Biomedical subjects

A Matus

Publications and source records attributed to A Matus.

106 records · Page 6Linked to original sources

PubMed1981

Regularity and differentiation within the structure of brain postsynaptic densities.

Postsynaptic densities (PSDs) isolated from rat forebrain were examined in samples prepared for electron microscopy by negative staining. Two structurally distinct areas could be distinguished within each individual PSD, a peripheral zone composed of a planar array of spherical subunits with a mean diameter of 18 nm and one or more islands of fine granular material enclosed by the subunits. These enclosures correspond in distribution and size to 'holes' which are known to occur in PSDs in intact brain tissue. The spherical subunits can occur singly in the isolated PSD preparations showing that the structure of each individual subunit does not depend upon its interaction with others. These observations indicate that the PSD structure has both regular and differentiated features. These are considered in relation to the possible roles of the PSD in defining the postsynaptic locus and mediating the postsynaptic events of synaptic transmission.

Animals↗

PubMed1981

High molecular weight microtubule-associated proteins are preferentially associated with dendritic microtubules in brain.

The distributions of tubulin and high molecular weight microtubule-associated proteins (HMWPs) in brain were determined by immunoperoxidase histochemistry with specific antisera. Tubulin was found in microtubules of both neurons and glia and both axons and dendrites. HMWPs were found only in neurons where, in all cases examined, they were associated with dendritic microtubules but not those in axons. Both tubulin and HMWPs were also found in postsynaptic densities. These results indicate that brain microtubules vary in chemical composition. The preferential association of HMWPs with dendritic microtubules suggests that they may play a role in distinguishing between dendritic and axonal export routes from the cell body.

Animals↗

PubMed1980

Brain postsynaptic densities: the relationship to glial and neuronal filaments.

Preparations of isolated brain postsynaptic densities (PSDs) contain a characteristic set of proteins among which the most prominent has a molecular weight of approximately 50,000. Following the suggestion that this major PSD protein might be related to a similarly sized component of neurofilaments (F. Blomberg et al., 1977, J. Cell Biol., 74:214-225), we searched for evidence of neurofilament proteins among the PSD polypeptides. This was done with a novel technique for detecting protein antigens in SDS-polyacrylamide gels (immunoblotting) and an antiserum that was selective for neurofilaments in immunohistochemical tests. As a control, an antiserum against glial filament protein (GFAP) was used because antisera against GFAP stain only glial cells in immunohistochemical tests. They would, therefore, not be expected to react with PSDs that occur only in neurons. The results of these experiments suggested that PSDs contain both neuronal and also glial filament proteins at higher concentrations than either synaptic plasma membranes, myelin, or myelinated axons. However, immunoperoxidase staining of histological sections with the same two antisera gave contradictory results, indicating that PSDs in intact brain tissue contain neither neuronal or glial filament proteins. This suggested that the intermediate filament proteins present in isolated PSD preparations were contaminants. To test this possibility, the proteins of isolated brain intermediate filaments were labeled with 125I and added to brain tissue at the start of a subcellular fractionation schedule. The results of this experiment confirmed that both neuronal and glial filament proteins stick selectively to PSDs during the isolation procedure. The stickiness of PSDs for brain cytoplasmic proteins indicates that biochemical analysis of subcellular fractions is insufficient to establish a given protein as a synaptic junctional component. An immunohistochemical localization of PSDs in intact tissue, which has now been achieved for tubulin, phosphoprotein I, and calmodulin, appears to be an essential accessory item of evidence. Our findings also corroborate recent evidence which suggests that isolated preparations of brain intermediate filaments contain both neuronal and glial filaments.

Brain↗

PubMed1979