bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vivo Autoxidation of Dopamine in Guinea Pig Striatum Increases with Age
Authors: Fornstedt Bodil , Pileblad Erik , Carlsson Arvid 
Published: October 2006

AbstractCatechols are known to react readily with molecular oxygen to form the corresponding quinones together with reduced oxygen species. These products have been shown to be toxic in in vivo and in vitro systems. 5‐S‐Cysteinyl adducts of catechols are believed to be formed through the spontaneous reaction between quinones and thiol‐containing compounds, like cysteine and glutathione (GSH). Thus, the brain levels of these adducts probably indicate the autoxidation rate of catechols in vivo. In the present study, the striatal concentrations of 5‐S‐cysteinyldopamine (5‐S‐cysteinyl‐DA), 5‐S‐cysteinyl‐3,4‐dihydroxyphenylalanine (5‐S‐cysteinyl‐DOPA), and 5‐S‐cysteinyl‐3,4‐dihydroxyphenylacetic acid (5‐S‐cysteinyl‐DOPAC) were determined in 2‐week‐, 2‐month‐and 3‐year‐old guinea pigs. In addition, brain levels of DA, the DA metabolite DOPAC, and GSH were assessed. The concentration of 5‐S‐cysteinyl‐DA increased markedly with age. The 3‐year‐old guinea pigs had the highest level, i.e., 248% of the concentration in the 2‐week‐old animals and 219% of the concentration in the 2‐month‐old animals. Furthermore, the striatal 5‐S‐cysteinyl‐DOPA level in the 3‐year‐old group was 68% higher than in the 2‐week‐old group and 46% higher than in the 2‐month‐old group. No age difference in the striatal concentration of DA was found. In contrast, the concentration of DOPAC increased with age: The DOPAC level in the 3‐year‐old animals was 153% of the level in the 2‐week‐old animals and 116% of the level in the 2‐month‐old animals. A slight decrease in brain GSH content was observed between 2 weeks and 2 months, whereas the level in the 3‐year‐old animals was not significantly different from the concentration in the 2‐month‐old animals. Thus, the present study has shown an increase in 5‐S‐cysteinyl‐DA and 5‐S‐cysteinyl‐DOPA levels with age in guinea pig striatum. The rise in 5‐S‐cysteinyl‐DA content was larger than the increase in content of the DA metabolite DOPAC, a finding indicating that DA to a greater extent undergoes autoxidation with increasing age. This may be part of the mechanism underlying the loss of dopaminergic neurons in senescence and in Parkinson's disease.
Cyclic AMP‐Dependent Induction of Serotonin N‐Acetyltransferase Activity in Photoreceptor‐Enriched Chick Retinal Cell Cultures: Characterization and Inhibition by Dopamine
Authors: Iuvone P. Michael , Avendano Gary , Butler Bonnie Johnson , Adler Ruben 
Published: October 2006

AbstractThe activity of serotonin N‐acetyltransferase (NAT), a key regulatory enzyme in the melatonin biosynthetic pathway, was examined in low‐density monolayer cultures of chick embryo retinal cells prepared with three levels of photoreceptor enrichment. In cultures prepared from embryonic day 8 retinas (E8), photoreceptors represented approximately 30% of the total cell population, whereas in those prepared from embryonic day 6 retinas (E6), approximately 70% of the cells were photoreceptors. In E8 retinas treated with kainic acid to destroy neurons (E8K), the relative content of photoreceptors was increased to approximately 50%. NAT activity was detectable in the cultures under all conditions studied, and was markedly increased by drugs that increase intracellular cyclic AMP levels and cyclic AMP‐dependent protein kinase activity: 8‐bromocyclic AMP, forskolin, and 3‐isobutyl‐1‐methylxanthine (IBMX). Consistent with the hypothesis that NAT is localized in photoreceptors, the effects of the stimulatory treatments were significantly greater in E6 and E8K cultures than in E8 cultures. The stimulation of NAT activity in E6 cultures was inhibited by actinomycin D and cycloheximide, suggesting the involvement of RNA and protein synthesis. Dopamine inhibited the induction of NAT activity by forskolin and IBMX, but not that elicited by 8‐bromocyclic AMP. The dopamine‐mediated suppression of activity was significantly inhibited by pertussis toxin and by spiperone and sulpiride, both D2‐dopamine receptor antagonists, but not by SCH 23390, a D1‐dopamine receptor blocker, or antagonists of α‐adrenergic, β‐adrenergic, or serotonergic receptors. Because the inhibitory effect of dopamine on E6 and E8K cultures was at least as great as that on E8 cultures, the results suggest that dopamine acts on D2‐like receptors on photoreceptors. The receptors appear to be coupled to adenylate cyclase through an inhibitory GTP‐binding protein and to mediate inhibition of cyclic AMP synthesis and consequent induction of NAT activity.
Comparison of α1‐Adrenergic Receptor‐Stimulated Inositol Phosphate Formation in Primary Neuronal and Glial Cultures
Authors: Wilson Karen M. , Gilchrist Siobhan , Minneman Kenneth P. 
Published: October 2006

Abstractα1‐Adrenergic receptor binding sites and norepinephrine‐stimulated 3H‐inositol phosphate (3H‐InsP) accumulation were measured in primary cultures of neurons and glia from 1‐day‐old rat brains. The density of α1‐adrenergic receptor binding sites was ˜three times higher in membranes from neurons compared to glia. Although norepinephrine was slightly more potent in stimulating 3H‐InsP formation in neurons than in glia, the maximal response was greater in glial cells. Norepinephrine‐stimulated 3H‐InsP formation remained constant for [3H]inositol prelabelling periods of 1–14 days in neurons, whereas the response increased with time in glia and was maximal after 7–10 days of prelabelling. Both the incorporation of [3H]inositol into lipid and basal levels of 3H‐InsPs were lower in glial cells than in neurons, which accounted for the greater percent stimulation in glia. Pre‐treatment with phenoxybenzamine decreased norepinephrine‐stimulated 3H‐InsP formation in a dose‐dependent manner in both neurons and glia by decreasing the maximal response without altering potency. HPLC separation showed that similar types of 3H‐InsPs were accumulated in neurons and glial cells. These results demonstrate that α1‐adrenergic receptors exist on both neurons and glial cells and activate 3H‐InsP accumulation in both cell types. Although receptor density is higher in neurons than in glia, the 3H‐InsP response is higher in glia. This difference does not appear to be due to different receptor reserves, but may be due to differential coupling mechanisms in the two cell types.
Modulation of Protein Kinase C Translocation by Excitatory and Inhibitory Amino Acids in Primary Cultures of Neurons
Authors: Vaccarino Flora M. , Liljequist Sture , Tallman John F. 
Published: October 2006

AbstractIn primary cultures of neurons from rat cerebral cortex and neostriatum, excitatory amino acids stimulate the translocation of protein kinase C (PKC) from the cytoplasm to the membrane. In the presence of a physiological concentration of Mg2+ in the extracellular medium, glutamate induces PKC translocation by binding to both TV‐methyl‐D‐aspartate (NMDA) and α‐amino‐3‐hydroxy‐5‐methylisoxazolepropionic acid (AMPA) excitatory amino acid receptors. Quisqualate translocates the enzyme by stimulating primarily AMPA receptors and possibly metabotropic receptors. NMDA receptor‐induced PKC translocation is sodium independent, whereas quisqualate receptor‐induced PKC translocation is sodium dependent; none of the agonists is active in the absence of calcium from the extracellular medium. Muscimol does not modify excitatory amino acid stimulation; however, blockade of γ‐aminobutyric acidA receptors by bicuculline greatly enhances glutamate‐induced PKC translocation. This enhancement is blocked by the NMDA receptor antagonist (+)‐5‐methyl‐10, 11‐dihydro‐5H‐ dibenzo[a,d]cyclohepten‐5, 10‐imine hydrogen maleate (MK‐801) and by tetrodotoxin.
Purification and Properties of p 103, a Novel 103‐kDa Component of Postsynaptic Densities
Authors: Hayes Nandini V. L. , Rayner Denise A. , Baines Anthony J. 
Published: October 2006

AbstractA 103‐kDa protein present in membrane cytoskeletal preparations from bovine brain has been identified. We have purified this protein to >95% homogeneity using gel filtration and ion‐exchange chromatography. This protein, p 103, is an asymmetric dimer in dilute solution and has two major variants that can be distinguished by isoelectric focussing, pI 5.60 and 5.75. Using subcellular fractionation, it is most enriched in postsynaptic densities. Immunolocalization with anti‐p 103‐specific antibodies reveals that it is confined to the dendrites and perikarya; it is apparently absent from spinal cord axons. It coextracts from brain membrane‐skeletal preparations with brain spectrin and actin, but in vitro, it does not interact with them.
Changes Induced in Astrocyte Cathepsin D by Cytokines and Leupeptin
Authors: Whitaker J. N. , Herman P. K. , Sparacio S. M. , Zhou S. R. , Benveniste E. N. 
Published: October 2006

AbstractCathepsin D is widely, but unevenly, distributed among cells and is capable of degrading a number of neural peptides and proteins. The present study was undertaken to examine the level of cathepsin D in astrocytes that might be relevant to its induction in inflammatory demyelination. Primary astrocytes were cultured from neonatal rat cerebrums according to the method of McCarthy and de Vellis. Based on staining for cell markers, cultures were >95% astrocytes and <3% microglia. Under serum‐free conditions, leupeptin induced a 1.4‐ to 2.0‐fold increase, maximal by 48 hours, in cathepsin D protein quantified by a radioimmunoassay. Cathepsin D enzymatic activity, inhibitable by pepstatin, also increased. Northern blot analysis demonstrated that leupeptin also increased cathepsin D mRNA expression. Kinetic analysis indicated that maximal cathepsin D mRNA levels are detected 24 h after stimulation with leupeptin. Exposure of astrocytes under the same conditions to rat recombinant interferon‐γ, human recombinant tumor necrosis factor‐α, human recombinant interleukin‐1β, lipopolysaccharide, calcium ionophore, or a combination of these reagents did not increase the level of cathepsin D above controls. These results indicate that astrocytic cathepsin D mRNA and protein can be induced by selected materials. Furthermore, the effects attributed to leupeptin as a proteinase inhibitor may be modified by its ability to increase cathepsin D activity.
Retrograde Axonal Transport of Locally Synthesized Phosphoinositides in the Rat Sciatic Nerve
Authors: Padilla Stephanie , Pope Carey N. 
Published: October 2006

AbstractAlthough autoradiography has demonstrated local incorporation of [3H]inositol into axonal phospholipids after intraneural injection, retrograde axonal transport of phosphatidylinositol has only been demonstrated after injection of lipid precursor into the cell body regions (L4 and L5 dorsal root ganglia) of the sciatic nerve. We now report the retrograde axonal transport of inositol phospholipids synthesized locally in the axons. Following microinjection of myo‐[3H]inositol into the rat sciatic nerve (50–55 mm distal to L4 and L5 dorsal root ganglia), a time‐dependent accumulation of 3H label occurred in the dorsal root ganglia ipsilateral to the injection site. The ratio of dpm present in the ipsilateral dorsal root ganglia to that in the contralateral dorsal root ganglia was not significantly different from unity between 2 and 8 h following isotope injection but increased to 10–12‐fold between 24 and 72 h following precursor injection. By 24 h following precursor injection, the ipsilateral/contralateral ratio of the water‐soluble label in the dorsal root ganglia still remained ∼ 1.0, whereas the corresponding ratio in the chloroform/methanol‐soluble fraction was ∼20. The time course of appearance of labeled lipids in the ipsilateral dorsal root ganglia after injection of precursor into the nerve at various distances from the dorsal root ganglia indicated a transport rate of at least 5 mm/h. Accumulation of label in the dorsal root ganglia could be prevented by intraneural injection of colchicine or ligation of the sciatic nerve between the dorsal root ganglia and the isotope injec tion site. These results demonstrate that inositol phospholipids synthesized locally in the sciatic nerve are retrogradely transported back to the nerve cell bodies located in the dorsal root ganglia.
Purification and Characterization of a Nonvesicular Vesamicol‐Binding Protein from Electric Organ and Demonstration of a Related Protein in Mammalian Brain
Authors: Hicks Barry W. , Rogers Gary A. , Parsons Stanley M. 
Published: October 2006

AbstractA protein that binds vesamicol has been purified from a soluble fraction of the Torpedo electric organ homogenate that docs not contain synaptic vesicles. The purified vesamicol‐binding protein (VBP) has a molecular mass of 470 kDa composed of 30‐ and 24‐kDa subunits. Chemical deglycosylation yielded a single, heterogeneous protein of 24 kDa. The 30‐kDa subunit is also sensitive to endo‐β‐galactosidase. The dissociation constant of the VBP vesamicol complex is 0.9 μM, and the Bmax is 5,500 pmol/mg. Antiserum raised to the 30‐kDa subunit cross‐reacts with the 24‐kDa subunit, but not with synaptic vesicles. Drug binding studies and Western blot analysis show that VBP is present in other Torpedo tissues as well as mammalian brain. Immunofluorescence microscopy demonstrates that VBP‐like immunoreactivity is not localized exclusively to the nerve terminal regions of the electric organ. Thermal stability, the pH dependence of vesamicol binding, and pharmacological comparisons demonstrate that the VBP is not the cholinergic synaptic vesicle receptor for vesamicol. The implications of this finding for current efforts to develop in vivo diagnostics of cholinergic nerve terminal status based on vesamicol are discussed.
Effect of Soman and Sarin on Phosphatidylcholine Asymmetry in the Electroplax from the Electric Eel
Authors: Supernovich Carrie , Grain Richard , Rosenberg Philip 
Published: October 2006

AbstractSome effects of organophosphorus anticholinesterase compounds that are unrelated to cholinesterase inhibition and that are sometimes long lasting may be due to alterations at the cellular membrane level. Phosphatidylcholine exchange protein was used to assess the effects of sarin and soman on Phosphatidylcholine asymmetry in the inner and outer leaflets of the plasma membrane bilayer of the electroplax. Exposure of electroplax (30 min in vitro) to soman (10−4, 10−6M) or sarin (10−4, 10−6, 5 × 10−9M) increased the percentage of Phosphatidylcholine in the outer monolayer of the innervated plasma membrane bilayer and decreased the percentage in the inner monolayer. These changes by sarin were observed at concentrations that produced 100% cholinesterase inhibition (10−4, 10−6 M) and at a concentration (5 × 10−9 M) where no inhibition occurred, suggesting that these effects are not directly due to cholinesterase inhibition. A 1‐week exposure of live eels to soman (10−8M) in vivo caused an increase in Phosphatidylcholine labeling in the outer monolayer of the innervated and noninnervated surfaces of the electroplax. Two weeks after stopping exposure to soman, increased labeling was still observed, suggesting that this may be a long‐term effect. Because the organophosphates did not increase the permeability of the electroplax, all of these changes in labeling appear to be due to a redistribution of Phosphatidylcholine from the inner to the outer monolayer of the plasma membrane bilayer.
One‐Line Monitoring of Extracellular Brain Glucose Using Microdialysis and a NADPH‐Linked Enzymatic Assay
Authors: van der Kuil Jan H. F. , Korf Jakob 
Published: October 2006

AbstractA method to monitor extracellular glucose in freely moving rats, based on intracerebral microdialysis coupled to an enzyme reactor is described. The dialysate is continuously mixed with a solution containing the enzymes hexokinase and glucose‐6‐phosphate dehydrogenase, and the fluorescence of NADPH formed enables the on‐line registration of extracellular glucose. The method is applied to monitor changes in extracellular brian glucose during the infusion of glucose, electrically induced seizure, immobilization stress, and repetitive hypoxia. After glucose loading or after seizure, hippocampus dialysate glucose concentration was increased transiently. During immobilization, there was a short‐lasting decrease and, therafter, an increase in the extracellular hippocampus glucose. During repetitive hypoxia in rats with a unilaterally occluded carotid artery, the content of glucose of striatal dialysates followed closely changfes in blood pressure. These results illustrate the usefulness of the method in studying changes in brain glucose concentrations underpathological and physiological conditions.
Increase in β‐1,4‐Galactosyltransferase Activity During PC12 Cell Differentiation Induced by Forskolin and 2‐Chloroadenosine
Authors: Roth Jerome A. , Marcucci Kenda , Lin Wei‐hsung , Napoli Joseph L. , Wagner John A. , Rabin Richard 
Published: October 2006

AbstractGalactosyltransferase (GAL Tase) activity was measured in differentiating PC12 cells induced by either forskolin or 2‐chloroadenosine. The specific activity of GALTase in whole cells and isolated Golgi membranes increased as early as 3 h after initiating treatment with 2‐chloroadenosine, and maximal activity was reached at approximately 12 h. In two mutant PC12 cell lines deficient in protein kinase A, both forskolin and 2‐chtoroadenosine failed to increase GALTase activity. The adenosine A2 receptor antagonist, xanthine amine congener, prevented 2‐chloroadenosine stimulation of GALTase, demonstrating that this adenosine derivative was mediating its effect via the A2 receptor. These data suggest that GALTase activity during PC12 cell differentiation is regulated by cyclic AMP (cAMP)‐ and protein kinase A‐dependent processes. In support of the role of cAMP in regulating GALTase activity were studies with murine F9 carcinoma cells demonstrating that the greatest stimulation of GALTase activity occurred with cells treated with both retinoic acid and dibutyryl cAMP.
The Slow Cyclic GMP Increase Caused by Serotonin in NG108‐15 Cells Is Not Inhibited by Antagonists of Known Serotonin Receptors: Possible Existence of a New Receptor Subtype Coupled with Membrane‐Bound Guanylate Cyclase
Authors: Tohda Michihisa , Sakuma Ichiro , Nomura Yasuyuki 
Published: October 2006

AbstractCharacterization of the serotonin (5‐HT>induced cyclic GMP (cGMP) elevation was investigated in comparison with bradykinin‐ and ANP‐induced elevations in NG108‐15 cells. At 20 s, l,2‐bis(2‐aminophenoxy)ethaae‐N,N,N′,N′‐tetraaoetic acid tetraacetoxymethyl ester (BAPTA‐AM, 100 μM), a membrane‐permeabilized Ca2+ chelator, or N‐monomethyl‐L‐arginine (NMMA, 300 μM), an inhibitor of L‐arginine‐derived nitric oxide (NO) synthesis, inhibited 5‐HT‐induced elevation by approximately 40%, and completely inhibited bradykinin‐induced response. Neither 5‐HT‐ nor ANP‐induced cGMP elevation at 10 rain was affected by BAPTAAM or NMMA. The cGMP elevated by 5‐HT as well as by ANP was effluxed to the extracellular medium. These results and our previous report suggest that 5‐HT stimulates two subtypes of 5‐HT receptors in NG108‐15: first, 5‐HT3 subtype stimulating Ca2+‐sensitive cytosolic guanylate cyclaje through NO derived from L‐arginine and second, a probably novel 5‐HT receptor subtype involved in activation of membrane‐bound guanylate cyclase.
Involvement of Nerve Growth Factor and Its Receptor in the Regulation of the Cholinergic Function in Aged Rats
Authors: Alberch Jordi , Pérez‐Navarro Esther , Arenas Ernest , Marsa Jordi 
Published: October 2006

Abstract: The role of nerve growth factor (NGF) and its receptor (NGFR) in the regulation of cholinergic activity has been studied during the aging process. NGFRs were quantified in cortical membranes using a radioactive binding assay. NGF levels and choline acetyltransferase (ChAT) activity were determined in cortex, hippocampus, neostriatum, and septum. These assays were performed in both adult (6‐month‐old) and aged (36‐month‐old) rats. High‐and low‐affinity 125I‐NGF binding sites were present in cortex of adult and aged rats. Furthermore, we observed a decrease in number and affinity of both NGFRs in aged rats. ChAT activity in these rats was lower (⋍30%) than in adult rats in all the brainregions examined. NGF levels were not modified in cortex and hippocampus and were decreased in neostriatum (55%) and septum (35%). In conclusion, our results suggest that, during the aging process, the cholinergic impairment is related to a decrease in NGF levels in neostriatum but not in cortex and hippocampus. The reduction in level of NGF protein in septum could be due to a decrease in number of high‐affinity 125I‐NGF binding sites.
Tryptophan Hydroxylase Synthesis Is Induced by 3′, 5′‐Cyclic Adenosine Monophosphate During Circadian Rhythm in the Rat Pineal Gland
Authors: Ehret Mireille , Pevet Paul , Maitre Michel 
Published: October 2006

Abstract: Tryptophan hydroxylase in the rat pineal gland undergoes diurnal rhythmic activity. Rat pineal glands exhibit increased tryptophan hydroxylase activity when incubated with a cyclic AMP analogue in vitro. Cyclic AMP‐dependent protein kinase phosphorylates tryptophan hydroxylase, purified from rat brain, without any modification of its enzyme activity under our experimental conditions. Actinomycin O or cydoheximide decreases the stimulating effect of the cyclic AMP analogue on pineal tryptophan hydroxylase activity. Incubation of pineal glands in the presence of [35S]mcthionine showed a cyclic AMP‐induced increase in tryptophan hydroxylase synthesis. These results explain the circadian rhythm of tryptophan hydroxylase activity in the rat pineal gland and suggest that the regulation of tryptophan hydroxylase expression by cyclic AMP occurs probably either at the translational level or via transient expression of a transcriptional regulatory element
Differential Involvement of the Arachidonic Acid Cascade on the α1‐Adrenergic Potentiation of Vasoactive Intestinal Peptide‐Versus β‐Adrenergic‐Stimulated Cyclic AMP and Cyclic GMP Accumulation in Rat Pinealocytes
Authors: Chik Constance L. , Young Indranie , Ho Anthony K. 
Published: October 2006

Abstract: In the rat pineal gland, α1‐adrenergic agonists, which stimulate arachidonic add release, also potentiate vasoactive intestinal peptide.(VIP)‐or β‐adrenergic‐stimulated cyclic AMP (cAMP) and cyclic GMP (cGMP) accumulation. In this study, the possible involvement of the arachidonic acid pathway in the potentiation mechanism was examined in dispersed rat pinealocytes using two inhibitors of the arachidonic acid cascade, indomethacin and nordihydroguaiaretic acid. These two inhibitors appeared to have differential effects on the α1‐adrenergic potentiation of VIP‐or β‐adrenergic‐stimulated cAMP and cGMP responses. Whereas nordihydroguaiaretic acid was effective in suppressing both the α1‐adrenergic potentiation of VIP‐or β‐adrenergic‐stimulated cAMP and cGMP responses, indomethacin inhibited selectively the VIP‐mediated cAMP and cGMP responses. The role of arachidonic acid metabolites was further determined using several prostaglandins—A2, I2, E2, and F2α—and leukotrienes—B4, C4, and D4. Of the seven compounds tested, prostaglandins E2 and F2α stimulated basal cAMP but not cGMP accumulation. The prostaglandin E2‐and F2α‐stimulated cAMP responses were additive to those stimulated by VIP or β‐adrenergic receptors. The other five compounds had no effects on basal or VIP‐or β‐adrenergic‐stimulated cAMPor cGMP accumulation. Taken together, these findings indicate that the arachidonic acid cascade is likely involved in the α1‐adrenergic potentiation of VIP‐or β‐adrenergic‐stimulated cAMP and cGMP accumulation. However, the specific arachidonic acid metabolite involved in the potentiation mechanisms of VIP‐versus β‐adrenergic‐stimulated cyclic nucleotide responses may be different.