Clusters of the Heavier Elements of Main Groups 14–16: A Novel Synthetic Route for Polyanions in Molten Crown Ether

A novel procedure allows the synthesis of homoatomic polyanions directly from the elements E (E = Sn, As, Sb, Te) in molten A/18-crown-6 as reaction medium (A = K, Rb) at temperatures between 40 and 80° [1]. The reactions are carried out by adding E to mixtures of A and 18-crown-6 that proved to form stable melts under these conditions. Further work off using ethylenediamine or DMF as solvent yielded single crystals of the following compounds: [K(18-crown-6)]4Sn9 (1), [K(18-crown-6)]3KSn9·en (2), [K(18-crown-6)]3As7 (3), [K([2.2.2]crypt)]2[K(18-crown-6)]Sb7·0.5en (4), [Rb(18-crown-6)]3Sb7 (5), [K(18-crown-6)]2Te4 (6), and [K(18-crown-6)]2Te4·en (7). In all compounds short contacts between the Zintl ions and A-atoms are observed. The influence of cation-anion interactions on the structure of these anions is discussed

Measuring cellular traction forces on non-planar substrates

Animal cells use traction forces to sense the mechanics and geometry of their environment. Measuring these traction forces requires a workflow combining cell experiments, image processing and force reconstruction based on elasticity theory. Such procedures have been established before mainly for planar substrates, in which case one can use the Green's function formalism. Here we introduce a worksflow to measure traction forces of cardiac myofibroblasts on non-planar elastic substrates. Soft elastic substrates with a wave-like topology were micromolded from polydimethylsiloxane (PDMS) and fluorescent marker beads were distributed homogeneously in the substrate. Using feature vector based tracking of these marker beads, we first constructed a hexahedral mesh for the substrate. We then solved the direct elastic boundary volume problem on this mesh using the finite element method (FEM). Using data simulations, we show that the traction forces can be reconstructed from the substrate deformations by solving the corresponding inverse problem with a L1-norm for the residue and a L2-norm for 0th order Tikhonov regularization. Applying this procedure to the experimental data, we find that cardiac myofibroblast cells tend to align both their shapes and their forces with the long axis of the deformable wavy substrate.Comment: 34 pages, 9 figure

Interleukin-1β-Induced Inhibition of Hair Growth In Vitro Is Mediated by Cyclic AMP

Interleukin (IL)-1 has been shown to be a potent inhibitor of hair growth in vitro. We hypothesized that this cytokine might be a decisive factor causing hair loss during the lymphocytic attack in alopecia areata. Neither the intracellular pathways involved in hair growth inhibition mediated by IL-1β nor the signal transduction processes within hair follicles in general are known. We therefore investigated the intracellular signals involved in human hair growth in vitro. Hair follicles were isolated from scalp biopsies by microdissection and hair growth was measured daily by image analysis. We assessed intracellular signal transducing elements using specific inhibitors or activators either alone or in combination with IL-1β. The calcium ionophore A 23187 induced a rapid and complete arrest of hair growth and phorbol-12-myristate-13-acetate (PMA), genistein, or IL-1β decreased hair growth by approximately 60%-80%. IL-1β-elicited hair growth arrest was not antagonized by calphostin C, a specific inhibitor of protein kinase C. In contrast, coincubation of IL-1β with pertussis toxin or H 1004 neutralized the effect of IL-1β and dibutyryl-cAMP and cholera toxin, an activator of adenylate cyclase, inhibited hair growth. These data suggest that cAMP acts as a second messenger for IL-1β-induced inhibition of hair growth. Moreover, our data indicate that in vitro hair growth is dependent on intracellular Ca2+ levels and activation of tyrosine kinase as well as protein kinase C. We were unable to detect a signal transducing element responsible for enhanced hair growth in vitro

Identification of cDNAs from Japanese pufferfish (Fugu rubripes) and Atlantic salmon (Salmo salar) coding for homologues to tetrapod prion proteins

AbstractWe identified cDNAs coding for homologues to tetrapod prion proteins (PrPs) in Atlantic salmon (Salmo salar) and Japanese pufferfish (Fugu rubripes), which were termed ‘similar to PrPs’ (stPrPs). Besides significant sequence homologies the fish stPrPs display characteristic structural features in common with tetrapod PrPs. In addition, two stPrPs were shown to be highly expressed in brain tissue. None of the so far identified PrP-homologues of fish resembles doppel. Hence, the duplication of the PrP gene, which generated doppel, may have occurred not in fish but later in the tetrapod lineage. The identification of fish PrPs provides a basis to address concerns about a possible susceptibility of fish to prion infections