Assessment of nicotine uptake from cigarette smoke: comparison of a colorimetric test strip (NicCheck I™) and gas chromatography/mass selective detector.

Colorimetric test strip assays are a convenient and inexpensive means for the determination of cotinine in human urine because they can be performed in a nonlaboratory environment using a trained technician. Four hundred human urine samples were separated into four categories: (1) heavy smokers (>20 cigarettes smoked per day), (2) light smokers (<20 cigarettes smoked per day), (3) non-smokers, and (4) vegetarian non-smokers. Samples were evaluated by a gas chromatography/mass selective detector (GC/MSD) method as a reference and using NicCheck I™ (DynaGen, Inc.). Colour intensity can range from 0 (no colour) to 14 (deep pink). Qualitative values were assigned as negative (0), low (1-6) and high (7-14). Comparison of the test strip and GC/MSD results showed: (1) 43 (10.75%) false negatives using the criterion of a GC/MSD cotinine level above 200 ng ml(-1) and test strip reading of 0, (2) 31 (7.75%) false positives using the criterion of a GC/MSD cotinine level below 1 ng ml(-1) and a test strip reading of 1 or greater, and (3) no correlation between the test strip and GC/MSD results (r = 0.597, p < 0.05). The fact that the colorimetric reaction is sensitive to many nicotine metabolites and/or heterocyclic amine structures whereas the GC/MSD method measures nicotine and cotinine selectively might explain the false positive results. False negative results were likely to be due to a lack of sensitivity of the test strip.

Selenosis, hepatic selenium accumulation, and plasma glutathione peroxidase activity in chicks as affected by a factor in linseed meal.

Linseed meal has previously been reported to contain an organic factor that reduces toxicity of selenium in animals. The purpose of the studies reported here was to obtain information on the mechanism of action of the linseed meal factor in counteracting selenosis in chicks. Feeding a diet containing 20% linseed meal to chicks partially counteracted the growth depression caused by including high levels of selenium (10-40 ppm) in the diet. In contrast to the rat, chicks fed diets containing selenium did not accumulate significantly more of the element per unit of liver dry matter when the diet contained linseed meal, and at two selenium levels accumulated significantly less. Linseed meal did not interfere with the absorption of an oral dose of 75Se as measured by tissue retention 24 hours later. A methanol extract of linseed meal did not interfere with the normal increase in plasma glutathione peroxidase activity in chicks fed diets supplemented with low levels of selenium even though the extract counteracted the growth depression obtained by adding 20 ppm selenium. Linseed meal contains a factor that interacts with selenium in the tissues in some unknown way to reduce the toxic effects of the element, but does not prevent normal synthesis of glutathione peroxidase.