Biomedical subjects

Carlos Guerrero

Publications and source records attributed to Carlos Guerrero.

4 recordsLinked to original sources

PubMed2005

Efficient approach for the reliable quantification and confirmation of antibiotics in water using on-line solid-phase extraction liquid chromatography/tandem mass spectrometry.

The potential of solid-phase extraction coupled on-line to liquid chromatography/electrospray tandem mass spectrometry (SPE-LC-ESI-MS/MS) has been investigated in this paper for the efficient sensitive quantification and confirmation of 16 antibiotics in water. The list of targeted analytes included 10 quinolones (oxolinic acid (OXO), nalidixic acid (NAL), flumequine (FLU), marbofloxacine (MAR), ofloxacine (OFLO), enrofloxacine (ENR), pefloxacine (PEF), ciprofloxacine (CIP), pipemidic acid (PIPE), norfloxacine (NOR)) and 6 penicillins (penicillin G (PEN), oxacillin (OXA), dicloxacillin (DIC), piperacillin (PIP), cloxacillin (CLO) and ampicillin (AMP)) that were determined in ground and surface water. The procedure is based on the injection of 9.8 mL of sample into the SPE-LC-MS/MS system and the measurement of antibiotics by selected reaction monitoring mode, using a triple quadrupole analyser. The method has been validated at realistic low concentrations that might be present in environmental water, i.e. 10 and 100 ng L(-1), obtaining recoveries between 74% and 123% with relative standard deviation lower than 14%. Matrix effects were not relevant in most of cases, except for ampicillin in surface water, where notable signal suppression was observed. The limits of detection were as low as 0.4-4.3 ng L(-1). The method developed allows the rapid screening and quantification of all the analytes selected by acquiring one MS/MS transition (normally the most sensitive) for each compound. It was applied to a number of actual surface and groundwater samples with several compounds being detected, mainly quinolones, at low ng L(-1) levels. Special attention was given to the confirmation of compounds detected in water due to the difficulties of obtaining confident confirmation at low ng L(-1). This matter has been of growing concern in the last few years as reflected by recent papers and correspondence. The acquisition of several MS/MS transitions for each compound detected in a second independent analysis allowed the unequivocal confirmation of identity, avoiding reporting false-positives. Finally, the potential of QTOF instruments to confirm positive samples has also been evaluated and compared with triple quadrupole analysers.

Anti-Bacterial Agents↗

PubMed2005

Technical strategies to approach aneurysms of the vertebral and posterior inferior cerebellar arteries.

OBJECT: Aneurysms of the vertebral artery (VA) and proximal posterior inferior cerebellar artery (PICA) are rare and challenging lesions, as they are located in front of the brainstem and surrounded by the lower cranial nerves. Many different approaches have been described for their treatment, and have yielded different results. With the use of different examples of lesions, the authors describe their surgical strategy in the management of VA and PICA aneurysms. METHODS: The far-lateral approach was used, and the potential of its different extensions according to the specific anatomical location and configuration of different types of aneurysms is emphasized. CONCLUSIONS: With the present knowledge of the microsurgical anatomy in the region of the foramen magnum, the far-lateral approach can be tailored to the specific anatomical and morphological configuration of an aneurysm in this region with good surgical results.

Cerebellum↗

PubMed2004

Identifying and structurally characterizing CD1b in Aotus nancymaae owl monkeys.

This study reports the molecular characterization and tissue expression of the non-human Aotus nancymaae primate CD1b isoform in the search for an experimental animal model to be used in evaluating the role of non-peptide antigen-presentation molecules in the immune response to infectious agents. CD1b expression on the surface of A. nancymaae peripheral blood monocyte-derived dendritic cells, shown by flow cytometry, was made possible by using human CD1b isoform antibodies. Studying the expression of CD1b-encoded transcripts revealed this molecule's broad distribution in several tissues. The A. nancymaae CD1b transcript-encoded amino-acid sequence showed 95.5% identity with the human sequence. Such high sequence homology was reflected in the identical structural conservation of how pockets A', C' and F' and tunnel T' conforming the antigen's binding site are organized, the similar arrangement of those amino-acids interacting with the T-cell receptor (TCR) during antigen presentation, and the conservation of YQNI-motif sequence in the cytoplasmatic tail (responsible for the molecule's intracellular trafficking in humans). Comparing the structure of human CD1a and CD1b and mouse CD1d proteins with CD1b structure in A. nancymaae obtained by minimization revealed that changes in the latter molecule's alpha1 and alpha2 domains imposed a narrowing of the antigen-binding groove in A. nancymaae CD1b. The high structural similarity between A. nancymaae CD1b and that from humans presented in this study leads to A. nancymaae being proposed as a suitable experimental animal model for analyzing CD1b in vivo, mainly in bacterial and parasite infections such as tuberculosis and malaria, respectively.

Amino Acid Sequence↗

PubMed2003

Optimization of access-port placement for the lap-band system.

BACKGROUND: The technical aspects of access-port (AP) placement are not generally described in Lap-Band series. METHODS: From November 2000 to April 2002, we performed Lap-Band procedures laparoscopically on 180 patients. A retrospective review was conducted of 3 consecutive AP-placement techniques in nonselected and demographically identical groups. In Group A (n=48, Nov. 2000 to July 2001), the AP was placed at the left subcostal margin. In Group B (n=23, Aug. 2001 to Sept. 2001), the AP was tunneled over the subcostal fascia towards the subxiphoid area. In Group C (n=109, Oct. 2001 to Apr. 2002), the AP tubing was tunneled over the subcostal fascia and connected to the AP, which was inserted through a 3-cm subxiphoid incision. RESULTS: AP-related problems occurred within the first few months following surgery. In Group A, 24 of the APs (50%) were tilted, and 14 (29%) were completely flipped over. 11 APs (23%) were found to be broken. 19 patients (40%) underwent an additional AP-related procedure. In group B, 12 APs (52%) were tilted and 1 patient required surgery to turn the AP. In Group C, 8 APs (7%) were turned slightly. 1 AP was found to be broken and required surgery to replace it. In this group, all APs were accessible for adjustment in the office. CONCLUSIONS: Tunneling the AP along the left subcostal area is an important technique to protect the AP system from breakage, by changing AP-tube position from vertical to horizontal in relation to abdominal wall movement. This technique also keeps the AP-tube connection over the fascia and protects it from "wear and tear" forces. The addition of fixation at the subxiphoid location helps maintain a straight orientation of the AP for easier adjustments.

Adult↗