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At least 793 records · Page 44Linked to original sources
PubMed1991

Comparative evaluation of an enzyme-linked immunosorbent assay (ELISA) to detect antibodies directed against glycoprotein I of pseudorabies virus and a conventional ELISA and neutralization tests.

To determine whether a newly developed enzyme-linked immunosorbent assay (ELISA), which detects antibodies directed against glycoprotein I (gI) of pseudorabies virus, is suitable for serodiagnosis, it was compared with a conventional ELISA and two neutralization tests. The gI ELISA was 99.2% as sensitive and 100% as specific as the conventional ELISA. Antibody titers measured by the gI ELISA were lower than those measured by the conventional ELISA, comparable to those measured by the 24-h neutralization test, and higher than those measured by the 1-h neutralization test. After experimental infections in pigs, antibodies were first detected by the gI ELISA on postinoculation day (PID) 14, by both neutralization tests on PID 7, and by the ELISA on PID 10. All four tests showed the same rate of decline of maternal antibodies in pigs born to sows that had been vaccinated with inactivated vaccine. Thus, not only is the gI ELISA unique in being able to differentiate infected pigs from those vaccinated with gI-negative vaccines, but it is also as useful as a conventional ELISA and as neutralization tests for serodiagnosis.

Animals↗
PubMed1983

Contrast detection and direction discrimination of drifting gratings.

Observers performed simple detection and left/right discrimination of drifting sinusoidal gratings. Ratio of detection to discrimination sensitivities was measured under variations in several experimental parameters. In the first experiment, it was found that combinations of spatial and temporal frequency which resulted in the same velocity produced similar detection-discrimination ratios. At an exposure duration of 800 msec, the relationship between the ratio and velocity described a power function with the intercept at 0.6 sec-1. Decreasing duration shifted the curve to higher velocities. I examined the effect of grating orientation in a second experiment. Visual sensitivity was poorer for oblique than for vertical gratings with detection and discrimination exhibiting similar size anisotropies. In a third experiment, observers viewed gratings presented to different retinal loci. Visual performance in both detection and discrimination fell with greater eccentricity. However, motion discrimination fell more steeply resulting in an increase in the ratio. The results demonstrate that form and motion analyzing mechanisms cannot be distinguished by their response to changes of spatial frequency, orientation or retinal locus.

Discrimination, Psychological↗
PubMed2002

On-column complexation of metal ions using 2,6-pyridinedicarboxylic acid and separation of their anionic complexes by capillary electrophoresis with direct UV detection.

On-column complexation of metal ions with 2,6-pyridinedicarboxylate (2,6-PDC) to form anionic complexes enabled their separation by capillary zone electrophoresis with direct UV detection at 214 nm. Nine metal ions, Cu2+, Zn2+, Ni2+, Cd2+ Mn2+, Pb2+, Fe3+, Al3+ and Ca2+, were determined in less than 7 min using 10 mM 2.6-PDC solution containing 0.75 mM tetradecyltrimethylammonium bromide at pH 4.0. Satisfactory working ranges (20-300 microM), detection limits (3-10 microM) and good repeatability of the peak areas (RSD 2.1-4.2%, n=5) were obtained using hydrodynamic injection (30 s). The proposed method was used successfully for the determination of Mn2+, Fe3+, Al3+ and Ca2+ in groundwaters.

Electrophoresis, Capillary↗
PubMed2000

Approaching a million-fold sensitivity increase in capillary electrophoresis with direct ultraviolet detection: cation-selective exhaustive injection and sweeping

A novel method that combines two on-line concentration techniques in capillary electrophoresis (CE), namely, sample stacking with electrokinetic injection (field-enhanced sample injection, FESI) and sweeping, afforded the detection of positively chargeable analytes in parts per trillion (ppt) levels. The main idea is to selectively introduce by FESI as many molecules of cationic analytes as possible from a very dilute sample solution and focus the resulting zone by sweeping. Limit of detection values (signal-to-noise ratio 3) of 4.1 and 8.0 ppt-the lowest concentration reported by direct UV detection in CE-with average plate numbers of 3.6 x 10(5) and 4.4 x 10(5) are obtained for laudanosine and naphthylamine (standard solutions), respectively. This translates to improvements in peak heights compared with usual injection approaching a million-fold. Optimization schemes and application to quantitative and qualitative analyses are also investigated.

Journal Article↗
PubMed1987

Detection of herpes simplex virus in direct specimens by immunofluorescence assay using a monoclonal antibody.

A monoclonal antibody (MAb), designated CHA 437, was developed against herpes simplex virus (HSV). This MAb (isotype, immunoglobulin G2b K) reacted with HSV type 1 and HSV type 2. It showed no cross-reactivity with varicella-zoster virus, cytomegalovirus, or Epstein-Barr virus. Direct detection of HSV antigen in clinical specimens using indirect immunofluorescence with this MAb was compared with tissue culture isolation. For the 682 specimens tested, the direct specimen test gave a sensitivity of 84.6% and a specificity of 95.7%.

Animals↗
PubMed2004

Native fluorescence detection of flavin derivatives by microchip capillary electrophoresis with laser-induced fluorescence intensified charge-coupled device detection.

To widen the scope of laser-induced fluorescence (LIF) for detection in microchip capillary electrophoresis (CE), a microchip CE LIF-ICCD (intensified charge-coupled device) system based on a tunable wavelength dye laser pumped by a pico-second pulse nitrogen laser for excitation and a spectrograph with ICCD for detection had developed to demonstrate the enhancement in detection sensitivity by the following three approaches: direct detection of native fluorescence, improvement of signal-to-noise ratio by pulse laser excitation and time delay detection, and selective spectral acquisition by multi-channel detection. Riboflavin, flavin mononucleotide (FMN) and flavin-adenine dinucleotide (FAD) have been selected as they are dietetically important and microchip CE provides a promising onsite detection method. The results indicate a strong effect of wavelength on detection sensitivity and the need to tune wavelength for direct detection. Under optimized conditions (excitation 450 nm, emission 520 nm, gate delay time 45 ns, 20 mM phosphate buffer at pH 7.1), the following results were obtained under static condition: Working ranges (0.6-350 microg/l, r > 0.99), detection limits (0.15-1.0 microg/l) and peak height repeatability (1.8-2.2% R.S.D.), all within the applicability range for body fluids or beverages such as human urine and cow milk. Baseline separation of three flavins was obtained under dynamic condition and the fluorescence spectra acquired assist the identification of alkaline-degraded products of riboflavin. Thus, the capability to check peak purity and identify unknown peaks has been demonstrated.

Electrophoresis, Capillary↗
PubMed1997

A two year prospective study to compare culture and polymerase chain reaction amplification for the detection and diagnosis of Lyme borreliosis.

AIM: To compare polymerase chain reaction (PCR) amplification of borrelial DNA and culture isolation of spirochaetes for the diagnosis of Lyme borreliosis by direct detection of Borrelia burgdorferi sensu lato in patients with erythema migrans and acrodermatitis chronica atrophicans lesions. METHODS: Skin biopsy specimens from erythema migrans and acrodermatitis chronica atrophicans lesions were subdivided and tested by PCR amplification assay and culture using two artificial growth media, Barbour-Stoenner-Kelly II (BSK II) and modified Kelly-Pettenkofer (MKP). Five classes of lesions were studied: typical erythema migrans, spontaneously resolved erythema migrans, atypical/partially treated erythema migrans, typical acrodermatitis chronica atrophicans, and atypical/partially treated acrodermatitis chronica atrophicans. RESULTS: For both erythema migrans and acrodermatitis chronica atrophicans lesions, the most sensitive detection method was MKP culture. PCR was less sensitive than MKP culture, but more sensitive than BSK II culture. Results for 758 typical erythema migrans specimens showed positivity rates of 36% for MKP, 25% for PCR, and 24% for BSK II. Differences were statistically significant. The overall positivity rate for all three methods combined was 54%, but few specimens (6%) were positive by all three methods. Examination of multiple erythema migrans lesions from the same patient increased the diagnostic yield. These findings, and similar results for acrodermatitis chronica atrophicans lesions, suggest that the distribution of spirochaetes in skin biopsies is not homogeneous. CONCLUSIONS: Although possessing the potential to provide a rapid diagnosis, PCR is not more sensitive than culture for the direct detection of borrelia. Spirochaetes appear to be unevenly distributed throughout biopsy specimens, suggesting that diagnosis of Lyme borreliosis by direct detection of the causative agent in skin lesions in vulnerable to sample bias.

Acrodermatitis↗
PubMed2003

[Molecular diagnosis of mycobacteria].

Tuberculosis is one of the leading infectious diseases in the world. Using conventional methods, the isolation, identification, and drug susceptibility testing of Mycobacterium tuberculosis and other clinically important mycobacteria can take several weeks. During the past several years, molecular methods have been developed for direct detection, species identification, and drug susceptibility testing of mycobacteria. These methods can potentially reduce the diagnostic time from weeks to hours. For direct detection of Mycobacterium tuberculosis from clinical specimens, several molecular assays are commercially available today. They have been shown useful for the routine diagnostic laboratory. DNA probes and polymerase chain reaction-based sequencing have been widely used to identify mycobacterial species. Molecular methods have also been applied for the detection of mutations that confer drug resistance in mycobacteria. All in all, the future of clinical mycobacteriology appears to be heading toward direct detection, species identification and drug resistance determination using molecular methods.

DNA Probes↗
PubMed2005

Direct fluorescence detection of Pb2+ and Cd2+ by high-performance liquid chromatography using 1-(4-aminobenzyl)ethylenediamine-N,N,N',N'-tetraacetate as a pre-column derivatizing agent.

A highly sensitive HPLC with direct fluorescent detection (lambda(ex) = 235 nm, lambda(em) = 355 nm) was developed for Pb2+ and Cd2+ complexes with an aromatic polyaminocarboxylate, 1-(4-aminobenzyl)ethylenediamine-N,N,N',N'-tetraacetate as a pre-column derivatizing agent. A reversed phase partition column pretreated by a cationic surfactant was employed. Although this ligand forms thermodynamically stable complexes with various metal ions, only peaks of Pb2+ and Cd2+ were detected with the ligand-centered emission in the HPLC due to the emissive activity and kinetic stability in the dissociation reaction. The detection limits obtained were 1.5x10(-8) and 3.3x10(-9) mol l(-1) for Pb2+ and Cd2+, respectively.

Acetates↗
PubMed2005

Direct NMR detection of the "invisible" alkali metal cations tightly bound to G-quadruplex structures.

We report the first direct solution NMR detection of the alkali metal cations (23Na+, 39K+, and 87Rb+) residing inside G-quadruplex channel structures formed by guanosine 5'-monophosphate and a DNA oligomer, d(TG4T). In solution, these channel alkali metal cations are tightly bound to the G-quadruplex structure and have been considered to be "invisible" to NMR spectroscopy for many years. Our finding that it is possible to directly observe these alkali metal cations by NMR spectroscopy provides a new tool for studying cation binding affinity and dynamics in G-quadruplex DNA.

Cations↗
PubMed2002

Surfactant bilayers for the direct electrochemical detection of affinity interactions.

Simple methods of preparing the direct affinity sensors are proposed. Due to the self-consistent introduction of a hydrocarbon chain bound with oligonucleotide pentadecathymidylate (dT(15)) into the hydrophobic region of surfactant bilayer or the adsorption of antibodies on the bilayer surface, the immobilizations of oligonucleotide or antibodies were carried out correspondingly. The responses were detected by impedance spectroscopy. Whereas the specific DNA-coupling caused the decrease of real part of impedance, the antibody-antigen interaction caused the increase of real part. The obtained results give an opportunity for the development of impedimetric affinity sensors for clinical analysis or for the detection of various environmental pollutants.

Electrochemistry↗
PubMed1999

High sensitivity simultaneous determination in hair of the major constituents of ecstasy (3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyamphetamine and 3,4-methylene-dioxyethylamphetamine) by high-performance liquid chromatography with direct fluorescence detection.

A simple, but sensitive and specific high-performance liquid chromatographic assay for the simultaneous determination of the major constituents of "ecstasy" [i.e. 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxyethylamphetamine (MDE)] with direct fluorimetric detection, particularly intended for the routine analysis of hair, is described. Hair samples (100 mg) were overnight incubated in 1 ml of 0.25 M HCl at 45 degrees C and extracted with a commercial liquid-liquid method. The dried residue reconstituted with 500 microl of 0.05 M NaH2PO4 pH 5.2 was injected. Isocratic reversed-phase liquid chromatography was carried out on a column (250x4.6 mm I.D.) packed with spherical 5-microm poly(styrene-divinylbenzene) particles; the mobile phase was composed of 0.1 M potassium phosphate (pH 3)-acetonitrile (82:18). The excitation and the emission wavelengths were set to 285 and 320 nm, respectively. Under the described conditions, MDA, MDMA and MDE eluted in symmetric peaks with an analysis time of 30 min. The limit of detection was lower than 1 ng/ml, with a signal-to-noise ratio of 5, for each compound in solution, allowing a cut-off of 0.1 ng/mg in the hair matrix to be established. The intra-day precision (n = 6) of the assay was characterised by RSDs between 1.0 and 3.0% and between 0.52 and 0.88% for concentrations of 10 and 100 ng/ml, respectively; in day-to-day precision tests (n = 6), RSDs ranged between 5.12 and 11.12%, respectively, for the same concentrations. Interferences from as many as 92 therapeutic and/or abused drugs currently in use in the population were excluded, including N-methyl-1-(3,4-methylenedioxyphenyl)-2 butanamine (MBDB).

Chromatography, High Pressure Liquid↗
PubMed1985

Detection of Chlamydia trachomatis with fluorescent monoclonal antibody.

Commercial kits of fluorescein-labelled monoclonal antibody against Chlamydia trachomatis have been evaluated (1) as an alternative to Giemsa staining for detection of chlamydia inclusions in cell culture and (2) for direct detection of chlamydia in conjunctival, urethral and cervical smears. The inclusion-detection kit (Micro Trak Culture Confirmation Test) was tested on 270 cultures and was found to be highly sensitive, detecting all 16 Giemsa-positive specimens plus an additional 3 that were negative by Giemsa. It was also superior to Giemsa-staining in terms of simplicity of use, ease of detection, and readability with toxic specimens. The direct detection kit (Micro Trak Direct Specimen Test) gave results which agreed with the culture result for all 33 genital tract specimens and for 32 of 34 conjunctival specimens tested in parallel. The kit is considered to be a valuable test for diagnosis of chlamydial infection by laboratories lacking adequate tissue-culture facilities.

Antibodies, Monoclonal↗
PubMed2002

On-column complexation and simultaneous separation of vanadium(IV) and vanadium(V) by capillary electrophoresis with direct UV detection.

An on-column complexation method has been developed for the simultaneous determination of V(IV) and V(V). Vanadium species were chelated with aminopolycarboxylic acids to form anionic complexes which were separated by capillary zone electrophoresis (CZE) with direct UV detection. Ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentacetric acid (DTPA), nitrilotriacetic acid (NTA), and N-2-hydroxyethylethlendiaminetriacetric acid (HEDTA) were investigated as both ligand and running electrolyte. Of the ligands studied the complexes of EDTA with V(IV) and V(V) resulted in the highest selectivity and UV response. The conditions used for on-column complexation and separation, including pH, and electrolyte ligand concentration, were examined to achieve reasonable separation selectivity and detection sensitivity. The optimum separation of the anionic forms of V(IV) and V(V) was obtained by use of CZE with UV detection at 185 nm and an electrolyte containing 5 mmol L(-1) EDTA at pH 4.0. Linear calibration plots were obtained in the concentration range10-300 micro mol L(-1); detection limits were 3 micro mol L(-1) for V(IV) and 1 micro mol L(-1) for V(V). The proposed method was demonstrated for the determination of vanadium in groundwater spiked with V(IV) and V(V).

Edetic Acid↗
PubMed1994

[Nucleic probes and PCR: application in the diagnosis of bacterial infections].

Probes and amplification systems represent new technologic developments in the domain of clinical microbiology. In spite of their high specificity, simple applicability and high velocity the DNA probes show only little sensitivity especially for the direct detection of microorganisms in clinical samples. This sensitivity lead to the development of DNA-amplification technics. PCR is the most famous of them and the most often used one. Next to the direct detection of microorganisms in clinical samples without culture these technics also allow the direct isolation of bacterial toxins, of genes for resistance to antibiotics as well as a systematic search for pathogens in diseases with unknown cause. Different problems of these methods in daily clinical practice are illustrated by four applications 1. direct detection of mycobacterium tuberculosis complex (M. tbc) in clinical samples, 2. rapid identification of mycobacterial species, 3. their typing for epidemiologic intentions, 4. rapid detection of resistance to antibiotics.

Bacterial Infections↗
PubMed2004

Migratory birds use head scans to detect the direction of the earth's magnetic field.

Night-migratory songbirds are known to use a magnetic compass , but how do they detect the reference direction provided by the geomagnetic field, and where is the sensory organ located? The most prominent characteristic of geomagnetic sensory input, whether based on visual patterns or magnetite-mediated forces , is the predicted symmetry around the north-south or east-west magnetic axis. Here, we show that caged migratory garden warblers perform head-scanning behavior well suited to detect this magnetic symmetry plane. In the natural geomagnetic field, birds move toward their migratory direction after head scanning. In a zero-magnetic field , where no symmetry plane exists, the birds almost triple their head-scanning frequency, and the movement direction after a head scan becomes random. Thus, the magnetic sensory organ is located in the bird's head, and head scans are used to locate the reference direction provided by the geomagnetic field.

Animal Migration↗
PubMed1998

Validation of a monoclonal antibody-based ELISA to detect antibodies directed against swine vesicular disease virus.

A simple, rapid and sensitive competitive monoclonal antibody-based ELISA for the detection of antibodies directed against swine vesicular disease virus (SVDV) was developed. The ELISA was validated using field sera originating from SVDV-infected and non-infected Dutch pig herds, reference sera obtained from the Community Reference Laboratory for Swine Vesicular Disease at the Institute for Animal Health, Pirbright Laboratory, UK, and sera from animals infected experimentally. When testing 4277 sera originating from non-infected Dutch pig herds and collected as part of the national screening program, this ELISA had only 0.6% false positive results, whereas approximately 2% of false positive results were obtained with a conventional blocking ELISA used until recently. A sensitivity relative to the virus neutralisation test of > 97% was achieved when testing sera collected from Dutch pig farms where an outbreak of SVDV had occurred. All international reference sera scored consistently correct. Sera collected sequentially from pigs experimentally infected with SVDV isolates representing all currently recognized antigenic groups, were scored positive slightly earlier by the ELISA compared to the virus neutralisation test. This monoclonal antibody-based competitive ELISA for SVDV antibodies designated the Ceditest ELISA for SVDV-Ab, is as sensitive but more specific than the ELISA used until recently. Because sera are tested at a single dilution (1:5), incubations are carried out at room temperature and test results are available within 3 h, this ELISA is simple, easy to automate and therefore very suitable for screening large numbers of serum samples.

Animals↗