| Abstract: | By the weight changes, the rat's eye grows during the whole life, whereas its scleral sector with the area equal to that of pigment epithelium of the retina grows most intensively between the 2nd and 5th days after birth. During this period, its weight attains half of the value characteristic of the scleral sector for one year old rats. This period of growth of the scleral sector coincides with the previously established peak of proliferative activity and appearance of first binuclear cells in the pigment epithelium. From the 5th day till the 12th month after birth, the weight of scleral sector increases twice and its area 6 times. This suggests that the mechanical tension of the scleral sector walls is one of the factors of growth of this eye part. On the basis of comparison of the scleral sector growth, changes in proliferative activity and number of polyploid cells in the pigment epithelium of the central zone of fundus oculi, the following periodization of the life cycle of cell population of the pigment epithelium is proposed: (1) from birth till the 15th day--period of principal determination (the number of binuclear tetraploid cells attains 80%), (2) from the 15th day till, at least, the 5th month--period of stabilization, (3) after 5 months--period of senescence characterized by the accumulation of highly ploid tri- and tetranuclear cells; its lower limit is not clearly defined. |
