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The components of the hematoxylin and eosin (H & E) stain (i.e. hemalum and eosin Y), their contributions to the typical staining pattern, and the reasons why the H & E stains are the preferred oversight stains for routine diagnostic histopathology are discussed. The essential diagnostic significance of effective nuclear staining by hemalum, providing information on nuclear morphology and texture, is emphasized; as is the ironic advantage for routine diagnostic histopathology of the limited range of colors provided by H & E staining, that allows recognition of significant features under low microscopic magnifications. Standardization of hemalum is considered, along with probable reasons why users show resistance to such a concept. Counterstaining with anionic (acid) dyes is discussed, as is the important phenomenon of contrast. The particular advantages and disadvantages of eosin Y and phloxin B as counterstains to hemalum are outlined. The concept of an "ideal routine histological stain" is considered, and H & E is compared to such an ideal case. Finally, deficiencies of H & E staining are discussed, and a program to develop an improved oversight stain is introduced.

A panoptic histological stain, PHTA, is introduced for routine use in developmental biology. The protocol is based on three dyes, hematoxylin and, after tannic acid treatment, phloxine B and azure B. It was optimized for differential staining of extracellular matrix, cytoplasm and chromatin. The method is quick, inexpensive and well-reproducible. The mouse placenta is used here to demonstrate the excellent suitability of PHTA for routine morphology.

The need for the standardization of reagents and methods used in the histology laboratory is demonstrated. After definitions of dyes, stains, and chromogenic reagents, existing standards and standards organizations are discussed. This is followed by practical instructions on how to standardize dyes and stains through the preparation of reference materials and the development of chromatographic methods. An overview is presented of the problems concerned with standardization of the Romanowsky-Giemsa stain for cytological and histological application. Finally, the problem of how to convince routine dye and stain users of the need for standardization in their histology laboratories is discussed.

The purpose of the present study was to investigate the influence of chromatin compactness on the kinetics of acid hydrolysis in the Feulgen reaction in cytology. Tissue imprints of rabbit liver, of human bronchial carcinoma and of human blood smears, fixed with alcohol, formaldehyde or with Böhm's solution with and without prior air drying, were stained with a standardized pararosanilin-Feulgen reagent. The time for hydrolysis varied between 7.5 and 120 min. The integrated optical density (IOD) of the cell nuclei was measured with an image analyzer (IBAS 2000). Cells with condensed chromatin (lymphocytes, small cell carcinoma, formaldehyde fixed cells) showed a slow increase of staining intensity and late plateau phase as compared with cells with decondensed chromatin. DNA in condensed nuclei was less susceptible to acid hydrolysis. The degree of chromatin compactness which determines the sensitivity of DNA to hydrolysis is influenced by the type of fixation, cell type and by the functional status of the cell. The conclusion is that Feulgen staining intensities of cells with different degrees of chromatin compactness cannot be compared unless measured in the respective plateau phases of the relevant hydrolysis curves which must be determined individually for each cell type.

In the present study we have investigated the uptake of cationic thiazine dyes and of the anionic Eosin Y by red blood cells (RBCs). Blood smears were stained with Azure B-Eosin Y, Methylene Blue-Eosin Y, Thionin-Eosin Y and with the cationic and anionic dyes alone at varying concentrations. Dye content of erythrocytes was measured with a Vickers M 85a microdensitometer. Nuclear chromatin features of white blood cells were investigated with the IBAS 2000 image analyser. Azure B favoured Eosin Y uptake of RBCs remarkably, and vice versa. There was no clear indication of that type of molecular interaction which characterizes the generation of the colour purple on polyanions. Methylene Blue and Thionin left Eosin Y uptake unaffected, but contamination of the standard Azure B-Eosin Y stain with Methylene Blue obviously affected Azure B-Eosin Y uptake, probably by competition of Methylene Blue and Azure B binding in RBCs. Furthermore, Methylene Blue contamination of the standard stain increased the rate of error in image analysis of white blood cell nuclei due to variations of staining intensity. For cytophotometry and image analysis of blood smears the standard Azure B-Eosin Y stain is by far superior to the commercial stain which normally is contaminated with Methylene Blue and some of the lower azures.

The morphologic and spectroscopic characteristics of a new and reproducible modification of the Papanicolaou stain are briefly described. The main features of this modification are (1) replacement of the natural dye hematoxylin by the synthetic and chemically well defined dye thionin, (2) introduction of an alcoholic counterstain consisting of eosin gamma and fast green FCF only and (3) employment of alcoholic solutions only. The absorption characteristics of hematoxylin and thionin bound to chromatin are influenced by the cytoplasmic counterstaining, especially by the two green dyes, the absorption peaks of which are close to those of the nuclear stains. The implications of these results for visual and automated cytologic diagnosis are briefly discussed.

An extensive review is presented of the various factors involved in the standardization of dyes and stains for cytologic material, which is a crucial point in achieving objective and reproducible measurements of cells for recognition by automated microscopy (high-resolution cell image analysis; automated cell pattern recognition [ACPR]). Two principal methods of standardization are considered at length: (1) standardization based on the physical and chemical characterization of the dyes (physicochemical standardization), as adopted by the German Bureau of Standards, and (2) standardization based on direct visual assessment of stain performance (performance standardization), as adopted by the United States Biological Stain Commission. The procedures, achievements and problems of both methodologies are discussed, as are such related matters as staining time, solution pH, etc., especially with regard to the two most important stains in diagnostic cytology: the Papanicolaou stain and the Romanowsky-Giemsa stain. The standardization of these two stains is considered in detail, with an eye towards their suitability for ACPR. The mechanisms of the staining results produced by these stains are examined, as are the extant problems with each. The Papanicolaou stain, while neither standardized nor stoichiometric, has proven to be of use in cytophotometry. Similarly, the Romanowsky-Giemsa stain, while standardized, is also not a stoichiometric stain. Yet both have been successfully used in some aspects of ACPR; no "ideal" stain has yet been found that would make cell samples ideally suited for machine evaluation. It is concluded that the standardization of biologic dyes and stains, which can contribute to the success of ACPR, should be undertaken by multidisciplinary expert panels, in which the current concerned organizations could play a role. It is also concluded that ACPR may, in fact, contribute to the standardization of dyes and stains: that computer-directed morphometry and automated image analysis with sophisticated statistical analysis may become major tools in the validation of data on staining. For example, computer analysis could be used to pinpoint the particular variant of the Papanicolaou stain that leads to the best overall reproducibility of cell descriptors, in effect achieving "preliminary standardization by computer judgment of stain performance."

A method is described for the purification of the dye azure B in quantities sufficient for biological staining experiments on a larger scale. The method is based on the use of column chromatography. Two columns are employed. In column A with silica gel as adsorbent the azure B fraction is isolated from a suitable substrate ('technical' azure B gained by a modification of Bernthsen's synthesis of methylene blue, or polychrome methylene blue) using an acetate-formate mixture as eluent. In column B, on an Amberlite polymeric adsorbent (XAD-2) the acetate-formate anions are exchanged in chloride. Regeneration of both columns is possible: KMnO4, Na2S2O4 and water are run through column A; 5% NaOH, methanol and water through column B. Purification of azure B on economic terms is thus attained. The opinion is expressed that this method is also applicable to the purification of other cationic dyes.