The identification of the eight chromosome types in the C-group in the human metaphase plate offers very great difficulties with conventional methods. The fluorescence patterns after quinacrine mustard treatment are, however, clearly different for all the chromosome types. In order to test whether these differences between patterns are statistically significant eight sets of patterns, one set from each chromosome type, have been subjected to Fourier analysis in a computer and the statistical validity of the individual types of patterns calculated. The result was that the pattern types are clearly separated significantly in a statistical sense. Furthermore, the observations show that the pattern curves can be characterized by a relatively low number of Fourier parameters, making automatic machine recognition and classification of the chromosomes easy. For the other human chromosome groups the situation is still simpler. Work towards still further automatization of the chromosome sorting in human metaphases is in progress.
Various degrees of cellular atypia were induced in the bronchial epithelium of dogs by means of repeated submucous 20-methylcholanthrene injections. Thereafter, the 20-methylcholanthrene treatment was stopped, and the outcome of the bronchial cell atypias in individual dogs was studied using cytomorphological and cytochemical methods. The results suggest that the various degrees of 20-methylcholanthrene-induced cellular atypias, including those cytologically interpreted as malignant, may reflect reversible cellular alterations which disappear after removal of the carcinogen. Similar observations were made in a group of cigarette smokers who, after malignant-appearing cells were observed in the sputum material, stopped smoking or significantly reduced their cigarette consumption.
Quantitative optical cytochemistry permits the determination of many different parameters in whole cells or parts of cells. Total amounts of DNA, RNA, and protein and/or the amounts of these substances in nucleus or nucleolus are examples. Techniques in this field have contributed considerably to the development of our present conceptions of normal cell growth and regulation. Normal cell study has, however, predominated so that tumor work has not yet been very extensive, even though quite eqrly on, in the 1940's, a conspicuous cytochemical peculiarity was found in cancers, namely, a pronounced variability between cells with regard to several measurable parameters. The result has been different kinds of technical difficulties, which are especially great in work on tumor material. However, as years passed, a fair amount of information was accumulated from studies of different parameters in tumors. Only a few years ago this experience clearly indicated that, provided very considerable improvements were made in technique, several cytochemical methods could be used as efficient supplements to morphological cytodiagnostic work, especially in such important clinical fields as preneoplasia identification, malignancy grading, and judgment of the state of growth of for instance, hormone-stimulated populations and also the distinction, so difficult in morphology, between "atypical hyperplasia" and "truly malignant" states. In an effort to eliminate the foremost of these technical difficulties, during the last few years we have developed a comprehensive system for large-scale uni- and multiparameter measurements aimed specifically at the types of specimens encountered in cytopathological work. The system is based on cytophotometry in ultraviolet and visible light, interferometry, and fluorometry and also encompasses special arrangements to simplify the identification and recovery of individual cells for different types of study. Instruments for facilitation of the comparison of cytochemical results with morphological findings are also included.
