Towards a methodology for taking physical degradation of ecosystems into account in LCA

An analytic procedure has been followed to select adequate methods to express ecosystem degradation in LCA. This procedure consisted of problem definition, identification of relevant issues, of a quantitative expression for ecosystem degradation and of possible nature value indicators and building a framework of criteria for selecting adequate methods. With the selection framework a first screening of methods was performed. For full quantification the following formula is proposed: ED = L (N_r- N_a), with land use I. = A t and nature value change (N_r- N_a) Degradation due to an activity appears difficult to operationalise, but ecosystem suppression by activities can well be assessed. N_r is then the natural background or would-be natural situation. N_a can best be described by the actual state during the activity, unless hard data on restoration is available. N_a and N_r can be expressed in the biomass production indicator NPP - NCR Biodiversity and/or erosion may be added to include irreversible effects.     

Polyphosphate kinase is a component of the Escherichia coli RNA degradosome

Xer site-specific recombination functions in the stable inheritance of circular plasmids and bacterial chromosomes. Two related recombinases, XerC and XerD, mediate this recombination, which 'undoes' the potential damage of homologous recombination. Xer recombination on natural plasmid sites is preferentially intramolecular, converting plasmid multimers to monomers. In contrast, recombination at the Escherichia coli recombination site, dif , occurs both intermolecularly and intramolecularly, at least when dif is inserted into a multicopy plasmid. Here the DNA sequence features of a family of core recombination sites in which the XerC- and XerD-binding sites, which are separated by 6 bp, were analysed in order to ascertain what determines whether recombination will be preferentially intramolecular, or will occur both within and between molecules. Sequence changes in either the XerC- or XerD-binding site can alter the recombination outcome. Preferential intramolecular recombination between a pair of recombination sites requires additional accessory DNA sequences and accessory recombination proteins and is correlated with reduced affinities of recombinase binding to recombination core sites, reduced XerC-mediated cleavage in vitro , and an apparent increased overall bending in recombinase–core-site complexes.     

Distribution and disappearance of the radiolabeled carbon derived from L-arginine and taurine in the mouse

L-arginine and taurine are still in the center of physiological and pharmacological research. Although the fate of nitrogen of both compounds and of the ³⁵S-taurine is well-documented, the fate of the carbon skeleton has not been elucidated yet. We studied the organ distribution of ¹⁴C arginine and ¹⁴C taurine over time in the mouse using whole body autoradiography with densitometric image analysis. We describe different organ distribution patterns. Kidney, heart, lung, the Harderian gland, the central nervous system, intestine and testis showed a comparable pattern of arginine disappearance in contrast to rapid disappearance in the salivary gland and the accumulation pattern in bone and spleen. Data on ¹⁴C taurine of liver, kidneys, lung, testis and Harderian gland resembled the arginine pattern; Accumulation of taurine carbon was found in salivary gland, bone, intestine, heart and brain. Our studies challenge and demand further related studies to obtaining more information on the fate of the carbon skeleton of these amino acids.     

Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans

Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and D. simulans for two common allozyme forms, as well as for several other less common variants. Parallel latitudinal clines in the frequencies of the common EST6-F and EST6-S allozymes in these species have previously been interpreted in terms of a shared amino acid polymorphism that distinguishes the two variants and is subject to selection. Here we compare the sequences of four D. simulans Est-6 isolates and show that overall estimates of nucleotide heterozygosity in both coding and 5' flanking regions are more than threefold higher than those obtained previously for this gene in D. melanogaster. Nevertheless, the ratio of replacement to exon silent-site polymorphism in D. simulans is less than the ratio of replacement to silent divergence between D. simulans and D. melanogaster, which could be the result of increased efficiency of selection against replacement polymorphisms in D. simulans or to divergent selection between the two species. We also find that the amino acid polymorphisms separating EST6- F and EST6-S in D. simulans are not the same as those that separate these allozymes in D. melanogaster, implying that the shared clines do not reflect shared molecular targets for selection. All comparisons within and between the two species reveal a remarkable paucity of variation in a stretch of nearly 400 bp immediately 5' of the gene, indicative of strong selective constraint to retain essential aspects of Est-6 promoter function.      

Plant transformation by particle bombardment of embryogenic pollen

Summary Direct delivery of DNA into embryogenic pollen was used to produce transgenic plants in tobacco. A plasmid bearing the ß-glucuronidase (GUS) marker gene in fusion with the 35S-promoter was introduced by microprojectile bombardment into mid-binucleate pollen of Nicotiana tabacum that had been induced to form embryos by a starvation treatment. In cytochemical expression assays, 5 out of 10⁴ pollen grains were GUS⁺. Visual selection by staining with a non-lethal substrate for GUS was used to manually isolate transformed embryos. From the initial population of embryogenic GUS⁺ pollen, 1–5% developed into multicellular structures and 0.02% formed regenerable embryos. Two haploid transformants were regenerated. GUS expression was detected in different parts of the plants, and Southern analysis confirmed stable integration of the foreign DNA. Diploidisation was induced by injection of colchicine into the stem near adventitious buds. Offspring from selfings and backcrosses of one transformant were tested for GUS expression and by Southern blots. All F1-plants were transgenic, in accordance with Mendelian inheritance.Abbreviations GUS ß-glucuronidase - CaMV Cauliflower Mosaic Virus - MCS multicellular structure - NPTII neomycin phosphotransferase - PEG polyethylene glycol - X-gluc 5-bromo-4-chloro-3-indolyl glucuronide - DAPI 4,6-diamidino-2-phenylindole - Tris Tris(hydroxymethyl)aminomethane hydrochloride - EDTA ethylenedinitrilo tetraacetic acid, disodium salt dihydrate     

Thermochemiluminescent assay of porcine, rat, and human erythrocytes for antioxidative deficiencies

The thermal induction of chemiluminescence of luminol-horseradish peroxidase-labeled erythrocytes from pigs, rats, and man was studied. The luminescent responses of rat, porcine, and human erythrocytes to heating were linear in respect to logs of counts per minute versus temperature. Landrace-Duroc crossbred pigs with a history of malignant hyperthermia (porcine stress syndrome) and Poland-China-miniature pigs inbred for malignant hyperthermia (MH) yielded erythrocytes with high-level thermochemiluminescence (TCL). Sprague-Dawley rat erythrocytes were intermediate in their production of TCL. Normal human and MH-resistant miniature swine erythrocytes produced low-level TCL. However, pretreatment of human erythrocytes with 1-chloro-2,4-dinitrobenzene (CDNB) resulted in high-level TCL. Furthermore, halothane enhanced the TCL of CDNB-treated human erythrocytes and Landrace-Duroc porcine erythrocytes that were not treated with CDNB. Red blood cells from pigs susceptible to the porcine stress syndrome demonstrated a TCL response very similar to CDNB-treated erythrocytes.     

σ Complexes as biochemical and biophysical probes: 4. Development of a novel reporter group delivery system

A novel reporter group delivery system for the chemical modification of proteins and the investigation of enzyme mechanisms is proposed. The design of this system is based on structural analogy with pyridoxal phosphate and σ-complex adduct formation. Progress is described toward the synthesis of suitable compounds, via three different approaches involving structural modification of the pyridine nucleus. A number of new compounds have been prepared, and other directions for future investigations are indicated.     

Species interactions in a mixed colony of common terns (Sterna hirundo) and black skimmers (Rynchops niger)

Black skimmers (Rynchops niger) frequently nest among common terns (Sterna hirundo) on coastal islands from North Carolina to New York. Behavioural interactions among terns, skimmers, and several potential avian predator species were quantified during the 1973 breeding season at Fisherman Island, Virginia. Common terns were dominant to skimmers, chasing and dive-attacking neighbouring pairs, while skimmers rarely chased terns. Despite agonistic interactions, nesting success of both species was no different whether nearest neighbours were conspecifics or heterospecifics. Common terns chased away potential avian predators much more frequently than did skimmers. Black skimmers, then, appear to derive a ‘protective cover’ benefit from nesting among the terns. Neither nest-site limitation nor food ‘information-sharing’ appear to account for the species associations.