Rapid and reversible humidity-dependent colour change by water film formation in a scaled springtail.

Colour is often not a static trait but can change over time either through biotic or abiotic factors. Humidity-dependent colour change can occur through either morphological change (e.g. to feather barbules in birds) or by the replacement of air by water causing a shift in refractive index, as seen in arthropod multi-layer cuticles or scales. The scaled springtail Lepidocyrtus cyaneus has scales that produce colour largely via thin film interference from their lamina. We observed a marked colour change from golden to violet/purple coloration in humid conditions. Light microscopy, micro-spectrophotometry, contact angle goniometry and optical modelling indicate that the formation of a thin film of water on top of the hydrophilic scales increases their laminar thin film thickness, causing a shift towards violet/purple colour. Evaporation of the water film causes the metallic golden colour to return. This constitutes a remarkably rapid colour change (in the order of seconds), only limited by the speed of water film condensation and evaporation, that may serve as inspiration for new dynamically coloured materials and sensors.

Springtail coloration at a finer scale: mechanisms behind vibrant collembolan metallic colours.

The mechanisms and evolution of metallic structural colours are of both fundamental and applied interest, yet most work in arthropods has focused on derived butterflies and beetles with distinct hues. In particular, basal hexapods-groups with many scaled, metallic representatives-are currently poorly studied and controversial, with some recent studies suggesting either that thin-film (lamina thickness) or diffraction grating (longitudinal ridges, cross-ribs) elements produce these colours in early Lepidoptera and one springtail (Collembola) species. Especially the collembolan basal scale design, consisting of a single lamina and longitudinal ridges with smooth valleys lacking cross-ribs, makes them an interesting group to explore the mechanisms of metallic coloration. Using microspectroscopy, Raman spectroscopy, electron microscopy and finite-difference time-domain optical modelling, we investigated scale colour in seven springtail species that show clear metallic coloration. Reflectance spectra are largely uniform and exhibit a broadband metallic/golden coloration with peaks in the violet/blue region. Our simulations confirm the role of the longitudinal ridges, working in conjunction with thin-film effects to produce a broadband metallic coloration. Broadband coloration occurs through spatial colour mixing, which probably results from nanoscale variation in scale thickness and ridge height and distance. These results provide crucial insights into the colour production mechanisms in a basal scale design and highlight the need for further investigation of scaled, basal arthropods.

Electrospinning repellents in polyvinyl alcohol-nanofibres for obtaining mosquito-repelling fabrics.

Recently, the use of repellents for preventing the transmission of mosquito-borne diseases is getting increasingly more attention. However, most of the current repellents are volatile in nature and must be frequently re-applied as their efficacy is only limited to a short period of time. Therefore, a slow release and abrasion-resistant mechanism is needed for prolonging the protection time of the repellents. The focus of this study is on the direct micro-encapsulation of repellents from an emulsion and integration of already encapsulated repellents into nanofibres via electrospinning. Different repellents were electrospun in polyvinyl alcohol (PVA) nanofibrous structures, namely p-menthane-3,8-diol micro-capsules, permethrin, chilli and catnip oil. The repellents were successfully incorporated in the nanofibres and the tensile properties of the resulting samples did not have a significant change. This means that the newly created textiles were identical to current PVA nanofibrous textiles with the added benefit of being mosquito repellent. Principally, all incorporated repellents in the nanofibrous structures showed a significantly reduced number of mosquito landings compared to the control. Consequently, the currently described method resulted in a new and very effective repelling textile material that can be used in the prevention against mosquito-associated diseases.

Life from the ashes: survival of dry bacterial spores after very high temperature exposure.

We found that spores of Bacillus amyloliquefaciens rank amongst the most resistant to high temperatures with a maximum dry heat tolerance determined at 420 °C. We found that this extreme heat resistance was also maintained after several generations suggesting that the DNA was able to replicate after exposure to these temperatures. Nonetheless, amplifying the bacterial DNA using BOXA1R and (GTG)5 primers was unsuccessful immediately after extreme heating, but was successful after incubation of the heated then cooled spores. Moreover, enzymes such as amylases and proteases were active directly after heating and spore regeneration, indicating that DNA coding for these enzymes were not degraded at these temperatures. Our results suggest that extensive DNA damage may occur in spores of B. amyloliquefaciens directly after an extreme heat shock. However, the successful germination of spores after inoculation and incubation indicates that these spores could have a very effective DNA repair mechanism, most likely protein-based, able to function after exposure to temperatures up to 420 °C. Therefore, we propose that B. amyloliquefaciens is one of the most heat resistant life forms known to science and can be used as a model organism for studying heat resistance and DNA repair. Furthermore, the extremely high temperature resistivity of these spores has exceptional consequences for general methodology, such as the use of dry heat sterilization and, therefore, virtually all studies in the broad area of high temperature biology.

Morphometric and preliminary genetic characteristics of Branchinecta orientalis populations from Iran (Crustacea: Anostraca).

Branchinecta orientalis is a fairy shrimp endemic to the Palearctic region, from Mongolia to Spain. The patchy nature of its habitat is thought to result in a high degree of subdivision among populations, potentially promoting speciation. We combined morphometric characteristics with molecular phylogeny of cytochrome c oxidase I (COI) to test whether B. orientalis could be a species complex and whether there is any correlation between the genetic variation, morphometric characteristics and geographical variables. We studied six populations from Iran based on the comparison of morphometric and molecular datasets, we confirmed that the Aigher Goli (AIG) population is biometrically well separated from the Akh Gol, Hassar, Rashakan, Khaslou and Garagojanlou populations in northwestern Iran. The relatively high genetic divergence in the AIG from the other populations and its congruence with morphometric data were observed in B. orientalis populations. However, as these results were generated using a small sample size and on a limited sampling range, they should be considered as preliminary.

Long-term results after endovascular abdominal aortic aneurysm repair using the Cook Zenith endograft.

OBJECTIVE: This study assessed the long-term outcome of patients with abdominal aortic and aortoiliac aneurysms treated with the Cook Zenith endovascular graft (Cook Inc, Bloomington, Ind). METHODS: Between September 1998 and October 2003, 143 patients underwent elective endovascular aneurysm repair (EVAR) using the Cook Zenith endograft. Data from these patients were reviewed from a prospective database in October 2008. Primary outcome measures were overall survival, intervention-free survival, and freedom from aneurysm rupture. Secondary outcome measures were early and late postoperative complications, including endoleaks. RESULTS: Mean follow-up was 66.4 months (range, 1.9-121.0 months). Overall survival was 72.1% at the 5-year follow-up and 50.9% at the 8-year follow-up. Intervention-free survival was 77.1% at 5 years and 63.8% at 8 years. There were no reintervention-related deaths. Six patients had a late aneurysm rupture, which was fatal in three. Freedom from aneurysm rupture was 98.1% at 5 years and 91.0% at 8 years. Late complications occurred throughout the follow-up period, with a tendency for aneurysm rupture and surgical conversion to occur at a later stage in the follow-up period. Aneurysm sac enlargement during follow-up was associated with late aneurysm rupture and with the need for reintervention. CONCLUSION: Elective EVAR using the Cook Zenith endograft provides excellent results through a mean follow-up of >5 years. There is a low aneurysm-related mortality and an acceptable rate of postoperative complications and reinterventions. The occurrence of late complications throughout the follow-up period stresses the need for continued postoperative surveillance in EVAR patients.

Silkworm and spider silk scaffolds for chondrocyte support.

OBJECTIVE: To create scaffolds with silkworm cocoon, spider egg sac and spider dragline silk fibres and examine their use for chondrocyte attachment and support. METHODS: Three different kinds of scaffolds were developed with Bombyx mori cocoon, Araneus diadematus egg sac and dragline silk fibres. The attachment of human articular cartilage cells were investigated on these bioprotein matrices. The chondrocytes produced an extracellular matrix which was studied by immunostaining. Moreover, the compression behaviour in relation to the porosity was studied. RESULTS: The compression modulus of a silkworm silk scaffold was related to its porosity. Chondrocytes were able to attach and to grow on the different fibres and in the scaffolds for several weeks while producing extracellular matrix products. CONCLUSION: Porous scaffolds can be made out of silkworm and spider silk for cartilage regeneration. Mechanical properties are related to porosity and pore size of the construct. Cell spreading and cell expression depended on the porosity and pore-size.

Biocompatibility and biodegradability of spider egg sac silk.

Spider egg sac silk (SpESS) were enzymatically cleaned and their biodegradation in vivo and in vitro, as well as their biocompatibility were studied. Proteinase K treatment diminished the tenacity and the strain of the SpESS fibers in proportion to the enzyme concentration. Fibers treated with trypsin were not significantly affected. Tensile properties of Vicryl, SpESS and of silkworm (Bombyx mori) silk fibers (SWS) were measured after incubation in phosphate buffered saline (PBS) at 37 degrees C up to 12 weeks. Biodegradation of SpESS and SWS was insignificant compared to Vicryl. Five milligram SpESS fibers from laboratory grown spiders (Araneus diadematus) were treated with proteinases before sterilization and subcutaneously implanted in Wistar rats. After 1, 4 and 7 weeks the immunological reaction was compared to untreated SpESS and polyglactin (Vicryl) control samples. SpESS samples treated with trypsin only or in combination with a Proteinase K treatment induced less inflammatory reactions than untreated silk fibers. The enzymatical cleaning could diminish the tensile properties, but enhanced the biocompatibility of the SpESS fibers rendering them appropriate for use in biomaterial application where the slow biodegradability is an advantage.

Recurrent hemarthrosis of the knee caused by pseudoaneurysm of a composed femoropopliteal bypass graft.

We report on a case of recurrent hemarthrosis of the knee caused by a false aneurysm of a composed femoropopliteal bypass graft. Treatment consisted of resection and interposition grafting. The pathogenesis and treatment options of anastomotic false aneurysms are also reviewed briefly.

Heavy metal concentrations in the spiders Pirata piraticus (Clerck, 1757) and Clubiona phragmitis (C.L. Koch, 1843) along the Scheldt Estuary (Belgium).

Wetland ecosystems may be affected by deposition and accumulation of heavy metals. Metal concentrations in the spiders Pirata piraticus and Clubiona phragmitis living in marshes along the river Scheldt (Flanders, Belgium) were analyzed. The organisms were sampled on seven sites along a gradient from freshwater to brackish marshes. Except for lead, P. piraticus contained higher metal concentrations than C. phragmitis. This is related to physiological and ecological differences between species. No correlation was found between metal concentration in the organisms and soil total concentration.