[Characteristics of the development of the small intestine mucosa in man and rat]

The process of the small intestine tunica mucosa embryonal development has been studied in 75 rat embryos from 10 to 21 days of development and in 82 human embryos at equivalent stages of development (from 28 days up to 13 weeks). The changes observed in the tunica mucosa structure and indices of the cellular activity [mitotic index, nuclear volumes, RNA content, alkaline phosphatase (APh), acid phosphatase (AcPh), succinic dehydrogenase (SDG), lactate dehydrogenase (LDG) activity] make it possible to distinguish 3 periods in the process of the small intestine tunica mucosa embryonal development: 1 - period of the germinal differentiation, 2 - prespecific and 3 - specific differentiation period, the latter is characterized by common signs for the man and the rat. Together with some retardation in the rat organogenesis (postnatal formation of criptae) its tunica mucosa is characterized by a higher, than in the man, activity of all the enzymes studied; AcPh and LDG activities are the most intensive, that is connected with low content of glycogen. This low content of glycogen and 4-5 times higher LDG activity than in the man demonstrate a more intensified utilization of glycogen, evidently, connected with a high level of anaerobic respiration in the rat embryos.