Expression of the α and β subunits of Ca2+/calmodulin kinase II in the cerebellum of jaundiced Gunn rats during development: a quantitative light microscopic analysis

The homozygous (jj) jaundiced Gunn rat model for hyperbilirubinemia displays pronounced cerebellar hypoplasia. To examine the cellular mechanisms involved in bilirubin toxicity, this study focused on the effect of hyperbilirubinemia on calcium/calmodulin-dependent kinase II (CaM kinase II). CaM kinase II is a neuronally enriched enzyme which performs several important functions. Immunohistochemical analysis of alternating serial sections were performed using monoclonal antibodies for the alpha and beta subunits of CaM kinase II. Measurements were made of the total numbers of stained cells in each of the deep cerebellar nuclei and of Purkinje and granule cell densities in cerebellar lobules II, VI, and IX. The beta subunit was present in Purkinje cells and deep cerebellar nuclei of both groups at all ages, but only granule cells which had migrated through the Purkinje cell layer showed staining for beta subunit; external granule cells were completely negative. Many Purkinje cells had degenerated in the older animals, and the percent of granule cells stained for beta subunit was significantly reduced. The alpha subunit was found exclusively in Purkinje cells, although its appearance was delayed in the jaundiced animals. Sulfadimethoxine was administered to some jj rats 24 h or 15 days prior to sacrifice to increase brain bilirubin concentration. Results showed that bilirubin exposure modulated both alpha and beta CaM kinase II subunit expression in selective neuronal populations, but sulfadimethoxine had no acute effect on enzyme immunoreactivity. Thus, developmental expression of the alpha and beta subunits of CaM kinase II was affected by chronic bilirubin exposure during early postnatal development of jaundiced Gunn rats.     

Immunohistochemical localization of calcium-binding protein in the cerebellum, hippocampal formation and olfactory bulb of the rat

The immunohistochemical localization of calcium-binding protein (CaBP) in the cerebellum, hippocampal formation and olfactory bulb of the rat was examined using rabbit anti-human or sheep anti-chick antisera purified by affinity chromatography. CaBP-like immunoreactivity was observed within the somata and dendrites of: (1) cerebellar Purkinje cells; (2) dentate granule cells, CA1 pyramidal cells and scattered interneurons in the stratum radiatum of the hippocampus; (3) periglomerular cells in the olfactory bulb. Staining was conspicuously absent in certain major cell types in each of these structures including cerebellar granule cells, hippocampal pyramidal cells in the CA3 region and both mitral and granule cells in the olfactory bulb. Immunoreactive fibers in the cerebellum presumably corresponding to climbing fiber inputs from the inferior olive and efferent projections to the deep cerebellar nuclei, were also observed. In the hippocampus intense staining was present in the mossy fiber projection to the CA3 region and in the terminal regions of the perforant path projection from entorhinal cortex.     

Distribution of the protein kinase C substrates MARCKS and MRP in the postnatal developing rat brain

The myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP) are both membrane-associated phosphoproteins that interact with calmodulin and filamentous actin in a protein kinase C phosphorylation-dependent manner. In the present study, we examined MARCKS and MRP gene expression in the postnatal (P) rat brain (1, 7, 14, 21, and 90 days after birth) by using quantitative in situ hybridization. At P1, MRP expression was high in neocortex, striatum, thalamus, cerebellar cortex, and hippocampus (CA1–CA3, hilus, and granule cell layer) but low in brainstem and, between P7 and P14, exhibited a dramatic decline in each of these regions except hippocampal CA1 and granule cell layers. Between P14 and P21, MRP expression increased in white matter regions including the corpus callosum, fimbria/fornix, and cerebellar deep white matter. At P90 (adult), MRP remained strongly expressed in the olfactory bulb, medial habenula, hippocampal CA1, and the inner two-thirds of granule cell layer, temporal, and entorhinal cortices, the corpus callosum and fimbria/fornix, and cerebellar white matter. At P1, MARCKS was strongly expressed in the majority of brain regions except the brainstem, which subsequently declined gradually to approximate adult levels by P14. Between P14 and P21, MARCKS expression declined gradually in the hilus, remained elevated in hippocampal CA1, CA3, and granule cell layers, and increased dramatically in the corpus callosum and fimbria/fornix. At P90, MARCKS expression declined in hippocampal CA3 and hilus and remained strongly expressed in hippocampal CA1 and granule cell layers, regions of the olfactory bulb, the medial habenula, temporal cortex, and cerebellar granule and Purkinje cells. Expression of both MARCKS and MRP in regions undergoing neuronal proliferation, migration, and neurite outgrowth suggest a common role in these developmental events, whereas differences in expression during development and in the adult brain provide evidence of differential regulation. J. Comp. Neurol. 397:337–356, 1998. © 1998 Wiley-Liss, Inc.     

Distribution of Kv3.3 potassium channel subunits in distinct neuronal populations of mouse brain

Kv3.3 proteins are pore-forming subunits of voltage-dependent potassium channels, and mutations in the gene encoding for Kv3.3 have recently been linked to human disease, spinocerebellar ataxia 13, with cerebellar and extracerebellar symptoms. To understand better the functions of Kv3.3 subunits in brain, we developed highly specific antibodies to Kv3.3 and analyzed immunoreactivity throughout mouse brain. We found that Kv3.3 subunits are widely expressed, present in important forebrain structures but particularly prominent in brainstem and cerebellum. In forebrain and midbrain, Kv3.3 expression was often found colocalized with parvalbumin and other Kv3 subunits in inhibitory neurons. In brainstem, Kv3.3 was strongly expressed in auditory and other sensory nuclei. In cerebellar cortex, Kv3.3 expression was found in Purkinje and granule cells. Kv3.3 proteins were observed in axons, terminals, somas, and, unlike other Kv3 proteins, also in distal dendrites, although precise subcellular localization depended on cell type. For example, hippocampal dentate granule cells expressed Kv3.3 subunits specifically in their mossy fiber axons, whereas Purkinje cells of the cerebellar cortex strongly expressed Kv3.3 subunits in axons, somas, and proximal and distal, but not second- and third-order, dendrites. Expression in Purkinje cell dendrites was confirmed by immunoelectron microscopy. Kv3 channels have been demonstrated to rapidly repolarize action potentials and support high-frequency firing in various neuronal populations. In this study, we identified additional populations and subcellular compartments that are likely to sustain high-frequency firing because of the expression of Kv3.3 and other Kv3 subunits.     

Distribution of soluble guanylyl cyclase in the rat brain

The diffusible messenger nitric oxide (NO) acts in the brain largely through activation of soluble guanylyl cyclase (sGC), a heterodimer comprising alpha and beta subunits. We used immunohistochemistry to study the distribution of both sGC subunits in the brain of adult rats. alpha and beta subunits gave similar widespread staining throughout the CNS, which was strongest in neostriatum, olfactory tubercle, and supraoptic nucleus. Double-labeling experiments showed striking cellular colocalization in most brain regions, suggesting that the two subunits may be organized into enzymatically active alpha/beta heteromers. Mismatches were observed in cerebellar cortex: Purkinje cells and Bergmann glia were positive for both subunits, whereas granule cells and interneurons in the molecular layer were strongly immunopositive for beta but only weakly stained for the alpha subunit. By using multiple labeling, we compared the localization of sGC with neuronal nitric oxide synthase (NOS-I, the NO-producing enzyme in neurons). In forebrain, the distribution of sGC and NOS-I was complementary, with only occasional colocalization. In contrast, cellular colocalization was common in midbrain and cerebellum. These data support a widespread role for the NO/sGC/cGMP pathway in the CNS and suggest that, in addition to its role as paracrine messenger, NO may also be an intracellular autocrine agent.     

Polarized distribution of alpha5 integrin in dendrites of hippocampal and cortical neurons

The distribution of immunoreactivity for the alpha5 subunit of the fibronectin receptor was evaluated in adult rat brain with particular interest in the cellular localization of immunostaining in the hippocampal formation and neocortex. Beyond localization to neuronal perikarya and short dendritic fragments within most brain areas, alpha5 immunoreactivity (-ir) was particularly dense within primary apical dendrites of pyramidal cells in both hippocampus and neocortex and within the dendritic arbors of cerebellar Purkinje cells. In hippocampal and cortical pyramidal cells, immunostaining was clearly polarized: alpha5-ir was not detectable in basal dendrites in hippocampal neurons and was limited to proximal arbors or absent from basal dendrites in pyramidal cells in superficial and deep layers of neocortex. Beyond this, alpha5-ir was distributed within the dendritic ramifications of the dentate gyrus granule cells and within perikarya and dendrites of occasional nonpyramidal neurons. Developmental studies demonstrated that, in both hippocampus and neocortex, alpha5-ir appears first within perikarya and is distributed to dendrites during the second postnatal week. These results are in accord with the broad hypothesis that integrins contribute to apical-basal differences in dendrites and that the integrin fibronectin (alpha5beta1) receptor, in particular, contributes to some late developing features of dendritic structure or function.     

Brain damage after heat stroke

Cerebellar syndromes and radiologic cerebellar atrophy after hyperpyrexia have occasionally been reported, mostly in neuroleptic malignant syndromes, but neuropathologic studies are extremely rare. We studied 3 patients (a 74-year-old woman, a 63-year-old man, and an 80-year-old man) who had heat stroke during heat waves in France. One patient had generalized seizures and died 28 hours after admission. The other patients survived one month and 2 months after admission; both had palatal myoclonus, and in one case, magnetic resonance imaging showed high signal intensity in the cerebral peduncles. The main neuropathology in the 3 cases was severe diffuse loss of Purkinje cells associated with heat shock protein 70 expression by Bergmann glia. In situ end labeling was negative in surviving Purkinje cells, suggesting that the mechanism of neuronal death was not apoptosis. Degeneration of Purkinje cells axons resulted in myelin pallor of the white matter of the folia and of the hilum of the dentate nuclei. DNA internucleosomal breakages were identified by in situ end labeling in the dentate nuclei and centromedian nuclei of the thalamus and were associated with degeneration of the cerebellar efferent pathways: superior cerebellar peduncles, decussation of the superior cerebellar peduncles (Wernekinck commissure), and dentatothalamic tract. These findings suggest that the mechanisms of neuronal death in the dentate nuclei and centromedian nuclei of the thalamus was different from that in Purkinje cells and more likely resulted from deafferentation. Ammon's horn and other areas susceptible to hypoxia were spared. These observations confirm the selective vulnerability of Purkinje cells to heat-induced injury and involvement of the cerebellar efferent pathways in palatal myoclonus.     

Transient expression of GABAA receptor alpha2 and alpha3 subunits in differentiating cerebellar neurons

In the adult mammalian brain, synaptic transmission mediated by gamma-amino butyric acid (GABA) plays a role in inhibition of excitatory synaptic transmission. During brain development, GABA is involved in brain morphogenesis. To clarify how GABA exerts its effect on immature neurons, we examined the expression of the GABAA receptor alpha2 and alpha3 subunits, which are abundantly expressed before alpha1 and alpha6 subunits appear, in the developing mouse cerebellum using in situ hybridization. Proliferating neuronal precursors in the ventricular zone and external granular layer expressed neither alpha2 nor alpha3 subunits. Hybridization signals for the alpha2 and alpha3 subunit mRNAs first appeared in the differentiating zone at embryonic day 13 (E13). The alpha2 subunit was detected in the migrating and differentiating granule cells and cerebellar nucleus neurons until postnatal day 14 (P14). Hybridization signals for the alpha3 subunit mRNA, on the other hand, were localized in the developing Purkinje cells and cerebellar nucleus neurons, and disappeared from Purkinje cells by the end of first postnatal week. Taken together, this indicated that the alpha2 and alpha3 subunits were abundantly expressed in distinct types of cerebellar neurons after completing cell proliferation while forming the neural network. These results suggest that GABA might extrasynaptically activate the GABAA receptors containing alpha2 and/or alpha3 subunits on the differentiating neurons before finishing the formation of synapses and networks, and could be involved in neuronal differentiation and maturation in the cerebellum.     

Cerebellar benzodiazepine receptors: cellular localization and consequences of neurological mutations in mice

The distribution of cerebellar [3H]flunitrazepam binding sites was studied autoradiographically in Purkinje cell degeneration (pcd/pcd), weaver (wv/wv), staggerer (sg/sg) and reeler (rl/rl) mutant mice. In the normal 78-day-old C57BL/6J mouse cerebellum, the highest concentration of [3H]flunitrazepam binding sites was observed over the molecular layer. Intermediate grain density was present over the Purkinje cell layer and intermediate to high density over the deep cerebellar nuclei. Low labeling was observed over the granule cell layer. Negligible concentrations of binding sites were seen in the white matter. In 45-49-day-old Purkinje cell degeneration mutants, where essentially all Purkinje cells have disappeared by day 45, there was a small decrease in grain density over the cerebellar cortex. Concomitantly, a substantial increase in grain density was observed over the deep cerebellar nuclei of the pcd/pcd mutants when compared to littermate controls. A significant increase in [3H]flunitrazepam labeling was observed over the cerebellar cortex of 81-86-day-old wv/wv mutants; this was most pronounced in the vermis where the granule cell loss was greatest. Over the hemispheres, where fewer granule cells degenerate, a lower density of binding sites was seen. Grain density over the wv/wv deep cerebellar nuclei was comparable to that of littermates. Substantially lower [3H]flunitrazepam labeling was detected over the cerebellar cortex of 25-27-day-old sg/sg mutants in which the number of granule, Purkinje and Golgi cells is greatly reduced; the labeling over the deep nuclei, however, was significantly increased. In 27-29-day-old rl/rl mutant cerebella, where all classes of cells are malpositioned, labeling density over all areas of the cerebellar cortex, including the Purkinje cell masses, was increased. Our autoradiographic data suggest that a proportion of cerebellar cortical benzodiazepine receptors are associated with Purkinje cells; we propose that the remainder of the receptors are localized on Golgi cells, while granule cells are devoid of receptors. In the deep cerebellar nuclei, the observed increase in benzodiazepine receptors in the pcd/pcd and sg/sg mutants may be a manifestation of denervation supersensitivity subsequent to the loss of innervation by Purkinje cell axon terminals. The finding of a high receptor density in the Purkinje cell masses of the rl/rl mutant, where Purkinje cells are devoid of afferent basket cell input, suggests that benzodiazepine receptors are expressed and maintained in the absence of a full complement of GABAergic afferents.     

Cerebellar histamine-H1 receptor distribution: An autoradiographic study of purkinje cell degeneration, staggerer, weaver and reeler mutant mouse strains

The distribution of 3H-mepyramine binding sites in cerebellae of normal mice and Purkinje cell degeneration, staggerer, weaver and reeler mutant mice was studied by light microscopic autoradiography. The binding of 3H-mepyramine to 20 micron coronal sections through the cerebellum and medulla had the characteristics expected of histamine-H1 receptor labeling. In the cerebellar cortex of normal mice, a high density of 3H-mepyramine binding was observed over the molecular layer and an intermediate density over the Purkinje cell layer, while the granule cell layer and white matter were almost devoid of labeling. The deep cerebellar nuclei were labeled to an intermediate density. In the 54 day old Purkinje cell degeneration mutant cerebellum, which is depleted of Purkinje cells, a greatly reduced labeling of the cerebellar cortex was observed. Labeling in the deep cerebellar nuclei was unaffected. In the 27 day old staggerer cerebellum, a mutation characterized by Purkinje cells which are almost devoid of spines and which do not form synaptic contacts with granule cells, a higher than normal grain density was seen over the cerebellar cortex, while normal grain density was observed over the deep cerebellar nuclei. The cerebellar cortex of 81 day old weaver mice, which is almost devoid of granule cells, had a high grain density over medial regions of the cortex, while the portion of the granule cell layer which remained relatively unaffected in the lateral parts of the cerebellum was unlabeled. The deep cerebellar nuclei had grain densities similar to littermate controls. In the 29 day old reeler cerebellae, which contain malpositioned Purkinje cells, high grain density regions corresponding to the heterotopically located Purkinje cells were observed. The present observations suggest that cerebellar cortical histamine-H1 receptors are associated predominantly with Purkinje cells. Furthermore, the expression of these H1 receptors appears not to be adversely affected by several alterations in the Purkinje cell environment, which have previously been shown to dramatically influence Purkinje cell morphology.     

Gene expression of Ca2+/calmodulin-dependent protein kinase of the cerebellar granule cell type or type IV in the mature and developing rat brain.

The localization and ontogenic changes of expression of the mRNA for Ca2+/calmodulin-dependent protein kinase of the cerebellar granule cell type or type IV (CaM kinase Gr or IV) in the rat brain were examined by in situ hybridization histochemistry. At the young adult stage, intense expression signals for this kinase mRNA were detected in the cerebellar granule cells, the hippocampal pyramidal cells, the dentate granule cells, and the piriform cortex. Moderate levels of the mRNA were expressed in the thalamic nuclei and the cerebral cortex. No distinct expression signals were detected in the Purkinje cells and most brainstem nuclei except for the pontine nuclei, locus ceruleus and inferior olive which showed weak expression. During development, two chronological patterns of changes in the gene expression for this kinase were discerned. The first was a high and persistent expression from the developing stages till the adult stage, which was observed in the cerebellar granule cells, the hippocampal pyramidal cells and the dentate granule cells. The other was a transiently high expression during limited developmental periods, which was observed in the Purkinje cells, neurons in the inferior olive, various brain stem nuclei, and the subventricular neuronal cells. These findings suggest that this Ca2+/calmodulin-dependent protein kinase is involved differentially in multiple Ca2+ signaling pathways in different developing and mature neurons.     

Immunological evidence that the beta isoform of Ca2+/calmodulin-dependent protein kinase IV is a cerebellar granule cell-specific product of the CaM kinase IV gene.

Ca2+/calmodulin-dependent protein kinase IV (CaM kinase IV) exists as two monomeric isoforms, alpha and beta. In this study, we raised an antibody against the beta isoform and provided immunohistochemical evidence for specific expression of the beta isoform in cerebellar granule cells as a single gene-derived translational product distinct from the alpha isoform. Immunohistochemical examination showed that the beta-immunoreactivity was confined to the nuclei of the cerebellar granule cells, in contrast to the more widespread immunoreactivity for the alpha isoform in both nuclei and cytoplasm of the cerebellar granule cells and many other neurons with dominant nuclear localization. In developing cerebella, the beta-immunoreactivity gradually appeared in the internal granule cells during the postnatal 2nd and 3rd weeks, while the alpha-immunoreactivity had already appeared in the internal granule cells in the 1st postnatal week. Unlike the alpha isoform, beta-immunoreactivity was not detected in the Purkinje cells at any developmental stages. The differential expression of the alpha and beta isoforms suggests that each isoform may be involved in different cerebellar functions.     

Comparative distribution of myristoylated alanine-rich C kinase substrate (MARCKS) and F1/GAP-43 gene expression in the adult rat brain

Myristoylated alanine-rich C-kinase substrate (MARCKS) and F1/GAP-43 (B-50/neuromodulin) are both major specific substrates for protein kinase C (PKC) and appear to play an important role in the regulation of neuroplastic events during development and in the adult brain. Since PKC isozymes are differentially expressed in brain and the expression of F1/GAP-43 and MARCKS mRNAs are differentially regulated by PKC through posttranslational mechanisms, the present study examined the relative distribution of both mRNAs in the adult rat brain by using in situ hybridization histochemistry. MARCKS hybridization was most pronounced in the olfactory bulb, piriform cortex (layer II), medial habenular nucleus, subregions of the amygdala, specific hypothalamic nuclei, hippocampal granule cells, neocortex, and cerebellar cortex, intermediate in the superior colliculus, hippocampal CA1, and certain brainstem nuclei including the locus coeruleus, and low-absent in regions of the caudate-putamen, geniculate nuclei, thalamic nuclei, lateral habenular nucleus, and hippocampal CA3 pyramidal and hilar neurons. Consistent with previous reports, prominent F1/GAP-43 hybridization was observed in neocortex, medial geniculate, piriform cortex (layer II), substantia nigra pars compacta, hippocampal CA3 pyramidal cells, thalamic and hypothalamic nuclei, lateral habenular nucleus, locus coeruleus, raphe nuclei, and cerebellar granule cells, intermediate in regions of the thalamus, hypothalamus, and amygdala, and low-absent in regions of the olfactory bulb, caudate-putamen, medial habenular nucleus, hippocampal granule cells, and superior colliculus. Overall, F1/GAP-43 was highly expressed in a greater number of regions compared to MARCKS and, in a number of regions, including the hippocampus, habenular complex, ventral tegmentum, geniculate, and certain brain stem nuclei, a striking inverse pattern of expression was observed. These results indicate that MARCKS gene expression, like that of F1/GAP-43, remains elevated in select regions of the adult rat brain which are associated with a high degree of retained plasticity. The potential role of PKC in the regulation of MARCKS and F1/GAP-43 gene expression in brain is assessed. J. Comp. Neurol. 379:48-71, 1997. © 1997 Wiley-Liss, Inc.     

Developmental expression of voltage-gated potassium channel beta subunits.

Expression of potassium channel beta subunits (Kvbeta) was determined in the developing mouse CNS using an antiserum against an amino acid sequence present in the C-terminus of Kvbeta1, Kvbeta2, and Kvbeta3. Using the anti-Kvbeta antiserum, we determined that Kvbeta expression is restricted to the spinal cord and dorsal root ganglia in the embryonic CNS. At birth, Kvbeta expression is detected in brainstem and midbrain nuclei, but was not detected in the hippocampus, cerebellum or cerebral cortex. During the first postnatal week, Kvbeta expression is present in hippocampal and cortical pyramidal cells and in cerebellar Purkinje cells. Expression of Kvbeta subunits reaches adult levels by the third postnatal week in all of the brain regions examined. A rabbit antiserum directed against a unique peptide sequence in the N-terminus of the Kvbeta1 protein demonstrates that this subunit displays a novel expression pattern in the developing mouse brain. Kvbeta1 expression is high at birth in all brain regions examined and decreases with age. In contrast, Kvbeta2 expression is low at birth and increases with age to reach adult levels by the third postnatal week. These findings support the notion that the differential regulation of distinct potassium channel beta subunits, in the developing mouse nervous system, may confer the functional diversity required to mediate both neuronal survival and maturation.     

Increased subcortical and laminar cortical 2-deoxy[14C]glucose uptake during cerebellar stimulation

2-Deoxy[¹⁴C]glucose (2DG) uptake was mapped in brains of conscious rats during cerebellar hemisphere electrical stimulation and compared with sham-operated controls. The 2DG uptake increased bilaterally in cerebellar cortex and deep nuclei, the largest increases being ipsilateral to the stimulating electrode. Structures which increased 2DG uptake bilaterally but had larger contralateral increases included the red nucleus, inferior olive, zona incerta, substantia nigra, globus pallidus, deep mesencephalic nucleus, habenula, reticular tegmental nucleus of the pons, ventroanterolateral and ventromedial nuclei of thalamus, several other thalamic nuclei, and motor-somatosensory cortex. Most of these structures receive efferent fibers from cerebellar nuclei. Cerebellar stimulation produced two bands of 2DG uptake bilaterally in rat motor-somatosensory neocortical laminae IV and Vc-VIa. Shamoperated controls had one band of 2DG uptake in neocortical lamina IV. We postulate that cerebellar stimulation increased 2DG uptake polysynaptically in lamina Vc-VIa by the following pathway: Purkinje cells → deep cerebellar nuclei → ventrolateral and/or ventromedial nuclei of thalamus → lamina Vc-VIa of neocortex. Activation of these cortical laminae could affect cortical seizure foci.     

Apoptosis and necrosis occur in separate neuronal populations in hippocampus and cerebellum after ischemia and are associated with differential alterations in metabotropic glutamate receptor signaling pathways.

It was evaluated whether postischemic neurodegeneration is apoptosis and occurs with alterations in phosphoinositide-linked metabotropic glutamate receptors (mGluRs) and their associated signaling pathways. A dog model of transient global incomplete cerebral ischemia was used. The CA1 pyramidal cells and cerebellar Purkinje cells underwent progressive delayed degeneration. By in situ end-labeling of DNA, death of CA1 and Purkinje cells was greater at 7 days than 1 day after ischemia, whereas death of granule neurons in dentate gyrus and cerebellar cortex was greater at 1 than at 7 days. Ultrastructurally, degenerating CA1 pyramidal neurons and cerebellar Purkinje cells were necrotic; in contrast, degenerating granule neurons were apoptotic. In agarose gels of regional DNA extracts, random DNA fragmentation coexisted with internucleosomal fragmentation. By immunoblotting of regional homogenates, mGluR1alpha, mGluR5, phospholipase Cbeta (PLCbeta), and Galphaq/11 protein levels in hippocampus at 1 and 7 days after ischemia were similar to control levels, but in cerebellar cortex, mGluR1alpha and mGluR5 were decreased but PLCbeta was increased. By immunocytochemistry, mGluR and PLCbeta immunoreactivity dissipated in CA1 and cerebellar Purkinje cell/ molecular layers, whereas immunoreactivities for these proteins were enhanced in granule neurons. It was concluded that neuronal death after global ischemia exists as two distinct, temporally overlapping forms in hippocampus and cerebellum: necrosis of pyramidal neurons and Purkinje cells and apoptosis of granule neurons. Neuronal necrosis is associated with a loss of phosphoinositide-linked mGluR transduction proteins, whereas neuronal apoptosis occurs with increased mGluR signaling.     

On the cellular localization of cerebellar muscarinic receptors: An autoradiographic analysis of weaver, reeler, purkinje cell degeneration and staggerer mice

Light microscopic autoradiography of [3H]quinuclidinyl benzilate binding sites was used to study the distribution of muscarinic cholinergic receptors in mouse mutants which have abnormalities affecting specific cerebellar cell types. In the normal C57BL/6J mouse, binding sites were distributed throughout the cerebellar cortex, with the highest levels in the granule cell layer and deep cerebellar nuclei. Normal binding site density was observed in the cerebellum of the weaver mutant in which the majority of granule cells had degenerated. The density of [3H]quinuclidinyl benzilate binding sites was elevated in the cortex of the reeler, despite a reduction in the number of granule cells. The concentration of binding sites was also high over the Purkinje cell masses where granule cells were largely absent. No significant reduction in cortical [3H]quinuclidinyl benzilate binding site density was detected in the Purkinje cell degeneration mutant, in which essentially all Purkinje cells had degenerated. In contrast, receptor binding in the deep cerebellar nuclei of this mutant was significantly increased. A substantial increase in labeling was observed in the cortex and deep nuclei of the staggerer cerebellum in which a large fraction of Golgi II cells, Purkinje cells, granule cells and mossy fibers have degenerated. We discuss the possibility that the persistence of [3H]quinuclidinyl benzilate binding sites in all four mutants may imply a non-neuronal localization for a large proportion of muscarinic receptors in the mouse cerebellar cortex.     

The cellular pathology of Menkes steely hair syndrome

The principal neuropathologic abnormality observed in three autopsy cases of Menkes steely hair syndrome was widespread nerve cell loss and gliosis, especially severe in the cerebral and cerebellar cortex and in the relay nuclei of the thalamus. Granular stellate cells of neocortical layer IV and the granule cells of the cerebellum are cell classes which were particularly severely depopulated. The degree of reduction of myelinated axons is consistent with axonal degeneration secondary to nerve cell loss. There are also prominent abnormalities in the patterns of dendritic arborization of surviving cortical pyramids and cerebellar Purkinje cells as seen in Golgi impregnations. The deviant neuronal forms are probably due, in part, to failure of innervation by afferent fiber systems during the fetal as well as postnatal epochs.