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PubMed1987

[Ultrastructure and the number of nucleoli in the neurons of the rat cerebellar cortex].

The ultrastructure and number of nucleoli in rat cerebellar nervous cells (the Purkinje and granule cells) were studied using the silver staining procedure and serial ultrathin sections. In the Purkinje cells one large nucleonemal nucleolus about 4 mcm in diameter was usually observed; fibrillar centers are weakly expressed. About 6% of the Purkinje cells had two nucleoli different in size. In granule cells 2-3 nucleoli about 1 mcm in diameter were detected. They contained a distinct fibrillar center and a dense fibrillar RNP-component, RNP-granules were barely visible. These data show that the Purkinje cells are more active transcriptionally than granule cells. The distinctions in the ultrastructure and number of nucleoli in the Purkinje and granule cells correspond to an earlier reported hypothesis about the intra- and interpopulation heterogeneity of cerebellar nervous cells for topography of ribosomal genes.

Animals↗
PubMed1998

Distribution of TAG-1 and synaptophysin in the developing cerebellar cortex: relationship to Purkinje cell dendritic development.

During postnatal cerebellar development, differentiating Purkinje cell (PC) dendrites extend towards the pial surface and progressively contact immature granule cell parallel fiber (PF) axons in the deep external granule layer (EGL), thus forming a zone of synaptic contact called the molecular layer (ML). The neuronal cell adhesion molecule, TAG-1, is transiently expressed on PF axons in the deep EGL (Yamamoto et al. [1986] J. Neurosci. 12:3576-3594). To determine the spatiotemporal relationship between Purkinje cell dendritic differentiation and the cessation of TAG-1 expression, sagittal sections from developing rat cerebellum were double-labeled for TAG-1 and the Purkinje cell-specific marker, calbindin, by using indirect immunofluorescence. At postnatal day 2 (P2) and P5, confocal microscopy revealed that TAG-1 immunoreactivity began above the furthest superficial extent of the Purkinje cell apical dendritic cap. By P10, PC dendrites penetrated partially into the TAG-1-positive deep EGL, creating a narrow region of overlap in TAG-1/calbindin staining at the deep EGL/ML border. In contrast, at P15 and P20, TAG-1 staining began directly above the furthest superficial extent of the Purkinje cell dendrites, with little or no overlap in TAG-1/calbindin staining. Staining for the synaptic vesicle glycoprotein, synaptophysin, was dim throughout most of the TAG-1-positive deep EGL, although bright synaptophysin immunoreactivity was observed throughout the ML. Overlap in TAG-1/synaptophysin staining was observed primarily at the deep EGL/ML border, suggesting that robust expression of synaptophysin in granule cells does not begin until after contact with Purkinje cell dendrites has been initiated. Our results suggest that factors present in the developing ML may influence the cessation of TAG-1 expression and the initiation of synaptophysin expression at the border region between the ML and the deep EGL.

Animals↗
PubMed1997

Carbonic anhydrase II and carbonic anhydrase-related protein in the cerebellar cortex of normal and lurcher mice.

The developmental profiles of carbonic anhydrase II (CA-II) and a carbonic anhydrase related protein (CARP) were studied in rat and mouse cerebella. Enzyme histochemistry, immunohistochemistry, in situ hybridisation and Western blotting were used to study the synthesis and expression of these enzymes in cerebellar sections from age matched control, CA-II deficient and lurcher mice, the latter being characterised by Purkinje cell degeneration. Both CA-II and CARP were first found to be expressed in the Purkinje cells in the 9 day old mouse, and the immunoreactivity of both peptides increased with time. Immunohistochemistry showed more intense staining of CARP than of CA-II in Purkinje cells throughout the developmental profile of the mouse, and this was mirrored by the mRNA levels determined by in situ hybridisation. Immunohistochemistry of CA-II and CARP also demonstrated the progressive dendritic growth of the mouse and rat Purkinje cells. CA-II and CARP immunoreactivity ceased by the end of cerebellar maturation. The onset of Purkinje cell degeneration was detected at day 10 in the lurcher mouse, with concomitant marked decrease in CA-II level: however CARP expression was found to be unchanged. By postnatal day 16 neither CA-II mRNA, protein, nor activity was detectable in contrast to CARP which remained at a decreased level unit the Purkinje cells population had completely degenerated. Our findings suggest a role of CA-II in the degenerative processes of the lurcher Purkinje cells, with CARP playing an important role in the development and maturation of the cerebellar cortex.

Animals↗
PubMed1988

Structural components in the synaptic cleft captured by freeze-substitution and deep etching of directly frozen cerebellar cortex.

Structural components in the synaptic cleft were examined in cerebellar excitatory synapses by conventional electron microscopy and by rapid freezing followed by freeze-substitution or deep etching. Two transverse components and one parallel element were identified in the clefts of rapidly frozen and freeze-substituted synapses: (i) bridging fibrils, 4-6 nm in diameter, that span the cleft; (ii) columnar pegs, 4-6 nm wide and 8-15 nm high, projecting from the postsynaptic surface; and (iii) intervening fine fibrils running parallel to the apposed synaptic membranes. These were more clearly visible in deep-etched synapses, although the postsynaptic pegs were difficult to distinguish from intramembrane particles in the cross-fractured postsynaptic membranes. Deep etching also revealed other fibrils on the cytoplasmic surface of the postsynaptic membrane. These appear to contact the membrane surface or the intramembrane particles. Freeze-substituted materials also displayed the fibrillar components in the postsynaptic dense fuzz, but failed to display the presynaptic dense projections typically observed in thin sections or deep-etched replicas of the conventionally fixed materials. The bridging fibrils are likely to play a mechanical role in holding the synapse together, while the short pegs may be integral parts of the receptor molecules.

Animals↗
PubMedDate not supplied

Differential effect of dithiothreitol and DuP 753 on angiotensin II receptor subtypes in bovine cerebellar cortex.

Angiotensin II (AII) receptor subtypes were investigated in bovine cerebellar cortical membranes (BCCM) using agonists and antagonists. Differences were observed whether the tissue for the characterization was used fresh or frozen. In fresh BCCM, AII and angiotensin III (AIII) (not selective), p -aminophenylalanine6 -AII ([pNH2Phe6]AII) (AT2 selective), and DuP 753 (AT1 selective) interacted with two sites, at high and low affinity. In the presence of 10 mM dithiothreitol (DTT), the low-affinity site for AIII and [pNH2Phe6]AII and the high-affinity site for DuP 753 were no longer detectable. The same effect was obtained with 1 microM DuP 753, with only the low-affinity component of [pNH2Phe6]AII being resistant to this blocker. In frozen BCCM, DuP 753, PD 123319 (AT2 selective), and sarcosine1, isoleucine8-AII ([Sar1Ile8] AII) yielded monophasic curves. These data confirm the presence of multiple receptors (AT1 and AT2) for AII on BCCM and suggest the possibility that within the AT2 receptors, one subtype, DTT sensitive, may exist. Alternatively, a heterogeneity in the AT1 class, with respect to the sensitivity to DuP753, may be considered.

Angiotensin Receptor Antagonists↗
PubMed2004

Imaging parallel fiber and climbing fiber responses and their short-term interactions in the mouse cerebellar cortex in vivo.

A major question in the study of cerebellar cortical function is how parallel fiber and climbing fiber inputs interact to shape information processing. Emphasis has been placed on the long-term effects due to conjunctive stimulation of climbing fibers and parallel fibers. Much less emphasis has been placed on short-term interactions and their spatial nature. To address this question the responses to parallel fiber and climbing fiber inputs and their short-term interaction were characterized using optical imaging with Neutral Red in the anesthetized mouse in vivo. Electrical stimulation of the cerebellar surface evoked an increase in fluorescence consisting of a transverse optical beam. The linear relationship between the optical responses and stimulus parameters, high spatial resolution and close coupling to the electrophysiological recordings show the utility of this imaging methodology. The majority of the optical response was due to activation of postsynaptic alpha-amino-3-hydroxyl-5-methyl-4-isoxazole propionate (AMPA) and metabotropic glutamate receptors with a minor contribution from the presynaptic parallel fibers. Stimulation of the inferior olive evoked parasagittal bands that were abolished by blocking AMPA glutamate receptors. Conjunctive stimulation of the cerebellar surface and inferior olive resulted in inhibition of the climbing fiber evoked optical responses. This lateral inhibition of the parasagittal bands extended out from both sides of an activated parallel fiber beam and was mediated by GABA(A) but not GABA(B) receptors. One hypothesized role for lateral inhibition of this type is to spatially focus the interactions between parallel fiber and climbing fiber input on Purkinje cells. In summary optical imaging with Neutral Red permitted visualization of cerebellar cortical responses to parallel fiber and climbing fiber activation. The GABA(A) dependent lateral inhibition of the climbing fiber evoked parasagittal bands by parallel fiber stimulation shows that cerebellar interneurons play a short-term role in shaping the responses of Purkinje cells to climbing fiber input.

Animals↗
PubMed2001

Heroin-induced changes of catecholamine-containing particles in male rat cerebellar cortex.

The content and distribution of catecholamine-containing formations in the cerebellum of untreated and heroin-treated male rats, was visualized by glyoxylic acid-induced histofluorescence, in an attempt to define the adaptive mechanisms leading to heroin dependent tolerance as well as identify a biological role for these formations. Repeated heroin administration increased the number of specifically organized intracellular catecholamine containing particles, including grain (diameter less than 0.8 microm) and aggregate (diameter greater than 1 microm) forms, in all cerebellar cortical layers examined one hour after the last injection of the drug, relative to controls. The number of grains in all cerebellar cortical layers examined and aggregates in the granular layer, returned to normal or near normal baseline levels within twenty four hours after the last injection of the drug. The analogous baseline of the aggregates in the Purkinje cell layer primarily and the Molecular layer secondarily remained significantly elevated by 86% and 50% respectively, relative to controls. Catecholamine-heroin interactions most likely mediated this elevation that was related directly to the heroin-dependent state of tolerance. These findings indicate that heroin administration to heroin-tolerant rats leads to the formation of unusually large intracellular aggregates with catecholamines in the Purkinje cells of the cerebellum primarily and support a direct role for these formations in the modulation of biogenic amine bioavailability. We conclude that adaptation to drug exposure involves multiple homeostatic interactions, with sympathetic activation at the level of catecholamine reorganization and redistribution playing a major role in rat cerebellar cortex.

Animals↗
PubMed1988

The feline oculomotor nucleus: morphological subdivisions and projection to the cerebellar cortex and nuclei.

The cytoarchitecture of the feline oculomotor nucleus was examined in sections stained with thionin and neutral red. Five different subdivisions (caudal central, paramedian, ventral, dorsomedial and dorsolateral divisions) can be identified on each side of the midline. This observation is discussed, and our findings are compared to previous studies of the cytoarchitecture or central muscular representation of the oculomotor nucleus in which different subgroups have been distinguished. Implants or injections of the wheat germ agglutinin-horseradish peroxidase complex have revealed that all five subdivisions project to different parts of the cerebellar cortex and nuclei. Retrogradely labelled cells were found in the oculomotor nucleus in 18 cases following deposition of tracer in the fastigial and interposed nuclei and certain regions of the anterior, posterior and flocculonodular lobes. The projection is bilateral and appears to have its main termination in flocculus. It originates from small neurons, especially from those located along the dorsal border of the oculomotor nucleus.

Afferent Pathways↗