Phosphate sink containing two-component signaling systems as tunable threshold devices.

Published onlineJournal ArticleResearch Support, Non-U.S. Gov'tSynthetic biology aims to design de novo biological systems and reengineer existing ones. These efforts have mostly focused on transcriptional circuits, with reengineering of signaling circuits hampered by limited understanding of their systems dynamics and experimental challenges. Bacterial two-component signaling systems offer a rich diversity of sensory systems that are built around a core phosphotransfer reaction between histidine kinases and their output response regulator proteins, and thus are a good target for reengineering through synthetic biology. Here, we explore the signal-response relationship arising from a specific motif found in two-component signaling. In this motif, a single histidine kinase (HK) phosphotransfers reversibly to two separate output response regulator (RR) proteins. We show that, under the experimentally observed parameters from bacteria and yeast, this motif not only allows rapid signal termination, whereby one of the RRs acts as a phosphate sink towards the other RR (i.e. the output RR), but also implements a sigmoidal signal-response relationship. We identify two mathematical conditions on system parameters that are necessary for sigmoidal signal-response relationships and define key parameters that control threshold levels and sensitivity of the signal-response curve. We confirm these findings experimentally, by in vitro reconstitution of the one HK-two RR motif found in the Sinorhizobium meliloti chemotaxis pathway and measuring the resulting signal-response curve. We find that the level of sigmoidality in this system can be experimentally controlled by the presence of the sink RR, and also through an auxiliary protein that is shown to bind to the HK (yielding Hill coefficients of above 7). These findings show that the one HK-two RR motif allows bacteria and yeast to implement tunable switch-like signal processing and provides an ideal basis for developing threshold devices for synthetic biology applications.Exeter University Science Strateg

Performance-based building and innovation: Balancing client and industry needs

One reason for the interest in performance-based building is that it is commonly advocated as a powerful way of enhancing innovation performance by articulating building performance outcomes, and by offering relevant procurement actors the discretion to innovate to meet these performance requirements more effectively and/or efficiently. The paper argues that the current approach to performance-based building assumes that relevant actors have the capacity, ability and motivation to innovate from a business perspective. It is proposed that the prevailing conceptualization of PBB is too restrictive and should be broadened explicitly to accommodate the required business logic that must be in place before actors will innovate. The relevant performance-based building and innovation literature is synthesized to support the assertion. The paper concludes with an innovation-focused definition of performance-based building

Beyond aridification: multiple explanations for the elevated diversification of cacti in the New World Succulent Biome

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106989/1/nph12752.pd

The Relationship Between HR Practices and Firm Performance: Examining Causal Order

Significant research attention has been devoted to examining the relationship between HR practices and firm performance, and the research support has assumed HR as the causal variable. Using data from 45 business units (with 62 data points), this study examines how measures of HR practices correlate with past, concurrent, and future operational performance measures. The results indicate that correlations with performance measures at all three times are both high and invariant, and that controlling for past or concurrent performance virtually eliminates the correlation of HR with future performance. Implications are discussed

Arterial oxygen content is precisely maintained by graded erythrocytotic responses in settings of high/normal serum iron levels, and predicts exercise capacity: an observational study of hypoxaemic patients with pulmonary arteriovenous malformations.

Oxygen, haemoglobin and cardiac output are integrated components of oxygen transport: each gram of haemoglobin transports 1.34 mls of oxygen in the blood. Low arterial partial pressure of oxygen (PaO2), and haemoglobin saturation (SaO2), are the indices used in clinical assessments, and usually result from low inspired oxygen concentrations, or alveolar/airways disease. Our objective was to examine low blood oxygen/haemoglobin relationships in chronically compensated states without concurrent hypoxic pulmonary vasoreactivity.165 consecutive unselected patients with pulmonary arteriovenous malformations were studied, in 98 cases, pre/post embolisation treatment. 159 (96%) had hereditary haemorrhagic telangiectasia. Arterial oxygen content was calculated by SaO2 x haemoglobin x 1.34/100.There was wide variation in SaO2 on air (78.5-99, median 95)% but due to secondary erythrocytosis and resultant polycythaemia, SaO2 explained only 0.1% of the variance in arterial oxygen content per unit blood volume. Secondary erythrocytosis was achievable with low iron stores, but only if serum iron was high-normal: Low serum iron levels were associated with reduced haemoglobin per erythrocyte, and overall arterial oxygen content was lower in iron deficient patients (median 16.0 [IQR 14.9, 17.4]mls/dL compared to 18.8 [IQR 17.4, 20.1]mls/dL, p<0.0001). Exercise tolerance appeared unrelated to SaO2 but was significantly worse in patients with lower oxygen content (p<0.0001). A pre-defined athletic group had higher Hb:SaO2 and serum iron:ferritin ratios than non-athletes with normal exercise capacity. PAVM embolisation increased SaO2, but arterial oxygen content was precisely restored by a subsequent fall in haemoglobin: 86 (87.8%) patients reported no change in exercise tolerance at post-embolisation follow-up.Haemoglobin and oxygen measurements in isolation do not indicate the more physiologically relevant oxygen content per unit blood volume. This can be maintained for SaO2 ≥78.5%, and resets to the same arterial oxygen content after correction of hypoxaemia. Serum iron concentrations, not ferritin, seem to predict more successful polycythaemic responses

Seeking legitimacy through CSR: Institutional Pressures and Corporate Responses of Multinationals in Sri Lanka

Arguably, the corporate social responsibility (CSR) practices of multinational enterprises (MNEs) are influenced by a wide range of both internal and external factors. Perhaps most critical among the exogenous forces operating on MNEs are those exerted by state and other key institutional actors in host countries. Crucially, academic research conducted to date offers little data about how MNEs use their CSR activities to strategically manage their relationship with those actors in order to gain legitimisation advantages in host countries. This paper addresses that gap by exploring interactions between external institutional pressures and firm-level CSR activities, which take the form of community initiatives, to examine how MNEs develop their legitimacy-seeking policies and practices. In focusing on a developing country, Sri Lanka, this paper provides valuable insights into how MNEs instrumentally utilise community initiatives in a country where relationship-building with governmental and other powerful non-governmental actors can be vitally important for the long-term viability of the business. Drawing on neo-institutional theory and CSR literature, this paper examines and contributes to the embryonic but emerging debate about the instrumental and political implications of CSR. The evidence presented and discussed here reveals the extent to which, and the reasons why, MNEs engage in complex legitimacy-seeking relationships with Sri Lankan institutions

‘1L=10L for Africa’: Corporate social responsibility and the transformation of bottled water into a ‘consumer activist’ commodity

In recent years, it has become an increasingly common marketing practice to connect the sale of consumer products to corporate social responsibility (CSR) initiatives, such as aid and development projects in so-called ‘developing’ countries. One example is Volvic’s pioneering ‘1L=10L for Africa’ campaign (2005–2010), which linked the sale of each liter of bottled water in ‘developed’ countries with the promise by Danone, Volvic’s owner, to provide 10 liters of drinking water in Africa. In this article, we engage with this ‘cause-related marketing’ campaign, using critical discourse analysis (CDA) to uncover its mechanisms and ideological functioning. We show how Volvic was able to transform an ordinary commodity, bottled water, into a consumer activist brand through which consumers could take part in solving global social problems, such as the access to safe drinking water in ‘developing’ countries. Our analysis of this exemplary case shows the ways that CSR often operates to deflect ethical critiques, consolidate brand loyalty and corporate profits, and defuse political struggles around consumption. By doing so, we suggest that CSR forms part of a complex strategy deployed to legitimize particular brands and commodities. In this way CSR can be seen as playing an important role in the ideological makeup of contemporary consumer capitalism. </jats:p

Comparative study between the 3D‐liver spheroid models developed from HepG2 and immortalized hepatocyte‐like cells with primary hepatic stellate coculture for drug metabolism analysis and anticancer drug screening

Liver spheroids may be the best alternative models for evaluating efficacy and toxicity of the new anticancer candidates and diagnostics for hepatocellular carcinoma (HCC). Here, novel 3D-liver spheroid models are constructed from human hepatoma cells (HepG2)/ immortalized human hepatocyte-like cells (imHCs) with primary hepatic stellate cells (HSCs) coculture using the ultralow attachment technique. Spheroid morphology, HSC distribution, metabolic activity, protein expressions, and drug penetration are evaluated. All developed 3D spheroid models exhibit in spherical shape with narrow size distribution, diameter between 639–743 (HepG2-10%HSC) and 519–631 (imHC-10%HSC) µm. Both imHC mono and coculture models significantly express normal liver biomarkers at the higher level than HepG2 models. While 3D-HepG2 models significantly exhibit HCC biomarkers at the higher level than imHC models. HepG2 and imHC spheroids express basal cytochrom P450 (CYP450) enzymes at different levels depending on cell types, culture period, and ratio of coculture. Their metabolic activities for dextromethorphan (CYP2D6) tolbutamide (CYP2C9) and midazolam (CYP3A4) are routinely evaluated. For midazolam metabolism, imHC models allow the detection of phase II metabolic enzymes (UGT2B4 and UGT2B7). The presence of HSC in HepG2-HSC model increases biological barrier for doxorubicin (DOX) penetration, and escalates IC50 of DOX from 61.4 to 127.2 µg mL−1