DIG-labeled Probes Research Articles

Detection of Y-bearing porcine spermatozoa by in situ hybridization using digoxigenin-labeled, porcine male-specific DNA probe produced by polymerase chain reaction.

This study was carried out to determine whether Y-bearing porcine spermatozoa could be detected by in situ hybridization using a digoxigenin (Dig)-labelled DNA probe specific to the Y chromosome produced by polymerase chain reaction (PCR). A conventional PCR (with Dig-dUTP) was performed using a set of oligonucleotide primers (5'-AAGTGGTCAGCGTGTCCATA-3' and 5'-TTTCTCCTGTATCCTCCTGC-3') for 236 bp fragment of porcine male-specific DNA sequence and 1.25 x 10(4) template white blood cells obtained from a boar. When fluorescence in situ hybridization with the Dig-labelled DNA probe was applied to the metaphase chromosome spreads prepared from both boar and gilts, the fluorescein signal was only detected on the long arm of the Y chromosome. In addition, immunocytochemical detection with the Dig-labelled DNA probe and alkaline phosphatase-labeled anti-Dig was applied to both sperm nuclei pretreated with dithiothreitol and white blood cells; 51% of sperm nuclei and 96% of white blood cells obtained from boar were labelled, whereas none of white blood cells obtained from gilts were labelled with the Dig-labelled DNA probe. The results indicated that in situ hybridization with porcine male-specific DNA probe produced by PCR made possible the direct visualization of Y-bearing porcine spermatozoa by in situ hybridization.

Gene Diagnosis of Viroids: Comparisons of Return-PAGE and Hybridization Using DIG-labeled DNA and RNA Probes for Practical Diagnosis of Hop Stunt, Citrus Exocortis and Apple Scar Skin Viroids in Their Natural Host Plants.

Return-PAGE was reliable for diagnosis of HSVd in hop, CEVd in citron and ASSVd in apple, but was not reliable for HSVd in grapevine and citron, and ASSVd in pear, because of their low concentration. A disadvantage of return-PAGE was possible appearance of double or triple bands in case of mix-infecting samples such as hop or citron. Although DIG-labeled DNA probe was 2.5 to 25 times more sensitive than return-PAGE, the practical reliability of this method was not so superior to return-PAGE. DIG-labeled RNA probe was the most sensitive of the three methods examined in this experiment, which was 25-125 times and 100-625 times more sensitive than DIG-DNA probe and return-PAGE, respectively. Furthermore, DIG-RNA probe was sensitive enough to detect HSVd in grapevine, a symptomless host of the pathogen, although negative sample was emphasized to be re-examined by the other sensitive method such as cucumber bioassay or RT-PCR. DIG-RNA probe, however, is not sensitive enough to detect HSVd in citrus and ASSVd in pear. Based on the results obtained in this experiment, we proposed appropriate amounts of plant tissues for the successful diagnosis of the three viroids.

An improved, sensitive, non‐radioactive in situ hybridization method for the detection of cytokine mRNAs

We established an improved non-radioactive in situ hybridization (ISH) method to detect mRNA of cytokines in cell preparations and tissues. Via this method we could demonstrate various cytokines in stimulated peripheral blood mononuclear cells (PBMC), lymphoid cell lines and human lymphoid tissues. The probes for the in situ hybridization were made by labelling cytokine-specific PCR products with digoxigenin (Dig) in a repeated PCR. This resulted in an intrinsic labelling of the probe with several Dig-UTP molecules. Incorporation of Dig-11-dUTPs was shown on ethidium bromide-stained agarose gels by a higher molecular weight of the PCR products with incorporated Dig-dUTPs when compared to control PCR products without digoxigenin. Cytospin-centrifuged cells of PHA-stimulated PBMC or lymphoid cell lines and frozen sections of various human lymphoid tissues were hybridized with the Dig-labelled cytokine probes and the hybridized probes were detected immuno-histochemically. In this way, we detected and localized cytokine mRNAs (IL-2, IL-4, IL-6, IL-8, IL-10) in PBMC, in the human T-cell line Jurkat, in the follicular lymphoma cell line DoHH2, and in human lymph nodes and tonsils. The in situ hybridization had a high sensitivity as the results correlated closely with the detection of cytokine mRNA by reverse transcriptase-PCR (RT-PCR) data from the same samples. We showed that Jurkat and DoHH2 cells produce several cytokines constitutively and that, after activation with the phorbol ester PMA, expression of several cytokine mRNAS was enhanced.

A Method for Distinguishing Human and Mouse Cells in Solid Tumors Using in Situ Hybridization

A common technique used in the study of human malignancies involves the inoculation of nude mice with human neoplastic cells. It is usually assumed that the tumor arising is composed predominantly of human cells with mouse tissue present only to provide minimal stromal support. Several reports, however, have shown evidence of host cell neoplastic transformation. Therefore, in order to effectively study and characterize such xenografts, it is important to establish the relative involvement of human and mouse cells. In the present study, a method for easily distinguishing human and mouse cells is described. The method involves in situ hybridization of formalin-fixed tissues using DIG-labeled oligomer probes which correspond to species-specific portions of Alu sequences. This method can be applied to archival material either as a means of confirming that the tissue taken from nude mice xenografts is predominantly human or as a vehicle for studying the mechanisms of host cell neoplastic transformation and their relevance to human malignant spread. The proposed technique may also serve as a basis for other in situ applications, particularly those involving formalin-fixed tissues and oligomer probes.

Multimeric non-radioactive cRNA probes improve detection of potato spindle tuber viroid (PSTVd)

Experimental data showed that multimeric, complementary RNA (cRNA) probes, labelled with non-radioactive digoxigenin (DIG), improved sensitivity of detection of the potato spindle tuber viroid (PSTVd) RNA by 2- to 30-fold as compared with corresponding multimeric cDNA probes. The degree of PSTVd detectability improvement depended upon the type of alkaline phosphatase substrate (colorimetric vs. chemiluminescent) used. Use of hexameric DIG-labelled cRNA probes in combination with chemiluminescent (Lumi-Phos 530) substrate resulted in detection of 0.48 pg of PSTVd RNA. The size of the synthesized cRNA probes corresponded to the size of the respective PSTVd cDNA templates. Interestingly, there was no relationship between the size of the synthesized, DIG-labelled DNA probes and that of the PSTVd cDNA template. This type of anomaly was not observed with other plant viral cDNA templates. Monomeric or multimeric cDNA probes detected both a mild and a severe PSTVd strain in viroid-infected potato leaf extracts diluted 1024 to 2048 times. In comparison, cRNA probes exhibited a much greater dilution end point; PSTVd RNA was detectable in viroid-infected potato leaf tissue diluted up to 16 384 times. Comparable levels of PSTVd sensitivity of detection were obtained with viroid-infected potato tuber tissue.

Detection of parvovirus B19 in a skin biopsy of a patient with erythema infectiosum

We report the findings on a skin biopsy taken from a child acutely infected with parvovirus B19 showing the typical exanthematous rash. By indirect immunofluorescence with a monoclonal antibody to B19, viral capsid proteins were detected in epidermal cells localized mainly in the stratum basale. Additionally, B19 DNA was detected in epidermal cells of the stratum basale by in situ hybridization using a Dig-labelled B19 DNA probe. The detection of viral capsid proteins and viral DNA suggests the presence of complete viral particles. It is therefore concluded that B19 plays a direct role in the formation of the exanthematous rash in erythema infection.

Light and electron microscopic in situ hybridization: non-radioactive labeling and detection, double hybridization, and combined hybridization-immunocytochemistry.

We performed light and electron microscopic in situ hybridization, according to the same protocol and without pretreatment of sections, on Lowicryl- and LR Gold-embedded cells. Digoxigenin (DIG)- or biotin-labeled riboprobes were visualized by direct or indirect immunodetection using commercially available gold-antibody conjugates with 0.8-10-nm gold grains. At the ultrastructural level, the main findings were that DIG-labeled probes gave a slightly higher labeling intensity (grains per signal) than biotin. The direct detection method produced a more compact signal, which led to better resolution at medium and high magnifications. Labeling intensities of all gold grain sizes were essentially equal. Grain sizes of 5 nm and larger were highly preferable because available enhancement methods are unsatisfactory for ultrasmall grains. The optimized immunodetection protocols are suitable for double hybridization with two different probes and for combined hybridization and immunocytochemistry.

A PCR-microplate hybridization method for plant virus detection

A sensitive nonradioactive method for detection of plant viruses was evaluated. A cDNA fragment from the coat protein coding region of the potato virus Y (PVY) RNA genome amplified by reverse transcription (RT) followed by polymerase chain reaction (PCR), was directly adsorbed onto polystyrene microplate wells after heat denaturation. The adsorbed cDNA was hybridized with a digoxigenin (DIG)-labelled cDNA probe without a prehybridization step. The probe was also prepared by PCR using the same pair of primers to amplify the target sequence from a cDNA clone of part of the viral genome. The hybrid of the adsorbed cDNA and DIG-labelled probe was reacted with alkaline phosphatase-conjugated anti-DIG antibody. The enzyme activity was then detected by hydrolysis of a substrate, and the absorbance values were measured using a microplate reader. Highest absorbance values were obtained when the amplified DNA fragments were diluted 100 or 125-fold in 10 × SSC (1.5 M NaCl, 0.15 M sodium citrate) for adsorption. Highly concentrated DNA gave lower absorbance values. The absorbance values differed depending on the microplates used, and the highest value was obtained using Nunc Immunopiate II-Maxisorp microplates. DNA fragments longer than 300 bp all gave similar absorbance values, which were twice as high as those obtained with shorter fragments. When the amplified DNA was diluted 100-fold, 10 fg of PVY genomic RNA could be detected by this method, which is called PCR-microplate hybridization. This is about 10000 times more sensitive than enzyme-linked immunosorbent assay (ELISA). By this method, PVY was detected from five field potato samples showing to be free from PVY by ELISA. PCR-microplate hybridization is nucleic acid-based ELISA-like highly sensitive diagnostic method, and may be generally applicable for detection of plant viruses, viroids, and possibly other plant pathogens.

A polymerase chain reaction-sequence-specific oligonucleotide procedure for HLA class II typing using biotin- and digoxigenin-labeled probes simultaneously in hybridization

To simplify PCR-SSO HLA-DRB generic typing, we labeled eight of 15 oligonucleotide probes with DIG and the others with biotin, and hydridizied each dot blot with both a biotin-labeled probe and a DIG-labeled probe simultaneously. We chose oligonucleotide pairs which require the same hybridization and stringent washing conditions and do not compete with each other during hybridization. After incubation with a mixture of anti-DIG Fab fragment-alkalikne phosphatase and streptavidin-peroxidase conjugates, specific binding of the DIG-labeled probe was revealed by a chemiluminescent substrate (CSPD) and specific binding of the biotin-labeled probe was subsequently visualized by a chromogenic substrate (TMB). The sensitivity of both probes was similar and gave comparable hybridization signals. Using this simplified procedure, the number of hybridizations or dot blots can be reduced to half the usual amount and the labor involved in PCR-SSO typing significantly reduced.

Chromosomal DNA probes for the identification of Bacteroides tectum and Bacteroides fragilis from the oral cavity of cats

A dot-blot hybridisation assay using high molecular weight DNA as whole chromosomal probes was used to differentiate Bacteroides tectum from Bacteroides fragilis. 32P-labelled probes were compared with digoxigenin (DIG)-labelled probes. The whole chromosomal probes were specific — differentiating B. tectum from B. fragilis and both from a variety of other species (including other members of the genera Bacteroides, Fusobacterium, Eubacterium, and Prevotella) found in normal and abnormal mouths of cats and horses. However, even at very high stringencies, B. tectum homology groups I, II and III were not distinguishable from one another using either 32P-labelled or DIG-labelled wh probes. Thus, DIG-labelled whole chromosome probes directed against cellular DNA released directly onto nitrocellulose membranes is considered a useful method for diagnostic veterinary laboratories wishing to identify B. tectum and distinguish it from B. fragilis and other oral anaerobic flora of cats.

Chromosomal DNA probes for the identification of asaccharolytic anaerobic pigmented bacterial rods from the oral cavity of cats

A dot-blot hybridisation assay using isolated high molecular weight DNA as whole chromosomal probes of the cat pigmented asaccharolytic Bacteroides/Porphyromonas species was used against both purified high molecular weight DNA and DNA released on membranes from whole cells for the identification of B. salivosus and for its differentiation from the other anaerobic species isolated from normal and diseased mouths of cats and horses. 32P-labelled probes were compared with digoxigenin (DIG)-labelled probes (Boehringer-Mannheim). The whole chromosomal probes were specific — differentiating B. salivosus from a variety of species (including members of the genera Bacteroides, F Fusobacterium, Eubacterium, and Prevotella) found in normal and abnormal mouths of cats and horses. Likewise, asaccharolytic black pigmented Group 2 strains were distinguishable from all strains tested. However, cat strains of P. gingivalis which show 68–76% DNA-DNA homology with human strain P. gingivalis ATCC 33277 T, were not distinguishable from each other using either 32P-labelled or DIG-labelled probes. The minimum amount of pure Bacteroides DNA which could be detected by the 32P-labelled probe was 100–300 pg, while the amount of pure DNA detected by the DIG system was 1–3 ng after room temperature colour development for 1 h and 100–300 pg after 6 h colour development.

Production of digoxigenin-labelled parvovirus DNA probe by PCR

A 560-bp digoxigenin(Dig)-labelled DNA-probe was produced by PCR using a 699-bp parvovirus DNA fragment as template with introduction of Dig-dTUP into the PCR reaction mixture. It was found to be very important to pay close attention to the amount of template employed, the number of cycles used, predenaturation of target DNA and optimization of the percentage of dTTP substituted by Dig-DUTP in the reaction mixture. The same 560-bp DNA fragment produced by PCR without the incorporation of Dig-DUTP in the reaction mixture, was subsequently labelled with Dig-dUTP by the random primed labelling method. Both of the Dig-labelled parvovirus DNA probes described above showed the same DNA detection level (about 1 pg), but production of the probe with Dig-DUTP incorporated in the PCR reaction mixture was much simpler.