bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of protein tyrosine phosphorylation in the NGF response
Authors: Maher P. A. 
Published: January 2005

AbstractThe role of protein tyrosine phosphorylation in the response of PC12 cells to NGF was investigated by using a variety of agents which affect NGF‐induced neurite outgrowth. K‐252a, a kinase inhibitor, was previously found to selectively inhibit many of the actions of NGF on PC12 cells. In the present study, it was shown to inhibit NGF‐induced protein tyrosine phosphorylation. However, sphingosine, an inhibitor of protein kinase C and NGF‐induced differentiation of PC12 cells, did not alter the phosphorylation of proteins on tyrosine stimulated by NGF. Disruption of either actin microfilaments or microtubules also had no effect on NGF‐induced protein tyrosine phosphorylation in PC12 cells. The effect of vanadate, an inhibitor of phosphotyrosyl phosphatases, on the differentiation of PC12 cells was also examined. Vanadate did not promote neurite outgrowth but did stimulate protein tyrosine phosphorylation. Taken together, these results suggest that protein tyrosine phosphorylation is one of the first events in the NGF pathway in PC12 cells but alone is not sufficient to induce morphological differentiation. Finally, the distribution of phosphotyrosine‐containing proteins in untreated and NGF‐treated cells was examined by immunofluorescence microscopy. The distribution of these proteins was altered by treatment of the cells with NGF and appeared to correlate with the distribution of actin filaments, particularly in growth cones.
Molecular cloning of human myelin‐associated glycoprotein
Authors: Spagnol G. , Williams M. , Srinivasan J. , Golier J. , Bauer D. , Lebo R. V. , Latov N. 
Published: January 2005

AbstractThe nucleotide sequence for human myelin‐associated glycoprotein (MAG) and its deduced amino acid sequence, obtained by analysis of two overlapping cDNA clones isolated from a human brain cDNA library, is presented and compared to that reported for rat MAG.The sequence provides an open reading frame of 1,878 nucleotides encoding a peptide of 626 amino acids with a calculated molecular weight of 69.1 kD. It is 89% homologous in nucleotide sequence to the large isoform of rat MAG, with 95% homology in the amino acid sequence. It contains 9 potential glycosylation sites, one more than in rat, and shares other key features with rat MAG, including 5 immunoglobulin‐like regions of internal homology, an RGD sequence, and potential phosphorylation sites. Its structure appears to be highly conserved in evolution, possibly suggesting a close interdependence between its structure and function. The human gene is located on the proximal long arm of chromosome 19 (19q12 → q13.2).
Denervation and hyperinnervation in the nervous system of diabetic animals. II. Monoaminergic and peptidergic alterations in the diabetic encephalopathy
Authors: Di Giulio A. M. , Tenconi B. , La Croix R. , Mantegazza P. , Abbracchio M. P. , Cattabeni F. , Gorio A. 
Published: January 2005

AbstractThe monoaminergic innervation of the central nervous system (CNS) is characterized by long and short projecting neurons. The neurological correlates of diabetes are usually referred to as processes of degenerative atrophy affecting motor and sensory peripheral nerves. We have found that the long serotoninergic axons innervating the spinal cord and the cerebral cortex are unaffected in diabetic animals and that the noradrenergic innervation of the cortex is normal as well. The serotonin content is doubled in the hypothalamus with no apparent alteration of 5‐HIAA levels, suggesting a supernumerary innervation that is accompanied by a reduced release. In pons medulla oblongata, serotonin and dopamine with the relative metabolites 5‐HIAA and DOPAC are significantly reduced, whereas noradrenaline is markedly increased. In the hippocampus, there is a reduction of serotonin content. The serotoninergic alterations are peculiar as suggested by the sparing of the most distal projections that is accompanied by hyperinnervation of the hypothalamus and the loss of shorter collaterals in the pons medulla oblongata. In the hypothalamus and in the striatum of diabetic rats, there are significant higher levels of substance P and met‐enkephalin, respectively. The abundance of proenkephalin A mRNA is also increased in the striatum. Conversely, in the lumbar cord of diabetic animals, the levels of substance P and met‐enkephalin are significantly reduced. Such alterations likely reflect retrograde degeneration of the peripheral sensory input. The CNS changes are unlikely due to vascular abnormalities in the brain of diabetic rats; rather, we suggest that the persistent lack of insulin is the major factor involved as a trigger of the monoaminergic changes in the diabetic brain.
Chemical deglycosylation on a micro‐scale of membrane glycoproteins with retention of phosphoryl‐protein linkages
Authors: Horvath E. , Edwards A. M. , Bell J. C. , Braun P. E. 
Published: January 2005

AbstractWe provide here an easy and convenient procedure for the chemical deglycosylation of membrane glycoproteins that can be done rapidly and inexpensively on large numbers of membrane samples on a microscale without prior isolation of the glycoprotein in question. We have used the procedure successfully on three different glycoproteins and additionally have shown that covalent linkages of the polypeptide to phosphoryl residues are preserved.
GM1 Ganglioside treatment after global ischemia protects changes in membrane fatty acids and properties of Na+, K+‐ATPase and Mg2+‐ATPase
Authors: Mahadik S. P. , Hawver D. B. , Hungund B. L. , Li Y. S. , Karpiak S. E. 
Published: January 2005

AbstractAn examination was made of the effects of ganglioside GM1 (i.m.) on the losses of membrane fatty acids (palmitic, stearic, oleic, linoleic, and arachidonic), the plasma membrane enzyme Na+, K+‐ATPase, and the mitochondrial membrane enzyme Mg2+‐ATPase, associated with global ischemia 24 hr after permanent unilateral occlusion of the carotid artery in Mongolian gerbils. While there was a significant loss of fatty acids in saline controls, no loss was detected in membranes from GM1‐injected gerbils. Rather, we found an increase in membrane fatty acid content, indicative of altered turnover. A 38% loss of Na+, K+‐ATPase and a 36% loss of mitochondrial Mg2+‐ATPase observed in membranes from saline controls was reduced in membranes from GM1‐injected animals to losses of 15% and 8% respectively. These effects are further described by analyses of enzyme kinetics (apparent Vmax and apparent Km). After 1 week of storage, the activities of both membrane ATPases from saline controls decreased substantially more than from GM1‐injected animals, suggesting that the GM1 membranes were better “preserved.” Since there was a minimal loss in protein content after 24 hr of ischemia, these results indicate that systemically injected GM1 may protect structure and function of plama membranes during the acute phases of ischemic injury.
Free radicals mediate peroxidative damage in guinea pig hippocampus in vitro
Authors: Pellmar T. C. , Neel K. L. , Lee K. H. 
Published: January 2005

AbstractPrevious studies have shown that peroxide caused electrophysiological damage. The present study investigates the action of agents that interfere with a free radical process in an effort to define the mechanism of peroxide damage. Deferoxamine chelates iron, making it unavailable for the Fenton reaction and thereby preventing the formation of hydroxyl free radicals from peroxide. Dimethylsulfoxide (DMSO) scavenges hydroxyl free radicals. Trolox‐C, a water soluble Vitamin E analog, is an antioxidant that can scavenge peroxy radicals. Slices of hippocampus were removed from brains of euthanized guinea pigs. Electrical stimulation of an orthodromic pathway to CA1 region evoked a synaptic response and a population spike. Input‐output curves were generated to evaluate the protection by deferoxamine, Trolox‐C, and DMSO on the synaptic damage and impaired spike generation caused by peroxide. Lipid peroxidation was measured by the thiobarbituric acid test. Peroxide was found to increase lipid peroxidation. Deferoxamine and Trolox‐C protected against the peroxide‐induced synaptic damage, impaired spike generation, and lipid peroxidation. DMSO was ineffective synaptically but reduced peroxide damage to spike generating mechanisms and further lipid peroxidation. The data support the hypothesis that peroxide causes damage through a free radical mechanism.
Transforming growth factor‐β and γ‐interferon have dual effects on growth of peripheral glia
Authors: Eccleston P. A. , Jessen K. R. , Mirsky R. 
Published: January 2005

AbstractThe influence of transforming growth factor‐β (TGF‐β) and γ‐interferon on DNA synthesis in Schwann cells and enteric glia in culture has been studied. TGF‐β stimulated the DNA synthesis of short‐term (less than 2 weeks in culture) Schwann cells, whereas γ‐interferon was ineffective. The stimulatory effect of TGF‐β was additive to the stimulation of DNA synthesis due to axonal membrane fragments. In contrast to their effect on short‐term Schwann cells, both TGF‐β and γ‐interferon inhibited DNA synthesis in enteric glial cells and in long‐term (over 3 months in culture) Schwann cells. When short‐term Schwann cells were stimulated to divide by axolemma or glial growth factor, γ‐interferon did not inhibit this enhanced DNA synthesis although it suppressed DNA synthesis induced by cAMP analogues. These results raise the possibility that TGF‐β and γ‐interferon might have a role in controlling glial proliferation during development and/or regeneration of the peripheral nervous system.
Simultaneous up‐regulation of neurofilament proteins during the postnatal development of the rat nervous system
Authors: Schlaepfer W. W. , Bruce J. 
Published: January 2005

AbstractThe expression of neurofilament (NF) proteins was examined during postnatal development of the rat nervous system in order to elucidate the nature of NF expression during the period of transition from the embryonic (immature) to the adult (mature) stages of NF expression. mRNAs to the light (NF‐L), mid‐sized (NF‐M), and heavy (NF‐H) NF proteins were compared by Northern blots and by in situ hybridizations, in NF‐rich (i.e., DRG, spinal cord and brainstem) and in NF‐poor (i.e., cerebellum and cerebral cortex) regions of the developing rat nervous system. NF proteins were analyzed by gel electrophoresis and by immunoblots. In each tissue, the expression of NF‐H was delayed compared to that of NF‐L and NF‐M, as previously reported. The present study now shows that the dealayed compared to that of NF‐L and NF‐M, as previously reported. The present study now shows that the delayed expression of NF‐H is accompanied by parallel up‐regulations in the expressions of NF‐L and NF‐M, both at the levels of mRNA and protein. Similar rates of increase of all three NF mRNAs occur between postnatal days 5 (P5) and 24 (P24) in rat spinal cord and DRG. Furthermore, the postnatal up‐regulation of NF expression is characterized by a progressive accumulation of all three NF proteins in the tissues. The findings indicate that the adult pattern of NF expression (with high levels of expression of all three NF proteins) becomes established during the postnatal period of development, raising questions as to the nature of factors that coregulate the expression of NF subunits.
Activation of arginine metabolism to glutamate in rat brain synaptosomes in thioacetamide‐induced hepatic encephalopathy: An adaptative response?
Authors: Albrecht J. , Hilgier W. , Rafalowska U. 
Published: January 2005

AbstractCrude (P2) synaptosomes derived from rats with acute hepatic encephalopathy (HE) induced with thioacetamide showed a slightly increased uptake of radiolabeled arginine (ARG) and a 2.5‐fold enhanced conversion of newly taken‐up ARG to both glutamate (GLU) and γ‐aminobutyric acid (GABA) as compared with control synaptosomes with a high potassium medium decreased their radioactive GLU and GABA content without affecting the content of the precursor ARG. This result, which was identical with control or HE preparations, appears to indicate that ARG contributes at least, in part, to the synthesis of neurotransmitter GLU or GABA. As measured in purified synaptosomal preparations, HE increased by about 50% the activities of arginase and ornithine‐δ‐aminotransferase‐the two enzymes of the ARG to GLU shunt. It is postulated that increased conversion of ARG to GLU may compensate for excessive utilization of the latter amino acid as an ammonia trap during HE and, as such, may be considered as an adaptative response of the synaptic compartment to this pathological condition.
Regulation of apolipoprotein E gene expression after injury of the rat sciatic nerve
Authors: LeBlanc A. C. , Poduslo J. F. 
Published: January 2005

AbstractThe expression of apolipoprotein E (apo E) is dramatically increased following peripheral nerve injury. This increased expression has been postulated to be negatively influenced by unknown mechanisms during subsequent axonal regeneration (Muller et al.: Science 228:499–501, 1985). The present study investigates the role of the regenerating axon in regulating apo E gene expression in two experimental paradigms which permit or prevent axonal regeneration in the adult rat sciatic nerve—the crush or permanent transection injuries. The nerves in these two models undergo axonal degeneration, demyelination, and Schwann cell proliferation; however, subsequent axonal regeneration and remyelination occur only in the distal segment of the crush‐injured and not in the permanently transected nerve. The steady‐state levels of apo E mRNA in both models increase sharply between 1 and 4 days and reach a maximum level at 12–14 days, which did not change significantly between 14 and 35 days after injury. No significant difference is observed in the steady‐state levels of apo E mRNA between the crushed and permanently transected nerves as a function of time after injury. The steady‐state protein level of apo E in the endoneurial segments initially increases, peaks at 14–21 days, and then decreases between 35 and 60 days after injury in both models. In contrast, the rate of newly translated and secreted apo E significantly increases by fourfold (P < 0.005) between 35 and 60 days after permanent transection whereas it does not significantly differ at these times after crush injury. The increased rate of translation and secretion of apo E after transection compared to the constant rate observed after crush injury, together with the comparable steady‐state levels of apo E mRNA and protein in both models, suggests translational or post‐translational control, but not transcriptional and/or post‐transcriptional control, by the regenerating axons. Furthermore, the increasing rate of biosynthesis and secretion of apo E after permanent transection concomitant with the decreasing steady‐state levels of the protein suggests that apo E is either removed from the endoneurium or subsequently utilized or degraded by mechanisms that are independent from nerve regeneration.
Development of A1 adenosine receptors in the chick embryo retina
Authors: de Carvalho R. Paes 
Published: January 2005

AbstractAdenosine inhibits cyclic AMP synthesis induced by dopamine in embryonic but not in post‐hatched chick retinas. N6‐Cyclohexyladenosine (CHA), which preferntially activates A1 receptors as well as 2‐chloroadenosine, inhibits cyclic AMP accumulation induced by dopamine in retinas from 10‐day‐old embryos (E10) with IC50's of 0.1 and 0.5 μM, respectively, but this effect is not detectable after hatching. In order to verify if this developmental change reflects variations in the number of affinity of A1 adenosine receptors, their development during chick retina ontogeny was studied. Binding studies using 3(H)CHA revealed the presence of A1 receptors at all stages of development examined, including the post‐hatched retina. The number of binding sites increased between E10 and E17, and then decreased in post‐hatched animals. In the latter, 3(H)CHA binding was to a single site with a Bmax of 128.6 ± 13.4 fmol/mg protein and a Kd of 2.1 + 0.2 nM. Various ligands showed similar hierachies of affinity for the A1 receptor in embryonic and post‐hatched retinas, namely, CHA > R‐N6‐phenylisopropyladenosine (1‐PIA)> 5′,‐N‐ethylcarbox‐amideadenosine (NECA) > isobuthylmethyl‐xanthine (IBMX). Given that CHA inhibited forskolin‐induced cyclic AMP production and Gpp(NH)p inhibited 3(H)CHA binding in both embryonic and posthatched retinas, it appears that receptor coupling to adenylate cyclase is present since early embryonic stages. The results suggest that the A1 receptors may have different functions in the embryonic as compared to the mature chick retina.
Permissive and non‐permissive reactive astrocytes: Immunofluorescence study with antibodies to the glial hyaluronate‐binding protein
Authors: Mansour H. , Asher R. , Dahl D. , Labkovsky B. , Perides G. , Bignami A. 
Published: January 2005

AbstractTwo distinct types of reactive astrocytes were studied in rat CNS. Reactive astrocytes secondary to penetrating trauma (anisomorphic gliosis) were induced by stab wounds to the brain. Reactive astrocytes secondary to Wallerian degeneration (isomorphic gliosis) were induced in spinal cord dorsal columns by dorsal rhizotomy proximal to dorsal root ganglia. Anisomorphic glial scars did not stain with antibodies to the glial hyaluronate‐binding protein (GHAP), a structural glycoprotein of white matter extracellular matrix. Conversely, isomorphic glial scars were still GHAP‐positive 3 months after dorsal root transection. Only after 5 months did GHAP immunoreactivity start to disappear from the isomorphic glial scar. Extensive dorsal rhizotomy was performed at the lumbar level to produce Wallerian degeneration of spinal cord dorsal columns. One month later, the rats were reoperated and two thoracic dorsal roots were implanted in the degenerated dorsal columns. The rats were examined 1 month after grafting. As expected, there was a dense anisomorphic glial scar at the site of surgery, while the dorsal columns above the graft showed isomorphic gliosis. Extensive axonal growth was observed in the dense glial scar surrounding the graft. Conversely, no axonal growth was observed in the degenerated dorsal columns undergoing isomorphic gliosis above the implant. The findings suggested that GHAP‐negative astrocytes responding to traumatic injury are permissive for axonal growth and that GHAP‐positive astrocytes responding to Wallerian degeneration are not permissive.
Modification of anoxic neuronal injury by human recombinant epidermal growth factor and its possible mechanism
Authors: Kinoshita A. , Yamada K. , Hayakawa T. , Kataoka K. , Mushiroi T. , Kohmura E. , Mogami H. 
Published: January 2005

AbstractA primary culture of cortical neurons was established from a 17‐day rat embryo. Twenty‐four hours after plating, the culture medium was changed to a chemically defined one, and human recombinant EGF (rEGF) was added to the medium at concentrations of 1,10, and 100 ng/ml. Anoxic stress was exerted on the cultured neurons for 4 hr. Without anoxia, rEGF at a concentration of 10 ng/ml supported neuronal survival. When rEGF was not present in the culture medium, anoxic stress reduced neuronal density to one‐tenth that of the nonanoxic group. The rEGF improved neuronal recovery from anoxia significantly, with survival dependent on rEGF dosage. Monoclonal antibody for EGP receptors canceled the effect of rEGF on survival of neurons in a dose‐dependent manner. Therefore, rEGF functioned to support neuronal survival from anoxia through EGF receptors. Ontogeny of the EGF receptors was detected immunocytochemically with anti‐EGF receptor antibody. About 70% of the cultured neurons were stained by the anti‐EGF receptor antibody 3 days after change of medium, and immunoreactivity for EGF receptors was found to be located on the soma of neurons. Binding activity of EGF receptors was detected 5 days after change of medium with receptor binding assay and Scatchard analysis. High‐affinity binding sites were detected only in neurons cocultured with rEGF (10 ng/ml) for 5 days. The data indicate that rEGF in sufficient concentration induces high‐affinity sites of the EGF receptor and that EGF may have an antianoxic effect through the EGF receptors.
Role of nerve growth factor in oxidant‐antioxidant balance and neuronal injury. I. Stimulation of hydrogen peroxide resistance
Authors: Jackson G. R. , Apffel L. , Werrbach‐Perez K. , Perez‐Polo J. R. 
Published: January 2005

AbstractThe nerve growth factor protein (NGF) regulates neuronal cell death during the development of embryonic sensory and sympathetic neurons in the peripheral nervous system (PNS). NGF protects the rat pheochromocytoma line PC12, a useful model of NGF responsive peripheral neurons, from hydrogen peroxide, which interacts with ferrous iron to generate hydroxyl radicals. Exogenous catalase provides protection, whereas superoxide dismutase (SOD) has no effect on neuronal survival when PC12 cells are challenged with hydrogen peroxide. NGF treatment of PC12 cells increases the activity of catalase. NGF protection from hydrogen peroxide is partially abolished by aminotriazole (Az), a low molecular weight catalase inhibitor. Taken together, these data are consistent with the hypothesis that NGF protects from peroxidative events and consequent cell death via an induction of free radical detoxifying mechanisms, such as catalase activity.
Vasoactive intestinal peptide: A neurotrophic releasing agent and an astroglial mitogen
Authors: Brenneman Douglas E. , Nicol T. , Warren D. , Bowers L. M. 
Published: January 2005

AbstractVasoactive intestinal peptide (VIP) increases neuronal survival in dissociated spinal cord cultures during a critical period of development. In the present study, two mechanisms contributing to this action of VIP have been observed: (1) VIP was shown to be a secretagogue for neuron survival‐promoting activity; and (2) VIP was found to be an astroglial mitogen. A high molecular weight substance (>30 kDa), which increased neuronal survival in tetrodotoxin (TTX)‐treated spinal cord cultures, was detected in the medium from nonneuronal cells incubated for 1 hr with 0.1 nM VIP. In addition, 3H‐thymidine autoradiography and glial fibrillary acid protein (GFAP) immunocytochemistry were used to show that a 5 day treatment with (VIP) increased astroglial mitosis. This effect was specific for astroglia, as silver grain‐positive cells not exhibiting GFAP immunoreactivity did not increase in number after VIP treatment. The dual action of VIP may regulate glial‐derived trophic substances that are important for neuronal survival during the course of development.