Pituitary grafts

Obal F Jr, Kacsoh B, Bredow S, Guha-Thakurta N, Krueger JM. Sleep in rats rendered chronically hyperprolactinemic with anterior pituitary grafts. Brain Res 1997 755 130-136. 

Steger RW, Matt KS, Klemcke HG, Bartke A (1985) Interactions of photoperiod and ectopic pituitary grafts on hypothalamic and pituitary function in male hamsters. Neuroendocrinology 47 89-96. 

Doherty, P C., Bartke, A. Smith, M.S. Davis, S.T. 1985. Increased serum prolactin levels mediate the suppressive effects of ectopic pituitary grafts on copulatory behavior in male rats. Horm. Behav. 19, 111—121. 

STRUCTURE AND FUNCTION OF PITUITARY GRAFTS,RELATED TO THE PROBLEM OF HYPOTHALAMIC CONTROL OF HYPOPHYSEAL ACTIVITY... 

Later, we studied pituitary grafts under the kidney capsule in hypophysectomized rats (Desclin, 1950). In those animals, the genital tract remained atrophic. Injected with oestrogen however. 

But even some points concerning the pituitary graft under the kidney capsule are worth mentionning before we consider the study of the hypothalamic pituitary transplants. 

Some discording results however derive from the study of pituitary grafts in hypophysectomized males which, after a rather long time, are irregularly able to restore normal testicles and spermatogenesis (Cutuly, Courrier and Colonge, Ahren, etc...). 

The actual evidence Is that blastocyst implantation is only possible if some oestrogen has been produced under the influence of the pituitary graft. Electron microscopic studies of pituitary grafts under the kidney capsule show that FSH and LH cells are still present in this tissue (Rennels, Potvliege). The overwhelming dominant type of cells is however the typical prolactin cell. 

In conclusion, we might say that the pituitary graft without contact with the hypothalamus has a very uniform structure and does not, with the usual techniques show basophilic cells, either gonadotrophs or thyrotrophs. When present, these elements are very rare. If some FSH and LH and also TSH is secreted, this is only a residual secretion. This structure is entirely different if the graft is in contact with the median eminence as has been shown in the experiments of Nikitovitch-Winer and Everett. Basophils are numerous under these conditions. 

So we now come to the study of pituitary grafts implanted, not under the median eminence, in contact with the portal vessels, but within the hypothalamus itself. These experiments have been done in my laboratory by J. Flament-Durand. Small pituitaries from 10 days old rats have been implanted with a Krieg-Johnson stereotaxic apparatus into the hypothalamus of adult male and female rats. Some of these rats were hypophysectomized. Various types of experiments have been done to study the types of cells, gonadotrophs, thyrotrophs and prolactin cells, and also to study the physiologic activity of the transplanted gland. 

We should like to mention also briefly our results concerning the luteotrophic activity of the pituitary grafts where we are facing a similar situation. It is well established and we have confirmed that the transplantation of a pituitary under the kidney capsule in a normal female induces a succession of pseudogestations resulting from the continuous production of prolactin released from the transplant. 

Our localization for the LRF and FRF is consistent with the findings that pituitaries grafted to this region retain gonadotrophs (34,35) and that gonadotrophin secretion can continue after isolation of the medial basal tuberal region from the rest of the CNS (36). 

Clifton, K.H. and Crowley, J.J. (1978). Effects of radiation type and dose and the rate of glucocorticoids, gonadectomy, and thyroidectomy in mammary tumor induction in mammotrophic-secreting pituitary tumor-grafted rats, Cancer Res. 38,1507. 

Here again, the pituitary tissue seems to have difficulties in the liberation of its products into the blood. The situation is different as far as the thyrotrophic activity is concerned. Providing that the graft has been located in the thyrotrophic area, thyroid weight and height of the epithelial cells is restored to normal,... 

Residual function of the pituitary in the absence of hypothalamic influence. When the pituitary gland is removed from its normal position and grafted to a distant site, gonadotropin secretion is markedly impaired in agreement with the concept of neuro-... 

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