Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Direct detection”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43Linked to original sources
PubMed1993

Direct colorimetric detection of a receptor-ligand interaction by a polymerized bilayer assembly.

Detection of receptor-ligand interactions is generally accomplished by indirect assays such as enzyme-linked immunosorbent assay. A direct colorimetric detection method based on a polydiacetylene bilayer assembled on glass microscope slides has been developed. The bilayer is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene. The polydiacetylene layer is functionalized with an analog of sialic acid, the receptor-specific ligand for the influenza virus hemagglutinin. The sialic acid ligand serves as a molecular recognition element and the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. Direct colorimetric detection by polydiacetylene films offers new possibilities for diagnostic applications and screening for new drug candidates or binding ligands.

Acetylene↗
PubMed1989

Diagnosis of herpes simplex virus infection in a clinical setting by a direct antigen detection enzyme immunoassay kit.

A commercial 4-h direct herpes simplex virus (HSV) antigen detection enzyme immunoassay (EIA) kit (Du Pont Herpchek) was evaluated by using 273 clinical specimens obtained in a hospital-based infectious disease practice. The EIA was compared with a standard culture method in which WI38 cells were inoculated within 20 min of sample collection. Cultures were observed for 2 weeks, and positive findings were confirmed by fluorescein-labeled monoclonal antibody (FA) staining. The values for the overall HSV detection rate were 40.7% by the standard culture method and 41.4% by EIA. In eight cases, the EIA was positive, while the culture method was negative; however, clinical data and confirmatory blocking EIA suggested that a true HSV infection was present. For six FA-confirmed, culture-positive samples, the direct EIA was negative; however, an EIA performed on the supernatants of these cultures was positive, suggesting that the failure of the EIA to detect these samples was not due to lack of strain specificity of the test. After confirmatory tests of standard culture and EIA discrepant results, the overall sensitivity of the test was 95.0% (113 of 119) and the specificity was 100% (154 of 154).

Acyclovir↗
PubMed1990

Detection and direct typing of herpes simplex virus by polymerase chain reaction.

A method for the detection and direct typing of herpes simplex virus (HSV) by the polymerase chain reaction (PCR) technique has been developed. One common upstream primer and two type-specific downstream primers were prepared to amplify DNA from the HSV type 1 and type 2 DNA polymerase gene. Using these three primers simultaneously in the PCR reaction mixtures, both types of HSV DNA were amplified to produce products of different sizes. By direct gel analysis, the products of standard HSV type 1 and type 2 strains had the predictive sizes of 469 and 391 base pairs, respectively, and the difference in molecular mass enabled us to type the HSV strain. A total of 24 strains (type 1; 16 and type 2; 8 strains) were examined by PCR, and the results were consistent with those determined by immunofluorescence using type-specific monoclonal antibodies. No specific amplification was observed using other herpes virus or human genomic DNAs. The PCR method was then applied to clinical specimens. Of 15 samples obtained from oral lesions of children with herpetic gingivostomatitis, all (100%) were HSV positive by PCR, compared with 13 (86.7%) using standard cell culture methods. Three specimens from vulvar lesions of women with genital herpes were positive using both PCR and cell cultures. There was complete agreement in the typing of HSV strains using the PCR method or virus isolation. On the basis of these results, it is suggested that DNA amplification and typing by PCR is particularly useful for material from which virus isolation might be difficult.

Animals↗
PubMed2006

Determination of bromate ion in drinking water by capillary zone electrophoresis with direct photometric detection.

Bromate ion in drinking water was determined by capillary zone electrophoresis (CZE) with direct photometric detection. Bromate ion in the sample solution was introduced and concentrated into the capillary by electrokinetic injection for 50s at -10 kV. Electrophoretic separation was made at an applied voltage of -25 kV and bromate ion was detected at wavelength 193 nm, at which the baseline was stabilized with less UV-absorbing acidic phosphate buffer. Bromate ion was detected within 5 min in the electropherogram. By increasing the electric conductivity in the migrating solution with 10 mM Na2SO4, a limit of detection (LOD) of 9 x 10(-10)M (0.1 microg/L BrO3-) was achieved. The proposed method was applied to the analysis of tap water and river water samples, but bromate ion was not detected. Because the practical samples contain relatively large amount of foreign ionic substances, the tap water sample was diluted to avoid the matrix ions. Bromate ion added in a tap water at the concentration of 8 x 10(-8)M was quantitatively recovered by diluting it 1/10.

Bromates↗
PubMed2001

Detection of directed gaze in rhesus monkeys (Macaca mulatta).

To examine the ability of monkeys to detect the direction of attention of other individuals, the authors quantitatively investigated the visual scanning pattern of rhesus monkeys (Macaca mulatta) in response to visually presented images of a human frontal face. The present results demonstrated not only that monkeys predominantly gaze at the eyes as compared with other facial areas in terms of duration and number of fixations, but also that they gaze at the eyes for a longer time period and more frequently when a human face, presented as a stimulus, gazed at them than when the gaze was shifted. These results indicate that rhesus monkeys are sensitive to the directed gaze of humans, suggesting that monkeys pay more attention to the human whose attention is directed to them.

Animals↗
PubMed1991

Diagnosis and prevalence of persistent chlamydia infection in infertile women: tissue culture, direct antigen detection, and serology.

Specimens for chlamydial culture, direct fluorescent antibody (DFA) test, two enzyme immunoassays (EIA) for antigen detection, and serum for chlamydial antibodies were collected from 256 infertile women. Specimens were taken from the tubes during tuboplasty and from the cervix and endometrium during laparoscopy or tuboplasty. Antibodies to Chlamydia trachomatis were found four times more often in patients with signs of prior pelvic inflammatory disease (PID) than in infertile women with normal pelvic findings. Only 48 (37%) of 131 patients with signs of prior PID had a history of PID. Ten or more C. trachomatis elementary bodies (EBs) per smear were found in 21 (8.2%) of 256 patients. Six patients had a positive culture or a positive antigen EIA test. All six had high numbers of EBs in the DFA test. We conclude that routine culture and EIA antigen tests detect only a minority of persistent chlamydia infections in this population, but subjective factors in the interpretation of DFA methods must be considered.

Adult↗
PubMed1984

Diagnosis of respiratory syncytial virus infection in children: comparison of viral antigen detection and serology.

Direct detection of viral antigen in nasopharyngeal secretion by radioimmunoassay was compared with serology by IgG antibody enzyme immunoassay for diagnostic efficacy in 77 children with clinically suspected respiratory syncytial virus (RSV) infections. Antigen detection gave a positive diagnosis in 26 of 33 (79%) children in whom RSV infection was diagnosed by any of the two methods. The diagnostic efficacy of antigen detection was dependent upon the interval after onset at which specimens were collected; 88% of specimens taken during the first 5 days and 50% of specimens taken 6-10 days after onset of illness were positive. It was also dependent on the age of the patients, the diagnostic efficacy being 88 and 76% in children under and over 6 months of age, respectively.

Antigens, Viral↗
PubMed1999

[Direct, rapid detection for rifampin susceptibility to M. tuberculosis].

OBJECTIVE: To evaluate the use of molecular biotechnology for direct, rapid detection of rifampicin-resistance mutations in M. tuberculosis. METHODS: 45 M. tuberculosis clinical isolates and 70 sputum samples were tested by polymerase chain reaction-single stranded conformation polymorphism (PCR-SSCP) technique. M. tuberculosis strain H37Rv was used as control and compared with the result of susceptibility test. DNA sequencing was also performed in some of the strains. RESULTS: All tested susceptible isolates displayed identical SSCP patterns. Of 29 RFP resistance strains, 26(90%) had distinct mobility shifts that can be discriminated from susceptible isolates. 9 sputum samples which were succeasfully evaluated by PCR-SSCP showed concordant result acquired from BACTEC 460 method. As the result of DNA sequencing, it was observed that seven RFP-resistance phenotype of M. tuberculosis strains had missense mutation, in which 5 isolates displayed TCG-->TTG or CAG mutations at codon 531.2 had CAC-->TAC mutation at codon 526. On the other hand, one strain which was susceptible to rifampin exhibited identical nucleotide alignment to the sequence of rpoB gene. CONCLUSIONS: PCR-SSCP could be used as a method for simple, rapid, and reliable detection of rifampicin-resistance mutations in clinical samples of M. tuberculosis.

Antibiotics, Antitubercular↗
PubMed1994

Reversed-phase high-performance liquid chromatographic determination of cocaine in plasma and human hair with direct fluorimetric detection.

A simple, but sensitive and specific, high-performance liquid chromatographic assay for cocaine with direct fluorimetric detection, particularly intended for the routine analysis of hair and blood samples, is described. Benzoylecgonine, eluting before cocaine in a completely resolved peak, is also detectable. Detection is based on the weak native fluorescence of cocaine and benzoylecgonine, depending on the benzene ring present in both molecules. Hair samples (20-200 mg) were incubated overnight in 2 ml of 0.25 M HCl at 45 degrees C and extracted with a commercial liquid-liquid method; the dried residue reconstituted with 500 microliters of 0.05 M NaH2 PO4 (PH 5.2) was injected. Blood plasma samples (200 microliters) were mixed with 150 microliters of 0.1 M Na2 HPO4 (pH 8.9) and extracted with 5 ml of chloroform-2-propanol (9:1); the organic phase was evaporated and the residue dissolved and injected as above. Isocratic reversed-phase liquid chromatography was carried out on a column (150 x 4.6 mm I.D.) packed with spherical 5-microns poly(styrene-divinylbenzene) particles; the mobile phase was 0.1 M potassium phosphate (pH 3)-methanol-tetrahydrofuran (70:25:5). The excitation and emission wavelengths were set at 230 and 315 nm, respectively. Under the described conditions, cocaine eluted in a symmetrical peak with a capacity factor of about 5. The limit of detection was about 1 ng/ml (0.2 ng injected), with a signal-to-noise ratio of 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗
PubMed2003

Growth and siderophore production of staphylococci in human peritoneal dialysate.

Although activity of iron uptake system (IUS) was thought to play an important role in staphylococcal growth in human peritoneal dialysate (HPD) solution, siderophore production, one of the well-known IUS, was not yet detected directly in HPD solution. Therefore, we tried to detect siderophore production directly in HPD solution by using a newly developed chrome azurol S (CAS) agar diffusion assay and to investigate the effect of IUS activity on bacterial growth in HPD solution. According to the susceptibility test for streptonigrin and the productivity of siderophore in the iron-deficient (ID) medium, Staphylococcus aureus ATCC 6538 strain and Staphylococcus epidermidis clinical isolate had higher IUS activity and grew better than S. aureus ATCC 25923 strain in the ID medium. These bacteria did not grow and produce siderophore in the unused chronic ambulatory peritoneal dialysis solution. However, these bacteria grew and produced siderophore in the HPD solution. Moreover, S. aureus ATCC 25923 strain with lower activity of IUS grew poorly and produced smaller amount of siderophore in HPD compared to S. aureus ATCC 6538 strain and S. epidermidis clinical isolate with higher activity of IUS like in the ID medium. To the best of our knowledge, this is the first report that siderophore production is directly detected in the HPD by CAS agar diffusion assay. These results indicated that activity of IUS plays an important role in bacterial growth in the HPD solution and pathogenesis of continuous ambulatory peritoneal dialysis peritonitis.

Biological Assay↗
PubMed2002

The determination of bromide in a local anaesthetic hydrochloride by capillary electrophoresis using direct UV detection.

The determination of residual amounts of bromide in a local anaesthetic hydrochloride by capillary electrophoresis was developed. Direct UV detection at 200 nm was used for the determination of the bromide content. The separation capacity of the system must be sufficient when bromide is determined in the presence of a large excess of chloride since electromigration dispersion of the highly concentrated chloride peak may impair the resolution. The background electrolyte (BGE) contained both acetonitrile and methanesulphonic acid in order to improve the selectivity and minimise the electromigration dispersion. The system was optimised with respect to resolution of the chloride and the bromide peaks by statistical experimental design using a multivariate optimisation program. The developed method was validated in accordance with the ICH guidelines and proved to be suitable for its intended use.

Anesthetics, Local↗
PubMed2003

Prenatal diagnosis of factor X deficiency using a combination of direct mutation detection and linkage analysis with an intragenic single nucleotide polymorphism.

OBJECTIVE: To present a family in which it was possible to perform prenatal diagnosis for recessively inherited factor X deficiency using both direct mutation detection as well as linkage analysis. METHODS: In a family where both parents were known to be carriers of factor X deficiency, fetal DNA was obtained from an ongoing pregnancy by CVS in the first trimester. Direct DNA sequencing was used to detect a previously identified factor X mutation, and linkage analysis using a single nucleotide polymorphism (SNP) was used to follow the segregation of the other parent's factor X alleles. RESULTS: Our studies predicted the fetus in question to be a heterozygote carrier of factor X deficiency, and this was demonstrated to be correct at birth. CONCLUSIONS: This is the first reported case of prenatal diagnosis of factor X deficiency. In addition, this case demonstrates the remarkable utility of SNPs in linkage analysis of rare genetic disorders.

Adult↗
PubMed2005

Identification and quantification of (polymeric) hindered-amine light stabilizers in polymers using pyrolysis-gas chromatography-mass spectrometry and liquid chromatography-ultraviolet absorbance detection-evaporative light scattering detection.

Direct analysis of polymers containing polymeric hindered amine light stabilizers (HALS) by using pyrolysis coupled to GC-MS is applied successfully for fast and straightforward identification of these HALS additives. Each of the HALS additives shows different pyrolysis gas chromatograms containing characteristic pyrolysis products. As a result, HALS additives with very similar chemical structures, e.g. Chimassorb 944 and Chimassorb 2020, can be distinguished. A HPLC method with both ultraviolet (UV) and evaporative light scattering detection (ELSD) is developed to quantify the various HALS additives in extracts of polymers. The critical factor of the HPLC method is the use of a basic amine, like n-hexylamine, as a solvent additive to facilitate the elution of HALS additives. The various HALS additives can be distinguished according to retention time and peak shape and by using different detection methods. The suitability of the developed methods is demonstrated by the analytical performance of the HPLC method and the identification and determination of the actual content of HALS additives in polyolefines using pyrolysis GC-MS and HPLC. The HPLC method can also be used for the determination of the specific migration of HALS additives from food contact materials.

Amines↗
PubMed1985

Determination of drugs in untreated body fluids by micellar chromatography with fluorescence detection.

Direct serum and urine injection, without sample extraction or protein precipitation steps, into a liquid chromatographic system using sodium dodecyl sulfate (SDS) with 10% added propanol as the mobile phase, is described for measurement of drug levels. The ability of SDS micelles to form soluble protein-SDS complexes, with no on-column precipitation, provides a simple, rapid method for routine determination of quinine, quinidine, propranolol, morphine and codeine at concentration levels found in serum and urine following administration of therapeutic doses. Absolute limits of detection ranged from 0.2 to 6 ng. Variation of the surfactants mobile phase concentration allows control of selectivity and analysis time, although a minimum concentration is required to prevent protein precipitation. Chromatographic efficiencies are improved by the addition of propanol to the micellar mobile phase, and sensitivities improved by use of fluorescence detection. The sensitivities are more than adequate for therapeutic drug monitoring of concentration ranges normally encountered in serum and urine.

Body Fluids↗
PubMed2003

Rapid detection of vanA and vanB genes directly from clinical specimens and enrichment broths by real-time multiplex PCR assay.

A real-time PCR assay previously developed for use on the Roche LightCycler platform was investigated as an alternative to culture for the direct detection of vancomycin-resistant enterococci (VRE) in clinical specimens. PCR primers and fluorescence resonance energy transfer hybridization probes specific for the vanA and vanB genes were combined in a multiplex real-time PCR assay performed directly with fecal material obtained by rectal swabbing and with enrichment broth samples. DNA was prepared from the rectal swabs and enrichment broths with a commercially available DNA preparation column designed specifically for use with fecal specimens. One hundred eighty duplicate rectal swabs were obtained from 42 patients who were previously found to be positive for VRE and who were being monitored for carriage of VRE. Direct and enrichment broth cultures were performed with one swab, while PCR was performed with the other swab as well as any corresponding presumptive positive enrichment broth. In total, 100 specimens from 30 patients remained positive for VRE by at least one method. The multiplex real-time PCR was positive for 88 enrichment broths of rectal swabs from 27 patients but for only 45 rectal swabs from 15 patients. Direct culture was positive for VRE for only 43 specimens from 11 patients, while enrichment broth culture was positive for VRE for 75 specimens from 22 patients. Inhibition studies for the multiplex real-time PCR assay, performed by spiking the DNA extracts from 50 negative rectal swabs and the corresponding enrichment broths with between 1 and 10 CFU of a VanB Enterococcus faecium strain, detected inhibition rates of 55.1 and 10%, respectively. PCR performed directly with enrichment broths was found to be significantly more sensitive than enrichment broth culture (P < 0.025). Negative samples were identified significantly earlier by PCR than by culture alone.

Anti-Bacterial Agents↗
PubMed2005

Determination of beta2-agonists by ion chromatography with direct conductivity detection.

A simple method for the simultaneous detection of four beta2-agonists (salbutamol, fenoterol, clorprenaline, and clenbuterol) using ion chromatography (IC) with direct conductivity detection (CD) based on their ionization in acidic medium without chemical suppression is presented. The mixture of 1.8 mM HNO3 and 2% (v/v) acetonitrile was used as eluent. The method could be applied to the determination of the beta2-agonists in pharmaceutical preparations. The recovery of salbutamol and clenbuterol in tablets was more than 97% (n=3) and the relative standard deviation (n=11) less than 2.8%. With the proposed method, salbutamol could also be successfully detected in human plasma. In a single chromatographic run, the four beta2-agonists can be separated and determined in less than 8 min. The linear ranges were of 7.0-1.4 x 10(3)ng/ml for salbutamol, 34-7.8 x 10(3)ng/ml for fenoterol, 8.0-1.6 x 10(3)ng/ml for clorprenaline, and 25-7.5 x 10(3)ng/ml for clenbuterol. The detection limits were 2.0 ng/ml for salbutamol, 10 ng/ml for fenoterol, 3.0 ng/ml for clorprenaline, and 10 ng/ml for clenbuterol.

Adrenergic beta-2 Receptor Agonists↗
PubMed1994

[Loudness scaling. A procedure for quantitative recruitment detection].

Direct loudness scaling has been known as an audiological tool for about four decades. Although numerous publications have shown its clinical importance, loudness scaling has not been used in audiology and hearing aid fitting until now. This might be due to the lack of audiometers equipped with loudness scaling devices as well as missing evidence for its clinical applicability. In this study normal data for a single-step direct scaling procedure were established and loudness determinations of 105 patients with sensorineural hearing losses collected. The results show that normal level loudness functions exhibit very similar shapes for narrow band stimulation in the frequency range of 500 to 4000 Hz. However, loudness scaling is affected by the gender of the subjects: females scale systematically louder than do males. In hearing-impaired subjects the slopes of the level loudness functions tend to decrease with increasing hearing loss, indicating negative recruitment. This holds particularly true in the high-frequency range, e.g. at 4000 Hz. Our long-term experience with single-step direct loudness scaling has proven its clinical feasibility in typical patients of an audiology unit. Loudness scaling will prove useful for the localization of hearing impairments, as it can be employed as a quantitative indicator of recruitment without any restrictive preconditions. In addition, it allows the evaluation of hearing aids and cochlear implants by frequency-specific gain measurement.

Audiometry, Pure-Tone↗