Biomedical subjects

H W Kerster

Publications and source records attributed to H W Kerster.

4 recordsLinked to original sources

PubMed1987

Estimating mutagen mass in indeterminate mixtures: micronuclei in Tradescantia.

Short-term biological tests are used to evaluate environmental damage caused by toxic chemicals. Risk or damage to an ecological system exposed to chemicals is assessed using ecological studies or inferences derived from biological-effect data after identification and quantification of contaminants. The compositions of environmental contaminant mixtures are generally indeterminate; there are no direct methods for identifying and comprehensively quantifying all the mutagens, carcinogens, and other types of biologically active chemicals in these mixtures. We present a method for using the induction of micronuclei (MCN) in Tradescantia during the tetrad stage of meiosis to estimate the total quantity of active chemicals. Component identification is not needed. The lognormal distributions of the estimated minimum effective dose (EMED) for 23 compounds tested in solution and 11 tested as vapors (Ma, T. H., Harris, M. M., Anderson, V. A., Ahmed, I., Mohammed, K., Bare, J. L., and Lin, G., 1984, Mutat. Res. 138, 157-167) are used to determine the median-mutagen activity for each exposure route. These activities are 203 mg/liter for aqueous exposures and 14,854 ppm-min for vapor exposures. The method is illustrated using the responses of Tradescantia exposed to a hexachloroethane/zinc chloride aerosol for 30 min at 50 and 100 m. The response at 50 m was equivalent to exposure to a median-active mutagen at 365 ppm for 30 min.

Anthelmintics↗

PubMed1985

Estimating the mass of mutagens in indeterminate mixtures.

A method is shown for estimating the quantity (mass) of genotoxic compounds in complex mixtures without prior identification of components. This method uses fractiles of the probability distribution of responses from the assay of interest and dose-response of the mixture. The method depends upon the assumption of additivity, on average, in the interaction of mutagens and on lognormality of the distribution of mutagen molecular weights. Mass estimates are necessary for hazard characterization, risk estimation, and risk assessment. The method is illustrated using Ames assay results from a coke plant wastewater.

Coke↗

PubMed1983

Brine shrimp (Artemia salina) nauplii as a teratogen test system.

Brine shrimp increase in length rapidly after hatching. A teratogen test system is based on disruption of elongation between 24 and 48 hr after wetting of the cysts. Teratogenicity of substances dissolved in the medium is assayed by comparison of average lengths of animals raised for the test period in suspect solution with average lengths of controls. The system is fast, inexpensive, and requires little skill. Brine shrimp are suited to testing industrial wastes, chemical formulations, drugs, and food additives that can be dissolved in water at 25 degrees C. The method appears unsuited to testing the teratogenicity of gases, particulates, very dilute wastes, or natural waters. Cadmium, mercury, lead, zinc, bromoform, n-butylphthalate, 1,2-dichloroethane, nitrobenzene, tetrachloroethylene, toluene, 1,2,4-trichlorobenzene, and 1,1,3-trichloroethane were found teratogenic. Chromium (III), chromium (VI), copper, chlorobenzene, chloroform, dimethyl sulfoxide (DMSO), and phenol were found not teratogenic. Other aquatic organism teratogen test systems are surveyed.

Animals↗

PubMed1970

Temporal phenotypic heterogeneity as a substrate for selection.

The interaction of temporal phenotypic heterogeneity with a population level fitness function was explored through the use of a simple model. The model, based upon experimental data, assumes that the exploitation of pollinators, and seed-set within plant populations are dependent upon the frequency of a pink flower morph in populations composed of pink and white morphs. An increase in pink frequency is accompanied by an increase in seed-set for both morphs. The model also assumes that seed-set within a population is the same for pink and white individuals. In perennials and annuals with long-lived seeds, fluctuations in morph balance from one season to another may lead to reproductive pulses or drags, depending upon which morph was in excess. The reproductive differential which stems from different levels of pollinator service leads to an increase in pink frequency and an attendant fitness gain. The perennial habit and long-lived seeds provide a population with a memory which permits the current population image to compete with images of previous years. As a consequence, fitness gains may be achieved in the absence of interplant or interpopulation selection.

Journal Article↗