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Biomedical subjects

J Piette

Publications and source records attributed to J Piette.

At least 199 records · Page 11Linked to original sources
PubMed1979

Influence of the DNA structure on the free radical induction due to proflavine and light treatment.

Induction of peroxide free radicals (detected by Electron Paramagnetic Resonance at 77 K) due to the photodynamic activity of proflavine was measured on bacteriophage phi X174 DNA either single-stranded (ss) as isolated from the virion, or double-stranded supercoiled (RFI) as isolated from the infected bacteria. Comparison was made with calf thymus DNA photosensitization. In order to use equivalent DNA-proflavine complexes, binding of the dye to the three DNA's was first determined under those conditions of high ionic strength favourable to the photodynamic reaction. Free radical induction was maximal for definite amounts of bound proflavine (which varied depending upon the DNA substrate) and at an ionic strength value of 0.5. The level of the maximal reaction increased in the following order: from phi Xss DNA to calf thymus DNA and finally to phi XRFI DNA. The conformation of the proflavine-DNA complex was thus a determinant for the efficiency of the photodynamic process. The ionic strength effect could not be explained by the evolution of the proflavine triplet state in irradiated proflavine-calf thymus DNA complexes.

Acridines↗
PubMed1978

Photodynamic activity of dyes with different DNA binding properties I. free-radical induction in DNA.

The photosensitizing efficiencies of eight dyes have been compared; two acridines, two xanthene derivatives, one sulphur-containing dye and three chemotherapeutic agents. The analysed reaction was the photosensitized induction of free radicals in calf-thymus DNA at low temperature. The binding of these dyes to DNA was first measured. Both strong (process I) and weak (process II) binding, with different intensities, either alone or together, were observed as mode of fixation. Whatever the nature of their binding, all the dyes used revealed a photosensitizing power as inducers of peroxide radicals in DNA. Their relative efficiencies, expressed as a function of the amount of dye molecules bound to DNA, were found to be very different. Intercalation, however, appeared to favour the free-radical induction as the first strongly bound molecules were more efficient.

Acridines↗
PubMed1978

Photodynamic activity of dyes with different DNA binding properties II. T4 phage inactivation.

The photosensitizing efficiency of six dyes--proflavine, 9-aminoacridine, ethidium bromide, thiopyronine, pyronine and acridine red--have been compared on the basis of the inactivation of sensitized T4 phage caused by light irradiation. This reaction was only measurable after diffusion of the dye through the phage capsid and was not observed in the presence of either chloroquine or quinacrine; it followed a single-hit kinetics as a function of the irradiation time. With each dye, a double reciprocal plot of the inactivation constant versus the dye concentration present gave rise to a linear relationship. From this relation, parameters were deduced which expressed the relative photosensitizing efficiencies. Dye-binding to the phages was measured and the proflavine-mediated inactivation appeared to be related to the amount of strongly bound molecules. Such a conclusion could not be reached in the case of 9-aminoacridine and ethidium bromide, which were much less efficient photosensitizers than proflavine, but which were also strongly bound to the phages. Thiopyronine was weakly bound to the phages; it had, however, the highest photosensitizing activity observed. These results indicate that various mechanisms are involved when the phage photosensitization is due to one dye or another.

Acridines↗
PubMedDate not supplied

Communication of preferences for care among human immunodeficiency virus-infected patients. Barriers to informed decisions?

OBJECTIVE: To examine the way patients with serious, progressive illnesses communicate their care preferences to their physician. DESIGN: An observational, cross-sectional survey of 1031 clients with acquired immunodeficiency syndrome (AIDS) or symptomatic human immunodeficiency virus disease. Self-report of communication was assessed in 861 clients who stated a treatment preference focused on extending life or focused on comfort even if it shortened life. SETTING: The Robert Wood Johnson AIDS Health Services Program in 9 US cities. PARTICIPANTS: Eight hundred sixty-one of 1031 clients recruited to the AIDS Health Services Program. RESULTS: Eight hundred sixty-one subjects expressed a preferred treatment approach; however, only 35.8% had spoken to their physician about their preferred treatment. Black clients were half as likely (odds ratio, 0.49; confidence interval, 0.29-0.85) to have discussed their preferred treatment approach even after adjustment for age, function, education, income, and other covariates. Black clients were half as likely to prefer an approach to care that focused only on comfort (odds ratio, 0.51; 95% confidence interval, 0.34-0.76). Clients with AIDS who were symptomatic daily, college educated, and more functionally impaired were more likely to have discussed a preferred treatment approach with their physician. CONCLUSIONS: Most persons with symptomatic human immunodeficiency virus infection have not discussed their preferred treatment approach with a physician. This disparity is greater for blacks, who were less likely to want a palliative treatment approach.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Differences in access to zidovudine (AZT) among symptomatic HIV-infected persons.

OBJECT: To evaluate socioeconomic factors that determine whether symptomatic HIV-infected persons are offered zidovudine (AZT). DESIGN: Cross-sectional survey conducted as part of the Robert Wood Johnson Foundation's AIDS Health Services Program. SETTING: Public hospital clinics and community-based AIDS organizations in nine American cities. PATIENTS: 880 HIV-seropositive outpatients interviewed between October 1988 and May 1989. MAIN RESULTS: Males were more likely to have been offered AZT than were females (adjusted odds ratio 2.99; 95% confidence interval 1.67 to 5.36), those with insurance were more likely to have been offered AZT than were those without (adjusted odds ratio 2.00; 95% confidence interval 1.25 to 3.21), and whites more likely to have been offered AZT than were non-whites (adjusted odds ratio 1.73; 95% confidence interval 1.11 to 2.69). Intravenous drug users were less likely to have been offered AZT than were non-drug users (adjusted odds ratio 0.44; 95% confidence interval 0.28 to 0.69). Persons who had had an episode of Pneumocystis carinii pneumonia were more likely to have been offered AZT than were persons who had AIDS and had not had Pneumocystis carinii pneumonia (adjusted odds ratio 2.95; 95% confidence interval 1.71 to 5.11). CONCLUSION: The authors conclude that traditionally disadvantaged groups have less access to AZT, the only antiretroviral agent demonstrated to increase survival of patients who have symptomatic HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Cytotoxic and genotoxic effects of extracellular generated singlet oxygen in human lymphocytes in vitro.

The induction of sister-chromatid exchanges (SCE) together with the proliferation rate index (PRI) were studied in human lymphocytes in vitro after treatment with singlet oxygen. When produced outside the cells, singlet oxygen can increase the duration of the cellular cycle as measured by an enhancement of the differences between the proliferation rate indexes of the control and the treated cells. A dose-dependent increase in the SCE rate per chromosome was also detected after contact between the singlet oxygen and lymphocytes.

Cells, Cultured↗
PubMedDate not supplied

Differential expression of proteins in response to ceramide-mediated stress signal in colon cancer cells by 2-D gel electrophoresis and MALDI-TOF-MS.

Comparative cancer cell proteome analysis is a strategy to study the implication of ceramides in the transmission of stress signals. To better understand the mechanisms by which ceramide regulate some physiological or pathological events and the response to the pharmacological treatment of cancer, we performed a differential analysis of the proteome of HCT-116 (human colon carcinoma) cells in response to these substances. We first established the first 2-dimensional map of the HCT-116 proteome. Then, HCT116 cell proteome treated or not with C6-ceramide have been compared using two-dimensional electrophoresis, matrix-assisted laser desorption/ionization-mass spectrometry and bioinformatic (genomic databases). 2-DE gel analysis revealed more than fourty proteins that were differentially expressed in control cells and cells treated with ceramide. Among them, we confirmed the differential expression of proteins involved in apoptosis and cell adhesion.

Apoptosis↗
PubMedDate not supplied

Induction of a factor that binds to the polyoma virus A enhancer on differentiation of embryonal carcinoma cells.

The cell type specificity of certain enhancers, competition experiments and the interactions that occur between proteins and enhancer sequences demonstrate that enhancers are the targets of specific factors involved in transcription control. The 246-base pair BclI-PvuII restriction enzyme fragment of polyoma virus has been shown to include two distinct enhancers, Py A and Py B, composed of several subdomains which interact with nuclear proteins from mouse fibroblasts. Embryonal carcinoma (EC) cells do not permit polyoma virus infection: both viral transcription and DNA replication are blocked. Host-range mutants of polyoma virus (EC mutants) capable of overcoming the expression block in EC cells have mutations or sequence rearrangements in their enhancer region. In an attempt to understand the molecular basis of this host restriction we compared the binding patterns displayed on the viral enhancer sequences by nuclear proteins prepared from EC cells or from fibroblasts. We show that one of the fibroblast factors required for Py A enhancer function, almost undetectable in EC cells, is induced after differentiation of these cells into parietal endoderm, suggesting that this protein is crucial in the regulation of viral gene expression during cellular differentiation, and perhaps more generally in the control of gene expression during early embryonic development.

Animals↗
PubMedDate not supplied

Uptake of oligonucleotides by keratinocytes.

Oligonucleotides (ODNs) conjugated to rhodamin (Rh) and 4-[(N-2-chloroethyl-N-methyl)amino] benzylamine were used to investigate ODNs transport into keratinocytes. Affinity labeling of two proteins, 63 and 35 kDa, and the inhibition of the affinity labeling and ODNs uptake by the cells in the presence of nucleic acids, polyanions and trypsin suggest, that the proteins are involved in transport of nucleic acids in keratinocytes.

Autoradiography↗