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Biomedical subjects

M Torres

Publications and source records attributed to M Torres.

At least 19 recordsLinked to original sources
PubMed2007

Evidence that individual variations in TP53 and CDKN1A protein responsiveness are related to inherent radiation sensitivity.

We tested the hypothesis that individual variations in the induction of the TP53 tumor suppressor protein by radiation are related to inherent radiosensitivity. Thirty-two fibroblast cell strains were examined. Radiosensitivity was measured by a clonogenic survival assay. The induction of TP53 and its transcriptionally activated CDKN1A (p21) protein were studied by Western blotting 3 h after a single dose of 5 Gy. The relative cell culture age, as determined by the colony size distribution, was studied as a confounding factor. Survival curves showed wide range of radiosensitivity. The surviving fraction at 2 Gy (SF2) ranged between 0.02 and 0.49 (mean = 0.29, SD = 0.13). TP53 induction ranged between 1.28 and 2.34 (mean = 1.80, SD = 0.31). CDKN1A showed a wider induction (1.09-4.05, mean = 2.33, SD = 0.78). Positive correlations were observed between SF2 and TP53 induction (R(2) = 0.62, P < 0.001) and CDKN1A (R(2) = 0.64, P < 0.001). No correlation with the colony size distribution was observed. In conclusion, these results suggest that the individual variations in radiosensitivity and in the level of induction of TP53 (and consequently CDKN1A) are congruent, irrespective of the genetic background of these nontransformed fibroblasts. It is postulated that underlying mechanisms culminating in a stronger TP53 induction lead to higher survival, presumably due to more efficient repair of radiation-induced damage.

Blotting, Western↗
PubMed2006

Quasicrystalline and rational approximant wave patterns in hydrodynamic and quantum nested wells.

The eigenfunctions of nested wells with an incommensurate boundary geometry, in both the hydrodynamic shallow water regime and quantum cases, are systematically and exhaustively studied in this Letter. The boundary arrangement of the nested wells consists of polygonal ones, square or hexagonal, with a concentric immersed, similar but rotated, well or plateau. A rich taxonomy of wave patterns, such as quasicrystalline states, their crystalline rational approximants, and some other exotic but well known tilings, is found in these mimicked experiments. To the best of our knowledge, these hydrodynamic rational approximants are presented here for the first time in a hydrodynamic-quantum framework. The corresponding statistical nature of the energy level spacing distribution reflects this taxonomy by changing the spectral types.

Journal Article↗
PubMed2006

Strong far-field coherent scattering of ultraviolet radiation by holococcolithophores.

By considering the structure of holococcoliths (calcite plates that cover holococcolithophores, a haploid phase of the coccolithophore life cycle) as a photonic structure, we apply a discrete dipolar approximation to study the light backscattering properties of these algae. We show that some holococcolith structures have the ability to scatter the ultraviolet radiation. This property may represent an advantage for holococcolithophores possessing it, by allowing them to live higher in the water column than other coccolithophores.

Journal Article↗
PubMed2006

Evaluation of Pluchea carolinensis extracts as antioxidants by the epinephrine oxidation method.

Many methods have been used to evaluate synthetic and natural products as hydroxyl radical scavengers. In this study a spectrophotometric method to evaluate the scavenger activity of the hydroxyl radical produced in Fenton reaction is proposed. The oxidation of l-epinephrine to adrenochrome permitted the detection of the hydroxyl radical by spectrophotometry and its possible scavenging by hydroquinone, a well known antioxidant. The method was used to evaluate the antioxidant activity of Pluchea carolinensis leaves.

Antioxidants↗
PubMed2006

Oncogenic human papillomavirus (HPV) type distribution and HPV type 16 E6 variants in two Spanish population groups with different levels of HPV infection risk.

The aim of this study is to determine oncogenic human papillomavirus (HPV) types and HPV type 16 (HPV16) variant distribution in two Spanish population groups, commercial sex workers and imprisoned women (CSW/IPW) and the general population. A multicenter cross-sectional study of 1,889 women from five clinical settings in two Spanish cities was conducted from May to November 2004. Oncogenic HPV infection was tested by an Hybrid Capture II (HC2) test, and positive samples were genotyped by direct sequencing using three different primer sets in L1 (MY09/11 and GP5+/GP6+) and E6/E7. HPV16 variants were identified by sequencing the E6, E2, and L1 regions. Four hundred twenty-five samples were positive for the HC2 test, 31.5% from CSW/IPW and 10.7% from the general population. HPV16 was the most frequent type. Distinct profiles of oncogenic HPV type prevalence were observed across the two populations. In order of decreasing frequency, HPV types 16, 31, 58, 66, 56, and 18 were most frequent in CSW/IPW women, and types 16, 31, 52, 68, 51, and 53 were most frequent in the general population. We analyzed HPV16 intratype variants, and a large majority (78.7%) belonged to the European lineage. AA variants were detected in 16.0% of cases. African variants belonging to classes Af1 (4.0%) and Af2 (1.3%) were detected. Different HPV types and HPV16 intratype variants are involved in oncogenic HPV infections in our population. These results suggest that HPV type distribution differs in CSW/IPW women and in the general population, although further analysis is necessary.

Adolescent↗
PubMed2006

[Prevalence of methylenetetrahydrofolate reductase C677T mutation among patients with acute ischemic cerebrovascular disease in Aragon].

BACKGROUND: Mutation C677T of the methylenetetrahydrofolate reductase (MTHFR) is the main cause of mild hyperhomocysteinemia. Hyperhomocysteinemia is a recognized risk factor for aterothrombosis. MTHFR C677T patients have higher levels of homocysteine in absence of dietary folates. METHODS: Retrospective study over data from patients studied for MTHFR C677T diagnosed of ischemic stroke (IS) younger 50 or older 50 without classic vascular risk factors or with familiar or personal history suggesting thrombophilia in a period of 3 years. MTHFR C677T was screened in 90 healthy blood donors as a control group. Computer database was used for descriptive statistics. RESULTS: Blood samples from 99 patients and from 90 donors (control). Mean age: 44.3 with Standard deviation (SD) 13.9 years in IS group and 39.1 with SD 8.3 years in control group. We found 19 (19.19%) homozygotes for MTHFR C677T in IS group and 14 (15.55%) in control group. CONCLUSIONS: Homozygosis for MTHFR C667T is more frequent in the IS group than in the control one, although there is no significant differences. Anyway, we suggest that, because of the high prevalence of the mutation MTHFR C677T found, screening should be made in the thombophilia studies, so that we could find patients with a risk factor that could be lowered by folates in the diet.

Adult↗
PubMed2005

Simplified dynamic model for the motility of irregular echinoids.

Inspired by the locomotion mechanism of sea urchins, we study the locomotion of an irregular echinoid by means of a simplified dynamical model. We prove that if two conjectures are assumed, the geometrical arrangement of the five ambulacral petals of irregular echinoids should form a eutactic star in order to optimize motility. We firstly propose an adequate "measure" of eutacticity that allows us to to verify the statistical tendency to such a property for a representative collection of fossil specimens. Next, regarding dynamics, the biological advantage of eutactic stars is addressed as a minimal path problem. Finally, we study the stability of some eutactic stars under small perturbations.

Animals↗
PubMed2005

Inhibition of N- and P/Q-type Ca2+ channels by cannabinoid receptors in single cerebrocortical nerve terminals.

Since cannabinoid receptors inhibit excitatory synaptic transmission by reducing glutamate release, we have examined whether this might occur through the direct inhibition of presynaptic Ca2+ channels. In cerebrocortical nerve terminals, activation of cannabinoid receptors with WIN55,212-2 reduces the KCl-evoked release of glutamate. However, this inhibition is attenuated when N- and P/Q-type Ca2+ channels are blocked. Through Ca2+ imaging in single nerve terminals, we found that WIN55,212-2 reduced the influx of Ca2+ both in nerve terminals that contain N-type Ca2+ channels and those that contain P/Q-type Ca2+ channels. Thus, cannabinoid receptors modulate the two major Ca2+ channels coupled to glutamate release in the cerebral cortex.

Animals↗
PubMed2004

Polyhedral truncations as eutactic transformations.

An eutactic star is a set of N vectors in Rn (N > n) that are projections of N orthogonal vectors in RN. First introduced in the context of regular polytopes, eutactic stars are particularly useful in the field of quasicrystals where a method to generate quasiperiodic tilings is by projecting higher-dimensional lattices. Here are defined the concepts of eutactic transformations (as mappings that preserve eutacticity) and of vector radiations (vectors that stem from the vectors of an eutactic star), which are used to describe and parameterize polyhedral truncations. The polyhedral truncations preserve eutacticity, a result of relevance to the faceting and habit-forming characteristics of quasicrystals.

Journal Article↗
PubMed2004

Ultrasonic band gaps and negative refraction.

The first experimentally observed ultrasonic band gaps in periodic bidimensional composited are reviewed here. The studied basic structure consists of an aluminum alloy plate with a periodic arrangement of cylindrical holes filled with mercury. Localization phenomena in linear and point defects have been observed and an ultrasonic waveguide capable to bend the ultrasonic radiation by 90 degrees has been achieved. We also revisit twinned-square periodic structures for ultrasonic wave bending and splitting. Such devices allow 45 degrees bending of waves, whereas an extreme anomalous refraction law at the grain boundaries has also been experimentally observed. Finally, a preliminary study about the possibility of "left-handed" behaviour in ultrasonic crystals is presented in this work. The device consists of a slab of the above mentioned metallic composite attached to an epoxy wedge. In this system, clues to negative refraction are theoretically shown.

Journal Article↗
PubMed2004

[Genotype and phenotypic expression of hereditary hemochromatosis in Spain].

INTRODUCTION: The prevalence of C282Y homozygosity in patients with hereditary hemochromatosis (HH) has been reported to be markedly lower in the Mediterranean Basin than in northern Europe. In Spain, the available data are contradictory and limited to small series in specific regions. The objective of this study is to determine the prevalence of the 2 main HFE gene mutations in a large series of unrelated Spanish patients with HH from different geographical origins. PATIENTS AND METHOD: The criteria for HH diagnosis were: repeat serum transferrin saturation index (> 45% plus C282Y homozygosity and/or hepatic iron index (> 1.9 of dry liver weight in non-cirrhotic patients or (> 4.1 in patients with liver cirrhosis. Cases in related individuals were excluded. Demographic data, clinical expression, iron parameters and HFE gene mutations (C282Y and H63D) were assessed in 222 patients. RESULTS: A total of 83.3% of patients were C282Y homozygous and 5% were compound heterozygous (C282Y/H63D). No significant differences in phenotypic expression or in the frequency of C282Y homozygosity were observed between patients born in the North and South of Spain. CONCLUSION: The genotypic and phenotypic expression of HH in Spain is very similar to that reported in Northern Europe. Thus, the genetic heterogeneity described in some Southern European regions cannot be considered a common feature to all countries of the Mediterranean Basin.

Female↗
PubMed2004

Fine mapping of 10q and 18q for familial Alzheimer's disease in Caribbean Hispanics.

Familial Alzheimer's disease (AD [MIM 104300]) has been a focus of intense investigation, primarily in Caucasian families from Europe and North America families. Although the late-onset form of familial AD, beginning after age 65 years, has been linked to regions on chromosomes 10q and 12p, the specific genetic variants have not yet been consistently identified. Using a unique cohort of families of Caribbean Hispanics ancestry, we screened the genome using 340 markers on 490 family members from 96 families with predominantly late-onset AD. We observed the strongest support for linkage on 18q (LOD=3.14). However, 17 additional markers (chromosomes 1-6, 8, 10, 12, and 14) exceeded a two-point LOD score of 1.0 under the affecteds-only autosomal dominant model or affected sibpair model. As we previously reported the fine-mapping effort on 12p showing modest evidence of linkage, we focused our fine-mapping efforts on two other candidate regions in the current report, namely 10q and 18q. We added 31 family members and eight additional Caribbean Hispanic families to fine map 10q and 18q. With additional microsatellite markers, the evidence for linkage for 18q strengthened near 112 cM, where the two-point LOD score for D18S541 was 3.37 and the highest NPL score in that region was 3.65 (P=0.000177). This narrow region contains a small number of genes expressed in the brain. However, at 10q (134-138 cM), the NPL score decreased from 3.15 (P=0.000486) to 2.1 (P=0.0218), but two broad peaks remained overlapping with previously reported peaks. Our results provide modest support for linkage on 10q and 12p in this cohort of Caribbean Hispanic families with familial Alzheimer's disease, and strong evidence for a new locus on 18q.

Aged↗
PubMed2004

Loss of wild-type Trp53 protein in mouse fibroblasts leads to increased radioresistance with consequent decrease in repair of potentially lethal damage.

It has been reported that the loss of function of Trp53 protein is associated with a reduction in the expression of radiation-induced potentially lethal damage (PLD). These studies, however, were carried out using either transformed or transfected cell lines, and other factors may have existed that could interfere with PLD repair. In this study, we used isogenic fibroblasts derived from Trp53 knockout mice to study radiation sensitivity, PLD repair, and repair of DNA double-strand breaks (DSBs). Experiments were carried out using wild-type (Trp53(+/+)), heterozygous (Trp53(+/-)) and homozygous mutant (Trp53(-/-)) cells. This is an ideal system because the only difference in the three cell strains is the status of the Trp53 protein. DSB repair was measured by pulsed-field-gel electrophoresis (PFGE), while radiosensitivity and PLD repair were studied using the clonogenic survival assay. Cells were irradiated in plateau phase and then trypsinized and plated either immediately or 24 h later to allow for PLD repair. The results of Western blot analyses showed that Trp53(-/-) cells expressed a putative mutant form of Trp53 that was unable to transcriptionally activate Cdkn1a (p21) protein in response to irradiation. The Trp53(-/-) cells were significantly more radioresistant than the Trp53(+/+) cells, and this was associated with a moderate reduction in PLD repair. DNA repair experiments showed no difference in DSB rejoining capability between the two cell lines. In conclusion, our results show that loss of wild-type Trp53 leads to increased radioresistance with consequent reduction in PLD repair but with no effect on DNA DSB repair.

Animals↗
PubMed2004

[The current importance of veterinary public health: the SAPUVET project].

The authors propose reviewing the current needs for implementing veterinary public health programmes, from both the teaching and professional standpoints. This is warranted by the fact that veterinary public health has become extremely important in various fields of work, beyond conventional food inspection. The article discusses the public health role which veterinarians must play and the interactions between their activities and those of other groups such as doctors, epidemiologists, ecologists, chemists, or even sociologists and anthropologists. The authors also study and assess the basic working tool in veterinary public health--epidemiological surveillance--and how it operates on the basis of diagnosis and risk analysis. The second part of the article discusses the need to unify criteria for veterinary public health training and the role which the SAPUVET network is playing in doing so (SAPUVET is a European Union-supported project within the ALFA programme that is designed to establish links between Latin American and European veterinary faculties).

Animals↗
PubMed2003

Theory for tailoring sonic devices: diffraction dominates over refraction.

Acoustic crystal devices, with dimensions on the order of several wavelengths, are studied by using the finite-difference time domain method in the moderately long wavelength propagation regime. From the focusing and imaging process performed by a square shaped lens, it is shown that diffractive effects dominate over those due to refraction. The major role of the device edge diffraction is shown by means of the well known Babinet principle. The first examples of imaging with a sonic plane lens, both with crystal structure and massive, and with an acoustic prism able to change the propagation direction of a plane wave, are presented.

Journal Article↗