bluuebunny/crossref_metadata_2025 huggingface dataset:
Down for the count? Getting reference counting back in the ring
Authors: Shahriyar Rifat , Blackburn Stephen M. , Frampton Daniel
Published: January 2013

Reference counting and tracing are the two fundamental approaches that have underpinned garbage collection since 1960. However, despite some compelling advantages, reference counting is almost completely ignored in implementations of high performance systems today. In this paper we take a detailed look at reference counting to understand its behavior and to improve its performance. We identify key design choices for reference counting and analyze how the behavior of a wide range of benchmarks might affect design decisions. As far as we are aware, this is the first such quantitative study of reference counting. We use insights gleaned from this analysis to introduce a number of optimizations that significantly improve the performance of reference counting.

We find that an existing modern implementation of reference counting has an average 30% overhead compared to tracing, and that in combination, our optimizations are able to completely eliminate that overhead. This brings the performance of reference counting on par with that of a well tuned mark-sweep collector. We keep our in-depth analysis of reference counting as general as possible so that it may be useful to other garbage collector implementers. Our finding that reference counting can be made directly competitive with well tuned mark-sweep should shake the community's prejudices about reference counting and perhaps open new opportunities for exploiting reference counting's strengths, such as localization and immediacy of reclamation.
A generalized theory of collaborative caching
Authors: Gu Xiaoming , Ding Chen
Published: January 2013

Collaborative caching allows software to use hints to influence cache management in hardware. Previous theories have shown that such hints observe the inclusion property and can obtain optimal caching if the access sequence and the cache size are known ahead of time. Previously, the interface of a cache hint is limited, e.g., a binary choice between LRU and MRU.

In this paper, we generalize the hint interface, where a hint is a number encoding a priority. We show the generality in a hierarchical relation where collaborative caching subsumes non-collaborative caching, and within collaborative caching, the priority hint subsumes the previous binary hint. We show two theoretical results for the general hint. The first is a new cache replacement policy, priority LRU, which permits the complete range of choices between MRU and LRU. We prove a new type of inclusion property---non-uniform inclusion---and give a one-pass algorithm to compute the miss rate for all cache sizes. Second, we show that priority hints can enable the use of the same hints to obtain optimal caching for all cache sizes, without having to know the cache size beforehand.
Identifying the sources of cache misses in Java programs without relying on hardware counters
Authors: Inoue Hiroshi , Nakatani Toshio
Published: January 2013

Cache miss stalls are one of the major sources of performance bottlenecks for multicore processors. A Hardware Performance Monitor (HPM) in the processor is useful for locating the cache misses, but is rarely used in the real world for various reasons. It would be better to find a simple approach to locate the sources of cache misses and apply runtime optimizations without relying on an HPM. This paper shows that pointer dereferencing in hot loops is a major source of cache misses in Java programs. Based on this observation, we devised a new approach to identify the instructions and objects that cause frequent cache misses. Our heuristic technique effectively identifies the majority of the cache misses in typical Java programs by matching the hot loops to simple idiomatic code patterns. On average, our technique selected only 2.8% of the load and store instructions generated by the JIT compiler and these instructions accounted for 47% of the L1D cache misses and 49% of the L2 cache misses caused by the JIT-compiled code. To prove the effectiveness of our technique in compiler optimizations, we prototyped object placement optimizations, which align objects in cache lines or collocate paired objects in the same cache line to reduce cache misses. For comparison, we also implemented the same optimizations based on the accurate information obtained from the HPM. Our results showed that our heuristic approach was as effective as the HPM-based approach and achieved comparable performance improvements in the SPECjbb2005 and SPECpower_ssj2008 benchmark programs.
Toward scalable internet traffic measurement and analysis with Hadoop
Authors: Lee Yeonhee , Lee Youngseok
Published: January 2013

Internet traffic measurement and analysis has long been used to characterize network usage and user behaviors, but faces the problem of scalability under the explosive growth of Internet traffic and high-speed access. Scalable Internet traffic measurement and analysis is difficult because a large data set requires matching computing and storage resources. Hadoop, an open-source computing platform of MapReduce and a distributed file system, has become a popular infrastructure for massive data analytics because it facilitates scalable data processing and storage services on a distributed computing system consisting of commodity hardware. In this paper, we present a Hadoop-based traffic monitoring system that performs IP, TCP, HTTP, and NetFlow analysis of multi-terabytes of Internet traffic in a scalable manner. From experiments with a 200-node testbed, we achieved 14 Gbps throughput for 5 TB files with IP and HTTP-layer analysis MapReduce jobs. We also explain the performance issues related with traffic analysis MapReduce jobs.
Comments on bufferbloat
Authors: Allman Mark
Published: January 2013

While there has been much buzz in the community about the large depth of queues throughout the Internet---the so-called "bufferbloat" problem---there has been little empirical understanding of the scope of the phenomenon. Yet, the supposed problem is being used as input to engineering decisions about the evolution of protocols. While we know from wide scale measurements that bufferbloat
can
happen, we have no empirically-based understanding of how often bufferbloat
does
happen. In this paper we use passive measurements to assess the bufferbloat phenomena.
Observations from the 2012 mobile world congress in barcelona
Authors: Grunenberger Yan , Smith Jonathan M.
Published: January 2013

We attended the 2012 Mobile World Congress in Barcelona, Spain. This note reports on some of our observations that we believe might be relevant to the SIGCOMM community.
Network management game
Authors: Arslan Engin , Yuksel Murat , Gunes Mehmet Hadi
Published: January 2013

Management and automated configuration of large-scale networks is one of the crucial issues for Internet Service Providers (ISPs). Since wrong configurations may lead to loss of an enormous amount of customer traffic, highly experienced network administrators are typically the ones who are trusted for the management and configuration of a running ISP network. We frame the management and experimentation of a network as a "game" for training network administrators without having to risk the network operation. The interactive environment treats the trainee network administrators as players of a game and tests them with various network failures or dynamics.
Internet on the move
Authors: Sathiaseelan Arjuna , Crowcroft Jon
Published: January 2013

The Computer Laboratory, University of Cambridge hosted a workshop on "Internet on the Move" on September 22, 2012. The objective of the workshop was to bring academia, industry and regulators to discuss the challenges in realizing the notion of ubiquitous mobile Internet. The editorial summarises a general overview of the issues discussed on enabling universal mobile coverage and some of the solutions that have been proposed to alleviate the problem of having ubiquitous mobile connectivity.
Report of the DIMACS working group on abstractions for network services, architecture, and implementation
Authors: Rexford Jennifer , Zave Pamela
Published: January 2013

A workshop on Abstractions for Network Services, Architecture, and Implementation brought together researchers interested in creating better abstractions for creating and analyzing networked services and network architectures. The workshop took place at DIMACS on May 21-23, 2012. This report summarizes the presentations and discussions that took place at the workshop, organized by areas of abstractions such as layers, domains, and graph properties.
Anatomical and functional characterization of a duodeno-pancreatic neural reflex that can induce acute pancreatitis
Authors: Li Cuiping , Zhu Yaohui , Shenoy Mohan , Pai Reetesh , Liu Liansheng , Pasricha Pankaj Jay
Published: January 2013

Neural cross talk between visceral organs may play a role in mediating inflammation and pain remote from the site of the insult. We hypothesized such a cross talk exists between the duodenum and pancreas, and further it induces pancreatitis in response to intraduodenal toxins. A dichotomous spinal innervation serving both the duodenum and pancreas was examined, and splanchnic nerve responses to mechanical stimulation of these organs were detected. This pathway was then excited on the duodenal side by exposure to ethanol followed by luminal mustard oil to activate transient receptor potential subfamily A, member 1 (TRPA1). Ninety minutes later, pancreatic inflammation was examined. Ablation of duodenal afferents by resiniferatoxin (RTX) or blocking TRPA1 by Chembridge (CHEM)-5861528 was used to further investigate the duodeno-pancreatic neural reflex via TRPA1. ∼40% of dorsal root ganglia (DRG) from the spinal cord originated from both duodenum and pancreas via dichotomous peripheral branches; ∼50% splanchnic nerve single units responded to mechanical stimulation of both organs. Ethanol sensitized TRPA1 currents in cultured DRG neurons. Pancreatic edema and myeloperoxidase activity significantly increased after intraduodenal ethanol followed by mustard oil (but not capsaicin) but significantly decreased after ablation of duodenal afferents by using RTX or blocking TRPA1 by CHEM-5861528. We found the existence of a neural cross talk between the duodenum and pancreas that can promote acute pancreatitis in response to intraduodenal chemicals. It also proves a previously unexamined mechanism by which alcohol can induce pancreatitis, which is novel both in terms of the site (duodenum), process (neurogenic), and receptor (TRPA1).
Chymase-mediated intestinal epithelial permeability is regulated by a protease-activating receptor/matrix metalloproteinase-2-dependent mechanism
Authors: Groschwitz Katherine R. , Wu David , Osterfeld Heather , Ahrens Richard , Hogan Simon P.
Published: January 2013

Mast cells regulate intestinal barrier function during disease and homeostasis. Secretion of the mast cell-specific serine protease chymase regulates homeostasis. In the present study, we employ in vitro model systems to delineate the molecular pathways involved in chymase-mediated intestinal epithelial barrier dysfunction. Chymase stimulation of intestinal epithelial (Caco-2 BBe) cell monolayers induced a significant reduction in transepithelial resistance, indicating decreased intestinal epithelial barrier function. The chymase-induced intestinal epithelial barrier dysfunction was characterized by chymase-induced protease-activated receptor (PAR)-2 activation and matrix metalloproteinase (MMP)-2 expression and activation. Consistent with this observation, in vitro analysis revealed chymase-induced PAR-2 activation and increased MAPK activity and MMP-2 expression. Pharmacological and small interfering RNA-mediated antagonism of PAR-2 and MMP-2 significantly attenuated chymase-stimulated barrier dysfunction. Additionally, the chymase/MMP-2-mediated intestinal epithelial dysfunction was associated with a significant reduction in the tight junction protein claudin-5, which was partially restored by MMP-2 inhibition. Finally, incubation of Caco-2 BBe cells with chymase-sufficient, but not chymase-deficient, bone marrow-derived mast cells decreased barrier function, which was attenuated by the chymase inhibitor chymostatin. Collectively, these results suggest that mast cell/chymase-mediated intestinal epithelial barrier function is mediated by PAR-2/MMP-2-dependent pathways.
p-21-Activated kinase 1 mediates gastrin-stimulated proliferation in the colorectal mucosa via multiple signaling pathways
Authors: Huynh Nhi , Yim Mildred , Chernoff Jonathan , Shulkes Arthur , Baldwin Graham S. , He Hong
Published: January 2013

Gastrins, including amidated (Gamide) and glycine-extended (Ggly) forms, function as growth factors for the gastrointestinal mucosa. The p-21-activated kinase 1 (PAK1) plays important roles in growth factor signaling networks that control cell motility, proliferation, differentiation, and transformation. PAK1, activated by both Gamide and Ggly, mediates gastrin-stimulated proliferation and migration, and activation of β-catenin, in gastric epithelial cells. The aim of this study was to investigate the role of PAK1 in the regulation by gastrin of proliferation in the normal colorectal mucosa in vivo. Mucosal proliferation was measured in PAK1 knockout (PAK1 KO) mice by immunohistochemistry. The expression of phosphorylated and unphosphorylated forms of the signaling molecules PAK1, extracellular signal-regulated kinase (ERK), and protein kinase B (AKT), and the expression of β-catenin and its downstream targets c-Myc and cyclin D1, were measured in gastrin knockout (Gas KO) and PAK1 KO mice by Western blotting. The expression and activation of PAK1 are decreased in Gas KO mice, and these decreases are associated with reduced activation of ERK, AKT, and β-catenin. Proliferation in the colorectal mucosa of PAK1 KO mice is reduced, and the reduction is associated with reduced activation of ERK, AKT, and β-catenin. In compensation, antral gastrin mRNA and serum gastrin concentrations are increased in PAK1 KO mice. These results indicate that PAK1 mediates the stimulation of colorectal proliferation by gastrins via multiple signaling pathways involving activation of ERK, AKT, and β-catenin.
Intestinal alkaline phosphatase inhibits the proinflammatory nucleotide uridine diphosphate
Authors: Moss Angela K. , Hamarneh Sulaiman R. , Mohamed Mussa M. Rafat , Ramasamy Sundaram , Yammine Halim , Patel Palak , Kaliannan Kanakaraju , Alam Sayeda N. , Muhammad Nur , Moaven Omeed , Teshager Abeba , Malo Nondita S. , Narisawa Sonoko , Millán José Luis , Warren H. Shaw , Hohmann Elizabeth , Malo Madhu S. , Hodin Richard A.
Published: January 2013

Uridine diphosphate (UDP) is a proinflammatory nucleotide implicated in inflammatory bowel disease. Intestinal alkaline phosphatase (IAP) is a gut mucosal defense factor capable of inhibiting intestinal inflammation. We used the malachite green assay to show that IAP dephosphorylates UDP. To study the anti-inflammatory effect of IAP, UDP or other proinflammatory ligands (LPS, flagellin, Pam3Cys, or TNF-α) in the presence or absence of IAP were applied to cell cultures, and IL-8 was measured. UDP caused dose-dependent increase in IL-8 release by immune cells and two gut epithelial cell lines, and IAP treatment abrogated IL-8 release. Costimulation with UDP and other inflammatory ligands resulted in a synergistic increase in IL-8 release, which was prevented by IAP treatment. In vivo, UDP in the presence or absence of IAP was instilled into a small intestinal loop model in wild-type and IAP-knockout mice. Luminal contents were applied to cell culture, and cytokine levels were measured in culture supernatant and intestinal tissue. UDP-treated luminal contents induced more inflammation on target cells, with a greater inflammatory response to contents from IAP-KO mice treated with UDP than from WT mice. Additionally, UDP treatment increased TNF-α levels in intestinal tissue of IAP-KO mice, and cotreatment with IAP reduced inflammation to control levels. Taken together, these studies show that IAP prevents inflammation caused by UDP alone and in combination with other ligands, and the anti-inflammatory effect of IAP against UDP persists in mouse small intestine. The benefits of IAP in intestinal disease may be partly due to inhibition of the proinflammatory activity of UDP.
Angiogenesis-related factors in skeletal muscles of COPD patients: roles of angiopoietin-2
Authors: Mofarrahi Mahroo , Sigala Ioanna , Vassilokopoulos Theodoros , Harel Sharon , Guo Yeting , Debigare Richard , Maltais Francois , Hussain Sabah N. A.
Published: January 2013

The role of angiogenesis factors in skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease (COPD) is unknown. The first objective of this study was to assess various pro- and antiangiogenic factor and receptor expressions in the vastus lateralis muscles of control subjects and COPD patients. Preliminary inquiries revealed that angiopoietin-2 (ANGPT2) is overexpressed in limb muscles of COPD patients. ANGPT2 promotes skeletal satellite cell survival and differentiation. Factors that are involved in regulating muscle ANGPT2 production are unknown. The second objective of this study was to evaluate how oxidants and proinflammatory cytokines influence muscle-derived ANGPT2 expression. Angiogenic gene expressions in human vastus lateralis biopsies were quantified with low-density real-time PCR arrays. ANGPT2 mRNA expressions in cultured skeletal myoblasts were quantified in response to proinflammatory cytokine and H2O2 exposure. Ten proangiogenesis genes, including ANGPT2, were significantly upregulated in the vastus lateralis muscles of COPD patients. ANGPT2 mRNA levels correlated negatively with forced expiratory volume in 1 s and positively with muscle wasting. Immunoblotting confirmed that ANGPT2 protein levels were significantly greater in muscles of COPD patients compared with control subjects. ANGPT2 expression was induced by interferon-γ and -β and by hydrogen peroxide, but not by tumor necrosis factor. We conclude that upregulation of ANGPT2 expression in vastus lateralis muscles of COPD patients is likely due to oxidative stress and represents a positive adaptive response aimed at facilitating myogenesis and angiogenesis.
Implications of complex anatomical junctions on conductance catheter measurements of coronary arteries
Authors: Choi Hyo Won , Zhang Zhen-Du , Farren Neil D. , Kassab Ghassan S.
Published: January 2013

In vivo, the position of the conductance catheter to measure vessel lumen cross-sectional area may vary depending on where the conductance catheter is deployed in the complex anatomical geometry of arteries, including branches, bifurcations, or curvatures. The objective here is to determine how such geometric variations affect the cross-sectional area (CSA) estimates obtained using the cylindrical model. Computer simulations and in vitro and in vivo experiments were used to assess how the electric field and associated CSA measurement accuracy are affected by three typical in vivo conditions: 1) a vessel with abrupt change in lumen diameter (e.g., transition from aorta to coronary ostia); 2) a vessel with a T-bifurcation or a Y-bifurcation; and 3) a vessel curvature, such as in the right coronary artery, aorta, or pulmonary artery. The error in diameter from simulation results was shown to be relatively small (<7%), unless the detection electrodes were placed near the junction between two different lumen diameters or at a bifurcation junction. Furthermore, the present findings show that the effect of misaligned catheter-vessel geometrical configuration and vessel curvature on measurement accuracy is negligible. Collectively, the findings support the accuracy of the conductance method for sizing blood vessels, despite the geometric complexities of the cardiovascular system, as long as the detection electrodes are not placed at a large discontinuity in diameter or at bifurcation junctions.
Adiponectin concentration is associated with muscle insulin sensitivity, AMPK phosphorylation, and ceramide content in skeletal muscles of men but not women
Authors: Høeg Louise D. , Sjøberg Kim A. , Lundsgaard Anne-Marie , Jordy Andreas B. , Hiscock Natalie , Wojtaszewski Jørgen F. P. , Richter Erik A. , Kiens Bente
Published: January 2013

Adiponectin is an adipokine that regulates metabolism and increases insulin sensitivity. Mechanisms behind this insulin-sensitizing effect have been investigated in rodents, but little is known in humans, especially in skeletal muscle. Women have higher serum concentrations of adiponectin than men and are generally more insulin sensitive in skeletal muscle than men. We show here that large differences exist between men and women with regard to apparent adiponectin regulation of insulin-stimulated glucose uptake in skeletal muscle. Serum adiponectin was significantly associated with leg glucose uptake in healthy, young, lean men, but the association was absent in women. In addition, serum adiponectin was significantly associated with AMP-activated protein kinase (AMPK) phosphorylation in skeletal muscles of men but not in women. Serum adiponectin was also significantly, negatively associated with skeletal muscle ceramide content in men only, and interestingly, ceramide content was negatively associated with adiponectin receptor 1 (AdipoR1) expression in skeletal muscles of men. Women had lower AdipoR1 expression in skeletal muscle and a lower percentage of glycolytic adiponectin-sensitive type 2 muscle fibers than men. These associations suggest that the insulin-sensitizing effect of adiponectin on human male skeletal muscles may be mediated via AdipoR1 to activation of AMPK, leading to lowering of ceramide content. The lower skeletal muscle AdipoR1 protein expression and lower expression of adiponectin-sensitive type 2 muscle fibers in women than in men may explain the apparent lesser sensitivity to adiponectin in women.
The disembodiment effect of negation: negating action-related sentences attenuates their interference on congruent upper limb movements
Authors: Bartoli Eleonora , Tettamanti Andrea , Farronato Paolo , Caporizzo Armanda , Moro Andrea , Gatti Roberto , Perani Daniela , Tettamanti Marco
Published: January 2013

Human languages can express opposite propositions by means of the negative operator “not,” which turns affirmative sentences into negative ones. Psycholinguistic research has indicated that negative meanings are formed by transiently reducing the access to mental representations of negated conceptual information. Neuroimaging studies have corroborated these findings, showing reduced activation of concept-specific embodied neural systems by negative versus affirmative sentences. This “disembodiment effect” of sentential negation should have two distinct consequences: first, the embodied systems should be computationally more free to support concurrent tasks when processing negative than affirmative sentences; second, the computational interference should only be reduced when there is a strict semantic congruency between the negated concept and the referent targeted by concurrent tasks. We tested these two predictions in two complementary experiments involving the comprehension of action-related sentences and kinematic measurements of its effects on concurrent, congruent actions. Sentences referred to actions involving either proximal or distal arm musculature. In experiment 1, requiring a proximal arm movement, we found interference reduction for negative proximal sentences. In experiment 2, requiring a distal arm movement, we found interference reduction for negative distal sentences. This dissociation provides the first conclusive evidence in support of a disembodiment theory of negation. We conclude that the computational cost resulting from the insertion of an additional lexical item (“not”) in negative sentences is compensated by solely storing a concept in affirmative form in semantic memory, since its negative counterpart can be produced by transiently reducing the access to such stored semantic information.
Senescence Sensitivity of Breast Cancer Cells Is Defined by Positive Feedback Loop between CIP2A and E2F1
Authors: Laine Anni , Sihto Harri , Come Christophe , Rosenfeldt Mathias T. , Zwolinska Aleksandra , Niemelä Minna , Khanna Anchit , Chan Edward K. , Kähäri Veli-Matti , Kellokumpu-Lehtinen Pirkko-Liisa , Sansom Owen J. , Evan Gerard I. , Junttila Melissa R. , Ryan Kevin M. , Marine Jean-Christophe , Joensuu Heikki , Westermarck Jukka
Published: January 2013

Senescence induction contributes to cancer therapy responses and is crucial for p53-mediated tumor suppression. However, whether p53 inactivation actively suppresses senescence induction has been unclear. Here, we show that E2F1 overexpression, due to p53 or p21 inactivation, promotes expression of human oncoprotein CIP2A, which in turn, by inhibiting PP2A activity, increases stabilizing serine 364 phosphorylation of E2F1. Several lines of evidence show that increased activity of E2F1-CIP2A feedback renders breast cancer cells resistant to senescence induction. Importantly, mammary tumorigenesis is impaired in a CIP2A-deficient mouse model, and CIP2A-deficient tumors display markers of senescence induction. Moreover, high CIP2A expression predicts for poor prognosis in a subgroup of patients with breast cancer treated with senescence-inducing chemotherapy. Together, these results implicate the E2F1-CIP2A feedback loop as a key determinant of breast cancer cell sensitivity to senescence induction. This feedback loop also constitutes a promising prosenescence target for therapy of cancers with an inactivated p53–p21 pathway.

Significance: It has been recently realized that most currently used chemotherapies exert their therapeutic effect at least partly by induction of terminal cell arrest, senescence. However, the mechanisms by which cell-intrinsic senescence sensitivity is determined are poorly understood. Results of this study identify the E2F1-CIP2A positive feedback loop as a key determinant of breast cancer cell sensitivity to senescence and growth arrest induction. Our data also indicate that this newly characterized interplay between 2 frequently overexpressed oncoproteins constitutes a promising prosenescence target for therapy of cancers with inactivated p53 and p21. Finally, these results may also facilitate novel stratification strategies for selection of patients to receive senescence-inducing cancer therapies. Cancer Discov; 3(2); 182–97. ©2013 AACR.

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Omi/HtrA2 and XIAP are components of platelet apoptosis signalling
Authors: Winkler Jeannine , Rand Margaret , Schmugge Markus , Speer Oliver
Published: January 2013

Although platelets possess the hallmarks of apoptosis such as activation of caspases, cytochrome c release and depolarisation of the mitochondrial transmembrane potential (ΔΨm), their entire apoptotic-signalling pathway is not totally understood. Therefore we studied the expression of various apoptotic proteins and found that platelets contain the pro-apoptotic proteins Omi/HtrA2 and Smac/Diablo, as well as their target the X-linked inhibitor of apoptosis XIAP. Omi/HtrA2 and Smac/Diablo were released from mitochondria into the platelet cytosol together with cytochrome c after induction of apoptosis by the Ca2+ ionophore A23187 or the BH3 mimetic ABT-737, and to a lesser extent, after platelet stimulation with collagen and thrombin. Inhibition of Omi/HtrA2 led to decreased levels of activated caspase-3/7 and caspase-9, but did not abolish loss of ΔΨm or prevent release of Omi/HtrA2 from mitochondria. These results indicate that platelets have a functional intrinsic apoptotic-signalling pathway including the pro-apoptotic protease Omi/HtrA2 and its target protein XIAP.
Zinc: An important cofactor in haemostasis and thrombosis
Authors: Vu Trang , Fredenburgh James , Weitz Jeffrey
Published: January 2013

There is mounting evidence that zinc, the second most abundant transition metal in blood, is an important mediator of haemostasis and thrombosis. Prompted by the observation that zinc deficiency is associated with bleeding and clotting abnormalities, there now is evidence that zinc serves as an effector of coagulation, anticoagulation and fibrinolysis. Zinc binds numerous plasma proteins and modulates their structure and function. Because activated platelets secrete zinc into the local microenvironment, the concentration of zinc increases in the vicinity of a thrombus. Consequently, the role of zinc varies depending on the microenvironment; a feature that endows zinc with the capacity to spatially and temporally regulate haemostasis and thrombosis. This paper reviews the mechanisms by which zinc regulates coagulation, platelet aggregation, anticoagulation and fibrinolysis and outlines how zinc serves as a ubiquitous modulator of haemostasis and thrombosis.
Significance of F8 missense mutations with respect to inhibitor formation
Authors: Pavlova Anna , Albert Thilo , Caspers Michael , Oldenburg Johannes , Schwaab Rainer
Published: January 2013

We have identified 1,135 haemophilia A patients with missense mutations associated with mild (46%), moderate (22%), severe (16%), and mixed haemophilia phenotypes (11%). Altogether, we detected 374 different missense mutations of which 195 are not listed in the HAMSTeRS database. While missense mutations are strongly underrepresented within the factor VIII (FVIII) B-domain, they are evenly distributed throughout the entire F8 cDNA sequence. Only 36 (5%) of 720 patients with missense mutations and known inhibitor status showed an association with inhibitor formation. Inhibitor prevalence was four-fold higher for severe haemophilia compared to mild/moderate phenotypes. Mutations associated with inhibitor formation were especially clustered within the C1/C2 domain compared to the other domains (8.7% C1/C2 domain vs. 3.6% non-C1/C2-domain; p-value: 0.01). Three different missense mutations (T314A [T295A], S2010P [S1991P], R2169H [R2150H]) were associated twice with inhibitor formation. Importantly, we found that the risk of inhibitor formation in association with FVIII missense mutations is significant higher if the amino acid substitution belongs to another physicochemical class than the original residue (p-value 0.039). For this purpose distinct classes of substitutions were grouped in association with side chains properties: class I, small/hydrophobic; class II, neutral; class III, acidic; class IV, basic. Thus, although missense mutations were associated with an overall lower risk of inhibitor formation compared to other F8 gene mutation types, different missense mutations correlate with specific risks for inhibitor formation. These differences have to be identified in assigning risk profiles to aid in choice of preventative treatments designed to prevent inhibitor formation.
The concurrent use of antithrombotic therapies and the risk of bleeding in patients with atrial fibrillation
Authors: Azoulay Laurent , Dell’Aniello Sophie , Simon Teresa , Renoux Christel , Suissa Samy
Published: January 2013

Patients with atrial fibrillation (AF) often receive, in addition to warfarin, antithrombotic drugs to manage other comorbid conditions. To date, few population-based studies have quantified the bleeding risk associated with the concurrent use of these therapies. The United Kingdom General Practice Research Database was used to identify a cohort of 70,760 patients newly-diagnosed with AF between 1993 and 2008. A nested case-control analysis was conducted within that cohort, and conditional logistic regression was used to estimate adjusted rate ratios (RRs) of bleeding associated with current use of warfarin, aspirin, and clopidogrel in single therapy, as well as in dual and triple therapy, as compared with non-use of any therapy. A total of 10,850 patients experienced a bleeding event during follow-up. In single therapy, warfarin was associated with the highest increased risk (RR: 2.08, 95% confidence interval [CI]: 1.95–2.23), followed by clopidogrel (RR: 1.57, 95% CI: 1.37–1.81) and aspirin (RR: 1.25, 95% CI: 1.17–1.34). In dual therapy, combinations containing warfarin were associated with a higher increased risk (warfarin-aspirin: RR: 2.87, 95% CI: 2.58–3.19, and warfarin-clopidogrel: RR: 2.74, 95% CI: 2.14–3.51), than those not containing warfarin (aspirin-clopidogrel: RR: 1.68, 95% CI: 1.44–1.97). Triple therapy of warfarin-aspirin-clopidogrel was associated with the highest increased risk (RR: 3.75, 95% CI: 2.71–5.19). This large population-based study suggests that while all antithrombotic therapies are associated with an elevated risk of bleeding, the risks increase in an additive fashion with dual and triple therapy, particularly in combinations containing warfarin.
Hereditary angioedema: a bradykinin-mediated swelling disorder
Authors: Björkqvist Jenny , Sala-Cunill Anna , Renné Thomas
Published: January 2013

Edema is tissue swelling and is a common symptom in a variety of diseases. Edema form due to accumulation of fluids, either through reduced drainage or increased vascular permeability. There are multiple vascular signalling pathways that regulate vessel permeability. An important mediator that increases vascular leak is the peptide hormone bradykinin, which is the principal agent in the swelling disorder hereditary angioedema. The disease is autosomal dominant inherited and presents clinically with recurrent episodes of acute swelling that can be life-threatening involving the skin, the oropharyngeal, laryngeal, and gastrointestinal mucosa. Three different types of hereditary angiodema exist in patients. The review summarises current knowledge on the pathophysiology of hereditary angiodema and focuses on recent experimental and pharmacological findings that have led to a better understanding and new treatments for the disease.
Discrepancies between ADAMTS13 activity assays in patients with thrombotic microangiopathies
Authors: Langley Katy , Chitolie Andrew , Liesner Ri , Scully Marie , Machin Samuel , Peyvandi Flora , Mackie Ian
Published: January 2013

ADAMTS13 activity assays are sometimes useful in confirming the clinical diagnosis or to distinguish different thrombotic microangiopathies (TMA). We investigated the commonly used clinical assays for ADAMTS13 activity. 159 samples from normal subjects or acquired TMA patients were studied in collagen binding (CBA), Fret and chromogenic peptide substrate assays. Frozen aliquots of pooled normal plasma gave similar values by CBA, Fret-VWF73 peptide, Fret-VWF86 and chromogenic VWF73 ELISA (chr-VWF73). Two lyophilised commercial calibrants gave lower ADAMTS13 activity by CBA than peptide substrate assays. The addition of solid HEPES to normal plasma caused a significant fall in CBA, but not Fret-VWF73 activity and might partly explain the differences, since lyophilised plasmas are often HEPES buffered. Normal plasmas showed good agreement between CBA and Fret assays, although chr-VWF73 gave slightly higher values. In acquired TMA, there was reasonable agreement between assays for samples with <11% ADAMTS13 activity (83% of samples showed agreement between CBA, Fret-VWF73 and chr-VWF73), but samples with moderate deficiency frequently showed lower CBA levels (only 41–52% agreement). However, there were also some discrepancies among the peptide substrate assays, with Fret-VWF86 sometimes giving slightly higher values than the VWF73 substrate assays. An International reference plasma might improve standardisation, but is not the only problem. It is unclear which assay has greatest clinical utility, this may depend on the nature of the sample. If the activity does not match the clinical picture, an alternative method should be performed. Where therapeutic monitoring is required, the same activity assay should be used throughout.
Hirudin anticoagulation allows more rapid determination of P2Y12 inhibition by the VerifyNow P2Y12 assay
Authors: Daly Rebecca , Mehra Sonal , Dhutia Amrita , Howgego Kate , Ecob Rosemary , Judge Heather , Morton Allison , Storey Robert , Sumaya Wael
Published: January 2013

VerifyNow (VN) P2Y12 is a point-of-care assay used to assess response to P2Y12 inhibitors. Sodium citrate (citrate) is the standard anticoagulant used for this assay but requires a pre-incubation period. Hirudin is an alternative anticoagulant for platelet function studies that maintains physiological divalent cation levels. We investigated whether hirudin anticoagulation might allow more rapid testing of P2Y12 inhibition at the time of percutaneous coronary intervention (PCI). Blood was collected from the arterial sheath of aspirin-treated patients undergoing elective, urgent or emergency coronary angiography ± PCI and aliquots were anticoagulated with either citrate or hirudin. For each anticoagulant, VN P2Y12 was performed both immediately and after 20 minutes. A total of 98 patients were included in this study following pre-treatment with clopidogrel (n = 88), prasugrel (n = 6) or no P2Y12 inhibitor (n = 4). PRU with hirudin immediately (PRU_H_Imm) and PRU with citrate 20 minutes post sampling (PRU_C_20) were very strongly correlated (R = 0.95) though PRU_H_Imm tended to be lower than PRU_C_20 so that optimal correlation was estimated by the equation PRU_H_Imm = 0.95 x PRU_C_20 (p < 0.001). Bland-Altman plots showed good agreement between PRU_H_Imm and (0.95 x PRU_C_20). Platelet reactivity was more stable over the studied time course with hirudin as compared to citrate. We therefore conclude that VN P2Y12 with hirudin anticoagulation can be performed more rapidly and results are strongly correlated with delayed citrate measurements. Further studies are warranted to assess the utility of this method for improving clinical outcomes in patients undergoing PCI.
Left Ventricular Wall Thickness and the Presence of Asymmetric Hypertrophy in Healthy Young Army Recruits
Authors: Lee Phong T. , Dweck Marc R. , Prasher Sparsh , Shah Anoop , Humphries Steve E. , Pennell Dudley J. , Montgomery Hugh E. , Payne John R.
Published: January 2013

Background—

To use cardiovascular magnetic resonance to investigate left ventricular wall thickness and the presence of asymmetrical hypertrophy in young army recruits before and after a period of intense exercise training.

Methods and Results—

Using cardiovascular magnetic resonance, the left ventricular wall thickness was measured in all 17 segments and a normal range was calculated for each. The prevalence of asymmetrical wall thickening was assessed before and after training and defined by a ventricular wall thickness ≥13.0 mm that was >1.5× the thickness of the opposing myocardial segment. Five hundred forty-one men (mean age, 20±2 years) were recruited, 309 underwent repeat scanning. Considerable variation in wall thickness was observed across the ventricle with progressive thickening on moving from the apex to base (
P
<0.001) and in the basal and midcavity septum compared with the lateral wall (11.0±1.4 versus 10.1±1.3 mm;
P
<0.001). Twenty-three percent had a maximal wall thickness ≥13.0 mm, whereas the prevalence of asymmetrical wall thickening increased from 2.2% to 10% after the exercise-training program. In those who developed asymmetry, the wall thickness/diastolic volume ration remained normal (0.09±0.02 mm⋅m
2
⋅mL
−1
), indicative of a remodeling response to exercise.

Conclusions—

In a cohort of healthy young white men, we have demonstrated that wall thickness frequently measures ≥13.0 mm and that asymmetrical wall thickening is common and can develop as part of the physiological response to exercise. A diagnosis of hypertrophic cardiomyopathy in young athletic men should, therefore, not be made purely on the basis of regional wall thickening.
Visceral Adipose Tissue-derived Serine Proteinase Inhibitor Inhibits Apoptosis of Endothelial Cells as a Ligand for the Cell-Surface GRP78/Voltage-dependent Anion Channel Complex
Authors: Nakatsuka Atsuko , Wada Jun , Iseda Izumi , Teshigawara Sanae , Higashio Kanji , Murakami Kazutoshi , Kanzaki Motoko , Inoue Kentaro , Terami Takahiro , Katayama Akihiro , Hida Kazuyuki , Eguchi Jun , Ogawa Daisuke , Matsuki Yasushi , Hiramatsu Ryuji , Yagita Hideo , Kakuta Shigeru , Iwakura Yoichiro , Makino Hirofumi
Published: January 2013

Rationale:

Visceral adipose tissue-derived serine proteinase inhibitor (vaspin) is an adipokine identified from visceral adipose tissues of genetically obese rats.

Objective:

The role of vaspin in the diabetic vascular complications remains elusive, and we investigated the effects of vaspin on the vascular function under the diabetic milieu.

Methods and Results:

Adenovirus carrying the full length of the vaspin gene (Vaspin-Ad) ameliorated intimal proliferation of balloon-injured carotid arteries in diabetic Wistar rats. The expression of Ccl2, Pdgfb, and Pdgfrb genes was significantly reduced by the treatment of Vaspin-Ad. In cuff-injured femoral arteries, the intimal proliferation was ameliorated in vaspin transgenic (Vaspin Tg) mice. The application of recombinant vaspin and Vaspin-Ad promoted the proliferation and inhibited the apoptosis of human aortic endothelial cells. Adenovirus expressing vaspin with calmodulin and streptavidin-binding peptides was applied to human aortic endothelial cells, subjected to tandem tag purification and liquid chromatography-tandem mass spectrometry, and we identified GRP78 (78-kDa glucose-regulated protein) as an interacting molecule. The complex formation of vaspin, GRP78, and voltage-dependent anion channel on the plasma membrane was confirmed by the immunoprecipitation studies using aortas of Vaspin Tg mice. The binding assay using
125
I-vaspin in human aortic endothelial cells revealed high-affinity binding (dissociation constant = 0.565×10
–9
m) by the treatment of 5 μM thapsigargin, which recruited GRP78 from the endoplasmic reticulum to plasma membrane by inducing endoplasmic reticulum stress. In human aortic endothelial cells, vaspin induced phosphorylation of Akt and inhibited the kringle 5-induced Ca
2+
influx and subsequent apoptosis.

Conclusions:

Vaspin is a novel ligand for the cell-surface GRP78/voltage-dependent anion channel complex in endothelial cells and promotes proliferation, inhibits apoptosis, and protects vascular injuries in diabetes mellitus.
Molecular Imaging of the Paracrine Proangiogenic Effects of Progenitor Cell Therapy in Limb Ischemia
Authors: Ryu Jae Choon , Davidson Brian P. , Xie Aris , Qi Yue , Zha Daogang , Belcik J. Todd , Caplan Evan S. , Woda Juliana M. , Hedrick Catherine C. , Hanna Richard N. , Lehman Nicholas , Zhao Yan , Ting Anthony , Lindner Jonathan R.
Published: January 2013

Background—

Stem cells are thought to enhance vascular remodeling in ischemic tissue in part through paracrine effects. Using molecular imaging, we tested the hypothesis that treatment of limb ischemia with multipotential adult progenitor cells (MAPCs) promotes recovery of blood flow through the recruitment of proangiogenic monocytes.

Methods and Results—

Hind-limb ischemia was produced in mice by iliac artery ligation, and MAPCs were administered intramuscularly on day 1. Optical imaging of luciferase-transfected MAPCs indicated that cells survived for 1 week. Contrast-enhanced ultrasound on days 3, 7, and 21 showed a more complete recovery of blood flow and greater expansion of microvascular blood volume in MAPC-treated mice than in controls. Fluorescent microangiography demonstrated more complete distribution of flow to microvascular units in MAPC-treated mice. On ultrasound molecular imaging, expression of endothelial P-selectin and intravascular recruitment of CX
3
CR-1-positive monocytes were significantly higher in MAPC-treated mice than in the control groups at days 3 and 7 after arterial ligation. Muscle immunohistology showed a >10-fold-greater infiltration of monocytes in MAPC-treated than control-treated ischemic limbs at all time points. Intravital microscopy of ischemic or tumor necrosis factor-α–treated cremaster muscle demonstrated that MAPCs migrate to perimicrovascular locations and potentiate selectin-dependent leukocyte rolling. In vitro migration of human CD14
+
monocytes was 10-fold greater in response to MAPC-conditioned than basal media.

Conclusions—

In limb ischemia, MAPCs stimulate the recruitment of proangiogenic monocytes through endothelial activation and enhanced chemotaxis. These responses are sustained beyond the MAPC lifespan, suggesting that paracrine effects promote flow recovery by rebalancing the immune response toward a more regenerative phenotype.
Efficacy and Safety of Oral Treprostinil Monotherapy for the Treatment of Pulmonary Arterial Hypertension
Authors: Jing Zhi-Cheng , Parikh Keyur , Pulido Tomas , Jerjes-Sanchez Carlos , White R. James , Allen Roblee , Torbicki Adam , Xu Kai-Feng , Yehle David , Laliberte Kevin , Arneson Carl , Rubin Lewis J.
Published: January 2013

Background—

Pulmonary arterial hypertension (PAH) is a progressive, fatal disease with no cure. Parenteral and inhaled prostacyclin analogue therapies are effective for the treatment of PAH, but complicated administration requirements can limit the use of these therapies in patients with less severe disease. This study was designed to evaluate the safety and efficacy of the oral prostacyclin analogue treprostinil diolamine as initial treatment for de novo PAH.

Methods and Results—

Three hundred forty-nine patients (intent-to-treat population) not receiving endothelin receptor antagonist or phosphodiesterase type-5 inhibitor background therapy were randomized (treprostinil, n=233; placebo, n=116). The primary analysis population (modified intent-to-treat) included 228 patients (treprostinil, n=151; placebo, n=77) with access to 0.25-mg treprostinil tablets at randomization. The primary end point was change from baseline in 6-minute walk distance at week 12. Secondary end points included Borg dyspnea index, clinical worsening, and symptoms of PAH. The week 12 treatment effect for 6-minute walk distance (modified intent-to-treat population) was 23.0 m (
P
=0.0125). For the intent-to-treat population, 6-minute walk distance improvements were observed at peak (26.0 m;
P
=0.0001) and trough (17.0 m;
P
=0.0025) plasma study drug concentrations. Other than an improvement in the combined 6-minute walk distance/Borg dyspnea score, there were no significant changes in secondary end points. Oral treprostinil therapy was generally well tolerated; the most common adverse events (intent-to-treat) were headache (69%), nausea (39%), diarrhea (37%), and pain in jaw (25%).

Conclusions—

Oral treprostinil improves exercise capacity in PAH patients not receiving other treatment. Oral treprostinil could provide a convenient, first-line prostacyclin treatment option for PAH patients not requiring more intensive therapy.

Clinical Trial Registration:—

URL:
http://www.clinicaltrials.gov
. Unique identifier:
NCT00325403
.