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SUMMARY We have developed a new confocal laser scanning microscope equipped with two galvanometer mirrors which swing the laser beam. With this set up we can observe large and fragile specimens. Using a focused laser beam as light source to minimize ‘flare’ and a pinhole in front of a photodetector to eliminate out‐of‐focus data, we could obtain a depth‐discriminated fluorescence image. The scanning apparatus of our system can eliminate mechanical vibration and sweep widely, to obtain images at a low magnification. A thinly sectioned image with high resolution and high contrast could be obtained optically from an in situ thick specimen. We have called this technique ‘microscopic tomography’. Combining the laser scanning microscope with the colour image analyser generated semi‐automatically a three‐dimensional picture of the biological material with information on its interior.

In an attempt to analyse the kinetics of angiogenesis in the brain, we developed a new lectin-histochemical staining technique for identifying the vasculature. Three horseradish-peroxidase-conjugated lectins, i.e., Griffonia simplicifolia agglutinin 1 (GS1), Ricinus communis agglutinin 1 (RCA1) and soybean agglutinin (SBA), selectively stained vascular walls in brain-tissue sections. When these lectins were injected into the circulation of ether-anesthetized animals via the pulsating left ventricle, they bound specifically to the inner surface of endothelial cells and revealed the three-dimensional architecture of the vascular network within thick tissue preparations. When this technique, referred to a lectin angiography, was combined with 5-bromo-2-deoxyuridine (BudR) immunohistochemistry, proliferating capillary cells could be easily identified in three-dimensional structures of the developing vasculature. Because of its simplicity and wide applicability, lectin angiography should be useful for analysing the kinetics of angiogenesis in developmental, regenerative, and pathological conditions in various tissues and organs.