bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional brain activation during arithmetic processing in females with fragile X syndrome is related to FMR1 protein expression
Authors: Rivera Susan M. , Menon Vinod , White Christopher D. , Glaser Bronwyn , Reiss Allan L.
Published: September 2002

Arithmetic processing deficits in persons with fragile X Syndrome (fraX), the most common heritable cause of mental retardation, are well known. In this study, we characterize the neural underpinnings of these performance deficits using functional MRI. Given that a single gene defect (FMR1) is known to be responsible for this disorder, we also assess whether brain activation in arithmetic processing areas is related to amount of FMR1 protein expression (FMRP). Subjects included 16 females with fraX, and 16 female age‐matched controls. Subjects viewed arithmetic equations with two (1 + 3 = 4) or three (2 + 3 − 1 = 5) operands, and were asked to judge whether the results were correct or not. Subjects with fraX showed significant impairment in behavioral performance on the 3‐operand but not the 2‐operand arithmetic equations. Significant brain activation was observed bilaterally in the prefrontal and parietal cortices for unaffected subjects, and bilateral prefrontal and left angular gyrus for subjects with fraX, for both trial types. Subjects with fraX exhibited less overall activation than did unaffected subjects in both types of trials; and, unlike the unaffected group, did not show increased extent of activation in association with greater task difficulty. During the 3‐operand trials, activation in bilateral prefrontal and motor/premotor, and left supramarginal and angular gyri were positively correlated with FMRP, suggesting that decreased FMR1 protein expression underlies deficits in math performance in persons with fraX. More broadly, this investigation demonstrates a unique bridging of cognitive and molecular neuroscience and represents a useful approach for the study of brain development and function. Hum. Brain Mapping 16:206–218, 2002. © 2002 Wiley‐Liss, Inc.
Modality independence of word comprehension
Authors: Booth James R. , Burman Douglas D. , Meyer Joel R. , Gitelman Darren R. , Parrish Todd B. , Mesulam M. Marsel
Published: September 2002

Functional magnetic resonance imaging (fMRI) was used to examine the functional anatomy of word comprehension in the auditory and visual modalities of presentation. We asked our subjects to determine if word pairs were semantically associated (e.g., table, chair) and compared this to a reference task where they were asked to judge whether word pairs rhymed (e.g., bank, tank). This comparison showed task‐specific and modality‐independent activation for semantic processing in the heteromodal cortices of the left inferior frontal gyrus (BA 46, 47) and left middle temporal gyrus (BA 21). There were also modality‐specific activations in the fusiform gyrus (BA 37) for written words and in the superior temporal gyrus (BA 22) for spoken words. Our findings are consistent with the hypothesis that word form recognition (lexical encoding) occurs in unimodal cortices and that heteromodal brain regions in the anterior as well as posterior components of the language network subserve word comprehension (semantic decoding). Hum. Brain Mapping 16:251–261, 2002. © 2002 Wiley‐Liss, Inc.
Dissecting an enzyme—model compounds for the galactose oxidase radical site
Authors: Halcrow Malcolm A.
Published: September 2002

The active site of the enzyme galactose oxidase (GOase) contains square‐pyramidal monocopper site, one of whose ligands is a tyrosinate side‐chain that is oxidized to an unusually stable radical in the active enzyme. The structure of this non‐innocent tyrosinate is unique in two ways. First, the tyrosine ring is crosslinked to a neighboring cysteine residue, affording an orthoalkylsulfanyl‐substituted phenoxide ligand. Second, this assembly is protected by a π–π interaction to a tryptophan indole group. We describe here a series of compounds designed to model various aspects of the structure of this unusual cofactor. Our studies have shown that the thermodynamic stability of the GOase radical can be attributed almost exclusively to its thioether substituent, that the π–π interaction contributes little to this stability, and that the assignment of the optical spectrum of the GOase radical is more complex than had been previously suggested. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:494–500, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10091
PN ligands in lanthanide chemistry
Authors: Roesky Peter W.
Published: September 2002

The coordination chemistry of inorganic amides in Group 3 and lanthanide chemistry is discussed. Three different ligand systems (phosphino‐amides, bis(phosphino)amides, and bis(phosphinimino)methanides) that consist of one or more PN units were used. In this series the steric demand of the ligands is increased in a stepwise fashion and the negative charge is delocalized over more atoms. These properties were used in the design of new lanthanide complexes. For all three compounds the synthesis of the alkali metal derivatives is reported first, followed by the reaction of the alkali metal salts with various lanthanide trichlorides. Further reactions of the obtained lanthanide complexes as well as their application as catalysts are discussed. Most of the reported complexes show a dynamic behavior in solution. In phosphinoamide and bis(phosphino)amide complexes, in which the phosphorus atom is in oxidation state +3, there is always a weak coordination of the phosphorus atom to the lanthanide atom observed. In bis(phosphinimino)methanide complexes, in which the phosphorus atom is in oxidation state +5, no such interaction is noticeable. Instead a weak coordination of the methine atom to the center metal can be seen in the solid state. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:514–520, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10096
Self‐assembly of anion‐binding supramolecular cage complexes
Authors: Paul Rowena L. , Bell Zöe R. , Fleming James S. , Jeffery John C. , McCleverty Jon A. , Ward Michael D.
Published: September 2002

Three tetradentate ligands, in which two bidentate pyrazolyl–pyridine binding sites are connected by an aromatic spacer unit, have been used to prepare adamantoid tetrahedral cages of the form [Co4L6(X)][X]7 (where X is a uninegative, noncoordinating counterion such as perchlorate, tetrafluoroborate, or hexafluorophosphate). In these complexes an approximately tetrahedral array of metal ions occurs, with a bridging ligand spanning each of the six edges of this tetrahedron; each metal ion is accordingly six coordinate and the cages can have either T or C3 symmetry, depending on the ligand. The central cavity of each cage is occupied by an anion. In the cases where the anion is a good fit for the central cavity, it is tightly bound (no exchange in solution with external anions) and acts as a template for assembly of the cage, with a mixture of Co(II) and the bridging ligand in the correct proportions not assembling into the Co4L6 cage until the templating anion is added. With a longer bridging ligand, the central cavity is too large to encapsulate the anion completely, and accordingly the encapsulated anion can exchange freely with external anions; this behavior can be “frozen out” in the NMR spectra at low temperatures. The host–guest chemistry of the cage complexes is therefore strongly dependent on the size of the central cavity. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:567–573, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10101
Silver(I) fluoride and related compounds in chemical synthesis
Authors: Tyrra Wieland
Published: September 2002

Silver(I) fluoride is a versatile tool in desulfuration‐fluorination reactions with thiuram disulfides and thioureas. Reactions of AgF and trimethyl(perfluoroorgano)‐ and trimethyl(alkynyl)‐silanes offer a convenient approach to the corresponding organosilver derivatives, which are excellent reagents for oxidative organylations of group 12–16 elements. Reactions of AgF and elements of groups 13–16 open a convenient access to the corresponding fluorides. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:561–566, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10102
Keeping nurses at work: a duration analysis
Authors: Holmås Tor Helge
Published: September 2002

A shortage of nurses is currently a problem in several countries, and an important question is therefore how one can increase the supply of nursing labour. In this paper, we focus on the issue of nurses leaving the public health sector by utilising a unique data set containing information on both the supply and demand side of the market. To describe the exit rate from the health sector we apply a semi‐parametric hazard rate model. In the estimations, we correct for unobserved heterogeneity by both a parametric (Gamma) and a non‐parametric approach. We find that both wages and working conditions have an impact on nurses' decision to quit. Furthermore, failing to correct for the fact that nurses' income partly consists of compensation for inconvenient working hours results in a considerable downward bias of the wage effect. Copyright © 2002 John Wiley & Sons, Ltd.
Rational addiction to alcohol: panel data analysis of liquor consumption
Authors: Baltagi Badi H. , Griffin James M.
Published: September 2002

Utilizing a panel data set of 42 states over the period 1959–1994, this paper estimates a rational addiction model for liquor consumption for the US. The empirical evidence is consistent with the rational addiction hypothesis proposed by Becker and Murphy. However, the results are sensitive to the assumption of homogeneity across states or over time. Copyright © 2002 John Wiley & Sons, Ltd.
Real‐time recurrent learning neural network for stream‐flow forecasting
Authors: Chang F.‐John , Chang Li‐Chiu , Huang Hau‐Lung
Published: September 2002

Various types of neural networks have been proposed in previous papers for applications in hydrological events. However, most of these applied neural networks are classified as static neural networks, which are based on batch processes that update action only after the whole training data set has been presented. The time variate characteristics in hydrological processes have not been modelled well. In this paper, we present an alternative approach using an artificial neural network, termed real‐time recurrent learning (RTRL) for stream‐flow forecasting. To define the properties of the RTRL algorithm, we first compare the predictive ability of RTRL with least‐square estimated autoregressive integrated moving average models on several synthetic time‐series. Our results demonstrate that the RTRL network has a learning capacity with high efficiency and is an adequate model for time‐series prediction. We also investigated the RTRL network by using the rainfall–runoff data of the Da‐Chia River in Taiwan. The results show that RTRL can be applied with high accuracy to the study of real‐time stream‐flow forecasting networks. Copyright © 2002 John Wiley & Sons, Ltd.
Effects of land‐cover changes on the hydrological response of interior Columbia River basin forested catchments
Authors: VanShaar James R. , Haddeland Ingjerd , Lettenmaier Dennis P.
Published: September 2002

The topographically explicit distributed hydrology–soil–vegetation model (DHSVM) is used to simulate hydrological effects of changes in land cover for four catchments, ranging from 27 to 1033 km2, within the Columbia River basin. Surface fluxes (stream flow and evapotranspiration) and state variables (soil moisture and snow water equivalent) corresponding to historical (1900) and current (1990) vegetation are compared. In addition a sensitivity analysis, where the catchments are covered entirely by conifers at different maturity stages, was conducted. In general, lower leaf‐area index (LAI) resulted in higher snow water equivalent, more stream flow and less evapotranspiration. Comparisons with the macroscale variable infiltration capacity (VIC) model, which parameterizes, rather than explicitly represents, topographic effects, show that runoff predicted by DHSVM is more sensitive to land‐cover changes than is runoff predicted by VIC. This is explained by model differences in soil parameters and evapotranspiration calculations, and by the more explicit representation of saturation excess in DHSVM and its higher sensitivity to LAI changes in the calculation of evapotranspiration. Copyright © 2002 John Wiley & Sons, Ltd.
Physical controls on septic leachate movement in the vadose zone at the hillslope scale, Putnam County, New York, USA
Authors: Sherlock Mark D. , McDonnell Jeffrey J. , Curry Debra S. , Zumbuhl Albert T.
Published: September 2002

The fate and transport of contaminants in the vicinity of septic fields remains poorly understood in many hydrogeomorphological environments. We report hydrometric data from an intensive hillslope‐scale experiment conducted between 29 August and 11 November 1998 at a residential leach field in New York State. The objective of our study was to characterize water flux within the vadose zone, understand the physical controls on the flux, and predict how this ultimately will affect subsurface water quality. Soil‐water flux was calculated using matric potential measurements from a network of 25 tensiometer nests, each nest consisting of three tensiometers installed to depths of 10, 50 and 130 cm. Unsaturated hydraulic conductivity curves were derived at each depth from field‐determined time‐domain reflectometry–tensiometry moisture‐release curves and borehole permeametry measurements. Flownets indicated that a strong upward flux of soil water occurred between rainstorms. Following the onset of (typically convective) rainfall, low near‐surface matric potentials were rapidly converted to near‐saturated and saturated conditions, promoting steep vertical gradients through the near‐surface horizons of the hillslope. Lateral hydraulic gradients were typically 10 times smaller than the vertical gradients. Resultant flow vectors showed that the flux was predominantly vertical through the vadose zone, and that the flux response to precipitation was short‐lived. The flux response was controlled primarily by the shape of the unsaturated hydraulic conductivity curves, which indicated a rapid loss of conductivity below saturation. Thus, soil water had a very high residence time in the vadose zone. The absence of rapid wetting at 130 cm and the delayed and small phreatic zone response to rainfall indicated that water movement through macropores did not occur on this hillslope. These results are consistent with a Cl tracing experiment, which demonstrated that the tracer was retained in the vadose zone for several months after injection to the system. Copyright © 2002 John Wiley & Sons, Ltd.
The maximum depth of a river as a stochastic process
Authors: Moisello Ugo
Published: September 2002

The maximum depth of a river section is schematized as a non‐stationary continuous‐parameter continuous stochastic process, with a three‐parameter lognormal distribution. Two processes, represented by a first‐order and a second‐order differential equation, are considered. Non‐stationarity is accounted for by the mean, the other parameters being assumed constant. The continuous processes are then discretized as AR(1) and ARMA(2,1) processes respectively, and used for computing the conditional probability (which is of practical interest) for a given maximum depth not to be exceeded in a period of given length. The models are applied to the River Po (Italy) and the AR(1) model is found to be preferable. An analysis of the effect of discretizing the parameter is also carried out, considering the second‐order model and the conditional probability, for which analytical results for the continuous‐parameter model are available. Copyright © 2002 John Wiley & Sons, Ltd.
Parent, child, and contextual predictors of childhood physical punishment
Authors: Woodward Lianne J. , Fergusson David M.
Published: September 2002

Data gathered over the course of an 18‐year longitudinal study of 1025 New Zealand children were used to: (a) develop a profile of the maternal, child, and contextual factors associated with differing levels of exposure to maternal physical punishment, and (b) identify the key predictors of maternal physical punishment as reported by young people at age 18. Results revealed the presence of clear linear associations between the extent of young people's reported exposure to physical punishment and a wide range of maternal, child, and contextual factors. The key predictors of physical punishment suggested that the psychosocial profile of those mothers at greatest risk of physically punishing or mistreating their child was that of a young woman with a personal history of strict parenting who entered motherhood at an early age, and who was attempting to parent a behaviourally difficult child within a dysfunctional family environment characterized by elevated rates of inter‐parental violence and childhood sexual abuse. These findings were consistent with a cumulative risk factor model in which increasing risk factor exposure is associated with increasing levels of child physical punishment/maltreatment. Copyright © 2002 John Wiley & Sons, Ltd.
The melody of surprise: maternal surprise vocalizations during play with her infant
Authors: Reissland Nadja , Shepherd John , Cowie Lily
Published: September 2002

Two groups of mothers and their infants (24 infants, mean age=3.5 months and 24 infants, mean age=5.5 months) were video‐ and audio‐taped in their homes while playing with a Jack‐in‐the‐box. The mean fundamental frequency of spontaneous surprise exclamations of mothers when opening the toy were analysed, and infant and maternal facial expressions of surprise were coded in three regions of the face. A t‐test established that significantly more of the older children in comparison with younger children showed surprise (t=−2.96, df=46, p<0.005, 2‐tailed). Twenty‐nine per cent of the younger infants, in comparison with 67% of the older children showed facial expressions of surprise. A t‐test of maternal pitch height (Hz) indicated that mothers exclaimed in surprise with a higher pitch when the child did not show a surprise facial expression (mean=415.61 Hz) in comparison with the child showing surprise (mean=358.97 Hz; t=2.9, df=46, p=0.006, 2‐tailed). A multiple regression established that infant's expression was a stronger predictor of maternal vocal pitch than was the age of the infant. These results are discussed in terms of maternal use of emotional expressions as ‘social signals’. Copyright © 2002 John Wiley & Sons, Ltd.
Role for β3 integrins in human melanoma growth and survival
Authors: Trikha Mohit , Timar Jozsef , Zacharek Alex , Nemeth Jeffrey A. , Cai Yinlong , Dome Balazs , Somlai Beata , Raso Elisabeth , Ladanyi Andrea , Honn Kenneth V.
Published: September 2002

The role of αIIbβ3 integrin in regulating platelet function is well appreciated, whereas its role in tumor progression and metastasis is not. The purpose of our study was to determine a functional relevance to expression of αIIbβ3 integrin in cells derived from human solid tumors. A study of human melanoma biopsies (n = 24) showed that αIIbβ3 expression increased with tumor thickness, which is indicative of metastatic propensity. Expression of αIIbβ3 was 8% (±1.8), 33% (±10.4) and 62% (±5) in melanomas ranging in thickness from 0–1.5 mm, 1.5–4.0 mm and >4 mm, respectively; αvβ3 was equally high all categories. To determine biological function, we stably transfected αIIbβ3 into human melanoma cells that express αvβ3, but not αIIbβ3. Surface expression of αvβ3 remained unaltered between αIIbβ3 (+) and mock transfected counterparts. The αIIbβ3 (+) cells possessed increased ability to adhere, spread and migrate on fibrinogen. They had decreased ability to attach, spread and migrate on vitronectin. Immunocytochemistry showed that expression of αIIbβ3 displaced αvβ3 from focal contact points. When implanted subcutaneously into SCID mice, the αIIbβ3 (+) cells developed ∼4‐fold larger tumors when compared to their mock counterparts and the level of apoptosis was reduced within the tumors. Results suggest that co‐expression of the 2 β3 integrins, αvβ3 and αIIbβ3, in human melanoma cells enhanced cell survival and promoted growth in vivo. © 2002 Wiley‐Liss, Inc.
Escape of p53 protein from E6‐mediated degradation in HeLa cells after cisplatin therapy
Authors: Węsierska‐Gądek Józefa , Schloffer Daniela , Kotala Vladimir , Horky Marcel
Published: September 2002

We previously reported that therapy of human cervical carcinoma HeLa cells with CP induced segregation of nucleoli and changes of nuclei characteristic of apoptosis. We raised the question of whether p53 can be reactivated by chemotherapy in HeLa cells despite the presence of HPV‐encoded E6 activity. Cellular levels of p53 protein increased after CP treatment, reaching a maximum after 6 hr. p53 protein accumulated preferentially in the nucleoli, with a peak after 15 hr. CP‐induced nucleolar targeting of p53 appears to be selective because p73, another member of the p53 gene family, accumulated primarily in nuclei in response to CP. Monitoring of the intranuclear distribution of Hdm‐2, a negative regulator of p53, revealed this protein in the nucleoli of untreated controls translocated into chromatin during CP therapy. Interestingly, p14ARF showed an inverse intranuclear redistribution. Proteasome inhibitors were not able to mimic the effect of CP on p53 levels. Since the reduced stability of wild‐type p53 protein in HeLa cells is a consequence of its enhanced ubiquitination by virally encoded E6 protein, resulting in its accelerated degradation, we checked the cellular level of E6 during CP therapy. Six hours after application of CP, E6 protein expression was markedly reduced. This coincided with the increase of cellular p53 and preceded the nucleolar accumulation of p53 protein, indicating that repression of virally coded E6 protein by CP contributes to the restoration of p53 expression. © 2002 Wiley‐Liss, Inc.
Target validation for genomics using peptide‐specific phage antibodies: A study of five gene products overexpressed in colorectal cancer
Authors: van Beijnum Judy R. , Moerkerk Peter T.M. , Gerbers Andrea J. , de Bruïne Adriaan P. , Arends Jan‐Willem , Hoogenboom Hennie R. , Hufton Simon E.
Published: September 2002

Genomic approaches are providing a wealth of information on differential gene expression in cancer. To identify the most interesting genes amongst the many identified, high‐throughput methods for analysis of genes at the translational level are required. We have used a rapid method for the in vitro selection of antibodies to peptide antigens for the generation of probes to 5 gene products that we have found to be overexpressed in colorectal cancer. The rationale of our study was to select a non‐immune phage displayed human antibody library on peptides designed from the coding regions of the gene sequences and to verify whether such antibodies would be suitable probes for the parental protein in immunohistochemical and Western blot analysis. After the generation of a profile of genes overexpressed in primary colorectal cancer (CRC) we selected 5 genes, Ese‐3b, Fls353, PBEF, SPARC and Smad5 for a more detailed analysis using phage display‐derived antibodies. For these 5 antigens we designed 14–20 amino acid peptides predicted to be exposed on the surface of the parental protein. Selection of a large phage displayed antibody library resulted in specific antibodies for 6 of 8 different peptides with between 2 and 15 different antibodies isolated per peptide. Of 20 antibodies tested, 2 antibodies recognized the putative parental protein from primary CRC tissue. An antibody specific for a PBEF‐derived peptide (Fab/PBEF‐D4) was shown to recognize a protein product of the expected molecular weight in Western blotting and showed overexpression in n = 6/8 matched tumor/normal protein lysates. Furthermore, in immunohistochemistry this antibody showed restricted staining of the tumor stromal compartment with no detectable staining of epithelial cells. The discovery that PBEF is overexpressed in cancer is unexpected given that the normal function of PBEF is as a cytokine required for the maturation of B cell precursors. We also report on the isolation of an antibody (Fab/SMAD‐50) specific for a Smad5‐derived peptide that showed cytoplasmic staining of epithelial cells in both CRC tumor and matched normal mucosa. Fab/SMAD‐50 also bound to a group of proteins in Western blotting with molecular weights consistent with belonging to the Smad family. These antibodies may be suitable probes for further investigation of the roles of PBEF and Smad5 in cancer. The amenability of phage display to automation suggests that this approach may be developed for implementation on a genomics scale. Indeed, the large‐scale generation of antibody probes that can be used to study protein expression in situ would be of great value in target validation for functional genomics. © 2002 Wiley‐Liss, Inc.
Autoantibodies to tubulin are specifically associated with the young age onset of the nasopharyngeal carcinoma
Authors: Jalbout Majida , Bel Hadj Jrad Besma , Bouaouina Noureddine , Gargouri Jalel , Yacoub Salwa , Zakhama Abdelfatteh , Khlifa Ridha , Chouchane Lotfi
Published: September 2002

By far the highest incidence of the Epstein‐Barr virus (EBV)‐associated nasopharyngeal carcinomas in young subjects was found in North Africa, a region of intermediate risk for adults. We used the immunofluorescence analysis and ELISA to characterize the presence of IgG autoantibodies to the cytoskeleton and nuclear proteins in sera of 82 Tunisian patients with primary nasopharyngeal carcinoma and those of 82 healthy subjects. To assess the specificity of the sera autoreactivity, inhibition tests were carried out using free autoantigens. Analysis of sera autoreactivity in patients with nasopharyngeal carcinoma and in control subjects showed that 23% of the patients had serum reactivity against more than 1 autoantigen tested compared to 1.2% in the control group (p = 10−4). The most frequent auto reactivity in patient's sera was found with tubulin and nuclear proteins (19.5% and 22% respectively vs. 6.1% and 1.2% in controls). The IgG auto reactivity inhibition studies indicate that all autoantigens, except native DNA, showed low values of IC50 (concentration of antigen causing 50% inhibition of the antibody binding) reflecting the high affinity of these IgG autoantibodies. When patients and controls were stratified according to their age, IgG autoantibodies to tubulin were found specifically associated with the young age onset of the nasopharyngeal carcinoma (age under 25 years). IgG auto reactivity comparison before and after cancer therapy showed that only anti‐tubulin reactivity was significantly affected by treatment. Our results demonstrate that the autoantibodies to the cytoskeleton and nuclear proteins are associated with the nasopharyngeal carcinoma in Tunisians. The anti‐tubulin IgG autoantibodies may represent a serologic marker for the nasopharyngeal carcinoma in children and adolescents Tunisians. © 2002 Wiley‐Liss, Inc.
CDH1 c‐160a promotor polymorphism is not associated with risk of stomach cancer
Authors: Pharoah Paul D.P. , Oliveira Carla , Machado José Carlos , Keller Gisella , Vogelsang Holger , Laux Holger , Becker Karl‐Friedrich , Hahn Heidi , Paproski Suzanne M. , Brown Lindsay A. , Caldas Carlos , Huntsman David
Published: September 2002

We have combined data from case control studies designed to test the hypothesis that the c‐160a promotor polymorphism in the gene coding for the cell adhesion molecule E‐cadherin (CDH1) is associated with stomach cancer. A total of 899 individuals (433 patients and 466 controls) were analyzed. The genotype frequencies did not differ significantly between cases and controls, and the genotype‐specific risks were not significantly different from unity, with an odds ratio for heterozygotes compared with the common homozygote of 1.3 (95% CI 0.98–1.8) and 1.2 (0.68–2.0) for rare homozygotes compared with common homozygotes. We found no evidence for differences in risk for the intestinal‐ and diffuse‐type histopathologic subgroups. © 2002 Wiley‐Liss, Inc.
Combined karyotyping, CGH and M‐FISH analysis allows detailed characterization of unidentified chromosomal rearrangements in Merkel cell carcinoma
Authors: Van Gele Mireille , Leonard J. Helen , Van Roy Nadine , Van Limbergen Heidi , Van Belle Simon , Cocquyt Veronique , Salwen Helen , De Paepe Anne , Speleman Frank
Published: September 2002

Merkel cell carcinoma (MCC) is a rare aggressive neuroendocrine tumor of the skin. Cytogenetic studies have indicated that deletions and unbalanced translocations involving chromosome 1 short arm material occur in 40% of the investigated cases. Recurrent chromosomal imbalances detected by comparative genomic hybridization (CGH) analysis were loss of 3p, 10q, 13q and 17p and gains of 1q, 3q, 5p and 8q. In order to study genomic aberrations occurring in MCC in further detail, we combined karyotyping, CGH and multiplex‐fluorescence in situ hybridization (M‐FISH), a strategy that proved to be successful in the analysis of other malignancies. Analysis of 6 MCC cell lines and 1 MCC tumor revealed mostly near‐diploid karyotypes with an average of 5 chromosomal rearrangements. The observed karyotypic changes were heterogeneous, with 3–27 breakpoints per case, leading to imbalance of the involved chromosomal regions that was confirmed by CGH. Chromosomal rearrangements involving the short arm of chromosome 1, the long arm of chromosome 3 and gain of 5p material were the most frequently observed abnormalities in our study. In keeping with previous observations, this series of MCCs showed no evidence for high‐level amplification. We provid a detailed description of chromosomal translocations occurring in MCC that could be useful to direct future intensive investigation of these chromosomal regions. © 2002 Wiley‐Liss, Inc.
A geographic analysis of prostate cancer mortality in the United States, 1970–89
Authors: Jemal Ahmedin , Kulldorff Martin , Devesa Susan S. , Hayes Richard B. , Fraumeni Joseph F.
Published: September 2002

The recently published atlas of cancer mortality in the United States revealed that prostate cancer mortality rates were elevated among white men in the Northwest, the Rocky Mountain states, the north‐central area, New England and the South Atlantic area, and among black men in the South Atlantic area. Here we determine whether the elevated regional rates were statistically different from rates in the rest of the country and whether the pattern can be explained by selected regional characteristics. A spatial scan statistic was applied to county‐based mortality data from 1970 through 1989 to identify geographic clusters of the elevated rates for prostate cancer. Five clusters of elevated mortality were detected in white men (p < 0.005) and 3 in black men (p = 0.0001–0.056). For white men, the primary cluster was in the northwestern quadrant, followed by clusters in New England, the eastern part of the north‐central area, the mid‐Atlantic states and the South Atlantic area, whereas for black men the primary cluster was in the South Atlantic area, followed by clusters in Alabama and the eastern part of the north‐central area. Further analyses of these clusters revealed several significant subclusters (p < 0.05). None of the selected demographic and socioeconomic factors, separately or collectively, accounted for the primary clusters in the U.S. white and black populations. The patterns observed could not be attributed to selected demographic or socioeconomic characteristics but should provide leads for further study into the risk factors and the medical or reporting practices that may contribute to geographic variation in mortality from prostate cancer. © 2002 Wiley‐Liss, Inc.
Indoleamine 2,3‐dioxygenase contributes to tumor cell evasion of T cell‐mediated rejection
Authors: Friberg Maria , Jennings Ronald , Alsarraj Marwan , Dessureault Sophie , Cantor Alan , Extermann Martine , Mellor Andrew L. , Munn David H. , Antonia Scott J.
Published: September 2002

The priming of an appropriate anti‐tumor T cell response rarely results in the rejection of established tumors. The characteristics of tumors that allow them to evade a T cell‐mediated rejection are unknown for many tumors. We report on evidence that the expression of the immunosuppressive enzyme, indoleamine 2,3‐dioxygenase (IDO) by mononuclear cells that invade tumors and tumor‐draining lymph nodes, is 1 mechanism that may account for this observation. Lewis lung carcinoma (LLC) cells stimulated a more robust allogeneic T cell response in vitro in the presence of a competitive inhibitor of IDO, 1‐methyl tryptophan. When administered in vivo this inhibitor also resulted in delayed LLC tumor growth in syngeneic mice. Our study provides evidence for a novel mechanism whereby tumors evade rejection by the immune system, and suggests the possibility that inhibiting IDO may be developed as an anti‐cancer immunotherapeutic strategy. © 2002 Wiley‐Liss, Inc.
A new vascular prosthesis coated with polyamino‐acid urethane copolymer (PAU) to enhance endothelialization
Authors: Wang Chunren , Zhang Qing , Uchida Shinji , Kodama Makoto
Published: September 2002

Clinically available synthetic ePTFE vascular grafts frequently fail when used for small‐diameter arterial substitution. The lower long‐term patency of ePTFE grafts is due mainly to thrombogenicity and poor healing. We developed a new small‐diameter (1.5‐mm) ePTFE vascular prosthesis coated with polyamino‐acid urethane copolymer (PAU) to enhance endothelialization. Coating with PAU made the hydrophobic ePTFE vascular graft hydrophilic. Scanning electron microscopy (SEM) observation showed that PAU was homogeneously coated on the ePTFE graft while maintaining the graft's porous structure. Fourier transform infrared attenuated total reflectance (FTIR‐ATR) spectra showed PAU was present on graft inner surfaces. Noncoated and PAU‐coated ePTFE vascular grafts were implanted into the rat abdominal aorta and evaluated within 1 week and at 8 weeks after implantation. We evaluated the extent of neoendothelialization by SEM, light microscopy, and immunohistochemical staining. Noncoated grafts showed partial endothelialization at proximal and distal areas of grafts but none at midsection. One‐percent PAU‐coated grafts showed incomplete neoendothelialization, but endothelial cells were observed in the midsection of grafts. Three‐percent PAU‐coated ePTFE grafts showed complete endothelialization with typical endothelial cell layers under SEM and histologic observation. Immunohistochemical staining also showed that an endothelial cell lining positively reacted with anti‐von Willebrand factor (endothelial cell marker) antibody. We conclude that PAU‐coated ePTFE vascular grafts enhance endothelialization. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 315–322, 2002
Bone formation by rat bone marrow cells cultured on titanium fiber mesh: Effect of in vitro culture time
Authors: van den Dolder Juliette , Vehof Johan W. M. , Spauwen Paul H. M. , Jansen John A.
Published: September 2002

The objective of this study was to examine the effect of cell culture time on bone formation by rat bone marrow cells seeded in titanium fiber mesh. As a seeding technique, a high cell suspension was used (3 × 106 cells/mL). Therefore, 30 meshes were repeatedly rotated in a 10 mL tube (containing 30 × 106 cells) on a rotation plate (2 rpm) for 3 h. Osteogenic cells were cultured for 1, 4, and 8 days on titanium fiber mesh and finally implanted subcutaneously in rats. Meshes without cells were also implanted subcutaneously in rats. DNA and scanning electron microscopy (SEM) analyses and calcium measurements determined cellular proliferation and differentiation during the in vitro incubation period of the mesh implants. Four weeks after implant insertion, the animals were sacrificed. The implants, with their surrounding tissue, were retrieved and prepared for histologic evaluation and calcium measurements. DNA analysis of the in vitro experiment showed a lag phase from day 1 through day 4, but a 42% increase in DNA between days 4 and 8. SEM and calcium measurements indicated an increase in calcium from day 1 to day 4, yet only a small but significant increase from days 4 to 8. Histologic analysis demonstrated that bone was formed in all day 1 and day 4 implants, and that the bone‐like tissue was present uniformly through the meshes. The bony tissue was morphologically characterized by osteocytes embedded in a mineralized matrix, with a layer of osteoid and osteoblasts at the surface. The day 8 implants showed only calcium phosphate deposition in the titanium fiber mesh. Calcium measurements of the implants revealed that calcification in day 1 implants was significantly higher (p < 0.05) compared to day 4 and day 8 implants. No significant difference in calcium content existed between day 4 and day 8 implants. On the basis of our results, we conclude that 1) bone formation was generated more effectively in osteogenic cells by a short culture time after seeding in titanium fiber mesh; 2) dynamic cell seeding is probably more effective than static cell seeding; and 3) selection of the right cells from the heterogenous bone marrow population remains a problem. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 350–358, 2002
Carbon dioxide extraction of residual chloroform from biodegradable polymers
Authors: Koegler Wendy S. , Patrick Carmen , Cima Michael J. , Griffith Linda G.
Published: September 2002

Biodegradable polymeric devices for drug delivery and tissue engineering are often fabricated with the use of organic solvents and may still contain significant amounts of solvent (> 1 wt%) even after aggressive vacuum drying. This excess solvent can interfere with tissue response and the mechanical properties of the devices. The aim of this article is to demonstrate that liquid CO2 extraction can be used to reduce residual solvent in dense poly(L‐lactide‐co‐glycolide) devices to 50 ppm relatively quickly and with minimal changes in architecture under some conditions. Two liquid CO2 extraction systems were developed to examine the removal of residual solvents from bar‐shaped PLGA devices: (1) a low‐pressure (1400 psi) batch system, and (2) a high‐pressure (5000 psi) continuous‐flow system. Eight hours of extraction in the high‐pressure system reduced residual chloroform in 3 mm thick bars below the 50‐ppm target. A simple Fickian diffusion model was fit to the extraction results. Diffusion coefficients ranged from 1.10×10−6 cm2/s to 2.64×10−6 cm2/s. The model predicts that ∼1 h is needed to dry 1‐mm bars to chloroform levels below 50 ppm, and 7 h are needed for 3 mm thick bars. The micro‐ and macroarchitectures of porous PLGA scaffolds created by particulate leaching were not significantly altered by CO2 drying if the salt used to make the pores was not removed before drying. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 567–576, 2002
Novel approach for achieving double‐layered cell sheets co‐culture: overlaying endothelial cell sheets onto monolayer hepatocytes utilizing temperature‐responsive culture dishes
Authors: Harimoto Masami , Yamato Masayuki , Hirose Motohiro , Takahashi Chie , Isoi Yuki , Kikuchi Akihiko , Okano Teruo
Published: September 2002

Confluent human aortic endothelial cells (HAECs) cultured on thermo‐responsive culture dish grafted with poly (N‐isopropylacrylamide) were recovered as a contiguous cell sheet. The double‐layered co‐culture was achieved by placing the recovered HAEC sheet onto the rat hepatocyte layer directly. The double‐layered structure of HAEC and hepatocytes remained in tight contact during culture. Hepatocytes in the layered co‐culture system with the HAEC sheet maintained the differentiated cell shape and the albumin expression for over 41 days of culture, whereas the functions disappeared within 10 days of culture in control hepatocytes without the HAEC sheet. The layered co‐culture of hepatocytes and the HAEC sheets, which allows for the expression of differentiated functions of hepatocyte continuously, such as liver lobule, offers a major advancement in liver tissue engineering. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 464–470, 2002
Characterization of cartilagenous tissue formed on calcium polyphosphate substratesin vitro
Authors: Waldman Stephen D. , Grynpas Marc D. , Pilliar Robert M. , Kandel Rita A.
Published: September 2002

Successful joint resurfacing by tissue‐engineered cartilage has been limited, in part, by an inability to secure the implant to bone. To overcome this, we have developed the methodology to form a cartilage implantin vitroconsisting of a layer of cartilagenous tissue overlying a porous, biodegradable calcium polyphosphate (CPP) substrate. As bone will grow into the CPP after implantation, it will result in anchorage of the cartilage. In this study, the cartilagenous tissue formedin vitroafter 8 weeks in culture was characterized and compared to native articular cartilage. Light microscopic examination of histological sections showed that there was a continuous layer of cartilagenous tissue on, and integrated with the subsurface of, the CPP substrate. Thein vitro‐formed tissue achieved a similar thickness to native articular cartilage (mean ± SEM:in vitro= 0.94 ± 0.03 mm;ex vivo= 1.03 ± 0.01 mm). The cells in thein vitro‐formed tissue synthesized large proteoglycans (Kav ± SEM:in vitro= 0.27 ± 0.01;ex vivo= 0.27 ± 0.01) and type II collagen similar to the chondrocytes in theex‐vivocartilage. Thein vitro‐formed tissue had a similar amount of proteoglycan (GAG μg/mg dry wt.:in vitro= 198 ± 10;ex vivo= 201 ± 13) but less collagen than the native cartilage (hydroxyproline μg/mg dry wt.:in vitro= 21 ± 1;ex vivo= 70 ± 8). Thein vitro‐formed tissue had only about 3% of the load‐bearing capacity and stiffness of the native articular cartilage, determined from unconfined mechanical compression testing. Although low, this was within the range of properties reported by others for tissue‐engineered cartilage. It is possible that the limited load‐bearing capacity is the result of the low collagen content and further studies are required to identify the conditions that will increase collagen synthesis. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62:323–330, 2002
Collagen fiber disruption occurs independent of calcification in clinically explanted bioprosthetic heart valves
Authors: Sacks Michael S. , Schoen Frederick J.
Published: September 2002

The durability of bioprosthetic heart valves (BHV) is severely limited by tissue deterioration, manifested as calcification and mechanical damage to the extracellular matrix. Extensive research on mineralization mechanisms has led to prevention strategies, but little work has been done on understanding the mechanisms of noncalcific matrix damage. The present study tested the hypothesis that calcification‐independent damage to the valvular structural matrix mediated by mechanical factors occurs in clinical implants and could contribute to porcine aortic BHV structural failure. We correlated quantitative assessment of collagen fiber orientation and structural integrity by small angle light scattering (SALS) with morphologic analysis in 14 porcine aortic valve bioprostheses removed from patients for structural deterioration following 5–20 years of function. Calcification of the explants varied from 0 (none) to 1+ (minimal) to 4+ (extensive), as assessed radiographically. SALS tests were performed over entire excised cusps using a 0.254‐mm spaced grid, and the resultant structural information used to generate maps of the local collagen fiber damage that were compared with sites of calcific deposits. All 42 cusps showed clear evidence of substantial noncalcific structural damage. In 29 cusps that were calcified, structural damage was consistently spatially distinct from the calcification deposits, generally in a distribution similar to that noted in porcine BHV subjected to in vitro durability testing. Our results suggest a mechanism of noncalcific degradation dependent on cuspal mechanics that could contribute to porcine aortic BHV failure. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 359–371, 2002
Liquid acrylate‐endcapped biodegradable poly(ϵ‐caprolactone‐co‐trimethylene carbonate). I. Preparation and visible light‐induced photocuring characteristics
Authors: Mizutani Manabu , Matsuda Takehisa
Published: September 2002

Photocurable liquid biodegradable copolymers were prepared by ring‐opening copolymerization of ϵ‐caprolactone (CL) and trimethylene carbonate (TMC) in the presence of a multifunctional hydroxyl group‐bearing substance (di‐, tri‐, and tetra‐functional alcohol and poly(ethylene glycol) (PEG) and its four‐branched derivative) as an initiator and subsequent endcapping with acryloyl chloride at their hydroxyl terminals. These multifunctional, viscous liquid copolymers (molecular weights; approximately 2 × 103 to 7 × 103 g/mol) were converted to crosslinked solids by visible‐light irradiation in the presence of camphorquinone as an initiator. The photocuring rate of these copolymers was enhanced by both higher functionality and lower molecule weight of the copolymers used. The photocuring rate depended on the amount of reducing agent (methacrylic acid 2‐dimethylaminoethyl ester). Upon immersion in a phosphate buffer solution (pH 7.4), hydrolysis occurred preferentially on the surface except for photocured PEG‐based copolymers that were degraded faster via both surface erosion and bulk degradation than low molecular weight alcohols‐based copolymers. Cylindrical photocured constructs prepared by photoirradiation to the whole body in a mold filled with the liquid copolymer was demonstrated as an example of shape fabrication of biodegradable biomedical devices. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 387–394, 2002
Liquid acrylate‐endcapped biodegradable poly(ϵ‐caprolactone‐co‐trimethylene carbonate). II. Computer‐aided stereolithographic microarchitectural surface photoconstructs
Authors: Matsuda Takehisa , Mizutani Manabu
Published: September 2002

Advanced micromedical devices may require computer‐aided photofabrication, by which microarchitectural surface design and entire macroshaped body design are feasible. Liquid acrylate‐endcapped poly(ϵ‐caprolactone‐co‐trimethylene carbonate)s, poly(CL/TMC)s, prepared using trimethylene glycol (TMG) or poly(ethylene glycol) (PEG) as an initiator and an acrylate group for subsequent terminal capping, were used as photocurable copolymers. The stereolithographically microarchitectured photoconstructs were prepared using a custom‐designed apparatus with a moving ultraviolet (UV) light pen driven by a computer‐assisted design program. The prepared photoconstructs included microneedles, a microcylinder and microbanks on surfaces. In vitro hydrolytic degradation proceeded with surface erosion when hydrophobic TMG‐based photocured copolymers were employed, whereas very fast degradation of hydrophilic PEG‐based photocured copolymers probably via concerted actions of surface erosion and bulk degradation was observed. In vivo hydrolytic behavior upon subcutaneous implantation in rats indicated that surface erosion proceeded for TMG‐based photoconstructs. Anti‐inflammatory drug (indomethacin) loading into microneedle‐structured surfaces minimized inflammatory reactions. The possible biomedical microarchitectural three dimensinal in biomedical application photoconstructs was discussed. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 395–403, 2002