The androgenic and the male-inducing (androtermonic) activities of 11-ketotestosterone were evaluated respectively by its abilities to stimulate a secondary sex character and to reverse gonadal sex differentiation in a teleost, the medaka (Oryzias latipes). The median effective dose (ED 50) of this steroid necessary to induce the formation of papillar process on the anal fin was 37 pg/g of food. The androgen is therefore about 8 times more potent than testosterone propionate and 17 times more potent than pure testosterone in the same test. The ED 50 for androtermonic activity (reversal of genetic females to phenotypic males) was found to be about 110 pg/g of food. Compared with testosterone propionate the 11-keto compound is about five times more potent. Thus, in teleosts, 11-ketotestosterone appears to be the most potent androgen of vertebrate origin for both androgenic and androtermonic potencies. The ratio of androtermonic to androgenic potencies (ED 50s) for Il-ketotestosterone is 3.0.
Although numerous investigations have been done on the respiration of fish eggs during early development, relatively few attempts have been made to analyze the respiratory metabolism. AMBERSON and ARMSTRONG (1933) have shown in Fundulus eggs that the respiratory quotient is high in the first day and it declines continuously to lower values during development. This indicates that the egg uses first carbohydrates, then proteins and fats in the order presented by NEEDHAM (1931). On the other hand, BRACHET (1934) reported in the frog egg that the respiratory quotient has a low value during segmentation and this value increases sharply at the beginning of gastrulation. Similar results have been obtained by OHMAN (1940) and HUTCHENS, KELTCH, KRAHL and CLOWES (1942) in the sea urchin egg. Furthermore, TRIFONOVA and her collaborators (1937, 1939) have shown in the eggs of the perch that cyclic changes of respiration and glycolysis take place between fertilization and neurulation. In Fundulus eggs, however, such fluctuations are not found a t least in respiration where increases have been shown to occur continuously (PHILIPS 1940). Thus, the results of these investigations remain somewhat contradictory regarding the respiratory changes during fish development. The purpose of the present study is to try and resolve this problem, using eggs of the medaka, Oryzias latipes.Before going further, the writers wish to express their gratitude to Prof. T. YAMAMOTO for his encouragement and valuable advice. Thanks are also due to Dr. J. ISHIDA of Tokyo University for his helpful suggestion and criticism.
MATERIALS AND METHODS
Materials.Materials used were eggs of the orange-red variety of the medaka, Oryzias latipes.Adult females lay eggs daily for a considerable period during spring and summer. Spawned eggs hang in a tiny cluster from the female's vent and they may be removed by suction of a wide-mouthed pipette. For the experiments, eggs were washed with distilled water and were separated one by one. This procedure is necessary to improve the synchrony of development. Then, eggs were allowed to develop in the isotonic RINGER'S solution (M/7.5 NaCl 100 parts, M/7.5 KCI 2.0 parts, M/11 CaClz 2.1 parts, M/10 NaHC03 0.25 parts, pH 7.3) until desired stages were reached at room temperature (25-28" C-). At 25" C., the embryos hatch out in 10 days. Enzymatic activities. The oxygen uptake was measured in WARBURG manometers, with a vessel capacity of about 5 ml. 0.2 ml. of 10 per cent KOH was placed in the center cup. For the determination of the cyanide inhibition, the KOH was replaced by KREBS' (1935) KCN-KOH mixture. The temperature was regulated to 30" C. and the shaking rate was 100 to 110 cycles per minute with a 4 cm. amplitude. The gas space was filled with air.In the experiments with intact eggs, 100 to 300 eggs were suspended in MI50 RINGER'S solution so that the total volume was 2 ml. and were transferred t o each vessel. The pH of media was adjusted to 7.3 by the addition of phosphate buffer. For the preparation of homoge...
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