine roots. Noteworthy was the fact that, at high Gln‐accumulation rates, the N‐uptake system in fine roots of ash was probably lower under feedback inhibition by the amino acid.

No abstract.

Abstract: The present study was undertaken to examine possible aluminum (Al) accumulation in the brain of rats and to investigate whether subchronic exposure to the metal leads to behavioral and neurophysiological changes in both treated and control groups. Each of the groups consisted of 10 animals. Aluminum chloride (AlCl3) at a low (50 mg/kg/d) or high (200 mg/kg/d) dose was applied to male Wistar rats by gavage for 8 wk. Al-free water by gavage was given to the control group throughout the experiment. Behavioral effects were evaluated by open-field (OF) motor activity and by acoustic startle response (ASR). Electrophysiological examination was done by recording spontaneous activity and sensory-evoked potentials from the visual, somatosensory, as well as auditory cortex. The Al content of each whole brain was determined by electrothermal atomic absorption spectrophotometry. Subchronic Al exposure slightly caused some changes in the evoked potentials and electrocorticograms and in the OF and ASR performance, but these results were not statistically significant. The brain Al levels of the control and the low and high dose of Al-exposed groups were measured as 0.717±0.208 µg/g (wet weight), 0.963±0.491 µg/g (wet weight) and 1.816±1.157 µg/g (wet weight), respectively.

The degradation of unsaturated fatty acids by β-oxidation involves Δ3,Δ2-enoyl-CoA isomerases (enoyl-CoA isomerases) that catalyze 3-cis→ 2-transand 3-trans→ 2-transisomerizations of enoyl-CoAs and the 2,5 → 3,5 isomerization of dienoyl-CoAs. An analysis of rat liver enoyl-CoA isomerases revealed the presence of a monofunctional enoyl-CoA isomerase (ECI) in addition to mitochondrial enoyl-CoA isomerase (MECI) in mitochondria, whereas peroxisomes contain ECI and multifunctional enzyme 1 (MFE1). Thus ECI, which previously had been described as peroxisomal enoyl-CoA isomerase, was found to be present in both peroxisomes and mitochondria. This enzyme seems to be identical with mitochondrial long-chain enoyl-CoA isomerase (Kilponen, J.M., Palosaari, P.M., and Hiltunen, J.K. 1990. Biochem. J. 269, 223–226). All three hepatic enoyl-CoA isomerases have broad chain length specificities but are distinguishable by their preferences for one of the three isomerization reactions. MECI is most active in catalyzing the 3-cis→ 2-transisomerization; ECI has a preference for the 3-trans→ 2-transisomerization, and MFE1 is the optimal isomerase for the 2,5 → 3,5 isomerization. A functional characterization based on substrate specificities and total enoyl-CoA isomerase activities in rat liver leads to the conclusion that the 3-cis→ 2-transand 2,5 → 3,5 isomerizations in mitochondria are catalyzed overwhelmingly by MECI, whereas ECI contributes significantly to the 3-trans→ 2-transisomerization. In peroxisomes, ECI is predicted to be the dominant enzyme for the 3-cis→ 2-transand 3-trans→ 2-transisomerizations of long-chain intermediates, whereas MFE1 is the key enzyme in the 2,5 → 3,5 isomerization.

Field investigations with Scots pine trees (Pinus sylvestris L.) were performed in eastern Germany, where ambient SO2, NOxand O3concentrations differed significantly in 1992-99 at three sites, namely Neuglobsow (yearly mean SO2in 1992: 9 µg m-3), Taura (yearly mean SO2in 1992: 54 µg m-3and Rösa (yearly mean SO2in 1992: 73 µg m-3). To investigate the effects of SO2, NOxand O3on antioxidants (superoxide dismutase, ascorbic acid, glutathione, glutathione reductase, a-tocopherol) and pigments including chlorophyll fluorescence as well as visible damage symptoms in the form of needle yellowing and tip necroses, needles of the 1st and 2nd age class from young and mature trees were collected at the sites every October. Eight years after the start of the field study in 1992, the ambient SO2concentrations had decreased significantly at Neuglobsow (yearly mean SO2in 1999: 4 µg m-3), Taura (yearly mean SO2in 1999: 5 µg m-3) and Rösa (yearly mean SO2in 1999: 5 µg m-3). NOxand O3differed less at the three sites and showed no temporal variations. Whole needle glutathione continuously decreased, although concentrations were higher in needles of the 1 st and 2nd age class from the polluted sites Taura and Rösa than the unpolluted site Neuglobsow. The activities of glutathione reductase exhibited the same site-related differences and temporal variations and were correlated with concentrations of oxidized glutathione (GSSG). In contrast, the activities of the enzyme superoxide dismutase and the concentrations of whole needle ascorbic acid remained unchanged over the period. Only at the end of the investigation period did the concentrations of oxidized ascorbic acid (dehydroascorbate) increase in six-month-old needles at the polluted sites Taura and Rösa. Despite the clear decreases in SO2, the visible symptoms of needle tip necroses remained unchanged, especially at the polluted sites Taura and Rösa, although the needles contained higher pigment concentrations than needles from the unpolluted sites. The results of measurements with antioxidants as biomarkers for SO2-mediated stress in pine needles show that the adult Scots pine trees at the polluted sites suffered from greater oxidative stress than the needles from the less polluted site.

2,4-Dienoyl-CoA reductase is an enzyme that is required for the β-oxidation of unsaturated fatty acids with even-numbered double bonds. The 2,4-dienoyl-CoA reductase from Escherichia coli was studied to explore the catalytic and structural properties that distinguish this enzyme from the corresponding eukaryotic reductases. The E. coli reductase was found to contain 1 mol of flavin mononucleotide and 4 mol each of acid-labile iron and sulfur in addition to 1 mol of flavin adenine dinucleotide per mole of protein. Redox titrations revealed a requirement for 5 mol of electrons to completely reduce 1 mol of enzyme and provided evidence for the formation of a red semiquinone intermediate. The reductase caused a significant polarization of the substrate carbonyl group as indicated by an enzyme-induced red shift of 38 nm in the spectrum of 5-phenyl-2,4-pentadienoyl-CoA. However, suspected cis → trans isomerase and Δ3,Δ2-enoyl-CoA isomerase activities were not detected in this enzyme. It is concluded that the 2,4-dienoyl-CoA reductases from E. coli and eukaryotic organisms are structurally and mechanistically unrelated enzymes that catalyze the same type of reaction with similar efficiencies.

The alcohol dehydrogenase (ADH) activity of human short-chain L-3-hydroxyacyl-CoA dehydrogenase (SCHAD) has been characterized kinetically. The kcat of the purified enzyme was estimated to be 2.2 min-1, with apparent Km values of 280 mM and 22μM for 2-propanol and NAD+, respectively. The kcat of the ADH activity was three orders of magnitude less than the L-3-hydroxyacyl-CoA dehydrogenase activity but was comparable with that of the enzyme's hydroxysteroid dehydrogenase (HSD) activity for oxidizing 17β-oestradiol [He, Merz, Mehta, Schulz and Yang (1999) J. Biol. Chem. 274, 15014-15019]. However, the kcat values of intrinsic ADH and HSD activities of human SCHAD were found to be two orders of magnitude less than those reported for endoplasmic-reticulum-associated amyloid β-peptide-binding protein (ERAB) [Yan, Shi, Zhu, Fu, Zhu, Zhu, Gibson, Stern, Collison, Al-Mohanna et al. (1999) J. Biol. Chem. 274, 2145-2156]. Since human SCHAD and ERAB apparently possess identical amino acid sequences, their catalytic properties should be identical. The recombinant SCHAD has been confirmed to be the right gene product and not a mutant variant. Steady-state kinetic measurements and quantitative analyses reveal that assay conditions such as pH and concentrations of coenzyme and substrate do not account for the kinetic differences reported for ERAB and SCHAD. Rather problematic experimental procedures appear to be responsible for the unrealistically high catalytic rate constants of ERAB. Eliminating the confusion surrounding the catalytic properties of this important multifunctional enzyme paves the way for exploring its role(s) in the pathogenesis of Alzheimer's disease.

Here we report the preliminary characterization of Yor180Cp, a novel peroxisomal protein involved in fatty acid metabolism in the yeast Saccharomyces cerevisiae.A computer-based screen identified Yor180Cp as a putative peroxisomal protein, and Yor180Cp targeted GFP to peroxisomes in a PEX8-dependent manner. Yor180Cp was also detected by mass spectrometric analysis of an HPLC-separated extract of yeast peroxisomal matrix proteins. YOR180Cis upregulated during growth on oleic acid, and deletion of YOR180Cfrom the yeast genome resulted in a mild but significant growth defect on oleic acid, indicating a role for Yor180Cp in fatty acid metabolism. In addition, we observed that yor180cΔ cells fail to efficiently import the enzyme Δ3,Δ2-enoyl-CoA isomerase (Eci1p) to peroxisomes. This result suggested that Yor180Cp might associate with Eci1p in vivo,and a Yor180Cp–Eci1p interaction was detected using the yeast two-hybrid system. Potential roles for Yor180Cp in peroxisomal fatty acid metabolism are discussed.

Kurzfassung: An Sedimenten des Ruhrstausees Hengsen (Schwerte) wurden geochemische Untersuchungen des Porenwassers und der Festphase durchgefhrt. Durch die Bilanzierungen von Stoffflssen gelingt es, die bisher unterschtzte Rolle des Sediments als Kohlenstoffquelle fr die Aufrechterhaltung der Redoxreaktionen bei der Infiltration des Oberflchenwassers ins Grundwasser abzuschtzen. Die Ergebnisse belegen, da es mglich ist, den gesamten Kohlenstoffbedarf aus dem Seesediment zu decken. Damit erklrt sich die aktuelle Lage der Redoxreaktionsfronten, die sich, entgegen frherer Prognosen, innerhalb des letzten Jahrzehnts in Richtung der Infiltration verlagert haben, wodurch bereits am Stauseerand eine abgeschlossene Sulfatreduktion beobachtet wird. Die ermittelten Spurengehalte der Festphase spiegeln die zunehmende Verbesserung der Ruhrwasserqualitt wider. Vor allem die Elemente Kupfer, Arsen und Molybdn weisen auf einen wichtigen Leithorizont in, der auf den Bruch der fluaufwrts gelegenen Mhnentalsperre im Jahre 1943 zurckzufhren ist.

Here we describe the identification and characterization of a novel mouse gene, PDCR, that encodes a peroxisomal Δ2,Δ4-dienoyl-CoA reductase. The mouse PDCRcDNA contains an 892-base pair open reading frame and is predicted to encode a 292-amino acid protein with a deduced molecular mass of 31,298 Da that terminates in a consensus type-1 peroxisomal targeting signal. Purified recombinant PDCR protein was generated from Escherichia coliand catalyzed the NADPH-dependent reduction of Δ2-trans,Δ4-trans-decadienoyl-CoA with a specific activity of 20 units/mg. Enzymatic characterization followed by high pressure liquid chromatography analysis of the products revealed that PDCR converted Δ2-trans,Δ4-trans-decadienoyl-CoA to a Δ3-enoyl-CoA but not to a Δ2-enoyl-CoA. Kinetic analyses demonstrated that PDCR is active on a broad range of Δ2,Δ4-dienoyl-CoAs. Although the observed substrate preference was to Δ2-trans,Δ4-trans-decadienoyl-CoA, PDCR was also active on a C22substrate with multiple unsaturations, a result consistent with the role of peroxisomes in the oxidation of complex, very long chain, polyunsaturated fatty acids. The presence of a type-1 peroxisomal targeting signal Ala-Lys-Leu-COOH at the C terminus of PDCR suggested that this protein may be peroxisomal. We observed that tagged PDCR was efficiently transported to the peroxisome lumen in normal human fibroblasts but not in cells derived from a Zellweger syndrome patient with a specific defect in peroxisomal matrix protein import. We conclude that this protein resides within the peroxisome matrix and therefore represents the first mammalian peroxisomal Δ2,Δ4-dienoyl-CoA reductase to be characterized at the molecular level.

We report here the identification and characterization of human and mouse PECI, a novel gene that encodes a monofunctional peroxisomal Δ3,Δ2-enoyl-CoA isomerase. Human and mousePECIwere identified on the basis of their sequence similarity to Eci1p, a recently characterized peroxisomal Δ3,Δ2-enoyl-CoA isomerase from the yeastSaccharomyces cerevisiae. Cloning and sequencing of the human PECIcDNA revealed the presence of a 1077-base pair open reading frame predicted to encode a 359-amino acid protein with a mass of 39.6 kDa. The corresponding mouse cDNA contains a 1074-base pair open reading frame that encodes a 358-amino acid-long protein with a deduced mass of 39.4 kDa. Northern blot analysis demonstrated human PECImRNA is expressed in all tissues. A bacterially expressed form of human PECI catalyzed the isomerization of 3-cis-octenoyl-CoA to 2-trans-octenoyl-CoA with a specific activity of 27 units/mg of protein. The human and mouse PECI proteins contain type-1 peroxisomal targeting signals, and human PECI was localized to peroxisomes by both subcellular fractionation and immunofluorescence microscopy techniques. The potential roles for this monofunctional Δ3,Δ2-enoyl-CoA isomerase in peroxisomal metabolism are discussed.

The mitochondrial metabolism of unsaturated fatty acids with conjugated double bonds at odd-numbered positions,e.g.9-cis,11-trans-octadecadienoic acid, was investigated. These fatty acids are substrates of β-oxidation in isolated rat liver mitochondria and hence are expected to yield 5,7-dienoyl-CoA intermediates. 5,7-Decadienoyl-CoA was used to study the degradation of these intermediates. After introduction of a 2-trans-double bond by acyl-CoA dehydrogenase or acyl-CoA oxidase, the resultant 2,5,7-decatrienoyl-CoA can either continue its pass through the β-oxidation cycle or be converted by Δ3,Δ2-enoyl-CoA isomerase to 3,5,7-decatrienoyl-CoA. The latter compound was isomerized by a novel enzyme, named Δ3,5,7,Δ2,4,6-trienoyl-CoA isomerase, to 2,4,6-decatrienoyl-CoA, which is a substrate of 2,4-dienoyl-CoA reductase (Wang, H.-Y. and Schulz, H. (1989)Biochem. J. 264, 47–52) and hence can be completely degraded via β-oxidation. Δ3,5,7,Δ2,4,6-Trienoyl-CoA isomerase was purified from pig heart to apparent homogeneity and found to be a component enzyme of Δ3,5,Δ2,4-dienoyl-CoA isomerase. Although the direct β-oxidation of 2,5,7-decatrienoyl-CoA seems to be the major pathway, the degradation via 2,4,6-trienoyl-CoA makes a significant contribution to the total β-oxidation of this intermediate.

Human brain short chainl-3-hydroxyacyl-CoA dehydrogenase (SCHAD) was found to catalyze the oxidation of 17β-estradiol and dihydroandrosterone as well as alcohols. Mitochondria have been demonstrated to be the proper location of this NAD+-dependent dehydrogenase in cells, although its primary structure is identical to an amyloid β-peptide binding protein reportedly associated with the endoplasmic reticulum (ERAB). This fatty acid β-oxidation enzyme was identified as a novel 17β-hydroxysteroid dehydrogenase responsible for the inactivation of sex steroid hormones. The catalytic rate constant of the purified enzyme was estimated to be 0.66 min−1with apparent Kmvalues of 43 and 50 μmfor 17β-estradiol and NAD+, respectively. The catalytic efficiency of this enzyme for the oxidation of 17β-estradiol was comparable with that of peroxisomal 17β-hydroxysteroid dehydrogenase type 4. As a result, the human SCHAD gene product, a single-domain multifunctional enzyme, appears to function in two different pathways of lipid metabolism. Because the catalytic functions of human brain short chain l-3-hydroxyacyl-CoA dehydrogenase could weaken the protective effects of estrogen and generate aldehydes in neurons, it is proposed that a high concentration of this enzyme in brain is a potential risk factor for Alzheimer's disease.

EHpH diagrams have been calculated using the PHREEQC programme in order to establish the predominance fields of Mn, Fe, Co, Ni, Cu and As in bottom waters from the Angola Basin. Predominance fields are presented separately for both aquatic species and solid mineral phases in order to simplify interpretation of the data. The diagrams show significant differences from standard EHpH diagrams for these elements calculated for freshwater at 25 °C and 1 bar which assume an element concentration of 10-6M. In particular, our diagrams show that Mn2+and NiCO30are the predominant aquatic species for Mn and Ni in bottom seawater and FeOOH, Fe2O3, Fe3O4, CoFe2O4, CuFe2O4, CuFeO2, and Ba3(AsO4)2the predominant solid phases for Fe, Co, Cu and As, respectively. Mn and Ni are therefore undersaturated and Fe, Co, Cu and As supersaturated in bottom seawater from the Angola Basin. Neither rhodochrosite (MnCO3) nor siderite (FeCO3) can form in this marine environment in equilibrium with seawater. A mixed Mn-Ca carbonate is therefore formed within the pore waters of reducing sediments. The high Ni/Cu ratios in cobalt-rich manganese crusts formed adjacent to the oxygen minimum zone may be explained by the change from Cu2+to CuCl32-as the dominant aquatic species of Cu in seawater at an EHof +0.48 V.

Wie geochemisch-thermodynamische Modellierungen gezeigt haben, können während des Betriebs einer geothermischen Heizanlage durch Druck- und Temperaturveränderungen Baryt, Anhydrit/Gips oder Cölestin ausfallen. Das Fällungsverhalten der Erdalkalisulfate wurde unter In-situ-Bedingungen (Druck, Temperatur, Salinität 216 g/l) in einem Durchströmungsversuch bestimmt. Es wird eine Durchströmungsanlage vorgestellt, die Drucke bis zu 250 bar und hohe Temperaturen bei der Durchströmung eines Sandsteinkerns zuläßt. Ergänzende Fällungsexperimente bestätigen eine zu erwartende Reaktion zweiter Ordnung bei der Kristallisation von Baryt mit einer mittleren Geschwindigkeitskonstanten von 2,5 · 10−4l · mg−1· h−1. Die real lösliche Menge Baryt (2,5 mg/l Ba und 450 mg/ISO4) ist höher als das thermodynamische Gleichgewicht vorhersagt. Cölestin und Anhydrit oder Gipsausfällungen konnten nicht nachgewiesen werden. Bei der Durchströmung des Sandsteinkerns unter In-situ-Bedingungen findet keine Ausfällung von Baryt, Anhydrit/Gips oder Cölestin statt. Obwohl Kristallisationskeime im Sandstein vorhanden sind, erfolgt keine Fällung aus den metastabilen Lösungen. On the basis of thermodynamical modelling it was proves that pressure and temperature variations may induce precipitation of barite, anhydrite/gypsum and celestite in geothermyl power plants. The precipitation dynamics of earth-alkaline sulfates has been investigated in a column experiment simulating in-situ conditions for pressure, temperature, and salinity (216 g/l). In this paper we describe the experimental setup for simulating pressures up to 250 bar and high temperatures in a sandstone core. Additional precipitation experiments confirmed the expected second-orer reaction for the precipitation of barite at a medium rate of 2.5 · 10−4l · mg−1· h−1. The experiments show that the solubility of barite (2.5 mg/l Ba and 450 mg/ISO4) is higher than the model forecast. Precipitation of celestite and anhydrite/gypsum was not observed. During the column experiments with a sandstone core under in-situ conditions no precipitation of barite, anhydrite/gypsum and celestite took place.

Fluvioglacial sanders in northern Germany with a certain calcite content have been subject to weathering and decalcification by percolating seepage water since their deposition. A model conception programmed in FORTRAN is used to model the longtime process of decalcification from the surface. The model takes into account as input data the original calcite content of the sand, cation composition at the exchange sites, selectivity coefficients describing cation exchange equilibria, partial pressure of CO2 in the unsaturated zone and chemical composition of the precipitation. The finite element model uses data for seepage velocity and dispersion, which were known for the area. For modelling calcite dissolution kinetics under natural groundwater conditions a conception recently published by BAUMANN et al. (1985) is used and a new method with the determination of a saturation curve is proposed.

The subcellular location of 3-hydroxyacyl-CoA epimerase (EC 5.1.2.3) was studied by differential centrifugation and Percoll density gradient centrifugation of a rat liver homogenate. The enzyme was found to be associated with peroxisomes but not with mitochondria. This observation proves that 3-hydroxy-acyl-CoA epimerase does not function in mitochondrial β-oxidation ofpolyunsaturated fatty acids which are degraded by a modified pathway.

Di- and polyamines have been determined in the femtomol range by liquid chromatography on a reversed-phase C8 column with a linear gradient of acetate buffer/acetonitrile as mobile phase and fluorimetric detection at 265/310 nm after simple derivatization with 9-fluorenylmethyl chloroformate (FMOC) within 3 min at pH 7.8 in presence of aspartic acid to remove excess reagent. The FMOC—polyamine-derivatives have been stable in a methanol—water-solution for at least 10 h. The method can be directly applied to crude plant extracts, and it is not interfered by carbohydrates and phenolics.

A novel l-3-hydroxyacyl-CoA dehydrogenase from human brain has been cloned, expressed, purified, and characterized. This enzyme is a homotetramer with a molecular mass of 108 kDa. Its subunit consists of 261 amino acid residues and has structural features characteristic of short chain dehydrogenases. It was found that the amino acid sequence of this human brain enzyme is identical to that of an endoplasmic reticulum amyloid β-peptide-binding protein (ERAB), which mediates neurotoxicity in Alzheimer's disease (Yan, S. D., Fu, J., Soto, C., Chen, X., Zhu, H., Al-Mohanna, F., Collison, K., Zhu, A., Stern, E., Saido, T., Tohyama, M., Ogawa, S., Roher, A., and Stern, D. (1997) Nature389, 689–695). The purification of human brain short chainl-3-hydroxyacyl-CoA dehydrogenase made it possible to characterize the structural and catalytic properties of ERAB. This NAD+-dependent dehydrogenase catalyzes the reversible oxidation of l-3-hydroxyacyl-CoAs to form 3-ketoacyl-CoAs, but it does not act on the d-isomers. The catalytic rate constant of the purified enzyme was estimated to be 37 s−1with apparent Kmvalues of 89 and 20 μmfor acetoacetyl-CoA and NADH, respectively. The activity ratio of this enzyme for substrates with chain lengths of C4, C8, and C16was ∼1:2:2. The human short chain l-3-hydroxyacyl-CoA dehydrogenase gene is organized into six exons and five introns and maps to chromosome Xp11.2. The amino-terminal NAD-binding region of the dehydrogenase is encoded by the first three exons, whereas the other exons code for the carboxyl-terminal substrate-binding region harboring putative catalytic residues. The results of this study lead to the conclusion that ERAB involved in neuronal dysfunction is encoded by the human short chainl-3-hydroxyacyl-CoA dehydrogenase gene.

Zusammenfassung: Die Forstwirtschaft in Mitteleuropa hat neben der Produktion des Rohstoffes Holz groe—wenn auch nicht immer optimale—Leistungen fr die Gesunderhaltung unseres Lebensraummen erbracht. Dennoch finden heute besonders diejenigen Stimmen das Ohr der ffentlichkeit, welche den bisherigen Beitrag der Forstwirtschaft fr die Wohlfahrtswirkungen unserer Landschaft schmlern und den Einflu\ der einheimischen Holzproduktion auf unsere Volkswirtschaft weitgehend verkennen. Im Rahmen eines Kolloquiums, in dem viele Meinungen gehrt wurden, erschien es deshalb angemessen, die Rolle des Rohstoffes Holz fr die Welt und die Bedeutung der einheimischen Holzproduktion fr Gegenwart und Zukunft einmal mehr und pointiert herauszustellen. Zusammenfassend ergibt sich daraus die Notwendigkeit, alle mglichen Wege zu suchen, die eine vielseitige, ausreichend hohe Holzproduktion und eine gesunde, in den volkswirtschaftlichen Proze vielseitig verzahnte Holzindustrie mit den Erfordernissen der Erhaltung unseres Lebensraumes in Einklang bringen. Dabei sollte man davon ausgehen, da zwischen der Holzproduktion und den Wohlfahrtswirkungen der Wlder auch in dicht besiedelten Gebieten der Welt zunchst kein beweisbarer, grundstzlicher Widerspruch bestcht, vor allem dann nicht, wenn man ihn an allen anderen Wirtschaftszweigen mit.

The subcellular location of cardiac carnitine acetyltransferase (CAT) was investigated by measuring the release of carnitine acetyltransferase and of marker enzymes from isolated rat myocytes permeabilized with digitonin. Additionally, the carnitine acetyltransferase activity exposed to the cytosolic compartment was quantified. The results indicate that soluble acetyl transferase is not present in the cytosol, and that only 5% of the cellular carnitine acetyltransferase activity is positioned to catalyse the formation of cytosolic acetyl coenzyme A. This situation makes it unlikely that the energy-linked regulation of cardiac fatty acid oxidation proceeds by mechanisms which require the conversion of acetylcarnitine to acetyl coenzyme A in the cytosol.

The often restricted amount of data obtained in the field and their spatial distribution are major problems in the interpretation of data for possibly underlying local structures. A procedure for regionalisation on the basis of very low data density is presented for a marine geochemical example. The aim was to evaluate a regional distribution pattern for diffusive benthic phosphate flux rates in the eastern South Atlantic. With the help of geostatistic methods (variogram) it could be shown that the investigated locations correlate spatially and structurely up to a distance of 7° (ca. 800 km) regarding phosphate release and fixation. On the basis of these results a regionalisation was carried out using the krigeage-method. The regional structures of this distribution pattern showed the expected relationship between the nutrient flux rates and the organic matter primarily produced in the photic zone. In case the used procedure was not applicable due to regional very different data density an interpretive fit of the computerised regionalisation was carried out with correlative references to rate determining factors such as primary production, water depth and current patterns. A map of regional distribution patterns was produced showing good agreement with recent oceanographical and sedimentological conditions.

In the sediment column ferric oxides and hydroxides like oxygen, nitrate and manganese oxides and hydroxides act as acceptors for electrons and protons during the microbial catalysed decomposition of organic matter and the oxidation of reduced inorganic species. Laboratory studies revealed that the microbial ferric reduction depends on the size of mineral surface (e. g. goethite, magnetite and hematite). Calculating a balance of electrons transferred during the redox reactions showed an excess of electrons released during oxidation. Hence ferric reduction seems to be coupled with fermentative processes, which took place simultaneously. It could be proved that ferric reduction may take place during sulfate reduction and methane fermentation. The mineralisation of organic matter was mainly caused by sulfate reduction, while the available ferric oxides and hydroxides where only partially reduced. As authigenic mineral formations ferric phosphates, ferric sulfides, ferric and manganese carbonates as well as calcium and magnesium carbonates could be identified.

Zusammenfassung Geochemische Verwitterungsvorgänge vollziehen sich im wesentlichen in der wasserungesättigten Zone und im erdoberflächennahen Grundwasser. In diesem Bereich bestimmen klimatische, biologische, biochemische und geochemische Vorgänge die Zersetzung des Ausgangsgesteins. Als Transportmittel für gelöste und flüchtige Umsetzungsprodukte wirken Sickerwasser, Grundwasser und Grundluft.

The change of peroxidase activity in the leafs of all studied bottom plants enables a significant quantitative indication of simulated disturbance. The indication proved is dependent on concentration and time. Deschampsia flexuosand Calamagrostis villosashow an indication for one vegetation period (short time intensity), Vaccinium myrtillusshows an indication for at least two vegetation periods (long time intensity). The dosis-effect-curves of Calamagrostis villosaand Deschampsia flexuosaare sigmoid and the dependence of concentration consists only in a little rango of disturbance

A comparative analysis of forest precipitation depositions was performed using pine tree barks as biomonitoring tools and throughfall collectors in pine stands at various test sites in eastern Germany. For the elements sulfate sulfur (SO4-S), nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), calcium (Ca), and iron (Fe), regression equations with r2values between 0.81 and 0.96 were derived, enabling yearly conversion of bark loads to throughfall rates (TFRs) in pine stands (g*m-2*year-1).Applying this method to a network of 53 measuring sites in Dübener Heide nature park, north of Leipzig, lead to discovering spatial patterns of TFRs for SO4-S, NO3-N, and NH4-N in 1994. Differences between the TFRs of sulfur and nitrogen were traced back to different emission sources and the temporal trend related to major infrastructural changes in that region since 1990. Results suggest that the bark method will be particularly suited to identifying forest precipitation depositions of ecotoxicologically relevant airborne pollutants on regional scales.

The subcellular location of 3‐hydroxyacyl‐CoA epimerase (EC 5.1.2.3) was studied by differential centrifugation and Percoll density gradient centrifugation of a rat liver homogenate. The enzyme was found to be associated with peroxisomes but not with mitochondria. This observation proves that 3‐hydroxy‐acyl‐CoA epimerase does not function in mitochondrial β‐oxidation ofpolyunsaturated fatty acids which are degraded by a modified pathway.

A long chain enoyl-CoA hydratase, which in addition to crotonase is present in pig heart muscle, has been isolated and partially purified. This enzyme appears to be located in the mitochondria and is tighter membrane-bound than crotonase. It catalyzes the hydration of medium and long chain trans-Δ2,3-enoyl-CoA substrates to their corresponding l-3-hydroxy derivatives but it is nearly inactive toward crotonyl-CoA. The highest Vmaxwas observed with Δ2,3-octenoyl-CoA, while longer chain substrates gave progressively decreasing values. However, the same Kmvalue of 24 µmwas obtained for all even numbered Δ2,3-enoic acid derivatives containing 8 to 14 carbons. The pH optimum of this enzyme was found to be 8.5.

A new class of borneol esters that might be considered as biological analogs of paclitaxel regarding their action on microtubules has been found. By structure-activity optimizations, compounds stabilizing microtubules much better than paclitaxel while showing a remarkably reduced cytotoxic activity were obtained. This dissoziation will open completely new therapeutic areas.

The accumulation of β-oxidation intermediates was studied by incubating normal and β-oxidation enzyme-deficient human fibroblasts with [2H4]linoleate and L-carnitine and analyzing the resultant acylcarnitines by tandem mass spectrometry. Labeled decenoyl-, octanoyl-, hexanoyl-, and butyrylcarnitines were the only intermediates observed with normal cells. Intermediates of longer chain length, corresponding to substrates for the β-oxidation enzymes associated with the inner mitochondrial membrane, were not observed unless a cell line was deficient in one of these enzymes, such as very-long-chain acyl-CoA dehydrogenase, long-chain 3-hydroxyacyl-CoA dehydrogenase, or electron transfer flavoprotein dehydrogenase. Matrix enzyme deficiencies, such as medium- and short-chain acyl-CoA dehydrogenases, were characterized by elevated concentrations of intermediates corresponding to their respective substrates (octanoyl- and decenoylcarnitines in medium-chain acyl-CoA dehydrogenase deficiency and butyrylcarnitine in short-chain acyl-CoA dehydrogenase deficiency). These observations agree with the notion of intermediate channeling due to the organization of β-oxidation enzymes in complexes. The only exception is the incomplete channeling from thiolase to acyl-CoA dehydrogenase in the matrix. This situation may be a consequence of only one 3-ketoacyl-CoA thiolase being unable to interact with the several acyl-CoA dehydrogenases in the matrix.

From a sedimentcore of Kiel Bight (Western Baltic) depth profiles as well of porewater as of solid phase contents were measured by groups of students. Those existing for porewater are the following: alkalinity, pH, Eh, O2, H2S, NH4, NO3, PO4, Cl, SO4, F, Fe, Ca, Mg, Mn, Ba, Sr, and Si. Solidphase was analysed on Fe, Al, Ca, Mg, Ba, Sr, Mn, Cu, Ni, Pb, and Zn. This work treats data of heavy metals, while porewater profiles are consulted for correct interpretation. Concentracion profiles of some heavy metals in the solid-phase (Cu, Pb, Zn) show a significant anthropogenic enrichment in the upper part of the core compared to the preindustrially deposited background. However, influence of early diagenetic processes (especially for Mn and Ni) and in the case of the Manganese concentration profile more anoxic bottomwater conditions are also relevant.

This paper presents the computer model CoTReM (Column Transport and Reaction Model) to simulate one-dimensional transport of solutes, sorption, redox reactions, and thermodynamic equilibrium processes in porous media. The diffusive transport of non-reacting solutes is well known and can easily be simulated by numerical procedures. The present model uses the Crank-Nicolson scheme for the solution of the hydrodynamical equation. Early diagenetic redox reactions are calculated with the modul REDOX, which is based on a set of redox half-reactions. Thermodynamic equilibrium is calculated by the modul PHREEQC. The model is applied to porewater data of marine sediments of the slope off Namibia. The simulation results explain in a step by step mode the different tasks of the single moduls.

The transport behavior of trace elements in natural environments is strongly affected by the redox-conditions of the system. Groundwater samples from a bank filtration site reveal the dissolution of As and Mo as well as the loss of mobility of U when the redox-state of the system changes from oxic to anoxic conditions. In order to examine the processes these observations are based on, we decided to carry out anoxic column experiments with materials from the bank filtration site. The input of acetate as an electron donor leads to reducing conditions up to sulfate reduction within a few weeks. The electron-balance for the sum reactions could be calculated with success. The overall results give evidence for a simultaneous occurrence of all microbial mediated redox-reactions within a few centimeters. The experiments show the coupling between biotic and abiotic redox-reactions. Especially the Mn(III/IV)-contents of the studied sediments have a great influence on the behavior of the system. The mobility of As, Mo and U reflects these affects. Finally it can be stated that not the redox-reactions of the trace elements themselves, but the redoxdepending reactions of the potential scavenger-phases, Fe and Mn, are responsible for the mobility.

A reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reductase with the ability to reduce diacetyl has been isolated from Escherichia coliand has been purified 800-fold to near homogeneity. The product of the reduction of diacetyl was shown to be acetoin. The enzyme proved to catalyze the oxidation of NADPH in the presence of both uncharged α- and β-dicarbonyl compounds. Even monocarbonyl compounds showed slight activity with the enzyme. On the basis of its substrate specificity, it is suggested that the enzyme functions as a diacetyl reductase. In contrast to other diacetyl reductases, the one reported here is specific for NADPH and does not possess acetoin reductase activity. The pH optimum of this enzyme was found to be between 6 and 7. The maximal velocity for the NADPH-dependent reduction of diacetyl was determined to be 9.5 μmol per min per mg of protein and the Kmvalues for diacetyl and NADPH were found to be 4.44 mM and 0.02 mM, respectively. The molecular weight was estimated by gel filtration on Sephadex G-100 to be approximately 10,000.

Zusammenfassung: Methodische Untersuchungen ber die Mglichkeit der Drehwnchsfeststellung an verschiedenen Stanmeseiten und in verschiedenen Alterszonen an Erche und Buche fhrten zu den folgenden Ergebnissen:

Summary: The influence of the extraordinary climate in 1959 on the width of annual rings, distribution of cell types, fibre length and width of vessels was investigated on samples taken from oak, beech, spruce and pine. The origin of the specimens, the preparation and the measuring methods are described in detail. The fibres were prepared with the help of so-called Tesa-film. For evaluating the width of the vessels, a Zeiss particle-size analysator TGZ3 was used for the first time. The extremely warm and dry climate caused some structural changes of the following nature. The widths of annual rings were evidently smaller during the vegetation period of 1959, as became visible in the respective diagrams. In the cross-section of oak, a remarkably higher percentage of springwood- and a lower one of summerwood-vessels and fibres could be observed. Beech, on the other hand, showed no differences in this respect. All the species investigated had shorter fibres than in former years. In beechwood the vessel of the 1959 annual ring differed from others, particularly in the width of summerwood-vessels. In oakwood, the width of the vessels was affected in all zones of the ring. Springwood showed a smaller percentage of mediumsized vessels, and in summerwood a clear contraction of the vessels, in the middle as well as towards the end of the annual ring, could be stated.