Allometric variation among juvenile, adult male and female eastern bearded dragons Pogona barbata (Cuvier, 1829), with comments on the behavioural implications

The functional significance of allometric change in reptiles has received limited attention and the reason for such changes has been regarded as ‘obscure’. In this paper we report data on the Australian Pogona barbata, the eastern bearded dragon, from across their range and review changes in allometric growth among juveniles, and adult males and females and consider the functional relevance of these changes. There were significant differences in the population for mass, tail length, tail width, rear leg length and jaw length. These differences were consistent with differences required in locomotor performance and thus habitat use, together with access to different preferred dietary components.     

Discovery of a new class of glucosylceramide synthase inhibitors

A novel series of potent inhibitors of glucosylceramide synthase are described. The optimization of biochemical and cellular potency as well as ADME properties led to compound 23c. Broad tissue distribution was obtained following oral administration to mice. Thus 23c could be another useful tool compound for studying the effects of GCS inhibition in vitro and in vivo.     

Expansion-repression mechanism for scaling the Dpp activation gradient in Drosophila wing imaginal discs

Maintaining a proportionate body plan requires the adjustment or scaling of organ pattern with organ size. Scaling is a general property of developmental systems, yet little is known about its underlying molecular mechanisms. Using theoretical modeling, we examine how the Dpp activation gradient in the Drosophila wing imaginal disc scales with disc size. We predict that scaling is achieved through an expansion-repression mechanism [1] whose mediator is the widely diffusible protein Pentagone (Pent). Central to this mechanism is the repression of pent expression by Dpp signaling, which provides an effective size measurement, and the Pent-dependent expansion of the Dpp gradient, which adjusts the gradient with tissue size. We validate this mechanism experimentally by demonstrating that scaling requires Pent and further, that scaling is abolished when pent is ubiquitously expressed. The expansion-repression circuit can be readily implemented by a variety of molecular interactions, suggesting its general utilization for scaling morphogen gradients during development.     

Study of elastic collisions of Myxococcus xanthus in swarms

In very low density situations where a single myxobacterial cell is isolated from direct contact with other cells, the slime capsule interaction with the substrate or slime tracks on the substrate produce a viscous drag that results in a smooth gliding motion. Viscoelastic interactions of myxobacteria cells in a low-density domain close to the edge of a swarm are studied using a combination of a cell-based three-dimensional computational model and cell-tracking experiments. The model takes into account the flexible nature of Myxococcus xanthus as well as the effects of adhesion between cells arising from the interaction of the capsular polysaccharide covering two cells in contact with each other. New image and dynamic cell curvature analysis algorithms are used to track and measure the change in cell shapes that occur as flexible cells undergo significant bending during collisions resulting in direct calibration of the model parameters. Like aspect-ratio and directional reversals, the flexibility of cells and the adhesive cell-cell and cell-substrate interactions of M. xanthus play an important role in smooth gliding and more efficient swarming.     

Do edge responses cascade up or down a multi‐trophic food web?

Despite nearly 100?years of edge studies, there has been little effort to document how edge responses 'cascade' to impact multi-trophic food webs. We examined changes within two, four-tiered food webs located on opposite sides of a habitat edge. Based on a 'bottom-up' resource-based model, we predicted plant resources would decline near edges, causing similar declines in specialist herbivores and their associated predators, while a generalist predator was predicted to increase due to complementary resource use. As predicted, we found declines in both specialist herbivores and predators near edges, but, contrary to expectations, this was not driven by gradients in plant resources. Instead, the increase in generalist predators near edges offers one alternative explanation for the observed declines. Furthermore, our results suggest how recent advances in food web theory could improve resource-based edge models, and vice versa.     

ReAsH/FlAsH Labeling and Image Analysis of Tetracysteine Sensor Proteins in Cells

Fluorescent proteins and dyes are essential tools for the study of protein trafficking, localization and function in cells. While fluorescent proteins such as green fluorescence protein (GFP) have been extensively used as fusion partners to proteins to track the properties of a protein of interest¹, recent developments with smaller tags enable new functionalities of proteins to be examined in cells such as conformational change and protein-association ^{2, 3}. One small tag system involves a tetracysteine motif (CCXXCC) genetically inserted into a target protein, which binds to biarsenical dyes, ReAsH (red fluorescent) and FlAsH (green fluorescent), with high specificity even in live cells ². The TC/biarsenical dye system offers far less steric constraints to the host protein than fluorescent proteins which has enabled several new approaches to measure conformational change and protein-protein interactions ^4-7. We recently developed a novel application of TC tags as sensors of oligomerization in cells expressing mutant huntingtin, which when mutated aggregates in neurons in Huntington disease ⁷. Huntingtin was tagged with two fluorescent dyes, one a fluorescent protein to track protein location, and the second a TC tag which only binds biarsenical dyes in monomers. Hence, changes in colocalization between protein and biarsenical dye reactivity enabled submicroscopic oligomer content to be spatially mapped within cells. Here, we describe how to label TC-tagged proteins fused to a fluorescent protein (Cherry, GFP or CFP) with FlAsH or ReAsH in live mammalian cells and how to quantify the two color fluorescence (Cherry/FlAsH, CFP/FlAsH or GFP/ReAsH combinations).Download video file.^{(77M, mov)}     

Identification of genes with allelic imbalance on 6p associated with nasopharyngeal carcinoma in southern Chinese

Nasopharyngeal carcinoma (NPC) is a malignancy of epithelial origin. The etiology of NPC is complex and includes multiple genetic and environmental factors. We employed case-control analysis to study the association of chromosome 6p regions with NPC. In total, 360 subjects and 360 healthy controls were included, and 233 single nucleotide polymorphisms (SNPs) on 6p were examined. Significant single-marker associations were found for SNPs rs2267633 (p = 4.49 × 10(-5)), rs2076483 (most significant, p = 3.36 × 10(-5)), and rs29230 (p=1.43 × 10(-4)). The highly associated genes were the gamma-amino butyric acid B receptor 1 (GABBR1), human leukocyte antigen (HLA-A), and HLA complex group 9 (HCG9). Haplotypic associations were found for haplotypes AAA (located within GABBR1, p-value = 6.46 × 10(-5)) and TT (located within HLA-A, p = 0.0014). Further investigation of the homozygous genotype frequencies between cases and controls suggested that micro-deletion regions occur in GABBR1 and neural precursor cell expressed developmentally down-regulated 9 (NEDD9). Quantitative real-time polymerase chain reaction (qPCR) using 11 pairs of NPC biopsy samples confirmed the significant decline in GABBR1 and NEDD9 mRNA expression in the cancer tissues compared to the adjacent non-tumor tissue (p<0.05). Our study demonstrates that multiple chromosome 6p susceptibility loci contribute to the risk of NPC, possibly though GABBR1 and NEDD9 loss of function.     

An electrochemical functional assay for the sensing of nitric oxide release induced by angiogenic factors

Nitric oxide (NO) is a critical biological mediator involved in numerous diseases. However, the short lifetime of this molecule in biological conditions can make its study in situ complicated. Here, we review some recent results on the role of NO in angiogenesis, obtained using a biocompatible microelectrode array. This simple system allowed for the quick and easy quantification of NO released from cells grown directly on the surface of the sensor. We have used this technology to demonstrate that angiogenin induces NO release, and to partially elucidate its intracellular transduction pathway.     

Evaluation of chylomicron effect on ASP production in 3T3-L1 adipocytes

In the past few years, there has been increasing interest in the production and physiological role of acylation-stimulating protein (ASP), identical to C3adesArg, a product of the alternative complement pathway generated through C3 cleavage. Recent studies in C3 (-/-) mice that are ASP deficient have demonstrated a role for ASP in postprandial triglyceride clearance and fat storage. The aim of the present study was to establish a cell model and sensitive ELISA assay for the evaluation of ASP production using 3T3-L1 adipocytes. 3T3-L1 preadipocytes were differentiated into adipocytes, then cultured in different media such as serum-free (SF), Dulbecco's modified Eagle's medium (DMEM)/F12 + 10% fetal calf serum (FBS), and at varying concentrations of chylomicrons and insulin + chylomicrons up to 48 h. ASP production in SF and DMEM/F12 + 10% FBS was compared. Chylomicrons stimulated ASP production in a concentration- and time-dependent manner. By contrast, chylomicron treatment had no effect on the production of C3, the precursor protein of ASP, which was constant over 48 h. Addition of insulin (100 nM) to a low-dose of chylomicrons (100 μg TG/ml) significantly increased ASP production compared with chylomicrons alone at 48 h (P < 0.001). Furthermore, addition of insulin significantly increased C3 secretion at both 18 and 48 h of incubation (P < 0.05, P < 0.001, respectively). Overall, the proportion of ASP to C3 remained constant, indicating no change in the ratio of C3 cleaved to generate ASP. This study demonstrated that 3T3-L1 adipocyte is a useful model for the evaluation of C3 secretion and ASP production by using a sensitive mouse-specific ELISA assay. The stimulation of ASP production with chylomicrons demonstrates a physiologically relevant response, and provides a strategy for further studies on ASP production and function.