Oscar Riddle

A New Hormone of the Anterior Pituitary

Riddle and Braucher 1 showed that the effective stimulus for the enlargement and functioning (formation of “crop-milk”) of the crop-glands of pigeons is a substance derivable from the anterior hypophysis only; and the luteinizing substance derived from pregnant urine is not that substance. They were unable to decide “whether the principle activating the crop-gland is the growth, the sex maturity, or a third and now unknown anterior pituitary hormone.” We have now shown (a) that the principle which evokes the crop-gland response is a third anterior pituitary hormone, and (b) have identified this same hormone, which we shall here call “Prolactin” as the hitherto undefined pituitary principle which is essential for lactation in mammals. To prepare this hormone relatively free from the growth and gonad-stimulating principles frozen anterior pituitaries of beef or sheep were ground, defatted with acetone and alcohol and dried. This powder was extracted 3 times in aqueous medium at a pH of approximately 2.5. The acid extracts were precipitated isoelectrically. The isoelectric precipitate was redissolved and reprecipitated 3 times to free it of maturity hormone and then dried with acetone. About 10% of the original weight of dried powder is thus obtained in an acid-soluble isoelectric-insoluble form. The addition (to suspensions) of 0.2% cresol to complete the destruction of the growth principle does not markedly affect the “Prolactin”. Assays of several of our preparations, and some of the growth and gonad-stimulating extracts of others, have been made on immature common pigeons and ring doves of both sexes. Table I shows only a part of data from male ring doves. The crop-gland response is equally decisive in either species and sex; the gonadstimulating response is more pronounced in males. Neither species has been adequately tested as to its suitability for the assay of the growth hormone; we therefore show here the absence of the “Prolactin” effect from growth hormone preparations of Drs. M. O. Lee and M. K. Schaffer, Boston, who kindly supplied very potent samples assayed on hypophysectomized rats.

Maternal Behavior Induced in Virgin Rats by Prolactin

Summary In virgin rats aged 67-81 days, with ovaries stimulated by Prolan or F.S.H. administration during 5 days, the injection of purified and previously heated prolactin induced maternal behavior in 6 of 10 rats after 6-10 injections. Previous conditioning by concaveation was limited to a single 12-hour period in 4 of these rats. The maternal instinct, in somewhat varying degrees, was exhibited by all these rats while the daily subcutaneous injections were in progress. Six of 7 rats of the control and F.S.H. injected groups, all showing little or no maternal behavior during a 25-day test, later developed or greatly accentuated their maternal behavior after 1 to 8 days treatment with prolactin. Four rats which showed no maternal behavior under prolactin also later failed to show such behavior after repriming and 13 days of administration of unfractionated pituitary extract. Prolactin is the anterior pituitary hormone specifically concerned in the activation of maternal behavior in virgin rats.

Temporary Suppression of Estrous Cycles in the Rat by Prolactin

Conclusions In the regulation of the ovarian activity of rats prolactin is shown to be capable of playing a part, directly or indirectly. Prolactin can not be summarily omitted from lists of pituitary principles having action on the gonads of mammals. The suggestion of Dresel that lactation anestrus in mice is induced by prolactin is supported by these tests on mature non-parous rats. But under effective prolactin dosage the corpora of rats remain large, and at the age of 10-12 days their large cells show no clear evidence of degeneration. The failure of daily injections of low or moderate doses of progesterone to affect the estrous cycles of rats suggests that in this rodent, though the corpus luteum hormone plays its part, it is perhaps not the hormone primarily responsible for the anestrous of either gestation or lactation.

Sex and seasonal differences in weight of liver and spleen

Conclusion (1) Weights of liver and spleen obtained at all months of the year on 499 male and 444 females, healthy, adult ring doves demonstrate that a true sex difference exists. Though the male body weight is slightly larger, the male livers and spleens are smaller, 9.476, and 23.5%, respectively. (2) A true seasonal increase in size of liver and spleen occurs in spring and summer in both sexes (10.4% and 12.0% in 8; 6.1% and 4.3% in 9 9). (3) These changes in spleen and liver are positively correlated with size changes in testis and ovary; and negatively correlated with size changes in the thyroids of these animals.

Stimulation of adrenal cortex of pigeons by ant. pituitary hormones and by their secondary products

Summary Increase of weight in the adrenals of the normal immature (1.9 mo.) pigeon, and degree of maintenance of adrenal weight during 10 days following hypophysectomy in the pigeon, and also cytological evidence of stimulation in their cortical cells, are found to agree satisfactorily with Moons method of assay of adrenocorticotropin in 21-day rats. As tested by these 3 methods the ability of pituitary extracts to stimulate cortical tissue is independent of their prolactin, FSH and thyrotropin potencies. Gamone stimulates both cortical and medullary tissue in both normal and hypophysectomized pigeons. Estrone stimulates cortical tissue at least in intact birds. Thyroxine, plus vitamin supplements, gave evidence of ability to stimulate cortical tissue in hypophysectomized pigeons.

A STUDY OF FUNDAMENTAL BARS IN FEATHERS

The structure and development of feathers have been studied by many investigators. The pigments of feathers have also been the subject of a very great number of researches. In spite, however, of these numerous studies of feather structures and pigments, we know almost nothing of structural differences be tween pigmented and non-pigmented areas, and nothing at all of the causes which lead to the orderly and definite distribution of pigment into the often complex color-patterns commonly found in birds. In connection with a research directed to these two points it was thought advisable to make a study of certain defects which were known to appear occasionally in feathers. It is a preliminary account of my results in this more restricted field —? which, however, proved to be a rather significant one —? that is to be found in this paper. The work was undertaken in

Evidence from Dwarf Mice Against the Individuality of Growth Hormone

Summary Prolactin alone, desiccated thyroid alone, or thyreotropic hormone probably unaffected by any contaminating constituent of the preparations used by us, promotes growth in the dwarf mouse. In these mice prolactin and thyreotropic show a synergistic action (32 to 242×) upon body growth. Though the concept of a growth hormone as an individual entity has been useful it does not seem to be true.

Secretion of Crop-Milk in the Castrate Male Pigeon

Riddle and Braucher 1 showed that the cyclical extreme enlargement of two areas of the crop wall, and the resulting crop-milk formation—both well known to occur at or near the end of the brooding period in pigeons—are under control of a hormone of the anterior pituitary. Only anterior pituitary tissue or extracts were found capable of initiating these processes, but with such tissue or extracts these phenomena could be produced in birds of both sexes and at all ages. While unaware of the results of Riddle and Braucher a report was later published by Kaufman and Dabrowska 2 in which the conclusion is drawn that the hormone of the testis is necessary for the normal cyclical functioning of the cropgland in the male pigeon. Kaufman and Dabrowska castrated a male pigeon which had previously secured a female mate within a group of pigeons. After the male was castrated he ceased to copulate and express ardor, but nevertheless still maintained a special interest in his former mate. This female mate continued to lay fertile eggs—thus showing that another male (or other males) were copulating with her, and was wholly or in part stimulating the growth and ovulation of the eggs which she laid. It would therefore be a matter of much surprise if the castrate male began to incubate at the time this female laid eggs; for, even an unmutilated male pigeon who has been solely responsible for stimulating egg production in his mate is sometimes 2 to 5 days out of syncrony 3 with his mate in the impulse to begin to brood or sit; again, apparently normal males sometimes brood for a few days only and fail to complete the cycle. Indeed, it is of much interest that a castrate pigeon will incubate at all, and (though apparently unaware of this) Kaufman and Dabrowska have observed what seems to be the first recorded case.

On the Protein Nature of Prolactin and of Follicle-Stimulating Hormones:

Summary Prolactin is a protein-like substance which at pH 8.0 is almost completely destroyed by trypsin in 2 hours at 37°C. In confirmation of previous work though using the bird testis instead of the rodent ovary to test potency, it is found that the follicle-stimulating hormone obtained from the anterior pituitaries of cattle is very rapidly destroyed by trypsin under the above-named conditions. The methods used in the separation and purification of prolactin suggest that this hormone is a protein, but since it has not yet been obtained in a pure state the possibility of its adsorption on inert protein is not thus excluded. It is therefore desirable to learn whether prolactin is affected by tryptic digestion. That prolactin is rapidly destroyed by trypsin is shown by the data of Table I. Almost complete destruction in 2 hours by a purified trypsin is obtained. The prolactin preparation used in this test was relatively pure and highly potent. Both the control and digest were, at the beginning of the test, at pH 8.0 and were similarly kept at 37°C. At pH 8.0 we have repeatedly found that prolactin will withstand boiling for 1 hour with only slight or moderate loss of potency. No earlier observations on the effect of digestive enzymes on prolactin have been reported. The rapid destruction of follicle-stimulating hormone (F.S.H.), obtained from the anterior pituitaries of beef by methods previously described, 1 is shown by the data of Table II. The testes of both birds given F.S.H., heated at pH 8.0 but not subjected to trypsin, are indicated as having increased by something more than 500%. The testes of all of the 4 birds receiving the trypsin digest (birds I and J got double dosage) showed only or relatively insignificant gains in weight. Since size increase in testes of the immature dove represents a specific response to the F.S.H. (here the weight is not increased by a Prolan B factor) this result has definite significance. Under these conditions still other relatively pure preparations of F.S.H. have been shown to withstand heating to 37° for 2 and for 4 hours with little loss of potency. A quite different test for F.S.H. potency has been used in another study; that test likewise shows that trypsin rapidly destroys the F.S.H. derived from both pituitary and pregnant urine.

Effects of Prolactin and Cortical Hormones on Body Weight and Food Intake of Adrenalectomized Pigeons

Summary Adrenalectomized young Carneau pigeons fed 1.75 g of a salt mixture daily showed an average period of survival of 9 days. Such pigeons eat little food and lose weight. Prolactin induced more than normal gains in body weight when adrenal insufficiency was not acute and restored food intake to a level almost equal to that of unoperated birds. Either adrenal cortical extract or desoxycorticosterone acetate maintained life in adrenalectomized pigeons. Daily doses of 2 mg of desoxycorticosterone acetate fully restored the rate of increase of body weight and the daily food consumption to levels characteristic of normal unoperated pigeons. A group of birds given high dosage of both prolactin and adrenal cortical extract showed more rapid gains in body weight and larger food intake than has ever been observed in normal unoperated pigeons of the age used here.