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Background—Although a large number of allergens have been characterised, the structural, functional, and biochemical features that these molecules have in common, and that could explain their ability to elicit powerful IgE antibody responses, are still uncertain. Recently, there has been considerable interest in the role of the cysteine protease activity of the house dust mite allergen Der p 1 in biasing the immune response in favour of IgE production. Aims—To search for remote homologues of Der p 1 with sequences similar to the 30 conserved amino acids surrounding the catalytic cysteine residue (Cys34). Methods—Potential homologues were analysed by examining their three dimensional structures and multiple sequence alignments using the programs PROPSEARCH, ClustalW, GeneDoc, and Swiss Pdb Viewer. Results—Diverse allergens (for example, the plant cysteine protease papain, the transport protein lipocalin Mus m 1, and the ragweed allergen Amb a 5) have a similar structural motif; namely, a groove resembling the substrate binding groove of Der p 1. The groove is located inside an α–β motif, between an α helix on one side and an antiparallel β sheet on the other side. A similar common motif (a cysteine stabilised α–β fold) can also be found in some toxins and defensins. Conclusion—Allergens of diverse sources have a common structural motif, namely a groove located inside an α–β motif, which could potentially serve as a ligand binding site.

Nicotine is recognized to be the major inducer of tobacco dependence. The smoking of cigarettes as an advantageous delivery system for nicotine, accelerates and aggravates cardiovascular disease, and is causally associated with increased risks for chronic obstructive lung disease, cancer of the lung and of the upper aerodigestive system, and cancer of the pancreas, renal pelvis, and urinary bladder. It is also associated with cancer of the liver, cancer of the uterine cervix, cancer of the nasal cavity, and myeloid leukemia. In 1950, the first large-scale epidemiological studies documented that cigarette smoking induces lung cancer and described a dose-response relationship between number of cigarettes smoked and the risk for developing lung cancer. In the following decades these observations were not only confirmed by several hundreds of prospective and case-control studies but the plausibility of this causal association was also supported by bioassays and by the identification of carcinogens in cigarette smoke. Whole smoke induces lung tumors in mice and tumors in the upper respiratory tract of hamsters. The particulate matter of the smoke elicits benign and malignant tumors on the skin of mice and rabbits, sarcoma in the connective tissue of rats, and carcinoma in the lungs of rats upon intratracheal instillation. More than 50 carcinogens have been identified, including the following classes of compounds: polynuclear aromatic hydrocarbons (PAH), aromatic amines, and N-nitrosamines. Among the latter, the tobacco-specific N-nitrosamines (TSNA) have been shown to be of special significance. Since 1950, the makeup of cigarettes and the composition of cigarette smoke have gradually changed. In the United States, the sales-weighted average "tar" and nicotine yields have declined from a high of 38 mg "tar" and 2.7 mg nicotine in 1954 to 12 mg and 0.95 mg in 1992, respectively. In the United Kingdom, the decline was from about 32 mg "tar" and 2.2 mg nicotine to less than 12 mg "tar" and 1.0 mg nicotine per cigarette. During the same time, other smoke constituents changed correspondingly. These reductions of smoke yields were primarily achieved by the introduction of filter tips, with and without perforation, selection of tobacco types and varieties, utilization of highly porous cigarette paper, and incorporation into the tobacco blend of reconstituted tobacco, opened and cut ribs, and "expanded tobacco." In most countries where tobacco blends with air-cured (burley) tobacco are used, the nitrate content of the cigarette tobacco increased. In the United States nitrate levels in cigarette tobacco rose from 0.3-0.5% to 0.6-1.35%, thereby enhancing the combustion of the tobacco. More complete combustion decreases the carcinogenic PAH, yet the increased generation of nitrogen oxides enhances the formation of the carcinogenic N-nitrosamines, especially the TSNA in the smoke. However, all analytical measures of the smoke components have been established on the basis of standardized machine smoking conditions, such as those introduced by the Federal Trade Commission, that call for 1 puff to be taken once a minute over a 2-s period with a volume of 35 ml. These smoking parameters may have simulated the way in which people used to smoke the high-yield cigarettes; however, they no longer reflect the parameters applicable to contemporary smokers, and especially not those applicable to the smoking of low- and ultra-low-yield filter cigarettes. Recent smoking assays have demonstrated that most smokers of cigarettes with low nicotine yield take between 2 and 4 puffs per minute with volumes up to 55 ml to satisfy their demands for nicotine. The overview also discusses further needs for reducing the toxicity and carcinogenicity of cigarette smoke. From a public health perspective, nicotine in the smoke needs to be lowered to a level at which there is no induction of dependence on tobacco.

A method for detection of cyanide gas release from solutions and from suspensions of plant material is described which offers advantages in speed, safety and simplicity over the picric acid method.

The carbon monoxide deliveries of 20 major Canadian brands of cigarettes, determined by gas chromatography and using standard smoking conditions, were estimated and found to vary by a factor of about two. The CO yields were found to increase with puff volume and tobacco moisture, decrease with increased paper porosity, but remain essentially constant with puff duration. The data suggest that reduced CO deliveries can be achieved by increasing the cigarette paper porosity. Combustion temperature presumably also influences CO deliveries, but the relative role ascribed to dilution and combustion is not clear. It may be concluded that smokers can lower their CO exposure by reducing their puff volume, smoking cigarettes manufactured from high porosity paper, by taking fewer puffs, and decreasing their tendency to inhale. Since CO and tar deliveries are correlated, these measures would also tend to decrease a smoker's exposure to tar.

Mercury in cigarettes of domestic and foreign products was measured by Magon's method, and the sample of a domestic brand was burned by a smoking machine and the smoke was collected for the measurement of mercury. In tobacco leaf and paper, only inorganic mercury was found in both domestic and foreign products. Its amount in tobacco leaf and paper of a piece of cigarette was about 60 ng in domestic products and about 30 ng in foreign products. By burning, the unit length of a cigarette released about 5-7 ng of mercury into smoke.