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Biomedical subjects

D A Dunn

Publications and source records attributed to D A Dunn.

10 recordsLinked to original sources
PubMed2001

Choosing to remain smoke-free: the experiences of adolescent girls.

PURPOSE: To develop an understanding of the experiences of nonsmoking girls and determine how these girls avoid smoking. METHODS: A grounded theory approach was used to direct the discovery of process(es) that nonsmoking females undertake to remain nonsmokers. Seventeen nonsmoking females between the ages of 13 and 17 years were interviewed using open-ended questions designed by the authors. The interviews were tape-recorded and then analyzed using the techniques described by Strauss and Corbin. RESULTS: The data revealed that the process of remaining a nonsmoker is composed of three phases: making sense of smoking, rejecting smoking, and declaring oneself to be a nonsmoker. The process of remaining a nonsmoker appears to be rooted in developing self-confidence. As girls rejected smoking, self-confidence was boosted because they learned that their choice would be accepted and their strategies were effective in rejecting smoking. CONCLUSIONS: The findings of this study offer new insights into the experiences of adolescent nonsmokers. Our assumption that there is a process that underlies remaining a nonsmoker was supported. The findings suggest that adolescents use several strategies in this process. These strategies are noteworthy because they offer those who work in the field of health promotion new insights into ways in which they might contribute to increasing the ranks of nonsmokers.

Adolescent↗
PubMed1998

The relation of ERP components to complex memory processing.

The relation between various ERP components generated during encoding of a word and its subsequent recall were investigated using a "rote" serial-order and an "elaborative" category memory task. Words (flashed separately) were time-locked to EEG recordings from 21 cortical sites. ERP components from the five subjects having the highest recall scores were compared to the five lowest scoring subjects. Results based on the P200 peak amplitude data as well as the N400 and late positive component peak amplitude and latency data suggest that anterior and posterior distributional differences are elicited during encoding of words for rote and elaborative memory tasks. Furthermore, strong individual differences in these patterns were found as a function of task. A tentative argument was made that the obtained anterior and posterior differences may index different word feature selection and encoding processes, which are differentially utilized by high and low recallers.

Adult↗
PubMed1993

T-cell receptor V beta expression in normal human skin.

The skin-associated immune system is the first line of defense against pathogenic attack from the environment and is simultaneously tolerant to localized autoantigens and to antigens of the normal microbial flora. The T-cell receptor (TCR) repertoire of skin lymphocytes may therefore be influenced by the skin microenvironment. We studied the expression of TCR beta-chain variable region (V beta) genes in normal skin by a polymerase chain reaction-based comparative method. When comparing the amplification of V beta genes in peripheral blood and normal skin, we found that TCR V beta 1, -7, -14, and -16 were often highly expressed in skin relative to peripheral blood, whereas V beta 5.1 was often highly expressed in peripheral blood mononuclear cells but not in skin. These results demonstrate that the TCR repertoire of skin lymphocytes is not determined by random sampling of peripheral blood mononuclear cells but may be molded by the interaction with self antigens and/or the normal microbial flora in the microenvironment of the skin.

Base Sequence↗
PubMed1992

Base-selective oxidation and cleavage of DNA by photochemical cosensitized electron transfer.

A photochemical mechanism for single-strand cleavage of DNA is proposed in which a photoexcited intercalator transfers an electron to an externally bound cosensitizer. Once formed, the oxidized intercalator oxidizes an adjacent base, creating a charge-separated complex from which reactions leading to cleavage of the sugar-phosphate backbone occur in competition with back electron transfer. Using ethidium bromide (EB) as the intercalator and methyl viologen (MV) as the externally bound cosensitizer, a 10-fold enhancement in the rate of single-strand break formation was found in pBR322 DNA over that for EB alone using 488-nm excitation. The rate of cleavage correlated with the amount of MV bound to DNA. In accord with the expected redox properties of the one-electron-oxidized EB and the DNA bases, cleavage occurs selectively at guanines. Although the reaction proceeds in nitrogen-purged solutions, the rate of cleavage in air-saturated solutions was enhanced 2-fold. Treatment of irradiated samples with alkali leads to a 2-fold increase in the yield of single-strand breaks. These results support a mechanism in which cleavage occurs by selective oxidation of guanines in DNA, initiated by photochemical cosensitized electron transfer from intercalated EB to externally bound MV, and may provide a basis for the development of light-activated base-selective DNA cleaving agents.

DNA↗
PubMed1991

The role of ground state complexation in the electron transfer quenching of methylene blue fluorescence by purine nucleotides.

The effect of three purine nucleotides on the fluorescence of methylene blue in aqueous buffer has been investigated. Guanosine-5'-monophosphate (GMP) and xanthosine-5'-monophosphate cause fluorescence quenching while adenosine-5'-monophosphate causes a red shift in the fluorescence maximum. All three nucleotides form ground state complexes with the nucleotides as indicated by absorption spectroscopy. The fluorescence changes at nucleotide concentrations less than 30 mM are best described by a static mechanism involving the formation of non-fluorescent binary and ternary complexes in competition with dimerization of the dye. Quenching of the fluorescence decay (tau = 368 ps) at high GMP concentrations (10-100 mM) occurs at the rate of diffusion. The mechanism of fluorescence quenching may involve electron transfer within the singlet excited dye-nucleotide complex although published values of the oxidation potentials of various purine derivatives would suggest that all three nucleotides should cause quenching. Evidence for electron transfer was obtained from flash photolysis experiments in which 100 mM GMP was found to cause the appearance of a long lived transient species absorbing in the region expected for semimethylene blue.

DNA↗
PubMed1990

Influence of education and advertising on the uptake of smoking by children.

How effective are peer-led programmes in preventing the uptake of smoking by children? In 1981, we conducted a randomized controlled trial of a school-based educational programme for the prevention of smoking in children who were in their seventh year at school. In this article, the reported results of two years of follow-up confirm an earlier report that both teacher-led and peer-led programmes resulted in a reduction, to about the same degree, in the uptake of smoking by girls, while only the teacher-led programme appeared to be effective in boys. In girls, both the teacher-led and peer-led programmes maintained their effects over the two years of follow-up with adjusted differences in prevalence rates of the uptake of smoking relative to the control group of -6.6% (95% CL, -17.3%, 4.0%) and -8.1% (95% CL, -18.9%, 2.7%), respectively, after two years. In boys, the effect of the teacher-led programme was reduced substantially by the second year with a difference in the prevalence rate of -2.8% (95% CL, -11.2%, 5.6%); for the peer-led programme the difference in the prevalence rate was +6.4% (95% CL, -3.6%, 16.4%). Other variables which had a significant effect on the smoking behaviour were the perceived response to cigarette advertising, parental and sibling smoking status, the perceived parental sanctions on smoking behaviour, selected peer influences and the intention to smoke. The children's perceived responses to cigarette advertising showed the strongest and most consistent evidence of an effect on the uptake of smoking by children who initially were non-smokers. After adjustment for the effects of other variables there was an excess of 15.0% (95% CL, 2.1%, 27.9%) in the prevalence rate of smoking after two years for girls who thought that they were influenced by advertising compared with those who did not. The corresponding difference for boys was 15.3% (95% CL, 4.0%, 26.6%). As smoking-prevention programmes only may delay the onset of smoking in children, it is important that legislative measures be introduced to reduce the effects of cigarette advertising.

Advertising↗
PubMed1982

Aortoiliac reconstruction for occlusive disease: comparison of end-to-end and end-to-side proximal anastomoses.

Between 1968 and 1979, 192 aortofemoral bifurcation grafts were placed for aortoiliac occlusive disease. The proximal anastomosis was end-to-end in 101 and end-to-side in 91 patients. Anastomoses were end-to-end in 38 (37%) of 104 patients from 1968 to 1976 and 63 (72%) of 88 patients from 1977 to 1979. Embolization occurred intraoperatively in four end-to-end and five end-to-side anastomoses. The grafts became occluded in the early postoperative period in two patients with end-to-end proximal anastomoses. There were two aortoduodenal fistulas, both associated with end-to-side proximal anastomosis. The cumulative patency rate at 5 years was 87% for end-to-end and 85% for end-to-side anastomoses. An end-to-end proximal anastomosis is indicated for associated aneurysmal disease or in the presence of aortic occlusion, while an end-to-side anastomosis is indicated when there are low-lying accessory renal arteries or in the presence of occlusive disease in the external iliac arteries. The author's experience suggests that there is no difference in the incidence of intraoperative embolization or late occlusion between end-to-side and end-to-end proximal anastomosis. The incidence of aortoduodenal fistula appears to be lower with end-to-end proximal anastomosis possibly because of better tissue apposition at the anastomosis.

Aorta↗