One of the most active and currently vigorously pursued research area in endocrinology in the identification of the receptors for the various hormones. An understanding of the role of hormones receptors in activation of specific genes will further our knowledge regarding the specifically of hormone action. The overall aim of this research proposal is to gain an indepth understanding of one of the primary actions of the insect juvenile hormone: The induction of the yolk protein precursor, Vitellogenin (Vg). Juvenile hormone is a sesquiterpenoid molecule and as such chemically unique among animal hormones. It is hypothethized that also here receptors mediate the hormonal message in analogy to the findings for vertebrate steroid and thyroid hormones. The fundamental importance to endocrinology in general is implied. In order to achieve this goal, the receptor for JH (so far physiologically identified) will be purified to homogeneity. Polyclonal and monoclonal antibodies to this receptor will be generated and used to monitor the stage and sex specific occurrence of this receptor. In addition, the Vg gene will be isolated and the hormone responsive element (HRE) will be identified. Since species such as cockroaches date evolutionarily back to more than 200 M years, analogous findings to those from certain vertebrate hormones will gain significance in evolutionary terms. Cockroach species have been amenable for basic research. Many of the aspects regarding the control of insect reproduction have been worked out on appropriate cockroach species first. The easy manipulation of these animals and their cost efficiency make them perhaps the animals of choice for certain basic research in biology. Furthermore, the identification and characterization of the receptor for JH may lead to the design of new chemicals that can be used in control of agriculturally and medically injurious insect species, since hormone receptors are the key to hormone action.