Interaction of diphtheria toxin fragment A and of elongation factor 2 with Cibacron blue

Diphtheria toxin fragment A interacts with Cibacron blue in solution, although it is not retained by blue Sepharose columns. Difference spectral titration of fragment A with the dye gives a dissociation constant of the order of 10^–5 M and a 11 stoichiometry for the complex. In equilibrium dialysis experiments Cibacron blue behaves as a competitive inhibitor of the binding of NAD to diphtheria toxin fragment A. The dye inhibits in a non-competitive way the fragment A-catalysed transfer of ADP-ribose from NAD to elongation factor 2 (EF2). By affinity chromatography on blue Sepharose a binding of EF2 and of ADP-ribosyl-EF2 with the dye is also demonstrated. GDP, GTP and GDP(CH₂)P are able to displace EF2 from blue Sepharose.     

Two new Dematiaceous Hyphomycetes from humid tropic forest litter

Abstract

Two Dematiaceous Hyphomycetes, Beltraniella lyrata and Beltraniopsis fabularis, found on tropical forest litter in the Tai National Park in Ivory Coast are proposed as new species and described.     

« Chaetopsina ivoriensis » a new species of Dematiaceous Hyphomycetes

Abstract

The discover and morphological characters of a Dematiaceous Hyphomycetes are described. The material, studied under a morphological point of view directly collected on the natural substratum, allows us to establish the appartenance to the genus Chaetopsina. Since this species does not appeare described till now, the Authors propose for it the nomenclature ivoriensis as a new species.     

Sertoli cells initiate testicular innate immune responses through TLR activation

TLRs play a crucial role in early host defense against invading pathogens. In the seminiferous epithelium, Sertoli cells are the somatic nurse cells that mechanically segregate germ cell autoantigens by means of the blood-tubular barrier and create a microenvironment that protects germ cells from both interstitial and ascending invading pathogens. The objective of this study was to examine TLR expression and their functional responses to specific agonists in mouse Sertoli cells. We measured the expression of TLR2, TLR4, TLR5, and TLR6 mRNAs and confirmed by FACS analysis the presence of proteins TLR2 and TLR5 on which we focused our study. Stimulation of Sertoli cells with macrophage-activating lipopeptide-2, agonist of TLR2/TLR6, and with flagellin, agonist of TLR5, induces augmented secretion of the chemokine MCP-1. To assess the functional significance of MCP-1 production following TLR stimulation, conditioned medium from either macrophage-activating lipopeptide-2 or flagellin-treated Sertoli cells was tested for in vitro chemotaxis assay, and a significant increase of macrophage migration was observed in comparison with unstimulated conditioned medium. Moreover, we studied the role of NF-kappaB and of MAPKs in regulating TLR-mediated MCP-1 secretion by using inhibitors specific for each transduction pathway and we demonstrated a pivotal role of the IkappaB/NF-kappaB and JNK systems. In addition, TLR2/TLR6 and TLR5 stimulation induces increased ICAM-1 expression in Sertoli cells. Collectively, this study demonstrates the novel ability of Sertoli cells to potentially respond to a wide variety of bacteria through TLR stimulation.     

A neurofibrillar body in the perikaryon of nervus terminalis ganglion cells in teleosts

Summary In three species of Teleosts (Tinea tinea L., Leuciscus cephalus cabeda Risso, Epinephelus guaza L.) a round strongly argentophilic body of considerable size occurs in the cytoplasm of the nervus terminalis ganglion cells. In Tinea, surgical interruption of functional connections of the ganglion cells does not produce any apparent change either in the number or in the size of these cytoplasmic bodies.Electron microscopical observations show that the neurofibrillar body is made up of densely packed and irregularly arranged bundles. In cross section, each of these bundles appears to be composed of neurofilaments (100 Å in thickness) and neurotubules (diameter: 300 Å). Each tubule is surrounded by 9–10 filaments equi-distant from one another, and at a distance of 30–40 Å from the central tubule.The authors are indebted to Prof. G. Palladini for helpful histochemical advice, to Prof. B. Bertolini for electron micrographs and to Mr. D. Scorsini for skilful technical assistance.     

Dielectrophoretic trapping in microwells for manipulation of single cells and small aggregates of particles

In this work we present a novel concept of active microwells based on cylindrical wells able to vertically trap and control single particles by means of negative dielectrophoresis. The device is fabricated by drilling through holes on a polyimide substrate with copper-gold or aluminum metals, forming three annular electrodes within the well. A channel under the device provides a fluid flow filling the microwell by capillarity. Particles are delivered from the top by a microdispenser and applying sinusoidal signals to the electrodes at frequencies ranging from 100kHz to 1.5MHz and amplitudes between 2V and 7V they are successfully trapped and levitated at the level of the central electrode in the middle of microwells with a diameter of 125mum. By changing signal phases, other configurations are also enabled to load particles in the well or eject them from the bottom. The extension to an array of microwells is presented and design rules are described for routing electrode connections and setting signal parameters. K562 cells cultured with Ara-C 1000nM were successfully trapped and controlled in physiological media. Polystyrene beads were also levitated in water and were used for experimental measurements on minimum amplitudes and phase differences in the signals required to levitate beads, confirming the results obtained by simulation.     

Sam68 regulates translation of target mRNAs in male germ cells,necessary for mouse spermatogenesis

Sam68 is a KH-type RNA-binding protein involved in several steps of RNA metabolism with potential implications in cell differentiation and cancer. However, its physiological roles are still poorly understood. Herein, we show that Sam68^−/− male mice are infertile and display several defects in spermatogenesis, demonstrating an essential role for Sam68 in male fertility. Sam68^−/− mice produce few spermatozoa, which display dramatic motility defects and are unable to fertilize eggs. Expression of a subset of messenger mRNAs (mRNAs) is affected in the testis of knockout mice. Interestingly, Sam68 is associated with polyadenylated mRNAs in the cytoplasm during the meiotic divisions and in round spermatids, when it interacts with the translational machinery. We show that Sam68 is required for polysomal recruitment of specific mRNAs and for accumulation of the corresponding proteins in germ cells and in a heterologous system. These observations demonstrate a novel role for Sam68 in mRNA translation and highlight its essential requirement for the development of a functional male gamete.     

Schede micologiche III contributo micromiceti della Valle del Tevere

Riassunto Tre ifali rinvenuti su legno morto diPopulus alba L., raccolto nel Lazio, sono identificati come nuove specie, una del nuovo genereDephilippia e due del genereAcrotheca Fuckel, I caratteri tassonomici riguardano gli organi vegetativi e riproduttivi sviluppati sul substrato naturale.

---

Summary Three Hyphomycetes found on dead wood ofPopulus alba L., collected in Lazio, have been identified as new species, one belonging to the new genusDephilippia and two to the genusAcrotheca Fuckel. The taxonomic characters have been represented based on the vegetative and reproductive organs developed on natural substratum.

---

---

Il lavoro è stato eseguito presso la Sezione di Protezione Fitosanitaria, sotto la guida del Consulente Prof.C. Sibilia.