Bird mercury concentrations change rapidly as chicks age: toxicological risk is highest at hatching and fledging

Toxicological risk of methylmercury exposure to juvenile birds is complex due to the highly transient nature of mercury concentrations as chicks age. We examined total mercury and methylmercury concentrations in blood, liver, kidney, muscle, and feathers of 111 Forster's tern (Sterna forsteri), 69 black-necked stilt (Himantopus mexicanus), and 43 American avocet (Recurvirostra americana) chicks as they aged from hatching through postfledging at wetlands that had either low or high mercury contamination in San Francisco Bay, California. For each waterbird species, internal tissue, and wetland, total mercury and methylmercury concentrations changed rapidly as chicks aged and exhibited a quadratic, U-shaped pattern from hatching through postfledging. Mercury concentrations were highest immediately after hatching, due to maternally deposited mercury in eggs, then rapidly declined as chicks aged and diluted their mercury body burden through growth in size and mercury depuration into growing feathers. Mercury concentrations then increased during fledging when mass gain and feather growth slowed, while chicks continued to acquire dietary mercury. In contrast to mercury in internal tissues, mercury concentrations in chick feathers were highly variable and declined linearly with age. For 58 recaptured Forster's tern chicks, the proportional change in blood mercury concentration was negatively related to the proportional change in body mass, but not to the amount of feathers or wing length. Thus, mercury concentrations declined more in chicks that gained more mass between sampling events. The U-shaped pattern of mercury concentrations from hatching to fledging indicates that juvenile birds may be at highest risk to methylmercury toxicity shortly after hatching when maternally deposited mercury concentrations are still high and again after fledging when opportunities for mass dilution and mercury excretion into feathers are limited.     

A colored avocado seed extract as a potential natural colorant

There is an increasing consumer demand for and scientific interest in new natural colorants. Avocado (Persea americana) seed when crushed with water develops an orange color (= 480 nm) in a time-dependent manner. Heat treatment of the seed prevented color development, whereas the addition of exogenous polyphenol oxidase (PPO), but not peroxidase restored color development. Color development was also inhibited by the addition of tropolone, an inhibitor of PPO. Color formation resulted in a decrease in the concentration of polyphenols indicating utilization for color formation. The orange color intensified as the pH was adjusted from 2.0 to 11.0, and these changes were only partially reversible when pH was adjusted from 7.5 to 11.0 in the presence of oxygen, but completely reversible when the pH was changed in the absence of oxygen. The color was found to be stable in solution at -18 °C for 2 mo. These results suggest that the avocado seed may be a potential source of natural colorant, and that color development is PPO-dependent. PRACTICAL APPLICATION: There is growing public and scientific interest in the development of natural alternatives to synthetic colorants in foods. Extracts of turmeric, paprika, and beets are examples of food-derived natural colorants. Avocado seeds, which represent an under-utilized waste stream, form a stable orange color when crushed in the presence of air. Our data indicate that avocado seed represents a potential source of new natural colorants for use in foods.     

Modeling the thermal inactivation kinetics of heat-resistant Salmonella Enteritidis and Oranienburg in 10 percent salted liquid egg yolk

There is no suitable model for predicting thermal inactivation kinetics of Salmonella spp. for many types of liquid egg products, including salted liquid egg yolk, for use in updating U.S. Department of Agriculture (USDA) pasteurization guidelines. This is because, in part, of the variations in Salmonella strains and the changes in the processing of liquid egg products over the past 40 years. The objectives of the present study were to determine the thermal inactivation kinetics and to create a general thermal inactivation kinetics model that can be used for estimating log reductions of salmonellae in 10% salted liquid egg yolk for temperatures between 62.2 and 69°C. This model can be used by processors to help ensure adequate pasteurization. This was accomplished by studying the inactivation kinetics of a three-strain composite of heat-resistant Salmonella serovars Enteritidis and Oranienburg, inoculated into commercially processed 10% salted liquid egg yolk. The survival curves were convex, with asymptotic D-values. From these curves, a general model was developed to predict log reductions for given times at specified temperatures. For example, at a temperature of 67.3°C (153.1°F) for 3.5 min, our model predicts a 5-log reduction would be obtained, whereas with the current USDA minimum required pasteurization regimen (63.33°C [146°F] for 3.5 min), our model predicts that a reduction of only 2.7 log would be obtained. The results of this study provide information that can be used by processors to aid in producing safe, pasteurized egg yolk products, and for satisfying USDA pasteurization performance standards and developing industry guidance.     

Use of Caenorhabditis elegans for preselecting Lactobacillus isolates to control Salmonella Typhimurium

Host-specific probiotics have been used to control enteric pathogens, including foodborne pathogens, in food animal production. However, evaluation of the efficacy of these probiotics requires costly in vivo assays in the target animal. The nematode Caenorhabditis elegans has been used for prescreening of antimicrobial agents and for studies of host-pathogen interactions. In the present study, 17 Lactobacillus isolates from chicken and pig intestines were tested with C. elegans, and the ability of these isolates to prevent death from Salmonella infection was variable. Two Lactobacillus isolates (S64, which gave full protection, and CL11, which gave no protection) were further studied. Both isolates exhibited a similar colonization profile in the C. elegans intestine. Although different culture fractions of CL11 were not protective, both live and heat-killed S64 cells provided full or partial protection of C. elegans from death caused by Salmonella infection. In contrast, different culture fractions from both isolates had similar effects on the colonization of the nematode intestine by Salmonella Typhimurium DT104. Our preliminary results from a pig performance trial revealed a correlation between the degree of protection in the C. elegans survival assay and the performance of 35-day-old weaned piglets that were treated with the same Lactobacillus isolates, suggesting that C. elegans can be used as a laboratory animal model for preselecting probiotics for control of Salmonella infections.     

The intestinal microbiota and its modulation for Salmonella control in chickens

Salmonella control has been one of the major tasks in poultry production to ensure poultry food safety. Effective control is difficult due to the numerous potential sources of Salmonella infection and product contamination in integrated poultry enterprises. In addition, the lack of clinical symptoms of infection in poultry further increases the challenge of achieving proper control. The chicken intestinal microbiota plays an important role in the host health and its modulation has achieved considerable success in the past to reduce Salmonella contamination at the farm level. The use of pro/prebiotics has been the major approach in modulating the microbiota. There is increased consumer pressure demanding the reduction of antibiotics in feed and elimination of Salmonella from poultry and their products. Modulation of the chicken intestinal microbiota continues to offer an attractive option for natural control and sustainable chicken production. In this article, the role of intestinal microbiota in chicken health and the progress in microbiota modulation for Salmonella control have been reviewed. Major technologies for modulating intestinal microbiota, such as the use of probiotics, prebiotics, or phytobiotics (essential oils) and phage therapy that have either received much attention in research and application or demonstrated promise in the development of novel techniques for Salmonella control, are discussed. The potential and drawbacks of each of these are also critically reviewed.     

Observation of two resistance switching modes in TiO2 memristive devices electroformed at low current

We report the observation of two resistance switching modes in certain 50 nm × 50 nm crossbar TiO(2) memristive devices that have been electroformed with a low-current process. The two switching modes showed opposite switching polarities. The intermediate state was shared by both modes (the ON state of the high-resistance mode or the OFF state of the low-resistance mode) and exhibited a relaxation to a more resistive state, including an initial transient decay. The activation energies of such a decay and ON-switching to the intermediate state were determined to be 50-210 meV and 1.1 eV, respectively. Although they are attributed to the coexistence of charge trapping and ionic motion, the ionic motion dominates in both switching modes. Our results indicate that the two switching modes in our system correspond to different switching layers adjacent to the interfaces at the top and bottom electrodes.     

Does willingness to pay for green energy differ by source?

We present the findings of a choice experiment designed to estimate consumer preferences and willingness-to-pay (WTP) for voluntary participation in green energy electricity programs. Our model estimates WTP for a generic “green energy” source and compares it to WTP for green energy from specific sources, including wind, solar, farm methane, and biomass. Our results show that there exists a positive WTP for green energy electricity. Further, individuals have a preference for solar over a generic green and wind. Biomass and farm methane are found to be the least preferred sources.     

metaXCMS: second-order analysis of untargeted metabolomics data

Mass spectrometry-based untargeted metabolomics often results in the observation of hundreds to thousands of features that are differentially regulated between sample classes. A major challenge in interpreting the data is distinguishing metabolites that are causally associated with the phenotype of interest from those that are unrelated but altered in downstream pathways as an effect. To facilitate this distinction, here we describe new software called metaXCMS for performing second-order ("meta") analysis of untargeted metabolomics data from multiple sample groups representing different models of the same phenotype. While the original version of XCMS was designed for the direct comparison of two sample groups, metaXCMS enables meta-analysis of an unlimited number of sample classes to facilitate prioritization of the data and increase the probability of identifying metabolites causally related to the phenotype of interest. metaXCMS is used to import XCMS results that are subsequently filtered, realigned, and ultimately compared to identify shared metabolites that are up- or down-regulated across all sample groups. We demonstrate the software's utility by identifying histamine as a metabolite that is commonly altered in three different models of pain. metaXCMS is freely available at http://metlin.scripps.edu/metaxcms/.     

Image charge detection mass spectrometry: pushing the envelope with sensitivity and accuracy

A novel image charge detection mass spectrometer (CDMS) with improved sensitivity and mass accuracy is described. The improved detector design and method of data analysis allow us to measure a reliable mass for a single macroion that is an order of magnitude smaller than previously achieved with CDMS. The apparatus employs an image charge detector array consisting of 22 detectors. The detectors are divided into two groups that can be floated at different potentials. The signals from the detector array are analyzed using a correlation approach to yield the velocities in the two groups of detectors and the charge. These quantities, together with the voltage difference between the two groups of detectors, provide a value for the mass. The mass, m/z, and charge distributions recorded for 300 kDa poly(ethylene oxide) (PEG) are presented. The mass distribution shows a peak at around 300 kDa with a width close to that expected from the polymer size distribution. In addition, there are broad peaks in the mass distribution at around 100 and 500 MDa. The 300 kDa ions have m/z ratios of ～2 kDa/e, and the 100 and 500 MDa ions have m/z ratios of ～40 kDa/e. The 100 and 500 MDa ions probably result from PEG aggregates that are either present in solution or the residue of large electrospray droplets.     

Ultrafast surface enhanced resonance Raman scattering detection in droplet-based microfluidic systems

The development of ultrafast Raman-based detection is one of the most interesting challenges underpinning the application of droplet-based microfluidics. Herein, we describe the use of surface-enhanced resonance Raman spectroscopy (SERRS) with submillisecond time resolution as a powerful detection tool in microdroplet reactors. Individual droplets containing silver nanoparticle aggregates functionalized with Raman reporters are interrogated and characterized by full spectra acquisitions with high spatial resolution in real time. Whereas previous works coupling SERRS with droplet-based microfluidics acquire a single spectrum over single or multiple droplets, we build upon these results by increasing our temporal resolution by 2 orders of magnitude. This allows us to interrogate multiple points within one individual droplet. The SERRS signals emitted from the aggregates are utilized to access the influence of flow rate on droplet size and throughput. Accordingly, our approach allows for high-throughput analysis that facilitates the study of other biological assays or molecular interactions.