The activity of nitric oxide synthase (NOS) has recently been shown to increase transiently but dramatically in chick embryonic myoblasts that are competent for fusion and that NO acts as a messenger for the cell fusion. Here we show that the rise in NOS activity is tightly correlated with an increase in NOS protein level, and its synthesis is under transcriptional control. In addition, a partial cDNA sequence of NOS obtained by reverse transcription PCR on total RNA from chick myoblasts was found to be identical with that of the inducible type of NOS (iNOS) from chick macrophage. Thus chick myoblast NOS must belong to the family of iNOS. Consistently, pyrrolidine dithiocarbamate, a potent inhibitor of nuclear factor kappaB (NF-kappaB), prevented the expression of myoblast NOS. Furthermore the antioxidant also strongly inhibited cell fusion, and its inhibitory effect was reversed by treatment with sodium nitroprusside, an NO-generating agent. In addition, nuclear extracts obtained from myoblasts that were competent for fusion, but not those from proliferating cells or from fully differentiated myotubes, were capable of binding to the consensus NF-kappaB site in the promoter region of the gene encoding iNOS. These results suggest that NF-kappaB-dependent expression of NOS is an important step in membrane fusion of chick embryonic myoblasts.
The effect of Cu on the hydrogen reduction of molybdenum oxide powders was investigated by measuring the humidity change during a non-isothermal process of hydrogen reduction. The presence of Cu induced a shift in the reduction temperature and strongly affected the reduction processes of MoO3→Mo4O11→MoO2, which comprised the contained chemical vapor transport of MoOx(OH)2. This study suggests that the surface of the Cu grains acts as a nucleation site for the reduction of MoOx(OH)2 to MoO2 particles from MoO3 or Mo4O11 phases. Such an activated reduction process results in the deposition of metallic Mo and MoO2 particles on the surface of the Cu grains.
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