Fine structure of complex ocelli of a cubomedusan,Tamoya bursaria Haeckel

Summary The ultrastructure of adult male rat pinealocytes was studied after orchidectomy and orchidectomy followed by LH-RH administration. Castration causes an increased development of the rough endoplasmic reticulum and the Golgi apparatus as well as an increase in the number of lipid droplets and lysosomes. The changes after orchidectomy followed by LH-RH administration were more marked than after castration alone.The ultrastructural features observed after castration can be interpreted as a morphological equivalent of increased protein synthesis. The observations reported appear to indicate mutual interaction between the pineal organ and the hypothalamo-hypophyseo-gonadal system. A working hypothesis is put forward implying the presence of a negative feedback mechanism between the pineal and the adenohypophysis.Dedicated to Professor W. Bargmann in honour of his 70th birthdayIBRO/UNESCO fellow Acknowledgements. We thank Dr. P. Pevet for fruitful discussions and Miss M.T. Mud and Mr. P.S. Wolters for skillful technical assistance