Holocentric Chromosomes of Luzula elegans Are Characterized by a Longitudinal Centromere Groove, Chromosome Bending, and a Terminal Nucleolus Organizer Region

The structure of holocentric chromosomes was analyzed in mitotic cells of Luzula elegans. Light and scanning electron microscopy observations provided evidence for the existence of a longitudinal groove along each sister chromatid. The centromere-specific histone H3 variant, CENH3, colocalized with this groove and with microtubule attachment sites. The terminal chromosomal regions were CENH3-negative. During metaphase to anaphase transition, L. elegans chromosomes typically curved to a sickle-like shape, a process that is likely to be influenced by the pulling forces of microtubules along the holocentric axis towards the corresponding microtubule organizing regions. A single pair of 45S rDNA sites, situated distal to Arabidopsis-telomere repeats, was observed at the terminal region of one chromosome pair. We suggest that the 45S rDNA position in distal centromere-free regions could be required to ensure chromosome stability. Copyright (C) 2011 S. Karger AG, Base

Features and Cost Comparison of Biologically Inspired Vision Systems

The economic analysis of the advantages of known analogues of biologically inspired systems for unmanned aerial vehicles (UAVs), quadrocopters, etc

Angle Sensitive Pixels for Lensless Imaging on Spherical Sensors

We propose OrbCam, a lensless architecture for imaging with spherical sensors. Prior work in lensless imager techniques have focused largely on using planar sensors; for such designs, it is important to use a modulation element, e.g. amplitude or phase masks, to construct a invertible imaging system. In contrast, we show that the diversity of pixel orientations on a curved surface is sufficient to improve the conditioning of the mapping between the scene and the sensor. Hence, when imaging on a spherical sensor, all pixels can have the same angular response function such that the lensless imager is comprised of pixels that are identical to each other and differ only in their orientations. We provide the computational tools for the design of the angular response of the pixels in a spherical sensor that leads to well-conditioned and noise-robust measurements. We validate our design in both simulation and a lab prototype. The implications of our design is that the lensless imaging can be enabled easily for curved and flexible surfaces thereby opening up a new set of application domains

Analysis of heterochromatic epigenetic markers in the holocentric chromosomes of the aphid Acyrthosiphon pisum

Monomethylated-K9 H3 histones (Me9H3) and heterochromatin protein 1 (HP1) are reported as heterochromatin markers in several eukaryotes possessing monocentric chromosomes. In order to confirm that these epigenetic markers are evolutionary conserved, we sequenced the HP1 cDNA and verified the distribution of Me9H3 histones and HP1 in the holocentric chromosomes of the aphid Acyrthosiphon pisum. Sequencing indicates that A. pisum HP1 cDNA (called ApHP1) is 1623 bp long, including a 170 bp long 5’UTR and a 688 bp long 3’UTR. The ApHP1 protein consists in 254 amino acidic residues, has a predicted molecular mass of 28 kDa and a net negative charge. At the structural level, it shows an N terminal chromo domain and a chromo shadow domain at the C terminus linked by a short hinge region. At the cytogenetic level, ApHP1 is located exclusively in the heterochromatic regions of the chromosomes. The same heterochromatic regions were labelled after immuno-staining with antibodies against Me9H3 histones confirming that Hp1 and Me9H3 co-localize at heterochromatic chromosomal areas. Surprisingly, aphid heterochromatin lacks DNA methylation and methylated cytosine residues were mainly spread at euchromatic regions. Finally, the absence of DNA methylation is observed also in aphid rDNA genes that have been repeatedly described as mosaic of methylated and unmethylated units in vertebrates