bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fiber density of electrospun gelatin scaffolds regulates morphogenesis of dermal–epidermal skin substitutes
Authors: Powell H. M. , Boyce S. T. 
Published: August 2007

AbstractPorous, nowoven fibrous gelatin scaffolds were prepared using electrospinning. Electrospun scaffolds with varying fiber diameter, interfiber distance, and porosity were fabricated by altering the concentration of the electrospinning solution. Solution concentration was a significant predictor of fiber diameter, interfiber distance, and porosity with higher solution concentration correlated with larger fiber diameters and interfiber distances. The potential of electrospun gelatin as a scaffolding material for dermal and epidermal tissue regeneration was also evaluated. Interfiber distances >5.5 μm allowed deeper penetration of human dermal fibroblasts into the scaffold, whereas cells in scaffolds with more densely packed fibers were able to infiltrate only into the upper regions. Scaffolds with interfiber distances ≤10 μm exhibited well‐stratified dermal and epidermal layers including a continuous basal keratinocyte layer. These scaffolds were shown to form a keratinized layer like in normal skin, which acts as a barrier to infection and fluid loss. Interfiber distances between 5 and 10 μm appear to yield the most favorable skin substitute in vitro, demonstrating high cell viability, optimal cell organization, and excellent barrier formation. These results demonstrate the feasibility of electrospun gelatin as a scaffold for dermal–epidermal composite skin substitutes. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Bioglass®‐derived glass–ceramic scaffolds: Study of cell proliferation and scaffold degradation in vitro
Authors: Chen Q. Z. , Efthymiou A. , Salih V. , Boccaccini A. R. 
Published: August 2007

AbstractCell support function as well as cell proliferation on highly porous Bioglass®‐derived glass–ceramic scaffolds (designed for bone tissue engineering) have been assessed in vitro using osteoblast‐like cells (MG 63) cultured for up to 6 days. The biodegradation and mechanical stability of the scaffolds in the cell‐culture medium have also been investigated. It was found that the scaffolds had excellent cell supporting ability, with cells effectively infiltrating into and surviving at the center of the scaffolds. A quantitative study using the AlamarBlue™ assay revealed that the proliferation of cells on the glass–ceramic materials was comparable to that on the noncrystallized Bioglass®. While the crystalline phase in the glass–ceramic scaffolds transformed into a biodegradable amorphous calcium phosphate phase during cell culture, the mechanical strength of the scaffolds was maintained when compared with that of scaffolds incubated in simulated body fluid or immersed in cell‐free culture medium. It is believed that the attached cells and collagen secreted by cells could fill the micropores and microcracks on the surface of the foam struts, thus contributing to the mechanical stability of the degrading scaffolds. In summary, the developed glass–ceramic scaffolds possess the most essential features of a scaffold for bone tissue engineering: they are capable to support and foster relevant cells, able to provide temporary mechanical function, and biodegradable. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Mechanical, tribological, and biocompatibility properties of ZrN‐Ag nanocomposite films
Authors: Kertzman Z. , Marchal J. , Suarez M. , Staia M.H. , Filip P. , Kohli P. , Aouadi S.M. 
Published: August 2007

AbstractNanocomposite films of ZrN‐Ag were produced by reactive unbalanced magnetron sputtering, and their structural, chemical, mechanical, tribological, haemocompatibility, and antibacterial properties were studied as a function of film composition. The films formed a dense and homogeneous microstructure whereby nanocrystals of Ag are distributed evenly throughout the ZrN matrix. For small additions of silver, the hardness was found to increase, whereas the elastic modulus was found to decrease drastically. In the process of optimizing the deposition conditions, three kinds of coatings were prepared on 316 L surgical steel and tested by accelerated electrochemical polarization tests in order to detect the influence of Ag and the value of the bias potential on the corrosion performance of the system. Films produced under the optimum deposition conditions were, subsequently, deposited on medical grade Ti‐Al‐V and worn against ball‐bearing steel using a ball‐on‐disk tribotester in bovine serum and were found to have superior tribological properties compared with single‐phase ZrN coatings. The haemocompatibility of the films was assessed by investigating the adsorption of human serum albumin and fibrinogen on samples with different phase compositions. Quantification of the protein adsorption was carried out using spectroscopic ellipsometry, which confirmed the haemocompatibility of the films. Antibiotic activity of the films was quantified by incubating the films in bacterial cultures, namely, Staphylococcus epidermis, Staphylococcus aureus, and Escherichia coli. Films with a silver content > 10% exhibited superior antibacterial activity compared with the uncoated samples. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Effects of topographical surface modifications of electron beam melted Ti‐6Al‐4V titanium on human fetal osteoblasts
Authors: Ponader Sabine , Vairaktaris Eleftherios , Heinl Peter , Wilmowsky Cornelius v. , Rottmair Andreas , Körner Carolin , Singer Robert F. , Holst Stefan , Schlegel Karl A. , Neukam Friedrich W. , Nkenke Emeka 
Published: August 2007

AbstractThe aim of the study was to assess the suitability of different Ti‐6Al‐4V surfaces produced by the electron beam melting (EBM) process as matrices for attachment, proliferation, and differentiation of human fetal osteoblasts (hFOB 1.19). Human osteoblasts were cultured in vitro on smooth and rough‐textured Ti‐6Al‐4V alloy disks. By means of cell number and vitality and SEM micrographs cell attachment and proliferation were observed. The differentiation rate was examined by using quantitative real‐time PCR analysis for the gene expression of alkaline phosphatase (ALP), type I collagen (Coll‐I), bone sialoprotein (BSP) and osteocalcin (OC). After 3 days of incubation there was a significant higher vitality (p < 0.02) and proliferation (p < 0.02) of hFOB cells on smooth surfaces (Ra = 0.077 μm) and compact surfaces with adherent partly molten titanium particles on the surface (Ra ≤ 24.9 μm). On these samples cells spread over almost the whole surface. On porous surfaces with higher Ra values, cell proliferation was reduced significantly. Quantitative real‐time PCR analysis showed that the expression of osteogenic differentiation markers was not influenced by surface characteristics. Gene expression did not differ more than twofold for the different samples. Compact titanium samples with adherent partly molten titanium particles on the surface (Ra ≤ 24.9 μm) fabricated by the EBM process turned out to be best suited for cell proliferation, while highly rough surfaces (Ra ≥ 56.9 μm) reduced proliferation of hFOB cells. Surface characteristics of titanium can easily be changed by EBM in order to further improve proliferation. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Sp3‐Mediated VEGF regulation is dependent on phosphorylation by extra‐cellular signals regulated kinases (Erk)
Authors: Pagès Gilles 
Published: August 2007

AbstractWe have previously demonstrated that phosphorylation by Erk of Sp1 was essential for its full activity in the context of the VEGF promoter. Here, we show that Sp3, which, as Sp1, belongs to the GC‐rich binding transcription factor family, is also phosphorylated by Erk in vitro on serine 73. We have established cell lines in which expression of wild‐type Sp3 or a serine 73 to alanine (S73A) mutant is controlled by tetracycline. One of these cells lines also express the Raf:ER chimera which permits stimulation of Erk by tamoxifen. Difference in electrophoretic mobility and antibody directed against the phosphorylated serine 73 demonstrate that it is phosphorylated in vivo. Wild‐type Sp3 half‐life is increased upon Erk activation but the S73 is poorly implicated in this mechanism suggesting that Erk‐dependent Sp3 stability depends on other(s) domain(s) of the protein. Electro‐mobility shift assays and utilization of Gal4/Sp3 chimeric proteins show that Erk does not alter Sp3 DNA binding capacity but enhances its transcriptional activity. The S73A mutant Sp3 posses a reduced activity in Erk‐stimulated cells. In the inducible cell lines, expression of wild‐type form of Sp3 increases VEGF production whereas the S73A form has a reduced potential reflecting its lower transcriptional activity. Altogether our results described a new link between constitutive Erk activity and the regulation of VEGF expression two common denominators implicated in tumor angiogenesis. J. Cell. Physiol. 213: 454–463, 2007. © 2007 Wiley‐Liss, Inc.
Chemical characterization of medium‐chain‐length polyhydroxyalkanoates (PHAs) recovered by enzymatic treatment and ultrafiltration
Authors: Kathiraser Yasotha , Aroua Mohamed Kheireddine , Ramachandran Kadathur B , Tan Irene Kit Ping 
Published: August 2007

AbstractBACKGROUND: Medium‐chain‐length polyhydroxyalkanoates (PHAs) are biodegradable polyesters accumulated intracellularly as energy resources by bacterial species such as Pseudomonas putida. The most popular method for PHA recovery is solvent extraction using trichloromethane (chloroform) and methyl alcohol (methanol). An alternative method is enzymatic treatment, which eliminates usage of these hazardous solvents. This research focuses on the characterization of PHAs recovered by enzymatic treatments and ultrafiltration. Comparisons are made with conventional solvent extracted PHA.RESULTS: The purity of PHA in water suspension recovered by enzymatic treatments as analyzed by gas chromatography was 92.6%. Enzymatically recovered PHA was comparable to conventional solvent‐extracted PHA, which had a purity of 95.5%. PHA was further characterized for functional group analysis, structural composition analysis and molecular weight determination. It was found that the molecular weight of the PHA recovered by enzymatic treatment was less than solvent‐extracted PHA, probably due to degradation of the lipopolysaccharide layer. However, functional group and structural composition analyses showed similar results for PHA recovered by both methods.CONCLUSION: PHAs recovered through enzymatic digestion treatment have good comparability with solvent‐extracted PHAs. Thus enzymatic digestion has great potential as an alternative recovery method. Copyright © 2007 Society of Chemical Industry
Imaging of lung ventilation and respiratory dynamics in a single ventilation cycle using hyperpolarized He‐3 MRI
Authors: Holmes James H. , Korosec Frank R. , Du Jiang , O'Halloran Rafael L. , Sorkness Ronald L. , Grist Thomas M. , Kuhlman Janet E. , Fain Sean B. 
Published: August 2007

AbstractPurposeTo image respiratory dynamics and three‐dimensional (3D) ventilation during inhalation, breath‐hold, and exhalation for evaluation of obstructive lung disease using a single dose of hyperpolarized (HP) He‐3 during MRI.Materials and MethodsA single 2D‐3D projections inside Z encoding (PRIZE)‐2D acquisition was performed that consisted of a rapid 2D radial acquisition phase during inhalation of the HP He‐3, a 3D acquisition phase during a breath‐hold interval, and finally the same 2D radial acquisition during a forced exhalation maneuver followed by tidal breathing. The 3D PRIZE acquisition was comprised of radial sampling in the coronal plane and Fourier encoding in the patient's anterior–posterior direction. Nine patients with mild/moderate to severe asthma were studied (two individuals were studied twice) using this technique.ResultsBreath‐hold and dynamic imaging results showed physiological abnormalities and were compared with results from standard spirometry, body plethysmography, and computed tomography (CT). Dynamic images depicted regions of differential gas clearance and trapping observed during and after forced exhalation that were corroborated as regions of air trapping on CT imaging.ConclusionThe 2D‐3D PRIZE‐2D acquisition allowed for 3D depiction of ventilation during a breath‐hold, as well as detection of gas trapping. Imaging results were confirmed with spirometry, body plethysmography, and CT. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Three dimensional myoarchitecture of the human tongue determined in vivo by diffusion tensor imaging with tractography
Authors: Gaige Terry A. , Benner Thomas , Wang Ruopeng , Wedeen Van J. , Gilbert Richard J. 
Published: August 2007

AbstractPurposeTo study the anatomical relationships involving the intrinsic and extrinsic myofiber populations of the human tongue employing diffusion tensor imaging (DTI) with tractography.Materials and MethodsImages of the human tongue in vivo were obtained using a twice‐refocused spin echo DTI pulse sequence at 1.5T, isotropic 3 × 3 × 3 mm3 voxels, b‐value 500 seconds/mm2, and 90 different diffusion sensitizing gradient directions. Multivoxel tracts were generated along the vectors, corresponding to the directions of maximal diffusion in each voxel. The data was visualized using custom fiber tracking software and images compared with known anatomy.ResultsDTI tractography depicts the complete three‐dimensional (3D) myoarchitecture of the human tongue, specifically demonstrating the geometric relationships between the intrinsic and extrinsic myofiber populations. These results define the manner in which key extrinsic fiber populations merge with the longitudinally‐, transversely‐, and vertically‐aligned intrinsic fibers.ConclusionThe current results display for the first time the use of DTI tractography in vivo to visualize the complete structural anatomy of the human tongue and allow us to consider fundamental structure‐function relationships. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Superparamagnetic iron oxides and low molecular weight gadolinium chelates are synergistic for direct visualization of advanced liver fibrosis
Authors: Hughes‐Cassidy Fiona , Chavez Alyssa D. , Schlang Adrienne , Hassanein Tarek , Gamst Anthony , Wolfson Tanya , Sirlin Claude 
Published: August 2007

AbstractPurposeTo compare the contrast‐to‐noise ratio (CNR) of advanced liver fibrosis on nonenhanced (NE), gadolinium enhanced (Gd), superparamagnetic iron oxides enhanced (SPIO), and combined contrast‐enhanced (CCE) spoiled gradient echoes (SGEs).Materials and MethodsThis retrospective study assessed 83 consecutive patients with cirrhosis and 10 consecutive patients without fibrosis. All patients had NE, Gd, SPIO, and CCE images at 1.5T. A total of six breathhold SGE sequences with varying imaging parameters were assessed. MR images were evaluated qualitatively and, in 15 cirrhotics who underwent liver transplantation, compared to gross pathology. CNR of fibrosis to background liver was compared across sequences and contrast enhancement types.ResultsIn cirrhotic patients, CCE images on all sequences showed fibrosis as a meshwork of high‐signal 1‐mm to 3‐mm thick reticulations surrounding 2‐mm to 5‐mm low‐signal regenerative nodules. Fibrosis was less visible on Gd and SPIO images and was barely visible on NE images. CNR was significantly higher for CCE than for NE, Gd, or SPIO images in eight of nine comparisons (P < 0.0001–0.05). The liver had a homogeneous appearance in subjects without fibrosis.ConclusionCCE imaging depicts advanced liver fibrosis with higher CNR than NE, Gd, or SPIO SGEs. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Linear free energy relationships in CN bond dissociations in molecular ions of 4‐substituted N‐(2‐furylmethyl)anilines in the gas phase
Authors: Solano Espinoza Eduardo A. , Stashenko Elena , Martínez Jairo , Mora Uriel , Kouznetsov Vladimir 
Published: August 2007

AbstractThe substituent effect on the reactivity of the CN bond of molecular ions of 4‐substituted N‐(2‐furylmethyl)anilines toward two dissociation pathways was studied. With this aim, six of these compounds were analyzed by mass spectrometry using electron ionization with energies between 7.8 and 69.9 eV. Also, the UB3LYP/6‐31G (d,p) and UHF/6‐31G (d, p) levels of theory were used to calculate the critical energies (reaction enthalpies at 0 K) of the processes that lead to the complementary ions [C5H5O]+ and [M − C5H5O]+, assuming structures that result from the heterolytic and homolytic CN bond cleavages of the molecular ions, respectively. A kinetic approach proposed in the 1960s was applied to the mass spectral data to obtain the relative rate coefficients for both dissociation channels from ratios of the peak intensities of these ions. Linear relationships were obtained between the logarithms of the relative rate coefficients and the calculated critical energies and other thermochemical properties, whose slopes showed to be conditioned by the energy provided to the compounds within the ion source. Moreover, it was found that the dissociation that leads to [C5H5O]+ is a process strongly dependent upon the electron withdrawing or donating properties of the substituent, favored by those factors that destabilize the molecular ion. On the contrary, the dissociation that leads to [M − C5H5O]+ is indifferent to the polar electronic effects of the substituent. The abundance of both products was governed by the rule of Stevenson–Audier, according to which the major ion is the one of less negative electronic affinity. Copyright © 2007 John Wiley & Sons, Ltd.
Simultaneous determination of ampicillin, cefoperazone, and sulbactam in pharmaceutical formulations by HPLC with β‐cyclodextrin stationary phase
Authors: Tsou Tai‐Li , Huang Yu‐Chuan , Lee Chiu‐Wey , Lee An‐Rong , Wang Hsian‐Jenn , Chen Su‐Hwei 
Published: August 2007

AbstractAn accurate and reproducible method for the simultaneous determination of ampicillin (AMP), sulbactam (SUL), and cefoperazone (CFP) in pharmaceutical formulations by using HPLC with β‐CD stationary phase was developed. It involved the use of the added tetraethylammonium acetate (TEAA) reagent, pH, and methanol as the significant parameters to find the optimum separation condition. A high resolution and selectivity of analytes was obtained by running the mobile phase in methanol–5 mM TEAA buffer = 35:65 (v/v, pH 4.5) at 280 nm. The mean recoveries ranged from 96.6 to 103.3% for AMP in the synthetic mixture, 97.6 to 103.0% for SUL, and 97.0 to 104.0% for CFP. The low LOD (<1.8 μg/mL) and low CV (<0.9%) assured that this method was sensitive and reproducible. The assay of analytes in commercial products exhibited that it was convenient and reproducible for routine analyses of these components in sterilized H2O, saline, or 5% dextrose injection solutions.
Dissolving Cellulose in a NaOH/Thiourea Aqueous Solution: A Topochemical Investigation
Authors: Yan Lifeng , Chen Juan , Bangal Prakriti R. 
Published: August 2007

AbstractVarious kinds of cellulose/cellulose‐aggregate films have been prepared on newly cleaved mica by the deposition of the suspensions of microcrystalline cellulose in water in the presence or in absence of NaOH/thiourea at different temperatures. The topochemistry of the cellulose surfaces have been directly observed by employing both SEM‐EDX and AFM. These studies show that both NaOH and thiourea have a homogeneous distribution around the cellulose fibers during the dissolving process, and it is believed that their synergic interactions play a key role to dissolve the cellulose aggregates. It is also found that the dissolving process is continuous while the ice state formation promotes the dissolving process.magnified image
Effect of Branch Length on 13C NMR Relaxation Properties in Molten Poly[ethylene‐co‐(α‐olefin)] Model Systems
Authors: Parkinson Matthew , Klimke Katja , Spiess Hans Wolfgang , Wilhelm Manfred 
Published: August 2007

AbstractThe potential of branch length discrimination for branches containing six and more carbons via bulk NMR relaxation properties in the melt‐state has been explored. A systematic increase in the 13C spin‐lattice relaxation time (T) of the terminal branch carbons 1 and 2 was observed when the branch increased from 6 to 16 carbons in length. The measurement of T via inversion recovery at high‐field showed the most reliable data. The effects of saturation and NOE were addressed by using recycle delays longer than 5 × T and the use of the saturation recovery was found to be unsatisfactory. All nuclear relaxation times were determined in a highly time efficient manner using a previously developed melt‐state MAS NMR method.magnified image
Initial value problems for singular and nonsmooth second order differential inclusions
Authors: Biles Daniel C. , Ángel Cid J. , López Pouso Rodrigo 
Published: August 2007

AbstractWe study the existence of W2,1 solutions for singular and nonsmooth initial value problems of the type
equation image
whereT > 0 is a priori fixed, x0, x1 ∈ ℝ, and F: [0, T ] × ℝ → 𝒫(ℝ) \ {∅︁} is a multivalued mapping. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Controlled Release of DNA from Self‐Degrading Microcapsules
Authors: Borodina Tatiana , Markvicheva Elena , Kunizhev Stanislav , Möhwald Helmuth , Sukhorukov Gleb B. , Kreft Oliver 
Published: August 2007

AbstractSelf‐disintegrating microcapsules were prepared by encapsulating a highly active mix of proteases (Pronase®) into biodegradable polyelectrolyte shells. Pronase was captured by micron‐sized calcium carbonate particles that were subsequently embedded into onion‐like shells of poly(L‐arginine) and poly(L‐aspartic acid). EDTA treatment was used to extract the calcium carbonate constituents from the resulting core‐shell particles. As a consequence, Pronase was released into the capsule interior and started to digest the surrounding polyelectrolyte shell. Lifetimes of such self‐disintegrating capsules could be successfully adjusted to seconds, hours or days by varying the amount of encapsulated Pronase. The enzyme‐mediated, sustained release of encapsulated DNA is presented as a prospective application in drug delivery.magnified image
Konstitutive Beschreibung eines 10 %Cr‐Stahls zur Berechnung betriebsnaher Kriechermüdungsbeanspruchung
Authors: Simon A. , Samir A. , Scholz A. , Berger C. 
Published: August 2007

AbstractLeistungsschwankungen regenerativer Kraftwerksformen wie z. B. Windkraftanlagen erfordern eine flexible Nutzung von schnell zuschaltbaren konventionellen Spitzenlastkraftwerken wie z. B. GuD‐Kraftwerken. Hierbei steht aber die Forderung nach einer schnell zuschaltbaren und zugleich flexiblen Nutzung dieser Anlagen im Konflikt mit der Ermüdungsempfindlichkeit insbesondere der massiven Kraftwerkskomponenten durch Temperatur‐ und Leistungsschwankungen. Die Kriechermüdungsbeanspruchung dieser Anlagen ist dabei durch das auf die Oberfläche aufgebrachte Temperaturprofil vorgegeben. Dies bedingt eine anisotherme Betrachtung dieser Materialbeanspruchung mit der Forderung nach einer ebenfalls anisothermen Materialbeschreibung. Es wurde daher eine konstitutive Materialbeschreibung auf Basis Chaboche zur Beschreibung des anisothermen Materialverhaltens angepasst und anhand von Verifikationsexperimenten an einem modernen 10 %Cr‐Schmiedestahl überprüft. Als wesentliches Verifikationsexperiment wurde dabei eine in Anlehnung an ein Temperaturprofil auf der Oberfläche eines Dampfturbinenrotors abgeleitete einaxiale Beanspruchung nachgerechnet. Weiter wurden Versuche an Kerbproben durchgeführt um die Schädigungsentwicklung bei mehraxialen Beanspruchungen zu überprüfen. Eine modifizierte Dehnungsenergiefreisetzungrate als treibende Kraft der Schädigungsevolution konnte dabei das von herkömmlichen warmfesten Stähle abweichende Verhalten des 10 %Cr‐Wellenstahls gut beschreiben.