Postembryonic development of the unique antenna of Mantophasmatodea (Insecta)

The postembryonic antennal development and life cycle of a member of the insect order Mantophasmatodea (Lobatophasma redelinghuysense) was investigated using a series of annulus counts and a time sequence of head capsule measurements. The life cycle comprised six instars. Females achieved significantly larger head capsules from instar 2 onwards, resulting in adult females having a larger mean head capsule diameter (2.58 mm) than males (2.27 mm). Antennae of first instar larvae comprised a smooth four-segmented basiflagellum and a seven-segmented, sensilla-rich distiflagellum. Lengthening of the basiflagellum was achieved by the addition of two annuli per moult, generated by division of the basal annulus (meriston). Annulus number and the unique annulation pattern of the distiflagellum remained constant until adulthood. The segmentation pattern of adult antennae (comprising a basiflagellum and a distiflagellum of 14 and seven annuli respectively) and mode of antennal elongation was consistent for all 11 species examined. Subdivisions in basiflagellar annuli were observed in adults of all species examined, although they are not considered to be true annular divisions. The structure of the mantophasmatodean antenna appears to be autapomorphic within Insecta, bearing little resemblance to that of Grylloblattodea, Dictyoptera or Phasmatodea, all putative sister groups of the Mantophasmatodea. However, the mode of flagellar elongation most closely resembles that of Isoptera, Blattaria and Dermaptera.     

The development of 3-D, in vitro, endothelial culture models for the study of coronary artery disease

The response of the vascular endothelium to wall shear stress plays a central role in the development and progression of atherosclerosis. Current studies have investigated endothelial response using idealized in vitro flow chambers. Such cell culture models are unable to accurately replicate the complex in vivo wall shear stress patterns arising from anatomical geometries. To better understand this implication, we have created both simplified/tubular and anatomically realistic in vitro endothelial flow models of the human right coronary artery. A post-mortem vascular cast of the human left ventricular outflow tract was used to create geometrically accurate silicone elastomer models. Straight, tubular models were created using a custom made mold. Following the culture of human abdominal aortic endothelial cells within the inner lumen, cells were exposed to steady flow (Re = 233) for varying time periods. The resulting cell morphology was analyzed in terms of shape index and angle of orientation relative to the flow direction. In both models a progressive elongation and alignment of the endothelium in the flow direction was observed following 8, 12, and 24 hours. This change, however, was significantly less pronounced in the anatomical model (as observed from morphological variations indicative of localized flow features). Differences were also observed between the inner and outer walls at the disease-prone proximal region. Since morphological adaptation is a visual indication of endothelial shear stress activation, the use of anatomical models in endothelial genetic and biochemical studies may offer better insight into the disease process.     

Differential Effect of Weight Loss on Adipocyte Size Subfractions in Patients With Type 2 Diabetes

The size of adipocytes influences their function suggesting a differential responsiveness to intervention. We hypothesized that weight loss in patients with type 2 diabetes mellitus (T2DM) predominantly decreases the size of large and very‐large adipocyte subfractions in parallel with beneficial changes in serum adipokines and improved insulin sensitivity. A total of 44 volunteers from the Look Action for Health in Diabetes trial, who lost weight after 1‐year of intense lifestyle intervention, were included. Insulin sensitivity (hyperinsulinemic–euglycemic clamp), size of subcutaneous abdominal adipocytes (osmium fixation), and selected serum adipokines were measured. A 13% weight loss was accompanied by 46% improvement in insulin sensitivity (increased glucose disposal rate from 5.9 ± 2.2 to 8.6 ± 2.7 mg/min/kg fat‐free mass, P < 0.05) in parallel with a 36% increase in plasma adiponectin concentration (6.1 ± 3.1 to 8.3 ± 3.9 µg/ml, P < 0.05], but no changes in the proinflammatory cytokines interleukin‐6 and tumor necrosis factor‐α. Change in adiponectin correlated with changes in glucose disposal rate (r = 0.34, P < 0.05). Mean adipocyte size decreased (0.84 ± 0.25 to 0.64 ± 0.23 µl, P < 0.05), mainly due to changes in the large adipocyte subfraction (size 0.75–0.44 µl, relative number 19–26%; P < 0.05). Our data suggest that change in the large adipocyte subfraction may contribute to the improvement in insulin sensitivity via an increase in serum adiponectin. Such a relationship, which does not imply cause and effect, could not be obtained by measuring only mean adipocyte size. These data provide support for the measures of adipocyte size distribution in concert with in vitro adipokine secretion and lipolysis in future studies.     

NETs formed by human neutrophils inhibit growth of the pathogenic mold Aspergillus fumigatus

Neutrophil extracellular traps (NETs) represent a distinct mechanism to control and eliminate microbial infections. Our results show that conidia and germ tubes of the human pathogenic mold Aspergillus fumigatus are able to trigger the formation of NETs. Viable fungal cells are not essentially required for this host–pathogen interaction. Neutrophils engulf conidia and thereby inhibit their germination, a process that is independent of NETosis. In the experimental set-up used in this study neutrophils do not kill germ tubes, but reduce their polar growth and this inhibition depends on NETs as it can be overcome by the addition of DNase-1. The Zn²⁺ chelator calprotectin is associated with the Aspergillus-induced NETs and addition of Zn²⁺ abrogates the NET-mediated growth inhibition. In summary, our data provide evidence that NETs are not sufficient to kill A. fumigatus, but might be a valuable tool to confine infection.     

Development: Hedgehog does the two-step

Hedgehog signalling establishes spatial correspondence between olfactory receptor neurons and their targets in the brain through a two-step mechanism.     

Growth patterns in Onychophora (velvet worms): lack of a localised posterior proliferation zone

Background  

During embryonic development of segmented animals, body segments are thought to arise from the so-called "posterior growth zone" and the occurrence of this "zone" has been used to support the homology of segmentation between arthropods, annelids, and vertebrates. However, the term "posterior growth zone" is used ambiguously in the literature, mostly referring to a region of increased proliferation at the posterior end of the embryo. To determine whether such a localised posterior proliferation zone is an ancestral feature of Panarthropoda (Onychophora + Tardigrada + Arthropoda), we examined cell division patterns in embryos of Onychophora.     

Scratching beneath the surface: Bandicoot bioturbation contributes to ecosystem processes

Animals that forage for food or dig burrows by biopedturbation can alter the biotic and abiotic characteristics of their habitat. The digging activities of such ecosystem engineers, although small at a local scale, may be important for broader scale landscape processes by influencing soil and litter properties, trapping organic matter and seeds, and subsequently altering seedling recruitment. We examined environmental characteristics (soil moisture content, hydrophobicity and litter composition) of foraging pits created by the southern brown bandicoot (Isoodon obesulus; Peramelidae), a digging Australian marsupial, over a 6‐month period. Fresh diggings typically contained a higher moisture content and lower hydrophobicity than undisturbed soil. A month later, foraging pits contained greater amounts of fine litter and lower amounts of coarse litter than adjacent undug surfaces, indicating that foraging pits may provide a conducive microhabitat for litter decomposition, potentially reducing litter loads and enhancing nutrient decomposition. We tested whether diggings might affect seedling recruitment (seed removal by seed harvesters and seed germination rates) by artificially mimicking diggings. Although there were no differences in the removal of seeds, seedling recruitment for three native plant species (Acacia saligna, Kennedia prostrata and Eucalyptus gomphocephala) was higher in plots containing artificial diggings compared with undug sites. The digging actions of bandicoots influenced soil moisture and hydrophobicity, the size distribution of litter and seedling recruitment at a local scale. The majority of Australian digging mammals are threatened, with many suffering substantial population and range contraction. However, their persistence in landscapes plays an important role in maintaining the health and function of ecosystems.     

Investigating the cationic side chains of the antimicrobial peptide tritrpticin: hydrogen bonding properties govern its membrane-disruptive activities

The positively charged side chains of cationic antimicrobial peptides are generally thought to provide the initial long-range electrostatic attractive forces that guide them towards the negatively charged bacterial membranes. Peptide analogs were designed to examine the role of the four Arg side chains in the cathelicidin peptide tritrpticin (VRRFPWWWPFLRR). The analogs include several noncoded Arg and Lys derivatives that offer small variations in side chain length and methylation state. The peptides were tested for bactericidal and hemolytic activities, and their membrane insertion and permeabilization properties were characterized by leakage assays and fluorescence spectroscopy. A net charge of +5 for most of the analogs maintains their high antimicrobial activity and directs them towards preferential insertion into model bacterial membrane systems with a similar extent of burial of the Trp side chains. However the peptides exhibit significant functional differences. Analogs with methylated cationic side chains cause lower levels of membrane leakage and are associated with lower hemolytic activities, making them potentially attractive pharmaceutical candidates. Analogs containing the Arg guanidinium groups cause more membrane disruption than those containing the Lys amino groups. Peptides in the latter group with shorter side chains have increased membrane activity and conversely, elongating the Arg residue causes slightly higher membrane activity. Altogether, the potential for strong hydrogen bonding between the four positive Arg side chains with the phospholipid head groups seems to be a determinant for the membrane disruptive properties of tritrpticin and many related cationic antimicrobial peptides.