AMPHIBIAN LIMB REGENERATION
237
effects of hypophysectomy on regeneration. Thus an ectopic pituitary,
implanted successfully to the lower jaw, will support typical limb regeneration in the adult newt (Schotte and Tallon, 1960). Ectopic pituitaries of the land phase red eft will also support regeneration in hypophysectomized aquatic adult newts but the pituitary of the brown eft
(newly metamorphosed land phase) will not (Schotte and Droin, 1965).
These results are correlated with the fact that both aquatic adult and red
eft stages require the adult-type pituitary for limb regeneration but the
brown eft does not. In this respect the brown eft is comparable to the
larval urodele which can regenerate limbs in the total absence of pituitary
hormones (Schotte, 1961; Liversage, 1967). Thus a dependence on pituitary hormones by the urodele regenerating limb develops, not gradually,
but suddenly in the adult stage. The thought has been expressed (Schotte,
1961) that perhaps with the maturation of the pituitary after metamorphosis (cf. Rapola, 1963; Kerr, 1966), dependence on pituitary
hormones is imposed on regenerating limb tissues. However, ectopic
adult pituitary implantation and injections of adrenocorticotropic hormone (ACTH) do not modify the regenerative response of limbs of
Amby stoma larvae either during treatment or after withdrawal of the
pituitary therapy, indicating that larval limb tissues are refractory to
pituitary hormones whether these are in excess or absent (Tassava et al,
1968).
The analysis of the particular pituitary hormone (s) involved in supporting adult, urodele, limb regeneration has been limited to injections of
known pituitary preparations into intact and hypophysectomized adult
newts. Richardson (1945) found that Antuitrin G supported limb regeneration in hypophysectomized newts but that an improvement of
regeneration occurred when Antuitrin G was combined with thyroxin.
Schotte and Chamberlain (1955), on the other hand, obtained good limb
regeneration in hypophysectomized newts with ACTH injections. An
interesting difference to be noted in these studies is that Antuitrin G
enhanced regeneration in intact newts whereas ACTH delayed regeneration in newts with normal pituitaries. Bragdon and Dent (1954), however,
observed no effect on limb regeneration in the intact newt after ACTH
injection.
As the experiments of Richardson (1945) would indicate, pituitary
hormones other than ACTH have been found to be involved in supporting limb regeneration in the newt. Wilkerson (1963), using more refined
growth hormone preparations, found excellent limb regeneration in
hypophysectomized newts after injections of growth hormone (NIH)
237
effects of hypophysectomy on regeneration. Thus an ectopic pituitary,
implanted successfully to the lower jaw, will support typical limb regeneration in the adult newt (Schotte and Tallon, 1960). Ectopic pituitaries of the land phase red eft will also support regeneration in hypophysectomized aquatic adult newts but the pituitary of the brown eft
(newly metamorphosed land phase) will not (Schotte and Droin, 1965).
These results are correlated with the fact that both aquatic adult and red
eft stages require the adult-type pituitary for limb regeneration but the
brown eft does not. In this respect the brown eft is comparable to the
larval urodele which can regenerate limbs in the total absence of pituitary
hormones (Schotte, 1961; Liversage, 1967). Thus a dependence on pituitary hormones by the urodele regenerating limb develops, not gradually,
but suddenly in the adult stage. The thought has been expressed (Schotte,
1961) that perhaps with the maturation of the pituitary after metamorphosis (cf. Rapola, 1963; Kerr, 1966), dependence on pituitary
hormones is imposed on regenerating limb tissues. However, ectopic
adult pituitary implantation and injections of adrenocorticotropic hormone (ACTH) do not modify the regenerative response of limbs of
Amby stoma larvae either during treatment or after withdrawal of the
pituitary therapy, indicating that larval limb tissues are refractory to
pituitary hormones whether these are in excess or absent (Tassava et al,
1968).
The analysis of the particular pituitary hormone (s) involved in supporting adult, urodele, limb regeneration has been limited to injections of
known pituitary preparations into intact and hypophysectomized adult
newts. Richardson (1945) found that Antuitrin G supported limb regeneration in hypophysectomized newts but that an improvement of
regeneration occurred when Antuitrin G was combined with thyroxin.
Schotte and Chamberlain (1955), on the other hand, obtained good limb
regeneration in hypophysectomized newts with ACTH injections. An
interesting difference to be noted in these studies is that Antuitrin G
enhanced regeneration in intact newts whereas ACTH delayed regeneration in newts with normal pituitaries. Bragdon and Dent (1954), however,
observed no effect on limb regeneration in the intact newt after ACTH
injection.
As the experiments of Richardson (1945) would indicate, pituitary
hormones other than ACTH have been found to be involved in supporting limb regeneration in the newt. Wilkerson (1963), using more refined
growth hormone preparations, found excellent limb regeneration in
hypophysectomized newts after injections of growth hormone (NIH)