bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium‐dependent glutamate uptake as an activator of oxidative metabolism in primary astrocyte cultures from newborn rat
Authors: Eriksson Gun , Peterson Anders , Iverfeldt Kerstin , Walum Erik 
Published: May 2005

AbstractIn the present report we describe the effect of glutamate on respiratory activity in primary cultures of astrocytes, derived from cerebral cortex of newborn rat.Glutamate (100 μM) caused an increased oxygen consumption. This effect could not be inhibited by antagonists to the NMDA or AMPA/kainate receptors. Neither trans‐ACPD (an agonist to the metabotropic glutamate receptor) nor the Krebs cycle intermediate α‐ketoglutarate had any effect on the respiratory rate. An uncontrolled influx of Na+, caused by gramicidin, could mimic the glutamate effect on respiratory activity. In addition, the glutamate effect was abolished by addition of ouabain or replacement of Na+ by Li+ in the perfusion buffer.We conclude that the co‐transport of Na+, in the Na+ ‐dependent high‐affinity glutamate uptake system, mediated the glutamate‐induced increase in oxygen consumption through an increased activity of Na+/K+‐ATPases. © 1995 Wiley‐Liss, Inc.
Developmental regulation of Na+ and K+ conductances in glial cells of mouse hippocampal brain slices
Authors: Kressin Klaus , Kuprijanova Elena , Jabs Ronald , Seifert Gerald , Steinhäuser Christian 
Published: May 2005

AbstractThe relative contribution of voltage activated Na+ and K+ currents to the whole cell current pattern of hippocampal glial cells was analyzed and compared during different stages of postnatal maturation. The patch‐clamp technique was applied to identified cells in thin brain slices obtained from animals between postnatal day 5 and 35 (p5‐35). We focused on a subpopulation of glial cells in the CA1 stratum radiatum which most probably represents a pool of immature astrocytes, termed “complex” cells. These cells could not be labelled by 01/04 antibodies, but some of the older cells were positively stained for glial fibrillary acidic protein (GFAP). In the early postnatal days, the current pattern of the “complex” cells was dominated by two types of K+ outward currents: a delayed rectifier and a transient component. In addition, all cells expressed significant tetrodotoxin (TTX)‐sensitive Na+ currents. During maturation, the contribution of delayed rectifier and A‐type currents significantly decreased. Furthermore, almost all cells after p20 lacked Na+ currents. This down‐regulation of voltage gated Na+ and K+ outward currents was accompanied by a substantial increase in passive and inward rectifier K+ conductances. We found increasing evidence of electrical coupling between the “complex” cells with continued development. It is concluded that these developmental changes in the electrophysiological properties of “complex” glial cells could be jointly responsible for the well known impaired K+ homeostasis in the early postnatal hippocampus. © 1995 Wiley‐Liss, Inc.
Na+ channel aggregation in remyelinating mouse sciatic axons following transection
Authors: Tzoumaka Eleftheria‐Elda , Novaković Sanja D. , Rock Levinson S. , Shrager Peter 
Published: May 2005

AbstractMouse sciatic nerves from the degeneration‐resistant strain C57BL/6/Wld (Ola) were surgically injected with lysolecithin to induce focal demyelination. Three days later they were transected adjacent to the spinal cord to eliminate contact of the axons with their cell bodies. The Na+ channel distribution was assessed by immunocytochemistry and followed at several stages of remyelination. Control experiments were performed on nerves that were injected but not cut. At (3+4) days, namely, nerves cut 3 days post‐injection and examined 4 days after cutting, axons contained fully demyelinated regions. Na+ channel clusters appeared only at heminodes and at isolated sites that are likely to represent original nodes of Ranvier. During the next few days proliferating Schwann cells adhered to the axons and extended their processes. Clusters of Na+ channels appeared at their edges, and as the Schwann cells elongated the distance between these aggregates increased. A few clusters associated with neighboring Schwann cells approached each other and appeared to coalesce at sites where presumably new nodes of Ranvier would be formed. Beyond (3+6) days excessive degeneration of the transected axons precluded further observations. In the uncut controls, the spatio‐temporal sequence of Schwann cell proliferation and channel patch formation and movement was similar to that described above, although myelin formation was somewhat faster than in the cut axons. It is concluded that Na+ channel aggregation associated with the early stages of remyelination is not dependent upon continuous communication of the axon with its cell body and is under local control. © 1995 Wiley‐Liss, Inc.
Human epileptic astrocytes exhibit increased gap junction coupling
Authors: Lee S. H. , Magge S. , Spencer D. D. , Sontheimer H. , Cornell‐Bell A. H. 
Published: May 2005

AbstractFluorescence Recovery After Photobleach (FRAP) was used to quantify astrocyte gap junction coupling from tissues surgically resected from medically intractable epilepsy patients. Mesial temporal lobe cases provided hippocampus, surrounding hyperexcitable parahippocampus and normal cortex for culture. Cortical tumor cases yielded astrocytoma proper, cortex margins with normal EEG activity, and hyperexcitable cortex. Cells isolated from cortex surrounding astrocytomas and the parahippocampus surrounding the hippocampus showed an increase in glutamate‐induced Ca2+ oscillations and intercellular Ca2+ waves. Gap‐junction coupling was more pronounced in cells isolated from hyperexcitable tissue than from normal tissues as judged by their faster and more complete fluorescence recovery from laser bleach [FRAP]. This data suggests that intractable epilepsy may be associated with alterations in glial gap junction coupling. © 1995 Wiley‐Liss, Inc.
From rodent glial precursor cell to human glial neoplasia in the oligodendrocyte‐type‐2‐astrocyte lineage
Authors: Noble Mark , Gutowski Nick , Bevan Karen , Engel Ute , Linskey Mark , Urenjak Jutte , Bhakoo Kishore , Williams Steve 
Published: May 2005

AbstractWith only a few exceptions, the precursor cells representing the normal counterparts of human tumours are unknown. The comparative lack of information about the lineages involved in tissue development, and difficulties in growing many human tumors in a manner suitable for cellular biological analysis, together often make it difficult to study the differences between normal and tumor and tumor cells and to develop many of the model systems that would be useful in the study of human cancer. By applying techniques previously utilized to study glial progenitor cells, we have isolated a human glioblastoma multiforme (GBM)‐derived population that expresses many properties otherwise uniquely expressed by oligodendrocyte‐type‐2 astrocyte (O‐2A) progenitor cells. Hu‐O‐2A/Gb1 (for Human O‐2A lineage Glioblastoma number 1) cells responded to similar mitogens and differentiation modulators as rodent O‐2A progenitors, and generated cells with features of precursor cells, oligodendrocytes and astrocytes. Moreover, 1H‐NMR analysis of amino acid composition demonstrated a striking conservation of types and quantities of free amino acids between the human tumour cells and the rodent primary cells. Hu‐O‐2A/Gb1 cells represent the first human glioma‐derived population for which unambiguous lineage assignment has been possible, and our results indicate that the human O‐2A lineage can contribute to one of the most malignant of glial tumours. In addition, the highly diagnostic 1H‐NMR spectrum expressed by Hu‐O‐2A/Gb1 cells raises the possibility of eventual non‐invasive identification of tumors of this lineage. © 1995 Wiley‐Liss, Inc.
Physiology of transformed glial cells
Authors: Brismar Tom 
Published: May 2005

AbstractMuch of our present knowledge of glial cell function stems from studies of glioma cell lines, both rodent (C6, C6 polyploid, and TR33B) and human (1321N1, 138MG, D384, R‐111, T67, Tp‐301MG, Tp‐483MG, Tp‐378MG, U‐118MG, U‐251MG, U‐373MG, U‐787MG, U‐1242MG, and UC‐11MG). New methods such as patch clamp and Ca2+ imaging have lead to rapid progress the last few years in our knowledge about glial cells, where an unexpected presence and diversity of receptors and ion channels have emerged. Basic mechanisms related to membrane potential and K+ transport and the presence of voltage gated ion channels (Na+, inwardly rectifying K+, Ca2+ activated K+, Ca2+, and Cl− channels) have been identified. Receptor function and intracellular signaling for glutamate, acetylcholine, histamine, serotonin, cathecolamines, and a large number of neuropeptides (bradykinin, cholecystokinin, endothelin, opioids, and tachykinins) have been characterized. Such studies are facilitated in cell lines which offer a more homogenous material than primary cultures. Although the expression of ion channels and receptors vary considerably between different cell lines and comparative studies are rare, a few differences (compared to astrocytes in primary culture) have been identified which may turn out to be characteristic for glioma cells. Future identification of specific markers for receptors on glial and glioma cells related to cell type and growth properties may have great potential in clinical diagnosis and therapy. © 1995 Wiley‐Liss, Inc.
Tumor antigens in astrocytic gliomas
Authors: Kurpad Shekar N. , Zhao. X.‐G. , Wikstrand Carol J. , Batra Surinder K. , McLendon Roger E. , Bigner Darell D. 
Published: May 2005

AbstractGliomas affect 15,000 to 17,000 Americans every year and carry a dismal prognosis. The potential of immunologically mediated diagnosis and therapy, although greatly enhanced since the advent of monoclonal antibodies, has not been fully realized due to significant problems, most especially the challenge of identifying antigenic molecules specific to glial tumors. Other problematic issues include antigen‐associated factors such as heterogeneity, modulation, shedding, and cross‐reactivity with normal cells, and factors associated with therapeutic agent delivery, typically variable tumor perfusion and unfavorable diffusional forces in tumor microenvironment. An understanding of these problems called for the delineation of operationally specific antigens (tumor‐associated antigens not expressed by the normal central nervous system) combined with the use of compartmental therapeutic approaches to increase the specificity of therapy. Numerous antigens have been identified and are classified as extracellular/matrix‐associated, membrane‐associated, and intracellular antigens. Nevertheless, only a few have been demonstrated to be of significant therapeutic and diagnostic utility. These few include the extracellular matrix‐associated antigens tenascin and GP 240, defined by the antibody DMAb‐22. Recent identification of the overexpression of a deletion variant of the epidermal growth factor receptor (EGFRvIII) in up to 50% of the more malignant glial tumors and the subsequent creation of monoclonal antibodies that are specific to this molecule and do not recognize the wild‐type EGFR provide the most exciting development yet in the design of specific antiglioma immunoconjugates. In addition, the tumor‐specific nature of EGFRvIII combined with improved knowledge of immune mechanisms, especially in the context of the central nervous system, will facilitate the design of highly selective cell‐mediated therapeutic approaches with a view toward obtaining tumor‐specific immunity. © 1995 Wiley‐Liss, Inc.
Gene amplification in human gliomas
Authors: Collins V. P. 
Published: May 2005

AbstractGliomas represent the largest group of primary brain tumors in adults. The astrocytic variants are the most common and the adult forms are histologically stratified into three malignancy grades. Of these glioblastoma is the most common and the most malignant; it has also been best studied by molecular genetics and cytogenetics. Double‐minute chromosomes, known to represent amplified genes, are found in 50% of glioblastomas. Amplified genes are not detected in the most benign of the astrocytomas. Many genes have been shown to be amplified in more than single cases of gliomas and these include EGFR, CDK4, SAS, MDM2, GLI, PDGFAR, MYC, N MYC, MYCL1, MET, GADD153, and KIT. The most commonly amplified genes in glioblastomas are EGFR (in approximately 40%), CDK4, and SAS (in approximately 15%). The remainder of the genes are amplified at lower frequency. The best mapped amplicon in gliomas involves the 12q13–14 region. The amplicon is of undetermined size, encompasses a number of genes, and may be rearranged. It occurs in 15% of glioblastomas and almost always includes the CDK4 and SAS genes, in about 10% of tumors of MDM2 gene, and at lower frequency GLI, GADD153, and A2MR. All but A2MR are overexpressed if amplified. The amplified EGFR gene is frequently rearranged, resulting in changes in the regions of the transcript that codes for the extracellular domain. The resultant receptor is constitutively activated. These findings provide examples of the impact the use of modern molecular biological techniques has had on our understanding of oncogenic mechanisms in gliomas. © 1995 Wiley‐Liss, Inc.
The p53 gene and its role in human brain tumors
Authors: Bögler Oliver , Su Huang H.‐J. , Kleihues Paul , Cavenee Webster K. 
Published: May 2005

AbstractMutation of the p53 gene is among the most common lesions in a variety of human tumors, including those of the central nervous system. In most instances, mutation of one p53 allele is followed by loss of the remaining wild‐type allele, resulting in cells with a complete absence of functional wild‐type p53 protein. However, in some situations, such as at initiation of spontaneously arising gliomas or as the germline configuration of patients with the Li‐Fraumeni syndrome, cells clearly carry both wild‐type and mutant p53 alleles. These observations lead to the hypothesis that p53 mutations can give rise to loss of tumor suppressor functions as well as to gain of oncogenic transformation capabilities. In this review, we define the types of mutations that occur in the p53 gene in various glial tumors, contrast that with the spectra described in other human tumor types, and discuss the biochemistry and physiology of the p53 protein and its ability to regulate and be regulated by other gene products. We use this information to propose roles for p53 in the initiation and progression of human gliomas. © 1995 Wiley‐Liss, Inc.
A comparison of solute fluxes and sources from glacial and non‐glacial catchments over contrasting melt seasons
Authors: Lafrenière Melissa J. , Sharp Martin J. 
Published: May 2005

AbstractSolute and runoff fluxes from two adjacent alpine streams (one glacial and one non‐glacial) were investigated to determine how the inorganic solute chemistry of runoff responded to seasonal and interannual changes in runoff sources and volume, and to differences in physical catchment properties. Intercatchment differences in solute composition were primarily controlled by differences in catchment geology and the presence of soils, whereas differences in total solute fluxes were largely dependent on specific discharge. The glacial stream catchment had higher chemical denudation rates due to the high rates of flushing (higher specific discharge). The non‐glacial Bow River had higher overall concentrations of solutes despite the greater prevalence of more resistant lithologies in this catchment. This is likely the result of both longer average water–rock contact times, and a greater supply of protons from organic soils and/or pyrite oxidation. Increases in snowpack depth/snowmelt runoff reduced the retention of nitrate in the Bow River catchment (i.e. increased nitrate export), probably by reducing net biological uptake, or by reducing the proportion of runoff that had contact with biologically active soil horizons that tend to remove nitrate.The two streams exhibited opposite solute flux responses to climate perturbations over three melt seasons (1998, 1999, and 2000). The 1998 El Niño event resulted in an unusually thin winter snowpack, and increased runoff and solute fluxes from the glacial catchment, but decreased fluxes from the Bow River catchment. Solute fluxes in the Bow River increased proportionally to discharge, indicating that increased snowmelt runoff in this catchment resulted in a proportional increase in weathering rates. In contrast, the proportional variation in solute flux in the glacial stream was only ∼70–80% of the variation in water flux. This suggests that increased ablation of glacier ice and the development of subglacial channels during the 1998 El Niño year apparently reduced the average water–rock contact time in the glacial catchment relative to seasons when the subglacial drainage system was primarily distributed in character. Copyright © 2005 John Wiley & Sons, Ltd.
Fluxes of inorganic carbon from two forested catchments in the Appalachian mountains
Authors: Worrall Fred , Swank Wayne T. , Burt Tim 
Published: May 2005

AbstractThis study uses long‐term records of stream chemistry, discharge and air temperature from two neighbouring forested catchments in the southern Appalachians in order to calculate production of dissolved CO2 and dissolved inorganic carbon (DIC). One of the pair of catchments was clear‐felled during the period of the study. The study shows that: (1) areal production rates of both dissolved CO2 and DIC are similar between the two catchments even during and immediately after the period of clear‐felling; (2) flux of total inorganic carbon (dissolved CO2+ DIC) rises dramatically in response to a catchment‐wide acidification event; (3) DIC and dissolved CO2 are dominantly released on the old water portion of the discharge and concentrations peak in the early autumn when flows in the study catchments are at their lowest; (4) total fluvial carbon flux from the clear‐felled catchment is 11·6 t km−2 year−1 and for the control catchment is 11·4 t km−2 year−1. The total inorganic carbon flux represents 69% of the total fluvial carbon flux. The method presented in the study provides a useful way of estimating inorganic carbon flux from a catchment without detailed gas monitoring. The time series of dissolved CO2 at emergence to the stream can also be a proxy for the soil flux of CO2. Copyright © 2005 John Wiley & Sons, Ltd.
Analytical solutions of infiltration process under ponding irrigation
Authors: Chen Jiann‐Mou , Tan Yih‐Chi 
Published: May 2005

AbstractThe objective of this paper is to simulate the progress of the soil water content distribution in the soil profile with a water table at the bottom of the soil profile during ponding irrigation. This simulation can be done by solving the two‐dimensional Richards's equation for the assimilation of the advancing water jet, which uses the conditions of the two exponential functional forms k = ks eαψ and θ = θr + (θs − θr) eαψ to represent the hydraulic conductivity and volumetric water content, with ψ the pressure as the third variable. We assume that the ground surface becomes ponded and saturated as soon as the water flux passes the dry ground surface. By the technique of transformation, the analytical solution of these two‐dimensional Richards' equations has enabled figures of volumetric water content distribution to be obtained in successive time periods after irrigation. For the example of loam soil, it can simulate the variation of volumetric water content during and after irrigation in the soil profile. The analytical solutions of this paper reflect the real situation simulated, and can be applied to verify those complicated solutions from other analytical models. Copyright © 2005 John Wiley & Sons, Ltd.
A hybrid coating of biomimetic apatite and osteocalcin
Authors: Krout Ashley , Wen Hai Bo , Hippensteel Elizabeth , Li Panjian 
Published: May 2005

AbstractA novel hybrid coating of biomimetic apatite (BAp) and osteocalcin (OC) was prepared by incubating BAp‐coated Ti6A14V coupons in an osteocalcin‐containing medium. A significant amount (up to 1.0 wt %) of OC was adsorbed by the BAp coating within 3 h of incubation as demonstrated by high‐performance liquid chromatography. Characterizations of the hybrid coating with environmental scanning microscopy and X‐ray diffraction indicated that protein adsorption does not alter the microstructure of the coating. The presence of OC in the hybrid coating was visualized with fluorescence microscopy using an immunolabeling procedure. The affinity of OC to the BAp coating was examined using a 20‐h elution test in phosphate‐buffered saline and only a minimal amount (<10%) of the loaded OC was eluted out. When the coating was fully dissolved in hydrochloric acid solution after elution, about 78% of the loaded OC could be recovered. Enzyme‐linked immunosorbent assay and peptide sodium dodecylsulfate–polyacrylamide gel electrophoresis confirmed the integrity and activity of OC molecules throughout the tests. The preliminary cell culture tests showed a significant effect of OC on the attachment and proliferation of osteoblasts. The quick loading profile and high affinity of OC to the BAp coating make it an ideal candidate for the hybrid coating preparation in clinical environment. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005