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Biomedical subjects

G Lopez

Publications and source records attributed to G Lopez.

At least 19 recordsLinked to original sources
PubMed2003

Prevalence of headache in patients with Behçet's disease without overt neurological involvement.

The aims of the present study were to evaluate the prevalence of headache and the frequency of different headache syndromes in patients with Behçet's Disease (BD) without neurological involvement and to investigate the relationship with other clinical, and behavioural variables. Twenty-seven BD patients and 27 control subjects underwent a validated semistructured questionnaire based on the International Headache Society criteria. Levels of anxiety and depression, disease activity, and current medication were collected. Headache occurred in 88.9% of BD patients. There was no difference in the prevalence of the different headache syndromes between BD patients and controls. Only migraine without aura (MwA) was significantly more frequent in BD patients than controls (44.4% vs. 11.1%, respectively, P= 0.013). No relationship was found between MwA and clinical, and behavioural variables. Among headache syndromes, MwA showed the highest frequency in BD. A vascular or neuronal subclinical dysfunction could justify this association. A careful interview for migraine might be included in the diagnostic work-up of BD.

Adult↗
PubMed2002

Topotecan preceded by oxaliplatin using a 3 week schedule: a phase I study in advanced cancer patients.

Combinations of topoisomerase I (topo I) poisons and platinum derivatives have synergistic antitumoral effects. However, their clinical development is limited by supra-additive haematological toxicity. The aim of this study was to determine whether sustained doses of topotecan and oxaliplatin could be achieved using a synergistic sequence. 34 advanced cancer patients and 186 cycles were evaluable for toxicity over five dosing levels. Oxaliplatin at 85-110 mg/m(2) was given on day 1, followed by topotecan 0.5-1.25 mg/m(2)/day x 5 from day 1 to 5, every 3 weeks. Plasma pharmacokinetics (PK) of total and ultrafiltrable platinum, total and lactone forms of topotecan were determined in the first cycle. The dose-limiting toxicity (DT) was identified as grade 4 thrombocytopenia. The occurrence of grade 4 thrombocytopenia did not correlate with topotecan PK, but it did with the patient's characteristics. Severe thrombocytopenia was seen in 1/8 of patients without clinical or biological evidence of malnutrition, with a creatinine clearance higher than 1 ml/s, and no more than two previous chemotherapy regimens, while it was seen in 8/10 patients with one of these characteristics (P<0.004). In conclusion, the recommended doses of oxaliplatin 110 mg/m(2) and topotecan 1 mg/m(2)/day, every 3 weeks can be administered to patients with a favourable general status and pretreatment characteristics and a phase II study is worthwhile in ovarian cancer patients.

Adult↗
PubMed2002

Sensitivity and specificity of an indirect enzyme-linked immunoassay for the diagnosis of Brucella canis infection in dogs.

The diagnosis of B. canis infection in dogs is based on bacteriological examination and serological methods including agglutination and gel diffusion tests. Bacteriological studies are the only methods that have been considered specific but, as intermittent periods of abacteraemia may occur, a negative blood culture cannot be used as a criterion for excluding canine brucellosis. Close contact between people and infected dogs increases the risk of transmission; however, its impact on public health is probably underestimated due to lack of reporting and inadequate diagnostic services. This paper describes an indirect enzyme-linked immunoassay (IELISA) procedure for the diagnosis of brucellosis caused by B. canis in a population of normal and infected dogs previously screened by the buffered plate antigen test (BPAT) and rapid slide agglutination test (RSAT). The serological survey was performed with 446 field sera. The 270 sera from the asymptomatic group found negative by BPA, RSAT and blood culture showed IELISA specificities of 96.7% and 100%, respectively, when cut-off values of OD 0.237 and 0.281 were selected. For 52 sera from culture-positive dogs, IELISA sensitivity was 100% with cut-off values of OD414 0.237 and 0.281. OD414 0.281 was selected because this value provided the highest accuracy with minimal false-negative and false-positive results. This cut-off value was used to study 124 blood culture-negative but RSAT positive sera. IELISA produced 107 positive results; the 17 sera that were negative by IELISA presented a wide range of reactivities by RSAT (2 were RSAT positive at 1 in 2 dilution and 15 were weakly positive with pure serum). These samples were probably from animals at an early stage of the infection or were false-positive results. The IELISA described here detects IgG and IgA antibodies that are useful for evaluating the clinical status of dogs. Although RSAT is a practical screening test, a supplementary technique such as IELISA should be used on all positive RSAT samples to ensure diagnostic specificity. Furthermore, people in contact with infected dogs could be investigated for possible transmission. The procedure described in this study was relatively simple and could have widespread applications.

Agglutination Tests↗
PubMed2001

A case-control study of gastric cancer in Venezuela.

A case-control study to evaluate risk factors for gastric cancer was carried out among 292 cases of gastric cancer and 485 controls in a high-risk area of Venezuela. Subjects were interviewed using a structured questionnaire, which elicited information on residential history, socio-economic status, family history of gastric diseases, smoking, drinking and dietary habits. Habitual diet was estimated from a meal-structured food frequency questionnaire on 75 food items. There was a strong inverse association with social class, as measured by education and by indicators of poverty. The results of the dietary analysis suggest that a diet high in starch and low in meat, fish and fresh vegetables increases risk of gastric cancer. A protective effect was observed for frequent consumption of allium vegetables. Inverse associations were found with height, which may reflect nutritional status in childhood, and with refrigerator use in the first two decades of life. Alcohol and tobacco consumption was investigated among males only, since the prevalence of alcohol and tobacco use was very low in females. Alcohol drinkers were at higher risk than non-drinkers and there was a small excess risk for current smokers compared with never smokers. There was some evidence of familial aggregation of gastric cancer. These findings will have important implications in planning preventive strategies for gastric cancer in Venezuela.

Adult↗
PubMed2001

Self-assembly of mesoscopically ordered chromatic polydiacetylene/silica nanocomposites.

Nature abounds with intricate composite architectures composed of hard and soft materials synergistically intertwined to provide both useful functionality and mechanical integrity. Recent synthetic efforts to mimic such natural designs have focused on nanocomposites, prepared mainly by slow procedures like monomer or polymer infiltration of inorganic nanostructures or sequential deposition. Here we report the self-assembly of conjugated polymer/silica nanocomposite films with hexagonal, cubic or lamellar mesoscopic order using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. Polymerization results in polydiacetylene/silica nanocomposites that are optically transparent and mechanically robust. Compared to ordered diacetylene-containing films prepared as Langmuir monolayers or by Langmuir-Blodgett deposition, the nanostructured inorganic host alters the diacetylene polymerization behaviour, and the resulting nanocomposite exhibits unusual chromatic changes in response to thermal, mechanical and chemical stimuli. The inorganic framework serves to protect, stabilize, and orient the polymer, and to mediate its function. The nanocomposite architecture also provides sufficient mechanical integrity to enable integration into devices and microsystems.

Acetylene↗
PubMed2001

Dorsal subthalamotomy for Parkinson's disease.

We report our experience of unilateral subthalamotomy in patients with Parkinson's disease (PD). Eleven patients were included in a pilot, open-labeled study to assess the effect of unilateral lesion of the subthalamic nucleus (STN) with a minimum of 12 months of follow-up. The guidelines of CAPIT (Core Assessment Program for Intracerebral Transplantation) were followed for recruitment into the study and follow-up assessment. Levodopa equivalents daily intake (mean 967 mg) were unchanged during the first 12 months in all but one patient who stopped medication. The sensorimotor region of the STN was defined by semimicrorecording and stimulation and a thermolytic lesion was placed accordingly. There was a significant reduction in both UPDRS parts II and III in the "off" state at 1-, 6-, and 12-month follow-up. This effect was maintained in four patients up to 24 months. The dyskinesia score did not change postoperatively. Lesion-induced dyskinesias were not a management problem except in one patient who developed a large infarction several days postsurgery. This initial study indicates that a lesion of the STN is not generally associated with hemiballismus in PD. Subthalamotomy may induce considerable motor benefit and could become another surgical option under specific circumstances.

Aged↗
PubMed2001

Quantitation of human immunodeficiency virus type 1 (HIV-1) RNA in cell-free cervicovaginal secretions: comparison of reverse transcription-PCR amplification (AMPLICOR HIV-A MONITOR 1.5) with enhanced-sensitivity branched-DNA assay (Quantiplex 3.0).

Two commercially available hypersensitive assays for human immunodeficiency virus type 1 (HIV-1) RNA quantitation, AMPLICOR HIV-1 Monitor Test 1.5 and Quantiplex HIV RNA 3.0, were compared to detect and quantify HIV-1 RNA in the cell-free fraction of cervicovaginal secretions collected by vaginal washing. Three panel specimens were used: pooled cervicovaginal secretions spiked with HIV-1 subtype A or HIV-1 subtype B and cervicovaginal lavages from HIV-positive and HIV-negative women. Compared to the AMPLICOR HIV-1 Monitor Test 1.5 assay, the Quantiplex HIV-1 3.0 assay yielded higher estimates of HIV-1 RNA concentrations in several tested samples spiked with HIV-1 RNA subtype A, as well as subtype B, particularly samples containing low amounts of HIV-1 RNA. The sensitivity and specificity of the AMPLICOR HIV-1 Monitor Test 1.5 assay were 93 and 100%, respectively; the sensitivity and specificity of the Quantiplex HIV RNA 3.0 assay were 97 and 50%, respectively. In conclusion, in quantifying HIV-1 RNA in cervicovaginal secretions, the Quantiplex HIV RNA 3.0 may lack specificity, and the AMPLICOR HIV-1 Monitor Test 1.5 assay, although highly specific, may lack sensitivity.

Branched DNA Signal Amplification Assay↗
PubMed2000

Contribution of the multidrug efflux pump LfrA to innate mycobacterial drug resistance.

Multidrug resistance (MDR) in bacteria has been associated with efflux pumps that export structurally unrelated compounds and decrease cytoplasmic drug accumulation. To investigate MDR in mycobacteria, we studied the Mycobacterium smegmatis mutant mc(2)11, which is resistant to doxorubicin, tetracycline, rhodamine, ethidium bromide and the hydrophilic fluoroquinolones. A genomic library constructed from this mutant was used to select clones conferring resistance to doxorubicin. Surprisingly, the clone selected encodes the efflux pump LfrA, which has been reported to confer resistance to hydrophilic fluoroquinolones, ethidium bromide, rhodamine, and acriflavine. To define the contribution of LfrA to the innate mycobacterial drug resistance and to the MDR phenotype in mc(2)11, the lfrA gene was disrupted in both the mc(2)11 mutant and the mc(2)155 wild-type parent. LfrA disruption of the wild-type strain decreased resistance to ethidium bromide and acriflavine, and increased accumulation of ethidium bromide. However, disruption of lfrA gene results only in a 2-fold decrease in minimal inhibitory concentrations (MICs) for ciprofloxacin, doxorubicin, rhodamine, and accumulation of [(14)C]ciprofloxacin was unchanged. LfrA disruption of the MDR strain mc(2)11 produced a similar phenotype. Thus, LfrA contributes significantly to the intrinsic MICs of M. smegmatis for ethidium bromide and acriflavine, but not for ciprofloxacin, doxorubicin or rhodamine.

Acriflavine↗
PubMed2000

Oestrogen receptor function at classical and alternative response elements.

The oestrogen receptor (ER), bound to classical response elements (EREs) in the promoter of target genes, activates transcription by recruiting coactivator proteins. We will describe structural studies that show that oestrogens allow the formation of a hydrophobic cleft on the surface of the ER that serves as a docking site for coactivators. Anti-oestrogens displace part of the receptor, which then occludes the site, blocking coactivator access. In addition to activating at classical EREs, the ER activates transcription at alternative elements such as AP-1 sites. These bind the Jun/Fos proteins but not ER. Interestingly both oestrogen and tamoxifen activate transcription at AP-1 sites. We propose a mechanism whereby oestrogen and anti-oestrogen allow ER to activate transcription from alternative response elements. ER binds to the coactivators, CBP and GRIP1, that have been recruited by Jun/Fos and through this contact 'triggers' these coactivators into full activity. In this circumstance the ER is part of the coactivator complex for Jun/Fos.

Animals↗
PubMed2000

Protective effect of the tachykinin NK2 receptor antagonist nepadutant in acute rectocolitis induced by diluted acetic acid in guinea-pigs.

We have evaluated the potential protective activity of nepadutant, a selective tachykinin NK2 receptor antagonist, in a model of acute rectocolitis induced by an enema with 7.5% acetic acid in guinea-pigs. The injury was quantified visually by using a macroscopic injury score, and histologically by using a necrosis score. In addition, changes in myeloperoxidase activity, a marker for neutrophil infiltration, and plasma protein extravasation were evaluated. The injury caused by 7.5% acetic acid was mild, affecting the superficial layers and producing a strong edema of the submucosa. A single administration of nepadutant (0.3-10 mg/kg s.c., 1 h before acetic acid) markedly reduced the macroscopic damage and necrosis score and the increase in plasma protein extravasation induced by 7.5% acetic acid in the early phase of the injury. Single administration of nepadutant (3 mg/kg s.c.) reduced the macroscopic score and myeloperoxidase activity at the top (24 h) of inflammation. Repeated administration (3 mg/kg s.c. three times during 24 h) or co-administration of the tachykinin NK1 receptor antagonist MEN 11467 (3 mg/kg s.c.) did not enhance the antiulcer effect obtained with the single treatment with nepadutant. These data suggest the involvement of tachykinin NK2 receptors in the first phases of inflammation induced by acetic acid.

Acetic Acid↗
PubMed2000

Efficacy of preoxygenation with tidal volume breathing. Comparison of breathing systems.

BACKGROUND: Preoxygenation before tracheal intubation is intended to increase oxygen reserves and delay the onset of hypoxemia during apnea. Various systems are used for preoxygenation. Designed specifically for preoxygenation, the NasOral system uses a small nasal mask for inspiration and a mouthpiece for exhalation. One-way valves in the nasal mask and the mouthpiece ensure unidirectional flow. This investigation compares the efficacy of preoxygenation using the standard circle system with the NasOral system and five different resuscitation bags. METHODS: Twenty consenting, healthy volunteers were studied in the supine position for 5-min periods of tidal volume breathing using the circle absorber system, the NasOral system, and five resuscitation bags in a randomized order. Data were collected during room air breathing and at 30-s intervals during 5 min of oxygen administration. Inspired oxygen, end-tidal oxygen, and end-tidal nitrogen were measured by mass spectrometry. RESULTS: At 2. 5 min of oxygenation, end-tidal oxygen plateaued at 88.1 +/- 4.8 and 89.3 +/- 6.4% (mean +/- SD) for the circle absorber and NasOral systems, respectively. This was associated with inverse decreases in end-tidal nitrogen. At no time did these end-tidal oxygen or nitrogen values differ from each other. Three of the resuscitation bags (one disk type and two duck-bill type with one-way exhalation valves) delivered inspired oxygen more than 90%, and the end-tidal oxygen plateaued between 77 and 89% at 2 min of tidal volume breathing. The other two resuscitation bags (both duck-bill bags without exhalation valves) delivered inspired oxygen less than 40%, and the end-tidal oxygen values ranged between 21.8 +/- 5.0 and 31.9 +/- 8.7%. CONCLUSIONS: The circle absorber and NasOral systems were equally effective in achieving maximal preoxygenation during tidal volume breathing. Resuscitation bags differed markedly in effectiveness during preoxygenation; those with duck-bill valves without one-way exhalation valves were the least effective. Thus, the use of these bags should be avoided for preoxygenation.

Adult↗
PubMed2000

Lewis antigen alterations in a population at high risk of stomach cancer.

Anomalous Lewis(a) antigen and sulfomucin expression are considered as markers of progression in precursor lesions of gastric cancer. Additionally, Lewis antigen and secretor phenotype have been related to Helicobacter pylori infection and gastric epithelial damage. The two objectives of this study were to correlate Lewis antigen alterations with histochemical changes and to explore the relationship between Lewis and secretor phenotypes and gastric epithelial damage related to H. pylori infection. The study subjects were selected from a chemoprevention trial in Tachira State, Venezuela, an area with a high risk of gastric cancer. Anomalous Lewis(a) antigen expression in Lewis (a-b+) phenotype individuals was closely related to the severity of the histological lesions, especially to dysplasia and type III intestinal metaplasia lesions. A weak relationship was observed between nonsecretor individuals and more advanced lesions of IM, but this association was not statistically significant. There was no relationship between secretor phenotype and H. pylori status, atrophy, regenerative activity, erosion, or ulcer.

Adult↗
PubMed2000

Helicobacter pylori and stomach cancer: a case-control study in Venezuela.

The role of Helicobacter pylori infection in gastric cancer was evaluated in a high-risk population in Venezuela using serological assays in a study of 302 cases and 483 neighborhood controls. To investigate the claim that assays for H. pylori should use antigens derived from local strains, four different assays derived from Venezuelan and European strains were used. Prevalence of IgG H. pylori antibodies in controls was very high, with estimates between 72 and 92%. Prevalence was similar in cases and controls. However, cases had lower antibody titers. This effect was observed only in subjects with low pepsinogen (PG) levels PGI/PGII <3.0), which suggested that extensive atrophy in cases causes a loss of H. pylori infection, with a consequent reduction in antibody titer. In addition, advanced cases (stage II or higher) had lower antibody titers than less advanced cases, which indicated that the lower antibody titers in cases may be attributable partially to a diminished immune response. All of the four assays for anti-H. pylori antibodies gave similar results. No evidence was found for the superiority of the assay based on Venezuelan strains. These results are consistent with other case-control studies in high-risk populations and highlight the difficulties of investigating H. pylori infection in retrospective studies.

Adult↗
PubMed1999

Effect of MEN 11467, a new tachykinin NK1 receptor antagonist, in acute rectocolitis induced by acetic acid in guinea-pigs.

The aim of this study was to evaluate the effect of MEN 11467 (1R,2S)-2-N[1(H)indol-3-yl-carbonyl]-1-N{N-(p-tolylacetyl)-N-(meth yl)-D-3(2-Naphthyl)alanyl}diaminocyclohexane), a new potent tachykinin NK1 receptor antagonist, in an experimental model of acute rectocolitis induced by an enema with 7.5% acetic acid in guinea-pigs. This effect was compared to that of mesalazine (5-amino-2-hydroxybenzoic acid). The injury was quantified visually by using a macroscopic injury score and histologically by using a necrosis score. In addition, changes in myeloperoxidase activity, a marker for neutrophil infiltration, and plasma protein extravasation were evaluated. The injury caused by 7.5% acetic acid was mild, affecting the superficial layers and producing a strong edema of the submucosa. A single administration of MEN 11467 (0.3-10 mg/kg s.c., I h before acetic acid) reduced the macroscopic damage and necrosis score and the increase in plasma protein extravasation induced by 7.5% acetic acid in the early acute phase of the injury (death at 2.5 h). Mesalazine (100 mg/kg p.o., 1 h before) reduced the macroscopic score but not the plasma protein extravasation. Repeated administration of MEN 11467 (1-3 mg/kg s.c., -1, +6 and +23 h after 7.5% acetic acid) reduced the macroscopic score and myeloperoxidase activity but not the plasma protein extravasation induced in the late phase of acute injury (death at 24 h). At this time mesalazine markedly reduced the macroscopic score, myeloperoxidase activity and plasma protein extravasation induced by 7.5% acetic acid. These results suggest a greater involvement of tachykinin NK1 receptors in the early phase than in the late phase of colonic inflammation in response to chemical injury.

Acetic Acid↗
PubMed1998

Isolation and characterization of iridoviruses from the giant toad Bufo marinus in Venezuela.

In this communication we describe for the first time the isolation of 7 iridoviruses from the toad Bufo marinus and an unknown species of frog Leptodactylus in Venezuela, South America. The viruses are icosahedral with electron-dense cores, each of which is surrounded by an inner membrane, capsid and a cell-derived envelope. The virus(es) have an average vertex to vertex diameter of 160 nm and replicate in the cytoplasm of a range of cell lines. Within the cytoplasm of infected cells, rarefied areas could be observed; structures lacked cellular organelles and contained complete, empty and developing viruses. Results from antigen-capture enzyme-linked immunosorbent assays (ELISA) with polyclonal antibody raised against epizootic haematopoietic necrosis virus (EHNV) indicated cross-reactivity between these isolates, Bohle iridovirus (BIV) and frog virus 3 (FV3). Comparison of polypeptide and genomic profiles indicated that the Venezuelan viruses shared many polypeptides of equivalent molecular weight with type species FV3. There were, however, differences between the group of Venezuelan viruses and FV3 and BIV. The viruses belongs to the family Iridoviridae and the genus Ranavirus.

Animals↗
PubMed1998

Giant toads Bufo marinus in Australia and Venezuela have antibodies against 'ranaviruses'.

A serological survey was conducted for antibodies against 'ranaviruses' in the giant toad Bufo marinus in Australia and Venezuela. Sera containing antibodies against 'ranaviruses' were found in both countries. In Australia positive antibodies were identified in populations throughout most of the known range of B. marinus. Results were confirmed by immunofluorescence and immunoelectron microscopy where a characteristic staining pattern of 'ranaviruses' in infected cells was observed. Whilst a 'ranavirus(es)' has been isolated from populations of B. marinus in Venezuela, no virus has been isolated from Australian B. marinus populations. The significance of 'ranavirus' sero-positive B. marinus in Australia is discussed.

Animals↗