Ectopic Grafts Research Articles

Structural and functional relationships of grafted vasopressin neurons

Fetal vasopressin neurons were grafted into adult Long-Evans rats with vasopressin deficiencies created by neural lobe ablation one week prior to implantation. Control animals and recipients with ectopic grafts still possessed significant deficits in fluid regulation 6 weeks following implantation. However, recipients with grafts fused to the host median eminence and containing magnocellular vasopressin neurons juxtaposed to the host portal vasculature showed restored peripheral vasopressin activity as measured by normal urine volumes and osmolalities. These findings suggest that structural integration of grafted neuroendocrine tissue with the appropriate target in the host brain is a necessary prerequisite for physiological activity.

Comparison of haemopoiesis in young and old mice

Haemopoietic status and functions have been compared in young (2–3-month-old) and old (2–2.5-year-old) BDF 1 mice. The parameters measured include total marrow cellularity, CFU-S, CFU-mix, GM-CFC, BFU-E and CFU-F. In all cases the numbers of these cells in the femoral marrow of the old mice was equal to or greater than those in the femoral marrow of young mice. In addition to these parameters we have compared the ability of marrow from young and old mice to (1) repopulate the marrow of recipient mice whose marrow had been eliminated by radiation; (2) to grow in long-term bone marrow cultures; (3) to produce ectopic grafts of marrow beneath the renal capsule of normal recipients; and (4) to supply inhibitor and stimulator of stem cell proliferation in the marrow and to resynthesise these substances. We could detect no differences in any of these functions with the exception of that of resynthesis of the stem cell regulator substances, which appears to be somewhat slower in the old mice. This, however, does not impose any limitation upon the ability of the marrow to function either under normal conditions or in conditions requiring rapid proliferation. Therefore we can find no evidence whatsoever to suggest that aging of the haemopoietic system plays any part in aging of the individual or influencing the life-span.

Recruitment of cytotoxic cells by ectopic grafts of xenogeneic, but not allogeneic, trophoblast.

In previous studies we showed that survival of Mus caroli embryos in the Mus musculus uterus was dependent on trophoblast genotype; M musculus trophoblast was protective while M caroli trophoblast was not. In this report we compare the immune response of M musculus to ectopic grafts of pure trophoblast of M caroli and M musculus genotypes to elucidate further differences between the properties of trophoblast from the two species that might account for the failure of M caroli trophoblast to protect the fetus. Grafts of M caroli or DBA/2J ectoplacental cone (EPC) or embryonic tissue (E) were placed beneath the renal capsule of Ha(ICR) mice that were untreated or had been immunized with M caroli lymphocytes or with P815 mastocytoma cells. No consistent morphological difference could be demonstrated between the xenografts and allografts by gross or histological examination. Cellular infiltration of allogeneic and xenogeneic EPC graft sites occurred in immunized mice within 5 days of grafting. Cells specifically cytotoxic to M caroli lymphoblasts were isolated from the xenogeneic graft sites, but no allogeneically sensitized cytotoxic cells could be demonstrated. These results show that xenoantigens expressed on trophoblast induce a cytotoxic immune response more readily than alloantigens.

Tissue differentiation in ectopic grafts after cultivation of rat embryonic shieldsin vitro

ABSTRACTDifferentiation of rat embryonic shields in vitro is inferior to that obtained in grafts under the kidney capsule. To see whether the in vitro differentiation is stable or whether it can be improved in a better environment, rat embryonic shields, isolated on gestation days 8 and 9, were transplanted under the kidney capsule after a period of 7 or 14 days in vitro.After transfer, some tissues appear in the kidney that never appear in vitro. Many but not all tissues appear more frequently in grafts than in vitro. Most tissues differentiate further in grafts than in vitro, though skeletal muscle, when cultivated for 14 days before transplantation, is an exception.Thus the effect on differentiation of imperfect culture conditions can be counteracted, for some tissues but not all, by grafting to the kidney. The effect depends partly on the time spent in vitro before transfer.

Central neurotransmitters and control of prolactin secretion

Despite extensive study during the last 10 years, several aspects of the neural control of prolactin secretion are still unelucidated. In mammals, the most important feature of this control is the existence of a predominant inhibitory regulation, as demonstrated by a number of older experiments involving hypothalamo-hypophyseal deconnexion, interruption of the portal circulation, ectopic grafts of the pituitary, as well as in vitro incubations of adenohypophyseal tissue (see review in Meites and Nicoll, 1966 and Pasteels, 1967). Under all these conditions, elimination of hypothalamic influences induces a remarkable stimulation of prolactin secretion. This powerful repressor effect of the hypothalamus often masked more limited stimulatory effects, which, nevertheless, can be expressed under certain physiological or experimental conditions. In other species like birds (Kragt and Meites, 1965 ; Gourdji and TixierVidal, 1966), such stimulatory effects even appear more important than the inhibitory component of the regulation. The complexity of mechanisms regulating prolactin release reflects the large variety of physiological situations in which changes in prolactin levels can be observed (stages of the estrous cycle, pregnancy, lactation, stress etc.). A variety of inputs may thus result in elevated prolactin production. In the present paper, we will attempt to describe some of the neural factors which modulate the release of prolactin, focussing

Function and cytology of the normal and autotransplanted pars distalis of the hypophysis in the toad Bufo bufo (L)

The functional activity of the pars distalis following heterotopic and homoiotopic autotransplantation has been studied in adult toads of both sexes in the spring, about a month after breeding, and in the autumn on toads with mature gonads. Gonadotropic Function. In males, the homoiotopic grafting of the pars distalis maintained about normal spermatogenesis and interstitial cell activity, but ectopic transplants caused a strong reduction of interstitial cell activity, though spermatogenesis was only slightly reduced. In the spring experiment, there was no significant difference in the ovaries of the two graft-bearing groups, which were intermediate between the normal and the hypophysectomized controls. In autumn females, however, the ovaries of 5 of 8 toads with homoiotopic grafts atrophied, as in the hypophysectomized controls. The 3 remaining toads had ovaries of nearly normal size filled with mature eggs, but there were strong indications that in these 3 toads also the mature eggs that were present at the time of operation degenerated immediately after the operation, and was followed by a phase of extensive growth and maturation of small oocytes during the 2 months of the experiment. All females with ectopic grafts had atrophic ovaries at the end of the experiment. Adrenocorticotropic Function. This function was normal in the toads with homoiotopic grafts. No corticotropic function could be demonstrated in the ectopic grafts although the cytological study of males in the spring experiment showed that, in general, the adrenocortical cells in the toads bearing ectopic grafts appeared more active than those in the hypophysectomized controls. Thyrotropic Function. Thyroidal uptake of 131I in the autumn experiment was used to evaluate thyrotropic function. Uptake was normal in toads with homoiotopic grafts, but reduced in the toads with ectopic grafts. In the males with ectopic grafts, the 131I accumulation in the thyroids was not significantly higher than in the thyroids of the hypophysectomized controls. Fat Bodies. In the autumn experiment, feeding was insufficient to maintain body weight, and the fat bodies were greatly reduced in both normal controls and in the toads with homoiotopic grafts. Hypophysectomized controls, however, possessed large fat bodies despite an even greater loss of body weight. In the toads with ectopic grafts, net mobilization of fat from the fat bodies was intermediate between the normal and hypophysectomized controls. In the spring experiment, feeding was efficient. All groups increased in weight, and all showed fat deposition. Cytology of Pars Distalis. Four of the five tinctorial cell types, described for the pars distalis of Bufo bufo, were observed: carminophils, orangeophils, globular basophils, and violet cells. In most of the controls the carminophils and orangeophils were storing secretory granules; the globular basophils and the violet cells showed signs of secretory activity. All four cell types remained largely unchanged in the area of the homoiotopic grafts, bordering the median eminence and pars intermedia. In the rest of such grafts and in the heterotopic transplants cysts were formed, and degeneration and dedifferentiation of cells took place; carminophils and orangeophils had slightly degranulated, globular basophils had become strongly regressed in number and granulation, and violet cells had almost completely disappeared. Generally, there existed a close correlation between the state of the target organs and the morphological signs of secretory activity of the pars distalis cells. It is suggested that not only the globular basophils, but also the violet cells have a gonadotropic function, and are responsible for the development and maintenance of the interstitial Leydig cells in the testis.

PERMANENT ISOLATION OF THE ADENOHYPOPHYSIS FROM HYPOTHALAMIC CONTROL IN RATS WITH DIABETES INSIPIDUS.

SUMMARY Electrolytic lesions in the posterior part of the median eminence of rats caused diabetes insipidus, and aldehyde-fuchsin-positive material disappeared from the infundibular process but not from the hypothalamus. The lesions were consistently followed by infarction of the central pars distalis and depression of the thyroid uptake of radioactive iodine, but the effects on the gonads and adrenal cortex were very variable. Chronic adrenal atrophy occurred in some females in association with recurrent pseudopregnancy, atrophic but hyperluteinized ovaries, and cytological changes in the pituitary similar to those in ectopic grafts. After a short post-operative period of pseudopregnancy other rats recovered normal cycles and had, in general, adrenals of normal weight; their pituitaries resembled ectopic grafts returned to the median eminence. It is suggested that the difference between the two groups of rats with chronic lesions depended on the permanence or otherwise of the damage to the long portal veins. No evidence could be found of a separate corticotrophin-releasing mechanism in the median eminence, nor of any dependence of the secretion of corticotrophin on the release of vasopressin.