Histochemical and ultrastructural features

The developing enteric nervous systern of the hurnan foetus has been analyzed at the 10th and 18th week of gestation with a special reference to the development of nerve-rnuscle contacts. The rnyenteric plexus forrnation was analyzed by rneans of electron microscopy and on whole-mounts after NADH diaphorase histochernistry. The developrnent of noradrenergic innervation as an extrinsic inhibitory supply was followed by means of a glyoxylic acidinduced fluorescence rnethod. Differentiated neurons and neuroblasts both occurred in rnyenteric ganglia of the 10- and 18-week-old foetus although the ganglionic neuropil was almost unidentifiable ultrastructurally at the 10th week of gestation but was rnature looking at the 18th week. The nerve plexuses connecting the ganglia frequently forrned distant and close rnyoneural contacts. NADH-diaphorase histochernistry revealed that in the 18-week-old hurnan foetus rnost of the neural perikarya was within the ganglia. Also, at the 18th week of gestation a well-defined fluorescent network was dernonstrated within the ganglia, as well as in the internodal segrnents. On the basis of these observations we concluded that the time between the 10th and 18th week of gestation has pararnount irnportance for both the rnorphological and functional rnaturation of the enteric nervous systern

Sequential pattern of nerve-muscle contacts in the small intestine of developing human fetus. An ultrastructural and immunohistochemical study

The developing enteric nervous system of the human fetus has been studied by means of electron microscopy and neuron-specific enolase immunocytochemistry between the 10th and 26th week of gestation, with special reference to the development of nervemuscle contacts. In the 10th week of gestation the circular muscle layer is formed, followed by the appearance of a primitive myenteric plexus, and the longitudinal smooth muscle layer in the 12th week of gestation. Adherens-type junctions between the smooth muscle cells and the elements of the myenteric plexus, interdigitation of nerve and muscle processes, and also contacts without any morphological specialization are frequent until the 18th week, when the mechanical points of attachment are relocated from the circular to the longitudinal muscle layer. By this time the developing myenteric plexus becomes ensheathed by non-neuronal cells, disrupting the direct contacts between smooth muscle cells and the primary strands of the myenteric plexus. The possible functional significance of these changing nerve-muscle contacts is discussed in the present paper

Subcellular localization of transaminase enzymes in fishes and their significance in the detection of water pollution

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