bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of TCR‐restricting MHC density and thymic environment on selection and survival of cells expressing low‐affinity T cell receptors
Authors: Martinic Marianne M. , Rocha Benedita , McCoy Kathy D. , Hengartner Hans , Zinkernagel Rolf M.
Published: March 2004

H‐Y‐specific T cell receptor (TCR) transgenic mice express an MHC class I H‐2Db‐restricted TCR specific for a male antigen‐derived peptide (H‐Y). Selection and survival of cells expressing this low‐affinity TCR were analyzed under optimal and sub‐optimal conditions. Optimal conditions were provided by a thymic environment with high H‐2Db density. Sub‐optimal conditions were provided by a thymic environment with decreased H‐2Db density or by an athymic environment with either high or low H‐2Db density. Whereas negative selection was still guaranteed under sub‐optimal conditions, selection and survival efficiency of cells expressing the transgenic TCR were strongly dependent on optimal conditions. These results indicated that both a thymic microenvironment and a high density of TCR‐restricting MHC molecules were needed to ensure selection and maintenance of cells expressing TCR with low affinity and hence a more diverse T cell repertoire.
Mini‐review: Presentation of pathogen‐derived antigens in vivo
Authors: Lauvau Grégoire , Glaichenhaus Nicolas
Published: March 2004

Most intracellular pathogens induce robust T cell responses upon infection of mammalian hosts. In most cases, these T cell responses are protective and result in pathogen clearance. It is therefore important to determine how T cells are primed and how they differentiate into cytokine‐secreting and/or cytotoxic effector cells. In contrast to B cells, which recognize soluble Ag, CD8+ and CD4+ T cells react to Ag‐derived peptides bound to MHC I or MHC II molecules, respectively. Therefore, elucidating the mechanisms by which pathogen‐derived Ag become available for presentation is necessary to understand how pathogens trigger T cell responses in vivo. Although many excellent reviews have focused on the mechanisms involved in Ag processing, very few have pointed to the specificity of host–pathogen interactions. In this respect, it should be noticed that these interactions are very different from one pathogen to another, and may result in the involvement of different cells and molecules. Because of space limitations, we have decided to focus this review on two intracellular pathogens — vaccinia virus and Listeria monocytogenes. We have chosen these two pathogens because they both induce a strong CD8+ T cell response and because they have been extensively studied by both microbiologists and immunologists.
Synthesis, Structural and Spectroscopic Characterization of Four [(η6‐PAH)Cr(CO)3] Complexes (PAH = Pyrene, Perylene, Chrysene, 1,2‐Benzanthracene)
Authors: Arrais Aldo , Diana Eliano , Gervasio Giuliana , Gobetto Roberto , Marabello Domenica , Stanghellini Pier Luigi
Published: March 2004

The thermal reaction of hexacarbonylchromium with the polycyclic aromatic hydrocarbons (PAHs) pyrene, perylene, chrysene and 1,2‐benzanthracene has afforded four organometallic complexes of the type [(η6‐PAH)Cr(CO)3], whose unprecedented structures were obtained by single‐crystal X‐ray analysis. The topology of the coordination of the Cr(CO)3 fragment and its asymmetry with respect to the coordinating ring may depend on the opportunity to maintain the maximum aromaticity of the complexed ligand. DFT calculations, 1H NMR, FT‐IR and Raman spectroscopy have been used to elucidate the type of interaction between the PAH ligand and the carbonylmetal moiety, giving insight into the ligand‐to‐metal donor capacity and the intra‐ and intermolecular interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis and Structure of an Unprecedented Layered Vanadate Complex Containing Double‐Helical Chains: [{CoIII(phen)2}2V8O23]
Authors: Xiao Dongrong , Xu Yan , Hou Yu , Wang Enbo , Wang Shutao , Li Yangguang , Xu Lin , Hu Changwen
Published: March 2004

A novel two‐dimensional organic−inorganic hybrid vanadate complex [{CoIII(phen)2}2V8O23] has been hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, XPS spectroscopy, TG analysis and single‐crystal X‐ray diffraction. The single‐crystal X‐ray diffraction analysis reveals that compound 1 contains an unprecedented neutral 2D framework constructed of 4,10,12‐net sheets. To the best of our knowledge, compound 1 represents the first example of 2D layered vanadium oxide complex constructed of 4,10,12‐net sheets. Furthermore, the title compound consists of left‐handed and right‐handed helical chains, which are further interconnected to form the double‐helical chains. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis, Structural Characterizations and Magnetic Properties of a Series of Mono‐, Di‐ and Polynuclear Manganese Pyridinecarboxylate Compounds
Authors: Huang Deguang , Wang Wenguo , Zhang Xiaofeng , Chen Changneng , Chen Feng , Liu Qiutian , Liao Daizheng , Li Licun , Sun Licheng
Published: March 2004

Seven new manganese(II, III, IV) pyridinecarboxylate compounds (Et4N)[MnCl2(pic)2] (1, Hpic = picolinic acid) [MnCl(pic)2(H2O)]·H2O (2), [MnCl(pic)(H2O)2]n (3), [Mn(pic)2]n (4), [MnCl(pic)]n (5), [MnCl2(4‐C5H4NHCOO)]n (6) and [Mn2O2(pic)4] (7) were synthesized and structurally characterized. The picolinate ligand coordinates to the Mn ion forming a chelating five‐membered ring which constructs diverse architectures by various bridging modes, such as μ‐Cl, μ1,1‐ and μ1,3‐carboxylate bridges (syn‐syn and syn‐anti modes). The interaction between the pyridyl rings is discussed, displaying a face‐to‐face π‐π stacking for complex 6 and a T‐shaped C−H···π attraction for complex 4. Complex 3 has an infinite zigzag chain structure in which two neighboring Mn ions are linked by a carboxylate bridge in a syn‐anti mode. In complex 4, the Mn(pic)2 fragments are joined to each other by double μ1,1‐carboxylate bridges, forming a 2D layer structure. Complex 5 contains Mn4O4 square subunits which are connected by double μ‐Cl bridges to form a grid‐like 2D structure. The isonicotinate complex 6 has a zigzag chain structure containing mixed double μ‐Cl and μ1,3‐carboxylate bridges in a syn‐syn mode. Protonation at the pyridyl‐N position was found and identified by the IR and magnetic properties of 6. The participation of an oxidizing agent like MnO4− leads to complexes containing higher valent manganese (1, 2 and 7). The IR spectra of these complexes are discussed and found to be consistent with the structural features. The magnetic properties of complexes 4, 5 and 6 have been investigated. Antiferromagnetic coupling interactions were observed and satisfactory fitting results were obtained with J values ranging from −0.63 cm−1 to −2.35 cm−1. The magnetic parameters of these complexes, together with the parameters of other Mn complexes with comparable structures, are compared and discussed based on the bridging modes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Syntheses, Crystal Structures and Electrospray Mass Spectra of Coordination Polymers of an N,N′‐Bis(3‐pyridylmethyl)‐1,4‐benzenebis(methylamine) Ligand and Silver(I) Salts
Authors: Zhu Hui‐Fang , Kong Ling‐Yan , Okamura Taka‐aki , Fan Jian , Sun Wei‐Yin , Ueyama Norikazu
Published: March 2004

Four new coordination frameworks {[Ag2(L1)](NO3)2·2H2O}n (1), {[Ag(L1)](CF3COO)·2.5H2O}n (2), {[Ag2(L1)2][1,4‐C6H4(COO)2]·7H2O}n (3) and {[Ag(L1)]ClO4}n (4) were obtained by the reaction of N,N′‐bis(3‐pyridylmethyl)‐1,4‐benzenebis(methylamine) (L1) with the corresponding silver(I) salts. X‐ray diffraction analyses reveal that complex 1 has an infinite 1D chain structure, in which L1 acts as a tetradentate ligand. Complexes 2, 3 and 4 have 2D network structures, and the L1 ligands in these complexes adopt two different coordination modes: one kind of ligand coordinates four silver(I) atoms using its four N atoms, and the other kind of ligand connects only two silver(I) atoms with the two N atoms of the benzenebis(methylamine) unit, while the pyridine units remain free of coordination. Complex {[Ag(L2)]ClO4}n (5) was synthesized by reaction of N,N′‐bis(3‐pyridylmethyl)‐1,4‐benzenebis(methyleneamine) (L2) with silver(I) perchlorate. It has a novel 1D chain structure, which is different from that of 4 due to the different flexibility of the ligands L1 and L2. All of these complexes form 2D or 3D structures stabilized by hydrogen bonding, C−H···π and π‐π interactions. The results revealed that the nature of the counteranions and the flexibility of the ligand have an impact on the structure of the supramolecular architectures. The complexes were also characterized by electrospray mass spectrometry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Self‐Assembly of Bis(pyrrol‐2‐ylmethyleneamine) Ligands with CuII Controlled by Bridging [−(CH2)n−] Spacers and Weak Intermolecular C−H···Cu Hydrogen Bonding
Authors: Yang Lanying , Chen Qingqi , Li Yan , Xiong Shaoxiang , Li Genpei , Ma Jin Shi
Published: March 2004

Bis(pyrrol‐2‐ylmetyhleneamine) ligands linked by alkyl spacers between the imine nitrogens are shown to give dinuclear dimers or mononuclear monomers, depending on the length of the alkyl linker, upon coordination with CuII. Ligands containing ethylene or hexylene linkers −(CH2)n− (n = 2, 6) give dinuclear dimers 5 and 8, while propylene and butylene chains (n = 3, 4) give mononuclear monomers 6 and 7. X‐ray crystal structural analysis reveals that 5 exists as two very similar isomers 5a and 5b, in which the two ligands are bound to two CuII centers to form a distorted helical conformation. In the unit cells of 8, two entirely different isomers 8a and 8b are found. In 8a two ligands are side‐by‐side bound to two CuII centers to form a rectangular macrocycle, while in 8b they are bonded to two CuII centers to form a distorted double‐stranded helix. Moreover, X‐ray structural analysis reveals that complexes 5−8 are further assembled into one‐dimensional polymers through weak, intermolecular C−H···Cu hydrogen bonding, which plays a crucial role in stabilizing the crystal lattice. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Syntheses and Structural Characterization of AgI Complexes with the N,N′‐Di(2‐pyridyl)oxamide Ligand
Authors: Hsu Yi‐Fen , Chen Jhy‐Der
Published: March 2004

A series of the silver(I) complexes {[Ag(L)][NO3]}∞ (1), {[Ag(L)(CH3CN)][ClO4]}∞ (2), {[Ag2(L)3(CH3CN)2][PF6]2}∞ (3), and [Ag3(L)4(CH3CN)4][BF4]3 (4) [where L = N,N′‐di(2‐pyridyl)oxamide] have been prepared by the reactions of AgX (X = NO3−, ClO4−, PF6− and BF4−) with L. All the complexes have been structurally characterized by X‐ray crystallography, confirming that 1−3 are coordination polymers whereas 4 is a trinuclear complex. Complex 1 forms helical chains which are interlinked through a series of Ag···O interactions and C−H···O hydrogen bonds. In complexes 2 and 3, a new set of interactions involving two Ag···O interactions and self‐complementary double N−H···O hydrogen bonds were found to link the linear chains and ladder structures into polymer pairs (for 2) and molecular sheets (for 3). In complex 4, the molecules are interlinked by extensive Ag···N interactions and π−π stacking interactions to form molecular bands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Amino‐Substituted Ferra‐bis(tricarbollides) − Metallatricarbaboranes Designed for Linear Molecular Constructions
Authors: Grüner Bohumír , Bačkovský Jaroslav , Sillanpää Reijo , Kivekäs Raikko , Císařová Ivana , Teixidor Francesc , Viñas Clara , Štíbr Bohumil
Published: March 2004

Reactions between high purity FeCl2 and the anion [nido‐7‐(tBuHN)‐7,8,9‐C3B8H10)]− (1−) have been used for efficient syntheses of the twelve‐vertex double‐cluster metallatricarbollide complexes of the para,para (p,p) type [closo‐9,9′(RHN)2‐commo‐2,2′‐FeII‐1,7,9‐(C3B8H10)‐1′,7′,9′‐(C3B8H10)] (2) (2a, R = tBu and 2b, R = H) (yields 42−45% for 2a). Compound 2b, which contains two reactive amino substituents conveniently attached to the tricarbollide subclusters in p‐positions with respect to the metal center, was prepared via facile cleavage of the tBu substituent in 2a either by AlCl3 or by thermal means. The structure of 2b constitutes a good setting for the synthesis of building blocks for constructing linear metallatricarbollide rods of high stability. Two isomeric compounds of the para,meta (p,m) type 3, [closo‐9,10′‐(RHN)2‐commo‐2,2′‐Fe‐1,7,9‐(C3B8H10)‐1′,7′,10′‐(C3B8H10)] (where R = tBu 3a and/or H 3b), were isolated in smaller yields from reactions of high purity FeCl2 with 1− at higher temperatures. Also reported is the characterization of the m,m‐type complex, [closo‐10,10′‐(tBuHN)2‐commo‐2,2′‐FeII‐1,7,10‐(C3B8H10)‐1′,7′,10′‐(C3B8H10)] (4a), and the two zwitterionic species of the new 7‐L‐7,8,10‐C3B8H10 type (6) [L = Me3N 6a and tBu(Me)HN 6b] isolated in moderate yields from the reaction of reagent grade FeCl2 with 1−. The molecular structures of 2b, 3a, and 6b were determined by single‐crystal X‐ray diffraction studies. Multinuclear (1H and 11B), two‐dimensional [11B‐11B]‐COSY, and 1H{11B(selective)} magnetic resonance measurements enabled complete assignments of all resonances for all compounds and are in excellent agreement with the structures proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Metal Telluride Clusters — From Small Molecules to Polyhedral Structures
Authors: Wachter Joachim
Published: March 2004

Niobocene ditelluride complexes [(tBuC5H4)2Nb(Te2)H] (1) and [(C5Me5)2Nb(Te2H)] (2) are useful starting materials for the synthesis of heterometallic telluride complexes and clusters. The presence of free electron pairs, the propensity for Te−Te bond cleavage and the ability to eliminate Te ligands allow stepwise formation of polyhedral structures in reactions with binary transition metal carbonyl complexes or reactive organometallic fragments. Among the products are the first examples of organometallic derivatives of the elusive [MTe4]2− ion. Ligand cross‐transfer (CO versus Te) from one metal center to the other and subsequent charge separation lead to the formation of anionic metal telluride clusters and cationic carbonylniobocene species. The latter play a decisive role in tuning the electronic properties of the cluster units. Whereas the 17‐electron fragment (tBuC5H4)2Nb(CO) is directly anchored at the cluster cores by Te bridges, the 18‐electron cation [Cp*2Nb(CO)2]+ (Cp* = C5Me5) formed in situ is able to stabilize large and differently charged cluster anions. This is particularly the case in cobalt telluride cluster chemistry which is characterized by hexacapped cubic Co@Co8 or heptacapped pentagonal‐prismatic Co@Co10 polyhedra. These compounds exhibit pronounced electron‐sponge behavior, and crystallographic studies of differently charged clusters allow a correlation of different cluster charges and bond parameters important for understanding electronic structures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Tissue‐specific expression of cre recombinase from the Pax8 locus
Authors: Bouchard Maxime , Souabni Abdallah , Busslinger Meinrad
Published: March 2004

The transcription factor Pax8 is expressed in the developing thyroid gland, inner ear, kidney, and mid‐hindbrain region. Pax8 mutant mice die only postnatally due to a thyroid gland defect. Here we report the generation and expression analysis of a Pax8cre allele. Cre recombinase activity was detected in known Pax8 expression domains of Pax8cre/+ and Pax8cre/cre embryos carrying the Z/AP transgene, which expresses alkaline phosphatase only after Cre‐mediated excision of lacZ sequences. Alkaline phosphatase expression was additionally detected in the adrenal gland and in the facial, vestibulocochlear, and cuneate nerves, which have so far not been associated with Pax8 expression. Our data indicate that the Pax8cre allele provides a novel important tool for conditional gene manipulation and lineage tracing in different Pax8 expression domains. genesis 38:105–109, 2004. © 2004 Wiley‐Liss, Inc.
Dorsal telencephalon‐specific expression of Cre recombinase in PAC transgenic mice
Authors: Iwasato Takuji , Nomura Ryochi , Ando Reiko , Ikeda Toshio , Tanaka Mika , Itohara Shigeyoshi
Published: March 2004

The ability to restrict gene expression or disruption to specific regions of the brain would enhance understanding of the molecular basis for brain development and function. For this purpose, brain region‐restricted promoters are essential. Here we report the isolation of a DNA fragment containing the Emx1 gene promoter, which is responsible for dorsal telencephalon‐specific expression. The Cre recombinase gene was inserted into a mouse PAC (P1‐derived artificial chromosome) Emx1‐locus clone (PAC‐Emx1#1 clone) and utilized to generate three transgenic mouse lines. In all three lines, especially Tg3, Cre‐mediated recombination was highly restricted to Emx1‐expressing cell lineages, from embryonic stages to adulthood. Immunohistochemical analyses showed that Cre protein is expressed in the dorsal telencephalon in all three lines in adulthood. Thus, the PAC‐Emx1#1 clone contains essentially all regulatory elements necessary for Emx1 gene expression. Our results suggest that Emx1‐Cre Tg3 mice and the PAC‐Emx1#1 clone constitute powerful tools for dorsal telencephalon‐specific gene manipulation. genesis 38:130–138, 2004. © 2004 Wiley‐Liss, Inc.
Conditional gene deletion in primary nociceptive neurons of trigeminal ganglia and dorsal root ganglia
Authors: Agarwal Nitin , Offermanns Stefan , Kuner Rohini
Published: March 2004

The use of Cre‐loxP technology for conditional mutagenesis in pain pathways had been restricted by the unavailability of mice expressing Cre recombinase selectively in functionally distinct components of the nociceptive system. Here we describe the generation of transgenic mouse lines which express Cre recombinase selectively in sensory ganglia using promoter elements of the Nav1.8 gene (Scn10a). Cre‐mediated recombination was greatly evident in all nociceptive and thermoreceptive neurons of the dorsal root ganglia and trigeminal ganglia, but only in a small proportion of proprioceptive neurons. Cre‐mediated recombination was not detectable in the brain, spinal cord, or any nonneural tissues and began perinatally after invasion of primary afferents into the developing spinal cord. Thus, these mice enable selective deletion of genes in subsets of sensory neurons and offer a wide scope for studying potential functions of genes in pain perception, independent of secondary effects arising from developmental defects or global gene ablation. genesis 38:122–129, 2004. © 2004 Wiley‐Liss, Inc.
A reliable lacZ expression reporter cassette for multipurpose, knockout‐first alleles
Authors: Testa Giuseppe , Schaft Julia , van der Hoeven Frank , Glaser Stefan , Anastassiadis Konstantinos , Zhang Youming , Hermann Thomas , Stremmel Wolfgang , Stewart A. Francis
Published: March 2004

Alteration of the mouse genome through homologous recombination in embryonic stem (ES) cells is the most accurate and versatile way to dissect gene function in a vertebrate model. Most often, a selectable marker is used to create a knockout allele by replacing an essential part of the gene. However, knockout strategies are limited because the mutation is present constitutively. Conditional approaches based on the Cre‐loxP site‐specific recombination (SSR) system address this limitation; however, it requires that all parts of the targeted gene remain in ES cells. Here we report success with a “knockout‐first” strategy that ablates gene function by insertion of RNA processing signals without deletion of any of the target gene. Incorporation of site‐specific recombination target sites creates a multipurpose allele for both knockout and conditional applications. genesis 38:151–158, 2004. © 2004 Wiley‐Liss, Inc.
p38/SAPK2 controls gap junction closure in astrocytes
Authors: Zvalova Darina , Cordier Jocelyne , Mesnil Marc , Junier Marie‐Pierre , Chneiweiss Hervé
Published: March 2004

Astrocyte gap junction communication (GJC) is thought to contribute to death signal propagation following central nervous system injury, noteworthy in some ischemia/anoxia models. The inhibition of p38/stress‐activated protein kinase 2 (p38/SAPK2) by a pyrimidyl imidazole derivative has been reported to reduce the extent of the lesion area after cerebral ischemia. Therefore, interleukin‐1β (IL‐1β), which contributes to stroke‐induced brain injury and activates p38/SAPK2, and hyperosmolarity induced by sorbitol, a potent stimulus of p38/SAPK2 in non‐neuronal cells, were used to investigate a possible involvement of p38/SAPK2 in GJC modulation in mouse cultured astrocytes. Both stimuli inhibited dye coupling within minutes. The IL‐1β effect was transient, while that of sorbitol lasted up to 90 min. Both stimuli induced a rapid p38/SAPK2 activation, the kinetic of which matched that of induction of dye coupling inhibition. Immunocytochemical studies showed that IL‐1β and sorbitol induced a p38/SAPK2 translocation from the nucleus to the cytoplasm. The pharmacological agent SB203580 specifically blocked p38/SAPK2 activation, cytoplasmic translocation and reversed the IL‐1β and sorbitol‐induced inhibition of GJC. Further characterization of the p38/SAPK2 mode of action on GJC, performed with sorbitol, revealed an increased phosphorylation of protein kinase C (PKC) substrates abolished by both PKC inhibitors and SB203580. Expression and serine phosphorylation of connexin 43, the main component of astrocyte gap junctions, were unchanged, suggesting the existence of additional intracellular signaling mechanisms modulating the channel gating. Altogether, these results demonstrate that p38/SAPK2 is a central mediator of IL‐1β and sorbitol inhibitory actions on GJC and establish PKC among the distal effectors of p38/SAPK2. © 2004 Wiley‐Liss, Inc.
Triethyltin‐induced stress responses and apoptotic cell death in cultured oligodendrocytes
Authors: Stahnke Thomas , Richter‐Landsberg Christiane
Published: March 2004

Triethyltin (TET)‐induced neurotoxicity in the brain causes the formation of myelin edema and loss. Myelin deficits produced by early postnatal exposure to TET are permanent and cannot be repaired as the brain matures. The underlying causes have not been resolved. To investigate whether TET directly affects oligodendrocytes, the myelin‐forming cells of the central nervous system, cultured rat brain oligodendrocytes were prepared and treated with TET. The data show that TET was cytotoxic for oligodendrocytes and led to the onset of programmed cell death, as indicated by DNA fragmentation. Cellular membranous extensions were severely damaged, and the nuclei appeared to be condensed and fragmented. Concomitantly, the small heat shock protein HSP32, also known as heme oxygenase‐1 (HO‐1), and an indicator of oxidative stress, as well as the activation of extracellular signal‐regulated kinases 1 and 2 (ERK1,2), were observed. ERK1,2 have been implicated to participate in the regulation of cell death and survival. Myelin‐specific proteins MBP and CNP were not affected. In TET‐treated cells mitochondria redistributed from the processes to the cell somata near the nucleus, possibly as a consequence of microtubule disorganization. A disturbance of the mitochondrial membrane potential and mitochondrial fragmentation occurred. Hence, it might be hypothesized that oligodendroglial PCD, rather than axonal degeneration, contributes to myelin damage and deficits observed in rats after treatment with TET in vivo. © 2004 Wiley‐Liss, Inc.
Prostaglandin E2 and 6‐keto‐prostaglandin F1α production is elevated following traumatic injury to sciatic nerve†
Authors: Muja Naser , DeVries George H.
Published: March 2004

Sciatic nerve explants cultured either alone or in the presence of peritoneal macrophages were used to study prostaglandin E2 (PGE2) and 6‐keto‐PGF1α production following traumatic peripheral nerve injury. Although barely detectable at early time points (1–3 h in vitro), the production of PGE2 and 6‐keto‐PGF1α by sciatic nerve explants increased significantly after 18 h and remained elevated for up to 96 h. The cyclooxygenase‐2 (COX‐2) selective inhibitor, NS‐398, inhibited PGE2 and 6‐keto‐PGF1α production by injured sciatic nerve in a dose‐dependent manner. Consistent with the observed effect of NS‐398, peripheral nerve explants, as well as Schwann cells and perineural fibroblasts cultured from neonatal sciatic nerve, each contained COX‐2 immunoreactivity after 24 h in vitro. Both Schwann cells and perineural fibroblasts produced significant amounts of PGE2 and 6‐keto‐PGF1α; but only in the presence of arachidonic acid. As observed for injured sciatic nerve, the production of PGE2 and 6‐keto‐PGF1α by primary Schwann cells and perineural fibroblasts was completely inhibited by NS‐398. Compared to macrophages cultured alone, macrophages cultured in the presence of sciatic nerve explants produced large amounts of PGE2, whereas the level of 6‐keto‐PGF1α was unchanged. In contrast, macrophages treated with adult sciatic nerve homogenate did not produce significant amounts of either PGE2 or 6‐keto‐PGF1α during the entire course of treatment. We conclude that injured sciatic nerves produce PGE2 and 6‐keto‐PGF1α by a mechanism involving COX‐2 activity and that macrophages produce large amounts of PGE2 in response to soluble factors produced by injured nerve but not during the phagocytosis of peripheral nerve debris. Published 2004 Wiley‐Liss, Inc.
BDNF‐dependent stimulation of dopamine D5 receptor expression in developing striatal astrocytes involves PI3‐kinase signaling
Authors: Brito Veronica , Beyer Cordian , Küppers Eva
Published: March 2004

It is well known that brain‐derived neurotrophic factor (BDNF) and the early nigrostriatal dopaminergic input are implicated in the regulation of developmental processes in the neostriatum. There is growing evidence that interactions between these developmental signals rather than singular actions are critical for cellular differentiation and compartmentation of the striatum. In the present report, our goal is to identify striatal target cells for BDNF and dopamine. Using primary neuronal and astroglial cell cultures, we have demonstrated that BDNF selectively regulates D5 but not D1 receptor expression in astrocytes. This effect was not observed in neurons. Pharmacological approaches indicated that BDNF effects on dopamine D5 receptor expression were mediated at the intracellular level by an activation of the PI3‐ but not MAP‐kinase cascade. FACS analysis and confocal laser microscopy revealed that the newly synthesized D5 receptors were integrated into the plasma membrane of astrocytes. Our findings clearly show that developing striatal astrocytes are targets for BDNF. Furthermore, BDNF appears to regulate the dopamine responsiveness of astrocytes. This implicates that functional interactions between BDNF, dopamine, and astrocytes are necessary to warrant proper differentiation of the striatal anlage. © 2004 Wiley‐Liss, Inc.
Microglia expressing interleukin‐13 undergo cell death and contribute to neuronal survival in vivo
Authors: Shin Won Ho , Lee Da‐Yong , Park Keun Woo , Kim Seung Up , Yang Myung‐Soon , Joe Eun‐Hye , Jin Byung Kwan
Published: March 2004

How to minimize brain inflammation is pathophysiologically important, since inflammation induced by microglial activation can exacerbate brain damage. In the present report, we show that injection of lipopolysaccharide (LPS) into the rat cortex led to increased levels of interleukin‐13 (IL‐13) and to IL‐13 immunoreactivity, followed by the substantial loss of microglia at 3 days post‐LPS. IL‐13 levels in LPS‐injected cortex reached a peak at 12 h post‐injection, remained elevated at 24 h, and returned to basal levels at day 4. In parallel, IL‐13 immunoreactivity was detected as early as 12 h post‐LPS and maintained up to 24 h; it disappeared at 4 days. Surprisingly, IL‐13 immunoreactivity was detected exclusively in microglia, but not in neurons or astrocytes. Following treatment with LPS in vitro, IL‐13 expression was also induced in microglia in the presence of neurons, but not in the presence of astrocytes or in cultured pure microglia alone. In experiments designed to determine the involvement of IL‐13 in microglia cell death, IL‐13‐neutralizing antibodies significantly increased survival of activated microglia at 3 days post‐LPS. Consistent with these results, the expression of inducible nitric oxide synthase (iNOS) and tumor necrosis factor‐α (TNF‐α) was sustained in activated microglia and neuronal cell death was consequently increased. Taken together, the present study is the first to demonstrate the endogenous expression of IL‐13 in LPS‐activated microglia in vivo, and to demonstrate that neurons may be required for IL‐13 expression in microglia. Our data strongly suggest that IL‐13 may control brain inflammation by inducing the death of activated microglia in vivo, resulting in an enhancement of neuronal survival. © 2004 Wiley‐Liss, Inc.
IGF‐I prevents glutamate‐mediated bax translocation and cytochrome C release in O4+oligodendrocyte progenitors
Authors: Ness Jennifer K. , Scaduto Russell C. , Wood Teresa L.
Published: March 2004

Oligodendroglial death due to overactivation of the AMPA/kainate glutamate receptors is implicated in white matter damage in multiple CNS disorders. We previously demonstrated that glutamate induces caspase‐3 activation and death of the late oligodendrocyte progenitor known as the pro‐oligodendroblast (pro‐OL) via activation of the AMPA/kainate glutamate receptors. We also demonstrated that IGF‐I had the unique ability to sustain activation of Akt in the pro‐OL and provide long‐term protection of these cells from glutamate‐mediated apoptosis. The goal of these studies was to investigate the mechanisms of glutamate toxicity and IGF‐I‐mediated survival in the pro‐OL. IGF‐I prevented glutamate‐induced loss of mitochondrial membrane potential, cytochrome c release, and caspase‐9 activation. In contrast to IGF‐I mediated survival mechanisms in neurons, IGF‐I had no effect on the influx or recovery of intracellular calcium levels or on levels of major pro‐ and anti‐apoptotic molecules including Bax or Bcl‐xL. Rather, IGF‐I prevented the glutamate‐induced translocation of Bax to the mitochondria. Moreover, IGF‐I prevented caspase‐3 activation in pro‐OLs as long as 8 h after exposure of the cells to glutamate, suggesting that delayed activation of IGF‐I‐mediated survival pathways can block glutamate‐mediated apoptosis in pro‐OLs. The results of these experiments define the mechanisms by which glutamate kills oligodendrocyte progenitor cells and by which IGF‐I blocks glutamate‐induced apoptosis in these cells. The data also demonstrate that IGF‐I disrupts the glutamate‐mediated apoptotic pathway in the pro‐OL through mechanisms that are distinct from its survival‐promoting actions in neurons. © 2004 Wiley‐Liss, Inc.
Diverse microglial motility behaviors during clearance of dead cells in hippocampal slices
Authors: Petersen Mark A. , Dailey Michael E.
Published: March 2004

We used two‐channel three‐dimensional time‐lapse fluorescence confocal imaging in live rat hippocampal slice cultures (1–7 days in vitro) to determine the motility behaviors of activated microglia as they engage dead and dying cells following traumatic brain tissue injury. Live microglia were labeled with a fluorescently conjugated lectin (IB4), and dead neurons were labeled with a membrane‐impermeant fluorescent DNA‐binding dye (Sytox Orange or To‐Pro‐3). Tissue injury during the slicing procedure induced neuronal death and microglial activation, but the density of dead cells diminished ∼ 10‐fold by 7 days in vitro as resident microglia cleared dead cells. In time‐lapse movies (4–20 h long), activated microglia exhibited varying levels of motile and locomotory activity. The motility of microglia could change abruptly following contact by other microglia or death of nearby cells. When neighboring cells died, some microglia rapidly moved toward or extended a process to engulf the dead cell, consistent with a chemotactic signaling response. Dead cell nuclei usually were engulfed and carried along by highly motile and locomoting microglia. The mean time to engulfment was ∼ 5 times faster for newly deceased cells (33 min) than for extant dead cells (160 min), suggesting that the efficacy of microglial phagocytosis in situ might vary with time after cell death or mode of cell death. These observations demonstrate that activated microglia are heterogeneous with respect to motile activity following traumatic tissue injury and further indicate that cell motility in situ is temporally regulated at the single cell level, possibly by direct cell‐cell contact and by diffusible substances emanating from nearby dead cells. © 2004 Wiley‐Liss, Inc.
Transient upregulation of Nkx2.2 expression in oligodendrocyte lineage cells during remyelination
Authors: Watanabe Masahiko , Hadzic Tarik , Nishiyama Akiko
Published: March 2004

While numerous oligodendrocyte progenitor cells (OPCs) exist in the adult central nervous system (CNS), the molecular signals that promote or inhibit their differentiation into mature oligodendrocytes (OLs) are not known. To investigate whether remyelination in the adult CNS is regulated by the same mechanisms that promote developmental myelination, we used an acute demyelinating/remyelinating lesion in the adult rat spinal cord to examine the expression of the homeodomain transcription factor Nkx2.2, which has previously been implicated in oligodendrocyte differentiation during embryonic development. After a demyelinating insult, Nkx2.2 expression was upregulated first in NG2‐expressing OPCs surrounding the lesion and subsequently in both precursors and OLs that appeared inside the lesion prior to the onset of remyelination. The temporal and spatial pattern of Nkx2.2 upregulation coincided with that of oligodendrocyte differentiation characterized in our previous study (Watanabe et al., J Neurosci Res 69:826–836, 2002). A similar increase in the level of Nkx2.2 expression was observed in the postnatal developing optic nerve in a wave from the proximal to the distal retinal end. In vitro Nkx2.2 was expressed in OPCs and immature OLs isolated from postnatal rat spinal cord but was absent from mature OLs. These observations indicate that the process of generating new OLs in a remyelinating lesion recapitulates the developmental program involving activation of the Nkx2.2 gene, which may trigger the existing NG2‐expressing precursors in the adult CNS to undergo terminal differentiation into remyelinating OLs. © 2004 Wiley‐Liss, Inc.
Cranial variation in British mustelids
Authors: Lee S. , Mill P.J.
Published: March 2004

Nineteen measurements were made on 136 skulls belonging to seven mustelid species: Meles meles (Eurasian badger), Mustela nivalis, (weasel), Mustela erminea (stoat), Mustela putorius (polecat), Lutra lutra (otter), Mustela furo (ferret), and Mustela vison (American mink), and polecat‐ferret hybrids. To investigate shape, size‐related effects were eliminated by dividing all measurements by their geometric means. Canonical variate analysis was used to reveal major interspecies distinctions. Excluding the ferrets and polecat‐ferrets from the analysis, only 3.2% of the skulls misclassified (one mink, one weasel, and two stoats). Three groups separated on the first canonical axis: 1) badgers, 2) polecats, mink, and otters, and 3) stoats and weasels. The important variables were width of zygomatic arch and height of sagittal crest opposed to the postorbital distance, condylobasal length, and basilar length. Otters separated out on the second canonical axis; the most important variables were postorbital breadth and width of the postorbital constriction opposed to the basioccipital width. There was reasonable separation of polecats from mink on a combination of the second and third canonical axes. On the latter the most important variables were postorbital breadth opposed to postorbital distance. Addition of the ferret data showed that they lay closest to, and overlapped with, the polecats. The stoat and weasel data alone gave complete separation, with height of sagittal crest and width of zygomatic arch opposed to basioccipital width. However, using size‐in data the best separation was the relationship between postorbital breadth and either basioccipital width or postorbital distance. Sexual dimorphism was demonstrated in the skulls of badgers but was shown to be relatively insignificant when compared to the interspecific differences. J. Morphol. 260:57–64, 2004. © 2004 Wiley‐Liss, Inc.
Seasonal variation in body mass and locomotor kinetics of the fat‐tailed dwarf lemur (Cheirogaleus medius)
Authors: Lemelin Pierre , Schmitt Daniel
Published: March 2004

The fat‐tailed dwarf lemur (Cheirogaleus medius) is unusual among primates in storing large amounts of fat subcutaneously prior to hibernating during the winter months. In doing so, it increases its body mass by more than 50%, with a substantial weight gain in the tail. This seasonal increase in mass provides a unique natural experiment to examine how changes in body mass affect substrate reaction forces during locomotion. As body mass increases, it is expected that the limbs of the fat‐tailed dwarf lemur will be subjected to greater peak vertical substrate reaction forces during quadrupedal walking. However, whether or not these peak substrate reaction forces will increase proportionally across forelimbs and hindlimbs as body mass increases is unknown. Substrate reaction forces were collected on four adult C. medius walking quadrupedally on a 28‐mm pole attached to a force platform. Peak vertical substrate reaction forces (Vpk) (N) were analyzed and compared for a cross‐sectional sample of different body masses (180–300 g). Forelimb and hindlimb Vpk were positively correlated with body mass, with hindlimb Vpk always higher than forelimb Vpk. However, the rate at which Vpk increased relative to body mass was higher for the hindlimb than the forelimb. This disproportion in weight distribution between the forelimbs and hindlimbs as body mass increases appears to be linked to the accumulation of fat in the tail. It is likely that storing fat in the tail region may shift the center of mass more caudally, from a more cranial position when the tail is thinner. Such a caudal shift of the center of mass—either morphological or dynamic—is believed to have played an important role in the functional differentiation of the limbs and the evolution of locomotor modes of several tetrapod groups, including dinosaurs and primates. J. Morphol. 260:65–71, 2004. © 2004 Wiley‐Liss, Inc.
Brain and sense organ anatomy and histology in hemoglobinless Antarctic icefishes (Perciformes: Notothenioidei: Channichthyidae)
Authors: Eastman Joseph T. , Lannoo Michael J.
Published: March 2004

The Channichthyidae, one of five Antarctic notothenioid families, includes 16 species and 11 genera. Most live at depths of 200–800 m and are a major component of fish biomass in many shelf areas. Channichthyids are unique among adult fishes in possessing pale white blood containing a few vestigal erythrocytes and no hemoglobin. Here we describe the brains of seven species and special sense organs of eight species of channichthyids. We emphasize Chionodraco hamatus and C. myersi, compare these species to other channichthyids, and relate our findings to what is known about brains and sense organs of red‐blooded notothenioids living sympatrically on the Antarctic shelf. Brains of channichthyids generally resemble those of their bathydraconid sister group. Among channichthyids the telencephalon is slightly regressed, resulting in a stalked appearance, but the tectum, corpus cerebellum, and mechanoreceptive areas are well developed. Interspecific variation is present but slight. The most interesting features of channichthyid brains are not in the nervous tissue but in support structures: the vasculature and the subependymal expansions show considerable elaboration. Channichthyids have large accessory nasal sacs and olfactory lamellae are more numerous than in other notothenioids. The eyes are relatively large and laterally oriented with similar duplex (cone and rod) retinae in all eight species. Twin cones are the qualitatively dominant photoreceptor in histological sections and, unlike bathydraconids, there are no species with rod‐dominated retinae. Eyes possess the most extensive system of hyaloid arteries known in teleosts. Unlike the radial pattern seen in red‐blooded notothenioids and most other teleosts, channichthyid hyaloid arteries arise from four or five main branches and form a closely spaced anastomosing series of parallel channels. Cephalic lateral line canals are membranous and some exhibit extensions (canaliculi), but canals are more ossified than those of deeper‐living bathydraconids. We conclude that, with respect to the anatomy and histology of the neural structures, the brain and sensory systems show little that is remarkable compared to other fishes, and exhibit little diversification within the family. Thus, the unusual habitat and a potentially deleterious mutation resulting in a hemoglobinless phenotype are reflected primarily in expansion of the vasculature in the brain and eye partially compensating for the absence of respiratory pigments. Neural morphology gives the impression that channichthyids are a homogeneous and little diversified group. J. Morphol. 260:117–140, 2004. © 2004 Wiley‐Liss, Inc.
Axotomy‐dependent and ‐independent synapse elimination in organ cultures of Wlds mutant mouse skeletal muscle
Authors: Parson Simon H. , Ribchester Richard R. , Davie Neil , Gandhi Nirav P. , Malik Rabia Q. , Gillingwater Thomas H. , Thomson Derek
Published: March 2004

Progressive “dying back” neurodegenerative diseases are debilitating due to loss of connectivity after nerve terminal and axonal withdrawal, which impairs peripheral nerve function and leads ultimately to neuronal cell death. The mutant mouse (Wallerian degeneration slow; Wlds) provides an accessible model system to understand orthograde and retrograde degeneration, because in these mice axotomy induces slow, progressive withdrawal of nerve terminals from motor endplates. Axon degeneration itself is about 10 times slower than in wild‐type mice. We describe an organ culture paradigm that permits direct observation of the progressive changes in morphology of neuromuscular junctions in Wlds mutant mice. Normal nerve terminal and motor endplate morphology were maintained at most Wlds neuromuscular junctions for up to 72 hr in vitro. At others, synaptic boutons were removed from postsynaptic junctional folds in piecemeal fashion, as observed in adults in vivo. By contrast, nerve terminals degenerated rapidly and synchronously in wild‐type muscle cultures, resembling Wallerian degeneration in vivo. These observations confirm that in Wlds mice, axotomy triggers a mechanism of nerve‐terminal withdrawal that seems qualitatively different from that in wild‐type animals. The piecemeal dismantling of presynaptic terminals resembles that occurring during neonatal synapse elimination. Organ cultures of neonatal Wlds muscle maintained for 1–2 days in vitro also showed no evidence of synaptic terminal degeneration, but elimination of polyneuronal innervation progressed in vitro at approximately the same rate as in vivo. Taken together, the data suggest that both natural and axotomy‐induced forms of synapse withdrawal may be accessible to continuous observation and analysis, in organ‐cultures of WldS mouse muscles. This offers several advantages over repeated visualization of synaptic remodeling that has thus far been possible only in vivo. © 2004 Wiley‐Liss, Inc.
Emerging roles for bone morphogenetic proteins in central nervous system glial biology
Authors: Hall Alison K. , Miller Robert H.
Published: March 2004

Bone morphogenetic proteins, members of the TGFβ superfamily have been implicated in a variety of roles in the developing and mature nervous system. These divergent functions are a reflection of the closely defined spatial and temporal expression of BMPs in the CNS, and the potential interactions of the BMP signaling pathway with the STAT and MAP kinase pathways. In this review we discuss the roles of BMPs in early patterning of the CNS, determination of neural cell fate, and regulation of oligodendrocyte maturation during CNS development. Additional functions for members of the TGFβ superfamily in CNS injury responses are emerging suggesting these molecules represent useful targets for manipulating neural responses to CNS insults. © 2004 Wiley‐Liss, Inc.
Stromal cell‐derived factor 1‐mediated CXCR4 signaling in rat and human cortical neural progenitor cells
Authors: Peng Hui , Huang Yunlong , Rose Jeremy , Erichsen David , Herek Shelley , Fujii Nobutaka , Tamamura Hirokazu , Zheng Jialin
Published: March 2004

Stromal cell‐derived factor 1 (SDF‐1) and the chemokine receptor CXCR4 are highly expressed in the nervous system. Knockout studies have suggested that both SDF‐1 and CXCR4 play essential roles in cerebellar, hippocampal, and neocortical neural cell migration during embryogenesis. To extend these observations, CXCR4 signaling events in rat and human neural progenitor cells (NPCs) were examined. Our results show that CXCR4 is expressed in abundance on rat and human NPCs. Moreover, SDF‐1α induced increased NPCs levels of inositol 1,4,5‐triphosphate, extracellular signal‐regulated kinases 1/2, Akt, c‐Jun N‐terminal kinase, and intracellular calcium whereas it diminished cyclic adenosine monophosphate. Finally, SDF‐1α can induce human NPC chemotaxis in vitro, suggesting that CXCR4 plays a functional role in NPC migration. Both T140, a CXCR4 antagonist, and pertussis toxin (PTX), an inactivator of G protein‐coupled receptors, abrogated these events. Ultimately, this study suggested that SDF‐1α can influence NPC function through CXCR4 and that CXCR4 is functional on NPC. © 2004 Wiley‐Liss, Inc.
Effects of cyclin‐dependent kinase‐5 activity on apoptosis and tau phosphorylation in immortalized mouse brain cortical cells
Authors: Shelton Shirley B. , Krishnamurthy Pavan , Johnson Gail V.W.
Published: March 2004

Cyclin‐dependent kinase‐5 (CDK5), a unique CDK family member, is active primarily in the central nervous system (CNS). Previous studies suggest that CDK5 is proapoptotic and contributes to tau hyperphosphorylation and neurodegeneration in Alzheimer's disease. The objective of this study was to examine CDK5 effects on apoptotic progression and tau phosphorylation. Immortalized embryonic mouse brain cortical cells were used to establish a stable cell line that overexpressed wild‐type human tau. In these studies, thapsigargin, which induces endoplasmic reticulum stress and can cause accumulation of misfolded proteins, was used to induce apoptosis. Caspase‐3 activity and poly‐(ADP‐ribose)‐polymerase (PARP) cleavage, as measures of apoptosis, were significantly increased 24 and 48 hr after thapsigargin treatment, and these events were unaffected by tau expression. Although transient coexpression of CDK5 and its activator, p25, increased CDK5 activity greater than tenfold, increases in caspase‐3 activity in response to thapsigargin treatment were unaffected by the presence of CDK5/p25. Tau phosphorylation at the PHF‐1 epitope, but not the Tau‐1 epitope, was increased significantly in CDK5/p25‐transfected cells compared to cells transfected with dominant negative CDK5 (DNCDK5). The PHF‐1 epitope remained phosphorylated until 48 hr after thapsigargin treatment in the CDK5/p25‐transfected cells. Over the course of apoptosis in this model, phosphorylation of the Tau‐1 epitope was unaffected in cells transfected with DNCDK5, vector, or CDK5/p25. In summary, these results demonstrate that CDK5 does not have a significant impact on tau phosphorylation and thapsigargin‐induced apoptosis in this neuronal cell model. © 2004 Wiley‐Liss, Inc.