Holger Jastrow, Marc-A. von Mach, Michael Hainz and Lutz Vollrath
Anatomisches Institut der J. Gutenberg-Universität Mainz, Becherweg 13, D-55128 Mainz

Profile counts of synaptic bodies (SBs) in the mammalian pineal gland have shown that SBs undergo a day-night rhythm being larger and more frequent at night. Similar results have been obtained in chicken pineal glands. These results can be criticised because of the counting procedure applied since enlargement of organelles inevitably will cause higher profile numbers per SB. Thus it is uncertain whether SBs actually increase in number at night. To obtain unbiased data we have now developed a modification of the physical disector which is independent of particle size and shape. The counting frame was determined by measuring the lengths of the ultrathin section's edges using a Morphomat, measuring SB profile lengths as well, multiplied by the width of the tissue zone under investigation, which corresponds to the diameter of the electron microscope screen at x 20.000. The evaluated tissue stripes were scrutinised along the edges of adjacent sections of a series ensuring that areas corresponded exactly. Effectiveness of the disector counts was increased by simultaneous evaluation of both sections (bi-directional disector). Disector counted synaptic bodies and their profile numbers determined by the previously applied counting method referring to areas (standard 20,000 µm²) were correlated. The results obtained for chickens show that both profile numbers and particle numbers were significantly larger at night than day. Moreover mean SB profile length increased by 11.4 %.