bluuebunny/crossref_metadata_2025_split huggingface dataset:
Localisation of specific heparan sulfate proteoglycans during the proliferative phase of brain development
Authors: Ford‐Perriss Miriam , Turner Kirsty , Guimond Scott , Apedaile Anwyn , Haubeck Hans‐Dieter , Turnbull Jeremy , Murphy Mark 
Published: May 2003

AbstractEarly brain development is characterised by the proliferation of neural precursor cells. Several families of signalling molecules such as the fibroblast growth factors (FGFs) and Wnts are known to play important roles in this early phase of brain development. Accumulating evidence demonstrates that signalling of these molecules requires the presence of heparan sulfate chains attached to a proteoglycan core protein (HSPG). However, the specific identity of the HSPG components in the developing brain is unknown. To determine which HSPGs might be involved at this early phase, we analysed the expression of the major cell surface HSPG families in the developing brain at a time of most active proliferation. Syndecan‐1 and glypican‐4 were the most highly expressed in the developing brain during the time of peak proliferation and localise to ventricular regions of the brain, where the precursor cells are proliferating. Syndecan‐4, although less abundant, also localises to cells in the ventricular zone. We have also examined HSPG involvement in brain development using cultures of embryonic neural precursor cells. We find that FGF2 stimulation of proliferation is inhibited in the presence of sodium chlorate, an inhibitor of heparan sulfate synthesis, and is rescued by addition of exogenous heparan sulfate. These data support a requirement for heparan sulfate in FGF signalling for proliferation of brain precursor cells. The expression of these specific HSPGs within the proliferative zone of the brain suggests that they may be involved in regulation of early brain development, such as FGF‐stimulated proliferation. Developmental Dynamics 227:170–184, 2003. © 2003 Wiley‐Liss, Inc.
Analysis of regulatory elements of E‐cadherin with reporter gene constructs in transgenic mouse embryos
Authors: Stemmler Marc P. , Hecht Andreas , Kinzel Bernd , Kemler Rolf 
Published: May 2003

AbstractProper regulation of E‐cadherin–mediated cell adhesion is important during early embryonic development and in organogenesis. In mice, E‐cadherin is expressed from the fertilized egg onward and becomes down‐regulated during gastrulation in mesoderm and its derivatives, but its expression is maintained in all epithelia. E‐cadherin promoter analyses led to the identification of binding sites for two transcriptional repressors, Snail and SIP1, which are able to mediate down‐regulation in vitro, but little is known about the regulatory elements that govern E‐cadherin transcriptional activity in vivo. Here, we compared the developmentally regulated expression of a series of lacZ‐reporter transgenes fused to different sequences of the murine E‐cadherin gene between −6 kb, including the promoter, and +16 kb, covering one third of intron 2. Four different segments with distinct regulatory properties were identified. The promoter fragment from +0.1 to −1.5 kb remains inactive in most cases but occasionally induces ectopic expression in mesodermal tissues, although it contains binding sites for the repressors Snail and SIP1. This promoter fragment also lacks positive elements needed for the activation of transcription in ectoderm and endoderm. Sequences from −1.5 to −6 kb harbor regulatory elements for brain‐specific expression and, in addition, insulator or silencer elements, because they are consistently inactive in the mesoderm. Only if sequences from +0.1 to +11 kb are combined with the promoter fragments is E‐cadherin–specific transgene expression observed in endoderm and certain epithelia. Sequences between +11 and +16 kb contain cis‐active elements that generally enhance transcription. Our analyses show that E‐cadherin expression is governed by a complex interplay of multiple regulatory regions dispersed throughout large parts of the locus. Developmental Dynamics 227:238–245, 2003. © 2003 Wiley‐Liss, Inc.
Intracellular calcium plays an essential role in cardiac development
Authors: Porter George A. , Makuck Ryan F. , Rivkees Scott A. 
Published: May 2003

AbstractIntracellular calcium signaling plays an essential role in cardiac physiology and modulates cardiac gene expression. However, the role that intracellular calcium signaling plays during cardiac development is not known. To address this issue, we examined the effects of altered intracellular calcium levels on cardiac morphogenesis. In acutely cultured mouse embryos, L‐type calcium channel blockade decreased resting intracellular calcium levels and inhibited calcium transients. Embryos cultured at embryonic day (E) 7.5–8.5 in the presence of the L‐type calcium channel blockers nifedipine and verapamil developed hearts that had a large left ventricle, lacked a right ventricle and had a long, thin outflow tract. If embryos were cultured at E7.5, calcium channel blockade also induced an abnormal, anterior cardiac loop. These alterations in development were not due to altered cardiac function, as heart rates at the end of the culture period were not affected by calcium channel blockade and blood flow was observed. Treatment with nifedipine altered the mRNA expression of the transcription factor Gata4, which was absent in the developing ventricles, and the sarcomeric protein Mylpc (myosin light chain 2V), which was decreased distal to the left ventricle and was absent at the site of the developing right ventricle. In contrast, the expression pattern of other cardiac transcription factor (Hand1, Hand2, Mef2c, Nkx2‐5) and cytoskeletal protein (Myhca, Tagln) mRNA did not change with calcium channel blockade. These data demonstrate that proper intracellular calcium signaling is essential for normal cardiac looping, gene expression, and organ development. Developmental Dynamics 227:280–290, 2003. © 2003 Wiley‐Liss, Inc.
A Compact and Lipophilic Enantiomer Showing a Bilayer Crystal Structure − Free Energy of Spontaneous Resolution of the Racemic Compound into the Crystalline Enantiomers
Authors: Roux María Victoria , Jiménez Pilar , Vacas Araceli , Cano Félix H. , Apreda‐Rojas María del Carmen , Ros Francisco 
Published: May 2003

AbstractThe melting points and the enthalpies and entropies of fusion of (R)‐1 and rac‐1, with the racemate both as the conglomerate and as the true racemic compound, were determined by differential scanning calorimetry: the melting points were 113.2 ± 0.3, 90.7 ± 0.4, and 80.5 ± 0.6 °C, respectively, the ΔHfus values 8.82 ± 0.03, 7.94 ± 0.27, and 5.98 ± 0.59 kcal·mol−1, respectively, and the ΔSfus values 22.8 ± 0.1, 21.8 ± 0.7, and 16.9 ± 1.7 cal·deg−1·mol−1, respectively. The specific heat of fusion (ΔCfus) of the pure enantiomer 1 calculated from these data is 39.1 cal·deg−1·mol−1. The ΔHfus, ΔSfus, and ΔCfus values of these enantiomers are consistently high relative to average values for organic compounds. The enthalpy, entropy, and free energy of formation of the racemic compound from the crystalline enantiomers are 1.56 kcal·mol−1, 3.8 cal·deg−1·mol−1, and 0.22 kcal·mol−1, as calculated from the above data. The positive sign of the free energy of formation bears out the observed spontaneous resolution of the racemic compound into the crystalline enantiomers. A statistical thermodynamic model of melting, weighing the different mechanical contributions to the crystalline and the liquid states, is described in conjunction with the interpretation of the data. It is concluded that both the interaction potential energy of the crystal of the pure enantiomer 1 and the vibrational mobility of the crystal structure are low, features pertinent to a low enthalpy and entropy of the crystal, respectively. X‐ray crystallography of (R)‐1 revealed a simple bilayer arrangement of the roughly ellipsoidal molecules: a characteristic bilayer consists of two monomolecular layers with interactions between the lipophilic groups in between, featuring a methyl−phenyl interaction, while the cyano groups project towards the outsides of the bilayer, which stacks by means of dipolar interactions to a constant distance. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
ZnBr2/CuCN‐Promoted, Highly Regioselective SN2′ Reactions of Some Functionalised Organolithium Compounds with Allylic and Propargylic Halides
Authors: Yus Miguel , Gomis Joaquín 
Published: May 2003

AbstractTreatment of lithium (2‐lithiomethylphenyl)methoxide (2a) and lithium 2‐(2‐lithiomethylphenyl)ethoxide (2b) [easily prepared by ring opening of phthalan (1a) and isochroman (1b), respectively, by the use of lithium and a catalytic amount of 4,4′‐di‐tert‐butylbiphenyl (DTBB)] with zinc bromide and copper cyanide, both in equimolecular amounts, in THF at room temperature, followed by treatment with different allylic chlorides or bromides 3 at −78 or 20 °C, almost exclusively provides (after hydrolysis with water) the corresponding alcohols 4′ resulting from an SN2′ displacement, the process being highly regioselective. The same procedure with intermediates 2a and 2b was applied to propargylic chlorides or bromides 5, exclusively yielding the corresponding allenylic alcohols 6′, resulting from an SN2′ reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Astrocytes as stem cells: Nomenclature, phenotype, and translation
Authors: Steindler Dennis A. , Laywell Eric D. 
Published: May 2003

AbstractRecently discovered multipotent astrocytic stem cells are discussed in light of current nomenclature for glial precursor and lineage‐associated cells in the developing, postnatal, and adult mammalian brain. Defining the phenotype of any immature cell in the nervous system is a challenge, and a position is stated that includes the need for categorizing cells within a continuum of differentiation potential. The possibility for dedifferentiating glial cells into clonogenic stem‐like cells offers numerous possibilities for translating knowledge and technology from this subfield of stem cell biology to regenerative medicine. Along with the need for developing a new lexicon for defining the cellular players that contribute to the generation of glia and neurons in the developing and mature central nervous system, the relationships also need to be established among potency, repopulation attempts, and tumorigenesis of cells meeting the criteria of glial stem cells. Finally, it is possible that understanding the normal differentiation, de‐ and transdifferentiation potential of glial stem‐like cells in the mature central nervous system will provide insights into the possible use of these cells, or biogenic factors associated with their growth and differentiation, in therapeutic approaches for a variety of neurological disorders. GLIA 43:62–69, 2003. © 2003 Wiley‐Liss, Inc.
Radial glia and somal translocation of radial neurons in the developing cerebral cortex
Authors: Nadarajah Bagirathy 
Published: May 2003

AbstractA series of recent studies have demonstrated that radial glia are neural precursors in the developing cerebral cortex. These studies have further implied that these cells are the sole precursor constituents of the dorsal forebrain ventricular zone that generate the projection neurons of the cortex. In view of these new findings, this review discusses radial neurons, a progeny of cortical neurons that are generated by radial glia and adopt somal translocation as the mode of migration. GLIA 43:33–36, 2003. © 2003 Wiley‐Liss, Inc.
Radial glia diversity: A matter of cell fate
Authors: Kriegstein Arnold R. , Götz Magdalena 
Published: May 2003

AbstractEarly in development of the central nervous system, radial glial cells arise from the neuroepithelial cells lining the ventricles around the time that neurons begin to appear. The transition of neuroepithelial cells to radial glia is accompanied by a series of structural and functional changes, including the appearance of “glial” features, as well as the appearance of new signaling molecules and junctional proteins. However, not all radial glia are alike. Radial glial lineages appear to be heterogeneous both within and across different brain regions. Subtypes of neurogenic radial glia within the cortex, for example, may have restricted potential in terms of the cell types they are able to generate. Radial glia located in different brain regions also differ in their expression of growth factors, a diverse number of transcription factors, and the cell types they generate, suggesting that they are involved in regionalization of the developing nervous system in several aspects. These findings highlight the important but complex role of radial glia as participants in key steps of brain development. GLIA 43:37–43, 2003. © 2003 Wiley‐Liss, Inc.
Use of a biomimetic strategy to engineer bone
Authors: Holy C. E. , Fialkov J. A. , Davies J. E. , Shoichet M. S. 
Published: May 2003

AbstractEngineering trabecular‐like, three‐dimensional bone tissue throughout biodegradable polymer scaffolds is a significant challenge. Using a novel processing technique, we have created a biodegradable scaffold with geometry similar to that of trabecular bone. When seeded with bone‐marrow cells, new bone tissue, the geometry of which reflected that of the scaffold, was evident throughout the scaffold volume and to a depth of 10 mm. Preseeded scaffolds implanted in non‐healing rabbit segmental bone defects allowed new functional bone formation and bony union to be achieved throughout the defects within 8 weeks. This marks the first report of successful three‐dimensional bone‐tissue engineering repair using autologous marrow cells without the use of supplementary growth factors. We attribute our success to the novel scaffold morphology. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 447–453, 2003
Adhesion of human leukocytes to biomaterials: An in vitro study using alkanethiolate monolayers with different chemically functionalized surfaces
Authors: Barbosa Judite N. , Barbosa Mário A. , Águas Artur P. 
Published: May 2003

AbstractThe adhesion of human leukocytes to self‐assembled monolayers of well‐defined surface chemistry was investigated in vitro. Polymorphonuclear (PMN) and mononuclear leukocytes were isolated from human blood by centrifugation techniques. The effect on adhesion of cell activation produced by pre‐incubation of leukocytes with phytohemagglutinin (PHA) and phorbol 12‐myristate 13‐acetate (PMA) was also studied. Gold substrates were modified by treatment with alkanethiols with three different terminal chemical groups: COOH, OH, and CH3. After incubation with the two subpopulations of leukocytes, the monolayers were washed, treated with fixative, stained with a Giemsa method, and observed by light microscopy to quantify the number of attached leukocytes. Comparative quantification of the density of leukocyte adhesion to the three types of self‐assembled monolayers was determined. The hydrophobic surface expressing CH3 was found to be the one that induced the highest adhesion density of leukocytes, both of PMN and mononuclear cells. In vitro activation of both mononuclear and PMN leukocytes further increased cell adhesion to the chemically defined monolayers that were used. This enhancement was higher for PHA‐activated than for PMA‐stimulated mononuclear cells, whereas PMA treatment of neutrophils resulted in a higher rate of adhesion of these cells than PHA stimulation. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 429–434, 2003
Engineering integrin‐specific surfaces with a triple‐helical collagen‐mimetic peptide
Authors: Reyes Catherine D. , García Andrés J. 
Published: May 2003

AbstractIntegrin‐mediated cell adhesion to extracellular matrix proteins anchors cells and triggers signals that direct cell function. The integrin α2β1 recognizes the glycine‐phenylalanine‐hydroxyproline‐glycine‐glutamate‐arginine (GFOGER) motif in residues 502–507 of the α1(I) chain of type I collagen. Integrin recognition is entirely dependent on the triple‐helical conformation of the ligand similar to that of native collagen. This study focuses on engineering α2β1‐specific bioadhesive surfaces by immobilizing a triple‐helical collagen‐mimetic peptide incorporating the GFOGER binding sequence onto model nonadhesive substrates. Circular dichroism spectroscopy verified that this peptide adopts a stable triple‐helical conformation in solution. Passively adsorbed GFOGER‐peptide exhibited dose‐dependent HT1080 cell adhesion and spreading comparable to that observed on type I collagen. Subsequent antibody blocking conditions verified the involvement of integrin α2β1 in these adhesion events. Focal adhesion formation was observed by immunofluorescent staining for α2β1 and vinculin on MC3T3‐E1 cells. Model functionalized surfaces then were engineered using three complementary peptide‐tethering schemes. These peptide‐functionalized substrates supported α2β1‐mediated cell adhesion and focal adhesion assembly. Our results suggest that this peptide is active in an immobilized conformation and may be applied as a surface modification agent to promote α2β1–specific cell adhesion. Engineering surfaces that specifically target certain integrin–ligand interactions and signaling cascades provides a biomolecular strategy for optimizing cellular responses in biomaterials and tissue engineering applications. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 511–523, 2003
Local infusion of FGF‐2 enhances bone ingrowth in rabbit chambers in the presence of polyethylene particles
Authors: Goodman Stuart B. , Song Yong , Yoo Juh Yung , Fox Nora , Trindade Michael C.D. , Kajiyama Glen , Ma Ting , Regula Donald , Brown Jim , Smith R. Lane 
Published: May 2003

AbstractOsseointegration of porous‐coated implants during revision arthroplasty procedures is often impeded due to the presence of residual granuloma, particulate debris, and a sclerotic, dysvascular bone bed. We hypothesized that local infusion of recombinant fibroblast growth factor (FGF‐2) would increase bone ingrowth in an in vivo model of tissue differentiation in the rabbit tibia in the presence of phagocytosable polyethylene particles. A drug test chamber (DTC) was implanted in the proximal medial tibial metaphysis of mature rabbits unilaterally. The chamber contained a 1× 1 × 5‐mm tunnel for tissue ingrowth, and was connected to an osmotic diffusion pump. FGF‐2 was infused at dosages of 0, 0.5, 5, 50, or 500 ng/day for a 3‐week period, with subsequent harvesting of the ingrown tissue after each 3‐week treatment. The effects of ultrahigh molecular weight polyethylene particles (0.5‐μm diameter) on tissue ingrowth were determined by adding particles to the chamber at concentrations of 5.8 × 1011 (low dose) or 1.7 × 1012 (high dose) particles/mL, with and without infusion of 50 ng/day of FGF for 3 weeks. The tissue forming in the chamber was harvested after each treatment for histologic processing and morphometric analysis of bone ingrowth. Statistical analysis was performed using parametric tests (ANOVA), nonparametric tests (Kruskal–Wallis test) and post hoc tests. In the absence of particles, infusion of 50 ng FGF‐2 per day yielded the greatest amount of bone ingrowth. The high dose of particles suppressed bone ingrowth into the chamber, but the low dose particles did not (p = 0.0002, 95% confidence limits = 9.19–18.80). Infusion of 50 ng FGF‐2 per day significantly increased net bone formation in the presence of high‐dose UHMWPE particles (p = 0.039, 95% confidence limits = 1.41–6.79). There was a trend for decreased numbers of vitronectin‐receptor positive (osteoclast‐like) cells with the addition of FGF‐2, compared to particles alone (p = 0.08). Local delivery of FGF‐2 may prove useful in mitigating the adverse effects of wear debris (e.g., in treating early osteolytic lesions), and facilitating osseointegration of revision total joint replacements in situations where the bone bed is suboptimal and residual particles and granulomatous tissue are present. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 454–461, 2003
Vitamin D enhances mitogenesis mediated by keratinocyte growth factor receptor in keratinocytes
Authors: Gamady Anat , Koren Ruth , Ron Dina , Liberman Uri A. , Ravid Amiram 
Published: May 2003

AbstractThe hormonally active vitamin D metabolite, 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3), and keratinocyte growth factor (KGF) belong to the network of autocrine and paracrine mediators in the skin. Both were shown to modulate keratinocyte proliferation, to reverse epidermal atrophy, to increase wound healing, and to reduce chemotherapy‐induced alopecia. The overlap between their activities may suggest that vitamin D exerts some of its actions by modulation of KGF activities in the skin. This notion was examined by using HaCaT keratinocytes cultured in serum‐free medium in the absence of exogenous growth factors and in the presence of the EGF receptor tyrosine kinase inhibitor AG 1478 that blocks their autonomous proliferation. These cells could be stimulated to proliferate by different fibroblast growth factors (FGFs). The relative mitogenic efficacy of basic FGF, acidic FGF, or KGF was in correlation with their affinities for the KGF receptor (KGFR). Forty‐eight hour co‐treatment with 1,25(OH)2D3 enhanced KGFR‐mediated cell proliferation in a dose dependent manner. Both ERK1/2 and c‐Jun N‐terminal kinase (JNK) were activated by the FGFs. Treatment with 1,25(OH)2D3 increased the activation of ERK but reduced the activation of JNK. Treatment with 1,25(OH)2D3 increased the levels of KGFR in the presence but not in the absence of KGF, probably due to inhibition of ligand‐induced receptor degradation. Inhibition of protein kinase C with bisindolylmaleimide did not interfere with the effect of 1,25(OH)2D3 on KGFR‐mediated ERK activation. Our results support the notion that the paracrine KGF–KGFR system in the skin can act in concert with the autocrine vitamin D system in keratinocytes to promote keratinocyte proliferation and survival under situations of stress and injury. J. Cell. Biochem. 89: 440–449, 2003. © 2003 Wiley‐Liss, Inc.
Retaining of the assembly capability of vimentin phosphorylated by mitogen‐activated protein kinase‐activated protein kinase‐2
Authors: Cheng Ting‐Jen , Tseng Yu‐Fang , Chang Whei‐meih , Chang Margaret Dah‐Tsyr , Lai Yiu‐Kay 
Published: May 2003

AbstractIntermediate filament (IF) networks can be regulated by phosphorylation of unit proteins, such as vimentin, by specific kinases leading to reorganization of the IF filamentous structure. Recently, we identified mitogen‐activated protein kinase‐activated protein kinase‐2 (MAPKAP kinase‐2) as a vimentin kinase (Cheng and Lai [1998] J. Cell. Biochem. 71:169–181). Herein we describe the results of further in vitro studies investigating the effects of MAPKAP kinase‐2 phosphorylation on vimentin and the effects of the phosphorylation on the filamentous structure. We show that MAPKAP kinase‐2 mainly phosphorylates vimentin at Ser‐38, Ser‐50, Ser‐55, and Ser‐82, residues all located in the head domain of the protein. Surprisingly, and in stark contrast to phosphorylation by most other kinases, phosphorylation of vimentin by MAPKAP kinase‐2 has no discernable effect on its assembly. It suggested that structure disassembly is not the only obligated consequence of phosphorylated vimentin as regulated by other kinases. Finally, a mutational analysis of each of the phosphorylated serine residues in vimentin suggested that no single serine site was primarily responsible for structure maintenance, implying that the retention of filamentous structure may be the result of the coordinated action of several phosphorylated serine sites. This also shed new lights on the functional task(s) of vimentin that is intermediate filament proteins might provide a phosphate reservoir to accommodate the phosphate surge without any structural changes. J. Cell. Biochem. 89: 589–602, 2003. © 2003 Wiley‐Liss, Inc.