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Use of [32P]RNA probes for the dot-hybridization detection of potato spindle tuber viroid.

A dot-hybridization assay using 32P-labelled RNA probes (+RNA and cRNA) transcribed from potato spindle tuber viroid (PSTV) cDNA was described. A complete cDNA copy of PSTV, originally cloned in pBR 322 (pAV 401) was subcloned in the BamHI site of a 'Riboprobe' cloning vectors pSP 64 and pSP 65 in opposite orientations. The reconstructed plasmids were designated pDX 1 and pDX 4, respectively. Transcription of pDX 1 and pDX 4 plasmids by SP6 RNA polymerase resulted in the generation of PSTV-specific RNA (+RNA) and PSTV complementary RNA (cRNA), respectively. The cRNA probe was much more sensitive than the +RNA probe and the nick-translated cDNA probe from the plasmid pAV 401 for the detection of PSTV in clarified plant sap. As little as 1.4 pg of purified PSTV mixed in clarified sap from uninoculated tomato leaves has been detected using cRNA probe. A relatively simple procedure using cetyltrimethyl ammonium bromide (CTAB) as nucleic acid precipitant and an enrichment step for the purification of PSTV was described.

DNA Restriction Enzymes↗

Identification of African horse sickness virus in cell culture using a digoxigenin-labeled RNA probe.

A digoxigenin-labeled RNA probe was synthesized from a plasmid containing a portion of the African horse sickness virus (AHSV) serotype 4 genome segment coding for nonstructural protein 1. In an in situ hybridization procedure, this probe hybridized successfully to Vero cells infected with each of the 9 serotypes of AHSV. There was no hybridization with noninfected cell cultures or cell cultures infected with bluetongue virus.

African Horse Sickness Virus↗

Analysis of RNA stability and (-) strand content in viral infections using biotinylated RNA probes.

Non-radioactive biotinylated RNA probes specific for plus (+) and minus (-) sense RNAs of brome mosaic virus (BMV) were synthesized in vitro from a plasmid bearing a 200 base pair fragment complementary to the 3' terminus of each of the three genomic RNAs of the virus. Using virion RNAs isolated from BMV infected barley plants, the sensitivity of biotinylated RNAs as hybridization probes was compared with that of 32P-labeled probes in Northern hybridization assays. Although the sensitivity of biotinylated and 32P-labeled probes is similar (approximately 5 pg), the time required to detect the RNA bands was much less than for autoradiography; (-) sense RNAs could be detected in 30 min whereas 48 h or more were required by autoradiography. The value of biotinylated probes for following RNA stability was exemplified by the detection of supplied inocula in protoplasts 24 h post-inoculation. Quantitation of relative accumulation of progeny (+) and (-) sense RNAs by densitometry of the Northern blots probed with biotinylated RNAs paralleled that of radiolabeled probes. The application of these probes was extended to the detection of RNAs in barley protoplasts and BMV infected plant sap by dot hybridization. In these tests, viral RNAs were detected in as few as 250 protoplasts and sap dilutions up to 1:2000. The merits of these non-radioactive probes in monitoring the replication events by the detection and quantitation of mutant progeny RNAs of BMV are discussed.

Biotin↗

Plasmodium berghei: quantitation of in vitro effects of antimalarial drugs on exoerythrocytic development by a ribosomal RNA probe.

A stage-specific ribosomal RNA probe has been used to quantitate exoerythrocytic development of Plasmodium berghei in primary cultures of mouse hepatocytes. Parasite rRNA could be detected as soon as 6 hr after sporozoite invasion and was increased during schizogony to a maximum at 48 hr, when mature schizonts were identified by microscopy. As few as 10 exoerythrocytic schizonts could be detected by filter blot hybridization, followed by autoradiography and liquid scintillation counting. By hybridizing the culture rRNA samples with either parasite-specific or universal rRNA probes, the in vitro tissue schizonticidal activity and hepatotoxicity of primaquine, two of its analogues, and pyrimethamine, could be assessed. After a 48-hr exposure of the culture to serial dilutions of each drug, a quantitative relationship was demonstrated between the decrease of the parasite rRNA and the increase of the drug concentrations. No significant parasite-specific rRNA could be detected at the concentration achieving complete inhibition of schizont formation but causing no cytotoxic effects on host hepatocytes. In contrast to microscopic-based assays, this molecular approach provides an objective and quantitative in vitro method for rapid screening and evaluation of tissue schizonticidal antimalarials.

Aminoquinolines↗

Evaluation of strand-specific RNA probes visualized by colorimetric and chemiluminescent reactions for the detection of B19 parvovirus DNA.

A dot-blot hybridization assay was developed to detect B19 DNA using strand-specific RNA probes labelled with digoxigenin. The sensitivity of the assays was evaluated either using 'plus' and 'minus' sense RNA probes in two different hybridization assays, or in two successive reactions of the same assay. The hybridized probes were revealed immunoenzymatically using anti-digoxigenin Fab fragments conjugated with alkaline phosphatase. The enzyme was visualized by colorimetric reaction. Since 'minus' sense RNA probe gave the best results in the dot-blot procedures, we increased the sensitivity of the hybridization assay visualizing the 'minus' sense digoxigenin-labelled RNA probe by chemiluminescent reaction. In these experimental conditions up to 20 fg of target B19 DNA could be visualized. In the search for B19 DNA, 4656 serum samples were analyzed by chemiluminescent reaction of 'minus' sense digoxigenin-labelled RNA probe and for comparison with the digoxigenin-labelled DNA probe. Positive results were confirmed by Southern blotting. Out of 4656 serum samples analyzed, 4648 gave negative results, 1 resulted positive to all the hybridization assays, 6 only using RNA probe and 1 only by DNA probe.

Adult↗

Time-resolved fluorometric hybridization assays with RNA probes synthesized from polymerase chain reaction-generated DNA templates.

DNA templates suitable for direct synthesis of RNA probes are produced by the polymerase chain reaction. The nucleic acid sequence of interest is amplified using a downstream primer carrying the T7 RNA polymerase promoter sequence. The modified primer is incorporated into the amplified DNA, which is subsequently used for RNA probe synthesis in the presence of T7 RNA polymerase and a hapten-labeled ribonucleotide (digoxigenin-UTP). As a model, we prepared RNA probes specific for the BCR-ABL mRNA characteristic of chronic myelogenous leukemia. The probes are used in time-resolved fluorometric hybridization assays. Mixtures of BCR-ABL positive and negative cells, as well as whole blood samples, are analyzed. The sample mRNA is amplified using a biotinylated upstream primer. The amplified product (target DNA) is captured onto streptavidin-coated wells and hybridized to the RNA probe. The hybrids are detected with an alkaline phosphatase (ALP)-labeled antibody. ALP hydrolyzes the phosphate ester of fluorosalicylic acid, and the fluorosalicylate produced forms highly fluorescent ternary complexes with Tb(3+)-EDTA, which can be quantified by measuring the Tb3+ fluorescence in a time-resolved mode. As low as 0.4 fmol of target DNA can be detected. Also, a single leukemic cell may be detected in the presence of 0.5 million "normal" cells.

Base Sequence↗

A simple RNA probe system for analysis of Listeria monocytogenes polymerase chain reaction products.

The synthesis of an RNA probe specific for the hlyA gene of Listeria monocytogenes by in vitro transcription from a polymerase chain reaction (PCR)-generated template incorporating bacteriophage T7 promoter sequences is described. This simple method produced a high yield of RNA which hybridized specifically with hlyA PCR products on a membrane, resulting in RNA-DNA hybrids which were detected by an immunoenzymatic assay with an anti-RNA-DNA hybrid antibody. The RNA probe hybridization system was more sensitive in the analysis of the PCR products than was the conventional agarose gel electrophoresis method. When applied to the analysis of PCR samples from cultures of various Listeria and non-Listeria organisms, the RNA probe was reactive in the assay of 62 different L. monocytogenes isolates but not other Listeria species. Among the non-Listeria organisms tested, only Enterococcus faecalis gave a weak positive reaction with more than 10(9) cells per ml. This reactivity disappeared at lower cell densities. This strategy for the synthesis and application of RNA probes should facilitate the analysis of PCR products in the detection of L. monocytogenes and possibly other food pathogens.

Base Sequence↗

RNA probes detect nucleotide sequence homology between members of two different nairovirus serogroups.

Cloned cDNA derived from the small (S) and medium (M) genomic RNA segments of Dugbe (DUG) virus, isolate ArD44313, a member of the Nairobi sheep disease (NSD) serogroup of nairoviruses (family, Bunyaviridae) was used to prepare 32P-labelled DNA and RNA probes. The S and M segments of six isolates of DUG virus all hybridised to both DNA and RNA probes, although the M segment of isolate KT281/75 reacted only weakly. Of nine other nairoviruses tested, representing all the six other serogroups within the Nairovirus genus, none hybridised to the DNA probes. However, under conditions of low stringency, the DUG S and M RNA probes hybridised to the respective S and M segments of Ganjam (GAN) virus (another member of the NSD serogroup). The DUG S RNA probe also hybridised to the S segments of Crimean-Congo haemorrhagic fever (CCHF) virus and Hazara (HAZ) virus (members of the CCHF serogroup). The indicated sequence relationships between DUG, GAN, CCHF and HAZ viruses show that the NSD serogroup is more closely related to members of the CCHF serogroup than it is to nairoviruses of the other five serogroups.

Animals↗

In situ hybridization methods for the detection of somatostatin mRNA in tissue sections using antisense RNA probes.

In situ hybridization studies with [32P] and [3H] labelled antisense RNA probes were undertaken to determine optimal methods of tissue fixation, tissue sectioning, and conditions of hybridization, and to compare the relative merits of the two different radioactive labels. The distribution of somatostatin mRNA in neurons of rat brain using a labelled antisense somatostatin RNA probe was employed as a model for these studies. The highest degree of sensitivity for in situ hybridization was obtained using paraformaldehyde fixation and vibratome sectioning. Optimal autoradiographic localization of mRNA was obtained within 7 days using [32P] labelled probes. However, due to the high energy emittance of [32P], precise intracellular localization of hybridization sites was not possible. [3H] labelled RNA probes gave more precise cellular localization but required an average of 18-20 days autoradiographic exposure. The addition of the scintillator, PPO, decreased the exposure time for the localization of [3H] labelled probes to seven days. We also report a method for combined in situ hybridization and immunocytochemistry for the simultaneous localization of somatostatin in mRNA and peptide in individual neurons.

Animals↗

In situ hybridization for light and electron microscopy: a comparison of methods for the localization of viral RNA using biotinylated DNA and RNA probes.

We report procedures for in situ hybridization at the light and electron microscopic level for localization of viral RNA in poliovirus-infected, Lowicryl-embedded cells. We compare specificity and signal intensity of biotinylated, double-stranded DNA and single-stranded, strand-specific RNA probes, both corresponding to the same region of the poliovirus genome. The hybrids were detected with antibiotin antibodies or streptavidin with colloidal gold as a marker. Hybridization with the RNA probe was more sensitive and gave lower background than with DNA. Detection with immunogold proved to be by far more sensitive than with streptavidin. The hybridization and detection protocols for the DNA and the RNA probes could be applied without modification to light microscopic semi-thick sections as well as to electron microscopic ultrathin sections.

Biotin↗

Detection of caprine arthritis--encephalitis virus RNA in macrophages by in situ hybridization using fluorescein-labelled single-stranded RNA probes.

The use of in situ hybridization (ISH) for the detection of caprine arthritis-encephalitis virus (CAEV) RNA with fluorescein-11-UTP-labelled single-stranded RNA probes is described. Three different probes were made by PCR amplification of proviral CAEV DNA (strain 75-G63). The PCR products were cloned into the plasmid pAM-18, and labelled single-stranded RNA probes were synthesized by the use of RNA polymerase. The LTR probe was able to detect viral RNA in CAEV-infected, cultured caprine macrophages, while probes based on the genes for the matrix and transmembrane proteins failed to do so. A few macrophages were positive for CAEV RNA 24 h post infection (p.i.) while most cells were positive 96 h p.i. The use of fluorescein-labelled RNA probes made this method feasible for kinetic in vitro studies of CAEV.

Animals↗

Double-label in situ hybridization using biotin and digoxigenin-tagged RNA probes.

We describe a double-label in situ hybridization protocol based on the optimized synthesis of biotin-labeled RNA probes. Biotin-labeled probes are used in conjunction with digoxigenin-labeled probes to simultaneously visualize two different transcripts. One transcript is hybridized with a biotin-labeled RNA probe and visualized as a brown peroxidase reaction product, and the other transcript is hybridized with a digoxigenin-labeled RNA probe and visualized as a blue alkaline phosphatase reaction product. We present several examples in which this double-labeling method has proven useful in determining the spatial and temporal relationships between various transcripts expressed during Drosophila embryogenesis, indicating that this method should be of general use in establishing the relationship of two independent transcription patterns.

Biotin↗

Detection of DNA targets with biotinylated and fluoresceinated RNA probes. Effects of the extent of derivitization on detection sensitivity.

The substituted nucleotide aminohexyl-ATP (AH-ATP) was used for synthesis of RNA probes from a plasmid template using the T7 phage promoter. Following synthesis, RNA probes were modified by reaction with N-hydroxysuccinimide (NHS) esters of biotin or fluorescein. Nearest-neighbor analysis was used to quantitate both the incorporation of the substituted nucleotide into RNA and the subsequent modification of the incorporated nucleotide by the NHS esters. The results indicate that AH-ATP is efficiently incorporated into RNA and that modification of the amine group is also efficient. The T7 polymerase shows a bias for ATP over AH-ATP and truncated transcripts are produced if 100% AH-ATP is used for synthesis. However, the use of 50% AH-ATP in the synthesis reaction yields full-length RNA probes that contain on average one amine-labeled nucleotide every 12 bases. This RNA is readily modified by the respective NHS esters to obtain one biotin group per 15-18 total RNA bases or one fluorescein group per 25-35 bases. Probes modified with biotin or fluorescein were used to detect picogram levels of target DNA in a dot blot hybridization format.

Adenosine Monophosphate↗

Detection of the bunyavirus Germiston in VERO and Aedes albopictus C6/36 cells by in situ hybridization using cDNA and asymmetric RNA probes.

Using Germiston virus infected vertebrate (VERO) and invertebrate (Aedes albopictus C6/36) cells, paraformaldehyde-glutaraldehyde fixative allowed the best preservation of cellular morphology and the highest hybridization signals with cDNA and asymmetric RNA probes against the viral S segment. Asymmetric RNA probes always gave higher sensitivity and better specificity of in situ hybridization than the nick-translated symmetric DNA probe in both vertebrate and invertebrate cells. The study of Aedes albopictus C6/36 cells persistently infected with Germiston virus showed that only a small number of cells contained the S segment, and that the replication and transcription of the S segment took place in the cytoplasm of acutely and persistently infected cells.

Aedes↗

Two subgingival plaque-sampling strategies used with RNA probes.

BACKGROUND: The purpose of this study was to compare the results of microbiological RNA-probe analysis after subgingival plaque sampling applying two different strategies. METHODS: In 220 patients, clinical examinations were obtained prior to commencement of therapy for aggressive or generalized severe chronic periodontitis (n = 113), after combined mechanical and antibiotic anti-infective periodontal therapy (n = 43), or because of periodontal pockets despite adequate therapy (n = 64). Subgingival plaque samples were obtained from the three pockets with the deepest probing depths. Two sterile paper points were inserted simultaneously into the periodontal pockets. One paper point from each pocket was put into a separate transport vial; the second paper point was pooled (multiple site test [MT3]) with paper points from each of the two other sampling sites from the respective patient into a transport vial. The content of each vial was analyzed separately for Actinobacillus actinomycetemcomitans, Tannerella forsythensis, Porphyromonas gingivalis, and Treponema denticola (Td) with a commercially available RNA-probe test. RESULTS: For all tested pathogens, log-transformed numbers of bacteria were higher in pooled samples compared to the mean values for the separate samples (P < or =0.01). However, for Td only, statistically significant differences in frequency were seen between the separate samples and MT3. These findings were observed over all samples as well as after evaluation of subgroups separately. CONCLUSIONS: Pooling of plaque samples increased the bacterial counts per analysis compared to separate samples and thus may increase the probability of detecting existing pathogens. However, this observation only was statistically significant for the frequency of Td.

Aggregatibacter actinomycetemcomitans↗

Quantification of biotinylated RNA probes for in situ hybridization using chemiluminescence.

For reliable detection of mRNA by non-radioactive in situ hybridization, calibration and standardization of the individual steps involved are essential. We describe a method that allows determination of the size and integrity as well as quantification of biotinylated RNA probes in a single experiment. Serial dilutions of biotinylated RNA probes generated by promoter-mediated in vitro transcription were size-separated by gel electrophoresis in the presence of known amounts of 5'-biotinylated oligomers which served as internal standard. Following immobilization onto nylon membranes and visualization by chemiluminescence, optical densities of probes and internal standards were measured by densitometry and analysed by linear regression. RNA probes complementary to the human homeobox genes HOX-C6, -C8 and -C9 were quantified. Four different 5'-biotinylated oligomers (20, 35, 50 and 75 bases) were tested as internal standards. Concerning the separation of probe and oligomer in the gel, transfer properties and efficiency of binding to the membrane, the oligomer of 35 bases was found to be the best internal standard with highest reproducibility. Comparison of probe concentration by spectrophotometry and the described method showed a good correlation, indicating that our method is a reliable assay for quantitative and qualitative control of biotin-labelled probes.

Biotin↗

Comparison of biotinylated DNA and RNA probes for rapid detection of varicella-zoster virus genome by in situ hybridization.

We describe a general method for the production of nonisotopic DNA and RNA probes for the detection of the varicella-zoster virus (VZV) genome by in situ hybridization. VZV DNA was extracted from purified viral nucleocapsids, cleaved with restriction enzyme (RE) BamHI, and cloned into plasmid pBR322 by the standard vector insert procedure. We cloned over 85% of the VZV genome and obtained 18 recombinants. Plasmids containing the B, F, G, H, and J fragments of VZV DNA were labeled by the nick translation method with biotin-11-dUTP as the dTTP analog. Additionally, the B fragment was cleaved with RE AvaI, subcloned into the plasmid pGEM-4 transcription vector, and subsequently linearized with REs PstI and EcoRI. RNA was transcribed with T7 or SP6 polymerase, with a substitution of allylamine-UTP as the UTP analog, and labeled with epsilon-caproylamidobiotin-N-hydroxysuccinimide ester. The DNA and RNA probes were used under full-stringency conditions for in situ hybridization with alkaline phosphatase as the detector and 5-bromo-4-chloro-3-indolyl phosphate-Nitro Blue Tetrazolium as the substrate. When tested under comparable conditions, the RNA probe was slightly more sensitive than was the DNA probe: both probes showed homology only with VZV-infected cells and clinical tissues and not with the other herpesviruses. Probes prepared from variable regions of the genome (fragments F and J) performed as well as did those from conserved regions (fragments B. G. and H). Biotinylated probes have distinct advantages over isotopic probes and retain their full potency for more than 2 years when stored properly.

Biotin↗