6533b82dfe1ef96bd1291bec

RESEARCH PRODUCT

Changes in the Three Dimensional Structure of Synaptic Ribbons in the Pineal Gland of the Guinea-Pig Caused by Constant Light

subject

description

Synaptic bodies (SBs) are dynamic synaptic organelles of afferent synapses of the 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 an 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 super-imposition 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 3-D array was further processed by NeurOPS (neurosurgical operation-planning and simulation software developed at the Institut fur Medizinische Statistik und Dokumentation), allowing 3-D 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 lie opposite 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 and plates orientated in parallel were less frequent.