الفهرس 
الملخص العربى
Marphology and HistologyOnly 14 pages are availabe for public view
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Abstract
The effect of vitamin A on the in vitro development of the undifferentiated tail bud, oesophagus and stomach of the toad, Bufo regularis has been investigated.
The Liquid culture medium, Trowell T 8 (Lacking vitamin A) and different concentrations of vitamin A (L-10 i.u./mL) have been used.
The present study revealed the following points:
I- Morphology and Histology
a-Tail bud:
1-Earlier growth of the tail bud occurred in cultures containing vitamin A than in those Lacking it (control).
2-Culture medium, Trowell T 8, containing 2-4 i.u. of vitamin A was found to be more suitable for the growth of the tail bud than either that Lacking the vitamin or that containing a higher concentration (8- 10 i.u.).
3-Tail buds cultivated for 10-14 days become atrophied and their caudal fins disappear.
b-Oesophagus:
1-The histologiol differentiation of the oesophagus occurred earlier in treated cultures (containing 2-4 i.u. of vitamin A) than in the control cultures.
2-The differentiation of the various tunics of the cultivated oesophagus has been shown to be essentially similar that normally occurs in vivo.
3-The oesophageal mucosa consisted in 6- day cultures containing 2-4 i.u. of vitamin A, of tall columnar epithelial cells.
In control cultures, the latter were partially ciliated and besides few secretory cells developed after 10 days`cultivation.
c-Stomach:
1-The stomach cultivated for 3 days in a medium containing low (2- 4 i.u.) and high (8-10 i.u.) concentrations of vitamin A proved to be more developed and better differentiated than that of the control.
2-The mucosal epithelium of the stomach consisted in 3-day cultures containing 8-10 i.u. of vitamin A, of tall ciliated columnar cells and few small secretory ones.
3- A thin muscular cost represent by circularly disposed muscle fibres developed in 3-day cultures containing 8-10 i.u. of vitamin A/ml culture medium but in 6-day control cultures.
II-Histochemistry
1-The carbohydrate contents of the control cultivated specimens (tail buds, oesophagus and stomach) were increased in the period between 2-6 days of cultivation.
These contents were decreased at the tenth day of cultivation.
2- The treatment with low (1 i.u. and 2-4 i.u.) doses of vitamin A resulted in the increase of carbohydrates after 2-3 days of cultivation.
The depletion of these contents take place at the sixth day of cultivation.