SECTION 11 



IMMUNOGENETICS 



11.1. Am Immunochemical Study of the NADP linked 

 Glutamic Dehydrogenase and Mutant Forms of 

 the Protein in Neurospora crassa. D. B. 



Roberts (Cambridge, Great Britain). 



Sera containing antibodies against the normal 

 NADP-linked glutamic dehydrogenase of Neu- 

 rospora crassa, have been prepared in rabbits. 

 These sera have been used to study the immuno- 

 logical relationships between the normal and 

 mutant forms of the enzyme. The survey has 

 been carried out on double diffusion plates and 

 on immunoelectrophoretic plates. The line of the 

 enzyme-antibody complex in the gel has been 

 identified by a stain which acts specifically on 

 this complex. 



A detailed comparison has been made be- 

 tween the wild type enzyme and the protein 

 from one of the mutants, am-3. The am-3 protein 

 shows activity if incubated with the substrate 

 glutamate. At a concentration of 33 mM of 

 substrate the am-3 activity is about one-third of 

 wild type activity and at a concentration of 

 133 mM is slightly greater than wild type activity. 

 At a concentration of 33 mM of substrate small 

 quantities of serum appear to enhance the activ- 

 ity of the am-3 protein, larger quantities inhibit 

 the activity slightly. At 133 mM concentration 

 of substrate the am-3 activity is greatly inhibited 

 if incubated with the serum before incubation 

 with the substrate. If the am-3 protein is incu- 

 bated with the substrate before the serum or 

 with both together, the serum has less of an 

 inhibitory effect. At both substrate concentra- 

 tions the serum inhibits wild type activity and 

 there is no substrate protection. 



These results suggest a different relationship 

 between antibody-enzyme in wild type to that 

 in am-3, and also a difference in the enzyme 

 activity-antibody relationship of the am-3 

 protein at different substrate concentrations. 



11.2. The Role of Cytoplasm and Nucleus in the 

 Determination of Serotype in Paramecium. 



John R. Preer, Jr., Mary Bray, and Sa- 

 daaki Koizumi (Philadelphia, U.S.A.). 



Sixteen years ago T. M. Sonneborn demon- 



strated that in Paramecium the cytoplasm at 

 nuclear reorganization is important in deter- 

 mining the expression of genes for serotype. 

 Although it has been assumed that a system of 

 cytoplasmic inheritance is involved, an alter- 

 native possibility is that different cytoplasms 

 induce stable macronuclear states in the develop- 

 ing macronuclei. Dryl recently' 1 ' showed that 

 serotypes change more readily at nuclear reor- 

 ganization than at vegetative reproduction. On 

 the hypothesis of macronuclear determination, 

 conditions inducing change in macronuclear 

 anlagen should not cause developing macronu- 

 clear fragments produced at macronuclear re- 

 generation to change so readily. 



We have studied the frequency of change from 

 serotype B to A in macronuclear regeneration 

 induced in exconjugants of stock 51, Paramecium 

 aurelia. Five hours at 380 C followed by 31° 

 induced both macronuclear regeneration and 

 serotype change. Four lines were obtained 

 from each of several hundred exconjugants. 

 24 exconjugants produced both changing and 

 stable lines, as well as macronuclear regenerating 

 and normally reorganizing lines. In 22 of the 

 24 groups of four the macronuclear regenerates 

 were stable B, while 75 per cent ( 3 5 \) of the nor- 

 mally reorganizing lines changed to A. These 

 results support the notion of nuclear control. 

 Possibly, however, secondary factors associated 

 with macronuclear regeneration favor serotype B 

 more than A, and the results, while suggesting 

 nuclear control, do not really prove it. Attempts 

 are being made to extend the study to the A to B 

 change which is induced by low temperature. 



1. S. Dryl, /. Protozool. 6 suppl.), 25, 1959. 



11.3. Blood Group Investigations of Two Marine 

 Animals. J. E. Cushing, D. Vann, D. Bo- 

 raker (Santa Barbara, U.S.A.). 



Current investigations involving the blood 

 group antigens of two marine forms are reported. 

 The first concerns the use of Dolichos bifiorus 

 lectin in detecting an antigen in the California 



189 



