Fundamental understanding and characterization of neural response to substrate topography is essential in the development of next generation biomaterials for nerve repair. Aerogels are a new class of materials with great potential as a biomaterial. In this work, we examine the extension of neurites by PC12 cells plated on matrigel-coated and collagen-coated mesoporous aerogel surfaces. We have successfully established the methodology for adhesion and growth of PC12 cells on polyurea crosslinked silica aerogels. Additionally, we have quantified neurite behaviors and compared their response on aerogel substrates with their behavior on tissue culture (TC) plastic, and polydimethylsiloxane (PDMS). We found that, on average, PC12 cells extend longer neurites on crosslinked silica aerogels than on tissue culture plastic, and, that the average number of neurites per cluster is lower on aerogels than on tissue culture plastic. Aerogels are an attractive candidate for future development of smart neural implants and the work presented here creates a platform for future work with this class of materials as a substrate for bioelectronic interfacing.

Externally applied electrical stimulation (ES) has been shown to enhance the nerve regeneration process and to influence the directionality of neurite outgrowth. In addition, the physical and chemical properties of the substrate used for nerve-cell regeneration is critical in fostering regeneration. Previously, we have shown that polyurea-crosslinked silica aerogels (PCSA) exert a positive influence on the extension of neurites by PC-12 cells, a cell-line model widely used to study neurite extension and electrical excitability. In this work, we have examined how an externally applied electric field (EF) influences the extension of neurites in PC-12 cells grown on two substrates: collagen-coated dishes versus collagen-coated crosslinked silica aerogels. The externally applied direct current (DC) bias was applied in vitro using a custom-designed chamber containing polydimethysiloxane (PDMS) embedded copper electrodes to create an electric field across the substrate for the cultured PC-12 cells. Results suggest orientation preference towards the anode, and, on average, longer neurites in the presence of the applied DC bias than with 0 V DC bias. In addition, neurite length was increased in cells grown on silica-crosslinked aerogel when compared to cells grown on regular petri-dishes. These results further support the notion that PCSA is a promising material for nerve regeneration.

Chytridiomycosis, the amphibian disease caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), is fatal to adults of many species. Bd is largely sublethal to amphibian larvae; however, it is known to reduce larval (i.e. tadpole) growth rates, with possible long-term effects on population dynamics and fitness. We conducted an experiment to test how Bd altered southern leopard frog Lithobates sphenocephalus tadpole mouthpart damage, percentage of food ingested, and subsequent body size. We examined our results using path analyses. We hypothesized that Bd would increase mouthpart damage, causing less food to be ingested, and ultimately reduce body size. In our model, both Bd exposure and increased mouthpart damage significantly reduced food ingested and subsequent body size. However, our study provides evidence against the long-standing hypothesis of mouthpart damage as a pathway for Bd-induced reductions in larval group. Here we provide evidence for reduced foraging efficiency (percentage of food ingested) as a mechanism for Bd-induced reductions in body size. This work highlights the importance of studying the sublethal effects of Bd on larval amphibians. KEY WORDS: Chytrid fungus · Feeding · Larvae · Life history traits · Path analysisResale or republication not permitted without written consent of the publisher © Inter-Research 2015 · www.int-res.com Dis Aquat Org 112: [237][238][239][240][241][242] 2015 al. (2013) showed that Bd exposure reduced tadpole size, and mouthpart damage reduced the size of tadpole guts relative to body size. In other words, studies have shown that Bd causes mouthpart damage, damage reduces foraging efficiency, and reduced efficiency reduces growth. So it can be inferred that Bd-induced mouthpart damage potentially reduces growth. However, this pathway has never been proven. While previous studies have provided evidence for possible pathways by which Bd-induced reductions in tadpole growth may occur, a direct pathway from Bd-induced mouthpart damage to reduced growth has yet to be confirmed.Much work has focused on the direct, lethal effects of Bd on host populations. While such research is imperative to our understanding of the disease, the sublethal effects of Bd, especially on larval amphibians, could have lasting carry-over effects that negatively alter natural populations. To address the sublethal impact(s) of Bd on tadpoles and identify a pathway whereby Bd reduces growth and development, we tested the hypothesis that Bd would cause mouthpart damage, food intake, and subsequent growth. We conducted a laboratory study using southern leopard frog Lithobates sphenocephalus tadpoles. Using path analyses, we tested how Bd, mouthpart damage, and percentage of food in the gut (hereafter gut content), directly or indirectly influenced body size (growth measure). We predicted that Bd would increase mouthpart damage, in turn reducing gut content and subsequent body size. Also, independent of Bd exposure, we predicted that increased mouthpart damage would negati...

One prediction of optimal digestion theory is that organisms will increase the relative length of their digestive tracts when food resources become limited. We used theory of optimal digestion to test whether tadpoles can adjust the relative length of their intestines when challenged with the fungal pathogen Batrachochytrium dendrobatidis (Bd). The degree of tadpole mouthpart damage, a symptom of Bd infections that reduces food consumption, was associated positively with the length of tadpole intestines relative to their body size, consistent with optimal digestion theory. After controlling for mouthpart damage, tadpoles exposed to Bd had shorter intestines relative to their body size, opposite to the predictions of optimal digestion theory. One explanation of why tadpoles with higher Bd loads have shorter relative intestinal lengths is that they divert energy from maintaining intestinal and overall growth towards anti-parasite defences.

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The amphibian disease chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), has been linked to significant amphibian declines over the past three decades. The most severe effects of the pathogen have been primarily observed in relatively pristine areas that are not affected by many anthropogenic factors.One hypothesis concerning improved amphibian persistence with Bd in disturbed landscapes is that contaminants may abate the effects of Bd on amphibians. Recent laboratory studies have shown that pesticides, specifically the fungicide thiophanate-methyl (TM), can kill Bd outside of hosts and clear Bd infections within hosts. Using aquatic mesocosms, we tested the hypothesis that TM (0.43 mg/L) would alter growth and development of Lithobates sphenocephalus (southern leopard frog) tadpoles and Bd-infection loads in infected individuals. We hypothesized that the scope of such alterations and infection clearing would be affected by aquatic community variables, specifically zooplankton. TM altered zooplankton diversity (reduced cladoceran and increased copepod and ostracod abundances) and caused mortality to all tadpoles in TM-exposed tanks. In TM-free tanks, Bd-exposed tadpoles in high-density treatments metamorphosed smaller than Bd-unexposed, effects that were reversed in low-density treatments. Our study demonstrates the potential adverse effects of a fungicide and Bd on tadpoles and aquatic systems.

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Non-invasive rapid in vivo imaging and detection of biomedical implants is a critical part of the design and implementation of smart implants. Thermographic phosphors offer a precise and remotely accessible sensing method that has been utilised here. We present the first in vivo X-ray images of La2O2S:Eu-doped crosslinked silica aerogels and polydimethylsiloxane (PDMS) with increasing dopant concentrations. Results show that native PDMS and crosslinked silica aerogel do not show noticeable attenuation of X-rays while image analysis yields values of the absorption coefficient of 0.014 for the doped aerogel and a range of 0.015 to 0.017 for the doped PDMS.