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1.  A novel risk of air embolism with intravenous paracetamol 
BMJ Case Reports  2012;2012:bcr0120125488.
doi:10.1136/bcr.01.2012.5488
PMCID: PMC3316787  PMID: 22605689
2.  The ‘Dark Side’ and ‘Bright Side’ of Personality: When Too Much Conscientiousness and Too Little Anxiety Are Detrimental with Respect to the Acquisition of Medical Knowledge and Skill 
PLoS ONE  2014;9(2):e88606.
Theory suggests that personality traits evolved to have costs and benefits, with the effectiveness of a trait dependent on how these costs and benefits relate to the present circumstances. This suggests that traits that are generally viewed as positive can have a ‘dark side’ and those generally viewed as negative can have a ‘bright side’ depending on changes in context. We test this in a sample of 220 UK medical students with respect to associations between the Big 5 personality traits and learning outcomes across the 5 years of a medical degree. The medical degree offers a changing learning context from pre-clinical years (where a more methodical approach to learning is needed) to the clinical years (where more flexible learning is needed, in a more stressful context). We argue that while trait conscientiousness should enhance pre-clinical learning, it has a ‘dark side’ reducing the acquisition of knowledge in the clinical years. We also suggest that anxiety has a ‘bright side’ enhancing the acquisition of skills in the clinical years. We also explore if intelligence enhances learning across the medical degree. Using confirmatory factor analysis and structural equation modelling we show that medical skills and knowledge assessed in the pre-clinical and clinical years are psychometrically distinguishable, forming a learning ‘backbone’, whereby subsequent learning outcomes are predicted by previous ones. Consistent with our predictions conscientiousness enhanced preclinical knowledge acquisition but reduced the acquisition of clinical knowledge and anxiety enhanced the acquisition of clinical skills. We also identified a curvilinear U shaped association between Surgency (extraversion) and pre-clinical knowledge acquisition. Intelligence predicted initial clinical knowledge, and had a positive total indirect effect on clinical knowledge and clinical skill acquisition. For medical selection, this suggests that selecting students high on conscientiousness may be problematic, as it may be excluding those with some degree of moderate anxiety.
doi:10.1371/journal.pone.0088606
PMCID: PMC3937323  PMID: 24586353
3.  TBC1D13 IS A RAB35 SPECIFIC GAP THAT PLAYS AN IMPORTANT ROLE IN GLUT4 TRAFFICKING IN ADIPOCYTES 
Traffic (Copenhagen, Denmark)  2012;13(10):1429-1441.
Insulin stimulates glucose transport in adipocytes by triggering translocation of GLUT4 glucose transporters to the plasma membrane (PM) and several Rabs including Rab10 have been implicated in this process. To delineate the molecular regulation of this pathway, we conducted a TBC/RabGAP overexpression screen in adipocytes. This identified TBC1D13 as a potent inhibitor of insulin-stimulated GLUT4 translocation without affecting other trafficking pathways. To determine the potential Rab substrate for TBC1D13 we conducted a yeast two-hybrid screen and found that the GTP bound forms of Rabs 1 and 10 specifically interacted with TBC1D13 but not with eight other TBC proteins. Surprisingly, a comprehensive in vitro> screen for TBC1D13 GAP activity revealed Rab35 but not Rab10 as a specific substrate. TBC1D13 also displayed in vivo GAP activity towards Rab35. Overexpression of constitutively active Rab35 but not constitutively active Rab10 reversed the block in insulin-stimulated GLUT4 translocation observed with TBC1D13 overexpression. These studies implicate an important role for Rab35 in insulin-stimulated GLUT4 translocation in adipocytes.
doi:10.1111/j.1600-0854.2012.01397.x
PMCID: PMC3470861  PMID: 22762500
4.  Environmental physiology research presented at ICEE2013 
The 15th International Conference on Environmental Ergonomics, Queenstown, New Zealand, February 11 to 15, 2013 (ICEE2013) brought together researchers interested in work and exercise physiology, safety, comfort and performance in various stressful and extreme environments.
doi:10.1186/2046-7648-2-22
PMCID: PMC3710081  PMID: 23849452
Heat Stress; Cold; Exercise; Hypoxia; Adaptation; Climate Change; Space; Physiology; Comfort
5.  Dynamic Adipocyte Phosphoproteome Reveals that Akt Directly Regulates mTORC2 
Cell Metabolism  2013;17(6):1009-1020.
Summary
A major challenge of the post-genomics era is to define the connectivity of protein phosphorylation networks. Here, we quantitatively delineate the insulin signaling network in adipocytes by high-resolution mass spectrometry-based proteomics. These data reveal the complexity of intracellular protein phosphorylation. We identified 37,248 phosphorylation sites on 5,705 proteins in this single-cell type, with approximately 15% responding to insulin. We integrated these large-scale phosphoproteomics data using a machine learning approach to predict physiological substrates of several diverse insulin-regulated kinases. This led to the identification of an Akt substrate, SIN1, a core component of the mTORC2 complex. The phosphorylation of SIN1 by Akt was found to regulate mTORC2 activity in response to growth factors, revealing topological insights into the Akt/mTOR signaling network. The dynamic phosphoproteome described here contains numerous phosphorylation sites on proteins involved in diverse molecular functions and should serve as a useful functional resource for cell biologists.
Graphical Abstract
Highlights
•MS/MS identified >37,000 phosphorylation sites in adipocytes•Insulin regulates the phosphoproteome over a wide temporal timescale•Akt phosphorylates SIN1 on T86 in response to insulin•SIN1 phosphorylation activates a positive feedback loop between Akt and mTORC2
doi:10.1016/j.cmet.2013.04.010
PMCID: PMC3690479  PMID: 23684622
6.  Genetic and Biochemical Characterizations of Enzymes Involved in Streptococcus pneumoniae Serotype 2 Capsule Synthesis Demonstrate that Cps2T (WchF) Catalyzes the Committed Step by Addition of β1-4 Rhamnose, the Second Sugar Residue in the Repeat Unit 
Journal of Bacteriology  2012;194(23):6479-6489.
Five genes (cps2E, cps2T, cps2F, cps2G, and cps2I) are predicted to encode the glycosyltransferases responsible for synthesis of the Streptococcus pneumoniae serotype 2 capsule repeat unit, which is polymerized to yield a branched surface structure containing glucose-glucuronic acid linked to a glucose-rhamnose-rhamnose-rhamnose backbone. Cps2E is the initiating glycosyltransferase, but experimental evidence supporting the functions of the remaining glycosyltransferases is lacking. To biochemically characterize the glycosyltransferases, the donor substrate dTDP-rhamnose was first synthesized using recombinant S. pneumoniae enzymes Cps2L, Cps2M, Cps2N, and Cps2O. In in vitro assays with each of the glycosyltransferases, only reaction mixtures containing recombinant Cps2T, dTDP-rhamnose, and the Cps2E product (undecaprenyl pyrophosphate glucose) generated a new product, which was consistent with lipid-linked glucose-rhamnose. cps2T, cps2F, and cps2I deletion mutants produced no detectable capsule, but trace amounts of capsule were detectable in Δcps2G mutants, suggesting that Cps2G adds a nonbackbone sugar. All Δcps2F, Δcps2G, and Δcps2I mutants contained different secondary suppressor mutations in cps2E, indicating that the initial mutations were lethal in the absence of reduced repeat unit synthesis. Δcps2T mutants did not contain secondary mutations affecting capsule synthesis. The requirement for secondary mutations in mutants lacking Cps2F, Cps2G, and Cps2I indicates that these activities occur downstream of the committed step in capsule synthesis and reveal that Cps2T catalyzes this step. Therefore, Cps2T is the β1-4 rhamnosyltransferase that adds the second sugar to the repeat unit and, as the committed step in type 2 repeat unit synthesis, is predicted to be an important point of capsule regulation.
doi:10.1128/JB.01135-12
PMCID: PMC3497468  PMID: 23002227
7.  The Rab GTPase-Activating Protein TBC1D4/AS160 Contains an Atypical Phosphotyrosine-Binding Domain That Interacts with Plasma Membrane Phospholipids To Facilitate GLUT4 Trafficking in Adipocytes 
Molecular and Cellular Biology  2012;32(24):4946-4959.
The Rab GTPase-activating protein TBC1D4/AS160 regulates GLUT4 trafficking in adipocytes. Nonphosphorylated AS160 binds to GLUT4 vesicles and inhibits GLUT4 translocation, and AS160 phosphorylation overcomes this inhibitory effect. In the present study we detected several new functional features of AS160. The second phosphotyrosine-binding domain in AS160 encodes a phospholipid-binding domain that facilitates plasma membrane (PM) targeting of AS160, and this function is conserved in other related RabGAP/Tre-2/Bub2/Cdc16 (TBC) proteins and an AS160 ortholog in Drosophila. This region also contains a nonoverlapping intracellular GLUT4-containing storage vesicle (GSV) cargo-binding site. The interaction of AS160 with GSVs and not with the PM confers the inhibitory effect of AS160 on insulin-dependent GLUT4 translocation. Constitutive targeting of AS160 to the PM increased the surface GLUT4 levels, and this was attributed to both enhanced AS160 phosphorylation and 14-3-3 binding and inhibition of AS160 GAP activity. We propose a model wherein AS160 acts as a regulatory switch in the docking and/or fusion of GSVs with the PM.
doi:10.1128/MCB.00761-12
PMCID: PMC3510527  PMID: 23045393
9.  Activation of AMPK by Bitter Melon Triterpenoids Involves CaMKKβ 
PLoS ONE  2013;8(4):e62309.
We recently showed that bitter melon-derived triterpenoids (BMTs) activate AMPK and increase GLUT4 translocation to the plasma membrane in vitro, and improve glucose disposal in insulin resistant models in vivo. Here we interrogated the mechanism by which these novel compounds activate AMPK, a leading anti-diabetic drug target. BMTs did not activate AMPK directly in an allosteric manner as AMP or the Abbott compound (A-769662) does, nor did they activate AMPK by inhibiting cellular respiration like many commonly used anti-diabetic medications. BMTs increased AMPK activity in both L6 myotubes and LKB1-deficient HeLa cells by 20–35%. Incubation with the CaMKKβ inhibitor, STO-609, completely attenuated this effect suggesting a key role for CaMKKβ in this activation. Incubation of L6 myotubes with the calcium chelator EGTA-AM did not alter this activation suggesting that the BMT-dependent activation was Ca2+-independent. We therefore propose that CaMKKβ is a key upstream kinase for BMT-induced activation of AMPK.
doi:10.1371/journal.pone.0062309
PMCID: PMC3636144  PMID: 23638033
10.  Can the 12-item general health questionnaire be used to identify medical students who might ‘struggle’ on the medical course? A prospective study on two cohorts 
BMC Medical Education  2013;13:48.
Background
Students who fail to thrive on the Nottingham undergraduate medical course frequently suffer from anxiety, depression or other mental health problems. These difficulties may be the cause, or the result of, academic struggling. Early detection of vulnerable students might direct pastoral care and remedial support to where it is needed. We investigated the use of the short-form General Health Questionnaire (GHQ-12) as a possible screening tool.
Methods
Two consecutive cohorts (2006 and 2007) were invited to complete the GHQ-12. The questionnaire was administered online, during the second semester (after semester 1 exams) for the 2006 cohort and during the first semester for the 2007 cohort. All data were held securely and confidentially. At the end of the course, GHQ scores were examined in relation to course progress.
Results
251 students entered the course in 2006 and 254 in 2007; 164 (65%) and 160 (63%), respectively, completed the GHQ-12. In both cohorts, the study and non-study groups were very similar in terms of pre-admission socio-demographic characteristics and overall course marks. In the 2006 study group, the GHQ Likert score obtained part-way through the first year was negatively correlated with exam marks during Years 1 and 2, but the average exam mark in semester 1 was the sole independent predictor of marks in semester 2 and Year 2. No correlations were found for the 2007 study group but the GHQ score was a weak positive predictor of marks in semester 2, with semester 1 average exam mark again being the strongest predictor. A post-hoc moderated-mediation analysis suggested that significant negative associations of GHQ scores with semester 1 and 2 exams applied only to those who completed the GHQ after their semester 1 exams. Students who were identified as GHQ ‘cases’ in the 2006 group were statistically less likely to complete the course on time (OR = 4.74, p 0.002). There was a non-significant trend in the same direction in the 2007 group.
Conclusions
Results from two cohorts provide insufficient evidence to recommend the routine use of the GHQ-12 as a screening tool. The timing of administration could have a critical influence on the results, and the theoretical and practical implications of this finding are discussed. Low marks in semester 1 examinations seem be the best single indicator of students at risk for subsequent poor performance.
doi:10.1186/1472-6920-13-48
PMCID: PMC3616988  PMID: 23548161
11.  The UK clinical aptitude test and clinical course performance at Nottingham: a prospective cohort study 
BMC Medical Education  2013;13:32.
Background
The UK Clinical Aptitude Test (UKCAT) was introduced in 2006 as an additional tool for the selection of medical students. It tests mental ability in four distinct domains (Verbal Reasoning, Quantitative Reasoning, Abstract Reasoning, and Decision Analysis), and the results are available to students and admission panels in advance of the selection process. Our first study showed little evidence of any predictive validity for performance in the first two years of the Nottingham undergraduate course.
The study objective was to determine whether the UKCAT scores had any predictive value for the later parts of the course, largely delivered via clinical placements.
Methods
Students entering the course in 2007 and who had taken the UKCAT were asked for permission to use their anonymised data in research. The UKCAT scores were incorporated into a database with routine pre-admission socio-demographics and subsequent course performance data. Correlation analysis was followed by hierarchical multivariate linear regression.
Results
The original study group comprised 204/254 (80%) of the full entry cohort. With attrition over the five years of the course this fell to 185 (73%) by Year 5. The Verbal Reasoning score and the UKCAT Total score both demonstrated some univariate correlations with clinical knowledge marks, and slightly less with clinical skills. No parts of the UKCAT proved to be an independent predictor of clinical course marks, whereas prior attainment was a highly significant predictor (p <0.001).
Conclusions
This study of one cohort of Nottingham medical students showed that UKCAT scores at admission did not independently predict subsequent performance on the course. Whilst the test adds another dimension to the selection process, its fairness and validity in selecting promising students remains unproven, and requires wider investigation and debate by other schools.
doi:10.1186/1472-6920-13-32
PMCID: PMC3621812  PMID: 23442227
12.  Expression of a glycosylphosphatidylinositol-anchored ligand, growth hormone, blocks receptor signalling 
Bioscience Reports  2012;32(Pt 6):653-660.
We have investigated the interaction between GH (growth hormone) and GHR (GH receptor). We previously demonstrated that a truncated GHR that possesses a transmembrane domain but no cytoplasmic domain blocks receptor signalling. Based on this observation we investigated the impact of tethering the receptor's extracellular domain to the cell surface using a native lipid GPI (glycosylphosphatidylinositol) anchor. We also investigated the effect of tethering GH, the ligand itself, to the cell surface and demonstrated that tethering either the ecGHR (extracellular domain of GHR) or the ligand itself to the cell membrane via a GPI anchor greatly attenuates signalling. To elucidate the mechanism for this antagonist activity, we used confocal microscopy to examine the fluorescently modified ligand and receptor. GH–GPI was expressed on the cell surface and formed inactive receptor complexes that failed to internalize and blocked receptor activation. In conclusion, contrary to expectation, tethering an agonist to the cell surface can generate an inactive hormone receptor complex that fails to internalize.
doi:10.1042/BSR20120088
PMCID: PMC3497723  PMID: 23013472
cytokine antagonist; growth hormone; growth hormone receptor; glycosylphosphatidylinositol anchor; signal transduction; receptor trafficking; CMV, cytomegalovirus; GFP, green fluorescent protein; GH, growth hormone; GHR, growth hormone receptor; ecGHR, extracellular domain of GHR; GPI, glycosylphosphatidylinositol; HEK, human embryonic kidney; LHRE, lactogenic hormone response element; LL, long linker; PE, phycoerythrin; RFP, red fluorescent protein; RL, Renilla luciferase; wtGH, wild-type GH
13.  Fibroblast Growth Factor Receptor-Mediated Activation of AKT-β-Catenin-CBP Pathway Regulates Survival and Proliferation of Murine Hepatoblasts and Hepatic Tumor Initiating Stem Cells 
PLoS ONE  2012;7(11):e50401.
Fibroblast Growth Factor (FGF)-10 promotes the proliferation and survival of murine hepatoblasts during early stages of hepatogenesis through a Wnt-β-catenin dependent pathway. To determine the mechanism by which this occurs, we expanded primary culture of hepatoblasts enriched for progenitor markers CD133 and CD49f from embryonic day (E) 12.5 fetal liver and an established tumor initiating stem cell line from Mat1a−/− livers in media conditioned with recombinant (r) FGF10 or rFGF7. FGF Receptor (R) activation resulted in the downstream activation of MAPK, PI3K-AKT, and β-catenin pathways, as well as cellular proliferation. Additionally, increased levels of nuclear β-catenin phosphorylated at Serine-552 in cultured primary hepatoblasts, Mat1a−/− cells, and also in ex vivo embryonic liver explants indicate AKT-dependent activation of β-catenin downstream of FGFR activation; conversely, the addition of AKT inhibitor Ly294002 completely abrogated β-catenin activation. FGFR activation-induced cell proliferation and survival were also inhibited by the compound ICG-001, a small molecule inhibitor of β-catenin-CREB Binding Protein (CBP) in hepatoblasts, further indicating a CBP-dependent regulatory mechanism of β-catenin activity.
Conclusion: FGF signaling regulates the proliferation and survival of embryonic and transformed progenitor cells in part through AKT-mediated activation of β-catenin and downstream interaction with the transcriptional co-activator CBP.
doi:10.1371/journal.pone.0050401
PMCID: PMC3540100  PMID: 23308088
14.  Multispectral image alignment using a three channel endoscope in vivo during minimally invasive surgery 
Biomedical Optics Express  2012;3(10):2567-2578.
Sequential multispectral imaging is an acquisition technique that involves collecting images of a target at different wavelengths, to compile a spectrum for each pixel. In surgical applications it suffers from low illumination levels and motion artefacts. A three-channel rigid endoscope system has been developed that allows simultaneous recording of stereoscopic and multispectral images. Salient features on the tissue surface may be tracked during the acquisition in the stereo cameras and, using multiple camera triangulation techniques, this information used to align the multispectral images automatically even though the tissue or camera is moving. This paper describes a detailed validation of the set-up in a controlled experiment before presenting the first in vivo use of the device in a porcine minimally invasive surgical procedure. Multispectral images of the large bowel were acquired and used to extract the relative concentration of haemoglobin in the tissue despite motion due to breathing during the acquisition. Using the stereoscopic information it was also possible to overlay the multispectral information on the reconstructed 3D surface. This experiment demonstrates the ability of this system for measuring blood perfusion changes in the tissue during surgery and its potential use as a platform for other sequential imaging modalities.
doi:10.1364/BOE.3.002567
PMCID: PMC3469985  PMID: 23082296
(170.2150) Endoscopic imaging; (170.3010) Image reconstruction techniques; (170.6510) Spectroscopy, tissue diagnostics
15.  The Weak Complex between RhoGAP Protein ARHGAP22 and Signal Regulatory Protein 14-3-3 Has 1∶2 Stoichiometry and a Single Peptide Binding Mode 
PLoS ONE  2012;7(8):e41731.
ARHGAP22 is a RhoGAP protein comprising an N-terminal PH domain, a RhoGAP domain and a C-terminal coiled-coil domain. It has recently been identified as an Akt substrate that binds 14-3-3 proteins in response to treatment with growth factors involved in cell migration. We used a range of biophysical techniques to investigate the weak interaction between 14-3-3 and a truncated form of ARHGAP22 lacking the coiled-coil domain. This weak interaction could be stabilized by chemical cross-linking which we used to show that: a monomer of ARHGAP22 binds a dimer of 14-3-3; the ARHGAP22 PH domain is required for the 14-3-3 interaction; the RhoGAP domain is unlikely to participate in the interaction; Ser16 is the more important of two predicted 14-3-3 binding sites; and, phosphorylation of Ser16 may not be necessary for 14-3-3 interaction under the conditions we used. Small angle X-ray scattering and cross-link information were used to generate solution structures of the isolated proteins and of the cross-linked ARHGAP22:14-3-3 complex, showing that no major rearrangement occurs in either protein upon binding, and supporting a role for the PH domain and N-terminal peptide of ARHGAP22 in the 14-3-3 interaction. Small-angle X-ray scattering measurements of mixtures of ARHGAP22 and 14-3-3 were used to establish that the affinity of the interaction is ∼30 µM.
doi:10.1371/journal.pone.0041731
PMCID: PMC3429473  PMID: 22952583
16.  Identification of RhoGAP22 as an Akt-Dependent Regulator of Cell Motility in Response to Insulin▿‡ 
Molecular and Cellular Biology  2011;31(23):4789-4800.
Insulin exerts many of its metabolic actions via the canonical phosphatidylinositide 3 kinase (PI3K)/Akt pathway, leading to phosphorylation and 14-3-3 binding of key metabolic targets. We previously identified a GTPase-activating protein (GAP) for Rac1 called RhoGAP22 as an insulin-responsive 14-3-3 binding protein. Insulin increased 14-3-3 binding to RhoGAP22 fourfold, and this effect was PI3K dependent. We identified two insulin-responsive 14-3-3 binding sites (pSer16 and pSer395) within RhoGAP22, and mutagenesis studies revealed a complex interplay between the phosphorylation at these two sites. Mutating Ser16 to alanine blocked 14-3-3 binding to RhoGAP22 in vivo, and phosphorylation at Ser16 was mediated by the kinase Akt. Overexpression of a mutant RhoGAP22 that was unable to bind 14-3-3 reduced cell motility in NIH-3T3 fibroblasts, and this effect was dependent on a functional GAP domain. Mutation of the catalytic arginine of the GAP domain of RhoGAP22 potentiated growth factor-stimulated Rac1 GTP loading. We propose that insulin and possibly growth factors such as platelet-derived growth factor may play a novel role in regulating cell migration and motility via the Akt-dependent phosphorylation of RhoGAP22, leading to modulation of Rac1 activity.
doi:10.1128/MCB.05583-11
PMCID: PMC3232915  PMID: 21969604
17.  Caught in the slips 
BMJ Case Reports  2010;2010:bcr08.2009.2186.
We report a case where a patient slipped from the operating table during positioning for a laparoscopic colectomy. This occurred due to failure of the Velcro holding the mattress to the operating table. On further inspection, although the amount of Velcro was satisfactory to hold the patient, it had failed due to a combination of its poor positioning, table design and the build up of ‘fluff’ on the Velcro from the use of incorrect cleaning products. The episode was reported as a critical incident and review lead to the implementation of changes across theatres to prevent such an episode happening again.
doi:10.1136/bcr.08.2009.2186
PMCID: PMC3047178  PMID: 22753299
18.  Collaborative Gaze Channelling for Improved Cooperation During Robotic Assisted Surgery 
Annals of Biomedical Engineering  2012;40(10):2156-2167.
The use of multiple robots for performing complex tasks is becoming a common practice for many robot applications. When different operators are involved, effective cooperation with anticipated manoeuvres is important for seamless, synergistic control of all the end-effectors. In this paper, the concept of Collaborative Gaze Channelling (CGC) is presented for improved control of surgical robots for a shared task. Through eye tracking, the fixations of each operator are monitored and presented in a shared surgical workspace. CGC permits remote or physically separated collaborators to share their intention by visualising the eye gaze of their counterparts, and thus recovers, to a certain extent, the information of mutual intent that we rely upon in a vis-à-vis working setting. In this study, the efficiency of surgical manipulation with and without CGC for controlling a pair of bimanual surgical robots is evaluated by analysing the level of coordination of two independent operators. Fitts’ law is used to compare the quality of movement with or without CGC. A total of 40 subjects have been recruited for this study and the results show that the proposed CGC framework exhibits significant improvement (p < 0.05) on all the motion indices used for quality assessment. This study demonstrates that visual guidance is an implicit yet effective way of communication during collaborative tasks for robotic surgery. Detailed experimental validation results demonstrate the potential clinical value of the proposed CGC framework.
doi:10.1007/s10439-012-0578-4
PMCID: PMC3438393  PMID: 22581476
Robotic surgery; Human–robot interface; Eye tracking; Perceptual docking; Collaborative surgical task
19.  An unusual case of unequal chest expansion 
BMJ Case Reports  2010;2010:bcr11.2009.2437.
doi:10.1136/bcr.11.2009.2437
PMCID: PMC3028266  PMID: 22448188
20.  Amplification and Demultiplexing in Insulin-regulated Akt Protein Kinase Pathway in Adipocytes* 
The Journal of Biological Chemistry  2011;287(9):6128-6138.
Background: Akt plays a major role in insulin regulation of metabolism.
Results: Akt operates at 5–22% of its dynamic range. This lacks concordance with Akt substrate phosphorylation, GLUT4 translocation, and protein synthesis.
Conclusion: Akt is a demultiplexer that splits the insulin signal into discrete outputs.
Significance: This study provides better understanding of the Akt pathway and has implications for the role of Akt in diseases.
Akt plays a major role in insulin regulation of metabolism in muscle, fat, and liver. Here, we show that in 3T3-L1 adipocytes, Akt operates optimally over a limited dynamic range. This indicates that Akt is a highly sensitive amplification step in the pathway. With robust insulin stimulation, substantial changes in Akt phosphorylation using either pharmacologic or genetic manipulations had relatively little effect on Akt activity. By integrating these data we observed that half-maximal Akt activity was achieved at a threshold level of Akt phosphorylation corresponding to 5–22% of its full dynamic range. This behavior was also associated with lack of concordance or demultiplexing in the behavior of downstream components. Most notably, FoxO1 phosphorylation was more sensitive to insulin and did not exhibit a change in its rate of phosphorylation between 1 and 100 nm insulin compared with other substrates (AS160, TSC2, GSK3). Similar differences were observed between various insulin-regulated pathways such as GLUT4 translocation and protein synthesis. These data indicate that Akt itself is a major amplification switch in the insulin signaling pathway and that features of the pathway enable the insulin signal to be split or demultiplexed into discrete outputs. This has important implications for the role of this pathway in disease.
doi:10.1074/jbc.M111.318238
PMCID: PMC3307283  PMID: 22207758
Adipocyte; Akt PKB; Insulin Resistance; Protein Synthesis; Signal Transduction; IRS1; PDGF; mTOR; Rapamycin
21.  Intrinsic Depot-Specific Differences in the Secretome of Adipose Tissue, Preadipocytes, and Adipose Tissue–Derived Microvascular Endothelial Cells 
Diabetes  2010;59(12):3008-3016.
OBJECTIVE
Visceral adipose tissue (VAT) is more closely linked to insulin resistance than subcutaneous adipose tissue (SAT). We conducted a quantitative analysis of the secretomes of VAT and SAT to identify differences in adipokine secretion that account for the adverse metabolic consequences of VAT.
RESEARCH DESIGN AND METHODS
We used lectin affinity chromatography followed by comparison of isotope-labeled amino acid incorporation rates to quantitate relative differences in the secretomes of VAT and SAT explants. Because adipose tissue is composed of multiple cell types, which may contribute to depot-specific differences in secretion, we isolated preadipocytes and microvascular endothelial cells (MVECs) and compared their secretomes to those from whole adipose tissue.
RESULTS
Although there were no discrete depot-specific differences in the secretomes from whole adipose tissue, preadipocytes, or MVECS, VAT exhibited an overall higher level of protein secretion than SAT. More proteins were secreted in twofold greater abundance from VAT explants compared with SAT explants (59% versus 21%), preadipocytes (68% versus 0%), and MVECs (62% versus 15%). The number of proteins in the whole adipose tissue secretome was greater than the sum of its cellular constituents. Finally, almost 50% of the adipose tissue secretome was composed of factors with a role in angiogenesis.
CONCLUSIONS
VAT has a higher secretory capacity than SAT, and this difference is an intrinsic feature of its cellular components. In view of the number of angiogenic factors in the adipose tissue secretome, we propose that VAT represents a more readily expandable tissue depot.
doi:10.2337/db10-0483
PMCID: PMC2992760  PMID: 20841607
22.  Toward a population genetic framework of developmental evolution: the costs, limits, and consequences of phenotypic plasticity 
Adaptive phenotypic plasticity allows organisms to cope with environmental variability, and yet, despite its adaptive significance, phenotypic plasticity is neither ubiquitous nor infinite. In this review, we merge developmental and population genetic perspectives to explore costs and limits on the evolution of plasticity. Specifically, we focus on the role of modularity in developmental genetic networks as a mechanism underlying phenotypic plasticity, and apply to it lessons learned from population genetic theory on the interplay between relaxed selection and mutation accumulation. We argue that the environmental specificity of gene expression and the associated reduction in pleiotropic constraints drive a fundamental tradeoff between the range of plasticity that can be accommodated and mutation accumulation in alternative developmental networks. This tradeoff has broad implications for understanding the origin and maintenance of plasticity and may contribute to a better understanding of the role of plasticity in the origin, diversification, and loss of phenotypic diversity.
doi:10.1002/bies.200900132
PMCID: PMC3151734  PMID: 20020499
costs and limits; development; modularity; mutation accumulation; phenotypic plasticity; pleiotropy; relaxed selection
23.  Disinfection of the Access Orifice in NOTES: Evaluation of the Evidence Base 
Introduction. Appropriate prevention of infection is a key area of research in natural orifice translumenal endoscopic surgery (NOTES), as identified by the Natural Orifice Surgery Consortium for Assessment and Research (NOSCAR). Methods. A review of the literature was conducted evaluating the evidence base for access orifice preparation/treatment in NOTES procedures in the context of infectious complications. Recommendations based on the Oxford Centre for Evidence-Based Medicine guidelines were made. Results. The most robust evidence includes several experimental randomised controlled trials assessing infectious complications in the transgastric approach to NOTES. Transvaginal procedures are long established for accessing the peritoneal cavity following disinfection with antiseptic. Only experimental case series for transcolonic and transvesical approaches are described. Conclusion. Grade C recommendation requiring no preoperative preparation can be made for the transgastric approach. Antiseptic irrigation is recommended for transvaginal (grade C) NOTES access, as is current practice. Further human trials need to be conducted to corroborate the current evidence base for transgastric closure. It is important that future trials are conducted in a methodologically robust fashion, with emphasis on clinical outcomes and standardisation of enterotomy closure and postoperative therapy.
doi:10.1155/2011/245175
PMCID: PMC3138109  PMID: 21785559
24.  Behavioral Characteristics and Neural Mechanisms Mediating Performance in a Rodent Version of the Balloon Analog Risk Task 
Neuropsychopharmacology  2010;35(8):1797-1806.
The tendency for some individuals to partake in high-risk behaviors (eg, substance abuse, gambling, risky sexual activities) is a matter of great public health concern, yet the characteristics and neural bases of this vulnerability are largely unknown. Recent work shows that this susceptibility can be partially predicted by laboratory measures of reward seeking under risk, including the Balloon Analog Risk Task. Rats were trained to respond on two levers: one of which (the ‘add lever') increased the size of a potential food reward and a second (the ‘cash-out lever') that led to delivery of accrued reward. Crucially, each add-lever response was also associated with a risk that the trial would fail and no reward would be delivered. The relative probabilities that each add-lever press would lead to an addition food pellet or to trial failure (risk) were orthogonally varied. Rats exhibited a pattern of responding characteristic of incentive motivation and risk aversion, with a subset of rats showing traits of high-risk taking and/or suboptimal responding. Neural inactivation studies suggest that the orbitofrontal cortex supports greater reward seeking in the presence or absence of risk, whereas the medial prefrontal cortex is required for optimization of patterns of responding. These findings provide new information about the neural circuitry of decision making under risk and reveal new insights into the biological determinants of risk-taking behaviors that may be useful in developing biomarkers of vulnerability.
doi:10.1038/npp.2010.47
PMCID: PMC3055471  PMID: 20375994
decision; frontal; addiction; reward; risk; cognition; Animal models; Cognition; Addiction & Substance Abuse; Behavioral Science; Depression, Unipolar/Bipolar; decision; frontal; reward; addiction; risk
25.  Use of conservative and surgical foot care in an inception cohort of patients with rheumatoid arthritis 
Rheumatology (Oxford, England)  2011;50(9):1586-1595.
Objectives. To describe conservative and surgical foot care in patients with RA in England and explore factors that predict the type of foot care received.
Methods. Use of podiatry and type of foot surgery were outcomes recorded in an inception cohort involving nine rheumatology centres that recruited patients with RA between 1986 and 1998 across England. Associations between patient-specific factors and service use were identified using univariate logistic regression analyses. The independence of these associations was then verified through multiple binary logistic regression modelling.
Results. Data were collected on 1237 patients with RA [66.9% females, mean (s.d.) age at disease onset = 54.36 (14.18) years, median DAS = 4.09 (1st quartile = 3.04, 3rd quartile = 5.26), median HAQ = 1 (0.50, 1.63)]. Interventions involving the feet in the cohort were low with only 364 (30%) out of 1218 receiving podiatry and 47 (4%) out of 1237 patients having surgery. At baseline, female gender, increasing age at onset, being RF positive and higher DAS scores were each independently associated with increased odds of seeing a podiatrist. Gender, age of onset and baseline DAS were independently associated with the odds of having foot surgery.
Conclusions. Despite the known high prevalence of foot pathologies in RA, only one-third of this cohort accessed podiatry. While older females were more likely to access podiatry care and younger patients surgery, the majority of the RA population did not access any foot care.
doi:10.1093/rheumatology/ker130
PMCID: PMC3157630  PMID: 21504991
Rheumatoid arthritis; Foot; Podiatry; Surgery; Orthopaedic surgery; Foot care; Access to service

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