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Christopher R Jones

Publications and source records attributed to Christopher R Jones.

10 recordsLinked to original sources
PubMed2006

Internal exposure, health effects, and cancer risk of humans exposed to chloronitrobenzene.

Chloronitrobenzenes (CNBs) are important intermediates for the production of dyes, pesticides, rubber chemicals, and drugs. 2CNB and 4CNB are possible human carcinogens. Therefore, it is important to develop methods to biomonitor people exposed to these occupational and environmental pollutants. We developed a method to determine hemoglobin (Hb) adducts of CNBs. Nitrobenzenes and the resulting arylamines yield the same sulfinamide adducts. Therefore, after base hydrolysis of the isolated Hb the corresponding arylamines are released and quantified by GC-MS. The method was applied to monitor 39 Chinese workers exposed to CNB and 15 control workers from the same factory. The determined Hb adduct levels were compared to the measured air levels, the clinical blood and urine parameters, and health effects identified in the workers. The median Hb adduct levels resulting from exposure to 2CNB and 4CNB were 82.9 and 1013 pg/mg of Hb, respectively. The median air concentrations determined from personal samplers were 0.37 and 0.87 mg/m3 for 2CNB and 4CNB, respectively. The air levels did not correlate with the Hb adduct levels. The median Hb adduct levels were higher in workers with fatigue, eye irritation, splenomegaly, and cardiovascular effects. Most negative urinary clinical parameters were present at higher median Hb adduct levels. The clinical blood parameters decreased at higher adduct levels. The daily dose was estimated from the Hb adduct levels and used to estimate the cancer risk.

Amides↗
PubMed2006

Biomarkers of exposure, effect, and susceptibility in workers exposed to nitrotoluenes.

Nitrotoluenes, such as 2-nitrotoluene, 2,4-dinitrotoluene (24DNT), and 26DNT, are carcinogenic in animal experiments. Humans are exposed to such chemicals in the workplace and in the environment. It is therefore important to develop methods to biomonitor people exposed to nitrotoluenes to prevent the potential harmful effects. For the present study, workers exposed to high levels of these chemicals were investigated. The external dose (air levels), the internal dose (urine metabolites), the biologically effective dose [hemoglobin (Hb) adducts and urine mutagenicity], and biological effects (chromosomal aberrations and health effects) were determined. Individual susceptibility was assessed by determining genetic polymorphisms of enzymes assumed to function in nitrotoluene metabolism, namely glutathione S-transferases (GSTM1, GSTT1, GSTP1), N-acetyltransferases (NAT1, NAT2), and sulfotransferases (SULT1A1, SULT1A2). The levels of urinary metabolites did not correlate with the air levels. The urinary mutagenicity levels determined in a subset of workers correlated with the levels of a benzylalcohol metabolite of DNT. The Hb-adducts correlated with the urine metabolites but not with the air levels. The frequency of chromosomal aberrations (gaps included) was increased (P < 0.05) in the exposed workers in comparison with a group of factory controls and correlated with the level of 24DNT Hb-adducts in young subjects (<31 years). The GSTM1-null genotype was significantly more prevalent in the controls than in the exposed group, which probably reflected an elevated susceptibility of the GSTM1-null genotype to adverse health effects of DNT exposure, such as nausea (odds ratio, 8.8; 95% confidence interval, 2.4-32.2). A statistically significant effect was seen for SULT1A2 genotype on a 24DNT Hb-adduct; GSTP1 genotype on a 2,4,6-trinitrotoluene Hb-adduct; and SULT1A1, SULT1A2, NAT1, GSTT1, and GSTP1 genotypes on chromosomal aberrations in the exposed workers.

Adult↗
PubMed2005

Functional consequences of a CKIdelta mutation causing familial advanced sleep phase syndrome.

Familial advanced sleep phase syndrome (FASPS) is a human behavioural phenotype characterized by early sleep times and early-morning awakening. It was the first human, mendelian circadian rhythm variant to be well-characterized, and was shown to result from a mutation in a phosphorylation site within the casein kinase I (CKI)-binding domain of the human PER2 gene. To gain a deeper understanding of the mechanisms of circadian rhythm regulation in humans, we set out to identify mutations in human subjects leading to FASPS. We report here the identification of a missense mutation (T44A) in the human CKIdelta gene, which results in FASPS. This mutant kinase has decreased enzymatic activity in vitro. Transgenic Drosophila carrying the human CKIdelta-T44A gene showed a phenotype with lengthened circadian period. In contrast, transgenic mice carrying the same mutation have a shorter circadian period, a phenotype mimicking human FASPS. These results show that CKIdelta is a central component in the mammalian clock, and suggest that mammalian and fly clocks might have different regulatory mechanisms despite the highly conserved nature of their individual components.

Amino Acid Sequence↗
PubMed2005

Genetic approaches to human behavior.

Tremendous progress in the field of human genetics has made a major impact over the last two decades into our understanding of many Mendelian disorders affecting humans. It is much more difficult to approach the genetics of complex disorders and is particularly challenging in the case of dissecting genetics of the wide range of behavioral variation in the general population. Knowledge of the biology and genetics of Mendelian traits is beginning to inform studies in complex genetics. Furthermore, the convergence of this growing knowledge with increasingly powerful new tools now put complex genetics of behavior within reach. The bottleneck in such studies and the greatest challenge to investigators is the rigorous phenotyping of human research subjects.

Aged↗
PubMed2004

Hemoglobin adducts in workers exposed to nitrotoluenes.

Nitrotoluenes are important intermediates in the chemical industry. 2,6-Dinitrotoluene (26DNT), 2,4-dinitrotoluene (24DNT) and 2-nitrotoluene are carcinogenic in animals and possibly carcinogenic in humans. It is therefore important to develop methods to biomonitor workers exposed to such chemicals. Hemoglobin (Hb) adducts of nitroarenes are established markers of the biological effective dose. We developed a method to measure Hb adducts in biological samples. Hb adducts were measured in rats after a single exposure (0.5 mmol/kg) of 24DNT, 26DNT, 2,4-toluenediamine (24TDA) and 26TDA. Hydrolysis of Hb from rats dosed with 24DNT yields, 4-amino-2-nitrotoluene (4A2NT) (16.3 nmol/g Hb), 24TDA (4.3 nmol/g Hb) and 4-acetylamino-2-aminotoluene (4AA2AT) (0.51 nmol/g Hb). Hydrolysis of Hb from rats dosed with 26DNT yields three amines, 2-amino-6-nitrotoluene (2A6NT) (2.5 nmol/g Hb), 26TDA (1.2 nmol/g Hb) and 2-acetylamino-6-aminotoluene (2AA6AT) (0.17 nmol/g Hb). A similar Hb adduct pattern was found in Chinese workers exposed to nitrotoluenes. With respect to 24DNT, 4A2NT was the predominant adduct, and the amount was approximately 24-fold higher than 24TDA. With respect to 26DNT, 2A6NT was the predominant adduct, and the amount was approximately 20-fold higher than 26TDA. With respect to the mononitrotoluenes, the Hb adduct of 2NT was present in the highest concentrations. Each worker was examined for adverse health effects linked to exposure to DNT. The health effects were compared with the Hb adduct levels using logistic regression analysis. The odds of suffering from inertia were 3.2 times higher [95% confidence interval (CI) = 1.8-5.8] when the level of 4A2NT Hb adducts increased by one log-unit. Similar odds ratios were observed with somnolence (3.1, CI = 1.4-6.9), nausea (2.4, CI = 1.3-4.3) and dizziness (5.5, CI = 1.3-24.2). These results inferred that quantification of DNT-Hb adducts provided an effective biomarker of toxicity and could be used to estimate the risk associated with a particular exposure to DNT.

Animals↗
PubMed2003

Identification of DNA adducts using HPLC/MS/MS following in vitro and in vivo experiments with arylamines and nitroarenes.

Arylamines and nitroarenes are suspected of playing a key role in chemical carcinogenesis. Therefore, the study of DNA adduct formation is an important step to determine the genotoxic potential of these compounds. Calf thymus DNA was modified in vitro by reaction with activated N-hydroxyarylamines: 2-chloroaniline (2CA), 4-chloroaniline (4CA), 2-methylaniline (2MA), 4-methylaniline (4MA), 2,4-dimethylaniline (24DMA), 2,6-dimethylaniline (26DMA), 2-aminobiphenyl (2ABP), 3-aminobiphenyl (3ABP), and 4-aminobiphenyl (4ABP). Female Wistar rats (n = 2) were given a single dose of the above arylamines and their analogous nitro derivatives by oral gavage and sacrificed after 24 h. Hepatic DNA and in vitro modified DNA were hydrolyzed enzymatically to individual 2'-deoxyribonucleosides. Adducts were determined using HPLC/MS/MS by comparison to synthesized standards. The hydrolysis efficiency was monitored by HPLC with UV detection. Each arylamine described above formed adducts to 2'-deoxyguanosine and 2'-deoxyadenosine after in vitro reaction with DNA. DNA adducts were found in rats dosed with 4ABP or with 4-nitrobiphenyl. DNA adducts were not detected in rats dosed with 2CA, 4CA, 2MA, 4MA, 24DMA, 26DMA, 2ABP, 3ABP, 2-chloronitrobenzene, 4-chloronitrobenzene, 2-nitrotoluene, and 4-nitrotoluene. All compounds formed hydrolyzable hemoglobin adducts. Therefore, biologically available N-hydroxyarylamines yielded hemoglobin adducts but not hepatic DNA adducts, except for 4ABP.

Amines↗
PubMed2003

Hemoglobin and DNA adducts in rats exposed to 2-nitrotoluene.

2-Nitrotoluene (2NT) is an important commercial chemical intermediate. A recent National Toxicology Programme (NTP)-study demonstrated clear evidence of carcinogenic activity of 2NT in rats. In the present study male WELS-Fohm rats were dosed chronically with 2NT, 5 days a week for 12 weeks. Hemoglobin (Hb) adducts and hepatic DNA adducts were analyzed. After mild base treatment of Hb, 2-methylaniline (2MA) was released and quantified using gas chromatography/mass spectrometry. 2'-Deoxyguanosine (dG) and 2'-deoxyadenosine (dA) adducts of 2MA were found in hepatic DNA using electrospray-mass spectrometry (ESI-MS/MS). The dG adduct found in vivo did not co-elute with N-(2'-deoxyguanosine-8-yl)-2-methylaniline which is the expected adduct for arylamines. The dG adduct detected in the dosed rats was not present in calf thymus-DNA (ct-DNA) modified in vitro with N-acetoxy-2MA. The dA adduct detected in rats was a very minor product in ct-DNA modified in vitro. The dG and dA adducts found in the 2NT-dosed rats increased with the dose. The same increase was seen for the Hb adduct levels measured in the same animals. The increase of DNA and Hb adduct levels were supralinear. There was a very strong linear relationship between the level of dG-2MA adducts and dA-2MA adducts in hepatic DNA from rats administered 2NT over the whole dose range studied (r(2) = 0.9). A strong linear relationship also existed between the level of dG-2MA or dA-2MA adducts, in hepatic DNA, and Hb adducts, over the whole dose range (r(2) > or = 0.9). Thus, there was strong evidence to support the notion that Hb adducts were an effective surrogate marker for the hepatic DNA damage of rats chronically administered 2NT.

Animals↗
PubMedDate not supplied

Biomonitoring of arylamines and nitroarenes.

Arylamines and nitroarenes are very important intermediates in the industrial manufacture of dyes, pesticides and plastics, and are significant environmental pollutants. The metabolic steps of N-oxidation and nitroreduction to yield N-hydroxyarylamines are crucial for the toxic properties of arylamines and nitroarenes. Nitroarenes are reduced by microorganisms in the gut or by nitroreductases and aldehyde dehydrogenase in hepatocytes to nitrosoarenes and N-hydroxyarylamines. N-Hydroxyarylamines can be further metabolized to N-sulphonyloxyarylamines, N-acetoxyarylamines or N-hydroxyarylamine N-glucuronide. These highly reactive intermediates are responsible for the genotoxic and cytotoxic effects of this class of compounds. N-Hydroxyarylamines can form adducts with DNA, tissue proteins, and the blood proteins albumin and haemoglobin in a dose-dependent manner. DNA and protein adducts have been used to biomonitor humans exposed to such compounds. All these steps are dependent on enzymes, which are present in polymorphic forms. This article reviews the metabolism of arylamines and nitroarenes and the biomonitoring studies performed in animals and humans exposed to these substances.

Aniline Compounds↗