Dendroecological reconstruction and interpretation of larch budmoth (Zeiraphera diniana) outbreaks in two central alpine valleys of Switzerland from 1470 – 1990

 Outbreaks of the larch budmoth (LBM) (Zeiraphera diniana) recur cyclically approximately every 7 to 10 years in subalpine larch-cembran pine and montane to subalpine larch-Norway spruce forests of the relatively dry valleys of the European Alps. By dendroecologically analyzing increment cores from 570 host (European larch –Larix decidua) and non-host trees (cembran pine –Pinus cembra, Norway spruce –Picea abies) through the use of skeleton plots, at least 57 (59) outbreaks could be reconstructed in the optimum Upper Engadine Valley (suboptimum Goms Valley), Switzerland, during the time period 1503 (1472) to 1990. The average interval between initial years of successive outbreaks was 8.58 (8.95) years, SD 1.66 (2.13) years. Over the centuries spatial shifts of LBM activity between the two study areas occurred, probably due to climatic changes. Clear, site-specific differences in LBM attack could only be found in the suboptimum area where high-lying (>1800 m) and/or south-facing stands were infested most. LBM-afflicted trees proved to be unsuitable for climate reconstructions because the impact of the persistently recurring outbreaks on tree growth is dominant. In order to provide sufficient information for a detailed ecological interpretation of the course of an outbreak, latewood widths and/or densities have to be analyzed in addition to the ring-widths. Received: 11 February 1995 / Accepted: 19 July 1996     

Characterization of crystals of the thermostable DNA polymerase I from thermus aquaticus

Thermus aquaticus DNA polymerase I is an enzyme that is of both physiological and technological interest. It carries out template-directed polymerization of DNA at elevated temperatures and is widely used in polymerase chain reaction (PCR). We have obtained crystals of the enzyme that diffracts X-rays to at least 3.0 Å resolution in a cubic space group. Determination of the three-dimensional structure of the native enzyme along with those of relevant complexes will greatly enhance our knowledge of molecular events involved in DNA replication, will permit improvements in PCR, and will add to our knowledge of the structural bases of thermo stability in proteins. © 1995 Wiley-Liss, Inc.     

Is hydrogen peroxide a second messenger of salicylic acid in systemic acquired resistance?

Elevated levels of salicylic acid (SA) are required for the induction of systemic acquired resistance (SAR) in plants. Recently, a salicylic acid-binding protein (SABP) isolated from tobacco was shown to have catalase activity. Based on this finding elevated levels of hydrogen peroxide (H₂O₂) were postulated to act as a second messenger of SA in the SAR signal transduction pathway. A series of experiments have been carried out to clarify the role of H₂O₂ in SAR-signaling. No increase of H₂O₂ was found during the onset of SAR. Induction of the SAR gene, PR-1, by H₂O₂ and H₂O₂-inducing chemicals is strongly suppressed in transgenic tobacco plants that express the bacterial salicylate hydroxylase gene, indicating that H₂O₂ induction of SAR genes is dependent on SA accumulation. Following treatment of plants with increasing concentrations of H₂O₂, a dose-dependent accumulation of total SA species was found, suggesting that H₂O₂ may induce PR-1 gene expression through SA accumulation. While the results do not support a role for H₂O₂ in SAR signaling, it is suggested that SA inhibition of catalase activity may be important in tissues undergoing a hypersensitive response.     

Microelectrode studies of the active Na transport pathway of frog skin

When the outer surface of short-circuited frog skin was penetrated with microelectrodes, stable negative potentials that averaged near -100 mV were recorded consistently, confirming the results of Nagel (W. Nagel. 1975. Abstracts of the 5th International Biophysics Congress, Copenhagen. P-147.). The appearance of these stable potentials, V(O), concurrent with the observations that (a) a high resistance outer barrier R(O) accounting for approximately 75 percent or more of the transcellular resistance of control skins had been penetrated and that (b) 10(-5) M amiloride and reduced [Na] outside caused the values of V(O) to increase towards means value near -130 mV while the values of percent R(O) increased to more than 90 percent. It was of relationships were the same as the values of E(1) observed in studies of the current-voltage relationships were the same as the values of E’(1) defined as the values of voltage at the inner barrier when the V(O) of the outer barrier was reduced to zero by voltage clamping of the skins. Accordingly, these data are interpreted to mean that the values of E(1), approximately 130 mV, represent the E(Na) of the sodium pump at the inner barrier. 2,4-DNP was observed to decrease the values of transepithelial voltage less than E(1) the V(O) was negative. These data can be interpreted with a simple electrical equivalent circuit of the active sodium transport pathway of the frog skin that includes the idea that the outer membrane behaves as an electrical rectifier for ion transport.     

A rapid and sensitive assay for arginase

An assay for arginase is described that uses l-[guanido-¹⁴C]arginine as substrate. Unhydrolyzed arginine is removed in a batch procedure with sulfonate resin and the [¹⁴C]urea product is determined quantitatively in the resin supernatant. The assay requires 5 min and is performed in one tube. The sensitivity is approximately 0.1 munits of arginase. Arginase activities in fetal calf serum and in murine macrophage extract have been determined and the bovine liver enzyme has been used as a reference.     

Changes in nitrogen contents and in proteolytic activities in different parts of field-grown wheat ears (Triticum aestivum L.) during maturation

Aminopeptidase, carboxypeptidase and neutral endopeptidase activitieswere analyzed in glumes and in kernels of field-grown wheat(Triticum aestivum L.) during ear development. Kernels harvestedon two dates were subdivided into outer pericarp, cross cells,endosperm and embryo. In developing parts with a net nitrogeninflux (young glumes, embryo, endosperm) the aminopeptidaseactivity is high, but in nitrogen-mobilizing tissues (senescingglumes, Outer pericarp) this activity decreases. Carboxypeptidaseis most active in fully expanded tissues. Neutral endopeptidaseshows the highest activity in the nitrogen mobilizing partsand extremely low activity in the embryo and the endosperm. (Received July 15, 1978; )     

Computation of the fraction of induced cells in enzyme induction systems

A theoretical model is developed for continuous multistage enzyme production systems, which consist of a growth fermentor used for growing microorganisms rapidly without enzyme production and a subsequent system of induction reactors in which enzymes induction and production occurs. The model allows the computation of the fraction of induced cells residing in the induction reactor for organisms exhibiting a lag phase in enzyme induction. For this model a general analytical solution was obtained for the cumulative internal residence time distribution of a series of n well-stirred vessels with a recycle. The theoretical results are compared in a preliminary way with experimentally measured cellulase productivities of continuous multistage cellulose fermentations with Trichoderma viride QM 9414.     

Interactions of acetylcholine receptor and acetylcholinesterase with lipid monolayers

The interaction of acetylcholine receptor and acetylcholinesterase with lipid monolayers was followed by measuring changes in surface pressure.When injected into the subphase of a lipid monolayer, the proteins caused increases in surface pressure from 5 to 10 dynes/cm, indicating a penetration of protein into the monolayer. At pH values below the isoelectric point of the proteins the incorporation was improved. The same was observed when Ca²⁺ (2 mM) was added.The presence of the enzyme in the mixed film could be demonstrated by using diiso[³H]propyl fluorophosphate-labelled acetylcholinesterase as well as by measuring enzyme activity. Acetylcholine receptor was shown to be present in the mixed film by using a complex made of the receptor and α-[³H]neurotoxin.