Intrinsic organization of the medial cerebral cortex of the lizard Lacerta pityusensis: A golgi study

The morphology of cells and the organization of axons were studied in Golgi-Colonnier and toluidine blue stained preparations from the medial cerebral cortex of the lizard Lacerta pityusensis. In the medial cortex, six strata were distinguished between the superficial glial membrane and the ependyma. Strata I and II formed the outer plexiform layer, stratum III formed the cellular layer, and strata IV go VI the inner plexiform layer. The outer plexiform layer contained smooth bipolar neurons; their dendrites were oriented anteroposteriorly and their axons were directed towards the posterior zone of the brain. Five neuronal types were observed in the cellular layer. The spinous pyramidal neurons had well-developed apical dendrites and poorly developed basal ones. Their axons entered the inner plexiform layer and gave off collaterals oriented anteroposteriorly. The small, sparsely spinous pyramidal neurons had poorly developed dendrites and their axons entered the inner plexiform layer. The spinous bitufted neurons had well-developed apical and basal dendritic tufts. Their axons gave off collaterals that reached the outer and inner plexiform layers of both the dorsomedial and dorsal cortices. The sparsely spinous horizontal neurons had dendrites restricted to the outer plexiform layer. Their axons entered the inner plexiform layer. The sparsely spinous, multipolar neurons had their soma close to stratum IV and their axons entered the outer plexiform layer. In stratum V of the inner plexiform layer were large, spiny polymorphic neurons; they had dendrites with long spines, and their axons reached the cellular layer. On the basis of these results, we have subdivided the medial cortex into two subregions: the superficial region, which contains the neurons of the cellular layer and their dendritic domains, and the deep region, strata V and VI, which contains the large, spiny polymorphic neurons. The neurons in the medial cortex of these lizards resembles those in the area dentata of mammals. On this basis, the superficial region may be compared to the dentate gyrus and the deep region to the hilar region of the hippocampus of mammals.     

Neurons and their interconnections in the frontal cortex of monkeys

It was shown by the Golgi and Golgi-Kopsch method that pyramidal cells of layers II–IV in the frontal cortex of the monkeyMacaca rhesus have numeruous, mainly recurrent axon collaterals by means of which they form vertical connections. Pyramidal cells with ascending axons are found. Axons of stellate basket neurons unite pyramidal cells in both horizontal (modules) and vertical (micromodules) directions; depending on the direction of the axon collaterals, two groups of stellate neurons can be distinguished. Groups of 14 to 16 pyramidal cells whose apical dendrites are connected into bundles were found. Axons of pyramidal cells in layers II–IV descend in the composition of the pyramidal tract and give off collaterals which run toward the bodies and dendrites of neighboring pyramidal cells, united into the same group, forming terminal and en passant junctions. Besides bundles, special kinds of "local" cell groups with U-shaped axons are found.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 15, No. 2, pp. 115–120, March–April, 1983.     

Thoughts on the cerebral cortex

The cortex is often described as a network processing information in the direction from sensory to motor areas. However, the structure of the cortex is asymmetrical only in the vertical direction, suggesting an input-output transformation between layers rather than between areas. This operation must be a very generally applicable one, since the plan of the cortex is basically the same everywhere. In an attempt to understand it, a skeleton cortex of only pyramidal cells is considered. They are characterized by a double dendritic expansion, an apical one in the first layer, which is considered as the input layer, and a basal one which receives excitation from the axon collaterals of other pyramidal cells. If pyramidal cells learn (perhaps by growing dendritic spines) to respond to frequent constellations of activity in their afferents, each will learn a property of the input (through its apical dendrites) provided that it was preceded by other properties sensed by neighbouring pyramidal cells (which influences it through its basal dendrites). Thus the pyramidal cells will code the input in terms of properties which have a tendency to follow each other. This will be a coding which reflects the causal structure of the world. Various uses of a network embodying the conditional probabilities of events in the input are described, including recognition of familiar sequences and prediction. The local variation of fiber patterns in the cerebral cortex of man, described as myeloarchitectonics, is interpreted as a macroscopical expression of the different statistics of the set of conditional probabilities linking the events represented by individual pyramidal cells in different areas (in different functional contexts).     

Close homolog of L1 modulates area-specific neuronal positioning and dendrite orientation in the cerebral cortex

We show that the neural cell recognition molecule Close Homolog of L1 (CHL1) is required for neuronal positioning and dendritic growth of pyramidal neurons in the posterior region of the developing mouse neocortex. CHL1 was expressed in pyramidal neurons in a high-caudal to low-rostral gradient within the developing cortex. Deep layer pyramidal neurons of CHL1-minus mice were shifted to lower laminar positions in the visual and somatosensory cortex and developed misoriented, often inverted apical dendrites. Impaired migration of CHL1-minus cortical neurons was suggested by strikingly slower rates of radial migration in cortical slices, failure to potentiate integrin-dependent haptotactic cell migration in vitro, and accumulation of migratory cells in the intermediate and ventricular/subventricular zones in vivo. The restriction of CHL1 expression and effects of its deletion in posterior neocortical areas suggests that CHL1 may regulate area-specific neuronal connectivity and, by extension, function in the visual and somatosensory cortex.     

Polarized secretory trafficking directs cargo for asymmetric dendrite growth and morphogenesis

Proper growth of dendrites is critical to the formation of neuronal circuits, but the cellular machinery that directs the addition of membrane components to generate dendritic architecture remains obscure. Here, we demonstrate that post-Golgi membrane trafficking is polarized toward longer dendrites of hippocampal pyramidal neurons in vitro and toward apical dendrites in vivo. Small Golgi outposts partition selectively into longer dendrites and are excluded from axons. In dendrites, Golgi outposts concentrate at branchpoints where they engage in post-Golgi trafficking. Within the cell body, the Golgi apparatus orients toward the longest dendrite, and this Golgi polarity precedes asymmetric dendrite growth. Manipulations that selectively block post-Golgi trafficking halt dendrite growth in developing neurons and cause a shrinkage of dendrites in mature pyramidal neurons. Further, disruption of Golgi polarity produces neurons with symmetric dendritic arbors lacking a single longest principal dendrite. These results define a novel polarized organization of neuronal secretory trafficking and demonstrate a mechanistic link between directed membrane trafficking and asymmetric dendrite growth.     

Neural recognition molecules CHL1 and NB-3 regulate apical dendrite orientation in the neocortex via PTP alpha

Apical dendrites of pyramidal neurons in the neocortex have a stereotypic orientation that is important for neuronal function. Neural recognition molecule Close Homolog of L1 (CHL1) has been shown to regulate oriented growth of apical dendrites in the mouse caudal cortex. Here we show that CHL1 directly associates with NB-3, a member of the F3/contactin family of neural recognition molecules, and enhances its cell surface expression. Similar to CHL1, NB-3 exhibits high-caudal to low-rostral expression in the deep layer neurons of the neocortex. NB-3-deficient mice show abnormal apical dendrite projections of deep layer pyramidal neurons in the visual cortex. Both CHL1 and NB-3 interact with protein tyrosine phosphatase alpha (PTPalpha) and regulate its activity. Moreover, deep layer pyramidal neurons of PTPalpha-deficient mice develop misoriented, even inverted, apical dendrites. We propose a signaling complex in which PTPalpha mediates CHL1 and NB-3-regulated apical dendrite projection in the developing caudal cortex.     

Ontogeny of the mouse motor cortex. The polymorph layer or layer VI. A Golgi and electronmicroscopical study

Summary The development of neurons and their synapses of the mouse motor cortex has been studied from the first postnatal day up to an age of three weeks both electronmicroscopically and with the Golgi method. Special attention has been paid to the maturation of the different cell types in the sixth cortical layer and their dendritic organization within this layer.The polymorph layer is subdivided into two zones: an internal (VIb) and an external one (VIa). In these zones six different cell types can be identified both electronmicroscopically and with the Golgi method: large, small and inverted pyramidal cells in VIa; horizontal cells, star cells and small pyramidal cells in VIb.Spines of apical dendrites of large pyramidal cells in sublayer VIa can be detected as early as the 6th postnatal day. About the ninth day the basal dendrites as well show emerging spines. Somatic spines are found only on the large pyramidal cells and disappear slowly towards the end of the 3rd postnatal week.The small pyramidal cells show developing spines on their apical dendrite in the first half of the second postnatal week. The final density and distribution of spines is reached by the stem dendrites towards the end of the second week, by the basal dendrites during the third week. The maturation process of the improperly orientated neurons occurs in time in between the large and the small pyramidal cells.The axo-somatic synapses appear in general at a later date than the axo-dendritic ones. In the horizontal cells axo-somatic synapses are visible already at the seventh postnatal day.At the end of the first week especially in layer VIb many immature neurons with an ovoid or round nucleus are present having little if any endoplasmic reticulum organised as ergastoplasm.Towards the end of the second week however most neurons in the polymorph layer have a well developed endoplasmic reticulum.Electronmicroscopical pictures reveal in outgrowing dendrites many enlargements filled with vesicles, these correspond to the varicosities seen in Golgi pictures. At nine days postnatally the first myelinated fibres appear.Aided by grant (R-209-67) from the United Cerebral Palsy Research and Educational Foundation, New York.     

Changes in dendritic spine density on layer 2/3 pyramidal cells within the cingulate cortex of late pregnant and postpartum rats

A rapid upregulation of astrocytic protein expression within area 2 of the cingulate cortex (Cg2) of the maternal rat occurs within 3 h postpartum and persists throughout lactation. Previous studies have shown that similar changes in astrocytic proteins can signal changes in local synapses and dendritic spines. Thus, here we used the Golgi-Cox impregnation technique to compare spine density in layer 2 and 3 pyramidal cells of Cg2, the CA1 region of the hippocampus and the parietal cortex (ParCx) among metestrus, late pregnant (LP), 3-hour postpartum (3H PP) and 16-day postpartum rats (D16 PP). Rats in the 3H PP group had higher numbers of dendritic spines/10 μm on the apical dendrites of pyramidal neurons in both Cg2 and CA1 than the other groups, which did not differ. A similar pattern was observed in basilar dendrites but this failed to reach significance. In Cg2, Sholl analysis revealed that rats in the D16 PP group had a significantly greater extent of dendritic arborization in the basilar region than any other group. These data suggest that the changes in astrocytic proteins that occur in Cg2 in the postpartum period are associated with neuronal plasticity in pyramidal layers 2 and 3.     

Light and scanning electron microscopic study of cerebellar cortex of teleost fishes

Summary The teleostean cerebellar cortex has been studied with respect to its cytoarchitectonic arrangement and intracortical neuronal circuits. Samples of fish cerebellum were fixed either by immersion or vascular perfusion in 5% glutaraldehyde solution and processed for light and scanning electron microscopy. The cerebellar cortex shows four distinct layers: granular; fibrous stratum; Purkinje cell; and molecular layers. In the granular layer, mossy and climbing fiber glomeruli were characterized. The mossy glomerular region appeared as polygonal, round or ovoid clews formed by the convergence of up to 17 dendritic profiles upon a thick mossy fiber branch. The en passant nature of mossy fiber-granule cell dendrite synaptic relationship was clearly appreciated. The climbing fibers showed tendril and glomerular collaterals. The latter form thin, elongated glomeruli. Remnants of a neuroglial envelope were observed in the mossy fiber glomeruli but are apparently absent from the climbing fiber glomeruli. The beaded-shape Golgi cell axonal ramifications were observed participating in the formation of both glomerular types. Velate protoplasmic astrocytes and oligodendrocytes were also identified. The fibrous stratum appeared to be formed by compact bundles of thick and thin myelinated axons, running horizontally beneath the Purkinje cell layer and apparently belonging to ascending climbing fibers and descending Purkinje cell axons. At the Purkinje cell layer a selective removal of Bergmann glial cells was observed allowing the visualization of the pericellular basket and the pinceaux. Climbing fiber stems and their tendril collaterals were seen on their way to the molecular layer ascending parallel to the Purkinje dendritic ramifications. Stellate neuron processes were found passing through the fan-like arborescence of Purkinje cell dendrites.     

Spatial organization and interneuronal relations in various areas of the neocortex in Cetacea

The data on pyramidal neurons joining in the parietal and temporal areas of the dolphin neocortex by means of apical dendrites fasciculi are presented. The fasciculi also contain dendrites of spindle-like and stellate cells. The vertical fasciculi of the dendrites unite neurons of the layer V and of the sublayer III2. In the sublayer III1, after dichotonic division of the apical dendrites, fasciculi of the second order are formed, to them the dendrites of the pyramidal neurons of the sublayer III1 and the layer II join. Several forms of the interneuronal contacts have been revealed: axo-dendritic, axo-spinous and dendro-dendritic. Synaptic complexes of the converged and divergent types have been shown. A suggestion is made on formation of larger neuronal modules++, having common afferent entrance and demonstrating selectivity to the stimulus properties.     

Computational simulation of the input-output relationship in hippocampal pyramidal cells

The precise mapping of how complex patterns of synaptic inputs are integrated into specific patterns of spiking output is an essential step in the characterization of the cellular basis of network dynamics and function. Relative to other principal neurons of the hippocampus, the electrophysiology of CA1 pyramidal cells has been extensively investigated. Yet, the precise input-output relationship is to date unknown even for this neuronal class. CA1 pyramidal neurons receive laminated excitatory inputs from three distinct pathways: recurrent CA1 collaterals on basal dendrites, CA3 Schaffer collaterals, mostly on oblique and proximal apical dendrites, and entorhinal perforant pathway on distal apical dendrites. We implemented detailed computer simulations of pyramidal cell electrophysiology based on three-dimensional anatomical reconstructions and compartmental models of available biophysical properties from the experimental literature. To investigate the effect of synaptic input on axosomatic firing, we stochastically distributed a realistic number of excitatory synapses in each of the three dendritic layers. We then recorded the spiking response to different stimulation patterns. For all dendritic layers, synchronous stimuli resulted in trains of spiking output and a linear relationship between input and output firing frequencies. In contrast, asynchronous stimuli evoked non-bursting spike patterns and the corresponding firing frequency input-output function was logarithmic. The regular/irregular nature of the input synaptic intervals was only reflected in the regularity of output inter-burst intervals in response to synchronous stimulation, and never affected firing frequency. Synaptic stimulations in the basal and proximal apical trees across individual neuronal morphologies yielded remarkably similar input-output relationships. Results were also robust with respect to the detailed distributions of dendritic and synaptic conductances within a plausible range constrained by experimental evidence. In contrast, the input-output relationship in response to distal apical stimuli showed dramatic differences from the other dendritic locations as well as among neurons, and was more sensible to the exact channel densities. Action Editor: Alain Destexhe     

Differentiation of Apical and Basal Dendrites in Pyramidal Cells and Granule Cells in Dissociated Hippocampal Cultures

Hippocampal pyramidal cells and dentate granule cells develop morphologically distinct dendritic arbors, yet also share some common features. Both cell types form a long apical dendrite which extends from the apex of the cell soma, while short basal dendrites are developed only in pyramidal cells. Using quantitative morphometric analyses of mouse hippocampal cultures, we evaluated the differences in dendritic arborization patterns between pyramidal and granule cells. Furthermore, we observed and described the final apical dendrite determination during dendritic polarization by time-lapse imaging. Pyramidal and granule cells in culture exhibited similar dendritic patterns with a single principal dendrite and several minor dendrites so that the cell types were not readily distinguished by appearance. While basal dendrites in granule cells are normally degraded by adulthood in vivo, cultured granule cells retained their minor dendrites. Asymmetric growth of a single principal dendrite harboring the Golgi was observed in both cell types soon after the onset of dendritic growth. Time-lapse imaging revealed that up until the second week in culture, final principal dendrite designation was not stabilized, but was frequently replaced by other minor dendrites. Before dendritic polarity was stabilized, the Golgi moved dynamically within the soma and was repeatedly repositioned at newly emerging principal dendrites. Our results suggest that polarized growth of the apical dendrite is regulated by cell intrinsic programs, while regression of basal dendrites requires cue(s) from the extracellular environment in the dentate gyrus. The apical dendrite designation is determined from among multiple growing dendrites of young developing neurons.     

Topological characterization of neuronal arbor morphology via sequence representation: II - global alignment

Background

The increasing abundance of neuromorphological data provides both the opportunity and the challenge to compare massive numbers of neurons from a wide diversity of sources efficiently and effectively. We implemented a modified global alignment algorithm representing axonal and dendritic bifurcations as strings of characters. Sequence alignment quantifies neuronal similarity by identifying branch-level correspondences between trees.

Results

The space generated from pairwise similarities is capable of classifying neuronal arbor types as well as, or better than, traditional topological metrics. Unsupervised cluster analysis produces groups that significantly correspond with known cell classes for axons, dendrites, and pyramidal apical dendrites. Furthermore, the distinguishing consensus topology generated by multiple sequence alignment of a group of neurons reveals their shared branching blueprint. Interestingly, the axons of dendritic-targeting interneurons in the rodent cortex associates with pyramidal axons but apart from the (more topologically symmetric) axons of perisomatic-targeting interneurons.

Conclusions

Global pairwise and multiple sequence alignment of neurite topologies enables detailed comparison of neurites and identification of conserved topological features in alignment-defined clusters. The methods presented also provide a framework for incorporation of additional branch-level morphological features. Moreover, comparison of multiple alignment with motif analysis shows that the two techniques provide complementary information respectively revealing global and local features.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-015-0605-1) contains supplementary material, which is available to authorized users.     

Corticosterone replacement restores normal morphological features to the hippocampal dendrites, axons and synapses of adrenalectomized rats

A thorough evaluation of hippocampal dendrites, axons and synaptic contacts has not been undertaken following prolonged periods of absence of corticosteroids despite the marked granule cell loss which occurs in the dentate gyrus of adrenalectomized rats. Thus, we have applied morphometric techniques to analyse the dendrites of granule and pyramidal cells, the mossy fiber system, and the number and morphology of synapses between the mossy fibers and the excrescences of CA3 pyramidal cells in rats submitted to different periods of adrenalectomy. In addition, to search for the presence of neuritic reorganisation in the hippocampal formation once normal corticosteroid levels were re-established, we incorporated in this study a group of rats replaced with corticosterone one month after adrenalectomy. The results obtained in adrenalectomized rats showed a striking impoverishment of the dendrites of surviving granule cells, subtle alterations in the apical dendritic arborization of CA3 pyramidal cells and no changes in the apical dendrites of CA1 pyramidal cells. In addition, in adrenalectomized rats there was a progressive reduction in the total number of synapses established between mossy fibers and CA3 pyramids, as a consequence of a reduction in the volume of the suprapyramidal part of the mossy fiber system, and profound changes in the morphology of mossy fiber terminals and CA3 dendritic excrescences. A remarkable reorganisation of neurites was found to occur following the administration of low doses of corticosterone, completely reversing the adrenalectomy-induced synaptic loss and partially restoring the morphology of hippocampal axons and dendrites. These plastic mechanisms provide a sound structural basis for the reversibility of cognitive deficits observed after corticosterone administration to adrenalectomized rats.     

Intrinsic organization of snake dorsomedial cortex: an electron microscopic and golgi study.

The cellular populations present in dorsomedial cortex in the snakes Constrictor constrictor, Natrix sipendon and Thamnophis sirtalis are described at the light microscopic level using Nissl and Golgi preparations as well as at the ultrastructural level. This area plays a central role in cortical organization in snakes by participating in major commissural and association projections. Systematic analyses of Golgi preparations indicate that five populations of neurons are present in dorsomedial area and have a preferential laminar distribution. Layer 1 stellate cells have somata positioned in the center of the outermost cortical layer, layer 1. Their dendrites are confined to this layer. Double pyramidal cells have their somata loosely packed in layer 2. Their dendrites bear a moderate population of spines, ascending through layer 1 to the pial surface and descending partially through layer 3. Some double pyramidal cells have somata displaced downwards into the upper third of layer 3. These neurons closely resemble the layer 2 double pyramidal cells. Layer 3 stellate cells have somata positioned in the middle third of layer 3. Their dendrites extend in all directions throughout layer 3 and through layer 2 into layer 1. Finally, horizontal cells have their somata positioned deep in layer 3, near the ventricle, and dendrites aligned concentric with the ventricle. Comparison of the organization of the known afferents to dorsomedial area with the distribution of the five cell types suggests that the laminations of both afferent fibres and dorsomedial neurons places specific neuronal populations in synaptic contact with specific sets of afferents.     

Intrinsic organization of snake lateral cortex

Lateral cortex is the most laterally placed of the four cortical areas in snakes. Earlier studies suggest that it is composed of several subdivisions but provide no information on their organization. This paper first investigates the structure of lateral cortex in boa constrictors (Constrictor constrictor), garter snakes (Thamnophis sirtalis), and banded water snakes (Natrix sipedon) using Nissl and Golgi preparations; and secondly examines the relation of main olfactory bulb projections to the subdivisions of lateral cortex using Fink-Heimer and electron microscopic preparations. Lateral cortex is divided on cytoarchitectonic grounds into two major parts called rostral and caudal lateral cortex. Each part is further divided into dorsal and ventral subdivisions so that lateral cortex has a total of four subdivisions: dorsal rostral lateral cortex (drL), ventral rostral lateral cortex (vrL), dorsal caudal lateral cortex (dcL) and ventral caudal lateral cortex (vcL). Systematic analyses of Golgi preparations indicate that the rostral and caudal parts each contain distinct populations of neurons. Rostral lateral cortex contains bowl cells whose dendrites arborize widely in the outer cortical layer (layer 1). The axons of some bowl cells can be traced medially into dorsal cortex, dorsomedial cortex and medial cortex. Caudal lateral cortex contains pyramidal cells whose somata occur in layers 2 and 3 and whose dendrites extend radially up to the pial surface. In addition, three populations of neurons occur in both rostral and caudal lateral cortex. Stellate cells occur in all three layers and have dendrites which arborize in all directions. Double pyramidal cells occur primarily in layer 2 and have dendrites which form two conical fields whose long axes are oriented radially. Horizontal cells occur in layer 3 and have dendrites oriented concentric with the ependyma. Fink-Heimer preparations of snakes which underwent lesions of the main olfactory bulb show that the primary olfactory projections to cortex are bilateral and restricted precisely to rostral lateral cortex. Electron microscopic degeneration experiments indicate that the olfactory bulb fibers end as terminals which have clear, spherical vesicles and asymmetric active zones. The majority are presynaptic to dendritic spines in outer layer 1. These studies establish that lateral cortex in snakes is heterogeneous and contains two major parts, each containing two subdivisions. The rostral and caudal parts have characteristic neuronal populations. Primary olfactory input is restricted to rostral lateral cortex and seems to terminate heavily on the distal dendrites of bowl cells. Axons of some of these cells leave lateral cortex, so that the rostral lateral cortex forms a direct route by which olfactory information reaches other cortical areas. The functional role of caudal lateral cortex is not clear.     

Signal integration on the dendrites of a pyramidal neuron model

This paper studied the synaptic and dendritic integration with different spatial distributions of synapses on the dendrites of a biophysically-detailed layer 5 pyramidal neuron model. It has been observed that temporally synchronous and spatially clustered synaptic inputs make dendrites perform a highly nonlinear integration. The effect of clustering degree of synaptic distribution on neuronal responsiveness is investigated by changing the number of top apical dendrites where active synapses are allocated. The neuron shows maximum responsiveness to synaptic inputs which have an intermediate clustering degree of spatial distribution, indicating complex interactions among dendrites with the existence of nonlinear synaptic and dendritic integrations.     

Dendritic morphology and spine density is not altered in motor cortex and dentate granular cells in mice lacking the ganglioside biosynthetic gene B4galnt1 - A quantitative Golgi cox study

Gangliosides are characteristic plasma membrane constituents of vertebrate brain used as milestones of neuronal development. As neuronal morphology is a good indicator of neuronal differentiation, we analyzed how lack of the ganglioside biosynthetic gene Galgt1 whose product is critical for production of four major adult mammalian brain complex gangliosides (GM1, GD1a, GD1b and GT1b) affects neuronal maturation in vivo. To define maturation of cortical neurons in mice lacking B4galnt1 we performed a morphological analysis of Golgi-Cox impregnated pyramidal neurons in primary motor cortex and granular cells of dentate gyrus in 3, 21 and 150 days old B4galnt1-null and wild type mice. Quantitative analysis of basal dendritic tree on layer III pyramidal neurons in the motor cortex showed very immature dendritic picture in both mice at postnatal day 3. At postnatal day 21 both mice reached adult values in dendritic length, complexity and spine density. No quantitative differences were found between B4galnt1-null and wild type mice in pyramidal cells of motor cortex or granular cells of dentate gyrus at any examined age. In addition, the general structural and neuronal organization of all brain structures, qualitatively observed on Nissl and Golgi-Cox, were similar Our results demonstrate that neurons can develop normal dendritic complexity and length without presence of complex gangliosides in vivo. Therefore, behavioral differences observed in B4galnt1-null mice may be attributed to functional rather than morphological level of dendrites and spines of cortical pyramidal neurons.     

Widespread distribution of the major polypeptide component of MAP 1 (microtubule-associated protein 1) in the nervous system

We prepared a monoclonal antibody to microtubule-associated protein 1 (MAP 1), one of the two major high molecular weight MAP found in microtubules isolated from brain tissue. We found that MAP 1 can be resolved by SDS PAGE into three electrophoretic bands, which we have designated MAP 1A, MAP 1B, and MAP 1C in order of increasing electrophoretic mobility. Our antibody recognized exclusively MAP 1A, the most abundant and largest MAP 1 polypeptide. To determine the distribution of MAP 1A in nervous system tissues and cells, we examined tissue sections from rat brain and spinal cord, as well as primary cultures of newborn rat brain by immunofluorescence microscopy. Anti-MAP 1A stained white matter and gray matter regions, while a polyclonal anti-MAP 2 antibody previously prepared in this laboratory stained only gray matter. This confirmed our earlier biochemical results, which indicated that MAP 1 is more uniformly distributed in brain tissue than MAP 2 (Vallee, R.B., 1982, J. Cell Biol., 92:435-442). To determine the identity of cells and cellular processes immunoreactive with anti-MAP 1A, we examined a variety of brain and spinal cord regions. Fibrous staining of white matter by anti-MAP 1A was generally observed. This was due in part to immunoreactivity of axons, as judged by examination of axonal fiber tracts in the cerebral cortex and of large myelinated axons in the spinal cord and in spinal nerve roots. Cells with the morphology of oligodendrocytes were brightly labeled in white matter. Intense staining of Purkinje cell dendrites in the cerebellar cortex and of the apical dendrites of pyramidal cells in the cerebral cortex was observed. By double-labeling with antibodies to MAP 1A and MAP 2, the presence of both MAP in identical dendrites and neuronal perikarya was found. In primary brain cell cultures anti-MAP 2 stained predominantly cells of neuronal morphology. In contrast, anti-MAP 1A stained nearly all cells. Included among these were neurons, oligodendrocytes and astrocytes as determined by double-labeling with anti-MAP 1A in combination with antibody to MAP 2, myelin basic protein or glial fibrillary acidic protein, respectively. These results indicate that in contrast to MAP 2, which is specifically enriched in dendrites and perikarya of neurons, MAP 1A is widely distributed in the nervous system.     

An immunofluorescence microscopical study of the neurofilament triplet proteins, vimentin and glial fibrillary acidic protein within the adult rat brain

A collection of antibodies specific to different intermediate filament proteins were applied to frozen sections of adult rat brains. The relative distribution of these proteins was then studied using double label immunofluorescence microscopy. Antibodies specific to each of the neurofilament "triplet" proteins (of approximate molecular weight 68 K, 145 K and 200 K) stained exclusively neuronal structures. The distribution of these three antigens was in general identical, except that certain neurofilament populations such as those in the dendrites and cell bodies of pyramidal cells of the hippocampus and cerebral cortex, contained relatively little if any 200 K protein. Some neurone populations, such as the granule cells of the cerebellar cortex, could not be visualized by neurofilament antibodies, indicating that neurofilaments may not be essential for function of all neurones in vitro. Antibodies to GFA and vimentin stained an entirely different population of processes, none of which stained with any of the neurofilament antibodies. Vimentin antibody stained sheath material around the brain, a monolayer of ependymal cell bodies lining the ventricles, fibrous material associated within the choroid plexus, the walls of blood vessels and capillaries, and the processes of cells in certain regions. GFA antibody stained a second layer of sheath material under the vimentin layer, and numerous processes visible throughout the brain. Some specific populations of GFA-positive processes proved to stain also with vimentin. These included the processes of Golgi "epithelial" cells (Bergmann glial fibres), those of certain astrocytes in bundles of myelinated fibers. In addition, some processes apparently derived from ependymal cells proved to stain for both vimentin and GFA, whilst other could only be reliably visualized by vimentin alone. These results are discussed in terms of the previously described morphological characteristics of the various cell types of the brain.