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Biomedical subjects

F Sanchez

Publications and source records attributed to F Sanchez.

At least 19 recordsLinked to original sources
PubMed2002

The effect of storage in an inert atmosphere on the release of inorganic constituents during intermittent wetting of a cement-based material.

Monolithic waste materials (e.g. Portland cement treated wastes) in many field scenarios do not remain continuously saturated, but experience intermittent wetting interspersed with periods of storage in an unsaturated environment. During storage, the matrix may loss moisture to the environment, promoting precipitation or redistribution of species. In addition, the matrix may react with the surrounding atmosphere through carbonation or oxidation. Upon subsequent leaching, changes in the chemical and physical composition incurred over the storage interval can influence the release of inorganic species. Current assessment approaches, which use continuous leaching data to project release over some assessment interval, do not allow for changes in leachability resulting from intermittent wetting and storage. Thus, this study evaluates the effect of storage intervals in an inert atmosphere on subsequent release of inorganic species from a synthetic Portland cement matrix. Tank leaching in deionized water was interspersed with storage at three relative humidity (RH) levels (nominally 0, 50 and 100% RH) in a 100% nitrogen atmosphere. Leaching data from the three intermittent wetting cases were compared to continuous leaching for the release of structural species (Ca, OH), highly soluble species (Na, K, Cl) and pH-dependent species (As, Cd, Pb). The RH of storage environment, which acted as a boundary condition for the drying process, influenced the precipitation of species within dried pores and relaxation of pH and concentration gradients within water-filled regions. Gradient relaxation resulted from continued mass transport within saturated pores over the storage interval and was most evident when storage was conducted at 98% RH. However, when storage RH promoted drying of the matrix, the effect of gradient relaxation was balanced by precipitation. When release was normalized to total leaching time, relaxation of concentration gradients of highly soluble species resulted in greater cumulative release for the intermittently wetted cases than in the case of continuous leaching. The release of pH-dependent constituents was controlled by relaxation of the pH gradient and species solubility as a function of local pore water pH. Application of a current assessment protocol to estimate intermittent wetting release resulted in either over or underestimation of actual cumulative release, depending on the nature of the constituent of interest. These results imply that long-term constituent release from Portland cement-based waste forms should not be made by simple correction of saturated release assessments because alterations to the matrix leachability induced by the storage environment need to be considered.

Chemical Phenomena↗
PubMed2002

Leaching of inorganic contaminants from cement-based waste materials as a result of carbonation during intermittent wetting.

Characterization of the leaching behavior of wastes is a crucial step in the environmental assessment for reuse or disposal scenarios. The release of inorganic contaminants from waste materials is typically evaluated by tank leaching of continuously water-saturated material. However, materials, in many field or management scenarios, experience cyclic wetting and drying under varied environmental conditions (i.e. variable relative humidity, atmospheric CO2 or CO2 from biologic activities). During periods of storage in an unsaturated environment, many processes may occur that can influence the release potential and release rate of inorganic constituents. The research presented here was carried out to examine how the phenomena of carbonation during drying influence the release of inorganic contaminants from Portland cement-based materials during cyclic wetting and storage. Batch equilibrium leaching tests were used to determine constituent solubility as a function of pH. Dynamic leaching tests on monolithic material were carried out to determine the rate of constituent release as a function of leaching time and intermittent storage conditions. This paper presents the results observed for three typical waste constituents, arsenic, cadmium and lead.

Carbon Dioxide↗
PubMed2001

High-Dose interferon-alpha2b plus ribavirin for retreatment of interferon-nonresponsive patients infected with genotype 1 hepatitis C virus.

Ten patients with interferon-nonresponsive chronic hepatitis C were treated with high-dose interferon-alpha2b (IFN-alpha2b; 20 MU/day for two days, then 3 MU/day for 24 weeks, followed by 3 MU three times weekly for 24 more weeks) plus ribavirin (1000-1200 mg/day). End-of-treatment virologic responses occurred in 50% of cases and sustained virologic responses in 37.5%. Hepatitis C virus RNA decreased significantly (2.15 logs; P < 0.0001) after the two 20-MU interferon doses but rebounded when the interferon dose was lowered to 3 MU/day. Thereafter, hepatitis C virus RNA showed a progressive, significant decrease, most notably at week 10 (3.3 logs; P = 0.001). Patients with a sustained response exhibited a more pronounced hepatitis C virus RNA decrease, especially from weeks 3 to 8 (P = 0.036). Two patients discontinued therapy because of adverse events, and one patient required a ribavirin dose reduction. Retreatment with an initial high-dose IFN-alpha2b plus ribavirin significantly reduces viral load in genotype 1-infected, interferon-nonresponsive patients.

Adult↗
PubMed2000

Prevalence of Haemophilus influenzae carriers in the Catalan preschool population. Working Group on Invasive Disease Caused by Haemophilus influenzae.

This study was designed to determine the prevalence of healthy Haemophilus influenzae carriers in a random sample of the preschool population in Catalonia. Oropharyngeal swabs were collected and cultured on chocolate agar supplemented with 260 microg/ml of bacitracin. Four hundred two of the 734 (54.8%) children studied were detected as Haemophilus influenzae carriers: 7 (0.9%) carried serotype b, 14 (1.9%) serotype e, 6 (0.8%) serotype f, and 375 (51%) carried nontypable strains. The results show that, although the prevalence of Haemophilus influenzae carriers is similar to figures reported from other countries, the prevalence of Haemophillus influenzae serotype b carriers is lower and corresponds with the low incidence of invasive disease observed in the Catalan community.

Carrier State↗
PubMed2000

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Journal Article↗
PubMed2000

Short-term regulation of NHE3 by EGF and protein kinase C but not protein kinase A involves vesicle trafficking in epithelial cells and fibroblasts.

NHE3 is an intestinal epithelial isoform Na+/H+ exchanger that is present in the brush border of small intestinal, colonic, and gallbladder Na(+)-absorbing epithelial cells. NHE3 is acutely up- and downregulated in response to some G protein-linked receptors, tyrosine kinase receptors, and protein kinases when studied in intact ileum, when stably expressed in PS120 fibroblasts, and in the few studies reported in the human colon cancer cell line Caco-2. In most cases this is due to changes in Vmax of NHE3, although in response to cAMP and squalamine there are also changes in the K'(H+)i of the exchanger. The mechanism of the Vmax regulation as shown by cell surface biotinylation and confocal microscopy in Caco-2 cells and biotinylation in PS120 cells involves changes in the amount of NHE3 on the plasma membrane. In addition, in some cases there are also changes in turnover number of the exchanger. In some cases, the change in amount of NHE3 in the plasma membrane is associated with a change in the amount of plasma membrane. A combination of biochemical studies and transport/inhibitor studies in intact ileum and Caco-2 cells demonstrated that the increase in brush border Na+/H+ exchange caused by acute exposure to EGF was mediated by PI 3-kinase. PI 3-kinase was also involved in FGF stimulation of NHE3 expressed in fibroblasts. Thus, NHE3 is another example of a transport protein that is acutely regulated in part by changing the amount of the transporter on the plasma membrane by a process that appears to involve vesicle trafficking and also to involve changes in turnover number.

Animals↗
PubMed1999

Identification of 9 novel FBN1 mutations in German patients with Marfan syndrome.

We report 9 new mutations in German patients presenting with classical Marfan syndrome. All mutations occur in exons with calcium-binding (cb) epidermal growth factor-like (EGF) domains. Five mutations are missense involving exons 12, 27, 30, 44, and 52 with the resultant substitution of cysteine by phenylalanine (C504F), cysteine by tyrosine (C1129Y), tyrosine by cysteine (Y1261C), cysteine by serine (C1833S), and cysteine by tyrosine (C2142Y), respectively. The other four mutations are single base deletions in exons 39, 43, 48, and 58, at nucleotide A4826, C5311, T6018, and A7291, respectively, each resulting in frameshift with premature termination. Four mutations were detected in sporadic cases and are likely to be de novo.

Adult↗
PubMed1999

Effects of dietary fatty acids on lipid metabolism in streptozotocin-induced diabetic rats.

We measured the activity of liver delta9- and delta6-desaturases and examined plasma and liver microsome phospholipid fatty acid composition in control and diabetic rats fed a basal diet supplemented with 5% (by weight) olive oil (OO), sunflower oil (SO), or fish oil (FO), respectively. Plasma glucose, cholesterol, triacylglyceride, and phospholipid levels were also measured. An increase in plasma and liver microsome oleic acid and a decrease in arachidonic acid were found in diabetes. In the liver, docosahexaenoic acid levels were higher in diabetic versus control rats. Diabetes increased liver delta9-desaturase in OO-fed rats and did not modify delta6-desaturase activity in OO- or SO-fed rats. Both enzymatic activities were decreased in diabetic rats fed the FO diet. As a main conclusion, it appears that diet-induced alterations in membrane composition provide a mechanism for improving the diabetic condition in animals and overcoming the effect of insulin deficiency on desaturase activities. Plasma cholesterol was not modified either by diabetes or by diet. In diabetes, OO-fed rats showed the lowest levels of triglycerides. Plasma phospholipids were significantly higher in OO-fed versus FO-fed rats. These findings suggest that OO contributes to a better control of the hypertriglyceridemia accompanying diabetes as compared with the other two diets in this rat model.

Animals↗
PubMed1999

Rhizobium nod factors induce increases in intracellular free calcium and extracellular calcium influxes in bean root hairs

Application of Nod factors to growing, responsive root hairs of the bean Phaseolus vulgaris induces marked changes in both the intracellular cytosolic free calcium (Ca2+) and in the influx of extracellular [Ca2+]. The intracellular [Ca2+], which has been measured by ratiometric imaging in cells microinjected with fura-2-dextran (70 kDa), elevates within 5 min from approximately 400 nM to 1500 nM in localised zones in the root hair apex. Of particular note is the observation that the elevated regions of [Ca2+] appear to shift position during short time intervals. Increases in and fluctuations of the intracellular [Ca2+] are also observed in the perinuclear region after 10-15 min treatment with Nod factors. The extracellular Ca2+ flux, detected with the non-invasive, calcium specific vibrating electrode, is inwardly directed and also increases quickly in response to Nod factors from 13 pmol cm-2 s-1 to 28 pmol cm-2 s-1. Chitin-oligomers, which are structurally similar but biologically inactive when compared to the active Nod factors, fail to elicit changes in either intracellular or extracellular Ca2+. The similar timing and location of the intracellular elevations and the increased extracellular influx provide support for the idea that Ca2+ participates in secretion and cell wall remodelling, which occur in anticipation of root hair deformation and curling.

Journal Article↗
PubMed1999

Increase in quinolone resistance in a Haemophilus influenzae strain isolated from a patient with recurrent respiratory infections treated with ofloxacin.

The increase in the level of quinolone resistance of Haemophilus influenzae clinical isolates during ofloxacin therapy of a patient with recurrent respiratory infections was investigated. The first isolate (MIC of ciprofloxacin of 2 microg/ml) and the second isolate (MIC of 32 microg/ml) belonged to the same clone, as shown by pulsed-field gel electrophoresis, and the increase in the resistance level was associated with a substitution in Ser-84 to Arg in the ParC protein. These results emphasize the potential risk of development of quinolone-resistant H. influenzae during fluoroquinolone therapy in patients with recurrent respiratory infection.

Amino Acid Substitution↗
PubMed1998

Indications of the protective role of natural killer cells in human cutaneous leishmaniasis in an area of endemicity.

The role of natural versus acquired immunity to Leishmania aethiopica infection in humans is the focus of our studies. We found in previous studies that mononuclear cells from nonexposed healthy Swedish donors responded to Leishmania antigen stimulation by proliferation and gamma interferon production. The main cell type responding was CD3- CD16/56+ natural killer (NK) cells. These findings led us to suggest that the potential to produce a rapid, nonacquired NK cell response may be a protective phenotype. In order to test this hypothesis, an area in Ethiopia where Leishmania is endemic was selected, and peripheral blood mononuclear cells were obtained from individuals who had lived in the area most of their lives but had no evidence of past or present leishmaniasis. Their responses were compared with those of confirmed leishmaniasis patients from the same region with active lesions or cured leishmaniasis lesions. Cells from these donors were stimulated in vitro with L. aethiopica antigen. Responses were measured by proliferation, cytokine production, and phenotype analysis by fluorescence-activated cell sorting. The association of NRAMP1 alleles with the studied phenotype and susceptibility to L. aethiopica-induced leishmaniasis was also evaluated. The results show that Leishmania antigens can induce NK cell and CD8+-T-cell responses in vitro. This is clearly seen in proliferating cells from the cured (immune) individuals and the apparently protected controls from the area of endemicity. It contrasted with the reactivity of the patients, where some NK proliferation was coupled with enhanced CD4+-T-cell proliferation. We conclude from these observations that NK cells and CD8(+) cells proliferating in response to Leishmania stimulation are involved in protection from and healing of (Ethiopian) cutaneous leishmaniasis; however, such mechanisms appear to be unrelated to the NRAMP1 host resistance gene.

Adult↗
PubMed1998

Recurrent Pseudomonas aeruginosa pneumonia in ventilated patients: relapse or reinfection?

A prospective observational study was performed to determine whether recurrent episodes of pneumonia caused by Pseudomonas aeruginosa in ventilated patients were due to a relapse of the previous clone or to reinfection with a new one. Diagnosis was based on quantitative cultures of secretions obtained by bronchoscopy. Comparison of strains was made by chromosomal fingerprinting based on pulsed field gel electrophoresis (PFGE). Thirty-three (89.1%) of 37 patients survived the initial week after pneumonia diagnosis; six survivors (18.1%) had multiple episodes caused by the same species. Presence of adult respiratory distress syndrome (83.3% versus 22.2%, p = 0.02) was the only factor significantly associated with clinical recurrences. The 16 isolates from five patients (nine recurrences) were analyzed by PFGE. All new isolates from recurrent episodes, excepting one, were considered as relapses. These data suggest that most recurrent episodes of P. aeruginosa pneumonia in ventilated patients occur due to persistence of strains present in a prior infection.

Adult↗
PubMed1997

Presence of tetrahydro-beta-carboline-3-carboxylic acids in foods by gas chromatography-mass spectrometry as their N-methoxycarbonyl methyl ester derivatives.

Various tetrahydro-beta-carboline-3-carboxylic acids (TH beta C-3-COOH) are identified in commercial foods and drinks by GC-MS. Positive identification of 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCA) is demonstrated in soy and tabasco sauces, wine, beer, wine vinegar, cider, orange juice, toasted bread, blue cheese and yoghurt. 1,2,3,4-Tetrahydro-beta-carboline-3-carboxylic acid (THCA) occurs in toasted bread, beer, cider, wine vinegar, soy and tabasco sauce, orange juice and blue cheese. MTCA and THCA are reported for the first time in several of these products. MTCA appears as a mixture of two diastereoisomers with the same mass spectra. MTCA is the major TH beta C-3-COOH in foodstuffs except for toasted bread that contains more THCA. GC-MS analysis of N-methoxycarbonyl methyl ester derivatives of TH beta C-3-COOHs was used for chemical identification. Those derivatives were synthesized in a qualitatively using methyl chloroformate or methyl chloroformate and diazomethane reagents. Electron impact mass spectra of N-methoxycarbonyl-TH beta C-3-COOH methyl esters are reported and fragmentation assigned and discussed. These results prove the presence of TH beta C-3-COOHs in commercial foodstuffs suggesting their uptake during the daily consumption of foods.

Carbolines↗
PubMed1997

Serial surveillance cultures of skin and catheter hub specimens from critically ill patients with central venous catheters: molecular epidemiology of infection and implications for clinical management and research.

A prospective study of 45 central venous catheters was conducted to assess, by strain delineation, the turnover of skin and catheter hub (superficial) colonization and the relative contributions of catheter hub and skin colonization to catheter tip colonization. Serial quantitative cultures of skin and catheter hub were performed. Catheter tip, blood, and specimens for culture from targeted superficial sites (TSSs) were also collected at the time of catheter removal. Strains from 17 tip-positive catheters were delineated by pulsed-field gel electrophoresis. Only 12 (28.6%) of 42 skin strains and 14 (31.1%) of 45 catheter hub strains were found to be present at the time of catheter removal. In addition, only 9 (29.0%) of the 31 tip-colonizing strains were present on TSSs. Moreover, 15 (48.4%) of the 31 tip-colonizing strains had a superficial origin, and the other 16 (51.6%) were of unknown origin. In catheters suspected of infection, cultures of TSSs had a negative predictive value for catheter-related bacteremia of 94.4% but a positive predictive value of 44.4%. When the causative agent was identified (to the strain level) these values dropped to 80.9 and 18.7%, respectively. The study shows that skin and catheter hub colonization is a common, dynamic phenomenon. Strains recovered from TSSs showed a low level of correlation with strains from previous cultures of specimens from superficial sites and catheter tip isolates. Consequently, TSSs cannot be recommended for use in determining the therapy. However, catheter-related bacteremia is uncommon when cultures of TSSs are negative.

Bacteria↗