bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nurr1 enhances transcription of the human dopamine transporter gene through a novel mechanism
Authors: Sacchetti Paola , Mitchell Todd R. , Granneman James G. , Bannon Michael J. 
Published: March 2003

The importance of the nuclear receptor nurr1 for the appropriate development of mesencephalic dopamine‐synthesizing neurons has been clearly demonstrated through the targeted disruption of the nurr1 gene. The persistence of nurr1 expression in adult tissue suggests a possible role for this transcription factor in the maintenance, as well as development, of the dopaminergic phenotype. To address this issue, we analyzed the effects of nurr1 on the transcriptional expression of the human dopamine transporter gene (hDAT), one of the most specific phenotypic markers for dopaminergic neurons. Nurr1 enhanced the transcriptional activity of hDAT gene constructs transiently transfected into a newly described cell line (SN4741) that expresses a dopaminergic phenotype, whereas other members of the NGFI‐B subfamily of nuclear receptors had lesser or no effects. Nurr1 activation of hDAT was not dependent upon heterodimerization with the retinoid X receptor. Unexpectedly, functional analysis of a series of gene constructs revealed that a region of the hDAT 5′‐flanking sequence devoid of NGFI‐B response element (NBRE)‐like sites mediated nurr1 activation. Additional experiments using a nurr1 mutant construct suggest that nurr1 activates hDAT transcription via a novel NBRE‐independent mechanism.
Differential splicing of transcripts encoding the orphanin FQ/nociceptin precursor
Authors: Arjomand Jamshid , Evans Chris J. 
Published: March 2003

Orphanin FQ or nociceptin (OFQ/N), the heptadecapeptide agonist for the NOP receptor, is derived by proteolytic processing from a precursor protein, preproOFQ/N. Previous studies have reported alternative splicing between exons 3 and 4 of the mouse OFQ/N transcript, which, upon translation, would yield precursor proteins with different C‐termini. Using RT‐PCR, we identified similar alternative splicing of preproOFQ/N transcripts in humans and rats. In addition, we identified two novel human preproOFQ/N splice variants from which exon 2 has been excised and which also undergo alternative splicing between exons 3 and 4. Exon 2 contains the translational start site for preproOFQ/N and encodes the signal peptide sequence. In vitro translation of cRNAs lacking exon 2 yields shorter translation products which arise from an alternative initiator methionine located within exon 3. The resulting proteins would lack a signal peptide sequence, which would likely alter their cellular trafficking and processing.
Prostaglandin release by spinal cord injury mediates production of hydroxyl radical, malondialdehyde and cell death: a site of the neuroprotective action of methylprednisolone
Authors: Liu Danxia , Li Liping , Augustus Lezel 
Published: March 2003

The present study explores in vivo whether and how prostaglandin F2α (PGF2α), a membrane phospholipid hydrolysis product, causes neuronal death. The concentration of PGF2α measured by microdialysis sampling increased threefold immediately following impact injury to the rat spinal cord. Administration of PGF2α into the cord through a dialysis fiber caused significant cell loss, increased extracellular levels of hydroxyl radicals and malondialdehyde – an end product of membrane lipid peroxidation – to 3.3 and 2.3 times basal levels, respectively. This suggests that PGF2α‐induced cell death is partly due to hydroxyl radical‐triggered peroxidation. Generating hydroxyl radical by administering Fenton's reagents into the cord through the fibers significantly increased malondialdehyde production – the first direct in vivo evidence that hydroxyl radical triggers membrane lipid peroxidation. Methylprednisolone significantly reduced the release of PGF2α upon spinal cord injury and blocked PGF2α‐induced hydroxyl radical and malondialdehyde production, but did not significantly reduce Fenton's reagent‐induced malondialdehyde production, despite the production of more malondialdehyde by PGF2α. This suggests that methylprednisolone may not directly scavenge hydroxyl radical, and that its ‘antioxidant’ effect is a consequence of blocking the pathways for producing toxic PGF2α and for PGF2α‐induced hydroxyl radical formation, thereby reducing membrane lipid peroxidation.
Cerebroside synthesis as a measure of the rate of remyelination following cuprizone‐induced demyelination in brain
Authors: Jurevics Helga , Hostettler Janell , Muse Evan D. , Sammond Deanne W. , Matsushima Glenn K. , Toews Arrel D. , Morell Pierre 
Published: March 2003

We studied markers of myelin content and of the rate of myelination in brains of mice between 8 and 20 weeks of age. During the 12‐week time‐course, control animals showed slight increases in the content of oligodendroglial‐specific cerebroside, as well as cholesterol (enriched in, but not specific to, myelin). In contrast, synthesis of these lipids, as assayed by in vivo incorporation of 3H2O, was substantial, indicating turnover of 0.4% and 0.7% of total brain cerebroside and cholesterol, respectively, each day. We also studied mice exposed to a diet containing 0.2% of the copper chelator, cuprizone. After 6 weeks 20%, and by 12 weeks, over 30% of brain cerebroside was gone. Demyelination was accompanied by down‐regulation of mRNA expression for enzymes controlling myelin lipid synthesis (ceramide galactosyl transferase for cerebroside; hydroxymethylglutaryl‐CoA reductase for cholesterol), and for myelin basic protein. Synthesis of myelin lipids was also greatly depressed. The 20% cerebroside deficit consequent to 6 weeks of cuprizone exposure was restored 6 weeks after return to a control diet. During remyelination, expression of myelin‐related mRNA species, as well as cerebroside and cholesterol synthesis were restored to normal. However, in contrast to the steady state metabolic turnover in the control situation, all the cerebroside and cholesterol made were accumulated. To the extent that accumulating cerebroside is targeted for eventual inclusion in myelin (discussed) the rate of its synthesis is proportional to remyelination. With our assay, in vivo rates of cerebroside synthesis can be determined for a time window of the order of hours. This offers greater temporal resolution and accuracy relative to classical methods assaying accumulation of myelin components at time intervals of several days. We propose this experimental design, and the reproducible cuprizone model, as appropriate for studies of how to promote remyelination.
The specificity of monoclonal antibody A2B5 to c‐series gangliosides
Authors: Saito Megumi , Kitamura Hisayo , Sugiyama Kiyoshi 
Published: March 2003

To examine the specificity of monoclonal antibody A2B5, four A2B5‐reactive gangliosides (designated as G‐1, G‐2, G‐3 and G‐4) were purified from bonito fish brain. Ganglioside‐1, ‐2, and ‐3 migrated above GD1b, below GQ1b, and far below GQ1b on thin‐layer chromatography. Ganglioside‐4 had the slowest chromatographic mobility and migrated below G‐3. The structures of these gangliosides were characterized by overlay analysis with glycolipid‐specific ligands, product analysis after sialidase or mild acid treatment, and electrospray ionization‐mass spectrometry (ESI‐MS). Accordingly, G‐1, G‐2 and G‐3 were identified to be GT3, GQ1c and GP1c, respectively. The ganglioside G‐4 was shown to have the following structure: NeuAc‐NeuAc‐NeuAc‐Galβ1‐3Gal NAcβ1‐4(NeuAc‐NeuAc‐NeuAcα2‐3)Galβ1‐4Glcβ1‐1′Cer. The antibody A2B5 reacted with these c‐series gangliosides, but not with GD3 and other gangliosides and neutral glycosphingolipids. The antigenic epitope for A2B5 was assumed to include the trisialosyl residue connected to the inner galactose of the hemato‐ or ganglio‐type oligosaccharide structure of gangliosides. Phylogenetic analysis of brain gangliosides using the A2B5 preparation demonstrated that c‐series gangliosides are enriched in lower animals, especially bony fish of different species. The monoclonal antibody A2B5 would be a useful tool for examining the distribution and function of c‐series gangliosides.
Cleavage of Bax is mediated by caspase‐dependent or ‐independent calpain activation in dopaminergic neuronal cells: protective role of Bcl‐2
Authors: Choi Won‐Seok , Lee Eun‐Hee , Chung Chul‐Woong , Jung Yong‐Keun , Jin Byung K. , Kim Seung U. , Oh Tae H. , Saido Takaomi C. , Oh Young J. 
Published: March 2003

Two cysteine protease families, caspase and calpain, are known to participate in cell death. We investigated whether a stress‐specific protease activation pathway exists, and to what extent Bcl‐2 plays a role in preventing drug‐induced protease activity and cell death in a dopaminergic neuronal cell line, MN9D. Staurosporine (STS) induced caspase‐dependent apoptosis while a dopaminergic neurotoxin, MPP+ largely induced caspase‐independent necrotic cell death as determined by morphological and biochemical criteria including cytochrome c release and fluorogenic caspase cleavage assay. At the late stage of both STS‐ and MPP+‐induced cell death, Bax was cleaved into an 18‐kDa fragment. This 18‐kDa fragment appeared only in the mitochondria‐enriched heavy membrane fraction of STS‐treated cells, whereas it was detected exclusively in the cytosolic fraction of MPP+‐treated cells. This proteolytic cleavage of Bax appeared to be mediated by calpain as determined by incubation with [35S]methionine‐labelled Bax. Thus, cotreatment of cells with calpain inhibitor blocked both MPP+‐ and STS‐induced Bax cleavage. Intriguingly, overexpression of baculovirus‐derived inhibiting protein of caspase, p35 or cotreatment of cells with caspase inhibitor blocked STS‐ but not MPP+‐induced Bax cleavage. This appears to indicate that calpain activation may be either dependent or independent of caspase activation within the same cells. However, cotreatment with calpain inhibitor rescued cells from MPP+‐induced but not from STS‐induced neuronal cell death. In these paradigms of dopaminergic cell death, overexpression of Bcl‐2 prevented both STS‐ and MPP+‐induced cell death and its associated cleavage of Bax. Thus, our results suggest that Bcl‐2 may play a protective role by primarily blocking drug‐induced caspase or calpain activity in dopaminergic neuronal cells.
Cyclic AMP‐dependent protein kinase phosphorylates group III metabotropic glutamate receptors and inhibits their function as presynaptic receptors
Authors: Cai Zhaohui , Saugstad Julie A. , Sorensen Scott D. , Ciombor Kelly J. , Zhang Congxiao , Schaffhauser Hervé , Hubalek Frantisek , Pohl Jan , Duvoisin Robert M. , Conn P. Jeffrey 
Published: March 2003

Recent evidence suggests that the functions of presynaptic metabotropic glutamate receptors (mGluRs) are tightly regulated by protein kinases. We previously reported that cAMP‐dependent protein kinase (PKA) directly phosphorylates mGluR2 at a single serine residue (Ser843) on the C‐terminal tail region of the receptor, and that phosphorylation of this site inhibits coupling of mGluR2 to GTP‐binding proteins. This may be the mechanism by which the adenylyl cyclase activator forskolin inhibits presynaptic mGluR2 function at the medial perforant path‐dentate gyrus synapse. We now report that PKA also directly phosphorylates several group III mGluRs (mGluR4a, mGluR7a, and mGluR8a), as well as mGluR3 at single conserved serine residues on their C‐terminal tails. Furthermore, activation of PKA by forskolin inhibits group III mGluR‐mediated responses at glutamatergic synapses in the hippocampus. Interestingly, β‐adrenergic receptor activation was found to mimic the inhibitory effect of forskolin on both group II and III mGluRs. These data suggest that a common PKA‐dependent mechanism may be involved in regulating the function of multiple presynaptic group II and group III mGluRs. Such regulation is not limited to the pharmacological activation of adenylyl cyclase but can also be elicited by the stimulation of endogenous Gs‐coupled receptors, such as β‐adrenergic receptors.
Presence of NK2 binding sites in the rat brain
Authors: Saffroy Monique , Torrens Yvette , Glowinski Jacques , Beaujouan Jean‐Claude 
Published: March 2003

Attempts were made to label tachykinin NK2 binding sites in the adult rat brain using [125I]neurokinin A (NKA) as ligand in the presence of NK1 and NK3 agonist or antagonist to avoid labelling of NK1 and NK3 binding sites, respectively. A high‐affinity, specifically NK2‐sensitive, [125I]NKA‐binding, temperature‐dependent, reversible, sensitive to GTPγS and correspondence to a single population of binding sites (KD and Bmax values: 2.2 nm and 7.3 fmol/mg protein) was demonstrated on hippocampal membranes. Competition studies performed with tachykinins and tachykinin‐related compounds indicated that the pharmacological properties of these NK2‐sensitive [125I]NKA binding sites were identical to those identified in the rat urinary bladder and duodenum. NKA, neuropeptide K, and neuropeptide γ, as well as the potent and selective NK2 antagonists SR 144190, SR 48968 and MEN 10627, presented a nanomolar affinity for these sites. The regional distribution of these NK2‐sensitive [125I]NKA binding sites differs markedly from those of NK1 and NK3 binding sites, with the largest labeling being found in the hippocampus, the thalamus and the septum. Binding in other brain structures was low or negligible. A preliminary autoradiographic analysis confirmed [125I]NKA selective binding in hippocampal CA1 and CA3 areas, particularly, and in several thalamic nuclei.
Isolation and characterization of VGF peptides in rat brain. Role of PC1/3 and PC2 in the maturation of VGF precursor
Authors: Trani E. , Giorgi A. , Canu N. , Amadoro G. , Rinaldi A. M. , Halban P. A. , Ferri L. , Possenti R. , Schininà† M. E. , Levi A. 
Published: March 2003

AbstractThe neurotrophin responsive gene vgf is widely expressed in central and peripheral neurones, and in certain neuroendocrine cell populations. Its encoded VGF precursor protein (proVGF1: 617 amino acids in rat, 615 in man, > 85% homology) gives rise to several low molecular weight species. We studied a range of neuroendocrine and neuronal cells, in which VGF‐processing products were prominent with an apparent molecular weight of 20 and 10 kDa (VGF20 and VGF10, respectively). Such peptides were recognized by antibodies specific for the C‐terminal rat VGF nonapeptide, thus indicating that they included the C‐terminus of proVGF. Ectopic expression of the neuroendocrine‐specific prohormone convertases PC1/3 or PC2 in GH3 cells showed that both could generate VGF20, while VGF10 was preferentially produced by PC1/3. Site‐directed mutagenesis was used to identify the KRKRKK488 motif as the target within VGF sequence which leads to the production of VGF20. Molecular characterization of rat VGF10, on the other hand, revealed that this peptide is produced by cleavage at the RPR555 site. By the combined use of high‐resolution separation techniques, matrix‐assisted laser desorption/ionization time of flight (MALDI‐ToF) mass spectrometry and manual Edman degradation we identified in rat brain a VGF fragment analogous to bovine peptide V and two novel peptides also derived from the C‐terminal region of proVGF.
β‐Amyloid catabolism: roles for neprilysin (NEP) and other metallopeptidases?
Authors: Carson Julie A. , Turner Anthony J. 
Published: March 2003

AbstractThe steady‐state level of amyloid β‐peptide (Aβ) represents a balance between its biosynthesis from the amyloid precursor protein (APP) through the action of the β‐ and γ‐secretases and its catabolism by a variety of proteolytic enzymes. Recent attention has focused on members of the neprilysin (NEP) family of zinc metalloproteinases in amyloid metabolism. NEP itself degrades both Aβ1−40and Aβ1−42in vitroandin vivo, and this metabolism is prevented by NEP inhibitors. Other NEP family members, for example endothelin‐converting enzyme, may contribute to amyloid catabolism and may also play a role in neuroprotection. Another metalloproteinase, insulysin (insulin‐degrading enzyme) has also been advocated as an amyloid‐degrading enzyme and may contribute more generally to metabolism of amyloid‐forming peptides. Other candidate enzymes proposed include angiotensin‐converting enzyme, some matrix metalloproteinases, plasmin and, indirectly, thimet oligopeptidase (endopeptidase‐24.15). This review critically evaluates the evidence relating to proteinases implicated in amyloid catabolism. Therapeutic strategies aimed at promoting Aβ degradation may provide a novel approach to the therapy of Alzheimer's disease.
Age‐related loss of extrastriatal dopamine D2‐like receptors in women
Authors: Kaasinen Valtteri , Kemppainen Nina , Någren Kjell , Helenius Hans , Kurki Timo , Rinne Juha O. 
Published: March 2003

AbstractPositron emission tomography (PET) studies have indicated that thein vivoavailability of dopamine D2‐like receptors declines with age in the human brain. Most of the studies have been carried out with healthy male subjects, or with subject groups containing both sexes. The authors have recently demonstrated that the availability of D2‐like receptors in the frontal cortex is higher in women than in men. The present study was aimed to further examine this phenomenon. Thirty‐seven healthy women (age range 22–78 years) were examined with PET and [11C]FLB 457, a high‐affinity tracer for the extrastriatal D2‐like receptors. A negative relationship between age and dopamine D2‐like receptor availability was seen in the frontal cortex (decrease of 12% per decade of life), the temporal cortex (9%) and the thalamus (6%). A non‐linear s‐shape association explained the relationship only in the frontal cortex, while in other regions the association was linear. Neither oestradiol nor progesterone levels had a significant relationship with the [11C]FLB 457 uptake in any of the brain regions studied after the effect of age was partialled out. The results indicate that: (i) the extrastriatal D2‐like receptor availability decreases with age in healthy women with the fastest rate in the frontal cortex and with the overall rate close to the rate reported in healthy men; (ii) around midlife (age 40–60 years) in women, the frontal receptor decline plateaus while the decline continues to be linear in other extrastriatal brain regions; and (iii) serum oestradiol or progesterone levels are not associated with cortical or thalamic D2‐like receptor availability in women. The results may prove to be important in studies where the biochemical basis of clinical sex differences is examined in patients with dopamine‐related neuropsychiatric disorders.
Docosahexaenoic acid provides protection from impairment of learning ability in Alzheimer's disease model rats
Authors: Hashimoto Michio , Hossain Shahdat , Shimada Toshio , Sugioka Kozo , Yamasaki Hiroshi , Fujii Yoshimi , Ishibashi Yutaka , Oka Jun‐Ichiro , Shido Osamu 
Published: March 2003

AbstractDocosahexaenoic acid (C22:6, n‐3), a major n‐3 fatty acid of the brain, has been implicated in restoration and enhancement of memory‐related functions. Because Alzheimer's disease impairs memory, and infusion of amyloid‐β (Aβ) peptide (1–40) into the rat cerebral ventricle reduces learning ability, we investigated the effect of dietary pre‐administration of docosahexaenoic acid on avoidance learning ability in Aβ peptide‐produced Alzheimer's disease model rats. After a mini‐osmotic pump filled with Aβ peptide or vehicle was implanted in docosahexaenoic acid‐fed and control rats, they were subjected to an active avoidance task in a shuttle avoidance system apparatus. Pre‐administration of docosahexaenoic acid had a profoundly beneficial effect on the decline in avoidance learning ability in the Alzheimer's disease model rats, associated with an increase in the cortico‐hippocampal docosahexaenoic acid/arachidonic acid molar ratio, and a decrease in neuronal apoptotic products. Docosahexaenoic acid pre‐administration furthermore increased cortico‐hippocampal reduced glutathione levels and glutathione reductase activity, and suppressed the increase in lipid peroxide and reactive oxygen species levels in the cerebral cortex and hippocampus of the Alzheimer's disease model rats, suggesting an increase in antioxidative defence. Docosahexaenoic acid is thus a possible prophylactic means for preventing the learning deficiencies of Alzheimer's disease.
Phospholipase C‐mediated signalling is not required for histamine‐induced catecholamine secretion from bovine chromaffin cells
Authors: Donald Amanda N. , Wallace Damian J. , McKenzie Sacha , Marley Philip D. 
Published: March 2003

AbstractA possible role for signalling through phospholipase C in histamine‐induced catecholamine secretion from bovine adrenal chromaffin cells has been investigated. Secretion evoked by histamine over 10 min was not prevented by inhibiting inositol‐1,4,5‐trisphosphate receptors with 2‐APB, by blocking ryanodine receptors with a combination of ryanodine and caffeine, or by depleting intracellular Ca2+ stores by pretreatment with thapsigargin. Inhibition of protein kinase C with Ro31‐8220 also failed to reduce secretion. Inhibition of phospholipase C with ET‐18‐OCH3 reduced both histamine‐ and K+‐induced inositol phosphate responses by 70–80% without reducing their secretory responses. Stimulating phospholipase C with Pasteurella multocida toxin did not evoke secretion or enhance the secretory response to histamine. The secretory response to histamine was little affected by tetrodotoxin or by substituting extracellular Na+ with N‐methyl‐d‐glucamine+ or choline+, or by substituting external Cl– with nitrate–. Blocking various K+ channels with apamin, charybdotoxin, Ba2+, tetraethylammonium, 4‐aminopyridine, tertiapin or glibenclamide failed to reduce the ability of histamine to evoke secretion. These results indicate that histamine evokes secretion by a mechanism that does not require inositol‐1,4,5‐trisphosphate‐mediated mobilization of stored Ca2+, diacylglycerol‐mediated activation of protein kinase C, or activation of phospholipase C. The results are consistent with histamine acting by depolarizing chromaffin cells through a phospholipase C‐independent mechanism.
Microglial activation‐mediated delayed and progressive degeneration of rat nigral dopaminergic neurons: relevance to Parkinson's disease
Authors: Gao Hui‐Ming , Jiang Janwei , Wilson Belinda , Zhang Wanqin , Hong Jau‐Shyong , Liu Bin 
Published: March 2003

AbstractThe etiology of sporadic Parkinson's disease (PD) remains unknown. Increasing evidence has suggested a role for inflammation in the brain in the pathogenesis of PD. However, it has not been clearly demonstrated whether microglial activation, the most integral part of the brain inflammatory process, will result in a delayed and progressive degeneration of dopaminergic neurons in substantia nigra, a hallmark of PD. We report here that chronic infusion of an inflammagen lipopolysaccharide at 5 ng/h for 2 weeks into rat brain triggered a rapid activation of microglia that reached a plateau in 2 weeks, followed by a delayed and gradual loss of nigral dopaminergic neurons that began at between 4 and 6 weeks and reached 70% by 10 weeks. Further investigation of the underlying mechanism of action of microglia‐mediated neurotoxicity using rat mesencephalic neuron‐glia cultures demonstrated that low concentrations of lipopolysaccharide (0.1–10 ng/mL)‐induced microglial activation and production of neurotoxic factors preceded the progressive and selective degeneration of dopaminergic neurons. Among the factors produced by activated microglia, the NADPH oxidase‐mediated release of superoxide appeared to be a predominant effector of neurodegeneration, consistent with the notion that dopaminergic neurons are particularly vulnerable to oxidative insults. This is the first report that microglial activation induced by chronic exposure to inflammagen was capable of inducing a delayed and selective degeneration of nigral dopaminergic neurons and that microglia‐originated free radicals play a pivotal role in dopaminergic neurotoxicity in this inflammation‐mediated model of PD.