One electron transfer properties and phytotoxicity of a diquaternary salt from 2,2′:6′,2″-terpyridine

Zusammenfassung 2, 2:6, 2-Terpyridin gibt mit Aethylendibromid ein diquartäres Salz, das durch Reduktion mit Zink eine Radikalkation liefert. Es handelt sich um ein Redox-System und das Salz besitzt herbizide Wirksamkeit.     

Molecular mechanism for duplication 17p11.2- the homologous recombination reciprocal of the Smith-Magenis microdeletion

Recombination between repeated sequences at various loci of the human genome are known to give rise to DNA rearrangements associated with many genetic disorders. Perhaps the most extensively characterized genomic region prone to rearrangement is 17p12, which is associated with the peripheral neuropathies, hereditary neuropathy with liability to pressure palsies (HNPP) and Charcot-Marie-Tooth disease type 1A (CMT1A;ref. 2). Homologous recombination between 24-kb flanking repeats, termed CMT1A-REPs, results in a 1.5-Mb deletion that is associated with HNPP, and the reciprocal duplication product is associated with CMT1A (ref. 2). Smith-Magenis syndrome (SMS) is a multiple congenital anomalies, mental retardation syndrome associated with a chromosome 17 microdeletion, del(17)(p11.2p11.2) (ref. 3,4). Most patients (>90%) carry deletions of the same genetic markers and define a common deletion. We report seven unrelated patients with de novo duplications of the same region deleted in SMS. A unique junction fragment, of the same apparent size, was identified in each patient by pulsed field gel electrophoresis (PFGE). Further molecular analyses suggest that the de novo17p11.2 duplication is preferentially paternal in origin, arises from unequal crossing over due to homologous recombination between flanking repeat gene clusters and probably represents the reciprocal recombination product of the SMS deletion. The clinical phenotype resulting from duplication [dup(17)(p11.2p11.2)] is milder than that associated with deficiency of this genomic region. This mechanism of reciprocal deletion and duplication via homologous recombination may not only pertain to the 17p11.2 region, but may also be common to other regions of the genome where interstitial microdeletion syndromes have been defined.     

Stimulation of polydnavirus replication by 20-hydroxyecdysone.

During oviposition the endoparasitic wasp Campoletis sonorensis, introduces a polydnavirus into parasitized insects where viral gene expression is required for endoparasite survival. The polydnavirus is integrated into wasp chromosomal DNA and replicates only in the ovary. Ecdysteroids regulate the developmental expression of many insect genes and may regulate polydnavirus replication. Direct verification of viral replication was performed by dot blot hybridization and by amplifying DNA sequences containing the viral integration site; this 'junction' fragment cannot be amplified from integrated virus. Thoracic ligations and in vitro ecdysteroid treatments of wasp ovaries support the hypothesis that polydnavirus DNA replication is regulated by ecdysteroid during parasite development.     

A low density of 0.8 g cm(-3) for the Trojan binary asteroid 617 Patroclus

The Trojan population consists of two swarms of asteroids following the same orbit as Jupiter and located at the L4 and L5 stable Lagrange points of the Jupiter-Sun system (leading and following Jupiter by 60 degrees ). The asteroid 617 Patroclus is the only known binary Trojan. The orbit of this double system was hitherto unknown. Here we report that the components, separated by 680 km, move around the system's centre of mass, describing a roughly circular orbit. Using this orbital information, combined with thermal measurements to estimate the size of the components, we derive a very low density of 0.8(- 0.1)+0.2 g cm(-3). The components of 617 Patroclus are therefore very porous or composed mostly of water ice, suggesting that they could have been formed in the outer part of the Solar System.     

Biomaterials: silk-like secretion from tarantula feet

An unsuspected attachment mechanism may help these huge spiders to avoid catastrophic falls. Spiders spin silk from specialized structures known as abdominal spinnerets--a defining feature of the creatures--and this is deployed to capture prey, protect themselves, reproduce and disperse. Here we show that zebra tarantulas (Aphonopelma seemanni) from Costa Rica also secrete silk from their feet to provide adhesion during locomotion, enabling these spiders to cling to smooth vertical surfaces. Our discovery that silk is produced by the feet provides a new perspective on the origin and diversification of spider silk.     

Cell fusion-independent differentiation of neural stem cells to the endothelial lineage

Somatic stem cells have been claimed to possess an unexpectedly broad differentiation potential (referred to here as plasticity) that could be induced by exposing stem cells to the extracellular developmental signals of other lineages in mixed-cell cultures. Recently, this and other experimental evidence supporting the existence of stem-cell plasticity have been refuted because stem cells have been shown to adopt the functional features of other lineages by means of cell-fusion-mediated acquisition of lineage-specific determinants (chromosomal DNA) rather than by signal-mediated differentiation. In this study we co-cultured mouse neural stem cells (NSCs), which are committed to become neurons and glial cells, with human endothelial cells, which form the lining of blood vessels. We show that in the presence of endothelial cells six per cent of the NSC population converted to cells that did not express neuronal or glial markers, but instead showed the stable expression of multiple endothelial markers and the capacity to form capillary networks. This was surprising because NSCs and endothelial cells are believed to develop from the ectoderm and mesoderm, respectively. Experiments in which endothelial cells were killed by fixation before co-culture with live NSCs (to prevent cell fusion) and karyotyping analyses, revealed that NSCs had differentiated into endothelial-like cells independently of cell fusion. We conclude that stem-cell plasticity is a true characteristic of NSCs and that the conversion of NSCs to unanticipated cell types can be accomplished without cell fusion.