Holger Jastrow¹, Dirk Schmanke², Jörg Weinert³, Udo Jendrysiak³ and Lutz Vollrath¹

¹ Anatomisches Institut, Johannes Gutenberg-Universität Mainz, Becherweg 13, D-55128 Mainz,
² Zentrum für Datenverarbeitung, J. Gutenberg-Universität, Bentzelweg 12, D-55128 Mainz,
³ Institut für Medizinische Statistik und Dokumentation (IMSD), J. Gutenberg-Universität, Obere Zahlbacher Str. 69, D-55101 Mainz

Synaptic bodies (SBs) are dynamic synaptic organelles of afferent synapses of retina, inner ear, lateral line organ and pineal gland in vertebrates. When investigated in a transmission electron microscope their electron-dense rod-like, round or irregular profiles are surrounded by electron-lucent vesicles. The three-dimensional structure of pineal SBs is not precisely known. Pineal glands of two guinea-pigs (one kept under a LD cycle of 12:12 h; one kept in constant light for 8 weeks) were investigated. SBs were reconstructed in three dimensions to visualise morphological changes in constant light. Transmission electron microscope micrographs from up to 18 serial sections with a known distance (50 nm) of groups of SBs were scanned and processed (controlled superimposition of corresponding organelles from adjacent sections, involving rotation and shifting of the scanned image) by a self - written programme in the Interactive Data Language (IDL®). The resulting 3D-array was further processed by NeurOPS (neurosurgical operation-planning and simulation software developed at the IMSD) allowing 3D visualisation of SBs. The three-dimensional images were printed from different angles to elucidate the appearance of SBs in space. It was found that under constant light SBs lay opposite to one another in adjacent pinealocytes, closely related to the cell membrane. Further, bent plates appearing under the form of V- and U-shaped shields were seen. Smaller lumps or spherical masses of SB material were more often seen than in the control animal, while parallel oriented plates as seen under a normal lighting regime were less frequent.