John Ball

Functional capacity of ectopic pituitary transplants in the teleost Poecilia formosa, with a comparative discussion on the transplanted pituitary

The capacity of the pars distalis to secrete its hormones when removed from connexions with the hypothalamus has been assessed in the teleost Poecilia formosa. Mortality, integumentary characters, body growth, fin regeneration, freshwater adaptation, liver reserves, fat stores, haematology, and the histology of the thyroid gland, interrenal tissue and ovary, have been studied in intact fish, in hypophysectomized fish, and in hypophysectomized fish bearing a pituitary homotransplant in the musculature of the caudal peduncle. Growth, fin regeneration, liver reserves, fat stores, interrenal and ovary, have been studied also in sham-hypophysectomized fish. It is concluded that the ectopic pituitary transplant in this fish secretes thyrotrophin (TSH) at a higher rate than normal, adrenocorticotrophin (. at a subnormal rate, and growth hormone (GH) only in very small amounts. The transplant secretes the prolactin-like hormone essential for freshwater adaptation, but does not secrete gonadotrophin. The extensive literature on the ectopic pituitary has been surveyed, and the present results were compared with those obtained for other vertebrate groups. The hypothalamic influence on TSH secretion in Poecilia appears to be inhibitory, in contrast to the stimulatory relationship in mammals, and the pituitary of this teleost seems to have greater autonomy in the secretion of ACTH than the mammalian gland. The hypothalamic control of GH, prolactin and gonadotrophin, however, is probably essentially the same in Poecilia as in mammals.

Identification of ACTH cells in the pituitary of two teleosts, Poecilia latipinna and Anguilla anguilla: Correlated changes in the interrenal and in the pars distalis resulting from administration of metopirone (SU 4885)

Abstract The adrenocortical inhibitor SU 4885 (metopirone, Ciba) was administered to intact and hypophysectomized Poecilia latipinna and Anguilla anguilla. In both species the drug produced hypertrophic and hyperplastic changes in the interrenal tissue, and these changes were entirely (Poecilia) or largely (Anguilla) dependent on the presence of the pituitary gland; this, and other evidence, indicated that the drug induced a hypersecretion of ACTH by the pituitary. The stimulation of the interrenal tissue in intact fishes was paralled by hyperactive changes in one cell-type in the rostral pars distalis of the pituitary. It is concluded that this cell-type, the epsilon cell, secretes ACTH in these teleosts.

Investigations on hypothalamic control of adenohypophysial functions in teleost fishes

Abstract Various kinds of evidence for hypothalamic influences on teleost adenohypophysial functions are reviewed. Discordancies amongst the results available appear to spring from the different investigative techniques employed, and from differences among teleost species. Until the isolation of specific chemical entities, the terms “hypothalamic factor” or “hypothalamic hormone,” borrowed from mammalian literature, must be regarded simply as convenient ways of referring to hypothalamic mechanisms or influences inferred from experimental results. Within these limits, and bearing in mind the small number of species studied, we conclude that for certain species there is strong evidence for a thyrotropin-inhibitory factor and a gonadotropin-releasing factor; that there is fairly strong evidence for a corticotropin-releasing factor and a somatotropin-releasing factor; that there is evidence for both a releasing factor and an inhibiting factor for melanophore-stimulating hormone; that there appears to be a releasing factor controlling the pars intermedia PAS-positive cells of uncertain function; and that the existence of a prolactin-inhibiting factor is probable but not certain.

Histological study of functional ectopic pituitary transplants in a teleost fish (Poecilia formosa)

The histological study of the homotransplanted pituitary of Poecilia formosa, grafted for 7 weeks in fish that were hypophysectomized 3 weeks after the transplantation, revealed considerable variation in the size and cellular composition of the grafts. However, certain general conclusions were drawn from the study. Apart from one graft that was infiltrated with connective tissue, eta cells (secreting the teleostean prolactin-like hormone) are invariably present. These cells remain chromophilic with an active appearance, and they appear to ensure the survival in fresh water of the grafted-hypophysectomized fish and to assist in the maintenance of the normal appearance of the skin. Growth hormone (alpha) cells are found rarely in the grafts and in feeble numbers, despite evidence of a limited secretion of growth hormone. Corticotrophs (epsilon) Cells are almost always to be found, though their appearance of activity varies from graft to graft; they are usually associated with the maintenance of a slightly stimulated interrenal, and with the maintenance of normal blood cell counts. Thyrotrophs (delta) Cells are among the most active-looking cells in the grafts, and do not appear to be dependent on hypothalamic stimulation for the secretion of large amounts of TSH, which maintained normal thyroid histology and provoked hyperplasia of the thyroid in several cases. In contrast to the above cells, the gonadotrophs in the grafts are regressed and no longer able to stimulate the ovary; a hypothalamic factor appears to be essential for the maintenance of structure and function in these cells. The pars intermedia and neurohypophysis, intimately associated in teleosts, simultaneously undergo a marked involution accompanied by the disappearance of typical neurosecretory material. The identification of the various cell-types in the grafts is generally more difficult than in the normal pituitary, but is nevertheless possible, most easily in those grafts which retain a general structure comparable to that of the normal gland. These findings have been compared with those obtained in the higher vertebrates.

Use of Sumner Lines in Navigation

MAY I venture to point out, in the interests of navigational science, that although the article by Capt. Tizard in NATURE of July 1 under the above title is an admirably clear and concise account of the application of Sumner lines in navigation at the date given in his examples, it is scarcely descriptive of the best practice of to-day?

Distance of the Visible Horizon

THE subject of terrestrial refraction and its effect on the distance of the visible horizon, about which Mr. Backhouse inquires in NATURE of September 25, is very fully discussed in the second volume of Jordans “Handbuch der Vermessungskunde.” The formula there proved is where a=distance of visible horizon. r=earths radius. k=coefficient of refraction (mean value 0.13). h=height of observer. This formula reduces to Distance in statute miles=1.312√height in feet.

Dana's Proof of Darwin's Theory of Coral Reefs

I THINK Mr. Crossland, in his letter to NATURE of April 3, is in assigning a fault origin to the narrow “khors” which form the harbours along the Rea Sea coast. I visited a number of these during a land journey from Halaib to Port Sudan in 1908, and although I had not much time for detailed investigation, I saw nothing which pointed to any other origin than erosion and subsidence. The steep-sided character of the shallow valleys, which Mr. Crossland takes as indicative of a fault origin, is, I think, merely a consequence of the toughness of the coral-rock and the smallness of the rainfall in these regions. It is a character common to many inland “wadis” where there is no suspicion of rift action.

The Chance of Survival of New Varieties

AN argument first urged by the writer of an article on the “Origin of Species” in the North British Review for June 1867, regarding the probability of the preservation of a new modification or variety among the descendants of a plant or animal, has of late attracted much attention. It has been discussed at length by Mr. Mivart, one of the ablest critics of the Darwinian theory, and Mr. Darwin himself has, with characteristic candour, ascribed great, and as I believe undue, importance to the inferences drawn from it.

The Temperature of the Sun

HAVING been absent from home I have but just seen Mr. Ericssons article on the “Temperature of the Sun” in NATURE, (NO. 1O1, p. 449. All who feel an interest in the subject must be indebted to Mr. Ericsson for the experimental evidence which he has contributed to the investigation, and for such further light as his ingenuity will doubtless enable him to throw upon it; but few, I think, will be inclined to admit that the reasoning advanced in his recent article justifies in any degree the inferences which he has there drawn.