bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial variation in mink and muskrat interactions in Canada
Authors: Erb John , Boyce Mark S. , Stenseth Nils ChR.
Published: December 2004

We investigated the spatial attributes of mink (Mustela vison) and muskrat (Ondatra zibethicus) interactions in Canada using 160 geographically paired historic time series of mink (n=80) and muskrat (n=80) harvest data obtained from Hudson's Bay Co. Archives. All series were 25 years in length (1925–1949) and were distributed primarily throughout five ecozones. We used autoregressive models and cross‐correlation analysis to characterize the interactions between mink and muskrat. Model selection results did not differ among ecozones, and indicated that a predator‐prey autoregressive model incorporating a delayed density‐dependent term best described both the mink and muskrat harvest time series. Subsequent analysis of autoregressive coefficients and estimated lags indicated that mink and muskrat interactions vary throughout Canada. In western Canada, the trophic interactions appear to be strong, and mink population cycles lag behind muskrats 2–3 years. In central Canada, mink harvests lagged behind muskrats 1 year, and mink and muskrat interactions in central Canada, with the exception of the Hudson Plains ecozone, were intermediate. In eastern Canada, the trophic interactions appeared weakest, and there were no distinct time lags between mink and muskrat. Stronger interactions in western Canada may be a result of decreased prey diversity, forcing mink to specialize more on muskrats, whereas comparatively stronger perturbations stemming from other trophic interactions may alter the estimated interaction between mink and muskrat in eastern Canada.
Are goose nesting success and lemming cycles linked? Interplay between nest density and predators
Authors: Bêty Joël , Gauthier Gilles , Giroux Jean‐François , Korpimäki Erkki
Published: December 2004

The suggested link between lemming cycles and reproductive success of arctic birds is caused by potential effects of varying predation pressure (the Alternative Prey Hypothesis, APH) and protective association with birds of prey (the Nesting Association Hypothesis, NAH). We used data collected over two complete lemming cycles to investigate how fluctuations in lemming density were associated with nesting success of greater snow geese (Anser caerulescens atlanticus) in the Canadian High Arctic. We tested predictions of the APH and NAH for geese breeding at low and high densities. Goose nesting success varied from 22% to 91% between years and the main egg predator was the arctic fox (Alopex lagopus). Nesting associations with snowy owls (Nyctea scandiaca) were observed but only during peak lemming years for geese nesting at low density. Goose nesting success declined as distance from owls increased and reached a plateau at 550 m. Artificial nest experiments indicated that owls can exclude predators from the vicinity of their nests and thus reduce goose egg predation rate. Annual nest failure rate was negatively associated with rodent abundance and was generally highest in low lemming years. This relationship was present even after excluding goose nests under the protective influence of owls. However, nest failure was inversely density‐dependent at high breeding density. Thus, annual variations in nest density influenced the synchrony between lemming cycles and oscillations in nesting success. Our results suggest that APH is the main mechanism linking lemming cycles and goose nesting success and that nesting associations during peak lemming years (NAH) can enhance this positive link at the local level. The study also shows that breeding strategies used by birds (the alternative prey) could affect the synchrony between oscillations in avian reproductive success and rodent cycles.
Inter‐ and intraspecific relationships between shade tolerance and shade avoidance in temperate trees
Authors: Henry Hugh A. L. , Aarssen Lonnie W.
Published: December 2004

Patterns of physiological and architectural adaptation and acclimation to decreasing light availability were investigated along a light gradient for saplings of 12 common species of temperate deciduous trees in southeastern Ontario, Canada. Physiological adaptation and acclimation (shade tolerance physiology) were quantified at the leaf level by measuring leaf mass per unit area (LMA), dark respiration per unit leaf nitrogen, chlorophyll per unit leaf nitrogen and the chlorophyll a:b ratio for the newest fully expanded leaf on the leader. Architectural adaptation and acclimation (shade avoidance) were quantified by measuring branching intensity and side shoot:main shoot length ratios for the most recent three years of growth on the leader and selected side branches. Within species, increases in LMA, chlorophyll a:b ratio and respiration per unit nitrogen and decreases in chlorophyll per unit nitrogen indicated that shade tolerance physiology generally increased with decreasing canopy openness. Increases in the branching intensity and side shoot:main shoot ratios of the leader and side branches indicated that shade avoidance also increased with decreasing canopy openness for the majority of species; however, in some species, stem bending under deep shade resulted in lateral growth. Interspecific variation in shade tolerance physiology was minimal when species were compared under equal amounts of canopy openness. In contrast, interspecific variation in shade avoidance variables was relatively high under equal canopy openness, with saplings of shade tolerant canopy species exhibiting higher shade avoidance than saplings of shade tolerant understory species.
Statistical significance versus fit: estimating the importance of individual factors in ecological analysis of variance
Authors: Graham Michael H. , Edwards Matthew S.
Published: December 2004

Although analysis of variance (ANOVA) is widely used by ecologists, the full potential of ANOVA as a descriptive tool has not been realized in most ecological studies. As questions addressed by ecologists become more complex, and experimental and sampling designs more complicated, it is necessary for ecologists to estimate both statistical significance and fit when comparing the relative importance of individual factors in an explanatory model, especially when models are multi‐factorial. Yet, with few exceptions, ecologists are only presenting significance values with ANOVA results. Here we review methods for estimating statistical fit (magnitude of effect) for individual ANOVA factors based on variance components and provide examples of their application to field data. Furthermore, we detail the potential occurrence of negative variance components when determining magnitude of effects in ANOVA and describe simple remediation procedures. The techniques we advocate are efficient and will greatly enhance analyses of a wide variety of ANOVA models used in ecological studies. Estimation of magnitude of effects will particularly benefit the analysis of complex multi‐factorial ANOVAs where emphasis is on interpreting the relative importance of many individual factors.
The effects of gap creation on competitive interactions: separating changes in overall intensity from relative rankings
Authors: Suding Katharine Nash
Published: December 2004

A central assumption of disturbance ecology equates gap creation with the reduction of overall competitive intensity. I develop the idea that gap creation, due to changes in addition to biomass removal, could also alter the relative competitive rankings among species. I present a quantitative review using meta‐analysis in which I separate the effect of gap creation from the effect of competition for species characteristic of different disturbance regimes. Twenty‐one studies (with a total of 136 comparisons) directly examined species competitive abilities under gap (disturbed) and matrix (undisturbed) conditions. Overall competitive intensity generally declined in gap conditions, although species characteristic of gap areas responded more strongly to gap creation than did species characteristic of undisturbed matrix areas. Under matrix conditions, matrix species were less affected by competition than gap species, supporting one widespread assumption. However, under gap conditions, matrix and gap species were inhibited to a similar degree by neighbor biomass. These results suggest that gap creation, in addition to decreasing overall competitive intensity, may affect species competitive rankings, possibly due to changes in the environment where the interactions occur.
Shift to mutualism in parasitic lineages of the fig/fig wasp interaction
Authors: Jousselin Emmanuelle , Rasplus Jean‐Yves , Kjellberg Finn
Published: December 2004

The interaction between Ficus and their pollinating wasps (Chalcidoidea, Agaonidae) represents a striking example of mutualism. Figs also host numerous non‐pollinating wasps belonging to other chalcidoid families. We show that six species of Ficus that are passively pollinated by the agaonid genus Waterstoniella also host specific wasps belonging to the chalcidoid genera Diaziella (Sycoecinae) and Lipothymus (Otitesellinae). Both belong to lineages that are considered as parasites of the fig/fig wasp mutualism. We show that these wasps are efficient pollinators of their hosts. Pollen counts on wasps of a species of Diaziella hosted by Ficus paracamptophylla show that Diaziella sp. transports more pollen than the associated pollinator when emerging from its natal fig. Further, the number of pollinated flowers in receptive figs is best explained by the number of Diaziella plus the number of Waterstoniella that had entered it. Figs that were colonised by Diaziella always produced seeds: Diaziella does not overexploit its host. Similarly, figs of Ficus consociata that were colonised solely by a species of Lipothymus produced as many seeds as figs that were colonised only by the legitimate pollinator Waterstoniella malayana. Diaziella sp. and Lipothymus sp. seem to pollinate their host fig as efficiently as do the associated agaonid wasps. Previous studies, on actively pollinated Ficus species, have found that internally ovipositing non‐agaonid wasps are parasites of such Ficus species. Hence, mode of pollination of the legitimate pollinator conditions the outcome of the interaction between internally ovipositing parasites and their host.
Catastrophic response of lakes to benthivorous fish introduction
Authors: Zambrano Luis , Scheffer Marten , Martínez‐Ramos Miguel
Published: December 2004

Introduction of the benthivorous common carp (Cyprinus carpio) has been identified as one of the main causes of loss of biodiversity and water clarity in numerous shallow lakes and ponds worldwide. Recent observations in experimental fish ponds suggest that the effect of carp on the ecosystem is catastrophic in the sense that a substantial impact occurs only when a critical carp density is exceeded. In search for an explanation, we analyzed a simple model of the interaction between benthivorous fish and their invertebrate benthic prey, and of sediment resuspension resulting from fish feeding behavior. Our results suggest that benthic prey populations should be only moderately depressed until predator fish abundance grows to a critical biomass at which benthos collapses due to overexploitation. This drop in prey density is predicted to result in a sharp increase in water turbidity due to an increase in prey search activity of the fish. For less eutrophic and deeper lakes, where benthos productivity and hence benthivorous fish carrying capacity are lower, water turbidity is predicted to be much less affected. The qualitative patterns are quite robust against assumptions on parameter values and correspond closely to the experimental results and data from lakes suggesting that the model may capture the essence of the mechanism causing a discontinuous effect of benthivorous fish on lake ecosystems.
Costs of aggregation: shadow competition in a sit‐and‐wait predator
Authors: Lubin Yael , Henschel Joh R. , Baker Mitchell B.
Published: December 2004

Shadow competition, when sedentary foragers closer to a source of food reduce its availability to those further away, is predicted to increase with the size and density of a group. We tested the occurrence of shadow competition and examined its consequences for a burrowing spider Seothyra henscheli (Eresidae) in the Namib Desert. Differences between individual spiders occurring inside or on the periphery of clusters compared to solitary spiders were examined in a natural population, by experimental manipulation of densities and by computer simulation of the experimental manipulation. Spiders in the population grew more slowly in clusters than did solitary spiders and this was confirmed by the experiment. The experiment showed that spiders grew more rapidly on the periphery of a cluster than inside it, but that survival showed the opposite trend. The largest effect was in the highest density, where all spiders maintained active webs throughout the experiment, indicating a state of hunger. Modeling indicated that such effects may be explained by the way ants, the principal prey of the spiders, reach spider webs at different locations within the patches of different densities. Modeling confirmed that shadow competition adequately explains the patterns of foraging, growth and survival of sedentary foragers such as these spiders, and is likely to have wider implications for other sit‐and‐wait predators.
The use of general foraging kairomones in a generalist parasitoid
Authors: Steidle Johannes L. M. , Lanka Judith , Müller Caroline , Ruther Joachim
Published: December 2004

Almost no comparative studies are available on the use of general and specific infochemical cues by generalist parasitoids with hosts from different families feeding on host plants also from different families. Based on literature, two hypotheses were developed and tested with host recognition cues used by the larval parasitoid Lariophagus distinguendus. This generalist parasitizes beetle species from different families developing in seeds of plant species from the Poaceae and Fabaceae. The first hypothesis predicts that for initial encounters with host species, natural enemies should innately use general cues, which are common to all hosts and their food plants. The second hypothesis predicts that natural enemies should learn specific cues from host plant and host after experience with a host species. The first hypothesis was partly confirmed. L. distinguendus innately reacted to faecal cues from several host species and chemical analyses of faeces from these hosts revealed the common occurrence of chemicals that are used for host recognition by L. distinguendus. In disagreement with the first hypothesis, parasitoids did not innately respond to cues from plant seeds. Preference experiments on the influence of experience demonstrated an increased host recognition response towards a host after experience with it. In support of the second hypothesis, L. distinguendus females learned specific cues from herbivore‐damaged wheat, rice and cowpea seeds and from the faeces of the bean weevil Callosobruchus maculatus.
Habitat diversity and species diversity: testing the competition hypothesis with juvenile salmonids
Authors: Young Kyle A.
Published: December 2004

I experimentally tested two predictions of the hypothesis that the positive relationship between habitat diversity and species diversity arises from a reduction in the negative effects of interspecific competition. By allowing species to partition habitat and avoid competition, habitat diversity should 1) facilitate the addition of an ecologically intermediate species into an existing community, and 2) reduce the negative effects of that species on existing members of the community. I tested these predictions with juveniles of three sympatric salmonid species: coho salmon (Oncorhynchus kisutch), steelhead trout (O. mykiss), and cutthroat trout (O. clarki), which in natural streams occupy deep low‐velocity pools, shallow high‐velocity riffles, and intermediate habitats, respectively. I introduced two (coho and steelhead) and three species communities into each of three artificial stream habitats: pools, riffles, and diverse. The results provide partial support for the predictions. Cutthroat trout grew fastest in the diverse stream habitat. Though habitat diversity did not eliminate the negative effects of competition, in the three species community coho and steelhead grew as fast in the diverse habitat as in either homogeneous habitat. The results are consistent with data on species number and evenness from natural communities, where variation along other niche axes confounds the relationship between habitat diversity, interspecific competition, and species diversity.
Galling insect diversity patterns: the resource synchronisation hypothesis
Authors: De Souza Mendonça, Jr. Milton
Published: December 2004

A new hypothesis is proposed to explain the insect gall‐maker species richness pattern found by Price et al. (1998; J. Biogeogr. 25: 581–591). First, it is necessary to consider an explicit model for speciation in this group of insects, and host‐shifts seem to be the most likely way by which gall‐makers can speciate. Since most galls are induced on young plant tissue, and mainly on leaves, the dynamics of leaf flushing in different vegetation types (how many plant species flush synchronously) can be of capital importance determining possible host‐shifts for dispersing insect females. I suggest that vegetation types with synchronous leaf flushing are more likely to harbour higher insect gall‐maker species richness, and this is why the pattern found by Price et al. (1998) showed low species richness of these insects for tropical rain forests and high richness for Mediterranean‐like vegetation. Additionally, Mediterranean‐like vegetation suffers seasonal influence of fires, and plants resprouting in response to this can provide further synchronous leaf flushes during which more host‐shifts can occur. Plant diversity is also of capital importance underlying the host‐shifting process in different biomes. Finally, I suggest a few possible ways of testing the hypothesis.
Optimality modeling and fitness trade‐offs: when should plants become pollinator specialists?
Authors: Aigner Paul A.
Published: December 2004

The assumption that flowers readily evolve specializations for pollination by particular animals has been central to a standard view of pollinator‐mediated adaptive divergence in angiosperms. Stebbins’ Most Effective Pollinator Principle (MEPP) formalized this assumption in proposing that a plant should always evolve specializations to its most effective pollinator. I argue that the MEPP and its corollaries are unsupported by basic models of phenotypic selection which predict that a plant should evolve greater specialization to a particular pollinator when the marginal fitness gain exceeds the marginal fitness loss from becoming less adapted to all other pollinators. Differences in pollinator effectiveness are neither necessary nor sufficient to predict specialization. Differences in effectiveness certainly can foster floral specialization to the most effective pollinator in some cases, but when adaptation to a relatively ineffective pollinator requires little loss in the fitness contribution of a more effective pollinator, plants may exhibit striking specializations for the less effective pollinator. Recognizing that the effectiveness of pollinators is not tightly coupled to their importance in selecting for phenotypic novelty may resolve the mismatch between floral features that appear to represent clear evolutionary responses to specific pollinators and patterns of flower visitation that often seem generalized. To shed light on agents of selection and the adaptive value of floral traits I argue that we must go beyond measures of pollinator effectiveness to investigate pollinator‐mediated fitness trade‐offs over a range of floral phenotypes.
Mechanisms for delayed density‐dependent reproductive traits in field voles, Microtus agrestis: the importance of inherited environmental effects
Authors: Ergon Torbjørn , MacKinnon James L. , Stenseth Nils Chr. , Boonstra Rudy , Lambin Xavier
Published: December 2004

Reproductive traits of voles vary with the phases of the population density fluctuations. We sought to determine whether the source of this variation resides in the individuals or in their environment. Overwintering field voles (Microtus agrestis) from two cyclic out‐of‐phase populations (increase and peak phases) were sampled in early spring and bred in the laboratory for two generations under standardised conditions with ambient light and temperature. Monitoring of the source populations by capture‐mark‐recapture showed large differences in reproductive performance. In the increase area, reproduction started six weeks earlier, the probability of maturation of young‐of‐the‐year was more than ten times higher during mid‐summer, and reproduction continued nearly two months later in the autumn than in the peak area. These differences were not found to be associated with a difference in age structure of overwintered animals between the two areas (assessed by the distribution of eye lens masses from autopsy samples). Although the population differences in reproductive traits were to some degree also present among the overwintered animals in the laboratory, we found no difference in reproductive traits in the laboratory‐born generations. There was a strongly declining seasonal trend in probability of sexual maturation both in the field and in the laboratory under ambient light conditions. However, in the field there were large population differences in the steepness of the seasonal decline that were not seen under the standardised laboratory conditions. We conclude that seasonal decline in maturation rates is governed by change in photoperiod, but that the population level variation in the shape of the decline is caused by a direct response to the environment and not due to variation in any intrinsic state of the individuals reflecting the environment experienced by the previous generation(s).
Herbaceous plant strategies in disturbed habitats
Authors: Schippers Peter , Van Groenendael Jan M. , Vleeshouwers Leo M. , Hunt Roderick
Published: December 2004

A systematic theoretical evaluation has been made of three important plant life history traits: adult longevity, seed longevity and seed mass, where seed mass is interpreted as being indicative of dispersal distance and seedling vigour. This model study examined the role of these three traits in relation to environmental disturbance. We chose temperate grasslands, widespread in north Western Europe and northern and eastern America, as our reference system for our simulations. Eight plant strategies were defined by allowing two levels in each of the three and combining them in all eight possible ways. A simple, spatially explicit model was developed to simulate competition among individuals with these eight trait combinations at different levels of disturbance.  Simulation results were compared with the actual occurrence over a disturbance gradient of species with similar plant trait combinations in a large database from the Sheffield area (UK). This showed that with increasing disturbance level, non‐dormant perennials, dormant perennials, non‐dormant annuals and dormant annuals, respectively, became dominant but only if small‐seeded, indicating the relative viability of these particular strategies with respect to disturbance.  A new prediction from the model was that stable coexistence occurs between plant strategies with dormant and with non‐dormant seeds over a range of levels of disturbance. Plant strategies with large seeds were inferior to small‐seeded ones if competitive ability of seedlings is proportional to seed weight. This difference was highest at low seed densities and low germination probabilities, indicating that large‐seeded species secure no advantage from being dormant (i.e. having a low germination probability). Finally, the results indicated that dormancy is superior to dispersal as a method of coping with disturbance.
Effects of competitive stress on vegetative growth, storage, and regrowth after defoliation in Phleum pratense
Authors: Cheplick Gregory P. , Chui Tina
Published: December 2004

The capacity for resource storage is important to population persistence in nonforaging plants with a consolidation strategy. In a competitive environment, selection may favor genetic variants with a well‐developed ability to store resources for future vegetative growth or to regrow following herbivory. To determine the evolutionary potential for changes in vegetative growth, storage and regrowth after defoliation in response to competitive stress, half‐sib families of the caespitose grass Phleum pratense were grown in pots in a glasshouse either alone or in competition with four individuals of Lolium perenne. They were defoliated after 16 wk and permitted to regrow for 8 wk. Production of new tillers, leaf area and leaf dry mass were recorded before and after defoliation; resource storage was estimated by the dry mass of stem bases. Tiller numbers, leaf area and mass, regrowth, and stem base mass were significantly reduced by competition; however, there was significant variation among families for many variables. A significant proportion of the variation in clipped and regrowth leaf mass, and in stem base mass, was due to a competition by family interaction. Storage in stem bases was correlated with total accumulated leaf mass in both control and competition groups. Genetic variation for competitive ability and the ability to regrow rapidly after defoliation exist in this P. pratense population. A well‐developed ability to regrow following release from competitive or grazing pressures is likely to be a critical adaptation of caespitose grasses.
On similarity among local communities in biodiversity experiments
Authors: Fukami Tadashi , Naeem Shahid , Wardle David A.
Published: December 2004

As a potential mechanism to explain how biodiversity loss may influence variability in ecosystem functioning, we examine the hypothesis that biodiversity loss lowers similarity in species composition among local communities and that this decreased similarity in turn lowers ecosystem reliability. Ecosystem reliability refers to the probability that a system will provide a consistent level of performance over a given unit of time. This hypothesis is compared with other hypotheses that make similar predictions, including the sampling effect, insurance, and resource use complementarity hypotheses. We provide evidence for the similarity hypothesis through a reanalysis of a recent experiment and show that a key assumption of the hypothesis may be robust through computer simulations. We also address problems and possible solutions regarding how to separately test the similarity and other hypotheses in biodiversity experiments.
Immunohistochemical detection of amelogenin and cytokeratin 19 in epithelial odontogenic tumors
Authors: Kumamoto H , Yoshida M , Ooya K
Published: December 2004

OBJECTIVE: Epithelial odontogenic tumors exhibit considerable histological variation and are classified into several benign and malignant entities. Expression of amelogenin and cytokeratin 19 (CK19), that are potentially useful polypeptides for identification of odontogenic epithelial components, was evaluated in various types of epithelial odontogenic tumors.

MATERIALS AND METHODS: Specimens of 33 ameloblastomas, three calcifying epithelial odontogenic tumors (CEOTs), two clear cell odontogenic tumors (CCOTs) and five malignant ameloblastomas were examined by immunohistochemistry using anti‐amelogenin and anti‐CK19 antibodies.

RESULTS: Immunohistochemical reactivity for amelogenin was detected in many peripheral columnar or cuboidal cells and some central polyhedral cells in ameloblastomas, and histological variants showed various degrees of amelogenin expression. Expression of CK19 was diffusely present in neoplastic cells in ameloblastomas, and decreased expression was found in keratinizing cells of acanthomatous variants and some neoplastic cells of desmoplastic variants. In CEOTs, immunohistochemical reactivity for amelogenin was detected in neoplastic cells and intercellular amyloid‐like materials, whereas CK19 was expressed in neoplastic cells. CCOTs showed positive reactivity for amelogenin and CK19 in neoplastic cells. Malignant ameloblastomas exhibited various degrees of amelogenin expression with constant CK19 expression in neoplastic cells.

CONCLUSION: Diverse types of epithelial odontogenic tumors express amelogenin and CK19, suggesting that these tumors have ameloblastic differentiation or odontogenic epithelial properties.
Maryland dental hygienists' knowledge and opinions of oral cancer risk factors and diagnostic procedures
Authors: Syme SE , Drury TF , Horowitz AM
Published: December 2004

OBJECTIVES: To examine Maryland dental hygienists' (DHs) knowledge of oral cancer risk factors and diagnostic procedures, as well as opinions about the currency and adequacy of their oral cancer knowledge, educational preparation, interest in, and preferred types of, continuing education courses.

METHODS: Seven hundred DHs were randomly selected from a registry of 2677 Maryland licensed dental hygienists. A mailed survey instrument provided baseline data on 331 (RR = 60%) DHs. Stratified tabular and logistic analytical techniques were employed (alpha level ≤0.05).

RESULTS: Most correctly identified tobacco use (99.7%) and alcohol use (89%) as risk factors; however, 31% incorrectly identified poor oral hygiene as a risk factor. 64% of DHs correctly identified older age as a risk factor, yet only 16% identified that the majority of oral cancers are diagnosed in the 60+ year old age group. Nearly 91% correctly identified the examination procedures of the tongue for oral cancer detection; while only 16% of DHs correctly identified erythroplakia and leukoplakia as the conditions most likely associated with oral cancer.

CONCLUSIONS: Gaps in knowledge exist and strongly suggest the need for continuing education courses to clarify risk factors and diagnostic procedures associated with earlier oral cancer detection and prevention.
The psychosocial aspects of children exposed to war: practice and policy initiatives
Authors: Barenbaum Joshua , Ruchkin Vladislav , Schwab‐Stone Mary
Published: December 2004

The atrocities of war have detrimental effects on the development and mental health of children that have been documented since World War II. To date, a considerable amount of knowledge about various aspects of this problem has been accumulated, including the ways in which trauma impacts child mental health and development, as well as intervention techniques, and prevention methods. Considering the large populations of civilians that experience the trauma of war, it is timely to review existing literature, summarize approaches for helping war‐affected children, and suggest future directions for research and policy.
Specific reading disability (dyslexia): what have we learned in the past four decades?
Authors: Vellutino Frank R. , Fletcher Jack M. , Snowling Margaret J. , Scanlon Donna M.
Published: December 2004

We summarize some of the most important findings from research evaluating the hypothesized causes of specific reading disability (‘dyslexia’) over the past four decades. After outlining components of reading ability, we discuss manifest causes of reading difficulties, in terms of deficiencies in component reading skills that might lead to such difficulties. The evidence suggests that inadequate facility in word identification due, in most cases, to more basic deficits in alphabetic coding is the basic cause of difficulties in learning to read. We next discuss hypothesized deficiencies in reading‐related cognitive abilities as underlying causes of deficiencies in component reading skills. The evidence in these areas suggests that, in most cases, phonological skills deficiencies associated with phonological coding deficits are the probable causes of the disorder rather than visual, semantic, or syntactic deficits, although reading difficulties in some children may be associated with general language deficits. Hypothesized deficits in general learning abilities (e.g., attention, association learning, cross‐modal transfer etc.) and low‐level sensory deficits have weak validity as causal factors in specific reading disability. These inferences are, by and large, supported by research evaluating the biological foundations of dyslexia. Finally, evidence is presented in support of the idea that many poor readers are impaired because of inadequate instruction or other experiential factors. This does not mean that biological factors are not relevant, because the brain and environment interact to produce the neural networks that support reading acquisition. We conclude with a discussion of the clinical implications of the research findings, focusing on the need for enhanced instruction.
Mannose‐binding lectin and the prognosis of fulminant hepatic failure caused by HBV infection
Authors: Hakozaki Yukiya , Yoshiba Makoto , Sekiyama Kazuhiko , Seike Eiji , Iwamoto Junichi , Mitani Keiji , Mine Masafumi , Morizane Toshio , Ohtani Katsuki , Suzuki Yasuhiko , Wakamiya Nobutaka
Published: December 2004

Abstract: Background/Aims: The mannose‐binding lectin (MBL) gene was reported to play an important role in determining the clinical outcome of persistent hepatitis B virus (HBV) infection. We investigated serum MBL concentrations and MBL gene mutations to determine whether they were related to the prognosis of patients with fulminant hepatic failure (FHF) caused by HBV infection. Methods: We investigated serum MBL concentrations and MBL gene mutations in 43 HBV‐infected Japanese patients with FHF and 260 HBsAg‐negative healthy controls. Serum MBL concentrations were measured by an enzyme‐linked immunosorbent assay, and mutations in the MBL gene were analysed by nested PCR and direct DNA sequencing. Results: Only a mutation in codon 54 of the MBL gene was found. The frequency of this mutation in nonsurvivors (40%, 8/20) was higher than in survivors (13%, 3/23), and the difference was slightly significant (p = 0.043). The H allele frequency in survivors (70.5%, 31/44) was higher than in nonsurvivors (39.5%, 15/38) (p = 0.0048). Because of these factors the mean serum MBL concentration in survivors, 1.61 μg/ml (range 0.3–3.86), was significantly higher than in nonsurvivors, 0.79 μg/ml (range 0.04–1.51) (p < 0.0001). The likelihood ratio for nonsurvival was 0 for over 2.0 μg/ml, 0.67 for 1.0–2.0 μg/ml, and 2.24 for 0–1.0 μg/ml. Conclusions: The mutation in codon 54 of the MBL gene tended to be higher in nonsurvivors than in survivors. The H allele frequency (high producing allele in H/Y) in survivors was higher than that in nonsurvivors. High levels of serum MBL correlated with the survival of patients with FHF due to HBV infection. Serum MBL may be useful as a predictive factor for the survival of patients with FHF caused by HBV.
The mode of tumour progression in combined hepatocellular carcinoma and cholangiocarcinoma: an immunohistochemical analysis of E‐cadherin, alpha‐catenin and beta‐catenin
Authors: Asayama Yoshiki , Taguchi Ken‐ichi , Aishima Shin‐ichi , Nishi Hidehiro , Masuda Kouji , Tsuneyoshi Masazumi
Published: December 2004

Abstract: Background/Aim: To investigate the mode of progression of combined hepatocellular carcinoma and cholangiocarcinoma (cHCC‐CC). Methods: An immunohistochemical study for E‐cadherin (ECD) and alpha‐ and beta‐catenins was performed on 29 cases of cHCC‐CC. Results: Reduced expression of ECD was significantly correlated with the tumour grade of the hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC) components, intrahepatic metastasis (IM) of HCC, IM of CC, and vascular invasion of CC (p < 0.05, respectively). There was a significant relationship between the reduced expression of beta‐catenin and the tumour grade of HCC components (p < 0.05). Cases showing concurrent intrahepatic metastasis composed of HCC, CC, or both, numbered 6, 5, and 2, respectively. The expression patterns of ECD and beta‐catenin of IM were similar to those of primary lesion in most cases. On the other hand, expression of ECD and beta‐catenin of IM of HCC component were preserved, even though those of the primary sites were reduced in two cases and one case, respectively. ECD and beta‐catenin were significantly correlated with tumour differentiation and tumour progression. Conclusions: Preserved or recovered ECD and beta‐catenin expression may be of beneficial effect for re‐establishing the tissue architecture at the metastatic site.
Expression of human telomerase reverse transcriptase in regenerative and precancerous lesions of cirrhotic livers
Authors: Kotoula Vassiliki , Hytiroglou Prodromos , Pyrpasopoulou Athina , Saxena Romil , Thung Swan N. , Papadimitriou Constantine S.
Published: December 2004

Abstract: Background/Aims:
The catalytic subunit of human telomerase (hTERT) is known to be expressed in a variety of malignant tumours, including hepatocellular carcinoma (HCC). We studied hTERT expression in regenerative and precancerous lesions arising in cirrhosis. Methods/Results: As shown by in situ hybridisation, hTERT mRNA was absent in normal liver, but present in varying numbers of hepatocytes and HCC cells of diseased livers, as well as in biliary epithelial cells, lymphocytes, sinusoidal‐lining cells and tumour endothelial cells. RT‐PCR for two hTERT transcript regions demonstrated hTERT expression in 11 out of 15 cirrhotic liver samples, in 20 out of 21 large regenerative nodules/low‐grade dysplastic nodules, in 5 out of 5 high‐grade dysplastic nodules, and in 4 out of 4 HCCs. The beta‐splice variant was identified in all hTERT‐positive cases, while the corresponding full‐length transcript was found only in 13 out of 29 positive large nodular lesions and in 4 out of 11 positive cirrhotic samples. The full‐length transcript was always found in the presence of the beta‐splice variant, usually in low relative levels, and tended to correlate with telomerase activity in the samples, while the beta‐splice variant did not. Conclusions: This study shows that hTERT re‐expression takes place both in hepatic regeneration occurring in cirrhosis and in the early steps of hepatocarcinogenesis, and involves mainly the beta‐splice variant of this molecule. Additional regulatory mechanisms may be required for the expression of the full‐length hTERT transcript.
Apoptosis of biliary epithelial cells in primary biliary cirrhosis and primary sclerosing cholangitis
Authors: Tinmouth Jill , Lee Mary , Wanless Ian R. , Tsui Florence W. L. , Inman Robert , Heathcote E. Jenny
Published: December 2004

Background/Aims:

Primary biliary cirrhosis (PBC) is an autoimmune disease characterized by inflammatory destruction of small bile ducts. Primary sclerosing cholangitis (PSC) is a different, presumed autoimmune cholestatic liver disease where the bile ducts are also destroyed. In this study, apoptosis and portal triad inflammation in liver tissue from patients with PBC is examined and compared to that from patients with PSC and patients with normal liver.

Methods:

Explanted liver tissue from patients with PBC and PSC and normal liver from patients with metastases to liver were examined. The liver samples were stained for apoptosis using the terminal deoxynucleotidyl triphosphate (TdT)‐mediated deoxyuridine triphosphate nick end labelling (TUNEL) assay. The biliary epithelial cells (BEC) were then scored on the basis of their TUNEL stain and the degree of periductal inflammation.

Results:

In PBC, apoptosis of BEC, as detected by the TUNEL assay, was significantly increased in the presence of inflammation. Regardless of the presence or absence of inflammation, the small bile ducts in PBC liver tissue exhibited greater evidence of apoptosis than did similar ducts from PSC or control livers.

Conclusion:

These findings suggest that in PBC, unlike PSC, the apoptosis of BEC in PBC is secondary to the invasion of inflammatory cells.
Single nucleotide polymorphisms and microsatellite alleles of tumor necrosis factor alpha and interleukin‐10 genes and the risk of advanced chronic alcoholic liver disease
Authors: Ladero José M. , Fernández‐Arquero Miguel , I. Tudela José , Agúndez José A.G. , Díaz‐Rubio Manuel , Benítez Julio , De La Concha Emilio G.
Published: December 2004

Background:

Only a minority of ethanol abusers develop advanced chronic alcoholic liver disease (CALD). In CALD there is a disbalance between TNFα and IL‐10, which may be modulated by several polymorphisms at both genetic loci. Our aim has been to elucidate the possible relation between these polymorphisms and the risk of CALD.

Patients and Methods:

147 patients with advanced CALD and 355 healthy controls (all white Spaniards) were included. TNFα biallelic single nucleotide polymorphisms (SNP) at positions −238, −308, and −376 and IL‐10 biallelic SNP at positions −597, − 824, and − 1087 were investigated by polymerase chain reaction (PCR) amplification and dot blot hybridization. Moreover, polymorphic microsatellites TNFa, TNFb, IL‐10.R and IL‐10.G were investigated in a multiplex PCR and alleles were estimated in an automatic sequencer.

Results:

No differences were found in the distribution of any of the studied polymorphisms, except by an excess of the haplotype formed by the allele 11 of the microsatellite IL‐10.G and the GCC arrangement of the SNPs at the promoter of IL‐10 gene in patients (15.7 vs. 8.24%, odds ratio: 2.08, 95% C.I. = 1.31–3.31).

Conclusions:

The studied polymorphisms at TNFα and IL‐10 genetic loci are not clearly related to the risk of CALD. The excess of G11‐GCC haplotype found in CALD patients needs independent confirmation.
The correlation between portal myofibroblasts and development of intrahepatic bile ducts and arterial branches in human liver
Authors: Libbrecht Louis , Cassiman David , Desmet Valeer , Roskams Tania
Published: December 2004

Background/Aims:

The development of the intrahepatic bile ducts most likely requires interactions between epithelial and mesenchymal cells. In view of the epithelial–mesenchymal interactions between portal myofibroblasts (pMFs) and biliary epithelial cells in adult diseases of the bile ducts, we investigated the presence and function of pMFs during the development of intrahepatic bile ducts, as well as the development of intrahepatic branches of the hepatic artery.

Methods:

We performed haematoxylin‐eosin‐stainings and immunohistochemistry for alpha‐smooth‐muscle actin, cytokeratin 19 and vimentin on serial sections of 45 fetal and postnatal liver biopsies.

Results:

The mesenchyme of portal tracts in the ductal plate stage devoid of a hepatic artery branch, contained numerous and diffusely scattered pMFs. Portal tracts with a hepatic artery branch were always larger than those without and showed a decreasing number of pMFs. In the remodeling stage, all portal tracts contained a hepatic artery branch, and pMFs were restricted to the periductal mesenchyme. These periductal pMFs disappeared after full incorporation of the bile duct.

Conclusion:

Our findings strongly suggest interactions between pMFs and epithelial cells of the developing bile ducts. The development of the intrahepatic arterial branches always precedes the incorporation of the tubular segments of the ductal plate.
Partial Likelihood Inference For Time Series Following Generalized Linear Models
Authors: Fokianos Konstantinos , Kedem Benjamin
Published: December 2004

Abstract. The present article offers a certain unifying approach to time series regression modelling by combining partial likelihood (PL) inference and generalized linear models. An advantage gained by resorting to PL is that the joint distribution of the response and the covariates is left unspecified, and furthermore, PL allows for temporal or sequential conditional inference with respect to a filtration generated by all that is known to the observer at the time of observation. Two real data examples illustrate the methodology.
Kernel matching scheme for block bootstrap of time series data
Authors: Kim Tae Yoon , Hwang Sun Young
Published: December 2004

Abstract.  The block bootstrap for time series consists in randomly resampling blocks of the original data with replacement and aligning these blocks into a bootstrap sample. Recently several matching schemes for the block bootstraps have been suggested to improve its performance by reduction of bias [Bernoulli 4 (1998), 305]. The matching schemes are usually achieved by aligning with higher likelihood those blocks which match at their ends. The kernel matching scheme we consider here takes some of the dependence structure of the data into account and is based on a kernel estimate of the conditional lag one distribution. In this article transition probabilities of the kernel matching scheme are investigated in detail by concentrating on a simple case. Our results here discuss theoretical properties of the transition probability matrix including ergodicity, which shows the potential of the matching scheme for bias reduction.
On the Autocorrelation Properties of Long‐Memory GARCH Processes
Authors: Karanasos Menelaos , Psaradakis Zacharias , Sola Martin
Published: December 2004

Abstract.  This paper derives the autocorrelation function of the squared values of long‐memory GARCH processes. Such processes are of much interest as they can produce the long‐memory conditional heteroskedasticity that many high‐frequency financial time series exhibit. An empirical application illustrating the practical use of our results is also discussed.
M‐Estimation for regressions with integrated regressors and arma errors
Authors: Shin Dong Wan , Lee Oesook
Published: December 2004

Abstract.  General M‐estimation is developed for regression models with integrated regressors and autoregressive moving average (ARMA) errors, in which the ARMA parameters are jointly estimated with the regression parameters. The large sample distribution of the M‐estimator is derived. Allowing the regressors to be dependent on the error terms, a parametric ‘fully modified’ (FM) M‐estimator is proposed. In cases of ARMA errors, a Monte‐Carlo experiment reveals superiority of the parametric estimators over the semiparametric FM M‐estimator of Phillips Econometric Theory 11 (1995, p 912) in terms of empirical mean squared error.
Monitoring terrestrial mammals in the UK: past, present and future, using lessons from the bird world
Authors: BATTERSBY JESSAMY E. , GREENWOOD JEREMY J. D.
Published: December 2004

1. A monitoring network for UK terrestrial mammals, the Tracking Mammals Partnership, is currently being set up to provide a coordinated programme to collect surveillance and monitoring data.

2. Monitoring UK mammals is important for a number of reasons including: setting conservation priorities; measuring the effects of conservation management; managing populations of problem species and the sustainable use of game species; assessing the effects of agriculture and other human activities; providing evidence for the need for policy change; and because of obligations under intergovernmental treaties and national legislation.

3. The bird world, largely but not solely through the work carried out by the British Trust for Ornithology, has provided a useful model for mammal surveillance and some important lessons in setting up and running a UK wide multispecies monitoring programme.

4. Lessons include the importance: of annual monitoring; of long‐term data sets of population indices rather than absolute population sizes; and of the use of volunteers in data collection.

5. Two scoping studies have been carried out to assess the feasibility and costs of setting up a mammal surveillance and monitoring network and the survey methods that could be used for different species.

6. The Tracking Mammals Partnership, comprising 23 organizations, has the remit of implementing the recommendations of the scoping studies. There are a number of programmes operating within the Partnership including the National Dormouse Monitoring Programme, the National Bat Monitoring Programme and the Breeding Bird Survey Mammal Monitoring. There are also a number of pilot schemes being tested.

7. Reports on the population trend data collected should enable more informed policy and management decisions concerning UK mammal species.