bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined hemoperfusion‐hemodialysis in organophosphate poisoning
Authors: Nagler J. , Braeckman R. A. , Willems J. L. , Verpooten G. A. , de Broe M. E.
Published: October 2006

We report on a patient treated with combined prolonged hemoperfusion (HP, Adsorba 300 C, Gambro, Sweden) and hemodialysis (HD, C‐DAK 1.2, Cordis Dow, USA) for severe dimethoate poisoning. This procedure was adopted since the combination of dialysis and adsorption may improve overall drug removal. Combined HP–HD was performed during 24 h using the same charcoal column and dialyser. Adequate heparinization was obtained by monitoring the whole blood activated partial thromboplastin time. The patient (a 34‐year‐old female) ingested approximately 10 g of dimethoate (Teletox 10) in a suicide attempt, 30 min before admission to the hospital. On admission, serum level of dimethoate (analysed by gas chromatography) was 2340 ng ml−1. She received conventional treatment and combined HP–HD was started within 2 h after admission. At this time serum levels had risen to 3110 ng ml−1. However, they declined constantly during the epuration and after 18 h no more dimethoate could be detected in the serum. She was discharged 3 days after treatment. During the 24 h of HP–HD treatment, 110.8 mg dimethoate entered the epuration system via the plasma. 55.3 mg were extracted by the charcoal column and 25.3 mg by hemodialysis.
Acrylamide neurotoxicity in the mouse: A behavioral, electrophysiological and morphological study
Authors: von Burg R. , Penney D. P. , Conroy P. J.
Published: October 2006

The development of acrylamide induced neutrotoxicity was followed for 3 weeks in the mouse by behavioral testing, determination of conduction velocities and electron microscopic examination of peripheral nerves. Neurotoxic signs began to appear during the second week of treatment. A condition of severe intoxication developed within 21 days. Behavioral assessment for neurological deficits proved to be more sensitive than sensory or motor conduction velocity determinations either in isolated preparations or in situ. In general, such electrophysiological determinations did not result in reproducible, statistically significant, differences from control animals until the third week of acrylamide administration. However, there was a suggestion that temperature reduction may provide a provocative change to increase the sensitivity of such electrophysiological measurements. Electron microscopic examination of the nerves of severely poisoned animals revealed myelin corrugation and delamination to be the most consistent damage. Acrylamide appeared to produce a nonselective attack since degenerating fibers were found intermingled with almost normal fibers of approximately the same diameter. In general, the production of neutrotoxicity in the mouse closely resembled that seen in the rat but some differences were noted.
Placental transport and embryonic utilization of essential metabolites in the rat at the teratogenic dose of cadmium
Authors: Webb M. , Samarawickrama G. P.
Published: October 2006

Administration of Cd2+ to the 12–day pregnant rat caused a dose‐dependent inhibition of placental 65Zn2+ transport. At 4 h after the injection of the teratogenic dose (1.25 mg Cd2+ per kg body weight), transport of 65Zn2+ to the embryo was inhibited by 75%. This inhibition decreased with time and at 48 h was no longer statistically significant. In contrast with Zn2+, the administration of Cd2+ did not affect the transport of sugar, amino acids and nucleic acid precursors from the maternal circulation to the embryo at any time. The incorporation of [14C]thymidine into embryonic DNA, however, was inhibited by about 50% at 4 h and by 75% at 20 h. By 48 h it returned to control levels. Incorporation of [14C]formate into DNA also was reduced. Inhibition of the incorporation of L‐[14C]leucine into protein was apparent at 20 h, but not at 4 h, after the administration of Cd2+. Inhibition of DNA synthesis, which led to a significant reduction in embryonic DNA concentration at 20 h, was associated with a marked decrease in the activity in embryonic thymidine kinase. In extracts of embryos from Cd2+‐treated dams, the activity of this enzyme was restored to the control level by the addition of 7.7 μM zinc acetate to the assay system. In vivo, the simultaneous injection of Zn2+ at a 2:1 atomic ratio with Cd2+ prevented the inhibition of thymidine incorporation into DNA. At the teratogenic dose, only about 16 ng Cd2+ per g wet weight is incorporated into the embryo. The inhibition of placental transport, particularly of Zn2+, therefore, may be of prime importance in the teratogenic response.
Comparative studies on the distribution of gold, copper and zinc in the livers and kidneys of rats and hamsters after treatment with sodium [195/Au]‐aurothiomalate
Authors: Mogihricka Ewa M. , Webb M.
Published: October 2006

The distribution of gold, copper and zinc in the livers and kidneys of female rats and hamsters was determined after intraperitoneal injection of sodium [195Au]‐aurothiomalate. After five doses of sodium [195Au]‐aurothiomalate (1 mg Au(I) per kg body weight), the hepatic and renal concentrations of Au were greater in rats than in hamsters. In the former species, treatment with the Au(I)‐compound led to an increase in the Cu‐concentration of the kidney and to the synthesis of a (Cu, Au)‐metallothionein. In either species binding of Au to the hepatic metallothionein was insignificant. The renal (Cu, Au)‐metallothionein from the sodium [195Au]‐aurothiomalate‐treated rat appeared to be extremely heterogeneous and was resolved into at least four components on ion exchange chromatography.
Effects of kola‐nut extract administration on the liver, kidney, brain, testis and some serum constituents of the rat
Authors: Ikegwuonu F. I. , Aire T. A. , Ogwuegbu S. O.
Published: October 2006

Kola‐nut extract induced a number of overt neurotoxicological signs in male albino rats. A decrease in the total body weight and an increase in the absolute weights of the liver, kidney, brain and testis were observed after 18 weeks oral administration of kola‐nut extract to the rats. Total protein, RNA and DNA of these organs were significantly depressed. The activity of β‐glucuronidase and β‐galactosidase was induced only in the kidney, brain and testis of treated animals. While the levels of serum phosphomonoesterases and total cholesterol were significantly enhanced due to kola‐nut intake, serum total and conjugated bilirubin levels were significantly decreased.
Electrospun polyphosphazene nanofibers for in vitro rat endothelial cells proliferation
Authors: Carampin Paolo , Conconi Maria Teresa , Lora Silvano , Menti Anna Michela , Baiguera Silvia , Bellini Silvia , Grandi Claudio , Parnigotto Pier Paolo
Published: October 2006

A large variety of natural and synthetic polymers have been explored as scaffolds for the seeding and growth of different types of cells. To fabricate a scaffold that can be used as a synthetic extracellular matrix (ECM), it is important to replicate the nanoscale dimensions of natural ECM. The electrospinning process allows to produce ultrathin fibers so that this method represents a suitable approach to scaffold fabrication for tissue engineering applications. In this work, the feasibility of obtaining flat or tubular matrices from biocompatible poly[(ethyl phenylalanato)1.4 (ethyl glycinato)0.6 phosphazene] by electrospinning was evaluated and the effect of process parameters on the diameter of nanofibers was examined. The adhesion and growth of rat neuromicrovascular endothelial cells cultured on sheets and tubes composed by the polymer with an average fiber diameter of 850 ± 150 nm were also reported. Microscopic examination of the seeded tubes demonstrated that, after 16 days of incubation, endothelial cells formed a monolayer on the whole surface. These results are the first step to demonstrate that tubes of biodegradable polyphosphazenes might be a feasible model to construct human tissues such as vessels or cardiac valves. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Detection of in vivo lipid peroxidation using the thiobarbituric acid assay for lipid hydroperoxides
Authors: Kirkpatrick Daniel T. , Guth Daniel J. , Mavis Richard D.
Published: October 2006

Thiobarbituric acid (TBA) assays which have been modified for detection of lipid hydroperoxides appear to be useful for demonstration of in vivo lipid peroxidation. Since these methods require heating tissue membranes with the buffered TBA, there is a possibility of interference from the detection of autoxidation that occurs during heating. These studies were undertaken to investigate conditions which favor TBA color production from hydroperoxide while limiting autoxidation during the assay. An acetic acid‐sodium acetate buffered (pH 3.6) TBA assay was used. Heating linoleic acid hydroperoxide with 50 μM ferric iron or under nitrogen nearly doubled color production compared to heating it with no added iron or under air. The lipid antioxidant butylated hydroxytoluene inhibited color production from fatty acid hydroperoxides. When tissue fractions, including liver and lung microsomes and lung whole membranes, were heated in the assay, color production was greater under air than under nitrogen and was much greater under oxygen. When liver microsomes from carbon tetrachloride‐exposed rats were used, color was increased only when oxygen was present in the heating atmosphere. The results with tissue fractions appear to demonstrate autoxidation during color development rather than the presence of preformed hydroperoxides. Finally, it was found that color production from membrane fractions was dependent on the vitamin E content of the membranes. It appears that autoxidation during heating should be limited by heating under nitrogen and not by adding antioxidants, which inhibit color production from hydroperoxides. As the vitamin E effect demonstrates, antioxidant status must be considered, since a change in color production could result from a change in antioxidant content without the accumulation of lipid hydroperoxides.
Potentiation by chlordecone of the defect in hepatic microsomal calcium sequestration induced by carbon tetrachloride
Authors: Hegarty Joel M. , Glende Eric A. , Recknagel Richard O.
Published: October 2006

The effect of carbon tetrachloride (CCl4) on the capacity of hepatic microsomes to sequester calcium was studied following pretreatment of rats with chlordecone. Chlordecone pretreatment alone had no effect on the kinetics of calcium uptake by hepatic microsomes. It was found, however, that chlordecone pretreatment of rats potentiated by sixfold the potency of CCl4 to suppress microsomal calcium sequestration capacity when measured one hour after CCl4 administration.
The in vitro metabolism and bioactivation of 1,2‐dibromoethane (ethylene dibromide) by human liver
Authors: Wiersma David A. , Schnellmann Rick G. , Sipes I. Glenn
Published: October 2006

The nematocide, grain fumigant, and gasoline additive 1,2‐dibromoethane (DBE) is both a cellular and a genetic toxin that is metabolically activated in rats and mice by mixed function oxidases (MFO) as well as glutathione S‐transferases (GST). The purpose of this study was to determine whether DBE is similarly metabolized and bioactivated by human liver in vitro.

Human liver microsomal and cytosolic metabolism of DBE was monitored by the production of aqueous‐soluble metabolites from [14‐C]‐DBE. Reactive intermediates were detected as irreversibly bound adducts to protein or DNA. 1,2‐Dibromoethane was metabolized by human liver cytosolic GST, microsomal GST, and microsomal MFO. Cytosolic GST activity (9 ± 2 nmol/20 min/mg protein) was about four times greater than the other two activities. Only MFO activity resulted in adducts irreversibly bound to protein (1.5 ±.4 nmol/20 min/mg protein) and was inhibited by the presence of glutathione. Both MFO and GST activity resulted in irreversibly bound adducts to DNA. Microsomal and cytosolic GST activity each produced about twice as many DNA adducts as microsomal MFO activity.

These results suggest that human liver, like rat and mouse liver, metabolizes DBE to aqueous‐soluble metabolites by both MFO and GST activity. Furthermore, each of these activities produces reactive metabolites that can irreversibly bind to cellular macromolecules.
In vivo and in vitro synthesis, release, and uptake of [3‐H]‐dopamine in mouse striatal slices after in vivo exposure to chlordecone
Authors: Fujimori Kannosuke , Benet H. , Mehendale H. M. , Ho I. K.
Published: October 2006

Effects of treatment of mice with chlordecone (25 mg/kg/d) on striatal dopaminergic activities such as synthesis, turnover, uptake, and release were investigated in vivo and in vitro. In mice receiving chlordecone for five days, there were no significant changes in in vivo dopamine (DA) synthesis and turnover in striatum and in vitro [3‐H]‐dopamine uptake and K+‐stimulated [3‐H]‐dopamine release in striatal slices. In mice receiving chlordecone for eight days, the in vivo synthesis of [3‐H]‐dopamine from [3‐H]‐tyrosine in striatum was slightly inhibited and the in vitro [3‐H]‐dopamine synthesis in striatal slices was significantly decreased. Furthermore, both uptake and K+‐stimulated release of [3‐H]‐dopamine from striatal slices were significantly reduced. The turnover rate of newly synthesized [3‐H]‐dopamine from [3‐H]‐tyrosine in striatal slices was unchanged after eight consecutive days of chlordecone administration. These results suggest that chlordecone may cause impairments in pre‐ and/or postsynaptic membranes of dopaminergic neurons which modulate motor function.
Immunochemical characterization of human lung epoxide hydrolases
Authors: Guenthner Thomas M. , Karnezis Thomas A.
Published: October 2006

Immunochemical techniques were used to investigate the biochemical properties of human lung epoxide hydrolases. Two epoxide hydrolases with different immunoreactive properties were identified. These two epoxide hydrolases were found in both cytosolic and microsomal cell fractions. Immunotitration of enzyme activity showed that enzymes that catalyze the hydration of benzo(a)pyrene 4,5‐oxide react with antiserum to rat microsomal epoxide hydrolase; those that hydrate trans‐stilbene oxide do not. Immunotitration and Western blot experiments showed that microsomal and cytosolic benzo(a)pyrene 4,5‐oxide hydrolases have significant structural homology. Immunohistochemical staining of human lung benzo(a)pyrene 4, s‐oxide hydrolase showed that the enzyme is localized primarily in the bronchial epithelium. No cell type‐specific localization was observed. An enzyme‐linked immunosorbent assay was developed which allows direct quantitation of benzo(a)pyrene 4,5‐oxide hydrolase protein. Levels of enzyme protein detected by this assay correlated well with enzyme levels determined by substrate conversion assays.
2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin causes elevation of the levels of the protein tyrosine kinase pp60c‐src
Authors: Bombick David W. , Matsumura Fumio
Published: October 2006

2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin (TCDD) has been found to cause increases in cellular levels of pp60src, a protein tyrosine kinase in hepatocytes from the rat and guinea pig, in the thymus of the mouse in vivo and in NIH‐3T3 mouse fibroblast cell lines in vitro. Such cellular changes take place in vivo at early stages of TCDD poisoning (as early as one day after treatment in the case of mouse thymus) and at very low doses (single intraperitoneal injections of 1 μg/kg for guinea pigs, 25 μg/ kg for rats, and 30 μg/kg for mice). In addition such an effect of TCDD was observed only in a TCDD‐responsive mouse strain but not in a nonresponsive strain. This effect of TCDD is a long‐lasting one (eg, even 25 days after single dosing, the levels of pp60src in the hepatic membrane remained high). In vitro this effect was observed in a wild‐type 3T3 cell line but was more pronounced in one of the transfected lines with a v‐src gene, a virus‐derived oncogene known to code for pp60src protein.
Possible antiestrogenic activity of lindane in female rats
Authors: Chadwick Robert W. , Cooper Ralph L. , Rehnberg Georgia L. , McElroy W. Keith , Chang Jerjang
Published: October 2006

During chronic peroral (PO) treatment of weanling, female Fischer 344 rats with daily injections (0.069 mmol/kg) of either 1,1′‐(2,2,2‐trichloroethylidene) bis [4‐chlorobenzene] (p,p′‐DDT), 2,4‐dichlorophenoxy acetic acid (2,4‐D), or γ‐hexachlorocyclohexane (lindane), the lindane treatment induced a significant 20% increase in body weight after 110 days. Further investigation with 0,5,10,20, and 40 mg/kg lindane confirmed a significant increase in average body weight gain at the two highest doses after ten weeks of treatment. Significantly greater food consumption was observed, and the Lee index indicated that lindane treatment induced obesity. In addition to obesity, lindane caused a delay in vaginal opening, disrupted estrous cycling, reduced pituitary and uterine weight, and elevated food consumption during proestrus (when appetite is normally suppressed by estradiol). These responses suggest that, by inducing alterations in the reproductive function of the female rat and by interfering with hormonal regulation of energy balance, lindane may be antiestrogenic rather than estrogenic as previously proposed.
Neuropathy target esterase in hens after sarin and soman
Authors: Crowell J. A. , Parker R. M. , Bucci T. J. , Dacre J. C.
Published: October 2006

To estimate the potential of small doses of sarin (types I and II) and soman to cause delayed neuropathic effects, 400, 200, 61, and 0 μg/kg of sarin‐I, 280, 140, 70, and 0 μg/kg of sarin‐II, and 14.2, 7.1, 3.5, and 0 μg of soman by gavage were compared with 510 mg/kg tri‐o‐cresyl phosphate (TOCP) in 14‐to 18‐month‐old SPF white leghorn hens (4/dose) protected with atropine (100 mg/kg). The neuropathy target esterase (NTE) activity 24 hr after dosing was determined in brain, spinal cord, and lymphocytes and in plasma and brain for cholinesterase and carboxylesterase. None of the compounds showed statistically significant NTE decreases. Sarin‐II showed a dose‐related trend in the lymphocyte NTE (to 33% of control at 280 μg/kg), suggesting that longer exposure to lower doses might cause a cumulative neurotoxic insult. All of the agents decreased the activity of plasma and brain cholinesterase and carboxylesterase. Using more than 70% inhibition of brain NTE as a biochemical predictor of delayed neuropathy, sarin and soman appear unable to cause delayed neuropathy at nonlethal doses within this protocol.
Subacute inhalation of cigarette smoke by pregnant and lactating rodents: Ahh changes in perinatal tissues
Authors: Bilimoria M. H. , Ecobichon D. J.
Published: October 2006

To study the transplacental acquisition of tobacco smoke products and the effects on fetal tissue enzymes, pregnant rats, guinea pigs, and hamsters were exposed to freshly generated cigarette smoke via a nose‐only inhalation system on a daily basis through the latter one‐third (guinea pigs) or latter half (rats, hamsters) of the gestational period. Following euthanasia on the day of parturition, micro‐somal aryl hydrocarbon hydroxylase (AHH) activities were determined in the lungs, livers, and kidneys of both dams and fetuses. The possible acquisition of tobacco smoke products via the milk was studied by exposing lactating dams to cigarette smoke daily for either 4 or 14 days (rats), 4 or 7 days (guinea pigs), or 10 days (hamsters), with analysis of tissues from the euthanized pups for AHH. Pups were also exposed directly (nose only) to cigarette smoke. In the treated pregnant and lactating rat, maternal pulmonary, hepatic, and renal AHH was significantly increased but only fetal lung and the liver of 14‐day‐old pups showed a marked induction of AHH activity. In the pregnant and lactating guinea pig, only the pulmonary and renal AHH activities were increased following exposure, whereas in the fetuses and nursing pups, none of the tissue AHH activities was significantly altered by exposure. In the pregnant and lactating hamster, only the pulmonary AHH was increased following exposure to cigarette smoke, whereas the activity in fetal and pup tissues remained unchanged from the levels observed in control animals. Direct exposure of 7‐and 14‐day‐old rat pups to cigarette smoke resulted in a significant induction of AHH in lung, liver, and kidney at both ages. In the 7‐and 14‐day‐old hamster pups, increased AHH activity was measured only in the lungs of 14‐day‐old animals. In the guinea pip pups at 2 days of age, AHH levels were increased significantly only in the kidney.
Induction of cytochrome p‐450 isozymes by mirex and chlordecone
Authors: Lewandowski Margaret , Levi Patricia , Hodgson Ernest
Published: October 2006

The effect of the insecticides, mirex and chordecone (Kepone), on the cytochrome P‐450 monooxygenase system in C57BL/6N mouse liver microsomes was studied. Mice were treated intraperitoneally with low (6 mg/kg) and high (30 mg/kg) doses of mirex and chlordecone in corn oil for 2 days. For comparison, mice were also treated with either phenobarbital (PB) or 3‐methylcholanthrene (3‐MC). All treatments significantly increased the hepatic microsomal P‐450 content over that of controls. Benzphetamine N‐demethylase, ethoxyresorufin O‐deethylase, benzo[a]pyrene hydroxylase, and acetanilide hydroxylase activities were also determined. Mirex and chlordecone resembled phenobarbital with respect to the induction of monooxygenase activities. Immunoquantitation with antibodies to purified P‐450 IIB1 (Pb‐induced P‐450) and P‐450 IA1 (3‐MC‐induced P‐450) indicated that mirex and chlordecone induced P‐450 IIB1 in a dose‐dependent manner. The high dose of mirex also induced a small amount of a protein cross reacting with the antibody to IA1. The induction of this isozyme did not, however, contribute significantly to the monooxygenase activities measured.
Hepatic Ah Receptor from the Wistar Rat: Role of Solvation in Receptor Structure and Inactivation
Authors: Landers James P. , Bunce Nigel J.
Published: October 2006

Repeated freezing and thawing, the addition of salts, and elevated temperatures all promote the inactivation of the rat hepatic Ah receptor. The reduced availability of bulk water to solvate the protein is proposed to be the factor linking all these routes for inactivation. Prospective protocols for purification of unliganded Ah receptor should therefore minimize the number of freeze/thaw cycles; long‐term freezing of cytosolic samples at −20°C is inadequate to maintain long‐term viability of the unliganded receptor. The stability of rat hepatic receptor is greatly increased upon binding the ligand, and the extent of ligand‐induced stabilization is much greater than what is observed with steroid hormone receptors. Concentrations of NaCl and K2HPO4 up to 0.5 M inactivate the unbound Ah receptor irreversibly, with the loss of approximately 50% of the specific binding. At 2.0 M NaCl, a further reversible reduction in ligand binding activity is observed. The results at lower salt concentrations are interpreted in terms of the irreversible dissociation of a single binding unit from the trimeric cytosolic Ah receptor (which consists of two ligand‐binding units and a 90‐kDa heat shock protein), with the release of bound ligand from that subunit.
Induction of drug metabolism enzymes by dihalogenated biphenyls
Authors: van Bree L. , Commandeur J. , Lamberts B. , Cornelissen M. , van Roon M. , Laterveer H. , de Vries J.
Published: October 2006

The effects of pretreatment with symmetrically dihalogenated biphenyls (DXBs, X‐F, Cl(C), Br(B) and I) on rat liver drug metabolism enzymes were investigated. 4,4′‐DFB, ‐DCB, and ‐DBB as well as 2,2′‐DFB appeared to be inducers of microsomal cytochrome P‐450‐linked monoxygenases (N‐demethylases of aminopyrine and ethylmorphine). However, no structure‐induction relationship was found. 4,4′‐DXBs also induced a cytochrome P‐448‐linked mono‐oxygenase (ethoxyre‐sorufin O‐deethylase), and their order of induction potential seemed to parallel the increase of the size of the halogen substituent. Therefore, 4,4′‐DXB's may be categorized as mixed‐type inducers, the cytochrome P‐450 component being the more pronounced. Data on the cytochrome P‐448 induction by dihalogenated biphenyls with only para substituents may be considered as a refinement of the previously described structure‐activity relationship in this respect. All of the DXBs except 3,3′‐DCB and 4,4′‐DIB, enhanced, like phenobarbital, the activity of UDP‐glucuronyltransferase toward 4‐hydroxybiphenyl. Only 4,4′‐DFB was able to induce the activity of glutathione S‐transferase toward 1,2‐epoxy‐3‐(p‐nitrophenoxy)propane. Studies after 4,4′‐DBB‐treatment revealed, like phenobarbital, a preferential induction of ethylmorphine N‐demethylase on rough endoplasmic reticulum‐derived microsomes, whereas UDP‐glucuronyltransferase activity toward 4‐hydroxybiphenyl was induced to a larger extent on smooth endoplasmic reticulum microsomes, suggesting a dissimilar enzyme induction in microsomal subfractions.
The Interference of Aroclor 1254 with Progesterone Metabolism in Guinea Pig Adrenal and Testes Microsomes
Authors: Goldman Daphne , Yawetz Aminadav
Published: October 2006

The effects of Aroclor 1254 on cytochrome P‐450‐mediated steroidogenic activities were investigated in adrenal and testis microsomes of male guinea pigs. A significant decrease was recorded in the tissue content of adrenal microsomal cytochrome P‐450 as well as a significant reduction in the overall conversion of progesterone to steroid products., The effects of exposure to Aroclor 1254 on activities of cytochrome P450 21‐hydroxylase and cytochrome P450 17α‐hydroxylase /C17,20‐lyase were selective. Cytochrome P‐450 21‐Hydroxylase activity was inhibited, as reflected by a decrease in production of 11‐deoxycortisol and 11‐deoxycorticosterone, whereas the cytochrome P‐450 17α‐hydroxylase / C17,20‐lyase activities, represented by the production of 17α‐hydroxyprogesterone and androstenedione were elevated. The same and even more pronounced pattern of altered progesterone metabolism elicited by Aroclor 1254 was observed in vitro, when Aroclor 1254 was introduced into incubation mixtures prepared with adrenal microsomes from untreated animals. Under such experimental conditions, a decrease in the overall metabolism of progesterone was observed as well as a decrease in cytochrome P‐450 21‐hydroxylase activity, while there was significant elevation in the 17α‐hydroxylase /C17,20‐lyase activities.

The effect of Aroclor 1254 on the testes differed largely from its effect on the adrenal cortex. In testis microsomes, pretreatment with Aroclor 1254 resulted in no changes in the cytochrome P‐450 content, contrary to the decrease observed in adrenal microsomes. In contrast to its inductive effect on the normally suppressed androgen producing pathway in adrenal microsomes, Aroclor 1254 had no effect on the 17‐hydroxylase /C17,20‐lyase activities in testis microsomes, both in the pretreated animals as well as when it was present in the incubation mixtures containing microsomes of untreated animals. The results of this study indicate a difference in the response of steroidogenic tissues to Aroclor 1254. In adrenal microsomes Aroclor 1254 may have modulated the steroidogenic activities at a posttranscriptional level, possibly by interfering with membrane regulation of these metabolic activities. At the same time, the results obtained do not exclude the possibility that Aroclor 1254 alters the composition of cytochrome P‐450 isozymes present in adrenal tissue.
Aflatoxin B1 metabolism by 3‐methylcholanthrene‐induced hamster hepatic cytochrome P‐450s
Authors: Lai T. S. , Chiang J. Y. L.
Published: October 2006

We have studied the activation of aflatoxin B1 by hamster liver microsomes and purified hamster cytochrome P‐450 isozymes using a umu mutagen test. The hamster liver microsomes or S‐9 fractions were much more active than rat liver microsomes or S‐9 fractions in the activation of umu gene expression by aflatoxin B1 metabolites. 3‐Methylcholanthrene treatment increased aflatoxin B1 activation by hamster liver microsomes. Two major 3‐methylcholanthrene‐inducible cytochrome P‐450 isozymes, P‐450 MC1 (IIA) and P‐450 MC4 (IA2), were purified from 3‐methylcholanthrene‐treated hamster liver microsomes, and the metabolism of aflatoxin B1 by these two cytochromes was studied. In the reconstituted enzyme system, both P‐450 MC1 and P‐450 MC4 were highly active in the activation of aflatoxin B1, and antibodies against these P‐450s specifically inhibited these activities. Antibody against P‐450 MC1 inhibited the activation of aflatoxin B1 by 20% in the presence of 3‐methylcholanthrene‐treated hamster liver microsomes. In contrast, antibody against P‐450 MC4 stimulated the activity by 175%. These results indicated that hamster P‐450 MC1 might convert aflatoxin B1 to more toxic metabolite(s), whereas P‐450 MC4 might convert aflatoxin B1 to less toxic metabolite(s), than aflatoxin B1 in liver microsomes. The metabolite(s) produced by both hamster cytochrome P‐450 MC1 and MC4 were genotoxic in the umu mutagen test.
Inhibition of carbon tetrachloride‐induced lipid peroxidation by novel antioxidants in rat hepatic microsomes: Dissociation from hepatoprotective effects in vivo
Authors: Wolfgang G. H. I. , Jolly R. A. , Donarski W. J. , Ochoa R. , Petry T. W.
Published: October 2006

The ability of two novel antioxidants, U‐74,006F and U‐78,517G, as well as the known antioxidant N,N′‐diphenyl‐p‐phenylenediamine to inhibit lipid peroxidation induced by carbon tetrachloride (CCl4) was investigated in Aroclor 1254‐induced rat hepatic microsomes. All three compounds completely inhibited lipid peroxidation in microsomes as measured by the formation of thiobarbituric acid reactive substances (TBARS). Inhibition of lipid peroxidation was not a function of decreased bioactivation of CCl4, as the compounds did not substantially inhibit benzphetamine N‐demethylase activity or covalent binding of [14‐C]CCl4 to lipid or protein. Parallel studies examined the hepatoprotective effects of the compounds in vivo. Rats were pretreated with antioxidant or vehicle prior to administration of CCl4 (300 or 600 μL/kg i.p.). Sera were collected 24 h postadministration of CCl4 and analyzed for alanine aminotransferase (ALT) and alkaline phosphatase (ALP) activities and total bilirubin. Administration of CCl4 produced elevations in ALT, moderate changes in bilirubin, and no change in ALP activities. Histological examination of CCl4‐treated livers revealed lipidosis and centrilobular necrosis. The antioxidants partially improved the clinical chemistry parameters, but had minimal effects on the histological lesion. In contrast to the complete inhibition of lipid peroxidation observed in the in vitro studies, none of the antioxidants markedly protected against CCl4‐induced toxicity in vivo.
In vivo toxicity and pulmonary effects of promazine and chlorpromazine in rats
Authors: Kodavanti Urmila P. , Lockard Virginia G. , Mehendale Harihara M.
Published: October 2006

Cationic amphiphilic drugs induce a phospholipid storage disorder known as phospho‐lipidosis. Halogenated analogs of the drugs are more potent inducers of phospholipidosis when compared to nonhalogenated analogs. Two such antipsychotic drugs, promazine and chlorpromazine, are effectively taken up by the lungs and induce lamellar inclusions in vitro. We compared the in vivo toxicity and efficacy of promazine and chlorpromazine to induce phospholipidosis in the lung and in pulmonary alveolar macrophages. Male Sprague‐Dawley rats were given promazine or chlorpromazine (25 mg/kg/day, P.O., in water) for 5 weeks. Food intake was decreased in promazine‐ and chlorpromazine‐treated rats, chlorpromazine rats being affected more than promazine rats. To minimize experimental error due to starvation, control rats were pair‐fed. The body weight gain was decreased in chlorpromazine rats in comparison to pair‐fed controls. Chlorpromazine‐treated rats, but not promazine‐treated rats, showed increased mortality over the 5‐week treatment period. Histopathologic examination of lung revealed loss of alveolar macrophages with no other gross abnormalities in chlorpromazine‐treated rats. Quantitative analysis of lung lavage also showed significant reduction in the number of macrophages. This finding is in contrast to other cationic amphiphilic drugs, which induce phospholipidosis as well as accumulation of alveolar macrophages. Phospholipid level increased in alveolar macrophages but not in lavaged lung following chlorpromazine treatment. Acid phos‐phatase activity in lavaged lung homogenate and macrophages of promazine‐ and chlorpromazine‐treated rats,taken as an index of toxicity to cells, did not differ significantly from control rats. In vivo binding of promazine and chlorpromazine to the lamellar bodies isolated from lungs was quantitated using 1,6‐diphenyl‐1,3,5‐hexatriene and 1‐anilino‐8‐naphthalene sulfonate as fluorescence probes for hydrophobic and hydrophilic moieties, respectively. 1,6‐Diphenyl‐1,3,5‐hexatriene or 1‐anilino‐8‐naph‐thalene sulfonate fluorescence with lamellar bodies did not differ in control, promazine‐, or chlorpromazine‐treated rats, indicating that sufficient drug was not bound to lamellar bodies to be sensitive enough to detect using fluorescence probes. Thin‐layer chro‐matography identification of these drugs from lung extract revealed no detectable spots against the authentic drug standards indicating that promazine and chlorpromazine may not accumulate significantly in the lung in vivo to be detected by thin‐layer chromatography. These results indicate that chlorpromazine is more toxic to rats than promazine and decreases the alveolar macrophages, suggesting that macrophages are the targets of chlorpromazine‐in‐duced phospholipidosis. Long‐term chlorpromazine and promazine treatment may lead to phospholipidosis in alveolar macrophages, which can be a sensitive indicator of this disorder.
Sublethal effects of pentachlorophenol in the abalone (haliotis rufescens) as measured by in vivo 31P NMRSpectroscopy
Authors: Tjeerdema Ronald S. , Fan Teresa W.‐M. , Higashi Richard M. , Crosby Donald G.
Published: October 2006

The sublethal biochemical effects of pentachlorophenol (PCP) were investigated in live, intact red abalones (Haliotis rufescens), using a flow‐through exposure system, by in vivo 31P NMR spectroscopy. Based on rangefinding tests (6‐hr LC50 = 1.6 mg/L; 6‐hr no‐observable‐effect‐level (NOEL) = 0.8 mg/L), three abalones were separately exposed to a sublethal concentration (1.2 mg/L) for 5 hr, followed by a 13 hr recovery period. Effects in foot muscle included both a decrease in phosphoarginine and an increase in inorganic monophosphate concentrations ([PA] and [Pi], respectively); both foot muscle concentrations of adenosine triphosphate [ATP] and intracellular pH (pHi) also declined. Parallel in vitro experiments revealed that concentrations of glycerol 3‐phosphate, lactate, citrate, succinate, malate, and alanine (Ala) all increased, while those of glyceraldehyde 3‐phosphate and glutamine (Gln) remained stable. Also, these effects were not evident until 2 hr into exposure, possibly the time required for PCP to attain an effective concentration in foot muscle. During recovery, while Pi declined to pre‐exposure levels, [PA] completely recovered in only one individual. Also, realkalinization of pHi was similar to recovery of [Pi], and ATP returned to near‐initial levels, as did glycerol 3‐phosphate, lactate, succinate, malate, and Ala; glyceraldehyde 3‐phosphate, citrate, and Gln levels declined. Recovery responses corresponded to the time for PCP clearance from foot muscle. The effects of PCP were similar to those of hypoxia, fatigue, hypersalinity, and arginine kinase inhibitors, and so sublethal PCP concentrations may also inhibit electron transport and arginine kinase as well as uncouple mitochondrial oxidative phosphorylation in intact molluscs. Thus, the effects of pollutants on key biochemical processes may now be measured in intact aquatic organisms as they occur, improving our ability to accurately assess the environmental effects of pollutants in the laboratory.
Effects of inhibition of cystathionase activity on glutathione and metallothionein levels in the adult rat
Authors: Houghton Caroline B. , Cherian M. George
Published: October 2006

The effects of alterations in sulfur metabolism on hepatic and renal metallothionein and glutathione metabolism were studied in the adult rat using inhibition of two enzymes of these pathways, hepatic cystathionase and renal gamma‐glutamyl transpeptidase. Rats were fed a diet containing both methionine (0.66%) and cystine (0.20%) for 1 week before receiving three consecutive daily intraperitoneal injections of propargylglycine, a selective cystathionase inhibitor, at various doses (2.5–375 μmol/kg). When hepatic cystathionase was inhibited greater than 90% (≥50 μmol propargylglycine/kg), renal and hepatic metallothionein and hepatic glutathione were unaltered except at the highest dose. On the other hand, renal glutathione was increased twofold with a concomitant decrease in renal gamma‐glutamyl transpeptidase activity (50% of control). In another experiment, when renal gamma‐glutamyl transpeptidase was inhibited greater than 90% with three consecutive daily injections of acivicin, a selective gamma‐glutamyl transpeptidase inhibitor (10 mg/kg IP), renal glutathione content was unaltered while hepatic glutathione was decreased. Renal and hepatic metallothionein were not changed. Thus, the cysteine pools for metallothionein and glutathione appear unrelated under the present experimental conditions. In addition, following either propargylglycine or acivicin injections, renal and hepatic glutathione pools appear to be altered differently. These results suggest that renal glutathione may be preferentially maintained even when hepatic glutathione is decreased.
Activation of γ‐aminobutyric acid insensitive chloride channels in mouse brain synaptic vesicles by avermectin B1a
Authors: Payne Gregory T. , Soderlund David M.
Published: October 2006

The interaction of avermectin B1a (AVMB1a) with mouse brain chloride channels was characterized using a radiochloride efflux assay. The loss of intravesicular chloride from synaptoneurosomes preloaded with 36Cl involved an initial rapid phase followed by a slower phase that approached equilibrium within 10 min. AVMB1a stimulated a 30% loss of intravesicular chloride within the first 2 s of exposure; however, AVMB1a had no effect on the rate of the slower phase of chloride loss. Experiments with lysed synaptoneurosomes showed that both chloride loading and basal and AVMB1a‐stimulated chloride release required the presence of intact vesicles. The efflux of 36Cl from mouse brain synaptosomes and the stimulation of efflux by AVMB1a were qualitatively similar to the results obtained with synaptoneurosomes but involved much lower overall levels of chloride loading and release. AVMB1a produced halfmaximal stimulation of chloride efflux from synaptoneurosomes at a concentration of 2.1 ± 0.3 μM and a 35.4 ± 1.4% maximal loss of intravesicular chloride at saturating concentrations. γ‐Aminobutyric acid (GABA), bicuculline, or the chloride channel blockers picrotoxinin, t‐butylbicyclophosphorothionate (TBPS) 4,4′‐diisothiocyanatostilbene‐2,2′‐disulfonic acid (DIDS), and anthracene 9‐carboxylic acid (9‐CA) had little or no effect on the loss of chloride from synaptoneurosomes either in the presence or the absence of AVMB1a. However, the chlorinated cycloalkane insecticides dieldrin and lindane were equally effective as inhibitors of GABA‐dependent chloride uptake and AVMB1a‐stimulated chloride efflux. These data demonstrate that AVMB1a‐stimulated chloride efflux from mouse brain synaptic vesicles results from the activation of GABA‐insensitive chloride channels and that this action is distinct from their previously documented effects on GABA‐gated chloride channels in mouse brain preparations. Our findings imply that both GABA‐gated and GABA‐insensitive chloride channels may be toxicologically significant targets for the action of avermectins.
Species differences in ciprofibrate induction of hepatic cytochrome p450 4A1 and peroxisome proliferation
Authors: Makowska Janet M. , Gibson G. Gordon , Banner Frank W.
Published: October 2006

Six species (CD‐1 mouse, Fischer 344 rat, Syrian golden hamster, Duncan‐Hartley guinea pig, half‐lop rabbit and marmoset monkey) were treated orally with ciprofibrate, a potent oxyisobutyrate hypolipidaemic drug for 14 days. A dosedependent liver enlargement was observed in the mouse and rat and at the high dose level in the hamster. A marked dose‐dependent increase in the 12‐hydroxylation of lauric acid was observed in the treated mouse, hamster, rat, and rabbit, associated with a concomitant elevation in the specific content of cytochrome P‐450 4A1 apoprotein, determined by an ELISA technique. Similarly, in these responsive species, an increase in mRNA levels coding for cytochrome P450 4A1 was observed. Lauric acid 12‐hydroxylation was unchanged in the guinea pig and marmoset after ciprofibrate pre‐treatment, and cytochrome P‐450 4A1 was not detected immunochemically in liver microsomes from these latter species. In the untreated mouse, hamster, rat, and rabbit, the 12‐hydroxylation of lauric acid was more extensive than the 11‐hydroxylation, whereas in the guinea pig and marmoset the activity ratios were reversed, with 11‐hydroxylation predominating. Peroxisomal fatty acid β‐oxidation was markedly induced in the mouse, hamster, rat, and rabbit on treatment at the higher dose level (39‐, 3‐, 13‐ and 5‐fold, respectively) and was slightly increased in the marmoset (2‐fold), yet was unchanged in the guinea pig following treatment. In the marmoset the increase in peroxisomal β‐oxidation was 3‐ to 4‐fold at the high dose level; however, the dose levels used in the marmoset were 20 and 100 mg/kg as opposed to 2 and 20 mg/kg in the other species. The differences in the foregoing hepatic enzyme responses to ciprofibrate between the species examined in our studies indicate a specific pattern of enzyme changes in responsive species. In the responsive species (rat, mouse, hamster, and rabbit), cytochrome P‐450 4A1 specific content and related enzyme activity were increased concomitant with elevated peroxisomal β‐oxidation. By contrast, the marmoset and guinea pig lack the coordinate hepatic induction of peroxisomal and microsomal parameters and may be categorized as less responsive species. Accordingly, the rat hepatic responses to peroxisome proliferators cannot confidently be used to predict biological responses in primates, with obvious implications for the extrapolation of animal data to man.
Influence of single and concurrent clofibrate and phenobarbital administration on cytochrome P450‐dependent mixed function oxidase activities and peroxisome proliferation in male rat liver
Authors: Close Ian , Shackleton Gareth , Goldfarb Peter S. , Gibson G. Gordon , Sharma Raj , Howes Doug
Published: October 2006

The influence of both single and concurrent administration of phenobarbital and clofibrate on hepatomegaly, cytochrome P450‐depen‐dent mixed function oxidase activities, and peroxisome proliferation in male rat liver have been studied. Both xenobiotics separately increase the liver :body weight ratio and their combined administration results in greater hepatomegaly than either compound alone. Both compounds induce NADPH‐cytochrome c(P450) reductase activity and laurate ω‐ and ω‐1‐hydroxylase activities, but only phenobarbital induces pentoxyresorufin‐O‐de‐alkylase. None of the drug treatments induced microsomal cytochrome b5. Phenobarbital did not cause peroxisome proliferation and inhibited the corresponding clofibrate‐dependent proliferation. Taken collectively, our studies have demonstrated that concomitant treatment with phenobarbital and clofibrate are largely permissive with respect to the hepatic mixed function oxidase system but have opposing effects on the phenomenon of peroxisome proliferation in the same tissue.
Perfluorooctanoic acid has persistent effects on peroxisome proliferation and related parameters in mouse liver
Authors: Sohlenius Anna‐Karin , Lundgren Bo , DePierre Joseph W.
Published: October 2006

Male C57B1/6 mice were treated for 5 days with 0.05% perfluorooctanoic acid (PFOA) in their diet. This treatment resulted in a potent induction of peroxisomal fatty acid β‐oxidation in the liver. In order to investigate recovery from treatment with PFOA, mice were given normal laboratory chow for up to 20 days after termination of PFOA administration. It was established that the activities of peroxisomal lauoryl‐CoA oxidase and palmitoyl‐CoA oxidation were still elevated 2–3 weeks after termination of treatment. The catalase activity recovered in the cytosolic fraction was also still significantly elevated after 20 days with normal laboratory chow. Furthermore, the protein content of the mitochondrial fraction was increased by PFOA and had not returned to control level at the end of the recovery period. Perfluorooctanoic acid also caused a persistent effect in omega hydroxylation of lauric acid (cytochrome P‐452). The activities of cytosolic DT‐diaphoreses and glutathione transferase were also enhanced by PFOA. However, these two enzymes recovered relatively rapidly from the treatment (2–20 days). This study reveals two different patterns of recovery from PFOA treatment, one involving parameters that recovered completely, or almost completely, from PFOA treatment after 20 days and another involving parameters that were still elevated at the end of the recovery period.
Studies on the interaction of furan with hepatic cytochrome P‐450
Authors: Parmar Devendra , Burka Leo T.
Published: October 2006

In vitro incubation of rat liver micro‐somes with [14C]‐furan in the presence of NADPH resulted in the covalent incorporation of furan‐derived radioactivity in microsomal protein. Compared to microsomes from untreated rats a two‐ to threefold increase in binding was observed with microsomes from phenobarbital‐treated rats and a four‐ to five‐fold increase was observed with microsomes from rats pretreated with imidazole or pyrazole. Covalent binding was reduced with microsomes from rats pretreated with β‐naphthoflavone. Chemicals containing an amine group (semicarbazide), those in which the amine group is blocked but have a free thiol group (N‐acetylcysteine), and those which have both an amine and a thiol group (glutathione) effectively blocked binding of [14C]‐furan to microsomal protein. A decrease in cytochrome P‐450 (P‐450) content and decreases in the activities of P‐450‐dependent aniline hydroxylase, 7‐ethoxycoumarin‐O‐deethylase (BCD), and 7‐ethoxyresorufin‐O‐deethylase (ERD) was observed 24 hours after a single oral administration of 8 or 25 mg/kg of furan, suggesting that the reactive intermediate formed during P‐450 catalyzed metabolism could be binding with nucleophilic groups within the P‐450. In vitro studies indicated a significant decrease in the activity of aniline hydroxylase in pyrazole microsomes and BCD in phenobarbital microsomes without any significant change in the CO‐binding spectrum of P‐450 or in the total microsomal heme content, suggesting that furan inhibits the P‐450s induced by PB and pyrazole. An almost equal distribution of furan‐derived radioactivity in the heme and protein fractions of the CO‐binding particles after In vitro treatment of microsomes with furan suggests binding of furan metabolites with heme and apoprotein of P‐450, and, probably, due to this interaction, furan is acting as a suicide inhibitor of P‐450.