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PubMed1989

Interaction of unfused tricyclic aromatic cations with DNA: a new class of intercalators.

Unfused tricyclic aromatic ring systems 1-6 with one or two cationic side chains have been synthesized and their interactions with DNA and synthetic polymers probed with a variety of techniques. Molecular mechanics calculations indicate that the torsional angle between ring planes in the minimum energy conformation of the tricyclic molecules can range from 0 degree to as high as 50 degrees depending on the type of rings and substituents. Viscometric titrations with linear and supercoiled DNA, linear dichroism, and NMR studies indicated that all compounds with torsional angles of approximately 20 degrees or less bind to DNA by intercalation. The more highly twisted intercalators caused significant perturbation of DNA structure. Unfused intercalators with twist angles of approximately 20 degrees have reduced binding constants, suggesting that they could not form an optimum interaction with the DNA base pairs. Unfused intercalators with twist less than 20 degrees formed strong complexes with DNA. The structures of these unfused intercalators are more analogous to typical groove-binding molecules, and an analysis of their interaction with DNA provides a better understanding of the subtle differences between intercalation and groove-binding modes for aromatic cations. The results indicate that intercalation and groove-binding modes should be viewed as two potential wells on a continuous energy surface. The results also suggest design strategies for intercalators that can optimally complement DNA base pair propeller twist or that can induce bends in DNA at the intercalation site.

Cations↗
PubMed1995

Anti-human immunodeficiency virus (HIV) activities of halogenated gomisin J derivatives, new nonnucleoside inhibitors of HIV type 1 reverse transcriptase.

Halogenated gomisin J (a derivative of lignan compound), represented by the bromine derivative 1506 [(6R, 7S, S-biar)-4,9-dibromo-3,10-dihydroxy-1,2,11,12-tetramethoxy-6, 7-dimethyl-5,6,7,8- tetrahydrodibenzo[a,c]cyclo-octene], was found to be a potent inhibitor of the cytopathic effects of human immunodeficiency virus type 1 (HIV-1) on MT-4 human T cells (50% effective dose, 0.1 to 0.5 microM). Gomisin J derivatives were active in preventing p24 production from acutely HIV-1-infected H9 cells. The selective indices (toxic dose/effective dose) of these compounds were as high as > 300 in some systems. 1506 was active against 3'-azido-3'-deoxythymidine-resistant HIV-1 and acted synergistically with AZT and 2',3'-ddC. 1506 inhibited HIV-1 reverse transcriptase (RT) in vitro but not HIV-1 protease. From the time-of-addition experiment, 1506 was found to inhibit the early phase of the HIV life cycle. A 1506-resistant HIV mutant was selected and shown to possess a mutation within the RT-coding region (at position 188 [Tyr to Leu]). The mutant RT expressed in Escherichia coli was resistant to 1506 in the in vitro RT assay. Some of the HIV strains resistant to other nonnucleoside HIV-1 RT inhibitors were also resistant to 1506. Comparison of various gomisin J derivatives with gomisin J showed that iodine, bromine, and chlorine in the fourth and ninth positions increased RT inhibitory activity as well as cytoprotective activity.

Antiviral Agents↗
PubMed1995

Distribution of toxic and radiation components in air particulates.

The concentrations of several toxic heavy metals and volatile organic compounds (VOCs) in various types of Hungarian fly-ash fine particulates were investigated by means of instrumental neutron activation analysis, X-ray fluorescence analysis and gas chromatography, coupled with mass spectrometry. Within a power station, particulate samples were taken from the boiler zone (BO), from the electrostatic dust filter chamber (FI) and from the flue-gas at the top of the stack (ST). Enrichment rates of the toxic metals both in FI and ST particulate fractions related to the BO concentrations were calculated to enable the temperature dependence on the adsorption of the toxic components to be studied. In addition, both the total amounts of the VOCs and their partial distributions in accordance with the number of carbon atoms were also studied in fly-ash particulates. From them, 31 organic species were identified and determined. Since Hungarian brown coals have high uranium and thorium contents, the specific radioactivities of the daughter isotopes of both the 232Th and 238U decay series were also measured and are discussed.

Air Pollutants↗
PubMed1986

Genotoxicity and polynuclear aromatic hydrocarbon analysis of environmental tobacco smoke samples from restaurants.

Acetone-extracted samples of airborne particulate matter collected in three restaurants were analysed for their content of polynuclear aromatic hydrocarbons (PAH) and related polynuclear aromatic compounds (PAC) as well as for genotoxic activity using the Salmonella/microsome assay (strains TA98 and TA100) and sister chromatid exchange (SCE) induction in Chinese hamster ovary (CHO) cell cultures. The total particulate matter varied considerably in the restaurants, being 1.37 mg/m3 at the highest; in the same restaurant the highest amount of total PAHs (168 ng/m3) was also detected. Altogether, 13-22 individual PACs were identified in the samples, ranging from phenanthrene to benzothionaphthene. All of the six samples caused significant increases both in bacterial revertant and SCE frequencies. In the Salmonella assay, the mutagenic activity detected was primarily with metabolic activation. However, in the CHO cell cultures the induction of SCEs was also seen without an exogenous metabolic activation system. The cytotoxicity of the extracts limited the concentration range tested in the SCE assay. Only a partial correspondence of the total PAH content with the genotoxic activity of the samples was found. The genotoxicity of restaurant air exceeded by one to two orders of magnitude the previously reported activities detected by similar methods in urban outdoor and indoor air samples.

Animals↗
PubMed1999

Methylenedioxy group and cyclooctadiene ring as structural determinants of schisandrin in protecting against myocardial ischemia-reperfusion injury in rats.

As a preliminary investigation to exploring whether the methylenedioxy group and the cyclooctadiene ring of the dibenzo[a,c]cyclooctadiene (schisandrin) molecule plays an important role in the protection against myocardial ischemia-reperfusion (IR) injury, we examined the effects of three schisandrins, namely schisandrin A (Sch A), schisandrin B (Sch B), and schisandrin C (Sch C), and the effect of dimethyl-4,-4'-dimethoxy-5,6,5',6'-dimethylene-dioxy-biphenyl-2,2' -bicarboxylate (DDB), an intermediate compound derived from the synthesis of Sch C, on myocardial IR injury in isolated Langendorff-perfused rat hearts. While pretreating rats with Sch A or DDB at a daily oral dose of 1.2 mmol/kg for 3 days did not protect the isolated-perfused hearts against IR-induced damage, pretreatment with Sch B or Sch C at the same dosage regimen produced cardioprotective action. The extent of cardioprotection afforded by Sch B or Sch C pretreatment correlated well with the degree of enhancement in myocardial glutathione antioxidant status, as indicated by significant increases in the tissue-reduced glutathione level and Se-glutathione peroxidase (EC 1.11.1.9), glutathione transferases (EC 2.5.1.18), and glutathione reductase (EC 1.6.4.2) activities in ischemic-reperfused hearts when compared with the unpretreated IR control. Our results indicate that both the methylenedioxy group and the cyclooctadiene ring of the schisandrin molecule are important structural determinants in mediating the protection against myocardial IR injury.

Animals↗
PubMed2002

Dietary exposure of finfish to aromatic contaminants and tissue distribution.

Large rainbow trout (400 g) were exposed to food pellets spiked with four polycyclic aromatic compounds (PACs). Muscle, liver, internal organs, fatty tissue, and blood were analyzed after 5, 10, 15, and 19 weeks for PAC, lipid, and moisture content. At all collection times, concentrations expressed on a per gram basis were higher in fatty tissue and internal organs, followed by liver and muscle, and lowest levels were observed in blood. When examining the tissue burden, the highest bioaccumulations of carbazole, dibenzofuran, dibenzothiophene, and fluorene were in muscle and internal organs, intermediate in fatty tissue, and lowest in blood and liver. Carbazole with the lowest log K(OW) showed the lowest concentration within any tissue. Levels in tissues were significantly correlated to log K(OW) (> 5% level of significance), especially with longer exposure, and were more highly correlated when examining muscle, fatty tissue, and internal organs (> 0.05%). Different tissues displayed different time trends, and ratios between organs help determine the length of exposure. The most striking change in levels observed with time was in internal organs relative to other tissues, particularly when compared to daily exposure. The elimination of contaminants in feces and gallbladder bile was also compared, because they represent additional tools to assess recent exposure.

Animals↗
PubMed1985

The role of receptors in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity.

There is good evidence that the Ah-(TCDD-) receptor plays a role in the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and its congeners. TCDD and other chlorinated aromatic hydrocarbons with chlorine atoms in lateral positions (2,3,7,8-tetrachlorodibenzofuran, 3,3',4,4'-tetrachloroazoxybenzene, 3,3',4,4'(5,5')-tetra(hexa)chlorobiphenyl), all bind to the receptor and show a similar pattern of toxicity, although there is a wide range in potency. The Ah-receptor is viewed as the major product of the regulatory gene of the Ah-locus in the mouse. Several of the toxicities of TCDD and congeners (teratogenesis, thymic involution and hepatic porphyria) have been shown to segregate with the Ah-locus. In vitro studies using keratinizing cells or fetal thymus organ culture have shown a good correlation between activity as ligands of the receptor and toxicity for the compounds discussed. The great differences in toxic potency of these compounds in vivo may therefore be a result of variation in rate of metabolism and excretion rather than differences in affinity for the Ah-receptor. The physiological role of the Ah-receptor is discussed, whether it has developed as a response to exposure to toxic substances in the environment, as a means of induction of P-450-dependent polysubstrate mono-oxygenase activities in order to make those substances more liable for excretion--or is there a physiological ligand? TCDD has a long half-life in the body, and a sustained competition for binding to the receptor between TCDD and a ligand of importance for normal cell functions may result in toxicities such as the wasting syndrome. This tentative ligand could be of varying importance in different species, which might explain the great variation in sensitivity between species, the hamster being about 5000 times less sensitive than the guinea pig.

Abnormalities, Drug-Induced↗
PubMed2003

Influence of heavy metals on the formation and the distribution behavior of PAH and PCDD/F during simulated fires.

Combustion experiments were performed with an artificial fire load (polystyrene and quartz powder) in a laboratory scale incinerator in the presence of gaseous HCl to simulate accidental fire conditions. The aim of this investigation was to trace back the alterations of the formation and the distribution behavior of PAH and PCDD/PCDF to the presence of CuO or a mixture of metal oxides (CdO, CuO, Fe(2)O(3), PbO, MoO(3), ZnO). The total amount of the 16 PAH target compounds was reduced by the factor of 5-9 when the mixture of metal oxides was present rather than merely CuO. PAH patterns as well as their distribution behavior were significantly influenced by these oxides. In general, transportation inside the installation was enhanced for most of the 16 analyzed PAH. Only fluorene and dibenzo[a,h]anthracene were transported to a smaller extent. In contrast to PAH, total concentrations of PCDD were increased by factor 9 and of PCDF by factor 10, respectively, when CuO was present. Adding the mixture of metal oxides resulted in an increase of PCDD by factor 14 and of PCDF by factor 7. CuO and the mixture of metal oxides had a different influence on the PCDD/F homologue patterns. For instance, the HxCDF to OCDF ratio after incineration without any metal oxide was 1 to 6, whereas addition of CuO or the mixture of the metal oxides shifted the HxCDF to OCDF ratios towards 1 to 40 or 1 to 17, respectively. Combustion along with CuO increased transportation of higher chlorinated PCDF congeners, whereas the mixture of the metal oxides caused a strong decrease of PCDF distribution throughout the system.

Fires↗
PubMed1996

Cytochrome P4501A induction in avian hepatocyte cultures: a promising approach for predicting the sensitivity of avian species to toxic effects of halogenated aromatic hydrocarbons.

Concentration-dependent effects of halogenated aromatic hydrocarbons (HAHs) on cytochrome P4501A (CYP1A) induction in primary hepatocyte cultures prepared from embryos of chickens (four breeds), pheasants, turkeys, ducks (three breeds), and herring gulls were determined. CYP1A activity was estimated by measuring ethoxyresorufin O-deethylase (EROD) activity and the concentration of immunodetectable CYP1A was estimated using mouse monoclonal antibody 1-12-3 that was prepared against scup (Stenotomus chrysops) CYP1A1. The HAHs studies were 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 3,3',4,4'-tetrachlorobiphenyl (PCB 77, IUPAC nomenclature), 3,4,4',5-tetrachlorobiphenyl (PCB 81), 3,3',4,4',5-pentachlorobiphenyl (PCB 126), 3,3',4,4',5,5'-hexachlorobiphenyl (PCB 169), 2,3,3',4,4'-pentachlorobiphenyl (PCB 105), and 2,3',4,4',5-pentachlorobiphenyl (PCB 118). Two general types of comparisons were made: (1) relative potencies of compounds within a species (expressed relative to TCDD as induction equivalency factors, IEFs) and (2) relative sensitivity of each species to EROD induction by each compound. Three methods for estimating potency were compared. These were: (1) the concentration of inducer that produced a half-maximal (EC50) EROD response, (2) the concentration producing a response equivalent to 10% of the maximal response produced by TCDD (ECTCDD 10%), and (3) a slope ratio method. For each method, the rank order in potency was TCDD > or = TCDF > PCB 126 > PCB 81 > PCB 77 > PCB 169 in chicken, pheasant, and turkey hepatocytes. The rank order was similar in duck and herring gull hepatocytes with the following exceptions: TCDF was approximately 2- to 4-fold more potent than TCDD in duck hepatocytes; PCB 169 induced EROD in gulls, but PCB 77 had no measurable effect in this species. PCB 118 was a relatively weak EROD inducer in most species/breeds, but it did not induce EROD in Pekin ducks or gulls. PCB 105 was a weak inducer in White Leghorn chicken and turkey hepatocytes, but it did not induce EROD in other species. The EC50, ECTCDD10% and slope ratio methods for estimating potencies generally gave similar IEFs for compounds that produced a maximal response that was at least 60% of the maximal response produced by TCDD. For compounds that caused a response that was 50% or lower than that produced by TCDD, EC50-based IEFs were greater (10- to 100-fold) than ECTCDD10%-based IEFs or slope-ratio-based IEFs. Among species, the rank order in sensitivity to EROD induction was chicken > pheasant > turkey > or = duck > or = herring gull. The relative sensitivity of avian hepatocyte cultures to EROD induction by PCB 77 was similar to the relative sensitivity of these species (reported elsewhere) to lethality after in ovo injection of PCB 77. Chicken hepatocyte cultures were 5-10 times more sensitive to EROD induction by TCDD than were pheasant hepatocyte cultures, which is identical to the difference in sensitivity of these species to the lethal effect of TCDD after in ovo injection. Measuring the sensitivity of hepatocyte cultures to EROD induction might be useful for estimating the sensitivity of avian species (including rare or endangered species, where it is impossible to conduct in vivo studies) to the embryotoxic effects of TCDD, non-ortho substituted PCBs, and other aryl hydrocarbon receptor agonists.

Animals↗
PubMed1991

Interrelationships between bioaccumulation of organic trace pollutants (PCBs, organochlorine pesticides and PAHs), and MFO-induction in fish.

1. Hydrophobic compounds that are more easily biotransformed (e.g. PAHs) generally show less bioaccumulation in fish than the more persistent PCBs and DDTs. 2. In lake Nieuwe Meer, with the highest levels of organic micropollutants, the hepatic MFO activity was elevated in three fish species. This indicates that MFO activity might be a sensitive indicator for organic micropollutants in the aquatic environment. 3. Activities of the 3-MC type inducible isozymes were most pronounced in all three fish species studied. Though further research is required, indications for the existence of a PB-type inducible enzyme system have been demonstrated for two fish species, i.e. pike and eel. 4. Fish liver enlargement as a consequence of MFO induction could not be demonstrated in fish from the most polluted lake. 5. In fish, a correlation was observed between PCB or OCP tissue concentrations on the one hand, and hepatic MFO activities on the other. The low PAH fish/sediment ratios are further reduced when MFO systems are induced due to organic micropollution. The interrelationship between bioaccumulation and enzyme induction demonstrates the importance of an integrated study of these phenomena in field research.

Animals↗
PubMedDate not supplied

The acrosome reaction-inducing effect of human follicular and oviductal fluid.

The human sperm acrosome reaction (AR) can be induced in vitro by a variety of naturally occurring and synthetic compounds. The present investigation determined the effect of human natural cycle periovulatory follicular (hFF) and oviductal fluids (hOF) on the human sperm AR in dose-response fashion using the synchronous AR assay. When hFF (30% v/v) or hOF (40% v/v) was added to non-capacitated spermatozoa, no significant (P > 0.05) increase in the % AR was detected in comparison to the non-treatment control. When either of these compounds was added (10%, 20%, and 30% v/v hFF; 20%, 30%, and 40% v/v hOF) to capacitated spermatozoa (3 hour incubation), a significant (P < 0.05) stimulation of the AR was detected. Bovine oviductal fluid (bOF) was tested (20%, 30%, and 40% v/v) to determine if it might have an effect similar to hOF. In contrast to hOF, the highest concentration of bOF (40% v/v) tested failed to stimulate a significant (P > 0.05) increase in the % AR of capacitated spermatozoa in comparison to control. Inhibitors of protein kinases A (KT5720) and C (calphostin C) were tested to determine their effects on the hFF-induced AR. In comparison to hFF treatment alone, the kinase A inhibitor KT5720 (50 nM, 100 nM) prevented hFF (20%) stimulation of the AR when added at the end of the capacitation period and 5 minutes prior to the addition of inducer. Similarly, the kinase C inhibitor calphostin C (50 nM, 100 nM) prevented hFF (20%) stimulation of the AR. The present data demonstrate that periovulatory hFF and hOF stimulate the human sperm AR.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrosome↗
PubMed1989

The effect of gomisin A on immunologic liver injury in mice.

The hepatoprotective effect of Gomisin A (TJN-101), which is a lignan compound isolated from Schizandra fruits, was studied on three immunologic liver injury models in mice. The first liver injury model was produced by the injection of anti-basic liver protein (BLP) antibody into DBA/2 mice which had been previously immunized with rabbit IgG (RGG). Other models were effected by injection of anti-liver specific protein (LSP) antibody into DBA/2 mice or by the injection of bacterial lipopolysaccharide (LPS) into ddY mice pretreated with Corynebacterium parvum (C. parvum). TJN-101 inhibited the elevation of transaminase (GOT and GPT) activities and showed the tendency to inhibit the histopathological changes of the liver in all models. Moreover, TJN-101 inhibited deoxycholic acid-induced release of transaminase from cultured rat hepatocytes in vitro, but did not affect the formation of hemolytic plaque forming cells in immunized mice spleens and hemolytic activity of guinea pig complement in immunohemolysis reaction. These results, therefore, suggested that the hepatoprotective effect of TJN-101 could be related to the protecting effect of hepatocyte plasma membrane rather than the inhibiting effects of the antibody formation and complement activity.

Alanine Transaminase↗
PubMed1992

Effect of calmodulin and protein kinase C inhibitors on globally ischemic rat hearts.

Several calmodulin inhibitors have been reported to be cardioprotective, but the ability of these compounds to inhibit protein kinase C (PKC) suggests that calmodulin inhibition may not be the sole mechanism responsible. To distinguish between the effects, we determined the cardioprotective activity of several calmodulin inhibitors with differing PKC inhibitory potencies in isolated globally ischemic rat hearts. Twenty-five minutes of global ischemia caused significant myocardial dysfunction, contracture formation, and lactate dehydrogenase (LDH) release on reperfusion in vehicle-treated hearts. The calmodulin inhibitors trifluoperazine, W-7, calmidazolium, W-13, and CGS 9343B improved postischemic contractile function and/or reduced LDH release. They also reduced preischemic cardiac function, although cardioprotection did not appear to be correlated with cardiodepression. Calmodulin inhibitors increased preischemic coronary flow (CF) and decreased heart rate (HR), but controlling these parameters did not affect the cardioprotection. Pretreatment of ischemic hearts with trifluoperazine was associated with preservation of myocardial ATP. Pretreatment of ischemic rat hearts with the PKC inhibitors staurosporine, calphostin C, polymyxin B, and H-7 did not result in cardioprotection. Thus, calmodulin inhibition causes cardioprotection that appears to be independent of PKC inhibition.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2004

Influence of the carbon/nitrogen/phosphorus ratio on polycyclic aromatic hydrocarbon degradation by Mycobacterium and Sphingomonas in soil.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in the environment is often limited due to unfavorable nutrient conditions for the bacteria that use these PAHs as sole source of carbon and energy. Mycobacterium and Sphingomonas are 2 PAH-degrading specialists commonly present in PAH-polluted soil, but not much is known about their specific nutrient requirements. By adding different inorganic supplements of nitrogen (N) and phosphorus (P), affecting the overall carbon/nitrogen/phosphorus ratio of soil in soil slurry degradation tests, we investigated the impact of soil inorganic N and P nutrient conditions on PAH degradation by PAH-degrading Sphingomonas and Mycobacterium strains. The general theoretically calculated C/N/P ratio of 100/10/1 (expressed in moles) allowed rapid PAH metabolization by Sphingomonas and Mycobacterium strains without limitation. In addition, PAH-degradation rate and extent was not affected when ca. ten times lower concentrations of N and P were provided, indicating that Sphingomonas and Mycobacterium strains are capable of metabolizing PAHs under low nutrient conditions. Nor does PAH-degradation seem to be affected by excesses of N and P creating an imbalanced C/N/P ratio. However, supplements of N and P salts increased the salinity of soil slurry solutions and seriously limited or even completely blocked biodegradation.

Biodegradation, Environmental↗
PubMed1989

Effects of prototypic PCBs on benzo[a]pyrene mutagenic activity related to vitamin A intake.

The effects of vitamin A dietary intake (2 and 20 IU */g of food) on the mutagenic activity of benzo[a]pyrene (B(a)P) toward Salmonella typhimurium (TA98) were studied either in control rats or in animals treated by the PCB congeners 2,4,5,2',4',5'-hexachlorobiphenyl [2,4,5)2Cl) and 3,4,3',4'-tetrachlorobiphenyl [3,4)2Cl). (3,4)2Cl (a planar compound) strongly increased B(a)P monooxygenase (B(a)PMO) activity and glutathione transferase, (2,4,5)2Cl (a non-planar PCB) was a strong inducer of epoxide hydrolase and a weak inducer of B(a)PMO. Enzyme induction was not modified by changes in vitamin A dietary intake. A higher mutagenic effect was observed in the (3,4)2Cl group than in the (2,4,5)2Cl one. This could be related to the specific form of cytochrome P-450 induced by (3,4)2Cl. In the untreated animals, the activation of B(a)P was higher in the 2-IU group than in the 20-IU one. Conversely, in PCB-treated rats the mutagenic activity of B(a)P was higher in the 20-IU group than in the 2-IU one. PCB induction increased the liver content of vitamin C in both the 2-IU and the 20-IU groups but only increased the glutathione levels in the 2-IU groups. This suggests that glutathione content in cellular fractions may be one of the determining parameters for the mutagenic activity of B(a)P.

Animals↗
PubMed2003

Determination and comparison of nitrated-polycyclic aromatic hydrocarbons measured in air and diesel particulate reference materials.

The National Institute of Standards and Technology has issued numerous environmental matrix standard reference materials (SRMs) for the measurement of polycyclic aromatic hydrocarbons; however, only one SRM (diesel particulate material) was issued with certified and reference values for four nitrated-polycyclic aromatic hydrocarbons (nitro-PAH). The objective of this study was to develop an improved analytical procedure to quantify 28 mononitro- and dinitro-PAHs, including numerous isomers, in air and diesel particulate SRMs. Two air particulate matrix SRMs, SRM 1649a Urban Dust and SRM 1648 Urban Particulate Matter, and fine particulate matter, collected from Baltimore MD for use as an "interim reference material" for the determination of organic contaminants, have been characterized for nitro-PAHs. Concentrations of nitro-PAHs in all three air particulate materials were at the ng/g level with the highest nitro-PAH concentration being 2-nitrofluoranthene (range between 246 and 340 ng/g). For the three diesel particulate-related SRMs, SRM 1650a Diesel Particulate Matter, SRM 1975 Diesel Particulate Extract, and SRM 2975 Diesel Particulate Matter (Industrial Fortlift), concentrations of nitro-PAHs were in the microg/g range, with 1-nitropyrene as the dominant nitro-PAH (range between 18 and 40 microg/g). Distinct nitro-PAH isomer patterns were present between the air and diesel particulate materials. These results will provide isomer identification and reference concentrations for a large number of nitro-PAHs in the existing diesel and air particulate SRMs. Published by Elsevier Science Ltd.

Air Pollutants↗
PubMedDate not supplied

Toxicity evaluation of petroleum blending streams: inhalation subchronic toxicity/neurotoxicity study of a light catalytic cracked naphtha distillate in rats.

A 15-week, whole-body inhalation study of the vapors of a distillate (LCCN-D) of light catalytic cracked naphtha (CAS no. 64741-55-5, LCCN) was conducted with Sprague-Dawley rats. Target exposure concentrations were 0, 750, 2500, and 7500 ppm for 6 hours/day, 5 days/week. Over the course of the study, animals received at least 65 exposures. For a portion of the control and 7500-ppm groups, a 4-week postexposure period was included in the study. Subchronic toxicity was evaluated using standard parameters. During life, neurotoxicity was evaluated by motor activity assessment and a functional observational battery. Selected tissues from animals in all exposure groups were examined microscopically. Neuropathologic examination of selected neuronal tissues from animals in the control and high-exposure groups was also conducted. No compound-related effects were seen on survival, clinical chemistry, food consumption, or physical signs. No evidence of neurotoxicity was seen at any exposure level. Slight decreases in hematocrit and hemoglobin concentrations were seen in male rats at the end of exposure to 7500 ppm LCCN-D. However, values were within normal physiological ranges and recovery occurred. Slight decreases in mean body weights and body weight gain were observed in high-exposure females during the first 7 weeks of exposure, but this decrease was not seen during the second half of the study. Male rat nephropathy involving hyaline droplet formation and alpha-2micro-globulin accumulation was seen in mid- and high-exposure males, an effect not relevant to humans. The incidence and severity of goblet cell hypertrophy/hyperplasia and respiratory epithelium hyperplasia in nasoturbinal tissues were greater in high-exposure animals, but recovery occurred. None of the effects observed were considered toxicologically significant. The no-observable-adverse-effect level (NOAEL) for subchronic and neurotoxicity of LCCN-D was > or = 7500 ppm.

Alkanes↗
PubMed1993

Aromatic hydrocarbon binding to cytochrome P450 and other enzyme binding sites: are hydrophobic compounds drawn into the active site or pushed from the aqueous phase?

The subject of hydrocarbon inhibition of cytochrome P450-dependent reactions as well as data on other enzyme-catalyzed reactions from the literature was examined to determine the relationship between the "hydrophobicity" of the hydrocarbons and their ability to act as inhibitors. The compounds used in these studies (benzene, toluene, ethylbenzene, n-propylbenzene, and n-butylbenzene) behave as competitive inhibitors, with the affinity increasing as the size of the inhibiting hydrocarbon increases. A similarity was seen in the size dependence for both hydrocarbon inhibition of cytochrome P450-dependent activities (-0.6 to -0.7 kcal/mol/methylene group) and transfer of these compounds between aqueous and organic phases (-0.68 kcal/mol/methylene group), suggesting that the active site of cytochrome P450, in some ways, is comparable to an organic solvent in its ability to accommodate hydrophobic compounds. A more detailed examination of this process was initiated to separate the "hydrophobic effect" into its two component processes: (i) hydration of the hydrocarbon ligand and (ii) transfer of the unhydrated hydrocarbon onto the enzyme active site. In other words, do larger hydrocarbons bind more avidly to the active site because they are drawn more effectively into that site (pull), or is the size-dependent increase in hydrocarbon binding the result of the larger compounds being more efficiently expelled from the aqueous medium (push)? The results indicate that the predominant force involved in binding is the ability of the active site of cytochrome P450 and an impressive number of other enzymes to draw the hydrocarbon from the aqueous medium. The hydration of the hydrocarbon is much less dependent on the size of the hydrocarbon, indicating that dehydration or partial dehydration of the hydrocarbon molecule (upon leaving the solution and combining with the enzyme) contributes to the overall binding process to a much lesser extent; hydrophobic binding in the most widely used sense (entropy driven) is not the primary driving force that is responsible for the observed size dependence effects. It is pointed out that not all types of binding would be expected to follow the law which describes the size dependence for simple hydrocarbons because of heat-entropy relationships. The different temperature dependence of these heat-entropy relationships further complicates the analogy between enzyme-ligand binding and ligand partitioning between aqueous and organic phases. The maximum contribution that can be attributed to entropy driven hydrophobic binding (in the most widely used sense) is -0.1 to -0.2 kcal/mol/methylene group for the aromatic hydrocarbons examined here.

Animals↗