Optimal design for the precise estimation of an interaction threshold: the impact of exposure to a mixture of 18 polyhalogenated aromatic hydrocarbons.

Traditional additivity models provide little flexibility in modeling the dose-response relationships of the single agents in a mixture. While the flexible single chemical required (FSCR) methods allow greater flexibility, its implicit nature is an obstacle in the formation of the parameter covariance matrix, which forms the basis for many statistical optimality design criteria. The goal of this effort is to develop a method for constructing the parameter covariance matrix for the FSCR models, so that (local) alphabetic optimality criteria can be applied. Data from Crofton et al. are provided as motivation; in an experiment designed to determine the effect of 18 polyhalogenated aromatic hydrocarbons on serum total thyroxine (T(4)), the interaction among the chemicals was statistically significant. Gennings et al. fit the FSCR interaction threshold model to the data. The resulting estimate of the interaction threshold was positive and within the observed dose region, providing evidence of a dose-dependent interaction. However, the corresponding likelihood-ratio-based confidence interval was wide and included zero. In order to more precisely estimate the location of the interaction threshold, supplemental data are required. Using the available data as the first stage, the Ds-optimal second-stage design criterion was applied to minimize the variance of the hypothesized interaction threshold. Practical concerns associated with the resulting design are discussed and addressed using the penalized optimality criterion. Results demonstrate that the penalized Ds-optimal second-stage design can be used to more precisely define the interaction threshold while maintaining the characteristics deemed important in practice.

Heterocyclic aromatic amine [HCA] intake and prostate cancer risk: effect modification by genetic variants.

The association between heterocyclic aromatic amine (HCA) intake and prostate cancer (PCa) risk may be modified by genetic variation in enzymes involved in HCA metabolism. We examined this question in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition Heidelberg cohort. The study included 204 PCa cases and 360 matched controls. At baseline, participants provided dietary and lifestyle data and blood samples that were used for genotyping. Dietary HCA intake-2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP), 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx), and 2-amino-3,4,8-dimethylimidazo [4,5-f]quinoxaline (DiMeIQx-was estimated using information on meat consumption, cooking methods, and browning degree. Risk estimates for gene × HCA interactions were calculated by unconditional logistic regression. We found inverse associations between PhIP, MeIQx, or DiMeIQx intake and PCa risk when having <2 deletions of the GSTT1 and GSTM1 genes (P(interaction): 0.03, 0.01, and 0.03, respectively), which is supported by analysis of darkly browned meat consumption data. Statistically significant effect modification of both HCA (DiMeIQx) and darkly browned meat intake and PCa risk was observed for allelic variants of MnSOD (rs4880) (P(interaction): 0.02). Despite limitations due to study size, we conclude that the association between HCA intake and PCa risk could be modified by polymorphisms of GSTT1, GSTM1, and MnSOD.

Inhalation of computer duster spray among adolescents: an emerging public health threat?

BACKGROUND: Anecdotal reports and recent medical examiner and poison control center studies suggest that computer duster spray (CDS) inhalation is an emerging public health threat. However, there is a current dearth of empirical data on CDS use. OBJECTIVES: Study aims were to examine the prevalence, frequency, correlates, and modalities of CDS use among a treatment sample of antisocial youth. METHODS: A battery of standardized psychosocial instruments was administered via interview of 723 Missouri adolescents in residential care for antisocial behavior. RESULTS: Lifetime CDS use was prevalent (14.7%) in this young service population (97.7% of whom participated). CDS users were significantly more likely to report histories of perinatal injuries or illness, traumatic experiences, suicidality and physician-diagnosed mental illness, and evidenced higher levels of psychiatric symptoms, antisocial attitudes and behaviors, and polydrug use than CDS nonusers. CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE: CDS use was endemic in this treatment sample of adolescents and associated with a range of clinically significant comorbidities. Current findings describe an underrecognized and potentially dangerous form of substance misuse that has rarely been studied but that may be of growing importance.

Neurobehavioral effects of acute exposure to aromatic hydrocarbons.

This article reports the results of neurobehavioral tests on representative aromatic constituents, specifically C(9) to C(11) species. The testing evaluated effects in several domains including clinical effects, motor activity, functional observations, and visual discrimination performance. Exposures ranging from 600 to 5000 mg/m(3), depending on the molecular weights of the specific aromatic constituents, produced minor, reversible effects on the central nervous system (CNS), particularly in the domains of gait and visual discrimination. There was little evidence of effects at lower exposure levels. There was some evidence of respiratory effects at 5000 mg/m(3) in 1 study, and there were also minor changes in body weight and temperature. The CNS effects became less pronounced with repeated exposures, corresponding to lower concentrations in the brain of 1 representative substance, 1,2,4-trimethyl benzene (TMB). At high exposure levels, the alkyl benzenes apparently induced their own metabolism, increasing elimination rates.

Differential effects of topically applied formalin and aromatic compounds on neurogenic-mediated microvascular leakage in rat skin.

Various volatile organic compounds (VOCs) act as a causative agent of skin inflammation. We investigated the effect of topical application of several VOCs and formalin on microvascular leakage in rat skin. We tested capsaicin, which is a reagent that specifically causes the skin response via endogenously released tachykinins. Evans blue dye extravasation served as an index of the increase in skin vascular permeability. After shaving the abdomen, we applied formalin, m-xylene, toluene, styrene, benzene, ethylbenzene, acetone, diethyl ether, hexane, heptane, cyclohexane and capsaicin to the skin. At 40min after application, skin samples were collected. Among all of the VOCs tested, all of the aromatic compounds significantly produced skin microvascular leakage that was similar to formalin and capsaicin. We also investigated the skin responses seen after the intravenous administration of CP-99,994 (1.5 or 5mg/kg), which is a tachykinin NK1 receptor antagonist, ketotifen (1 or 3mg/kg), which is a histamine H1 receptor antagonist that stabilizes the mast cells, and the topical application of capsazepine (22.5 or 50mM), which is the transient receptor potential vanilloid 1 (TRPV1) antagonist. The response induced by formalin and capsaicin was completely inhibited by CP-99,994. On the other hand, the antagonist partially reduced the response induced by m-xylene, toluene and styrene by 39%, 50% and 46%, respectively. Capsazepine and ketotifen did not alter the response induced by formalin or any of the aromatic compounds. Like capsaicin, formalin and the aromatic compounds at least partially caused skin microvascular leakage, which was due to tachykinin NK1 receptor activation related to the release of tachykinins from the sensory nerve endings. However, it is unlikely that mast cells and TRPV1 play an important role in the skin response.

Derivation of a chronic reference dose and reference concentration for trimethylbenzenes and C9 aromatic hydrocarbon solvents.

Trimethylbenzenes (TMBs) and C9 aromatic hydrocarbon solvents are structurally similar and have similar toxicity. Based on a review of the entire TMB and C9 aromatic hydrocarbon solvents toxicology database, oral and inhalation studies were identified to serve as the basis for a Reference dose (RfD) and Reference concentrations (RfC). The RfD and RfC were derived using standard USEPA methods and assumptions. The RfD was calculated to be 0.4 mg/kg/day using a 90-day oral study that resulted in a NOAEL of 600 mg/kg/day, based on a lack of adverse effects at the highest dose level (reversible effects such as increased serum phosphorus levels and liver and kidney weights), along with a total uncertainty factor of 1000. For the RfC, three studies were considered based on different study designs and toxicological endpoints, including neurotoxicity, systemic toxicity, and potential developmental and reproductive toxicity. For all three studies, as the calculated RfCs were consistent (3-4 mg/m3), the most conservative RfC, 3mg/m3, was selected. The C9 aromatic hydrocarbon solvents referred to herein are based on chemistries assessed as part of the TSCA Section 4 Test Rule. These solvents contain primarily ethyl toluene and tri-methyl benzene isomers, but the specific compositions can vary based on feedstock and manufacturing process, thus, it is important to consider the composition of any specific solvent to assess similarity to that assessed in the TSCA Section 4 Test Rule program.

GW406381, a novel COX-2 inhibitor, attenuates spontaneous ectopic discharge in sural nerves of rats following chronic constriction injury.

There are several lines of evidence to suggest that cyclooxygenase-2 (COX-2) plays an important role in the generation and maintenance of neuropathic pain states following peripheral nerve injury. However, COX-2 inhibitors are generally ineffective in reversing mechanical allodynia and hyperalgesia in models of neuropathic hypersensitivity. Here, we have investigated the effects of GW406381, a novel COX-2 inhibitor, on mechanical allodynia, hyperalgesia and generation of spontaneous ectopic discharge in rats following chronic constriction injury (CCI) of the sciatic nerve and compared it with rofecoxib. GW406381 (5mg/kg, 5 days of treatment) significantly reversed the CCI-induced decrease in paw withdrawal thresholds (PWTs), assessed using both von Frey hair and paw pressure tests, whereas an equi-effective dose of rofecoxib (5mg/kg, 5 days of treatment) in inflammatory pain models was ineffective. In rats treated with GW406381, the proportion of fibres showing spontaneous activity was significantly lower (15.58%) than that in the vehicle (32.67%)- and rofecoxib (39.66%)-treated rats. Ibuprofen, a non-selective COX inhibitor, at 5mg/kg, orally dosed three times a day for 5 days did not significantly affect the PWTs in CCI rats. In naïve rats, GW406381 did not significantly change the PWTs. These results illustrate that COX-2 may indeed play an important role in the maintenance of neuropathic pain following nerve injury, but that only certain COX-2 inhibitors, such as GW406381, are effective in this paradigm. Whilst the mechanisms underlying this differential effect of GW406381 are not clear, differences in drug/enzyme kinetic interactions may be a key contributing factor.

An interesting thinner intoxication case: intrathoracic injection.

Thinners, including aromatic hydrocarbons such as toluene, xylene, and N-hexane, are widely used in industry for the production of plastics, varnish, paint, and glue. Use of these toxic agents frequently leads to chronic intoxication caused by abuse or misuse of solvents, which are usually taken in through inhalation. Thinners may have neurotoxic, myotoxic, hepatotoxic, nephrotoxic, and cardiotoxic systemic effects. The patient described in this report attempted to commit suicide by injecting 10 cc thinner into the left hemithorax. Acute chemical empyema developed at the left hemithorax. No bacterial growth was noted in empyema liquid and blood samples. Empyema was treated with tube thoracostomy, and full remission was observed after 33 d. No systemic toxic signs were noted, other than a low level of hepatotoxicity. Although pleural effusion, atelectasis, and pleural thickening were observed at the acute phase on computed tomography (CT) of the thorax, only pleural thickening persisted on CT of the thorax after 1 y. Investigators could not find a documented case of parenteral use of thinners in the medical literature.

Chemotopic representations of aromatic odorants in the rat olfactory bulb.

Our laboratory has characterized spatial patterns of evoked neural activity across the entire glomerular layer of the rat olfactory bulb using primarily aliphatic odorants that differ systematically in functional groups and hydrocarbon structures. To represent more fully the true range of odorant chemistry, we investigated aromatic compounds, which have a more rigid molecular structure than most aliphatic compounds and are particularly salient olfactory stimuli for humans. We first investigated glomerular patterns of 2-deoxyglucose uptake in response to aromatic compounds that differ in the nature and position of their functional groups (e.g., xylenes, trimethylbenzenes, tolualdehydes, benzaldehydes, methyl toluates, and anisaldehydes). We also studied the effects of systematic increases in the number and length of alkyl substituents. We found that most aromatic compounds activated glomeruli in the dorsal part of the bulb. Within this general area, aromatic odorants with oxygen-containing substituents favored activation of more rostral regions, and aromatic hydrocarbons activated more posterior regions. The nature of substituents greatly affected the pattern of glomerular activation, whereas isomers differing in substitution position evoked very similar overall patterns. These relationships between the structure of aromatic compounds and their spatial representation in the bulb are contrasted with our previous findings with aliphatic odorants.

Comparison of estimated daily intakes of flavouring substances with no-observed-effect levels.

This study was conducted to determine the margins of safety between no-observed-effect levels (NOELs) and estimates of daily intake for 809 flavouring substances evaluated by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) between 2000 and 2004. Estimates of daily intake were calculated using two methods, the maximized survey-derived daily intake (MSDI) and the possible average daily intake (PADI). The MSDI estimates were based on the production volume of flavouring agents as reported by industry, whereas the higher more conservative PADI estimates were derived by multiplying the anticipated average use level of a flavouring substance in each of 33 food categories by the average amount of food consumed daily from that food category and summing the intake over all 33 food categories. These intake estimates were used to calculate the margins of safety for the flavouring agents to determine whether adequate margins of safety would still exist in the event that the MSDIs used by JECFA to evaluate the safety of flavouring substances underestimated daily intakes. Based on the calculation of the margins of safety using the MSDI values, 99.9% of the 809 flavouring substances evaluated by JECFA have margins of safety of greater than 100. In comparison, 98% of flavouring substances have margins of safety of greater than 100 when the margins of safety were calculated from PADI values. The results indicate that if the MSDI estimates used by JECFA for the evaluation of the safety of flavouring substances were underestimated, a wide margin of safety exists for all but a few of the flavouring substances even when intakes were estimated from PADI values.

New phenylpropane and anti-inflammatory diterpene derivatives from Amentotaxus formosana.

One new diterpene, 8(14),15-sandaracopimaradiene-2alpha,3beta,18-triol (1), two new phenylpropane derivatives, i.e., (E)-methyl 2-(3,4-methylene-dioxyphenyl)-3-methoxypropenoate (2) and (E)-2-(3,4-methylene-dioxyphenyl)-3-methoxypropenoic acid (3), and two known diterpenes, ent-8(14),15-sandaracopimaradiene-2alpha,18-diol (4) and 8(14),15-sandaracopimaradiene-2alpha,18,19-triol (5), were isolated from the heartwoods and barks of Amentotaxus formosana, respectively. The anti-inflammatory activity of the diterpenes 1, 4, and 5 was assessed in vitro by determining their inhibitory effects on the chemical mediators released from mast cells, neutrophils, macrophages, and microglial cells. Compounds 1, 4, and 5 showed significant concentration-dependent inhibitory effects on the release of beta-glucuronidase from rat neutrophils in response to formyl-Met-Leu-Phe/cytochalasin B (fMLP/CB) with IC50 values of 5.5 +/- 1.8, 8.4 +/- 2.9 and 19.2 +/- 3.3 microM, respectively. Compounds 1 and 5 also showed significant concentration-dependent inhibitory effects on superoxide anion generation in rat neutrophils stimulated with fMLP/CB and phorbol 12-myristate 13-acetate (PMA) with IC50 values of 12.6 +/- 1.2 and 9.4 +/- 1.7, and 10.7 +/- 3.3 and 12.9 +/- 0.9 microM, respectively.

Intoxicación por administración parenteral de insecticidas organoclorados e hidrocarburos aromáticos / Intoxication due to injection of organochlorines and aromatic hydrocarbons

La intoxicación por vía parenteral debida a insecticidas organoclorados e hidrocarburos aromáticos, es muy poco frecuente. La toxicidad comporta efectos locales y sistémicos que pueden llegar a comprometer la vida del paciente. Se presenta el caso clínico de un varón que desarrolló una importante reacción local necrótico-inflamatoria, con leve afectación sistémica hepática y renal, tras administrarse los mencionados productos por vía parenteral en una tentativa de suicidio. (AU)

A comparison of intraperitoneal and oral gavage administration in comet assay in mouse eight organs.

One of the important advantages of the comet assay is its ability to detect genotoxicity in many different organs. Since the exposure route of the test compounds is likely to influence the genotoxicity detected in a given organ, it is an important factor to consider when conducting the assay. In this study, we compared the effects of numerous model compounds on eight organs when administered to mice by intraperitoneal (i.p.) injection and oral (p.o.) gavage. Groups of four mice were treated once i.p. or p.o. at the identical proportion of LD50 for each route, and the stomach, colon, liver, kidney, bladder, lung, brain, and bone marrow were sampled 3, 8, and 24h after treatment. For 19 of the 20 tested mutagens with various modes of action, genotoxicity in some organs varied with treatment route; only the genotoxicity of methyl methane sulfonate was not affected. Treatment route, however, did not produce a qualitative difference in the genotoxicity of promutagens at the sites of conversion to ultimate mutagens, with aromatic hydrocarbons as the exception. When chemicals with positive responses in at least one organ were considered to be comet assay-positive, the administration route made no difference. Since azo reduction is mediated by azo reductase synthesized in the gastrointestinal wall and by gut microflora and i.p.-administered azo dyes bypass their activation site (colon), the administration route is expected to make a difference in their in vivo genotoxicity. Direct-acting mutagens are expected to affect the mucosa of the gastrointestinal tract when given p.o. For those mutagens, however, the administration route did not make a qualitative difference in gastrointestinal tract genotoxicity. Moreover, although the gastrointestinal mucosa is the first site to be exposed to p.o. administered agents, the peak times in the stomach tended to be the same as in most other organs. Based on those results, we concluded that the genotoxicity at high exposures was due to a systemic effect, and that both routes are acceptable for the comet assay when the liver and gastrointestinal organs are sampled, so long as appropriate dose levels for systemic exposure are selected for each route.

Effects of a branched-chain amino acid-enriched diet on chronic hepatic encephalopathy in dogs.

A decreased ratio of branched-chain amino acids (BCAA) to aromatic amino acids (AAA) is considered an important pathogenetic factor in hepatic encephalopathy (HE). A relationship between the deranged BCAA/AAA ratio and dopaminergic dysfunction through the formation of "false" neurotransmitters has been postulated. The intermediate lobe of the pituitary is more pronounced in dogs than in humans and because it is primarily under dopaminergic inhibitory influence, it may serve as an indicator of alterations in dopaminergic neurotransmission. We investigated the effects of a diet with a high BCAA/AAA ratio (HR) and an isonitrogenous diet with a low BCAA/AAA ratio (LR) on several physical and biochemical parameters including pituitary function in dogs with portocaval shunts and 40% hepatectomy and in sham-operated pair-fed controls, in a double-blind, randomized cross-over study. Portocaval-shunted dogs had hyperammonemia (33+/-3 microM (mean +/- SEM) before and 214+/-21 after surgery)) and signs of HE. Their BCAA/AAA ratio in plasma and CSF decreased from 4.3+/-0.3 and 2.3+/-0.3 before surgery to 1.3+/-0.1 and 0.5+/-0.1 after surgery, respectively. These parameters remained unaltered in the control dogs. The consumption of the LR diet was significantly higher than consumption of the HR diet. In the portocaval-shunted dogs, plasma ammonia concentration was higher on the HR diet than on the LR diet (344+/-52 v 246+/-45) and the HE grade was worse. The BCAA/AAA ratio remained abnormal in HE dogs during the feeding of both diets. The basal and haloperidol-stimulated release of alpha-melanotropin and cortisol in plasma were not significantly different between or within groups during any period. In contrast, urinary cortisol excretion was increased in the HE dogs after surgery (urinary cortisol:creatinine ratio (x10(-6)) 8.5+/-1.4 before and 30.4+/-8.9 after surgery). The basal plasma concentration of adrenocorticotropin in HE dogs was decreased after surgery (68.3+/-10.2 ng/L before and 40.8+/-4.4 after surgery). This indicates a non-pituitary-dependent hyperresponsiveness of the adrenals. We conclude from these results that chronic HE in dogs is not associated with an abnormal dopaminergic neurotransmission at least at the level of the pituitary, and that it is not the content of the dietary neutral amino acids but rather the total protein intake that may have a beneficial effect on HE.