Changes of cytochemical properties in the Golgi apparatus during in vivo differentiation of the ameloblast in developing rat molar tooth germs

Relation between the trans-Golgi network and the Golgi stack on development of the Golgi apparatus of the ameloblast in developing rat molar tooth germs

BACKGROUND

The problem of how the functional compartments of the Golgi apparatus organizes during cell differentiation to become a well-formed Golgi apparatus is as yet an unresolved issue. This study was designed to define the involvement of the trans-Golgi network (TGN) and the Golgi stack in organizing the Golgi apparatus.

METHODS

The distribution of the TGN marker enzyme was examined in the ameloblast of developing rat molar tooth germs using cytochemistry with Co-enzyme A phosphatase (CoA Pase) and cytidine monophosphatase (CMPase).

RESULTS

Typically formed Golgi apparatus was observed in the secretory ameloblast but not in the presecretory ameloblast. Organization of the Golgi apparatus through the presecretory ameloblast was noted. In the presecretory ameloblast, Golgi stacks of different sizes and clusters of small vesicles were located in the cytoplasm lateral to the nucleus. The saccules with enzymes marked for TGN were also observed in the cytoplasm lateral to the nucleus. These saccules were adjacent to the cluster of small vesicles and/or the Golgi stack. Upon cell differentiation, Golgi stacks were seen in line along the long axis of the cell, and the file of the stacks in the cytoplasm lateral to the nucleus was formed. The positive saccule was seen in a parallel line equal to the length of the Golgi stacks.

CONCLUSIONS

In organizing the Golgi apparatus, the development process of the TGN and the Golgi stack appear to be different, and new Golgi stacks seem to be formed through the accumulation of small vesicles near the pre-existing TGN.

Thiamine pyrophosphatase cytochemistry in rat endometrium during the oestrous cycle

The functional morphology of the Golgi apparatus was studied in various types of cells in the rat endometrium during the oestrous cycle. A cerium-based enzyme-cytochemical method was used for the ultrastructural visualization of the activity of thiamine pyrophosphatase (TPPase). The cerium-based method was evidently superior to the classical lead technique, which was used for comparison. TPPase activity in luminal and glandular epithelial cells displayed cyclical modulation and redistribution. It was restricted to only one or two narrow trans lamellae during dioestrus but extended during proestrus and oestrus into nearly all trans-to-cis lamellae of the well-compartmentated Golgi apparatus. A homogeneous staining reaction, which was particularly intense during the latter two phases and only partly due to unspecific alkaline phosphatase, was confined to the apical and basolateral plasma membranes of luminal epithelial cells. In the stromal fibroblasts, only one short Golgi saccule was positive at dioestrus, whereas three or more trans Golgi lamellae were filled with reaction product during oestradiol-dominated oestrus. TPPase activity was furthermore observed in the lysosomes in epithelial cells, stromal fibroblasts, capillary endothelial cells and pericytes. The present findings of cyclic changes in TPPase activity in epithelial cells and stromal fibroblasts provide the first evidence of cyclic modulation and redistribution of this enzyme in the endometrium.

Changes of lectin staining pattern of the Golgi stack during differentiation of the ameloblast in developing rat molar tooth germs

Changes of lectin staining patterns in the Golgi stack during cell differentiation were examined in the ameloblasts of developing rat molar tooth germs, using HRP-labeled lectins: Canavalia ensiformis (Con A), Griffonia simplicifolia I (GS-I), Glycine max (SBA), Ulex europeus I (UEA-I), Triticum vulgaris (WGA), and Arachis hypogaea (PNA). The Golgi stacks of the inner enamel epithelial cells and the presecretory ameloblasts were stained with the lectins, although the staining strength and pattern varied among the stacks with each lectin. In some cases, the reaction products for the lectins were observed in most or all saccules of the Golgi stack. In the secretory ameloblasts, however, discrete staining patterns of the Golgi stack were found for each lectin. The reaction products deposited in definite saccules of the Golgi stack of the secretory ameloblast, especially for UEA-I and PNA which stained only the trans Golgi saccules of the stack. The reaction-positive saccules distributed more extensively in the Golgi stack of the inner enamel epithelial cell and the presecretory ameloblast than in the secretory ameloblast. These findings suggest that the Golgi stack is not fully compartmentalized in the inner enamel epithelial cell and the presecretory ameloblast. It is proposed that, in the differentiating ameloblast, various glycosyltransferases may coexist in most saccules of the Golgi stack.