Study on the aging changes of DNA and protein synthesis of bipolar and photoreceptor cells of mouse retina by light and electron microscopic radioautography.

The DNA and protein synthesis of the bipolar cells and photoreceptor cells of aging mouse retina from fetal to postnatal 1 year were studied by light and electron microscopic radioautography. Meanwhile the ultrastructure of these cells was observed by electron microscopy. The bipolar and photoreceptor cells incorporated 3H-thymidine from embryonic day 19 until 1 week after birth, while 3H-leucine from embryonic day 19 to postnatal 1 year. The 3H-thymidine labelled cells had undeveloped cell organelles in their cytoplasm. On the contrary, the unlabelled cells had well developed cell organelles, mainly mitochondria and endoplasmic reticulum in their cytoplasm. The mitochondria became elongated when the outer segments were well developed. The protein synthesis of the bipolar cells and photoreceptor cells as demonstrated with 3H-leucine labeling was vigorous at embryonic day 19 and early postnatal days when the inner and outer segments were formed. The peak of this phenomenon was observed at 1 day after birth. The activity of protein synthesis was also detected at the adult stage. However there was no significant fluctuation in any stages from 14 days after birth to 1 year.