bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of l‐3,4‐Bihydroxyphenylalanine by Tyrosine Hydroxylase cDNA‐Transfected C6 Cells: Application for Intracerebral Grafting
Authors: Uchida Kohichi , Takamatsu Ken , Kaneda Norio , Toya Shigeo , Tsukada Yasuzo , Kurosawa Yoshikazu , Fujita Keisuke , Nagatsu Toshiharu , Kohsaka Shinichi 
Published: October 2006

AbstractIn the present study, we obtained genetically manipulated nonneuronal cells which synthesize a catecholamine precursor for future use in intracerebral grafting. Human type 1 tyrosine hydroxylase (TH; EC 1.14.16.2) cDNA was inserted into eukaryotic expression vector pKCRH2 and was co‐transfected into C6 cells with plasmid pSV2neo. Expression of the TH minigene was screened by immuno‐histochemical staining with TH antibody and immunoblot‐ting analysis. Several clones of the C6 transfectahts that produce TH molecules were obtained. These cells showed TH activity, and the product, L‐3,4‐dihydroxyphenylalanine (L‐DOPA), was detected intracellulary due to the ajbsence of L‐amino acid decarboxylase (EC 4.1.1.28) activity. It was found that a large amount of L‐DOPA was released from the cells into the culture medium. These transfectants were transplanted into rat brain, and the expression of TH was examined immunohistochemically. On the 10th day following transplantation, a mass of C6 cells which was heavily stained with TH antibody was observed in the brain. These findings may provide us with an opportunity to investigate the effects of intracerebral transplantation of nonneuronal cells that produce catecholamine or its precursor.
Muscarinic and Quisqualate Receptor‐Induced Phosphoinositide Hydrolysis in Primary Cultures of Striatal and Hippocampal Neurons. Evidence for Differential Mechanisms of Activation
Authors: Ambifosini Anna , Meldolesi Jacopo 
Published: October 2006

AbstractSeveral neurotransmitters activate polyphosphoinositide (PPI) hydrolysis in CNS neurons as the first step of a transmembrane signalling cascade that may lead to neuronal ircuit modulation. Muscarinic and quisqualate rejceptor‐riggered PPI hydrolysis was investigated in neuronal primary cultures. A clear increase in inositol phosphates (Ins‐Ps) was detected as early as 15 s after the agonist addition;! at this time, the increases of inositol 1,4,5‐trisphosphate (measured by HPLC) were relatively larger with respect to the other Ins‐Ps. Ins‐P accumulation was maintained in part in a. Ca2+‐free medium, excluding that Ca2+ entry is the fundamental step of the receptor‐induced PPI hydrolysis. Acute dell pre‐treatment with phorbol dibutyrate, an activator of protein kinase C, was able to inhibit 50% of the response to carbachol, and almost completely the quisqualate effect, suggesting a negative feedback modulation by the enzyme. Finaljly, per tussis toxin failed to inhibit muscarinic responses, whereas it blocked ±70% of the quisqualate stimulation. The two receptors therefore appear coupled to phosphodiesterase by two different G proteins. The comparison of the results obtained by stimulating the two receptor systems suggests that the generation of the same intracellular signal at two distinct receptor types may occur by different coupling mechanisms, and be differently regulated even in the same neuronal preparations.
Differential Effects of Iodide and Chloride on Allosteric Interactions of the GABAA Receptor
Authors: Abel Marc S. , Blume Arthur J. , Garrett Kennon M. 
Published: October 2006

Abstract t‐[35S]Butylbicyclophosphorothionate ([35S]TBPS) has been shown to bind to the GABAA receptor complex. The binding is modulated allosterically by drugs that interact at components of the receptor complex. The present studies were designed to evaluate the influence of ionic environment and state of equilibrium on the allosteric modification of [35S]TBPS binding. In both I‐ and Cl‐ under nonequilibrium conditions, diazepam, γ‐aminobutyric acid (GABA), and pentobarbital (PB) stimulate and methyl 6,7‐dimethoxy‐4‐ethyl‐β‐carboline‐3‐carboxylate (DMCM) inhibits [35S]TBPS binding. In addition, there is an inhibitory component to the effect of GABA and PB at higher drug concentrations. These effects are blocked by the appropriate antagonists for each drug. In Cl‐, the stimulation of [35S]TBPS binding by drugs disappears at equilibrium, whereas the inhibition by GABA and PB persists. The inhibitory effect of DMCM in Cl‐ also disappears at equilibrium. When assayed in I‐ at equilibrium. however, DMCM stimulates [35S]TBPS binding. In addition, bicuculline, which is without effect under nonequilibrium conditions in either Cl‐ or I‐, stimulates [35S]TBPS binding in I‐ at equilibrium. The persistent effects of DMCM, bicuculline, and GABA in I‐ are accompanied by alterations in the affinity of [35S]TBPS for its receptor. In addition, the stimulation of [35S]TBPS binding by GABA is associated with a decreased number of [35S]TBPS binding sites. These data demonstrate that receptor complex interactions with anions influence the responsiveness to drug binding.
Effects of Dihydropyridine Calcium Channel Ligands on Rat Brain γ‐Aminobutyric AcidB Receptors
Authors: Al‐Dahan Muna I. , Thalmann Robert H. 
Published: October 2006

AbstractThis study shows that low nanomolar concentrations of the calcium channel antagonist nifedipine displaced [3H]baclofen labeling of γ‐aminobutyric acidB (GABAB) receptors, whereas similar concentrations of two calcium channel agonists stimulated this GA‐BAB receptor labeling. Neither effect was likely to be due to dihydropyridine (DHP) binding to baclofen recognition sites, because the inhibitory ligand nifedipine primarily affected apparent receptor density rather than affinity. Although these results could reflect the coupling of GABAB receptors with calcium channels, they do not rule out other, possibly more direct interactions between GABAB receptors and DHP binding sites. These DHP effects occur at much lower concentrations and display other significant differences from previously reported effects of DHPs on other transmitter receptors.
Use of Microdialysis for Monitoring Tyrosine Hydroxylase Activity in the Brain of Conscious Rats
Authors: Westerink B. H. C. , De Vries J. B. , Duran R. 
Published: October 2006

Abstract:An on‐line microdialysis system was developed which monitored the 3,4‐dihydroxyphenylalanine (DOPA) formation in the striatum during infusion of a submicromolar concentration of an l‐aromatic amino‐acid decarboxylase inhibitor (NSD 1015). The absence of DOPA in dialysates of 6‐hydroxydopamine‐pretreated rats and the disappearance of DOPA after administration of α‐methyl‐p‐tyrosine indicated that the dialyzed DOPA was derived from dopaminergic nerve terminals. Next we investigated whether the steady‐state DOPA concentration in striatal dialysates could be considered as an index of tyrosine hydroxylase activity. The increase in DOPA output after intraperitoneal administration of haloperidol or γ‐butyrolactone and the decrease in DOPA output after intraperitoneal administration of apomorphine are in excellent agreement with results of postmortem studies, in which a decarboxylase inhibitor was used to measure the activity of tyrosine hydroxylase. The effect of haloperidol on DOPA formation was not visible when a U‐shaped cannula (0.80 mm o.d.) was used. Some methodological problems related to microdialysis of the haloperidol‐induced increase in DOPA formation are discussed. We concluded that the proposed model is a powerful and reliable in vivo method to monitor tyrosine hydroxylase activity in the brain. The method is of special interest for investigating the effect of compounds which are not able to pass the blood‐brain barrier. As an application of the method in the latter situation, we report the effect of infusion the neurotoxin 1‐methyl‐4‐phenylpyridinium ion (10 mmol/L infused over 20 min) on the activity of striatal tyrosine hydroxylase.
Lipid Compositions of Different Regions of the Human Brain During Aging
Authors: Söderberg M. , Edlund C. , Kristensson K. , Dallner G. 
Published: October 2006

Abstract:The neutral and phospholipid compositions of various regions of the human brain were analyzed using autopsy material covering the life period between 33 and 92 years of age. The protein content was also measured and, on a weight basis, this content is unchanged in the cerebellum, pons, and medulla oblongata, whereas in the 90‐year‐old group it decreases in the hippocampus, gray matter, and nucleus caudatus. In white matter, the protein content decreases continuously with age. The phospholipid composition is characteristic of the region investigated, but remains unchanged during aging. The total phospholipid content exhibits only a 5–10% decrease in the oldest age group. The content of dolichol and its polyisoprenoid pattern are also characteristic of the region analyzed. Between 33 and 92 years of age, the amount of dolichol in all portions of the brain increases three‐to fourfold, but the isoprenoid pattern remains constant. The level of dolichyl‐P varies between different regions, but only a moderate increase is seen with age. Ubiquinone content is highest in the nucleus caudatus, gray matter, and hippocampus, and in all areas this content is decreased to a great extent in the oldest age groups. All regions of the human brain are rich in cholesterol, but alterations in the amount of this lipid are highly variable during aging, ranging from no change to a 40% decrease.
Synthesis of Apolipoprotein A‐1 in Pig Brain Microvascular Endothelial Cells
Authors: Weiler‐Güttler Hartmut , Sommerfeldt Michaela , Papandrikopoulou Anastasia , Mischek Uwe , Bonitz Dorothea , Frey Andreas , Grupe Matthias , Scheerer Joachim , Gassen Hans G. 
Published: October 2006

Abstract:In an approach toward the identification of hitherto unknown proteins involved in the function of the blood–brain barrier, we constructed a pig brain microvessel‐derived cDNA library that is enriched in blood–brain barrier specific sequences by means of subtractive cloning. Sequence analysis of selected clones revealed that one of the cDNAs encoded porcine apolipoprotein (apo) A‐1. The identity of apo A‐1 mRNA was further confirmed by in vitro translation of RNA from brain microvascular endothelial cells and subsequent immunoprecipitation with an antibody against human apo A‐1. We further investigated the expression of apo A‐1 mRNA in several tissues and in endothelial cells of the pig. It is shown that cultured brain microvascular endothelial cells provide an in vitro model to study the expression and function of apo A‐1 in the microvasculature of the brain.
Glutamate Increases Glycogen Content and Reduces Glucose Utilization in Primary Astrocyte Culture
Authors: Swanson Raymond A. , Yu Albert C. H. , Chan Pak H. , Sharp Frank R. 
Published: October 2006

Abstract:The glycogen content of primary cultured astrocytes was approximately doubled by incubation with 1 mM L‐glutamate or L‐aspartate. Other amino acids and excitatory neurotransmitters were without effect. The increase in glycogen level was not blocked by the glutamate receptor antagonist kynurenic acid but was completely blocked by the glutamate uptake inhibitor threo‐3‐hydroxy‐D,L‐aspartate and by removal of Na+ from the medium. Incubation with radiolabeled glucose and glutamate revealed that the increased glycogen content was derived almost entirely from glucose. Glutamate at 1 mM was also found to cause a 53 ± 12% decrease in glucose utilization and a 112 ± 69% increase in glucose‐6‐phosphate levels. These results suggest that the glycogen content of astrocytes is linked to the rate of glucose utilization and that glucose utilization can, in turn, be affected by the availability of alternative metabolic substrates. These relationships suggest a mechanism by which brain glycogen accumulation occurs during decreased neuronal activity.
12‐O‐Tetradecanoylphorbol 13‐Acetate and Forskolin Modify Muscarinic Receptor‐Linked Ca2+ Mobilization in SH‐SY5Y Neuroblastoma Cells Through Different Mechanisms
Authors: Åkerman Karl E. O. , Heikkilä Jari E. 
Published: October 2006

Abstract:The phorbol ester, 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), which causes differentiation of SH‐SY5Y neuroblastoma cells, reduces carbachol binding and carbachol‐stimulated Ca2+ mobilization in these cells. The decrease in responsiveness to carbachol is due partially to a reduction in the amount of Ca2+ released by the cells and partially to a decrease in the sensitivity of the cells to carbachol. These effects probably can be attributed to a reduction in muscarinic receptor number and a decrease in receptor affinity, respectively. Forskolin, an alkaloid known to cause an increase in cellular cyclic AMP, enhances Ca2+ influx into the cells without affecting the cytosolic free Ca2+ concentration. The alkaloid causes an apparent restoration of the reduced Ca2+ release, caused by TPA, but does not affect the sensitivity of the cells to carbachol. Forskolin increases the decay of carbachol‐induced increase in cytosolic Ca2+. The effects of TPA appear to be linked directly to receptor function, whereas those of forskolin are due to the effect of cyclic AMP on cellular Ca2+ metabolism.
Tetrasialoganglioside GQ1b Reactive Monoclonal Antibodies: Their Characterization and Application for Quantification of GQ1b in Some Cell Lines of Neuronal and Adrenal Origin(S)
Authors: Yamamoto Hideki , Tsuji Shuichi , Nagai Yoshitaka 
Published: October 2006

Abstract:Seven monoclonal antibodies (MAbs) directed tetrasialoganglioside (GQ1b) were established, purified GQ1b being used for immunization and hybridoma screening. All of the MAbs reacted strongly with GQ1b, although they also reacted with other gangliosides, with different specificities and reactivities. Some MAbs (1H10, 2C7, and 3F4) reacted with GD3, GT1a, GQ1b, and GP1c. MAb 1H4 showed broad specificity. It reacted with GD3, GD1b, GD2, GT1a, GT1b, GQ1b, GQ1c, and GP1c. MAbs 7F5, 4E7, and 4F10 recognized GT1a, GQ1b, and GP1c. MAb 4F10 was more specific for GQ1b than the other MAbs. Using MAb 4F10, we determined, by means of an immunoassay, the quantities of endogenous GQ1b in some neuronal and adrenal cell lines, GOTO (human neuroblastoma), Neuro2a (mouse neuroblastoma), and PC12 (rat pheochromocytoma). PC12 and Neuro2a cells contained at least 5.1 X 106 and 3.9 X 105 molecules/cell of GQ1b, respectively. In contrast, no GQ1b was detected in GOTO cells, which are known for their specific neuritogenic response to this particular ganglioside when exogenously added.
Comparison of the Soluble and Membrane‐Bound Forms of the Puromycin‐Sensitive Enkephalin‐Degrading Aminopeptidases from Rat
Authors: Dyer Simon H. , Slaughter Clive A. , Orth Kim , Moomaw Carolyn R. , Hersh Louis B. 
Published: October 2006

Abstract:Enkephalin degradation in brain has been shown to be catalyzed, in part, by a membrane‐bound puromycinsensitive aminopeptidase. A cytosolic puromycin‐sensitive aminopeptidase with similar properties also has been described. The relationship between the soluble and membrane forms of the rat brain enzyme is investigated here. Both of these aminopeptidase forms were purified from rat brain and an antiserum was generated to the soluble enzyme. Each of the aminopeptidases is composed of a single polypeptide of molecular mass 100 kilodaltons as determined by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and sizeexclusion chromatography. The antisoluble aminopeptidase antiserum reacts with both enzyme forms on immunoblots and inhibits both with nearly identical inhibition curves. The isoelectric points (pI = 5.0) of both forms were shown to be identical. N‐terminal sequencing yielded a common sequence (P‐E‐K‐R‐P‐F‐E‐R‐L‐P‐T‐E‐V‐S‐P‐I‐N‐Y) for both enzyme forms, and peptide mapping yielded 26 peptides that also appeared identical between the two enzyme forms. Studies on the nature of the association of the membrane enzyme form with the cell membrane suggest that this enzyme form does not represent the soluble form trapped during the enzyme preparation. It is suggested that the membrane form of the puromycin‐sensitive aminopeptidase is identical to the soluble enzyme and that it associates with the membrane by interactions with other integral membrane proteins.
(R)‐N‐[4,4‐Bis(3‐Methyl‐2‐Thienyl)but‐3‐en‐1‐yl]Nipecotic Acid Binds with High Affinity to the Brain γ‐Aminobutyric Acid Uptake Carrier
Authors: Braestrup Claus , Nielsen Erik B. , Sonnewald Ursula , Knutsen Lars J. S. , Andersen Knud Erik , Jansen Jens Aas , Frederiksen Kristen , Andersen Peter H. , Mortensen Alicja , Suzdak Peter D. 
Published: October 2006

Abstract: (R)‐N‐[4,4‐Bis(3‐methyl‐2‐thienyl)but‐3‐en‐l‐yl]nipecotic acid (NO 328) has previously been shown to be a potent anticonvulsant in both mice and rats. Here, we report that NO 328 is a potent inhibitor of γ‐[3H]aminobutyric acid ([3H]GABA) uptake in a rat forebrain synaptosomal preparation (IC50= 67 nM) and in primary cultures of neurons and astrocytes. Inhibition of [3H]GABA uptake by NO 328 is apparently of a mixed type when NO 328 is preincubated before [3H]GABA uptake; the inhibition is apparently competitive without preincubation. NO 328 itself is not a substrate for the GABA uptake carrier, but NO 328 is a selective inhibitor of [3H]GABA uptake. Binding to benzodiazepine receptors, histamine H1 receptors, and 5‐hydroxytryptaminelA receptors was inhibited by NO 328 at 5—30 μM, whereas several other receptors and uptake sites were unaffected. [3H]NO 328 showed saturable and reversible binding to rat brain membranes in the presence of NaCI. The specific binding of [3H]NO 328 was inhibited by known inhibitors of [3H]GABA uptake; GABA and the cyclic amino acid GABA uptake inhibitors were, however, less potent than expected. This indicates that the binding site is not identical to, but rather overlapping with, the GABA recognition site of the uptake carrier. The affinity constant for binding of [3H]NO 328 is 18 nM, and the Bmax is 669 pmol/g of original rat forebrain tissue. The regional distribution of NaCl‐dependent [3H]NO 328 binding followed that of synaptosomal [3H]GABA uptake. It is concluded that NO 328 is a potent and selective inhibitor of neuronal and glial GABA uptake and that [3H]NO 328 is a useful radioligand for labeling the GABA uptake carrier in brain membranes. In the mouse brain in vivo, [3H]NO 328 likewise showed saturable and reversible binding that could be displaced by analogues of NO 328. Further studies are needed to demonstrate whether the uptake carrier is indeed labeled by [3H]NO 328 in vivo.
Interactions of Phencyclidine Receptor Agonist MK‐801 with Dopaminergic System: Regional Studies in the Rat
Authors: Rao Tadimeti S. , Kim Helen S. , Lehmann John , Martin Louis L. , Wood Paul L. 
Published: October 2006

Abstract:Interactions of the potent phencyclidine receptor agonist MK‐801 with the dopaminergic system were examined in various brain regions in the rat. MK‐801 increased dopamine (DA) metabolism in the pyriform cortex, entorhinal cortex, prefrontal cortex, striatum, olfactory tubercle, amygdala, and septum without affecting DA metabolism in the cingulate cortex and nucleus accumbens. In pyriform cortex and amygdala, MK‐801 was more potent than phencyclidine at increasing DA metabolism. Local injections of MK‐801 into ventral tegmental area and into the amygdala/pyriform cortex interface indicated that MK‐801 may act at the cell body as well as the nerve terminal level to increase DA metabolism and that ongoing dopaminergic neuronal activity is a prerequisite for full drug action.
Acid Homeostasis Following Partial Ischemia in Neonatal Brain Measured In Vivo by 31P and 1H Nuclear Magnetic Resonance Spectroscopy
Authors: Corbett Ronald J. T. , Laptook Abbot R. 
Published: October 2006

Abstract:The purpose of this study was to investigate neonatal brain energy metabolism, acid, and lactate homeostasis in the period immediately following partial ischemia. Changes in brain buffering capacity were quantified by measuring mean intracellular brain pH, calculated from the chemical shift of Pi, in response to identical episodes of hypercarbia before and after ischemia. In addition, the relationship between brain buffer base deficit and intracellular pH was compared during and following ischemia. Thus, in vivo 31P and 1H nuclear magnetic resonance spectra were obtained from the brains of seven newborn piglets exposed to sequential episodes of hypercarbia, partial ischemia, and a second episode of hypercarbia in the postischemic recovery period. For the first episode of hypercarbia, brain buffering was similar to values reported for adult animals of other species (percentage pH regulation = 54 ± 16%). During ischemia, the brain base deficit per unit change in pH was −19 ± 5 mM/pH unit, which is similar to values reported for adult rats. By 20–35 min postischemia, brain acidosis partly resolved in spite of a net increase in lactate concentration. Therefore, the consumption of lactate could not explain acid homeostasis in the first 35 min following ischemia. We conclude that H+/HCO‐3 or other proton equivalent translocation mechanisms must be sufficiently developed in piglet brain to support acid regulation. This is surprising, because a substantial body of evidence implies these processes would be less active in immature brain. The second episode of hypercarbia, from 35 to 65 min postischemia, resulted in a smaller decrease in brain pH compared with the first episode, a result indicating an increase in brain buffering capacity (percentage pH regulation = 79 ± 29%). This was associated with a parallel decrease in brain lactate content, and therefore acid regulation could be attributed to either continued ion translocation or the consumption of lactate. A mild decrease in brain pH and content of energy metabolites was observed, a finding suggesting that the metabolic consequences of severe postischemic hypercarbia are neither particularly dangerous or beneficial.
α1‐Adrenergic Receptor Mediates Arachidonic Acid Release in Spinal Cord Neurons Independent of Inositol Phospholipid Turnover
Authors: Kanterman Robert Y. , Felder Christian C. , Brenneman Douglas E. , Ma Alice L. , Fitzgerald Sandra , Axelrod Julius 
Published: October 2006

Abstract:The α1‐adrenergic receptor has been shown to mediate the release of arachidonic acid in FRTL5 thyroid cells and MDCK kidney cells. In primary cultures of spinal cord cells, norepinephrine stimulated release of arachidonic acid (from neurons only) and turnover of inositol phospholipids (from neurons and glia) via α1‐adrenergic receptors. These two responses were dissociated by treatment with phorbol ester and pertussis toxin, which inhibited production of inositol phosphates with no appreciable effect on release of arachidonic acid. Extracellular calcium was required for release of arachidonic acid, but not for production of inositol phosphates. The calcium channel blockers nifedipine and verapamil inhibited release of arachidonic acid only. However, 8‐(N,N‐diethylamino)octyl‐3,4,5‐trimethoxybenzoate (TMB‐8), a compound that blocks intracellular calcium release, diminished production of inositol phosphates, but had little effect on release of arachidonic acid. These results suggest that α1‐adrenergic receptors couple to release of arachidonic acid in primary cultures of spinal cord cells by a mechanism independent of activation of phospholipase C, possibly via the activation of phospholipase A2.