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Biomedical subjects

A I Matus

Publications and source records attributed to A I Matus.

At least 19 recordsLinked to original sources
PubMed1992

Directional control of neurite outgrowth from cultured hippocampal neurons is modulated by the lectin concanavalin A.

Cell surface carbohydrates play an important role in the regulation of neurite outgrowth during neuronal development. We have investigated the actions of the plant lectin concanavalin A (Con A), a carbohydrate-binding protein, on neurite outgrowth from hippocampal pyramidal neurons in primary cell culture. Neurons plated in culture medium containing nanomolar concentrations of Con A have a larger number of primary neurites arising directly from the cell soma than do neurons plated in culture medium alone. Furthermore, Con A causes counterclockwise turning of neurites in over 70% of the cultured neurons. Both of these effects of Con A are blocked by the hapten sugar alpha-methyl-D-mannopyranoside, suggesting that they result from the interaction of Con A with a cell surface carbohydrate. Another lectin with a different sugar specificity, wheat germ agglutinin, does not modulate neurite outgrowth. Analysis of neurite outgrowth using video-enhanced microscopy reveals that the counterclockwise turning is accompanied by directionally biased extension of filopodia from the growth cones of growing neurites. Treatment of the neurons with cytochalasin, which disrupts actin polymerization, eliminates the neurite turning induced by Con A, suggesting that actin microfilaments are involved in directional control of neurite outgrowth.

Actins↗
PubMed1988

Neuronal microtubule-associated proteins in the embryonic avian spinal cord.

We have used monoclonal antibodies to study the distribution of three developmentally regulated microtubule-associated proteins-MAP2, MAP5, and tau-during the morphogenesis of the thoracic spinal cord and peripheral nervous system in the quail. MAP5 is the only one of the three that is present in growing motor neuron processes in the day 3 embryo. The low-molecular weight form of MAP2, MAP2c, is found in motor neuron cell bodies at embryonic day 3. At later stages MAP2c appears in axons and in glia; it decreases in abundance between embryonic days 5 and 7. High-molecular weight MAP2 appears in motor neuron cell bodies and spinal cord gray matter at embryonic day 4, and is never encountered in axons. Tau is found in axons, but only at embryonic day 3.5, after they have commenced active extension. The molecular form and patterns of intracellular compartmentalization of each of the microtubule-associated proteins studied is conserved in mammalian and avian neurons. We conclude that MAP5 may be involved in the active growth of neuronal processes, whereas MAP2 and tau are not, and that high-molecular weight MAP2 and tau may stabilize dendritic and axonal processes, respectively.

Animals↗
PubMed1988

Differential localization of the high- and low-molecular weight variants of MAP2 in the developing retina.

Microtubule-associated protein 2 (MAP2) occurs in developing mammalian neuronal tissue as both high (280 kDa)- and low (70 kDa)-molecular weight forms with temporally regulated expression. We have studied the developing avian retina with a monoclonal antibody that recognizes both the high- and low-molecular weight forms of MAP2 and a second monoclonal antibody that recognizes only high-molecular weight MAP2. The developmentally regulated, low-molecular weight protein, MAP2c, has a more widespread distribution in the embryonic avian retina than high-molecular weight MAP2. Our results suggest that MAP2c is the first form of MAP2 to appear in differentiated embryonic retinal neurons, and that the high-molecular weight isoforms of MAP2 appear only later when they may confer stability to neuronal processes.

Aging↗
PubMed1988

Microtubule-associated proteins characteristic of embryonic brain are found in the adult mammalian retina.

We have used monoclonal antibodies against each of the major mammalian brain microtubule-associated proteins (MAPs), MAP1, MAP2, MAP3, MAP5, and tau, to study the timing of appearance and the cytological distribution of these proteins during the development of the rat retina. Western blots of adult rat retina reveal MAPs that are characteristic of embryonic brain, i.e., MAP5 and the low-molecular-weight forms of MAP2 (MAP2c) and tau (juvenile tau). At the onset of neuronal differentiation within the embryonic retina, MAP5, MAP3, MAP2c, and tau are found in the perikarya or extending axons of ganglion cells. High-molecular-weight MAP2, a dendrite marker, does not appear in the retina until the second day of postnatal development, when ganglion cell dendrites ramify within the inner plexiform layer. MAP1, which is characteristic of adult brain, does not appear in the retina until 1 week after birth, and is limited to ganglion cells and their processes. In the adult retina, MAP5 and MAP2c are concentrated within the inner segments and cell bodies of photosensitive cells, whereas tau is found in horizontal cells and more internal cell layers. Since photosensitive cells are unique among retinal neurons in their constant regeneration of their primary processes, the photoreceptive outer segments, both MAP5 and MAP2c appear not only to be involved in events associated with the embryonic differentiation and growth of neurites, but also in process regeneration in adult neurons that maintain some embryonic characteristics.

Age Factors↗
PubMed1988

The sequential appearance of low- and high-molecular-weight forms of MAP2 in the developing cerebellum.

Mammalian microtubule-associated protein 2 (MAP2) exists in high-molecular-weight (Mr approximately 280,000) and low-molecular-weight (Mr approximately 70,000) forms, with the latter protein being more abundant in embryonic brain homogenates than in preparations from mature brain (Riederer and Matus, 1985). In the current study, we have shown that avian MAP2 also exists as both high- (Mr approximately 260,000) and low-molecular-weight (Mr approximately 65,000) forms whose relative abundance changes during brain maturation, indicating a conserved function for these proteins during vertebrate neuronal morphogenesis. Using indirect immunohistochemistry, we have determined the cellular distribution of the high- and low-molecular-weight forms of MAP2 in the developing avian cerebellum. In the embryonic cerebellum, low-molecular-weight MAP2 is found in the external granular layer and in epithelial cells. High-molecular-weight MAP2 is found only in neurons that have commenced dendrogenesis, i.e., Purkinje cells and neurons within the internal granular layer. Thus, low-molecular-weight MAP2 is not only more abundant in embryonic nervous tissue than in the adult, but it also appears in glia and in differentiating neurons before the high-molecular-weight form. We have also shown that in the mature cerebellum high-molecular-weight MAP2 cannot be detected with monoclonal antibodies or polyclonal antisera in Purkinje cell dendrites. Polyclonal antisera against the regulatory subunit of the cAMP-dependent protein kinase, which is associated with MAP2 in the Purkinje cell dendrites of the rat, also fail to stain Purkinje cell dendrites in the mature quail cerebellum. This suggests that high-molecular-weight MAP2 may be necessary for the establishment of dendrites but is not necessary for the maintenance of dendritic form.

Animals↗
PubMed1987

Developmental regulation of two microtubule-associated proteins (MAP2 and MAP5) in the embryonic avian retina.

Previous studies with the mammalian brain have shown that the expression of a number of neuronal microtubule-associated proteins (MAPs) is developmentally regulated. For example, the low-molecular-weight form of MAP2 (MAP2c) is abundant in neonatal rat brains and is less abundant in adults. Similarly, MAP5 levels decrease during postnatal development. Using monoclonal antibodies, we have followed the time of first appearance, cellular distribution, and molecular form of MAP2 and MAP5 during the morphogenesis of the quail retina. MAP2 first appears in ganglion cell bodies and in the axons of the optic fibre layer (OFL) at embryonic day 4 (E4). Anti-MAP2 staining remains restricted to these sites until E10, when staining appears in the inner plexiform layer (IPL). At E14, one day before hatching, anti-MAP2 staining is found in three broad laminae in the IPL, as well as in photosensitive cells. MAP5 is present in ganglion cell axons from the onset of neurite elongation at E3 and is limited to the OFL until E10. The intensity of anti-MAP5 staining in the OFL and optic nerve decreases after E7, which corresponds with a decrease in the number of actively growing ganglion cell axons. By E14, anti-MAP5 stains five layers in the IPL that correspond with layers of amacrine cell process arborizations. Western blots of E10 brain microtubule proteins show that MAP2 is represented by both a 260 x 10(3) Mr protein and a 60-65 x 10(3) Mr protein; the latter is much more abundant. Anti-MAP5 recognizes a 320 x 10(3) Mr brain microtubule protein in both the quail and the rat. We conclude that the cellular distribution, developmental regulation and molecular forms of MAP2 and MAP5 are similar in the rat and quail, suggesting that these molecules have conserved and hence fundamental roles in the growth and differentiation of neuronal processes.

Animals↗
PubMed1981

Ultrastructural localization of cyclic GMP and cyclic AMP in rat striatum.

The subcellular localization of cyclic GMP and cyclic AMP in the rat caudate-putamen has been studied using horseradish peroxidase immunocytochemistry. Both of the putative neurotransmitter second messengers were visualized in neurons and glial cells at light microscopic resolutions, but not all cells of either category gave detectable staining. This was confirmed at the ultrastructural level where both stained and unstained elements of the same cell type were found within the same field. A striking variation was seen in cyclic nucleotide staining intensity within individual neural and glial cells. Both of the cyclic nucleotides were detected within postsynaptic terminal boutons and within astroglial processes. Cyclic GMP postsynaptic staining was stronger than glial staining, whereas the localization pattern was reversed for cyclic AMP. The synaptic localization of cyclic AMP and cyclic GMP immunoreactivity adds support to the idea that these compounds have an influential role in synaptic function within the striatum.

Animals↗
PubMed1979

Immunohistochemical localization of neurofilament antigen in rat cerebellum.

The distribution of neurofilaments in the rat cerebellar cortex was studied by immunoperoxidase histochemistry using an antiserum raised against neurofilaments isolated from brain (anti-NF). In light microscope preparations, this antiserum selectively stained known neurofilament-containing structures. Staining was most intense in myelinated axons of the white matter and in the terminal branches of basket cell axons. No staining was apparent in either neuronal or glial cell bodies or in glial cell processes. These findings were confirmed in electron microscopic preparations of the same material. Neurofilaments stained by the antiserum were abundant in basket cell axons and also occurred in small bundles in mossy fibre terminals. Adjacent microtubules were not stained by the antiserum. There was no evidence of stained cytoplasmic filaments in glial cell processes. Thus it appears that neurofilaments contain unique antigens which do not occur in either microtubules or in glial cytoplasmic filaments. The antiserum did not induce staining of synaptic junctional structures, a result which contradicts previous suggestions that neurofilaments are structural components of synaptic densities.

Animals↗
PubMed1978

Morphology and molecular composition of isolated postsynaptic junctional structures.

The solubilization of isolated brain synaptosomal plasma membranes by various detergents was studied and in each case found to depend upon detergent concentration. By using conditions sufficient to extract maximally protein and phospholipid from the membranes, postsynaptic junctional particles were isolated with each of four detergents and their ultrastructural appearances and protein contents compared. Two basic structural forms were identified. One, isolated with Triton X-100, consists of a planar array of dense-staining particles ca. 20 nm in diameter. It resembles the postsynaptic density seen in undigested synaptosomal plasma membranes. The other, isolated with sodium deoxycholate, contains less protein. It has the same overall shape and dimensions as the postsynaptic density, but consists of a branching network of short 5 nm fibres (the postsynaptic junctional lattice) making up an array of contiguous polygons, each ca. 20 nm across. The interior of these polygonal elements seems to be hydrophobic since it cannot be penetrated by metallic salts used for negative staining. It is suggested that the dense-staining 20 nm subunits observed at the postsynaptic junctional site may be composed of hydrophobic proteins inserted into the hollow cores of the lattice polygons. Electrophoretic analysis of the proteins present in the various postsynaptic junctional preparations identified two major common components with molecular masses of 275000 and 47500. The latter is tentatively identified as actin. Components comigrating respectively with alpha- and beta-tubulin are present, and the relation of the lattice structure to subjacent microtubules is discussed.

Animals↗
PubMed1976

Type 1 and 2 synaptic junctions: differences in distribution of concanavalin A binding sites and stability of the junctional adhesion.

Two classes of synaptosomes have been distinguished in subcellular fractions from rat forebrain. They differ in morphology and distribution of concanavalin A binding sites. Morphological examination suggests that the two classes correspond to the type 1 (excitatory) and type 2 (inhibitory) synapses of intact brain tissue. Under the conditions of incubation employed in this study, type 1 synaptosomes show splitting of the synaptic junctions, but the type 2 junctions are apparently stable. The chemical differences illustrated by the differences in concanavalin A binding sites suggest that type 1 and type 2 synaptic junctions differ fundamentally in supramolecular structure rather than being superficial variants of basically similar structures.

Animals↗
PubMed1975

Immunohistochemical demonstration of antigen associated with the post-synaptic lattice.

The binding of amtosera against synaptosomes from rat cerebral cortex to dissociated cells from both cerebral cortex and liver was assessed by immunofluorescent labelling. This showed that none of the liver cells bound antisynaptosome antibodies but that some of the cerebral cortex cells bound antibody on their surfaces. Immunofluorescent labelling showed that all the particles in the crude mitochondrial fraction from rat cortex bound antibodies present in the unadsorbed antisera. However, when the antisera were absorbed with purified mitochondria and myelin, only a proportion of the mitochondrial fraction particles then bound antibody. Isolated IgG from the adsorbed antisera was labelled with ferritin and incubated with the crude mitochondrial fraction. Examination in the electron microscope showed that the ferritin and hence the antisynaptosome antibody was bound to the post-synaptic thickenings of about 20% of synaptosomes having their junctions in the plane of section.

Animals↗
PubMed1975

Junctional ultrastructure in isolated synaptic membranes.

The ultrastructure of synaptic junctions in whole brain tissue and isolated synaptic membranes has been compared. Type 1 junctions are present in the isolated membranes,readily identified by the presence of dense-staining material associated with the postsynaptic membrane, but the dense projections present at the presynaptic membrane in intact tissue are absent. Type 2 junctions are not easily recognized because of the absence of prominent junctional densities, but apposed membranes with the appearance of type 2 junctions are seen in isolated membrane preparations. Junctions without dense-staining material are also seen among SYNAPtosomes and survive the hypotonic conditions used during isolation of the membranes. It thus seems probable that both type 1 and 2 junctions are present in isolated synaptic membrane preparations. In type 1 junctions after isolation,the postsynaptic thickening and cleft substance are together seen to be composed of an array of 200 A dense-staining subunits spanning the postsynaptic unit membrane. The relationship of this structure to the ultrastructure of the cleft substance and postsynapticthickening in intact tissue is discussed.

Animals↗
PubMed1975

Ultrastructure of the synaptic junctional lattice isolated from mammalian brain.

Synaptic membranes can be treated with detergents to yield postsynaptic densities from which the lipid unit membrane has been removed. The ultrastructure of these densities is identical to THAT of the synaptic lattice observed in undigested synaptic membranes; a1000-3000 A diameter planar array of 200 A diameter dense-staining subunits. The persistence of this synaptic lattice in the absence of lipid membrane may reflect a functional role in the maintenance of defined synaptic junctional structures in intact tissue.

Animals↗