Effects of Hypophyseal Hormones Upon Amblystoma Larvae,Following Transplantation or Injection,With Special Reference to the Gonads.

Abstract

When the hypophysis of an adult western axolotl is transplanted intact into young larvae of Amblystoma trigrinum, 30-35 mm. in length, the graft usually establishes itself permanently. The results are soon manifested in the following order: (1) the pigmentary system responds by a gradual expansion of the melanophores and an increase in number culminating in sooty blackness; (2) a marked growth stimulation with acromegalic symptoms; (3) a hypertrophic effect upon the immature gonads, which is relatively enormous and occurs without exception in the case of the testis, but is relatively slight and frequently absent in the case of the ovary. There is a tendency to metamorphose earlier than normals reared under identical conditions of environment and nutrition.

The pigmentary reaction begins several days after implantation, and first appears as an intensification of the dark areas in the normal pattern. Soon, however, darkening of the lighter areas begins, and in 2 to 3 weeks a uniform blackness of sooty intensity is attained. This effect is attributable to the hormone produced by the pars intermedia, and is well known from the work of many, among whom may be mentioned Smith and Smith, 1 and Allen. 2 The effect upon growth is seen in a tendency to slightly greater length, greater girth, and a conspicuously enlarged head in which the ratio of width to length is noticeably increased. The growth effect and acromegalic condition are attributed to the hyperstimulative action of the pars anterior. This stimulation of growth is, conversely, to be expected from the work of Allen 3 and Smith, 4 both of whom observed retardation of growth following hypophysectomy in frog tadpoles. Also, Evans and Long 5 produced gigantism in rats by administration of an alkaline extract of the mammalian anterior hypophysis.