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Biomedical subjects

C Otero

Publications and source records attributed to C Otero.

At least 19 recordsLinked to original sources
PubMed2005

General characterization of noncommercial microbial lipases in hydrolytic and synthetic reactions.

Fourteen noncommercial preparations of microbial lipases were investigated with respect to their catalytic activity for hydrolysis and synthesis of ester bonds. Six of the lipases were derived from microorganisms that have not previously been described as lipase producers, and another four were characterized for the first time. The synthetic reactions were carried out in two solvents of different polarities (n-heptane and acetone) using a series of fatty acids and primary and secondary alcohols with different chain lengths. Under the culture conditions employed, Pseudomonas cepacia produced more active enzyme than the other microorganisms. The lipase preparations produced using Ovadendron sulphureo-ochraceum, Monascus mucoroides, Monascus sp., Fusarium oxysporum, Penicillium chrysogenum, Rhodotorula araucariae, Pseudomonas cepacia, Streptomyces halstedii, and Streptomyces sp.were the most efficient catalysts for hydrolysis at lipid-water interfaces. Enzyme preparations from P. cepacia, Streptomyces sp., S. halstedii, and R. araucariae were good biocatalysts for esterification in the polar medium (acetone). When the lipase preparations with the greatest activity for hydrolytic reactions were excluded, regression analysis of the data for the hydrolytic and synthetic activities of the remaining lipase preparations yielded high multiple correlation coefficients for these reactions in both n-heptane and acetone (R = 0.82 and 0.91, respectively).

Acetone↗
PubMed2004

[Metabolic imaging by positron emission tomography using [18F] fluorodeoxiglucose in developmental disorders].

INTRODUCTION: Developmental disorders are a common pathological condition in Neuropaediatrics and do not usually present characteristic anatomical alterations in the different neuroanatomical imaging tests that can be employed, such as computerised axial tomography or magnetic resonance (MR). Positron emission tomography (PET) using [18F] fluorodeoxiglucose (PET FDG), one of the battery of imaging tests currently available, enables us to obtain data about brain activity in a non invasive manner. PATIENTS AND METHODS: A group of 39 patients with developmental disorders from the Hospital del Mar was analysed. They were submitted to PET FDG brain metabolism tests and in some cases hybrid PET MR images were also obtained; findings were then correlated against the clinical progression of the patients. RESULTS AND CONCLUSIONS: The alterations that were observed showed predominantly bilateral thalamic, mesial temporal and orbital frontal hypometabolism. This alteration of the limbic system, which has no correlation with anatomical damage, can be a predictor of the clinical progression and of the confirmation of the presence of alterations in the brain functions in this type of patients.

Brain↗
PubMed2001

Part III. Direct enzymatic esterification of lactic acid with fatty acids.

Lipase catalyzed esterification reactions between lactic acid and several fatty acids have been studied. Difficulties arise in esterifying lactic acid because of the potential for this substance to act both as an acyl donor and as a nucleophile. These difficulties were minimized via strategies which greatly increased the yield of the desired ester. Use of the companion fatty acid in excess with respect to lactic acid in an apolar solvent (n-hexane) in which the lactic is not completely dissolved has been employed to minimize the potential for lactic acid to act as an acyl donor in a self-polymerization reaction.Beneficial and sinergistic effects of both silica gel and molecular sieves on conversion to the desired product are described. However, careful control of the amount of molecular sieves used is required. This fact is a consequence of two opposing effects of this material: i.e. adsorption of both lactic acid and water from the reaction mixture. For reaction between caprylic and lactic acids, use of an excessive amount of enzyme reduces the extent of conversion to 2-O-caproyl-lactic acid.A very pure ester of the L-enantiomer (optical rotation of [alpha]D(25) = -23.5) can be prepared in n-hexane using a four fold excess of caprylic acid and Candida antarctica lipase. Optimum reaction conditions lead to 35% yield of 2-O-caproyl-lactic acid, a result which is close to the maximum yield that can be enantioselectively obtained from commercial grade lactic acid (68 mole per cent monomer).

Journal Article↗
PubMed2001

Kinetics of the lipase-catalyzed synthesis of glucose esters in acetone.

A simple kinetic model derived from a ping-pong bi-bi mechanism is proposed to describe the lipase-catalyzed esterification of glucose with fatty acids. The mathematical expressions derived from this model have been tested using several sets of data obtained from reactions carried out under different reaction conditions. The predicted values provide very good fits of the experimental data for temperatures from 30 to 60 degrees C, enzyme loadings from 90 to 180 mg, and fatty acid concentrations from 0.33M to 1M. Experiments conducted at different temperatures permit one to estimate an activation energy of approximately 12 kcal/mol for the rate-limiting step of the reaction (formation of the acyl-enzyme complex). The model also considers the kinetics of inactivation of the biocatalyst during the reaction.

Acetone↗
PubMed2001

Enzymatic synthesis of amide surfactants from ethanolamine.

The condensation of a primary amine with fatty acids has been studied to determine optimum conditions for selective formation of amide surfactants via enzymatic amidification. Monoacylated ethanolamide and the diacylated amide-ester can be isolated from the reaction mixture, but the monoacylated ester cannot be isolated. The selectivity of the reaction depends on the solubility of the intermediate amide. Continuous precipitation of this product decreases the amount of amide-ester produced. Solubility values of the desired product (amide) are reported for different conditions.In acetonitrile, the ethyl ester of the corresponding fatty acid has been used successfully to avoid formation/precipitation of the ion-pair of the precursor reagents. In this medium, use of the transacylation reaction permits one to accelerate the reaction without producing a significant change in the selectivity toward the intermediate amide. This strategy is not successful in n-hexane where the solubilities of both ethanolamine and its ion-pair with lauric acid are similar.Results obtained for high loadings of substrates have been analyzed. In n-hexane and acetonitrile, the kinetics of the direct acylation reactions are controlled by the limited solubility of the ion pair formed by the two precursor reagents For the transacylation reaction in acetonitrile, at a sustrate loading of 2 mol l(-1,) selective production of as much as 92 mole percent N-acyl ethanolamine was observed in only 1.5 h.

Journal Article↗
PubMed2001

Visual and semiquantitative analysis of 18F-fluorodeoxyglucose positron emission tomography using a partial-ring tomograph without attenuation correction to differentiate benign and malignant pulmonary nodules.

OBJECTIVE: Many studies have reported the use of attenuation-corrected positron emission tomography with 18F-fluorodeoxyglucose (FDG PET) with full-ring tomographs to differentiate between benign and malignant pulmonary nodules. We sought to evaluate FDG PET using a partial-ring tomograph without attenuation correction. METHODS: A retrospective review of PET images from 77 patients (range 38-84 years of age) with proven benign or malignant pulmonary nodules was undertaken. All images were obtained using a Siemens/CTI ECAT ART tomograph, without attenuation correction, after 185 MBq 18F-FDG was injected. Images were visually graded on a 5-point scale from "definitely malignant" to "definitely benign," and lesion-to-background (LB) ratios were calculated using region of interest analysis. Visual and semiquantitative analyses were compared using receiver operating characteristic analysis. RESULTS: Twenty lesions were benign and 57 were malignant. The mean LB ratio for benign lesions was 1.5 (range 1.0-5.7) and for malignant lesions 5.7 (range 1.2-14.1) (p < 0.001). The area under the ROC curve for LB ratio analysis was 0.95, and for visual analysis 0.91 (p = 0.39). The optimal cut-off ratio with LB ratio analysis was 1.8, giving a sensitivity of 95% and a specificity of 85%. For lesions thought to be "definitely malignant" on visual analysis, the sensitivity was 93% and the specificity 85%. Three proven infective lesions were rated as malignant by both techniques (LB ratio 2.6-5.7). CONCLUSIONS: FDG PET without attenuation correction is accurate for differentiating between benign and malignant lung nodules. Results using simple LB ratios without attenuation correction compare favourably with the published sensitivity and specificity for standard uptake ratios. Visual analysis is equally accurate.

Adult↗
PubMed2000

Vaginal bacterial microflora modifications during the growth of healthy cows.

The aim of this work was first, to determine the predominant groups capable of colonizing the vagina and maintaining high numbers with time. The normal microbial flora of the cow's vagina and its evolution from weaning to service was then studied using standard microbiological methods. The results show that the most dominant bacteria belong to the streptococci, followed by the staphylococci, with similar levels during the whole study period. Enterobacteriaceae and lactobacilli were present at very low levels, the latter increasing during the cow's growth, suggesting some kind of hormonal influence. The results will allow the selection of micro-organisms with probiotic characteristics, classified as GRAS (Generally Regarded as Safe), to be used in the prevention of infections in the vaginal tract of cows, such as metritis, which produces delayed periods between partum and conception, and consequent economic losses.

Animals↗
PubMed1999

[Respiratory failure in the Guillain Barré syndrome].

Severe involvement of the respiratory muscles is seen in 25% of patients with a diagnosis of Guillain Barré syndrome. In order to evaluate the clinical characteristics and evolution of this disorder we reviewed the clinical records of patients admitted with this diagnosis to our Hospital between January 1987 and December 1996. We identified 44 patients with respiratory failure. The age was 34.0 +/- 14.1 years, 31 patients were male and 13 female; 70.5% required mechanical ventilation (MV). The time elapsed between the beginning of symptoms and MV was 9.4 +/- 8.0 days. Total duration of MV was 1,224 +/- 1,208 hours. Patients who required ventilatory support during the first 48 hours of evolution had a significantly longer duration of MV compared to the rest of the group (2,100 +/- 2,076 vs 934 +/- 735 hours, p < 0.05). Two of the survivors needed ventilatory support for more than 6 months. All patients showed quadriparesia, 55% had cranial nerve involvement and 43% had autonomic dysregulation. Twenty-four percent had a positive serologic titer for cytomegalovirus infection. The vital capacity measured before the beginning of MV was 1,050 +/- 378 ml and at discharge 2,837 +/- 1,080 ml. Mortality was 18%, with a higher mean age among those who died (44.9 +/- 17.5 years vs 31.9 +/- 12.5, p < 0.02). Mortality was also related to sepsis, barotrauma and severe autonomic dysfunction. In our group, we identified male preponderance, a high percentage of MV with an extended duration, and a longer MV time in the group of patients with a faster evolution.

Adolescent↗
PubMed1998

Quantitative enzymatic production of 1,6-diacyl sorbitol esters

The enzymatic synthesis of several sorbitol diesters whose HLB values are similar to those of monoglycerides (the largest single type of food-grade emulsifiers) has been studied. The procedure is carried out by the simple addition of the polyol to a solution of the fatty acid and is based on continuous precipitation of the diester formed at a low temperature. A solvent of relatively low toxicity (acetone) was used. Pure fatty acids of different chain lengths (lauric and caprylic acids) were employed. The procedure was also tested using the acids obtained from total hydrolysis of olive oil, as an example of industrial feedstocks of fatty acids. This synthesis strategy gave complete conversion of sorbitol and >95% yields of the corresponding 1,6-diesters. In addition, a strategy to reduce the reaction time is reported. The enzymatic procedure permits minimization of the solvent/sugar ratio because it does not require complete dissolution of the sugar in the organic solvent. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗
PubMed1998

Quantitative enzymatic production of 6-O-acylglucose esters

Selective production of emulsifiers from glucose and fatty acids has been achieved using an immobilized Candida antarctica lipase. Optimization of process selectivity considers the solubilities of the sugar and its monoesters in acetone at different temperatures, the percentage of this organic solvent in the reaction mixture, and the reaction temperature. The solvent (acetone) is both easily eliminated and accepted by the European Community for use in the manufacture of foods and/or food additives. Different fatty acids with a longer length chain than that of caprylic acid may be employed. For saturated fatty acids longer than lauric acid, continuous precipitation of the monoester as it is formed at 40 degrees C permits nearly complete conversion (98%) of glucose to the monoester within 2-3 days. The procedure does not require total dissolution of the sugar, and precipitation of the monoester permits selective conversion of charges of glucose higher than 100 mg/mL solvent. A scaleup of the process under the optimum conditions gives high yields of 6-O-lauroyl glucose, which may be readily prepared on a gram scale. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗
PubMed1996

[The serum markers in the pregnant population of the basic health area of El Natahoyo (Gijón)].

OBJECTIVES: To find the prevalence of markers of rubeola, Toxoplasma, lues, HIV and hepatitis A, B and C viruses in the pregnant women of a health district; and these markers' correlations with epidemiological and socio-demographic antecedents. PATIENTS: 129 pregnant women from the 5.3 Health District in Asturias with birth predicted for between August 1994 and October 1995. A descriptive study of epidemiological, socio-demographic and serological data; statistical calculation with RSigma. RESULTS: 109 pregnant women (84.5%) were assessed, average age 28.6, including 9 abortions with path. analysis in the first three months. HIV was tested in 15 cases, all negative. Toxoplasma was positive in 46 cases, with no association with other variables. Rubeola was negative in 6 cases, all > 25 years old, with overall vaccination coverage of 42.2% and 64.7% for < 26-year-olds. One case of lues was found. The HC test was negative in all the pregnant women, with 4% of HBsAg+, related to being gypsy and to AF of hepatopathy. HA IgG was positive in 52 cases (52%) and more common among gypsies vs. the rest. In the latter group there was increasing prevalence according to age. CONCLUSIONS: 1) HIV screening is not common. 2) There is a high percentage of pregnant women with no immunity to Toxoplasma. 3) Low rubeola vaccination coverage among women under 26 was found. 4) There is a higher percentage of HBsAg+ cases in comparison with other areas, but not with the HC virus. 5) A high percentage of cases had no previous contact with the HA virus.

Adult↗
PubMed1996

A controlled study of intravenous immunoglobulin in demyelinating neuropathy with IgM gammopathy.

Eleven patients with demyelinating polyneuropathy associated with monoclonal IgM antibodies were randomized to receive IVIg or placebo, monthly, for 3 months in a double-blind study. After a washout period, they crossed over to the alternate therapy. Response was gauged by evaluating muscle strength, sensation, and neuromuscular symptoms at baseline, after 3 months, and at treatment's end. After IVIg therapy, the strength improved in only 2 of 11 patients, by 28 and 38.5 points from baseline, and declined after placebo. In 1 other patient, the sensory score improved by 13 points. Antibody titers to MAG/SGPG or gangliosides did not appreciably change. We conclude that IVIg has only a modest benefit to not more than 18% of patients with IgM paraproteinemic demyelinating neuropathy.

Age of Onset↗
PubMed1996

[Intracardiac thrombosis in a patient with primary antiphospholipid syndrome. Report of a case].

Antiphospholipid antibody syndrome is characterized by arterial or venous thrombosis associated to the presence of antiphospholipid antibodies. We report a 32 atrial thrombus. Four months later, being with anticoagulant treatment, he had a deep venous thrombosis. A new echocardiogram did not show the atrial thrombus. The laboratory work-up confirmed an antiphospholipid syndrome. Five months later the patient has not presented new thrombotic episodes and is receiving oral anticoagulants and antiplatelet therapy.

Adult↗
PubMed1995

Influence of the hydrophobicity of lipase isoenzymes from Candida rugosa on its hydrolytic activity in reverse micelles.

Two isoenzymes of Candida rugosa lipase, having the same mol.wt., size and similar aminoacid sequence, were studied in reverse micelles of AOT. The results demonstrated the relevance of lipase hydrophobicity in reactions in anionic micelles. This is a key factor in mitigating the inhibition effect of charged micelles. The more hydrophobic isolipase A was a better biocatalyst for hydrolytic processes in these systems. Its alpha-helix content increased from 31% to 49% of the total structure in reverse micelles. A fluorescence study indicated a more apolar environment for the more hydrophobic isolipase A. Emission spectra of this isolipase in the AOT systems were blue shifted. At omega 0 values where each isolipase presented its maximum activity, a decrease of the emission intensity of Trp was found. An enzyme and substrate dependence of optimal omega 0 is reported. The different interaction of isolipases A and B with the micellar system produced an opposite omega 0 dependence to their stabilities. The more hydrophobic lipase A had higher stability at higher droplet sizes.

Candida↗
PubMed1994

Effect of high-dose intravenous immunoglobulin on amyotrophic lateral sclerosis and multifocal motor neuropathy.

OBJECTIVE: To determine if high-dose intravenous immunoglobulin therapy is effective in improving muscle strength or in arresting the pace of disease progression in patients with rapidly progressive amyotrophic lateral sclerosis. DESIGN: An open-label pilot study of intravenous infusions of high-dose immunoglobulin administered once a month for 3 months in nine patients with classic amyotrophic lateral sclerosis. Selected patients had a rapidly progressive course with signs of worsening noticeably evident every 6 weeks prior to therapy. A patient with multifocal motor neuropathy with conduction block that presented as a lower motor neuron syndrome was concurrently treated to document the efficacy of the same preparation of immunoglobulin in a potentially treatable disease that simulates lower motor neuron syndrome. The efficacy of high-dose intravenous immunoglobulin infusions was assessed by objective measurement of maximum voluntary isometric contraction in all muscle groups of two limbs before and after therapy. SETTING: The Clinical Center of the National Institutes of Health, Bethesda, Md. RESULTS: All patients with amyotrophic lateral sclerosis worsened during the study. By the end of the third month, their mean total muscle scores (megascores) had declined by 71.2 points, from a mean of 369.7 (range, 200 to 605) to 298.5 (range, 130 to 552) points. The pace of progression did not change during the 4-month observation period. In contrast, the patient with multifocal motor neuropathy responded to intravenous immunoglobulin therapy and increased his megascores by 146 points after 3 months. The GM1 antibody titers were normal in all the patients. CONCLUSIONS: High-dose intravenous immunoglobulin, a prohibitively expensive drug, has no apparent therapeutic role in improving the symptoms or arresting the pace of progression in patients with amyotrophic lateral sclerosis. In contrast, multifocal motor neuropathy is an immunopathologically different disease that responds to intravenous immunoglobulin therapy.

Adult↗