Hepatic and extrahepatic metabolism of 14C-styrene oxide.

With 8-(14)C-styrene oxide as substrate, specific glutathione S-transferase and epoxide hydrase activities were determined in subcellular fractions of liver, lungs, kidney, and intestinal mucosa from rabbit, rat, and guinea pig. Liver had the highest enzyme activities in each species. Rat and guinea pig had higher glutathione S-transferase activity in both liver and kidney than rabbit. Rat testis also had appreciable glutathione S-transferase activity. The perinatal development of epoxide hydrase and glutathione S-transferase was followed in liver and several extrahepatic tissues of fetal and neonatal guinea pigs and rabbits. The rates at which enzyme activities reached adult levels in the extrahepatic tissues differed from the liver in both species. Epoxide hydrase and glutathione S-transferases developed at different rates in each organ, demonstrating that the relative importance of these two detoxifying pathways for styrene oxide may shift before and after birth. The effects of pretreating male and female rats with phenobarbital (PB), 1,2,3,4-dibenzanthracene (DBA), pregnenolone-16alpha-carbonitrile (PCN), or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on hepatic and extrahepatic epoxide hydrase and glutathione S-transferase activities toward styrene oxide were determined. PB increased both enzyme activities in liver of both sexes. PCN induced only glutathione S-transferase activity in female liver. Extrahepatic epoxide hydrase and glutathione S-transferase activities were unaffected except that TCDD doubled female renal epoxide hydrase activity and PB increased intestinal epoxide hydrase activity in both sexes. Styrene oxide biotransformation was studied in isolated, perfused rat liver and rabbit lung preparations. Conjugation with glutathione was a major metabolic pathway although significant amounts of diol were also formed in each instance. In rat liver, 27-40% of the administered styrene oxide was excreted via the bile mainly as S-(1-phenyl-2-hydroxyethyl)glutathione.

Neoplastic transformation of cells by soluble but not particulate forms of metals used in orthopaedic implants.

Recent developments in cell culture techniques have made it possible to study the cellular mechanisms involved in carcinogenesis and to apply these methods as screening tools in vitro. This study investigated and compared the ability of the metals most commonly used in orthopedic implants to induce toxicity and neoplastic transformation in the C3H10T1/2 mouse fibroblast cell line. Eight metals (cobalt, chromium, nickel, iron, molybdenum, aluminium, vanadium and titanium) and their alloys (stainless steel, cobalt-chrome alloy and titanium alloy) were tested, both as soluble salts and as solid particles. There were marked differences between the various metals in terms of both toxicity and transforming ability. Significant increases in the incidence of cell transformation were seen with soluble forms of cobalt, chromium, nickel and molybdenum but not with iron, aluminium, vanadium or titanium. For most of the metals. transforming ability was directly related to toxicity, although this correlation did not hold for either molybdenum or vanadium. The physical form of the metal was critically important in determining its effects, and transformation occurred only with soluble metal salts.

Biocompatibility of particles of GORE-TEX cruciate ligament prosthesis: an investigation both in vitro and in vivo.

This research was to determine the biocompatibility of simulated wear particles from a GORE-TEX cruciate ligament prosthesis using in vitro and in vivo techniques. Exposure of normal human synovial fibroblasts and primary mouse peritoneal macrophages to the particles revealed no cytotoxicity, as determined by lactate dehydrogenase release, but beta-N-acetyl-D-glucosaminidase was released from macrophages at high concentrations, showing inflammatory potential. This was not seen when the particles were injected into mouse knees, where no adverse reactions were observed. These simulated wear particles were shown to be biocompatible using these in vitro and in vivo systems.

Biocompatibility of diamond-like carbon coating.

Diamond-like carbon coating is an inert, impervious hydrocarbon coating with properties suitable for use in the biomedical field, particularly in orthopaedic implants. Mouse peritoneal macrophages and mouse fibroblasts were grown on tissue culture plates treated with diamond-like carbon and the biocompatibility assessed both biochemically and morphologically. This investigation showed that diamond-like carbon coating caused no adverse effects on cells in culture and therefore merits further investigation as a coating for biomedical use.

Biocompatibility of particulate polymethylmethacrylate bone cements: a comparative study in vitro and in vivo.

The biocompatibility of particles of four different commercial polymethylmethacrylate (PMMA) bone cements was evaluated by exposing human synovial fibroblasts and mouse peritoneal macrophages to particles of cement. Cell integrity and inflammatory potential were assessed using enzyme release and microscopical examination. Results suggested the occurrence of cell damage in both cell types and macrophage studies indicated inflammatory potential. The response in vivo was investigated by intra-articular injection of the particles into mouse knee joints. Clinical and histological evaluation was performed over 2-52 wk. Particles of all four cements were well tolerated in the joints.

A urine collection system for studying the excretion of xenobiotics from Dungeness crabs.

A technique is described for collecting urine from the Dungeness crab, Cancer magister (Dana), a commercially important seafood and an indicator species of aquatic pollution. The technique has been modified from previously published methods to study the role of urinary excretion in the elimination of lipophilic pollutants by the Dungeness crab. The improved urine collection system uses chemically resistant and nonreactive materials that are better suited to pharmacological and toxicological studies than those used in previous methods. The improved method was tested by injecting a vital dye into catheterized Dungeness crabs and by measuring urine flows for 10 days. This technique can be used to determine the urinary excretion of xenobiotics and facilitate the characterization of chemicals and their metabolites accumulated by crabs.

Effects of cigarette smoke and 3-methylcholanthrene on the disposition of phencyclidine and its N-ethylamine analogue in the isolated perfused lung of rats.

The isolated perfused lung (IPL) of rats were used to examine the pulmonary disposition and metabolism of radiolabeled phencyclidine (PCP) and N-ethyl-1-phenylcyclohexylamine (PCE). The IPL removed PCP and PCE from the perfusate and converted them to free and conjugated metabolites. At the conclusion of a 1-h perfusion, the lung accumulated at least 20% of the administered radioactivity and metabolized more than 30% of the added drug. Pretreatment of rats with 3-MC or cigarette smoke enhanced significantly PCP and PCE metabolism by the IPL. The concentration of conjugated PCE metabolite in the perfusate of the IPL was increased significantly by both 3-MC and cigarette smoke pretreatments whereas the concentration of conjugated PCP metabolite was not affected by cigarette smoke exposure and increased only slightly after 3-MC pretreatment. Pretreatment of rats with 3-MC or cigarette smoke also altered the amount of radioactivity accumulated by the lung tissue at the conclusion of a 1-h perfusion. Inasmuch as PCP and PCE are often abused by humans via smoke inhalation, a significant amount of these drugs may be stored or metabolized by the lung.

Reliability and reproducibility of a Chinese-language visual function assessment.

OBJECTIVE: The purpose of the study was to validate a Chinese-language visual function assessment within the context of a routine cataract surgery practice and to assess the contribution of the method of questionnaire administration. DESIGN: The visual function assessment (VFA) was translated into Chinese. Two groups of study subjects were recruited: Chinese who did not speak English and Chinese conversant in English. Consecutive preoperative cataract patients of Chinese ancestry presenting to an urban ophthalmology practice were recruited. The questionnaire was administered in person or by telephone interview. Pre-operative visual acuity was recorded. Visual function scores were analyzed to assess reliability and correlation with visual acuity. RESULTS: Among the 186 potential study subjects, 155 patients completed the study The Chinese-language visual function assessment had good internal consistency (Cronbach alpha = 0.97, inter-item correlations = 0.43 to 0.96) . Reliability (with regard to the English version) and test-retest reproducibility of the Chinese questionnaire were strong with intraclass correlation coefficients greater than 0.60. The method of administration contributed to the measures of reliability and reproducibility. CONCLUSION: These results show that a Chinese-language version of the VFA questionnaire is reliable and valid. In industrialized countries with large Chinese-speaking populations and newly developed countries of East and Southeast Asia, the visual function assessment may be helpful in assisting routine clinical patient evaluation and cross-cultural outcome assessment programmes. Our findings also suggest that self-administered visual function assessments may be more reliable and valid than interview-generated assessments.

Effects of nitrogen dioxide and 3-methylcholanthrene on pulmonary enzymes.

Guinea pig lung phenol-O-methyltransferase, catechol-O-methyltransferase, and benzpyrene hydroxylase activities were examined after nitrogen dioxide and 3-methylcholanthrene treatment. While benzypyrene hydroxylase activity was enhanced by 3-methylcholanthrene, none of the pulmonary enzyme activities was altered after exposure to either 40 or 70 ppm of nitrogen dioxide for 2 hr.

Evidence of 14C-furazolidone metabolite binding to the hepatic DNA of trout.

Furazolidone (FZ) is a nitrofuran drug commonly used in aquaculture. In the present study, [methylidene-14C]-FZ or [oxazolone-4,5-14C]-FZ was offered to rainbow trout (Oncorhyncus mykiss) in medicated feed at a daily dose of 135 mg/kg b. wt. for 10 days. The trout were sacrificed at specific time points post-dosing and the liver removed for DNA-bound 14C characterization. Both forms of the 14C-labelled FZ were converted by trout to reactive metabolite(s) which bound irreversibly to the hepatic DNA. The amount of 14C bound to the hepatic DNA increased with post-dosing time and was higher in trout pretreated with [methylidene-14C]-FZ than in trout pretreated with [oxazolone-4,5-14C]-FZ. The identity of the FZ reactive metabolite(s) remained to be elucidated. However, a part of the FZ reactive metabolite(s) could be released as 3-amino-2-oxazolidone by acid hydrolysis. An appreciable amount of 14C was also found to bind irreversibly with the hepatic DNA of trout following an i.v. injection of [oxazolone-4,5-14C]-FZ. Results of these studies indicate that FZ is metabolized by trout to a reactive metabolite(s) which binds irreversibly to the DNA of trout liver.

Benzo(a)pyrene toxicokinetics in the cricket following injection into the haemolymph.

The metabolic disposition of (14)C-labelled benzo(a)pyrene (BP) in the cricket (Acheta domesticus) was investigated after injection into the haemolymph. (14)C-BP was taken up rapidly by the nerve cord, malpighian tubules, reproductive organs, gut, and muscle:cuticle of the cricket. The elimination half-lives of (14)C-BP in these tissues ranged from 8.9 to 17.8 h. The haemolymph (14)C-BP concentration-time curve could be described by a one-compartment open pharmacokinetic model. (14)C-BP was metabolized by the cricket mainly to unconjugated and conjugated BP metabolites since very little unchanged (14)C-BP was found in the excreta at 48 h post-dosing. GLPC-MSD and HPLC/ES-MS analyses showed the presence of at least two BP metabolites in the excreta. The BP metabolites were identified tenatively as the diol derivatives of benzo(a)pyrene and benzo(a)pyrene quinone.

The dispositional kinetics of phencyclidine and its N-ethylamine analogue in rats.

The uptake kinetics of [3H]-labelled phencyclidine (PCP) and N-ethyl-l-phenycyclohexylamine (PCE) in rats, measured in terms of decreases in the blood concentrations of the drugs after i.v. administration of a single 1.09 mumol dose, were not significantly different. Within a week of administration, the rats excreted about 93% of the [3H]-PCP and about 65% of [3H]-PCE via their urine and faeces; their urine contained nore [3H], mainly as metabolites of [3H]-PCP and of [3H]-PCE, than their faeces. Similarly, more [3H] remained in the tissues of rats treated with [3H]-PCE than in the tissues of [3H4-PCP-treated rats. The fact that PCE is metabolized and excreted more slowly than PCP may account for the higher psychotropic effects of PCE.

Biotransformation and elimination of 1-nitropyrene in the isolated perfused lung: effects of pretreating rats with phenobarbitone, beta-naphthoflavone, benz(A)anthracene or their mixtures.

The isolated perfused rat lung (IPL) was perfused with 60 ml of recirculating Krebs-Ringer solution containing 150 micrograms of 1-nitropyrene (1-NP) for 1 h. The 1-NP was administered to the IPL by the intratracheal or intravascular route. At specific time points after 1-NP administration, perfusate samples were removed from the IPL and analysed for 1-NP and its metabolites by HPLC. Monohydroxynitropyrenes, dihydroxynitropyrenes and 1-NP were found to be present in the perfusate. The time course of 1-NP concentrations in the perfusate could be described by a one-compartment pharmacokinetic model. Pretreatment of rats with beta-naphthoflavone (BNF), benz(a) anthracene (BA) or a mixture of phenobarbitone (PB) and BNF (PB + BNF) significantly enhanced the metabolism of 1-NP and decreased the mean residence time (MRT) of 1-NP in the perfusate. Pretreatment of rats with these mixed-function oxidase inducers also increased significantly the absorption of 1-NP by the lung when it was administered intratracheally. In contrast, pretreatment of rats with PB did not appear to have any effect on the pharmacokinetics of 1-NP in the IPL.

Rates of phencyclidine metabolism by the isolated perfused lung, lung microsomes, and liver microsomes of rabbits.

The metabolism of phencyclidine (PCP) was examined in the isolated perfused lung (lPL), lung microsomes, and liver microsomes of rabbits. The concentration of PCP in the IPL perfusate decreased rapidly with concomitant increases in the concentrations of PCP metabolites. The total rate of PCP metabolite appearance in the perfusate of the IPL was 77.4 nmol/lung/min. The apparent Vmax of PCP metabolism by the lung and liver microsomes were 1.52 and 22.9 nmol of PCP metabolised per mg of microsomal protein per min, respectively. Extrapolated to the whole lung, the apparent Vmax of PCP metabolism by lung microsomes was equivalent to 78.6 nmol of PCP metabolized per lung per min, essentially the same as that for the IPL.

Nitrite mediated T lymphocyte responses in the intestinal immune system of mice infected with Trichinella spiralis nematode.

The effects of orally administered sodium nitrite (20 mg NaNO2/kg b. w) on the responses of T and B lymphocytes collected from the mesenteric lymph nodes were studied in resistant AKR/J, H-2(k) haplotype mice infected with Trichinella spiralis nematode. On days 6, 9, and 12 postinfection, the mesenteric lymph node cells (MLNC) were collected from the mice and assayed for lymphocyte subsets (CD4(+), CD8(+), B220(+)), cytokines (IL-2, IL-5), and INF-gamma. At the same time, the number of adult worms in the small intestine were counted. Infection of the nitrite-treated mice with T. spiralis L1 larvae caused a marked increase in the number of adult worms in the small intestine. However, preincubation of T. spiralis L1 larvae with nitrite before infecting the mice resulted in a significant reduction in the number of adult worms (p < 0.05). Preincubation of T. spiralis L1 larvae with nitrite also caused an increase in the number of CD4(+) and CD8(+) cells as well as IL-2, IL-5, and INF-gamma levels. An increased level of CD8(+) subsets and a depression of IL-2 and IL-5 production by MLNC were observed in mice infected with larvae without nitrite pretreatment. Since supplementary rIL-1alpha was found to alter INF-gamma secretion by MLNC in vitro, the pattern of MLNC proliferation was examined further with the nitrite-treated mice. Sodium nitrite increased thymidine incorporation into the MLNC. However, INF-gamma production was not enhanced when rIL-1alpha was added to the MLNC culture obtained from nitrite-treated mice.

Effects of drug and chemical pretreatments on biliary excretion of phenylcyclohexene in the rat.

The biliary excretion of 14C-phenylcyclohexene and its metabolites were studied in rats pretreated with an inducer or inhibitor of mixed-function oxidases or with an agent known to deplete liver glutathione. Pretreatment of rats with 3-methylcholanthrene or phenobarbital enhanced the biliary excretion of 14C-phenylcyclohexene and/or its metabolites. Conversely, pretreatment of rats with SKF-525A or piperonyl butoxide decreased the biliary excretion of 14C-phenylcyclohexene and/or its metabolites. In contrast, pretreatment of rats with diethylmaleate did not alter significantly the rate of biliary excretion of radioactivity.