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Biomedical subjects

V Hernandez

Publications and source records attributed to V Hernandez.

18 recordsLinked to original sources
PubMed2006

Blast2GO goes grid: developing a grid-enabled prototype for functional genomics analysis.

The vast amount in complexity of data generated in Genomic Research implies that new dedicated and powerful computational tools need to be developed to meet their analysis requirements. Blast2GO (B2G) is a bioinformatics tool for Gene Ontology-based DNA or protein sequence annotation and function-based data mining. The application has been developed with the aim of affering an easy-to-use tool for functional genomics research. Typical B2G users are middle size genomics labs carrying out sequencing, ETS and microarray projects, handling datasets up to several thousand sequences. In the current version of B2G. The power and analytical potential of both annotation and function data-mining is somehow restricted to the computational power behind each particular installation. In order to be able to offer the possibility of an enhanced computational capacity within this bioinformatics application, a Grid component is being developed. A prototype has been conceived for the particular problem of speeding up the Blast searches to obtain fast results for large datasets. Many efforts have been done in the literature concerning the speeding up of Blast searches, but few of them deal with the use of large heterogeneous production Grid Infrastructures. These are the infrastructures that could reach the largest number of resources and the best load balancing for data access. The Grid Service under development will analyse requests based on the number of sequences, splitting them accordingly to the available resources. Lower-level computation will be performed through MPIBLAST. The software architecture is based on the WSRF standard.

Computational Biology↗
PubMed2005

The Healthgrid White Paper.

Over the last four years, a community of researchers working on Grid and High Performance Computing technologies started discussing the barriers and opportunities that grid technologies must face and exploit for the development of health-related applications. This interest lead to the first Healthgrid conference, held in Lyon, France, on January 16th-17th, 2003, with the focus of creating increased awareness about the possibilities and advantages linked to the deployment of grid technologies in health, ultimately targeting the creation of a European/international grid infrastructure for health. The topics of this conference converged with the position of the eHealth division of the European Commission, whose mandate from the Lisbon Meeting was "To develop an intelligent environment that enables ubiquitous management of citizens' health status, and to assist health professionals in coping with some major challenges, risk management and the integration into clinical practice of advances in health knowledge." In this context "Health" involves not only clinical procedures but covers the whole range of information from molecular level (genetic and proteomic information) over cells and tissues, to the individual and finally the population level (social healthcare). Grid technology offers the opportunity to create a common working backbone for all different members of this large "health family" and will hopefully lead to an increased awareness and interoperability among disciplines. The first HealthGrid conference led to the creation of the Healthgrid association, a non-profit research association legally incorporated in France but formed from the broad community of European researchers and institutions sharing expertise in health grids. After the second Healthgrid conference, held in Clermont-Ferrand on January 29th-30th, 2004, the need for a "white paper" on the current status and prospective of health grids was raised. Over fifty experts from different areas of grid technologies, eHealth applications and the medical world were invited to contribute to the preparation of this document.

Computer Communication Networks↗
PubMed2003

Dental and periodontal lesions in patients with gastro-oesophageal reflux disease.

OBJECTIVE: Dental erosion has been considered an extraesophageal manifestation of gastro-oesophageal reflux disease, but few reports have studied the relationship between this disease and other periodontal or dental lesions. The aim of this study was to investigate the prevalence of dental and periodontal lesions in patients with gastro-oesophageal reflux disease. PATIENTS AND METHODS: A total of 253 subjects were prospectively studied between April 1998 and May 2000. Two study groups were established: 181 patients with gastro-oesophageal reflux disease and 72 healthy volunteers. Clinical assessment, including body mass index and consumption of tobacco and alcohol, was performed in all subjects, as well as a dental and periodontal examination performed by a dentist physician, blind as to the diagnosis of subjects. Parameters evaluated were: (a) presence and number of dental erosion, location and severity, according to the Eccles and Jenkins index [Prosthet Dent 1979;42:649-53], modified by Hattab [Int J Prosthes 2000;13:101-71; (b) assessment of dental condition by means of the CAO index; and (c) periodontal status analysed by the plaque index, the haemorrhage index, and gingival recessions. RESULTS: Clinical parameters were similar in both groups (p > 0.05). Age was statistically associated with the CAO index, presence of dental erosion, and gingival recession (p < 0.001, Student's t-test). Compared with the control group, the percentage of dental erosion was significantly higher in the gastro-oesophageal reflux disease group (12.5 vs. 47.5%, p < 0.001, chi2-test), as was the number and severity of dental erosions (p < 0.001, Student's t-test). Location of dental erosion was significantly different between groups. Age was not statistically related to either the amount or severity of dental erosion. CAO and periodontal indices were similarly distributed between groups. CONCLUSIONS: Dental erosion may even be considered as an extraesophageal manifestation of gastro-oesophageal reflux disease. The fact that the prevalence of caries and periodontal lesions is similar in patients with gastro-oesophageal reflux disease and in healthy volunteers suggests a lack of relationship with gastro-oesophageal reflux disease.

Adolescent↗
PubMed2001

[Comparison of 2 administration protocols (continuous or discontinuous) of a time-dependent antibiotic, Tazocin].

A predictive parameter of beta-lactam therapeutic efficacy is the time (T > MIC) while antibiotic serum concentrations are above the MIC of suspected bacteriological agents. This led us to carry out a randomised open study to compare the usually used intermittent administration of Tazocin (three injections of 4 g/0.5 g a day) and continuous perfusion of 12 g/1.5 g a day by calculating these T > MIC. Patients from digestive reanimation department were randomised within two arms: continuous or intermittent administration. Sixteen takings of blood were executed over a forty-hour period. After liquid/liquid extraction, piperacillin and tazobactam serum concentrations were determined by HPLC with a reversed phase column (C18) and a UV spectrophotometry detection. Then, from the time-concentration curves we have evaluated the T > MIC for an enterobacteria (MIC = 8 micrograms/mL) and for Pseudomonas (MIC = 16 micrograms/mL). Concerning intermittent administration T > MIC were 74% (c > MICenterobacteria) and 62% (c > MICPseudomonas). These percentages in the continuous arm were 100% (c > MICenterobacteria) and 99% (c > MICPseudomonas). Tazobactam concentrations were low and even undetectable between each injection in the intermittent administration arm. This was not found within the continuous administration arm. In conclusion, for the intermittent administration, we observed some long periods occurring before each injection while antibiotic concentrations were under the MIC of most bacteria. During these same periods tazobactam concentrations were under the efficacy threshold. These periods were not observed within the continuous administration arm.

Adolescent↗
PubMed2001

Inverse relation between input resistance and threshold current in canine cardiac syncytium.

INTRODUCTION: The present study was designed to examine the extent to which differences in input resistance contribute to the heterogeneity of excitability in canine endocardium. METHODS AND RESULTS: The experiments were performed in isolated canine right anterior papillary muscles. The preparations were superfused with oxygenated Tyrode's solution at 36 degrees to 37 degrees C. Conventional methods were used for recording and stimulation. To obtain pertinent data, two microelectrodes were inserted into the same cell or into two contiguous cells. One microelectrode injected intracellular hyperpolarizing current to polarize the membrane; the second microelectrode recorded the changes in transmembrane potential. The two micreoelectrodes were separated by 8 to 10 microm. The procedure used provided input resistance and threshold current values for the doubly impaled cell or the two contiguous cell units. The same procedure was repeated at different sites of the preparation. The plot of input resistance versus threshold current showed a good fit (R2 = 0.97) between the experimental data and the curve for the rectangular hyperbola XY = 30 mV; therefore, the input resistance and the threshold current are inversely related. CONCLUSION: The results indicate that the canine cardiac syncytium is nonhomogeneous with respect to input resistance and that input resistance is inversely related to the minimal current needed to reach threshold. Accordingly, the electrical excitability of the cells studied also is inhomogeneous.

Animals↗
PubMed2000

Differences in genotypes of Helicobacter pylori from different human populations.

DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution.

Amino Acid Isomerases↗
PubMed1998

Music does not reduce alfentanil requirement during patient-controlled analgesia (PCA) use in extracorporeal shock wave lithotripsy for renal stones.

To evaluate the impact of music on opioid requirements and pain levels during renal lithotripsy using alfentanil patient-controlled analgesia (PCA), we conducted a prospective, blinded, randomized controlled trial. Patients undergoing lithotripsy were instructed in PCA use and asked to rate their anxiety and select their preferred type of music. They were then premedicated with morphine and ketorolac and randomly allocated into two groups. Group 1 (n = 97) had music started 10 min before the procedure and maintained until 10 min after its conclusion. Group 2 (n = 96) had music begun at the conclusion of lithotripsy and continued for 10 min. Pain intensity, alfentanil requirement, side effects, quality of analgesia, patient satisfaction, and acceptance of the technique were evaluated. Demographics, alfentanil requirement, pain levels, side effects, quality of analgesia, and patient satisfaction were similar in both groups. The addition of music did not provide any benefit. This result raises the possibility that some nonpharmacologic therapies have minimal impact in settings where the painful stimulus is moderate to severe and adequate pharmacotherapy is available.

Adolescent↗
PubMed1997

Synaptophysin immunoreactivity in the aging rat pituitary gland.

The density of synaptophysin (SN)-immunoreactivity (IR) was examined in pituitary glands of aging male Sprague-Dawley rats. SN-IR was observed as dense dots among endocrine cells of the intermediate lobe, while the neural lobe contained numerous, highly dense immunopositive regions. Some anterior lobe secretory cells contained SN-IR within the cytoplasm, suggestive of the presence of the protein in secretory granules, but no dot-like staining was observed between endocrine cells of that region. A quantitative analysis of the dot-like SN-immunostaining within the intermediate lobe found that tissue from groups of rats aged 13 months, or 15-17 months, contained significantly fewer SN-immunopositive areas than did tissues from 8-month-old animals. Diminished SN immunostaining is suggestive of reduced numbers of synapses in the intermediate lobe, which may lead to alterations in regulation of pituitary hormone secretion from endocrine cells in the older animals.

Aging↗
PubMed1996

Junction potentials and action potentials of the crayfish myocardium.

INTRODUCTION: The purpose of this investigation was to study the properties of junction and action potentials elicited by nerve stimulation in the absence of the cardiac ganglion in crayfish myocardium. METHODS AND RESULTS: The cardiac ganglion was surgically removed in isolated crayfish hearts. Electrical stimulation of one of the peripheral anterolateral nerves provided isolated junction potentials and action potentials free of the usual postspike bursts of junction potentials. The single junction potentials displayed amplitudes of up to 25 mV and slow exponential decay; the mean time constant was 170 +/- 13 msec (approximately x +/- SD). In fully recovered tissue, the junction potentials triggered action potentials free of repetitive subthreshold discharges. Tetrodotoxin did not alter the amplitude or shape of action potentials initiated by direct electrical stimulation of the muscle cells. Calcium channel blocking agents such as Cd2+ and Ni2+ eliminated the action potentials but not the junction potentials. Tetraethylammonium markedly prolonged the action potential duration. CONCLUSIONS: Our data suggest that: (1) A slow decay of the junction potentials may result from the disappearance of the neurotransmitter; this process also accounts for the late slow repolarization of the final part of the action potentials; (2) The equilibrium potential of the junction potentials is close to 0 mV; (3) The upstroke of the action potentials is carried by calcium currents; (4) The fast repolarization phase of the action potentials is likely caused by the delayed rectifier; and (5) The refractory phase outlasts the duration of the action potential.

Action Potentials↗
PubMed1993

Melatonin inhibits the proliferation of retinal pigment epithelial (RPE) cells in vitro.

The possible antiproliferative effect of melatonin on retinal pigment epithelial (RPE) cells in vitro was investigated. Bovine RPE cells cultured in Ham's F12 medium supplemented with 10% fetal bovine serum had a nuclear density of 73.6 +/- 6.1 nuclei/mm2 at 72 h after seeding. The nuclear density at this time-point was doubled if either 50 or 100 ng/ml human epidermal growth factors (hEGF) was added to the culture medium. When these hEGF-stimulated cells were treated with melatonin from 10 to 500 pg/ml, the proliferation was suppressed with a dose-response relationship. At 250 and 500 pg/ml melatonin, the nuclear densities of the melatonin-treated cells were similar to those of the control cells. Using mitotically active SV-40 transformed human fetal RPE cells cultured in a serum-free medium, melatonin was also shown to be antiproliferative. In the presence of 500 pg/ml melatonin, the proliferation of these cells was inhibited to 77% as compared to the control. These results were further supported by the reduced [H3]thymidine uptake in the melatonin-treated cells. We propose that melatonin, at physiologic concentrations, has an antiproliferative effect, and that cultured RPE cells stimulated to proliferate by either hEGF treatment or SV-40 transfection are responsive to melatonin. Melatonin may either inhibit mitosis in actively dividing cells or modulate hEGF action.

Animals↗