Cardiovascular response to arousal from sleep under controlled conditions of central and peripheral chemoreceptor stimulation in humans.

The cardiovascular response to an arousal occurring at the termination of an obstructive apnea is almost double that to a spontaneous arousal. We investigated the hypothesis that central plus peripheral chemoreceptor stimulation, induced by hypercapnic hypoxia (HH), augments the cardiovascular response to arousal from sleep. Auditory-induced arousals during normoxia and HH (>10-s duration) were analyzed in 13 healthy men [age 24 +/- 1 (SE) yr]. Subjects breathed on a respiratory circuit that held arterial blood gases constant, despite the increased ventilation associated with arousal. Arousals were associated with a significant increase in mean arterial blood pressure at 5 s (P < 0.001) and with a significant decrease in the R-R interval at 3 s (P < 0.001); however, the magnitude of the changes was not significantly different during normoxia compared with HH (mean arterial blood pressure: normoxia, 91 +/- 4 to 106 +/- 4 mmHg; HH, 91 +/- 4 to 109 +/- 5 mmHg; P = 0.32; R-R interval: normoxia, 1.12 +/- 0.04 to 0.90 +/- 0.05 s; HH, 1.09 +/- 0.05 to 0.82 +/- 0.03 [corrected] s; P = 0.78). Mean ventilation increased significantly at the second breath postarousal for both conditions (P < 0.001), but the increase was not significantly different between the two conditions (normoxia, 5.35 +/- 0.40 to 9.57 +/- 1.69 l/min; HH, 8.57 +/- 0.63 to 11.98 +/- 0.70 l/min; P = 0.71). We conclude that combined central and peripheral chemoreceptor stimulation with the use of HH does not interact with the autonomic outflow associated with arousal from sleep to augment the cardiovascular response.     

Correlation between ventilation and EEG-defined arousal during sleep onset in young subjects

Trinder, John, John A. Van Beveren, Philip Smith, JanKleiman, and Amanda Kay. Correlation between ventilation and EEG-defined arousal during sleep onset in young subjects.J. Appl. Physiol. 83(6):2005-2011, 1997.In studies of elderly individuals, ventilationand EEG-defined arousal have been shown to vary periodically andsynchronously. Such results have been interpreted as indicating theprimacy of sleep/wake state in causing ventilatory instability duringsleep onset. However, because the elderly individuals studied wereperiodic breathers, the results do not unequivocally support thisconclusion. In this study the relationship between ventilation andEEG-defined arousal was assessed in a group of 21 young, healthy men inwhom ventilatory instability during sleep onset was not periodic.Ventilation and EEG(O₁-A₂)recordings were collected, and the longest uncontaminated periods fromearly and late in sleep onset were selected for subsequent analysis.The 84 time series (21 subjects, 2 variables, and 2 occasions in sleeponset) were subjected to spectral analysis to identify periodicity, and the relationship between the two variables was determined bycross-correlational methods. The results indicated that the time serieswere nonperiodic, yet significant correlations were observed betweenthe two variables. The data support the view that during sleep onsetventilatory instability is driven primarily by variations in sleep/wakearousal level.

     

Types of respiratory activity in Moniliella tomentosa during growth under different conditions.

The osmophilic yeastlike fungus Moniliella tomentosa is an obligate aerobe and is not susceptible to glucose repression. Respiration is greatest in exponentially growing cells and is then highly sensitive to cyanide. Respiration in older cells or in chloramphenicol-grown cells is mediated by a cyanide-insensitive respiration which is sensitive to salicyl hydroxamic acid. Growth of cells under reduced oxygen does not influence the respiratory capacity of the cells but results in a longer generation time and a lower final cell yield. Low aeration levels and growth in the presence of chloramphenicol have a profound effect on ethanol and polyol production.     

Cardiovascular variability after arousal from sleep: time-varying spectral analysis.

We performed time-varying spectral analyses of heart rate variability (HRV) and blood pressure variability (BPV) recorded from 16 normal humans during acoustically induced arousals from sleep. Time-varying autoregressive modeling was employed to estimate the time courses of high-frequency HRV power, low-frequency HRV power, the ratio between low-frequency and high-frequency HRV power, and low-frequency power of systolic BPV. To delineate the influence of respiration on HRV, we also computed respiratory airflow high-frequency power, the modified ratio of low-frequency to high-frequency HRV power, and the average transfer gain between respiration and heart rate. During cortical arousal, muscle sympathetic nerve activity and heart rate increased and returned rapidly to baseline, but systolic blood pressure, the ratio between low-frequency and high-frequency HRV power, low-frequency HRV power, the modified ratio of low-frequency to high-frequency HRV power, and low-frequency power of systolic BPV displayed increases that remained above baseline up to 40 s after arousal. High-frequency HRV power and airflow high-frequency power showed concommitant decreases to levels below baseline, whereas the average transfer gain between respiration and heart rate remained unchanged. These findings suggest that 1) arousal-induced changes in parasympathetic activity are strongly coupled to respiratory pattern and 2) the sympathoexcitatory cardiovascular effects of arousal are relatively long lasting and may accumulate if repetitive arousals occur in close succession.     

Tracheal occlusion in the newborn piglet. Effects of sleep state and occlusion timing on arousal and respiratory responses.

Twelve piglets of 3-5 days of age were instrumented for determination of sleep state and performance of midtracheal occlusions. After spontaneously occurring sleep the occlusions were performed either at end-inspiration or end-expiration in quiet and active sleep. The time from occlusion to arousal differed significantly between quiet and active sleep. Arousal from quiet sleep following end-expiratory occlusions occurred after a mean of 3.1 s. After similar, end-expiratory occlusions in quiet sleep were commonly followed by apneas, presumably a manifestation of the Hering-Breuer reflex. Such apneas were rare in active sleep (P less than 0.01). The arousal response to midtracheal occlusions in the newborn piglet is qualitatively similar to that previously described in the newborn lamb, but occurs more rapidly. Our results suggest that the response to vaguely mediated information from pulmonary stretch receptors is impaired inactive sleep.     

Nitrous oxide and dinitrogen emissions from urine-affected soil under controlled conditions

A ¹⁵N labelling technique was used to measure N₂O and N₂ emissions from an undisturbed grassland soil treated with cow urine and held at 30 cm water tension and 20°C in a laboratory. Large emissions of dinitrogen were detected immediately following urine application to pasture. These coincided with a rapid and large increase in soil water-soluble carbon levels, some of this increase being attributed to solubilization of soil organic matter by high pH and ammonia concentrations. Emissions of nitrous oxide generally increased with time in contrast to dinitrogen fluxes which decreased as time progressed. Estimated losses of N₂O and N₂ over a 30 day period were between 1 to 5% and 30 to 65% of the urine N applied plus N mineralized from soil organic matter, respectively. Most of the N₂ and N₂O originated from denitrification with nitrification-denitrification being of minor significance as a source of N₂O. Comparisons of the ¹⁵N enrichments in the soil mineral N pools and the evolved N₂O suggested that much of the N₂O was produced in the 5–8 cm zone of the soil. It is concluded that established grassland soils contain large amounts of readily-oxidizable organic carbon which may be used by soil denitrifying organisms when nitrate is non-limiting and soil redox potential is lowered due to high rates of biological activity and high soil moisture contents. ei]{gnR}{fnMerckx}     

Comparison of responses to CO2 under the conditions of natural respiration and controlled artificial pulmonary ventilation

The relationship between the sensation of lack of air caused by the addition of carbon dioxide to inhaled air and minute pulmonary ventilation was studied in eight healthy male volunteers. Under the conditions of both natural respiration and controlled artificial ventilation of the lungs, ventilation increased in proportion to the increase in the partial pressure of CO₂ in the end-tidal exhaled air. The individual differences in the ventilation responses to CO₂ under the conditions of controlled ventilation and natural ventilation are regarded as a property of voluntary control.     

A brainstem-to-mediodorsal thalamic pathway mediates sound-induced arousal from slow-wave sleep

1. Download : Download high-res image (93KB)
2. Download : Download full-size image

     

Aphid moulting under controlled electrical conditions

The moulting of MYZUS PERSICAE under constant conditions of temperature, light (200 w filament light-bulb, d.c.) and almost constant relative humidity was studied. Maxima of moulting, counted at one-hour intervals between 12:00 and 15:00 hr under shielded conditions, could be traced more clearly when the air exchange in the shielded room was avoided. In electrical fields, to which the populations were exposed for 15–20 min, depressions of moulting numbers could be observed with relatively high electrical intensities (10 v),an increase, with medium electrical intensities (1 v), and a delayed increase of moulting with low intensities (0.1 v).Increases of moulting figures in comparison to the daily mean were also found in air negatively ionized (10–20 min application) by means of both high voltage corona discharge and radioactive tritium. It was found, that activity changes in the aphids (increase of moulting) often took place with a sudden rise of negative air ion density or with a drastic reduction of high positive air ion concentration.

---

Zusammenfassung MYZUS PERSICAE-HÄutungen in konstantem Licht (200 Watt-Glühbirne,Gleichstrom),konstanter Temperatur und annÄhernd konstanter relativer Luftfeuchtigkeit wurden stündlich ausgezÄhlt.Die unter verschieden abgeschirmten Bedingungen festgestellten HÄutungsmaxima zwischen 12:00–15:00 h traten klarer zutage,wenn die abgeschirmte Kabine hermetisch geschlossen wurde. In künstlich erzeugten elektrischen Feldern schienen höhere elektrische IntensitÄten (10 v) eine Depression, mittlere (1 v)HÄutungszunahme zu ergeben, die bei niedrigen FeldstÄrken (0,1 v) mit einstündiger VerspÄtung in Erscheinung trat. Relative HÄutungszunahmen (Mittelwertgegenüberstellungen) waren auch nach künstlicher negativer Ionisation der Luft mit Hilfe der stillen Corona-Entladung oder einer radioaktiven Tritium-Quelle festzustellen.Die beobachteten HÄutungsanstiege fielen dabei zeitlich sowohl mit plötzlichem, starkem Ansteigen negativer als auch mit drastischer Verminderung hoher positiver Ionenkonzentrationen zusammen.

---

Résumé Les mues de MYZUS PERSICAE en lumière (ampoule electrique, courant continu, 200 Watt), temperature constante et humidité relative de l'air approximativement constante ont été comptées une fois par heure.Les maximas de midi entre 12.00–15.00 h, constatés sous des conditions d'écran differents se montraient plus nettes si la cabine écran était hermetiquement fermé. Il semblait que dans des champs électriques artificiels des intensités de champ plus grandes (10 v) provoquent une dépression, des intensités moyennes (1 v) par contre une augmentation du nombre de mues — qui ne se montraient qu'après une heure de retard si l'intensité du champ était petite (0,1 v).De mÊme on constatait souvent une augmentation relative des mues (comparaison des valeurs moyennes) après une ionisation négative artificielle de l'air à l'aide d'une décharge corona,ainsi qu'à l'aide d'une source radioactive de Tritium. Les augmentation du nombre de mues observées coÏncidaient aussi bien avec une augmentation abrupte et forte de la concentration d'ions négatifs qu'avec une diminution frappante de la concentration d'ions positifs.

     

Upper airway anesthesia delays arousal from airway occlusion induced during human NREM sleep.

Six healthy subjects (5 males and 1 female, 26-40 yr old) were studied during non-rapid-eye-movement (NREM) sleep to assess the role of upper airway (UA) afferents in the arousal response to induced airway occlusion. Subjects wore an airtight face mask attached to a low-resistance one-way valve. A valve in the inspiratory circuit allowed instantaneous inspiratory airway occlusion and release; the expiratory circuit remained unoccluded at all times. Each subject was studied during two nights. On one night, occlusions were created during stable stage 2 NREM sleep before and after application of 4% lidocaine to the oral and nasal mucosa. On the other night, the protocol was duplicated with saline ("sham anesthesia") rather than lidocaine. The order of nights was randomized. Occlusions were sustained until electroencephalographic arousal. Three to 12 occlusions were performed in each subject for each of the four parts of the protocol (pre- and post-lidocaine, pre- and post-saline). The auditory threshold for arousal (1,500-Hz tone beginning at 30 dB) was also tested before and after UA lidocaine. For the group, arousal time after UA anesthesia was prolonged compared with preanesthesia arousal time (P less than 0.001); arousal time after sham anesthesia did not significantly increase from before sham anesthesia (P = 0.9). The increase in arousal time with UA anesthesia was greater than the increase with sham anesthesia (P less than 0.001). The auditory arousal threshold did not increase after UA anesthesia. Inspiratory mask pressure, arterial O2 saturation of hemoglobin, and end-tidal PCO2 during occlusions were similar before and after UA anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Leaf temperatures under controlled environmental conditions

A wind tunnel and an external microwave energy source formed the basis of an experimental technique to investigate many complex functional relationships between climatic parameters and leaf temperatures. The results of preliminary experimental plant-environment interactions are compared with published theoretical results obtained by solving the energy balance equation for a single leaf.