Positive-Temperature-Coefficient Effect in Graphite–Cristobalite Composites

An anomalous positive temperature coefficient (PTC) of resistance was found in a conductor–insulator ceramic composite. The composite materials was composed of randomly dispersed conducting graphite and insulating cristobalite-form SiO₂ particles. The PTC effect occurred at exactly 230°C, that is, at a reversible phase inversion point with a large thermal expansion of cristobalite. The magnitude of the PTC anomaly was high in composites located in the middle of the percolation curve, and loaded with large graphite and fine SiO₂ particles.     

Genotype analysis of prepro-vasopressin signal peptide in vasopressin-producing and -non-producing lung tumors

A polymorphism in the nucleic acid sequence encoding the signal peptide of the human prepro-vasopressin (AVP) has been reported in an AVP producing small cell lung carcinoma (SCLC) cell line. The difference predicts expression in tumor cells of a variant signal peptide with Pro for Leu 11. To clarify whether this difference is required for AVP secretion from SCLC cells and/or reflects increased mutagenesis in malignant tumors, the exon encoding the signal peptide of prepro-AVP in two AVP producing SCLC and 9 non-producing lung tumors was amplified using polymerase chain reaction. The variant sequence was neither found by direct sequencing nor by restriction enzyme analysis. These results suggest that similar to the hypothalamus the normal signal peptide is functional in tumor cells and that the variant signal peptide is not a prerequisite for AVP secretion from SCLC cells.     

Non-polarized memory-switching characteristics of ZnTe thin films

ZnTe thin films were prepared by the conventional vacuum-deposition method. Polycrystalline thin films could be deposited on a glass substrate at substrate temperature between 20 and 450°C. Epitaxial thin films could be obtained on GaAs and InAs single crystals at substrate temperatures higher than 200°C.Memory switching could be observed in metal-ZnTe-metal sandwich devices prepared on glass substrates. Both switching transitions, from off to on and on to off, could be performed without changing the bias polarity if a suitable value of series resistance was selected for each transition. Typical values of the series resistor were 20 KΩ for off to on and 200 Ω for on to off transitions. Transition from off to on is explained as a result of the formation of a filamentary path in the off state, followed by the formation of a metallic filament in the on state. Transition from on to off is considered a result of thermal rupture of the metallic filament.     

Structure-function relationship of T-2 toxin and its metabolites in inducing thymic apoptosis in vivo in mice

Recently we found that a single administration of T-2 toxin (T-2), a trichothecene mycotoxin, into mice induced DNA fragmentation, a biochemical hallmark of apoptosis, in the thymus. In this study, we investigated the effective chemical structure(s) of T-2-derived metabolites capable of inducing thymic apoptosis in vivo in mice. Metabolic conversion of T-2 to 3'-hydroxy-T-2 toxin (3'-OH-T-2) did not diminish the apoptosis-inducing activity, since essentially the same level of fragmented DNA was detected in the thymus taken from mice injected with either T-2 or 3'-OH-T-2. In contrast, hydrolysis of T-2 and 3'-OH-T-2 at the carbon-4 (C-4) position to HT-2 toxin (HT-2) and 3'-hydroxy-HT-2 toxin (3'-OH-HT-2), respectively, greatly decreased the level of DNA fragmentation. Similarly, hydrolysis of T-2 at the carbon-8 (C-8) position to neosolaniol strongly diminished its ability to induce DNA fragmentation. T-2 tetraol, having no ester groups, was unable to induce apoptosis. Based on the data presented in this study, we concluded that both the acetyl group at the C-4 position and the isovaleryl or 3'-hydroxyisovaleryl group at the C-8 position of the T-2 molecule are important for inducing cell death through apoptosis in the thymus.     

The product of the proto-oncogene c-cbl: a negative regulator of the Syk tyrosine kinase

Engagement of antigen and immunoglobulin receptors on hematopoietic cells is directly coupled to activation of nonreceptor protein tyrosine kinases (PTKs) that then phosphorylate critical intracellular substrates. In mast cells stimulated through the FcvarepsilonRI receptor, activation of several PTKs including Syk leads to degranulation and release of such mediators of the allergic response as histamine and serotonin. Regulation of Syk function occurred through interaction with the Cbl protein, itself a PTK substrate in this system. Overexpression of Cbl led to inhibition of Syk and suppression of serotonin release from mast cells, demonstrating its ability to inhibit a nonreceptor tyrosine kinase. Complex adaptor proteins such as Cbl can directly regulate the functions of the proteins they bind.     

Photo-oxidative coupling polymerization of methoxy acetonitrile and thermal behavior of the polymer obtained

Photo-oxidative coupling polymerization of methoxy acetonitrile was carried out by using organic peroxide as an oxidizing agent under UV light irradiation at ambient temperature. The acetonitrile gave a homopolymer with a molecular weight of about 1000-1600 in moderate yield. ¹H-NMR and ESR spectra demonstrated the production of the polymer with the structure of 1,1-disubstituted polymethylene through a methoxycyanomethyl radical intermediate. It was also found that the polymer easily produced unpaired electrons in the structure only by heating and it initiated the polymerization of methyl methacrylate above 70°C. In addition, the acetonitrile also afforded a copolymer with diphenylmethane by the coupling polymerization.     

Association between MICA gene A4 allele and acute anterior uveitis in white patients with and without HLA-B27

Because all known influenza A subtypes exist in the aquatic bird reservoir, influenza is not an eradicable disease; prevention and control are the only realistic goals. If people, pigs, and aquatic birds are the principal variables associated with interspecies transfer of influenza virus and the emergence of new human pandemic strains, influenza surveillance in these species is indicated. Live-bird markets housing a wide variety of avian species together (chickens, ducks, geese, pigeon, turkeys, pheasants, guinea fowl), occasionally with pigs, for sale directly to the public provide outstanding conditions for genetic mixing and spreading of influenza viruses; therefore, these birds should be monitored for influenza viruses. Moreover, if pigs are the mixing vessel for influenza viruses, surveillance in this population may also provide an early warning system for humans.