The Regulatory Status of Genome‐edited Crops

Genome editing with engineered nucleases (GEEN) represents a highly specific and efficient tool for crop improvement with the potential to rapidly generate useful novel phenotypes/traits. Genome editing techniques initiate specifically targeted double strand breaks facilitating DNA‐repair pathways that lead to base additions or deletions by non‐homologous end joining as well as targeted gene replacements or transgene insertions involving homology‐directed repair mechanisms. Many of these techniques and the ancillary processes they employ generate phenotypic variation that is indistinguishable from that obtained through natural means or conventional mutagenesis; and therefore, they do not readily fit current definitions of genetically engineered or genetically modified used within most regulatory regimes. Addressing ambiguities regarding the regulatory status of genome editing techniques is critical to their application for development of economically useful crop traits. Continued regulatory focus on the process used, rather than the nature of the novel phenotype developed, results in confusion on the part of regulators, product developers, and the public alike and creates uncertainty as of the use of genome engineering tools for crop improvement.     

Problem formulation in the environmental risk assessment for genetically modified plants

Problem formulation is the first step in environmental risk assessment (ERA) where policy goals, scope, assessment endpoints, and methodology are distilled to an explicitly stated problem and approach for analysis. The consistency and utility of ERAs for genetically modified (GM) plants can be improved through rigorous problem formulation (PF), producing an analysis plan that describes relevant exposure scenarios and the potential consequences of these scenarios. A properly executed PF assures the relevance of ERA outcomes for decision-making. Adopting a harmonized approach to problem formulation should bring about greater uniformity in the ERA process for GM plants among regulatory regimes globally. This paper is the product of an international expert group convened by the International Life Sciences Institute (ILSI) Research Foundation.     

Foraging behavior and prey of sea otters in a soft- and mixed-sediment benthos in Alaska

Sea otter (Enhydra lutris kenyoni) foraging behavior and prey preference were studied from June to August 2001–2004 in Simpson Bay, Prince William Sound, Alaska. The study area has an average water depth of 30 m and a benthos primarily of soft- and mixed-sediment with no canopy-forming kelps. A total of 1816 foraging dives from 211 bouts were recorded. Overall, dives ranged in depth from <5 to 82 m; most dives were less than 15 m (40%) with smaller, secondary peaks at 25–30 m (10%) and 50–55 m (7%). Average dive depth and duration were 27 m ± 19.5 and 1.89 min ± 0.88, respectively. Dive durations were all significantly different: male > unknown > female. Dive depths reflected the bathymetry (percentage of the bay within a depth range) of Simpson Bay but favored shallow areas. 87% of foraging dives were successful, and 44% of the prey was positively identified: 75% clams, 9% Pacific blue mussels, 6% crabs, 2% Reddish scallops and a variety of other invertebrates. There was no evidence for prey specialization among the sexes. Although sea otters in Simpson Bay rely heavily on bivalves, their diet has remained unchanged for the past 18 years, and the minimum summer population has been constant for at least the past nine years. It appears that bivalves are the predominant and stable component of the diet, and their productivity is sufficient to sustain a stable population of sea otters with a minimum peak summer density of 4.3 adult otters km^?2 and an average annual density of ca. 2.9 adult otters km^?2 for the past nine years and probably longer.     

Cadmium Exposure in the South Korean Population: Implications of Input Assumptions for Deterministic Dietary Assessment

Dietary exposure to Cadmium (Cd) is of increasing interest globally because of the adverse health effects of Cd arising from multiple sources. The assumptions used when undertaking deterministic assessment of Cd in global or regional diets have implications when applied to specific national cases representing local variation in food composition and consumption patterns different from global or regional norms. We have conducted deterministic dietary Cd exposure assessments for the South Korean population using a variety of schemes for point estimation. Consumption data from the Korean Nutrition Survey (2001 to 2003) and monitoring data from the Korea Food and Drug Administration were used as the basis for the exposure estimates. The average daily per capita Cd exposure was 14 μ g for the South Korean population, representing about 27% of tolerable daily intake (TDI) and is similar to that reported in other countries. The hazard index (HI, the ratio of total Cd exposure to the TDI) typically ranged from 0.3 to 0.9 depending on assumptions used in deterministic estimates of dietary exposure. Even though the current exposure of the South Korean population at large is found to be safe on the basis of these estimates, consideration of high-end patterns of Cd level and consumption suggests the need for continued vigilance in dietary Cd monitoring.     

Summer activity pattern and Field Metabolic Rate of adult male sea otters (Enhydra lutris) in a soft sediment habitat in Alaska

Individual follows and instantaneous sampling were used to examine the behavior of adult male sea otters (Enhydra lutris) in Simpson Bay, Prince William Sound, Alaska, during the summer (May to August) of 2005 and 2006. Six behaviors (foraging, grooming, interacting with other otters, patrolling, resting, and swimming at the surface) were observed during four time periods (dawn, day, dusk, and night) to create 24-h activity budgets. Adult male sea otters were observed during 190 focal follows, representing 98 h of observation. Male otters allocated 27% of their time (over a 24-h period) to resting, 26% to swimming, 19% to grooming, 14% foraging, 9% to patrolling and 5% to interacting with other otters. Field Metabolic Rate (FMR) was estimated by combining the energetic costs for foraging, grooming, resting, and swimming behavior of captive otters from Yeates et al. (2007) with our activity budgets. Our study considered ‘patrolling’ to be energetically similar to ‘swimming’ and therefore the two categories were combined. This combined category accounted for the greatest percentage (43%) of energy expended each day followed by grooming (23%), resting (15%), feeding (13%) and other (5%). The estimated weight specific FMR for all activities was 686.7 kJ day^− 1 kg^− 1 and the total FMR was 19.04 MJ day^− 1. The FMR was 6.6 times the resting metabolic rate and 2.2 times greater than the allometric prediction for terrestrial mammals of similar size but similar to other marine mammals. With a peak summer sea otter density in 5.6 otters km^− 2, the low percentage of time spent foraging (even after correction for possible sampling biases) indicates that Simpson Bay is still below equilibrium density.     

Quantitation of elastin through measurement of its pentapeptide content

Digestion of insoluble porcine elastin with thermolysin produces a number of discrete small peptides. That present in highest concentration is the pentapeptide valyl-glycyl-valyl-prolyl-glycine (VGVPG) derived from the portion of the polymer containing extensive repeats of this sequence. Among eukaryotes, this sequence appears to be found only in elastin and its precursor tropoelastin. In the pig this is represented by peptide W4 of a tropoelastin tryptic digest (Sandberg, L.B., et al. Path. Biol. 33, 266-274, 1985). Quantitation of this peptide by HPLC separation, monitoring its absorption at 212 nm, offers a simple reliable means of measuring purified insoluble elastin as well as non-purified elastin in fat-free tissue samples. Digestion times and incubation temperatures are discussed. The method is sensitive enough to accurately quantitate elastin at the 2 to 3 microgram level.     

Assessing Risk of Unintended Antigen Occurrence in Food: A Case Instance for Maize-Expressed LT-B

Plant-based antigen production represents an innovative strategy for low cost vaccine production and delivery. Successfully advancing plant-made antigen production in open field systems requires understanding of confinement integrity and consequences of inadvertent occurrence in the food supply. The food safety implications of confinement loss and inadvertent antigen occurrence in the food supply can be effectively addressed using quantitative exposure assessment along with knowledge of properties of specific antigens. We report here a food safety risk assessment for the maize-expressed heat-labile enterotoxin subunit B of Escherichia coli (LT-B). In addition to dietary exposure assessment, food safety considerations for maize-expressed LT-B included assessment of allergenic potential, levels and sites of transgenic protein expression, history of use, post-translational glycosylation, protein processing and digestive stability, mammalian functionality and toxicity, and compositional characteristics of the transformed plant. As shown for LT-B, inadvertent occurrence in the food supply of a plant-produced antigen constitutes a minimal human health concern principally because of limited exposure potential.     

Effects of thiopental on transport and metabolism of glutamate in cultured cerebellar granule neurons

This study was performed to analyze the effects of the barbiturate thiopental on neuronal glutamate uptake, release and metabolism. Since barbiturates are known to bind to the GABA(A) receptor, some experiments were carried out in the presence of GABA. Cerebellar granule neurons were incubated for 2 h in medium containing 0.25 mM [U-(13)C]glutamate, 3 mM glucose, 50 microM GABA and 0.1 or 1 mM thiopental when indicated. When analyzing cell extracts, it was surprisingly found that in addition to glutamate, aspartate and glutathione, GABA was also labeled. In the medium, label was observed in glutamate, aspartate and lactate. Glutamate exhibited different labeling patterns, indicating metabolism in the tricarboxylic acid cycle, and subsequent release. A net uptake of [U-(13)C]glutamate and unlabeled glucose was seen under all conditions. The amounts of most metabolites synthesized from [U-(13)C]glutamate were unchanged in the presence of GABA with or without 0.1 mM thiopental. In the presence of 1 mM thiopental, regardless of the presence of GABA, decreased amounts of [1,2, 3-(13)C]glutamate and [U-(13)C]aspartate were found in the medium. In the cell extracts increased [U-(13)C]glutamate, [1,2, 3-(13)C]glutamate, labeled glutathione and [U-(13)C]aspartate were observed in the 1 mM thiopental groups. Glutamate efflux and uptake were studied using [(3)H]D-aspartate. While efflux was substantially reduced in the presence of 1 mM thiopental, this barbiturate only marginally inhibited uptake even at 3 mM. These results may suggest that the previously demonstrated neuroprotective action of thiopental could be related to its ability to reduce excessive glutamate outflow. Additionally, thiopental decreased the oxidative metabolism of [U-(13)C]glutamate but at the same time increased the detectable metabolites derived from the TCA cycle. These latter effects were also exerted by GABA.