Mechanism of age-dependent involution in embryonic chick notochords.
To study the possible mechanism of the age-dependent involution of the notochord, isolated mesenchyme-free notochords of chick embryos were cultured in vitro and compared with their counterparts in vivo. Two different aspects were evaluated: (1) DNA synthesis measured by [3H]thymidine incorporation and visualized by autoradiography and (2) cell death quantified by counting the number of pyknotic nuclei. The results demonstrate that [3H]thymidine uptake by notochords shows an age-dependent decrease in vitro as well as in vivo. The number of [3H]thymidine-labelled notochord cells, however, is higher in vitro than in vivo. At the same time, there is an age-dependent increase in pyknosis in the notochord in vivo and in vitro. So, during the aging process, the number of both pyknotic nuclei and of [3H]thymidine-labelled nuclei suggest a high turnover of notochord cells in vitro. From these results, we can conclude that the process of involution in aging notochord seems to be controlled by a programmed intrinsic process, which might be influenced partially by the microenvironment in vivo.
Ghanem
E
E
Department of Anatomy, Embryology and Histology, University of Gent, Belgium.
Cornelissen
M
M
Thierens
H
H
De Ridder
L
L
D000818:Animals; D001345:Autoradiography; D016923:Cell Death; D002642:Chick Embryo; D046508:Culture Techniques; D004247:DNA / Q000096:biosynthesis; D009672:Notochord / Q000166:cytology* / Q000502:physiology; D013997:Time Factors
D004247:DNA