bluuebunny/crossref_metadata_2025_split huggingface dataset:
Refining the stress‐gradient hypothesis for competition and facilitation in plant communities
Authors: Maestre Fernando T. , Callaway Ragan M. , Valladares Fernando , Lortie Christopher J. 
Published: January 2009

Summary

The stress‐gradient hypothesis (SGH) predicts that the frequency of facilitative and competitive interactions will vary inversely across abiotic stress gradients, with facilitation being more common in conditions of high abiotic stress relative to more benign abiotic conditions. With notable exceptions, most tests of the SGH have studied the interaction between a single pair or a few pairs of species, and thus have evaluated shifts in the magnitude and direction of pair‐wise interactions along stress gradients, rather than shifts in the general frequency of interactions.
The SGH has been supported by numerous studies in many ecosystems, has provided a crucial foundation for studying the interplay between facilitation and competition in plant communities, and has a high heuristic value. However, recent empirical research indicates that factors like the variation among species and the nature of the stress gradient studied add complexity not considered in the SGH, creating an opportunity to extend the SGH's general conceptual framework.
We suggest that one approach for extending the SGH framework is to differentiate between the original idea of how ‘common’ interactions might be along stress gradients and the ubiquitous empirical approach of studying shifts in the strength of pair‐wise interactions. Furthermore, by explicitly considering the life history of the interacting species (relative tolerance to stress vs. competitive ability) and the characteristics of the stress factor (resource vs. non‐resource) we may be able to greatly refine specific predictions relevant to the SGH.
We propose that the general pattern predicted by the SGH would hold more frequently for some combinations of life histories and stress factor, particularly when the benefactor and beneficiary species are mostly competitive and stress‐tolerant, respectively. However, we also predict that other combinations are likely to yield different results. For example, the effect of neighbours can be negative at both ends of the stress gradient when both interacting species have similar ‘competitive’ or ‘stress‐tolerant’ life histories and the abiotic stress gradient is driven by a resource (e.g. water).
Synthesis. The extension of the SGH presented here provides specific and testable hypotheses to foster research and helps to reconcile potential discrepancies among previous studies. It represents an important step in incorporating the complexity and species‐specificity of potential outcomes into models and theories addressing how plant–plant interactions change along stress gradients.
Sleep architecture in agenesis of the corpus callosum: laboratory assessment of four cases
Authors: NIELSEN TORE , MONTPLAISIR JACQUES , LASSONDE MARYSE 
Published: January 2009

SUMMARY  Whether the corpus callosum is essential for normal human sleep cannot be decided from current knowledge. We thus studied sleep architecture in four subjects with agenesis of the corpus callosum (ACC) and four control subjects matched for age, gender, and hand preference. All‐night EEG, EOG, and EMG activity were monitored in the laboratory for one adaptation night and one data acquisition night. Standard sleep variables were calculated for the second night.Agenesis subjects were found to have a greater percentage of stage 3 + 4 sleep and a lower percentage of stage 2 sleep than control subjects. Agenesis subjects also tended to have more REM sleep periods and a shorter REM cycle length than controls.The pattern of results is similar to that produced by partial callosotomy. It is also relevant to two hypotheses about the function of the corpus callosum in sleep. First, the corpus callosum may facilitate synchronization of activity between homologous regions in the two hemispheres but interfere with synchronization of neuronal populations within each hemisphere. Its absence may thus explain both an augmentation of slow‐wave activity (and thus more slow‐wave sleep) and a decrease in interhemispheric EEG coherence. Secondly, the corpus callosum may play a role in the regulation of the ultradian rhythm which underlies timing and duration of REM sleep.
24‐h variation of vigilance in the cockroach Blaberus giganteus
Authors: TOBLER IRENE , NEUNER‐JEHLE MARTIN 
Published: January 2009

SUMMARY  Our objective was to investigate whether sleep‐like states occur in the cockroach, Blaberus giganteus by applying the methods formerly used for another cockroach species, Leucophaea maderae and the scorpions, Heterometrus and Pandinus. The behaviour of isolated animals (n= 10) kept under LD 12:12 h was recorded by time‐lapse video for three consecutive 24‐h periods. Nine behavioural states were scored for 1‐min real‐time epochs. Rest was subdivided into 4 sub‐states on the basis of body posture and the position of the antennae. The cockroaches showed a nocturnal behaviour exhibiting a bout of locomotion at dark onset which lasted several hours, and a preference for rest in the light period. Immobility with both the body and the antennae touching the substrate (state 1) was the predominating state in the light period.In order to establish whether the sub‐states of rest represented different levels of vigilance the arousal threshold was measured by determining the latency of a behavioural response to a vibration stimulus. The levels of arousal differed significantly in four behavioural states in the light period but not in the dark period. In state 1 the animals exhibited the lowest arousal whereas in the activity states arousal was the highest. The state with the highest arousal threshold occurred in the beginning of the light period. Thereafter, arousal progressively increased and remained relatively high during the dark period.The effect of 6‐h deprivation of rest by the gentle shaking of the cages whenever the animals were immobile, resulted in a reduced latency to state 1, a small increase of state 1 and a more prominent initial increase of activity during recovery.In conclusion, this study provides evidence for the existence of a 24‐h variation of vigilance in the cockroach. It further indicates that a ‘rest deficit’ gives rise to a compensatory response. The data support the notion that sleep‐like states are present in these insects.
Sleep, snoring and smoking in high school students
Authors: DELASNERIE‐LAUPRETRE NICOLE , PATOIS ELISABETH , VALATX JEAN‐LOUIS , KAUFFMANN FRANCINE , ALPEROVITCH ANNICK 
Published: January 2009

SUMMARY  The relationship between snoring, sleep and smoking was investigated in young students from a survey by self‐administered questionnaire on sleep habits, conducted in high schools in the educational district of Lyons (France). Our sample consisted of 11,417 boys and 13,265 girls between 15 and 20 years of age.We found that 28.4% of girls and 38.8% of boys reported that they snored. In both sexes, snoring was associated with short (<7h) and long (>10h) sleep length, nocturnal awakenings and daytime sleepiness. Smoking was a risk factor for snoring. Multiple logistic regression showed that the odds‐ratio for habitual snoring increased when tobacco consumption increased from a 1.30 (moderate smokers) to 2.26 (heavy smokers) in girls and from 1.38 to 2.09 in boys.This dose‐effect relationship between smoking and snoring suggests that a substantial proportion of snoring cases is attributable to tobacco consumption in young students.
Renin as a biological marker of the NREM‐REM sleep cycle: effect of REM sleep suppression
Authors: BRANDENBERGER G. , CHARIFI C. , MUZET A. , SAINI J. , SIMON C. , FOLLENIUS M. 
Published: January 2009

SUMMARY  We have previously described that, in normal man, the nocturnal oscillations of plasma renin activity (PRA) exactly reflect the rapid eye movement (REM)–non(N)REM sleep cycles, with increasing PRA levels during NREM sleep and decreasing levels during REM sleep. This study was carried out to determine whether REM sleep suppression affects nocturnal renin profiles and to define which sleep stage is essential for renin release.In a first experimental series, REM sleep was suppressed by using clomipramine, a tricyclic antidepressant. Seven healthy young men were studied once during a night when a placebo was given and once during a night following a single dose of 50 mg clomipramine. Blood was collected every 10 min from 23.00 hours to 07.00 hours. PRA was measured by radio‐immunoassay and the nocturnal profiles were analysed using the pulse detection program ULTRA. Clomipramine suppressed REM sleep in all subjects but one, but did not affect the number of SWS episodes nor their duration. Similar PRA profiles were observed in both experimental conditions. Neither the mean levels, nor the number and the amplitude of the oscillations were modified and the normal relationship between slow wave sleep and increasing PRA levels was preserved.In a second experimental series, REM sleep was prevented by rapidly awakening the subjects as soon as they fell into REM sleep. The four subjects studied attempted several times to go into REM sleep, but only when PRA levels were decreasing. The interruption of REM sleep by short waking periods did not disturb PRA for which the oscillations remained unaffected. Again, the relationship between SWS and increasing PRA levels was preserved.These results provide evidence that mechanisms increasing slow‐wave activity are principally involved in increasing PRA levels and that replacing REM sleep by waking periods and light sleep does not modify nocturnal PRA oscillations.
Sleep apnoea in the Prader‐Willi syndrome
Authors: CLIFT S. , DAHLITZ M. , PARKES J. D. 
Published: January 2009

SUMMARY  Seventeen children and young adults with the Prader‐Willi syndrome were investigated. Twelve of 17 subjects had excessive daytime sleepiness as determined by their own or parental report, a high Epworth Sleepiness Scale score or a short mean sleep latency. Night sleep disturbances were reported in seven subjects with snoring, mouth‐breathing, breath‐holding and occasional nocturnal enuresis. Polysomnography showed abnormalities of sleep structure with rapid eye movements without reduction in muscle tone at sleep onset in 12 subjects, and a high respiratory event index with frequent brief apnoeas, particularly in REM sleep, in 16 subjects. Most apnoeas were not accompanied by arousals. Seven subjects, all of whom were obese, were considered to have symptomatic sleep apnoea and were treated with continuous positive airway pressure (CPAP) but this was poorly tolerated in two. Five subjects continued CPAP over a 6‐month period resulting in subjective improvement in excessive daytime sleepiness in 3.Excessive daytime sleepiness occurs in approximately two‐thirds of subjects with the Prader‐Willi syndrome. It is mainly of central origin but obstructive sleep apnoea may increase sleepiness, particularly in obese subjects.
Plasma insulin and lipid levels in untreated obstructive sleep apnoea and snoring; their comparison with matched controls and response to treatment
Authors: DAVIES R. J. O. , TURNER R. , CROSBY J. , STRADLING J. R. 
Published: January 2009

SUMMARY  Obstructive sleep apnoea (OSA), and snoring are associated with coronary heart disease. To assess whether OSA or snoring may contribute to this by raising fasting lipid or insulin levels, venous fasting total cholesterol, triglyceride, very‐low‐density lipoprotein, low‐density lipoprotein, high‐density lipoprotein, and insulin were measured in 15 untreated OSA patients and 18 snorers. Each of these subjects was individually matched to a control of the same sex, age ± 10%, body index ± 15%, smoking and drinking habits. This produced study groups which did not differ significantly by any of these criteria. Fasting venous blood samples were collected at 06.30 hours following polysomnography, and analysed blind of the subjects respiratory status. The OSA patients were then treated with nasal continuous positive airway pressure. In 10 of these subjects lipid and insulin levels were repeated after more than three months treatment. Lipid and insulin levels were also remeasured in the controls matched to these 10 subjects. The end points were compared with paired t‐tests.There was no difference in any of the end points when the untreated OSA patients and the snorers were compared to their matched controls (P>0.25 for all comparisons), and none of the indices changed when OSA was corrected with nasal continuous positive airway pressure (P > 0.25 for all comparisons).Patients with obstructive sleep apnoea or snoring do not have significant fasting hyperlipidaemia or hyperinsulinaemia when compared to carefully matched controls. These factors are therefore unlikely to be the cause of the excess cardiovascular mortality experienced by this patient group.
Effects of a cognitive‐behavioural weight loss programme on overweight obstructive sleep apnoea patients
Authors: KAJASTE S. , TELAKIVI T. , MUSTAJOKI P. , PIHL S. , PARTINEN M. 
Published: January 2009

SUMMARY  Thirty‐two obese patients (Body Mass Index (BMI) = 38.5 ± 3.7) with obstructive sleep apnoea (the average number of oxygen desaturations per hour of sleep exceeding 4% from the baseline (OD14) = 38.6 ± 23.9) underwent a one‐year cognitive‐behavioural weight reduction programme with a one year follow‐up period.The criteria for successful treatment were (i) a decrease in OD14 to less than 10 and (ii) a decrease in OD14 that was greater than 50%. Fourteen (44%) patients were considered to be treated successfully at six months. When the patients were grouped according to weight loss 23 patients had lost more than 5 kg; 12 (52%) of them belonged to the group treated successfully. At 24 months, however, only three (9%) patients could be regarded as treated successfully and six patients had been transferred to other treatment modes (Nasal Continuous Positive Airway Pressure (nCPAP) and uvulopalatopharyngoplasty (UPPP)). The changes in weight correlated with the changes in OD14 (r = 0.47 and 0.63 at the 6‐month and the 24‐month evaluation, respectively).
Treatment in the narcoleptic syndrome: self assessment of the action of dexamphetamine and clomipramine
Authors: Chen S. Y. , Clift S. J. , Dahlitz M. J. , Dunn G. , Parkes J. D. 
Published: January 2009

Subjective evaluation of the effect of treatment of excessive daytime sleepiness (EDS) with dexamphetamine and of cataplexy with clomipramine was made in 124 subjects with the narcoleptic syndrome. Drug effects were evaluated by self‐report of the propensity to EDS and cataplexy as determined by the Epworth Sleepiness Scale and a rating scale of anticipation‐associated loss of postural motor tone during long‐term therapy. The effects of dexamphetamine alone (60 subjects), clomipramine alone (16 subjects) and combined dexamphetamine‐clomipramine treatment (48 subjects) were evaluated.Self‐reports indicated that the propensity to EDS was reduced by approximately 20% by dexamphetamine (mean dosage 16 mg/24 h, range 5–60: mean treatment period 21 years, range 2–45). The propensity to cataplexy was reduced by 23% by clomipramine (mean dosage 64 mg/24 h, range 25–125: mean treatment period 14 years, range 1–24). Dexamphetamine alone, in addition to reducing the propensity to EDS also reduced the propensity to cataplexy. Clomipramine alone reduced cataplexy, but not EDS. Combined dexamphetamine‐clomipramine treatment caused a reduction in the propensity to EDS and cataplexy of similar magnitude to that caused by dexamphetamine alone. Less than 10% of all subjects with the narcoleptic syndrome reported a daytime sleep propensity in the normal range whilst on dexamphetamine and no subject on clomipramine reported complete control of cataplexy. Long‐term treatment with dexamphetamine was associated with weight increase more commonly than weight loss. Weight gain was reported by two‐thirds of subjects taking clomipramine alone. Reports of weight loss were as common as reports of weight gain by subjects on combined dexamphetamine‐clomipramine treatment. Constipation, dry mouth and impaired sexual function were reported by 25%, 38% and 19% (respectively) of subjects on clomipramine.This retrospective long‐term self‐report study investigated the propensity to, rather than the frequency of, episodes of EDS and cataplexy in subjects with the narcoleptic syndrome. This study suggests that long‐term drug treatment in the narcoleptic syndrome results in only minor reduction in attack propensity, in contrast to the findings of many previous short term objective studies, which suggest 50–80% reduction in attack frequency. Major factors limiting response to dexamphetamine in the narcoleptic syndrome include physician prescription of sub‐optimal drug dosages, and a low index between the limited therapeutic efficacy and frequent side‐effects of this drug.
Firing of inferior colliculus neurons in response to low‐frequency sound stimulation during sleep and waking
Authors: MORALES‐COBAS GABRIELA , FERREIRA MARÍA INÉS , VELLUTI RICARDO A. 
Published: January 2009

SUMMARY  In vivo extracellular recordings of 102 units in the central nucleus of the inferior colliculus (IC), were made in chronically implanted guinea‐pigs during the sleep/wake cycle. During wakefulness, the units were classified according to their response characteristics. Most neurons (63%) recorded showed changes, increasing or decreasing in the number of evoked discharges during the animal's transitions between wakefulness and slow‐wave sleep. In the paradoxical sleep phase, the result was similar; changes were observed in most neurons, while only 11% of units did not shift their discharge pattern during ipsilateral sound stimulation.The post‐stimulus time histogram of the overall evoked pattern of discharge showed sleep/wake dependency, i.e. changed in 35% of the units recorded during the 50 ms of sound stimulation.Fifty‐five percent of auditory neurons did not show any change in the spontaneous firing rate during slow‐wave sleep as compared to the previous waking period, while 22% exhibited a discharge increase and 23% decreased their firing. During paradoxical sleep, 14 out of 17 cells increased their spontaneous firing rate. The IC auditory neurons send descending connections to regions such as the dorsal pontine nuclei, known to mediate sleep processes. Thus, for constant auditory input, the firing rate or number of discharge variations are due to functional shifts in the sleeping brain. Auditory processing is present during sleep and differs from that observed during wakefulness. Differences were observed in the evoked firing number and/or spontaneous rate, as well as in the pattern of discharge. The ultimate reason for auditory unit shifts during sleep remains yet unexplained.
Non‐invasive measurement of haemodynamics during sleep apnoea
Authors: ESCOURROU P. , TESSIER O. , BUREAU A. , NEDELCOUX H. , BOURGIN P. 
Published: January 2009

SUMMARY  Sleep apnoeas are accompanied by large variations in heart rate (HR) and blood pressure (BP). This nocturnal variability in BP may be involved in the increased cardiovascular morbidity of these patients. Due to the complex interaction between asphyxia, intrathoracic pressure, cardiac function and autonomic activation, the exact haemodynamic mechanisms are unclear.To evaluate the components of the BP surges at resumption of breathing (RB) a non‐invasive beat‐to‐beat measurement was taken of cardiac output (CO) by the pulse contour analysis of the Finapres signal. Six male normotensive patients, free of medication (37–60 y, BMI 26.5–43.0 kg m‐2) were studied during polysomnography (apnoea index: 22–69 h‐1). Systolic blood pressure rose from 126.5 ± 1.3 mmHg at beginning apnoea (P1) to 140.4 ±1.3 at RB (P<0.01, ANOVA). During sleep Stages 2 and 3, stroke volume decreased during RB to 96% of P1 value (NS). Due to an opposite change in HR, CO tended to rise at RB to 106% of P1. Computed total peripheral resistance rose during RB to 105% of P1 value (P <0.01).Therefore, it is concluded that the surge in BP at RB after apnoea is due to concomitant increases in CO and in TPR. Both rises are presumably a consequence of sympathetic nervous activation by the arterial chemoreceptors.
Intrathoracic pressure changes and cardiovascular effects induced by nCPAP and nBiPAP in sleep apnoea patients
Authors: BECKER HEINRICH , GROTE LUDGER , PLOCH THOMAS , SCHNEIDER HARTMUT , STAMMNITZ AXEL , PETER JÖRG HERMANN , PODSZUS THOMAS 
Published: January 2009

SUMMARY  The effect of nasal continuous positive airway pressure (nCPAP) and nasal bi‐level positive airway pressure (nBiPAP) on intrathoracic pressure and haemodynamics during wakefulness was studied in a group of nine patients with severe sleep apnoea. No patient took cardiovascular medication.Patients were studied with a Swan Ganz catheter, an arterial line and an oesophageal balloon. nCPAP and nBiPAP were applied in the following pressure sequence: 5, 10 and 15 cm H2O of CPAP and 10/5 and 15/10 cm H2O of nBiPAP. Measurements were made at the end of a 5‐min period at each pressure level. Intrathoracic pressure was noted to increase to a level of approximately 50% of the pressure delivered at the mask. At a CPAP of 10 cm H2O and above, as well as at BiPAP of 10/5 or higher, there was a decrease in cardiac output (CO) and cardiac index (CI). CI fell below the normal value in two of the patients. Transmural pulmonary artery pressure (PPAtm) decreased at a CPAP of 15 cm H2O and at both BiPAP levels. Transmural right atrial pressure (PRAtm) decreased at both BiPAP levels. There were no differences in CO, CI, PPAtm and PRAtm between nCPAP and nBiPAP at equal inspiratory pressures. SaO2 increased during BiPAP 15/10 cm H2O, whereas heart rate and arterial blood pressure did not change significantly. The data presented here are consistent with the literature on positive end‐expiratory pressure (PEEP) applied via intratracheal tube and are likely to be due to a reduced venous return. It is concluded that nasally applied positive pressure may have acute negative effects on cardiac function in patients with sleep apnoea.
Polygraphic findings in young infants with Joubert's syndrome
Authors: SCHLÜTER B. , BUSCHATZ D. , TROWITZSCH E. , ANDLER W. , AKSU F. , STUTE M. 
Published: January 2009

SUMMARY  In three young infants with Joubert's syndrome polygraphic recordings were carried out in the awake state and during REM and NREM sleep in order to characterize the respiratory disorder associated with this condition.In all three states disturbed respiration parameters were found in variable amounts. The highest breath rate occurred in the awake state followed by REM and NREM sleep. The highest incidence of apnoea and periodic breathing was observed in NREM sleep, followed by REM sleep and the awake state.
Polysomnographic recordings of respiratory disturbances in Rett syndrome
Authors: SCHLÜTER B. , AGUIGAH G. , BUSCHATZ D. , TROWITZSCH E. , AKSU F. 
Published: January 2009

SUMMARY Polygraphic recordings in the awake state and during sleep were performed in two girls with Rett syndrome, aged 9 y and 17 y, in order to characterize the clinically manifest breathing disorder of these patients.Primary hyperventilation was detected, leading to hypocapnia and compensatory apnoea. Hypoxaemia occurred as the consequence of prolonged apnoea. In the younger patient these disturbances were observed only in the awake state, whereas in the older patient they were found in the awake state and during sleep.