Biomedical subjects
D M Burns
Publications and source records attributed to D M Burns.
Natural occurrence of an inhibitor of mammalian cell growth in human and mouse cells of normal and tumor origin.
N6-(delta2-isopentenyl)adenosine was found both as a component of tRNA and as the cytoplasmic mononucleotide in human leukemic lymphoblasts and myeloblasts from peripheral blood and bone marrow samples. This hypermodified nucleotide was also found in the tRNA and as a mononucleotide in human (MRC-5 and KB) and mouse (A9, FLV, LM, and RAG) cell lines. The relative amounts of this hypermodified nucleotide in the tRNA of the cell lines and the human leukemias were similar (the mean value being 0.06 +/- 0.03 mole % of the total tRNA nucleotide content); whereas the amounts occurring as the free cytoplasmic mononucleotide were more varied but still comparable (the mean value being 0.53 +/- .09 mole % of all cytoplasmic nucleotides) for all cells investigated with the notable exception of all normal, diploid cell lines under study (0.04 mole%). A possible relationship of the free cytoplasmic mononucleotide with the nucleotide in the tRNA for control of mammalian cell protein synthesis in vivo was investigated by addition of N6-(delta2-isopentenyl)adenosine to the culture medium. The exogenously added nucleoside caused inhibition of cell growth within 3 h and cell death within 36 h at concentrations as low as 0.4 muM. No comparable effects were seen when adenosine, adenine, or N6-(delta2-isopentenyl)-adenine were added to the cultures. The simultaneous presence of adenosine in cultures containing N6-(delta2-isopentenyl)adenosine did not alter the detrimental effects of the hypermodified nucleoside on cell growth even when the concentration of adenosine was 50-fold that of N6-(delta2-isopentenyl)adenosine. Addition of N6-(delta2-isopentenyl)adenosine to cell cultures caused within the first 6 h a significant reduction in the rates of RNA and protein synthesis; whereas DNA synthesis continued at a rate comparable to control and adenosine-treated cells for 18 h before decreasing.
Sympathetic ophthalmia after glaucoma surgery.
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Cigarette smoking among the elderly: disease consequences and the benefits of cessation.
The disease consequence of smoking occurs disproportionately among the elderly because of the long duration of cumulative injury or change that underlies the bulk of tobacco-caused disease. Older smokers are less likely than younger smokers to attempt quitting, but they are more likely to be successful in the attempts that they do make to quit. Excess absolute rates of disease incidence and mortality due to smoking increase steadily with increasing age and duration of smoking, and there is little evidence to suggest that the disease consequences of smoking diminish among the elderly. Although cardiovascular disease is the most common cause of excess mortality among younger smokers, lung cancer is the largest cause of excess smoking-related mortality over the age of 60 years; and at older ages the excess death rate from chronic obstructive lung disease equals that for cardiovascular disease. Because of the dramatic increases in smoking-related excess mortality with advancing age, approximately 70% of the 400,000 or more deaths occur among those over age 60 years. The benefits of cessation are proportionately somewhat less among the elderly and may manifest more slowly than among younger smokers, but cessation remains the most effective way of altering smoking-induced disease risks at all ages, including those over the age of 60 years.
Use of media in tobacco control programs.
Media messages have the potential to change public health. Changes in media have been associated with major changes in smoking behavior, but only when the rest of the social structure actively changed the environment for the smoker. These changes act synergistically with media messages, and cessation or behavior change occurs. Only when we put media into the larger construct of the society within which we live, and when that society is receptive to media messages, can one expect to see an effect. It is perhaps not a specific attitude change that is so critical, but rather the presence of those messages which can grow in the smoker's environment and eventually become strong enough to allow that smoker to quit for the long term.