bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential modulation of glutamate metabolizing enzymes in mouse and chick cultured glial cells by insulin
Authors: Sena A. , Ferret‐Sena V. , Sarliéve L. L. , Tholey G. 
Published: January 2005

AbstractThe effect of physiological concentrations of insulin (2 and 20 ng/ml) on glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities were compared in mouse and chick glial cells in culture. Addition of insulin to serum‐containing medium increased the level of GS and GDH activities in glial cells prepared from 14–15‐day‐old embryonic mice. A similar but less pronounced effect was observed with glia derived from newborn mouse brain. In absence of serum, addition of insulin had no effect on the tested enzymes.The effects of insulin on enzymatic activities of glial cells from 14–15‐day‐old embryonic chick brain hemispheres were, in contrast, quite different. A significant decrease of GS activity was induced by the hormone, only in the absence of serum. Conversely, the presence of serum enhanced an inhibitory effect of insulin toward chick GDH. The different effects of insulin and the different serum dependence observed for the mammalian and the avian model could reflect fundamental chemical differences between both species as indicated by immunoelectrophoretic analysis. However, it can be concluded that insulin may be a physiological factor regulating glial maturation and amino acid neurotransmitter metabolism in the central nervous system.
Major rat brain membrane‐associated and cytosolic enkephalin‐degrading aminopeptidases: Comparison studies
Authors: Hui Koon‐Sea , Hui M. P.‐P. , Lajtha A. 
Published: January 2005

AbstractThe major cytosolic and membrane‐associated enkephalin‐degrading aminopeptidases were purified in parallel by column chromatography successively on DEAE‐cellulose, AH‐Sepharose, hydroxylapatite, Sephadex G‐200, Affigel Blue, AH‐Sepharose, and hydroxylapatite. With the final hydroxylapatite column, the cytosol (S) and the membrane (M) enzymes could each be resolved into two peaks, one eluted with 0.05 M phosphate (SI, MI) and the other with 0.25 M phosphate (SII, MII). The overall purification, with Arg BNA as substrate, for the SI and MI was about 450‐fold; for SII and MII, 1,200‐fold. The yield for each enzyme was about 2%, the major protein integral units of the four enzymes are similar; they are single polypeptide chains with a molecular weight of 100,000 daltons. Their pH optimum, substrate specificity, and sensitivity to puromycin show that they are similar to lysosomal aminopeptidase (EC 3.4.11.‐). The two forms of the cytosol and the membrane enzymes have slightly different kinetic constants. With the inhibitors, SII is more sensitive to proctolin, whereas MII is more sensitive to bestatin and Arg‐Phe‐Ala. Mn2+ activates SI on Met‐enkephalin degradation, but inhibits SII, MI, and MII.
Components of neurite outgrowth that determine neuronal cytoarchitecture: Influence of calcium and the growth substrate
Authors: Mattson Mark P. , Guthrie P. B. , Kater S. B. 
Published: January 2005

AbstractThe present study examined the cellular mechanisms underlying the generation of neuroarchitecture. Identified Helisoma neurons in isolated cell culture normally require factors present in brain‐conditioned medium (CM) in order to display the different components of neurite outgrowth (sprouting, elongation, branching, and growth cone motility), which ultimately determine their overall architecture. We report here that cell calcium and cell‐substrate interactions can play quite specific roles in the regulation of these different components of neuronal outgrowth. CM‐induced neurite outgrowth was inhibited by calcium ionophore A23187. In the absence of CM the calcium channel blocker La3+ (10μM) reduced intracellular calcium levels and induced neurite sprouting and elongation; growth cone motility and branching were greatly reduced in the La3+ ‐induced neurites. Neurons plated into an environment containing La3+ and a fibronectin substrate exhibited all of the components of neuronal outgrowth normally seen in response to CM. Fibronectin alone had little outgrowthpromoting activity. Neurite elongation rates and branching were increased by exposure to La3+ in neurons on either a CM or fibronectin substrate. The neurons growing on CM or fibronectin whose outgrowth was accelerated by La3+ elaborated neuritic arbors that differed from those of neurons grown in resposne to CM; differences were seen in neurite length, area of outgrowth, branching frequency, and varicosity numbers. Taken together, these results indicate that (1) calcium and the growth substrate can exert specific effects on neurite sprouting, elongation, growth cone motility, and branching; (2) appropriate levels of activation of these two sytems can elicit neurite outgrowth that closely resembles that induced by endogenous growth factors; (3) both the differential expression of the separate components of outgrowth and the kinetics of outgrowth determine a neuron' morphology.
Extraction of major acidic Ca2+ dependent phosphoproteins from synaptic membranes
Authors: Perrone‐Bizzozero N. I. , Weiner D. , Hauser G. , Benowitz L. I. 
Published: January 2005

AbstractThe association of several phosphoproteins with the synaptosomal plasma membrane (SPM) was investigated by phosphorylating SPM fractions from neonatal rat brain in the presence of Ca2+ and then exposing these to a variety of agents. Extraction of the major acidic phosphoproteins, GAP‐43, pp40, and pp80, was assessed by two‐dimensional gel electrophoresis and fluorography. All three proteins were best extracted from the membrane by high pH and by guanidine hydrochloride. GAP‐43 was not extracted in the presence of either low‐or high‐ionic‐strength buffers, reducing agents, or chelating agents; pp80 and pp40, however, showed a significant extraction even under low‐ionic‐strength conditions. Partition experiments with Triton X‐114 revealed an amphiphilic behavior for GAP‐43 and a strong affinity for hydrophobic environments for pp80 and pp40. None of the phosphoproteins was released from the membrane by the use of a phosphatidylinositol‐specific phospholipase C. The extraction properties of GAP‐43, pp80, and pp40 are similar to those of known extrinsic membrane proteins and therefore suggest that these phosphoproteins are peripheral rather than integral to the membrane compartment.
Calcium‐activated neutral proteinase in rat brain myelin and subcellular fractions
Authors: Chakrabarti A. K. , Yoshida Y. , Powers J. M. , Singh I. , Hogan E. L. , Banik N. L. 
Published: January 2005

AbstractThe activity of calcium‐activated neutral proteinase (mMCANP) was determined in subcellular fractions of rat brain. The CANP activity in whole homogenate and its membrane fractions including myelin was increased tenfold following treatment with Triton X‐100. The majority of the activity (60%) was in the primary particulate fractions P1 (nuclear), P2 (mitochondrial), and P3 (microsomal). Following subfractionation of each particulate fraction, most of the activity (50%) was found in the myelin‐enriched fractions (P1A, P2A, and P3A) and separated at the interface of 0.32–0.85 M sucrose. Only 20–30% of the total homogenate activity was in cytosol. The enrichment in the myelin fractions resembled that for 2′, 3′‐cyclic nucleotide 3′‐phosphohydrolase (CNPase) activity.Immunoblotting revealed that the CANP was mainly in myelin and cytosol. In addition to the presence of 72–76 Kd and 80 Kd bands, there were faint highmolecular‐weight CANP bands ranging from 110–150 Kd and lower‐molecular‐weight forms in the region of 30–50 Kd in both purified myelin and cytosol. These studies suggested that CANP is present in myelin and cytosol and that it exists in the brain in membranebound and soluble forms.
Rat β‐nerve growth factor sequence and site of synthesis in the adult hippocampus
Authors: Whittemore S. R. , Friedman P. L. , Larhammar D. , Persson H. , Gonzalez‐Carvajal M. , Holets V. R. 
Published: January 2005

AbstractA rat b̃‐nerve growth factor (NGF) genomic sequence encoding the entire 3′ exon of preproNGF was cloned, and its nucleotide sequence was determined. Rat NGF shows very high homology with other known NGFs in both the prepropeptide and the 3′ untranslated regions. The presumptive signal sequence, the cysteine residues important for tertiary structure, possible glycosylation sites, and dibasic amino acids required for proteolytic cleavage to mature NGF are conserved across species. Comparison of the hydrophobicity plots and amino acid sequences revealed an evolutionary divergent domain on the external surface of NGF, which may account for the poor immunologic crossreactivities of the various NGFs. In situ hydridization with a rat‐specific oligodeoxynucleotide indicated high levels of NGF mRNA synthesis in both hippocampal granule and pyramidal cell layers. These results are consistent with one role for NGF in the CNS as a neuronally released, retrogradely transported neurotrophic factor for basal forebrain cholinergic neurons.
GM1 ganglioside protects nucleus basalis from excitotoxin damage: Reduced cortical cholinergic losses and animal mortality
Authors: Mahadik S. P. , Vilim F. , Korenovsky A. , Karpiak S. E. 
Published: January 2005

AbstractTen days after bilateral injections of ibotenic acid into the nucleus basalis, rats injected daily (i.m.) with ganglioside GM1 were protected from anterograde degeneration of cholinergic projections to the frontolateral cortex. This protection was reflected by reduced losses (associated with ibotenic acid lesions) of cortical acetylcholinesterase, choline acetyltransferase, and lowered animal mortality.
Volume regulation in astrocytes: A role for taurine as an osmoeffector
Authors: Morales H. Pasantes , Schousboe A. 
Published: January 2005

AbstractAstrocytes in culture regulate their volume under anisosmotic conditions by as yet unclear mechanisms. In a number of other cells this process involves a loss of intracellular osmotically active solutes, including taurine. The possibility that taurine participates as an osmoeffector in astrocytes was examined in cultured astrocytes exposed to hyposmolar conditions.Astrocytes responded to decreases in osmolarity by rapid swelling followed by a volume regulatory phase. Hyposmotic conditions induced a dramatic increase of 3H‐taurine efflux, with a time course corresponding to the cell volume regulatory phase. Decreasing osmolarity from 310 to 254, 198 or 150 m osmoles resulted in the release of 8.2%, 17%, and 54%, respectively, of 3H‐taurine previously accumulated by astrocytes. Endogenous taurine concentration decreased 64%. The efflux of 3‐H GABA, 3H‐glycine, or 3H‐D‐aspartate was much less affected under similar conditions. These results suggest a role for taurine as an osmoeffector in astrocytes.
Ganglioside metabolism in the hippocampus after septal lesion in rats
Authors: Domańska‐Janik K. 
Published: January 2005

AbstractThe changes in ganglioside compositon and metabolism of deafferentated rat hippocampus were estimated after septal lesion. A significant decrease in total ganglioside concentration was found 7 days after the lesion. The reduced level of total gangliosides persisted at 17 and 25 days. Relative increase in the proportion of GD1b and Gx (O‐acetylated GT1b) and decrease in GM1 were found in hippocampus only at 25 days post‐lesion.The incorporation of 3H‐N‐acetylamannoseamine into gangliosides was examined in rats whose hippocampi were lesioned 25 days prior to radioprecursor injection. Differences in the labeling pattern of total and individual gangliosides were found. Increases in the label in GM1, GD3, and GD1a and decreases in GT1b and GQ1b were found 10 hr after isotope injection. However, decreases in the specific activity of all gangliosides except GT1b and GQ1b were observed 24 hr after 3H‐N‐acetylomannosamine injection, suggesting the activated turnover of gangliosides in postlesioned hippocampus. The significance of these changes has been discussed in terms of cellular damage and repair in the hippocampal tissue.
Secretion of newly synthesized proteins into the extracellular fluid of the rabbit hippocampus
Authors: Nyström B. , Karlsson J.‐O. , Hamberger A. 
Published: January 2005

AbstractExtracellular proteins were collected continuously from the hippocampus of the rabbit by slow perfusion of a protein‐permeable thin tubing. After pulse labelling with radioactive amino acids via the tubing a rapid appearance of labelled proteins was seen in the extracellular fluid. The half‐life of the proteins in the extracellular space varied between 15 min and 2 h. Protein fractions were separated with gel electrophoresis or HPLC. The extracellular fraction differed distinctly from intracellular proteins with respect to the labelling pattern.
Changes in protein kinase C activities are correlated with the metaplastic transformation of schwann cell precursors of avian embryos into melanocytes
Authors: Hess L. , Chamberlin T. , Ciment Gary 
Published: January 2005

AbstractIn previous work, we found that the phorbol ester drug 12‐0‐tetradecanoyl phorbol acetate (TPA) reverses the developmental restriction of melanogenesis that occurs early in neural crest development, causing Schwann cell precursors to undergo a metaplastic transformation into melanocytes. In this study, we examine whether these effects of TPA may be mediated by changes in endogenous levels of protein kinase C (PKC) activities. We report that low levels of PKC activity are correlated with this adventitious pigmentation in the crest‐derived cells of dorsal root ganglia both during normal development and following TPA treatment in culture. These results suggest that regulation of endogenous levels of PKC plays a role in developmental decisions that neural crest cells make during early embryogenesis.
Distribution and function of tenascin during cranial neural crest development in the chick
Authors: Bronner‐Fraser M. 
Published: January 2005

AbstractTenascin is a glycoprotein associated with the extra‐cellular matrix and the surface of some cell types. Here, the distribution and possible function of tenascin have been examined along the pathways followed by cranial neural crest cells. During early stages of neural crest migration, tenascin was observed in a dense matrix surrounding premigratory cranial neural crest cells. Along the neural tube, tenascin immunoreactivity was observed in a dorsoventral gradient and was also noted under the ectoderm and around the notochord. During advanced neural crest migration, tenascin immunoreactivity colocalized with and appeared to be on the surface of migrating neural crest cells. At later stages, tenascin was present around the otic vesicles, retina, lens, and in an interstitial matrix in the region of the branchial arches. At the level of the occipital somites, tenascin immunoreactivity was observed around the neural tube, notochord, dermamyotome, and on the basal surface of the ectoderm. Tenascin was also observed in an interstitial matrix within the sclerotome. At early stages of vagal neural crest migration, immunoreactivity was uniform within the sclerotome, whereas at later stages tenascin colocalized with vagal neural crest cells within the rostral half of each sclerotome. The possible function of tenascin was tested by injecting antitenascin antibodies lateral to the mesencephalic neural tube. Two predominant defects were noted in injected embryos: (1) ectopic aggregates of cranial neural crest cells external to the neural tube and sometimes located on the apical side of the ectoderm; and (2) open and deformed neural tubes. Both the distribution and results of the perturbation experiment suggest that tenascin is required for proper cranial neural crest migration.
Regional expression of myelin protein genes in the developing mouse brain: In situ hybridization studies
Authors: Verity A. N. , Campagnoni A. T. 
Published: January 2005

AbstractExpression of mRNAs for the two major myelin proteins, myelin basic protein (MBP) and proteolipid protein (PLP), was examined in a number of regions of the developing mouse brain using in situ hybridization. In general, MBP and PLP mRNAs were observed to be coexpressed during ontogeny, prior to the histological appearance of myelin. Expression of both mRNAs was detected as early as 6 hours postpartum in the medulla oblongata and, with development, expression of these mRNAs progressed in a caudal to rostral direction. Peak expression occurred at approximately postnatal day 20 in most regions examined, regardless of time of onset of expression. As myelination proceeded, two different labeling patterns were observed with the PLP and MBP 35S‐labeled cDNA probes. In the earliest stages of myelinogenesis MBP mRNA labeling was restricted to oligodendrocyte cell bodies, but shortly after the gene began to be expressed the labeling became more diffuse. In contrast, PLP mRNA labeling remained over or surrounding oligodendrocyte cell bodies at all stages of myelinogenesis. These two distinctly different patterns of labeling are consistent with alternative intracellular trafficking of MBP and PLP mRNAs, in which PLP mRNAs remain associated with ribosomes within the cell soma and MBP mRNAs move from the cell soma to the oligodendrocyte processes at a specific stage early in myelinogenesis. However, there appeared to be a clear time lag between the onset of MBP mRNA expression and the movement of ribosomes carrying MBP mRNAs into the oligodendrocyte processes. Additionally, the in situ hybridization studies revealed a population of unidentified cells residing in cortical molecular layers that express PLP mRNA in the absence of MBP mRNA.
Stimulation of oligodendrocyte differentiation in culture by growth in the presence of a monoclonal antibody to sulfated glycolipid
Authors: Bansal R. , Gard A. L. , Pfeiffer S. E. 
Published: January 2005

AbstractPerturbation of myelinogenesis by monoclonal antibodies against galactolipids is being used to study the role of these lipids in oligodendrocyte differentiation. We report here a marked stimulatory effect on oligodendrocyte differentiation when mixed primary cultures initiated from 19–21 day fetal rat telencephala are grown in the presence of a monoclonal antibody against sulfogalactolipids. When such cultures were grown in the presence of the IgM antibody 04 [Sommer and Schachner, Dev Biol 83:311–327 1981], the oligodendrocytes formed aggregates connected by fasciculated processes. Immunofluorescence microscopy and biochemical analyses of treated cultures demonstrated 2–3 fold increases in the fraction of 04‐positive cells expressing myelin basic protein, and in the levels of myelin basic protein RNA, myelin basic protein, 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase activity, and 35SO4 incorporation into sulfatide. Greater than 90% of the cells positive for myelin basic protein in treated cultures were in aggregates. The specific activities of oligodendrocyte markers were unaffected in control cultures grown with nonspecific myeloma IgM. Since there was no increase in the total number of 04‐positive cells in treated cultures, the increases in the specific activities of the myelin protein markers appears to be due to an increase in the fraction of cells expressing these markers. Time course studies demonstrated that both the rate and extent of oligodendrocyte differentiation were enhanced in treated cultures. These data are discussed with regard to possible mechanisms of the stimulation, considering not only potential direct effects of the antibody on the cell physiology, but also possible indirect effects due to antibody‐induced aggregation.
Interference reflection microscopic study of dorsal root growth cones on different substrates: Assessment of growth cone–substrate contacts
Authors: Gundersen R. W. 
Published: January 2005

AbstractThe contact between dorsal root growth cones and substrates of type IV collagen, fibronectin, poly‐L‐lysine, and laminin were studied using interference reflection microscopy (IRM) coupled with detaching growth cones from these substrates and observing substrate‐associated membrane (SAM). IRM images of growth cones on collagen and fibronectin indicate substantial dark areas of close association between the substrate and basal region of the growth cone. The thin membranous veils and lamellapodia appear bright, indicating a greatly decreased association with the substrate. Filopodia can appear either entirely dark or light but usually are dark interspersed with brighter areas indicating varying degrees of contact. IRM images of growth cones on polylysine and laminin suggest a decreased association between the basal region of the growth cone and the substrate. The appearance of veils and lamellapodia was similar to that observed on collagen and fibronectin. Observations of SAM indicate an increased degree of contact between growth cones and substrates of collagen and fibronectin compared to laminin and polylysine. Collectively these data indicate that simple increases in adhesion are not adequate to explain substrate preference and enhancement of neurite elongation. Overall decreases in adhesion may accomplish, the same phenomena, suggesting that it is perhaps more important to consider the regional distribution of adhesive contacts in relation to growth cone movement.
Intracellular messengers in the generation and degeneration of hippocampal neuroarchitecture
Authors: Mattson M. P. , Guthrie P. B. , Kater S. B. 
Published: January 2005

AbstractThe actions and interactions of the neurotransmitter glutamate and the intracellular messengers calcium, cyclic AMP, and protein kinase C (PKC) in the regulation of neurite outgrowth and cell survival were examined in hippocampal pyramidal‐like neurons in isolated cell culture. Low, subtoxic levels of glutamate (10–100 μM) caused the regression of dendrites but not axons; millimolar levels caused cell death. Calcium ionophore A23187 (50–100 nM) and the PKC activator phorbol‐12‐myristate‐13‐acetate (PMA; 10–50 nM) caused the regression of both axons and dendrites, whereas the adenylate cyclase activator forskolin enhanced outgrowth rates in both axons and dendrites. The effects of glutamate, A23187, PMA, and forskolin on outgrowth were mediated locally at the growth cones; dendrites were more sensitive than axons to each of these agents. High levels of A23187 (1 μM) or PMA (100 nM) significantly reduced cell survival. Co2+ and trifluoperazine each significantly reduced glutamate‐induced dendritic regression and neurotoxicity suggesting that calcium influx and/or PKC activation mediated glutamate's actions. Fura‐2 measurements showed that glutamate caused a rapid rise in intracellular calcium levels; this rise was prevented by Co2+. PMA and forskolin did not alter intracellular calcium levels, nor did these agents affect glutamate‐induced calcium rises. Taken together, the results indicate that parallel intracellular messenger pathways that influence neurite outgrowth and cell survival are operative in hippocampal neurons; these messengers may play roles in the formation and modification of neuronal circuitry.
Secreted peptides as regulators of neuron–glia and glia–glia interactions in the developing nervous system
Authors: Giulian D. , Vaca K. , Johnson B. 
Published: January 2005

AbstractSecreted peptides of the nervous system help to regulate neuron–glia and glia–glia interactions during development. These regulatory factors, referred to as glia‐promoting factors (GPFs), act on specific classes of glia and include oligodendroglia‐stimulating peptides, interleukin‐1 (IL‐1), colony‐stimulating factors (CSF), and fibroblast growth factor (FGF). The maturity of secretory and target cells determines, in part, the ability of a factor to influence glial proliferation, activation, or differentiation. During neural development, GPFs help to control such fundamentally important events as cell movement, neurite outgrowth, and myelination.