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r% Vol. 7. No. I Family Praetice Synthetic Cigarettes May Not. Be Safer Luernarlunat Medicnl News Senlre ATLANTA - Although two poten- tially marketable synthetic cigarettes yield lower carbon monoxide and car- boxyhemoglobin concentrations with less total particulates than natural cig- arettes, they offer only a small im- provement in ability to prevent dam- age to the antibacterial defenses of the lung, Dr. G. Clinton Sornberger said at the annual scientific assembly of the American College of Chest Physi- cians. These nicotine-free cigarettes, known as Cytrel and NSM (New Smoking Material), are blends of to- bacco and synthetic smoking material, said Dr. Sornberger, of Harvard Med- ical ical School, Boston. " Real" cigarettes were the focus of two other Harvard studies presented at the assembly. Dr. Gary L. Huber found that pro- longed moderate exposure to tobacco smoke in experimental animals does not impair pulmonary alveolar mac- rophage function, the key host de- fense cell of the lung. In his study of the morphology of macrophages, Dr. Paul Davies found that after exposure to cigarette smoke, the lipid deposition in the pulmonary alveolar macrophages of experimental animals was 10 times greater than in age-matched control animals. In the synthetic-smoking study, male co rats were exposed to the two synthetic cigarettes and the natural ft'set,&Co. I cigarette using a 30-port automated Lorillard smoking machine. The natural cigarette was the_ stan- dard research one, equivalent to an unfiltered commercial tobacco cig- arette produced in the United States in the mid-1950's. The animals were exposed to a rela- tively high dose: 12 cigarettes of each product at 6-hour intervals, Dr. Sornherger said. Carbon monoxide concentrations in the whole smoke were 18,000 and 23,000 ppm, respectively, for the synthetic cigarettes and 32,000 for the tobacco bacco cigarette. Carboxyhemoglobin levels were "markedly different" for the three cigarettes: 2.4% and 8.6% for the synthetics in comparison to 14.9'7 for the tobacco, he said. Both the total particulate matter of the smoke collected in the exposure apparatus and the estimate of how much was retained in the rat lungs were less for the synthetic products than for the natural tobacco. The synthetics reached only 16% and 20% of the amount of total particulate mat- ter collected from the tobacco. The retained matter in the rat lungs was estimated to be 2.8%_ and 2.7%, com- pared with 3.5% for the tobacco. In experiments to determine the damage_ to the antibacterial defenses of the lung, the synthetic materials caused less impairment to the host de- fense system, yet the three cigarettes were "very similar" in their rate of Dr. Huber bacterial inactivation, Dr. Sornberger said. In the study of macrophage func- tion, Dr. Huber developed a model airway system to determine how much of the gas-phase components of tobacco smoke reached the alveolar macrophages of human smokers to help explain the discrepancy between macrophages being impaired in in- vitro studies but not in vivo ones. "We would hypothesize ... that potential macrophage gas-phase cyto- toxins are removed, for the most part, by the wet surface lining of the air- ways and do not reach the pulmonary macrophages in the alveolar spaces," he said. However, in Dr. Davies' study, al- veolar macrophages were found to contain 10 times more lipid inclusions in experimental animals after they were exposed to cigarette smoke than in nonexposed controls. , Using a :-techniqub~; known as stereology, a`quantitative estimate of . the structure of the macrophages was obtained. Stereology i5 "a technique that de- ` rives three-dimensional . information from random two-dimensional sec- . tions or linear intcrcepts.'-'•, It measures the volume density of subcellular components, the surface areas of boundary membranes, the numerical density of cellular organel- les, and the length of fibers. In cells from animals exposed_ to smoke for 30 days, the average vol- ume density of lipid inclusions in total cytoplasm was 10 times greater than in cells from control animals, he said. Micrographs of smoke-treated cells contained eight times more lipid inclu- sion ion profiles than control cells did. "We can therefore conclude that the increase in volume density of lipid inclusions in the smoke-treated cells is a result of an n increase in number and an increase in size," . Davies said. In the synthetic smoking study, Dr. Sornberger's associates were Drs. Vijay Mahajan, Alan Homans, Carl- ton McCarthy, and Gary L. Huber. In the macrophage function study, Dr. Huber's associate was Dr. John Shea. In the study of lipid deposition in macrophages, Dr. r. Davies' associates were Drs. G. Clinton Sornberger• Helen Benes, Gail Korman, and Gary L. Huber. I

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