bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional verification of task partitioning for multiprocessor embedded systems
Authors: Das Dipankar , Chakrabarti P. P. , Kumar Rajeev
Published: October 2007

With the advent of multiprocessor embedded platforms, application partitioning and mapping have gained primacy as a design step. The output of this design step is a multithreaded partitioned application where each thread is mapped to a processing element (processor or ASIC) in the multiprocessor platform. This partitioned application must be verified to be consistent with the native unpartitioned application. This verification task is called application (or task) partitioning verification.

This work proposes a code-block-level
containment-checking
-based methodology for application partitioning verification. We use a UML-based code-block-level modeling language which is rich enough to model most designs. We formulate the application partitioning verification problem as a special case of the containment checking problem, which we call the
complete containment checking problem
. We propose a state space reduction technique specific to the containment checking, reachability analysis, and deadlock detection problems. We propose novel data structures and token propagation methodologies which enhance the efficiency of containment checking. We present an efficient containment checking algorithm for the application partitioning verification problem. We develop a containment checking tool called TraceMatch and present experimental results. We present a comparison of the state space reduction achieved by TraceMatch with that achieved by formal analysis and verification tools like Spin, PEP, PROD, and LoLA.
Incremental hierarchical memory size estimation for steering of loop transformations
Authors: Hu Q. , Kjeldsberg P. G. , Vandecappelle A. , Palkovic M. , Catthoor F.
Published: October 2007

Modern embedded multimedia and telecommunications systems need to store and access huge amounts of data. This becomes a critical factor for the overall energy consumption, area, and performance of the systems. Loop transformations are essential to improve the data access locality and regularity in order to optimally design or utilize a memory hierarchy. However, due to abstract high-level cost functions, current loop transformation steering techniques do not take the memory platform sufficiently into account. They usually also result in only one final transformation solution. On the other hand, the loop transformation search space for real-life applications is huge, especially if the memory platform is still not fully fixed. Use of existing loop transformation techniques will therefore typically lead to suboptimal end-products. It is critical to find all interesting loop transformation instances. This can only be achieved by performing an evaluation of the effect of later design stages at the early loop transformation stage.

This article presents a fast incremental hierarchical memory-size requirement estimation technique. It estimates the influence of any given sequence of loop transformation instances on the mapping of application data onto a hierarchical memory platform. As the exact memory platform instantiation is often not yet defined at this high-level design stage, a platform-independent estimation is introduced with a Pareto curve output for each loop transformation instance. Comparison among the Pareto curves helps the designer, or a steering tool, to find all interesting loop transformation instances that might later lead to low-power data mapping for any of the many possible memory hierarchy instances. Initially, the source code is used as input for estimation. However, performing the estimation repeatedly from the source code is too slow for large search space exploration. An incremental approach, based on local updating of the previous result, is therefore used to handle sequences of different loop transformations. Experiments show that the initial approach takes a few seconds, which is two orders of magnitude faster than state-of-the-art solutions but still too costly to be performed interactively many times. The incremental approach typically takes just a few milliseconds, which is another two orders of magnitude faster than the initial approach. This huge speedup allows us for the first time to handle real-life industrial-size applications and get realistic feedback during loop transformation exploration.
Compilation for compact power-gating controls
Authors: You Yi-Ping , Huang Chung-Wen , Lee Jenq Kuen
Published: October 2007

Power leakage constitutes an increasing fraction of the total power consumption in modern semiconductor technologies due to the continuing size reductions and increasing speeds of transistors. Recent studies have attempted to reduce leakage power using integrated architecture and compiler power-gating mechanisms. This approach involves compilers inserting instructions into programs to shut down and wake up components, as appropriate. While early studies showed this approach to be effective, there are concerns about the large amount of power-control instructions being added to programs due to the increasing amount of components equipped with power-gating controls in SoC design platforms. In this article we present a
sink-n-hoist
framework for a compiler to generate balanced scheduling of power-gating instructions. Our solution attempts to merge several power-gating instructions into a single compound instruction, thereby reducing the amount of power-gating instructions issued. We performed experiments by incorporating our compiler analysis and scheduling policies into SUIF compiler tools and by simulating the energy consumption using Wattch toolkits. The experimental results demonstrate that our mechanisms are effective in reducing the amount of power-gating instructions while further reducing leakage power compared to previous methods.
Adaptive correctness monitoring for wireless sensor networks using hierarchical distributed run-time invariant checking
Authors: Herbert Douglas , Sundaram Vinaitheerthan , Lu Yung-Hsiang , Bagchi Saurabh , Li Zhiyuan
Published: October 2007

This article presents a hierarchical approach for detecting faults in wireless sensor networks (WSNs) after they have been deployed. The developers of WSNs can specify “invariants” that must be satisfied by the WSNs. We present a framework, Hierarchical SEnsor Network Debugging (H-SEND), for lightweight checking of invariants. H-SEND is able to detect a large class of faults in data-gathering WSNs, and leverages the existing message flow in the network by buffering and piggybacking messages. H-SEND checks as closely to the source of a fault as possible, pinpointing the fault quickly and efficiently in terms of additional network traffic. Therefore, H-SEND is suited to bandwidth or communication energy constrained networks. A specification expression is provided for specifying invariants so that a protocol developer can write behavioral level invariants. We hypothesize that data from sensor nodes does not change dramatically, but rather changes gradually over time. We extend our framework for the invariants that includes values determined at run-time in order to detect data trends. The value range can be based on information local to a single node or the surrounding nodes' values. Using our system, developers can write invariants to detect data trends without prior knowledge of correct values. Automatic value detection can be used to detect anomalies that cannot be detected in existing WSNs. To demonstrate the benefits of run-time range detection and fault checking, we construct a prototype WSN using CO
2
and temperature sensors coupled to Mica2 motes. We show that our method can detect sudden changes of the environments with little overhead in communication, computation, and storage.
The role of roles in supporting reconfigurability and fault localizations for open distributed and embedded systems
Authors: Ren Shangping , Yu Yue , Chen Nianen , Tsai Jeffrey J.-P. , Kwiat Kevin
Published: October 2007

One of the main characteristics of open distributed embedded systems is that the involved entities are often very dynamic—different individual entities may join or leave the systems frequently. Therefore, systems built of these dynamic entities must be runtime reconfigurable. In addition, large classes of open embedded systems often have high availability and dependability requirements. However, the openness makes these requirements more difficult to achieve and the system more vulnerable to attacks.

This article presents a coordination model, the Actor, Role and Coordinator (ARC) model, that aims to support reconfigurability and fault localization for open distributed embedded software systems. In particular, the actor model is used to model concurrent embedded entities, while the system's reconfigurability and dependability requirements are encapsulated within coordination objects: roles and coordinators, and are achieved through coordination among the actors. Roles, as a key thrust in the ARC model not only represent an abstraction for a set of behaviors shared by a group of actors so that reconfiguration within the roles becomes transparent to entities outside the roles, but also assume coordination responsibilities among the member actors. The article also argues from both analytical and empirical perspectives that with the support of the role, faults can be localized within actors, and actor level reconfiguration becomes transparent to the system.
Program-ing finger trees in C
oq
Authors: Sozeau Matthieu
Published: October 2007

Finger Trees (Hinze & Paterson, 2006) are a general purpose persistent data structure with good performance. Their genericity permits developing a wealth of structures like ordered sequences or interval trees on top of a single implementation. However, the type systems used by current functional languages do not guarantee the coherent parameterization and specialization of Finger Trees, let alone the correctness of their implementation. We present a certified implementation of Finger Trees solving these problems using the Program extension of Coq. We not only implement the structure but also prove its invariants along the way, which permit building certified structures on top of Finger Trees in an elegant way.
Experience report
Authors: Wazny Jeremy
Published: October 2007

C-Rules is a business rules management system developed by Constraint Technologies International
1
(CTI), designed for use in transportation problems. Users define rules describing various aspects of a problem, such as solution costs and legality, which are then queried from a host application, typically an optimising solver. At its core, C-Rules provides a functional expression language which affords users both power and flexibility when formulating rules. In this paper we will describe our experiences of using functional programming both at the end-user level, as well as at the implementation level. We highlight some of the benefits we, and the product's users, have enjoyed from the decision to base our rule system on features such as: higher-order functions, referential transparency, and static, polymorphic typing. We also outline some of our experiences in using Haskell to build an efficient compiler for the core language.
On Barron and Strachey's cartesian product function
Authors: Danvy Olivier , Spivey Michael
Published: October 2007

Over forty years ago, David Barron and Christopher Strachey published a startlingly elegant program for the Cartesian product of a list of lists, expressing it with a three nested occurrences of the function we now call
foldr
. This program is remarkable for its time because of its masterful display of higher-order functions and lexical scope, and we put it forward as possibly the first ever functional pearl. We first characterize it as the result of a sequence of program transformations, and then apply similar transformations to a program for the classical power set example. We also show that using a higher-order representation of lists allows a definition of the Cartesian product function where
foldr
is nested only twice.
Tangible functional programming
Authors: Elliott Conal M.
Published: October 2007

We present a user-friendly approach to unifying program creation and execution, based on a notion of "tangible values" (
TVs
), which are visual and interactive manifestations of pure values, including functions. Programming happens by gestural composition of TVs. Our goal is to give end-users the ability to create parameterized, composable content without imposing the usual abstract and linguistic working style of programmers. We hope that such a system will put the essence of programming into the hands of many more people, and in particular people with artistic/visual creative style.

In realizing this vision, we develop algebras for visual presentation and for "deep" function application, where function and argument may both be nested within a structure of tuples, functions, etc. Composition gestures are translated into chains of combinators that act simultaneously on statically typed values and their visualizations.
Termination analysis and call graph construction for higher-order functional programs
Authors: Sereni Damien
Published: October 2007

The analysis and verification of higher-order programs raises the issue of control-flow analysis for higher-order languages. The problem of constructing an accurate call graph for a higher-order program has been the topic of extensive research, and numerous methods for flow analysis, varying in complexity and precision, have been suggested.

While termination analysis of higher-order programs has been studied, there has been little examination of the impact of call graph construction on the precision of termination checking. We examine the effect of various control-flow analysis techniques on a termination analysis for higher-order functional programs. We present a termination checking framework and instantiate this with three call graph constructions varying in precision and complexity, and illustrate by example the impact of the choice of call graph construction.

Our second aim is to use the resulting analyses to shed light on the relationship between control-flow analyses. We prove precise inclusions between the classes of programs recognised as terminating by the same termination criterion over different call graph analyses, giving one of the first characterisations of expressive power of flow analyses for higher-order programs.
Relating complexity and precision in control flow analysis
Authors: Van Horn David , Mairson Harry G.
Published: October 2007

We analyze the computational complexity of
k
CFA, a hierarchy of control flow analyses that determine which functions may be applied at a given call-site. This hierarchy specifies related decision problems, quite apart from any algorithms that may implement their solutions. We identify a simple decision problem answered by this analysis and prove that in the 0CFA case, the problem is complete for polynomial time. The proof is based on a nonstandard, symmetric implementation of Boolean logic within multiplicative linear logic (MLL). We also identify a simpler version of 0CFA related to η-expansion, and prove that it is complete for logarithmic space, using arguments based on computing paths and permutations.

For any fixed
k
>0, it is known that
k
CFA (and the analogous decision problem) can be computed in time exponential in the program size. For
k
=1, we show that the decision problem is NP-hard, and sketch why this remains true for larger fixed values of
k
. The proof technique depends on using the
approximation
of CFA as an essentially nondeterministic computing mechanism, as distinct from the exactness of normalization. When
k
=
n
, so that the "depth" of the control flow analysis grows linearly in the program length, we show that the decision problem is complete for exponential time.

In addition, we sketch how the analysis presented here may be extended naturally to languages with control operators. All of the insights presented give clear examples of how straightforward observations about linearity, and linear logic, may in turn be used to give a greater understanding of functional programming and program analysis.
Compiling with continuations, continued
Authors: Kennedy Andrew
Published: October 2007

We present a series of CPS-based intermediate languages suitable for functional language compilation, arguing that they have practical benefits over direct-style languages based on
A
-normal form (ANF) or monads. Inlining of functions demonstrates the benefits most clearly: in ANF-based languages, inlining involves a re-normalization step that rearranges let expressions and possibly introduces a new 'join point' function, and in monadic languages, commuting conversions must be applied; in contrast, inlining in our CPS language is a simple substitution of variables for variables.

We present a contification transformation implemented by simple rewrites on the intermediate language. Exceptions are modelled using so-called 'double-barrelled' CPS. Subtyping on exception constructors then gives a very straightforward effect analysis for exceptions. We also show how a graph-based representation of CPS terms can be implemented extremely efficiently, with linear-time term simplification.
Experience report
Authors: Beshers Clifford , Fox David , Shaw Jeremy
Published: October 2007

We report on our experience using functional programming languages in the development of a commercial GNU/Linux distribution, discussing features of several significant systems: hardware detection and system configuration; OS installer CD creation; package compilation and management. Static typing helps compensate for the lack of a complete testing lab and helps us be effective with a very small team. Most importantly, we believe that going beyond merely using functional languages to using purely functional
designs
really helps to create simple, effective tools.
Experience report
Authors: Cooper Jonathan , McKeever Steve
Published: October 2007

In this paper we present our use of functional programming (FP), specifically Haskell, to provide an operational semantics for a domain-specific language, CellML, that describes mathematical models of biological processes. We analyse the benefits and shortcomings of this approach, in comparison with other semantic definitions for CellML.

It is our claim that using FP for our semantics results in a more concise and useful artifact for describing what such a model means. The use of lazy evaluation removes the need to explicitly determine an evaluation order for the model, resulting in a more elegant interpreter. Crucially, using FP enables us to prove the correctness of optimisation techniques for such models. This gives us more confidence in scientific deductions from simulation results. We compare the Python implementation of these optimisation techniques with our use of Haskell in proving their correctness.
Implicit phasing for R6RS libraries
Authors: Ghuloum Abdulaziz , Dybvig R. Kent
Published: October 2007

The forthcoming Revised
6
Report on Scheme differs from previous reports in that the language it describes is structured as a set of libraries. It also provides a syntax for defining new portable libraries. The same library may export both procedure and hygienic macro definitions, which allows procedures and syntax to be freely intermixed, hidden, and exported.

This paper describes the design and implementation of a portable version of R
6
RS libraries that expands libraries into a core language compatible with existing R
5
RS implementations. Our implementation is characterized by its use of inference to determine when the bindings of an imported library are needed, e.g., run time or compile time, relieving programmers of the burden of declaring usage requirements explicitly.
Gadget crazy!
Authors: Rowell Laurie
Published: October 2007

In the 1960s comedy series "Get Smart," Maxwell Smart spent a lot of time talking into his shoe. The show was a spoof on spies and the gadgets they used in the movies and TV series of the time. When Smart called out, he used a rotary dial, and when the phone rang it startled everyone in the room and required him to take off his shoe to answer it. But there was something endearing about Smart's phone that made it the quintessential gadget. It was geeky and clunky, but kind of a good idea---a phone you could carry anywhere.
Internet ubiquity---this time, in your pocket
Authors: Treese Win
Published: October 2007

I got lost today. Well, not actually lost, since I knew exactly where I was. The store I was looking for wasn't where I thought it was, and I didn't have the address written down. Ten years ago, I might have tried asking around to find out where it might be, or maybe found a pay phone to call information to locate the store. Five years ago, I wouldn't have needed the pay phone---I'd have used my cell phone.
Indoleamine 2,3-dioxygenase gene transfer prolongs cardiac allograft survival
Authors: Li Jianping , Meinhardt Andrea , Roehrich Marc-Estienne , Golshayan Dela , Dudler Jean , Pagnotta Maria , Trucco Massimo , Vassalli Giuseppe
Published: October 2007

Cells that express indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme in the catabolism of tryptophan, suppress T cell responses and promote immunological tolerance. However, their role in solid organ transplantation is incompletely understood. We analyzed T cell responses to allogeneic dendritic cells (DCs) genetically modified to express the gene encoding IDO in vitro and IDO gene transfer into the donor heart in a cardiac transplant model in vivo. Bone marrow-derived DCs transduced with the gene encoding IDO produced active IDO protein. This was associated with decreased stimulation of allogeneic T cell proliferation in the mixed leukocyte reaction in vitro. In a cardiac transplant model, adenovirus-mediated IDO gene transfer into the donor heart resulted in transgene expression predominantly in cardiomyocytes. Fischer-344 rat donor hearts transduced with the gene encoding IDO survived for longer periods of time when placed in Lewis rat recipients compared with control vector or vehicle alone [median survival times of 17 (range: 12–22) days vs. 10 (range: 8–14) and 9 (range: 8–13) days, respectively, P < 0.0001]. IDO gene transfer combined with low-dose cyclosporin A (CsA) was more effective than CsA alone ( P < 0.05). Numbers of monocytes/macrophages, CD4+ cells, and CD8α+ cells infiltrating the graft as well as intragraft cytokine transcript levels for IFN-γ, IL-1, TNF-α, regulated upon secretion, normal T cell expressed, and secreted/chemokine (C-C motif) ligand 5 were decreased after IDO gene transfer ( P < 0.05). In conclusion, DCs genetically engineered to overexpress IDO modulate T cell alloresponses in vitro. IDO gene transfer into the donor heart attenuates acute cardiac allograft rejection. Regulation of tryptophan catabolism by means of IDO overexpression may be a useful approach in heart transplantation.
The validation of a generalized Hooke's law for coronary arteries
Authors: Wang Chong , Zhang Wei , Kassab Ghassan S.
Published: October 2007

The exponential form of constitutive model is widely used in biomechanical studies of blood vessels. There are two main issues, however, with this model: 1) the curve fits of experimental data are not always satisfactory, and 2) the material parameters may be oversensitive. A new type of strain measure in a generalized Hooke's law for blood vessels was recently proposed by our group to address these issues. The new model has one nonlinear parameter and six linear parameters. In this study, the stress-strain equation is validated by fitting the model to experimental data of porcine coronary arteries. Material constants of left anterior descending artery and right coronary artery for the Hooke's law were computed with a separable nonlinear least-squares method with an excellent goodness of fit. A parameter sensitivity analysis shows that the stability of material constants is improved compared with the exponential model and a biphasic model. A boundary value problem was solved to demonstrate that the model prediction can match the measured arterial deformation under experimental loading conditions. The validated constitutive relation will serve as a basis for the solution of various boundary value problems of cardiovascular biomechanics.
A new method to determine the electrical transfer function of the human thorax
Authors: Goldberger Jeffrey J. , Subacius Haris , Sen-Gupta Indranil , Johnson David , Kadish Alan H. , Ng Jason
Published: October 2007

Traditional analyses have assumed that cardiac electrical activity is reflected on the surface ECG without distortion as the signal passes through the body tissues. This study aims to explore the frequency dependence of thoracic attenuation of surface-recorded intracardiac electrical activity. Twenty patients (14 men, 55 ± 15 yr of age) undergoing electrophysiological study were enrolled. Rectangular unipolar stimuli were applied from a catheter positioned in the right ventricular apical area and another in the posteroseptal area without contact with the myocardium. An orthogonal Frank-lead surface ECG and a unipolar intracardiac electrogram near the pacing site were recorded. Frequency domain characteristics of the signal-averaged pacing impulses were analyzed. Linear regression analysis showed significant frequency-dependent attenuation in the magnitude transfer functions ( R2= 0.84–0.89, P < 0.0001) and good linear fit for the phase transfer characteristics ( R2= 0.98–1.0, P < 0.0001). Age, physical dimension, and respiratory characteristics had significant effects on the magnitude and phase characteristics of the transfer functions. Application of models of the low- and high-slope transfer functions to signal-averaged ECGs from 33 subjects showed differences in the attenuation of P and T waves relative to the QRS.
Interaction of angiogenic microvessels with the extracellular matrix
Authors: Krishnan Laxminarayanan , Hoying James B. , Nguyen Hoa , Song Helen , Weiss Jeffrey A.
Published: October 2007

The extracellular matrix (ECM) plays a critical role in angiogenesis by providing biochemical and positional cues, as well as by mechanically influencing microvessel cell behavior. Considerable information is known concerning the biochemical cues relevant to angiogenesis, but less is known about the mechanical dynamics during active angiogenesis. The objective of this study was to characterize changes in the material properties of a simple angiogenic tissue before and during angiogenesis. During sprouting, there was an overall decrease in tissue stiffness followed by an increase during neovessel elongation. The fall in matrix stiffness coincided with peak matrix metalloproteinase mRNA expression and elevated proteolytic activity. An elevated expression of genes for ECM components and cell-ECM interaction molecules and a subsequent drop in proteolytic activity (although enzyme levels remained elevated) coincided with the subsequent stiffening. The results of this study show that the mechanical properties of a scaffold tissue may be actively modified during angiogenesis by the growing microvasculature.
Acute antihypertensive action of Tempol in the spontaneously hypertensive rat
Authors: Chen Xueguang , Patel Kinjal , Connors Stephanie G. , Mendonca Margarida , Welch William J. , Wilcox Christopher S.
Published: October 2007

Acute intravenous Tempol reduces mean arterial pressure (MAP) and heart rate (HR) in spontaneously hypertensive rats. We investigated the hypothesis that the antihypertensive action depends on generation of hydrogen peroxide, activation of heme oxygenase, glutathione peroxidase or potassium conductances, nitric oxide synthase, and/or the peripheral or central sympathetic nervous systems (SNSs). Tempol caused dose-dependent reductions in MAP and HR (at 174 μmol/kg; ΔMAP, −57± 3 mmHg; and ΔHR, −50 ± 4 beats/min). The antihypertensive response was unaffected by the infusion of a pegylated catalase or by the inhibition of catalase with 3-aminotriazole, inhibition of glutathione peroxidase with buthionine sulfoximine, inhibition of heme oxygenase with tin mesoporphyrin, or inhibition of large-conductance Ca2+-activated potassium channels with iberiotoxin. However, the antihypertensive response was significantly ( P < 0.01) blunted by 48% by the activation of adenosine 5′-triphosphate-sensitive potassium (KATP) channels with cromakalim during maintenance of blood pressure with norepinephrine and by 31% by the blockade of these channels with glibenclamide, by 40% by the blockade of nitric oxide synthase with Nω-nitro-l-arginine methyl ester (l-NAME), and by 40% by the blockade of ganglionic autonomic neurotransmission with hexamethonium. l-NAME and hexamethonium were additive, but glibenclamide and hexamethonium were less than additive. The central administration of Tempol was ineffective. The acute antihypertensive action of Tempol depends on the independent effects of potentiation of nitric oxide and inhibition of the peripheral SNS that involves the activation of KATPchannels.
Interaction between bradykinin subtype 2 and angiotensin II type 2 receptors during post-MI left ventricular remodeling
Authors: Isbell David C. , Voros Szilard , Yang Zequan , DiMaria Joseph M. , Berr Stuart S. , French Brent A. , Epstein Frederick H. , Bishop Sanford P. , Wang Hongkun , Roy Rene J. , Kemp Brandon A. , Matsubara Hiroaki , Carey Robert M. , Kramer Christopher M.
Published: October 2007

Angiotensin II type 2 receptor (AT2R) overexpression (AT2TG) attenuates left ventricular remodeling in a mouse model of anterior myocardial infarction (MI). We hypothesized that the beneficial effects of cardiac AT2TG are mediated via the bradykinin subtype 2 receptor (B2R). Fourteen transgenic mice overexpressing the AT2R (AT2TG mice), 10 mice with a B2R deletion (B2KO mice), 13 AT2TG mice with B2R deletion (AT2TG/B2KO mice), and 11 wild-type (WT) mice were studied. All mice were on a C57BL/6 background. Mice were studied by cardiac magnetic resonance imaging at baseline and days 1, 7, and 28 after MI induced by 1 h of occlusion of the left anterior descending artery followed by reperfusion. Short-axis images from apex to base were used to compare ventricular volumes and ejection fraction (EF). At baseline, end-diastolic volume index (EDVI) and end-systolic volume index (ESVI) were lower and EF higher in AT2TG mice compared with the other three strains. Infarct size was similar between groups. No differences were observed in global remodeling parameters at day 28 between AT2TG and AT2TG/B2KO mice; however, EDVI and ESVI were lower and EF higher in both transgenic groups than in WT or B2KO mice. Both strains lacking B2R demonstrated increased collagen content and less hypertrophy in adjacent noninfarcted regions at day 28. Attenuation of postinfarct remodeling by overexpression of AT2R is not directly mediated via a B2R pathway. However, B2R does appear to have a role in the smaller cavity size and hyperdynamic function observed at baseline in AT2TG mice and in limiting collagen deposition during postinfarct remodeling.
Dimethylarginine dimethylaminohydrolase (DDAH): expression, regulation, and function in the cardiovascular and renal systems
Authors: Palm Fredrik , Onozato Maristela L. , Luo Zaiming , Wilcox Christopher S.
Published: October 2007

Asymmetric ( NG, NG)-dimethylarginine (ADMA) inhibits nitric oxide (NO) synthases (NOS). ADMA is a risk factor for endothelial dysfunction, cardiovascular mortality, and progression of chronic kidney disease. Two isoforms of dimethylarginine dimethylaminohydrolase (DDAH) metabolize ADMA. DDAH-1 is the predominant isoform in the proximal tubules of the kidney and in the liver. These organs extract ADMA from the circulation. DDAH-2 is the predominant isoform in the vasculature, where it is found in endothelial cells adjacent to the cell membrane and in intracellular vesicles and in vascular smooth muscle cells among the myofibrils and the nuclear envelope. In vivo gene silencing of DDAH-1 in the rat and DDAH +/− mice both have increased circulating ADMA, whereas gene silencing of DDAH-2 reduces vascular NO generation and endothelium-derived relaxation factor responses. DDAH-2 also is expressed in the kidney in the macula densa and distal nephron. Angiotensin type 1 receptor activation in kidneys reduces the expression of DDAH-1 but increases the expression of DDAH-2. This rapidly evolving evidence of isoform-specific distribution and regulation of DDAH expression in the kidney and blood vessels provides potential mechanisms for nephron site-specific regulation of NO production. In this review, the recent advances in the regulation and function of DDAH enzymes, their roles in the regulation of NO generation, and their possible contribution to endothelial dysfunction in patients with cardiovascular and kidney diseases are discussed.
Roles of platelet and endothelial cell COX-1 in hypercholesterolemia-induced microvascular dysfunction
Authors: Tailor Anitaben , Wood Katherine C. , Wallace John L. , Specian Robert D. , Granger D. Neil
Published: October 2007

Aspirin is a common preventative therapy in patients at risk for cardiovascular diseases, yet little is known about how aspirin protects the vasculature in hypercholesterolemia. The present study determines whether aspirin, nitric oxide-releasing aspirin (NCX-4016), a selective cyclooxygenase (COX)-1 inhibitor (SC560), or genetic deficiency of COX-1 prevents the inflammatory and prothrombogenic phenotype assumed by hypercholesterolemic (HC) venules. Aspirin or NCX-4016 (60 mg/kg) was administered orally for the last week of a 2-wk HC diet. COX-1-deficient (COX-1−/−) and wild-type (WT) mice were transplanted with WT (WT/COX-1−/−) or COX-1−/−(COX-1−/−/WT) bone marrow, respectively. HC-induced adhesion of platelets and leukocytes in murine intestinal venules, observed with intravital fluorescence microscopy, was greatly attenuated in aspirin-treated mice. Adhesion of aspirin-treated platelets in HC venules was comparable to untreated platelets, whereas adhesion of SC560-treated platelets was significantly attenuated. HC-induced leukocyte and platelet adhesion in COX-1−/−/WT chimeras was comparable to that in SC560-treated mice, whereas the largest reductions in blood cell adhesion were in WT/COX-1−/−chimeras. NCX-4016 treatment of platelet recipients or donors attenuated leukocyte and platelet adhesion independent of platelet COX-1 inhibition. Platelet- and endothelial cell-associated COX-1 promote microvascular inflammation and thrombogenesis during hypercholesterolemia, yet nitric oxide-releasing aspirin directly inhibits platelets independent of COX-1.
Induction of hypertrophy in vitro by mechanical loading in adult rabbit myocardium
Authors: Bupha-Intr Tepmanas , Holmes Jeffrey W. , Janssen Paul M. L.
Published: October 2007

To study myocardial hypertrophy under in vitro conditions, we developed an experimental system and protocol in which mechanical conditions of isolated multicellular myocardium can be controlled while function can be continuously assessed. This in vitro culture system now allows us to investigate how mechanical overload impacts on cardiac hypertrophy in the absence of systemic factors. In this system, small right ventricular rabbit trabeculae were subjected to different modes of mechanical load, while being electrically stimulated to contract at 1 Hz at 37°C. Muscles subjected to prolonged isometric contractions at high, but physiological, pre- and afterload showed a rapid induction of cardiac hypertrophy; overall muscle diameter increased by 4.3 ± 1.4 and 17.9 ± 4.0% after 24 and 48 h, respectively. This finding was confirmed at the cellular level; individual myocyte width significantly increased after 24 and 48 h. In muscles subjected to a low preload, or in the absence of afterload, this hypertrophic response was absent. Functionally, after 24 h of isometric contractions at high load, active developed tension had gradually increased to 168 ± 22% of starting values. Proteomic analysis of this cultured myocardium demonstrated reproducible changes in the protein expression pattern and included an upregulation of myofilament proteins, myosin light chain isoforms, α-b crystalline, and breast cancer 1 protein, and a downregulation of myoglobin. We conclude that multicellular myocardium can be stressed to undergo rapid hypertrophy in vitro, and changes in function and protein expression can be investigated during the transition from healthy myocardium to early hypertrophy.
Functional role and species-specific contribution of arginases in pulmonary fibrosis
Authors: Kitowska Kamila , Zakrzewicz Dariusz , Königshoff Melanie , Chrobak Izabella , Grimminger Friedrich , Seeger Werner , Bulau Patrick , Eickelberg Oliver
Published: October 2007

Lung fibrosis is characterized by increased deposition of ECM, especially collagens, and enhanced proliferation of fibroblasts. l-arginine is a key precursor of nitric oxide, asymmetric dimethylarginine, and proline, an amino acid enriched in collagen. We hypothesized that l-arginine metabolism is altered in pulmonary fibrosis, ultimately affecting collagen synthesis. Expression analysis of key enzymes in the arginine pathway, protein arginine methyltransferases (Prmt), arginine transporters, and arginases by quantitative (q) RT-PCR and Western blot revealed significant upregulation of arginase-1 and -2, but not Prmt or arginine transporters, during bleomycin-induced pulmonary fibrosis in mice. HPLC revealed a concomitant, time-dependent decrease in pulmonary l-arginine levels. Arginase-1 and -2 mRNA and protein expression was increased in primary fibroblasts isolated from bleomycin-treated mice, compared with controls, and assessed by qRT-PCR and Western blot analysis. TGF-β1, a key profibrotic mediator, induced arginase-1 and -2 mRNA expression in primary and NIH/3T3 fibroblasts. Treatment of fibroblasts with the arginase inhibitor, NG-hydroxy-l-arginine, attenuated TGF-β1-stimulated collagen deposition, but not collagen mRNA expression or Smad signaling, in fibroblasts. In human lungs derived from patients with idiopathic pulmonary fibrosis, arginase activity was unchanged, but arginase-1 expression significantly decreased when compared with donor lungs. Our results thus demonstrate that arginase-1 is expressed and functionally important for collagen deposition in lung fibroblasts. TGF-β1-induced upregulation of arginase-1 suggests an interplay between profibrotic agents and l-arginine metabolism during the course of lung fibrosis in the mouse, whereas species-specific regulatory mechanisms may account for the differences observed in mouse and human.
Epidermal growth factor-like domain 7 protects endothelial cells from hyperoxia-induced cell death
Authors: Xu Dong , Perez Ricardo E. , Ekekezie Ikechukwu I. , Navarro Angels , Truog William E.
Published: October 2007

Hyperoxia is one of the major contributors to the development of bronchopulmonary dysplasia (BPD), a chronic lung disease in premature infants. Emerging evidence suggests that the arrested lung development of BPD is associated with pulmonary endothelial cell death and vascular dysfunction resulting from hyperoxia-induced lung injury. A better understanding of the mechanism of hyperoxia-induced endothelial cell death will provide critical information for the pathogenesis and therapeutic development of BPD. Epidermal growth factor-like domain 7 (EGFL7) is a protein secreted from endothelial cells. It plays an important role in vascular tubulogenesis. In the present study, we found that Egfl7 gene expression was significantly decreased in the neonatal rat lungs after hyperoxic exposure. The Egfl7 expression was returned to near normal level 2 wk after discounting oxygen exposure during recovery period. In cultured human endothelial cells, hyperoxia also significantly reduced Egfl7 expression. These observations suggest that diminished levels of Egfl7 expression might be associated with hyperoxia-induced endothelial cell death and lung injury. When we overexpressed human Egfl7 ( hEgfl7) in EA.hy926 human endothelial cell line, we found that hEgfl7 overexpression could partially block cytochrome c release from mitochondria and decrease caspase-3 activation. Further Western blotting analyses showed that hEgfl7 overexpression could reduce expression of a proapoptotic protein, Bax, and increase expression of an antiapoptotic protein, Bcl-xL. Theses findings indicate that hEGFL7 may protect endothelial cell from hyperoxia-induced apoptosis by inhibition of mitochondria-dependent apoptosis pathway.
Hog barn dust slows airway epithelial cell migration in vitro through a PKCα-dependent mechanism
Authors: Slager Rebecca E. , Allen-Gipson Diane S. , Sammut Alexi , Heires Art , DeVasure Jane , Von Essen Susanna , Romberger Debra J. , Wyatt Todd A.
Published: October 2007

Agricultural work and other occupational exposures are responsible for ∼15% of chronic obstructive pulmonary disease (COPD). COPD involves airway remodeling in response to chronic lung inflammatory events and altered airway repair mechanisms. However, the effect of agricultural dust exposure on signaling pathways that regulate airway injury and repair has not been well characterized. A key step in this process is migration of airway cells to restore epithelial integrity. We have previously shown that agents that activate the critical regulatory enzyme protein kinase C (PKC) slow cell migration during wound repair. Based on this observation and direct kinase measurements that demonstrate that dust extract from hog confinement barns (HDE) specifically activates the PKC isoforms PKCα and PKCε, we hypothesized that HDE would slow wound closure time in airway epithelial cells. We utilized the human bronchial epithelial cell line BEAS-2B and transfected BEAS-2B cell lines that express dominant negative (DN) forms of PKC isoforms to demonstrate that HDE slows wound closure in BEAS-2B and PKCε DN cell lines. However, in PKCα DN cells, wound closure following HDE treatment is not significantly different than media-treated cells. These results suggest that the PKCα isoform is an important regulator of cell migration in response to agricultural dust exposure.
Mechanical ventilation uncouples synthesis and assembly of elastin and increases apoptosis in lungs of newborn mice.
Authors: Bland Richard D. , Ertsey Robert , Mokres Lucia M. , Xu Liwen , Jacobson Berit E. , Jiang Shu , Alvira Cristina M. , Rabinovitch Marlene , Shinwell Eric S. , Dixit Anjali
Published: October 2007

Prolonged mechanical ventilation (MV) with O2-rich gas inhibits lung growth and causes excess, disordered accumulation of lung elastin in preterm infants, often resulting in chronic lung disease (CLD). Using newborn mice, in which alveolarization occurs postnatally, we designed studies to determine how MV with either 40% O2or air might lead to dysregulated elastin production and impaired lung septation. MV of newborn mice for 8 h with either 40% O2or air increased lung mRNA for tropoelastin and lysyl oxidase, relative to unventilated controls, without increasing lung expression of genes that regulate elastic fiber assembly (lysyl oxidase-like-1, fibrillin-1, fibrillin-2, fibulin-5, emilin-1). Serine elastase activity in lung increased fourfold after MV with 40% O2, but not with air. We then extended MV with 40% O2to 24 h and found that lung content of tropoelastin protein doubled, whereas lung content of elastin assembly proteins did not change (lysyl oxidases, fibrillins) or decreased (fibulin-5, emilin-1). Quantitative image analysis of lung sections showed that elastic fiber density increased by 50% after MV for 24 h, with elastin distributed throughout the walls of air spaces, rather than at septal tips, as in control lungs. Dysregulation of elastin was associated with a threefold increase in lung cell apoptosis (TUNEL and caspase-3 assays), which might account for the increased air space size previously reported in this model. Our findings of increased elastin synthesis, coupled with increased elastase activity and reduced lung abundance of proteins that regulate elastic fiber assembly, could explain altered lung elastin deposition, increased apoptosis, and defective septation, as observed in CLD.
Hypertriglyceridemia and Recurrent Pancreatitis following Splenectomy
Authors: Butman Michael , Taylor David , Boström Kristina , Quinones Manuel , Nicholas Susanne B.
Published: October 2007

Hyperlipoproteinemia represents a constellation of clinical syndromes that frequently includes hypertriglyceridemia. Because of the degree of elevation in the triglyceride levels frequently seen in these syndromes, they are associated with complications not generally observed among those patients with essential hypertriglyceridemia, including as in this case report, recurrent pancreatitis. Here, we present a case of a patient with hyperlipoproteinemia who developed acute worsening of his hypertriglyceridemia and onset of acute panceatitis that became recurrent following elective splenectomy for suspected lymphoma. In particular, we discuss the dietary management of hypertriglyceridemia which significantly reduced the number of episodes of acute pancreatitis in this patient.
Does Glucose in Dialysis Fluid Protect Erythrocytes in Patients with Chronic Renal Failure?
Authors: Dolegowska B. , Stepniewska J. , Ciechanowski K. , Safranow K. , Millo B. , Bober J. , Chlubek D.
Published: October 2007

Background/Aims: The aim of this study was to assess the multifaceted influence of glucose present in dialyzing fluid on erythrocytes of patients with chronic renal failure (CRF) undergoing regular hemodialysis. Methods: A group of 44 subjects with CRF undergoing regular hemodialysis was studied. Two tests were used: osmotic fragility and resistance to the hemolytic agent saponin. The total content of isoprostane 8-iso-prostaglandin F2α type III (8-iPF2α-III) in plasma and erythrocyte’s membrane were determined by the ELISA method. Results: The presence of glucose in the dialysate is associated with lower intravascular hemolysis markers and high total 8-iPF2α-III concentrations in plasma. Conclusion: The presence of glucose in dialyzing fluid could protect erythrocytes. It limits hemolysis in patients with CRF, but, on the other hand, increases the oxidative processes. This kind of treatment along with other therapeutic intervention such as administration of antioxidants (e.g. α-tocopherol, ascorbic acid, N-acetylcysteine) could improve the condition of erythrocytes and outcome in CRF.
Granulocyte Macrophage Colony-Stimulating Factor Deficiency Affects Vascular Elastin Production and Integrity of Elastic Lamellae
Authors: Weissen-Plenz Gabriele , Eschert Heike , Völker Wolfgang , Sindermann Jürgen R. , Beissert Stefan , Robenek Horst , Scheld Hans H. , Breithardt Günter
Published: October 2007

Background: Granulocyte macrophage colony-stimulating factor (GM-CSF) deficiency affects the production and fiber assembly/organization of the vascular collagenous matrix; structural alterations to the elastic system were observed. The present study elaborates the effect of GM-CSF deficiency on the vascular elastin system. Methods and Results: Histological examination of the aorta of GM-CSF-deficient mice revealed structurally altered elastic fibers. The elastic fiber area was significantly enhanced, whereas the remaining medial area was not affected. Aortic size was significantly increased. Reverse transcription polymerase chain reaction demonstrated decreased expression levels of tropoelastin, lysyl oxidase and bone morphogenetic protein 1 (BMP-1). Cell culture studies on vascular smooth muscle cells showed that after clearance of GM-CSF with GM-CSF antibodies, the tropoelastin mRNA expression was markedly reduced. Concomitantly, lysyl oxidase and BMP-1 mRNA levels were decreased. Treatment with GM-CSF stimulated the expression of these mRNAs. Conclusions: Our studies demonstrate that disorganization of elastic lamellae as induced by GM-CSF deficiency is associated with adaptive vascular remodeling. The decreased tropoelastin expression observed is associated with elastic fiber hypertrophy. This paradox effect may be explained by decreased expression levels of lysyl oxidase and BMP-1, both mediating cross-linkage and thus assembly and organization of elastic fibers. From our data, we conclude that GM-CSF is a prerequisite for the maintenance of structural integrity of the vessel wall.