bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Synaptic Vesicle‐Associated Phosphoprotein: SVAPP‐120
Authors: Bahler Martin , Klein Ronald L. , Wang James K. T. , Benfenati Fabio , Greengard Paul 
Published: October 2006

AbstractGeneration of antibodies and direct protein sequencing were used to identify and characterize proteins associated with highly purified synaptic vesicles from rat brain. A protein doublet of low abundance of 119 and 124 kDa apparent molecular mass [synaptic vesicle‐associated phosphoprotein with a molecular mass of 120 kDa (SVAPP‐120)] was identified using polyclonal antibodies. SVAPP‐120 was found to copurify with synaptic vesicles and to be enriched in the purified synaptic vesicle fraction to the same extent as synapsin I. Like synapsin I, SVAPP‐120 is not an integral membrane protein because it was released from synaptic vesicles by high salt concentrations. This protein was demonstrated to be brain specific, and its distribution in various brain regions paralleled the distribution of synapsin I and synaptophysin. During the postnatal development of the rat cortex and cerebellum, its expression correlated with synaptogenesis. SVAPP‐120 was demonstrated to be a phosphoprotein both in vivo and in vitro. It was shown to be phosphorylated on serine and to a lesser extent on threonine residues. These results provide evidence that SVAPP‐120 represents a novel synaptic vesicle‐associated phosphoprotein. In addition, aldolase, a glycolytic enzyme, and αc‐adaptin, a clathrin assembly‐promoting protein, were identified on purified synaptic vesicles by direct protein sequencing.
Protein Kinase C (αand β) Immunoreactivity in Rabbit and Rat Retina: Effect of Phorbol Esters and Transmitter Agonists on Immunoreactivity and the Translocation of the Enzyme from Cytosolic to Membrane Compartments
Authors: Osborne N. N. , Broyden N. J. , Barnett N. L. , Morris N. J. 
Published: October 2006

AbstractUsing a monoclonal antibody against protein kinase C (PKC) that recognises the isoenzymes α, βI, and βII, positive immunoreactivity was observed throughout the cytoplasm of bipolar cells in both rat and rabbit retinas. PKC immunoreactivity was also associated with the outer segment of photoreceptors in the rabbit retina and presumed amacrine cells in the rat retina. The PKC immunoreactivity in the retina was unaffected in content or localisation in rats kept in continuous dark or light conditions over a period of 6 days. The localisation of PKC immunoreactivity in retinas was similar in 6‐day‐old, 16 day‐old, or adult rabbits. However, the content of PKC was lowest at the youngest stage and highest in the adult rabbit retinas. Of the two active phorbol esters studied, only phorbol 12, 13‐dibutyrate (PDbut) at a concentration of 1 μM caused the PKC immunoreactivity in rabbit retina bipolar cells to be „transported” from the perikarya towards the axonal terminal processes. Biochemical analyses showed that most of the cytosolic PKC was translocated to the membrane compartment following such treatment. The other phorbol ester, phorbol 12‐myristate 13‐acetate, even at a concentration of 10 μM did not cause a similar transport of PKC immunoreactivity in the bipolar cells, although a partial translocation of the enzyme could be followed biochemically. Both the translocation and transport of PKC by PDbut could be reversed by simply incubating the retinas in physiological solution for 60 min. The „transport” and translocation processes were not obviously affected by the transport inhibitor colchicine or by known PKC inhibitors such as staurosporine, H‐7, sphingosine, or polymyxin B. In addition, agonists known to stimulate inositol phosphates in the retina, viz., carbachol, noradrenaline, and quisqualate, or 4‐aminopyridine did not cause a translocation or „transport” of PKC as observed for the phorbol esters.
Effects of Inhibitors of Oligosaccharide Processing on P0Protein Synthesis and Incorporation into PNS Myelin
Authors: Smith Marion E. 
Published: October 2006

AbstractFour inhibitors of Oligosaccharide processing were used to investigate their effects on the transport of PNS myelin glycoproteins through the secretory pathway, as well as to gain further insight into the structure of the Oligosaccharide chains of the Po and 19‐kDa glycoproteins. Several different inhibitors of Oligosaccharide processing were incubated with chopped peripheral nerves from young rats (21–24 days of age) and the uptake of 14C‐amino acid and [3H] fucose or [3H] mannose was measured in Po and the 19‐kDa glycoprotein after separation of homogenate and myelin proteins on polyacrylamide gels. [3H] Mannose was not found as suitable as [3H] fucose as an Oligosaccharide precursor because glucose used as an energy source profoundly inhibited the uptake of [3H] mannose. The substitution of pyruvate as an energy source, however, resulted in incomplete glycosylation, poor amino acid uptake, and truncated Oligosaccharide chains. Endoglycosidase H cleaved ∼50% of the Po labeled with [3H] fucose and 14C‐amino acid. The lower molecular weight protein resulting from endoglycosidase H cleavage contained approximately one‐half the [3H] fucose label on the protein, whereas one‐half remained on the Oligosaccharide chain of the undegraded Po, indicating that at least one‐half the Pohas a hybrid structure. Deoxynojirimycin, deoxymannojirimycin, and castanospermine inhibited incorporation of [3H] fucose into the Oligosaccharide chains of Po and the 19‐kDa glycoprotein as predicted from their action in blocking various stages of trimming of high mannose structures before the addition of fucose. Po synthesized in the presence of these inhibitors was cleaved to a greater extent by endoglycosidase H than the normal protein, indicating increased vulnerability to this enzyme with arrest of normal processing. Similar results were obtained for the 19‐kDa glycoprotein. Both the incompletely processed Po and the 19‐kDa glycoprotein formed in the presence of these inhibitors appeared to be transported normally into myelin.
Interstitial 3‐Methoxytyramine Reflects Striatal Dopamine Release: An In Vivo Microdialysis Study
Authors: Brown Erin E. , Damsma Geert , Gumming Paul , Fibiger Hans C. 
Published: October 2006

AbstractPrevious ex vivo studies have provided indirect evidence that the dopamine (DA) metabolite 3‐methoxytyramine (3‐MT) may be a useful index of DA release in vivo. In the present study, in vivo microdialysis was utilized to assess directly the relationship between extracellular DA and 3‐MT in the striatum of rats following a variety of pharmacological manipulations. Apomorphine, a DA receptor agonist, produced a rapid, transient decrease in both DA and 3‐MT. Conversely, the DA receptor antagonist haloperidol produced a concomitant increase in extracellular DA and 3‐MT. Increases in DA and 3‐MT were also noted following the administration of the DA uptake inhibitor, bupropion. Local application of tetrodotoxin resulted in the complete elimination of measurable amounts of DA and 3‐MT in the dialysate. γ‐Butyrolactone also greatly decreased DA and 3‐ MT. Finally, d‐amphetamine produced a large increase in DA and 3‐MT in animals that had been treated previously with γ‐butyrolactone. The Pearson correlation coefficients for DA and 3‐MT following these manipulations ranged from 0.87 to 0.97. These data indicate that interstitial 3‐MT is an accurate index of DA release. However, when compared with previous ex vivo findings, the present results also suggest that changes in tissue concentrations of 3‐MT may not reliably reflect DA release following certain pharmacological manipulations.
A Specific Trarisduction Mechanism for the Glutamate Action on Phosphoinositide Metabolism via the Quisqualate Metabotropic Receptor in Rat Brain Synaptoneurosomes: I. External Na+ Requirement
Authors: Guiramand Janique , Vignes Michel , Mayat Ebrahim , Lebrun Fabienne , Sassetti Isabella , Récasens Max 
Published: October 2006

Abstract: The characteristics of the transduction mechanism(s) activated by glutamate (Glu) via the quisqualate metabotropic receptor, as well as by depolarizing agents, to trigger formation of inositol phosphates (IPs) were investigated in 8‐day‐old rat forebrain Synaptoneurosomes. The replacement of external Na+ by various compounds (Li+, Tris+, N‐methyl‐D‐glucamine+, and sucrose) induces an increase in basal accumulation of IPs and depolarizes synaptoneurosome membranes. Under these conditions, Gluand K+‐induced accumulations of IPs are inhibited, whereas the carbachol (Carb)‐elicited response of IPs parallels the basal one. Agents increasing Na+ influx, such as veratridine and monensin, depolarize Synaptoneurosomes and stimulate formation of IPs. These stimulations are not additive with responses of IPs elicited by Glu or K+. These data suggest that (a) Glu activates phosphoinositide metabolism via a specific mechanism (distinct from that of cholinergic agonists), (b) depolarizing agents and Glu share at least one common intermediate step in their mechanisms of activation of the metabolism of IPs, and (c) the depolarization may correspond to this common step. ID addition, Na+ seems to be required for Glu stimulation of metabolism of IPs. The depolarization associated with the action of Glu on formation of IPs results neither from an influx via tetrodotoxin‐sensitive voltage‐dependent Na+ channels nor from an entry via the classically characterized Na+/Ca2+ or Na+/H+ exchangers. In fact, tetrodotoxin (2 μM) has no effect on the Glu‐or K+‐elicited response of IPs. Amiloride (>50 μM) and some of its derivatives similarly inhibit not only Glu‐and K+‐but also Carb‐evoked formation of IPs.
Neuronal Nicotinic Acetylcholine Receptors in Drosophila: Antibodies Against an α‐Like and a Non‐α‐Subunit Recognize the Same High‐Affinity α‐Bungarotoxin Binding Complex
Authors: Schloss Patrick , Betz Heinrich , Schroder Christiane , Gundelfinger Eckart D. 
Published: October 2006

Abstract: ALS and ARD proteins are thought to represent a ligand binding and a structural subunit, respectively, of Drosophila nicotinic acetylcholine receptors (nAChRs). Here, antibodies raised against fusion constructs encompassing specific regions of the ALS and ARD proteins were used to investigate a potential association of these two polypeptides. Both ALS and ARD antisera removed 20‐30% of the high‐affinity binding sites for the nicotinic antagonist 125I‐α‐bungarotoxin (125I‐α‐Btx) from detergent extracts of fly head membranes. Combinations of both types of antisera also precipitated the same fraction of α‐Btx binding sites, a result suggesting that both polypeptides are components of the previously defined class I 125I‐α‐Btx binding sites in the Drosophila CNS. 125I‐α‐Btx binding to a MS2 polymerase‐ALS fusion protein containing the predicted antagonist binding region showed that the ALS protein indeed constitutes the ligand binding subunit of a nicotinic receptor complex. These data are consistent with neuronal nAChRs in Drosophila containing at least two types of subunits, ligand binding and structural ones.
Adenosine Receptors in Myelin Fractions and Subtractions: The Effect of the Agonist (R)‐Phenylisopropyladenosine on Myelin Membrane Microviscosity
Authors: Casadó Vincent , Mallol Josefa , Lluis Carmen , Franco Rafael , Canela Enric I. 
Published: October 2006

Abstract: In this article the existence of A1 adenosine receptors and the absence of A2 adenosine receptors in myelin membranes purified from pig brain white matter are demonstrated. The characterization of (R)‐[3H]phenylisopropyladenosme ([3H]R‐PIA) binding to purified myelin fractions was performed. The distribution of high‐and low‐affinity species of the A1 adenosine receptor was different in heavy, medium, and light myelin. The fluidity of myelin subfractions and of pig brain cortical membranes was estimated; the microviscosity of heavy myelin (5.4 poises) and of cortical membranes (5.1 poises) was similar and less than that of medium (7.8 poises) and light (8.2 poises) myelin. It was also demonstrated that the agonist R‐PIA modifies the microviscosity of myelin membranes and that the degree of modification depends on the fluidity of the membrane assayed. These results suggest that adenosine receptors may have an important role in the functionality of myelin membranes.
Internal Ca2+ Mobilization by Muscarinic Stimulation Increases Secretion from Adrenal Chromaffin Cells Only in the Presence of Ca2+ Influx
Authors: Yamagami Kazuhiko , Nishimura Shigeto , Sorimachi Masaru 
Published: October 2006

Abstract: The cytosolic free Ca2+ concentration ([Ca2+]m) in single cat and bovine adrenal chromaffin cells was measured to determine whether or not there was any correlation between the [Ca2+]m and the catecholamine (CA) secretion caused by muscarinic receptor stimulation. In cat chromaffin cells, methacholine (MCh), a muscarinic agonist, raised [Ca2+]m by activating both Ca2+ influx and intracellular Ca2+mobilization with an accompanying CA secretion. In bovine cells, MCh elevated [Ca2+]m by mobilizing intracellular Ca2+but did not cause CA secretion. The MCh‐induced rise in [Ca2+]m in cat cells was much higher than that in bovine cells, but when Ca2+ influx was blocked, the rise was reduced, with a concomitant loss of secretion, to a level comparable to that in bovine cells. Intracellular Ca2+ mobilization due to muscarinic stimulation substantially increased secretion from depolarized bovine and cat cells, where a [Ca2+]m elevated above basal values was maintained by a continuous Ca2+influx. These results show that Ca2+ released from internal stores is not effective in triggering secretion unless Ca2+ continues to enter across the plasma membrane, a conclusion suggesting that secretion depends on [Ca2+]m in a particular region of the cell.
Histamine: A Neurotransmitter Candidate for Drosophila Photoreceptors
Authors: Sarthy P. Vijay 
Published: October 2006

Abstract: Recent experimental evidence suggests that histamine might be the synaptic transmitter used by invertebrate photoreceptors. In the present study, we have examined whether histamine is a transmitter candidate for Drosophila photoreceptors. Our findings are as follows; (a) Large amounts of histamine are synthesized by wild‐type heads, whereas heads from the eye‐deficient mutants, eyes absent and sine oculis, show reduced histamine synthesis, (b) Histidine de‐carboxylase activity is ⋍ 10‐fold higher in extracts of normal heads compared with that ia the mutants, (c) Histamine taken up by fly heads is metabolized into N‐acetylhistamine and imidazole‐4‐acetic acid, (d) Immunostaining of normal and sevenless heads with histamine‐specific antisera demonstrates that histamine is present in photoreceptors R1–6 and R8. (e) Histamine synthesized from exogenously supplied [3H]‐histidine can be released by depolarization with 50 mM K+, and the release is Ca2+ dependent. These observations strongly suggest that histamine is a major neurotransmitter used by Drosophila photoreceptors.
Cannabinoid Receptor‐Regulated Cyclic AMP Accumulation in the Rat Striatum
Authors: Bidaut‐Russell Michelle , Hewlett Allyn C. 
Published: October 2006

Abstract: The present study demonstrates that desacetyllevo‐nantradol, a synthetic cannabinoid analog, reduces cyclic AMP levels in rat striatal slices stimulated with vasoactive intestinal peptide or SKF 38393, a D1‐dopamine agonist. Desacetyllevonantradol and the D2 agonist LY 171555 both inhibited D1‐stimulated cyclic AMP accumulation in the striatum. Spipcrone, a specific D2‐dopamine antagonist, fully reversed the inhibitory effect of LY 171555 but not that of desacetyllevonantradol, indicating that this cannabinoid response is not occurring through a D2‐dopaminergic mechanism. Morphine also inhibited cyclic AMP accumulation in striatal slices stimulated with either SKF 38393 or vasoactive intestinal peptide. Naloxone, an opioid antagonist, fully reversed the effect of morphine but not that of desacetyllev‐onantradol, indicating that cannabinoid drugs are not acting via a mechanism involving opioid receptors. The response to maximally effective concentrations of desacetyllevonan‐tradol was not additive to that of maximally effective concentrations of either morphine or LY 171555, suggesting that dopaminergic, opioid, and cannabinoid receptors may be present on the same populations of cells.
Dopaminergic Receptors Linked to Adenylate Cyclase in Human Cerebromicrovascular Endothelium
Authors: Bacic Fatima , Uematsu Sumio , McCarron Richard M. , Spatz Maria 
Published: October 2006

Abstract: Cultured endothelium derived from three fractions of human cerebral microvessels was used to characterize dopamine (DA) receptors linked to adenylate cyclase activity. DA or D1 agonist, (±)‐SKF‐82958 hydrobromide, stimulated endothelial cyclic AMP formation in a dose‐dependent manner. The selective D, antagonist, (±)SCH‐23390, inhibited in a dose‐dependent manner the production of cyclic AMP induced by DA. The affinity for the D1 receptor appeared to be greater in endothelium derived from large and small microvessels than from capillaries. Cholera toxin ADP‐ribosylation of Gs proteins abolished the DA stimulatory effect on endothelial adenylate cyclase, whereas pertussis toxin ADP‐ribosylation enhanced the DA‐inducible formation, indicating the presence of both D1 and D2 receptors. Agonists of α1‐adrenergic receptors (phenylephrine, 6‐fluoronorepinephrine) or serotonin (5‐HT), which stimulated the production of cyclic AMP, had no additive effect on DA‐stimulated cyclic AMP formation. Incubation of these agents with DA produced the same or lower levels of cyclic AMP as compared to that formed by DA alone. The effect of α1‐adrenergic agonists or 5‐HT on DA production of cyclic AMP was partially prevented by the D2 antagonist, S(‐)‐sulpiride, or ketanserin (5‐HT2 > α1 > H1 antagonists), respectively. These findings represent the first demonstration of D1‐(stimulatory) and D2‐(inhibitory) receptors linked to adenylate cyclase in microvascular endothelium derived from human brain. The data also indicate that dopaminergic receptors can interact with either α1adrenergic or 5‐HT receptors in endothelium on the adenylate cyclase level. These results provide strong support for the previously contemplated existence of a central dopaminergic mechanism in cerebral vessels, a notion that is clinically important.
Stimulation of Transglutaminase Activity by GM1‐Ganglioside and α‐Sialylcholesterol in Superior Cervical and Nodose Ganglia Excised from Adult Rat
Authors: Ando Masato , Nakashima Yuhzo , Nagata Yutaka 
Published: October 2006

AbstractChanges in transglutaminase (TG) activity in superior cervical ganglia (SCG) and nodose ganglia (NG) excised from adult rats were examined following application of selected membrane transport‐altering agents, including GM1‐ganglioside (GM1) and α‐sialylcholesterol (α‐SC). Although TG activity of freshly dissected SCG and NG was relatively low, it increased gradually during 30 min of incubation, and it stayed at this elevated level for 2 h. Addition of α‐SC at its maximal effective concentration, 20 μM, stimulated TG activity more than eightfold in SCG and more than twofold in NG by 30 min. Addition of GM1 at its most effective concentration, 5 nM, had similar effects, but of lesser magnitude. Cydoheximide, a potent inhibitor of protein biosynthesis, did not affect the GM1‐or α‐SC‐evoked increases in ganglionic TG activity, suggesting that enzyme activation rather than synthesis of new enzyme was occurring. The stimulation of TG activity in both ganglia caused by either GM1 or α‐SC was associated with a decrease in Km and an increase in Vmax values. Addition of cholera toxin B. which specifically masks the oligosaccharide chain of GM1. reduced the GM1‐induced increase in TG activity by approximately 60% in SCG and 88% in NG. The α‐SC‐induced increase in TG activity was only partially mimicked by free cholesterol. Although application of either dibutyryl cyclic AMP or dibutyryl cyclic GMP produced little change in TG activity of either ganglion, phorbol ester clearly inhibited the enzymic activity. Because TG is a calcium‐dependent enzyme, we measured 45Ca2+ influx into either ganglion, and found that it was reduced by GM1 and a‐SC in SCG and by α‐SC in NG. The GM1‐induced decrease in 45Ca2+ influx was prevented by cholera toxin B in SCG, whereas the α‐SC‐induced decrease was not mimicked by cholesterol in either ganglion. These results suggest that the sialic acid moiety of GM1 and α‐SC is responsible for the activation of ganglionic TG and that activation may occur via a protein kinase C‐regulated pathway linked with calcium ion movement.
The Cysteine Residue in the Carboxyl‐Terminal Domain of the m2 Muscarinic Acetylcholine Receptor Is Not Required for Receptor‐Mediated Inhibition of Adenylate Cyclase
Authors: Van Koppen Chris J. , Nathanson Neil M. 
Published: October 2006

AbstractMuscarinic acetylcholine receptors (mAChRs) share with many other receptors of the guanine nucleotide‐binding protein‐coupled receptor family a highly conserved cysteine residue in the putative cytoplasmic carboxyl‐terminal region of the protein. Because elimination of this cysteine in the β2‐adrenergic receptor has been reported to decrease functional responsiveness, we determined if this cysteine residue is essential for mAChR‐effector coupling by replacing Cys457 of the m2 mAChR with glycine and expressing wild‐type and mutant receptor in Chinese hamster ovary (CHO) cells. The mutant and wild‐type receptors exhibited similar affinities for binding of muscarinic ligands. In addition, the mutation did not affect cell surface localization or receptor‐mediated inhibition of adenylate cyclase. These results indicate that the cysteine residue in the carboxyl‐terminal domain of the m2 mAChR is not required for ligand binding or mAChR‐mediated inhibition of adenylate cyclase in CHO cells.
Ryanodine Inhibits Caffeine‐Evoked Ca2+ Mobilization and Catecholamine Secretion from Cultured Bovine Adrenal Chromaffin Cells
Authors: Teraoka Hiroki , Nakazato Yoshikazu , Ohga Akira 
Published: October 2006

AbstractThe effects of ryanodine, a selective inhibitor of the Ca2+‐induced Ca2+ release mechanism, on caffeine‐evoked changes in cytosolic Ca2+ concentration ([Ca2+]i) and cate‐cholamine secretion were investigated using cultured bovine adrenal chromaffin cells. Caffeine (5–40 mM) caused a concentration‐dependent transient rise in [Ca2+]i and catecholamine secretion in Ca2+/Mg2+‐free medium containing 0.2 mM EGTA. Ryanodine (5 × 10–5M) alone had no effect on either [Ca2+]i or catecholamine secretion. Although the application of ryanodine plus caffeine caused the same increase in both [Ca2+]i and catecholamine secretion as those induced by caffeine alone, ryanodine (4 × 10–7–5 × 10–5M) irreversibly prevented the increase in both [Ca2+]i and catecholamine secretion resulting from subsequent caffeine application over a range of concentrations. The secretory response to caffeine was markedly enhanced by replacement of Na+ with sucrose in Ca2/Mg2+‐free medium, and this enhanced response was also blocked by ryanodine. Caffeine was found to decrease the susceptibility of the secretory apparatus to Ca2+ in digitonin‐permeabilized cells. These results indicate that caffeine mobilizes Ca2+ from intracellular stores, the function of which is irreversibly blocked by ryanodine, resulting in the increase in catecholamine secretion in the bovine adrenal chromaffin cell.
Pergolide Presynaptically Inhibits Calcium‐Stimulated Release of γ‐Aminobutyric Acid
Authors: Drew Kelly L. , Ungerstedt Urban 
Published: October 2006

AbstractThe release of γ‐aminobutyric acid (GABA) in rat dorsolateral striatum was studied using in vivo microdialysis. Dialysis was conducted 2 days after probe implantation in awake, freely moving rats using a modified Ringer solution. Calcium induced a reversible increase in GABA release that was abolished by tetrodotoxin but was only slightly attenuated by a maximally effective dose of pergolide, a D2 receptor agonist. It was thus concluded that pergolide inhibits calcium‐stimulated release of GABA presynaptically by a mechanism distinct from that of tetrodotoxin.