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Biomedical subjects

A Cruz

Publications and source records attributed to A Cruz.

At least 19 recordsLinked to original sources
PubMed2006

Determination of parathion in biological fluids by means of direct solid-phase microextraction.

A new and simple procedure for the determination of parathion in human whole blood and urine using direct immersion (DI) solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) is presented. This technique was developed using only 100 microL of sample, and ethion was used as internal standard (IS). A 65-microm Carbowax/divinylbenzene (CW/DVB) SPME fibre was selected for sampling, and the main parameters affecting the SPME process such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH effect were optimized to enhance the sensitivity of the method. This optimization was also performed to allow the qualitative determination of parathion's main metabolite, paraoxon, in blood. The limits of detection and quantitation for parathion were 3 and 10 ng/mL for urine and 25 and 50 ng/mL for blood, respectively. For paraoxon, the limit of detection was 50 ng/mL in blood. The method showed linearity between the LOQ and 50 microg/mL for both matrices, with correlation coefficients ranging from 0.9954 to 0.9999. Precision and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries were 35.1% for urine and 6.7% for blood. Other parameters such as dilution of sample and stability were also validated. Its simplicity and the fact that only 100 microL of sample is required to accomplish the analysis make this method useful in forensic toxicology laboratories to determine this compound in intoxications, and it can be considered an alternative to other methods normally used for the determination of this compound in biological media.

Humans↗
PubMed2006

Determination of quinalphos in blood and urine by direct solid-phase microextraction combined with gas chromatography-mass spectrometry.

A new method based on direct solid-phase microextraction (DI-SPME) followed by gas chromatography-mass spectrometry was developed for the purpose of determining quinalphos in blood and urine. Two types of coated fibre have been assayed and compared: carbowax/divinylbenzene (CW/DVB 65 microm) and polydimethylsiloxane (PDMS 100 microm). The main parameters affecting the SPME process such as temperature, salt addition, pH, stirring and adsorption/desorption time profiles were optimized to enhance the sensitivity of the procedure. The method was developed using only 100 microL of blood and urine. Limits of detection of the method for blood and urine matrices were, respectively, 10 and 2 ng/mL. Linearity was established over concentration ranges from 0.05 to 50 microg/mL for blood, and 0.01 to 50 microg/mL for urine, with regression coefficients ranging between 0.9991 and 0.9999. Intra- and interday precision values were less than 13%, and accuracy was within +/-15% of the nominal concentration for all studied levels in both matrices. Absolute recoveries were 14 and 26% for blood and urine, respectively.

Adsorption↗
PubMed2006

Solid-phase microextraction for gas chromatographic/mass spectrometric analysis of dimethoate in human biological samples.

A new, simple and rapid procedure for the determination of dimethoate in urine and blood samples was developed using direct immersion solid-phase microextraction and gas chromatography/mass spectrometry. This technique required only 0.1 mL of sample, and ethion was used as internal standard. Two types of coated fibre were compared (100 microm polydimethylsiloxane, and 65 microm Carbowax/divinylbenzene). Other parameters, such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH, were optimized to enhance the sensitivity of the method. Limits of detection (LODs) and quantitation (LOQs) were 50 and 100 ng/mL for urine and 200 and 500 ng/mL for blood, respectively. The method was found to be linear between the LOQ and 40 microg/mL for urine, and between the LOQ and 50 microg/mL for blood, with correlation coefficients ranging from 0.9923-0.9996. Precision (intra- and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries of dimethoate were 1.24 and 0.50% for urine and blood, respectively. Because of its simplicity and the fact that small volumes of sample are used, the described method can be successfully used in the diagnosis of poisoning by this pesticide, namely in those situations where the sample volume is limited, as frequently occurs in forensic toxicology.

Dimethoate↗
PubMed2006

Human papillomavirus in men: comparison of different genital sites.

OBJECTIVE: To elucidate which anatomical sites need to be sampled to detect human papillomavirus (HPV) infection in the lower male genital tract. METHOD: In an HPV survey of Mexican soldiers (median age 24 years; range 16-50 years), a cell sample from 2 cm deep into the distal urethra (group 1; n = 168 men), or 0.5 cm deep into the meatus urethralis (group 2; n = 414 men) was collected, along with a sample from the external genitalia. The different samples were tested for 27 HPV types using a polymerase chain reaction based strip assay. RESULTS: HPV DNA was detected more frequently in external genitalia samples (46.4%) than in the urethra (20.8%) or meatus samples (12.1%). Lack of samples from the urethra or meatus would have led to 5.1% and 1.5% false HPV negative results, respectively. The most frequently detected high risk HPV types (HPV 59, 52, 51, and 16) were similar in different sites, whereas low risk types were found rarely in urethra samples. CONCLUSIONS: The addition of cell samples from the meatus to those from external genitalia contributed negligibly to the evaluation of the prevalence of HPV in men. HPV detection was slightly improved by the addition of urethra samples, but the gain may not justify the discomfort of the procedure in large epidemiological studies.

Adolescent↗
PubMed2005

Ab initio study of the reaction of H2 with an AuPt3 cluster.

The study of the interaction of a pyramidal tetramer of AuPt3 with H2 is carried out by means of Hartree-Fock self-consistent field (SCF) calculations using relativistic effective core potentials and multiconfigurational SCF plus multireference variational and perturbational on second-order Moller-Plesset configuration interaction calculations. The AuPt3-H2 interaction was carried out in C(s) symmetry. The three lowest electronic states X 2A", A 2A', and a 4A' of the bare cluster were considered in order to study this interaction. The AuPt3+H2 reaction by a Pt vertex shows that AuPt3 cluster in the three lowest-lying electronic states can spontaneously capture and dissociate the H2 molecule. While, by the AuPt2 face side, the AuPt3 cluster only in the A 2A' electronic state can capture and dissociate the H2 molecule after surmounting a small energy barrier. For the Au vertex, this cluster in the three electronic states can also spontaneously capture and dissociate the H2 molecule. On the other hand, by the Pt3 face side, the AuPt3 cluster is able to capture and dissociate the H2 molecule after surmounting energy barriers, where the AuPt3 (X 2A" and 4A'-H2 adsorption are slightly activated.

Journal Article↗
PubMed2005

Liquid chromatography-electrospray ionisation mass spectrometry for the determination of nine selected benzodiazepines in human plasma and oral fluid.

A new simple and rapid liquid chromatographic-mass spectrometric technique was designed for the determination of nine benzodiazepines in plasma and oral fluid. Benzodiazepines were extracted from alkalinised spiked and clinical plasma and oral fluid samples using a single step, liquid-liquid extraction procedure with diethyl ether. The chromatographic separation was performed with a Xterra RP18, 5 microm (150 x 2.1 mm i.d.) reversed-phase column using deuterated analogues of the analytes as internal standard. The recovery ranged from 70.3 to 86.9% for plasma and 63.9 to 77.2% for oral fluid. The limits of detection ranged from 0.5 to 1 ng/ml in plasma and 0.1 to 0.2 ng/ml for oral fluid. The method was validated for all the compounds, including linearity and the main precision parameters. The procedure, showed to be sensitive and specific, was applied to real plasma and oral fluid samples. The method is especially useful to analyse saliva samples from drivers undergoing roadside drug controls.

Benzodiazepines↗
PubMed2005

Interfacial properties of pulmonary surfactant layers.

The composition of the pulmonary surfactant and the border conditions of normal human breathing are relevant to characterize the interfacial behavior of pulmonary layers. Based on experimental data methods are reviewed to investigate interfacial properties of artificial pulmonary layers and to explain the behavior and interfacial structures of the main components during compression and expansion of the layers observed by epifluorescence and scanning force microscopy. Terms like over-compression, collapse, and formation of the surfactant reservoir are discussed. Consequences for the viscoelastic surface rheological behavior of such layers are elucidated by surface pressure relaxation and harmonic oscillation experiments. Based on a generalized Volmer isotherm the interfacial phase transition is discussed for the hydrophobic surfactant proteins, SP-B and SP-C, as well as for the mixtures of dipalmitoylphosphatidylcholine (DPPC) with these proteins. The behavior of the layers depends on both the oligomerisation state and the secondary structure of the hydrophobic surfactant proteins, which are controlled by the preparation of the proteins. An example for the surface properties of bronchoalveolar porcine lung washings of uninjured, injured, and Curosurf treated lavage is discussed in the light of surface behavior. An outlook summarizes the present knowledge and the main future development in this field of surface science.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2005

Randomized clinical trial of the effect of intravenous fluid administration on hormonal and renal dysfunction in patients with obstructive jaundice undergoing endoscopic drainage.

BACKGROUND: Renal dysfunction in patients with biliary obstruction is associated with extracellular water depletion. This study examined the effect of preoperative saline infusion before biliary drainage on hormonal and renal functional derangements in patients with obstructive jaundice. METHODS: In a randomized study, 49 patients with malignant obstructive jaundice were investigated at baseline, on the day of drainage, and at 24 h, 72 h and 7 days after internal endoscopic biliary drainage. Patients were randomized to receive (n = 22) or not to receive (n = 27) 3000 ml normal saline intravenously for 24 h before drainage. Variables analysed included extracellular water volume, creatinine clearance, and serum levels of aldosterone, renin, atrial natriuretic peptide (ANP), vasopressin and albumin. RESULTS: Preoperative saline infusion produced a rise in creatinine clearance, diuresis, ANP concentration and extracellular water volume but this did not translate into better recovery of renal function after operation. Drainage produced a fall in creatinine clearance in all patients, but hormonal and renal function had recovered by 2 days after restoration of bile flow, independently of preoperative hydration. CONCLUSION: Fluid administration expands the extracellular water compartment before drainage but fails to improve renal function after drainage. Definitive improvement in endocrine and renal function requires the restoration of bile flow into the duodenum.

Adult↗
PubMed2005

Multivariate analysis of factors associated with renal dysfunction in patients with obstructive jaundice.

BACKGROUND: The aim was to evaluate the factors determining preoperative renal dysfunction in patients with obstructive jaundice. METHODS: In a prospective cross-sectional observational study, 63 patients, 27 with benign and 36 with malignant obstructive jaundice, were investigated at admission and compared with 25 healthy control subjects. Variables analysed included extracellular body water (ECW) compartment, plasma levels of aldosterone, renin, atrial natriuretic peptide, vasopressin, nitric oxide, endothelin (ET) 1 and prostaglandin E2 (PGE2), urinary nitric oxide and PGE2, serum albumin and renal function. RESULTS: The metabolic profile of obstructive jaundice was characterized by a depletion of the ECW (P = 0.004), and increased plasma levels of atrial natriuretic peptide (P < 0.001), ET-1 (P = 0.044), vasopressin (P = 0.017), aldosterone (P = 0.005) and renin (P = 0.001). Increased plasma (P < 0.001) and urinary (P = 0.001) PGE2 levels were also found. Fifty-four per cent of patients had a creatinine clearance of less than 70 ml/min. In multivariate analysis, serum bilirubin, renin, ET-1, PGE2, decreased urinary sodium excretion and age were identified as predictors of renal dysfunction. CONCLUSIONS: Renal dysfunction in patients with obstructive jaundice was associated with the degree of biliary obstruction, age of the patient and reduced urinary sodium excretion. These alterations were closely related to derangements in sodium- and water-regulating hormones.

Atrial Natriuretic Factor↗
PubMed2005

Ultrasonographic findings in knee osteoarthritis: a comparative study with clinical and radiographic assessment.

OBJECTIVE: To compare ultrasonographic (US) findings with clinical and radiographic assessment in knee osteoarthritis (OA). METHODS: Fifty patients with primary knee OA were studied. Clinical assessment of both knees was performed by the same rheumatologist who recorded a visual analogue scale (VAS) for pain (VASP). All patients underwent a US examination of their knees by a second blinded rheumatologist. Weight-bearing anteroposterior and lateral knee radiographs were read by a third blinded rheumatologist who assessed the Kellgren and Lawrence (K-L) grade, the femorotibial (FT) space width and the presence of patello-femoral degenerative signs. RESULTS: Forty patients had bilateral symptomatic knee OA and 10 unilateral symptomatic OA. All knees showed radiographic FT degenerative signs. US findings in symptomatic knees were effusion (47%), protrusion of the medial meniscus (MMP) with displacement of the medial collateral ligament (MCLD) (61%) and Baker's cyst (22%). US effusion, MMP and MCLD were associated with a significantly higher VAS score for pain (P<0.05). MMP was associated with medial FT space width (P<0.05). Patients who had a difference between VAS score for pain in each knee greater than 30 (28 patients) showed significantly more unilateral effusion, MMP, MCLD and worse K-L grade in the more symptomatic knee than those with a difference lesser than 30 (22 patients). CONCLUSION: Knee effusion and MMP with MCLD are associated with pain in knee OA. In addition, MMP may contribute to the radiographic medial FT space narrowing. We propose US for assessing periarticular and intraarticular abnormalities involved in the pathophysiology of knee OA.

Aged↗
PubMed2005

Neonatal BCG protection against tuberculosis lasts for 20 years in Brazil.

Bacille Calmette-Guérin (BCG) efficacy against pulmonary disease is highly variable; until very recently there was no evidence of protection after 10 years. In the control arm of a trial of efficacy of revaccination of schoolchildren in Brazil we found substantial protection (39%; 95%CI 9-58) of neonatal BCG against all forms of tuberculosis (TB) 15-20 years after vaccination, much longer than previously believed. This confirms recent findings from an earlier trial, and must be considered in the design of trials of new TB vaccines and in policy decisions based on assumed lack of neonatal BCG protection with time.

Adolescent↗
PubMed2004

Development and validation of a method for the quantitation of Delta9tetrahydrocannabinol in oral fluid by liquid chromatography electrospray-mass-spectrometry.

Analysis of Delta(9)tetrahydrocannabinol (Delta(9)THC) and its metabolites in biological samples is of great relevance for forensic purposes. In the case of oral fluid (OF), the analysis should determine Delta(9)THC, whereas in urine, it detects the inactive metabolite tetrahydrocannabinol carboxylic acid (THC-COOH). Most laboratories analyze Delta(9)THC in such samples using GC-MS methods, but these procedures are time-consuming and involve unavoidable previous extraction and derivatization. No data is yet available on the application of liquid chromatography-mass-spectrometry to detect Delta(9)THC in oral fluid. We report a validation method in which the Delta(9)THC is isolated from oral fluid by a simple liquid-liquid extraction with hexane and subsequently analyzed by liquid chromatography-mass-spectrometry. The method here reported for the determination of Delta(9)THC in oral fluid only requires 200 microl of sample and achieves limits of detection of 2 ng/ml, and has been used to analyze oral fluid samples collected from current drug users.

Calibration↗
PubMed2004

Theoretical study of the H(2) reaction with a Pt(4) (111) cluster.

The C(s) symmetry reaction of the H(2) molecule on a Pt(4) (111) clusters, has been studied using ab initio multiconfiguration self-consistent field plus extensive multireference configuration interaction variational and perturbative calculations. The H(2) interaction by the vertex and by the base of a tetrahedral Pt(4) cluster were studied in ground and excited triplet and singlet states (closed and open shells), where the reaction curves are obtained through many avoided crossings. The Pt(4) cluster captures and activates the hydrogen molecule; it shows a similar behavior compared with other Pt(n) (n=1,2,3) systems. The Pt(4) cluster in their lowest five open and closed shell electronic states: (3)B(2), (1)B(2), (1)A(1) (3)A(1), (1)A(1), respectively, may capture and dissociate the H(2) molecule without activation barriers for the hydrogen molecule vertex approach. For the threefolded site reaction, i.e., by the base, the situation is different, the hydrogen adsorption presents some barriers. The potential energy minima occur outside and inside the cluster, with strong activation of the H-H bond. In all cases studied, the Pt(4) cluster does not absorb the hydrogen molecule.

Journal Article↗
PubMed2004

Anaerobic/aerobic treatment of colorants present in textile effluents.

The operation of an anaerobic/aerobic process used to degrade the colorants present in textile wastewater is presented. The objective is to produce water that can be reused. Two particular cases were studied: the degradation of a synthetic wastewater containing the colorant disperse blue 79 (DB79) as a model compound and a real textile effluent containing reactive azo dyes. The biodegradation was achieved using a single tank operated as sequencing batch reactor. It was observed that the DB79 was biotransformed to amines in the anaerobic stage decolorizing the wastewater. The amines formed were subsequently mineralized in the aerobic phase. An increase of toxicity was observed in the anaerobic stage due to the amines formation, but the wastewater was detoxified after the aerobic treatment. Removal efficiencies of DB79 around 92% were observed after the treatment. Around 96% of the initial color of the real wastewater was effectively removed. It was observed that the biomass pre-acclimatized to the degradation of DB79 was more effective for the color removal than a freshly inoculum used.

Azo Compounds↗
PubMed2003

Behaviour of Mycobacterium sp. NRRL B-3805 whole cells in aqueous, organic-aqueous and organic media studied by fluorescence microscopy.

The present work aimed at quantifying the viability and morphological changes occurring during the time course of the side-chain cleavage of beta-sitosterol, in aqueous, two-phase organic-aqueous and organic media by free resting cells of Mycobacterium sp. NRRL B-3805. The solvent used was bis(2-ethylhexyl) phthalate (BEHP). A 66.3% reduction in cell viability was observed after 24 h when the cells were incubated in phosphate buffer only, but the percentage of viable cells was constant thereafter. In biphasic systems with BEHP, cell viability was maintained at higher values in the first 48 h, during which complete degradation of substrate was achieved. The availability of oxygen, which should be higher in the biphasic system than in the aqueous system, and of a carbon and energy source, thus seem important for the cells to retain their viability. In biphasic systems, cells tended to shrink and decrease their surface roughness, i.e. to decrease their surface area, possibly as a way to protect themselves from mechanical stress due to the presence of organic-aqueous interfacial forces, which resulted in disaggregation of cell clusters. A method used to visualise BEHP droplets with a standard optical microscope showed that the cells adhered to the surface of the solvent droplets, but no cells were observed inside these. In pure BEHP medium, cells retained their viability level for at least 150 h, independently of a pre-incubation period, which did not seem to induce any adaptation effect. Solvent biocompatibility, higher oxygen availability and reduced interfacial stress could have contributed to this maintenance of viability.

Androstenedione↗
PubMed2002

[Characteristics of acute renal failure in elderly patients admitted to a small town hospital].

We studied the features of acute renal failure (ARF) in elderly patients treated in a hospital, without an intensive care unit, to identify etiological factors and establish adequate preventive measures and treatment. During twelve consecutive months we studied prospectively 99 patients with ARF diagnosed by conventional criteria, an incidence of 1,238 cases per million per year. ARF affected 1.78% of patients admitted to hospital. We analyzed age, sex, serum creatinine, diuresis, etiology, type of ARF, preexisting chronic diseases, treatment, complications and outcome. Preexisting chronic diseases were common, the most frequent being hypertension (54%) and diabetes (39%). Previous treatments for cardiovascular diseases were frequent (angiotensin-renin system blockade 35.4%, diuretics 50.5%). 79% of ARF arose in hospital, 21% outside hospital. ARF was pre-renal in 60%, renal in 31% and post-renal in 9%. 34.7% were caused by volume depletion, 23.4% by low cardiac output and 23.4% by infection. 44.4% of ARF patients had oliguria or anuria latrogenic factors contributed to the ethiology of ARF in 35.3% of patients. Hospital stay was doubled by ARF the presence of ARF and the mortality was 36.4%. The rate was higher in ARF arising in hospital than in ARF acquired before admission. Factors that had a significant influence on the mortality rate were comorbid conditions, oliguroanuria, ARF of renal origin and serum albumin. We conclude that ARF has a high incidence, morbidity and mortality in this elderly population. Volume depletion, associated cardiovascular pathology and pharmacological treatment are important etiological factors in those with ARF outside hospital. Adequate treatment of ARF and avoidance of nephrotoxic medications are necessary in hospital.

Acute Kidney Injury↗
PubMed2001

Superficial disposition of the N-terminal region of the surfactant protein SP-C and the absence of specific SP-B-SP-C interactions in phospholipid bilayers.

A dansylated form of porcine surfactant-associated protein C (Dns-SP-C), bearing a single dansyl group at its N-terminal end, has been used to characterize the lipid-protein and protein-protein interactions of SP-C reconstituted in phospholipid bilayers, using fluorescence spectroscopy. The fluorescence emission spectrum of Dns-SP-C in phospholipid bilayers is similar to the spectrum of dansyl-phosphatidylethanolamine, and indicates that the N-terminal end of the protein is located at the surface of the membranes and is exposed to the aqueous environment. In membranes containing phosphatidylglycerol (PG), the fluorescence of Dns-SP-C shows a 3-fold increase with respect to the fluorescence of phosphatidylcholine (PC), suggesting that electrostatic lipid-protein interactions induce important effects on the structure and disposition of the N-terminal segment of the protein in these membranes. This effect saturates above 20% PG molar content in the bilayers. The parameters for the interaction of Dns-SP-C with PC or PG have been estimated from the changes induced in the fluorescence emission spectrum of the protein. The protein had similar K(d) values for its interaction with the different phospholipids tested, of the order of a few micromolar. Cooling of Dns-SP-C-containing dipalmitoyl PC bilayers to temperatures below the phase transition of the phospholipid produced a progressive blue-shift of the fluorescence emission of the protein. This effect is interpreted as a consequence of the transfer of the N-terminal segment of the protein into less polar environments that originate during protein lateral segregation. This suggests that conformation and interactions of the N-terminal segment of SP-C could be important in regulating the lateral distribution of the protein in surfactant bilayers and monolayers. Potential SP-B-SP-C interactions have been explored by analysing fluorescence resonance energy transfer (RET) from the single tryptophan in porcine SP-B to dansyl in Dns-SP-C. RET has been detected in samples where native SP-B and Dns-SP-C were concurrently reconstituted in PC or PG bilayers. However, the analysis of the dependence of RET on the protein density excluded specific SP-B-Dns-SP-C associations.

1,2-Dipalmitoylphosphatidylcholine↗