Community structure of insect herbivores is driven by conservatism,escalation and divergence of defensive traits in Ficus

Escalation (macroevolutionary increase) or divergence (disparity between relatives) in trait values are two frequent outcomes of the plant‐herbivore arms race. We studied the defences and caterpillars associated with 21 sympatric New Guinean figs. Herbivore generalists were concentrated on hosts with low protease and oxidative activity. The distribution of specialists correlated with phylogeny, protease and trichomes. Additionally, highly specialised Asota moths used alkaloid rich plants. The evolution of proteases was conserved, alkaloid diversity has escalated across the studied species, oxidative activity has escalated within one clade, and trichomes have diverged across the phylogeny. Herbivore specificity correlated with their response to host defences: escalating traits largely affected generalists and divergent traits specialists; but the effect of escalating traits on extreme specialists was positive. In turn, the evolution of defences in Ficus can be driven towards both escalation and divergence in individual traits, in combination providing protection against a broad spectrum of herbivores.     

Oxylipins from both pathogen and host antagonize jasmonic acid‐mediated defence via the 9‐lipoxygenase pathway in Fusarium verticillioides infection of maize

Oxylipins are a newly emerging group of signals that serve defence roles or promote virulence. To identify specific host and fungal genes and oxylipins governing the interactions between maize and Fusarium verticillioides, maize wild‐type and lipoxygenase3 (lox3) mutant were inoculated with either F. verticillioides wild‐type or linoleate‐diol‐synthase 1‐deleted mutant (ΔFvlds1D). The results showed that lox3 mutants were more resistant to F. verticillioides. The reduced colonization on lox3 was associated with reduced fumonisin production and with a stronger and earlier induction of ZmLOX4, ZmLOX5 and ZmLOX12. In addition to the reported defence function of ZmLOX12, we showed that lox4 and lox5 mutants were more susceptible to F. verticillioides and possessed decreased jasmonate levels during infection, suggesting that these genes are essential for jasmonic acid (JA)‐mediated defence. Oxylipin profiling revealed a dramatic reduction in fungal linoleate diol synthase 1 (LDS1)‐derived oxylipins, especially 8‐HpODE (8‐hydroperoxyoctadecenoic acid), in infected lox3 kernels, indicating the importance of this molecule in virulence. Collectively, we make the following conclusions: (1) LOX3 is a major susceptibility factor induced by fungal LDS1‐derived oxylipins to suppress JA‐stimulating 9‐LOXs; (2) LOX3‐mediated signalling promotes the biosynthesis of virulence‐promoting oxylipins in the fungus; and (3) both fungal LDS1‐ and host LOX3‐produced oxylipins are essential for the normal infection and colonization processes of maize seed by F. verticillioides.     

Endothelial cells as early sensors of pulmonary interstitial edema.

We studied responses of endothelial and epithelial cells in the thin portion of the air-blood barrier to a rise in interstitial pressure caused by an increase in extravascular water (interstitial edema) obtained in anesthetized rabbits receiving saline infusion (0.5 ml.kg(-1).min(-1) for 3 h). We obtained morphometric analyses of the cells and of their microenvironment (electron microscopy); furthermore, we also studied in lung tissue extracts the biochemical alterations of proteins responsible for signal transduction (PKC, caveolin-1) and cell-cell adhesion (CD31) and of proteins involved in membrane-to-cytoskeleton linkage (alpha-tubulin and beta-tubulin). In endothelial cells, we observed a folding of the plasma membrane with an increase in cell surface area, a doubling of plasmalemma vesicular density, and an increase in cell volume. Minor morphological changes were observed in epithelial cells. Edema did not affect the total plasmalemma amount of PKC, beta-tubulin, and caveolin-1, but alpha-tubulin and CD-31 increased. In edema, the distribution of these proteins changed between the detergent-resistant fraction of the plasma membrane (DRF, lipid microdomains) and the rest of the plasma membrane [high-density fractions (HDFs)]. PKC and tubulin isoforms shifted from the DRF to HDFs in edema, whereas caveolin-1 increased in DRF at the expense of a decrease in phosphorylated caveolin-1. The changes in cellular morphology and in plasma membrane composition suggest an early endothelial response to mechanical stimuli arising at the interstitial level subsequently to a modest (approximately 5%) increase in extravascular water.     

Phenoxyl free radical formation during the oxidation of the fluorescent dye 2',7'-dichlorofluorescein by horseradish peroxidase. Possible consequences for oxidative stress measurements.

The oxidation of the fluorescent dye 2',7'-dichlorofluorescein (DCF) by horseradish peroxidase was investigated by optical absorption, electron spin resonance (ESR), and oxygen consumption measurements. Spectrophotometric measurements showed that DCF could be oxidized either by horseradish peroxidase-compound I or -compound II with the obligate generation of the DCF phenoxyl radical (DCF(.)). This one-electron oxidation was confirmed by ESR spin-trapping experiments. DCF(.) oxidizes GSH, generating the glutathione thiyl radical (GS(.)), which was detected by the ESR spin-trapping technique. In this case, oxygen was consumed by a sequence of reactions initiated by the GS(.) radical. Similarly, DCF(.) oxidized NADH, generating the NAD(.) radical that reduced oxygen to superoxide (O-(2)), which was also detected by the ESR spin-trapping technique. Superoxide dismutated to generate H(2)O(2), which reacted with horseradish peroxidase, setting up an enzymatic chain reaction leading to H(2)O(2) production and oxygen consumption. In contrast, when ascorbic acid reduced the DCF phenoxyl radical back to its parent molecule, it formed the unreactive ascorbate anion radical. Clearly, DCF catalytically stimulates the formation of reactive oxygen species in a manner that is dependent on and affected by various biochemical reducing agents. This study, together with our earlier studies, demonstrates that DCFH cannot be used conclusively to measure superoxide or hydrogen peroxide formation in cells undergoing oxidative stress.     

Biological and conformational studies on analogues of a synthetic peptide enhancing HIV-1 infection

We have previously demonstrated that a 23-amino acid peptide derived from the V3 loop of the surface glycoprotein of the HIV-1 strain MN is able to bind CD4 and to enhance HIV-1 infection. Further studies have suggested that the peptide/CD4 interaction induces an increase in both CD4 expression and CD4/gp120 binding affinity. This paper describes the biological and physico-chemical characterization of three analogues of reduced sequence that have been designed in order to identify the minimum active sequence of this peptide corresponding to the MN-HIV-1 principal neutralizing domain. Biological studies indicate that the entire sequence is required for biological activity and that the sequence 1–18 presents an inhibitory activity. CD and FT-IR absorption data are discussed here in order to identify possible structure-function correlations. © 1998 European Peptide Society and John Wiley & Sons, Ltd.     

Oligonucleotides specific for pathogenic and saprophytic leptospira occurring in water

Sets of primers specific for both pathogenic (SPL) and saprophytic (SSL) Leptospira were designed from ribosomal 16S genes (rrs) available in databases. They were used as two sets of primer pairs for the PCR amplification of known pathogenic and saprophytic strains. It was possible to identify pathogenic strains by the use of SPL primers and saprophytic ones by SSL primers. Serovars from L. meyeri, of controversial pathogenicity status, confirmed the heterogeneity of the species representatives in this respect. Serovars ranarum, sofia and perameles were amplified by SPL and not SSL. Conversely, serovar semaranga was amplified by SSL and not SPL. In order to use SPL primers for the detection of pathogenic leptospires from a natural water environment, we set up an additional semi-nested PCR by employing a second internal primer which succeeded in detecting as few as 5 pathogenic leptospires per ml of water.     

Isolation of lactoferrin from milk of different species: calorimetric and antimicrobial studies

Lactoferrin (LF) is an iron-binding glycoprotein found in different biological fluids of mammals and in neutrophils. It has been proposed to be involved in many functions, including protection from pathogens. In this work, purification of lactoferrin using an ion-exchange chromatography (SP-Sepharose) was attempted for the milk of the following animals: sheep (Ovis aries), goat (Capra hircus), camel (Camelus bactrianus), alpaca (Lama pacos), elephant (Elephas maximus) and grey seal (Halichoerus grypus), as well as human (Homo sapiens). Lactoferrin was identified in all the milks apart from that from grey seal. The thermal stability of the purified lactoferrins, in their native and iron-saturated forms, was studied by differential scanning calorimetry (DSC). Maximum temperature, onset temperature and enthalpy change of denaturation were higher when lactoferrins were saturated with iron than in their native form, indicating an increase in the stability of the protein structure upon iron-binding. Human lactoferrin was found to be the most heat-resistant and the other lactoferrins presented different degrees of thermoresistance, that of elephant being the least resistant. The antimicrobial activity of the different isolated lactoferrins was investigated against Escherichia coli 0157:H7. The minimal inhibitory concentrations (MICs) were determined by measuring the absorbance at 620 nm. The minimum bactericidal concentrations (MBCs) were also measured and it was found that camel lactoferrin was the most active lactoferrin against E. coli 0157:H7, whereas alpaca and human lactoferrins were the least active.