Synaptic bodies (SBs) are electron-dense structures of pinealocytes,
photoreceptor- and hair-cells surrounded by synaptic vesicles. SB profiles
appear as tiny rods (~ 200 x 35 nm) requiring investigation at x 20.000
(transmission electron microscope). The mostly plate-like SBs undergo changes
in number and size. Therefore they were quantified by the disector, which,
in contrast to counts in a standard area, is not influenced by varying
shape and size of particles expressing their number per volume. Due to
their rareness tissue areas overlaying more than 10 TEM screens have to
be scrutinised just to find one profile. Since application of the disector
requires scrutinising 2 serial sections simultaneously this method markedly
increases time of evaluation in contrast to counts on a single section.
To improve effectiveness a proportion factor has been introduced for specimens
of each experimental group. This factor results from the relation of SB-profile
number and the amount of SBs determined once by the disector for each group.
Thus counting of SB-profiles allows calculation of SB-numbers per volume
for other animals of an identically treated group after using the disector
on one specimen of the latter. Thus the overall examination time is reduced
by more than 50%. Chicken and rat pineal gland were examined using these
two methods. Profile counts were performed on areas >20.000 ?m2 in the
same tissue that was evaluated by the disector. Based on the data obtained,
a conversion factor of 2.98 / 3,2 for the chicken / rat pineal gland was
found. The reliability of this conversion factor is discussed.