The joint effects of larval density and C-14-cypermethrin on the life history and population growth rate of the midge Chironomus riparius

1. Chemical effects on organisms are typically assessed using individual-level endpoints or sometimes population growth rate (PGR), but such measurements are generally made at low population densities. In contrast most natural populations are subject to density dependence and fluctuate around the environmental carrying capacity as a result of individual competition for resources. As ecotoxicology aims to make reliable population projections of chemical impacts in the field, an understanding of how high-density or resource-limited populations respond to environmental chemicals is essential. 2. Our objective was to determine the joint effects of population density and chemical stress on the life history and PGR of an important ecotoxicological indicator species, Chironomus riparius, under controlled laboratory conditions. Populations were fed the same ration but initiated at different densities and exposed to a solvent control and three concentrations of C-14-cypermethrin in a sediment-water test system for 67 days at 20 +/- 1 degreesC. 3. Density had a negative effect on all the measured life-history traits, and PGR declined with increasing density in the controls. Exposure to C-14-cypermethrin had a direct negative effect on juvenile survival, presumably within the first 24 h because the chemical rapidly dissipated from the water column. Reductions in the initial larval densities resulted in an increase in the available resources for the survivors. Subsequently, exposed populations emerged sooner and started producing offspring earlier than the controls. C-14-cypermethrin had no effect on estimated fecundity and adult body weight but interacted with density to reduce the time to first emergence and first reproduction. As a result, PGR increased with cypermethrin concentration when populations were initiated at high densities. 4. Synthesis and applications. The results showed that the effects of C-14-cypermethrin were buffered at high density, so that the joint effects of density and chemical stress on PGR were less than additive. Low levels of chemical stressors may increase carrying capacity by reducing juvenile competition for resources. More and perhaps fitter adults may be produced, similar to the effects of predators and culling; however, toxicant exposure may result in survivors that are less tolerant to changing conditions. If less than additive effects are typical in the field, standard regulatory tests carried out at low density may overestimate the effects of environmental chemicals. Further studies over a wide range of chemical stressors and organisms with contrasting life histories are needed to make general recommendations.

The influence of larval density, food availability and habitat longevity on the life history and population growth rate of the midge Chironomus riparius

Despite long-standing interest in the forms and mechanisms of density dependence, these are still imperfectly understood. However, in a constant environment an increase in density must reduce per capita resource availability, which in turn leads to reduced survival, fecundity and somatic growth rate. Here we report two population experiments examining the density dependent responses under controlled conditions of an important indicator species, Chironomus riparius. The first experiment was run for 35 weeks and was started at low density with replicate populations being fed three different rations. Increased ration reduced generation time and increased population growth rate (pgr) but had no effect on survival, fecundity and female body weight in the first generation. In the second generation there was a six-fold increase in generation time, presumably due to the greatly reduced per capita resource availability as the estimated initial densities of the second generation were 300 times greater than the first. Juvenile survival to emergence, fecundity, adult body weight and pgr declined by 90%, 75%, 35% and 99%, respectively. These large between-generation effects may have obscured the effects of the threefold variation in ration, as only survival to emergence significantly increased with ration in the second generation. These results suggest that some chironomid larvae survive a reduction in resource availability by growing more slowly. In the ephemeral habitats sometimes occupied by C. riparius, the effects of population density may depend crucially on the longevity of the environment. A second experiment was therefore performed to measure pgr from six different starting densities over an eight-week period. The relationship between pgr and density was concave, viewed from above. At densities above 16 larvae per cm(2), less than 1% of the population emerged and no offspring were produced. Under the conditions of experiment 2 - an 8-week habitat lifespan carrying capacity was estimated as 8 larvae per cm(2).

Weaning preterm infants: a randomised controlled trial

Objective: To assess the effect on growth and iron status in preterm infants of a specially devised weaning strategy compared with current best practices in infant feeding. The preterm weaning strategy recommended the early onset of weaning and the use of foods with a higher energy and protein content than standard milk formula, and foods that are rich sources of iron and zinc. Subjects and design: In a blinded, controlled study, 68 preterm infants (mean (SD) birth weight 1470 (430) g and mean (SD) gestational age 31.3 (2.9) weeks) were randomised to either the preterm weaning strategy group (n = 37) or a current best practice control group (n = 31), from hospital discharge until 1 year gestation corrected age (GCA). Main outcome measures: Weight, supine length, occipitofrontal head circumference, and intakes of energy, protein, and minerals were determined at 0, 6, and 12 months GCA. Levels of haemoglobin, serum iron, and serum ferritin were assayed at 0 and 6 months GCA. Results: Significant positive effects of treatment included: greater increase in standard deviation length scores and length growth velocity; increased intake of energy, protein, and carbohydrate at 6 months GCA and iron at 12 months GCA; increased haemoglobin and serum iron levels at 6 months GCA. Conclusions: The preterm weaning strategy significantly influenced dietary intakes with consequent beneficial effects on growth in length and iron status. This strategy should be adopted as the basis of feeding guidelines for preterm infants after hospital discharge. School of Applied Statistics Faculty of Life Sciences

Growth of copper nanoparticles within VOx nanotubes

The synthesis of new Cu-VOx nanotubes has been achieved by exchanging a Cu(II) salt against the protonated template in the parent dodecylamine-VOx nanotubes. The intercalation of Cu(II) species induces some significant morphological and structural changes within the material, but the tubular shape is still well preserved. Controlled thermolysis under nitrogen of the Cu(II) species initially dispersed within the multiwalls induces the growth and sintering of copper nanoparticles, which are formed without destroying the tubular morphology of the host carrier. (C) 2002 Elsevier Science B.V. All rights reserved.

Exopolysaccharides produced by Bifidobacterium longum IPLA E44 and Bifidobacterium animalis subsp lactis IPLA R1 modify the composition and metabolic activity of human faecal microbiota in pH-controlled batch cultures

Exopolysaccharides (EPS) isolated from two Bifidobacterium strains, one of human intestinal origin (Bifidobacterium longum subsp. longum IPLA E44) and the other from dairy origin (Bifidobacterium animalis subsp. lactis IPLA R1), were subjected to in vitro chemically simulated gastrointestinal digestion. which showed the absence of degradation of both polymers in these conditions. Polymers were then used as carbon sources in pH-controlled faecal batch cultures and compared with the non-prebiotic carbohydrate glucose and the prebiotic inulin to determine changes in the composition of faecal bacteria. A set of eight fluorescent in situ hybridisation oligonucleotide probes targeting 16S rRNA sequences was used to quantify specific groups of microorganisms. Growth of the opportunistic pathogen Clostridium histolyticum occurred with all carbohydrates tested similarly to that found in negative control cultures without added carbohydrate and was mainly attributed to the culture conditions used rather than enhancement of growth by these substrates. Polymers E44 and RI stimulated growth of Lactobacillus/Enterococcus, Bifidobacterium, and Bacteroides/Prevotella in a similar way to that seen with inulin. The EPS RI also promoted growth of the Atopobium cluster during the first 24 h of fermentation. An increase in acetic and lactic acids was found during early stages of fermentation (first 10-24 h) correlating with increases of Lactobacillus, Bifidobacterium, and Atopobium. Propionic acid concentrations increased in old cultures, which was coincident with the enrichment of Clostridium cluster IX in cultures with EPS RI and with the increases in Bacteroides in cultures with both microbial EPS (RI and E44) and inulin. The lowest acetic to propionic acid ratio was obtained for EPS E44. None of the carbohydrates tested supported the growth of microorganisms from Clostridium clusters XIVa+b and IV, results that correlate with the poor butyrate production in the presence of EPS. Thus, EPS synthesized by bifidobacteria from dairy and intestinal origins can modulate the intestinal microbiota in vitro, promoting changes in some numerically and metabolically relevant microbial populations and shifts in the production of short chain fatty acids. (C) 2009 Elsevier B.V. All rights reserved.

Effect of pH and dose on the growth of gut bacteria on prebiotic carbohydrates in vitro

The effect of pH and substrate dose on the fermentation profile of a number of commercial prebiotics was analysed in triplicate using stirred, pH and temperature controlled anaerobic batch culture fermentations, inoculated with a fresh faecal slurry from one of three healthy volunteers. Bacterial numbers were enumerated using fluorescence in situ hybridisation. The commercial prebiotics investigated were fructooligosaccharides (FOS), inulin, galactooligosaccharides (GOS), isomaltooligosaccharides (IMO) and lactulose. Two pH values were investigated, i.e. pH 6 and 6.8. Doses of 1% and 2% (w/v) were investigated, equivalent to approximately 4 and 8 g per day, respectively, in an adult diet. It was found that both pH and dose altered the bacterial composition. It was observed that FOS and inulin demonstrated the greatest bifidogenic effect at pH 6.8 and 1% (w/v) carbohydrate, whereas GOS, IMO and lactulose demonstrated their greatest bifidogenic effect at pH 6 and 2% (w/v) carbohydrate. From this we can conclude that various prebiotics demonstrate differing bifidogenic effects at different conditions in vitro. (C) 2003 Elsevier Science Ltd. All rights reserved.

In vitro fermentation of carbohydrates by porcine faecal inocula and their influence on Salmonella Typhimurium growth in batch culture systems

The aim of this study was to evaluate in vitro the influence of fermentable carbohydrates on the activity of porcine microbiota and survival of Salmonella Typhimurium in a batch culture system simulating the porcine hindgut. The carbohydrates tested were xylooligosaccharides, a mixture of fructooligosaccharides/inulin (FIN), fructooligosaccharides (FOS), gentiooligosaccharides (GEO) and lactulose (LAC). These ingredients stimulated the growth of selected Bifidobacterium and Lactobacillus species in pure cultures. In batch cultures, the carbohydrates influenced some fermentation parameters. For example, GEO and FIN significantly increased lactic acids compared with the control (no added carbohydrate). With the exception of LAC, the test carbohydrates increased the production of short-chain fatty acid (SCFA) and modified SCFA profiles. Quantitative analysis of bacterial populations by FISH revealed increased counts of the Bifidobacterium group compared with control and, with exception of FOS, increased Lactobacillus, Leuconostoc and Weissella spp. counts. Salmonella numbers were the lowest during the fermentation of LAC. This work has looked at carbohydrate metabolism by porcine microbiota in a pH-controlled batch fermentation system. It provides an initial model to analyse interactions with pathogens.

The activity of ribosome modulation factor during growth of Escherichia coli under acidic conditions

Expression of the gene encoding ribosome modulation factor (RMF), as measured using an rmf-lacZ gene fusion, increased with decreasing pH in exponential phase cultures of Escherichia coli. Expression was inversely proportional to the growth rate and independent of the acidifying agent used and it was concluded that expression of rmf was growth rate controlled in exponential phase under acid conditions. Increased rmf expression during exponential phase was not accompanied by the formation of ribosome dimers as occurs during stationary phase. Nor did it appear to have a significant effect on cell survival under acid stress since the vulnerability of an RMF-deficient mutant strain was similar to that of the parent strain. Ribosome degradation was increased in the mutant strain compared to the parent strain at pH 3.75. Also, the peptide elongation rate was reduced in the mutant strain but not the parent during growth under acid conditions. It is speculated that the function of RMF during stress-induced reduction in growth rate is two-fold: firstly to prevent reduced elongation efficiency by inactivating surplus ribosomes and thus limiting competition for available protein synthesis factors, and secondly to protect inactivated ribosomes from degradation.

A systematic review of the routine monitoring of growth in children of primary school age to identify growth-related conditions

Objectives: To clarify the role of growth monitoring in primary school children, including obesity, and to examine issues that might impact on the effectiveness and cost-effectiveness of such programmes. Data sources: Electronic databases were searched up to July 2005. Experts in the field were also consulted. Review methods: Data extraction and quality assessment were performed on studies meeting the review's inclusion criteria. The performance of growth monitoring to detect disorders of stature and obesity was evaluated against National Screening Committee (NSC) criteria. Results: In the 31 studies that were included in the review, there were no controlled trials of the impact of growth monitoring and no studies of the diagnostic accuracy of different methods for growth monitoring. Analysis of the studies that presented a 'diagnostic yield' of growth monitoring suggested that one-off screening might identify between 1: 545 and 1: 1793 new cases of potentially treatable conditions. Economic modelling suggested that growth monitoring is associated with health improvements [ incremental cost per quality-adjusted life-year (QALY) of pound 9500] and indicated that monitoring was cost-effective 100% of the time over the given probability distributions for a willingness to pay threshold of pound 30,000 per QALY. Studies of obesity focused on the performance of body mass index against measures of body fat. A number of issues relating to human resources required for growth monitoring were identified, but data on attitudes to growth monitoring were extremely sparse. Preliminary findings from economic modelling suggested that primary prevention may be the most cost-effective approach to obesity management, but the model incorporated a great deal of uncertainty. Conclusions: This review has indicated the potential utility and cost-effectiveness of growth monitoring in terms of increased detection of stature-related disorders. It has also pointed strongly to the need for further research. Growth monitoring does not currently meet all NSC criteria. However, it is questionable whether some of these criteria can be meaningfully applied to growth monitoring given that short stature is not a disease in itself, but is used as a marker for a range of pathologies and as an indicator of general health status. Identification of effective interventions for the treatment of obesity is likely to be considered a prerequisite to any move from monitoring to a screening programme designed to identify individual overweight and obese children. Similarly, further long-term studies of the predictors of obesity-related co-morbidities in adulthood are warranted. A cluster randomised trial comparing growth monitoring strategies with no growth monitoring in the general population would most reliably determine the clinical effectiveness of growth monitoring. Studies of diagnostic accuracy, alongside evidence of effective treatment strategies, could provide an alternative approach. In this context, careful consideration would need to be given to target conditions and intervention thresholds. Diagnostic accuracy studies would require long-term follow-up of both short and normal children to determine sensitivity and specificity of growth monitoring.

A double-blind, placebo-controlled, cross-over study to establish the bifidogenic effect of a very-long-chain inulin extracted from globe artichoke (Cynara scolymus) in healthy human subjects

There is growing interest in the use of inulins as substrates for the selective growth of beneficial gut bacteria such as bifidobacteria and lactobacilli because recent studies have established that their prebiotic effect is linked to several health benefits. In the present study, the impact of a very-long-chain inulin (VLCI), derived from globe artichoke (Cynara scolymus), on the human intestinal microbiota compared with maltodextrin was determined. A double-blind, cross-over study was carried out in thirty-two healthy adults who were randomised into two groups and consumed 10 g/d of either VLCI or maltodextrin, for two 3-week study periods, separated by a 3-week washout period. Numbers of faecal bifidobacteria and lactobacilli were significantly higher upon VLCI ingestion compared with the placebo. Additionally, levels of Atopobium group significantly increased, while Bacteroides–Prevotella numbers were significantly reduced. No significant changes in faecal SCFA concentrations were observed. There were no adverse gastrointestinal symptoms apart from a significant increase in mild and moderate bloating upon VLCI ingestion. These observations were also confirmed by in vitro gas production measurements. In conclusion, daily consumption of VLCI extracted from globe artichoke exerted a pronounced prebiotic effect on the human faecal microbiota composition and was well tolerated by all volunteers.

Cognitive tests used in chronic adult human randomised controlled trial micronutrient and phytochemical intervention studies

In recent years there has been a rapid growth of interest in exploring the relationship between nutritional therapies and the maintenance of cognitive function in adulthood. Emerging evidence reveals an increasingly complex picture with respect to the benefits of various food constituents on learning, memory and psychomotor function in adults. However, to date, there has been little consensus in human studies on the range of cognitive domains to be tested or the particular tests to be employed. To illustrate the potential difficulties that this poses, we conducted a systematic review of existing human adult randomised controlled trial (RCT) studies that have investigated the effects of 24 d to 36 months of supplementation with flavonoids and micronutrients on cognitive performance. There were thirty-nine studies employing a total of 121 different cognitive tasks that met the criteria for inclusion. Results showed that less than half of these studies reported positive effects of treatment, with some important cognitive domains either under-represented or not explored at all. Although there was some evidence of sensitivity to nutritional supplementation in a number of domains (for example, executive function, spatial working memory), interpretation is currently difficult given the prevailing 'scattergun approach' for selecting cognitive tests. Specifically, the practice means that it is often difficult to distinguish between a boundary condition for a particular nutrient and a lack of task sensitivity. We argue that for significant future progress to be made, researchers need to pay much closer attention to existing human RCT and animal data, as well as to more basic issues surrounding task sensitivity, statistical power and type I error.

Roles of the translationally controlled tumour protein (TCTP) and the double-stranded RNA-dependent protein kinase, PKR, in cellular stress responses

Translationally controlled tumour protein (TCTP) is a highly conserved protein present in all eukaryotic organisms. Various cellular functions and molecular interactions have been ascribed to this protein, many related to its growth-promoting and antiapoptotic properties. TCTP levels are highly regulated in response to various cellular stimuli and stresses. We have shown recently that the double-stranded RNA-dependent protein kinase, PKR, is involved in translational regulation of TCTP. Here we extend these studies by demonstrating that TCTP is downregulated in response to various proapoptotic treatments, in particular agents that induce Ca++ stress, in a PKR-dependent manner. This regulation requires phosphorylation of protein synthesis factor eIF2α. Since TCTP has been characterized as an antiapoptotic and Ca++-binding protein, we asked whether it is involved in protecting cells from Ca++-stress-induced apoptosis. Overexpression of TCTP partially protects cells against thapsigargin-induced apoptosis, as measured using caspase-3 activation assays, a nuclear fragmentation assay, using fluorescence-activated cell sorting analysis, and time-lapse video microscopy. TCTP also protects cells against the proapoptotic effects of tunicamycin and etoposide, but not against those of arsenite. Our results imply that cellular TCTP levels influence sensitivity to apoptosis and that PKR may exert its proapoptotic effects at least in part through downregulation of TCTP via eIF2α phosphorylation.

Prebiotic evaluation of cocoa-derived flavanols in healthy humans by using a randomized, controlled, double-blind, crossover intervention study

BACKGROUND: The absorption of cocoa flavanols in the small intestine is limited, and the majority of the flavanols reach the large intestine where they may be metabolized by resident microbiota. OBJECTIVE: We assessed the prebiotic potential of cocoa flavanols in a randomized, double-blind, crossover, controlled intervention study. DESIGN: Twenty-two healthy human volunteers were randomly assigned to either a high-cocoa flavanol (HCF) group (494 mg cocoa flavanols/d) or a low-cocoa flavanol (LCF) group (23 mg cocoa flavanols/d) for 4 wk. This was followed by a 4-wk washout period before volunteers crossed to the alternant arm. Fecal samples were recovered before and after each intervention, and bacterial numbers were measured by fluorescence in situ hybridization. A number of other biochemical and physiologic markers were measured. RESULTS: Compared with the consumption of the LCF drink, the daily consumption of the HCF drink for 4 wk significantly increased the bifidobacterial (P < 0.01) and lactobacilli (P < 0.001) populations but significantly decreased clostridia counts (P < 0.001). These microbial changes were paralleled by significant reductions in plasma triacylglycerol (P < 0.05) and C-reactive protein (P < 0.05) concentrations. Furthermore, changes in C-reactive protein concentrations were linked to changes in lactobacilli counts (P < 0.05, R(2) = -0.33 for the model). These in vivo changes were closely paralleled by cocoa flavanol-induced bacterial changes in mixed-batch culture experiments. CONCLUSION: This study shows, for the first time to our knowledge, that consumption of cocoa flavanols can significantly affect the growth of select gut microflora in humans, which suggests the potential prebiotic benefits associated with the dietary inclusion of flavanol-rich foods. This trial was registered at clinicaltrials.gov as NCT01091922.

Metabolism of anthocyanins by human gut microflora and their influence on gut bacterial growth

Consumption of anthocyanins has been related with beneficial health effects. However, bioavailability studies have shown low concentration of anthocyanins in plasma and urine. In this study, we have investigated the bacterial-dependent metabolism of malvidin-3-glucoside, gallic acid and a mixture of anthocyanins using a pH-controlled, stirred, batch-culture fermentation system reflective of the distal human large intestine conditions. Most anthocyanins have disappeared after 5 h incubation while gallic acid remained constant through the first 5 h and was almost completely degraded following 24 h of fermentation. Incubation of malvidin-3-glucoside with fecal bacteria mainly resulted in the formation of syringic acid, while the mixture of anthocyanins resulted in formation of gallic, syringic and p-coumaric acids. All the anthocyanins tested enhanced significantly the growth of Bif idobacterium spp. and Lactobacillus−Enterococcus spp. These results suggest that anthocyanins and their metabolites may exert a positive modulation of the intestinal bacterial population.

Analysis of growth physiology and phytochemical content of Eruca and Diplotaxis Cultivars under different light and temperature regimes

Rocket is a leafy brassicaceous salad crop that encompasses two major genera (Diplotaxis and Eruca) and many different cultivars. Rocket is a rich source of antioxidants and glucosinolates, many of which are produced as secondary products by the plant in response to stress. In this paper we examined the impact of temperature and light stress on several different cultivars of wild and salad rocket. Growth habit of the plants varied in response to stress and with different genotypes, reflecting the wide geographical distribution of the plant and the different environments to which the genera have naturally adapted. Preharvest environmental stress and genotype also had an impact on how well the cultivar was able to resist postharvest senescence, indicating that breeding or selection of senescence-resistant genotypes will be possible in the future. The abundance of key phytonutrients such as carotenoids and glucosinolates are also under genetic control. As genetic resources improve for rocket it will therefore be possible to develop a molecular breeding programme specifically targeted at improving stress resistance and nutritional levels of plant secondary products. Concomitantly, it has been shown in this paper that controlled levels of abiotic stress can potentially improve the levels of chlorophyll, carotenoids and antioxidant activity in this leafy vegetable.