Scale sensitivity of synthetic long‐term vegetation time series derived through overlay of short‐term field records

Questions: Is change in cover of dominant species driving the velocity of succession or is it species turnover (1)? Is the length of the time‐step chosen in sampling affecting our recognition of the long‐term rate of change (2)1 Location: 74 permanent plots located in the Swiss National Park, SE Switzerland, ca. 1900 m a.s.l. Methods: We superimpose several time‐series from permanent plots to one single series solely based on compositional dissimilarity. As shown earlier (Wildi & Schütz 2000) this results in a synthetic series covering about 400 to 650 yr length. Continuous power transformation of cover‐percentage scores is used to test if the dominance or the presence‐absence of species is governing secondary succession from pasture to forest. The effect of time step length is tested by sub‐samples of the time series. Results: Altering the weight of presence‐absence versus dominance of species affects the emerging time frame, while altering time step length is uncritical. Where species turnover is fast, different performance scales yield similar results. When cover change in dominant species prevails, the solutions vary considerably. Ordinations reveal that the synthetic time series seek for shortest paths of the temporal pattern whereas in the real system longer lasting alternatives exist. Conclusions: Superimposing time series differs from the classical space‐for‐time substitution approach. It is a computation‐based method to investigate temporal patterns of hundreds of years fitting between direct monitoring (usually limited to decades) and the analysis of proxy‐data (for time spans of thousands of years and more).     

Food utilization by insects: Interpretation of observed differences between dry weight and energy efficiencies

Over 80% of the values of approximate digestibility (AD), efficiency of conversion of assimilated food to biomass (ECD) and efficiency of conversion of ingested food (ECI) calculated using energy terms are greater than the corresponding dry weight (DW) values, based on data for over 65 species (38 studies; number of comparative values: AD=139, ECD=128 and ECI=169). Largest positive differences (energy > DW values) are 30 (AD, ECD) and 24 (ECI) percentage points and largest negative differences (energy < DW values) are 9 (AD), 11 (ECD) and 8 (ECI) percentage points. These differences generally are least for ECI (71% of the differences fall between 0 and +5 percentage points), and AD (68%), followed by ECD (only 47% fall between 0 and +5), and they may vary with temperature, food and other factors. The differences tend to increase (esp. for ECD and ECI) when comparing later with earlier instars. Energy > DW efficiency values are commonly expected for AD because of the generally greater energy content of food than feces, and for ECD and ECI because of the generally greater energy content of insect biomass than ingested and assimilated food. Deviations from predicted differences in surveyed literature data are discussed in terms of possible methodological sources of error.

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Résumé Plus de 80% des valeurs de la digestibilité approchée (AD), de l'efficacité de la conversion de la nourriture assimilée en biomasse (ECD) et de l'efficacité de la conversion de l'aliment ingéré (ECI), calculées en termes énergétiques, et obtenus à partir de données sur 65 espèces, sont supérieures aux valeurs des poids secs correspondants (DW): 38 études; valeurs comparatives: AD=139, ECD=128, ECI=169. Les plus importantes différences positive (énergie>valuers DW) sont de 30 (AD, ECD) et de 24 (ECI) centièmes (les différences négatives les plus fortes = 9 (AD), 11 (ECD) et 8 (ECI); ces différences sont moindres pour ECI (71% des différences tombent à 0 et +5 centièmes), et AD (68%), suivi de ECD (seulement 47% tombent entre 0 et +5). Ces différences peuvent varier avec la température, l'alimentation et d'autres facteurs; les différences tendent à croître (particulièrement pour ECD et ECI) quant on les compare plus tard avec des stades plus précoces. Energie > aux valeurs d'efficacité DW sont généralement attendues pour AD par suite du contenu énergétique supérieur de l'aliment à celui des excréments, et pour ECD et ECI par suite du contenu énergétique généralement plus élevé pour la biomasse de l'insecte que pour l'aliment ingéré et assimilé. Les écarts par rapport aux différences prédites dans les données de la littérature examinée sont analysées en considérant les sources possibles d'erreurs méthodologiques.

     

Alcohol dehydrogenase isozymes in the mouse: Genetic regulation, allelic variation among inbred strains and sex differences of liver and kidney A2 isozyme activity

Genetic analysis of a proposed cis-acting temporal locus ( Adh-3t ), which regulates alcohol dehydrogenase C₂ (ADH-C₂) acitivity in mouse epididymis extracts, among F₁ (ddN × BALB/c) × ddN male backcross progeny provided evidence for genetic distinctness between the structural ( Adh-3 ) and temporal ( Adh-3t ) loci on chromosome 3. Genetic analysis also confirmed the close, linkage of Adh-1 (encoding liver and kidney ADH-A₂) and Adh-3 (encoding stomach ADH-C₂) to within 0.3 centimorgans on the mouse genome. Evidence is presented for a proposed closely linked cis-acting temporal locus (designated Adh-1t ) for the A₂ isozyme (encoded by Adh-1 ) controlling the activity of this enzyme in mouse kidney extracts, but having no apparent affect on liver and intestine ADH-A₂ activities. An extensive survey of the distribution of Adh-1, Adh-3 and Adh-3t alleles among 65 strains of mice is reported — with the exception of two Japanese strains (ddN and KF), linkage disequilibrium between Adh-3 and Adh-3t was observed. Sex differences in mouse liver and kidney ADH-A₂ activities were observed, with male/female ratios of approximately 0.6 and 3 respectively for these tissue extracts.     

Conditional Maximum Likelihood Estimation Following a Group Sequential Test

We consider estimation after a group sequential test. An estimator that is unbiased or has small bias may have substantial conditional bias (Troendle and Yu, 1999, Coburger and Wassmer, 2001). In this paper we derive the conditional maximum likelihood estimators of both the primary parameter and a secondary parameter, and investigate their properties within a conditional inference framework. The method applies to both the usual and adaptive group sequential test designs. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

VARIATION IN ALCOHOL DEHYDROGENASE ACTIVITY AND FLOOD TOLERANCE IN WHITE CLOVER,TRIFOLIUM REPENS

Flooding results in induction of anaerobic metabolism in many higher plants. As an important component of anaerobic energy production, alcohol dehydrogenase (ADH) activity increases markedly in response to flooding in white clover, Trifolium repens. Significant inter-individual variation in flood-induced ADH activity exists in natural populations of T. repens. The genetic basis of this variation was analyzed by offspring-midparent regression of data from 75 greenhouse reared families; the estimated heritability of flood-induced ADH activity was 0.55 (±0.13). Genetic variation in flood-induced ADH activity has pronounced effects on physiological response and flood tolerance in this species. ADH activity is positively correlated with the rate of ethanol production, indicating that observed in vitro activity differences are manifested in in vivo physiological function. T. repens plants with higher ADH activities during flooding have greater flood tolerance (measured as growth rate when flooded/unflooded growth rate). Variation in ADH activity during flooding accounts for more than 79% of the variance in flood tolerance. On the basis of a limited field survey of populations occupying three sites differing in exposure to flooding conditions, individuals from site C, the most frequently flooded site, expressed significantly higher average ADH activity when flooded than individuals from site A, a site with no history of flooding. Since ADH activity levels are not correlated with electrophoretic mobility variation in T. repens, this work supports previous suggestions that regulatory variation in enzyme activity may play a central role in biochemical adaptations to environmental stress.     

Lignin degradeation by white rot fungi

Abstract. The wood-degrading white-rot fungus Phanerochaete chrysosporium , has been the subject of intensive research in recent years and, based upon isolation of the extracellular enzyme ligninase, major advances have now been made toward elucidating the mechanism by which this fungus degrades lignin. From these developments, a model emerges which could explain the process by which wood-degrading fungi in general, attack lignin.     

NAD(P)H oxidase and peroxidase activities in purified plasma membranes from cauliflower inflorescences

An NAD(P)H oxidase activity stimulated by phenolic compounds has been investigated in purified plasma membranes (pm) and in an intracellular membrane (icm) fraction depleted in plasma membranes, both obtained from a microsomal fraction from cauliflower inflorescences ( Brassica oleracea L.). The phenolic compounds salicylhydroxamic acid (SHAM), ferulic acid, coniferyl alcohol, n -propyl gallate, naringenin, kaempferol and caffeic acid all strongly stimulated the activity. Peroxidase (EC 1.11.1.7), or a peroxidase-like enzyme, was responsible for the NAD(P)H oxidase activity, which proceeded through a free-radical chain reaction and was inhibited by catalase (EC 1.11.1.6), superoxide dismutase (EC 1.15.1.1) and KCN. Most of the total activity was soluble; however, the membrane-bound activity was highly enriched in the pm compared to the icm. The catalase activity was 6 times higher in the icm-fraction than in the pm-fraction, but this was not the reason for the much lower phenol-stimulated NADH oxidase activity in the icm. Peroxidase activity measured with o -dianisidine and H₂O₂ had about the same specific activities in the pm-and icm-fractions.
Neither the phenol-stimulated NADH oxidase nor the peroxidase activity could be washed away from the pm even by 0.7 M NaCl, indicating that these activities are truly membrane-bound. SHAM as well as the other phenolic compounds capable of stimulating the NADH oxidase reaction were potent inhibitors of blue light-induced cytochrome b -reduction in the pm fraction.     

Anaerobic metabolism enzymes as markers of flooding stress in maize seeds

Maize (Zea mays L.) seeds differ in their relative tolerance to the anaerobic environment caused by flooding. Seed tolerance to flooding stress depends on cellular and metabolic processes since gross anatomical responses have not developed at the pre-emergence stage. The study reported here characterizes the activities of four anaerobic respiratory enzymes: pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), and malic enzyme (ME) in the flood-tolerant A632 and floodsusceptible Mo 17 inbred maize seeds during flooding at 10 and 25°C. Each inbred consisted of two seed lots possessing 95% and 75% germination levels. Flooding increased the activities of all four enzymes. However, no consistent correlation between anaerobic enzyme activity and flood tolerance was observed across genotype, seed quality and flooding temperature. The results indicate that it may not be feasible to use whole-seed anaerobic enzyme activities to predict maize seed performance under flooding stress. Contribution from the Soil Drainage Research Unit, USDA-ARS, Columbus, OH, in cooperation with the Ohio Agricultural Research and Development Center, The Ohio State University. OARDC Journal Article No. 66–86.     

The genetic relationships between the kringle domains of human plasminogen,prothrombin, tissue plasminogen activator,urokinase, and coagulation factor XII

Summary A computer-based statistical evaluation of the optimal alignments of the kringle domains of human plasminogen, human prothrombin, human tissue plasminogen activator, human urokinase, and human coagulation Factor XIIa, as well as the putative kringle of human haptoglobin, has been performed. A variety of different alignments has been examined and scores calculated in terms of the number of standard deviations (SD) of a given match from randomness. With the exception of human haptoglobin, it was found that very high alignment scores (8.9–23.0 SD from randomness) were obtained between each of the kringles, with the kringle 1 and kringle 5 regions of human plasminogen displaying the highest similarity, and the S kringle of human prothrombin and the human Factor XII kringle showing the least similarity. The relationships obtained were employed to construct an evolutionary tree for the kringles. The predicted alignments have also allowed nucleotide mutations in these regions to be evaluated more accurately. For those regions for which nucleotide sequences are known, we have employed the maximal alignments from the protein sequences to assess nucleotide sequence similarities. It was found that a range of approximately 40–55% of the nucleotide bases were placed at identical positions in the kringles, with the highest number found in the alignment of the two kringles of human tissue plasminogen activator and the lowest number in the alignment of the S kringle of prothrombin with the second kringle of tissue plasminogen activator. From both protein and nucleotide alignments, we conclude that haptoglobin is not statistically homologous to any other kringle.Secondary structural comparisons of the kringle regions have been predicted by a combination of the Burgess and Chou-Fasman methods. In general, the kringles display a very high number of -turns, and very low -helical contents. From analysis of the predicted structures in relationship to the functional properties of these domains, it appears as though many of their functional differences can be related to possible conformational alterations resulting from amino acid substitutions in the kringles.