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Biomedical subjects

D M Burns

Publications and source records attributed to D M Burns.

At least 19 recordsLinked to original sources
PubMed1992

Protection from environmental tobacco smoke in California. The case for a smoke-free workplace.

OBJECTIVE: To determine the extent of exposure of nonsmoking indoor workers to environmental tobacco smoke (ETS) according to type of work-site smoking policy, work area, workplace size, and demographic characteristics. DESIGN AND PARTICIPANTS: Participants included 7162 adult, nonsmoking, indoor workers who were interviewed as part of the 1990 California Tobacco Survey. Respondents were asked whether anyone had smoked in their work area within the past 2 weeks. RESULTS: An estimated 2.2 million California nonsmokers were exposed to tobacco smoke at indoor work sites in 1990. Nonsmoker exposure to ETS was 9.3% for those working in a smoke-free worksite, 23.2% for those working where there was only a work-area restriction, 46.7% for those working where there was a policy that did not include the work area, and 51.4% for those working where there was no work-site smoking policy. After adjustment for type of work area (eg, office, open area), workplace size, and demographic factors, it was determined that nonsmokers working where there was only a work-area ban were 2.8 times more likely to be exposed to ETS than those working in a smoke-free work site. In workplaces with no policy or a policy not covering the work area, nonsmokers were over eight times more likely to be exposed to ETS than those who worked in a smoke-free work site. Nonsmokers who were 18 to 24 years of age, male, or Hispanic, and those with less than a high school education had more exposure to ETS. CONCLUSION: These results indicate that adequate protection of nonsmokers from ETS exposure requires a smoke-free work site.

Adolescent↗
PubMed1992

Positive evidence on effectiveness of selected smoking prevention programs in the United States.

Various smoking intervention approaches have been demonstrated to successfully alter smoking behavior among individual smokers, but it is difficult to demonstrate the benefit of these individual cessation approaches across the population of smokers. In contrast, efforts that concentrate on altering the social and economic environment within which the smoker smokes, most notably the media, taxation, and changing the social acceptability of smoking, have been linked to substantial shifts in the smoking behavior of the US population. Attacking tobacco use as a form of sociological carcinogenesis, rather than focusing on the individual smoker, allows alteration at the root of smoking behavior, ie, its personal, social, and psychological utility for the smoker.

Health Education↗
PubMed1991

Does tobacco advertising target young people to start smoking? Evidence from California.

OBJECTIVE: To evaluate whether tobacco advertising encourages teenagers younger than 18 years to start smoking. DESIGN: Comparison of 1990 California telephone survey data with data from a 1986 national telephone survey (both used a random-digit dialing system); 95% confidence intervals were calculated. To test our hypothesis, we considered whether the perception of advertising was related to age, whether the pattern of market share across age and sex groups followed the pattern of perceived advertising, and whether changes in market share paralleled changes in advertising as perceived by the youngest age group. PARTICIPANTS: There were 24,296 adults and 5040 teenagers. RESULTS: The most advertised brands of cigarettes were Marlboro, according to 33.6% of adults and 41.8% of teenagers, and Camel, according to 13.7% of adults and 28.5% of teenagers--named most often by 12- to 13-year-olds (34.2%). The brands that were purchased most often were Marlboro and Camel. Together these were the brands of choice of 79.9% of males and 85% of females aged 12 through 17 years. Marlboro's market share increased in youths and young adults up to age 24 years and then decreased gradually with age; Camel's market share decreased abruptly with age: it was the brand of choice of 24.5% +/- 5.8% of males aged 12 through 17 years but was chosen by only 12.7% +/- 3.6% of males aged 18 through 24 years; for females, 21.7% +/- 13.7% aged 12 through 17 years chose Camels, while only 5.5% +/- 3.2% aged 18 through 24 years preferred this brand. Both Marlboro and Camel brands had a higher market share in California in 1990 compared with that for the United States in 1986. Of interest is that the market share for Camel increased among the younger smokers but was more evenly distributed for Marlboro. CONCLUSIONS: Perception of advertising is higher among young smokers; market-share patterns across age and sex groups follow the perceived advertising patterns; and changes in market share resulting from advertising occur mainly in younger smokers. Cigarette advertising encourages youth to smoke and should be banned.

Adolescent↗
PubMed1991

Cigarettes and cigarette smoking.

Tobacco use was widespread in the New World by the time of the first voyage of Columbus; however, it is only in the last century that the use of tobacco as cigarettes has been prevalent. The milder tobacco and more acidic smoke of cigarettes lead to the deeper inhalation of tobacco into the lung with resultant deposition and absorption of the addicting, toxic, and carcinogenic components of the smoke. More than 4000 individual constituents have been identified in cigarette smoke, and the relative concentrations of these constituents vary widely between brands of cigarettes. Tar yield, a measure of the total particulate matter of the smoke, varies markedly with the characteristics of the cigarette manufacture and with the pattern of inhalation. As a result, tar is not a good measure of the dose of toxic or carcinogenic agents received by the individual smoker. The particle size of cigarette smoke is in the range that will lead to deposition in the airways and alveoli of the lung, and many of the gas-phase constituents are absorbed across the alveolar capillary membrane. The irritant agents in the smoke cause acute and chronic changes in lung structure and function that may result in greater retention of carcinogens within the lung and increased vulnerability of the lung to the effects of these carcinogens. Carcinogens and other constituents of cigarette smoke are also absorbed into the blood and metabolized to active forms through microsomal enzyme systems induced by cigarette smoke. The cellular influx of neutrophils and alveolar macrophages that is part of the inflammatory response may be the precursor of the alveolar wall destruction that results in emphysema. The prevalence of smoking is not uniformly distributed across the population. Men began smoking in large numbers very early in the century, but women began to smoke in large number only at the time of the Second World War. Men born after 1930 have been less likely to take up smoking than their older counterparts. The prevalence of smoking is currently declining in both men and women.

Cardiovascular Diseases↗
PubMed1990

Evolution of the tryptophan synthetase of fungi. Analysis of experimentally fused Escherichia coli tryptophan synthetase alpha and beta chains.

During evolution of fungi, the separate tryptophan synthetase alpha and beta polypeptides of bacteria appear to have been fused in the order alpha-beta rather than the beta-alpha order that would be predicted from the order of the corresponding structural genes in all bacteria. We have fused the tryptophan synthetase polypeptides of Escherichia coli in both orders, alpha-beta and beta-alpha, with and without a short connecting (con) sequence, to explore possible explanations for the domain arrangement in fungi. We find that proteins composed of any of the four fused polypeptides, beta-alpha, beta-con-alpha, alpha-beta, and alpha-con-beta, are highly active enzymatically. However, only the alpha-beta and alpha-con-beta proteins are as active as the wild type enzyme. All four fusion proteins appear to be less soluble in vivo than the wild type enzyme; this abnormal characteristic is minimal for the alpha-con-beta enzyme. The alpha and beta domains of the four fusion polypeptides were not appreciably more heat labile than the wild type polypeptides. Competition experiments with mutant tryptophan synthetase alpha protein, and the fusion proteins suggest that in each fusion protein the joined alpha and beta domains have a functional tunnel connecting their alpha and beta active sites. Three tryptophan synthetase beta'-alpha fusion proteins were examined in which the carboxyl-terminal segment of the wild type beta polypeptide was deleted and replaced by a shorter, unnatural sequence. The resulting deletion fusion proteins were enzymatically inactive and were found predominantly in the cell debris. Evaluation of our findings in relation to the three-dimensional structure of the tryptophan synthetase enzyme complex of Salmonella typhimurium (5) and the results of mutational analyses with E. coli suggest that tryptophan synthetase may have evolved via an alpha-beta rather than a beta-alpha fusion because in beta-alpha fusions the amino-terminal helix of the alpha chain cannot assume the conformation required for optimal enzymatic activity.

Amino Acid Sequence↗
PubMed1989

Nucleotide sequence of the Neurospora crassa trp-3 gene encoding tryptophan synthetase and comparison of the trp-3 polypeptide with its homologs in Saccharomyces cerevisiae and Escherichia coli.

The complete nucleotide sequence of the Neurospora crassa trp-3 gene-encoding tryptophan synthetase has been determined; we present an analysis of its structure. A comparison of the deduced amino acid sequence of the trp-3 polypeptide with its homologs in Saccharomyces cerevisiae (encoded by the TRP5 gene) and Escherichia coli (encoded by the trpA and trpB genes) shows that the A and B domains (amino acid segments homologous to the trpA and trpB polypeptides, respectively) of the N. crassa and yeast polypeptides are in the same order (NH2-A-B-COOH). This arrangement is the reverse of the gene order characteristic of all prokaryotes that have been examined. N. crassa tryptophan synthetase has strong homology to the yeast TRP5 polypeptide (A domains have 54% identity; B domains have 75% identity), and somewhat weaker homology to the E. coli trpA and trpB polypeptides (A domains have 31% identity; B domains have 50% identity). The two domains of the N. crassa polypeptide are linked by a connector of 54-amino acid residues that has less than 25% identity to the 45-residue connector of the yeast polypeptide, although secondary structure analysis predicts both connectors would be alpha-helical. In contrast to the yeast TRP5 gene, which has no introns, the trp-3 coding region is interrupted by two introns 77 and 71 nucleotides in length. Both introns are located near the 5'-end of the gene and therefore not near the segment encoding the connector.

Amino Acid Sequence↗
PubMed1989

Diurnal variation in norepinephrine-stimulated release of pineal serotonin in vitro.

Adult, male rats were maintained under 12L:12D with lights on at 06.00h. Their pineal glands were incubated at 37 degrees C in the presence or absence of 10(-4)M norepinephrine (NE). 5-HT and various metabolites were quantitated in post-incubation media and pineal glands by high performance liquid chromatography coupled with electrochemical detection. No differences were observed in the quantities of 5-HT released by pineal glands in four hour incubations starting at either 06.00, 13.00 or 18.00 h; however, a highly significant decrease below these levels was observed at 01.00h. NE significantly stimulated 5-HT release at 13.00 and 18.00 h, but was ineffective at 01.00 and 06.00h. These results confirm recently reported stimulatory effects of NE on the release of 5-HT into pineal gland incubation medium and further suggest a diurnal rhythm of pineal gland sensitivity to NE in vitro with maximum stimulation of 5-HT release at midphotophase.

Animals↗
PubMed1989

Procalcitonin's amino-terminal cleavage peptide is a bone-cell mitogen.

The parafollicular-cell (C-cell) hormone calcitonin (CT) can preserve or even augment skeletal mass by inhibiting osteoclast-mediated bone resorption. The possibility of an additional anabolic skeletal influence has also been raised: C cells might, via CT or other secretory products, affect osteoblast-mediated bone formation. The 57-residue amino-terminal procalcitonin cleavage peptide, N-proCT, has recently been identified in human and rat C cells, where it is made and secreted in equimolar amounts with CT. The coelaboration of N-proCT and CT and N-proCT's sequence conservation during evolution prompted us to investigate the potential skeletal bioactivity of N-proCT. We found that synthetic human N-proCT, at nanomolar concentrations, stimulated proliferation of normal and neoplastic human osteoblasts. At maximally effective doses, human N-proCT caused more than a 100% increase above the control rate of DNA synthesis, an effect comparable to the maximal growth effect of insulin, a potent mitogen for osteoblasts. Human N-proCT exerted a similar maximal mitogenic effect in chicken osteoblast cultures but at 1000-fold greater concentrations than in human bone-cell cultures. The bone-cell action of N-proCT was potentiated with insulin with a greater than 200% increase in DNA synthesis at high insulin concentrations. In sharp contrast to these findings for N-proCT, the other bioactive C-cell peptides, CT and somatostatin, showed no mitogenic effects in human or chicken osteoblast cultures. Our results indicate that the action of N-proCT on cultured bone cells is separate from and potentiated by insulin, a known growth factor. Unlike insulin and related growth factors such as insulin-like growth factor I, N-proCT is not mitogenic in skin fibroblast cultures. We propose that N-proCT is a C-cell hormone that promotes bone formation via stimulatory actions on osteoblasts and preosteoblasts.

Amino Acid Sequence↗
PubMed1989

A neuroendocrine peptide derived from the amino-terminal half of rat procalcitonin.

The sequence of rat procalcitonin reveals that calcitonin is located within the precursor's midregion, flanked by two potential polybasic cleavage sites that separate it from amino- and carboxyl-terminal domains. Cleavage at the polybasic sites during precursor processing to generate the 32-residue calcitonin should also generate 57- and 16-residue peptides from the amino- and carboxyl-terminal flanking regions. The carboxyl-terminal flanking hexadecapeptide and its coordinate secretion from C cells with calcitonin have been previously reported. In the present study we have focused on the predicted 57-residue amino-terminal procalcitonin cleavage peptide (N-proCT). We raised antisera to synthetic peptides homologous to the carboxyl- and amino-terminal regions of the putative 57-amino-acid N-proCT and screened calcitonin-rich neoplastic and nonneoplastic C-cells for these two immunoreactivities. A single species of 7.4 kilodaltons detected in C cells by gel filtration and reversed-phase HPLC analyses accounts for most of the carboxyl- and amino-terminal immunoreactivities and possesses the biochemical and biological features predicted for N-proCT. When C cell hyperplasia is induced by a high fat diet, thyroidal levels of calcitonin and N-proCT increase in parallel. In neoplastic C cell cultures, N-proCT and calcitonin concentrations are nearly equimolar in both cellular extracts and basal medium; dexamethasone increases both the cellular and secreted concentration of these peptides. Basal and dexamethasone-treated cultures show calcium-dependent, parallel secretion of N-proCT and calcitonin. Thus, the 57-residue N-proCT predicted from analysis of the procalcitonin sequence is a secretory peptide that appears to be present in equimolar amounts and coordinately regulated with calcitonin in vivo and in vitro.

Animals↗
PubMed1988

Biologic interactions between smoking and occupational exposures.

Cigarette smoking is a major cause of cancer and lung disease in the U.S. population. The biological processes that underlie the response of the lung to cigarette smoke are important considerations for designing analyses of the effects of occupational exposures. Interactions between cigarette smoking and occupational exposures may occur through a combined effect on the mechanism of disease production, through an effect on the dose of the toxic substances that reach the target issue, or through an effect on the response of the lung to the toxic agents. Disease due to occupational exposures can occur in a similar pattern in both smokers and nonsmokers; however, as more complex interactions are examined, different responses to the same occupational exposure may be identified for smokers and nonsmokers. It is only through the successful intermingling of biologic information with epidemiologic data that these interactions can be fully examined.

Carcinogens, Environmental↗
PubMed1988

Seroepidemiologic studies on the acquisition of antibodies to cytomegalovirus, herpes simplex virus, and human immunodeficiency virus among general hospital patients and those attending a clinic for sexually transmitted diseases.

A total of 731 sera were collected from general hospital patients, divided into five distinct subgroups, and tested for the presence of immunoglobulin (IgG) to cytomegalovirus (CMV) and herpes simplex virus (HSV). The results indicate a high level of association between the two viruses, although HSV was found to be more prevalent in the earlier years of life, whereas CMV was acquired constantly throughout life. An increase in age was also accompanied by significantly higher antibody levels to both viruses. Individuals with antibody to HSV were significantly more likely to have antibodies to CMV, suggesting that these viruses are transmitted by similar routes (?saliva). In addition, 430 sera from 94 homosexual and 336 heterosexual males attending a clinic for sexually transmitted diseases were tested for antibody to CMV, HSV, and human immunodeficiency virus (HIV). Homosexual males were more likely to have antibody to CMV and HIV than were heterosexuals, but no difference was seen for HSV antibodies. The levels of CMV-specific IgG were significantly raised in homosexuals, compared with heterosexuals, but again no difference was seen for HSV antibodies as in the general hospital patients, however, individuals with HSV antibodies were significantly more likely to possess antibodies to CMV. However, the additional association of CMV antibodies with a homosexual lifestyle suggests that an alternative route for acquisition of this virus exists (?semen). As raised levels of CMV antibodies, but not HSV antibodies, were found among homosexuals, this suggests that frequent CMV reinfections, rather than merely reactivation of latent herpes viruses, may be occurring.

Antibodies, Viral↗
PubMed1988

Possible involvement of the hypothalamic dopaminergic system in the prolactin-inhibitory effects of the pineal gland in blind-anosmic male rats.

The purpose of the present study was to assess whether the pineal-induced suppression of prolactin (PRL) cell activity in blind-anosmic (BA) rats was possibly mediated via the hypothalamic dopaminergic system. Prepubertal male rats were divided into the following groups: sham-operated (Sham), BA and blind-anosmic-pinealectomized (BAP). Animals from each group were sacrificed 1, 4 and 8 weeks after the operations. Blinding and anosmia resulted in pineal-dependent decreases in the weight of the testes, accessory organs and anterior pituitaries at 4 and 8 weeks but not 1 week after the operations. Likewise serum PRL levels were significantly decreased in BA rats at 4 and 8 weeks but this effect was not prevented in BAP rats. Hypothalamic dopamine (DA) turnover in BA rats at 1 week was twice that seen in either the Sham or BAP groups at that time; this effect ended by 4 weeks. There were no effects of any treatment on DA turnover at 8 weeks. Finally, PRL cell sensitivity to DA inhibition was determined by measuring the release of PRL from pituitaries incubated in vitro with either vehicle or 5 x 10(-7) M DA. None of the treatments caused significant alterations in the response to DA, though this must be interpreted with caution since only one dose of DA was used. From these data we conclude that: (1) there is an increase in DA neuron activity that precedes the inhibition of both PRL secretion and the reproductive system in BA rats, and (2) the inhibition of PRL cell activity in these animals is apparently not due to an increase in sensitivity to DA.

Animals↗
PubMed1987

Infection with human immunodeficiency virus (HIV) and cytomegalovirus in a London health district 1980-4.

By testing serum samples taken between 1980 and 1984 from men attending a department of sexually transmitted diseases, it was shown that antibodies to human immunodeficiency virus (HIV) first appeared in 1981. Homosexual men were significantly more likely to have antibodies to HIV and to cytomegalovirus (CMV) than were heterosexual men attending the same clinic. This shows that homosexuals are exposed to both HIV, the cause of the acquired immune deficiency syndrome (AIDS), and to CMV, which can reactivate to cause life threatening disease once immunosuppression has developed. All homosexuals, not just those with antibodies against HIV, had raised levels of CMV antibodies. This suggests that they experience frequent antigenic stimulation after reinfections with CMV or reactivation of endogenous virus.

Adolescent↗