Search PubMed⌕ Search

Biomedical subjects

A R Rodriguez

Publications and source records attributed to A R Rodriguez.

At least 19 recordsLinked to original sources
PubMed2005

Determination of (fluoro)quinolone antibiotic residues in pig kidney using liquid chromatography-tandem mass spectrometry. Part II: intercomparison exercise.

A recently in-house validated method for the liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination of eleven (fluoro)quinolone antibiotics (FQs) in pig kidney has been fully validated through an intercomparison exercise. This ring trial involved eight European laboratories and was based on the Commission Decision 2002/657/CE for validation of method and on the IUPAC protocol for method-performances studies. The laboratories data were submitted to a one-way analysis of variance. Satisfactory results were obtained for each FQ with regards to within- and between-laboratory reproducibility and accuracy. The method was validated for the simultaneous qualitative and quantitative determination of the eleven FQs in pig kidney around their maximum residue limit (MRL) as defined in the European Council Regulation 2377/90/EEC.

Animals↗
PubMed2005

Determination of (fluoro)quinolone antibiotic residues in pig kidney using liquid chromatography-tandem mass spectrometry. I. Laboratory-validated method.

A new LC-MS/MS method has been developed for the multiresidue determination of 11 (fluoro)quinolone antibiotics (FQs), including acidic and amphoteric species, around their maximum residue level (MRL) in pig kidney. The procedure involves a common sample preparation by solid-phase extraction on disposable extraction cartridges followed by a fast reversed-phase liquid chromatography-tandem mass spectrometry analysis. The method was validated according to the Commission Decision 2002/657/CE. The accuracy of the method was satisfactory with recoveries included in the interval 80-100%. The precision results showed mean repeatability and reproducibility coefficients of 7.4% and 11.8%, respectively. Limits of quantification much lower than the MRLs could be obtained.

Animals↗
PubMed2003

Study of the feasibility of using a pellicular anion-exchange column for separation of transferrin isoforms in human serum by HPLC with UV detection.

A method has been optimised for the separation of glycoforms of human serum transferrin, using a high-performance pellicular anion-exchange chromatographic column. The effect of the eluent pH and of the column temperature on the separation of transferrin glycoforms was studied using a standard solution of commercially available human serum transferrin. An HPLC system equipped with an ultraviolet detector was used for the analysis. No immunoassay was used after the anion-exchange chromatographic separation of the glycoforms, in contrast with most currently used methods. The method was applied to the separation and quantification of transferrin glycoforms in serum from a healthy, non-pregnant woman, after saturation of transferrin with iron and further precipitation of lipoproteins. The whole chromatographic run, including re-equilibration of the column, took 35 min.

Chromatography, High Pressure Liquid↗
PubMed2002

Development of new analytical methods for selenium speciation in selenium-enriched yeast material.

A sequential extraction allowing the discrimination of water-soluble and non-soluble selenium fractions has been developed to evaluate the availability of selenium (Se) in an Se-enriched yeast candidate reference material. The fractionation of selenium-containing compounds in the extracts was achieved on preparative grade 200 Superdex 75 and columns. It showed that water-soluble selenium is present in several fractions with a large mass distribution. Low-molecular- (< or = 10,000) and high-molecular-mass selenocompounds (range 10,000-100,000) were considered separately for further experiments. The analytical approach for low-molecular-mass selenocompounds was based onanion-exchange HPLC with on-line inductively coupled plasma (ICP) MS for quantitative analysis. Selenocystine, selenomethionine, selenite and selenate were quantified in the fractions isolated in preparative chromatography. The study revealed the existence of various unidentified Se species in yeast material. The Se-containing proteins in the yeast material have been further separated and selenium quantified by the combination of gel electrophoresis and electrothermal vaporization-ICP-MS. This new approach allows the separation of the proteins with high resolution by sodium dodecylsulfate-polyacrylamide gel electrophoresis and the sensitive determination of selenium in the protein bands.

Calibration↗
PubMed2002

Validation of a liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of 11 (fluoro)quinolone antibiotics in swine kidney.

A LC-MS-MS method has been validated for the simultaneous quantification of 11 (fluoro)quinolone antibiotics at the maximum residue level (MRL) in swine kidney. The studied compounds were danofloxacine, cinoxacine, ciprofloxacine, noxacine, enrofloxacine, flumequine, marbofloxacine, nalidixic acid, norfloxacine, ofloxacine and oxolinic acid. The method involves solid-phase extraction of these compounds followed by LC-MS-MS analysis using an electrospray ionisation interface. Limits of quantification < or = 50 microg/kg could be obtained in swine kidney, much lower than every MRL. The validation is discussed. This work was carried out in order to support the European Union policy on consumer health

Animals↗
PubMed2002

Identification, characterization and determination of metal-binding proteins by liquid chromatography. A review.

The use of liquid chromatography in the separation and determination of metal-binding proteins is reviewed. Advantages and drawbacks of different chromatographic techniques based on various principles: size exclusion, ion exchange (cationic and ionic), reversed phase and affinity, are presented and discussed. The topic "metal-binding proteins" is considered and presented from two different points of view. The first one regards metal speciation in biological samples (serum and blood). In metal speciation studies, the exact identity of the protein to which the metal is bound often remains unknown. The second point of view is that, frequently, the interest of analyzing metal-binding proteins is not related anymore to the metallic fraction of the protein, but to other chemical structures attached to the protein, such as carbohydrates, which indirectly determine how good the function of the protein is. In this review, special attention is paid to studies dealing with the glycosylation of transferrin, and with the glycated isoform of haemoglobin.

Chromatography, Liquid↗
PubMed2001

Identification and quantification of major bovine milk proteins by liquid chromatography.

In the field of food quality, bovine milk products are of particular interest due to the social and economic importance of the dairy products market. However, the risk of fraudulent manipulation is high in this area, for instance, replacing milk powder by whey is very interesting from an economic point of view. Therefore, there is a need to have suitable analytical methods available for the determination of all milk components, which is currently not the case, especially for the main proteins. The detection of potential manipulations requires then a clear analytical characterisation of each type of bovine milk, what constitutes the goal of this work. The separation of the major milk proteinic components has been carried out by ion-pair reversed-phase HPLC with photodiode array detection, using a C4 column. The overall optimisation has been achieved using a statistical experimental design procedure. The identification of each protein was ascertained using retention times, peak area ratios and second derivative UV spectra. Quantification was based on calibration curves drawn using purified proteins. Major sources of uncertainty were identified and the full uncertainty budget was established. The procedure was initially developed using the skimmed milk powder certified reference material CRM 063R and then applied to various types of commercial milks as well as to raw milk. The method is able to separate and quantify the seven major proteins (K-casein, alphas2-casein, alphas1-casein, beta-casein, alpha-lactalbumin, beta-lactoglobulin B and beta-lactoglobulin A) in one run and also to provide precise determinations of the total protein concentration. These are important results towards the further development of a reference method for major proteins in milk. In addition, the use of a certified material reference is suggested in order to make comparisons of method performances possible.

Animals↗
PubMed2001

Uncertainty estimation on the quantification of major milk proteins by liquid chromatography.

A detailed uncertainty budget is evaluated for the quantification of major milk proteins separated by reversed phase ion-pair high performance liquid chromatography (RP-IP HPLC). Recommendations from the International Organisation for Standardisation, Guide to the Expression of Uncertainty and the EURACHEM/CITAC Guide "Quantifying Uncertainty in Analytical Measurement" were followed resulting in the expression of combined uncertainties as an expanded uncertainty. The authors have identified the lack of a detailed description on all possible sources of uncertainty on chromatographic milk protein separations. Up to now, uncertainty has only been expressed as a random chromatographic variability, being exclusively measured by regression equations. On the contrary, the establishment of a full uncertainty budget permits a complete identification of all sources of uncertainty associated with the measurement. Thus, a better comprehension of the method is obtained. Having identified all sources of uncertainty, to the best of our knowledge, they are minimised (whenever possible) and combined. The importance of this identification is crucial, in particular, concerning previously neglected sources, in this example the combination of the interpolated injected mass of protein and its purity, having a dominant influence on the total combined uncertainty. The quality of the measurement (measured by its associated uncertainty statement, which should be based on a full uncertainty budget evaluation) is demonstrated. Moreover, due to the high precision of the proposed method, the total protein content, in addition to the group protein composition (i.e. total casein and whey protein content) is calculated with high reliability, which is an extremely useful factor regarding the establishment of milk provenance/adulteration. Combined relative standard uncertainties ranging from 3.3 up to 12.5% for individual protein concentration were found, whereas for total protein content, an overall combined relative standard uncertainty of 2.7% (liquid) and 3.3% (powdered samples) was achieved.

Animals↗
PubMed1997

Paracentric inversion involving the long arm of chromosome 9 resulting in deletion of abl gene.

We report on a new chromosomal finding in a newborn male with hypertelorism, apparently low-set malformed ears with patent canal, micrognathia with narrow high-arched palate, bilateral webbing of neck with low posterior hairline, widely spaced nipples, and complex heart anomalies. Initially, what appeared to be a simple paracentric inversion of the long arm of chromosome 9, that is, 46,XY, inv(9)(q31q34) by routine GTG-banding technique was later determined to be a paracentric inversion with deletion of the band 9q34.1 by FISH technique using an abl unique sequence DNA probe. Thus the cytogenetic diagnosis was modified to 46,XY,der(9) inv(9)(q31q34.1)del(q34.1). Nevertheless, the presence of telomeric repeat sequences in the inverted chromosome 9 suggests that either healing has occurred by adding [TTAGGG]n sequences to the non-telomeric end (q31) by the enzyme telomerase or telomeric sequences were not affected during this inversion process. This abnormality is a rare occurrence and has never been reported before either because of a high rate of lethality or it has been undetected by routine cytogenetic techniques. The other abnormal cases with apparent paracentric inversions could also have a complex nature with congenital anomalies associated with loss of "few" DNA sequences as exemplified here.

Abnormalities, Multiple↗
PubMed1997

Determination of copper, zinc and iron in broncho-alveolar lavages by atomic absorption spectroscopy.

Concentrations of Zn, Cu and Fe were measured in 157 broncho-alveolar lavages (BAL), before and after centrifugation, collected at the Leuven University Hospital (Belgium). Zn was measured by flame-atomic absorption spectroscopy, using direct calibration, while Cu and Fe were determined by electrothermal atomic absorption spectroscopy, using the method of standard additions. For Fe only 56 samples were measured. Most of the studied elements are present in the liquid phase (supernatant). About 90% of Cu concentrations lie between 0 and 15 micrograms/kg, while 90% of Zn concentrations are lower than 230 micrograms/kg, with 30% between 30 and 70 micrograms/kg, and 50% between 100 and 200 micrograms/kg. There seems to be a reverse relationship between Cu and Zn levels with high Cu going along with low Zn and vice versa.

Bronchoalveolar Lavage Fluid↗
PubMed1994

Mental health services under health reform: the less government, the better.

Federal and state governments are now rapidly preparing to restructure the delivery and financing of health care services in the United States. Unfortunately, the bureaucratic structures promised under managed competition do not acknowledge the successes of private sector "market-regulated" programs. A needlessly costly and burdensome system could evolve that will undermine the goals of improved access and quality of care.

Competitive Medical Plans↗
PubMed1992

Rotational ablation of coronary artery lesions using single, large burrs.

Previous clinical use of the Rotablator in coronary artery disease has involved a sequential increase in burr sizes up to 2 mm in diameter and has often utilized balloon adjunct to achieve an optimal result. We report our experience and describe our technique using a single, large burr (2.25, 2.5, or 2.75 mm diameter) without balloon assistance. The burr size was selected to approximate 70-90 percent of the apparent normal lumen diameter. Thirty-one patients with 36 lesions of complex morphology (eccentric, irregular, calcified, ulcerated, at bends, at bifurcations, completely occluded, as well as balloon failures) were successfully treated with the Rotablator. Results were assessed by computerized quantitative angiography. The percent diameter stenosis (mean +/- SD) for the group was reduced from 69.8 +/- 11.3% to 30.9 +/- 10% (p less than 0.001). The mean absolute diameter stenosis increased from 0.9 +/- 0.3 mm to 2.2 +/- 0.3 mm (p less than 0.001). Angiographically visible dissections were seen in 4 patients and were uncomplicated in 2. One patient had a non-Q-wave myocardial infarction. A fourth patient had a presumed acute occlusion 36 hr after the procedure, necessitating emergency bypass surgery, but without Q waves on the electrocardiogram or wall-motion abnormalities on the echocardiogram. Nitroglycerin was infused through the Rotablator catheter and has considerably lowered the degree and frequency of spasm. No other acute complications occurred. The mean procedure time using a single burr was shorter than when multiple burrs were used: 56.5 vs. 97.3 min, respectively (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Effects of dietary fiber and phytic acid on mineral availability.

In general, it has been shown that dietary fiber may bind metallic cations in both in vitro and in vivo studies. However, there clearly are many unresolved questions on the effects of high-fiber diets on mineral availability. On one side, the effects of fiber on the utilization of nutrients vary greatly with the amount and type of fiber. In addition, there are many agents in both food and the digestive tract that may affect the mineral binding to fiber: some agents may inhibit binding, while others will enhance it. Also, there are several major difficulties in drawing conclusions from the in vitro and in vivo studies due to the different experimental conditions, methods used to follow the mineral balance, etc. Finally, it must be borne in mind that fiber and phytic acid occur together in fiber-rich diets and, thus, it is difficult to separate the effects of fiber and phytate in the utilization of most essential polyvalent metallic ions. The studies summarized in this review show that the recommendation for increasing dietary fiber in Western communities would not be expected to have any adverse effect on mineral absorption if we increase not only the intake of fiber, but also the dietary intake of other food components such as protein (both vegetable and animal protein) and ascorbic, citric, and oxalic acids (in fruits and vegetables). The adequate intake of minerals, fat, and simple sugars are maintained with this type of diet. The recommendations should be best interpreted in such a way as to prevent the consumption of excessive amounts of phytate, particularly for those whose mineral needs are great. Further studies are still needed in this field in order to understand the conflicting results published in the literature regarding the effects of fiber on the utilization of minerals; however, the studies reviewed in this article may give us an idea of the complexity of mineral availability in fiber-rich, phytate-rich diets.

Animals↗
PubMed1990

Factors influencing the outcome of balloon aortic valvuloplasty in the elderly.

This study describes the short- and long-term outcome of 44 consecutive percutaneous balloon aortic valvuloplasty procedures performed in 42 elderly patients (age 77.8 +/- 7 years) with calcific aortic stenosis. The initial success rate was 95%, with the peak aortic valve pressure gradient declining from a mean of 82 +/- 32 mm Hg to 44 +/- 23 mm Hg and aortic valve area increasing from a mean of 0.59 +/- 0.15 cm2 to 0.83 +/- 0.40 cm2. One procedure-related death occurred and an additional three patients died less than or equal to 30 days after balloon aortic valvuloplasty. These patients all had New York Heart Association (NYHA) class IV heart failure symptoms prior to the procedure and their mean left ventricular ejection fraction (LVEF) (28 +/- 7%) was lower than that of hospital survivors (52 +/- 13%) (as was their ratio of left ventricular [LV] wall thickness-to-cavity ratio [0.50 +/- 0.10 versus 0.70 +/- 0.15]). At the time of hospital discharge after valvuloplasty, 76% of patients were asymptomatic or markedly improved (NYHA class I or II). After a mean follow-up of 15.5 months (range 2 to 26 months), however, 10 patients had died and 15 had undergone aortic valve replacement for recurrence of NYHA class III or IV symptoms. The adjusted 1- and 2-year survivals were 0.68 and 0.62, respectively, and adjusted 2-year event-free survival was 0.25. Proportional hazard regression analysis indicated that LVEF less than 40% was the only variable affecting survival (p less than 0.01) and was a possible indicator of event-free survival (p = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗