The importance of quantitative electron microscopic study of neurons and synapses has been increasingly recognized. However, this kind of neuroanatomy is very difficult and time-consuming work, and reliable methods for such studies have not yet been developed.
Proposed here is a method dealing with quantitative synaptology which treats all recorded synapses and boutons around the neuron marked with HRP, rather than a qualitative or a piecemeal quantitative study of a particular synapse and/or bouton which is not positioned in the neuron. This approach requires the development of both neuroanatomical procedures, by which a specialized whole neuronal profile is identified, and valuable specialized tools, which support gathering and analysing of a huge volume of morphometric data from a photomontage of electron micrographs, to reduce the burden of the morphologist.
The present report is concerned mainly with the computer system which has been under development in our laboratory for such morphometric synaptology. The system consists of a large sized tablet digitizer, a YHP system 45 desk top computer, hard disk drives, an X-Y plotter, and a line printer. The system is designed as a semi-automatic interactive computer system, because electron micrographs of nervous tissues have very complex textures and weak contrast. In our system, a morphologist performs the pattern recognition portion and decides what to do next in the system, and the computer functions conventionally, computing, storing and controlling. Measurement, count, and computation about morphological parameters, such as 1) cross sectional perimeter and area of a soma and boutons, 2) number of boutons and a variety of organelles, 3) contacting length of boutons, 4) classification of boutons, are made by means of the interactive method using a tablet digitizer and a menu-sheet. Further morphometric parameters, such as the S/F ratio, the covering ratio, mean values, deviation, and distribution, are computed from the quantitative data. As morphometric data are all stored in hard disks and programs for various analyses are available, we can analyse them and make a comparison between groups of neurons. In this manner, the proposed system is quite useful and efficient, and can be used as easily as a notebook, for morphometric synaptology. The system also drastically decreases the time spent on this time-consuming procedures. Some examples of morphometric measurements and analyses are also given.
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