471 research outputs found
Short-term complexity of cardiac autonomic control during sleep: REM as a potential risk factor for cardiovascular system in aging.
peer reviewedINTRODUCTION: Sleep is a complex phenomenon characterized by important modifications throughout life and by changes of autonomic cardiovascular control. Aging is associated with a reduction of the overall heart rate variability (HRV) and a decrease of complexity of autonomic cardiac regulation. The aim of our study was to evaluate the HRV complexity using two entropy-derived measures, Shannon Entropy (SE) and Corrected Conditional Entropy (CCE), during sleep in young and older subjects. METHODS: A polysomnographic study was performed in 12 healthy young (21.1+/-0.8 years) and 12 healthy older subjects (64.9+/-1.9 years). After the sleep scoring, heart period time series were divided into wake (W), Stage 1-2 (S1-2), Stage 3-4 (S3-4) and REM. Two complexity indexes were assessed: SE(3) measuring the complexity of a distribution of 3-beat patterns (SE(3) is higher when all the patterns are identically distributed and it is lower when some patterns are more likely) and CCE(min) measuring the minimum amount of information that cannot be derived from the knowledge of previous values. RESULTS: Across the different sleep stages, young subjects had similar RR interval, total variance, SE(3) and CCE(min). In the older group, SE(3) and CCE(min) were reduced during REM sleep compared to S1-2, S3-4 and W. Compared to young subjects, during W and sleep the older subjects showed a lower RR interval and reduced total variance as well as a significant reduction of SE(3) and CCE(min). This decrease of entropy measures was more evident during REM sleep. CONCLUSION: Our study indicates that aging is characterized by a reduction of entropy indices of cardiovascular variability during wake/sleep cycle, more evident during REM sleep. We conclude that during aging REM sleep is associated with a simplification of cardiac control mechanisms that could lead to an impaired ability of the cardiovascular system to react to cardiovascular adverse events
Optical continuum reverberation in the dwarf Seyfert nucleus of NGC 4395
Funding information: LCO telescope time was granted by NOIRLab through the Mid-Scale Innovations Program (MSIP). MSIP is funded by NSF. This Letter is based on observations made with the MuSCAT3 instrument, developed by the Astrobiology Center and under financial supports by JSPS KAKENHI (JP18H05439) and JST PRESTO (JPMJPR1775), at Faulkes Telescope North on Maui, HI, operated by the Las Cumbres Observatory. Research at UC Irvine was supported by NSF grant AST-1907290. D.H.G.-B. acknowledges CONACYT support #319800. J.V.H.S. acknowledges support from STFC grant ST/R000824/1.In order to constrain the size of the optical continuum emission region in the dwarf Seyfert 1 galaxy NGC 4395 through reverberation mapping, we carried out high-cadence photometric monitoring in the griz filter bands on two consecutive nights in 2022 April using the four-channel MuSCAT3 camera on the Faulkes Telescope North at HaleakalÄ Observatory. Correlated variability across the griz bands is clearly detected, and the r-, i-, and z-band light curves show lags of - + 7.72 +1.01 -1.09, 14.16 +1.22-1.25, and 20.78 Â +1.99-2.09Â minutes with respect to the g band when measured using the full-duration light curves. When lags are measured for each night separately, the Night 2 data exhibit lower cross-correlation amplitudes and shorter lags than the Night 1 light curves. Using the full-duration lags, we find that the lagâwavelength relationship is consistent with the Ď â Îť4/3 dependence found for more luminous active galactic nuclei. Combining our results with continuum lags measured for other objects, the lag between g and z band scales with optical continuum luminosity as Ďgz â L0.56Âą0.05, similar to the scaling of broad-line region size with luminosity, reinforcing recent evidence that diffuse continuum emission from the broad-line region may contribute substantially to optical continuum variability and reverberation lags.Publisher PDFPeer reviewe
Oxidative stress in cerebral small vessel disease dizziness patients, basally and after polyphenol compound supplementation
Leukoaraiosis (LA) is a common radiological finding in elderly, frequently associated with several clinical disorders, including unexplained dizziness. The pathogenesis of LA is multifactorial, with a dysfunction of cerebral microcirculation resulting in chronic hypoperfusion and tissue loss, with oxidative stress involved in this cascade. The aim of this study was to analyse some oxidative stress biomarkers in a cohort of LA patients. In a subgroup of 33 patients with LA and unexplained dizziness, we have then performed an open study to evaluate if 60-day supplementation with a poliphenol compound may modify these biomarkers and influence quality of life, analysed with the Dizziness handicap Inventory (DHI) scale. At baseline, blood oxidative stress parameters values were outside normal ranges and compared to matched healthy controls. After the two months supplementation, we observed a significant decrement of advanced oxidation protein products values and a significant improvement of DHI. Oxidative stress biomarkers may be useful to detect redox imbalance in LA and to provide non-invasive tools to monitor disease status and response to therapy
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Deacetylation of p53 induces autophagy by suppressing Bmf expression
Interferon Îł (IFN-Îł)âinduced cell death is mediated by the BH3-only domain protein, Bik, in a p53-independent manner. However, the effect of IFN-Îł on p53 and how this affects autophagy have not been reported. The present study demonstrates that IFN-Îł down-regulated expression of the BH3 domain-only protein, Bmf, in human and mouse airway epithelial cells in a p53-dependent manner. p53 also suppressed Bmf expression in response to other cell deathâstimulating agents, including ultraviolet radiation and histone deacetylase inhibitors. IFN-Îł did not affect Bmf messenger RNA half-life but increased nuclear p53 levels and the interaction of p53 with the Bmf promoter. IFN-Îłâinduced interaction of HDAC1 and p53 resulted in the deacetylation of p53 and suppression of Bmf expression independent of p53âs proline-rich domain. Suppression of Bmf facilitated IFN-Îłâinduced autophagy by reducing the interaction of Beclin-1 and Bcl-2. Furthermore, autophagy was prominent in cultured bmfâ/â but not in bmf+/+ cells. Collectively, these observations show that deacetylation of p53 suppresses Bmf expression and facilitates autophagy
Mathematical practice, crowdsourcing, and social machines
The highest level of mathematics has traditionally been seen as a solitary
endeavour, to produce a proof for review and acceptance by research peers.
Mathematics is now at a remarkable inflexion point, with new technology
radically extending the power and limits of individuals. Crowdsourcing pulls
together diverse experts to solve problems; symbolic computation tackles huge
routine calculations; and computers check proofs too long and complicated for
humans to comprehend.
Mathematical practice is an emerging interdisciplinary field which draws on
philosophy and social science to understand how mathematics is produced. Online
mathematical activity provides a novel and rich source of data for empirical
investigation of mathematical practice - for example the community question
answering system {\it mathoverflow} contains around 40,000 mathematical
conversations, and {\it polymath} collaborations provide transcripts of the
process of discovering proofs. Our preliminary investigations have demonstrated
the importance of "soft" aspects such as analogy and creativity, alongside
deduction and proof, in the production of mathematics, and have given us new
ways to think about the roles of people and machines in creating new
mathematical knowledge. We discuss further investigation of these resources and
what it might reveal.
Crowdsourced mathematical activity is an example of a "social machine", a new
paradigm, identified by Berners-Lee, for viewing a combination of people and
computers as a single problem-solving entity, and the subject of major
international research endeavours. We outline a future research agenda for
mathematics social machines, a combination of people, computers, and
mathematical archives to create and apply mathematics, with the potential to
change the way people do mathematics, and to transform the reach, pace, and
impact of mathematics research.Comment: To appear, Springer LNCS, Proceedings of Conferences on Intelligent
Computer Mathematics, CICM 2013, July 2013 Bath, U
Moderate and heavy metabolic stress interval training improve arterial stiffness and heart rate dynamics in humans
Traditional continuous aerobic exercise training attenuates age-related increases of arterial stiffness, however, training studies have not determined whether metabolic stress impacts these favourable effects. Twenty untrained healthy participants (n = 11 heavy metabolic stress interval training, n = 9 moderate metabolic stress interval training) completed 6 weeks of moderate or heavy intensity interval training matched for total work and exercise duration. Carotid artery stiffness, blood pressure contour analysis, and linear and non-linear heart rate variability were assessed before and following training. Overall, carotid arterial stiffness was reduced (p  0.05). This study demonstrates the effectiveness of interval training at improving arterial stiffness and autonomic function, however, the metabolic stress was not a mediator of this effect. In addition, these changes were also independent of improvements in aerobic capacity, which were only induced by training that involved a high metabolic stress
Neuronal characteristics of small-cell lung cancer
Wide ranging experimental evidence suggests that human small-cell lung cancer (SCLC) has a number of molecular and subcellular characteristics normally associated with neurones. This review outlines and discusses these characteristics in the light of recent developments in the field. Emphasis is placed upon neuronal cell adhesion molecules, neurone-restrictive silencer factor, neurotransmitters/peptides and voltage-gated ion, especially Na+ channels. The hypothesis is put forward that acquisition of such characteristics and the membrane âexcitability' that would follow can accelerate metastatic progression. The clinical potential of the neuronal characteristics of SCLC, in particular ion channel expression/activity, is discussed in relation to possible novel diagnostic and therapeutic modalities
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