On the Magnetic Susceptibilities of Troponoid System. II : Diamagnetism of Methyl Ether Derivatives

The magnetic susceptibiilties of tropolone methyl ether (Ia), 2-methoxy-7-bromo-tropone (o-bromo-tropolone methyl ether) (II) and α-thujaplicin methyl ether(III) have been measured by use of the Gouy balance described in the previous article.^ The experimental results (-χ_M×10^6) obtained for (Ia), (II) and (III) are 71, 88 and 105 respectively. The susceptibility of crystalline form of (Ia), i. e., (C_8H_8O_2)_2H_2O (Ib), has been also measured, the result being - 160 ×10^ per mole. It has been shown that the value of ΔK_M, which shows the diamagnetic anisotropy of the tropolone ring belonging to each compound, can be easily derived approximately from the experimental value by the application of the empirical additive rule. The remarkable diamagnetic decrements have been observed in the ΔK_M values, the amounts of which depend upon the kinds of the substituents, i. e., OCH_3, Br and isopropyl groups. The results have shown that the ΔK_M value of (II) is almost zero and that of (Ia) is half the value of tropolone itself

On the Magnetic Susceptibilities of Troponoid-System. I : Diamagnetism of Hinokitiol (β-Thujaplicin) and α-Thujaplicin

The diamagnetic susceptibilities of hinokitiol ((β-thujaplicin) and α-thujaplicin in powdered crystal form have been measured and the structures of the tropolone-ring are discussed. The observed molar susceptibilities obtained in the present experiments are -(102±1)×10 for hinokitiol, -(100±3)×10 for α-thujaplicin (colourless, m. p. 34°), and -(97±2)×10 for α-thujaplicin (light yellow, m. p. 24°). These observed data have been compared with calculated values, which were computed by use of the four methods ; the Pascal\u27s additive law, the Slater-Angus method, Langevin\u27s formula referring to the diamagnetism for the planar orbit, and the theory of diamagnetic anisotropy of molecular orbitals (London\u27s method), with the result that there are six π-electrons, within each tropolone-ring of these compounds, which are able to revolve along the closed circuit constructed out of the periphery of seven membered ring. As a necessary consequence of this condition, it follows the ionization between one of the carbon atoms in the ring system and the oxygen atom in the carbonyl group, assuming the former a positive charge and the later a negative one

Opposing Tumor-Promoting and -Suppressive Functions of Rictor/mTORC2 Signaling in Adult Glioma and Pediatric SHH Medulloblastoma.

Most human cancers arise from stem and progenitor cells by the sequential accumulation of genetic and epigenetic alterations, while cancer modeling typically requires simultaneous multiple oncogenic events. Here, we show that a single p53 mutation, despite causing no defect in the mouse brain, promoted neural stem and progenitor cells to spontaneously accumulate oncogenic alterations, including loss of multiple chromosomal (chr) regions syntenic to human chr10 containing Pten, forming malignant gliomas with PI3K/Akt activation. Rictor/mTORC2 loss inhibited Akt signaling, greatly delaying and reducing glioma formation by suppressing glioma precursors within the subventricular zone stem cell niche. Rictor/mTORC2 loss delayed timely differentiation of granule cell precursors (GCPs) during cerebellar development, promoting sustained GCP proliferation and medulloblastoma formation, which recapitulated critical features of TP53 mutant sonic hedgehog (SHH) medulloblastomas with GLI2 and/or N-MYC amplification. Our study demonstrates that Rictor/mTORC2 has opposing functions in neural stem cells and GCPs in the adult and the developing brain, promoting malignant gliomas and suppressing SHH-medulloblastoma formation, respectively

A Spectroscopic Study of Pyrazine in Mixed Acidic Solvents

Absorption Spectrum of pyrazine was examined in mixed solvents of trifluoroacetic acid-hexane (I), trifluoroacetic acid-water (II), isobutyric acid-hexane (III), and isopropyl alcohol-hexane (IV). Basicity constant pK_ of pyrazine was determined to be 0.6 in the mixture II, whereas the determination of pK_> was unsuccessful, Spectral data showed no discernible amount of protonated species in the mixtures III and IV. The concentration dependence of the absorption coefficient of a n-π^* transition in the mixture III can be interpreted by assuming that pyrazine forms two hydrogen bonds with two isobutyric acid molecules

Identification of two Wnt-responsive elements in the intron of RING finger protein 43 (RNF43) gene.

RING finger protein 43 (RNF43), an E3-type ubiquitin ligase, is frequently up-regulated in human colorectal cancer. It has been shown that expression of RNF43 is regulated by the Wnt-signaling pathway. However the regulatory region(s) for its transcriptional activation has not been clarified. In this study, we have shown for the first time that RNF43 is a direct target of TCF4/β-catenin complex, and that its expression is regulated by a regulatory region containing two Wnt-responsive elements (WREs) in intron2. A reporter gene assay revealed that nucleotide substitutions in the WREs decreased the reporter activity in colon cancer cells, suggesting that both WREs are involved in the transcriptional activation. Knockdown of β-catenin by siRNA suppressed the reporter activity. In addition, ChIP assay showed that both elements associate with TCF4/β-catenin complex in colon cancer cells. These data indicate that expression of RNF43 is regulated by the canonical Wnt/β-catenin pathway through binding of the WREs with TCF4/β-catenin complex. These findings should be useful for the understanding of the regulatory mechanism of RNF43 and may contribute to the clarification of signaling pathways regulated by RNF43