| Research Abstract |
As is well known, lectins are carbohydrate-binding proteins or glycoproteins of non-immune origin. In histochemistry and cytochemistry, labeled lectins have been widely used as a probe for the detection of carbohydrates. With the use of exogenously administered lectins, changes in glycoconjugates during the course of development, aging malignant transformation and degeneration have been successfully visualized in situ. Visualization of lectin binding pattern can be achieved not only by conventional light and electron microscopy but also by employing confocal laser scanning microscope and a combination of high voltage transmission electron microscopy and backscattered scanning electron imaging.
Recently, in addition to so-called "exogenous lectins" as above, much attention has been paid to "endogenous lectins", in particular, animal lectins, with special reference to their expression and also possible roles.
In vertebrates, β-galactoside-binding lectins, galectins, have been isolated from
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several tissues of different animals. Chick embryos, for example, have at least two different kinds of galectins, the 14- and 16-kD lectins, which belong to the family of animal metal-independent lectins or S-type, and exist in differentiating chick skin. Both cDNA and genomic DNA for these galectins were cloned, and the nucleotide sequence as well as the complete amino acid sequence were determined. Immunohistochemically these two isolectins revealed changes in expression in the epidermis and dermis of chick embryonic tarsometatarsal skin during the course of development both in vivo and in vitro. Differences between the 14, and 16-kD lectins were obvious particularly in in vitro experiments such as in retinol-induced mucous metaplasia. Changes in expression of these isolectins were in parallel with those in in situ hybridization signals. Both 14- and 16-kD galectins should play an important role in differentiation of the skin, and the gene expression of these two lectins is regulated independently.
We already examined the localization of an endogenous 14-kD galectin in normal humall skin, and the 16-kD and the 32-kD galectins in the developing nematode Caenorhabditis elegans. Besides, we investigated expression of macrophage galactos/N-acetylgalactosamin-specific C-type lectin in normal mouse tissues and found that its location varied at different stages of development as well.
Endogenous animal lectins and their complementary sugars have been round to be involved in fundamental and key roles playing in cells and tissues. In combination with both of the exogenous and endogenous lectins, the lectin histo- and cytochemistry should contribute much in elucidation in situ of function and significance or glycoconjugates. Less
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