Effects of Habitat Fragmentation on Abundance, Larval Food and Parasitism of a Spider-Hunting Wasp.

Habitat fragmentation strongly affects species distribution and abundance. However, mechanisms underlying fragmentation effects often remain unresolved. Potential mechanisms are (1) reduced dispersal of a species or (2) altered species interactions in fragmented landscapes. We studied if abundance of the spider-hunting and cavity-nesting wasp Trypoxylon figulus Linnaeus (Hymenoptera: Crabronidae) is affected by fragmentation, and then tested for any effect of larval food (bottom up regulation) and parasitism (top down regulation). Trap nests of T. figulus were studied in 30 agricultural landscapes of the Swiss Plateau. The sites varied in the level of isolation from forest (adjacent, in the open landscape but connected, isolated) and in the amount of woody habitat (from 4 % to 74 %). We recorded wasp abundance (number of occupied reed tubes), determined parasitism of brood cells and analysed the diversity and abundance of spiders that were deposited as larval food. Abundances of T. figulus were negatively related to forest cover in the landscape. In addition, T. figulus abundances were highest at forest edges, reduced by 33.1% in connected sites and by 79.4% in isolated sites. The mean number of spiders per brood cell was lowest in isolated sites. Nevertheless, structural equation modelling revealed that this did not directly determine wasp abundance. Parasitism was neither related to the amount of woody habitat nor to isolation and did not change with host density. Therefore, our study showed that the abundance of T. figulus cannot be fully explained by the studied trophic interactions. Further factors, such as dispersal and habitat preference, seem to play a role in the population dynamics of this widespread secondary carnivore in agricultural landscapes.

Stage-dependent strategies of host invasion in the egg-larval parasitoid Chelonus inanitus.

Chelonus inanitus (Braconidae) is a solitary egg-larval parasitoid which lays its eggs into eggs of Spodoptera littoralis (Noctuidae); the parasitoid larva then develops in the haemocoel of the host larva. Host embryonic development lasts approx. 3.5 days while parasitoid embryonic development lasts approx. 16 h. All stages of host eggs can be successfully parasitized, and we show here that either the parasitoid larva or the wasp assures that the larva eventually is located in the host's haemocoel. (1) When freshly laid eggs, up to almost 1-day-old, are parasitized, the parasitoid hatches while still in the yolk and enters the host either after waiting or immediately through the dorsal opening. (2) When 1-2-day-old eggs are parasitized, the host embryo has accomplished final dorsal closure and is covered by an embryonic cuticle when the parasitoid hatches; in this case the parasitoid larva bores with its moving abdominal tip into the host. (3) When 2.5-3.5-day-old eggs are parasitized, the wasp oviposits directly into the haemocoel of the host embryo; from day 2 to 2.5 the embryo is still very small and the wasps, after probing, often restrain from oviposition for a few hours.

The geomorphology and morphometry of the banded terrain in Hellas basin, Mars

Hellas basin is a large impact basin situated in the southern highlands of Mars. The north-western part of the basin has the lowest elevation (-7.5 km) on the planet and contains a possibly unique terrain type, which we informally call “banded terrain”. The banded terrain is made up of smooth-looking banded deposits that display signs of viscous behavior and a paucity of superimposed impact craters. In this study, we use newly acquired high spatial resolution images from the High Resolution Imaging Science Experiment (HiRISE) in addition to existing datasets to characterize the geomorphology, the morphometry and the architecture of the banded terrain. The banded terrain is generally confined to the NW edge of the Alpheus Colles plateau. The individual bands are ~3–15 km-long, ~0.3 km-wide and are separated by narrow inter-band depressions, which are ~65 m-wide and ~10 m-deep. The bands display several morphologies that vary from linear to concentric forms. Morphometric analysis reveals that the slopes along a given linear or lobate band ranges from 0.5° to 15° (average~6°), whereas the concentric bands are located on flatter terrain (average slope~2–3°). Crater-size frequency analysis yields an Amazonian-Hesperian boundary crater retention age for the terrain (~3 Gyr), which together, with the presence of very few degraded craters, either implies a recent emplacement, resurfacing, or intense erosion. The apparent sensitivity to local topography and preference for concentrating in localized depressions is compatible with deformation as a viscous fluid. In addition, the bands display clear signs of degradation and slumping at their margins along with a suite of other features that include fractured mounds, polygonal cracks at variable size-scales, and knobby/hummocky textures. Together, these features suggest an ice-rich composition for at least the upper layers of the terrain, which is currently being heavily modified through loss of ice and intense weathering, possibly by wind.

A collaborative study on larval excretory/secretory antigens of Toxocara canis for the immunodiagnosis of human toxocariasis with ELISA.

Two batches of excretory/secretory (E/S) antigens from second stage larvae of Toxocara canis maintained in vitro were prepared independently in two different laboratories (Zürich and Basel) and analysed in order to obtain information for future efforts to standardize the enzyme-linked immunosorbent assay (ELISA) used for the serodiagnosis of human toxocariasis. SDS-PAGE and "Western-blotting" revealed at least 10 different antigenic components common to the two antigen preparations. However, distinct qualitative and quantitative differences among the two E/S-antigens were observed, since one antigen had a more complex composition than the other. Despite these differences, an accordance of serodiagnosis was obtained in 80% of 25 sera from patients with suspected Toxocara infection tested independently in two different ELISA systems (Basel and Zürich) with the corresponding E/S-antigens. The specificity was 93% as determined (BS-antigen, BS-ELISA) by testing 46 out of 3396 sera from patients with parasitologically proven extra-intestinal helminthic infections. Cross-reactions occurred mainly with sera from patients infected with filariae (5 from 13 cases) exhibiting very high extinction values in their homologous ELISA-system. The reproducibility (intra- and inter-test variations) of two ELISA systems using the corresponding E/S-antigens varied from 5-15%. The results demonstrate that T. canis E/S-antigens may well be applicable for standardization of the ELISA used for the serodiagnosis of human toxocariasis.

3D morphometry using automated aortic segmentation in native MR angiography: an alternative to contrast enhanced MRA?

INTRODUCTION Native-MR angiography (N-MRA) is considered an imaging alternative to contrast enhanced MR angiography (CE-MRA) for patients with renal insufficiency. Lower intraluminal contrast in N-MRA often leads to failure of the segmentation process in commercial algorithms. This study introduces an in-house 3D model-based segmentation approach used to compare both sequences by automatic 3D lumen segmentation, allowing for evaluation of differences of aortic lumen diameters as well as differences in length comparing both acquisition techniques at every possible location. METHODS AND MATERIALS Sixteen healthy volunteers underwent 1.5-T-MR Angiography (MRA). For each volunteer, two different MR sequences were performed, CE-MRA: gradient echo Turbo FLASH sequence and N-MRA: respiratory-and-cardiac-gated, T2-weighted 3D SSFP. Datasets were segmented using a 3D model-based ellipse-fitting approach with a single seed point placed manually above the celiac trunk. The segmented volumes were manually cropped from left subclavian artery to celiac trunk to avoid error due to side branches. Diameters, volumes and centerline length were computed for intraindividual comparison. For statistical analysis the Wilcoxon-Signed-Ranked-Test was used. RESULTS Average centerline length obtained based on N-MRA was 239.0±23.4 mm compared to 238.6±23.5 mm for CE-MRA without significant difference (P=0.877). Average maximum diameter obtained based on N-MRA was 25.7±3.3 mm compared to 24.1±3.2 mm for CE-MRA (P<0.001). In agreement with the difference in diameters, volumes obtained based on N-MRA (100.1±35.4 cm(3)) were consistently and significantly larger compared to CE-MRA (89.2±30.0 cm(3)) (P<0.001). CONCLUSIONS 3D morphometry shows highly similar centerline lengths for N-MRA and CE-MRA, but systematically higher diameters and volumes for N-MRA.

Presence of polydnavirus transcripts in an egg-larval parasitoid and its lepidopterous host

The parasitoid Chelonus inanitus (Braconidae, Hymenoptera) oviposits into eggs of Spodoptera littoralis (Noctuidae, Lepidoptera) and, along with the egg, also injects polydnaviruses and venom, which are prerequisites for successful parasitoid development. The parasitoid larva develops within the embryonic and larval stages of the host, which enters metamorphosis precociously and arrests development in the prepupal stage. Polydnaviruses are responsible for the developmental arrest and interfere with the host's endocrine system in the last larval instar. Polydnaviruses have a segmented genome and are transmitted as a provirus integrated in the wasp's genome. Virions are only formed in female wasps and no virus replication is seen in the parasitized host. Here it is shown that very small amounts of viral transcripts were found in parasitized eggs and early larval instars of S. littoralis. Later on, transcript quantities increased and were highest in the late last larval instar for two of the three viral segments tested and in the penultimate to early last larval instar for the third segment. These are the first data on the occurrence of viral transcripts in the host of an egg-larval parasitoid and they are different from data reported for hosts of larval parasitoids, where transcript levels are already high shortly after parasitization. The analysis of three open reading frames by RT-PCR revealed viral transcripts in parasitized S. littoralis and in female pupae of C. inanitus, indicating the absence of host specificity. For one open reading frame, transcripts were also seen in male pupae, suggesting transcription from integrated viral DNA.

Aortic morphometry at endograft position as assessed by 3D image analysis affects risk of type I endoleak formation after TEVAR

PURPOSE The purpose of this study was to identify morphologic factors affecting type I endoleak formation and bird-beak configuration after thoracic endovascular aortic repair (TEVAR). METHODS Computed tomography (CT) data of 57 patients (40 males; median age, 66 years) undergoing TEVAR for thoracic aortic aneurysm (34 TAA, 19 TAAA) or penetrating aortic ulcer (n = 4) between 2001 and 2010 were retrospectively reviewed. In 28 patients, the Gore TAG® stent-graft was used, followed by the Medtronic Valiant® in 16 cases, the Medtronic Talent® in 8, and the Cook Zenith® in 5 cases. Proximal landing zone (PLZ) was in zone 1 in 13, zone 2 in 13, zone 3 in 23, and zone 4 in 8 patients. In 14 patients (25%), the procedure was urgent or emergent. In each case, pre- and postoperative CT angiography was analyzed using a dedicated image processing workstation and complimentary in-house developed software based on a 3D cylindrical intensity model to calculate aortic arch angulation and conicity of the landing zones (LZ). RESULTS Primary type Ia endoleak rate was 12% (7/57) and subsequent re-intervention rate was 86% (6/7). Left subclavian artery (LSA) coverage (p = 0.036) and conicity of the PLZ (5.9 vs. 2.6 mm; p = 0.016) were significantly associated with an increased type Ia endoleak rate. Bird-beak configuration was observed in 16 patients (28%) and was associated with a smaller radius of the aortic arch curvature (42 vs. 65 mm; p = 0.049). Type Ia endoleak was not associated with a bird-beak configuration (p = 0.388). Primary type Ib endoleak rate was 7% (4/57) and subsequent re-intervention rate was 100%. Conicity of the distal LZ was associated with an increased type Ib endoleak rate (8.3 vs. 2.6 mm; p = 0.038). CONCLUSIONS CT-based 3D aortic morphometry helps to identify risk factors of type I endoleak formation and bird-beak configuration during TEVAR. These factors were LSA coverage and conicity within the landing zones for type I endoleak formation and steep aortic angulation for bird-beak configuration.

Susceptibility versus resistance in alveolar echinococcosis (larval infection with Echinococcus multilocularis).

Epidemiological studies have demonstrated that the majority of human individuals exposed to infection with Echinococcus spp. eggs exhibit resistance to disease as shown by either seroconversion to parasite--specific antigens, and/or the presence of 'dying out' or 'aborted' metacestodes, not including hereby those individuals who putatively got infected but did not seroconvert and who subsequently allowed no development of the pathogen. For those individuals where infection leads to disease, the developing parasite is partially controlled by host immunity. In infected humans, the type of immune response developed by the host accounts for the subsequent trichotomy concerning the parasite development: (i) seroconversion proving infection, but lack of any hepatic lesion indicating the failure of the parasite to establish and further develop within the liver; or resistance as shown by the presence of fully calcified lesions; (ii) controlled susceptibility as found in the "conventional" alveolar echinococcosis (AE) patients who experience clinical signs and symptoms approximately 5-15 years after infection, and (iii) uncontrolled hyperproliferation of the metacestode due to an impaired immune response (AIDS or other immunodeficiencies). Immunomodulation of host immunity toward anergy seems to be triggered by parasite metabolites. Beside immunomodulating IL-10, TGFβ-driven regulatory T cells have been shown to play a crucial role in the parasite-modulated progressive course of AE. A novel CD4+CD25+ Treg effector molecule FGL2 recently yielded new insight into the tolerance process in Echinococcus multilocularis infection.

Immunoregulation in larval Echinococcus multilocularis infection.

Alveolar echinococcosis (AE) is a clinically very severe zoonotic helminthic disease, characterized by a chronic progressive hepatic damage caused by the continuous proliferation of the larval stage (metacestode) of Echinococcus multilocularis. The proliferative potential of the parasite metacestode tissue is dependent on the nature/function of the periparasitic immune-mediated processes of the host. Immune tolerance and/or down-regulation of immunity are a marked characteristic increasingly observed when disease develops towards its chronic (late) stage of infection. In this context, explorative studies have clearly shown that T regulatory (Treg) cells play an important role in modulating and orchestrating inflammatory/immune reactions in AE, yielding a largely Th2-biased response, and finally allowing thus long-term parasite survival, proliferation and maturation. AE is fatal if not treated appropriately, but the current benzimidazole chemotherapy is far from optimal, and novel options for control are needed. Future research should focus on the elucidation of the crucial immunological events that lead to anergy in AE, and focus on providing a scientific basis for the development of novel and more effective immunotherapeutical options to support cure AE by abrogating anergy, anticipating also that a combination of immuno- and chemotherapy could provide a synergistic therapeutical effect.

Host insulin stimulates Echinococcus multilocularis insulin signalling pathways and larval development.

BACKGROUND The metacestode of the tapeworm Echinococcus multilocularis is the causative agent of alveolar echinococcosis, a lethal zoonosis. Infections are initiated through establishment of parasite larvae within the intermediate host's liver, where high concentrations of insulin are present, followed by tumour-like growth of the metacestode in host organs. The molecular mechanisms determining the organ tropism of E. multilocularis or the influences of host hormones on parasite proliferation are poorly understood. RESULTS Using in vitro cultivation systems for parasite larvae we show that physiological concentrations (10 nM) of human insulin significantly stimulate the formation of metacestode larvae from parasite stem cells and promote asexual growth of the metacestode. Addition of human insulin to parasite larvae led to increased glucose uptake and enhanced phosphorylation of Echinococcus insulin signalling components, including an insulin receptor-like kinase, EmIR1, for which we demonstrate predominant expression in the parasite's glycogen storage cells. We also characterized a second insulin receptor family member, EmIR2, and demonstrated interaction of its ligand binding domain with human insulin in the yeast two-hybrid system. Addition of an insulin receptor inhibitor resulted in metacestode killing, prevented metacestode development from parasite stem cells, and impaired the activation of insulin signalling pathways through host insulin. CONCLUSIONS Our data indicate that host insulin acts as a stimulant for parasite development within the host liver and that E. multilocularis senses the host hormone through an evolutionarily conserved insulin signalling pathway. Hormonal host-parasite cross-communication, facilitated by the relatively close phylogenetic relationship between E. multilocularis and its mammalian hosts, thus appears to be important in the pathology of alveolar echinococcosis. This contributes to a closer understanding of organ tropism and parasite persistence in larval cestode infections. Furthermore, our data show that Echinococcus insulin signalling pathways are promising targets for the development of novel drugs.

Prospective longitudinal voxel-based morphometry study of major depressive disorder in young individuals at high familial risk

BACKGROUND Previous neuroimaging studies indicate abnormalities in cortico-limbic circuitry in mood disorder. Here we employ prospective longitudinal voxel-based morphometry to examine the trajectory of these abnormalities during early stages of illness development. METHOD Unaffected individuals (16-25 years) at high and low familial risk of mood disorder underwent structural brain imaging on two occasions 2 years apart. Further clinical assessment was conducted 2 years after the second scan (time 3). Clinical outcome data at time 3 was used to categorize individuals: (i) healthy controls ('low risk', n = 48); (ii) high-risk individuals who remained well (HR well, n = 53); and (iii) high-risk individuals who developed a major depressive disorder (HR MDD, n = 30). Groups were compared using longitudinal voxel-based morphometry. We also examined whether progress to illness was associated with changes in other potential risk markers (personality traits, symptoms scores and baseline measures of childhood trauma), and whether any changes in brain structure could be indexed using these measures. RESULTS Significant decreases in right amygdala grey matter were found in HR MDD v. controls (p = 0.001) and v. HR well (p = 0.005). This structural change was not related to measures of childhood trauma, symptom severity or measures of sub-diagnostic anxiety, neuroticism or extraversion, although cross-sectionally these measures significantly differentiated the groups at baseline. CONCLUSIONS These longitudinal findings implicate structural amygdala changes in the neurobiology of mood disorder. They also provide a potential biomarker for risk stratification capturing additional information beyond clinically ascertained measures.