REM sleep-dependent short-term and long-term hourglass processes in the ultradian organization and recovery of REM sleep in the rat.

Study Objectives: To evaluate the contribution of long-term and short-term REM sleep homeostatic processes to REM sleep recovery and the ultradian organization of the sleep wake cycle.

Methods: Fifteen rats were sleep recorded under a 12:12 LD cycle. Animals were subjected during the rest phase to two protocols (2T2I or 2R2I) performed separately in non-consecutive experimental days.

Melatonin Relations With Respiratory Quotient Weaken on Acute Exposure to High Altitude.

High altitude (HA) exposure may affect human health and performance by involving the body timing system. Daily variations of melatonin may disrupt by HA exposure, thereby possibly affecting its relations with a metabolic parameter like the respiratory quotient (RQ). Sea level (SL) volunteers (7 women and 7 men, 21.

Envelope analysis links oscillatory and arrhythmic EEG activities to two types of neuronal synchronization.

Traditionally, EEG is understood as originating from the synchronous activation of neuronal populations that generate rhythmic oscillations in specific frequency bands. Recently, new neuronal dynamics regimes have been identified (e.g.

Post-Learning Sleep Transiently Boosts Context Specific Operant Extinction Memory.

Operant extinction is learning to supress a previously rewarded behavior. It is known to be strongly associated with the specific context in which it was acquired, which limits the therapeutic use of operant extinction in behavioral treatments, e.g.

Age-related arrhythmogenesis on ascent and descent: "autonomic conflicts" on hypoxia/reoxygenation at high altitude?

Purpose: To discern whether arrhythmogenesis at high-altitude (HA) may differ depending on ascent or descent, as well as on age.

Methods: Male subjects (37.9±12.

Envelope analysis of the airflow signal to improve polysomnographic assessment of sleep disordered breathing.

Study Objectives: Given the detailed respiratory waveform signal provided by the nasal cannula in polysomnographic (PSG) studies, to quantify sleep breathing disturbances by extracting a continuous variable based on the coefficient of variation of the envelope of that signal.

Design: Application of an algorithm for envelope analysis to standard nasal cannula signal from actual polysomnographic studies.

Setting: PSG recordings from a sleep disorders center were analyzed by an algorithm developed on the Igor scientific data analysis software.

Visualization and clustering of sleep states in a frequency domain feature space.

Sleep studies assess the recurrent manifestation of stereotype configurations of relevant biosignals. These configurations are known as states (Wake, REM sleep and NonREM sleep) and stages (N1-N3 within NREM sleep). These two fundamental descriptive domains, time course and variable configuration, can be readily rendered available through improved visualization techniques.

The time course of the probability of transition into and out of REM sleep.

Study Objectives: A model of rapid eye movement (REM) sleep expression is proposed that assumes underlying regulatory mechanisms operating as inhomogenous Poisson processes, the overt results of which are the transitions into and out of REM sleep.

Design: Based on spontaneously occurring REM sleep episodes ("Episode") and intervals without REM sleep ("Interval"), 3 variables are defined and evaluated over discrete 15-second epochs using a nonlinear logistic regression method: "Propensity" is the instantaneous rate of into-REM transition occurrence throughout an Interval, "Volatility" is the instantaneous rate of out-of-REM transition occurrence throughout an Episode, and "Opportunity" is the probability of being in non-REM (NREM) sleep at a given time throughout an Interval, a requisite for transition.

Setting: 12:12 light:dark cycle, isolated boxes.

On-line analysis of biosignals for the automation of total and specific sleep deprivation in the rat.

A computer-based system that automates sleep studies, including sleep deprivation paradigms, is described. The system allows for total or REM-specific sleep deprivation and is based on a reliable, fast-responding, on-line state detection algorithm linked to a dependable intervention device. Behavioral state detection is achieved by dimension reduction of short-term EEG power spectrum.

Frequency domain analysis of sleep EEG for visualization and automated state detection.

Conventional analysis of EEG signals for sleep scoring is based on the time domain assessment of wave patterns. Human experts carry out this task relying on the direct visualization of EEG epochs. Techniques that enhance an intuitive visualization may encourage a wider use of more abstract descriptors, such as frequency domain features.

Short-term homeostasis of REM sleep throughout a 12:12 light:dark schedule in the rat.

Study Objectives: Intervals extending from the end of a rapid eye movement (REM) sleep episode until the triggering of the next tend to be longer when they follow a longer REM sleep episode. A short-term REM sleep homeostatic process has been hypothesized to explain this effect. The present study assessed and modeled the REM sleep episode-interval relationship and compared its expression at different phases of a 12:12 light: dark schedule.

Short-term homeostasis of REM sleep assessed in an intermittent REM sleep deprivation protocol in the rat.

An intermittent rapid eye movement (REM) sleep deprivation protocol was applied to determine whether an increase in REM sleep propensity occurs throughout an interval without REM sleep comparable with the spontaneous sleep cycle of the rat. Seven chronically implanted rats under a 12 : 12 light-dark schedule were subjected to an intermittent REM sleep deprivation protocol that started at hour 6 after lights-on and lasted for 3 h. It consisted of six instances of a 10-min REM sleep permission window alternating with a 20-min REM sleep deprivation window.

[Computers in biomedical research II: experimental control, data acquisition and storage].

During the last decade, there has been a significant increase in the use of computers in biomedical research. In particular, the use of these instruments in experimental control, as well as in the acquisition and storage of experimental data, has become universal. The current capacity of these machines enables the precise manipulation of many experimental variables and allows for very fast acquisition of data.

[Computers in biomedical research: I. Analysis of bioelectrical signals].

A personal computer equipped with an analog-to-digital conversion card is able to input, store and display signals of biomedical interest. These signals can additionally be submitted to ad-hoc software for analysis and diagnosis. Data acquisition is based on the sampling of a signal at a given rate and amplitude resolution.

Homeostasis of REM sleep after total and selective sleep deprivation in the rat.

During specific rapid eye movement (REM) sleep deprivation its homeostatic regulation is expressed by progressively more frequent attempts to enter REM and by a compensatory rebound after the deprivation ends. The buildup of pressure to enter REM may be hypothesized to depend just on the time elapsed without REM or to be differentially related to non-REM (NREM) and wakefulness. This problem bears direct implications on the issue of the function of REM and its relation to NREM.

Role of Küpffer cells and PMN leukocytes in hepatic and systemic oxidative stress in rats subjected to tourniquet shock.

Küpffer cells (KCs) have been implicated in leukocyte recruitment and microvascular dysfunction associated with liver inflammation. The overall objective of this study was to assess the role of KCs and polymorphonuclear (PMN) leukocytes on the oxidative stress elicited in the liver as a consequence of hind limb reperfusion in rats subjected to tourniquet shock, a shock model that differs from other models in that hepatic injury is a consequence of remote organ damage. Colloidal carbon clearance from blood and its incorporation into KCs demonstrate that these cells are activated after the 2 h hind limb reperfusion period and that they are responsible for the observed oxidative stress and for PMN leukocyte recruitment and activation.

Inhibition of nitric oxide synthesis aggravates hepatic oxidative stress and enhances superoxide dismutase inactivation in rats subjected to tourniquet shock.

The role of nitric oxide (NO) on liver oxidative stress and tissue injury in rats subjected to tourniquet shock was investigated. This shock model differs from others in that injury is a consequence of remote organ damage. Liver oxidative stress becomes evident after hind limb reperfusion, as evidenced by the loss of total tissue thiols; by increases in tissue oxidized glutathione (GSSG), lipid peroxidation (LPO), plasma aminotransferases (alanine aminotransferase (ALT) and (aspartate aminotransferase (AST)), and plasma nitrites; and by a 36% loss in total superoxide dismutase (SOD) activity.

Ibuprofen protects rat livers from oxygen-derived free radical-mediated injury after tourniquet shock.

Rats subjected to tourniquet shock suffer a severe form of circulatory shock, tissue and organ oxidative stress, and final multiple system organ failure (MSOF) and death of the animals within 24 h of tourniquet release. The oxidative damage observed in hind-limb muscle tissue after reperfusion does not by itself account for the final systemic and lethal MSOF. We have postulated that organ failure has its genesis in a primary perfusion abnormality, e.

Short-term homeostasis of active sleep and the architecture of sleep in the rat.

1. Sixteen rats were recorded continuously for 3 days using an automated system that detected, quantified, and stored the incidence of cortical delta waves, cortical sigma spindles, hippocampal theta rhythm, and electromyographic activity. A time series then was constructed wherein 15-s epochs were ascribed to one behavioral state: wakefulness (W), quiet sleep (QS), or active sleep (AS, a state also referred to as REM sleep).

Measures of location and dispersion of sleep state distributions within the circular frame of a 12:12 light: dark schedule in the rat.

Distributions within a 12:12 light:dark schedule of wakefulness (W), active sleep (AS), quiet sleep (QS) and of QS rich in delta (QSD) and in spindle (QSS) activities were evaluated for 52 days from 15 rats. Angular statistics were applied for each state by equating their hourly incidence to data distributed around a circle. Measures of location (mean angle, median angle, mode angle, maximum semicircle), dispersion (mean vector, standard deviation, quartile deviation), skewness and kurtosis were computed and their intra- and interindividual variabilities were compared.

Oxygen-derived free radicals mediate liver damage in rats subjected to tourniquet shock.

The placement of rubber band tourniquets upon rat hind-limbs for 5 h followed by reperfusion of the extremities results in a severe form of circulatory shock characterized by hypotension and death within 24 h of tourniquet release. Oxidative damage to muscle tissue is an early consequence of hind-limb reperfusion on tourniquet release, yet this local damage does not explain the lethal hypotensive shock state which evolves within the next 24 h. Multiple system organ failure (MSOF), of as of yet unknown causes, is usually described in relation to several shock states.