bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glutamate‐induced Release of the Nitric Oxide Precursor, Arginine, From Glial Cells
Authors: Grima Gilbert , Benz Beatrix , Do Kim Quang 
Published: April 2006

AbstractArginine, the nitric oxide precursor, is predominantly localized in glial cells, whereas the constitutive nitric oxide synthase is mainly found in neurons. Therefore, a transfer of arginine from glial cells to neurons is needed to replenish the neuronal precursor pool. This is further supported by the finding that arginine is released upon selective pathway stimulation both in vitro and in vivo. We investigated the mechanism underlying this glial‐neuronal interaction by analysing the effect of glutamate receptor agonists on the extracellular [3H]arginine level in cerebellar and cortical slices and in cultures of either cortical astroglial cells or neurons. We present data indicating that arginine is released from cerebellar and cortical slices and astroglial cell cultures upon activation of ionotropic non‐NMDA glutamate receptors. Glutamate had no effect on the extracellular [3H]arginine level in neuronal cultures. Moreover, the effect of glutamate in cerebellar slices was tetrodotoxin‐insensitive, and the calcium ionophore A23187 evoked the release of [3H]arginine from astroglial cell cultures. Thus, nitric oxide synthesis and nitric oxide transmission may be based on the glial‐neuronal transfer of arginine which is induced by activation of excitatory amino acid receptors on glial cells.
Spatially and Temporally Regulated Modification of the Receptor‐like Protein Tvrosine Phosphatase ζ/β isoforms with Keratan Sulphate in the Developing Chick Brain
Authors: Hamanaka Hiroki , Maeda Nobuaki , Noda Masaharu 
Published: April 2006

AbstractProtein tyrosine phosphatase ζ (PTPζRPTPβ) is a proteoglycan‐type receptor‐like protein tyrosine phosphatase specifically expressed in the brain. In addition to the transmembrane form (PTPζ‐A), the extracellular splice variant (PTPζ‐S) occurs as a major soluble chondroitin sulphate proteoglycan in the brain. We prepared antibodies which specifically recognize PTPζ‐A and ‐S, and analysed the carbohydrate structures on the two PTPζ isoforms in the developing chick brain. lmmunoprecipitation experiments using these antibodies revealed that almost all of the keratan sulphate recognized by a monoclonal antibody (5D4) was exclusively bound to PTPζ‐A and PTPζ‐S. Addition of keratan sulphate to these proteoglycans markedly increased from embryonic day (E) 11, in contrast to the addition of LeX and HNK‐1 carbohydrates, which gradually increased during development in accordance with expression of the core proteins, suggesting that keratan sulphate modification plays some specific roles. Moreover, at the early embryonic stage keratan sulphate was observed only in several restricted regions, especially at boundary regions such as the roof plate of the tectum, the zona limitans intrathalamica in the diencephalon, and the mesencephalon‐metencephalon boundary. At the mesencephalon‐metencephalon boundary, keratan sulphate modification of PTPζ isoforms was specifically observed from E3 to E6 on a ring of cells encircling the neural tube and their radially oriented processes, which were identified as radial glial fibres. This expression pattern of keratan sulphate spatiotemporally corresponded well to the formation of the fovea isthmi, a groove separating the mesencephalon from the metencephalon. These results suggest that carbohydrates including keratan sulphate on PTPζ isoforms play important roles in brain development by modulating the cell‐cell and/or cell‐substrate interactions mediated by these molecules.
Polysialylated Neural Cell Adhesion is Involved in Target‐induced Morphological Differentiation of Arcuate Dopaminergic Neurons
Authors: Loudes Catherine , Rougon Geneviève , Kordon Claude , Faivre‐Bauman Annie 
Published: April 2006

AbstractWe have previously shown that the morphological and biochemical maturation of developing rat hypothalamic dopaminergic neurons is accelerated when they are cocultivated with pituitary intermediate lobe cells, one of their targets. Only two subsets of hypothalamic dopaminergic neurons (arcuate, A12, and periventricular, A14, nuclei) may project to the pars intermedia. In order to determine whether the two populations are equally responsive to coculture conditions, we microdissected the hypothalamus of 17‐day‐old rat fetuses in two fragments containing cell bodies from the A12 and from the A14 regions, prepared neuronal cultures from both portions and incubated them separately with intermediate lobe cells. The presence of intermediate lobe cells increased tyrosine hydroxylase levels in both dopaminergic neuron subsets, but morphological differentiation was accelerated in dopaminergic neurons originating in the arcuate nucleus only. We then investigated whether physical contact between developing arcuate neurons and their target cells was a prerequisite of the morphological effect by interposing a semipermeable membrane between cultivated neurons and intermediate lobe cells in transwell culture dishes. The morphological effect was no longer observed under transwell coculture conditions, pointing to the involvement of membrane‐bound molecules. Accordingly, the stimulating effect of coculture on arcuate dopaminergic neurons was completely abolished by the removal of polysialic acid on neural cell adhesion molecules by endoneuraminidase N treatment. Thus, maturation of A12 and A14 dopaminergic neurons exhibits differential susceptibility to intermediate lobe target cells, and polysialylated‐NCAM is required for the contact‐dependent effect.
Increased Expression of NGFI‐A mRNA in the Rat Striatum Following Burst Stimulation of the Medial Forebrain Bundle
Authors: Chergui Karima , Svenningsson Per , Nomikos George G. , Gonon François , Fredholm Bertil B. , Svennson Torgny H. 
Published: April 2006

AbstractUsing in situ hybridization, we examined the mRNA expression for several immediate early genes in dopamine‐innervated brain areas following electrical burst vs. regular stimulation of the medial forebrain bundle in anaesthetized rats. Two hours after 5 Hz burst stimulation, the expression of the nerve growth factor‐inducible clone A (NGFI‐A) mRNA was increased in the medial part of the striatum. This increase was prevented by pretreatment with the dopamine‐D1 receptor antagonist, SCH23390 (0.1 mg/kg i.p.). After 8 Hz burst stimulation, NGFI‐A mRNA expression was increased in the medial, central and lateral parts of the striatum. Induction occurred predominantly in cells expressing mRNAs for the dopamine‐D1 receptor, substance P and dopamine and CAMP‐regulated phosphoprotein (DARP‐32). Regular stimulation had no effect on NGFI‐A mRNA expression. The induction of NGFI‐A was related to the levels of dopamine released by burst or regular stimulation as demonstrated with in vivo amperometry. Two hours after stimulation, the expression of none of the other genes studied was altered. One hour after 8 Hz burst stimulation, the expression of NGFI‐A, NGFI‐B and jun‐B mRNAs was increased in the striatum and that of NGFI‐A, NGFI‐6, c‐fos, fos‐B and jun‐B mRNAs was variably increased in the nucleus accumbens and lateral septum. These results provide additional support for the physiological importance of burst firing activity in midbrain dopamine neurons for the activation of their target cells. They demonstrate a spatial and temporal specificity as regards the brain region, the gene activated, the receptor involved and the phenotype of the cells affected.
Csk and BatK Show Opposite Temporal Expression in the Rat CNS: Consistent with its Late Expression in Development, BatK Induces Differentiation of PC12 Cells
Authors: Kuo Sophia S. , Armanini Mark P. , Phillips Heidi S. , Caras Ingrid W. 
Published: April 2006

AbstractBatK is a second member of the Csk family of regulatory kinases that phosphorylate a key inhibitory tyrosine on Src family kinases, leading to down‐regulation. To investigate the roles of BatK and Csk, both of which are expressed in the brain, we compared their temporal expression patterns during development of the central nervous system (CNS) in rats. BatK mRNA is undetectable at embryonic day 12 (E12), appears in the developing nervous system at approximately E15, and its expression progressively increases up to the time of birth, thereafter remaining high throughout the adult brain. In striking contrast, Csk is highly expressed throughout embryonic development and remains high in the CNS until birth. It is then dramatically down‐regulated in the adult brain except in the olfactory bulb. BatK and Csk thus exhibit complementary temporal expression patterns. Since BatK expression correlates with late‐stage development and terminal differentiation, we speculated that it might be involved in regulating neuronal differentiation. Using PC12 cells as a model system, we show that overexpression of BatK is sufficient to induce neurite outgrowth in the absence of nerve growth factor. Further, overexpression of BatK activates the mitogen‐activated protein kinase cascade. We propose a model suggesting that, despite overlapping in vifro activities, BatK and Csk regulate different targets in vivo and have different functions during and after neuronal development, BatK being the dominant regulator of Src kinases in the fully differentiated adult brain.
Histaminergic System in Co‐cultures of Hippocampus and Posterior Hypothalamus: A Morphological and Electrophysiological Study in the Rat
Authors: Diewald L. , Heimrich B. , Busselberg D. , Watanabe T. , Haas H. L. 
Published: April 2006

AbstractNeurons of the tuberomammillary nucleus in the posterior hypothalamus diffusely project to most parts of the central nervous system, where their main transmitter, histamine, modulates the excitability of the target neurons. The development of a histaminergic hypothalamo‐hippocampal pathway and its function were studied in organotypic co‐cultures. lmmunocytochemistry for histidine decarboxylase, the specific synthesizing enzyme, stained clusters of neurons in the hypothalamic tuberomammillary area. lmmunolabelled varicose processes innervated the co‐cultured hippocampus and established a few synaptic contacts on dendrites. Cultured tuberomammillary neurons displayed their typical membrane properties and were spontaneously active. In hippocampal pyramidal cells of the CA3 region the long‐lasting afterhyperpolarization was reduced by histamine or impromidine and increased by the H2 antagonist cimetidine, but not by the H1 antagonist mepyramine. The membrane potential was depolarized in presence of an H2 agonist and hyperpolarized by an H2 antagonist. In single hippocampal cultures histamine antagonists did not affect afterhyperpolarization and membrane potential. Histaminergic neurons retain their main morphological and physiological characteristics in slice cultures and establish a functional connection with co‐cultured target cells.
The Pontine A5 Noradrenergic Cells which Project to the Spinal Cord Dorsal Horn are Reciprocally Connected with the Caudal Ventrolateral Medulla in the Rat
Authors: Tavares Lsaura , Lima Deolinda , Coimbra Antonio 
Published: April 2006

AbstractA disynaptic pathway linking the caudal ventrolateral medulla (VLM) to the spinal cord via the A5 noradrenergic cell group of the pons has recently been described in the rat. In the present work, the projections of the A5 to the VLM and to the spinal dorsal horn were studied with double‐tracing techniques combined with immunostaining of the noradrenaline‐synthesizing enzyme dopamine‐β‐hydroxylase. Cholera toxin subunit B (CTb) injected into the VLM and fluoro‐gold injected into the spinal dorsal horn produced double retrograde labelling of A5 neurons immunoreactive for dopamine‐β‐hydroxylase, which received appositions of fibre varicosities labelled anterogradely with CTb injected into the VLM. After injecting CTb into the A5, retrogradely labelled neurons occurred in the VLM. These neurons were contacted by anterogradely labelled fibres from the A5 group. These observations indicate that the VLM cells acting upon the A5 spinally projecting neurons, which are likely to exert an α2‐adrenoreceptor‐mediated inhibition on the spinal cord, are targeted by collaterals of the A5 spinal cord‐bound axons. The A5‐VLM pathway may be the anatomical substrate of a negative feedback circuit whereby the modulatory action of the VLM on the spinal cord is self‐inhibited through activation of the A5.
The Oxytocin‐induced Inward Current in Vagal Neurons of the Rat is Mediated by G Protein Activation but not by an Increase in the lntracellular Calcium Concentration
Authors: Alberi Stefano , Dreifuss Jean Jacques , Raggenbass Mario 
Published: April 2006

AbstractThe neuropeptide oxytocin can depolarize parasympathetic preganglionic neurons in the dorsal motor nucleus of the vagus nerve of the rat by generating a sustained inward current, which is sodium‐dependent and tetrodotoxin‐insensitive. The second messenger activated by oxytocin receptor binding is, however, not yet known. In the present study, we attempted to characterize it by using the whole‐cell recording technique and brainstem slices. When loaded with GTP‐γ‐S, a non‐hydrolysable analogue of GTP, vagal neurons generated a persistent inward current in the absence of agonist and the oxytocin effect was suppressed, suggesting that the peptide‐evoked current was mediated by G‐protein activation. Loading vagal neurons with the calcium chelator 1,2–bis(2–aminophenoxy)ethane‐N,N,N′,N′,‐tetraacetic acid (BAPTA) suppressed a calcium‐dependent, slowly decaying potassium aftercurrent but did not affect the oxytocin response, suggesting that the latter was not mediated by an agonist‐induced increase in the intracellular calcium concentration. Protein kinase C (PKC) activation was probably not involved, since the peptide‐evoked current was not modified by loading neurons with the PKC inhibitor H7. Thus, the oxytocin‐evoked current in vagal neurons was probably not mediated by phospholipase C‐β (PLC‐β) activation. Loading neurons with 8–Br‐CAMP or with an adenylyl cyclase activator (forskolin) reduced the oxytocin‐evoked current by about half. SQ 22536, an adenylyl cyclase inhibitor, reduced this current by a similar amount. However, the peptide‐evoked current was unaffected by Rp‐CAMPS and Sp‐CAMPS, an inhibitor and an activator, respectively, of CAMP‐dependent protein kinase (PKA). We suggest that oxytocin activates two distinct signalling pathways in vagal neurons: one which is CAMP‐dependent, but PKA‐independent, and one, unidentified, which is PLC‐β‐and CAMP‐independent. Each pathway accounts for about half of the peptide effect and both appear to involve G‐protein activation.
NMDA Receptor Modulation by a Conditioned Medium Derived from Rat Cerebellar Granule Cells
Authors: Dus Laura , Canu Nadia , Zona Cristina , Ciotti Maria Teresa , Calissano Pietro 
Published: April 2006

AbstractOur previous studies have shown that the response to the excitotoxic action of glutamate by cultured cerebellar granule cells depends upon the cell density or the volume of medium in which they have been grown: the higher the cell density or the lower the volume, the higher the response to glutamate. We have hypothesized that this variable response is due to the formation in culture of a glutamate‐sensitizing activity GSA more abundantly in conditioned medium derived from high‐density or low‐volume cultures than that present in low‐density or high volume cultures and capable of restoring sensitivity in previously resistant granule cells. In order to elucidate the mechanism of action of glutamate‐sensitizing activity, we measured the extent and function of NMDA receptors in low‐ and high‐volume cultures and assessed the effect of glutamate‐sensitizing activity on the same receptors. We found that under high‐volume conditions the extent of MK‐801 binding, the amount of NMDA receptor type 1, the currents evoked in whole cells after an NMDA pulse and the response of cultured cells to this ligand were markedly reduced compared with low‐volume cultures. Addition of glutamate‐sensitizing activity to high‐volume cultures increased their glutamate sensitivity, the NMDA‐evoked currents, the extent of MK‐801 binding and the amount of NMDA receptor type 1 protein present. The corresponding mRNA transcripts, on the contrary, were unchanged in high‐volume, low‐volume and high‐volume GSA‐treated cultures.
Developmental Changes in Neuronal Responsiveness to the CNS Myelin‐associated Neurite Growth Inhibitor N I‐35/250
Authors: Bandtlow Christine E. , Loschinger Jurgen 
Published: April 2006

AbstractThe extent of fibre regeneration in the adult injured vertebrate nervous system appears to be primarily determined by the local environment. Thus, the failure of axon regrowth in the central nervous system (CNS) is crucially influenced by the presence of the myelin‐associated neurite growth inhibitor Nl‐35/250 and possibly also by molecules such as the myelin‐associated glycoprotein and the proteoglycans. Developmental time course studies have shown that the capacity for regeneration declines sharply with the appearance of mature oligodendrocytes and myelin, which indicates a role of Nl‐35/250 in restricting CNS regeneration and plasticity. However, recent in vitro and in vivo studies showed that embryonic neurons are capable of extending fibres on and in adult CNS tissue apparently unaffected by myelinated areas. A possible explanation is that very immature neurons have yet to express the appropriate receptors and response mechanisms for factors that normally induce growth inhibition at a later stage of development. Here we report that embryonic rat dorsal root ganglion and chick retinal ganglion cells display different sensitivity to bovine Nl‐35/250 compared with mature neurons. In older neurons Nl‐35/250 could evoke long‐lasting collapse responses accompanied by a large increase in the intracellular calcium level, persisting for several minutes. In contrast, their embryonic counterparts collapsed only transiently when exposed to Nl‐35/250, and increases in intracellular calcium concentration were small and transient. Calcium influx induced experimentally by the calcium ionophore A23187 revealed that it was not the maximal size of the calcium increase but rather the duration of elevated calcium concentration that was the most important determinant for subsequent morphological alterations of the growth cone. Our data further suggest that developing neurons acquire their complete sensitivity for Nl‐35/250 around the time of myelination.
Consumer knowledge and expectations of restaurant menus and their governing legislation: a qualitative assessment
Authors: Thomas Lionel , Mills Juline E. 
Published: April 2006

AbstractMany consumers feel that it is the social responsibility of restaurants to inform them of the nutritional content of food items that may be detrimental to their health or contrary to their beliefs. Current legislation, through the Truth‐in‐Menu Law, protects consumers from misleading advertisements, but does not mandate that restaurant establishments provide nutritional information. This qualitative study aims to assess how much consumers really know about menu labeling legislation and what information they consider to be most important on restaurant menus. This study found that consumers feel consistency between item description and actual presentation, accuracy of claims, disclosure of ingredients, nutritional information, value and the availability of competent servers to explain any ambiguities were most important. The article concludes with recommendations on where legislation should go and what restaurants can do to provide menus that meet customer expectations.
Cell Division of
Giardia intestinalis
: Flagellar Developmental Cycle Involves Transformation and Exchange of Flagella between Mastigonts of a Diplomonad Cell
Authors: Nohýnková Eva , Tůmová Pavla , Kulda Jaroslav 
Published: April 2006

ABSTRACT

Giardia intestinalis
is a binucleated diplomonad possessing four pairs of flagella of distinct location and function. Its pathogenic potential depends on the integrity of a complex microtubular cytoskeleton that undergoes a profound but poorly understood reorganization during cell division. We examined the cell division of
G. intestinalis
with the aid of light and electron microscopy and immunofluorescence methods and present here new observations on the reorganization of the flagellar apparatus in the dividing
Giardia
. Our results demonstrated the presence of a flagellar maturation process during which the flagella migrate, assume different position, and transform to different flagellar types in progeny until their maturation is completed. For each newly assembled flagellum it takes three cell cycles to become mature. The mature flagellum of
Giardia
is the caudal one that possesses a privileged basal body at which the microtubules of the adhesive disk nucleate. In contrast to generally accepted assumption that each of the two diplomonad mastigonts develops separately, we found that they are developmentally linked, exchanging their cytoskeletal components at the early phase of mitosis. The presence of the flagellar maturation process in a metamonad protist
Giardia
suggests that the basal body or centriole maturation is a universal phenomenon that may represent one of the core processes in a eukaryotic cell.
The Highly Conserved Family of
Tetrahymena thermophila
Chromosome Breakage Elements Contains an Invariant 10-Base-Pair Core
Authors: Hamilton Eileen P. , Williamson Sondra , Dunn Sandra , Merriam Virginia , Lin Cindy , Vong Linh , Russell-Colantonio Jessica , Orias Eduardo 
Published: April 2006

ABSTRACT

As a typical ciliate,
Tetrahymena thermophila
is a unicellular eukaryote that exhibits nuclear dimorphism: each cell contains a diploid, germ line micronucleus (MICN) and a polyploid, somatic macronucleus (MACN). During conjugation, when a new MACN differentiates from a mitotic descendant of the diploid fertilization nucleus, the five MICN chromosomes are site-specifically fragmented into 250 to 300 MACN chromosomes. The classic chromosome breakage sequence (CBS) is a 15-bp element (TAAACCAACCTCTTT) reported to be necessary and sufficient for chromosome breakage. To determine whether a CBS is present at every site of chromosome fragmentation and to assess the range of sequence variation tolerated, 31 CBSs were isolated without preconception as to the sequence of the chromosome breakage element. Additional CBS-related sequences were identified in the whole-genome sequence by their similarities to the classic CBS. Forty CBS elements behaved as authentic chromosome breakage sites. The CBS nucleotide sequence is more diverse than previously thought: nearly half of the CBS elements identified by unbiased methods have a variant of the classic CBS. Only an internal 10-bp core is completely conserved, but the entire 15-bp chromosome breakage sequence shows significant sequence conservation. Our results suggest that any one member of the CBS family provides a necessary and sufficient
cis
element for chromosome breakage. No chromosome breakage element totally unrelated to the classic CBS element was found; such elements, if they exist at all, must be rare.