bluuebunny/crossref_metadata_2025_split huggingface dataset:
The increased prevalence of allergy and the hygiene hypothesis: missing immune deviation, reduced immune suppression, or both?
Authors: Romagnani Sergio 
Published: December 2004

SummaryAllergic atopic disorders, such as rhinitis, asthma, and atopic dermatitis, are the result of a systemic inflammatory reaction triggered by type 2 T helper (Th2) cell‐mediated immune responses against ‘innocuous’ antigens (allergens) of complex genetic and environmental origin. A number of epidemiological studies have suggested that the increase in the prevalence of allergic disorders that has occurred over the past few decades is attributable to a reduced microbial burden during childhood, as a consequence of Westernized lifestyle (the ‘hygiene hypothesis’). However, the mechanisms by which the reduced exposure of children to pathogenic and nonpathogenic microbes results in enhanced responses of Th2 cells are still controversial. The initial interpretation proposed a missing immune deviation of allergen‐specific responses from a Th2 to a type 1 Th (Th1) profile, as a result of the reduced production of interleukin‐12 and interferons by natural immunity cells which are stimulated by bacterial products via their Toll‐like receptors. More recently, the role of reduced activity of T regulatory cells has been emphasized. The epidemiological findings and the experimental evidence available so far suggest that both mechanisms may be involved. A better understanding of this question is important not only from a theoretical point of view, but also because of its therapeutic implications.
Divide and conquer: the importance of cell division in regulating B‐cell responses
Authors: Tangye Stuart G. , Hodgkin Philip D. 
Published: December 2004

SummaryProliferation is an essential characteristic of clonal selection and is required for the expansion of antigen reactive clones leading to the development of antibody of different isotypes and memory cells. New data for mouse and human B cells point to an important role for division in regulating isotype class and in optimizing development of protective immunity by the regulated entry of cells to the plasma cell lineage.
Foraging inequalities in large groups: quantifying depletion experienced by individuals in goose flocks
Authors: Rowcliffe J. Marcus , Pettifor Richard A. , Carbone Chris 
Published: December 2004

Summary

Inequalities between individuals represent a major force driving patterns of animal dispersion. Here we use a novel approach to the analysis of feeding competition in large groups, based on photographic sequences of barnacle goose flocks over time. The spatial distributions of individuals derived from these photos were used to describe how individual feeding performance may be affected by patch depletion caused by other members of the flock. This was assessed indirectly by estimating the variation in prior grazing time experienced by individuals.
The most successful foragers in a flock (i.e. those experiencing the least prior grazing time) are largely unaffected by depletion arising during the life span of the flock, while the least successful foragers experience very substantial depletion. Furthermore, for the less successful individuals, the average level of depletion increases continuously with both flock size and time spent in the flock.
Skew in depletion experienced could not be assessed accurately, although it is likely that there is moderate right skew, i.e. a few individuals do very badly, but more than half do better than the mean.
This study suggests that the degree of depletion experienced is related to position within the group, while previous studies of this system have shown that there is strong competition for the better positions. Dominance status is therefore likely to be a strong determinant of feeding performance. Subordinate individuals, being unable to obtain leading positions, may be forced to adopt alternative strategies to improve feeding performance, such as moving more frequently in order to maximize time in smaller or more recently formed groups.
Modelling the joint effects of predator and prey diversity on total prey biomass
Authors: Fox Jeremy W. 
Published: December 2004

Summary

Niche differentiation is widely thought to promote both coexistence of many species within a trophic level, and higher total biomass of those species. However, the joint effects of changes in diversity within multiple trophic levels are unknown. The potential for niche differences to promote high diversity and biomass within a trophic level may depend on the diversity and composition of adjacent trophic levels.
Using a simple mechanistic model, I examine the joint consequences of changes in diversity on two adjacent trophic levels (‘predators’ and ‘prey’) for the total biomass of prey. Niche differences among prey reflect a trade‐off between ability to compete for resources and ability to avoid/sustain predation. Niche differences among predators reflect differences in ability to consume different prey species.
Total prey biomass is a complex, joint function of prey and predator diversity. In particular, transgressive overyielding (when a diverse polyculture of prey outperforms any prey monoculture) can occur for some parameter values when a specialist predator mediates prey coexistence, and for a different set of parameter values when a specialist and a generalist predator together mediate prey coexistence, but is impossible when a generalist predator alone mediates prey coexistence.
Increased initial predator diversity tends to reduce total prey biomass even when predators cannot coexist, due to a ‘selection’ effect for the most effective predator. Predators coexist only in prey polycultures. Coexisting predators can, but do not necessarily, reduce total prey biomass to a lower level than could any predator alone.
The niche differences that permit coexistence strongly constrain the rank order of total prey biomass across all prey and predator combinations. Knowledge of the key trade‐offs that promote coexistence within food webs can allow powerful qualitative predictions of the effects of species loss on ecosystem‐level properties such as total biomass.
The role of competition in adaptive radiation: a field study on sequentially ovipositing host‐specific seed predators
Authors: Després Laurence , Cherif Mehdi 
Published: December 2004

SummaryWe propose an alternative model to the host‐shifting model of sympatric speciation in plant–insect systems. The role of competition in driving ecological adaptive radiation was evaluated in a seed predator exploiting a single host‐plant species. Sympatric speciation may occur through disruptive selection on oviposition timing if this shift decreases competition among larvae feeding on seeds.The globeflower flyChiastochetapresents a unique case of adaptive radiation, with at least six sister species co‐developing in fruits ofTrollius europaeus. These species all feed on seeds, and differ in their oviposition timing, one species ovipositing in 1‐day‐old flowers (early species), while all the other species sequentially oviposit throughout the flower life span (late species). We evaluated the impact of conspecific and heterospecific larvae on larval installation success, and on larval fresh mass and area, for early and late species, in natural conditions.None of the three larval traits measured was correlated with fruit size, and no fruit lost all seeds to predation, suggesting that seed availability was not a limiting factor for larval development.Our results show strong intraspecific competition among early larvae for larval installation, and among late larvae for larval mass. By contrast, larval competition between species was weak. These results are consistent with the hypothesis that shifts in oviposition promoted rapid radiation in globeflower flies by lowering competition among larvae.
Preferences for sugars and amino acids and their conditionality in a diverse nectar‐feeding ant community
Authors: Blüthgen Nico , Fiedler Konrad 
Published: December 2004

Summary

Feeding preferences of nectarivorous ants for sugars and amino acids were studied in an Australian tropical rain forest using artificial nectar solutions. Fifty‐one ant species were recorded feeding on the solutions.
Preferences among carbohydrates were principally concordant between ant species. In paired tests, sucrose was often preferred over fructose, glucose, maltose, melezitose, raffinose and xylose, respectively. Attractiveness of sucrose baits increased with concentration.
Many ant species preferred sugar solutions containing mixtures of amino acids over pure sugar solutions. However, preferences among seven pairs of single amino acids in sugar solutions differed substantially between ant species, including several cases where different ant species displayed significant opposite choices.
Ant selectivity between solutions was significantly reduced when different ant species co‐occurred on the same bait. Preferences for single amino acids were also reduced when colonies fed extensively on the same compound prior to the experiment for 2 days.
Our results indicate that both interspecific variability in gustatory preferences and conditional effects such as competition and colony requirements affect resource selection in multispecies communities. These processes may be crucial in niche partitioning of species‐rich nectarivore assemblages.
Individual access to preferred habitat affects fitness components in female roe deer Capreolus capreolus
Authors: Nilsen Erlend B. , Linnell John D. C. , Andersen Reidar 
Published: December 2004

Summary

Many studies have reported variation in life‐history traits and reproductive success within populations. One potential source for the reported variation is fine‐scale spatial variation in habitat quality.
In this study the effects of differences in home‐range quality on individual fitness were investigated in a roe deer population in an agricultural–woodland mosaic landscape in central Norway.
Compositional analysis revealed that woodland was the most preferred habitat: its availability was therefore used as an index of home‐range quality.
It was found that the quality of the does’ winter home‐range affected fawn production in the subsequent spring, as females with greatest availability of preferred habitat during winter produced the larger litters the subsequent spring.
Furthermore, the winter weights of the fawns seemed to be affected by home‐range quality in a complex way. First, home‐range quality in the prenatal winter seems to influence the birthdate and in turn the weight of the fawns in August. Also there was an immediate effect of the quality of the home‐range that the fawns occupied during the postnatal winter.
These results are not consistent with the ideal free distribution theory, suggesting that the mechanisms for roe deer spacing behaviour should be re‐examined.
Alien species and interspecific competition: effects of introduced eastern grey squirrels on red squirrel population dynamics
Authors: Gurnell John , Wauters Luc A. , Lurz Peter W. W. , Tosi Guido 
Published: December 2004

Summary

Throughout much of Britain, Ireland and north Italy, red squirrels (Sciurus vulgaris L.) have been replaced by alien grey squirrels (S. carolinensis Gmelin) introduced from North America. We have studied squirrels in two mixed woodlands in north Italy and two conifer forests in north England. In each country, one site was occupied by red squirrels and one site by both species.
We have previously considered interference competition and exploitation competition for food and space between red and grey squirrels and have showed that grey squirrels caused reduced body growth in juvenile and subadult red squirrels, and compete for tree seeds cached by adult red squirrels in spring. Here we report on the effects of grey squirrels on three fitness components in red squirrels that have consequence at the population level: fecundity, residency and recruitment.
Litter production peaked in the spring and summer, but fewer females bred in the summer with grey squirrels present. In addition, fewer individual red squirrel females produced two litters per year in the sites with grey squirrels. Moreover, red squirrel recruitment rate and, in the mixed broadleaf sites, red squirrel juvenile residency, decreased with increasing grey squirrel density.
Fecundity of individual female red squirrels was lower in red–grey than in red‐only sites because they had a lower body mass in sites with grey squirrels.
Overall, there was no significant effect of grey squirrels on residency of adult red squirrels or on population turnover rate. However, the presence of grey squirrels resulted in a reduction in red squirrel fitness which was evident by lower population summer breeding and a lower recruitment. Over time, this will result in a decline in population size and eventually population extinction.
Within‐sex density dependence and population dynamics of red squirrels Sciurus vulgaris
Authors: Wauters Luc A. , Matthysen Erik , Adriaensen Frank , Tosi Guido 
Published: December 2004

Summary

Social organization and dispersal of red squirrels (Sciurus vulgaris L.) differ between sexes, and intrasexual competition is intense. Therefore, we predicted that demographic parameters should be gender‐specific: that is density‐dependent factors will be more strongly related to density of the same sex than to density of the opposite sex. We studied the relative importance of within‐ and between‐sex density‐dependent factors and of density‐independent factors (habitat type, food abundance, winter temperature) on different demographic parameters, in two populations in northern Belgium.
Spring density of males was positively correlated with tree‐seed abundance in the previous year, but this was not the case for females. None of the population parameters we measured differed between habitats, indicating that the same density‐dependent and density‐independent mechanisms prevailed in coniferous and deciduous habitat.
Within each sex, we found several demographic parameters that were dependent on the densities of the same sex; however, none of these parameters was found to be dependent on the density of the opposite sex.
Reproductive rate increased with food abundance and decreased with female density. Adult survival of females decreased with female density in autumn–winter, while survival of adult males in spring–summer increased with the size of the previous year's seed crop.
Immigration rate of males was higher in spring than in autumn, and spring immigration increased with food abundance. Male recruitment rate, in both seasons, increased with food abundance, but was male density dependent. However, spring–summer loss rates also increased when food supplies were good, suggesting that despite high food availability, emigration of juvenile and subadult males increased when intrasexual competition was intense. Recruitment rate of females decreased with increasing female density. After a good seed crop, more subadult females dispersed, but their settlement success (recruitment) was lower at high female density.
Seed crop size positively affected red squirrel densities through increased reproduction, immigration and adult survival of males, but density‐dependent reproduction and within‐sex density‐dependent recruitment of locally born juveniles and dispersing subadults limit the fluctuations in numbers and regulate densities in winter–early spring, as well as in summer.
Connectivity and homogenisation of population sizes: an experimental approach in Lacerta vivipara
Authors: Lecomte Jane , Boudjemadi Katia , Sarrazin François , Cally Karine , Clobert Jean 
Published: December 2004

Summary

At regional scales, dispersal is known to prevent metapopulation extinction by buffering stochastic processes. Theory predicts that connectivity, through density‐dependent dispersal rates, should spatially homogenize population density and synchronize local population dynamics in the long term. However, empirical evidence for the effect of connectivity on synchrony and local population dynamics remains scarce.
We experimentally manipulated connectivity in order to investigate the homogenisation effect on population size. The experimental design consisted of 16 patches of common lizard populations (Lacerta vivipara), half of which were connected by dispersal. The design allowed us to identify candidates for dispersal in unconnected patches.
We found that population sizes became spatially more and more homogeneous with time in connected patches, whereas extinctions or demographic explosions were observed in unconnected patches. Juvenile dispersal was density‐dependent in connected patches but not in unconnected ones. These results suggest that the loss of connection modifies population functioning by influencing how dispersal is determined by local conditions.
Finally, population explosions in unconnected patches were followed by a sharp decrease in population size. So non‐extinct, unconnected populations did not stabilize. This could be due to over‐compensatory density dependence.
Population viability analysis models suggest that environmental stochasticity and catastrophic events, in addition to the density‐dependent process, are required to explain population size variation and extinction.
Peripheral parenteral nutrition in a case of chyle leak following neck dissection
Authors: Morris S. A. , Taylor S. J. 
Published: December 2004

AbstractChylothorax is an uncommon condition which is potentially life‐threatening if untreated. The following case study of a 75‐year‐old man with chyle leak following surgery shows how prompt dietetic action prevented further compromise in immune function and nutritional status. Dietetic recommendation to minimize enteral intake rapidly stopped chyle flow and promoted wound closure. Peripheral parenteral nutrition (PPN) was administered in order to prevent malnutrition. There is limited literature available for evidence of best practice for cases of chyle leakage, however, this particular case demonstrates PPN should be considered despite the potential risks.
The long‐term effect of dietary advice on the diet of men with angina: the diet and angina randomized trial
Authors: Ness A. R. , Ashfield‐Watt P. A. L. , Whiting J. M. , Smith G. D. , Hughes J. , Burr M. L. 
Published: December 2004

AbstractIntroduction  The long‐term effects on diet of dietary advice to eat fruit and vegetables or fatty fish are not well described.Materials and methods  From 1990 to 1996 3114 men aged 37–70 with treated angina were recruited from general practices in South Wales. A dietitian randomly allocated the eligible men to receive advice to eat more fruit and vegetables, or advice to eat more fatty fish, or both these types of advice or neither. In 2000, a brief self‐completion questionnaire was sent to a sample of 1191 of the men known to be alive at the end of March 1999.Results  The questionnaire was returned by 944 of the 1036 men alive at the time the questionnaire was sent. Those given fish advice were consuming more fatty fish but the difference was modest 21.9 g day−1 vs. 14.0 g day−1 (P < 0.01). The differences in fruit and vegetables intake between those given fruit advice and those not given fruit advice were small 373.2 g day−1 vs. 351.7 g day−1 (P = 0.05).Discussion  Men of this age group may be particularly resistant to fruit and vegetables advice; population‐based interventions or interventions targeted at women might be more effective.
Current approaches to obesity management in UK Primary Care: the Counterweight Programme
Authors:   The Counterweight Project Team
Published: December 2004

AbstractBackground/Aims  Primary care is expected to develop strategies to manage obese patients as part of coronary heart disease and diabetes national service frameworks. Little is known about current management practices for obesity in this setting. The aim of this study is to examine current approaches to obesity management in UK primary care and to identify potential gaps in care.Method  A total of 141 general practitioners (GPs) and 66 practice nurses (PNs) from 40 primary care practices participated in structured interviews to examine clinician self‐reported approaches to obesity management. Medical records were also reviewed for 100 randomly selected obese patients from each practice [body mass index (BMI) ≥30 kg m−2, n = 4000] to review rates of diet counselling, dietetic or obesity centre referrals, and use of anti‐obesity medication. Computerized medical records for the total practice population (n = 206 341, 18–75 years) were searched to examine the proportion of patients with a weight/BMI ever recorded.Results  Eighty‐three per cent of GPs and 97% of PNs reported that they would raise weight as an issue with obese patients (P < 0.01). Few GPs (15%) reported spending up to 10 min in a consultation discussing weight‐related issues, compared with PNs (76%; P < 0.001). Over 18 months, practice‐based diet counselling (20%), dietetic (4%) and obesity centre (1%) referrals, and any anti‐obesity medication (2%) were recorded. BMI was recorded for 64.2% of patients and apparent prevalence of obesity was less than expected.Conclusion  Obesity is under‐recognized in primary care even in these 40 practices with an interest in weight management. Weight management appears to be based on brief opportunistic intervention undertaken mainly by PNs. While clinicians report the use of external sources of support, few patients are referred, with practice‐based counselling being the most common intervention.
Old patients with hypertension. A 25‐year observational study of a geographically defined population (Dalby), aged 67 years at entry
Authors: Lidfeldt J. , Lanke J. , Sundquist J. , Lindholm L. H. 
Published: December 2004

Abstract  Lidfeldt J, Lanke J, Sundquist J, Lindholm LH (Lund University, Lund, Sweden). Old patients with hypertension – a 25‐year observational study of a geographically defined population (Dalby), aged 67 years at entry. J Intern Med 1998; 244: 469–78. Objectives.  To evaluate the impact of hypertension and other risk factors on mortality, in particular cardiovascular mortality, in a geographically defined population of elderly subjects. Design.  An observational 25‐year study of a total population. Setting.  The local health centre in the village of Dalby in southern Sweden. Subjects.  All men and women born in 1902 or 1903, living in Dalby, were, at the age of 67, invited for medical and psychological examinations. The population comprised 188 subjects (109 men and 79 women); 156 (83%) of them took part in the first medical examination. Blood pressure, heart rate, weight and height were measured and laboratory tests performed at entry. Blood pressures were thereafter recorded six times, and this report is based on a 25‐year follow‐up period ending in October 1994. Main outcome measures.  Survival analyses were performed, based on definition of underlying causes of death, divided into all‐cause and cardiovascular. Results.  At entry, females had higher blood pressure than males, both at baseline and during the first 16 years of the study, regardless of whether they were hypertensives or not. Most men smoked but only a few women. At the end of the follow‐up of the present study in 1994, 138 out of 156 (88%) subjects had died and only 18 (12%) remained alive; 78 (57%) had died of a cardiovascular disease. In men, a diagnosis of hypertension as well as increased blood pressure at entry was associated with increased mortality. In women this was the case for blood pressure and risk of cardiovascular mortality. In men, both systolic and diastolic blood pressures during the study were significant risk factors for death, whereas in women this was not the case. Conclusions.  Elderly male hypertensives ran an increased mortality risk even though they were treated according to the then current guidelines; female hypertensives seemed to run the same risk of dying as normotensive females.