GROWTH AND DIFFERENTIATION OF THE SECONDARY PALATE IN A TELEOSTEAN FISH, ONCORHYNCHUS-KISUTCH

A study was undertaken to examine the growth and differentiation of se condary palate in a teleostean fish, Oncorhynchus kisutch. The rate, p attern, and time of synthesis of various macromolecules, which play a crucial role during palate development in higher vertebrates, were exa mined in the developing palate of fish. A spurt in DNA synthesis durin g mid-morphogenesis of fish palate appeared to be related to temporal regulation of palate development. RNA synthesis was high during the ti me of primordial appearance and increased again from day 4 post hatchi ng (PK) to correspond with differentiation of palate. Protein synthesi s remained low initially but its trend paralleled that of RNA synthesi s after day 4 PH. Glycosaminoglycan synthesis increased initially with the cartilaginous growth and then with the appearance of mucous cells . An increase in collagen synthesis corresponded with the thickening o f collagen layer in the basement membrane. Cyclic AMP activity increas ed initially prior to the increase in DNA synthesis and subsequently r emained high indicating its involvement in both growth and differentia tion of fish palate. These profiles of synthesis of various macromolec ules in teleostean fish differ considerably from that seen in higher v ertebrates. On the basis of comparative analysis, it was suggested tha t the timing of mesenchymal differentiation may be one of the features in determining the characteristics of palate development in different classes of vertebrates. (C) 1995 Wiley-Liss, Inc.