PubMed Health⌕ Search

Biomedical subjects

L Barrios

Publications and source records attributed to L Barrios.

At least 37 records · Page 2Linked to original sources
PubMed2000

Nonhistological diagnosis of human cerebral tumors by 1H magnetic resonance spectroscopy and amino acid analysis.

We describe a multivariate analysis procedure to classify human cerebral tumors nonhistologically in vitro, combining the use of 1H magnetic resonance spectroscopy (MRS) with automatic amino acid analysis of biopsy extracts. Eighty-one biopsies were obtained surgically and classified histologically in eight classes: high-grade astrocytomas (class 1, n = 19), low-grade astrocytomas (class 2, n = 10), normal brain (class 3, n = 9), medulloblastomas (class 4, n = 4), meningiomas (class 5, n = 18), metastases (class 6, n = 8), neurinomas (class 7, n = 9), and oligodendrogliomas (class 8, n = 4). Perchloric acid extracts were prepared from every biopsy and analyzed by high resolution 1H MRS and automatic amino acid analysis by ionic exchange chromatography. Intensities of 27 resonances and ratios of resonances were measured in the 1H MRS spectra, and 17 amino acid concentrations were determined in the chromatograms. Linear discriminant analysis provided the most adequate combination of these variables for binary classifications of a biopsy between any two possible classes and in multiple choice comparisons, involving the eight possible classes considered. Correct diagnosis was obtained when the class selected by the computer matched the histological diagnosis. In binary comparisons, consideration of the amino acid profile increased the percentage of correct classifications, being always higher than 75% and reaching 100% in many cases. In multilateral comparisons, scores were: high-grade astrocytomas, 80%; low-grade astrocytomas, 74%; normal brain, 100%; medulloblastomas, 100%; meningiomas, 94.5%; metastases, 86%; neurinomas, 100%; and oligodendrogliomas, 75%. These results indicate that statistical multivariate procedures, combining 1H MRS and amino acid analysis of tissue extracts, provide a valuable classifier for the nonhistological diagnosis of biopsies from brain tumors in vitro.

Algorithms↗
PubMed1999

Comparison of X-ray dose-response curves obtained by chromosome painting using conventional and PAINT nomenclatures.

PURPOSE: The compare the suitability of PAINT and conventional nomenclature systems for the construction of chromosome aberration dose-effect curves for X-rays using FISH techniques, and to compare these curves with those based on solid-stained dicentrics analysed in first division metaphases by the FPG technique. MATERIALS AND METHODS: Blood samples were irradiated at 0.1, 0.25, 0.50, 0.75, 1, 1.5, 2, 3, 4 and 5 Gy 180 kV X-rays. FISH painting was performed using probes for chromosomes 1, 4 and 11 in combination with a pan-centromeric probe. RESULTS: Translocations showed a higher background frequency than dicentrics. This influences the ratio of translocations:dicentrics at the lower doses and the uncertainties of dose-effect curves for translocations. The dose-effect curves for dicentrics obtained by FISH and solid stain were in close agreement. CONCLUSION: For short-term biological dosimetry purposes by FISH, the use of dic(BA) (PAINT nomenclature) or total dicentrics (conventional nomenclature) should give similar dose estimates. For dose reconstruction, the use of total or complete translocations result in similar uncertainties.

Adult↗
PubMed1998

Relationship between the DNA content of human chromosomes and their involvement in radiation-induced structural aberrations, analysed by painting.

PURPOSE: To study the relationship between the DNA content of human chromosomes and their involvement in radiation-induced structural chromosome aberrations. MATERIAL AND METHODS: Human lymphocytes were cultured after exposure to 5 Gy of X-rays. FISH-painting was performed for all human chromosomes. RESULTS: The results indicate that with the exception of chromosome 20, there was a good fit between the DNA content and the number of exchange-type aberrations and the number of breaks. However, there was a significant tendency for short chromosomes to be more affected than expected and for long chromosomes to be less affected than expected. A better fit was observed when, instead of DNA content, the surface area of the chromosome territories obtained from a spherical model was taken into consideration. CONCLUSIONS: The tendency for short chromosomes to be more involved and long chromosomes to be less involved in exchange-type aberrations could be related not only to their DNA content but also to their interphase territory surface area.

Chromosome Aberrations↗
PubMed1998

Effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on murine bone marrow and spleen erythropoiesis.

100 micrograms/kg of recombinant human granulocyte colony-stimulating factor was injected twice daily into normal adult CF1 female mice for a period of 15 days. After that time we have observed a decrease 59Fe marrow incorporation with a parallel increase in the spleen. During the first 9 days the marrow plus spleen erythroid cells number decreased to 60% of control approximately, but recovered thereafter and were not significantly different from normal values at 12-15 days. In addition, our studies demonstrate that the spleen erythropoiesis is quantitatively more important at the final time than marrow erythropoiesis. For this reason, splenic compensatory erythropoiesis maintained the hematocrit values between normal ranges. Regarding the granulocytic compartment, 15 days of rhG-CSF treatment produce a marked increase in total count of splenic granulocytes (a 7.7 fold rise from control values). Marrow granulocytes shows a 2-fold increment, but considering the absolute counts, bone marrow still was predominant as a granulopoieitc organ. Our results indicate that the spleen is a more important erythropoietic organ than marrow after 15 days of rhG-CSF treatment.

Animals↗
PubMed1997

Infarct size, myocardial hemorrhage, and recovery of function after mechanical versus pharmacological reperfusion: effects of lytic state and occlusion time.

BACKGROUND: Whether myocardial reperfusion obtained with thrombolysis or primary angioplasty is associated with a similar recovery of function and with the same risk of hemorrhagic infarction is unknown. We evaluated the effects of mechanical and pharmacological reperfusion (with or without a plasma lytic state) on infarct size, myocardial hemorrhage, and left ventricular (LV) function in a canine model. METHODS AND RESULTS: Six groups of six dogs were subjected to balloon occlusion of the left anterior descending coronary artery (LAD) followed by 2 hours of reperfusion. The study had a two-by-three factorial design with two occlusion periods (90 and 240 minutes) and three different reperfusion strategies (placebo, 0.4 mg/kg recombinant tissue plasminogen activator, and 40 microg/kg recombinant staphylokinase). In a seventh control group, LAD occlusion was maintained without reperfusion. All dogs received aspirin and heparin. A systemic lytic state was present in staphylokinase-treated dogs. Planimetry of LV slices showed larger infarcts (percent of area at risk) and more hemorrhage (percent of IA) after 240 minutes of occlusion than after 90 minutes of occlusion (54+/-17% versus 37+/-18% and 52+/-27% versus 29+/-27%, respectively; P<.01 for both comparisons), with no significant difference among treatments. Hemorrhage was not observed in the control group without reperfusion. LV angiography showed no differences in global and regional LV function between mechanical and pharmacological reperfusion. CONCLUSIONS: In this experimental model, hemorrhagic infarctions of similar extent were observed after both pharmacological and mechanical reperfusion. The extent of hemorrhage was increased by the delay in reperfusion but not by the presence of a lytic state.

Animals↗
PubMed1997

Comparison of clinical complications, angiographic results, and device usage of coronary angioplasty using low- and high-compliance balloons.

We randomized 800 patients in a prospective study comparing the angiographic results, device usage and in-hospital outcome of balloon angioplasty of primary stenoses of native coronary vessels with low-compliant and highly compliant balloons. The cumulative incidence of prespecified clinical endpoints was 8.0% in both treatment groups. The primary angiographic success rates were 83.9% and 78.9% in the high- and low-compliance group, respectively (P = 0.05). For the lesions dilated with one study balloon only, the quantitative angiographic findings were virtually identical in the two treatment groups. The total number of dissections was slightly but not significantly higher in the lesions treated with a highly compliant balloon. The global usage of angioplasty balloons was similar in both treatment groups. We conclude that, in general, there is no objective reason to prefer one balloon material to another on the basis of its compliance characteristics.

Angioplasty, Balloon, Coronary↗
PubMed1997

Biological dosimetry in simulated in vitro partial irradiations.

The assessment by biological dosimetry of the dose received in cases of partial-body exposure to ionizing radiation can be underestimated because irradiated lymphocytes are mixed with non-irradiated ones. To determine if the exposure affects the whole body or only part of it, it may be useful to know the distribution of cells with more than one dicentric chromosome. We established a dose-effect calibration curve for X-rays by analysis of chromosome aberrations. Moreover, in the present work, 20 partial irradiations for four different doses of X-rays (2, 3, 4 and 5 Gy) have been simulated by mixing irradiated and non-irradiated blood in different proportions. In all cases, the 95% confidence intervals of the estimated dose included the real dose of irradiation. However, some difficulties were found for the estimation of the fraction of irradiated cells. In the present study, D0 = 3.8 allows to obtain the best fit between the estimated and the real fraction of irradiated cells.

Cells, Cultured↗
PubMed1996

Decreased sensitivity to the cytogenetic effects of bleomycin in individuals occupationally exposed to ionizing radiation.

In the present work, 12 individuals occupationally exposed to ionizing radiation and 11 unexposed ones were studied to determine the cytogenetic effect of a challenge dose of bleomycin on their phytohemagglutinin stimulated lymphocytes. After bleomycin treatment, the frequencies of chromatid breaks and gaps were significantly lower in the exposed population (p < 0.025 for both types of chromatid alterations). These results could indicate that occupational exposure to ionizing radiation can induce an adaptive response that can be detected by a subsequent treatment with bleomycin.

Adaptation, Physiological↗
PubMed1996

The effects of volcanoes on health: preparedness in Mexico.

The article reviews the most important aspects of volcanic eruptions and presents a summary of the harmful materials they emit. The main health effects can be classified as either physical (trauma, respiratory diseases, etc.) or psychological (depression, anxiety, nightmares, neurosis, etc.). Popocatépetl, the most famous active volcano in Mexico, lies on the borders of the States of Mexico, Puebla and Morelos. In 1993, seismic activity intensified, as did as the emission of fumaroles, followed in December 1994 by moderate tremors and strong emissions of gases and ash. In 1996, a number of seismic events led to an unexpected explosion. A daily emission of 8,000 to 15,000 tonnes of sulfur dioxide has been measured. Popocatépetl is located in a densely populated region of Mexico. A complex network to monitor the volcano using sophisticated equipment has been set up, including visual surveillance, seismic, geochemical and geodesic monitoring. An early warning system (SINAPROC/CENAPRED) has been developed to keep the population permanently informed. The warning system uses colour codes: green for normal, yellow for alert, and red for warning and evacuation. An emergency plan has been prepared, including evacuation and preparation for medical centres and hospitals in the region, as well as intense public information campaigns.

Air Pollutants↗
PubMed1995

A randomized trial of recombinant staphylokinase versus alteplase for coronary artery patency in acute myocardial infarction. The STAR Trial Group.

BACKGROUND: Recombinant staphylokinase (STAR) was shown recently to offer promise for coronary arterial thrombolysis in patients with evolving myocardial infarction. The present multicenter randomized open trial was designed to assess the thrombolytic efficacy, safety, and fibrin specificity of STAR relative to accelerated alteplase (recombinant tissue-type plasminogen activator [RTPA]). METHODS AND RESULTS: One hundred patients with evolving myocardial infarction of < 6 hours' duration and with ST-segment elevation were allocated to accelerated and weight-adjusted RTPA over 90 minutes (52 patients) or to STAR (the first 25 patients to 10 mg and the next 23 patients to 20 mg given intravenously over 30 minutes). All patients received aspirin and intravenous heparin. The main end points were coronary artery patency and plasma fibrinogen levels at 90 minutes. Thrombolysis in Myocardial Infarction (TIMI) perfusion grade 3 at 90 minutes was achieved in 62% of STAR patients versus 58% of RTPA patients (risk ratio, 1.1; 95% CI, 0.76 to 1.5). With 10 mg STAR, TIMI grade 3 patency was 50% (risk ratio, 0.86; 95% CI, 0.54 to 1.4 versus RTPA); with 20 mg STAR, it was 74% (risk ratio, 1.3; 95% CI, 0.90 to 1.8 versus RTPA). Residual fibrinogen levels at 90 minutes were 118 +/- 47% (mean +/- SD) of baseline with STAR and 68 +/- 42% with RTPA (P < .0005). STAR therapy was not associated with an excess mortality or electric, hemorrhagic, mechanical, or allergic complications. However, patients developed antibody-mediated STAR-neutralizing activity from the second week after STAR treatment. As an addendum to the randomized study, 5 patients were given 40 mg STAR over 30 minutes, resulting in TIMI perfusion grade 3 at 90 minutes in 4 patients without fibrinogen breakdown (residual levels at 90 minutes of 105 +/- 8% of baseline). CONCLUSIONS: STAR appears to be at least as effective for early coronary recanalization as and significantly more fibrin-specific than accelerated RTPA in patients with evolving myocardial infarction.

Angioplasty, Balloon, Coronary↗
PubMed1995

Establishment and validation of a dose-effect curve for gamma-rays by cytogenetic analysis.

A dose-effect curve obtained by analysis of dicentric chromosomes after irradiation of peripheral blood samples, from one donor, at 11 different doses of gamma-rays is presented. For the elaboration of this curve, more than 18,000 first division metaphases have been analyzed. The results fit very well to the linear-quadratic model. To validate the curve, samples from six individuals (three controls and three occupationally exposed persons) were irradiated at 2 Gy. The results obtained, when compared with the curve, showed that in all cases the 95% confidence interval included the 2 Gy dose, with estimated dose ranges from 1.82 to 2.19 Gy.

Blood↗
PubMed1995

Occupational exposure to radiation induces an adaptive response in human lymphocytes.

The in vitro pretreatment of phytohaemagglutinin stimulated human lymphocytes with tritiated thymidine or with low doses of X-rays induces a response that makes these cells less susceptible to further genetic damage induced by subsequent high doses of radiation. This phenomenon has been called 'Adaptive Response' because it is similar to the one described in E. coli. In the present study, we describe that lymphocytes irradiated in vitro at 2 Gy, from individuals occupationally exposed to X and gamma rays, show lower frequencies of dicentrics than those from non-occupationally exposed individuals irradiated in the same conditions. Our results could indicate that an adaptive response can also be induced in lymphocytes in vivo by very low occupational doses of radiation, and that for biological dosimetry purposes it is necessary to know the individual's history of exposure to mutagens.

Adaptation, Physiological↗
PubMed1995

Human origin of micronuclei in human x hamster two-cell embryos.

Using fluorescence in situ hybridization techniques with either human or hamster genomic DNA probes, we studied the origin of micronuclei in two-cell hybrid embryos obtained from hamster oocytes and gamma-irradiated human spermatozoa. Our study demonstrates that over 99% of micronuclei hybridize with human DNA probes and not with hamster DNA, revealing their human origin. Thus, the micronucleus test represents a good method to evaluate genetic damage in human germ cells, since it is simpler and faster than sperm chromosome studies.

Animals↗
PubMed1994

Intravascular ultrasound versus angiography for measurement of luminal diameters in normal and diseased coronary arteries.

Quantitation of coronary luminal diameter with a 20 MHz mechanically rotating intravascular ultrasound (IVUS) catheter was compared with orthogonal-view cineangiography by use of a semiautomated edge-detection algorithm in 48 patients undergoing coronary angioplasty. Quantitative comparison of 196 matched segments was attempted, but in only 174 (88.8%) was a direct comparison of the two techniques possible. In angiographically normal coronary arteries (46 segments) the correlation between the values obtained by quantitative coronary angiography (QCA) and those achieved by IVUS was excellent (r = 0.92, p < 0.0001). For mild stenoses (80 segments) the correlation coefficient was only fair (r = 0.467, p < 0.001). After percutaneous transluminal coronary angioplasty the correlation coefficient between IVUS and QCA data (48 segments) was very weak (r = 0.282, p < 0.05). In conclusion, coronary IVUS is feasible and safe and even for a limited range of coronary arterial narrowing, significant correlations between IVUS and QCA measurements of minimal lumen diameter were found. They were excellent in normal coronary arteries, moderate in mildly diseased arteries, and weak after balloon angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1993

Cytogenetic analysis of lymphocytes from hospital workers occupationally exposed to low levels of ionizing radiation.

Cytogenetic studies were performed in lymphocytes from hospital workers exposed to low doses of radiation (1.6-42.71 mSv). When compared with controls, exposed workers showed a significant increase in structural chromosome-type aberrations, acentric fragments being the most frequent alteration. Our results suggest that acentric fragments are good indicators of exposure to very low doses of radiation, although no dose-effect correlation was observed. The incidence of numerical abnormalities (hyperdiploidy) was significantly increased.

Adult↗
PubMed1992

Induction of premature centromere division affecting all chromosomes under culture conditions of fragile site expression.

In a study of chromosome fragility carried out under folate and thymidine deficiency conditions, we observed a seven- to ninefold increase of the incidence of premature centromere divisions (PCDs) affecting all chromosomes. This early separation of centromeres is clearly a culture effect and distinct from PCD and centromere splitting (CS), which imply a defect in the centromere of one or more chromosomes.

Cells, Cultured↗
PubMed1992

A method to extract DNA for molecular studies from cells fixed in Carnoy.

We describe a simple method for isolation of high-molecular-weight DNA from cells fixed in Carnoy's solution for cytogenetic studies. DNA samples were extracted from NIH3T3 cells, and no apparent degradation was noticed. This method should be useful for molecular analysis of cells fixed for cytogenetic studies.

3T3 Cells↗