HURD H, ELLAMS K M., MAJOR M, WEBB T J.
Centre for Applied Entomology and Parasitology, Department of Biological Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK
J Insect Physiol. 1997 Apr;43(4):337-343. doi: 10.1016/s0022-1910(96)00109-6.
Beetles infected with metacestodes of the rat tapeworm, Hymenolepis diminuta, exhibit reduced fecundity, due to alterations in vitellogenesis. Follicle cell patency is retarded and inefficient vitellogenin uptake ensues. Here, we have reassessed patency and its stimulation by JH III at day 3 post-infection, when the most detrimental changes are observed in other ovarian processes. In Rhodnius prolixus, patency is believed to be brought about by the action of a JH-dependent membrane-bound Na(+)/K(+) ATPase (EC 3.6.1.3); however, this had not been established in Tenebrio molitor. Therefore, the properties of the enzyme, with respect to optimal assay conditions and juvenile hormone dependency, are reported. Maximal stimulation occurred between 50 and 500 nM JH III, a range over which greatest increases in patency were also observed. In infected insects, a 35% reduction in Na(+)/K(+) ATPase activity was noted, but exposure to 50 nM JH III is sufficient for stimulation to a specific activity 89% that of JH-treated controls. In a similar fashion, patency in infected insects is reduced, but can be 'rescued' by 50 nM JH III. Moreover, in the absence of exogenous hormone, patency in infected beetles can be elevated to control levels after in vitro culture (6 h), with exchange of medium every 2 h. The possibility that such reversible decreases in enzyme activity and patency are caused by a JH binding inhibitor molecule is discussed. Copyright 1997 Elsevier Science Ltd. All rights reserved
感染了微小膜壳绦虫（Hymenolepis diminuta）囊尾蚴的甲虫，由于卵黄生成过程的改变，其繁殖力会降低。卵泡细胞的开放受到阻碍，随后卵黄原蛋白的摄取效率低下。在此，我们重新评估了感染后第3天卵泡细胞的开放情况以及保幼激素III（JH III）对其的刺激作用，此时在其他卵巢过程中观察到了最有害的变化。在南美锥蝽（Rhodnius prolixus）中，卵泡细胞的开放被认为是由一种依赖保幼激素的膜结合钠钾ATP酶（EC 3.6.1.3）的作用引起的；然而，在黄粉虫（Tenebrio molitor）中尚未得到证实。因此，本文报道了该酶在最佳测定条件和对保幼激素依赖性方面的特性。在50至500 nM的JH III之间出现最大刺激，在此范围内卵泡细胞开放的增加也最为显著。在受感染的昆虫中，钠钾ATP酶活性降低了35%，但暴露于50 nM的JH III足以刺激其比活性达到经JH处理的对照的89%。以类似的方式，受感染昆虫的卵泡细胞开放减少，但可被50 nM的JH III “挽救”。此外，在没有外源激素的情况下，将受感染甲虫的卵泡细胞在体外培养（6小时），每2小时更换一次培养基，其开放情况可提高到对照水平。本文还讨论了酶活性和卵泡细胞开放的这种可逆性降低是否由一种JH结合抑制分子引起的可能性。版权所有1997爱思唯尔科学有限公司。保留所有权利
