Biomedical subjects

L Sánchez

Publications and source records attributed to L Sánchez.

At least 19 recordsLinked to original sources

PubMed2006

Disturbance of erythrocyte lipid bilayer by amino acid-based surfactants.

In an attempt to increase our knowledge regarding the mechanisms of surfactant membrane interaction, we studied the action of several anionic and cationic amino acid-based surfactants on membrane fluidity using fluorescence anisotropy. Anisotropy measurements demonstrated that almost all of the surfactants studied disturbed the external region of the erythrocyte membrane without affecting the core of the bilayer. How the physico-chemical properties and structure of these compounds affect dynamics of the lipid bilayer is discussed in detail.

Amino Acids↗

PubMed2006

The biological properties of lysine-derived surfactants.

We examine the effects of aquatic toxicity on Daphnia magna, the antimicrobial activity of new anionic lysine-derivative surfactants, and the influence of different-sized counterions associated with the surfactants. Surfactants with Tris and Lithium had less of a toxic effect on Daphnia, while all surfactants proved highly active against yeasts and the gram-negative bacteria Bordetella bronchiseptica. Counterion size was found to have no effect on aquatic toxicity or antimicrobial activity.

Animals↗

PubMed2006

GINsim: a software suite for the qualitative modelling, simulation and analysis of regulatory networks.

This paper presents GINsim, a Java software suite devoted to the qualitative modelling, analysis and simulation of genetic regulatory networks. Formally, our approach leans on discrete mathematical and graph-theoretical concepts. GINsim encompasses an intuitive graph editor, enabling the definition and the parameterisation of a regulatory graph, as well as a simulation engine to compute the corresponding qualitative dynamical behaviour. Our computational approach is illustrated by a preliminary model analysis of the inter-cellular regulatory network activating Notch at the dorsal-ventral boundary in the wing imaginal disc of Drosophila. We focus on the cross-regulations between five genes (within and between two cells), which implements the dorsal-ventral border in the developing imaginal disc. Our simulations qualitatively reproduce the wild-type developmental pathway, as well as the outcome of various types of experimental perturbations, such as loss-of-function mutations or ectopically induced gene expression.

Animals↗

PubMed2006

[Vascular access outcome in patients aged over 75 years].

UNLABELLED: We report a retrospective study on the results of 132 native fistulas, 12 grafts and 27 tunneled catheters followed during 30 months in 144 patients on hemodialysis. The results were compared according to patient age: 75 years or over (n = 58, 80.3 +/- 3.5) vs below 75 years (n = 86, 59.5 +/- 13.3). Gender, presence of diabetes and type of fistula were also included in the analysis. RESULTS: There were no statistically significant differences between both groups in the use of tunneled catheters or grafts (8.6% vs 5.8% y 5.2% vs 10.5% respectively), primary failure of native fistulas (7.1% in those aged 75 years or over vs 25.5% in patients below 75 years), rate of thrombosis (0.03 vs 0.09/patient year at risk respectively) or number of percutaneous or surgical procedures in order to maintain the fistula patency (0.11 vs 0.16/patient year at risk respectively). At the same time no differences were seen in the primary, primary assisted and secondary patency of the native fistulas. The mean age of the patients when the first access fistula was created was different according to the area of surgery (74.9 +/- 9.3 for the elbow vs 64.9 +/- 16.2 years for the forearm, p < 0.005). Diabetes was an unfavourable factor for primary (HR Cox 2.08, p < 0.05) or secondary (Log Rank, p <0.05) patency. CONCLUSION: The vascular access for hemodialysis in elderly patients presents a similar evolution to that seen in younger populations if the access creation is based on an exhaustive study, including ecodoppler of the vascular map and the use of more proximal fistulas if necessary. Therefore the more frequent use of grafts or catheters in elderly patients is not justified.

Age Factors↗

PubMed2005

Field study of methidathion in soil amended with biosolid and a cationic surfactant under different irrigation regimes. Solute transport modeling.

Four experimental plots located in Granada (Spain) were used to investigate the potential movement of the insecticide methidathion during three treatments in a period of three years. To increase pesticide soil retention a municipal biosolid and the cationic surfactant, tetradecyl trimethyl ammonium bromide (TDTMA), were used as soil amendments. The presence of the insecticide was monitored in soil and water samples at different depths up to one meter. Soil solution was sampled by ceramic suction cups installed at three depths (25, 75 and 100 cm). No effect of the amendments on pesticide mobility was observed. Experimental results showed that pesticide leaching occurred in the upper soil layer. Although some sporadic high water soil concentrations were found, these were attributed to preferential flow processes. This was confirmed by the absence of high pesticide concentration in soil samples at similar depths. Pesticide mobility was mainly affected by the irrigation employed. Experimental results were compared with theoretical data simulated with the mathematical model FocusPelmo. The resemblance between theoretical and experimental soil data seems to confirm the preferential flow processes. Otherwise, the lack of fit between the soil water data were attributed to the ceramic devices employed, that could suffer an "ageing process" which would cause bias in the determinations.

Agriculture↗

PubMed2005

Modeling of geochemical processes related to uranium mobilization in the groundwater of a uranium mine.

This paper describes the processes leading to uranium distribution in the groundwater of five boreholes near a restored uranium mine (dug in granite), and the environmental impact of restoration work in the discharge area. The groundwater uranium content varied from <1 microg/L in reduced water far from the area of influence of the uranium ore-containing dyke, to 104 microg/L in a borehole hydraulically connected to the mine. These values, however, fail to reflect a chemical equilibrium between the water and the pure mineral phases. A model for the mobilization of uranium in this groundwater is therefore proposed. This involves the percolation of oxidized waters through the fractured granite, leading to the oxidation of pyrite and arsenopyrite and the precipitation of iron oxyhydroxides. This in turn leads to the dissolution of the primary pitchblende and, subsequently, the release of U(VI) species to the groundwater. These U(VI) species are retained by iron hydroxides. Secondary uranium species are eventually formed as reducing conditions are re-established due to water-rock interactions.

Journal Article↗

PubMed2005

Cell-cycle-associated markers and clinical outcome in human epithelial cancers: a tissue microarray study.

The development and progression of epithelial cancers are the result of an imbalance in signals promoting and inhibiting cellular proliferation and apoptosis. The aim of this study is to evaluate the expression of cell-cycle and apoptosis regulators and correlate them with clinical outcome in the most frequent carcinomas, in order to establish common prognostic biomarkers independent of cancer origin. Using tissue microarrays (TMAs), we have analysed the immuno-expression of Ki-67, Bcl-2, Bax, cyclin D1, cyclin D3, CDK1, CDK2, CDK6, p16, p21, and p27 in a series of 205 carcinomas of the large bowel, breast, lung and prostate (80, 73, 37 and 15 cases, respectively). By univariate analysis, positivity for p27, p16 and Bcl-2 was associated with better overall survival (P<0.0135, P<0.0442 and P<0.0001, respectively). The risk of mortality was 2.3-fold greater in patients without Bcl-2 expression. TMA immunohistochemical analysis identified a subset of epithelial cancers with overlapping alterations in cell-cycle checkpoints, apoptosis regulators and tumour suppressor pathways. We found that in most common epithelial cancers, regardless of origin, Bcl-2 appears to be the key biological factor influencing clinical behaviour.

Adult↗

PubMed2005

Mapping of tachykinins in the cat spinal cord.

Using an indirect immunoperoxidase technique, the location of cell bodies and fibers containing substance P, neurokinin A and neurokinin B was studied in the cat spinal cord. The former two neuropeptides showed a widespread distribution throughout the whole spinal cord, whereas the distribution of neurokinin B was more restricted. Neurokinin A-immunoreactive structures showed a more widespread distribution and a higher density than the immunoreactive structures observed to contain substance P. In the cat spinal cord, we observed cell bodies containing neurokinin A, but no cell bodies containing neurokinin B or substance P were found. These cell bodies were located in laminae V (sacral 1 and 2 levels), VI (sacral 1 and 3), VII (lumbar 7, sacral 1 and 3, caudal 1) and X (sacral 1). Laminae I and II showed the highest density of immunoreactive fibers for each of the three tachykinins studied, being in general lamina IV who showed the lowest number of immunoreactive fibers containing substance P, neurokinin A or B. The anatomical distribution of the three tachykinins studied in the cat spinal cord indicates that the neuropeptides could be involved in the neurotransmission and/or in the neuromodulation of nociceptive information, as well as in autonomic and affective responses to pain. Moreover, the involvement of substance P, neurokinin A or B in other functions unrelated to the transmission of pain is also possible (autonomic and motor functions). The distribution of the neuropeptides studied in the cat is compared with the location of the same neuropeptides in the spinal cord of other species. The possible origin of the tachykinergic fibers in the cat spinal cord is also discussed.

Animals↗

PubMed2005

[Enzyme replacement therapy in Fabry's disease].

We report a 56-year-old man with history of chronic renal failure, who was diagnosed to have Fabry's disease after performing a percutaneous kidney biopsy. The diagnosis was confirmed by the deficient level of activity of alpha-galactosidase A and by the identification of the mutation. A enzime replacement therapy with alpha-galactosidase A was administered. After 18 months of treatment, a second kidney biopsy was performed showing renal deposits of globotriaosylceramide (we did not evaluate the percentage of histologic clearance of the deposits). Six months after the end of the therapy, a reduction in the impairment of renal function is observed, and the classic manifestations of the disease are absent.

Adult↗

PubMed2004

[Prevalence of malnutrition in outpatients with stable chronic obstructive pulmonary disease].

OBJECTIVE: To determine the prevalence of malnutrition in outpatients with stable chronic obstructive pulmonary disease (COPD) followed at a respiratory clinic. MATERIAL AND METHOD: In this prospective study, we assessed the nutritional status of consecutive outpatients with stable COPD by investigating various anthropometric parameters. Patients were malnourished (low body weight) if their body mass index was within the bottom quartile of a reference population. Muscle mass was determined from the midarm muscle area and if this mass was at or within the bottom quartile, muscle wasting was present. Albumin and transferrin plasma concentrations were used as a measure of visceral protein stores. Fat stores were assessed from body fat and if this value was at or within the bottom quartile, calorific malnutrition was present. All patients underwent arterial blood gas sampling at rest and spirometry. RESULTS: A total of 178 patients--one woman (0.6%) and 177 men (99.4%)--were enrolled in the study, with a mean (SD) age of 69 (9) years. We found low body weight in 19.1% of the patients, muscle wasting in 47.2%, visceral protein depletion in 17.4%, and fat depletion in 19.1%. Of the patients with normal weight, 62.9% showed muscle wasting. The proportion of patients with a body mass index or midarm muscle area at or within the bottom quartile increased significantly with increased bronchial obstruction (P<.001 and P=.015, respectively), though 35.7% of the patients showed muscle wasting even when COPD was mild. CONCLUSIONS: Many patients with stable COPD suffer malnutrition. Nutritional state is worse with more severe COPD. Depletion involves both fat stores and muscle and visceral protein stores, but the greatest effect is seen in muscle wasting. A significant number of patients with normal weight also suffer muscle wasting. Although changes in body composition were common in our patients, low body weight was less prevalent than has been reported for populations in countries that are socially and economically similar to Spain.

Aged↗

PubMed2004

[Successful pregnancy in a patient with systemic lupus erythematosus on hemodialysis].

We report a twenty-nine-year-old patient, on renal replacement treatment (including 2 kidney transplants) since she was 11 years old, because of systemic lupus erythematosus. The patient became pregnant on hemodialysis, concluding the pregnancy successfully. The evolution and management of pregnancy were described and the related literature was revised. We concluded that, although pregnancy on hemodialysis and/or systemic lupus erythematosus patients involves a high risk for the mother and the fetus that makes advisable contraception, an increase in success in pregnancies in systemic lupus erythematosus patients on remission during the previous months, has been recently observed. Moreover, the increase of frequency and duration of hemodialysis sessions, has improved the neonatal survival around the 50% in pregnancies on dialysis. We emphasize the difficulty to maintain the mother's hemoglobin at an adequate target, as well as the high frequency of fetal prematury.

Adult↗

PubMed2003

Chemical and physical factors affecting the extractability of methidathion from soil samples.

Determination of methidathion in soil samples using Soxhlet extraction has been studied. Several factors were investigated for their effect on methidathion recovery. Some were related to the extraction procedure, for example solvent type used for the extraction (acetone or hexane/toluene), extraction time, soil humidity, and type of sterilisation system employed. Other factors tested included the addition of organic matter to the soil, for example urban sewage sludge and the cationic surfactant TDTMA. Experimental designs were used to determine the effects of the different factors. Acetone resulted in higher recoveries and was less affected by the presence of water. Autoclaving was the most appropriate sterilisation method. Thimerosal resulted in a decrease in insecticide recovery. Methidathion recovery increased as the amount of cationic surfactant was increased, but decreased as the amount of sewage sludge added to the soil was increased. In general, because the factors studied were not always independent of each other, a clear description of the methodology used is needed when analysing pollutants in environmental samples.

Journal Article↗

PubMed2003

Gynogenesis assessment using microsatellite genetic markers in turbot ( Scophthalmus maximus).

Gynogenesis was assessed by different methods in 2 families of gynogenetic offspring in turbot ( Scophthalmus maximus). Karyotype analysis in embryos and larvae demonstrated high accuracy in estimation of ploidy level, but performance was uneven given the low quality and number of plates obtained. The use of silver staining to estimate the number of nucleoli per nucleus resulted in a straightforward and easy method to evaluate the ploidy of the samples studied. However, the existence of a nucleolus organizer region polymorphism in turbot determined a small error in ploidy estimation, important when checking ploidy in specific individuals. The use of a set of 11 highly variable microsatellite loci proved to be a powerful method to confirm the exclusive maternal inheritance to gynogenetic offspring in turbot, with probabilities of detection of putative paternal genetic contribution above 99.99%.

Animals↗

PubMed2003

Differential regulation of rat peripheral 5-HT(2A) and 5-HT(2B) receptor systems: influence of drug treatment.

Most studies of 5-HT(2) receptor regulation have been carried out on the central nervous system (CNS) (which expresses 5-HT(2A) and 5-HT(2C) receptors); very few in vitro studies have addressed the peripheral receptors 5-HT(2A) and 5-HT(2B). The aim of this investigation was to compare the possible short- and long-term processes regulating these peripheral receptors in the rat. The in vitro contractile response elicited by serotonin (5-HT, 10 micro M) in the rat gastric fundus (5-HT(2B) receptor system) was rapid and followed by a partial fade to a steady state, in contrast with the rat thoracic aorta response (5-HT(2A) receptor system), which was more stable, slower and sustained. To characterize drug-receptor interactions, cumulative concentration/response curves (CCRCs) for 5-HT were constructed ex vivo for rat tissues treated with drugs acting at these receptors. Rats were examined 4 or 24 h after a single, i.p. administration of (+/-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane [(+/-)DOI, 1 or 2.5 mg/kg], clozapine, cyproheptadine or rauwolscine (10 mg/kg), 48 h after a single i.p. administration of (+/-)DOI (2.5 mg/kg), clozapine or cyproheptadine (10 mg/kg) or 24 h after the last of with 15 daily i.p. administrations of (+/-)DOI (1 or 2.5 mg/kg), clozapine, cyproheptadine or rauwolscine (10 mg/kg). In the aorta, E(max) (the maximum response elicited by 5-HT) was unchanged 4 h after a single dose of any of the drugs tested. However, 24 h after a single dose, E(max) was lower in animals treated with (+/-)DOI (2.5 mg/kg), clozapine or cyproheptadine than in controls, whilst 48 h after a single dose of (+/-)DOI (2.5 mg/kg), clozapine or cyproheptadine there was no difference in E(max) between experimental and control animals. After chronic treatment with (+/-)DOI (2.5 mg/kg), clozapine and cyproheptadine, E(max) was lower than in controls. In the gastric fundus, E(max) 4 h after a single dose of each drug was lower than in controls, and the response recovered by 24 or 48 h. Following chronic treatment, E(max) was significantly lower than in controls for each drug used. These findings suggest first, that regulation of peripheral 5-HT(2) receptors (5-HT(2A) and 5-HT(2B)) is a functionally significant phenomenon in vivo, and occurs after administration of both agonists and antagonists. Second, the kinetics of peripheral 5-HT(2) receptor regulation were similar in both in vivo and ex vivo experiments. The 5-HT(2B) receptors in rat gastric fundus are more sensitive to drug-induced regulation than the 5-HT(2A) rat aortic receptors. Finally, long-term regulation of both receptors stabilizes short-term desensitization for longer.

Amphetamines↗

PubMed2003

Molecular analysis and developmental expression of the Sex-lethal gene of Sciara ocellaris (Diptera order, Nematocera suborder).

This paper reports the cloning and characterization in Sciara ocellaris of the gene homologous to Sex-lethal (Sxl) of Drosophila melanogaster. This gene plays the key role controlling sex determination and dosage compensation in the latter species. The Sciara Sxl gene produces a single transcript encoding a single protein in both males and females. This protein, found inside the nucleus, is expressed in all tissues. Both Sciara and Drosophila Sxl proteins are highly conserved at their two RNA-binding domains. In both Sciara sexes, the Sxl protein co-localizes with transcription-active regions dependent on RNA polymerase II but not on RNA polymerase I. It would appear that in Sciara, Sxl does not appear to play the key discriminative role in controlling sex determination and dosage compensation that it plays in Drosophila.

Amino Acid Sequence↗

PubMed2003

EEG and behavioral changes following neurofeedback treatment in learning disabled children.

Neurofeedback (NFB) is an operant conditioning procedure, by which the subject learns to control his/her EEG activity. On one hand, Learning Disabled (LD) children have higher values of theta EEG absolute and relative power than normal children, and on the other hand, it has been shown that minimum alpha absolute power is necessary for adequate performance. Ten LD children were selected with higher than normal ratios of theta to alpha absolute power (theta/alpha). The Test Of Variables of Attention (TOVA) was applied. Children were divided into two groups in order to maintain similar IQ values, TOVA values, socioeconomical status, and gender for each group. In the experimental group, NFB was applied in the region with highest ratio, triggering a sound each time the ratio fell below a threshold value. Noncontingent reinforcement was given to the other group. Twenty half-hour sessions were applied, at a rate of 2 per week. At the end of the 20 sessions, TOVA, WISC and EEG were obtained. There was significant improvement in WISC performance in the experimental group that was not observed in the control group. EEG absolute power decreased in delta, theta, alpha and beta bands in the experimental group. Control children only showed a decrease in relative power in the delta band. All changes observed in the experimental group and not observed in the control group indicate better cognitive performance and the presence of greater EEG maturation in the experimental group, which suggests that changes were due not only to development but also to NFB treatment.

Behavior↗

PubMed2002

Laparoscopic diagnosis of acute lower abdominal pain in women of reproductive age.

OBJECTIVES: To compare the accuracy of laparoscopy performed within 24 h of admission and the conventional method based on clinical observation in the etiological diagnosis of non-specific acute lower abdominal pain (NSLAP) in women of reproductive age. METHODS: A total of 110 patients who met the selection criteria and were seen from November 1997 to June 2000 at the Instituto Materno Infantil, a referral hospital for maternal and perinatal care in Bogotá, were randomly divided into two groups. The effectiveness of each method was evaluated according to number of diagnoses reached, length of in-patient stay before diagnosis, complications, and diagnostic accuracy when compared with a standard given by microbiological and histopathological findings as well as clinical course. RESULTS: The early laparoscopy group did not experience more accurate diagnoses (85% vs. 79%, P=0.61) or a greater number of complications (11% vs. 9%, P=0.48), although the patients' stay was shorter (1.3 vs. 2.3 days, P=0.008) than the stay of the conventional-diagnosis group. Sensitivity analysis showed more accurate judgements with laparoscopy in four of the five NSLAP causes, but only in two of the cases did this greater accuracy have clinical significance. CONCLUSIONS: Early laparoscopy did not show a clear benefit in women with NSLAP.

Abdomen, Acute↗

PubMed2002

Sex-dependent synaptic behaviour in triploid turbot, Scophthalmus maximus (Pisces, Scophthalmidae).

A surface-spreading synaptonemal complex (SC) technique was used to analyse spermatocytes and oocytes of triploid turbot (Scophthalmus maximus) in order to visualise the process of chromosome synapsis. The most conspicuous characteristic of triploid oocytes is that, in the trivalents, the lateral elements of the SC were frequently associated in threes, either completely along the length of the trivalent, or partially, forming a variety of forked structures. In these nuclei, synapsis usually occurred among homologous chromosomes and the number of bivalents observed was significantly higher than that expected under the assumption of random chromosome association among all partners. However, the frequency of trivalents was very low in triploid spermatocytes, triple synapsis being also scarce. In these nuclei chromosomes that were excluded from homologous synapsis become engaged in random SC formation, and, therefore a considerable number of non-homologous associations are produced. The causes of the synaptic differences observed in triploid males and females of turbot and their possible relation to the sterility displayed by these animals are discussed.

Animals↗