Morphometric changes between one-day-old and adult chicken neurons of the nucleus isthmi.

The most important parameters of the neuronal soma of neurons of the chicken nucleus isthmi have been analyzed, with photo and morphometric techniques, in order to quantify the morphological variations present during the first months of the life to determine if the developmental changes of both neuronal populations of the nucleus are similar or different. The study was carried out on neurons of the parvicellular part and magnocellular part of the Nucleus Isthmi in one day and four month-old chickens. The soma shape did not change during this time interval in parvicellular neurons. The magnocellular neurons became more fusiform. In-one-day old chickens, the section shapes of the neuronal soma and optical density, are similar in both the magnocellular and parvicellular parts of the nucleus. The area and the maximum and minimum diameters do not present significant differences between magnocellular and parvicellular neurons. In adults, the maximum diameter, neuronal area and optical density are higher in magnocellular neurons than in parvicellular neurons. In summary, magnocellular neurons of the nucleus Isthmi of adults are bigger, darker and more elongated than the ones that constitute the parvicellular territory.

Development of the chicken oculomotor nucleus: a quantitative study of cresyl violet and colloidal iron stained neurons.

The characteristics of new-born chicken oculomotor neurons have been studied comparatively with adults (four-months), applying both, the Cresyl Violet and Colloidal Iron stain methods. A cytophotometric study has been performed on the neurons, obtaining optical density maps. Afterwards, a statistical study on the nuclear and somatic parameters, and the optical density values, were made. The existence of two nerve-cell types has been proved: clear ones-big, eggshape with nucleus and an obvious nucleolus; and darker ones-smaller, fusiforms, with nucleus and a less perceptible nucleolus. These characteristics of the neuronal-cells are present in new-born and four-month old animals. The ratio is different for each stage: in younger chickens there is a bigger proportion of clear nerve-cells (70%) than dark ones (30%); and in four-month old chickens there is a bigger proportion of dark nerve-cells (95%) than clear ones (5%). During postnatal development, oculomotor nucleus nerve-cells increased the neuronal area 28% in the clear cells and 30% in the dark cells. The optical density histograms for clear cells of one-day old animals and four-month old animals were similar, as were the histograms for both developmental stages of the dark cells. Glycosaminoglycans were shown with the colloidal Iron, there being strong positive reactions on the cell periphery, prolongations, and Golgi apparatus of four-month old specimens. But in the nex-born animals the reaction was weaker, with the maximum intensity on the pericaryon periphery.