Metabolism research needs

PAHs are widely distributed in the environment as evidenced by their detection in sediments, soils, air, surface waters, and plant and animal tissues. However, the ecological impact of PAHs is uncertain. PAHs show little tendency for bioconcentration despite their high lipid solubility (Pucknat 1981), probably because most PAHs are rapidly metabolized. Sims and Overcash (1983) list a variety of research needs regarding PAHs in soil-plant systems. Specifically, research is needed to establish the rates of PAH decomposition in soils the soil PAH levels above which PAH constituents adversely affect the food chain and enhancement factors that increase degradation rates of PAHs, especially PAHs with more than three rings. Once these factors have been determined, PAH disposal into soils may become feasible at environmentally nonhazardous levels. 

Researchers have used a specially designed calorimeter, called a human calorimeter, to monitor the heat that is produced by metabolic reactions in humans. Research the human calorimeters that are used to study metabolic reactions. What are the design features of these calorimeters What factors do researchers need to take into account Why are the experiments with human calorimeters important Design an investigation that incorporates the results of your research. 

Considering these developments, the HMA could be employed more frequently. However, in practice, the HMA continues to be used infrequently in genetic toxicology and is applied primarily for specialized research needs. In addition, the need for the HMA has been supplanted in recent years by the use of metabolically competent cell lines and new in vivo mutation detection systems such as the transgenic Big Blue or Mutamouse systems, which in some ways may be viewed as more technologically advanced forms of the HMA. 

The development of sensitive analytical methods had been an indispensible tool in advancing research in aflatoxins, whether the research need was for survey of agricultural crops, transmission of residues from feed to food, following the course of detoxification, preparation of spiked meals for experimental use, or for toxicologic and metabolic studies. Methods had to be developed as the... 

This chapter describes the mechanistic basis of metal-induced alterations in porphyrin metabolism as derived from experimental studies and summarizes the evidence supporting the utility of porphyrin measurements as a biomarker of exposure and effects of specific metals in human subjects, with specific emphasis on lead, mercury, and arsenic. Some perspectives and research needs regarding the use of porphyrin measurements as biomarkers of metal exposures and effects in human populations are also presented. 

In parallel with studies of As carcinogenicity, additional research is needed on the metabolic fate and toxicity of iAs and organoAs species. The complete speciation of As by valence and form in tissues and excreta of As-exposed humans and experimental animals will provide much-needed data on the capacity for the reduction and oxidation of iAs and for its methyla-tion and on the distribution and retention of all As species. This aspect of the As research is central to a wide range of studies on As metabolism. Hence, the development and validation of improved analytical methods are primary research needs. 

A general conclusion from the review of the distribution of plutonium between different compartments of the ecosystem was that the enrichment of plutonium from water to food was fairly well compensated for by man s metabolic discrimination against plutonium. Therefore, under the conditions described above, it may be concluded that plutonium from a nuclear waste repository in deep granite bedrock is not likely to reach man in concentrations exceeding permissible levels. However, considering the uncertainties in the input equilibrium constants, the site-specific Kd-values and the very approximate transport equation, the effects of the decay products, etc. — as well as the crude assumptions in the above example — extensive research efforts are needed before the safety of a nuclear waste repository can be scientifically proven. 

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