Section 10 — Developmental Genetics 



involved in phenylalanine metabolism. In DD 

 and Dd l the activity of phenylalanine alpha- 

 ketoglutarate transaminase rises rapidly after 

 birth to a peak at 14 days and then falls off 

 about 50 per cent during the third week to the 

 adult level; the activity in d x d l increases similarly 

 only until 7 days at which low level it remains 

 until toward the end of the third week when 

 it falls slightly to the normal adult level. The 

 activity of phenylalanine hydroxylase increases 

 at the same rate in all three genotypes until 

 17 days; following this dhi 1 remains the same 

 while DD and Dd 1 continue to increase reaching 

 the high adult levels at about four weeks. The 

 low hydroxylase activity in dilute-lethals is due 

 to the presence of an inhibitor rather than to a 

 failure in enzyme formation. The inhibitor, 

 associated with the microsome fraction in brain, 

 kidney, heart, etc., as well as liver can be solu- 

 bilized with deoxycholate. Evidence suggests the 

 inhibitor may be an enzyme. Reduced transa- 

 minase and hydroxylase activities can account 

 for significantly higher serum phenylalanine 

 levels in dilute-lethals (e.g. d l d l ten times DD 

 at 14 days). Excess circulating phenylalanine 

 may be associated with the myelin degeneration 

 observed in brains of dilute-lethals. 



Supported by U.S. Public Health Service 

 Grant GM 05921. 



10.37. Effect of Somatotropin^ the Weight Gain of 

 Yellow Dwarf (A* a dw dw) Mice. George L. 

 Wolff and Barbara Resnick (Philadelphia, 

 U.S.A.). 



Possible involvement of somatotropin (STH) 

 in the increased fat deposition by yellow (/4>~) 

 mice was investigated with yellow dwarf (Ay a dw 

 dw) and non-yellow dwarf (aa dw dw) mice 

 known to be deficient in STH. Ay a dwdw and 

 aa dwdw mice of both sexes were injected with 

 0.5 USP unit bovine STH daily for 29 days be- 

 ginning at about 8 weeks of age. Weekly weights 

 were recorded for injected and control mice for 

 over six months. During the treatment period, 

 weight increase was about the same for both 

 genotypes. After injections were stopped, the 

 Ay a dwdw mice continued gaining weight while 

 the aa dwdw mice stopped gaining weight im- 

 mediately. By 9 months of age the A? a dwdw 

 males had reached a mean plateau weight of 

 about 50 g and females about 45 g. These are 

 similar to plateau weights of normal yellow 

 (Ay a Dw) mice. — Results from current ex- 



periments with 0.05 USP unit Bovine STH 

 indicate that weight gain of yellow and non- 

 yellow dwarf mice is increased to the same 

 degree during the injection period and is propor- 

 tional to the STH dosage. Apparently the per- 

 centage increase in weight of yellow as compared 

 with non-yellow mice is independent of the 

 STH level in the body. Since excess weight gain 

 of normal yellow (Ay a Dw~) mice does not 

 usually begin until after about 8 weeks of age, 

 a metabolic process which depends on a cer- 

 tain maturation of the animal may be involved. 

 Administration of STH to Aya dwdw mice 

 may merely allow maturation to proceed to the 

 stage at which excess fat deposition begins. 



Supported in part by USPHS Grants RG-6275 

 and GM 10112-01 and American Cancer So- 

 ciety Grant IN-49. 



10.38. The Effect of Hormonally induced Changes 

 During Development and During Adult Life of 

 Drosophila. K. C. Sondhi (Baltimore, U.S.A.). 



The present experiments describe the effect 

 of ring gland transplantations in Drosophila 

 melanogaster. The experiments were performed 

 on Samarkand inbred line, which was inbred for 

 over 200 generations and was structurally homo- 

 zygous for all the chromosomes. Three mature 

 ring glands were transplanted into the body 

 cavities of host larvae. Two synchronous control 

 populations were maintained, one consisting of 

 individuals which were allowed to develop nor- 

 mally and the other of individuals in which only 

 Ringer's solution was injected. The times of 

 emergence of flies were recorded. To minimize 

 the nutritional differences affecting body weight, 

 the flies were weighed on a torsion balance im- 

 mediately after eclosion. 



The results of these experiments showed that 

 the transplantation of extra ring glands increases 

 the mean body weight of Drosophila over 35 

 per cent compared to controls. The response of 

 females to hormone secreting ring glands was 

 found to be much greater than in males. The 

 effect of altering the hormonal balance on re- 

 productive ability and on the adult life-span is 

 under investigation. 



10.39. Growth Equations and Late Moiphogenesis of 

 Quantitative Characters. G. Fabian, J. Ern- 

 haft and M. Varga (Godollo, Hungary). 



The basic growth equations were used pre- 



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