The role of plant species in biomass production and response to elevated CO2 and N

In an experiment that factorially manipulated plant diversity, CO₂, and N, we quantified the effects of the presence of species on assemblage biomass over 10 time points distributed over 5 years. Thirteen of the 16 species planted had statistically significant effects on aboveground and/or belowground biomass. Species differed dramatically in their effects on biomass without any relationship between aboveground and below‐ground effects. Temporal complementarity among species in their effects seasonally, successionally, and in response to a dry summer maintained the diversity–biomass relationships over time and may be the cause behind higher diversity plots having less variation in biomass over time. The response of plant biomass to elevated N, but not CO₂, was at times entirely dependent on the presence of a single species.     

Rhodocetin antagonizes stromal tumor invasion in vitro and other alpha2beta1 integrin-mediated cell functions.

The pleiotropic effects of Calloselasma rhodostoma venom is caused by various toxins, among them kistrin and ancrod, which block platelet activation triggered by RGD-dependent integrins and the blood clotting cascade, respectively. Here, we demonstrate that rhodocetin, another component of this venom, acts as alpha2beta1 integrin inhibiting disintegrin and antagonizes important cellular responses to type I collagen. Cell adhesion, migration, and collagen lattice contraction in vitro were specifically inhibited by rhodocetin, whereas expression of collagen-degrading matrix metalloproteases was differently modulated. Moreover, cell invasion of HT1080 fibrosarcoma cells into a type I collagen matrix, but not into a fibrin gel or a basement membrane-extracted matrigel was efficiently blocked by rhodocetin. Unlike its natural ligand collagen, rhodocetin failed to cluster alpha2beta1 integrin, despite similar binding affinities. Hence, in the absence of focal adhesions cells do not attach firmly to rhodocetin and do not respond with any of alpha2beta1-triggered cell reactions, except for MMP-1 production. Therefore, this disintegrin may be a valuable tool to specifically target stromal tumor invasion and to manipulate other alpha2beta1 integrin-mediated functions, such as excessive scar contraction and fibrosis. Rhodocetin might be therapeutically useful because of its lack of interference with RGD-dependent integrins, low molecular mass, high solubility, and biochemical stability.     

IADS, a decomposition product of DIDS activates a cation conductance in Xenopus oocytes and human erythrocytes: new compound for the diagnosis of cystic fibrosis.

DIDS (4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid) is a commonly used blocker of plasma membrane anion channels and transporters. We observed that DIDS undergoes decomposition while stored in DMSO (dimethyl sulfoxide) forming a biologically active compound. One decomposition product, called IADS, was identified and synthesized. Voltage-clamp and patch clamp experiments on Xenopus laevis oocytes and human erythrocytes revealed that IADS is able to activate a plasma membrane cation conductance in both cell types. Furthermore, we found that IADS induces hemolysis in red blood cells of healthy donors but fails to hemolyze erythrocytes of donors with cystic fibrosis. Thus, IADS stimulated activation of a cation conductance could form the basis for a novel diagnostic test of cystic fibrosis.     

Turnover of passerine birds on islands in the Aegean Sea (Greece)

Aim We wish to determine the effect of migratory status on turnover rates in island birds. Because turnover is influenced by factors other than migratory status, we also considered the influence of body size and physical characteristics of the islands inhabited on the probabilities of extinction and immigration. Location The Mediterranean islands of Delos, Astypalea, Paros, Naxos and Lesvos in the Aegean Sea, Greece. Methods The passerine birds of these islands were surveyed between 1954 and 1961 by G.E. Watson, and were resurveyed between 1988 and 1992. The effects of migratory status and body size on the probabilities of extinction and immigration were examined by G‐tests of linear trend in proportion, and analysis of variance, respectively. A combined analysis of migratory status, body size and physical characteristics of the islands was carried out using logistic regressions of the probabilities of extinction and immigration on these factors. Results Species number on each island changed little between surveys, with no island's species number changing by more than one species. Twelve population extinctions and 11 immigrations were recorded. The smallest island, Delos (6 km²), had the highest annualized relative turnover rate (1.08), while the four larger islands (96–1614 km²) had lower and mutually similar rates (0.21–0.27). Populations on higher elevation islands were less likely to go extinct. There is no evidence for an effect of body size on the probabilities of extinction or immigration. Migratory status affected extinction and immigration probabilities differently: migratory species were more likely to immigrate, but less likely to go extinct. Main conclusions The position of the Aegean islands along a major north–south flyway may account for the observed effects of migratory status. The annual passage of large numbers of migrants may, via the rescue effect, decrease the chances of extinction, while at the same time increasing the chances of colonization of unoccupied islands. The likelihood of both extinction and immigration involves a complex interaction between life‐history traits and island characteristics. The effects of migratory status will depend not only on consideration of vagility, vulnerability and stochasticity identified by previous authors, but also upon the location of the islands in relationship to migratory pathways.     

Matrilins mediate weak cell attachment without promoting focal adhesion formation.

The matrilins form a family of non-collagenous adaptor proteins in the extracellular matrix. The extracellular ligand interactions of matrilins have been studied in some detail, while the potential interplay between matrilins and cells has been largely neglected. Except for matrilin-4, all matrilins mediate cell attachment, but only for matrilin-1 and -3 the binding is clearly dose dependent and seen already at moderate coating concentrations. Even so, much higher concentrations of matrilin-1 or -3 than of fibronectin are required for cell attachment to reach plateau values. Integrins contribute to the matrilin-mediated cell attachment, but the binding does not lead to formation of focal contacts and reorganisation of the actin cytoskeleton. Cells deficient in beta1 integrins are able to adhere, although weaker, and matrilins do not bind the soluble integrin alpha1beta1 and alpha2beta1 ectodomains. Cell surface proteoglycans may promote the attachment, as cells deficient in glycosaminoglycan biosynthesis adhere less well to matrilin-3. Even so, exogenous glycosaminoglycans are not able to compete for the attachment of HaCaT cells to matrilins.     

Modular optical topometric sensor for 3D acquisition of human body surfaces and long-term monitoring of variations.

Optical topometric 3D sensors such as laser scanners and fringe projection systems allow detailed digital acquisition of human body surfaces. For many medical applications, however, not only the current shape is important, but also its changes, e.g., in the course of surgical treatment. In such cases, time delays of several months between subsequent measurements frequently occur. A modular 3D coordinate measuring system based on the fringe projection technique is presented that allows 3D coordinate acquisition including calibrated color information, as well as the detection and visualization of deviations between subsequent measurements. In addition, parameters describing the symmetry of body structures are determined. The quantitative results of the analysis may be used as a basis for objective documentation of surgical therapy. The system is designed in a modular way, and thus, depending on the object of investigation, two or three cameras with different capabilities in terms of resolution and color reproduction can be utilized to optimize the set-up.     

The Serratia marcescens hemolysin is secreted but not activated by stable protoplast-type L-forms of Proteus mirabilis

The outer-membrane protein ShlB of Serratia marcescens activates and secretes hemolytic ShlA into the culture medium. Without ShlB, inactive ShlA (termed ShlA*) remains in the periplasm. Since Proteus mirabilis L-form cells lack an outer membrane and a periplasm, it was of interest to determine in which compartment recombinant ShlA* and ShlB are localized and whether ShlB activates ShlA*. The cloned shlB and shlA genes were transcribed in P. mirabilis stable L-form cells by the temperature-inducible phage T7 RNA polymerase. Radiolabeling, Western blotting, and complementation with C-terminally truncated ShlA (ShlA255) identified inactive ShlA* in the culture supernatant. ShlB remained cell-bound and did not activate ShlA without integration in an outer membrane. Although hemolytic ShlA added to L-form cells had access to the cytoplasmic membrane, it did not affect L-form cells. Synthesis of the large ShlA protein (165 kDa) in P. mirabilis L-form cells under phage T7 promoter control demonstrates that L-form cells are suitable for the synthesis and secretion of large recombinant proteins. This property and the easy isolation of released proteins make L-form cells suitable for the biotechnological production of proteins. Received: 17 February 1998 / Accepted: 30 June 1998     

Genomic organization of four β-1,4-endoglucanase genes in plant-parasitic cyst nematodes and its evolutionary implications

The genomic organization of genes encoding β-1,4-endoglucanases (cellulases) from the plant-parasitic cyst nematodes Heterodera glycines and Globodera rostochiensis (HG-eng1, Hg-eng2, GR-eng1, and GR-eng2) was investigated. HG-eng1 and GR-eng1 both contained eight introns and structural domains of 2151 and 2492 bp, respectively. HG-eng2 and GR-eng2 both contained seven introns and structural domains of 2324 and 2388 bp, respectively. No significant similarity in intron sequence or size was observed between HG-eng1 and HG-eng2, whereas the opposite was true between GR-eng1 and GR-eng2. Intron positions among all four cyst nematode cellulase genes were conserved identically in relation to the predicted amino acid sequence. HG-eng1, GR-eng1, and GR-eng2 had several introns demarcated by 5′-GC…AG-3′ in the splice sites, and all four nematode cellulase genes had the polyadenylation and cleavage signal sequence 5′-GAUAAA-3′—both rare occurences in eukaryotic genes. The 5′- flanking regions of each nematode cellulase gene, however, had signature sequences typical of eukaryotic promoter regions, including a TATA box, bHLH-type binding sites, and putative silencer, repressor, and enhancer elements. Database searches and subsequent phylogenetic comparison of the catalytic domain of the nematode cellulases placed the nematode genes in one group, with Family 5, subfamily 2, glycosyl hydrolases from Scotobacteria and Bacilliaceae as the most homologous groups. The overall amino acid sequence identity among the four nematode cellulases was from 71 to 83%, and the amino acid sequence identity to bacterial Family 5 cellulases ranged from 33 to 44%. The eukaryotic organization of the four cyst nematode cellulases suggests that they share a common ancestor, and their strong homology to prokaryotic glycosyl hydrolases may be indicative of an ancient horizontal gene transfer.     

Nonbacterial pneumonitis with multidrug antineoplastic therapy in breast carcinoma

Seventeen patients with metastatic breast carcinoma were treated with a combination of 5-fluorouracil, methotrexate, vincristine, cyclophosphamide and prednisone. Six of the patients (35%) developed a syndrome consisting of fever, malaise, dyspnea, hypoxemia and bilateral pulmonary interstitial infiltrates from 41 to 148 days after institution of therapy. The syndrome varied from a mild to a life-threatening illness with recovery in 10 to 60 days. It is believed that these cases represent examples of methotrexate-induced pneumonitis. The high incidence of the syndrome in this patient group may be related to the concomitant administration of cyclophosphamide with methotrexate. The observations also suggest that patients with previous adrenalectomies may have pneumonitis with an especially severe and protracted course.