Section 5 — Mutagenesis 



radiation effects in the males mated with them. 

 Measurements of fecundity have proved the 

 prolongation to be correlated with the radiation- 

 induced sterilization of the females. This has 

 been confirmed furthermore by investigations 

 with unirradiated virgin females having a low 

 fecundity, with females of a special strain 

 showing a high radiation resistance with regard 

 to fecundity, and with chemically (by TEM) 

 sterilized females. 



In the males mean survival-time, Tso, Tioo, and 

 the time of the highest mortality decrease 

 linearly when plotted logarithmically against a 

 raster of linearly increasing doses. The females 

 show in the same raster corresponding curves, 

 except a sharp increase caused by the prolon- 

 gation of lifespan. This makes the LD50 of 

 females (96 kr) twice that of males. The linearity 

 of these curves is interpreted with an always 

 identical type of damage. In both sexes the 

 normal distribution of the mortality rate over 

 the days after irradiation is altered at doses [>90 

 kr. A second peak appears at the third day, 

 growing with increasing doses. Corresponding 

 to this, at 90-100 kr the gradient of the declining 

 survival time curve is strengthened. So a new 

 type of mortality seems to be manifested at 

 high doses. In agreement with the radiation 

 syndrome at these doses it is interpreted as a 

 central-nervous-death. 



5.53. Cytological Interpretations of Five Types of 

 Induced Modification in the Oviposition-pattern 

 of the Wasp Habrobracon. Daniel S. 

 Grosch (Raleigh, U.S.A.). 



In contrast to Diptera where ovaries may not 

 mature for several days, at eclosion, differen- 

 tiated and transitional cells are present in the 

 sequential series provided by the polytrophic 

 ovariole of the parasitoid wasp Habrobracon. 

 Furthermore, ovariole sinvariably number only 

 four, and quantitative modifications of the 

 pattern of egg deposit may be traced back to the 

 cellular state of their contents. 



When eggs are plotted against days, control 

 females quickly reach a sloping plateau main- 

 tained for about 15 days until the sharp senile 

 decline occurs. Low and moderate radiation 

 exposures result in (1) a two-humped curve. 

 The interposed valley, which can dip to tempo- 

 rary infecundity, attests to the vulnerability of 

 transitional cells which undergo five successive 

 mitotic divisions. High doses of radiation destroy 

 the oogonia as well as transitional cells. This 

 results in (2) a rapid decline to permanent in- 



fecundity within the first week. Single-meal 

 ingestion of metal cations and classic organic 

 enzyme inhibitors produce a constant deficit 

 throughout life, reflected as (3) a curve lower and 

 parallel to that of controls. A general debility of 

 somatic tissues ensues rather than a direct effect 

 upon the gonads. Ingested animetabolites can 

 also give type 3 curves, but more typical is (4> 

 an initial lag phase of up to five days resulting 

 from oocyte retardation and degeneration 

 attendant interference with nurse cell function. 

 Nuclear disturbance is involved and may be 

 obtained with agents influencing either protein 

 or nucleic acid synthesis. Aureomycin, metho- 

 trexate, DON, or FUDR give similar type 4 

 curves when used in proper concentration. 

 Antimitotic agents provide still another type of 

 curve (5) characterized by a compensatory 

 deposit of temporarily arrested cells which make 

 up for earlier deficits. 



5.54. Virus-host Relationship and the Effects of X-ray 

 Induced Mutants in Heterozygous Condition. R. 



C. Baumiller (Woodstock, U.S.A.) 



The only reported phenotypic effect of the 

 "virus'' sigma has been to make its Drosophila 

 host sensitive to CO2. L'Heritier ( J > has reported 

 strains of virus carrying flies which differ 

 according to the stability of the virus-host 

 relationship. The experiments, presently com- 

 municated, examined the effects during develop- 

 mental stages of X-ray induced mutants in 

 heterozygous condition on several of these 

 strains W. 



Sensitive (S) and sibling cured (R) virgin 

 females were collected from the strain to be 

 tested and mated to sibling cured males who 

 had (X) or had not (U) received 3000r of X-rays. 

 In a cured line the presence of the virus can no 

 longer be demonstrated. After a two-day mating 

 period the females were placed in net-enclosed 

 cylinders and eggs were collected over one-half 

 hour periods. Each hour, beginning with the 

 21st hour after oviposition, the number of larvae 

 hatching were scored. 



The effect of mutants in heterozygous condi- 

 tion on time of egg hatching varied according 

 to the stability of the virus in the strain tested. 

 The reasons for this difference in effect will be 

 discussed. 



A portion of this work was supported by a 

 grant to Dr. I. H. Herskowitz from the Atomic 

 Energy Commission (Contract AT (ll-l)-633) 



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