bluuebunny/crossref_metadata_2025 huggingface dataset:
An Automated Water Vapor Diffusion Test Method for Fabrics, Laminates, and Films
Authors: Gibson Phillip , Kendrick Cyrus , Rivin Donald , Sicuranza Linda , Charmchi Majid
Published: March 2007

An automated apparatus has been developed to measure the transport of water vapor through coated and uncoated fabrics, fabric laminates, thin foams, and solid films under a variety of conditions. The apparatus is more convenient to use than the traditional test methods for textiles and clothing materials; it allows one to use a wider variety of test conditions to investigate the concentration-dependent and nonlinear transport behavior of many of the semipermeable membrane laminates that are now available. The dynamic moisture permeation cell (DMPS) has been auto mated to permit multiple setpoint testing under computer control and to facilitate in vestigation of transient phenomena. Results generated with the DMPC are in agree ment with and of comparable accuracy to those from the ISO 11092 (sweating guarded hot plate) method of measuring water vapor permeability.
Alternative Curing Methods
Authors: Bluestein Claire
Published: March 2007

The current (1995) state of the art in UV/EB coatings manufacturing technology is described Major commercial applications are summarized and illus trated. Research projects aimed at development of UV/EB technology for coated fabrics are discussed together with possible reasons for lack of commercialization fol lowup. Suggestions are given for potential paths to future commercial development.
An Overview of Carpet Laminates
Authors: Stamper Kelvin
Published: March 2007

Carpet Laminating is a process that has progressed from "Black Magic" to a science over the last thirty years. What is this strange science and what are the principles that govern it? This paper will try to answer these questions. Recently there has been a great interest in VOC emissions from carpet that has resulted in a renewed awareness of carpet backcoatings. This presentation will focus on five topics that directly relate to SBR Latex and Carpet Laminating: Market, SBR Latex Manufacture, Carpet Laminating, Carpet Emissions, and Market.
Quality Management for the Textile Industry
Authors: Topf Wolfgang
Published: March 2007

Traditionally the textile industry has been driven primarily by fashion and creativity rather than by a focus on quality assurance. However, new aproaches such as quality management (QM), accreditation, certification, and conformity are now required. Such approaches have long been standard practice in the automobile industry, and it is recommended that the textile industry take the QM systems of the automobile industry as an example when developing its own systems.
A New Generation of Silicone Elastomers for Airbag Coatings
Authors: Bohin Fabrice , Pouchelon Alain , Surprenant Richard
Published: March 2007

When airbag technology appeared on an industrial scale in the middle of the 1980s, the first bags were neoprene coated. Although the neoprene met initially the performance requirements of airbags, its efficiency was question able in the long term.
Campaign Effects in Theory and Practice
Authors: WLEZIEN CHRISTOPHER , ERIKSON ROBERT S.
Published: March 2007

Although scholars debate the influence of election campaigns on electoral decision making, they agree that campaigns do have effects. Empirically identifying the effects of the campaign is not straightforward, however. We simply do not have regular readings of voter preferences over the election cycle, and the readings we do have are imperfect. Clearly then, an important question is, Can we actually detect the effects of election campaigns? In this article, the authors consider the practice of identifying campaign effects, focusing particularly on survey error and its consequences for empirical analysis. Using selected poll data from the 2000 presidential election cycle, they illustrate how the various forms of survey error complicate the study of campaign effects. The authors also offer certain solutions, although these only take us part of the way. Indeed, given the available data, it appears that all that can be offered are fairly general conclusions about the effects of election campaigns.
Issue Alignment and the American Party System, 1956-1976
Authors: Piereson James E.
Published: March 2007

Recent commentaries on the American party system have developed conflicting interpretations of the ways in which it changed during the 1960s and 1970s. Studies based upon individual behavior conclude that because of the intense conflicts of the 1960s, voters became more issue-oriented in their evaluations of the parties. Thus, an emerging basis for a "responsible" party system is visible in the changes of this period. System-level studies, on the other hand, point in exactly the opposite direction—to the growing instability of party alignments. The present study attempts to assess these interpretations in terms of the concept of "issue alignment," which refers to the degree to which citizens prefer the same party across a range of issues. Using data from national election surveys taken between 1956 and 1976, it is shown that issue alignment declined after 1956 and certainly did not increase during the 1960s and 1970s. Thus it appears that party alignments across issues are less stable presently than they were in the 1950s. It is suggested that we may have been exaggerating the degree of political change that occurred during the 1960s.
Criteria for Choice
Authors: Dantico Marilyn K.
Published: March 2007

This article begins with a definition of politics as a problem-solving process. Thus, to understand politics we need to understand how people solve problems. This research focuses on the ways individuals perceive, evaluate, and use a limited amount of informa tion in solving problems in a criminal justice context.

An experiment was used to control information and assess performance levels. In the first wave of the experiment Ss read "criminal court transcripts" from an assault and battery case, in which characteristics of the information source were varied. In the second treatment Ss read excerpts of the Miranda case. The data analysis presented here examines the effects of information source, individual level of cognitive complexity, and decision making rules or logics on verdicts.
Social Interaction and Contextual Influences On Political Participation
Authors: Leighley Jan E.
Published: March 2007

Though individual-level attributes typically dominate models of political participation, many studies have shown that the social context also influences individuals' likelihood of participation. This article considers two questions concerning the impact of the social context on participation. First, it examines whether specific features of individuals' discussion networks (size, politicization, and homogeneity) influence their likelihood of participation. Second, it considers whether social interaction influences only participation that is socially based, as suggested by studies of the effects of aggregate contextual characteristics on participation. The analysis uses data from the 1976 American National Election Study, which is merged with 1970 census data. Social interaction affects participation in both individually based and socially based participation, although not always in the expected direction. Aggregate contextual measures are then used to replicate previous studies that established the distinction between individually based and socially based participation. That similar results are not obtained suggests that this distinction is not valid and that the social context is likely to influence all types of participation.
The Refugee Act of 1980 and the Depoliticization of Refugee/Asylum Admissions
Authors: Yarnold Barbara M.
Published: March 2007

One of the objectives of the Refugee Act of 1980 was to eliminate a bias that existed in U.S. refugee admissions in favorof aliens from hostile countries of origin (countries with communist, socialist, and leftist forms of government). This analysis finds that the hostile country bias in refugee admissions was perpetuated (and even, in the case of the State Department, intensified) through policy implementation by agencies within the immigration bureaucracy since passage of the Refugee Act of 1980. Specifically, the INS and the State Department, in their post-1980 decision making on asylum and refugee applications, continue to favor aliens from hostile countries.
Confidence in Government During the 1980s
Authors: Miller Arthur H. , Borrelli Stephen A.
Published: March 2007

Data from the American National Election Studies are used to examine trends in political trust for the period of 1980 to 1988. The data reveal a substantial growth in trust during the first half of the eighties, followed by plummeting confidence in government at the end of the decade. A number of plausible explanations for these shifts in public trust are examined. The analysis reveals that the downturn in trust after 1984 was not a response to the Iran-Contra scandal of 1986. Rather, it reflected the emerging perception that Reagan lacked compassion, as well as growing dissatisfaction with foreign and domestic policies.
Ideology, Role Orientations, and Behavior in the State Courts of Last Resort
Authors: Scheb John M. , Bowen Terry , Anderson Gary
Published: March 2007

Judicial role theory holds that variance in judges' perceptions of their decisional roles is related to variance in decision making indirectly, by determining the degree to which judges permit their political attitudes and policy preferences to influence their votes. Judicial "activists" are thus presumed to be more overtly ideological in their decisions than "restraintists." This study tests judicial role theory against attitudinal and behavioral data for a national sample of state supreme court justices. As hypothesized, judicial activists are shown to be more ideological than their restraintist counterparts. The findings suggest that judicial role orientation is an important element of any comprehensive theory of judicial behavior.
The Convention Bump
Authors: Campbell James E. , Cherry Lynna L. , Wink Kenneth A.
Published: March 2007

Do the national conventions of the Democratic and Republican parties affect the poll standings of the presidential candidates they nominate? This study investigates whether these poll stand ings are bumped upwards following the party conventions. The convention bump is examined with Gallup and Harris time series data of presidential trial-heats throughout the course of seven campaigns from 1964 to 1988. We find that (1) with few exceptions, there is a convention bump; (2) the bump typically adds about 5 to 7 percentage points to the nominee's postoonvention poll standing; (3) the effects of conventions carry well into the general election campaign; (4) the first convention in the campaign sequence, held by the out-party, generates an additional but temporary increase in the nominee's support; and (5) convention bumps may be greater for harmonious conventions following divisive nomination contests.
Race Trumps Gender?
Authors: Overby L. Marvin , Henschen Beth M.
Published: March 2007

In this article the authors examine with greater precision the impacts of various constituencies in the struggle over the confirmation of Clarence Thomas to the Supreme Court. Using multivariate logistical regression models, they challenge the conventional interpretation that racial constituency concerns "trumped" gender constituency concerns in the voting decisions of senators. Rather, their findings indicate that senators from states with more professionalized female workforces were more, not less, likely to vote in favor of Thomas's confirmation. In a concluding section, they provide an explanation for these findings and discuss their implications.
Party Support in the House of Representatives
Authors: Nye Mary Alice
Published: March 2007

Research exploring variation in party support in Congress often focuses solely on the impact of generational replacement. Generational replacement suggests that new generations of congressmen account for varying levels of party support. Recent work by Rohde (1992) and Hibbing (1992) points to the need to explore life cycle effects and period effects. The life cycle hypothesis suggests that members may become less supportive of party as their tenure increases. Period effects focus on the extent to which variation in party voting is explained by changes in support by continuing members. Cohort analysis allows investigation of each type of effect through measurement of cross-sectional, longitudinal, and time-lag differences. Results do not support a life cycle trend in party support. Findings indicate only limited support for the generational replacement hypothesis with support for the impact of period effects occurring in over 70% of the Congresses analyzed.
Clarifying the Relationship Between Education and Turnout
Authors: Jackson Robert A.
Published: March 2007

This study explores the influence of education on turnout. Although the basic relationship is well established, previous research has failed to investigate adequately the underlying causal mechanisms. In this study, four of the most prominent explanations are addressed: (a) education instills a sense of civic duty, (b) education increases sense of political efficacy, (c) education makes registration easier, and (d) education enhances political sophistication or awareness. Although each explanation has some merit, causal modeling reveals that education's positive influence on registration likelihood and political awareness is especially important in accounting for its relationship to turnout.
Presidential Use of Executive Orders, 1953-1994
Authors: Krause George A. , Cohen David B.
Published: March 2007

The frequency with which presidents issue executive orders is an important area of inquiry for students of executive politics, because this instrument can shape policy in a quick, direct manner that is outside the purview of the legislative arena. We construct a probabilistic-based empirical model that is used to explain variation in the number of presidential executive orders issued during the 1953-1994 annual period. Using event count regression techniques, these results indicate that the use of executive orders by presidents is significantly related to the legislative success they enjoy, the partisan composition of Congress, macroeconomic conditions, and the rate of growth in federal executive branch employment. The main implication of the study is that a president's willingness to issue executive orders is significantly related to a combination of legislative, public prestige, and managerial/institutional considerations. Thus, presidential use of executive orders is conditioned on different types of causal factors, and not solely attributable to the "institutionalized presidency" or legislative relations with Congress, as suggested in previous research on the topic.
Participation in the 1990 Decennial Census
Authors: Couper Mick P. , Singer Eleanor , Kulka Richard A.
Published: March 2007

Theoretical perspectives on survey participation suggest that survey participation is a form of community involvement, reflecting a sense of civic obligation that also motivates such behavior as voting, serving on juries, and paying taxes. Using data from the Survey of Census Participation (SCP), we investigate this hypothesis with respect to mail response to the 1990 census. We examine such motivating factors as structural and attitudinal measures of alienation as well as more proximal measures of knowledge of and attitudes toward the census and concerns about privacy and confidentiality. We also examine a variety of constraining factors, including literacy, facility with the English language, and available time to complete the form. Using multivariate analysis, we explore the relative effects of these factors on the likelihood of returning the completed census form by mail and discuss the implications of our findings for participation in the census and political participation more generally.
Money or the Machine
Authors: Gierzynski Anthony , Kleppner Paul , Lewis James
Published: March 2007

This article presents results of a study of the impact of money on Chicago city council elections in 1991 and 1995 Chicago, with its reputation for strong party organizations, would be the last place most people would expect to find campaign expenditures playing an important role To our surprise, however, the results of the analysis indicate that campaign spending is related to candidates' vote share Even Chicago, it seems, has not escaped the trend toward cash-based, candidate-centered campaigns.
Traditional Peoples and the Circle of Healing
Authors: Freeman Lynda W. , Morgan Robert , Farquhar Tom
Published: March 2007

In March 2002, the White House Commission on Complementary and Alternative Medicine Policy will present its recommendations to President Bush on CAM education, training, licensing, coordination of research, dissemination of informa tion, access and delivery of services. The Commission's report will have implica tions for the medical care of indigenous peoples. This article discusses traditional healing in Alaska and responds to Commission questions on traditional healer designation, selection, credentialing, licensing, preservation and the potential integration of traditional healing with conventional care. Philosophy underlying allopathic medicine and traditional healing is explained. An integrative model of care, The Circle of Healing, is described. "We are rebels, someone to flout. They drew a square that shut us out. But love and we had the will to win. We drew a circle that let them in." (Anonymous, 1997)
Chronic Akinetic Mutism After Mesencephalic-Diencephalic Infarction: Remediated with Dopaminergic Medications
Authors: Alexander Michael P.
Published: March 2007

Objective: Akinetic mutism (AKM) is an uncommon disorder with a complex neuropathology. There is no generally accepted treatment, and it is not known if late treatments are effective. The relationship between AKM and abulia is uncertain. Methods: The effects of dopaminergic treatment of a patient with chronic AKM after discrete bilateral infarctions of the mesencephalic ventral tegmental area and the lat eral hypothalamus were studied with motor measures, the Functional Independence Measure (FIM), and neuropsychological tests. Results: Treatment with a combination of carbidopa/levodopa and pergolide produced prompt amelioration of AKM with dra matic and rapid improvement in FIM. An apathetic, amotivational state persisted de spite resolution of akinesia and normal frontal executive functions. Conclusions: AKM may respond to dopaminergic treatment even after months of severe akinesia. The mechanism of abulia is more complex than simply a partial dopaminergic deficiency state and may persist even when AKM is treated and frontal cognitive functions are normal. Key Words: Akinetic mutism—Dopamine—Abulia.
The Basis of Anglican Fellowship: Some Challenges for Today
Authors: Sykes Stephen
Published: March 2007

This article examines a central concern for the Anglican Communion, namely how a Communion without a strong central authority structure can maintain its unity in the face of potentially church-dividing issues. At present the major such issue relates to human sexuality, but the underlying problem itself is not new, and the article draws a parallel with the Kikuyu controversy of 1913 and subsequent years. The author questions the customary practice of beginning from a universal doctrine of the Church and seeing it as ‘translated’ or ‘inculturated’ into a diversity of contexts. He argues that the New Testament pattern is different. There, the experience of a variety of local churches is the starting point. Drawing on the terminology of the political philosopher Michael Walzer, he designates the local embodiment of the Church as ‘thick’ and its universal expression as ‘thin’. The concrete local embodiments of the Church should be our conceptual starting point, not an idealized picture of the Church universal.
The Interaction of Crystallinity, Elastoplasticity, and a Two-Phase Model on Blown Film Bubble Shape
Authors: Campbell G.A. , Cao B.
Published: March 2007

Historically, simulations of the blown film process have been carried out only to the freeze line; a point which is often well below the actual frost line for the process. This limitation in previous simulations was discovered to be related to the interaction of the process boundary conditions with the rheological equation of state used in previous analyses to represent the stretching of the polymer film. A new approach has been developed that allows the process to be simulated to the real frost line. This has been accomplished by using a two-phase model incorporating viscoplasticity and crystallization of the polymer melt into the physical description of the blown film process. Prediction of the bubble shape, temperature, and velocity from the die to the frost line agree fairly well with experimental data. By improving the rheological models used in the simulation, this approach has the potential of being able to pre dict physical properties of polymeric film from molecular and process parameters.
Sensory Descriptors for a Taint in Water Packed in Test Pouches Made of Polyethylene Lined Aluminium
Authors: Linssen Jozef P. H. , Janssens Johanna L. G. M. , Roozen Jacques R. , Posthumus Maarten A.
Published: March 2007

A panel of 48 assessors evaluated a taint in water, packed in test pouches made of low density polyethylene (LDPE) lined aluminium. This panel agreed upon eight descriptive attributes (in Dutch): metallic (metaal), syn thetic (synthetisch), dry (droog), rough (stroef), astringent (wrang), musty (muf), sickly (wee) and penetrating (doordringend). Fourteen assessors, selected with a standard triangle test, were asked to judge intensities for these attri butes on a visual analogue scale. Factor analysis reduced the original data- matrix to a six dimensional one losing only 6.4% of the original variance. Syn thetic and penetrating loaded high on one factor as well as rough and astringent on another one. Musty, sickly, metallic and dry loaded high on sepa rate factors.

Direct dynamic headspace analysis of the LDPE-lined test pouches gave mainly peaks of branched alkanes of 12 carbon atoms. However, dynamic head space analysis of water in contact with the LDPE layer of the test pouches showed no alkanes but (C4 - C11) aldehydes and ketones.
Cryogenic Impact Properties of Medical Packaging Films
Authors: Woo Lecon , Ling Michael T. K.
Published: March 2007

In many transport and storage situations, medical packages are exposed to cryogenic conditions. In this article we describe the impact behavior of many of the commonly used medical film materials as a function of tempera ture from about —140 to + 20 ° C. High speed stress-strain data were generated on an instrumented impact tester fitted with a cryogenic sample conditioning chamber. In addition, the observed impact properties were correlated to the Dynamic Mechanical spectrum to provide better understanding of the molec ular basis for physical property behavior.
Environmentally Friendly Films Made With a New Family of Linear Ethylene Polymers
Authors: Halle Richard W.
Published: March 2007

The public's ever-increasing environmental consciousness is driv ing the plastics packaging industry to constantly consider the complete life cy cle of their products. One avenue by which packaging film producers are responding to the "green" movement is by manufacturing polyolefin-based films containing Post-Consumer Recycled (PCR) polyolefins. These types of films are commercial in a wide variety of end uses, many of which have been tradition ally serviced by films made from high pressure process-low density polyethyl ene (HRLDPE). One obvious technical approach toward improving on this effort is to produce a film having as high a recycle content as possible but with a strength and toughness similar to that of the original HP-LDPE films. Any polymer which could effectively incorporate very high (50% +) levels of PCR into these type films would be of significant interest to the industry.

Several new linear ethylene polymers have been used to increase the recycle content of these type films to very high levels while maintaining good film toughness properties. A series of blown films produced during an early screen ing study demonstrated the good physical properties and acceptable processing characteristics of these high PCR content blends containing these unique linear ethylene polymers.
The Anomalous Beasts: Hooligans and the Sociology of Education
Authors: Delamont Sara
Published: March 2007

This paper argues that the subspecialism of sociology of education has, for a century, been ambivalent about the `hooligan'. It has both celebrated and excoriated the anti-school working-class boy. Similarly, the mainstream of sociology has been ambivalent about sociologists of education, both relying on them and ignoring them. Thirdly, the paper speculates on the position of hooligans in Britain in 2025 and the relationship between mainstream sociology and the sociology of education in that year.
`The Same People in the Same Places'? Socio-Spatial Identities and Migration in Youth
Authors: Jones Gill
Published: March 2007

Concern is expressed about the demise of rural communities resulting from processes of out-migration of young people and in-migration of newcomers. Youth out-migration is the result of a combination of structural and motivational factors. Here the relationship between agency and structure in explaining migration behaviour is explored through the study of one factor: the development of socio-spatial identities in youth. This is of interest not only as a facet of identity construction in childhood and youth, the product of an internal-external dialectic, but also because it appears to represent, alongside structural factors such as local disadvantage, an important but under-recognised factor influencing migration or staying-on decisions among young people brought up in rural communities. Here, the construction of socio-spatial identities, the respective roles of the community and the individual in processes of inclusion and exclusion, inter-generational processes of social reproduction and, finally, the relationship between identity and migration behaviour are explored through the accounts of young people from the Scottish Borders.
Job Scarcity: The Perverted Form of a Potential Blessing
Authors: Bowring Finn
Published: March 2007

This article advances the argument that we are becoming a post-work society, and that the restoration of work-centred society is an irrational and untenable goal. I consider the phenomenon of jobless growth and suggest that the economy's declining need for labour is underestimated due to the influence of three factors: a statistical dependence on jobs held rather than hours worked; the growth of socially unproductive personal services; and the growth of destructive, defensive and unsustainable forms of production. I show that the decentring of work in people's lives is a process well under way, and conclude that the `crisis' of work-based society derives not from the scarcity of work, but from a theoretical and practical failure to give the decline of work a human meaning.
How cost-effective is screening for abdominal aortic aneurysms?
Authors: Kim L G , Thompson S G , Briggs A H , Buxton M J , Campbell H E
Published: March 2007

Objective: To provide reliable estimates of the long-term cost-effectiveness of abdominal aortic aneurysm screening in men.

Methods: A Markov health economic decision model for screening is described and extrapolated to 30 years. The strategy modelled involves a one-off scan at age 65 years, with annual and three-monthly follow-up scans for small and medium aneurysms, respectively. Referral for elective surgery occurs at an aortic diameter of 5.5 cm. Model parameters are estimated from patient-level data from the UK Multi-centre Aneurysm Screening Study. Model structure is validated on this trial's data, and input parameter uncertainty is addressed by probabilistic sensitivity analysis. Costs and life-years gained are obtained for both screening and no systematic screening strategies.

Results: Cost-effectiveness improves dramatically when considered over longer timescales. Taking a 30-year perspective, screening for abdominal aortic aneurysms in men is highly cost-effective at £2320 per life-year gained (95% uncertainty interval: £1600 to £4240). Adjusting life-years for the age-specific health-related quality of life experienced in this population gave a figure of £2970 (95% uncertainty interval: £2030 to £5430) per quality-adjusted life-year gained. The additional cost of screening the UK male population is estimated to be £19 m per year.

Conclusions: The long-term cost-effectiveness of screening for abdominal aortic aneurysms in men is highly attractive and this evidence provides further support for a national screening programme in the UK.
New Mechanism of Selective Killing of Activated Hepatic Stellate Cells
Authors: Dodig Milan , Mullen Kevin D.
Published: March 2007

Background & Aims: Hepatic stellate cells play an important role in liver fibrogenesis, and hepatic stellate cell death may be involved in the termination of this response. Methods: Molecular mechanisms of hepatic stellate cell killing were studied in hepatic stellate cell/Kupffer cell cocultures. Results: Lipopolysaccharide stimulation of hepatic stellate cell/Kupffer cell cocultures, but not of hepatic stellate cell monocultures, induced profound alterations of hepatic stellate cell morphology and hepatic stellate cell death. Kupffer cell–induced hepatic stellate cell killing required hepatic stellate cell/Kupffer cell contacts and was prevented by dexamethasone, prostaglandin E(2), tumor necrosis factor–related apoptosis–inducing ligand (TRAIL) receptor 2 antagonists, and down–regulation of receptor–interacting protein, but not by antioxidants, tumor necrosis factor receptor, or CD95 antagonists. Hepatic stellate cell death was characterized by activation of caspases 3, 8, and 9, terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick–end labeling negativity, lack of gross calcium overload, and TRAIL trafficking to the plasma membrane. Inhibition of caspase 9, but not of caspases 3, 8, or 10, prevented hepatic stellate cell death. Lipopolysaccharide induced a dexamethasone– and prostaglandin E(2)–sensitive expression of TRAIL in Kupffer cells. TRAIL receptors 1 and 2, FLIP (caspase 8–inhibitory protein), and receptor–interacting protein were up–regulated during hepatic stellate cell transformation; however, TRAIL addition did not induce hepatic stellate cell death. Hepatic stellate cell susceptibility toward Kupffer cell–induced death paralleled receptor–interacting protein and TRAIL–receptor expression levels. Conclusions: Activated Kupffer cell can effectively kill hepatic stellate cell by a caspase 9– and receptor–interacting protein–dependent mechanism, possibly involving TRAIL. The data may suggest a novel form of hepatic stellate cell death.
Are Cultured Liver Cells the Right Tool to Investigate Mechanisms of Liver Disease or Hepatotoxicity?
Authors: Jaeschke Hartmut
Published: March 2007

Microarray technology allows the simultaneous analysis of mRNA expression levels of thousands of genes. In the field of toxicogenomics, this technology could help to identify potentially unsafe compounds based on the changes in mRNA expression patterns they induce. Rodent in vivo and in vitro systems are currently the experimental models of choice for predictive toxicology, especially in early phases of development. This study characterizes several hepatic in vitro systems based on mRNA expression profiles, comparing them to gene expression in liver tissue. The in vitro systems investigated comprise two rat liver cell lines (BRL3A and NRL clone 9), primary hepatocytes in conventional monolayer or in sandwich culture, and liver slices. The results demonstrate that liver slices exhibit the strongest similarity to liver tissue regarding mRNA expression, whereas the two cell lines are quite different from the whole liver. We were able to identify genes with strong changes in expression levels in all or at least one of the in vitro systems relative to whole liver. In particular, for some cytochrome P450s the differences observed on the mRNA expression level were paralleled by protein expression and enzymatic activity. In addition, the effect of time in culture was assessed. We were able to show a profound effect of the duration of culture. Expression patterns change most rapidly soon after cell isolation and culture initiation and stabilize with time in culture. The findings are discussed with respect to the usefulness of the various hepatic in vitro systems for microarray–based toxicological testing of compounds.
Overexpression of cholesterol transporter StAR increases In Vivo rates of bile acid synthesis in the rat and mouse
Authors: Ren Shunlin , Hylemon Phillip B. , Marques Dalila , Gurley Emily , Bodhan Patricia , Hall Elizabeth , Redford Kaye , Gil Gregorio , Pandak William M.
Published: March 2007

Bile acid synthesis (BAS) occurs mainly via two pathways: the “neutral” pathway, which is initiated by highly regulated microsomal CYP7A1, and an “acidic” pathway, which is initiated by mitochondrial CYP27A1. Previously, we have shown that overexpression of the steroidognic acute regulatory protein (StAR), a mitochondrial cholesterol transport protein, increases bile acid biosynthesis more than 5-fold via the acidic pathway in primary rat hepatocytes. This observation suggests that mitochondrial cholesterol transport is the ratelimiting step of BAS via this pathway. The objective of this study was to determine the effect of increased StAR on rates of BAS in vivo. Overexpression of StAR and CYP7A1 were mediated via infection with recombinant adenoviruses. BAS rates were determined in chronic biliary-diverted rats and mice, and in mice with an intact enterohepatic circulation. The protein/messenger RNA levels of StAR and CYP7A1 increased dramatically following overexpression. Overexpression of StAR or CYP7A1 led to a similar 2-fold (P < .01) increase in BAS over up-regulated (approximately 2-fold) 3-day chronic biliary-diverted control rats. Additionally, overexpression of StAR led to more than 3- and 6-fold increases over controls in the rates of BAS in biliary-diverted and intact mice, respectively (P < .01). In conclusion, in both rats and mice in vivo, overexpression of StAR led to a marked increase in the rates of BAS initiated by delivery of cholesterol to mitochondria containing CYP27A1. (Hepatology 2004;40:910-917).
Bile acids induce mitochondrial ROS, which promote activation of receptor tyrosine kinases and signaling pathways in rat hepatocytes
Authors: Fang Youwen , Han Song Iy , Mitchell Clint , Gupta Seema , Studer Elaine , Grant Steven , Hylemon Phillip B. , Dent Paul
Published: March 2007

Previous studies have demonstrated in hepatocytes that deoxycholic acid (DCA) promotes inactivation of protein tyrosine phosphatases (PTPases) and activation of ERBB1 and the extracellular-regulated kinase (ERK) 1/2 pathway. The present studies have determined the biochemical mechanism(s) through which these events occur. DCA and taurodeoxycholic acid (TDCA) (100 μmol/L) caused activation of ERBB1, insulin receptor, and the ERK1/2 and AKT pathways in primary rodent hepatocytes. DCA- and TDCA-induced receptor and signaling pathway activations were blocked by the reactive oxygen species (ROS) scavengers N-acetyl cysteine (NAC) and Trolox (TX), as well as by cyclosporin A (CsA) and bongkrekic acid (BKA). DCA activated the ERK1/2 pathway in HuH7 human hepatoma cells that was blocked by the incubation of cells with an ERBB1 inhibitor, NAC, TX, CsA, or BKA. DCA did not activate the ERK1/2 pathway in mitochondria-defective HuH7 Rho 0 cells. In HuH7 cells and primary hepatocytes, DCA enhanced the production of ROS, an effect that was abolished in Rho 0 cells and by prior incubation of cells with CsA or BKA. In hepatocytes and HuH7 cells, DCA inhibited PTPase activity. Incubation of hepatocytes with either CsA or BKA prevented DCA-induced inhibition of PTPase activity. Loss of mitochondrial function in Rho 0 cells also abolished the inhibitory effects of DCA on PTPase activity. In conclusion, DCA and TDCA cause ROS generation in hepatocytes that is dependent on metabolically active mitochondria. The generation of ROS is essential for PTPase inactivation, receptor tyrosine kinase activation, and enhanced signaling down the ERK1/2 and AKT pathways. (Hepatology 2004;40:961-971).
Evidence for the dissociation of the hepatobiliary MRI contrast agent Mn‐DPDP
Authors: Gallez Bernard , Bacic Goran , Swartz Harold M.
Published: March 2007

These experiments assessed and quantitated the release of free manganese Mn++ from the hepatobiliary contrast agent Mn‐DPDP (manganese dipyridoxal diphosphate), using several magnetic resonance techniques (EPR spectroscopy, 31P‐NMR spectroscopy, and relaxometry) to differentiate between free Mn++ and Mn++ in complexes in various preparations. The presence of calcium and magnesium in physiological concentrations in aqueous solutions induced the release of Mn++ from the complex, as did incubation of the complex in liver homogenates. After intravenous injection of 15 μmol/kg of Mn‐DPDP, both EPR and 31P‐NMR spectroscopy demonstrated that Mn‐DPDP is partly dissociated (approximately 25%) in the liver. By comparing in vitro and ex vivo data from the liver, we concluded that the dissociation of Mn‐DPDP occurs primarily in the liver, whereas a minor portion of the dissociated Mn found in the liver comes from dissociation of the complex in the blood. Most of the dissociated Mn in liver becomes bound to macromolecules and is responsible for the enhancement of relaxivity observed with this agent.
Perfusion changes in human skeletal muscle during reactive hyperemia measured by echo‐planar imaging
Authors: Toussaint Jean‐François , Kwong Kenneth K. , M′Kparu Fidelis , Weisskoff Robert M. , Laraia Paul J. , Kantor Howard L.
Published: March 2007

Muscle performance is markedly influenced by tissue perfu‐sion. Techniques that allow quantification of microvascular flow are limited by the use of ionizing radiation. In this investigation, we apply an NMR model previously developed by Detre ef al. to the measurement of human muscle perfusion during reactive hyperemia. We compare our results with conventional plethysmography adapted to NMR. Using echo‐planar imaging, T1 and T2 were measured in 14 subjects during rest, ischemia, and reactive hyperemia. Mean leg muscle T1 in healthy volunteers is 850 ms at rest and 834 ms at reperfusion, leading to a calculated reactive hyperemia flow increase (T1 flow) of 103 ± 40 ml/100 ml/min. T1 flows correlate well with NMR‐plethysmography values. Changes in T2, which are sensitive to both deoxyhemoglobin content and vessel diameter variations, are also correlated with perfusion measurements. T1 changes allow quantification of regional perfusion in human muscle during reactive hyperemia.
Perfusion imaging with compensation for asymmetric magnetization transfer effects
Authors: Pekar James , Jezzard Peter , Roberts David A. , Leigh John S. , Frank Joseph A. , McLaughlin Alan C.
Published: March 2007

The effects of off‐resonance radio‐frequency irradiation on the intensity of the MR signal from water protons in the cat brain are asymmetric around the chemical shift of the water signal. This asymmetry, which could arise from a shift in the magnetization transfer spectrum ˜1.5 ppm upfield from the solvent water signal, must be taken into account to compensate for magnetization transfer effects inherent in arterial spin tagging approaches that use a single radio‐frequency coil. Two approaches that either correct for, or circumvent, the apparent upfield shift of the magnetization transfer spectrum are presented, and a perfusion image of the cat brain, using flow‐induced adiabatic inversion of arterial water protons, is presented. Other problems in obtaining quantitative cerebral blood flow values using the arterial spin tagging approach are discussed.
Reperfused ischemia of the rat intestine: Detection by MR imaging with polylysine‐Gd‐DTPA enhancement
Authors: Mottet Isabelle , van Beers Bernard E. , Delos Monique , Goudemant Jean‐François , Jamart Jacques , Demeure Roger , Pringot Jacques
Published: March 2007

To detect reperfused ischemia of the rat intestine, T2‐weighted spin‐echo images were acquired, followed by T1‐weighted images before and after administration of polylysine‐Gd‐DTPA or Gd‐DTPA. Before administration of the contrast agent, the reperfused intestine was hyperintense on T2‐weighted images, and to a lesser extent on T1‐weighted images. After administration of polylysine‐Gd‐DTPA, the reperfused intestine enhanced more than the normal one, giving a significantly better contrast‐to‐noise (CNR) ratio than on unenhanced images. Gd‐DTPA induced the same enhancement of the reperfused and the normal intestine and the CNR was lower than on unenhanced T2‐weighted images. Reperfused intestinal ischemia could thus be better detected on polylysine‐Gd‐DTPA‐enhanced MR images than on unenhanced images or on Gd‐DTPA‐ enhanced images.
Noninvasive measurement of protein concentration
Authors: Jiao Xiaoqi , Bryant Robert G.
Published: March 2007

At selected magnetic field strengths, protein and water proton spin‐lattice relaxation rates are sensitive to the concentration of rotationally immobilized peptide nitrogen because of field dependent heteronuclear cross relaxation coupling between protein proton and nitrogen‐14 spins that is carried to the water by proton homonuclear cross‐relaxation. Measurement of the water proton spin‐lattice relaxation time, or a signal amplitude proportional to it, may provide a noninvasive measure of peptide bond concentration, which provides a direct measure of immobilized protein content in most tissues. The approach using protein gels in two magnetic field strengths is demonstrated. At 66.7 mT, the proton Zeeman energy matches one of the peptide nitrogen transitions dominated by the unaveraged nuclear electric quadrupole interaction; cross‐relaxation between the protons and nitrogen‐14 is efficient At 77.5 mT, the proton Zeeman energy is not matched with the nitrogen energy and proton‐nitrogen cross‐relaxation is not efficient. It is shown that the difference in the water proton spin‐lattice relaxation rates on and off the energy level match condition is a linear function of the rotation‐ally immobilized protein concentration.
Effects of osmotically driven cell volume changes on diffusion‐weighted imaging of the rat optic nerve
Authors: Anderson Adam W. , Zhong Jianhui , Petroff Ognen A. C. , Szafer Aaron , Ransom Bruce R. , Prichard James W. , Gore John C.
Published: March 2007

The apparent diffusion coefficient (ADC) of the rat optic nerve was measuredIn vitro, using magnetic resonance imaging, to determine the effects of changes in cellular volume fraction on the diffusion of tissue water. Nerve ADC was determined under conditions of cell membrane depolarization and (i) increased intracellular volume, (ii) decreased intracellular volume, and (iii) negligible volume change. Depolarization alone had little affect on ADC, whereas volume changes produced strong, reversible effects. Increased cell volume decreased ADC andvice versa. These results are consistent with the view that changes in the extracellular space are the major source of ADC changes in brain tissue.
Comparison of ultrafast dipyridamole magnetic resonance imaging with dipyridamole sestamibi SPECT for detection of perfusion abnormalities in patients with one‐vessel coronary artery disease: Assessment by quantitative model fitting
Authors: Matheijssen Niels A. A. , Louwerenburg Hans W. , van Rugge F. Paul , Arens Ruud Pj. H. , Kauer Ben , de Roos Albert , van der Wall Ernst E.
Published: March 2007

The value of ultrafast MRI for detection of myocardial perfusion abnormalities in patients with coronary artery disease (CAD) was assessed in 10 patients with stable angina pectoris and angiographically proven one‐vessel CAD using double‐level short‐axis ultrafast MRI with bolus injection of gadolinium‐DTPA and tomographic technetium‐99m SestaMIBI imaging (SPECT) during dipyridamole‐induced coronary hy‐peremia. Abnormally perfused regions were assessed with SPECT and MRI in all (100%) patients. Agreement in localization between arteriography and SPECT was 80%; between arteriography and MR, 70%; and between SPECT and MR, 90%. The signal intensity increase after the bolus injection of gadolinium‐DTPA using a linear fit, and the slope of gado‐linium‐DTPA wash‐in using double exponential model fitting were significantly different between abnormally and normally perfused regions. These preliminary results demonstrate the potential of dipyridamole ultrafast MR to monitor stress‐induced flow maldistribution in patients with single vessel CAD.
Calibration of the radio frequency field for magnetic resonance imaging
Authors: Foxall David L. , Hoppel Bernice E. , Hariharan Hari
Published: March 2007

We have developed and validated the performance of a novel slice selective pulse sequence that allows direct calibration of the RF field using a simple rectangular pulse. The new sequence offers a number of substantial advantages. It operates at steady state and has an accurate calibration response at short repetition times. The slice selection train is insensitive to RF field strength changes caused by patient loading. The issue of patient motion has been addressed in our data collection and analysis routines. The applicability of the method to human scanning has been demonstrated in the automated RF power calibration routine of a commercial imaging system.
A new ytterbium chelate as contrast agent in chemical shift imaging and temperature sensitive probe for MR spectroscopy
Authors: Aime Silvio , Botta Mauro , Fasano Mauro , Terreno Enzo , Kinchesh Paul , Calabi Luisella , Paleari Lino
Published: March 2007

A paramagnetic Yb(lll) complex that is the prototype of a novel class of probes for MRI and MRS has been developed. The complex displays highly shifted 1H resonances that are characterized by short relaxation times and, as such, may prove to be a valuable alternative in applications that currently require fluorine‐containing probes. Selective excitation of the para‐magnetically shifted resonances allows the spatial distribution of the complex to be mapped. This communication reports the images that were obtained by selectively exciting the most intense methyl group (−14.2 ppm at 27°C) for complex concentrations ranging from 0.003−0.1 M. Spectroscopically, the complex may be used as a temperature probe since the proton chemical shifts exhibit a strong temperature dependence. In human serum the chemical shift difference of a selected pair of proton resonances was observed to follow a gradient of −0.42 ± 0.01 ppm/°C. Furthermore, since the chemical shift of the methyl resonance displays a temperature coefficient of −0.04 ± 0.01 ppm/°C, it should be possible to use the image phase for thermal mapping.