Behaviour of Aspergillus flavus in presence of Aspergillus niger during biosynthesis of aflatoxin B1

Aspergillus niger or Aspergillus tamarii when grown as mixed cultures with toxigenic A. flavus inhibits biosynthesis of aflatoxin by A. flavus, owing primarily to its ability to produce inhibitors of aflatoxin biosynthesis and to their ability to degrade aflatoxin. Gluconic acid partly prevents aflatoxin production. The other factors such as changes in pH of the medium and the effect on the growth of A. flavus have no role in imparting capabilities to these cultures to inhibit aflatoxin production by A. flavus.     

Identification and mapping in spring wheat of genetic factors controlling stem rust resistance and the study of their epistatic interactions across multiple environments

Stem rust (Puccinia graminis f. sp. tritici) is responsible for major production losses in hexaploid wheat (Triticum aestivum L.) around the world. The spread of stem rust race Ug99 and variants is a threat to worldwide wheat production and efforts are ongoing to identify and incorporate resistance. The objectives of this research were to identify quantitative trait loci (QTL) and to study their epistatic interactions for stem rust resistance in a population derived from the Canadian wheat cultivars AC Cadillac and Carberry. A doubled haploid (DH) population was developed and genotyped with DArT^® and SSR markers. The parents and DH lines were phenotyped for stem rust severity and infection response to Ug99 and variant races in 2009, 2010 and 2011 in field rust nurseries near Njoro, Kenya, and to North American races in 2011 and 2012 near Swift Current, SK, Canada. Seedling infection type to race TTKSK was assessed in a bio-containment facility in 2009 and 2012 near Morden, MB. Eight QTL for stem rust resistance and three QTL for pseudo-black chaff on nine wheat chromosomes were identified. The phenotypic variance (PV) explained by the stem rust resistance QTL ranged from 2.4 to 48.8 %. AC Cadillac contributed stem rust resistance QTL on chromosomes 2B, 3B, 5B, 6D, 7B and 7D. Carberry contributed resistance QTL on 4B and 5A. Epistatic interactions were observed between loci on 4B and 5B, 4B and 7B, 6D and 3B, 6D and 5B, and 6D and 7B. The stem rust resistance locus on 6D interacted synergistically with 5B to improve the disease resistance through both crossover and non-crossover interactions depending on the environment. Results from this study will assist in planning breeding for stem rust resistance by maximizing QTL main effects and epistatic interactions.     

Obesity in China: The Differential Impacts of Covariates Along the BMI Distribution

Growing prosperity and changing diets have contributed to a surge in obesity prevalence in China. Previous research has investigated the relationships between BMI and several socioeconomic, diet‐related, and health‐related variables in China. This study proposes that such relationships are likely to differ along the conditional BMI distribution, and seeks to investigate such quantile‐dependent variation in effects. Special attention is paid to how variables affect the upper tail of the conditional BMI distribution where overweight and obesity concerns are more acute. Quantile regressions (QRs) and ordinary least squares (OLS) regressions are estimated. The sample consists of 3,407 adult individuals aged 20–45 who participated in the China Health and Nutrition Survey (CHNS), 2006. Substantial cross quantile variation is observed in the relationships between several key variables and BMI. The QR shows that the relationship between energy intake and BMI is largely insignificant in the lower and middle quantiles, whereas the upper quantiles show a positive and significant effect substantially larger than predicted by the least squares regression and by previous studies. This implies that a food‐based strategy aimed at limiting energy intake can be an effective way to fight obesity in China. The negative association between smoking and BMI, on the other hand, is found largely to hold only in the lower and middle quantiles, with the upper tail relatively unaffected by smoking status. Thus, smoking cessation policies may not exacerbate obesity.     

Global patterns and predictions of seafloor biomass using random forests

A comprehensive seafloor biomass and abundance database has been constructed from 24 oceanographic institutions worldwide within the Census of Marine Life (CoML) field projects. The machine-learning algorithm, Random Forests, was employed to model and predict seafloor standing stocks from surface primary production, water-column integrated and export particulate organic matter (POM), seafloor relief, and bottom water properties. The predictive models explain 63% to 88% of stock variance among the major size groups. Individual and composite maps of predicted global seafloor biomass and abundance are generated for bacteria, meiofauna, macrofauna, and megafauna (invertebrates and fishes). Patterns of benthic standing stocks were positive functions of surface primary production and delivery of the particulate organic carbon (POC) flux to the seafloor. At a regional scale, the census maps illustrate that integrated biomass is highest at the poles, on continental margins associated with coastal upwelling and with broad zones associated with equatorial divergence. Lowest values are consistently encountered on the central abyssal plains of major ocean basins The shift of biomass dominance groups with depth is shown to be affected by the decrease in average body size rather than abundance, presumably due to decrease in quantity and quality of food supply. This biomass census and associated maps are vital components of mechanistic deep-sea food web models and global carbon cycling, and as such provide fundamental information that can be incorporated into evidence-based management.     

Feeding Preferences of Abyssal Macrofauna Inferred from In Situ Pulse Chase Experiments

Climatic fluctuations may significantly alter the taxonomic and biochemical composition of phytoplankton blooms and subsequently phytodetritus, the food source for the majority of deep-sea communities. To examine the response of abyssal benthic communities to different food resources we simulated a food sedimentation event containing diatoms and coccolithophorids at Station M in the NE Pacific. In one set of experiments we measured incorporation of _diatomC and _coccoN into the macrofauna using isotopically enriched ¹³C-diatoms and ¹⁵N-coccolithophores. In a second experiment we measured incorporation of C and N from dual-labelled (¹³C and ¹⁵N) diatoms. The second experiment was repeated 2 months later to assess the effect of seasonality. The simulated food pulses represented additions of 650 – 800 mg C m⁻² and 120 mg N m⁻² to the seafloor. In all cases rapid incorporation of tracer was observed within 4 days, with between 20% and 52% of the macrofauna displaying evidence of enrichment. However, incorporation levels of both _diatomC and _coccoN were low (<0.05% and 0.005% of the added C and N). Incorporation of labelled diatoms was similar during both June and September suggesting that the community was not food limited during either period. We found no evidence for selective ingestion of the different food types in the metazoan fauna suggesting that macrofauna do not have strong preferences for diatom vs. coccolithophore dominated phytodetrital pulses. C∶N ratios from both experiments suggest that the metazoan macrofauna community appear to have higher C demands and/or assimilation efficiencies compared to N. Concomitantly, the foraminifera preferentially selected for _diatomN over _coccoN, and we suggest that this may be related to foraminiferal requirements for intracellular nitrate. These experiments provide evidence that abyssal faunal feeding strategies are in part driven by an organism''s internal stoichiometric budgets and biochemical requirements.     

Carbon monoxide and biliverdin prevent endothelial cell sloughing in rats with type I diabetes

Hyperglycemia has been linked to increased oxidative stress, a resultant endothelial cell dysfunction, and, ultimately, apoptosis. Heme oxygenases (HO-1/HO-2) and the products of their activity, biliverdin/bilirubin and carbon monoxide (CO), play a physiological role in the vascular system. The effects of heme-mediated HO-1 induction, CO, and biliverdin on urinary 8-epi-isoprostane PGF₂ and endothelial cell sloughing were examined in an animal model of streptozotocin (STZ)-induced diabetes. Hyperglycemia itself did not affect HO-1 and HO-2 protein levels, but caused a net decrease in HO activity. Weekly heme administration induced HO-1 protein, as demonstrated by immunohistochemistry and Western blot analyses. Administration of biliverdin or the CO donor, CORM-3, decreased urinary 8-epi-isoprostane PGF₂, P < 0.5 compared to diabetes. Hyperglycemia increased endothelial cell sloughing; 8.2 ± 0.8 cells/ml blood in control rats vs. 48 ± 4.8 cells/ml blood in diabetic rats (P < 0.05). Heme administration significantly increased endothelial cell sloughing in diabetic rats (98 ± 8.1 cells/ml blood, P < 0.0007) whereas biliverdin modestly decreased endothelial cell sloughing (26 ± 3.5 cells/ml blood, P < 0.003). Administration of CORM-3 to diabetic rats resulted in a significant decrease in endothelial cell sloughing to 21.3 ± 2.3 (P < 0.001). Administration of SnMP to CORM-3 diabetic rats only partially reversed the protective effects of CORM-3 on endothelial cell sloughing from 21.3 ± 2.3 to 29 ± 2.1 cells/ml, thus confirming a direct protective of CO, in addition to the ability of CORM-3 to induce HO-1 protein. These results demonstrate that exogenously administered CO or bilirubin can prevent endothelial cell sloughing in diabetic rats, likely via a decrease in oxidative stress, and thus represents a novel approach to prophylactic vascular protection in diabetes.