bluuebunny/crossref_metadata_2025 huggingface dataset:
Deletion of Trp‐557 and Lys‐558 in the juxtamembrane domain of the c‐kit protooncogene is associated with metastatic behavior of gastrointestinal stromal tumors
Authors: Wardelmann Eva , Losen Inge , Hans Volkmar , Neidt Iris , Speidel Nicola , Bierhoff Erhard , Heinicke Thomas , Pietsch Torsten , Büttner Reinhard , Merkelbach‐Bruse Sabine
Published: August 2003

Gastrointestinal stromal tumors (GISTs) typically express high levels of the Kit‐receptor. The majority of GISTs carry mutations in the c‐kit protooncogene clustering in exon 11. The significance of c‐kit mutations for the biological behavior of GISTs is still under discussion. We evaluated 55 sporadic GISTs with available follow‐up data for c‐kit mutations in the juxtamembrane domain and detected mutations in 35 cases (63.6%). We found a mutational hotspot in codons 557 (tryptophan) and 558 (lysine) preferentially in histomorphologically malignant tumors. In the group of GISTs carrying c‐kit mutations, 16 of 21 malignant, but only 3 of 8 benign GISTs and 3 of 6 lesions with uncertain malignant potential, carried mutations of Trp‐557 and/or Lys‐558. We investigated whether mutations in these 2 amino acids had an impact on biological behavior. Trp‐557 and/or Lys‐558 were mutated in all 15 metastatic GISTs carrying c‐kit mutations but only in a minority of nonmetastatic tumors. A combined deletion of Trp‐557 and Lys‐558 occurred exclusively in 8 metastatic GISTs. We conclude that in addition to histomorphological evaluation determination of mutations in exon 11 may be an additional parameter for predicting the metastatic risk of GISTs and may be important for the decision that patients will need close clinical follow‐up or further adjuvant treatment with kit antagonists. © 2003 Wiley‐Liss, Inc.
Green tea catechins inhibit VEGF‐induced angiogenesis in vitro through suppression of VE‐cadherin phosphorylation and inactivation of Akt molecule
Authors: Tang Feng‐Yao , Nguyen Nhan , Meydani Mohsen
Published: August 2003

Studies have indicated that the consumption of green tea is associated with a reduced risk of developing certain forms of cancer and angiogenesis. The mechanism of inhibition of angiogenesis by green tea or its catechins, however, has not been well‐established. Vascular endothelial (VE)‐cadherin, an adhesive molecule located at the site of intercellular contact, is involved in cell–cell recognition during vascular morphogenesis. The extracellular domain of VE‐cadherin mediates initial cell adhesion, whereas the cytosolic tail binding with β‐catenin is required for interaction with the cytoskeleton and junctional strength. Therefore, the cadherin–catenin adhesion system is implicated in cell recognition, differentiation, growth and migration of capillary endothelium. Using tube formation of human microvascular endothelial cells (HMVEC) in culture as an in vitro model of angiogenesis, we reported that vascular endothelial growth factor (VEGF)‐induced tube formation is inhibited by anti‐VE‐cadherin antibody and dose‐dependently by green tea catechins. We also demonstrated here that inhibition of tube formation by epigallocatechin gallate (EGCG), one of the green tea catechins, is in part mediated through suppression of VE‐cadherin tyrosine phosphorylation and inhibition of Akt activation during VEGF‐induced tube formation. These findings indicate that VE‐cadherin and Akt, known downstream proteins in VEGFR‐2‐mediated cascade, are the new‐targeted proteins by which green tea catechins inhibit angiogenesis. © 2003 Wiley‐Liss, Inc.
Mortality from cancer and other causes among male airline cockpit crew in Europe
Authors: Blettner Maria , Zeeb Hajo , Auvinen Anssi , Ballard Terri J. , Caldora Massimiliano , Eliasch Harald , Gundestrup Maryanne , Haldorsen Tor , Hammar Niklas , Hammer Gaël P. , Irvine David , Langner Ingo , Paridou Alexandra , Pukkala Eero , Rafnsson Vilhjálmur , Storm Hans , Tulinius Hrafn , Tveten Ulf , Tzonou Anastasia
Published: August 2003

Airline pilots and flight engineers are exposed to ionizing radiation of cosmic origin and other occupational and life‐style factors that may influence their health status and mortality. In a cohort study in 9 European countries we studied the mortality of this occupational group. Cockpit crew cohorts were identified and followed‐up in Denmark, Finland, Germany, Great Britain, Greece, Iceland, Italy, Norway and Sweden, including a total of 28,000 persons. Observed and expected deaths for the period 1960–97 were compared based on national mortality rates. The influence of period and duration of employment was analyzed in stratified and Poisson regression analyses. The study comprised 547,564 person‐years at risk, and 2,244 deaths were recorded in male cockpit crew (standardized mortality ratio [SMR] = 0.64, 95% confidence interval [CI] = 0.61–0.67). Overall cancer mortality was decreased (SMR = 0.68; 95% CI = 0.63–0.74). We found an increased mortality from malignant melanoma (SMR = 1.78, 95% CI = 1.15–2.67) and a reduced mortality from lung cancer (SMR = 0.53, 95% CI = 0.44–0.62). No consistent association between employment period or duration and cancer mortality was observed. A low cardiovascular mortality and an increased mortality caused by aviation accidents were noted. Our study shows that cockpit crew have a low overall mortality. The results are consistent with previous reports of an increased risk of malignant melanoma in airline pilots. Occupational risk factors apart from aircraft accidents seem to be of limited influence with regard to the mortality of cockpit crew in Europe. © 2003 Wiley‐Liss, Inc.
Effects of oral UFT combined with or without zoledronic acid on bone metastasis in the 4T1/luc mouse breast cancer
Authors: Hiraga Toru , Ueda Akimi , Tamura Daisuke , Hata Kenji , Ikeda Fumiyo , Williams Paul J. , Yoneda Toshiyuki
Published: August 2003

Bone metastasis is one of the major causes of increased morbidity and eventual mortality in breast cancer patients. Therefore, intervention of bone metastases is one of the important targets in the management of breast cancer. In the present study, we examined the effects of the orally administrable chemotherapeutic agent UFT (a combination of tegafur and uracil at a molar ratio of 1:4) on bone metastases using an animal model of the 4T1/luc mouse breast cancer. The 4T1/luc cells developed spontaneous metastases to bone following orthotopic cell inoculation. Oral daily administration of UFT (20 mg/kg/day) significantly reduced the orthotopic tumor burden; however, the lower dose (15 mg/kg/day) did not. In contrast, histologic examination showed that both doses of UFT significantly suppressed bone metastases in a dose‐dependent manner. Since clinical studies have demonstrated that bisphosphonates (BPs), specific inhibitors of osteoclastic bone resorption, are beneficial for breast cancer patients with bone metastases, we next examined the effects of UFT combined with the BP zoledronic acid (ZOL) on established bone metastases. The combination of UFT (20 mg/kg/day) with ZOL (250 μg/kg) caused an enhanced reduction of bone metastases compared with UFT alone. In vitro studies showed that 5‐fluorouracil (5‐FU), an active metabolite of UFT, and ZOL increased apoptosis in 4T1/luc cells and inhibited osteoclast‐like cell formation in an additive fashion. Our results suggest that oral UFT is an effective chemotherapeutic agent for advanced breast cancer accompanying bone metastases and that the combination with BP increases its benefits for bone metastases. © 2003 Wiley‐Liss, Inc.
Human papillomavirus type 16 E6 variants and HLA class II alleles among Japanese women with cervical cancer
Authors: Matsumoto Koji , Yasugi Toshiharu , Nakagawa Shunsuke , Okubo Mitsuo , Hirata Ranko , Maeda Hiroo , Yoshikawa Hiroyuki , Taketani Yuji
Published: August 2003

The enhanced oncogenicity of particular human papillomavirus type 16 (HPV16) E6 variants is population‐dependent, implying the involvement of additional genetic cofactors. This study was designed to investigate the association between E6 variants and human leukocyte antigen (HLA) polymorphism within a Japanese population. Fifty‐seven women with HPV16‐positive cervical cancer were analyzed for E6 sequence variation and its relationship to HLA class II alleles. Compared with local controls (n = 138) and published controls (n = 916), DRB1*1501 and DQB1*0602 frequencies were significantly increased among patients with HPV16 E6 prototype (n = 11). Additionally, DRB1*1502 was positively associated with a particular E6 variant designated D25E (n = 25), although we could not find a significant association between HLA class II alleles and L83V variants (n = 16). Our observations suggest that a specific match between E6 variant proteins and HLA types may contribute to HPV16‐related cervical carcinogenesis. © 2003 Wiley‐Liss, Inc.
A comprehensive natural history model of HPV infection and cervical cancer to estimate the clinical impact of a prophylactic HPV‐16/18 vaccine
Authors: Goldie Sue J. , Grima Daniel , Kohli Michele , Wright Thomas C. , Weinstein Milton , Franco Eduardo
Published: August 2003

The object of our study is to project the impact of a prophylactic vaccine against persistent human papillomavirus (HPV)‐16/18 infection on age‐specific incidence of invasive cervical cancer. We developed a computer‐based mathematical model of the natural history of cervical carcinogenesis to incorporate the underlying type‐specific HPV distribution within precancerous lesions and invasive cancer. After defining plausible ranges for each parameter based on a comprehensive literature review, the model was calibrated to the best available population‐based data. We projected the age‐specific reduction in cervical cancer that would occur with a vaccine that reduced the probability of acquiring persistent infection with HPV 16/18, and explored the impact of alternative assumptions about vaccine efficacy and coverage, waning immunity and competing risks associated with non‐16/18 HPV types in vaccinated women. The model predicted a peak age‐specific cancer incidence of 90 per 100,000 in the 6th decade, a lifetime cancer risk of 3.7% and a reproducible representation of type‐specific HPV within low and high‐grade cervical precancerous lesions and cervical cancer. A vaccine that prevented 98% of persistent HPV 16/18 was associated with an approximate equivalent reduction in 16/18‐associated cancer and a 51% reduction in total cervical cancer; the effect on total cancer was attenuated due to the competing risks associated with other oncogenic non‐16/18 types. A vaccine that prevented 75% of persistent HPV 16/18 was associated with a 70% to 83% reduction in HPV‐16/18 cancer cases. Similar effects were observed with high‐grade squamous intraepithelial lesions (HSIL) although the impact of vaccination on the overall prevalence of HPV and low‐grade squamous intraepithelial lesions (LSIL) was minimal. In conclusion, a prophylactic vaccine that prevents persistent HPV‐16/18 infection can be expected to significantly reduce HPV‐16/18‐associated LSIL, HSIL and cervical cancer. The impact on overall prevalence of HPV or LSIL, however, may be minimal. Based on the relative importance of different parameters in the model, several priorities for future research were identified. These include a better understanding of the heterogeneity of vaccine response, the effect of type‐specific vaccination on other HPV types and the degree to which vaccination effect persists over time. © 2003 Wiley‐Liss, Inc.
Hereditary ovarian cancer in Poland
Authors: Menkiszak Janusz , Gronwald Jacek , Górski Bohdan , Jakubowska Anna , Huzarski Tomasz , Byrski Tomasz , Foszczyńska‐Kłoda Małgorzata , Haus Olga , Janiszewska Hanna , Perkowska Magdalena , Brożek Izabela , Grzybowska Ewa , Zientek Helena , Góźdź Stanisław , Kozak‐Klonowska Beata , Urbański Krzysztof , Miturski Roman , Kowalczyk Jerzy , Plużańska Anna , Niepsuj Stanisław , Koc Jan , Szwiec Marek , Drosik Kazimierz , Mackiewicz Andrzej , Lamperska Katarzyna , Stróżyk Elwira , Godlewski Dariusz , Stawicka Małgorzata , Waśko Bernard , Bebenek Marek , Rozmiarek Andrzej , Rzepka‐Górska Izabella , Narod Steven A. , Lubiński Jan
Published: August 2003

There is increasing evidence that hereditary factors play a greater role in ovarian cancer than in any of the other common cancers of adulthood. This is attributable, to a large extent, to a high frequency of mutations in the BRCA1 or BRCA2 genes. In Poland, 3 common founder mutations in BRCA1 account for the majority of families with identified BRCA mutations. Our study was conducted in order to estimate the prevalence of any of 3 founder BRCA1 mutations (5382insC, C61G and 4153delA) in 364 unselected women with ovarian cancer, and among 177 women with ovarian cancer and a family history of breast or ovarian cancer. A mutation was identified in 49 out of 364 unselected women with ovarian cancer (13.5%) and in 58 of 177 women with familial ovarian cancer (32.8%). The majority of women with ovarian cancer and a BRCA1 mutation have no family history of breast or ovarian cancer. The high frequency of BRCA1 mutations in Polish women with ovarian cancer supports the recommendation that all Polish women with ovarian cancer should be offered testing for genetic susceptibility, and that counseling services be made available to them and to their relatives. It is important that mutation surveys be conducted in other countries prior to the introduction of national genetic screening programs. © 2003 Wiley‐Liss, Inc.
Quasi‐rational and ex ante price expectations in commodity supply models: an empirical analysis of the US broiler market
Authors: Holt Matthew T. , McKenzie Andrew M.
Published: August 2003

A statistically optimal inference about agents' ex ante price expectations within the US broiler market is derived using futures prices of related commodities along with a quasi‐rational forecasting regression equation. The modelling approach, which builds on a Hamilton‐type framework, includes endogenous production and allows expected cash price to be decomposed into anticipated and unanticipated components. We therefore infer the relative importance of various informational sources in expectation formation. Results show that, in addition to the quasi‐rational forecast, the true supply shock, future prices, and ex post commodity price forecast errors have, at times, been influential in broiler producers' price expectations. Copyright © 2003 John Wiley & Sons, Ltd.
A new coincident index of business cycles based on monthly and quarterly series
Authors: Mariano Roberto S. , Murasawa Yasutomo
Published: August 2003

Popular monthly coincident indices of business cycles, e.g. the composite index and the Stock–Watson coincident index, have two shortcomings. First, they ignore information contained in quarterly indicators such as real GDP. Second, they lack economic interpretation; hence the heights of peaks and the depths of troughs depend on the choice of an index. This paper extends the Stock–Watson coincident index by applying maximum likelihood factor analysis to a mixed‐frequency series of quarterly real GDP and monthly coincident business cycle indicators. The resulting index is related to latent monthly real GDP. Copyright © 2002 John Wiley & Sons, Ltd.
Inferring the private information content of trades: a regime‐switching approach
Authors: Nyholm Ken
Published: August 2003

This paper presents an empirical model for inferring the private information content of trades at the transaction level. The trade‐indicator model of Glosten and Harris (1988) is extended to a two‐state regime‐switching setting, and the model is estimated using tick‐by‐tick data from the New York Stock Exchange (NYSE). The specialist is found to react in accordance with the proposed model. Bid–ask quotes set after the execution of a trade reflect the conjectured information content of that particular trade. Based on the estimated model four empirical results emerge: (a) the suggested regime‐switching model fit data well; (b) the reverse J‐shaped pattern of intra‐daily quoted spreads is shown to agree with the clustering of costs incurred by the specialist through trading with better‐informed agents; (c) on average 9% of all trades are found to reveal private: information to the specialist; (d) results regarding the trading volume of informed traders support the stealth trading hypothesis suggested by Barclay and Warner (1993). Copyright © 2003 John Wiley & Sons, Ltd.
Combinatorial characterization of cell interactions with polymer surfaces
Authors: Meredith J. Carson , Sormana Joe‐L. , Keselowsky Benjamin G. , García Andrés J. , Tona Alessandro , Karim Alamgir , Amis Eric J.
Published: August 2003

We report a novel combinatorial methodology for characterizing the effects of polymer surface features on cell function. Libraries containing hundreds to thousands of distinct chemistries, microstructures, and roughnesses are prepared using composition spread and temperature gradient techniques. The method enables orders of magnitude increases in discovery rate, decreases variance, and allows for the first time high‐throughput assays of cell response to physical and chemical surface features. The technique overcomes complex variable spaces that limit development of biomaterial surfaces for control of cell function. This report demonstrates these advantages by investigating the sensitivity of osteoblasts to the chemistry, microstructure, and roughness of poly(D,L‐lactide) and poly(ϵ‐caprolactone) blends. In particular, we use the phenomenon of heat‐induced phase separation in these polymer mixtures to generate libraries with diverse surface features, followed by culture of UMR‐106 and MC3T3‐E1 osteoblasts on the libraries. Surface features produced at a specific composition and process temperature range were discovered to enhance dramatically alkaline phosphatase expression in both cell lines, not previously observed for osteoblasts on polymer blends. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 483–490, 2003
Fracture toughness of human dentin
Authors: Iwamoto Nanako , Ruse N. Dorin
Published: August 2003

The purpose of this study was to determine the fracture toughness (KIC) of human dentin and to test the null hypothesis that KIC is not affected by the orientation of dentinal tubules relative to the plane of crack propagation. Triangular prisms (4 × 4 × 4 × 8 mm) were obtained from human molars and tested using the notchless triangular prism (NTP) specimen KIC test. Dentin prisms were prepared so that the plane of crack propagation would have three different orientations relative to the orientation of dentinal tubules: perpendicular (PE), parallel aligned (PAA), and parallel transverse (PAT). The prepared specimens were secured in the specimen holder and loaded in tension until fracture or crack arrest. The maximum load recorded was used to calculate KIC. There was no significant difference between the KIC of PAA specimens (1.97 ± 0.17 MPa/m1/2) and PAT (2.02 ± 0.18 MPa/m1/2). The KIC for the PE specimens (1.13 ± 0.36 MPa/m1/2) was significantly lower. The SEM images of the fractured surfaces showed distinct differences that were correlated with the determined KIC values. The fractured surfaces of PAA and PAT specimens were rougher compared to PE specimens. Both the hyper mineralized peritubular dentin and the orientation of collagen fibrils surrounding the tubules could be responsible for the significant differences in KIC. The results of this study identified a significant anisotropy of dentin with respect to its KIC. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 507–512, 2003
Chondrocytes seeded onto poly (L/DL‐lactide) 80%/20% porous scaffolds: A biochemical evaluation
Authors: Grad Sibylle , Zhou Lin , Gogolewski Sylwester , Alini Mauro
Published: August 2003

Repair of articular cartilage remains a clinical and scientific challenge. The use of implantable chondrocyte‐seeded constructs offers a promising treatment option. The present study is focused on the culture of chondrocytes onto 3‐D poly (L‐/DL‐lactide) 80%/20% porous scaffolds. Scaffolds were seeded with bovine articular chondrocytes and cultured for up to 42 days. After an initial decrease, although not significant, the DNA content of the constructs remained constant over the culture time. A progressive increase in glycosaminoglycans and collagen was observed in the constructs during the culture period. However, a significant release of matrix molecules into the culture medium also was noticeable. On the transcriptional level, aggrecan mRNA expression was highest on day 14 and gradually decreased thereafter. Procollagen I mRNA expression constantly increased whereas procollagen II mRNA expression decreased after day 14, indicating that cells were dedifferentiating. Histologic analysis of the constructs demonstrated the deposition of a proteoglycan‐rich extracellular matrix by day 42 of culture. The present data demonstrate that poly (L‐/DL‐lactide) 80%/20% porous scaffolds support the development of a cartilage‐like extracellular matrix. The limitations of the system are the diffusion of large amounts of matrix molecules into the culture medium and the dedifferentiation of the chondrocytes with prolonged time in culture. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 571–579, 2003
Mineralization of matrix vesicles isolated from a human osteosarcoma cell line in culture with water‐soluble chitosan‐containing medium
Authors: Yamada Shizuka , Ohara Naoko , Hayashi Yoshihiko
Published: August 2003

Chitosan is a natural bioactive material. Although it has been reported that chitosan promotes osteogenesis in bone lesions, little is known about how chitosan modulates this process. The present study was designed to investigate the effect of water‐soluble chitosan relative to initiation of biologic mineralization, especially in the matrix‐vesicles‐(MVs) mediated processin vitro. A human osteoblastic cell line (NOS‐1) was used. After 3 days of incubation, the number of cells and alkaline phosphatase (ALP) activity increased significantly in the chitosan group. RT‐PCR analysis revealed that chitosan induced an increase in the expression of bone morphogenetic protein‐2 mRNA after 7 days of incubation. MVs were isolated from NOS‐1 cells using a collagenase digestion and ultracentrifugation method. ALP activity of MVs isolated from chitosan‐supplemented cells was significantly higher than that of the control group. Furthermore, isolated MVs were incubated in medium supplemented with Na‐β‐glycerophosphate without fetal bovine serum. Needle‐like crystals were observed in association with MVs after 24 h of incubation. These needle‐like crystals were densely accumulated in the chitosan group. The present findings suggest that water‐soluble chitosan would promote osteoblast proliferation and differentiation and may be useful for the acceleration of initial biologic mineralization. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 500–506, 2003
Expression of nitric oxide, peroxynitrite, and apoptosis in loose total hip replacements
Authors: Puskas Brian L. , Menke Nora E. , Huie Phil , Song Yong , Ecklund Kier , Trindade Michael C. D. , Smith R. Lane , Goodman Stuart B.
Published: August 2003

Nitric oxide (NO) is an effector molecule associated with inflammation, immune function, bone metabolism, and the induction of apoptosis. This study examined the role of NO, peroxynitrite (ONOO−), and apoptosis in cases of revision total hip replacements (THRs). We hypothesized that apoptosis and excess production of NO contribute to the inflammatory reaction to orthopedic biomaterial wear debris that is associated with loosening and osteolysis. Periprosthetic membranous specimens were collected from revised cemented acetabular components with simple loosening and ballooning osteolysis. Synovial samples from patients undergoing primary THR were used as controls. The presence of macrophages (CD68+) and levels of inducible nitric oxide synthase (INOS), endothelial nitric oxide synthase (EcNOS), ONOO− (Nitro, assayed by the amount of nitrated tyrosine residues), and apoptosis (TUNEL staining) were examined using immunohistochemistry. Increased expression for INOS, EcNOS, and ONOO− in both the loose/osteolytic and the loose/non‐osteolytic groups was observed when compared to the synovium group. There were no significant differences between the loose/osteolytic group and loose/non‐osteolytic group for these biologic markers. TUNEL staining showed a significant increase in apoptosis in the loose/osteolytic group compared to the loose/non‐osteolytic group and synovial tissues. These findings suggest that NO and NO‐derived molecules, such as ONOO−, may be involved in sustaining the foreign‐body reaction to wear debris. NO and ONOO− may prove to be useful markers of prosthetic loosening whereas apoptosis may be a marker distinguishing ballooning from simple osteolysis. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 541–549, 2003
An effective method for quantitative evaluation of proteins adsorbed on biomaterial surfaces
Authors: Lü X. Y. , Huang Y. , Qian W. P. , Tang Z. M. , Lu Z. H.
Published: August 2003

An effective method for the quantitative evaluation of proteins adsorbed on biomaterial surfaces has been developed. First, the kinetic behavior of a range of human fibrinogen (Fib) adsorbed onto polystyrene (PS) films was investigated by using a reflectometry interference spectroscopy setup. The specific molecular number of adsorbed proteins, Np, was then defined. According to the definition, the numbers of Fib molecules adsorbed on PS films were calculated. An atomic force microscope (AFM) was used to scan the lateral distribution of the Fib molecules adsorbed on the PS films. From the AFM images, the practical specific molecular numbers were obtained by direct counting of the molecules. In order that the adsorbed number of Fib molecules on a unit area of the PS films could be counted easily, the solution concentration of proteins was reduced to 5 ag/mL (10−18g/mL). There was good consistency between the numbers calculated with the formula defined by us and the numbers counted from AFM images. Therefore, the results of the present study prove the validity of our definition of the specific molecular number of adsorbed proteins and the effectiveness of the reflectometry interference spectroscopy‐based method for quantitative evaluation of adsorptive proteins. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 722–727, 2003
Novel therapeutic strategy for prevention of malignant tumor recurrence after surgery: Local delivery and prolonged release of adenovirus immobilized in photocured, tissue‐adhesive gelatinous matrix
Authors: Okino Hidenobu , Manabe Tatsuya , Tanaka Masao , Matsuda Takehisa
Published: August 2003

We have been developing a new gene delivery method using a styrenated gelatin‐based tissue‐adhesive matrix that allows in situ adenovirus‐immobilized gel formation on living tissue and sustained virus release to permeate carcinoma tissue. Styrenated gelatin was synthesized by the condensation reaction of gelatin with 4‐vinylbenzoic acid. Aqueous styrenated gelatin solution premixed with AdLacZ, adenovirus encoding β‐galactosidase cDNA, and carboxylated camphorquinone (CQ) as a photoinitiator was irradiated with visible light to form a styrenated gelatin gel. The in vitro adenovirus release from the styrenated gelatin gel to a medium strongly depended not on styrenated gelatin concentration but on CQ concentration. Maximal β‐galactosidase expression was observed on day 1, followed by a rapid decrease that continued up to 1 month for a styrenated gelatin gel prepared with a low styrenated gelatin concentration and a low CQ concentration. Dose‐dependent reduced expression of β‐galactosidase activity with increasing CQ under photoirradiation was observed. AdLacZ‐immobilized styrenated gelatin gel was formed on a hybrid tissue, which is a cell traction‐induced collagenous gel entrapped with fibroblasts, and lacZ gene expression of fibroblasts in the hybrid tissue was observed for more than one month. The result of this in vitro model experiment implies that the tissue‐adhesive styrenated gelatin may be applicable for the delivery of adenovirus encoding cDNA for tumor dormancy therapy into malignant tissue to prevent tumor recurrence after surgery when cDNA is properly selected. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 643–651, 2003
Biologic effects of surface roughness and fluorhydroxyapatite coating on osteointegration in external fixation systems: An in vivo experimental study
Authors: Savarino L. , Fini M. , Ciapetti G. , Cenni E. , Granchi D. , Baldini N. , Greco M. , Rizzi G. , Giardino R. , Giunti A.
Published: August 2003

The concomitant influence of surface roughness and fluorhydroxyapatite (FHA) coating of titanium (Ti) implants on bone response was investigated. For this purpose, titanium screw‐shaped implants with a lower degree (Y371) and a higher degree (TiPore300) of surface roughness, coated with FHA and uncoated, were transversally inserted into the diaphyses of sheep tibiae for 12 weeks. Four sheep received Y371 (group A) and Y371 + FHA (group B) screws and four sheep received TiPore300 (group C) and TiPore300 + FHA (group D) screws. For each type of material, the morphology and microstructure of implant–facing bone were evaluated. The host bone of each tibia was used as a control. In all groups the bone tissue did not reach a complete maturation. The higher degree of roughness, perhaps due to an excessive irregularity of the surface, induced the worst osteointegration: a fibrous tissue layer between screw and new bone tissue was often present. Nevertheless, as viewed by XRD, no crystallographic change of the apatite lattice was observed in any of the implants. In contrast, the microhardness value, an index of bone mineralization, was higher in the uncoated screws and decreased progressively in the following order: group C > group A > group B > group D. The association of plasma spraying with roughness treatment constitutes a complex system that seems to interfere with bone mineralization. A chemical change of the surface, perhaps with more Ti release or more coating degradation, could be responsible for such impairment. The authors emphasize the necessity for simultaneous evaluation of surface topography and chemistry as well as an improvement in plasma‐spraying and post‐processing techniques and in standard procedures for materials characterization. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 652–661, 2003
Enhancing mechanical properties of tissue‐engineered constructs via lysyl oxidase crosslinking activity
Authors: Elbjeirami Wafa M. , Yonter Edward O. , Starcher Barry C. , West Jennifer L.
Published: August 2003

A number of strategies have been investigated to enhance the mechanical stability of engineered tissues. In this study, we utilized lysyl oxidase (LO) to enzymatically crosslink extracellular matrix (ECM) proteins, particularly collagen and elastin, to enhance the mechanical integrity of the ECM and thereby impart mechanical strength to the engineered tissue. Vascular smooth muscle cells (VSMCs) were liposomally transfected with the LO gene. Both Northern and Western analyses confirmed increased LO expression. Increased LO activity was demonstrated using a fluorescent enzyme substrate assay and by observation of the presence of increased levels of desmosine, a product of LO crosslinking, in the ECM. The mechanical effects of altered crosslink densities within tissue‐engineered constructs were demonstrated in a VSMC‐populated collagen gel model. When smooth muscle cells transfected with lysyl oxidase were seeded in collagen gels, the tensile strength and elastic modulus in these constructs increased by approximately two‐fold compared to constructs seeded with mock‐transfected VSMCs. Also, desmosine levels in the LO‐populated collagen gels were higher than they were in mock‐seeded gels, as demonstrated via immunohistochemical staining. Compositional analysis of the ECM deposited by the transformed cells showed similar collagen and elastin levels, and cell proliferation rates were similar as well, thus attributing increased mechanical properties to ECM crosslinking. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 513–521, 2003
Quantitative analysis of osteoblast behavior on microgrooved hydroxyapatite and titanium substrata
Authors: Lu Xiong , Leng Yang
Published: August 2003

The effects of implant surface topography and chemistry on osteoblast behavior have been a research focus because of their potential importance in orthopedic and dental applications. This work focused on the topographic effects of hydroxyapatite (HA) and titanium (Ti) surface that had identical micropatterns to determine whether there was synergistic interaction between surface chemistry and surface topography. Surface microgrooves with six different groove widths (4, 8, 16, 24, 30, and 38 μm) and three different groove depths (2, 4, and 10 μm) were made on single crystalline silicon wafers using microfabrication techniques. Ti and HA thin films were coated on the microgrooves by radio‐frequency magnetron sputtering. After that, human osteoblast‐like cells were seeded and cultured on the microgrooved surfaces for up to 7 days. The cells' behavior was examined using scanning electron microscopy after cells were fixed and dehydrated. Statistical analysis was based on quantitative data of orientation angle, evaluating the contact guidance, and form index, describing cell shape or cell morphology changes. The contact guidance and cell shape changes were observed on the HA and Ti microgrooves. No difference in orientation angle between HA and Ti microgrooves was found. This might suggest that surface chemistry was not a significant influence on cell guidance. However, the form index analysis indicated an interaction between topographic effects and surface chemistry. Thus, conclusions about surface topographic effects on cell behavior drawn from one type of material cannot simply be applied to another type of material. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 677–687, 2003
Novel in vivo method for evaluation of healing around implants in bone
Authors: Eriksson Cecilia , Broberg Marita , Nygren Håkan , Öster Lars
Published: August 2003

A material implanted in bone is always inserted into coagulating blood. Protein and cell interactions during this initial implantation time will govern later healing. Many studies have focused on the tissue surrounding implants. We have developed a method for evaluation of healing around implants in bone by studying cells adhering to the implant surface. Hydrophilic titanium discs were inserted into rat tibiae. Samples were retrieved after 1, 2, 4, and 8 days of implantation and were analyzed by fluorescence microscopy techniques and scanning electron microscopy. Both proliferating and apoptotic cells were found on the surface. Generally, cells closest to the implant surface were nonviable whereas cells in the fibrin network a distance from the surface were viable. Bone morphogenetic protein‐2 (BMP‐2) is an osteogenic substance. An increase in BMP‐2‐positive cells was seen during the implantation period, and a population of large BMP‐2‐positive cells appeared on the surface after 4 days of implantation. The method developed here is a suitable tool for rapid evaluation of the initial healing around implant material. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 662–668, 2003
Fluoroapatite glass‐ceramic coating on alumina: Surface behavior with biological fluids
Authors: Bosetti M. , Vernè E. , Brovarone C. Vitale , Moisescu C. , Sabbatini M. , Cannas M.
Published: August 2003

The results of a surface analysis performed on a fluoroapatite‐based glass ceramic (SAF) also coating a full‐density α‐alumina substrate (SAF‐alumina coating) are presented. These two materials have also been evaluated after soaking in simulated body fluid to understand their ability to induce hydroxyapatite growth on them. Aiming to understand the fluoroapatite glass‐ceramic interaction with some plasma proteins, in the second part of this study, fibronectin, albumin, immunoglobulin G, IgA, and complement factor C3c SAF binding have been evaluated; surface activity on complement activation has also been quantified. SAF‐alumina coating provides good sites for the nucleation and growth of an apatite layer, equivalent to the mineral component of bone and binds preferentially plasma fibronectin, which is well known to enhance cell adhesion and spreading. Moreover, SAF‐alumina coating reduces alumina complement activation directly or via reduced IgA binding. Alumina was shown to bind the same C3 fragments as Zymosan, used as complement activating control, and to induce increased levels of serum soluble iC3b and Bb. A mechanical resistant material with enhanced bioactivity, bone integration, and reduced inflammatory potential respect to alumina has been obtained. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 615–621, 2003
Inhibitor of complement, Compstatin, prevents polymer‐mediated Mac‐1 up‐regulation of human neutrophils independent of biomaterial type tested
Authors: Schmidt S. , Haase G. , Csomor E. , Lütticken R. , Peltroche‐Llacsahuanga H.
Published: August 2003

The inflammatory reaction after cell contact with polymer materials is primarily mediated by activated neutrophils and may, in some cases, lead to exhaustion of neutrophil cell function. A direct consequence of this can be impairment of local or even systemic host defense mechanisms, which in turn can result in foreign body infections. Neutrophil activation, as indicated by the up‐regulation of the Mac‐1 adhesion receptor, is a reliable parameter for estimating the inflammatory risk due to implanted biomaterials. Because at blood contact, biomaterials immediately acquire a material‐specific layer of blood proteins on their surface, including fibrinogen, complement, and immunoglobulin G, it is generally believed that after biomaterial contact, neutrophil activation primarily occurs by interaction with this protein layer. In this study, using our recently established polymer bead in vitro assay, we investigated whether complement inhibition alone can reduce biomaterial‐mediated neutrophil activation, independent of the type of polymer and, hence, also its surface chemistry. Complement inhibition was achieved by using Compstatin, a recently developed complement inhibitor that binds to the complement component C3 preventing C3 convertase formation. We revealed significantly reduced (p ≤ 0.025) Mac‐1 receptor expression levels after 45 min of blood contact with the following polymers (without and with Compstatin): 1. polyurethane, 98.3%, 13.6%; 2. polymethylmetacrylate, 88.5%, 11.0%; and poly‐D,L‐lactide, 71.8%, 8.4%. Although these three polymer types acquire material‐specific protein layers because of their different surface chemistry, complement inhibition by Compstatin alone proved to be sufficient to reduce neutrophil activation after surface contact, thus reducing the risk of biomaterial‐mediated inflammatory reaction. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 491–499, 2003
Synthesis and characterization of a novel polymer–ceramic system for biodegradable composite applications
Authors: Yang Liu , Wang Jian , Hong Jason , Santerre J. Paul , Pilliar Robert M.
Published: August 2003

The objective of this study was to develop a biodegradable polymer resin that could be used for the fabrication of an interpenetrating phase composite (IPC) made of porous calcium polyphosphate (CPP) and an organic polymer resin. The resin was synthesized from a polycarbonate‐based divinyl oligomer and monomers containing ionic groups. The physical and chemical properties of the polymer resin and polycarbonate‐based divinyl oligomer were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, and swelling studies. The in vitro degradation of the polymer resins was assessed using cholesterol esterase in a buffer solution at 37°C for 3 weeks. Scanning electron microscopy of the degraded samples indicated that the hydrolysis of the resin was catalyzed by the enzyme. The relative interfacial shear strength between the polymer resin and the CPP ceramic was studied using a microbond test. The addition of ionic groups into the polymer resin chains appeared to improve the chemical bonding between the polymer and the CPP. Preliminary mechanical properties of the IPC were investigated by determining bending strength using a three point bending test. The data showed a sevenfold increase in strength over that of the monolithic CPP, and the addition of more ionic groups into the resin led to a higher bending strength for the newly formed CPP/polycarbonate resin system. Sample cross sections of the IPC examined using scanning electron microscopy suggested that the resin had infiltrated almost all of the pores of the CPP. The results of this study indicate that the IPC could potentially be used for fabricating novel biodegradable load‐bearing implants. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 622–632, 2003
Model porous surfaces for systematic studies of material‐cell interactions
Authors: Petronis Sarunas , Gretzer Christina , Kasemo Bengt , Gold Julie
Published: August 2003

A model system for studying cell‐surface interactions, based on microfabricated cell culture substrates, has been developed and is described here. Porous surfaces consisting of interconnecting channels with openings of subcellular dimensions are generated on flat, single crystal, silicon substrates. Channel size (width, depth), distribution, and surface coating can be varied independently and used for systematic investigation of how topographical, chemical, and elastic surface properties influence cell or tissue biological responses. Model porous surfaces have been produced by using two different microfabrication methods. Submicron‐sized channels with very high depth‐to‐width aspect ratios (up to 30) have been made by using electron beam lithography and anisotropic reactive ion etching into single‐crystal silicon. Another method uses thick‐resist photolithography, which can be used to produce channels wider than 1 μm and with depth‐to‐width aspect ratios below 20 in an epoxy polymer. Preliminary cell culture tests show that fibroblasts bridge 0.8‐ to 1.8‐μm‐wide channels with very few exceptions (i.e., a continuous space below the cell‐surface interface is created). It has also been shown that variation of channel periodicity significantly affects fibroblast morphology and attachment density. With this model system, it is possible to load the channels with bioactive substances intended to interact with cells at or near the surface in a time‐dependent manner. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 707–721, 2003
Deposition of complement protein C3b on mixed self‐assembled monolayers carrying surface hydroxyl and methyl groups studied by surface plasmon resonance
Authors: Hirata Isao , Hioki Yasunori , Toda Mitsuaki , Kitazawa Takayuki , Murakami Yoshinobu , Kitano Etsuko , Kitamura Hajime , Ikada Yoshito , Iwata Hiroo
Published: August 2003

Since complement activation is recognized as a common response of the host defense system when an artificial medical device is applied to a patient, great effort has been devoted to studies on the interaction of the complement system with artificial materials. However, some uncertainties remain, partially because of the lack of well characterized surfaces and suitable analytic methods for study of the surface phenomena that occur on artificial materials under physiologic conditions. In this study, we employed self‐assembled monolayers (SAMs) and the surface plasmon resonance (SPR) technique to study interactions of the serum complement with well characterized surfaces. Self‐assembled monolayers carrying various concentrations of hydroxyl groups were prepared using 11‐mercapto‐1‐undecanol (C11‐OH) and one of n‐nonanethiol, n‐dodecanethiol, and n‐hexadecanethiol. The amount of NHS deposition on the SAMs increased with increasing C11‐OH content of the SAMs, and the amount of anti‐C3b antibody immobilization formed on the NHS deposition layers increased with increasing C11‐OH content of the SAMs. These results clearly demonstrate that a large amount of C3b, produced through the activation of the complement system, binds covalently to and is adsorbed by hydroxyl‐group‐rich surfaces. The combination of SAMs and the SPR technique is suitable for studying the interaction of the complement system with solid surfaces, and the results should give basic information needed for a rational design of biocompatible surfaces on synthetic materials. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 669–676, 2003
Spatially organized layers of cardiomyocytes on biodegradable polyurethane films for myocardial repair
Authors: McDevitt Todd C. , Woodhouse Kimberly A. , Hauschka Stephen D. , Murry Charles E. , Stayton Patrick S.
Published: August 2003

Tissue engineering constructs should match the physical and mechanical properties of the native tissue. This implies that pliable scaffolds might be better suited for soft‐tissue applications than rigid polymeric materials. In this study, we examined spatially organized cardiomyocyte cultures on biodegradable, elastomeric polyurethane films patterned by microcontact printing of laminin lanes. The resulting cardiomyocyte patterns on polyurethane displayed a similar morphology to those previously achieved for up to 7–10 days on other substrates, such as polystyrene dishes. However, the integrity of the cardiomyocyte patterns on thin, spin‐cast or solvent‐cast polyurethane films was retained for up to 4 weeks in culture. When additional cardiomyocytes (labeled with Cell Tracker reagents) were seeded onto the patterned cultures, secondary and tertiary cell populations aligned between and on top of the primary patterned cells to form a multilayered, organized tissue construct approximately 2–3 cell layers thick. In addition, dense, highly aligned monolayers of patterned cardiomyocytes were able to contract the thin, solvent‐cast polyurethane films. These results indicate that elastomeric, biodegradable polyurethane films can serve as an appropriate scaffold material to support stably the engineering of spatially organized layers of cardiomyocytes in vitro. This approach may serve as a novel method for transplantation of organized cardiac tissue constructs to the heart for myocardial repair. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 586–595, 2003
In vitro biocompatibility assessment of sulfonated polyrotaxane‐immobilized polyurethane surfaces
Authors: Park Hyung Dal , Lee Won Kyu , Ooya Tooru , Park Ki Dong , Kim Young Ha , Yui Nobuhiko
Published: August 2003

Sulfonated polyrotaxanes (PRx‐SO3's), in which sulfonated α‐cyclodextrins (α‐CDs) were threaded onto the poly(ethylene glycol) (PEG) segments in a PEG‐b‐poly(propylene glycol) (PPG)‐b‐PEG triblock copolymer (Pluronic) capped with benzyloxycarbonyl (Z)‐L‐phenylalanine (Z‐L‐Phe), were prepared as a novel surface‐modifying biomaterial. Surface modification of the polyurethane (PU) was carried out by blending the PRx‐SO3's with a PU solution, followed by solution casting. The incorporated PRx‐SO3's led to the enhanced hydrophilicity by changing the surface properties of the PU matrix. Modified PUs showed the stable entrapment of the PRx‐SO3's with little extraction into water and enhanced mechanical properties after exposure to water compared to the PU control. The incorporated PRx‐SO3's repelled the proteins and kept them from closely approaching the surface areas, prevented platelet activation by thrombin, and effectively repelled bacteria. These results suggest that both the supramolecular structure of the polyrotaxanes and exposure of the sulfonated groups onto the surfaces contribute to these phenomena. Thus, surface modification with PRx‐SO3's is suggested to be useful for the fabrication of biocompatible medical devices. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 596–604, 2003