Stone B F, Nolan J, Schuntner C A
Aust J Biol Sci. 1976 Jul;29(3):265-79. doi: 10.1071/bi9760265.
Three aspects of the biochemical genetics of resistance to organophosphorus compounds in the Biarra (B), Mackay (M) and Ridgelands (R) strains of the cattle tick B. microplus were studied. These were: decreased acetylcholinesterase (AChE) activity in adult brains of strains B and M; decreased AChE sensitivity to inhibitors in adult brains and in larvae of strains B, M and R; and increased detoxication in larvae and adult females of strain M. Comparisons were made with a susceptible reference strain (S). Microspectrophotometric estimations of AChE activity in histochemical preparations of whole brains showed that hybrids had levels of activity approximately intermediate between those of the parental strains. Homogenates of brains from hybrids assayed biochemically gave similar but more precise results which indicated that decreased brain AChE activity was neither recessive nor dominant (degree of dominance, D = +0-02) in strain B and incompletely recessive (D = -0-26) in strain M. The proportions of brains showing decreased AChE activity in testcross and F2 progenies indicated that decreased AChE activity in strains B and M is controlled by single autosomal genes. Inhibition of AChE at diagnostic concentrations of coroxon in brains of B, B x S hybrid and S types suggested that decreased sensitivity of AChE in strain B is incompletely dominant (D = +0-10). Kinetic studies on coroxon inhibition of AChE in brain homogenates of B, B x S hybrid and S types revealed the presence of each parental AChE component in hybrids in equal amounts and the absence of a hybrid enzyme. Dimethoxon inhibition of AChE in brains, their homogenates and larval homogenates of B, M and R types showed that decreased AChE sensitivity was a major mechanism of resistance to dimethoate strongly expressed in B x S and M x S hybrids. The proportion of brains showing decreased AChE sensitivity to coroxon in testocross and F2 progenies indicated that decreased AChE sensitivity in strain B is controlled by a single autosomal gene. The degree of dominance of increased degradative metabolism of coumaphos in strain M was variable; the hydrolytic rate in all M x S hybrids was similar to that of M but the overall detoxication rate in hybrids was lower. Genetic control of detoxication is discussed.
对微小牛蜱的比亚拉（B）、麦凯（M）和里奇兰兹（R）品系中对有机磷化合物抗性的生化遗传学的三个方面进行了研究。这些方面包括：B品系和M品系成虫脑中乙酰胆碱酯酶（AChE）活性降低；B品系、M品系和R品系成虫脑和幼虫中AChE对抑制剂的敏感性降低；以及M品系幼虫和成年雌蜱中解毒作用增强。与敏感参考品系（S）进行了比较。通过对全脑组织化学制剂中AChE活性的显微分光光度法估计表明，杂种的活性水平大致介于亲本品系之间。对杂种脑匀浆进行生化分析得到了类似但更精确的结果，这表明脑AChE活性降低在B品系中既不是隐性也不是显性（显性度，D = +0.02），在M品系中是不完全隐性（D = -0.26）。在测交和F2后代中显示AChE活性降低的脑的比例表明，B品系和M品系中AChE活性降低由单个常染色体基因控制。在B品系、B×S杂种和S型品系的脑中，用诊断浓度的氧桥氯甲桥萘抑制AChE表明，B品系中AChE敏感性降低是不完全显性（D = +0.10）。对B品系、B×S杂种和S型品系脑匀浆中氧桥氯甲桥萘抑制AChE的动力学研究表明，杂种中每种亲本AChE成分等量存在，且不存在杂种酶。在B品系、M品系和R品系的脑、脑匀浆和幼虫匀浆中，乐果对AChE的抑制作用表明，AChE敏感性降低是对乐果抗性的主要机制，在B×S和M×S杂种中强烈表达。在测交和F2后代中显示对氧桥氯甲桥萘AChE敏感性降低的脑的比例表明，B品系中AChE敏感性降低由单个常染色体基因控制。M品系中谷硫磷降解代谢增加的显性程度是可变的；所有M×S杂种中的水解速率与M品系相似，但杂种中的总体解毒速率较低。讨论了解毒作用的遗传控制。
