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At least 523 records · Page 29Linked to original sources
PubMed1979

An approach to direct detection of sinus nodal activity in man.

We are reporting a series of 13 out of a total of 16 patients in whom sinus nodal activity was recorded with the use of intra-atrial electrodes, during diagnostic His-bundle electrocardiography investigations. The protocol consisted of the simultaneous monitoring of the following intra-atrial points: high right atrium, low lateral right atrium, left atrium and the His-bundle electrogram (HBE), which accompanied the detecting sonde placed as a loop in the superior vena cava, with the electrodes facing the sinus nodal area. This permitted an adequate assessment of the sequence of the depolarizing activity. All patients showed sinus nodal potentials preceding the initiation of the P-wave in the surface-EKG or the atrial potential in the high right atrial lead, respectively, in the range of 60 to 270 msec depending upon the functional status of the sinus node in each patient. Such waves were clearly separated from the initiation of the atrial potential by an isoelectric line and showed functional traits compatible with the S-A nodal functions, as many authors have previously reported in experimental animal models. The text contains a review of the relevant literature and discussion upon the diagnostic significance of this method in the assessment of sinus nodal disease.

Adult↗
PubMed2002

Direct detection of singlet oxygen via its phosphorescence from cellular and fungal cultures.

In summary, we have developed methods to detect 1O2 spectrally from viable keratinocytes and fungal mycelial cultures. Both time-resolved and steady-state spectrophotometers were used, providing complementary information on optimal conditions for the unambiguous detection of 1O2 phosphorescence. By using our techniques, we were able to confirm that photosensitizers in contact with living cells indeed generate 1O2. The model systems and the procedures described can be adopted for other studies involving 1O2 and oxidative stress in living cells.

Ascomycota↗
PubMed2002

Direct detection of isotopically labeled metabolites bound to a protein microarray using a charge-coupled device.

A charge-coupled device (CCD) was used to quantitatively detect isotope-labeled ligands bound to a protein microarray. Protein microarrays with protein dots, 10-50 microm in diameter, were fabricated on an aluminized Mylar film using an electrospray deposition technique. Proteins in dots were immobilized by cross-linking in glutaraldehyde vapor. After contact with solutions of isotope-labeled metabolites, the protein microarrays were washed, dried and placed face down onto the surface of a standard B/W video CCD chip with the protective window removed. We show here that such a simple inexpensive CCD detector can be used to quantify distribution of 14C and other radioactive isotopes on microarrays.

Automation↗
PubMed1997

Direct detection of Mycobacterium tuberculosis using polymerase chain reaction assay among patients with hepatic granuloma.

BACKGROUND: In liver tuberculosis, demonstration of acid bacilli by conventional methods remains futile. Since the definitive diagnosis of liver tuberculosis is based on the histologic evidence of granulomatous process with caseation necrosis, seen in only a third of cases, the diagnosis is made retrospectively by response to empirical anti-tuberculous drug therapy. AIMS: Our objective is to establish a polymerase chain reaction assay for detection of Mycobacterium tuberculosis affecting the liver using the paraffin-embedded liver biopsy specimens obtained from patients with hepatic granulomas. METHODS: As positive control, patients having either "definitive" (n=8) or "presumptive" (n=9) tuberculosis on the basis of clinical, microbiological, histologic data and their positive response to empirical treatment of anti-tuberculous drugs were used. Patients with hepatic granulomas secondary to schistosomiasis (n=6), sarcoidosis (n=2) and other liver diseases (n=10) were used as negative control. RESULTS: Of those patients who were diagnosed as having "definitive" and "presumptive" liver tuberculosis, positivity by one-step polymerase chain reaction was 100% and 44%, respectively. Using the nested polymerase chain reaction, positivity increased to 78% with "presumptive" liver tuberculosis. In contrast, the polymerase chain reaction assays were negative among all patients with hepatic granuloma due to non-tuberculous-in-origin and other liver diseases. CONCLUSIONS: The overall positivity of this polymerase chain reaction assay (88%) compares favorably with that of other conventional methods (12%). Thus, this polymerase chain reaction assay may be a reliable diagnostic tool for liver tuberculosis in a patient population in which the prevalence of diseases associated with hepatic granuloma is common.

Adolescent↗
PubMed1998

Separation of a range of cations by nonaqueous capillary electrophoresis using indirect and direct detection.

The use of nonaqueous media and indirect detection is reported for the separation and detection of a range of small cations. The novel applications involved separation of a range of metal ions, small nonchromophoric amines, cationic ion-pair reagents and cationic surfactants. Separations were achieved using acidified methanol containing imidazole as the UV co-ion for indirect detection. The methods produced different selectivity compared to aqueous methods using acidified aqueous imidazole solutions. Advantages of the methods include speed of analysis and prevention of sample micellerisation. The methods were shown to be quantitative and reproducible by their application to the determination of Tris content.

Amines↗
PubMed2000

Direct detection of dissolution of 14C-labeled compounds into an oil phase by the fat scintillation proximity method.

Traditional analysis of the dissolution of lipophilic compounds from aqueous phase into oil is often hampered by the necessity to separate the receiver oil compartment from the aqueous phase. In order to avoid possible artefacts associated with additional separation methods, a procedure was developed to selectively detect the entry of a compound into the oil phase of a oil/water dispersion. When a combination of a primary and secondary scintillator was predissolved in the oil, and solid 14C-tetrahydrolipstatin was added, increasing signals from the same container were measured upon prolonged incubation. The data are consistent with the hypothesis that 14C-THL that has dissolved in the oil phase is essentially responsible for the measured signal. The obtained dissolution profiles of 14C-THL into oil match with parallel experiments using classical procedures.

Carbon Radioisotopes↗
PubMedDate not supplied

Development of a ceuE-based multiplex polymerase chain reaction (PCR) assay for direct detection and differentiation of Campylobacter jejuni and Campylobacter coli in Thailand.

A novel ceuE-based multiplex PCR system was developed as an efficient diagnostics test to detect and differentiate C. jejuni and C. coli. There is no cross reactivity between C. jejuni and C. coli. In addition, the assay does not produce a positive signal from other enteric bacteria including Salmonella, Shigella and Escherichia coli strains. Campylobacter detection sensitivity was determined to be equivalent to previously reported PCR for other enteric bacteria. We also noticed that silicon dioxide extraction can improve Campylobacter detection sensitivity from infected stool samples. It was demonstrated that the PCR assay developed in this study had a much better Campylobacter detection rate than the traditional culturing method (77% versus 56%). However, we also identified small numbers of culture positive stools (8%, or 16 out of 202 samples) that did not yield PCR positive results for Campylobacter. These PCR negative/culture positive stools were proven to be inhibitory to PCR amplification.

Bacterial Proteins↗
PubMed2003

Evaluation of the BDProbeTec ET system as screening tool in the direct detection of mycobacterium tuberculosis complex in respiratory specimens.

We evaluated the BDProbeTec ET System (Becton Dickinson) for the routine detection of Mycobacterium tuberculosis complex (MTC) in respiratory specimens and pleural fluids, comparing with microscopy (Ziehl Neelsen stain, ZN) and culture in liquid (BACTEC MGIT 960, MGIT) and solid (Löwenstein Jensen, LJ) media. Five hundred and two specimens, collected from 266 patients, of which 257 with suspected tuberculosis and 9 receiving anti-tuberculosis treatment, were investigated. Thirty-nine specimens were positive by any method, including false positives. Mycobacteria were isolated from 33 specimens (32 Mycobacterium tuberculosis and 1 Mycobacterium chelonae). Thirty-six specimens were BDProbeTec ET positive, 33 specimens were MGIT positive, 27 were LJ positive and 22 were ZN positive. With BDProbeTec ET, 2 specimens were false negative (culture positive), and 2 specimens from non-treated patients were false positive (culture negative). The overall sensitivity, specificity, and positive and negative predictive values for BDProbeTec ET compared to culture were 93.7, 98.7, 83.3, and 99.5%, respectively, while with smear-positive and smear-negative specimens the sensitivities were 100% and 81.5% respectively. In five treated patients the disappearance of MTC could be monitored using BDProbeTec ET in parallel with culture. The overall inhibition rate was 0.2%. BDProbeTec ET can be very useful for rapid detection of MTC, especially in smear-negative respiratory specimens.

Bacterial Typing Techniques↗
PubMed1998

Direct detection of radicals in intact soybean nodules: presence of nitric oxide-leghemoglobin complexes.

Electron paramagnetic resonance spectroscopy has been employed to examine the nature of the metal ions and radicals present in intact root nodules of soybean plants grown in the absence of nitrate. The spectra obtained from nodules of different ages using this non-invasive technique show dramatic differences, suggesting that there are both qualitative and quantitative changes in the metal ion and radical species present. A major component of the spectra obtained from young nodules is assigned to a complex (Lb-NO) of nitric oxide (NO.) with the heme protein leghemoglobin (Lb). This Lb-NO species, which has not been previously detected in intact root nodules of plants grown in the absence of nitrate, is thought to be formed by reaction of nitric oxide with iron(II) leghemoglobin. The nitric oxide may be generated from arginine via a nitric oxide synthase-like activity present in the nodules of the soybean plants, in a manner analogous to that recently described for Lupinus albus. This Lb-NO complex is present at lower concentrations in older nodules, and is almost completely absent from senescent nodules. Exposure of young and mature nodules to oxidant stress, in the form of hydrogen peroxide, results in changes in the EPR spectra, with the loss of the signals from the Lb-NO complex and appearance of absorptions similar to those from untreated senescent nodules. These results suggest that there are characteristic changes in both the metal ion complexes and radicals present in intact root nodules of different ages, and support the theory that nitric oxide and other radicals play a significant role in determining the nitrogen fixing activity of root nodules; the modulatory activity of NO. may involve regulation of gene activity.

Electron Spin Resonance Spectroscopy↗
PubMedDate not supplied

Rapid diagnosis of Rift Valley fever: a comparison of methods for the direct detection of viral antigen in human sera.

Human sera collected during the 1987 Rift Valley fever (RVF) epidemic in the Senegal River basin were analysed using three enzyme immunoassays to establish the best method for rapid diagnosis of RVF. A biotin-avidin-enhanced antigen detection method utilizing monoclonal antibodies proved most sensitive. Eighty-two viremic human sera were tested, and this assay detected antigen in 29.3% of the samples.

Africa, Western↗
PubMed2002

Development, validation, and application of an acetylcholinesterase-biosensor test for the direct detection of insecticide residues in infant food.

A highly sensitive and rapid food-screening test based on disposable screen-printed biosensors was developed, which is suitable for monitoring infant food. The exposure of infants and children to neurotoxic organophosphates and carbamates is of particular concern because of their higher susceptibility to adverse effects. The European Union has, therefore, set a very low limit for pesticides in infant food, which must not contain concentrations exceeding 10 microg/kg for any given pesticide. The maximum residue limit (MRL) has been set to be near the determination threshold that is typically achieved for pesticides with traditional analytical methods. The biosensor method could detect levels lower than 5 microg/kg and thus clearly fulfills the demands of the EU. To substantiate these measurements, recovery rates were determined and amounted on average to 104% in food. Matrix effects were eliminated by the introduction of a special electrode treatment. The test was compared with two traditional pesticide multiresidue analysis methods (GC-MS, LC-MS) using 26 fruit and vegetable samples from local markets and 23 samples of processed infant food from Germany, Spain, Poland and USA. Three infant food samples exceeded the MRL of 10 microg/kg when analyzed by either biosensor test or multiresidue methods.

Acetylcholinesterase↗
PubMed1999

Development of sensors for direct detection of organophosphates. Part I: Immobilization, characterization and stabilization of acetylcholinesterase and organophosphate hydrolase on silica supports.

Biosensors for organophosphates in solution may be constructed by monitoring the activity of acetylcholinesterase (AChE) or organophosphate hydrolase (OPH) immobilized to a variety of microsensor platforms. The area available for enzyme immobilization is small (< 1 mm2) for microsensors. In order to construct microsensors with increased surface area for enzyme immobilization, we used a sol-gel process to create highly porous and stable silica matrices. Surface porosity of sol-gel coated surfaces was characterized using scanning electron microscopy; pore structure was found to be very similar to that of commercially available porous silica supports. Based upon this analysis, porous and non-porous silica beads were used as model substrates of sol-gel coated and uncoated sensor surfaces. Two different covalent chemistries were used to immobilize AChE and OPH to these porous and non-porous silica beads. The first chemistry used amine-silanization of silica followed by enzyme attachment using the homobifunctional linker glutaraldehyde. The second chemistry used sulfhydryl-silanization followed by enzyme attachment using the heterobifunctional linker N-gamma-maleimidobutyryloxy succinimide ester (GMBS). Surfaces were characterized in terms of total enzyme immobilized, total and specific enzyme activity, and long term stability of enzyme activity. Amine derivitization followed by glutaraldehyde linking yielded supports with greater amounts of immobilized enzyme and activity. Use of porous supports not only yielded greater amounts of immobilized enzyme and activity, but also significantly improved long term stability of enzyme activity. Enzyme was also immobilized to sol-gel coated glass slides. The mass of immobilized enzyme increased linearly with thickness of coating. However, immobilized enzyme activity saturated at a porous silica thickness of approximately 800 nm.

Acetylcholinesterase↗
PubMed2004

Direct detection of Staphylococcus aureus from adult and neonate nasal swab specimens using real-time polymerase chain reaction.

Nasal carriage of Staphylococcus aureus is considered a source of subsequent infection in health care settings. Utilization of real-time polymerase chain reaction (PCR) for detection of S. aureus has the potential to dramatically affect infection control practice by rapidly identifying S. aureus-colonized patients. We developed and validated the use of real-time PCR for detection of S. aureus colonization in two patient populations. Paired nasal swabs were collected from 299 neonates and from 151 adult patients at Evanston Hospital. One swab was used for culture and the other placed into a bacterial lysis solution containing achromopeptidase. The DNA liberated was used as the template for real-time PCR with primers for the femA gene. SYBR Green was used for amplicon detection. In the neonatal population the sensitivity, specificity, predictive value positive and predictive value negative for culture and PCR was 92% versus 96%, 100% versus 100%, 100% versus 100%, and 98% versus 99%, respectively. In the adults the results were 90% versus 100%, 100% versus 98%, 100% versus 96%, and 95% versus 100%, respectively. Real-time PCR was able to detect S. aureus in 2 hours compared to 1 to 4 days for culture and provided sensitivity equal to or greater than culture.

Adult↗
PubMed1995

Inactivation of the Enterobacter cloacae P99 beta-lactamase by a fluorescent phosphonate: direct detection of ligand binding at the second site.

The synthesis of a fluorescent beta-lactamase inhibitor, p-nitrophenyl [(dansylamido)methyl]-phosphonate is described. The compound inactivated the class C beta-lactamase of Enterobacter cloacae P99 with stoichiometric release of p-nitrophenol, presumably, as with other phosphonate inhibitors, by phosphonylation of the active site serine. The inhibited enzyme exhibited typical dansyl fluorescence emission at 533 nm with excitation maxima at 345 and 283 nm; the latter excitation peak probably arises from radiationless energy transfer to the dansyl group from aromatic chromophores on the protein-inspection of the crystal structure shows that the closest are tyrosines. The fluorescence of the p-nitrophenyl phosphonate and the inhibited enzyme varied with pH in a very similar fashion, reflecting dissociation of the dimethylammonium ion in the ground state at low pH and of the sulfonamide in the excited state above pH 6. No perturbation of the fluorescence of the inhibited enzyme due to active site functional groups was observed. This may reflect the distance between the dansyl fluorophore and the phosphonyl group and/or the high pKa's of the protonated active site functional groups in the presence of the phosphonate. The addition of certain small molecular weight N-acyl amino acids, of preferred structure D-RCONHCHR'CO2-, to the inhibited enzyme led to an enhancement of dansyl fluorescence intensity and a blue shift in the emission maximum. This suggested that these molecules bind to the beta-lactamase at a site other than the active site and supports previous kinetic data to this effect [Dryjanski, M., & Pratt, R. F., (1995) Biochemistry 34, preceding paper in this issue].(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗