bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical changes in powdered infant formulas during storage
Authors: Guerra‐Hernández E , Leon C , Corzo N , García‐Villanova B , Romera J M 
Published: March 2003

Hydroxymethylfurfural (HMF), furosine (FUR), lactulose (LU), lysine loss, ascorbic acid and colour (ΔE) were determined in powdered infant formulas stored under nitrogen and oxygen conditions at 20°C and 55°CC during 15, 30 and 90 days. The indicators of the assay at 20°C showed similar behaviour in nitrogen or oxygen atmospheres. Changes in furosine and lysine loss after 90 days occurred under oxygen. Storage at 55°C produced considerable browning. Browning was always greater in nitrogen than in oxygen. Most of the studied parameters increased with the storage time and are useful in controlling the extent of browning in powdered infant formulas under adverse storage conditions.
Tyrosine phosphorylation of ionotropic glutamate receptors by Fyn or Src differentially modulates their susceptibility to calpain and enhances their binding to spectrin and PSD‐95
Authors: Rong Yongqi , Lu Xiaoying , Bernard Anne , Khrestchatisky Michel , Baudry Michel 
Published: March 2003

Both tyrosine phosphorylation and calpain‐mediated truncation of ionotropic glutamate receptors are important mechanisms for synaptic plasticity. Previous work from our laboratory has shown that calpain activation results in truncation of the C‐terminal domains of several glutamate receptor subunits. To test whether and how tyrosine phosphorylation of glutamate ionotropic receptor subunits modulates calpain susceptibility, synaptic membranes were phosphorylated by Fyn or Src, two members of the Src family tyrosine kinases. Tyrosine phosphorylation of synaptic membranes by Src significantly reduced calpain‐mediated truncation of both NR2A and NR2B subunits of NMDA receptors, but not of GluR1 subunits of AMPA receptors. In contrast, phosphorylation with Fyn significantly protected calpain‐mediated truncation of GluR1 subunits of AMPA receptors, but enhanced calpain‐mediated truncation of NR2A subunits of NMDA receptors. Similar results were observed with NR2A and NR2B C‐terminal domain fusion proteins phosphorylated by Fyn or Src before incubation with calpain and calcium. In addition, phosphorylation of NR2A and NR2B C‐terminal fusion proteins by Fyn or Src enhanced their binding to spectrin and PSD‐95. Thus, tyrosine phosphorylation impairs or facilitates calpain‐mediated truncation of glutamate receptor subunits, depending on which tyrosine kinase is activated. Such mechanisms could serve to regulate receptor integrity and location, in addition to modulating channel properties.
Role of phosphatidylinositide 3‐kinase in brain‐derived neurotrophic factor‐induced DARPP‐32 expression in medium size spiny neurons in vitro
Authors: Stroppolo Antonella , Guinea Barbara , Tian Chai , Sommer John , Ehrlich Michelle E. 
Published: March 2003

Brain‐derived neurotrophic factor (BDNF) regulates several properties of striatal dopaminoceptive medium‐sized spiny neurons (MSNs) in vivo and in vitro, including expression levels of DARPP‐32 (dopamine and cyclic adenosine 3′,5′‐monophosphate‐regulated phosphoprotein, 32 kDa). DARPP‐32 is expressed in 96% of the MSNs, and is a key modulator of dopamine actions. We investigated the intracellular signal transduction pathways activated by BDNF in MSNs and via which BDNF induces DARPP‐32 expression. We found that phosphorylation of the cyclic AMP response element binding protein (CREB) is only transiently increased following stimulation of MSNs by BDNF, whereas increased phosphorylation of the extracellular signal regulated kinases 1 and 2 (Erk1/2) and Akt is sustained for longer than 4 h. Treatment of cultures with inhibitors of mitogen‐activated protein kinase kinase (MEK) or phosphatidylinositide 3‐kinase (PI3K) showed that the majority of the BDNF‐induced increase in DARPP‐32 requires the PI3K pathway. We also found that inhibition of PI3K reduces BDNF‐induced Erk phosphorylation, indicating that cross‐talk between these pathways may play a prominent role in MSNs.
Chronic nutritional deprivation of n‐3 α‐linolenic acid does not affect n‐6 arachidonic acid recycling within brain phospholipids of awake rats
Authors: Contreras Miguel A. , Chang Michael C. J. , Rosenberger Thad A. , Greiner Rebecca Sheaff , Myers Carol S. , Salem Norman , Rapoport Stanley I. 
Published: March 2003

Using an in vivo fatty acid model and operational equations, we reported that esterified and unesterified concentrations of docosahexaenoic acid (DHA, 22 : 6 n‐3) were markedly reduced in brains of third‐generation (F3) rats nutritionally deprived of α‐linolenic acid (18 : 3 n‐3), and that DHA turnover within phospholipids was reduced as well. The concentration of docosapentaenoic acid (DPA, 22 : 5 n‐6), an arachidonic acid (AA, 20 : 4 n‐6) elongation/desaturation product, was barely detectable in control rats but was elevated in the deprived rats. In the present study, we used the same in vivo model, involving the intravenous infusion of radiolabeled AA to demonstrate that concentrations of unesterified and esterified AA, and turnover of AA within phospholipids, were not altered in brains of awake F3‐generation n‐3‐deficient rats, compared with control concentrations. Brain DPA‐CoA could be measured in the deprived but not control rats, and AA‐CoA was elevated in the deprived animals. These results indicated that AA and DHA are recycled within brain phospholipids independently of each other, suggesting that recycling is regulated independently by AA‐ and DHA‐selective enzymes, respectively. Competition among n‐3 and n‐6 fatty acids within brain probably does not occur at the level of recycling, but at levels of elongation and desaturation (hence greater production of DPA during n‐3 deprivation), or conversion to bioactive eicosanoids and other metabolites.
Quantitative dual‐probe microdialysis: evaluation of [3H]mannitol diffusion in agar and rat striatum
Authors: Höistad Malin , Chen Kevin C. , Nicholson Charles , Fuxe Kjell , Kehr Jan 
Published: March 2003

AbstractDual‐probe microdialysis was used to study interstitial diffusion in the rat brain. A radiolabelled tracer, [3H]mannitol, was continuously infused at different concentrations via a probe acutely implanted into the striatum of an anaesthetized male rat or into a dilute agar gel. Samples were collected by a second probe placed 1 mm away from the first, and the recovered [3H]mannitol was measured by liquid scintillation counting. In the striatum, the delivery of [3H]mannitol was counteracted by its removal from the extracellular space by passive uptake into cells and clearance into the microcirculation, causing the diffusion profile to approach quasi steady‐state levels within 2 h. Diffusion data from brain and agar were analysed using a mathematical model. The apparent (effective) diffusion coefficient for [3H]mannitol wasD* = 2.9 × 10−6cm2/s, the effective volume fraction α* = 0.30 and the clearance rate constant κ = 2.3 × 10−5/s. A tortuosity, λ = 1.81, and penetration distance Γ = 4.2 mm, were calculated. We conclude that, using dual‐probe microdialysis, parameters reflecting geometric and dynamic tissue properties may be obtained using appropriate mathematical analysis. Quantitative dual‐probe microdialysis will be valuable in characterizing interstitial diffusion and the clearance processes underpinning volume transmission in the brain.
Contribution of Ca2+ calmodulin‐dependent protein kinase II and mitogen‐activated protein kinase kinase to neural activity‐induced neurite outgrowth and survival of cerebellar granule cells
Authors: Borodinsky Laura N. , Coso Omar A. , Fiszman Mónica L. 
Published: March 2003

AbstractIn this report we describe our studies on intracellular signals that mediate neurite outgrowth and long‐term survival of cerebellar granule cells. The effect of voltage‐gated calcium channel activation on neurite complexity was evaluated in cultured cerebellar granule cells grown for 48 h at low density; the parameter measured was the fractal dimension of the cell. We explored the contribution of two intracellular pathways, Ca2+ calmodulin‐dependent protein kinase II and mitogen‐activated protein kinase kinase (MEK1), to the effects of high [K+]e under serum‐free conditions. We found that 25 mm KCl (25K) induced an increase in calcium influx through L subtype channels. In neurones grown for 24–48 h under low‐density conditions, the activation of these channels induced neurite outgrowth through the activation of Ca2+ calmodulin‐dependent protein kinase II. This also produced an increase in long‐term neuronal survival with a partial contribution from the MEK1 pathway. We also found that the addition of 25K increased the levels of the phosphorylated forms of Ca2+ calmodulin‐dependent protein kinase II and of the extracellular signal‐regulated kinases 1 and 2. Neuronal survival under resting conditions is supported by the MEK1 pathway. We conclude that intracellular calcium oscillations can triggered different biological effects depending on the stage of maturation of the neuronal phenotype. Ca2+ calmodulin‐dependent protein kinase II activation determines the growth of neurites and the development of neuronal complexity.
Involvement of glycogen synthase kinase‐3β and tau phosphorylation in neuronal Golgi disassembly
Authors: Elyaman Wassim , Yardin Catherine , Hugon Jacques 
Published: March 2003

AbstractThe dissociation of the neuronal Golgi complex is a classical feature observed in neurodegenerative disorders including Alzheimer's disease. The goal of this study is to determine if the phosphorylation of tau protein is involved in neuronal Golgi disassembly. Primary cortical cultures were exposed to two Golgi toxins, brefeldin A (BFA) or nordihydroguaiaretic acid (NDGA). Immunocytochemical studies using the anti58 k antibody revealed that Golgi disassembly started in exposed neurons a few minutes after treatment. BFA and NDGA induced a rapid and transient increase in tau phosphorylation in a site‐specific manner on immunoblots. In addition, the increase in tau phosphorylation directly correlated with a transient dissociation of tau from the cytoskeleton and a decrease of the acetylated tubulin. Furthermore, the activity of glycogen synthase kinase‐3β (GSK‐3β) increased transiently, as demonstrated by the kinase activity assay and by immunoblottings of serine‐9 and tyrosine‐216 phosphorylated of GSK‐3β. A decrease of the Akt phosphorylated form was also shown. The increase in tau phosphorylation was inhibited by the GSK‐3β inhibitor, lithium. Finally, morphometric studies showed that lithium partially blocked the Golgi disassembly caused by BFA or NDGA. Together these findings indicate that GSK‐3β activity and tau phosphorylation state are involved in the maintenance of the neuronal Golgi organization.
A novel seven transmembrane receptor induced during the early steps of astrocyte differentiation identified by differential expression
Authors: De Smet Charles , Nishimori Hiroyuki , Furnari Frank B. , Bögler Oliver , Huang H.‐J. Su , Cavenee Webster K. 
Published: March 2003

AbstractThe rat glial progenitor cell line CG‐4 can be induced to differentiate into either oligodendrocytes or type‐2 astrocytes. In order to identify genes whose expression varies coincident with such phenotypic differentiation, we employed representational difference analysis (RDA) of mRNA. Here, we report 38 cDNAs induced in type‐2 astrocytes, oligodendrocytes, or both differentiated states. Among these were known transcription factors, membrane receptors, extracellular matrix proteins, secreted signaling modulators, chromatin regulators and myelin sheath components. In addition several novel genes were identified; among these was a gene induced during the very early stages of astrocyte differentiation that we have named Ieda (induced early in differentiating astrocytes). Several Ieda transcripts were detected by RT‐PCR, and appeared to be produced by alternative splicing and promoter usage. The protein deduced from the longest Ieda mRNA exhibited sequence features characteristic of G‐protein coupled receptors, including seven putative transmembrane domains, while the shorter Ieda transcripts encoded proteins that lacked several transmembrane segments. In the adult rat, Ieda transcripts were found exclusively in brain and testis. In the developing rat brain, Ieda expression was first detected at embryonic day 16, that is two days before the first appearance of mature astrocytes. Thus, this approach has yielded a potential source of markers for differentiation states of these two cellular types as well as genes predicted to be functionally involved in the differentiation process itself.
ATP‐driven, Na+‐independent inward Cl– pumping in neuroblastoma cells
Authors: Bettendorff Lucien , Lakaye Bernard , Margineanu Ilca , Grisar Thierry , Wins Pierre 
Published: March 2003

AbstractIn immature neurones, the steady‐state intracellular Cl− concentration [Cl−]i is generally higher than expected for passive distribution, and this is believed to be due to Na+–K+−2Cl– co‐transport. Here, we show that N2a neuroblastoma cells, incubated in HEPES‐buffered NaCl medium maintain a [Cl−]i around 60 mm, two‐ to threefold higher than expected for passive distribution at a membrane potential of − 49 mV. When the cells were transferred to a Cl−‐free medium, [Cl−]i decreased quickly (t1/2 < 5 min), suggesting a high Cl− permeability. When the intracellular ATP concentration was reduced to less than 1 mm by metabolic inhibitors, the initial rate of 36Cl− uptake was strongly inhibited (60–65%) while steady‐state [Cl−]i decreased to 24 mm, close to the value predicted from the Nernst equilibrium. Moreover, after reduction of [ATP]i and [Cl−]i by rotenone, the subsequent addition of glucose led to a reaccumulation of Cl−, in parallel with ATP recovery. Internal bicarbonate did not affect Cl− pumping, suggesting that Cl−/HCO3– exchange does not significantly contribute to active transport. Likewise, Na+–K+−2Cl– co‐transport also appeared to play a minor role: although mRNA for the NKCC1 form of the co‐transporter was detected in N2a cells, neither the initial rate of 36Cl− uptake nor steady‐state [Cl−]i were appreciably decreased by 10 µm bumetanide or replacement of external Na+ by choline. These results suggest that a highly active ATP‐dependent mechanism, distinct from Na+–K+−2Cl– co‐transport, is responsible for most of the inward Cl− pumping in N2a cells.
Modification of tyrosine hydroxylase activity by chloral derived β‐carbolines in vitro
Authors: Riederer Franz , Luborzewski Alexander , God Ralf , Bringmann Gerhard , Scholz Joachim , Feineis Doris , Moser Andreas 
Published: March 2003

Abstractβ‐Carbolines have been suggested to be involved in the pathogenesis of Parkinson's disease as a result of their structural similarity to the neurotoxin N‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP). The chloral‐derived β‐carboline derivative 1‐trichloromethyl‐1,2,3,4‐tetrahydro‐β‐carboline (TaClo) causes cell loss in neuronal and glial cell cultures and induces a slowly developing neurodegenerative process in rats. In our experiments, effects of TaClo and its derivatives 2‐methyl‐TaClo (2‐Me‐TaClo), and 1‐dichloromethylene‐1,2,3,4‐tetrahydro‐β‐carboline (1‐CCl2‐THβC) on tyrosine hydroxylase (TH) activity were investigated in TH assays using homogenate preparations of the rat nucleus accumbens and recombinant human TH (hTH1). TH activity was determined in vitro by measuring l‐DOPA production with HPLC‐ECD. Using homogenate preparations, TaClo, 2‐Me‐TaClo, and 1‐CCl2‐THβC inhibited TH in concentrations of 0.1 mm, while 1‐CCl2‐THβC in low concentrations enhanced TH activity. When TH was activated by PACAP‐27, TaClo, 2‐Me‐TaClo, or 1‐CCl2‐THβC also inhibited activated enzyme activity in high concentrations. However, in the case of 2‐Me‐TaClo and 1‐CCl2‐THβC a biphasic effect was observed with a marked increase of TH activity in the nanomolar range. In our experiments using recombinant hTH1, TaClo, 2‐Me‐TaClo, or 1‐CCl2‐THβC did not modify enzyme activity. After activation of hTH1 by PKA all the tetrahydro‐β‐carbolines investigated in this study decreased l‐DOPA formation. We suggest that these β‐carbolines modulate dopamine synthesis by interacting with a protein kinase TH‐activating system.
The neuropeptide FF analogue, 1DMe, reduces in vivo dynorphin release from the rat spinal cord
Authors: Ballet Sébastien , Braz Joao , Mauborgne Annie , Bourgoin Sylvie , Zajac Jean‐Marie , Hamon Michel , Cesselin François 
Published: March 2003

AbstractIntrathecal infusion of the neuropeptide FF analogue, [D‐Tyr1,	(NMe)Phe3]neuropeptide FF (1DMe; 0.1 µm−0.1 mm) in anaesthetized rats produced a concentration‐dependent decrease in the spinal outflow of dynorphin A (1–8)‐like material, which persisted for at least 90 min after treatment with 10 µm−0.1 mm of the compound. Co‐administration of d‐Phe‐Cys‐Tyr‐D‐Trp‐Orn‐Thr‐Pen‐Thr‐NH2 (CTOP; 1 µm) to block spinal µ‐opioid receptors did not modify this effect, whereas naltrindole (10 µm) totally prevented it and nor‐binaltorphimine (10 µm) reduced the post‐effect. These data suggest that 1DMe triggers the release of endogenous opioids that stimulate mainly δ‐opioid receptors, and secondarily κ‐opioid receptors, thereby exerting a negative influence on dynorphin A (1–8)‐like material outflow. Because dynorphin has pronociceptive properties, such a decrease in spinal dynorphin A (1–8)‐like material release might underlie the long‐lasting antinociceptive effects of intrathecally administered neuropeptide FF and analogues.
The role of muscarinic acetylcholine receptor‐mediated activation of extracellular signal‐regulated kinase 1/2 in pilocarpine‐induced seizures
Authors: Berkeley Jennifer L. , Decker Michael J. , Levey Allan I. 
Published: March 2003

AbstractPilocarpine‐induced seizures are mediated by the M1 subtype of muscarinic acetylcholine receptor (mAChR), but little is known about the signaling mechanisms linking the receptor to seizures. The extracellular signal‐regulated kinase (ERK) signaling cascade is activated by M1 mAChR and is elevated during status epilepticus. Yet, the role of ERK activation prior to seizure has not been evaluated. Here, we examine the role of pilocarpine‐induced ERK activation in the induction of seizures in mice by pharmacological and behavioral approaches. We show that pilocarpine induces ERK activation prior to the induction of seizures by both western blot and immunocytochemistry with an antibody to phosphorylated ERK. In addition, we show that the ERK pathway inhibitor SL327 effectively blocks the pilocarpine‐induced ERK activation. However, SL327 pretreatment has no effect on the initiation of seizures. In fact, animals treated with SL327 had higher seizure‐related mortality than vehicle‐treated animals, suggesting activated ERK may serve a protective role during seizures. In addition, ERK inhibition had no effect on the development of the long‐term sequelae of status epilepticus (SE), including mossy fiber sprouting, neuronal death and spontaneous recurrent seizures.
Mayhem of the multiple mechanisms: modelling neurodegeneration in prion disease
Authors: Brown David R. 
Published: March 2003

AbstractThis review examines recent attempts to advance the understanding of the mechanism by which neurones die in prion disease. Prion diseases or transmissible spongiform encephalopathies are characterized by the conversion of a normal glycoprotein, the prion protein, to a protease‐resistant form that is suggested to be both the infectious agent and the cause of the rapid neurodegeneration in the disease. Death of the patient results from this widespread neuronal loss. Thus understanding the mechanism by which the abnormal form of the prion protein causes neuronal death might lead to treatments that would prevent the life‐threatening nature of these diseases.
Identification of three cAMP‐dependent protein kinase (PKA) phosphorylation sites within the major intracellular domain of neuronal nicotinic receptor α4 subunits
Authors: Guo Xiang , Wecker Lynn 
Published: March 2003

AbstractThis study determined whether all protein kinase A (PKA) and protein kinase C (PKC) phosphorylation sites on the α4 subunit of rat α4β2 neuronal nicotinic receptors could be localized to the M3/M4 cytoplasmic domain of the protein, and investigated specific amino acid substrates for the kinases through two‐dimensional phosphopeptide mapping and site‐directed mutagenesis. Experiments were conducted using α4β2 receptors expressed in Xenopus oocytes and a fusion protein corresponding to the M3/M4 cytoplasmic domain of α4 (α4333−594). When oocytes expressing α4β2 receptors were incubated with [32P]orthophosphate in order to label endogenous ATP stores, phosphorylation of α4 subunits was evident. Incubation of either immunoprecipitated receptors or the fusion protein with [32P]ATP and either PKA or PKC followed by trypsinization of the samples demonstrated that the kinases phosphorylated α4 subunits on multiple phosphopeptides, and that the phosphorylated full‐length α4 protein and fusion protein produced identical phosphopeptide maps. Site‐directed mutagenesis of Ser365, Ser472 and Ser491 to alanines in the fusion protein eliminated phosphopeptides phosphorylated by PKA, but not by PKC. Other mutations investigated, Ser470, Ser493, Ser517 and Ser590, did not alter the phosphopeptide maps. Results indicate that Ser365, Ser472 and Ser491 on neuronal nicotinic receptor α4 subunits are phosphorylated by PKA and are likely to represent post‐translational regulatory sites on the receptor.
The role of NADPH oxidase, neuronal nitric oxide synthase and poly(ADP ribose) polymerase in oxidative neuronal death induced in cortical cultures by brain‐derived neurotrophic factor and neurotrophin‐4/5
Authors: Hwang Jung‐Jin , Choi So‐Young , Koh Jae‐Young 
Published: March 2003

AbstractCertain neurotrophins promote or induce oxidative neuronal death in cortical cultures. However, the effector mechanisms mediating this phenomenon have not been delineated. In this study, we investigated the possibility that NADPH oxidase and nitric oxide synthase (NOS) function as such effectors. Western blot analysis showed that treatment with brain‐derived neurotrophic factor (BDNF) and neurotrophin (NT)‐4/5 increased the levels of NADPH oxidase subunits. Moreover, neurotrophin treatment resulted in membrane translocation of p67phox, a characteristic feature of NADPH oxidase activation. Administration of the specific NADPH oxidase inhibitor, 4‐(2‐aminoethyl)benzenesulfonylfluoride (AEBSF), attenuated increases in oxygen free radicals thereby suggesting that NADPH oxidase contributes to the oxidative stress induced by neurotrophins. Furthermore, neuronal death induced by BDNF or NT‐4/5 was significantly attenuated by AEBSF. Treatment with BDNF has previously been shown to induce neuronal NOS (nNOS). Our data indicated that inhibitors of nNOS attenuated neuronal death induced by BDNF or NT‐4/5, consistent with an active role of nNOS in the mediation of neurotrophin neurotoxicity. As in other models of oxidative cell death, BDNF‐induced neuronal death was accompanied by poly(ADP ribose) polymerase (PARP) activation. AEBSF or N‐nitro‐l‐arginine (NNA) reduced BDNF‐mediated PARP activation. PARP and poly(ADP ribose) glycohydrolase (PARG) are actively involved in mediating neurotrophin neurotoxicity since inhibitors of PARP and PARG significantly reduced levels of cell death. These results suggest that NADPH oxidase and nNOS contribute to increased oxidative stress, subsequent activation of PARP/PARG, and neuronal death induced by prolonged neurotrophin exposure.