Stable carbon isotopes in tree rings of beech: climatic versus site-related influences

 Stable carbon isotopes in tree rings are a promising tool in palaeoclimate research, provided attempts are made to disentangle climatic from local effects (e.g. soil properties, competition, light). The ¹³C/¹²C variations in cellulose of tree rings of beech (Fagus sylvatica) were determined at several sites in the Swiss Central Plateau covering the last 50 years. We chose sites which differ in moisture conditions and sampled cores from four to six trees per site. The mean ¹³C/¹²C series from the different dry sites (distant by up to 40 km) are closely interrelated suggesting a common external cause. Correlation analysis with climate data proved the total precipitation in the months May, June and July to have the strongest effect on the carbon isotopes (r =  – 0.73). This result is in agreement with the commonly used model which relates the isotope discrimination to the water use efficiency. On the other hand, the isotope series of the wet sites are not as well correlated to the climate. At two of the sites (a dry and a humid) tree ring width suddenly increased. We used this effect as a test-case to study the influence of local growth conditions on the climate-isotope relationship. Received: 17 April 1996 / Accepted: 2 September 1996     

Crystallization of acetate kinase from Methanosarcina thermophila and prediction of its fold.

The unique biochemical properties of acetate kinase present a classic conundrum in the study of the mechanism of enzyme-catalyzed phosphoryl transfer. Large, single crystals of acetate kinase from Methanosarcina thermophila were grown from a solution of ammonium sulfate in the presence of ATP. The crystals diffract to beyond 1.7 A resolution. Analysis of X-ray data from the crystals is consistent with a space group of C2 and unit cell dimensions a = 181 A, b = 67 A, c = 83 A, beta = 103 degrees. Diffraction data have been collected from the crystals at 110 and 277 K. Data collected at 277 K extend to lower resolution, but are more reproducible. The orientation of a noncrystallographic two-fold axis of symmetry has been determined. Based on an analysis of the predicted amino acid sequences of acetate kinase from several organisms, we hypothesize that acetate kinase is a member of the sugar kinase/actin/hsp70 structural family.     

Deuterostomic Actin Genes and the Definition of the Chordates: cDNA Cloning and Gene Organization for Cephalochordates and Hemichordates

The evolutionary relationship of muscle and nonmuscle actin isoforms in deuterostomia was studied by the isolation and characterization of two actin genes from the cephalochordate Branchiostoma lanceolatum and two from the hemichordate Saccoglossus kowalevskii The Branchiostoma genes specify a muscle and a nonmuscle actin type, respectively. Together with earlier results on muscle actins from vertebrates and urochordates, a N-terminal sequence signature is defined for chordate muscle actins. These diagnostic amino acid residues separate the chordates from the echinoderms and other metazoa. Although the two Saccoglossus actins characterized so far lack the diagnostic residues, in line with the presumptive phylogenetic position of hemichordates outside the chordates, a definitive conclusion can only be expected once the full complement of actin genes of Saccoglossus is established. Comparison of the intron patterns of the various deuterostomic actin genes shows that intron 330-3, which is present in all vertebrate genes, is conspicuously absent from nonvertebrate genes. The possible origin of this intron is discussed. Received: 4 July 1997 / Accepted: 29 August 1997     

Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.     

Refined solution structure of human profilin I.

Profilin is a ubiquitous eukaryotic protein that binds to both cytosolic actin and the phospholipid phosphatidylinositol-4,5-bisphosphate. These dual competitive binding capabilities of profilin suggest that profilin serves as a link between the phosphatidyl inositol cycle and actin polymerization, and thus profilin may be an essential component in the signaling pathway leading to cytoskeletal rearrangement. The refined three-dimensional solution structure of human profilin I has been determined using multidimensional heteronuclear NMR spectroscopy. Twenty structures were selected to represent the solution conformational ensemble. This ensemble of structures has root-mean-square distance deviations from the mean structure of 0.58 A for the backbone atoms and 0.98 A for all non-hydrogen atoms. Comparison of the solution structure of human profilin to the crystal structure of bovine profilin reveals that, although profilin adopts essentially identical conformations in both states, the solution structure is more compact than the crystal structure. Interestingly, the regions that show the most structural diversity are located at or near the actin-binding site of profilin. We suggest that structural differences are reflective of dynamical properties of profilin that facilitate favorable interactions with actin. The global folding pattern of human profilin also closely resembles that of Acanthamoeba profilin I, reflective of the 22% sequence identity and approximately 45% sequence similarity between these two proteins.     

Dynamics of the cytoskeleton inAmoeba proteus: II. Influence of different agents on the spatial organization of microinjected fluorescein-labeled actin

Summary Iodoacetamido-fluorescein-(IAF)-labeled actin was microinjected into normal locomotingAmoeba proteus. Thereafter (30–60 minutes) changes in the cytoplasmic fluorescence distribution pattern and contractile activity were induced by internal and external chemical stimulation. Different agents such as phalloidin, procaine, 2.4-dinitrophenol (DNP), puromycin, ouabain and n-ethyl maleimide (NEM) interfere with the excitation-contraction mechanism involved in ordered pseudopodium formation during ameboid movement and cause various morphogenetic reactions based on actin polymerization-depolymerization cycles. Most frequent changes are (a) local condensation of IAF-actin and formation of a continuous IAF-actin layer at the cytoplasmic surface of the cell membrane and around the pulsating vacuole, (b) immobilization and hyalo-granuloplasm separation by combined contraction and detachment of the IAF-actin layer from the cell membrane, (c) organized and disorganized formation of pseudopodia by local contraction and disintegration of the IAF-actin layer, and (d) alterations in the rheological properties of the protoplasmic matrix by changes in the molecular state of soluble actin not incorporated into the cytoskeleton. The experimental approaches to the function of the actomyosin system in large amebas attainable by the method ofin vivo molecular cytochemistry are discussed in detail with respect to the participation of the cytoskeleton in motive force generation for cytoplasmic streaming and ameboid movement.     

Effects of Macroposthonia xenoplax on the Growth of Concord Grape

Concord grape (Vitis labrusca) plants were inoculated with Macroposthonia xenoplax at levels of 100, 1,000, and 10,000 nematodes. After 4 months, plants inoculated with 10,000 M. xenoplax were stunted, and root systems were darker and had fewer feeder roots than those in other treatments. The lower nematode inoculation levels suppressed top growth but did not affect root growth. M. xenoplax reproduced well on Concord grapes.     

The sub-membrane reticulum of the human erythrocyte: A scanning electron microscope study

A web-like reticulum underlying the human erythrocyte membrane was studied at a resolution of 5–10 nm by means of a scanning electron microscope. The network was visualized in isolated membranes (ghosts) torn open to reveal their interior space and in residues derived from ghosts extracted with Triton X-100. It formed a continuous (rather than patchy) cover over the entire cytoplasmic surface, except where lifted off or torn away. Filaments (5–40 nm in diameter), annular figures (40–60 nm in diameter), and nodes (30–100 nm in diameter) were prominent in different networks. The dimensions of the filaments and the interstices in the reticulum varied with conditions, suggesting that the network has elastic properties. This reticulum is probably related to the erythrocyte membrane proteins spectrin and actin.     

Alkaline opening of imidazole ring of 7-methylguanosine. 2. Further studies on reaction mechanisms and products

High performance liquid chromatography (HPLC) was used to follow the kinetics of the alkaline induced opening of the imidazole ring of 7-methylguanosine (7-meGuo). The kinetics show an initial rapid formation of a major transient intermediate and some minor products that were chromato-graphically separable into seven peaks. This phase of the reaction is followed by the formation of a dominant pyrimidine derivative whose liquid chromatography retention time in a 6% methanol, 0.01 M NH₄H₂PO₄ (pH 5.1) solvent is 6 min; during the rest of the reaction time this dominant species was progressively converted to a co-dominant species that has a 4.5-min column retention. Mass spectroscopy confirmed the existence of two species of ring opened 7-methylguanine (7-meGua), one formylated and another deformylated. Schiff's reaction demonstrated that the species in the second HPLC peak is the formylated one. The ring opened 7-methylguanine (rom⁷Gua) released by formamidopyrimidine (FAPy)-DNA glycosylase was shown to coelute with the formylated species. These results demonstrate that the enzyme excises formylated rom⁷Gua from DNA Analysis of rom⁷Guo by NMR showed that there are two signals assignable to methyl protons and two to formyl protons. These chemical shifts were interpreted as being due to the opening of the imidazole ring at two sites and to the formation of formylated and deformylated rom⁷Gua.     

Degree-day Models for Predicting Egg Hatch and Population Increase of Criconemella xenoplax

A degree-day model was derived to predict egg hatch for Criconemella xenoplax. Eggs collected from gravid females were incubated in distilled water at constant temperatures of 10-35 C. Sixty-six percent of all eggs hatched between 13 and 32 C, and 42% hatched at 10 C. All eggs aborted above 32.5 C. Between 25 and 32 C, 8.5 ± 0.5 days were required for egg hatch. Degree-day requirement for egg hatch at 10-30 C was estimated to be 154 ± 5 with a base of 9.03 ± 0.04 C. This base of 9 C was adopted in studies of the relationship between degree-days and nematode population increase on Prunus seedlings grown 9-11 weeks in a greenhouse. Degree-day accumulations were based upon daily averages from maximum and minimum air temperatures. Ratios of final to initial population densities exhibited an exponential pattern in relation to degree-day accumulations with proportionate doubling increment of 0.100 ± 0.049 every 139 ± 8 degree-days. These results provide a means of predicting nematode population increase under greenhouse conditions and a basis for choosing sampling intervals when evaluating nematode multiplication.