摘要:

Pharmacokinetic models provide novel approaches in the environmental arena for evaluating toxicological problems. For example, pharmacokinetic parameters play an important and even determinant role in risk assessment and policy making. The present contribution reviews the most basic pharmacokinetic models, their development, and their applications in toxicology. The theory, principles, and data requirements are critically discussed. The fundamental differences among various pharmacokinetic models are compared and contrasted. The techniques and philosophy for model validation are discussed and illustrated.Key words: Pharmacokinetics, toxicology, modeling, philosophy, statistics, validation.

ISSN:1208-6053    

DOI:10.1139/a99-003

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The perception of, and interest in, the boreal mixedwood forests has changed dramatically over the last two decades. This is particularly true of British Columbia, as shown by the recent wave of biodiversity-related legislation. The static notion of the boreal mixedwoods as a collection of low-yield, competition-prone, mixed-species stands is being replaced by that of a diverse, shifting landscape mosaic containing a wide array of resources. As this change in perception continues, it will be necessary to formulate a new conceptual framework within which to manage the boreal mixedwoods to meet a much broader range of objectives. This review argues that the traditional stand-level model of mixedwood management is inadequate as a management paradigm for the future. A more holistic view of mixedwood management is required that considers processes at all scales, and takes into account the wide temporal and spatial variability that occurs naturally in this type of disturbance-driven forest.Key words: boreal mixedwoods, landscape-level, succession, disturbance, variability.

ISSN:1208-6053    

DOI:10.1139/a99-007

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Increased levels of active oxygen species or free radicals can create an oxidative stress. Concentration of free radicals in living cells increases as a result of exposure to environmental stresses that lead to aging, carcinogenesis, and immunodeficiencies in animals, and membrane leakage, senescence, chlorophyll destruction, and decreased photosynthesis in plants. The antioxidative system of higher plants consists of enzymes, low molecular weight compounds (among them peptides, vitamins, flavonoids, phenolic acids, alkaloids, etc.), and integrated detoxification chains. Enzymatic defense in plants include enzymes capable of removing, neutralizing, or scavenging oxy-intermediates. Catalases and superoxide dismutases are the most efficient antioxidant enzymes. Free radicals cause cell damage by a lipid peroxidation mechanism, which results in a blockade of natural antioxidant systems. Application of synthetic antioxidants can assist in coping with oxidative stress. There are very few publications on effects of synthetic antioxidants on plant growth and physiology. One of the examples of such synthetic antioxidant is 2-methyl-4-dimethylaminomethyl-5-hydroxybenzimidazole (Ambiol), which substantially promoted growth of agricultural and forestry plant species. Ambiol also demonstrated antitranspirant properties, increasing drought tolerance of conifers and agricultural species. The response of plants to Ambiol is under high genetic control. The identification of genes responsible for the reaction of plants to Ambiol may lead to attempts in genetic engineering of organisms with increased tolerance to oxidative stress. It seems impossible to find a universal scavenger trapping all free radicals active in the organism. However, analysis of the structure–activity relationships in antioxidants can contribute to the search for effective antioxidants.Key words: oxidative stress, lipid peroxidation, free radicals, natural and synthetic antioxidants, Ambiol

ISSN:1208-6053    

DOI:10.1139/a99-004

出版商:NRC Research Press    

年代:1999

数据来源: NRC