Holger Jastrow1, Dirk Schmanke2, Jörg Weinert3, Udo Jendrysiak3Klaus Merle2 and Lutz Vollrath1
1 Department of Anatomy, J. Gutenberg-University,
Saarstr. 19-21, 55099 Mainz, Germany,
2 Center of Data Processing, J. Gutenberg-University, Saarstr. 19-21, 55099 Mainz, Germany,
2 Institute for Medical Statistics and Documentation, J. Gutenberg-University, Obere Zahlbacher Str. 69, 55101 Mainz, Germany
In vertebrates, synaptic ribbons (SR) are conspicuous synaptic organelles
of afferent synapses of retina, inner ear, lateral line organ and pineal
gland, expressing a circadian rhythm in number and size in some organs.
In electron microscopic sections they appear as electron-dense organelles
surrounded by electron-lucent vesicles. SR appear mainly under two forms:
ribbon- or rod-like profiles (SRr) measuring 30 - 40 nm in width and about
150 - 200 nm in length can be distinguished from a second population of
spherical SR (SRsp), measuring > 100 nm in diameter (Vollrath '81; Mc Nulty
'92). Since it is not known whether the SRr are rod- or plate-like in the
third dimension, it was the aim of this investigation to reconstruct the
structure of different SR in guinea-pig pinealocytes in three dimensions.
Transmission electron microscope photos from 27 serial sections with a known distance (50nm) of a group of SR were scanned and processed (manual superimposition of corresponding organelles from adjacent sections, involving rotation and shifting of the scanned image) by a self - written programme in Interactive Data Language (IDL®).
The resulting 3D-array was further processed by Neurops® allowing 3D visualisation of SR. The three-dimensional images were printed from different angles to elucidate the appearance of SR in space. It was found that all SRr were plate-like with irregular edges. No rod-like SRr were noted. The SRsp were indeed spherical or ovoid.
The presently used method to evaluate scanned photographs can be used for producing 3D- reconstructions from serial images in general.
McNulty, J. A. and Fox, L. Pinealocyte synaptic ribbons and neuroendocrine function. Microsc Res Tech 21: 175-187 (1992).
Vollrath, L. The pineal organ. In: Oksche, A. and Vollrath, L. (eds) Handbuch der mikroskopischen Anatomie des Menschen, Springer (1981).