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Biomedical subjects

M Olivares

Publications and source records attributed to M Olivares.

At least 19 recordsLinked to original sources
PubMed2006

Lactobacillus salivarius CECT 5713, a potential probiotic strain isolated from infant feces and breast milk of a mother-child pair.

In this study, Lactobacillus salivarius CECT 5713 was originally isolated from feces of a one-month-old breast-fed infant. Since it has been suggested that the gut microbiota of breast-fed infants reflects that of the maternal breast milk, we investigated if this specific strain was present in breast milk of the respective mother. RAPD and PFGE analysis revealed the presence of the strain L. salivarius CECT 5713 in this biological fluid. To our knowledge, this is the first report of a L. salivarius strain isolated from breast milk. L. salivarius CECT 5713 produced l-lactate, acetate and hydrogen peroxide, which may be responsible for its antimicrobial activity against most of the indicator organisms used in this study; in addition, this strain showed a high survival rate after exposition to conditions simulating those found in the gastrointestinal tract. Finally, it was strongly adhesive to Caco-2 and HT-29 cells did not produce biogenic amines and were unable to degrade gastric mucin in vitro.

Acetic Acid↗
PubMed2006

Antimicrobial potential of four Lactobacillus strains isolated from breast milk.

AIMS: The antimicrobial potential of four lactobacilli (Lactobacillus salivarius CECT5713, Lactobacillus gasseri CECT5714, L. gasseri CECT5715 and Lactobacillus fermentum CECT5716), isolated from fresh human breast milk, was evaluated in this study and compared with Lactobacillus coryniformis CECT5711, a reuterin-producing strain isolated from an artisan goat's cheese. METHODS AND RESULTS: Agar diffusion tests, competitive adhesion assays and mucin expression assays were carried out in order to value the antibacterial properties of the lactobacilli strains. The antibacterial capability of the strains was tested in vivo by using a murine infection model with Salmonella choleraesuis. The results revealed that all the strains studied, displayed antibacterial properties against pathogenic bacteria. However, the antibacterial potential varied among the lactobacilli tested and, in fact, L. salivarius CECT5713 showed not only the best in vitro antibacterial activity, but also the highest protective effect against a Salmonella strain in the murine infection model. CONCLUSION: The four breast-milk lactobacilli, and particularly L. salivarius CECT5713, possess potent antibacterial activities that result in a higher protection against S. choleraesuis CECT4155 in a mouse infection model. SIGNIFICANCE AND IMPACT OF THE STUDY: These results suggest that lactobacilli from breast milk could contribute to an anti-infective protection in neonates and would be excellent candidates for the development of infant probiotic products.

Animals↗
PubMed2006

Accurate skin dose measurements using radiochromic film in clinical applications.

Megavoltage x-ray beams exhibit the well-known phenomena of dose buildup within the first few millimeters of the incident phantom surface, or the skin. Results of the surface dose measurements, however, depend vastly on the measurement technique employed. Our goal in this study was to determine a correction procedure in order to obtain an accurate skin dose estimate at the clinically relevant depth based on radiochromic film measurements. To illustrate this correction, we have used as a reference point a depth of 70 micron. We used the new GAFCHROMIC dosimetry films (HS, XR-T, and EBT) that have effective points of measurement at depths slightly larger than 70 micron. In addition to films, we also used an Attix parallel-plate chamber and a home-built extrapolation chamber to cover tissue-equivalent depths in the range from 4 micron to 1 mm of water-equivalent depth. Our measurements suggest that within the first millimeter of the skin region, the PDD for a 6 MV photon beam and field size of 10 x 10 cm2 increases from 14% to 43%. For the three GAFCHROMIC dosimetry film models, the 6 MV beam entrance skin dose measurement corrections due to their effective point of measurement are as follows: 15% for the EBT, 15% for the HS, and 16% for the XR-T model GAFCHROMIC films. The correction factors for the exit skin dose due to the build-down region are negligible. There is a small field size dependence for the entrance skin dose correction factor when using the EBT GAFCHROMIC film model. Finally, a procedure that uses EBT model GAFCHROMIC film for an accurate measurement of the skin dose in a parallel-opposed pair 6 MV photon beam arrangement is described.

Computer Simulation↗
PubMed2006

Erythrocyte CuZn superoxide dismutase activity is decreased in iron-deficiency anemia.

Iron and copper are essential microminerals that are intimately related. The present study was performed to determine the effect of iron-deficiency anemia (IDA) and treatment with iron on laboratory indicators of copper status. Hemoglobin, mean corpuscular volume erythrocyte Zn protoporphyrin, serum ferritin, serum copper, serum ceruloplasmin, and erythrocyte CuZn-superoxide dismutase (SOD) activity were studied in 12 adult women with IDA before and after iron treatment for 60-90 d (100 mg/d Fe, as ferric polymaltose) and in 27 women with normal iron status. Prior to treatment with iron, serum copper and ceruloplasmin were not different between the groups and treatment with iron did not affect these measures. IDA women, before and after treatment with iron, presented a 2.9- and 2-fold decrease in erythrocyte CuZn-SOD activity compared to women with normal iron status (p < 0.001). Treatment with iron increased erythrocyte CuZn-SOD activity of the IDA group; however, this change was not statistically significant. In conclusion, CuZn-SOD activity is decreased in IDA. Measurement of this enzyme activity is not useful for evaluating copper nutrition in iron-deficient subjects.

Adult↗
PubMed2005

Characterization of a reuterin-producing Lactobacillus coryniformis strain isolated from a goat's milk cheese.

Lactobacillus coryniformis CECT 5711, a strain isolated from a goat's milk cheese, displayed a broad-spectrum antimicrobial activity; as a consequence, its ability to produce the antagonistic compounds associated to lactic acid bacteria, including bacteriocins, hydrogen peroxide, lactic acid, acetic acid, and reuterin (3-hydroxypropionaldehyde, 3-HPA) was investigated. Production of bacteriocins or hydrogen peroxide by this strain could not be detected. However, in addition to lactic acid and acetic acid, it produced reuterin and cobalamin, a cofactor required for conversion of glycerol to 3-HPA through a glycerol dehydratase. The gene encoding a glycerol dehydratase subunit was detected by PCR and the corresponding amplicon was sequenced. This strain showed a high survival after exposition to conditions simulating those existing in the gastrointestinal tract as well as a notable ability to adhere to intestinal cells, which suggests that its reuterin-producing ability may be used for the host benefit. In addition, the strain showed a strong beta-galactosidase activity. Production of biogenic amines and degradation of mucin could not be detected.

Aldehydes↗
PubMed2005

The balance between caseins and whey proteins in cow's milk determines its allergenicity.

Cow's milk allergy is quite common in the first years of human life. Protein composition plays an important role in this pathology, particularly the casein/whey protein ratio. It is known that milks from different species have different sensitization capacities although their protein sources are quite similar. Thus, the objective of this work was to compare the allergenicity of native cow's milk and milk with a modified ratio of casein and whey proteins in a murine model of atopy. Twenty-four Balb/c mice were orally sensitized to native cow's milk or modified cow's milk with a casein/whey protein ratio of 40:60. During the sensitization period, the number of mice suffering from diarrhea was significantly higher in the native cow's milk-sensitized group than in the modified milk-sensitized group. Once mice were killed, plasma histamine levels were shown to be significantly higher in native cow's milk-sensitized mice. In addition, cow's milk proteins induced a higher lymphocyte sensitization in the native milk-sensitized mice, with a significant increase in the specific proliferation ratio of these cells. These results suggest that the balance between caseins and whey proteins plays an important role in the sensitization capacity of cow's milk, and its modification might be a way to reduce the allergenicity of cow's milk.

Animals↗
PubMed2004

Association between aminolevulinate dehydrase genotypes and blood lead levels in children from a lead-contaminated area in Antofagasta, Chile.

Childhood environmental lead exposure in the city of Antofagasta, Chile, was generated by the accumulation of recently removed lead stores derived from mining activities for a long period of time. Susceptibility to harmful lead effects may be associated with polymorphisms of delta-aminolevulinic acid dehydratase (ALAD) because of the differential binding of lead to the codified proteins. We assessed the associations and possible interactions among the following variables: blood lead levels, ALAD genotypes, and distance to the source of lead contamination in Chilean children exposed to lead contamination in Antofagasta, Chile. Ninety-three children were recruited from schools located near a lead- contaminated area. Lead blood levels were measured by atomic absorption spectrophotometry. ALAD genotypes were determined by polymerase chain reaction and restriction fragment-length polymorphism analysis. The frequency of the ALAD-2 allele was estimated at 0.054. Children with the ALAD-2 genotype had higher blood lead levels than noncarriers (p = 0.06). As expected, blood lead levels were inversely correlated with the distance from lead stores. Interestingly, ALAD-2 carriers were more frequent within the area defined by a distance of 200 m from lead deposits (27%) than in areas >200 m (5%) away. Children living within a maximum distance of 200 m from the lead stores showed higher blood lead levels in ALAD-2 carriers (geometric mean = 16.4 microg/dl, range 6 to 27) than in noncarriers (geometric mean = 12.1 microg/dl, range 0 to 26) without achieving statistical significance (p = 0.13). A trend for higher blood lead levels in ALAD-2 carriers compared with ALAD-1 homozygous children has been observed. Because ALAD-2 frequency was higher in subjects living within 200 m from the lead deposits, we hypothesized that a long-term selective pressure against the presence of the ALAD-1 allele is the cause of the overrepresentation of the ALAD-2 allele in children living in proximity to the recently removed lead stores.

Child↗
PubMed2004

Health and aesthetic impacts of copper corrosion on drinking water.

Traditional research has focused on the visible effects of corrosion--failures, leaks, and financial debits--and often overlooked the more hidden health and aesthetic aspects. Clearly, corrosion of copper pipe can lead to levels of copper in the drinking water that exceed health guidelines and cause bitter or metallic tasting water. Because water will continue to be conveyed to consumers worldwide through metal pipes, the water industry has to consider both the effects of water quality on corrosion and the effects of corrosion on water quality. Integrating four key factors--chemical/biological causes, economics, health and aesthetics--is critical for managing the distribution system to produce safe water that consumers will use with confidence. As technological developments improve copper pipes to minimize scaling and corrosion, it is essential to consider the health and aesthetic effects on an equal plane with chemical/biological causes and economics to produce water that is acceptable for public consumption.

Copper↗
PubMed2003

Comparison of measured and Monte Carlo calculated dose distributions in inhomogeneous phantoms in clinical electron beams.

Calculations of dose distributions in heterogeneous phantoms in clinical electron beams, carried out using the fast voxel Monte Carlo (MC) system XVMC and the conventional MC code EGSnrc, were compared with measurements. Irradiations were performed using the 9 MeV and 15 MeV beams from a Varian Clinac-18 accelerator with a 10 x 10 cm2 applicator and an SSD of 100 cm. Depth doses were measured with thermoluminescent dosimetry techniques (TLD 700) in phantoms consisting of slabs of Solid Water (SW) and bone and slabs of SW and lung tissue-equivalent materials. Lateral profiles in water were measured using an electron diode at different depths behind one and two immersed aluminium rods. The accelerator was modelled using the EGS4/BEAM system and optimized phase-space files were used as input to the EGSnrc and the XVMC calculations. Also, for the XVMC, an experiment-based beam model was used. All measurements were corrected by the EGSnrc-calculated stopping power ratios. Overall, there is excellent agreement between the corrected experimental and the two MC dose distributions. Small remaining discrepancies may be due to the non-equivalence between physical and simulated tissue-equivalent materials and to detector fluence perturbation effect correction factors that were calculated for the 9 MeV beam at selected depths in the heterogeneous phantoms.

Algorithms↗
PubMed2003

The endonuclease NL1Tc encoded by the LINE L1Tc from Trypanosoma cruzi protects parasites from daunorubicin DNA damage.

In the present paper we show that the overexpression of the NL1Tc protein, encoded by the L1Tc non-LTR retrotransposon from Trypanosoma cruzi, led to a reduction of about 60% of DNA damage caused by daunorubicin treatment. This repair effect is not observed in transfected parasites overexpressing the NL1Tc mutated in the aspartic acid located in the active site of the enzyme. In addition, NL1Tc overexpression protects the parasite from the negative effect that daunorubicin has on parasite's growth rate. Thus, parasites overexpressing NL1Tc show, after treatment with 4 microM of daunorubicin, growth rate two to three times higher than the growth rate observed in treated control parasites transformed with the empty vector or overexpressing the mutated NL1Tc. Likewise, parasites overexpressing the NL1Tc protein and irradiated with a single dose of gamma-radiation (6 or 9 Gy) show higher growth rates than the parasites overexpressing the mutated NL1Tc or the control transfected parasites.

Animals↗
PubMed2003

Characterization of reverse transcriptase activity of the L1Tc retroelement from Trypanosoma cruzi.

The recombinant protein RTL1Tc, encoded by the non-LTR (long terminal repeat) retrotransposon L1Tc from Trypanosoma cruzi, has been shown to have reverse transcriptase (RT) activity using poly(rA)/oligo(dT) and poly(rC)/oligo(dG) homopolymers as template/primers. The optimal RT activity was detected at a concentration of 5 mM Mg2+, pH 8 and between 28 and 37% degrees C. Site-directed mutagenesis in the RT catalytic site proved that substitution of aspartic acid 313 for isoleucine (RT D313IL1Tc) practically abolishes the RT activity of the RTL1Tc protein. RT-polymerase chain reaction assays revealed that the RTL1Tc protein has the ability to use both homologous and heterologous RNA templates. Also, it is shown that the RTL1Tc protein is capable of synthesizing complementary DNA molecules by consecutive switching of the oligo molecule, which the protein uses as a template. This template switching may be involved in the retroelement integration process.

Animals↗
PubMed2001

Nausea threshold in apparently healthy individuals who drink fluids containing graded concentrations of copper.

Ingestion of drinking water with a high copper content may induce acute gastrointestinal effects, mainly nausea and vomiting, rarely diarrhea and abdominal pain. The objectives of this study were to define nausea threshold in apparently healthy adult volunteers who received graded concentrations of copper and to explore how individual thresholds were modified by delivering copper in an orange-flavored drink. Sixty-one healthy subjects received 200 mL of a copper-containing solution in purified water, at concentrations 0, 2, 4, 6, 8, 10, and 12 mg/L, as copper sulfate, in random order. Nausea threshold concentration for first response was established and then this threshold was confirmed. Subsequently, following the same design, subjects received the same copper concentrations (up to 12 mg/L), delivered in an orange-flavored drink, starting at the confirmed threshold concentration found in water. Mild nausea shortly after ingestion of copper-containing water was the most frequent finding (33/61 subjects), starting at 4 mg/L; vomiting was observed in 7 individuals, starting at 6 mg/L. The NOEL for copper in purified water was 2 and 4 mg/L for nausea and vomiting, respectively. When copper was provided as an orange-flavored drink, 11 subjects (18%) reported nausea, starting at 8 mg Cu/L, and no subjects vomited up to 12 mg Cu/L. It is concluded that after consumption of copper in purified water, the NOEL is 2 mg Cu/L and the LOAEL 4 mg Cu/L for nausea, while tolerable intake is between 2 and 4 mg Cu/L in water depending on whether apparent or confirmed nausea is used as the criterion to define critical effects.

Administration, Oral↗
PubMed2001

Determination of an acute no-observed-adverse-effect level (NOAEL) for copper in water.

A prospective, double-blind controlled study was designed to determine the acute no-observed-adverse-effect level (NOAEL) of nausea in an apparently healthy population of 179 individuals who drank copper-containing water as the sulfate salt. Subjects were recruited at three different international sites and given a blind, randomly selected dose (0, 2, 4, 6, or 8 mg Cu/L) in a bolus of 200 ml (final total copper dose was equivalent to 0, 0.4, 0.8, 1.2, and 1.6 mg) once weekly over a consecutive 5-week period. Gastrointestinal (GI) symptoms of nausea, abdominal pain, vomiting, or diarrhea were screened for a period of up to 24 h. Nausea was the most frequently reported effect and was reported within the first 15 min of ingestion. For the combined trisite population (n=179), 8, 9, 14, 25, and 44 subjects responded positively to one or more GI symptoms at 0, 2, 4, 6, and 8 mg Cu/L, respectively. Analysis of the data demonstrated a clear dose response to the combined positive GI effects and to nausea alone. Statistically significant greater reporting of effects occurred at 6 and 8 mg Cu/L. Therefore, an acute NOAEL and lowest-observed-adverse-effect level of 4 and 6 mg Cu/L (0.8 and 1.2 mg Cu), respectively, were determined in drinking water for a combined international human population.

Adult↗
PubMed2001

Effect of acute copper exposure on gastrointestinal permeability in healthy volunteers.

In vitro studies indicate that treating cells with copper results in alteration of tight junction permeability. In humans, ingestion of a single bolus of up to 10 mg Cu/L (as copper sulfate) causes nausea and vomiting in approximately 20 and 5% of the volunteers, respectively. To understand better the gastric and intestinal effects of copper, in this study we evaluated in asymptomatic volunteers (1) the effects of acute copper ingestion on gastric and intestinal permeability and (2) whether the appearance of gastrointestinal symptoms is associated with changes in mucosal permeability. Thirty-one asymptomatic subjects were assessed in a randomized, double-blind, crossover study that included two permeability tests, one after ingesting 200 ml distilled water and the other after ingesting 200 ml water containing 10 mg Cu/L (as copper sulfate). Fifteen minutes after ingestion subjects drank a second solution containing 40 g sucrose, 7.5 g lactulose, and 2 g mannitol, and urine was collected for 5 hr. Sugar concentrations were determined by gas chromatography. Symptoms during the trials were recorded in self-administered questionnaires. Ingestion of the 10 mg/L copper solution significantly increased gastric permeability to sucrose [20.8 (11.8-73.4) vs 28.4 (16.6-113.9) mg, respectively; P = 0.0064] but did not change intestinal permeability to lactulose/mannitol [0.87 (0.53-2.06) vs 1.17 (0.58-2.39)%, respectively; P = 0.18]. Gastrointestinal symptoms were reported during both the basal and the experimental conditions, but after copper ingestion they increased to 22.6% of the subjects and were significantly more intense than under basal conditions (P = 0.047). However, changes in permeability were not related to the appearance of symptoms. These results indicate that acute oral exposure to 10 mg Cu/L exerts an effect on gastric but not intestinal mucosa, reducing the gastric mucosal barrier capacity, independently of the appearance of gastrointestinal symptoms.

Adult↗
PubMed2001

Determination of the taste threshold of copper in water.

Copper effects on human health represent a relevant issue in modern nutrition. One of the difficulties in assessing the early, acute effects of copper ingested via drinking water is that the taste of copper may influence the response and the capacity to taste copper in different waters is unknown. The purpose of the study was to determine the taste threshold of copper in different types of water, using soluble and insoluble salts (copper sulfate and copper chloride). Copper-containing solutions (range 1.0-8.0 mg/l Cu) were prepared in tap water, distilled deionized water and uncarbonated mineral water. Sixty-one healthy volunteers (17-50 years of age), with no previous training for sensory evaluation, participated in the study. A modified triangle test was used to define the taste threshold value. The threshold was defined as the lowest copper concentration detected by 50% of the subjects assessed. To evaluate the olfactory input in the threshold value obtained, 15 of 61 subjects underwent a second set of triangle tests with the nose open and clamped, using distilled water with copper sulfate at a concentration corresponding to the individual's threshold. The taste threshold in tap water was 2.6 mg/l Cu for both copper sulfate and copper chloride. The corresponding values for distilled deionized water were 2.4 and 2.5 mg/l Cu for copper sulfate and copper chloride, respectively. In uncarbonated mineral water the threshold values were slightly higher, 3.5 and 3.8 mg/l Cu for copper sulfate and for copper chloride, respectively, which are significantly higher than those observed in tap and distilled waters (P < 0.01, Kruskal-Wallis test). The taste threshold did not change significantly when the nose was clamped. In conclusion, the median values for copper taste threshold were low, ranging between 2.4 and 3.8 mg/l Cu, depending on the type of water.

Adolescent↗
PubMed2001

Electron fluence correction factors for various materials in clinical electron beams.

Relative to solid water, electron fluence correction factors at the depth of dose maximum in bone, lung, aluminum, and copper for nominal electron beam energies of 9 MeV and 15 MeV of the Clinac 18 accelerator have been determined experimentally and by Monte Carlo calculation. Thermoluminescent dosimeters were used to measure depth doses in these materials. The measured relative dose at dmax in the various materials versus that of solid water, when irradiated with the same number of monitor units, has been used to calculate the ratio of electron fluence for the various materials to that of solid water. The beams of the Clinac 18 were fully characterized using the EGS4/BEAM system. EGSnrc with the relativistic spin option turned on was used to optimize the primary electron energy at the exit window, and to calculate depth doses in the five phantom materials using the optimized phase-space data. Normalizing all depth doses to the dose maximum in solid water stopping power ratio corrected, measured depth doses and calculated depth doses differ by less than +/- 1% at the depth of dose maximum and by less than 4% elsewhere. Monte Carlo calculated ratios of doses in each material to dose in LiF were used to convert the TLD measurements at the dose maximum into dose at the center of the TLD in the phantom material. Fluence perturbation correction factors for a LiF TLD at the depth of dose maximum deduced from these calculations amount to less than 1% for 0.15 mm thick TLDs in low Z materials and are between 1% and 3% for TLDs in Al and Cu phantoms. Electron fluence ratios of the studied materials relative to solid water vary between 0.83+/-0.01 and 1.55+/-0.02 for materials varying in density from 0.27 g/cm3 (lung) to 8.96 g/cm3 (Cu). The difference in electron fluence ratios derived from measurements and calculations ranges from -1.6% to +0.2% at 9 MeV and from -1.9% to +0.2% at 15 MeV and is not significant at the 1sigma level. Excluding the data for Cu, electron fluence correction factors for open electron beams are approximately proportional to the electron density of the phantom material and only weakly dependent on electron beam energy.

Electrons↗
PubMed2001

Gastrointestinal effects associated with soluble and insoluble copper in drinking water.

The aim of this study was to determine whether total copper or soluble copper concentration is associated with gastrointestinal signs and symptoms. Forty-five healthy adult women (18-55 years of age), living in Santiago, Chile, ingested tap water with 5 mg/L of copper containing different ratios of soluble copper (copper sulfate) and insoluble copper (copper oxide) over a 9-week period. Three randomized sequences of the different copper ratios (0:5, 1:4, 2:3, 3:2, and 5:0 mg/L) were followed. Subjects recorded their water consumption and gastrointestinal symptoms daily on a special form. Mean water consumption was similar among groups. Serum copper levels, ceruloplasmin, and activities of liver enzymes were within normal limits. No differences were detected between the means of biochemical parameters at the beginning and at the end of the study. Twenty subjects presented gastrointestinal disturbances at least once during the study, 9 suffered diarrhea (with or without abdominal pain and vomiting), and the other 11 subjects reported abdominal pain, nausea, or vomiting. No differences were found in incidence of abdominal pain, nausea, vomiting, and diarrhea regardless of the ratio of copper sulfate to copper oxide. In conclusion, both copper sulfate (a soluble compound) and copper oxide (an insoluble compound) have comparable effects on the induction of gastrointestinal manifestations, implying that similar levels of ionic copper were present in the stomach.

Abdominal Pain↗