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At least 1,423 records · Page 79Linked to original sources
PubMed1999

Filtration capture immunoassay for bacteria: optimization and potential for urinalysis.

A novel assay utilizing immuno-labeling, filtration, and electrochemistry for the rapid detection of bacteria has been optimized for the detection of Escherichia coli O157:H7. Bacteria were specifically labeled with alkaline phosphatase conjugated polyclonal antibodies and captured on a polycarbonate track-etched membrane filter (0.2 microm pore size). The filter was then placed directly against a glassy carbon electrode, incubated with enzyme substrate, and the product detected by square wave voltammetry. The high speed and capture efficiency of membrane filtration and inherent sensitivity of electrochemical detection produced a 25-min assay with a detection limit of 5 x 10(3) E. coli O157:H7 per ml using a filtration volume of 100 microl (i.e. 500 cells filtered). The labeling, filtration, and electrochemical steps were optimized, and the assay performance using electrochemical and colorimetric detection methods was compared. The assay was used to detect E. coli O157:H7 that was spiked into filter-sterilized urine at clinically relevant concentrations.

Bacteriological Techniques↗
PubMed2001

Using skeleton-based tracking to increase the reliability of optical motion capture.

Optical motion capture provides an impressive ability to replicate gestures. However, even with a highly professional system there are many instances where crucial markers are occluded or when the algorithm confuses the trajectory of one marker with that of another. This requires much editing work on the user's part before the complete animation is ready for use. In this paper, we present an approach to increasing the robustness of a motion capture system by using an anatomical human model. It includes a reasonably precise description of the skeleton's mobility and an approximated envelope. It allows us to accurately predict the 3-D location and visibility of markers, thus significantly increasing the robustness of the marker tracking and assignment, and drastically reducing--or even eliminating--the need for human intervention during the 3-D reconstruction process.

Algorithms↗
PubMed1997

Antigen presentation by MHC class II molecules: invariant chain function, protein trafficking, and the molecular basis of diverse determinant capture.

Major histocompatibility complex class II molecules are heterodimeric integral membrane proteins whose primary function is the presentation of antigenic peptides derived from proteins entering the endocytic pathway to CD4+ T lymphocytes. To accomplish this physiologic function, class II molecules must assemble in the secretory pathway without undergoing irreversible ligand association at that site, traffic efficiently to the endocytic pathway, and productively interact with protein ligands in these organelles before their ultimate expression on the plasma membrane. Here we review our work describing how invariant chain promoters the assembly and transport process, the complex itinerary of class II-invariant chain complexes through the endocytic pathway, the role of large protein fragments as substrates for class II binding, and the existence of a second pathway for antigen capture by mature class II molecules that complements that involving newly synthesized dimers. We integrate these observations into a coherent model for the operation of a class II-dependent antigen processing and presentation system able to capture diverse antigenic determinants present in proteins of varying structure.

Antigen Presentation↗
PubMed2003

Using capture-recapture methods to assess varicella incidence in a community under active surveillance.

The Varicella (chickenpox) Active Surveillance Project (VASP) has been conducting active surveillance since 1 January 1995 in the high desert community known as Antelope Valley, CA (population 300,000) among 300 public and private schools, daycares, and healthcare providers. Capture-recapture methods were applied to estimate reporting completeness for 1995 varicella incidence data and these were compared with the national average incidence rates by age reported by the National Health Interview Survey (NHIS). Varicella cases reported among individuals aged <20 years reflect under-reporting in excess of 50%. Despite limitations on accuracy, capture-recapture estimates are a reasonably accurate, quick, and inexpensive approach in epidemiologic studies.

Adolescent↗
PubMedDate not supplied

Capture EIA for determination of IgE to diphtheria and tetanus toxins in comparison to RIA.

A capture IgE assay in EIA with diphtheria toxin and tetanus toxoid as model systems was developed and evaluated in relation to RIA in a DT booster study. The EIA and the RIA gave very similar results, although the EIA determined IgE over a wider range of concentrations, without interference by other subclasses. The comparison to the capture EIA indicated that the RIA gave more reliable results when a toxin as antigen. Weak correlations between local side effects and IgE responses and differences between vaccine groups were noted by RIA but not by EIA, which correlated better with the clinical findings.

Antibodies, Bacterial↗
PubMed2000

Anomalies on capture nets of Hydropsyche slossonae larvae (Trichoptera; Hydropsychidae) following a sublethal chronic exposure to cadmium.

A laboratory study on the sublethal effects of cadmium (Cd) on the net-spinning process of the larvae of Hydropsyche slossonae was conducted in order to assess the potential of net anomalies as an indicator of chronic exposure to Cd. Two major anomalies with different frequency levels were identified after chronic exposure to 0.37, 1.2, 11.6, 21.4 and 43.3 microg l(-1) of Cd. The first was a distortion of the midline meshes where the diamond-shape structure is disrupted and the meshes are separated by extra strands (called 'midline' anomaly). The second aberration consisted of a distortion of the rectilinear structure of net opening by strands being fused or added over the meshes (called 'crossover' anomaly). The midline distortion may be linked to a physiological stress caused by Cd, which can affect the control of the net-spinning process. It was not possible to relate the crossover aberrations to a specific toxic action of Cd, but data indicated that both anomalies are independent from each other and that two modes of action could be implicated. Protein analyses of capture nets have revealed silk polypeptide modifications at the highest Cd concentration tested, indicating a possible effect of Cd interaction with silk proteins. However, neither a gradient-concentration nor a time-dependent response could be established with both aberration frequencies. Silk protein modifications would rather play a secondary role in the appearance of both net anomalies, and mostly at a high concentration level. Finally, the toxicity curves (EC(50)) show that the sensitivity threshold for both types of aberration ranged from 1 to 5 microg l(-1) which is highly sensitive compared with other sublethal effects of Cd on other macroinvertebrate species. Hence, the use of capture-net anomalies of hydropsychid larvae would represent a valuable indicator of sublethal toxicity induced by Cd and possibly by other metals in running waters.

Journal Article↗
PubMed2001

Determination of 14-3-3 protein levels in cerebrospinal fluid from Creutzfeldt-Jakob patients by a highly sensitive capture assay.

The level of 14-3-3gamma protein was determined in the cerebrospinal fluid (CSF) from patients with Creutzfeldt-Jakob disease (CJD) and non-CJD patients applying a new and fast microplate assay (14-3-3 protein capture assay), based on the binding to a peptide comprising a phosphorylated recognition motif of 14-3-3 protein. The levels of the gamma-isoform of 14-3-3 protein in CSF samples from CJD patients (n=41) were significantly higher than those observed in patients with non-CJD dementias (n=36) suggesting that this capture assay is a reliable method in the diagnosis of CJD. Since this assay allows the direct measurement of 14-3-3 protein in the CSF without prior concentration it is an easy and simple alternative to the conventionally applied immunoblotting procedures.

14-3-3 Proteins↗
PubMed2002

Detection of circulating hypodermin C: an antigen capture ELISA for diagnosis of cattle grub (Diptera: Oestridae) infestations.

An antigen capture assay for the detection of circulating hypodermin C was developed for diagnosis of hypodermosis. A murine monoclonal antibody to recombinant hypodermin C was raised using rapid immunization and a one-step hybridization-cloning technique. A highly reactive, specific monoclonal antibody was tested using sera spiked with known quantities of purified, native hypodermin C or with recombinant hypodermin C. Sensitivity of 96.4% and specificity of 95.6% for the antigen capture assay was assessed using a panel of sera from animals unexposed to cattle grubs and from cattle with palpation proven cattle grub infestations. Data from this panel of sera was used to establish the cut-off OD for further testing. The kinetics of circulating hypodermin C was assessed using the assay in three groups of cattle artificially infested with 50, 100 or 200 first instar Hypoderma lineatum. Antigen was first detected approximately 6 weeks after infestation. The amount of antigen detected increased in each group of animals reaching peaks at different times in each group. Levels of antigen fell quickly following arrival of grubs at the back and completion of the molt to second instar.

Animals↗
PubMed1998

Chromosomal sequencing using a PCR-based biotin-capture method allowed isolation of the complete gene for the outer membrane protein A of Klebsiella pneumoniae.

By employing a novel biotin- and PCR-assisted capture method, which allows determination of unknown sequences on chromosomal DNA, the gene for the outer membrane protein A (OmpA) of Klebsiella pneumoniae has been isolated and sequenced to completion. The method involves linear amplification of DNA from a biotinylated primer annealing to a region with known sequence. After capture of the amplified single-stranded DNA on to paramagnetic beads, unspecifically annealing primers, i.e. arbitrary primers, were used to generate sequences with only partly determined nt sequences. The homology of the sequenced gene to ompA of related bacteria is discussed, and the gene fragment was assembled for intracellular expression in Escherichia coli, and two different fusion proteins were produced and recovered with good yields. The importance of the novel chromosomal sequencing method for gene isolation in general and the potential use of the OmpA fusion proteins are discussed.

Amino Acid Sequence↗
PubMed2002

Detection of Mycobacterium avium subsp. paratuberculosis by buoyant density centrifugation, sequence capture PCR and dot blot hybridisation.

Detection of Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) by polymerase chain reaction (PCR) is often hampered by the lack of efficient methods for sample treatment. We report a protocol for analysis of faecal samples based on buoyant density centrifugation in Percoll and IS900 sequence capture PCR combined with a dot blot assay for detection of low-grade infection of M. paratuberculosis. Serial dilutions of M. paratuberculosis genomic DNA and M. paratuberculosis bacteria were used to assess the sensitivity of the method. The final evaluation was performed with spiked faecal samples, which also were analysed by culture. The presence of PCR inhibitory substances in processed faecal samples was evaluated by including a PCR internal control. By using buoyant density centrifugation, sequence capture PCR, and dot blot hybridisation, we achieved a sensitivity of 10(3)CFU (colony forming units)/g of faeces. The detection limit by culture was assessed to 10(2)CFU/g of faeces. We conclude that the described protocol is a fast and sensitive alternative to bacterial culture of faecal samples.

Animals↗
PubMed1980

Electron-capture gas chromatography of plasma sulphonylureas after extractive methylation.

Conditions for the extractive alkylation of eight sulphonylurea hypoglycemic drugs have been evaluated. Extractive methylation of the compounds was achieved within 90 min using tetrabutylammonium as counter-ion (0.1 M at pH = 6.9) with 5% methyl iodide in dichloro-methane as organic phase. Mass spectral analysis showed derivatives methylated at the sulphonamide nitrogen. A higher pH or use of tetrapentylammonium as counter-ion caused hydrolysis of the sulphonylureas. The derivatives showed a high electron-capture response with minimum concentrations detectable in the range 1-4 x 10(-16) moles sec-1. Therapeutic plasma concentrations of glipzide and tolbutamide were determined by direct extractive methylation of the compounds from the plasma sample. The glipizide derivative was determined by electron-capture gas chromatography down to about 20 ng/ml in a 0.5-ml plasma sample. The relative standard deviation at the 0.2 microgram/ml level of glipizide was 6% (n = 6). The corresponding figure in the determination of tolbutamide at the 10 microgram/ml level was 3% (n = 10).

Chromatography, Gas↗
PubMed1978

Quantitative analysis of prazepam and its metabolites by electron capture gas chromatography and selected ion monitoring. Application to diaplacetal passage and fetal hepatic metabolism in early human pregnancy.

Methods have been developed for the determination of the benzodiazepine tranquilizer prazepam and its metabolites desmethyl diazepam, 3-hydroxy-prazepam and oxazepam by electron capture gas chromatography and selected ion monitoring with diazepam as the internal standard. The benzodiazepines were isolated from blood serum or homogenized tissue samples, either by extraction with ethyl acetate or on small Extrelut columns packed with porous silica. The concentrated extracts were directly injected into the gas chromatograph equipped with an electron capture detector. Following trimethylsilylation, analysis on a gas chromatography--mass spectrometry--computer system operated in the selected ion-monitoring mode was performed. Using 50--200 mg (microliter) biological material, concentrations of prazepam and metabolites of 5 ng/g(ml) could be determined with signal-to-noise ratios of greater than 10. Using 1 g(ml) samples, the same signal-to-noise ratios were obtained with 1 ng/g(ml) concentrations. The methods developed were applied to the analysis of the diaplacental transfer of prazepam and desmethyl diazepam in early human pregnancy. Furthermore, prazepam metabolism in human fetal liver and cell cultures was studied.

Cells, Cultured↗
PubMed1987

Capillary column gas chromatographic method using electron-capture detection for the simultaneous determination of nicardipine and its pyridine metabolite II in plasma.

A rapid, specific and direct method based on capillary column gas chromatography with electron-capture detection is described for the simultaneous determination of nicardipine, a new calcium antagonist, and its pyridine metabolite II in human plasma. In this method, the nicardipine, its pyridine metabolite II and internal standard are extracted from the plasma and then partially purified by acid-base partitioning prior to the final injection onto the capillary column gas chromatograph for quantification by means of an electron-capture detector. The quantification limit of the method is 1 ng/ml of plasma for both nicardipine and its pyridine metabolite II. The coefficients of variation for nicardipine and the pyridine metabolite II at concentrations of 1-50 ng/ml are less than 7% and less than 9% (n = 4), respectively. The method has been validated against a previously developed high-performance liquid chromatographic method (sensitivity 5 ng/ml).

Chromatography, Gas↗
PubMed1997

Electron-capture detection: difluorobenzyl and related electrophores.

Difluorobenzyl derivatives (several isomers were tested) of 4-hydroxyacetophenone were synthesized and found to have similar properties (retention and response) by both reversed-phase HPLC and GC-ECD relative to each other, and also relative to that of a corresponding conventional pentafluorobenzyl derivative. The same was true for a representative difluorobenzyl derivative of thymine and 1-naphthoic acid. Overall, the responses by GC-ECD for the same core structure were only about two- to four-fold lower for a difluorobenzyl compared to a corresponding pentafluorobenzyl derivative. This makes a difluorobenzyl derivative attractive as an HPLC-UV retention marker, and sometimes as a substitute for a pentafluorobenzyl derivative (to help overcome an interference) in a method based on detection by electron capture. We also observed, somewhat as an aside, that the GC-ECD response of the benzyl derivative of 4-hydroxyacetophenone was only seven-fold lower than that of the corresponding pentafluorobenzyl derivative, and that this former benzyl derivative gave a 2.10(4) higher response than acetophenone. Thus, replacing the ring hydrogen atoms of a benzyl group with fluorine atoms had a relatively small impact on both the hydrophobicity and electron capture properties of the compounds tested here.

Chromatography, Gas↗
PubMed2000

Determination of refractory periods and conduction velocity during atrial fibrillation using atrial capture in dogs: direct assessment of the wavelength and its modulation by a sodium channel blocker, pilsicainide.

OBJECTIVES: The purposes of this study were to measure the atrial refractory period and the conduction velocity (CV) during atrial fibrillation (AF) and to explore the antiarrhythmic mechanism of a sodium channel blocker, pilsicainide, during AF. BACKGROUND: Sodium channel blockers not only decrease the CV, but also prolong the atrial refractory period, particularly during rapid excitation. Because these effects on the wavelength are counteractive and rate dependent, it is critical to measure these parameters during AF. METHODS: In eight dogs, after AF was induced under vagal stimulation, a single extra-stimulus was repeatedly introduced from the left atrium and its capture was statistically determined for each coupling interval. The local CV was also measured during constant capture of the fibrillating atrium by rapid pacing. The same procedure was repeated after pilsicainide administration. RESULTS: Pilsicainide significantly increased the mode of AF intervals from 81 +/- 10 to 107 +/- 16 ms (p < 0.01). While the CV was decreased from 0.9 +/- 0.1 to 0.7 +/- 0.1 m/s (p < 0.02), the effective refractory period during AF was increased from 69 +/- 11 ms to 99 +/- 17 ms (p < 0.01). As a result, the wavelength was significantly increased by pilsicainide from 6.6 +/- 0.9 to 7.6 +/- 1.2 cm (p < 0.05). CONCLUSIONS: During AF, whereas the sodium channel blocker pilsicainide decreases CV, it lengthens the wavelength by increasing the refractory period, an action that is likely to contribute to the drug's ability to terminate the arrhythmia. The direct measurement of refractoriness and CV during AF may provide new insights into the determinations of the arrhythmia and antiarrhythmic drug action.

Animals↗
PubMed1997

Season and migration alters the corticosterone response to capture and handling in an Arctic migrant, the white-crowned sparrow (Zonotrichia leucophrys gambelii).

The Gambel's race of white-crowned sparrow (Zonotrichia leucophrys gambelii) migrates each year from their wintering grounds in the Southwestern United States to the Arctic to breed. Associated with this migration is a change in both the nonstressed and the stress-induced levels of circulating plasma corticosterone. Birds were captured at two sites on their wintering grounds (New Mexico and Arizona). Although stress-induced corticosterone levels were elevated at each site compared to nonstressed levels, there were no differences between wintering sites. These were also similar to levels in birds caught in Washington state during fall migration. In contrast, nonstressed corticosterone values were greatly elevated in birds on their breeding grounds in Alaska and similar to stress-induced levels in wintering birds. Corticosterone levels rose even further in response to the stress of capture and handling in breeding birds. These augmented corticosterone levels during breeding were not associated with weather. Both nonstressed and stress-induced corticosterone levels were similar in birds caught on their breeding grounds on two different years, one with temperatures during mid-May of approximately 0 degree C during a snow storm and the other with temperatures in the mid-20s. These results suggest that seasonal physiological changes, and not local conditions, underlie seasonal changes in corticosterone levels. Furthermore, birds caught in Washington state during spring migration had intermediate levels of both nonstressed and stress-induced corticosterone. Corticosterone release may function differently during spring and fall migrations.

Adipose Tissue↗
PubMed1994

Posterior capsulorhexis with optic capture: maintaining a clear visual axis after pediatric cataract surgery.

We describe a technique for preventing secondary membrane formation after pediatric cataract extraction. This technique involves capture of an intraocular lens (IOL) optic through a posterior curvilinear capsulorhexis opening in an attempt to maintain a clear visual axis in children after cataract surgery. This maneuver ensures centration of the posterior chamber IOL because the haptics remain in the capsular bag and the optic is captured in the posterior capsular opening. Also, the need for an anterior vitrectomy may be eliminated. Apposition of the anterior and posterior capsule leaflets anterior to the optic may limit the migration of Elschnig pearls, reducing the incidence of secondary membranes and the need for additional procedures.

Cataract↗