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Biomedical subjects

B Salles

Publications and source records attributed to B Salles.

90 records · Page 5Linked to original sources
PubMed1983

cis-Pt(NH3)2Cl2 and trans-Pt(NH3)2Cl2 inhibit DNA synthesis in cultured L1210 leukemia cells.

A comparison of the inhibition of DNA synthesis by the two geometrical bidentate isomers cis- and trans-Pt(NH3)2Cl2 and by the monodentate [Pt(dien)Cl]Cl in a model used for screening potential antitumor compounds, the L1210 leukemia cells, is presented. The efficacy of penetration after a 2 hours Pt treatment is in the order trans (8) greater than cis (1) approximately dien (0.7). DNA replication is reduced to 50% of the control when 1.8 X 10(-4), 2.4 X 10(-4) and 80 X 10(-4) Pt atoms were bound per nucleotide for cis, trans and dien derivatives, respectively. If we admit that DNA is the pharmacological target of Pt antitumor compounds, these results suggest that a quantitative inhibition of DNA synthesis is certainly not correlated with antitumor activity.

Animals↗
PubMed1983

Uptake and cytofluorescence localization of ellipticine derivatives in sensitive and resistant Chinese hamster lung cells.

Uptake of two ellipticine derivatives, 2-N-methyl-ellipticinium (NME) and 2-N-methyl-9-hydroxy-ellipticinium, by sensitive and resistant Chinese hamster lung cells was studied. The results show that uptake and retention of these molecules by both types of cells were identical, thus indicating that the resistance to ellipticines, in this system, is not related to an impaired permeability of the cells to the drugs. However, influx and efflux kinetics, as well as experiments at increasing external concns, showed that both drugs accumulate within the cells in different ways. A cellular overconcentration of the drugs, which does not require an energy-dependent process, is observed. Fluorescence microscopy showed that, in both sensitive and resistant cells, NME is mainly, if not entirely, located in the cytoplasm.

Alkaloids↗
PubMed1983

Lack of single-strand DNA-binding protein amplification under conditions of SOS induction in E. coli.

A two site immunoradiometric assay (IRMA) for quantification of the recA protein has been recently described (Paoletti et al. 1982). We have used a similar technique to monitor the possible amplification of the ssb protein in E. coli after induction of the SOS repair process by various DNA damaging agents. Under these conditions, while we have been able to detect a full amplification of recA protein, we failed to observed any amplification of the ssb protein.

Bacterial Proteins↗
PubMed1983

Control of UV induction of recA protein.

The basal level of recA protein in Escherichia coli K-12 was estimated by an immunoradiometric assay; it is approximately equal to 1,200 molecules per wild-type bacteria in midexponential phase of growth, slightly more in an excision-deficient (uvrA) strain, and markedly more in recF mutants. Kinetics of induction after UV irradiation showed a rapid increase of recA protein content, which reached a peak level after 60-90 min (20- to 55-fold amplification) and then decreased by dilution of the protein in the growing population. In order to obtain an identical extent of induction of recA protein, a 10-fold higher UV dose was necessary in a wild-type strain compared to the uvrA mutant strain. In the uvrA strain, the presence of one or only very few pyrimidine dimers on DNA was accompanied by a measurable increase of the constitutive level of recA protein; however, the unexcised dimers were unable to permanently induce the formation of recA protein. The derepressed promoter of recA gene is one of the strongest in E. coli. Its sequence displays many similarities with that of the strongest early promoters of T5 phage. Mutants (umuC uvrB and recF uvrB) unable to carry out W-reactivation produced high levels of recA protein after UV irradiation. The data suggested that the recF and umuC genes negatively control the regulation of recA protein level.

Bacterial Proteins↗
PubMed1982

An immunoradiometric quantitative assay of Escherichia coli recA protein.

A two-site immunoradiometric assay of Escherichia coli recA protein is described ; its sensitivity allows the detection of 0.1 ng of recA protein ; it yields a linear response for amounts of recA protein in the 0.1-7 ng range. It can be directly applied to extracts of Escherichia coli obtained by sonication. Salmonella typhimurium extracts contain some cross-reacting material which share common antigenic determinants with Escherichia coli recA protein but differ from it.

Antigen-Antibody Reactions↗
PubMed1982

Isolation and properties of Chinese hamster lung cells resistant to ellipticine derivatives.

Chinese hamster lung cells resistant to 9-OH-ellipticine (9-OH-E) were selected in vitro by adding stepwise increasing drug concentrations to the cell growth medium. This selection procedure resulted in the isolation of two sublines, about tenfold and 12-fold resistant to 9-OH-E. This level of resistance did not increase even after about 30 months of drug exposure. Cytogenetic studies revealed that the resistant cells carry several discrete karyotype modifications, the most striking being the absence of one No. 5 chromosome and the presence of a marker chromosome characterized by peculiar G-banding. Development of 9-OH-E resistance was also associated with some changes in cell properties such as modifications of morphology and growth parameters, lower oncogenic potential, and cross-resistance to a variety of antitumor agents. Although these results suggest that the resistance is associated with a modification of cell membrane properties, drug uptake studies did not show any significant difference between the parental sensitive cells and the resistant sublines.

Alkaloids↗
PubMed1976

[Acid-base equilibrium during acute fetal hypoxia. Experimental study].

The authors studied the effects of acute hypoxia of short duration in eight pregnant ewes that had been anaesthetised. They showed that during the experiment the E.E.G. as well as the pH and pCO and the maternal lactate levels were not changed and that therefore changes that can be found in the fetus are due solely to its own hypoxia and not due to transmission from the mother. In the fetus the trace flattens in about 30 minutes on an average. After this interval a moderate drop in pH occurs at the same time as an increase in lactacidemia and the relationship between lactate and pyruvate. The heart rate is changed in a variable manner: it accelerates if the basal rate is less than 180 beats a minute and slows if it is above 180. Blood pressure rises. Changes in the cardio-vascular system always precede those in the electroencephalograms.

Acid-Base Equilibrium↗
PubMedDate not supplied

Repair of oxidative DNA damage in vitro: a tool for screening antioxidative compounds.

Reactive oxygen species (ROS) provoke the formation of base DNA alterations that are processed by an excision step of the lesion followed by a repair synthesis and ligation step to restore the strand continuity. We have reported previously the detection of DNA adducts by an in vitro chemiluminescence DNA repair synthesis assay (Salles et al., 1995) which allows the measurement of repair synthesis by cell-free extracts in damaged plasmid DNA adsorbed on sensitized microplate wells. The 3D (DNA damage detection) assay was performed in the presence of biotin-dUTP which was incorporated during the repair synthesis step. The extent of repair synthesis was measured in an ELISA reaction with ExtrAvidin-horse radish peroxidase and chemiluminescence detection. The 3D assay allows detection of any type of base alterations including base oxidation. Interestingly, under controlled production of ROS a screening procedure of antioxidants might be carried out with the 3D assay. By taking advantage of plasmid DNA adsorption, oxidative base damage can be recognized by the Escherichia coli Fpg protein which was detected in an ELISA reaction with specific antibody and chemiluminescence measurement (4D assay). With the sceening procedure of antioxidative compounds in mind, the development of such assays and their drawbacks are discussed.

Antioxidants↗
PubMedDate not supplied

Measurement of recA protein induction in Salmonella typhimurium: a possible biochemical test for the detection of DNA damaging agents.

RecA protein was purified from S. typhimurium and its concentration was measured in crude extracts by an immunoradiometric assay. The dose-response relations and the kinetics of recA protein induction following treatment of the cells with ultra-violet light, nalidixic acid, mitomycin C, and cisplatin were studied in E. coli and S. typhimurium. The recA protein amplification was complete in a few hours and was stable for at least 3 hours. Dose-response curves showed a linear region for low doses of all the inducer agents tested. This direct relation between the recA protein level and the amount of inducer agent allows the quantification of the recA protein inducing potency of chemicals. The recA protein amplification was very sensitive to low doses of inducer agents: an UV dose of 0.25 J/M2, 500 ng of NAL or 50 ng of MMC induced a two-fold increase in cellular recA protein content. In addition, the measurement of RecA protein induction did not require the survival of the cells. These observations led us to suggest a new biochemical assay for detecting DNA damaging substances by the direct measurement of the recA protein level following treatment of the cells.

Antibiotics, Antineoplastic↗
PubMedDate not supplied

RECA immunological assay as a tool to analyze the SOS response.

The content of RECA protein, one of the SOS genes product, was determined in a bacterial extract by a two site-radioimmunometric assay. The variation of the RECA concentration after induction by physical or chemical treatments was used as a probe to analyze the SOS response. Relationships between either the number or the nature of DNA lesions and the level of the relative amplification of RECA have been established. The modulation of the recA gene expression is discussed.

DNA Repair↗
PubMedDate not supplied

DNA damage excision repair in microplate wells with chemiluminescence detection: development and perspectives.

The development of in vitro repair assays with human cell-free extracts led to new insights on the mechanism of excision of DNA damage which consists of incision/excision and repair synthesis/ligation. We have adapted the repair synthesis reaction with cells extracts incubated with damaged plasmid DNA performed in liquid phase to solid phase by DNA adsorption into microplate wells. Since cells extracts are repair competent in base excision and nucleotide excision repair, all types of substrate DNA lesions were detected with chemiluminescence measurement after incorporation of biotin-deoxynucleotide during the repair synthesis step. Derivatives of our initial 3D-assay (DNA damage detection) have been set up to: i) screen antioxidative compounds and NER inhibitors; ii) capture genomic DNA (3D(Cell)-assay) that allows detection of alkylated base and consequently determines the kinetics of the cellular repair; and iii) immunodetect the repair proteins in an ELISA reaction (3D(Rec)-assay). The 3D derived assays are presented and discussed.

Animals↗
PubMedDate not supplied

Regulation of the DNA-dependent protein kinase (DNA-PK) activity in eukaryotic cells.

The DNA-dependent protein kinase (DNA-PK) is a trimeric nuclear serine/threonine protein kinase consisting of a large catalytic sub-unit and the Ku heterodimer that regulates kinase activity by its association with DNA. DNA-PK is a major component of the DNA double strand break repair apparatus, and cells deficient in one of its component are hypersensitive to ionizing radiation. DNA-PK is also required to lymphoid V(D)J recombination and its absence confers in mice a severe combined immunodeficiency phenotype. The purpose of this review is to summarize the current knowledge on the mechanisms that contribute to regulate DNA-PK activity in vivo or in vitro and relates them to the role of DNA-PK in cellular functions. Finally, the studies devoted to drug-inhibition of DNA-PK in order to enhance cancer therapy by DNA-damaging agents are presented.

Animals↗