The Fine-Structural Localization of Phosphatases in Neurosecretory Cells Within the Ganglia of Certain Gastropod Snails

Abstract

The neurosecretory cells in the cerebral ganglia of the snail, Planorbis trivolvis, have been examined for structural details and distribution of phosphatase activities. A more preliminary study on the localization of phosphatases in the neurosecretory cells of Helix aspersa has also been made. These neurons in both species contain typical elementary neurosecretory granules which appear to be elaborated or condensed in the Golgi saccules. Immature elementary granules are identifiable as “primary lysosomes” in that they contain acid phosphatase activity as well as nucleoside phosphatases. The mature elementary granules display no phosphatase activity. Some saccules of the Golgi are also reactive for several nucleoside phosphatases, including thiamine pyrophosphatase (TPPase). In Planorbis, TPPase is also present in the cisternae of the endoplasmic reticulum. Larger, membrane bound, electron-dense bodies (lipochondria) are found in close spatial association with the Golgi region. These also possess acid phosphatase; in addition, they contain nucleoside diphosphatases and (in Planorbis) adenosine triphosphatase. Their content of acid phosphatase and the features of their fine structure indicate that they are lysosomes akin to the dense bodies of vertebrate neurones. The significance and implications of these results are considered, as are other details of the neuronal and glial structure in Planorbis.