bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple Signalling Pathways Interact in the Regulation of Nerve Growth Factor Production in L929 Fibroblasts
Authors: D'Mello Santosh R. , Heinrich Gerhard 
Published: October 2006

Abstract: Fibroblasts are one of several cell types producing nerve growth factor (NGF) in neuronal targets. In previous studies we found that NGF production is up‐regulated by 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) and serum, down‐regulated by corticosterone, and unaffected by dibutyryl‐cyclic AMP (db‐cyclic AMP) in fibroblasts. As fibroblasts in vivo are likely to be exposed to regulatory effects by more than one of these agents at any given time, we examined the effects of combinations of them on NGF production using L929 fibroblasts as a model system. TPA and serum together stimulated NGF production 10‐fold more than either agent alone. Corticosterone reduced NGF mRNA and NGF production to < 10% of basal levels whether or not TPA or serum, or both, were present but not in the presence of the gluco‐corticoid antagonist RU486. Corticosterone did not increase the rate of NGF mRNA degradation. Forskolin and db‐cyclic AMP prevented NGF mRNA induction by TPA and serum without changing basal levels. TPA induced c‐fos and junB mRNAs transiently and preceding NGF mRNA induction but c‐jun mRNA remained undetectable. Forskolin enhanced the induction of both junB and c‐fos mRNA whereas corticosterone prolonged junB mRNA induction. Thus, TPA induction of NGF mRNA is modulated differentially by corticosterone and cyclic AMP. c‐fos and junB may play a role in the underlying mechanisms.
Stress‐and Endotoxin‐Induced Increases in Brain Tryptophan and Serotonin Metabolism Depend on Sympathetic Nervous System Activity
Authors: Dunn Adrian J. , Welch Jon 
Published: October 2006

Abstract: Stressful treatments and immune challenges have been shown previously to elevate brain concentrations of tryptophan. The role of the autonomic nervous system in this neurochemical change was investigated using pharmacological treatments that inhibit autonomic effects. Pretreatment with the ganglionic blocker chlorisondamine did not alter the normal increases in catecholamine metabolites, but prevented the increase in brain tryptophan normally observed after footshock or restraint, except when the duration of the footshock period was extended to 60 min. The footshock‐and restraint‐related increases in 5‐hydroxyindoleacetic acid (5‐HIAA) were also prevented by chlorisondamine. The increases in brain tryptophan caused by intraperitoneal injection of endotoxin or interleukin‐1 (IL‐1) were also prevented by chlorisondamine pretreatment. The footshock‐induced increases in brain tryptophan and 5‐HIAA were attenuated by the β‐adrenergic antagonist propranolol but not by the α‐adrenergic antagonist phenoxybenzamine or the muscarinic cholinergic antagonist atropine. Thus the autonomic nervous system appears to be involved in the stress‐related changes in brain tryptophan, and this effect is due to the sympathetic rather than the parasympathetic limb of the system. Moreover, the main effect of the sympathetic nervous system is exerted on β‐as opposed to α‐adrenergic receptors. We conclude that activation of the sympathetic nervous system is responsible for the stress‐related increases in brain tryptophan, probably by enabling increased brain tryptophan uptake. Endotoxin and IL‐1 also elevate brain tryptophan, presumably by a similar mechanism. The increase in brain tryptophan appears to be necessary to sustain the increased serotonin catabolism to S‐HIAA that occurs in stressed animals, and which may reflect increased serotonin release.
Phosphorylation of Nuclear Proteins in Myelinating Oligodendrocytes and Its Control by Cyclic AMP
Authors: Sato‐Bigbee Carmen , Yu Robert K. 
Published: October 2006

Abstract: Oligodendroglial nuclei isolated from rat brains at different stages of myelinogenesis (10,18, and 30 days of age) were incubated with (γ‐32P]ATP and extracted with 0.75 Mperchloric acid to yield a fraction of nonacidic chromatin proteins. The protein extracts were then analyzed by poly‐acrylamide gel electrophoresis. The phosphorylation pattern of these proteins was found to be different for different age groups. In 10‐day‐old rat Oligodendrocytes the most extensive phosphorylation occurred in low molecular mass species (<30 kDa), in contrast to fractions obtained from 18‐and 30‐day‐old rat Oligodendrocytes which showed a significantly higher labeling of the proteins with molecular masses >30 kDa. The phosphorylation of the latter species was greatly stimulated by the presence of cyclic AMP in the incubation media. The results suggest that the phosphorylation of specific nuclear proteins, which may play a regulatory role at different stages of oligodendroglial maturation and myelinogenesis, may be at least partially modulated by intracellular cyclic AMP.
Intracellular pH and Catecholamine Secretion from Bovine Adrenal Chromaffin Cells
Authors: Kao Lung‐Sen , Ho Mei‐Ying , Cragoe Edward J. 
Published: October 2006

Abstract: To study the role of intracellular pH (pH1) in catecholamine secretion and the regulation of pHi in bovine chromaffin cells, the pH‐sensitive fluorescent indicator [2′,7′‐bis(carboxyethyl)‐5(6)‐carboxyfluorescein] was used to monitor the on‐line changes in pHi. The pHi of chromaffin cells at resting state is ⋍7.2. The pH1 was manipulated first by incubation of the cells with NH4+, and then the solution was replaced with a NH4+‐frce solution to induce acidification of the cytoplasm. The pH1 returned toward the basal pH value after acidification within 5–10 min in the presence of Na+or Li+, but the pH1 stayed acidic when Na+‐free buffers were used or in the presence of amiloride and its analogues. These results suggest that the pH recovery process after an acid load is due to the Na+/H+ exchange activity in the plasma membrane of the chromaffin cells. The Catecholamine secretion evoked by carbachol and Na+ removal was enhanced after the cytoplasm had been made more acidic. It appears that acidic pH favors the occurrence of exocytosis.
Lactate Utilization by Isolated Cells from Early Neonatal Rat Brain
Authors: Vicario Carlos , Arizmendi Carmen , Malloch Gavin , Clark John B. , Medina José M. 
Published: October 2006

Abstract: The utilization of lactate, glucose, 3‐hydroxybutyrate, and glutamine has been studied in isolated brain cells from early newborn rats. Isolated brain cells actively utilized these substrates, showing saturation at concentrations near physiological levels during the perinatal period. The rate of lactate utilization was 2.5‐fold greater than that observed for glucose, 3‐hydroxybutyrate, or glutamine, suggesting that lactate is the main metabolic substrate for the brain immediately after birth. The apparent Km for glucose utilization suggested that this process is limited by the activity of hexokinase. However, lactate, 3‐hydroxybutyrate, and glutamine utilization seems to be limited by their transport through the plasma membrane. The presence of fatty acid‐free bovine serum albumin (BSA) in the incubation medium significantly increased the rate of lipogenesis from lactate or 3‐hydroxybutyrate, although this was balanced by the decrease in their rates of oxidation in the same circumstances. BSA did not affect the rate of glucose utilization. The effect of BSA was due not to the removal of free fatty acid, but possibly to the binding of long‐chain acyl‐CoA, resulting in the disinhibition of acetyl‐CoA carboxylase and citrate carrier.
Cyclic AMP Accumulation Induces a Rapid Desensitization of the Cyclic AMP‐Dependent Protein Kinase in Mouse Striatal Neurons
Authors: Chneiweiss Herve , Cordier Jocelyne , Glowinski Jacques 
Published: October 2006

Abstract: Striatal neurons from the mouse brain embryo grown in primary culture express high levels of cyclic AMP (cAMP)‐dependent protein kinase (PK A) activity. To study the modulation of PKA in intact neurons, a rapid method based on Zn2+‐protein precipitation was developed. This strategy allowed analysis of the stimulation of PKA under conditions of intracellular cAMP concentration increases. Whereas increases up to 1 μM lead to an activation, large and sustained accumulations of cAMP result in a loss of the enzyme activity. With 8‐bromo‐cAMP (8‐Br‐cAMP) at 100 μM, the PKA refractoriness occurs within 2 min. It is rapidly reversible because incubation of treated neurons in fresh medium leads to a complete recovery of PKA activity within 30 min. The decrease in assayable PKA does not involve an activation of phosphatases because the histone dephosphorylation rate is not affected by 8‐Br‐cAMP treatment Finally, not only 8‐Br‐cAMP‐but also forskolin‐and vasoactive intestinal peptide‐induced increases in intracellular cAMP concentration can lead to the PKA desensitization. Altogether, these data unravel a new mechanism of PKA regulation.
Regulation of Cyclic AMP Levels by Calcium in Bovine Adrenal Medullary Cells
Authors: Keogh Rosemary , Marley Philip D. 
Published: October 2006

Abstract: Both nicotine and histamine have been reported to increase cyclic AMP levels in chromaffin cells by Ca2+‐dependent mechanisms. The present study investigated whether Ca2+ was an adequate and sufficient signal for increasing cyclic AMP in cultured bovine adrenal medullary cells. Depolarization with 50 mM K+ caused a two‐to threefold increase in cellular cyclic AMP levels over 5 min, with no change in extracellular cyclic AMP. This response was abolished by omission of extracellular Ca2+ and by 100 μM methoxyverapamil, and was unaffected by 1 μM tetrodotoxin and by 1 mM isobutylmethylxanthine. Veratridine (40 μM) also increased cellular cyclic AMP levels by two‐to fourfold. This response was abolished by either methoxyverapamil or tetrodotoxin. The Ca2+ ionophore A23187 (10–50 μM) had little or no effect on cellular cyclic AMP levels. When the concentration of K+ used to depolarize the cells was reduced to 12–15 mM, the catecholamine release was similar to that induced by 50 μM A23187, and the cyclic AMP response was almost abolished. The results suggest that Ca2+ entry into chromaffin cells is a sufficient stimulus for increasing cellular cyclic AMP production. The possible involvement of a Ca2+/calmodulin‐dependent isozyme of adenylate cyclase is discussed.
Interactions Between the Argininyl Moieties of Neurotensin and the Catechol Protons of Dopamine
Authors: Schenk James O. , Morocco Martin T. , Ziemba Victoria A. 
Published: October 2006

Abstract: The interaction between dopamine and neurotensin as well as other Arg‐containing peptides was studied to provide more chemical details of how dopamine binds to the neuropeptide neurotensin. The stoichiometry of 1:1, dopamine to neurotensin, was confirmed by additional electroanalytical and ultraviolet‐visible spectroscopic studies. By analyses of the 205‐to 340‐nm difference spectra of fixed concentrations of dopamine in the presence of increasing amounts of neurotensin, the dissociation constant of the interaction was found to be 5.9 × 10−8 mol/L. This finding confirmed (by a second physical method) the previously reported KD value obtained by electroanalytical techniques. The associations between dopamine and neurotensin as well as the neurotensin fragment Pro7‐Arg8‐Arg9‐Pro10 were found to be pH dependent when the dissociation constant was measured as a function of pH (in 150 mmol/L NaCl). The results of studies of the formal potential of dopamine in the presence of Arg and Arg‐containing peptides confirmed that catechol protons are directly involved in the association and that the chemical species of dopamine associated with neurotensin is a cate‐cholate form. The (pseudo)‐first‐order rate constant of dissociation of the complex at pH 7.6, measured by the chronoamperometric and rotating disk electroanalytical techniques, was found to be ⋍105 s−1, indicating that the rate of formation of the complex is under diffusion control. A hypothetical chemical structure of the neurotensin‐dopamine complex is suggested.
Hypothermia Prevents the Ischemia‐Induced Translocation and Inhibition of Protein Kinase C in the Rat Striatum
Authors: Cardell Monika , Boris‐Möller Fredrik , Wieloch Tadeusz 
Published: October 2006

Abstract: The effect of hypothermia on the ischemia‐induced changes in the subcellular distribution of protein kinase C (PKC)(γ), ‐(βII), and ‐(α) and the activity of PKC was studied in striatal homogenates of rats subjected to 20 min of cerebral ischemia. The effect of post‐ischemic cooling was also studied. During normothermic ischemia, PKC(γ) and ‐(βII) increased 3.9‐and 2.9‐fold, respectively, in the particulate fraction, signifying a translocation of PKC to cell membranes. The levels of PKC(α) did not change significantly. PKC activity decreased during ischemia by 52% and 47% (p < 0.05) in the paniculate and cytosolic fractions, respectively, and remained inhibited for the 1 h recovery period. In hypothermic animals, there was no evidence of translocation, and the inhibition of PKC activity was completely abolished. Hypothermia induced in the recovery phase, however, did not affect PKC distribution or activity. The protective effect of intraischemic hypothermia may in part be due to the prevention of the ischemia‐induced translocation and subsequent downregulation of PKC, possibly through a temperature‐dependent modification of the cell membranes.
Regulation of 109Cd2+ Uptake into Isolated Neurohypophysial Peptidergic Nerve Terminals
Authors: Toescu Emil C. 
Published: October 2006

AbstractCadmium (109Cd2+) uptake was studied in a preparation of isolated neurohypophysial nerve terminals. By use of a filter separation method, together with a permeabilizing agent (Triton X‐100), two cellular Cd2+ pools have been distinguished. The uptake into the intraterminal pool was governed mainly by a process that displayed saturable kinetics, with a Vmax of 0.15 nmol of Cd2+/mg of protein /min and a Km of 0.18 mM, consistent with a transport system. The superficially bound Cd2+ pool (Triton insensitive), which represented 30–50% of the total Cd2+ bound to the cellular system, was very sensitive to the ionic composition of the incubation medium. Reducing the extracellular Ca2+ or Na+ concentration caused a significant increase in the size of the Triton‐insensitive Cd2+ pool. Whereas Na+ did not affect Cd2+ uptake, Ca2+ induced a small, but significant, increase of Cd2+ uptake into the terminals. It is concluded that there is a significant intraterminal uptake of Cd2+, which could explain several physiological effects of this ion.
Suppression of In Vivo Neostriatal Acetylcholine Release by Vesamicol: Evidence for a Functional Role of Vesamicol Receptors in Brain
Authors: Marien Marc R. , Richard Jean W. , Allaire Catherine , Altar C. Anthony 
Published: October 2006

AbstractExperiments examined the effects of peripheral and central administration of the vesicular acetylcholine transport blocker vesamicol (AH5183) on the content, synthesis, and release of acetylcholine in the rat brain in vivo. In time course studies, a single intraperitoneal dose of dl‐vesamicol (5 mg/kg) rapidly and reversibly (within 2 h) doubled the content of acetylcholine in the striatum and hippocampus, without affecting choline levels or the rate of transmitter synthesis. In microdialysis experiments, the same peripheral dose of drug produced a reversible 55% reduction in endogenous striatal acetylcholine release. A similar inhibitory effect was produced by direct intrastriatal perfusion with vesamicol. Moreover, this effect of vesamicol was (a) concentration‐dependent and saturable (EC50= 68 nM), (b) rapidly reversible, (c) stereospecific for the l‐isomer, and (d) poorly mimicked by a vesamicol analog with lower plasma membrane permeability. This profile of effects is consistent with an interaction with a specific vesamicol receptor as defined by previous in vitro binding studies. These results support a functional role for vesamicol receptors in modulating central cholinergic transmission in vivo.
1‐Methyl‐ 1,2,3,4‐Tetrahydroisoquinoline, Decreasing in 1‐Methyl‐4‐Phenyl‐1,2,3,6‐Tetrahydropyridine‐Treated Mouse, Prevents Parkinsonism‐Like Behavior Abnormalities
Authors: Tasaki Yoshikazu , Makino Yukiko , Ohta Shigeru , Hirobe Masaaki 
Published: October 2006

AbstractIn l‐methyl‐4‐phenyl‐l,2,3,6‐tetrahydropyridine (MPTP)‐treated mouse brain, there was no significant increase or decrease in the content of an endogenous amine, 1,2,3,4‐tctrahydroisoquinoline (TIQ), which is well noted for inducing parkinsonism, whereas another endogenous amine, 1‐methyl‐1,2,3,4‐tetrahydroisoquinoline (1‐MeTIQ), was markedly reduced. This result agrees with the finding in human idiopathic parkinsonianism, confirmed by our previous research. In addition, pretreatment with 1‐MeTIQ completely prevented MPTP‐ or TIQ‐inducing bradykinesia, a symptom of parldnsonism. This study confirmed that 1‐MeTIQ plays an important role in preventing the pathogenesis of parldnsonism and is a possible leading compound of anti‐parkinsonism agents.
Two Possibly Distinct Prostaglandin E1 Receptors in N1E‐115 Clone: One Mediating Inositol Trisphosphate Formation, Cyclic GMP Formation, and Intracellular Calcium Mobilization and the Other Mediating Cyclic AMP Formation
Authors: Kanba Shigenobu , Sasakawa Nobuyuki , Nakaki Toshio , Kanba Kiyoko‐Shimizu , Yagi Gohei , Kato Ryuichi , Richelson Elliott 
Published: October 2006

AbstractProstaglandin E1 (PGE1)‐mediated transmembrane signal control systems were investigated in intact murine neuroblastoma cells (clone N1E‐115). PGE1 increased intra‐cellular levels of total inositol phosphates (IP), cyclic GMP, cyclic AMP, and calcium ([Ca2+]i). PGE1 transiently increased inositol 1,4,5‐trisphosphate formation, peaking at 20 s. There was more than a 10‐fold difference between the ED50 for PGE1 at cyclic AMP formation (70 nM) and its ED50 values at IP accumulation (1 μM), cyclic GMP formation (2 μM), and[Ca2+]i increase (5 μM). PGE1‐mediated IP accumulation, cyclic GMP formation, and [Ca2+]i increase depended on both the concentration of PGE1 and extracellular calcium ions. PGE1 had more potent intrinsic activity in cyclic AMP formation, IP accumulation, and cyclic GMP formation than did PGE2, PGF2α, or PGD2. A protein kinase C activator, 4β‐phorbol 12β‐myristate 13α‐acetate, had opposite effects on PGE1‐mediated IP release and cyclic GMP formation (inhibitory) and cyclic AMP formation (stimulatory). These data suggest that there may be subtypes of the PGE1 receptor in this clone: a high‐affinity receptor mediating cyclic AMP formation, and a low‐affinity receptor mediating IP accumulation, cyclic GMP formation, and intracellular calcium mobilization.
Synergistic Regulation of Cytosolic Ca2+ Concentration in Mouse Astrocytes by NK1 Tachykinin and Adenosine Agonists
Authors: Delumeau Jean C. , Petitet François , Cordier Jocelyne , Glowinski Jacques , Prémont Joël 
Published: October 2006

AbstractThe effects on cytosolic Ca2+ concentration of 2‐chloroadenosine and [L‐Pro9]‐substance P, a selective agonist of NK1 receptors, were investigated on astrocytes from embryonic mice in primary culture. Cells responded to [L‐Pro9]‐ substance P with a transitory increase in cytosolic Ca2+ which was of shorter duration when external Ca2+ was removed. A transient response to 2‐chloroadenosine alone occurred. When simultaneously applied, [L‐Pro9]‐substance P and 2‐chloroadenosine evoked a prolonged elevation of cytosolic Ca2+ (up to 30 min). This phenomenon was dependent on the presence of extracellular Ca2+, but insensitive to dihy‐dropyridines, La3+, and Co2+, excluding the implication of voltage‐operated Ca2+ channels. Arachidonic acid also induced a sustained elevation of cytosolic Ca2+, but did not increase further the response evoked by [L‐Pro9]‐substance P and 2‐chloroadenosine. The activation of protein kinase C by a diacylglycerol analogue mimicked the effect of [L‐Pro9]‐substance P in potentiating the 2‐chloroadenosine‐evoked response. Like 2‐chloroadenosine, pinacidil, which hyper‐polarizes the cells by opening K+ channels, prolonged the elevation of cytosolic Ca2+ concentration induced by [L‐Pro9]‐substance P. Conversely, depolarization with 50 mM KC1 canceled the effects of either pinacidil or 2‐chloroadenosine applied with [L‐Pro9]‐substance P. Pertussis toxin pretreatment suppressed all the effects induced by 2‐chloroadenosine.
The Posttranslational Processing of β‐Endorphin in Human Hypothalamus
Authors: Millington William R. , Smith Debra L. 
Published: October 2006

Abstractβ‐Endorphin is posttranslationally processed to six derivatives, which, although structurally similar, produce distinctly different biological effects. β‐Endorphin 1–31 is a potent opioid receptor agonist, but β‐endorphin 1–27 exhibits antagonist properties, and β‐endorphin 1–26 and the α‐N‐ acetyl derivatives of all three peptides lack opioid receptor activity. In the present study, we identified the β‐endorphin peptides synthesized in human hypothalamus using cation exchange HPLC. First, we tested whether postmortem changes occur by storing rat hypothalami at 4°C. This demonstrated that relative amounts of the six β‐endorphin forms did not change for up to 24 h, although total β‐endorphin immunoreactivity significantly declined after 6 h. HPLC analysis of human hypothalami revealed that β‐endorphin 1–31 was the principal form, constituting 58.4 ± 5.4% of total immunoreactivity. Substantial amounts of β‐endorphin 1–27 (13.4 ± 1.2%) and β‐endorphin 1–26 (13.1 ± 1.6%) were also present, but α‐N‐acetylated forms were quantitatively minor, each comprising ∼5% of total β‐endorphin. A similar processing pattern occurred in preoptic and supra‐ chiasmatic areas of the hypothalamus. These results show that, despite differences in primary sequence, β‐endorphin is processed similarly in both rat and human hypothalamus. Opiate‐active β‐endorphin 1–31 is the principal form in both species.
Polyamines Modulate the Binding of [3H]MK‐801 to the Solubilized N‐Methyl‐D‐Aspartate Receptor
Authors: Romano Carmelo , Williams Keith , Molinoff Perry B. 
Published: October 2006

AbstractSpermine and spermidine enhance the binding of [3H](+)‐5‐methyl‐10,11‐dihydro‐5H‐dibenzo[a, d]cyclohepten‐5,10‐imine ([3H]MK‐801) to N‐methyl‐D‐aspartate (NMDA) receptors in membranes prepared from rat brain. These polyamines also enhance binding of [3H]MK‐801 to NMDA receptors that have been solubilized with deoxycholate. Other polyamines selectively antagonize this effect, a finding indicating that the polyamine recognition site retains pharmacological and structural specificity after solubilization. In the presence of spermidine, an increase in the affinity of the solubilized NMDA receptor for [3H]MK‐801 is observed. However, the rates of both association and dissociation of [3H]MK‐801 binding to solubilized NMDA receptors are accelerated when assays are carried out in the presence of spermidine. When kinetic data are transformed, pseudo‐first‐order association and first‐order dissociation plots are nonlinear in the presence of spermidine, an observation indicating a complex binding mechanism. Effects of spermidine on solubilized NMDA receptors are similar to effects previously described in studies of membrane‐bound receptors. The data indicate that polyamines interact with a specific recognition site that remains associated with other components of the NMDA receptor complex after detergent solubilization.