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Biomedical subjects

F Cortés

Publications and source records attributed to F Cortés.

At least 19 recordsLinked to original sources
PubMed2006

Topoisomerase II inhibition and high yield of endoreduplication induced by the flavonoids luteolin and quercetin.

Luteolin and quercetin are widely distributed plant flavonoids that possess a variety of chemical and biological activities, including free-radical scavenging and antioxidant activity. Recently, both flavonoids have been reported to inhibit DNA topoisomerases I and II (topo I and topo II), a property that, together with their ability to induce DNA and chromosome damage, has made them candidate anticancer compounds. In the present study, we confirmed that both compounds are topo II inhibitors by conducting a comparative study of their effect on topo II activity from Chinese hamster ovary AA8 cells. Because interference with the function of topo II to resolve DNA entanglement at the end of replication results in chromosome malsegregation at mitosis, we investigated whether luteolin and quercetin are effective in inducing endoreduplication in AA8 cells. Concentrations of luteolin and quercetin that inhibited topo II catalytic activity resulted in extraordinarily high yields of metaphases showing diplochromosomes. Given the established relationship of polyploidy with tumor development via aneuploidy and genetic instability, these results question the usefulness of luteolin and quercetin in cancer therapy.

Animals↗
PubMed2005

Induction of genotoxic and cytotoxic damage by aclarubicin, a dual topoisomerase inhibitor.

The anthracycline aclarubicin (ACLA) is an intercalative antibiotic and antineoplastic agent that efficiently binds to DNA, leading to a secondary inhibition of the catalytic activity of topoisomerase II (topo II) on DNA. Besides this activity, ACLA has been reported to exert a concomitant poisoning effect on topo I, in a fashion similar to that of the antitumor drug camptothecin and its derivatives. As a consequence of this dual (topo II catalytic inhibiting/topo I poisoning) activity of ACLA, the picture is somewhat confusing with regards to DNA damage and cytotoxicity. We studied the capacity of ACLA to induce catalytic inhibition of topo II as well as cytotoxic effects and DNA damage in cultured Chinese hamster V79 cells and their radiosensitive counterparts irs-2. The ultimate purpose was to find out whether differences could be observed between the two cell lines in their response to ACLA, as has been widely reported for radiosensitive cells treated with topo poisons. Our results seem to agree with the view that the radiosensitive irs-2 cells appear as hypersensitive ACLA as compared with radiation repair-proficient V79 cells. The recovery after ACLA treatment was also followed-up, and the irs-2 mutant was found to be less proficient than V79 to repair DNA strand breaks induced by ACLA.

Aclarubicin↗
PubMed2004

[The ontogenesis of the hematopoietic system revisited].

The ontogenesis of hematopoiesis is classically described as a series of successive steps: the first takes in the yolk sac where blood islands differentiate. Then, cells deriving from these structures migrate and populate the transient hematopoietic organs such as the liver and the spleen. At last, the eventual migration allows the establishment of bone marrow hematopoiesis. This theory described in almost all the textbooks of Human Embryology does not fit with recent experimental data. Indeed, the construction of quail-chick chimeras shows that the yolk sac does not contribute to the adult hematopoiesis in birds. Adult hematopoietic cells arise from a population located on the ventral side of the aorta both in birds and mammals. The aortic population derives from the para-aortic splanchnopleura and its derivative, the so-called AGM (Aorta-Gonad-Mesonephros). These new data provide new concepts to understand the process of ontogenesis of the hematopoietic system in vertebrates.

Animals↗
PubMed2003

DNA strand breaks induced by the anti-topoisomerase II bis-dioxopiperazine ICRF-193.

The bis-dioxopiperazine ICRF-193 has long time been considered as a pure topoisomerase II catalytic inhibitor able to exert its inhibitory effect on the enzyme without stabilization of the so-called cleavable complex formed by DNA covalently bound to topoisomerase II. In recent years, however, this concept has been challenged, as a number of reports have shown that ICRF-193 really "poisons" the enzyme, most likely through a different mechanism from that shown by the classical topoisomerase II poisons used in cancer chemotherapy. In the present investigation, we have carried out a study of the capacity of ICRF-193 to induce DNA strand breaks, as classical poisons do, in cultured V79 and irs-2 Chinese hamster lung fibroblasts using the comet assay and pulsed-field gel electrophoresis (PFGE). Our results clearly show that ICRF-193 readily induces breakage in DNA through a mechanism as yet poorly understood.

Animals↗
PubMed2001

Testing the SCE mechanism with non-poisoning topoisomerase II inhibitors.

There are controversial theoretical models about a possible involvement of DNA topoisomerase II (topo II) in the molecular mechanism of sister chromatid exchanges (SCEs). In order to clarify the role of this enzyme, if any, in such recombinational event, CHO parental AA8 and mutant EM9 cells, which shows and extremely high baseline frequency of SCE, have been treated with different doses of the non-poisoning topoisomerase inhibitors, ICRF-193 and bufalin. The frequencies of SCEs after the treatments have been determined and the inhibitory effect of these compounds has been assessed using a topo II activity assay. The results indicate that ICRF-193 and bufalin effectively inhibit topo II activity in AA8 and EM9 cell lines. ICRF-193 induced a moderate increase in the frequency of SCEs in both types of cells, while bufalin did not modify the level of SCEs in any of them. The results are discussed taking into account the apparently unlike mechanisms of inhibition of topo II by ICRF-193 and bufalin.

Animals↗
PubMed2001

Electronic delocalization contribution to the anomeric effect evaluated by computational methods.

This study proposes the determination of the electronic delocalization contribution to the Anomeric Effect (EDCAE, Delta Delta E(deloc), eq 3) as a computational alternative in the evaluation of the excess of the axial preference shown by an electronegative substituent located at alpha position to the annular heteroatom of a heterocyclic compound (anomeric position) in both the presence and the absence of electronic delocalization retaining the same molecular geometry. The determination of the EDCAE is computationally accessible through the application of the natural bond orbital analysis (NBO). This type of analysis allows the comparison of hypothetical molecules lacking electronic delocalization (Lewis molecules, in which the electrons are strictly located in bonds and lone pairs) with the fully delocalized molecules retaining the same geometry and the evaluation of the anomeric effect in terms of eq 3. The role of the Lewis molecules is the same as the cyclohexane used experimentally to evaluate the anomeric effect. The advantage of doing this is that Lewis molecules are stereoelectronically inert. Applying this methology to cyclic and acyclic molecules at B3LYP/6-31G(d,p) and HF/6-31G(d,p)//B3LYP/6-31G(d,p) levels of theory, we found that the anomeric effect shown by Cl in 1,3-dioxane; F, Cl, SMe, PH(3), and CO(2)Me groups in 1,3-dithiane is of stereoelectronic nature while the preference of F, OMe, and NH(2) in 1,3-dioxane and the P(O)Me(2) group in 1,3-dithiane is not. Furthermore, this methodology shows that anomeric effects without stereoelectronic origin can modify the molecular geometry in agreement with the geometric pattern required by the double-bond no-bond model, as recently proposed by Perrin.

Journal Article↗
PubMed2001

Assessment of genotoxic damage by the comet assay in white storks (Ciconia ciconia) after the Doñana Ecological Disaster.

Single cell gel electrophoresis, the so-called "Comet" assay, was performed as a genotoxicity test in white storks sampled in an area heavily contaminated after the ecological disaster in south western Spain. This disaster occurred as a consequence of a massive toxic spillage of acid waste rich in heavy metals that impacted on the Doñana National Park. The importance of this protected area as a breeding and wintering site for many endangered bird species makes this analysis of DNA damage of special interest. Our results clearly show that white storks born in the contaminated area 1 year after the toxic spill bear a high burden of genetic damage as compared with control individuals. The possible implications for future survival as well as reproductive rate are discussed.

Animals↗
PubMed2001

Ionizing radiation damage repair: a role for topoisomerases?

In parallel with the developing field of DNA topoisomerase poisons in tumor chemotherapy, the basic features of these nuclear enzymes have been unfolded. The role of topoisomerases in fundamental processes involving DNA metabolism has been shown to outpace by far the initial expectations. While DNA topoisomerases are involved in relaxation of chromatin to relieve tension during DNA replication and transcription, as well as for recombinational processes and chromosome segregation and condensation, the possible role, either direct or indirect, of these enzymes in DNA repair is still a matter of discussion. In this survey the possible relationship of topoisomerases with the repair of ionizing radiation damage in mammalian cells is considered, on the basis of attractive 'clues' and in the light of a number of observations.

DNA↗
PubMed2001

[Frequency of neural tube defects in public maternity during 1999 in Santiago, Chile].

BACKGROUND: Fortification of wheat flour with folic acid in Chile, started in January 2000. This fortification should decrease the incidence of neural tube defects. AIM: To study the incidence of neural tube defects among Chilean newborns, during 1999. MATERIAL AND METHODS: The records of all newborns and stillbirths with a birth weight over 500 g from 9 public maternity hospitals in Santiago in 1999, were reviewed. All neural tube defects, associated or not to other malformations were taken into account. RESULTS: During the study period, 59.627 newborns and 455 stillbirths were analyzed. The global incidence of neural tube defects was 1.56 per 1.000 born (57% women, 42% men and 1% ambiguous sex). Spina bifida was the most frequent neural tube defect found. CONCLUSION: These baseline data will be useful to assess the impact of folic acid fortification of wheat flour.

Chile↗
PubMed2001

[Molecular diagnosis of Prader-Willi and Angelman syndromes: methylation, cytogenetics and FISH analysis].

BACKGROUND: The diagnosis of Prader-Willi and Angelman syndromes is difficult, since their phenotypic manifestations are variable and unspecific. The study of the methylation state of DNA in 15(q11-q13) using polymerase chain reaction, called methylation test, allows the diagnosis of most patients with Prader-Willi and Angelman syndromes, irrespective if the underlying molecular alteration is a deletion, uniparental disomy or a punctual imprinting mutation. AIM: To assess the effectiveness of methylation test in the diagnosis of Prader-Willi and Angelman syndromes. PATIENTS AND METHODS: Thirty seven cases with a presumptive diagnosis of Prader-Willi syndrome and 25 with the presumptive diagnosis of Angelman syndrome were studied. Methylation test was done in genomic DNA obtained from peripheral lymphocytes. RESULTS: Methylation test confirmed the clinical diagnosis in 11 of 37 patients with Prader Willi (30%) and 6 of 25 patients with Angelman syndrome (24%). CONCLUSIONS: Clinical criteria overestimate the diagnosis of Prader-Willi and Angelman syndromes. The initial diagnosis should be confirmed with the methylation test and, if necessary, with FISH that will detect most deletions in the region.

Adolescent↗
PubMed2001

DNA topoisomerases in cancer chemotherapy: basic and applied aspects.

These conserved nuclear enzymes catalyse a variety of interconversions of DNA which take place between topological isoforms of the molecule, through transient cleavage, strand passing and re-ligation. In this context the DNA topoisomerases have been generally considered as good candidates to play a role in the enzymatic repair processes going on in the cell after DNA damage inflicted by either physical or chemical agents. It has been suggested that this role could be direct, with the actual participation of topoisomerases in the molecular mechanism of lesion repair, as for example in the excision of base damage or DNA strand break repair. Alternatively, it could be indirectly responsible for the preparative steps in the relaxation of chromatin in order to allow repair enzymes to gain access to damaged DNA.

Animals↗
PubMed2001

DNA damage in birds after the mining waste spill in southwestern Spain: a Comet assay evaluation.

In April 1998, an ecological disaster resulting from a massive toxic spill of mining acid waste rich in heavy metals posed a serious threat to the Doñana National Park in southwestern Spain. This especially important protected area is the nesting and breeding site for many endangered bird species; white storks (Ciconia ciconia) and black kites (Milvus migrans) are considered the more representative. The suitability of the Comet assay as a biomarker for genotoxic analysis in environmental biomonitoring has been recently validated in studies using different sentinel organisms such as fish, amphibians, rodents, or mollusks. Birds preying on a variety of invertebrate and vertebrate species in the marshlands are appropriate for evaluating the potential deleterious effects of the toxic spill on wildlife of the Dofiana area. Our study on wetland birds high on the aquatic trophic chain sampled within a few months after the toxic spill in the area around Doñana National Park has shown the accumulation of heavy metals. Fourteen months after the mine waste spill, blood samples from white storks and kites collected in the neighborhood of the park and from control birds at reference areas for comparison were examined by fluorescence image analysis after lymphocyte isolation, and by subsequent alkaline single-cell gel (SCG) electrophoresis, known as the Comet assay. Our results indicate that the exposed birds had a significantly increased level of genotoxic damage compared with control animals from noncontaminated locations.

Accidents, Occupational↗
PubMed2000

Yield of SCEs and translocations produced by 3 aminobenzamide in cultured Chinese hamster cells.

Different concentrations of 3-aminobenzamide (3AB), a strong inhibitor of poly(ADP-ribose) polymerase (PARP), were used to study their effect on the BrdU-substituted DNA of the Chinese hamster AA8 cell line. The frequencies of sister chromatid exchanges (SCEs) and translocations were determined using the fluorescence plus Giemsa (FPG) and fluorescence in situ hybridization (FISH) techniques, respectively. The results indicate that 3AB effectively induced a dose-dependent increase in the frequency of SCEs, but this enhancement in the yield of SCEs was not paralleled by an increase in translocations. These results are discussed in terms of the as yet poorly understood molecular mechanisms of action of the enzyme PARP.

Animals↗
PubMed2000

Glucosylated isoflavones as DNA topoisomerase II poisons.

Since topoisomerase poisons allow the enzyme to cut and covalently bind to DNA but abort the subsequent rejoining of the molecule after relieving the torsional stress. To study their action we have made use of a supercoiled form of the pRYG plasmid that bears a specific topoisomerase recognition and binding region. The conversion of the supercoiled circular double-stranded DNA to the linear and open circle forms in the presence of a topoisomerase II poison and a denaturation step by proteinase K-SDS is indicative of the efficiency of our test agents to stabilize the cleavable complex. Using this system, three glucosylated isoflavones (6'-methoxy-pseudobaptigenin-7-O-beta-glucoside, genistin, and daidzin) isolated from cytotoxic chloroform and ethyl acetate extracts of Retama sphaerocarpa Boissier, were found to have the ability to stabilize the cleavage complex human DNA topoisomerase II.

DNA↗
PubMed2000

Thalidomide in the treatment of cutaneous lupus refractory to conventional therapy.

OBJECTIVE: We describe a prospective treatment study of thalidomide in a series of 22 patients with cutaneous lupus refractory to other treatments. METHODS: From 1992 to 1998, 22 patients with cutaneous lupus (9 with discoid lupus erythematosus, 7 with subacute cutaneous lupus, 4 with profundus lupus, 2 with nonspecific rash) were treated with thalidomide. Initial treatment was started at 100 mg daily. If the cutaneous lesions vanished, the dose was lowered to 50-25 mg daily as a maintenance therapy and it was considered a complete remission. If the lesions improved but remained, this was considered a partial response and treatment was continued until the lesions were not further modified. Periodically, adverse effects were evaluated. RESULTS: Three patients discontinued treatment because of side effects such as vertigo, persistent drowsiness, or paresthesia. Rash improved in 16/19 patients (84%). Complete remission occurred in 12/16 (75%). In 9 (65%) the rash resolved, but recurred 4-16 weeks after withdrawal of thalidomide; when it was used again, they improved. Partial response was achieved in 4/16 (25%) patients. No response occurred in 3/19 (16%). Many patients noted improvement within 2 weeks after starting thalidomide and maximum benefit was achieved within 3 months. Five of the 14 women had amenorrhea during the treatment with thalidomide. CONCLUSION: Thalidomide is effective in the treatment of cutaneous lupus refractory to other treatments. However, only some patients had a remission; the remainder relapsed when treatment was withdrawn, or required low doses of thalidomide to preserve inactive lesions. Amenorrhea was observed as a new secondary effect of thalidomide.

Adolescent↗
PubMed2000

[The importance of folic acid in current medicine].

Lately, folic acid deficiency is gaining a predominant role in the pathogenesis of congenital malformations and cardiovascular diseases in adults. The planning of individual and population preventive strategies for these diseases must consider this deficiency. This paper reviews the anatomical, biochemical and molecular bases of neural tube defects and cardiovascular diseases in adults. In these two frequent diseases, folic acid supplementation has shown a clear cut protective effect.

Adult↗