The metabolism of two nasal carcinogens, N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), was investigated using cultured nasal septa of F344 rats. The explants were cultured with 14C-labeled N-nitrosamines, and unbound metabolites present in the medium were quantitated by high-performance liquid chromatography. The results indicated that the mucosa of the n...

Epidemiologic data have shown increased risks of lung cancer in nonsmokers exposed to environmental tobacco smoke (ETS). We measured biomarkers in urine samples from nonsmokers before and after a 4-h visit to a casino where smoking is allowed. The tobacco-specific lung carcinogen, NNK [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone] is a constituent of ETS. Urinary metabolites of NNK, 4-(methyl...

Epidemiologic data have shown increased risks of lung cancer in nonsmokers exposed to environmental tobacco smoke (ETS). We measured biomarkers in urine samples from nonsmokers before and after a 4-h visit to a casino where smoking is allowed. The tobacco-specific lung carcinogen, NNK [4-(methylnitrosamino)-1-(3-pyridyl)-1butanone] is a constituent of ETS. Urinary metabolites of NNK, 4-(methyln...

Epidemiological studies indicate that vegetable consumption protects against lung cancer in humans, but the protective constituents have not been identified. Phenethyl isothiocyanate (PEITC), which is release upon chewing of watercress (nasturtium officinale), is a chemopreventive agent against lung cancer induced by the tobacco-specific lung carcinogen 4- (methylnitrosamino)-1-(3-pyridyl-1-but...

OBJECTIVES It is especially difficult for hospitality workers to avoid secondhand smoke (SHS), meaning that they are likely particularly vulnerable the effects of SHS. The authors aimed determine degree which smoke-free laws protect from SHS exposure, by examining biochemical markers such exposure. MATERIAL AND METHODS This was a cross-sectional study exposure in non-smoking employees working s...

Let U be a set of elements and d a distance function defined among them. Let NNk(u) be the k elements in U−{u} having the smallest distance to u. The k-nearest neighbor graph (knng) is a weighted directed graph G(U, E) such that E = {(u, v), v ∈ NNk(u)}. Several knng construction algorithms are known, but they are not suitable to general metric spaces. We present a general methodology to constr...