Effects of 5-fluorouracil on collagen synthesis during quail secondary palate development.

A study was undertaken to examine the involvement of collagen synthesis during palate development in quail where mammalian-type shelf reorientation is absent. Teratological observation showed that 100 micrograms 5-fluorouracil (FU) on day 4 of incubation increased the gap between the palatal shelves. Light microscopic observation indicated that the quail palatal shelves develop as horizontal ridges on day 5 and approximate on day 8 of incubation but never fuse. FU treatment affected the approximation of palatal shelves. In separate experiments, both the control and FU-treated quail embryonic palates, which were dissected between days 5 and 10 of incubation, were incubated in a growth medium supplemented with 14C-proline. The rate of collagen synthesis, total protein, hydroxyproline (HYP) levels, and collagen isotype were determined. The result showed that in control palates the rate of collagen synthesis increased fivefold between days 6 and 8 of incubation but dropped thereafter. In FU-exposed palates, the rate of collagen synthesis was lower than that in controls. It increased threefold between days 7 and 8 of incubation. High performance liquid chromatographic measurement of HYP levels indicated that, in comparison to controls, HYP accumulation in FU-treated palates was reduced by 50% on day 6 and 75% on day 8 of incubation. Total protein content in FU-treated palate were also 50-70% lower than those in their control counterparts between days 5 and 10 of incubation. Gel electrophoresis showed that only type I collagen was synthesized in the developing palate of both the control and FU-treated quail embryo. An analysis of results of the present study, along with the data from literature on mammals, corroborate the proposition that an increased collagen synthesis may contribute to the acquisition of volume of vertebrate's secondary palatal shelf for its continuing morphogenesis.

Genesis of hadacidin-induced cleft palate in hamster: morphogenesis, electron microscopy, and determination of DNA synthesis, cAMP, and enzyme acid phosphatase.

A morphological, electron microscopic, and biochemical study was undertaken to analyze the genesis of hadacidin-induced cleft palate in hamster fetuses. Gross and light microscopic observations indicated that hadacidin affected the growth of vertical palatal shelves to induce cleft palate. Electron microscopic observations showed that initial hadacidin-induced changes were seen in the mesenchymal cells. Within 12 hr of drug administration, the perinuclear space was swollen and a lysosomal response injury was evident in the mesenchymal cells. Subsequently, 24 hr after hadacidin treatment, lysosomes appeared in the epithelial cells; changes were also seen in the basal lamina which included separation of the lamina densa from the basal cells, duplication of lamina densa, and complete loss of basal lamina. Between 36 and 42 hr post-treatment, the cellular and basal lamina changes subsided, and the epithelium of vertical shelves underwent stratification. Biochemical determination of enzyme acid phosphatase indicated that the levels of enzyme activity in both the control and treated palatal tissues corresponded to the appearance of lysosomes. Measurement of cAMP levels suggested that the peak activity of cAMP corresponded to that of enzyme acid phosphatase and cell injury. The cAMP activity in hadacidin-injured cells, however, was significantly lower in comparison to that of the dying cells of control palates. Hadacidin treatment also affected DNA synthesis in the developing primordia of the palate. It was suggested that hadacidin injures the precursor cells of the palate prior to the appearance of the primordia, and subsequently affects their proliferative behavior, stunting the vertical growth of the palatal shelves and inducing a cleft palate.