Ascorbic acid and tetrahydrobiopterin potentiate the EDHF phenomenon by generating hydrogen peroxide

Aims Our objective was to investigate whether pro-oxidant properties of ascorbic acid (AA) and tetrahydrobiopterin (BH4) modulate endothelium-dependent, electrotonically mediated arterial relaxation. Methods and results In studies with rabbit iliac artery (RIA) rings, NO-independent, endotheliumderived hyperpolarizing factor (EDHF)-type relaxations evoked by the sarcoplasmic endoplasmic reticulum Ca2þ-ATPase inhibitor cyclopiazonic acid and the G protein-coupled agonist acetylcholine (ACh) were enhanced by AA (1 mM) and BH4 (200 mM), which generated buffer concentrations of H2O2 in the range of 40–80 mM. Exogenous H2O2 potentiated cyclopiazonic acid (CPA)- and ACh-evoked relaxations with a threshold of 10–30 mM, and potentiation by AA and BH4 was abolished by catalase, which destroyed H2O2 generated by oxidation of these agents in the organ chamber. Adventitial application of H2O2 also enhanced EDHF-type dilator responses evoked by CPA and ACh in RIA segments perfused intraluminally with H2O2-free buffer, albeit with reduced efficacy. In RIA rings, both control relaxations and their potentiation by H2O2 were overcome by blockade of gap junctions by connexinmimetic peptides (YDKSFPISHVR and SRPTEK) targeted to the first and second extracellular loops of the dominant vascular connexins expressed in the RIA. Superoxide dismutase attenuated the potentiation of EDHF-type relaxations by BH4, but not AA, consistent with findings demonstrating a differential role for superoxide anions in the generation of H2O2 by the two agents. Conclusion Pro-oxidant effects of AA and BH4 can enhance the EDHF phenomenon by generating H2O2, which has previously been shown to amplify electrotonic hyperpolarization-mediated relaxation by facilitating Ca2þ release from endothelial stores

A micro costing of NHS cancer genetic services

This paper presents the first full micro costing of a commonly used cancer genetic counselling and testing protocol used in the UK. Costs were estimated for the Cardiff clinic of the Cancer Genetics Service in Wales by issuing a questionnaire to all staff, conducting an audit of clinic rooms and equipment and obtaining gross unit costs from the finance department. A total of 22 distinct event pathways were identified for patients at risk of developing breast, ovarian, breast and ovarian or colorectal cancer. The mean cost per patient were £97–£151 for patients at moderate risk, £975–£3072 for patients at high risk of developing colorectal cancer and £675–£2909 for patients at high risk of developing breast or ovarian cancer. The most expensive element of cancer genetic services was labour. Labour costs were dependent upon the amount of labour, staff grade, number of counsellors used and the proportion of staff time devoted to indirect patient contact. With the growing demand for cancer genetic services and the growing number of national and regional cancer genetic centers, there is a need for the different protocols being used to be thoroughly evaluated in terms of costs and outcomes

GA4GH: International policies and standards for data sharing across genomic research and healthcare.

The Global Alliance for Genomics and Health (GA4GH) aims to accelerate biomedical advances by enabling the responsible sharing of clinical and genomic data through both harmonized data aggregation and federated approaches. The decreasing cost of genomic sequencing (along with other genome-wide molecular assays) and increasing evidence of its clinical utility will soon drive the generation of sequence data from tens of millions of humans, with increasing levels of diversity. In this perspective, we present the GA4GH strategies for addressing the major challenges of this data revolution. We describe the GA4GH organization, which is fueled by the development efforts of eight Work Streams and informed by the needs of 24 Driver Projects and other key stakeholders. We present the GA4GH suite of secure, interoperable technical standards and policy frameworks and review the current status of standards, their relevance to key domains of research and clinical care, and future plans of GA4GH. Broad international participation in building, adopting, and deploying GA4GH standards and frameworks will catalyze an unprecedented effort in data sharing that will be critical to advancing genomic medicine and ensuring that all populations can access its benefits

On the probability of extinction of the Haiti cholera epidemic

More than three years after its appearance in Haiti, cholera has already caused more than 8,500 deaths and 695,000 infections and it is feared to become endemic. However, no clear evidence of a stable environmental reservoir of pathogenic Vibrio cholerae, the infective agent of the disease, has emerged so far, suggesting the possibility that the transmission cycle of the disease is being maintained by bacteria freshly shed by infected individuals. Should this be the case, cholera could in principle be eradicated from Haiti. Here, we develop a framework for the estimation of the probability of extinction of the epidemic based on current information on epidemiological dynamics and health-care practice. Cholera spreading is modeled by an individual-based spatially-explicit stochastic model that accounts for the dynamics of susceptible, infected and recovered individuals hosted in different local communities connected through hydrologic and human mobility networks. Our results indicate that the probability that the epidemic goes extinct before the end of 2016 is of the order of 1 %. This low probability of extinction highlights the need for more targeted and effective interventions to possibly stop cholera in Haiti

Siblings of children with autism:The Siblings Embedded Systems Framework

Purpose of review: a range of interacting factors/mechanisms at the individual, family, and wider systems levels influences siblings living in families where one sibling has autism. We introduce the Sibling Embedded Systems Framework which aims to contextualise siblings’ experience and characterise the multiple and interacting factors influencing family and, in particular, sibling outcomes.Recent findings: findings from studies that have reported outcomes for siblings of children with autism are equivocal, ranging from negative impact, no difference, to positive experience. This is likely due to the complex nature of understanding the sibling experience. We focus on particular elements of the framework and review recent novel literature to help guide future directions for research and practice including the influence of culture, methodological considerations, and wider participatory methods.Summary: the Siblings Embedded System Framework can be used to understand interactive factors that affect sibling adjustment and to develop clinically, educationally and empirically based work that aims to enhance and support sibling adjustment, relationships, and well-being in families of children with autism.<br/

Endogenous Nitric Oxide Synthesis Differentially Modulates Pressure-Flow and Pressure-Conductance Relationships in the Internal and External Carotid Artery Circulations of the Rat

The role of endogenous nitric oxide (NO) synthesis was investigated in the regulation of the internal (ICA) and external carotid artery (ECA) beds of ventilated, anesthetized rats in a model in which the left common carotid artery was perfused from the aorta via an extracorporeal circuit under conditions of non-pulsatile controlled flow. The territories supplied by the extracranial ICA and ECA were studied separately following occlusion of the appropriate artery. An inhibitor of nitric oxide synthesis, NG-monomethyl-L-arginine (L-NMMA), and the NO synthase substrate L-arginine were administered via a jugular venous catheter. NO synthesis exerted an important influence on the pressure-flow relationships of the ICA and ECA circulations as L-NMMA increased input perfusion pressure at any given flow rate. However, in the presence of NO synthesis, hydraulic conductance increased rapidly with flow in the ICA, thereby stabilizing perfusion pressures over a wide range of flow rates, whereas this phenomenon was not evident in the ECA territory. Differences between the two circulations were further emphasized by observations that L-arginine antagonized the systemic hemodynamic response to L-NMMA and its effects on the conductance of the ECA bed, whereas the effects of L-NMMA were irreversible in the ICA territory

The obligatory link: role of gap junctional communication in endothelium-dependent smooth muscle hyperpolarization

Although an endothelium-derived hyperpolarizing factor (EDHF) has often been hypothesized to underpin vascular relaxations that are independent of nitric oxide (NO) and prostanoids, bioassay techniques have failed to confirm the existence of a freely transferable EDHF in a consistent fashion. Indeed, observations that inhibitors of direct cell–cell coupling such as connexin–mimetic peptides (e.g. Gap 26 and 27) and glycyrrhetinic acid derivatives attenuate “EDHF-type” smooth muscle hyperpolarizations and relaxations suggest that an electrotonic spread of endothelial hyperpolarization via myoendothelial and homocellular smooth muscle gap junctions plays an obligatory role in such responses. The endothelial hyperpolarization that initiates relaxation results from the opening of KCa channels and is sustained by capacitative Ca2+ entry triggered by the depletion of intracellular Ca2+ stores in the endoplasmic reticulum. EDHF-type relaxations are also associated with a prostanoid-independent synthesis of cAMP that increases the conductance of gap junction channels and enhances the transmission of endothelial hyperpolarization through the vascular wall in a permissive fashion. This review will discuss the roles of these interacting signalling pathways in the mediation of the EDHF phenomenon

The effect of chronic subarachnoid hemorrhage on basal endothelium-derived relaxing factor activity in intrathecal cerebral arteries

The authors have investigated the hypothesis that loss of endothelium-derived relaxing factor (EDRF) activity contributes to cerebral vasospasm after subarachnoid hemorrhage. Adventitial exposure to hemoglobin was studied angiographically by injecting purified hemoglobin solution or autologous whole blood into the cisterna magna of anesthetized pigs. Both interventions induced intra- but not extracerebral vasoconstriction, which persisted for 2 and 7 days, respectively. Cyclic guanosine monophosphate (cGMP) levels were measured in isolated buffer-perfused pig intrathecal arteries to quantify inhibition of basal EDRF activity by hemoglobin. Adventitial exposure was less effective than intimal exposure, 10 µM hemoglobin applied adventitially for 30 minutes having an effect equivalent to that of 1 µM applied intraluminally for 5 minutes. The depression of cGMP levels by hemoglobin was reversible and equivalent to the effect of endothelial denudation or incubation with NG-nitro-L-arginine methyl ester, so that the effects of hemoglobin can be attributed to a specific action on EDRF rather than interaction with a nitric oxide-like substance produced by vascular smooth muscle or adventitial nerves. Cyclic GMP levels in isolated arteries were unchanged after in vivo exposure to hemoglobin for either 2 or 7 days or to whole blood for 2 days, and were reduced by intraluminal perfusion with 1 µM hemoglobin. In contrast, after 7 days of in vivo exposure to whole blood, cGMP levels were already depressed, and not further reduced by intraluminal perfusion with 1 µM hemoglobin. The findings support the view that adventitially applied hemoglobin can inhibit basal EDRF activity and that in vivo adventitial exposure to whole blood leads to a reduction in basal cGMP levels in association with vasoconstriction of intrathecal arteries. Both mechanisms could contribute to the clinical syndrome of cerebral vasospasm after subarachnoid hemorrhage

Activities of endothelin-1 in the vascular network of the rabbit ear: a microangiographic study

1 The effects of endothelin-1 on perfusion pressure and on arterial and venous diameters were examined simultaneously in a rabbit isolated ear preparation perfused with physiological buffer. The effects of hypoxia and inhibition of endothelium-derived relaxant factor (EDRF) activity on vascular responses to endothelin-1 were also investigated. 2 Endothelin-1 was potent at increasing perfusion pressure (ED50 = 46.7 ± 11.0 pmol; Rmax = 85.3 ± 5.3 mmHg). The potency and maximum reactivity were not significantly affected by hypoxia, inhibition of EDRF activity with 50 μm N-nitro-l-arginine methyl ester (NAME) or a combination of hypoxia and NAME. 3 Endothelin-1 caused equipotent dose-dependent constrictions of the first four generations of arterial branch vessels (G1-G4) but did not influence the diameter of the central ear artery except at high doses of the peptide when ‘paradoxical dilatation’ was observed. The peptide was also equipotent at causing constriction of the smaller venous vessels (V1-V4) but did not affect the large veins (V0). 4 Under conditions of hypoxia the potency of endothelin-1 was reduced in G2 and G3, was unaffected in G4 and the peptide did not significantly constrict either G0 or G1. Hypoxia reduced the potency of endothelin-1 in the smaller venous vessels (V1-V4), but conversely unmasked a marked constriction of the large veins (V0), which was not observed under normoxic conditions. 5 NAME 50 μm abolished the vasodilator effects of acetylcholine in this preparation. Inhibition of EDRF activity with NAME under normoxic conditions did not influence the constrictor activity of endothelin-1 on the arterial or venous branch vessels. However, inhibition of EDRF activity under hypoxic conditions prevented the reduction of potency of endothelin-1 as a constrictor of arterial and venous branch vessels which occurred in hypoxia. In the presence of NAME endothelin-1 constricted V0 in both normoxia and hypoxia with equipotency but the maximum effect was greatest in hypoxia. 6 In conclusion, endothelin-1 is a powerful vasoconstrictor which acts with greater potency in veins than arteries in the rabbit isolated ear. Although hypoxia does not influence pressor responses it nevertheless alters the spatial pattern of vasoconstriction. In particular hypoxia unmasks constriction of the large veins by endothelin-1. Constriction of these veins was also observed in the absence of EDRF in normoxia, but to a much lesser degree so that the effect of hypoxia may only be partially due to reduced EDRF activity. Hypoxia may therefore directly or indirectly increase the sensitivity of the main veins to endothelin-1