bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stable transfection of cDNAs targeting specific steps of glycogen metabolism supports the existence of active gluconeogenesis in mouse cultured astrocytes
Authors: Bernard‐Hélary Katy , Ardourel Maryvonne , Magistretti Pierre , Hévor Tobias , Cloix Jean‐François 
Published: October 2004

AbstractIn order to assess the participation of astrocytic gluconeogenesis in the synthesis of glycogen, mouse astrocytes were stably transfected with antisense cDNA of fructose‐1,6‐bisphosphatase (FBPase) and with sense and antisense cDNAs of glycogen synthase (GS). The antisenses of FBPase and GS have similar significant effect in decreasing astrocyte glycogen content by 60%, while sense GS significantly increased glycogen content by 100%. The FBPase activity was decreased by all three cDNAs used, while glycogen phosphorylase was not altered. The activity of GS was decreased by the antisense GS and increased by the sense GS. These data demonstrate that the gluconeogenesis in astrocytes is involved in the glycogenesis modulation. GLIA 37:379–382, 2002. © 2002 Wiley‐Liss, Inc.
BK channels in human glioma cells have enhanced calcium sensitivity
Authors: Ransom Christopher B. , Liu Xiaojin , Sontheimer Harald 
Published: October 2004

AbstractWe have previously demonstrated the expression of large‐conductance, calcium‐activated potassium (BK) channels in human glioma cells. In the present study, we characterized the calcium sensitivity of glioma BK channels in excised membrane patches. Channels in inside‐out patches were activated at −60 mV by 2.1 × 10−6 M cytosolic Ca2+, were highly K+‐selective, and had a slope conductance of ≈210 pS. We characterized the Ca2+ sensitivity of these channels in detail by isolating BK currents in outside‐out patches with different free [Ca2+]i. The half‐maximal voltage for channel activation, V0.5, of glioma BK currents in outside‐out patches was +138 mV with 0 Ca2+/10 EGTA. V0.5 was shifted to +81 mV and −14 mV with free [Ca2+]i of 1.5 × 10−7 M and 2.1 × 10−6 M, respectively. These results suggest that glioma BK channels have a higher Ca2+ sensitivity than that described in many other human preparations. Data obtained from a cloned BK channel (hbr5) expressed in HEK cells support the conclusion that glioma BK channels have an unusually high sensitivity to calcium. In addition, the sensitivity of glioma BK channels to the BK inhibitor tetrandrine suggests the expression of BK channel auxiliary β‐subunits by glioma cells. Expression of the auxiliary β‐subunit of BK channels by glioma cells may relate to the high Ca2+ sensitivity of glioma BK channels. GLIA 38:281–291, 2002. © 2002 Wiley‐Liss, Inc.
Life imaging of peroxynitrite in rat microglial and astroglial cells: Role of superoxide and antioxidants
Authors: Possel Heiko , Noack Heiko , Keilhoff Gerburg , Wolf Gerald 
Published: October 2004

AbstractFree radicals, such as superoxide and nitric oxide, are known to play a role in a number of inflammatory and degenerative brain diseases, in which resident microglia upregulate the inducible nitric oxide synthase (iNOS) and thus produce large amounts of nitric oxide. Simultaneously, microglia generate superoxide mainly via NADPH‐oxidase, which reacts at a diffusion‐limited rate with nitric oxide to form the powerful oxidant peroxynitrite. We used mixed astroglial/microglial cultures to study the effects of iNOS induction by lipopolysaccharide and interferon‐γ on free radical formation. Using the fluorogenic compound 2,7‐dihydrodichlorofluorescein diacetate, we monitored cellular peroxynitrite formation by confocal laser microscopy. Peroxynitrite formation in continuously nitric oxide‐producing microglial cells was rather limited. However, activation of the superoxide‐generating enzyme NADPH‐oxidase dramatically increased DCF fluorescence within a few minutes. We conclude that superoxide is the limiting factor for peroxynitrite formation. Since the formation and oxidant activity of peroxynitrite depends strongly on the availability of cellular antioxidants, we investigated the capacity of several compounds to influence peroxynitrite formation. Among the substances under investigation in this study, glutathione and the synthetic compound ebselen had a major effect on preventing peroxynitrite formation, whereas ascorbate failed to decrease peroxynitrite levels. GLIA 38:339–350, 2002. © 2002 Wiley‐Liss, Inc.
RhoA inhibition is a key step in pituicyte stellation induced by A1‐type adenosine receptor activation
Authors: Rosso Lia , Peteri‐Brunbäck Brigitta , Vouret‐Craviari Valérie , Deroanne Christophe , Troadec Jean‐Denis , Thirion Sylvie , Van Obberghen‐Schilling Ellen , Mienville Jean‐Marc 
Published: October 2004

AbstractPituicyte stellation in vitro represents a useful model with which to study morphological changes that occur in vivo in these cells during times of high neurohypophysial hormone output. This model has helped us establish the hypothesis of a purinergic regulation of pituicyte morphological plasticity. We first show that ATP induces stellation in 37% of pituicytes, an effect that is secondary to the metabolism of ATP to adenosine. Adenosine‐induced stellation of pituicytes appears to be mediated by A1‐type receptors. The effect is independent of intracellular calcium and does not involve the mitogen‐activated protein kinase pathway. The basal (nonstellate) state of pituicytes depends on tonic activation of a Rho GTPase because both C3 transferase (a Rho inhibitor) and Y‐27632 (an inhibitor of p160Rho kinase) can induce stellation. Lysophosphatidic acid, a Rho activator, blocks the morphogenic effect of adenosine dose‐dependently. Using a specific RhoA pull‐down assay, we also show that downregulation of activated RhoA is the key event coupling A1 receptor activation to pituicyte stellation, via F‐actin depolymerization and microtubule reorganization. Finally, both vasopressin and oxytocin can prevent or reverse adenosine‐induced stellation. The effects of vasopressin, and those of high concentrations of oxytocin, are mediated through V1a receptors. Placed within the context of the relevant literature, our data suggest the possibility of a purinergic regulation of pituicyte morphological plasticity and subsequent modulation of hormone release, with these hormones providing a negative feedback mechanism. GLIA 38:351–362, 2002. © 2002 Wiley‐Liss, Inc.
Combined endovascular and surgical treatment of head and neck paragangliomas—A team approach
Authors: Persky Mark S. , Setton Avi , Niimi Yasunari , Hartman Jonathan , Frank Douglas , Berenstein Alex 
Published: October 2004

AbstractBackgroundParagangliomas are highly vascular tumors of neural crest origin that involve the walls of blood vessels or specific nerves within the head and neck. They may be multicentric, and they are rarely malignant. Surgery is the preferred treatment, and these tumors frequently extend to the skull base. There has been controversy concerning the role of preoperative angiography and embolization of these tumors and the benefits that these procedures offer in the evaluation and management of paragangliomas.MethodsForty‐seven patients with 53 paragangliomas were treated from the period of 1990–2000. Initial evaluation usually included CT and/or MRI. All patients underwent bilateral carotid angiography, embolization of the tumor nidus, and cerebral angiography to define the patency of the circle of Willis. Carotid occlusion studies were performed with the patient under neuroleptic anesthesia when indicated. The tumors were excised within 48 hours of embolization.ResultsCarotid body tumors represented the most common paraganglioma, accounting for 28 tumors (53%). All patients underwent angiography and embolization with six patients (13%), demonstrating complications (three of these patients had embolized tumor involving the affected nerves). Cerebral angiography was performed in 28 patients, and 5 of these patients underwent and tolerated carotid occlusion studies. The range of mean blood loss according to tumor type was 450 to 517 mL. Postoperative cranial nerve dysfunction depended on the tumor type resected. Carotid body tumor surgery frequently required sympathetic chain resection (21%), with jugular and vagal paraganglioma removal frequently resulting in lower cranial nerve resection. These patients required various modes of postoperative rehabilitation, especially vocal cord medialization and swallowing therapy.ConclusionsThe combined endovascular and surgical treatment of paragangliomas is acceptably safe and effective for treating these highly vascular neoplasms. Adequate resection may often require sacrifice of one or more cranial nerves, and appropriate rehabilitation is important in the treatment regimen. © 2002 Wiley Periodicals, Inc.
In vitro degradation and fracture toughness of multilayered porous poly(propylene fumarate)/β‐tricalcium phosphate scaffolds
Authors: Wolfe Michael S. , Dean David , Chen Jeffrey E. , Fisher John P. , Han Seungho , Rimnac Clare M. , Mikos Antonios G. 
Published: October 2004

AbstractThis study investigated the in vitro degradation of poly(propylene fumarate)/β‐tricalcium phosphate (PPF/β‐TCP) scaffolds in pH 7.4 phosphate‐buffered saline at 37°C. Scaffold design consisted of three layers: two solid layers about a central layer of porous PPF foam. Solid PPF with molecular weights of 810 and 1450 Da was crosslinked under UV light. PPF foam was prepared by a photocrosslinking, porogen‐leaching method with an initial porogen content of 80 wt % and two sizes, 150–300 and 300–500 μm. Comparison of initial and residual weights demonstrated a 14.3 ± 2.0% loss of mass at 3 weeks and a 16.6 ± 1.8% loss of mass at 6 weeks. Observed pH values for all constructs remained stable (7.15–7.40) throughout the 3 to 6 weeks. Scanning electron micrographs of these scaffolds revealed some loss of foam material between 3 and 6 weeks; however, foam microarchitecture was intact. Solid PPF fracture toughness was tested for high and low molecular weight PPF, 0.376 ± 0.004 and 0.134 ± 0.015 MPa(m)1/2, respectively. These values are roughly one magnitude less than human cortical bone. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 159–164, 2002
Transmission electron microscopic visualization of the degradation and phagocytosis of a poly‐L‐lactide screw in cancellous bone: A long‐term experimental study
Authors: Laitinen Outi , Pihlajamäki Harri , Sukura Antti , Böstman Ole 
Published: October 2004

AbstractThe increasing clinical use of biodegradable implants in orthopedic surgery makes it necessary to determine their long‐term behavior in tissues. In this study, a biodegradable screw made of poly‐L‐lactide (PLLA) was inserted axially into the right distal femur in 18 rabbits. The degradation and phagocytosis process of PLLA was assessed histologically and by transmission electron microscopy (TEM). The follow‐up times were 3 and 4.5 years for groups of nine and eight animals, respectively. Abundant birefringent polymeric material was still present in the center of the implant channel in all specimens in both follow‐up groups. The PLLA material studied appeared to be a biologically relatively inert material, with only sparse reactive cellular activity at the tissue–implant boundary. In the TEM specimens, polymeric particles of an average area of 2 μm2 were seen to be located intracellularly within phagocytic cells. The spheric and polygonal particles were membrane‐bound and to a great extent filled up each phagocyte. In the 4.5‐year specimens, the size of the polymeric particles, measured as area and perimeter, was significantly smaller (p < 0.02) than that of the 3‐year specimens. The findings indicate that the ultimate degradation process of PLLA is much longer than it previously was thought to be. Complete degradation probably still would have taken years after the 4.5‐year span of this study. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 33–39, 2002
Detection of microscopic cracks in dental ceramic materials by fluorescent penetrant method
Authors: Fischer Horst , Karaca Fatma , Marx Rudolf 
Published: October 2004

AbstractCeramic materials are used as implants and prostheses because of their excellent biocompatibility and in the dental field beyond that, because of esthetic advantages and the little plaque accumulation. A disadvantage is their sensitivity to microscopic cracks because of their brittleness. Strength‐deteriorating microscopic cracks can be introduced into the ceramic surface by the manufacturing process. The objective of this study was to evaluate three methods on their efficiency to detect microscopic surface cracks of clinical relevance in dental ceramic materials. These methods were light‐optical microscopy, fluorescent microscopy after penetration with a fluorescent liquid, and scanning electron microscopy (SEM). It was found that microscopic cracks of critical sizes can be detected using the fluorescent penetrant method, which was not to be proven by light‐optical microscopy and even not by SEM. We conclude from our study that the fluorescent penetrant method could help to decrease clinical failures of dental ceramic components that are caused by surface microscopic cracks from the manufacturing process, if this method was routinely performed before the clinical use of the ceramic components. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 153–158, 2002
Biomaterial implants induce the inflammation marker CRP at the site of implantation
Authors: Löbler Marian , Saß Marko , Kunze Carmen , Schmitz Klaus‐Peter , Hopt Ulrich T. 
Published: October 2004

AbstractFollowing implantation of biomaterial patches into the gastrointestinal tract, we analyzed the host's response towards the foreign material. Asymmetric patches of polydioxanone covered Vicryl or poly‐3‐hydroxybutyrate were sutured onto the rat stomach. Tissue samples were generated at distinct time intervals after surgery, and RNA profiles were compared by Differential Display. RT‐PCR analysis of gene candidates that seemed differentially expressed showed that vitamin D binding protein mRNA was induced in stomach tissue after implantation of the biomaterial patches. In parallel, the amount of C‐reactive protein mRNA was found to be increased transiently as well. Implants induce a tissue response that is specific for a given material. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 165–167, 2002
Improved sample preparation of biomaterials for in vitro genotoxicity testing using reference materials
Authors: Müller Boris P. , Ensslen Silke , Dott Wolfgang , Hollender Juliane 
Published: October 2004

AbstractNew biomaterial related reference materials with known genotoxic properties were produced in order to study the sample preparation and in vitro genotoxicity testing of biomaterials. We incorporated genotoxic substances like benzo[a]pyrene into the biomaterial Tecoflex®, a polyurethane frequently used for catheters and other applications. We demonstrated that the model compound benzo[a]pyrene is sufficiently extracted by organic solvents, whereas cell culture medium only extracts very limited quantities. By changing the medium several times during extraction the extracted amount was augmented. Using higher amounts of organic solvent in relation to the reference material's surface led to a higher recovery of extracted benzo[a]pyrene. For the in vitro genotoxicity testing using the Mammalian Cell Gene Mutation Test (HPRT test), Mammalian Chromosome Aberration Test, and bacterial umu‐ and SOS‐tests, concentration of extracts is a prerequisite because of the low sensitivity of the test systems. Often cytotoxicity interferes with the evaluation of genotoxic effects. We demonstrated that some recommendations of the ISO 10993‐Part 3 and 12,1, 2 dealing with the biological evaluation of medical devices, seem to be insufficient, and new rules for the in vitro genotoxicity testing of biomaterials have to be established. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 83–90, 2002
Experimental studies on bone induction using low‐molecular‐weight poly (DL‐lactide‐co‐glycolide) as a carrier for recombinant human bone morphogenetic protein‐2
Authors: Bessho K. , Carnes D. L. , Cavin R. , Ong J. L. 
Published: October 2004

AbstractAn appropriate carrier acting as a slow delivery vehicle for the BMPs is required for maximal clinical effectiveness of these bone‐inductive proteins. The purpose of this study was to evaluate a low‐molecular‐weight PLGA copolymer as a synthetic, biodegradable carrier for rhBMP‐2 implantation in vivo. Two, 10, or 50 μg of recombinant human BMP‐2 were mixed with 10 mg of a poly (DL‐lactide‐co‐glycolide) (PLGA) 50:50 copolymer and implanted into the calf muscles of Wistar rats. Soft X‐ray analysis and histologic examination indicated that new bone formation occurred at all rhBMP‐2‐implanted sites within 3 weeks after implantation. Correlation of rhBMP‐2 concentration with the amount of bone induction was confirmed by specific alkaline phosphatase activity and calcium content assay. In vitro analysis indicated that 78.5% of the PLGA copolymer was degraded to smaller molecular weight material after 14 days in PBS solution. It is suggested that rhBMP‐2 was released in an active form at the implant site during the degradation of the copolymer, resulting in the induction of new bone formation. Thus this low‐molecular‐weight PLGA copolymer material represents a promising delivery vehicle for BMPs, and possibly other growth factors, around dental and orthopedic implants. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 61–65, 2002
Conformational analysis of thiopeptides: derivation of sp2 sulfur parameters for the CFF91 force field
Authors: Tran Tran Trung , Treutlein Herbert , Burgess Antony W. 
Published: October 2004

AbstractWhen a sulfur atom is used to substitute for the oxygen in peptide bonds, its bulkiness should restrict the conformational space available to an amino acid. This conformational restriction as well as the ability to confer resistance to enzymatic degradation in the body means that thio‐substituted amino acids are potentially useful building blocks for drug design. To simulate the effects of thio substitution, force field parameters for sp2 sulfur are required. In this article, parameters for the thioamide group have been derived for the molecular mechanics CFF91 force field (available at http://www.ludwig.edu.au/archive/tran). The bond increment charges were obtained by fitting to ab initio charges and dipoles. The van der Waals parameters were obtained by fitting to high‐resolution crystallographic data, and the nonbonded parameters were verified by comparing with experimentally derived lattice energy. The bonded parameters were derived by least‐square fits to the ab initio calculated energy surfaces, i.e., conformational energy as well as their first and second derivatives of seven model thioamide molecules. When the sp2 sulfur parameters were tested on a set of seven X‐ray crystallographic structures from the Cambridge Structural Database, they satisfactorily reproduced the bond lengths, bond angles, torsional angles, and nonbonded distances of all the crystal structures. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1010–1025, 2001
Conformational analysis of thiopeptides: (ϕ,ψ) maps of thio‐substituted dipeptides
Authors: Tran Tran Trung , Treutlein Herbert , Burgess Antony W. 
Published: October 2004

AbstractNoncoded amino acids such as isobutyric acid have been used extensively in the process of drug design and protein engineering. This article focuses on a noncoded amino acid where the oxygen in the peptide unit is replaced with a sp2 sulfur. It was hypothesized that the conformational space as well as the conformational preferences of thiopeptides will be more restricted and altered by the bulkier atom with different electrostatic properties. In vacuo conformational minima as well as associated energies for the thio‐substituted alanine dipeptides were calculated at the ab initio HF/6‐31G* level. When the bulkier sulfur atom acts as a hydrogen bond acceptor in the C5 conformation or in the C\documentclass{article}\pagestyle{empty}\begin{document}$^{\mathrm{axial}}_{7}$\end{document} and C\documentclass{article}\pagestyle{empty}\begin{document}$^{\mathrm{equatorial}}_{7}$\end{document} conformations, the hydrogen bond lengths are much longer than that of normal peptides. Consequently, the ϕ, ψ dihedral angles of the C5, C\documentclass{article}\pagestyle{empty}\begin{document}$^{\mathrm{axial}}_{7}$\end{document}, and C\documentclass{article}\pagestyle{empty}\begin{document}$^{\mathrm{equatorial}}_{7}$\end{document} conformations change to accommodate the longer hydrogen bonds. The thiopeptide group is a poorer hydrogen bond acceptor and a better hydrogen bond donor than the normal peptide group. Therefore, thio‐substitution at the amino terminal leads to disfavoring of the C7 conformations relative to the C5 conformations and thio‐substitution at the carboxyl terminal leads to favoring of the C7 conformations relative to the C5 conformation. To simulate the conformations in solution, (ϕ,ψ) conformational energy maps were calculated for the glycine and alanine dipeptides at various dielectric constants using the CFF91 force field with our previously derived parameters for the thioamide group. The results show that thio‐substitution does restrict the conformations available to amino acids residues in peptides. Thio substitution at the amino terminal introduces unfavorable interactions near ϕ=−120 and 120, where there are increased overlaps between Sn−1Hβ, and Sn−1Cβ atoms, respectively. Thio substitution at the carboxyl terminal restricts the conformations near ψ=60, −60, and 180, which correspond with increase overlaps between SnCβ, SnHβ′ and SnNn atoms, respectively. The effects of dithio substitutions of either the alanine or the glycine dipeptides are similar to the combined effects of the two single thio substitutions. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1026–1037, 2001
Repeated‐annealing sampling combined with multicanonical algorithm for conformational sampling of bio‐molecules
Authors: Kamiya Narutoshi , Higo Junichi 
Published: October 2004

AbstractA novel conformational sampling method (repeated‐annealing sampling method) is proposed to execute an efficient conformational sampling at a reasonable computational cost. In the method, a molecular dynamics simulation is done with repeating an elemental process. An elemental process consists of four subprocesses: high‐temperature run, annealing, room‐temperature run, and fast heating. The sampling is done automatically according to a temperature‐control schedule. The room‐temperature run is treated with the multicanonical algorithm, and the other subprocesses are done with the conventional molecular dynamics algorithm. The method, differing from the generalized ensemble methods recently developed, is not warrantable to give the canonical ensemble because of the nonphysical process in the annealing. However, we observed that the slower the annealing and the longer the high‐temperature run, the closer the sampled conformations to those of the canonical ensemble. A test was performed with tri‐N‐acetyl‐D‐glucosamine in vacuo, and the results were compared with those from the conventional multicanonical simulation. Not only the reweighted canonical distribution function but also the energy landscape were in good agreement with those from the conventional multicanonical simulation. The potential of mean force also showed a fairly good agreement with that from the conventional multicanonical simulation in the room‐temperature region. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1098–1106, 2001