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Biomedical subjects

J Segura

Publications and source records attributed to J Segura.

At least 109 records · Page 6Linked to original sources
PubMed1996

Detection of non-steroidal anti-inflammatory drugs in equine plasma and urine by gas chromatography-mass spectrometry.

A gas chromatographic-mass spectrometric (GC-MS) procedure for the detection of seventeen non-steroidal anti-inflammatory drugs (NSAIDs) in equine plasma and urine samples is described. The extraction of the compounds from the biological matrix was performed at acidic pH (2-3) with diethyl ether. Ethereal extracts were washed with a saturated solution of sodium hydrogencarbonate (urine) or treated with a solid mixture of sodium carbonate and sodium hydrogencarbonate (plasma). The ethereal extracts were dried and derivatized by incubation at 60 degrees C with methyl iodide in acetone in the presence of solid potassium carbonate. Mono- or bismethyl derivatives of the NSAIDs were obtained. After derivatization kinetic studies, 90 min was the incubation time finally chosen for screening purposes for adequate methylation of all the compounds under study. For individual confirmation analyses, shorter incubation times can be used. The chromatographic analysis of the derivatives was accomplished by GC-MS with a run time of 13 min. In general, extraction recoveries ranged from 23.3 to 100% in plasma and from 37.5 to 83.8% in urine samples. Detection limits from less than 5 to 25 ng/ml were obtained for both plasma and urine samples using selected-ion monitoring. The procedure was applied to the screening and confirmation of NSAIDs in routine doping control of equine samples.

Animals↗
PubMed1996

A partially automated pretreatment module for routine analyses for seventeen non-steroid antiinflammatory drugs in race horses using gas chromatography/mass spectrometry.

A partially automated module for the routine determination of illicit non-steroid antiinflammatory drugs (NSAIDs) in biological fluids from race horses was built, tested, refined, and shown to work. This pretreatment module retains 17 NSAIDs on an Amberlite XAD-2 column before back-elution derivatization with methyl iodide in acetonitrile. Methylated derivatives are manually injected into a gas chromatograph connected to a mass spectrometer. The quantification limits thus achieved are 50-100 ng/mL in 1 mL of urine or plasma. The proposed method is more expeditious than its manual liquid-liquid and liquid-solid extraction counterparts and is similar in speed to a typical gas chromatographic program.

Animals↗
PubMed1996

Determination of beta 2-agonists in hair by gas chromatography/mass spectrometry.

A method is described for the determination of the beta 2-agonists clenbuterol and salbutamol in hair. The method involves washing hair in sodium dodecyl hydrogensulphate solution, chemical digestion of the hair matrix in alkaline medium, solid-phase extraction, derivatization with methylboronic acid and analysis by gas chromatography/electron impact mass spectrometry in either the selected-ion monitoring or the scan mode. the effects of chemical digestion and of extraction on the recovery of the analytes were evaluated. Derivatization with methyl-boronic acid was compared with trimethylsilylation for GC/MS analysis of hair extracts, and was found to give mass spectra which showed more structural information with less chemical noise and better sensitivity. The proposed method was tested on real hair samples obtained from guinea pigs treated with growth-promoting doses of clenbuterol and salbutamol. Both compounds could be detected in hair of treated animals.

Adrenergic beta-Agonists↗
PubMed1996

Direct determination of anabolic steroids in human urine by on-line solid-phase extraction/liquid chromatography/mass spectrometry.

A fully automated method is presented for the determination of anabolic steroids in human urine. On line solid-phase extraction with automatic cartridge exchange is used for sample clean-up followed by an high-performance liquid chromatographic isocratic separation. A narrow-bore 5 microns reversed-phase column (250 x 2.1 mm i.d.) at a flow rate of 0.2 ml min-1 is connected to a particle beam interface linked to a single-quadrupole mass spectrometer. No derivatization is needed and normal electron impact mass spectra are obtained for a series of up to 28 steroids and metabolites. Urine samples collected following the ingestion of therapeutic doses of some of the steroids were analysed and the detection and confirmation of excreted compounds accomplished. A dramatic reduction in human intervention and overall analysis time was achieved compared with other common approaches.

Anabolic Agents↗
PubMed1996

Chemical methods for assessing systemic exposure to dietary heterocyclic amines in man.

A significant proportion of the mutagenic material present in cooked beef is accounted for by 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) which are formed during the cooking of meat. N-hydroxylation catalyzed by CYP1A2 is the major pathway of metbolism of MeIQx and PhIP and is solely responsible for the generation of mutagenic species. Assays for MeIQx and PhIP in foods and body fluids were developed utilising gas chromatography/mass spectrometry with stable isotope labelled analogues as internal standards. Studies using these assays have demonstrated that both MeIQx and PhIP are well absorbed and extensively metabolised following ingestion of amine-containing beef by humans. Studies in which furafylline, a potent and selective inhibitor of human CYP1A2, was administered before ingestion of beef revealed that more than 90% of MeIQx and 70% of PhIP are N-hydroxylated in vivo, probably pre-systemically in the liver. The results demonstrate that unchanged MeIQx and PhIP in urine are accurate and sensitive measures of systemic exposure to the amines.

Carcinogens↗
PubMed1996

Reduction of thrombotic and hemorrhagic complications after stent implantation.

This study compared two consecutive antithrombotic strategies after Palmaz-Schatz stent implantation and involved 918 patients. Patients treated between May 1991 and May 1994 (group 1; n = 379) received aspirin, dipyridamole, and intravenous unfractionated heparin until oral anticoagulation was effective, between June 1994 and August 1995, 539 patients (group 2) were treated for 1 month with subcutaneous low-molecular-weight heparin (Fragmin), ticlopidine, and aspirin. There were no differences between the groups in terms of sex, clinical condition, vessel diameter, and severity and location of stenosis. Patients in group 1 were younger than those in group 2 (4% were > 70 years old compared with 12%, respectively; p < 0.01). Group 1 patients had more frequent unplanned stenting (48% vs 18%, respectively; p < 0.01) and fewer endoprostheses in the same artery than those in group 2 (1.1 +/- 0.5 vs 1.2 +/- 0.5, respectively; p < 0.01). Among group 2 patients, there was a significant reduction in thrombotic and hemorrhagic complications compared with group 1 patients. No subacute thrombosis occurred in patients in group 2 in contrast with a 5.8% incidence in patients in group 1 (p < 0.01). In addition, a lower incidence of groin and systemic bleeding was observed in patients in group 2 compared with patients in group 1 (2.6% vs 15%, respectively; p < 0.01). The association of low-molecular-weight heparin and antiplatelets provides a simpler antithrombotic strategy in patients treated with intracoronary stents and reduces the incidence of stent thrombosis and hemorrhagic complications. Our findings suggest that this antithrombotic regimen may prevent or completely avoid stent thrombosis.

Acute Disease↗
PubMed1996

Morphogenesis in leaf and single-cell cultures of mature Juniperus oxycedrus.

Single cells were mechanically isolated from leaf-derived callus of mature Juniperus oxycedrus L. These cells divided and gave rise to callus when plated on medium containing growth regulators. Best plating efficiency was obtained on a modified Schenk and Hildebrandt medium supplemented with 0.6 micro M 2,4-dichlorophenoxyacetic acid and 100 mg l(-1) casein hydrolyzate. Although single-cell-derived callus showed poor morphogenic potential, both adventitious shoots and embryogenic tissues differentiated from the callus. We also achieved induction of somatic embryogenesis in leaf explants of mature J. oxycedrus trees cultured in the presence of 6.0 or 10.0 micro M 2,4-dichlorophenoxyacetic acid or picloram. Frequency of embryogenic callus ranged from 6 to 18%; however, under the culture conditions tested, isolated embryos failed to develop into plants.

Journal Article↗
PubMed1996

Doping control in sports medicine.

Doping control has become one of the strongest measures to reduce the impact of doping in sports. The rationale for doping control is based on the need to maintain both ethical and medical principles. Among the banned pharmacological substances, the most relevant to sports medicine are anabolic agents, stimulants, narcotic, peptide hormones, diuretics, masking agents, and adrenergic beta-blockers. Optimized use of state-of-the-art analytical methodology and suitable quality control mechanisms warrant reliability in the laboratory. Adequate interpretation of results requires knowledge of pharmacology, toxicology, drug metabolism, and pharmacokinetics. The detection and confirmation of doping using endogenous substances are especially difficult for urine testing. The alteration caused in indirect markers in other biological materials, such as blood, will be the focus of further developments in the field.

Doping in Sports↗
PubMed1996

[Directional coronary atherectomy in ostial lesions of the anterior descending coronary artery].

INTRODUCTION AND OBJECTIVES: Coronary stenoses at ostial level, when treated by balloon angioplasty, show a primary success rate much lower than those located in other parts of the coronary tree. Balloon dilation of lesions located at the left anterior descending ostium is associated with a high degree of restenosis, elastic recoil and the possibility of retrograde dissection to the left main coronary artery. Simpson atherectomy may be considered a percutaneous alternative in this particular location, since this technique produces fewer incidents of elastic recoil than balloon dilation. The purpose of the present study is to evaluate directional atherectomy in the treatment of patients with symptoms deriving from severe to stenosis at the origin of the left anterior descending artery. MATERIAL AND METHODS: From a total number of 302 patients treated by Simpson atherectomy, we have analyzed 45 with severe stenosis at the left anterior descending ostium (less than 3 mm from its origin). The mean age was 54 +/- 12 years. Eighty two percent of the patients were male. The clinical condition was stable in unstable in 34; eleven had had a previous myocardial infarction. Six had multivessel coronary disease, all of them underwent combined balloon angioplasty of other segments. The treated lesion was native in 41 patients and previously dilated by balloon (restenosis) in 4. Two patients needed balloon predilation with 2 and 2.5 mm to facilitate the pass of the atherocatheter. The size of the Simpson atherocatheter was mainly 7F (78%). The weight of the resected arteriosclerotic material was 11 +/- 7 mg. RESULTS: Primary success (residual stenosis < 40% without major complications) was obtained in 42 out of 45 patients (93%); 3 patients (7%) had major complications (1 death, 1 emergency surgery, and 1 non-Q wave myocardial infarction). A follow-up angiography study was available in 31 patients 7 +/- 8 months later. Restenosis was evidenced in 12 (39%). CONCLUSIONS: Simpson atherectomy for left anterior descending artery ostial lesions is an effective transluminal alternative in selected patients providing a high rate of primary success (93%) and an acceptable restenosis rate (39%).

Adult↗
PubMed1995

Influence of the injection technique on the thermal degradation of cocaine and its metabolites in gas chromatography.

Thermal degradation of some substances due to high temperature at the injection port and/or the type of injection technique used may limit the usefulness of gas chromatography with conventional detectors or coupled to mass spectrometry. To minimize thermal degradation of cocaine and its metabolites, chromatography was performed using two different insert liners and a cool on-column inlet. When using a packed liner, marked degradation of all compounds was observed. The degradation process was reduced by the use of an open liner and, when the cool on-column inlet was employed, essentially no degradation occurred.

Cocaine↗
PubMed1995

Balloon-expandable stent repair of severe coarctation of aorta.

Experimental studies have shown that stents implanted at the aorta become incorporated within the aortic wall and can be further expanded in growing animals. This study evaluates the feasibility and immediate results of balloon-expandable stent implantation in 10 patients with severe coarctation of aorta. The ages of the patients ranged from 1 month to 43 years; 1 was an infant, 8 were children (mean age 5.3 +/- 4 years), and 1 was an adult. All had an unfavorable anatomy for balloon angioplasty; 9 had isthmus hypoplasia. Balloon predilation was first performed and its immediate effect evaluated. Then a balloon-expandable stent that was 30 mm long and covered the isthmus and coarctation levels was deployed, and it was further expanded to the preselected final diameter (12 +/- 4 mm). A final hemodynamic and angiographic evaluation was then obtained. Full deployment of an incompletely expanded and distally displaced stent in the infant led to aortic disruption that was controlled by a second stent covering the disrupted zone and the isthmus. After balloon angioplasty alone was done, the mean gradient (43 +/- 12 vs 31 +/- 10 mm Hg) and the percentage stenosis (72% +/- 11% vs 54% +/- 11%) had an insufficient decrease. However, after stent implantation was done, the gradient almost disappeared (mean 2 +/- 3 mm Hg). The angiographic stenosis disappeared in 7 patients and was markedly reduced in 3. The ratio of isthmus/descending aorta changed from 0.65 +/- 0.14 to 1 +/- 0.08 (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1995

Follow-up patency of side branches covered by intracoronary Palmaz-Schatz stent.

To assess the risk of late side branch occlusion after Palmaz-Schatz stent deployment, we analyzed the angiographic evolution of 62 patients treated by successful stent implantation who had a total of 85 side branches starting from the stented segment. Side branches were considered minor (n = 39) when the diameter was < 1 mm and intermediate (n = 46) when the vessel had > or = 1 mm diameter. One angiographic follow-up study was available in all patients at 8 +/- 5 months. Eight minor branches presented some degree of stenosis at origin before stent deployment (4 totally occluded). After stent deployment, 32 (82%) of 39 remained unchanged and 3 became occluded. Late progression at origin occurred in 4 of 34 (3 occluded). Before stent deployment, 48% of the intermediate branches had some compromise degree at their starting point (1 totally occluded). Eight of 45 intermediate branches became occluded after stent implantation. Late progression at origin happened in 5 of 32 branches (2 occluded). Some degree of follow-up stenosis regression at the origin was observed in 22 (26%) of 85 arteries. Neither clinical nor angiographic factors could be identified as predictors of late side branch occlusion or stenosis progression at its origin. Later occlusion or progression at origin of a side branch covered by a Palmaz-Schatz stent seems to be an uncommon occurrence (7% and 12% respectively) that cannot be predicted by angiographic or clinical factors. On the contrary, regression at follow-up of a side branch-origin stenosis can also come about.

Adult↗
PubMed1995

Determination of cocaine and its metabolites in human urine by gas chromatography/mass spectrometry after simultaneous use of cocaine and ethanol.

Cocaethylene is an active metabolite produced when cocaine is consumed jointly with ethanol. The development of analytical techniques for determining cocaethylene and other cocaine metabolites is highly relevant for pharmacokinetic and toxicology studies of the cocaine and alcohol interaction in humans. The gas chromatography/mass spectrometry (GC/MS) method here reported is based on a single solid-phase extraction together with deuterated internal standards previously added to urine, followed by derivatization with pentafluoropropionic anhydride (hydroxyl and amine functions) and 1,1,1,3,3,3 hexafluor-2-propanol (carboxylic acid function) and injection into a capillary GC system coupled to a mass spectrometric detector in the selected ion monitoring acquisition mode. A sensitivity of 1-2 ng ml-1 for the quantitative analysis of cocaine and its main metabolites (ecgonine methyl ester, benzoylecgonine, cocaethylene and norcocaine) was achieved. In addition, some other minor metabolites were easily extracted and detected.

Adult↗
PubMed1995

Axillary shoot proliferation in cultures of explants from mature Juniperus oxycedrus trees.

We developed procedures for the micropropagation of Juniperus oxycedrus L. using shoot apices or nodal segments from mature plants. Of the media and explants examined, best culture establishment was obtained with shoot apices cultured on modified Schenk and Hildebrandt medium (SH medium) without growth regulators; however, shoot multiplication was only achieved when shoot apices isolated from shoots grown on SH medium without growth regulators were subcultured on SH medium containing 0.5 micro M benzyladenine. None of the auxins and methods tested for root induction provided satisfactory results.

Journal Article↗