DNA synthesis and mitotic activity during early development of chick lens

Denervated forelimbs and contralateral innervated forelimbs of Ambystoma larvae were injured internally distal to the elbow by compression with watchmaker's forceps. Innervated controls completely repaired the crush injury within one week; denervated limbs failed to repair the injury and exhibited varying degrees of limb regression. Histological examination revealed that the process of tissue dedifferentiation initiated by injury was more extensive in denervated, regressing limbs than in controls. In innervated limbs, both the DNA labelling index and the mitotic index peaked approximately 4–6 days after the injury and returned to baseline levels by 10 days. In denervated limbs, the DNA labelling index also increased and remained at an elevated level for at least 2 weeks after the injury, but significant mitotic activity was not observed. The data indicate that intact nerves are not needed for cellular dedifferentiation, cell cycle re-entry, and DNA synthesis in injured limbs, but are required for the cells to proliferate and repair the injury. These results are discussed together with those of similar experiments on the role of nerves during the initiation of epimorphic regeneration in amputated limbs.

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Stimulation of DNA synthesis and mitotic activity of thymic lymphocytes by cyclic adenosine 3′5′-monophosphate

Experimental Cell Research ◽

10.1016/0014-4827(69)90135-9 ◽

1969 ◽

Vol 58 (1) ◽

pp. 188-191 ◽

Cited By ~ 95

Author(s):

J.P. MacManus ◽

J.F. Whitfield

Keyword(s):

Dna Synthesis ◽

Mitotic Activity ◽

Stimulation Of

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DNA CONTENT OF PLACENTAL NUCLEI

The Journal of Cell Biology ◽

10.1083/jcb.13.2.183 ◽

1962 ◽

Vol 13 (2) ◽

pp. 183-191 ◽

Cited By ~ 45

Author(s):

Michael Galton

Keyword(s):

Cell Proliferation ◽

Dna Synthesis ◽

Mitotic Activity ◽

Dna Content ◽

Reproductive Capacity ◽

Interphase Nuclei ◽

Daughter Cells ◽

Reproductive Ability ◽

Dna Values ◽

Rapid Accumulation

The DNA content of individual nuclei in four immature human placentas was determined by microspectrophotometric analysis of Feulgen-stained sections. The absence of mitosis in the syncytiotrophoblast, taken together with the finding of a diploid unimodal distribution, at a time of rapid placental growth, indicated that the syncytiotrophoblast possessed little or no intrinsic reproductive capacity. In contrast, the cytotrophoblast displayed considerable mitotic activity and was found to contain a high proportion of nuclei with DNA values in excess of the diploid amount, corresponding to DNA synthesis in interphase nuclei preparatory to division. From the complementary behavior of the two layers of trophoblast, with respect to evidence of reproductive ability, it is concluded that the rapid accumulation of nuclei in the syncytiotrophoblast, during the early development of the placenta, is accounted for by cell proliferation within the cytotrophoblast followed by alignment and coalescence of some daughter cells in the syncytiotrophoblast.

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