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J Beltran

Publications and source records attributed to J Beltran.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of two quantitative GC-MS methods for analysis of tomato aroma based on purge-and-trap and on solid-phase microextraction.

Two analytical procedures, one based on purge-and-trap and the other on solid phase microextraction, both followed by GC-MS measurement using an ion-trap mass spectrometer in the electron impact mode, have been developed for determination and quantitation of up to 39 aroma compounds in fresh tomatoes. The method based on purge-and-trap for isolation of the volatile compounds uses Tenax as adsorbent and a hexane-diethyl ether mixture as solvent for elution. The method was validated for linearity, precision (better than 20% for most compounds), and limit of detection, which was approximately 1 ng g(-1). This method enabled identification of up to 30 compounds in real samples. Use of SPME was considered as an alternative, to simplify sample treatment while maintaining the information level for the samples (e.g. the number of compounds detected) and quality of quantitation. A procedure based on SPME using a Carboxen/polydimethylsiloxane fibre was developed and validated for determination of 29 aroma compounds; precision was better than 20% and limits of detection ranged from 4 to 30 ng g(-1).

Gas Chromatography-Mass Spectrometry↗
PubMed2003

Application of solid-phase microextraction for the determination of pyrethroid residues in vegetable samples by GC-MS.

A solid-phase microextraction (SPME) method has been developed for the determination of 7 pyrethroid insecticides (bifenthrin, lambda-cyhalothrin, permethrin, cyfluthrin, cypermethrin, fenvalerate, and tau-fluvalinate) in water, vegetable (tomato), and fruit (strawberry) samples, based on direct immersion mode and subsequent desorption into the injection port of a GC/MS. The SPME procedure showed linear behavior in the range tested (0.5-50 microg L(-1) in water and 0.01-0.1 mg kg(-1) in tomato) with r(2) values ranging between 0.97 and 0.99. For water samples limits of detection ranged between 0.1 and 2 microg L(-1 )with relative standard deviations lower than 20%. Detection limits for tomato samples were between 0.003 and 0.025 mg kg(-1) with relative standard deviations around 25%. Finally, the SPME procedure has been applied to vegetable (tomato) and fruit (strawberry) samples obtained from an experimental plot treated with lambda-cyhalothrin, and in both cases the analyte was detected and quantified using a calibration curve prepared using blank matrix. SPME has been shown to be a simple extraction technique which has a number of advantages such as solvent-free extraction, simplicity, and compatibility with chromatographic analytical systems. Difficulties with the correct quantification in a complex matrix are also discussed.

Food Analysis↗
PubMed2002

Role of dopamine in renal dysfunction during laparoscopic surgery.

BACKGROUND: Sympathetic vascular insult and hemodynamic changes represent the most reliable explanation of renal impairment resulting from acute intraabdominal pressure. We evaluated the effects of low-dose dopamine administration during a long-lasting surgical laparoscopic procedure. METHODS: For this study 40, patients submitted to a colorectal laparoscopic procedure with 15 mmHg of intraabdominal pressure were randomly allocated to two groups: 20 receiving 2 mg/kg/min of dopamine and 20 receiving the same perfusion of saline. Hemodynamic parameters, renal function, urinary output, and creatinine clearance, were studied. RESULTS: The hemodynamic parameters were similar in both groups. The urinary output decreased during the intraoperative period only the saline group (p = 0.4). Then 2 h postoperatively, it increased in both groups, and no statistically significant differences were found between the groups. The creatinine clearance decreased in both groups during the intraoperative time, but it was worse in the saline group (-28 +/- 120 vs -194 +/- 106; p = 0.022). During the postoperative period, both groups showed improvement, but in control group the values remained lower than at baseline (p = 0.04), and significantly lower than in the dopamine group (230 +/- 337 vs 100 +/- 192; p = 0.012). CONCLUSIONS: An intrabdominal pressure of 15 mmHg induces a time-limited renal dysfunction, and low doses of dopamine could prevent this undesirable effect.

Colorectal Neoplasms↗
PubMed2002

Headspace solid-phase microextraction in combination with gas chromatography and tandem mass spectrometry for the determination of organochlorine and organophosphorus pesticides in whole numan blood.

A method for the determination of several organochlorine and organophosphorus pesticides in human whole blood samples was developed. The combination of solid-phase microextraction in headspace mode with gas chromatography with tandem mass spectrometry allowed the determination of 11 selected pesticides at ppb levels, minimizing the sample treatment. Quantitation was carried out by means of calibration curves prepared in blood using labelled surrogate/internal standards. The method showed good linearity between 1 and 50 ng ml(-1) (0.5-25 ng ml(-1) for HCB) using second-order calibration curves. Precision was found to be better than 20% at the three concentration levels assayed in the range of ng ml(-1). The detection limits obtained were in the range 0.02-0.7 ng ml(-1), except for p,p'-DDT (3 ng ml(-1)). The developed procedure was applied to blood and serum samples obtained from agricultural workers. HCB. beta-HCH and p,p'-DDE were most frequently detected in the samples analyzed.

Gas Chromatography-Mass Spectrometry↗
PubMed2001

Interferon alpha2b gene delivery using adenoviral vector causes inhibition of tumor growth in xenograft models from a variety of cancers.

A recombinant adenovirus expressing human interferon alpha2b driven by the cytomegalovirus promoter, IACB, was shown to produce and secrete biologically active protein in vitro and in vivo. Intravenous administration of IACB in Buffalo rats resulted in circulating levels of biologically active human interferon at 70,000 international units/mL for up to 15 days. Distribution of interferon protein after IACB administration was different from that seen with the subcutaneous delivery of interferon protein. Higher levels of interferon protein were observed in liver and spleen after IACB delivery compared to protein delivery. The antitumor efficacy of IACB, as measured by suppression of tumor growth, was tested in athymic nude mice bearing established human tumor xenografts from different types of human cancer. Subcutaneous tumors most responsive to the intratumoral administration of IACB ranked as U87MG (glioblastoma) and K562 (chronic myelogenous leukemia), followed by Hep 3B (hepatocellular carcinoma) and LN229 cells (glioblastoma). Intravenous administration of IACB in animals bearing U87MG or Hep 3B xenografts was also effective in suppressing tumor growth, although to a lesser extent than the intratumoral administration. IACB was also tested in a metastatic model in beige/SCID mice generated with H69 (small cell lung carcinoma) cells and was found to prolong survival in tumor-bearing animals. This suggested that interferon gene delivery can be effective in suppressing tumor growth in a wide variety of cells.

Adenoviridae↗
PubMed2001

MR imaging of bone lesions of the ankle and foot.

MR imaging is frequently used to evaluate patients with ankle and foot pain, with or without a relationship to trauma or other known clinical outcomes. Abnormal signal intensity of the bone marrow is the common denominator of all entities described in this article, including bone contusion, fractures, osteonecrosis, transient osteoporosis, and reflex sympathetic dystrophy. Specific MR imaging features in association with the available clinical and radiographic findings can be helpful not only to supply an accurate diagnosis but also to provide valuable information for staging and proper management of the condition.

Ankle Injuries↗
PubMed2000

L-arginine reduces liver and biliary tract damage after liver transplantation from non-heart-beating donor pigs.

BACKGROUND: To evaluate whether L-arginine reduces liver and biliary tract damage after transplantation from non heart-beating donor pigs. METHODS: Twenty-five animals received an allograft from non-heart-beating donors. After 40 min of cardiac arrest, normothermic recirculation was run for 30 min. The animals were randomly treated with L-arginine (400 mg x kg(-1) during normothermic recirculation) or saline (control group). Then, the animals were cooled and their livers were transplanted after 6 hr of cold ischemia. The animals were killed on the 5th day, liver damage was assessed on wedged liver biopsies by a semiquantitative analysis and by morphometric analysis of the necrotic areas, and biliary tract damage by histological examination of the explanted liver. RESULTS: Seventeen animals survived the study period. The histological parameters assessed (sinusoidal congestion and dilatation, sinusoidal infiltration by polymorphonuclear cells and lymphocytes, endothelitis, dissociation of liver cell plates, and centrilobular necrosis) were significantly worse in the control group. The necrotic area affected 15.9 +/- 14.5% of the liver biopsies in the control group and 3.7 +/- 3.1% in the L-arginine group (P<0.05). Six of eight animal in the control group and only one of eight survivors in the L-arginine group developed ischemic cholangitis (P<0.01). L-Arginine administration was associated with higher portal blood flow (676.9 +/- 149.46 vs. 475.2 +/- 205.6 ml x min x m(-2); P<0.05), higher hepatic hialuronic acid extraction at normothermic recirculation (38.8 +/- 53.7% vs. -4.2 +/- 18.2%; P<0.05) and after reperfusion (28.6 +/- 55.5% vs. -10.9 +/- 15.5%; P<0.05) and lower levels of alpha-glutation-S-transferase at reperfusion (1325 +/- 1098% respect to baseline vs. 6488 +/- 5612%; P<0.02). CONCLUSIONS: L-Arginine administration during liver procurement from non heart beating donors prevents liver and biliary tract damage.

Animals↗
PubMed2000

Solid-phase microextraction in pesticide residue analysis.

The applications of solid-phase microextraction (SPME) for sample preparation in pesticide residue analysis are reviewed in this paper taking into account the different approaches of this technique coupled mainly to gas chromatography but also to high-performance liquid chromatography. A complete revision of the existing literature has been made considering the different applications divided according to the pesticide families (organochlorine, organophosphorus, triazines, thiocarbamates, substituted uracils, urea derivatives and dinitroanilines among others) and the sample matrices analysed which included environmental samples (water and soil), food samples and biological fluids. Details on the analytical characteristics of the procedures described in the reviewed papers are given, and new trends in the applications of SPME in this field are discussed.

Chromatography, Gas↗
PubMed2000

Use of solid-phase microextraction for the quantitative determination of herbicides in soil and water samples.

An in-depth study of SPME optimization and application has been made, considering not only aqueous (surface water and groundwater samples) but also the more complex soil samples. Seven herbicides widely used in the area of study have been selected including five triazine herbicides (atrazine, simazine, terbumeton, terbuthylazine, terbutryn), molinate, and bromacil. linearity range was between 0.1 and 10 ng/mL and the repeatability below 10% when applying the optimized SPME procedure to water samples. Reproducibility was found to be lower than 20% at the 1 ng/mL level, and the limits of determination in environmental water samples using GC/MS (SIM mode) were well below 0.1 ng/mL (values ranging from 10 to 60 ng/L). Extraction of selected herbicides from soil was carried out by microwave-assisted solvent extraction using methanol in screw-capped vials, leading to recoveries over 80% in spiked soil samples at the 5-200 ng/g level. SPME application over methanolic soil extracts required a 10-fold dilution with distilled water. The recommended procedure was found to be fully applicable for quantitative determination of selected herbicides in soils containing low organic matter content with coefficients of variation below or around 10% and limits of determination ranging from 1 to 10 ng/g. Both procedures were applied to real-world surface water and soil samples where several pesticides were detected including atrazine, simazine, terbuthylazine, and molinate.

Herbicides↗
PubMed2000

Traumatic musculotendinous injuries of the knee: diagnosis with MR imaging.

Magnetic resonance (MR) imaging is the imaging modality of choice for evaluation of acute traumatic musculotendinous injuries of the knee. Three discrete categories of acute injuries to the musculotendinous unit can be defined: muscle contusion, myotendinous strain, and tendon avulsion. Among the quadriceps muscles, the rectus femoris is the most susceptible to injury at the myotendinous junction due to its superficial location, predominance of type II fibers, eccentric muscle action, and extension across two joints. Among the muscles of the pes anserinus, the sartorius is the most susceptible to strain injury due to its superficial location and biarticular course. The classic fusiform configuration of the semimembranosus along with a propensity for eccentric actions also make it prone to strain injury. MR imaging findings associated with rupture of the iliotibial tract include discontinuity and edema, which are best noted on coronal images. The same mechanism of injury that tears the arcuate ligament from its fibular insertion can also result in avulsion injury of the biceps femoris. The gastrocnemius muscle is prone to strain injury due to its action across two joints and its superficial location. Injuries of the muscle belly and myotendinous junction of the popliteus are far more common than tendinous injuries.

Contusions↗
PubMed2000

From the RSNA Refresher Courses. Radiological Society of North America. MR imaging of the ankle and foot.

Magnetic resonance (MR) imaging has opened new horizons in the diagnosis and treatment of many musculoskeletal diseases of the ankle and foot. It demonstrates abnormalities in the bones and soft tissues before they become evident at other imaging modalities. The exquisite soft-tissue contrast resolution, noninvasive nature, and multiplanar capabilities of MR imaging make it especially valuable for the detection and assessment of a variety of soft-tissue disorders of the ligaments (eg, sprain), tendons (tendinosis, peritendinosis, tenosynovitis, entrapment, rupture, dislocation), and other soft-tissue structures (eg, anterolateral impingement syndrome, sinus tarsi syndrome, compressive neuropathies [eg, tarsal tunnel syndrome, Morton neuroma], synovial disorders). MR imaging has also been shown to be highly sensitive in the detection and staging of a number of musculoskeletal infections including cellulitis, soft-tissue abscesses, and osteomyelitis. In addition, MR imaging is excellent for the early detection and assessment of a number of osseous abnormalities such as bone contusions, stress and insufficiency fractures, osteochondral fractures, osteonecrosis, and transient bone marrow edema. MR imaging is increasingly being recognized as the modality of choice for assessment of pathologic conditions of the ankle and foot.

Ankle Injuries↗
PubMed2000

Superior labrum anterior-posterior lesions: diagnosis with MR arthrography of the shoulder.

PURPOSE: To determine the accuracy of magnetic resonance (MR) arthrography in the diagnosis of superior labrum anterior-posterior (SLAP) lesions of the shoulder. MATERIALS AND METHODS: From January 1995 to June 1998, MR arthrography of the shoulder was performed in 159 patients with a history of chronic shoulder pain or instability. Fifty-two patients underwent arthroscopy or open surgery 12 days to 5 months after MR arthrography. Diagnostic criteria for SLAP lesion included marked fraying of the articular aspect of the labrum, biceps anchor avulsion, inferiorly displaced bucket handle fragment, and extension of the tear into the biceps tendon fibers. Surgical findings were correlated with those from MR arthrography. RESULTS: SLAP injuries were diagnosed at surgery in 19 of the 52 patients (37%). Six of the 19 lesions (32%) were classified as type I, nine (47%) as type II, one (5%) as type III, and three (16%) as type IV. MR arthrography had a sensitivity of 89% (17 of 19 patients), a specificity of 91% (30 of 33 patients), and an accuracy of 90% (47 of 52 patients). The MR arthrographic classification showed correlation with the arthroscopic or surgical classification in 13 of 17 patients (76%) in whom SLAP lesions were diagnosed at MR arthrography. CONCLUSION: MR arthrography is a useful and accurate technique in the diagnosis of SLAP lesions of the shoulder. MR arthrography provides pertinent preoperative information with regard to the exact location of tears and grade of involvement of the biceps tendon.

Adult↗
PubMed2000

Morton's neuroma: is it always symptomatic?

OBJECTIVE: We determined the prevalence of clinically silent Morton's neuroma and searched for distinguishing MR imaging features of Morton's neuroma in patients with clinical complaints related to this entity and in patients with clinically silent lesions. MATERIALS AND METHODS: One radiologist who was unaware of clinical findings retrospectively reviewed 85 consecutive foot MR examinations. MR imaging criteria for Morton's neuroma included a low- to intermediate-signal-intensity soft-tissue mass in the intermetatarsal space. The size, location, and signal intensity of each neuroma and the presence of intermetatarsal bursae were recorded. The patients were subdivided into symptomatic or asymptomatic groups on the basis of the patients' answers on a questionnaire documenting the locations and characteristics of symptoms and discussions with each referring physician about clinical findings. Surgical confirmation was available in eight of 25 symptomatic patients. RESULTS: The prevalence of Morton's neuroma in patients with no clinical evidence of this condition was 33% (19/57). Twenty-five patients had symptomatic Morton's neuroma, 19 had Morton's neuroma based on MR imaging findings with no clinical manifestations, and 41 did not have Morton's neuroma. Slightly larger lesions were observed in the symptomatic group, although significant overlap was noted between the two groups. The mean transverse diameter of symptomatic neuromas was 5.3 mm (standard deviation, 2.14) compared with 4.1 mm (standard deviation, 1.75) for asymptomatic neuromas; this difference was marginally significant (p = 0.05). CONCLUSION: The MR imaging diagnosis of Morton's neuroma does not imply symptomatology. Careful correlation between clinical and MR imaging findings is mandatory before Morton's neuroma is considered clinically relevant.

Adolescent↗
PubMed1999

Glenohumeral instability: evaluation using MR arthrography of the shoulder.

In the setting of glenohumeral instability or when internal derangement of the shoulder joint is suspected, MR arthrography has been demonstrated to be an accurate diagnostic imaging technique. Knowledge of the complex anatomy of the shoulder and its variations is essential in order to maximize diagnostic accuracy.

Humans↗
PubMed1999

Evaluation of ischemic injury during liver procurement from non-heart-beating donors.

UNLABELLED: The aim of this study was to assess liver viability after different periods of cardiac arrest and the predictive value of two markers of ischemia-reperfusion injury. METHODS: A pig liver transplantation model of non-heart-beating donors was studied. Four donor groups were designed; three groups were submitted to different periods of cardiac arrest (20, 30 and 40 min), and the fourth group served as the control group (without cardiac arrest). In the non-heart-beating donor groups, normothermic recirculation was established 30 min prior to total body cooling. Aminotransferase, alpha-glutathione-S-transferase, and hyaluronic acid determinations as well as liver biopsies, were serially performed. RESULTS: Although hepatocellular function could be preserved after 40 min of cardiac arrest, histological lesions at 5 days were considered irreversible due to the presence of a necrotic biliary tract. An overall significant relationship was found between the time period of cardiac arrest (20, 30 or 40 min) and the levels of hyaluronic acid (p = 0.004) or alpha-glutathione-S-transferase (p = 0.01) obtained during liver procurement and transplantation. CONCLUSIONS: The period of cardiac arrest is the determinant factor of liver viability after liver transplantation from non-heart-beating donors. As early markers of endothelial or hepatocellular damage, hyaluronic acid or alpha-glutathione-S-transferase levels may help to evaluate the ischemic injury of a potential donor.

Alanine Transaminase↗
PubMed1999

Detecting anti-SSA and anti-SSB antibodies in routine analysis: a comparison between double immunodiffusion and immunoblotting.

The aim of this study was to assess the performance of a commercially available procedure for detecting anti-Sjögren's syndrome A (anti-SSA) and anti-Sjögren's syndrome B (anti-SSB) antibodies by immunoblotting (IB) and compare it with double immunodiffusion (DID). We also studied the clinical significance of these profiles in a series of unselected anti-SSA positive patients. Serum samples from 534 patients that were positive on an immunofluorescent screening test using HEp-2 cells were analysed for anti-SSA and anti-SSB antibodies by DID and IB (Biolab Anablot System II), and the results on anti-SSA antibodies were confirmed by an enzyme-linked immunosorbent assay (ELISA). Fifty-five serum samples were found to be positive for anti-SSA antibodies. Among these, 24 were anti-SSA negative by IB but positive by DID and ELISA ('non-blotter sera'), whereas only three serum samples were anti-SSA negative by DID but positive by IB and ELISA. Of the 18 anti-SSB positive serum samples, eight were negative by DID. All the serum samples that were anti-SSB positive by DID were also positive by IB. Anti-SSB antibodies showed a significant association with eye dryness and leucopenia. Anti-52 kDa SSA antibodies were associated with anti-SSB antibodies but showed no significant association with sicca symptoms, while anti-60 kDa SSA antibodies were associated with lower rates of leucopenia. The 'non-blotter' profile showed no significant association with any clinical parameter. IB is less sensitive than DID for detecting anti-SSA antibodies but more sensitive than DID for detecting anti-SSB antibodies. The determination of anti-SSA immunoblotting profiles in patients positive for anti-SSA antibodies by DID does not significantly improve the clinical usefulness of this test. As expected, anti-SSB antibodies were associated with clinical features of Sjögren's disease. Non-blotting (probably conformational) anti-SSA antibodies did not show any further association with clinical parameters and seem to have no clinical relevance.

Autoantibodies↗
PubMed1998

Comparison of simplified methods for pesticide residue analysis. Use of large-volume injection in capillary gas chromatography.

The combination of manual and automated extraction procedures using low sample volumes (5-50 ml) with large-volume oncolumn injection (LVI) (200 microliters) in capillary gas chromatography with flame photometric detection (GC-FPD) has allowed the determination of 16 organophosphorus pesticides in clean water samples at the low ng l-1 level with an important simplification in the sample preparation step. A simple and fast offline liquid-liquid microextraction procedure (2-5 ml water/l ml methyl tert.-butyl ether) has been applied to spiked groundwater samples (containing 0.5 ng of each pesticide) with good recoveries (over 80%) and precision (better than 10%), giving detection limits between 5 and 100 ng l-1 using 200 microliters injections in the GC-FPD system. The application of an inline automated liquid-liquid microextraction-LVI-GC procedure (2 ml water/2 ml methyl tert.-butyl ether: injection of 200 microliters in GC-FPD) using the autosampler ASPEC XL led to lower recoveries (> 50%) as a result of the low efficiency for mixing organic and aqueous phases, although with very satisfactory coefficients of variation (lower than 7%) and detection limits between 20 and 200 ng l-1. Manual and automated solid-phase extraction procedures using the well known C18 cartridges and the new Oasis HLB have been applied to groundwater samples (5-50 ml) spiked with 1 ng of each pesticide. Results obtained for both the manual and the automated procedures were satisfactory (recoveries over 80%) and the limits of detection for 50 ml sample volume ranged from 1 to 6 ng l-1.

Autoanalysis↗