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H B Matthews

Publications and source records attributed to H B Matthews.

At least 109 records · Page 6Linked to original sources
PubMed1977

Distribution and excretion of 2,4,5,2',4',5'-hexabromobiphenyl, the major component of Firemaster BP-6.

The intestinal absorption, distribution, and excretion of the major component of Firemaster BP-6,2,4,5,2',4',5'-hexabromobiphenyl, has been studied in the male rat. This polybrominated biphenyl was readily absorbed from the intestine, initially distributed throughout the body, and eventually stored primarily in the adipose tissue, was not subject to appreciable metabolism, and was excreted almost exclusively in the feces and at a very slow rate. Approximately 90% of an oral dose was absorbed from the intestine, and extrapolation of the rate of excretion to infinity indicates that less than 10% of the total dose would ever be excreted.

Animals↗
PubMed1977

Pharmacokinetic models for lipophilic compounds.

In many instances pharmacokinetic modeling offers the best method of interpreting the significance to man of results obtained with laboratory animals but first we must have accurate models for our laboratory animals. A physiological pharmacokinetic model has been used to simulate the disposition of polychlorinated biphenyls (PCBs) in the rat and to extrapolate results obtained with the rat to predict the disposition of PCBs in the mouse. The modeling methods have also been extended to predict the disposition of a polybrominated biphenyl (PBB) in the rat following IV, oral, and multiple oral doses. It is anticipated that with additional experience and work a physiological pharmacokinetic model can be used to predict the disposition of these and other xenobiotics in man.

Animals↗
PubMed1976

Hair and its associated lipids as an excretory pathway for chlorinated hydrocarbons.

1. Chlorinated hydrocarbon insecticides and other halogenated compounds, probably biphenyls, were found to be associated with human hair at concentrations less than 1 p.p.m. 2. In experiments with rats, chlorinated 14C-hydrocarbon insecticides and polychlorinated biphenyls were excreted in hair in all instances, but excretion was less with the more labile compounds. 3. Excretion via hair may be a significant factor in eliminating chlorinated hydrocarbons which resist metabolism.

Animals↗
PubMedDate not supplied

Activation of methanol by hepatic postmitochondrial supernatant: formation of a condensation product with 2,4-diaminotoluene.

2,4-Diaminotoluene, an aromatic amine hepatocarcinogen in rats and mice, reacts extensively with formaldehyde produced by the oxidation of methanol to form a single reaction product. Using 1H and 13C NMR and high-resolution mass spectroscopy, this product was shown to be bis(2,4-diamino-5-tolyl)methane. This reaction product is shown to occur under conditions whereby methanol is metabolized to formaldehyde by rat hepatic postmitochondrial supernatant. These results demonstrate a novel reaction of aromatic amines and formaldehyde in biological samples and indicate that methanol as a solvent may become activated in vitro and produce complex interactions with solutes.

Animals↗
PubMedDate not supplied

Metabolism, bioaccumulation, and incorporation of diethanolamine into phospholipids.

Diethanolamine (DEA) is a major industrial chemical which has low acute toxicity, but, on repeat exposure, has significant cumulative toxicity. The present work suggests that the cumulative toxicity can be attributed to the fact that, unlike most small polar molecules, DEA accumulates to high concentrations in certain tissues following repeat exposure. The highest concentrations of DEA were seen in liver, kidney, spleen, and brain. Investigations described here have determined that DEA is metabolized by biosynthetic routes common to ethanolamine and is conserved, O-phosphorylated, N-methylated, and incorporated into phosphoglyceride and sphingomyelin analogues as the parent compound and as its N-methyl and N,N-dimethyl derivatives. This is the first report of the conjugation of a xenobiotic headgroup with a natural ceramide to form aberrant sphingomyelins. DEA-derived phosphoglycerides constituted the majority of aberrant phospholipid following acute administration. On repeat administration, DEA bioaccumulated to plateau levels at approximately 8 weeks. This bioaccumulation was accompanied by an increasing degree of methylation and accumulation of aberrant sphingomylenoid lipids in tissues. Uptake and incorporation of DEA into ceramide derivatives in human liver slices were also demonstrated in the present studies. It is speculated that the cumulative toxicity observed on repeat administration of DEA to rats is caused in part by increasing levels of aberrant phospholipids derived from this unnatural alkanolamine.

Animals↗
PubMedDate not supplied

Disposition and metabolism of 4-chloro-2-nitroaniline in the male F344 rat.

The disposition and metabolism of 14C-labeled 4-chloro-2-nitroaniline (CNA) was studied in male F344 rats following oral or intravenous (iv) administration. The gastrointestinal absorption of CNA was found to be near complete and was not affected by the dose in the range studied (0.788-78.8 mumol/kg). Following either oral or iv administration, CNA was rapidly distributed throughout the tissues and showed no marked affinity for any particular tissue. [14C]CNA was rapidly cleared by metabolism and excretion in urine and to a lesser extent in feces. The whole-body half-life of CNA in the rat was approximately 1 h, and clearance of radioactivity from the body was near complete in 3 d. The known carcinogen and potential metabolite of CNA, 4-chloro-o-phenylenediamine, was not detected in rat tissues or excretia following administration of CNA. Approximately 70% of the dose was detected in urine as a sulfate conjugate of a single metabolite of CNA. The remainder of the dose was excreted in the form of seven additional metabolites and a trace of the parent compound. CNA-derived radioactivity had little potential for bioaccumulation, and there was no evidence for saturation of any mechanism involved in the absorption, distribution, metabolism, or excretion of CNA in the dose range studied.

Adipose Tissue↗