Host plant selection and development in Spodoptera exigua: do mother and offspring know best?

We examined the ovipositional preference and larval development of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) on two common hosts in southern California, Chenopodium murale L. (Chenopodiaceae) and Apium graveolens L. (Umbelliferae) to determine if female oviposition preference is correlated with offspring performance. Greenhouse oviposition choice tests indicated that S. exigua oviposit more frequently on C. murale than on A. graveolens. However under laboratory conditions, larvae reared on C. murale had longer development times, lower relative growth rate, and lower survivorship than larvae reared on A. graveolens. larval and pupal masses were significantly greater on A. graveolens than on C. murale. Furthermore, pupal masses were significantly greater for individuals reared on A. graveolens than on C. murale. Because pupal masses and adult fecundity are positively correlated for Spodoptera spp., the fitness of S. exigua on A. graveolens is likely to be substantially higher than its fitness on C. murale. Despite better larval performance on A. graveolens, previous results from choice tests with whole plants and leaf discs indicate that the highly mobile S. exigua larvae strongly prefer C. murale over A. graveolens. Hypotheses attempting to explain this lack of correlation between larval and adult host preference versus development and survival in this system are discussed.     

Evolution of chromosome Y in primates

We have investigated, by fluorescence in situ hybridization (FISH), the cytogenetic evolution of the Y chromosome in primates using 17 yeast artificial chromosomes, representative of the Y-specific euchromatic region of the human chromosome Y. The FISH experiments were performed on great apes (Homo sapiens, Pan troglodytes, Gorilla gorilla and Pongo pygmaeus pygmaeus), and on two Old World monkeys species as an outgroup (Cercopitecidae Macaca fascicularis and Papio anubis). The results showed that this peculiar chromosome has undergone rapid and unconstrained evolution both in sequence content and organization. Received: 16 January 1998; in revised form: 29 May 1998 / Accepted: 24 June 1998     

Spatial synchrony of planthopper species with contrasting outbreak behaviour

1 We studied the synchrony of two sympatric delphacids species with different outbreak behaviours over a range of 250 km in Argentina. 2 The spatial synchrony in the dynamics of Delphacodes kuscheli and Toya propinqua was quantified by collecting individuals of both species simultaneously at three sampling heights: ground, 1.5 m and 6 m above the ground. Synchrony between paired sampling sites separated by increasing distances was estimated using a nonparametric covariance function. 3 A significant difference was found between the spatial synchrony of the species studied. Delphacodes kuscheli individuals collected at 6 m above the ground showed consistent spatial synchrony over long distances with correlation values declining by 40%. Population dynamics showed declining synchrony as site separation increased. Toya propinqua populations did not show this pattern. This species had a lower mean regional synchrony at at 6 m above the ground, but their ground height synchrony was greater than that observed for D. kuscheli. 4 One possible synchronizing mechanism is seasonality and the dispersal strategies of each species. The main host plants of D. kuscheli are winter cereals sown as pasture for cattle grazing and the synchrony of the crop may affect the general pattern of dispersing individuals of this species. The lack of synchrony observed in T. propinqua populations was probably due to the wider host range of this species.     

Modulation of lyso-platelet activating factor:acetyl-CoA acetyltransferase from rat splenic microsomes. The role of cyclic AMP-dependent protein kinase

Incubation of rat splenic microsomes with the catalytic subunit of cyclic AMP-dependent protein kinase in the presence of Mg-ATP stimulated 2-3-fold lyso-platelet-activating factor:acetyltransferase activity. This activation was due to an increase in the $\text{V}{}_{\mathrm{<mtext>max</mtext>}}$ of the acetylation reaction, whereas the $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ for acetyl-CoA was not affected. The ATP derivative, AMPPNP, could not replace ATP and preincubation of the microsomes with the heat-stable inhibitor of protein kinase prevented the activation by Mg-ATP obtained in the presence of the protein kinase. Activation of the acetylation reaction by the protein kinase was reversible. Evidence is provided that the reversal of activation is due to dephosphorylation of the enzyme. These data provide evidence that in vitro lyso-platelet-activating factor:acetyltransferase from splenic microsomes is regulated by phosphorylation.     

The PGE2/IL-10 Axis Determines Susceptibility of B-1 Cell-Derived Phagocytes (B-1CDP) to Leishmania major Infection

B-1 cells can be differentiated from B-2 cells because they are predominantly located in the peritoneal and pleural cavities and have distinct phenotypic patterns and activation properties. A mononuclear phagocyte derived from B-1 cells (B-1CDP) has been described. As the B-1CDP cells migrate to inflammatory/infectious sites and exhibit phagocytic capacity, the microbicidal ability of these cells was investigated using the Leishmania major infection model in vitro. The data obtained in this study demonstrate that B-1CDP cells are more susceptible to infection than peritoneal macrophages, since B-1CDP cells have a higher number of intracellular amastigotes forms and consequently release a larger number of promastigotes. Exacerbated infection by L. major required lipid bodies/PGE₂ and IL-10 by B-1CDP cells. Both infection and the production of IL-10 were decreased when PGE₂ production was blocked by NSAIDs. The involvement of IL-10 in this mechanism was confirmed, since B-1CDP cells from IL-10 KO mice are more competent to control L. major infection than cells from wild type mice. These findings further characterize the B-1CDP cells as an important mononuclear phagocyte that plays a previously unrecognized role in host responses to L. major infection, most likely via PGE₂-driven production of IL-10.     

Alphavirus Replicon DNA Expressing HIV Antigens Is an Excellent Prime for Boosting with Recombinant Modified Vaccinia Ankara (MVA) or with HIV gp140 Protein Antigen

Vaccination with DNA is an attractive strategy for induction of pathogen-specific T cells and antibodies. Studies in humans have shown that DNA vaccines are safe, but their immunogenicity needs further improvement. As a step towards this goal, we have previously demonstrated that immunogenicity is increased with the use of an alphavirus DNA-launched replicon (DREP) vector compared to conventional DNA vaccines. In this study, we investigated the effect of varying the dose and number of administrations of DREP when given as a prime prior to a heterologous boost with poxvirus vector (MVA) and/or HIV gp140 protein formulated in glucopyranosyl lipid A (GLA-AF) adjuvant. The DREP and MVA vaccine constructs encoded Env and a Gag-Pol-Nef fusion protein from HIV clade C. One to three administrations of 0.2 μg DREP induced lower HIV-specific T cell and IgG responses than the equivalent number of immunizations with 10 μg DREP. However, the two doses were equally efficient as a priming component in a heterologous prime-boost regimen. The magnitude of immune responses depended on the number of priming immunizations rather than the dose. A single low dose of DREP prior to a heterologous boost resulted in greatly increased immune responses compared to MVA or protein antigen alone, demonstrating that a mere 0.2 μg DREP was sufficient for priming immune responses. Following a DREP prime, T cell responses were expanded greatly by an MVA boost, and IgG responses were also expanded when boosted with protein antigen. When MVA and protein were administered simultaneously following multiple DREP primes, responses were slightly compromised compared to administering them sequentially. In conclusion, we have demonstrated efficient priming of HIV-specific T cell and IgG responses with a low dose of DREP, and shown that the priming effect depends on number of primes administered rather than dose.     

Enhanced Amphiphilic Profile of a Short β-Stranded Peptide Improves Its Antimicrobial Activity

SB056 is a novel semi-synthetic antimicrobial peptide with a dimeric dendrimer scaffold. Active against both Gram-negative and -positive bacteria, its mechanism has been attributed to a disruption of bacterial membranes. The branched peptide was shown to assume a β-stranded conformation in a lipidic environment. Here, we report on a rational modification of the original, empirically derived linear peptide sequence [WKKIRVRLSA-NH₂, SB056-lin]. We interchanged the first two residues [KWKIRVRLSA-NH₂, β-SB056-lin] to enhance the amphipathic profile, in the hope that a more regular β-strand would lead to a better antimicrobial performance. MIC values confirmed that an enhanced amphiphilic profile indeed significantly increases activity against both Gram-positive and -negative strains. The membrane binding affinity of both peptides, measured by tryptophan fluorescence, increased with an increasing ratio of negatively charged/zwitterionic lipids. Remarkably, β-SB056-lin showed considerable binding even to purely zwitterionic membranes, unlike the original sequence, indicating that besides electrostatic attraction also the amphipathicity of the peptide structure plays a fundamental role in binding, by stabilizing the bound state. Synchrotron radiation circular dichroism and solid-state ¹⁹F-NMR were used to characterize and compare the conformation and mobility of the membrane bound peptides. Both SB056-lin and β-SB056-lin adopt a β-stranded conformation upon binding POPC vesicles, but the former maintains an intrinsic structural disorder that also affects its aggregation tendency. Upon introducing some anionic POPG into the POPC matrix, the sequence-optimized β-SB056-lin forms well-ordered β-strands once electro-neutrality is approached, and it aggregates into more extended β-sheets as the concentration of anionic lipids in the bilayer is raised. The enhanced antimicrobial activity of the analogue correlates with the formation of these extended β-sheets, which also leads to a dramatic alteration of membrane integrity as shown by ³¹P-NMR. These findings are generally relevant for the design and optimization of other membrane-active antimicrobial peptides that can fold into amphipathic β-strands.     

Survey of Sand Flies (Diptera: Psychodidae) in an Environmentally Protected Area in Brazil

Brazil is one of the most important endemic areas for leishmaniasis worldwide. Protected areas that are tourist attractions likely present an important risk of transmission of cutaneous leishmaniasis (CL). Furthermore, with the geographical expansion of visceral leishmaniasis (VL), several studies have recorded the occurrence of its vector, Lutzomyia longipalpis, and cases of human and canine VL in such tourist areas. The Parque Estadual do Sumidouro is an environmentally protected area located in the Brazilian Cerrado biome and in an important area endemic for leishmaniasis in the state of Minas Gerais. The purpose of this study was to monitor the sand fly fauna in areas of tourist activity in the park. Sampling was performed every month, from September 2011 to August 2013, using CDC light traps at six sites of differing environmental characteristics. Sampled specimens were identified following Galati (2003), and females were submitted to molecular techniques for the detection and identification of Leishmania DNA. A total of 4,675 sand fly specimens of 25 species belonging to nine genera were collected. The most abundant species were Micropygomyia quinquefer, Lutzomyia renei and Pintomyia pessoai, although only Pi. pessoai is implicated in the transmission of Leishmania braziliensis. The species accumulation curve reached saturation on the 16th sampling event. Species richness, diversity and evenness differed among the sampled areas. The seasonal curve was not determined by a single unique species, and no single species was the most abundant in all environments sampled. The main vector of Leishmania (Leishmania) infantum, Lutzomyia longipalpis, accounted for only 5.35% of the specimens collected. Proven or suspected vectors of Leishmania (Viannia) braziliensis were recorded, and one female of the cortellezzii complex tested positive for Le. braziliensis DNA. Even with a low infection rate (0.62%), these data indicate the circulation of the parasite and reinforce the need for entomological and epidemiological surveillance in the park and its surroundings.