Suzanne Couineau's scientific contributions

In this quantitative study (23 cats) we aimed to compare the frequency of the intranuclear rodlets of sympathetic neurons in a stellate ganglion taken as reference and in the controlateral ganglion submitted to electrical stimulation. We examined 15,616 nuclear sections and 662 nuclear inclusions.In the reference ganglia great individual variations were observed (1–7 fold). The electrical stimulation provoked an increase in the frequency (1.5–13.6 fold) independent of sex and the side chosen for stimulation. This increase is inversely proportional to the frequency in the reference ganglion. In most cases only a small amount of the neurons taken as reference showed such inclusions, whereas stimulation provoked at least one such structure in each neuron.These results show for the first time that intranuclear rodlets constituted by microfilaments and microtubules are dynamic structures and that their frequency is related to the activity level of the neuron. In a more general view, we now have a biological meaning to these structures which remained enigmatic since their discovery by neurohistologists of the last century.

Nuclear inclusions of sympathetic neurons which can be correlated to « intranuclear rodlets of light microscopy are mainly, if not exclusively, of protein nature. They offer a wide variety of aspects when observed in usual conditions under electron microscope. The electron microscope goniometer observation, done on several hundred inclusions, show that they are formed by two fundamental elements: microfilaments and microtubules which we consider as normal constituents of the nucleus. They built up filamentous and tubulofilamentous inclusions. The tubulofilamentous inclusions are either spindles formed by parallel microfilaments covered by one layer of microtubules or complex crystalloids. In this last case the microfilaments are in parallel layers (usually 12) forming a 60° angle with each other. We have observed a granular satellite body present in all inclusions. In the case of tubulofilamentous inclusions we have found two other associated structures: a granular shell and a short microtubular bundle. This study is discussed with regard to the problems raised by the neuronal fibrous proteins. Hypothesis are proposed concerning the dynamics of the interrelation between the different varieties of inclusions.