The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
Caloric restriction increases life span in many types of animals. This article proposes a mechanism for this effect based on the hypothesis that metabolic stability, the capacity of an organism to maintain steady state values of redox couples, is a prime determinant of longevity. We integrate the stability-longevity hypothesis with a molecular model of metabolic activity (quantum metabolism), and an entropic theory of evolutionary change (directionality theory), to propose a proximate mechanism and an evolutionary rationale for aging.
This article discusses the significance of mouse models as a basis for elucidating the aging process in humans. We identify certain parallels between mouse and human systems and review the theoretical and empirical support for the claim that the large divergence in the rate of aging between the two species resides in differences in the stability of their metabolic networks. We will show that these differences in metabolic stability have their origin in the different ecological constraints the species experience during their evolutionary history.
Depth of anaesthesia has proved to be a complex process to quantify. Monitors based on bispectral analysis of the electroencephalogram and auditory evoked potential have been available, but only recently has a monitor based on entropy become available. This study determined state entropy and response entropy in nine healthy volunteers during propofol hypnosis with a brief intervening period of wakefulness. Both the calculated entropy indices decreased with increasing levels of sedation (r2 = 0.58 and 0.61, respectively) and they showed a high correlation with each other (r2 = 0.94).
BACKGROUND: Time-frequency balanced spectral entropy of electroencephalogram (EEG) and frontal electromyogram (FEMG) is a novel measure of hypnosis during anesthesia. Two Entropy parameters are described: Response entropy (RE) is calculated from EEG and FEMG; and State Entropy (SE) is calculated mainly from EEG. This study was performed to validate their performance during transition from consciousness to unconsciousness under different anesthetic agents.
BACKGROUND: The purpose of this investigation was to describe the pharmacodynamic interaction between propofol and remifentanil for probability of no response to shaking and shouting, probability of no response to laryngoscopy, Bispectral Index (BIS), and electroencephalographic approximate entropy (AE). METHODS: Twenty healthy volunteers received either propofol or remifentanil alone and then concurrently with a fixed concentration of remifentanil or propofol, respectively, via a target-controlled infusion.
BACKGROUND: The Bispectral Index (BIS) and spectral entropy of the electroencephalogram can be used to assess the depth of hypnosis. Ketamine is known to increase BIS in anaesthetized patients and may confound that index as a guide to steer administration of hypnotics. We compared the effects of ketamine on BIS, response entropy (RE) and state entropy (SE) during surgery under sevoflurane anaesthesia. METHODS: Twenty-two women undergoing gynaecological surgery were enrolled in this double-blind, randomized study. Anaesthesia was induced i.v. and maintained with sevoflurane.
BACKGROUND AND OBJECTIVE: Thiopental has been reported to reduce sympathetic tone, however, it is not clear whether change in heart rate variability is associated with depth of anaesthesia. The purpose of the present study was to evaluate changes in heart rate variability at different depths of hypnosis during induction of anaesthesia with thiopental. METHODS: We studied 17 ASA I patients scheduled for minor surgery. The depth of hypnosis was monitored by the BIS.
BACKGROUND: The Datex-Ohmeda S/5 Entropy Module (Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland), using time-frequency balanced Spectral Entropy, is a novel tool for monitoring the hypnotic state during anesthesia. The Entropy Module produces two values, State Entropy (SE) and Response Entropy (RE), and in adults, it has been shown to measure reliably the hypnotic effects of various drugs. In children, Spectral Entropy has been only preliminary studied.
Computer-based measuring of the level of sedation and hypnosis is difficult and has proven to be challenging. The electroencephalogram (EEG) has been proposed as a potential method. Response entropy (RE) and state entropy (SE) are multifactor, dimensionless parameters of a new technology of EEG monitoring, and we investigated them for the first time in acupuncture research within this study. Both parameters have been alleged to reflect changes in the clinical state of sedation.