bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tissue nutrient concentrations in freshwater aquatic macrophytes: high inter‐taxon differences and low phenotypic response to nutrient supply
Authors: DEMARS BENOÎT O. L. , EDWARDS A. C. 
Published: August 2007

Summary1. The elemental composition and stoichiometry of aquatic plants has often been suggested to reflect the nutrient enrichment of aquatic habitats. However, the relationship is often weak. Moreover, uncertainties remain in the relevance of laboratory derived critical plant tissue nutrient concentrations to maximum yield or growth rates in the field.2. Aquatic vascular plants and bryophytes, overlying water and sediment samples were collected to test whether freshwater aquatic macrophytes: (i) show tissue nutrient deficiencies when growing in oligotrophic freshwater habitats, and (ii) have strict homeostatic stoichiometry.3. Plant nutrient concentrations were significantly related to total inorganic nitrogen (or nitrate), total dissolved phosphorus and sediment total phosphorus. However, these relationships were weak. Virtually all the variance in plant tissue nutrient concentrations, however, could be explained by species (taxon) identity.4. Critical tissue nutrient concentrations for 95% maximum yield or 95% maximum growth rate in aquatic angiosperms, determined from laboratory bioassays, suggested that nutrients should not limit yield in wild aquatic macrophytes. However, there were a substantial number of samples where potential growth rate limitation was possible, particularly due to phosphorus.5. Strict C : N : P stoichiometric ratios were found for both vascular plants and bryophytes, suggesting little scope for plants as indicators of nutrient enrichment, but provide robust stoichiometric data for studies on ecosystem metabolism and nutrient cycling.
Ecosystem input of nitrogen through biological fixation in feather mosses during ecosystem retrogression
Authors: LAGERSTRÖM A. , NILSSON M.‐C. , ZACKRISSON O. , WARDLE D. A. 
Published: August 2007

Summary

Ecosystem retrogression occurs during the very long‐term absence of major disturbances, and it is characterized by decreases in productivity, decomposition rates and nutrient availability. Ratios of total soil nitrogen (N) to phosphorus (P) also characteristically increase during retrogression, but the nature of N inputs to ecosystems undergoing retrogression has seldom been explored.
We studied a 5000‐year‐old chronosequence involving 30 islands that differed greatly in history of disturbance (wildfire through lightning strike), with increasing time since disturbance leading to ecosystem retrogression. For each island, we quantified N inputs through biological fixation by cyanobacteria hosted by each of two feather moss species that dominate the ground layer vegetation (Pleurozium schreberi and Hylocomium splendens), and compared these with N inputs through atmospheric deposition.
Both N2 fixation per unit land area and fixation per unit moss mass increased significantly with increasing time since disturbance for both moss species. As retrogression progressed, the amount of total N input through biological fixation increased to levels comparable to that of input through atmospheric deposition.
Across the chronosequence, N has been accumulating in the humus layer at a rate of 1·8 kg ha−1 year−1 in the absence of fire during the past 5000 years. The added N input from biological fixation in this area of low atmospheric N deposition helps explain this relatively high rate of sequestration.
Our results show that, contrary to several claims in the literature, biological N2 fixation is not only important in early‐successional ecosystems but also in late‐successional systems that have undergone retrogression. This fixation can contribute both to the elevated N : P ratios that occur during retrogression and to accumulation of N capital in the soil. However, much of this N may exist in forms that are relatively unavailable to co‐existing plant species.
What is the required minimum landscape size for dispersal studies?
Authors: FRANZÉN MARKUS , NILSSON SVEN G. 
Published: August 2007

SummaryAmong small animals dispersal parameters are mainly obtained by traditional methods using population studies of marked individuals. Dispersal studies may underestimate the rate and distance of dispersal, and be biased because of aggregated habitat patches and a small study area. The probability of observing long distance dispersal events decreases with distance travelled by the organisms. In this study a new approach is presented to solve this methodological problem.An extensive mark–release–recapture programme was performed in an area of 81 km2in southern Sweden. To estimate the required size of the study area for adequate dispersal measures we examined the effect of study area size on dispersal distance using empirical data and a repeated subsampling procedure. In 2003 and 2004, two species of diurnal burnet moths (Zygaenidae) were studied to explore dispersal patterns.The longest confirmed dispersal distance was 5600 m and in total 100 dispersal events were found between habitat patches for the two species. The estimated dispersal distance was strongly affected by the size of the study area and the number of marked individuals. For areas less than 10 km2most of the dispersal events were undetected. Realistic estimates of dispersal distance require a study area of at least 50 km2.To obtain adequate measures of dispersal, the marked population should be large, preferably over 500 recaptured individuals. This result was evident for the mean moved distance, mean dispersal distance and maximum dispersal distance.In general, traditional dispersal studies are performed in small study areas and based on few individuals and should therefore be interpreted with care. Adequate dispersal measures for insects obtained by radio‐tracking and genetic estimates (gene flow) is still a challenge for the future.
Head posture and dental wear evaluation of bruxist children with primary teeth
Authors: VÉLEZ A. L. , RESTREPO C. C. , PELÁEZ‐VARGAS A. , GALLEGO G. J. , ALVAREZ E. , TAMAYO V. , TAMAYO M. 
Published: August 2007

Summary  The aim of the present study was to compare the head position and dental wear of bruxist and non‐bruxist children with primary dentition.Methods:  All the subjects had complete primary dentition, dental and skeletal class I occlusion and were classified as bruxist or non‐bruxist according to their anxiety level, bruxism described by their parents and signs of temporomandibular disorders. The dental wear was drawn in dental casts and processed in digital format. Physiotherapeutic evaluation and a cephalometric radiograph with natural head position were also performed for each child to evaluate the cranio‐cervical position for the bruxist group (n = 33) and the control group (n = 20). The variables of the two groups were compared, using the Student t‐test and Mann–Whitney U‐test.Results:  A more anterior and downward head tilt was found in the bruxist group, with statistically significant differences compared with the controls. More significant dental wear was observed in the bruxist children.Conclusions:  Bruxism seems to be related to altered natural head posture and more intense dental wear. Further studies are necessary to explore bruxism mechanisms.
Improving actigraphic sleep estimates in insomnia and dementia: how many nights?
Authors: VAN SOMEREN EUS J. W. 
Published: August 2007

SummaryIn order to investigate how the duration of actigraphic recordings affects the reliability of actigraphic estimates of sleep and 24‐h activity rhythm variables, two to 3 weeks of actigraphy were recorded, from which pairs of variables derived from two periods of increasing length (1–10 days) were compared. Two groups were studied: (1) 10 subjects suffering from primary insomnia; and (2) 12 demented elderly subjects living semi‐independently in group care facilities of homes for the elderly. Actigraphic estimates of primary measures of sleep (duration and efficiency) and of the 24‐h activity pattern (interdaily stability, intradaily variability and amplitude) were calculated on variable lengths of the actigraphic recordings. The average absolute difference of two estimates decreased – and reliability increased – strongly with an increasing number of days analysed. An acceptable reliability of the interdaily stability estimate required more than 7 days of recording. It can be concluded that a valuable improvement in the reliability of actigraphic sleep estimates can be obtained by simply increasing the number of recording nights. The results support the importance of day‐to‐day variability in insomnia and dementia that has already been previously noted by others, and even suggest the presence of ’week‐to‐week’ variability. This variability may have been involved in the equivocal results of treatment studies in insomnia and dementia where outcome measures were based on a limited number of nights. Such studies could profit from extension of the recording duration to, e.g. 2 weeks, and from the inclusion of variability measures as measures of clinical interest.
Posturographic sleepiness monitoring
Authors: FORSMAN PIA , WALLIN ANDERS , TIETÄVÄINEN AINO , HÆGGSTRÖM EDWARD 
Published: August 2007

SummaryAlthough reduced sleep often underlies traffic and occupational accidents, convenient sleepiness testing is lacking. We show that posturographic balance testing addresses this issue, because balance testing predicts hours of wakefulness, which could facilitate sleepiness testing. Here, we equate balance scores from separate trials, blinded to the experimenter, with those recorded as a function of known and increasing time awake (i.e. during sustained wakefulness); we show, that the time awake in separate trials is posturographically measurable: positive predictive value 69%, sensitivity 56%, and specificity 96%. These results encourage further work developing posturographic sleepiness monitoring.
Prevalence of papilloedema in patients with sleep apnoea syndrome: a prospective study
Authors: PETER LAURE , JACOB MAUD , KROLAK‐SALMON PIERRE , PETITJEAN THIERRY , BASTUJI HÉLÈNE , GRANGE JEAN‐DANIEL , VIGHETTO ALLAIN 
Published: August 2007

SummaryThe association of papilloedema (PO) with respiratory diseases and especially obstructive sleep apnoea (OSA) syndrome has been emphasised in many reports. The pathophysiology could rely on the episodic increase of intracranial pressure related to apnoeic episodes during night sleep. Nevertheless, prevalence of papilloedema in patient with OSA syndrome remains unknown. As this information could improve diagnosis and therapeutic strategies, the aim of the present study was to investigate the prevalence of PO in an OSA syndrome population. From 95 successive, recently diagnosed OSA patients, 35 answered a questionnaire about visual symptoms and underwent fundoscopic examination. Visual symptoms suggestive of PO were present in 40% of the patients, but none had PO. As a conclusion, PO does not seem to be frequently associated with OSA syndrome and systematic screening of PO in these patients does not seem to be warranted. Nevertheless, patients with visual complaints evocative of papilloedema should have their eye fundus checked since the association between OSA and PO exists. Further studies, including more patients, might be useful to establish which patients are at particular risk for this complication.
Periodic leg movements during sleep and wakefulness in narcolepsy
Authors: DAUVILLIERS YVES , PENNESTRI MARIE‐HÉLÈNE , PETIT DOMINIQUE , DANG‐VU THANH , LAVIGNE GILLES , MONTPLAISIR JACQUES 
Published: August 2007

SummaryThe objectives of the study were to measure the prevalence of periodic leg movements during NREM and REM sleep (PLMS) and while awake (PLMW) and to assess the impact of PLMS on nocturnal sleep and daytime functioning in patients with narcolepsy. One hundred and sixty‐nine patients with narcolepsy and 116 normal controls matched for age and gender were included. Narcoleptics with high and low PLMS indices were compared to assess the impact of PLMS on sleep and Multiple Sleep Latency Test (MSLT) variables. More narcoleptics than controls had a PLMS index greater than 5 per hour of sleep (67% versus 37%) and an index greater than 10 (53% versus 21%). PLMS indices were higher both in NREM and REM sleep in narcoleptic patients, but the between‐group difference was greater for REM sleep. A significant increase of PLMS index was also found with aging in both narcoleptic patients and controls. PLMW indices were also significantly higher in narcoleptic patients. Patients with an elevated index of PLMS had a higher percentage of stage 1 sleep, a lower percentage of REM sleep, a lower REM efficiency and a shorter MSLT latency. The present study demonstrates a high frequency of PLMS and PLMW in narcolepsy, an association between the presence of PLMS and measures of REM sleep and daytime functioning disruption. These results suggest that PLMS represent an intrinsic feature of narcolepsy.
Daytime sympathetic hyperactivity in OSAS is related to excessive daytime sleepiness
Authors: DONADIO VINCENZO , LIGUORI ROCCO , VETRUGNO ROBERTO , CONTIN MANUELA , ELAM MIKAEL , WALLIN B. GUNNAR , KARLSSON TOMAS , BUGIARDINI ENRICO , BARUZZI AGOSTINO , MONTAGNA PASQUALE 
Published: August 2007

SummaryThe aim of this study was to investigate the relationships among sympathetic hyperactivity, excessive daytime sleepiness (EDS) and hypertension in obstructive sleep apnoea syndrome (OSAS). Ten newly diagnosed OSAS patients with untreated EDS and daytime hypertension underwent polysomnography (PSG) and daytime measurements of plasma noradrenaline (NA), ambulatory blood pressure (BP), muscle sympathetic nerve activity (MSNA) by microneurography and objective assessment of EDS before and during 6 months of compliance‐monitored continuous positive airway pressure (CPAP) treatment. One month after the start of CPAP, BP, MSNA and NA were significantly lowered, remaining lower than baseline also after 3 and 6 months of treatment. CPAP use caused a significant improvement of sleep structures, and reduced EDS. A statistical correlation analysis demonstrated that EDS was not correlated with sleep measures obtained from baseline PSG (% sleep stages, apnoea and arousal index, mean oxygen saturation value), whereas daytime sleepiness was significantly correlated with MSNA. Furthermore, MSNA and BP showed no correlation. Our data obtained from selected patients suggest that the mechanisms inducing EDS in OSAS are related to the degree of daytime sympathetic hyperactivity. Additionally, resting MSNA was unrelated to BP suggesting that factors other than adrenergic neural tone make a major contribution to OSAS‐related hypertension. The results obtained in this pilot study need, however, to be confirmed in a larger study involving more patients.
Pulsed radio‐frequency electromagnetic fields: dose‐dependent effects on sleep, the sleep EEG and cognitive performance
Authors: REGEL SABINE J. , TINGUELY GILBERTE , SCHUDERER JÜRGEN , ADAM MARTIN , KUSTER NIELS , LANDOLT HANS‐PETER , ACHERMANN PETER 
Published: August 2007

SummaryTo establish a dose–response relationship between the strength of electromagnetic fields (EMF) and previously reported effects on the brain, we investigated the influence of EMF exposure by varying the signal intensity in three experimental sessions. The head of 15 healthy male subjects was unilaterally exposed for 30 min prior to sleep to a pulse‐modulated EMF (GSM handset like signal) with a 10 g‐averaged peak spatial specific absorption rate of (1) 0.2 W kg–1, (2) 5 W kg–1, or (3) sham exposed in a double‐blind, crossover design. During exposure, subjects performed two series of three computerized cognitive tasks, each presented in a fixed order [simple reaction time task, two‐choice reaction time task (CRT), 1‐, 2‐, 3‐back task]. Immediately after exposure, night‐time sleep was polysomnographically recorded for 8 h. Sleep architecture was not affected by EMF exposure. Analysis of the sleep electroencephalogram (EEG) revealed a dose‐dependent increase of power in the spindle frequency range in non‐REM sleep. Reaction speed decelerated with increasing field intensity in the 1‐back task, while accuracy in the CRT and N‐back task were not affected in a dose‐dependent manner. In summary, this study reveals first indications of a dose–response relationship between EMF field intensity and its effects on brain physiology as demonstrated by changes in the sleep EEG and in cognitive performance.
Nocturnal sleep, daytime sleepiness, and napping among women with significant emotional/behavioral premenstrual symptoms
Authors: LAMARCHE LYNNE J. , DRIVER HELEN S. , WIEBE SABRINA , CRAWFORD LEAH , DE KONINCK JOSEPH M. 
Published: August 2007

SummaryThe objective of this study is to examine daytime sleepiness and alertness and nap characteristics among women with significant emotional/behavioral premenstrual symptoms, and to determine their relationship with nocturnal sleep. Participants spent one night during the follicular phase and two nights during the late‐luteal phase, one of which occurred after a 40 min opportunity to nap, sleeping in the laboratory. Subjective measures of sleepiness and alertness were completed during the afternoon of each recording. Setting took place at the sleep laboratory at the University of Ottawa. A total number of participants were 10 women with significant and nine women with minimal emotional/behavioral premenstrual symptoms (mean age 26 years). The results were compared with the follicular phase, both groups of women had less slow wave sleep and more stage 2 sleep at night, as well as a higher daytime and nocturnal mean and maximum temperature during the late‐luteal phase. Women with significant symptoms were sleepier and less alert during the late‐luteal phase and had a higher overall mean nocturnal temperature compared with women with minimal symptoms. No significant differences were found between the two groups on nap characteristics and nocturnal sleep characteristics. Results show that women with more severe premenstrual symptoms are sleepier during the late‐luteal phase than women with minimal symptoms. The increased daytime sleepiness seems to be unrelated to nocturnal sleep or nap characteristics.
Adverse childhood experiences associated with sleep in primary insomnia
Authors: BADER KLAUS , SCHÄFER VALÉRIE , SCHENKEL MAYA , NISSEN LUKAS , SCHWANDER JÜRG 
Published: August 2007

SummaryThe objectives were to explore the association between self‐reported adverse childhood experiences (ACE) and sleep in adults suffering from primary insomnia and to examine the impact of presleep stress on this relationship. Fifty‐nine patients with primary insomnia, aged 21–55 years, were administered the Childhood Trauma Questionnaire (CTQ) and then divided into two groups according to the achieved scores: with moderate/severe or low/no reports of ACE. The participants spent three consecutive nights in the sleep laboratory in order to record polysomnographic and actigraphic sleep parameters. A stress induction technique was administered by activating negative autobiographical memories immediately before sleep in the second or third night. Results show that 46% of the insomniac patients reported moderate to severe ACE. This group exhibited a significantly greater number of awakenings and more movement arousals compared to patients with low or no reports of ACE. Actigraphic data also indicated more disturbed sleep and increased nocturnal activity for the high‐ACE group. On the other hand, no specific group differences were found with regard to stress condition. The results support the assumption that it is possible to identify a subgroup among patients with primary insomnia who has experienced severe maltreatment in childhood and adolescence. This subgroup appears to differ in several sleep parameters, indicating a more disturbed sleep compared to primary insomniacs with low or no reports of ACE. With regard to sleep‐disturbing nightly patterns of arousal, parallels between individuals with high ACE and trauma victims as well as post‐traumatic stress disorder‐patients suggest themselves.
The recent spread of a vertically transmitted virus through populations of Drosophila melanogaster
Authors: CARPENTER JENNIFER A. , OBBARD DARREN J. , MASIDE XULIO , JIGGINS FRANCIS M. 
Published: August 2007

AbstractThe sigma virus is a vertically transmitted pathogen that commonly infects natural populations of Drosophila melanogaster. This virus is the only known host‐specific pathogen of D. melanogaster, and so offers a unique opportunity to study the genetics of Drosophila–viral interactions in a natural system. To elucidate the population genetic processes that operate in sigma virus populations, we collected D. melanogaster from 10 populations across three continents. We found that the sigma virus had a prevalence of 0–15% in these populations. Compared to other RNA viruses, we found that levels of viral genetic diversity are very low across Europe and North America. Based on laboratory measurements of the viral substitution rate, we estimate that most European and North American viral isolates shared a common ancestor approximately 200 years ago. We suggest two explanations for this: the first is that D. melanogaster has recently acquired the sigma virus; the second is that a single viral type has recently swept through D. melanogaster populations. Furthermore, in contrast to Drosophila populations, we find that the sigma viral populations are highly structured. This is surprising for a vertically transmitted pathogen that has a similar migration rate to its host. We suggest that the low structure in the viral populations can be explained by the smaller effective population size of the virus.
Macoma balthica in the White and Barents Seas: properties of a widespread marine hybrid swarm (Mollusca: Bivalvia)
Authors: STRELKOV PETR , NIKULA RAISA , VÄINÖLÄ RISTO 
Published: August 2007

AbstractA main molecular subdivision in the circumpolar Macoma balthica complex has been described between Atlantic and Pacific taxa. In NE Europe, the clams of the White and Barents Seas, however, show deviant genetic structures. Using allozyme and mitochondrial DNA data, we explore the hypothesis that these deviations result from hybridization between an Atlantic (M. b. rubra) and an invading Pacific (M. b. balthica) lineage. A practically pure Atlantic Macoma extends from France north to the Varanger Peninsula (NE Norway), whereas populations farther east have genetic compositions intermediate between true Atlantic and true Pacific. Admixture estimates range from 32 to 90% Pacific contribution, with a notable deviation in a nearly pure Atlantic outpost in the Mezen Bay (NE White Sea). The pattern of variation is not one of a simple collinear mixing however. Different characters exhibit different degrees of introgression, and the relative introgression varies regionally. Yet, there are practically no interlocus genotypic disequilibria between the diverged loci, which brings out the White Sea–Barents Sea M. balthica as the best‐documented marine animal hybrid swarms so far, arisen through amalgamation of genomes previously isolated since pre‐Pleistocene times. On top of the main admixture pattern, strong geographical structuring is also seen in characters unrelated to the principal systematic distinction. The persistence of the regional patterns indicates restricted gene flow at the present time, despite the high dispersal potential of the species. The causes of this structuring could be in a complex history of colonization events and features of local hydrography enhancing isolation and divergence of populations.