Biomedical subjects

W Slob

Publications and source records attributed to W Slob.

8 recordsLinked to original sources

PubMed1995

Congener-specific bioavailability of PCDD/Fs and coplanar PCBs in cows: laboratory and field measurements.

To estimate congener-specific bioavailabilities for 17 PCDD/Fs in cows grazing near a MSW incinerator both a controlled lab study and a field study were performed. In the lab study the estimates were derived from the elevated concentrations in milk from two cows after administration of a single dose of contaminated fly ash. In the field study, located near a large MSW incinerator, daily samples of grass and milk collected over a period of 60 days were pooled to two monthly bulk samples. The concentrations in these bulk samples of grass and milk were used to estimate the bioavailabilities of the 17 PCDD/Fs as well as of three coplanar PCBs. With the concentrations of PCDD/Fs expressed in I-TEQs the bioavailability in cows was estimated at +/- 7.5% in the field study. The congener-specific bioavailabilities correlated well between the two studies, as well as with previously reported values in the literature. However, the absolute levels differed considerably between studies, indicating a strong matrix effect.

Animals↗

PubMed1994

Immunogenicity testing of diphtheria and tetanus vaccines by using isogenic mice with possible implications for potency testing.

The antitoxin response of isogenic mice (inbred strains and F1 hybrids), immunized with diphtheria and tetanus reference vaccines, was compared with the response of animals from an NIH outbred stock. The variance in antitoxin response was smaller within the groups of isogenic mice than within the group of mice from the outbred strain. The case for estimating the potency of diphtheria and tetanus vaccines by using isogenic mice is discussed. It is concluded that the general introduction of one common inbred strain or F1 hybrid selected on the basis of sensitivity would increase the comparability of data between laboratories and would enable an estimated reduction in the use of animals of about 35% or an improvement in the precision of the estimate of potency.

Animals↗

PubMed1993

Confidence limits for hazardous concentrations based on logistically distributed NOEC toxicity data.

This paper deals with the calculation of Hazardous Concentrations of toxic substances from small sets of laboratory toxicity data, e.g., NOECs. A procedure due to Van Straalen and Denneman, as adapted from Kooijman (case n = 1), in which one seeks a concentration that protects 95% of the biological species is modified to account for the uncertainty in the estimates. New constants are obtained by simulation. These allow the calculation of the one-sided 95% left confidence limit of the Hazardous Concentration, from the mean and standard deviation of a sample of (laboratory) toxicity data. This 95% confidence limit is always lower than the 95% certainty value calculated with the Kooijman (n = 1)/Van Straalen method. The authors also derive constants to calculate a one-sided 50% confidence value, that overpredicts as often as it underpredicts. This value may be used as a median guess of the Hazardous Concentration. It will always be higher than the 95% certainty value of the Kooijman (n = 1)/Van Straalen method. However, by using the 50% value, one runs the risk of protecting substantially less than 95% of the biological species.

Confidence Intervals↗

PubMed1993

Modeling long-term exposure of the whole population to chemicals in food.

This paper discusses a statistical exposure model (STEM) that can be used to estimate the percentage of the population exceeding ingestion intake criteria (e.g., ADI or TDI). In addition, STEM may be linked to toxicokinetic models to evaluate the interindividual variability in internal doses that results from variability in consumption habits. The assumptions of STEM are investigated by analyzing dioxin and cadmium intake data for the Dutch population.

Cadmium↗

PubMed1990

Comparative antidotal efficacy of activated charcoal tablets, capsules and suspension in healthy volunteers.

The efficacy of several formulations of activated charcoal (AC) was compared by measuring the intestinal absorption of a solution of 1 g paracetamol administered 2 min before administration of 5 g AC as suspension (200 ml), tablets (40 of 125 mg) or capsules (25 of 200 mg). The suspension medium without AC was used as the control treatment. Based on the results of a pilot experiment, an 8 subject panel was used in a two 4 x 4 Latin square design. All treatments with AC resulted in a statistically significant decrease in paracetamol absorption compared to the control treatment. The suspension was considerably and significantly more effective than the tablets or capsules. Treatment with tablets was slightly but significantly more effective than capsules. The intake of large numbers of tablets and capsules was difficult. In the hospital AC suspensions are available. For first aid elsewhere, at home, at the working place or in the general practitioner's surgery a preservable and easily redispersible AC formulation would be preferable to the present solid forms.

Acetaminophen↗

PubMed1988

Survival characteristics of the mollusc Lymnaea stagnalis under constant culture conditions: effects of aging and disease.

Survival characteristics of seven different populations of the mollusc Lymnaea stagnalis were studied under constant culture conditions. On the basis of these characteristics four populations were considered as healthy and three as infected. In the healthy populations senescence started at an age of about 200 days, 50% survival age varied from 282 to 372 days, 10% survival age from 417 to 508 days and the maximum age from 528 to 673 days. Infected populations differed from healthy ones: (1) in behaviour of the animals; and (2) in shape of survival curve and age-specific death rate. It is concluded that in aging studies in addition to the absolute age of the animals, the following information should be given: the percentage of survival of the population at the time of sampling and a quantitative estimate of the quality of the cultures from which the animals were sampled. The parameters of the Weibull function seem to be suitable for such estimations.

Aging↗

PubMed1988

A quantitative method to evaluate the quality of interrupted animal cultures in aging studies.

A method is described for a quantitative estimation of the quality of interrupted animal cultures. It is applicable when survival can be described by a Weibull or by a Gompertz function. Application to four healthy and three infected cultures of Lymnaea stagnalis shows that survival curves can be successfully predicted from cultures censored at 25%, 50%, and 75% survival. The parameters of these predicted survival curves can be used to evaluate experimental results from single (longitudinal or cross-sectional) aging studies, and to evaluate comparisons among different aging studies.

Aging↗

PubMed1986

Age-related decrease in electrical coupling of two identified neurons in the mollusc Lymnaea stagnalis.

Electrophysiological characteristics of two identified giant electrotonically coupled neurosecretory cells in the central nervous system of the mollusc Lymnaea stagnalis were studied in mature animals of different age. The coupling coefficient of the neurons decreased considerably with age. The possibility that the decrease is due to an increase in the junctional resistance between the cells is discussed.

Aging↗