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Biomedical subjects

P Sánchez

Publications and source records attributed to P Sánchez.

At least 19 recordsLinked to original sources
PubMed2006

Effects of testosterone on brain mRNA levels of steroid 5alpha-reductase isozymes in early postnatal life of rat.

The enzyme 5alpha-reductase (5alpha-R) (EC 1.3.99.5) exists as two isoforms, 5alpha-R type 1 (5alpha-R1) and 5alpha-R type 2 (5alpha-R2), and both are present in the brain. 5alpha-R1 has been proposed as a constitutive enzyme that essentially plays a catabolic and neuron protective role whereas 5alpha-R2 has been associated with sexually dimorphic functions of the male. In this work, we studied the effects of testosterone (T), the masculinizing hormone of the central nervous system (CNS), on mRNA levels of both 5alpha-R isoforms in the prefrontal cortex of male and female rats during the postnatal sexual differentiation of the CNS in the rat, using one-step quantitative RT-PCR coupled with laser-induced fluorescence capillary electrophoresis (LIF-CE). We found an increase in 5alpha-R2 mRNA levels in both male and female rats after T treatment, while 5alpha-R1 mRNA levels were decreased in the same experimental conditions. Our results clearly indicated that T regulates the expression of both 5alpha-R1 and 5alpha-R2 genes in an opposite manner and independently of the sex. This could point to a crucial role of T in the sexual dimorphism for both 5alpha-R isozymes in the neonatal brain. These results open up a new research line that could improve understanding of the role of 5alpha-R isozymes in the physiology of the CNS.

Animals↗
PubMed2006

[Preliminary results of DERMATEL: prospective randomized study comparing synchronous and asynchronous modalities of teledermatology].

INTRODUCTION: There is considerable variability in the results of studies that evaluate diagnostic reliability in teledermatology. There are only two studies that compare the synchronous and asynchronous modalities of teleconsult in the same sample. We present the results of the pilot project DERMATEL, a study of diagnostic concordance that aims to increase the evidence of these aspects. MATERIAL AND METHODS: One-hundred-fifty.nine patients referred by the general practitioner in the first consult were randomized (algorithm 3:2:1) in three arms: asyncronous teledermatology (store-and-forward or SAF), synchronous teldermatology (real-time or VTC), and conventional consult (CC). We used high-quality, fixed digital images in all cases. The patients on the VTC teledermatology arm were also evaluated by videoconference. Finally all patients attended a face-to-face consult, considered the gold standard of patient care. A second dermatologist evaluated the diagnostic and management concordance between the teleconsults and the face-to-face consults. RESULTS: One-hundred.forty-seven patients completed the study as follows: 74 in the SAF teledermatology arm, 47 in the VTC teledermatology arm and 26 in the conventional consult (control group). The teledermatological (SAF and VTC) and face-to-face evaluations were identical in 100 of 121 patients (82.6%). The errors were mild in 14 cases (11.6%) and severe in 7 (5.8%). The diagnostic concordance was very high (kappa=0,813). The errors grouped by diseases were as follows: 6/54 (11%) for tumors, 10/30 (33.3%) for inflammatory conditions, 1/20 (5%) for infectious diseases, 3/12 (25%) for alopecia/acne and 1/5 (20%) for others. There were 15 errors in the SAF teledermatology arm (20.3%) and 6 in the VTC teledermatology arm (12.8%); these differences were not statistically significant (chi2 1.12; p=0.288). CONCLUSION: The reliability of dermatological teleconsult is very high, especially for tumoral or infectious diseases. The synchronous interaction with audio requires more resources, is difficult to coordinate and its diagnostic efficacy is not superior to SAF teledermatology.

Adolescent↗
PubMed2005

Separation of binary granular mixtures under vibration and differential magnetic levitation force.

The application of both a strong magnetic field and a magnetic field gradient to a diamagnetic or paramagnetic material can produce a vertical force that acts in concert with the force of gravity. We consider a binary granular mixture in which the two components have different magnetic susceptibilities and therefore experience different effective forces of gravity when subjected to an inhomogeneous magnetic field. Under vertical vibration, such a mixture may rapidly separate into regions almost pure in the two components. We investigate the conditions for this behavior, studying the speed and completeness of separation as a function of differential effective gravity and the frequency and amplitude of vibration. The influence of the cohesive magnetic dipole-dipole interactions on the separation process is also investigated. In our studies insight is gained through the use of a molecular dynamics simulation model.

Journal Article↗
PubMed2004

Stripe formation in granular mixtures due to the differential influence of drag.

We describe an investigation of fluid-immersed granular mixtures subjected to horizontal vibration. For sufficiently large amplitudes of vibration, a mixture of equal-sized glass and bronze particles in water is found to separate into a striped pattern. Numerical simulations based on soft-sphere molecular dynamics coupled to the interstitial fluid are able to capture many of the features observed experimentally. We propose a general pattern-formation mechanism based on the differential influence of drag on the components of the mixture. An expression for the number of stripes as a function of the system parameters is derived and shown to be in good agreement with experiments.

Journal Article↗
PubMed2003

Numerical simulations of air-driven granular separation.

Recently it has been shown that binary mixtures of equal-sized fine granular materials exhibit spontaneous separation under vertical vibration in the presence of air [Science 295, 1877 (2002)]. Here we describe a model of this behavior based on soft-sphere molecular dynamics coupled to the motion of the surrounding air. It exhibits many of the features observed experimentally including almost complete separation of the components into well defined regions with extremely sharp boundaries. The basic separation mechanism is robust and insensitive to many of the model parameters. Our results show that the forced flow of air through the bed, induced by vibration of the container, is responsible for this form of separation.

Journal Article↗
PubMed2003

Quantitation and comparison of anti-Gal-alpha-1,3-Gal antibodies in sera of healthy individuals and patients waiting for kidney transplantation.

Highly sensitized patients have poor prospects of being offered an allogeneic donor transplant, therefore, they could become primary candidates for xenogeneic organ transplantation. Hyperacute rejection is initiated by anti-Gal-(alpha)-1,3-Gal antibodies (xenoAb) and this rejection will have to be avoided if xenotransplantation is introduced into clinical practice. Hence, the aim of the study was to determine if sensitized patients against HLA antigens have higher titers of xenoAb than nonsensitized individuals. We determined immunoglobulin (Ig)M and IgG xenoAb in the serum of 100 volunteer blood donors and 98 sensitized patients and compared antibody titers from nonsensitized individuals to those with HLA specific antibodies classified into 5 panel-reactive antibody (PRA) groups: I, 0%; II, >0% and < or =10%; III, >10% and < or =50%; IV, >50% and < or =80%; and V, >80%. Analysis of the isotype specific quantification of the xenoAb revealed great interindividual variation but there were no significant differences in the range of titers of xenoAb. No significant PRA group-related variations were observed for xenoAb. In fact, there was no demonstrable correlation between levels of PRA and levels of xenoAb because the scattergram showed no statistically significant association by nonparametric statistic analysis. The results presented herein revealed that the presence of HLA specific antibody has no demonstrable relationship to the presence of higher titers of xenoAb. Thus, sensitized patients do not present a greater risk of rejection or are more difficult to treat for natural xenoreactivity than nonsensitized patients.

Antibodies↗
PubMed2003

Defective regulation of the protective IgE response against intestinal helminth Ascaris lumbricoides in malnourished children.

It is well established that malnutrition affects the immune response and increases the susceptibility to parasitic infection. In the present study we evaluated some aspects of the cellular and cytokine network that regulate the IgE responses, which are important components of host defence mechanisms against helminthic parasites in children infected with the intestinal helminth Ascaris lumbricoides, and with differing degrees of malnutrition. We found a defective T cell response in malnourished children, as indicated by diminished levels of circulating total (CD3+), helper (CD4+), IL-2-receptor-bearing (CD4+CD25+) and memory helper T cell responses (CD4+CD45RO+) in keeping with the decreased specific IgE levels against Ascaris lumbricoides. In contrast, the proportions of total B cells (CD20+), and those bearing the low-affinity IgE receptor (CD23+) were increased in the moderated malnourished children. Moreover, serum IL-4 levels and total IgE were also increased in these children. We suggest that malnutrition can cause an imbalance in T cell subpopulations that may lead to a defective T cell maturation and a decreased specific anti-Ascaris IgE response thus increasing the susceptibility to such infections. The high levels of total IgE observed may be related to a non-specific stimulation of the proliferation of activated B cells, probably caused by helminthic parasites and other infectious agents that are frequent in malnourished children.

Analysis of Variance↗
PubMed2002

Chaotic dynamics of an air-damped bouncing ball.

A ball bouncing elastically upon a vertically vibrated platform is one of the simplest examples of a chaotic system. If dissipation is introduced at each bounce through a coefficient of restitution, the motion is no longer chaotic; the trajectories exhibit locking solutions that result in periodic behavior. Here we investigate the dynamics of a bouncing ball influenced by air damping. We consider the effects of both static air and air moving with the platform, and show that there is an exact mapping between them. In either case, the system has a rather complex dynamical behavior including truly chaotic trajectories. Our results highlight the importance of air effects for fine particulate systems.

Journal Article↗
PubMed2001

[Staphylococcus lugdunensis infection: Report of thirteen cases].

INTRODUCTION: Staphylococcus lugdunensis is a coagulase-negative staphylococcus associated with infections such as aggressive endocarditis, repeated abscess formation and opportunist infections. MATERIALS AND METHODS: S. lugdunensis isolates recovered at our hospital during three years (1997-2000) were studied. The fibrinogen affinity factor and tube free-coagulase were analysed. The identification was made by the Crystal GPID (Becton-Dickinson) and Wider (Soria Melguizo) systems. Antibiotic sensitivity testing was performed with Wider panels. The clinical records of patients with S. lugdunensis recovered were studied. RESULTS: Thirteen S. Lugdunensis isolates were recovered from the following sources: abscess (9), surgical wound (2), blood culture (1), and urine (1). In ten cases the microorganism was obtained in pure culture; in the remaining three cases, S. lugdunensis grew in mixed culture. Two cases were excluded, as S. lugdunensis was considered not to be associated with the clinical condition. Lesions were located at: inguinal region (4), gluteal region (2), breast (2), abdominal wall (1), foot (1), unknown (1). Tent of the 13 isolates (76%) had fibrinogen affinity factor. Penicillin sensitivity was observed in 11/13 strains (84.6%). In one case, the isolate was beta-lactamase producer (7.6%); and in other case, the isolate was resistant to methicillin (7.6%). CONCLUSIONS: In this study we observed that S. lugdunensis is associated with skin and soft tisue infections, particularly abscess formation. The infection occurs most frequently in cancer patients, as observed in three cases in our series. The necessity of correctly identifying S. Lugdunensis is underscored. The recovery of coagulase-negative staphylococci should not reassure us unless a potentially pathogen species has been ruled out.

Adult↗
PubMed2001

Differential staining of DNA strand breaks in dried comet assay slides.

The comet assay involves embedding cells in agarose on microscope slides. After lysis and electrophoresis, staining is usually performed with a fluorescent DNA-binding dye and observation is carried out on fresh wet slides through an epifluorescence microscope. We present here a simple alternative for preservation of the agarose comet slides and a fluorescent staining that allows fine differential analysis of DNA strand breaks under confocal microscopy. Lymphocytes were processed according to previous published methods. Slides were quickly dehydrated in a hot oven at 50C for 20 min. Once the agarose layer was dried and reduced to a thin film, slides were treated with RNase. Image analysis showed higher tail length, total area, and tail moment. Using confocal microscopic optical sectioning, a thickness of approximately 180 microm for wet slides and 12 microm for dehydrated gels was calculated. Acridine orange, used for DNA differential staining, allowed quantitation of metachromasia and orthochromasia with confocal scanning microscopy. Differences between alkaline and neutral comet assay with AO were clear-cut and, in principle, a metachromatic index can be calculated. (J Histochem Cytochem 49:921-922, 2001)

Acridine Orange↗
PubMed2001

The Sonic Hedgehog-Gli pathway regulates dorsal brain growth and tumorigenesis.

The mechanisms that regulate the growth of the brain remain unclear. We show that Sonic hedgehog (Shh) is expressed in a layer-specific manner in the perinatal mouse neocortex and tectum, whereas the Gli genes, which are targets and mediators of SHH signaling, are expressed in proliferative zones. In vitro and in vivo assays show that SHH is a mitogen for neocortical and tectal precursors and that it modulates cell proliferation in the dorsal brain. Together with its role in the cerebellum, our findings indicate that SHH signaling unexpectedly controls the development of the three major dorsal brain structures. We also show that a variety of primary human brain tumors and tumor lines consistently express the GLI genes and that cyclopamine, a SHH signaling inhibitor, inhibits the proliferation of tumor cells. Using the in vivo tadpole assay system, we further show that misexpression of GLI1 induces CNS hyperproliferation that depends on the activation of endogenous Gli1 function. SHH-GLI signaling thus modulates normal dorsal brain growth by controlling precursor proliferation, an evolutionarily important and plastic process that is deregulated in brain tumors.

Animals↗
PubMed2001

Mucocutaneous leishmaniasis in a patient with the human immunodeficiency virus.

We report a case of mucocutaneous leishmaniasis (MCL) in a patient with the human immunodeficiency virus (HIV), Centers for Disease Control (CDC) Stage A2, with no previous history of cutaneous or systemic leishmaniasis. The patient had not travelled outside the province of Málaga, on the Mediterranean coast of southern Spain, so that it concerns an indigenous case, extremely unusual in this area. The HIV infection may well have influenced the defence against leishmania, but the exact mechanism by which this occurred is unknown.

Adult↗
PubMed2000

Rapid and cost-effective multiparameter toxicity tests for soil microorganisms.

Three biochemical parameters, DNA quantification in soil samples and two enzymatic activities, beta-galactosidase and dehydrogenase have been assessed as potential end-points for the use in cost-effective toxicity tests on soil microorganisms. The assessment included the development of a classical dose-response 24-h assay and the incorporation of measurements of the effects on microbial activities in soil column leaching studies and multispecies miniaturised terrestrial systems (MTS). Four different chemicals, copper, a new herbicide, thiabendazole and fenthion were studied. A rapid fluorescence DNA quantification technique did not produce adequate responses. The efforts to quantify DNA after extraction and clean-up procedures failed due to the presence of humic acids. From the protocol of the technique one could see that the technical procedure is time-consuming and expensive and, for this reason, not suitable for use as a parameter in rapid and cost-effective tests. However, the enzymatic activities showed their potential as toxicity end-points. Copper produced a concentration/response inhibition of beta-galactosidase and dehydrogenase with EC50 values of 78.39 and 24.77 mg Cu/kg soil, respectively. In the soil column study, these endpoints allowed the measurement of the microbial activities through the column. The effects of the new herbicide on beta-galactosidase and dehydrogenase activities were statistically significant for the highest application dose (40 g/ha). Thiabendazole affected the microbial activity when mixed within the soil, but no effects were observed when this fungicide was applied on the soil surface. Fenthion produced effects when applied either in the soil or on the soil surface. These results can be explained by the low mobility of thiabendazole. The results show the capabilities of these biochemical parameters to be included as endpoints in cost-effective bioassays.

Biological Assay↗