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PubMed1998

Direct detection of regional myocardial ischemia with technetium-99m nitroimidazole in rabbits.

UNLABELLED: Conventional perfusion scintigraphy assesses disparities in regional myocardial blood flow but does not directly detect hypoxic tissue. Nitroimidazoles labeled with positron-emitting radionuclides have recently shown promise as direct markers of myocardial hypoxia. This study evaluates a new 99mTc-labeled nitroimidazole of potential benefit in standard myocardial scintigraphy. METHODS: Technetium-99m-labeled nitroimidazole was administered to rabbits during the early reperfusion phase after 10 min (Group 1) or 60 (Group 2) min of coronary occlusion or after 10 min of a fixed coronary occlusion (Group 3). Tracer retention at 1 hr was assessed in relation to microsphere-determined blood flow during coronary occlusion and at tracer injection. The pattern of nitroimidazole retention on autoradiographs was then compared with the pattern of myocardial hypoperfusion defined by fluorescein photography to precisely define tracer localization. RESULTS: The retention of nitroimidazole in Group 1 rabbits (brief occlusion) was independent of both occlusion and reperfusion blood flow and was uniformly distributed on the autoradiographs. In contrast, nitroimidazole retention in Groups 2 and 3 increased with the severity of hypoperfusion during the occlusion phase and precisely delineated the ischemic zone on all autoradiographs. CONCLUSION: This 99mTc-labeled hypoxia-avid tracer delineates severe ischemia even after blood flow to the compromised myocardium has been restored. This class of compounds can potentially enhance the physiological assessment of patients with ischemic heart disease.

Animals↗
PubMed1993

An enzyme immunoassay for the direct detection of adenovirus in clinical specimens.

A total of 414 clinical samples were tested by an enzyme immunoassay (EIA) for direct detection of adenovirus as well as cultured in Graham 293, A549, and human diploid foreskin fibroblast cells. Adenovirus was detected in 69 (16.7%) of 414 clinical specimens. The EIA detected adenovirus in 51 (12.3%) of 414 specimens; two were EIA positive only. Adenovirus was isolated from 67 (16.2%) of 414 specimens; 18 were culture positive only. Compared with viral isolation, EIA had a sensitivity of 73.4% and a specificity of 99.4%, with a positive predictive value of 96% and a negative predictive value of 95%.

Adenovirus Infections, Human↗
PubMed1994

A particle counting immunoassay for the direct detection of Clostridium difficile serogroup specific antigen in faecal specimens.

The potential of a particle counting immunoassay (PACIA) for the direct detection of Clostridium difficile serogroup G specific antigen in faecal specimens was evaluated. F(ab')2 fragments from a rabbit anti-serogroup G antiserum were covalently coupled to carboxylated latex beads. This reagent was mixed with acid extracts of faecal specimens and the reaction was assayed with an optical counter which discriminated unagglutinated from agglutinated latex particles. Culture for C. difficile, faecal cytotoxin detection, PACIA and serogrouping of C. difficile isolates were performed on 249 stools. Of the 71 culture-negative specimens, none gave a positive result in the cytotoxin assay or in PACIA. Faecal cytotoxin was detected in 100 of the 178 culture-positive specimens. PACIA was positive for 63 of the 71 faecal specimens that yielded serogroup G C. difficile on culture. PACIA gave negative results for all other culture-positive stools tested with one exception, from which a serogroup A7 C. difficile strain was isolated. PACIA detection of serogroup G antigen in faecal specimens showed a sensitivity of 88.7%, a specificity of 99.7%, a predictive value of a positive culture with a serogroup G strain of 98.4%, and a predictive value for specimens that were culture-negative for a serogroup G strain of 95.6%. The results indicate that PACIA with specific antiserum is a rapid and reliable method for detecting serogroup specific antigens of C. difficile in faecal specimens. Clinical applications of the method are discussed.

Agglutination Tests↗
PubMed1991

Use of the polymerase chain reaction for direct detection of Listeria monocytogenes in soft cheese.

The polymerase chain reaction (PCR) amplification technique was investigated as a tool for direct detection of Listeria monocytogenes in soft cheeses. Different sets of oligonucleotide primers were used, and parts of the L. monocytogenes Dth 18-gene could be amplified specifically when either a plasmid vector carrying the cloned gene or chromosomal DNA was used a template. The detection limit for L. monocytogenes in dilutions of pure cultures was between 1 and 10 colony-forming units. In extracts from soft cheeses containing L. monocytogenes DNA, the amplification was strongly inhibited. This inhibition could be reduced by an additional purification step. Despite this the detection limit showed a large variation, depending on the brand of cheese used. In some cheeses 10(3) cfu/0.5g could be visualized whereas in others the presence of 10(8) cfu/0.5 g did not yield a detectable quantity of amplified product.

Base Sequence↗
PubMed1997

Direct detection and isolation of plasmid-bearing virulent serotypes of Yersinia enterocolitica from various foods.

A procedure was developed for direct detection, isolation, and maintenance of plasmid-bearing virulent serotypes of Yersinia enterocolitica from different food sources. Plasmid-bearing virulent strains of Y. enterocolitica representing five serotypes were simultaneously detected and isolated from enriched swab samples of artificially contaminated pork chops, ground pork, cheese, and zucchini, using Congo red binding and low-calcium-response tests. The method was also effective in isolating plasmid-bearing virulent strains of Y. enterocolitica from naturally contaminated porcine tongues. Virulence of the strains isolated from these foods was confirmed by PCR, the expression of plasmid-associated phenotypes, and mouse pathogenicity.

Animals↗
PubMed1994

Direct detection of the porcine reproductive and respiratory syndrome (PRRS) virus by reverse polymerase chain reaction (RT-PCR).

A method for direct detection of the porcine reproductive and respiratory syndrome (PRRS) virus was developed, based on reverse transcription of the viral RNA coupled to DNA amplification by polymerase chain reaction. A set of primers was designed from Lelystad virus sequence within ORF 7 encoding nucleocapsid protein. From seven Spanish field isolated strains the 312 bp amplified fragment was cloned and sequenced. Alignment with Lelystad virus sequence revealed a 96-97% homology. A maximum sensitivity of 6.7 TCID50 was achieved with the reported procedure in experimentally infected swine alveolar macrophages cultures. The sensitivity obtained in crude clinical samples from experimentally infected 3-weeks old pigs was approximately 10(2) TCID50. High specificity for the PRRS virus was demonstrated for the method, as none of the seven common swine virus assayed rendered DNA amplification product.

Animals↗
PubMedDate not supplied

Direct detection of therapeutic concentrations of tricyclic antidepressants in whole hemolyzed blood using the EMITtox serum tricyclic antidepressant assay.

A simple, rapid, and sensitive method for the direct detection of tricyclic antidepressant drugs in whole hemolyzed blood using an enzyme immunoassay technique is described. A methanolic extract prepared from as little as 200 microL of whole blood is analyzed directly using the EMITtox serum tricyclic antidepressant assay, allowing it to be used with whole blood rather than only serum. The minimum detectable concentration of most of the tricyclics is in the range of 25-50 ng/mL, a therapeutic or subtherapeutic, rather than toxic, concentration. The proposed assay shows excellent precision with a mean coefficient of variation (CV) of 0.7%. The cross-reactivity of 12 tricyclic antidepressant drugs is reported. The relationship between drug structure and relative assay response is thoroughly investigated. The relative assay response due to each of nine separate molecular features is calculated. The relationship between the molecular structure and EMIT assay response on a molar basis is shown to be not only quantitative but also additive. This should allow the quantitative prediction of EMIT assay response for drugs or compounds having similar structures.

Antidepressive Agents, Tricyclic↗
PubMed1991

Direct detection of molluscum contagiosum virus in clinical specimens by dot blot hybridization.

A dot blot hybridization protocol was developed for the direct detection of molluscum contagiosum virus (MCV) DNA in clinical specimens submitted for virus isolation. Samples were concentrated by high-speed centrifugation and treated with proteinase K; this was followed by a single phenol-chloroform extraction step. The DNA was denatured, and the entire volume was spotted onto a nitrocellulose membrane. A biotinylated DNA probe specific for the BamHI-C region of MCV type 1 was used for hybridization. Evidence of MCV DNA was visualized by using streptavidin alkaline phosphatase conjugate and 5-bromo-4-chloro-3-indolyl phosphate-nitroblue tetrazolium as the substrate. Results showed that nonspecific hybridization does not occur with herpes simplex virus- or orf virus-infected clinical specimens and that dot blotting is more sensitive and reproducible than electron microscopy.

DNA Probes↗
PubMed2003

Development of real-time detection direct test for hepatitis B virus and comparison with two commercial tests using the WHO international standard.

AIMS: A highly reproducible and sensitive hepatitis B virus real-time detection direct (HBV RTD-direct) test using DNA extraction by magnetic beads coated with polyclonal anti-HBsAg, followed by the real-time detection polymerase chain reaction (PCR) method, was developed for the detection of HBV DNA. METHODS: The HBV DNA could be extracted from the HBsAg positive viral particles without resulting in viral DNA fragmentation. The HBV RTD-direct test was validated using a serial dilution panel of the WHO standard HBV DNA 97/746 I. RESULTS: The test had a dynamic range of 0.7-8.0 log10 international units (IU) per mL and the results were shown to be comparable to those obtained with two commercially available tests: the HBV DNA transcription-mediated amplification-hybridization protection assay and the Amplicor HBV Monitor test. In addition, the HBV RTD-direct test, based on magnetic extraction, successfully eliminated PCR inhibitors in clinical specimens. CONCLUSION: We conclude that the HBV RTD-direct test is an excellent alternative for monitoring patients undergoing antiviral treatment or for screening various clinical specimens.

DNA, Viral↗
PubMed1990

Direct detection of group B streptococci from vaginal specimens compared with quantitative culture.

Determination of prenatal vaginal carriage of group B streptococci (GBS) is important in the management of newborns. A pronase extraction-latex particle agglutination method (Streptex; Wellcome Diagnostics, Dartford, England) was used to rapidly detect GBS species-specific antigen directly from vaginal specimens. It was compared with quantitative and broth enrichment cultures. A total of 434 vaginal swab specimens were obtained before delivery. GBS cultures were positive for 14.7% of the specimens (64 of 434). Colony counts ranged from 2 to greater than 10(6) CFU per swab. The sensitivities of the direct antigen analysis were 19% (12 of 64) for all cultures and 63% (12 of 19) for specimens heavily colonized with GBS (greater than 10(4) CFU per swab). The specificity of the antigen test was 99.7%, with only one false-positive. There were three false-negative tests with colony counts of greater than 10(6) CFU per swab. The predictive values were 92% for a positive antigen test and 88% for a negative antigen test. The direct immunochemical detection of GBS antigen can be useful in a population of heavily colonized women. Direct latex particle agglutination does not appear to be salutary for a lightly colonized population and does not appear to be able to replace either culture or antigen detection after growth amplification at this time.

Antigens, Bacterial↗
PubMed1989

Direct detection of radical production in the ischaemic and reperfused myocardium: current status.

Electron spin resonance (e.s.r.) spectroscopy, which is a specific method for directly detecting free radicals in biological systems, has now been used in a number of studies to examine free radical generation in both ischaemic and reperfused myocardial tissue. This review critically assesses the information which has been obtained to date with particular reference to the elucidation of the nature and source of the radicals observed in these studies.

Animals↗
PubMed2006

Silicon avalanche photodiodes for direct detection of X-rays.

Silicon avalanche photodiodes (APDs) are discussed as fast X-ray detectors for synchrotron radiation. The emphasis is on ;direct' detection, where the X-ray is absorbed within the silicon APD itself, and, therefore, on use with medium-energy X-rays, <30 keV. The impact of APD structure on device performance is examined, and representative data from many different commercial devices are presented. Specific areas discussed include signal shapes, high-rate behavior, time resolution and pulse-height response. Data from several APD arrays are also presented, as is a detailed description of an integrated package system. Tables are included comparing commercially available devices, including arrays.

Equipment Design↗
PubMed1994

Direct detection of Mycobacterium tuberculosis complex in respiratory specimens by a target-amplified test system.

A total of 938 respiratory specimens (633 sputa, 249 bronchial and tracheal aspirates, and 56 bronchoalveolar lavages) from 589 patients were tested for direct detection of Mycobacterium tuberculosis complex by the Gen-Probe amplified Mycobacterium tuberculosis direct test (MTD), and the results were compared with those of the conventional methods of fluorescence microscopy and cultivation (solid and radiometric media). One series of specimens (n = 515) was decontaminated with N-acetyl-L-cysteine (NALC)-NaOH: the other one (n = 423) was decontaminated with sodium dodecyl (lauryl) sulfate (SDS)-NaOH. Of the specimens decontaminated with NALC, 39 were MTD and culture positive, 455 were MTD and culture negative, 18 were MTD positive and culture negative, and 3 were MTD negative and culture positive, indicating a sensitivity of 92.9% and a specificity of 96.2% for the MTD. Of the specimens decontaminated with SDS, 35 were MTD and culture positive, 372 were MTD and culture negative, 15 were MTD positive and culture negative, and 1 was MTD negative and culture positive, indicating a sensitivity of 97.2% and a specificity of 96.1% for the MTD. After resolution of discrepant results by review of the patients' clinical data, the sensitivity of the MTD was 93.9%, the specificity was 97.6%, the positive predictive value was 80.7%, and the negative predictive value was 99.3% for the NALC series; the corresponding values were 97.4, 96.9, 76.0, and 99.7%, respectively, for the SDS series. In conclusion, the MTD is a highly sensitive and specific technique for detecting M. tuberculosis complex within hours in both smear-positive and smear-negative respiratory specimens.

Adult↗
PubMed1994

Direct detection of radical generation in rat liver nuclei on treatment with tumour-promoting hydroperoxides and related compounds.

EPR spin trapping has been employed to directly detect radical production in isolated rat liver nuclei on exposure to a variety of hydroperoxides and related compounds which are known, or suspect, tumour promoters. The hydroperoxides, in the absence of reducing equivalents, undergo oxidative cleavage, generating peroxyl radicals. In the presence of NADPH (and to a lesser extent NADH) reductive cleavage of the O-O bond generates alkoxyl radicals. These radicals undergo subsequent rearrangements and reactions (dependent on the structure of the alkoxyl radical), generating carbon-centred radicals. Acyl peroxides and peracids appear to undergo only reductive cleavage of the O-O bond. With peracids this cleavage can generate aryl carboxyl (RCO2.) or hydroxyl radicals (HO.); with acyl peroxides, aryl carboxyl radicals are formed and, in the case of t-butyl peroxybenzoate, alkoxyl radicals (RO.). The radicals detected with each peroxide are similar in type to those detected in the rat liver microsomal fraction, although the extent of radical production is lower. The subsequent reactions of the initially generated radicals are similar to those determined in homogeneous chemical systems, suggesting that they are in free solution. Experiments with NADPH/NADH, heat denaturation of the nuclei and various inhibitors suggest that radical generation is an enzymatic process catalysed by haemoproteins, in particular cytochrome P-450, and that NADPH/cytochrome P-450 reductase is involved in the reductive cleavage of the O-O bond. The generation of these radicals by the rat liver nuclear fraction is potentially highly damaging for the cell due to the proximity of the generating source to DNA. Several previous studies have shown that some of the radicals detected in this study, such as aryl carboxyl and aryl radicals, can damage DNA, via various reactions which result in the generation of strand breaks and adducts to DNA bases: these processes are suggested to play an important role in the tumour promoting activity of these hydroperoxides and related compounds.

Animals↗
PubMed2002

SPIFI: a direct-detection imaging spectrometer for submillimeter wavelengths.

The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind-a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI's focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 microm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI's sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument's large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope.

Journal Article↗
PubMed1999

Evaluation of three nucleic acid amplification methods for direct detection of Mycobacterium tuberculosis complex in respiratory specimens.

Two hundred thirty respiratory specimens from 230 patients were analyzed by using COBAS AMPLICOR PCR, Amplified Mycobacterium tuberculosis Direct Test, and ligase chain reaction methods. Results were compared with those of smear microscopy and radiometric culture (Bactec) methods. No significant differences were observed among the results of the three methods, which are acceptable for direct detection of M. tuberculosis complex in respiratory specimens.

Bacteriological Techniques↗