Biomedical subjects

A R Tricker

Publications and source records attributed to A R Tricker.

65 records · Page 4Linked to original sources

PubMed1984

N-nitroso compounds and polycyclic aromatic hydrocarbons in Icelandic smoked cured mutton.

Five samples of Icelandic smoked cured mutton were analysed for volatile N-nitrosamines, N- nitrosoamino acids, total N-nitroso content and several polycyclic aromatic hydrocarbons. Levels varied considerably from sample to sample but generally the levels of polycyclic aromatic hydrocarbons and N-nitrosamines (as judged by N- nitrosoproline , N- nitrosohydroxyproline and total N-nitroso content) varied in the same way. It is suggested that in this product the smoking procedure is responsible for both groups of contaminants and that the curing process is relatively unimportant.

Animals↗

PubMedDate not supplied

Volatile N-nitrosamines in mainstream cigarette smoke: occurrence and formation.

Analytical data is presented for the occurrence of the three major volatile N-nitrosamines in cigarette tobacco and mainstream smoke, namely N-nitrosodimethylamine (NDMA),- N-nitrosoethylmethylamine (NEMA) and N-nitrosopyrrolidine (NPYR) as well as for the occurrence of the corresponding precursor amines and non-volatile N-nitrosamino acids in tobacco. Experimental studies using the C20 reference cigarette show that NPYR present in mainstream smoke results from direct transfer of preformed NPYR (ca. 1.5%), decarboxylation of N-nitrosoproline in tobacco (ca. 10%), pyrolytic nitrosation of pyrrolidine in tobacco (ca. 37%) and concerted decarboxylation/nitrosation of proline (ca. 52%) during tobacco pyrolysis.

Chromatography, Gas↗

PubMedDate not supplied

Uptake of tobacco smoke constituents on exposure to environmental tobacco smoke (ETS).

For the purpose of risk evaluation, passive smoking is frequently regarded as low-dose cigarette smoking. However, since the physical, chemical and biological properties of mainstream smoke (MS), which is inhaled by the smoker and environmental tobacco smoke (ETS), which is breathed by the passive smoker are quite different, risk extrapolation from active smoking to passive smoking is of doubtful value. In a series of experimental exposure studies we compared the uptake of tobacco smoke constituents by active and passive smoking. The results show that biomarkers which were found to be elevated after experimental ETS exposure, such as nicotine and cotinine in plasma and urine as well as thioethers in urine, indicate gas-phase exposure in passive smokers, but particle-phase exposure in active smokers. Biomarkers which should indicate the uptake of particle-bound, genotoxic substances with ETS, such as urinary mutagenicity, metabolites of polycyclic aromatic hydrocarbons (PAH) and DNA adducts, were not found to be elevated even after extremely high ETS exposure. From these results we conclude that a risk evaluation for passive smoking on the basis of dosimetric data is currently not possible.

Acetylcysteine↗

PubMedDate not supplied

Carcinogenic N-nitrosamines in the diet: occurrence, formation, mechanisms and carcinogenic potential.

Nitrosamines form a large group of genotoxic chemical carcinogens which occur in the human diet and other environmental media, and can be formed endogenously in the human body. N-Nitroso compounds can induce cancer in experimental animals. Some representative compounds of this class induce cancer in at least 40 different animal species including higher primates. Tumours induced in experimental animals resemble their human counterparts with respect to both morphological and biochemical properties. Extensive experimental, and some epidemiological data suggest that humans are susceptible to carcinogenesis by N-nitroso compounds and that the presence of these compounds in some foods may be regarded as an aetiological risk factor for certain human cancers including cancers of the oesophagus, stomach and nasopharynx.

Animals↗

PubMedDate not supplied

The occurrence of N-nitrosocompounds [corrected] in zarda tobacco.

The levels of tobacco-specific nitrosamines (TSNA), N-nitrosodiethanolamine, volatile and non-volatile N-nitroso compounds in zarda, a partially fermented Indian tobacco product are presented. Total identified N-nitroso compound concentrations ranged from 1.6 to 240 mg/kg fresh weight tobacco, TSNA accounted for 76-91% of the total N-nitroso compound burden. Preformed N-nitrosoethylmethylamine as well as the non-volatile compounds N-nitrososarcosine, N-nitrosoazetidine-4-carboxylic acid and N-nitrosothiazolidine-4-carboxylic acid were identified for the first time in tobacco products. The high levels of N-nitroso compounds present in zarda tobacco indicate that zarda chewing communities are exposed to a considerable exogenic burden of potentially carcinogenic compounds, in particular TSNA.

Carcinogens↗

PubMedDate not supplied

Incidence of some non-volatile N-nitroso compounds in cured meats.

Procedures are described for the use of high-performance liquid chromatography and gas chromatography with a chemiluminescence detector in the analysis of N-nitrosoamino acids, N-nitrosothiazolidine-4-carboxylic acid, N-nitroso-oxazolidine-4-carboxylic acids and N-nitroso dipeptides N-terminal in N-nitrosoproline in cured meat products. The detection limit is around 5-10 micrograms/kg. Evidence is presented for the presence of all these species except the N-nitrosated dipeptides.

Animals↗

PubMedDate not supplied

Synthesis of three N-nitroso dipeptides N-terminal in proline and a method for their determination in food.

The terminal N-nitroso derivatives of L-prolyl-L-alanine, L-prolylglycine and L-prolyl-4-hydroxy-L-proline have been synthesized and characterized. A procedure suitable for their analysis in biological samples has been developed and is based on the preparation of an aqueous extract, extraction into an organic solvent, separation by high-performance liquid chromatography and detection by a chemiluminescence method. The average recovery in all cases was above 69% at the level of 200 micrograms/kg using cured meat as a food matrix; the detection limit was 10 micrograms/kg.

Animals↗

PubMedDate not supplied

N-Nitrosopyrrolidine formation in bacon.

Evidence is presented that the likely major amine precursors to N-nitrosopyrrolidine in cooked bacon are free proline in the adipose tissue and to a lesser extent, collagenous connective tissues. A model system in which animal lipid is replaced with hydrogenated vegetable oil is described and used in investigating the potential role of prolyl derivatives as precursors to N-nitrosopyrrolidine.

Adipose Tissue↗

PubMedDate not supplied

Characterization studies on insoluble total N-nitroso compounds in bacon adipose connective tissue.

Enzymic hydrolysis was employed to solubilize 35% of the total N-nitroso compounds associated with bacon adipose connective tissue. Size exclusion chromatography of the digest showed that 95% of the solubilized N-nitroso compounds had molecular weights equivalent to those of di-, tri- and tetrapeptides. The likely identity of these compounds is discussed in the light of their extractability from acidified solution into ethyl acetate and their thermal and pH stability.

Adipose Tissue↗

PubMedDate not supplied

Review of the occurrence and formation of non-volatile N-nitroso compounds in foods.

A review of the literature published prior to July 1991 covers the occurrence and formation of non-volatile N-nitrosamines occurring in foods and beverages. The presence of identified volatile and non-volatile N-nitrosamines accounts for less than 10% of the total apparent N-nitrosamine concentration. N-Nitrosoproline and N-nitrosothiazolidine-4-carboxylic acid are the most commonly identified non-volatile N-nitrosamines in the diet. Non-volatile N-nitrosamines account for 12 of the 21 currently identified N-nitroso compounds in foods and beverages.

Beverages↗

PubMedDate not supplied

Biomarkers of exposure and potential harm in adult smokers of 3-7 mg tar yield (Federal Trade Commission) cigarettes and in adult non-smokers.

The paper reports levels of 24-h urine nicotine and five of its major metabolites (expressed as nicotine-equivalents) and blood carboxyhaemoglobin as biomarkers of exposure to particulate- and gas-phase cigarette smoke, respectively, from an exploratory pilot study of adult smokers of 3.0-6.9 mg tar delivery (Federal Trade Commission (FTC) method) cigarettes. On multiple occasions over 6 weeks, blood high-sensitivity C-reactive protein (hs-CRP), fibrinogen, HDL- and LDL-cholesterol, and 24-h urine 8-epi-prostaglandin F2alpha (8-epi-PGF2alpha) and 11-dehydro-thromboxane B2 (11-dehydro-TxB2) were also evaluated as biomarkers of potential harm. All the biomarkers examined, except for LDL-cholesterol, discriminated with high sensitivity and specificity between adult smokers and non-smokers overall. Except for HDL-cholesterol, all biomarker medians were greater in adult smokers than in non-smokers: urine nicotine-equivalents 64.514 versus < 0.034 nmol mg-1 creatinine (p<0.001), carboxyhaemoglobin 4.0 versus 0.4% saturation (p<0.001), hs-CRP 0.27 versus 0.12 mg dl-1 (p=0.05), fibrinogen 292 versus 248 mg dl-1 (p<0.001), HDL-cholesterol 46 versus 53 mg dl-1 (p=0.003), LDL-cholesterol 119 versus 109 mg dl-1 (p=0.18), urine 8-epi-PGF2alpha 1935 versus 1034 pg mg-1 creatinine (p<0.001) and urine 11-dehydro-TxB2 973 versus 710 pg mg-1 creatinine (p<0.001). All the biomarkers of exposure and most of the biomarkers of potential harm showed no time of sampling (by visit week) effect.

Biomarkers↗