Evaluating the potential of Unmanned Aerial Systems for mapping weeds at field scales: a case study with Alopecurus myosuroides.

Mapping weed densities within crops has conventionally been achieved either by detailed ecological monitoring or by field walking, both of which are time-consuming and expensive. Recent advances have resulted in increased interest in using Unmanned Aerial Systems (UAS) to map fields, aiming to reduce labour costs and increase the spatial extent of coverage. However, adoption of this technology ideally requires that mapping can be undertaken automatically and without the need for extensive ground-truthing. This approach has not been validated at large scale using UAS-derived imagery in combination with extensive ground-truth data. We tested the capability of UAS for mapping a grass weed, Alopecurus myosuroides, in wheat crops. We addressed two questions: (i) can imagery accurately measure densities of weeds within fields and (ii) can aerial imagery of a field be used to estimate the densities of weeds based on statistical models developed in other locations? We recorded aerial imagery from 26 fields using a UAS. Images were generated using both RGB and Rmod (Rmod 670-750 nm) spectral bands. Ground-truth data on weed densities were collected simultaneously with the aerial imagery. We combined these data to produce statistical models that (i) correlated ground-truth weed densities with image intensity and (ii) forecast weed densities in other fields. We show that weed densities correlated with image intensity, particularly Rmod image data. However, results were mixed in terms of out of sample prediction from field-to-field. We highlight the difficulties with transferring models and we discuss the challenges for automated weed mapping using UAS technology.

Bluetongue virus infection in naïve cattle: Identification of circulating serotypes and associated Culicoides biting midge species in Trinidad.

To better understand risks associated with trading cattle, it is important to know which serotypes of Bluetongue virus (BTV) are circulating within the exporting and importing country. Hence, this study was conducted to identify the circulating serotypes of BTV in Trinidad. Blood samples were collected monthly from sixty BTV- naïve imported cattle over a six month period after their arrival in the country. Virological (PCR and virus isolation) and serological (ELISA) analyses were carried out on the samples and CDC light traps were placed near the cattle enclosure to trap and identify the species of Culicoides biting midges that were present. All of the cattle seroconverted for BTV antibodies within three months of their arrival in the country and real-time reverse transcription PCR (rRT-PCR) detected BTV-RNA in the samples throughout the remainder of the study. The patterns of infection observed in the cattle indicated serial infections with multiple serotypes. A combination of BTV serotype-specific rRT-PCR on the original blood samples and virus isolation followed by serotype-specific rRT-PCR on selected samples, confirmed the presence of BTV serotypes 1, 2, 3, 5, 12 and 17. This is the first report of BTV-2 and BTV-5 in Trinidad. Light-suction traps placed in close proximity to the cattle predominantly trapped Culicoides insignis Lutz 1913 species (96%), with a further six Culicoides species making up the remaining 4% of trapped samples. The circulation of multiple BTV serotypes in Trinidad underlines the need for regular surveillance, which will contribute to the development of risk assessments for trade in livestock.

Saving cells from ultrasound-induced apoptosis: quantification of cell death and uptake following sonication and effects of targeted calcium chelation.

Applications of ultrasound for noninvasive drug and gene delivery have been limited by associated cell death as a result of sonication. In this study, we sought to quantify the distribution of cellular bioeffects caused by low-frequency ultrasound (24 kHz) and test the hypothesis that Ca(2+) chelation after sonication can shift this distribution by saving cells from death by apoptosis. Using flow cytometry, we quantitatively categorized sonicated cells among four populations: (i) cells that appear largely unaffected, (ii) cells reversibly permeabilized, (iii) cells rendered nonviable during sonication and (iv) cells that appear to be viable shortly after sonication, but later undergo apoptosis and die. By monitoring cells for 6 h after ultrasound exposure, we found that up to 15% of intact cells fell into this final category. Those apoptotic cells initially had the highest levels of uptake of a marker compound, calcein; also had highly elevated levels of intracellular Ca(2+); and contained an estimated plasma membrane wound radius of 100-300 nm. Finally, we showed that chelation of intracellular Ca(2+) after sonication reduced apoptosis by up to 44%, thereby providing a strategy to save cells. We conclude that cells can be saved from ultrasound-induced death by appropriate selection of ultrasound conditions and Ca(2+) chelation after sonication.

Neurodevelopmental effects: making the case for biologic plausibility.

It has been suggested that the most critical missing link between science and policy is causality; that is, the establishment of a definite cause-effect relationship between exposure and adverse health effects. As has been clearly demonstrated by the decades-long tobacco debate, causality is extremely difficult to establish with absolute certainty, particularly in the minds of scientists. Because of this, it has been suggested that a "weight of evidence" approach based on biologic plausibility should be used as a surrogate for causality when translating science into policy and public health practice. In the case of neurodevelopmental effects, the case for biologic plausibility is supported by scientific findings from three broad areas consisting of wildlife biology, toxicology, and epidemiology. A striking example of this is provided by research findings from the Great Lakes Basin, an area which has been the focus of significant scientific research for the last thirty years in these three broad areas. In this paper, we examine relevant findings from the Great Lakes Basin and elsewhere as they relate to establishing and supporting the biologic plausibility of neurodevelopmental effects associated with environmental exposures to persistent toxic substances.

Key environmental human health issues in the Great Lakes and St. Lawrence River basins.

In May 1997, Health Conference '97-Great Lakes/St. Lawrence, an international conference on the effects of the environment on human health in the Great Lakes and St. Lawrence River basins, was held in Montreal, Québec, Canada. This was the third international conference on this topic sponsored by agencies in the United States and Canada. More than 120 platform and poster presentations were given by scientists of different disciplines from the Great Lakes region and elsewhere. The presentations represented the most current research findings on the effects of the Great Lakes environment on human health. The reports covered environmental contaminant levels of persistent toxic substances (PTSs), routes and pathways of exposure, exposure assessment and human tissue levels of PTSs, human health outcomes, risk communication and assessment, and approaches to scientific collaboration. Reports indicate that levels of contaminants in the Great Lakes and St. Lawrence River basins have generally declined since the 1970s, although certain contaminants have plateaued or slightly increased. The findings include elevated body burden levels of contaminants in persons who consume large amounts of some Great Lakes sport fish, developmental deficits and neurologic problems in children of some fish-consuming parents, nervous system dysfunction in adults, and disturbances in reproductive parameters. The findings underscore the need for better public health intervention strategies.

Health effects classification and its role in the derivation of minimal risk levels: developmental effects.

Agency for Toxic Substances and Disease Registry (ATSDR) utilizes chemical-specific minimal risk levels (MRLs) to assist in evaluating the public health risk associated with exposure to hazardous substances. The MRLs are derived based on the health effects data compiled from current literature searches and presented in ATSDR's toxicological profiles. Health effects are categorized according to their degree of severity (e.g., serious, less serious, minimal, and not adverse). This evaluation is important, because each respective category can be assigned a different amount of uncertainty, thus affecting the final value of the calculated MRL. From the total of 272 MRLs derived as of December 1997, 21 were based on developmental effects. ATSDR's ranking of developmental health effects as described in the Guidance for Developing Toxicological Profiles and specific examples of how the categorized health effects were used in MRL derivations are provided in this paper.

Assimilation in visibility: additional evidence.

The present research tested the theory that a less visible target increases in similarity to a more visible simultaneous context, and that therefore the target increases in visibility. This assimilation-in-visibility theory was tested using context + targets that were either 3-line brackets or 2-line right angles, contexts and targets that were the component lines of these context + targets, with the target always the identical single top line. Experiments with a total of 204 participants indicated that the 3-line context + targets resulted in better context + target versus context discriminations than target versus background discriminations than did the 2-line context + targets. This was so for both over-all errors and misses but not false alarms. It is concluded that only the 3-line context + targets increased the visibility of the 1-line target. Additional analysis indicated that the 2-line contexts of the 3-line context + targets were more visible than all the 1-line stimuli. So, the 1-line target assimilated to a simultaneous more visible 2-line context and thereby increased in visibility, thus improving the context + target versus context discrimination. This support for the assimilation-in-visibility theory is of interest because assimilation and contrast in visibility may play a large role in perception.

The Great Lakes: a historical overview.

The Great Lakes are collectively the largest inland body of freshwater on this planet. For more than two hundred years, the Great Lakes basin has been used as a resource for industry, agriculture, shipping, and recreation. The physical characteristics of the basin and the long retention time of chemicals in the lakes combine to make this huge freshwater resource a repository for chemical by-products of these activities. Many of the more than one thousand chemicals detected in the waters, sediment, or biota of the Great Lakes have known toxic effects. This overview will identify the 11 most persistent toxic chemicals known as "critical" Great Lakes pollutants. It also will describe some of the adverse health effects that have been observed in fish and other wildlife because of exposure to these pollutants. Finally, it will discuss some of the early human health studies that 1) have demonstrated a correlation between increased body burdens and fish consumption, and 2) suggest an association between consumption of contaminated Great Lakes fish and adverse human health effects.

Harmonizing human health studies in the Great Lakes.

Epidemiological studies of exposed human populations can provide valuable evidence of human health effects. Information has been sparse on human health effects associated with consumption of contaminated Great Lakes fish. As part of its Great Lakes Human Health Effects Research Program, the Agency for Toxic Substances and Disease Registry (ATSDR) has funded ten projects. Of these studies, eight are epidemiologic investigations of human exposure and potential health effects from consumption of contaminated fish. To strengthen and to enhance the findings and comparability across the health studies, ATSDR has initiated several activities. These activities include harmonizing questionnaires, analytical protocols, human health end points, and contaminants tested. Also included is the establishment of a quality assurance and quality control (QA/QC) program and tissue bank. These activities will allow ATSDR to enhance exposure assessment in the Great Lakes basin. In addition, these research activities allow ATSDR to evaluate and to interpret data across all the projects, including a basin-wide health risk analysis on exposure, levels of contaminants or body burden, and the potential for human health effects from exposure to Great Lakes contaminants.

Context-produced increase in visibility.

UNLABELLED: It has not been clearly shown that context (e.g., three lines of a square) increases the visibility of a feature (e.g., the fourth line of the same square). To investigate this possibility, four sets of context+feature, context, feature, and BLANK (empty field) stimuli were used. For three out of the four sets, the context+feature stimulus was less likely to be falsely identified as the context and BLANK stimuli (i.e., the stimuli without the feature) than was the feature stimulus. For the same three sets, discriminating between the context+feature and context stimuli produced fewer false identifications (FIs) than discriminating between the feature and BLANK stimuli. THE CONCLUSION: the context components of context+feature stimuli increased the visibility of the feature components of the same stimuli.

Additional calculations of radionuclide production following nuclear explosions and Pu isotopic ratios for Nevada Test Site events.

A method is reviewed for calculating dry ground deposition of any radionuclide in off-site fallout from a nuclear explosion. Calculations are in agreement with measurements. A list of all calculations to date is presented, along with how to obtain copies. In addition, a table of ratios of 240Pu:239Pu and 241Pu:239Pu for NTS explosions is included.

Charcoal lung. Bronchiolitis obliterans after aspiration of activated charcoal.

Activated charcoal usually provides effective and safe treatment for drug overdose. We describe a patient who developed bronchiolitis obliterans and respiratory failure following aspiration of activated charcoal. This patient had a markedly reduced vital capacity with roentgenographic evidence of airtrapping. Chest roentgenograms did not demonstrate the large amount of charcoal identified at postmortem examination.

Differences in morphology, growth rate, and protein synthesis between cultured arterial and venous endothelial cells.

Intrinsic differences between aortic and venous endothelial cells were demonstrated by studies of morphology, growth rates, and protein synthesis. Endothelial cells from bovine thoracic aortas (AECs) and inferior vena caval (VECs) were harvested, maintained in cell culture, and characterized. VECs were consistently larger (mean cell diameter 14.3 micron vs 12.7 micron; p less than 0.001) and more pleomorphic than were AECs. Scanning electron microscopy revealed that VECs were thinner than AECs and that VECs had numerous fine, cellular processes that were much less abundant on the AECs. Enzymatic disaggregation of confluent cells resulted in a reduced generation time by the AECs compared with VECs. Moreover, VECs responded to disaggregation by a significantly larger increase in cell size than the AECs. Protein synthesis was quantitated by computer analysis of autoradiograph of two-dimensional gel eletrophoresis and separation of 998 35S-methionine-labeled proteins from cell lysates. Synthesis of 257 proteins was significantly different (p less than 0.05); synthesis of 239 proteins by VECs was either decreased (219) or undetectable (20) compared with those of AECs. In contrast, only 18 proteins were produced in significantly greater quantity by VECs than by AECs. The cytoskeletal proteins actin and alpha- and beta-tubulins were produced in significantly greater quantity by AECs than VECs. These results indicate that cultured endothelial cells of arterial origin are substantially different from those of the venous circulation. These phenotypic differences are maintained in vitro despite eliminating variability in hemodynamic stress and interaction with other cellular elements of the vessel wall.

The in vivo biosynthesis of embryonic proteins after maternal administration of phenytoin in the mouse.

Pregnant A/J mice received 60 mg phenytoin/kg body weight on Day 10 of gestation. Eighteen hours after phenytoin injection, animals were injected (ip) with 20 microCi/g of [35S]methionine. After 6 hr of incorporation animals were sacrificed and the embryos were removed. Protein synthesis in the embryo, as measured by [35S]methionine incorporation into trichloroacetic-precipitable protein, was analyzed by SDS-PAGE and quantitation of autoradiograms. The results of gel electrophoresis indicate that in embryonic primary palates and limb buds from phenytoin-treated mothers there is an increase in synthesis of 66-, 50-, 44-, and 13-kDa proteins and a decrease in synthesis of an 18-kDa protein compared with values for the control counterpart. No role has been assigned to the 66-, 44-, or 13-kDa proteins but the 50-kDa band comigrates with tubulin and the 18-kDa band comigrates with calmodulin. Palatal cells in vitro stained positively with specific antibody to both these proteins. An adverse effect of the anticonvulsant drug phenytoin, when administered to pregnant A/J mice is an increase in the incidence of cleft lip with or without cleft palate [CL(P)] in their offspring. These alterations in protein synthesis may be a direct or secondary result of maternal phenytoin treatment and may play a role in CL(P) formation in vivo.

The water, DNA, collagen and noncollagen protein contents in embryos after maternal administration of a teratogenic dose of phenytoin.

The growth of developing A/J mouse embryos was studied after maternal administration of phenytoin (Dilantin), an anticonvulsant drug. Wet weight, dry weight, protein and DNA contents of the embryos were quantitated 24 h after drug administration. Collagen content was investigated because of its importance in cellular differentiation. The wet and dry weight of embryos from phenytoin-treated mothers were 52.3 and 57.5%, respectively, of that of embryos of control mothers. DNA and protein contents were also decreased in embryos from phenytoin-treated mothers. Collagen represented only 0.07% of the protein present in day 11 control embryos, but was increased 4.9-fold in embryos from phenytoin-treated mothers in comparison to controls. These results suggest that phenytoin reduces overall embryonic growth but stimulates collagen synthesis.

Maternal phenytoin administration affects DNA and protein synthesis in embryonic primary palates.

Recent studies have shown that phenytoin (Dilantin) administration to pregnant A/J mice on day 10 causes reduced growth in embryonic primary palates. The current investigation concentrates on biochemical and autoradiographic changes toward the end of primary palate formation (gestational day 11), which coincides with the developmental period used for the previously conducted morphological studies. On gestational day 10, one group of pregnant A/J mice was injected intraperitoneally (IP) with 60 mg/kg phenytoin and the other group with vehicle. Twenty-three hours after phenytoin administration, all animals were injected (IP) with either [3H]-thymidine or [3H]-leucine. After one hour of incorporation, animals were sacrificed, embryos removed and placed in ice-cold Eagle's minimum essential medium containing 0.02% NaN3 for biochemical assay or fixed immediately in Bouin's solution for autoradiography. For biochemical analyses, palates and limb buds were removed, homogenized, TCA precipitated, lyophilized, and acid hydrolyzed. Examination of the data revealed that DNA synthesis in control palates was 3.8-fold greater than in primary palates from embryos of phenytoin-treated mothers. Results were similar for limb buds from control embryos and from embryos of phenytoin-treated mothers. Experiments utilizing [3H]-leucine indicated that protein synthesis was 2.6-fold greater in primary palates from phenytoin-treated mothers than in control primary palates. Similar results were obtained for protein synthesis in limb-bud tissue from controls and embryos of phenytoin-treated mothers. Autoradiographic data supported the biochemical findings. DNA synthesis in primary palates from embryos of phenytoin-treated mothers decreased 3-fold; protein synthesis increased 2.2-fold compared with control primary palates.(ABSTRACT TRUNCATED AT 250 WORDS)