Abstract
Two principal conditions favor uterine growth, (1) hormonal, such as occurs in the presence of oestrone 1 and progesterone, 2 and (2) local, such as is observed in the gravid horn of a unilateral pregnancy. The growth of such a cornu is much greater than that which takes place in the non-gravid horn exposed to the identical hormonal environment. 3 The difference has been ascribed to the presence of the fetuses. Local uterine growth is also observed when, during pseudopregnancy, a uterine cornu is distended with rolled rubber dam. 4 Thus the 2 growth factors may be said to be essentially hormonal and physical. The present note is concerned with experiments in which an isolation of these factors is achieved, and uterine growth induced by physical factors alone in the absence of ovarian hormonal influence.
The procedure is as follows: mature rabbits are ovariectomized at the end of a week of pseudopregnancy, at which time the uteri of the various animals are in comparable structural states. After one week of castration paraffin pellets (m.p. 54°) of 2 sizes (1/8“ and 1/4” diameter, respectively, and 1/2-3/4“ in length) are inserted per vaginam into a uterine horn and anchored there by a loose stitch at each end of the pellet. Control sections of uterine tissue are distended, excised and fixed in formol-acetic fixative solution.
In each of 11 experiments it has been found that, in the absence of ovarian hormonal influences, marked uterine enlargement occurs. The muscle cells undergo hypertrophy, connective tissue increases and dilatation of the small vessels takes place. The endometrium, after 2 weeks of chronic distension, is in a state of active proliferation but contains no secreting cells. These changes take place concurrently with some atrophy in non-distended portions of the same uterus.
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