| Abstract: | In this paper two examples are presented of the application of laser fluorescent microirradiationto biology. The experiments, performed using a pulsed-laser microfluorometer with high spatial and temporal resolution, concern: (i) a study of the functional state of chromatin and (ii) a study of the fluorescence properties of Hematoporphyrin-derivative in tissue- and culture-cells. (i) The in situ evaluation of the functional state of chromatin has been done in chromosomes and nuclei “in toto” stained with the fluorescent probe Quinacrine Mustard. It has been found that chromatin fractions with different degree of activity, morphologically recognizable at the microscope, present fluorescence decay times markedly different, with a longer decay time for active chromatin. This result has been attributed to the stainability of DNA, which appears to be lower for active chromatin than for the inactive one. A similar result has been obtained in a preliminary experiment on cultures of human lymphocytes, after activation with Phytohemagglutinin. (ii) The fluorescent properties of Hematoporphyrin-derSvative have been studied in single cells, obtained from both normal and tumor tissues and cultures. In agreement with the results obtained with other techniques in tissues, it has been found that the tumor cells examined present an HpD uptake higher than that of the normal cells of the corresponding tissue, and that, within a cell, HpD becomes localized mainly in the cytoplasm. Preliminary results indicate a difference in the fluorescence decay time between stimulated and unstimulated human lymphocytes treated with HpD. Furthermore, it has been found that the fluorescence decay time is different in cells as compared with HpD solution and that the presence of HpD stabilizes cell autofluorescence. |
