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PubMed2000

In Situ Polymerase Chain Reaction Visualization of Vibrio halioticoli Using Alginate Lyase Gene AlyVG2.

A prokaryotic in situ polymerase chain reaction (PI-PCR) technique was applied to visualize Vibrio halioticoli cells using alginate lyase gene alyVG2 as a target gene. Prior to PI-PCR, a primer set, VG2-OS3, for specific amplification of an approximately 1.0-kb fragment from V. halioticoli genomic DNA was developed with amplified fragments from V. pelagius and V. fischeri DNAs as reference strains. One-stage PI-PCR using the primer set, digoxigenin-labeled dUTP, and indirect alkaline-phosphatase-linked fluorescence detection technique (HNPP/Fast Red TR as a substrate) failed to differentiate V. halioticoli IAM14596(T) cells from ATCC25916(T) cells of the closely related species V. pelagius. However, two-stage PI-PCR adding the extension and digoxigenin-labeling step of the amplified fragment into the first amplification stage allowed us to differentiate V. halioticoli cells from V. pelagius cells.

Journal Article↗

PubMed2006

A specific picomolar hybridization-based ELISA assay for the determination of phosphorothioate oligonucleotides in plasma and cellular matrices.

PURPOSE: To develop and validate an ultrasensitive and specific hybridization-based enzyme-linked immunosorbent assay method for quantification of two phosphorothioate oligonucleotides (PS ODNs) (G3139 and GTI-2040) in biological fluids. METHODS: This assay was based on hybridization of analytes to the biotin-labeled capture ODNs followed by ligation with digoxigenin-labeled detection ODN. The bound duplex was then detected by anti-digoxigenin-alkaline phosphatase using Attophos (Promega, Madison, WI, USA) as substrate. S1 nuclease and major factors such as the hybridization temperature, concentration of capture probe, and the use of detergent were evaluated toward assay sensitivity, selectivity, and accuracy. RESULTS: The method is selective to the parent drugs with minimal cross-reactivity (<6%) with 3'-end deletion oligomers for both G3139 and GTI-2040. A linear range of 0.05 to 10 nM (r2 > 0.99) was observed for GTI-2040 in a variety of biological matrices. For both G3139 and GTI-2040, the within-day precision and accuracy values were found to be <20% and 90-110%, respectively; the between-day precision and accuracy were determined to be <20% and 90-120%. Addition of S1 nuclease combined with washing step greatly improved the assay linearity and selectivity. The utility of this assay was demonstrated by simultaneous determination of GTI-2040 in plasma and its intracellular levels in treated acute myeloid leukemia patients. CONCLUSIONS: The validated hybridization enzyme-linked immunosorbent assay method is specific for quantitation of PS ODNs in biological samples to picomolar level. This method provides a powerful technique to evaluate plasma pharmacokinetics and intracellular uptake of PS ODNs in patients and shows its utility in clinical evaluations.

Acute Disease↗

PubMed1992

In situ hybridization in suspension and flow cytometry as a tool for the study of gene expression.

We describe a method to detect mRNA expression using in situ hybridization in suspension and flow cytometry. Our model was glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression in the leukemic cell line K562. A GAPDH cDNA probe was labeled with digoxigenin-11-dUTP and detected using an FITC-labeled anti-digoxigenin antiserum. We obtained good resolution in specific signals against background (GAPDH signal/control plasmid signal ratio +/- SE 3.5 +/- 0.9). The technique was optimized taking into account several hybridization variables, like fixation, hybridization time, effect of blocking agents, and stringency wash variations. This method also allowed us to quantitate the GAPDH RNA copy number/cell using a fluorescence standard; we obtained a figure of about 1200 copies/cell, which is in good agreement with the dot blot hybridization assay result. Flow cytometric analysis of in situ hybridization represents an original method to study gene expression. This technique has the potential to develop into a multiparametric tool for cell biology studies, examining specific mRNA production together with DNA content or membrane molecules expression, and offering the possibility to purify by sorting a cell population expressing a specific mRNA.

Base Sequence↗

PubMed1984

Endogenous digitalis-like factors: in vitro comparison of biological and immunological activities of peptide and steroid candidates.

Endogenous substances that modulate the activity of (Na+ + K+)-ATPase through interaction at the cardiac glycoside site have been postulated. Reports of digitalis-like biological and immunological activity exhibited by certain ACTH/MSH peptides and 14-OH steroids make these compounds potential candidates as endogenous digitalis-like factors. We tested several ACTH/MSH peptides and 14 alpha-OH steroids in four in vitro assays and detected no significant cardiac glycoside-like activity. On the other hand, chlormadinone acetate, a progesterone derivative shown to bind with high affinity to the digitalis receptor, was nearly equipotent to digoxigenin in a [3H]ouabain radioreceptor assay. In a [3H]digoxin radioimmunoassay, however, digoxigenin and digoxin were equipotent but chlormadinone acetate was inactive. A clear dissociation between radioreceptor assay and radioimmunoassay activity was also observed using 15 beta-OH-progesterone. Our findings indicate that (a) ACTH/MSH peptides and 14 alpha-OH steroids are not viable candidates as endogenous digitalis-like factors, (b) digoxin antibodies are not necessarily directed at molecular determinants critical for biological activity, and (c) among the compounds reported to exhibit digitalis-like activity and postulated to share structural features with an endogenous steroidal digitalis-like factor, only chlormadinone acetate and its congeners appear to constitute tenable models.

Adrenocorticotropic Hormone↗

PubMed1995

Quantitation of IL-1 beta mRNA by a combined method of RT-PCR and an ELISA based on ion-sensitive field effect transistor.

A method for quantitative RT-PCR using ELISA detection was developed and applied to the quantitation of IL-1 beta mRNA in clinical samples. To compensate for the 'tube effect' of RT-PCR, a synthetic RNA, pRSET RNA, was added to sample solutions as an internal standard and co-amplified with IL-1 beta mRNA. Sense primers for IL-1 beta and pRSET were labeled with digoxigenin and FITC, respectively, while anti-sense primers for both were labeled with biotin. Double-stranded PCR products were captured by two solid-phase pipettetips. One was coated with an anti-digoxigenin antibody and another with an anti-FITC antibody, and sandwiched by avidin-urease, and their activities were measured by coupling them with a pH-FET in a pH-measuring cell containing urea solution. The ratio of the signal intensity for IL-1 beta to that for pRSET was used to quantify the concentration of IL-1 beta mRNA. A calibration curve was obtained by using a known amount of AW 109 RNA as an external standard of IL-1 beta RNA. It was found that 10(2)-10(6) copies of IL-1 beta mRNA were measurable by the present method. Expression levels of IL-1 beta mRNA in clinical samples, such as monocytes of peripheral blood or synovial cells from patients with RA or OA, were determined.

Base Sequence↗

PubMed1994

Rapid nonradioactive in situ hybridization for interleukin-2 mRNA with riboprobes generated using the polymerase chain reaction.

In situ hybridization is a technique with widespread application. However, its usefulness has been limited by the need for radioactive materials and the requirement for the DNA to be cloned onto an appropriate vector. We have utilized the polymerase chain reaction to directly incorporate a T7 RNA polymerase promoter sequence onto the cDNA for interleukin-2. Digoxigenin-labelled riboprobes were then synthesized using this PCR product as a template. The digoxigenin-labelled riboprobes were then used in non-radioactive in situ hybridization to detect messenger RNA for interleukin-2 in mitogen stimulated peripheral blood mononuclear cells. This methodology has the potential for widespread application in immunology and cytokine research.

Base Sequence↗

PubMed1996

A fluorescent in situ hybridization method in flow cytometry to detect HIV-1 specific RNA.

In HIV+ patients, the presence of HIV-RNA in plasma and circulating cells has been reported to be a marker of progression but the percentage of transcriptionally active infected cells remains unclear. We have developed a reliable fluorescent in situ hybridization method for the detection of HIV specific RNA by flow cytometry. The procedure was applied to a panel of chronically infected cell lines and to an acutely infected cell line mimicking normal peripheral blood lymphocytes in susceptibility to HIV-1. The cells were fixed in suspension and hybridized by means of an HIV-1 genomic probe labeled with digoxigenin-11-dUTP. An FITC-labeled anti-digoxigenin antiserum was then applied and the resulting fluorescence signals were analyzed both by flow cytometry and confocal microscopy. Different procedures for double staining HIV-RNA together with virus induced proteins or surface markers were also developed. Flow cytometric detection of in situ hybridization offers the possibility of analyzing thousands of cells in a few seconds and of collecting multiparametric information at the single cell level, thus providing a potential tool for detecting the rare HIV-RNA expressing cells in peripheral blood samples.

Antigens, CD↗

PubMed1996

Oligonucleotide ligation assay for detection of the factor V mutation (Arg506-->Gln) causing protein C resistance.

A point mutation in the Factor V (FV) gene at the activated protein C cleavage site, FV Arg (R)506-->FV Gln (Q)506, is the reported molecular basis for resistance to activated protein C (APC-R). This mutation has been reported in approximately 20-50% of individuals with previously unexplained thrombophilia and 3-5% of the general population. We have adapted an oligonucleotide ligation assay (OLA) for nonisotopic detection of the FV:Q506 mutation which permits rapid screening for this mutation. First, the polymerase chain reaction (PCR) was used for target DNA amplification, thus permitting nonisotopic reporters in the DNA analysis. Then thermostable ligase was used for ligation or covalent coupling of adjacent wild-type and mutant oligonucleotide probes which occurs only when the probes are annealed to a matched amplicon. A colorimetric ELISA-based detection assay was then used to capture 5' biotinylated probes in 96-well streptavidin-coated plates and by virtue of ligation, detection of a 3' digoxigenin reporter probe. Following the addition of anti-digoxigenin conjugate and enhanced alkaline phosphatase signal amplification, colorimetric substrate change was measured in an ELISA plate reader. This assay correctly identified FV genotypes of 290 samples.

Base Sequence↗

PubMed1994

Detection of interleukin-5 messenger RNA and interleukin-5 protein in bronchial biopsies from asthma by nonradioactive in situ hybridization and immunohistochemistry.

Recently direct evidence for the role of interleukin-5 (IL-5) in eosinophilic inflammation in the airways of persons with asthma has been provided by an in situ hybridization study that used radioisotope-labeled IL-5 complementary RNA probes. Radioisotope-labeled probes, although sensitive, require autoradiographic detection, which is time-consuming. In the most recent study we attempted to detect IL-5 messenger RNA in the bronchial biopsy specimens from patients with asthma using nonradioactive in situ hybridization, which gives rapid results. Bronchial biopsy specimens were obtained from eight patients with asthma and seven diseased control subjects. IL-5 complementary DNA probes were labeled with digoxigenin-deoxyuridine triphosphate and hybridized to permeabilized sections. Hybridization signals were visualized by an immunohistochemistry technique. Positive hybridization signals were observed in six of the eight biopsy specimens from patients with asthma. Pretreatment with ribonuclease or hybridization with an unrelated probe produced negative results. Immunohistochemical staining of serial sections with a monoclonal antibody to IL-5 revealed that a few cells within the mucosa positively stained, suggesting active synthesis of IL-5. Biopsy results from the seven diseased control subjects did not show any hybridization signal. These results confirm and extend previous observations of IL-5 messenger RNA expression in the airways of patients with asthma, and suggest that digoxigenin-labeled IL-5 complementary DNA probes would be a powerful research tool.

Adult↗

PubMed1991

Enhanced chemiluminescence-based hybridization analysis for PCR-mediated HIV-1 DNA detection offers an alternative to 32P-labelled probes.

The efficiency of enhanced chemiluminescence based on a novel generation substrate for alkaline phosphatase, adamantyl-1,2-dioxetane phosphate, was compared with that of 32P-labelled probe for visualization of human immunodeficiency virus type 1 (HTV-1)-specific DNA-DNA hybrids. The probe used for nonisotopic detection was digoxigenin labelled and targeted by anti-digoxigenin antibody Fab-fragments conjugated to alkaline phosphatase. The dot-blot hybridization analysis performed on a dilution series of HIV-1 proviral DNA demonstrated a lower sensitivity limit of 0.5 pg with the nonisotopic method. However, one order of magnitude less DNA could still be detected by a random-primed 32P-labelled probe. The ability of nonradioactive and radioactive probes to detect 590-bp gag gene-specific target sequences generated by the polymerase chain reaction (PCR)-mediated amplification of HIV-1 DNA was also compared. Analysis of 20 samples from individuals at increased risk for HIV infection by using the two assayed systems produced virtually equivalent signal images on corresponding specimens. Furthermore, complete concordance in the performance was found when HIV-1 proviral DNA was investigated by PCR in additional 50 samples of human blood mononuclear cells.

Adamantane↗

PubMed1992

A new method for measuring reverse transcriptase activity by ELISA.

A new and sensitive assay of reverse transcriptase (RT) activity of retroviruses measures the incorporation of digoxigenin-labelled dUTP in newly synthesized DNA instead of radioactively labelled (3H- or 32P-)dTTP. To avoid difficulties associated with separation of non-incorporated nucleotides from the newly synthesized DNA, biotin-labelled dUTP is added to the reaction mixture in very low concentrations. After reverse transcription, the newly synthesized, doubly labelled DNA is immobilized on streptavidin-coated ELISA wells and evaluated photometrically by binding of peroxidase-conjugated anti-digoxigenin-antibodies (sheep) and subsequent colour development with 2,2'-azino-di[3-ethylbenzthiazolin-sulfonate(6)] (ABTSR) as substrate. For better standardization, it is suggested that RT activity is given in units (one unit of RT is the amount of enzyme incorporating one nanomole of labelled dNTP in 10 min at 37 degrees C into an acid precipitable DNA) rather than in cpm (counts per minute). The method is specific and easy to perform.

Avian Myeloblastosis Virus↗

PubMed1992

Detection of CMV DNA in clinical samples of AIDS patients by chemiluminescence hybridization.

A sensitive chemiluminescence dot-blot hybridization assay for the detection of CMV DNA in clinical samples of AIDS patients is described. In the chemiluminescence hybridization assay, digoxigenin-labelled CMV DNA probes were used and when hybridized they were detected by anti-digoxigenin Fab fragments conjugated with alkaline phosphatase. Adamantyl 1,2-dioxetane phenyl phosphate was used as the chemiluminescent substrate. The results were recorded by instant photographic films. The results obtained with the chemiluminescence hybridization assay were compared with the results obtained by hybridization with colourimetric detection. The chemiluminescent assay proved specific, sensitive and reliable and thus can be used as a valuable routine diagnostic test for the detection of CMV DNA in clinical samples.

Acquired Immunodeficiency Syndrome↗

PubMed1994

Chemiluminescent microwell hybridization assay for direct detection of human parvovirus B19 DNA.

A method for the direct detection of human parvovirus DNA in serum samples that uses a digoxigenin-labeled RNA probe to hybridize with target B19 DNA, followed by capture of the hybrid onto a microtiter plate wells previously coated with a second oligonucleotide probe was developed. The captured hybrid is then detected with anti-digoxigenin-alkaline phosphatase conjugate and chemiluminescent substrate and the reaction read on a scintillation counter. The relative sensitivities of the microwell and standard dot blot hybridization assays were compared. The chemiluminescent microwell hybridization assay was more sensitive than dot-blot hybridization and could be performed in a few hours. This format, therefore, permits rapid and sensitive detection of parvovirus DNA suitable for the clinical setting.

Base Sequence↗

PubMed1996

Detection and variant identification of HHV-6 by a non-radioactive hybridization microplate assay for amplimers detection.

A non-radioactive hybridization microtiter plate assay was developed and evaluated for detection of the HHV-6 genome and to identify HHV-6 variants A and B. The viral DNA is amplified by the polymerase chain reaction using a 5'-end-biotinylated primer. The biotinylated amplimers are captured on avidin-coated microtiter plates, denaturated with sodium hydroxide and hybridized to a 3'-end-digoxigenin-labelled probe. Subsequently, anti-digoxigenin Fab fragments conjugated with alkaline phosphatase are used for the revelation of the hybridized probe. The result is obtained by measuring the intensity of light emitted with a spectrophotometer. This new assay was compared to the standard analysis of amplified products by Southern hybridization consisting of gel electrophoresis of the amplimers, transfer onto a nylon membrane, and hybridization with a 32P-labelled oligomeric probe. Both methods exhibited the same sensitivity and specificity. Thus, a non-radioactive hybridization microtiter plate assay may be a suitable alternative to isotopic techniques.

Biotin↗

PubMed1996

Detection of herpes simplex virus DNA in cerebrospinal fluid samples using the polymerase chain reaction and microplate hybridization.

As conventional polymerase chain reaction (PCR) procedures are time-consuming and laborious, we developed and evaluated a rapid semi-automatic microplate method to detect the amplified PCR products. The use of PCR, with subsequent hybridization in microplates, is described for the detection of herpes simplex virus (HSV) DNA in cerebrospinal fluid samples. The principle of the method is based on two phases. Firstly, the amplification of the viral DNA in the sample is undertaken using a pair of primers of which one is biotinylated. Secondly, the amplified viral genomic sequences are bound to the wells of streptavidin-coated microplates and hybridized with digoxigenin-labeled oligonucleotide probes which are then detected using anti-digoxigenin antibody enzyme conjugates and either a photometric, fluorometric or luminometric substrate and microplate reader. The method is highly sensitive allowing the detection of as few as five purified DNA molecules. Compared to conventional gel electrophoresis followed by Southern blotting the established microplate hybridization is also much less time-consuming and involves less manual work. The applicability of the method is described for use as a routine diagnostic procedure for detection of early central nervous system infections caused by HSV-1 and HSV-2.

Animals↗

PubMed1990

Recent progress in the use of the technique of non-radioactive in situ hybridization histochemistry: new tools for molecular neurobiology.

Recent developments in DNA and oligonucleotide chemistry have made it possible to modify nucleotides and link quite complex molecules to the modified nucleotides. These advancements in DNA chemistry provide a number of possibilities for labelling oligonucleotide probes for DNA or RNA detection by non-radioactive methods. Over the years a number of non-radioactive detection systems for mRNA or chromosomal DNA have been developed. As reporter molecules, biotin, acetylaminofluorene, dinitrophenol, digoxigenin, sulfonized nucleotides, and mercury have been used and may be detected with a variety of high-affinity detectors, e.g. avidin (in the case of biotin) or antibodies specific to digoxigenin. These various 'indirect methods' of detection have used a number of chemical amplification procedures in attempts to improve their sensitivity. However, the sensitivity of these methods is often less than that of conventional radioactive methods. A sensitive non-radioactive technique would have a number of advantages over the complex and specialized radioactive in situ hybridization methods. In our laboratory we have recently found that simple enzyme-labelled probes provide excellent sensitivity (equivalent to that found with radioactive methods) and substantially improved cellular resolution. In this article, we describe the principle of the method and illustrate some applications of this novel non-radioactive in situ method.

Animals↗

PubMed1996

Chemiluminescent enzyme immunoassay for detection of PCR-amplified enterotoxin A from Clostridium perfringens.

A PCR protocol was developed for the rapid and specific detection of Clostridium perfringens strains harboring the enterotoxin A gene in artificially contaminated ground beef. A biotinylated primer pair was designed for amplification of a 750 bp fragment of the C. perfringens enterotoxin A gene. A combination of 4 h enrichment incubation and nucleic acid extraction, followed by 2 h of PCR amplification allowed detection at levels below 10 CFU of freshly grown cells in raw and cooked beef samples. PCR amplified products were confirmed by a Southern hybridization assay using a digoxigenin-labeled internal probe, and two hybridization ELISA protocols (PCR-ELISA) applying a streptavidin capture step for the hybridized PCR products. Both enzyme immunoassays utilized chemiluminescent detection with Lumiphos 530TM as substrate, after hybridization to an internal digoxigenin-labeled probe or a 5' conjugated alkaline phosphatase-labeled probe. The PCR-ELISA resulted in faster confirmation of the PCR products while providing a level of sensitivity comparable to Southern hybridization, and has potential for development into an automated method.

Bacterial Toxins↗

PubMed1992

Organization of central cholinergic neurons revealed by combined in situ hybridization histochemistry and choline-O-acetyltransferase immunocytochemistry.

Digoxigenin-labeled riboprobes and in situ hybridization of choline-O-acetyltransferase mRNA, both alone and in combination with immunohistochemical procedures for the synthetic enzyme of acetylcholine, were used to map the topography of putative cholinergic neurons in the rat central nervous system. Only the anti-sense riboprobe yielded specific labeling, which was absent in brain sections processed with sense riboprobe. Telencephalic neurons demonstrating the mRNA for choline-O-acetyltransferase and choline-O-acetyltransferase-like immunoreactivity were found in the caudate-putamen nucleus, nucleus accumbens, olfactory tubercule, Islands of Calleja complex, medial septal nucleus, vertical and horizontal limbs of the diagonal band, substantia innominata, nucleus basalis, and nucleus of the ansa lenticularis, as well as occasionally in the amygdala. Neurons in the cerebral cortex, hippocampus, and primary olfactory structures did not demonstrate hybridization signal, even though some cells in those areas were observed to exhibit choline-O-acetyltransferase-like immunopositivity. Thalamic cells were devoid of hybrido- and immunoreactivity, with the exception of several neurons located primarily in the ventral two-thirds of the medial habenula. A few cell bodies labeled with riboprobe and co-localizing choline-O-acetyltransferase-like immunopositivity were found in the lateral hypothalamus, caudal extension of the internal capsule, and zona incerta. Neurons in the pedunculopontine and laterodorsal tegmental nuclei evinced moderate hybridization signal, whereas cells of the parabigeminal nucleus were very weakly reactive. In contrast, motor neurons of the cranial nerve nuclei demonstrated high levels of choline-O-acetyltransferase mRNA and choline-O-acetyltransferase-like immunoreactivity. Putative cholinergic somata in the ventral horns and intermediolateral cell columns of the spinal cord and around the central canal were also labeled with riboprobe. It is concluded that hybridocytochemistry with digoxigenin-labeled riboprobes confirms the existence of cholinergic neurons in most of the neural regions believed to contain them on the basis of acetylcholinesterase pharmacohistochemistry and choline-O-acetyltransferase immunocytochemistry, with the prominent exceptions of the cerebral cortex, hippocampus, olfactory bulb, anterior olfactory nucleus, and caudal raphe nuclei, which apparently do not possess neurons expressing detectable levels of the mRNA for the synthetic enzyme of acetylcholine.

Animals↗