Biomedical subjects

J R Withey

Publications and source records attributed to J R Withey.

22 records · Page 2Linked to original sources

PubMed1976

Quantitative analysis of styrene monomer in polystyrene and foods including some preliminary studies of the uptake and pharmacodynamics of the monomer in rats.

A variety of food containers, drinking cups and cutlery, fabricated from polystyrene (PS) or polystyrene-related plastic, were analyzed for their styrene monomer content. Samples of yogurt, packaged in PS cups, were similarly analyzed and the leaching of styrene monomer from PS containers by some food simulants was also determined. Blood level studies with rats, dosed with styrene monomer by various routes, illustrated uptake phenomena that were dependent on the dose and route of administration and were also affected by the vehicle used to convey the styrene monomer.

Animals↗

PubMedDate not supplied

Distribution of benzo[a]pyrene in pregnant rats following inhalation exposure and a comparison with similar data obtained with pyrene.

Eight pregnant rats were exposed, on the 17th day of gestation, for 95 min to a microcondensation aerosol of benzo[a]pyrene at five different atmospheric concentrations between 200 and 800 mg m-3 in a 'head-only' inhalation chamber. Five rats were killed immediately following the exposure and three were killed at 6 h post-dosing. Concentrations of the radiolabel and 'free' benzo[a]pyrene were measured in the individual fetuses and in the maternal blood, fat, kidney, liver and lung. Distribution to the fetus did not appear to be related to its position on the uterine horn and the uptake of benzo[a]pyrene was non-linear with increasing exposure concentrations, which was similar to the observations previously reported for pyrene. The levels of benzo[a]pyrene were much higher in the fetus and, especially, the lung than those observed in the pyrene study; so also were the levels of total metabolites in these tissues, which might, in part, account for the carcinogenic potency of benzo[a] pyrene.

Administration, Inhalation↗

PubMedDate not supplied

The distribution and pharmacokinetics of styrene monomer in rats by the pulmonary route.

Exposures (5 hr) of individual rats to atmospheres having styrene concentrations of from 50 to 2,000 ppm yield uptake blood profiles which show a continued and increasing absorption of styrene, proportional to the styrene atmospheric concentration, over the entire absorption period. Post-exposure elimination follows a dose-dependent two compartment model, similar to that observed after I.V. administration, although the initial stage of the elimination is more rapid and the terminal stage much slower than is observed in the I.V. case. A two-compartment pharmacokinetic model, with zeroth-order input, is proposed to interpret the uptake kinetics. Tissue concentrations of styrene in the heart, liver, lung, kidney, spleen, brain and perirenal fat show a different pattern of distribution as the dose increases. At all exposure concentrations the concentration of styrene in the perirenal fat is ten times that in any organ. At the lowest exposure concentration the kidney registered the highest concentration while a higher level of styrene is found in the liver, brain and kidney as the exposure level increases and for these tissues the concentration of styrene is always greater than that in the blood.

Animals↗

PubMedDate not supplied

Chlorinated aliphatic hydrocarbons used in the foods industry: the comparative pharmacokinetics of methylene chloride, 1,2 dichloroethane, chloroform and trichloroethylene after I.V. administration in the rat.

the pharmacokinetics of methylene chloride, CH2Cl2, 1,2-dichloroethane, CH2ClCH2Cl, chloroform, CHCl3 and trichloroethylene, CHCl.CCl2 were determined, after i.v. administration to male Wistar rats, at five dose levels ranging from 3 to 15 mg/kg. The elimination of chloroform followed a three compartment model at all dose levels. The remaining compounds gave data that fitted a two compartment model at low doses which changed to a three compartment model at higher dose levels. All data were fitted to a two and three compartment model and the model that gave the best fit was selected on the basis of the smallest residual mean squared error. Very few differences, apart from the change in the nature of the pharmacokinetic model, were seen in the rate coefficients over the dose range tested. At the highest dose level, the rates of uptake and elimination for the major tissues were similar to those observed for the blood but were much slower for the perirenal fat.

Animals↗