Imprägnation Der Mitochondrien Als Eine Methode Zum Studium Der Synapsenanordnung Im Neuropil (Licht- Und Elektronenmikroskopische Untersuchungen Am Hirnstamm Der Katze)

Summary Impregnation of mitochondria as a method for studying the arrangement of synapses in neuropil (light and electron microscopic observations in brain stem of cat) (1) A modified Nauta's method (Němecek) demonstrates mitochondria in central nervous system electively at the light microscopical level. Reduced silver particles as seen in the electron microscope are deposed within the matrix of mitochondria. (2) All impregnation techniques for mitochondria in CNS inclusive so-called ‘synaptic mitochondrial stains’ (e.g. Rasmussen, Armstrong) tend to label mitochondria incompletely. The phenomenon of ‘complete’ and ‘incomplete’ impregnation is described and discussed. Methods for the variation of completeness have been worked out. (3) Mitochondria in neuropil besides being distributed discretely appear as two types of aggregates in complete impregnation: (I) homogeneous, smoothly contoured; (II) heterogeneous, pleomorphic aggregates. Electron microscopic correlation confirmed that the first type mainly corresponds to boutons, while the second type is produced by locally accumulated boutons and dendrites, which may contain postsynaptically aggregated mitochondria (complex synapses). Since boutons contain a variable number of mitochondria, it is not possible to estimate their size. (4) In neuropil of different brain stem nuclei and subnuclei the distribution of single and aggregated mitochondria can be distinguished. Therefore mitochondrial architecture of neuropil can be demonstrated, which corresponds to the distribution of boutons and complex synapses. Therefore, these methods are an additional tool for studying synaptoarchitecture. Complete impregnation of mitochondria seems especially useful as detector for complex synapses.

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