RESUMO
The effects of tumour promoters and carcinogens on bud formation were investigated in an attempt to clarify the primary process of bud formation in hydra. Treatment with 1.0ng/ml 12-O-tetradecanoylphorbol-13-acetate (TPA), phorbol-12,13-didecanoate (PDD) or mezerein added immediately after feeding rapidly and completely inhibited the formation of new buds in Hydra japonica. Treatment with TPA 3-6 h after feeding also suppressed bud formation 24 h later, but suppressed buds appeared 48 h later. Buds suppressed by TPA also formed in the presence of a diluted homogenate of hydra and during starvation. Carcinogens, such as benzo(a)pyrene and 20-methylcholanthrene, did not have an inhibitory effect on bud formation within 2 days. The tumour promoters and carcinogens used in this experiment did not inhibit the regeneration of tentacles. These results indicate that tumour-promoting phorbol esters, but not carcinogens, rapidly suppress the process by which the formation of buds is initiated by hydra, and the effects of these esters depend on the timing of treatment after feeding.
RESUMO
Regenerating terminal buds of Corydoras aeneus were observed by electron microscopy to determine how terminal buds developed with respect to microtubule formation. After surgical removal of the fish barbel, it and the terminal bud began to regenerate 1.5 weeks later at 25°C. The regenerating terminal buds were ovoid in shape and contained three types of cells. The first type of cell had extended cellular processes which contained numerous microtubules and tubules. A bundle of three or four microtubules ran parallel to the long axis of the cellular process. Receptor villi protruded from the cell two weeks later, suggesting that it is a receptor cell. The second cell type, which appeared 1.5 weeks after barbel removal, had numerous microtubules oriented along the long axis of the cellular process; and numerous dense granules appeared two weeks later, suggesting that it is a supporting cell. The third type of cell observed was a basal cell without cellular processes. These results suggest that microtubule formation plays an important role in the elongation of regenerating terminal buds.
RESUMO
Degeneration of the premetamorphic papillae and development of the fungiform papillae during metamorphosis of bullfrog tadpoles were investigated by electrophysiological and scanning electron microscopic methods. Premetamorphic papillae were observed during the early metamorphic stages, and these degenerated rapidly at about metamorphic stage 20. The anlage of the tongue appeared at about metamorphic stage 10, but the anlage of the fungiform papillae appeared at about metamorphic stage 18. The microvilli at the apex of the fungiform papillae were observed at about metamorphic stage 21. At metamorphic stage 24 the fungiform papillae had a similar structure to that of adult frogs. Taste responses were recorded from the glossopharyngeal nerve of the tadpole. The responses to 1 M sucrose and 0.01 M quinine hydrochloride could be observed at metamorphic stage 6 or later, though during stage 20 the responses were very weak. The response to 0.02 M ammonium chloride appeared at metamorphic stage 6, but disappeared at stage 20 and did not reappear later. These results indicate that the fungiform papillae become functional as chemo-receptor organs at about metamorphic stage 21 and that, before the fungiform papillae function, the premetamorphic papillae serve as chemoreceptor organs in the tadpole.
