SUMMARY
An instrument for combined scanning electron microscopy (SEM) and light microscopy (LM) to which a photometer unit is attached is described. A special stage in the vacuum chamber of a scanning electron microscope incorporates light microscope optics (objective and condenser) designed for transmission and epi‐illumination fluorescence LM. An optical bridge connects these optics to a light microscope, without objective and condenser. The possibility of performing quantitative DNA measurements in this combined microscope (the LM/SEM) was tested using preparations of either chicken erythrocytes, human lymphocytes, or mouse liver cells. The cells were fixed, brought on a cover‐glass, quantitatively stained for DNA, dehydrated, and critical point dried (CPD). After mounting the cells were coated with gold. The specimens were brought into the vacuum chamber of the combined microscope and individual cells were studied with SEM and LM. Simultaneously DNA measurements were performed by means of the photometer unit attached to the microscope. It is shown in this study that DNA measurements of cells in the combined microscope give similar results when compared to DNA measurements of embedded cells performed with a conventional fluorescence microscope. Furthermore, it is shown that although the gold layer covering the LM/SEM specimens weakens the fluorescence signal, it does not interfere with the DNA measurements.
SUMMARY
A survey of methods combining light microscopy and scanning electron microscopy is presented. A simple correlation is made when two preparations from adjacent parts of one specimen are investigated in two different microscopes. A more sophisticated method is the consecutive investigation of one specimen with two microscopes. A major problem in this method is the relocation of the area of interest. Several authors have presented solutions for this problem. It is preferable when one preparation is investigated in only one instrument, combining the two microscopical (LM and SEM) techniques, thus making relocation redundant.
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