bluuebunny/crossref_metadata_2025_split huggingface dataset:
Co‐extrusion of biocompatible polymers for scaffolds with co‐continuous morphology
Authors: Washburn Newell R. , Simon Carl G. , Tona Alessandro , Elgendy Hoda M. , Karim Alamgir , Amis Eric J. 
Published: August 2002

AbstractA methodology for the preparation of porous scaffolds for tissue engineering using co‐extrusion is presented. Poly(ϵ‐caprolactone) is blended with poly(ethylene oxide) in a twin‐screw extruder to form a two‐phase material with micron‐sized domains. Selective dissolution of the poly(ethylene oxide) with water results in a porous material. A range of blend volume fractions results in co‐continuous networks of polymer and void spaces. Annealing studies demonstrate that the characteristic pore size may be increased to larger than 100 μm. The mechanical properties of the scaffolds are characterized by a compressive modulus on the order of 1 MPa at low strains but displaying a marked strain‐dependence. The results of osteoblast seeding suggest it is possible to use co‐extrusion to prepare polymer scaffolds without the introduction of toxic contaminants. Polymer co‐extrusion is amenable to both laboratory‐ and industrial‐scale production of scaffolds for tissue engineering and only requires rheological characterization of the blend components. This method leads to scaffolds that have continuous void space and controlled characteristic length scales without the use of potentially toxic organic solvents. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 20–29, 2002
Effects of pH on human bone marrow stromal cells in vitro: Implications for tissue engineering of bone
Authors: Kohn David H. , Sarmadi Mojgan , Helman Joseph I. , Krebsbach Paul H. 
Published: August 2002

AbstractThe objective of this study was to address the hypothesis that changes in extracellular pH alter collagen gene expression, collagen synthesis, and alkaline phosphatase activity in bone marrow stromal cells (BMSCs). Potential effects of pH on cell function are of particular importance for tissue engineering because considerable effort is being placed on engineering biodegradable polymers that may generate a local acidic microenvironment on degradation. Human and murine single‐cell marrow suspensions were plated at a density of 2 × 104 cells/cm2. After 7 days in culture, the pH of the culture medium was adjusted to one of six ranges: ≥7.8, 7.5.–7.7, 7.2–7.4, 6.9–7.1, 6.6–6.8, or ≤6.5. After 48 h of exposure to an altered pH, alkaline phosphatase activity and collagen synthesis decreased significantly with decreasing pH. This decrease was two‐to threefold as pH decreased from 7.5 to 6.6. In contrast, α1(I) procollagen mRNA levels increased two‐ to threefold as pH was decreased. The trend in osteocalcin mRNA expression was opposite to that of collagen. Small shifts in extracellular pH led to significant changes in the ability of BMSCs to express markers of the osteoblast phenotype. These pH effects potentially relate to the microenvironment supplied by a tissue‐engineering scaffold and suggest that degrading polymer scaffolds may influence the biologic activity of the cells in the immediate environment. © 2002 John Wiley & Sons, Inc. J Biomed Mater Res 60: 292–299, 2002; DOI 10.1002/jbm.10050
Initial interaction of U2OS cells with noncoated and calcium phosphate coated titanium substrates
Authors: ter Brugge P. J. , Dieudonne S. , Jansen J. A. 
Published: August 2002

AbstractFrom previous studies, we know that calcium phosphate (CaP) coated implants stimulate bone formation compared to uncoated implants. Nevertheless, the mechanism by which substrate surface characteristics affect cell function is unclear. In this study, we examined the initial interaction (30 min to 24 h) of U2OS cells with titanium substrates with or without a CaP coating. The effect of substrate roughness was also studied. When cell attachment was studied, we found that cells attached more readily to rough than to smooth surfaces. Also, more cells attached to the uncoated than to the CaP coated surface. After 24 h, cell numbers were similar for all substrate surfaces. Further, cells spread to a larger area on noncoated titanium than on the CaP coated substrates. At 24 h, the sequence of cell size was smooth titanium > rough titanium > CaP coated titanium. Shape measurements showed differences in cell shape between the cells on the different materials only at 7 h, not at different culture times. Cells expressed α2, α3, α5, α6, αv, and β1 subunits. Expression of α1, α4, αvβ3, β3, β4, and β7 was extremely low or was not found.The β1 integrin expression was higher on the coated than on the noncoated titanium at 3 h, but not on the other studied times. Expression of α2, α5, α6, and αv expression was found to be upregulated at 24 h compared to earlier culture times on coated titanium, but not on uncoated titanium substrates. From this we conclude that the surface characteristics of a material (roughness and composition) can affect the initial interaction of cells with the material. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 399–407, 2002
Slow‐releasing potential of vancomycin‐loaded porous hydroxyapatite blocks implanted into MRSA osteomyelitis
Authors: Saito Tomoyuki , Takeuchi Ryohei , Hirakawa Kazuo , Nagata Nobuhito , Yoshida Takuji , Koshino Tomihisa , Okuda Kenji , Takema Morio , Hori Toshihiko 
Published: August 2002

AbstractAlthough antibiotic‐loaded hydroxyapatite blocks have been used for the treatment of chronic osteomyelitis, their long‐term potential for releasing antibiotic into human bones is not well known. Five patients with chronic osteomyelitis due to methicillin‐resistant Staphylococcus aureus (MRSA) infection were effectively treated with local implantation of vancomycin‐loaded hydroxyapatite blocks. Blocks were removed during the following reconstructive surgeries when the releasing capability of the blocks, and the bacteriocidal activity of the remaining vancomycin in these blocks could be evaluated. Vancomycin was rapidly released within 1 month after implantation, and by 3 months 90% of vancomycin had leaked from the blocks. At 18 months vancomycin still remained in a bacteriocidal form in the hydroxyapatite blocks, though the blocks had no releasing potential or the eluted vancomycin had been changed to a different form. Vancomycin‐loaded porous hydroxyapatite blocks would be useful for the treatment of chronic osteomyelitis or implant‐associated osteomyelitis due to MRSA.© 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 245–251, 2002
Early dissolution of a morsellised impacted silicate‐free bioactive glass in metaphyseal defects
Authors: Griffon D. J. , Dunlop D. G. , Howie C. R. , Gilchrist T. , Salter D. M. , Healy D. M. 
Published: August 2002

AbstractThe purpose of this study was to evaluate the biological properties of idealized, morsellised impacted Corglaes®, a soluble silicate‐free glass. Twenty‐two sheep underwent implantation of pellets in six metaphyseal defects in both rear limbs. Particle size distribution of all aggregates (except the autograft) approached the ideal logarithmic grading line and all implants were impacted to a standard compactive effort. Treatment groups consisted of (1) empty defect (negative control), (2) autograft (positive control), (3) allograft (clinical control), (4) allograft idealized with Corglaes®, (5) 50/50 allograft/Corglaes® and (6) Corglaes®. Defects were sealed with polymethylmethacrylate. Healing of the defects was evaluated at 7 weeks (n=6) and 14 weeks (n=16) with computed tomography, histology, and histomorphometry. Remnants of Corglaes® were found within one of the defects 7 weeks after implantation. Defects filled with mixtures containing 50% or 100% Corglaes® were less dense, contained less bone and more fibrous tissue than defects with allograft, autograft, or allograft idealized with Corglaes®. Allograft idealized with Corglaes®may be considered for impaction grafting in revision hip arthroplasty, as well as local delivery of antibiotics. However, further studies and potential revision of the agent are required before mixtures containing concentrations of Corglaes® equal to or higher than 50% can be recommended.
Biodegradable poly(ethylene oxide)/poly(ϵ‐caprolactone) multiblock copolymers
Authors: Cohn Daniel , Stern Theodor , González M. Fernanda , Epstein Julia 
Published: August 2002

AbstractA series of poly(ethylene oxide) (PEO)/poly(ϵ‐caprolactone) (PCL) containing biodegradable poly(ether ester urethane)s, covering a wide range of compositions, were synthesized and characterized. The synthesis consisted of a two‐step process. During the first step, the ring‐opening reaction of ϵ‐caprolactone was carried out, initiated by the hydroxyl terminal groups of the PEO chain. The second step involved the chain extension of these PCL–PEO–PCL tri‐ mers with hexamethylene diisocyanate. By varying either the ethylene oxide/ϵ‐caprolactone ratio or the length of both segments, we obtained a series of polymers having different morphologies and displaying a broad range of properties. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 273–281, 2002
Prospective, randomized, sequential, crossover trial of large‐volume vs. normal‐volume leukapheresis procedures: Effects on subpopulations of CD34+ cells
Authors: A. Humpe , J. Riggert , S. Koch , T.J. Legler , U. Munzel , M. Köhler 
Published: August 2002

AbstractSome data exist on the influence of leukapheresis volume on the number of harvested peripheral blood hematopoietic progenitor cells (HPC), but less is known about the influence on the composition of HPC. We therefore performed a prospective, randomized crossover trial to evaluate the effect of large‐volume (LVL) vs. normal‐volume leukapheresis (NVL) on subpopulations of CD34+ cells in the harvest product of 15 patients with breast cancer and 8 patients with non‐Hodgkin's lymphoma. Patients were randomly assigned to start either with an LVL on day 1 followed by an NVL on day 2 or vice versa. The number of HPC, the extraction efficiency defined as difference between yield in the harvest and decrease in peripheral blood, and the relative proportion as well as the absolute numbers of CD34+ cells coexpressing CD38, CD90, HLA‐DR, CD117, CD7, CD19, CD41, or CD33 were evaluated. There was no significant difference with regard to the percentages of the subsets on comparison of LVL to NVL procedures. Only the absolute median number of CD34+HLA‐DR− cells was significantly (P=0.02) higher in LVL harvests compared with the corresponding NVL components, which can be explained on the basis of the higher yield and the higher extraction efficiency in LVL compared with NVL. LVL results in a higher yield of CD34+ cells and leads to an intra‐apheresis recruitment of HPC but the relative composition of the harvested CD34+ cells is not changed significantly. In addition, the amount of early, HLA‐DR−, hematopoietic HPC seems to be increased by an LVL. J. Clin. Apheresis. 16:109–113, 2001. © 2001 Wiley‐Liss, Inc.
Arsenite stabilizes IκBα and prevents NF‐κB activation in IL‐1 β‐stimulated Caco‐2 cells independent of the heat shock response*
Authors: Hershko Dan D. , Robb Bruce W. , Hungness Eric S. , Luo Guangju , Hasselgren Per‐Olof 
Published: August 2002

AbstractRecent studies suggest that sodium arsenite downregulates NF‐κB activity by inhibiting phosphorylation and subsequent degradation of IκBα. Many effects of sodium arsenite are secondary to induction of heat shock proteins. The role of the heat shock response in arsenite‐induced inhibition of NF‐κB, however, is not known. We examined the involvement of the heat shock response in arsenite‐induced inhibition of NF‐κB activity in IL‐1β‐stimulated Caco‐2 cells, a human colorectal adenocarcinoma cell line with enterocytic properties. Treatment of the cells with IL‐1β resulted in increased IκB kinase activity, reduced levels of IκBα and increased NF‐κB DNA binding activity. Sodium arsenite blocked all of these responses to IL‐1β without inducing changes in heat shock factor activity or heat shock protein levels. Results from additional experiments showed that the protective effect of sodium arsenite on IκBα was not influenced by the oxygen radical scavenger catalase or by inhibitors of the MAP‐kinase signaling pathway. The present results suggest that sodium arsenite stabilizes IκBα and prevents NF‐κB activation in IL‐1β‐stimulated Caco‐2 cells independent of the heat shock response. In addition, stabilization of IκBα by sodium arsenite does not require oxygen radical formation or activation of the MAP kinase signaling pathway. J. Cell. Biochem. 84: 687–698, 2002. © 2002 Wiley‐Liss, Inc.
Oxidative stress signalling in the apoptosis of Jurkat T‐lymphocytes
Authors: Chiaramonte Raffaella , Bartolini Enrico , Riso Patrizia , Calzavara Elisabetta , Erba Daniela , Testolin Giulio , Comi Paola , Sherbet Gajanan V. 
Published: August 2002

AbstractThe pathways of transduction of oxidative stress signals have been studied using the Jurkat T cell model. The oxidative stress was induced by exposure of the cells to 100 μM H2O2. DNA damage was detected within 15 min after commencement of treatment. DNA damage repair occurred within about 1 h in cells exposed to oxidative stress for 15 min. In continuous exposure to stress, DNA repair was slower and control levels of DNA integrity were not reached. DNA repair did not involve gene transcription. H2O2 at 100 μM caused cell death by necrosis as well as by apoptosis. Both these processes were induced by 15 min exposure to the stress stimulus. However, some important differences were found between necrosis and apoptosis. Necrosis was more rapid, began within an hour of treatment and continued to increase during the full duration of the experiment. But apoptosis was seen after 4 h from treatment and was conspicuous between 6 and 20 h after the start of treatment. The necrotic phase preceded apoptosis, although these did show an overlap. In the necrotic phase, Bcl‐2, Caspase 8 genes were down regulated. The 6–20 h phase characterised by a marked increase in apoptosis is accompanied by the up regulation of both Bcl‐2 and Caspase genes. Expression of the Fas and p53 genes was not altered in either phase. We also analysed the levels of expression of the scavenging genes whose gene products are involved in detoxification. No modulation of the antioxidant enzymes, catalase, Cu/Zn superoxide dismutase and glutatione peroxidase was detectable. J. Cell. Biochem. 82:437–444, 2001. © 2001 Wiley‐Liss, Inc.
Immortalization of human WI38 cells is associated with differential activation of the c‐myc origins
Authors: Tao Liang , Dong Zhifeng , Zannis‐Hadjopoulos Maria , Price Gerald B. 
Published: August 2002

AbstractTo study the possible relationships between origin activities and cellular processes leading to malignancy, we used an isogenic system of human embryo lung fibroblast cells WI38 and a SV40‐transformed variant, WI38 VA13 2RA (WI38(SV40)). We found that the activities of all initiation sites at the c‐myc locus were approximately two‐fold as high in WI38(SV40) cells as in WI38 cells. Thus, higher initiation frequency of origins at certain loci is induced with cell immortalization, one of the steps in the multi‐step process leading to malignancy. We measured the activities of the four c‐myc promoters P0, P1, P2, and P3 with nuclear runon assay in the two cell lines in order to detect potential individual promoter changes that may be also associated with immortalization by SV40 virus. The results show that the activities of the promoters P0, P1, and P3 did not significantly change, but the activity of the major promoter P2 in WI38(SV40) cells was about 7.5‐ to 8.0‐fold as high as that in WI38 cells. The increased activity of promoter P2, although ∼600 bp downstream of one of the major DNA replication initiation sites, had no preferential influence on the major sites of origin activity. Since the distribution of nascent strand abundance was not significantly altered, binding of transcription factors does not seem to facilitate the assembly of pre‐replication complex (pre‐RC) or otherwise preferentially alter the activities of the DNA replication proteins at this major initiation site. J. Cell. Biochem. 82:522–534, 2001. © 2001 Wiley‐Liss, Inc.
Low‐density caveolae‐like membrane from Xenopus laevis oocytes is enriched in Ras
Authors: Sadler Susan E. 
Published: August 2002

AbstractDetergent‐free discontinuous sucrose density gradient centrifugation was used to resolve low‐ and high‐density membrane fractions from Xenopus laevis oocytes. Compared to high‐density membrane, low‐density oocyte membrane is enriched two‐fold in cholesterol and highly enriched in ganglioside GM1. Protein immunoblotting of membrane fractions from whole cells with polyclonal anti‐human caveolin antibody detected multiple bands, including a distinctive triad with apparent molecular weights of 21, 33, and 48 kDa. To more clearly determine which of these caveolin‐like protein(s) is associated with the oocyte plasma membrane, microdissection was used to separate external membrane (cortical preparations containing plasma membrane) from intracellular membrane. Cortical membrane preparations displayed a single 21‐kDa caveolin‐like protein in low‐density membrane. Internal oocyte membrane displayed the higher molecular weight bands of 33 and 48 kDa and a lesser amount of the 21‐kDa protein in low‐density membrane fractions. Monoclonal anti‐human Ras antibody detected a single 23‐kDa immunoblot band that is enriched an average of eight‐fold in low‐density membrane fractions prepared from whole cells. This is the first report of caveolin‐associated, low‐density membrane in amphibian oocytes, and is consistent with a role for caveolin and caveolae‐like microdomains in oocyte signal transduction. © 2001 Wiley‐Liss, Inc.
Molecular cloning and characterization of a RING‐H2 finger protein, ANAPC11, the human homolog of yeast Apc11p*
Authors: Chan Anna H. , Lee Simon M.Y. , Chim Stephen S. , Kok Louis D.S. , Waye Mary M.Y. , Lee Cheuk‐Yu , Fung Kwok‐Pui , Tsui Stephen K.W. 
Published: August 2002

AbstractYeast Apc11p together with Rbx1 and Roc2/SAG define a new class of RING‐H2 fingers in a superfamily of E3 ubiquitin ligases. The human homolog of Apc11p, ANAPC11 was identified during a large‐scale partial sequencing of a human liver cancer cDNA library and partial characterization was performed. This 514 bp full‐length cDNA has a predicted open reading frame (ORF) encoding 84 amino acids. The ORF codes for ANAPC11, the human anaphase promoting complex subunit 11 (yeast APC11 homolog), which possesses a RING‐H2 finger motif and exhibits sequence similarity to subunits of E3 ubiquitin ligase complexes. In Northern blot hybridization with poly(A) RNA of various human tissues using radio‐labelled ANAPC11 cDNA probe, we found strong signals detected in skeletal muscle and heart; moderate signals detected in brain, kidney, and liver; and detectable but low signals in colon, thymus, spleen, small intestine, placenta, lung, and peripheral blood leukocyte. The ANAPC11 gene is located at the human chromosome 17q25. ANAPC11 is distributed diffusely in the cytoplasm and nucleus with discrete accumulation in granular structures in all the cell lines (AML 12, HepG2, and C2C12) transfected. Expression level of ANAPC11 is found higher in certain types of cancer determined in the RNA dot blot experiment. J. Cell. Biochem. 83: 249–258, 2001. © 2001 Wiley‐Liss, Inc.
Putative basal lateral membrane receptors for 24,25‐dihydroxyvitamin D3 in carp and Atlantic cod enterocytes: Characterization of binding and effects on intracellular calcium regulation
Authors: Larsson Dennis , Nemere Ilka , Sundell Kristina 
Published: August 2002

AbstractThe vitamin D metabolite, 24R,25‐dihydroxyvitamin D3 (24R,25(OH)2D3), was tested for its ability to specifically bind to basal lateral membranes isolated from intestinal epithelium of Atlantic cod (a seawater fish), carp (a freshwater fish), and chicken. Specific saturable binding was demonstrated in membranes from all three species. Membranes from Atlantic cod, carp, and chicken revealed Kd's of 7.3 ± 0.9, 12.5 ± 0.9 and 7.8 ± 0.1 nM, and a Bmax for each species estimated to 57.9 ± 2.9, 195.1 ± 8.4 and 175 ± 0.8 fmol/mg protein, respectively. Scatchard analyses indicated a convex curvature and Hill analyses revealed apparent Hill coefficients of 1.84 ± 0.28, 1.80 ± 0.29, and 1.78 ± 0.27 for Atlantic cod, carp and chicken, suggesting a positive cooperative binding in all three species. Basal lateral membranes from Atlantic cod and carp were used to further characterize the binding moiety. In competition studies, basal lateral membranes from Atlantic cod or carp did not discriminate between 24R,25(OH)2D3 and the 24S,25(OH)2D3 isomer, whereas, 1,25(OH)2D3 and 25(OH)D3, were less effective in competing with [3H]24R,25(OH)2D3 for binding to basal lateral membranes in Atlantic cod and carp. In both the Atlantic cod and carp enterocyte basal lateral membranes, the binding activity could be extracted equally well with high salt as with detergent, indicating a peripheral membrane protein rather than an integral membrane binding protein. Finally, isolated Atlantic cod and carp enterocytes were chosen for analyses of signal transduction events mediated by the putative receptor. In both species, 24R,25(OH)2D3 but not 24S,25(OH)2D3, suppressed Ca2+‐uptake by enterocytes in a dose‐dependent manner. Enterocytes from Atlantic cod and carp, acclimated to Ca2+‐free media, responded by an intracellular Ca2+‐release within seconds after addition of 24R,25(OH)2D3 or 24S,25(OH)2D3. The effects on intracellular Ca2+‐release were dose‐dependent for both metabolites. 24S,25(OH)2D3 was effective at lower concentrations and triggered a higher response compared to 24R,25(OH)2D3. These results suggest that the binding molecule(s) for 24R,25(OH)2D3 and 24S,25(OH)2D3 is/are capable of acting as a receptor, mediating rapid, non‐genomic responses in intestinal cells. © 2001 Wiley‐Liss, Inc. J. Cell. Biochem. 83: 171–186, 2001. © 2001 Wiley‐Liss, Inc.
Retinoblastoma protein complexes with C/EBP proteins and activates C/EBP‐mediated transcription*
Authors: Charles Amos , Tang Xiaoren , Crouch Erika , Brody Jerome S. , Xiao Zhi‐Xiong Jim 
Published: August 2002

AbstractThe retinoblastoma protein (RB) recruits histone deacetylase (HDAC) to repress E2F‐mediated transactivation that plays a critical role in cell cycle regulation. RB is also involved in activation of expression of a number of tissue specific‐ and differentiation‐related genes. In this study, we examined the mechanism by which RB stimulated the expression of a differentiation‐related gene, the surfactant protein D (SP‐D), which plays important roles in innate host defense and the regulation of surfactant homeostasis. We demonstrated that RB specifically stimulated the activity of human SP‐D gene promoter. The RB family member, p107 but not p130, also increased SP‐D promoter activity. Activation by RB was mediated through a NF‐IL6 (C/EBPβ) binding motif in the human SP‐D promoter, and this sequence specifically bound to C/EBPα, C/EBPβ, and C/EBPδ. RB formed stable complexes with all three C/EBP family members. RB small pocket (amino acid residues 379–792), but not the C‐pocket (amino acid residues 792–928), was necessary and sufficient for its interaction with C/EBP proteins. Furthermore, we demonstrated that the complexes containing RB and C/EBP proteins directly interacted with C‐EBP binding site on DNA. These findings indicate that RB plays a positive, selective, and direct role in the C/EBP‐dependent transcriptional regulation of human SP‐D expression. J. Cell. Biochem. 83: 414–425, 2001. © 2001 Wiley‐Liss, Inc.