Cell surface molecules are not only important for cell–cell interactions but also useful for a marker to define cell types and differentiation stages. Unlike hematopoietic system in which numerous such antigens have been identified, only a few cell surface molecules have been used to define differentiation stage of hepatocytes. In order to identify such cell surface molecules, we performed DNA microarray analysis using mRNA from fetal hepatocytes in E12.5 and E17.5 mice and cDNAs encoding a membrane protein were selected. Northern blot analysis was employed to confirm the genes upregulated during maturation of fetal hepatocytes and neuritin, a GPI‐anchored protein, was found as a membrane protein expressed in hepatocytes, but not in nonparenchymal cells. Its expression increased along with liver development and the maximum expression was achieved from the neonatal to adult stage. The neuritin protein was localized in sinusoidal lumen of hepatocytes in adult liver. Partial hepatectomy transiently downregulated the expression of neuritin. The expression of neuritin mRNA in C/EBPα deficient liver was reduced to about 50% of that of wild type mice. Thus, neuritin expression is well correlated to the maturation of hepatocytes and can be a useful tool to define the differentiation stage of hepatocytes.
A photoexcitation is one of the promising external fields to control the material phases. Here, the authors have demonstrated that the magnetic and structural properties of a spin-crossover complex, Fe(phen)2(NCS)2 (phen=1,10-phenanthroline), can be reversibly switched by the on-off action of the continuous photoexcitation at the same temperature. The structural data suggest that the density of the high-spin Fe2+ in the photoinduced phase is about 0.88. Suppressed atomic vibrations of the photoinduced phase exclude the conventional heating effect as the origin for the observed optical switching.
A cDNA clone encoding a new type of GalNAc alpha 2,6-sialyltransferase (ST6GalNAc II) with a structure similar to that of a previously cloned GalNAc alpha 2,6-sialyltransferase (ST6GalNAc I; Kurosawa, N., Hamamoto, T., Lee, Y.-C., Nakaoka, T., Kojima, N., and Tsuji, S. (1994) J. Biol. Chem. 269, 1402-1409) was obtained from chicken testes. The predicted amino acid sequence of ST6GalNAc II encodes a protein with type II transmembrane topology, as found for other glycosyltransferases, and showed 32% identity with that of ST6GalNAc I. Transfection of the full length ST6GalNAc II gene into COS cells led to GalNAc alpha 2,6-sialyltransferase activity with a different substrate specificity from that of ST6GalNAc I. Moreover, asialofetuin after treatment with beta-galactosidase did not serve as an acceptor for this enzyme. 14C-Sialylated oligosaccharides obtained from resialylated asialobovine submaxillary mucin with this enzyme were identical to Gal beta 1,3([14C]NeuAc alpha 2,6)GalNAc-ol but not [14C]NeuAc alpha 2,6GalNAc-ol. These results clearly show that the expressed enzyme is a novel type of sialyltransferase that requires beta-galactoside residues linked to GalNAc residues, whereas sialic acid residues linked to galactose residues are not essential for the activity.
We have found a photoinduced phase transition (PIPT) in the mixed-valence (MV) gold complex ${\mathrm{Cs}}_{2}{\mathrm{Au}}_{2}{\mathrm{Br}}_{6}$ from the MV state (ambient pressure phase) to the single-valence (SV) phase (high-pressure phase) in the pressure region from 6.4 to 6.8 GPa. We have observed an accumulation of the photoirradiation effect of each pulse shot, and have ascribed it to stabilization of the photogenerated SV clusters due to the cooperative Jahn-Teller instability of ${\mathrm{Au}}^{2+}$ ions. The PIPT shows a distinct threshold behavior against the photon density as well as the shots number, which has been interpreted in terms of the critical nucleation of the photoinjected SV clusters. We further found that the phototransformed SV phase is not stable below 5.5 GPa, and changes into the former MV phase after a long dead time of $\ensuremath{\sim}{10}^{4}$ s.
We have performed the single crystal X-ray structure analysis of the three-dimensional halogen-bridged mixedvalence compound, Cs2AuIAuIIICl6 under high pressures up to 18 GPa. The high pressure apparatus used is a diamond-anvil-cell with helium gas as an inert and hydrostatic pressure-transmitting medium. The pressure dependence of the unit cell parameters indicates a structural phase transition from tetragonal to cubic at 12. 5 GPa. The high pressure phase has a space group, Pm3m.
