Home About us Contact
|
Home About us Contact | ||
|
|
||
Molecular Layer (molecular + layer)
Kinds of Molecular Layer Selected AbstractsFunctions of glutamate transporters in cerebellar Purkinje cell synapsesACTA PHYSIOLOGICA, Issue 1 2009Y. Takayasu Abstract Glutamate transporters play a critical role in the maintenance of low extracellular concentrations of glutamate, which prevents the overactivation of post-synaptic glutamate receptors. Four distinct glutamate transporters, GLAST/EAAT1, GLT-1/EAAT2, EAAC1/EAAT3 and EAAT4, are distributed in the molecular layer of the cerebellum, especially near glutamatergic synapses in Purkinje cells (PCs). This review summarizes the current knowledge about the differential roles of these transporters at excitatory synapses of PCs. Data come predominantly from electrophysiological experiments in mutant mice that are deficient in each of these transporter genes. GLAST expressed in Bergmann glia contributes to the clearing of the majority of glutamate that floods out of the synaptic cleft immediately after transmitter release from the climbing fibre (CF) and parallel fibre (PF) terminals. It is indispensable to maintain a one-to-one relationship in synaptic transmission at the CF synapses by preventing transcellular glutamate spillover. GLT-1 plays a similar but minor role in the uptake of glutamate as GLAST. Although the loss of neither GLAST nor GLT-1 affects cerebellar morphology, the deletion of both GLAST and GLT-1 genes causes the death of the mutant animal and hinders the folium formation of the cerebellum. EAAT4 removes the low concentrations of glutamate that escape from uptake by glial transporters, preventing the transmitter from spilling over into neighbouring synapses. It also regulates the activation of metabotropic glutamate receptor 1 (mGluR1) in perisynaptic regions at PF synapses, which in turn affects mGluR1-mediated events including slow EPSCs and long-term depression. No change in synaptic function is detected in mice that are deficient in EAAC1. [source] Environmental impoverishment and aging alter object recognition, spatial learning, and dentate gyrus astrocytesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2010Daniel G. Diniz Abstract Environmental and age-related effects on learning and memory were analysed and compared with changes observed in astrocyte laminar distribution in the dentate gyrus. Aged (20 months) and young (6 months) adult female albino Swiss mice were housed from weaning either in impoverished conditions or in enriched conditions, and tested for episodic-like and water maze spatial memories. After these behavioral tests, brain hippocampal sections were immunolabeled for glial fibrillary acid protein to identify astrocytes. The effects of environmental enrichment on episodic-like memory were not dependent on age, and may protect water maze spatial learning and memory from declines induced by aging or impoverished environment. In the dentate gyrus, the number of astrocytes increased with both aging and enriched environment in the molecular layer, increased only with aging in the polymorphic layer, and was unchanged in the granular layer. We suggest that long-term experience-induced glial plasticity by enriched environment may represent at least part of the circuitry groundwork for improvements in behavioral performance in the aged mice brain. [source] TARPs ,-2 and ,-7 are essential for AMPA receptor expression in the cerebellumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2010Maya Yamazaki Abstract The ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors require auxiliary subunits termed transmembrane AMPA receptor regulatory proteins (TARPs), which promote receptor trafficking to the cell surface and synapses and modulate channel pharmacology and gating. Of six TARPs, ,-2 and ,-7 are the two major TARPs expressed in the cerebellum. In the present study, we pursued their roles in synaptic expression of cerebellar AMPA receptors. In the cerebellar cortex, ,-2 and ,-7 were preferentially localized at various asymmetrical synapses. Using quantitative Western blot and immunofluorescence, we found severe reductions in GluA2 and GluA3 and mild reduction in GluA4 in ,-2-knockout (KO) cerebellum, whereas GluA1 and GluA4 were moderately reduced in ,-7-KO cerebellum. GluA2, GluA3 and GluA4 were further reduced in ,-2/,-7 double-KO (DKO) cerebellum. The large losses of GluA2 and GluA3 in ,-2-KO mice and further reductions in DKO mice were confirmed at all asymmetrical synapses examined with postembedding immunogold. Most notably, the GluA2 level in the postsynaptic density fraction, GluA2 labeling density at parallel fiber,Purkinje cell synapses, and AMPA receptor-mediated currents at climbing fiber,Purkinje cell synapses were all reduced to approximately 10% of the wild-type levels in DKO mice. On the other hand, the reduction in GluA4 in ,-7-KO granular layer reflected its loss at mossy fiber,granule cell synapses, whereas that of GluA1 and GluA4 in ,-7-KO molecular layer was caused, at least partly, by their loss in Bergmann glia. Therefore, ,-2 and ,-7 cooperatively promote synaptic expression of cerebellar AMPA receptors, and the latter also promotes glial expression. [source] Somatodendritic localization of EFA6A, a guanine nucleotide exchange factor for ADP-ribosylation factor 6, and its possible interaction with ,-actinin in dendritic spinesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2007Hiroyuki Sakagami Abstract EFA6A is a member of the guanine nucleotide exchange factors that can specifically activate ADP ribosylation factor 6 (ARF6). In this study, we identified ,-actinin-1 as a possible interacting protein with EFA6A by the yeast two-hybrid screening with its C-terminal region as bait. The central region of ,-actinin-1 containing a part of spectrin repeat 1 and spectrin repeats 2,3 is responsible for this interaction. In the hippocampal formation, EFA6A immunoreactivity occurred at a high level as numerous fine puncta in the strata oriens, radiatum, lacunosum-moleculare of the hippocampal CA1,3 subfields and the dentate molecular layer, whereas the immunoreactivity was faint in the neuronal cell layers and the stratum lucidum, the mossy fiber-recipient layer of the CA3 subfield. Double-immunofluorescent analyses revealed a partial overlapping of EFA6A and ,-actinin at the dendritic spines of in vivo and cultured hippocampal neurons. Our present findings suggest that EFA6A may form a protein complex with ,-actinin and activate ARF6 in close proximity of the actin cytoskeleton and membrane proteins in the dendritic spines. [source] Segregation of two endocannabinoid-hydrolyzing enzymes into pre- and postsynaptic compartments in the rat hippocampus, cerebellum and amygdalaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2004A. I. Gulyas Abstract Fatty acid amide hydrolase (FAAH) and monoglyceride lipase (MGL) catalyse the hydrolysis of the endocannabinoids anandamide and 2-arachidonoyl glycerol. We investigated their ultrastructural distribution in brain areas where the localization and effects of cannabinoid receptor activation are known. In the hippocampus, FAAH was present in somata and dendrites of principal cells, but not in interneurons. It was located mostly on the membrane surface of intracellular organelles known to store Ca2+ (e.g. mitochondria, smooth endoplasmic reticulum), less frequently on the somatic or dendritic plasma membrane. MGL immunoreactivity was found in axon terminals of granule cells, CA3 pyramidal cells and some interneurons. In the cerebellum, Purkinje cells and their dendrites are intensively immunoreactive for FAAH, together with a sparse axon plexus at the border of the Purkinje cell/granule cell layers. Immunostaining for MGL was complementary, the axons in the molecular layer were intensively labelled leaving the Purkinje cell dendrites blank. FAAH distribution in the amygdala was similar to that of the CB1 cannabinoid receptor: evident signal in neuronal somata and proximal dendrites in the basolateral nucleus, and hardly any labelling in the central nucleus. MGL staining was restricted to axons in the neuropil, with similar relative signal intensities seen for FAAH in different nuclei. Thus, FAAH is primarily a postsynaptic enzyme, whereas MGL is presynaptic. FAAH is associated with membranes of cytoplasmic organelles. The differential compartmentalization of the two enzymes suggests that anandamide and 2-AG signalling may subserve functional roles that are spatially segregated at least at the stage of metabolism. [source] Post-lesion transcommissural growth of olivary climbing fibres creates functional synaptic microzonesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003Izumi Sugihara Abstract In the adult mammalian central nervous system, reinnervation and recovery from trauma is limited. During development, however, postlesion plasticity may generate alternate paths, providing models to investigate reinnervating axon,target interactions. After unilateral transection of the neonatal rat olivocerebellar path, axons from the ipsilateral inferior olive grow into the denervated hemicerebellum and develop climbing fibre (CF)-like arbors on Purkinje cells (PCs). However, the synaptic function and extent of PC reinnervation remain unknown. In adult rats pedunculotomized on postnatal day 3 the morphological and electrophysiological properties of reinnervating olivocerebellar axons were studied, using axonal reconstruction and patch-clamp PC recording of CF-induced synaptic currents. Reinnervated PCs displayed normal CF currents, and the frequency of PC reinnervation decreased with increasing laterality. Reinnervating CF arbors were predominantly normal but 6% branched within the molecular layer forming smaller secondary arbors. CFs arose from transcommissural olivary axons, which branched extensively near their target PCs to produce on average 36 CFs, which is six times more than normal. Axons terminating in the hemisphere developed more CFs than those terminating in the vermis. However, the precise parasagittal microzone organization was preserved. Transcommissural axons also branched, although to a lesser extent, to the deep cerebellar nuclei and terminated in a distribution indicative of the olivo-cortico-nuclear circuit. These results show that reinnervating olivocerebellar axons are highly plastic in the cerebellum, compensating anatomically and functionally for early postnatal denervation, and that this reparation obeys precise topographic constraints although axonal plasticity is modified by target (PC or deep nuclear neurons) interactions. [source] The KCl cotransporter, KCC2, is highly expressed in the vicinity of excitatory synapses in the rat hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2001A. I. Gulyás Abstract Immunocytochemical visualization of the neuron-specific K+/Cl, cotransporter, KCC2, at the cellular and subcellular level revealed an area- and layer-specific diffuse labelling, and a discrete staining outlining the somata and dendrites of some interneurons in all areas of the rat hippocampus. KCC2 was highly expressed in parvalbumin-containing interneurons, as well as in subsets of calbindin, calretinin and metabotropic glutamate receptor 1a-immunoreactive interneurons. During the first 2 postnatal weeks, an increase of KCC2 staining was observed in the molecular layer of the dentate gyrus, correlating temporally with the arrival of entorhinal cortical inputs. Subcellular localization demonstrated KCC2 in the plasma membranes. Immunoreactivity in principal cells was responsible for the diffuse staining found in the neuropil. In these cells, KCC2 was detected primarily in dendritic spine heads, at the origin of spines and, at a much lower level on the somata and dendritic shafts. KCC2 expression was considerably higher in the somata and dendrites of interneurons, most notably of parvalbumin-containing cells, as well as in the thorny excrescences of CA3 pyramidal cells and in the spines of spiny hilar and stratum lucidum interneurons. The data indicate that KCC2 is highly expressed in the vicinity of excitatory inputs in the hippocampus, perhaps in close association with extrasynaptic GABAA receptors. A high level of excitation is known to lead to a simultaneous net influx of Na+ and Cl,, as evidenced by dendritic swelling. KCC2 located in the same microenvironment may provide a Cl, extrusion mechanism to deal with both ion and water homeostasis in addition to its role in setting the driving force of Cl, currents involved in fast postsynaptic inhibition. [source] NMDA receptor subunits GluR,1, GluR,3 and GluR,1 are enriched at the mossy fibre,granule cell synapse in the adult mouse cerebellumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2001Kazuyuki Yamada Abstract Cerebellar N -methyl- d -aspartate (NMDA) receptors are concentrated in the granular layer and are involved in motor coordination and the induction of long-term potentiation at mossy fibre,granule cell synapses. In the present study, we used immunohistochemistry to examine the distribution of NMDA receptor subunits in the adult mouse cerebellum. We found that appropriate pepsin pretreatment of sections greatly enhanced the sensitivity and specificity of immunohistochemical detection. As a result, intense immunolabelling for GluR,1 (NR2A), GluR,3 (NR2C), and GluR,1 (NR1) all appeared in synaptic glomeruli of the granular layer. Double immunofluorescence showed that these subunits were colocalized in individual synaptic glomeruli. Within the glomerulus, NMDA receptor subunits were located between centrally-located huge mossy fibre terminals and peripherally-located tiny Golgi axon terminals. By immunoelectron microscopy, all three subunits were detected at the postsynaptic junction in granule cell dendrites, forming synapses with mossy fibre terminals. Consistent with the known functional localization, GluR,1, GluR,3, and GluR,1 are, thus, anatomically concentrated at the mossy fibre,granule cell synapse. By contrast, immunohistochemical signals were very low in Purkinje cell somata and dendrites in the molecular layer. The lack of GluR,1 immunolabelling in Purkinje cells was unexpected because the cells express GluR,1 mRNA at high levels and high levels of GluR,1 protein in the molecular layer were revealed by immunoblot. As Purkinje cells are exceptionally lacking GluR, expression, the discrepant result may provide in vivo evidence suggesting the importance of accompanying GluR, subunits in synaptic localization of GluR,1. [source] Glutamate transporter expression in astrocytes of the rat dentate gyrus following lesion of the entorhinal cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2001C. Hein Abstract The glutamate transporters GLT-1 and GLAST localized in astrocytes are essential in limiting transmitter signalling and restricting harmful receptor overstimulation. To show changes in the expression of both transporters following lesion of the entorhinal cortex (and degeneration of the glutamatergic tractus perforans), quantitative microscopic in situ hybridization (ISH) using alkaline-phosphatase-labelled oligonucleotide probes was applied to the outer molecular layer of the hippocampal dentate gyrus of rats (termination field of the tractus perforans). Four groups of rats were studied: sham-operated controls, and animals 3, 14 and 60 days following unilateral electrolytic lesion of the entorhinal cortex. The postlesional shrinkage of the terminal field of the perforant path, ipsilateral to the lesion side, was determined and considered in the evaluation of quantitative ISH data. Statistical analysis revealed that ipsilateral to the lesion side there was a significant decrease of the GLT-1 mRNA at every postlesional time-point and of the GLAST mRNA at 14 and 60 days postlesion. The maximal decrease was ,,45% for GLT-1 and ,,35% for GLAST. In the terminal field of the perforant path contralateral to the lesion side, no significant changes of ISH labelling were measured. The results were complemented by immunocytochemical data achieved using antibodies against synthetic GLT-1 and GLAST peptides. In accordance with ISH results, there was an obvious decrease of GLT-1 and GLAST immunostaining in the terminal field of the perforant path ipsilateral to the lesion side. From these data we conclude that, following a lesioning of the entorhinal cortex, the loss of glutamatergic synapses in the terminal field of the perforant path resulted in a strong downregulation of glutamate transporters in astrocytes. The decrease of synaptically released glutamate or of other neuronal factors could be involved in this downregulation. [source] The chondroitin sulphate proteoglycan brevican is upregulated by astrocytes after entorhinal cortex lesions in adult ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2000Niklas Thon Abstract The chondroitin sulphate proteoglycan brevican is one of the most abundant extracellular matrix molecules in the adult rat brain. It is primarily synthesized by astrocytes and is believed to influence astroglial motility during development and under certain pathological conditions. In order to study a potential role of brevican in the glial reaction after brain injury, its expression was analysed following entorhinal cortex lesion in rats (12 h, 1, 2, 4, 10, 14 and 28 days and 6 months post lesion). In situ hybridization and immunohistochemistry were employed to study brevican mRNA and protein, respectively, in the denervated outer molecular layer of the fascia dentata and at the lesion site. In both regions brevican mRNA was upregulated between 1 and 4 days post lesion. The combination of in situ hybridization with immunohistochemistry for glial fibrillary acidic protein demonstrated that many brevican mRNA-expressing cells are astrocytes. In the denervated zone of the fascia dentata, immunostaining for brevican was increased by 4 days, reached a maximum by 4 weeks and remained detectable up to 6 months post lesion. Electron microscopic immunocytochemistry showed that brevican is a component of the extracellular matrix compartment. At the lesion site a similar time course of brevican upregulation was observed. These data demonstrate that brevican is upregulated in areas of brain damage as well as in areas denervated by a lesion. They suggest a role of brevican in reactive gliosis and are compatible with the hypothesis that brevican is involved in the synaptic reorganization of denervated brain areas. [source] Localization of the A kinase anchoring protein AKAP79 in the human hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2000Attila Sík Abstract The phosphorylation state of the proteins, regulated by phosphatases and kinases, plays an important role in signal transduction and long-term changes in neuronal excitability. In neurons, cAMP-dependent protein kinase (PKA), protein kinase C (PKC) and calcineurin (CN) are attached to a scaffold protein, A kinase anchoring protein (AKAP), thought to anchor these three enzymes to specific sites of action. However, the localization of AKAP, and the predicted sites of linked phosphatase and kinase activities, are still unknown at the fine structural level. In the present study, we investigated the distribution of AKAP79 in the hippocampus from postmortem human brains and lobectomy samples from patients with intractable epilepsy, using preembedding immunoperoxidase and immunogold histochemical methods. AKAP79 was found in the CA1, presubicular and subicular regions, mostly in pyramidal cell dendrites, whereas pyramidal cells in the CA3, CA2 regions and dentate granule cells were negative both in postmortem and in surgical samples. In some epileptic cases, the dentate molecular layer and hilar interneurons also became immunoreactive. At the subcellular level, AKAP79 immunoreactivity was present in postsynaptic profiles near, but not attached to, the postsynaptic density of asymmetrical (presumed excitatory) synapses. We conclude that the spatial selectivity for the action of certain kinases and phosphatases regulating various ligand- and voltage-gated channels may be ensured by the selective presence of their anchoring protein, AKAP79, at the majority of glutamatergic synapses in the CA1, but not in the CA2/CA3 regions, suggesting profound differences in signal transduction and long-term synaptic plasticity between these regions of the human hippocampus. [source] Hippocampal mossy fiber sprouting and elevated trkB receptor expression following systemic administration of low dose domoic acid during neonatal developmentHIPPOCAMPUS, Issue 11 2007Paul B. Bernard Abstract We have previously reported that serial systemic injections of low-dose (subconvulsive) domoic acid (DOM) during early postnatal development produces changes in both behavior and hippocampal cytoarchitecture in aged rats (17 months) that are similar to those seen in existing animal models of temporal lobe epilepsy. Herein we report further hippocampal changes, consisting of mossy fiber sprouting and associated changes in the trkB receptor population in young adult (3 months) rats, and further, report that these changes show regional variation throughout the septo-temporal axis of the hippocampus. Groups of Sprague Dawley rat pups were injected daily from postnatal day 8,14 with either saline (n = 23) or 20 ,g/kg DOM (n = 25), tested for key indicators of neonatal neurobehavioral development, and then left undisturbed until ,90 days of age, at which time brain tissue was removed, hippocampi were dissected, fixed and processed using either Timm's stain to visualize hippocampal mossy fiber sprouting (MFS) or trkB immunohistochemistry to visualize full length trkB receptors. Multiple sections from dorsal, mid, and ventral hippocampus were analyzed separately and all measures were conducted using image analysis software. The results indicate significant increases in MFS in the inner molecular layer in treated animals with corresponding changes in trkB receptor density. Further we identified significant increases in trkB receptor density in the hilus of the dentate gyrus and area CA3 and report increased mossy fiber terminal density in the stratum lucidum in treated rats. The magnitude of these changes differed between sections from dorsal, mid, and ventral hippocampus. We conclude that low dose neonatal DOM produces cytoarchitectural changes indicative of abnormal development and/or synaptic plasticity that are progressive with age and show regional variation within the hippocampal formation. © 2007 Wiley-Liss, Inc. [source] Loss of input from the mossy cells blocks maturation of newly generated granule cellsHIPPOCAMPUS, Issue 7 2007Ana-Isabel Marqués-Marí Abstract The objective of this work is to check whether the input from the mossy cells to the inner molecular layer is necessary for the integration and maturation of the newly generated granule cells of the dentate gyrus (DG) in mice, and if after status epilepticus the sprouting of the mossy fibers can substitute for this projection. Newly generated cells were labeled by administration of 5-bromo-deoxyuridine either before or after pilocarpine administration. The neuronal loss in the hippocampus after administration of pilocarpine combined with scopolamine and diazepam seemed restricted to the hilar mossy cells. The maturation of the granule cells was studied using immunohistochemistry for calretinin and NeuN in combination with detection of 5-bromo-deoxyuridine. The sprouting of the mossy fibers was detected using Timm staining for zinc-rich boutons. In normal conditions, granule cells took about 2 weeks to lose the immature marker calretinin. After the loss of the mossy cells, newly generated granule cells remained expressing calretinin for more than a month, until the sprouting of the mossy fibers substituted for the projection of the mossy cells in the inner molecular layer of the DG. Therefore, a proper pattern of connectivity is necessary for the normal development and integration of newly generated granule cells in the adult brain. In a changed environment they cannot adapt transforming in other cell types; simply they are unable to mature. The sprouting of the mossy fibers, although aberrant and a probable source of epileptic activity, may be important for the correct physiology of the granule cells, restoring a likeness of normality in their connective environment. The survival of granule cells incorporated as mature neurons was increased after pilocarpine when compared with normal conditions. Thus, it is likely that the reorganization of the circuitry after the loss of the mossy cells facilitates the survival and incorporation of the newly generated granule cells. © 2007 Wiley-Liss, Inc. [source] Comparison of commissural sprouting in the mouse and rat fascia dentata after entorhinal cortex lesionHIPPOCAMPUS, Issue 6 2003Domenico Del Turco Abstract Reactive axonal sprouting occurs in the fascia dentata after entorhinal cortex lesion. This sprouting process has been described extensively in the rat, and plasticity-associated molecules have been identified that might be involved in its regulation. To demonstrate causal relationships between these candidate molecules and the axonal reorganization process, it is reasonable to analyze knockout and transgenic animals after entorhinal cortex lesion, and because gene knockouts are primarily generated in mice, it is necessary to characterize the sprouting response after entorhinal cortex lesion in this species. In the present study, Phaseolus vulgaris -leucoagglutinin (PHAL) tracing was used to analyze the commissural projection to the inner molecular layer in mice with longstanding entorhinal lesions. Because the commissural projection to the fascia dentata is neurochemically heterogeneous, PHAL tracing was combined with immunocytochemistry for calretinin, a marker for commissural/associational mossy cell axons. Using both techniques singly as well as in combination (double-immunofluorescence) at the light or electron microscopic level, it could be shown that in response to entorhinal lesion mossy cell axons leave the main commissural fiber plexus, invade the denervated middle molecular layer, and form asymmetric synapses within the denervated zone. Thus, the commissural sprouting response in mice has a considerable translaminar component. This is in contrast to the layer-specific commissural sprouting observed in rats, in which the overwhelming majority of mossy cell axons remain within their home territory. These data demonstrate an important species difference in the commissural/associational sprouting response between rats and mice that needs to be taken into account in future studies. © 2003 Wiley-Liss, Inc. [source] Distribution and morphology of serotonin-immunoreactive axons in the hippocampal region of the New Zealand white rabbit.HIPPOCAMPUS, Issue 1 2003Abstract This study provides a detailed light microscopic description of the morphology and distribution of immunohistochemically stained serotonergic axons in the hippocampal region of the New Zealand white rabbit. The serotonergic axons were segregated morphologically into three types: beaded fibers, fine fibers, and stem-axons, respectively. Beaded fibers were thin serotonergic axons with large varicosities, whereas thin axons with small fusiform or granular varicosities were called fine fibers. Finally, thick straight non-varicose axons were called stem-axons. Beaded fibers often formed large conglomerates with numerous boutons (pericellular arrays) in close apposition to the cell-rich layers in the hippocampal region, e.g., the granular and hilar cell layers of the dentate area and the pyramidal cell layer ventrally in CA3. The pericellular arrays in these layers were often encountered in relation to small calbindin-D28K -positive cells, as shown by immunohistochemical double staining for serotonin and calbindin-D28K. The beaded and fine serotonergic fibers displayed a specific innervation pattern in the hippocampal region and were encountered predominantly within the terminal field of the perforant path, e.g., the stratum moleculare hippocampi and the outer two-thirds of the dentate molecular layer. These fibers were also frequently seen in the deep part of the stratum oriens and the alveus, forming a dense plexus in relation to large multipolar calbindin-D28K -positive cells and their basal extensions. Stem-axons were primarily seen in the fimbria and alveus. This innervation pattern was present throughout the entire hippocampal formation, but there were considerable septotemporal differences in the density of the serotonergic innervation. A high density of innervation prevailed in the ventral/temporal part of the hippocampal formation, whereas the dorsal/septal part received only a moderate to weak serotonergic innervation. These results suggest that the serotonergic system could modulate the internal hippocampal circuitry by way of its innervation in the terminal field of the perforant path, the hilus fasciae dentatae, and ventrally in the zone closely apposed to the mossy fiber layer and the pyramidal cells of CA3. This modulation could be of a dual nature, mediated directly by single serotonergic fibers traversing the hippocampal layers or indirectly by the pericellular arrays and their close relation to the calbindin-D28K -positive cells. The marked septotemporal differences in innervation density point toward a difference between the ventral and dorsal parts of the hippocampal formation with respect to serotonergic function and need for serotonergic modulation. Hippocampus 2003;13:21,37. © 2003 Wiley-Liss, Inc. [source] Long-lasting increased excitability differs in dentate gyrus vs.HIPPOCAMPUS, Issue 3 2002CA1 in freely moving chronic epileptic rats after electrically induced status epilepticus Abstract A paired-pulse (PP) stimulation protocol was used to examine changes in field potentials (fEPSPs), locally evoked in CA1 via Schaffer/commissural fiber stimulation and in the dentate gyrus (DG) through angular bundle stimulation, in freely moving epileptic rats. This epilepsy model is characterized by recurrent spontaneous seizures that occur after a latent period of 1,2 weeks following an electrically induced status epilepticus (SE). In the control period, i.e., before induction of SE, the PP stimulation protocol given at the appropriate intensity evoked fEPSPs with a pronounced paired-pulse depression (PPD). In the acute period, immediately after SE, the fEPSPs in the CA1 and DG areas were generally depressed. During the latent period in the CA1 stratum radiatum, the negative fEPSP was followed by a large positive potential that remained for the rest of the recording period. CA1 PPD, observed during the control period, was changed to paired-pulse facilitation (PPF) that remained for the rest of the recording period. Also during the latent period, a broad late component appeared in DG fEPSPs. The initial decrease in PPD was partly restored in the following weeks. Timm staining at different time points after SE showed an increase of mossy-fiber sprouting in the inner molecular layer within 6 days, which was robust within 6 weeks. We noted Timm granules positioned on parvalbumin immunoreactive neurons in the granule-cell layer of rats that had survived SE, suggesting that restoration of PPD could be partly due to reinnervation of a population of GABAergic neurons. The broad late component of DG fEPSPs, which was sensitive to the NMDA receptor antagonist ketamine, was still present for at least 6 weeks into the chronic epileptic phase, indicating lasting increased excitability. These observed changes indicate a lasting increased excitability in CA1 and DG networks that could play a role in the recurrence of spontaneous seizures. Hippocampus 2002;12:311,324. © 2002 Wiley-Liss, Inc. [source] Progress with Molecular Electronic Junctions: Meeting Experimental Challenges in Design and FabricationADVANCED MATERIALS, Issue 43 2009Richard L. McCreery Abstract Molecular electronics seeks to incorporate molecular components as functional elements in electronic devices. There are numerous strategies reported to date for the fabrication, design, and characterization of such devices, but a broadly accepted example showing structure-dependent conductance behavior has not yet emerged. This progress report focuses on experimental methods for making both single-molecule and ensemble molecular junctions, and highlights key results from these efforts. Based on some general objectives of the field, particular experiments are presented to show progress in several important areas, and also to define those areas that still need attention. Some of the variable behavior of ostensibly similar junctions reported in the literature is attributable to differences in the way the junctions are fabricated. These differences are due, in part, to the multitude of methods for supporting the molecular layer on the substrate, including methods that utilize physical adsorption and covalent bonds, and to the numerous strategies for making top contacts. After discussing recent experimental progress in molecular electronics, an assessment of the current state of the field is presented, along with a proposed road map that can be used to assess progress in the future. [source] Effect of Corticosteroid Treatment In Vitro on Adrenalectomy-Induced Impairment of Synaptic Transmission in the Rat Dentate GyrusJOURNAL OF NEUROENDOCRINOLOGY, Issue 3 2000Stienstra Removal of the rat adrenals results after 3 days in the appearance of apoptotic cells in the dentate gyrus. Apoptosis is accompanied by an impaired synaptic transmission in the dentate gyrus. Substitution in vivo with a low dose of corticosterone was found to prevent both the appearance of apoptotic cells and the functional impairment. In the present study we determined whether the functional normalisation after corticosterone treatment critically depends on prevention of apoptosis. To address this question, brain slices from rats showing apoptosis after adrenalectomy were treated in vitro with the mineralocorticoid aldosterone (3 nM) or with 30 nM corticosterone, which is assumed to activate both mineralo- and glucocorticoid receptors. Steroids were briefly applied either during recording (acute effects) or several hours before recording (long-term effects). While the slope of the fEPSP recorded in the outer molecular layer of the dentate gyrus in response to perforant path stimulation was not affected up to 1 h after acute administration of the steroids, fEPSP slopes recorded 2.5,3 h after corticosterone or aldosterone treatment were significantly increased, to the level of the sham-operated controls. The results indicate that delayed corticosteroid effects through in vitro activation of mineralocorticoid receptors (MRs) are sufficient to normalise synaptic transmission in the dentate gyrus of ADX rats, even in the presence of apoptotic cells. We tentatively conclude that the impaired synaptic transmission seen after ADX is probably not primarily caused by the appearance of apoptotic cells. [source] Developmental change and function of chondroitin sulfate deposited around cerebellar Purkinje cellsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2005Yumiko Shimazaki Abstract Chondroitin sulfate is a long sulfated polysaccharide with enormous structural heterogeneity that binds with various proteins, such as growth factors, in a structure-dependent manner. In this study, we analyzed the expression of chondroitin sulfate in the postnatally developing cerebellar cortex by using three monoclonal antibodies against chondroitin sulfate, MO-225, 2H6, and CS-56, which recognize different structural domains in this polysaccharide. During the first postnatal week, the patterns of immunohistochemical staining made by these antibodies were quite similar, and the molecular layer, the granule cell layer, and Bergmann glial fibers in the external granular layer were densely stained. After postnatal day 12 (P12), the expression of 2H6 epitopes was down-regulated in the molecular layer, and the expression of CS-56 epitopes in this layer was also reduced after P16. On the other hand, the strong expression of MO-225 epitopes, GlcA(2S),1,3GalNAc(6S) (D unit)-containing structures, remained until adulthood. These chondroitin sulfate epitopes were observed around Purkinje cells, including cell soma and dendrites. Detailed immunohistochemical analysis suggested that chondroitin sulfate was deposited between Purkinje cell surfaces and the processes of Bergmann glia. Furthermore, the amount of pleiotrophin, a heparin-binding growth factor, in the cultured cerebellar slices was remarkably diminished after treatment with chondroitinase ABC or D unit-rich chondroitin sulfate. With the previous findings that pleiotrophin binds to D unit-rich chondroitin sulfate, we suggest that the D-type structure is important for the signaling of pleiotrophin, which plays roles in Purkinje cell,Bergmann glia interaction, and that the structural changes of chondroitin sulfate regulate this signaling pathway. © 2005 Wiley-Liss, Inc. [source] Phospholipid composition of articular cartilage boundary lubricantJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2001A. V. Sarma The mechanism of lubrication in normal human joints depends on loading and velocity conditions. Boundary lubrication, a mechanism in which layers of molecules separate opposing surfaces, occurs under severe loading. This study was aimed at characterizing the phospholipid composition of the adsorbed molecular layer on the surface of normal cartilage that performs as a boundary lubricant. The different types of phospholipid adsorbed onto the surface of cartilage were isolated by extraction and identified by chromatography on silica gel paper and mass spectroscopy. The main phospholipid classes identified were quantified by a phosphate assay. Gas chromatography and electrospray ionization mass spectrometry were used to further characterize the fatty acyl chains in each major phospholipid component and to identify the molecular species present. Phosphatidylcholine (41%), phosphatidylethanolamine (27%) and sphingomyelin (32%) were the major components of the lipid layer on the normal cartilage surface. For each lipid type, a mixture of fatty acids was detected, with a higher percentage of unsaturated species compared to saturated species. The most abundant fatty acid observed with all three lipid types was oleic acid (C18:1). Additional work to further quantify the molecular species using electrospray ionization mass spectrometry is recommended. © 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Speed- and topography-dependent boundary friction characteristics of steelLUBRICATION SCIENCE, Issue 8 2010Saiko Aoki Abstract A novel tribometer that undergoes significant changes at ultra-slow (>5.0,µm,s,1) to moderate (<20,cm,s,1) sliding speeds was developed in order to study the friction-speed characteristics of steel lubricated with oil. Three different surface topographies were applied to the specimens, and the friction characteristics with an additive-free base oil (MO91) and a stearic acid-formulated oil (StA/MO91) were studied to understand the effects of surface textures on the lubrication performance of an adsorbed molecular layer formed by StA. Friction reduction behaviour of the adsorbed layer observed in the transverse direction was attributed to microscopic hydrodynamic action that maintained the load-carrying performance of the adsorbed layer. Copyright © 2010 John Wiley & Sons, Ltd. [source] MM2-cortical-type sporadic Creutzfeldt-Jakob disease with early stage cerebral cortical pathology presenting with a rapidly progressive clinical courseNEUROPATHOLOGY, Issue 6 2008Yoshiki Niimi We report the case of a 67-year-old man with MM2-cortical-type sporadic Creutzfeldt-Jakob disease (sCJD) with a rapidly progressive clinical course of 5 months. Initial symptoms were progressive memory disturbance and dementia. MRI revealed high signal-intensity lesions on diffusion-weighted images in the bilateral frontal and occipital cortices. Myoclonus and periodic sharp-wave complexes on the electroencephalogram were observed in the early disease stage. The clinical diagnosis was typical sCJD. Neuropathologic examination at autopsy showed widespread, characteristic cerebral neocortical involvement with large confluent vacuole-type spongiform change. Spongiform degeneration was also evident in the striatum and medial thalamus. In the cerebellar cortex, slight depletion of Purkinje neurons was evident without spongiform change in the molecular layer or apparent neuron loss in the granule cell layer. The inferior olivary nucleus showed slight hypertrophic astrocytosis without neuron loss. Prion protein (PrP) immunostaining showed widespread, characteristic perivacuolar-type PrP deposits with irregular plaque-like PrP deposits in the cerebral neocortex, striatum and medial thalamus. We believe this patient showed early-stage cerebral cortical pathology of MM2-cortical-type sCJD, which may provide clues regarding the pathologic progression of this rare sCJD subtype. Although MM2-cortical-type sCJD generally shows slow progression without myoclonus or periodic sharp-wave complexes, the present patient showed a rapidly progressive clinical course similar to that of MM1-type sCJD. [source] Phenotypic variability in the brains of a family with a prion disease characterized by a 144-base pair insertion in the prion protein geneNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 2 2003A. King The use of prion protein (PrP) immunohistochemistry in neuropathology has allowed identification of prion diseases with otherwise atypical histological features. The brains from family members with familial prion diseases can show marked histological variation. A histological and immunohistochemical study was performed on 10 brains of patients with a familial prion disease caused by a 144-base pair (bp) insertion in the prion protein gene. The histology from the cases showed variability in the severity of spongiform change and astrocytosis in both the cerebellum and the cerebrum. There was also variability in the density of microglial cells. The PrP immunohistochemistry revealed that in nine cases there was a similar patch-like deposition of PrP within the molecular layer of the cerebellum. Although in the cerebellum there did seem to be some correlation between the severity of spongiform change, astrocytosis and the density of microglial cells, there was no such correlation between any of these three parameters and the density of PrP staining. There was deposition of ,-amyloid precursor protein (,-APP) in the cerebellum, suggesting that disrupted axonal transport had a possible role in the evolution of the disease. The cases illustrate the histological variability that can occur in familial prion diseases despite similarity in PrP staining. They also reveal that the relationship between PrP deposition and cerebral or cerebellar damage might be complex. [source] Assembly, structure, and performance of an ultra-thin film organic field-effect transistor (OFET) based on substituted oligothiophenesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008K. Haubner Abstract We report on the improved assembly and characterization of a small molecule organic field-effect transistor (OFET). Novel ,,,-dicyano substituted ,,,,-dibutylquaterthiophene molecules (DCNDBQT) were synthesized and characterized by UV,Vis spectroscopy, differential scanning calorimetry, thermal gravimetric analysis and cyclic voltammetry. The ultra-thin organic film formation on TiO2 templates was effectively promoted through the specifically designed bifunctional self assembly molecules (SAM) 5-cyano-2-(butyl-4-phosphonic acid)-3-butylthiophene (CNBTPA). Excellent structural properties were found for up to 9 DCNDBQT molecule thick films prepared through UHV vacuum sublimation as investigated with UHV non-contact atomic force microscopy (nc-AFM) and X-ray diffraction. Both X-ray and nc-AFM data indicate that the DCNDBQT molecules form a well-ordered terraced structure exhibiting step heights of 1.5 nm to 2.0 nm layers. Hence, the DCNDBQTmolecules are linked to the functional SAM interface layer by H-bond interactions (see structure model) standing quasi perpendicular to the TiO2 template, and thus providing optimal orbital overlap neigh-bouring thiophene rings. The vacuum sublimated DCNDBQT molecules form a closed packed and dense molecular layer that was used to construct and operate a nanoscopic OFET-structure. The resulting field mobilities of 10,5 cm2 V,1 s,1 reflect a high current density in our ultrathin but highly ordered structure. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cluster ion beam profiling of organics by secondary ion mass spectrometry , does sodium affect the molecular ion intensity at interfaces?RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2008Felicia M. Green The use of cluster ion beam sputtering for depth profiling organic materials is of growing technological importance and is a very active area of research. At the 44th IUVSTA Workshop on "Sputtering and Ion Emission by Cluster Ion Beams", recent results were presented of a cluster ion beam depth profile of a thin organic molecular layer on a silicon wafer substrate. Those data showed that the intensity of molecular secondary ions is observed to increase at the interface and this was explained in terms of the higher stopping power in the substrate and a consequently higher sputtering yield and even higher secondary ion molecular sputtering yield. An alternative hypothesis was postulated in the workshop discussion which may be paraphrased as: "under primary ion bombardment of an organic layer, mobile ions such as sodium may migrate to the interface with the inorganic substrate and this enhancement of the sodium concentration increases the ionisation probability, so increasing the molecular ion yield observed at the interface". It is important to understand if measurement artefacts occur at interfaces for quantification as these are of great technological relevance , for example, the concentration of drug in a drug delivery system. Here, we evaluate the above hypothesis using a sample that exhibits regions of high and low sodium concentration at both the organic surface and the interface with the silicon wafer substrate. There is no evidence to support the hypothesis that the probability of molecular secondary ion ionisation is related to the sodium concentration at these levels. © Crown copyright 2008. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] Expression of SV2 in the Seveloping Chick Cerebellum: Comparison with Calbindin and AMPA Glutamate Receptors 2/3THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 5 2008Detlev Grabs Abstract The well-organized cerebellum is an ideal model to investigate the developmental appearance and localization of pre- and postsynaptic structures. One of the synaptic proteins abundant in the central nervous system and localized in presynaptic vesicle membranes is the synaptic vesicle protein 2 (SV2). SV2 was shown to be involved in priming and modulating synaptic vesicles and having an effect in epileptic diseases. So far there are no data available describing the developmental localization of this protein in the cerebellum. We followed the expression pattern of SV2 and compared it with the expression of the neuronal calcium-binding protein Calbindin and the AMPA glutamate receptor subunits 2/3 (GluR 2/3), both shown to be early expressed in the developing chick cerebellum predominantly in Purkinje cells. We detected the expression of SV2 in presynaptic terminals (mainly from climbing and mossy fibers) as soon as they are formed at embryonic day 16 in the inner molecular layer. Purkinje cells express Calbindin and GluR 2/3 in the soma and postsynaptically in the primary dendrites at this stage. With ongoing development, the pattern of SV2 expression follows the development of Purkinje cell dendrites in the molecular layer, suggesting a synaptic refinement of labeled climbing and later parallel fibers. Anat Rec, 291:538,546, 2008. © 2008 Wiley-Liss, Inc. [source] Spatiotemporal characteristics of astroglial death in the rat hippocampo-entorhinal complex following pilocarpine-induced status epilepticusTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 5 2008Duk-Soo Kim Astroglial reactive gliosis in the rat hippocampus at 8 weeks after pilocarpine-induced status epilepticus. GFAP (red) positive reactive astrocytes in the stratum lacunosum-moleculare show strong GS (green) immunoreactivity, while GFAP-positive astrocytes show no GS immunoreactivity in the molecular layer of the dentate gyrus. Blue is DAPI counterstaining. J. Comp. Neurol. 511:581,598, 2008. © 2008 Wiley-Liss, Inc. [source] Adenosine signalling at immature parallel fibre,Purkinje cell synapses in rat cerebellumTHE JOURNAL OF PHYSIOLOGY, Issue 18 2009Alison Atterbury The purine adenosine is an extracellular signalling molecule involved in a large number of physiological and pathological conditions throughout the mammalian brain. However little is known about how adenosine release and its subsequent clearance change during brain development. We have combined electrophysiology and microelectrode biosensor measurements to investigate the properties of adenosine signalling at early stages of cerebellar development, when parallel fibre,Purkinje cell synapses have recently been formed (postnatal days 9,12). At this stage of development, we could detect little or no inhibitory A1 receptor tone in basal conditions and during trains of stimuli. Addition of pharmacological agents, to inhibit adenosine clearance, had only minor effects on synaptic transmission suggesting that under basal conditions, the concentration of adenosine moving in and out of the extracellular space is small. Active adenosine release was stimulated with hypoxia and trains of electrical stimuli. Although hypoxia released significant concentrations of adenosine, the release was delayed and slow. No adenosine release could be detected following electrical stimulation in the molecular layer. In conclusion, at this stage of development, although adenosine receptors and the mechanisms of adenosine clearance are present there is very little adenosine release. [source] Auto-inhibition of rat parallel fibre,Purkinje cell synapses by activity-dependent adenosine releaseTHE JOURNAL OF PHYSIOLOGY, Issue 2 2007Mark J. Wall Adenosine is an important signalling molecule involved in a large number of physiological functions. In the brain these processes are as diverse as sleep, memory, locomotion and neuroprotection during episodes of ischaemia and hypoxia. Although the actions of adenosine, through cell surface G-protein-coupled receptors, are well characterized, in many cases the sources of adenosine and mechanisms of release have not been defined. Here we demonstrate the activity-dependent release of adenosine in the cerebellum using a combination of electrophysiology and biosensors. Short trains of electrical stimuli delivered to the molecular layer in vitro, release adenosine via a process that is both TTX and Ca2+ sensitive. As ATP release cannot be detected, adenosine must either be released directly or rapidly produced by highly localized and efficient extracellular ATP breakdown. Since adenosine release can be modulated by receptors that act on parallel fibre,Purkinje cell synapses, we suggest that the parallel fibres release adenosine. This activity-dependent adenosine release exerts feedback inhibition of parallel fibre,Purkinje cell transmission. Spike-mediated adenosine release from parallel fibres will thus powerfully regulate cerebellar circuit output. [source] Mechanism of the first-order phase transition of an acylurea derivative: observation of intermediate stages of transformation with a detailed temperature-resolved single-crystal diffraction methodACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2003Daisuke Hashizume The process of the first-order solid-to-solid phase transition of 1-ethyl-3-(4-methylpentanoyl)urea (1) was observed by means of a detailed temperature-resolved single-crystal diffraction method, which resembles watching a series of stop-motion photographs. The transition consists of two elementary processes, one supramolecular and the other molecular. Crystal structures from before and after the phase transition are isostructural. The straight-ribbon-like one-dimensional hydrogen-bonding structure is formed and stacked to form a molecular layer. The geometry of the layer is retained during the phase transition. The relative position of the layer with its neighbours, on the other hand, changes gradually with increasing temperature. The change is accelerated at the temperature representing the start of the endotherm seen in the DSC curves of (1). The structural variation yields void space between the neighbouring layers. When the void space grows enough that the crystal is unstable, the 3-methylbutyl group on the last of the molecules turns into a disordered structure with drastic conformational changes to fill up the void space. The phase transition process is well supported with simple force-field calculations. A crystal of 1-(4-methylpentanoyl)-3-propylurea (2), which shows no solid-to-solid phase transitions, was also analysed by the same method for comparison. [source] | |||||||||||||||||||||||||||||||||||||