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Biomedical subjects

A Beltrán

Publications and source records attributed to A Beltrán.

At least 19 recordsLinked to original sources
PubMed2006

Density functional theory study of the brookite surfaces and phase transitions between natural titania polymorphs.

The present study is concerned with the structural and electronic properties of the low-index surfaces of the brookite form of titanium dioxide. A theoretical investigation is carried out using the density functional formalism under the nonlocal B3LYP approximation to calculate surface energies, band energy values, and to interpret the response to hydrostatic pressure of the bulk and surfaces of the brookite structure. In addition, phase transformations with pressure are predicted from the anatase and the rutile to the brookite polymorph at about 3.8 and 6.2 GPa, respectively. The orthorhombic structure and the fractional coordinates of brookite vary isotropically with the rise in pressure. The calculated band gap energy is 3.78 eV for the bulk brookite. The brookite surface stabilities follow the sequence (010) < (110) < (100), and the minimum gap energy value is found for the (110) surface.

Journal Article↗
PubMed2003

Nitric oxide disrupts VE-cadherin complex in murine microvascular endothelial cells.

Vascular endothelial cadherin (VE-cadherin), which is localized at adherent junctions, is involved in the control of vascular permeability. A growing body of evidence indicates that NO modulates the movement of fluid and proteins out of the vasculature. In this paper, we investigated whether NO can disrupt the VE-cadherin complex. We found that treatment with two NO donors (SIN-1 and SNAP) markedly reduced the amount of VE-cadherin in a murine microvascular endothelial cell line (H5V) as demonstrated by immunoprecipitation analysis, cellular ELISA, and Northern blot analysis. Beta- and gamma-catenins were also found to be affected by the two NO donors. Moreover, the disruption of the complex, induced by NO donors, correlated with increases in vascular permeability using both in vivo and in vitro models. These results clearly demonstrate a role for NO in vascular permeability.

Animals↗
PubMed2003

Epidemiological study of resistance to nalidixic acid and other antibiotics in clinical Yersinia enterocolitica O:3 isolates.

Forty-six Yersinia enterocolitica O:3 clinical isolates resistant to nalidixic acid were studied. The use of molecular typing techniques, other indicators of resistance patterns, the plasmid profile, and the presence of genes that encode aminoglycoside-modifying enzyme production suggested to us a clonal dissemination of the studied strains.

Anti-Infective Agents↗
PubMed2001

Albumin-derived advanced glycation end-products trigger the disruption of the vascular endothelial cadherin complex in cultured human and murine endothelial cells.

Endothelial cell (EC) junctions regulate in large part the integrity and barrier function of the vascular endothelium. Advanced glycation end-products (AGEs), the irreversibly formed reactive derivatives of non-enzymic glucose-protein condensation reactions, are strongly implicated in endothelial dysfunction that distinguishes diabetes- and aging-associated vascular complications. The aim of the present study was to determine whether AGEs affect EC lateral junction proteins, with particular regard to the vascular endothelial cadherin (VE-cadherin) complex. Our results indicate that AGE-modified BSA (AGE-BSA), a prototype of advanced glycated proteins, disrupts the VE-cadherin complex when administered to ECs. AGE-BSA, but not unmodified BSA, was found to induce decreases in the levels of VE-cadherin, beta-catenin and gamma-catenin in the complex and in total cell extracts, as well as a marked reduction in the amount of VE-cadherin present at the cell surface. In contrast, the level of platelet endothelial cell adhesion molecule-1 (PECAM-1), which is located at lateral junctions, was not altered. Supplementation of the cellular antioxidative defences abolished these effects. Finally, the loss of components of the VE-cadherin complex was correlated with increases in vascular permeability and in EC migration. These findings suggest that some of the AGE-induced biological effects on the endothelium could be mediated, at least in part, by the weakening of intercellular contacts caused by decreases in the amount of VE-cadherin present.

Acetylcysteine↗
PubMed2001

High frequency of association of rheumatic/autoimmune diseases and untreated male hypogonadism with severe testicular dysfunction.

Our goal in the present work was to determine whether male patients with untreated hypogonadism have an increased risk of developing rheumatic/autoimmune disease (RAD), and, if so, whether there is a relation to the type of hypogonadism. We carried out neuroendocrine, genetic, and rheumatologic investigations in 13 such patients and 10 healthy male 46,XY normogonadic control subjects. Age and body mass index were similar in the two groups. Nine of the 13 patients had hypergonadotropic hypogonadism (five of whom had Klinefelter's syndrome [karyotype 47,XXY]) and 4 of the 13 had hypogonadotropic hypogonadism (46,XY). Of these last four, two had Kallmann's syndrome and two had idiopathic cryptorchidism. Eight (61%) of the 13 patients studied had RADs unrelated to the etiology of their hypogonadism. Of these, four had ankylosing spondylitis and histocompatibility B27 antigen, two had systemic lupus erythematosus (in one case associated with antiphospholipids), one had juvenile rheumatoid arthritis, and one had juvenile dermatomyositis. In comparison with the low frequencies of RADs in the general population (about 0.83%, including systemic lupus erythematosus, 0.03%; dermatomyositis, 0.04%; juvenile rheumatoid arthritis, 0.03%; ankylosing spondylitis, 0.01%; rheumatoid arthritis, 0.62%; and other RAD, 0.1%), there were surprisingly high frequencies of such disorders in this small group of patients with untreated hypogonadism (P < 0.001) and very low serum testosterone levels (P = 0.0005). The presence of RADs in these patients was independent of the etiology of their hypogonadism and was associated with marked gonadal failure with very low testosterone levels.

Adolescent↗
PubMed1997

Preoperative embolization of solid cervicomedullary junction hemangioblastomas: report of two cases.

Solid cervicomedullary haemangioblastomas represent a small but technically challenging subset of posterior fossa haemangioblastomas because of their site, high vascularity and tendency to bleed. We present our experience with preoperative embolisation of two solid cervicomedullary haemangioblastomas. In both cases the main feeding artery was the posterior inferior cerebellar artery. Arterial pedicles were catheterised with a microcatheter. The embolic material was small particles (150-250 microm) of polyvinyl alcohol. The result was almost complete preoperative obliteration of the vessels of the tumours. The procedure was well tolerated and facilitated easier bloodless, successful resection in both cases, 24 h after embolisation.

Adult↗
PubMed1996

Primary intraosseous meningiomas.

PURPOSE: A retrospective study was performed to evaluate the clinical, radiological and histological findings of 14 intraosseous meningiomas. MATERIAL AND METHODS: 14 histologically proved intraosseous meningiomas were studied with plain skull film and CT. Pathological records were reviewed. RESULTS: We found 9 calvarial cases and 5 spheno-orbital ones. The most common symptom in the calvarial cases was a lump in the scalp, and in the spheno-orbital lesions it was exophtalmos. Hyperostosis was present in all 5 spheno-orbital cases and in 3 out of the 9 calvarial ones; in the other 6 cases it had a mixed pattern. Enhanced dura was present in 3 calvarial cases and in 2 sphenoidal ones. Dura was involved in 5 cases: 2 with inflammatory changes, 2 with a minimal intradural tumour and one with a subdural tumour. CONCLUSION: CT better detected both the bony reaction and the intraosseous extension of the tumour. The dural changes were not specific of tumoural involvement. The differential diagnosis comprises: fibrous dysplasia, osteoma, blastic metastasis and mainly meningioma en plaque (MEP). Comparing our findings with other series, we noticed that in some cases the term MEP was used for similar cases. As the name MEP is merely descriptive and both entities share a larger number of similarities than differences, we believe that a differentiation between hyperostotic en plaque meningioma and intraosseous meningioma can hardly be made.

Adult↗
PubMed1989

Keeping quality of vacuum-packed smoked sardine fillets: microbiological aspects.

The effect of mixed smoking (2 h at 30 degrees C and 45 min at 75 degrees C was studied on the keeping quality of lean and fatty sardine fillets from fish caught in the Mediterranean Sea in March and June, respectively. Raw material for smoking included both fresh and frozen sardine fillets. Microbiological and sensory analyses were performed over the storage period, which lasted for 120 days at 0 +/- 1 degrees C. Smoking reduced the viable microbial flora values from 3-5 x 10(4) cfu/g to 2 x 10(2) cfu/g. The antimicrobial action of smoking, combined with that of vacuum packaging, had the effect of producing a gram-positive flora made up mainly of lactic acid bacteria. A practical consequence of this was to extend the shelf life of the smoked sardines for a period of 4 months. Frozen storage of samples at -18 degrees C for 6 months prior to smoking affected the behaviour of the microbial flora during cold storage at 0 degrees C, but did not affect the behaviour of the flora over a period of 3 months frozen storage, since the initial numbers of bacteria decreased and microbial growth was retarded. Furthermore, at the end of the storage period, the number of bacteria in the samples of frozen fatty sardines were higher than in the samples of frozen lean sardine. Physical conditions, therefore appear to exert an influence on bacterial growth. Sulphite-reducing Clostridia were not detected during the storage period.

Animals↗
PubMedDate not supplied

Nitrate exported in drainage waters of two sprinkler-irrigated watersheds.

Nitrate contamination of surface waters has been linked to irrigated agriculture across the world. We determined the NO3-N loads in the drainage waters of two sprinkler-irrigated watersheds located in the Ebro River basin (Spain) and their relationship to irrigation and N management. Crop water requirements, irrigation, N fertilization, and the volume and NO3-N concentration of drainage waters were measured or estimated during two-year (Watershed A; 494 irrigated ha) and one-year (Watershed B; 470 irrigated ha) study periods. Maize (Zea mays L.) and alfalfa (Medicago sativa L.) were grown in 40 to 60% and 15 to 33% of the irrigated areas, respectively. The seasonal irrigation performance index (IPI) ranged from 92 to 100%, indicating high-quality management of irrigation. However, the IPI varied among fields and overirrigation occurred in 17 to 44% of the area. Soil and maize stalk nitrate contents measured at harvest indicated that N fertilizer rates could be decreased. Drainage flows were 68 mm yr(-1) in Watershed A and 194 mm yr(-1) in Watershed B. Drainage NO3-N concentrations were independent of drainage flows and similar in the irrigated and nonirrigated periods (average: 23-29 mg L(-1)). Drainage flows determined the exported mass of NO3-N, which varied from 18 (Watershed A) to 49 (Watershed B) kg ha(-1) yr(-1), representing 8 (Watershed A) and 22% (Watershed B) of the applied fertilizer plus manure N. High-quality irrigation management coupled to the split application of N through the sprinkler systems allowed a reasonable compromise between profitability and reduced N pollution in irrigation return flows.

Agriculture↗