Determination of the molecular weight distribution of non-enzymatic browning products formed by roasting of glucose and glycine and studies on their effects on NADPH-cytochrome c-reductase and glutathione-S-transferase in Caco-2 cells

After thermal treatment of a mixture of glucose and glycine for 2 h at 125 degreesC, about 60% of the starting material was converted into nonsoluble, black pigments, whereas 40% of the mixture was still water-soluble. Dialysis of the latter fraction revealed 30.4% of low molecular weight compounds (LMWs; MW <10 000 De) and 10.0% high-molecular weight products [HMWs; MW greater than or equal to 10000 Dal. The water-soluble Maillard reaction products (MRPs) were separated by gel permeation chromatography and ultrafiltration, revealing that 60% of the water-soluble products of the total carbohydrate/amino acid mixture had MWs <1 000 Da and consisted mainly of non-coloured reaction products. MRPs with MWs between 1000 and 30000 Da were Found in comparatively low yields (about 1.3%). In contrast, about 31.1% of the MRPs exhibited MWs > 30000 Da, amongst which 14.5% showed MWs > 100000 Da, thus indicating an oligomerisation of LMWs to melanoidins under roasting conditions. To investigate the physiological effects of these MRPs, xenobiotic enzyme activities were analysed in intestinal Caco-2 cells. For Phase-I NADPH-cytochrome c-reductase, the activity in the presence of the LMW and HMW fraction was decreased by 13% and 22%: respectively. Phase-II glutathione-S-transferase activity decreased by 15% and 18%, respectively, after incubation with the LMW and the HMW fractions. Considering the different yields, 30% and 10%, respectively, of the LMW and the HMW fractions, the total amount of the LMW fraction present in the glucose-glycine mixture is more active in modulating three enzyme activities than that of the HMW fraction.

Foraging ecology, fluctuating food availability and energetics of wintering brent geese

Changing energy requirements and dramatic shifts in food availability are major factors driving behaviour and distribution of herbivores. We investigate this in wintering East Canadian High Arctic light-bellied brent geese Branta bernicla hrota in Northern Ireland. They followed a sequential pattern of habitat use, feeding on intertidal Zostera spp. in autumn and early winter before moving to predominantly saltmarsh and farmland in late winter and early spring. Night-time feeding occurred throughout and made a considerable contribution to the birds' daily energy budget, at times accounting for > 50% of energy intake. Nocturnal feeding, however, is limited to the intertidal, possibly because of predation risk on terrestrial habitat, and increases with moonlight. The amount of Zostera spp., declined dramatically after the arrival of birds, predominantly, but not entirely, due to consumption by the birds. Birds gained fat reserves in the first 2 months but then this was dramatically lost as their major food source collapsed and their daily energy intake declined. Single birds consistently fared worse than paired birds and pairs with juveniles fared better than those without suggesting a benefit of having a family to compete for food. Many birds leave the Lough at this time of reduced Zostera spp. for other sea inlets in Ireland but some remain. Body condition of the latter gradually improved in early spring and reflected a heavy reliance on terrestrial habitats, particularly farmland, to meet the birds' daily energy requirements. However, even in the period immediately before migration to the breeding ground, the birds did not regain the amount of abdominal fatness observed in November. The dramatic changes in available food and requirements of the birds drive the major changes seen in foraging behaviour as the birds evade starvation in the wintering period.

Experimenting with the Coxian Phase-Type Distribution to Uncover Suitable Fits

In the past few decades, Coxian phase-type distributions have become increasingly more popular as a means of representing survival times. In healthcare, they are considered suitable for modelling the length of stay of patients in hospital and more recently for modelling the patient waiting times in Accident and Emergency Departments. The Coxian phase-type distribution has not only been shown to provide a good representation of real survival data, but its interpretation seems reasonably initiative to the medical experts. The drawback, however, is fitting the distribution to the data. There have been many attempts at accurately estimating the Coxian phase-type parameters. This paper wishes to examine the most promising of the approaches reported in the literature to determine the most accurate. Three performance measures are introduced to assess the fitting process of the algorithms along with the likelihood values and AIC to examine the goodness of fit and complexity of the model. Previous research suggests that the fitting process is strongly influenced by the initial parameter estimates and the data itself being quite variable. To overcome this, one experiment in this research paper will use the same initial parameter values for each estimation and perform the fits on the data simulated from a Coxian phase-type distribution with known parameters.

Body mass-abundance relationships are robust to cascading effects in marine food webs

Body mass has been shown to scale negatively with abundance in a wide range of habitats and ecosystems. It is believed that this relationship has important consequences for the distribution and maintenance of energy in natural communities. Some studies have shown that the relationship between body mass and abundance may be robust to major food web perturbations, fuelling the belief that natural processes may preserve the slope of this relationship and the associated cycling of energy and nutrients. Here, we use data from a long-term experimental food web manipulation to examine this issue in a semi-natural environment. Similar communities were developed in large experimental mesocosms over a six month period. Some of the mesocosms were then subjected to species removals, based on the mean strength of their trophic interactions in the communities. In treatments where the strongest interactors were removed, a community-level trophic cascade occurred. The biomass density of invertebrates increased dramatically in these communities, which led to a suppression of primary production. In spite of these widespread changes in ecosystem functioning, the slope of the relationship between body mass and abundance remained unchanged. This was the case whether average species body mass and abundance or individual organism size spectra were considered. An examination of changes in species composition before and after the experimental manipulations revealed an important mechanism for maintaining the body mass-abundance relationship. The manipulated communities all had a higher species turnover than the intact communities, with the highest turnover in communities that experienced cascading effects. As some species increased in body mass and abundance, new species filled the available size-abundance niches that were created. This maintained the overall body mass-abundance relationship and provided a stabilising structure to these experimental communities.

Macroecological patterns and niche structure in a new marine food web

The integration of detailed information on feeding interactions with measures of abundance and body mass of individuals provides a powerful platform for understanding ecosystem organisation. Metabolism and, by proxy, body mass constrain the flux, turnover and storage of energy and biomass in food webs. Here, we present the first food web data for Lough Hyne, a species rich Irish Sea Lough. Through the application of individual-and size-based analysis of the abundance-body mass relationship, we tested predictions derived from the metabolic theory of ecology. We found that individual body mass constrained the flux of biomass and determined its distribution within the food web. Body mass was also an important determinant of diet width and niche overlap, and predator diets were nested hierarchically, such that diet width increased with body mass. We applied a novel measure of predator-prey biomass flux which revealed that most interactions in Lough Hyne were weak, whereas only a few were strong. Further, the patterning of interaction strength between prey sharing a common predator revealed that strong interactions were nearly always coupled with weak interactions. Our findings illustrate that important insights into the organisation, structure and stability of ecosystems can be achieved through the theoretical exploration of detailed empirical data.

Distribution and abundance of Pale-bellied Brent Geese and Wigeon on Strangford Lough, Northern Ireland

Strangford Lough, County Down holds internationally important numbers of wintering Pale-bellied Brent Geese Branta bernicla hrota with peak counts of up to 16 000. In the past, the Lough was also important for overwintering Wigeon Anas penelope with peak counts up to 20 000 in the early 1970s. However, this population has declined drastically with winter peaks at fewer than 2000 since the mid-1980s. As the overall flyway numbers of Wigeon have not fallen over this period, it has been suggested that the reasons for the decline are intrinsic to Strangford Lough. Wigeon did not decline uniformly throughout Strangford Lough. The greatest fall in numbers occurred on the northern mudflats suggesting a decline in carrying capacity. Factors responsible for this decline may include the reduction of Eelgrass Zostera spp. which is the main food of both species, and increases in human activity near and on the foreshore, especially in the case of Wigeon. Indirect interspecific interactions between Brent Geese and Wigeon are discussed as they may have been significant in reducing the numbers of Wigeon in the system.

THE DISTRIBUTION AND POPULATION REGULATION OF THE WOOD MOUSE APODEMUS-SYLVATICUS ON FIELD BOUNDARIES OF PASTORAL FARMLAND

1. The population characteristics and distribution of wood mice Apodemus sylvaticus (L.) were investigated along field margins of farmland dominated by grass production. 2. Turnover, sex ratio, breeding season, spatial density dependence and density dependence in reproductive activity indicated that the population ecology of A. sylvaticus is consistent in different habitats in the same geographical region. 3. Spatial variation in the abundance of A.sylvaticus was related negatively to percentage of land under pasture and distance from woodland and positively related to variables associated with food supply and cover. 4. Variation in numbers of overwintered mice at the start of the breeding season was related more closely to breeding opportunity than to environmental factors. This was particularly so in males. 5. The association of overwintered male and female A. sylvaticus remained evident in the later half of the breeding season. Young males and females of the year, however, were distributed more with respect to physical and biological features than towards adults or reproductive opportunity. 6. A. sylvaticus is an important species of field margins, even where these are poorly developed and agriculture is pastoral rather than arable. Further studies of this species in a wider range of agricultural systems are desirable.

Global change alters the stability of food webs

Recent research has generally shown that a small change in the number of species in a food web can have consequences both for community structure and ecosystem processes. However 'change' is not limited to just the number of species in a community, but might include an alteration to such properties as precipitation, nutrient cycling and temperature. How such changes might affect species interactions is important, not just through the presence or absence of interactions, but also because the patterning of interaction strengths among species is intimately associated with community stability. Interaction strengths encompass such properties as feeding rates and assimilation efficiencies, and encapsulate functionally important information with regard to ecosystem processes. Interaction strengths represent the pathways and transfer of energy through an ecosystem. We review the best empirical data available detailing the frequency distribution of interaction strengths in communities. We present the underlying (but consistent) pattern of species interactions and discuss the implications of this patterning. We then examine how such a basic pattern might be affected given various scenarios of 'change' and discuss the consequences for community stability and ecosystem functioning.

Weak interactions, omnivory and emergent food-web properties

Empirical studies have shown that, in real ecosystems, species-interaction strengths are generally skewed in their distribution towards weak interactions. Some theoretical work also suggests that weak interactions, especially in omnivorous links, are important for the local stability of a community at equilibrium. However, the majority of theoretical studies use uniform distributions of interaction strengths to generate artificial communities for study. We investigate the effects of the underlying interaction-strength distribution upon the return time, permanence and feasibility of simple Lotka-Volterra equilibrium communities. We show that a skew towards weak interactions promotes local and global stability only when omnivory is present. It is found that skewed interaction strengths are an emergent property of stable omnivorous communities, and that this skew towards weak interactions creates a dynamic constraint maintaining omnivory. Omnivory is more likely to occur when omnivorous interactions are skewed towards weak interactions. However, a skew towards weak interactions increases the return time to equilibrium, delays the recovery of ecosystems and hence decreases the stability of a community. When no skew is imposed, the set of stable omnivorous communities shows an emergent distribution of skewed interaction strengths. Our results apply to both local and global concepts of stability and are robust to the definition of a feasible community. These results are discussed in the light of empirical data and other theoretical studies, in conjunction with their broader implications for community assembly.

How do grazers achieve their distribution? A continuum of models from random diffusion to the ideal free distribution using biased random walks

A conceptual model is described for generating distributions of grazing animals, according to their searching behavior, to investigate the mechanisms animals may use to achieve their distributions. The model simulates behaviors ranging from random diffusion, through taxis and cognitively aided navigation (i.e., using memory), to the optimization extreme of the Ideal Free Distribution. These behaviors are generated from simulation of biased diffusion that operates at multiple scales simultaneously, formalizing ideas of multiple-scale foraging behavior. It uses probabilistic bias to represent decisions, allowing multiple search goals to be combined (e.g., foraging and social goals) and the representation of suboptimal behavior. By allowing bias to arise at multiple scales within the environment, each weighted relative to the others, the model can represent different scales of simultaneous decision-making and scale-dependent behavior. The model also allows different constraints to be applied to the animal's ability (e.g., applying food-patch accessibility and information limits). Simulations show that foraging-decision randomness and spatial scale of decision bias have potentially profound effects on both animal intake rate and the distribution of resources in the environment. Spatial variograms show that foraging strategies can differentially change the spatial pattern of resource abundance in the environment to one characteristic of the foraging strategy.</

Emergency slaughter of casualty cattle increases the prevalence of anthelmintic drug residues in muscle

The ProSafeBeef project studied the prevalence of residues of anthelmintic drugs used to control parasitic worms and fluke in beef cattle in Ireland. Injured (casualty) cattle may enter the human food chain under certain conditions, verified by an attending veterinarian and the livestock keeper. An analytical survey was conducted to determine if muscle from casualty cattle contained a higher prevalence of anthelmintic drug residues than healthy (full slaughter weight) cattle as a result of possible non-observance of complete drug withdrawal periods. A validated analytical method based on matrix solid-phase dispersive extraction (QuEChERS) and ultra-performance liquid chromatography-tandem mass spectrometry was used to quantify 37 anthelmintic drugs and metabolites in muscle (assay decision limits, CCa, 0.15-10.2 µg kg -1). Of 199 control samples of beef purchased in Irish shops, 7% contained detectable anthelmintic drug residues but all were compliant with European Union Maximum Residue Limits (MRL). Of 305 muscle samples from injured cattle submitted to abattoirs in Northern Ireland, 17% contained detectable residues and 2% were non-compliant (containing either residues at concentrations above the MRL or residues of a compound unlicensed for use in cattle). Closantel and ivermectin were the most common residues, but a wider range of drugs was detected in muscle of casualty cattle than in retail beef. These data suggest that specific targeting of casualty cattle for testing for anthelmintic residues may be warranted in a manner similar to the targeted testing for antimicrobial compounds often applied in European National Residues Surveillance Schemes. © 2012 Copyright Taylor and Francis Group, LLC.

The distribution of arsenic in the body tissues of wood mice and bank voles

Arsenic is accumulated by free-living small mammals, but there is little information on the resultant concentrations in different tissues other than liver and kidney. Such information is important because the severity of toxicological effects may be related to the amount of arsenic accumulated in specific organs, and the availability of arsenic to predators is, in part, dependent on which tissues accumulate arsenic. The objective of this study was to quantify the arsenic concentrations and the percentage of the total body burden (%TBB) accumulated in different body tissues of free-living small mammals and to determine how these factors varied with severity of habitat contamination. Arsenic concentrations were measured in various tissues of wood mice (Apodemus sylvaticus) and bank voles (Clethrionomys glareolus) from a range of arsenic-contaminated sites in southwest Britain. Arsenic concentrations in the gastrointestinal (GI) tract (including contents), liver, kidneys, spleen, lung, femur, and fur of both species varied significantly between sites and were higher in mice and voles from heavily contaminated areas. Heart and brain arsenic concentrations did not vary with degree of environmental contamination. The GI tract and excised carcass contained roughly equal amounts of arsenic and, in sum, comprised 75-85% of the TBB on uncontaminated sites and 90-99% on contaminated sites. Although the excised carcass contains about half of the TBB, its importance in food-chain transfer of arsenic to predators may depend on the bioavailability of arsenic sequestered in fur. In contrast, the GI tract and its contents, provided that it is consumed, will always be a major transfer pathway for arsenic to predators, regardless of the severity of habitat contamination.

Distribution and Translocation of Selenium from Soil to Grain and Its Speciation in Paddy Rice (Oryza sativa L.)

Selenium, an essential micronutrient for humans, is insufficient in dietary intake for millions of people worldwide. Rice as the most popular staple food in the world is one of the dominant selenium (Se) sources for people. The distribution and translocation of Se from soil to grain were investigated in a Se-rich environment in this study. The Se levels in soils ranged widely from 0.5 to 47.7 mg kg(-1). Selenium concentration in rice bran was 1.94 times higher than that in corresponding polished rice. The total Se concentrations in the rice fractions were in the following order: straw > bran > whole grain > polished rice > husk. Significant linear relationships between different rice fractions were observed with each other, and Se in the soil has a linear relationship with different rice fractions as well. Se concentration in rice can easily be predicted by soil Se concentrations or any rice fractions and vice versa according to their linear relationships. In all rice samples for Se speciation, SeMet was the major Se species, followed by MeSeCys and SeCys. The average percentage for SeMet (82.9%) and MeSeCys (6.2%) was similar in the range of total Se from 2.2 to 8.4 mg kg(-1) tested. The percentage of SeCys decreased from 6.3 to 2.8%, although its concentration elevated with the increase in total Se in rice. This could be due to the fact that SeCys is the precursor for the formation of other organic Se compounds. The information obtained may have considerable significance for assessing translocation and accumulation of Se in plant.

Food miles or carbon emissions? Exploring labeling preference for food transport footprint with a stated choice study

The ecological footprint of food transport can be communicated using carbon dioxide emissions (CO2 label) or by providing information about both the length of time and the mileage travelled (food miles label). We use stated choice data to estimate conventional unobserved taste heterogeneity models and extend them to a specification that also addresses attribute nonattendance. The implied posterior distributions of the marginal willingness to pay values are compared graphically and are used in validation regressions. We find strong bimodality of taste distribution as the emerging feature, with different groups of subjects having low and high valuations for these labels. The best fitting model shows that CO2 and food miles valuations are much correlated. CO2 valuations can be high even for those respondents expressing low valuations for food miles. However, the reverse is not true. Taken together, the results suggest that consumers tend to value the CO2 label at least as much and sometimes more than the food miles label.