bluuebunny/crossref_metadata_2025 huggingface dataset:
Indicating shear stress with FST‐hemispheres ‐ effects of stream‐bottom topography and water depth
Authors: DITTRICH ANDREAS , SCHMEDTJE URSULA
Published: May 2006

1. In order to quantify the effects of substratum roughness on shear stress and Fliesswasserstammtisch‐(FST)‐hemisphere movement, hemispheres were calibrated against shear stress in a laboratory flume with fully developed turbulent flow. In five different runs, substratum roughness, water depth and location of hemispheres in relation to the surrounding particles, were varied.

2. FST‐hemisphere results were strongly influenced by bottom topography. In the case of hydraulically rough flow a linear relationship exists between shear stress (χc) and hemisphere density (ρh), whereas in the case of quasi‐smooth flow a power law was obtained for the χc/ρh, relationship. Shear stress for a given hemisphere and relative roughness h/k > 4 (h= water depth; k= height of the roughness elements) deviated up to one order of magnitude between roughnesses. In water depths, where h/k 4, the χc/ρh relationships are dependent on the ratio h/k, due to water surface effects on hemisphere movement. In the case of k = d90=rh (d90= characteristic diameter of the largest particles of the bottom substratum; rh= radius of the hemispheres), the location of the hemispheres in respect to the roughness elements is of secondary importance.

3. In the case of hydraulically rough flow and wake interference between the roughness elements, the turbulent flow field close to the substratum is three‐layered, each layer being characterized by its own velocity distribution laws (Dittrich & Hammann de Salazar, 1993). Depending on the height of the roughness elements, FST‐hemispheres will be subjected mainly to flow forces of the near‐bed layer (in rough substrata) or to flow forces distant from the near‐bed zone (in fine substrata). The dominant flow forces acting on bottom particles, organisms, or FST‐hemispheres are shear force and lift force.

4. The Local Shear Stress Model (Lamouroux et al., 1992) leads to a correct prediction of hemisphere distribution in a stream with a cobble size substratum, but to an overestimation of hemisphere numbers in a sandy‐bottom stream. The substratum‐dependent shear stress values therefore need to be entered into the model and a measure of substratum roughness included.

5. Macroinvertebrate abundance correlates well with the movement of FST‐hemispheres. Samples from points with very high or very low roughness did not contribute to scatter in the data, indicating that the sum of the near‐bed flow forces is relevant to macroinvertebrate distribution, not shear stress alone. We conclude, that FST‐hemispheres are well suited to characterize near‐bottom hydraulics and therefore the microhabitat of the benthos.
The effects of catchment liming on the chemistry and biology of upland Welsh streams: testing model predictions
Authors: RUNDLE S.D. , WEATHERLEY N.S. , ORMEROD S.J.
Published: May 2006

1. The catchments of three acidified streams in mid Wales were limed in 1987/88. Here we assess their chemical and biological response in comparison with unmanipulated reference streams over a period of 5 years post‐liming.

2. Stream chemistry was measured weekly/fortnightly between 1985 and 1992, while macroinvertebrates were sampled annually. Colonization by acid‐sensitive taxa was assessed and trends in community structure were monitored by TWINSPAN. Real biological responses were compared with those predicted by an empirical model constructed using chemical data.

3. There were marked changes in stream chemistry following liming: calcium concentrations and pH values increased, while aluminium concentrations decreased to levels similar to those in naturally circumneutral streams. These conditions have persisted since liming.

4. Empirical models predicted that stream invertebrates would respond to the altered stream chemistry, with the establishment of communities typical of circumneutral conditions.

5. Following liming, the taxon richness and abundance of acid‐sensitive taxa was significantly higher in limed compared with reference streams. Colonization by, and persistence of acid‐sensitive taxa was patchy, however, and richness was still substantially lower than in naturally circumneutral streams. Moreover, contrary to the model predictions, there were no wholesale changes in the structure of macroinvertebrate communities.

6. We conclude that liming has created and maintained chemical conditions suitable for macroinvertebrate communities typical of circumneutral streams, but these chemical changes have not been matched by sustained responses among the biota. The views expressed in this article are those of the authors and do not necessarily reflect those of the NRA.
The role of nutrition in regulation of predator‐induced crests of Daphnia carinata
Authors: BARRY MICHAEL J.
Published: May 2006

1. The effects of food level on the development of crests by Daphnia carinata in the presence of Anisops grains (Notonectidae) were investigated in two laboratory experiments and in the field.

2. In the laboratory experiments D. carinata were grown at different food levels either in the presence of A. gratus or in predator‐free water. In the field study the effects of six variables (temperature, food level, density of Daphnia, density of Anisops, brood size and maternal nutrition) on development of crests in the next generation of Daphnia were investigated over a 12‐month period at a single field site.

3. In the laboratory food level had a small but significant effect on relative crest height of D. carinata. In the presence of notonectid predators the rate of crest growth relative to body length was higher than for control D. carinata only during embryogenesis and/or the first two neonatal instars. Beyond this age the rate of crest growth was similar in both morphs.

4. In the field study, crest height was negatively correlated with density of Daphnia and positively correlated with density of Anisops and maternal nutrition (maternal nutrition was defined as the somatic weight of a female with a body length of 2.5 mm, calculated from the length‐dry weight regression based on a sample of the population). However, these data were biased by a short period when no Anisops were present in the pond. When these data were excluded, the only factor which significantly correlated with crest height was maternal nutrition. This finding indicated that relative crest height of the next generation was determined primarily during embryogenesis on the basis of maternal feeding success and possibly on food availability during the first two instars.
Seasonal dynamics of picophytoplankton in Lake Kinneret, Israel
Authors: MALINSKY‐RUSHANSKY N. , BERMAN T. , DUBINSKY Z.
Published: May 2006

1. Picophytoplankton (picocyanobacteria and picoeukaryotes) communities in Lake Kinneret were studied from 1988 to 1992. No prochlorophytes were observed in the lake.

2. Picocyanobacteria were a prominent and ubiquitous component of the phytoplankton, being present at all depths throughout the year, with concentrations ranging from 2 ± 10–8 ± 105 cells ml−1. Low cell numbers in winter and spring were followed at the end of the annual dinoflagellate bloom by maximal abundances in summer‐autumn in the epilimnion. High cell numbers (> 104 cells ml−1) were sometimes also found in the anaerobic hypolimnion. Net growth rates for picocyanobacteria ranged from 0.29 to 0.60 divisions day−1.

3. Picoeukaryotes were a very minor constituent of the picoplankton, mostly present in winter and spring, and sometimes at the end of autumn, with concentrations ranging from 44 to 5700 cells ml−1. Higher cell numbers tended to occur in the near surface water layers. In August‐September, picoeukaryotes were found only in the hypolimnion. In December, the occurrence of picoeukaryotes in the deep water layers probably resulted from advection with cold water currents from the Jordan river. Net growth rates for picoeukaryotes ranged from 0.26 to 0.43 divisions day−1.

4. Overall, the contribution of picophytoplankton to the phytoplankton standing crop in Lake Kinneret was limited; picocyanobacteria and picoeukaryotes accounted for no more than 7.0 and 0.1% of total algal biomass (semiannual average), respectively.

5. Picophytoplankton cell numbers in pelagic waters were usually similar to those in shallower lake stations.

6. Picocyanobacteria appear to be an autochthonous population, whereas picoeukaryotes are probably brought annually by the Jordan River and do not maintain themselves in the lake.
Distribution fields for aquatic ecosystem components: method of identification of correlation zones
Authors: KALIKHMAN I. , OSTROVSKY I. , WALLINE P. , GOPHEN M. , YACOBI Y. Z.
Published: May 2006

1. Data from the two multidisciplinary surveys of Lake Kinneret (Israel), including acoustic surveys of fish concentrations and concurrent sampling of plankton at stations, were used to reconstruct fish and plankton distributions. No significant lake‐wide correlations for the distribution fields were found. With respect to patchiness of the fish and plankton distributions, we hypothesized that they might be correlated in localized zones.

2. A method is suggested for the identification of areas where there are strong correlations of two distribution fields. The method is based on outlining zones where the gradients of the two fields of interest are in the same direction (or are opposite). Only areas larger than the autocorrelation circles (or ellipses) for the fields are considered. The correlation of the fields is calculated for each of the zones selected.

3. The method was used in analysing data from the multidisciplinary surveys. We were able to detect areas of the lake where there were correlations for fish and plankton distributions. Analysis of specific conditions inside the correlation zones made it possible to construct hypotheses concerning the causes for the observed patterns of fish and plankton distributions.
Temporal scale, phytoplankton ecology and palaeolimnology
Authors: ANDERSON N. J.
Published: May 2006

1. Scales of temporal analysis in limnology generally cover dial through to interannual changes, with occasional longer studies with up to 50 years continuous sampling data. Lakes, however, have been changing over much longer time periods than this, as is apparent from palaeolimnological studies. Temporal scales are, however, largely relative, with an individual's perspective controlling what is deemed short or long term.

2. Phytoplankton populations are variable over a variety of timescales, and the sediment record can readily record these changes from interannual through to 103‐year timescales. Because of anthropogenic influences, such as acidification and eutrophication, phytoplankton communities probably have been altered dramatically in many lakes, often before routine sampling began. Records of changing phytoplankton populations at timescales relevant to limnologists can be derived from, for example, varved sediments and used to address specific problems, such as the degree of long‐term interannual variability and timescales of sexual reproduction.

3. Palaeolimnologists tend to interpret changes in sediment assemblages in terms of ecological and physiological processes which are relevant at scales that may not be resolvable in lake sediments. There is a clear need for sediment records to be interpreted in terms of the processes which operate at timescales that match the resolution of that sediment sequence.

4. Increasingly fine sampling resolutions are being attempted by palaeolimnologists, often without consideration of the reasons for such an approach or to the repeatability of the results. The increased variability associated with high‐resolution sampling can make it difficult to separate noise from the ecological signal. There is a clear need for replication.

5. The necessary temporal resolution is defined by the aim of any given palaeolimnological study. If the main emphasis of a study is, for example, establishing background phosphorus concentrations, a coarser sampling resolution is probably acceptable than that required for many ‘ecological’studies.
Growth limitation of submerged aquatic macrophytes by inorganic carbon
Authors: VADSTRUP METTE , MADSEN TOM VINDBÆK
Published: May 2006

1. This study determined the effects of CO2and HCO3‐ enrichment onin situgrowth of two submerged macrophytes,Elodea canadensisandCallitriche cophocarpa, in two Danish lakes: Lake Hampen and Lake Væng. Lake Hampen is an oligotrophic low‐alkaline lake (0.4 meq−1) and Lake Væng is mesotrophic with an alkalinity of 1.1 meq 1‐−1. In Lake Hampen experiments were carried out throughout the growth season, whereas experiments in Lake Væng were restricted to late summer. The CO2and HCO3‐enrichment procedures used increased the concentration of free‐CO2by 500–1000 μM and the concentration of HCO3‐ by about 80 μM.

2. The concentration of free‐CO2in Lake Hampen was about five times atmospheric equilibrium concentration (55 μM) in early summer declining to virtually zero at the end of summer.

3. Under ambient conditionsCallitriche, which is restricted to CO2use, was unable to grow and survive in both lakes. In contrast,Elodea, which has the potential to use HCO3‐ in photosynthesis, grew at rates varying from 0.046 to 0.080 day−1over the season.

4. Under CO2enrichment the growth rate ofCallitrichevaried from 0.089 to 0.124 day−1and forElodeafrom 0.076 to 0.117 day−1over the season. Enrichment with HCO3‐affectedElodeaonly and only to a limited extent. This may be a result of insufficient increase in [HCO3‐] upon enrichment or to a limited capacity of the plants to take up HCO3‐.

5. The substantial stimulation ofin situgrowth ofElodeaandCallitricheby enhanced concentrations of free‐CO2shows that inorganic carbon is an important determinant of growth of submerged macrophytes and that inorganic carbon limitation ofin situgrowth may be a common phenomenon in nature, even in lakes with an alkalinity as high a 1 meq 1‐−1. Inorganic carbon, however, is only one of many parameters important for growth, and the growth rates ofElodeaat both ambient and high free‐CO2were closely coupled to day length and photon irradiance, indicating that light had an ultimate control on growth.
Empirically estimating the lateral transport of riparian leaf litter to lakes
Authors: FRANCE R.L.
Published: May 2006

1. An experimental study found the lateral transport of riparian leaf litter to increase in relation to surface slope, exposure to precipitation, and absence of ground flora. Deciduous leaves displayed greater lateral redistribution than did coniferous needles.

2. When these results were combined with the proportional representation of different slopes, canopy exposures and ground roughness measured from transects throughout the riparian zones of sixteen north‐western Ontario lakes, the average annual lateral transport distance of coniferous needles was estimated to be 0.3 m and that of deciduous leaves to be 0.5 m.

3. Data on the annual riparian litterfall and distributional proximity of trees to the shorelines suggested that the lateral input of riparian litter was 2 g m−1 forested shoreline yr−1, an amount which represents 6% of the total annual allochthonous input of leaf‐fall to these study lakes.
Prevention of sulphide accumulation and phosphate mobilization by the addition of iron(II) chloride to a reduced sediment: an enclosure experiment
Authors: SMOLDERS A.J.P. , NIJBOER R.C. , ROELOFS J.G.M.
Published: May 2006

1. In an enclosure experiment carried out in a ditch receiving sulphate‐enriched seepage water, iron(II) chloride was added to the sediment. In the sediment pore water of the iron‐treated enclosures sulphide levels decreased to very low values (<1 μmol 1−1) immediately after the iron addition while in the control enclosures sulphide reached values up to 500 μmoll−1.

2. The sulphide levels in the sediment pore water were also strongly correlated with temperature. In summer, phosphate mobilization was observed in the non‐treated enclosures while in the iron‐treated enclosures phosphate levels remained low.

3. Total phosphate levels increased greatly in the water layer of the non‐treated enclosures, coincident with an algal bloom and increased turbidity. It is suggested that phosphate mobilization in summer is caused by the reduction of iron(III) phosphate complexes and in this high sulphate water body probably also by the reduction of iron(III) by sulphide and the consequential precipitation of iron(II) sulphide.

4. Iron addition appeared to prevent sulphide toxicity in Potamogeton acutifolius Link which was planted in the enclosures immediately after iron(II) addition. In the non‐iron‐treated enclosures P. acutifolius plants decayed within a few weeks probably as a result of sulphide toxicity.
Spatial and temporal distribution patterns of drifting pupal exuviae of Chironomidae (Diptera) in streams of tropical northern Australia
Authors: HARDWICK R.A. , COOPER P.D. , CRANSTON P.S. , HUMPHREY C.L. , DOSTINE P.L.
Published: May 2006

1. Periodic collecting of floating cast pupal cuticles of chironomids (exuviae) in two tropical northern Australian streams demonstrates (i) spatial heterogeneity in species composition across a wide stream, (ii) temporal heterogeneity in the maximum abundance of each species, and that (iii) species accumulate as a function of sample size and duration of sampling,

2. Spatial heterogeneity is ascribed to variation in larval microhabitat across the wide stream, combined with short exuvial drift duration and restricted upstream mixing.

3. Temporal heterogeneity is ascribed to diel periodicity in adult emergence and, as with spatial heterogeneity, to the short floating life.

4. The consequences of spatial and temporal variation for the sampling of exuvial drift are discussed in relation to the objectives of particular programmes. Thus, if the objective is assessment of chironomid species composition for inventory purposes such as faunistics or conservation, the large sample sizes attained by 24‐h sampling are necessary and appropriate. However, for rapid assessment that requires comparable samples at different sites, species numbers may be optimized by temporally and spatially restricted sampling of the maximal emergence period, which in this study is at dusk, or by subsampling from a 24‐h sample.
Species‐specific phytoplankton responses to nutrients and zooplankton manipulations in enclosure experiments
Authors: PÉREZ‐MARTÍNEZ CARMEN , CRUZ‐PIZARRO LUIS
Published: May 2006

1. In situ enclosure experiments were performed in the mesotrophic Bermejales reservoir to evaluate the algal response to changes in the nutrient supply and in the zooplankton size structure and density in a 2 × 2 factorial design. The experiments were conducted during the spring bloom of nanoplanktonic diatoms in 1989.

2. Nutrient enrichment promoted a great increase of phytoplankton biomass indicating a strong nutrient limitation on phytoplankton growth. Total phytoplankton biomass was significantly lower in the Daphina‐added enclosures at a given nutrient level and strong direct an indirect effect of zooplankton on phytoplankton community structure and nutrient availability were observed.

3. Most of the nanoplanktonic species were effectively grazed but species with protective coverings and large size colonies were favoured by grazers and small chlorococcales were unaffected probably because of their compensatory high growth rates. The decrease in total biomass imposed by grazers is attributable mainly to the decrease of Cyclotella ocellata, the most abundant species. This taxon suffers two net effects of zooplankton: direct grazing and the indirect decrease of Si availability caused by the growth of C. ocellata which was promoted by P excretion by zooplankton. Indirect effects of grazers on Si availability should, therefore, be taken into account in explaining phytoplankton succession and community structure.

4. In this experiment grazers affected considerably the nanoplanktonic community in Bermejales reservoir. The extent which they were affected, however, depended not only on the algal size as a determinant of edibility but also greatly on the specific nutrient requirements and taxonomic features of the algal species.
Food preference of freshwater invertebrates: comparing fresh and decomposed angiosperm and a filamentous alga
Authors: KORNIJÓW RYSZARD , GULATI RAMESH D. , OZIMEK TERESA
Published: May 2006

1. Fresh and decomposed Mougeotia sp. (a filamentous green alga) and Elodea nuttallii (a vascular plant) were offered as food to three species of aquatic macroinvertebrates (Lymnaea peregra, Asellus meridianus and Endochironomus albipennis) to test: (i) if filamentous algae are preferred to aquatic higher plants (hereafter, called ‘macrophytes’) and (ii), as is known for higher plants, if decomposition also results in greater palatability of filamentous algae.

2. Compared with the alga, the macrophyte in both states was of higher nutritional value. Conditioning improved the nutritional value of both food types, but especially of the macrophyte.

3. Both fresh alga and fresh macrophyte were eaten little by all animals except A. meridianus feeding upon the macrophyte. Consumption was higher for both plants in their decomposed state. However, L. peregra consumed more decomposed macrophyte than the decomposed alga. Both decomposed plants were eaten most by E. albipennis followed by A. meridianus and L. peregra.

4. Digestibility of both plants, but especially of the macrophyte, increased significantly after decomposition. The assimilation efficiencies of all animals on the fresh E. nuttallii were higher than on fresh Mougeotia sp. After decomposition, the efficiency increased significantly only on the alga. Consequently, both decomposed plants were assimilated with similar efficiency by all test animals.

5. Amongst aquatic macrophytes, the increase of their consumption and digestibility upon decomposition has hitherto been known only for vascular plants but not for filamentous algae.
The vulnerability of juvenile signal crayfish to perch and eel predation
Authors: BLAKE M.A. , HART P.J.B.
Published: May 2006

1. We conducted laboratory experiments to determine how juvenile signal crayfish (Pacifastacus leniusculus) responded to two predators with different foraging behaviours (European eel Anguilla anguilla and European perch Perca fluviatilis), and whether these responses affected their vulnerability.

2. By accelerating a model predator towards crayfish which had been temporarily blinded, we assessed whether crayfish had to see predators in order to escape. Blind crayfish escaped later than did sighted crayfish attacked in the same manner.

3. Both eels and perch elicited similar evasive behaviour when approaching and attacking sighted crayfish. Crayfish usually escaped these initial attacks but perch chased and caught more crayfish than did eels.

4. In a third experiment, perch preyed more rapidly on a population of crayfish than did eels. By the end of the experiment, however, crayfish survival rates were similar in response to eel and perch predation.

5. Our results show that crayfish are well adapted to evade predatory attacks based on rapid responses to both visual and/or mechanical stimuli. The results also suggest that behaviourally, crayfish are more vulnerable to attacks by perch than by eels. We discuss these findings in relation to other factors that affect the vulnerability of crayfish to these predators.
APPLIED ISSUES Replacement of the native crayfish Astacus astacus by the introduced species Pacifastacus leniusculus in a Swedish lake: possible causes and mechanisms
Authors: BÄCK BJÖRN SÖDER
Published: May 2006

1. The introduced North American crayfish Pacifastacits leniusculus is currently replacing the native crayfish Astacus astacus in a Swedish lake. Using field data from co‐occurring populations on life‐history traits and population size structure of the two species, this study evaluated possible mechanisms behind the replacement.

2. Pacifastacus showed a higher capacity for population increase; the species had a higher individual growth rate, reached sexual maturity at a smaller size and lower age, and had a higher per capita egg production than Astacus.

3. A higher frequency of non‐lethal injuries in Astacus suggested the predominance of Pacifastacus in interference interactions. These results support a competitive exclusion hypothesis.

4. A dramatic change in relative abundance of the two species in recent years was the result of an almost complete cessation in recruitment of young‐of‐the‐year (YOY) in Astacus. Poor recruitment in Astacus was probably caused by the combined effects of interspecific competition and predation, resulting in increased mortality among YOY Astacus, and by reproductive interference, suppressing the less common species.

5. The results support the hypothesis that the observed replacement of Astacus by Pacifastacus is governed by a combination of several interacting mechanisms, of which
APPLIED ISSUES Increasing litter retention in moorland streams: ecological and management aspects of a field experiment
Authors: DOBSON MIKE , HILDREW ALAN G. , ORTON STUART , ORMEROD S.J.
Published: May 2006

1. The retention characteristics of two moorland streams in mid‐Wales were manipulated for 2 years by the addition of small traps which accumulated detritus. Leaf litter was also added to these essentially treeless streams at regular intervals to simulate natural inputs to a woodland stream.

2. Leaf traps retained a significantly higher biomass of detritus ‐ both naturally occurring and added ‐ than either the surrounding stream bed or unmanipulated reference sections. They also supported significantly higher numbers of nemourid, leuctrid, tipulid and elminthid insect larvae.

3. Among functional feeding groups, detritivores and, to a lesser extent, predators responded to increased detritus availability. Numbers of mayfly larvae were low in leaf packs, suggesting a negative effect of detritus aggregations on their numbers.

4. The taxa which responded positively to increased detrital biomass, particularly stonefly larvae, are known to be tolerant of low pH conditions, whereas those affected detrimentally are generally absent from acid waters. It is proposed therefore that increasing detrital inputs and litter retention in culturally acidified upland streams may serve to increase their invertebrate productivity.
Carotenoid accumulation strategies for becoming a colourful House Finch: analyses of plasma and liver pigments in wild moulting birds
Authors: MCGRAW K. J. , NOLAN P. M. , CRINO O. L.
Published: May 2006

Male House Finches (Carpodacus mexicanus) colour their sexually selected plumage with carotenoid pigments, and there has been much interest in the factors that affect their ability to become bright red rather than drab yellow.

There is good support for the notions that health, nutritional condition and total carotenoid intake influence colour expression, but there are also suggestions that acquiring particular types of carotenoids from the diet may be important for developing red plumage.

We used high‐performance liquid chromatography (HPLC) to analyse the types and amounts of endogenous (in plasma and liver) and integumentary (in newly grown feathers) carotenoids in a wild, native population of moulting male and female House Finches from the south‐western United States to determine the carotenoid‐accumulation strategies for becoming optimally colourful.

Four plant carotenoids – lutein, zeaxanthin, β‐cryptoxanthin and β‐carotene – were detected in plasma and liver. However, as was found previously, 11 carotenoids were observed in colourful plumage, with xanthophylls (e.g. lutein, dehydrolutein) predominant in yellow feathers and ketocarotenoids (e.g. adonirubin, 3‐hydroxy‐echinenone) in red feathers. This indicates endogenous modification of ingested carotenoids.

Birds that accumulated more of one type of carotenoid in plasma and liver did not necessarily accumulate more of all other types, suggesting that individuals are not employing a simple ‘more is better’ strategy for coloration. Instead, when forward stepwise regression was used to examine the ability of individual types of carotenoids in plasma and liver to explain variation in red plumage pigments and plumage redness, we found that the lone variable remaining in all models was β‐cryptoxanthin concentration.

This supports the idea that, unlike some other songbirds (e.g. yellow Carduelis finches), there is a specialized biochemical strategy that male House Finches follow to become red and most sexually attractive – to accumulate as much β‐cryptoxanthin in the body as possible. β‐Cryptoxanthin is a less common dietary carotenoid than the typical xanthophylls and carotenes in grains and fruits and may be limited enough in the diet that, to become colourful, House Finches might adopt selective foraging strategies for the most β‐cryptoxanthin‐rich foods.
Puromycin insensitive leucyl‐specific aminopeptidase (PILSAP) is required for the development of vascular as well as hematopoietic system in embryoid bodies
Authors: Abe Mayumi , Sato Yasufumi
Published: May 2006

We have shown that puromycin insensitive leucyl‐specific aminopeptidase (PILSAP) is required for regulation of angiogenesis. However, it remains unclear whether PILSAP plays a role in endothelial cell (EC) differentiation. We examined the role of PILSAP by using an embryoid bodies (EBs) culture system. Fms‐like tyrosine kinase‐1 (Flk‐1) showed two expression peaks on days 4 and 10 of culture. These two peaks represent populations of mesodermal precursors and mature ECs, respectively. Endothelial markers such as VE‐cadherin, CD34, CD31 and Tie2 followed the first peak of Flk‐1. Interestingly, the expression of PILSAP showed a pattern similar to that of Flk‐1. ES cells transfected with mutant PILSAP (mtPILSAP) cDNA of a dominant negative activity organized less vascular structure and showed decreased levels of vascular lineage markers. The similar results were obtained in EBs treated with leucinethiol, a specific inhibitor of leucine aminopeptidase or siRNA for PILSAP. However, Flk‐1 expression was unaffected on day 4. The expression of markers for hematopoietic lineage and muscle cells in mtPILSAP‐EBs was also reduced. These results suggest that although PILSAP may not function in the initial generation of Flk‐1 positive mesodermal precursors, it dose play a role in growth of vascular, hematopoietic, and muscular lineage population from those precursors.
Further dental treatment needs of children receiving exodontia under general anaesthesia at a teaching hospital in the UK
Authors: KAKAOUNAKI E. , TAHMASSEBI J. F. , FAYLE S. A.
Published: May 2006

Summary.  Objectives.  The aim of this study was to investigate the subsequent dental treatment needs of children who had dental extractions under general anaesthesia (GA) in 1997 in the Day Case Unit at Leeds Dental Institute (LDI), Leeds, UK, and the reasons for repeat dental GAs (DGAs).

Study design.  The authors conducted a retrospective longitudinal analysis.

Subjects and methods.  Information collected from hospital records for the 6‐year period following the first DGA included: reasons for the DGA in 1997 and teeth extracted; the number of subsequent DGAs, reasons and treatment; incidents of and reasons for toothache or swelling after 1997; treatment under local anaesthesia (LA) or inhalation sedation (IS) at LDI during the 6 years following the DGA in 1997.

Results.  The study population consisted of 484 children, who received GA exodontia at LDI with a mean age of 6·35 years [95% confidence interval (CI) = 6·1, 6·6] and age range of 1–16 years. The most common reason for extractions at the original DGA in 1997 was dental caries, and the mean number of extractions was 4·24 (95% CI = 4·05, 4·43). Primary teeth extractions accounted for 82% of the cases. In total, 143 children (27·5%) had a record of follow‐up treatment at LDI. Of these children, 32% had treatment under LA, 7% under LA and IS, and 15% received preventive care only. The overall repeat rate for DGA was 10·7%, with caries (84%) being the main reason for this. Of the teeth subsequently extracted, 72% were recorded as caries‐free or unerupted at the time of the DGA in 1997.

Conclusions.  A large proportion of the follow‐up visits were to treat newly developed dental disease during the 6 years following the DGA in 1997. A more proactive approach towards preventive care may have resulted in the reduction of the development of new dental disease.
Nurses’ and patients’ perceptions of expert palliative nursing care
Authors: Johnston Bridget , Smith Lorraine N.
Published: May 2006

Aim.  This paper reports a study of the perceptions of patients and nurses of palliative care and, in particular, the concept of the expert palliative nurse.

Background.  Palliative care is a growing speciality and is practised globally. There is, however, limited information on patients’ views about palliative care. While the idea of expertise in nursing is not new, few studies have explored the concept of the expert nurse in palliative care. Some evidence exists on palliative nurses’ perceptions of their care, that it is supportive and involves maintaining therapeutic relationships with patients. Facing a terminal illness has been identified as a stressful and fearful experience that affects all aspects of life. It has also been revealed that dying patients may have unmet care needs, mainly in the areas of pain and symptom control, emotional support, and spending time alone.

Methods.  A phenomenological study was carried out, using in‐depth interviews and thematic content analysis. A convenience sample of 22 Registered Nurses and 22 dying patients was interviewed in 1996–1997.

Findings.  Dying patients had a desire to maintain independence and remain in control. Palliative care nurses experienced both effective and ineffective interpersonal communication, the building of therapeutic relationships with dying patients and attempting to control patients’ pain and distressing symptoms. Patients and nurses agreed that the two most important characteristics of an expert palliative nurse were interpersonal skills and qualities such as kindness, warmth, compassion and genuineness.

Conclusion.  Although the study was conducted in the United Kingdom, the findings have relevance for palliative care practice globally in terms of dependence, issues of patient choice, nurses being interpersonally skilled and building therapeutic relationships with patients.
Role discrepancy: is it a common problem among nurses?
Authors: Takase Miyuki , Maude Phillip , Manias Elizabeth
Published: May 2006

Aim.  This paper reports a study of nurses’ perceptions of the differences between ideal and actual nursing roles, how these perceptions differ according to length of experience and the factors that might contribute to these perceived differences.

Background.  The literature suggests that nurses tend to experience role discrepancy or a mismatch between their ideal and actual roles. Although it has been assumed that experienced nurses perceive less role discrepancy than inexperienced nurses, either because the former adjust themselves to their actual practice or because they have the expertise to improve their practice, this assumption has not been tested.

Methods.  A survey design was used and the data were collected in 2003. Selected items from the Jefferson Survey of Attitudes Toward Physician–Nurse Inventory and the Staff Nurse Role Conception Inventory were administered to 216 Registered Nurses in Victoria, Australia to measure their perceptions of ideal and actual nursing roles. Data were analysed using a t‐test and regression analysis.

Results.  Nurses with more clinical experience rated their ideal and actual nursing roles more positively than those with less experience. However, the results showed that both groups of nurses experienced the same degree of role discrepancy. Both groups perceived strong role discrepancy in the areas of organizational decision‐making and provision of patient education. Experienced nurses also perceived moderate role discrepancy in developing nursing care plans and in the freedom to initiate referrals.

Conclusions.  Role discrepancy cannot be resolved by having more clinical experience. While clinical experience enhances nurses’ conceptions of their ideal roles, it can also lead to role discrepancy if there are organizational barriers that prevent nurses from engaging in their ideal roles. It is important to find a way whereby nurses can actualize their ideal views of practice in the current healthcare environment.
Response of bird communities to silvicultural thinning of Mediterranean maquis
Authors: DE LA MONTAÑA E. , REY‐BENAYAS J. M. , CARRASCAL L. M.
Published: May 2006

Woodland management should consider biodiversity conservation world‐wide. Landowners in some European Mediterranean regions receive subsidies to thin dense maquis. This practice eliminates most shrubs and saplings while the tallest trees are pruned to produce more open woodland stands. We investigated the impact of this practice on the conservation status of bird communities.

We designed a large‐scale ‘natural experiment’ that included 21 paired thinned and unthinned maquis stands in central Spain. Every stand was sampled by means of five point counts, each consisting of a 50‐m radius plot, in two consecutive years and in winter and spring. The vegetation structure was characterized after bird censuses in 10‐m radius plots that coincided with the centres of the bird point counts. Data analyses were based on repeated‐measures anovas.

Thinning was responsible for a significant increase in species richness, but did not have any effect on total bird density. The average body mass of species in thinned stands was significantly larger than in unthinned, more densely vegetated, stands. The density of ground searchers was indistinguishable in thinned and unthinned stands, whereas the density of foliage gleaners was higher in unthinned stands. The winter density of granivorous species was marginally higher in thinned stands, whereas insectivorous and frugivorous species were marginally more abundant in unthinned stands.

Thinned areas were occupied by higher densities of bird species whose European conservation status is of high concern. Winter density of gamebirds was also higher in thinned stands.

Synthesis and applications. This is the first time that a large‐scale experimental manipulation of habitat structure and vegetation volume has demonstrated the predicted allometric effect of habitat structural complexity on the average body mass of a bird community. Thinning of dense Mediterranean woodland enhanced habitat heterogeneity and suitability for several bird species and increased species richness. It was also beneficial for species of conservation concern and for non‐threatened gamebirds. However, some unthinned patches should be preserved to provide refuge for the few species that are impacted by thinning.
The identification of 100 ecological questions of high policy relevance in the UK
Authors: SUTHERLAND WILLIAM J. , ARMSTRONG‐BROWN SUSAN , ARMSWORTH PAUL R. , TOM BRERETON , BRICKLAND JONATHAN , CAMPBELL COLIN D. , CHAMBERLAIN DANIEL E. , COOKE ANDREW I. , DULVY NICHOLAS K. , DUSIC NICHOLAS R. , FITTON MARTIN , FRECKLETON ROBERT P. , GODFRAY H. CHARLES J. , GROUT NICK , HARVEY H. JOHN , HEDLEY COLIN , HOPKINS JOHN J. , KIFT NEIL B. , KIRBY JEFF , KUNIN WILLIAM E. , MACDONALD DAVID W. , MARKER BRIAN , NAURA MARC , NEALE ANDREW R. , OLIVER TOM , OSBORN DAN , PULLIN ANDREW S. , SHARDLOW MATTHEW E. A. , SHOWLER DAVID A. , SMITH PAUL L. , SMITHERS RICHARD J. , SOLANDT JEAN‐LUC , SPENCER JONATHAN , SPRAY CHRIS J. , THOMAS CHRIS D. , THOMPSON JIM , WEBB SARAH E. , YALDEN DEREK W. , WATKINSON ANDREW R.
Published: May 2006

Evidence‐based policy requires researchers to provide the answers to ecological questions that are of interest to policy makers. To find out what those questions are in the UK, representatives from 28 organizations involved in policy, together with scientists from 10 academic institutions, were asked to generate a list of questions from their organizations.

During a 2‐day workshop the initial list of 1003 questions generated from consulting at least 654 policy makers and academics was used as a basis for generating a short list of 100 questions of significant policy relevance. Short‐listing was decided on the basis of the preferences of the representatives from the policy‐led organizations.

The areas covered included most major issues of environmental concern in the UK, including agriculture, marine fisheries, climate change, ecosystem function and land management.

The most striking outcome was the preference for general questions rather than narrow ones. The reason is that policy is driven by broad issues rather than specific ones. In contrast, scientists are frequently best equipped to answer specific questions. This means that it may be necessary to extract the underpinning specific question before researchers can proceed.

Synthesis and applications. Greater communication between policy makers and scientists is required in order to ensure that applied ecologists are dealing with issues in a way that can feed into policy. It is particularly important that applied ecologists emphasize the generic value of their work wherever possible.
A numerical approach to resonance frequency analysis for the investigation of oral implant osseointegration
Authors: NATALI A. N. , PAVAN P. G. , SCHILEO E. , WILLIAMS K. R.
Published: May 2006

summary  Experimental devices based on vibration testing are employed as non‐destructive procedures for evaluating implants osseointegration. Their behaviour was evaluated considering the outcome of numerical analysis. The purpose was to use the finite element method for assessing the ability of frequency analysis in detecting the degree of oral implant osseointegration. A three‐dimensional model of a mandible was obtained from tomographic survey. A single implant was considered in canine region. Two configurations were analysed, with and without a mass linked to the implant as a cantilever, reproducing experimental devices. Simulation consisted of analysing the response to impulse forces for different osseointegration levels, thus evaluating the biomechanical efficiency of the implant‐bone compound. A good correlation between frequency response and osseointegration level was obtained. This was carried out by providing an impulse excitation of the implant that resulted in a vibration pattern. Within the limit of finite element analysis, the outcomes showed that numerical investigation provides understanding the behaviour of testing devices based on frequency measurements, confirming the potential of vibrations technique as non‐invasive analysis for osseointegration process.
A genome rearrangement has orphaned the Escherichia coli K‐12 AcpT phosphopantetheinyl transferase from its cognate Escherichia coli O157:H7 substrates
Authors: De Lay Nicholas R. , Cronan John E.
Published: May 2006

Phosphopantetheinyl transferases (PPTases) are enzymes that catalyse the transfer of a 4′‐phosphopantetheine moiety from CoA to a conserved serine residue of a carrier protein. These carrier proteins use the 4′‐phosphopantetheine thiol to shuttle intermediates between the active sites of biosynthetic enzymes involved in fatty acid, non‐ribosomal peptide and polyketide synthesis. Three PPTases have been previously been identified in Escherichia coli K‐12 and other E. coli strains by homology searches and are encoded by the genes acpS, entD and acpT. Both AcpS and EntD have been well studied whereas the function of AcpT has been an enigma because no carrier protein substrate could be found. We report genetic and biochemical evidence that AcpT modifies two carrier proteins encoded in O‐island 138, a cluster of fatty acid biosynthesis‐like genes located adjacent to acpT in the genome of the pathogenic E. coli strain O157:H7 (E. coli K‐12 and several other sequenced E. coli and Shigella strains lack O‐island 138). The two carrier proteins of O‐island 138 of strain O157:H7 are not modified (or only very poorly modified) by AcpS, the PPTase responsible for 4′‐phosphopantetheine attachment to the acyl carrier protein (AcpP) of fatty acid synthesis. We demonstrate that AcpT cannot functionally replace AcpS in E. coli K‐12 either in its native chromosomal location or upon insertion of acpT into the acpS chromosomal location. However, in the absence of AcpS activity AcpT does allow very slow growth thus providing a rationale for its retention in the absence of its cognate substrates. These results together with phylogenetic analyses and comparisons of the E. coli and Shigella strains of known genome sequence strongly argue that AcpT has been orphaned from its cognate substrates by a deletion event that occurred in a common ancestor of these organisms. This seems one of the few cases where a chromosomal rearrangement has been functionally demonstrated to be a deletion event rather than an insertion event in the reference organism. We also show that the previously reported suppression of an acpS mutation by the deletion of Lon protease is an artifact of the increased capsular polysaccharide production of lon strains.
Induction of transient ethylene and reduction in severity of tomato bacterial wilt by Pythium oligandrum
Authors: Hase S. , Shimizu A. , Nakaho K. , Takenaka S. , Takahashi H.
Published: May 2006

Pythium oligandrum (PO) is a mycoparasite on a wide range of fungi and suppresses diseases caused by fungal pathogens when colonizing the rhizosphere. PO and its cell wall proteins (CWPs) have elicitor activity that induces defence responses in plants. The potential of a mycelial homogenate of PO to suppress bacterial diseases was studied in roots of tomato (Lycopersicon esculentum cv. Micro‐Tom) inoculated with Ralstonia solanacearum. PO‐treated plants showed enhanced resistance to R. solanacearum and reduction in severity of wilt symptoms. As ethylene often acts as one of the signal molecules for induced resistance, its production following treatment of tomato roots with the mycelial homogenate or CWP of PO was measured. The level of ethylene in PO‐ and CWP‐treated plants was transiently elevated six‐ to 11‐fold at 4–8 h after treatment, followed by high expression of three basic ethylene‐inducible defence‐related genes (PR‐2b, PR‐3b and PR‐5b). Analysis of PR‐5b gene expression in the leaves of PO‐ and CWP‐treated plants suggested that PR gene expression was induced systemically. The expression of LeERF2 and LeETR4, which confer an ethylene‐dependent signalling pathway, was also significantly accelerated by such treatments. These results indicate that PO has the potential to control bacterial wilt disease and that CWP may play an important role in the induction of resistance to R. solanacearum accompanying the activation of the ethylene‐dependent signalling pathway.