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M Colonnier

Publications and source records attributed to M Colonnier.

8 recordsLinked to original sources
PubMed1989

Synaptophysin expression during synaptogenesis in the rat cerebellar cortex.

In order to study the mechanisms of synaptogenesis in the rat cerebellar cortex, a library of monoclonal antibodies has been generated against proteins of the isolated synapse. One recognizes a glycosylated 38 kDa protein that is concentrated in the synaptic vesicle fraction and resembles synaptophysin biochemically in its molecular weight, charge, and pattern of glycosylation. In the adult cerebellar cortex, the antisynaptophysin(mabQ155) immunoreactivity is codistributed with synapses. Immunoreactivity is strongest in the molecular layer where punctate deposits of reaction product outline the Purkinje cell dendrites. Discrete small profiles, consistent with the distribution of basket cell axon terminals, surround the Purkinje cells, and in the granular layer the synaptic glomeruli are intensely stained. There is no immunoreactivity in the white matter axon tracts. Electron microscope immunocytochemistry confirms the synaptic location of the antigen and suggests that the reaction product is associated with synaptic vesicles. Both round and flat vesicle populations are immunoreactive. Antisynaptophysin(mabQ155) has been used to follow synaptogenesis in the developing rat cerebellum. In the newborn rat (P0), despite the paucity of synapses, there is some specific immunoreactivity, especially in the subcortical white matter. Electron microscopy shows that the antigenicity is associated with vesicles within growth cones, filopodia, and immature axon profiles. During development, antisynaptophysin immunoreactivity increases progressively, along with the maturing cell populations, for both the granule cell-Purkinje cell and the mossy fiber-granule cell synapses. Quantitative biochemical analysis confirms the cytochemical results. These data suggest that neuronal growth cones express a synapse-specific antigen before complete morphological synapses are present.

Aging↗
PubMed1979

An electron microscope study of synaptic contacts in the abdominal ganglion of Aplysia californica.

The fine structure of the abdominal ganglion of Aplysia californica has been studied in preparations fixed by immersion in aldehydes, either directly or after a survival of a few hours in artificial sea water. The central core of neuropil is surrounded by a rind of neuronal cell bodies floating in a subcapsular space containing a loose meshwork of neuronal and glial processes, separated by wide extracellular spaces. Large primary processes with deeply infolded membranes leave the neuronal perikarya and enter the neuropil where they branch into smaller processes containing either neurofilaments, neurotubules or both. Some have the appearance of initial segments. The neuropil is not a homogeneous structure. Rather, four types of zones can be distinguished: (1) zones of fibers of passage coursing together in the neuropil and making few synaptic contacts: (2) zones of neurosecretory fibers containing large granules and dense-core vesicles, again making few synaptic contacts: (3) zones with a great variety of synaptic contacts between medium size and small profiles; and (4) glomerular zones. The differentiated membranes of the synapses are characterized by a slight increase in density and by being regularly parallel to each other. Presynaptic densities are sometimes quite prominent but specialized dense cytoplasmic opacities have never been seen bordering the postsynaptic membranes, i.e., all synapses are of the symmetrical type. Interlemmal opacities vary considerably in density. In zone 3, the synaptic vesicles are of several sizes, are round, oval or flat, and are either clear or filled with different types of dense material. The population of vesicles within a single profile may consist either of a homogeneous group of similar vesicles or of various mixtures of two or three kinds of vesicles. In profiles with mixtures of clear and large dense-core vesicles, it is often only the clear vesicles which agglomerate towards the differentiated membranes. In such cases the large dense-core vesicles lie as a peripheral halo around the clear vesicles. Here, and especially in other large neuronal profiles not forming contact in the plane of section, they can be seen to associate specifically with mitochondria and glycogen. It is proposed that they do not contain neurotransmitters but are related to mitochondrial activities such as the storage of ATP or the movement of calcium ions. In profiles with mixtures of clear and small dense-core vesicles, both types of vesicles often touch the presynaptic membrane, suggesting the release of two transmitters or of a modulator or neurohormone with a transmitter, by a single terminal. Serial synapses are present in this zone. The glomerular zones contain small profiles forming many synaptic contacts, some of which are arranged in such a way as to suggest the existence of "reciprocal" serial synapses.

Animals↗
PubMed1979

Synaptic contacts on glial cells in the abdominal ganglion of Aplysia californica.

Two types of glial cells have been identified in the neuropil and in the subcapsular space of the abdominal ganglion of Aplysia californica. In the neuropil, a first type of glial cell has a light staining cytoplasm and gives rise to processes which may contain bundles of filaments, a flocculent material or bundles of microtubules and membranous sacs. Synaptic contacts have been seen very rarely on their somata and more frequently on their "filamentous" and "flocculent" processes. A second type of glial cell has a darkly staining cytoplasm and gives rise to dense processes. Synaptic contacts are frequently seen on these processes. In the subcapsular zone, there are also two types of glial cells, one with a clear and the other with a dense cytoplasm. The processes of the clear glial cells contain glycogen-like particles and sometimes bundles of filaments. These processes surround the bundles of neuronal profiles which form the perisomatic plexus. Such enveloping processes receive synaptic contacts from the neuronal profiles in the bundles. The dense glial cells of the subcapsular zone also receive synaptic contacts, but this is a rare occurrence.

Animals↗
PubMed1977

Thalamic projections of the superior colliculus in the rhesus monkey, Macaca mulatta. A light and electron microscopic study.

The projections of the superior colliculus to the thalamus have been studied in the monkey, Macaca mulatta, with anterograde degeneration techniques. The superior colliculus has been shown to project to the inferior nucleus of the pulvinar in a topographical manner with the lower visual field represented dorsomedially and the upper field ventrolaterally. The peripheral zone is located along the medial border and the fovea at the dorsolateral angle adjacent to the lateral geniculate nucleus. The superior colliculus also sends a dense projection to the ipsilateral intralaminar complex, i.e., to the parafascicular, central lateral and paracentral nuclei, and a lesser projection to the same contralateral nuclei. Degenerating tectal fibers were also found in the lateral geniculate nuclei. Four types of vesicle containing profiles were observed in the inferior pulvinar and paracentral nucleus. The large RL and small RS terminals contain round vesicles of uniform size and form asymmetric contacts mainly with large and small dendrites respectively. The F terminal contains a mixture of small round and flat vesicles. It forms symmetric contacts with dendrites and cell somata. The P profile is very pale and contains a relatively sparse population of vesicles showing a great variation in size. It forms symmetric contacts with medium to large dendrites. It is frequently found postsynaptic to the other types, especially the RL terminal, and is regularly seen as the intermediate element of serial and triadic synaptic arrangements. The experimental electron microscopic study has shown that many fibers from the superior colliculus terminate as RL profiles, undergoing direct dense degeneration, in both the inferior pulvinar and the paracentral nucleus. Others probably end as smaller RS terminals.

Afferent Pathways↗
PubMed1975

Synaptic patterns in the visual cortex of turtle: an electron microscopic study.

The part of turtle general cortex that receives afferent fibers from the dorsal lateral geniculate nucleus and that shows evoked potentials to light stimuli has been studied with the electron microscope. This cortex consists of an outer molecular layer, a perikaryal layer, and a subcellular layer lying on a row of ependymal cell bodies. Neurons in the perikaral lamina are characterized by long spine-bearing apical dendrites ascending through the outer molecular layer and short finer basal dendrites in the subcellular zone. Scattered neurons without apical dendrites occur in both the molecular and subcellular zones. Two types of dendritic spines can be distinguished. Some are large, have a complex irregular shape, contain a variety of membranous sacs and mitochondria, and occasionally, a single bundle of microtubules embedded in an electron-dense background [corrected] opacity. These large spines are the most common postsynaptic element in the outer third of the molecular layer, where they are located on the distal enlargement that contains only electron-dense fuzz. They are the most common post-synaptic element in the lower two-thirds of the molecular layer where they arise from the proximal portion of apical dendrites. Most synaptic contacts are found on the dendritic spines and are of the "round-asymmetrical" type. Not infrequently "flat-symmetrical" synapses are coupled to "round-asymmetrical" contacts on individual large spines. The few contacts present on spine-bearing dendritic shafts are of both types. Axo-somatic contacts are mainly of the "flat-symmetrical" variety. Thus the synaptic patterns on the principal cells of turtle visual cortex are remarkably similar to those found on pyramidal cells of mammalian neocortex. In addition, however, axon terminals, dendrites and glial (ependymal) processes were often seen to give rise to membranous pouches containing large vacuoles and invaginating into dendritic shafts or spines. Rarely, axon terminals were seen to form contacts, identical in appearance to synaptic contacts, on cell bodies in the ependymal lining. More frequently, unusual types of membrane differentiations were present at the site of apposition of the membranes of axon terminals and ependymal processes. They are interpreted as functional neuroependymal contacts.

Animals↗