Genetic effects of combined gamma-rays-ENU treatments as revealed by the Medaka specific-locus test system

根据过去十年来通过检查90多万个胚胎所积累的数据。240万个位点，我们认为Medaka特异性位点检测系统的基础已经很好地建立起来。由于在我们的研究中迄今采用的治疗方法是暴露于包括伽马射线、ENU或反应堆辐射在内的单一介质中，因此我们决定先使用Medaka特异性位点测试系统检查伽马射线- ENU联合治疗的遗传效应。将50只野生型成年雄樱菌株在室温下暴露于4.75 Gy的γ射线下，然后在20 ~ 30分钟后暴露于0.5mM ENU下，在27ºC下暴露2小时。每只处理过的雄性都与我们的测试菌株AA2的雌性交配。从联合处理后的第一天到30天，进行了广泛的顺序收集胚胎。检测的遗传终点为显性致死型、总突变型和活突变型。将观察到的结果与已有的伽玛射线或ENU单独处理的结果进行了比较。显性致死性、总突变性和活突变性分别为0.0557[0.0566/0.0550]/个配子、3.79 [5.51/2.61]× 10^<-5>/个位点和4.17 [12.6/1.38]× 10^<-6>/个位点，初步计算了加性或增效性。精子、精细胞、精母细胞、分化精原细胞和干精原细胞的优势致死率分别为0.584[0.605/0.565]、0.550[0.563/0.537]、0.394[0.413/0.375]、0.123[0.134/0.114]和0.0493[0.0525/0.464]。包括精子、精子和精母细胞在内的减数分裂后的观察值高于基于简单加和性的预期值，但低于基于协同性的预期值。然而，对于包括分化性和干性精原细胞在内的早产儿，观察到的显性死亡率低于两种预期的死亡率。观察到的总突变率和预期的总突变率之间的情况几乎与显性致死的情况相同。观察到的减数分裂后和减数分裂前的活突变频率与基于简单加性的预期没有显著差异，基于协同作用的预期频率几乎是前两组比率的10倍。总突变率与活体细胞突变率之比由辐射型变为enu型，由减数分裂后暴露变为减数分裂前暴露。少

On the basis of the data accumulated during the last ten years by examining more than 900,000 embryos corresponding to approx.2,400,000 loci, we consider that the basis of the Medaka specific-locus test system has been well setablished. Because the treatment so far adopted in our study was exposure to a single agent including gamma-rays, ENU or reactor radiation, we decided to precede to examine the genetic effects of combined gamma-rays-- ENU treatments by using the Medaka specific-locus test system.Fifty wild type adult males of the Sakura strain were exposed at room temperature to 4.75 Gy of gamma-rays followed 20 to 30 min.later by an exposure to 0.5mM ENU for 2 hours at 27ﾟC.Each treated male was mated to a female of our tester strain AA2. Extensive sequential collection of embryos was done from the first day through 30 days after the combined treatments. The genetic endpoints examined were dominant lethals, total mutations and viable mutations. Observed results were compared with … More those already obtained for separate treatments with gamma-rays or ENU.The additivity or synergism was tentatively calculated on the basis of fold-increase over spontaneous rates [90% upper confidence limit/lower limit], which were 0.0557 [0.0566/0.0550]/gamete, 3.79 [5.51/2.61]x10^<-5>/locus, and 4.17 [12.6/1.38]x 10^<-6>/locus, respectively, for dominant lethals, total mutation and viable mutation.The observed dominant lethal rates for sperm, spermatids, spermatocytes, differentiating spermatogonia and stem spermatogonia were, respectively, 0.584 [0.605/0.565], 0.550 [0.563/0.537], 0.394 [0.413/0.375], 0.123 [0.134/0.114], and 0.0493 [0.0525/0.464]. The observed values for the postmeiotics including sperm, spermatids and spermatocytes were higher than the value expected on the basis of simple additivity, but lower than that expected on the basis of synergism. With regard to the premeiotics including differentiating and stem spermatogonia, however, the observed dominant lethal rates were lower than both the two expected rates. The situation between the observed and expected rates of total mutations was almost the same as that for dominant lethals. The observed viable mutation frequencies for the postmeiotics as well as the premeiotics were not significantly different from that expected on the basis of simple additivity, the rates expected on the basis of synergism being almost 10-fold higher than the previous two sets of rates. The ratio of total mutation rate to viable one changed from radiation-type to ENU-type with changes from postmeitic exposure to premeiotic exposure. Less