Molecular function of the novel α7β2 nicotinic receptor

The α7 nicotinic receptor is a promising drug target for neurological and inflammatory disorders. Although it is the homomeric member of the family, a novel α7β2 heteromeric receptor has been discovered. To decipher the functional contribution of the β2 subunit, we generated heteromeric receptors with fixed stoichiometry by two different approaches comprising concatenated and unlinked subunits. Receptors containing up to three β2 subunits are functional. As the number of β2 subunits increases in the pentameric arrangement, the durations of channel openings and activation episodes increase progressively probably due to decreased desensitization. The prolonged activation episodes conform the kinetic signature of α7β2 and may have an impact on neuronal excitability. For activation of α7β2 receptors, an α7/α7 binding-site interface is required, thus indicating that the three β2 subunits are located consecutively in the pentameric arrangement. α7-positive allosteric modulators (PAMs) are emerging as novel therapeutic drugs. The presence of β2 in the pentamer affects neither type II PAM potentiation nor activation by an allosteric agonist whereas it impairs type I PAM potentiation. This first single-channel study provides fundamental basis required to decipher the role and function of the novel α7β2 receptor and opens doors to develop selective therapeutic drugs.     

Synopsis of ‘onychocellid’ cheilostome bryozoan genera

Genera assigned to the cheilostome bryozoan family Onychocellidae are revised based on the skeletal morphology of the type species and, when possible, the type material of these species. All genera are illustrated using scanning electron micrographs, some for the first time. Onychocellidae, which ranges from the Cenomanian stage of the Cretaceous to the Recent, has been a particularly troublesome family because of poorly defined generic concepts correlating at least in part with a paucity of morphological characters. Thirty-five genera are described in this review. Of these, two are recognised as subjective synonyms of other onychocellid genera (Rhebasia and Semieschara), one cannot be sufficiently characterised from the type material (Collura), and two are new: Aechmellina gen. nov. (type species Aechmella falcifera) and Kamilocella gen. nov. (type species Eschara latilabris). A neotype is chosen for Rhagasostoma hexagonum, the type species of Rhagasostoma. A key is provided to assist in the identification of onychocellid genera. Phylogenetic relationships between genera remain obscure and are unlikely to be fully resolved based on skeletal morphology alone. The family as an entity is loosely circumscribed and almost certainly paraphyletic, containing stem genera of other anascan familes such as Lunulitidae, Coscinopleuridae and Aspidostomatidae.

www.zoobank.org/urn:lsid:org:pub:63A31AD2-F049-42CB-A45B-557014DC286E     

Predation on eggs of Schneider’s dwarf caiman,Paleosuchus trigonatus (Schneider, 1807), by armadillos and other predators

Nests of Schneider’s dwarf caiman, Paleosuchus trigonatus, were located in the forests around three streams that drain into the Xingu River, Brazilian Amazonia, in October 2014. Camera traps were installed at the edge of four nests to document predators and female parental care. At two nests, females unsuccessfully defended their nests against one or more giant armadillos, Priodontes maximus, and nine-banded armadillos, Dasypus novemcinctus. Both armadillo species responded to the attack by fleeing and returning on the opposite side of the nest by going around the tree under which the nest was located. Giant armadillos have never before been recorded consuming caiman eggs and their diet has been described as consisting mostly of ants and termites. Another species of armadillo, Cabassous unicinctus, was also registered digging into a nest and probably consuming eggs, though it is generally considered to be primarily insectivorous. A tayra (Eira barbara), lizard (Tupinambis teguixin) and coati (Nasua nasua) were also registered taking eggs from nests during the day, but we obtained no registers of nest defence by caimans during the day. The three nests were attacked after 60 days of incubation, when the eggs were well developed.     

Tribbles: novel regulators of cell function; evolutionary aspects

Identification of rate-limiting steps or components of intracellular second messenger systems holds promise to effectively interfere with these pathways under pathological conditions. The emerging literature on a recently identified family of signalling regulator proteins, called tribbles gives interesting clues for how these proteins seem to link several ‘independent’ signal processing systems together. Via their unique way of action, tribbles co-ordinate the activation and suppression of the various interacting signalling pathways and therefore appear to be key in determining cell fate while responding to environmental challenges. This review summarises our current understanding of tribbles function and also provides an evolutionary perspective on the various tribbles genes. Received 10 January 2006; received after revision 20 March 2006; accepted 5 April 2006     

Structural characterization of two papaya chitinases, a family GH19 of glycosyl hydrolases

Two chitinases, able to use tetra-N-acetylglucosamine, chitin and chitosan as substrates, were characterized after purification from Carica papaya latex. The complete amino acid sequence of the major form and about 40% of the minor one were determined through proteolytic digestions and mass spectroscopy analysis. Sequencing demonstrated that both papaya chitinases are members of the family 19 of glycosyl hydrolases (GH19). Based on the known 3-D structures of other members of family GH19, it was expected that papaya chitinases would adopt all-alpha structures. However, circular dichroism and infrared spectroscopy indicated, for the papaya chitinases, a content of 15–20% of extended structures besides the expected 40% of alpha helices. Since the fully sequenced papaya chitinase contains a large number of proline residues the possibility that papaya chitinase contains polyproline II stretches was examined in the context of their resistance against proteolytic degradation. Received 11 July 2006; received after revision 13 October 2006; accepted 25 October 2006     

In vivo matrix-guided human mesenchymal stem cells

Microfracture of subchondral bone results in intrinsic repair of cartilage defects. Stem or progenitor cells from bone marrow have been proposed to be involved in this regenerative process. Here, we demonstrate for the first time that mesenchymal stem (MS) cells can in fact be recovered from matrix material saturated with cells from bone marrow after microfracture. This also introduces a new technique for MS cell isolation during arthroscopic treatment. MS cells were phenotyped using specific cell surface antibodies. Differentiation of the MS cells into the adipogenic, chondrogenic and osteogenic lineage could be demonstrated by cultivation of MS cells as a monolayer, as micromass bodies or mesenchymal microspheres. This study demonstrates that MS cells can be attracted to a cartilage defect by guidance of a collagenous matrix after perforating subchondral bone. Protocols for application of MS cells in restoration of cartilage tissue include an initial invasive biopsy to obtain the MS cells and time-wasting in vitro proliferation and possibly differentiation of the cells before implantation. The new technique already includes attraction of MS cells to sites of cartilage defects and therefore may overcome the necessity of in vitro proliferation and differentiation of MS cells prior to transplantation. Received 3 November 2005; received after revision 15 December 2005; accepted 4 January 2006