bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of strand breaks and interstrand cross‐links in DNA by methylglyoxal
Authors: Rahman Arshad , Shahabuddin  , Hadi S. M. 
Published: October 2006

AbstractMethylglyoxal (MG), a dietary mutagen, is present in various frequently consumed beverages and foods and in cigarette smoke. A combination of S1 nuclease hydrolysis and alkaline unwinding assay was used to demonstrate the formation of single‐strand breaks and interstrand cross‐links in DNA upon treatment with MG. Calf thymus DNA, when treated with increasing concentrations of MG, showed an increasing degree of S1 nuclease hydrolysis. It also showed the formation of an increasing number of strand breaks per molecule as determined by an alkaline unwinding assay. Incubation of DNA with relatively higher concentrations of methylglyoxal or prolonged treatment gave increased thermal melting temperatures and an enhanced rate of reannealing after thermal denaturation. These results indicated the formation of interstrand cross‐links. Upon treatment with MG, A‐T base pair depleted DNA showed a reduced number of single‐strand break formation. It also showed a significantly lower decrease in Tm as compared with MG‐treated normal DNA. These results showed that under the conditions used, MG primarily reacts with A‐T base pairs in duplex DNA.
Studies on the mechanism of haloacetonitrile‐induced gastrointestinal toxicity: Interaction of dibromoacetonitrile with glutathione and glutathione‐S‐transferase in rats
Authors: Ahmed Ahmed E. , Hussein Gamal I. , Loh Jiann‐Ping , Abdel‐Rahman Sherif Z. 
Published: October 2006

AbstractThe haloacetonitrile, dibromoacetonitrile (DBAN), is a direct‐acting genotoxic agent that has been detected in drinking water. In a time course study, male Sprague‐Dawley rats were treated with DBAN (75 mg/kg PO), and killed at 0.5, 1, 2, and 4 hr after treatment. In a dose response study, animals were treated orally with various doses of DBAN (25, 50, 75, and 100 mg/kg) and killed at one‐half hour after treatment. Control animals received 1 ml/kg PO of the vehicle dimethyl sulfoxide (DMSO). In both experiments blood and organs were collected and stored at −80°C until the time of analysis. At 0.5 hr after treatment, a single oral dose of DBAN caused a significant decrease of glutathione (GSH) concentrations in liver (54% of control) and stomach (6% of control). Hepatic GSH depletion was maximal at 0.5 hr and rebound to the control levels by 4 hr. In contrast, gastric GSH concentrations remained low at all time points. DBAN caused an insignificant change in both kidney and blood GSH levels. DBAN significantly inhibited glutathione‐S‐transferase (GST) activity in liver and stomach. Hepatic GST inhibition was maximal (34% of control) at 2 hr and minimal (80% of control) at 4 hr. Meanwhile, in the stomach GST activity was inhibited at 1 hr (60% of control) and remained low at all times after treatment. Both GSH depletion and GST inhibition were dose‐dependent. This study indicates that GSH and GST play an important role in the metabolism and detoxification of DBAN in rats. The prolonged depletion of GSH and inhibition of GST in the gastrointestinal (GI) tissues suggest that the GI tract is a major target for DBAN toxicity.
Drug‐metabolizing enzymes in liver, olfactory, and respiratory epithelium of cattle
Authors: Longo V. , Mazzaccaro A. , Naldi F. , Gervasi P. G. 
Published: October 2006

AbstractThe drug‐metabolizing enzymes of olfactory and respiratory epithelium of cattle were determined. The data of nasal tissues were compared to those of bovine liver. Both oxidative and nonoxidative enzyme activities were investigated. Many compounds including testosterone were used as substrates for the P450‐dependent monooxygenase activities. The results demonstrated that the P450 content and all the activities assayed including reduced nicotinamide adenine dinucleotide phosphate (NADPH)‐cytochrome P450 reductase were much higher in the olfactory than in the respiratory mucosa and for some activities (hexamethyl‐phosphoramide and dimethylnitrosamine N‐demethylase, aniline hydroxylase, and ethoxycoumarin O‐deethylase) the values in the olfactory tissue were even markedly higher than those of liver. Also the activities of some nonoxidative enzymes such as glutathione S‐transferase, uridine 5′‐diphosphate (UDP)‐glucuronyl‐transferase, and epoxide hydrolase were higher in the olfactory than in the respiratory mucosa but lower than in liver. The results taken together suggest that the olfactory and respiratory epithelium of cattle, which contain in addition to a wide array of nonoxidative enzymes multiple forms of P450, can be useful and easily available tissues to study the biotrans‐formation processes of odorants.
Anatoxin‐A(S), a naturally occurring organophosphate, is an irreversible active site‐directed inhibitor of acetylcholinesterase (EC 3.1.1.7)
Authors: Hyde Edward G. , Carmichael Wayne W. 
Published: October 2006

AbstractAnatoxin‐a(s) is a guanidine methyl phosphate ester (unprotonated molecular ion equals 252 daltons) isolated from the freshwater cyanobac‐terium (blue‐green alga) Anabaena flos‐aquae strain NRC 525–17. Previous work has shown anatoxin‐a(s) to be a potent irreversible inhibitor of electric eel ace‐tylcholinesterase (EC 3.1.1.7, AChE). In the present study the interaction of anatoxin‐a(s) with AChE was investigated by protection studies and since similarities have been noted between anatoxin‐a(s) and the synthetic organophosphate anticholinesterases, the ability of reactivators to reactivate the inhibited enzyme was investigated. Treatments directed toward eliminating poisoning symptoms and in vivo protection from anatoxin‐a(s) poisonings were investigated using oxime reactivators and atropine or pretreatment with a carbamate and atropine. Anatoxin‐a(s) was shown to be an active site‐directed inhibitor of acetyl‐cholinesterase which is resistant to oxime reactivation due to the structure of its enzyme adduct. In vivo pretreatment with physostigmine and high concentrations of 2‐PAM were the only effective antagonists against a lethal dose of anatoxin‐a(s).
Expression of cytochrome P‐450lpr Is developmentally regulated and limited to house fly
Authors: Wheelock Geoffrey D. , Konno Yasuhiko , Scott Jeffrey G. 
Published: October 2006

AbstractExpression of house fly cytochrome P‐450lpr was examined using immunoblotting in male and female adult LPR house flies, mixed sex adult house flies at 12 different ages, larvae, and pupae. P‐450lpr was expressed in both male and female adult house flies. P‐450lpr was clearly present in all adult stages examined, was barely detectable in pupae, and could not be detected in larvae. Thus, cytochrome P‐450lpr is developmentally regulated and present in both sexes of house fly.Expression of cytochrome P‐450, immunologically homologous to house fly cytochrome P‐450lpr was examined in other species using immunoblot analysis. Eleven animal species were tested in the orders Diptera, Hymenoptera, Lepidoptera, Orthoptera, Acari, and Rodentia, using microsomes in some species from both induced and noninduced animals or insecticide‐resistant and susceptible strains. P‐450lpr appears to be restricted to house flies, as none of these species contained cytochrome P‐450 that reacted with antiserum to cytochrome P‐450lpr.
Renal excretion of perfluorooctanoic acid in male rats: Inhibitory effect of testosterone
Authors: Vanden Heuvel John P. , Davis John W. , Sommers Rebecca , Peterson Richard E. 
Published: October 2006

AbstractThere is a marked sex difference in the whole‐body elimination of perfluorooctanoic acid (PFOA) in rats, with females excreting the perfluorinated acid much more rapidly (half life [t1/2] < 1 day) than males (t1/2=15 days). Our objective was to determine if androgens or estrogens are involved in causing this sex difference in PFOA elimination. Castration of males greatly increased the elimination of [1‐14C]PFOA (9.4 μmiol/kg, i.p.) in urine, demonstrating that a factor produced by the testis was responsible for the slow elimination of PFOA in male rats. Castration plus 17β‐estradiol had no further effect on PFOA elimination whereas castration plus testosterone replacement at the physiologic level reduced PFOA elimination to the same level as rats with intact testes. Thus, in male rats, testosterone exerts an inhibitory effect on renal excretion of PFOA. In female rats, neither ovariectomy nor ovariectomy plus testosterone affected the PFOA urinary elimination, demonstrating that the inhibitory effect of testosterone on PFOA renal excretion is a male‐specific response. Probenecid decreased the high rate of PFOA renal excretion in castrated males but had no effect on male rats with intact testes. We conclude that testosterone is a key determinant of the sex difference in PFOA elimination in rats.
Evidence for the involvement of a distinct form of cytochrome p450 3a in the oxidation of digitoxin by rat liver microsomes
Authors: Eberhart Delmont , Fitzgerald Kathleen , Parkinson Andrew 
Published: October 2006

AbstractThe preceding paper (B. Gemzik, D. Greenway, C. Nevins, and A. Parkinson (1992). Regulation of two electrophoretically distinct proteins recognized by antibody against rat liver cytochrome P450 3A1. J. Biochem. Toxicol, 7 (43–52).) described the regulation of two rat liver microsomal proteins (50‐ and 51‐kDa) recognized by antibody against P450 3A1. It was also shown that changes in the levels of the 51‐kDa 3A protein were usually paralleled by changes in the rate of testosterone 2β‐, 6β‐, and 15β‐hydroxylation. The present study demonstrates that age‐ and sex‐dependent changes in the 50‐kDa protein were paralleled by changes in the rate of digitoxin oxidation to digitoxigenin bisdigitoxoside. Induction or suppression of the 50‐kDa protein by treatment of rats with various xenobiotics were also paralleled by changes in the rate of digitoxin oxidation. These results suggest that, contrary to previous assumptions, the conversion of digitoxin to digitoxigenin bisdigitoxoside and the conversion of testosterone to 2β‐, 6β‐ and 15β‐hydroxytestosterone are primarily catalyzed by different forms of P450 3A. Further evidence for this coclusion was obtained from studies in which the suicide inhibitor, chloramphenicol, was administered to mature female rats previously treated with pregnenolone‐16α‐carbonitrile (PCN), which induces both the 50‐kDa and the 51‐kDa protein. Treatment of mature female rats with PCN alone caused a marked increase (16‐ to 18‐fold) in the 6β‐hydroxylation of testosterone and the rate of digitoxin oxidation. Treatment of PCN‐induced rats with chloramphenicol caused a ∼70% decrease in liver microsomal testosterone 6β‐hydroxylation, but had no effect on the rate of conversion of digitoxin to digitoxigenin bisdigitoxoside. The oxidation of testosterone by purified 3A1 (a 51‐kDa protein) was also inhibited by chloramphenicol in a time‐ and reduced nicotinamite adenine dinucleotide phosphate (NADPH)‐dependent manner. In addition to testosterone and chloramphenicol, purified 3A1 also metabolized trole‐andomycin, but it was unable to convert digitoxin to digitoxigenin bisdigitoxoside. Testosterone inhibited the microsomal oxidation of digitoxin, but digitoxin did not inhibit testosterone oxidation. This suggests that testosterone is a substrate for the 3A enzyme that metabolizes digitoxin, but that this form of P450 3A does not contribute significantly to testosterone oxidation by rat liver microsomes. We propose that the 2SbT‐, 6β‐, and 15β‐hydroxylation of testosterone by rat liver microsomes is primarily catalyzed by the 51‐kDa 3A proteins (either 3A1 or 3A2 depending on the source of microsomes), whereas digitoxin oxidation is primarily catalyzed by the 50‐kDa protein.
Species differences in membrane susceptibility to lipid peroxidation
Authors: Singh Yasmin , Hall Gregory L. , Miller Marion G. 
Published: October 2006

AbstractThe susceptibility of liver microsomes to lipid peroxidation was evaluated in seven species: rat, rabbit, trout, mouse, pig, cow, and horse. Lipid peroxidation was measured as thiobarbituric acid reactive substances formed in the presence of either FeCl3‐ADP/ascorbate or FeCl2/H2O2 initiating systems. For rat, rabbit, and trout microsomes, the order of susceptibility to peroxidation was rat > rabbit >> trout. The lack of peroxidation in trout microsomes could be explained by high microsomal vitamin E levels. Membrane fatty acid levels differed between species. Docosahexaenoic acid predominated in the trout, arachidonic acid in the rat, and linoleic acid in the rabbit. The contribution of individual fatty acids to lipid peroxidation reflected the degree of unsaturation with docosahexaenoic > arachidonic >>> linoleic. For all species except trout, the predicted susceptibility to peroxidation, based on the response of individual fatty acids, agreed well with directly measured microsomal peroxidation. With the exception of the trout, vitamin E content ranged from 0.083–0.311 nmol/mg microsomal protein between species, and low levels did not influence susceptibility to peroxidation. Trout microsomes peroxidized only after vitamin E depletion by prolonged incubation. The data indicate that below a vitamin E threshold, species differences in membrane susceptibility to peroxidation can be reasonably predicted based only on content of individual peroxidizable fatty acids.
Modulation of aortic protein phosphorylation by benzo(a)pyrene: Implications in PAH‐induced atherogenesis
Authors: Ou Xiaolan , Ramos Kenneth S. 
Published: October 2006

AbstractThe toxicity of polycyclic aromatic hydrocarbons such as benzo(a)pyrene, 7,12‐dimethylbenz(a)anthracene, and 3‐methylcholanthrene has been associated with alterations in the proliferation of vascular smooth muscle cells and the development of lesions of mesenchymal origin. Because phosphorylation of endogenous substrates plays a central role in the regulation of smooth muscle cell growth, the present studies were conducted to evaluate the phosphorylation pattern of medial aortic protein upon repeated in vivo exposure of Japanese quail to benzo(a)pyrene (BaP). Medial aortic homogenates from quail treated for 10 weeks with 10 mg/kg benzo(a)pyrene or vehicle were processed for in vitro measurements of protein phosphorylation. In vitro phosphorylation of endogenous or exogenous proteins stimulated in vitro by phorbol myristate acetate/phosphatidyl‐serine or cyclic AMP, known activators of protein kinase C and cyclic AMP‐dependent protein kinase, respectively, was examined in the cytosolic and particulate fractions of homogenates from control and treated animals. Benzo(a)pyrene treatment significantly enhanced the basal phosphorylation of Mr 113, 35, and 23 kDa proteins in the cytosolic fraction. Modest increases in the phosphorylation of Mr 71, 52, and 38 kDa were also observed under basal conditions. No changes in the basal phosphorylation of particulate proteins were observed. Phosphorylation of endogenous protein substrates by protein kinase C in the cytosolic fraction was not altered by benzo(a)pyrene treatment. In contrast, inhibition of C‐kinase‐mediated phosphorylation of endogenous Mr 272, 72, and 45 kDa proteins was observed in the particulate fraction of aortic homogenates from benzo(a)pyrene‐treated quail relative to controls. Exogenous histone phosphorylation by PKC in the particulate, but not cytosolic fraction, was decreased by benzo(a)pyrene treatment. The effects of benzo(a)pyrene on the C‐kinase system were specific, since cAMP‐mediated phosphorylation of endogenous proteins, as well as exogenous histone, was not altered by benzo(a)pyrene. Interestingly, benzo(a)pyrene treatment was associated with a selective increase of Mr 200, 80, and 67 kDa proteins in the cytosolic fraction. Collectively, these data are consistent with the hypothesis that medial protein phosphorylation is a significant molecular target of benzo(a)pyrene within the vascular wall.
Pharmacokinetics of propetamphos following intravenous administration in the F344 rat
Authors: Dix Kelly , Burka Leo T. , Dauterman Walter C. 
Published: October 2006

AbstractPropetamphos [(E)‐l‐methylethyl 3[[(ethylamino)methoxyphosphinothioyl]oxy]‐2‐bu‐tenoate], the active ingredient in Safrotin,® is an organophosphate developed by Sandoz, Ltd.® (Switzerland) as an insecticide (1). Although metabolism of propetamphos has been previously investigated (2,3), there is no pharmacokinetic data available in the literature. The current studies were undertaken to investigate the pharmacokinetics of propetamphos following intravenous administration in male and female Fischer 344 (F344) rats. Rats were dosed via an indwelling jugular cannula at a dose of 12 mg/kg (one‐tenth the oral LD‐50). Blood samples were withdrawn via the cannula at predetermined timepoints to quantitate plasma concentrations of propetamphos over time. Propetamphos is highly bound to plasma proteins (free fraction = 0.06). Free propetamphos concentration in plasma vs. time data were analyzed by noncompartmental methods. The terminal elimination rate constant, λ, was significantly different for males versus females (0.015 min−1 for males and 0.037 min−1 for females, p = 0.001). Plasma was cleared of unbound propetamphos at rates of 0.559 ± 0.069 and 0.828 ± 0.181 L/min/kg for males and females (mean ± standard error). Mean residence times (MRTs) for propetamphos in the body for males and females were 28.3 ± 5.7 and 14.4 ± 3.5 min, and the volume of distribution at steady state (Vss) was 14.7 ± 2.6 and 12.3 ± 4.5 L/kg. The differences in these parameters, clearance (CI), MRT, and Vss, were not statistically significant at the p < 0.05 level for males versus females, but MRT was nearly significantly different (p = 0.08). Because of the rapid elimination of propetamphos from plasma following intravenous administration, it is unlikely that propetamphos would bioaccumulate in environmentally exposed animals. Although the pharmacokinetic parameters were not statistically different for males and females in these studies, there was a clear clinical difference in their susceptibility to propetamphos toxicity. Female rats presented with overt signs of organophosphate intoxication, whereas males were only slightly effected. The observed gender‐related clinical difference in susceptibility to toxicity suggests that there may be a difference in the extent of elimination due to activation versus detoxication of propetamphos in males and females. Another possible explanation for the clinical difference in propetamphos toxicity is that inhibition of acetyl‐cholinesterase by the activated, oxygenated form of propetamphos (propetamphos oxon) may be greater in females than in males.
Potentiation of carbon tetrachloride‐induced hepatotoxicity and pneumotoxicity by pyridine
Authors: Day Brian J. , Carlson Gary P. , Denicola Dennis B. 
Published: October 2006

AbstractInduction of P450HE1 by pyridine was compared with that by ethanol, and the resulting potentiation of the pneumotoxicity and hepato‐toxicity following carbon tetrachloride inhalation by pyridine was examined. Rats were treated with ethanol as either a 10% solution in the drinking water or as a daily bolus (3 ml/kg, ip) dose for 7 days or one bolus dose of pyridine (200 mg/kg, ip) and compared for P450IIE1 apoprotein content by immunoblot analysis. Ethanol in the drinking water and pyridine elevated both hepatic and pulmonary P450IIE1 apoprotein content, but bolus dose ethanol did not. The induction was greatest in the pyridine group. In the interaction study, rats were treated with pyridine (200 mg/kg, ip) and 12 hours later were exposed to CC14 (8000 ppm for 3 hours). Pulmonary injury and hepatic damage were assessed 24 hours later by bronchoalveolar lavage fluid (BALF) analysis [γ‐glutamyl transpeptidase (GGT), lactate dehydrogenase (LDH), and total protein] and serum sorbitol dehydrogenase (SDH) activity, respectively. Pyridine alone had no effect on BALF or SDH but enhanced GGT and LDH release into the BALF and SDH release into the serum when compared with CC14 exposure alone. Evaluation of the liver at the light microscopic level revealed characteristic CCl4‐induced centrilobular necrosis which was potentiated by pyridine. No changes were observed in the lung by light microscopic evaluation. Pyridine induced pulmonary and hepatic microsomal apoprotein levels of cytochrome P450IIE1 two‐ and 2‐ to sixfold, respectively. Exposure to CC14 decreased hepatic but not pulmonary P450IIE1 levels. Induction of cytochrome P450IIE1 by pyridine increases the bioactivation of CC14 in both the liver and lung, leading to enhanced toxicity.
Differential cellular effects in the toxicity of haloalkene and haloalkane cysteine conjugates to rabbit renal proximal tubules
Authors: Groves Carlotta E. , Schnellmann Rick G. , Hayden Patrick J. , Lock Edward A. 
Published: October 2006

AbstractThe relationship between the covalent binding, uptake, and toxicity produced by S‐(1,2‐dichlorovinyl)‐L‐cysteine (DCVC) and S‐(1,1,2,2‐tetrafluoroethyl)‐L‐cysteine (TFEC) was investigated in suspensions of rabbit renal proximal tubules (RPT). The DCVC and TFEC at concentrations of 25 μM produced a time‐dependent (1–6 hours) loss of RPT viability. The TFEC was bio‐transformed rapidly by β‐lyase to a reactive metabolite which bound covalently to tubular protein. Approximately 63% of the TFEC‐equivalents inside the cell were bound to protein. Covalent binding of TFEC‐equivalents was associated with a 30% decrease in tubular basal and state 3 respiration, a sevenfold increase in lipid peroxidation, and, ultimately, cell death. The DCVC was biotransformed rapidly to a reactive metabolite which bound covalently to tubular protein. Approximately 90% of the DCVC‐equivalents inside the cell were bound covalently to tubular protein. Following exposure to 25 μM DCVC, the binding of DCVC‐equivalents was associated with a 17‐fold increase in lipid peroxidation but, in contrast to TFEC, had no effect on tubular respiration. However, exposure of RPT to 100 μM DCVC resulted in a ninefold increase in the binding of DCVC‐ equivalents and a 30% decrease in tubular state 3 respiration. The β‐lyase inhibitor aminooxyacetic acid (AOAA) blocked the covalent binding, mitochondrial dysfunction, lipid peroxidation, and cell death produced by TFEC. The AOAA decreased the covalent binding and the lipid peroxidation produced by DCVC by approximately 60–70% but had no effect on cell death. These results suggest that mitochondria! bioactivation of TFEC by β‐lyase is critical for TFEC‐induced mitochondrial dysfunction and the resulting cell death. These results also suggest that cytosolic bioactivation and binding, but not mitochondrial bioactivation and dysfunction, are important in the toxicity produced by DCVC to rabbit RPT. The lack of protection against DCVC toxicity by AOAA may be related to incomplete inhibition of DCVC metabolism or bioactivation of DCVC by pathways other than β‐lyase.
The effect of mainstream and sidestream cigarette smoke exposure on oxygen defense mechanisms of guinea pig erythrocytes
Authors: Mukherjee Shyamali , Woods Letha , Weston Zada , Williams Arthur B. , Das Salil K. 
Published: October 2006

AbstractWe have studied the effects of short‐term exposure of guinea pigs to cigarette smoke under both mainstream (MS) and sidestream (SS) conditions on the activities of major antioxidant enzymes and lipid peroxidation potential of erythrocytes. The smoke‐exposed groups had an increase in the activity of superoxide dismutase (SOD), a decrease in the activities of glutathione peroxidase (GSH‐Px) and NADPH generating enzymes, and no change in the activity of catalase. Furthermore, there was a significant increase in the in vitro lipid peroxidation potential of erythrocytes in both MS‐ and SS‐exposed groups. However, the lipid peroxidation potential was higher in the MS‐exposed group than that in the SS‐exposed group.