bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconstruction of extended cortical sources for EEG and MEG based on a Monte‐Carlo‐Markov‐chain estimator
Authors: Kincses Wilhelm Emil , Braun Christoph , Kaiser Stefan , Grodd Wolfgang , Ackermann Hermann , Mathiak Klaus
Published: January 2003

A new procedure to model extended cortical sources from EEG and MEG recordings based on a probabilistic approach is presented. The method (SPMECS) was implemented within the framework of maximum likelihood estimators. Neuronal activity generating EEG or MEG signals was characterized by the number of sources and their location and extension. Based on the noise distribution of the measured data, source configurations were associated with the according value of the likelihood function. To find the most likely source, i.e., the maximum likelihood estimator, and its level of confidence, a stochastic solver (Metropolis algorithm) was applied. The method presented supports the incorporation of virtually any constraint, e.g., based on physiological and anatomical a priori knowledge. Thus, ambiguity of the ill‐posed inverse problem was reduced considerably by confining sources to the cortical surface extracted from individual MR images. The influence of different levels and types of noise on the outcome was investigated by means of simulations. Somatosensory evoked magnetic fields analyzed by the method presented suggest that larger extended cortical areas are involved in the processing of combined finger stimulation as compared to single finger stimulation. Hum. Brain Mapping 18:100–110, 2003. © 2002 Wiley‐Liss, Inc.
Improvement in variability of the horizontal meridian of the primary visual area following high‐resolution spatial normalization
Authors: Kochunov P. , Hasnain M. , Lancaster J. , Grabowski T. , Fox P.
Published: January 2003

We investigated the decrease in intersubject functional variability in the horizontal meridian (HM) of the primary visual area (V1) before and after individual anatomical variability was significantly reduced using a high‐resolution spatial normalization (HRSN) method. The analyzed dataset consisted of 10 normal, right‐handed volunteers who had undergone both an O‐15 PET study, which localized retinotopic visual area (V1), and a high‐resolution anatomical MRI. Individual occipital lobes were manually segmented from anatomical images and transformed into a common space using an in‐house high‐resolution regional spatial normalization method called OSN. Individual anatomical and functional variability was quantified before and after HRSN processing. The reduction of individual anatomical variability was judged by the reduction in gray matter (GM) mismatch and by the improvement in overlap frequency between individual calcarine sulci. The reduction in intersubject functional variability of HM was determined by measurements of the overlap frequency between individual HM areas and by improvement in intersubject Z‐score maps. The HRSN processing significantly reduced the individual anatomical variability: GM mismatch was reduced by a factor of two and the mean calcarine sulcus overlap frequency was improved from 37 to 68%. The reduction in functional variability was more subtle. However, both HM mean overlap (increased from 18 to 28%) and the average Z‐score (increased from 2.2 to 2.55) were significantly improved. Although, functional registration was significantly improved by matching sulci, there was still residual variability. This is believed to be the variability of individual areas within the calcarine sulcus, and cannot be resolved by sulcal match. Thus, the proposed methodology provides an efficient, unbiased, and automated way to study structure‐functional relationship in human brain. Hum. Brain Mapping 18:123–134, 2003. © 2002 Wiley‐Liss, Inc.
Tubewells and arsenic in Bangladesh: challenging a public health success story
Authors: Caldwell Bruce K. , Caldwell John C. , Mitra S. N. , Smith Wayne
Published: January 2003

Bangladesh has seen one of the developing world's great public health successes, the conversion of the drinking water source for 94% of the rural population to ‘safe water’, in the form of tubewells, with the aim of reducing morbidity and mortality from water‐borne disease. Now, that success is being endangered by the discovery that 20 million people may be in great danger and another 20 million in lesser danger of being poisoned by arsenic contamination from tubewell water. This article reports findings from the first national probability sample survey of the rural population and a census of tubewells investigating the social, demographic and epidemiological context of the crisis. The survey covered 3780 households containing 20260 people. The tubewell census covered 9174 tubewells. The article presents data on the respondents' history of drinking tubewell water, knowledge of the arsenic problem, identification of arsenicosis, as well as the impact upon them of the national campaign, the testing of tubewells, and their subsequent sources of water. Eighty‐seven per cent of households drank water from ordinary tubewells (at most risk from arsenic poisoning) and 7% from deep tubewells. Among males, 47.5% had heard that something may be wrong with tubewell water, compared with 39.6% of females. A much lower proportion (20.6% males, 11.3% females) had heard that the water contained a poison called arsenic. Only about 1.5% of the entire population had stopped using tubewell water. Of survey respondents, 0.5% of males and 0.4% of females reported symptoms consistent with chronic arsenicosis. Suggestions are made for a more effective programme. Copyright © 2003 John Wiley & Sons, Ltd.
History of pay equity studies
Authors: Barbezat Debra A.
Published: January 2003

Emperical estimates of salary differentials by race and sex for academic employees are presented by decade, along with proposed explanations of pay gaps.
Issues in conducting an institutional salary‐equity study
Authors: Ferber Marianne A. , Loeb Jane W.
Published: January 2003

This chapter investigates the effects of several different specifications of a salary model on findings of gender differences in salary and on their corrections.
Discovery and design of novel inhibitors of botulinus neurotoxin A: targeted ‘hinge’ peptide libraries
Authors: Hayden J. , Pires J. , Roy S. , Hamilton M. , Moore G. J.
Published: January 2003

Intoxication by the zinc protease botulinus neurotoxin A (BoNT‐A) results from cleavage of a single Q–R bond in the neuronal protein SNAP‐25, which disables the docking mechanism required for neurotransmitter release. In the present study, potential inhibitors of BoNT‐A were assessed from their effects on the BoNT‐A cleavage of a synthetic 17‐mer peptide (SNAP‐25, residues 187–203) spanning the Q–R cleavage site. Compounds that inhibited BoNT‐A included thiols (zinc chelators) such as dithiothreitol, dimercaptopropanesulfonic acid, mercaptosuccinic acid and captopril. In addition, compounds containing multiple acidic functions, such as the SNARE motif V2 (ELDDRADALQ), the tripeptide Glu‐Glu‐Glu and the steroid glycoside glycyrrhizic acid, were effective inhibitors. ‘Hinge’ peptide mini‐libraries (PMLs) having the structure acetyl‐X1‐X2‐linker‐X3‐X4‐NH2 or X1‐X2‐linker‐X3, where X1–X4 were mixtures of selected amino acids and the flexible linker was 4‐aminobutyric acid, also provided effective inhibition. Targeted PMLs containing the acidic amino acids Asp and Glu, the scissile‐bond amino acids Gln and Arg and the zinc chelators His and Cys produced pronounced inhibition of BoNT‐A. Deconvolution of these libraries will provide novel ligands with improved inhibitory potency as leads in the design of peptide mimetics to treat BoNT poisoning. Copyright ? 2003 Crown in the right of Canada. Published by John Wiley and Sons, Ltd.
Influence of paraoxon (POX) and parathion (PAT) on apoptosis: a possible mechanism for toxicity in low‐dose exposure
Authors: Saleh A. M. , Vijayasarathy C. , Fernandez‐Cabezudo M. , Taleb M. , Petroianu G.
Published: January 2003

The acute effects of poisoning with organophosphorus compounds (OPCs) are well known and have been described extensively. Most of the clinical symptoms are due to inhibition of acetylcholinesterase. Although acute OPC poisoning is a well‐established clinical entity, the existence of chronic poisoning due to exposure to low levels of OPC (below the threshold required for cholinergic clinical symptoms) is a hotly debated issue. Recent studies have suggested the involvement of OPCs in apoptotic processes. However, the mechanisms by which they modulate this process are poorly investigated. In the present study we evaluated the toxic effect of different concentrations of paraoxon (POX) and parathion (PAT) in murine EL4 T lymphocytes. We examined cellular responses, including induction of apoptosis, involvement of a caspase cascade, the activity of effector caspase (caspase‐3) and the biochemical and morphological changes that are the hallmarks of classical apoptosis. The results of our study indicate that at doses below IC50 POX is a potent inducer of apoptosis, as opposed to PAT that shows little apoptotic effect. Copyright © 2003 John Wiley & Sons, Ltd.
Toxicity of some bis mannich bases and corresponding piperidinols in the brine shrimp (Artemia salina) Bioassay
Authors: Gul H. Inci , Gul Mustafa , Erciyas Ercin
Published: January 2003

Some acetophenone‐derived bis Mannich bases were synthesized: bis[β‐benzoylethyl]ethylamine hydrochloride (IIa), bis[β‐(p‐methylbenzoyl)ethyl]ethylamine hydrochloride (IIb), bis[β‐(p‐chlorobenzoyl)ethyl]ethy‐ lamine hydrochloride (IId), bis[(2‐thienylcarbonyl)ethyl]ethylamine hydrochloride (IIe); some corresponding piperidinol derivatives: 3‐benzoyl‐1‐ethyl‐4‐phenyl‐4‐piperidinol hydrochloride (IIIa), 1‐ethyl‐3‐(p‐methyl‐ benzoyl)‐4‐(p‐methylphenyl)‐4‐piperidinol hydrochloride (IIIb), 1‐ethyl‐3‐(p‐methoxybenzoyl)‐4‐(p‐methoxy‐ phenyl)‐4‐piperidinol hydrochloride (IIIc), 1‐ethyl‐3‐(p‐chlorobenzoyl)‐4‐(p‐chlorophenyl)‐4‐piperidinol hydrochloride (IIId), 1‐ethyl‐4‐(2‐thienyl)‐3‐(2‐thienylcarbonyl)‐4‐piperidinol hydrochloride (IIIe); and some representative quaternary piperidinols: 3‐benzoyl‐1‐ethyl‐4‐hydroxy‐1‐methyl‐4‐phenylpiperidinium iodide (IIIf), 1‐ethyl‐4‐hydroxy‐1‐methyl‐3‐(p‐methylbenzoyl)‐4‐(p‐methylphenyl)piperidinium iodide (IIIg). Toxicity was tested by the brine shrimp bioassay as an intermediate test before further in vivo animal experiments. Piperidine derivatives were found to be more potent than bis Mannich bases. Quaternary piperidine derivatives IIIf and IIIg and also non‐quaternary piperidine derivatives IIIb, IIIe, IIIc and IIId were more toxic than 5‐fluorouracil in brine shrimp bioassay. Except for IIe, bis Mannich bases were not effective. Quaternization and conversion of bis Mannich bases to corresponding piperidines improved the toxicity. The lipid solubility of the compounds may not affect the toxicity. From these findings the quaternary piperidine derivatives IIIf and IIIg could be used in further drug development and also for in vivo experiments. Copyright © 2003 John Wiley & Sons, Ltd.
Application of pharmacokinetic/pharmacodynamic and stochastic modelling to 6‐mercaptopurine micronucleus induction in mouse bone marrow erythrocytes
Authors: Klés Virginie , Hyrien Ollivier , Poul Jean‐Michel , Sanders Pascal
Published: January 2003

This study investigates the kinetics of bone marrow micronucleated polychromatic erythrocytes and some mechanistic aspects of micronuclei induction using mathematical models. Female mice were administered a single intraperitoneal injection of the purine antagonist 6‐mercaptopurine at 50 mg kg−1. The time course evolution of the drug concentrations in the plasma and the micronucleated polychromatic erythrocyte kinetic rate in bone marrow were observed. Two mathematical models were developed for this study. The first model was built from a simultaneous pharmacokinetic/pharmacodynamic approach, but was invalidated after comparing its predictions to experimental data. The second model was a stochastic model based on some biological hypotheses involved in micronuclei induction. This model predicted a wavy kinetic rate of micronucleated polychromatic erythrocytes that was confirmed by a second data set obtained from a specifically built experimental design. The biological hypotheses were then discussed. It turned out from this work that mathematical modelling could be used as a tool to explore the cellular mechanisms of toxicity of the compound: for instance, the assumptions that 6‐mercaptopurine induced micronuclei mainly in cells entering the S phase, and not only during the last cell cycle but during one of the earlier cycles preceding the extrusion of the main nucleus, were confirmed. Moreover, the use of the stochastic model would help to schedule more accurately the bone marrow or blood harvesting times in the in vivo rodent micronucleus test. Copyright © 2003 John Wiley & Sons, Ltd.
Study of novel chitosan‐gelatin artificial skin in vitro
Authors: Mao Jinshu , Zhao Liguo , de Yao Kang , Shang Qingxin , Yang Guanghui , Cao Yilin
Published: January 2003

A novel absorbable scaffold composed of chitosan and gelatin was fabricated by freezing and lyophilizing methods, resulting in an asymmetric structure. This bilaminar texture is suitable for preparing a bilayer skin substitute. The methods employed to confirm the applicability of this chitosan‐gelatin scaffold as an ideal skin substitute were a water uptake ability test, in vitro fibroblast proliferation, and scaffold tests in which fibroblasts were co‐cultured with keratinocytes. The chitosan‐gelatin scaffolds were more wettable and adsorbed more water than did chitosan alone. In static cell culture the thinner scaffold is better than the thicker one, and because of diffusion limitations in the scaffold, culture time must be within 3 weeks before transplantation to living tissues. Keratinocytes were co‐cultured with fibroblasts in chitosan‐gelatin scaffolds to construct an artificial bilayer skin in vitro. The artificial skin obtained was flexible and had good mechanical properties. Moreover, there was no contraction observed in the in vitro cell culture tests. The data from this study suggest that chitosan‐gelatin scaffolds are suitable for skin tissue engineering goals. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 301–308, 2003
Titanium surface topography alters cell shape and modulates bone morphogenetic protein 2 expression in the J774A.1 macrophage cell line
Authors: Takebe J. , Champagne C. M. , Offenbacher S. , Ishibashi K. , Cooper L. F.
Published: January 2003

Macrophage cytokine expression significantly affects wound healing. Macrophage secretion of transforming growth factor beta 1 (TGFβ1) and bone morphogenetic proteins (BMP) may affect osteogenesis at endosseous implant surfaces. The aim of this investigation was to determine the effect of commercially pure titanium (cpTi) substrate topography on adherent macrophage osteogenic and osteoinductive cytokine expression. J774A.1 murine macrophage cell adhesion was examined by scanning electron microscopy, 0–72 h following plating onto polished, machined, and grit‐blasted cpTi surfaces. TGFβ1 and BMP‐2 gene expression by adherent macrophages was determined by the reverse transcription polymerase chain reaction. Macrophage adhesion increased with time on all surfaces and spreading increased with increasing surface roughness (polished < machined < grit‐blasted). BMP‐2 expression was not evident for cells adherent to polished cpTi at 24 h. In contrast, BMP‐2 expression occurred at 24 h in cells adherent to machined and grit‐blasted cpTi. BMP‐2 expression was evident on all surfaces at 72 h and was greatest in grit‐blasted titanium adherent cells. Increasing concentrations of cytochalasin B (0–50 μM) inhibited macrophage spreading and reduced BMP‐2 mRNA expression, suggesting a relationship between cell shape and BMP‐2 expression. This was further characterized using anti‐β1 and anti‐β3 integrin antibodies. The anti‐β1 integrin antibodies inhibited adherent macrophage BMP‐2 mRNA expression. Anti‐β3 integrin antibody treatment only modestly reduced BMP‐2 mRNA expression. Endosseous implant surface topography induced changes in macrophage shape that were associated with changes in BMP‐2 expression in J774A.1 mouse macrophage cell line. This first demonstration of BMP‐2 expression by cpTi adherent macrophages suggests that the macrophage may contribute surface‐specific osteoinductive signals during bone formation at implanted alloplastic surfaces. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 207–216, 2003
An atelocollagen honeycomb‐shaped scaffold with a membrane seal (ACHMS‐scaffold) for the culture of annulus fibrosus cells from an intervertebral disc
Authors: Sato Masato , Asazuma Takashi , Ishihara Masayuki , Kikuchi Toshiyuki , Masuoka Kazunori , Ichimura Shoichi , Kikuchi Makoto , Kurita Akira , Fujikawa Kyosuke
Published: January 2003

The aim of this study was to investigate the possibility of using the atelocollagen honeycomb‐shaped scaffold with a membrane seal (ACHMS‐scaffold) for the culture of annulus fibrosus (AF) cells in tissue engineering procedures of intervertebral disc repair. AF cells from the intervertebral discs of Japanese white rabbits were cultured for up to 3 weeks in the ACHMS‐scaffold to allow a high density, three‐dimensional culture. Although the DNA content in the scaffold increased at a lower rate than in the monolayer culture, scanning electron microscopy data showed that the scaffold was filled with the grown AF cells and produced extracellular matrix on day 21. The amount of type II collagen and its mRNA expression by the scaffold cultured cells were determined using Western blotting and Northern blotting analyses, respectively, and remained at a higher level than in the monolayer cultured cells. Furthermore, glycosaminoglycan (GAG) accumulation in the scaffold culture was at a higher level than in the monolayer culture. Western blot analysis for extracted proteoglycans from the scaffold culture also exhibited a much higher proteoglycan accumulation than the monolayer culture. These results indicate that the AF cells are able to grow and remain phenotypically stable in the scaffold. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 249–256, 2003
In vitro and in vivo degradation of biomimetic octacalcium phosphate and carbonate apatite coatings on titanium implants
Authors: Barrère F. , van der Valk C. M. , Dalmeijer R. A. J. , van Blitterswijk C. A. , de Groot K. , Layrolle P.
Published: January 2003

Calcium phosphate (Ca‐P) coatings have been applied onto titanium alloys prosthesis to combine the srength of metals with the bioactivity of Ca‐P. It has been clearly shown in many publications that Ca‐P coating accelerates bone formation around the implant. However, longevity of the Ca‐P coating for an optimal bone apposition onto the prosthesis remains controversial. Biomimetic bone‐like carbonate apatite (BCA) and Octacalcium Phosphate (OCP) coatings were deposited on Ti6Al4V samples to evaluate their in vitro and in vivo dissolution properties. The coated plates were soaked in α‐MEM for 1, 2, and 4 weeks, and they were analyzed by Back Scattering Electron Microscopy (BSEM) and by Fourier Transform Infra Red spectroscopy (FTIR). Identical coated plates were implanted subcutaneously in Wistar rats for similar periods. BSEM, FTIR, and histomorphometry were performed on the explants. In vitro and in vivo, a carbonate apatite (CA) formed onto OCP and BCA coatings via a dissolution‐precipitation process. In vitro, both coatings dissolved overtime, whereas in vivo BCA calcified and OCP partially dissolved after 1 week. Thereafter, OCP remained stable. This different in vivo behavior can be attributed to (1) different organic compounds that might prevent or enhance Ca‐P dissolution, (2) a greater reactivity of OCP due to its large open structure, or (3) different thermodynamic stability between OCP and BCA phases. These structural and compositional differences promote either the progressive loss or calcification of the Ca‐P coating and might lead to different osseointegration of coated implants. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 378–387, 2003
Biochemical characterization of atherosclerotic plaque constituents using FTIR spectroscopy and histology
Authors: Li C. , Ebenstein D. , Xu C. , Chapman J. , Saloner D. , Rapp J. , Pruitt L.
Published: January 2003

The behavior of vulnerable atherosclerotic plaques is believed to be closely related to plaque composition. There is a need for an effective in vivo technique for examining plaque constituent properties. In this study, Fourier transform infrared spectroscopy using attenuated total reflectance (FTIR‐ATR) was used to assess and analyze the biochemical properties of human atherosclerotic plaques. FTIR spectra clearly revealed prominent spectral features corresponding to plaque constituents of interest: the 2930 cm−1 and 2850 cm−1 peaks (indicating the presence of lipids), the 1730 cm−1 peak (lipid esters), the 1550 cm−1 and 1650 cm−1 peaks (fibrous tissues), and the 1100–1000 cm−1 broad phosphate peak (calcification). Spectral data examined on a qualitative basis correlated well with both gross tissue anatomy and histologic features. Gross spatial mappings of tissue sections of both lipidic and calcified plaques were performed. Spectra from various regions of the plaques demonstrated the evolution of lipid peaks, fibrous tissue peaks, and the phosphate calcification band within the plaques. Histologic analysis corroborated the spectral findings in this study. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 197–206, 2003
Human serum albumin incorporating synthetic heme: Red blood cell substitute without hypertension by nitric oxide scavenging
Authors: Tsuchida Eishun , Komatsu Teruyuki , Matsukawa Yasuko , Nakagawa Akito , Sakai Hiromi , Kobayashi Koichi , Suematsu Makoto
Published: January 2003

The administration of extracellular, hemoglobin‐based oxygen carriers often elicits an acute increase in blood pressure by vasoconstriction. This side effect is now recognized to be due to the depletion of nitric oxide (endothelial‐derived relaxing factor) by the extravasuated hemoglobins. We have recently found that the administration of a recombinant human serum albumin (rHSA)‐based oxygen carrier involving synthetic tetraphenyporphinatoiron(II) derivative (FeP) (rHSA‐FeP) does not induce such hypertensive action, because of its low permeability through the vascular endothelium. The heart rate responses after the rHSA‐FeP injection were also negligibly small. Visualization of the intestinal microcirculatory changes clearly revealed the widths of the venule and arteriole to be fairly constant. The entirely synthetic rHSA‐FeP becomes a promising material as a new type of red blood cell substitute. © 2002 Wiley Periodicals Inc. J Biomed Mater Res 64A: 257–261, 2003
Comparison of chemical treatments on the chain dynamics and thermal stability of bovine pericardium collagen
Authors: Samouillan V. , Dandurand J. , Lacabanne C. , Thoma R. J. , Adams A. , Moore M.
Published: January 2003

A new approach for the replacement of heart valves consists of obtaining an acellular matrix from animal aortic valves that performs mechanically, is nonantigenic, and is free from calcification and fibroblast proliferation. Novel biochemical treatments must be developed for this purpose. In this work, we focus on the characterization of collagen in acellular bovine cardiovascular tissues, fresh or glutaraldehyde treated, and stored in different solutions [phosphate‐buffered saline (PBS), ethanol, octanol, and glutaraldehyde], to determine whether the resulting fibrous material is structurally preserved. The preservation of the triple helical structure of collagen is checked by differential scanning calorimetry (DSC), which is a well suited technique to analyze thermal transitions in proteins, such as denaturation. To get insight into the molecular dynamics of collagen in the nanometric range, we used thermally stimulated currents, a dielectric technique running at low frequency, that measure the dipolar reorientations in proteins submitted to a static electrical field. The combined use of these two techniques allowed us to evaluate the physical structure and conformation of collagen after the different chemical treatments. We have found that the glutaraldehyde treatment followed by octanol storage preserves the triple helical conformation of the polypeptidic chains of collagen, contrary to the ethanol and PBS storage that induce drastic changes in the thermal and dielectric behavior of the protein. Moreover, this particular chemical treatment stabilizes the collagen structure (shift toward high temperature of the collagen denaturation and stiffening of the chains by a cross‐linking action) when compared to the control sample, and so could provide interesting fibrous material for the conception of bioprosthetic heart valve. © 2002 Wiley Periodicals, Inc., J Biomed Mater Res 64A: 330–338, 2003
Aggregation behaviors and their pH sensitivity of cholesterol‐conjugated proteinoids composed of glutamic acid and aspartic acid matrix
Authors: Bae Soo Kyoung , Kim Jong‐Duk
Published: January 2003

Cholesterol‐conjugated proteinoids and their aggregation behaviors were investigated with model proteinoid systems. Model proteinoids of molecular weights in the range of 4000 to 6000 were synthesized by anhydrous thermal condensation forming a matrix with glutamic acid and aspartic acid and of naturally occurring amino acids. Nuclear magnetic resonance and Fourier transform infrared spectra suggested that cholesterol was conjugated to carboxyl group–forming pendants. Native water‐soluble proteinoids can form microspheres in acidified or heated conditions, but the cholesterol‐conjugated proteinoids were found to form aggregates in water, regardless of the temperature or pH of the solutions. The hydrophobic pendant moieties come to a compact association in core, whereas the hydrophilic chains provide a shield layer. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 282–290, 2003
Polymer design for corneal epithelial tissue adhesion: Pore density
Authors: Evans M. D. M. , Taylor S. , Dalton B. A. , Lohmann D.
Published: January 2003

A porous polymer is required to sustain corneal epithelial tissue on the anterior surface of an implantable contact lens (corneal onlay). Porosity creates topography on the polymer surface and, if defined, this can be manipulated to elicit a particular tissue response. Previous work identified pores of 100‐nm diameter to be the critical size of a discontinuity in a polymer surface to facilitate the migration, stratification, and sustained adhesion of corneal epithelial tissue. Now we address the issue of pore density. Corneal epithelial tissue was grown for 21 days on nonporous polycarbonate and polycarbonate track‐etched with pores 100‐nm diameter with pore densities ranging from 0.27 and 14.4% of the total polymer surface area. Histology was used to score epithelial structure, and electron microscopy was used to quantitate the formation of adhesive structures (basal lamina and hemidesmosomes) at the tissue‐polymer interface. Data showed that epithelial tissue stratified and epithelial adhesive structures formed on polycarbonate surfaces with pore densities between 0.52 and 14.4% inclusive. This means that epithelial tissue can be maintained on a polymer where up to 14.4% of the surface is dedicated to small discontinuities in the form of pores 100‐nm diameter. These figures can be used to specify the design of a polymer for applications requiring epithelial cover. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 357–364, 2003
Effect of subtoxic concentrations of metal ions on NFκB activation in THP‐1 human monocytes
Authors: Lewis Jill B. , Randol Tabitha M. , Lockwood Petra E. , Wataha John C.
Published: January 2003

THP‐1 human monocytes and human peripheral blood monocytes have altered inflammatory cytokine secretion profiles after exposure to a variety of metal ions known to be released from biomaterials. Transcriptional regulation of these cytokines often involves activation of the transcription factor NFκB. The present study was designed to determine whether metal ion treatment of monocytes results in changes in levels of activated NFκB. THP‐1 cells were grown in suspension in the presence of sublethal concentrations of ions of Ag+, Co2+, Cu2+, Hg2+, Ni2+, and Pd2+. After 24 h of exposure to metal ions, the cells were harvested, counted, and the nuclear proteins extracted. Electrophoretic mobility shift assays were performed using a 32P‐ATP end‐labeled oligonucleotide consensus sequence for the NFκB transcription factor. DNA/protein complexes were quantified by phosphorimage analysis and compared by ANOVA (Tukey, α = 0.05). Exposure of THP‐1 cells to 100 μM of Pd2+ caused a significant increase in activated NFκB (p < 0.05) whereas treatment with 5 μM of Ag+ resulted in significantly decreased levels of nuclear NFκB (p < 0.05). No other metal ions tested caused a significant change in basal levels of nuclear NFκB (Co2+, Hg2+, Ni2+, and Cu2+). However, exposure to 50 μM of Cu2+ resulted in a reproducible, though not significant, increase in nuclear NFκB levels. These results indicate that inflammatory responses to some metal ions may be influenced by NFκB‐mediated transcriptional regulation. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 217–224, 2003
Sugar‐mediated chitosan/poly(ethylene glycol)‐β‐dicalcium pyrophosphate composite: Mechanical and microstructural properties
Authors: Wang Jian‐Wen , Hon Min‐Hsiung
Published: January 2003

The microstructural and mechanical properties of sugar‐mediated chitosan/poly(ethylene glycol)‐based scaffolds and composites, which are composed of β‐dicalcium pyrophosphate (β‐DCP) and sugar‐mediated scaffolds, were investigated. All of the scaffolds were prepared by various freeze‐drying protocols. The differences in the freeze‐drying process of the sugar‐mediated chitosan/poly(ethylene glycol) scaffold for three types of sugar (sucrose, glucose, and D‐fructose) were determined by scanning electron microscopic observation, water retention, density, and porosity analyses. The sugar‐mediated scaffolds prepared by scheme I of the freeze‐drying process show large pores, poorly connective interlayers, and disintegrated inner structures, different from the small pores and well‐connective channel structures as shown in the scheme II freeze‐drying process. The key factors for controlling pore structure and size in the scheme I freeze‐drying process were formulation and composition, but for the scheme II freeze‐drying process, the key factor was freeze protocol. The composite scaffolds were macroporous, and the microstructure changed considerably with added β‐DCP content. The incorporation of β‐DCP granules caused a significant enhancement of compressive modulus and yield strength. The increased mechanical strength may be attributable not only to the physical complexation between the sugar‐mediated scaffold and β‐DCP, but also the chemical reaction to apatite formed on the cell wall. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 262–272, 2003
Biological performance of biomimetic calcium phosphate coating of titanium implants in the dog mandible
Authors: Schliephake H. , Scharnweber D. , Dard M. , Röβler S. , Sewing A. , Hüttmann C.
Published: January 2003

The aim of the present study was to analyze the in vivo effect of biomimetic calcium phosphate coating of titanium implants on periimplant bone formation and bone‐/implant contact. Five types of implants were used: 1) Ti6Al4V implants with a polished surface; 2) Ti6Al4V implants with collagen coating; 3) Ti6Al4V implants with a mineralized collagen layer; 4) Ti6Al4V implants with sequential coating of hydroxyapatite (HA) and collagen; and 5) Ti6Al4V implants with HA coating only. All implants had square cross sections with an oblique diameter of 4.6 mm and were inserted press fit into trephine burr holes of 4.6 mm in the mandibles of ten beagle dogs. The implants of five animals each were evaluated after a healing period of 1 month and 3 months, respectively, during which time sequential fluorochrome labeling of bone formation had been performed. Bone formation was evaluated by morphometric measurement of the newly formed bone around the implants and the percentage of implant bone contact. After 1 month, there was a significantly higher percentage of mean bone/implant contact in the HA‐coated implants compared to those with polished surface and those with the collagen‐coated surface. After 3 months, these differences were not present anymore. Bone apposition was significantly higher next to implants with sequential HA/collagen coating compared to polished surfaces and mineralized collagen layer. It is concluded that biomimetic coating of titanium implants with HA has shown the clearest trend to increase bone–implant contact in the early ingrowth period. The addition of collagen to an HA coating layer may hold some promise when used as sequential HA/collagen coating with mineralized collagen as the surface layer. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 225–234, 2003
Flow perfusion culture of marrow stromal osteoblasts in titanium fiber mesh
Authors: van den Dolder Juliette , Bancroft Gregory N. , Sikavitsas Vassilios I. , Spauwen Paul H. M. , Jansen John A. , Mikos Antonios G.
Published: January 2003

The objective of this study was to evaluate the effect of two cell culture techniques, static and flow perfusion, on the osteogenic expression of rat bone marrow cells seeded into titanium fiber mesh for a period up to 16 days. A cell suspension of rat bone marrow stromal osteoblasts (5 × 105 cells/300 μL) was seeded into the mesh material. Thereafter, the constructs were cultured under static conditions or in a flow perfusion system for 4, 8, and 16 days. To evaluate cellular proliferation and differentiation, constructs were examined for DNA, calcium content, and alkaline phosphatase activity. Samples were also examined with scanning electron microscopy (SEM) and plastic‐embedded histological sections. Results showed an increase in DNA from day 4 to day 8 for the flow perfusion system. At day 8, a significant enhancement in DNA content was observed for flow perfusion culture compared with static culture conditions, but similar cell numbers were found for each culture system at 16 days. Calcium measurements showed a large increase in calcium content of the meshes subjected to flow perfusion at day 16. The SEM examination revealed that the 16‐day samples subjected to flow perfusion culture were completely covered with layers of cells and mineralized matrix. In addition, this matrix extended deep into the scaffolds. In contrast, meshes cultured under static conditions had only a thin sheet of matrix present on the upper surface of the meshes. Evaluation of the light microscopy sections confirmed the SEM observations. On the basis of our results, we conclude that a flow perfusion system can enhance the early proliferation, differentiation, and mineralized matrix production of bone marrow stromal osteoblasts seeded in titanium fiber mesh. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 235–241, 2003
Behavior of the bone–titanium interface after push‐in testing: A morphological study
Authors: Zaffe Davide , Rodriguez y Baena Ruggero , Rizzo Silvana , Brusotti Cesare , Soncini Monica , Pietrabissa Riccardo , Cavani Francesco , Quaglini Virginio
Published: January 2003

Fourteen titanium dental implants (Tioblast™) were implanted singly in the proximal tibia of New Zealand rabbits for 120 days. A bone defect was surgically produced and filled with Bio‐Oss® around six of these implants. After the animals were sacrificed and their organs harvested, bone segments were fixed and methacrylate embedded after the push‐in test had been performed. Microradiography was performed on longitudinal sections of the implants, whereas scanning electron microscope analysis was performed on the remaining embedded half‐implants using secondary electrons only. The results showed that the implants were apically and coronally surrounded by bone, whether Bio‐Oss® was used or not. Fractures were evident through the newly formed bone and between the pre‐existing and newly formed bone. Some fracture lines propagated through the bone and stopped at the implant surface without continuing along the bone–titanium interface. Detachment between the implant and the bone occurred at the coronal extremity of the implants and along its cervical region. These results highlight the fact that the bone–titanium interface has a high resistance to loading. It exhibited greater resistance than the newly formed bone and seems to behave in a manner similar to the cement lines of osteons. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 365–371, 2003
Chondrogenesis of human mesenchymal stem cells encapsulated in alginate beads
Authors: Ma Hsiao‐Li , Hung Shih‐Chieh , Lin Shan‐Yang , Chen Yuh‐Lien , Lo Wai‐Hee
Published: January 2003

Mesenchymal stem cells (MSCs) have the capacity for self‐renewal and can form bone, fat, and cartilage. Alginate forms a viscous solution when dissolved in 0.9% saline and gels on contact with divalent cations. The viability and phenotype maintenance of chondrocytes in alginate beads have been well documented. However, little is known about the effect of microencapsulation in alginate on chondrogenesis of MSCs. In this study, human MSCs encapsulated in alginate beads were cultured in serum‐free medium with the addition of transforming growth factor (TGF)β1 (10 ng/mL), dexamethasone (10−7M), and ascorbate 2‐phosphate (50 μg/mL). The MSCs in alginate assumed a rounded morphology with lacunae around them after 1 week in culture. Cell aggregates were observed at 2 weeks or longer in culture. Histological findings agreed with the clinical determination of hyaline cartilage, characterized by isolated cells with ground substance positive in Safranin‐O staining and immunohistochemistry for collagen type II at the periphery of cells. Reverse transcriptase–polymerase chain reaction (RT‐PCR) revealed the expression of COL2A1 and COL10A1, marker of chondrocytes and hypertrophy chondrocytes, respectively. These results indicate MSCs in alginate can form cartilage and the MSCs‐alginate system represents a relevant model for the study of the molecular mechanisms involved in the chondrogenesis and endochondral ossification. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 273–281, 2003
Vascularization and tissue infiltration of a biodegradable polyurethane matrix
Authors: Ganta Sudhakar R. , Piesco Nicholas P. , Long Ping , Gassner Robert , Motta Luis F. , Papworth Glenn D. , Stolz Donna B. , Watkins Simon C. , Agarwal Sudha
Published: January 2003

Urethanes are frequently used in biomedical applications because of their excellent biocompatibility. However, their use has been limited to bioresistant polyurethanes. The aim of this study was to develop a nontoxic biodegradable polyurethane and to test its potential for tissue compatibility. A matrix was synthesized with pentane diisocyanate (PDI) as a hard segment and sucrose as a hydroxyl group donor to obtain a microtextured spongy urethane matrix. The matrix was biodegradable in an aqueous solution at 37°C in vitro as well as in vivo. The polymer was mechanically stable at body temperatures and exhibited a glass transition temperature (Tg) of 67°C. The porosity of the polymer network was between 10 and 2000 μm, with the majority of pores between 100 and 300 μm in diameter. This porosity was found to be adequate to support the adherence and proliferation of bone‐marrow stromal cells (BMSC) and chondrocytes in vitro. The degradation products of the polymer were nontoxic to cells in vitro. Subdermal implants of the PDI–sucrose matrix did not exhibit toxicity in vivo and did not induce an acute inflammatory response in the host. However, some foreign‐body giant cells did accumulate around the polymer and in its pores, suggesting its degradation is facilitated by hydrolysis as well as by giant cells. More important, subdermal implants of the polymer allowed marked infiltration of vascular and connective tissue, suggesting the free flow of fluids and nutrients in the implants. Because of the flexibility of the mechanical strength that can be obtained in urethanes and because of the ease with which a porous microtexture can be achieved, this matrix may be useful in many tissue‐engineering applications. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 242–248, 2003
Porous PEOT/PBT scaffolds for bone tissue engineering: Preparation, characterization, and in vitro bone marrow cell culturing
Authors: Claase Menno B. , Grijpma Dirk W. , Mendes Sandra C. , de Bruijn Joost D. , Feijen Jan
Published: January 2003

The preparation, characterization, and in vitro bone marrow cell culturing on porous PEOT/PBT copolymer scaffolds are described. These scaffolds are meant for use in bone tissue engineering. Previous research has shown that PEOT/PBT copolymers showed in vivo degradation, calcification, and bone bonding. Despite this, several of these copolymers do not support bone marrow cell growth in vitro. Surface modification, such as gas‐plasma treatment, is needed to improve the in vitro cell attachment. Porous structures were prepared using a freeze‐drying and a salt‐leaching technique, the latter one resulting in highly porous interconnected structures of large pore size. Gas‐plasma treatment with CO2 generated a surface throughout the entire structure that enabled bone marrow cells to attach. The amount of DNA was determined as a measure for the amount of cells present on the scaffolds. No significant effect of pore size on the amount of DNA present was seen for scaffolds with pore sizes between 250–1000 μm. Light microscopy data showed cells in the center of the scaffolds, more cells were observed in the scaffolds of 425–500 μm and 500–710 μm pore size compared to the ones with 250–425 μm and 710–1000 μm pores. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 291–300, 2003
Bone formation on two‐dimensional poly(DL‐lactide‐co‐glycolide) (PLGA) films and three‐dimensional PLGA tissue engineering scaffolds in vitro
Authors: Karp Jeffrey M. , Shoichet Molly S. , Davies John E.
Published: January 2003

For some bone tissue engineering strategies, direct contact of newly synthesized bone with a scaffold is important for structural continuity and stability at the scaffold/bone interface. Thus, as the polymer degrades, the support function of the scaffold could be adopted by the developing bone structure. This study was designed to determine whether poly(DL‐lactide‐co‐glycolide) with a comonomer ratio of 75:25 supports bone apposition in vitro. Osteogenic cells derived from rat bone marrow cells were cultured for 2 weeks on polymeric two‐dimensional films and three‐dimensional tissue engineering scaffolds. Bacteriological grade polystyrene and tissue culture polystyrene dishes served as negative and positive controls for interfacial bone deposition, respectively. The surfaces of the prepared substrates were characterized by X‐ray photoelectron spectroscopy, dynamic water contact angle, scanning electron microscopy, and atomic force microscopy. After cell culture, the elaborated matrix was examined using scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The results show that poly(DL‐lactide‐co‐glycolide) supports appositional bone growth on both two‐dimensional films and three‐dimensional scaffolds, including the formation of a mineralized cement line matrix. Furthermore, surface topographical features are not required for the adherence of the cement line matrix to the polymer. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 388–396, 2003
Surface‐dependent conformations of human plasma fibronectin adsorbed to silica, mica, and hydrophobic surfaces, studied with use of Atomic Force Microscopy
Authors: Bergkvist Magnus , Carlsson Jan , Oscarsson Sven
Published: January 2003

Human plasma fibronectin (Fn) is a large flexible protein stabilized by intermolecular ionic interactions forming a compact structure. On altering solution conditions, the structure can revert to a more expanded state, thereby exposing previously hidden domains (e.g., cell‐binding sites). Electron microscopy images of Fn air‐sprayed onto mica surfaces show elongated protein structures, indicating a surface‐induced structural change. This makes it interesting to investigate the influence of surface properties on the structure of adsorbed Fn. We have used intermittent‐contact Atomic Force Microscopy to investigate the structure of Fn adsorbed onto mica, silica, and methylated silica surfaces. We observed that on silica surfaces, which is hydrophilic, most (70%) of the molecules had an elongated structure with partial intramolecular chain interactions, compare to molecules adsorbed on hydrophobic, methylated surfaces, where a compact structure predominated (70%). On mica surfaces, both compact and elongated protein structures were observed, with a slight preference for the elongated form (53%). Results show that surface physical properties influence the molecular structure of fibronectin on adsorption, which could provide useful information in understanding surface‐induced in vivo responses. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 349–356, 2003
Hydrogels based on poly(ethylene oxide) and poly(tetramethylene oxide) or poly(dimethyl siloxane). III. In vivo biocompatibility and biostability
Authors: Hyung Park Jae , Bae You Han
Published: January 2003

To investigate the effects of polymer chemistry and topology (linear or graft copolymer) on in vivo biocompatibility and biostability based on cage implant system, various hydrogels, composed of short hydrophilic [polyethylene oxide (PEO)] and hydrophobic block, were prepared by polycondensation reaction. Poly(tetramethylene oxide) (PTMO) or poly(dimethyl siloxane) (PDMS) was chosen as a hydrophobic block because of their wide utilization as a biomaterial. By using the specimens retrieved from rats killed after 1, 2, 3, 5, and 7 weeks' implantation, cellular and material responses were assessed. Most hydrogels showed a comparable value of macrophage density to Pellethane®, control polymer, whereas they did significantly lower foreign body giant cell (FBGC) density and coverage because of the presence of PEO. However, PEO block length and polymer topology did not affect macrophage adhesion and FBGC formation in our polymer composition. The hydrogel based on PDMS alone showed significantly lower macrophage density and FBGC density than Pellethane®, indicating that PDMS plays a role in inhibiting cellular adhesion. The results obtained from gel permeation chromatography curve and Fourier transform infrared spectra exhibited that all the polymers were susceptible to oxidative degradation in vivo. Although Pellethane® revealed surface degradation by 5 weeks in vivo, hydrogels showed rapid degradation in the bulk within 2 weeks because of the penetration of oxidative chemicals released from phagocytic cells into PEO domain of phase‐separated hydrogels. The more significant degradation was observed in the hydrogels with longer PEO block and PTMO as a hydrophobic block instead of PDMS. It was evident that the minor degradation could be achieved by grafting PEO and adopting PDMS as a hydrophobic block in the hydrogel. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 64A: 309–319, 2003