Switching the centromeres on and off: epigenetic chromatin alterations provide plasticity in centromere activity stabilizing aberrant dicentric chromosomes

Abstract The kinetochore, which forms on a specific chromosomal locus called the centromere, mediates interactions between the chromosome and the spindle during mitosis and meiosis. Abnormal chromosome rearrangements and/or neocentromere formation can cause the presence of multiple centromeres on a single chromosome, which results in chromosome breakage or cell cycle arrest. Analyses of artificial dicentric chromosomes suggested that the activity of the centromere is regulated epigenetically; on some stably maintained dicentric chromosomes, one of the centromeres no longer functions as a platform for kinetochore formation, although the DNA sequence remains intact. Such epigenetic centromere inactivation occurs in cells of various eukaryotes harbouring 'regional centromeres', such as those of maize, fission yeast and humans, suggesting that the position of the active centromere is determined by epigenetic markers on a chromosome rather than the nucleotide sequence. Our recent findings in fission yeast revealed that epigenetic centromere inactivation consists of two steps: disassembly of the kinetochore initiates inactivation and subsequent heterochromatinization prevents revival of the inactivated centromere. Kinetochore disassembly followed by heterochromatinization is also observed in normal senescent human cells. Thus epigenetic centromere inactivation may not only stabilize abnormally generated dicentric chromosomes, but also be part of an intrinsic mechanism regulating cell proliferation

Shear Resistance Mechanisms on Steel Sheet Shear Walls with Burring Holes and Cross-Rails

Steel sheet shear walls with burring holes are employed in low and mid-rise buildings in seismically active regions. A configuration with burrs on the inside enables the thinner wall and omitting the machining of equipment holes. The effects of cross-rails which are generally designed to strengthen the bearing capacities of the studs, on 2.73~4.53m height shear walls were clarified by finite element analysis and experiments. Post-buckling behavior depends on tension fields restrained by the cross-rails. The formulas of the allowable strengths and the indexes of ultimate strengths were developed using the mechanisms

Shear Resistance Mechanisms on Steel Sheet Shear Walls with Burring Holes and Cross-Rails

Steel sheet shear walls with burring holes are employed in low and mid-rise buildings in seismically active regions. A configuration with burrs on the inside enables the thinner wall and omitting the machining of equipment holes. The effects of cross-rails which are generally designed to strengthen the bearing capacities of the studs, on 2.73~4.53m height shear walls were clarified by finite element analysis and experiments. Post-buckling behavior depends on tension fields restrained by the cross-rails. The formulas of the allowable strengths and the indexes of ultimate strengths were developed using the mechanisms

Absorption and Accumulation of Carotenoid and Retinoid Production in Rat

植物性食品に広く含まれるカロテノイドのうち,β-caroteneなどはプロビタミンA効果以外に抗ガン,抗酸化防止効果などが注目されているが,カロテノイドの消化・吸収機構及び体内分布に関する基礎的知見は少ない,カロテノイド非蓄積動物と呼ばれるラットについてβ-carotene単独投与及びホウレンソウカロテノイドとを投与し,それぞれにおける各カロテノイドの吸収挙動と吸収カロテノイド及び生成retinolの体内存在状態を調べた.β-caroteneは単独に投与すると約50%の吸収率となるが,xanthophyll共存下では数%にまで低下する.これはβ-caroteneの吸収をxanthophyllが妨害していることを示す.β-caroteneは肝臓にもっとも多く蓄積されneoxanthinがこれを次いでいる.もっとも多く吸収されたluteinは肝臓にはほとんど検出されず,血液中に少量存在していた.このような両カロテノイドの挙動はカロテノイド非蓄積動物に特徴的なものと考えられる.カロテノイドを含まない飼料を投与すると一時的にretinolの血中濃度は上昇し,肝濃度は低下するが,カロテノイドを投与すると恒常的血中retinol濃度に速やかに戻る.β-carotene及びホウレンソウカロテノイドを25日間投与したときのretinolの正味増加量はそれぞれ474μgと522μgであるが血中のretinolレベルはほとんど変化していない.このことは肝に充分量のretinol存在しておれば血中retinolレベルはほぼ一定に保たれる制御作用のあることを示している

Noncontact Detection of Sleep Apnea Using Radar and Expectation-Maximization Algorithm

Sleep apnea syndrome requires early diagnosis because this syndrome can lead to a variety of health problems. If sleep apnea events can be detected in a noncontact manner using radar, we can then avoid the discomfort caused by the contact-type sensors that are used in conventional polysomnography. This study proposes a novel radar-based method for accurate detection of sleep apnea events. The proposed method uses the expectation-maximization algorithm to extract the respiratory features that form normal and abnormal breathing patterns, resulting in an adaptive apnea detection capability without any requirement for empirical parameters. We conducted an experimental quantitative evaluation of the proposed method by performing polysomnography and radar measurements simultaneously in five patients with the symptoms of sleep apnea syndrome. Through these experiments, we show that the proposed method can detect the number of apnea and hypopnea events per hour with an error of 4.8 times/hour; this represents an improvement in the accuracy by 1.8 times when compared with the conventional threshold-based method and demonstrates the effectiveness of our proposed method.Comment: 8 pages, 12 figures, 3 tables. This work is going to be submitted to the IEEE for possible publicatio