Ultra-sensitive FISH using peroxidase-mediated deposition of biotin- or fluorochrome tyramides

Imaging individual mRNA molecules using multiple singly labeled probes

We describe a method for imaging individual mRNA molecules in fixed cells by probing each mRNA species with 48 or more short, singly labeled oligonucleotide probes. This makes each mRNA molecule visible as a computationally identifiable fluorescent spot by fluorescence microscopy. We demonstrate simultaneous detection of three mRNA species in single cells and mRNA detection in yeast, nematodes, fruit fly wing discs, and mammalian cell lines and neurons.

Tyramide signal amplification (TSA) systems for the enhancement of ISH signals in cytogenetics

This unit provides a series of techniques that dramatically improve the sensitivity of direct and indirect in situ detection. TSA is a peroxidase-based signal amplification system which is compatible with all in situ hybridization as well as immunocytochemical detection systems. The assay is performed on a glass slide and combines the use of fluorescent probes in either direct or indirect format using either an enzyme-labeled streptavidin or antibody. Protocols are provided for brightfield and fluorescent detection of single DNA targets, DNA or RNA in cultured cells, multitarget detection for DNA/RNA and DNA and RNA. In addition a protocol is included for the TSA plus system, a DNP-based detection system using horseradish peroxidase and alkaline phosphatase.

Combination DNA/RNA FISH and immunophenotyping

This unit presents methods for combining immunophenotyping with DNA/RNA FISH. The approach is used in so-called genotype/phenotype analysis to identify chromosomal aberrations in sub-populations of cells present in heterogenous populations. Combining RNA and DNA detection with identification of cellular proteins is quite difficult. This series of protocols is provided to enable the successful application of the combination of these techniques.

High-resolution fluorescent in situ hybridization of Drosophila embryos and tissues

INTRODUCTIONFluorescent in situ hybridization (FISH) is commonly used to analyze the three-dimensional distribution of RNAs in intact embryos and tissues. Tyramide signal amplification (TSA) significantly increases the sensitivity and resolution of FISH probe signals. This protocol includes optimized TSA-FISH procedures for Drosophila embryos, ovaries, and larval tissues. Instructions are given for the preparation of RNA probes, the collection and fixation of tissues, and the hybridization and TSA-mediated detection of probes, including options for high-throughput processing in 96-well plates. Variations of the procedure for RNA-RNA and RNA-protein costaining are also described.

High-resolution FISH analysis

Map order, orientation, and gap or overlap distance of closely linked DNA probes may be determined using fluorescent hybridization to decondensed DNA. The linear arrangement of released chromatin fibers not only simplifies the task of gene ordering, but also provides higher resolution with probes separated by greater distances than can be achieved in FISH with intact interphase nuclei. The Basic Protocol 1 of this unit describes an alkaline lysis procedure for generating free chromatin from cultured cells for FISH analysis. A support protocol describes an empirical approach to optimize conditions for preparation of free chromatin. An Alternate Protocol 1 provides a method for producing free chromatin from cultured lymphocytes with drug treatment. The Basic Protocol 2, high-resolution FISH mapping with free chromatin, is a modification of the method used for FISH mapping of interphase nuclei.

Methods in neuroendocrine histopathology, a methodological overview

Light microscopy is still the main tool in diagnostic histopathology, though it does not always lead to a definitive diagnosis. It has therefore been a constant ambition to develop methods which can add further information to the diagnosis. In endocrine pathology, a major problem has been to distinguish between neuroendocrine and non-neuroendocrine tumours. The silver stains, such as the Bodian, Grimelius and Sevier-Munger methods, were the first useful "general neuroendocrine" markers. Electron microscopy can also be useful for identifying neuroendocrine tumours. A further step forward was the introduction of histochemical fluorescence methods, as these could identify biogenic amines. With the introduction of immunohistochemical techniques, tumours could be characterized in a more specific way regarding peptide hormones and biogenic amines content, proliferation factors, hormone receptors, etc. Another method, DNA cytometry, has been used mainly in predicting the prognosis. In situ hybridization can be a useful complement to the histopathological diagnosis when other methods have failed to demonstrate the neuroendocrine nature of the tumour. Some endocrine tumours, especially the well-differentiated ones, still cause diagnostic problems in predicting tumour behaviour, why further complementary methods would be of great value.

Fluorescent in situ hybridization protocols in Drosophila embryos and tissues

Fluorescent in situ hybridization is the standard method for visualizing the spatial distribution of RNA. Although traditional histochemical RNA detection methods suffered from limitations in resolution or sensitivity, the recent development of peroxidase-mediated tyramide signal amplification provides strikingly enhanced sensitivity and subcellular resolution. In this chapter, we describe optimized fluorescent in situ hybridization protocols for Drosophila embryos and tissues utilizing tyramide signal amplification, either for single genes or in a high-throughput format, which greatly increases the sensitivity, consistency, economy, and throughput of the procedure. We also describe variations of the method for RNA-RNA and RNA-protein codetection.

Current status and the future of fluorescence in situ hybridization (FISH) in plant genome research

Fluorescence in situ hybridization (FISH), which allows direct mapping of DNA sequences on chromosomes, has become the most important technique in plant molecular cytogenetics research. Repetitive DNA sequence can generate unique FISH patterns on individual chromosomes for karyotyping and phylogenetic analysis. FISH on meiotic pachytene chromosomes coupled with digital imaging systems has become an efficient method to develop physical maps in plant species. FISH on extended DNA fibers provides a high-resolution mapping approach to analyze large DNA molecules and to characterize large genomic loci. FISH-based physical mapping provides a valuable complementary approach in genome sequencing and map-based cloning research. We expect that FISH will continue to play an important role in relating DNA sequence information to chromosome biology. FISH coupled with immunoassays will be increasingly used to study features of chromatin at the cytological level that control expression and regulation of genes.

Identification of the epidermal growth factor-TM7 receptor EMR2 and its ligand dermatan sulfate in rheumatoid synovial tissue

OBJECTIVE

EMR2 and CD97 are closely related members of the epidermal growth factor (EGF)-TM7 family of adhesion class 7-span transmembrane (TM7) receptors. Chondroitin sulfates (CS) have recently been identified as ligands for EMR2 and CD97. CS have been implicated in the pathogenesis of rheumatoid arthritis (RA). We undertook this study to determine the expression of EMR2 and the distribution of EMR2 and CD97 ligands within RA synovial tissue (ST).

METHODS

ST samples were obtained by arthroscopy from 19 patients with RA, 13 patients with inflammatory osteoarthritis (OA), and 13 patients with reactive arthritis (ReA). Immunohistochemistry was performed with a monoclonal antibody against EMR2, and stained STs were analyzed by digital image analysis. Coexpression of EMR2 with cell lineage- and activation-specific markers was determined by double immunofluorescence microscopy. To evaluate the expression of EMR2 and CD97 ligands in RA synovium, binding assays were performed using EMR2- and CD97-specific multivalent fluorescent probes.

RESULTS

EMR2 expression in the synovial sublining was found to be significantly higher in RA patients compared with OA and ReA control patients. Most EMR2+ cells were macrophages and dendritic cells expressing costimulatory molecules and tumor necrosis factor alpha. Dermatan sulfate was shown to be the ligand of the largest isoforms of EMR2 and CD97 in rheumatoid synovium. In addition, the smaller isoforms of CD97, but not those of EMR2, bound CD55 on fibroblast-like synoviocytes.

CONCLUSION

The EGF-TM7 receptors EMR2 and CD97 are abundantly expressed on myeloid cells in ST of RA patients where their cognate ligands dermatan sulfate and CD55 are detected. These results suggest that these interactions may facilitate the retention of activated macrophages in the synovium.

Advanced molecular cytogenetics in human and mouse

Fluorescence in situ hybridization, spectral karyotyping, multiplex fluorescence in situ hybridization, comparative genomic hybridization, and more recently array comparative genomic hybridization, represent advancements in the field of molecular cytogenetics. The application of these techniques for the analysis of specimens from humans, or mouse models of human diseases, enables one to reliably identify and characterize complex chromosomal rearrangements resulting in alterations of the genome. As each of these techniques has advantages and limitations, a comprehensive analysis of cytogenetic aberrations can be accomplished through the utilization of a combination approach. As such, analyses of specific tumor types have proven invaluable in the identification of new tumor-specific chromosomal aberrations and imbalances (aneuploidy), as well as regions containing tumor-specific gene targets. Application of these techniques has already improved the classification of tumors into distinct categories, with the hope that this will lead to more tailored treatment strategies. These techniques, in particular the application of tumor-specific fluorescence in situ hybridization probes to interphase nuclei, are also powerful tools for the early identification of premalignant lesions.

Physical mapping of barley genes using an ultrasensitive fluorescence in situ hybridization technique

The primary objective of this study was to elucidate gene organization and to integrate the genetic linkage map for barley (Hordeum vulgare L.) with a physical map using ultrasensitive fluorescence in situ hybridization (FISH) techniques for detecting signals from restriction fragment length polymorphism (RFLP) clones. In the process, a single landmark plasmid, p18S5Shor, was constructed that identified and oriented all seven of the chromosome pairs. Plasmid p18S5Shor was used in all hybridizations. Fourteen cDNA probes selected from the linkage map for barley H. vulgare 'Steptoe' x H. vulgare 'Morex' (Kleinhofs et al. 1993) were mapped using an indirect tyramide signal amplification technique and assigned to a physical location on one or more chromosomes. The haploid barley genome is large and a complete physical map of the genome is not yet available; however, it was possible to integrate the linkage map and the physical locations of these cDNAs. An estimate of the ratio of base pairs to centimorgans was an average of 1.5 Mb/cM in the distal portions of the chromosome arms and 89 Mb/cM near the centromere. Furthermore, while it appears that the current linkage maps are well covered with markers along the length of each arm, the physical map showed that there are large areas of the genome that have yet to be mapped.

New methods for molecular diagnosis and demonstration of the (CCTG)n mutation in myotonic dystrophy type 2 (DM2)

Myotonic dystrophy types 1 and 2 are autosomal dominant, multisystemic disorders with many similarities in their clinical manifestations. Myotonic dystrophy type 1 is caused by a (CTG)n expansion in the 3' untranslated region of the DMPK gene in 19q13.3 and myotonic dystrophy type 2 by a (CCTG)n expansion in intron 1 of ZNF9 in 3q21.3. However, the clinical diagnosis of myotonic dystrophy type 2 is more complex than that of myotonic dystrophy type 1, and conventional molecular genetic methods used for diagnosing myotonic dystrophy type 1 are insufficient for myotonic dystrophy type 2. Herein we describe two in situ hybridization protocols for the myotonic dystrophy type 2 mutation detection. Chromogenic in situ hybridization was used to detect both the genomic expansion and the mutant transcripts in muscle biopsy sections. Chromogenic in situ hybridization can be used in routine myotonic dystrophy type 2 diagnostics. Fluorescence in situ hybridization on extended DNA fibers was used to directly visualize the myotonic dystrophy type 2 mutation and to estimate the repeat expansion sizes.

Localization and regulation of the growth hormone receptor and growth hormone-binding protein in the rat growth plate

Growth hormone (GH) has direct effects on the growth plate to stimulate longitudinal growth, but it is not clear which chondrocyte populations GH acts on. The dual effector theory suggests that GH would act primarily on the "stem cells." However, staining with a GH receptor (GHR) antibody is found in all layers of the growth plate in rabbits and humans. We now have investigated the localization and regulation of GHR and the related GH binding protein (GHBP) in the rat growth plate using a sensitive immunohistochemical method involving tyramide signal amplification (TSA) and antibodies specific for GHR or GHBP. Both GHR and GHBP were shown in the germinal and proliferative chondrocytes, but most clearly in early maturing chondrocytes at the interface between proliferative and hypertrophic cells. Staining for GHR and GHBP was located in both the cytoplasm and the nucleus. Expression of GHR mRNA and GHBP mRNA in the growth plate was confirmed by reverse-transcription polymerase chain reaction (RT-PCR). Immunohistochemical staining for GHR and GHBP decreased with age; in 12-week-old normal rats, only the early maturing chondrocytes were stained. In GH-deficient dwarf rats, staining seemed less than in normal rats, and in hypophysectomized (Hx) rats, staining for GHBP was clearly reduced. Treatment of Hx rats with thyroid hormones (T3 + T4), via subcutaneously (sc) implanted osmotic minipumps, induced little growth and induced a small layer of GHR-positive and GHBP-positive early maturing chondrocytes. Treatment with GH and thyroid hormones (TH) resulted in greater growth and a broader layer of GHR-positive and GHBP-positive cells, indistinguishable from normal rats. In contrast, dexamethasone treatment of normal rats inhibited their growth and reduced GHR and GHBP staining in the growth plate. These results show that GHR and GHBP in the growth plate are under hormonal control. The localization of GHR/GHBP suggests that in addition to actions on germinal and proliferative cells in young rats, GH also has effects on early maturing chondrocytes and may be involved in their differentiation to a fully hypertrophic chondrocyte.

Clustered sites of DNA repair synthesis during early nucleotide excision repair in ultraviolet light-irradiated quiescent human fibroblasts

The ubiquitous process of nucleotide excision repair includes an obligatory step of DNA repair synthesis (DRS) to fill the gapped heteroduplex following excision of a short (approximately 30-nucleotide) damaged single-strand fragment. Using 5-iododeoxyuridine to label repair patches during the first 10-60 min after UV irradiation of quiescent normal human fibroblasts we have visualized a limited number of discrete foci of DRS. These must reflect clusters of elementary DRS patches, since single patches would not be detected. The DRS foci are attenuated in normal cells treated with alpha-amanitin or in Cockayne syndrome (CS) cells, which are specifically deficient in the pathway of transcription-coupled repair (TCR). It is therefore likely that the clusters of DRS arise in chromatin domains within which RNA polymerase II transcription is compartmentalized. However, we also found significant suppression of DRS foci in xeroderma pigmentosum, complementation group C cells in which global genome repair (GGR) is defective, but TCR is normal. This suggests that the TCR is responsible for the DRS cluster formation in the absence of GGR. The residual foci detected in CS cells indicate that, even at early times following UV irradiation, GGR may open some chromatin domains for processive scanning and consequent DRS independent of transcription.

c-MYC activation in primary and metastatic ductal adenocarcinoma of the pancreas: incidence, mechanisms, and clinical significance

Amplification and overexpression of c-MYC is a common event in various neoplasias. Recently, comparative genomic hybridization (CGH) of primary pancreatic adenocarcinomas revealed a distinct high-level amplification of 8q23-qter, suggesting that c-MYC located on 8q24 may be a candidate oncogene. To evaluate the biological significance and prognostic value of c-MYC activation in pancreatic carcinoma, we performed interphase fluorescence in situ hybridization (FISH) and immunohistochemistry on a series of 69 primary pancreatic adenocarcinomas, 19 corresponding lymph node metastases, and 5 pancreatic intraductal lesions. Dual color FISH using a probe for c-MYC (8q24) and a centromeric probe for chromosome 8 revealed amplification of c-MYC in 32.3% and 29.4% of primary and metastatic tumors, respectively. Immunostaining identified c-MYC protein overexpression in 43.5% of primaries and 31.6% of metastases. Low concordance between positive FISH and immunostaining (13.4%) suggests multiple independent regulatory pathways of c-MYC activation. Statistical evaluation revealed significant correlation (alpha = 0.033) between c-MYC protein overexpression and histopathological tumor grade but absence of correlation with tumor stage or lymph node status. Analysis of pancreatic intraductal lesions showed c-MYC amplification and protein overexpression in two of five cases in which invasive carcinoma exhibited identical aberrations. We conclude that deregulation of c-MYC protein is common in pancreatic cancer and that it may be involved in early neoplastic development and progression rather than in locoregional spread of invasive cancer.

CD8+ T cells in cutaneous T-cell lymphoma: expression of cytotoxic proteins, Fas Ligand, and killing inhibitory receptors and their relationship with clinical behavior

PURPOSE

We investigated the number, phenotype, and prognostic significance of CD8+ T cells in patients with mycosis fungoides (MF) and CD30- primary cutaneous large T-cell lymphoma (PCLTCL).

PATIENTS AND METHODS

Immunohistochemical stainings for CD8, granzyme B (GrB), T cell-restricted intracellular antigen (TIA-1), Fas ligand (FasL), and killer-cell inhibitory receptors (KIRs; CD95, CD158a, and CD158b) were performed on 83 first-diagnostic biopsy samples obtained from patients with plaque-stage MF (n = 42), tumor-stage MF (n = 20), and CD30- PCLTCL (n = 21).

RESULTS

Serial sections and double-staining experiments showed that the large majority of CD8+ T cells in MF and CD30- PCLTCL expressed TIA-1 and FasL, whereas only a minority expressed GrB, which suggested that these CD8+ T cells were partly activated cytotoxic T lymphocytes (CTLs). These CD8+ CTLs never or rarely expressed KIRs. This phenotype was a constant feature of CD8+ CTLs and did not alter with disease progression. In contrast, the median percentage of CD8+ CTLs in plaque-stage MF (22%), tumor-stage MF (7%), and CD30- PCLTCL (3%) differed significantly (P < .0001) and was associated with a significant decrease in 5-year survival. Also within the group of tumor-stage MF, a significant relation between CD8+ CTLs and survival was found. Multivariate analysis in the total group of MF demonstrated that both skin stage and percentage of CD8+ CTLs were independent parameters of survival.

CONCLUSION

Our results demonstrated that partly activated CD8+ CTLs were present in CTCL and that high proportions of these cells correlated with a better prognosis. This suggested that these CD8+ CTLs could play an important role in the antitumor response in these conditions.

Visualization of focal nuclear sites of DNA repair synthesis induced by bleomycin in human cells

In this study, we examined DNA repair synthesis in human cells treated with the radiomimetic drug bleomycin, which efficiently induces double-strand breaks (DSBs). Using tyramide-biotin to amplify fluorescent signals, discrete nuclear foci from the incorporation of 5-iododeoxyuridine (IdU) were detected in proliferating human cells treated with bleomycin. We believe this comes from the repair of DSBs. An increase in the number of foci (>5 per nucleus) was detected in a major fraction (75%) of non-S-phase cells labeled for 30 min with IdU 1 h after the end of bleomycin treatment. The fraction of cells with multiple IdU-containing foci was found to decrease 18 h after treatment. The average number of foci per nucleus detected 1 h after bleomycin treatment was found to decrease twofold between 1 and 3.5 h, indicating that the foci may be associated with the slow component of DSB repair. The presence of DSBs in bleomycin-treated cells was confirmed using antibodies against phosphorylated histone H2AX (gamma-H2AX), which is strictly associated with this type of DNA damage. After treatment with bleomycin, non-S-phase cells also displayed heterogeneous nuclear foci containing tightly bound proliferating cell nuclear antigen (PCNA), suggesting an ongoing process of unscheduled DNA synthesis. PCNA is known to be involved in base excision repair, but a fraction of the PCNA foci may also be associated with DNA synthesis occurring during the repair of DSBs.

Strategies for signal amplification in nucleic acid detection

Many aspects of molecular genetics necessitate the detection of nucleic acid sequences. Current approaches involving target amplification (in situ PCR, Primed in situ Labeling, Self-Sustained Sequence Replication, Strand Displacement Amplification), probe amplification (Ligase Chain Reaction, Padlock Probes, Rolling Circle Amplification) and signal amplification (Tyramide Signal Amplification, Branched DNA Amplification) are summarized in the present review, together with their advantages and limitations.

DNA fiber mapping techniques for the assembly of high-resolution physical maps

High-resolution physical maps are indispensable for directed sequencing projects or the finishing stages of shotgun sequencing projects. These maps are also critical for the positional cloning of disease genes and genetic elements that regulate gene expression. Typically, physical maps are based on ordered sets of large insert DNA clones from cosmid, P1/PAC/BAC, or yeast artificial chromosome (YAC) libraries. Recent technical developments provide detailed information about overlaps or gaps between clones and precisely locate the position of sequence tagged sites or expressed sequences, and thus support efforts to determine the complete sequence of the human genome and model organisms. Assembly of physical maps is greatly facilitated by hybridization of non-isotopically labeled DNA probes onto DNA molecules that were released from interphase cell nuclei or recombinant DNA clones, stretched to some extent and then immobilized on a solid support. The bound DNA, collectively called "DNA fibers," may consist of single DNA molecules in some experiments or bundles of chromatin fibers in others. Once released from the interphase nuclei, the DNA fibers become more accessible to probes and detection reagents. Hybridization efficiency is therefore increased, allowing the detection of DNA targets as small as a few hundred base pairs. This review summarizes different approaches to DNA fiber mapping and discusses the detection sensitivity and mapping accuracy as well as recent achievements in mapping expressed sequence tags and DNA replication sites.

Overview of fluorescence in situ hybridization techniques for molecular cytogenetics

This unit presents an overview of the FISH methodology. It covers such topics as direct versus indirect methods, sensitivity, multiplicity, resolution, and applications.

Immunocytochemical detection

This unit provides detailed descriptions for direct and indirect in situ hybridization methods. Protocols are designed for bright-field microscopy using a precipitating chromogenic substrate and for immunofluorescence detection using a hapten-labeled probe. Several alternative procedures are provided together with an excellent discussion of the strategy used for selecting a detection method.

HLA-G expression in trophoblast cells circulating in maternal peripheral blood during early pregnancy

OBJECTIVE

The aim of this study was to assess the use of circulating trophoblast cells in maternal peripheral blood for noninvasive prenatal diagnosis of numeric chromosomal aberrations.

STUDY DESIGN

A combined procedure for immunocytochemical identification and deoxyribonucleic acid fluorescence in situ hybridization was used after a single enrichment step consisting of density gradient centrifugation. A specific HLA-G monoclonal antibody was used in combination with X and Y chromosome specific probes in deoxyribonucleic acid fluorescence in situ hybridization to confirm fetal identity of cells bearing HLA-G in the case of a male fetus.

RESULTS

We detected fetal trophoblast cells expressing HLA-G in maternal blood starting at 9 weeks' gestation. In addition to fetal sex prediction with X and Y chromosome-specific probes, fetal aneuploidy was confirmed in peripheral blood from a pregnancy complicated by trisomy 21.

CONCLUSION

Although the numbers of fetal cells were extremely low, the proof of concept was demonstrated. Early noninvasive prenatal screening for numeric chromosomal abnormalities with fetal trophoblast cells is feasible.

Tissue distribution of the human CD97 EGF-TM7 receptor

CD97 is a founding member of the EGF-TM7 family of class II seven-span transmembrane (7-TM) receptors. CD97 has an extended extracellular region with several N-terminal epidermal growth factor (EGF)-like domains, which mediate binding to CD55. Previous studies demonstrated the expression of CD97 on activated lymphocytes, monocytes, macrophages, granulocytes, and numerous haematopoietic and nonhaematopoietic cell lines. Here, we determined the cellular distribution of human CD97 in situ by immunohistochemistry (IH) and immunofluorescence (IF). Abundant expression of CD97 was detected on all types of macrophages and dendritic cells, except for microglia. Within the lymphoid lineage, most T cells but only a few B cells express CD97. Germinal centre B cells do not express the molecule. Except for smooth muscle cells, no staining was found on other cells outside the immune system. However, analysis of a restricted set of epithelial tumors revealed CD97 expression on the malignant cells in thyroid and gastrointestinal tract cancer.

Amplification methods for the immunolocalization of rare molecules in cells and tissues

The needs to precisely assign macromolecules to specific locations and domains within tissues and cells and to reveal antigens which are present in low or even in trace amounts, led to the elaboration of a wide spectrum of immunocytochemical amplification procedures. These arise from the successive improvements of tissue preparation techniques, of antigen retrieval procedures and of immunological or non-immunological detection systems. Improvement of detection systems may be the most active in the development of amplification techniques. Since the early work of Coons, in which by the introduction of the indirect technique has started amplifying the signal, different systems have succeeded in increasing the sensitivity of antigens detection. Indeed, amplification techniques such as the multiple antibody layers, the multiple bridges, the enzyme complexes, the avidin-biotin, the silver intensification, and the numerous variations and combinations among these have increased the sensitivity for the detection of scarce tissue antigens. However, as shown by the recent progress carried out with new approaches such as the catalyzed reporter deposition (CARD) and the enhanced polymer one-step staining (EPOS), more efficient methods are still needed. In electron microscopy, few techniques have reached the resolution afforded by the post-embedding immunogold approach. In spite of this and in order to further increase its sensitivity, new probes and novel approaches are allowing combination of the gold marker with the amplification capacity of enzymes afforded by the CARD technique. Immunogold amplification strategies, such as the multiple incubations with the primary antibody and the use of an anti-protein A antibody have also led to enhanced signals displaying the advantages in terms of resolution and possibilities of quantification inherent to the colloidal gold marker.

Integration of the Aedes aegypti mosquito genetic linkage and physical maps

Two approaches were used to correlate the Aedes aegypti genetic linkage map to the physical map. STS markers were developed for previously mapped RFLP-based genetic markers so that large genomic clones from cosmid libraries could be found and placed to the metaphase chromosome physical maps using standard FISH methods. Eight cosmids were identified that contained eight RFLP marker sequences, and these cosmids were located on the metaphase chromosomes. Twenty-one cDNAs were mapped directly to metaphase chromosomes using a FISH amplification procedure. The chromosome numbering schemes of the genetic linkage and physical maps corresponded directly and the orientations of the genetic linkage maps for chromosomes 2 and 3 were inverted relative to the physical maps. While the chromosome 2 linkage map represented essentially 100% of chromosome 2, approximately 65% of the chromosome 1 linkage map mapped to only 36% of the short p-arm and 83% of the chromosome 3 physical map contained the complete genetic linkage map. Since the genetic linkage map is a RFLP cDNA-based map, these data also provide a minimal estimate for the size of the euchromatic regions. The implications of these findings on positional cloning in A. aegypti are discussed.

Localization of single-copy T-DNA insertion in transgenic shallots (Allium cepa) by using ultra-sensitive FISH with tyramide signal amplification

The sensitivity of fluorescence in situ hybridization (FISH) for mapping plant chromosomes of single-copy DNA sequences is limited. We have adapted for plant cytogenetics a new signal-amplification method termed tyramide-FISH (Tyr-FISH). Until present this technique has only been applied to human chromosomes. The method is based on enzymatic deposition of fluorochrome-conjugated tyramide. With Tyr-FISH it was possible to detect target T-DNA sequences on plant metaphase chromosomes as small as 710 bp without using a cooled CCD camera. Short detection time and high sensitivity, in combination with a low background, make the Tyr-FISH method very suitable for routine application in plant cytogenetic research. With Tyr-FISH we analysed the position of T-DNA inserts in transgenic shallots. We found that the inserts were preferentially located in the distal region of metaphase chromosomes. Sequential fluorescence in situ hybridization with a 375 bp satellite sequence suggested that a specific T-DNA insert was located within the satellite sequence hybridization region on a metaphase chromosome. Analysis of less-condensed prophase and interphase chromosomes revealed that the T-DNA was integrated outside the satellite DNA-hybridization region in a more proximal euchromatin region.

Detection of viral RNA in CD4(-)CD8(-) and CD4(-)CD8(+) lymphocytes in vivo in rhesus monkeys infected with simian immunodeficiency virus of macaques

A definition of the specific cell types that support HIV replication early in the course of infection will be important for understanding AIDS pathogenesis and designing strategies for preventing infection. Observations have indicated that the population of lymphocytes susceptible to productive infection extends beyond activated CD4(+) T cells. To explore this issue, we have employed laser scanning cytometry technology and the techniques of lymphocyte surface immunophenotyping followed by fluorescent in situ hybridization to detect simian immunodeficiency virus of macaques (SIVmac) RNA in phenotypically defined rhesus monkey lymphocytes. The immunophenotype of productively infected cells in either a rhesus monkey T cell line or in PBMCs infected in vitro with SIVmac was remarkably similar to that observed in productively infected PBMCs obtained from monkeys during primary infection. We observed low levels or no detectable expression of CD4 on cells infected in vitro or on PBMCs of infected monkeys. However, a substantial number of SIVmac-infected PBMCs both in cultured lymphocytes and sampled directly from infected monkeys expressed CD8 but not CD4. These observations are consistent with the possibility that the CD4 molecule may be modulated off the surface of CD4(+)CD8(-) or CD4(+)CD8(+) lymphocytes after infection or that infection occurred via a CD4-independent mechanism. Moreover, there was no preferential expression of CD25 on cells positive for SIVmac RNA, which might have been predicted if replication of the virus was occurring selectively in activated lymphocytes. These results broaden the range of lymphocytes that support productive SIVmac infection to include CD4(-)CD8(-) and CD4(-)CD8(+) subsets, and are consistent with virus replication occurring in nonactivated cells.

Dedifferentiation of a well-differentiated liposarcoma to a highly malignant metastatic osteosarcoma:

Well-differentiated liposarcomas (WDLPS), especially those located in the retroperitoneum, may occasionally undergo dedifferentiation. Although this process is associated with a more aggressive clinical course, dedifferentiated liposarcomas rarely produces metastases. The case reported here is rather uncommon: A retroperitoneal WDLPS gave lung metastases that were diagnosed as highly malignant osteosarcomas. We used comparative genomic hybridization (CGH), fluorescence in situ hybridization (FISH), and Southern blot analyses to characterize the copy number changes and genetic aberrations occurring at different stages of the disease. In the primary tumor, the only detectable aberration was amplification of 12q13-q14, which was present only in a fraction of the cells and revealed by FISH analysis. High-level amplification of 12q13-q14, involving CDK4, MDM2, and HMGIC, was seen both in the relapse and the metastases. The second most common change, gain or high-level amplification of 1q22-q24, was detectable by CGH only in the osteogenic metastases, as was loss of the distal 2q. FISH analyses revealed considerable heterogeneity in the samples, and the percentage of cells showing aberrations was significantly higher in the metastatic samples. In particular, increased copy numbers of 789f2, a marker for 1q21 amplification in sarcomas, was observed in more than 65% of the cells in the metastatic samples, but in less than 10% of the cells from the recurrent samples. These observations could indicate that 1q amplification, in particular, may be indicative of a more malignant phenotype and ability of metastasis in WDLPS, as has also been suggested by others.

Chromosome painting in plants

The current 'state-of-art' as to chromosome painting in plants is reviewed. We define different situations described as painting so far: i) Genomic in situ hybridisation (GISH) with total genomic DNA to distinguish alien chromosomes on the basis of divergent dispersed repeats, ii) 'Chromosomal in situ suppression' (CISS) hybridisation with chromosome-derived DNA probes and blocking of interchromosomally dispersed repeats by total genomic or C0t-1 DNA in excess, iii) exceptional cases of single chromosome painting by probes containing chromosome-specific dispersed repeats, and iv) Fluorescence in situ hybridisation (FISH) with extended contigs of large insert clones for painting of those chromosomes of a euploid complement which harbour the cloned sequences. While GISH was successfully applied in most plant hybrids and/or their derivatives, painting of individual chromosomes by CISS hybridisations of chromosome-specific DNA probes have so far not revealed convincing results in plants. The reason for this failure and the use of possible alternative approaches are discussed. At least for small plant genomes, painting by large insert single sequence clones provides a promising alternative tool to solve cytogenetic questions, which up to now could not be tackled otherwise. An example of such a painting is described in detail for Arabidopsis thaliana.

Human granzyme B mediates cartilage proteoglycan degradation and is expressed at the invasive front of the synovium in rheumatoid arthritis

OBJECTIVE

To investigate the cartilage-degrading capacity of granzyme B and the presence of granzyme B-positive cells at sites of erosion in the rheumatoid synovium.

METHODS

Granzyme B was added to [(3)H]proline/[(35)S]sulphate-labelled cartilage matrices and to cartilage explants. Proteoglycan degradation was assessed by the release of (35)S and glycosaminoglycans into the medium and collagen degradation was assessed by the release of (3)H and hydroxyproline and by measuring the fraction of denatured collagen. Granzyme B expression was studied at the invasive front of the synovium by immunohistochemistry.

RESULTS

Granzyme B induced loss of both newly synthesized, radiolabelled proteoglycans in cartilage matrices and resident proteoglycans of the cartilage explants. No effect on collagen degradation was found. Granzyme B-positive cells were present throughout the synovium and at the invasive front.

CONCLUSION

The presence of granzyme B-positive cells at the invasive front of the synovium together with its ability to degrade articular proteoglycans supports the view that granzyme B may contribute to joint destruction in rheumatoid arthritis.

Interleukin-17 and CD40-ligand synergistically enhance cytokine and chemokine production by renal epithelial cells

Renal allograft rejection is characterized by an influx of inflammatory cells. Interaction between infiltrating T cells and resident parenchymal cells might play an important role in the ongoing inflammatory response. The present study demonstrates that CD40L, a product of activated T cells, is locally expressed in kidneys undergoing rejection. Furthermore, during rejection, CD40 expression not only is present on most graft infiltrating cells but also is increased on resident tubular epithelial cells (TEC). To obtain more detailed insight in the consequences of T cell/TEC interaction, we analyzed the production of chemokines, including interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation, normal T cell expressed and secreted (RANTES), and the production of IL-6 by cultured human primary TEC in response to activation with CD40L in vitro. In addition, we studied the interaction with IL-17, a T-cell-specific cytokine previously demonstrated to be present during renal allograft rejection. The results, obtained by enzyme-linked immunosorbent assay, indicate that simultaneous activation of TEC with IL-17 and CD40L synergistically enhances production of IL-6 (2.1-fold higher than sum of single stimulations) and the chemokines IL-8 (15-fold) and RANTES (5.8-fold) as demonstrated by statistical analysis (P: < 0.05), whereas effects on MCP-1 (1.4-fold) are additive. Part of the synergy can be explained by increased CD40 expression on TEC upon IL-17 stimulation. The synergy is not unique for TEC, because similar responses were found with human synoviocytes and a foreskin fibroblast cell line (FS4). Stimulation of TEC with CD40L results in activation of NF-kappaB and induction of cytokine production by IL-17 and CD40L is prevented by addition of the NF-kappaB inhibitor pyrrolidine dithiocarbamate. These data suggest an important role for T cells in renal allograft rejection by acting on parenchymal cells via both soluble mediators and direct cellular contact.

Dual fluorescent in situ hybridization and immunohistochemical detection with tyramide signal amplification

To understand the biological relationships among various molecules, it is necessary to define the cellular expression patterns of multiple genes and gene products. Relatively simple methods for performing multi-label immunohistochemical detection are available. However, there is a paucity of techniques for dual immunohistochemical (IHC) and mRNA in situ hybridization (ISH) detection. The recent development of improved non-radioactive detection systems and simplified ISH protocols has prompted us to develop a tyramide signal amplification method for sequential multi-label fluorescent ISH and IHC detection in either frozen or paraffin-embedded tissue sections. We used this method to examine the relationship between glial cell line-derived neurotrophic factor receptor alpha2 (GFRalpha2) mRNA expression and IHC localization of its co-receptor Ret in the trigeminal ganglion of postnatal Day 0 mice. We found that approximately 70% of Ret-immunoreactive neurons possessed GFRalpha2 mRNA and virtually all GFRalpha2-expressing neurons contained Ret-immunoreactive protein. Finally, we used paraformaldehyde-fixed, paraffin-embedded sections and a monoclonal antibody against neuron-specific nuclear antigen (NeuN) to demonstrate the neuronal specificity of GFRalpha2 mRNA expression in adult mouse brain. This multi-labeling technique should be applicable to a wide variety of tissues, antibodies, and probes, providing a relatively rapid and simple means to compare mRNA and protein localization.

Alpha satellite DNA variant-specific oligoprobes differing by a single base can distinguish chromosome 15 homologs

The ability to distinguish homologous chromosomes is a powerful cytogenetic tool. However, traditional techniques can only distinguish extreme physical variants and are highly dependent on sample preparation. We have previously reported oligonucleotide probes, specific for human chromosome 17 alpha satellite DNA sequence variants, that distinguish cytogenetically normal homologous chromosomes by FISH. Here we report the development of similar oligoprobes, differing at a single nucleotide position, that not only distinguish homologous chromosomes 15 but can be used to follow the transmission of a chromosome from parents to their offspring. We also identified a novel array-size polymorphism in another family. The alphoid array of one chromosome is quite small and below the detection threshold for our oligoprobes, although it is detectable by conventional FISH probes. This size polymorphism provides an additional FISH-based method for distinguishing homologs. Most importantly, this work illustrates the potential applicability of the technique to the entire human chromosome complement.

Signal amplification in immunohistochemistry at the light microscopic level using biotinylated tyramide and nanogold-silver staining

Signal amplification techniques greatly enhance the sensitivity of immunohistochemical (IHC) and in situ hybridization (ISH) methods. In particular, catalyzed signal amplification (CSA) using labeled tyramide or Nanogold-silver staining is an important signal amplification tool. We have applied a combination of both techniques, as has been introduced for ISH, for a further increase in sensitivity of an IHC method to detect cathepsin B. This lysosomal proteinase can also be expressed extracellularly, particularly in relation to cancer metastasis. Higher sensitivity of the IHC method was needed because existing methods failed to demonstrate cathepsin B protein where cathepsin B activity was found with a fluorescence enzyme histochemical method. Combined CSA and Nanogold-silver staining provided the sensitivity that was required. Moreover, this signal amplification method enabled the use of a 10-fold lower concentration of primary antibody (1 microg/ml). Nonspecific background staining was low provided that endogenous biotin, avidin, and peroxidase were completely blocked. The method was reproducible when all steps, and particularly the silver enhancement step, were rigidly controlled. The method resulted in localization patterns of cathepsin B protein that were in agreement with those of cathepsin B activity in serial sections of rat liver containing colon cancer metastases. We concluded that combined application of CSA and Nanogold-silver staining provides high sensitivity for immunohistochemical methods and that activity localization by an enzyme histochemical method is a very attractive alternative to IHC localization of an enzyme because it is at least as sensitive, it is rapid and simple, and it provides direct information on the function of an enzyme.

Application of CARD-ISH for Assessment of Numerical Chromosome Aberrations in Interphase Nuclei of Human Tumor Cells

In this study based on the study of a centromeric DNA probe specific for chromosome 8 the authors standardized a method for the enzymatic detection of specific chromosome copy numbers on interphase nuclei from tumor tissue samples. Since the in situ hybridization (ISH) of chromosome 8 specific probe was revealed with a catalyzed reporter deposition (CARD), which allows a high amplification of the hybridization signal, the method was designated as CARD-ISH. This method has been standardized on interphase nuclei isolated from clinical samples of pituitary adenomas, as well as on human normal lymphocytes. On the same samples, they also evaluated chromosome 8 copy number distribution by FISH. Comparison between CARD-ISH and FISH results showed no significant differences between the two methods, proposing CARD-ISH as a reliable alternative to FISH for chromosome numerical aberration assessment in laboratories that do not have specific facilities for epifluorescence microscopy or cytogenetics and that need a long-term storage of slides that had been used for diagnostic purposes. Int J Surg Pathol 8(3):201-206, 2000

Primaquine interferes with membrane recycling from endosomes to the plasma membrane through a direct interaction with endosomes which does not involve neutralisation of endosomal pH nor osmotic swelling of endosomes

The anti-malaria drug primaquine is a weak base which accumulates in endosomes in a protonated form and consequently neutralises the endosomal pH. Bafilomycin A1 prevents endosome acidification by inhibiting the vacuolar proton pump. Although both agents neutralise the endosomal pH, only primaquine has a strong inhibitory effect on recycling of endocytosed proteins to the plasma membrane (Van Weert et al. (1995), J. Cell Biol. 130, 821-834). This suggests that primaquine interferes with a parameter, other than endosomal pH, that is essential for membrane recycling. In the presence of 0.3 mM primaquine, endocytosed transferrin-receptors accumulated intracellularly, but not in the additional presence of bafilomycin A1. Thus, at relative low concentrations proton pump-driven accumulation of primaquine in endosomes was required to inhibit membrane recycling, suggesting that the target of primaquine is associated with endosomes. The inhibitory effect of 1 mM primaquine on transferrin receptor recycling was not reversed by the additional presence of bafilomycin A1, indicating that osmotic swelling of endosomes due to accumulation of protonated primaquine could also not explain its effect. To study endosome swelling morphologically, we introduce a novel technique for fluorescent labelling of endosomes involving HRP-catalysed biotinylation. In the presence of 0.2 mM primaquine endosomal vacuoles with diameters up to 2 microm were observed. Endosome swelling was not observed when in addition to primaquine also bafilomycin A1 was present, supporting the notion that vacuolar proton pump activity lowers the dose response for primaquine. Factors that are crucial for membrane recycling and may be affected by primaquine are discussed.

All infiltrating T-lymphocytes in Hodgkin's disease express immunohistochemically detectable T-cell receptor zeta-chains in situ

AIM

We studied the expression of TCR zeta-chain on tumour-infiltrating lymphocytes in EBV-positive and EBV-negative cases of Hodgkin's disease (HD), to assess whether downregulation of TCR zeta-chain on tumour-infiltrating lymphocytes might be a mechanism for immune escape of the neoplastic cells.

METHODS AND RESULTS

By immunohistochemistry we investigated tissue of 27 cases of primary HD, both paraffin embedded and frozen, for the presence of T-cell receptor complex zeta-chain and other T-cell markers on the reactive cells. Strong membranous staining of TCR zeta-chain was present in all cases in frozen tissue. In contrast, in paraffin-embedded material substantial loss of TCR zeta-chain was detected in old (> 6 years) tissues. However, no differences in either the number of positive cells or their staining intensity were observed in EBV-positive and negative cases of HD as detected in frozen tissue. Storage of paraffin-embedded tissue leads to a rapid and substantial loss of TCR zeta-chain reactivity compared to frozen material of the same HD cases. Staining reactivity of other T-cell markers (CD3, CD4 and CD8) on paraffin-embedded material remained unaffected. Immunofluorescent double-staining confirmed colocalization and coexpression of TCR zeta-chain and CD3.

CONCLUSIONS

In frozen biopsies of primary HD TCR zeta-chain was expressed on all reactive CD3-positive cells, both in EBV-positive and EBV-negative cases. This suggests that zeta-chain downregulation is not a likely mechanism whereby neoplastic cells of HD can escape immune surveillance.

Expression of the thioredoxin-thioredoxin reductase system in the inflamed joints of patients with rheumatoid arthritis

OBJECTIVE

To examine the expression of the thioredoxin (TRX)-thioredoxin reductase (TR) system in patients with rheumatoid arthritis (RA) and patients with other rheumatic diseases.

METHODS

Levels of TRX in plasma and synovial fluid (SF) were measured using enzyme-linked immunosorbent assay. Cellular distribution of TRX was determined by flow cytometry and histochemistry. Cellular expression of TR was studied by in situ messenger RNA (mRNA) hybridization. The effect of oxidative stress and tumor necrosis factor alpha (TNF alpha) on TRX expression by cultured rheumatoid fibroblast-like synoviocytes was studied.

RESULTS

Significantly increased TRX levels were found in the SF from 22 patients with RA, when compared with plasma levels in the same patients (P < 0.001) and compared with SF TRX levels in 15 patients with osteoarthritis (P < 0.001), 13 patients with gout (P < 0.05), and 9 patients with reactive arthritis (P < 0.0001). The presence of TRX could be demonstrated within the SF-derived mononuclear cells and synovial tissue (ST) of RA patients. Concordantly, expression of TR mRNA was observed in the ST of these patients. Stimulation of synovial fibroblast-like synoviocytes with either H2O2 or TNF alpha induced an increase in the production of TRX.

CONCLUSION

The data demonstrate significantly increased concentrations of TRX in the SF and ST of RA patients when compared with the levels in patients with other joint diseases. Evidence is presented that the local environment in the rheumatic joint contributes to increased TRX production. Based on its growth-promoting and cytokine-like properties, it is proposed that increased expression of TRX contributes to the disease activity in RA.

Intranuclear relocalization of matrix binding sites during T cell activation detected by amplified fluorescence in situ hybridization

We describe a method for analyzing the nuclear localization of specific DNA sequences, with special emphasis on their binding status to the nuclear matrix, depending on the developmental stage of the cells. This method employs high-resolution fluorescence in situ hybridization procedures. For our studies, it was important to examine the nuclear localization of a particular gene locus. Previously, however, it was not possible to detect a single-copy genomic sequence using a DNA probe less than several kilobases in size. We describe here a signal amplification technique based on tyramide which makes such a task possible. Using this method, we monitored single-copy loci using a short, 509-bp DNA sequence that binds in vivo to the T cell factor SATB1 within T cell nuclei, high-salt-extracted nuclei (histone-depleted nuclei generating "halos" with distended chromatin loops), and the nuclear matrix, before and after T cell activation. We found that these loci were anchored onto the nuclear matrix, creating new bases of chromatin loops, only after T cell activation. This experimental strategy, therefore, enabled us to detect the changes in higher order chromatin structure upon activation and study gene regulation at a new dimension: the loop domain structure. The methods shown here can be widely applied to explore other functions involving chromatin, including recombination and replication.

A novel signal amplification technology based on catalyzed reporter deposition and its application in a Dot-ELISA with ultra high sensitivity

A novel strategy to improve significantly antigen detection sensitivity of Dot-ELISA by catalyzed reporter deposition (CARD) method of signal amplification has been developed. The method, termed Super-CARD, utilizes synthesized electron rich proteins having multiple binding sites as blocking agents. After completion of conventional Dot-ELISA, the solid phase bound horseradish peroxidase (HRP) oxidises the added labeled substrate, which deposits onto the solid phase. This deposition is markedly increased in the presence of immobilized electron rich proteins, which not only amplifies the signal but also increases the sensitivity. The high specificity of the amplification reaction avoids the generation of any false positive signal. The extremely high sensitivity of Super-CARD technology permits visual detection of as few as 800 rabbit IgG molecules (1.33 x 10(-21) mol). The method is approximately 10(5)-fold more sensitive than conventional Dot-ELISA. Direct comparison with existing CARD methods demonstrates approximately 1.6 x 10(4)-fold enhancement in detection sensitivity which is much higher than that of any other existing methods. The Super-CARD technology is specific, flexible and may be applied to clinical diagnostics.

Expression of the activation antigen CD97 and its ligand CD55 in rheumatoid synovial tissue

OBJECTIVE

Fibroblast-like synoviocytes (FLS) express decay-accelerating factor (CD55) at high levels. Recently, it was found that CD55 is a specific cellular ligand for the 7-span transmembrane receptor CD97. The objective of this study was to define the expression of this receptor-ligand pair in synovial tissue (ST) to provide more insight into the interaction between FLS and surrounding cells.

METHODS

Antibodies against CD97 and CD55 were used for immunohistologic analysis of synovial biopsy specimens from 16 patients with rheumatoid arthritis (RA) and 15 patients with osteoarthritis (OA). In addition, an enzyme-linked immunosorbent assay system was used to determine the expression of soluble CD97 (sCD97) in synovial fluid (SF) from 30 patients with RA, 13 with OA, and 10 with reactive arthritis (ReA).

RESULTS

In both RA and OA ST sections, strong expression of CD55 was confirmed on FLS in the intimal lining layer, where it was also found that all macrophages expressed CD97. The percentage of macrophages that expressed CD97 was lower in the synovial sublining (P = 0.005). The mean levels of sCD97 in SF were significantly higher in RA patients than in patients with OA or ReA (P < 0.0001).

CONCLUSION

These results suggest that FLS are able to interact with macrophages via the CD97/CD55 receptor-ligand system. In this respect, the CD97/CD55 pair may account for the specific architecture of the intimal lining layer and may be of primary importance in maintaining and amplifying synovial inflammation. The specific increase in sCD97 levels in RA SF might be related to the presence of activated proteolytic systems or to the increase in synovial mass, rather than a consequence of local receptor-ligand interaction.

Tyramide signal amplification in brain immunocytochemistry: adaptation to electron microscopy

The tyramide signal amplification (TSA) technique is well-established in light microscopic immunohistochemistry and in situ hybridization to improve the signal-to-noise ratio. The present study deals with its adaptation to the electron microscopic level using the pre-embedding technique and a modified protocol. The outcome of immunolabeling of most of the antigens tested in brain tissue, including endothelial and neuronal nitric oxide synthase, glial fibrillary acidic protein, and isolectin B4, was greatly improved. If signal amplification is required, the TSA-technique proved to be reliable with high specificity and good ultrastructural resolution.

An optimized method for in situ hybridization with signal amplification that allows the detection of rare mRNAs

In situ hybridization (ISH) using nonradioactive probes enables mRNAs to be detected with improved cell resolution but compromised sensitivity compared to ISH with radiolabeled probes. To detect rare mRNAs, we optimized several parameters for ISH using digoxygenin (DIG)-labeled probes, and adapted tyramide signal amplification (TSA) in combination with alkaline phosphatase (AP)-based visualization. This method, which we term TSA-AP, achieves the high sensitivity normally associated with radioactive probes but with the cell resolution of chromogenic ISH. Unlike published protocols, long RNA probes (up to 2.61 kb) readily permeated cryosections and yielded stronger hybridization signals than hydrolyzed probes of equivalent complexity. RNase digestion after hybridization was unnecessary and led to a substantial loss of signal intensity without significantly reducing nonspecific background. Probe concentration was also a key parameter for improving signal-to-noise ratio in ISH. Using these optimized methods on rat taste tissue, we detected mRNA for mGluR4, a receptor, and transducin, a G-protein, both of which are expressed at very low abundance and are believed to be involved in chemosensory transduction. Because the effect of the tested parameters was similar for ISH on sections of brain and tongue, we believe that these methodological improvements for detecting rare mRNAs may be broadly applicable to other tissues. (J Histochem Cytochem 47:431-445, 1999)

Immunogold signal amplification: Application of the CARD approach to electron microscopy

Catalyzed reporter deposition (CARD) is a technique that allows amplification of routine immunolabeling in light microscopy. This procedure takes advantage of the horseradish peroxidase (HRP) from an HRP-avidin complex to catalyze the accumulation of reporter-conjugated tyramine (a phenolic compound) onto a surface displaying biotinylated antigen-antibody complexes. The large amount of labeled tyramine deposited allows the detection of an antigenic site with multiple reporter molecules. In this study we modified this amplification protocol to combine it with the immunogold technique for the ultrastructural localization of antigens in electron microscopy. We constructed various tyramide conjugates that permit the combination of this amplification method with a particulate colloidal gold marker. The new probes yield results of high specificity and enhanced intensity. Assessment of the level of resolution of the labeling has demonstrated that, in spite of the amplification, the resolution remains very good. Therefore, once associated, the immunogold and the CARD techniques lead to specific, high-resolution, sensitive and amplified signals that exhibit the advantages of both approaches.(J Histochem Cytochem 47:421-429, 1999)

Concentration dependent and adverse effects in immunohistochemistry using the tyramine amplification technique

Although the tyramine amplification technique to enhance sensitivity in immunohistochemistry has been described in numerous methodological papers, it has not yet gained access to diagnostic immunohistochemistry. This is mainly due to problems and pitfalls occurring in adaptation of this method to routine application. In this study a monoclonal antibody and a polyclonal antiserum (pan-cytokeratin and anti-myoglobin) were tested in tissues with different amounts of epitopes, using a checkerboard table and testing a total of 133 different dilution combinations of both the tyramide solution and the primary antibodies. The specific tissue investigated, i.e. the amount of accessible epitope to be detected and the applied concentration of the tyramide solution mainly influenced the staining reaction. Several pitfalls such as an uneven distribution of the staining or dramatic overstaining (paradoxical overstaining) must be considered to achieve optimal results. In conclusion, our data confirm methodological studies that the tyramine amplification technique is a powerful method to enhance immunohistochemical sensitivity. However, for reliable daily practice several pitfalls of the technique have to be circumvented.

Amplification methods to increase the sensitivity of in situ hybridization: play card(s)

In situ hybridization (ISH) has proved to be an invaluable molecular tool in research and diagnosis to visualize nucleic acids in their cellular environment. However, its applicability can be limited by its restricted detection sensitivity. During the past 10 years, several strategies have been developed to improve the threshold levels of nucleic acid detection in situ by amplification of either target nucleic acid sequences before ISH (e.g., in situ PCR) or the detection signals after the hybridization procedures. Here we outline the principles of tyramide signal amplification using the catalyzed reporter deposition (CARD) technique, present practical suggestions to efficiently enhance the sensitivity of ISH with CARD, and discuss some applications and possible future directions of in situ nucleic acid detection using such an amplification strategy.