bluuebunny/crossref_metadata_2025 huggingface dataset:
An Analysis of an Axonal Gradient of Phosphorylated MAP 1B in Cultured Rat Sensory Neurons
Authors: Bush Maxwell S. , Goold Robert G. , Moya Fernando , Gordon‐Weeks Phillip R.
Published: April 2006

The present study investigated the cellular distribution of a developmentally regulated phosphorylated form of MAP 1B recognized by monoclonal antibody (mAb) 150 in cultures of dorsal root ganglia. The cell soma and the whole axon, when it first appears, are labelled, but longer axons label with a proximodistal gradient, such that the cell soma and proximal axon become unlabelled, whilst the distal axon and growth cone label strongly. Double‐labelling experiments with mAb 150 and a polyclonal antibody (N1–15) that recognizes all forms of MAP 1B demonstrated that MAP 1B is distributed along the entire length of axons with gradients, so the gradient of phosphorylated MAP 1B is not due to a loss or absence of MAP 1B from the proximal axon. The proportion of axons from 20 h cultures that were labelled with a mAb 150 gradient was at least 80% and this proportion was independent of the nerve growth factor concentration of the culture medium. Analysis of axons ranging in length from 100 to 700 μm and labelled with a gradient showed that the unlabelled proximal portions of axons increased in length more slowly than the labelled distal axon. Axons labelled along their entire length accounted for no more than 19% of the axonal population and analysis of these showed them to be frequently <400 μm long. After simultaneously fixing and detergent‐extracting cultures this proportion rose significantly to 93%, suggesting that in the proximal axon the mAb 150 epitope is masked by some factor(s) that is removed by detergent extraction. The possibility that mAb 150 could not access the epitope in the proximal axon was discounted because another IgM, mAb 125, which recognizes a different phosphorylation epitope on MAP 1B, labelled the proximal axon of conventionally fixed cultures. In growth cones of fixed and extracted neurons examined by immunofluorescence, the mAb 150 labelling strongly colocalized to bundled microtubules in the distal axon shaft and the C‐domain. In the P‐domain, mAb 150 staining was weaker and more widely distributed than the microtubules. Immunogold electron microscopy confirmed that antibody N1–15 and mAb 150 strongly labelled the bundled microtubules in the C‐domain and also showed that individual microtubules in the P‐domain, some of which lie alongside actin filament bundles of filopodia, were labelled lightly and discontinuously with both antibodies. This suggests that the phosphorylated isoform of MAP 1B recognized by mAb 150 may be involved in bundling microtubules in the proximal region of the growth cone and in the interaction between microtubules and actin filaments in the P‐domain.
Kinematic Analysis of the Cat Shoulder Girdle during Treadmill Locomotion: an X‐ray Study
Authors: Boczek‐Funcke A. , Kuhtz‐Buschbeck J. P. , Illert M.
Published: April 2006

A quantitative kinematic analysis of the movements of the shoulder girdle in the three dimensions of space during treadmill locomotion (velocity range 0.33–1.2 m/s) was performed in two cats. Since the movement patterns of the scapula and the humeroscapular joint can only vaguely be estimated through the overlying skin we used implanted metal spheres placed on the scapula in combination with three‐dimensional pulsed X‐ray cinematography (time resolution 20 ms) to reconstruct the excursions of the scapula, the humerus and the elbow and to calculate the respective angular amplitudes and velocities. The movements of the scapula relative to the Th4 spinous process consist of four major components: (i) a monophasic flexion (caudocranial movement of the glenoid fossa during swing)/extension (craniocaudal movement of the glenoid fossa during stance) sequence, the fulcrum for which sequence is situated near the vertebral border of the scapula at the medial elongation of the scapular spine; (ii) a vertical monophasic up/down sequence of the fulcrum relative to the trunk, the highest vertical position being reached during mid‐stance and the lowest vertical position during mid‐swing; (iii) a biphasic abduction/adduction sequence during swing and during stance respectively; and (iv) small rotations along the scapular spine. The trajectory recordings of the scapula indicate that the scapula yields relative to the trunk under the body weight after ground contact. The angular excursions of the humeroscapular joint consist of: (i) a flexion/extension sequence during swing, a yield after ground contact and a final extension at the end of stance; (ii) an adduction and outward rotation during the early swing phase flexion; (iii) an abduction and inward rotation during the late swing phase extension; and (iv) an adduction during the yield with only minor rotations during the whole stance phase. The movement patterns are discussed in view of the muscular synergies necessary to guide the scapula and the humerus during stance and swing, and in relation to the implications for the organization of these patterns in spinal neuronal systems.
A p65/p95 Neural Surface Receptor is Expressed at the S‐G2 Phase of the Cell Cycle and Defines Distinct Populations
Authors: Rebai Najet , Almazan Guillermina , Wei Ling , Greene Mark I. , Uri Saragovi H.
Published: April 2006

A surface receptor complex of Mr˜65 000 (p65) and ˜95 000 (p95) is expressed in cells of the central nervous system of mice. This receptor is recognized by monoclonal antibody 87.92.6 or by reovirus type 3 haemagglutinin as unnatural ligands. The p65/p95 receptor is expressed mostly in neural embryonic precursors undergoing proliferation, especially those in the S‐G2 phase of the cell cycle. Receptor expression decreases progressively throughout embryogenesis to low but detectable levels in the adult brain. Biochemical characterization revealed that the neural p65/p95 receptor complex is indistinguishable from the p65/p95 receptor expressed in T cells, where receptor ligation leads to a mitogenic block. In neural and lymphoid tissues the p65/p95 receptor (or an associated protein) possesses a tyrosine kinase enzymatic activity. Receptor ligation in neural cells resulted in the rapid tyrosine phosphorylation of cellular proteins which are different from substrates phosphorylated in T cells. Differential substrate coupling to the receptor may account for differences in signal transduction and biology between neural cells and T cells. Further study of this receptor complex may help define important features of neural proliferation, differentiation and survival.
Less Segregated Processing of Visual Information in V2 than in V1 of the Monkey Visual Cortex
Authors: Tamura Hiroshi , Sato Hiromichi , Katsuyama Narumi , Hata Yoshio , Tsumoto Tadaharu
Published: April 2006

To test the possibility of cross‐talk between parallel pathways dealing with different aspects of visual information, such as orientation, direction of motion and colour in cortical area V2, we quantitatively analysed visual responses of 121 V2 cells recorded from anaesthetized and paralysed macaques and compared them with those of 147 V1 cells. A selectivity index of visual responses was calculated for each neuron, which was then classified as selective or not to a particular attribute of visual stimuli. Twenty‐one percent of the V2 neurons had dual selectivity to both colour and direction of stimulus motion (C&D cells). In V1, only 5% of the cells were C&D cells. Thus, the proportion of C&D cells significantly increased from V1 to V2. We also carried out cross‐correlation analysis of spike trains recorded simultaneously from pairs of V2 neurons or pairs of V1 neurons. In V2, correlated firings could be observed between cells with completely different optimal orientation, such as orthogonal, while it was never observed in V1. The cross‐correlation analysis further indicated that functional interactions in V2 were more widespread than those in V1. These results suggest that neurons which have different functional properties become less segregated, and that functional interactions become more widespread in V2 than in V1.
Tissue‐specific and Developmental Expression of Pituitary Adenylate Cyclase‐activating Polypeptide (PACAP) Receptors in Rat Brain
Authors: D'Agata Velia , Cavallaro Sebastiano , Stivala Franca , Travali Salvatore , Canonico Pier Luigi
Published: April 2006

The two forms of pituitary adenylate cyclase‐activating polypeptide, PACAP27 and PACAP38, are novel members of the vasoactive intestinal peptide (VIP)/secretin/glucagon family of peptides. PACAP receptors that are positively coupled to adenylate cyclase and phospholipase C have been recently identified. We examined the expression of PACAP receptors in the rat cortex, hippocampus, cerebellum and hypothalamus during postnatal development. Functional studies revealed PACAP stimulation of cAMP formation in all the brain areas examined and [3H]inositol monophosphate ([3H]insP) accumulation only in the cerebellum and hypothalamus. Throughout development, the efficacy of PACAP in stimulating cAMP formation slightly increased in the cortex and hypothalamus and decreased in the hippocampus and cerebellum; PACAP stimulation of [3H]lnsP formation decreased in the cerebellum and remained steady in the hypothalamus. The effects of PACAP27 and PACAP38 on cAMP levels and inositol phospholipid hydrolysis were dose‐dependent between 1 and 100 nM. In the same brain areas, treatment with VIP increased cAMP formation at doses greater than 100 nM and failed to affect [3H]lnsP content, thus suggesting the existence of type‐l PACAP receptors. The reverse transcription polymerase chain reaction (RT‐PCR) was used to analyse the mRNA expression of type‐l PACAP receptor splice variants. PACAP receptor gene expression in the central nervous system was regulated in a developmental‐ and tissue‐specific manner. The PACAP‐R transcript was detected in all the brain areas examined whereas PACAP‐R‐hop mRNA occurred only in the cerebellum and hypothalamus. The different expression profiles and functional properties of PACAP receptors in the developing rat brain suggest an involvement of PACAP in histogenesis, maturation and neurotransmission.
The Intrinsic Optical Signal Evoked by Chiasm Stimulation in the Rat Suprachiasmatic Nuclei Exhibits GABAergic Day‐Night Variation
Authors: Trachsel Lorenz , Dodt Hans‐Ulrich , Zieglgänsberger Walter
Published: April 2006

Infrared light transmittance imaging was used in rat hypothalamic slices to record an intrinsic optical signal (IOS) of the cell ensemble in the suprachiasmatic nuclei (SCN), the locus of the endogenous circadian clock. Upon optic chiasm stimulation, a transient IOS was observed in an area conforming to the known retinohypothalamic tract innervation in the ventral SCN. An increase in extracellular Mg2+ concentration to 10 mM reduced the IOS, suggesting that the elicited IOS is dependent on synaptic transmission. D‐2‐Amino‐5‐phosphonopentanoic acid and muscimol suppressed the elicited IOS, indicating that NMDA and GABAA receptor‐mediated mechanisms were involved in cell ensemble activity reflected in the IOS. The extracellularly recorded spiking of SCN neurons located outside the IOS area remained largely unaffected by the afferent stimulus. Neurons located within the IOS area responded with a depressed electrical discharge, manifesting an inverse relationship between single‐unit discharge and the optical measure. The influence of the endogenous circadian rhythm on the elicited IOS was assessed by carrying out daytime‐dependent concentration‐response experiments. NMDA and non‐NMDA receptor specific compounds did not exhibit significant day‐night differences, whereas GABA‐specific ligands showed a significant day‐night variation in activity. The competitive GABAA receptor antagonist bicuculline enhanced the IOS exclusively in the daytime SCN. 5α‐Pregnane‐3α, 21‐diol‐20‐one (allotetrahydrodeoxy‐corticosterone), a neuroactive steroid that potentiates GABAergic inhibition, suppressed the IOS in the night‐time SCN more than in the daytime SCN. This suggests that in the rat the level of extracellular GABA is higher in the night‐time SCN compared to the daytime SCN.
A Single‐cell Study of the Axonal Projections Arising from the Posterior Intralaminar Thalamic Nuclei in the Rat
Authors: Deschênes Martin , Bourassa Jacques , Doan Van Diep , Parent André
Published: April 2006

Thalamostriatal projections arising from the posterior intralaminar nuclei (Pl; the parafascicular nucleus and the adjacent caudalmost part of the posterior thalamic group) were studied in rats by tracing the axons of small pools of neurons labelled anterogradely with biocytin. Thirteen Pl cells were also stained by juxtacellular application of the tracer. Relay cells of Pl nuclei have a morphology that differs radically from the classical descriptions of the bushy cells which represent the main neuronal type of the sensory thalamic relay nuclei. Pl cells have ovoid or polygonal somata of ˜20–25 μm, from which emerge four or five thick, long and poorly branched dendrites bearing spines and filamentous appendages; their dendritic domains extend for up to 1.5 mm. Before leaving the nucleus 20% of axons give off collaterals that ramify locally. All axons course through the thalamic reticular nucleus, where they emit one or two poorly branched collaterals, traverse the globus pallidus, where they also distribute collaterals, and arborize massively in the striatum and sparsely in the cerebral cortex. At the striatal level four or five collaterals leave the main axon and terminate in patches scattered dorsoventrally within a rostrocaudally oriented slab. As revealed by calbindin D‐28k immunohistochemistry, only the matrix compartment receives terminations from Pl axons. The cortical branch forms small terminal puffs centred upon layer VI of the motor cortex. Before entering the striatum some axons of the parafascicular nucleus give rise to descending collaterals that arborize in the entopeduncular nucleus, in the subthalamic nucleus and in the vicinity of the red nucleus. Other axons arising from the caudal part of the posterior group send descending branches only to the entopeduncular nucleus. These findings show that Pl cells belong to a distinct category of thalamic relay neurons which, beside their massive projection to the striatum, also distribute collaterals to other components of the basal ganglia. Moreover, these results provide the first direct evidence that virtually all Pl cells project to both striatum and cerebral cortex. Finally, it is proposed on the basis of morphological, histochemical and hodological criteria that the caudal part of the posterior thalamic group in the rat is homologous to the suprageniculate‐limitans nuclei of cats and primates.
Calpain Inhibitors Protect Against Depolarization‐induced Neurofilament Protein Loss of Septo‐hippocampal Neurons in Culture
Authors: Kampfl A. , Zhao X. , Whitson J. S. , Posmantur R. , Dixon C. E. , Yang K. , Clifton G. L. , Hayes R. L.
Published: April 2006

We examined the effect of a 6 min depolarization with 60 mM KCl and 1.8, 2.8 or 5.8 mM extracellular CaCl2 on neurofilament proteins of high (NF‐H), medium (NF‐M) and low (NF‐L) molecular weight in primary septo‐hippocampal cultures. One day after depolarization, Western blot analyses revealed losses of all three neurofilament proteins. Increasing the extracellular calcium concentration from 1.8 to 5.8 mM CaCl2 in the presence of 60 mM KCl produced increased losses of all three neurofilament proteins to ˜80% of control values in the absence of cell death. Calcium‐dependent losses of the neurofilament proteins correlated with calcium‐dependent increases in calpain 1‐mediated breakdown products of alpha‐spectrin. Calpain inhibitors 1 and 2, applied immediately after depolarization and made available to cultures for 24 h, reduced losses of all three neurofilament proteins to ˜14% of control values. The protective effects of calpain inhibitors 1 and 2 were influenced by different levels of extracellular calcium. Qualitative immunohistochemical evaluations confirmed semiquantitative Western blot data on neurofilament loss and protection by calpain inhibitors 1 and 2. We propose that brief depolarization causes loss of neurofilament proteins, possibly due to calpain activation. Thus, calpain inhibitors could represent a viable strategy for preserving the cytoskeletal structure of injured neurons.
Planning and Spatial Working Memory: a Positron Emission Tomography Study in Humans
Authors: Owen Adrian M. , Doyon Julien , Petrides Michael , Evans Alan C.
Published: April 2006

Previous work with both neurosurgical and neurodegenerative patient groups has suggested that high level planning is mediated by neural circuitry which includes both the prefrontal cortex and the striatum. In this study, the functional anatomy of cognitive planning was investigated further, using positron emission tomography (PET). Regional cerebral blood flow (rCBF) was measured in 12 normal volunteers while performing easy and difficult versions of (i) a modified Tower of London planning task; (ii) a mnemonic variant of this task that required short‐term retention and reproduction of problem solutions; and (iii) a control condition that involved identical visual stimuli and motor responses. Significant increases in rCBF were observed in the left hemisphere, in both the mid‐dorsolateral frontal cortex and in the head of the caudate nucleus, when the difficult planning task was compared with the control condition. Moreover, subtraction of a simple planning condition from the more difficult one revealed focal increases in rCBF in the caudate nucleus and the thalamus only. During both mnemonic variants of the planning task, changes were also observed in the mid‐dorsolateral frontal cortex and in more ventral frontopolar regions, bilaterally. When compared directly, the planning and memory conditions differed in terms of these ventral activation foci, but not in the pattern of activation observed in the mid‐dorsolateral frontal cortex. These findings further implicate frontostriatal circuitry in high‐level planning and provide evidence for functionally distinct contributions from ventral and dorsolateral frontal regions to spatial working memory.
Organization of the Visual Reticular Thalamic Nucleus of the Rat
Authors: Coleman Kristina A , Mitrofanis John
Published: April 2006

The visual sector of the reticular thalamic nucleus has come under some intense scrutiny over recent years, principally because of the key role that the nucleus plays in the processing of visual information. Despite this scrutiny, we know very little of how the connections between the reticular nucleus and the different areas of visual cortex and the different visual dorsal thalamic nuclei are organized. This study examines the patterns of reticular connections with the visual cortex and the dorsal thalamus in the rat, a species where the visual pathways have been well documented. Biotinylated dextran, an anterograde and retrograde tracer, was injected into different visual cortical areas [17; rostral 18a: presumed area AL (anterolateral); caudal 18a: presumed area LM (lateromedial); rostral 18b: presumed area AM (anteromedial); caudal 18b: presumed area PM (posteromedial)] and into the different visual dorsal thalamic nuclei (posterior thalamic, lateral posterior, lateral geniculate nuclei), and the patterns of anterograde and retrograde labelling in the reticular nucleus were examined. From the cortical injections, we find that the visual sector of the reticular nucleus is divided into subsectors that each receive an input from a distinct visual cortical area, with little or no overlap. Further, the resulting pattern of cortical terminations in the reticular nucleus reflects largely the patterns of termination in the dorsal thalamus. That is, each cortical area projects to a largely distinct subsector of the reticular nucleus, as it does to a largely distinct dorsal thalamic nucleus. As with each of the visual cortical areas, each of the visual dorsal thalamic (lateral geniculate, lateral posterior, posterior thalamic) nuclei relate to a separate territory of the reticular nucleus, with little or no overlap. Each of these dorsal thalamic territories within the reticular nucleus receives inputs from one or more of the visual cortical areas. For instance, the region of the reticular nucleus that is labelled after an injection into the lateral geniculate nucleus encompasses the reticular regions which receive afferents from cortical areas 17, rostral 18b and caudal 18b. These results suggest that individual cortical areas may influence the activity of different dorsal thalamic nuclei through their reticular connections.
Full‐length Cloning, Expression and Cellular Localization of Rat Plasmolipin mRNA, a Proteolipid of PNS and CNS
Authors: Gillen C. , Gleichmann M. , Greiner‐Petter R. , Zoidl G. , Kupfer S. , Bosse F. , Auer J. , Müller H. W.
Published: April 2006

We have isolated a 1.476 bp cDNA (NTII11) representing a transcript that is differentially expressed during sciatic nerve development and regeneration in the rat. Nucleotide sequence comparison indicates partial identity with a recently isolated plasmolipin cDNA. However, our clone extends the published sequence by 234 bp at the 5’end and predicts a protein that contains an additional 25 amino acids at the N‐terminus. The open reading frame of the NTII11 transcript encodes a 19.4 kDa protein with four putative transmembrane domains. Northern blot analyses revealed a tissue‐specific expression of the plasmolipin transcript that is restricted to sciatic nerve, brain and kidney. The neural expression was confirmed by in situ hybridization, and cellular localization of plasmolipin mRNA was demonstrated in Schwann cells of the sciatic nerve and in glial cells of myelinated brain structures. The steady‐state levels of plasmolipin mRNA were markedly altered (i) during development of the sciatic nerve and brain, (ii) after sciatic nerve injury, and (iii) in cultured Schwann cells maintained under different conditions of cell growth and arrest. Our data indicate a function of plasmolipin during myelination in the central as well as in the peripheral nervous system.
Expression of Glycine Receptor α Subunits and Gephyrin in Cultured Spinal Neurons
Authors: Béchade C. , Colin I. , Kirsch J. , Betz H. , Triller A.
Published: April 2006

The inhibitory glycine receptor is a pentameric membrane protein composed of α and β subunits. In the postsynaptic membrane, the glycine receptor and the copurifying peripheral membrane protein gephyrin are clustered underneath glycine‐releasing nerve terminals. Here, we describe the expression of gephyrin and the neonatal and adult glycine receptor α subunit isoforms α1 and α2 during in vitro differentiation of rat spinal neurons. Analysis by immunoassays and the reverse transcriptase—polymerase chain reaction showed that gephyrin and α subunit mRNA and protein levels exhibited a marked increase from 1 to 5 days in vitro, i.e. prior to the formation of functional synaptic contacts. Using confocal and standard immunofluorescence, we determined the number of immunoreactive cells and the cellular localization of the α subunits and gephyrin. At 3 days in vitro, glycine receptor immunoreactivity revealed by the monoclonal antibody mAb4a was found in >10% of cells and was mainly localized intracellularly; in contrast, gephyrin was detected in <50% of cells. At 7 days in vitro, gephyrin was essentially localized at the neuronal surface. At this stage, the number of glycine receptor‐positive cells approached that of gephyrin‐containing neurons (50%), and glycine receptor antigen was found both intracellularly and at the periphery of the cells. The antibody mAb2b, which binds exclusively to the α1 subunit, revealed aggregates at the surface of a few neurons. At 10 days in vitro, glycine receptor and gephyrin staining was localized in clusters at the periphery of the soma and the neurites. This quantitative analysis corroborates temporal differences in the cellular distribution of gephyrin and glycine receptor α subunits, the former being accumulated first at the neuronal surface.
Age‐related Changes in Excitability and Recurrent Inhibition in the Rat CA1 Hippocampal Region
Authors: Papatheodoropoulos Costas , Kostopoulos George
Published: April 2006

In hippocampal slices from male Wistar rats aged 1–34 months, we recorded the synaptic field potential responses of the CA1 neurons to stimulation of Schaffer collaterals. Eight electrophysiological indexes were extracted from input/output curves and compared in 11 age groups from 1 to 30 months. Neuronal excitability presented a U‐shaped curve of development with a minimum at ˜7–8 months of age. There was a significant continuous increase in neuronal excitability, i.e. a decrease in excitatory postsynaptic potential (EPSP) producing both the threshold and half‐maximal population spike from middle age (8–10 months) to senescence (30 months). Synaptic efficiency also increased in old rats to reach a maximum during senescence, i.e. both the current for threshold EPSP and that for half‐maximal EPSP reached a minimum in senescence, although the earlier developmental patterns of these two indexes were non‐linear. The duration of the field EPSP elicited with maximal stimulation presented an abrupt decay after the first month. Aged animals presented a relatively small maximal population spike. Recurrent inhibition was most prominent on neuronal excitability rather than synaptic strength. Measured as the percentage change in the half‐maximal EPSP and half‐maximal population spike, recurrent inhibition was found to decrease during the first 7–10 months of life and remained small in later development.
Interleukin 6 in Intact and Injured Mouse Peripheral Nerves
Authors: Reichert Fanny , Levitzky Rubina , Rotshenker Shlomo
Published: April 2006

The multifunctional cytokine interleukin 6 (IL‐6) has direct growth, survival and differentiation effects on peripheral and central neurons. Furthermore, it can modulate the production by non‐neuronal cells of other cytokines and growth factors, and thereby affect nerve cells indirectly. We have studied IL‐6 expression and production in intact and injured peripheral nerves of C57/BL/6NHSD mice, which display the normal rapid progression of Wallerian degeneration. The IL‐6 mRNA was detected in nerves degenerating in vitro or in vivo, but not in intact nerves. In vitro‐ and in vivo‐degenerating nerve segments and neuroma nerve segments synthesized and secreted IL‐6. The onset of IL‐6 production was rapid and prolonged. It was detected as early as 2 h after injury and persisted for the entire period of 21 days tested after the injury. Of the non‐neuronal cells that reside in intact and injured nerves, macrophages and fibroblasts were the major contributors to IL‐6 production. We also studied IL‐6 production in intact and injured nerves of mutant C57BL/6‐WLD/OLA/NHSD mice, which display very slow progression of Wallerian degeneration. Injured nerves of C57BL/6‐WLD/OLA/NHSD mice produced significantly lower amounts of IL‐6 than did rapidly degenerating nerves of C57/BL/6NHSD mice.
Differential Expression of Ubiquitous and Neuronal Kinesin Heavy Chains During Differentiation of Human Neuroblastoma and PC12 Cells
Authors: Vignali G. , Niclas J. , Sprocati M. T. , Vale R. D. , Sirtori C. , Navone F.
Published: April 2006

Kinesin is a microtubule‐based motor protein involved in intracellular organelle transport. Neurons are characterized by the presence of at least two isoforms of conventional kinesin: ubiquitous kinesin, expressed in all cells and tissues, and neuronal kinesin, whose pattern of expression is confined to neuronal cells. In order to investigate whether the two kinesin motors, which are encoded by different genes, may play distinct biological roles in neurons, we studied their expression during neuronal differentiation. Human neuroblastoma SH‐SY5Y and IMR32 cells and rat phaeochromocytoma PC12 cells were used as an in vitro system for neuronal differentiation and were induced to differentiate in the presence of retinoic acid, a combination of dibutyryl cAMP and 5‐bromodeoxyuridine, and nerve growth factor respectively. The expression level of each kinesin isoform was evaluated by quantitative immunoblot before and after pharmacological treatment. We found that in all cell types the expression level of neuronal kinesin, but not of ubiquitous kinesin, is stimulated during differentiation. In particular, SH‐SY5Y cells show a 4.5‐fold, IMR32 cells a 3‐fold and PC12 cells a 7‐fold increase in the level of expression of neuronal kinesin. By Northern blot analysis we found that the selective increase in the expression of neuronal kinesin is paralleled by an increase in its mRNA, indicating that there is a transcriptional control of the expression of this kinesin isoform during differentiation of neuroblastoma and PC12 cells. Our results suggest that these cells represent an adequate model to study the function of conventional kinesin and its isoforms.
Regulation of Rat Schwann Cell Po Expression and DNA Synthesis by Insulin‐like Growth Factors In Vitro
Authors: Stewart Helen J. S. , Bradke Frank , Tabernero Arantxa , Morrell David , Jessen Kristjan R. , Mirsky Rhona
Published: April 2006

Myelination by Schwann cells is likely to be regulated in Vitro by positive and negative epigenetic factors. In Vitro, the positive regulation of myelin differentiation, in particular expression of the major myelin protein Po, can be mimicked by cAMP elevating agents, while serum, transforming growth factor (TGF)βs, and fibroblast growth factor (FGF)2 have been shown to exert a negative effect on this differentiation. Growth factors which promote Po induction have not, however, been identified previously. Using a forskolin concentration (0.4 μM) which alone produces little Po mRNA or protein induction, we show that insulin‐like growth factor (IGF)‐I, IGF‐II and high concentrations of insulin promote high levels of Po induction, although in the absence of forskolin they have no effect. Another event related to Schwann cell differentiation, induction of galactocerebroside expression in response to cAMP analogues, is also potentiated by IGFs. In a different context, IGFs regulate Schwann cell DMA synthesis. We find that in defined medium forskolin plus FGF2, TGFβ or platelet‐derived growth factor (PDGF) BB causes minimal DNA synthesis in the absence of IGFs and that IGFs act as potent mitogens under these conditions. IGFs also potentiate DNA synthesis induced by β isoforms of neu‐differentiation factors (NDFs), although in this case considerable DNA synthesis occurs even in the absence of IGF. These results show that IGFs can act as powerful stimulators of both proliferation and differentiation in Schwann cells, and that the total growth factor input determines which of these pathways IGFs will promote.
Effects of the Uncompetitive NMDA Receptor Antagonist Memantine on Hippocampal Long‐term Potentiation, Short‐term Exploratory Modulation and Spatial Memory in Awake, Freely Moving Rats
Authors: Barnes Carol A. , Danysz Wojciech , Parsons Chris G.
Published: April 2006

Chronic treatment of adult male F‐344 rats (9–12 months old) with therapeutically relevant doses of memantine (30 mg/kg/day in chow for <8 weeks) increased the maintenance of long‐term potentiation of field excitatory postsynaptic potentials from perforant path—granule cell hippocampal synapses recorded in the fascia dentata in vivo. In contrast, there was no effect of memantine on baseline synaptic responses or population spikes. Likewise, short‐term exploratory modulation of these hippocampal evoked responses was not different between memantine‐treated and control rats. Both groups of rats were able to learn the spatial version of the Morris water task equally well, but the memantine‐treated group showed a strong tendency to show more selective spatial search patterns in the training quadrant of the water pool during a final probe trial. As such, these studies provide the first electrophysiological evidence that memantine can increase the durability of synaptic plasticity and provide preclinical confirmation of the cognitive improvement seen with memantine in the treatment of demented patients.
Activation and Proliferation of Murine Microglia are Insensitive to Glucocorticoids in Wallerian Degeneration
Authors: Castaño A. , Lawson L. J. , Fearn S. , Perry V. H.
Published: April 2006

Activation and proliferation of microglia are commonly described in the central nervous system after a wide range of insults, but the mechanisms that regulate their phenotype in vivo are still poorly understood. We have studied the effect that adrenalectomy and dexamethasone treatment have on the proliferation and activation of microglia during Wallerian degeneration of the optic nerve in BALB/c mice. We found that the onset and rate of microglia proliferation is independent of glucocorticoids. There was an increase in F4/80‐positive cells 3 days after optic nerve crush, with a peak at 7 days, both in the optic nerve and its target, the superior colliculus. The numbers of F4/80‐positive cells remained high up to 3 weeks after crush, the longest time point examined. We also found that up‐regulation of F4/80 and the complement receptor type 3 and expression of major histocompatibility complex class II antigens were not affected by adrenalectomy or dexamethasone treatment. These observations show that, unlike microglia in vitro or peripheral macrophages, microglia do not readily respond to glucocorticoids, which could indicate a lack of or reduced expression of glucocorticoid receptor in these cells.
Clusterin (SGP‐2) Induction in Rat Astroglial Cells Exposed to Prion Protein Fragment 106–126
Authors: Chiesa Roberto , Angeretti Nadia , Lucca Elisa , Salmona Mario , Tagliavini Fabrizio , Bugiani Orso , Forloni Gianluigi
Published: April 2006

Prion‐related encephalopathies are characterized by the accumulation of an abnormal prion protein isoform (PrPSc) associated with neuronal degeneration and astrogliosis. The synthetic peptide homologous to PrP fragment 106–126 (PrP 106–126) induced in vitro neuronal apoptosis and glial proliferation. We used Northern blot analysis and the RNA polymerase chain reaction to assess the expression of several genes associated with programmed cell death and proliferation. Blots of total RNA extracted from neuronal and astroglial cells exposed to PrP 106–126 for between 1 h and 7 days were hybridized with probes recognizing c‐fos, c‐jun, c‐myc, p53, hsp‐70 and bcl‐2 mRNA. Except for a slight decrease in bcl‐2 mRNA in neuronal cells, no change in other transcripts was evident. Since clusterin (apolipoprotein J) mRNA levels are increased in prion‐related encephalopathies and clusterin immunoreactivity has been located in association with PrPSc in Gerstmann‐Sträussler‐Scheinker brain, the expression of clusterin was determined in neuronal and astroglial cells chronically exposed to PrP 106–126. Although the induction of clusterin has been involved in the apoptotic mechanism in other experimental conditions, its expression was unchanged in PrP 106–126‐treated neurons, while a three‐fold induction of clusterin mRNA was observed in astrocytes exposed to PrP 106–126. To investigate whether the clusterin up‐regulation was simply associated with the astroglial proliferative stimulus of PrP 106–126 or was specifically induced by the peptide, we measured clusterin expression in astrocytes cultured in fetal calf serum‐free medium and exposed to PrP 106–126 or fetal calf serum restoration. In this condition the PrP peptide, like fetal calf serum, increased the glial proliferation rate, but only PrP 106–126 doubled clusterin mRNA. The selectivity of this effect indicates that PrPSc is directly involved in the clusterin up‐regulation seen in prion‐related encephalopathies and is associated with astroglial cells.
Muscarinic Activation of a Novel Voltage‐sensitive Inward Current in Rabbit Prevertebral Sympathetic Neurons
Authors: Delmas P. , Niel J. P. , Gola M.
Published: April 2006

The muscarinic activation of rabbit prevertebral sympathetic neurons was studied in non‐dissociated coeliac and superior mesenteric ganglia using whole‐cell patch‐clamp techniques. In the presence of nicotinic blockers, carbachol, muscarine and oxotremorine‐M (1–50 μM) induced tonic firing by activating a persistent inward current. These effects were abolished by atropine. They persisted when the M‐current was blocked with Ba2+ (1 mM) and intracellular Cs+. The muscarinic inward current was found to be time‐ and voltage‐dependent. It peaked at ‐60 mV, decreased at large hyperpolarizations and was tonically activated between —110 and —20 mV, which gave steady‐state I—V curves an N‐shape between —96 and —54 mV. The negative slope accounted for the large hyperpolarizing responses generated by current pulses in carbachol‐treated cells. The muscarinic current was abolished when Na+ was replaced by choline, Tris+, sucrose, N‐methyl‐D‐glucamine and Cs+ but not Li+. It was resistant to tetrodotoxin (3 μM), amiloride (3 μM), benzamil (10 μM) and tetraethylammonium (5–20 mM). No involvement of K+ and Cl‐ could be detected. We therefore styled it lNa, M, in reference to its ionic selectivity and its coupling to muscarinic receptors. Low Ca2+‐Mg2+ salines enhanced the Na, M‐current. The current was blocked by Cd2+, Co2+, La3+ (1 mM) and Ba2+ (5 mM) but insensitive to methoxyverapamil hydrochloride, nicardipine, nifedipine and ω‐conotoxin MVII A (2–20 μM). These effects were ascribed to the binding of di‐ and trivalent ions to the Na, M‐channels. Spike bursts transiently blocked lNa, M. With high intracellular ethylene glycol bis(b‐aminoethyl ether)‐N, N'‐tetraacetic acid or 1, 2‐bis(2‐aminophenoxy)ethane‐N, N, N', N'‐tetraacetic acid (20–50 mM), this effect was reduced, whereas lNa, M persisted in long‐term recordings and its amplitude increased twofold, indicating that intracellular calcium negatively regulated the Na, M‐channels. We conclude that we have described a novel muscarinic receptor‐coupled channel which appears to play a major part in regulating the firing behaviour of sympathetic neurons.
Autocrine Role of Insulin‐like Growth Factor II Secretion by the Rat Choroid Plexus
Authors: Nilsson Christer , Hultberg Birthe Mørck , Gammeltoft Steen
Published: April 2006

Insulin‐like growth factor II (IGF‐II) is expressed and secreted by the choroid plexus and has been suggested to act as a trophic factor in the adult mammalian central nervous system. The aim of the present study was to investigate whether IGF‐II has an autocrine role in the choroid plexus. Using in situ hybridization we demonstrate that IGF‐II is primarily expressed in the epithelium of adult rat choroid plexus. Conditioned medium from primary cultures of purified rat choroid plexus epithelial cells, intact choroid plexus tissue, as well as rat CSF, displaced IGF‐II binding to a 23 HMM melanoma cell line in an IGF‐II radioreceptor assay. The presence of IGF‐II and IGF binding protein‐2 in conditioned medium was shown by Western immunoblot. The mitotic activity in choroid plexus epithelial cell cultures was quantified by immunohistochemical staining of bromodeoxyuridine incorporated into cell nuclei. A monoclonal antibody towards IGF‐II inhibited cell division by 35%, while IGF‐I increased the number of stained nuclei by 75%. Basic fibroblast growth factor stimulated cell division at low concentrations, but had no effect at high concentrations. Growth hormone had no effect. We conclude that IGF‐II in the choroid plexus could have an autocrine role in the regulation of choroid plexus epithelial cell growth.
Functional Anatomy of Visuomotor Skill Learning in Human Subjects Examined with Positron Emission Tomography
Authors: Doyon Julien , Owen Adrian M. , Petrides Michael , Sziklas Viviane , Evans Alan C.
Published: April 2006

The present study was designed to examine patterns of regional cerebral blood flow (CBF) associated with the learning of a repeated visuomotor sequence both in the early and late phases of the acquisition process. In addition, changes in blood flow related to the implicit versus explicit aspects of learning such a skill were investigated. Fourteen normal control subjects were scanned while performing the task (i) in both early and advanced learning stages of the visuomotor sequence; (ii) after having acquired explicit knowledge of the sequences; and (iii) in two control conditions (perceptual and random sequence). Subtraction of the random condition from the highly learned condition revealed specific areas of activity in the right ventral striatum and dentate nucleus of the cerebellum. Blood flow changes in the right hemisphere were also seen in the medial posterior parietal and prestriate regions, as well as in the anterior cingulate cortex. Finally, once the subjects had acquired explicit knowledge of the embedded sequence that was presented in the highly learned condition, increased CBF activity was observed only in the mid‐ventrolateral frontal area in the right hemisphere. These findings confirm that both the striatum and the cerebellum are involved in the implicit acquisition of a visuomotor skill, especially in the advanced stages of the learning process, and furthermore that the ventrolateral prefrontal cortex contributes preferentially to the declarative aspect of this task.
Erythropoietin Gene Expression in Human, Monkey and Murine Brain
Authors: Marti Hugo H. , Wenger Roland H. , Rivas Luis A. , Straumann Urs , Oigicaylioglu Murat , Henn Volker , Yonekawa Yasuhiro , Bauer Christian , Gassmann Max
Published: April 2006

The haematopoietic growth factor erythropoietin is the primary regulator of mammalian erythropoiesis and is produced by the kidney and the liver in an oxygen‐dependent manner. We and others have recently demonstrated erythropoietin gene expression in the rodent brain. In this work, we show that cerebral erythropoietin gene expression is not restricted to rodents but occurs also in the primate brain. Erythropoietin mRNA was detected in biopsies from the human hippocampus, amygdala and temporal cortex and in various brain areas of the monkey Macaca mulatta. Exposure to a low level of oxygen led to elevated erythropoietin mRNA levels in the monkey brain, as did anaemia in the mouse brain. In addition, erythropoietin receptor mRNA was detected in all brain biopsies tested from man, monkey and mouse. Analysis of primary cerebral cells isolated from newborn mice revealed that astrocytes, but not microglia cells, expressed erythropoietin. When incubated at 1% oxygen, astrocytes showed >l OO‐fold time‐dependent erythropoietin mRNA accumulation, as measured with the quantitative reverse transcription‐polymerase chain reaction. The specificity of hypoxic gene induction in these cells was confirmed by quantitative Northern blot analysis showing hypoxic up‐regulation of mRNA encoding the vascular endothelial growth factor, but not of other genes. These findings demonstrate that erythropoietin and its receptor are expressed in the brain of primates as they are in rodents, and that, at least in mice, primary astrocytes are a source of cerebral erythropoietin expression which can be up‐regulated by reduced oxygenation.
Open Channel Block by Physostigmine and Procaine in Embryonic‐like Nicotinic Receptors of Mouse Muscle
Authors: Bufler J. , Franke C. , Parnas H. , Dudel J.
Published: April 2006

Embryonic‐like nicotinic channels were studied in mouse myotubes. Channel currents were measured by patch‐clamping outside‐out excised patches to which pulses of agonists and drugs could be applied by a liquid filament switch. The holding potential of the patches was generally around ‐40 mV. Pulses of 10‐4 M acetylcholine elicited average channel currents which reached a peak open probability, Po, peak, of 0.93 within 0.5 ms and decayed with a time constant of desensitization of 20‐80 ms. When physostigmine (10‐5 to 10‐3 M) or procaine (3 × 10‐5 to 10‐3 M) was added to the acetylcholine pulses, a fast decay component of the current appeared which shortened to a time constant of 0.5 ms for the maximal drug concentrations. The fast decay was followed by a slow one which declined in amplitude with increasing concentrations of the drugs. After the end of pulses of 10‐4 M acetylcholine plus 3 × 10‐4 M physostigmine the average current rose again, reaching a peak with ‐5 ms delay, and then decayed slowly. The amplitude of this recovery current was ‐0.4 Po, peak after 5 ms pulses and decreased with increasing pulse duration due to desensitization. The results can be quantitatively modelled based on a circular reaction scheme involving desensitization. Physostigmine and procaine bind to the open state to cause channel block. Also, the blocked channel was subject to desensitization. The rate constants of block were 6 × 10‐6 M‐1 s‐1 for physostigmine and 2 × 106 M‐1 s‐1 for procaine, and the rate of unblocking was 200 s‐1 for both blockers (at ‐40 mV and 20°C).
Ultrastructural Localization of a Voltage‐gated K+ Channel a Subunit (Kv1.2) in the Rat Cerebellum
Authors: McNamara N. M. C. , Averill S. , Wilkin G. P. , Dolly J. O. , Priestley J. V.
Published: April 2006

A highly specific monoclonal antibody and pre‐embedding immunocytochemistry were employed to examine the distribution of the K+ channel a subunit Kv1.2 in the rat cerebellum. At the light microscopic level, the heaviest immunoreactivity was seen in the basket cell pinceau at the base of Purkinje cells, with lighter staining of basket and Golgi cell bodies and a punctate pattern in the granule cell and molecular layers. Electron microscopy was performed to identify the ultrastructural location of Kv1.2 α subunit in these labelled structures. This revealed that the labelling of the pinceau was confined to the preterminal axonal plexus, the area immediately around the Purkinje axon initial segment being relatively devoid of staining. Basket cell parent axons were not immunostained, but gave rise to heavily stained fine processes. Immunoreactivity was also seen in myelinated axons in the granule cell layer and in the medial cerebellar nucleus, the staining being most concentrated at the juxtaparanodal regions of the axons. An unusual pattern of staining was seen in some mossy fibre terminals, with staining restricted to fine protuberances of mossy fibre glomeruli. Structures contacted by these protuberances included adjoining glial processes. Immunostaining was absent from Purkinje cell bodies, dendrites, their axon initial segments and their terminals in the medial cerebellar nucleus. In this study, the a subunit Kv1.2 was localized to a number of different cell types in the cerebellum. Each neuronal type displays a distinct subcellular distribution of the subunit.
Morphological Changes in Met5‐enkephalin‐immunoreactive Synaptic Boutons in the Rat Neostriatum after Haloperidol Decanoate Treatment
Authors: Mijnster M. J. , Ingham C. A. , Meredith G. E. , Docter G. J. , Arbuthnott G. W.
Published: April 2006

The morphological plasticity of an identified population of synaptic boutons in the rat neostriatum was investigated 24 h (short‐term treatment) or 14 days (long‐term treatment) after administration of the depot neuroleptic, haloperidol decanoate. Specific methionine5‐enkephalin antiserum was used to label bouton profiles in the dorsal neostriatum. The size and shape of these boutons was subsequently analysed with quantitative methods at the ultrastructural level. Immunoreactive synaptic bouton profiles were found to have a larger cross‐sectional area, to be less circular in shape and to have a longer maximum diameter after long‐term neuroleptic treatment. These parameters were not significantly affected by short‐term neuroleptic treatment. The morphological parameters indicate that methionine5‐enkephalin‐immunoreactive boutons become enlarged, probably by elongating. This suggests that boutons containing methionine5‐enkephalin increase their potential synaptic efficacy in the long term after neuroleptic treatment.