bluuebunny/crossref_metadata_2025 huggingface dataset:
Smoking, DNA repair capacity and risk of nonsmall cell lung cancer
Authors: Shen Hongbing , Spitz Margaret R. , Qiao Yawei , Guo Zhaozheng , Wang Li‐E , Bosken Carol H. , Amos Christopher I. , Wei Qingyi
Published: August 2003

Tobacco‐related carcinogens cause a variety of DNA damage that is repaired by different enzymatic pathways, suggesting that DNA repair plays an important role in tobacco‐induced carcinogenesis. In a large hospital‐based case‐control study, we investigated DNA repair capacity (DRC) as a biomarker for susceptibility to nonsmall cell lung cancer (NSCLC) and evaluated the possible interaction between DRC and tobacco smoke in 467 newly diagnosed NSCLC patients and 488 cancer‐free controls. We measured DRC in cultured peripheral lymphocytes using the host‐cell reactivation assay with a reporter gene damaged by an activated tobacco carcinogen, benzo[a]pyrene diol epoxide. The results showed that current smokers exhibited the highest DRCs as compared to former and nonsmokers both among patients and control subjects. There were no differences of DRC among 3 different histopathologic types of NSCLC. Logistic regression analysis revealed that suboptimal DRC and pack‐years smoked were independent predictors of NSCLC risk. The overall 15.5% reduction in DRC observed in the cases (7.84%) compared to the controls (9.28%) (p<0.001) was associated with an approximately 2‐fold increased risk of NSCLC (adjusted odds ratio (OR) = 1.85, 95% confidence interval (CI) 1.42–2.42). There was a significant dose‐response association between decreased DRC and increased risk of lung cancer. Furthermore, we observed a nonstatistically significant additive but not multiplicative interaction between DRC and pack‐years smoked on lung cancer risk, particularly in the histopathologic types of NSCLC other than adenocarcinoma. The results suggest that suboptimal DRC is associated with increased risk of NSCLC and DRC may modulate the risk of lung cancer associated with smoking but the latter needs to be verified in larger studies. © 2003 Wiley‐Liss, Inc.
Promoter methylation of the TSLC1 gene in advanced lung tumors and various cancer cell lines
Authors: Fukami Takeshi , Fukuhara Hiroshi , Kuramochi Masami , Maruyama Tomoko , Isogai Kana , Sakamoto Michiie , Takamoto Shinichi , Murakami Yoshinori
Published: August 2003

We previously identified TSLC1, a tumor suppressor gene in human nonsmall cell lung cancer (NSCLC). TSLC1 belongs to immunoglobulin superfamily molecules and is involved in cell adhesion. Loss of TSLC1 expression was strongly correlated with the promoter hypermethylation in several NSCLC cell lines. Here, we examined the methylation status of the TSLC1 gene promoter in 48 primary NSCLC tumors by bisulfite SSCP in combination with bisulfite sequencing. Six CpG sites around the promoter regions were significantly methylated in 21 of 48 primary NSCLC tumors (44%). Promoter methylation was more likely to be observed in relatively advanced tumors with TNM classification of pT2, pT3 or pT4 (19 of 33, 58%) than in those with pT1 (2 of 15, 13%), suggesting that alteration of TSLC1 would be involved in the progression of human NSCLC. Loss of TSLC1 expression was also observed in 20 of 46 (43%) human cancer cell lines, including those from esophageal (3 of 3), gastric (8 of 9), ovarian (2 of 5), endometrial (2 of 2), breast (1 of 3), colorectal (2 of 8) and small cell lung cancers (2 of 10). Combined analysis of promoter methylation and the allelic state in these cell lines indicated that the TSLC1 gene was often silenced not only by mono‐allelic methylation associated with loss of the other allele but also through bi‐allelic methylation. These results suggest that alteration of TSLC1 would be involved in advanced NSCLC as well as in many other human cancers. © 2003 Wiley‐Liss, Inc.
Human papillomavirus and risk factors for cervical cancer in Chennai, India: A case‐control study
Authors: Franceschi Silvia , Rajkumar Thangarajan , Vaccarella Salvatore , Gajalakshmi Vendhan , Sharmila Ajit , Snijders Peter J.F. , Muñoz Nubia , Meijer Chris J.L.M. , Herrero Rolando
Published: August 2003

To evaluate the role of human papillomavirus (HPV) and other risk factors in the aetiology of invasive cervical carcinoma (ICC), we conducted a hospital‐based case‐control study in Chennai, Southern India. A total of 205 ICC cases (including 12 adenocarcinomas) and 213 frequency age‐matched control women were included. HPV DNA in cervical cells was evaluated by means of a polymerase chain‐reaction assay. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were computed by means of unconditional multiple logistic regression models. HPV infection was detected in all but one ICC cases and in 27.7% of control women (OR = 498). Twenty‐three different HPV types were found. HPV 16 was the most common type in either cases or controls, followed by HPV 18 and 33. The association of ICC with HPV 18 and HPV 16‐associated types was somewhat stronger than the one with HPV 16. Multiple HPV infections did not show a higher OR for ICC than single infections. Other than HPV infection, high parity (OR for >4 vs. ≤2 births = 7.3), a woman's report of her husband's extramarital sexual relationships (OR = 10.0) and early menopause (OR for <45 vs. ≥45 years = 4.2) were significantly associated with ICC, also after restricting the analysis to HPV‐positive cases and controls. Poor hygienic conditions were associated with an increased risk of HPV infection among control women but not with ICC risk among HPV‐positive women. A vaccine against HPV 16 and 18 may be effective in more than three‐quarters of ICC in the study area. © 2003 Wiley‐Liss, Inc.
Multiple myeloma and diesel and other occupational exposures in swedish construction workers
Authors: Lee Won Jin , Baris Dalsu , Järvholm Bengt , Silverman Debra T. , Bergdahl Ingvar A. , Blair Aaron
Published: August 2003

We examined the relationships between occupational exposures and the risk of multiple myeloma among male construction workers in Sweden. A total of 446 myeloma subjects were identified among 365,424 male workers followed from 1971 to 1999. Occupational exposure was assessed using a semiquantitative job‐exposure matrix, based on a survey carried out by the Construction Industry's Organization for Working Environment, Occupational Safety and Health in Sweden. Rate ratios (RRs) in the exposed groups relative to the unexposed groups were estimated by Poisson regression. We found an increased risk (RR = 1.3, 95% CI 1.04–1.71) among construction workers exposed to diesel exhaust. Adjustment for other occupational exposures did not change this estimate (RR = 1.3, 95% CI 1.00–1.77). However, there was no monotonic increase in risk with estimated level of exposure (RR for low = 1.4, moderate = 1.1, high = 1.4). There was no evidence of increased risk associated with the other occupational exposures among these construction workers, including asbestos, asphalt, cement dust, metal dust, mineral wool, organic solvents, stone dust and wood dust. Occupational exposure to diesel exhaust in the Swedish construction industry may present a small risk of multiple myeloma, but lack of an exposure–response trend tempers our ability to draw clear conclusions. © 2003 Wiley‐Liss, Inc.
Inhibition of tumor growth by biodegradable microspheres containing all‐trans‐retinoic acid in a human head‐and‐neck cancer xenograft
Authors: Choi Yongdoo , Kim Sang Yoon , Kim Sun Hee , Yang Jehoon , Park Kyeongsoon , Byun Youngro
Published: August 2003

Retinoids play essential roles in the regulation of cell differentiation and in the proliferation of various epithelial tissues, and atRA is one such active metabolite of retinoids. However, despite the known functions of atRA, its clinical applications are limited due to the induced metabolism by the specific cytochrome P‐450s in the liver. To overcome the limitation, parenteral administration of atRA‐loaded biodegradable microspheres, the PDLLA/PLE microspheres containing atRA, was suggested previously. We evaluated chemotherapeutic efficacy of atRA‐loaded microspheres in a human head‐and‐neck xenograft/nude mouse model. When atRA‐loaded microspheres were administered s.c. at 200 mg/kg body weight to athymic nude mice, plasma concentration of atRA could be maintained in a range of 1.2 to 3.7 × 10−8 M for 4 weeks. As a result, the tumor volume of human head‐and‐neck cancer was reduced compared to the control group by 51.3% (p < 0.01) at 14 days and by 49.2% (p < 0.05) at 28 days. © 2003 Wiley‐Liss, Inc.
Risk modification by CYP1A1 and GSTM1 polymorphisms in the association of environmental tobacco smoke and lung cancer: A case‐control study in Japanese nonsmoking women
Authors: Kiyohara Chikako , Wakai Kenji , Mikami Haruo , Sido Koichi , Ando Masahiko , Ohno Yoshiyuki
Published: August 2003

Genetic backgrounds may modify the association of environmental tobacco smoke (ETS) with lung cancer risk. Polymorphisms of both the activating and detoxifying enzymes, cytochrome P4501A1 (CYP1A1) and glutathione‐S‐transferase M1 (GSTM1), may be important as genetic factors. We conducted a multicenter case‐control study in Japanese nonsmoking women. Cases were women aged 30–89 years and newly diagnosed as having lung cancer from November 1997 to March 2001 in 4 study areas. We also recruited age‐matched (5‐year strata) and hospital‐matched nonsmoking controls. A total of 158 cases and 259 hospital controls supplied blood for genotyping. Detailed information on ETS exposure from husbands and that in other situations and on potential confounders was collected by interview. Odds ratios (ORs) were estimated by using conditional logistic models. We found no increase in the risk of lung cancer for CYP1A1 Msp I genotypes. For the GSTM1 null genotype vs. nonnull genotype, the OR was 1.37 [95% confidence interval (CI) 0.90–2.09], which indicated a somewhat increased risk for the GSTM1 null genotype. A gene‐environment interaction was suggested, with combined GSTM1 null genotype and high‐dose ETS exposure (≥40 pack‐years by husbands) conferring significantly higher risk (OR = 2.27, 95% CI 1.13–4.57) compared to the GSTM1 nonnull genotype and low‐dose ETS exposure (<40 pack‐years). Our results do not support a major role of Msp I polymorphism of the CYP1A1 gene as a risk factor for lung cancer among nonsmoking women. In contrast, the GSTM1 null genotype posed an increased, although not significant, risk among them. Additional studies are warranted to confirm the ETS‐GSTM1 polymorphism interaction suggested in our present study. © 2003 Wiley‐Liss, Inc.
History of antibiotic use and risk of non‐Hodgkin's lymphoma (NHL)
Authors: Kato Ikuko , Koenig Karen L. , Baptiste Mark S. , Lillquist Patricia P. , Frizzera Glauco , Burke Jerome S. , Watanabe Hiroko , Shore Roy E.
Published: August 2003

A population‐based, incidence case‐control study was conducted among women in upstate New York to determine whether histories of certain infections and antibiotic use are associated with risk of non‐Hodgkin's lymphoma (NHL). Our study involved 376 cases of NHL identified through the New York State Cancer Registry and 463 controls selected from the Medicare beneficiary files and state driver's license records. Information about use of common medications including antibiotics, history of selected infectious diseases and potential confounding variables was obtained by telephone interview. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using an unconditional logistic regression model. There was a progressive increase in risk of NHL with increasing frequency and duration of systemic antibiotic use, as assessed over the period of 2–20 years before the interview. The ORs for the highest exposure categories, ≥36 episodes and ≥366 days of use, were 2.56 (95% CI 1.33–4.94) and 2.66 (95% CI 1.35–5.27), respectively. These associations were primarily due to antibiotic use against respiratory infections and dental conditions. Moreover, the association with frequency of antibiotic use for respiratory infections was pronounced for marginal zone B‐cell lymphoma and for respiratory tract lymphoma. Analyses by class of antibiotics did not suggest that a general cytotoxic effect of antibiotics was responsible for these increased risks. Although recall bias and selection bias remain potential concerns in our study, the results are generally consistent with the hypothesis that persistent infection/inflammation predisposes individuals to the development of NHL. However, a direct role of antibiotics in NHL induction has not been ruled out. © 2003 Wiley‐Liss, Inc.
Incidence trends of mesothelioma in Norway, 1965–1999
Authors: Ulvestad Bente , Kjaerheim Kristina , Møller Bjørn , Andersen Aage
Published: August 2003

Asbestos exposure is considered to be the only important risk factor for malignant mesothelioma. The importation of asbestos to Norway increased after World War II and peaked in 1970. Stringent regulations took effect in 1977, and importation and use of asbestos practically ended in Norway in the late 1970s, until importation was prohibited in 1982. Our study aimed to analyze the incidence of mesothelioma in Norway according to temporal variation, to study the consequences of the use of asbestos and the asbestos ban effectiveness. An age‐period‐cohort model was used to analyze time trends for pleural mesotheliomas. From 1965–1999, the annual number of pleural mesotheliomas rose gradually both in males and females, and the highest annual number of pleural mesotheliomas was recorded in 1999 with 73 new cases diagnosed. The age‐adjusted log linear drift of malignant mesothelioma of the pleura during the observation period rose 31.1% per 5 years among men and 15.9% among women. In 1995–1999, the age‐adjusted incidence rate for men was 16.6 per million person‐years for men and 2.3 for women. Cohort‐specific risks increased for men born up to around 1935. After this the risks seem to stabilize. The rates were determined by age and by birth cohort. The delayed period effect of the asbestos regulation by the late 1970s will probably have its greatest effects on the mesothelioma rates around 2010. © 2003 Wiley‐Liss, Inc.
Polymorphic variation at the ‐202 locus in IGFBP3: Influence on serum levels of insulin‐like growth factors, interaction with plasma retinol and vitamin D and breast cancer risk
Authors: Schernhammer Eva S. , Hankinson Susan E. , Hunter David J. , Blouin Marie J. , Pollak Michael N.
Published: August 2003

Previous reports have suggested an association between circulating IGFBP‐3 levels and the risk of premenopausal breast cancer, and a single nucleotide polymorphism (SNP) in the promoter region of IGFBP‐3 (nucleotide ‐202) was shown to influence transcription. There is prior evidence that the action of antiproliferative agents such as retinoids and selective estrogen receptor modulators (SERMs) act in part by upregulating IGFBP3 gene expression. We identified 677 women with incident breast cancer and 834 matched controls from the Nurses' Health Study (NHS) and genotyped them at the ‐202 locus. For 943 of these women, we had previously measured IGF‐I and IGFBP‐3 plasma levels, and for 861 of these subjects, plasma retinol levels were available. Age‐adjusted mean circulating IGFBP‐3 levels were highest in the individuals with the AA genotype and decreased significantly in a stepwise manner in the presence of 1 or 2 copies of the C allele (4,426 ng/ml, 4,060 ng/ml and 3,697 ng/ml, respectively). We found a positive relation between age‐adjusted IGFBP‐3 levels and plasma retinol (14% difference in IGFBP‐3 in top vs. bottom tertiles of retinol, p for trend < 0.001; Spearman correlation coefficient r = 0.25), which was similar across genotypes at the ‐202 IGFBP3 locus (interaction term, F = 0.10, p = 0.91). Breast cancer risk was not significantly related to genotype at the ‐202 locus in our prospective analyses. We confirmed a relation between the ‐202 IGFBP3 polymorphism and IGFBP‐3 serum levels and observed a positive correlation between circulating retinol levels and circulating IGFBP‐3 levels, providing further evidence that retinoids may influence IGF physiology. Our data do not demonstrate a significant influence of this locus on breast cancer risk, but we cannot exclude a minor influence or an influence confined to subgroups. © 2003 Wiley‐Liss, Inc.
Cancer occurrence in Ardabil: Results of a population‐based Cancer Registry from Iran
Authors: Sadjadi Alireza , Malekzadeh Reza , Derakhshan Mohammad H. , Sepehr Alireza , Nouraie Mehdi , Sotoudeh Masoud , Yazdanbod Abbas , Shokoohi Behrooz , Mashayekhi Afshin , Arshi Shahnam , Majidpour Ali , Babaei Masoud , Mosavi Alireza , Mohagheghi Mosavi Mohammad Ali , Alimohammadian Masomeh
Published: August 2003

The provincial health authority reported a high mortality rate from upper GI cancer in the newly established Ardabil Province of northwest Iran. A comprehensive search was undertaken to survey and register all cases of cancer during a 4‐year (1996–1999) period among the indigenous population of Ardabil Province, including subjects seeking care in the cities of Tabriz and Tehran. Diagnosis of cancer was based on histopathology in 71.4%, clinical or radiologic findings in 25% and death certificate in 3.6% of cases. A total of 3,455 cancers (mean age 57.1 ± 17.3 years) was found during the study. Of these, 60% (2,072) were in males. ASRs for all cancers in males and females were 132.0 and 96.3, respectively. The top 5 cancers in males (excluding skin cancer) according to the calculated ASR were stomach (25.4), esophagus (15.4), lung and bronchus (7.9), colon and rectum (7.9) and bladder (7.6); in females, these were stomach (25.42), esophagus (14.4), breast (7.6), colon and rectum (5. 9) and lung and bronchus (3.6). Compared to rates obtained 30 years ago, the incidence of upper GI cancer in this region has increased about 100%, and there is a striking increase in the incidence of gastric cancer with a decline in the esophageal cancer rate. ASRs for gastric cancer in Ardabil were 49.1 for males and 25.4 for females, while for esophageal cancer these were 15.4 and 14.4, respectively. The ASR for cervical cancer was the lowest (0.4) recorded in the world before. Gastric cancer alone constitutes one‐third of all cancers in Ardabil, the ASR of which is the highest reported from Iran up to now and one of the highest in the world. © 2003 Wiley‐Liss, Inc.
Changing epidemiology of malignant cutaneous melanoma in Europe 1953–1997: Rising trends in incidence and mortality but recent stabilizations in Western Europe and decreases in Scandinavia
Authors: de Vries Esther , Bray Freddie I. , Coebergh Jan Willem W. , Parkin Donald M. ,   European Network of Cancer Registries
Published: August 2003

We analyzed time trends in incidence of and mortality from malignant cutaneous melanoma in European populations since 1953. Data were extracted from the EUROCIM database of incidence data from 165 cancer registries. Mortality data were derived from the WHO database. During the 1990s, incidence rates were by far highest in northern and western Europe, whereas mortality was higher in males in eastern and southern Europe. Melanoma rates have been rising steadily, albeit with substantial geographic variation. In northern Europe, a deceleration in these trends occurred recently in persons aged under 70. Joinpoint analyses indicated that changes in these trends took place in the early 1980s. In western Europe, mortality rates have also recently leveled off [estimated annual percentage change (EAPC) from −13.6% (n.s.) to 3.3%], whereas in eastern and southern Europe both incidence and mortality rates are still increasing [incidence EAPCs 2.3–8.9%, mortality EAPCs −1.8% (n.s.) to 7.2%]. Models including the effects of age, period and birth cohort were required to adequately describe the rising incidence trends in most European populations, with a few exceptions. Time trends in mortality were adequately summarized on fitting either an age‐cohort model (with the leveling off of rates starting in birth cohorts between 1930 and 1940) or an age‐period‐cohort model. The most plausible explanations for the deceleration or decline in the incidence and mortality trends in recent years in northern (and to a lesser extent western) Europe are earlier detection and more frequent excision of pigmented lesions and a growing public awareness of the dangers of excessive sunbathing. © 2003 Wiley‐Liss, Inc.
Plasma insulin, IGF‐binding proteins‐1 and ‐2 and risk of colorectal cancer: A prospective study in Northern Sweden
Authors: Palmqvist Richard , Stattin Pär , Rinaldi Sabina , Biessy Carine , Stenling Roger , Riboli Elio , Hallmans Göran , Kaaks Rudolf
Published: August 2003

Chronically elevated plasma insulin levels have been postulated to increase colon cancer risk, either directly through colonic insulin receptors or indirectly through downregulation of IGFBP‐1 and/or IGFBP‐2, thus increasing IGF activity. Our aim was to examine the relationships of plasma insulin and IGFBPs‐1 and ‐2 with risks of colon and rectal cancers. We conducted a case‐control study nested within the prospective Northern Sweden Health and Disease Cohort. Insulin and IGFBPs were measured in prediagnostic plasma samples from 168 men and women who developed cancers of the colon (n = 110) or rectum (n = 58) and from 336 matched controls. Conditional logistic regression analyses showed no significant relationship of plasma insulin with risk of colon or rectal cancer. In subjects whose blood samples had been collected after more than 4 hr of fasting, insulin showed a moderate but still nonsignificant association with colorectal cancer risk [ORs over quartiles: 1.00, 0.70 (95% CI 0.35–1.39), 1.06 (95% CI 0.55–2.07), 1.63 (95% CI 0.82–3.24); ptrend = 0.10]. Plasma IGFBP‐1 and IGFBP‐2 showed no association with risk of colon and/or rectal cancer, either in the full study population or among the fasting subjects. Our results only moderately support a possible relationship of chronic hyperinsulinemia with colon cancer risk. © 2003 Wiley‐Liss, Inc.
Injectable magnetic liposomes as a novel carrier of recombinant human BMP‐2 for bone formation in a rat bone‐defect model
Authors: Matsuo Toshihiro , Sugita Takashi , Kubo Tadahiko , Yasunaga Yuji , Ochi Mitsuo , Murakami Teruo
Published: August 2003

Small‐sized magnetic liposomes with incorporated recombinant human bone morphogenetic protein‐2 (rhBMP‐2) were prepared, and the efficiency for bone formation after topical injection was evaluated in a rat bone‐defect model. A critical‐sized segmental bone defect was created in the mid‐part of the femoral shaft, and a permanent magnet was attached. Topical injection onto the defects was performed with different liposomal preparations (nonmagnetic and magnetic liposomes) using different treatment modalities (different doses and different treatment timing of rhBMP‐2). Weekly evaluations were made radiographically and microcomputed tomographically, histologically, and/or by mechanical testing at 9 weeks after surgery. A single topical application of magnetic liposomes with an appropriate amount of rhBMP‐2 (≈3 μg) incorporated under magnetic induction immediately after surgery was effective for new bone formation. The combined treatment of topical magnetic rhBMP‐2 liposomes and magnetic implantation at the injury site was effective for the treatment of bone defects. This injectable carrier for BMP is expected to have many advantages over solid carriers because it can be prepared easily and can be less invasively applied to the injured site at any time after surgery. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 747–754, 2003
Evaluation of thermal‐ and photo‐crosslinked biodegradable poly(propylene fumarate)‐based networks
Authors: Timmer Mark D. , Ambrose Catherine G. , Mikos Antonios G.
Published: August 2003

Biodegradable networks of poly(propylene fumarate) (PPF) and the crosslinking reagent poly(propylene fumarate)‐diacrylate (PPF‐DA) were prepared with thermal‐ and photo‐initiator systems. Thermal‐crosslinking was performed with benzoyl peroxide (BP), which is accelerated by N,N‐dimethyl‐p‐toluidine (DMT) and enables injection and in situ polymerization. Photo‐crosslinking was accomplished with bis(2,4,6‐trimethylbenzoyl) phenylphosphine oxide (BAPO), which is activated by long‐wavelength UV light and facilitates material processing with rapid manufacturing techniques, such as stereolithography. Networks were evaluated to assess the effects of the initiators and the PPF/PPF‐DA double bond ratio on the mechanical properties. Regardless of the initiator system, the compressive properties of the PPF/PPF‐DA networks increased as the double bond ratio decreased from 2 to 0.5. BAPO/UV‐initiated networks were significantly stronger than those formed with BP/DMT. The compressive modulus of the photo‐ and thermal‐crosslinked PPF/PPF‐DA networks ranged from 310 ± 25 to 1270 ± 286 MPa and 75 ± 8 to 332 ± 89 MPa, respectively. The corresponding fracture strengths varied from 58 ± 7 to 129 ± 17 MPa and 31 ± 13 to 105 ± 12 MPa. The mechanical properties were not affected by the initiator concentration. Characterization of the network structures indicated that BAPO was a more efficient initiator for the crosslinking of PPF/PPF‐DA, achieving a higher double bond conversion and crosslinking density than its BP counterpart. Estimated average molecular weights between crosslinks (Mc) confirmed the effects of the initiators and PPF/PPF‐DA double bond ratio on the mechanical properties. This work demonstrates the capability to control the properties of PPF/PPF‐DA networks as well as their versatility to be used as an injectable material or a prefabricated implant. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 811–818, 2003
Pluronic‐grafted poly‐(L)‐lysine as a new synthetic gene carrier
Authors: Jeon Eunjung , Kim Hee‐Doo , Kim Jin‐Seok
Published: August 2003

Genes are attractive candidates as therapeutic agents, and the development of safe and effective gene carriers is essential for the success of human gene therapy. To develop a gene delivery vector that shows low cytotoxicity and high efficiency, we synthesized poly‐L‐lysine‐g‐pluronic by conjugating poly‐L‐lysine (PLL) to pluronic, which is partially functionalized with para‐nitrophenyl carbonate groups, and evaluated for its efficiency as a possible nonviral gene carrier candidate. Structural analysis of synthesized polymer was performed by using 1H‐NMR. Gel retardation assay, ζ potential and size measurement confirmed that the new gene carrier made a compact complex with plasmid DNA. pCMV‐β‐gal was used as a reporter gene, and the in vitro transfection efficiency was measured in HeLa cells by using the o‐nitrophenyl‐β‐D‐galactopyranoside assay. The highest transfection efficiency among those tested was achieved at the 1:1 weight ratio of polymer:DNA, and a 3‐fold increase in transfection efficiency was achieved by treatment of a lysosomotropic agent, chloroquine. Compared with unmodified PLL, PLL‐g‐pluronic showed about 2‐fold increase in transfection efficiency with similar cytotoxicity specifically at the 1:1 weight ratio of polymer:DNA. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 854–859, 2003
Polyvinylpyrrolidone modified bioactive glass fibers as tissue constructs: In vitro mesenchymal stem cell response
Authors: Hatcher Brian M. , Seegert Charles A. , Brennan Anthony B.
Published: August 2003

The sol–gel synthesis of a bioactive glass (BAG) sol with the incorporation of polyvinylpyrrolidone and the subsequent spraying of short, discontinuous fibers is reported. The incorporation of the polymer into the BAG sol allowed for increased control of the rheological properties and resulted in a more homogeneous fibrous material when sprayed through an air gun. Reaction kinetics and sol viscosity were monitored and analyzed during synthesis, and fibers were characterized using scanning electron microscopy and thermal analysis. Fibers were sintered at 900°C and were examined for in vitro bioactivity in a simulated body fluid solution. The presence of hydroxyapatite crystals is confirmed by examination with scanning electron microscopy, energy dispersive X‐ray spectroscopy (EDX), and X‐ray diffraction (XRD). Both the proliferation rate and cell density of rat mesenchymal stem cells cultured on BAG fiber constructs of varying porosities were shown to be dependent upon fiber spacing. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 840–849, 2003
Interactions of fibrinolytic system proteins with lysine‐containing surfaces
Authors: McClung W.G. , Clapper D.L. , Anderson A.B. , Babcock D.E. , Brash J.L.
Published: August 2003

Studies on the interactions of tissue plasminogen activator (tPA) and plasminogen with polyurethane surfaces containing ϵ‐lysine moieties (ϵ‐amino group free) are reported. These surfaces are considered to have the potential to dissolve nascent clots that may be formed on them. For adsorption from both single protein solutions and plasma, the surfaces were found to have a high capacity for tPA as well as plasminogen. A significant fraction of preadsorbed tPA was displaced from the ϵ‐lysine surfaces upon contact with plasma. These surfaces, when preadsorbed with tPA and then incubated with plasma, were able to dissolve incipient clots formed around them. However, the clot‐dissolving capacity diminished as the time of plasma incubation increased, presumably due to loss of tPA. It was also shown that in plasma, preadsorbed tPA is displaced from these surfaces largely by plasminogen, which thus appears to have a greater binding affinity than tPA for the ϵ‐lysine moieties. Finally, it was found that in plasma, the ϵ‐lysine surfaces interact with plasminogen in a dynamic manner, and that about 70% of the bound plasminogen is exchanging continuously with plasminogen in the plasma. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 795–801, 2003
A biodegradable electrical bioconductor made of polypyrrole nanoparticle/poly(D,L‐lactide) composite: A preliminary in vitro biostability study
Authors: Wang Zhaoxu , Roberge Christophe , Wan Ying , Dao Lê H. , Guidoin Robert , Zhang Ze
Published: August 2003

The electrical stability of a novel polypyrrole (PPy)/poly(D,L‐lactide) (PDLLA) composite was studied in vitro and compared with that of PPy‐coated polyester fabrics. Specimens were incubated in Ringer's solution at 37°C for up to 8 weeks with or without the circulation of DC current under a constant 100 mV voltage. In situ current variation with incubation time was recorded. The AC volume electrical conductivity of the specimens before and after incubation in phosphate‐buffered saline was recorded using a frequency analyzer. Water absorption and weight loss were monitored metrologically. Changes in the oxidation state of incubated PPy were analyzed with X‐ray photoelectron spectroscopy. The morphological changes were observed with scanning electron microscopy, and the glass transition temperature of the PDLLA was investigated using differential scanning calorimetry. The PPy/PDLLA composite in Ringer's solution sustained a relatively stable conductivity up to 8 weeks after an initial period of “conditioning.” The PPy‐coated fabrics experienced a rapid loss of conductivity when subjected to electrical circulation and regained part of it when disconnected. The volume conductivity of the nonincubated PPy/PDLLA membrane behaved as a typical conductor in the low‐frequency range. The mechanisms involved in the various electrical behaviours of the PPy/PDLLA composite and PPy‐coated fabrics are discussed. In conclusion, the PPy/PDLLA composite was able to deliver a biologically significant electrical current in a simulated biological solution for up to 8 weeks and therefore may be considered as a first‐generation synthetic biodegradable bioconductor. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 738–746, 2003
The role of titanium in the altered endotoxin‐induced nitric oxide synthase expression in alveolar macrophages from titanium‐alloy‐implanted rats
Authors: Yang Rong‐Sen , Chen Yi‐Hung , Lin‐Shiau Shoei‐Yn , Liu Tang‐Kue , Liu Shing‐Hwa
Published: August 2003

We have found that the concentration of titanium (Ti) in the blood of patients with loosened Ti‐alloy prostheses is elevated. An increase in the levels of elemental Ti in the blood and lung tissues of rats with an alloyed‐Ti implant also has been found. The cellular reaction to elevated elemental Ti in the circulation remains unclear. We further performed experiments to examine the changes of inducible nitric oxide synthase (iNOS) expression in alveolar macrophages from alloyed‐Ti‐implanted rats. The elevation of nitrite and iNOS expression induced by lipopolysaccharide (LPS) was suppressed. The in vitro effect of a soluble form of Ti was further investigated. Ti (0.01–0.06 mM) inhibited the LPS‐induced nitrite production and iNOS expression in alveolar macrophages from normal rats without any cytotoxic effects. LPS induced protein tyrosine phosphorylation, tyrosine‐phosphorylation of lyn (a CD14‐receptor‐associated‐tyrosine kinase), and degradation of IκB‐α protein (inhibitor of NF‐κB) in alveolar macrophages. These events were inhibited by co‐incubation with Ti. These results indicate that elemental Ti may impair iNOS expression in alveolar macrophages through the alteration of protein tyrosine phosphorylation and NF‐κB activation. The inhibitory action of Ti on cellular responses of alveolar macrophages may be anti‐inflammatory and thus may depress local defense mechanisms related to microbial killing. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 802–810, 2003
Suppression of subcritical crack growth in a leucite‐reinforced dental glass by ion exchange
Authors: Fischer Horst , Marx Rudolf
Published: August 2003

Glass‐ceramic materials are frequently used in prosthetic dentistry because of their excellent esthetics. Problematic aspects of glass ceramics are their limited strength, the scatter in their strength data, and their time‐dependent strength decrease due to subcritical crack growth effects. The short‐term strength level can be significantly increased by an ion‐exchange process in a potassium salt. A dual ion‐exchange process in KNO3/NaNO3 can additionally improve the scatter‐in‐strength. The objective of the present study was to examine the effect of a single and a dual ion‐exchange process on the characteristic time‐dependent strength decrease of a leucite‐reinforced dental glass. The parameters of subcritical crack growth were evaluated by using the constant stress rate flexural strength test. Both ion‐exchange processes showed a pronounced effect on the subcritical crack growth of the glass‐ceramic material. The exponential crack parameter n was increased from 25 to 52 by the single‐exchange and to 107 by the dual‐exchange process, respectively. We conclude that the time‐dependent strength decrease of a dental glass‐ceramic material can be significantly limited by the ion‐exchange process. This could improve the clinical reliability of dental restorations made from this class of materials. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 885–889, 2003
Room‐temperature preparation and characterization of poly (ethylene glycol)‐coated silica nanoparticles for biomedical applications
Authors: Xu Hao , Yan Fei , Monson Eric E. , Kopelman Raoul
Published: August 2003

Monodisperse, spherical, polyethylene glycol (PEG)–coated silica nanoparticles have been prepared at room temperature and characterized for the purpose of biomedical applications. The particles were synthesized by the hydrolysis of tetramethyl orthosilicate (TMOS) in alcohol media under catalysis by ammonia, and their size can range from about 50–350 nm in diameter. We studied the particle size and size distribution using a scanning electron microscope (SEM) and an asymmetric field‐flow fractionation (AFFF) multiangle static light‐scattering instrument. The chemical and/or physical binding of PEG to the silica nanoparticles was studied by infrared spectroscopy, and the weight percentage of PEG attached to the particles was quantified. The PEG‐coated silica nanoparticles showed enhanced colloidal stability when redispersed into aqueous solutions from the dried state as a result of the steric stabilization function of the PEG polymer grafted on the surface of particles. A nonspecific protein‐binding test was also carried out to show that the PEG coating can help reduce the protein adsorption onto the surface of the particles, relating to the biocompatibility of these PEG‐coated particles. Also, the inclusion of magnetic nanoparticles into the silica particles was shown as an example of the possible applications of PEG‐coated silica particles. These silica nanoparticles, as a matrix for encapsulation of certain reagents, have potential for applications to in vivo diagnosis, analysis, and measurements inside intact biologic systems. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 870–879, 2003
Microhardness of superficial and deep sound human dentin
Authors: Fuentes Victoria , Toledano Manuel , Osorio Raquel , Carvalho Ricardo M.
Published: August 2003

Our purpose in this study was to determine the microhardness of superficial and deep dentin by means of two indentation methods (Knoop and Vickers) under two different applied loads. Twelve dentin discs approximately 2‐mm thick were obtained from both superficial and deep dentin by transversally sectioning the crowns of sound, extracted human third molars with a diamond blade under water irrigation. Dentin surfaces were sequentially polished, and indentations (n = 20 per surface) were performed with either Vickers indentor at loads of 300 and 500 g, respectively, or Knoop indentor at loads of 50 and 100 g, respectively. Average Vickers hardness number (VHN) and Knoop hardness number (KHN) were calculated and treated with two‐way analysis of variance (ANOVA) and Student's t test. Microhardness of dentin was not influenced by the different loads applied for both indentation methods. Knoop hardness was significantly higher for superficial than for deep dentin (p < 0.05). Conversely, Vickers hardness was not significantly different for both substrates (p > 0.05). Differences in dentin hardness as a function of depth exist, but they might not be relevant, and no alteration of the distribution of stresses along the adhesive interface is expected. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 850–853, 2003
Extracellular matrix degrading enzymes are active in porcine stentless aortic bioprosthetic heart valves
Authors: Simionescu Dan T. , Lovekamp Joshua J. , Vyavahare Narendra R.
Published: August 2003

Glutaraldehyde‐fixed porcine aortic valve tissues are widely used for heart valve replacement surgery in the form of bioprosthetic heart valves (BHVs). The durability of BHVs in the clinical setting is limited by tissue degeneration, mechanical failure, and calcification. BHVs rely on the putative ability of glutaraldehyde to render biologic tissues metabolically inert and fully resistant to enzymatic attack. In the present study, we detected and partially characterized the activity of collagen and elastin‐degrading enzymes in unimplanted, glutaraldehyde‐fixed porcine aortic cusp and wall tissues and compared enzyme activities with those extracted from fresh tissues. Active enzymes capable of degrading extracellular matrix were found to be present in soluble form as well as immobilized on glutaraldehyde‐crosslinked tissue matrix. Total levels of collagenolytic activities were evaluated to approximately 0.25 μg of degraded collagen/mg of dry tissue/24 h for both glutaraldehyde‐fixed wall and cusp tissues. A major finding of this study was the ability of soluble tissue enzymes to partially degrade glutaraldehyde‐fixed collagen and particularly large amounts of glutaraldehyde‐fixed elastin. These calcium‐dependent gelatinases share many biochemical similarities with matrix metalloproteinases. These data strongly indicate that glutaraldehyde‐fixed porcine valvular tissues are not metabolically inert and are not entirely resistant to enzymatic attack, thereby rendering BHVs vulnerable to biologic degeneration and subsequent chronic failure. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 755–763, 2003
Biomimetic surface modification of poly (L‐lactic acid) with gelatin and its effects on articular chondrocytes in vitro
Authors: Cui Yuan Lu , Hou Xin , Qi Ai Di , Wang Xiang Hui , Wang Hong , Cai Kai Yong , Ji Yin Yu , De Yao Kang
Published: August 2003

Our objective in this study was to investigate the efficiency of two treatments for poly (L‐lactic acid) (PLLA) surface modification with gelatin, via entrapment and coupling, using 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDC) and N‐hydroxysuccinimide (NHS). The properties of original PLLA, gelatin‐entrapped, and coupled PLLA films were investigated by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). The water contact angle indicated that the incorporation of gelatin resulted in a change in hydrophilicity, and the ESCA data suggested that the modified PLLA films became enriched with nitrogen atoms. The cytocompatibility of modified PLLA films might be improved. Therefore, we examined the attachment and proliferation of bovine articular chondrocyte seeded on modified PLLA films and virgin films. A whole‐cell enzyme‐linked immunosorbent assay (cell ELISA) that detects 5‐bromo‐2′‐deoxyuridine (BrdU) incorporation during DNA synthesis and collagen type II secretion was applied to evaluate the chondrocytes on different PLLA films and tissue culture plates (TCPS). Cell viability was estimated by the MTT [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide] assay, and cell function was assessed by measuring glycosaminoglycan (GAG) secreted by chondrocytes. These results implied that gelatin used to modify the PLLA surface through entrapment and coupling could enhance chondrocyte adhesion, proliferation, and function. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 770–778, 2003
Adherent octacalciumphosphate coating on titanium alloy using modulated electrochemical deposition method
Authors: Lin Shujie , LeGeros Racquel Z. , LeGeros John P.
Published: August 2003

Our aims in this study were (1) to develop an electrochemical method of depositing adherent octacalciumphosphate (OCP) and other calcium phosphate coatings on titanium alloy (Ti6Al4V) substrates of different shapes and surface preparations, (2) to determine the properties of the coating (composition, morphology, thickness, dissolution), and (3) to observe transformation of OCP to carbonatehydroxyapatite (CHA) in simulated body fluid (SBF). Titanium (Ti)‐alloy plates, tensile bars with four types of surfaces (grit‐blasted with apatitic abrasive, chemically textured, arc‐deposited, and CoCr‐beaded) and dissolution cylinders were electrochemically coated with the use of modulated pulse time electric fields programmed with a custom‐made dual microprocessor. Modulated electrochemical deposition (MECD) was carried out with pH and temperature conditions favorable for OCP formation. Coatings were characterized using X‐ray diffraction, FT‐IR, scanning electron microscopy, tensile strength tests, and solubility tests. XRD and FT‐IR analyses showed that pure, uniform OCP coatings were produced on Ti6Al4V surfaces with coating‐to‐substrate tensile strengths greater than 7000 psi. Coatings on Ti arc‐deposited surfaces, chemically textured surfaces, and CoCr‐beaded surfaces all gave tensile strengths ranging from 5000 to 7000 psi, with no coating shadows in the crevices. Dissolution of OCP coating in 100 mL of 0.1 M Tris buffer solution was determined from the amount of calcium (Ca) released onto the buffer, which was 7.7 ± 1.0 ppm Ca at pH 7.3 after 4 h, and 22 ∓ 1.4 ppm Ca at pH 3 after 2 h. We found that OCP crystal size can be controlled by the current density and relative pulse time modulation. Our study demonstrated the following: (1) Highly adherent calcium phosphate (e.g., OCP) coating of uniform compositions (e.g., OCP) on Ti‐alloy substrates can be obtained at low temperatures with the use of MECD by optimizing pulse time modulation of the electric field, reaction pH, temperature, and electrolyte composition; and (2) OCP readily transforms to CHA when exposed to SBF. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 819–828, 2003
Immunocytochemical identification of type I collagen in acid‐etched dentin
Authors: Breschi Lorenzo , Perdigão Jorge , Gobbi Pietro , Mazzotti Giovanni , Falconi Mirella , Lopes Manuela
Published: August 2003

The hypothesis tested in this study is that the application of phosphoric acid prevents collagen fibrils (CF) from maintaining their structural morphology, as assessed by their immunochemical antigenicity. Dentin was conditioned with EDTA and with 35% H3PO4 for 15, 30, and 60 s. For a control there was no treatment. A pre‐embedding immunohistochemical procedure was evaluated under high‐resolution SEM and a postembedding immunolocalization technique was performed on ultrathin sections at TEM level. Conditioning with EDTA resulted in a weaker labeling signal than for dentin conditioned with H3PO4. The most intense labeling was observed after dentin had been etched with H3PO4 for 15 s. The least intensive labeling was evident when the acid was applied for 30 s or for 60 s. A very weak signal was detected on the untreated dentin surface. These results provide evidence that a 15‐s application of 35% H3PO4 causes mineral dissolution of the crystals enveloping the superficial CF without damaging the ultrastructure of the CF while longer applications of 35% H3PO4 cause alterations in the CF that decrease their antigenicity. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 764–769, 2003
Effects of materials parameters on mineralization and degradation of sol‐gel bioactive glasses with 3D‐ordered macroporous structures
Authors: Zhang Kai , Yan Hongwei , Bell David C. , Stein Andreas , Francis Lorraine F.
Published: August 2003

Bioactive glasses (BGs) with three‐dimensionally ordered macroporous (3DOM) structures were prepared by combining a sol‐gel synthesis with colloidal crystal templating. 3DOM sol‐gel BGs with two compositions (20 mol % CaO–80% SiO2 and 20 mol % CaO–4% P2O5–76% SiO2) and three macropore sizes (average: 345, 440, and 790 nm) were prepared. Glasses were separated into two particle sizes (212 μm < small < 355 μm and 600 μm < large < 1000 μm). The glasses were soaked in simulated body fluid at 37°C for 2 or 4 days and the effects of composition, particle size, and macropore size on the formation of apatite and glass degradation were characterized. Within the parameter range of the experiments, several comparisons could be made. First, the formation of apatite and degradation of the glass were slightly enhanced for the phosphate containing composition. Second, large particles formed less apatite and degraded less completely compared with small particles. Lastly, an increase in macropore size slowed down the glass degradation and apatite formation processes, an effect related to the decreased internal surface area of the larger pore materials. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 860–869, 2003