Identifying the predator complex of <Emphasis Type="Italic">Homalodisca vitripennis</Emphasis> (Hemiptera: Cicadellidae): a comparative study of the efficacy of an ELISA and PCR gut content assay

A growing number of ecologists are using molecular gut content assays to qualitatively measure predation. The two most popular gut content assays are immunoassays employing pest-specific monoclonal antibodies (mAb) and polymerase chain reaction (PCR) assays employing pest-specific DNA. Here, we present results from the first study to simultaneously use both methods to identify predators of the glassy winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae). A total of 1,229 arthropod predators, representing 30 taxa, were collected from urban landscapes in central California and assayed first by means of enzyme-linked immunosorbent assay (ELISA) using a GWSS egg-specific mAb and then by PCR using a GWSS-specific DNA marker that amplifies a 197-base pair fragment of its cytochrome oxidase gene (subunit I). The gut content analyses revealed that GWSS remains were present in 15.5% of the predators examined, with 18% of the spiders and 11% of the insect predators testing positive. Common spider predators included members of the Salticidae, Clubionidae, Anyphaenidae, Miturgidae, and Corinnidae families. Common insect predators included lacewings (Neuroptera: Chrysopidae), praying mantis (Mantodea: Mantidae), ants (Hymenoptera: Formicidae), assassin bugs (Hemiptera: Reduviidae), and damsel bugs (Hemiptera: Nabidae). Comparison of the two assays indicated that they were not equally effective at detecting GWSS remains in predator guts. The advantages of combining the attributes of both types of assays to more precisely assess field predation and the pros and cons of each assay for mass-screening predators are discussed.     

HDL and electronegative LDL exchange anti- and pro-inflammatory properties

Electronegative LDL [LDL(–)] is a minor modified LDL subfraction present in blood with inflammatory effects. One of the antiatherogenic properties of HDL is the inhibition of the deleterious effects of in vitro modified LDL. However, the effect of HDL on the inflammatory activity of LDL(–) isolated from plasma is unknown. We aimed to assess the putative protective role of HDL against the cytokine released induced in monocytes by LDL(–). Our results showed that LDL(–) cytokine release was inhibited when LDL(–) was coincubated with HDL and human monocytes and also when LDL(–) was preincubated with HDL and reisolated prior to cell incubation. The addition of apoliprotein (apo)AI instead of HDL reproduced the protective behavior of HDL. HDL preincubated with LDL(–) promoted greater cytokine release than native HDL. Incubation of LDL(–) with HDL decreased the electronegative charge, phospholipase C-like activity, susceptibility to aggregation and nonesterified fatty acid (NEFA) content of LDL(–), whereas these properties increased in HDL. NEFA content in LDL appeared to be related to cytokine production because NEFA-enriched LDL induced cytokine release. HDL, at least in part through apoAI, inhibits phospholipase-C activity and cytokine release in monocytes, thereby counteracting the inflammatory effect of LDL(–). In turn, HDL acquires these properties and becomes inflammatory.     

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) decoy receptor TRAIL-R3 is up-regulated by p53 in breast tumor cells through a mechanism involving an intronic p53-binding site

Tumor necrosis factor-related apoptosis-inducing ligand receptor 3 (TRAIL-R3) is a decoy receptor for TRAIL, a member of the tumor necrosis factor family. In several cell types decoy receptors inhibit TRAIL-induced apoptosis by binding TRAIL and thus preventing its binding to proapoptotic TRAIL receptors. We studied the regulation of TRAIL-R3 gene expression in breast tumor cells treated with the genotoxic drug doxorubicin (DXR). The breast tumor cell line MCF-7 (p53 wild type) responded to DXR with a marked elevation of TRAIL-R3 expression at the mRNA, total protein, and cell surface levels. In contrast, in EVSA-T cells (p53 mutant) DXR did not induce increased expression of TRAIL-R3. In MCF-7 cells overexpressing the human papillomavirus protein E6, which causes p53 degradation, DXR-induced TRAIL-R3 expression was notably reduced. Furthermore, in MCF-7 cells overexpressing a temperature-sensitive p53 mutant (Val135), shifting the cultures to the permissive temperature was sufficient to induce the expression of TRAIL-R3. We also cloned and characterized a p53 consensus element located within the first intron of the human TRAIL-R3 gene. This element binds p53 and confers responsiveness to genotoxic damage to constructs of the TRAIL-R3 promoter in transient transfection experiments. Our results indicate that genotoxic treatments such as DXR, frequently used in cancer therapy, may also induce genes such as TRAIL-R3 that potentially have antiapoptotic actions and thus interfere with the TRAIL signaling system. This is particularly important in view of the proposed use of TRAIL in antitumor therapy.     

Helicobacter pylori-specific antibodies impair the development of gastritis, facilitate bacterial colonization, and counteract resistance against infection

In recent years, Abs have been considered a correlate rather than an effector of resistance against Helicobacter pylori infection. However, it is still poorly understood to what extent Ab production correlates with gastric immunopathology. Here we report that Abs not only are dispensable for protection, but they are detrimental to elimination of the bacteria and appear to impair gastric inflammatory responses. We found that the initial colonization with H. pylori bacteria was normal in the B cell-deficient (microMT) mice, whereas at later times (>8 wk) most of the bacteria were cleared, concomitant with the development of severe gastritis. In contrast, wild-type (WT) mice exhibited extensive bacterial colonization and only mild gastric inflammation, even at 16 wk after inoculation. Oral immunizations with H. pylori lysate and cholera toxin adjuvant stimulated comparable levels of protection in microMT and WT mice. The level of protection in both strains correlated well with the severity of the postimmunization gastritis. Thus, T cells were responsible for the gastritis, whereas Abs, including potentially host cell cross-reactive Abs, were not involved in causing the gastritis. The T cells in micro MT and WT mice produced high and comparable levels of IFN-gamma to recall Ag at 2 and after 8 wk, whereas IL-4 was detected after 8 wk only, indicating that Th1 activity dominated the early phase of protection, whereas later a mixed Th1 and Th2 activity was seen.     

The development of a continuous isothermal titration calorimetric method for equilibrium studies

A continuous isothermal titration calorimetry (cITC) method for microcalorimeters has been developed. The method is based on continuous slow injection of a titrant into the calorimetric vessel. The experimental time for a cITC binding experiment is 12-20 min and the number of data points obtained is on the order of 1000. This gives an advantage over classical isothermal titration calorimetry (ITC) binding experiments that need 60-180 min to generate 20-30 data points. The method was validated using two types of calorimeters, which differ in calorimetric principle, geometry, stirring, and way of delivering the titrant into the calorimetric vessel. Two different experimental systems were used to validate the method: the binding of Ba(2+) to 18-crown-6 and the binding of cytidine 2'-monophosphate to RNAse A. Both systems are used as standard test systems for titration calorimetry. Computer simulations show that the dynamic range for determination of equilibrium constants can be increased by three orders of magnitude compared to that of classical ITC, making it possible to determine high affinities. Simulations also show an improved possibility to elucidate the actual binding model from cITC data. The simulated data demonstrate that cITC makes it easier to discriminate between different thermodynamic binding models due to the higher density of data points obtained from one experiment.     

Pseudomonas aeruginosa flagellin and alginate elicit very distinct gene expression patterns in airway epithelial cells: implications for cystic fibrosis disease

Infection with the opportunistic pathogen Pseudomonas aeruginosa remains a major health concern. Two P. aeruginosa phenotypes relevant in human disease include motility and mucoidy. Motility is characterized by the presence of flagella and is essential in the establishment of acute infections, while mucoidy, defined by the production of the exopolysaccharide alginate, is critical in the development of chronic infections, such as the infections seen in cystic fibrosis patients. Indeed, chronic infection of the lung by mucoid P. aeruginosa is a major cause of morbidity and mortality in cystic fibrosis patients. We have used Calu-3 human airway epithelial cells to investigate global responses to infection with motile and mucoid P. aeruginosa. The response of airway epithelial cells to exposure to P. aeruginosa motile strains is characterized by a specific increase in gene expression in pathways controlling inflammation and host defense. By contrast, the response of airway epithelia to the stimuli presented by mucoid P. aeruginosa is not proinflammatory and, hence, may not be conducive to the effective elimination of the pathogen. The pattern of gene expression directed by flagellin, but not alginate, includes innate host defense genes, proinflammatory cytokines, and chemokines. By contrast, infection with alginate-producing P. aeruginosa results in an overall attenuation of host responses and an antiapoptotic effect.     

Antibody response to Candida albicans cell wall antigens

The cell wall of Candida albicans is not only the structure where many essential biological functions reside but is also a significant source of candidal antigens. The major cell wall components that elicit a response from the host immune system are proteins and glycoproteins, the latter being predominantly mannoproteins. Both carbohydrate and protein moieties are able to trigger immune responses. Proteins and glycoproteins exposed at the most external layers of the wall structure are involved in several types of interactions of fungal cells with the exocellular environment. Thus, coating of fungal cells with host antibodies has the potential to profoundly influence the host-parasite interaction by affecting antibody-mediated functions such as opsonin-enhanced phagocytosis and blocking the binding activity of fungal adhesins to host ligands. In this review we examine various members of the protein and glycoprotein fraction of the C. albicans cell wall that elicit an antibody response in vivo. Some of the studies demonstrate that certain cell wall antigens and anti-cell wall antibodies may be the basis for developing specific and sensitive serologic tests for the diagnosis of candidiasis, particularly the disseminated form. In addition, recent studies have focused on the potential of antibodies against the cell wall protein determinants in protecting the host against infection. Hence, a better understanding of the humoral response triggered by the cell wall antigens of C. albicans may provide the basis for the development of (i) effective procedures for the serodiagnosis of disseminated candidiasis, and (ii) novel prophylactic (vaccination) and therapeutic strategies to control this type of infections.     

Nocturnal vision and landmark orientation in a tropical halictid bee

BACKGROUND: Some bees and wasps have evolved nocturnal behavior, presumably to exploit night-flowering plants or avoid predators. Like their day-active relatives, they have apposition compound eyes, a design usually found in diurnal insects. The insensitive optics of apposition eyes are not well suited for nocturnal vision. How well then do nocturnal bees and wasps see? What optical and neural adaptations have they evolved for nocturnal vision? RESULTS: We studied female tropical nocturnal sweat bees (Megalopta genalis) and discovered that they are able to learn landmarks around their nest entrance prior to nocturnal foraging trips and to use them to locate the nest upon return. The morphology and optics of the eye, and the physiological properties of the photoreceptors, have evolved to give Megalopta's eyes almost 30 times greater sensitivity to light than the eyes of diurnal worker honeybees, but this alone does not explain their nocturnal visual behavior. This implies that sensitivity is improved by a strategy of photon summation in time and in space, the latter of which requires the presence of specialized cells that laterally connect ommatidia into groups. First-order interneurons, with significantly wider lateral branching than those found in diurnal bees, have been identified in the first optic ganglion (the lamina ganglionaris) of Megalopta's optic lobe. We believe that these cells have the potential to mediate spatial summation. CONCLUSIONS: Despite the scarcity of photons, Megalopta is able to visually orient to landmarks at night in a dark forest understory, an ability permitted by unusually sensitive apposition eyes and neural photon summation.