Infundibular Lesions Research Articles

Developmental Relationship Between Pars Intermedia of Pituitary and Brain in Tadpoles

An inhibitory control of the growth and functional activity of the pars intermedia of the hypophysis of the tadpole through the in-fundibulum has been suggested by the author to account for the finding of overgrowth and excess activity of this gland in grafts, and after infundibular lesion. In his careful work with pituitary grafts in the salamander, however, Blount reported an intensity of pigmentation only in proportion to the number of grafts and no overgrowth in the grafts. Since in Blount's work successful grafts were secured only when brain was transplanted with the gland, whereas in this author's work with tadpoles the graft took successfully independently of the presence of brain it was thought that the circumstance of the presence of brain with the primordial graft might account for the difference in the characteristic growth picture of the graft in these two cases. This theory would be consistent with the first mentioned hypothesis of inhibitory control of the p. intermedia through the infundibulum. To test this, a series of grafts of the pituitary was made with and without brain. The experiment was performed on Rana pipiens tadpoles. The hosts were tadpoles which had been hypophysectomized in the tail-bud stage and used when about 12 mm total length. Only silver (successfully hypophysectomized) animals were used. The site for the implant was prepared by removing the eyeball through a slit in the dorsal skin, thus leaving a relatively large pocket for the reception of the graft. The grafts were taken from tail-bud embryos. In one series the pituitary primordium with as little adherent tissue as possible was used, and in the second series a variable amount of adjacent brain material was included with each graft.

Infundibular Lesion and Pars Intermedia Activity in the Tadpole

Vunder1 reported that the transplantation of a single hypophysis into an hypophysectomized Axolotl led to an excessive development of pigmentation. He ascribed this result to traumatic stimulation in the operation and supported his view by showing that the same result followed pricking the gland with a needle. In connection with the development of anterior lobe function in the tadpole, one of us2 has confirmed and extended Vunder's findings. His interpretation, however, seemed unacceptable since it was there found that transplantation of even primordia into the embryo led to the development of the pigmentation weeks later and also because the effect often persisted as long as the animal could be kept, in many cases over 4 months. In a brief report of some of this material3 it was suggested that the pituitary is under some restraint in its normal site, from which it is released on transplantation. It was further suggested that the source of this inhibition might be the nerve tract from the hypothalamus to ...