bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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

The 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

Anatoxin‐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

Expression 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

There 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

The 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

The 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

The 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

Propetamphos [(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

Induction 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

The 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

We 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.
Toxic effects of fatty acid anilides on the oxygen defense systems of guinea pig lungs and erythrocytes
Authors: Mukherjee Shyamali , Ghos Sukla , Rodgers Lisa , Nayyar Tultul , Desai Usha , Das Salil K.
Published: October 2006

Toxic oil syndrome (TOS) is caused by ingestion of denatured edible oils. Even though the etiology and pathogenesis of this disease are not fully known, it is quite clear that generation of free radicals caused by ingestion of fatty acid anilides is responsible for the pathogenetic mechanism in many TOS patients. Fatty acid anilides may also alter the free radical status of lungs and erythrocytes; this possibility may shed some light on understanding toxic oil syndrome. The present study describes the effects of oral administration of fatty acid anilides on the activities of major enzymes involved in the oxygen defense systems of lungs and erythrocytes. Feeding fatty acid anilides caused an increase in the superoxide dismutase (SOD) activity in erythrocytes, whereas it caused a decrease in the SOD activity in lungs. GSH‐Px activity was not significantly changed in erythrocytes but was decreased in lungs. Although the activity of catalase was increased only by a higher dose in the erythrocytes, it was not affected in the lung at any dosage. Even though the ingestion of fatty acid anilides caused an increase in the SOD activity in the erythrocytes and a decrease in the SOD activity in the lungs, there was an increase in the lipid peroxidation in both cases. The increase in lipid peroxidation in erythrocytes is probably caused by the accumulation of H2O2, and that in the lungs is due to the accumulation of superoxide anion.
Aluminum alters calcium transport in plasma membrane and endoplasmic reticulum from rat brain
Authors: Mundy William R. , Kodavanti Prasada Rao S. , Dulchinos Victoria F. , Tilson Hugh A.
Published: October 2006

Calcium is actively transported into intracellular organelles and out of the cytoplasm by Ca2+/Mg2+‐ATPases located in the endoplasmic reticulum and plasma membranes. We studied the effects of aluminum on calcium transport in the adult rat brain. We examined 45Ca‐uptake in microsomes and Ca2+‐ATPase activity in microsomes and synaptosomes isolated from the frontal cortex and cerebellum of adult male Long‐Evans rats. ATP‐dependent45Ca‐uptake was similar in microsomes from both brain regions. The addition of 50‐800 μM AICI3 resulted in a concentration‐dependent inhibition of 45Ca‐uptake. Mg2+‐dependent Ca2+‐ATPase activity was significantly lower in synaptosomes compared to microsomes in both frontal cortex and cerebellum. In contrast to the uptake studies, AICI3 stimulated Mg2+‐dependent Ca2+‐ATPase activity in both microsomes and synaptosomes from both brain regions. To determine the relationship between aluminum and Mg2+, we measured ATPase activity in the presence of increasing concentrations of Mg2+ or AICI3. Maximal ATPase activity was obtained between 3 and 6 mM Mg2+. When we substituted AICI3 for Mg2+, ATPase activity was also stimulated in a concentration‐dependent manner, but to a greater extent than with Mg2+. One interpretation of these data is that aluminum acts at multiple sites to displace both Mg2+ and Ca2+, increasing the activity of the Ca2+‐ATPase, but disrupting transport of calcium.
Molecular interaction of [2,3‐14C] acrylonitrile with DNA in gastric tissue of rat
Authors: Abdel‐Rahman Sherif Z. , Nouraldeen Amr M. , Ahmed Ahmed E.
Published: October 2006

Acrylonitrile (VCN) is used extensively in polymer industries, and is known to induce gastric cancer following oral administration, A paucity of information exists regarding the mechanism(s) by which acrylonitrile induces gastric neoplasia. The time course for uptake of radioactivity by gastric tissue and covalent binding of [2,3‐14C] VCN or its metabolites to gastric DNA were determined following a single oral dose of 46.5 mg/kg. The rates of DNA synthesis and repair, as measured by unscheduled DNA synthesis in the gastric tissue of VCN‐treated rats, were also studied. Maximum tissue uptake and covalent binding of radioactivity to gastric DNA were observed at 15 minutes following [2,3‐14C] VCN administration. At 6 hours following VCN administration, significant inhibition (37% of control) in gastric replicative DNA synthesis was observed. A rebound followed by an increase (211% of control) in replicative DNA synthesis was observed at 24 hours. A three‐fold elevation in unscheduled DNA synthesis was observed at 24 hours following treatment with VCN. These results indicate that VCN or its metabolites irreversibly interact with gastric DNA, causing DNA damage. The results also indicate that the delayed VCN‐induced DNA repair, determined as unscheduled DNA synthesis, is inefficient for the removal of the resulting DNA lesions.
Cyanide induces protein kinase C translocation: Blockade by NMDA antagonists
Authors: Rathinavelu A. , Sun P. , Pavlakovic G. , Borowitz J. L. , Isom G. E.
Published: October 2006

Activation and translocation of protein kinase C (PKC) during KCN‐induced histotoxic hypoxia was studied in rat brain slices prepared from cerebellum, hippocampus, and cortex. Treatment with 1–10 mM KCN produced a significant increase in PKC translocation and enzyme activity in the particulate fraction of cerebellar and hippocampal slices. In cortical slices, PKC activity was not affected by cyanide treatment. The membrane‐associated PKC activity reached a maximum 30 minutes after incubation with KCN and remained elevated up to 60 minutes in both the hippocampus and cerebellum. Pretreatment with MK‐801 and APV, specific NMDA receptor antagonists, blocked the cyanide‐stimulated translocation in the hippocampus and cerebellum, whereas CNQX, an AMPA/kainate receptor antagonist, did not alter the response. These results demonstrate that cyanide stimulates PKC activation and translocation from the cytosol to membranes in select brain areas and NMDA receptor activation mediates this process.
Differential modulation of hepatic cytochrome P‐450 enzymes in rat and syrian hamster by 4′‐trifluoromethyl‐2,3,4,5‐tetrachlorobiphenyl
Authors: Bani Marie‐Hélène , Narbonne Jean‐Franco̧is , Fukuhara Morio , Ushio Fusao , Robertson Larry W.
Published: October 2006

The effects of a single injection (40 mg/kg) of 4′‐trifluoromethyl‐2,3,4,5‐tetrachlorobiphenyl (CF3) on hepatic cytochrome P‐450 monooxygenases were assessed in rat and syrian hamster. The CF3 treatment significantly increased the total amount of cytochrome P‐450 in both species. In rats, CF3 treatment caused marked increases in ethoxyresorufin O‐deethylase (EROD), arylhydrocarbon hydroxylase (AHH), and testosterone 7α‐hydroxylase activities but significantly reduced the activities of benzphetamine N‐demethylase (BzND), erythromycin N‐demethylase (ErND), testosterone 6β, 16α, and 16β‐hydroxylases, and formation of androstenedione. Administration of CF3 to hamsters strongly induced the activities of EROD, AHH, BzND, testosterone 15α, and 16α‐hydroxylases, and androstenedione production, whereas ErND, testosterone 6β, and 7α‐hydroxylases were decreased. Administration of CF3 to rats induced the CYP1A family proteins and CYP2A1, while CF3 reduced the level of CYP2B1, and, to a lesser extent, of CYP6β2. In hamsters, CF3 treatment significantly induced the CYP1A2, CYP2A1, CYP2A8, and CYP2B1 isozymes, whereas the CYP6β2 level was decreased. The ability of hepatic microsomes to activate aflatoxin B1 and benzo(a)pyrene was elevated by CF3 treatment in hamsters, while activation of aflatoxin B1 was decreased in microsomes from CF3‐treated rats. These results showed differences in the CF3‐induced pattern of rat and hamster cytochrome P‐450 monooxygenases.
Evidence for two functionally distinct forms of the human Ah receptor
Authors: Perdew Gary H. , Hollenback Clayton E.
Published: October 2006

The Ah receptor (AhR) was visualized using monoclonal antibody Rpt 1 on protein blots of HeLa cell cytosol; two bands were detected at 104 and 106 kDa. The photoaffinity ligand, 2‐azido‐3‐[125I]iodo‐7,8‐dibromodibenzo‐p‐dioxin, was added to HeLa cells in culture, and after 1 hour the cells were UV irradiated. Cytosolic and high salt nuclear preparations were isolated and subjected to sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS‐PAGE), followed by transfer of the protein to membrane. The AhR was visualized on the membrane, revealing two bands. Alignment of an autoradiogram with the membrane revealed that only the 106 kDa (upper) band was photoaffinity labeled. The nuclear fraction contained only the photoaffinity‐labeled 106 kDa form of the AhR. The 104 kDa AhR does not appear to be a proteolytic product of the 106 kDa form. Cyanogen bromide fragmentation revealed that both forms contain the same size N‐terminal fragment. Sucrose density gradient analysis of HeLa cell cytosol indicated that both forms cosedimented at 9 S. Both the 106 and 104 kDa AhR bands were detected in four different human cell lines. Together, these results would indicate that the AhR in human cell lines exists in two distinct forms.
Lipoxygenase‐mediated glutathione oxidation and superoxide generation
Authors: Roy Partha , Sajan Mini P. , Kulkarni Arun P.
Published: October 2006

Soybean lipoxygenase‐mediated cooxidation of reduced glutathione (GSH) and concomitant superoxide generation was examined. The oxidation of GSH was dependent on the concentration of linoleic acid (LA), GSH, and the enzyme. The optimal conditions to observe maximal enzyme velocity included the presence of 0.42 mM LA, 2 mM GSH, and 50 pmole of enzyme/mL. The GSH oxidation was linear up to 10 minutes and exhibited a pH optimum of 9.0. The reaction displayed a Km of 1.49 mM for GSH and Vmax of 1.35 ± 0.02 μmoles/min/nmole of enzyme. Besides LA, arachidonic and γ‐linolenic acids also supported the lipoxygenase‐mediated GSH oxidation. Hydrogen peroxide and 13‐hydroperoxylinoleic acid supported GSH cooxidation, but to a very limited extent. Oxidized glutathione (GSSG) was identified as the major product of the reaction based on the depletion of nicotinamide‐adenine dinucleotide 3′‐phosphate (NADPH) in the presence of glutathione reductase. The GSH oxidation was accompanied by the reduction of ferricytochrome c, which can be completely abolished by superoxide dismutase (SOD), suggesting the generation of superoxide anion radicals. Under optimal conditions, the rate of superoxide generation (measured as the SOD‐inhibitable reduction of ferricytochrome c) was 10 ± 1.0 nmole/min/nmole of enzyme. These results clearly suggest that lipoxygenase is capable of oxidizing GSH to GSSG and simultaneously generating superoxide anion radicals, which may contribute to oxidative stress in cells under certain conditions.
Inhibition of lecithin:Cholesterol acyltransferase activity in human blood plasma by cigarette smoke extract and reactive aldehydes
Authors: Chen Chen , Loo George
Published: October 2006

Cigarette smoking is a risk factor for atherosclerosis. It is conceivable that reactive chemical components in cigarette smoke may adversely affect reverse cholesterol transport at the level of lecithin:cholesterol acyltransferase (LCAT) and promote atherogenesis. Hence, the effect of cigarette smoke extract (CSE) on the activity of LCAT in human plasma was studied. When incubated with plasma, CSE caused both concentration‐ and time‐dependent losses of LCAT activity. Addition of glutathione, but not ascorbate, to plasma prevented loss of LCAT activity caused by CSE. Incubation of plasma with some reactive aldehydes known to be present in cigarette smoke also inhibited LCAT activity. Among five aldehydes tested, acrolein was the strongest inhibitor of LCAT, with complete enzyme inhibition occurring at 1 mM. Acetaldehyde was the weakest inhibitor of LCAT, with 85% enzyme inhibition at 50 mM. Hexanal, formaldehyde, and malondialdehyde completely inhibited LCAT activity at 10, 50, and 50 mM, respectively. When plasma was incubated with 1 mM acrolein in the presence of 2.5 mM glutathione or dihydrolipoic acid, 100 and 57% of LCAT activity, respectively, remained after incubation. This finding suggests that reactive aldehydes may form adducts with certain free sulfhydryl groups functioning in the active site of LCAT to inhibit enzyme activity. It is concluded that reactive aldehydes are at least partially responsible for the reduction in LCAT activity in plasma treated with CSE.
Stereoselective sulfoxidation of the pesticide methiocarb by flavin‐containing monooxygenase and cytochrome P450‐dependent monooxygenases of rat liver microsomes. Anticholinesterase activity of the two sulfoxide enantiomers
Authors: Buronfosse T. , Moroni P. , Benoǐt E. , Rivière J. L.
Published: October 2006

Evidence based on thermal lability and enzyme inhibition data suggests that the sulfoxidation of methiocarb (an N‐methylcarbamate insecticide) by rat liver microsomes is catalyzed by flavin‐containing monooxygenase(s) (FMO) and by cytochrome(s) P450 (P450). In control rats, the relative proportion is ca. 50% P450:50% FMO. Stereoselective formation of methiocarb sulfoxide from the corresponding sulfide has also been examined to compare the enantioselectivity of the two different enzyme systems. Only the FMO‐dependent sulfoxidation presents a high stereoselectivity with an enantiomeric excess of 88% in favor of the (A)‐enantiomer. Pretreatment of rats with different P450 inducers such as phenobarbital, 3‐methylcholanthrene, dexamethasone, and pyrazole did not affect, or decreased, the rate of methiocarb sulfoxidation. Stereoselectivity of the reaction was modified, mainly because of changes in the relative involvement of FMO and P450 in sulfoxidase activity in pretreated animals. The acetylcholinesterase inhibition properties of methiocarb and its main metabolites were also investigated. Racemic methiocarb sulfoxide was slightly less inhibitory (Ki = 0.216 μM−1· min−1) than methiocarb, but a 10‐fold difference was observed between the bimolecular rate constants found for the two sulfoxides produced (0.054 and 0.502 μM−1·min−1 for the (A) and (B) enantiomers, respectively). © 1995 John Wiley & Sons, Inc.
Exposure to polychlorinated biphenyls causes endothelial cell dysfunction
Authors: Toborek Michal , Barger Steven W. , Mattson Mark P. , Espandiari Parvaneh , Robertson Larry W. , Hennig Bernhard
Published: October 2006

Environmental chemicals, such as polychlorinated biphenyls (PCBs), may be atherogenic by disrupting normal functions of the vascular endothelium. To investigate this hypothesis, porcine pulmonary artery‐derived endothelial cells were exposed to 3,3′,4,4′‐tetrachlorobiphenyl (PCB 77), 2,3,4,4′,5‐pentachlorobiphenyl (PCB 114), or 2,2′,4,4′,5,5′‐hexachlorobiphenyl (PCB 153) for up to 24 hours. These PCBs were selected for their varying binding avidities with the aryl hydrocarbon (Ah) receptor and differences in their induction of cytochrome P450. PCB 77 and PCB 114 significantly disrupted, in a dose‐dependent manner, endothelial barrier function by allowing an increase in albumin transfer across endothelial monolayers. These PCBs also contributed markedly to cellular oxidative stress, as measured by 2,7‐dichlorofluorescin (DCF) fluorescence and lipid hydroperoxides, and caused a significant increase in intracellular calcium ([Ca2+]i) levels. Enhanced oxidative stress and [Ca2+]i in PCB 77‐ and PCB 114‐treated cells were accompanied by increased activity and content of cytochrome P450 1A and by a decrease in the vitamin E content in the culture medium. In contrast to the effects of PCB 77 and PCB 114, cell exposure to PCB 153 had no effect on cellular oxidation, [Ca2+]i, or endothelial barrier function. These results suggest that certain PCBs may play a role in the development of atherosclerosis by causing endothelial cell dysfunction and a decrease in the barrier function of the vascular endothelium. It is possible that interaction of PCBs with the Ah receptor and activation of the cytochrome P450 1A subfamily are involved in this pathology. © 1995 John Wiley & Sons, Inc.
DNA single‐strand breakage in mammalian cells induced by redox cycling quinones in the absence of oxidative stress
Authors: Morgan Winston A.
Published: October 2006

Quinone‐induced cell death is often attributed to oxidative stress during which the formation of DNA strand breaks is thought to play an important role. In this study, extensive DNA damage was observed in human chronic myelogenous leukemic cells (K562) exposed for 15 minutes to low concentrations (15–100 μM) of the redox cycling quinones 2,3‐dimethoxy‐1,4‐naphthoquinone (2,3‐diOMe‐1,4‐NQ) and menadione. However, DNA strand breakage and cell death could not be attributed to oxidative stress as the intracellular level and redox status of the reducing equivalents NADP(H) and GSH were unaffected. The intracellular level of NAD+ was found to correlate well with the extent of DNA repair (r = 0.93, P < 0.02) and cell proliferation (r = 0.96, P < 0.01) in cells exposed to the quinones. In contrast, a significant decrease in the level of intracellular ATP was only observed in cells exposed to menadione (50–100 μM). These results suggest that redox cycling quinones are capable of inducing DNA damage in mammalian cells by a mechanism that does not involve oxidative stress. Following DNA damage, cell death is dependent on the availability of NAD+, which may be key to the rapid repair of strand breaks. © 1995 John Wiley & Sons, Inc.
Specificity studies of 3‐mercaptopyruvate sulfurtransferase
Authors: Porter Dale W. , Baskin Steven I.
Published: October 2006

3‐Mercaptopyruvate sulfurtransferase (E.C. 2.8.1.2; MST) is an enzyme believed to function in the endogenous cyanide (CN) detoxification system because it is capable of transferring sulfur from 3‐mercaptopyruvate (3‐MP) to CN, forming the less toxic thiocyanate (SCN). To date, 3‐MP is the only known sulfur‐donor substrate for MST. In an effort to increase the understanding of what chemical properties of 3‐MP affect its utilization as a substrate, in vitro enzyme kinetic studies of MST were conducted using two mercaptic acids that are structurally related to 3‐MP. Neither of these compounds was able to serve as a sulfur‐donor substrate for MST. Inhibitor studies determined that 3‐mercaptopropionic acid did not affect the Km of MST for 3‐MP but did decrease Vmax and, thus, was determined to be a noncompetitive inhibitor. Alternatively, 2‐mercaptopropionic acid 2‐MPA decreased Km and Vmax and was determined to be an uncompetitive inhibitor of MST with respect to 3‐MP. These data indicate that the α‐keto group of 3‐MP is necessary for its utilization as a substrate, and the inhibitor studies suggest that the position of the sulfur may also affect the binding of these compounds to the enzyme. These observations increase the understanding of what factors can affect the utilization of a compound as a sulfur‐donor substrate for MST and may aid in the development of alternative sulfur‐donor substrates for MST. © 1996 John Wiley & Sons, Inc.
The effect of nitrogen dioxide exposure on the release of surfactant isolated from neonatal rabbit type II pneumocytes in culture
Authors: Knight Matthew , Sekharam Madhavi , Patel Jay
Published: October 2006

Nitrogen dioxide (NO2) is a well‐known environmental air toxin, produced from a variety of sources, including cigarette smoke. Because of the growing knowledge of the harmful effects of passive smoking on children, we decided to study the effect of NO2 exposure on the release of surfactant from isolated neonatal type II pulmonary epithelial cells. After isolation from 1 to 4 day old rabbits, type II epithelial cells were allowed to adhere for 18 hours, washed, media changed, and were exposed to either 5% CO2 in room air or NO2, 5 ppm, for 2 hours (all results mean ± sd; comparisons, paired t‐test). There was no difference in cell number or viability prior to exposure. Cells exposed to NO2 had an increase in LDH release [LDH activity in media/(LDH in media + cells) x 100], air 12.6 ± 2.2%, NO2 21.7 ± 3.7%, (p < 0.05). NO2‐exposed cells also had an increase in total phospholipid (μg/cell culture dish) in media compared to air exposed, air 170.13 ± 7.54, NO2 195.15 ± 11.2, (p < 0.05). 3H‐choline incorporation as a precursor to disaturated phosphati‐dylcholine (DSPC) was also conducted during exposure to either air or NO2. Incorporation of 3H‐choline into surfactant lipid was increased in media from cells after NO2 exposure compared to air, 58.23 ± 15.16 air, 76.81 ± 19.86 NO2 (cpm/μg protein; p < 0.05). These results show that 2 hours of 5 ppm NO2 exposure is associated with an increase in release of surfactant from neonatal type II cells in culture. © 1996 John Wiley & Sons, Inc.
Head morphology in perinatal dolphins: A window into phylogeny and ontogeny
Authors: Rauschmann Michael A. , Huggenberger Stefan , Kossatz, Lars S. , Oelschläger Helmut H.A.
Published: October 2006

In this paper on the ontogenesis and evolutionary biology of odontocete cetaceans (toothed whales), we investigate the head morphology of three perinatal pantropical spotted dolphins (Stenella attenuata) with the following methods: computer‐assisted tomography, magnetic resonance imaging, conventional X‐ray imaging, cryo‐sectioning as well as gross dissection. Comparison of these anatomical methods reveals that for a complete structural analysis, a combination of modern imaging techniques and conventional morphological methods is needed. In addition to the perinatal dolphins, we include series of microslides of fetal odontocetes (S. attenuata, common dolphin Delphinus delphis, narwhal Monodon monoceros). In contrast to other mammals, newborn cetaceans represent an extremely precocial state of development correlated to the fact that they have to swim and surface immediately after birth. Accordingly, the morphology of the perinatal dolphin head is very similar to that of the adult. Comparison with early fetal stages of dolphins shows that the ontogenetic change from the general mammalian bauplan to cetacean organization was characterized by profound morphological transformations of the relevant organ systems and roughly seems to parallel the phylogenetic transition from terrestrial ancestors to modern odontocetes. J. Morphol., 2006. © 2006 Wiley‐Liss, Inc.
Right‐handed penises of the earwig Labidura riparia (Insecta, Dermaptera, Labiduridae): Evolutionary relationships between structural and behavioral asymmetries
Authors: Kamimura Y.
Published: October 2006

The number of penises vary in the insect suborder Forficulina (order Dermaptera; earwigs). Males of the families Diplatyidae, Pigidicranidae, Anisolabididae, Apachyidae, and Labiduridae have two penises (right and left), while those of the Spongipohridae, Chelisochidae, and Forficulidae have a single penis. The proposed phylogenetic relationships among these families suggest that the single‐penis families evolved from an ancestor possessing two penises. To date, examinations of double‐penis earwig species have found that only a single penis is used per single copulation. These diversities in structural and behavioral aspects of genitalia raises the following intriguing questions: How are the two penises used? Why did a penis degenerate in several earwig families, and which one was lost? To address these questions, structural and behavioral asymmetries were examined in detail for a representative species Labidura riparia (Labiduridae). Although there was no detectable morphological differentiation between the right and left penises, male L. riparia predominantly used the right one for insemination. This significant “right‐handedness” developed without any experience of mating and was also manifested in the resting postures of the two penises when not engaged in copulation. However, surgical ablation of the right penis did not influence the insemination capacity of males. In wild‐caught males, only about 10% were left‐handed; within this group, abnormalities were frequently observed in the right penis. These lines of evidence indicate that the left penis is merely a spare intromittent organ, which most L. riparia males are likely never to use. Additional observations of five species of single‐penis families revealed that the left penis degenerated in the common ancestor of this group. Considering the proposed sister relationship between the Labiduridae and the single‐penis families, it is possible that such behavioral asymmetries in penis' use, as observed in L. riparia, are parental to the evolutionary degeneration of the infrequently used left penis. J. Morphol., 2006. © 2006 Wiley‐Liss, Inc.
Metabolomic fingerprinting of plant extracts
Authors: Mattoli L. , Cangi F. , Maidecchi A. , Ghiara C. , Ragazzi E. , Tubaro M. , Stella L. , Tisato F. , Traldi P.
Published: October 2006

The standardization and quality control of plant extracts is an important topic, in particular, when such extracts are used for medicinal purposes. Consequently, the development of fast and effective analytical methods for metabolomic fingerprinting of plant extracts is of high interest. In this investigation, electrospray mass spectrometry (ESI‐MS) and 1H NMR techniques were employed with further statistical analyses of the acquired data. The results showed that negative ion mode ESI‐MS is particularly effective for characterization of plant extracts. Different samples of the same species appear well‐clustered and separated from the other species. To verify the effectiveness of the method, two other batches of extracts from a species, in which the principal components were already identified (Cynara scolymus), were analyzed, and the components that were verified by the principal component analysis (PCA) were found to be within the region identified as characteristic of Cynara Scolymus extracts. The data from extracts of the other species were well separated from those pertaining to the species previously characterized. Only the case of a species that was strictly correlated from a botanical point of view, with extracts that were previously analyzed, showed overlapping. Copyright © 2006 John Wiley & Sons, Ltd.