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Biomedical subjects

J C Mateos

Publications and source records attributed to J C Mateos.

16 recordsLinked to original sources
PubMed1999

Topoisomerase activities and levels in irradiated Chinese hamster AA8 cells and in its radiosensitive mutant EM9.

PURPOSE: To investigate possible variations in topoisomerase (topo) I and II activities and levels after X-ray treatment in the radiation repair proficient AA8 Chinese hamster cell line for comparison with the radiation sensitive mutant EM9. MATERIALS AND METHODS: AA8 and EM9 cells were irradiated with 5 Gy of X-rays and the activities of topoisomerases I and II in nuclear extracts were studied. Immunological detection of both topoisomerases was carried out in order to detect any changes in the expression of these enzymes as a consequence of irradiation. RESULTS: Topoisomerase activities and levels in irradiated EM9 cells were the same as in control non-irradiated cells. In fact, both topo I and topo II activities clearly increased shortly after irradiation in the parental AA8 cells, with a more rapid increase for topo I than for topo II. In the AA8 cells, an increased level of topo I detectable immunologically was only observed at a later time (1 h) after irradiation, while no similar change was detectable for topo II. CONCLUSIONS: While this hypothesis needs further testing, an attractive idea is that DNA topoisomerases might be involved in the cellular response to radiation damage, either through a direct participation in repair mechanisms or indirectly.

Animals↗
PubMed1998

Noradrenaline modulates the electrical activity of white adipocytes by a cAMP-dependent mechanism.

We studied the effect of the external addition of noradrenaline (NA) on the electrical activity of white adipocytes from rat epididymal tissue. NA modified the active voltage response recorded by the current clamp technique, and decreased the macroscopic membrane potassium currents measured by a whole-cell configuration patch-clamp technique in cells obtained by culturing differentiating preadipocytes. To analyse if cAMP is implicated in the effect of this hormone on potassium conductances, the changes in electrical activity caused by an increase in the intracellular concentration of cAMP were studied using intracellular recording. The addition of forskolin, or NN-dibutyryl cAMP plus 3-isobutyl-1-methylxanthine to the bath reduced active changes in membrane voltage responses to hyperpolarizing and depolarizing pulses. A similar effect was observed when vasoactive intestinal peptide was added to the superfusion chamber. These results suggest that NA could modulate K+ conductances in white adipocytes, mediated by cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Both bovine and rabbit lymphocytes conditioned with hydrogen peroxide show an adaptive response to radiation damage.

We have carried out experiments to study the possible induction of an adaptive response in cultured bovine and rabbit lymphocytes conditioned with subtoxic doses of hydrogen peroxide after stimulation and subsequently challenged with 1 Gy of X-rays. Peroxide treatment was given at different doses 48 h after the addition of PHA to stimulate the cells. A protective effect of pre-exposure to H2O2 against radiation damage detected as micronuclei in binucleated cells was evident for all the animals tested regardless the dose of H2O2 used, although this effect was in general of greater magnitude in bovine than in rabbit cells. These results lend further support to our previous finding in human lymphocytes that DNA single strand breaks induced by H2O2 (most likely due to the generation of hydroxyl radicals) is the most important lesion to trigger the adaptive response.

Adaptation, Physiological↗
PubMed1996

Voltage-dependent potassium channels in white adipocytes.

Macroscopic membrane currents of white adipocytes were studied using the whole-cell variant of the patch-clamp technique. These cells were obtained by differentiating preadipocytes fro rat epididymal tissue. In all differentiated cells outward currents exhibiting sigmoidal activation kinetics were observed with amplitudes ranging from 0.5 to 6 nA. The outward current showed activation thresholds at approximately -25 to -35 mV. The ion channels underlying the macroscopic current were highly selective for K+. Their selectivity was typical for K+ channels, with relative permeabilities of K+ > NH4+ > Cs+, Na+. The potassium current was blocked by tetraethylammonium, 4-aminopyridine, barium and cobalt. These results demonstrate the existence of voltage dependent potassium channels in mature white adipose cells.

4-Aminopyridine↗
PubMed1994

Differences in the adaptive response to radiation damage in G0 human lymphocytes conditioned with hydrogen peroxide or low-dose X-rays.

We have carried out experiments to study the adaptive response in G0 human lymphocytes conditioned with either hydrogen peroxide or low-dose X-rays and challenged with 1.5 Gy of X-rays after stimulation. Peroxide conditioning treatment was given at different times before stimulation, while the low-dose irradiation was delivered at different dose rates just before stimulation of lymphocytes. A protective effect of pre-exposure to H2O2 against radiation damage detected as micronuclei in binucleated cells was evident, regardless of the time of conditioning treatment during G0. For low-dose-irradiated cells, on the other hand, the adaptation observed seemed to depend upon the dose rate, and never reached the extent observed in cells treated with peroxide.

Adaptation, Physiological↗
PubMed1994

[Infective endocarditis in patients with permanent pacemaker].

Five patients who had permanent pacemaker and infective endocarditis were analyzed. Diagnose was confirmed by a positive blood cultures in all patients and 2 of them had identifiable vegetation in the echocardiogram too. The etiologic agent was Staphylococcus aureus in 3, Staphylococcus epidermidis in 1 and Staphylococcus viridans in 1. Three patients were treated with antibiotics alone: one had no clinical conditions to be operated, one died before surgery and one had good response to antimicrobial therapy alone. Two patients were submitted to antibiotic therapy and surgical removal of the pacemaker system, without complications. It was concluded that the surgical removal of the pacemaker system, as soon as possible, is the choice's therapy.

Adult↗
PubMed1992

Poly-D-lysine in G2 potentiates chromosome damage induced by X-rays and mitomycin C in CHO cells.

A number of reports suggest that the role of radiation-induced G2 arrest is to allow repair of potentially lethal damage in the cells before it comes to mitosis. Though the exact nature of the damage undergoing repair during the delayed G2 is not known, the yield of chromosomal aberrations observed in metaphase seems to be a good parameter to predict reproductive death of cells. In a previous paper, we have shown that poly-D-lysine, acting in a fashion reminiscent of that of caffeine in mammalian cells, is able to induce a premature onset of mitosis concomitant with an increase in the frequency of chromosomal aberrations in mutagen-treated plant cells. Cultured CHO cells were pre-exposed to either X-rays or mitomycin C and given different doses of the polycationic compound during G2 in order to analyze any effect on the frequency of chromatid-type aberrations as well as any modification of cell-cycle kinetics. A potentiation of chromosome damage and a premature arrival at mitosis were observed for both mutagens, though the effect was more evident in X-irradiated cells.

Animals↗
PubMed1992

A comparative study of the potentiating effect of caffeine and poly-D-lysine on chromosome damage induced by X-rays in plant cells.

X-Ray-induced chromosomal aberrations (CA) were potentiated by post-treatments in G2 with either caffeine (caff) or poly-D-lysine (PDL) in root-tip cells of Allium cepa. The enhancement of the yield of CA was concomitant with an increase in the frequency of mitosis. Our results seem to support the idea of a direct relationship between radiation-induced G2 delay and repair of chromosome damage. Here we report on similarities between caffeine and PDL in both decreasing G2 delay and enhancing chromatid aberration yield. The possible molecular mechanism(s) of action responsible for the cytogenetic effects observed are discussed.

Caffeine↗
PubMed1990

Evidence for an adaptive response to radiation damage in plant cells conditioned with X-rays or incorporated tritium.

Allium cepa root-tip cells were first exposed to low 'conditioning' doses of ionizing radiation: to X-rays (0.06 or 0.26 Gy) or to incorporated tritium (1.8 x 10(4) or 7.2 x 10(4) Bq/ml; specific activity: 740.0 GBq/mmol) and subsequently given a 'challenge' dose of 1.5 Gy of X-rays. A reduction in X-ray-induced chromosomal damage was brought about by prior exposure to 0.26 Gy of X-rays, while cells receiving the lower conditioning dose (0.06 Gy of X-rays) did not show any significant reduction. In cells grown in the presence of [3H]TdR on the other hand, the adaptive response was evident after both doses given. The results are essentially in agreement with those published by Wolff's group for human lymphocytes in showing that plant cells in vivo can become 'adapted' by exposure to low-level irradiation so that they become more resistant to the clastogenic effects of X-rays delivered subsequently.

Adaptation, Biological↗
PubMed1990

Adaptive response in human lymphocytes conditioned with hydrogen peroxide before irradiation with X-rays.

Cultured human lymphocytes were first exposed to a low 'conditioning' dose of hydrogen peroxide and, subsequently, irradiated with a 'challenge' dose of 1.5 Gy of X-rays in order to analyse the induction of an adaptive response to oxidative damage. A significant reduction in X-ray-induced chromosome damage was evident when H2O2 was given as a single 30 min pulse 24 h after setting up the cultures and the lymphocytes were exposed to X-rays at 48 h. In contrast, when the cells underwent a repeated exposure to H2O2 before irradiation the yield of aberrations was that expected from the combined treatment.

Cells, Cultured↗
PubMed1985

A geometric calculation of square and circular size equivalents for rectangular radiation fields in radiotherapy.

In radiotherapy the volume of irradiated tissue is determined by the cross-section of a beam of radiation that strikes the skin of a patient. The radiation dose delivered at a given depth is a function of this cross-section, known as the radiation field. The computing of that dose for rectangular fields can be simplified using a small number of data corresponding to square or circular fields. This procedure is called the equivalent field method. Two fields are said to be equivalent if they give equal doses of radiation at a given depth in tissue. In this work the equivalent circular and square fields are determined by the condition that the solid angle subtended by the field in the skin, as viewed from the exposed point, be the same.

Humans↗