Laboratory investigation of daily food intake and gut evacuation in larvae of African catfish Clarias gariepinus under different feeding conditions

Abstract Temporary accumulation of ascorbic acid 2-sulfate (AAS) was measured to estimate food intake and gut evacuation in larvae of African catfish. Fish larvae were fed decapsulated cysts of Artemia containing AAS. In a first experiment it was found that no biosynthesis of AAS occurs in the larvae of this species. In a second experiment, the gut contents of the fish larvae fed were calculated as they changed during development. In a third experiment, the gut evacuation rate of fish larvae was determined during continuous and discontinuous feeding regimes in the first five days after the start of exogenous feeding. Food consumption by catfish larvae increased from 46.5% of their body dry weight (BDW) on day 1 after the start of exogenous feeding to 53.8% BDW on day 3. Thereafter, food consumption decreased to 27.8% BDW on day 5. A similar pattern was observed for gut evacuation, which increased during the first days of exogenous feeding and decreased as fish growth continued. The rate of gut evacuation in a continuous feeding regime was significantly higher (P <0.05) than that under discontinuous feeding. On day 1 post-hatch and 7 h after first food ingestion the fish larvae evacuated 87% of the food in continuous feeding compared with 43% under discontinuous feeding. It was found that gut emptying differs during larval development. Under continuous feeding, on days 1 and 3 post-hatch and 11 h after the first meal 90% of the food was evacuated compared with 71% evacuated on day 5. The advantages and limitations of the AAS method for estimation of food consumption by fish larvae are discussed

Comparison of multiple methods for the study of the molecular epidemiology of Aspergillus fumigatus

Date du colloque&nbsp;: 01/2008</p

The content of ascorbic acid and tocopherol in the tissues and eggs of wild <i>Macrobrachium rosenbergii</i> during maturation

Variations in the concentrations of ascorbic acid (AA) and tocopherols in association with the gonadal development of the freshwater prawn Macrobrachium rosenbergii were investigated in females captured in the Mae Klong River, Thailand. Mean ovarian AA levels ranged from 210 to 540 µg/g dry weight (dw) and were at least 11-fold higher than midgut gland (MG) levels. Variations in ovarian AA levels are believed to be related to the biosynthesis of steroid hormones, the formation of collagen, and the deposition of egg yolk compounds. alpha-Tocopherol (alpha-T) was the predominant form of vitamin E in prawn tissues and eggs. The level of alpha-T in the MG was constant, whereas in the ovaries, it ranged from 143 to 425 µg/g dw. The incorporation of a-T into the ovary was highly correlated (r² = 0.87) to ovarian lipid levels, which probably reflects the role of this vitamin as a major antioxidant agent. The present results provide further evidence of the essentiality of these vitamins in crustacean reproduction

Al-2 quorum-sensing inhibitors affect the starvation response and reduce virulence in several <i>Vibrio</i> species, most likely by interfering with LuxPQ

The increase of disease outbreaks caused by Vibrio species in aquatic organisms as well as in humans, together with the emergence of antibiotic resistance in Vibrio species, has led to a growing interest in alternative disease control measures. Quorum sensing (QS) is a mechanism for regulating microbial gene expression in a cell density-dependent way. While there is good evidence for the involvement of auto-inducer 2 (AI-2)-based interspecies QS in the control of virulence in multiple Vibrio species, only few inhibitors of this system are known. From the screening of a small panel of nucleoside analogues for their ability to disturb AI-2-based QS, an adenosine derivative with a p-methoxyphenylpropionamide moiety at C-3′ emerged as a promising hit. Its mechanism of inhibition was elucidated by measuring the effect on bioluminescence in a series of Vibrio harveyi AI-2 QS mutants. Our results indicate that this compound, as well as a truncated analogue lacking the adenine base, block AI-2-based QS without interfering with bacterial growth. The active compounds affected neither the bioluminescence system as such nor the production of AI-2, but most likely interfered with the signal transduction pathway at the level of LuxPQ in V. harveyi. The most active nucleoside analogue (designated LMC-21) was found to reduce the Vibrio species starvation response, to affect biofilm formation in Vibrio anguillarum, Vibrio vulnificus and Vibrio cholerae, to reduce pigment and protease production in V. anguillarum, and to protect gnotobiotic Artemia from V. harveyi-induced mortality

The trans-ancestral genomic architecture of glycemic traits

Glycemic traits are used to diagnose and monitor type 2 diabetes and cardiometabolic health. To date, most genetic studies of glycemic traits have focused on individuals of European ancestry. Here we aggregated genome-wide association studies comprising up to 281,416 individuals without diabetes (30% non-European ancestry) for whom fasting glucose, 2-h glucose after an oral glucose challenge, glycated hemoglobin and fasting insulin data were available. Trans-ancestry and single-ancestry meta-analyses identified 242 loci (99 novel; P < 5 x 10(-8)), 80% of which had no significant evidence of between-ancestry heterogeneity. Analyses restricted to individuals of European ancestry with equivalent sample size would have led to 24 fewer new loci. Compared with single-ancestry analyses, equivalent-sized trans-ancestry fine-mapping reduced the number of estimated variants in 99% credible sets by a median of 37.5%. Genomic-feature, gene-expression and gene-set analyses revealed distinct biological signatures for each trait, highlighting different underlying biological pathways. Our results increase our understanding of diabetes pathophysiology by using trans-ancestry studies for improved power and resolution.A trans-ancestry meta-analysis of GWAS of glycemic traits in up to 281,416 individuals identifies 99 novel loci, of which one quarter was found due to the multi-ancestry approach, which also improves fine-mapping of credible variant sets.Diabetes mellitus: pathophysiological changes and therap

The Influence of Age and Sex on Genetic Associations with Adult Body Size and Shape : A Large-Scale Genome-Wide Interaction Study

Genome-wide association studies (GWAS) have identified more than 100 genetic variants contributing to BMI, a measure of body size, or waist-to-hip ratio (adjusted for BMI, WHRadjBMI), a measure of body shape. Body size and shape change as people grow older and these changes differ substantially between men and women. To systematically screen for age-and/or sex-specific effects of genetic variants on BMI and WHRadjBMI, we performed meta-analyses of 114 studies (up to 320,485 individuals of European descent) with genome-wide chip and/or Metabochip data by the Genetic Investigation of Anthropometric Traits (GIANT) Consortium. Each study tested the association of up to similar to 2.8M SNPs with BMI and WHRadjBMI in four strata (men 50y, women 50y) and summary statistics were combined in stratum-specific meta-analyses. We then screened for variants that showed age-specific effects (G x AGE), sex-specific effects (G x SEX) or age-specific effects that differed between men and women (G x AGE x SEX). For BMI, we identified 15 loci (11 previously established for main effects, four novel) that showed significant (FDR= 50y). No sex-dependent effects were identified for BMI. For WHRadjBMI, we identified 44 loci (27 previously established for main effects, 17 novel) with sex-specific effects, of which 28 showed larger effects in women than in men, five showed larger effects in men than in women, and 11 showed opposite effects between sexes. No age-dependent effects were identified for WHRadjBMI. This is the first genome-wide interaction meta-analysis to report convincing evidence of age-dependent genetic effects on BMI. In addition, we confirm the sex-specificity of genetic effects on WHRadjBMI. These results may providefurther insights into the biology that underlies weight change with age or the sexually dimorphism of body shape.Peer reviewe

Progress in biomedication using live foods

With the intensification of aquaculture production systems, mass mortality of fish and shellfish caused by bacterial infections is not unusual. Chemotherapy (treatment of infection with antimicrobial compounds) and immunoprophylaxis (vaccination and immunostimulation), are the common methods applied to treat bacterial infections. In search of an efficient and cost-effective delivery route for antimicrobial agents and/or immuno-prophylactics to treat fish and shrimp larvae, the use of live prey organisms bioencapsulated with drugs has been explored. This article provides an update on the use of the bioencapsulation technique in aquaculture

Enrichment of live food with essential fatty acids and vitamin C: effects on milkfish (<i>Chanos chanos</i>) larval performance

The effects of essential fatty acids (EFA) and vitamin C-enriched live food on growth, survival, resistance to salinity stress and incidence of deformity in milkfish larvae reared in tanks were investigated. Larvae were either fed rotifers cultured on Chlorella sp. and newly hatched Artemia nauplii (control), highly unsaturated fatty acid (HUFA)-enriched rotifers and Artemia nauplii or HUFA + vitamin C-enriched rotifers and Artemia nauplii. Milkfish growth in outdoor nursery ponds was also assessed to compare with growth in indoor tanks. Milkfish fed rotifers/Artemia enriched with HUFA (32-48 mg dry weight, DW) or HUFA + vitamin C (33-45 mg DW) exhibited significantly (P0.05) among the treatment groups. Forty-day-old milkfish fed HUFA + vitamin C-enriched live food had significantly lower (P<0.05) incidence of opercular deformity (mainly cleft branchiostegal membrane) (8.4-14.7%) compared with those given HUFA-enriched (15.8-23.5%) or unenriched (27.3-33.5%) live food. Results demonstrated the effect of HUFA enrichment in enhancing milkfish larval growth and resistance to salinity stress but not overall survival. Moreover, HUFA and ascorbate supplementation decreased but did not totally eliminate incidence of opercular deformity in milkfish larvae

Solid-phase extraction of ascorbic acid 2-sulfate from cysts of the brine shrimp <i>Artemia fransiscana</i>

Two producers are described for the solid-phase extraction of ascorbic acid 2-sulfate from cysts of the brine shrimp Artemia . The first one is based on reversed-phase ion pair extraction on an octadecylsilica cartridge using tetrabutylammonium as the counterion, followed by elution with methanol. In the second procedure ascorbic acid 2-sulfate is retained on a DEAE silica cartridge and eluted with 0.1M sodium salicylate. Both approaches were used as part of a quantitative reversed-phase ion pair liquid chromatographic method with detection at 254nm. The anion exchange extraction procedure is superior to its ion pair counterpart in terms of recovery (88.7±3,5% versus 63.0±12.7%), reproducibility (CVs of 3.6-7.7% versus 6.3-18.7%), and simplicity

Antioxidant effect of dietary tocopherol and ascorbic acid on growth and survival of <i>Litopenaeus vannamei</i> postlarvae

The nutritional effect of vitamin E in diets for Litopenaeus vannamei postlarve (PL19) was investigated. Four formulated diets with different combinations of alfa-tocophery1 acetate (alfa-TA), ascorbic acid (AA) and highly unsaturated fatty acids (HUFA) were tested, using four rep1icates. No significant differences in survival were observed among treatments after 34 days of feeding. However, shrimp fed with a diet containing 20/c fish oil (low n-3 HUFA content), 200 mg.kg-1 alfa-TA and 100 mg.kg-1 AA (diet H/E/C) showed significantly better growth than those fed a diet supp1emented with 5% fish oil (high n-3 HUFA content), 200 mg.kg-1 a- TA and 100 mg.kg-1 AA (diet H+/E/C). Shrimp fed with a diet containing 50/c fish oil, 900 mg.kg-1 alfa-TA and 100 mg.kg-1 AA (diet H+/E+/C) showed a significantly higher tissue level of n-6 PUFA than postlarvae fed diet H+/E/C. No definite conclusion could be drawn about a possible interaction between a- TA and AA, since a comparison of the diet containing 50% fish oil, 200 mg.kg-1 a-TA and 700 mg.kg-1 AA (H+/E+/C+) and the diet H+/E/C did not show any significant differences in any of the measured parameters. The antioxidative status of the shrimp tissue (measured by means of the thiobarbituric acid (TBA) assay and expressed as nM malonaldehyde (MA) per gramme dry weight) was equal for all treatments. Nevertheless, there was a slightly lower MA value with the diet H+/E/C+, indicating that AA may be an effective antioxidant in the aqueous phase and at the water/lipid interface of the tissue. The tissue levels of alfa- T and AA were highly dependent on the amounts in diets and no correlation between alfa- T and AA incorporation could be observed