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Biomedical subjects

M E Soares

Publications and source records attributed to M E Soares.

9 recordsLinked to original sources
PubMed2004

Simultaneous determination of amphetamine derivatives in human urine after SPE extraction and HPLC-UV analysis.

Amphetamine derivatives are a class of compounds increasingly abused as recreational drugs in various regions of the world. Although d-amphetamine (AMPH) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) are among the most commonly used, the abuse of other designer drugs such as 4-bromo-2,5-dimethoxyphenethylamine (2C-B) and 4-methylthioamphetamine (4-MTA) and their involvement in acute intoxications has been increasingly reported. There is evidence that abusers ingest these compounds either alone or in combination and the respective monitoring is important for both legal and health care purposes in hospital emergency. In the present study a simple and clean solid-phase extraction procedure from urine of AMPH and MDMA, and their major metabolites p-hydroxyamphetamine (OH-AMPH) and methylenedioxyamphetamine (MDA) and 2C-B and 4-MTA was developed. Analysis was performed by HPLC-UV and the precision of the technique was between 2.9 and 5.3% for all compounds. For the overall procedure, the precision values were between 3.3 and 5.9%. Recoveries obtained from spiked urines at three concentration levels were better than 84 +/- 4% for the six compounds. The limit of detection of the method for the compounds (between 5.3 and 84.0 ng) enables their identification in urine after ingestion of fatal and non-fatal doses. The main advantages of the present method lie in its simple, clean and reliable SPE extraction method of the six amphetamine derivatives from urine followed by their simultaneous detection and quantification by liquid chromatography with UV detection.

Amphetamines↗
PubMed2001

Determination of amphetamine and its metabolite p-hydroxyamphetamine in rat urine by reversed-phase high-performance liquid chromatography after dabsyl derivatization.

The consumption of amphetamine is illicit and controlled due to both the elicited behavioural deviations and the toxicity effects reported in abusers. Thus, amphetamine levels in biological samples must be monitored in several clinical and forensic circumstances. In spite of the interspecies differences in the preferred route of biotransformation, benzylmethylketone, benzoic acid and 4-hydroxyamphetamine are the principal metabolites of amphetamine. However, the clinical and forensic studies are focused in the parent compound and in 4-hydroxyamphetamine since benzylmethylketone is a minor metabolite in human and benzoic acid is also an endogenous compound. In the present study amphetamine and its metabolite, 4-hydroxyamphetamine, are quantified in urine by HPLC after derivatization with 4-dimethylaminoazobenzene-4'-sulfonyl chloride (dabsyl chloride). This derivatization procedure transforms amphetamine and its hydroxylated metabolite in compounds with similar lipofilicity, enabling their quantitative and simultaneous extraction with an organic solvent. The precision of the HPLC technique was 7.3 and 10.0% for amphetamine and 4-hydroxyamphetamine derivatives, respectively. For the overall procedure, including enzymatic hydrolysis, derivatization and extraction of the derivatives, the obtained values were 9.3 and 6.2%. Recoveries obtained from spiked urines for amphetamine and 4-hydroxyamphetamine were better than 97% and 94% (mean value), respectively. The detection limits of the method was 10 ng for both compounds. The principal advantages of the present proposed method are the stability of the dabsyl derivatives at room temperature and the detection carried out in the visible region, reducing the interferences detected.

Amphetamine↗
PubMed1998

Quantification of total chromium and hexavalent chromium in UHT milk by ETAAS.

Procedures for the quantification of total chromium and hexavalent chromium in UHT milk samples are presented. Total chromium was determined directly in milk with the addition of a surfactant and a mixture of Pd and Mg as a chemical modifier. For the selective separation of hexavalent chromium, the sample pre-treatment consisted in precipitation of proteins and elution of the supernatant through a Chromabond NH2 column. The metal was eluted with nitric acid. Both total chromium and hexavalent chromium were evaluated by atomic absorption spectrometry with electrothermal atomization using the same instrumental conditions. The detection limits were 0.2 and 0.15 microgram l-1 for total chromium and hexavalent chromium, respectively. The linearity ranges under the optimized conditions were 0.2-20 and 0.15-50 micrograms l-1. For total chromium the precision was 4.9 and 5.7% for the analytical and the over-all procedure, respectively, and for hexavalent chromium 4.3 and 4.9%, respectively. The validation of both procedures was performed by the standard additions method and the recoveries were higher than 93% in all cases. For total chromium, a certified reference material was also used to validate the methodology. The methods were applied to the determination of total chromium and hexavalent chromium in 60 UHT milk samples.

Animals↗
PubMed1997

d-Amphetamine-induced hepatotoxicity: possible contribution of catecholamines and hyperthermia to the effect studied in isolated rat hepatocytes.

Amphetamines are indirect-acting sympathomimetic drugs widely abused due to their physical and psychostimulating effects. However, the use of these drugs has been associated with numerous reports of hepatotoxicity. While glutathione depletion induced by amphetamines contributes to the exposure of hepatocytes to oxidative damage, other indirect effects attributed to amphetamines may have a role in cell injury. To examine this possibility, Wistar rats were used for plasma measurements of d-amphetamine and catecholamines (noradrenaline, adrenaline and dopamine) (15 min) after i.p. injection of d-amphetamine (5, 20 and 80 mg/kg). Freshly isolated rat hepatocytes were put into contact for 2 h with concentrations of d-amphetamine and catecholamines similar to those found in vivo. Since hyperthermia is a common consequence of acute amphetamine intake, the study using isolated hepatocytes was conducted at 37 degrees C and also at 41 degrees C in order to simulate high temperature levels. We found that hyperthermia was an important cause of cell toxicity: in vitro, a rise in incubation temperature from 37 to 41 degrees C causes oxidative stress in freshly isolated rat hepatocytes, as shown by a depletion of reduced glutathione (GSH; 23%), an increase of oxidized glutathione (GSSG; 157%), the induction of lipid peroxidation with 77% increase of thiobarbituric acid substances TBARS) and the consequent loss of cell viability (< or = 44%). Single treatment of isolated hepatocytes with catecholamines at 37 degrees C induced lipid peroxidation (29% increase of TBARS) but had no effect on glutathione or cell viability. Conversely, a single treatment with d-amphetamine induced glutathione depletion (< or = 24% depletion of GSH) with no effect on lipid peroxidation or cell viability. Also, d-amphetamine potentiated the induction by catecholamines of lipid peroxidation at 37 degrees C (< or = 48% increase of TBARS), while concomitant treatment of d-amphetamine and catecholamines potentiated cell death at 41 degrees C (< or = 56% of cell death) although no effect on viability was seen at 37 degrees C. It is concluded that the aforementioned modifications induced by d-amphetamine in vivo are cytotoxic to freshly isolated rat hepatocytes.

Amphetamines↗
PubMed1997

Changes in taurine levels in response to repeated administration of the beta 2-agonist salbutamol in lambs.

Repeated oral administration of salbutamol to lambs for 28 days was found to decrease levels of taurine significantly in the serum and heart, and the mean excretion of taurine into urine was significantly less than in controls. Serum urea, low density lipoprotein and high density lipoprotein were also significantly reduced. Consistent with these changes, fat content in muscle was reduced, whereas protein content was not significantly changed. Body weight was not significantly changed by salbutamol treatment but heart and kidney weights (relative to body weight) were significantly increased. Salbutamol excretion in urine was relatively constant and residues were detected in certain organs and tissues, notably liver, bile and kidney. Changes in urinary and serum taurine level may reflect subtle changes in protein metabolism not detectable as changes in body weight or gross protein content.

Adipose Tissue↗
PubMed1995

Determination of arsenic, cadmium and lead in porcine and bovine kidneys by electrothermal atomic absorption spectrometry.

This paper describes an ETAAS method to quantify residues of arsenic, cadmium and lead in porcine and bovine kidneys. The results of a survey conducted during 1993 are tabulated. Analysis was performed by ETAAS with a stabilized-temperature platform furnace. The determinations were performed in the linear ranges 0.5-150, 0.04-2.0 and 1.1-75 micrograms l-1 for As, Cd and Pb, respectively, in the acid digests which were obtained under controlled conditions of temperature in a tetrafluoroethylene apparatus after appropriate dilution and addition of a suitable chemical modifier. Extensive quality assurance of the methods was performed by the standard additions method and by comparison with a certified reference material. The precision was better than 9.9, 8.5 and 9.2% for As, Cd and Pb, respectively. Low relative standard deviations of 7.4, 7.0, and 2.8% for As, Cd and Pb, respectively, were obtained by comparing the levels found in the kidney reference material and the certified values, showing this method to be satisfactory and suitable for routine analysis. The mean levels of As, Cd and Pb in porcine kidney were 2.11 (1.11-5.49), 0.81 (0.02-4.22) and 0.18 (0.02-0.42) microgram g-1 respectively. Those in the adult bovine kidney were 1.77 (0.42-3.42), 1.26 (0.01-6.16) and 0.73 (0.19-2.55) microgram g-1, respectively, and in the young bovine kidney they were 1.33 (0.61-2.56), 0.49 (0.15-1.82) and 0.20 (0.12-0.29) microgram g-1.

Animals↗
PubMed1994

Bioavailability of residues of diazepam and its metabolites.

The present study was performed to determine the metabolic fate of the residues of diazepam and its metabolites in an in vivo model and using two different animal species, guinea pigs and rats, successively. Guinea pigs were orally dosed with diazepam at 100 mg/kg bw and 10 mg/kg bw. After 2 h the animals were sacrificed and their livers were removed. Rats were fed these livers and sacrificed 8 h later after having ingested the portion given. Blood, kidney, and liver of rats were collected to quantify drug residues. Oxazepam and demethyldiazepam were identified by HPLC-UV in liver and kidney rat extracts and also in some blood samples. Temazepam was only found in liver from rats that had eaten guinea pig liver dosed at the highest level. The identity of demethyldiazepam was confirmed in rat liver extracts by GC-MS. This study demonstrates the bioavailability of diazepam metabolites in a second animal (rat simulating a consumer) following a diazepam administration to a first animal (guinea pigs simulating a target animal). Residue concentrations were reduced from 9.7 and 243 micrograms in consumed guinea pig liver to 3.75 and 455 ng/g in rat liver for parent drug and oxazepam, the lowest and highest residues found, respectively.

Animals↗
PubMedDate not supplied

Selective determination of chromium (VI) in powdered milk infant formulas by electrothermal atomization atomic absorption spectrometry after ion exchange.

A previously developed method was adapted to the selective determination of hexavalent chromium in powdered milk infant formulas. The species in reconstituted milk was separated on an ion-exchange column, Chromabond NH2, and measured by electrothermal atomization atomic absorption spectrometry. The detection limit was 1.8 micrograms/L, and the linearity range under optimized conditions was 1.8-50.0 micrograms/L. The precision values were 4.1 and 6.5% for the analytical and overall procedures, respectively. The procedure was validated by the method of standard additions (5.0, 10.0, and 25.0 micrograms/L), and the recoveries were all > 93%. The developed method is sensitive, accurate, and precise for determination of Cr(VI) in powdered milks. It was applied to the determination of Cr(VI) in 20 commercial brands, i.e., 7 infant formulas, 5 follow-up milks, and 8 dietetic milks. The values found ranged from < 10 to 75 ng/g.

Chromatography, Ion Exchange↗