bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell‐Type‐Specific adhesion mechanisms mediated by fibronectin adsorbed to chemically derivatized substrata
Authors: Lewandowska Kristine , Pergament Edward , Sukenik Chaim N. , Culp Lloyd A. 
Published: December 2004

AbstractPlasma fibronectin (pFN) adhesion mechanisms on inert substrata were evaluated for murine fibroblasts (3T3) and human neuroblastoma (Platt) cells using glass coverslips Chemically derivatized with a self‐assembled monolayer of aliphatic chains terminated with a specific endgroup to interact with adsorbed pFN: [CH3], [SH], [SCOCH3], NH2 [S03H] or underivatized glass [SiOH]. All surfaces bound similar amounts of pFN and facilitated attachment of both cell types within narrow ranges. However, spreading/differentiation responses of cells differed considerably among the surfaces. While 3T3 cells spread and developed microfilament stress fibers comparably on all surfaces, inclusion of an RGDScontaining synthetic peptide i n t h e medium revealed variation in resistance to stress fiber formation mediated by an RGDS‐recognizing integrin: [NH3] > [CH3] >> [SiOH],[SH],[SCOCH3]. Different patterns of neurite formation were observed for neuroblastoma cells: [SiOH], [NH3]. Similarity in cell responses to both [CH3] and [NH2] surfaces argues against pattern dependent upon the hydrophobicity of substrata. When pFN was diluted to a subsaturable concentration with albumin for adsorption, neuroblastoma responses changed significantly from those observed on pFN‐saturated surfaces, for both spreading and neurite generation: [NH2],[S03H] >> [SH], [SCOCH3] > [SiOH],[CH3]. Responses to the pFN :albumin mixture were markedly improved from responses after sequential adsorptions, demonstrating optimization of pFN conformation (not merely binding) by coadsorption of albumin molecules. In most cases, the [NH2] surface yielded responses distinctively different from the other surfaces. Overall, these data suggest many variations in the conformation of pFN molecules adsorbed to specific inert surfaces, as well as variations in the responses of cell surface receptors to conformationally specific pFNs. They also reveal cell‐type‐specific changes in differentiated cell responses on derivatized substrata, mediated by different classes of cell surface receptors for the two cell types, and provide optimism for regulating FN‐dependent adhesion mechanisms in either positive or negative contexts on biomaterial surfaces derivatized with one or more of these chemical end‐groups. © John Wiley & Sons, Inc.
The ultrastructure of the bone‐hydroxyapatite interface in vitro
Authors: de Bruijn J. D. , Klein C. P. A. T. , de Groot K. , van Blitterswijk C. A. 
Published: December 2004

AbstractRat bone marrow cells were cultured on plasma‐sprayed hydroxyapatite (HA). The cells formed a mineralized extracellular matrix (ECM) that exhibited several characteristics of bone tissue. The interface between this mineralized ECM and the HA was studied at the ultrastructural level with scanning and transmission electron microscopy and x‐ray microanalysis. Initially, the deposition of a globular, afibrillar matrix was observed on HA. This was followed by the integration of collagen fibers in this matrix and their subsequent mineralization. At the bone‐HA interface two distinctly different interfacial structures were observed. An electron‐dense layer with a thickness of 20‐60 nm was regularly present, which contained both organic and inorganic material and was rich in glycosaminoglycans. The interfaces differed however, in the presence or absence of an amorphous zone which was free of collagen fibers and had an average thickness of 0.7‐0.8 μm. It was frequently seen interposed between the electron‐dense layer and the hydroxyapatite. Similar interfacial structures have also been described in the in vivo environment, where they were referred to as lamina limitans‐like or cement linelike. From the results of this study, it can be concluded that the described in vitro system is a suitable model to study bonebiomaterial interactions. © 1992 John Wiley & Sons, Inc.
Storage and elimination of titanium, aluminum, and vanadium salts, in vivo
Authors: Merritt K. , Margevicius R. W. , Brown S. A. 
Published: December 2004

AbstractHamsters were injected with titanium, aluminum, and vanadium salts either intraperitoneally or intramuscularly to study the transport, storage, and elimination of these metals. Blood samples were taken at 4 h or 24 h, and urine samples were taken a t 24, 48, and 72 h. The hamsters were then injected weekly for 5 weeks after the initial injection. Blood and portions of the kidneys, liver, lung, and spleen were taken at sacrifice. All samples were analyzed for titanium, aluminum, and vanadium concentrations using graphite furnace atomic absorption spectroscopy (GFAAS). Titanium was found not to be excreted in the urine, was found in low levels in the blood, and was elevated over control in the kidney, liver, and spleen. Aluminum detection via GFAAS showed wide standard deviations and high levels in controls; however, aluminum was found to be excreted in the urine, and to be transported by the blood in the experimental animals. A small amount accumulated in the liver and spleen. Vanadium was excreted in high levels in the urine. A small amount was found in the blood, and the level in the organs was below the reliable detection limits. The rapid excretion of vanadium might be related to its solubility in physiological conditions, while the limited excretion of titanium may be related to its being insoluble in the physiologic environment. © 1992 John Wiley & Sons, Inc.
In vivo versus in vitro degradation of controlled release polymers for intracranial surgical therapy
Authors: Wu Mary P. , Tamada Janet A. , Brem Henry , Langer Robert 
Published: December 2004

AbstractIntracranial studies to analyze the degradation kinetics of the bioerodible polymer poly[bis(p‐carboxyphenoxy)propane‐sebacic acid] [p(CPP‐SA) 20:80] copolymer wafers were conducted in a rat model. Rats were separated into four groups: those receiving (1) polymer, (2) polymer loaded with the chemotherapeutic agent BCNU,(3) drugloaded polymer with previous tumor implantation, and (4) polymer and an absorbable hemostatic material. A polymer wafer was surgically implanted into the brain of each animal. Residual polymer was harvested at varying times for chromatographic analysis. In vitro effects of pH, mixing, and water availability on degradation were also studied. The results of in vitro and in vivo studies were compared to understand the behavior of polymers in a clinical setting. We found that degradation of p(CPP‐SA) initially occurred more slowly in vivo than in vitro. The presence of BCNU, tumor, and absorbable hemostatic material did not affect the ultimate time of polymer degradation in vivo, and the intrinsic polymer degradation time of 1 mm thick p(CPP‐SA) 20:80 disks in vivo was 6–8 weeks. © 1994 John Wiley & Sons, Inc.
Evaluation of magnetic alginate beads as a solid support for positive selection of CD34+ cells
Authors: Pope Niedre M. , Alsop Roger C. , Chang Yu‐An , Smith Alan K. 
Published: December 2004

AbstractParamagnetic alginate beads with a 10–100 μm size range have been developed. These beads, when activated with chloroacetic anhydride and covalently coupled to avidin (30 μg/mg beads), were able to bind biotinylated goat anti‐mouse (B‐GAM) antibody (Ab). The beads with immobilized antibody were then used as a model system for the capture and non‐enzymatic release of CD34+ (KG1a) cells. A maximum of 82% KG1a (average = 65 ± 16.1%) cell capture, and 57% (average = 51 ± 5.9%) cell release has been attained using this model system. Optimization of the system in terms of further bead size reduction, and in terms of developing a system to recover released cells with high purity, will make an excellent system for cell capture and nonenzymatic release. © 1994 John Wiley & Sons, Inc.
Cell growth on poly(vinyl alcohol) hydrogel membranes containing biguanido groups
Authors: Iio Kokoro , Minoura Norihiko , Aiba Seiichi , Nagura Masanobu , Kodama Makoto 
Published: December 2004

AbstractA cationic, high‐water‐content hydrogel membrane composed of poly(vinyl alcohol) (PVA) and poly(allylbiguanido‐co‐allylamine) hydrochloride (PAB) with positively charged biguanido groups that resemble arginine residues was developed. The PAB was prepared by reacting poly(allylamine) hydrochloride (PAA) with guanyl‐O‐methyl isourea. PAB/PVA hydrogel membranes were prepared by repeated freezing and thawing. For comparison, hydrogel membranes composed of PAA and PVA were also prepared. The interaction between these hydrogel membranes and mouse fibroblast (L929) was studied by a cell culture method. The PAB hydrogel blend had a relatively low percentage of initial cell attachment. The cell growth on the PAB hydrogel membranes showed a maximum at 5 mol % PAB content that was as high as commercially available plastic films. However, cells on hydrogel membranes with 50 mol % PAB content and 0 mol % PAB content (only PVA) did not seem to grow; neither did the 5/95 PAA/PVA membranes. Water contact angles of hydrogel membranes did not vary with the PAB content. Morphology of the cell attachment was observed by SEM. On the PAB blend hydrogel surfaces, cells were not spindle‐shaped and monolayers, but rather cells aggregated in spherical clusters. © 1994 John Wiley & Sons, Inc.
Biocompatibility of potential wound management products: Fungal mycelia as a source of chitin/chitosan and their effect on the proliferation of human F1000 fibroblasts in culture
Authors: Chung Lip Yong , Schmidt Richard J. , Hamlyn Paul F. , Sagar Brian F. , Andrew Andrea M. , Turner Terence D. 
Published: December 2004

AbstractAspergillus oryzae, Mucor mucedo, and Phycomyces blakesleeanus cultures were examined as sources of chitin/chitosan. The nitrogen content of the alkali‐treated mycelia/sporangiophores of A. oryzae, M. mucedo, and P. blakesleeanus was 2.52, 3.61, and 6.27% w/w, which relates to an estimated chitin content of 37, 52, and 91%, respectively. The effect of these fungal materials on the rate of proliferation of human F1000 fibroblasts in culture was examined. At 0.01% w/v, all three materials exhibited significant (P<.05) proproliferant activity over a period of 13 days. However, at 0.05% w/v, P. blakesleeanus further enhanced cell proliferation, whereas A. oryzae and M. mucedo produced a significant (P<.05) antiproliferant effect. Higher concentrations of P. blakesleeanus (0.1 and 0.5%) caused marked inhibition of F1000 cell proliferation when measured on days 3 and 6. Only the proproliferant effect of these fungal materials appears to correlate to their chitin content. Furthermore, the cytomorphology of the fibroblasts indicated that P. blakesleeanus, and to a lesser extent M. mucedo, possessed cell attractant properties, again correlating with chitin content. If developed for use as wound management materials, the sporangiophores of P. blakesleeanus and the mycelium of M. mucedo could possibly promote the growth of fibroblasts and provide a matrix for their anchorage, thus contributing to the granulation phase of the healing cascade. © 1994 John Wiley & Sons, Inc.
A semianalytic method for computing the concentration distribution in enzyme–substrate fast reaction systems
Authors: Tse‐Tsai Li , Zheng‐Wen Shi , Guo‐Qiang Zhou , Kuo‐Chen Chou 
Published: December 2004

AbstractA semianalytic method is presented for computing the concentration distribution in enzyme–substrate fast reaction systems. By means of this method, not only can much computation work be saved but a semianalytic expression for the concentration distribution will be obtained. This expression is very useful for analysis and discussion of the kinetic characteristics of this kind of reaction system.
Carbodications. I. The structures and energies of C4H isomers
Authors: Chandrasekhar Jayaraman , Schleyer Paul Von Ragué , Krogh‐Jespersen Karsten 
Published: December 2004

AbstractAt high levels of ab initio theory (6‐31G*//4‐31G), the most stable C4H isomer is indicated to be the nonplanar cyclobutadiene dication (1a); the planar form, 1b, is indicated to be 7.5 kcal/mol less stable. The second most stable C4H isomer, the methylenecyclopropene dication, is indicated to prefer the perpendicular (2a) over the planar (2b) arrangement by 7 kcal/mol. The “anti van't Hoff” cyclo‐(HB)2CCH2 system (4), isoelectronic with 2, also prefers the perpendicular conformation (4a), and retains the CC double bond. The linear butatriene dication (3) is the least stable C4H species investigated. The perpendicular (D2d) arrangement (3a), permitting double allyl cationlike conjugation, is preferred over the planar D2h form (3b) by 26 kcal/mol. The heat of formation of the most stable form of C4H, 1a, is estimated to be 623–640 kcal/mol. This species should be thermodynamically stable toward dissociation into smaller charged fragments.
An algorithm for the generation of nuclear spin species and nuclear spin statistical weights
Authors: Balasubramanian K. 
Published: December 2004

AbstractThis article develops a set of algorithms for the computer generation of nuclear spin species and nuclear spin statistical weights potentially useful in molecular spectroscopy. These algorithms generate the nuclear spin species from group structures known as generalized character cycle indices (GCCIs). Thus the required input for these algorithms is just the set of all GCCIs for the symmetry group of the molecule which can be computed easily from the character table. The algorithms are executed and illustrated with examples.
Calculation of the average properties of atoms in molecules. II
Authors: Biegler‐könig Friedrich W. , Bader Richard F. W. , Tang Ting‐Hua 
Published: December 2004

AbstractThis article describes an algorithm for the calculation of the average properties of an atom in a molecule. The atom is defined within the topological theory of molecular structure, a theory which defines atoms, bonds, structure, and structural stability in terms of the topological properties of a system's charge distribution. The average properties of the atom so defined are uniquely determined by quantum mechanics. Results for a number of hydrocarbon molecules, obtained by the program PROAIM (properties of atoms in molecules) which implements this algorithm, are given. In general, this program enables one to calculate the average energy of an atom in a molecule to an accuracy of ±1 kcal/mol.
Coupled calculations of vibrational frequencies and intensities. III. IR and Raman spectra of ethylene oxide and ethylene sulfide
Authors: Spiekermann M. , Bougeard D. , Schrader B. 
Published: December 2004

AbstractThe experimental IR and Raman spectra of ethylene oxide have been reinvestigated with particular attention to the intensities. The absolute IR intensities have been measured for the gaseous state. The spectra have been simulated by using a normal coordinate analysis coupled with a CNDO determination of the intensities. The intensity calculation using polarization functions appears to be more reliable than the standard version. Furthermore, the force field has been extended for ethylene sulfide.
On evaluation of the characteristic polynomial for large molecules
Authors: Randić Milan 
Published: December 2004

AbstractExisting schemes for evaluation of the characteristic polynomial of a graph suffer from limited practicality. Their application to large molecules inordinately increases the amount of labor. Here a procedure is outlined which is useful even for large molecules. It is based on a not widely known property of the collection of characteristic polynomials for Ulam's subgraphs, which, when added, give the derivative of the characteristic polynomial of the initial graph. The characteristic polynomials for Ulam's subgraphs are, as a rule, easier to derive due to the presence of many pending bonds in graphs of chemical interest. The last step requires an integration of a polynomial (which is a straightforward step) and determining the constant of integration, which represents the determinant of the adjacency matrix. The available methods for determing the additive constant (the determinant) are combinatorially much simpler than the initial task of finding all of the coefficients of the characteristic polynomial. The approach is illustrated on selected benzenoid hydrocarbons, nonbenzenoid, and nonalternant systems. Construction of the characteristic polynomials can be accelerated by considering auxiliary fragments and irreducible subgraphs separately and combining them in the final expression. Many auxiliary fragments allow their characteristic polynomials to be expressed in a closed form using recursive relations. The results for complex molecules can thus be written in a relatively compact form. Finally, the derivative of the characteristic polynomial, expressed in terms of selected auxiliary functions and irreducible components, can be integrated directly to give the result in terms of contributions signifying various fragments rather than as an explicit function of x.
Conformational analysis by energy embedding
Authors: Crippen Gordon M. 
Published: December 2004

AbstractThe distance geometry approach to conformational calculation has been shown to be very effective at producing large molecular structures satisfying many given, long‐range constraints on the interatomic distances. I now present a significant extension of the method that handles strictly geometric constraints as well as before while also locating conformers of very low energy. The main feature of the algorithm is a projection of the molecule from a low energy conformation in a high dimensional space to three dimensions in such a way as to perturb the energy as little as possible. Tests of the method on very small systems with simple energy functions completely explored by independent means show that the global minimum of energy is sometimes attained. In every case the final energy is very low, and geometric constraints are completely satisfied.
Ab‐Initio studies on π‐nonbonded and through‐bonds interactions in n‐alkanes, n‐alkyl radicals, and polymethylene diradicals
Authors: Lee Ikchoon , Cheun Young Gu , Yang Kiyull 
Published: December 2004

AbstractAb‐initio studies were conducted on quantitative aspects of π‐nonbonded, σ–σ*, n–σ*, and throughbond interactions in R1CH2(CH2)N–1 CH2 R2, where R1 and R2 are H and/or nonbonding AO, n, and N = 2, 3, and 4. Geometrical preferences were found to depend both on π‐nonbonding and bond–antibonding interactions, the latter being more important. Level orderings and energy splittings involved in the through‐bond interactions of diradicals can be qualitatively predicted by examining the signs of the overlap between the n orbitals and a common vicinal σ* bond orbital, using simple orbital patterns and paying special attention to the “backside” tails of bond orbitals.
Electronic states and barriers to internal rotation in silaallenes
Authors: Krogh‐jespersen Karsten 
Published: December 2004

AbstractThe electronic states and barriers to internal rotation in allene (1a), 1‐silaallene (2a), and 2‐silaallene (3a) are investigated computationally using ab‐initio molecular orbital methods. Planar geometries with two‐, three‐, and four‐π‐electron configurations have been considered as possible transition states (1b–3d). Structures have been optimized at the Hartree–Fock level with a small split valence basis set (3‐21G) and higher level calculations with basis sets of split valence (6‐31G) and split valence plus polarization function (6‐31G*) quality include correlation energy estimates from Møller–Plesset second‐and third‐order perturbation theory. The electronic barrier to internal rotation in allene is estimated near 53 kcal/mol whereas the corresponding barriers in 1‐silaallene and 2‐silaallene are considerably smaller, ca. 35 and 20 kcal/mol, respectively. The transition states are predicted to possess bent geometries in all three molecules with open‐shell singlet, three‐π‐electron configurations in 1 and 2 (1c, 2c) but a closed‐shell singlet, two‐π‐electron configuration in 3 (3d).
Digital emulation of analog computer techniques for the solution of kinetic systems
Authors: Titchener M. R. , Stimpfle R. M. 
Published: December 2004

AbstractA low‐cost microcomputer and package of assembly language routines has been developed to emulate the structure and performance of a large analog computer. The advantages of the analog computer, as implemented in this scheme, include (1) a significant reduction in the programming effort involved in modeling complex dynamic systems and (2) the control of the simulation and model parameters in a completely interactive and flexible manner. The symbolic nomenclature and schematic representations involving devices, such as integrators, comparators, multipliers, and function generators, offers a powerful alternative to the more conventional numerical methods, that is, to provide very simply the solutions to large systems of differential equations. This approach invariably leads the user to a more thorough understanding of the dynamic character of the system. The technique is illustrated using a chemical kinetics example involving the simulation of laser‐induced fluorescence. The results of this work have provided an assessment of a systematic error that occurs when using induced resonance fluorescence to measure OH concentrations in the troposphere of the earth.
The thioketone–enethiol tautomerism of aliphatic thiocarbonyls: An ab initio study
Authors: Bruno Alfredo E. , Steer Ronald P. , Mezey Paul G. 
Published: December 2004

AbstractApproximate minimum energy reaction paths have been calculated for two thioketone–enethiol tautomeric systems using an ab initio SCF–MO method. The calculations indicate nearly equal stabil ties of the isolated tautomers in both systems and an energy barrier of ca. 85 kcal/mol for their interconversion. This barrier is expected to be significantly lower in solution as a result of solvent–solute interactions.
Divinylketone: Conformational preferences. Molecular geometry and vibrational force field in the ground state
Authors: Skancke Per N. 
Published: December 2004

AbstractThe conformational preferences of the molecule 1,4‐pentadien‐3‐one (divinylketone) have been studied by ab initio molecular orbital calculations and discussed in terms of interaction between molecular fragments. The calculations predict a molecular ground state having a fully coplanar s‐cis, s‐cis conformation. In addition, we find three other structures that represent local minima on the energy surface. These are a fully coplanar s‐cis, s‐trans form, and two nonplanar s‐trans, s‐trans forms having symmetries C2 and C1h, respectively. The energies of these forms relative to the ground state are 7.5, 19.2, and 35.9 kJ/mol, respectively. The coplanar s‐trans, s‐trans form represents a saddle point on the energy surface. All conformers and the saddle point have been completely geometry optimized by the gradient technique. For the ground state a complete in‐plane harmonic force field has been evaluated.
Standard deviation in reduced errors (SDRE): A criterion to assess the relative overall quality of approximate wavefunctions
Authors: Zeiss G. D. , Whitehead M. A. 
Published: December 2004

AbstractThe standard deviation in reduced errors (SDRE) quantitatively measures the similarity between an approximate and exact wavefunction. It is the Euclidean distance between the vector of the one‐electron property expectation values calculated using the approximate and exact expectation values.