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At least 289 records · Page 16Linked to original sources

PubMed2007

Characterization and online detection of aromatic alkaloids in the ascidian Lissoclinum cf. badium by liquid chromatography/UV detection mass spectrometry.

A detection method based on high-performance liquid chromatography coupled with ultraviolet diode-array detection and electrospray ionization ion trap tandem mass spectrometry (HPLC-UV-ESI-MS/MS) was developed to investigate the total alkaloids prepared from the ascidian Lissoclinum cf. badium. The aromatic alkaloids possessing polysulfide structures are the major bioactive constituents isolated from ascidians of the genera Lissoclinum, Eudistoma, and Polycitor. These compounds presented various important biological activities. The ESI-MS fragmentation behavior of this kind of alkaloids was studied, and the fragmentation was characterized by elimination of the NH(CH(3))(2) moiety. The use of reversed-phase HPLC/UV-ESI-MS allowed the online separation and detection of 25 aromatic alkaloids. This approach provided data that can be used for detection of biologically active aromatic alkaloids from marine organisms.

Alkaloids↗

PubMed1995

Biotin-labeled potato chymotrypsin inhibitor-1: a useful probe for the detection and quantitation of chymotrypsin-like serine proteinases on western blots and its application in the detection of a serine proteinase synthesised by articular chondrocytes.

Potato chymotrypsin inhibitor-1 (pCTI-1) was biotinylated by reaction with sulfosuccinimidyl-6-(biotinamido)hexanoate. This derivative was used as a probe on Western blots for the detection and quantitation of chymotrypsin and the detection of a chymotrypsin-like serine proteinase synthesized by ovine chondrocytes in alginate bead culture. Densitometric analysis demonstrated that there was a linear relationship between the amount of chymotrypsin electrophoresed, over the range 0.1 to 10 ng, and the intensity of the band detected on Western blots using biotinylated pCTI-1 as probe, indicating that the technique could be used for the quantification of active proteinases. The biotinylated pCTI-1 detection technique was convenient to use, reproducible, and more sensitive than zymography.

Animals↗

PubMed1993

Use of the single-strand conformational polymorphism method to detect recurrent and novel mutations in the low-density lipoprotein receptor gene in patients with familial hypercholesterolaemia: detection of a novel mutation Asp200-->Gly.

The single-strand conformational polymorphism (SSCP) method was used to look for mutations in the 3' half of exon 4 of the low-density lipoprotein receptor gene in patients with familial hypercholesterolaemia (FH). One set of conditions were found which allowed the detection of four of the mutations that have previously been reported in this part of the gene and detected in patients in the United Kingdom: the 3-bp deletion (del Gly197) the 2-bp deletion (STOP 216), the Asp206-->Glu mutation and the Cys210-->STOP. The method was used to screen 50 patients with definite or probable FH from London. Two were identified who were carriers of the 3-bp deletion of Gly197, one who was a carrier of the Asp206-->Glu mutation and one who was a carrier of a novel mutation that alters Asp200-->Gly. This mutation creates a cutting site for the restriction enzyme MspI. In a further sample of 200 patients from London with FH one additional apparently unrelated individual was detected who was a carrier of this defect. Thus in the sample of 50 patients, four (8%) had a mutation in this part of exon 4 that could be readily detected using the SSCP method, suggesting that this approach will be useful for rapid screening for mutations in patients with FH.

Aspartic Acid↗

PubMed1994

Doppler echocardiography during transesophageal atrial pacing in the detection of coronary artery disease. Stress Doppler echocardiography in the detection of coronary artery disease.

The aim of this study was to assess the applicability of the Doppler echocardiogram (EchoKG) during transesophageal atrial pacing (TAP) with respect to the detection of coronary artery disease (CAD). Aortic flow peak velocity (PV), mean acceleration (MA), stroke distance (SD), minute distance (MD) and time to PV were measured using pulsed Doppler EchoKG during sinus rhythm and at pacing rates of 120 and 140 bpm in 11 patients, taken as subjects, with CAD defined by coronary arteriography and 15 patients without CAD (the control group). Similar changes of PV, SD, MD and time to PV during TAP were observed in subjects with and without CAD. Only changes of MA were different between subjects with and without CAD:MA during TAP remained unchanged in the control group and decreased from 1055.2 +/- 49.7 cm/s2 (baseline) to 829.0 +/- 55.9 cm/s2 at pacing rate 140 bpm (p < 0.05) in subjects with CAD. On the basis of these data we suggest a new criterion for the detection of hemodynamically significant CAD: decrease of MA at a pacing rate of 140 bpm > 15% of initial value. Its specificity and sensitivity in the detection of CAD were respectively 87% and 82%. We conclude that the Doppler EchoKG during TAP is a relatively simple and reliable method for the diagnosis of CAD, and that the response of the Doppler EchoKG parameter of MA to TAP is a sensitive and specific index, useful for the detection of significant coronary artery stenosis.

Cardiac Pacing, Artificial↗

PubMed1996

Simple and sensitive detection of phencyclidine in body fluids by gas chromatography with surface ionization detection.

Phencyclidine (PCP) can be detected in body fluids with very high sensitivity by gas chromatography (GC) with surface ionization detection (SID) using pethidine as internal standard. PCP was extracted with Sep-Pak C18 cartridges from whole blood and urine samples, which gave clean extracts. The calibration curve for spiked whole blood was linear in the range 1.25-20 ng/ml. The detection limit of PCP was approximately 15 pg on-column (0.75 ng/ml sample), which was much lower than by GC-nitrogen phosphorus detection. The recovery of PCP and pethidine from spiked whole blood or urine samples was above 85%. This method seems very useful for the determination of PCP in forensic and clinical toxicology.

Body Fluids↗

PubMed2000

[Early detection of prostatic carcinoma in urologic practice with digital rectal examination and prostate-specific antigen. Early Detection Project Group].

For the early detection of prostate cancer, a patient should undergo digital rectal examination (DRE) and PSA investigation. Follow-up of increased PSA levels detects nearly 80% of cancers. Positive predictive value of suspicious DRE and PSA is about 50%. Whereas in the first evaluation of this case-finding trial about 70% of the patients had organ-confined cancers, nearly all of the detected cancers in the follow-up investigation were organ confined. The increased number of organ-confined cancers detected in early periodical examinations can lead to a reduction of mortality and morbidity from prostate cancer.

Adult↗

PubMed2002

Social users of alcohol and cannabis who detect substance-related changes in a change blindness paradigm report higher levels of use than those detecting substance-neutral changes.

RATIONALE: Understanding the cognitions underpinning substance use has stalled using the Stroop paradigm. OBJECTIVE: To employ a novel version of the flicker paradigm for induced change blindness to independently compare information processing biases in social users of alcohol and cannabis. METHOD: Alcohol and cannabis experiments were independently run. In both, participants were asked to view successively and repeatedly on a monitor two versions of a visual scene (an original and a slightly changed version) until the change was detected. In fact, in both experiments two simultaneous changes competed for detection: a substance-neutral and a substance-related change. RESULTS: In both the alcohol and the cannabis experiments, participants detecting the substance-related change reported higher levels of use than those detecting the substance-neutral change. CONCLUSION: A substance-related processing bias was independently revealed for both substances. The utility of the flicker paradigm for substance use research is demonstrated as sensitive and quick to administer (taking only 1 min).

Alcohol Drinking↗

PubMed2004

Ultra-sensitive fully automated immunoassay for detection of propanil in aqueous samples: steps of progress toward sub-nanogram per liter detection.

The widely-used pesticide propanil is a selective post-emergent general-use acetanilide herbicide registered for control of broadleaf and grass weeds in rice, small grain, and turf. Because broad application and quite heavy use of this herbicide lead to contaminated sites and, consequently, contaminated water, immunoanalytical methods with very low limits of detection (LOD) and low limits of quantification (LOQ) are becoming increasingly important for environmental analysis and, especially, for monitoring drinking-water quality. Environmental monitoring of pesticides, hormones, endocrine-disrupting chemicals, and antibiotics in aqueous samples (e.g. surface, ground, waste, or drinking water) with quite difficult matrices places large demands on chemical analysis. Biosensors have suitable characteristics such as efficiency in enabling very fast, sensitive, and cost-effective detection. Here we describe the steps of progress toward sub-nanogram per liter detection of propanil with a fully automated immunoassay. In contrast with common analytical methods such as GC-MS or HPLC-MS the biosensor used requires no sample pre-treatment and pre-concentration. The basis of our sensitive assay is an antibody with a high affinity constant toward propanil. During the optimization process, we compared different surface modifications (four different immobilized derivatives) and reduced the amount of antibody per sample. In fact, optimization of the assay resulted in an LOD of 0.6 ng L(-1) and an LOQ of 4.5 ng L(-1) without any sample pre-treatment and without pre-concentration. These results for propanil with the RIANA instrument, and its improved sensitivity for detection of a single pesticide at the low nanogram per liter range, show that biosensors can compete with common analytical methods in the field of water analysis.

Autoanalysis↗

PubMed1996

Selective detection of metal species in HPLC and FIA by means of pulsed amperometric detection (PAD).

Triple-step pulsed amperometry is used to detect selectively metal complex species after HPLC separation in the presence of coeluting matrix compounds. Optimized pulse parameters enable accurate and selective detection of species even in the presence of electroactive compounds such as phenols or sulfurcontaining peptides. Complexes of tin(IV) with rutin and of platinum(II) with glutathione are presented as examples for these classes of compounds. It is demonstrated that by changing the pulse waveform direct and indirect detection modes can be realized. The method is applied to detect platinum species in a grass extract and iron(II)-lactate in fruit juice. Furthermore it is shown, that pulsed amperometry can be used as a detector in FIA for determining the fraction of metal complex formed after mixing of metal and excess ligand without separation.

Journal Article↗

PubMed2001

Tumour detection rate of a new commercially available computer-aided detection system.

The aim of this study was to determine the tumour detection rate and false positive rate of a new mammographic computer-aided detection system (CAD) in order to assess its clinical usefulness. The craniocaudal and oblique images of 150 suspicious mammograms from 150 patients that were histologically proven to be malignant were analysed using the Second Look CAD (CADx Medical Systems, Quebec, Canada). Cases were selected randomly using the clinic's internal tumour case sampler. Correct marking of the malignant lesion in at least one view was scored as a true positive. Marks not at the location of the malignant lesion were scored as false positives. In addition, mammograms with histologically proven benign masses ( n=50) and microcalcifications ( n=50), as well as 100 non-suspicious mammograms, were scanned in order to determine the value of false-positive marks per image. The 150 mammograms included 94 lesions that were suspicious due to masses, 26 due to microcalcifications and 30 showed both signs of malignancy. The overall sensitivity was 90.0% (135 of 150). Sensitivity on subsets of the data was 88.7% (110 of 124) for suspicious masses (MA) and 98.2% (55 of 56) for microcalcifications. Eight of 14 false-negative cases were large lesions. The overall false-positive rate was observed as 0.28 and 0.97 marks per image of microcalcifications and masses, respectively. The lowest false-positive rates for microcalcifications and MA were observed in the cancer subgroup, whereas the highest false-positive rates were scored in the benign but mammographically suspicious subgroups, respectively. The new CAD system shows a high tumour detection rate, with approximately 1.3 false positive marks per image. These results suggest that this system might be clinically useful as a second reader of mammograms. The system performance was particularly useful for detecting microcalcifications.

Adenocarcinoma↗

PubMed1980

Echocardiographic detection of coronary artery disease. Detection of effects of ischemia on regional myocardial wall motion and visualization of left main coronary artery disease.

M mode and cross-sectional echocardiographic studies at rest have been used to detect regional left ventricular wall motion abnormalities as a sign of hemodynamically significant coronary artery disease. These techniques have proved to be fairly specific but not highly sensitive. Detection of new regional wall motion abnormalities with cross-sectional echocardiography during exercise appeared practical in 80 percent of patients in preliminary studies; the finding of such abnormalities is highly specific for the presence of coronary artery disease and, with this approach, the sensitivity of echocardiography is improved. Thus, patients with anatomically severe coronary artery disease on angiography may not manifest an echocardiographic abnormality in regional wall motion even during exercise. The direct noninvasive detection of the left main coronary artery in up to 90 percent of patients studied with cross-sectional echocardiography using the short axis or apical approach, or both, has been well defined. A high sensitivity and specificity of detecting anatomically severe left main coronary artery disease using the criteria of both luminal impingement and the presence of high intensity echoes have been confirmed. Further advances in imaging techniques may allow for better definition of the coronary arterial tree.

Coronary Disease↗

PubMed1993

Detection of airborne cocaine and heroin by high-throughput liquid-absorption preconcentration and liquid chromatography-electrochemical detection.

A high-throughput liquid-absorption preconcentrator (HTLAP) for rapid and/or ultrasensitive detection and analysis of trace contaminants samples air at a rate of 600-700 l/min and collects analytes from vapors or aerosols at an efficiency of 40-60% into a small volume of liquid absorbent dripping at a rate of 0.1-2 ml/min. These features combine to reduce the lower detection limit (LDL) of available analytical instrumentation by a factor of > 1000 and/or to permit faster sampling and far more rapid on-site air monitoring than were previously practicable. LDLs of ca. 1:10(13) (v/v) of alkaloids have been achieved with LC and electrochemical detection. The HTLAP is directly adaptable to most liquid-phase analyzers. The small rate of liquid collection is also compatible with available interfaces to mass spectrometers. Moreover, the HTLAP permits detection and quantitation of polar or highly reactive compounds that cannot be readily analyzed by conventional preconcentration and GC.

Air Pollutants↗

PubMed1986

Enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to protein-reactive drugs and metabolites: criteria for identification of antibody activity. Detection and hapten specificity of anti-DNP, anti-captopril and anti-sulphanilamidobenzoic acid.

Certain hypersensitivity reactions to drugs are thought to depend on coupling of reactive species (the drug itself or a metabolite) to macromolecules, leading to the formation of hapten-carrier conjugates. In assays for the detection of antibodies directed against such reactive species the drug or metabolite must be used in conjugated rather than free form. We describe ELISAs for the detection of anti-dinitrophenyl (DNP), anti-captopril (CP) and anti-sulphanilamidobenzoic acid (SABA) antibodies, in which the wells of microtitre plates are coated with hapten conjugated to protein. We define coating conditions and the following 3 criteria for identification of anti-hapten activity: Immunoglobulin in the test sample binds to the immobilised hapten-protein conjugate, but not to the immobilised protein alone. Binding is inhibited by preincubation of the test sample with protein conjugates incorporating the test hapten, but not by preincubation with the same unconjugated proteins, nor protein conjugates incorporating haptenic groups unrelated to the test hapten. The inhibitory hapten-protein conjugates are shown to be inactive in unrelated antigen-antibody interactions. Binding is blocked by preincubation of the test sample with low molecular weight chemical derivatives of the reactive hapten. The inhibitory derivatives must be shown to be inactive in unrelated antigen-antibody interactions. On the basis of these criteria, IgG anti-DNP and IgG anti-CP were detected in the sera of immunized rabbits. The IgG anti-DNP antibody recognised protein-conjugated DNP, DNP-lysine, N-acetyl-DNP-lysine and DNP-S-glutathione, whereas the IgG anti-CP antibody recognised CP-S-S-protein and CP-S-S-CP. By the same criteria IgG anti-SABA was detected in the sera of immunized mice. The antibody recognised free and protein-conjugated SABA, but not free sulphanilamide.

Animals↗

PubMed1992

An enhanced chemiluminescence detection system combined with a modified immunoblot technique for the detection of low molecular weight IgM in sera from healthy adults and neonates.

An enhanced chemiluminescence detection system combined with a modified immunoblot technique is described for the detection of low molecular weight IgM (LMW IgM) in human sera and cell culture supernatants at levels down to 2 pg/ml. This detection system is reliable, specific and more sensitive than the previously described chromogenic detection system. Importantly, this method has, for the first time, revealed LMW IgM in the sera from all 34 healthy adults and 26 neonatal cord bloods tested. A significant linear correlation was observed between the LMW IgM and the total circulating IgM in both the healthy adult sera (r = 0.88, p less than 0.001) and cord blood sera (r = 0.98, p less than 0.001).

Adult↗

PubMed1994

Detection and quantitation of hepatitis C virus RNA in serum using the polymerase chain reaction and a colorimetric enzymatic detection system.

A sensitive, non-isotopic method for detecting and quantifying hepatitis C virus (HCV) RNA in serum using the reverse transcriptase-polymerase chain reaction (RT-PCR) and a hybridization specific, colorimetric biotin-avidin peroxidase detection system has been developed. The sensitivity of the PCR-colorimetric system was determined using RNA synthesized from cloned HCV cDNA. The assay could detect as few as 10 molecules of HCV RNA, comparable to the sensitivity achieved with double PCR using nested primers. Thus, this colorimetric assay can detect low levels of HCV RNA in serum and appears to be quantitative, suggesting that this technique may be applied to rapid screening of large numbers of samples and to monitor the effect of antiviral therapy.

Animals↗

PubMed1993

Improvements in detection sensitivity for the determination of ivermectin in plasma using chromatographic techniques and laser-induced fluorescence detection with automated derivatization.

Improvement in detection sensitivity for the analysis of ivermectin was observed through utilization of laser-induced fluorescence detection and by manipulation of chromatographic conditions. Gradient elution used in combination with narrow-bore chromatography and conventional fluorescence detection resulted in a limit of quantitation for the major homologue of ivermectin of 0.01 ng/ml in dog plasma. Laser-induced fluorescence detection with isocratic chromatographic conditions also resulted in a limit of quantitation of 0.01 ng/ml in dog plasma, which is a six-fold improvement over previously reported methods. Introduction of an automated procedure for the derivatization and injection of samples reduced the amount of sample handling, eliminated the potential for analyte/internal standard degradation and contributed to the overall ease of analysis.

Animals↗

PubMed1995

Two high-performance liquid chromatographic assays for the determination of free and total silibinin diastereomers in plasma using column switching with electrochemical detection and reversed-phase chromatography with ultraviolet detection.

A combination of two stereoselective assays was developed using column-switching HPLC with electrochemical detection for the determination of free (unconjugated) silibinin and RP-HPLC with UV detection for the measurement of total (free and conjugated) silibinin in human plasma. After extraction of free silibinin and the internal standard hesperetin with diethyl ether the compounds were pre-separated on a RP-CN column. A cut fraction of eluate containing the analytes was then transferred to the RP-18 main column by means of a switching valve for final separation of the compounds. The limit of quantification with electrochemical detection for free silibinin was 0.25 ng/ml per diastereomer. For the determination of total silibinin diastereomers all conjugates were cleaved enzymatically using beta-glucuronidase/arylsulfatase at pH 5.6 followed by extraction with diethyl ether of the pH 8.5 alkalized solution. Separation of the diastereomers and of the internal standard naringenin was achieved on a RP-18 column. The limit of quantification with UV detection at 288 nm for total silibinin was 5 ng/ml per diastereomer. Both assays were successfully applied to the stereospecific analysis of silibinin in plasma samples from a pharmacokinetic study of silymarin in human volunteers.

Chromatography, High Pressure Liquid↗

PubMed1996

Optimization of the separation and detection of the enantiomers of isoproterenol in microdialysis samples by cyclodextrin-modified capillary electrophoresis using electrochemical detection.

Isoproterenol is a chiral catecholamine with a half-life of elimination of less than 10 min. In order to study the pharmacokinetics of this compound using microdialysis sampling, an analytical method was needed which could resolve the individual enantiomers of isoproterenol and required less than 1 microliter of sample. A capillary electrophoretic method using a run buffer containing methyl-O-beta-cyclodextrin as a chiral recognition agent was developed which could resolve the enantiomers of isoproterenol. The detection limits using UV absorbance detection were found to be too high to determine the concentration of isoproterenol in plasma for a sufficient time following administration to establish the pharmacokinetics. The detection limits were decreased three orders of magnitude to 3 ng/ml by using an amperometric detector. The detection limits were decreased to 0.6 ng/ml using an on-column concentration technique in which peak stacking was accomplished by following the sample injection with a plug of acid.

Animals↗