Zufelato M S, Bitondi M M, Simões Z L, Hartfelder K
Universidade de São Paulo, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Departamento de Biologia, Av. Bandeirantes 3900, 14040-901, Ribeirão Preto, São Paulo, Brazil.
Arthropod Struct Dev. 2000 Apr;29(2):111-9. doi: 10.1016/s1467-8039(00)00023-2.
The control of the pupal melanization in the honey bee by ecdysteroids, and the modulation of these processes by a juvenile hormone analog were investigated by a combination of in vivo and in vitro experiments. Injection of 1-5 microg of 20-hydroxyecdysone (20E) into unpigmented pupae showed a dose- and stage-dependent effect. The higher the dose and the later the injection was performed, the more pronounced was the delay in cuticle pigmentation. This inhibition of cuticular melanization by artificially elevated ecdysteroid titers was corroborated by in vitro experiments, culturing integument from unpigmented, dark-eyed pupae for 1-4 days in the presence of 20E (2 or 5 microg/ml culture medium). Topical application (1 microg) of pyriproxyfen to unpigmented, white-eyed pupae had the opposite effect, leading to precocious and enhanced melanization of the pupal cuticle. In vitro incubation of integuments in the presence of this juvenile hormone analog (1 microg/ml) confirmed these results, showing that pyriproxyfen is apparently capable of triggering melanization. The in vivo mode of action of pyriproxyfen was further investigated by quantifying hemolymph ecdysteroids by radioimmunoassays. Topical application leads to a delay of the pupal ecdysteroid peak by 4 days. The pyriproxyfen-induced low ecdysteroid titers during early pupal development could account for precocious pigmentation by removing an inhibition on prophenoloxidase activation normally imposed by the elevated ecdysteroid titer during this phase.
通过体内和体外实验相结合的方法，研究了蜕皮甾类对蜜蜂蛹黑化的控制作用，以及一种保幼激素类似物对这些过程的调节作用。向未着色的蛹注射1-5微克的20-羟基蜕皮酮（20E）显示出剂量和阶段依赖性效应。剂量越高且注射时间越晚，表皮色素沉着的延迟就越明显。通过体外实验证实了人工升高的蜕皮甾类滴度对表皮黑化的这种抑制作用，即将未着色、黑眼蛹的体壁在含有20E（2或5微克/毫升培养基）的条件下培养1-4天。将吡丙醚局部应用（1微克）于未着色、白眼蛹产生了相反的效果，导致蛹表皮早熟且黑化增强。在这种保幼激素类似物（1微克/毫升）存在的情况下对体壁进行体外培养证实了这些结果，表明吡丙醚显然能够引发黑化。通过放射免疫测定法对血淋巴蜕皮甾类进行定量，进一步研究了吡丙醚的体内作用方式。局部应用导致蛹蜕皮甾类峰值延迟4天。在蛹发育早期，吡丙醚诱导的低蜕皮甾类滴度可以通过消除在此阶段通常由升高的蜕皮甾类滴度对酚氧化酶原激活的抑制作用来解释早熟色素沉着的现象。
