RESEARCH
φ Fallout Particles Pose for Portraits As part of its studies on devising effective protection against fallout from nuclear explosions, the Naval Radiological De fense Laboratory. San Francisco, analyzes fallout particles themselves. Particles, as seen through a pétrographie microscope, reveal: Tower shots at Nevada (left and center) produce particles that are mostly small, metallic-looking spheres. Many are magnetic. T h e spheres are colorless glass with an outside layer of black radioactive material.
cancer-producing activity: a 5'"' concentration painted on the backs of mice produces 27r< incidence of cancer within five months. In contrast, tar from whole tobacco leaf requires a 50' r solution applied for a year to yield a single cancer. According to Wynder, every one of the cancer-producing substances identified in whole tar is present, and in greater amounts, in tne t a r from waxy coating. W y n d e r also notes that tar from the waxy coating is less carcinogenic when burned at lower temperatures. Studies are now under way to test the cancercausing activity of cigarettes made from tobacco from which the waxy coating has been removed. George Wright and associates of University of Toronto carried out the chemical aspect of this work. • Rebuttal. Asked to comment about Wynder's report, the Tobacco Industry Research Committee says (in part): "Sweeping assumptions have been m a d e by attempting to relate some mouse skin painting experiments to selected statistics about human lung cancer t h a t have themselves been questioned b y other scientists. . . . Mention of 'safer cigarettes' is clearly based on a n u m b e r of assumptions that have not b e e n scientifically established and must still stand the test of careful scientific review." 30
C & EN
APRIL
2 9,
1957
Silicates—feldspar and quartz in the Nevada soil—produce the glass. Radioactivity is concentrated in the iron-rich areas of the particles. Surface explosions at Nevada (cross section at right) throw out transparent, yellow-green spheres and irregular brown grains. The angular particles resemble the mineral grains mixed in the fireball. First shots of the particles were shown at the Naval Research Symposium, Washington, D. C , by NRDL's C. E. Adams.
Exploring Atherosclerosis Lipotropic preparations useless in treating atherosclerosis; despite claims made for such products J O - C A L L E D lipotropic factors that cause fat removal from tissue do not alter development of atherosclerosis when added to cholesterol-containing animal diets. According to Ruth Pick, Jeremiah Stamler, and Louis N. Katz of Michael Reese Hospital, various lipotropic factors have been tested to determine their possible action on atherosclerosis development in chicks. These include choline, inositol, pancreatin. activated whole pancreas, antifatty-liver factor, tocopherols, vitamin B1L>, lecithin, and others. The negative results obtained agree with those of most other workers studying other laboratory animals and man. Therefore, says Pick, there is no research basis to support the widely publicized claims that lipotropic preparations are useful in preventing and treating human atherosclerosis. Results with defatted brain extract preparations, as well as with plant sterols and other sterols closely resembling cholesterol, have been more en-
couraging. These materials, when fed to lab animals together with cholesterol, apparently prevent the gastrointestinal absorption of cholesterol, thus inhibiting atherosclerosis. However, recent studies indicate that some of these sterols may themselves be absorbed, with resulting atherogenesis. These substances must, therefore, still be considered experimental. Atherosclerosis is essentially a problem of cholesterol-lipide-lipoprotein metabolism in which nutrition plays a key role, she emphasizes. By alteration of cholesterol-lipide-lipoprotein metabolism, atherosclerosis can be induced in every one of the major laboratory animals. Atherosclerosis, however, is not exclusively a dietary disease, says Pick. In any large group of middle-aged Americans eating essentially similar diets, women have much less atherosclerosis. Among the men, a minority would exhibit clinical signs of coronary heart disease while a higher percentage would show coronary atherosclerosis if they were autopsied. Diet alone cannot account for such sex and individual differences. The problem of atherosclerosis apparently involves an intricate interplay between diet and individual differences in heredity, sex, physical activity, fatigue, stress, various metabolic diseases, local factors
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