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R P Rees

Publications and source records attributed to R P Rees.

5 recordsLinked to original sources
PubMed1978

The morphology of interneuronal synaptogenesis: a review.

This review has endeavored to present current findings on the morphology of synaptogenesis, summarized in Fig. 5. Though much has been discovered about the order of events and the origin of organelles, the crucial questions of why these events occur at the moment in space and time remain largely unanswered. For an understanding of the molecular basis of neuronal recognition, and of the assembly and maintenance of a functional synaptic active zone, further extensive multidisciplinary studies will be necessary.

Animals↗
PubMed1978

Structure of cell coats during initial stages of synapse formation on isolated cultured sympathetic neurons.

The mordant tannic acid was applied after routine aldehyde and osmium fixation in order to study the ultrastructure of membrane coat material during synaptogenesis in combination cultures of superior cervical ganglion neurons and spinal cord explants. All contact between cultured neurons was mediated by coat material; apposition of outer membrane leaflets never occurred. In most areas, the contact found between membrane coat material lacked special arrangement, but in areas of contact between spinal cord growth cones and sympathetic ganglion neurons, distinct patches of bilateral membrane specialization were seen. Here apposed coat material interdigitated across the intracellular gap, outer membrane leaflets were parallel and dense material was evident in the adjacent cytoplasm. These 'differentiated' contacts were seen both prior to and simultaneously with the appearance in the same area of other synaptic organelles; they did not appear to be precursors of synaptic active zones. Findings suggest that a mosaic of specificities in neuronal coat material may determine the site of 'differentiated' contacts and that these contacts may be relevant to the subsequent formation of a synaptic active zone.

Cell Membrane↗
PubMed1976

Morphological changes in the neuritic growth cone and target neuron during synaptic junction development in culture.

Our object was to characterize the morphological changes occurring in pre- and postsynaptic elements during their initial contact and subsequent maturation into typical synaptic profiles. Neurons from superior cervical ganglia (SCG) of perinatal rats were freed of their supporting cells and established as isolated cells in culture. To these were added explants of embryonic rat thoracic spinal cord to allow interaction between outgrowing cord neurites and the isolated autonomic neurons. Time of initial contact was assessed by light microscopy; at timed intervals thereafter, cultures were fixed for electron microscopy. Upon contact, growth cone filopodia became extensively applied to the SCG neuronal plasmalemma and manifested numerous punctate regions in which the apposing plasma membranes were separated by only 7-10 nm. The Golgi apparatus of the target neuron hypertrophied, and its production of coated vesicles increased. Similar vesicles were seen in continuity with the SCG plasmalemma near the close contact site; their apparent contribution of a region of postsynaptic membrane with undercoating was considered to be the first definitive sign of synapse formation. Tracer work with peroxidase and ferritin confirmed that the traffic of coated vesicles within the neuronal soma is largely from Golgi region to somal surface. Subsequent to the appearance of postsynaptic density, the form and content of the growth cone was altered by the loss of filopodia and the appearance of synaptic vesicles which gradually became clustered opposite the postsynaptic density. As the synapse matured, synaptic vesicles increased in number, cleft width and content increased, presynaptic density appeared, branched membranous reticulum became greatly diminished, and most lysosomal structures disappeared. Coated vesicles continued to be associated with the postsynaptic membrane at all stages of maturation. The incorporation of Golgi-derived vesicles into discrete regions of the cell membrane could provide the mechanism for confining specific characteristics of the neuronal membrane to the synaptic region.

Animals↗