RESUMEN
A silver impregnation technique (Linder, 1978) has been applied to whole mounts of the rat iris. The results suggest that only sensory fibres, both myelinated and non-myelinated, are stained. They disappear only after a trigeminal lesion and their distribution is different from that of catecholaminergic intrinsic fibres. Staining of the iris reveals a conspicuous pattern of innervation, characterised by a circular bundle and a thin plexus in the ciliary body, and by prominent bundles of fibres with a loose network of thin smooth fibres in the external part of the dilator plate and with a denser network in the central area. Nerve endings are seen on the dilator plate, in the sphincter as well as in the ciliary body. It is possible by a slight modification of the technique to stain myelinated and non-myelinated fibres separately. It results in a deep staining of the myelin while thin fibres are relatively clear. This method provides clear and reproducible staining of the nerves of the iris. It can be combined with various histochemical and immunocytochemical techniques. This will permit further studies to be made on the development of sensory and central nervous tissues, when grafted to the normal or the selectively denervated iris.
Asunto(s)
Iris/inervación , Animales , Catecolaminas/análisis , Desnervación , Técnica del Anticuerpo Fluorescente , Ganglios Parasimpáticos/fisiología , Fibras Nerviosas , Fibras Nerviosas Mielínicas , Ratas , Ratas Endogámicas , Plata , Coloración y Etiquetado/métodos , Simpatectomía , Sistema Nervioso Simpático/análisisAsunto(s)
Diferenciación Celular , Quimera , Nervios Craneales/citología , Ganglios/citología , Células Receptoras Sensoriales/citología , Animales , Movimiento Celular , Embrión de Pollo , Pollos , Coturnix , Nervio Facial/citología , Nervio Glosofaríngeo/citología , Microscopía Electrónica , Cresta Neural/citología , Neuroglía/citología , Neuronas/citología , Ganglio Nudoso/citología , Nervio Vago/citologíaRESUMEN
Orthotopic transplantation experiments have shown that in birds, under normal conditions, mesectodermal capabilities seem restricted to the cephalic neural crest down to the level of the 5th somite. In the present study the mesectodermal capabilities of trunk and lumbar neural crest were investigated at early stages of development by heterotopic, heterospecific transplantation of the neural primordium. The quail-chick nuclear marker system was used to identify the grafted cells. Mesectodermal cells did not arise from the trunk neural crest when this was implanted orthotopically, even though the neural primordium was taken early in development at the level of unsegmented plate mesoderm just anterior to Hensen's node. Mesectodermal derivatives (connective tissues, dermis and muscle but no cartilage or bone) developed from the same trunk neural crest fragments when they were heterotopically grafted at the cephalic level and mixed with host cephalic neural crest cells. These host cephalic neural crest cells emigrated from the contralateral neural primordium when the graft was unilateral or from the fringe area of the operation in cases of bilateral transplantations. As a control, unsegmented paraxial mesoderm was inserted alongside the cephalic neural tube; its cell did not migrate ventrally in the neural crest-derived area and they differentiated in the dorsal region of the host. These results indicate that mesectodermal capabilities, thought reduced, exist in the trunk neural crest at early stages of development but the differentiation of these mesectodermal derivatives is largely dependent upon environmental influences which may be found in early cephalic levels.