Spectral information as an orientation cue in dung beetles

During the day, a non-uniform distribution of long and short wavelength light generates a colour gradient across the sky. This gradient could be used as a compass cue, particularly by animals such as dung beetles that rely primarily on celestial cues for orientation. Here, we tested if dung beetles can use spectral cues for orientation by presenting them with monochromatic (green and UV) light spots in an indoor arena. Beetles kept their original bearing when presented with a single light cue, green or UV, or when presented with both light cues set 180° apart. When either the UV or the green light was turned off after the beetles had set their bearing in the presence of both cues, they were still able to maintain their original bearing to the remaining light. However, if the beetles were presented with two identical green light spots set 180° apart, their ability to maintain their original bearing was impaired. In summary, our data show that ball-rolling beetles could potentially use the celestial chromatic gradient as a reference for orientation.     

Image correction method for the colour contrast effect using inverse processes of the brain

In the colour contrast effect, the impression of a colour changes according to the situation; cases occur in which the colour appearance is misunderstood. We propose an image signal processing method for preventing such misperception of colour. Many conventional image improving methods emphasize the contrast of images as same as the brain does. However, by their processes, the colour contrast effect is not canceled; we misunderstand the colour. The objective of this study is to perceive original colour. Therefore, we propose an image correction method using inverse processes of the brain in order to cancel the processes of the brain, the colour contrast effect. We verified whether the proposed method corrected the colour contrast effect by conducting a psychological experiment. The results show that the method succeeds in canceling the colour contrast effect.     

Small‐angle scattering for structural biology—Expanding the frontier while avoiding the pitfalls

The last decade has seen a dramatic increase in the use of small‐angle scattering for the study of biological macromolecules in solution. The drive for more complete structural characterization of proteins and their interactions, coupled with the increasing availability of instrumentation and easy‐to‐use software for data analysis and interpretation, is expanding the utility of the technique beyond the domain of the biophysicist and into the realm of the protein scientist. However, the absence of publication standards and the ease with which 3D models can be calculated against the inherently 1D scattering data means that an understanding of sample quality, data quality, and modeling assumptions is essential to have confidence in the results. This review is intended to provide a road map through the small‐angle scattering experiment, while also providing a set of guidelines for the critical evaluation of scattering data. Examples of current best practice are given that also demonstrate the power of the technique to advance our understanding of protein structure and function.     

Predator perception of detritus and eggsac decorations spun by orb-web spiders Cyclosa octotuberculata:Do they function to camouflage the spiders?

Camouflage is one of the most widespread and powerful strategies that animals use to make detection/recognition more difficult. Many orb-web spiders of the genus Cyclosa add prey remains, plant debris, moults, and/or eggsacs to their webs called web decorations. Web decorations resembling spider body colour pattern have been considered to camouflage the spider from predators. While this camouflage is obvious from a human's perspective, it has rarely been investigated from a predator's perspective. In this s...     

Formation of amyloids by Abeta-(1-42) on NGF-differentiated PC12 cells: roles of gangliosides and cholesterol

The conversion of soluble, non-toxic amyloid beta-protein (Abeta) to aggregated, toxic Abeta could be the key step in the development of Alzheimer's disease. Liposomal studies have proposed that Abeta-(1-40) preferentially recognizes a cholesterol-dependent cluster of gangliosides and a conformationally altered form of Abeta promotes the aggregation of the protein. Cell experiments using fluorescein-labeled Abeta-(1-40) supported this model. Here, the interaction of native Abeta-(1-42) with unfixed rat pheochromocytoma PC12 cells was visualized using the amyloid-specific dye Congo red. Abeta-(1-42) preferentially bound to ganglioside and cholesterol-rich domains of cell membranes and formed amyloids in a time-dependent manner. These observations corroborate the model involving ganglioside-mediated accumulation of Abeta. The NGF-induced differentiation of PC12 cells into neuron-like cells caused a marked increase in both gangliosides and cholesterol, and thereby greatly potentiated the accumulation and cytotoxicity of Abeta-(1-42). NGF-differentiated cells exposed to Abeta-(1-42) had degenerated neurites, in which ganglioside and cholesterol-rich domains were localized, preceding cell death. A reduction in the amount of cholesterol by the cholesterol synthesis inhibitor compactin almost nullified the formation of amyloids by Abeta-(1-42). Our system using NGF-differentiated PC12 cells and Congo red is useful for screening inhibitors of the formation of amyloids by and cytotoxicity of Abeta.     

The motif of SPARC that inhibits DNA synthesis is not a nuclear localization signal

SPARC (secreted protein acidic and rich in cysteine), although primarily known as a secreted, matricellular protein, has also been identified in urothelial cell nuclei. Many biological activities, including inhibition of cell adhesion and repression of DNA synthesis, have been ascribed to SPARC, but the influence of its intracellular localization on each of these activities is unknown. When exposed by epitope retrieval and nuclear matrix unmasking techniques, endogenous SPARC was found to localize strongly to the nuclei and the nuclear matrix of cultured urothelial cells. Live-cell time-lapse imaging revealed that exogenous fluorescently labeled recombinant (r) SPARC was taken up from medium over a 16 h period and accumulated inside cells. Two variants of rSPARC with alterations in its putative nuclear localization signal (NLS) were generated to investigate the existence and effects of the NLS. These variants demonstrated similar biophysical characteristics as the wild-type protein. Visualization by a variety of techniques, including live-cell imaging, deconvolution microscopy, and cell fractionation, all concurred that exogenous rSPARC was not able to localize to cell nuclei, but instead accumulated as perinuclear clusters. Localization of the rSPARC NLS variants was no different than wild-type, arguing against the presence of an active NLS in rSPARC. Imaging experiments showed that only permeabilized, dead cells avidly took up rSPARC into their nuclei. The rSPARC(no NLS) variant proved ineffective at inhibiting DNA synthesis, whereas the rSPARC(strong NLS) variant was a more potent inhibitor of DNA synthesis than was wild-type rSPARC. The motif of SPARC that inhibits the synthesis of urothelial cell DNA is therefore not a nuclear localization signal, but its manipulation holds therapeutic potential to generate a "Super-SPARC" that can quiesce proliferative tissues.     

RGD targeted poly(L-glutamic acid)-cystamine-(Gd-DO3A) conjugate for detecting angiogenesis biomarker alpha(v) beta3 integrin with MRT, mapping

Cyclic Arg-Gly-Asp-D-Phe-Lys [c(RGDfK)] targeted poly(L-glutamic acid) (PGA)-(Gd-DO3A) conjugate with a biodegradable cystamine spacer was prepared and evaluated for in vivo detection of an angiogenesis biomarker, alpha(v)beta3 integrin, in neoplastic tissues with T1 mapping, a quantitative magnetic resonance imaging (MRI) technique. The binding activity of the c(RGDfK) containing conjugate was investigated using in vitro vitronectin assay with human prostate carcinoma DU145 cell line and Kaposi's sarcoma SLK cell line. The peptide c(RGDfK) and PGA-cystamine-(Gd-DO3A) conjugate were used as controls. The binding affinity of polymer bound c(RGDfK) was slightly lower than free c(RGDfK) peptide. The RGD targeted conjugate had higher binding affinity to the DU145 cells than the SLK cells, which was consistent to free c(RGDfK). The imaging of alpha(v)beta3 integrin with targeted PGA-cystamine-(Gd-DO3A) was evaluated in nude mice bearing DU145 and SLK xenografts at a dose of 5 micromol-Gd/kg. The targeted conjugate demonstrated higher in vivo binding affinity to the DU145 xenografts than the SLK xenografts, resulting in a significant decrease of T1 values of water protons in the periphery of the DU145 tumors as shown in the MR T1 maps. No significant decrease of T1 values was observed in the SLK tumor with the targeted conjugate and in both tumors with the non-targeted conjugate. The targeted polymeric Gd(III) chelate conjugate with a degradable spacer has the potential to be a new paradigm for safe and effective probes in molecular imaging with quantitative MR T1 mapping.     

Rapid diversification of male genitalia and mating strategies in Ohomopterus ground beetles

We analysed evolutionary diversification and covariation in male genitalia and four mating traits related to sexual selection, i.e. testis size, spermatophore size, copulation duration and post-copulatory guarding duration, in Ohomopterus ground beetles using phylogenetically independent contrasts. Male genital size and mating duration have evolved more rapidly than body size and the other traits studied. Male genital size was negatively correlated with copulation duration, suggesting that elongated male genitalia may enable decreased time investment in a single copulation because it is more effective at facilitating spermatophore deposition. Male genital size was positively correlated with spermatophore size, suggesting coevolution between offensive and defensive male mating tactics because the elongated male genitalia may be advantageous in displacement of rivals' plug-like spermatophores, and decreased mating duration may intensify sperm competition. Thus, the remarkable diversity of male genitalia in Ohomopterus may have been facilitated by the interplay between inter- and intrasexual selection processes.