Preparation and characterization of methyl green tetrafluoroborate

Modifications of the lactate dehydrogenase assay, a histochemical determinant of osteocyte viability--a qualitative study

We have refined a technique for assessment of osteocyte viability in a canine and murine model using a modification of the lactate dehydrogenase assay (LDH). With this method, viable osteocytes react to form non-reversible tetrazolium-formazan granules, while non-viable osteocytes are distinguished by a methyl green stain. LDH assay in canine and murine models have not been reported and our initial efforts were not successful. We examined the effect of (a) concentration of coenzyme and tetrazole (b) bone specimen thickness (c) ability to use frozen sections and (d) incubation time/dilution. We concluded that a 1000-fold increase in the concentration of coenzyme and tetrazole were required. Fresh bone produced optimal results and near-complete viability. Special considerations must be taken with smaller, more fragile specimens (e.g., mouse bone), such as increasing specimen thickness, dilution of incubation medium and/or the reduction of incubation time. Sections from thawed frozen bone resulted in a diffuse reaction. Osteocyte viability can be assessed via LDH assay in both dog and mouse bones; however, this approach requires modifications from the previous published method.

Methyl green-pyronin Y staining of nucleic acids: studies on the effects of staining time, dye composition and diffusion rates

Since the introduction of the methyl green-pyronin Y procedure as a differential histological stain more than 100 years ago, the method has become a histochemical procedure for differential demonstration of DNA and RNA. Numerous variants of the procedure have been suggested, and a number of hypotheses have been put forward concerning kinetics and binding mechanisms. Using both filter paper models containing DNA, RNA or heparin and histological sections, we have attempted to evaluate the kinetics of staining and the role of staining time for methyl green and pyronin Y by applying the dyes individually, simultaneously and sequentially. The results are presented as color charts approximating the observed staining patterns using a computerized palette. Our results indicate unequivocally that the differential staining is not time-dependent, but that it is dictated by the relative concentrations of methyl green and pyronin Y and by the pH of the staining solution.

Standardization in biological staining. The influence of dye manufacturing

The purpose of biological staining is to obtain specimens of biological material that can be assessed in the microscope. These specimens are influenced by all processes from removal from the intact organism to mounting on the microscopic slide. To achieve comparable results with various techniques for biological staining, standardization of all procedures and reagents is mandatory. In this paper, I focus particularly on dyes and consider the possibilities for obtaining standardized dyes. In general practice, most biological staining takes place with available commercial dyes. These dyes may or may not have been subjected to quality assessment either internally by the producer or vendor or externally by independent investigators or organizations such as the Biological Stain Commission. Concerted attempts at standardization in Europe are discussed. The latest results of this work, the European standard EN 12376, is presented. This standard is concerned with information supplied by the manufacturer with in vitro diagnostic reagents for biological staining. The standard has been prepared by a Working Group on Staining in Biology under Technical Committee 140, In Vitro Medical Devices, of the European committee for standardization, CEN.

Improving biological dyes and stains: quality testing versus standardization

This paper discusses the impact of both standardization and quality testing of dyes and stains in biology and medicine. After the brief review of why standardized dyes and strains are not presently available commercially, two types of testing and ways of improving dye quality are described. National or international organizations could be established to define standardization of dyes and stains. Standardization would be specifically defined as a list of physico-chemical parameters such as elaborated in this paper. Commercial batches of comparable quality may be labeled by the supplier as "standard dye," a procedure currently performed by the European Council for Clinical and Laboratory Standardization (ECCLS). Also recommended to improve dye quality is commercial dye testing by independent laboratories with subsequent certification for use. This sort of quality control is currently carried out in the United States by the Biological Stain Commission (BSC). The advantages and disadvantages of both techniques and the use of image analysis for the definition of standards are discussed. A combination of both the BSC testing protocols and the ECCLS standards should be established for extended quality control of biological dyes and stains.

Simultaneous quantification of DNA and RNA in tissue sections. A comparative analysis of the methyl green-pyronin technique with the gallocyanin chromalum and Feulgen procedures using image cytometry

For simultaneous cytophotometric measurement of DNA and RNA, the standardized Methyl Green-Pyronin Y technique is an obvious choice. It is, however, first necessary to correlate the uptake of Pyronin Y to the staining intensity of RNA. The material consisted of paraffin sections of formalin- or Carnoy-fixed rat liver. The sections were pretreated with water, buffer, deoxyribonuclease, ribonuclease, or both enzymes in sequence, and stained with the standardized Methyl Green-Pyronin Y procedure, Gallocyanin chromalum, or the Feulgen reaction. Sections stained directly without pretreatment served as controls. Staining intensities were measured with an image analyser for cell nuclei, nucleoli and cytoplasm. After deoxyribonuclease treatment, nuclear staining intensity with Methyl Green, Gallocyanin chromalum, and Schiff's reagent dropped nearly to zero. The same was seen for both nucleoli and cytoplasm with Pyronin Y and Gallocyanin chromalum after ribonuclease treatment. Staining intensity of Pyronin Y correlated directly with that of Gallocyanin chromalum for nucleoli and cytoplasm. After ribonuclease treatment, a direct correlation was found between the nuclear staining intensity of Methyl Green and nuclear absorption of Gallocyanin chromalum. We conclude that the standardized Methyl Green-Pyronin Y stain is reliable for the simultaneous quantitative assessment of both RNA and DNA. The simplicity of this technique makes it a valuable tool even for daily routine.

Standardization of biological dyes and stains: pitfalls and possibilities

The present paper gives a review of the actual state of standardization of biological dyes and stains. In a first part general information is given on practical problems encountered by the routine user of dyes with special emphasis on dye contamination. Some theoretical aspects of standardization are discussed. The second part of the paper gives more detailed information on commercial batches of hematoxylin-eosin-, Giemsa- and Papanicolaou-stains and on their standardization. Special problems arising with the application of image analysis techniques are briefly mentioned. User-oriented specifications for the standardization of dyes, stains and staining procedures are given. Fluorescent dyes and dyes used in chromogenic reagents such as the Feulgen-Schiff reaction are not included in this review.

The correlation between uptake of methyl green and Feulgen staining intensity of cell nuclei. An image analysis study

Paraffin sections of rat tissue fixed in either formaldehyde solution (3.6% w/v) or in Carnoy's fluid were stained using standardized Methyl Green-Pyronin procedures with the dyes used either simultaneously or in sequence. The sections were evaluated for the uptake of the two dyes by cell nuclei, nucleoli and cytoplasm using colour TV-image analysis. The parameters measured were integrated optical density and the surface area of the object. The sections were then destained and a Feulgen reaction was performed. The coordinates of the cells measured after the simultaneous Methyl Green-Pyronin method were stored in the computer, making it possible to measure the same cells in the Feulgen-restained sections. Image analysis gave results which invalidate the sequential methods as opposed to the simultaneous method. Mean optical densities were significantly increased for both dyes with the simultaneous method after formaldehyde fixation as compared to Carnoy fixation. The quantitative correlation of Methyl Green and DNA in the simultaneous technique was found to parallel exactly that of the Feulgen stain. In conclusion, the simultaneous Methyl Green-Pyronin technique is recommended while the sequential methods seem to be of less value.

Staining of the nucleolus with protein and RNA stains for automatic measurement of nucleolar size in paraffin sections

In this paper two staining methods for automatic assessment of nucleolar profile area in paraffin sections of breast carcinomas using the IBAS 2000 image analyzer are reported. In the first method, the nucleolar proteins are stained with phloxine B, in the second the nucleolar RNA is stained with methyl green-pyronin. Both methods are fully reproducible. Statistically, the profile areas observed for the same patient by the two methods were found not to differ significantly. Because of their rigidity and their size in relation to section thickness, nucleoli are particularly attractive cell structures for quantitation, for instance in studies of variables that might be useful in establishing the prognosis for carcinoma patients.

An investigation of new commercial samples of methyl green and pyronin Y

New commercial samples of Methyl Green (Gurr Certistain), Pyronine G (Gurr Certistain) and Pyronin Y (Polysciences) have been investigated using spectrophotometry, thin layer chromatography and nuclear magnetic resonance, in addition to standardized simultaneous and sequential staining methods using purified Ethyl Green and pure Pyronin Y as reference dyes. The Methyl Green was found to be Ethyl Green contaminated with Crystal Violet. It did not have any advantages compared with Ethyl Green supplied by American dye companies. The Pyronine G sample was Pyronin Y with a high dye content that gave good staining results when used with purified Ethyl Green. Pyronin Y from Polysciences was found to be essentially pure Pyronin Y.

Standardized methyl green-pyronin Y procedures using pure dyes

Fully standardized Methyl Green-Pyronin methods are presented. Pure Pyronin Y and purified Methyl Green or Ethyl Green are used either simultaneously in one dye bath or are used as a sequence of Pyronin Y and Ethyl or Methyl Green. Both methods, as shown by enzymatic pretreatment, give a reliable and reproducible staining in DNA with Ethyl or Methyl Green and of RNA with Pyronin Y on Carnoy fixed material. On formaldehyde fixed material it was found advantageous to use the sequential method as chromatin was hereby stained green instead of blue as seen with the simultaneous method.

Quantitation of dye binding by cell monolayers in a microtiter system

A semi-automated system has been developed for the quantitation of dye binding to cultured eukaryotic cells. It is based on staining precisely controlled numbers of cells seeded into microtiter trays. Cell-bound stain is then released using an appropriate solvent and quantitated in situ by measuring absorbance in a single beam ELISA reader with an interactive microcomputer link. In order to illustrate potential applications of this approach, the time course of dye-monolayer association and influence of cell number and stain concentration on staining has been examined for four dyes, Crystal Violet, Naphthol Yellow S, Ethyl Green and Pyronin Y. In addition, the effect of sequential and simultaneous staining was examined for Ethyl Green and Pyronin Y. The results provide evidence for the overall reliability of this approach as well as revealing several interesting features in the individual procedures examined. The combination of microtiter technology and computer link make the system particularly well suited to the efficient investigation of the permutations involved in optimizing conditions for a given staining procedure, as well as analysis of the thermodynamics of dye substrate interaction. Overall, the approach is viewed as an intermediate between artificial gel systems and microdensitometry.

Nucleic acid staining with the methyl green-pyronin method. A comparison of the use of pure dyes and commercially available dyes

We compared the staining obtained using commercially available pyronin Y samples with that obtained using pure pyronin Y in a standardized methyl green-pyronin procedure. In addition, the importance of the dye content of the anhydrous dye was investigated by varying the dye content by the addition of pure pyronin Y to one of the commercially available pyronin Y samples. We found that, for routine histological work, commercially available pyronin Y samples may produce acceptable results provided the sample can be shown by spectrophotometry to contain at least 43% pyronin Y.

1-Naphthol basic dye (1-NBD). An alternative to diaminobenzidine (DAB) in immunoperoxidase techniques

The usefulness of 1-naphthol as substrate for horseradish peroxidase (HRP) in immunohistochemistry was studied using the peroxidase-antiperoxidase (PAP) and avidin-biotin-complex (ABC) methods in the demonstration of glial fibrillary acidic protein (GFAP), vimentin, carbonic anhydrase C (CA.C), and factor VIII-related antigen (FVIII/RAg) in central nervous tissue and cerebral tumors. In the presence of ammonium carbonate, 1-naphthol is oxidized by HRP and hydrogen peroxide, producing a fine gray-violet precipitate. The oxidation product of 1-naphthol proved capable of binding a great number of basic dyes. For each stain the final reaction product had a characteristic color that was different from the spontaneous color of the dye and from the color displayed by nuclei. The final color obtained with this procedure was alcohol resistant and could be mounted in solvent-based mounting media. The results obtained with the 1-naphthol basic dye (1-NBD) method were compared with those obtained using the diaminobenzidine (DAB) reaction in the demonstration of GFAP-positive astrocytes. The DAB reaction produced a more intense staining but also a coarser precipitate than the 1-NBD reaction. The 1-NBD procedure showed more morphological detail of fine structures and did not obscure nuclei and mitosis. The very low toxicity of 1-naphthol compared with DAB (a suspected carcinogen) is an important advantage of the 1-NBD method, as is its high specificity and sensitivity.