ABSTRACT
Freshwater sediments with low levels of anthropogenic contamination and a broad range of geochemical properties were investigated using various sediment-contact tests in order to study the natural variability and to define toxicity thresholds for the various toxicity endpoints. Tests were performed with bacteria (Arthrobacter globiformis), yeast (Saccharomyces cerevisiae), nematodes (Caenorhabditis elegans), oligochaetes (Lumbriculus variegatus), higher plants (Myriophyllum aquaticum), and the eggs of zebrafish (Danio rerio). The variability in the response of some of the contact tests could be explained by particle size distribution and organic content. Only for two native sediments could a pollution effect not be excluded. Based on the minimal detectable difference (MDD) and the maximal tolerable inhibition (MTI), toxicity thresholds (% inhibition compared to the control) were derived for each toxicity parameter: >20% for plant growth and fish-egg survival, >25% for nematode growth and oligochaete reproduction, >50% for nematode reproduction and >60% for bacterial enzyme activity.
Subject(s)
Environmental Monitoring , Fresh Water/chemistry , Geologic Sediments/chemistry , Toxicity Tests , Water Pollutants/toxicity , Animals , Arthrobacter/drug effects , Caenorhabditis/drug effects , Ferns/drug effects , Oligochaeta/drug effects , Ovum/drug effects , Saccharomyces cerevisiae/drug effects , Water Pollutants/analysis , Zebrafish/physiologyABSTRACT
The long-term effect of total parenteral nutrition (TPN) was studied in rats. A failure to thrive developed and all animals died within 40 days of TPN. Autopsy invariably demonstrated the increased weight and volume of the liver and spleen. Multiple fat emboli were found in the lungs of all animals, and multiple epithelioid cell granulomas in the liver of all and in the spleen of most animals. Chronical low grade infection could not be demonstrated. Microorganisms were not found in blood or tissue specimens and endotoxin could not be demonstrated in plasma samples.
Subject(s)
Parenteral Nutrition, Total/adverse effects , Animals , Body Weight , Liver Diseases/etiology , Liver Diseases/pathology , Lung Diseases/etiology , Lung Diseases/pathology , Male , Rats , Spleen/pathology , Time FactorsABSTRACT
The feasibility of producing patient-specific beam attenuators for chest radiography has been investigated using an anthropomorphic phantom and a human volunteer. A low-dose test exposure is digitized, processed, and used to print a small cerium filter, which is placed in the x-ray beam near the collimator. The final radiograph is recorded on film. The technique results in relatively uniform film exposure, so that structures in all regions of the chest are simultaneously displayed with optimal film contrast. The equalized exposure improves image quality in the normally underpenetrated regions and reduces the role of cross-scatter from the lungs. The image is analogous to optical or computer-processed unsharp masking techniques, but the processing is accomplished in the x-ray beam and results in an improved exposure distribution, giving advantages that cannot be achieved with image processing techniques alone.