Ultrastructure and histochemistry of neurosecretory cells and neurohaemal areas in the pond snail Lymnaea stagnalis (L.)

Abstract

Sum man/. In t he central ganglia of Lymnaea stagnalis neurosecretory cell groups have previously been identified by means of chrome-haematoxylin or paraldehyde-fuchsin stains. In the present study seven types have been distinguished within the class of Gomori-positive cells on the basis of different staining reactions with the alcian blue/alcian yellow technique. Five types are located in the cerebral ganglia and in the lateral lobes, whereas two cell types occur in the ganglia of the visceral ring. No neurosecretory cells have been observed in tlie buccal and pedal ganglia.The staining technique used proved to be superior to the classic neurosecretory stains, because with this method the secretory substances can easily be distinguished from non-secretory Gomori-positive tissue constituents. One of the two Gomori-negative neurosecretory cell types of the cerebral ganglia react positively with the alcian blue/alcian yellow technique. In addition, two Gomori-negative neurosecretory cell types, which had not been described before, were identified in the visceral ring.The ultrastructure of the four neurosecretory cell types in the visceral ring is described. The electron microscope revealed that each of the histochemically distinguished secretory substances consists of elementary granules which differ in size and appearance from each other and from the neurosecretory elementary granules which have been described by other authors in the cerebral ganglia and in the lateral lobes.The neurohaemal areas of the neurosecretory cells in the visceral ring are very extensive and include the peripheral parts of the nuchal nerves and of the connectives and nerves of the ganglia of the ring. The perineurium and the adjacent parts of the connective tissue which surround the ganglia, the connectives and the nerves are regarded as additional neurohaemal zones, because in these regions many tiny nerves occur, which l/ 1/ consist mainly of neurosecretory axons ending non-synapticallv near parts of the vascular system. In the perineurium surrounding the cerebral ganglia and their neurohaemal area a similar network of neurosecretory fibres was observed.Indications of release of the secretory material were regularly observed. Release appa rently takes place by exocytosis. % / % /A circadian rhythmicity was observed in the release activity of some of the neurosecretory cell types.

Immunocytochemical demonstration of a novel system of neuroendocrine peptidergic neurons in the pond snail Lymnaea stagnalis, with antisera to the teleostean hormone hypocalcin and mammalian parathyroid hormone

“…13), parietal, and visceral gan glia, where they are found between fibers and terminals of axons originating from other types of neuroendocrine cells present in these ganglia (dark green cells, light green cells, and yellow cells). The granules of the light green and dark green cells are larger than those of the presumptive hypo calcin and PTH positive cells, but only slightly smaller than those of the yellow cells (Wendelaar Bonga, 1970). They differ…”

“…Many serves originate from the ganglia and innerate all parts of the body. The general hisology and ultrastructure of the central nerous system have been described earlier Wendelaar Bonga, 1970). A diagram (with>ut buccal ganglia) is presented in Fig.…”

“…These cells apparently form an important type of hitherto unknown peptidergic neu roendocrine cells. None of the various types of neuroendocrine cells reported so far by light or electron microscopy in one or more of these ganglia shows a similar type of distribution (Wendelaar Bonga, 1970;Schot et al, 1981). In the parietal and vis- ;eral ganglia, two types of neuroendocrine :ells have been described by the Alcian blue/Alcian yellow staining procedure: the yellow green cells (YGC) and the yellow cells (YC).…”

“…In the parietal and vis- ;eral ganglia, two types of neuroendocrine :ells have been described by the Alcian blue/Alcian yellow staining procedure: the yellow green cells (YGC) and the yellow cells (YC). The axons of these cells are end ing in the periphery of the parietopleural and parietovisceral connectives in the pe riphery of the proximal parts of all the nerves originating from the parietal and vis ceral ganglia and in the adjacent connective tissue (Wendelaar Bonga, 1970). The pe riphery of connectives, commissures, and the proximal parts of many nerves, as well as the adjacent connective tissue, represent the typical neurohemal areas of pulmonate snails (Boer et al, 1968;Wendelaar Bonga, 1970).…”

“…The axons of these cells are end ing in the periphery of the parietopleural and parietovisceral connectives in the pe riphery of the proximal parts of all the nerves originating from the parietal and vis ceral ganglia and in the adjacent connective tissue (Wendelaar Bonga, 1970). The pe riphery of connectives, commissures, and the proximal parts of many nerves, as well as the adjacent connective tissue, represent the typical neurohemal areas of pulmonate snails (Boer et al, 1968;Wendelaar Bonga, 1970). In these regions, axon swellings and terminals are in contact with the connective tissue and blood spaces.…”