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A Lopez

Publications and source records attributed to A Lopez.

At least 37 records · Page 2Linked to original sources
PubMed2001

Probing the lateral organization of membranes: fluorescence repercussions of pyrene probe distribution.

Phospholipids pyrene labeled are widely used to investigate dynamics and organizations of membranes. We studied pyrene probe lateral distribution by analyzing the variations of the molar absorption coefficient (epsilon) versus probe concentrations, in small unilamellar vesicles (SUV) made of phospholipids and/or glycolipids, with pyrene labeled phosphatidylcholine (PyPC) or phosphatidylglycerol (PyPG). The results were interpreted according to an infinite associative model. They indicated that an effective self-association process corresponding to K ranging from 30 to 100 M(-1) occurred with those probes incorporated in dimannosyl diacylglycerol (DMDG). In contrast, after SUV labeling of egg yolk phosphatidylcholine (EggPC) or phosphatidylglycerol (EggPG), K values < 1 M(-1) were determined. The corresponding percentages of various stacked forms of pyrene probes were calculated. They indicated that, for a 3% PyPG labeling, the monomer represented 21% of n-mers in DMDG and 94% in EggPC. The analysis of fluorescence experiments carried out on the same samples indicated that: (i) the fluorescence process of pyrene probes was generated by the monomers: and (ii) the excimer forming resulted from a diffusional encounter between one excited and one non-excited monomer. A correction of fluorescence data allowing a more correct interpretation of fluorescence measurements was proposed.

Cell Membrane↗
PubMed2001

SMART: The microstent's ability to limit restenosis trial.

In this randomized, prospective, multicenter trial (n = 661) of patients with de novo or restenotic coronary lesions, 330 patients received the MicroStent(R) II (MSII), and 331 received the Palmaz-Schatz (PS) stent. The short-term procedural success rates were 94.4% and 95.7%, respectively (P = 0.47). The 30-day cumulative incidence of major adverse events [death, myocardial infarction, CVA, target lesion revascularization (TLR)] was 6.4% for the MSII and 4.5% for the PS stent (P = 0.31). The in-stent binary restenosis rate at 6 months was 25.2% for the MSII and 22.1% for the PS stent (P = 0.636). Using Kaplan-Meier estimates, the incidence of clinically driven TLR was 8.9% for the MSII and 9.2% for the PS stent at 180 days; at 270 days, it was 12.8% and 12.1%, respectively (P = 0.83). MSII and the PS stents were comparable with respect to short-term procedural success, complications, and late clinical and angiographic restenosis.

Aged↗
PubMed2001

X-ray microanalysis of etoposide-induced apoptosis in the PC-3 prostatic cancer cell line.

Apoptosis comprises a critical intracellular defense mechanism against tumourigenic growth. We have been interested in the relationship between morphological changes and intracellular concentration of several cations after etoposide-induced apoptosis in androgen-independent prostate cancer cells. SEM and X-ray microanalysis were performed on freeze-dried PC3 cells after etoposide treatment, and correlated with the morphological features observed after examination by light and fluorescence microscopy. Cell viability assays were also performed. A significant decrease in intracellular Cl(-) and K(+)and a progressive increase in Mg(2+) and Na(+) were observed, with parallel changes in cellular volume as cells passed through three morphological stages of apoptosis. The use of EPXRMA made it possible to evaluate alterations in element composition in prostate cancer cell apoptosis and may be a helpful tool for further studies on apoptosis in prostate cancer.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Catalytic decomposition of the reactive dye Uniblue A on hematite. Modeling of the reactive surface.

Experimental results from the adsorption and subsequent catalytic combustion of the reactive dye Uniblue A on hematite indicate that this iron oxide can be used as an affordable catalyst for environmental purposes. Uniblue A was adsorbed on hematite and the products of the catalytic oxidation in O2 atmosphere were analyzed by thermal programmed gas-chromatography/mass spectrometry (STDS-GC-MS) analysis. The catalytic combustion of Uniblue A in the presence of hematite led to about 40% conversion of the dye C-content into CO2 at T = 275 degrees C. The activation energy (Ea) for the desorption of CO2 and other polyaromatic hydrocarbons (PAHs) from the hematite surface was determined to be 23.4 kcal mol-1. Identification of the species of Uniblue A in solution and those existing on the hematite surface was carried out in the framework of the generalized two-layer diffuse model. The modeling of the amount of dye absorbed on hematite is in good agreement with the experimental data.

Adsorption↗
PubMed2001

By-products formation during degradation of isoproturon in aqueous solution. I: Ozonation.

The degradation of the herbicide isoproturon during its ozonation in aqueous solution has been investigated with the aim of identifying intermediate as well as final by-products formed. At ambient temperature, phosphate-buffered (pH = 7) isoproturon aqueous solutions (10, 10(-1) and 10(-3) mg/l) were ozonated in a semi-batch reactor, under a continuous flow of ozonated air whose ozone concentration was 9 and 0.9 mg O3/lair for the highest and the two lower herbicide concentrations respectively. Measured steady-state ozone concentrations during the two sets of experiments (i.e. the highest and the lower isoproturon concentration) were 1.9 and 0.7 mg O3/l. Under all of the above conditions, isoproturon was always completely removed in a period ranging between 5 and 15 min, essentially by reacting with molecular ozone. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses indicate that primary degradation by-products are formed either by introducing OH groups in the aromatic ring and/or in the side-chain substituents, or by breaking down the isopropyl alkyl chain. The results also show that these primary intermediates are successively degraded yielding low molecular weight compounds such as aldehydes, simple organic acids and alpha-oxo-acids, which have been identified by gas chromatography-electron capture detection (GC-ECD), ion chromatography (IC) and GC-MS, respectively. On the basis of the analytical results, a pathway for the degradation of isoproturon by ozone has been proposed.

Chromatography, High Pressure Liquid↗
PubMed2001

By-products formation during degradation of isoproturon in aqueous solution. II: Chlorination.

After a previous study in which the considered oxidant was ozone (Part I), a laboratory investigation has been carried out to study the degradation of the herbicide isoproturon during its reaction with another oxidant, i.e. chlorine, in aqueous solution (Part II; this paper). The specific aim was to identify the by-products formed. The effects of pH and the presence of bromide ions were studied. Reactions have been carried out at room temperature, in phosphate buffered aqueous solutions, at four pHs (6, 7, 8 and 9). By-products identification was first performed using relatively high initial reagent concentrations which were analytically convenient ([isoproturon] = 40 mg/l, [HClO + ClO-] = 160 mg Cl/l, [Br-] = 80 mg/l). In follow-up studies, the by-products identified during this preliminary step were searched for when using concentration values closer to those actually encountered at real water treatment plants ([isoproturon] = 0.4 and 0.004 mg/l, [HClO + ClO-] = 1.6 mg Cl/l, [Br-] = 0.8 and 0.008 mg/l). Under all of the studied conditions, the results showed that isoproturon is completely degraded and that it decays much faster in the presence of bromide. The pH has a negligible influence when bromide ions are absent. On the contrary, if bromide ions are present, the isoproturon decay is slower at higher pH values. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses have led to the identification of several by-products as a result of simultaneous oxidation and substitution reactions, both occurring on the aromatic ring of the herbicide. However, the more abundant by-products are those resulting from the oxidation of the isoproturon aromatic ring. As far as halogenated by-products are concerned, the higher the bromide ion concentration the higher the ratio of brominated to chlorinated by-products. On the basis of the analytical results, a pathway for isoproturon degradation under the studied conditions is proposed.

Chlorine Compounds↗
PubMed2001

Formation of volatile halogenated by-products during chlorination of isoproturon aqueous solutions.

The present paper deals with the formation of volatile halogenated by-products (POX) during the chlorination (160 mg/l) of aqueous solutions of the herbicide isoproturon (40 mg/l). Chlorination reactions have been carried out over 48 h, at ambient temperature, at two pHs (6 and 9) and in the presence or not of bromide ions (80 mg/l). The main results obtained have been as follows: (1) in the presence of bromide, isoproturon degradation is rather fast and it results affected by pH, complete isoproturon degradation is achieved within 1 and 15 min at pH 6 and 9, respectively; (2) in the absence of bromide herbicide degradation is slow (complete degradation is achieved within 180 min) and it is not affected by pH; (3) at pH 6, regardless of the presence of bromide, the maximum amount of POX formed is low (approximately 15 micromol X-/l) and remains constant during the reaction; (4) at pH 9 the amount of POX formed is far greater and continuously increases during the reaction, reaching a value of about 110 micromol X-/l after 48 h; (5) two different groups of by-products have been identified by solid phase micro extraction (SPME)-gas chromatography (GC)-mass spectrometry (MS) for the reactions carried out with or without bromide; among them, aliphatic as well as aromatic by-products containing chlorine, bromine or both halogens are present even though the most abundant are halogenated-methane derivatives (haloforms); pH value affects the amount of these by-products but does not modify their chemical nature.

Chlorine↗
PubMed2001

Mechanisms of the effects of exogenous levodopa on the dopamine-denervated striatum.

The efficacy of exogenous levodopa (L-DOPA) is attributed to its conversion to dopamine by the enzyme aromatic L-amino-acid decarboxylase in striatal dopaminergic terminals. However, there is controversy about the mechanisms underlying the therapeutic and adverse effects of L-DOPA after almost all striatal dopaminergic afferents have disappeared (i.e. in the later stages of Parkinson's disease). After administration of 30mg/kg or 100mg/kg of L-DOPA, rats subjected to unilateral dopaminergic denervation showed intense contraversive rotation and a high density of Fos-immunoreactive nuclei throughout the denervated striatum, with no significant induction of Fos in the intact striatum. Injection of the central aromatic L-amino-acid decarboxylase inhibitor NSD-1015 30min before and 15min after the injection of L-DOPA suppressed the rotational behavior and the striatal induction of Fos. Comparison of results obtained in rats subjected to unilateral and bilateral dopaminergic denervation indicated that the presence of contralateral dopaminergic innervation does not significantly modulate the effects of L-DOPA on the denervated striatum. Serotonergic denervation led to slight and statistically non-significant decrease in the rotational behavior and Fos expression induced by high doses of L-DOPA (100mg/kg) in the dopamine-denervated striatum, but totally suppressed the rotational behavior and Fos expression induced by low doses of L-DOPA (30mg/kg). The present data indicate that the major effects observed after administration of exogenous L-DOPA are not due to a direct action of L-DOPA on dopamine receptors, or to extrastriatal release of dopamine, but to conversion of L-DOPA to dopamine by serotonergic terminals and probably some intrastriatal cells. Given that serotonergic neurons appear to play an important role in the action of L-DOPA in the later stages of Parkinson's disease, strategies targeting the serotonergic system should be considered for the treatment of Parkinson's disease and for combating undesirable side effects of L-DOPA therapy.

Animals↗
PubMed2001

Antiviral and antimicrobial activities of Colombian medicinal plants.

Strong antiviral and antimicrobial activities were detected in methanolic extracts of 24 plants used medicinally in the treatment of skin infections in four different regions of Colombia. Thirteen extracts displayed activity against herpes simplex virus (HSV) whereas none was active against poliovirus. The antiviral activity was indicated by a total inhibition of viral cytopathic effects (CPE) at a non-cytotoxic concentration of the extract. The most potent extract was obtained from Byrsonima verbascifolia (L.) HBK. which showed anti-HSV activity at a concentration as low as 2.5 microg/ml. Antimicrobial screening was conducted using the disc diffusion assay against Klebsiella pneumoniae, Escherichia coli, Streptococcus faecalis, Mycobacterium phlei, Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhimurium and the human pathogenic yeast, Candida albicans. Anti-Candida activity was observed for Piper lanceaefolium HBK. and Juglans neotropica Diels. Twenty-two extracts displayed activity against Gram-positive bacteria whereas none was active against the Gram-negative species. We concluded that these Colombian medicinal plants represent an untapped source of potentially useful antivirals and are worthy of further study.

Animals↗
PubMed2001

Long-term cortical atrophy after excitotoxic striatal lesion: effects of intrastriatal fetal-striatum grafts and implications for Huntington disease.

It is not currently clear whether the cortical atrophy observed in Huntington disease (HD) is entirely a direct consequence of the disease or at least partially a secondary consequence of striatal atrophy. This is of major importance for evaluating the possible therapeutic value of intrastriatal fetal-striatum grafts in HD. Cresyl violet-stained sections from rats that had received striatal excitotoxic lesions 1 wk or 4 wk previously showed small and statistically nonsignificant decreases in the thickness of cortical layers V and VI, while series from rats lesioned 12 months previously showed marked decreases in the thickness of the whole cortex (approximately 35% decrease), layer V (approximately 45%-50%) and layer VI (approximately 45%-50%), together with marked neuron loss in these layers. In deep layer V and layer VI, Fluoro-Jade staining showed labeled neurons in animals lesioned 1 wk previously, labeled neurons and astrocytes in animals lesioned 4 wk previously, and practically no labeling in animals lesioned 12 months previously. Intracortical injection of Phaseolus vulgaris leucoagglutinin revealed that corticostriatal fibers were practically absent from the lesioned area of striata lesioned 12 months previously. However, rats that received intrastriatal fetal-striatum grafts shortly after the lesion and were killed 12 months later showed a significant reduction in cortical atrophy, and a large number of labeled corticostriatal fibers surrounding and innervating the graft. In addition, a reduction in the number of Fluoro-Jade-labeled cells in the cortex was already apparent at 3 wk post-grafting. Regardless of whether HD has a primary effect on the cortex, the present results suggest that the striatal degeneration caused by HD contributes markedly to the cortical atrophy, and that intrastriatal grafts may ameliorate this secondary component of the cortical degeneration.

Animals↗
PubMed2001

Congenital toxoplasmosis: a review.

Toxoplasmosis is caused by infection with the protozoan parasite Toxoplasma gondii. In the United States, approximately 85% of women of childbearing age are susceptible to acute infection with T. gondii. Acute infections in pregnant women may cause serious health problems when the organism is transmitted to the fetus (congenital toxoplasmosis), including mental retardation, seizures, blindness, and death. An estimated 400 to 4000 cases of congenital toxoplasmosis occur in the U.S. each year. Manifestations of congenital toxoplasmosis may not become apparent until the second or third decade of life. Serologic tests are used to diagnose acute infection in pregnant women, but false-positive tests occur frequently, therefore, serologic diagnosis must be confirmed at a reference laboratory before treatment with potentially toxic drugs should be considered. Much of congenital toxoplasmosis can be prevented by educating women of childbearing age and pregnant women to avoid eating raw or undercooked meat, to avoid cross-contamination of other foods with raw or undercooked meat, and to use proper cat-litter and soil-related hygiene.

Animals↗
PubMed2001

Physical activity, biliary lipids, and gallstones in obese subjects.

OBJECTIVE: Gallstone disease is a major source of morbidity in the US. Reduced physical activity has been shown to be a risk factor for gallstone formation in recent studies; however, the mechanisms to explain how physical activity may protect against gallstone formation have not been well elucidated. We investigated the relationships between physical activity, biliary lipids, and gallstone disease. METHODS: Three types of habitual physical activity (work, sport, and leisure time), biliary lipids, and serum lipids were estimated or measured in 53 obese subjects undergoing gastric bypass surgery. These physical activities were defined as activity at work, sport activity during leisure time, and activity during leisure time excluding sports, respectively. RESULTS: We found that sport activity but not work and leisure time activities was inversely associated with gallstone disease. Lower levels of biliary bile salts and percent biliary bile salts (expressed in percentage of total biliary lipids) and higher levels of percent cholesterol were also found to be associated with gallstone disease. A lower level of sport activity appeared to be associated with higher levels of biliary cholesterol, percent biliary cholesterol, and serum triglycerides. CONCLUSION: Our findings demonstrate that low levels of physical activity are associated with gallstone formation. Our study also suggests that a possible mechanism for the protective effect of physical activity on gallstone formation is the lowering of biliary cholesterol levels, thus preventing cholesterol from precipitating in the bile. In addition, our data suggest that sport activity is a more effective form of physical activity than working and leisure activities in the prevention of gallstone disease.

Adult↗
PubMed2001

Survey of obstetrician-gynecologists in the United States about toxoplasmosis.

BACKGROUND: Although the incidence of toxoplasmosis is low in the United States, up to 6000 congenital cases occur annually. In September 1998, the Centers for Disease Control and Prevention held a conference about toxoplasmosis; participants recommended a survey of the toxoplasmosis-related knowledge and practices of obstetrician-gynecologists and the development of professional educational materials for them. METHODS: In the fall of 1999, surveys were mailed to a 2% random sample of American College of Obstetricians and Gynecologists (ACOG) members and to a demographically representative group of ACOG members known as the Collaborative Ambulatory Research Network (CARN). Responses were not significantly different for the random and CARN groups for most questions (p value shown when different). RESULTS: Among 768 US practicing ACOG members surveyed, 364 (47%) responded. Seven per cent (CARN 10%, random 5%) had diagnosed one or more case(s) of acute toxoplasmosis in the past year. Respondents were well-informed about how to prevent toxoplasmosis. However, only 12% (CARN 11%, random 12%) indicated that a positive Toxoplasma IgM test might be a false-positive result, and only 11% (CARN 14%, random 9%) were aware that the Food and Drug Administration sent an advisory to all ACOG members in 1997 stating that some Toxoplasma IgM test kits have high false-positive rates. Most of those surveyed (CARN 70%, random 59%; chi2 p < 0.05) were opposed to universal screening of pregnant women. CONCLUSIONS: Many US obstetrician-gynecologists will encounter acute toxoplasmosis during their careers, but they are frequently uncertain about interpretation of the laboratory tests for the disease. Most would not recommend universal screening of pregnant women.

Acute Disease↗
PubMed2001

Opioids for chronic nonmalignant pain. Attitudes and practices of primary care physicians in the UCSF/Stanford Collaborative Research Network. University of California, San Francisco.

BACKGROUND: We hoped to determine the attitudes and practices of primary care physicians regarding the use of opioids to treat chronic nonmalignant pain (CNMP). We also examined the factors associated with the willingness to prescribe opioids for CNMP. METHODS: A survey was mailed to primary care physicians in the University of California, San Francisco/Stanford Collaborative Research Network. This survey contained questions regarding treatment in response to 3 case vignettes, the use of opioids for CNMP in general, and the demographic characteristics of the physicians. RESULTS: Among 230 physicians surveyed, 161 (70%) responded. Two percent of the respondents were never willing to prescribe schedule III opioids (eg, acetaminophen with codeine) as needed for patients with CNMP that persisted unchanged after exhaustive evaluation and attempts at treatment. Thirty-five percent were never willing to prescribe schedule II opioids (eg, sustained-release morphine) on an around-the-clock schedule for these patients. The most significant predictor of willingness to prescribe opioids for patients with CNMP was a lower level of concern about physical dependence, tolerance, and addiction. CONCLUSIONS: Primary care physicians are willing to prescribe schedule III opioids as needed, but many are unwilling to use schedule II opioids around the clock for CNMP. Individual prescribing practices vary widely among primary care physicians. Concerns about physical dependence, tolerance, and addiction are barriers to the prescription of opioids by primary care physicians for patients with CNMP.

Adolescent↗
PubMed2001

Effects of estrogen/medrogestone therapy on the apoprotein B-containing lipoproteins in postmenopausal women with type 2 diabetes mellitus under satisfactory and non-satisfactory glycemic control.

BACKGROUND: Information is lacking on the effects of hormone replacement therapy in women with diabetes, especially during moderate chronic hyperglycemia. OBJECTIVES: To study the effects of HRT on the lipid profile and the low density lipoprotein subclass distribution in women with type 2 diabetes under satisfactory and non-satisfactory glycemic control. METHODS: Fifty-four postmenopausal women after a 6 week run-in diet were randomized to receive either placebo (HbA1c < 8%, n = 13; HbA1c > 8%, n = 17) or HRT (HbA1c < 8%, n = 11; HbA1c > 8%, n = 13) for 12 weeks. HRT consisted of cyclical conjugated estrogens 0.625 mg/day plus medrogestone 5 mg/day. At the beginning and at the end of each treatment period the LDL subclass distribution was estimated by density gradient ultracentrifugation. RESULTS: At the baseline and during the study, the HbA1c level was significantly higher in hyperglycemic patients than in the near-normoglycemic controls (baseline 10.2 +/- 2.9 vs. 6.5 +/- 0.7%, P < 0.01). They showed a trend for higher total and LDL cholesterol, triglycerides and lower high density lipoprotein-cholesterol compared to near-normoglycemic controls, as well as significantly higher triglyceride concentrations in very low density lipoprotein, intermediate density lipoprotein and LDL-1 particles and cholesterol content in LDL-1 and -2 particles. HRT decreased LDL-cholesterol in both groups. In the normoglycemic patients a small increase in HbA1c was observed (6.5 +/- 0.7 vs. 7.4 +/- 1%, P = 0.04). In all cases, HRT did not modify the proportion of LDL represented by denser LDLs. CONCLUSIONS: HRT did not modify the LDL subclass distribution, even in the presence of moderate chronic hyperglycemia in women with type 2 diabetes.

Aged↗
PubMed2000

Role of sterols in modulating the human mu-opioid receptor function in Saccharomyces cerevisiae.

This study provides evidence that the differences in membrane composition found from one cell type to another can represent a limiting factor to recovering the functionality of transmembrane proteins when expressed in heterologous systems. Restoring the properties of the human mu-opioid receptor in yeast (Saccharomyces cerevisiae), similar to those observed in native cells, was achieved by replacing ergosterol from yeast by cholesterol, which is normally found in mammalian plasma membranes. The results suggest that these two sterols have opposite effects with respect to the ligand binding function of the receptor. Ergosterol was found to constrain the mu-opioid receptor in an inactive state in yeast plasma membranes and cannot replace cholesterol in activating it. These data differ from previous works dealing with the function of related G-protein-coupled receptors (GPCR) in ergosterol-enriched membranes. This suggests that structural requirements of GPCR with respect to their modulation by lipid components differ from one protein to another. As a consequence, we assume that the presence of appropriate lipids around transmembrane proteins determines their function. This highlights the functional significance of lateral heterogeneities of membrane components within biological membranes.

Cholesterol↗
PubMed2000

Granulocyte-macrophage colony-stimulating factor inhibits HIV-1 replication in monocyte-derived macrophages.

BACKGROUND: Previous studies of the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on HIV-1 replication in macrophages have had inconsistent results, variously reporting no effect, augmentation or inhibition of viral replication. OBJECTIVE: To investigate the regulation of HIV-1 in monocyte-derived macrophages (MDM) by GM-CSF in vitro. METHODS: The role of GM-CSF on HIV-1 replication was assessed as supernatant and intracellular p24 antigen concentrations and by HIV-1 DNA and mRNA production under different culture conditions. Expression of CD4 and CCR5 receptors was examined. The effect of GM-CSF with an E21R mutation, which binds only to the alpha-chain of GM-CSF receptor, was used as an additional control. RESULTS: GM-CSF consistently suppressed HIV-1 replication in human MDM in vitro, as assessed by supernatant and intracellular p24 antigen concentrations and HIV-1 gag mRNA expression. The inhibitory effect of GM-CSF on HIV-1 replication was observed regardless of HIV-1 strain, source of GM-CSF, stage of MDM maturation or timing of GM-CSF exposure in relation to HIV-1 infection. The effect was dose dependent and reversed by addition of a neutralizing monoclonal antibody (4D4). Flow cytometric analysis of surface expression of CD4 and CCR5 indicates that GM-CSF does not affect HIV-1 entry into MDM. Analysis of intracellular HIV-1 DNA and mRNA suggests that HIV-1 replication is inhibited at or before transcription. E21R GM-CSF had no effect on HIV-1 replication in MDM. CONCLUSIONS: GM-CSF regulates HIV-1 replication in MDM, inhibiting HIV-1 replication through binding to the beta-chain of the GM-CSF receptor.

Cells, Cultured↗