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Biomedical subjects

M Murillo

Publications and source records attributed to M Murillo.

At least 19 recordsLinked to original sources
PubMed2005

Performance of a new nebulizer system for simultaneous determination of Sb, Sn (hydride generation), V, and Zn by ICP-OES.

A new nebulizer system is described that extends the analytical capability of the inductively coupled plasma technique to include the simultaneous determination of two elements Sb and Sn (hydride-forming), with two conventional elements, V and Zn. The main advantage of this system is its simultaneous determination of elements that form volatile hydrides and elements that do not, without any instrumental changes. Optimization of reaction and instrumental conditions was performed to characterize the new system. The performance of the new nebulizer system was evaluated by studying the effect of some transition metals (Ni, Cu, Co, and Fe, 1-1000 mg L(-1)) on the Sb, Sn, V, and Zn emission signals (1 mg L(-1)). Interferences from transition metal ions were found to be insignificant for determination of the four elements in presence of L: -cysteine. Long-term and short-term stability was also evaluated. The precision, expressed as RSD for 15 replicate measurements was 0.7% for Sb, 1.7% for Sn, 2.5% for V, and 2.3% for Zn at 200 microg L(-1) of each analyte. The detection limits obtained were 0.52, 1.3, 3.2, and 4.7 microg L(-1) for Sb, Sn, V, and Zn, respectively. Spike and recovery experiments were performed on the NIST 1643c trace metals in water standard reference material and results were in agreement with the certified values.

Journal Article↗
PubMed2005

Occurrence of ochratoxin A in cocoa beans: effect of shelling.

The aim of this study was to investigate the influence of the shelling process on the presence of ochratoxin A (OTA) in cocoa samples. Twenty-two cocoa samples were analysed for the determination of OTA before (cocoa bean) and after undergoing manual shelling process (cocoa nib). In order to determine OTA contamination in cocoa samples, a validated high-performance liquid chromatography (HPLC) method with fluorescence detection was used for the quantitative analysis of ochratoxin A (OTA). In both types of samples, OTA was extracted with methanol-3% sodium hydrogen carbonate solution and then purified using immunoaffinity columns prior to HPLC analysis. Due to the fact that different recovery values were obtained for OTA from both types of samples, a revalidation of the method in the case of cocoa nibs was needed. Revalidation was based on the following criteria: Selectivity, limits of detection and quantification (0.03 and 0.1 microg kg(-1), respectively), precision (within-day and between-day variability) and recovery 84.2% (RSD = 7.1%), and uncertainty (30%). Fourteen of the twenty-two cocoa bean samples (64%) suffered a loss of OTA of more than 95% due to shelling, six samples suffered a loss of OTA in the range 65-95%, and only one sample presented a reduction of less than 50%. The principal conclusion derived from this study is that OTA contamination in cocoa beans is concentrated in the shell; therefore, improvements of the industrial shelling process could prevent OTA occurrence in cocoa final products.

Cacao↗
PubMed2004

Influence of the co-encapsulation of different excipients on the properties of polyester microparticle-based vaccine against brucellosis.

This work evaluates the influence of different pharmaceutical auxiliaries (Pluronic F68, polyvinylpyrrolidone [PVP] or Tween 20), when mixed with an antigenic extract from Brucella ovis (hot saline; HS), on the characteristics of the resulting poly(epsilon-caprolactone) (PEC) and poly(lactide-co-glycolide) (PLGA) microparticles. In all cases, PEC microparticles were smaller than PLGA ones. Concerning the HS loading, PLGA microparticles were highly dependent on the type of the excipient used, whereas all the PEC formulations displayed similar encapsulation efficiencies. For both types of microparticles, the presence of PVP induced a burst release effect. On the contrary, the use of Tween 20 or Pluronic F68 dramatically modified this profile. For PLGA-Tween 20 and PEC-Pluronic F68 microparticles, the HS was released in a pulsatil way during the first 7 days followed by a continuous release for at least 3 weeks. The antigenicity of the HS components was kept in all cases. Phagocytosis by murine monocytes showed a clear difference based just on the hydrophobicity of the polymer, being PEC microparticles better engulfed. Cell activation quantified by the release of H2O2 did not showed major differences between batches, however, microparticles of PEC and Pluronic F68 induced the highest nitric oxide production. Together, these results confirm the advantageous qualities of the "HS-PEC-Pluronic F68 microparticles" as favorable candidate for vaccine purposes against brucellosis.

Animals↗
PubMed2004

Validation of a high-performance liquid chromatography analytical method for ochratoxin A quantification in cocoa beans.

A validated high-performance liquid chromatography (HPLC) method with fluorescence detection for the quantitative analysis of ochratoxin A (OTA) in cocoa beans is described. OTA was extracted with methanol-3% sodium hydrogen carbonate solution and then purified with immunoaffinity columns before its analysis by HPLC. The validation of the analytical method was based on the following criteria: selectivity, linearity, limit of detection and quantification, precision (within- and between-day variability) and recovery, robustness and uncertainty. Detection and quantification limits were 0.04 and 0.1 mug kg(-1), respectively. Recovery was 88.9% (relative standard deviation = 4.0%). This method was successfully applied to the measurement of 46 cocoa bean samples of different origins. A total of 63% of cocoa bean samples was contaminated with a level greater than the limit of detection. The means and medians obtained for cocoa bean were 1.71 and 1.12 mug kg(-1), respectively. Surveillance controls should be set up in both crops and factories involved in transformation processes to avoid this mycotoxin in final products.

Cacao↗
PubMed2003

The relationship between placental histopathology findings and perinatal outcome in preterm infants.

OBJECTIVE: To determine the correlation between placental histopathology findings and perinatal outcome in preterm infants. METHODS: Placental histopathology in 774 neonates delivered at 24-32 weeks between 1992 and 2000 was classified as follows: 254 (33%) had histological chorioamnionitis, 263 (34%) had coagulation-related lesions, 228 (30%) had vasculopathy. Perinatal outcome was compared between cases positive and negative for each histopathological classification. RESULTS: Histological chorioamnionitis occurred in 46% of cases with premature rupture of membranes and 45% with preterm labor. Positivity versus negativity for histological chorioamnionitis was associated with earlier presentation (191 vs. 205 days, p = 0.0001) and delivery (199 days vs. 209 days, p = 0.0001), increased risk of intraventricular hemorrhage (71% vs. 23%, p = 0.001, odds ratio (OR) 2.2), bronchopulmonary dysplasia (26% vs. 15%, p = 0.0001, OR 2), retinopathy (36% vs. 24%, p = 0.001, OR 1.8), neonatal sepsis (28% vs. 13%, p = 0.0001, OR 2.5) and neonatal death (12% vs. 7%, p = 0.012, OR 2). Vasculopathy versus no vasculopathy was associated with decreased birth weight (1245 g vs. 1341 g, p = 0.011), decreased Apgar score at 5 min (20% vs. 13%, p = 0.011, OR 1.7) and necrotizing enterocolitis (6% vs. 2%, p = 0.001, OR 4). Cases positive for coagulation-related lesions correlated only with necrotizing enterocolitis (5% vs. 2%, p = 0.02, OR 2.6). CONCLUSIONS: The presence of histological chorioamnionitis significantly increases the risk of earlier delivery and neonatal mortality. Vascular and coagulation placental findings increase the risk of necrotizing enterocolitis.

Apgar Score↗
PubMed2002

Modulation of the cellular immune response after oral or subcutaneous immunization with microparticles containing Brucella ovis antigens.

An antigenic extract (HS) from Brucella ovis was encapsulated in either poly-epsilon-caprolactone (PEC) or poly-lactic-co-glycolic acid 75:25 (PLGA) microparticles containing beta-cyclodextrin and Pluronic F-68 as stabilising agents. The resulting microparticles displayed sub-5 microm sizes. Antigen loading was 5.2 and 3.8 microg/mg for HS-PEC and HS-PLGA microparticles, respectively. Specific HS cytokine profiles were determined after subcutaneous and oral immunisation of BALB/c mice. Gut distribution studies of the formulations after oral administration showed that HS-PEC microparticles interacted more strongly with mucosa and Peyer's patches than HS-PLGA. Accordingly, oral immunisation with HS-PLGA induced a negligible immune response, whereas HS-PEC elicited a Th1 response although of low intensity. Subcutaneous immunisation with HS-PEC induced high IFN-gamma and IL-2 release; in contrast, HS-PLGA particles induced a Th2 profile characterized by significant levels of IL-4. Splenic cells from free-HS immunised mice released IFN-gamma and IL-2 but not IL-4. A less intense Th1 pattern was also found from HS stimulated nai;ve splenic cells. These results suggest that the HS itself possesses Th1 immunopotentiating properties, required to control brucellosis, that can be specifically increased by encapsulation in PEC microparticles. In contrast, PLGA microparticles modulate the response toward a Th2 pathway.

Administration, Oral↗
PubMed2002

Development of microparticles prepared by spray-drying as a vaccine delivery system against brucellosis.

The antigenic extract Hot Saline from Brucella ovis was microencapsulated by the spray-drying technique with different polyesters (poly-lactide-co-glycolide RG502H [PLGA], and blends with poly- epsilon -caprolactone [PEC]) in order to obtain microparticles smaller than 5 microm. Microparticles were tested for encapsulation efficiency, release studies, acidification of the in vitro release medium, and in vitro J744-macrophage experiments (phagocytosis and toxicity of the preparations) to determine the optimal formulation for vaccination purposes. Formulation containing no PCL showed the highest encapsulation efficiency, although the differences were not significant. The in vitro release kinetics were characterized by a high burst effect after 1 h of incubation, followed by a slow and continuous release. For the formulation based on PLGA, the pH of the medium during release dropped from 7.4 to 3.5 while the presence of PEC attenuated the pH drop. All formulations showed light toxicity by the MTT assay, but differences were observed in terms of phagocytosis, as particles prepared with PEC showed the higher uptake by J744-macrophages and cell respiratory burst, determined by oxygen peroxide release. All these characteristics suggest that the microparticulated antigenic formulation containing the higher ratio of PEC is susceptible to be used in animal vaccination studies.

Bacterial Vaccines↗
PubMed2002

Polyester microparticles as a vaccine delivery system for brucellosis: influence of the polymer on release, phagocytosis and toxicity.

Microparticles, containing an antigenic complex from Brucella ovis (HS), were evaluated for vaccine purposes against brucellosis. They were prepared by the double emulsion solvent evaporation method using two different polyesters, poly-lactide-co-glycolide acid (75:25; RG 756) and poly-epsilon-caprolactone. The encapsulation efficiency and release of HS from the microparticles, their capacity to be phagocytosed and also their toxicity on murine monocytes J774.2 were investigated. Both polymers lead to smooth and spherical sub-5 microm particles, with approximately 30% of the antigen initial dose encapsulated. SDS-PAGE and immunoblot of extracted antigens confirmed that the apparent molecular weight and antigenicity remained unaltered after the encapsulation procedure. However, the in vitro release of the antigens differed among them. The release profile for PLGA microparticles was continuous, whereas PEC ones released the antigens in a triphasic release pattern. Phagocytosis was clearly influenced by the hydrophobicity of the polymer, increasing in the case of PEC microparticles. Toxicity assay showed that both types of microparticles induced similar levels of mitochondrial damage. In conclusion, HS-PEC microparticles could be used as an effective vaccine against brucellosis, as the antigen is released in boosters and they are greatly phagocytosed by macrophages.

Animals↗
PubMed2001

A Brucella ovis antigenic complex bearing poly-epsilon-caprolactone microparticles confer protection against experimental brucellosis in mice.

A hot saline antigenic extract (HS) from Brucella ovis was encapsulated in poly-epsilon-caprolactone microparticles (PEC), and tested as a vaccine against B. ovis and B. abortus infections in mice. Subcutaneous but not oral administration in BALB/c mice of the HS-PEC induced high amounts of IFN-gamma and IL-2 but low quantities of IL-4 suggesting a combined Th1/Th2 cellular immune response. The vaccine administered either subcutaneously or orally protected mice against B. ovis infection. Such protection was similar to that provided by the reference living attenuated B. melitensis Rev. 1 vaccine. By contrast, only the subcutaneous vaccination with HS-PEC was as effective as Rev. 1 in conferring protection against B. abortus infection. The use of free HS or empty PEC microparticles did not produce any protective effect.

Animals↗
PubMed1999

Evidence for distinct intracellular signaling pathways in CD34+ progenitor to dendritic cell differentiation from a human cell line model.

Intracellular signals that mediate differentiation of pluripotent hemopoietic progenitors to dendritic cells (DC) are largely undefined. We have previously shown that protein kinase C (PKC) activation (with phorbol ester (PMA) alone) specifically induces differentiation of primary human CD34+ hemopoietic progenitor cells (HPC) to mature DC. We now find that cytokine-driven (granulocyte-macrophage CSF and TNF-alpha) CD34+ HPC-->DC differentiation is preferentially blocked by inhibitors of PKC activation. To further identify intracellular signals and downstream events important in CD34+ HPC-->DC differentiation we have characterized a human leukemic cell line model of this process. The CD34+ myelomonocytic cell line KG1 differentiates into dendritic-like cells in response to granulocyte-macrophage CSF plus TNF-alpha, or PMA (with or without the calcium ionophore ionomycin, or TNF-alpha), with different stimuli mediating different aspects of the process. Phenotypic DC characteristics of KG1 dendritic-like cells include morphology (loosely adherent cells with long neurite processes), MHC I+/MHC IIbright/CD83+/CD86+/CD14- surface Ag expression, and RelB and DC-CK1 gene expression. Functional DC characteristics include fluid phase macromolecule uptake (FITC-dextran) and activation of resting T cells. Comparison of KG1 to the PMA-unresponsive subline KG1a reveals differences in expression of TNF receptors 1 and 2; PKC isoforms alpha, beta I, beta II, and mu; and RelB, suggesting that these components/pathways are important for DC differentiation. Together, these findings demonstrate that cytokine or phorbol ester stimulation of KG1 is a model of human CD34+ HPC to DC differentiation and suggest that specific intracellular signaling pathways mediate specific events in DC lineage commitment.

Adult↗
PubMed1997

Siroheme biosynthesis in higher plants. Analysis of an S-adenosyl-L-methionine-dependent uroporphyrinogen III methyltransferase from Arabidopsis thaliana.

Siroheme, the prosthetic group for both nitrite and sulfite reductases, is a methylated, iron-containing modified tetrapyrrole. Here we report the first molecular characterization of the branch point enzyme in higher plants, which directs intermediates toward siroheme synthesis. A cDNA was cloned from Arabidopsis thaliana (UPM1) that functionally complements an Escherichia coli cysG mutant, a strain that is unable to catalyze the conversion of uroporphyrinogen III (Uro'gen-III) to siroheme. UPM1 is 1484 base pairs and encodes a 369-amino acid, 39.9-kDa protein. The UPM1 product contains two regions that are identical to consensus sequences found in bacterial Uro'gen-III and precorrin methyltransferases. Recombinant UPM1 protein was found to catalyze S-adenosyl-L-methionine-dependent transmethylation by UPM1 in a multistep process involving the formation of a covalently linked complex with S-adenosyl-L-methionine. The UPM1 product has a sequence at the amino terminus that resembles a transit peptide for localization to mitochondria or plastids. The protein produced by in vitro expression is able to enter isolated intact chloroplasts but not mitochondria. Genomic blot analysis showed that UPM1 is encoded in the A. thaliana genome. The genomic DNA corresponding to UPM1 was cloned and sequenced and found to contain at least five introns.

Amino Acid Sequence↗
PubMed1996

Sulfate reduction in higher plants: molecular evidence for a novel 5'-adenylylsulfate reductase.

Sulfate-assimilating organisms reduce inorganic sulfate for Cys biosynthesis. There are two leading hypotheses for the mechanism of sulfate reduction in higher plants. In one, adenosine 5'-phosphosulfate (APS) (5'-adenylysulfate) sulfotransferase carries out reductive transfer of sulfate from APS to reduced glutathione. Alternatively, the mechanism may be similar to that in bacteria in which the enzyme, 3'-phosphoadenosine-5'-phosphosulfate (PAPS) reductase, catalyzes thioredoxin (Trx)-dependent reduction of PAPS. Three classes of cDNA were cloned from Arabidopsis thaliana termed APR1, -2, and -3, that functionally complement a cysH, PAPS reductase mutant strain of Escherichia coli. The coding sequence of the APR clones is homologous with PAPS reductases from microorganisms. In addition, a carboxyl-terminal domain is homologous with members of the Trx superfamily. Further genetic analysis showed that the APR clones can functionally complement a mutant strain of E. coli lacking Trx, and an APS kinase, cysC. mutant. These results suggest that the APR enzyme may be a Trx-independent APS reductase. Cell extracts of E. coli expressing APR showed Trx-independent sulfonucleotide reductase activity with a preference for APS over PAPS as a substrate. APR-mediated APS reduction is dependent on dithiothreitol, has a pH optimum of 8.5, is stimulated by high ionic strength, and is sensitive to inactivation by 5'-adenosinemonophosphate (5'-AMP). 2'-AMP, or 3'-phosphoadenosine-5'-phosphate (PAP), a competitive inhibitor of PAPS reductase, do not affect activity. The APR enzymes may be localized in different cellular compartments as evidenced by the presence of an amino-terminal transit peptide for plastid localization in APR1 and APR3 but not APR2. Southern blot analysis confirmed that the APR clones are members of a small gene family, possibly consisting of three members.

Amino Acid Sequence↗
PubMed1995

Adenosine-5'-triphosphate-sulfurylase from Arabidopsis thaliana and Escherichia coli are functionally equivalent but structurally and kinetically divergent: nucleotide sequence of two adenosine-5'-triphosphate-sulfurylase cDNAs from Arabidopsis thaliana and analysis of a recombinant enzyme.

ATP-sulfurylase, the first enzyme of sulfate assimilation, catalyzes the formation of adenosine-5'-phosphosulfate from ATP and sulfate. Here we report that the higher plant, Arabidopsis thaliana, contains a three-member, expressed gene family encoding plastid localized forms of ATP sulfurylase. Three cDNAs from A. thaliana, designated APS1, APS2, and APS3, were isolated by their ability to functionally complement a met3 (ATP sulfurylase) mutant strain of Saccharomyces cerevisiae (yeast). The nucleotide sequence of APS1 was reported previously (1). APS2 and APS3, reported here, have 476- and 465-codon open-reading frames encoding 53.6- and 52.0-kDa polypeptides, respectively. The translation products of both clones are highly homologous to APS1 (66 and 86% identity, respectively) over their entire lengths, including amino terminal sequences resembling transit peptides for plastid localization. Both clones are less homologous to MET3 (25 and 30% identity, respectively). Genomic blot analysis of A. thaliana revealed only three genes with homology to the APS cDNAs and RNA blot analysis showed that APS1 is the most highly expressed member of this gene family. The APS polypeptides share homology with ATP-sulfurylases from fungi, a marine worm and a chemoautotrophic bacterium, but, not from Escherichia coli or Rhizobium meliloti. Analysis of recombinant APS3 showed that the protein is structurally and kinetically similar to fungal ATP-sulfurylase, but very different from the E. coli enzyme. The APS3 polypeptide is a homotetramer with specific activities (mumol primary product x mg protein-1 at pH 8.0, 25 degrees C) for 2.9 for APS synthesis, 30.1 for molybdolysis, and 48.7 for ATP synthesis. Despite the sequence, structural, and kinetic differences between higher plant and E. coli ATP-sulfurylases, APS2 and APS3 are able to functionally complement E. coli cysD and cysN (ATP-sulfurylase) mutant strains.

Amino Acid Sequence↗
PubMed1995

Serine acetyltransferase from Arabidopsis thaliana can functionally complement the cysteine requirement of a cysE mutant strain of Escherichia coli.

Serine acetyltransferase, a key enzyme in the L-cysteine biosynthetic pathway of sulfate assimilating organisms, catalyzes the formation of O-acetylserine, the immediate precursor of L-cysteine. In higher plants, it is thought that sulfur assimilation occurs primarily in leaf chloroplasts; however, serine acetyltransferase is not localized exclusively in this tissue and organelle. At least three genes for serine acetyltransferase have been identified in the higher plant Arabidopsis thaliana. Reported here is a cDNA corresponding to one of these genes, SAT1, a 1,079 bp clone with an open reading frame predicted to encode a 34-kDa protein that is able to functionally complement a serine acetyltransferase mutant strain of Escherichia coli. The predicted amino acid sequence of SAT1 shows significant homology with bacterial serine acetyltransferases. SAT1, expressed as a recombinant protein, shows serine acetyltransferase enzyme activity and cross-reacts with an antibody against the homologous E. coli enzyme. The first 40 amino acids of the SAT1 polypeptide resembles a plastid transit peptide, but the polypeptide is probably not plastid localized. Genomic DNA blot analysis of A. thaliana showed that SAT1 is a single copy gene and RNA blot analysis revealed that SAT1 is expressed in both leaves and roots.

Acetyltransferases↗
PubMed1994

Cloning of a cDNA encoding ATP sulfurylase from Arabidopsis thaliana by functional expression in Saccharomyces cerevisiae.

ATP sulfurylase, the first enzyme in the sulfate assimilation pathway of plants, catalyzes the formation of adenosine phosphosulfate from ATP and sulfate. Here we report the cloning of a cDNA encoding ATP sulfurylase (APS1) from Arabidopsis thaliana. APS1 was isolated by its ability to alleviate the methionine requirement of an ATP sulfurylase mutant strain of Saccharomyces cerevisiae (yeast). Expression of APS1 correlated with the presence of ATP sulfurylase enzyme activity in cell extracts. APS1 is a 1748-bp cDNA with an open reading frame predicted to encode a 463-amino acid, 51,372-D protein. The predicted amino acid sequence of APS1 is similar to ATP sulfurylase of S. cerevisiae, with which it is 25% identical. Two lines of evidence indicate that APS1 encodes a chloroplast form of ATP sulfurylase. Its predicted amino-terminal sequence resembles a chloroplast transit peptide; and the APS1 polypeptide, synthesized in vitro, is capable of entering isolated intact chloroplasts. Several genomic DNA fragments that hybridize with the APS1 probe were identified. The APS1 cDNA hybridizes to three species of mRNA in leaves (1.85, 1.60, and 1.20 kb) and to a single species of mRNA in roots (1.85 kb).

Amino Acid Sequence↗
PubMed1990

The first cases of Helicobacter pylori (Campylobacter pylori) reported from Costa Rica.

Two gastric antrum biopsies of each of 92 consecutive patients undergoing gastroendoscopy were studied. The first biopsy was cultured for Helicobacter (Campylobacter) pylori. The second specimen was fixed and processed for histopathological analysis. The bacteria were isolated from 34 (81%) of 42 patients with nonspecific chronic gastritis, 19 (90%) of 21 cases of duodenal or gastric peptic ulcer, and from 3 (23%) of 13 normal patients. The overall frequency of isolation was 62 (67%) of the 92 cases.

Adult↗
PubMedDate not supplied

[Controlled liberation of active principles by means of new galenic formulations].

Drugs inside a conventional galenic form are distributed between specific biological targets and other anatomical tissues. With the aim to obtain a more rational and a better therapeutic, one of the most promising possibilities by using the concept of vectorization: association of an active principle to an appropriate vector with the object to increase its action efficiency and efficacy. By this means, they do not just increase the affinity of the drug to the target but also active principle gets protected from a potentially hostile environment (hydrolytic enzymes, acid pH, etc.). The success in the extension of the applications of the vectorización depends more and more of an appropriate design, for what the fundamental objective of this revision will be the one of presenting the general characteristics and some of the current applications in these new galenic forms.

Drug Carriers↗