bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential modulation of organophosphate‐sensitive muscarinic receptors in rat brain by parathion and chlorpyrifos
Authors: Chaudhuri J. , Chakraborti T. K. , Chanda S. , Pope C. N. 
Published: October 2006

AbstractWe previously reported similar levels of brain cholinesterase inhibition but marked differences in toxicity following acute maximum tolerated doses of the organophosphate pesticides parathion and chlorpyrifos. Because extensive acetylcholinesterase inhibition often induces compensatory changes in cholinergic receptor populations, we compared the effects of parathion and chlorpyrifos on brain muscarinic receptors. Adult male rats were treated with vehicle or the maximum tolerated dose of parathion (18 mg/kg, sc) or chlorpyrifos (279 mg/kg, sc) and observed for signs of acute toxicity. Similarly treated animals were sacrificed at 2, 7, or 14 days after treatment for measurement of cholinesterase activity and binding to the nonselective muscarinic antagonist [3H]quinuclidinyl benzilate, the M2‐preferential antagonist [3H]AFDX‐384, and the high‐affinity agonist [3H]cis‐methyldioxolane. More acute toxicity was noted after parathion treatment. Both insecticides caused similar levels (> 85%) of maximal cholinesterase inhibition and reductions (up to 55%) in atropine‐sensitive quinuclidinyl benzilate binding (i.e., total muscarinic receptors) and [3H]AFDX‐384 binding in cortex and striatum. Parathion also reduced, whereas chlorpyrifos increased, total muscarinic receptor binding and [3H]AFDX‐384 binding in the cerebellum. When tissues were preincubated with paraoxon (10 μM), radiolabeling of a subset of quinuclidinyl benzilate binding sites was blocked and the apparent densities of these organophosphate‐sensitive receptors in all three tissues were decreased (16% maximal) by parathion but increased (up to 37%) by chlorpyrifos. Similarly, parathion decreased whereas chlorpyrifos increased [3H]cis‐methyldioxolane binding sites in all three brain regions. We propose that differential modulation of these organophosphate‐sensitive muscarinic receptors contributes to differences in acute toxicity following exposure to these pesticides.
Dietary supplementation with taurine and niacin prevents the increase in lung collagen cross‐links in the multidose bleomycin hamster model of pulmonary fibrosis
Authors: Blaisdell Robert J. , Schiedt Mary J. , Giri Shri N. 
Published: October 2006

AbstractTaurine and niacin have been previously found to block the accumulation of collagen in lung in the multidose bleomycin hamster model of pulmonary fibrosis. Previous studies have found an increase in the pulmonary collagen cross‐links dihydroxylysinonoroleucine (DHLNL) and hydroxypyridinium (OHP) in the single dose bleomycin rat model. In this study, we asked if taurine and niacin would block the increase in DHLNL and OHP in the multidose bleomycin hamster model of lung fibrosis. Hamsters were intratracheally instilled with three consecutive doses of saline or bleomycin sulfate 1 week apart (2.5, 2.0,1.5 units/ 5 mL/kg). Animals were fed diet containing either 2.5% niacin and 2.5% taurine or control diet throughout the experiment. The four groups were saline‐instilled with control diet (SCD), bleomycin instilled with control diet (BCD), bleomycin‐instilled with taurine‐niacin in diet (BTN), and saline‐instilled with taurine‐niacin in diet (STN). Animals were sacrificed at 1, 4, and 8 weeks after the last bleomycin instillation. Hydroxyproline per lung in the BCD group was significantly elevated by 38, 56, and 60% over the SCD group at 1, 4, and 8 weeks, respectively. There were no statistically significant differences among the four groups in DHLNL (mmole) per mole collagen at the 1 or 8 week time point. At four weeks, DHLNL was significantly elevated by 46.4% in the BCD group over the SCD group. The OHP (mmole) per mole of collagen at 1 and 4 weeks in the BCD group was not statistically different from the SCD group. However, at 8 weeks, this was significantly elevated by 31.4% over the SCD group. The DHLNL and OHP contents per mole of collagen were increased in the multidose bleomycin hamster model. Treatment with taurine and niacin in combination prevented the bleomycin‐induced increases in the DHLNL and OHP contents of the lung collagen and this may be one of the mechanisms for their antifibrotic effect in this multidose bleomycin hamster model of pulmonary fibrosis.
Partial characterization of neuropathy target esterase and related phenyl valerate esterases from bovine adrenal medulla
Authors: Sogorb M. A. , Viniegra S. , Reig J. A. , Vilanova E. 
Published: October 2006

AbstractThe mechanism by which organo‐phosphorus‐induced delayed polyneuropathy is induced relates to the specific inhibition and subsequent modification (“aging”) of a protein known as neuropathy target esterase (NTE), operatively defined as paraoxon‐resistant and mipafox‐sensi‐tive phenyl valerate (PV) esterase activity. This protein has fundamentally been investigated in hen brain, the latter being the habitually employed OPIDP study model. In the present article, a partial characterization is made of the NTE and other related PV esterases in the bovine adrenal medulla and brain; NTE sensitivity to the neurotoxic or‐ganophosphorus compound mipafox is investigated, and its subcellular distribution is studied. The NTE activity of the adrenal medulla was found to be the highest of those among the tissues studied to date (5000 ± 1400 mU/g tissue; ± SD, n = 12). This activity represented 93% of the PV esterase activity resistant to 40 μm paraoxon in the par‐ticulate fraction of the adrenal medulla and approximately 50% of total PV esterase activity. In the bovine brain, these proportions were 72 and 26%, respectively, i.e., similar to those described in hen brain. The mipafox inhibition curve of PV esterase activity resistant to 40μM paraoxon in the particulate fraction of the adrenal medulla suggests that NTE activity fundamentally comprises a mipafox‐sensitive component with an I 50 of 6.39 μM at 30 minutes, which is similar to the value reported in hen brain. NTE activity in the bovine adrenal medulla is almost exclusively limited to the particulate fraction, the microsomal fraction, plasma membrane, and chromaffin granule‐enriched fractions being the highest in terms of specific activity. On the contrary, the mitochondria‐enriched fraction was very poor in such activity. In bovine brain, most NTE activity was likewise limited to the particulate fraction.
Comparative kinetic study of the binding between 2,3,7,8‐tetrachlorodibenzo‐ρ‐dioxin and related ligands with the hepatic Ah receptors from several rodent species
Authors: Nakai Jamie S. , Winhall Martha J. , Bunce Nigel J. , Rosengren Rhonda , Safe Stephen 
Published: October 2006

AbstractKinetic analysis of the time course of association of [3H]‐2,3,7,8‐tetrachlorodibenzo‐ρ‐dioxin with hepatic cytosoi from five rodent species gave additional evidence for differences in the properties of the Ah receptor ligand binding subunit between species. A parallel study of the association of six tritiated polychlorinated dibenzopρ‐dioxins and dibenzofurans with hepatic Ah receptor from Wistar rat and C57BL/6 mouse showed that their rank order for kinetic affinity did not correlate with the rank ordering of their toxic potency‐ and may vary according to the source of the Ah receptor.
Arachidonic acid release in renal proximal tubule cell injuries and death
Authors: Schnellmann Rick G. , Yang Xiaonian , Carrick Joan B. 
Published: October 2006

AbstractArachidonic acid release and the effect of phospholipase inhibitors on various types of cell injuries and death to rabbit renal proximal tubule suspensions were determined. Proximal tubules were exposed to the mitochondrial inhibitor antimycin A (0.1 μM), the protonophore carbonyl cyanide ρ‐trifluoromethoxypheitylhydrazone (1 μM FCCP), the oxidant tertbutyl hydroperoxide (0.5 mM TBHP), or the calcium ionophore ionomycin (5 μM) in the absence or presence of the putative phospholipase inhibitors dibucaine, mepacrine, chlorpromazine, or U‐26384. The phospholipase inhibitors had no effect on the proximal tubule lactate dehydrogenase (LDH) release (a marker of cell death) produced by FCCP, antimycin A, or ionomycin after 1,2, or 2 hours of exposure, respectively. Only dibucaine and mepacrine decreased LDH release in TBHP‐treated proximal tubules without decreasing TBHP‐induced lipid peroxidation. Antimycin A and ionomycin did not release arachidonic acid from proximal tubules prelabeled with [1‐14C] arachidonic acid. In contrast, TBHP released arachidonic acid from proximal tubules prior to the onset of cell death, and dibucaine and mepacrine decreased the TBHP‐induced release. Thus, phospholipase inhibitors were cytoprotective in those injuries that produced arachidonic acid release. These results suggest that arachidonic acid release and phospholipase A2 activation play a contributing role in oxidant‐induced renal proximal tubule cell injury and death but not in mitochondrial inhibitor‐ or calcium ionophore‐induced proximal tubule cell injury and death.
Toxicology of cupric salts on honeybees IV — gluconate and sulfate action on hemolymph trehalose activity in vivo and in vitro
Authors: Nectoux M. , Bounias M. , Popeskovic D. 
Published: October 2006

AbstractA biphasic increase of hemolymph glucose levels was observed following injection to bees of cupric gluconate or sulfate, both potent agents for the control of Varroa jacobsoni, a parasitic mite of hives. The simultaneous injection to bees of 0.3 μM BAYg5421 (an inhibitor of α‐glucosidases) quenched the response, suggesting a direct effect of 2 nmol/bee cupric ions on trehaloses' activity. One nanomol of injected cupric gluconate increased the trehalose (Tre) activity by 233% in crude hemolymph extracts at 1 mM trehalose concentration, and exhibited biphasic dose‐related effects with a maximum 15% increase at 0.5 mM cupric ion and a stabilized 20% inhibition from 4 mM, regardless of the anionic moiety. Upon partial purification of the enzyme complex, two fractions (FI = 75% and FII = 25% of total activity) were isolated that exhibited, respectively, less and more marked positive cooperativity than crude extract. Form I showed almost no susceptibility to either cupric derivatives, which indicated form II as the most likely target, with 68% and 72% increases with 0.25 mM cupric sulfate and 0.5 mM cupric gluconate, in presence of 16 mM trehalose.
Nucleotide changes in oxidatively stressed lymphocytes
Authors: Palace Gerard P. , Lawrence David A. 
Published: October 2006

AbstractSimilar to HIV‐1‐induced suppression of thymus‐derived lymphocytes (T cells), oxidatively stressed T cells show inhibited DNA synthesis and proliferation. The influence of oxidative stress on nucleotide pools was explored using 3H‐uridine addition to OKT3‐stimulated peripheral blood lymphocytes. The cells were preincubated and stimulated in the presence of 1 mM buthionine sulfoximine to inhibit GSH synthesis. This treatment gave rise to a significant reduction in dUDP and TTP biosynthesis following 18–32 hours stimulation, indicating possible impairment of ribonucleotide reductase activity.
Characterization of the Ah receptor from human placental tissue
Authors: Nakai Jamie S. , Bunce Nigel J. 
Published: October 2006

AbstractThe rate of thermal inactivation of the unliganded human Ah receptor, studied by sucrose density gradient centrifugation, with respect to loss of ligand binding ability, was found to be greater than those of most rodents at 20°C, but the temperature coefficient of the rate constant was much smaller than for the rodent species. This implies that the unliganded human Ah receptor would be thermally more stable than the rodent analogs at physiological temperatures. The liganded form of the human Ah receptor was found to be less stable with respect to ligand release than the rodent receptors. These differences in behavior between human and rodent Ah receptors underline the difficulties in using rodent data in the development of receptor‐based models of dioxin toxicity. Attempts to develop an alternative to sucrose density gradient centrifugation, comparable with the hydroxylapatite adsorption method used to assay rodent hepatic Ah receptor, were unsuccessful.
Mechanism of antifibrotic effect of taurine and niacin in the multidose bleomycin‐hamster model of lung fibrosis: Inhibition of lysyl oxidase and collagenase
Authors: Blaisdell Robert J. , Giri N. 
Published: October 2006

AbstractIn the multiple‐dose bleomycin‐hamster model of pulmonary fibrosis, combined treatment with taurine and niacin blocks the increase in lung collagen deposition. We investigated the effects of taurine and niacin on lung lysyl oxidase and type I collagenase activities in this model. Hamsters were intratracheally instilled with three weekly doses of saline or bleomycin sulfate. Animals were fed either a diet containing 2.5% niacin and 2.5% taurine, or a control diet throughout the experiment. The four groups were saline‐instilled with the control diet (SCD), bleomycin‐instilled with control diet (BCD), bleomycin‐instilled with the diet containing taurine and niacin (BTN), and saline‐instilled with the diet containing taurine and niacin (STN). Animals were sacrificed at 1, 4, and 8 weeks after the last bleomycin instillation. Hydroxyproline per lung in the BCD group was significantly elevated by 38, 56, and 60% over the SCD group at 1, 4, and 8 weeks, respectively. Lysyl oxidase activity per lung in the BCD group was significantly elevated by 57.5 and 91.4% over the SCD controls at 1 and 4 week time periods, respectively. Type I collagenase activity per lung in the BCD group was significantly elevated by 65 and 80% over the SCD controls at 1 and 4 weeks, respectively. The combined treatment with taurine and niacin abolished the bleomycin‐induced increases in the lung hydroxyproline content and lysyl oxidase and collagenase activities. It was postulated that one of the mechanisms for the antifibrotic effect of taurine and niacin may be the blockage of bleomycin‐induced increases in the lung lysyl oxidase and collagenase activities. © 1995 John Wiley & Sons, Inc.
Organophosphorus inhibition and heat inactivation kinetics of particulate and soluble forms of peripheral nerve neuropathy target esterase
Authors: Barril J. , Tormo N. , Diaz‐Alejo N. , Vilanova E. 
Published: October 2006

AbstractNeuropathy target esterase (NTE) is the proposed target site for the mechanism of initiation of the so‐called organophosphorus‐induced delayed polyneuropathy (OPIDP). NTE is operationally defined in this article as the phenylvalerate esterase activity which is resistant to inhibition by 40 μM paraoxon and sensitive to 250 μM mipafox. Soluble (S‐NTE) and particulate (P‐NTE) forms of NTE had first been identified in hen sciatic nerve [E. Vilanova, J. Barril, V. Carrera, and M. C. Pellín (1990). J. Neurochem., 55, 1258–1265]. P‐NTE and S‐NTE showed different sensitivities to the inhibition by several organophosphorus compounds over a range of inhibitor concentrations for a 30 or 120 minute fixed inhibition time at 37°C. S‐NTE was less sensitive to the inhibition by O,O′‐diisopropyl phosphorofluoridate (DFP), hexyl 2,5‐dichlorophenyl phosphoramidate (H‐DCP), and mipafox than P‐NTE and brain NTE, while the opposite was true for O,S‐dimethyl phosphoroamidothioate (methamidophos). For each of the four inhibitors assayed, S‐NTE showed two components of different sensitivity according to the inhibition curves fitted with exponential models. However, the inhibition of P‐NTE by mipafox, DFP, and HDCP did not show the presence of a considerable proportion of a second component. The kinetics of heat inactivation showed that P‐NTE inactivated faster and to a greater extent than S‐NTE. It is concluded that (1) sciatic nerve S‐NTE is more different from brain NTE than P‐NTE; (2) P‐NTE and S‐NTE have different sensitivities to the inhibition by the studied organophosphorous compounds; (3) the inhibition curves suggest that S‐NTE has two different enzymatic components while these are not so evident for P‐NTE. © 1995 John Wiley & Sons, Inc.
Chromium‐induced production of reactive oxygen species, DNA single‐strand breaks, nitric oxide production, and lactate dehydrogenase leakage in J774A.1 cell cultures
Authors: Hassoun E. A. , Stohs S. J. 
Published: October 2006

AbstractThe involvement of oxidative stress in the toxicity of chromium (VI) and chromium (III) has been proposed. We have therefore examined the effects of these cations on the production of superoxide anion, nitric oxide (NO), and DNA single strand breaks (SSB) in J774A.1 macrophage cells in culture as well as the effects on lactate dehydrogenase (LDH) leakage and cell viability. Following a 48 hour incubation, over twofold increases in superoxide anion and NO production were observed at concentrations of approximately 0.30 and 50 μM for Cr (VI) and Cr (III), respectively. The patterns of cell viability and LDH leakage paralleled superoxide anion and NO production for Cr (VI) and Cr (III). A 50% decrease in viability was observed at approximately the concentrations that produced a twofold increase in superoxide and NO production. Concentration‐dependent increases in DNA‐SSB were observed after incubation with Cr (III) with maximum increases occurring at a concentration of approximately 60 μM. Cr (VI) had no effect on the incidence of DNA‐SSB at any of the tested concentrations. The results indicate that Cr (VI) and Cr (III) are toxic to the J774A.1 cell line, and the toxicity may be due at least in part to an oxidative stress induced by the production of reactive oxygen species. © 1996 John Wiley & Sons, Inc.
Isolation from bovine liver mitochondria and characterization of three distinct carboxylic acid:CoA ligases with activity toward xenobiotics
Authors: Vessey Donald A. , Hu Jie 
Published: October 2006

AbstractA mitochondrial freeze/thaw lysate was fractionated on a DEAE‐cellulose column into four distinct acyl‐CoA ligase fractions. First to elute was a 50 kDa short‐chain ligase that activated only short‐chain fatty acids. Next to elute were three ligases that had activity toward both medium‐chain fatty acids and xenobiotic carboxylic acids; these were termed xenobiotic/medium‐chain ligases (X‐ligases) and labeled XL‐I, XL‐II, and XL‐III, respectively, based on order of elution. The molecular weight of X‐ligases I, II, and III were ca. 55,000, 55,500 and 53,000, respectively. Form XL‐III showed no pH optimum; the rate increased steadily with pH beginning from pH 7.0. XL‐I and XL‐II showed the same behavior with benzoate as substrate, but with medium‐chain fatty acids, both forms had a pH optimum at 8.8. The three X‐ligases differed in substrate specificity. XL‐I was the predominant nicotinic acid activating form and had the lowest Km for benzoate. Form XL‐II was the only form with measurable salicylate activity, although it was extremely low. XL‐III was the only 2,4,6,8‐decatetraenoic acid activating form and also was the predominant medium‐chain fatty acid‐activating form. By comparison of substrate specificities, it was concluded that the two previously reported ligase preparations were mixtures of the three forms. When the ligase rates were compared to previously determined N‐acyltransferase rates toward benzoyl‐CoA and phenylacetyl‐CoA, the data showed that ligase activities are 100‐fold lower, and thus the ligase is rate limiting for the conjugation of both of these xenobiotics. © 1996 John Wiley & Sons, Inc.
Osteoderm morphology and development in the nine‐banded armadillo, Dasypus novemcinctus (Mammalia, Xenarthra, Cingulata)
Authors: Vickaryous Matthew K. , Hall Brian K. 
Published: October 2006

AbstractAmong modern mammals, armadillos (Xenarthra, Cingulata) are the only group that possesses osteoderms, bony inclusions within the integument. Along the body, osteoderms are organized into five discrete assemblages: the head, pectoral, banded, pelvic, and tail shields. The pectoral, banded, and pelvic shields articulate to form the carapace. We examined osteoderm skeletogenesis in the armadillo Dasypus novemcinctus using serial and whole‐mount histochemistry. Compared with the rest of the skeleton, osteoderms have a delayed onset of development. Skeletogenesis begins as condensations of osteoblasts secreting osteoid, localized within the papillary layer of the dermis. Osteoderm formation is asynchronous both within each shield and across the body. The first osteoderms to mineralize are situated within the pectoral shield of the carapace, followed by elements within the banded, head, pelvic, and tail shields. In general, within each shield ossification begins craniomedially and proceeds caudally and laterally, except over the head, where the earliest elements form over the frontal and parietal bones. The absence of cartilage precursors indicates that osteoderms are dermal elements, possibly related to the all‐encompassing vertebrate dermal skeleton (exoskeleton). The mode of development of D. novemcinctus osteoderms is unlike that described for squamate osteoderms, which arise via bone metaplasia, and instead is comparable with intramembranously derived elements of the skull. J. Morphol., 2006. © 2006 Wiley‐Liss, Inc.
Genome size and determination of DNA content of the X chromosomes, autosomes, and germ line‐limited chromosomes of Sciara coprophila
Authors: Rasch Ellen M. 
Published: October 2006

AbstractThe unique chromosome biology of the fungus fly Sciara coprophila has fascinated investigators for over 80 years. Male meiosis exhibits a monopolar spindle, nonrandom segregation of imprinted chromosomes and nondisjunction of the X chromosome. The unusual mechanism of sex determination requires selective elimination of X chromosomes in embryogenesis. Supernumerary (L) chromosomes are also eliminated from the soma during early cleavage divisions. Distinctive DNA puffs on the larval salivary gland chromosomes are sites of DNA amplification. As a foundation for future genome studies to explore these many unusual phenomena, we have used DNA‐Feulgen cytophotometry to determine genome size from hemocyte nuclei of male (X0) and female (XX) larvae and adults. The DNA content of the X chromosome is ∼0.05 pg DNA and the autosomal complement is ∼0.45 pg DNA. Measurements of DNA levels for individual sperm from adults showed that the DNA contribution of the germ line‐limited (L) chromosomes constitutes as much as 35% of the DNA of the male gamete. A parallel study using Sciara ocellaris, a related species lacking L chromosomes, confirmed the presence of two X chromosomes in the sperm of this species. J. Morphol., 2006. © 2006 Wiley‐Liss, Inc.
Determination of clavulanic acid in calf plasma by liquid chromatography tandem mass spectrometry
Authors: Reyns Tim , De Baere Siegrid , Croubels Siska , De Backer Patrick 
Published: October 2006

AbstractA method for the quantification of clavulanic acid in calf plasma using high‐performance liquid chromatography combined with electrospray ionization (ESI) mass spectrometry, operating in the negative ionization mode (LC‐MS/MS), is presented. Sample preparation includes a simple and fast deproteinization with acetonitrile and a back‐extraction of the acetonitrile with dichloromethane. Chromatography is performed on a reversed‐phase PLRP‐S polymeric column using 0.05% formic acid in water and acetonitrile. The limit of quantification is 25 ng/ml, which is lower than other published methods using ultraviolet (UV), fluorimetric or mass spectrometric detection. The limit of detection is calculated to be 3.5 ng/ml. The stability of clavulanic acid was demonstrated according to The Guidelines of Bioanalytical Method Validation of The Food and Drug Administration (FDA): freeze and thaw stability, short‐term stability, long‐term stability, stock solution stability and postpreparative stability. The method is used in a pharmacokinetic and bioequivalence study of amoxycillin/clavulanic acid formulations in calves. Copyright © 2006 John Wiley & Sons, Ltd.