Circadian fluctuation of susceptibility to haloperidol under constant conditions

An endogenous circadian rhythm of the sedative and antiapomorphine effects of haloperidol was observed under constant conditions for 7 days as well as under an entrained light-dark cycle.     

Receptor binding and internalization of immobilized transcobalamin II by mouse leukaemia cells

Membrane transport of vitamin B12 (cyanocobalamin; Cbl) into mammalian cells is mediated by the serum protein transcobalamin II (TCII). In mouse leukaemia L1210 cells, TCII-Cbl binds to membrane receptors in a rapid, temperature-independent step and is internalized by a slow, temperature-dependent process. To delineate the location of receptors on these cells, we have constructed a visual probe by covalently coupling purified TCII-Cbl to submicrometre latex particles (minibeads). We report here that when L1210 cells are incubated with minibeads containing TCII-Cbl at 4 degrees C and examined by scanning electron microscopy (SEM), the particles are found attached predominantly to microvilli. Incubation of the cells at 37 degrees C results in the internalization of the minibeads. As visualized by transmission electron microscopy (TEM), this endocytotic process seems to occur in clathrin-coated pits and vesicles at the cell surface.     

Ultrastructure of human myeloma cells studied by peroxidase conjugated antibodies directed to human immunoglobulin component chains

Zusammenfassung Menschliche Myelomazellen wurden immunchemischelektronenoptisch untersucht. Durch die Behandlung mit peroxidasekonjugiertem Antikörper gegen die Immunoglobuline H- oder L-Kette wurde keine H-Kette beobachtet.     

Two sulfur-containing ansamycin antibiotics from Streptomyces albolongus

Two sulfur-containing ansamycin antibiotics were isolated from the culture broth of Streptomyces albolongus C-46366; the major one was identical with awamycin and the minor one was a new ansamycin antibiotic, ansathiazin. Their structures were elucidated from their reactions and spectroscopic analyses. These antibiotics were active against gram-positive bacteria, acid-fast bacteria and a protozoan.     

Enzymatic catalysis of anti-Baldwin ring closure in polyether biosynthesis

Polycyclic polyether natural products have fascinated chemists and biologists alike owing to their useful biological activity, highly complex structure and intriguing biosynthetic mechanisms. Following the original proposal for the polyepoxide origin of lasalocid and isolasalocid and the experimental determination of the origins of the oxygen and carbon atoms of both lasalocid and monensin, a unified stereochemical model for the biosynthesis of polyether ionophore antibiotics was proposed. The model was based on a cascade of nucleophilic ring closures of postulated polyepoxide substrates generated by stereospecific oxidation of all-trans polyene polyketide intermediates. Shortly thereafter, a related model was proposed for the biogenesis of marine ladder toxins, involving a series of nominally disfavoured anti-Baldwin, endo-tet epoxide-ring-opening reactions. Recently, we identified Lsd19 from the Streptomyces lasaliensis gene cluster as the epoxide hydrolase responsible for the epoxide-opening cyclization of bisepoxyprelasalocid A to form lasalocid A. Here we report the X-ray crystal structure of Lsd19 in complex with its substrate and product analogue to provide the first atomic structure-to our knowledge-of a natural enzyme capable of catalysing the disfavoured epoxide-opening cyclic ether formation. On the basis of our structural and computational studies, we propose a general mechanism for the enzymatic catalysis of polyether natural product biosynthesis.     

Osteoprotection by semaphorin 3A

The bony skeleton is maintained by local factors that regulate bone-forming osteoblasts and bone-resorbing osteoclasts, in addition to hormonal activity. Osteoprotegerin protects bone by inhibiting osteoclastic bone resorption, but no factor has yet been identified as a local determinant of bone mass that regulates both osteoclasts and osteoblasts. Here we show that semaphorin 3A (Sema3A) exerts an osteoprotective effect by both suppressing osteoclastic bone resorption and increasing osteoblastic bone formation. The binding of Sema3A to neuropilin-1 (Nrp1) inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation by inhibiting the immunoreceptor tyrosine-based activation motif (ITAM) and RhoA signalling pathways. In addition, Sema3A and Nrp1 binding stimulated osteoblast and inhibited adipocyte differentiation through the canonical Wnt/β-catenin signalling pathway. The osteopenic phenotype in Sema3a?/? mice was recapitulated by mice in which the Sema3A-binding site of Nrp1 had been genetically disrupted. Intravenous Sema3A administration in mice increased bone volume and expedited bone regeneration. Thus, Sema3A is a promising new therapeutic agent in bone and joint diseases.     

Effects of Au nanoparticle addition to hole transfer layer in organic solar cells based on copper naphthalocyanine and fullerene

Organic solar cells based on copper naphthalocyanine(CuNc) and fullerene(C60) were fabricated, and their photovoltaic properties were investigated. C60 and CuNc were used as n-type and p-type semiconductors, respectively. In addition, the effect of Au nanoparticle addition on a hole transfer layer was investigated, and the power conversion efficiency of the devices was improved after blending the Au nanoparticles into the hole transport layer. Nanostructures of Au nanoparticles were investigated by transmission electron microscopy and X-ray diffraction. Energy levels of molecules were calculated by molecular orbital calculations, and the nanostructure and electronic properties were discussed.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.