Search

Insulin-like growth factor-1 could be a useful marker in the horse for diagnostic, selection, or forensic purposes, provided its physiological regulation is well understood. The objective of this study was to investigate factors, such as acute exercise, fitness training, time of day, sex, and age, that may influence serum IGF-1 in normal, healthy horses. Throughout a 9-wk training program, 6 geldings maintained a mean ( ± SEM) IGF-1 concentration of 302 ± 29 ng/mL. Moderate or high intensity exercise had no effect on IGF-1 concentrations, when pre- and postexercise values were compared. Over a 24-h period, there was some variation in IGF-1 concentrations but no clear diurnal rhythm. Concentrations of IGF-1 were measured in a large population of thoroughbred horses (1,880) on 3 continents. The population deviated slightly from a normal distribution (P< 0.001) because of large IGF-1 concentrations in 10 horses. The global mean IGF-1 concentration was 310 ± 2.2 ng/mL, with a greater mean value (P< 0.001) in gonad-intact males (336 ± 5.6 ng/mL) than in females (303 ± 3.2 ng/mL) or geldings (302 ± 3.2 ng/mL). However, the greatest IGF-1 concentrations observed for all stallions, mares, and geldings were 627, 676, and 709 ng/mL, respectively. In mares and geldings, IGF-1 concentrations showed a gradual decrease with advancing age (P< 0.001), but the effect was much less marked in stallions. This study confirms that IGF-1 concentrations are stable, compared with GH concentrations, in the horse and that a meaningful measure of IGF-1 status can be obtained from a daily serum sample.

There has been an evolution of the social organization of vertebrates from fish to man. Nevertheless, throughout this series the same components of social behavior may be recognized: (1) group attraction, (2) dominance behavior, (3) parental behavior and (4) suggestion. An improvement in the social organization has included: (1) a change from inborn species attraction to a learned group attraction, (2) from a dominance behavior, recognizing only the individual, to one recognizing groups, and (3) from a subordinate, that considers the dominant individual only as a despot, to one that considers the latter a protector and guide. At the fish level the mood of a member of a social group may be quickly transmitted by the character of the individual's movement to other members of the group. Among higher vertebrates these movements are supplemented by vocal expressions which have specific effects upon the behavior of individuals in the group. In the absence of the forebrain, no social behavior is complete in any vertebrate. Forebrain mechanisms essential for social behavior have shifted from the corpus striatum of fish and birds to the cortex of mammals. The elaboration of the cortex in the higher primates is correlated with an increase in the importance of tradition and insight in regulating social behavior.

Testosterone propionate, introduced in pellet form into intact, castrated or partially hypophysectomized immature male Anolis carolinensis, elicits both male and female sexual behavior, the latter including submission to copulation and display of a distinctive neck reflex. Testosterone-treated males fight more actively than controls, and the assumption of male or female behavior is apparently related to position as dominant or subordinate in fights among the group. Testosterone affects the reflexes involved in the copulation posture so that they are maintained in exaggerated form after the escape of the partner.

In 1926 de Beaumont showed that some of the secondary sexual characters of the male newt, Triturus cristatus, could be produced in the spayed female by testicular transplants. About the same time one of us (Noble, 1926) noted that cloacal glands could be made to arise de novo in the glandless cloaca of the female Desmognathus fuscus fuscus by the same method. Ponse (1923) with young females, and Welti (1925) with adult females, had previously demonstrated that toads which had been experimentally masculinised would develop nuptial pads. The above investigations were of interest in that they demonstrated, in both Caudata and Salientia, that structures not visible even as rudiments in the female could be made to appear and develop under the influence of the male sex gland.

A marked change in coloration occurs at the time of metamorphosis in most salamanders. We have obtained evidence that this change is not produced by the thyroid hormone in the case of red pigment formation. Thyroidectomized larvae of Hemidactylium scutatumwill assume the red coloration of the adult although they do not metamorphose.1Larvae of the red salamander Pseudotriton ruberwhen precociously metamorphosed with thyroid extracts are yellow and not red. Since the anterior pituitary is known to play a part in normal metamorphosis we have tested the effect of anterior pituitary implants upon red salamanders which have been precociously metamorphosed with thyroid solutions.Fifty larvae of Pseudotriton ruber, 30 to SO mm. in length, were metamorphosed in a solution of 1:15,000 desiccated thyroid. Before transformation was completed 7 of the largest specimens of the same size (Group A) were selected and each of 4 given subcutaneous implants of 2 pars anterior of toad pituitary. Three specimens received muscle, to serve as controls. The gland material was taken from freshly killed adult Bufo fowlerii, and given at regular intervals, 3 times a week. The salamanders, throughout the experiment, were kept without food, in separate dishes, at room temperature, with just enough spring water in the dish to keep the surfaces moist.A few days later 5 fully metamorphosed salamanders of the series (Group B) were implanted in the same manner, 3 serving as experimental, 2 as control animals. At the same time 9 more specimens (Group C), also completely transformed, were implanted, but on a different schedule. The 5 experimentals were implanted twice a week, with 3 pars anterior each, the 4 controls with muscle. A fourth group (D), of 4 specimens, completely transformed, received implants of pars intermedia plus pars posterior.

Testosterone propionate enlarges the Müllerian duct, keratinizes the cloaca and produces estrous behavior in Anolis.It also enlarges the epididymis, ductus deferens and sexual segment of the kidney, while producing male sex behavior. It has a gonado-tropic effect on the ovary but not on the testis.

A prolactin-like reaction is produced by implantations of hypophyses of animals representative of the main classes of vertebrates, also with livers of all submammalian classes. That this reaction implies the presence of the lactogenic hormone may be doubted because of the absence of fat granules in the proliferations.

AS I have been both misquoted and misrepresented by Prof. MacBride in a recent letter to NATURE (August 21, p. 264), I may be permitted to say a word in my own defence. My remarks on Kammerer's Alytes at the British Association were to the effect that the sections sent by Dr. Kammerer to America showed only asperities, not distinctive glands characteristic of the nuptial pads of other Salientia. The glands in his sections of the controls were the same size as those in his experimentals. Asperities may be formed on different parts of the body in one or both sexes of different species of frogs, and in some cases are apparently not correlated with a sex hormone. In the case of Kammerer's results, the question concerned the inheritance of spines, not of complete pads. Prof. MacBride seems to believe there has been some confusion in my mind on this subject.