bluuebunny/crossref_metadata_2025 huggingface dataset:
Importance of the predator's ecological neighborhood in modeling predation on migrating prey
Authors: DeAngelis Donald L. , Petersen James H.
Published: December 2004

Most mathematical descriptions of predator‐prey interactions fail to take into account the spatio‐temporal structures of the populations, which can lead to errors or misinterpretations. For example, a compact pulse of prey migrating through a field of quasi‐stationary predators may not be well described by standard predator‐prey models, because the predators and prey are unlikely to be well mixed; that is, the prey may be exposed to only a fraction of the predator population at a time. This underscores the importance of properly accounting for the ecological neighborhood, or effective feeding range, of predators in models. We illustrate this situation with a series of models of salmon smolts migrating through a reservoir arrayed with predators. The reservoir is divided into a number of longitudinal compartments or spatial cells, the length of each cell representing the upstream‐downstream range over which predators can forage. In this series of models a 100‐km‐long reservoir is divided, successively into 2, 5, 10, 25, 50, 100, 200, and 400 cells, with respective cell lengths of 50, 20, 10, 4, 2, 1, 0.5, and 0.25 km. We used a detailed individual‐based simulation model at first, but to ensure robustness of results we supplemented this with a simple analytic model. Both models showed sharp differences in the predicted mortality to a compact pulse of smolt prey moving through the reservoir, depending on the number of spatial cells in the model. In particular, models with fewer than about 10 cells vastly overpredicted the amount of mortality due to predators with activity ranges of not more than a few kilometers. These results corroborate recent theoretical and simulation studies on the importance of spatial scale and behavior in modeling predator‐prey dynamics.
Social flexibility in a primitively social allodapine bee (Hymenoptera: Apidae): results of a translocation experiment
Authors: Cronin Adam L.
Published: December 2004

Many species of social animals are known to exhibit intraspecific variation in social traits between different populations. In the social insects, geographically separate populations may show wide‐ranging forms of social behaviour, presumably because of variation in environmental parameters such as climate. For example, several bee species are known to exhibit eusocial or solitary behaviour depending on the latitude or altitude of the population. However, there is little or no empirical evidence to determine if this variation is a result of behavioural plasticity or long‐term adaptation to local conditions, both of which have implications for the evolution of sociality. In this study, colonies of the allodapine bees Exoneura robusta and E. nigrescens were translocated between a montane and heathland habitat in southern Australia to assess the effect of habitat change on social behaviour. Results indicate that brood development in translocated colonies of both species differed from control colonies, leading to opportunities for different forms of social behaviour. However, there was also a high degree of variation within each habitat, suggesting an influence of both within and between habitat factors.
Influence of herbivory and abiotic factors on the distribution of tall forbs along a productivity gradient: a transplantation experiment
Authors: Olofsson Johan
Published: December 2004

In arctic‐alpine areas tall herb vegetation is restricted to sites with high productivity. At higher elevation, low prostate forbs and narrow‐leaved graminoids dominate the vegetation in sites with a protecting snow cover during winter. In this study, I test whether herbivory or abiotic factors prevent tall forbs from growing at higher altitudes. Vegetation blocks from a tall herb meadow were transplanted to herbivore exclosures and open plots in a low‐productive snowbed and a productive tall herb meadow. The tall forbs performed equally well in the exclosures on the low‐productive snowbed as in the tall herb meadow, but decreased in the open plots on the low‐productive snowbed. Thus, even if abiotic factors are ultimately causing many of the vegetation patterns observed in arctic‐alpine plant communities, herbivory appears to be the main proximate factor responsible for the decreasing abundance of tall forbs along gradients of decreasing productivity in arctic‐alpine areas.
Larval gregariousness and neonate establishment of the eucalypt‐feeding beetle Chrysophtharta agricola (Coleoptera: Chrysomelidae: Paropsini)
Authors: Nahrung Helen F. , Dunstan Piers K. , Allen Geoff R.
Published: December 2004

The selective advantage offered to individuals living within groups may relate to natural enemy defence, but in leaf feeding insects may also relate to overcoming plant defences, especially with respect to feeding establishment. We conducted a series of experiments focusing on neonate larval survival, examining the effect of group size and leaf age on the survival of a eucalypt‐feeding beetle, Chrysophtharta agricola, which formed groups of up to 43 larvae on the foliage of Eucalyptus nitens in the field. In the laboratory, in the absence of natural enemies, we found that initial density, leaf age and damage to the leaf margin significantly affected larval survival. Survival of solitary first‐instar larvae on young foliage was around 80% whereas on older foliage it was around 11%. Prior damage to the leaf margin significantly increased survival on older leaves to around 61%. Initial larval density also affected survival, although mortality was always significantly higher on older leaves. On older leaves the larval group size above which mortality increased no further was over two‐fold that on young leaves. Observations of group feeding behaviour at each instar showed that the majority of larvae (75.7%) were aligned facing away from the feeding site and that only around 7.5%, or just 1–2 larvae per group, fed at any one time. Feeding larvae chewed the leaf edge by straddling the leaf margin. Measurements of leaf margins showed that older leaves had significantly thicker leaf margins and ‘thickness’ ratios (leaf margin to leaf lamina proper). In the field, approximately 85% of all larvae occurred on the first two expanded leaf pairs, and larval mortality was highest between eclosion and establishment of the first instar. However, beetles apparently did not adjust clutch size according to leaf age.
The evolution of egg size in socially polyandrous shorebirds
Authors: Liker A. , Reynolds J. D. , Székely T.
Published: December 2004

In classical and multi‐clutch polyandry, females lay multiple clutches during a breeding season for more than one mate. The production of multiple clutches may be energetically demanding. We used comparative analyses to investigate three possible ways of reducing such egg‐laying costs in polyandrous shorebirds: (1) reduction in egg size, (2) reduction in clutch size, and (3) evolutionary increase in female size. Paired comparisons of polyandrous and non‐polyandrous taxa showed that females of polyandrous shorebirds lay smaller eggs than females of closely related monogamous and polygynous species. Directional analyses corroborated this result by indicating a significant decrease in egg size after phylogenetically independent origins of polyandry. The comparative analyses uniformly rejected the two alternatives, i.e. neither clutch size nor female size is related to social mating pattern. We also tested and rejected three alternative explanations for reduced egg size in polyandrous taxa. First, we found no evidence that polyandrous females have evolved smaller egg sizes in response to selection to match smaller size of males, which provide the parental care in these species. Second, reduction in egg size was not related to longer breeding seasons (and hence more opportunity for re‐nesting). Third, reduced egg sizes were also not related to rates of clutch predation (another potential correlate of multiple clutch production). Our results are thus consistent with the hypothesis that selection for reducing laying costs explains small egg size in socially polyandrous shorebirds.
The effect of intra‐specific competition on seedlings of sexual and apomictic Taraxacum officinale
Authors: De Kovel Carolien G. F. , De Jong Gerdien
Published: December 2004

Because of their higher evolvability, sexuals may have an advantage relative to asexual organisms in a competitive environment with many biotic interactions. We tested this idea using sexual and apomictic Taraxacum, dandelions. Taraxacum seedlings were grown without competition and in different competing combinations in a greenhouse. Apomicts had more and longer leaves than sexuals, but the same dry weight at harvest as sexuals. Competition reduced growth to the same extent in both apomicts and sexuals. Therefore, we conclude that sexual dandelions are no superior competitors relative to apomicts. In Taraxacum, new apomictic lineages spin off from the sexual population with some unknown frequency. This may enable the apomictic community to keep up with the sexual population.
Clone‐specific response of Festuca rubra to natural variation in biomass and species composition of neighbours
Authors: Herben Tomáš , Krahulec František , Hadincová Věra , Pecháčková Sylvie
Published: December 2004

A long‐term implant experiment with four clones of Festuca rubra was performed to identify fine‐scale spatial variation in a competitive environment within a grassland sward of natural composition and density variation. Total above‐ground biomass and shoot counts of all species were recorded in 10×10 cm neighbourhoods of each implant, and their effect on the growth response of the implant was tested. Two types of response were recorded: (1) shoot sizes and vertical shoot growth dynamics, and (2) horizontal space encroachment by means of new shoot natality, mortality and their mode of formation (intravaginal or extravaginal). The vertical growth of individual shoots showed the strongest response to neighbourhood composition; it responded to the overall aboveground biomass of the neighbours, but not to their species composition. The responses in parameters of horizontal growth of individuals (natality, mortality, proportion of extravaginal shoots) were much weaker and not consistent over the observation period; however, both total biomass of the neighbours and species composition affected the response of the target plants.  The overall response was rather weak in spite of a tenfold variation in neighbouring density and a thirtyfold variation in neighbouring biomass. This indicates that the response to this variation is rather flat under field conditions, either due to high overall values of density or due to interactions with below‐ground processes. Consequently, though the plant is capable of remarkable plastic responses in both vertical growth and morphogenetic change, under field conditions this capacity for plastic response is expressed only to a limited degree.
Mate finding, dispersal distances and population growth in invading species: a spatially explicit model
Authors: South A. B. , Kenward R. E.
Published: December 2004

The expansion of populations into new areas is dependent upon dispersal distances and the ability of colonists to find mates. These factors interact through the spatial distribution of individuals. We develop a mechanistic, spatially explicit model to investigate the interaction between dispersal distances and mate finding in expanding populations. At high dispersal distances and low mate finding abilities, population growth was constrained by the inverse density dependent inability of adults to find mates (an Allee effect). In contrast, at low dispersal distances and high mate finding abilities, growth was constrained by the density dependent inability of dispersers to find vacant territories. Population growth was highest in between these extremes. We suggest that these spatial interactions play an important role in the expansion of populations into new areas and that this methodology provides a useful tool for investigating them.
Modelling the population consequences of age‐ and sex‐related differences in winter mortality in the oystercatcher, Haematopus ostralegus
Authors: Durell S. E. A. Le V. dit , Goss‐Custard J. D. , Clarke R. T.
Published: December 2004

A modelling approach is used to explore the effect of age and sex differences in oystercatcher (Haematopus ostralegus) winter mortality on population size, population structure and the population response to habitat loss or change. Increasing the mortality of first and second year birds reduced population size, but had very little effect on the proportion of the population that were adults. Increasing female mortality reduced population size and resulted in a male‐biased population. A sex bias amongst birds of breeding age meant that there were fewer potential breeding pairs for a given population size, reducing the size of the breeding population and the breeding output. Increasing the mortality of one sex relative to the other reduced population size, even when mean adult mortality rates remained unchanged. Increasing the strength of density‐dependent mortality in young birds caused a greater reduction in population size as habitat was lost. Increasing the strength of female density‐dependent mortality had the same effect, even though male density‐dependent mortality had been correspondingly reduced. Increasing density‐independent or density‐dependent winter mortality in one sex relative to another also exaggerated the disproportional effect of winter habitat loss on separate breeding subpopulations using the same overwintering area. These results suggest that any study of population dynamics should be aware of both age and sex differences in mortality. Conservationists should be particularly aware of any age or sex differences in diet or habitat use that may result in a differential response to environmental change.
Food availability dictates the timing of parturition in insectivorous mouse‐eared bats
Authors: Arlettaz Raphaël , Christe Philippe , Lugon Alain , Perrin Nicolas , Vogel Peter
Published: December 2004

Which of these two confounding factors, weather or food availability – that largely correlate and interact – controls the timing of parturition in insectivorous bats? To answer this question, we took advantage of a predator‐prey system that offers a unique opportunity to perform natural experiments. The phenology of reproduction of two sibling bat species that inhabit the same colonial roosts, but exploit different feeding niches, was investigated. Myotis myotis feeds mainly on carabid beetles, a food source available from the end of hibernation onwards, whereas bush crickets, the main prey of M. blythii, are not available early in the season due to their successive instars; cockchafers are actually the sole possible alternative prey for M. blythii at that time of the year, but they occur every third year only, independently of local weather conditions. By comparing the species responses to the presence/absence of cockchafers, we could test the hypothesis that food availability, rather than climate, influences the timing of bat parturition. Our data show that M. blythii gave birth, on average, 10 d later than M. myotis in years without cockchafers, whilst parturition (1) was synchronous during cockchafer years, and (2) did not show much among‐year time variation in M. myotis. This suggests that food availability is the chief factor regulating the timing of parturition in mouse‐eared bats.
Biodiversity effects of elevated CO2 in species‐rich model communities from the semi‐arid Negev of Israel
Authors: Grünzweig José M. , Körner Christian
Published: December 2004

Species‐specific responses to atmospheric CO2 enrichment may affect biodiversity, which in turn may alter ecosystem functioning. Here we have explored biodiversity effects in model assemblages of semi‐arid grassland of the northern Negev, Israel, at 280 ppm (pre‐industrial era), 440 ppm (early 21st century) and 600 ppm CO2 (mid to late 21st century). Thirty‐two mostly annual species were grown together in large containers (ca 400 kg each) on native soil and under a dynamic simulation of the Negev winter climate. CO2 enrichment increased concentrations of total non‐structural carbohydrates and C/N ratios, and reduced specific leaf area and nitrogen concentrations in leaves of all species. In contrast to these uniform CO2 effects on leaf quality, biomass and reproductive output remained unchanged in most species, and varied greatly among the few responsive ones (−80 to +145%). Biomass was significantly increased at elevated CO2 in Onobrychis crista‐galli (one of the six legume species) and was reduced in Biscutella didyma (Brassicaceae). Seed yield increased in three out of six legumes and in the root hemiparasite Parentucellia flaviflora, and decreased in the grass Aegilops peregrina. Fruit dry matter tended to be reduced in two Brassicaceae. Onobrychis, the largest and most responsive species present, was the most ‘mesic’ legume, and might have profited most from the higher soil moisture induced by CO2 enrichment. The significant CO2 response of only 5–6 out of 32 species, in particular their altered seed yield, suggests a potential shift in biodiversity. In a future CO2‐enriched atmosphere, ‘mesic’ legumes and root hemiparasites might be favored, while some Brassicaceae and grasses might decline. As indicated by significant 280‐ vs 440‐ppm differences, reductions in leaf nitrogen concentration of grasses and legumes are likely to be under way right now, and may negatively affect grazers. Altered seed yields were more pronounced between 440 and 600 ppm, suggesting that these changes could intensify as the atmospheric CO2 concentration continues to rise.
Density‐dependent dispersal in host‐parasitoid assemblages
Authors: French David R. , Travis Justin M. J.
Published: December 2004

Most spatial population models assume constant rates of dispersal. However, in a given community, dispersal may not only depend on the density of conspecifics, i.e. density‐dependent dispersal, but also on the density of other species, a phenomenon we term ‘community‐dependent dispersal’. We co‐vary the densities of both the beetle host Callosobruchus chinensis and its parasitoid wasp, Anisopteromalus calandrae, in a laboratory study and record the proportions of each species that disperse within a two‐hour period. The parasitoid in these systems exhibits community‐dependent dispersal – dispersing more frequently when parasitoid density is high and larval host density is low. This supported our prediction that individuals should disperse according to competition for available resources. However, in this study the host's dispersal was independent of density. We suggest that this may be due to less intense selection acting on host dispersal strategies than on the parasitoid. We consider some possible consequences of community‐dependent dispersal for a number of spatial population processes. A well‐known host‐parasitoid metapopulation model is expanded so that it includes a greater range of dispersal functions. When the model is parameterised with the parasitoid community‐dependent dispersal function observed in the empirical study, similar population dynamics are obtained as when fixed‐rate dispersal functions are applied. The importance of dispersal functions for invasions of both competitive and host‐parasitoid systems is also considered. The model results demonstrate that understanding how individuals disperse in response to different species’ population densities is important in determining the rate of spread of an invasion. We suggest that more empirical studies are needed to establish what determines dispersal rate and distance in a range of species, combined with theoretical studies investigating the role of the dispersal function in determining spatial population processes.
Dangerous liaisons: the ecology of private interest and common good
Authors: Van Baalen Minus , Jansen Vincent A. A.
Published: December 2004

Many ecological interactions that are called mutualistic are in fact mixtures of antagonistic and mutualistic aspects. For example, plasmids exploit their bacterial hosts but also protect them against external threats. In this study, we analyse the conditions for the evolution of what we call ‘dangerous liaisons’: interactions combining mutualistic and antagonistic aspects. Starting point of our analysis is a model that was proposed as early as 1934. In this model, partners have to form a complex (either temporary or long lasting) in order to interact. Using this model framework we then set out to define and tease apart private interests of the interacting partners from their common good. This dichotomy provides a unifying perspective to classify ecological interactions. We discuss some examples to illustrate how the outcome of the interaction may depend on densities or on other contextual variables. Finally, we note that having a common good is not a necessary condition for partners to have aligned interests. In a dangerous liaison partners may have interest to cooperate even when this does not bolster the common good.
Correlation between male size and territory quality: consequence of male competition or predation susceptibility?
Authors: Candolin Ulrika , Voigt Heinz‐Rudolf
Published: December 2004

Territory characteristics correlate with male characteristics in several species. This can result from male competition for the best territories, or from males varying in their ability to pay other costs of territoriality, such as predation risk costs. In a population of threespine sticklebacks, Gasterosteus aculeatus, we found the biggest males to defend the biggest territories with a low structural complexity and a high female encounter rate. By experimentally manipulating competition intensity and habitat structure, we show that both male competition and predation exposure influenced the distribution of territories among males. Males increased the size of their territory when a neighbouring male was removed, whereas they reduced their territory when habitat complexity and cover from predators were reduced, with large males reducing their territory size less than smaller males. This suggests that large males occupy large, open territories both because of their superior competitive ability and because of their either lower predation susceptibility or higher risk‐taking. Large, open territories were beneficial in mate attraction and male competition and predation exposure therefore biased mating opportunities towards large males. This suggests that cost of territoriality to males may reduce mate choice costs to females by securing that large males are encountered more often than small males, and by providing an additional cue, territory quality, which indicates which males are worth inspecting.
Analyzing the functional type concept in arctic plants using a dynamic vegetation model
Authors: Epstein Howard E. , Chapin III F. Stuart , Walker Marilyn D. , Starfield Anthony M.
Published: December 2004

Grouping organisms into categories based on common traits has been a tool of ecological scientists for some time now. Defining groups of species, examples being life forms and functional types, is an operational procedure, conducted to answer a particular question. This becomes rather practical when performing analyses at coarse spatial scales, given data limitations and the potential for species redundancy. However, the implications of aggregating organisms for modeling purposes are still unclear. Does averaging the traits of several species into a functional type sufficiently represent the dynamics of the individual components? How much variability is lost when we aggregate species into groups? In an attempt to address these questions, we examined how the level of vegetation aggregation affected a variety of ecosystem properties using a regional‐scale model of arctic tundra ecosystems (ArcVeg).  We used four levels of aggregation: species (15 dominant ones), functional types (7), life forms (4) and vegetation type (1), in addition to two methods of aggregation (simple vs weighted means of plant parameter values). We found that the level of aggregation consistently affected community composition, total community biomass and ecosystem net primary production (NPP). Neither simple means nor weighted means of aggregated parameter values adequately captured the ecosystem properties simulated at lower levels of aggregation. Aggregation of vegetation (i.e. reduced parameter variability) using simple means underestimated total biomass, whereas aggregation using weighted means overestimated total biomass. Aggregation led to increases in NPP with both methods. These findings suggest that aggregating vegetation, particularly to levels less detailed than plant functional types, will have important implications for regional‐scale modeling of vegetation dynamics and carbon cycling.
Behavioural responses to changing landscapes: flock structure and anti‐predator strategies of tits wintering in fragmented forests
Authors: Tellería José Luis , Virgós Emilio , Carbonell Roberto , Pérez‐Tris Javier , Santos Tomás
Published: December 2004

We analysed the effects of forest fragmentation on the flock structure of insectivorous forest passerines (Parus, Aegithalos, Certhia, Regulus, etc.), and on the anti‐predator behaviour and energy management of blue tits in these flocks. We surveyed flocks in Central Spain during two winters. Flocks in fragments comprised fewer individuals and species than flocks in unfragmented forests. The most abundant species in forest flocks (blue tit, Parus caeruleus, and firecrest, Regulus ignicapillus) were also the most abundant in fragments, while the rarest species in the area never occurred in small woodlots. We investigated how fragmentation and related changes in flock structure affect anti‐predator behaviour of blue tits, a widely distributed species in the area. In fragments but not in forests, blue tits increased scanning rates with decreasing flock size. Vigilance was relaxed when great tits, Parus major, were abundant as flock mates, suggesting that the absence of this dominant species in fragments could intensify anti‐predator behaviour of blue tits. Blue tits enhanced anti‐predator behaviour in the second winter parallel to an increase in the abundance of raptors. This behavioural change was stronger in fragments, where blue tits foraged deeper in the canopy and increased scanning and hopping rates. Under increased predation risk, birds are expected to reduce body mass to improve predator avoidance. On average, blue tits weighed similar in fragments and forests the second winter. However, they accumulated fat along the day in fragments only, and adjusted body mass to body size more closely in that habitat type. This suggests that blue tits perceived fragments as unpredictable habitats where fattening would help avoid starvation, but also as dangerous sites where overweight would further increase the risk of predation. In summary, our results support that fragmentation affects individual behaviour of blue tits, and show the potential of behavioural approaches to unravel how different species face the advancing fragmentation of their habitats.
Diet‐dependent body morphology and ontogenetic reaction norms in Eurasian perch
Authors: Hjelm Joakim , Svanbäck Richard , Byström Pär , Persson Lennart , Wahlström Eva
Published: December 2004

Individual morphology and performance are directly or indirectly under the influence of variation in resource levels. To study the effects of different resource conditions and their effects on morphology and ontogenetic reaction norms in young‐of‐the‐year (YOY) perch (Perca fluviatilis), we used three different approaches. First, we examined the morphological trajectories over early ontogeny in relation to lake‐specific resources in a field study. Second, one lake that lacked perch recruitment was stocked with perch eggs from a control lake in a whole‐lake experiment to study ontogenetic reaction norms. Third, we compared the development of YOY perch in the three lakes that mainly inhabited the littoral zone with YOY perch experimentally confined to enclosures in the pelagic zone of the lakes.  Overall body morphology of the YOY perch changed both as a function of size and as a function of diet. As perch increased in size they developed a deeper body morphology corresponding to an increased proportion of benthic macroinvertebrates in their diet. In pelagic enclosures where perch were constrained to feed mainly on zooplankton they had a more fusiform body morphology than perch in the lakes that fed on a mixture of zooplankton and macroinvertebrates. Similarly, the ontogenetic reaction norm of perch was related to the diet and lake‐specific zooplankton levels in the whole‐lake experiment.  In the pelagic enclosures, perch with high growth rates had a more fusiform body morphology than slow‐growing perch, whereas the opposite was found in the lakes, where perch included more macroinvertebrates in their diets. Perch in lakes with a higher proportion of macroinvertebrates in the diet also had deeper body morphology. The opposite morphology – growth rate relationship found between perch in the pelagic versus those using the whole lake suggest a morphological trade‐off between foraging on zooplankton and foraging on macroinvertebrates. Our results suggest that YOY perch show different ontogenetic reaction norms as a function of lake‐specific resource levels, which may allow YOY recruitment to later stages. Our results further suggest that diet‐related changes in morphology are a rapid process.
Relationships between ecological interaction modifications and diffuse coevolution: similarities, differences, and causal links
Authors: Inouye Brian , Stinchcombe John R.
Published: December 2004

A major empirical approach in community ecology is to describe the dynamics of a community by examining small subsets of species. Unfortunately, interaction modifications, which cause pair‐wise interaction coefficients to depend on the presence or absence of additional species, can make it difficult to predict the overall dynamics of species within a community from experiments with pairs of species. In a similar fashion, one of the major approaches in evolutionary ecology has been to describe the likely evolutionary dynamics of a single species by focusing on the selection imposed by a limited number of other species within the community. However, recent work on diffuse coevolution indicates that selection pressures due to one species can change in the presence of other species. The magnitude of the difficulty that interaction modifications and diffuse coevolution present for predicting ecological and evolutionary dynamics is an unresolved question. Here we outline the similarities and differences between the two topics, discuss experimental and statistical approaches to studying them, and make predictions about when ecological interaction modifications are likely to cause diffuse coevolution. Since the currencies for interaction modifications are usually fitness components such as growth, fecundity, or survival, is it likely that these will translate into corresponding differences in the relative fitness of individuals or genotypes, and thus in general these two phenomena will occur together. We argue that community ecologists and evolutionary ecologists will both benefit from experiments that test for the effects of interaction modifications, and that studies of the mechanisms driving interaction modifications and diffuse coevolution (e.g., changes in behavior, nonlinear effects on shared resources, genetic covariances) will aid our progress in understanding the ecological and evolutionary dynamics of communities.
Nitric oxide and tissue destruction
Authors: Kendall HK , Marshall RI , Bartold PM
Published: December 2004

Nitric oxide (NO) is a free radical which has complex roles in both health and disease. It is now recognized that NO is essential for a vast spectrum of intracellular and extracellular events in a wide variety of tissues. NO has also been implicated in the pathogenesis of numerous inflammatory and autoimmune diseases. In this review we consider the roles of NO generally and in particular the implications for periodontal diseases.
Adjunctive use of chlorhexidine in oral candidoses: a review
Authors: Ellepola ANB , Samaranayake LP
Published: December 2004

Oral candidosis is by far the commonest human fungal infection and manifests in a variety of clinical guises. The main reason for its high incidence appears to be the multiplicity of predisposing factors, which facilitate the conversion of oral commensal Candida to a parasitic existence. Despite the availability of a number of effective antimycotics for the treatment of oral candidoses, failure of therapy is not uncommon owing to the unique environment of the oral cavity where the flushing effect of saliva and the cleansing action of the oral musculature tend to reduce the drug concentration to sub‐therapeutic levels. For these and other reasons chlorhexidine is widely prescribed in dentistry both as an antiseptic mouthwash and a denture disinfectant in order to supplement other antifungals. Chlorhexidine has a broad spectrum of antimicrobial activity including Candida albicans and other common non‐albicans yeast species. In this review we outline the utility of chlorhexidine as an adjunct to conventional antimycotic therapy in the management of oral Candida infections.
Tobacco usage in relation to the anatomical site of oral leukoplakia
Authors: Schepman KP , Bezemer PD , Van Der Meij EH , Smeele LE , Van Der Waal I
Published: December 2004

OBJECTIVE: Tobacco usage is the most important known aetiological factor in the development of oral leukoplakia. The purpose of this study was to investigate the possible relation of tobacco usage to the anatomical site of the leukoplakia.

SUBJECTS AND METHODS: Clinical data regarding tobacco usage and localisation of leukoplakia obtained from 166 patients with oral leukoplakia.

RESULTS: Leukoplakias in the floor of mouth appeared to be statistically significantly more often present in smokers than in non‐smokers, compared to all other oral sites (P < 0.001; OR = 8.47 and 18.13 for men and women, respectively). On the contrary, leukoplakias on the borders of the tongue were statistically significantly more common among non‐smokers, than smokers, compared to all other oral sites (P < 0.001; OR = 0.22 and 0.12 for men and women, respectively).

CONCLUSION: The present study suggests that the influence of tobacco on the development of leukoplakia varies by anatomical site.
A comparison of salivary gland hypofunction in primary and secondary Sjögren's syndrome
Authors: Dawson LJ , Holt DJ , Higham SM , Longman LP , Field EA
Published: December 2004

OBJECTIVE: A commonly held view by clinicians is that the salivary gland hypofunction associated with primary Sjögren's syndrome (SS‐1) is more severe than that associated with secondary Sjögren's syndrome (SS‐2). This study aimed to determine if this view could be substantiated, when applied to a large sample group.

METHOD: Unstimulated and paraffin wax‐stimulated whole salivary flow rates were retrospectively compared for age and gender matched, patients diagnosed with SS‐1 or SS‐2 according to the preliminary European criteria. The patients had attended the Xerostomia Clinic, in the Oral Medicine Department, at the Liverpool University Dental Hospital.

RESULTS: Sixty‐seven patients with SS‐1 (average age 57.1 years) were matched with 67 patients with SS‐2 (average age 57.6 years), according to gender and age, within 5 years. The mean unstimulated whole salivary flow rates (±s.d.) for patients with SS‐1 and SS‐2 were 0.11 (±0.15) and 0.12 (±0.18) mL min−1 respectively. The mean paraffin wax stimulated, whole salivary flow rates (±s.d.) for patients with SS‐1 and SS‐22 were 0.45 (±0.02) and 0.47 (±0.49) mL/min−1 respectively. No significant differences, in either stimulated (P= 0.54) or unstimulated (P= 0.60) whole salivary flow rates were found between individuals with SS‐1 or SS‐2.

CONCLUSION: The severity of salivary gland hypofunction does not appear to be related to the clinical variant of Sjögren's syndrome.
Recurrent herpes labialis: efficacy of topical therapy with penciclovir compared with acyclovir (aciclovir)
Authors: Femiano F , Gombos F , Scully C
Published: December 2004

This study compares the effects of topical acyclovir and penciclovir in the treatment of recurrent herpes labialis. The study patients were a population of 40 patients with in excess of five recurrences annually, and were separated into four homogeneous groups each of 10 subjects. The antiviral creams were used to achieve total lesional cover, every 2 h during waking hours. The effects on the time to lesion crusting and to resolution of pain, were assessed. The results not only confirmed that aciclovir is ineffective, but confirmed that penciclovir is effective, and that penciclovir is superior to aciclovir.
Oral paracoccidioidomycosis: a retrospective study of 62 Brazilian patients
Authors: Bicalho RN , Do Espírito Santo MF , Ferreira de Aguiar MC , Santos VR
Published: December 2004

OBJECTIVE: The purpose of this study was to evaluate retrospectively the profile of patients with oral paracoccidioidomycosis referred to two Dental Schools in Belo Horizonte (MG, Brazil) between 1955 and 1998. Despite the importance of the oral manifestations of this disease, few papers in the English literature have provided epidemiological data.

SUBJECTS AND METHODS: The medical records of 62 patients presenting oral paracoccidioidomycosis were reviewed in detail. Patient age, gender, race, occupation, site of lesion and type of clinical manifestation of the disease were tabulated.

RESULTS: There was a predominance of male patients (97%), with a male:female ratio of 30:1. The mean age was 40 years. Most of the patients were farm workers (53%). Some patients presented multiple oral lesions (19 cases, 30%). The fungal lesions were found principally in the alveolar process and gingiva, but were also seen on the palate, lip and buccal mucosa. All patients had chronic proliferative mulberry‐like ulcerated oral lesions and the diagnosis was confirmed histologically. The clinical records did not contain notes about pulmonary involvement by the lesions.

CONCLUSION: The purpose of this study was to describe the epidemiological profile of a specific population with the diagnosis of oral paracoccidioidomycois. The major goal is to establish a scientific basis for initiating educational programs for prevention and early diagnosis of oral paracoccidioidomycosis.
Are dental infections a cause of brain abscess? Case report and review of the literature
Authors: Corson MA , Postlethwaite KP , Seymour RA
Published: December 2004

Dental pathology and/or treatment have been linked to a small number of brain abscesses as possible sources of infection. A further case is presented, in which a dental site is implicated. A review of the evidence was undertaken. A wide range of dental procedures had been implicated. In some cases the brain isolate was not of dental origin. In many, the diagnosis was one of exclusion. In order to confirm the role of odontogenic infection in the pathogenesis of brain abscess, modern sampling techniques should be used to precisely identify the isolates. The causal organism should be identified in both oral and cranial sites.
Seasonal variation of acute necrotising ulcerative gingivitis in South Africans
Authors: Arendorf TM , Bredekamp B , Cloete C‐A , Joshipura K
Published: December 2004

OBJECTIVES: To examine seasonal variations in the presentation of acute necrotising ulcerative gingivitis (ANUG) in a previously unstudied population in Cape Town, South Africa.

DESIGN: A descriptive study of all presenting cases of ANUG at a health center over 6 years; patients were examined at one point in time.

SETTING: A clinic‐based cross‐sectional study was carried out among patients presenting routinely to the oral medicine clinic at the University of the Western Cape. Patients at this clinic were mostly colored and black people, and were of low socioeconomic status.

SUBJECTS AND METHODS: All patients presenting to the periodontal clinic were examined during the period from 15 March 1992 to 15 March 1998 and interviews were conducted. A comprehensive clinical intra‐oral and peri‐oral examination was carried out using a dental mirror and blunt probe by three trained calibrated dental examiners. The minimum criteria for inclusion as an ANUG patient were painful, bleeding gums with irreversible destruction of the interdental papillae (cratering)and marginal gingiva. Patients with multiple small ulcerations not restricted to the gingiva, but including other oral sites such as the tongue and buccal mucosa were diagnosed as herpetic stomatitis. Other distinguishing characteristics of ANUG included presence of a pseudomembrane, odor, a strange taste in the mouth, and hypersalivation. Swabs and biopsies taken to verify the diagnosis when necessary. If there was any doubt as to the diagnosis of the lesion it was not included among the ANUG cases

MAIN OUTCOME MEASURE: Presence of ANUG.

RESULTS: Among the 19944 patients presenting for periodontal treatment, 684 were found to have ANUG. The ANUG patients consisted of 58% males; 73% of the ANUG patients were between the ages of 5 to 12 years. The majority of ANUG patients presented during the summer (55.4%), 27.7% in autumn and 8.4% during both winter and spring. Significant differences were evident between the numbers seen during the different seasons.

CONCLUSIONS: This study demonstrated a significant seasonal variation in the occurence of ANUG in Cape Town, South Africa.
Craniofacial tissues including tooth buds in fetal hypohidrotic ectodermal dysplasia
Authors: Nordgarden H , Reintoft I , Nolting D , Fischer‐Hansen B , Kjæ I
Published: December 2004

OBJECTIVE: Hypohidrotic ectodermal dysplasia (HED) comprises defects in hair, teeth, and sweat glands. Disturbances in other ectodermal tissues have been associated with the condition. Our objective was to examine ectodermal craniofacial structures histologically in a fetus with HED and to compare the findings to similar structures in normal control fetuses.

MATERIALS AND METHODS: A male fetus diagnosed with HED was therapeutically aborted in the 15th week of gestation. One male and two female healthy fetuses were used as normal controls. All fetuses were examined with parental consent, and had comparable sizes. Their bone maturation stage in the hand was identical. Tissue blocks from the craniofacial region were excised from all fetuses and prepared for histological analysis (formalin fixed, stained with toluidine blue or Alcian blue). The tissues examined were: tooth buds, skin and skin appendages, oral mucosa including minor salivary glands, major salivary glands, lacrimal glands, and adenohypophysis.

RESULTS: Fewer tooth buds, minor salivary glands, and hair follicles were observed in the HED fetus as compared to controls. The structures of the epidermal components in the developing HED organs were loose and disorganised. The adhesion between the ectodermal and mesenchymal organ components in the HED fetus seemed to be disturbed.
A model for internal derangement and osteoarthritis of the temporomandibular joint with experimental traction of the mandibular ramus in rabbit
Authors: Imai H , Sakamoto I , Yoda T , Yamashita Y
Published: December 2004

OBJECTIVES: The purpose of this study is to make a model of internal derangement (ID) and osteoarthritis (OA) by postero‐superior displacement of the mandible in the rabbit temporomandibular joint (TMJ).

MATERIALS AND METHODS: Sixteen Japanese white rabbits (8 months old) were subjected to traction of the mandibular ramus in the postero‐superior direction unilaterally using elastic force and five rabbits were used as the control. The operations were performed without surgical invasion of the TMJ capsule. Temporomandibular joint tissue was removed after 4 weeks and Technovit and paraffin sections with or without decalcification were observed histologically.

RESULTS: In contrast to the control group, it showed anterior disc displacement, disc deformity, resorption of subchondral bone and osteophyte formation in the drawing side of the experimental group. Intra‐articular fibrous adhesions were observed in both sides.

CONCLUSION: It is concluded that posterosuperior displacement of the mandible caused ID and OA in the rabbit TMJ. This model may contribute to the understanding of the etiology of human temporomadibular disorders (TMD).
Oro‐dental and craniofacial anomalies in LEOPARD syndrome
Authors: Yam AA , Faye M , Kane A , Diop F , Coulybaly‐Ba D , Tamba‐Ba A , Mbaye NG , Ba I
Published: December 2004

‘LEOPARD syndrome’ is a syndrome affecting many systems or organs. The main anomalies are summarized in the acronym LEOPARD in which each letter corresponds to the damage of a given organ. In the presented case, there are oro‐dental and craniofacial anomalies. The relationship between the LEOPARD syndrome and the given anomalies and the possibilities of the management and the follow‐up of the diseased are studied. The clinical case presented is a 4‐year‐old boy with LEOPARD syndrome showing retardation of dental development, delayed development and possible agenesis of permanent teeth, and craniofacial anomalies (osseous hypodevelopment). The bibliographical study shows that LEOPARD syndrome is due to damage of the neural crest cells. Thus, the dental and craniofacial anomalies arise since neural crest cells participate in the formation of the teeth and some cranofacial bones. Therefore, dental and craniofacial anomalies might be expected in some cases of the disease. The therapeutic management of the lesions, and the follow‐up of the patient would be done by a multidisciplinary team.
Management of child and adolescent eating disorders: the current evidence base and future directions
Authors: Gowers Simon , Bryant‐Waugh Rachel
Published: December 2004

Although eating disorders in children and adolescents remain a serious cause of morbidity and mortality, the evidence base for effective interventions is surprisingly weak. The adult literature is growing steadily, but this is mainly with regard to psychological therapies for bulimia nervosa and to some extent in the field of pharmacotherapy. This review summarises the recent research literature covering management in three areas, namely physical management, psychological therapies, and service issues, and identifies prognostic variables. Findings from the adult literature are presented where there is good reason to believe that these might be applied to younger patients. Evidence‐based good practice recommendations from published clinical guidelines are also discussed. Suggestions for future research are made, focusing on 1) the need for trials of psychological therapies in anorexia nervosa, 2) applications of evidence‐based treatments for adult bulimia nervosa to the treatment of adolescents, and 3) clarification of the benefits and costs of different service models.