Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Complex Mixtures”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources
PubMed1991

Antimutagenicity studies of chlorophyllin using the Salmonella arabinose-resistant assay system.

Studies with the arabinose-resistant Salmonella forward mutation assay system were performed to determine the antimutagenic activity of chlorophyllin against the mutagenic activity of aflatoxin B1 (AFB1), 2-aminoanthracene (2AA), benzo[a]pyrene (BaP), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and solvent extracts of coal dust (CD), diesel emission particles (DE), airborne particles (AP), tobacco snuff (TS), black pepper (BP) and red wine (RW). Various concentrations of each chemical and complex mixture extract were assayed for mutagenic activity with and/or without S9 in a preincubation test. One concentration of each chemical and complex mixture extract was then tested with various concentrations of chlorophyllin. Results showed that chlorophyllin, at concentrations of 2.5 mg/plate or less, completely or almost completely inhibited the mutagenicity of 2AA, AFB1, BaP, MNNG and solvent extracts of CD, DE and RW. With concentrations from 1.25 to 5 mg/plate, chlorophyllin inhibited over 50% of the mutagenicity of AP, TS and BP extracts. These results further substantiate the antimutagenic efficacy of chlorophyllin against chemicals and complex mixtures.

Aflatoxin B1↗
PubMed2006

NTP technical report on the toxicology and carcinogenesis studies of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (CAS No. 1746-01-6) in female Harlan Sprague-Dawley rats (Gavage Studies).

DIOXIN TOXIC EQUIVALENCY FACTOR EVALUATION OVERVIEW: Polyhalogenated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have the ability to bind to and activate the ligand-activated transcription factor, the aryl hydrocarbon receptor (AhR). Structurally related compounds that bind to the AhR and exhibit biological actions similar to TCDD are commonly referred to as "dioxin-like compounds" (DLCs). Ambient human exposure to DLCs occurs through the ingestion of foods containing residues of DLCs that bioconcentrate through the food chain. Due to their lipophilicity and persistence, once internalized, they accumulate in body tissue, mainly adipose, resulting in chronic lifetime human exposure. Since human exposure to DLCs always involves a complex mixture, the toxic equivalency factor (TEF) methodology has been developed as a mathematical tool to assess the health risk posed by complex mixtures of these compounds. The TEF methodology is a relative potency scheme that ranks the dioxin-like activity of a compound relative to TCDD, which is the most potent congener. This allows for the estimation of the potential dioxin-like activity of a mixture of chemicals based on a common mechanism of action involving an initial binding of DLCs to the AhR. The toxic equivalency of DLCs was nominated for evaluation because of the widespread human exposure to DLCs and the lack of data on the adequacy of the TEF methodology for predicting relative potency for cancer risk. To address this, the National Toxicology Program conducted a series of 2-year bioassays in female Harlan Sprague-Dawley rats to evaluate the chronic toxicity and carcinogenicity of DLCs and structurally related polychlorinated biphenyls (PCBs) and mixtures of these compounds. TCDD is not manufactured commercially other than for scientific research purposes. The main sources of TCDD releases into the environment are from combustion and incineration; metal smelting, refining, and processing; chemical manufacturing and processing; biological and photochemical processes; and existing reservoir sources that reflect past releases. TCDD (dioxin) was selected for study by the National Toxicology Program as a part of the dioxin TEF evaluation to assess the cancer risk posed by complex mixtures of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and PCBs. The dioxin TEF evaluation includes conducting multiple 2-year rat bioassays to evaluate the relative chronic toxicity and carcinogenicity of DLCs, structurally related PCBs, and mixtures of these compounds. While one of the aims of the dioxin TEF evaluation was a comparative analysis across studies, in this Technical Report, only the TCDD results are presented and discussed. TCDD was included because it is the reference compound for the dioxin TEF methodology. Female Harlan Sprague-Dawley rats were administered TCDD (at least 98% pure) in corn oil:acetone (99:1) by gavage for 14, 31, or 53 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, L5178Y mouse lymphoma cells, cultured Chinese hamster ovary cells, Drosophila melanogaster, and mouse bone marrow cells. 2-YEAR STUDY: Groups of 81 or 82 female rats were administered 3, 10, 22, 46, or 100 ng TCDD/kg body weight in corn oil:acetone (99:1) by gavage, 5 days per week, for up to 105 weeks; a group of 81 vehicle control female rats received the corn oil/acetone vehicle alone. Up to 10 rats per group were evaluated at 14, 31, or 53 weeks. A stop-exposure group of 50 female rats was administered 100 ng/kg TCDD in corn oil:acetone (99:1) by gavage for 30 weeks and then just the vehicle for the remainder of the study. Survival of dosed groups was similar to that of the vehicle control group. Mean body weights of 100 ng/kg core study and stop-exposure groups were less than those of the vehicle control group after week 13 of the study. Mean body weights of 46 ng/kg rats were less than those of the vehicle controls during year 2 of the study, and those of 22 ng/kg rats were less than those of the vehicle controls the last 10 weeks of the study. THYROID HORMONE CONCENTRATIONS: Alterations in serum thyroid hormone levels were evaluated at the 14-, 31- and 53-week interim evaluations. At 14 weeks, there were significant decreases in serum total and free thyroxine (T4) levels and increases in serum total triiodothyronine (T3) and thyroid stimulating hormone (TSH). At 31 weeks, there were significant decreases in serum total and free T4 levels and increases in serum total T3 but no significant effect on TSH. At 53 weeks, there were significant decreases in serum total T4 levels and increases in serum total T3. There were no significant effects on total T4 or TSH levels. HEPATIC CELL PROLIFERATION DATA: To evaluate hepatocyte replication, analysis of labeling of replicating hepatocytes with 5-bromo-2'-deoxyuridine was conducted at the 14-, 31-, and 53-week interim evaluations. The hepatocellular labeling index was significantly higher in the 22 ng/kg group compared to vehicle controls at 14 weeks. At the 31-week interim evaluation, the labeling indices in hepatocytes were significantly higher in all dosed groups than in the vehicle controls. At 53 weeks, labeling indices were significantly higher in the 46 and 100 ng/kg groups than in the vehicle controls. CYTOCHROME P450 ENZYME ACTIVITIES: To evaluate the expression of known dioxin-responsive genes, CYP1A1-associated 7-ethoxyresorufin-O-deethylase (EROD) activity and CYP1A2-associated acetanilide-4-hydroxylase (A4H) activity were evaluated at 14, 31, and 53 weeks. In addition, pentoxyresorufin-O-deethylase (PROD) activity was analyzed. Hepatic EROD, PROD, and A4H activities were significantly higher in all dosed groups relative to vehicle controls at the 14-, 31-, and 53-week interim evaluations. Pulmonary EROD was also significantly higher in all dosed groups compared to vehicle controls at 14, 31, and 53 weeks. DETERMINATIONS OF TCDD CONCENTRATIONS IN TISSUES: The tissue disposition of TCDD was analyzed in the liver, lung, fat, and blood of all animals in each group at the 14-, 31-, and 53-week interim evaluations and in 10 animals per group at the end of the 2-year study (105 weeks). The highest concentrations of TCDD were observed in the liver, followed by fat tissue. Liver and fat tissue concentrations of TCDD increased with increasing doses of TCDD. No measurable concentrations of TCDD were observed in blood from vehicle control or treated rats at any of the interim evaluations. Mean levels of TCDD in the liver and fat in the 100 ng/kg group at the end of the 2-year study were 9.3 and 3.2 ng/g, respectively. In liver tissue from the stop-exposure group, TCDD concentrations were slightly higher than those observed in the 3 ng/kg group. In the stop-exposure group, TCDD concentrations in fat were below the limits of quantitation. PATHOLOGY AND STATISTICAL ANALYSES: Absolute and/or relative liver weights were increased at 14, 31, and 53 weeks, with more severe effects occurring in the higher dosed groups. Increased liver weights correlated with increased incidences of hepatocyte hypertrophy at 14, 31, and 53 weeks. Exposure led to a treatment-related increase in hepatic toxicity with a broad spectrum of lesions. Incidences and severities of lesions increased at higher doses and longer durations of exposure. The earliest effects were increased incidences and severities of hepatocyte hypertrophy at 14 weeks. At 2 years, there was a significant increase in toxic hepatopathy characterized by increased incidences of numerous nonneoplastic liver lesions including hepatocyte hypertrophy, multinucleated hepatocytes, altered hepatocellular foci, inflammation, pigmentation, diffuse fatty change, necrosis, portal fibrosis, oval cell hyperplasia, bile duct hyperplasia, bile duct cysts, cholangiofibrosis, and nodular hyperplasia At 2 years, the incidence of hepatocellular adenoma was significantly increased in the 100 ng/kg core study group. Dose-related increased incidences of cholangiocarcinoma were seen in core study rats administered 22 ng/kg or greater. The highest incidence of cholangiocarcinoma was seen in the 100 ng/kg core study group and included a significant number of animals with multiple cholangiocarcinomas. Two cholangiocarcinomas and two hepatocellular adenomas were seen in the 100 ng/kg stop-exposure group. Two hepatocholangiomas were seen in the 100 ng/kg core study group, and one cholangioma was seen in the 100 ng/kg stop-exposure group. In the lung, the incidence of cystic keratinizing epithelioma of the lung was significantly increased at 2 years in the 100 ng/kg core study group. Nonneoplastic effects in the lung included increased incidences of bronchiolar metaplasia. The incidence of gingival squamous cell carcinoma of the oral mucosa was significantly increased in the 100 ng/kg core study group at 2 years and was accompanied by an increased incidence of gingival squamous hyperplasia. At 2 years, the incidence of squamous cell carcinoma of the uterus in the 46 ng/kg group was significantly increased, and there were two squamous cell carcinomas in the 100 ng/kg stop-exposure group. At 2 years, one acinar adenoma and two acinar cell carcinomas of the pancreas were seen in the 100 ng/kg core study group; one acinar carcinoma was seen in the 100 ng/kg stop-exposure group. The incidences of acinar cell adenoma or carcinoma (combined) exceeded the historical vehicle control range. Nonneoplastic effects in the lung included acinar cytoplasmic vacuolization, chronic active inflammation, acinar atrophy, and arterial chronic active inflammation. (ABSTRACT TRUNCATED)

Animals↗
PubMed2006

NTP technical report on the toxicology and carcinogenesis studies of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) (CAS No. 35065-27-1) in female Harlan Sprague-Dawley rats (Gavage studies).

UNLABELLED: DIOXIN TOXIC EQUIVALENCY FACTOR EVALUATION OVERVIEW: Polyhalogenated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have the ability to bind to and activate the ligand-activated transcription factor, the aryl hydrocarbon receptor (AhR). Structurally related compounds that bind to the AhR and exhibit biological actions similar to TCDD are commonly referred to as "dioxin-like compounds" (DLCs). Ambient human exposure to DLCs occurs through the ingestion of foods containing residues of DLCs that bioconcentrate through the food chain. Due to their lipophilicity and persistence, once internalized, they accumulate in body tissue, mainly adipose, resulting in chronic lifetime human exposure. Since human exposure to DLCs always involves a complex mixture, the toxic equivalency factor (TEF) methodology has been developed as a mathematical tool to assess the health risk posed by complex mixtures of these compounds. The TEF methodology is a relative potency scheme that ranks the dioxin-like activity of a compound relative to TCDD, which is the most potent congener. This allows for the estimation of the potential dioxin-like activity of a mixture of chemicals based on a common mechanism of action involving an initial binding of DLCs to the AhR. The toxic equivalency of DLCs was nominated for evaluation because of the widespread human exposure to DLCs and the lack of data on the adequacy of the TEF methodology for predicting relative potency for cancer risk. To address this, the National Toxicology Program conducted a series of 2-year bioassays in female Harlan Sprague-Dawley rats to evaluate the chronic toxicity and carcinogenicity of DLCs and structurally related polychlorinated biphenyls (PCBs) and mixtures of these compounds. 2,2',4,4',5,5'-Hexachlorobiphenyl (PCB 153) was produced as a component of some commercial PCB mixtures before 1977 for the electric industry as a dielectric insulating fluid for transformers and capacitors. Manufacture and use of the chemical was stopped due to increased PCB residues in the environment, but it continues to be released into the environment through the use and disposal of products containing PCBs, as by-products during the manufacture of certain organic chemicals, and during the combustion and biodegradation of some waste materials. Bioaccumulation of PCB 153 results in persistent levels in animal and human tissues. PCB 153 was selected for study by the National Toxicology Program as a part of the dioxin TEF evaluation to assess the cancer risk posed by complex mixtures of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs). The dioxin TEF evaluation includes conducting multiple 2-year rat bioassays to evaluate the relative chronic toxicity and carcinogenicity of DLCs, structurally related PCBs, and mixtures of these compounds. PCB 153 was included since it is present at the highest PCB concentrations in human samples on a molar basis. PCB 153 was also included in a mixture study with PCB 126, since previous studies have demonstrated interactions between PCB 153 and DLCs on pharmacokinetic and biological effects. While one of the aims of this study was a comparative analysis of effects seen with PCB 126 and the mixture of PCB 126 and PCB 153, in this Technical Report only the results of the present study of PCB 153 are presented and discussed. 2-YEAR STUDY: Female Harlan Sprague-Dawley rats were administered PCB 153 (greater than 99% pure) in corn oil:acetone (99:1) by gavage for 14, 31, or 53 weeks or 2 years. Groups of 80 (3,000 microg PCB 153/kg body weight), 81 (100, 300, and 1,000 microg/kg), or 82 (10 microg/kg) female rats received PCB 153 in corn oil:acetone (99:1) by gavage at doses of 10, 100, 300, 1,000, or 3,000 microg/kg 5 days per week for up to 105 weeks; a group of 81 female rats received the corn oil:acetone (99:1) vehicle alone. A stop-exposure group of 50 female rats was administered 3,000 microg/kg for 30 weeks and then the vehicle for the remainder of the study. Dose selection for the PCB 153 study was based on the range of PCB 153 doses used in the mixture study of PCB 126 and PCB 153 (10 to 3,000 microg/kg). Survival of dosed groups was similar to that of the vehicle control group. Mean body weights of 3,000 microg/kg core study rats were less than those of the vehicle controls after week 69 of the study. Thyroid Hormone Concentrations: Serum total thyroxine (T4), free T4, and total triiodothyronine (T3) concentrations in the 3,000 microg/kg group were significantly lower than those in the vehicle controls at the 14-week interim evaluation. At the 31-week interim evaluation, no significant differences were observed in serum total T4, free T4, T3, or thyroid stimulating hormone concentrations. At the 53-week interim evaluation, serum total T4 and free T4 concentrations in the 3,000 microg/kg group were significantly lower than in the vehicle controls. Hepatic Cell Proliferation Data: No significant differences in hepatocellular labeling index were observed between the vehicle control and dosed groups at any of the interim evaluations. Cytochrome P450 Enzyme Activities Hepatic pentoxyresorufin-O-deethylase activities were highly and significantly elevated relative to the vehicle control groups. Maximum increases over controls at 14, 31, and 53 weeks were 136-, 140-, and 40-fold, respectively. Hepatic 7-ethoxyresorufin-O-deethylase (EROD) and acetanilide-4-hydroxylase (A4H) activities were significantly elevated over controls at 14 and 31 weeks; increases were less than twofold. At 14 weeks, EROD activities in the lung were dose-dependently reduced compared to vehicle controls. Determinations of PCB 153 Concentrations in Tissues: In the fat from vehicle controls, detectable levels of PCB 153 were observed at 14, 31, and 53 weeks and at the end of the 2-year study. Fat concentrations of PCB 153 increased with increasing doses of PCB 153 and tended to increase with the longer exposure durations. In the fat of the 3,000 microg/kg stop-exposure group, PCB 153 concentrations were between the levels observed in the 300 and 1,000 microg/kg groups. In the liver of vehicle controls, no measurable concentrations of PCB 153 were observed at any time point. In dosed groups, hepatic concentrations of PCB 153 increased with increasing dose and longer exposure duration. Measurable concentrations of PCB 153 were observed in the lungs of vehicle control rats at 31 and 53 weeks and at 2 years. At all time points, PCB 153 lung and blood concentrations increased with increasing dose, and blood concentrations increased with duration of exposure. In liver, lung, and blood of rats from the 3,000 microg/kg stop-exposure group, PCB 153 concentrations were slightly above or below the levels observed in the 1,000 microg/kg group. Organ Weights: Absolute liver weights of 1,000 microg/kg rats and absolute and relative liver weights of 3,000 microg/kg rats were significantly greater than those of vehicle controls at week 14. At week 31, relative liver weights of 1,000 microg/kg rats and absolute and relative liver weights of 3,000 microg/kg rats were significantly greater than those of vehicle controls. At week 53, absolute and relative liver weights were significantly greater in rats administered 100 microg/kg or greater compared to vehicle controls. Absolute kidney weights of all exposed groups and the relative kidney weight of 3,000 microg/kg rats were significantly increased at week 53. Pathology and Statistical Analyses: The incidences of hepatocyte hypertrophy were significantly increased in the 1,000 and 3,000 microg/kg groups at 14 weeks and in all groups administered 300 microg/kg or greater at 31 and 53 weeks. At 2 years, the incidences of hepatocyte hypertrophy were significantly increased in all dosed groups. The incidences of diffuse fatty change in the 300 microg/kg or greater groups and bile duct hyperplasia of the liver in 300 microg/kg and 3,000 microg/kg (core and stop-exposure) groups were significantly increased. The incidences of oval cell hyperplasia and pigmentation of the liver were significantly increased in the 3,000 microg/kg core study group. At 2 years, two cholangiomas were seen in the 1,000 microg/kg group and two cholangiomas were seen in the 3,000 microg/kg stop-exposure group. A single hepatocellular adenoma was observed in the 3,000 microg/kg core study group. At 53 weeks, sporadic incidences of minimal to mild follicular cell hypertrophy of the thyroid gland occurred in all groups (except 10 microg/kg). At 2 years, the incidences of minimal to mild follicular cell hypertrophy were significantly increased in the 300 microg/kg and 3,000 microg/kg (core and stop-exposure) groups. At 2 years, significantly increased incidences of chronic active inflammation in the ovary and oviduct occurred in the 1,000 and 3,000 microg/kg core study groups. Incidences of suppurative inflammation of the uterus in the 1,000 microg/kg group and chronic active inflammation in the 3,000 microg/kg core study group were significantly greater than those in the vehicle control group. CONCLUSIONS: Under the conditions of this 2-year gavage study there was equivocal evidence of carcinogenic activity of PCB 153 in female Harlan Sprague-Dawley rats based on the occurrences of cholangioma of the liver. PCB 153 administration caused increased incidences of nonneoplastic lesions of the liver, thyroid gland, ovary, oviduct, and uterus in female rats.

Adenoma, Bile Duct↗
PubMed2006

NTP toxicology and carcinogenesis studies of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) (CAS No. 57465-28-8) in female Harlan Sprague-Dawley rats (Gavage Studies).

DIOXIN TOXIC EQUIVALENCY FACTOR EVALUATION OVERVIEW: Polyhalogenated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have the ability to bind to and activate the ligand-activated transcription factor, the aryl hydrocarbon receptor (AhR). Structurally related compounds that bind to the AhR and exhibit biological actions similar to TCDD are commonly referred to as "dioxin-like compounds" (DLCs). Ambient human exposure to DLCs occurs through the ingestion of foods containing residues of DLCs that bioconcentrate through the food chain. Due to their lipophilicity and persistence, once internalized they accumulate in adipose tissue resulting in chronic lifetime human exposure. Since human exposure to DLCs always occurs as a complex mixture, the Toxic Equivalency Factor (TEF) methodology has been developed as a mathematical tool to assess the health risk posed by complex mixtures of these compounds. The TEF methodology is a relative potency scheme that ranks the dioxin-like activity of a compound relative to TCDD that is the most potent congener. This allows for the estimation of the potential dioxin-like activity of a mixture of chemicals, based on a common mechanism of action involving an initial binding of DLCs to the AhR. The toxic equivalency of DLCs was nominated for evaluation, because of the widespread human exposure to DLCs and the lack of data on the adequacy of the TEF methodology for predicting relative potency for cancer risk. To address this, the National Toxicology Program conducted a series of 2-year bioassays in female Harlan Sprague-Dawley rats to evaluate the chronic toxicity and carcinogenicity of DLCs and structurally-related polychlorinated biphenyls (PCBs) and mixtures of these compounds. 3,3',4,4',5-Pentachlorobiphenyl (PCB 126) was produced commercially before 1977 for the electric industry as a dielectric insulating fluid for transformers and capacitors. Manufacture and use of the chemical was stopped because of increased PCB residues in the environment, but it continues to be released into the environment through the use and disposal of products containing PCBs, as by-products during the manufacture of certain organic chemicals, and during combustion of some waste materials. Bioaccumulation of PCB 126 results in persistent levels in animal and human tissues and the biological responses to PCB 126 are similar to those of TCDD, a known human carcinogen. PCB 126 was selected for study by the National Toxicology Program as a part of the dioxin TEF evaluation to assess the cancer risk posed by complex mixtures of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and PCBs. The dioxin TEF evaluation includes conducting multiple 2-year rat bioassays to evaluate the relative chronic toxicity and carcinogenicity of DLCs, structurally related PCBs, and mixtures of these compounds. PCB 126 was included since this is the most potent coplanar PCB that has dioxin-like activities. While one of the aims of the dioxin TEF evaluation was a comparative analysis across studies, in this Technical Report only the results of the PCB 126 study are presented and discussed. Female Harlan Sprague-Dawley rats were administered PCB 126 (99% pure) in corn oil with acetone by gavage for 14, 31, or 53 weeks or 2 years. 2-YEAR STUDY: Groups of 81 female rats were administered 30, 100, 175, 300, 550, or 1,000 ng PCB 126/kg body weight in corn oil:acetone (99:1) by gavage, 5 days per week, for up to 104 weeks; a group of 81 vehicle control female rats received the corn oil/acetone vehicle alone. A group of 28 rats received 10 ng/kg for up to 53 weeks only. Up to 10 rats per group were evaluated at 14, 31, or 53 weeks. A stop-exposure group of 50 female rats was administered 1,000 ng/kg PCB 126 in corn oil:acetone (99:1) by gavage for 30 weeks then the vehicle for the remainder of the study. Mean body weights of 30 and 100 ng/kg rats were similar to those of the vehicle controls during most of the study, mean body weights of 175 and 300 ng/kg rats were less than those of the vehicle controls during year 2 of the study, and mean body weights of 550 ng/kg, 1,000 ng/kg core study, and 1,000 ng/kg stop-exposure rats were less than those of the vehicle controls after week 17. THYROID HORMONE CONCENTRATIONS: Alterations in serum thyroid hormone levels were evaluated at the 14-, 31- and 53- week interim evaluations. In the 550 and 1,000 ng/kg rats, total thyroxine (T4) and free T4 were significantly lower than vehicle controls and serum triiodothyronine (T3) and thyroid stimulating hormone (TSH) levels were significantly higher than vehicle controls at the 14-week interim evaluation. Serum T3 was also significantly higher in the 300 ng/kg rats compared to vehicle controls at 14 weeks. At 31 weeks, T3 was significantly higher at doses of 100 ng/kg or greater compared to vehicle controls. TSH levels were higher in 550 and 1,000 ng/kg rats than in vehicle controls. At 53 weeks, significantly lower serum concentrations of total T4 and free T4 were observed compared to vehicle controls in groups administered 175 ng/kg or greater and 30 ng/kg or greater, respectively. Serum T3 levels were significantly higher at doses of 175 ng/kg or greater compared to vehicle controls. No changes in TSH were observed between vehicle controls and dosed rats at 53 weeks. HEPATIC CELL PROLIFERATION DATA: To evaluate hepatocyte replication, analysis of labeling of replicating hepatocytes with 5-bromo-2'-deoxyuridine was conducted at the 14-, 31-, and 53-week interim evaluations. The hepatocellular labeling index was significantly higher at doses of 300 ng/kg or greater at 14 weeks and 175 ng/kg or greater at 31 weeks compared to vehicle controls. No statistically significant differences were observed between vehicle controls and PCB 126 dosed rats at 53 weeks. However at 53 weeks, a 5.8-fold increase above the vehicle controls was observed in the 1,000 ng/kg group. CYTOCHROME P450 ENZYME ACTIVITIES: To evaluate the expression of known dioxin-responsive genes, CYP1A1 associated 7-ethoxyresorufin-O-deethylase (EROD) activity and CYP1A2-associated acetanilide 4-hydroxylase (A-4-H) activity were evaluated at the 14-, 31-, and 53-week interim evaluations. In addition, CYP2B associated pentoxyresorufin-O-deethylase (PROD) activity was also analysed. Hepatic PROD (CYP2B1) and hepatic and pulmonary EROD (CYP1A1) activity were significantly greater in all dosed groups than in vehicle controls at weeks 14, 31, and 53. Hepatic A-4-H (CYP1A2) activity was significantly greater in the 30, 100, 175, 300, 550, and 1,000 ng/kg groups compared to vehicle controls at weeks 14, 31, and 53. DETERMINATIONS of PCB 126 CONCENTRATIONS IN TISSUES: The tissue disposition of PCB 126 was analyzed in the liver, lung, fat, and blood of all rats in vehicle controls and all dosed groups at the 14-, 31-, and 53-week interim evaluations and in 10 rats per group including vehicle controls at the end of the 2-year study (104 weeks). Detectable concentrations of PCB 126 were observed in the liver, fat, lung, and blood. Measurable concentrations of PCB 126 were present in the liver and fat at weeks 31, 53, and 104. Hepatic and fat concentrations increased with increasing doses of PCB 126. Measurable concentrations of PCB 126 were present in vehicle control lung tissue at 53 and 104 weeks. No PCB 126 was observed in the blood from the vehicle control rats. Lung and blood concentrations tended to increase with increasing doses of PCB 126, with a few exceptions. In the stop-exposure group, PCB 126 concentrations in liver and fat were lower than the levels observed in the 30 ng/kg group. In the stop-exposure group, lung tissue PCB 126 concentrations were equivalent to the levels observed in the 30 ng/kg group. In blood from the stop-exposure group, PCB 126 concentrations were equivalent to the levels observed in the 100 ng/kg group. PATHOLOGY AND STATISTICAL ANALYSES: Absolute and relative liver weights were significantly increased at all time points and correlated with increased incidences of hepatocellular hypertrophy. At 2 years, there were significant treatment-related increases in the incidences of cholangiocarcinoma and hepatocellular adenoma. Three hepatocholangiomas were seen in the 1,000 ng/kg core study group and a single incidence of cholangioma each occurred in the 550 and 1,000 ng/kg core study groups. At 2 years, a significant dose-related increase in hepatic toxicity was observed and was characterized by increased incidences of numerous lesions including hepatocyte hypertrophy, multinucleated hepatocytes, diffuse fatty change, bile duct hyperplasia, bile duct cyst, oval cell hyperplasia, necrosis, pigmentation, inflammation, nodular hyperplasia, portal fibrosis, cholangiofibrosis, and toxic hepatopathy. The incidences of these lesions were generally decreased in the 1,000 ng/kg stop-exposure group compared to the 1,000 ng/kg core study group. The lung weights of 1,000 ng/kg rats were generally significantly increased at weeks 14, 31, and 53. At 2 years, treatment related increases in the incidences of cystic keratinizing epithelioma and squamous cell carcinomas were observed. In addition, dose-related increases in the incidences of bronchiolar metaplasia of the alveolar epithelium and squamous metaplasia were also observed. The incidence of gingival squamous cell carcinoma of the oral mucosa was significantly increased in the 1,000 ng/kg core study group at 2 years. Gingival squamous cell carcinoma, although reduced in incidence as compared to the 1,000 ng/kg core study group, was still present in the 1,000 ng/kg stop-exposure group. At 2 years, adenomas and/or carcinomas were present in the adrenal cortex of most core study groups and in the 1,000 ng/kg stop-exposure group. Dose-related effects on the incidences of adrenal cortex atrophy and cytoplasmic vacuolization were also seen. (ABSTRACT TRUNCATED)

Animals↗
PubMed2004

Characterizing complex peptide mixtures using a multi-dimensional liquid chromatography-mass spectrometry system: Saccharomyces cerevisiae as a model system.

A rugged, reproducible, multi-dimensional LC-MS system was developed to identify and characterize proteins involved in protein-protein interactions and/or protein complexes. Our objective was to optimize chromatographic parameters for complex protein mixture analyses using automated peptide sequence recognition as an analytical end-point. The chromatographic system uses orthogonal separation mechanisms by employing strong cation exchange (SCX) in the first dimension and reversed phase (RP) in the second dimension. The system is fully automated and sufficiently robust to handle direct injections of protein digests. This system incorporates a streamlined post analysis results comparison, called DBParser, which permitted comprehensive evaluation of sample loading and chromatographic conditions to optimize the performance and reproducibility. Peptides obtained from trypsin digestion of a yeast soluble extract provided an open-ended model system containing a wide variety and dynamic range of components. Conditions are described that resulted in an average (n = 4) of 1489 unique peptide identifications, corresponding to 459 non-redundant protein sequence database records (SDRs) in the 20 microg soluble fraction digest.

Chromatography, Liquid↗
PubMed2001

A mobile mass spectrometer for comprehensive on-line analysis of trace and bulk components of complex gas mixtures: parallel application of the laser-based ionization methods VUV single-photon ionization, resonant multiphoton ionization, and laser-induced electron impact ionization.

A newly developed compact and mobile time-of-flight mass spectrometer (TOFMS) for on-line analysis and monitoring of complex gas mixtures is presented. The instrument is designed for a (quasi-)simultaneous application of three ionization techniques that exhibit different ionization selectivities. The highly selective resonance-enhanced multiphoton ionization (REMPI) technique, using 266-nm UV laser pulses, is applied for selective and fragmentationless ionization of aromatic compounds at trace levels (parts-per-billion volume range). Mass spectra obtained using this technique show the chemical signature solely of monocyclic (benzene, phenols, etc.) and polycyclic (naphthalene, phenathrene, indol, etc.) aromatic species. Furthermore, the less selective but still fragmentationless single photon ionization (SPI) technique with 118-nm VUV laser pulses allows the ionization of compounds with an ionization potential below 10.5 eV. Mass spectra obtained using this technique show the profile of most organic compounds (aliphatic and aromatic species, like nonane, acetaldehyde, or pyrrol) and some inorganic compounds (e.g., ammonia, nitrogen monoxide). Finally, the nonselective ionization technique laser-induced electron-impact ionization (LEI) is applied. However, the sensitivity of the LEI technique is adjusted to be fairly low. Thus, the LEI signal in the mass spectra gives information on the inorganic bulk constituents of the sample (i.e., compounds such as water, oxygen, nitrogen, and carbon dioxide). Because the three ionization methods (REMPI, SPI, LEI) exhibit largely different ionization selectivities, the isolated application of each method alone solely provides specific mass spectrometric information about the sample composition. Special techniques have been developed and applied which allow the quasi-parallel use of all three ionization techniques for on-line monitoring purposes. Thus, a comprehensive characterization of complex samples is feasible jointly using the characteristic advantages of the three ionization techniques. Laboratory applications show results on rapid overview characterization of mineral oil-based fuels and coffee headspace. The first reported field applications include timely resolved on-line monitoring results on automobile exhausts and of waste incineration flue gas.

Journal Article↗
PubMed2004

Comprehensive on-line characterization of complex gas mixtures by quasi-simultaneous resonance-enhanced multiphoton ionization, vacuum-UV single-photon ionization, and electron impact ionization in a time-of-flight mass spectrometer: setup and instrument characterization.

This paper reports on a newly developed mobile mass spectrometer for comprehensive on-line analysis of complex gas mixtures such as ambient air or industrial process gases. Three ionization methods, namely, the resonance-enhanced multiphoton ionization (REMPI), vacuum-ultraviolet single-photon ionization (SPI), and electron impact ionization (EI) are implemented in this instrument and can be operated (quasi-) simultaneously. By means of this setup, a wide range of compounds can be analyzed due to the unique ionization selectivitiy and sensitivity profiles provided by the different ionization techniques. The mass spectrometer is designed for field application even under severe conditions. The REMPI technique is suitable for the selective and soft ionization (without fragmentation) of aromatic compounds at trace level (ppbv/pptv). The also soft but less selective SPI technique with 118-nm vacuum-ultraviolet laser pulses is used as a second laser-based ionization method. Mass spectra obtained by this technique show profiles of most organic compounds (aliphatic and aromatic species) and of some low IP inorganic substances (e.g., ammonia, nitrogen oxide) down to ppbv concentrations. In addition to the laser-based ionization techniques, EI ionization can be used for analysis of the bulk components such as water, oxygen, nitrogen, and carbon dioxide as well as for detection of inorganic minor components such as HCN or HCl from combustion flue gases at ppmv concentration levels. Each method yields specific mass spectrometric information of the sample composition. Special techniques have been developed to combine the three ionization methods in a single mass spectrometer and to allow the quasi-parallel application of all three ionization techniques.

Journal Article↗
PubMed2002

Plant antimutagens and their mixtures in inhibition of genotoxic effects of xenobiotics and aging processes.

The antimutagenic effect of the bioactive compounds from fruits of Morus alba L. (MA), Punica granatum L. (PG), Diospyros kaki L. (DK), Cydonia oblonga Mill. (CO) and roots of Glycyrrhiza glabra (GG) were investigated. The antimutagenic effects of compounds separately as well as their action in complex mixtures were studied on mutations induced by genotoxicants (X-rays, N-methylnitrosourea, cyclophosphamide, NaF) and aging in bone marrow cell chromosomes from mice and rats. When tested separately and in a complex mixture, the plant products showed an ability to decrease the frequency of chromosome aberrations. The antimutagenic properties of the complex mixtures were considerably greater than those of the separate components. More antimutagenic activity of the mixture was revealed when mutagenesis was the result of X-rays and the natural aging processes.

Aging↗
PubMed1999

Proteinchip(R) surface enhanced laser desorption/ionization (SELDI) mass spectrometry: a novel protein biochip technology for detection of prostate cancer biomarkers in complex protein mixtures.

Improving early detection, diagnosis, treatment monitoring and prognosis of cancer will require rapid and high throughput detection, identification, and measurement of multiple biomarkers. In this study, we demonstrate the versatility of the innovative SELDI ProteinChip(R) MS technology for the rapid, reproducible and simultaneous identification of four well-characterized prostate cancer-associated (PCA) biomarkers, prostate specific antigen (free and complexed forms), prostate specific peptide, prostate acid phophatase and prostate specific membrane antigen in cell lysates, serum and seminal plasma. Proteins corresponding to the mass of these biomarkers could readily be captured and detected using either chemically defined or antibody coated ProteinChip(R) arrays. Several (yet to be identified) proteins were found upregulated in cell lysates of pure populations of PCA cells procured by laser capture microdissection (LCM) when compared with mass spectra of normal cell lysates. Coupling LCM with SELDI provides tremendous opportunities to discover and identify the signature proteins associated with each stage of tumor development. Collectively, these observations demonstrate the potential of SELDI for the discovery and simultaneous detection of and clinical assay development for PCA biomarkers in complex biological mixtures.

Journal Article↗
PubMed2001

Comparison of complex DNA mixtures with generic oligonucleotide microchips.

The reproducibility of melting curves for repeated hybridizations of target DNA with generic oligonucleotide microchips is shown experimentally to depend on the character of matching between fragments of target DNA and immobilized oligonucleotides. The reproducibility of melting curves is higher for the perfect match duplexes and decreases as the number of mismatched pairs within duplexes increases. This effect was applied to the comparative analysis of complex DNA mixtures. We developed a scheme in which we can identify and discriminate between the probe oligonucleotides responsible for the distinctions between target DNA mixtures. A scheme is illustrated by comparing DNA mixtures corresponding to V-D-J genes connected with populations of mRNAs CDR3 TCR Vb (T-cell receptor beta complementarity determining region 3) from the thymus and pancreas of NOD mice. Our results demonstrate that generic microchips can be applied efficiently to the analysis of DNA mixtures.

Animals↗
PubMed2000

Comparison of comprehensive two-dimensional gas chromatography and gas chromatography--mass spectrometry for the characterization of complex hydrocarbon mixtures.

In this paper, we compare the current separation power of comprehensive two-dimensional gas chromatography (GCxGC) with the potential separation power of GC-mass spectrometry (GC-MS) systems. Using simulated data, we may envisage a GC-MS contour plot, that can be compared with a GCxGC chromatogram. Real examples are used to demonstrate the current potential of the two techniques in the field of hydrocarbon analysis. As a separation technique for complex hydrocarbon mixtures, GCxGC is currently about as powerful as GC-MS is potentially powerful. GC-MS has not reached its potential separation power in this area, because a universal, soft ionization method does not exist. The greatest advantage of GCxGC is, however, its potential for quantitative analysis. Because flame-ionisation detection can be used, quantitative analysis by GCxGC is much more robust, reliable and reproducible.

Chromatography, Gas↗
PubMed2004

Trilinear chemometric analysis of two-dimensional comprehensive gas chromatography-time-of-flight mass spectrometry data.

Two-dimensional comprehensive gas chromatography (GC x GC) is a powerful instrumental tool in its own right that can be used to analyze complex mixtures, generating selective data that is applicable to multivariate quantitative analysis and pattern recognition. It has been recently demonstrated that by coupling GC x GC to time-of-flight mass spectrometry (TOFMS), a highly selective technique is produced. One separation on a GC x GC/TOFMS provides retention times on two chromatographic columns and a complete mass spectrum for each component within the mixture. In this manuscript, we demonstrate how the selectivity of GC x GC/TOFMS combined with trilinear chemometric techniques such as trilinear decomposition (TLD) and parallel factor analysis (PARAFAC) results in a powerful analytical methodology. Using TLD and PARAFAC, partially resolved components in complex mixtures can be deconvoluted and identified using only one data set without requiring either signal shape assumptions or fully selective mass signals. Specifically, a region of overlapped peaks in a complex environmental sample was mathematically resolved with TLD and PARAFAC to demonstrate the utility of these techniques as applied to GC x GC/TOFMS data of a complex mixture. For this data, it was determined that PARAFAC initiated by TLD performed a better deconvolution than TLD alone. After deconvolution, mass spectral profiles were then matched to library spectra for identification. A standard addition analysis was performed on one of the deconvoluted analytes to demonstrate the utility of TLD-initiated PARAFAC for quantification without the need for accurate retention time alignment between sample and standard data sets.

Gas Chromatography-Mass Spectrometry↗
PubMed1990

Screening assays for carcinogenic agents and mixtures: an appraisal based on data in the IARC Monograph series.

To determine whether genotoxic and non-genotoxic carcinogens contribute similarly to the cancer burden in humans and which types of short-term test are more relevant for predicting human hazards, an analysis was performed on agents that were evaluated in IARC Monographs Supplements 6 and 7 for their carcinogenic effects in humans and animals and for activity in short-term genotoxicity tests. The prevalence of genotoxicity among four groups of agents, consisting of established human carcinogens (group 1, n = 30), probable human carcinogens (group 2A, n = 37), possible human carcinogens (group 2B, n = 113) and agents with limited evidence of carcinogenicity in animals (a subset of group 3, n = 66) was determined. Each of the groups 1, 2A and 2B contained a high proportion (80-90%) of genotoxic carcinogens, which were also multi-species or multi-tissue carcinogens. The distribution of carcinogenic potency in rodents did not reveal any specific characteristic of the human carcinogens in group 1 that would differentiate them from agents in groups 2A, 2B and many in group 3. Although limited by the data-base available through the Monographs series, this analysis implies that genotoxic carcinogens add more to the human cancer burden than non-genotoxic carcinogens. Thus, the continued use of in vitro/in vivo short-term tests, involving as endpoints DNA chromosomal or mutational damage, to identify genotoxic carcinogens or in the isolation of carcinogenic components in complex mixtures is fully justified. It is concluded that (a) an agent or complex mixture with unknown carcinogenic potential showing sufficient evidence of activity in genotoxicity assays in vitro or in vivo is likely to represent a hazard to humans and (b) an agent or complex mixture showing lack of activity in this spectrum of genotoxicity assays should undergo evaluation for carcinogenicity for rodent bioassay, in view of the present lack of validated short-term tests for non-genotoxic carcinogens.

Animals↗
PubMed1985

The urine mutagenicity assay system. Studies related to recovery, storage and concentration procedures.

Studies were conducted to determine (i) the effect of storage on the mutagenic activity of urine spiked with known mutagens, (ii) the efficiency of XAD-2 column on the recovery of complex mixtures from spiked urine samples, and (iii) whether the addition of XAD-7 resin to the column and/or the addition of methylene chloride to the elution process increases the recovery of mutagens from urine samples spiked with complex mixtures. Chemically spiked or nonspiked urine samples were concentrated with XAD resin and were tested for mutagenic activity with the Ames Salmonella/microsome assay system. The results indicate that the mutagenic activity of chemically spiked urine remains essentially unchanged after 7 d, but it decreases by approximately 50% for some compounds after 28 d of storage at -70 degrees C. The recovery of mutagens from mutagen-spiked urine varied from 0% to more than 100%. Mutagenic activities of concentrates from urine samples spiked with complex mixtures were higher if resin columns were eluted with both methylene chloride and acetone than with acetone alone. A slight increase in mutagenic activity was also found if a mixture of XAD-2 and XAD-7 instead of XAD-2 alone was used to concentrate urine spiked with air particle extracts.

Chromatography↗
PubMed2006

SNOSID, a proteomic method for identification of cysteine S-nitrosylation sites in complex protein mixtures.

Reversible addition of NO to Cys-sulfur in proteins, a modification termed S-nitrosylation, has emerged as a ubiquitous signaling mechanism for regulating diverse cellular processes. A key first-step toward elucidating the mechanism by which S-nitrosylation modulates a protein's function is specification of the targeted Cys (SNO-Cys) residue. To date, S-nitrosylation site specification has been laboriously tackled on a protein-by-protein basis. Here we describe a high-throughput proteomic approach that enables simultaneous identification of SNO-Cys sites and their cognate proteins in complex biological mixtures. The approach, termed SNOSID (SNO Site Identification), is a modification of the biotin-swap technique [Jaffrey, S. R., Erdjument-Bromage, H., Ferris, C. D., Tempst, P. & Snyder, S. H. (2001) Nat. Cell. Biol. 3, 193-197], comprising biotinylation of protein SNO-Cys residues, trypsinolysis, affinity purification of biotinylated-peptides, and amino acid sequencing by liquid chromatography tandem MS. With this approach, 68 SNO-Cys sites were specified on 56 distinct proteins in S-nitrosoglutathione-treated (2-10 microM) rat cerebellum lysates. In addition to enumerating these S-nitrosylation sites, the method revealed endogenous SNO-Cys modification sites on cerebellum proteins, including alpha-tubulin, beta-tubulin, GAPDH, and dihydropyrimidinase-related protein-2. Whereas these endogenous SNO proteins were previously recognized, we extend prior knowledge by specifying the SNO-Cys modification sites. Considering all 68 SNO-Cys sites identified, a machine learning approach failed to reveal a linear Cys-flanking motif that predicts stable transnitrosation by S-nitrosoglutathione under test conditions, suggesting that undefined 3D structural features determine S-nitrosylation specificity. SNOSID provides the first effective tool for unbiased elucidation of the SNO proteome, identifying Cys residues that undergo reversible S-nitrosylation.

Animals↗
PubMed2006

Protein thiol oxidation in health and disease: techniques for measuring disulfides and related modifications in complex protein mixtures.

Oxidant species are known to contribute to disease and dysfunction in biological systems. However, evidence has been progressively accumulating that demonstrates a more fundamental role for many oxidant species in the regulation of everyday function of healthy cells. Redox dependent signaling events involving the post-translational, oxidative modification of proteins has now been accepted as an important regulatory process, although the full extent of such mechanisms is yet to be determined. Some protein cysteinyl thiols are known to be susceptible to a number of redox-dependent modifications, including an interchange between the reduced thiol and several different oxidized disulfide states. Here, the role of oxidants as regulatory entities is reviewed, as are the many different ways protein disulfide formation can be analysed in complex protein mixtures. This includes an overview of many of the Proteomic strategies that can be used to identify proteins that form disulfides when pro-oxidizing conditions arise in cells, as well as related methods for studying intermediates that may precede disulfide formation.

Animals↗
PubMed2001

Application of an integrated matrix-assisted laser desorption/ionization time-of-flight, electrospray ionization mass spectrometry and tandem mass spectrometry approach to characterizing complex polyol mixtures.

Polyols are being used in a wide range of industrial applications including surfactants and precursors for grafted polymers. The characterization of polyols is of significance in correlating compositions and structures with their properties. We illustrate two real world examples where traditional analytical methods including GPC and NMR failed to reveal compositional differences, but the combination of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), electrospray ionization mass spectrometry (ESI MS), and MS/MS can produce compositional information required for problem solving. The first example involves failure analysis of four ethylene oxide and propylene oxide (EO/PO) copolymer products. The results from the mass spectrometry analysis unequivocally demonstrate that one of the samples has a small variation in copolymer composition, leading to its abnormal activity. The second example is in the area of deformulation of complex polyol mixtures. Two samples displaying similar properties and activities were found to be two different polyol blends. One of the samples is a more cost-effective product. These examples demonstrate that MALDI, ESI MS, and MS/MS should be seriously considered as an integrated component of an overall polyol characterization program in product failure analysis and deformulation.

Journal Article↗