P. W. Gregory

The Relation of Sulphydryl Concentration to Size Inheritance in the Rabbit

head, thorax and abdomen are absent, except that their basal rings remain. The fourth and fifth veins are sharply cut before they reach the wing margin. Often the second and sometimes the third wing veins fail to reach the margin. Triploicds furnish an intermediate step between the wild type and the heterozygous Hairless diploids. They also give a form beyond the heterozygous Hairless diploid. The reaction of the host to its gene content advances by steps determined by the balance between the wild type factor, +, and the Hairless, factor, H. In each step the effects of the Hairless factor have been extended to other structures than those which the lower genic balance affected. The graded nature of the series gives the basis for the hypothesis that when the balance becomes greatly altered the developmental effects are extended still further to eliminate or lethally alter vital structures. Mangelsdorf and Fraps2 have shown a similar graded effect of the factor for vitamin A content of corn endosperm. The endosperm cells are triploid and may be white, y y y, pale yellow, y y Y, medium yellow, y Y Y, or dark yellow, Y Y Y, in their appearance and genetic constitution. The step alteration in balance brought about by the addition of one yellow gene, Y, and the consequent subtraction of one white gene, y, results in a uniform unit increase of the vitamin A content of the grain. It is impossible to say what the quantitative effect of removing a bristle may be, but qualitatively the different grades of hairlessness produced by different ratios of the allelomorphs H and + in the Hairless locus are certainly in accord with the view that these genes act like those in the yellow locus of corn.

Glutathione concentration of livers and muscles of rats following injection of hypophyseal growth hormone.

We have previously reported 1 that there is an increase in concentration of glutathione in muscles of mature rats after 15 daily injections of a potent growth hormone obtained by alkaline extraction of beef pituitary. In control animals similarly treated with a heat inactivated solution of the hormone we found no such change. Analyses of the livers showed no significant change. However, if animals were sacrificed a few hours after a single injection of the potent hormone we found a decided fall in the glutathione concentration of the liver with only a slight change, if any, in the muscle glutathione. We have no explanation to offer for this sudden change in the liver but believe that it may furnish a method for estimation of the potency of the growth hormone that is more rapid than the usual method by measuring growth after 20 days of injection. It may prove to have a more important significance since by its use the fundamental biochemical reactions induced by the growth hormone may be studied quantitatively and thus it may be possible to obtain additional information concerning the chemical reactions involved in the synthesis of tissues. Mature female rats which had reached growth stasis normally were used. They were divided into 2 groups matched for weight. One group, the experimental, received a single injection of a growth hormone solution prepared according to the method of Evans. 2 In a previous trial daily injections of 1 cc. of this solution had induced an average growth of 50 gm. in 15 days in mature female rats. The control group received the same amount of the heat inactivated hormone. Both groups were injected then allowed to fast for periods varying from 8 hours to 24 hours, when they were killed.

Chemical and hematological studies on blood of bovine dwarfs.

Summary 1. Serum proteins, calcium, magnesium, and phosphorus of “short-headed” bovine dwarfs are all within normal limits. 2. Serum cholesterol and protein-bound iodine levels are within the normal range and indicate that the “short-headed” bovine dwarf is not a primary thyroid cretin. 3. All hematological values appear normal except for the differential count. Deviations from the normal are discussed.

Responses of the Snell dwarf mouse to pituitary tissue from a bovine dwarf mutant.

Summary Dwarf mice (Snell) from A dw (Albino-dwarf) stock, in which the thyroid-pituitary axis is abnormal, were injected with pituitary tissue extract from the achondroplastic brachycephalic bovine dwarf mutant, which suffers from achondroplasia but is reported to have a normal thyroid-pituitary axis. Controls were (i) dwarf mice injected with pituitary tissue extract from nonachondroplastic cattle of normal size and (ii) uninjected dwarf mice. The extracts from 2 sources were standardized so that both possessed the same concentration of pituitary tissue. As the weight of dwarf mice neared plateau, they were divided into 3 groups: one received pituitary extract from bovine dwarfs, one received pituitary extract from cattle of normal size, and one was untreated. Body weight response was checked by daily weighing. Injection of pituitary extract from bovine dwarfs stimulated mouse growth significantly, as did extract from normal cattle and the responses were identical. This supports the hypothesis that the bovine dwarf mutant and the mouse dwarf mutant are not homologous.