bluuebunny/crossref_metadata_2025_split huggingface dataset:
Voltage‐gated Currents in Rabbit Retinal Astrocytes
Authors: Clark Beverley A. , Mobbs Peter 
Published: April 2006

AbstractThe voltage‐gated currents of the astrocytes associated with the retinal capillaries of the rabbit retina were studied using whole‐cell patch clamp recording. The resting potential of these cells was −70 ± 4.8 mV (mean ± SEM; n= 54), and the input resistance and cell capacitance were 558 ± 3.6 MΩ and 19.5 ± 1.8 pF respectively. Depolarization to potentials positive to −50 mV evoked rapidly activating inward and outward currents. The inward current was transient, eliminated by substitution of choline for Na+ in the bathing solution, and reduced by 50% in the presence of 1 μM tetrodotoxin. The time‐to‐peak of the Na+ current was more than twice that for the Na+ current found in retinal neurons. The glial Na+ current was half‐inactivated at −55 mV. A transient component of the outward K+ current was blocked by external 4‐aminopyridine while a more sustained component was blocked by external tetraethylammonium. At potentials between −150 and −50 mV the membrane behaved Ohmically. Voltage‐gated currents in retinal astrocytes recorded in situ appear qualitatively similar to those described for some glial cells in vitro.
A Neurotoxic Prion Protein Fragment Induces Rat Astroglial Proliferation and Hypertrophy
Authors: Forloni Gianluigi , Del Bo Roberto , Angeretti Nadia , Chiesa Roberto , Smiroldo Simona , Doni Rinaldo , Ghibaudi Elena , Salmona Mario , Porro Monica , Verga Laura , Giaccone Giorgio , Bugiani Orso , Tagliavini Fabrizio 
Published: April 2006

AbstractPrion‐related encephalopathies are characterized by the accumulation of an abnormal prion protein isoform (PrPSc) and the deposition of PrP amyloid in the brain. This process is accompanied by neuronal loss and astrogliosis. We recently showed that a synthetic peptide corresponding to residues 106–126 of human PrP is amyloidogenic and causes neuronal death by apoptosis in vitro. In the present study we investigated the effects of 1‐ and 14‐day exposures of rat astroglial cultures to mtcromolar concentrations of this peptide as well as peptides homologous to other portions of PrP, a peptide corresponding to residues 25–35 of amyloid‐β protein, and a scrambled sequence of PrP 106–126. No significant changes were observed after 1‐day exposure of cultures to any peptide. Conversely, 14‐day treatment with PrP 106–126 (50 μM) resulted in a 5‐fold increase in glial fibrillary acidic protein (GFAP) expression, as evaluated by Northern and Western blot analyses, and a 1.5‐fold increment in cell number. Light and electron microscopy immunohistochemistry showed an enlargement in size and density of astroglial processes, and an increase in GFAP‐immunoreactive intermediate filaments. These changes were not observed after 14‐day treatment of cultures with the other peptides, including PrP 106–126 scrambled. The increase in GFAP expression of astroglial cultures exposed to PrP 106–126 was quantitatively similar to that found in scrapie‐infected hamster brains. These results suggest that the PrP region corresponding to residues 106–126 is biologically active, and that cerebral accumulation of peptides including this sequence might be responsible for both the neuronal degeneration and the astrogliosis that occur in prion‐related encephalopathies.
The Presynaptic Cell Determines the Number of Synapses in the Drosophila Optic Ganglia
Authors: Canal I. , Fariñas I. , Gho M. , Ferrús A. 
Published: April 2006

AbstractThe role of the pre‐ and postsynaptic cells in determining the number of synapses has been investigated in retina mosaics of the gigas (gig) mutant of Drosophila. Mutant photoreceptors are two to three times larger than those of the wild type, while adjacent cells in the mosaic retina and the lamina are normal in size. Serial electron microscope reconstructions of mosaic lamina cartridges show that gig photoreceptors establish more synapses upon lamina neurons than the normal photoreceptors do. By contrast, the number of feedback synapses that lamina neurons make onto gig photoreceptors does not increase. The increment in the number of synapses correlates positively with the increment of presynaptic cell membrane, resulting in constancy of synapse density. The phototactic response of flies bearing a gig eye is abnormal, indicating that the extra synapses are functional.
Acetylcholinesterase‐containing Intrinsic Neurons in the Rat Main Olfactory Bulb: Cytological and Neurochemical Features
Authors: Le Jeune H. , Jourdan F. 
Published: April 2006

AbstractAcetylcholinesterase (AChE) histochemistry in light and electron microscopy was used to identify cholinoceptive neurons in the olfactory bulb of adult and 15‐day‐old rats. Double‐labelling experiments using AChE histochemistry and either tyrosine hydroxylase or GABA immunocytochemistry with light microscopy were also performed in order to specify the chemical nature of cholinoceptive neurons. Superficial short‐axon cells and several morphological subtypes of deep short‐axon cells (second‐order interneurons) are the most numerous AChE‐containing intrinsic neurons in the olfactory bulb. Short‐axon interneurons seem to be the only neurons expressing AChE in the deep olfactory bulb since the numerous granule cells (first‐order interneurons) were never found to be AChE‐positive, even in electron microscopy. In the superficial olfactory bulb, cholinoceptive cells belong to several neuronal categories. In addition to the intensely labelled superficial short‐axon cells, a few periglomerular cells (first‐order interneurons) display weak but significant AChE expression, clearly visible in electron microscopy. Both ultrastructural and double‐labelling observations support the hypothesis that a subset of superficial tufted cells is also cholinoceptive. The coexistence of AChE and tyrosine hydroxylase in large neurons located in the glomerular and superficial external plexiform layers indicates that some, if not all, cholinoceptive tufted cells belong to the dopaminergic population previously observed in this area. These observations indicate that several types of intrinsic neurons express AChE and can be tentatively considered as cholinoceptive. Our results provide an anatomical substrate for hypotheses concerning the complex effects of acetylcholine in the processing of sensory information in the olfactory bulb.
Polarized Distribution of the Trans‐Golgi Network Marker TGN38 During the In Vitro Development of Neocortical Neurons: Effects of Nocodazole and Brefeldin A
Authors: Lowenstein P. R. , Morrison E. E. , Bain D. , Shering A. F. , Banting G. , Douglas P. , Castro M. G. 
Published: April 2006

AbstractNeurons are polarized secretory cells whose cytoplasm and plasma membrane are polarized to form two compartments: dendrites and axons. In mature, fully polarized neurons, the microtubule‐associated protein Map2 is targeted to dendrites, while tau is mainly restricted to axons. However, the intraneuronal distribution of secretory pathway organelles, such as the endoplasmic reticulum and the Golgi complex, which give rise to all constitutive, regulated and lysosome vesicles, is poorly understood. Thus, to investigate the distribution of the trans‐Golgi network during the development and maturation of rat neocortical neurons in vitro, we have utilized an antibody recognizing a 38 kDa trans‐Golgi network‐specific protein, TGN38, and immunofluorescence microscopy. Before neurons have established polarity, TGN38 immunoreactivity outlines several vesicles dispersed throughout the cell body cytoplasm; these converge close to a major Map2‐immunopositive process during the establishment of neuronal polarity, and later merge into a single structure located at the base of a thick Map2‐immunopositive process, ∼18 h after plating. At this stage TGN38 immunoreactivity is located within 45° of the major Map2‐immunoreactive process in 54% of neurons, while in only 6% of cells it is located at the opposite pole. After 3 days in vitro, during the segregation of microtubule‐associated proteins to either dendrites or axons, TGN38 immunoreactivity clusters continue to be located close to a major dendrite, and in some neurons these clusters begin to enter a major Map2‐immunoreactive process. At 10 days in vitro TGN38 immunoreactivity extends into a major dendrite for 5–30 μm in many neurons. Thus, the distribution of TGN38 immunoreactivity becomes polarized, being localized within a single, usually the major, neocortical dendrite. Our results also show that the morphological appearance of TGN38‐immunoreactive structures is microtubule‐dependent, since nocodazole treatment of polarized neurons induces scattering of TGN38‐immunoreactive vesicles throughout the cell body's cytoplasm. Treatment with brefeldin A induces scattering of small TGN38‐immunoreactive vesicles throughout the neuronal cytoplasm and processes, a different response to that observed in non‐neuronat cells.
Cytosolic Ca2+ Binding Proteins during Rat Brain Ageing: Loss of Calbindin and Calretinin in the Hippocampus, with no Change in the Cerebellum
Authors: Villa Antonello , Podini Paola , Panzeri Maria Carla , Racchetti Gabriella , Meldolesi Jacopo 
Published: April 2006

AbstractThe expression of two cytosolic, high affinity Ca2+‐binding proteins, calbindin‐28 and calretinin, has been investigated in the cerebellum and hippocampus of young and old rats (from 12 days to 30 months) by combining immunofluorescence and Western blotting. Three markers, calreticulin (the major Ca2+ binding protein within the lumen of the endoplasmic reticulum), MAP‐2 (a microtubule binding protein concentrated in neuronal dendrites) and synaptophysin (an integral protein of synaptic vesicles), were studied in parallel. In the cerebellar cortex a rise from 12 to 60 days was observed with calbindin‐28 and, especially, calretinin, concentrated in the Purkinje and granule neurons, respectively. The level of expression of the two proteins subsequently remained high and the distribution was unchanged, even in the cerebellum of old animals. A completely different pattern was observed in the hippocampus. Here calretinin, present especially in fibres and interneurons, was abundant in the young, decreased in the adult and reached low values in the old rats. Calbindin‐28 accumulated during growth, especially in a subpopulation of CA1 pyramidal cells and in the mossy fibres of CA3, then declined, although irregularily, during ageing. These changes of the two proteins were more marked in the dorsal and central parts than in the ventral part of the hippocampus. In the same brain areas the levels of expression of the three additional markers and their distribution within neurons and synapses were unchanged by ageing. These last results demonstrate that ageing is not accompanied by a marked loss of hippocampal neurons, yet most of the latter cells appear to modify their general Ca2+ homeostasis as a consequence of the decreased level of cytosolic Ca2+ binding proteins. These events could contribute to the changes in neuronal functioning that have been reported in the aged hippocampus, whereas those of the cerebellum appear to be sustained by other mechanisms.
Defined Neuronal Arborizations by Guided Outgrowth of Leech Neurons in Culture
Authors: Fromherz Peter , Schaden Herbert 
Published: April 2006

AbstractIdentified neurons of Hirudo medicinalis were cultivated on a protein extract of the extracellular matrix (ECM) of the leech. Microscopic patterns of active ECM protein were prepared by UV photolithography using aluminium masks. The shape of the patterns was visualized by a colour pattern formed in a dye–polymer substrate. The neurons were explanted on the root of branched ECM patterns. The patterns guided the outgrowth of neurites along linear lanes and they induced a bifurcation of the neurites under certain conditions. Neurons with a reproducible, regular shape of arborization were obtained within 1–2 days.
The Effects of Dopamine on the Subthreshold Electrophysiological Responses of Rat Prefrontal Cortex Neurons In Vitro
Authors: Geijo‐Barrientos Emilio , Pastore Carlos 
Published: April 2006

AbstractThe rat prefrontal cortex is densely innervated by dopaminergic fibres originating in the mesencephalic ventral tegmental area, and dopamine application in vivo has an inhibitory effect. We have studied the effects of dopamine on the persistent sodium current that is present in prefrontal cortex neurons and on the subthreshold electrophysiological responses generated by that current: a slow depolarization and a fast oscillatory activity. Experiments were made in coronal slices of rat frontal cortex (300–400 pm thickness) and intracellular recordings from regularly spiking cells were obtained with 3 M potassium acetate‐filled glass microelectrodes (80–150 MΩ). Dopamine was applied dissolved in the extracellular medium and, in current‐clamp recordings, reversibly inhibited the slow subthreshold depolarization. Dopamine was ineffective when applied after tetrodotoxin (1 μM) had blocked the action potentials. This inhibition was dose‐dependent in the range of 0.1–10 μM. Dopamine, applied at 10 μM, decreased the steady‐state firing frequency and also inhibited the subthreshold fast oscillatory activity. The currents activated in the subthreshold range were recorded with the single‐electrode voltage‐clamp technique and a clear persistent, tetrodotoxin‐sensitive component was isolated. This component was inhibited by 50% in a reversible way by 20 μM dopamine. These results show that dopamine increases the threshold for spike firing and suggest a mechanism for the inhibitory action of this neurotransmitter in the prefrontal cortex.
Regulation of Rat Sympathetic Nerve Density by Target Tissues and NGF in Maturity and Old Age
Authors: Thrasivoulou C. , Cowen T. 
Published: April 2006

AbstractPrevious studies in our laboratory using a transplantation model have shown that target tissues of some autonomic neurons, including cerebral blood vessels, exert a controlling influence on nerve fibre loss in old age. The present study was undertaken in order to discover whether the influence of targets extends to controlling age changes in specific populations of nerves. In old rats, we have demonstrated a significant decrease of ‐50% in the sympathetic innervation of middle cerebral arteries, using tyrosine hydroxylase‐like immunoreactivity. Following transplantation, tyrosine hydroxylase‐like immunoreactive nerve density on both young and old implanted middle cerebral arteries mirrored the nerve densities seen in normal, non‐transplanted vessels. Furthermore, implanted tissue from old donors became reinnervated with a nerve density ‐50% less than that of young implanted vessels. Treatment of transplants with nerve growth factor, however, was able to reverse these age changes and restore the sympathetic innervation of aged middle cerebral arteries to levels above those seen in young middle cerebral arteries. These results suggest that the pattern and density of sympathetic innervation that the middle cerebral artery receives is determined by the target rather than by the neurons supplying the tissue. The ability of nerve growth factor to induce regrowth in sympathetic neurons innervating ageing target tissues implies that age‐related neuronal atrophy may be due to reduced synthesis or availability of target‐derived neurotrophic factors.
Block of c‐Fos and JunB Expression by Antisense Oligonucleotides Inhibits Light‐induced‐Phase Shifts of the Mammalian Circadian Clock
Authors: Wollnik F. , Brysch W. , Uhlmann E. , Gillardon F. , Bravo R. , Zimmermann M. , Schlingensiepen K. H. , Herdegen T. 
Published: April 2006

AbstractLight‐induced phase shifts of circadian rhythmic locomotor activity are associated with the expression of c‐Jun, JunB, c‐Fos and FosB transcription factors in the rat suprachiasmatic nucleus, as shown in the present study. In order to explore the importance of c‐Fos and JunB, the predominantly expressed AP‐1 proteins for the phase‐shifting effects of light, we blocked the expression of c‐Fos and JunB in the suprachiasmatic nucleus of male rats, housed under constant darkness, by intracerebroventricular application of 2 μ1 of 1 mM antisense phosphorothioate oligodeoxynucleotides (ASO) specifically directed against c‐fos and JunB mRNA. A light pulse (300 lux for 1 h) at circadian time 15 induced a significant phase shift (by 125 ± 15 min) of the circadian locomotor activity rhythm, whereas application of AS0 6 h before the light pulse completely prevented this phase shift. Application of control nonsense oligodeoxynucleotides had no effect. ASO strongly reduced the light‐induced expression of c‐Fos and JunB proteins. In contrast, light pulses with or without the control nonsense oligodeoxynucleotides evoked strong nuclear c‐Fos and JunB immunoreactivity in the rat suprachiasmatic nucleus. These results demonstrate for the first time that inducible transcription factors such as c‐Fos and JunB are an essential part of fundamental biological processes in the adult mammalian nervous system, e.g. of light‐induced phase shifts of the circadian pacemaker.
A Minimal CGRP Gene Promoter is Inducible by Nerve Growth Factor in Adult Rat Dorsal Root Ganglion Neurons But Not in PC12 Phaeochromocytoma Cells
Authors: Watson Andrea , Ensor Elizabeth , Symes Aviva , Winter Janet , Kendall Giles , Latchman David 
Published: April 2006

AbstractThe calcitonin/CGRP gene is transcribed in thyroid C cells and some neuronal cells but not in other cell types. Although the promoter sequences mediating gene activity in thyroid C cells have been extensively studied, the elements responsible for promoter activity in neuronal cells and its stimulation by nerve growth factor (NGF) have not previously been defined. We report the first use of the calcium phosphate procedure to successfully transfect adult rat dorsal root ganglion neurons, which naturally express the calcitonin/calcitonin gene‐related peptide (CGRP) in an NGF‐inducible manner. This method was used to characterize the elements in the calcitonin/CGRP promoter which are responsible for its basal activity and NGF inducibility in DRG neurons and in PC12 cells, a neuronally derived cell line which does not naturally express the calcitonin/CGRP gene. Although the sequences required for basal activity are similar in each cell type, we show that a minimal calcitonin/CGRP promoter is NGF‐responsive in dorsal root ganglion cells, but that upstream sequences are required for such inducibility in PC12 cells.
The Classification and Properties of Nociceptive Afferent Units from the Skin of the Anaesthetized Pig
Authors: Lynn B. , Faulstroh K. , Pierau F.‐K. 
Published: April 2006

AbstractThe afferent properties of nerve fibres innervating the hairy skin of the pig hind limb were investigated by recording from 142 single units from the saphenous nerve. Identified single units were isolated using maximal electrical stimulation of the nerve trunk. Afferent units were classified on the basis of their responses to a range of stimuli, both thermal (heating to 60°C and cooling to 10°C) and mechanical (air jet, von Frey type filaments with forces of 0.1–250 mN, and strong pressure with a blunt needle). A‐fibre units (conduction velocity 6.3–64 m/s, n= 60) fell into categories that have been described in hairy skin in other mammalian species. Most were mechanoreceptors, although seven typical A‐fibre mechanical nociceptors with large, multipoint fields were also isolated. No cutaneous receptive field could be found for 15% of A‐fibre units. Out of 62 C‐fibre units (conduction velocity 0.49–2 m/s) 40% had no cutaneous field for pressure, heat or cold. Of the C‐fibre units with cutaneous fields, 42% were polymodal nociceptors, 38% were mechanoreceptors with a variety of properties, including some excited by noxious heat, and 19% were heat‐only nociceptors. C‐polymodal nociceptors had large receptive fields up to 12.5 mm across and did not sensitize following strong heating. Twenty units conducted at 2–6.3 m/s, between the main C‐ and A‐fibre bands, and were varied in their responses. Some had properties identical to C‐fibre mechanoreceptors whilst four were sensitive cold thermoreceptors and one was a polymodal nociceptor. Two units were mechanical nociceptors with small receptive fields. The innervation of pig skin thus has some features like that of primates, such as the presence of C‐heat nociceptors and the large receptive fields of C‐polymodal nociceptors. However, other features were like non‐primates (e.g. the minimal heat‐sensitivity of A‐mechanical nociceptors) or were unique (the heat‐sensitive mechanoreceptors and the lack of heat sensitization in C‐polymodal nociceptors from hairy skin).
Expression of the Highly Polysialylated Neural Cell Adhesion Molecule During Postnatal Myelination and Following Chemically Induced Demyelination of the Adult Mouse Spinal Cord
Authors: Oumesmar B. Nait , Vignais L. , Duhamel‐Clerin E. , Avellana‐Adalid V. , Rougon G. , Evercooren A. Baron‐Van 
Published: April 2006

AbstractWe have investigated the expression of the highly polysialylated neural cell adhesion molecule in the mouse spinal cord during postnatal myelination and in the adult after chemically induced demyelination. By double immunohistochemistry, using a monoclonal antibody (anti‐Men B) which specifically recognizes polysialic acid (PSA) units on neural cell adhesion molecule (N‐CAM), and an anti‐myelin basic protein, a caudorostral gradient of expression of PSA‐NCAM was observed at postnatal day 1 (P1), which was inversely related to the gradient of myelination. At P7, PSA‐NCAM labelling decreased relative to P1. In white matter, this decrease was correlated with the progression of myelination. PSA‐NCAM immunoreactivity persisted in as yet unmyelinated structures, i.e. the corticospinal tract, the dorsomedial part of the ventral funiculus and the lateral funiculi, and decreased with the onset of myelination of these structures at P15. In the adult, PSA‐NCAM expression remained in discrete structures, i.e. Iaminae I and II of the dorsal horn and lamina X around the central canal. The ependymal cells and the astrocyte endfeet under the meninges were also labelled. In addition, PSA‐NCAM expression was reinduced on various cells and structures after lysolecithin‐induced demyelination of the adult mouse spinal cord. At early times after demyelination, PSA‐NCAM was expressed on glial cells around the lesion but also at a distance from this zone. Seven days after injection, cellular PSA‐NCAM expression was found around but also within the lesion. This expression was totally abolished 15 days after injection. Double immunohistochemistry for PSA and cell‐specific markers showed that the cells which expressed PSA‐NCAM after demyelination were oligodendrocyte precursors, reactive astrocytes and Schwann cells. PSA‐NCAM re‐expression on all cell types was transient and ceased when myelin repair was accomplished. The spatial and temporal regulation of PSA‐NCAM expression during development and after demyelination suggests a role for PSA‐NCAM in glial plasticity during the myelination and remyelination processes.
Receptor Expression in Olfactory Neurons During Rat Development: In Situ Hybridization Studies
Authors: Strotmann J. , Wanner I. , Helfrich T. , Breer H. 
Published: April 2006

Abstract In situ hybridization approaches have been employed to explore the onset and time course of odorant receptor expression during the prenatal development of rats. The critical phase for the maturation of the olfactory system from embryonic day (E) 12 to E18 was analysed. The onset of expression of four receptor genes (OR5, OR14, OR37 and OR124) was found between day E12 and E14. In the early phase of development (E14) a distinct receptor subtype was expressed only in a few hundred neurons; the number increased about two‐ to three‐fold within a 2 day interval. From the very beginning, spatial segregation of receptor subtypes in distinct expression zones was observed.