EEG and subjective sleepiness during extended wakefulness in seasonal affective disorder: circadian and homeostatic influences.

BACKGROUND: Seasonal affective disorder (SAD) may reflect a disturbance of circadian phase relationships or a disturbance of sleep-wake dependent processes, both of which change daytime energy and sleepiness levels. METHODS: Under the unmasking conditions of a 40-hour constant routine protocol (CR), self-rated sleepiness and waking electroencephalogram (EEG) power density were assessed in women with SAD (n = 8) and in age-matched healthy control subjects (n = 9). RESULTS: There was no significant effect of season or light treatment in any of the measures. The time course of subjective sleepiness was characterized by a circadian modulation and an overall increase during extended wakefulness in both SAD patients and control subjects. A prominent circadian rhythm of subjective sleepiness was not different in SAD patients and control subjects; however, the progressive buildup of sleepiness, as quantified by nonlinear regression analysis, was significantly reduced in SAD patients, mainly because they were sleepier than control subjects during the first 12 hours of the CR. The time course of waking EEG theta-alpha activity showed a more rapid increase during the first 10 hours of the CR in SAD patients. In contrast to control subjects who showed a progressive increase in the course of the 40-hour episode of extended wakefulness, EEG theta-alpha activity in SAD patients did not further increase over the remainder of the CR. CONCLUSIONS: The data suggest that SAD patients may have a trait (rather than state) deficiency in the homeostatic buildup of sleep pressure during extended wakefulness as indexed by subjective sleepiness and EEG theta-alpha activity.

Accelerated post-glucose glycaemia and altered alliesthesia-test in Seasonal Affective Disorder.

BACKGROUND: Little is known about the link between mood, food and metabolic function in Seasonal Affective Disorder (SAD). METHODS: We investigated this link in a combined glucose tolerance-alliesthesia test in eight SAD patients in winter before and after one week light therapy, and in summer. RESULTS: SAD patients exhibited faster post-glucose glycaemic and insulin responses (p <0.05), and increased hedonic ratings of high concentrated sucrose solutions (p <0.035) when depressed in winter than when euthymic (one week after light treatment or in summer). CONCLUSIONS: The rapid glycaemic and insulin responses to an oral glucose load may be a result of accelerated gastric emptying. LIMITATIONS: The number of studied patients was rather small and no control group was studied in parallel. CLINICAL RELEVANCE: the more rapid post-glucose glycaemia may impair glucose homeostasis in depressed SAD patients.

Power spectral analysis of EEG in a multiple-bedroom, multiple-polygraph sleep laboratory.

OBJECTIVES: We describe the methods for power spectral analysis (PSA) of sleep electroencephalogram (EEG) data at a large clinical and research sleep laboratory. The multiple-bedroom, multiple-polygraph design of the sleep laboratory poses unique challenges for the quantitative analysis of the data. This paper focuses on the steps taken to ensure that our PSA results are not biased by the particular bedroom or polygraph from which the data were acquired. METHODS: After describing the data acquisition system hardware, we present our signal amplitude calibration procedure and our methods for performing PSA. We validate the amplitude calibration procedure in several experiments using PSA to establish tolerances for data acquisition from multiple bedrooms and polygraphs. RESULTS: Since it is not possible to acquire identical digitized versions of an EEG signal using different sets of equipment, the best that can be achieved is data acquisition that is polygraph-independent within a known tolerance. We are able to demonstrate a tolerance in signal amplitude of +/- 0.25% when digitizing data from different bedrooms. When different data acquisition hardware is used, the power tolerance is approximately +/- 3% for frequencies from 1 to 35 Hz. The power tolerance is between +/- 3 and +/- 7% for frequencies below 1 Hz and frequencies between 35 and 50 Hz. Additional data demonstrate that variability due to the hardware system is small relative to the inherent variability of the sleep EEG. CONCLUSION: The PSA results obtained in one location can be replicated elsewhere (subject to known tolerances) only if the data acquisition system and PSA method are adequately specified.

Maintenance nortriptyline effects on electroencephalographic sleep in elderly patients with recurrent major depression: double-blind, placebo- and plasma-level-controlled evaluation.

Our aim was to contrast the effects of maintenance nortriptyline and placebo on electroencephalographic sleep measures in elderly recurrent depressives who survived 1-year without recurrence of depression. Patients on nortriptyline took longer to fall asleep and did not maintain sleep better than patients on placebo; however, maintenance nortriptyline was associated with more delta-wave production and higher delta-wave density in the first non-REM (NREM) period relative to the second. Nortriptyline levels were positively but weakly related to all-night delta-wave production during maintenance (accounting for 6.6% of the variance in delta-wave counts). Total phasic REM activity increased 100% under chronic nortriptyline relative to placebo, with a robust increase in the rate of REM activity generation across the night. Effective long-term pharmacotherapy of recurrent major depression is associated with enhancement in the rate of delta-wave production in the first NREM period (i.e., delta sleep ratio) and of REM activity throughout the night.

Muscle artifacts in the sleep EEG: automated detection and effect on all-night EEG power spectra.

Owing to the use of scalp electrodes in human sleep recordings, cortical EEG signals are inevitably intermingled with the electrical activity of the muscle tissue on the skull. Muscle artifacts are characterized by surges in high frequency activity and are readily identified because of their outlying high values relative to the local background activity. To detect bursts of myogenic activity a simple algorithm is introduced that compares high frequency activity (26.25-32.0 Hz) in each 4-s epoch with the activity level in a local 3-min window. A 4-s value was considered artifactual if it exceeded the local background activity by a certain factor. Sensitivity and specificity of the artifact detection algorithm were empirically adjusted by applying different factors as artifact thresholds. In an analysis of sleep EEG signals recorded from 25 healthy young adults 2.3% (SEM: 0.16) of all 4-s epochs during sleep were identified as artifacts when a threshold factor of four was applied. Contamination of the EEG by muscle activity was more frequent towards the end of non-REM sleep episodes when EEG slow wave activity declined. Within and across REM sleep episodes muscle artifacts were evenly distributed. When the EEG signal was cleared of muscle artifacts, the all-night EEG power spectrum showed significant reductions in power density for all frequencies from 0.25-32.0 Hz. Between 15 and 32 Hz, muscle artifacts made up a substantial part (20-70%) of all-night EEG power density. It is concluded that elimination of short-lasting muscle artifacts reduces the confound between cortical and myogenic activity and is important in interpreting quantitative EEG data. Quantitative approaches in defining and detecting transient events in the EEG signal may help to determine which EEG phenomena constitute clinically significant arousals.

Sleep electroencephalogram in seasonal affective disorder and in control women: effects of midday light treatment and sleep deprivation.

The role of sleep regulation in Seasonal Affective Disorder (SAD) was studied in 11 female SAD patients and eight controls in winter before and after light treatment (LT, 6000 lux, 10-14h, 5 days). The sleep electroencephalogram (EEG) was recorded at baseline and after the total sleep deprivation (TSD) of a 40-h constant routine. The well-known effects of TSD on sleep parameters and on EEG power spectra were replicated, indicating normal homeostatic sleep regulation in SAD. Sleep improved after LT in both groups. Since the condition following LT was the second session, these improvements may be an order effect and/or an effect of LT itself. After LT, sleep EEG spectra of SAD patients, but not of controls, showed modifications resembling those of recovery sleep. Since only SAD patients curtailed their sleep while remitting during the LT period, these EEG modifications can be explained by normal sleep regulation alone. We conclude that the robust antidepressant effect of LT in SAD is unlikely to be mediated by changes in sleep, and that sleep regulatory mechanisms are not a crucial factor in the pathogenesis of winter depression.

Power density in theta/alpha frequencies of the waking EEG progressively increases during sustained wakefulness.

Electroencephalogram (EEG) power density and self-rated fatigue were assessed in nine healthy women during a 40-hour period of sustained wakefulness under constant behavioral and environmental conditions (constant routine protocol). Waking EEG recordings were performed for 4 minutes after 3, 10, 27 and 34 hours of prior wakefulness. EEG power density in the 6.25- to 9.0-Hz frequency range progressively increased across the four recordings, suggesting an endogenous homeostatic component in the regulation of the theta/alpha frequencies under constant conditions. Subjective fatigue also exhibited an increasing component in the course of the constant routine protocol, with a clear circadian modulation. Fatigue ratings and the theta/ alpha power density of the waking EEG recorded at the same four time points during the constant routine protocol correlated significantly. Our data demonstrate the presence of a homeostatic component in the control of EEG power density in the 6.25- to 9.0-Hz range.

Circadian rhythms and sleep regulation in seasonal affective disorder.

Seasonal affective disorder (SAD) is characterised by recurrent episodes in autumn and winter of depression, hypersomnia, augmented appetite with carbohydrate craving, and weight gain, and can be successfully treated with bright light. Circadian rhythm hypotheses (summarized in) have stimulated research into the pathophysiology of SAD, postulating that: 1.The illness is a consequence of delayed phase position, 2.It is correlated with diminished circadian amplitude, or 3.It results from changes in the nocturnal duration between dusk and dawn e.g. of low core body temperature or melatonin secretion. Light is considered to act directly on the circadian pacemaker ('Process C') and not on sleep dependent processes ('Process S'). Thus successful treatment of SAD must act via mechanisms within known retinohypothalamic pathways. Conversely, emergence of SAD symptoms may reflect inappropriate neurobiological response to decreasing daylength.

Dynamics of slow-wave activity and spindle frequency activity in the human sleep EEG: effect of midazolam and zopiclone.

Electroencephalographic slow-wave activity (SWA; power density in the 0.75 to 4.5 Hz band) and spindle frequency activity (SFA; 11.25 to 15.0 Hz) exhibit a typical time course and a distinct mutual relationship during sleep. Because benzodiazepines (BDZ) suppress SWA and enhance SFA, we investigated the effect of two BDZ-receptor agonists on the dynamics of these EEG parameters. A single dose of midazolam (15 mg), zopiclone (7.5 mg), or placebo was administered before bedtime to healthy young men. Although the two drugs reduced SWA and enhanced SFA, their time course across and within sleep cycles as well as their mutual relationship were little affected. The results constitute further evidence that hypnotics acting as BDZ-receptor agonists do not substantially interfere with the homeostatic aspect of sleep regulation.

Changes in sleep and sleep electroencephalogram during pregnancy.

The impairment of sleep quality is a common complaint during pregnancy. To investigate the changes in sleep in the course of pregnancy, the sleep electroencephalogram (EEG) was recorded and analyzed in nine healthy women on 2 consecutive nights during each trimester of pregnancy. Waking after sleep onset increased from the second (TR2) to the third (TR3) trimester, whereas rapid eye movement (REM) sleep decreased from the first trimester (TR1) to TR2. Spectral analysis of the EEG in nonrapid eye movement (NREM) sleep revealed a progressive reduction of power density in the course of pregnancy. In comparison to TR1, the values in TR2 were significantly lower in the 10.25-11.0-Hz and 14.25-17.0-Hz bands. In TR3, the significant reduction extended over the ranges of 1.25-12.0 Hz and 13.25-16.0 Hz. The largest decrease (30%) occurred in the 14.25-15.0-Hz band. In REM sleep, the spindle frequency range was not affected, and a minor reduction of power density in some frequency bins below 12 Hz was present only in TR3. The study documents major alterations of the sleep EEG that are not evident from the sleep scores and that may be associated with the characteristic hormonal changes occurring during pregnancy.

Solution structure of human interleukin-1 receptor antagonist protein.

Interleukin-1 receptor antagonist protein (IRAP) is a naturally occurring inhibitor of the interleukin-1 receptor. In contrast to IL-1 beta, IRAP binds to the IL-1 receptor but does not elicit a physiological response. We have determined the solution structure of IRAP using NMR spectroscopy. While the overall topology of the two 153-residue proteins is quite similar, functionally critical differences exist concerning the residues of the linear amino acid sequence that constitute structurally homologous regions in the two proteins. Structurally homologous residues important for IL-1 receptor binding are conserved between IRAP and IL-1 beta. By contrast, structurally homologous residues critical for receptor activation are not conserved between the two proteins.

Initial crystallographic analysis of a recombinant human interleukin-1 receptor antagonist protein.

We report the crystallization of samples of a recombinant preparation of human interleukin-1 receptor antagonist protein (IRAP) and solution of the crystal structure by isomorphous replacement methods. Crystals were obtained by the hanging-drop vapor-diffusion method at 277 K from solutions of PEG 4000 containing sodium chloride, dithiothreitol and PIPES [sodium piperazione-N,N'-bis(2-ethanesulfonate)] buffer at pH 7.0. Crystals appear within about a week and grow as truncated tetragonal bipyramids to 0.3-0.6 mm on an edge. X-ray diffraction data from these crystals specify space group P4(3)2(1)2 and unit-cell dimensions of a = b = 72.35(26), c = 114.7(8) A and Z = 16 (two molecules per asymmetric unit). Fresh crystals diffract to about 2.3 A resolution. The search for heavy-atom derivatives has produced two, potassium gold cyanide and trimethyl lead chloride, as same-site, single-site derivatives. Inspection of an electron-density map at 4 A resolution calculated with these derivatives confirms that the IRAP molecule is a member of the interleukin-1 structural family.

[Chronobiological sleep disorders and their treatment possibilities]. / Chronobiologische Schlafstörungen und ihre Behandlungsmöglichkeiten.

A temporal discrepancy between the endogenous sleep-wake cycle and the daily structure of the surrounding social network are characteristic for chronobiological sleep disturbances. Activity rhythms that are in abnormal relation to the environment are more frequent than commonly assumed. They can arise either from external causes (such as shift-work or jet-lag) or as a result of internal changes promoting abnormal sleep behaviour. Structuring daily activities by paying attention to natural daylight (dawn and dusk) and to the social routine strengthen the synchronizing effect of external timekeepers necessary for the concordance between inner and outer rhythmic phenomena. Treatment of chronobiological sleep/wake-cycle disturbances require correct diagnosis and modification of their causes, particularly changes in habits consolidating such disturbances. Early recognition of a chronobiological sleep disorder can reduce the risk of misuse of sleeping pills, caffeine and nicotine. Recently developed treatment approaches such as bright light, the pineal hormone melatonin and vitamin B12 have provided promising results.

Crystallographic analyses of an active HIV-1 ribonuclease H domain show structural features that distinguish it from the inactive form.

. An active recombinant preparation of the carboxy-terminal ribonuclease H (RNase H) domain of HIV-I reverse transcriptase has produced crystals of several different forms, including a trigonal prism form (P3(1); a = b = 52.03, c = 113.9 A with two molecules per asymmetric unit) and a hexagonal tablet form (P6(2)22 or P6(4)22; a = b = 93.5, c = 74.1 A with one molecule per asymmetric unit). The former appears to be isomorphous with crystals of a similar, but inactive, version of the enzyme that was used for a prior crystal structure determination [Davies, Hostomska, Hostomsky, Jordan & Matthews (1991). Science, 252, 88-95]. We have also obtained a structure solution for this crystal form and have refined it with 2.8 A resolution data (R = 0.216). We report here details of our crystallization studies and some initial structural results that verify that the preparation of active HIV-1 RNase H yields a protein that is not just enzymatically, but also structurally, distinguishable from the inactive form. Evidence suggests that region 538-542, which may be involved in the catalytic site and which is disordered in both molecules in the prior structure determination, is ordered in the crystal structure of the active enzyme, although the ordering may include more than one conformation for this loop. It should also be noted that, in the crystal structure of the trigonal form, RNase H monomers associate to form noncrystallographic twofold-symmetric dimers by fusing five-stranded mixed beta sheets into a single ten-stranded dimerwide sheet, an assembly that was not remarked upon by previous investigators.

Large scale purification and refolding of HIV-1 protease from Escherichia coli inclusion bodies.

The protease encoded by the human immunodeficiency virus type 1 (HIV-1) was engineered in Escherichia coli as a construct in which the natural 99-residue polypeptide was preceded by an NH2-terminal methionine initiator. Inclusion bodies harboring the recombinant HIV-1 protease were dissolved in 50% acetic acid and the solution was subjected to gel filtration on a column of Sephadex G-75. The protein, eluted in the second of two peaks, migrated in SDS-PAGE as a single sharp band of M(r) approximately 10,000. The purified HIV-1 protease was refolded into an active enzyme by diluting a solution of the protein in 50% acetic acid with 25 volumes of buffer at pH 5.5. This method of purification, which has also been applied to the purification of HIV-2 protease, provides a single-step procedure to produce 100 mg quantities of fully active enzyme.

Repeated partial sleep deprivation progressively changes in EEG during sleep and wakefulness.

The effect of repeated partial sleep deprivation on sleep stages and electroencephalogram (EEG) power spectra during sleep and wakefulness was investigated in nine healthy young subjects. Three baseline nights of 8 hours (2300-0700 hours) were followed by four nights with 4 hours of sleep (2300-0300 hours) and three recovery nights of 8 hours (2300-0700 hours). Sleep restriction curtailed sleep stages 1 and 2 as well as rapid eye movement (REM) sleep, but left slow wave sleep largely unaffected. In the first two recovery nights, total sleep time and REM sleep were enhanced, and sleep latency was shortened. Slow wave sleep was increased only in the first recovery night. In accordance with the prediction of the two-process model of sleep regulation, slow wave activity (SWA; spectral power density in the 0.75-4.5-Hz range) in nonrapid eye movement (NREM) sleep increased by approximately 20% in the first night following sleep restriction, remained at this level in the subsequent 3 nights and decreased immediately after the first recovery night. In contrast to these immediate changes, progressive and more persistent changes were seen in the EEG activity of higher frequencies. Thus, activity in the upper delta band tended to gradually increase from night to night during the sleep restriction period, whereas after an initial increase, activity in the theta-alpha band changed in the opposite direction. The progressive changes were also present in the EEG spectra of REM sleep and wakefulness. Because the time course of these changes paralleled the cumulative deficit in REM sleep, they may represent a correlate of REM sleep pressure.

A model of human sleep homeostasis based on EEG slow-wave activity: quantitative comparison of data and simulations.

EEG slow-wave activity (SWA; spectral power in the 0.75-4.5 Hz band) is a function of the duration of prior waking and, thereby, an indicator of sleep homeostasis. We present a model that accounts for both the declining trend of SWA during sleep and for its variation within the successive nonrapid eye movement (non-REM) sleep episodes. The values of the model parameters were estimated by an optimization procedure in which empirical SWA of baseline nights (16 subjects, 26 nights) served as a reference. A sensitivity analysis revealed the model to be quite robust to small changes (+/- 5%) of the parameter values. The estimated parameter values were used to simulate data sets from three different experimental protocols (sleep in the evening or sleep in the morning after prolonged waking, or extended sleep initiated at the habitual bedtime; n = 8 or 9). The timing of the REM trigger parameter was derived from the empirical data. A close fit was obtained between the simulated and empirical SWA data, and even the occasional late SWA peaks during extended sleep could be reproduced. Minor discrepancies suggest indirect or direct circadian influences on SWA. The simulations demonstrate that the concept of sleep homeostasis as proposed in the two-process model of sleep regulation can be refined to account in quantitative terms for empirical data and to predict the changes induced by the prolongation of waking or sleep.

The effects of ethanol on human sleep EEG power spectra differ from those of benzodiazepine receptor agonists.

A single dose of ethanol (0.60 g/kg of body weight) was administered to eight young healthy male subjects 35 minutes before bedtime. Compared to the average value of two baseline nights, subjective sleep and polysomnographically determined sleep parameters were not significantly affected. In the first 2 hours of sleep after ethanol intake, the combined value of wakefulness, stage 1, and movement time was reduced. In this interval, visually scored stage 4 sleep was increased, and electroencephalographic (EEG) power density in nonrapid-eye-movement (nonREM) sleep was enhanced in the lowest delta frequencies and reduced in the beta range. Computed for the entire sleep episode, power density in REM sleep was enhanced in some theta frequencies. In the sleep episode initiated 24 hours after ethanol intake, power density in nonREM and REM sleep was enhanced in delta and theta frequencies, and the subjectively perceived number of awakenings was reduced. The effects of ethanol on EEG power spectra during sleep differ from those published for benzodiazepine and nonbenzodiazepine hypnotics. This indicates that the effects of ethanol on the human sleep EEG are not mediated by the benzodiazepine receptor.

Proton, carbon, and nitrogen chemical shifts accurately delineate differences and similarities in secondary structure between the homologous proteins IRAP and IL-1 beta.

1H alpha, 13C alpha, and 15N alpha secondary shifts, defined as the difference between the observed value and the random coil value, have been calculated for interleukin-1 receptor antagonist protein and interleukin-1 beta. Averaging of the secondary chemical shifts with those of adjacent residues was used to smooth out local effects and to obtain a correlation dependent on secondary structure. Differences and similarities in the placement of secondary structure elements in the primary sequences of these structurally homologous proteins are manifested in the smoothed secondary chemical shifts of all three types of nuclei. The close correlation observed between the secondary chemical shifts and the previously defined locations of secondary structure, as defined by traditional methods, exemplifies the advantage of chemical shifts to delineate regions of secondary structure.

Secondary structure and topology of interleukin-1 receptor antagonist protein determined by heteronuclear three-dimensional NMR spectroscopy.

Interleukin-1 (IL-1) proteins, such as IL-1 beta, play a key role in immune and inflammatory responses. Interaction of these cytokines with the IL-1 receptor induces a variety of biological changes in neurologic, metabolic, hematologic, and endocrinologic systems. Interleukin-1 receptor antagonist protein (IRAP) is a naturally occurring inhibitor of the interleukin-1 receptor. The 153-residue protein binds to the receptor with an affinity similar to that of IL-1 beta but does not elicit any physiological responses. As a first step toward understanding IRAP's mode of action, we have used multidimensional, heteronuclear NMR spectroscopy to determine the antagonist's solution secondary structure and global fold. Using a combination of 3D 1H-15N NOESY-HMQC and TOCSY-HMQC and 3D 1H-15N-13C HNCA and HN(CO)CA experiments on uniformly 15N- or doubly 13C/15N-enriched IRAP, we have made resonance assignments for more than 90% of the main-chain atoms. Analysis of short- and long-range NOE's indicates that IRAP is predominantly beta-sheet, with the same overall topology as IL-1 beta but with different regions of the primary sequence comprising the beta-strands. Two short helical segments also were identified. The 14% sequence identity between IL-1 beta and IRAP increases to 25% when differences in the locations of secondary structure elements in the primary sequences are taken into account. Still, numerous differences in side chains, which ultimately play a major role in receptor interaction, exist.(ABSTRACT TRUNCATED AT 250 WORDS)