1006 



SPERM, OVA, AND PREGNANCY 



other hand, hypophysectomy at midpreg- 

 nancy or later does not interfere in the 

 maintenance of gestation in these species 

 (Pencharz and Long, 1933; Selye, Collip 

 and Thompson, 1933a, b; Pencharz and 

 Lyons, 1934 ) . In the dog, ferret, and rabbit, 

 hypophysectomy leads to abortion (Asch- 

 ner, 1912; McPhail, 1935a; White, 1932), 

 whereas the results in the cat seem contra- 

 dictory (Allan and Wiles, 1932; McPhail, 

 1935b) . 



Hypophysectomy of the rhesus monkey 

 does not always interfere with pregnancy. 

 Smith (1954) obtained normal pregnancies 

 in 10 of 20 hypophysectomized rhesus mon- 

 keys. The remaining animals aborted. Al- 

 though more data are needed, it seems that 

 the pituitary gland can be removed very 

 early in gestation without disturbing the 

 pregnancy. Whereas hypophysectomy be- 

 fore midterm invariably leads to abortion 

 or resorption in the rat or mouse, 1 of the 

 4 monkeys hypophysectomized between the 

 29th and 34th day of gestation carried its 

 young to term. Inasmuch as Hartman and 

 Corner (1947) showed that the placenta se- 

 cretes sufficient progesterone by the 25th 

 day of gestation to maintain pregnancy, it 

 is apparent that the placenta in the monkey 

 is able to maintain its endocrine secretory 

 activity independent of the pituitary and 

 at a sufficiently high level to replace the 

 ovary. 



Little, Smith, Jessiman, Selenkow, van't 

 Hoff, Eglin and Moore (1958) reported a 

 successful pregnancy in the 37-year-old 

 woman hypophysectomized the 25th week 

 of pregnancy. The mother w^as maintained 

 on thyroid, cortisone, and pitressin tannate 

 replacement therapy. The excretion of cho- 

 rionic gonadotropin and pregnandiol was 

 not markedly different from that seen in 

 normal gestation. Estrogen excretion was 

 slightly reduced and the 17-hydroxy corti- 

 costeroids dropped to zero when cortisone 

 therapy was discontinued. It would seem 

 that this phase of adrenocortical activity 

 was reduced and that ACTH or corticoid- 

 like substances from the placenta were in- 

 adequate. No interference in aldosterone 

 output was observed. 



Hypophysectomy on the 10th day of 

 gestation in mice terminated the pregnancy 



in only 3 of 19 animals (Gardner and Allen, 

 1942). Sixteen mice carried their litters to 

 term although 7 of the 16 had a difficult 

 and prolonged parturition. Body weight 

 curves were normal and the corpora lutea 

 appeared unaffected by the loss of the pitui- 

 tary gland, indicating either the independ- 

 ence of the corpus luteum or the presence 

 of a placental luteotrophin. Marked involu- 

 tion of the adrenal cortex was noted in all 

 instances. 



Simultaneous measurements of the con- 

 centration of cholesterol in the adrenal 

 gland and ACTH in the pituitary of the rat 

 revealed a drop in adrenal cholesterol and 

 pituitary ACTH on the 15th day of ges- 

 tation (Poulton and Reece, 1957). This was 

 followed by a marked increase of both sub- 

 stances on the 21st day of pregnancy and a 

 sharp drop at parturition. The authors con- 

 cluded that a gradual increase occurs in 

 the secretory activity of the adrenal cortex 

 which reaches a peak on the 15th day of 

 pregnancy in the rat. Thereafter the ac- 

 tivity decreased until parturition when a 

 marked increase was observed. The initial 

 decrease in pituitary ACTH potency fol- 

 lowed by an increase after day 15 is inter- 

 preted as an initial increase in ACTH re- 

 lease followed by a decreased release. The 

 decrease in pituitary ACTH potency at 

 parturition is compatible with the marked 

 increase in adrenocortical activity at this 

 time if the decreased pituitary ACTH ac- 

 tivity is interpreted as indicative of ACTH 

 release. 



Maintenance of pregnancy in rats hy- 

 l')ophysectomized early in pregnancy was 

 obtained with prolactin by Cutuly (1942), 

 although Lyons, Simpson and Evans (1943) 

 reported negative results with a purified 

 prolactin. However, a partial maintenance 

 of pregnancy was obtained with purified 

 prolactin and estrone. 



F. PLACENTA 



The placenta is not only involved in the 

 synthesis of hormones during pregnancy but 

 also in the transfer of substances between 

 mother and fetus. It is obvious that the 

 transfer of substances is limited and the 

 l^lacenta does offer a barrier. This problem 

 bears not onlv on the matter of fetal 



