Flavor nonconservation and CP violation from quark mixings with singlet quarks

Flavor nonconserving and CP violating effects of the quark mixings are investigated in electroweak models incorporating singlet quarks. Especially, the D^0 - {\bar D}^0 mixing and the neutron electric dipole moment, which are mediated by the up-type quark couplings to the neutral Higgs fields, are examined in detail for reasonable ranges of the quark mixings and the singlet Higgs mass scale. These neutral Higgs contributions are found to be comparable to or smaller than the experimental bounds even for the case where the singlet Higgs mass scale is of the order of the electroweak scale and a significant mixing is present between the top quark and the singlet quarks.Comment: 16 pages, 2 figures, Latex, 3 refs. added, grammatical improvemen

Thermoluminescence study of ordinary chondrites by TL spatial distribution readout system

The thermoluminescence (TL) image reading technique by the TL spatial distribution readout system is improved 1) to obtain a quantitative glow curve in any part of the TL image, 2) to get fine structure of a TL image and 3) to heat a sample to a higher temperature. This technique is applied to measure the natural and artificial TL glow curves of chondrules in ordinary chondrites, ALH-77294 (H5) and ALH-77216 (L3.8). The fluctuation in the natural LT/HT (region) ratios (LT(region); photons counted in a low temperature region, HT (region); in a high temperature region) of the equilibrated chondrite ALH-77294 is small though that in the unequilibrated chondrite ALH-77216 is large. The equivalent doses of ALH-77294 and ALH-77216 can be estimated from the correlation between natural LT (region) and artificial LT (region) to be about 240krad and 16krad respectively, and are consistent with isotopic ages

A cross-metathesis approach to the stereocontrolled synthesis of the AB ring segment of ciguatoxin

Synthesis of the AB ring segments of ciguatoxin is described. The present synthesis includes a Lewis acid mediated cyclization of allylstannane with aldehyde, cross-metathesis reaction introducing the side chain, and Grieco-Nishizawa dehydration on the A ring.</p

SHED-CM for ALS Treatment

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder, characterized by the loss of upper and lower motor neurons, for which an effective treatment has yet to be developed. Previous reports have shown that excessive oxidative stress, related to mitochondrial dysfunction and the accumulation of misfolding protein, contributes to ALS pathology. In terms of treatment, it remains necessary to identify effective medicines for multiple therapeutic targets and have additive effects against several disorders. In this study, we investigated stem cells from human exfoliated deciduous teeth (SHED), which release many factors, such as neurotrophic factors and cytokines, and are applied to treat neurological diseases. Specifically, we examined whether SHED-conditioned medium (CM), i.e., the serum-free culture supernatant of SHED, reduced mutant SOD1-induced intracellular aggregates and neurotoxicity. We found that SHED-CM significantly suppressed the mutant SOD1-induced intracellular aggregates and neurotoxicity. The neuroprotective effects of SHED-CM are partly related to heat shock protein and the activation of insulin-like growth factor-1 receptor. SHED-CM also had a protective effect on induced pluripotent stem cell-derived motor neurons. Moreover, SHED-CM was effective against not only familial ALS but also sporadic ALS. Overall, these results suggest that SHED-CM could be a promising treatment for slowing the progression of ALS

In vivo contribution of Class III alcohol dehydrogenase (ADH3) to alcohol metabolism through activation by cytoplasmic solution hydrophobicity

AbstractAlcohol metabolism in vivo cannot be explained solely by the action of the classical alcohol dehydrogenase, Class I ADH (ADH1). Over the past three decades, attempts to identify the metabolizing enzymes responsible for the ADH1-independent pathway have focused on the microsomal ethanol oxidizing system (MEOS) and catalase, but have failed to clarify their roles in systemic alcohol metabolism. In this study, we used Adh3-null mutant mice to demonstrate that Class III ADH (ADH3), a ubiquitous enzyme of ancient origin, contributes to alcohol metabolism in vivo dose-dependently resulting in a diminution of acute alcohol intoxication. Although the ethanol oxidation activity of ADH3 in vitro is low due to its very high Km, it was found to exhibit a markedly enhanced catalytic efficiency (kcat/Km) toward ethanol when the solution hydrophobicity of the reaction medium was increased with a hydrophobic substance. Confocal laser scanning microscopy with Nile red as a hydrophobic probe revealed a cytoplasmic solution of mouse liver cells to be much more hydrophobic than the buffer solution used for in vitro experiments. So, the in vivo contribution of high-Km ADH3 to alcohol metabolism is likely to involve activation in a hydrophobic solution. Thus, the present study demonstrated that ADH3 plays an important role in systemic ethanol metabolism at higher levels of blood ethanol through activation by cytoplasmic solution hydrophobicity