Complement activation by phospholipids: the interplay of factor H and C1q

Complement proteins in blood recognize charged particles. The anionic phospholipid (aPL) cardiolipin binds both complement proteins C1q and factor H. C1q is an activator of the complement classical pathway, while factor H is an inhibitor of the alternative pathway. To examine opposing effects of C1q and factor H on complement activation by aPL, we surveyed C1q and factor H binding, and complement activation by aPL, either coated on microtitre plates or in liposomes. Both C1q and factor H bound to all aPL tested, and competed directly with each other for binding. All the aPL activated the complement classical pathway, but negligibly the alternative pathway, consistent with accepted roles of C1q and factor H. However, in this system, factor H, by competing directly with C1q for binding to aPL, acts as a direct regulator of the complement classical pathway. This regulatory mechanism is distinct from its action on the alternative pathway. Regulation of classical pathway activation by factor H was confirmed by measuring C4 activation by aPL in human sera in which the C1q:factor H molar ratio was adjusted over a wide range. Thus factor H, which is regarded as a down-regulator only of the alternative pathway, has a distinct role in downregulating activation of the classical complement pathway by aPL. A factor H homologue, β2-glycoprotein-1, also strongly inhibits C1q binding to cardiolipin. Recombinant globular domains of C1q A, B and C chains bound aPL similarly to native C1q, confirming that C1q binds aPL via its globular heads.     

A tritrophic signal that attracts parasitoids to host-damaged plants withstands disruption by non-host herbivores

Background  

Volatiles emitted by herbivore-infested plants are highly attractive to parasitoids and therefore have been proposed to be part of an indirect plant defense strategy. However, this proposed function of the plant-provided signals remains controversial, and it is unclear how specific and reliable the signals are under natural conditions with simultaneous feeding by multiple herbivores. Phloem feeders in particular are assumed to interfere with plant defense responses. Therefore, we investigated how attack by the piercing-sucking cicadellid Euscelidius variegatus influences signaling by maize plants in response to the chewing herbivore Spodoptera littoralis.     

BIGSdb: Scalable analysis of bacterial genome variation at the population level

Background  

The opportunities for bacterial population genomics that are being realised by the application of parallel nucleotide sequencing require novel bioinformatics platforms. These must be capable of the storage, retrieval, and analysis of linked phenotypic and genotypic information in an accessible, scalable and computationally efficient manner.     

Distribution of transferrin binding protein B gene (<Emphasis Type="Italic">tbpB</Emphasis>) variants among <Emphasis Type="Italic">Neisseria</Emphasis>species

Background  

Transferrin binding protein B (tbpB), an outer membrane lipoprotein, is required for the acquisition of iron from human transferrin. Two tbpB families have been documented in Neisseria meningitidis: an isotype I tbpB gene of 1.8 kb and an isotype II tbpB gene of 2.1 kb, the former expressed by meningococci in the disease-associated ST-11 clonal complex and the latter found among meningococci belonging to the hyper-invasive clonal complexes including ST-8, ST-18, ST-32, ST-41/44 as well as N. gonorrhoeae isolates. The origin of the isotype I tbpB gene is unknown, however several features in common with non-pathogenic Neisseria and the ST-11 clonal complex N. meningitidis isolate FAM18 have been documented leading to the hypothesis that the isotype I tbpB gene may also be shared between non-pathogenic Neisseria and ST-11 meningococci. As a result, the diversity of the tbpB gene was investigated in a defined collection of Neisseria species.     

Evaluation of apoptosis markers in different cell lines infected with equine arteritis virus

Equine arteritis virus (EAV) induces apoptosis in infected cells. Cell death caused by EAV has been studied mainly using three cell lines, BHK-21, RK-13 and Vero cells. The mechanism of apoptosis varies among cell lines and results cannot be correlated owing to differences in EAV strains used. We evaluated different markers for apoptosis in BHK-21, RK-13 and Vero cell lines using the Bucyrus EAV reference strain. Acridine orange/ethidium bromide staining revealed morphological changes in infected cells, while flow cytometry indicated the extent of apoptosis. We also observed DNA fragmentation, but the DNA ladder was detected at different times post-infection depending on the cell line, i.e., 48, 72 and 96 h post-infection in RK-13, Vero and BHK-21 cells, respectively. Measurement of viral titers obtained with each cell line indicated that apoptosis causes interference with viral replication and therefore decreased viral titers. As an unequivocal marker of apoptosis, we measured the expression of caspase-3 and caspases-8 and -9 as extrinsic and intrinsic markers of apoptosis pathways, respectively. Caspase-8 in BHK-21 cells was the only protease that was not detected at any of the times assayed. We found that Bucyrus EAV strain exhibited a distinctive apoptosis pathway depending on the cell line.     

PCR gut analysis reveals that Tenuiphantes tenuis (Araneae: Linyphiidae) is a potentially significant predator of Argentine stem weevil,Listronotus bonariensis (Coleoptera: Curculionidae), in New Zealand pastures

Polymerase chain reaction (PCR) gut analysis was conducted on specimens of the introduced spider Tenuiphantes tenuis collected from dairy pasture in Canterbury, New Zealand. PCR primers were specifically designed to amplify a fragment of the mitochondrial gene cytochrome c oxidase subunit 1 (COI) from Listronotus bonariensis and revealed that this major pasture pest species is consumed in the field by T. tenuis. The field predation rate of L. bonariensis by T. tenuis was estimated from our PCR results together with published data on the degradation of DNA and the density of T. tenuis in Canterbury pastures. We found that T. tenuis is a potentially significant predator of L. bonariensis in New Zealand pastures.     

Indigo: an annotated bibliography

This bibliography lists and comments on publications describing the history, preparation, chemistry and some applications of indigo and related dyes. Note that the commentary by the author is in italics after the bibliographic information.     

Pharmacological inhibition of GSK-3 in a guinea pig model of LPS-induced pulmonary inflammation: II. Effects on skeletal muscle atrophy

Background

Chronic obstructive pulmonary disease (COPD) is accompanied by pulmonary inflammation and associated with extra-pulmonary manifestations, including skeletal muscle atrophy. Glycogen synthase kinase-3 (GSK-3) has been implicated in the regulation of muscle protein- and myonuclear turnover; two crucial processes that determine muscle mass. In the present study we investigated the effect of the selective GSK-3 inhibitor SB216763 on muscle mass in a guinea pig model of lipopolysaccharide (LPS)-induced pulmonary inflammation-associated muscle atrophy.

Methods

Guinea pigs were pretreated with either intranasally instilled SB216763 or corresponding vehicle prior to each LPS/saline challenge twice weekly. Pulmonary inflammation was confirmed and indices of muscle mass were determined after 12 weeks. Additionally, cultured skeletal muscle cells were incubated with tumor necrosis factor α (TNF-α) or glucocorticoids (GCs) to model the systemic effects of pulmonary inflammation on myogenesis, in the presence or absence of GSK-3 inhibitors.

Results

Repeated LPS instillation induced muscle atrophy based on muscle weight and muscle fiber cross sectional area. Intriguingly, GSK-3 inhibition using SB216763 prevented the LPS-induced muscle mass decreases and myofiber atrophy. Indices of protein turnover signaling were unaltered in guinea pig muscle. Interestingly, inhibition of myogenesis of cultured muscle cells by TNF-α or synthetic GCs was prevented by GSK-3 inhibitors.

Conclusions

In a guinea pig model of LPS-induced pulmonary inflammation, GSK-3 inhibition prevents skeletal muscle atrophy without affecting pulmonary inflammation. Resistance to inflammation- or GC-induced impairment of myogenic differentiation, imposed by GSK-3 inhibition, suggests that sustained myogenesis may contribute to muscle mass maintenance despite persistent pulmonary inflammation. Collectively, these results warrant further exploration of GSK-3 as a potential novel drug target to prevent or reverse muscle wasting in COPD.     

Selective breeding of entomopathogenic nematodes for enhanced attraction to a root signal did not reduce their establishment or persistence after field release

We recently showed that the efficacy of an entomopathogenic nematode (EPN) as a biological control agent against a root pest could be enhanced through artificial selection. The EPN Heterorhabditis bacteriophora was selected for higher responsiveness towards (E)-β-caryophyllene (EβC), a sesquiterpene that is emitted by maize roots in response to feeding damage by the western corn rootworm (WCR). EβC is normally only weakly attractive to H. bacteriophora, which is one of the most infectious nematodes against WCR. By selecting H. bacteriophora to move more readily along a EβC gradient we obtained a strain that was almost twice more efficient in controlling WCR population in fields planted with an EβC-producing maize variety. However, artificial selection for one trait may come at a cost for other important traits such as infectiousness, establishment and/or persistence in the field. Indeed, infectiousness was slightly but significantly reduced in the selected strain. Yet, this apparent cost was largely compensated for by the higher responsiveness to the root signal. Here we show that the selection process had no negative effect on establishment and persistence of field-released EPN. This knowledge, combined with the previously reported results, attest to the feasibility of manipulating key traits to improve the efficacy of beneficial organisms.Key words: entomopathogenic nematodes, tritrophic interactions, artificial selection, biological control, Diabrotica virgifera virgifera, western corn rootworm, persistence, establishmentDiabrotica virgifera virgifera LeConte (Chrysomelidae: Coleptera, western corn rootworm, WCR) is a major well established pest of maize in the American Corn Belt and more recently also in Europe.¹ The larval stages of this beetle can cause significant damages to maize roots, leading to reduction of plant growth, deficiencies in nutrient and water uptake, lodging, increased susceptibility to water stress and reduced grain yield.² This combination of factors result in an estimated loss of one billion US dollars per year in the USA.³ The pest has been introduced in Europe in the early ''90s,⁴ and it is expected that at full establishment the costs resulting from WCR damages will be half a billion Euros.⁵ Several strategies are available to control this soil-dwelling pest, including crop rotation, pesticides and transgenic Bt maize, but WCR can readily evolve resistance to each of these methods.^6–8 This is why efforts have been invested in biological control alternatives.Entomopathogenic nematodes (EPN) show great promise as biological agents against WCR.⁹ Root-produced volatiles appear to play an important role in the recruitment of EPN^10–13 and one such volatile, (E)-β-caryophyllene (EβC), has recently been identified for maize roots¹⁴ and was found to be an ideal below-ground alarm signal.¹⁵ EPN efficacy can be improved by exploiting the ability of WCR-damaged maize roots to emit the attractant.¹⁴ Further studies have shown the importance of choosing the right species of nematodes.¹⁶ Among the EPN species tested against WCR, Heterorhabditis bacteriophora has proven to be one of the most virulent nematodes,¹⁷ but it barely responds to EβC.¹⁶ We therefore recently selected H. bacteriophora for higher responsiveness to EβC.¹⁸ In the field, the selected strain exhibited better abilities to control WCR larvae, but logically only in maize plots with plants that emitted EβC. However, previous studies have shown that enhancing beneficial traits through selective breeding can incur costs and negatively alter other traits in the selected strain.¹⁹ For EPN such trade-offs after selective breeding have also been reported, for instance resulting in reduced storage stability²⁰ or a lower capacity to kill their hosts.²¹ After selection for enhanced responsiveness to EβC response, we observed a small, but significant negative effect on infectiousness of the selected strains. However, this drawback was readily outweighed by the improved ability to locate hosts in the field.¹⁸Not only infectiousness is a crucial trait for the successful use of EPN in biological control: establishment and persistence in the field are of decisive importance as well. These traits vary with EPN species and are determined by biotic factors such as pathogens and predators²² or abiotic factors such as soil type,²³ humidity,²⁴ temperature²⁵ or pH.²⁴ But the main factor that is thought to determine long-term persistence in the field is the presence of available host insects.²⁵ In field trials in Hungary, three EPN species, H. bacteriophora, H. megidis and Steinernema feltiae, were released to test their control potential against WCR. They all persisted at least as long WCR were present in soil, during the same year.²⁶ There was no significant difference between the three species in the establishment or persistence. Yet, independent of timing of application, EPN populations dramatically decreased within five months after application. The authors²⁶ propose that this short persistence is due to the absence of suitable alternative hosts in intensively cultivated crop fields in Europe.To determine if the selection for enhanced responsiveness to EβC went at a cost for establishment and persistence we compared these key traits for the original and the EβC-selected stains. Using a metal auger (2 cm diam.; 20 cm high), 310 soil samples were dug out either two days (establishment) or 28 days (persistence) after EPN application. The soil was placed in plastic boxes (4.5 cm diam.; 60 cm high) and as previously described²⁶ Tenebrio molitor (Coleoptera: Tenebrionidae) larva was placed as bait in the boxes. Presence/absence of EPN was evaluated by visually checking T. molitor larvae for EPN infection. Soil samples from areas where no EPN were applied served as controls. No significant differences were found between the original and selected strain of H. bacteriophora strain (factor “strain”), neither in establishment after two days nor in persistence after 28 days (factor “time”) (Fig. 1, two-way ANOVA, Ftime_1,35 = 2.937, p = 0.097; Fstrain_2,35 = 10.359, p < 0.001; Ftime × strain_2,35 = 1.202, p = 0.315, statistical differences within factors were calculated using a Bonferoni post-hoc test). Hence, the selection of H. bacteriophora for a better response to EβC had no consequence for how the nematodes settled in the experimental fields. Future efforts to improve the effectiveness H. bacteriophora against WCR might also include selection for increased persistence in soil. This would allow lower application rates and could provide growers with an affordable and efficient control strategy against this voracious pest.Open in a separate windowFigure 1Establishment and persistence of the original and a selected strain of H. bacteriophora. The selected strain (squares) established and persisted as well as the original strain (diamonds). The triangles represent control samples from plots where no nematodes were released. Establishment (after two days) and persistence (after 28 days) was equal for both strains. Moreover, the number of soil samples containing EPN after 28 days was not significantly lower than after 2 days, independently of treatment. A few nematodes were detected in the control samples but again no differences over time were detected. Error bars indicate the SEM. Different lower-case letters indicate statistical differences within establishment (after 2 days) or persistence (after 28 days) (p <0.05).So far, manipulation of tritrophic systems in order to improve biological control has been largely theoretical.^27–29 We show here that for EPN this approach is realistic and that their responsiveness to root-produced foraging signals can be enhanced without significant costs for other relevant traits. It has also been shown that the emissions of the signals by the plants can be enhanced.³⁰ Combining these strategies opens new perspectives for the development of ecologically sound strategies in pest management.