bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence of Avian-Pathogenic Escherichia coli Strain O1 Genomic Islands among Extraintestinal and Commensal E. coli Isolates
Authors: Johnson Timothy J. , Wannemuehler Yvonne , Kariyawasam Subhashinie , Johnson James R. , Logue Catherine M. , Nolan Lisa K.
Published: March 2012

Escherichia colistrains that cause disease outside the intestine are known as extraintestinal pathogenicE. coli(ExPEC) and include pathogens of humans and animals. Previously, the genome of avian-pathogenicE. coli(APEC) O1:K1:H7 strain O1, from ST95, was sequenced and compared to those of several otherE. colistrains, identifying 43 genomic islands. Here, the genomic islands of APEC O1 were compared to those of other sequencedE. colistrains, and the distribution of 81 genes belonging to 12 APEC O1 genomic islands among 828 human and avian ExPEC and commensalE. coliisolates was determined. Multiple islands were highly prevalent among isolates belonging to the O1 and O18 serogroups within phylogenetic group B2, which are implicated in human neonatal meningitis. Because of the extensive genomic similarities between APEC O1 and other human ExPEC strains belonging to the ST95 phylogenetic lineage, its ability to cause disease in a rat model of sepsis and meningitis was assessed. Unlike other ST95 lineage strains, APEC O1 was unable to cause bacteremia or meningitis in the neonatal rat model and was significantly less virulent than uropathogenicE. coli(UPEC) CFT073 in a mouse sepsis model, despite carrying multiple neonatal meningitisE. coli(NMEC) virulence factors and belonging to the ST95 phylogenetic lineage. These results suggest that host adaptation or genome modifications have occurred either in APEC O1 or in highly virulent ExPEC isolates, resulting in differences in pathogenicity. Overall, the genomic islands examined provide targets for further discrimination of the different ExPEC subpathotypes, serogroups, phylogenetic types, and sequence types.
Important Role for Mycobacterium tuberculosis UvrD1 in Pathogenesis and Persistence apart from Its Function in Nucleotide Excision Repair
Authors: Houghton Joanna , Townsend Carolin , Williams Alan R. , Rodgers Angela , Rand Lucinda , Walker K. Barry , Böttger Erik C. , Springer Burkhard , Davis Elaine O.
Published: March 2012

Mycobacterium tuberculosissurvives and replicates in macrophages, where it is exposed to reactive oxygen and nitrogen species that damage DNA. In this study, we investigated the roles of UvrA and UvrD1, thought to be parts of the nucleotide excision repair pathway ofM. tuberculosis. Strains in whichuvrD1was inactivated either alone or in conjunction withuvrAwere constructed. Inactivation ofuvrD1resulted in a small colony phenotype, although growth in liquid culture was not significantly affected. The sensitivity of the mutant strains to UV irradiation and to mitomycin C highlighted the importance of the targeted genes for nucleotide excision repair. The mutant strains all exhibited heightened susceptibility to representatives of reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI). TheuvrD1and theuvrA uvrD1mutants showed decreased intracellular multiplication following infection of macrophages. Most importantly, theuvrA uvrD1mutant was markedly attenuated following infection of mice by either the aerosol or the intravenous route.
Allele-Dependent Differences in Quorum-Sensing Dynamics Result in Variant Expression of Virulence Genes in Staphylococcus aureus
Authors: Geisinger Edward , Chen John , Novick Richard P.
Published: March 2012

Agr is an autoinducing, quorum-sensing system that functions in many Gram-positive species and is best characterized in the pathogen
Staphylococcus aureus
, in which it is a global regulator of virulence gene expression. Allelic variations in the
agr
genes have resulted in the emergence of four quorum-sensing specificity groups in
S. aureus
, which correlate with different strain pathotypes. The basis for these predilections is unclear but is hypothesized to involve the phenomenon of quorum-sensing interference between strains of different
agr
groups, which may drive
S. aureus
strain isolation and divergence. Whether properties intrinsic to each
agr
allele directly influence virulence phenotypes within
S. aureus
is unknown. In this study, we examined group-specific differences in
agr
autoinduction and virulence gene regulation by utilizing congenic strains, each harboring a unique
S. aureus
agr
allele, enabling a dissection of
agr
locus-dependent versus genotype-dependent effects on quorum-sensing dynamics and virulence factor production. Employing a reporter fusion to the principal
agr
promoter, P3, we observed allele-dependent differences in the timing and magnitude of
agr
activation. These differences were mediated by polymorphisms within the
agrBDCA
genes and translated to significant variations in the expression of a key transcriptional regulator, Rot, and of several important exoproteins and surface factors involved in pathogenesis. This work uncovers the contribution of divergent quorum-sensing alleles to variant expression of virulence determinants within a bacterial species.
The PhoP/PhoQ System and Its Role in Serratia marcescens Pathogenesis
Authors: Barchiesi Julieta , Castelli María Eugenia , Di Venanzio Gisela , Colombo María Isabel , García Véscovi Eleonora
Published: March 2012

Serratia marcescens
is able to invade, persist, and multiply inside nonphagocytic cells, residing in nonacidic, nondegradative, autophagosome-like vacuoles. In this work, we have examined the physiological role of the PhoP/PhoQ system and its function in the control of critical virulence phenotypes in
S. marcescens
. We have demonstrated the involvement of the PhoP/PhoQ system in the adaptation of this bacterium to growth on scarce environmental Mg
2+
, at acidic pH, and in the presence of polymyxin B. We have also shown that these environmental conditions constitute signals that activate the PhoP/PhoQ system. We have found that the two
S. marcescens
mgtE
orthologs present a conserved PhoP-binding motif and demonstrated that
mgtE1
expression is PhoP dependent, reinforcing the importance of PhoP control in magnesium homeostasis. Finally, we have demonstrated that
phoP
expression is activated intracellularly and that a
phoP
mutant strain is defective in survival inside epithelial cells. We have shown that the
Serratia
PhoP/PhoQ system is involved in prevention of the delivery to degradative/acidic compartments.
Multimodal observational assessment of quality and productivity benefits from the implementation of wireless technology for out of hours working
Authors: Blakey John D , Guy Debbie , Simpson Carl , Fearn Andrew , Cannaby Sharon , Wilson Petra , Shaw Dominick
Published: March 2012

Objectives

The authors investigated if a wireless system of call handling and task management for out of hours care could replace a standard pager-based system and improve markers of efficiency, patient safety and staff satisfaction.

Design

Prospective assessment using both quantitative and qualitative methods, including interviews with staff, a standard satisfaction questionnaire, independent observation, data extraction from work logs and incident reporting systems and analysis of hospital committee reports.

Setting

A large teaching hospital in the UK.

Participants

Hospital at night co-ordinators, clinical support workers and junior doctors handling approximately 10 000 tasks requested out of hours per month.

Outcome measures

Length of hospital stay, incidents reported, co-ordinator call logging activity, user satisfaction questionnaire, staff interviews.

Results

Users were more satisfied with the new system (satisfaction score 62/90 vs 82/90, p=0.0080). With the new system over 70 h/week of co-ordinator time was released, and there were fewer untoward incidents related to handover and medical response (OR=0.30, p=0.02). Broad clinical measures (cardiac arrest calls for peri-arrest situations and length of hospital stay) improved significantly in the areas covered by the new system.

Conclusions

The introduction of call handling software and mobile technology over a medical-grade wireless network improved staff satisfaction with the Hospital at Night system. Improvements in efficiency and information flow have been accompanied by a reduction in untoward incidents, length of stay and peri-arrest calls.
How does capacity building of health managers work? A realist evaluation study protocol
Authors: Prashanth N S , Marchal Bruno , Hoeree Tom , Devadasan Narayanan , Macq Jean , Kegels Guy , Criel Bart
Published: March 2012

Introduction

There has been a lot of attention on the role of human resource management interventions to improve delivery of health services in low- and middle-income countries. However, studies on this subject are few due to limited research on implementation of programmes and methodological difficulties in conducting experimental studies on human resource interventions. The authors present the protocol of an evaluation of a district-level capacity-building intervention to identify the determinants of performance of health workers in managerial positions and to understand how changes (if any) are brought about.

Methods and analysis

The aim of this study is to understand how capacity building works. The authors will use realist evaluation to evaluate an intervention in Karnataka, India. The intervention is a capacity-building programme that seeks to improve management capacities of health managers at district and subdistrict levels through periodic classroom-based teaching and mentoring support at the workplace. The authors conducted interviews and reviewed literature on capacity building in health to draw out the programme theory of the intervention. Based on this, the authors formulated hypothetical pathways connecting the expected outcomes of the intervention (planning and supervision) to the inputs (contact classes and mentoring). The authors prepared a questionnaire to assess elements of the programme theory—organisational culture, self-efficacy and supervision. The authors shall conduct a survey among health managers as well as collect qualitative data through interviews with participants and non-participants selected purposively based on their planning and supervision performance. The authors will construct explanations in the form of context–mechanism–outcome configurations from the results. This will be iterative and the authors will use a realist evaluation framework to refine the explanatory theories that are based on the findings to explain and validate an improved theory on ‘what works for whom and under what conditions’.

Discussion

The scope for applying realist evaluation to study human resource management interventions in health are discussed.
Tracking the impact of research on policy and practice: investigating the feasibility of using citations in clinical guidelines for research evaluation
Authors: Kryl David , Allen Liz , Dolby Kevin , Sherbon Beverley , Viney Ian
Published: March 2012

Objectives

To investigate the feasibility of using research papers cited in clinical guidelines as a way to track the impact of particular funding streams or sources.

Setting

In recent years, medical research funders have made efforts to enhance the understanding of the impact of their funded research and to provide evidence of the ‘value’ of investments in particular areas of research. One of the most challenging areas of research evaluation is around impact on policy and practice. In the UK, the National Institute of Health and Clinical Excellence (NICE) provide clinical guidelines, which bring together current high-quality evidence on the diagnosis and treatment of clinical problems. Research referenced in these guidelines is an indication of its potential to have real impact on health policy and practice.

Design

This study is based on analysis of the authorship and funding attribution of research cited in two NICE clinical guidelines: dementia and chronic obstructive pulmonary disease.

Results

Analysis identified that around a third of papers cited in the two NICE guidelines had at least one author based in the UK. In both cases, about half of these UK attributed papers contained acknowledgements which allowed the source of funding for the research to be identified. The research cited in these guidelines was found to have been supported by a diverse set of funders from different sectors. The study also investigated the contribution of research groups based in universities, industry and the public sector.

Conclusions

The study found that there is great potential for guidelines to be used as sources of information on the quality of the research used in their development and that it is possible to track the source of the funding of the research. The challenge is in harnessing the relevant information to track this in an efficient way.
PROSpER: PReferences for the Organisation of acute health Services for oldER people: protocol for a mixed methods study: Figure 1
Authors: Howard Kirsten , Arendts Glenn , Jan Stephen , Beck Matthew
Published: March 2012

Background

Organisation of acute care services for people living in residential aged care facilities (RACF) is a complex area of health policy. For people living in RACF, the emergency department is often used to provide acute care; needs of RACF residents, however, are not always well met. Alternative models of delivering care must be acceptable to a variety of stakeholders; however, little is known about the values and preferences that people attach to aspects of how and where care is delivered.

Methods/design

The PROSpER Study examines people's preferences for the organisation of acute healthcare services for older people in RACF. The authors aim to (1) determine which factors influence preferences of residents, carers and providers for how and where acute care is delivered and (2) determine the relative importance of these factors and the acceptable trade-offs between them. Qualitative and quantitative methods will be used. One-on-one interviews will be conducted with RACF residents, their families, staff of RACF and emergency department staff. A discrete choice study will then be designed to quantitatively assess preferences for alternative models of care delivery. Approximately 600 respondents from three respondent groups will be surveyed: older people living in RACF, family members of aged care residents and staff of RACF. A mixed logit model will be used; results will be expressed as parameter estimates (β) and odds of choosing one option over an alternative. Trade-offs between attributes will also be calculated.

Ethics and dissemination

The PROSpER Study has been approved by the University of Sydney, Human Research Ethics Committee (Protocol numbers 10653 and 14382) and Royal Perth Hospital Ethics Committee (reference 2009/045). Results will be published in peer-reviewed scientific journals and via conference presentations; a newsletter will also be provided to study participants. A stakeholder roundtable will also be held to discuss the results.
Do home-visit programs for mothers with infants reduce parenting stress and increase social capital in Japan?
Authors: Fujiwara Takeo , Natsume Keiko , Okuyama Makiko , Sato Takuyo , Kawachi Ichiro
Published: March 2012

Background

Distress during child rearing is known as a risk factor for child maltreatment. In addition, it is known that social capital can be a preventive factor for child maltreatment. The purpose of this study is to evaluate whether the home-visit program reduces parenting stress and increases the social capital in the community.

Methods

The home-visit program was implemented when the infants were 1–2 month of age (by public health nurses or midwives) and/or 4 months of age for those mothers who agreed to a home visit by trained community staff. Self-administered questionnaires on parenting stress scale and social capital were sent to all mothers who delivered a baby between August and November 2009 in two cities in the Aichi prefecture, Japan.

Results

Among 936 mothers, 347 mothers (follow-up rate: 37%) completed both questionnaires. Scores on parenting stress scale scores at 4 months were lower than those at 1–2 months among the four groups (no home visit, home visit at 1–2 months, home visit at 4 months and both). The social trust scores at 4 months were higher than those at 1–2 months in every group; however, multivariate regression analysis showed that there were no differences in the reduction of the parenting stress scale scores and increase in social trust between the four groups.

Conclusion

The home-visit program conducted once or twice by public health nurses or trained community staff for mothers with infants showed no substantial reduction in maternal stress and no increase in social trust.
CT-guided cryoablation for palliation of secondary trigeminal neuralgia from head and neck malignancy
Authors: Dar Suhail A , Love Zachary , Prologo John D , Hsu Daniel Pierce
Published: March 2012

Background

Facial pain is a common presentation secondary to tumoral invasion, rendering an individual unable to perform basic activities such as eating and talking. Cryotherapy may be appropriate in patients seeking immediate pain relief for trigeminal neuralgia (TN) near the end of life with its minimal invasiveness and procedural morbidity. While cryosurgery has been effectively demonstrated in the treatment of primary TN, this study is unique as it is the first documented use of CT guidance and treatment of secondary TN using percutaneous cryoablation.

Aim

To perform and report experience with CT-guided percutaneous cryoablation, a palliative treatment for TN secondary to recurrent invasive head and neck carcinoma, in patients previously treated with chemotherapy, radiotherapy and/or surgery with the goal of improving functional status and quality of life.

Methods

Palliative cryoablation procedures performed under CT guidance on recurrent head and neck malignancy between September 2010 and June 2011 were retrospectively analyzed. The procedure was performed under general anesthesia or conscious sedation. For each patient, 1–2 cryoprobes were placed in the tumor and two or four freeze-thaw cycles were performed. Patients were evaluated for facial pain relief immediately after treatment by telephone follow-up.

Results

Three patients underwent treatment for three masses using CT-guided percutaneous cryoablation. On imaging, technical success was achieved in all cases with hypodense ice formation encompassing symptomatic lesions on the CT scan. No procedural complications were encountered with post-procedure pain relief and reduction in required pain medication noted in all patients. One patient had 1 month of pain relief before the symptoms returned.

Conclusion

CT-guided percutaneous cryoablation is an efficient minimally invasive method for the palliative treatment of TN secondary to recurrent invasive head and neck carcinoma as a result of direct tumoral invasion of the extracranial divisions of the trigeminal nerve. Patients meeting the therapeutic criteria of individuals treated for musculoskeletal metastatic lesions may benefit from this treatment. The results suggest it may not currently be a curative technique as one patient's symptoms returned, but it could prove useful as an adjunct to current palliative therapies with minimal invasiveness and procedural morbidity, especially in patients seeking pain palliation, improved functional status and improved quality of life near the end of life.
The polysulfide diallyl trisulfide protects the ischemic myocardium by preservation of endogenous hydrogen sulfide and increasing nitric oxide bioavailability
Authors: Predmore Benjamin L. , Kondo Kazuhisa , Bhushan Shashi , Zlatopolsky Maxim A. , King Adrienne L. , Aragon Juan Pablo , Grinsfelder D. Bennett , Condit Marah E. , Lefer David J.
Published: March 2012

Diallyl trisulfide (DATS), a polysulfide constituent found in garlic oil, is capable of the release of hydrogen sulfide (H2S). H2S is a known cardioprotective agent that protects the heart via antioxidant, antiapoptotic, anti-inflammatory, and mitochondrial actions. Here, we investigated DATS as a stable donor of H2S during myocardial ischemia-reperfusion (MI/R) injury in vivo. We investigated endogenous H2S levels, infarct size, postischemic left ventricular function, mitochondrial respiration and coupling, endothelial nitric oxide (NO) synthase (eNOS) activation, and nuclear E2-related factor (Nrf2) translocation after DATS treatment. Mice were anesthetized and subjected to a surgical model of MI/R injury with and without DATS treatment (200 μg/kg). Both circulating and myocardial H2S levels were determined using chemiluminescent gas chromatography. Infarct size was measured after 45 min of ischemia and 24 h of reperfusion. Troponin I release was measured at 2, 4, and 24 h after reperfusion. Cardiac function was measured at baseline and 72 h after reperfusion by echocardiography. Cardiac mitochondria were isolated after MI/R, and mitochondrial respiration was investigated. NO metabolites, eNOS phosphorylation, and Nrf2 translocation were determined 30 min and 2 h after DATS administration. Myocardial H2S levels markedly decreased after I/R injury but were rescued by DATS treatment ( P < 0.05). DATS administration significantly reduced infarct size per area at risk and per left ventricular area compared with control ( P < 0.001) as well as circulating troponin I levels at 4 and 24 h ( P < 0.05). Myocardial contractile function was significantly better in DATS-treated hearts compared with vehicle treatment ( P < 0.05) 72 h after reperfusion. DATS reduced mitochondrial respiration in a concentration-dependent manner and significantly improved mitochondrial coupling after reperfusion ( P < 0.01). DATS activated eNOS ( P < 0.05) and increased NO metabolites ( P < 0.05). DATS did not appear to significantly induce the Nrf2 pathway. Taken together, these data suggest that DATS is a donor of H2S that can be used as a cardioprotective agent to treat MI/R injury.
Refractoriness of sarcoplasmic reticulum Ca2+ release determines Ca2+ alternans in atrial myocytes
Authors: Shkryl Vyacheslav M. , Maxwell Joshua T. , Domeier Timothy L. , Blatter Lothar A.
Published: March 2012

Cardiac alternans is a recognized risk factor for cardiac arrhythmia and sudden cardiac death. At the cellular level, Ca2+ alternans appears as cytosolic Ca2+ transients of alternating amplitude at regular beating frequency. Cardiac alternans is a multifactorial process but has been linked to disturbances in intracellular Ca2+ regulation. In atrial myocytes, we tested the role of voltage-gated Ca2+ current, sarcoplasmic reticulum (SR) Ca2+ load, and restitution properties of SR Ca2+ release for the occurrence of pacing-induced Ca2+ alternans. Voltage-clamp experiments revealed that peak Ca2+ current was not affected during alternans, and alternans of end-diastolic SR Ca2+ load, evaluated by application of caffeine or measured directly with an intra-SR fluorescent Ca2+ indicator (fluo-5N), were not a requirement for cytosolic Ca2+ alternans. Restitution properties and kinetics of refractoriness of Ca2+ release after activation during alternans were evaluated by four different approaches: measurements of 1) the delay (latency) of occurrence of spontaneous global Ca2+ releases and 2) Ca2+ spark frequency, both during rest after a large and small alternans Ca2+ transient; 3) the magnitude of premature action potential-induced Ca2+ transients after a large and small beat; and 4) the efficacy of a photolytically induced Ca2+ signal (Ca2+ uncaging from DM-nitrophen) to trigger additional Ca2+ release during alternans. The results showed that the latency of global spontaneous Ca2+ release was prolonged and Ca2+ spark frequency was decreased after the large Ca2+ transient during alternans. Furthermore, the restitution curve of the Ca2+ transient elicited by premature action potentials or by photolysis-induced Ca2+ release from the SR lagged behind after a large-amplitude transient during alternans compared with the small-amplitude transient. The data demonstrate that beat-to-beat alternation of the time-dependent restitution properties and refractory kinetics of the SR Ca2+ release mechanism represents a key mechanism underlying cardiac alternans.
Enhanced sensitivity of aged fibrotic hearts to angiotensin II- and hypokalemia-induced early afterdepolarization-mediated ventricular arrhythmias
Authors: Bapat Aneesh , Nguyen Thao P. , Lee Jong-Hwan , Sovari Ali A. , Fishbein Michael C. , Weiss James N. , Karagueuzian Hrayr S.
Published: March 2012

Unlike young hearts, aged hearts are highly susceptible to early afterdepolarization (EAD)-mediated ventricular fibrillation (VF). This differential may result from age-related structural remodeling (fibrosis) or electrical remodeling of ventricular myocytes or both. We used optical mapping and microelectrode recordings in Langendorff-perfused hearts and patch-clamp recordings in isolated ventricular myocytes from aged (24–26 mo) and young (3–4 mo) rats to assess susceptibility to EADs and VF during either oxidative stress with ANG II (2 μM) or ionic stress with hypokalemia (2.7 mM). ANG II caused EAD-mediated VF in 16 of 19 aged hearts (83%) after 32 ± 7 min but in 0 of 9 young hearts (0%). ANG II-mediated VF was suppressed with KN-93 (Ca2+/calmodulin-dependent kinase inhibitor) and the reducing agent N-acetylcysteine. Hypokalemia caused EAD-mediated VF in 11 of 11 aged hearts (100%) after 7.4 ± 0.4 min. In 14 young hearts, however, VF did not occur in 6 hearts (43%) or was delayed in onset (31 ± 22 min, P < 0.05) in 8 hearts (57%). In patch-clamped myocytes, ANG II and hypokalemia ( n = 6) induced EADs and triggered activity in both age groups ( P = not significant) at a cycle length of >0.5 s. When myocytes of either age group were coupled to a virtual fibroblast using the dynamic patch-clamp technique, EADs arose in both groups at a cycle length of <0.5 s. Aged ventricles had significantly greater fibrosis and reduced connexin43 gap junction density compared with young hearts. The lack of differential age-related sensitivity at the single cell level in EAD susceptibility indicates that increased ventricular fibrosis in the aged heart plays a key role in increasing vulnerability to VF induced by oxidative and ionic stress.
Role of KATP channel in electrical depression and asystole during long-duration ventricular fibrillation in ex vivo canine heart
Authors: Taylor Tyson G. , Venable Paul W. , Shibayama Junko , Warren Mark , Zaitsev Alexey V.
Published: March 2012

Long-duration ventricular fibrillation (LDVF) in the globally ischemic heart is characterized by transmurally heterogeneous decline in ventricular fibrillation rate (VFR), emergence of inexcitable regions, and eventual global asystole. Rapid loss of both local and global excitability is detrimental to successful defibrillation and resuscitation during cardiac arrest. We sought to assess the role of the ATP-sensitive potassium current ( IKATP) in the timing and spatial pattern of electrical depression during LDVF in a structurally normal canine heart. We analyzed endo-, mid-, and epicardial unipolar electrograms and epicardial optical recordings in the left ventricle of isolated canine hearts during 10 min of LDVF in the absence (control) and presence of an IKATP blocker glybenclamide (60 μM). In all myocardial layers, average VFR was the same or higher in glybenclamide-treated than in control hearts. The difference increased with time of LDVF and was overall significant in all layers ( P < 0.05). However, glybenclamide did not significantly affect the transmural VFR gradient. In epicardial optical recordings, glybenclamide shortened diastolic intervals, prolonged action potential duration, and decreased the percentage of inexcitable area (all differences P < 0.001). During 10 min of LDVF, asystole occurred in 55.6% of control and none of glybenclamide-treated hearts ( P < 0.05). In three hearts paced after the onset of asystole, there was no response to LV epicardial or atrial pacing. In structurally normal canine hearts, IKATP opening during LDVF is a major factor in the onset of local and global inexcitability, whereas it has a limited role in overall deceleration of VFR and the transmural VFR gradient.
Mechanisms of ventricular arrhythmias: a dynamical systems-based perspective
Authors: Cherry Elizabeth M. , Fenton Flavio H. , Gilmour Robert F.
Published: March 2012

Defining the cellular electrophysiological mechanisms for ventricular tachyarrhythmias is difficult, given the wide array of potential mechanisms, ranging from abnormal automaticity to various types of reentry and kk activity. The degree of difficulty is increased further by the fact that any particular mechanism may be influenced by the evolving ionic and anatomic environments associated with many forms of heart disease. Consequently, static measures of a single electrophysiological characteristic are unlikely to be useful in establishing mechanisms. Rather, the dynamics of the electrophysiological triggers and substrates that predispose to arrhythmia development need to be considered. Moreover, the dynamics need to be considered in the context of a system, one that displays certain predictable behaviors, but also one that may contain seemingly stochastic elements. It also is essential to recognize that even the predictable behaviors of this complex nonlinear system are subject to small changes in the state of the system at any given time. Here we briefly review some of the short-, medium-, and long-term alterations of the electrophysiological substrate that accompany myocardial disease and their potential impact on the initiation and maintenance of ventricular arrhythmias. We also provide examples of cases in which small changes in the electrophysiological substrate can result in rather large differences in arrhythmia outcome. These results suggest that an interrogation of cardiac electrical dynamics is required to provide a meaningful assessment of the immediate risk for arrhythmia development and for evaluating the effects of putative antiarrhythmic interventions.
Endothelium-specific sepiapterin reductase deficiency in DOCA-salt hypertension
Authors: Youn Ji Youn , Wang Ting , Blair John , Laude Karine M. , Oak Jeong-Ho , McCann Louise A. , Harrison David G. , Cai Hua
Published: March 2012

The endothelial nitric oxide synthase (eNOS) requires tetrahydrobiopterin (H4B) as a cofactor and, in its absence, produces superoxide (O2·−) rather than nitric oxide (NO·), a condition referred to as eNOS uncoupling. DOCA-salt-induced hypertension is associated with H4B oxidation and uncoupling of eNOS. The present study investigated whether administration of sepiapterin or H4B recouples eNOS in DOCA-salt hypertension. Bioavailable NO·detected by electron spin resonance was markedly reduced in aortas of DOCA-salt hypertensive mice. Preincubation with sepiapterin (10 μmol/l for 30 min) failed to improve NO·bioavailability in hypertensive aortas while it augmented NO·production from control vessels, implicating a hypertension-associated deficiency in sepiapterin reductase (SPR), the rate-limiting enzyme for sepiapterin conversion to H4B. Indeed, a decreased SPR expression was observed in aortic endothelial cells, but not in endothelium-denuded aortic remains, implicating an endothelium-specific SPR deficiency. Administration of hypertensive aortas with H4B (10 μmol/l, 30 min) partially restored vascular NO·production. Combined administration of H4B and the NADPH oxidase inhibitor apocynin (100 μmol/l, 30 min) fully restored NO·bioavailability while reducing O2·−production. In angiotensin II-induced hypertension, however, aortic endothelial SPR expression was not affected. In summary, administration of sepiapterin is not effective in recoupling eNOS in DOCA-salt hypertension, due to an endothelium-specific loss in SPR, whereas coadministration of H4B and apocynin is highly efficient in recoupling eNOS. This is consistent with our previous observations that in angiotensin II hypertension, endothelial deficiency in dihydrofolate reductase is alternatively responsible for uncoupling of eNOS. Taken together, these data indicate that strategies specifically targeting at different H4B metabolic enzymes might be necessary in restoring eNOS function in different types of hypertension.
Angiotensin-(1–7) attenuates hypertension in exercise-trained renal hypertensive rats
Authors: Shah Amin , Oh Young-Bin , Lee Sun Hwa , Lim Jung Min , Kim Suhn Hee
Published: March 2012

Angiotensin-(1–7) [ANG-(1–7)] plays a counterregulatory role to angiotensin II in the renin-angiotensin system. In trained spontaneous hypertensive rats, Mas expression and protein are upregulated in ventricular tissue. Therefore, we examined the role of ANG-(1–7) on cardiac hemodynamics, cardiac functions, and cardiac remodeling in trained two-kidney one-clip hypertensive (2K1C) rats. For this purpose, rats were divided into sedentary and trained groups. Each group consists of sham and 2K1C rats with and without ANG-(1–7) infusion. Swimming training was performed for 1 h/day, 5 days/wk for 4 wk following 1 wk of swimming training for acclimatization. 2K1C rats showed moderate hypertension and left ventricular hypertrophy without changing left ventricular function. Chronic infusion of ANG-(1–7) attenuated hypertension and cardiac hypertrophy only in trained 2K1C rats but not in sedentary 2K1C rats. Chronic ANG-(1–7) treatment significantly attenuated increases in myocyte diameter and cardiac fibrosis induced by hypertension in only trained 2K1C rats. The Mas receptor, ANG II type 2 receptor protein, and endothelial nitric oxide synthase phosphorylation in ventricles were upregulated in trained 2K1C rats. In conclusion, chronic infusion of ANG-(1–7) attenuates hypertension in trained 2K1C rats.
Shear stress modulates RAGE-mediated inflammation in a model of diabetes-induced metabolic stress
Authors: DeVerse J. Sherrod , Bailey Keith A. , Jackson Kaleena N. , Passerini Anthony G.
Published: March 2012

Atherosclerosis occurs preferentially at sites of disturbed blood flow despite the influence of risk factors contributing to systemic inflammation. The receptor for advanced glycation endproducts (RAGE) is a prominent mediator of inflammation in diabetes that is upregulated in atherosclerotic plaques. Our goal was to elucidate a role for arterial hemodynamics in the regulation of RAGE expression and activity. Endothelial RAGE expression was elevated at sites of flow disturbance in the aortas of healthy swine. To demonstrate a direct role for physiological shear stress (SS) in modulating RAGE expression, human aortic endothelial cells (HAEC) were exposed to high SS (HSS; 15 dyn/cm2), which downregulated RAGE by fourfold, or oscillatory SS (OSS; 0 ± 5 dyn/cm2), which upregulated RAGE by threefold, compared with static culture at 4 h. In a model of diabetes-induced metabolic stress, HAEC were chronically conditioned under high glucose (25 mM) and then simultaneously stimulated with TNF-α (0.5 ng/ml) and the RAGE ligand high mobility group box 1 (HMGB1). A 50% increase in VCAM-1 expression over TNF-α was associated with increased cytoplasmic and mitochondrial reactive oxygen species and NF-κB activity. This increase was RAGE-specific and NADPH oxidase dependent. In activated HAEC, OSS amplified HMGB1-induced VCAM-1 (3-fold) and RAGE (1.6-fold) expression and proportionally enhanced monocyte adhesion to HAEC in a RAGE-dependent manner, while HSS mitigated these increases to the level of TNF-α alone. We demonstrate that SS plays a fundamental role in regulating RAGE expression and inflammatory responses in the endothelium. These findings may provide mechanistic insight into how diabetes accelerates the nonrandom distribution of atherosclerosis in arteries.
Functional role of astrocyte glutamate receptors and carbon monoxide in cerebral vasodilation response to glutamate
Authors: Parfenova Helena , Tcheranova Dilyara , Basuroy Shyamali , Fedinec Alexander L. , Liu Jianxiong , Leffler Charles W.
Published: March 2012

In newborn pigs, vasodilation of pial arterioles in response to glutamate is mediated via carbon monoxide (CO), a gaseous messenger endogenously produced from heme degradation by a heme oxygenase (HO)-catalyzed reaction. We addressed the hypothesis that ionotropic glutamate receptors (iGluRs), including N-methyl-d-aspartic acid (NMDA)- and 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl) propanoic acid (AMPA)/kainate-type receptors, expressed in cortical astrocytes mediate glutamate-induced astrocyte HO activation that leads to cerebral vasodilation. Acute vasoactive effects of topical iGluR agonists were determined by intravital microscopy using closed cranial windows in anesthetized newborn pigs. iGluR agonists, including NMDA, (±)1-aminocyclopentane-cis-1,3-dicarboxylic acid (cis-ACPD), AMPA, and kainate, produced pial arteriolar dilation. Topical l-2-aminoadipic acid, a gliotoxin that selectively disrupts glia limitans, reduced vasodilation caused by iGluR agonists, but not by hypercapnia, bradykinin, or sodium nitroprusside. In freshly isolated and cultured cortical astrocytes constitutively expressing HO-2, iGluR agonists NMDA, cis-ACPD, AMPA, and kainate rapidly increased CO production two- to threefold. Astrocytes overexpressing inducible HO-1 had high baseline CO but were less sensitive to glutamate stimulation of CO production when compared with HO-2-expressing astrocytes. Glutamate-induced astrocyte HO-2-mediated CO production was inhibited by either the NMDA receptor antagonist (R)-3C4HPG or the AMPA/kainate receptor antagonist DNQX. Accordingly, either antagonist abolished pial arteriolar dilation in response to glutamate, NMDA, and AMPA, indicating functional interaction among various subtypes of astrocytic iGluRs in response to glutamate stimulation. Overall, these data indicate that the astrocyte component of the neurovascular unit is responsible for the vasodilation response of pial arterioles to topically applied glutamate via iGluRs that are functionally linked to activation of constitutive HO in newborn piglets.
Mice lacking macrophage 12/15-lipoxygenase are resistant to experimental hypertension
Authors: Kriska Tamas , Cepura Cody , Magier Devora , Siangjong Lawan , Gauthier Kathryn M. , Campbell William B.
Published: March 2012

In mouse arteries, Alox15 [leukocyte-type 12/15-lipoxygenase (LO)] is assumed to regulate vascular function by metabolizing arachidonic acid (AA) to dilator eicosanoids that mediate the endothelium-dependent relaxations to AA and acetylcholine (ACh). We used Alox15−/−mice, made by targeted disruption of the Alox15 gene, to characterize its role in the regulation of blood pressure and vascular tone. Systolic blood pressures did not differ between wild-type (WT) and Alox15−/−mice between 8–12 wk of age, but Alox15−/−mice exhibited resistance toward both NG-nitro-l-arginine-methyl ester (l-NAME)- and deoxycorticosterone acetate (DOCA)/high-salt-induced hypertension. ACh relaxed mesenteric arteries and abdominal aortas of WT and Alox15−/−mice to an identical extent. The LO inhibitor nordihydroguaiaretic acid attenuated the ACh relaxations by 35% in arteries from both WT and Alox15−/−mice. Reverse-phase HPLC analysis of [14C]AA metabolites in aorta and peritoneal macrophages (PM) revealed differences. Unlike PM, aorta tissue did not produce detectable amounts of 15-hydroxyeicosatetraenoic acid. Although Alox15 mRNA was detected in aorta, high-resolution gel electrophoresis with immunodetection revealed no Alox15 protein expression. Unlike aorta, Alox15 protein was detected in PM, intestine, fat, lung, spleen, and skin from WT, but not Alox15−/−, mice. Injection of WT PM, a primary source of Alox15 protein, into Alox15−/−mice abolished their resistance toward l-NAME-induced hypertension. On the other hand, WT mice acquired resistance to l-NAME-induced hypertension after depletion of macrophages by clodronate injection. These studies indicate that Alox15 is involved in development of experimental hypertension by altering macrophage functions but not via synthesis of the vasoactive LO metabolites in mouse arteries.
Frequency-dependent left ventricular performance in women and men
Authors: Wainstein Rodrigo V. , Sasson Zion , Mak Susanna
Published: March 2012

We aimed to determine whether sex differences in humans extend to the dynamic response of the left ventricular (LV) chamber to changes in heart rate (HR). Several observations suggest sex influences LV structure and function in health; moreover, this physiology is also affected in a sex-specific manner by aging. Eight postmenopausal women and eight similarly aged men underwent a cardiac catheterization-based study for force-interval relationships of the LV. HR was controlled by right atrial (RA) pacing, and LV +dP/d tmax and volume were assessed by micromanometer-tipped catheter and Doppler echocardiography, respectively. Analysis of approximated LV pressure-volume relationships was performed using a time-varying model of elastance. External stroke work was also calculated. The relationship between HR and LV +dP/d tmax was expressed as LV +dP/d tmax = b + mHR. The slope ( m) of the relationship was steeper in women compared with men (11.8 ± 4.0 vs. 6.1 ± 4.1 mmHg·s−1·beats−1·min−1, P = 0.01). The greater increase in contractility in women was reproducibly observed after normalizing LV +dP/d tmax to LV end-diastolic volume (LVVed) or by measuring end-systolic elastance. LVVed and stroke volume decreased more in women. Thus, despite greater increases in contractility, HR was associated with a lesser rise in cardiac output and a steeper fall in external stroke work in women. Compared with men, women exhibit greater inotropic responses to incremental RA pacing, which occurs at the same time as a steeper decline in external stroke work. In older adults, we observed sexual dimorphism in determinants of LV mechanical performance.
Suppression of Tak1 Promotes Prostate Tumorigenesis
Authors: Wu Min , Shi Lihong , Cimic Adela , Romero Lina , Sui Guangchao , Lees Cynthia J. , Cline J. Mark , Seals Darren F. , Sirintrapun Joseph S. , McCoy Thomas P. , Liu Wennuan , Kim Jin Woo , Hawkins Gregory A. , Peehl Donna M. , Xu Jianfeng , Cramer Scott D.
Published: March 2012

More than 30% of primary prostate cancers contain a consensus deletion of an approximately 800 kb locus on chromosome 6q15.1. The MAP3K7 gene, which encodes TGF-β activated kinase-1 (Tak1), is a putative prostate tumor suppressor gene within this region whose precise function remains obscure. In this study, we investigated the role of Tak1 in human and murine prostate cancers. In 50 well-characterized human cancer specimens, we found that Tak1 expression was progressively lost with increasing Gleason grade, both within each cancer and across all cancers. In murine prostate stem cells and Tak1-deficient prostatic epithelial cells, Tak1 loss increased proliferation, migration, and invasion. When prostate stem cells attenuated for Tak1 were engrafted with fetal urogenital mesenchyme, the histopathology of the grafts reflected the natural history of prostate cancer leading from prostatic intraepithelial neoplasia to invasive carcinoma. In the grafts containing Tak1-suppressed prostate stem cells, p38 and c-jun-NH2-kinase activity was attenuated and proliferation was increased. Together, our findings functionally validate the proposed tumor suppressor role of Tak1 in prostate cancer. Cancer Res; 72(11); 2833–43. ©2012 AACR.
Loss of the Ceramide Transfer Protein Augments EGF Receptor Signaling in Breast Cancer
Authors: Heering Johanna , Weis Nicole , Holeiter Monika , Neugart Felix , Staebler Annette , Fehm Tanja N. , Bischoff Annabell , Schiller Jürgen , Duss Stephan , Schmid Simone , Korte Thomas , Herrmann Andreas , Olayioye Monilola A.
Published: April 2012

Triple-negative breast cancers (TNBC) are especially refractory to treatment due to their negative hormone receptor and ErbB2/HER2 status. Therefore, the identification of cancer-associated deregulated signaling pathways is necessary to develop improved targeted therapies. Here, we show that expression of the ceramide transfer protein CERT is reduced in TNBCs. CERT transfers ceramide from the endoplasmic reticulum to the Golgi complex for conversion into sphingomyelin (SM). We provide evidence that by regulating cellular SM levels, CERT determines the signaling output of the EGF receptor (EGFR/ErbB1), which is upregulated in approximately 70% of TNBCs. CERT downregulation in breast cancer cells enhanced ErbB1 lateral mobility, ligand-induced autophosphorylation, internalization, and chemotaxis. Together, our findings provide a link between lipid metabolism at the Golgi with signaling at the plasma membrane, thereby implicating CERT loss in the progression of TNBCs. Cancer Res; 72(11); 2855–66. ©2012 AACR.
Estrogen Promotes ER-Negative Tumor Growth and Angiogenesis through Mobilization of Bone Marrow–Derived Monocytes
Authors: Iyer Vandana , Klebba Ina , McCready Jessica , Arendt Lisa M. , Betancur-Boissel Monica , Wu Meng-Fen , Zhang Xiaomei , Lewis Michael T. , Kuperwasser Charlotte
Published: March 2012

Estrogen has a central role in the genesis and progression of breast cancers whether they are positive or negative for the estrogen receptor (ER). While therapies that disrupt estrogen biosynthesis or ER activity can treat these diseases in postmenopausal women, in younger women where ovarian function remains intact, these anti-estrogen therapies are not as effective. Moreover, emerging clinical evidence suggests that estrogen may promote other cancers. Thus, circulating estrogens may participate in cancer pathogenesis in ways that are not yet understood. In this study, we show that estrogen can promote the outgrowth of murine xenograft tumors established from patient-derived ER-negative breast cancer cells by influencing the mobilization and recruitment of a proangiogenic population of bone marrow–derived myeloid cells. ERα expression was necessary and sufficient in the bone marrow–derived cells themselves to promote tumor formation in response to estrogen. Our findings reveal a novel way in which estrogen promotes tumor formation, with implications for the development and application of anti-estrogen therapies to treat cancer in premenopausal women. Cancer Res; 72(11); 2705–13. ©2012 AACR.
Tumor Infiltrating Immune Cells and Outcome of Merkel Cell Carcinoma: A Population-Based Study
Authors: Sihto Harri , Böhling Tom , Kavola Heli , Koljonen Virve , Salmi Marko , Jalkanen Sirpa , Joensuu Heikki
Published: March 2012

Purpose: Merkel cell carcinoma (MCC) is a rare skin cancer that often harbors Merkel cell polyomavirus (MCPyV) DNA. The clinical importance of intratumoral immune cells and their associations with MCPyV infection are poorly understood.

Experimental Design: We identified T lymphocytes (CD3-positive cells), T-cell subsets (CD4, CD8, and FoxP3-positive cells), natural killer cells (small CD16-positive cells), and macrophages (CD68 and CD163-positive cells) in tumors of 116 individuals diagnosed with MCC in Finland from 1979 to 2004 using immunohistochemistry and detected MCPyV DNA with quantitative PCR. The associations between immune cell counts, MCPyV DNA, patient and tumor characteristics, and patient outcome were examined.

Results: MCPyV DNA-positive cancers contained higher numbers of CD3+, CD8+, CD16+, FoxP3+, and CD68+ cells as compared with MCPyV DNA-negative carcinomas (all P values < 0.05). High intratumoral numbers of CD3+, CD8+, or FoxP3+ cells, and high CD8+/CD4+ or FoxP3+/CD4+ ratios, were significantly associated with favorable overall survival. Individuals with a high tumor CD3+ count had metastases less often and survived longer, irrespective of the tumor MCPyV status. Tumor CD3+ count and MCPyV DNA status had independent influence on survival in a Cox multivariable model that also included presence of locoregional metastases at diagnosis and gender as covariates.

Conclusions: High intratumoral T-lymphocyte counts are associated with favorable survival in MCC. Although the numbers of T cells are generally higher in MCPyV-positive than in MCPyV-negative MCC, high intratumoral T-cell counts are also associated with favorable survival in MCPyV-negative MCC. Clin Cancer Res; 18(10); 2872–81. ©2012 AACR.