Vitamin A Effect on Limb Regeneration: Studies on the Tadpoles of Anuran Amphibians

Pattern duplication by retinoic acid treatment in the regenerating limbs of Korean salamander larvae, Hynobius leechii, correlates well with the extent of dedifferentiation

“…In regenerating axolotl limbs, administration of RA either too soon, before cells are dedifferentiated, or too late, after cells have redifferentiated, results in little or no pattern duplication (Thorns and Stocum, 1984;Maden et al, 1985;Niazi et al, 1985;Scadding and Maden, 1986a). In the regenerating limbs of the anuran tadpole, Bufo melanosticus, RA treatment beyond stage 38 evoked small spike regeneration (Niazi et al, 1989). Therefore, the period of maximum sensitivity to RA for PD duplication seems to coincide with the period of dedifferentiation, and a dedifferentiated cellular state might be a prerequisite condition for the RA-evoked duplication.…”

“…In the case of amputation through the distal stylopodium, the MLP increased to a peak level more rapidly and remained at that level longer than the MLP of the zeugopodial level amputation. In fact, in regenerating hindlimbs of the Indian toad tadpole (Bufo melanostictus), retinol palmitate treatment caused amputated level and stage-specific duplication, i.e., the limbs which are amputated through thigh produce more proximally duplicated structure than the limbs amputated through ankle during the stage 30-34 (Niazi et al, 1989).…”

In vivo study of lens regeneration in Rana cyanophlyctis under influence of vitamin A and ascorbic acid

“…Thus, it can be suggested that retinoids play an important role in the transmission of their legends from the cell membrane to the nucleus where the pattern of gene activity may be altered. Whatever, the mechanism adopted, this can be equally applicable to the observations made by Jangir (1980), Jangir and Niazi (1978) and Niazi et al (1985Niazi et al ( , 1989 in limb regeneration of amphibian tadpoles. Vitamin A excess is also found to cause dissolution of cartilage and bone matrix in vivo and in vitro leading to liberation of healthy, dividing and undifferentiated cells.…”

Test of a model for the effects of retinoic acid on urodele limb regeneration

“…The idea that a blastema forms by intercalary regeneration in the anterodorsal quadrant of RA-treated whole limbs can explain a major difference in the response to RA of regenerating anuran limb buds vs. regenerating urodele limb buds and regenerating mature limbs. Systemically administered RA does not evoke transverse duplications on the anterior edge of regenerating urodele limbs and limb buds (Maden, 1982(Maden, , 1983aThoms and Stocum, 1984;Scadding and Maden, 1986) like it does in the regenerating limb buds of anurans treated systemically with retinoids (Maden, 1983b;Niazi et al, 1989). These observations suggest that in the regenerating anuran limb bud, RA posteriorizes only a population of anterior cells, leading to the presence of a second posterior boundary on the anterior edge of the limb bud.…”