White Matter Layer Research Articles

Reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry in the hippocampal formation of the new world monkey ( Saimiri sciureus)

Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) containing fibers and neurons within the hippocampal formation and entorhinal cortex of the new world monkey were determined using a direct histochemical procedure. Occasional intensely stained bipolar NADPH-d positive neurons were seen in the polymorphic zone within the hilus of the dentate gyrus and molecular layer of the hippocampus. Although virtually no intensely stained cells were seen in the CA subfields, a few small oval lightly stained NADPH-d perikarya were found subjacent to CA2. An occasional intensely stained multipolar NADPH-d containing neuron was observed in the subiculum, presubiculum and parasubiculum. In the entorhinal cortex, NADPH-d cells were scattered in all layers with the greatest preponderance in layers 5-6 and underlying white matter. Dense bands of NADPH-d fibers occurred in the outer layer of the molecular layer of the dentate gyrus and the hippocampo-subicular border. NADPH-d fibers also were seen in pre- and parasubicular regions. NADPH-d fiber staining in entorhinal cortex varied mediolaterally with an increasing laminar distribution more caudally. The heaviest bands of NADPH-d fibers occurred in layers 1 and 4 and the white matter-layer 6 border. The distribution patterns of this select neuronal population may be relevant to the study of hippocampal and entorhinal areas in neurodegenerative diseases.

Kernspintomographie bei laminarer Heterotopie

In one baby and 2 infants who presented with psychomotor retardation and epilepsy laminar heterotopic grey matter was demonstrated via magnetic resonance imaging. Laminar heterotopia is a rare migrational disorder with bilateral symmetric ribbons of grey matter within the centrum semiovale, separated from ventricular walls and from obviously normal-sized cortex by broad layers of white matter. The heterotopic grey matter has a signal intensity which is isointense compared with that of normal cortex irrespective of image weighting. On account of this signal behaviour differentiation against other white matter diseases is easy. The knowledge of these pathognomonic findings facilitates correct diagnosis, especially during the first and the second year of life, when signal intensities of white and grey matter differ from normal findings because of the occasionally delayed myelination process. Therefore, further diagnostic procedures can be avoided and early counseling of parents is possible.

Characterization of Annexins in Mammalian Brain

Three annexins--p68, endonexin, and p32--have been isolated from porcine brain using their calcium-dependent affinity for membranes. Large amounts (20-50 mg/kg of tissue) of p68 and p32 can be isolated from cerebrum and cerebellum. The p68 is present as up to 0.3% of total porcine brain protein. The p68 and p32 from porcine brain bind to phosphatidic acid (half-maximal binding at 6 and 34 microM free calcium, respectively) and to phosphatidylserine (8 and 34 microM, respectively). They do not bind to phosphatidylcholine at calcium concentrations up to 1 mM. Two other major proteins (Mr 180,000 and Mr 76,000) were isolated with the annexins in a calcium-dependent manner but do not bind to phospholipids. The 180-kilodalton protein is the heavy chain of clathrin. From immunohistochemical studies, p68 is strongly associated with the plasma membranes of Purkinje cell bodies and dendrites in porcine cerebellum. It is also an intracellular component of Purkinje cells localized to perinuclear structures. Staining of axons in the white matter and granule cell layer was also seen. In contrast, p32 is completely absent from Purkinje cells and their dendrites; it is predominantly located in the molecular layer and in white matter of the cerebellar folds. The distribution of p32 may be consistent with a predominantly glial localization.

Oligodendroglia development in cell culture as monitored with a monoclonal antibody

A new marker for young oligodendrocytes has been identified by a monoclonal antibody (mOg-1, IgM isotype) prepared from cerebellar plasma membrane stimulated mouse lymphocytes. mOg-1 reactive cells in the mouse cerebellum first appear at day 19 of gestation. Future white matter layers of fixed sections of neonatal rat cerebellum were labeled with mOg-1. Although EM analysis has shown cell-surface binding by presumptive oligodendroglia in neonatal cerebellum, the antibody does not bind to compact myelin. In cell cultures prepared from 6-d-old mice, 1.1% of the cells bound mOg-1 after 3 d in culture, but up to 5% of the cells bound mOg-1 after 2 weeks in culture. Of these same Og-1-positive cells, 69% bound anti-galactocerebroside and 65% bound anti-myelin basic protein. After a week in culture Og-1-positive cells often produced lamellar sheets extending a millimeter over the polylysine substratum in the absence of normal myelin formation. mOg-1 recognizes a cell-surface determinant distinct from well-characterized oligodendroglial molecules (galactocerebroside, sulfatide and myelin basic protein) that is expressed early in oligodendrocyte development. The antibody has been used to follow the maturation of oligodendrocytes in cultures of both normal and jimpy mouse cerebellum.

Cerebellar vermis involvement in monkey saccadic eye movements: Microstimulation

The cerebellar vermis (lobules V to VII) was focally stimulated (maximum current = 300 microA) through microelectrodes in alert monkeys trained to fixate on visual targets located at different positions in the eye movement field. Microstimulation of this area evoked saccades whose direction and amplitude were dependent on the spatial locus of the vermal point stimulated and on the position of the eye at the time of stimulation. Stimulation evoked saccades on most (70%) of the electrode penetrations. By alternatively stimulating and recording through the electrode as it advanced through the depth of the vermis, it was possible to map the threshold for evoking saccades along a penetration as well as to ascertain the type of tissue (white matter or Purkinje cell layer) situated at the stimulation points. On penetrations where saccades were evoked, there was generally one (90%) and sometimes two (10%) low-threshold region(s). These low-threshold regions were located in fiber tracks and not in the Purkinje or other cellular layers of the cerebellar cortex. The direction and size of the evoked saccades were dependent on position of the eye in the orbit. At a few sites, even the presence or the absence of an evoked saccade depended on the initial eye position. Postsaccadic drifts after termination of evoked saccades were also a common feature (50% of the tracks) associated with vermal microstimulation. The presence or absence as well as the direction of the postsaccadic drift were also dependent on initial eye position. These observations suggest that the vermal stimulations evoked saccades by the antidromic activation of mossy fiber afferent inputs that emanate from the brain stem saccadic burst generator. Furthermore, stimulation in this manner would actually bypass the cerebellar circuitry and produce saccades without the usual modifying influence of the cerebellum.

Expression of neural cell adhesion molecule L1 during development, in neurological mutants and in the peripheral nervous system

Neural cell adhesion molecule L1 consists of two glycoprotein bands of 140 and 200 kdaltons at all developmental stages studied (from birth to adulthood in murine cerebellum and cerebral hemispheres) and in the 4 neurological mouse mutants reeler, weaver, staggerer and Purkinje cell degeneration. In histological sections L1 antigen is detectable at birth in the Purkinje cell layer and fiber tracts in the prospective white matter, but not in the external granular layer. From postnatal day 4 onwards L1 antigen additionally appears in the inner part of the external granular layer, the zone of postmitotic premigratory granule cell neurons. The outer part of the external granular layer remains L1 antigen-negative until it disappears at approximately day 12. From then onwards, the antigen remains prominent in the nascent molecular layer and is less detectable in white matter and internal granular layer, the location of the cell bodies of postmigratory granule cells. The four neurological mouse mutants show development of L1 antigen expression analogous to the normal situation, despite an abnormal cellular architecture. In contrast to the central nervous system. Western blots of adult sciatic nerve show a more complex pattern of L1 immunoreactive bands. L1 antigen is detectable on most, if not all Schwann cells in histological sections of sciatic nerve from 17-day-old embryos. At postnatal day 2, only some Schwann cells appear L1 antigen-positive. From then onwards L1 seems most prominently associated with non-myelinating Schwann cells. In monolayer cultures of neonatal dorsal root ganglia the antigen is observed on the surface of neurons and of some Schwann cells. The mutant, trembler, shows a more immature staining pattern for L1 antigen in adult sciatic nerve.

GABAergic neurons of mammalian cerebral cortex: Widespread subclass defined by somatostatin content

GABAergic neurons are found in all layers of cerebral cortex and display many types of non-pyramidal morphology. Most are intensely immunoreactive for neuron-specific enolase, suggesting a high rate of metabolic activity. The molecular layer and subcortical white matter are strikingly enriched in GABAergic cell bodies compared to other cortical layers. In rat, cat and monkey, many GABAergic neurons in the subcortical white matter and certain cortical layers are also immunoreactive for the neuropeptide somatostatin. Somatostatin content may define a widespread subclass of GABAergic neurons in mammalian cerebral cortex. Some may be similar in function to reticular neurons of thalamus.

Regional distributions of choline acetyltransferase and acetylcholinesterase activities in layers of rat cerebellar vermis.

Entire sagittal sections of rat cerebellar vermis were dissected into microgram-sized samples of molecular, granular, and white matter layers. Assayed activities of choline acetyltransferase and acetylcholinesterase were plotted back onto sectional maps of exact sample locations. On the average, the activities of choline acetyltransferase and acetylcholinesterase in the granular layer were about four and five times, respectively, those in the molecular layer. The highest activity of both enzymes was in the granular layer of the vestibulocerebellum, the nodulus and ventral uvula (lobules X and IXc of Larsell). This activity might be related to the secondary vestibulocerebellar projection, terminating as mossy fibers in the granular layer of this region. Intermediate levels of activity were found in the granular layer of the dorsal uvula (lobule IX, a and b). The lowest activities of both enzymes in the granular layer were in the culmen (lobule V). A 7.1-fold difference in choline acetyltransferase activity and a 4.5-fold difference in acetylcholinesterase activity were found between the granular layer of lobules V and X. The numerical density of aggregates of acetylcholinesterase staining product in the granular layer correlated much better with assayed acetylcholinesterase activity than with choline acetyltransferase activity.

EM-autoradiography of cerebellar nucleocortical terminals in the cat.

The findings from the present EM-autoradiography experiments identify the cerebellar nucleocortical projection as a mossy fiber-type pathway. In these studies orthogradely labelled axons and terminals were observed in the folial white matter and granule cell layer, with only background levels of silver grains over the Purkinje cell and molecular layers. Most nucleocortical axons synapsed within cerebellar glomeruli either at en passant contacts along dilated segments of unmyelinated axons or at multilobulated (terminal) expansions of the axons. Typically these synaptic junctions were of the asymmetrical type containing clear round vesicles. Usually, each labelled mossy fiber rosette synapsed on a large number of small terminal dendrites of granule cells; however, occasionally a series of 4-8 asymmetric contacts were noted on a single large dendrite. Labelled nucleocortical terminals were occasionally present in the nonglomerular neuropil between granule cell bodies where they contacted large dendrites of Golgi cells.

Spreading depression in elasmobranch cerebellum

Spreading depression (SD) occurs in the cerebellum of an elasmobranch fish, the skate (Raja erinacea, Raja ocellata). The elasmobranch cerebellum, because of its unique separation of granular form molecular layer, provides an excellent opportunity to study the characteristics of SD in two distinct neuronal populations. Both the DC potential shifts and changes in neuronal activity effected by SD were analyzed. The SD DC potential shifts in both layers closely resembled those in mammalian cerebral cortices. Consisting of a predominantly negative extracellular potential shift, they were typically 1--10 min in duration and reached 5--40 mV peak amplitudes. The largest negative shifts were found in the granular layer, without any consistent positive phases in the white matter, molecular, or granular layers. The SD propagated radially from surface electrical stimulation at 0.78 mm/min (+/- 0.16, n = 8) in the molecular layer and 0.43 mm/min (+/- 0.17, n = 8) in the granular layer at 15 degrees C. At 18 degrees C, the molecular layer propagatory velocity was 1.1 mm/min (+/- 0.12, n = 20) while, at 10 degrees C, it was 0.52 mm/min (+/- 0.21, n = 20), suggesting a temperature-dependent Q10 factor of 2. A profound depression of both spontaneous and evoked neuronal activity accompanied the DC potential shift. Activation of Purkinje cells antidromically, white matter, and granular layer neurons was typically abolished by the peak of the negative DC shift. However, a significant increase in granular layer excitability often followed the neuronal depression, remaining so far up to an hour. Repeated waves of SD sometimes occurred in the absence of neuronal recovery. A similar post-SD excitability increase was not seen in molecular layer neurons. Intracellular recordings from Purkinje cells revealed a spontaneous burst of action potentials at the onset of SD, closely followed by a depolarization of membrane potential from an average of -64 mV (+/- 12 mV, n = 3) to -11 mV (+/- 5 mV, n = 3).

The spinal cord-ventral root junction in the trembler mouse.

The Trembler mouse suffers from an hereditary demyelinating neuropathy. Schwann cell myelination of peripheral nerve fibres in the Trembler mouse is abnormal. Myelination of central nerve fibres in the deeper layers of white matter of the spinal cord is normal. At the junction between the peripheral nervous system and the central nervous system in the ventral roots in the Trembler mouse central-type nerve fibres are abnormally thinly myelinated. It is suggested that the normal process of myelination of central nerve fibres in this region is affected by abnormalities of the Schwann cell in the peripheral nervous system.

β-HEXOSAMINIDASES IN THE NERVOUS SYSTEM: THE QUANTITATIVE HISTOCHEMISTRY OF β-GLUCOSAMINIDASE AND β-GALACTOSAMINIDASE IN THE CEREBELLAR CORTEX AND SUBJACENT WHITE MATTER

A modification of an existing fluorimetric method for the assay of β-glucosaminidase and β-galactosaminidase, based upon the hydrolysis of the corresponding 4-methylumbelliferyl glycosaminides, is described. The method is simple and convenient; its sensitivity is 3 x 10–8 M for the assay of β-glucosaminidase and 1 x 10–8 M for β-galactosaminidase. The results obtained on brain homogenates and dissected sections of cerebellar cortex and subjacent white matter of rat, rabbit and monkey were found to be similar to those obtained with the standard colorimetric procedures using p-nitrophenyl substrates. In each species, in each layer of cerebellar cortex and subjacent white matter, there were only minimal differences in the ratios of β-glucosaminidase to β-galactosaminidase activity, suggesting that a single enzyme possesses both activities. β-Glucosaminidase and β-galactosaminidase in the cerebellum were most active in the cellular granular layer, suggesting an association of β-hexosaminidase activity with neuronal cell bodies as has been found with other lysomal enzymes.

An electron microscopic study of degenerative changes in the cat cerebellum after intrinsic and extrinsic lesions.

AbstractDegenerative changes in the cerebellum of the cat have been observed electron microscopically 2 to 30 days after surgical lesions were placed in the inferior or middle cerebellar peduncles or after undercutting or isolating cerebellar folia. The changes were confined to the mossy fibers of the white matter and granular layer except when Purkinje cells were damaged buy undercutting. Mossy fiber terminals in the glomeruli underwent two kinds of change. Either the synaptic vesicles and mitochondria coalesced into dense clumps with loss of mitochondrial outer membranes and proliferation of cristae, or the vesicles and miotochondria disappeared leaving a swollen terminal containing only a few large pleomorphic vesicles and small dense polygonal bodies. Neurofilaments proliferated and filled a few terminals but most of the neurofilamentous hypertrophy and proliferation was confined to myelinated axons. Some phagocytosis of degenerated endings was observed and mild fibrous gliosis occurred in the glomeruli.All of the changes observed in the present study have been reported in degenerating synapses and axons elsewhere in the central and peripheral nervous system, but there appeared to be more pleomorphism and less predictability of changes in the cerebellar cortex than have been noted in other single areas of the central nervous system.

Reconstitution of the spinal cord following ablation in urodele larvae.

AbstractAfter ablation of 2 mm of spinal cord in the postbrachial region in larvae of Ambystoma maculatum studies were made on the reconstitution of the cord and the return of function posterior to the ablation level.Healing of the cord at anterior and posterior transection surfaces involves migration of ependymal cells to close the open central canal and movement of cells of the gray matter over the cut surface. Dilation of the central canal occurs at each transection level to form a terminal vesicle. Its wall is made up of ependyma, cells from the gray matter and an outer layer of white matter. Anterior and posterior terminal vesicles gradually increase in length bringing about a slow advance of their tips across the ablation gap, the anterior vesicle moving more rapidly than the posterior.Nerve fibers growing out from the white matter of each terminal vesicle extend across the ablation gap and eventually join the wall of the opposite vesicle. Thus are formed bridges of intracentral fibers between anterior and posterior vesicles. Broad nerve fiber bridges become the white matter of the reconstituted spinal cord. Continued advance of the terminal vesicles across the ablation region results finally in the union of the two vesicles, restoring the continuity of the spinal cord.Recovery of the use of hind limbs for walking and of trunk and tail muscles for swimming is correlated with the extent to which nerve fiber bridges have been established, but does not involve a complete fusion of terminal vesicles. All larvae which walked normally and the majority of those which swam normally possessed fiber bridges with an average diameter of at least 0.05 mm.

The distribution of RNA in the cerebellum of the rabbit

Abstract A microchemical investigation of the RNA content in different layers of the cerebellar cortical layers as well as that of the underlying white matter has been carried out. The results indicate considerable differences in RNA concentration of the different layers according to the following order of decreasing concentrations: Purkinje cells, granular layer, white matter and molecular layer. The data give no evidence for the existence of two or more populations of Purkinje cells, with regard to RNA content. Neurons from different parts of the cerebellar cortex have identical RNA contents on a per cent/volume basis.

Studies in Embryonic and Larval Development in Amphibia : I. The Embryology of Eleutherodactylus ricordii, with Special Reference to the Spinal Cord

ABSTRACT In the West Indian Anuran genus Eleutherodactylus the larval stage is wholly suppressed. As in other systems of organs there are features in the spinal cord which are correlated with this embryonic type of development. The cord in the trunk region resembles more that of a chick embryo than that of a larval Amphibian. Within the thick neuroepithelium mitoses in the ependymal zone persist much longer than in larval forms. There is a relatively thin layer of white matter. The Rohon-Beard system of sensory neurones persists, but does not precede the development of the dorsal root ganglia. In the trunk there are no conspicuous primary motor-cells as in larval Amphibia. The numbers of cells within the dorsal root ganglia and ventral motor horns have been counted both in the embryo and in the adult. From the first, the numbers of cells present in both are similar to those in the adult. During development, increase by mitosis is opposed by cell degeneration. Pycnotic nuclei are conspicuous in both spinal ganglia and ventral horns in the embryo. As soon as the spinal ganglia are recognizable, their relative sizes are similar to those of the adult. The ganglia at limb levels are already larger than those elsewhere a day before nerve fibres first enter the limb-buds.