bluuebunny/crossref_metadata_2025 huggingface dataset:
Variability in the dynamics of northern peripheral versus southern populations of two clonal plant species, Helianthus divaricatus and Rhus aromatica
Authors: Nantel Patrick , Gagnon Daniel
Published: March 2003

1
 The clonal perennial herb Helianthus divaricatus and the clonal shrub Rhus aromatica reach the northern limit of their distribution in southern Québec (Canada), where both are rare, but they are more common southwards in the adjacent province of Ontario. We tested whether peripheral populations of these species maintain themselves by having highly variable individual growth and survival rates. Their annual rates of population growth, λ, would then vary more, from year to year, than those of more southern populations in neighbouring Ontario, where the species are common.

2  Demographic analyses compared, over two transition intervals, size‐based transition matrices for two northern (Gatineau Park, southern Québec) and two southern populations (Pinery Park, southern Ontario) of each species. Comparisons used log‐linear analyses, bias‐corrected λ‐values with 95% confidence intervals, and elasticity values.

3
 For both species, the northern populations showed a larger variation between transition intervals and local populations in some of their vital rates and in λ‐values. For H. divaricatus, elasticity values combined with log‐linear analyses indicated that differences in the growth and survival of medium‐sized ramets contributed most to the differences in λ‐values between northern and southern populations. For R. aromatica, they indicated that differences in the fate of both medium and large ramets contributed to variation in λ.

4
 Most of our data indicated a greater demographic variability in the northern populations of H. divaricatus and R. aromatica. At the northern periphery, these species grow in very few of the numerous habitat patches that appear to be suitable for them, whereas the two species together present a near continuous cover in all suitable habitats further south. High demographic variability therefore appears to contribute to determining the distribution of plant species, by increasing the extinction probabilities of local populations at the distribution limit.
Can plasticity compensate for architectural constraints on reproduction? Patterns of seed production and carbohydrate translocation in Perilla frutescens
Authors: Preston Katherine A.
Published: March 2003

1 The architecture of Perilla frutescens was manipulated by growing plants in a greenhouse under two photoperiodic regimes, representing conditions near the northern and southern ends of the species’ range, to investigate its effect on patterns of seed production. Within each photoperiodic regime, plants were labelled with 14C at one of three developmental stages at one of three leaf positions to assess the effects of architecture on carbohydrate translocation.

2 Perilla flowers in response to short days, i.e. southern‐treatment plants flowered earlier and were smaller and more sparsely branched than northern‐treatment plants. Branch number limits inflorescence number in Perilla, and southern‐treatment plants therefore made fewer inflorescences. Inflorescences are, however, indeterminate, and the southern‐treatment plants made more flowers per inflorescence than the northern‐treatment plants, such that architecture did not constrain flower number.

3 As a result, plants in both treatments made a similar number of seeds and did not differ in total seed mass.

4 Increased seed production per inflorescence was associated with reduced carbohydrate movement between branches and more 14C‐labelled assimilate per seed at the labelled node.

5 In summary, plasticity at the level of the inflorescence largely compensated for architectural constraints on inflorescence number, and was associated with differences in carbon translocation patterns between the photoperiod treatments.
Seasonal occurrence of fire and availability of germinable seeds in Hakea sericea and Petrophile sessilis
Authors: Brown Claire L. , Whelan Robert J.
Published: March 2003

1 Although the season of fire occurrence is known to affect recruitment to plant populations, it has received little attention. This study investigated the dynamics of the canopy‐stored seed banks of two Australian obligate seeder shrubs, Petrophile sessilis and Hakea sericea (Proteaceae), with the objective of determining the changes in viable seed supply over a year.

2 The total number of germinable seeds in the canopy, each month for 12 months during 1996–97, was estimated from separate measures of (i) pre‐dispersal predation of fruits; (ii) seed predation of insect parasitoids; (iii) viability of intact seeds; and (iv) loss of seed viability following experimental heating.

3 The two species had very different seed bank dynamics throughout the year. The seed store of P. sessilis appeared to be being replaced annually, as seeds in the older fruits rapidly lost germinability and new fruits matured to replace them. For H. sericea, the seed store appeared to be accumulating each year, because older fruits retained a high level of germinability.

4 The study indicates that no one fire season will maximize the germinable seed release after fire for all species. Management strategies should therefore include varied seasons of prescribed burning to avoid compositional change and a decrease in diversity that may result from a single‐season approach.
Linking forest edge structure to edge function: mediation of herbivore damage
Authors: Cadenasso M. L. , Pickett S. T. A.
Published: March 2003

1 Forest edges, which are prominent features in the north‐eastern United States landscape, may control the flux of organisms between forest and non‐forest habitats. Previous studies have described edge structure rather than function, as determined by interaction with such fluxes.

2 The function of the forest edge may be linked to the structure of its vegetation. We tested this hypothesis by experimentally altering the structure of the vegetation at two deciduous forest edges in Millbrook, New York, USA. Intact and thinned plots were established at each edge and we determined whether the structure of the edges influenced the flux of herbivores, as measured by herbivore damage to transplanted tree seedlings.

3 Herbivore damage to seedlings at site 1 was affected by edge vegetation structure and by distance from the edge. The edge structure effect was due to herbivory by voles, which was significantly greater in the intact than in the thinned treatment. Regardless of treatment, voles damaged seedlings only on the edge and 30–40 m from the edge and did no damage in the forest interior (90–100 m), whereas deer damaged significantly more seedlings in the forest interior than on the edge. At site 2, where vole damage was concentrated on the edge, damage to seedlings was affected only by distance from the edge, not edge structure.

4 The two dominant herbivores, white‐tailed deer and meadow voles, preferentially damaged different seedling species. In addition, tree seedlings browsed by deer resprouted more frequently than those clipped by voles. Our results suggest that both edge structure and distance from the edge influence herbivore activity and, as a result, influence the spatial arrangement, density and composition of populations of tree seedlings during regeneration in forest fragments.
Designs for greenhouse studies of interactions between plants: an analytical perspective
Authors: Freckleton R. P. , Watkinson A. R.
Published: March 2003

1 Experiments on competition between plant species are frequently designed without considering the analysis stage of the study. We argue that this omission may lead to over‐complication of the issue of designing experiments.

2 An overwhelming number of studies have shown that the effects on performance of competition in plant mixtures may be described by simple (hyperbolic) regression models. The most natural view of the problem of measuring plant competition is therefore as a problem in regression.

3 Only with experiments designed explicitly to apply regression analyses can phenomena such as frequency dependence and the size dependence of measures of competition be identified. In contrast to previous assertions, this means that designs that are based around, or allow, regression analysis are the most robust as such effects may be tested for using appropriate statistics.

4 Experiments are probably most easily designed to measure competition as a function of the density of interacting species, rather than biomass. This is because the per unit biomass effect of competition on performance is a function of density. Competition measures based on biomass will hence be dependent on the density at which the experiment is performed. Furthermore, the most effective way to manipulate biomass is through changing species’ densities.

5 In terms of economy of design, we would recommend simple additive series. Whilst this does not allow the role of frequency dependence to be analysed, this phenomenon appears to be rare in any case.
Soil seed banks in Mediterranean Aleppo pine forests: the effect of heat, cover and ash on seedling emergence
Authors: Izhaki Ido , Henig‐Sever Nava , Ne'Eman Gidi
Published: March 2003

1
 East Mediterranean Aleppo pine (Pinus halepensis) forests are subjected to periodic stand‐replacing fires. We simulated two of the effects of fire on the germinable soil seed bank in four pine stands on Mt. Carmel, Israel, that differed in their post‐fire ages. Soil samples were heated to 100 °C, or covered by pine ash. Vermiculite was used to simulate litter cover.

2  Heat exposure increased overall seedling density, richness and taxon diversity in all stands, but density of annual taxa (e.g. grasses and legumes) were not clearly affected.

3  Ash cover dramatically decreased germination of all taxa and highest germination was achieved with heating and no cover. Vermiculite cover resulted in intermediate germination levels.

4  The combined effect of heat exposure and ash cover, simulating a post‐fire situation under a canopy of pine, reduced the germination level of all taxa in the soil seed bank. However, it also creates conditions that facilitate the establishment of pine seedlings from the canopy stored seed bank.
Fragmentation and changes in hydrologic function of tiger bush landscapes, south‐west Niger
Authors: Wu X. B. , Thurow T. L. , Whisenant S. G.
Published: March 2003

1 Fragmentation of tiger bush landscapes in south‐west Niger between 1960 and 1992 is evidenced by a reduction of percentage woody vegetation cover, changes in the spatial attributes of vegetation patches, and an increase in the spatial heterogeneity of the landscapes. The spatial patterns and dynamics of these landscapes were effectively captured using a combination of selected patch‐based landscape metrics that measured specific aspects of the spatial pattern.

2 Derived from the spatial distribution of the alternating bands of vegetation and bare ground, lacunarity curves provide a particularly effective quantitative measure of the spatial pattern and dynamics of tiger bush landscapes in terms of percentage vegetation cover, spatial heterogeneity, and the domain of scale of the landscape. Lacunarity curves can be used to characterize landscapes in areas with different climates and topographic settings, and are an effective and parsimonious indicator of the fragmentation of tiger bush.

3 The dynamics of the vegetation bands during the fragmentation process was anisotropic. A significantly larger proportion of woody vegetation reduction occurred in the downslope than upslope portions of woody patches, while the opposite was true for woody vegetation expansion. These results corroborate the hypothesis that tiger bush bands migrate upslope due to the upslope–downslope resource gradient across the vegetation band.

4 Fragmentation of the tiger bush landscapes reduced retention of water on site, significantly increasing the landscape permeability to surface flow. When vegetation bands were well connected in 1960, no transects were found that allowed surface water percolation. That is, no path travelling through the bare ground areas was found to connect the upslope edge and downslope edge of any of the 200‐m long transects, regardless of their width (50, 100 or 150 m). By 1992, within the same but now severely fragmented landscapes transects of all widths allowed water to percolate across them (44% if 50 m wide to 89% if 150 m wide). This increased landscape permeability to surface flow may have reduced the water available to the remaining fragmented vegetation bands and accelerated their degradation.
Effects of pollution‐induced habitat disturbance on the response of willows to simulated herbivory
Authors: Zvereva E. L. , Kozlov M. V.
Published: March 2003

Stress may affect compensatory plant growth and plant responses to herbivory may therefore be modified by pollution. We compared the effects of leaf clipping on growth, reproduction and developmental stability of two willow species (Salix borealisandS. caprea) growing at different distances from two copper‐nickel smelters (Monchegorsk, NW Russia and Harjavalta, SE Finland).

 In unpolluted sites, the defoliation of both willow species adversely affected sexual reproduction and increased the formation of epicormic shoots, but did not change either shoot growth or leaf size. Timing and extent of clipping had little effect on the responses.

 Compensatory responses to leaf clipping in polluted habitats were reduced, especially inS. borealis, as reflected by decrease in shoot growth and fruit production and an increase in leaf fluctuating asymmetry, a non‐specific indicator of stress.

 Activation of dormant buds was a common compensatory response to herbivory in unpolluted sites. The lack of an increase in epicormic shoots in polluted sites may be due to already weakened apical dominance.

 Compensatory abilities may be affected both by direct damage caused by pollutants and pollution‐induced increases in environmental stress. AlthoughS. borealisshows no visible sign of stress in polluted sites, regrowth from dormant buds and enhanced shoot growth were seen under these conditions. Resources were not therefore available for further compensation of damage caused by defoliation. Our results fit the hypothesis that fast growing plants have low compensative abilities.

 Salix capreashows more pollution‐induced stress thanS. borealis, expressed as increased developmental instability near the weaker and shorter shoots near the stronger pollution source. This may explain the differences in their compensatory responses in polluted sites.
Allometry and plasticity of meristem allocation throughout development in Arabidopsis thaliana
Authors: Bonser Stephen P. , Aarssen Lonnie W.
Published: March 2003

The three principal fates of axillary meristems in flowering plants are branching or vegetative growth, reproduction, and inactivity. We examined the relationship between allocation to each of these fates and plant size in five genotypes of Arabidopsis thaliana. Nutrient availability was used to obtain a range of plant size.

Allocation to each meristem fate was recorded at weekly intervals throughout development and at final developmental stage.

 There were significant allometric relationships between meristem allocation and plant size for each meristem fate throughout development in each genotype. Allometry and plasticity tended to be strongest early in development. In addition, although there were differences in allometry between genotypes, meristem allocation through development was generally consistent across genotypes.

 We interpret the results of this study as an adaptive response to nutrient availability. Increased allocation to growth meristems in high nutrient treatments early in development should maximize both size and the total number of meristems that can be committed to reproduction later in development. This suggests that the pattern of meristem allocation is a component of an adaptive strategy through development in Arabidopsis thaliana.
Habitat and successional status of plants in relation to the communities of their leaf‐chewing herbivores in Papua New Guinea
Authors: Lepš Jan , Novotný Vojtěch , Basset Yves
Published: March 2003

The spatial distribution of 30 woody species (15 species each of Euphorbiaceae and Moraceae) and their associated leaf‐chewing communities (Orthoptera, Phasmatodea, Coleoptera and Lepidoptera) were studied in coastal, riverine and rain forest habitats. A successional series, from abandoned gardens to primary forest, was examined. Host plant records for more than 27 000 insects, all verified by feeding experiments, and spatial distribution of almost 9000 plant specimens were evaluated.

 Phylogenetic (taxonomic) relatedness of host plants explained 56% of the variability in the composition of their herbivore communities, while the ecological (distribution) similarity of plants explained only 4%.

 The successional optimum of plant species was not an important determinant of the composition of their herbivore communities.

 Neither plant successional optimum nor plant palatability to a generalist herbivore were correlated with the number of species, abundance or host specificity of its herbivores, nor was there a correlation between a plant’s palatability to a generalist herbivore and its successional optimum.

 Herbivore communities became dominated increasingly by a few abundant species in later stages of succession.

 On average,Ficusspecies had lower palatability and supported more species of herbivores than species of Euphorbiaceae. The abundance of herbivores and their dominance index were not significantly different between the two plant families.

 These results contradict several previous studies of successional trends in temperate regions. Many tropical successions, however, start with pioneer trees, rather than with annual herbs, and may present a permanent and predictable habitat for insects even at the earliest stages, with no advantage for polyphagous species. Numerous pioneer trees in the tropics possess anti‐herbivore defences, resulting in their low palatability to generalists, increased host specificity of herbivores, and often idiosyncratic composition of herbivore communities. Even plant traits such as species richness of their herbivores or palatability may have a phylogenetic component which should not be ignored.
Persistence of coastal spruce refugia during the Holocene in northern New England, USA, detected by stand‐scale pollen stratigraphies
Authors: Schauffler Molly , Jacobson George L.
Published: March 2003

1 Pollen data from wet, forested hollows in five spruce (Picea) stands on the eastern coast of Maine, USA, reveal that spruce has been well‐established (spruce pollen > 6%) for at least 5000 years at four of the sites (Isle au Haut, Schoodic Peninsula, and Roque Island). Spruce became dominant in the fifth stand (Blackwoods, Mount Desert Island) only in the last 2000 years. This is in contrast to pollen stratigraphies from two inland forest hollows and from inland lakes that indicate a significant region‐wide increase in the abundance of spruce only 1000 years ago.

2 All five coastal pollen stratigraphies suggest that conditions along the east coast of Maine became cooler and moister sometime between 6000 and 5000 years ago. Mid‐Holocene changes in vegetation and sediment accumulation correspond with the timing of rapid increases in tidal amplitude and diurnal mixing of cold water in the Gulf of Maine, suggestive that these resulted in increased marine effects on the local climate at a time that was generally warmer than present.

3 Two inland forest‐hollow stratigraphies do not show evidence of mid‐Holocene cooling. Coastal effects therefore persisted for several thousand years despite regional climate changes.

4 The pollen data suggest that refugia along the coast (and probably in isolated sites inland), may have played a critical role in allowing the rapid regional expansion of spruce around 1000 years ago. The steep increases in the abundance of spruce pollen in all forest‐hollow and lake pollen stratigraphies in northern New England at that time corroborate other evidence of a region‐wide shift to cooler and moister conditions.

5 Pollen stratigraphies from small forested hollows provide a means to examine local vegetation dynamics and interpret those dynamics in the context of regional signals.
Why does fertilization reduce plant species diversity? Testing three competition‐based hypotheses
Authors: Rajaniemi Tara K.
Published: March 2003

1 Plant species diversity drops when fertilizer is added or productivity increases. To explain this, the total competition hypothesis predicts that competition above ground and below ground both become more important, leading to more competitive exclusion, whereas the light competition hypothesis predicts that a shift from below‐ground to above‐ground competition has a similar effect. The density hypothesis predicts that more above‐ground competition leads to mortality of small individuals of all species, and thus a random loss of species from plots.

2 Fertilizer was added to old field plots to manipulate both below‐ground and above‐ground resources, while shadecloth was used to manipulate above‐ground resources alone in tests of these hypotheses.

3 Fertilizer decreased both ramet density and species diversity, and the effect remained significant when density was added as a covariate. Density effects explained only a small part of the drop in diversity with fertilizer.

4 Shadecloth and fertilizer reduced light by the same amount, but only fertilizer reduced diversity. Light alone did not control diversity, as the light competition hypothesis would have predicted, but the combination of above‐ground and below‐ground competition caused competitive exclusion, consistent with the total competition hypothesis.
Temporal changes in spatial patterns of soil moisture following disturbance: an experimental approach
Authors: Guo Dali , Mou Pu , Jones Robert H. , Mitchell Robert J.
Published: March 2003

1 We quantified changes in spatial heterogeneity of soil moisture over 2.5 years in a Pinus elliottii Engelm. forest, following disturbance and succession. We harvested or girdled upper canopy trees and measured three components of heterogeneity – global (non‐spatial) variability, spatial dependence and temporal persistence – in replicate plots, using sample points arrayed at a fine scale (0.5–6 m) nested within a coarser scale (5–60 m).

2 Global variability increased after disturbance and then declined, eventually returning to the level recorded in an undisturbed plot. Harvesting resulted in greater, more rapid and more prolonged changes in global variability than girdling.

3 Geostatistical parameters for measuring spatial dependence were largely unaffected by disturbance. Spatial dependence was, however, quite variable across replicate plots and was stronger at the finer sampling scale.

4 Spearman rank correlations showed that the spatial pattern of soil moisture had greater long‐term persistence in the undisturbed and girdled plots than in the harvested plots.

5 Some elements of spatial heterogeneity appear to vary over time in a predictable manner. Detection of temporal trends may be improved if multiple components of heterogeneity are quantified, more than one scale of observation is used, replicate plots are employed and sole reliance on geostatistics is avoided.
Riposte to Guest Commentaries on ‘Problems associated with randomized controlled clinical trials in breast cancer’
Authors: Johnson Ann E.
Published: March 2003

This paper addresses the objections of Professor M. Baum and Mr W. J. Cunliffe to my thesis that the randomized controlled clinical trial is a poor tool for the investigation of the treatment of breast cancer, argued in a discussion paper entitled ‘Problems associated with randomized controlled clinical trials in breast cancer’ (A.E. Johnson, 1998, Journal of Evaluation in Clinical Practice4, 119–126). The objections range from those that have a philosophical basis, through those founded on differing concepts of the classification of primary tumours and the nature of the metastatic tumour, to those that question the reliability and usefulness of the clinical evaluation of response to treatment in terms of histological grade and rate of tumour shrinkage. An alternative approach to research through primary systemic therapy with selection of treatment according to predicted tumour behaviour was severely criticized, both on the preceding grounds and because it was assumed that the alternative to randomization is management by anecdote.

These objections are examined and evidence in support of reliable and useful clinical measurement of response is presented in some detail. The problems associated with randomization as a technique for the evaluation of treatments, when the intrinsic variability of tumours is very large without the intervention of treatment, remain unsolved.
EDUCATION: Mandatory practice self‐appraisal: moving towards outcomes based continuing education
Authors: Donen Neil
Published: March 2003

Abstract: Most organized physician continuing educational activities are undertaken without assessing their effects on long‐term changes in physician practice patterns, patient outcomes or return on investment. Practice audit and practice self‐appraisal are two activities that can be used to achieve these objectives. It is recommended that these be promoted from an educational perspective. A series of principles, including the mandatory application of practice audit and practice self‐appraisal are proposed to guide the process. The identification of issues relating to learning, diffusion of information and behavioural change required to facilitate this change are briefly discussed.
Publishing web‐based guidelines using interactive decision models
Authors: Sanders Gillian D. , Nease Robert F. , Owens Douglas K.
Published: March 2003

Commonly used methods for guideline development and dissemination do not enable developers to tailor guidelines systematically to specific patient populations and update guidelines easily. We developed a web‐based system,ALCHEMIST, that uses decision models and automatically creates evidence‐based guidelines that can be disseminated, tailored and updated over the web. Our objective was to demonstrate the use of this system with clinical scenarios that provide challenges for guideline development. We used theALCHEMISTsystem to develop guidelines for three clinical scenarios: (1)Chlamydiascreening for adolescent women, (2) antiarrhythmic therapy for the prevention of sudden cardiac death; and (3) genetic testing for the BRCA breast‐cancer mutation.ALCHEMISTuses information extracted directly from the decision model, combined with the additional information from the author of the decision model, to generate global guidelines.ALCHEMISTgenerated electronic web‐based guidelines for each of the three scenarios. UsingALCHEMIST, we demonstrate that tailoring a guideline for a population at high‐risk forChlamydiachanges the recommended policy for control ofChlamydiafrom contact tracing of reported cases to a population‐based screening programme. We usedALCHEMISTto incorporate new evidence about the effectiveness of implantable cardioverter defibrillators (ICD) and demonstrate that the cost‐effectiveness of use of ICDs improves from $74 400 per quality‐adjusted life year (QALY) gained to $34 500 per QALY gained. Finally, we demonstrate how a clinician could useALCHEMISTto incorporate a woman’s utilities for relevant health states and thereby develop patient‐specific recommendations for BRCA testing; the patient‐specific recommendation improved quality‐adjusted life expectancy by 37 days. TheALCHEMISTsystem enables guideline developers to publish both a guideline and an interactive decision model on the web. This web‐based tool enables guideline developers to tailor guidelines systematically, to update guidelines easily, and to make the underlying evidence and analysis transparent for users.
The potential influence of small group processes on guideline development
Authors: Pagliari Claudia , Grimshaw Jeremy , Eccles Martin
Published: March 2003

The authors discuss the important and often neglected role of psychosocial factors in guideline development. Such factors can influence the process by which guideline development groups interact, make decisions and achieve consensus, which may have important implications for the validity and reliability of the recommendations they produce. Particular attention is paid to the role of social influence within multidisciplinary groups and the importance of good chairmanship. Recommendations for participants, chairmen and guideline development bodies are given.
Medical ethics education: to what ends?
Authors: Gross Michael L.
Published: March 2003

The goals of medical ethics education comprise several dimensions: legal duties to secure informed consent, tell the truth and protect confidentiality; objective competencies that include an understanding of DNR regulations and surrogate decision‐making procedures; discursive moral skills such as moral sensitivity, reciprocity and moral development that combine into the capacity for moral dialogue and debate; and finally, behavioural goals that challenge moral education to nurture a more humane, sensitive and communicative physician. Part one of this paper describes each of these goals, together with some of the inherent difficulties affecting implementation. Part two presents survey data from medical ethics instructors (n= 126) who were asked about the importance of each goal and their ability to successfully achieve each aim. While each goal is highly rated, only those goals associated with legal duties and objective competencies are thought to be achieved with any degree of relative success. Goals associated with character transformation, unique to medical ethics education, are among the most difficult to achieve. Additional empirical data corroborate these impressions. Moreover, it is not clear that medical ethics education has much to do with good care. Empirical data are scarce and the conceptual relationship between ethics and care remains highly problematic. Part three offers a number of divergent interpretations of care and concludes that they have little to do with medical ethics. There is no reason to expect that medical competence should be affected by moral competence. Medical ethics therefore might then be viewed as an educational enhancement: unnecessary for healthy doctoring but desirable among a small percentage of the profession who maintain an interest in ethical problems.
Haemorrhagic kidney syndrome of Atlantic salmon, Salmo salar L.
Authors: Byrne  , MacPhee  , Ostland  , Johnson  , Ferguson
Published: March 2003

This report describes a new syndrome affecting farmed Atlantic salmon on the Canadian east coast that has resulted in increased morbidity and mortality in affected stocks. The major pathological findings are apparent only microscopically and include renal interstitial haemorrhage and acute tubular necrosis and tubular casting. As a result, the disease has become known as haemorrhagic kidney syndrome (HKS). Affected fish are lethargic and anorectic, and lack external lesions. Clinically, HKS fish are anaemic, hypoproteinaemic and hyperosmolalic, with increased serum concentrations of sodium and chloride. At necropsy, internal changes ranged from apparently normal to include one or several of the following: swelling and/or patchy reddening of the kidney, pale gills, exophthalmos, serosanguinous ascites, darkening of the posterior intestine and splenomegaly. Ultrastructurally, viral inclusions were found in the cytoplasm of erythrocytes of HKS fish, and there were unusual electron‐dense inclusions within the tips of renal tubular microvilli of HKS fish. The significance and relevance of the ultrastructural findings to HKS are unknown. Virus isolation was attempted using CHSE, RTG‐2, FH‐10, BB and EPC cell lines; no virus was isolated. Bacteriological analysis failed to reveal significant pathogens. Analysis of tissues for heavy metals and pesticides was negative. Assays for clostridial toxins, lipopolysaccharide and verotoxins were negative. The aetiology of HKS remains unresolved.
Examination of abdominal organs and diagnosis of deficient septum transversum in Atlantic salmon, Salmo salar L., using diagnostic ultrasound imaging
Authors: Poppe  , Midtlyng  , Sande
Published: March 2003

The use of diagnostic ultrasound for non‐invasive diagnosis of hypoplasia or aplasia of septum transversum in farmed Atlantic salmon, Salmo salar L., is described. This investigation shows that this method is fast and accurate (sensitivity = 100%; specificity 97.87%). We therefore recommend the method to be used both experimentally and in the field. As the causes of this malformation are unknown, it is recommended that broodfish with this anomaly should be excluded from the broodfish pool.
Non‐specific immune response of Nile tilapia, Oreochromis nilotica, to the extracellular products of Mycobacterium spp. and to various adjuvants
Authors: Chen  , Yoshida  , Adams  , Thompson  , Richards
Published: March 2003

Nile tilapia were immunized by injecting extracellular products (ECP) of Mycobacterium spp. (strain TB40, TB267 or the type strain Mycobacterium marinum) into their swim bladders. A variety of adjuvants – Freund's complete adjuvant (FCA), Freund's incomplete adjuvant (FIA) and Titremax – were similarly injected into additional groups of tilapia. Phosphate‐buffered saline (PBS) was used as a control. The number of nitroblue tetrazolium (NBT)‐positive cells observed in the swim bladder of the immunized fish had significantly increased by the fourth day post‐immunization. By day 8, the number of NBT‐positive cells in fish immunized with ECP from mycobacteria strains TB40 or TB267 were fewer than in fish immunized with ECP from M. marinum or fish injected with FCA or FIA. The level of lysozyme activity detected in the serum of fish 4 days after being immunized with ECP from various Mycobacterium spp. was also significantly higher than that found in the serum of the control fish. Head kidney macrophages showed an enhanced reduction of NBT when cultured in vitro with 1 μg ml–1 of ECP. Concentrations greater than this (10 or 100 μg ml–1) were found to suppress the reduction of NBT by the macrophages.
Channel catfish virus: interaction with the cytoskeleton
Authors: Pope R. K. , Scheetz R. W.
Published: March 2003

The infection of channel catfish ovarian cells with channel catfish virus results in the redistribution of all cytoskeletal elements during virus‐induced syncytium formation. Actin filaments are normally arranged as large stress fibres, even during early stages of infection, but become redistributed as densely staining regions near the centre of the syncytium in latent infection. Microtubules and vimentin filaments (easily visible in early infection) lose all visible organization during syncytium formation. Stabilization of microtubules with taxol results in the production of elongate syncytia with regularly organized microtubules. Conversely, disruption of microtubules with nocodazole inhibits cell fusion and causes a reduction in infectious virus production. This reduction upon treatment with nocodazole, and the subsequent rescue of virus production upon addition of taxol indicates that viral replication relies upon the presence of microtubules.
A rapid ELISA method for detecting specific antibody level against nodavirus in the serum of the sea bass, Dicentrarchus labrax (L.): application to the screening of spawners in a sea bass hatchery
Authors: Breuil G. , Romestand B.
Published: March 2003

The use of an indirect elisa for the detection of the sea bass, Dicentrarchus labrax (L.), antibody to nodavirus is described. The sera of 110 adult sea bass (78 females and 32 males) maintained in captivity were analysed, and the females were individually classified in seropositive (16%) and seronegative (56%) groups, while some fish (28%) with low but detectable antibody levels were not classified. The proportion of seropositive males was smaller (3.1%) than the females. Repeated serological examination of 18 individually labelled females (spawners) revealed no changes over 5 months. The immunization of sea bass females with heat‐killed nodavirus induced antibody titre as reflected by corresponding changes in
elisa optical density readings. The antibody level increased 4 weeks post‐immunization and was still detectable after 41 weeks. These preliminary results suggest the possibility of detecting virus‐positive or virus‐negative animals in attempts to reduce and prevent the vertical transmission of the virus in sea bass hatcheries.
Atypical bacterial gill disease: a new form of bacterial gill disease affecting intensively reared salmonids
Authors: Ostland V. E. , Byrne P. J. , Lumsden J. S. , MacPhee D. D. , Derksen J. A. , Haulena M. , Skar K. , Myhr E. , Ferguson H. W.
Published: March 2003

An unusual form of bacterial gill disease (BGD) was identified which affected five species of cultured salmonids from Canada (i.e. rainbow trout, chinook salmon and Atlantic salmon), Norway (i.e. brown trout) and Chile (i.e. coho salmon). All outbreaks occurred at low water temperatures (< 10 °C) and with clinical presentations distinct from classical BGD, which is caused by Flavobacterium branchiophilum. In contrast to classical BGD, fish did not show marked respiratory distress with flaring of the opercula, the animals did not orientate at the surface of the water column near inflow water or at the margins of the tanks, and the feed response of the fish was varied. While mortality was increased, it was not precipitous as in classical BGD. Eight outbreaks were examined in greater detail using histopathology, scanning electron microscopy, bacteriology and immunohistochemistry. Large numbers of small bacterial rods were seen adhering to the lamellar epithelium of affected gills from all outbreaks. Histologically, the lamellar epithelium appeared swollen, often with evidence of single cell degeneration and exfoliation. In more severe instances, the formation of lamellar synechiae was seen, usually associated with sequestration of bacteria between fused lamellae. By contrast with typical BGD, overt epithelial hyperplasia, lamellar fusion and filamental clubbing were not common sequelae to infection; instead, the end result was shortened and somewhat stubby lamellae covered with swollen epithelial cells. The predominant bacterium recovered from affected gills was a small, Gram‐negative, motile, fluorescent pigment‐producing rod that shared phenotypic characteristics with Pseudomonas fluorescens. Polyclonal antisera prepared against three representative isolates indicated a weak antigenic similarity among them. Immunohistochemistry corroborated this finding, in that the antisera reacted strongly with gill sections containing the homologous bacteria, but not against morphologically similar bacteria in heterologous sections. A Gram‐negative, yellow pigmented bacterium (YPB), identified as Flavobacterium psychrophilum, was also recovered, but only from the gills in the Ontario outbreaks. Antiserum prepared against this YPB indicated an antigenic similarity among isolates recovered from the Ontario outbreaks, but immunohistochemistry failed to recognize antigenically related bacteria on the gills of fish from the other outbreaks. Based on the unusual clinical presentation and the histopathological appearance of the gills, in conjunction with the absence of filamentous bacteria associated with and recovered from affected gills, the present authors have called this condition ‘atypical bacterial gill disease’ or ABGD.
Species‐specific polymerase chain reaction primers for Lactococcus garvieae
Authors: Aoki T. , Park C‐I. , Yamashita H. , Hirono I.
Published: March 2003

A dihydropteroate synthase gene from the chromosomal DNA of the fish‐pathogenic bacteria Lactococcus garvieae (formerly Enterococcus seriolicida) was cloned. This gene was then chosen as the target for polymerase chain reaction (PCR). The designated PCR primer set only amplified a 709‐bp DNA fragment from L. garvieae strains, and did not amplify the same molecular size fragment from related species of L. lactis, Enterococcus faecalis, E. faecium or β‐haemolytic Streptococcus sp. The kidney tissue of yellowtail, Seriola quinqueradiata (Temminck and Schlegel), a species which is naturally infected with L. garvieae, and also kidney tissue samples of healthy yellowtail were stored in TNES‐Urea. The DNA was extracted from tissue samples by a modification of the standard method and by a boiled‐extraction method. In particular, template DNA was utilized within 30 min following extraction and purification by the boiled‐extraction method. These species‐specific PCR primers could amplify a L. garvieae target sequence from yellowtail which were naturally infected with L. garvieae. The total procedure for the diagnosis of L. garvieae infections in fish, from the point of DNA extraction to observation in an agarose gel following electrophoresis, can be performed in less than 4 h.
Changes in immune and enzyme histochemical phenotypes of cells in the intestinal mucosa of Atlantic salmon, Salmo salar L., with soybean meal‐induced enteritis
Authors: Bakke‐McKellep A M , Press C McL , Baeverfjord G , Krogdahl Å , Landsverk T
Published: March 2003

Extracted soybean meal (SBM) in the diet for Atlantic salmon, Salmo salar L., causes an inflammatory response in the distal intestine. The morphological changes of the epithelial cells and a characterization of the inflammatory cell infiltrate of the distal intestinal mucosa were studied using a panel of enzyme and immunohistochemical markers. The salmon (average body weight 927 g) used in the study were fed either a fishmeal‐based diet (control diet) or a diet in which 30% of the fishmeal protein was replaced with SBM protein (SBM diet). In salmon fed SBM, there were markedly reduced enzyme reactivities in the distal intestinal epithelial cells, both in the brush border [5′‐nucleotidase (5′N), Mg2+‐ATPase, alkaline phosphatase (ALP) and leucine aminopeptidase (LAP)] and in the intracellular structures [alkaline and acid phosphatase, non‐specific esterase (NSE) and alanine aminopeptidase (AAP)]. There appeared to be an increased presence of cells of monocytic lineage, including macrophages, as well as neutrophilic granulocytes and immunoglobulin (Ig) M in the lamina propria of the SBM‐fed fish. The mid intestine showed little response to the diet. The results suggest that toxic/antigenic component(s) of SBM affect the differentiation of the distal intestinal epithelial cells and may help explain the reduced nutrient digestibilities previously reported in salmonids fed extracted SBM.
Induction of apoptosis in tilapia, Oreochromis aureus Steindachner, and in TO‐2 cells by Staphylococcus epidermidis
Authors: Huang S‐L , Liao I‐C , Chen S‐N
Published: March 2003

This study describes apoptosis induced in vivo and in vitro in tilapia, Oreochromis aureus Steindachner, by Staphylococcus epidermidis. In an in vivo experiment, tilapia were challenged using viable S. epidermidis and its cultured supernatant, respectively. Apoptosis was predominantly detected in lymphocytes and macrophages in spleen and kidney. Apoptotic figures were observed occasionally in the brain, liver, gonad, mesentery, stomach, intestine and skeletal muscle of infected fish. In an in vitro experiment, TO‐2 cells treated with brain heart infusion broth supernatant of the bacteria after 48 h revealed that the supernatant was able to induce the cell apoptosis. Fragmented DNA was also detected 48 h after treatment using 1.5% agarose gel electrophoresis. The smallest multimeric DNA fragment was approximately 180‐bp in length. Results of both the in vitro and in vivo experiments showed that products of the bacteria could induce tilapia cell apoptosis.
Immunohistochemical detection of neuromodulators in the intestine of Salmo trutta L. naturally infected with Cyathocephalus truncatus Pallas (Cestoda)
Authors: Dezfuli B S , Arrighi S , Domeneghini C , Bosi G
Published: March 2003

Pathological and immunohistochemical investigations were carried out on the middle intestine of uninfected and parasitized brown trout, Salmo trutta L., from the Ceresone Channel in North Italy. Eighty‐six brown trout were sampled by electrofishing, and 32 (37.2%) were infected with Cyathocephalus truncatus Pallas, 1781 (Cestoda). The intensity of infection ranged from 1 to 82 parasites per host and the most infected segments were the anterior (near the pyloric caeca region) and the central part of the middle intestine. Immunohistochemical tests were applied on sections of intestinal tissue of healthy and infected fish, and the presence of substance P (SP), calcitonin gene related peptide (CGRP), met‐enkephalin, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and serotonin (5‐HT) was documented. Endocrine epithelial cells of the tunica mucosa were positive to SP‐, CGRP‐, met‐enkephalin‐, and NPY‐like peptides and 5‐HT antisera; moreover, a higher number of these cells were recorded in the intestine of infected trout in comparison to uninfected fish. In addition, in parasitized S. trutta, SP‐like and 5‐HT immunoreactivities were found in likely immuno‐related cells of the tunica propria‐submucosa. Nerve cell bodies and terminals in the myenteric plexus were immunoreactive to almost all the tested peptides and 5‐HT antisera. These data provide evidence for the role of the neuroendocrine system of S. trutta in the modulation of inflammatory responses to C. truncatus. Results are discussed with respect to a peptidergic involvement and host immune response to an intestinal tapeworm.
Passive immunization of tilapia, Oreochromis niloticus (L.), with anti‐Streptococcus iniae whole sera
Authors: Shelby R A , Klesius P H , Shoemaker C A , Evans J J
Published: March 2003

Passive immunization of tilapia, Oreochromis niloticus, was conducted to determine whether anti‐Streptococcus iniae whole sera (ASI), heat inactivated anti‐S. iniae whole sera (HIASI) and normal whole sera (NWS) were protective when intraperitoneally (i.p.) injected into tilapia. The ASI was produced in tilapia actively immunized (challenged) with virulent S. iniae by i.p. injection. An antibody response against S. iniae was demonstrated by enzyme linked immunosorbent assay (ELISA) and 18% of the immunized fish died because of the S. iniae infection. The actively immunized tilapia demonstrated a secondary antibody response and immunity to S. iniae after challenge with S. iniae by i.p. injection. Survival was 100% in the actively immunized fish. The NWS was obtained from tilapia free of ASI antibody and susceptible to S. iniae infection (40% mortality). In two separate experiments, significantly higher mortality was noted in tilapia passively immunized with NWS (33 and 53%) and phosphate buffered saline (PBS) (30 and 60%), in comparison with mortalities of 0 and 10% or 3.3 and 6.7% in the fish passively immunized with ASI or HIASI 14 days after S. iniae infection by i.p. injection (P = 0.0003 and 0.0023). Results suggest that immunity provided by ASI and HIASI was because of antibody against S. iniae. Inactivation of complement in the HIASI treatment further suggests that ASI antibody plays a primary role in immunity against S. iniae infection.