bluuebunny/crossref_metadata_2025 huggingface dataset:
2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin causes an increase in protein kinases growth hepatic associated with epidermal factor receptor in the plasma membrane
Authors: Madhukar B. V. , Ebner Karl , Matsumura Fumio , Bombick D. W. , Brewster D. W. , Kawamoto T.
Published: October 2006

2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin (TCDD), administered to male rats at a single intraperitoneal (IP) injection dose of 25 μg/kg causes down‐regulation of epidermal growth factor (EGF) receptor in the plasma membrane of rat liver which starts after two days and continues throughout the experimental period (20 days). Using monoclonal antibody to EGF receptor, it was determined that TCDD‐caused EFG receptor down‐regulation in the rat liver was accompanied by increased protein kinase activity. Such an increase in the protein kinase activity involves, at least in part, an activation of protein tyrosine kinase. Examination of serum samples from control and treated rats revealed no detectable difference in the level of EGF itself or EGF receptor‐reacting substances (eg, hormones and other growth factors). In vivo TCDD caused early eye opening and tooth eruption and poor body weight gain and hair growth in mouse neonates similar to those observed with exogenously administered EGE The results indicate that such EGF receptor–mediated effect of TCDD has some toxocilogical significance in vivo. Although TCDD causes significant reduction in [125I]‐EGF binding in the hepatic plasma membrane in susceptible strains of mice, it has only modest effects in tolerant strains. The results are consistent with the idea that the action of TCDD on the EGF receptor is mediated through the cytosoliclnuclear TCDD receptor, which is known to be regulated by the Ah locus.
Sex and strain differences in the hepatotoxic response to acute cocaine administration in the mouse
Authors: Boyer C. Scott , Ross David , Petersen Dennis R.
Published: October 2006

Cocaine‐induced hepatotoxicity was examined in vivo in a dose‐responsive manner in C57BL/6Ibg, DBA/2Ibg, C3H/2Ibg, and Balb/cJ mice. Serum glutamic‐pyruvic transaminase (SGPT) activities were determined 24 hours after intraperitoneal (IP) administration of cocaine (20 to 100 mg/kg). Significant elevations (100‐ to 150‐fold) in SGPT were observed in male mice receiving cocaine. Significant differences in sensitivity to cocaine‐induced hepatotoxicity were found among males of the inbred strains, with Balb being most sensitive and C57BL being least sensitive and C3H and DBA strains exhibiting intermediate sensitivity. Female mice of the four inbred strains were more resistant than males to cocainemediated hepatotoxicity, as indicated by only twofold to tenfold elevations in SGPT values. Among the females, sensitivity of the four inbred strains—as indicated by dose response curves—fell into two categories: the sensitive strains (C3H and C57BL) and the resistant strains (Balb and DBA). Pretreatment of males of the four inbred strains with the P‐450 inducer phenobarbital resulted in enhancement of cocaine‐mediated hepatotoxicity in the C57BL and Balb but not the C3H and DBA mice. Phenobarbital pretreatment of females of the four inbred strains resulted in enhancement of the hepatotoxic response to cocaine in the C3H, DBA, and Balb mice. Phenobarbital‐pretreated C57BL females exhibited a 100% mortality rate after the acute cocaine dose, and thus no determination of hepatotoxicity could be established for them. These data demonstrate sex and strain differences in cocaine‐induced hepatotoxicity and suggest that phenobarbital pretreatment does not uniformly enhance the hepatotoxicity of cocaine.
Neonatal phenobarbital imprinting of rat hepatic microsomal testosterone hydroxylations
Authors: Haake J. M. , Safe S. H.
Published: October 2006

The effects of neonatally administered phenobarbital (PB) on adult rat hepatic microsomal metabolism of testosterone were examined in 60‐, 90‐, and 120‐day‐old animals. Phenobarbital‐induced imprinting was evident at all ages; however, female rats appeared to be more susceptible to the neonatal effects of phenobarbital than did male rats. In 60‐day‐old female rats, increased testosterone 2α‐hydroxylase activity was observed in microsomes from noninduced rats, whereas decreased testosterone oxidation at all positions except 2α and 15β was observed in microsomes from Aroclor 1254‐induced rats. The decreased oxidation of testosterone at specific sites in response to Aroclor 1254 induction was quite dramatic, decreasing the activities to near or below control levels. By contrast, phenobarbital‐treated 60‐day‐old males exhibited approximately a twofold increase in Aroclor 1254‐induced 16α and 2α‐hydroxylase activities. The pattern of changes in testosterone metabolism observed in phenobarbital‐treated animals was different at both 90 and 120 days from that at 60 days. Only minor alterations in the oxidation of testosterone were observed in 90‐day‐old animals of either sex. In 120‐day‐old animals the greatest effects of neonatal phenobarbital exposure were on Aroclor 1254–induced 16β‐hydroxylase activities. In induced female rats 16β‐hydroxylase activity was again decreased to noninduced levels, while in induced male rats a fourfold increase in this activity was observed. These results demonstrate that neonatal exposure to phenobarbital can alter both constitutive and Aroclor 1254–induced testosterone metabolism in adult rats and that the effects of neonatal phenobarbital exposure are age and sex differentiated.
The formation of 2‐aminofluorene‐dna adducts in vivo: Evidence for peroxidase‐mediated activation
Authors: Krauss Robert S. , Angerman‐Stewart Julie , Eling Thomas E. , Dooley Kenneth L. , Kadlubar Fred F.
Published: October 2006

Formation of DNA adducts in various tissues of dogs fed a single dose of the carcinogen 2‐aminofluorene was investigated. Adduct analysis was performed using a technique that allows measurement of both N‐(deoxyguanosin‐8‐yl)‐2‐aminofluorene, the adduct formed by reaction of N‐hydroxy‐2‐aminofluorene with DNA, as well as the polar 2‐aminofluorene‐DNA adducts formed when 2‐aminofluorene is activated by prostaglandin H synthase‐peroxidase in vitro. Two male beagle (A and B) dogs were examined and a different DNA adduct profile was observed with each dog. For the dog A, N‐(deoxyguanosin‐8‐yl)‐2‐aminofluorene was the major adduct found in hepatic DNA; no peroxidase‐derived adducts were detected in this tissue. In contrast, adducts eluting similarly to peroxidase‐derived adducts were found in urinary tract tissues of this dog with the relative abundance of these adducts in the order urothelium > renal medulla > renal cortex, which correlates with the respective tissues' prostaglandin H synthase activity. N‐(Deoxyguanosin‐8‐yl)‐2‐aminofluorene was detected in the renal tissues, but not in urothelium. For dog B, only the N‐(deoxyguanosin‐8‐yl)‐2‐aminofluorene adduct was observed in all tissues examined, including the urothelium. However, total binding to liver, kidney, and bladder were two‐, two‐, and four‐fold lower, respectively, than dog A. These data indicate that both prostaglandin H synthase‐mediated activation and N‐hydroxylation of 2‐aminofluorene occur in vivo and may be subjected to pharmacodynamic considerations. Furthermore, the tissue distribution of the peroxidase‐mediated 2‐aminofluorene adducts suggests this process may also be of importance in the bladder‐specific carcinogenicity of aromatic amines.
Nonideal behavior of alkoxyphenoxazone compounds (cytochrome P‐450 substrates) in aqueous solution
Authors: Rabovsky J. , Heflin E. , Judy D. J. , Sapola N. A.
Published: October 2006

Spectral properties of the cytochrome P‐450 substrates, methoxy‐, ethoxy‐, pentoxy‐, and benzyloxyphenoxazone (MeOPx, EtOPx, PeOPx, and BzOPx, respectively) were investigated from 350 to 600 nm in ethanol and aqueous buffer. In ethanol, each alkoxyphenoxazone displayed a λ max at 460 nm and a shoulder around 390 nm. Extinction coefficients (EmM) in ethanol were calculated as MeOPx, 20.5; EtOPx, 20.4; PeOPx, 24.7; and BzOPx, 22.4. In aqueous buffer, only MeOPx obeyed the Lambert‐Beer law (λmax =480 nm, EmM =22.1). Three substrates, EtOPx, PeOPx, and BzOPx, displayed anomalous behavior in aqueous solution, wherein the λmax shifted to lower wavelengths (480–430 nm) and EmM(apparent) decreased as the alkoxyphenoxazone concentration increased. This behavior was dependent on the side chain, and the concentrations at which the spectral changes took place were estimated as: BzOPx, 2 μM. PeOPx, 5 μM; EtOPx, 17 μM; and MeOPx, > 20 μM. The blue shift and decreased EmM (apparent) observed for PeOPx at high concentration in aqueous buffer was reversed at high temperature. Unlike EtOPx, PeOPx, and BzOPx, and like MeOPx, hydroxyphenoxazone (resorufin) and unsubstituted phenoxazone obeyed the Lambert‐Beer law in aqueous buffer and ethanol. The data suggest that the pentoxy and benzyloxy substituents facilitated a self‐association process among the phenoxazones in aqueous solution. The data further show that aqueous solutions should be avoided when spectral data are used to determine alkoxyphenoxazone concentrations.
Selective inhibition of cytosolic epoxide hydrolase activity in vitro by compounds that inhibit catalase
Authors: Guenthner Thomas M. , Thomas Hjelle J. , Whalen Robert
Published: October 2006

The ability of a number of known inhibitors of catalase activity to affect cytosolic and microsomal epoxide hydrolase activities in vitro, measured as enzymatic trans‐stilbene oxide hydrolysis and styrene oxide hydrolysis, respectively, was investigated. Catalase and cytosolic epoxide hydrolase activities are inhibited by hydroxylated metabolites of 2‐amino‐4,5‐diphenylthiazole (DPT). The metabolite hydroxylated on the 4‐phenyl ring (4OH‐DPT) and the metabolite hydroxylated on both phenyl rings (4,5‐DIOH‐DPT) are potent inhibitors of both enzymes; the metabolite hydroxylated on the 5‐phenyl ring (5OH‐DPT) is less potent. Unmetabolized DPT has no effect on either enzyme. 4OH‐DPT inhibits, but 5OH‐DPT enhances, microsomal epoxide hydrolase activity. 4,5‐DIOH‐DPT and DPT have no effect on this enzyme. Other compounds that inhibit both catalase and cytosolic epoxide hydrolase activities, but do not inhibit microsomal epoxide hydrolase activity, are nordihydroguaiaretic acid and 2‐aminothiazole. Microsomal epoxide hydrolase activity is enhanced by 2‐aminothiazole and levamisole in vitro. Thus these inhibitors of catalase are selective epoxide hydrolase inhibitors in that they inhibit cytosolic epoxide hydrolase activity in vitro, but have either no effect on, or increase the activity of, microsomal epoxide hydrolase in vitro. Conversely, the selective cytosolic epoxide hydrolase inhibitors 4‐phenylchalcone oxide and 4′‐phenylchalcone oxide do not inhibit catalase activity, nor does trichloropropene oxide, a selective microsomal epoxide hydrolase inhibitor.
Age‐related difference in bioenergetics of lung and heart mitochondria from rats exposed to ozone
Authors: Zychlinski Lech , Raska‐Emery Patricia , Balis John U. , Montgomery Mark R.
Published: October 2006

Bioenergetics of isolated lung and heart mitochondria from adult and aged rats were examined in the presence of glutamate (NAD‐linked substrate) or succinate + rotenone (FAD‐linked substrate) following ozone exposure (3.0 ppm, 8 hr). In controls, several differences were observed between adults and aged in both organ preparations. Following exposure, all bioenergetic parameters were decreased significantly in lung preparations from both adult and aged rats. In heart mitochondria, the respiration rates in state 3 and in uncoupled state, and the ADP/O ratio were decreased significantly in both exposed age groups. The respiratory control ratio (RCR) was decreased significantly only in the aged exposed rats. These results suggest that acute exposure to high levels of ozone alters energy production in both lung and heart mitochondria of adult and aged rats.
Differential enzyme induction of mouse liver and lung following a single low or high dose of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD)
Authors: Beebe L. , Park S. S. , Anderson L. M.
Published: October 2006

The induction response of cytochrome P‐450‐dependent enzyme activities to a single low (5 nmol/kg) or high (50 nmol/kg, intraperitoneal [ip] dose of TCDD was examined in liver and lung homogenates over a 12‐week time course in an outbred, Ah‐responsive strain of mice (National Institutes of Health [NIH] Swiss). Total hepatic cytochrome P‐450 was quantified, and the dealkylation of ethoxy‐ and benzyloxyresorufin (activities of P‐450 IA1 and IIB1, respectively) were measured in both tissues at 48 and 96 hr and at 1, 4, and 12 weeks post‐TCDD administration. Western immunoblotting with monoclonal antibody 1–7–1 was conducted to confirm the specific IA1‐inductive effects of each dose of TCDD over the same time course. Following the low dose, specific IA1 induction was apparent in liver at the earliest time point, was maximal at 1 week, and declined to control values at 12 weeks. Pulmonary IA1 was near‐maximally induced at 48 hr, and remained at that level for 4 weeks. In contrast, a tenfold higher dose of TCDD elicited similar IA1 induction profiles for both tissues, with a maximum at 1 week and a progressive loss at 4 and 12 weeks postexposure. P‐450 IIB1 activity was elevated in TCDD‐treated animals by enzymatic assay; however, Western immunoblotting did not confirm this finding. These data demonstrate persistent dose‐dependent P450 induction over many weeks by a single TCDD dose, with significant organ‐specific differences: (a) lung is more sensitive than liver to a nonmaximal inducing dose of TCDD, and (b) at a maximally inducing dose of TCDD, lung is very similar to liver in both the level and time course of IA1 induction.
Localization of the sulfur‐cyanolysis site of serum albumin to subdomain 3‐ab
Authors: Jarabak Rebecca , Westley John
Published: October 2006

The results of kinetic experiments measuring the effects of a variety of ligands on the sulfur‐cyanolysis reaction catalyzed by serum albumin point to the conclusion that the active site for cyanolysis is on subdomain 3‐AB. Relationships among the inhibition by short‐chain fatty acids, the activation by p‐nitrophenyl acetate, and the influence of bilirubin and L‐tryptophan on these effects indicate that the cyanolysis active site and the known primary binding site for indoles are both near, but on opposite sides of, tyrosine‐409 of bovine albumin (tyrosine‐411 of human albumin).
Effect of ascorbic acid esters on hepatic glutathione levels in mice treated with a hepatotoxic dose of acetaminophen
Authors: Mitra Ashoke , Kulkarni Arun P. , Ravikumar Vinnavadi C. , Bourcier Denis R.
Published: October 2006

Acetaminophen (APAP) with or without ascorbyl stearate (AS) or ascorbyl palmitate (AP) was administered by gavage to male Swiss‐Webster mice at a dose of 600 mg/kg for each chemical. The biochemical markers of hepatotoxicity, serum transaminases (serum glutamate pyruvate transaminase [SGPT], serum glutamate oxaloacetic transaminase [SGOT]) and serum isocitrate dehydrogenase (SICD) activities were monitored after APAP and APAP + AP or AS dosing. There were significant reductions in serum transaminase and SICD activities in the APAP‐ + ascorbate ester‐treated animals as compared to APAP‐positive controls. Oral coadministration of APAP with AP or AS did not prevent the initial hepatic GSH depletion (15 min‐4 hr postdosing). However, hepatic GSH content began to rise in the APAP + AS or AP‐treated animals at 4 hr and reached control values within 12 hr postdosing. Urinary mercapturate conjugates were also significantly higher in the APAP + AP or AS‐treated animals as compared to APAP alone when measured over a 60‐min postdosing period. Plasma sulfobromophthalein (BSP) retention was approximately eight times higher in APAP‐treated animals as compared to the APAP + ascorbate ester treatments indicating maintenance of hepatic excretory functions in presence of AP or AS. Prior depletion of hepatic GSH by diethyl maleate (DEM) did not alter hepatoprotective effects of AP or AS in the presence of APAP. Hepatic ascorbate levels also peaked at 4 hours after APAP + AP or AS treatments. The possible role of L‐ascorbic acid esters in GSH regeneration following co‐administration of a hepatotoxic dose and APAP is discussed.
Effect of different amino acidic pretreatments that protect the kidney against papillary necrosis induced by bromoethylamine on differential distribution of renal nonprotein sulfhydryls
Authors: Thielemann L. E. , Rosenblut G. , Cerda M. C. , Oberhauser E. W. , De Geyter M. A. , Videla L. A.
Published: October 2006

Content of nonprotein sulfhydryls (NPSH) was found to be higher in rat renal cortex than in external medulla and papilla. Administration of bromoethylamine (BEA), at a dose that produces extensive papillary necrosis and minor effects in the other renal segments, induced a significant reduction in NPSH levels of renal cortex and external medulla, with no changes in the papilla. Treatment with N‐acetyl‐L‐cysteine (NAC) elicited an increase in papillary NPSH and a decrease in the cortex, with opposite changes being observed with an amino acid mixture of glutamine, glycine, and cystine (AM). Similar results were found in animals pretreated with NAC or AM prior to BEA intoxication. These pretreatments protect the cortex, external medulla, and papilla from the necrosis induced by BEA. It is suggested that protection of BEA‐induced renal necrosis by NAC or AM pretreatments might be due to different mechanisms, with NPSH playing direct or indirect roles, respectively.
Calcium channel blocking agents protect against acetaminophen‐induced cytotoxicity in rat hepatocytes
Authors: Thibault N. , Peytavin G. , Claude J. R.
Published: October 2006

The effect on acetaminophen‐induced cytotoxicity of three calcium channel blocking agents‐diltiazem, verapamil and gallopamil‐was studied in primary cultures of rat hepatocytes and compared with the chelating agent EGTA. Using the measurement of cytosolic lactate dehydrogenase (LDH) as an index of cytotoxicity, it was demonstrated that a 1‐hr pretreatment with calcium channel blocking agents protected cells against acetaminophen cytotoxicity, but were less effective than EGTA. These data suggest that influx of extracellular Ca2+ into the cells could have a role in the genesis of hepatocyte injury by acetaminophen.
Effects of carbon tetrachloride, menadione, and paraquat on the urinary excretion of malondialdehyde, formaldehyde, acetaldehyde, and acetone in rats
Authors: Bagchi D. , Bagchi M. , Hassoun E. , Moser J. , Stohs S. J.
Published: October 2006

Excretions of the lipid peroxidation products, formaldehyde (FA), acetaldehyde (ACT), malondialdehyde (MDA), and acetone (ACON), were simultaneously identified and quantitated in the urine of female Sprague‐Dawley rats by gas chromatography‐mass spectroscopy (GC‐MS) and high pressure liquid chromatography (HPLC) following the acute administration of carbon tetra‐chloride, a model alkylating agent that does not induce glutathione depletion, and the redox cycling compounds paraquat and menadione. All three xenobiotics are well‐known inducers of oxidative stress. Oxidative stress was induced by oral administration of single doses of 2.5 mL of carbon tetrachloride/kg, 60 mg menadione/kg, and 75 mg paraquat/kg. These doses are approximately 50% of the LD50's for the three xenobiotics. Urinary excretion of FA, ACT, MDA, and ACON increased relative to control animals following treatment with all xenobiotics. Over the 48 hours of the study, the greatest increases in the excretion of MDA, FA, ACT, and ACON occurred after paraquat administration, with increases of approximately 2.7‐, 2.6‐, 4.3‐, and 11.0‐fold, respectively. This technique may have wide‐spread applicability as an effective biomarker for investigating altered lipid metabolism in disease states and exposure to environmental pollutants/xenobiotics.
Inhibition of insulin production by cyproheptadine in RINm5F rat insulinoma cells
Authors: Miller C. P. , Reape T. J. , Fischer L. J.
Published: October 2006

The clonal insulin producing cell line RINmSF was evaluated as a model for the action of cyproheptadine (CPH)‐like diabetogenic com pounds in the rat pancreas. Treatment with 10 μM CPH and selected structural analogs under culture conditions produced a progressive loss of cellular insulin which reached 30% of control within 24 hours. Comparison of the activities of the analogs 4‐diphenylmethylpiperidine (4‐DPMP) and 2‐di‐phenylmethylpiperidine (2‐DFMP) to produce cellular insulin depletion showed that 4‐DPMP was as active as CPH but 2‐DPMP had no activity at the highest concentration employed (10 μM). The CPH metabolite desmethyl CPH‐epoxide was five times more active than the parent compound in producing loss of insulin in RINm5F cells. These results are consistent with previously published results of CPH actions in vivo. An inhibition of insulin biosynthesis with no loss of preproinsulin mRNA occurred in RINm5F cells treated with CPH or DMCPH‐epoxide. This suggests that an effect on transcription may not be the primary action by which CPH and its analogs inhibit insulin synthesis in vivo.
Effects of P450 inhibition and induction on the olfactory toxicity of β, β′‐iminodipropionitrile (IDPN) in the rat
Authors: Genter M. B. , Deamer N. J. , Cao Y. , Levi P. E.
Published: October 2006

In addition to the neurotoxic effects of β, β′‐iminodipropionitrile (IDPN) which have been previously reported by other investigators, the olfactory toxicity of this compound has recently been uncovered in this laboratory. Due to the apparently conflicting observations that the IDPN‐induced lesion in the olfactory mucosa is very focal in nature (suggesting site‐specific activation) and the observation by other investigators that the behavioral effects of IDPN appear to be due to the parent compound, we initiated studies into the possible role of the cytochrome P450 enzymes in the olfactory toxicity of IDPN. Immunohistochemical studies with antibodies raised against several different P450 isoforms revealed good correlation between IDPN‐induced olfactory mucosal degeneration and the localization of a protein immunoreacting with an antibody to P450 2E1. Enzymatic studies revealed that there is approximately fivefold more ρ‐nitrophenol hydroxylation activity in the olfactory mucosa than in the liver on a per milligram microsomal protein basis. Administration of 1% acetone in the drinking water increased the levels of olfactory mucosal 2E1, and the increase in enzyme levels corresponded to increased olfactory toxicity of IDPN; inhibition of P450 activities with either metyrapone or carbon tetrachloride eliminated or significantly decreased the olfactory toxicity of IDPN, respectively. These studies suggest a role for cytochrome P450, specifically the 2E1 isoform, in the activation of IDPN within the nasal mucosa.
Biphasic modulation of protein kinase C (PKC) activity by polychlorinated dibenzo‐p‐dioxins (PCDDs) in serum‐deprived rat aortic smooth muscle cells
Authors: Weber Thomas J. , Ou Xiaolan , Merchant Mark , Wang Xiaohong , Safe Stephen H. , Ramos Kenneth S.
Published: October 2006

Previous studies in this laboratory have shown that benzo(a)pyrene (BaP) modulates protein kinase C (PKC)‐mediated phosphorylation of aortic smooth muscle cell (SMC) proteins. This observation is consistent with the ability of other aromatic hydrocarbons (AHs), such as 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD), to modulate kinase activities in cells of hepatic, testicular, and thymic origin. Because all these chemicals share the ability to bind the aryl hydrocarbon receptor (AhR), the present studies were conducted to determine if changes in PKC activity by AHs conform with established structure‐activity relationships. Experiments were conducted to examine the effects of TCDD, 2,3,7,8‐tetrachlorodibenzofuran (TCDF), and 2,8‐dichlorodibenzodioxin (DCDD) on the phosphorylation of exogenous histone type‐III under basal and PKC‐activating conditions. These congeners exhibit both high (TCDD and TCDF) and low (DCDD) AhR agonist activities. Measurements of kinase activity were conducted in the cytosolic and particulate fractions of growth‐arrested (i.e., serum‐deprived) cultured rat aortic SMCs incubated with 10 nM TCDD, TCDF, and DCDD for 0.5, 12, or 24 hours. No changes in basal kinase activity were induced by these chemicals at any of the times tested. Significant decreases in cytosolic and particulate PKC activity relative to controls were observed upon exposure of SMCs for 0.5 hours to 10 nM TCDD, TCDF, and DCDD. In contrast, SMCs exposed to TCDD and TCDF for 12 hours exhibited a significant increase in PKC activity in both cytosolic and particulate fractions. The PKC activity in cells exposed to DCDD for 12 hours was not altered. Prolonged exposure of SMCs to 10 nM TCDD, TCDF, and DCDD for 24 hours decreased PKC activity in the cytosolic fraction, while only TCDD and TCDF decreased particulate PKC activity. These data show that PKC activity is modulated differentially as a function of time in SMCs exposed to TCDD and related compounds. Collectively, the patterns of histone phosphorylation induced by these chemicals in rat aortic SMCs suggest that modulation of C‐kinase activity involves both receptor‐independent and receptor‐related events.
Characterization of heterologously expressed recombinant retinoic acid receptors with natural or synthetic retinoids
Authors: Kim Yang‐Won , Sharma Raghubir P. , Li Joseph K. K.
Published: October 2006

The first step in retinoid action is binding to their nuclear receptors. Therefore, characterization of binding characteristics of retinoids is of major importance. Human retinoic acid receptors α (hRARα), hRARβ, and mouse RARγ (mRARγ) were expressed heterologously in Escherichia coli as a recombinant glutathione S‐transferase (GST) fusion protein. The expressed fusion proteins were functional and bound specifically to the all‐trans‐retinoic acid (RA). The dissociation constants (Kd) for RA were 1.4 nM for GST‐hRARα, 1.4 nM for GST‐hRARβ, and 3.3 nM for GST‐mRARγ, respectively. The fusion proteins were further used for competitive displacement assays to determine the displacement constant (DC50) for other selected retinoids. All‐trans‐RA and 4‐oxo‐all‐trans‐RA have high affinity with all three receptors (DC50 = 0.8 ∼ 55 nM). The 13‐cis RA binds to hRARα with low affinity, but not to other RARs evaluated here. All‐trans‐N‐ethylretinamide, all‐trans‐retinylacetate, and an ethyl ester of tetrahydronaphthalene derivative had no affinity to any RARs. The hRARα and mRARγ receptors did not bind a naphthalene carboxylic acid derivative of RA, but hRARβ binds this chemical with high affinity. Results indicated that the three recombinant proteins were functional in binding various RA congeners. The affinity and binding data of these retinoids were compared to their observed teratogenic activity.
Absence of enantioselectivity in the pharmacodynamics of P450 2B induction by 5‐ethyl‐5‐phenylhydantoin in the male rat liver or in cultured rat hepatocytes
Authors: Nims Raymond W. , Sidhu Jaspreet S. , Thomas Paul E. , Mellini Donna W. , Nelson Victor C. , Omiecinski Curtis J. , Lubet Ronald A.
Published: October 2006

To explore the enantioselectivity of ligand interaction with the putative phenobarbital receptor, the pharmacodynamics of cytochrome P450 2B (CYP2B) induction by racemic 5‐ethyl‐5‐phen‐ylhydantoin and its two enantiomers were investigated in the male F344/NCr rat and in cultured adult male rat hepatocytes. Steady‐state serum drug concentrations, measured following 14 days of administration of the compounds in the diet (0‐1320 ppm, n = 3 rats per group), were used as an approximation of intrahepatocellular drug concentration. The serum xenobiotic concentrations associated with half‐maximal hepatic CYP2B induction were 5‐10 μM, based on measurement of pentoxy‐ or benzyloxyresorufin O‐dealkylation activities, or immunoreactive CYP2B1 protein. The corresponding potency values in the hepatocyte culture experiments were 8‐12 μM, based on measurement of total cellular RNA coding for CYP2B1. In both the in vivo and the hepatocyte culture experiments, the potencies for CYP2B induction were essentially equivalent for the racemate and the individual enantiomers of 5‐ethyl‐5‐phenylhydantion. In the case of this compound, there would appear to be no enantioselectivity for CYP2B induction. This finding may be interpreted as evidence against receptor mediation in the induction of CYP2B activity, although it is also possible that a receptor is involved that does not exhibit enantioselectivity.
Effect of phenobarbital and the peroxisome proliferator ciprofibrate on γ‐glutamyltranspeptidase activity and leukotriene C4 concentration in cultured rat hepatocytes
Authors: Hong Jin T. , Wilson Mary W. , Glauert Howard P.
Published: October 2006

Peroxisome proliferators induce hepatocellular carcinomas in rodents by an unknown mechanism. γ‐Glutamyltranspeptidase (GGT), a biochemical marker for identifying putative preneoplastic lesions in the liver, is highly expressed in phenobarbital (PB)‐promoted altered hepatic foci but not in those promoted by peroxisome proliferators. One of the substrates of GGT is the eicosanoid LTC4. Because peroxisome proliferators and PB have differing effects on eicosanoid metabolism in vivo, we hypothesized that PB would similarly increase LTC4 concentrations, whereas the peroxisome proliferator ciprofibrate (CIP) would not. Cultured hepatocytes were treated with the peroxisome proliferator ciprofibrate (CIP: 100 and 400 μM) or PB (PB: 0.5 and 2 mM). Competitive radioimmunoassay (RIA) was used to determine the concentration of LTC4 in extracts of cultured hepatocytes. CIP decreased the concentration of LTC4 throughout the culture period, but PB increased the LTC4 concentration. Both doses of CIP significantly inhibited the induction of GGT activity at 48 and 72 hours, whereas PB enhanced GGT activity. We therefore hypothesized that LTC4, a substrate of GGT, may induce GGT activity. LTC4, however, did not enhance GGT activity and inhibited it at very high concentrations. The results of this experiment show that CIP and PB have different effects on GGT activity and LTC4 concentration. LTC4, however, does not induce GGT in cultured hepatocytes. © 1996 John Wiley & Sons, Inc.
Reduced glutathione esters—antidotes to toxicity. Cytotoxicity induced by hydrogen peroxide, 1‐chloro‐2,4‐dinitrobenzene, and menadione in murine P388D1 macrophages in vitro
Authors: Minhas Harjit S. , Thornalley Paul J.
Published: October 2006

Repletion of depleted cellular reduced glutathione (GSH) levels in oxidative stress and exposure to arylating agents is a strategy for the development of antidotes to chemical toxicity. The effect of GSH, reduced glutathione ethyl monoester (GSHEt), and reduced glutathione ethyl diester (GSHEt2) on the cytotoxicity of hydrogen peroxide, 1‐chloro‐2,4‐dinitrobenzene (CDNB), and menadione to P388D1 macrophages in vitro was investigated. The median toxic concentration TC50 values of the toxicants were hydrogen peroxide 24 ± 2 mM (N = 19), CDNB 63 ± 6 μM (N = 18), and menadione 30 ± 4 μM (N = 22). Reduced glutathione, GSHEt, and GSHEt2 were poor antidotes to hydrogen peroxide toxicity. Indeed, the observed antidote effects were attributed to the nonenzymatic reaction of the GSH derivatives with hydrogen peroxide in the extracellular medium. Reduced glutathione ethyl diester was a more potent antidote of CDNB‐ and menadione‐mediated toxicity than GSHEt and GSH. For cell incubations with the approximate median toxic concentration TC50 values of hydrogen peroxide, CDNB, and menadione, the respective median effective antidote concentration EC50 values were GSHEt 23.8 ± 4.1 mM (N = 9), 3.6 ± 0.6 mM (N = 11), and 226 ± 93 μM (N = 12); and GSHEt2 20.4 ± 1.9 mM (N = 6), 603 ± 2 μM (N = 9), and 7.6 ± 2.3 μM (N = 12). Reduced glutathione ethyl diester was a potent antidote to CDNB‐ and menadione‐induced toxicities but not to hydrogen peroxide‐induced toxicity under acute intoxication conditions. © 1996 John Wiley & Sons, Inc.
Upregulation of glucose‐6‐phosphate dehydrogenase in response to hepatocellular oxidative stress: Studies with diquat
Authors: Cramer Clay T. , Cooke Susan , Ginsberg Leonard C. , Kletzien Rolf F. , Stapleton Susan R. , Ulrich Roger G.
Published: October 2006

The expression of hepatic glucose‐6‐phosphate dehydrogenase (G6PDH, E.C. 1.1.1.49) is hypothesized to be modulated by free radicals during oxidative stress. The ability of diquat, a compound known to enhance oxidative stress through generation of reactive oxygen species, to modulate the expression of G6PDH in primary cultures of Fischer‐rat hepatocytes was examined. Diquat‐treated hepatocytes maintained in a chemically defined medium showed both a time‐ and concentration‐dependent increase in G6PDH enzyme activity. This increase in enzyme activity was accounted for by an increase in both G6PDH mRNA and immunoreactive protein, suggesting control at a pretranslational level. The possibility that diquat increased transcription by transfecting cells with a chimeric gene containing 935 bp of the G6PDH promoter (‐878 to +57) linked to the gene for chloramphenicol acetyl‐transferase (CAT) was examined. Hepatocytes transiently transfected with this chimera, and subsequently treated with diquat, exhibited an increase in CAT activity. However, hepatocytes transfected with a chimera containing 287 bp of the G6PDH promoter (‐230 to +57) exhibited only basal CAT activity in the presence of diquat. These results suggest that regions in the DNA sequences required for diquat‐induced expression of G6PDH lie between base pairs ‐878 and ‐230 of the G6PDH gene. These findings are suggestive that oxidative stress in hepatocytes increased the expression of G6PDH activity and protein and that the increased expression is controlled at the transcriptional level. © 1996 John Wiley & Sons, Inc.
Lumbar body fusion with a bioresorbable cage in a goat model is delayed by the use of a carboxymethylcellulose‐stabilized collagenous rhOP‐1 device
Authors: Mullender Margriet G. , Krijnen Matthijs R. , Helder Marco N. , Smit Theo H. , Everts Vincent , Wuisman Paul I.J.M.
Published: October 2006

The purpose of this study was to evaluate the efficacy of recombinant human osteogenic protein‐1 (rhOP‐1) with a carboxymethylcellulose‐stabilized collagenous carrier as a bone graft substitute for instrumented lumbar spinal fusion in an established goat model. Twenty goats received a resorbable poly‐L‐lactic acid (PLLA) interbody cage packed with either rhOP‐1 and its carrier or autologous bone graft. The carrier material was bovine collagen type‐1 stabilized with carboxymethylcellulose. The fusion segments were retrieved at 3 or 6 months postimplantation and evaluated by radiographic and histologic analyses. The rhOP‐1 graft substitute, used in combination with the resorbable PLLA cage, showed inferior results as compared to autologous bone graft in the goat lumbar fusion model. Whereas four out of five segments from the autograft group were fused after 6 months, none of the four segments receiving the rhOP‐1 graft substitute were fused at this time point. Bone ingrowth into the cage was delayed or absent in the experimental group, whereas all autograft specimens showed advanced bone ingrowth (3 months) or fusion (6 months). We suggest that the fusion process was inhibited, because cells were unable to penetrate the rhOP‐1 graft material. This led to delayed bone formation and in some cases inadequate tissue formation. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:132–141, 2007
Distinguishing between recurrent primary sclerosing cholangitis and chronic rejection
Authors: Demetris Anthony Jake
Published: October 2006

Key Concepts:

1. Recurrent primary sclerosing cholangitis (PSC) is extremely difficult, if not impossible, to distinguish from other causes of biliary strictures or sclerosing cholangitis in allografts using needle biopsy evaluation alone. Technical problems with biliary reconstruction, long cold ischemic times, non-heart beating donors, ABO blood group incompatibility, antibody-mediated rejection, and small-for-size syndrome in reduced-size or living donor livers can also cause similar manifestations in a peripheral core biopsy.

2. Some difficulties in distinguishing between sclerosing cholangitis and chronic rejection (CR) arise because: a) at risk populations are similar; b) both can cause “cholestatic” elevation of liver injury tests; and c) both can lead to intrahepatic cholestasis and small bile duct loss.

3. Etiopathogenesis and pathology of CR and sclerosing cholangitis have some overlapping features, but show distinct differences that result in significantly different and discriminating pathologic manifestations.

4. Clues in the clinical history, evaluation of serial biopsies, and histopathology can be used to distinguish with confidence between sclerosing cholangitis and CR.

5. Potential discriminating features include liver size and gross appearance, and histopathology findings in the arterial tree, hilar lymph nodes, large and small bile ducts, interface zone, lobular, and perivenular regions. Liver Transpl 12:S68–S72, 2006. © 2006 AASLD.
Hepatitis B in liver transplant recipients
Authors: Gish Robert G. , McCashland Timothy
Published: October 2006

Key Concepts:

1. The use of low-dose immunosuppressive therapy along with pre- and posttransplantation nucleos(t)ide therapy and posttransplantation hepatitis B immunoglobulin (HBIG) has yielded marked improvements in survival.

2. Lamivudine (Epivir-HBV), adefovir (Hepsera), entecavir (Baraclude), tenofovir (Viread), emtricitabine (Emtriva), and the combination drugs tenofovir + emtricitabine (Truvada) and abacavir + lamivudine (Epzicom) are effective nucleos(t)ide antiviral agents that, in some cases, may help reverse liver disease sufficiently to avoid transplant.

3. In posttransplantation patients, virus suppression with some combination of HBIG and the nucleos(t)ide agents may prevent graft loss and death or the need for a second transplant.

4. In both the pre- and posttransplantation setting, the goal of hepatitis B virus management is complete virus suppression.

5. The use of low-dose intramuscular HBIG is evolving, with studies showing that dosing and cost can be reduced by 50–300% with a customized approach.

6. Elimination of HBIG from the treatment paradigm is currently under evaluation and may be possible with the use of newer medications that have no or low resistance rates.

7. Although there is growing evidence that some types of combination therapy may decrease the chance that drug resistance will develop and increase the likelihood of long-term success in preventing graft loss and death, additional research will be required to determine which combinations will work well in the long term, and which will not. Liver Transpl 12:S54–S64, 2006. © 2006 AASLD.
Medical informatics in context
Authors: Morris Theodore Allan , Assar Soraya , Detlefsen Ellen Gay , McKnight Michelynn
Published: October 2006

Medical informatics may be defined as “the application of information science and information technology to the theoretical and practical problems of biomedical research, clinical practice, and medical education.” As such, it has become increasingly important as a unifying force‐and forum for exchange‐among cognate and contributory fields in biomedicine and information science. Accordingly, increasing numbers of knowledge workers are involved in or affected by medical informatics‐related programs and activities.

This program will provide an overview of the field of medical informatics and illustrate how it “fits in” with other knowledge domains.

The panelists will discuss the roles and relationships among medical informatics, bioinformatics, information science, and medical librarianship, and their implications for research, application, and education.
Design and evaluation of a prototype user interface supporting sharing of search knowledge in information retrieval
Authors: Zhang Xiangmin , Li Yuelin , Jewell Sarah
Published: October 2006

This paper describes a prototype user interface system, CIRR tool, which allows searchers to share their relevance judgments, search queries, and search results by providing a system Task Console with a “Group Report” feature. The system was developed based on the assumption that knowledge sharing in information retrieval (IR) is helpful and important to improve search performance. A usability evaluation of this system was conducted. The test results show that in general the system is easy to learn and use. However, some usability problems are also observed. The paper discusses these issues and proposes future research directions.
Virtual reference for video collections: System infrastructure, user interface and pilot user study
Authors: Mu Xiangming , Luo Lili
Published: October 2006

A new video‐based Virtual Reference (VR) tool called VideoHelp was designed and developed to support video navigation escorting, a function that enables librarians to co‐navigate a digital video with patrons in the web‐based environment. A client/server infrastructure was adopted for the VideoHelp system and timestamps were used to achieve the video synchronization between the librarians and patrons. A pilot usability study of using VideoHelp prototype in video seeking was conducted and the preliminary results demonstrated that the system is easy to learn and use, and real‐time assistance from virtual librarians in video navigation is desirable on a conditional basis.
Managing and disseminating scientific data and information: A technical discussion
Authors: Qin Jian , Carroll Bonnie , Futrelle Joe , Jablonski Jon , Shawa Tsering Wangyal
Published: October 2006

The management of scientific data and information is becoming increasingly important as the data volume grows rapidly. Scientific data management is affected by many factors in policy, legal, and technical areas. What is involved in scientific data management? What is the status of research and development in this area? How are libraries and information institutions responding to this new area of collections and services? This panel brings experts in this area to address some of these questions.
Surveys of scientists and engineers: Ensuring reliable research evidence for good practice
Authors: Vaughan K. T. L. , Tenopir Carol , Brown Cecelia , Hemminger Bradley M. , Jablonski Jon
Published: October 2006

Information scientists around the globe have made tremendous progress in understanding how scientists and engineers find and use information by through the use of a wide variety of survey instruments. Librarians and publishers increasingly turn to the data generated by these instruments in an effort to design and implement information products and services that the scientific community needs and desires. Three researchers experienced in studying the information seeking behavior of academics will describe their current investigations distinguishing between the survey mechanisms found to be effective or ineffective. Discussion will be led and provoked by the moderator and reactor who both have experience providing library services to this community. The last third of the session will be an open discussion soliciting comments and questions about trends, survey design, and survey experiences.
Dual‐task performance as a measure of mental effort in searching a library system and the Web
Authors: Kim Yong‐Mi , Rieh Soo Young
Published: October 2006

This paper examines a dual‐task method for the assessment of mental effort during online searching, having the users engage in two tasks simultaneously. Searching was assigned as a primary task and a visual observation was set up as a secondary task. The study participants were asked to perform two searches, one on the Web and the other in a web‐based library system. Perceived search difficulty and mental effort for searching on the two types of systems were compared through participant self‐reports, dual‐task performance, and search log analysis. After the searches were completed, the subjects reported that library searching was more difficult to conduct and they had to concentrate more than when Web searching. However, the results of dual‐task performance do not reveal much difference in mental effort or concentration during searches in the two systems. Rather, they invested mental effort differently when viewing search results and reading retrieved documents. The findings indicate that a dual‐task method provides a useful technique to measure mental effort in online searching, and it has a great potential to be used to measure other aspects of information retrieval such as task complexity and multitasking information behavior.
Research classics and citation analysis
Authors: Wang Peiling , Bownas Jennifer
Published: October 2006

Research classics are recognized important works in a field. Citing authors' comments along with the classics were analyzed along with citation counts to identify the use contexts. In‐depth citation analysis of 11 highly cited classics show unusual longevity as highly cited works, strong associations with high co‐citations, a number of image‐makers contributing extremely high recitations, and diversity of citing journals. The nature of the classics was also investigated to shed lights on the success of the classics, reasons for low rate of citations to certain classics.
A hybrid approach to faceted classification based on analysis of descriptor suffixes
Authors: Loehrlein Aaron , Jacob Elin K. , Yang Kiduk , Lee Seungmin , Yu Ning
Published: October 2006

This study explores the construction of a faceted vocabulary that can be used as a mechanism for organizing Web‐based resources. After analyzing the manual process of faceted vocabulary construction using existing organizational structures to identify heuristics for automating the construction process, we modeled a hybrid, semi‐automatic approach to facet generation that integrates the strengths of manual and automatic methods. This approach is based on the organization of terms according to the meanings of their suffixes. Although this heuristic could not usefully organize the majority of terms of the lexicon bases to which it was applied, it nevertheless shows promise as a component of hybrid classification.
The digital museum in the life of the user
Authors: Chen Hsin‐liang , Marty Paul F.
Published: October 2006

This panel will explore the fascinating issue of the “digital museum in the life of the user.” As online museums, digital museum collections, and enhanced gallery devices become more common, it is important that we improve our understanding of how museum visitors make use of digital museum resources, online and in house. This panel, therefore, will discuss approaches to and the need for a better understanding of the users and usage of digital museums.
From prototype to deployable system: Framing the adoption of digital library services
Authors: D'Avolio Leonard W. , Borgman Christine L. , Champeny Leslie , Leazer Gregory H. , Gilliland Anne J. , Millwood Kelli A.
Published: October 2006

The Alexandria Digital Earth Prototype Project (ADEPT) is a 5‐year (1999–2004) effort, with a goal of developing effective models for implementing digital libraries in undergraduate instruction. The ADEPT team has created a digital learning environment (DLE) that adds educational value to a digital library by offering a suite of services for teaching. Encouraged by the results of implementations in undergraduate geography classrooms, the team now shifts its focus from experimental prototype to deployable system. Everett Rogers' Diffusion of Innovations theories are used as frameworks for analyzing this complex transition. Recommendations for lowering the barriers to adoption related to complexity, trialability, and observability include the prioritization of development efforts focused on stabilizing the system, the creation of documentation and an online demonstration, and anonymous logins to the system. To increase perceived relative advantage, existing technical and copyright issues in integrating the Alexandria Digital Library must be overcome. To increase compatibility, the speed at which pedagogical change is achieved must be rethought. Finally, recruitment efforts should focus on innovators and early adopters before moving on to early majority, late majority, or laggard adopters.